US2981375A - Hydraulic elevators - Google Patents

Description

April 25. 1961 J. H. BORDEN HYDRAULIC ELEvAToRs 5 Sheets-Sheet 1 Filed Aug. l2, 1959 JNVENTOR.

JOSEPH H. BORDEN BY 1 ywwwww ATTORN Ys l April 25, 1961 J. H. BORDEN 2,981,375

HYDRAULIC ELEVATORS med Aug. 12, 1959 5 sheets-sheet 2 INVENTOR.

JOSEPH H. BORDEN BY ATTO NEYS April 25, 1961 J. H. BORDEN 2,981,375

HYDRAULIC ELEVATORS Filed Aug. 12, 1959 5 Sheets-Sheet 5 JNVENTOR.

JOSEPH H. BORDEN ATTOR YS April 25, 1961 .1. H. BORDEN 2,981,375

HYDRAULIC ELEVATORS Filed Aug. 12, 1959 5 Sheets-Sheet 4 JOSEPH H. BORDEN ATTOR April 25, 1961 J. H. BoRDl-:N 2,981,375

HYDRAULIC ELEvAToRs JOSEPH H. BORDEN i ATTEEYS 7 2,981,375 Patented Apr. 25, 1961 HYDRAULIC ELEVATGRS Joseph H. Borden, Toledo, Ohio, assignor to Toledo Scale Corporation, Toledo, Ohio, a corporation of Ohio Filed Aug. 12, 1959, tSer. No. 833,203

38 Claims. (-Cl. IS7-28) This invention relates to hydraulic elevators.

Hydraulic elevators are particularly well suited for hauling freight and have certain advantages especially for low rise installations. However, heretofore, such elevators have been generally unsatisfactory in certain aspects. Many prior hydraulic elevators have two motor operated pumps each of a different capacity for slow, fast and intermediate speeds, even though it is desirable, from the standpoint of cost, simplicity of oper-ation, and optimum acceleration and deceleration, to operate such a system with only a single motor operated pump and with an inlinite number of speeds for any one load for smooth acceleration and deceleration. The prior hydraulic elevators -a'lso are unsatisfactory in that they do not provide by simple means `a uniform leveling speed and a uniform top or running speed for various loadings. None of the prior hydraulic elevators have a really satisfactory method for leveling the cars at landings. Furthermore, all of the prior hydraulic elevator systems are relatively complicated and bulky.

It is, accordingly, the principal object of this invention to provide an improved hydraulic elevator.

Another object of the invention is to provide a simplified hydraulic control system for an elevator.

A further object of the invention -is to provide, for an elevator, a hydraulic system which has an infinite number of speeds for any one load for smooth acceleration and deceleration.

Still another object is to provide, vfor an elevator, a hydraulic system which has a uniform leveling speed and a uniform top or running speed for variousfloadings.

Another object is to provide, for an elevator, a hydraulic system having improved meansfor leveling ya car at a,` landing. ,t Y

A still further objectl is to provide, for an elevator, a hydraulic system which `is exceedingly compact, easy. -to

operate, of low cost and, which istrouble free. ,v Tl1eseand-other objects and advantages are apparent from the `following description ofthe invention.- 4

According to the invention, the .hydraulic,elevatornin-` cludes a single motor operated pump-in aline connected `to atcylinder having a piston that' raises" and lowersan. elevator car.

tive for lifting the elevator car, the car starts up slowly at leveling speed, but accelerates to top speed asthe control valve slowly closes. The other by-pass and its dashpot connected control valve, i.e., the down control valve, is isolated from the system during the up travel by means of a fully closed on or off stop valve. As the car approaches the selected landing, the up control valve opens slowly to decelerate the car to leveling speed and when the car is level with the landing the pump is stopped to stop the car. This simple arrangement of a dashpot operated valve in a by-pass provides a smooth acceleration and deceleration in the up direction and in Combination with the down control valve together with its by-pass provides a system which is operable with only one pump.

Should the car settle slightly, the pump is started to raise the Vcar at leveling speedthis arrangement being another feature of the system.

Upon the registration of a down start signal, the down control valve which is normally closed starts to open slowly and the stop valve which is in series with the down control valve opens fully. During down travel thepump is not operated. 'Ille car starts down slowly at' levelingy speed under the influence of gravity, but accelerates as thevcontrol valve slowly opens. The up control valve together withV its by-pass is isolated from the system during the down travel by means of a check valve. As

the car approaches the selected landing, the down control valve closes slowly to decelerate the car to `leveling speed and when the'car is level withV the landing the stop valve is closed to stop the car. This simple arrangement of a dashpot operated valve in a by-pass provides a smooth lacceleration and deceleration in the down direction.

A further feature resides inthe compact design of the valve system which is located as a small unit adjacent the motor operated pump.

Another feature resides in a unique device for automatically operating the up and the down control valves according to the load in the car. This device, there being one for each of the two valves, includes a diaphragm l which is sensitive to line pressure and means operated by the diaphragm to control. the degree of opening and of closing of the control valve` and Athus to alter such openingfor various loadings to make the leveling and' top-speeds uniform. Such pressure is aI function of the elevator loading, `.the llow,` or volume ofhydraulic fluid delivered to .the cylinder controllingV the speed ofthe elevator car.

A preferred embodiment of the inventionris illustrated I in the accompanying drawings. t

In the drawings: p l Fig. Iv is a diagrammatic representation of a hydraulic elevator embodying the invention;

YTwo by-passes 'are provided inthe line;

between the pump 'and the cylinderfand` aty certain' times f in the .operation they returnhydr-aulicuid to a reservoirwhich supplies the pump. A control valve 'is located in eachof the `lay-passes4 and each of the valves is.pro

vided with'la dashpotso that it opens and closes slowly.

However, even whenffully closed, the valves lealfiluidI tothe reservoir. v

4 Upon thefregistration of any up startA sign-al, one. 'Off/the,

dashpot ,connected control valves, ie., theupjeontrol bfy-passedl through :the up.` control valve and returned to Y -the reservoir;` `.1 l`hererbeingV only 20% of thetluid eiec- Fig. Il is an elevational view of a subassrenibl-y of.v thel hydraulic elevator system with parts broken awayI andl sectioned; v

Fig. llgl is a'plan 4view taken along thelirle` III- III4v of'Fig'. Il, certa'in'parts being shown insection; g

Fig. I'V' is an `elevational view as seen .froma-.position substantially along ythe line IV--,IVl-of'Fig. IIII, -part:be-v

ing' shown in vertical section;

g'Fig. V is 'an elevationalfview a-s seen from aposition shown in vertical section;y

control valveV shown incorporated in the subassembly in Fig. IV; and v Fig; Vil is a schematic wiringV diagram of an electricalVV 1 jcontrol system-'forthe elevator.`v i ,f 'j

' These drawings and thefollowing description illustrate andi l:describe al preferred form 'of the Vinvention `but' 'are vnotintendedtolimit its scope.

v.-;,Referringafa te Fig.y I, the hydraulie @avatar instar-'1 lation is one in which an elevator car 1, only a fragment of the floor of which is shown, is movable in a hatchway 2 between a oor 3 and another oor located at the level of the car 1 in its position shown. While only operation between two landings will be described for the sake of simplicity, it is to be understood that the elevator may be arranged to serve more than two landings. The elevator car 1 is equipped with hand operated sliding gates or doors and the hatchway 2 is provided with a landing door at each floor; these doors are not shown since they are conventional. However, an example of conventional car doors and a landing door is shown and described in U.S. application Serial No. 671,040, tiled on July 10, 1957 in the name of D. L. Baker, wherein the car doors are so operatively and automatically connected to a landing door while the car is at a landing that such doors move together at the landing.

The elevator car 1 is secured to the top of a lifting plunger or piston 4 which extends downwardly into a cylinder 5 through a stuffing box 6. The cylinder 5 is connected to an oil reservoir 7 (Figs. II-V) by means of piping 8, there being a positive displacement pump 9 connected in the piping 8 between the cylinder 5 and the reservoir 7. A motor 10 functions to drive the pump 9 and a pressure wave neutralizing unit 11 connected in the piping 8 adjacent the pump 9 functions to substantially neutralize or eliminate pressure waves which are propagated from the pump. The unit 111 is shown and described in detail in U.S. application Serial No. 709,052, filed on January 15, 1958 in the name of I. H. Borden. The motor 10,l pump 9, neutralizing unit 11, and oil reservoir 7, together with various control valving and interconnecting piping hereinafter described, are suitably mounted in a frame 12 as shown in Fig. II in the form of a compact subassemblage that can be fabricated in lots at a factory and carried in stock. The pump 9 is connected to the reservoir `7 by means of a conduit 13, a screen 14 in the reservoir straining the oil before it flows by gravity from the reservoir which is under atmospheric pressure to the pump.

The positive displacement pump 9 may be of any desired type but preferably is of the type that is commonly known as a gear pump. The pump when driven by the motor 10 takes oil or another suitable hydraulic medium from the reservoir 7 and forces it through the unit 11 and piping 8 to the hydraulic cylinder 5 which contains the lifting piston 4 that is mechanically connected to the elevator car 1 tobe lifted. The hydraulic lifting piston, the elevator car and the connections therebetween may be of any preferred existing type and they therefore are not shown in detail in the drawings. 't

In the general operation of the elevator, assuming the car 1 is at floor 3, upon the issuance of an up start signal after thedo'ors are closed, the car 1 starts'up slowly at leveling speed, `accelerates to top speed and Icontinues at top speedruntil a normaly open switch 15 (Fig. I) carried by they elevator car is closed by a stationary cam 16 secured in the hatchway 2 and a :normally closed switch 17which is s tationarily mounted in the hatchway is opened -by a cam 18 that is carried by the car, the switch 15 being closed just before the' switch 17 is opened. The cat '1f then starts to decelerate and continues in its upwardl path untilthe vroller of the normally open switch 15 rollsjoff of the stationary/"cam 16.A This stops the car. Should-the oar settle',l the switch-15` again is closed, the hydraulic" pumpis actuated,` and the caris moved upwardly at levellingspeed to a position level with thesec- @ad neer. whiiethe carts lever 'with the naar, the svlitch17` is held open by the cam' 18 as shown inFig. I.

. Upon-the issuance of a down start signal, the car starts down slowly under the'influjence of gravity at leveling Y speedwacceleratesto top. speedjand continues at top speedfluntilfa"normaly open switch 19 Lcarried by the' arily mounted in the hatchway is opened by the cam 18 that is carried by the car, the switch 19 being closed just before the switch 21 is opened. The car then starts to decelerate and continues in its downward path until the roller of the normally open switch 19 rolls olf of the stationary cam 20. This stops the car. While the car is level with the Ioor, the switch 21 is held open by the cam 18.

The piping S is provided with two return by-passes or conduits each of which includes a manifold 22. The left hand manifold 22 as viewed in Fig. III leads to an up control valve 23 the lower end of which (Fig. 11V) opens into the oil reservoir 7 and also leads to a relief valve 24 which is a safety spring valve that is opened by excess pressure in the system to return oil from the piping 8 to the reservoir 7. Normally, the relief valve 24 remains closed. The right hand manifold as viewed in Fig. III leads to an on or off stop valve 25 which communicates with a down control valve 26 the lower end of which (Fig. H) opens into the oil reservoir 7 and also leads to a hand operated valve 27 that functions to run the car down in case of power failure. Opening of the valve 27 permits oil to ow from its lower end (Fig. II) into the reservoir 7. Normally, the valve 27 remains closed. A cover plate 28 on the reservoir keeps the oil therein from splashing or bubbling out, there being tight fitting rings 29 around the valves 23, 24, 26 and 27 that rest on gaskets 3)V on the cover plate 28 at the respective openings therethrough. Atmospheric pressure is maintained through an opening 31 in the cover plate 28 at a splash guard 32 (Fig. Il) which is supported by the cover late.

p During up travel, the stop valve 25, which is operated as hereinafter described by a solenoid 33 (Fig. VII, line 210), is closed to isolate the down control valve 26 from the system. Both of the control valves 23 and 26 are so constructed and operated that they port when in closed position. That is, when the up control valve 23 is fully closed and the pump 9 is operated, as an cxemplary figure only, 80% of the total flow at a check valve 34, which is located in the piping 8 between the manifolds 22, passes through the check valve 34 and 20% of the total ow is bypassed through the up control valve 23 to the reservoir. When the up control valve 23 is fully opened and the pump 9 is operated, as an exemplary figure only, 20% of the total flow at the check valve 34 passes through the check valve 34 and 80% of the total flow is diverted through the up control valve 23 to the reservoir.

During down travel, the check valve 34 isolates ythe up control valve 23 fromthe system, the elevator car descending under the influence of gravity with the motoroperated pump turned olf. Fluid flow is through the then opened solenoid stop valve -25 and the down control valve 26 to the reservoir. When the down control valve 26 is fully closed, it allows oil to leak into the reservoir in the same manner as the up control valve does. The control valves are identical except that the down control valve '26 is normally closed while the up control valve 23 is normally open. Hence, during up travel the failure of a solenoid35 (Fig. IV)l which operates the up control valve 23 does not prevent car operation. That is, the

I n normally open up control'valve 23 'when' allowed to open because of solenoid failure only passes'about 80% of cariis closed by a stationary cam 20 secured in theihatch` Y way Zaanda normallygclosed 'switch 21' Awhich isstationthe total ow at the check valve 34 so that the car will still loperate at slow or leveling speed when thev up control valve 23 is fully open and when the pump 9 is operating. As in the up direction, thecar candescend at leveling speed under the influence of gravity even when a solenoid 36- (Fig. V) which operatesv the -down control valve 26 fails. Th'at is, the normally closed down control' valve "26wh`en allowed to closebecause of solenoid failure still leaks oil to the'fres'ervoir so that thecar can descend'patleveling speedrf y Mechanism for opening and closing the up control valve 23 slowly and for operating the up control valve 23 according to the load in the car is illustrated in Fig. IV. The up control valve 23 includes a valve manifold 37 which communicates with the manifold 22 and that supports a lever pivot post 38 stationarily mounted thereon. An operating lever 39 is pivoted at lll atop the post 38 and it is attached at its left end as viewed in Fig. IV to the plunger 41 of an oil lled dashpost 42 which is pivotally mounted to compensate for the arcuate move-v ment of the lever by means of a pin 43 on a bracket 4.4 fixed to the top of the manifold 22, the. lever 39 being attached at its right end to a return spring 4S that has its lower end adjustably secured to a stationary bracket 46 carried by the solenoid 35 which is carried in turn on a plate 47 secured to the bottom of the valve manifold 37. A pair of small right angle brackets 48` and 49 is pivotally mounted on the lever 39 by means of pins 59 and 51 as spaced points intermediate the lever pivot il and the returnspring 45. The armature of the .solenoid 35 is'operatively connected to bracket 49 by means of a pair of nuts 52 and a valve operating rod 53 is connected to bracket i8l by means of a pair of nuts 54, the brackets 48 and 49 being rockable `about the axes of the pins 5t) and 51 to compensate for the arcuate motion of the lever 39 to which they are attached. Energizetion of the solenoid 35 causes the lever 3@ to be pivoted in a counterclockwise direction about the pivot 4h as viewed in Fig. lV in opposition to the return spring d5. This lifts the valve operating vrod 53, attached to the lever39, to close the normallyopen up control valve 23, Upondeenergization of the solenoid ,35, the return spring l5 pivotsthe lever 39 in a clockwise direction about the pivot 4@ to reopen the normally open up control valve 23.

The up control valve 23 opensrand closes slowly because of the damping eiect of the dashpot 62. This provides a smooth acceleration and deceleration'on up travel, since the open up control valve 23, i.e., the control valve in its levelingV speed position, by-passes perhaps 80% of the total ow at the check valve 3e to the reservoir 7 at the start of the up travel, leaving only 20% of the fluid effective for lifting `the car, andro-loses slowly to produce more and more ilow ory volume of fluid de-V livered to the cylinder and thus an'infnite number of speeds, whereby' a smooth acceleration in the up direction if obtained. The amount of ow of the hydraulic fluid which is delevired to the cylinder controls the speed of the car. Similarly, on approaching the selected floor slow opening of thev up control lvalve 23 leaks more and more oil to the reservoir`7 and the resulting lowery and lower flow to the cylinder" produces a smooth decelerationuntil the leveling speed is reached.

The degree of opening and of closing of the up con- 7 trol` valve 23 is altered foryariousloadings through automatically adjustable rangesA to make the leveling and ruiming speeds uniform'. This isy one of the more important features of ythe elevator system and is accomplished by means ofa compensator diaphragm 55 in the form of an oil resisting cylindrical block of flexible material that is so located inthe valve manifold-37 that itis contacted along its bottom surfacebyoil at line pressure. The diaphragm 55,".therefore, sensitive to the pressurein'the line which pressure Jis a function of the loading offthe elevator `car l.` A"componeat'orv guide 56 is stationarily mounted in the valvemanifold 37; it has a shoulder 57 and thevv'alve manifold 37 has an abutting surface 58 between which shoulder and surfacethe vcli-aphragm 55 is'held. High line pressure causes the diaphragm S5 to be bowed upwardly-in a space 59 above the diaphragm-` "A cylindrical compensator plunger 69" bears on the top of the cylindrical diaphragm 55 and lis concentric therewith; it is slidable in a vertical hole that extends through an "oversize hole in a stationary Y vvthrough the guide 56 and it carries a verticali'rod-61jy i v'valve sleeve 76 bears..

which is pivoted at its bifurcated end 65 at 66 to the post 38. A compression return spring 67 surrounding the rod 6l is held between a spring seat 68 at its upper end and the upper end of the plunger, the spring seat 68 having an oversize hole through which the rod`6 extends and being forced iby the spring 67 against the stationary spring retainingplate 62 that is held in an adjustable position atop a pair of adjustment bolts 69 threaded into the compensator` guide 56. Upward movement of the diaphragm is in opposition to the spring 67. The selected positions of the bolts 69 are retained by means of locknuts 70. The sensitivity of the compensator diaphragm 55 is varied by compressing the spring 67 more or less, i.e, the adjustable force applied by the spring 67 to the diaphragm SSthrough the plunger 6@ must be overcome by the hydraulic force applied by the oil to the bottom of the diaphragm before the hydraulic force is able to bow the diaphragm upwardly and move the plunger 60 and its attached rod 61 upwardly.

The valve operating rod 52'` extends through a hole 71 in the compensator lever 64 and carries on either side of `the hole 71 a pair of stop nuts 72 which when they contact the lever 64 limit the amount the up control valve 23- can be opened or closed. Since the position of the lever 66 is determinedby the hydraulic pressure upon the diaphragm 55 to which it is operatively connected, i.le., movement ofthe diaphragm pivots the lever 64 about its pivot 66, when the nuts 72 Contact the lever 64 they limit the amount the up control valve 23- can be opened or closed according to ythe line pressure and, hence, according to the loading of the car 1. Energiza-tion of the solenoid 35 causes the lever 319 to be pivoted in ay counterclockwise direction `as viewed in Fig. IV about the pivot Atti in opposition to the returnV spring 45 until the lower pair of the nuts 72 on the valve operating rod 53I connected to the lever 39 contact the bottom ofthe compensator lever 64. This closes the normally open up control valve 23` to an extent that is a function of the car loading. Upon deenergization of the solenoid 35, the return spring 45 pivots the lever 39 in' a clockwise direction about the pivot 40 until the upper pair of the nuts 72 contact the top of the compensator lever 64. This opens the normally open up'control valve 23Vl to an extent that is a functionof the car loading. The net result is an operation lof the up control valve 23! in accorda.

horizontal roiwof equally spaced round holes 77 and a horizontal row, below the row of round holes y777, of equally spaced triangular holes 78 is stationarily mounted concentrfically within the casing 73` by means lof astrap 79 that is` Secured tol the ring 75 and upon which the The valve sleeve 76 Yextends through Vthe ring and fits therein with a tight t vto prevent leakage` of'oil.V An .elongatedvalve Vguide 80' having a foot 81 is Vstatioriarily mounted atop the valve sleeve 76m oill `sealedrelationship by` means of screws 8-2 and extends from its foot 81 through :the casing 73 and through thewalvemanifold .37 in the form of a s leeve and is held against movement transverse to its axis by means of a tight ring 83 atop the valvernanifold: 37..

1 The valve operating rod 53 is located within the sleevel-ikevalve guide and it is secured at its lower end. to

the top of arvalve insert 84 which is slidably mounted within the sleeve 7 6. The valveinsert `84 is provided with a relatively` wide and deep'cirlcumferential groove 85,

averticalhole 86 along its axis, and' three equally spaced holes iljwhich lead fromithetop of thevalve insert at an angle -into the hole 86, the holes 87 functioning as bleed passages that carry any oil which leaks past the valve insert 84 to the vertical hole 86 in which it runs to the reservoir 7. Flow of oil is through the round holes 77 in the valve sleeve 76 into the circumferential groove 85 in the valve insert 84 and out of the triangular holes 78 in the valve sleeve 76 and down into the reservoir 7, the pressure within the casing 73 being at line pressure and the pressure at the triangular holes 78 in the reservoir being at atmospheric pressure. As shown in Fig. Vl, all of the triangular holes 78 are covered by the valve insert S4 except for a small portion at the apex of each triangle. This is the closed position ofthe valve, i.e., even when closed the valve leaks oil to the reservoir. Slight downward movement of the valve insert 84 from its position shown in Fig. VI has its effect magnified by the fact that the areas of the triangular holes that are exposed to oil ow increase rapidly in a direction downward from the apex. Similarly, slight upward movement of the valve insert 84 has its effect magnified. Hence, the valve is quite sensitive to any change in the range limits within which it operates, i.e., the limits set automatically by means of the pressure sensitive cornpensator diaphragm 55.

It was found that a relatively large solenoid 35 was required to operate the up control valve 23 insofar as it has been described. This was discovered to result from a pressure reduction at 88 in the valve insert 84 due to oil flow through the triangular holes 78. Hence, line pressure at 89l within the valve insert 84 overbalanced the reduced pressure at 88. This pressurel difference had to be overcome by the solenoid. The system is never sta-tic because the triangular holes 7S are never cornpletely closed. If they were, then the force at 88 in a downward vertical direction would exactly balance the force at 89l in the upward vertical direction because line pressure would be imposed on each of these equal areas. The unbalance of forces due to the pressure drop induced by tluid i'low across surface 88 is compensated for in the up control valve 23y by means of a pin 90 which has an upper surface 91 and that is arranged to slidein an opening through the foot 81 of the valve guide 80 and through an opening in a collar 92 that is stationarily mounted on the valve guide 80 as a guide for the pin 90. A stop 93 on the guide 80'limits upwar'd travelof the pin 90. The pin 90 bears upon a spacer' 94 that "bears in `turn upon the upper end of the valve insert 84 which isheld in place by means of the valve operating rod 53 that passes through an opening in the spacer 94. Force on the upper surface 91 of the pin 90' adds to the downward force applied at 88 to the valve insert 84 and so tends toward a balance of the forces in all directions on the valve insert 84 that the valve can be operated in either direction with relatively little effort. Hence, the solenoid 35I can be of relatively small' siz'e.

"The control valves are identical except that the down controlv valve 26'is normally closed while the up control valve 23 is normally open. Reference numbers in Figs. Il and V`which are applied to the down control valve 26 vand which lare similar to those applied to the up control valve 23'y identify similar parts. Mechanism for opening and closing thedown control valve 26 slowly and for operating the'doWn-control valve 26 according to the load in the car is illustrated in Fig.v V. The down control valve' 26 includes a valve manifold 95 which communicates with the stop valve 25 and that supports a lever pivot post96 stationarily mounted thereon. An

- operating lever 97 is pivoted at 98 atop the post 96 and it is attached intermediate itsrends to the plunger 99 of anA oil filled dashpot 100 which is pivotally mounted to compensate forthe arcuate movement of the lever by meansof a pin 101cm albracket 102 secured to the top ofthe right hand end, as viewed in Fig. V, of a bracket 103 which is secured in turn to the solenoid 36. A bracket 104 on the` lever 97 serves to join the lever to 8 the top of the plunger 99. The solenoid 36 is carried by a recumbent L-shaped bracket 'which is fixed to the valve manifold 95. The lever 97 is attached at its left end to a return spring 106 that has its lower end adjustably secured to the bracket 103 on the solenoid 36.

A pair of small right angle brackets 107 and 103 is pivotally mounted on the lever 97 by means of pins 109 and 110, the angle bracket 107 being located at the right end of the lever and the angle bracket 108 being located intermediate the return spring 106 and the dashpot 100. The armature of the solenoid 36 is operatively connected to bracket 108 by means of a pair of nuts 111 and the valve operating rod 53a is connected to bracket 107 by means of a pair of nuts 112, the brackets 107 and 10S being rockable about the axes of the pins 109 and 110 to compensate for the arcuate motion of the lever 97 to which they are attached. Energization of the solenoid 36 causes the lever 97 to be pivoted in a clockwise direction about the pivot 98 as viewed in Fig. V in opposition to the return spring 106. This lowers the valve operating rod 53a, attached to the right end of the lever 97, to open the normally closed down control valve 26. Upon deenergization of the solenoid 35, the return spring 106 pivots the lever 97 in a counterclockwise direction about the pivot 98 to reclose the normally closed down control valve 26.

The down control valve 26 opens and closes slowly because of the damping effect of the dashpot 100. This provides a smooth acceleration and deceleration on down travel in the same manner as the dashpot 4-2 (Fig. IV) produces smooth acceleration and deceleration on up travel as hereinbefore described.

The degree of opening and of closing of the down control valve 216- is altered for various loadings in the same way that the degree of opening and 0f closing of the up control valve 23 is altered as hereinbefore described. Reference numbers in Fig. V which are applied to the mechanism for operating the down control valve 26 according to the load in the car and which are similar to those applied to identical mechanism shown in Fig. IV identify like parts.

With reference to Fig. VII, relays and all other circuit elements are shown in an across-the-line diagram. The relay contacts therefore are often located remote from their actuating coils. In order to correlate the location of the actuating coils and contacts, a marginal key has been employed with the circuit diagram. With this key, the diagram has been divided into horizontal bands which are identiiied with line numbers in the right hand'margin. Relay symbols are located in the margin to the right of the linenumerals and in horizontal alignment with the coil positions. The location of each contact actuated by 'a relay coil is set forth to the right of the relay symbol in the key by the numeral of the line upon which it appears. The numerals designating the location of back contacts, those which are normally closed when the relay is de-energized and are open when it is energized, are underlined in the key to distinguish them from front contacts, those which are closed upon theiractuating coil being energized. Thus, the time relay ULT appearing in line 212 has a front contact at line 200 and a back contact at line 202 as signified by the numerals inthe margin of Fig. yVH at line 212.

An operator` for example, who wishes to go to the second tioor enters the car at the first iloor and closes theA car gate or door by hand, the car gate being so operatively connected to the hall doors that the hall doors also close as hereinbefore described and operates a push button 113 in line 216. Cams (not shown) lcarried by the gate and hall doors mechanically close normally open switches 114 and 115 in a supply lead 116. Current then flows from the supply lead 116 through the push button 113, the energizing coil of a sealing relay S in line 216, the normally closed switch 17 in line 216 which is in the cuit to the motor .10, the iirst circuit to 9 v hatchway and which is held open by means of the cam 18 on the car while the car is level with the second door, as shown in Pig, I, the energizing coil of an up relayU in line 216,` and down relay contacts D in line 216 to a return lead 121i. The sealing relay S in line 216 thereupon closes its contacts S in line 215 to provide a sealing circuit around the push button 113 and the up relay U in line 21:5 closes its contacts U in lines 219, 207, and 204, and opens .its contacts U in lines 21S, 2115 and 210. y 'l The opening of the up relay contacts U in line 21h insures that the energizing coil of a down relay D in line 218 cannot be energized accidentally at this time. The closing of the up relaycontacts U in line Zit/7 permits rectied current to ilow to the coil of the` up control valve solenoid 35 in line 2117, (also see Fig. 1V) and the normally open, dash-pot damped up control valve 23 starts to close. The opening of the up relay contactsU .in line 205 cuts off current flow to the energizing coil of a time relay DT in line 2115 which was energized by current flow from the supply lead 116 upon the closing of switches 114 and 115i. Deenergization yof the time relay DT causes its normally closed contacts DT in line 2114 to close after a brief delay, Le., the time relay has a slow drop out. (hnrentA then flows through the now closed timerelay contacts DT in line 21M and the now closed up relay contacts U in line 2114 to the motor 1111 in line 263 (alsosee Fig.A II). This starts the pump 9. The delay caused `by the slow drop out of the time relay DT in line 2115 allows the up control valve 23 to start to close before the. motor 11) starts. v

The closing of up relay contacts U in lin'e219` permits current to flow to the'energizing coil of .an auxiliary up relay lU1 in line 219. The energization of the auxiliaryv up relay U1 in line 219 causes it to close its contacts U1 in lines 2 12 and 213; The closing of auxiliary up relay contacts U1 in line 213 completes a circuit to the energizing coil of a retiring cam relay RS in line 213 and the closing of auxiliary up relay contacts U1 in line 212 completes a circuit to the energizing coil of a time relay ULT in line 212. Energization ofthe retiring earn relay RC in line 213 causes its contacts RC in line 2111 to open and the energization of the time relay ULT in line 212 causes its contacts ULT inline 20@ toclose and its contacts ULT in line 2112 to open.

The elevator car starts to movel upwardly as soon as i the motor starts at an increasing speed with a smooth acceleration until the up control valve 23 is fully closed and thus full speed is reached.` Asvthe car approaches the second floor, the normally open switch 15 in" line 201 (see also Fig. I) on the car is closed mechanically by the stationary ca1n'16 in the hatchway and shortly thereater the normally closed switch 17` in -line216finzthe hatchway is opened by means of the cam 18 on 'the oar.

yThe closing of switch 15 in line 201 completes a circuit to the energization coil of a leveling up' relayLU in line 2111, current flowing through such coiland through time .relay contacts ULTin Vline 21H1, Energization of the coil of the leveling uprela-y LU in line. 2111 causes it to close its contactsLU in line 203 which completes a 4second cirlthe motor 1@ being through the lead -at line 224, f j f The opening of switch 17 in line 216 opens the circuit to the up relay U in line 216 and its contaotsU inlines 219, 218, 207,215, 204 and 2111 return tol their original positions, i,e.,.theiripositions'shown in Fig. V11. The opening of up relay' contacts U in line2ti'7 breaks the f circuit tothe up control valve solenoid 35 in line 2197 and the normally open up control valve 23 starts to open slowlyv and, therefore, the elevator car starts to slow down with asmooth deceleration. The opening of up relay contacts Uin line2t14 breaks therrst circuit to the motor 1i), the motor still beingenergized,through; the circuit at line203;`y When the caris leveltwith the second door normally open switch 15. in line 261 :opens-breaking the circuit to the leveling up relay yLU in line 2111 and its contacts LU in line 203 open breaking the second circuit to the motor 10 and the car stops. In the up direction, there is no overrun of the car even with a light load, the car being operated at `slow or leveling speed just before it stops.

While the car is level with the second floor, switch v17 in line 216 continues to be held open as illustrated in Fig. I. Should the car settle slightly switch 15 in line 201 is closed again but switch 17 in line 216 continues to be held open to complete the circuit to the leveling up relay LU in line 2111 which then closes its contacts LU in line 203 to start. the motor 1u. This causes the car to be moved upward at Slow or leveling speed because lat this point up control valve solenoid 35 in line 207 is deenergized and the normally-open up control valve 23 is fully open. Whenthe vcaragain is level with the secondv iloor, they normally open switch 15- in line 21.31 opens breaking the circuit to the leveling up relay LU in line`2i1 and its contacts LU in line 2113 open breaking the circuit to the motor 10 and the car stops level with the floor.

As the car approached the second door, i.e., before the leveling up operation, the closing of switch 15 in line 201 completed a circuit to the energization coil of the leveling up relay LU in line 201, the current flowing through such coil and through the time relay contacts ULT in line 201i. However, in the levelingup oper-ation; the time relay contacts ULT in line 2110 are open, since switch 17 in line 216 is held open at this time opening i RC in lineV 261 are closed, Since the retiring cam relay Y RC in line 213 is deenergized by the opening of the auxiliaryup relay contacts closing of switch 15 in line 221 completes a circuit to the energization coil of the leveling up relay LU in line 2111 current lows through such coil and through the retiring camfcontacts RC in line 2&1 to the ,return lead 120. Deenergization of the tirne relay ULT in line 212 causes its normally open contacts ULT in line 20%) and its normally closed contacts ULT in line 202 to open and close, respectively, after a briet` delay,i.e., the time relay has a slow drop out. The delayed opening of the time Vrelay contacts VULT in line 21141 lassures lan unbroken circuit to the motor 10 at this time so that there is 11o discon- Y tinuity in motor operation before the retiring cam con tacts RC in tline 201 drop in while stopping on the up Vtrip. y t While only operationl between two landings has been described, it is tobe understood that the elevator may be arranged toserve more than two landings.

To start down, a push button 141 in line 218 is' operated. When* gate and door contacts 111i and 115 are closed, current then flows fromVV the supply lead 116 through the push button 141, the energizing ,coil ofa vsealing relay S1 inline 218, normally closed switch 21 in line 218' which is in the hatchway and which is held open `by means of the cam 18 on the car while the car is 'level 'with the iirstA floor, the energizing coil of the down relay D in line 218, and the Vup relay contactsuUl in line 218 to the return lead 1213. The sealing relay S1 inline 218 thereupon `closes its contacts S1 in line 217 to provide a sealing circuit aroundthe push button 141 and the down relay D in line 218 opensV its contacts D in line 216 and closes 208, respectively. v

The-openingof the downrelay contacts D in line 216 l insures that the energizing coil of thefup relay U in lineV U1 in line 213, and when the its contacts D in lines 214, 210 andl 216 cannot be energized accidentally at this time. The closing of the down relay contacts D in line 210 cornpletes a ycircuit to the coil of the stop valve solenoid 33 in line 210 whereupon the stop valve 25 (Fi-g. III) opens. At the same time, the closing of hte down valve contacts D in line 208 permits rectified current to flow to the coil of the down control valve solenoid 36 in line 208 and the normally-closed, dashpot-darnped down control valve 26 starts to open. The closing of the down valve contacts D in line 214 completes a circuit to the retiring cam relay RC in line 213 which opens its contacts RC in line 201.

The elevator car starts to move down under the influence of gravity as soon as the stop valve 2S is opened at slow or leveling speed and, as the down control valve 26 opens, at an increasing speed until full or running speed is reached` As the oar approaches the first iloor, the normally open switch 19 inline 202 on the. car is closed mechanically by the stationary cam 20 in the hatchway and shortly thereafter the normally closed switch 21 in line 218 in the hatchway is opened'by means of the cam 18 on the oar. The closing of switch'19 in line 202 conditions a circuit to be completed to the energization coil of a leveling down relay LD in line 202 as soon as the retiring cam contacts RC in line 201 close. The opening of switch 21 in line 21S breaks the circuit to the down relay D in line 218 and its contacts D in lines 216, 214, 210 and 208 return to their original positions, i.e., their positions shown in Fig. VII. The opening of the down relay contacts D in line 268 opens the circuit to the coil of the down control valve solenoid 36 in line 298 and the normally closed down control valve 26 starts to close slowly. This causes a reduction in the speed of the 'car to the slow or leveling speed. At the same time,

the opening of the down relay contacts D in line 214A breaks the circuit to the retiring cam relay RC in line 213 and its normally closed contacts RC in line 291 close to complete the circuit through the closed switch 19 in line 202, the coil of the leveling down relay LD in line 202, the time relay contacts ULT in line 202, and through the retiring cam contacts RC in line 219. Energization of the coil of the leveling down relay LD in line 202 causes it to close its contacts LD in line 211 to keep a circuit to the stop valve solenoid 33 closed even though the down relay contacts D in line 210 are now open. When the car is level with the tirst oor, normally open switch 19 in line 202 opens lbreaking the circuit to the leveling down relay LD in line 262 and its contacts LD in line 211 open breaking the circuit to the stop valve solenoid 33. The stop valve cioses and thus the car is stopped level with the rst floor. v

It may be desirable under some circumstances to control the system by means of a single compensated control valve. Such a system includes, with reference to Fig. HI, the motor-operated pump 9, the normally open control valve 23 in its by-pass to the reservoir, the check valve 34 and the cylinder `S, i.e., the manifold 2,2 for the stop valve 25, the stop valve 25 and the control valve 26 are eliminated from `the system. In place of such manifold 22, the stop valve 25 and the Vcontrol valve v2'6, a conduit from the cylinder to the control valve 23 is provided to by-pass the check valve 34, there being a solenoid operated o n or off valve in the conduit. Alternatively, such manifold 22, the stop valve 2S and the control valve 26 are eliminated and a solenoid operated check` valve which can be opened to permit flow of hydraulic medium from the cylinder to the control valve 23 issubstituted for the ordinary check valve 34. Y

To start up, the motor-operated pump is started 'and the normally open control valve 23 which is open prior to the start up is closed slowly to produce the acceleration, the check valve 34 and thesolenoid operated ou and olf valve in the conduit which lay-passes the check valve 34 or in-the alternative arrangement the solenoid operated check valve which issubstituted for the ordioff valve in the bypass around the check valve to the control val-ve 23 or in the alternative arrangement through the solenoid operated check valve which is substituted for the ordinary check valve 34 to the control valve 23. To stop on down travel, the now open control valve 23 is closed slowly to produce the deceleration and the elevator car is stopped by closing the solenoid operated on and off valve in the bypass around the check valve or in the alternative arrangement by closing the solenoid operated check valve which is substituted for t-he ordinary check valve 34 to stop all ow of hydraulic medium from the cylinder to lthe control valve 23.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of the invention.

Having described the invention, I claim:

1. In a hydraulic elevator system, in combination, a hydraulic cylinder, a reservoir containing a hydraulic medium, conduit means connecting the cylinder and the reservoir, pumping mechanism in the conduit means for transferring hydraulic medium from the reservoir to the cylinder to provide elevator up travel, a first return conduit between the cylinder and the reservoir for returning hydraulic medium to the reservoir to provide elevator down travel under the iniluence of gravity, a second return conduit between the cylinder and the pumping mechanism for returning hydraulic medium to the reservoir during elevator up travel, and a variable ow control valve operable 4through a continuous range in each of the return conduits for controlling the ow of the hydraulic medium through the return conduits and thus for controlling the flow of the hydraulic medium into and out of the cylinder.

2. In a hydraulic elevator system, in combination, a hydraulic cylinder, a reservoir containing a hydraulic medium, conduit means connecting the cylinder and the reservoir, pumping mechanism in .the conduit means for transferring 4hydraulic medium from the reservoir to the cylinder to provide elevator up travel, a rst return conduit between the cylinder and the reservoir for returning hydraulic medium to the reservoir to provide elevator down travel under the influence of gravity, a second return conduit between the cylinder and the pumping mechanism for returning hydraulic medium to the reservoir during elevator up travel, variable tlow valve means in the return conduits for controlling the ow of the hydraulic medium through the return conduits and thus for controlling the ow of the hydraulic medium into and out of the cylinder, and means, isolated from the hydraulic medium, for causing the valve means to open and close slowly providing controlled acceleration and deceleration on up travel and on down travel.

3. In a hydraulic elevator system, in combination, a hydraulic cylinder, a reservoir containing ay hydraulic medium, conduit means connecting the cylinder and the reservoir, pumping mechanism in the conduit means for transferring hydraulic medium from the reservoir'to the cylinder to provide elevator up travel, a rst return conduit between the cylinder and the reservoir for returning hydraulic medium .to the'rcservoir to provide elevator down travel under theinuence of gravity, a second return conduit between the cylinder and the pumping mechanism for returning hydraulic medium to the reservoir during elevator up travel, valve means in the return conduits for controlling the ilow of the hydraulic medium through the return conduits and thus for controlling the flow of the hydraulic medium into and out of the cylinder, the valve means providing an adjustable ilow, and means sensitive to .the pressure of the hydraulic medium for adjusting the valve means to vary valve range limits according to various loadings of the elevator, whereby uniform leveling and running speeds are provided.

4. In a hydraulic elevator system, 'in combination, a hydraulic cylinder, a reservoir containing a hydraulic medium, conduit means connecting the `cylinder and the reservoir, pumping mechanism in the conduit means for transferring hydraulic medium in forward now from the reservoir to the cylinder to provide elevator up travel, a first return conduit between the cylinder and the reservoir for returning hydraulic medium to the reservoir to provide elevator down travel under the iniiuance of gravity, a stop valve in the iirst return conduit for preventing said return of hydraulic medium to the reservoir during .elevator up travel, a second return conduit between the cylinder and the pumping mechanism for returning hydraulic medium to the reservoir during elevator up travel, means in the hydraulic circuit for preventing backward flow of hydraulic medium to the second return conduit, and a control valve in each ofthe return conduits for controlling the flow of the hydraulic medium through the lreturn conduits and thus for controlling the tlow of the hydraulic medium into andV out of the cylinder.

5. In a hydraulic elevator system, in combination, a hydraulic cylinder, a reservoir containing a hydraulic medium, conduit means connecting the cylinder and the reservoir, pumping mechanism in the conduit means for transferring hydraulic medium in forward ilow from the reservoir to the'cylinder to provide elevator up travel, a

iirst return conduit between the cylinder and the reservoir for returning hydraulic medium to the reservoir to provide elevator down travel under the influence of gravity, a stop valve in the trst return conduit for preventing said return of hydraulic medium to the reservoir during elevator up travel, a second return conduit between the cylinder and the pumping mechanism for returning hydraulic medium to the reservoir during elevator up travel, means in the hydraulic circuit for preventing backward flow of 4hydraulicnredium to the second return conduit, valve means in the return conduits for controlling the flow of the hydraulic medium through the return conduits and thus for controlling the flow of the hydraulic medium into and out of the cylinder, and means, isolated from the hydraulic medium, Ifor retarding'l operation of the valve means to provide controlled acceleration and decelerationon 'up'travl and on down travel.V

6. In alhydraulic elevator system, in combination, a hydraulic cylinder, la reservoir containing a hydraulic inedium,'c0nduit means connecting thecylinder )and the reservoir, pumping mechanism in the conduit means lfor transferring'hydraulic medium in forward flow from the lreservoir vtofthe cylinder to provide elevator up travel, a

first return conduit between the cylinder and the reservoir for `returning vhydraulic medium to thereservoir to provide elevator down travel under the iniiuenceof gravity, a stop valvein thewrst return conduit for-'preventing said return of :hydraulic medium to the reservoir during elevator uptravel, a second return conduit between the cylinder and the pumping mechanismtor returning hyhydraulic medium downtravel under means according to various loadings of the elevator, whereby uniform leveling and running speeds are provided.

7. In a control system for a hydraulic elevator having a hydraulic cylinder, in combination, variable flow valve means for controlling the ow of a hydraulic medium into and out of the cylinder, and means sensitive to the pressure of the hydraulic medium for controlling the degree of opening and of closing of the valve means to vary valve range limits according to various loadings of the elevator. i

8.v In a control system for a'hydraulic elevator having a hydraulic cylinder, in combination, valve means for controlling the flow of a hydraulic medium into and out of the cylinder, the valve means operating within range limits, and diaphragm means sensitive to the pressure of the hydraulic medium for adjusting the valve means to vary the range limits according to various loadings of the elevator.

9. In a control system for a hydraulic elevator having a hydraulic cylinder, in combination, adjustable stop means dening adjustable limits, |valve means operable within a range between the adjustable limits for controlling the flow of a hydraulic medium into and out of the cylinder, the degree of opening and of closing of the valve means and thus the range limits being 4adjustable by adjusting the stop means, and diaphragm means sensitive to the pressure of the hydraulic medium for adjusting the stop means for various elevator loadings.

l0. In a control system for a hydraulic elevator having a hydratdic cylinder, in combination, variable flow valve means for controlling the flow of hydraulic medium into and out ofthe cylinder, and dashpot the hydraulic medium, operatively connected to the valve means for retarding the opening and the closing of the valve means to provide controlled acceleration and deceleration on up travel and on down travel.

ll. In a control system for a hydraulic elevator having a hydraulic cylinder, in combination, an up control variabl-e flow valve for controlling the iow of a hydraulic medium into the cylinder, Ia down control variable` flow valve for controlling the flow of the hydraulic medium out of ythe cylinder, and a dashpot, isolated from the hyhydraulic medium, operatively connected to each of the valves `for retarding its opening'and closing to provide controlled acceleration and deceleration on uptravel and on'` down travel.

l2. In a hydraulic elevator system, in combination, a hydraulic cylinder, a reservoir 'containing a hydraulic medium, conduit means connecting the cylinder and the reservoir, pumping mechanism in the conduit means `for transferring hydraulic medium `from the ,reservoir to the cylinder to provide elevatorlup travel, a first return conduit between the cylinder and the reservoir for returning tothe reservoir to provide elevator the influence of gravity, a second return conduit between the cylinder and the ypumping mechanism for returning hydraulic medium'to the reserv voir duringjelevator'up travela'nd;a control valve in each draulic medium to the reservoir during elevator uptravel, f

means in the hydraulic circuit .for preventing backward flow of hydraulic .medium tothe second return conduit, valvev means in the return .conduits for controlling the flow/of 'the hydraulic medium;through the'return conduits `and thus foricontrolling the flow. of the hydraulic medium Vinto and out-o`f,thecylinder, the;valve means providing'an adjustable lrow, andrneans,` sensitive to the pressure of the hydraulic medium for adjusting the valve of the `return conduits iior controlling'the flow ofthe hydraulicnrnedium through the return conduits and thus for controlling the" flow of the hydraulic medium into land out of the'c'ylinder, each of the control valves including a casing communicating with the respective return lconduiL-a sleeve stationarily mounted within the casing and` having inlet ports for receiving the hydraulic medium v under relatively high pressure from the casing and outlet ports yfor dischargingthe hydraulic medium to the reservoir gat relatively.; low .pressurefand an insert which is slidablyy ,ountedjwithin thesleeve,v for'controlling the flow from the' outlet ports.

. 13. lna hydraulic elevator system,fn combination, a v

hydraulic cylinder, aV reservoir containin v a h draulicmedium, conduit'means connecting"thev cylinder andthe reservoir, pumping mechanism in the conduit-means for means, isolated fromy transferring hydraulic medium from the reservoir to the cylinder to provide elevator up travel, a iirst return conduit between the cylinder andthe reservoir for returning hydraulic medium to the reservoir to provide elevator down travel under the influence of gravity, a second return conduit between the cylinder and the pumping mechanism for returning hydraulic medium to the reservoir during elevator up travel, and a control valve in each of the return conduits for controlling the flow of the hydraulic medium through the return conduits and thus for controlling the flow of the hydraulic medium into and out of the cylinder, each of the control valves including a casing communicating with the respective return conduit, a sleeve stationarily mounted within the casing and having inlet ports for receiving the hydraulic medium under relatively high pressure from the casing and outlet ports for discharging the hydraulic medium to the reservoir at relatively low pressure, an insert which is slidably mounted within the sleeve for controlling the flow from the outlet ports, and means tending -to balance the forces on the insert even though it experiences a pressure drop adjacent the outlet ports.

14. In a hydraulic elevator system, in combination, a hydraulic cylinder, a reservoir containing a hydraulic medium, conduit means connecting the cylinder and the reservoir, pumping mechanism in the conduit means for transferring hydraulic medium in forward ow from the reservoir to the cylinder to provide elevator up travel, a lirst return conduit between the cylinder and the reservoir for returning hydraulic medium to the reservoir to provide elevator down travel under the influence of gravity, a stop valve in the rst return conduit for preventing said return of hydraulic medium to the reservoir during elevator up travel, a second return conduit between the cylinder and the pumping mechanism for returning hydraulic medium to the reservoir during elevator up travel, means in the hydraulic circuit for preventing backward ow of hydraulic medium to the second return conduit, and a control valve in each of the return conduits for controlling the iiow of t-he hydraulic medium through the return conduits and thus for controlling the flow of the hydraulic medium into and out of the cylinder, each of the control valves including a casing communieating with the respective return conduit, a sleeve stationarily mounted within the casing and having inlet ports for receiving'the hydraulic medium under vrelatively high pressure from the casing and outlet ports for discharging the hydraulic medium to the reservoir at relatively low pressure and an inseit which is slidably' mounted within the sleeve for controlling the -ilow from the outlet ports.

l5. In a hydraulic elevator system, in combination, a hydraulic cylinder, a reservoir containing a hydraulic medium, conduit means connecting the cylinder and the reservoir, pumping mechanism inl the conduit means for transferring hydraulic medium in forward flow from the reservoir to the cylinder to provide elevator up travel, a rst return conduit between the cylinder and the reservoir for returning hydraulic medium to the reservoir to provide elevator .down travel under the influence of gravity, a stop valve in the first return conduit for preventing said return of hydraulic medium to the reservoir during elevator up travel, a `second return Vconduit between the cylinder and the pumping mechanismv for returning hydraulic medium to the reservoir during elevator up travel, means in the hydraulic circuit for preventing backward ow of hydraulic medium to the second return conduit, and a control valve in each of thereturn conduits for controlling the flow of the hydraulic medium through the return conduits and thus for controlling the llow ofthe hydraulic medium. into and out of the cylinder, each of the control valves including a casing communicating with the respective return conduit, a

sleeve stationarily mounted within the casing and having inlet ports` for receiving the hydraulic medium under relatively high pressure from the casing and outlet ports for discharging the hydraulic medium to the reservoir at relatively low pressure, an insert which is slidably mounted within the sleeve for controlling the flow from the outlet ports, and means tending to balance the forces on the insert even though it experiences a pressure drop adjacent the outlet ports.

16. A hydraulic elevator system comprising, in combination, load carrying means, a plunger operatively connected to the load carrying means, a hydraulic cylinder for the plunger, a reservoir containing a hydraulic medium, conduit means connecting the cylinder and the reservoir, pumping mechanism in the conduit means for transferring hydraulic medium from the reservoir t0 the cylinder to provide elevator up travel, means for causing operation of the pumping mechanism to raise the load carrying means, up control valve means operable at the start of the pumping mechanism to cause acceleration of the load carrying means and operable as the load carrying means nears a selected level to cause deceleration of the load carrying means to a leveling speed, means for stopping the pumping mechanism and thus the load carrying means when the load carrying means becomes level with the selected level, a return conduit located between the cylinder and the reservoir for returning hydraulic medium to the reservoir to provide elevator down travel under the inuence of gravity, a stop valve in the return conduit which is closed during up travel, means for causing the opening of the stop valve to lower the load carrying means, a down control valve in the return conduit operable at the opening of the stop valve to cause acceleration of the load carrying means and operable as the load carrying means nears a selected level to cause deceleration of the load carrying means to a lleveling speed, and means for closing the stop valve and thus for stopping the load carrying means when the load carrying means becomes level with the selected level.

17. A hydraulic elevator system according to claim 16 wherein the means for stopping the pumping mechanism and thus the load carrying means when the load carrying means' becomes level with the selected level functions additionally to restart the pumping mechanism to raise the load carrying means at leveling speed should the stopped load carrying. means settle below the selected level and again stops the pumping mechanism and .thus the load carrying means when the load carrying means becomes level with the selected level. I 18. A hydraulic elevator system according to .claim 16 wherein delay means are provided to permit operation of the up control valve means to start before operation of the pumping mechanism begins on up travel.

19. A hydraulic elevator system according to claim 16 wherein the -up control valve means includes a by-pass located between thecylinder and the pumping mechanism for returning hydraulic medium to the reservoir during up ltravel and an up control valve in' the by-pass for controlling the flow of the hydraulic medium through the by-pass and thus for controlling the ow of the hydraulic medium into the cylinder. A

Y20. A hydraulic elevator systemaccording to claim 16 wherein the acceleration and deceleration provided by the up control valve means and by the down control valve is caused by jdashpot means isolated from the hydraulic medium and operatively connected to the-up control valve means and to the down control valve whereby they open and close slowly.

2l. A hydraulic elevator system according to claim 16 wherein means are provided which are sensitive to the pressure of the hydraulic medium in the conduit means for controlling the degree of opening and of closing of the up control valve means and thedown control'valve according to various loadings of the load carrying means, whereby uniform leveling and running speeds forl various loadings are obtained.A .if 22. A hydraulic elevator System according'to claim 17 19 wherein both of the control valves leak hydraulic medium to the reservoir even when such valves are closed.

23. A hydraulic elevatorsystem according to claim 22 wherein each of the control valves provides an adjustable leakage to the reservoir. v

24. A hydraulic elevator system according to claim 23 wherein diaphragm means are provided which are sensitive to the pressure of the hydraulic medium in the conduit means for adjusting the control valves automatically according to various loadings of the load carrying means.

l25. A hydraulic elevator system comprising, in combination, load carrying means, a plunger operatively connected to the load carrying means, a hydraulic cylinder for the plunger, a reservoir containing a hydraulic medium, conduit means connecting the cylinder and the reservoir, pumping mechanism in the conduit means for transferring hydraulic medium from the reservoir to the cylinder to provide elevator up travel, means for causing operation of the pumping mechanism to raise the load carrying means, up control valve means` for controlling the ow of the hydraulic medium into the cylinder operable at the start of the .pumping mechanism to cause acceleration of the load carrying means and operable as the load carrying means nears a selected level to cause deceleration of the load carrying means to a leveling speed, means for stopping the pumping mechanism and thus the load carrying means when the load carrying means becomes level with the selected level, means for returning hydraulic medium to the reservoir to provide elevator down travel under the influence of gravity, down control valve means for controlling the iiow of the hydraulic medium out of the cylinder operable at the start of the elevator down travel to cause acceleration of the load carrying rneans and operable as the load carrying means nears a selected level to cause deceleration of the load carrying means to a leveling speed, and means for stopping said return of hydraulic medium to the reservoir to stop the load carrying means when the load carrying means becomes level with the Selected level.

26. A hydraulic elevator system according to claim 25 wherein the means for stopping the pumping mechanism and thus the load carrying means when the load carrying means becomes level with the selected level functions additionally to restart the pumping mechanism to raise the load carrying means at leveling speed should the stopped load carrying means settle below the selected level and again stops the pumping mechanism and thus the load carrying means when the load carrying means becomes level with the selected level.

27. A hydraulic elevator system according to claim 25 wherein delay means are provided to permit operation of the up control valve means to start before operation of the pumping mechanism begins on up travel.

28. A hydraulic elevator system according to claim 25 wherein the up control valve means includes a bypass located between the cylinder and the pumping mechanism for returning hydraulic` medium to the reservoir during up travel and an up control valve in the by-pass for controlling the flow ofthe hydraulic medium through the by-pass and thus for controlling the llow of the hydraulic medium into the cylinder.

29. A hydraulic elevator system according to claim 25 18 wherein the acceleration and deceleration provided by the control valve means is caused by damping means, isolated from the hydraulic medium, operatively connected to the valve means for slow operation of the valve means.

30. A hydraulic elevator system according to claim 25 wherein diaphragm means are provided which are sensitive to the pressure of the hydraulic medium in the conduit means for controlling the operation of the control valve means according to load upon the load carrying means, whereby uniform leveling and running speeds for various loadings are obtained.

31. A hydraulic elevator system according to claim 25 wherein both of the control valve means leak hydraulic medium to the reservoir even when such valve means are closed.

32. A hydraulic elevator system according to claim 31 wherein each of the control valve means provides an adjustable leakage to the reservoir.

33. A hydraulic elevator system according to claim 32 wherein compensator means are provided which are sensitive to the pressure of the hydraulic medium in the conduit means for adjusting the control valve means automatically according to various loadings of the load carrying means.

34. In a control system for a hydraulic elevator having a hydraulic cylinder which is supplied with a hydraulic medium, in combination, valve means including at least one valve for controlling the ow of the hydraulic medium into and out of the cylinder, a valve operating rod for opening and closingfthe valve and valve stop means carried by the rod, compensator stop means movably mounted adjacent the valve stop means, means for moving the valve operating rod until the valve stop means contacts the compensator stop means, and compensator means sensitive to the pressure of the hydraulic medium `for positioning the compensator stop means according to such pressure and thereby controlling automatically the degree of opening and of closing of the valve according to various loadings of the elevator.

35. A control systemfor a hydraulic elevator according to claim 34 wherein a dashpot is connected to the means for moving the valve operating rod, whereby the valve is opened and closed slowly.

36. A control system for a hydraulic elevator according to claim 34 wherein the compensator means includes a diaphragm.

37. A control system for a hydraulic elevator according to claim 34 wherein the compensator means includes a diaphragm, a plunger that is operatively connected to the compensator stop and that is driven in one direction by the diaphragm, and a return spring for drivng the plunger in a return direction. 38. A control system for a hydraulic elevator according to claim 37 wherein means are provided to adjustably prestress the return springl to vary the sensitivity of the diaphragm.

References Cited in the le of this patent UNITED STATES PATENTS

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