US1768603A - Refrigerating apparatus - Google Patents

Description

r v a w July 1, 1930. H. B. HULL REFRIGERATING APPARATUS Original Filed Avg. 6, 19 25 Patented July 1, 1930 UNITED. STATES.

HABRYXB. HULL, or common, OHIO, nssmnon 'ro rnremnma. comm-r1511, or

P TENT OF CE DAYTON OHIO, A CORPORATION 01 DELAWARE BEFRIGEBATING APPARATUS Continuation of application Serial No. 48,525,111 August 8, 1925. This: applicatloii filed October 2, 1929 in, although not exclusively applicable to,

a system using an expansion valve, that is, the so-called dry system, this application being a continuation of my application Serial No. 48,525, filed August 6, 1925.

One of the objects of the invention is to reduce the cost of manufacture of apparatus of this type and at the same time to increase its reliability.

. Another object is to provide stable means for controlling the operation of the system in response to the pressure of the refrigerant.

Morespecifically it is an object of my in vention to provide means for. controlling the compressor in response to the steady pressure of the refrigerant, that is, the average of instantaneous pressure values over a considerable period" of time.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the inventlon is clearly shown.

.In the drawings:

- Fig. 1 is a diagrammatic view of the improved refrigerating system,

. Fig. 2 is a view showing a portion of a pressure-time chart on which is indicated the pressure on the low pressure side of the refrigerating system during the operation of the system, and

Fig. 3 is a sectional view, on an enlarged scale, of .the expansion valve shown in Fig. 1. r i

Referring particularly to Fig. 1, ,a compressor 20 is connected with an inlet ipe 21 anda high pressure outletpipe 22. ipe '22 connects with a condenser 23 which is connected by pipe 24 with an expansion valve 25 responsive to the pressure within the evaporator to control the flow of refrigerant into the expansion chamber or evaporator 27. The evaporator 27 includes a pipe coil which is connected by a pipe 29 to I a coupling 30 which is connected by the i Serial no. 396,652.

pipe 21 to the low pressure or suction side of the compressor 20.

The compressor. is driven by an electric motor 32 through a belt and'pulley connections 33, 34 and 35. The circuit to the motor is controlled by a controller 37 which is responsive to refrigeration demands on the be 0 thet' pe shown in the co ending aprsilication 0 Jesse G. King and ylvester M. chweller, Serial No. 670,357, filed October 23, 1923. For the purpose of the resent invention the diagrammatic showlng is refri crating system. This controller may V 38 actuates an arm through a lever 41 and said am) 40, actuates a snap switch 42 which controlscontacts 43 and 44 to open and close the motor circuit.

Referring more particularly to Fig. 3, the expansion valve 25 comprises a casing enclosing a chamber 51 and having an inlet connection 52 and outlet connection 53. Liquid refrigerant supplied through pipe 24 to the connection I 52 enters the chamber 51 through. an orifice 54 under the control of a needle valve 55 adjustably mounted in a.

yoke 56 attached to the center of a diaphragm 57. This diaphragm forms one wall of the chamber 51, being sealed to the' casing 50 by a clamping ring 58 fastened to the casing by bolts 59. The diaphragm is free to move inward against the force of a spring GOseated against an annular shoul .der 61 on the ring member and bearing against a nut 62 threaded on a stem 63 which passes through the annular shoulder and is secured to the centerbf the diaphragm 57 The spring normally holds the diaphragm in its central or neutral position with the needle valve 55seated in the orifice 54 and Reduction of pressure with the 51 causes the pressure existing on the outside of the diaphragm topush the inward Ens therefore closing communication between "the inlet? 52 and chamber 51. ,l chamber and open the valve an amount depending on the ressuref within the chamber.

T e spring 60 is enclosed in a casing 64 preferably formed integral with the ring member 58 and closed by a screw plug 65 Which gives access to the adjusting nut 62. A. gasket 66 seals the casing 64 providing an air-tight chamber on the outside of the diaphragm, to exclude moisture.

When the bellows expands due to a refrigerating demand, switch 42 closes the circuit to operate the compressor. This withdraws gaseous refrigerant from the evaporator 27 and pumps it. to the condenser 23 where it is condensed to liquid form. The liquid passes through the expansion valve 25 into the evaporater, where evaporation absorbs heat and produces refrigeration. When a sufiicient degree of cold has been produced the bellows 38' contracts and stops the compressor. 1

Pursuant to my invention, I make the operation of the bellows 38 responsive to t refrigerating demand on the system as follows: I transmit the pressure of the refrigerant in the low-pressure side of the system directly to the bellows by a conduit 39 connected to the interior of the bellows at one end and with the evaporater on low-pressure pipe at its other end, preferably at the con nection 30.

When refrigeration isrneeded, the evaporato r 27 is warm. Consequently the pressure of the gaseous refrigerant the evaporator, pipe 29, and compressor crank case is high. This high pressure expands the bellows to start the compressor. Operation of the compressor withdraws gaseous refrigerant from the evaporator and liquifies,the refrigerant in the condenser 23. .Withdrawal of refrigerant (with consequent reduction of the pressure in the evaporator) opens the needle valve 55 to admit liquid refrigerant from the condenser. The liquid admitted evaporates and produces refrigeration in the wellknown manner. I 4

As the evaporator 27 and valve 25 become colder the pressure of air sealed within the casing 64 diminishes which increases the ef-' fective force of spring 60 thus changing the setting of the needle valve, causing the latter to close somewhat. Consequently at low temperatures less liquid refrigerant is admitted to the evaporator and the pressure withinthe latter is less than the pressure at high temperature. This reduction in pressure follows the reduction in temperature making the absolute pressure within the evaporator an indication of refrigerating demand.

The bellows is set to collapse and stop the compressor at a pressure corresponding to h the temperature at which refrigeration is no longer required.

The difference between the so-called high and low pressures in the low pressure side, that is, the difference between pressures which will start and stop the compressor, is quite small, being of the order of one or two pounds per square inch. Consequently the pressure-responsive controlling means must be quite sensitive'and adjusted to operate on small differences of pressure. This necessary characteristic will produce unreliable operation due to slight fluctuations in pressure within the system, unless provision is made for eliminating the effect of such'fiuctuations. There are various causes of such fluctuations. In the first place, it has been found that when the compressor starts it may either removea considerable quantity of refrigerant from the evaporator 27 and pipe 29 before the svalve 25 opens, or-for a brief interval withdraw refrigerant from the evaporator faster than it flows through valve 25. .This condition may m0- mentarily reduce the pressure in the low-' pressure side to the value at which the belthe switch is held closed or a moment, re-

frigerant enters the evaporator and its vapor increases the pressure in the system to a value between the starting pressure and stopping pressure. The compressor will then continue to withdraw gas from the lowpressure side of the system, tending to reduce the pressure, and refrigerant flowing into and evaporating in the expansion chamber will tend to increase the pressure, thus maintaining a balance or steady pressure in the system. Secondly, it has been found that when the pressure is near the stopping value, the strokes of the piston in a compressor of the reciprocating type, may cause instantaneous low pressures which would, if transmitted to the bellows, permit it to collapse and stop. the compressor before the steady pressure in the system justified stopping. Thirdly, drops of oil in the evaporator tubing mayfcause' fluctuations in pressure.

.To eliminate the effect on the switch of these momentary low pressures, the passa e through the conduit 39 is made sufficient y small to offer a considerable resistance to the flow of gas through it. Incidentally the volume of the bellows is preferably by comparison, very large. -This arrangement results in interposing an appreciable time between a sudden change of pressure in the tube 29 and its resulting change of pressure in the bellows. This dampens out pressure pulsations due to reciprocation of the piston, and prevents the momentary reduction of pressure on starting the compressor from reaching the bellows. Consequentthe. bellows is insensitive to sudden q changes .of pressure'in the pipe 29, being responsive only to the steady pressure of the refrigerant. As an example, a conduit approximately seven feet long having an internal diameter of one twentieth of an inch has been found to offer sufiicient resistance vto the passage of gas to dampen out pulsations of pressure produced in a single cylinder reciprocating compressor having adisplacement of approximately three and one half cubic inches and operating at a speed of 400 revolutions per minute.

Referring to Fig. 2, the lines A'indicating time and the lines B t0-the left of 0 line indicating pressure in pounds above atmos pheric, and those to the right of O indicate vacuum measured in inches of mercury. The lines X, Y and Z indicate the pressure within the low pressure side of the refrigerating systems, when S0 is used as the refrigerant. I Considering one cycle of operation of the refrigerating system, the

compressor is rendered operative when the pressure within the low pressure side attains a certain high 'value herein shown in approximately eight pounds gauge and which is indicated at Z. The operation of the compressor will lower thepressure in-a relatively short length of time as indicated by line X so' that the pressure therein is equal to approximatel five inches of vacuum. This point is indicated at X. At this pressure, the expansion valve will permit dicates the pressure value corresponding to a temperature which issufliciently low that refrigeration is no longer required, and consequently at which the bellows collapses to open the switch. As shown in Fig. 2 this value is a vacuum of seven inchesof mercury. From the point Y the'curve Z indicates a rise of pressure in the evaporator due to anincrease of temperature of the evap orator when the compressor .is not running. It will be appreciated from Fig. 2 that the pressure limits X and Y between which refri eration is produced, are very close toget er, the total pressure difference in the ;low pressure side of the system during the refrigerating. phase of the operating cycle being inv the present case only about two inches of, mercury. The pressure variations causedby the operation of the compressor may be and, usually are "greater than this pressure difference. pressure variations were permitted to act on the bellows 38 at the time when the mean pressure is so close to the stopping value, the switch would open at some point along the curve Y between the points X and Y .and might even open at the point X. It will be readily seen that if the switch is open before the'steady pressure reaches the point Y that an insufiicient amount of refrigeration will be produced and that the compressor might even operate indefinitely without producing any refrigeration.

The tube 39 in permitting only the mean or steady pressure to act on the bellows insures operationof the compressor in strict" accordance with the refrigerating demand, and produces a simple, reliable and economical control device. The line Z indicates the rise in pressure on the low "pressure side when the compressor is inoperative.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming Within the scope of the claims which follow.

What is claimedis as follows:

1. Refrigerating apparatus including in combination an evaporating chamber, means responsive to the pressure of the eva orating chamber for admitting liquid re rigerant thereto, means for withdrawing gaseous refrigerant from the 'chamber, means responsive to a decreasing temperature of the evaporating chamber for modifying the action of the admitting means to reduce the Consequently if these pressure of the evaporator, means responsive to'the pressure of the refrigerant for controlling the withdrawing means; and means for preventing sudden changes of' pressure from affecting the controlling means.

2. Refrigerating apparatus including in combination an evaporating chamber, means responsive to the pressure of the evaporating chamber for admitting liquid refrigerant thereto, ineans for withdrawing gaseous refrigerant from the chamber, means responsive to a decreasing temperature of the evaporating chamber for modifying the action of the admitting means to reduce the pressure of the evaporator, pressure responsive means exposed to the pressure of the refrigerant for controlling the withdrawing means, and dampening means associated with the pressure responsive means to prevent sudden changes of pressure from affecting the controlling means.

3. Refrigerating apparatus including in combination an evaporating chamber, means responsive to the pressure of the eva orating chamber for admittin liquid re rigerant thereto, means for wit drawing gaseous refrigerant from the chamber, means responsive to a decreasing temperature of the evaporating chamber for modifying the action of the admitting means to reduce the pressure of the evaporator, pressure respontion of the admitting means to reduce the pressure of the evaporator, pressure responsive means exposed to the pressure of the refrigerant for controlling the withdrawing means, and means interposing a time inter-.

val between a change in pressure of the refrigerant and the resulting change in pressure in the pressure responsive means.

5. Refrigerating apparatus including in combination means containing refrigerant, means responsive to the pressure of the containing means for admitting liquid refrigerant thereto, a reciprocating pump for withdrawing refrigerant therefrom, means responsive to a decreasing temperature of the containing means for modifying the action of the admitting,means to reduce the pressure of the evaporator, means responsive to the pressure of the refrigerant for controlling the pump, and means preventing pulsations inpressure caused by the pump from affecting the control means.

6. Refrigerating apparatus comprising in combination. means containing a refrigerant, means responsive to the ressure of the containing means for admitting li uidrefrigerant thereto means for with awing refrigerant therefrom, means responsive to a decreasing temperature of the containing means for modifyin the action ofthe admitting means to re uce the pressure of the evaporator, controlling means for the withdrawing means, an expansible pressure chamber for operating the controlling means, a conduit connecting the pressure chamber with the containing means, the area of the passage through" the conduit being sufiiciently small to dampen out pulsations of pressure of the refrigerant.

I 7. Refrigerating apparatus comprising in combination means containing a refrigerant, means responsive to the pressure of the containing means for admitting 1i uid refrigerant thereto, means for with rawing refrigerant therefrom, means responsive to a'decreasing temperature of the containing means for modifying the action of the ad mitting means to reduce the pressure of the evaporator, controlling means for the withdrawing means, an expansible pressure chamber of relatively large volume for operating the controlling means, a condu1t havingga passage of relativel small area connecting 'the pressure cham er with the containing; means, the relation between the area 'of the; passage and volume of the pressure chamber being such as to provide a substantial time interval between a chan e of pressure in the containing means and t e resulting change of pressure in the pressure chamber. s i

8. Refrigerating apparatus comprising-in combination means containing a refrigerant, means responsive to the pressure of the containing means for admitting li uid refrigerant thereto, means for with rawing refrigerant therefrom, means responsive to a decreasing temperature of the containing means for modifyin the action of the admitting means to re uce'the pressure of the evaporator, pressure responsive means for operating the withdrawing means, a conduit connecting the containing means with the pressure res onsive means, said conduit being adapte to dampen out pulsations of pressure of the refrigerant.

9. Refrigerating apparatus comprising in combination means containing a refrigerant, means responsive to the pressure of the containing means for admitting 1i uid refrigerant thereto, means for with rawing refrigerant therefrom, means responsive to a decreasing temperature of the containing means for modifyin the action of the admitting means to re uce the pressure of the evaporator, pressure responsive means for controlling t e withdrawing means, and a conduit connecting the containing means and the pressure res onsive means, the length ofthe conduit 5 such as to interpoaeresistance -to fluid ow sufiicient to dampen out pulsations in pressure of the refrigerant. I

10. Refrigerating apparatus including in combination an evaporating chamber, means responsive to the pressure of the evaporating chamber for. admitting liquid refrigerant thereto, means for withdrawing gaseous 1 refrigerant from the chamber, means responsive to a decreasing temperature'of the evaporating-chamber for modifying the action of the admittingnmean's to reduce the pressure of the evaporator, snap acting means forv controlling the withdrawing.

means, and means for operating the snap acting means in response to the pressure in I the chamber, said operating means being insensitive to sudden changes of pressure in they evaporating chamber.

In testimony whereof I hereto afiix my signature.

" was; HULL.

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