US2811108A - Variable-capacity metering pump - Google Patents

Description

Oct. 29, 1957 D. B. HORTON El' AL VARIABLE-CAPACITY METERING PUMP Original Filed May 17, 1954 4 Sheets-Sheet 1 I A\' V ENTORS 00A/EL 50N a. Hon ra/v i Vvousl. A s ./oH/vs roN mm @H4614 Mw ATTORNEYS Oct. 29, 1957 D. B. HORTON ETAL 2,811,108

VARIABLE-CAPACITY METERING PUMP Original Filed May 17, 1954 4 Sheets-Sheet 2 ///IIIIIIl/IIII/ lf/ ////x /////Vwm k f ATTQRNHS BY/Z Oct. 29, 1957 D. B. HoRToN Erm. 2,811,108

VARIABLE-CAPACITY METERING PUMP 4 Sheets-Sheet 3 Original Filed May 17. 1954 Oct. 29, 1957 D. B. HoRToN ErAL 2,811,108

VARIABLE-CAPACITY METERING PUMP Original Filed May 17. 1954 4 Sheets-Sheet 4 ummmml "Wg-l INVENTORS www M7 www Y 2,811,108 VARIABLE-CAPACITY MErEnlNG PUMP Donelson B. Horton and Douglas Johnston, Huntsville, Ala., assignors to John Blue Company, Incorporated, Huntsville, Ala., a corporation of Alabama This invention relates to variable-capacity metering pumps, and more particularly to pumps for metering a pressurized normally-gaseous liquid. This invention is an improvement on the metering pump disclosed and claimed in the copending application of John Blue, Serial No. 80,957, tiled March l1, V1949, now Patent No. 2,696,785. This application is a division of our application'Serial No. 430,087 liled May 17, 1954, now Patent No.- 2,771,846,` granted November 27, 1956,

Thel pump disclosed in the aforementioned applications isused principally tonaccurately meter anhydrous ammonia for application to the. soil for agricultural purposes. While very satisfactory for its intended `purpose in actual practice, the pump is Asubject to several improvements which bothincrease its metering accuracy andrreduce maintenance expense. The pump disclosed in the above applications is of the positive displacement type, having a piston or pump plunger provided with an inlet check valve and reciprocable in a pumping cylinder. The cylinder is provided with an outlet check valve that is loaded by the pressure of the source of supply of the liquid being pumped independently ofthe Y rod is intermittently engaged and pushed inwardly of the pumping chamber for a discharge or pumping stroke by either a reciprocating crosshead driven by a connectingrod and crankshaft arrangement, or a rotating cam. The suction stroke of theV piston rod, i. e., movement of the rod outwardly of the pumping chamber, is effected by springs and also by the pressure of the source of supply of the liquid being pumped. The pump is of variable capacity, and the capacity is adjustable by means which serve to limit the stroke of the piston rod.

Y Inthe aforedescribed pump, when its capacity is adjusted to a setting below maximum, there is lost-motion engagement between the reciprocating crorsshead or rotatingcam and the piston rod. It also will be seen that, as the setting of the pump is progressively adjusted toward minimum, the extent of lost motion in the aforementioned engagement increases correspondingly. Fur- Vtherit will be seen that, since the suction stroke of the pump is effected solely by the aforementioned springs andthe pressure of the source of supply of the fluid being pumped, the suction stroke is not accomplished VLby a positive drive. In the event that the packing gland for Vthe piston or pump rod is too tight, the piston rod mayltend to stick so that a full suction stroke, at the adjusted setting of the pump, is not obtained, with consequent metering inaccuracies. The same result can possiblybe obtain at higher rates of pump operation, in that a full suction stroke may not occur before the piston rod States Patent-O M is again engaged by the positive drive for its discharge stroke. Furthermore, because the suction stroke of the pump is notobtained by a positive drive, the drive for the pump is under an intermittent or pulsating load.

' Additionally, the pump shown in the aforementioned applications has a valve-controlled purging passageway Il" on line'6-6 of Figure l.

2,811,108 Patented oct. 29, 1957 extending lbetween the pumping rchamber and the outlet chamber at the discharge side ofthe outlet check valve. The valve controlling the passagewayV must, of course, be constructed to withstand the full pressure developed within the pumping chamber.

`In addition to the foregoing, the pump shown in the aforedescribed applications has aV partially-open crankcase so that` ay portion, of the piston or pump rod, and the mechanism for adjusting its stroke, 4are exposed. Since the pump is utilized by farmers, there is a strong likelihood of dirt or trash accumulating in the aforedescribed exposed portion in the c'rankcase with resultant undue wear and abrasion of the thus-exposed moving parts of the pump. Y

l Therefore, it is an object of this invention toprovide avariable-capacity metering pump of the reciprocating type wherein pulsations in the loadon the pump drive aresmoothed out as much as possibley and the evenness of the load on the pumpdrive lis at maximum.

-It is .another object of this invention to provide'a pump of the type described that is accurate at higher rates of operation. e

It isanother object of this invention to provide means for` purging the pumping chamber of the type described which eliminates the need for ahigh-pressure valve.

vIt is another objectV of this invention to' providea pump ofthe type described that has a housing completely enclosing all moving parts of the mechanism for adjusting theV capacity of the pump.

`Other objects, andadvantages' ofthe invention "will become apparent from the following description `and accompanying drawings, in which:

VFigurelisaa' side elevationalview'of a metering Figure 5 is an enlarged fragmentary top plan viewlof the pumpl shown in Figure 2, with parts broken away to illustrate details.

Figure 6 is an enlarged vertical sectional view taken Figure 7 is an enlarged, vertical, sectional view taken on line 7-7 of Figure 3.

AFigure 8 is an enlarged, fragmentary, sectional `view taken on line 8-8 of Figure 2. t

Figure 9 is an enlarged fragmentary sectional view taken on line 9 9 of Figure 1. s

Referring now to the drawings, there is shown a pump embodying this invention. The pump includes an openended cylinder 10 having exterior circumferential end tlan'ges 12 and 14 and a liner 16 fitting against an interior shoulder 18. Engaging against the other endof the liner 16', with a gasket 20 therebetween, is a plug-like member 22 having a central valve po'rt 24`therethrough provided with an annular valve seat 26 at its -outer endtr A flanged cylinder head 28, secured by cap screws 30 to the cylinderl flange 14, has an annular boss 32.tting into one end 0f` the' cylinder 10 and engaging against thegplug-like member 22, with an approp-riate gasket 34 therebetween to retain the member 22 and the liner 16in proper Vposition within the cylinder. The boss 32 is provided witha central circular recess 36 opposed to the valve'seat'26 to form a discharge chamber 38 from which a passageway 40 leads to ran interiorly-threaded'opening 42 (FigureS) in the cylinder head 30 for connection to a discharge con` collar 162 are engaged so that on the return stroke lof theA crossheadA 148 the length of the suction strokev of the piston 84 will be at a maximum.

Referring now to Figure 4,.it will be seen that in this showing the adjusting nut 166 has been threaded rearwardly on the piston rod 86, so that in its return stroke the crosshead 148 will not pull the piston rod 86 rearwardly as far as when the nut 166 is in the position shown in Figure 3. Accordingly, as the crosshead 148v starts its discharge stroke, it moves a .considerable distance before engaging the end of the piston rod 86 to effect the discharge stroke of the same. Consequently, a lostmotion connection exists between the piston 'rod' 86 and the crosshead 148 at any position of adjustment of the nut 166 between minimum and maximum capacity of the pump. Y

As described before, the inlet chamber 100 and the pumping chamber 98 of the pump are under considerable pressure even during the suction stroke of the piston 84. This pressure, of course, urges the piston rod 86 outwardly of the pump chamber 98. Thus, while once the crosshead 148 engages the piston rod 86 the crosshead and the crankshaft 150 and its drive are under considerable load during the pumping stroke of the crosshead, unless otherwise provided for, the crosshead and its drive are under no load on the suction stroke. Therefore, unless otherwise provided for, the drive for the pump would be under a pulsating load, which would result in considerable wear and tear and possible breakage of some of the parts of the pump drive.

In order to eliminate this diiculty, a two-part transverse crossbeam 174 has its upper and lower parts clamped onto a reduced portion of the piston rod 86 and engaging against a rearwardly-facing shoulder 176 thereon. Clamped between the two parts of the crossbeam 174, at each end thereof, is a necked portion of a rod 178 which extends parallel to the axis of the piston rod 86 through aligned apertures in the crankcase housing 70 and in the stuing box plate 74 and outwardly along the cylinder 10. On the outer end of the rod 178 is a spring-retainer washer 180, retained by a snap ring 182, and between the washer 180 and the bottom 184 of a counterbore extending through the stuffing box plate 74 and into the housing 70 is a coil compression spring 186. Preferably, each spring 186 is enclosed in a separate tube 188 having one end thereof threaded into the flange 12 (Figure 5) on the end of the cylinder 10 and the other end thereof closed by a threaded plug 190. The intermediate portion of each tube 188 is supported in an apertured ear 192 on the flange 14 on the other end of the cylinder 10.

From the aforedescribed construction, it will be seen that the springs 186 oppose the suction stroke of the piston rod 86 so that the drive for the pump will be under a load during the suction stroke of the latter. At the same time, the springs 186 store up energy to somewhat relieve the load on the pump drive during the discharge or pumping stroke of the pump. Thus, when the pump is adjusted for less than maximum capacity and the crosshead 148 starts its discharge stroke, the springs 186 tend toy maintain the flange 164 on the adjusting nut 166 in engagement with the end of the collar 162 for an appreciable extent of the discharge stroke of the crosshead 148 and until the pressure in the pump chamber 98 is built up to such an extent that the springs 186 cannot overcome the same. At this time, the bottom 160 of the recess 156 in the crosshead 148 catches up with and engages the end of the piston rod 86 to effect a positive pumping stroke of the latter. Therefore, it will be seen that jars and impacts occasioned by the lost-motion connection between the piston rod 86 and the crosshead 148 are substantially lessened and minimized by the action of the springs 186.

Referring now to Figures 1 to 6 of the drawings, it will be seen that the crankshaft housing 70 includes two chambers 194 and 196joined by a lower passageway 198 beneath the crosshead bearing 149,;thjchamber 194 serving as an actual crankcase and the chamber 196 serving as a housing for the pump-capacity-adjusting mechanism and for the exposed portion ofthe piston' rod 86 and exposedl ends of the spring rods 178. In operation, the crankcase chamber 194 normally has oil therein which can flow, via the passageway 198, into the chamber 196 to maintain the moving parts therein rin a lubricated'condition. The top of the chamber 196 is' opem save for la 'longitudinally-extending bridge member 200, and. the upper edges ofthe end walls of ther chamber 196 are inclined laterally and downwardly to provide two upper openings 202 and 204 (Figure 6) to the chamber, one on each side of the bridge member 200, the upper edge f each opening lying in a downwardly and 'laterally-inclined plane. Closing the opening 202 is a closureplate 206, secured to the housing 70, as by screws 208. An apertured ear 210 at the lower edge of theclosure plate 206 has a wing bolt 212 extending therethroughy and into a tapped opening in the crankcase housing70.V The opening 204 on the other side of the bridge member 200 is closed by a similar closure plate 212 having a transparent window 214 therein for viewing the scale 172. The closure plate 212 is similarly secured in position by a wing bolt 216, but has no other securing screws. At their upper and adjacent edges, both closure plates 206 and 212 are provided with transversely-overlapping apertured ears 218 and are pivotally connected together by a longitudinally-extending pivot pin 220, so that either closure plate may be unfastened from Vthe crankcase housing 70 and raised upwardly for inspection of the interior of the chamber 196 and the parts therein.

Considering again the mechanism for adjusting the capacity of the pump, it will be seen that at each discharge stroke the piston 84 is pushed inwardly of the pumping chamber 98 almost into engagement with the member 22, so that at each discharge stroke of the pump the volume of the pumping chamber 98 is reduced to a minimum. Because of this fact, even if some gas is formed or enters into the cylinder, the effect of such gas on the accuracy of metering of the pump is minimized. On the other hand7 if the volume of the pumping chamber is not reduced to a minimum at each discharge stroke of the pump and gas is formed or enters into the pumping chamber, such gas might tend to accumulate until the pump became gas-locked.

It thus will be seen that the objects of the invention have been fully and effectively accomplished. It will be realized, however, that various changes may be made in the specific embodiment shown and described for the purpose of illustrating the principles of the invention. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.

We Claim:

l. A variable-capacity pump for accurately metering a pressurized uid comprising: means defining an expansible pumping chamber having a movable wall; a reciprocable pump rod secured to said wall and extending outside said chamber for moving said wall inwardly and outwardly thereof; a fixed throw reciprocating driving member opposed to the outer end of said rod and engageable with said rod end to effect a discharge stroke thereof; means defining a sleeve extending from said member and enclosing the end portion of said rod; means defining a radially-inwardly-extending circumferential ange on said sleeve; means defining a radially-outwardlyextending circumferential flange on said rod within said sleeve engageable with saidsleeve iiange to eifect a suction stroke of said rod, said rod flange means being threadedly mounted on said rod for axial adjustment therealong to vary the capacity of the pump; and a. longitudinally-extending scale on said rod, cooperable ,with-referencefrneansassociated with said4 rod flang means for indicating the adjusted capacity of the pump. '2. In avvariable .capacity pump the combination comprising: means defining an expansible pumping chamber having amovable wall; a reciprocating pump rod secured to said wall and extending outside said chamber for moving said wall inwardly and outwardly thereof for `discharge andVV suction strokes, respectively; a fixed-throw vreciprocating driving member having an abutment surface engageable with the outer end of said rod for moving the latter inwardly of said chamber; a sleeve on said driving member enclosing said rod outer end and having a radially-inwardly extending flange; and a nut threaded on saidrod and having a radially outwardly extending flange interposed between said surface and said sleeve flange and engageable by the latter Yfor moving said rod `outwardly of said chamber, rotation of said nut on said rod with resulting axial movement therealong serving to adjust the capacity of the pump, said nut being elongated and having a portionV disposed outside said sleeve to facilitate access to said nut.

t 3. The structure dened in claim 2 including a housing completely enclosing the driving member, the sleeve, the nut, and that portion of` the rod extending outside the chamber, said housing having an opening therein for access to the nut, and including a removable closure for said opening.

References Cited in the file of this patent

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