US2771846A - Variable-capacity metering pump - Google Patents

Description

Nov. 27, 1956 D. B. HoRToN ETAL 2,771,846

I VARIABLE-CAPACITY METERING PUMP Filed May 17, 1954 4 Sheets-Sheet 1 Nov. 27, 1956 D. B. HoRToN ET Al. 2,771,846

VARIABLE-CAPACITY METERING PUMP 4 Sheets-Sheet 2 Filed May 17, 1954 Nov. 27, 1956 D. B. HORTON ET AL 2,771,846

VARIABLE-CAPACITY METERING PUMP Filed May 17, 1954 4 Sheets-Sheet 3 BY Maw )l ATTORNEYS Nov. 27, 1956 D. B. HORTON ET AL 2,771,846

VARIABLE-CAPACITY METERING PUMP Filed May 17,' 1954 4 Sheets-Sheet 4 mwnmm mfg A Mgg V524 //6 f l'ff// INVENTORS VARIABLE-CAPACITY METERING PUMP Donelsou B. Horton and Douglas Johnston, Huntsville, Ala., assignors to John Blue Company, Incorporated, Huntsville, Ala., a corporation of Alabama Application May 17, 1954, Serial No. 430,087

4 Claims. (Cl. 10S-203) 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 ll, 1949, now Patent No. 2,696,785.

The pump disclosed in the aforementioned application is used principally to accurately meter anhydrous ammonia for application to the soil for agricultural purposes. While very satisfactory for its intended purpose in actual practice, the pump is subject to several improvements which both increase its metering accuracy and reduce maintenance expense. The pump disclosed in Vthe above application is of the positive displacement type, having a piston or pump plunger provided with an in-let 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 of the discharge from the pump. The piston rod or pump 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 connecting rod and crankshaft arrangement or a rotating cam. The suction stroke of the 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.

In the aforedescribed pump, when its capacity is adjusted to a setting below maximum, there is lost-motion engagement between the reciprocating crosshead or rotating cam 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. Further, it will be seen that, since the suction stroke of a pump is effected solely by the aforementioned springs and the pressure of the source of supply of the Huid being pumped, the suction stroke is not accomplished by a positive drive. ln the event that the packing gland for the piston or pump rod is too tight, the piston rod may tend to stick so that a full suction stroke, at the adjusted setting of the pump, i-s not obtained, with consequent metering inaccuracies. The same result can possibly obtain at higher rates of pump operation, in that a full suction stroke may not occur before the piston rod is again engaged by the positive drive for its discharge stroke. Furthermore, because the suction stroke of the pump is not obtained by a positive drive, the drive for the pump is under an intermittent or pulsating load.

Additionally, the pump shown in the aforementioned application has a valve-controlled purging passageway extending between the pumping chamber and the outlet chamber at the discharge side of the outlet check valve.

2,771,846 Patented Nov. 27, 1956 The valve controlling the passageway must, of course,

within the pumping chamber.

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

Therefore, it is an object of this invention to provide a variable-capacity metering pump of the reciprocating type wherein pulsa-tions in the load on the pump drive are smoothed out as much as possible and the evenness of the load on the pump drive is 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.

It is another object of this invention to provide means for purging the pumping chamber of the type described which eliminates the need for a high-pressure valve.

it yis another object of this invention to provide a pump tof the type described that has a housing completely enclosing all moving parts of the mechanism for adjusting the capacity of the pump. l

Other objects and advantages of the invention will become apparent from the following description and accompanying drawings, in which:

Figure 1 is a side elevational view of a metering pump embodying this invention.

Figure 2 is a plan view of the pump shown in Figure l, with parts broken away.

Figure 3 is a longitudinalsectional view taken on lines 3 3 of Figure 2 and showing the pump adjusted to its maximum capacity.

Figure 4 is a view corresponding to Figure 3, but showing the pump adjusted to a less than maximum capacity.

Figure 5 is an enlarged fragmentary top plan view of the pump shown in Figure 2, with parts broken away to lillustrate details.

Figure 6 is an enlarged vertical sectional view taken on line 6-6 of Figure 1.

Figure 7 is an enlarged vertical sectional View taken on line 7 7 of Figure 3.

Figure 8 is an enlarged fragmentary sectional view taken on line 8-8 of Figure 2.

Figure 9 is an enlarged fragmentary sectional view taken on line 9--9 of Figure l.

Referring now to the drawings, there is shown a pump embodying this invention. The pump includes an openended cylinder 10 having exterior circumferential end flanges 12 and 14 and a liner 16 iitting against an interior shoulder 18. Engaging against the other end of the liner 16, with a gasket 20 therebetween, is a plug-like member 22 having a central valve port 24 therethrough provided with an annular valve seat 26 at its outer end. A flanged cylinder head 28, secured by ycap screws 30 to the cylinder tiange 14, has an annular boss 32 fitting into one end of the cylinder 10 and engaging against the plug-like member 22, with an appropriate gasket 34 therebetween to retain the member 22 and the liner 16 in proper position within the cylinder. The boss 32 is provided with a central circular recess 36 opposed to the valve seat 26 to form a discharge chamber 33 from which a passageway 40 leads to an interiorly-threaded opening 42 (Figure 8) in the cylinder head 30 for connection to a discharge conduit or hose 44. A valve disc 46 having a recessed resilient valve washer 48 secured thereto by a screw 50 is adapted for seating engagement with the valve seat 26.

3 The valve disc 46 has a stern 5K2 slidably guided in a bore 54 in the cylinder head 28 for reciprocating seating and unseating movement of the valve disc. At its rearward end, the valve stem 52 has a reduced and threaded extension 56, with a flexible sealing cup 58 and a rigid cupretainer Washer 6i) secured thereon by an elongated nut 62 having a locking set screw 64 threaded into the other end thereof. A coil compression spring 66 is engaged between the nut 62 and a plug 68 threaded into the outer end of the bore 54 for urging the valve washer 48 to seat.

The ange 12 at the other end of the cylinder 10 is secured to an open end of a crankcase housing 70, as by cap screws 72, with a stuting box plate 74 clamped therebetween. The stufling box plate 74 has a circular portion 76 extending into the corresponding end of the cylinder to closethe same and a circular portion 78 on its opposite face extending into a circular opening 8l) in the crankcase housing 70 to close the same. An appropriate sealingV gasket 82 is interposed between the cylinder 10 and the sniffing box plate 74. Reciprocable within the cylinder liner 16 is a valved pump plunger or piston 84 having a piston rod or pump rod 86 threadedly engaged with one end thereof and slidably extending through a stuing box88 in therstuffing box plate 74 and into the c rankcase housing 70. The piston 84 is provided with a cup seal 90 secured in place by a cup-retainer washer 92 and snap ring 94 (Figure 3), and has a plurality of ports 96 extendingtherethrough from end to end thereof. The piston 84 divides the cylinder 10 into a pumping chamber 98 and an inlet chamber 100 to which a suction line 102 isconnected. The ends of the piston ports 96 which are exposed to the pumping chamber 98 are arranged in a circle and normally closed by a valve disc 104 reciprocable on a valve stud 106 centrally threaded into the corresponding end of the piston 84. The valve disc 104 is urged to seat against the end of the piston 84 to close the valve ports 96 by a coil compression spring 108 surrounding the stud 106 and retained thereon by a retainer washer 110held on the stud by a snap ring 112.

In operation, the pump is mounted on a tractor on a towed type of vehicle (not shown) and driven by mechanism later described by a drive from a ground-engaging Wheel of the vehicle. The liquid to be pumped, e. g., anhydrous ammonia, is contained in a supply tank (not shown), also mounted on the vehicle. Liquid anhydrous ammonia, when coniined, develops considerable pressure at ordinary room temperature, and when exposed to the heat of the sun in the aforementioned supply tank, develops an even greater pressure. Hence, this pressure of the liquid being pumped would require an extremely heavy and strong spring 66 for the outlet check valve 46 of the pump, were such spring the only instrumentality used to urge the outlet check valve to seat. To avoid this diiiculty, the outlet check valve 46 of the pump is loaded by the pressure of the source of supply of the uid being pumped. To this end, a housing 114 is secured, as by cap'screws 116, to thetop of the cylinder head 28 and has a bore 118 (Figures 8 and 9) aligned with a radial port 119 inthe cylinder head that is in communication with the bore`54 in the cylinder head rearwardly of the cup seal 58 on the valve stern 52. A 'conduit 120 connected to the inlet chamber 100 of the pump and to the bore 118 in the housing 114 conducts the pressure of the iiuid being pumpedto the bore 54 at the rear of the valve stem 52, to thus constantly urge the valve 46 to seat. lPreferably, the diameter of the valve stem 52 and they valve port 24 are equal, so thatpthe valve 46 is substantialiy pressurebalanced. Also, the bore 118 preferably includes a choke oritice 122 therein, for reasons described in the abovementionedcopending application.

The pmpthus'farshown and described is substantiallyV Before thel stangata pumping operation, becausethe Pump is. normally exposed t0 the heat Qt the, Sun, assistedescribed, the pumping chamber 98, inlet chamber 100, and the suction line 102 leading thereto are apart to be full of gas, or a mixture of gas and liquid. Since a mixture of gas and liquid cannot be metered with any degree of accuracy by the pump, it usually is essential to purge the pumping chamber 98, inlet chamber 100, and the supply line 102 leading thereto of gas before the starting of a pumping operation and to till such chambers and line with liquid. For this purpose, a two-part operating shaft 124 (Figure 9) extends through a stufling box 126 in the housing 114 transversely through the bore 118 and has a handle 128 on one end thereof for rocking the same.y The two parts 130 and 132 of the shaft 124 have threaded connection within the bore 118, and the corresponding end of the part 138 of the shaft is square, as at 134, for the rigid mounting of a lever 136 thereon that depends through the bore 118 and port 119 into an annular groove 138 in the nut 62. Accordingly, rocking movementl of the shaft 124 engages the lower end of the lever 136. with a side wall of the groove 13.8 to unseat the valve 4 6'. Upon release of the handle 128, the spring 66 immediately reseats the valve 46 with a normal seating force. The part 132 of the shaft extends into an exterior counterboret' 140 in the housing 114 and is retained therein by a snap ring 142 engaging the outer end of a sleeve 144 surrounding the shaft part 132, the inner end of the sleeve engage ing against the bottom of the -counterbore Preferably; a cap-like plug 146 is threaded into the counterbore 140l to prevent leakage.

For driving the pump, a crosshead 148 (Figures 3 and 4) is reciprocably mounted in .a longitudinal guiding bearing 149 formed interiorly `of the crankcase housing 70. The crosshead 148 is driven by a crankshaft 150; transversely journalled in the housing 70, and connected to the crosshead by a connecting rod 152. One end (of the crankshaft 150 projects out of the housing 70 for drive by a Vchain 154, engaging a sprocket on a ground-engage.. ing wheel (not shown) of the vehicle on which thepurnpr is mounted and a sprocket (not shown) rotatably mounted on the outer end of the crankshaft. Appropri` ate clutch mechanism (not shown), such as tha-t shown -in the aforementioned application, is employed to en-f gage and disengage the crankshaft sprocket into andtrom driving connection with the crankshaft 150.`

The crosshea-d 148 has a cylindrical recess `156 a-t the forward end thereof to define an integral forwardly-.pro-y jecting sleeve 158 coaxial with and receiving the rearward; end of the piston rod 86. The bottom 160 of.this.re cess 156 is dat for engagement with the correspondingly-.` at end of the .piston rod 86 to intermittently push the .latter inwardly of the pumping chamber 98 for a pumping or discharge stroke of the piston 84. Threaded into the end of the sleeve 158 is a collar 162, the inner endof which `forms an .abutment for engagement with a 'cor-g responding abutment formed by a circumferentialzange .164 on a nut 166 engaging a threaded portion 168 of the .piston rod 86. A lock nut is also threaded'onto the piston rod 86 for engagement with the forward veudof the Anut 166. A side of the threaded portion 168 of lthe piston rod 86 is flattened and has an elongatedA scale 172 secured thereto for cooperation with the forward endof the lock nut 170 to indicate the relative positionof the adjusting nut 166 with respect to the piston rod 86. This scale 172, as will become appa-rent, can'ibe graduated to 4indicate -the capacity of the pump, i. e.; vvthe adjusted capacity of the pump between maximum" and. minimum or zero capacity.

In the showing of Figure 3, the pump is adjusted to capacity; i. e., atthe beginning of a dischargeA stroke of the crosshead 148, the bottom 160 of the -recessxl engages the end ofthe piston rod -86 so thatia pumping `strokewof maximum Vlength will beeffectedf. Likewiseit will fbe seen that the ange y164 on the nut166.amzlgtlre collar 416,2, are engaged fso that .on thereturn-strokenfg.

arrastre the crosshead 148 the length of the suction stroke of the piston 84 will be at -a maximum.

Referring now to Figure 4, vit will Ibe 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 4cross-head 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 148 s-tarts its discharge stroke, it moves a considerable distance before eng-aging the end of the piston rod 86 to effect the discharge stroke of the same. Consequently, a lost-motion 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.

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 pumpin-g chamber 98. Thus, while once the crosshead 148 engages the piston rod 86 the crosshead and the crankshaft 1'50 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 wou-ld result in considerable wear and tear and possible breakage of some of the parts of the pump drive.

In order to eliminate this difiiculty, a two-part transverse crossbeam 174 has its upper land 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 l86 through yaligned apertures in the crankcase housing 70 and in the stuffing box plate 74 and outwardly along the Icylinder 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 bot-tom 184 of a counterbore extend-ing through the stuing box plate 74 and into the housing 70 is la coil compression spring 1-86. Preferably, each spring 186 is enclosed in a separate tube 188 having one end thereof threaded into the -ange 12 (Figure 5) on the end of the cylinder 10 and the other end thereof Iclosed by a threaded plug 190. The intermediate portion of each tube 188 is supported -in an apertured ear 192 on Ithe flange 14 on the other end of the cylinder 10.

From the aforedescribed construction, Iit 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 s-tore 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 to maintain the ange 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 1'86 cannot overcome the same. At this time, the bottom 160 of the recess 156 Iin the crosshead 148 catches up with and engages the end of the piston rod 86 to eiect a positive pumping stroke of the latter. Therefore, it will lbe seen that jars and impacts occasioned lby the lost-motion connection between the piston rod 86 and the ycrosshead 148 are substantially lessened and minimized by the action of the springs 186.

Referring now to Figures l to 6 of the drawings, it will be seen that the crankshaft housing 70 includes two chambers 194 and 196 joined by a lower passageway 198 beneath the crosshead bearing 149, the chamber 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 of the piston rod 86 and exposed 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 in a lubricated condition. The top of the chamber 196 is open, save for a longitudinally-extending bridge member 200, and the upper edges of the end walls of the 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 of each opening lying in a downwardly and laterallyinclined plane. Closing the opening 202 is a closure plate 206, secured to the housing 70, as by screws 208. An apertured ear 210 at the lower edge of the closure plate 206 has a wing bolt 212 extending therethrough and into a tapped opening in the crankcase housing 70. 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 the 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 hand, 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:

1. A pump for accurately metering a pressurized normally-gaseous liquid comprising: means defining an eX- pansible pumping chamber having an inlet and an outlet; an inlet check valve and an outlet check valve controlling said inlet and said outlet, respectively; means operable by liuid pressure for loading said outlet check valve independently of the discharge from said outlet; conduit means for supplying said fluid pressure operable means with pressure liuid from the source of the pressurized liquid being pumped; and manually-operable means having a lost-motion connection with said outlet check valve for opening the latter to purge said pumping chamber, said manually-operable means being normally at rest during movements of said outlet check valve occasioned by metering operation of said pump.

2. A pump for accurately metering a pressurized normally-gaseous liquid comprising: means defining anV eX- pansible pumping chamber having an .inlet and an outlet; an inlet valve and an outlet valve controlling said inlet and said outlet, respectively, said inlet valve being :aacheck valve andsaid outlet valve having areciprocab'le valve inengberc'vvhichi's urged .to' open Yby pressure'lin said chambermeans 'operable .by luid pressureinrdependent tensionextends into a space separate from `and out of .communication withthe discharge from 4the outlet, and tlieman'ually operable means includes a lever .having lost- .motion .engagement .with said extension, `whereby said lever is unaffected by reciprocating movements of the .valve .member effected by operation of the plunp.

A vpumpifor accurately metering a` pressurized nor- .mally-gaseousliquid comprising: lmeans defining an ex- .pansible pumping chamber having an inlet and an outlet;

,an .inlet valve and an outlet valve controlling said .inlet kand said outlet, respectively, said inlet valve` being a `'check 'valve and said outlet valve having a reciprocable Avalve member which is urged to'open by pressure .in

said chamber; means operable by fluid pressure independent of the discharge from said outlet for urging said .outlet valve `to close, said fluid pressure operable means including ahousing; conduit means operably associated `with said housing for supplying said pressure operable means with pressure uid from the source of the pressurized liquid being pumped; an extension on `said outlet .yalve' ,member opposite said outlet,-outside said cham- Pump- '.lber, land withinrsaid housing; andilever. means .mounted for pivotal movement.:'onlsaidmousing, .,xtrdnggtosthe eirterioi' thereof .iff manual operation, `and rhaving .lost- -motinienga`gement withfsaid extensionforopening sid .outlet..valve memberlto purge said lpumping chamber,

said lostmotionenga'gementserving 'toallow said lever .means .to remainlat rest Vduring metering operation lof said .1References',Citedinrthe Viile ofv this patent umm STATES .PATENTS

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