US3172363A - Constant delivery positive displacement pump - Google Patents

Description

March 1965 M. D. BENNETT ETAL 3,172,353

CONSTANT DELIVERY POSITIVE DISPLACEMENT PUMP Original Filed Dec. 5, 1957 2 Sheets-Sheet l March ,1965 M. D. BENNETT ETAL 3,172,363

CONSTANT DELIVERY POSITIVE DISPLACEMENT PUMP Original Filed Dec. 5, 1957 2 Sheets-Sheet 2 INVENTORS 4/4AV/A 0 BIA W577 United States Patent Ofifice 3,172,363 Federated Mar. 9, 1965 3,172,363 tIONd'lANT DELIVERY EQfil'i.

DlSPLACElr WNT IPUMP Marvin D. Bennett, Manhattan Beach, and Richard D.

Bennett, Pasadena, fialitl, assignors, by mesne assignrnents, to Royal industries, inc, Pasadena, Calii, a corporation of California Griginal application Dec. 5, i957, Ser. No. 790,894, new Patent No. 3,ll77,204, dated Feb. 12, 1963. Divided and this application Nov. 30, 1962, Ser. No. 242,578

8 Qlaims. (til, 163-9 This invention relates generally to positive displacement pumps and more particularly to a positive displacement pump designed to produce substantially constant fiuid delivery.

This application is a division of our co-pending application bearing Serial No. 700,894, filed on December 5, 1957, now Patent No. 3,077,204, and assigned to the sin e assignee as the present application.

Constant delivery fluid pumps find useful application in many fields. One field in which the pumps of this character are presently employed to advantage is the construction field wherein it is now relatively common practice in the construction field to apply cement and plaster to building surfaces by spraying. T he invention will be described with reference to the pumping of such material. it will become clear as the description proceeds, however, that the present pump is capable of general application and can be used for pumping any type of fluid or fluid-like material.

It a relatively uniform layer of plaster or cement material is to be applied to a building surface, the rate of flow of material from the spray nozzle of the spray unit must be relatively constant. This, in turn, requires a constant delivery pump capable of producing substantially constant rate of material flow to the spray nozzle.

Constant delivery pumps are, of course, known in the art. Most of these prior pumps, however, were deficient in that they were limited in the kind of material they could successfully pump, wer prone to wear, required power plants of excessive size, or did not produce truly constant fluid flow.

A broad object of the present invention is the provision of a new and improved constant delivery pump.

A more specific object is the provision of a constant delivery, positive displacement pump.

Another object is the provision of a constant delivery, positive displacement pump which requires only a relatively small power plant.

A further object is the provision of a constant delivery, positive displacement pump which is capable of pumping a wide variety of fluids and fluid-like materials and is ideally suited to the pumping of plaser, cement, and other abrasive materials.

Yet a further object is the provision of a constant delivery, positive displacement pump embodying ii.- proved valve means and means for effecting compensation for ditierent compressibilities of materials to be pumped.

A still further object is the provision of a constant delivery, positive displacement pump which produces substantially constant fluid delivery, which is adjustable to vary the rate of uniform delivery, and which is relatively simple in construction, inexpensive to manufacture, and immune to maloperation.

Briefly, the foregoing and other objects are achieved by the provision of a of communicating piston pump units. During operation, a first pump unit receives material to be pumped from a supply and delivers the material to the cylinder or the second pump unit.

The strokes of the units are timed so that the second pump unit undergoes its suction stroke during the delivery stroke of the first pump unit. The displacement of the second pump unit is somewhat less than that of the first pump unit.

During each delivery stroke of the first pump unit, a portion of the material pumped remains in the second pump unit and the remainder of the material flows to the discharge of the pump. During the suction stroke or" the first pump unit, the second pump unit undergoes its delivery stroke and delivers the remainder of the material, delivered by the first pump unit during its previous delivery stroke, to the discharge of the pump.

The exact timing of the pump units compensates for valve closure time and other factors. A substantially constant flow of material to the discharge of the pump is thereby maintained.

A better understanding of the invention may be had from the following detailed description taken in connection with the annexed drawings, wherein:

FIG. 1 is a view in perspective of an improved plaster pump and the like which embodies the invention;

FIG. 2 illustrates the operating means for one of the two pump units of the pump of FIG. 1;

FIG. 3 illustrates the operating means for the other pump unit of the pump of FIG. 1;

FIG. 4 is a top plan view of the operating means of FIG. 3;

FIG. 5 is a diagram illustrating the operation of the pump of FIG. 1;

FIG. 6 is a top plan View, partially in section, of the pump with parts omitted for the sake of clarity;

FIG. 7 is a detail in section illustrating certain check valve means shown in FIG. 6 in a second position of operation;

FIGS. 8 and 9 are enlarged sections illustrating the valve means embodied in the present pump; and

FIG. 10 illustrates a modified check valve.

Referring now to the drawings, the illustrated constant delivery pump will be seen to comprise a frame 16 of any suitable design. Mounted on this frame is a hopper T12 for receiving a charge of material to be pumped. The pump illustrated is especially designed to pump plaster and cement materials.

Indicated at 14 is a first, or main, piston pump unit. This unit includes a cylinder 16 having an inlet 18. This inlet has an intake passage 18 communicating to the hopper l2 and to the adjacent end of cylinder 16. Pump unit 14 also has a discharge passage 17. Positioned within the inlet 18 is the new and improved one-way check valve 2i) (FIG. 6). This valve, which will be presently described, allows flow of material into the cylinder 16 through the inlet 18 but blocks flow in the reverse direction.

Movable in the cylinder 16 is a piston 22 having a piston rod 24. Rod 24 is connected to the lower end of an arm 25, the upper end of which is pivoted on a cross shaft 25a on frame it). An intermediate point of arm 25 is pivotally connected through a telescopically adjustable link 26 to a crank 27a on a disc 27. Disc 27 is journalled on a terminally threaded, axial stud 28a projecting from the center of a circular flange 28 rigid on one end of a shaft 29 journalled on frame 10. Disc 27 is retained on the stud 28a by a nut, as shown. Fric tionally received in aligned holes in the disc and flange is a pin 30 which is sheared under excessive pumping loads to prevent damage to the equipment.

Shaft 29 is driven from a motor 31 to cause reciprocation of the piston 22; in the cylinder 16. Disc 27 is removable by removing its securing nut for replacement by another disc having a crank pin 27a with a different effective crank arm, for reasons to be seen.

Mounted on the frame it) is a second piston pump unit 32. This second pump unit includes an inlet conduit 34 through which extends the intake passage 34' for the latter unit. Conduit 34 is connected to the first pump unit 14 in such a way that intake passage 34 communicates with the discharge passage 17 of the first pump unit. Disposed in the conduit 34 is a second oneday check valve 36 identical to the one-way valve 20. Valve 36 permits fiow from the pump unit 14 to the pump unit 32 but blocks fiow in the reverse direction.

Second pump unit 32. includes a cylinder 38 in which is movable a piston 4d. Piston 4%) includes a rod 42, one end of which is pivotally attached to one end of an arm 44. The other end of arm 44 is pivoted on cross shaft 250. Pump 32 is provided with approximately twothirds of the displacement of pump 14 either by making the diameter of cylinder 38 less than that of cylinder 16 or by making the stroke of pump 32 less than that of pump 14.

Arm 44 journals an adjustable cam follower roller 46 which bears against a cam 48 removably keyed to the shaft 29. Roller 46 is adjustable along the arm to adjust the point of contact of the roller with cam 48. Cam 4% is thus rotated in synchronism with crank arm 27a and is operative to cause movement of the piston 40 to the left in its cylinder 38. The left-hand end of the cylinder 38 has an outlet 5%) adapted for connection to a discharge hose 52, for example. The discharge passage 50 of the second pump unit extends through this outlet 50. This hose terminates in nozzle (not shown). Cam 48 is removable for reasons to be seen.

Referring now to FIGS. 6 and 7 as well as FIGS. 8 and 9, illustrating valve it; in enlarged detail, the numeral 56 denotes an elastic check valve member in the form of a rubber ball. Ball 56 is contained in a cylindrical housing 58. Housing 58 has a passage extending therethrough which is formed witha reduced inlet portion bore 69 opening into an enlarged passage portion or chamber 62. Extending across the bore 69 are cross pins 64- which act as stops to limit left-hand travel of the ball 56 in bore 60.

Bore 6% has a diameter approximately the same as or just slightly less than the diameter of ball 56, while the diameter of chamber 62 is substantially larger than ball 56. Plus 66 act as stops to limit right-hand movement of ball 56 in chamber 62. From this description it will be seen that ball 56 is movable from bore 6% into chamber 62 in response to flow to the right through the valve. The clearance between the ball and the wall of chamber 62 provides a flow space about the ball.

When flow in the opposite direction occurs through the valve, ball 56 is forced into the bore 69 and against the cross pins 54 at the left-hand end of the bore. Axial pressure on the ball causes radial expansion of the latter against the wall of bore 60 to form a seal, as shown in FIG. 9. During movement of ball 56 into the bore 69, the wall of the latter is wiped clean by the ball (FIG. 8) so as to permit an efficient seal to be formed. Valve 36 is identical to valve 24 just described.

The illustrated valve is highly desirable for the use described since it is less prone to wear and accomplishes a liquid tight seal even with granular and abrasive materials, such as plaster and cement. Conventional check valves are not suitable for these latter materials inasmuch as any particles of the material on the seat of the check valve would prevent the latter from completely closing. During the pumping stroke, therefore, water in the material will be squeezed out past the slightly unseated check valve. This results in instantaneous setting of the material in the valve and jamming of the latter.

Operation of the illustrated pump thus far described is as follows. Assumin the hopper 12 to contain a charge of material to be pumped such as moist plaster or cement, each right-hand suction stroke of the piston 22 in the primary pump unit 14 draws material into the cylinder 16 from the hopper 12. This material is pumped from the cylinder 16 through conduit 34 to the second pump i unit 32 during the left-hand pumping stroke of the piston 22. A portion of this material flows into cylinder 3% of the second pump unit.

The material entering the cylinder 38 of the second pump unit 32 exerts a force on the piston 40 tending to move the latter to the right and force the roller 46 on arm 44 against the cam 43. As will be presently more fully described, the shape of the cam 48 is such as to allow controlled right-hand movement of piston 40 under the action of this force during the delivery stroke of the primary pump unit.

The parts are so proportioned that during this delivery stroke of the primary pump unit, a portion of the material delivered to the second pump unit is absorbed by right-hand movement of the piston 44 The remainder of the delivered material flows through the discharge 50 of the second pump unit to the hose 52.

During each suction stroke of the primary pump unit, the piston 40 of the second pump unit 32 is forced to the left by the cam 48. This pumping stroke of the second pump unit displaces the material remaining in the latter unit after the previous delivery stroke of the primary pump unit. Thus, during each delivery and suctio'n stroke of the primary pump unit 14, a portion of the material pumped by the latter pump unit is discharged through the discharge 5% of the second pump unit.

The second pump unit 32, therefore, in effect evens out the surges in the flow of the material from the first pump unit 14 so as to maintain a substantially uniform delivcry of material to the pump discharge 5% and hose 52. The manner in which this action is accomplished in the present pump will now be described in greater detail by reference to the daigram of FIG. 5.

In FIG. 5 curve A represents the pulsating flow of material delivered by the first pump unit 19 to the second pump unit 32, the area under the curve, of course, indicating the volume of material pumped. The reference point a on the curve denotes the start of the delivery stroke of the first pump unit at which time the pump piston 22 is at the extreme right-hand limit of its previous suction stroke.

Under ideal conditions, curve A would conform approximately to a sine wave since the piston 22 is driven in approximately simple harmonic motion. In practice with compressible materials, however, the initial portion of curve A between points a and b is distorted, as shown. This is due first to the time required to close the inlet check valve 29 and open the discharge check valve 36, which valves are, of course, closed and opened, respectively, at the start of the pumping stroke of the first pump unit, and second to the fact that the material in the first pump unit must be initially compressed a certain amount before it will start to fiow from the first pump unit to the second pump unit.

These delays introduced by valve operations and material compression cause the fiow from the first pump unit to the second pump unit during the first portion of the pumping stroke of piston 22 to remain zero for a short period of time, then increase slowly, and finally rise rapidly to point b on the curve. During the remainder of the pumping stroke, flow of material from the first pump unit is approximately sinusoidal, as indicated by the curve A between point I) and c.

From point c to point a at the start of its next delivery stroke, the piston 22 undergoes its suction stroke so that no material is delivered by the first pump unit.

Curve B represents the operating cycle of the second pump unit 32. As previously mentioned, this pump unit has approximately two-thirds of the displacement of the first pump unit and is operated by the cam 48 in a manner to maintain a substantially uniform delivery of material to the discharge 5% of the pump.

Thus, as earlier indicated, the piston 40 in the second pump will have been operated through its pumping stroke by the cam 48 during the suction stroke of the first pump unit just preceding the pumping stroke of the latter unit indicated by the curve A in FIG. 5. Cam 48 is so shaped that during the terminal portion of said pumping stroke of the second pump unit, which is denoted by the portion c] of curve B, and which will .be observed to overlap the initial portion of the pumping stroke of the first pump unit, the total volumetricrate of material delivered by the action of the two pump units to the pump discharge 50 remains substantially uniform and approximately equal to one-third of the maximum volumetric rate of material delivery produced by the first pump unit. This maximum delivery, of course, occurs at point g on curve A. Line C denotes one-third this maximum rate.

Referring to FIG. 2, illustrating the cam 48 in detail, the portion e-f' of the cam surface 48' is shaped to accomplish the controlled pumping action of the second pump unit occurring between points e and f on curve B. At point 1, on curve B, the piston 40 in the second pump unit is at the end of its pumping stroke, while the first pump unit is still undergoing its pumping stroke and delivering material at rate C. Curve B between points 1 and h thereon denotes the suction stroke of the second pump.

The material delivered by the first pump unit to the second pump unit during this suction stroke of the latter, of course, exerts .a force on the piston 40 tending to move the latter to the right, as viewed in FIG. 6. The cam surface 48', between points f'-h' thereon is shaped to permit controlled movement of the piston 40 to the right under the action of this force in such manner that the excess material delivered by the first pump, from point i to point 1' of curve A remains in the second pump unit and the remainder of the delivered material flows to the discharge 50. The rate of discharge from the pump during this period, therefore, remains substantially uniform at :the value C.

At point h on curve B the second pump unit reverses and commences its pumping stroke under the action of the cam 48. This occurs at point 1' of curve A whereat the first pump is again delivering at the rate C. Since the output of the first pump unit now drops below the line C, the second pump unit must deliver its retained charge of material at such a rate as to just olfset the decrease in material flow from the first unit and thereby maintain a uniform delivery to the pump discharge.

A certain volume of material delivered by the second pump unit is used to effect closure of the check valve 36. This closure occurs between points h and k on curve B. If the delivery of pump unit 32 was not momentarily increased during this period, therefore, the rate of dis charge fi'om the pump would drop off momentarily, as indicated by the dotted line curve between points h and k on curve B. To prevent this, cam surface 48' is formed with a relaitvely abrupt rise between points h and k which causes, during the above period, increased delivery of the second pump unit sufficient to maintain the effective delivery from the second pump unit and, therefore, from the pump discharge 50, substantially uniform at the volumetric rate C.

From point k to point I on curve B, the output of pump unit 32 is again caused to be approximately sinusoidal so that the combined delivery of both pump units remains uniform at the rate C. The delivery of the second pump unit during this period is effected by portion k-l' of the cam surface 48'.

Between points I and point e of the cam surface 48', the latter is shaped to effect a substantially constant volumetric rate of delivery from the second pump unit equal to the rate C. During this period, of course, the first pump unit is undergoing its suction stroke so that no material is delivered thereby. The above cycle is then repeat-ed.

Clearly then, the volumetric discharge rate from the pump, denoted by the line C, remains substantially uniform[ In the use of the illustrated pump for spraying cement, plaster, and other similar materials, it is desirable to vary the output of the pump for different jobs. Thus, when spraying a finish plaster coat, the rate of delivery of the pump is preferably less than for heavy base coats.

Adjustment of the pump output may be accomplished by replacing the crank plate 27 by one having a different effective crank arm for its crank pin 27a, and replacing the cam 48 by a similarly shaped cam which alter the total stroke of the second pump unit to fit the new stroke of the first pump unit.

Moreover, materials of the type under discussion have different compresison ratios. This difference in compression ratios of different materials, of course, will alter the shape of the curve A (FIG. 5) between points a and b there-on, that is, a greater or lesser portion of the pumping stroke of the first pump unit will be consumed in compressing the material to a point where actual delivery of the material to the second pump unit starts.

To maintain the output of the pump constant, of course, the output of the second pump unit must be varied accordingly during this period. Different compression ratios of material will, of course, also eifect the output of the second pump unit at the start of its pumping stroke, i.e., between points h and k on curve B.

To this end, the cam 48 is removable for replacement by a cam which is configured to suit the particular material to be pumped. Thus, several cams may be provided for selective mounting on the pump, each cam being designed for a particular material or materials whose compression ratios fall within a particular range.

Compensation for a change in the compression ratio from one material to another may also be accomplished by adjusting the travel of the ball 56 in the check valves 20 and 36 of the invention, as illustrated in FIG. 10. In this figure the numeral denotes a sleeve formed with the inlet bore 69, which is slidab-le in the valve housing 58'. This sleeve mounts the cross pins 64 which limit movement of the ball 56 in the bore 60.

Sleeve is adjusted in the axial directions indicated by a threaded shaft 102 operable exteriorly of the housing 58. This adjustment of the sleeve has the effect of varying the travel of the hall 56 during closure of the valve and hence the volume of material necessary to effect closure of the valve.

In use, when a material to be pumped has less compressibility than the particular material tor which the cam 48 is designed, the sleeve 100 will be shifted to the lefit, as viewed in FIG. 10, to increase the travel of the ball 56. This has the efliect of increasing the travel of the pump piston necessary to close the valve and hence compensating for the lesser travel of the piston required to compress the material. With materials having greater compressibility, of course, the sleeve 1100 is adjusted in the opposite direction.

Numerous modifications in design and arrangement of parts of the invention are possible Within the scope of the following claims.

What is claimed is:

1. In a constant delivery pump comprising a frame, a first piston pump unit on said frame including a first cylinder, a first piston movable in the cylinder, and a first intake and a first discharge passage opening to one end of the cylinder, a second piston pump unit on said frame of smaller displacement than said first unit and including a second cylinder, a second piston movable in the cylinder, a second intake passage opening to one end of the second cylinder and communicating with said first discharge passage, and a second discharge passage opening to said one end of the second cylinder, and valve means in said first intake passage and in said communicating passages for permitting flow of material to be pumped into said first cylinder through said first intake passage and from said first cylinder to said second cylinder through said communicating passages, and blocking flow of said material in the reverse direction through said first intake passage and communicating passages, a rotary driving shaft on said frame, a connection between said shaft and first piston for reciprocating the latter in its cylinder as the shaft rotates to effect an intermittent pumping action of the first unit, said connection including adjustable means for varying the stroke of the first piston, the second piston being movable in one direction in its cylinder by the pressure developed by the pumping action of the first unit, a rotary cam separate from said connection, means releasably connecting said cam to said shaft for rotation by the latter, and cam follower means engaging a limited portion of the surface of said cam and operatively connected to the second piston for moving the latter piston in the opposite direction in its cylinder and controlling the movement of the latter piston in said one direction in its cylinder as the shaft rotates, said cam surface having an irregular profile for effecting movement of said second piston in predetermined time relationship with respect to movement of the first piston, and said cam being removable from said shaft for replacement by a cam having a cam surface of different profile matching the adjusted stroke of the first piston.

2. In a constant delivery pump comprising a frame, a first piston pump unit on said frame including a first cylinder, a first piston movable in the cylinder, and a first intake and a first discharge passage opening to one end of the cylinder, a second piston pump unit on said frame of smaller displacement than said first unit and including a second cylinder, a second piston movable in the cylinder, a second intake passage opening to one end of the second cylinder and communicating with said first discharge passage, and a second discharge passage opening to said one end of the second cylinder, and valve means for permitting flow of material to be pumped into said first cylinder through said first intake passage and from said first cylinder to said second cylinder through said communicating passages, and blocking flow of said material in the reverse direction through said first intake passage and communicating passages, a rotary driving shaft on said frame, a connection between said shaft and first piston for reciprocating the latter in its cylinder as the shaft rotates to effect an intermittent pumping action of the first unit, the second piston being movable in one direction in its cylinder by the pressure developed by the pumping action of the first unit, a rotary cam separate from said connection, means releasably connecting said cam to said shaft for rotation by the latter, andcam follower means engaging a limited portion of the surface of said cam and operatively connected to the second piston for moving the latter piston in the opposite direction in its cylinder and controlling the movement of the latter pistonin said one direction in its cylinder as the shaft rotates, said cam surface having an irregular profile for effecting movement of said second piston in predetermined timed relationship with respect to movement of the first piston, said cam being removable from said shaft for replacement by a cam having a cam surface of different profile to permit adjustment of the stroke of the second piston to compensate for different compressibilities of materials to be pumped.

3. In a constant delivery pump comprising a frame, a first piston pump unit on said frame including a first cylinder, a first piston movable in the cylinder, and a first intake and a first discharge passage opening to one end of the cylinder, a second piston pump unit on said frame of smaller displacement than said first unit and including a second cylinder, at second piston movable in the cylinder, a second intake passage opening to one end of the second cylinder and communicating with said first discharge passage, and a second discharge passage opening to said one end of the second cylinder, and valve means in said first intake passage and in said communicating passages for permitting flow of material to be pumped into said first cylinder through said first intake passage and from said first cylinder to said second cylinder through said communicating passages, and blocking flow of said material in the reverse direction through said first intake passage and communicating passages, a rotary driving shaft on said frame, a connection between said shaft and first piston for reciprocating the latter in its cylinder as the shaft rotates to effect an intermittent pumping action of the first unit, the second piston being movable in one direction in its cylinder by the pressure developed by the pumping action of the first unit, a rotary cam separate from said connection driven by said shaft, a cam follower arm pivoted at one end to said frame, operatively connected at its other end to said second piston and mounting a cam followerelement engaging a limited portion of the cam surface for moving the latter piston in the opposite direction in its cylinder and controlling the movement of the latter piston in said one direction in its cylinder as the shaft rotates, said cam surface having an irregular profile for effecting movement of said second piston in predetermined timed relationship with respect to movement of the first piston, and means for adjusting the position of said cam follower element on said arm to shift the point of contact of the element with said cam surface.

4. A method for continuously spraying moist compressible materials such as plaster, concrete, mortar, and the like at a substantially uniform spray rate including the steps of introducing the moist material into a pumping unit, compressing the moist material in the pumping unit a preselected amount Without substantially altering the moisture content of the material to cause the material to flow in a stream, discharging a preselected portion of the flowing material from said pumping unit at a substantially uniform spray rate, temporarily storing the remainder of the discharged material in another pumping unit while maintaining it under compression and discharging same during a preselected period, a portion of which discharge period coincides with the discharge of the material from the first pumping unit whereby a continuous discharge of the material at a substantially uniform rate is provided.

5. In a constant delivery pump for moist compressible materials such as plaster, concrete, mortar, and the like comprising a frame, means for storing a preselected quantity of the compressible material to be pumped mounted on said frame, a first pumping unit mounted on said frame, conduit means including first control means communicating with said storage means and said pumping unit to allow the material to be pumped to be controllably passed to said pumping unit, said control means being re sponsive to a reduced pressure created by said pumping unit to allow the material to be pumped to charge the pumping unit and to be closed in response to the pumping of the material, a second pumping unit mounted on said frame, a discharge outlet, second conduit means including second control means communicating with said first and second pumping units and a discharge outlet, said second control means being responsive to the reduced pressure created by said first pumping unit to close the second conduit means to said second pumping unit and the discharge outlet and to open the second conduit means in response to the pumping of the material by said first pumping unit to allow the material to flow to the second pumping unit and the discharge outlet, and drive means mounted on the frame for operating the first and second pumping units in a timed-overlapping, pumping sequence to cause a continuous discharge of the material at the discharge outlet at a substantially uniform rate.

6. In a constant delivery pump of the type of claim 5 wherein said first and second control means comprise elastic ball check valves.

7. In a constant delivery pump of the type of claim 5 wherein the first and second pumping units comprise piston and cylinder units and said second unit is of a smaller displacement than said first unit.

8. A constant delivery pump for moist, compressible, heavy-bodied materials having an initial compressibility and then acting as essentially incompressible to thereby flow in a stream when pumped comprising first and second pumping units, means for alternately charging the first and second pumping units with said material to be pumped, conduit means including a discharge outlet communicating with each of said pumping units to allow the charged material to be discharged by said pumping units through the discharge outlet in a stream, and controllable drive means for alternately driving the first and second pumping units to discharge the materials through the discharge outlet, each of said pumping units being effective for initially compressing the material therein to cause the material to flow in a stream, the controllable drive means including means for operating the first and second pumping units in a timed overlapping discharge sequence to compensate for the initial action of compressing said material in each of the pumping units to maintain a continuous flow of the material at a substantially uniform rate through the discharge outlet.

References Cited in the file of this patent UNITED STATES PATENTS 111,293 Windhausen J an. 24, 1871 1,261,061 Seymour Apr. 2, 1918 2,281,767 Heckert May 5, 1942 2,424,750 Heckert July 29, 1947 2,448,104 Longenecker Aug. 31, 1948 2,702,008 Stockard Feb. 15, 1955 2,819,835 Newhall Jan. 14, 1958 2,858,767

Smith Nov. 4, 1958

Claims (1)

1. IN A CONSTANT DELIVERY PUMP COMPRISING A FRAME, A FIRST PISTON PUMP UNIT ON SAID FRAME INCLUDING A FIRST CYLINDER, A FIRST PISTON MOVABLE IN TH CYLINDER, AND A FIRST INTAKE AND A FIRST DISCHARGE PASSAGE OPENING TO ONE END OF THE CYLINDER, A SECOND PISTON PUMP UNIT ON SAID FRAME OF SMALLER DISPLACEMENT THAN SAID FIRST UNIT AND INCLUDING A SECOND CYLINDER, A SECOND PISTON MOVABLE IN THE CYLINDER, A SECOND INTAKE PASSAGE OPENING TO ONE END OF THE SECOND CYLINDER AND COMMUNICATING WITH SAID FIRST DISCHARGE PASSAGE, AND A SECOND DISCHARGE PASSAGE OPENING TO SAID ONE END OF THE SECOND CYLINDER, AND VALVE MEANS IN SAID FIRST INTAKE PASSAGE AND IN SAID COMMUNICATING PASSAGES FOR PERMITTING FLOW OF MATERIAL TO BE PUMPED INTO SAID FIRST CYLINDER THROUGH SAID FIRST INTAKE PASSAGE AND FROM SAID FIRST CYLINDER TO SECOND CYLINDER THROUGH SAID COMMUNICATING PASSAGES, AND BLOCKING FLOW OF SAID MATERIAL IN THE REVERSE DIRECTION THROUGH SAID FIRST INTAKE PASSAGE AND COMMUNICATING PASSAGES, A ROTARY DRIVING SHAFT ON SAID FRAME, A CONNECTION BETWEEN SAID SHAFT AND FIRST PISTON FOR RECIPROCATING THE LATTER IN ITS CYLINDER AS THE SHAFT ROTATES TO EFFECT AN INTERMITTENT PUMPING ACTION OF THE FIRST UNIT, SAID CONNECTION INCLUDING ADJUSTABLE MEANS FOR VARYING THE STROKE OF THE FIRST PISTON THE SECOND PISTON BEING MOVABLE IN ONE DIRECTION IN ITS CYLINDER BY THE PRESSURE DEVELOPED BY THE PUMPING ACTION OF TH FIRST UNIT, A ROTARY CAM SEPARATE FROM SAID CONNECTION, MEANS RELEASABLY CONNECTING SAID CAM TO SAID SHAFT FOR ROTATION BY THE LATTER, AND CAM FOLLOWER MEANS ENGAGING A LIMITED PORTION OF THE SURFACE OF SAID CAM AND OPERATIVELY CONNECTED TO THE SECOND PISTON FOR MOVING THE LATTER PISTON IN THE OPPOSITE DIRECTION IN ITS CYLINDER AND CONTROLLING THE MOVEMENT OF THE LATTER PISTON IN SAID ONE DIRECTION IN ITS CYLINDER AS THE SHAFT ROTATES, SAID CAM SURFACE HAVING AN IRREGULAR PROFILE FOR EFFECTING MOVEMENT OF SAID SECOND PISTON IN PREDETERMINED TIME RELATIONSHIP WITH RESPECT TO MOVEMENT OF THE FIRST PISTON, AND SAID CAM BEING REMOVABLE FROM SAID SHAFT FOR REPLACEMENT BY A CAM HAVING A CAM SURFACE OF DIFFERENT PROFILE MATCHING THE ADJUSTED STROKE OF THE FIRST PISTON.

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