US3107623A

US3107623A - Variable discharge pump

Info

Publication number: US3107623A
Application number: US141935A
Authority: US
Inventors: Budzich Tadeusz
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-08-10
Filing date: 1961-08-10
Publication date: 1963-10-22
Anticipated expiration: 1980-10-22

Description

Oct. 22, 1963 T. BUDZICH 3,107,623

VARIABLE DISCHARGE PUMP Filed Aug. 10, 1961 4 Sheets-Sheet 1 INVENTOR.

[ADEUSZ BUDZ/CH Attorney Oct. 22, 1963 'r. BUDZICH 3,

VARIABLE DISCHARGE PUMP Filed Aug. 10, 1961 4 Sheets-Sheet 2 TADEUSZ BUDZ/Ch BY 2 A t/om ey 3,107,623 VARIABLE DISCHARGE PUMP Tadeusz Budzieh, 3344 Colwyn Road, Cieveland, Ohio Filed Aug. 16, 1961, Ser. No. 141,935 13 {:laims. '(Cl. 103-37) This invention relates generally to fluid pressure translating devices, and more particularly to pumps having variable discharge volume.

It is often desireable to be able to vary the discharge volume of a pump. Several prior proposals for pumps having variable discharge volumes have used complicated and precision fitting parts in the high pressure zone of the pump to allow spill over from the piston to the low pressure chamber during a portion of the stroke, thereby regulating the discharge volume. Such devices are costly in that precision parts subjected to high pressure are required to mate exactly during a portion of the piston stroke.

It is therefore a principal object of this invention to provide a pump having a control mechanism subject to low pressure for regulating the discharge volume of a pump.

Another object of this invention is to provide a control mechanism for providing a variable discharge volume from a pump, which mechanism is protected from the high pressure region of the pump.

A more particular object of this invention is to provide a pump having a control mechanism in the low pressure region, which selectively actuates means to allow discharge during a portion of the pumping stroke.

Yet another more particular object of this invention is to provide a pump having a control mechanism which actuates sealing means which isolate the control mechanism from high pressure fluid and which means also seals the fluid in the high pressure region of the pump to open a discharge valve.

Other objects will become apparent and a fuller understanding of the invention may be had by reference to the following description and drawings in which:

FIGURE 1 is a longitudinal sectional View of single piston pump embodying this invention;

FIGURE 2 is a pump similar to that of FIGURE 1 with another embodiment of this invention;

FIGURE 3 is a sectional view taken along the plane designated by line 3-3 of FIGURE 1;

FIGURE 4 is a detailed view of a portion of the regulating mechanism, looking at the left side of FIGURE 3;

FIGURE 5 is the device of FIGURE 4, looking at the right side of FIGURE 3;

FIGURES 6, 7, and 8 are schematic representations of flow volumes in various positions of the control mechanism;

FIGURE 9 is a longitudinal sectional view of a multiple piston pump embodying this invention;

FIGURE 10 is a sectional view taken along the plane designated by line 10-10 of FIGURE 9;

FIGURE 11 is a detailed vertical sectional view of a portion of the control mechanism of FIGURE 9;

FIGURE 12 is a side elevational view of the control valve body of the pump of FIGURE 9;

FIGURE 13 is a side elevational view of the control body of the pump of FIGURE 9 rotated 180 from the position shown in FIGURE 12.

Referring now to the drawings, and particularly to FIGURE 1, a single piston pump is shown. The pump has a conventional housing 10, having an internal chamber 11. The chamber 11 communicates with a low pressure fluid inlet port or manifold 12. A cam shaft 13 is journaled for rotation by bearings 14, 15. The shaft atent O extends/through the. housing and aseal 16 is provided to prevent fluid loss around thershaf't.

The shaft 13 has an. eccentric portion 17. which acts against a piston 20. The piston 20 is slideably mounted in a cylinder bore 21. A spring 22 is provided surrounding a portion of the piston 20 which spring normally urges the lower end of the piston against the eccentric 17. Spring guides 23, 24 are provided to guide the spring 22.

The cylinder bore 21 communicates with a cavity 25 through an opening 26. A fluid conducting passage 349 communicates with the lower portion of the cavity 25 and with a low pressure cylindrical space 31. The low pressure cylindrical space 31 communicates with the internal chamber 11 through passages 32. A high pressure fluid outlet port or manifold 33 is provided at the upper end of the high pressure region. A check valve 34 is disposed in the cavity 25 and is normally urged against a valve seat 35 by a check valve spring 36. This closes off the outlet port 33 from the cavity 25. The check valve is shown in its closed position in dotted lines.

An annular sealing sleeve 40 is disposed in the cavity 25 between the check valve 34 and the opening 26. A portion of the sealing sleeve 40 is surrounded by a sleeve spring 41 which normally urges the sleeve into the open position shown in dotted lines. When the sleeve is in the open position and the check valve in the closed position upon the suction stroke of the piston 20, fluid will be drawn into the cylinder through the fluid conducting passage 30. The fluid reaches the fluid conducting passage 30 from the inlet port 12 through the internal chamber 11 thence through the passages 32 into the cylindrical space 31 which communicates with the fluid conducting passage 30. Upon the discharge stroke of the pump, if there is no imbalance of forces on the sealing sleeve it will remain in the open position and the check valve will stay in the closed position and the fluid will be discharged from the cylinder bore, through the fluid conducting passage 30. The passage 30 communicates with the low pressure inlet port 12, as explained above. Hence as long as the sealingsleeve 40 is open and the check valve 34 closed there will be no discharge from the high pressure outlet port 33. However, the sealing sleeve 40 is provided with a lower sealing surface 42, mated to seal against an annular seal 43 surrounding opening 26. The sealing sleeve 40 has an upper pressure face 44 which has a larger area than the combined area of the sealing surface 42 and a shoulder 45 around the sealing face 42. The sealing sleeve is slideably sealed in the cavity 25 preventing fluid from passing past pressure face 44 to the inlet port 12 through a vent passage 46. The purpose of this passage 46 will be described presently.

If during the discharge stroke of the piston, a resistance to fluid flow is provided in the fluid conducting passage 30, there will be a pressure build up in cavity 25. This pressure build up will cause an imbalance of force on the sealing sleeve 40, because the pressure face 44, on one end of the sleeve, has a greater area than the combined area of the sealing surface 42 and shoulder 45, on the other end of the sleeve. Since the rear of the pressure face 44 is vented to the low pressure inlet port 12, by the vent passage 46, the sleeve 40 will be pushed downwardly when the force imbalance overcomes the force of the spring 41 causing the sealing face 42 to seal against the seat 43, as shown in solid lines in FIGURE 1. The pressure build up in cavity 25 will cause the check valve 34 to unseat, thus providing communication between the cavity 25 and the outlet port 33.

Thus, at any time during the discharge stroke, if there is an increased resistance in the fluid conducting passage 30 sufficient to overcome the force of the spring 41, the

flow of fluid will be changed from recirculation to discharge. I

In order to provide for selective regulation of the resistance in the fluid conducting passage 30, a control mechanism is provided in the cylindrical space '31. The control mechanism includes an annular ring 50 mounted on the cam shaft 13. The ring 50. has first and

second slots

51, 52 separated by ribs 55 (FIGURES 4 and 5). FIGURES 6, 7 and 8 show the shape of these slots on a ring opened and laid flat. The ring 50 is rotatable with the cam shaft 13 and in contact with the housing in the region of the fluid conducting passage 30. The ring 50 is movable axially on the cam shaft 13. A pin 59a projects from the cam shaft 13 into an elongated slot 5% in the ring 50. This permits the ring 50 to be driven rotatively with the cam shaft 13 and be movable axially thereon. A pin 53 is provided which passes through the housing and abuts against the end of the ring 50 to provide axial movement thereof. A spring 54 normal-1y urges the ring 50 toward the extreme end of the cam shaft 13, and the pin 53 works against this spring to position the ring axially along the cam shaft 16 to an infinite number of positions dependent upon the setting of the pin 53.

The ring 50 is positioned on the cam shaft 13 in such a way that during the suction stroke of the piston the slot 51 is aligned with the fluid conducting passage 36 irrespective of the location to which the ring 59 is moved axially on the cam shaft 1 3. Thus during the suction stroke the passage '36 is in communication with the cylindrical space 31 through the slot 51. However the slot 52 is so shaped and positioned that its communication with the fluid conducting passage is dependent upon the axial location of the ring on the cam shaft 13. Depending upon the location of the ring 50 the slot 52 will not communicate at all with the passage '30 during the discharge stroke, or it will communicate during the entire discharge stroke, or for any selected portion of the discharge stroke. FIGURES 6 through 8 show diagrammatically the position of the fluid conducting passage 39 with respect to the two slots at various positions of rotation.

FIGURE 6 shows the positions at one extreme location of axial movement of the ring 50; FIGURE 7 shows the positions at an intermediate location; and FIGURE 8 shows the positions at the other extreme end of axial movement. For simplicity the fluid conducting passage (the circle) is shown as moving and the ring shown as stationary; however, actually the ring is rotating and the passage stationary. Referring to FIGURE 6, when the suction stroke is just completed the rib 55 passes the fluid conducting passage 30 at a point of zero discharge and the slot 52 registers with the fluid conducting passage 30, and then for the remainder of the revolution the slot 52 remains registered with the fluid conducting passage 30. Hence during both the suction stroke and the discharge stroke the fluid conducting passage 30 is unblocked and no increased pressure can be generated, and the fluid will recirculate during the discharge stroke.

Referring now to FIGURE 7, the ring 50 has been shifted axially on the cam shaft 13 about half way be tween its extreme positions. Again, during the suction stroke of the piston, the fluid conducting passage 30 is registered with the slot 51. Just at the end of the suction stroke the rib 55 passes the passage 30 and then the slot 52 registers with the passage 30. During about half of the discharge stroke of the piston the slot 52 is registered with the passage 30. However, at this point, because of the shape and position of the slot 52 the face of the ring 50 then registers with the passage 30. This increases resistance to fluid flow in the passage 30 which causes a pressure rise in the cavity 25. This pressure rise causes the sealing sleeve 40 to seat and the check valve 34 to open as described above. This will cause a discharge from the pump. The shaded portion of the curves of FIGURES 6 through 8 show the portion of the entire discharge stroke.

suction stroke, the passage 39 never registers with the slot 52, but is blocked by the face of the ring 50 for the Hence high pressure discharge occurs during the entire discharge stroke.

From the foregoing it can be seen that the portion of the discharge stroke during which the fluid is being discharged through the outlet port 33 is controlled by the relative axial location of the ring 56 onthe cam shaft 13. An infinite number of positions are selectable between the extreme ends of the movement at which extreme ends either full discharge or no discharge is effected. Thus, the volume of output can be changed by axially moving the ring 5 3 by means of the pin 53.

It will be noted that if at any time. during the discharge stroke the passage 30 is blocked, the sealing sleeve 49 will seat and the check valve 34 will open. This condition will remain during the remainder of the discharge stroke whether or not the passage 30 is subsequently unblocked.

One of the outstanding advantages of this invention is that once the pressure starts to build up in the passage 30 the sleeve blocks the passage 30. This isolates the control mechanism from the high discharge pressure and hence relatively inexpensive non-precision parts can be used for the control mechanism.

Referring now to FIGURE 2, another embodiment of the invention for a single piston pump is shown. The sealing sleeve 46 of FIGURE 1 is not used, and the check valve 34 seats against the end of the cylinder bore 21. The fluid conducting passage 36 communicates with the extreme end of the cylinder bore 21. A sealing rod or piston 61} is provided. The sealing rod 69 resides in rod chamber 61 which intersects the passage 30 transversely. The rod 60 has first and second enlarged spaced opposite ends 62, 63. The chamber 61 is vented at one end to the chamber 11 by vent passage 63a and has a passage 64 at the other end communicating with fluid conducting passage 30. When the fluid conducting passage 30 is blocked the pressure in the fluid conducting passage 30 will rise, causing an imbalance of force on the rod 69. The force on the opposite ends 62, 63- through the passage 30 will be in balance, but, because of the vent passage, there is no balancing force for the pressure on end 62 exerted through passage 64. Therefore the rod will be urged toward the left, as seen in FIGURE 2 and indicated by dotted lines, and the end 62 will block the passage 3%..

The pressure build up will cause the check valve 34 to open, which will allow discharge through the outlet port 33. The control mechanism for this embodiment is the same as for the embod ment of FIGURE 1.

Referring now to FIGURES 9 through 13, yet another embodiment of this invention is shown in a multiple piston rotary cam pump. The pump has a housing with a plurality of pistons positioned for reciprocation in cylinder bores 121. A cam plate 117 is disposed in an internal chamber 111 which cam plate is rotated by cam shaft 113. The pistons have return springs 122 nonmally urging them into contact with the cam plate 1-17 during the suction stroke of the piston.

A cavity 125 communicates with the cylinder bores 121 and with a fluid outlet port 133. A check valve 134 is positioned to seal the cavity 125 of each cylinder bore from the outlet port 133. A sealing sleeve similar to that of the embodiment of FIGURE 1 is provided between each cylinder bore 121 and its associated check valve 134. The sleeve 140 is surrounded in part by a sleeve spring 141 which normally urges the sleeve away from a seat 143. The sleeve 140 has a lower sealing surface 142 positioned to seat against the seat 143 in a manner similar to that of the embodiment of FIGURE 1. The check valve 134 is urged against valve seat 135 by check valve spring 136 normally closing off each cylinder from the outlet port 133.

Each cylinder bore 121 has a fluid conducting passage 130 communicating with it. Each fluid conducting passage 130 also communicates with a central opening or cylindrical space 13-1. The central opening 131 communicates at one end with the internal chamber 111, and at the other end with a low pressure inlet port .112.

A control mechanism is provided. The control mechanism includes a control shaft 170 mounted at one end to the cam plate 117 and extends into the central opening 131.

A control body 171 is provided in the central opening 131, and has a splined connection to the shaft 170, as shown at 172. As the cam plate rotates, some of the pistons 120 are on the suction stroke, and some are on the discharge stroke. The control body 171 is provided with a pair of

ribs

181, 182, aligned with the openings 130, which ribs functionally divide the central opening into a low pressure zone 183, and a control pressure zone 184.

The low pressure zone 183 communicates with all the pistons on the suction stroke, and the control pressure zone 184 communicates with all the pistons on the discharge stroke. The control pressure zone 184 is en closed, by a pair of spaced

lands

185, 186, each of which extends circumferentially from one rib to the other. The low pressure zone 183 communicates with the inlet port 112. The control body 171 is provided with a bottomed axial bore 188 into which a control rod 190 extends. The control body 171 is provided with a fluid passage 191 connecting the axial bore 188 with the low pressure zone 183, and with a fluid passage 192, connecting the axial bore 188 with the control pressure zone 18 The bottom of the axial bore 188 is vented by a vent passage 1% to the low pressure zone 183.

The control rod 190 has an annular relieved portion 194 with sealing

surfaces

195, 196 on opposite sides of the relieved portion 194. The sealing surfaces 195, 196 are in sealing engagement with the axial bore 188. The control rod 199 is connected to a control handle 197, as shown in FIGURE 9. Movement of the control handle 197 will move the control rod 191] axially in the axial bore 188.

In the position shown in solid lines in FIGURE 9 the sealing surface 195 seals the passage 192 from the passage 191, which prevents fluid from flowing from the control zone 184 to the low pressure zone 183. Hence, each piston on the discharge stroke will discharge the fluid into the control zone 184. However, the control zone 184 is sealed from the low pressure zone 183 and no fluid can be passed from the control zone to the low pressure zone. This will cause a pressure increase in the control zone which will actuate the sealing sleeve 140, causing a discharge through a check valve to the outlet port 13 3 from each piston which is on the discharge stroke.

When the control rod is in the position shown in dotted lines in FIGURE 9, the relieved portion 194 of the control rod is fully registered with the passages 19 11 and 1&2. This will provide communication of the control pressure zone 184 with the low pressure zone 183 through the axial bore 183. Hence fluid pumped from each piston on the discharge stroke will pass into the control zone, through the axial bore, and then into the low pressure zone. Therefore there will be no substantial pressure build up in the control pressure zone so the fluid sealing sleeves 140 will not be actuated and there will be no discharge through the check valves 134- to the high pressure outlet port. In this manner a pump can be fully loaded or unloaded depending upon the position of the control rod. The pressure level at which the sealing sleeves 14% are actuated is dependent upon the load of its spring 141. Since each of the cylinder bores having pistons on the discharge stroke are communicating with a single control pressure zone, the pressure in each is governed by the pressure in the control pressure zone 184. Therefore, by varying the load of the springs of each sealing sleeve a number of intermediate positions between the fully loaded condition and the fully unloaded condition of the pump can be obtained in the following manner. The control rod may be placed in an infinite number of positions between those shown in solid lines and those shown in dotted lines in FIGURE 9. These intermediate positions will provide a varying area of the passage "112 communicating with the relieved portion 194 of the control rod. This will control the pressure level in the control pressure zone. Hence any sealing sleeve which has a spring with a biasing force less than the force induced by the pressure level in the control pressure zone will be actuated, and discharge through the high pressure outlet port will occur from that cylinder during the entire discharge stroke of its piston. However, any sealing sleeve whose spring has a force greater than the force induced by the pressure load in the control chamber will not be actuated, and the flow from that cylinder bore will be through the passage 130, and thence through the control pressure zone to the low pressure zone. In this way, selectively, any number of sealing sleeves can be actuated during a revolution of the pump. In this way the volume output of the pump can be changed in steps equivalent to the number of pistons from maximum to Zero.

1 claim:

1. In a pump having a housing and at least one cylinder bore, a piston arranged for reciprocation in each cylinder bore and drive means to reciprocate each piston, a low pressure inlet manifold and high pressure discharge manifold, a pressure responsive high pressure manifold check valve. between each cylinder bore and said discharge manifold, the improvement which comprises, fluid conducting mean-s between each cylinder bore and said low pressure inlet manifold, pressure responsive shut-ofl means to close said fluid conducting means, control means interposed between said shut-01f means and said low pressure manifold means to selectively actuate said pressure responsive shut-off means, and means operatively connecting said control means to said drive means to time the actuation of said shut-01f means responsive to the position of said drive means, whereby the volume discharge of the pump can be varied.

2. The device of claim 1 further characterized by each pressure responsive shut-01f means being positioned between each cylinder bore and said fluid conducting means.

3. The device of claim 2 further characterized by said housing and said pressure responsive shut-off means having mating, selectively engageable sea-ling surfaces whereby said cylinder bore can be sealed from said fluid conducting means.

4. The device of claim 1 further characterized by each pressure responsive shut-off means having a first balancing surface, a passage to conduct fluid under pressure from said cylinder bore to said balancing surface, and biasing means opposing the force developed on said balancing surface by fluid pressure, whereby the pressure responsive shut-off means are normally urged to keep said fluid conducting means open.

5. The device of claim 4 further characterized by each pressure responsive shutoff means having sealing piston means, a first balancing surface defining one end of said sealing piston means, a passage to conduct fluid from said cylinder bore to said first balancing surface, second baiancing surface defining the opposite end of said sealing piston means, an opening connecting said second balancing surface and said low pressure inlet manifold, and spring means biasing said sealing piston means and opposing net force developed by fluid pressure on said first balancing surface, whereby said shut-01f means is normally urged to keep said fluid conducting means open.

6. The device of claim ll, further characterized by said shut-off means including a piston disposed across said fluid conducting means, said piston having a pressure face, passage means communicating with said face and said fluid conducting means, said piston being movable across said fluid conducting means from an open position to a closed position, biasing means normallyurging said piston into the open position, and said pressure face being positioned to be urged in a direction opposing the direction urged by the biasing means.

7. The device of claim 6, wherein each of the biasing means has a force different from that of every other biasing means, whereby by varying the resistance, any selectable number of shut-off means may be actuated per revolution of the pump to vary the discharge of the pump in stages.

8. in a pump having a housing and at least one cylinder bore, a piston arranged for reciprocation in each cylinder bore and drive means to reciprocate each piston, a low pressure inlet manifold and a high pressure discharge manifold, a pressure responsive high pressure manifold check valve between each cylinder bore and said discharge manifold, the improvement which comprises, fluid conducting means between each cylinder bore and said low pressure inlet manifold, pressure responsive shut-off means to close said fluid conducting means, control means between said shut-off means and said low pressure manifold means, said control means including means selectively positionable to increase the resistance to fluid flow in said fluid conducting means during a portion of the discharge stroke of at least one cylinder to actuate said shut-01f means, and means connecting said control means to said drive means to time the actuation of said shut-oft means responsive to the position of said drive means, whereby the effective length of the piston stroke can be varied.

E9. The device of claim 8, wherein said control means includes rotating means, said rotating means having at least one surface registrable with said fluid conducting means during a portion of the rotation and arranged to block the fluid conducting mean-s during a portion of the discharge stroke of the piston.

10. The device of claim 9, wherein said surface on said means is moveable to a plurality of locations to register with said fluid conducting means during a selectable portion of the discharge stroke of the piston.

11. In a pump having a housing and at least one cylinder bore, a piston arranged for reciprocation in each cylinder bore and drive means to reciprocate each piston, low pressure inlet manifold and high pressure discharge manifold, a pressure responsive high pressure discharge manifold, a pressure responsive high pressure manifold check valve between each cylinder bore and said discharge manifold, the improvement which comprises, fluid conducting means between each cylinder bore and said low pressure inlet manifold, pressure responsive shut off means to close said fluid conducting means, said pressure responsive shut-01f means including a sleeve between each cylinder bore and said fiuid conducting means, said sleeve having a sealing face positioned to seal against a sealing surface to seal the cylinder bore, from said fluid conducting means, biasing means normally urging said sealing face away from said sealing surface, said sleeve having a pressure surface positioned to transmit applied pressure in a direction opposite the direction of urging of the biasing means, control means between said fluid conducting means and said inlet manifold, said control means including a ring rotatably driven, said ring having a surface being selectively positionable to register with said fluid conducting means at a plurality of positions of the piston during its discharge stroke, whereby when said surface registers with said fluid conducting means, pressure will'be raised in the region of the sealing sleeve, and the sealing sleeve will close off the fluid conducting means from the cylinder bore.

12. In a pump having a housing and a plurality of cylinder bores in said housing circumferentially arranged about a central axis, pistons arranged for reciprocation in said cylinder bores, cam means to reciprocate said pistons, a low pressure inlet manifold, a high pressure discharge manifold, a pressure responsive check valve between each cylinder bore and the high pressure manifold, the improvement which comprises, fluid conducting means between each cylinder bore and said low pressure manifold, pressure responsive shut-off means between each cylinder bore and said low pressure manifold to close said fluid conducting means, said pressure responsive shut-off means including biasing means normally urging said shut-off means to an open position; control means between said shut-01f means and said low pressure manifold communicating with said fluid conducting means, said control means including a low pressure Zone and a control pressure zone, said control means being rotatable in timed relation with said cam means, passage means connecting said low pressure zone and said control pressure zone, and means to regulate resistance to fluid flow in said passage means, whereby by varying the resistance in the passage means the shut-01f means can be actuated to provide discharge through the high pres sure manifold.

13. The device of claim 12, whereas the biasing means of at least one shut-off means has a force different from the force of the remaining biasing means, whereby by varying the resistance in the passage means a selectable number of shut-oif means may be actuated to vary the discharge of the pump in stages.

References Cited in the file of this patent UNITED STATES PATENTS 2,160,978 Mock June 6, 1939 2,744,467 Bahniuk May 8, 1956 2,845,029 Gratzmuller July 29, 1958 2,928,352 Aldinger Mar. 15, 1960 2,940,396 M-isulis June 14, 1960 2,988,010 Fay June 13, 196-1 3,029,737 Bessiere Apr. 17, 1962 FOREIGN PATENTS 436,634 France -2 of 1911 459,578 Great Britain Jan. '11, 1937

Claims

1. IN A PUMP HAVING A HOUSING AND AT LEAST ONE CYLINDER BORE, A PISTON ARRANGED FOR RECIPROCATION IN EACH CYLINDER BORE AND DRIVE MEANS TO RECIPROCATE EACH PISTON, A LOW PRESSURE INLET MANIFOLD AND HIGH PRESSURE DISCHARGE MANIFOLD, A PRESSURE RESPONSIVE HIGH PRESSURE MANIFOLD CHECK VALVE BETWEEN EACH CYLINDER BORE AND SAID DISCHARGE MANIFOLD, THE IMPROVEMENT WHICH COMPRISES, FLUID COUNDUCTING MEANS BETWEEN EACH CYLINDER BORE AND SAID LOW PRESSURE INLET MANIFOLD, PRESSURE RESPONSIVE SHUT-OFF MEANS TO CLOSE SAID FLUID CONDUCTING MEANS, CONTROL MEANS INTERPOSED BETWEEN SAID SHUT-OFF MEANS AND SAID LOW PRESSURE MANIFOLD MEANS TO SELECTIVELY ACTUATE SAID PRESSURE RESPONSIVE SHUT-OFF MEANS, AND MEANS OPERATIVELY CONNECTING SAID CONTROL MEANS TO SAID DRIVE MEANS TO TIME THE ACTUATION OF SAID SHUT-OFF