US2240898A - Pump control - Google Patents

Description

E. WIEDMANN PUMP CONTROL May 6,- 1941.

Filed Nv. 6, 1937 8 shee'zs-sh'zvz INVENTDR RMS- WIEDMANN ATTURNEY.

May 6, 1941. E. wlEDMANN PUMP coN'TRoIJ Filed Nv. 6, 1937 3 Sheets-Sheet 3 llllLr..

E INVTDR RN |EpMANN BY 7 AT TDRNEY:

Patented May 6, 1941 PUMP CONTROL Ernst Wiedmann, Milwaukee, Wis., assignor to The Oilgear Company, Milwaukee, Wis., a. corporation of Wisconsin Application November 6, 1937, Serial No. 173,075

18 claims.

This invention relates to pump controls of the type which, in response to pump pressure reaching a predetermined value, will reduce the displacement of a pump until the pump is dellvering just suflicient liquid to maintain pump pressure at that value.

'An object of the invention is to provide a pump control which will automatically limit the pressure created by a pump to any one of a plurality of predetermined values.

Another object is to provide a. control which will cause a pump to successively maintain a plurality of predetermlned pressures substantially constant.

Another object is to provide a control of this character with means for rendering the control unresponsive to variations in pump pressure.

Other objects and advantages will appear from the description hereinafter given of a pump control in which the invention is embodied.

According to the invention in its general aspect and as ordinarily embodied in practice, the control is provided with a mechanism for varying pump displacement, a plurality of actuators each responsive to a different pump pressure for operating the displacement varying mechanism, and means for selectng any one of the actuators to operate the mechanism.

The invention is exemplied by the controller illustrated in the accompanying drawings in which the views are as follows:

Fig. 1 is a central section through a mechanism for shifting the stroke adjusting member of a pump.

Fig. 2 is a section on the irregular line 2-2 of Fig. l.

Fig. 3 is a schematic drawing illustrating the operation of the control.

Fig. 4 is a view showing a selector valve in a different position from that shown in Fig. 3.

Fig. 5 is a view showing a cut-out valve in a different position from that shown in Fg. 3.

The controller has been shown in Fig. 3 as applied to a pump I of the rolling piston type. Since this type of pump is fully illustrated a'nd described in Patent No. 2,074,068, it is deemed sufi'icient to state herein that the pump has its mechanism arranged within a c-asing 2, that its pistcns and cylinders are arranged radially in a rotatable cylinderv barrel 3 which is arranged within a thrust member or slide block 4, that the pistons react against an annular reaction surface 5 which in practice is formed in a rotatable thrust member carried by slide block 4 but which has been shown as being formed in slide block 4,

'stantially constant force which may be provided,

for example, by a spring or, as-shown, by liquid supplied at a substantially constant pressure to a cylinder 'I having fitted therein a piston 8 which is provided with a stem to engage slide block 4.

Liquid for Operating servo-motor 1-8 m'ay be supplied by a gear pump 9 which may be arranged within casing 2 and driven in unison with pump according to the usual practice. Gear pump 9 draws liquid from a reservoir Ill and delivers it into a channel ll one branch of which is connected to cylinder 1. Gear pump 9 discharges liquid at a rate in excess of requirements and the excess liquid is discharged through a relief valve |2, thereby enabling gear pump 9 to maintain a constant pressure in` channel il o and in cylinder l.

Slide block4 is adapted to be moved tow'ard the left to decrease pump displacement by a piston IB fitted in a cylinder l'l which is ordinarily formed integral with pump caslng 2 and closed at its outer end by a block |8 which is secured to casing 2.

As best shown in Fig. 1, piston IB consists primarily of a head |9 which is arranged in cylinder Il, a piston ring 20 which is fixed upon head |9 and closely fitted in cylinder ll, a sleeve 2| which is formed integral with head |9 and closely fitted for reciprocation within a bore 22 formed in block 8, and a disk 23 which is attached to the left end of head IB and is provided with a conical projection to engage a complementary surface formed upon an insert 24 fixed in slide block 4.

Liquid for Operating servo-motor |6--| l is supplied by gear pump 9 through channel ll which has one branch thereof connected to block IB in communication with a channel 25 leading to an annular port 26 formed in the wall of bore 22 and in the peripheral surface of sleeve 2|.

Port 26 communicates, through a plurality of openings 21 formed in the wall of sleeve 2|, with an annular port 28 formed in the wall of a cylindrical bore 29 which extends through sleeve 2| and head |9. Bore 29 is partly closed at its inner end by disk 23 which has a plurality of openings two Channels 54 and 55.

formed therein to permit liquid to escape from the closed end of cylinder |1 into the interior of pump casing 2 as will be presently explained. Bore 29 has a second annular port 3| formed in the wall thereof and communicating with the closed end of cylinder |1 through a plurality of openings 32 for-med in the wall of sleeve 2|.

The fiow of liquid to and from cylinder |1 is v controlled by a follow-up valve which has two pistons 36 and 31 formed thereon and closely iitted in bore 29 upon opposite sides of port 28.

'Piston 36 closes the outer end of bore 29 and prevents leakage of liquid therefrom. Piston 31 is exactly the same width as port 3| and is normally in alinement therewith. The arrangement is such that gear pump 9 is enabled to maintain a constant supply of liquid at a constant pressure in bore 29 between pistons 36 and 31.

When valve 35 is moved toward the left, liquid may fiow from borc 29 .through port 3| and openings 32 into cylinder |1 and-move piston |6 and slide block 4 toward the left to reduce the displacement of pump When valve 35 is moved toward the right, liquid may escape from cylinder |1 through openings 32, port 3|, the left end of bore 29 and openings 30 into the pump casing and permit servomotor 1-8 to move piston |6 and slide block 4 toward the right to increase the displacement of pump Since sleeve 2| is a part of piston |6, it will move with it and move port 3| into registry wi-th piston 31 as soon as valve 35 ceases to move, thereby preventing further movement of piston |^6 and slide block 4.

Valve 35 is urged toward the right by a spring 39 arranged in bore 29 between piston 31 and disk 23a Movement of valve 35 .toward the right is limited by a lever 39 which is arranged in block IB and pivoted intermediate its ends upon a. shaft 40.

Valve 35 engages the upper arm of lever 39 between shaft 40 and a spring 4| which is arranged in block |8 and urges the upper end of lever 39 toward the right. Spring 4| tends to move the lower end of lever 39 against a stop 42 which is fixed in block |8 and is ordinarily so adjusted at the factory that, when lever 39. is in contact therewith, valve 35 will be in the cor- .rect position to cause the displacement of the pump to be maximum.

'It is sometimes desirable to limit the volumetric delivery of a pump to a rate somewhat lower than the maximum rate of delivery. In order to obtain this result without altering the adjustment of stop 42, a stop bolt 43 is threaded through the upper part of a cover plate 44 which is attached to the right face of block |9. By turning bolt 43 inward, movement of the upper arm of lever 39 may be limited with 'a resultant limitation of the movement of slide block 4 toward its maximum displacement position.

Valve 3'5 is adapted to be moved toward the left to cause a reduction in pump displacement by a plurality of hydraulic actuators each of which is responsive to a different pump pressure to effect operation of valve 35. Any number of actuators may be employed. As shown, the lower arm of lever 39 is engaged by two plungers and 5| which are fitted, respectively, in cylinders 52 and 53 formed in block |8.

Liquid` for Operating plungers 50 and 5| is supplied to cylinders 52 and 53, respectively, through If the actuators are arranged different distances from shaft 40, one actuator will require a higher pressure than another actuator to overcome the resistneel of springs 38 and 4| due to the mechanical advantage of one actuator over another actuator. For example, if one actuator is 'arranged midway between the other actuator and shaft 40 as shown, the pressure required to operate it will be twice as great as the pressure required to operate the' other actuator.

Referring now to Fig. 3, delivery of liquid to cylinders 52 and 53 is controlled by a selector valve 60 which is fitted in the bore 6| of a valve casing 62. Bore 6| has four annular ports 53, 64, 65 and 66 formed in the wall thereof. Por-t 63 is connected to channel 54 through a channel 61 and a resistance valve 68 having a check valve 69 connected in parallel therewith. lPort 6'5 is connected to channel 55 through a channel 10 and 'a resistance valve 1| having a check valve 12 connected in parallel therewith. Port 55 and both ends of bore 6| are connected to a drain channel 13 which discharges into reservoir |0. Port 64 is connected by a channel 14 to a valve casing 15 in which a cut-oif valve 16 is fitted.

Valve 16 is urged toward the right by a spring 11 so that channel 14 is normally open to a drain channel 18 which is connected to both ends of valve casing 15. Valve 60 is urged to its uppermost position by a spring 19 in which position ports 64 and 65 are in communication with each other and port 63 is open to drain channel 13. With valves 60 'and 16 in the positions shown, liquid may escape freely from cylinders 52 and 53.

For the purpose of illustration, pump has been shown as being employed to supply liquid to a press to effect operation thereof. Since the press forms no part of the present invention, it has been represented diagrammatically by a fragment of a ram 8|, a ram cylinder 82 and 8. valve block 83 which controls operation of the press.

As shown, pump I delivers liquid to valve block 83 through a channel 64 and has liquid returned to it therefrom through a channel 85. A high pressure relief valve 86 is connected to channel 84 to limit the pressure which can be created by pump Valve 16 has a roller 81 'arranged upon the end of its stem and in the path of a cam 88 carried by ram 8| so that, when ram 8| is advanced a predetermined distance, cam 88 will engage roller 81 and move valve 16 toward the left to the position shown in Fig. 5 in which position of valve 16 channel 14 communicates with a channel 89 which connects pressure channel 84 to valve casing 15 intermediate the ends thereof.

Ram 8| also carries a cam 90 to engage the Operating rod 9| of an electric timer 92 which 'controls the energization of a solenoid 93 the core of which is connected to valve 50 to operate it. Timer 92 has not been illustrated in detail as it is a standard commercial article. It is deemed suiiicient to state herein that timer 92 will connect solenoid 93 into an electric circuit at the expiration of a predetermined period of time after Operating rod 9| has been actuated.

In order that pump may deliver liquid at its maximum rate to move ram at a rapid traverse speed until it approximately meets the work, and in order that pump may be capable of develop-. ing its maximum pressure to accelerate the ram when the press is of the upward pressure type, cams 88 and 90 are ordinarily so positioned relative to valve 16 land timer 92 that cam 08 will engage roller 81 and cam 90 will actuate operating rod 9| just as or just before ram 6| meets the work.

Assuming that pumps I and 8` are running, that the parts are in the positions shown in Fig. 3, and that a valve in valve block 83 has been operated to cause ram 8| to advance, the apparatus will function as follows:

' 1-8 can move slide block 4 toward the right to Pump will deliver liquid at its maximum rate shown in Fig'. 5 and timex' 82 will be started in operation. A

Shifting valve 16 to the position shown in Fig. 5 permits pump pressure to extend from channel 84 through channel 88, valve casing 15, channel 14, valve casing 62, channel 10, resistance valve 1| and channel 55 to cylinder 53. If the pump pressure required to rapid traverse the ram is greater than the desired holding pressure, the liquid delivered to cylinder 53 will immediately advance plunger 5|. If the pump pressure required to rapid traverse the ram is less than the desired holding pressure, pump pressure will rise as soon as the ram meets the work and the liquid delivered to cylinder 53 will advance .plunger 5|.

In either case, plunger 5| will swing lever 38 upon shaft 40 and cause the upper arm thereof to move valve 35 toward the left to effect a reduction in the displacement of pump as previously explained. Plunger 5| will continue to move outward and thereby continue to effect a reduction in the pump displacement until pump is delivering just suificient liquid to maintain in cylinder 82 the pressure determined by the pressure required to open resistance valve 1| and the pressure required to advance plunger 5|.

At the expiration of a predetermined interval of time after the ram meets the work, timer 82 will effect energization of solenoid 83 which will then shift selector valve 80 to the position shown in Fig. 4, thereby disconnecting channel 10 from channel 14 and connecting it to drain channel 13 and simultaneously disconnecting channel 61 from drain channel 13 and connecting it to channel 14. k

Connecting channel 10 .to drain channel 13 permits *pump displacement to increase until the pump develops .the pressure required t'o open resistance valve 88 and operate plunger 50. Then plunger 50 will move outward and effect a reduction in pump displacement until the pump is delivering just sufiicient liquid to maintain that pressure constant.

p After the second holding .pressure has been maintained for the desired length of time, ram 8| may be retracted by either automatic or manual operation of a valve in valve block 83. Shortly after ram 8| disengages the work, cams 88 and 00 will disengage roller 81 and rod 8|, thereby permitting spring 11 ,to shift valve 16 to the position shown in Fig. 3 and stopping operation of timer 92 so that solenoid 93 is deenergized and spring 19 permitted to shift valve 50 to the posi-` tionshown in Fig. 3.

With the valves 80 and 16 in the positions shown in Fig. 3, cylinders 52 and 53 are open to drain so that spring 4| can swing lever 30 against stop 42 or stop 43, thereby permitting spring 38 to move valve 35 toward the right so that liquid can escape from cylinder |1 and servo-motor increase pump displacement to maximum. Pump will then deliver liquid at its full volumetric rate to cause ram 8| to be retracted at high speed, but the pressure developed by the pump cannot cause operation of plunger 5| due to valve 18 blocking communication 'between ch'annels ,14 and 89.

In the foregoing example, the pump'first maintains a lower holding pressure and then a higher 'holding pressure but it is obvious that the order in which the pressures are maintained can 'be reversed -by simply reversing the connections of Channels 81 and 10 to selector valve case 62. It is also obvious 'that each of the holding premures may b`e varied through a wide range by simply varying the adjustment of the resistance valve.

When a pump was .provided with one of 'the prior controls which 'enabled it'to maintain a predetermined maximum pressure substantially constant, considerable difiiculty was encountered in'preventing the displacement varying mechanism of the pump from hunting.

This difiiculty is avoided in the present invention for the reason that, since the resistance of a compression spring increases as the spring is compressed, spring 4| permits plunger or 5| to start to swing lever 38 and thereby effect 'a reduction in pump displacement before pump pressure reaches the predetermined maximum. As the pump 'pressure continues to rise, spring 4| will continue to yield and permit pump displacement to be gradually reduced until pump pressure reaches the predetermined maximum at which time the pump is delivering just sufficient 'liquid to make up for leakage losses and thereby maintain the predetermined maximum pressure constant. Consequently, there is no tendency for plunger 50 or 5| to swing lever 38 so far that pump displacement is reduced too much.

Also, if spring 4| is quite stiff so that reduction in 'pump displacementbegins at a pressure considerably lower than maximum, the pump is 'at short stroke when pump pressure approaches maximum, thereby permitting the pump to be driven by a smaller electric motor than would otherwise be required.

The controller described herein is susceptible of various modifications and adaptations without departing from the scope of the invention as hereafter claimed.

The invention is hereby claimed as follows:

1. The combination, with a pump having a member movable in opposite directions to Yincrease or decrease pump displacement and urged in one of .said directions, of means for moving said member in the opposite direction, a plurality of means each responsive to a different fiuid pressure for eifecting operation of the aforesaid means, and means for selectively connecting said plurality of means to the outlet of said pump to thereby cause any one of a plurality of predetermined pump pressures to efi'ect adjustment of pump displacement.

2. 'I'he combination, with a pump having a member movable in opposite directions to increase or decrease pump displacement and urged in one of said directions, of a motor for moving said member in the opposite direction, means for supplying energy to said motor, a controller for controlling the operation of said motor a plurality of means each responsive to a different fluid pressure for efiecting operation of said controller, and means for selectively connectin said plurality of means to the outlet of said pump to thereby cause any one of a plurality of i'edetermined pump pressures to effect adjustent of pump displacement.

3. The combination, with a pump having a member movable 'in opposite directions to increase or decrease pump displacement and urged' in one of said directions, of means for moving said member in the opposite direction, a plurality of means each responsive to a different fiuid pressure for eifecting operation of the aforesaid means, means for selectively connecting said plurality of means to. the outlet of said pump to thereby cause any one of a plurality of predetermined pump pressures toeffect adjustment of pump displacement, and means for rendering said plurality of means effective or ineffective.

4. The combination, withia pump having a member movable-in opposite directions to increase or decrease pump displacement and urged in one of said directions, of a motor for moving said member in the opposite direction, `means for supplying energy to said motor, a controller .for controlling the operation of said motor, 'a

plurality of means each responsive to a different fluid pressure` for effecting operation of said controller, means for selectively connecting said plurality of means to the outlet of said pump to thereby cause any one of a plurality of predetermined pump pressures to effect adjustment of pump displacement, and means for rendering said plurality of means effective or ineifective.

- 5. The combination, with a pump having a displacement varying member urged in a direction' to increase pump displacement, of a mechanism for moving said member in a direction to decrease pump displacement, a plurality of means for eifecting operation of said mecha- 8. The combination, with a pump having a displacement varying member urged in a direction to increase pump displacement, of a motor for moving said member in a direction to decrease pump displacement, means for supplying energy to said motor, a controller for controlling the operation of said motor, a plurality of means for eflecting operation of said controller, said plurality of means being operable at different predetermined pressures, means for connecting any one ofsaid plurality of means to the outlet of said pump to thereby cause said motor to reduce pump displacement in response to pump pressure exceeding the value determined by that one of. said plurality of means, and means for rendering said. plurality of means effective or ineifective.

9. The combination, with Va pump having a displacement vVarylng member, of servo-motor means for moving said member in opposite directions to thereby vary pump displacement, means for supplying motive liquid to said servomotor means, a control valve for controlling the operation of said 'servo-motor means, means including a plurality of hydraulic actuato'rs each responsive to a different fiuid pressure for effecting operation of said valve, means including a selector valve for selectively connecting said actuators to the outlet of said pump, and means crease or decrease pump displacement and urged nism, said plurality of means being operable at different predetennined pressures, and means for connecting any one of said plurality of means to the outlet of said pump to thereby cause said mechanism to reduce pump displacement in response to pump pressure exceeding the'value' determined by that one of said plurality of means. w

6. The combination, with a pump-having a displacement varying member-urged in a direction to increase pump displacement, of a motor for moving said memlber in a direction to decrease pump displacement, means for supplying energy. to said motor,-a controller for controlling the operation of said motor, a plurality of means for eifecting operation of said controller, said plurality of means being operable at different 4predetermined pressures, and means for connecting any one of said plurality of means to the outlet of said pump to thereby causesaid motor to reduce pump displacement in response to pump pressure `exceeding the value determined by' that one of said 'plurality of means.

7. The combination, with a pump having a displacement varying member urged inA a direction to increase pump displacement, of a mechconnecting any one of said plurality of means to the outlet of said pump to thereby cause said mechanism to reduce pump displacement in redetermined by that one ofv said plurality of means, and-means for rendering said plurality of means effective or ineffective,

in one of said directions, of a hydraulic servomotor for moving said member in the opposite direction, means for supplying motive liquid to said servo-motor, a control valve for controlling the operation of said servo-motor, means including a plurality of hydraulic actuators each responsive to a different fiuid pressure for effecting operation of said valve, means including a selector valve for selectively connecting said actuators to the outlet of said pump, and means for operating said selector valve.

11. The combination, with a pump having a member movable in opposite directions to increase or decrease pump displacement and urged in one of said directions, of a hydraulic servomotor for moving said member in the opposite direction, means for supplying motivel liquid to said servo-motor, a control valve for controlling the operation of. said servo-motor, means including a plurality of hydraulic actuators each response to pump pressure exceeding the value sponsive to a different fiuid pressure for efi'cting 'operation of said valve, means including a selector valve for selectively connecting said actuators to thel outlet of said pump, means for operating said selector valve, and means for rendering said actuators effective or ineifective.

12. The combination, displacement varying member, of servo-motor means for moving said member in opposite directions to thereby vary-pump displacement, means for supplying motive liquid to said servomotor means, a follow-up valve' for controlling the operation ofsaid servo-motor means, valve' Operating means normally urging said valve in a direction to effect movement of said member in a direction to increase pump displacement, a plurality-of hydraulically actuated means each responsive to a different fiuid pressure for causing said valve Operating means to shift said valve in a direction to effect a reduction in' pump displacement, meansV including a selector valve for connecting said hydraulically actuated means with a'pump having a to the Outlet of said pump, and means for operating said selector valve.

13. The combination, with a pump having a displacement varying member, of servO-motor means for moving said member in Opposite directions to thereby vary pump displacement, means for supplying motive liquid to said servomotor means, a follow-up valve for controlling the operation of said servo-motor means, valve Operating means normally urging said valve in a direction to effect movement of said member in a direction to increase pump displacement, a plurality of hydraulically actuated means .each

' responsive to a different fluid pressure for causing said valve Operating means to shift said valve in a direction to effect a reduction in pump displacement, means including a selector valve for connectin'g said hydraulically actuated .means to the Outlet of said pump, means for Operating said selector valve, and means for rendering said hydraulically actuated means effective Or ineffective.

14. The combination, with a pump having a displacement varying member urged in a direction to increase pump displacement, of a hydraulic servo-motor for moving said member in the opposite direction, means for supplying motive liquid to said servo-motor, a follow-up valve for controlling the operation of said servO-motor, valve Operating means normally urging said valve in a direction to effect movement of said member in a directonto increase pump displacement,

'a plurality of hydraulic actuators for causing said valve Operating means to move said valve.

in the opposite direction to thereby effect a reduction in pump displacement, each 'of said actuators being responsive to a different fluid pressure to effect operation of said valve Operating means, and means for selectively connecting said actuators to the Outlet of said pump.

15. The combination, with a pump having a displacement varying member urged in a direction to increase pump displacement, ofv a hy- -draulic servo-motor for moving said member in the opposite direotion, means for supplying mo-' p tive liquid to said servo-motor, a follow-up valve for controlling the operation of said servo-motor, valve Operating means normally urging said valve in a direction to effect movement of said member in a direction to increase pump displacelectively connecting said actuators to the Outlet of said pump, and a resistance valve connected in series with each actuator to thereby determine the pump pressure required to cause each actuator to Operate said valve Operating means.

16. The gcombination, with a pump havinga displacement varying member urged in a direction to increase pump displacement, of a hydraulic servo-motor for moving said member in the Opposite direction; means for supplyin'g motive liquid to said serw-motor, a follow-up valve for controlling the operation Of said servo-motor, 4

valve Operating meansv normally. urging said valve in a direction tov effect movement of said member in a direotion to increase pump displacement, a plurality of hydraulic actuators for causing said valve Operating means to move said valve in the Opposite direction to thereby effect a reduction in pump displacement, each of said actuators havinga diiferent mechanical ad- Vantage in the operation of said valve Operating means, means including a selector valve for selectively connecting said actuators tO the Outlet of said pump, and a resistance valve connected in series with each actuator to thereby determine the pump pressure required to cause each actuator to operate said valve operatingmeans.

17. The combination, with a pump having a member movable in Opposite directions to increase or decrease pump displacement and urged in one of said directions, of means for moving said member in the Opposte direction, a plurality of means each responsive to a different fluid pressure for efi'ecting operation of the aforesaid means, and means responsive to motion created by liquid discharged by said pump for selectivelyconnecting said plurality of means to the Outlet of said pump to thereby cause any one of a plurality of predetermined pump pressures to effect adiustment of pump displacement.

.18. The combination, with a pump having a member movable in opposite directions to increase or decrease pump displacement and urged in one of said directions, of a motor for moving said member in the cpposite direction, means for supplying' energy to said motor, a controller for controlling the operation of said motor, a plurality of means each responsive to a different fluid pressure for effecting Operation of said controller, and means responsive to motion created by liquid discharged by said pump for selectlvely connecting said plurality of means to the Outlet of said pump to thereby cause any one of a plurality of predetermined pump pressures to effect adjustment of pump displacement.

. ERNS'I' WIEDMANN.

Images