US2243888A - Fluid pump control - Google Patents

Description

June 3, 19741. w SHELLY 2,243,888

FLUID PUMP CONTROL Filed Feb. 12, 1958 3 Sheets-Sheet l June 3, 1941.

L. w. SHELLY FLUID PUMP CONTROL Filed Feb. 12, 1938 3 Sheets-Sheet 2 June 3, 1941. L w. SHELLY 2,243,888

FLUID PUMP CONTROL Filed Feb. 12, 1938 3 Sheets-Sheet 5 Patented June 3, 1941 FLUID PUMP CONTROL Llewellyn W. Shelly, Allentown,

The Aldrich Pump Company, corporation of Pennsylvania Pa., asslgnor 'to A Allentown. Pa., a"

Application February 12, 1938, Serial No. 190,285

11 Claims. This invention relates to improvements in devices for loading and unloading piston pumps,

in'fluid pressure systems, and more particularly to devices of this character adapted to function automatically to maintain said pressure between predetermined limits, or, as in the case where said system includes an accumulator, to maintain the fluid in the accumulator between given maximum and minimum volumes.

The principal object of the invention is to provide improved means for automatically loading and unloading a piston pump in syncro-v nlsm with the movements of the pump pistons so that the loading and unloading operations may occur on the suction stroke or at any desired point in the suction strokes of the pistons.

The invention further resides in the novel apparatus and details of mechanism hereinafter described by which the aforesaid principal object and other useful ends, hereinafter set forth, are attained.

In the attached drawings:

Figure l is a side elevational view of a triplex power pump equipped with control means made in accordance with my invention;

Fig. 2 is a section on the line 2-2, Fig. 1;

Fig. 3 is an enlarged side elevational and partial sectional view of the control unit including a diagram of the associated electrical system;

Fig. 4 is a fragmentary sectional view illustrating the structural details of one of the elements of the mechanism;

Fig. 5 is a section on the line 5-5, Fig. 3;

Fig. 6 is a section on the line 66, Fig. 3;

Fig. 7 is a diagrammatic view illustrating the pressure system of the control device;.

Fig. 8 is a fragmentary elevational and partial sectional view of a modified control mechanism within the scope of my invention including a diagram of the associated electrical system, and

Fig. 9 is a diagrammatic view of the pressure system of the control device illustrated in Fig. 8.

With reference to Figs. 1 and 2 of the drawings, I have therein illustrated for the purpose of describing the invention a triple cylinlder pump comprising the usual frame I, cylinder block 2, and crank shaft 3, the latter being continuously operated from a suitable source of power through a pulley 4. prises three cranks set apart at angles of 120, and from these cranks piston rods 5 extend downwardly to pistons or plungers, 6, l and 8 respectively, which as shown in Fig. 2 operate in cylinders 9 in the block 2. Fluid is conducted The shaft 3 com stance is formed in to the cylinders 9 through an intake pipe H and a manifold l2, which in the present inthe block 2. From the manifold l2 a passage l3- extends to each of the cylinders 9, and each of these passages I2 is controlled by a spring-tensioned check valve H which permits flow of fluid through the passage l3 to the cylinder, but normally prevents. a reverse flow. From each of the cylinders 9 a discharge passage l5 extends to a manifold Ii, and thence to a discharge pipe l'|,'and the connection between each of the individual passages II and the manifold I6 is controlled by a springtensioned check valve 18 which permits flow of fluid from the cylinder to the manifold, but prevents flow in the reverse direction. In the normal operation of a pump of this type, when one of the plungers is moving upwardly on the suction stroke, fluid is drawn into the cylinder past the valve l4, and is discharged from the cylinder on the downward -or pressure stroke of the piston through the valve Mounted on the block 2 below each-of the suction valves I4 is a pressure cylinder, 2|, 22 and 23, respectively. As shown in Fig. 2, each of these cylinders contains a piston 24 from which a rod 25 extends upwardly through. the manifold chamber l2 to the underside of the valve I4. When the plunger 24 is at the top of the cylinder 2i as shown in Fig. 2, the rod 25 by engagement with the under side of the valve l4, which has previously been lifted by suction on an upward movement of the plunger 6, prevents the valve from closing on the downward or pressure stroke of the plunger, with the result that fluid drawn into the cylinder 9 on the suction stroke of the plunger will be forced back through the passage I 3 to the manifold l2. When the valve I4 is held open on the pressure stroke of the piston B as described, the valve l8 remains closed, and accordingly no fluid passes to the discharge II. Springs 28 tend to force the pistons 24 to the bottoms of the associated cylinder 2|, 22 and 23, in which position the rod 25 is depressed sufliciently to permit the suction valves I4 to close.

From the bottom of each of the cylinders 2t, 22 and 23, a pipe, 21, 28 and 29, respectively, extends to a distributing valve 2|. This valve, as shown in Fig. 3, comprises a casing 32 having formed in the upper end thereof three chambers, 33, 34 and 35, with which the pipes 21, 22 and 29 respectively, communicate. Each of the chambers 33, 34 and 35 communicates by means of a port 36 in its bottom wall with a manifold chamber 31, and each of the ports 38 is controlled by a poppet valve 38. The stem 319 of each of the valves 38 extends downwardly to a tappet 4! which engages the surface of a cam, 42, 43 and 44, respectively, secured to a shaft 45, and this shaft, as indicated in Figs. 1 and 2, is connected with the crank shaft 3 of the pump and rotates with the latter. Each of the valve stems 39 is provided with a spring 49 which forces the rod downwardly upon the tappet M and holds the tappet against the face of the associated cam. The cams 42, 43 and 44; are arranged on the shaft 45 so that they will. unseat the respective associated valves 38 in succession and at uniformly spaced intervals during one complete revolution of the shaft 45. There is also a direct relation between the positions of the cams 42, 43 and 44 and the positions of the cranks of the shaft 3 that produces a synchronized action, hereinafter described, between the plungers 6, 1 and 8 and the respective cams 42, 43 and 44.

From the manifold chamber 31 a pipe 4'5 extends to a port 41 in a solenoid-actuated valve 48. The port 41 is adapted to be connected through a valve element 49 with a pipe extending to a source of fluid supply, as hereinafter set forth. The valve 49 in a depressed position, as shown in Fig. 4, connects the pipe 56 with the port 41, so that the pipe 5! is in direct communication through said port with. the pipe 46 and the manifold chamber 31 of the distributor valve 3|. When the valve 49 is elevated, the connection between the pipe 5| and the port 41 is broken. The valve is operativeiy connected through a stem 52 and a link 53 with one end of a lever arm 54 which is pivotally mounted at 55 on the casing of the valve 48. A spring 56 connected to the same end of the lever 54 tends to hold that end of the lever in a depressed position, as shown in Fig. 4, in which position the valve 49 establishes communication between the pipe 5| and the port 41. The opposite end of the lever 54 is connected through a link 51 with the movable core 58 of a solenoid 59, and this solenoid when energized draws the core 58'downwardly from the extended position in which it is netic actuator of the switch M may be energized to close the solenoid circuit by means of switch F, which when closed forms a circuit comprising wires C C and C The switch F is normally open, but when momentarily closed effects a closing of the magnetic switch M and an immediate energization of the solenoid 59. Closing of the magnetic switch M, in addition to energizing the solenoid circuit, also closes a circuit comprising the wires C C H unloading switch H a wire H and a wire H this circuit including the magnetic switch actuator and acting as a holding circuit to maintain the switch M closed after switch F has been released or opened.-

After momentary closing and subsequent release of switch F, therefore, the magnetic switch will remain closed to thereby maintain the solenoid 59 in energized condition. The solenoid circuit remains closed until the switch H is opened by means hereinafter described, thereby breaking the holding circuit of the magnetic switch M and permitting that switch to open, as shown in Fig. 3. By reason of the broken circuit of the normally open switch F, subsequent closing of the switch H will not effect an actuation and closing of the magnetic switch M, so that after the shown in Fig. 4, and thereby elevates the valve 49 to disconnect the pipe 5| from the port 41.

Attached to the lever 54 on the solenoid side of the pivot 55 is a valve 6| which controls the connection between the port 41 and an exhaust pipe 62. When the solenoid 59 is deenergized and the spring 56 pulls the opposite end of the lever downwardly, as shown in Fig. 4, the valve Si is drawn upwardly to its seat, thereby shutting off the exhaust pipe 62 from the port 41.

When, on the other hand, the solenoid is energized, the valve 6| is moved downwardly from its seat, thereby connecting the port 41 with the pipe 62 and also, as previously described, drawing up the valve 49 to break the connection between the supply line 5| and the port 41. Under these circumstances, it will be apparent that the pipe 46 is directly connected through the port 41 with the exhaust pipe 62.

The electrical system, of which the solenoid 59 forms part, is illustrated in Fig. 3. In this system, as illustrated, electrical energy is supplied through line wires L and L The solenoid is adapted to be connected to the line wires L and L through the wires S and 8, this connection of the solenoid with the source of current being controlled by a magnetic switch M. The magswitch H has been opened to break the holding circuit, the solenoid 59 will remain deenergized until switch F is again momentarily closed, or until loading switch L is closed by means hereinafter described. The switch L is an element of a circuit including C C T timing switch T, T '1' and C Assuming that the switch F remains open, it is apparent that closing of the switch L accompanied by a completion of the circult through the timing switch T will effect an energization of the magnetic actuator of switch M and a reclosing of that switch with consequent reenergization of the solenoid 59. With the closing of the magnetic switch M, the holding circuit, which includes the unloading switch H as described above, will retain the magnetic switch in the closed position even after the breaking of the circuit C 0*, T T, T, L, T and C so that in spite of the opening of this latter circuit either through the loading switch L or the timing switch T, the solenoid 59 will remain in the energized condition until a subsequent opening of the switch 1-1.

It will be noted that loading of the pump may be accomplished either by momentarily closing the manual switch F, or by closing the switch L and holding this switch closed until the circuit has been completed at T. Unloading is effected either by the opening of the switch H or by opening a normally closed manually actuated and which is associated in the present instance with the switch F, the switch F being in serieswith the switch H as shown. The switches F and F constitute a convenient means for manually controlling loading and unloading under all conditions, emergency or otherwise, and may be actuated to load or unload at any time as may be necessary or desirable.

The discharge l1 of the pump may be connected to a pressure system or vesseel, and in the present instance to an accumulator 63, and the switches H and L are arranged for actuation in accordance with the accumulator travel. When under loading conditions the accumulator by reason of the increasing quantity of contained fluid approaches the outer limit of its travel, the unloading switch H is opened, but will immediately close when the volume of fluid in the accumulator falls below the predetermined maximum. The switch L on the other hand, which as stated is a loading switch, is arranged to be closed when the accumulator, by reason of the decreasing volume of its contained fluid, approaches the other end of its travel, and this-switch in turn will automatically .reopen as soon as the volume of fluid in the accumulator increases above the predetermined minimum. In the present instance, I have indicated diagrammatically the actuation of the switches H and L by mechanical connection with the moving element of the accumulator. When this element, indicated by the numeral 63 is elevated by an increasing quantity of fluid within the accumulator to the upper end of its predetermined travel, a cam 44 on the accumulator will engage the switch arm and open the switch. This same cam when the accumulator member has dropped by reason of withdrawals of fluid from the accumulator to the other end of its travel will engage the arm of the switch L, and will close that switch. Except when actuated by the cam 84, or by other means,

the switch If will be closed and the switch L open.

The operation of the device described above is as follows: As previously stated, when the solenoid 59 is deenergized and the elements of the associated valve occupy the positions shown in Fig. '4, fluid pressure admitted through the pipe 5!, which latter pipe may be. connected with the accumulator 63 or other source of fluid pressure, will be transmitted through the port 41 to the pipe 46, and through this pipe to the manifold chamber 31 of the distributor valve 3|. This pressure admitted to the cylinders 2|, 22 and 23 through action of the valves 38 and of the cams 42, 43 and 44 of the distributor valve will support the suction valves i4 of the pump cylinders in the open position, so that the pump in effect is unloaded and is prevented from feeding fluid to the accumulator 63. The solenoid 59 may now be energized to eflect loading of the pump by momentarily closing the normally open push button switch F, thereby energizing and closing the magnetic switch M and completing the solenoid circuit as well as the holding circuit controlled, as hereinbefore described, by the unloading switch H With the solenoid energized, the valve 49 is elevated to break the ,connection between the fluid supply pipe 5| and the port 41, and the valve 6| is opened to connect the pipe 46 through the port 4'! with the exhaust 62, so that the manifold 31 is exhausted. The pressure being thus released from the cylinders 2|, 22 and 23, the suction valves I4 of the pump will function in the normal manner. Fluid now flows into the accumulator until the volume reaches the predetermined maximum, at which time the switch H is automatically opened, breaking the holding circuit of the magnetic switch M and permitting that switch to open, thereby again deenergizing the solenoid 59, disconnecting the manifold 31 from the exhaust, and connecting the manifold with the fluid supply admitted through the pipe 5|. noted that by reason of the aforedescribed arrangement of the cams 42, 42 and 44 of the distributor valve with respect to the cranks of the shaft 3 of the pump, fluid pressure is'admitted to the cylinders 2!, 22 and 23 successively and at the time that the pump piston 6 of the associated cylinder of the pump is on its upward or suction stroke. The pistons 24 of the cylinders 2|, 22 and 23 are, therefore, elevated against negative pres- The pump now is unloaded, and it will be sure in the pump cylinders, and no effort aside from that required to overcome the weight of the piston 24 and its stem;25 and the pressure of the springs 26 is required to elevate the pistons. In other words, the unloading of each of the cylinders of the pump occurs on the suction stroke of its associated plunger.

With the pump unloaded, passage of fluid to the accumulator by the pump is interrupted until such time as the fluid in the accumulator has been exhausted to the predetermined minimum amount, at which time the switch L is automatically closed as previously described. Closing of the switch L, however, does not necessarily complete the circuit through the magnetic actuator of switch M, it being necessary, in order that this circuit be completed, that the ,timing switch T shall have moved to one or other of its several circuit-closing positions.

Assume in Figs, 3 and 6 that the timing switch T consists of a cylinder mounted on the shaft 45 and slidably engaged on its cylindrical surface by two brushes 66 and 61. In that portion of the circumference of the cylinder 65 engaged by the brush 66, the cylinder presents a continuous metallic surface, and in that portion of the cylinder engaged by the brush 61-, the metallic surface of the cylinder is interrupted by three relatively spaced insulated areas 68, 69 and 10. The electric circuit is completed, therefore, only when the brush 61 engages the metallic surface of the cylinder between the insulated areas 68, 69 and 10. By arranging the cylinder 65 so that the said insulated portions occupy predetermined positions with respect to the cranks of the shaft 3, it is apparent that the closing of the circuit may be regulated to occur at any desired point in the suction, strokes of the respective pump plungers. It is possible, therefore, to effect the loading of the pump or of the individual pump cylinders at the most advantageous point in the suction stroke of the pump plunger. trolling the electric circuit in conjunction with the earns 42, 43 and 44 affords a highly flexible regulation of the loading operation.

When, therefore, the switch L has been closed as described above and the circuit completed through the timing switch T to thereby energize and close the magnetic switch M, the resulting energization of the solenoid 59 will effect a loading of the pump cylinders, resulting in a building up of the fluid in the accumulator until such time as the maximum volume has again been attained. It will be noted in respect to the loading of the pump through closing ofthe switch L and operation of the timing switch T, that. when the magnetic switch M has been closed through a completion of the loading switch circuit, the holding circuit including the switch H which is now closed retains the magnetic switch closed until such time as the switch H is opened, such opening occurring automatically when the volume of fluid in the accumulator has reached the predetermined maximum.

The embodiment of my invention shown in Figs. 8 and 9 of the drawings operates on essentially the same principle as the embodiment previously described, but differs from that embodiment in that control of the loading and unloading operations resides entirely in the electrical system. To simplify description, the various elements of the pump mechanism and of the electrical control system corresponding to the elements of the embodiment shown in Fig. 3, are identified by the same reference numerals. In

This timing device con-- this instance, I employ three solenoid valves, corresponding in i'orm and operation to the valve 48 01 the preceding embodiment, to directly control the flow of fluid pressure through the pipe 58 to the cylinders 2|, 22 and 23, (the two first-named of these cylinders not being shown in the draw ings) which constitute the means for supporting the suction valves I4 of the pump cylinder in unseated position. The three solenoid valves, designated 48a, 48b and 480, when deenergized, connect the respective cylinders 23, 2| and 22 with the supply pipe 5| through the pipes l4, l2 and 13, respectively, and thereby eiiect the unloading of the pump as described above. When energized, the cylinders 2|, 22 and 23 are connected through the same pipes l2, l3 and I4, respectively, with the exhaust pipes 15, 16' and 11, and the pump is thereby unloaded.

Each of the solenoid valves 48a, 48b and 48c is adapted to be connected individually with a source of electrical energy through the line wires L and L and each of these individual connections of the solenoid valves is controlled by a magnetic switch, M M and M respectively. Flow of current to the magnetic switches and through these switches to the solenoid valves 48a, 48b and 480 is controlled, as in the previous embodiment, by the unloading and loading switches H and L, respectively, which are arranged for mechanical actuation by the accumulator as previously described. The unloading switch H in the present instance is located in one of the line wires L and the loading switch L is shunted by a circuit which includes the push button switch F adapted for manual actuation.

The timing of the energization of the solenoid valves 48a, 48b and 48c in synchronism with the movements of the pistons in the pump cylinders, so that actuation of these valves for loading occurs during the suction strokes of the respective pistons, is effected by means of a timer 88a carried by a shaft 45 connected with the crank shaft of the pump. This timer is'of the general character of that previously described above in connection with the preceding embodiment, but comprises in this case four brushes, l8, I8, 80 and 8|, the brushes I5, 88 and BI being associated respectively with the magnetic switches M, M and M The timer cylinder with which the brushes contact is provided with a plurality of contact elements 82, 83, 84, 85 and 86. The brushes 82 and 83 are arranged in alignment so that when the contact 82 meets the brush I8, the contact 83 will simultaneously meet the brush 8|, and the contacts 82 and 83' are electrically connected so that these contacts may complete a circuit between the said brushes I8 and 8|. Similarly the contact 84 is of a width suflicient to simultaneously engage the brushes l8 and 19, so that when this contact meets these last-named brushes a'circuit is completed therebetween. The contacts 85 and 88 are electrically joined and are arranged onthe timer cylinder so that when the contact 85 meets the brush 18, the contact 86 at the same time meets the brush 80. The contacts 82-83, 84, and 8586 are arranged in spaced relation around the timer cylinder at intervening angles of 120.

Assuming that the pump is unloaded and that the various switches of the electrical system are as shown in the drawings, the solenoid valves 48a, 48b and 48c are now deenergized, thereby admitting fiuid pressure from the supply 5| to the cylinders 2|, 22 and 23, and elevating the rods to maintain the suction valves 14 of the pump in the elevated or open position. Loading oi the pump can now be accomplished by closing the switch L or by a manual closing 01 the push button switch F, which as previously stated is establlshed in a circuit shunting the switch L. when either of these switches is closed and the contact 84 o! the timer meets the brushes 18 and it, a circuit is formed from L to L, which includes C actuator of magnetic switch M C 0, L or F and C" to L Energization oi the magnetic actuator of switch M closes that switch and thereby completes a circuit from L through C the actuator of the switch M 0', H H, H and H to L This is a. holding circuit which maintains the magnetic actuator of M in energized condition when and after the switch F or L, as the case may be, is opened. Closing of the magnetic switch M completes the circuit from L through (3*, S S and H to L, thereby energizing the solenoid valve 48a and connecting the pipe l4 0! the cylinder 23 with the exhaust pipe H, at the same time interrupting the flow oi fluid from the pipe 5| through the valve. Escape of fluid from the cylinder 23 permits the spring 28 to depress the rod 25, there by leaving the suction valve l4 free to close. Owing to the position of the contact 84 with respect to the pump crank shaft, energization oi the solenoid valve 48a and the consequent release of pressure in the cylinder 23 occurs on the suction stroke of the piston of the pump with which the said cylinder 23 and the related suction valve is associated. When the timer cylinder 66a is advanced through an angle of 120", the solenoid valve 48b is similarly energized, and an additional advance of 120 of the timer 88a results in an energization of the solenoid valve 480. In each case, the energization of the valve occurs on the suction stroke of the associated plunger of the pump. When the brushes l8 and 80 are connected through the contacts 85 and 88 of the timer, an electrical circuit is completed from L through C magnet M 0*, C switch F or L, C to L The magnetic switch M being thereby closed, a holding circuit for that switch is established through 0, magnet M C, H H, H and H to L so that this switch will remain closed regardless of the opening of the switch L or the switch F, or the further movement of the timer 86a. When the contacts 82 and 83 of the timer engage the brushes |8-8|, a circuit is made from L through C magnet M, C", C

switch F or L, C to L Resulting closing of the magnetic switch M establishes a holding circuit through C magnet M C", H H", H" and H to L The pump is now fully loaded, and this loading continues until such time as the unloading switch H is opened by action of the accumulator or switch F is opened manually. When this occurs, the magnetic switches M M and M are released, and the circuits of the solenoids 48a, 48b and 480 thereby broken, with the result that the pump is again unloaded. It is to be noted that in this case if the loading is effected through the manual push button switch F, this switch must be held closed until energization of all of the solenoid valves 48a, 48b and 480 is completed, occurring in one full revolution of the shaft I claim:

1. The combination with a fluid system including a reciprocating fluid pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain between predetermined maximum and minimum limits the volume oi fluid in said system, said means comprising a valve controlling said loading and switch, a loading switch adapted to be closed automat'ically when the volume of fluid in the sysautomatically when the volume of fluid in the I system has decreased to the said minimum and controlling flow of current to the actuator of said control switch, a timing switch operating in synchronism with the pump and arranged in series with said loading switch to operate jointly with the latter to control flow oi. current to the actuator oi said control switch, and a holding circuit for said control switch shunting said loading and timing switches and including a switch actuated simultaneously with and in the same phase as said control switch.

2. The combination with a fluid system including a multicylinder fluid pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain between predetermined maximum and minimum limits the volume of fluid in said system, said means comprising a valve controlling the loading and unloading of each of said pumpcylinders, a fluid motor for operating each of said valves, an electrlcally-actuated control valve for each of said motors, an electrically-actuated control switch for each of said valves, and an electric control system embracing said switches and including an unloading switch adapted to be opened automatically when the volume of fluid in the system attains said maximum and controlling flowoi current to the actuators of said control switches. a loading switch adapted to be closed automatically when th volume of fluid in the system has decreased to the said minimum and controlling flow of current to the actuators 01' said control switches, timing switches operating in synchronism with the pump and arranged individually in series with said loading switch to operate jointly with the latter to control the flow of current respectively to the actuators of said control switches, and a holding circuit for each 01' said control switches shunting the respective timing switches and said loading switch and each including a switch actuated simultaneously with and in the same phase as the associated control switch. a a

3. The combination with a fluid system including a reciprocating fluid pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain between predetermined maximum and minimum limits the volume of fluid in said system, said means comprising a valve controlling said loading and unloading, a fluid motor for operating said valve, an electrically-actuated control valve for said motor, an electrically-actuated control switch for said valve, a timing valve controlling the operation of said motor jointly with the electricallyactuated valve and operated in synchronism with the pump, and an electric control system including an unloading switch adapted to be opened automatically when the volume of fluid in the system attains the said maximum and controlling flow of current to the actuator of said control tem has decreased to the said minimum and controlling flow of current to the actuator of said control switch, a timing switch operating in synchronism with the pump and arranged in series with said loading switch to operate jointly with the latter to control flow of current to the actuator of said control switch, and a holding circuit for said control switch shunting said loading and timing switches and including a switch actuated simultaneously with and in the same phase as said control switch.

4. The combination with a fluid system including a multicylinder fluid pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain between predetermined maximum and minimum limits the volume of fluid in the system, said means comprising a valve controlling the loading and unloading of each of said pump cylinders, a fluid motor for operating each of said valves, an electrically-actuated control valve for each of said motors, an electrically-actuated control switch for each of said valves, and an electric control system embracing said switches and including an unloading switch adapted to be opened automatically when the volume of fluid in the system attains said maximum and controlling flow of current to the actuators of said control switches, a loading switch adapted to be closed automatically when the volume of fluid in the system has decreased to the said minimum and controlling flow of current to the actuators of said control switches, timing switches operated in synchronism with the pump and arranged individually in series with said loading switch to operate jointly with the latter to control the flow of current respectively to the actuators of said control switches, and a holding circuit for each of said control switches shunting the respective timing switches and said loading switch and each including a switch actuatai simultaneously with and in the same phase as the associated control switch.

5. The combination with a fluid system including a reciprocating fluid pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain between predetermined maximum and minimum limits the volume of fluid in said system, said means comprising a valve controlling said loading and unloading,a fluid motor for operating said valve, an electrically-actuated control valve for said motor, means controlled by the fluid in said system for operating said valve to maintain said volume within predetermined limits, a timing valve controlling the operation of said motor Jointly with the electrically-actuated valve and operated in synchronism'with the pump, and means operated in synchronism with said pump for timing the operations of said electricallyactuated valve by said fluid-controlled means.

6. The combination with a fluid system including a reciprocating fluid pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain between predetermined maximum and minimum limits the volume of fluid in said system, said means comprising a valve controlling said loading and unloading, a fluid motor for operating said valve,

a primary valve controlling the operation of said motor and means for automatically actuating said valve when the said fluid volume in the system approaches either of said limits, a secondary valve and means for actuating said valve in timed relation with the operation of the pump, said secondary valve being operative to synchronize 'the motor operations with the operation of said primary means actuated automatically when the said fluid volume in the system approaches either of said limits for controlling the operation of said motor, secondary motor control means actuated in timed relation with the operation of the pump and operative to synchronize the said motor and pump operation, and means also operating in timed relation with the pump for synchronizing operation of said primary and sec ondary control means.

8. The combination with a fluid system including a piston pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain the volume of fluid in said system between predetermined maximum and minimum limits, said means comprising a valve controlling said loading and unloading, a fluid-actuated piston for operating said valve, a valve controlling the operation of said piston, said valve being adapted in alternative positions of adjustment to permit passage of fluid to and from the piston respectively, one for loading and the other for unloading the pump, means for automatically moving said valve into said alternative positions respectively when the said fluid volume in the system approaches said limits, a second valve controlling passage'oi fluid to and from the piston and operating in timed relation with the pump for synchronizing the actuations of said motor with the movements of the pump piston, and means also operated in timed relation with the pump for synchronizing the operation of said valves in loading the pump.

9. The combination with a fluid system including a piston pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain the volume of fluid in said system between predetermined maximum and minimum limits, said means comprisinga valve controlling said loading andunloading, a fluid-actuated piston for operating said valve, a valve controlling the operation of said piston, said valve being adapted in alternative positions of adjustment to permit passage of fluid to and from the piston to unload and load the pump respectively, means for automatically adjusting said valve into position to admit fluid tothe piston when the said fluid volume in the system approaches the maximum limit and for automatically adjusting the valve into the other 0! said alternative positions when the fluid volume in the system approaches the minimum limit, a second valve controlling passage or fluid to and from the piston and operating in timed relation with the pump for synchronizing the actuations of said motor in loading and unloading the pump with the movements oithe-pump piston, and means also operated in timed relation with the pump for synchronizing the operation of the one valve wlth the other in the loading operation.

10. The combination with a fluid system ineluding a reciprocating fluid pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain the volume of fluid in said system between predetermined maximum and minimum limits, said means comprising a valve controlling said loading and unloading, a fluid motor for'operating said valve, an electrically-actuated primary valve controlling the operation of said motor, and means for automatically actuating said valve when the said fluid volume in the system approaches either of said limits, a secondary motor-control valve and .mechanical means for actuating said valve in timed relation with the operation of the motor, said secondary valve being operative to synchronize the motor operations with the operation of said pump, and electrical control means for said primary valve operating in timed relation with the pump to synchronize operations of said primary and secondary valves.

11. The combination with a fluid system including a multicylinder piston pump for supplying fluid thereto, of means for automatically loading and unloading said pump to maintain the volume of fluid in said system between predetermined maximum and minimum limits, said means comprising a valve controlling the loading and unloading of each of the pump cylinders, a fluid-actuated piston for operating each of said valves, a primary valve common to all of said pistons for controlling the passage of fluid to and from the latter, means for automatically actuating said valve when the said fluid volume in the system approaches either of said limits, a distributing valve operating in timed relation with the operation of the pump for controlling the passage of fluid to and from said pistons individually and for synchronizing the operation of each of said pistons with the associated pump piston, and means also operated in timed relation with the pump for synchronizing operations of said primary and distributing valves.

LLEWELLYN W. SHELLY.

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