US3491795A

US3491795A - Hydraulic starting system and valves therefor

Info

Publication number: US3491795A
Authority: US
Inventors: Lyston C Jennings; Howard C Spooner
Original assignee: General Signal Corp
Current assignee: SPX Corp
Priority date: 1966-08-03
Filing date: 1968-01-04
Publication date: 1970-01-27
Anticipated expiration: 1987-01-27

Description

Jan. 27, 1970. L. c. .nalwmmass E1 AL 3,491f795 HYDRAULIC STARTING SYSTEM AND VALVES THEREFOR Original Filed Aug. 5. 1966 3 Sheets-Sheetv l ATroRNExs Jan. 27,1970

n.. c. JENNINGS E1 A1.

HYDRAULIC STARTING SYSTEM AND VALVES THEREFOR Qriginal Filed Aug. 5. 1966 5 Sheets-Sheet 2 INVENTRS 'LYSTON C. JENNINGS HOMRD C. SFOONER ATTORNEYS Jan. 27, 1970 L. :.JENN1NGS ET AL HYDRAULIC STARTING SYSTEM AND VALVES THEREFOR Original Filed Aug. I5. 1966 I I iii!! 1 I 31| l l 'n 347 r I 3251 331C l fafa \\\l 325e 3 325C 2331i; h 33m I?. 346 22 @323 733nd 319 33| 331e 335 34% 33221)? 339 30Gb 31/8315 L33@ 322i:

Paw `332e b ,32h33, 33m 331g 3O3Q aow ab j H65 l FIG- 6. 1 2 1 3|5 l 306m\ 5 Q/ 306k 7%? 335- m l 3530i/ K \%3061- 36k 3oef/ I 342/ 343 v 34| INVENTORS 3062 LYsToN CJENNINGS 306(O HOWARD C. SPOONER F166 ,303!) 5 Sheets-Sheec 5 ATTORNEYS United States Patent O U.S. Cl. 137-609 4 Claims ABSTRACT OF THE DISCLOSURE Valving device useful in a hydraulic starting system employing an overcenter motor-pump unit which is supplied with motive fluid from an accumulator, and which causes the motoring-to-pumping selector control of the unit to maintain the latter in the motoring mode of operation as long as the start valve allows communication between the accumulator and the overcenter unit. The valving device pressurizes the selector control by allowing iiuid to ilow to it from the accumulator, but vents this icontrol exclusively through a separate exhaust path which is controlled by a valve that is actuated independently of accumulator pressure. Although the flow path to the selector control can pass through the start valve, preferably this path is controlled by a separate `valve which operates to pressu'rize the selector control before the start valve opens to deliver high pressure motive uid to the overcenter unit. In any event, it also is preferred that the start valve and the valving device be incorporated in a unitary package.

This application is a division of application Ser. No. 569,921, filed Aug. 3, 1966, now Patent No. 3,384,027.

This invention relates to hydraulic starting and pumping systems.

U.S. Patents 3,203,165, granted Aug. 31, 1965, and 3,234,889, granted Feb. 16, 1966, disclose systems of this kind which employ overcenter motor-pump units and which use an accumulator as the source of motive iluid for the starting operation. In each of these systems, the positioning mechanism for the displacement control element of the motor-pump unit includes a fluid pressure control motor, a lpressure responsive control valve having supply and exhaust positions in which it connects the control motor with the high pressure side of the system and the reservoir, respectively, and an actuating motor which is controlled by the engine start valve and which acts on the control valve in aid of its normal pressure reaction surface. During the starting cycle, the start valve connects the actuating motor with the high pressure side of the system for the purpose of holding the control valve in its supply position. On the other hand, during the pumping operation, the start valve vents the actuating motor and thereby allows the control valve to perform its normal supply and exhaust functions.

Experience with these prior systems indicates that if the start valve is maintained open, and consequently the actuating motor is maintained in communication with the high pressure side of the system, after either the accumulator is depleted of oil or the engine becomes self-sustaining, the displacement control element of the motorpump unit will oscillate rapidly between large displacement positions at opposite sides of the zero displacement position. The reason for this is that each of the events just mentioned causes a sudden, drastic reduction in the pressure in the high pressure side of the system which makes it impossible for the actuating motor to hold the ice control valve in its supply position. As a result, the control valve shifts to its vent position, the pressure in the control motor is suddenly dissipated, and the positioning mechanism rapidly moves the displacement control element over center. At this time, the motor-pump unit commences to discharge iluid to the high pressure side of the system and to raise its pressure. When the pressure is restored to the level required to enable the actuating motor to reposition the control valve in its supply position, the control motor is suddenly subjected to the full pressure then existing in the high pressure side of the system. Therefore, this motor rapidly shifts the displacement control element back to the other side of the zero displacement position and again reverses the direction of ow through the motor-pump unit. In cases where the engine is running, oscillation of the displacement control element continues until the start valve is closed and the control mechanism is set to hold the displacement control element at the proper side lof the zero displacement position for pumping operation. On the other hand, in the case of abortive starts, wherein the engine does not attain a self-sustaining speed, the oscillation continues until the torque load imposed by the motor-pump unit brings engine to rest. In either case, the oscillations produce pressure pulsations of large magnitude throughout the entire system which create excessive stresses in, and can even cause failure of, the various hydraulic components.

The object of this invention is to provide an improved starter system in which the severity of these oscillations of the displacement control element is greatly reduced. According to this invention, the system includes valving means for maintaining the actuating motor under the initial pressure of the accumulator from the commencement of the starting cycle until the start valve is closed. This improvement insures that the control valve will be maintained in its supply position regardless of the pressure in the high pressure side of the system, and thus absolutely prevents this valve from suddenly changing the pressure in the control motor. Now, the control motor always responds directly to the pressure in the high pressure side of the system during the starting cycle and does not produce the violent oscillations of the control element which have been encountered in the prior systems.

In the preferred embodiment of the invention, the valving means which insures proper operation of the actuating motor is incorporated in a package which also includes the engine start valve and a common actuator for the two valve units. This package may also incorporate means fo rinsuring that the positioning mechanism for the displacement control element is set for motoring operation before the motor-pump unit commences to develop torque. This feature precludes the undesirable momentary reverse rotation of the engine at the instant the start cycle is initiated which can be encountered with the prior systems. The packaged arrangement of the start valve and the valve means which controls the actuating motor is a desirable feature because it is less expensive than the alternative of providing separate valves, and, in addition, it permits the invention to be incorporated in existing systems in a routine manner by regular maintenance personnel.

The preferred and several alternative embodiments of the invention are described herein in detail with reference to the accompanying drawings in which:

FIG. l is a schematic diagram showing a hydraulic starting and pumping system of the type disclosed in U.S. Patent 3,234,889 and incorporating one form of the present invention. v

FIG. 2 is a schematic diagram of a similar starting and pumping system incorporating a second form of the invention.

FIG. 3 is a schematic diagram of the preferred valve package.

FIG. 4 is a sectional view of the actual preferred embodiment.

FIGS. 5 and 6 are sectional views taken on lines 5-5 and 6-6 of FIG. 4.

FIG. 7 is a sectional view taken on line 7-7 of FIG. 6and FIG. 8 is a sectional-view taken on lines 8 8 of FIG. 5 and lines 8--8 of FIG. 6.

The starting and pumping system shown in FIG. 1 is employed to start auxiliary and main turbine engines 11 and 12 and to provide hydraulic fluid under pressure to a utility circuit (not shown). The system includes an overcenter motor-pump unit 13 which is connected to drive and be driven by auxiliary engine 11, and which is provided with high and

low pressure ports

14 and 15 that are connected, respectively, with main conduit 16 and reservoir 17. Motive fluid for driving unit 13 as a motor is supplied by a gas-charged accumulator 18 through a

circuit including conduits

16a, 1611 and 16 and controlled by the auxiliary engine start valve 19. When unit 13 is being driven as a pump, it draws fluid from reservoir 17 and discharges it under pressure into conduit 16. This pressurized fluid may then flow to, and thus recharge, accumulator 18 through

conduits

16b, 16C and 16a, or pass through conduit 16d, main start valve 19 and conduit 16e to hydraulic starter 21, and thus be used as the motive lluid for starting main engine 12, or pass through conduit 16f to the utility circuit.

The start valves 19 and 19' are of the pilotoperated type disclosed in U.S. Patent 3,203,165, and each has a main valve which is spring biased to a closed position. When the pilot valve of either of the valves 19 and 1'9' is shifted from its venting to its pressurizing position by the associated

solenoid

19a or 19a', the connection between the piloted motor and reservoir 17 is interrupted, and this motor is connected with the conduit upstream of the start valve, that is, conduit 16a in the case of valve 19, and conduit 16d in the case of valve 19. As a result, the piloted motor shifts the -main valve to open position. Venting of either piloted motor allows the spring to close the main valve.

The displacement of and direction of ow through unit 13 is controlled by cam plate 22 which is movable in opposite directions from the illustrated neutral or zero displacement position about the axis of trunnion 23. Cam plate 22 is biased in the counterclockwise direction by a spring-motor assembly 24 including the coil compression spring 25 and a fluid pressure piston motor 26. The cylinder 27 of motor 26 is connected to the piston 28 of a shifting motor 29 and carries a spring seat having a longitudinal extension 31 which is arranged to abut the end of cylinder 32 when the two cylinders move toward each other. This extension 31 defines a limit stop for cam plate 22 which, during the pumping operation, prevents the cam plate from moving over center, i.e., through the neutral position. The piston 28 is designed to move between the illustrated position, in which it abuts stop 33, and a second position, in which its head abuts shoulder 34, for positioning assembly 24 for motoring and pumping operations, respectively.

Cam plate 22 is moved in the clockwise direction about the axis of trunnion 23 against the opposing bias of assembly 24 by a iluid pressure control motor 35. Fluid is supplied to and exhausted from the working chamber 36 of this motor through a pressure responsive control valve 37 with which it is connected by conduit 38. Control valve 37 includes an inlet chamber 39 which is connected with the main conduit 16 through conduit 16g, an outlet chamber 41 which communicates with conduit 38, an exhaust chamber 42 which is connected with reservoir 17, and a sliding valve spool 43. This valve spool has supply and exhaust positions and an intermediate lap position, and is biased to the illustrated exhaust position by a coil compression spring 44. In this position, land 45 isolates outlet chamber 41 from inlet chamber 39, and a tlat 46 on land 47 provides a flow path which connects outlet chamber 41 with exhaust chamber 42. The fluid pressure in chamber 39 acts upon the left end of spool 43 and serves to shift this member to the right, rst to a lap position in which lands 45 and 47 isolate chamber 41 from the other two chambers, and then to the supply position wherein land 47 continues to block communication between

chambers

41 and 42, and the flat 48 extending across land 49 connects outlet chamber 41 with inlet chamber 39.

The pressure in inlet chamber 39 required to hold valve spool 43 in the lap position against the opposition of spring 44 is termed the reference pressure, and Valve 47 includes two devices for changing this pressure. The rst, which raises the reference pressure, comprises a movable spring seat 51 for spring 44, and a piston motor which includes the right side of seat 51 and a working chamber 52. When working chamber 52 is vented, seat 51 assumes the illustrated low spring-load position, and, when the working chamber is pressurized, the seat is moved to the left to a high spring-load position defined by stop 53. A conduit 54 connects working chamber 52 with the pilot valve portion of main engine start valve 19', so that this chamber is vented and pressurized whenever the start valve 19 is closed and opened, respectively. The second device for changing the reference pressure acts to lower it from the normal value, and it comprises a piston motor 55 including the piston 56 which abuts the left end of spool 43, and a working chamber 57. The working chamber 57 is connected with the pilot valve portion of auxiliary engine start valve 19 through a pair of

conduits

58 and 59 and the valving device 100 provided by the present invention. As will appear below, this chamber 57 is continuously subjected to the initial pressure in accumulator 18 whenever valve 19 is open and, at all other times, it is vented to reservoir 17.

The piston 56 of motor 55 also serves as the valve spool of a selector valve 61 which simultaneously vents and pressurizes the working chambers 26a and 29a of motors 26 and 29. This valve comprises the inlet chamber 39 of control valve 47, an exhaust chamber 62 which is in continuous communication with reservoir 17, and an outlet chamber 63 which is connected with working chamber 29a'through conduit 64. An axial passage 28a in piston 28 interconnects working chamber 26a and 29a. During pumping operation, selector valve 61 assumes the illustrated position wherein land 65 blocks communication between

chambers

62 and 63, and the flat 66 extending across land 67

interconnects chambers

63 and 39. During thestarting operation, valve 61 shifts to the right to a position in which land 65 blocks communication between

chambers

63 and 39, and the at 68 extending across land 69 connects outlet chamber 63 with exhaust chamber 62. Thus, selector valve 61 vents and pressurizes the motors 26 and 29 during the pumping and motoring operations, respectively. Since the diameter of the end land 56 of piston 56 is greater than the diameter of lands 65 and 67, piston 56 will always shift to the right when the pressures in working chamber 57 and inlet chamber 39 are equal.

The valving device provided by the present invention includes a pair of ports 101 and 10-2 which are connected, respectively, with

conduits

59 and 58, and which are interconnected by passage 103 containing spring biased check valve 104. Check valve 104 is oriented to permit How from conduit 59 to conduit 58, but to block ow in the reverse direction. Valving unit 100 also includes an exhaust port 105 which is in continuous communication with reservoir 17 and which is connected with port 102 by a passage 106 containing a second spring biased check valve 107. The biasing spring 108 of this check valve has a movable seat 109 which is carried by the armature of a solenoid 111 so that the closing bias acting on the check valve changes as the solenoid is energized and de-energized. Solenoid 111 is connected in parallel with the solenoid 19a of auxiliary engine start valve 19 in an energization circuit which includes battery 112 and which is controlled by the manually operated start switch 113 and a speed controlled switch 114 that responds to the speed of engine 11.

Operation i Since U.S. Patent 3,234,889 contains a complete description of the operation of the system shown in FIG. l, and the improvements provided by the present invention affect only the motoring mode of operation, the following description of operation will treat only the starting cycle of engine 11.

Before commencement of the starting cycle, accumulator 1S is precharged with gas at a pressure of 1500 p.s.i. and is then charged with oil by a hand pump circuit (not shown). It is assumed that the fully charged pressure of the accumulator is 3000 p.s.i., and that the three reference pressures of control valve 37 are 1500 p.s.i., 3000 p.s.i. and 4000 p.s.i.

In order to start auxiliary engine 11 the operator closes switch 113 to energize solenoid 19a and open start valve 19. This permits uid from the accumulator 18 to ow into the high pressure port 14 of the motor-pump unit through

conduits

16a, 16h and 16, and also permits fluid at accumulator pressure to pass to the working chamber 57 of motor 55 through the pilot portion of valve 19, conduit 59, port 101, passage 103, check valve 104, port 102 and conduit 58. Since solenoid 111 is energized simultaneously with solenoid 19a, the load in spring 10S is now sufficient to keep check valve 107 closed and prevent bleed off of the pressure in working chamber 57. The pressure of 3000 p.s.i. in this chamber causes motor 55 to shift selector valve 61 to a position in which it vents motors 26 and 29, and to shift control valve 37 to its supply position in which control motor 35 is connected with main conduit 16. As a result, control motor 35 moves cam plate 22 in the clockwise direction to its maximum displacement position at the motoring side of neutral and maintains it in that position against the opposing bias of spring 25.

The fluid delivered to motor-pump unit 13 causes it to develop torque and accelerate engine 11. As the engine accelerates, the pressure of the uid delivered by accumulator 19 progressively decreases from its initial value of 3000 p.s.i. However, this change in pressure is not reected in working chamber 57 because the check valve 104 closes as soon as the pressure in conduit 59 begins to drop below the initial charge pressure of the accumulator. Therefore, as along as solenoid 111 is maintained energized and check valve 107 is held closed, the pressure in working chamber 57 remains at 3000 p.s.i. and valves 37 and 61 remain in their supply and vent positions, respectively` Because of this, the pressure in working chamber 36 of control motor 3S will be substantially the same as the pressure in main conduit 16 throughout the starting cycle.

Under normal conditions, engine 11 will have been ignited and will have achieved self-sustaining operation before accumulator pressure decreases to 1500 p.s.i. and the accumulator is depleted of oil. Since control motor 35 is dimensioned to hold cam plate 22 in the maximum displacement position as long as the pressure in its working chamber 36 is above 1500 p.s.i., it follows that the cam plate 22 in the normal case will not move away from its maximum displacement position during the starting cycle. When the engine reaches a self-sustaining speed, switch 114 automatically opens the holding circuit for switch 113 and allows this switch in tum to open and deenergize solenoids 19a and 111. De-energization of solenoid 19a allows auxiliary engine start valve 19 to close and interrupt the flow of iluid from the accumulator 18 to high pressure port 14. On the other hand, de-energization of solenoid 111 reduces the load in spring 108 and permits check valve 107 to open under the action of pressurized oil trapped in working chamber 57. Therefore, this oil may now escape to reservoir 17 through conduit 58, port 102, passage 106 and port 105. Since engine 11 is now driving motor-pump unit 13 as pump, and cam plate 22 is still at the motoring side of the neutral position, unit 13 will commence to evacuate 4main conduit 16. As a result, the pressure in this conduit and in the working chamber 36 of control motor 35 will decrease well below 1500 p.s.i., and spring 25 will move cam plate 22 in the counterclockwise direction to a small displacement position at the pumping side of the neutral position. At the same time, spring 44 will return

valves

36 and 61 to their illustrated vent and supply positions, repsectively. As soon as cam plate 22 moves over center, unit 13 cornmences to discharge oil under pressure to conduit 16 and thus quickly restores its pressure to 1500 p.s.i. As this is happening, selector valve 61 transmits system pressure to shifting motor 29 and causes it to move the spring-motor assembly 24 to its pumping position wherein the stop dened by extension 31 is effective to prevent the cam plate 22 from moving back to the motoring side of neutral. Cam plate 22 will now assume a position in which the displacement of unit 13 is equal to the rate of leakage from the system. At this time the pressure in inlet chamber 39 of valve 37 will move spool 43 to its lap position.

ln the abnormal case, where accumulator 18 is given an inadequate gas precharge or is charged with an insuicient quantity of oil from a start cycle, the engine 11 does not achieve a self-sustaining speed by the time accumulator 18 is depleted of oil. When this happens, the engine 11, which has considerable momentum, will cornmence to coast and drive unit 13 as a pump. Since cam plate 22 is at the motoring side of neutral position, unit 13 will draw fluid from conduit 1'6 and discharge it to reservoir 17. This pumping action will quickly decrease the pressure in conduit 16 toward zero. In the prior system of Patent 3,234,889, wherein cond-uit 58 is in constant, direct communication with conduit 59, this change in pressure causes valves 37 and 61 to shift to their exhaust and supply positions, respectively. This action resulted in sudden venting of working chamber 36, and in sudden pressurization of working chambers 26a and 29a, and caused the controls for cam plate 22 to move it rapidly to a large, and perhaps even the maximum, displacement position at the pumping side of neutral. Unit 13 would then commence to discharge oil to conduit 16 and recharge accumulator 18. As soon as the pressure in conduit 16 was restored to 1500 p.s.i., valves 37 and 61 would shift back to their supply and vent positions, respectively, and suddenly apply full system pressure to working chamber 36 and vent working chambers 26a and 29a. Now the controls would shift cam plate 22 rapidly back to a rather large displacement position at the motoring side of neutral. At this point, unit 13 would again commence to act as a motor and drive engine 11. However, as soon as accumulator 18 was again depleted of oil, the controls would produce another violent oscillation of cam plate 22. These oscillations continued until the engine 11 came to rest, and, since they were accompanied by severe pressure pulsations in the conduits connected with

ports

14 and 15, there was ample opportunity for the system components to be damaged.

In contrast to this, the valving device provided by the present invention holds the initial charge pressure of accumulator 18 in working chamber 57, and thus enables motor 55 to keep valves 37 and 61 in their supply and eX- haust positions, respectively, as long as solenoid 111 remains energized. Therefore, in this system the pressure changes in conduit 16 always are reflected directly in working chamber 36, and cannot cause valve 61 to pressurize motors 26 and 29. With this arrangement, motor 35 and spring 25 still move the cam plate 22 back and forth across the neutral position during an abortive start, but the rate of movement of the cam plate and the amplitude of its oscillation are much less than in the prior system. Actual experience with this improvement shows that it reduces to tolerable levels the pressure pulsations encountered during abortive starts.

Another abnormal case in which the invention effects an improvement concerns starts in which the switch 114 fails to open when the engine 11 reaches a self-sustaining speed. This situation produces the same effect as an abortive start, except that the unit 13 operates continuously as a pump which discharges alternately through

ports

14 and 15, and, since the engine is running under its own power, the oscillations of cam plate 22 continue until start switch 113 is opened manually. As in the case of the abortive start, the valving device 100 so reduces the severity of these oscillations that the pressure pulsations are kept within tolerable limits.

The FIGURE 2 embodiment The system shown in FIG. 2 is generally the same as the one of FIG. l, except that here the valves 204 and 207, which correspond to check

valves

104 and 107 embodied in the device 100 of FIG. 1, are combined with the auxiliary engine start valve in a single package 200. In this case, the passage which interconnects ports 1 and 202 has two enlarged sections 203m and 203b, which are separated by the main poppet 215 of the start valve, and the latter section leads to a delivery port 216 as well as to check valve 204. The

elements

201, 203a, 203b and 216 dene the supply path through which motive fluid is delivered to the motor-pump unit 13. The main poppet 215 is urged toward its seat 217 by a coil compression spring 218 and by the fluid pressure in a pilot chamber 219 which acts upon its upper surface 221. The poppet is shifted in the opening direction against this bias by the pressure in passage section 203a which acts upon the annular shoulder 222. Pilot chamber 219 is connected with inlet port 201 by passage section 203a and a restricted passage 223 formed in the poppet, and is connected with exhaust port 205 through a path comprising passages 224 and 225 and controlled by a pilot valve in the form of spring biased check valve 226. This check valve is oriented to normally block flow from pilot chamber 219, but is opened by push rod 227 whenever solenoid 211 is energized to hold valve 207 closed.

The valving package 200 is incorporated in the system by connecting

ports

202 and 205 with conduit 58 and reservoir 17, respectively, by connecting port 201 directly with accumulator 18 through conduit 16a, and by connecting port 216 with the

conduits

16b and 16 leading to the high pressure port 14 of motor-pump unit 13. This last mentioned connection includes a check valve 228 which permits ow from, b-ut not into, passage section 203b. When the FIG. 2 system is in standby condition, solenoid 211 is de-energized and

valves

204, 207 and 226 assume their illustrated positions. Although the fluid in passage section 203g is subjected to the full charge pressure of accumulator 18, and thus tends to open main poppet 215, the uid in pilot chamber 219 is under the same press-ure and acts on a larger reaction surface, namely upper surface 221. Therefore, the net pressure force acting on the poppet 215 supplements the biasing force developed by spring 218 and holds poppet 215 tightly against its seat 217. This precludes leakage from accumulator 18.

In order to start engine 11, the start switch (not shown) is closed to energize solenoid 211 and cause it to close and open the valves 207 and 226, respectively. Opening of valve 226 allows oil to escape from pilot chamber 219 to reservoir 17 at a rate greater than that at which it can enter this chamber through restricted passage 223. As a result, the pressure in chamber 219 decreases below that in passage section 203a, and the net pressure force acting on poppet 215 shifts this member to open position against the opposition of spring 218. Fluid under accumulator pressure now is delivered to the high pressure port 14 of unit 13 via passage section 203]), port 216, and con- 8

duits

16b and 16, and to the working chamber 57 of actuating motor 55 through passage section 20312, check valve 204, port 202 and conduit 58. The FIG. 2 system now effects starting of engine 11 in the same way as the FIG. 1 system.

During a normal starting cycle, solenoid 211 is de-energized as soon as engine 11 becomes self-sustaining. Therefore, at this time, valves 207and 226 are allowed to open and close, respectively. As soon as valve 226 closes, the pressures in chamber 219 and passage section 203a equalize, and main poppet 215 closes. Simultaneously, opening of Ivalve 207 automatically sets the controls for unit 13 to their pumping condition. Therefore, this unit can now recharge the accumulator 10 and perform its other pumping functions. In the case of an abortive start or a failure of switch 114, the valving device 200 serves to prevent violent oscillations of the cam plate of unit 13 in the way as its counterpart in FIG. l. While the cyclic variations in the pressure in conduit 16b during these conditions are reflected in passage section 203a, and may cause closing and opening movement of main poppet 215, this will not adversely affect the performance of the motorpump unit 13 or the starting system.

The preferred embodiment The preferred valving device 300, which is illustrated schematically in FIG. 3, is similar to device 200 in that it incorporates the start valve and the check valves necessary to trap fluid in actuator motor 55. However, in this embodiment, the path between the pilot chamber 319 of the start valve and exhaust port 305 includes a flow restrictor 329, and the inlet and

outlet ports

301 and 302 are interconnected by a path which comprises

passages

331 and 332 and which is controlled by check valve 333 rather than main pop-pet 315. The check valve 333 normally blocks flow from port 301 to port 302, but is mechanically unseated to permit such flow by an actuating rod 334 which is operated by solenoid 311. Thus, when the solenoid is energized to effect opening of pilot valve 326 and closure of the vent valve 307, it simultaneously opens valve 333 and permits fluid under accumulator pressure to flow to the actuating motor 55 through a path comprising port 301,

passages

332 and 331, valve 304, outlet port 302 and conduit 58.

It will be observed that, since spring 25 in motor-pump unit 13 biases cam plate 22 to a position at the pumping side of neutral when the starting system is at rest, unit 13 will momentarily rotate engine 11 in the reverse direction at the commencement of the starting cycle if it commences to develop torque before the controls have y been energized to move the cam plate over center. The preferred embodiment eliminates this condition. This is accomplished by so sizing flow restrictor 329 that, when

valves

326 and 333 are first opened, fluid under accumulator pressure is transmitted to outlet port 302 before the pressure in pilot chamber 319 can decrease suliciently to permit opening of main poppet 315. As a result of this delay, actuating motor 55 Will have time to shift valves 37 and 61 to the positions required for motoring operation before high pressure port 14 is subjected to full accumulator pressure. Since shifting of these valves vents motors 26 and 29 and places motor 35 in direct communication with conduit 16, and since the pressure required by motor 35 to shift the cam plate over center is much less than the pressure required by unit 13 to satisfy the break away torque requirement of engine 11, it should be apparent that, when main poppet 315 opens and the pressure in conduit 16 rises, motor 35 will move the cam plate to the motoring side of neutral before the unit 13 commences to rotate. Thus, the valving device 300 precludes any reverse rotation of engine 11.

It should -be noted that since outlet port 302 in the FIG. 3 embodiment is isolated from the high pressure conduit 1611 when solenoid 311 is de-energized, systems in- 9 corporating this form of the invention do not require the check valve 228 used in FIG. 2.

The details of the actual valving device 300 are shown in FIGS. 4-8, wherein the counterparts of the components shown in FIG. 3 are, as far as possible, identified by the same reference numerals. While the construction of this embodiment will be apparent from an inspection of these gures, it will be helpful to describe specifically the following flow paths shown schematically in FIG. 3:

(l) The path connecting inlet port 301 with check valve 333 is shown in FIG. 4 and comprises annular groove 303a formed in the outer periphery of sleeve 335, drilled housing passage 332a, annular housing chamber 332b, longitudinal passage 332e defined by a fiat on the outer periphery of sleeve 336, and

radial passages

332d and 332e.

(2) The path connecting check -valve 333 with port 302 is shown in FIGS. 4 and 5 and comprises axial passage 331a formed in block 337, drilled passage 331b, annular housing groove 331e, drilled

housing passages

331d, 331e and 331f, axial passage 331g formed in the seat sleeve 338, check valve 304, and the axial passage 331k formed in fitting 339.

(3) The path connecting outlet port 302 with exhaust port 305 is shown in FIGS. 5-8 and comprises axial passage 33111, radial passages 306a, and 30612, longitudinal passage 306C defined by a fiat on the outer periphery of sleeve 341 (see FIG. 5), annular housing chamber 306a', drilled housing passage 306e, housing chamber 306f (see FIGS. 6 and 8), slot 306g formed in plug 342, axial passage 30611 in seat block 343, check valve 307, radial passages 3061' and 3061' formed in sleeve 344, chamber 306k, drilled passage 3061, annular housing chamber 306m, and drilled housing passage 306n (see FIG. 7).

(4) The path connecting pilot chamber 319 with exhaust port 305 is shown in FIGS. 4 and 7 and comprises slot 325a formed in spring seat 345, check valve 326, chamber 325b formed in insert 346, drilled passages 325C and 325d formed in Iblock 347, annular housing chamber 325e, and drilled housing passage 30611. In this embodiment, either passage 325a or passage 325:1 may serve as the flow restrictor 329 of FIG. 3.

Although We have referred to two specific starting systems in which the invention may be used, it should be understood that there are other types of hydraulic starting systems which present the problem which the invention solves. One such system which deserves mention is disclosed in U.S. Patent 3,106,057, granted Oct. 8, 1963. In cases where the cam plate of the motor-pump unit in this prior system is provided with an unbalanced control, i.e., a control which automatically moves the cam plate to a pumping position rather than the neutral position when the accumulator is fully discharged, intolerable oscillations of the cam plate can occur under the two abnormal conditions mentioned earlier. The severity of these oscillations can be reduced by incorporating the present valving device in conduit 75 of the patent so that it serves to maintain motor 53 at'the initial charge pressure of the accumulator throughout the starting cycle.

As stated previously, the drawings and description relate only to the preferred and several alternative embodiments of the invention. Since the structures of these embodiments can be changed in many respects without departing from the inventive concept, the following claims should provide the sole measure of the scope of the invention.

What we claim is:

1. A valving device (100, 200 or 300) comprising a housing containing (a) three ports (101, 102, 105; 201, 202, 205 or 301,

302, 305); (b) a first passage (103; 203a, 203b or 303a, 331,

332) interconnecting the first and second ports;

(c) a check valve (104, 204 or 304) in the first passage arranged to prevent flow toward the first port;

(d) a second passage (106, 206 or 306) interconnecting the second and third ports;

(e) a second valve (107, 207 or 307) for opening and closing the second passage; and

(f) an actuator (111, 211 or 311) for operating the second valve independently of the pressure at the first port and of the rate of fiow from the first port to the second port.

2. A valving device (200) as defined in claim 1 which also includes (a) a third valve (215) interposed in the first passage between the check valve (204) and the first port (201) and arranged to open and close that passage;

(b) means (218) biasing the third valve closed;

(c) a fourth port (216) connected with the first passage at a point between the third valve (215) and the check valve (204);

(d) a third passage (219, 224, 225) interconnecting the first and third ports and containing a ow restriction (223);

(e) a fourth valve (226) interposed in the third passage between the flow restrictor (223) and the third port (205), the fourth valve being operated by said actuator (211) so that it opens and closes the third passage as the the second valve (207) closes and opens, respectively, the second passage (206);

(f) means (222) responsive to the pressure in the third passage lbetween the first port (201) and the flow restrictor (223) for urging the third valve (215 in the opening direction; and

(g) means (221) responsive to the pressure in the third passage between the flow restrictor (223) and the fourth valve (226) for urging the third valve (215) in the closing direction.

3. A valving device (300) as defined in claim 1 which also includes (a) a fourth port (316);

(b) a third passage (303a, 303b) connecting the fourth port (316) with the first port (301) and controlled by a third valve (315);

(c) a fourth passage (319, 324, 325) interconnecting the first and third ports (301, 305) and containing a flow restrictor (323);

(d) means (318) biasing the third valve (315) toward closed position;

(e) a fourth valve (326) interposed in the fourth passage between the flow restrictor (323) and the third port (305) `for controlling fiow through this passage;

(f) a fifth valve (333) interposed in the first passage (30311, 331, 332) between the first port (301) and the check valve (304) for controlling flow through this passage;

(g) means responsive to the pressure in the fourth passage between the first port (301) and the flow restrictor (323) for urging the third valve (315) in the opening direction;

(h) means (321) responsive to the pressure in the fourth passage between the flow restrictor (323) and the fourth valve (326) for urging the third valve (315) inthe closing direction; and

(i) means connecting the fourth (326) and fifth (333) valves with said actuator (311) so that these two valves are opened and closed, respectively, as the second valve (307) is closed and opened,

(j) the restriction to flow through the fourth passage from the flow restrictor (323) to the third port (305) being greater than the restriction to flow through the first passage from the first port (301) to the second port (302).

4. A valving device (300) as defined in claim 3 wherein (a) the second, fourth and fifth valves (307, 326, 333) are spring biased check valves, each valve having a stationary seat and a movable head whichis biased by a spring toward the seat, the fourth and fifth valves l(326, 333) being Oriented to prevent flow from the irst port (301), and the second valvev (307) being oriented to prevent fiow from the third port (305); and

(b) the actuator (311) comprises means (309, 327, 324) for mechanically moving the heads of the fourth and fth valves (326, 333) away from their seats While simultaneously increasing the load in the biasing spring (308) of the second valve (307), and for'allowing the heads of the fourth and fifth valves (326, 333) to move toward their seats while simultaneously decreasing the load in the spring (308) of the second valve (307 References Cited UNITED STATES PATENTS McKee 137-609 XR Betz 137-609 XR Tear 137-608 XR Baker 137-609 XR Guinard 137-609 XR Watson 137-609 XRl Froshe 137-609 XR Suechting 137-609 Doolittle et al. 137-609 XR SAMUEL SCOTT, Primary Examiner