US3362335A - Control system for fluid pressure source - Google Patents

Description

Jan. 9, 1968 w T. STEPHENS ETAL 3,362,335

CONTROL SYSTEM FOR FLUID PRESSURE SOURCE Filed March '7, 1966 p/zerzs, w tDavz'cZNPreUa Z'Z'ei."

United States Patent 3,362,335 CQNTROL SYSTEM FOR FLUID PRESSURE SOURCE William T. Stephens, Mentor, Ohio, and David N. Prevallet, Auburn, lind., assignors to Borg-Warner Corporation, Chicago, 11]., a corporation of Illinois Filed Mar. 7, 1966, Ser. No. 532,206 3 Claims. (Cl. 103-42) ABSTRACT OF THE DISCLOSURE A fluid pressure supply system having a fluid pump with two by-pass passages, one of said passagesbeing controlled by a manually actuated valve and the other being controlled by an automatic, damped pressure relief valve. The dual valve by-pass system allows the pump to operate without load upon starting and with full load when operating rpm. is reached.

This invention relates to a fluid pressure supplying device and more particularly relates to a fluid pressure supplying mechanism including an electric motor, a pump and an improved control valve mechanism for the pump.

It is an object of this invention to provide a fluid pressure supply device of the kind described having an improved control system including a control valve which, upon actuation of the motor, will initially open the main pressure supply passage to the sump and then gradually interrupt the connection as fluid pressure builds up. In this manner the electric motor is allowed to attain full or operational r.p.m. before being placed under load and thereby enable use of less powerful and less expensive electric motors for this type of installation.

The invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above stated object and such other objects as will appear from the following description of preferred embodiments of the invention illustrated with reference to the accompanying drawings wherein:

'FIGURE 1 is an overall view of the motor pump combination;

FIGURE 2 is a cross-sectional view taken along line 22 of FIGURE 1;

FIGURE 3 is a view illustrating the control valve in an operating position; and

FIGURE 4 is a modification of the structure of FIG- URE 2 illustrating a different type of control valve.

Referring to FIGURE 1, there is shown a motor 10, a valve casing 11 and a sump 12. Within the sump 12 is a pump 13. The combination shown in FIGURE 1 is a well known structure used as a pressure source in many environments wherein the unit can be mounted and the motor connected to a source of electrical energy to provide fluid pressure for performing work at desired locations.

' Referring to FIGURE 2, the improved control system for the motor-pump combination is illustrated. The control system for the pump 13 includes a manual valve 15, a check valve 16, and a variable pressure relief valve 17 mounted in casing 11. A manual lever 20 is provided which is mounted by a pin 21 to a valve casing 11 for rotation about the pin 21. The lever is operatively associated with an electrical switch 22 which is operative when actuated by manual lever 20 to connect the motor 10 to a source of electrical energy thereby activating motor 10 and operating pump 13. A spring 23 is provided which engages both the manual lever 20 and the valve casing 11. Manual lever 20 has a cam 24 formed on the end thereof which is operatively associated with manual valve 15.

The manual valve 15 includes a piston engaged by cam 24 and a smaller piston 31 each slida-ble Within a bore 32. Piston 31 has a ball 33 mounted on the right hand side thereof as viewed in FIGURE 2. An insert 34 is provided in bore 32 providing a seat 35 for ball 33.

A spring 38 urges the pistons 30 and 31 apart. Slots 39 are provided in piston 31 which allow fluid to pass therethrough. A return fluid passage 40 is provided which connects the bore 32 to the sump of the pump 13.

Valve casing 11 has a main pressure supply or output conduit therein having an access opening 46 to which may be connected a fluid pressure line leading to the hydraulic work cylinder or other device requiring fluid pressure. A branch passage 47 connects the manual valve 15 to the main pressure supply passage 45. Also provided in valve casing 11 is a port 50 which is connected to the output portion of pump 13. Port 50 is connected to a fluid passage 51 in casing 11.

A branch passage 52 connects passage 51 to relief valve 17. Passage 51 is connected to main pressure supply passage 45 through the check valve 16.

Check valve 16 is contained within a stepped bore 55 and is provided with a cap screw 56 to close the end of bore 55 and prevent leakage therefrom. The check valve 16 includes a ball 57 and a spring 58 engaging the ball 57 and urging it into engagement with a seat 59 provided on the end of fluid passage 51. Thus when the fluid pressure is higher in conduit 45, the check valve 16 will close and prevent flow of fluid pressure from conduit 45 into passage 51 and when the pressure in passage 51 connected to the pump outlet is at higher pressure than in conduit 45 ball check valve 16 will open and allow fluid pressure to flow into conduit 45 from passage 51.

The relief valve 17 is mounted within a bore 60 provided in valve casing 11. The bore 60 is provided with screw threads at 61. Bore 60 receives a valve sleeve 62 provided with external threads 63 by means of which the valve sleeve is secured within the bore 60. The valve sleeve 62 has a stepped bore 64 provided therein. A counter bored portion 65 is provided in bore 64 providing shoulders 66.

Enclosing the lower end of bore 64 is a plug 68 having external threads 69 thereon engaging mating threads within the bore 64. End plug 69 also includes a slot 70 for reception of the head of a screw driver by means of which the position of plug 68 may be adjusted. Mounted within bore 64 is a pilot piston 72 having a conical section 73. Springs 74 and 75 are provided which engage plug 68 and pilot piston 72. Adjustment of plug 68 thus will vary the spring loading on pilot piston 72.

Mounted within the. counter bore 65 is a piston 77 which has a central bore 78 extending therethrough. Piston 77 has a head portion 79 and body portion 81. Head portion 79, counter bore 65, body portion 81 and shoulders 66 define a damping chamber 82. A small or restricted passage 83 is provided which connects central bore 78 and the damping chamber 82. Piston 77 is thus slidable in an up and down direction as illustrated in FIGURE 2 within the counter bore 65. Conical portion 73 on pilot piston 72 may engage the end of central bore 78 in piston 77 and thus provide a fluid seal of bore 78 to block fluid communication between bore 78 and bore 64 of sleeve 62.

The operation of the described motor pump combination and improved control mechanism is as follows: spring 23 which engages the mnaual lever will hold the manual lever 21) in the position illustrated resting against electric switch 22 and at this time holding the ball 33 of piston 31 against the seat blocking fluid communication between output conduit and return passage 40. If the manual lever is moved counterclockwise slightly, the manual lever will close switch 22 thereby activating electric motor 10. With the manual lever in this position the ball 33 is held tightly aaginst seat 35 insuring the closure of branch passage 47, thus as the pump begins to pump fluid, fluid pressure would ordinarily be able to at this time flow to the hydraulic work cylinder or other device performing work.

When the switch 22 is actuated and the motor begins to operate pump 13, relief valve 17 is so designed that initially even with low pressure in passage 51 connected to the output port of pump 13, the pilot piston 72 will move from engagement with bore 78 and open pump output passage 51 to return through passage 35. Due to operation of relief valve 17 the electric motor initially has very little load imposed on it and may accelerate to operational r.p.m. before being placed under full load. When pressure in passage 51 is the same as pressure in passage 45, check valve 16 will open and allow fluid pressure to flow into output conduit 45 to flow to the hydraulic work cylinder.

The initial pressure in passage 51 will act on the upper surface of piston 77 tending to move piston 77 down as illustrated in FIGURE 2. As piston 77 is moved down, the force from springs 74 and '75 on poppet 73 is increased resulting in increased pressure in passage 51 to force oil past poppet 73. Piston 77 can move down until the head portion 79 engages the shoulder 66, formed by counter bore 65. In this position the relief setting will be at its maximum as determined by the position of plug 68. The time required for the piston 77 to move from one position to the other depends on the diameter of the small restricted radial passage 33, which relieves fluid from damping chamber 82.

Two springs, such as 74 and 75, are preferably used to provide the spring force on poppet 72. This eliminates the necessity of close tolerances, and provides a wider relief valve adjustment range. By using one spring with a low rate to hold the poppet 72 in place when the system is not pressurized, the relief valve has a low setting that will not change much with changes in dimensions and position of plug 68. The other Spring is a high rate spring which provides most of the force at the maximum pressure setting.

When the work cylinder has moved the load to the desired position the operator may let go of the manual lever 21) and the manual lever 20 will return from its counterclockwise position to the position illustrated in FIGURE 2 due to action of spring 23. In this position the connection between passage 45 and return passage 40 is still interrupted and an equilibrium position will thus be attained to hold the load such as a platform on the rear of a truck in selected position. When the manual lever 21)- is returned to the FIGURE 2 position switch 22 is no longer closed and the pump and motor stop operating. The operator may at this time when it is desired to lower the load, move the manual lever 20 clockwise which, due to the shape of the cam 24 on manual lever 20, will lighten the spring load of spring 38 on piston 31 and by careful adjustment of manual lever 20, the operator may thus allow fluid pressure to escape from passage 45 into return passage 40 and slowly lower the load. The operator may also allow manual lever 20 to return to its illustrated position which would again close off branch passage 47 and hold the load in some desired mid-position. Piston 31 and ball 33 can also be designed to act as a relief valve which, by selection of the size of spring 34, will allow only a predetermined maximum pressure in conduit 45 and prevent too high a pressure being attained in the system.

From the above it will be apparent that an improved control system has been devised for the motor-pump configuration disclosed due to the function of improved and novel valve 17. Electric motors of a smaller size and thus less expensive may be used in the environment described, since the motor is allowed to attain operational r.p.m. before being placed under load. Valve 17 initially dumps the pressure output side of the pump 13 to the sump and slowly builds up to its relief setting so that the motor has time to achieve operational r.p.m. before being loaded. The valve 17 is advantageous in that it is of simple construction and is adjustable in operation to accommodate various operational characteristics by adjustment of the spring loading on pilot piston 72.

Referring to FIGURE 3, valve 17 is shown in an intermediate position in which the piston 77 has moved down and is engaging conical portion 73 on pilot piston 72 and thus interrupting the connection from passage 51 to return passage 85.

Referring to FIGURE 4, a modified form of the valve 17 is illustrated although the construction of FIGURE 2 is the preferred construction. In FIGURE 4 control valve 17a is illustrated mounted in the valve casing 11a and has a stepped bore having a screw threaded portion 111. Secured within the bore 110 is a sleeve having threads 116 thereon, engaging threads 111. The sleeve 115 has a slot 117 for accommodation of a screw driver to provide for adjustment of the sleeve 115. The sleeve 115 has a stepped bore 124} therein in which is mounted a slidable piston 121. The branch passage 52a is connected to fluid passage 51a. A return fluid passage 125 opens into the stepped bore 110.

Slidably mounted within the piston 121 is a hollow tube 126. The tube 126 has a semi-spherical closure member 130 mounted on the upper end thereof which has a small bore or orifice 131 therethrough which communicates with the interior of tube 126. The hollow portion of the tube 126 at the lower end has an outlet port 132 which opens into the stepped bore 120 on the lower side of piston 121. Also mounted on the hollow tube 126 is a spring engaging member 135 which is engaged by spring 136 mounted within stepped bore 120. An additional spring 137 is provided which engages the closure member 130 and the slidable piston 121.

The operation of the control valve 17a illustrated in FIGURE 4 is similar to the operation of valve 17 of FIGURE 2 as described above and can be substituted for valve 17 in the device of FIGURE 2. As was the case with regard to the structure in FIGURE 2 when the pump initially begins to operate a small amount of fluid pressure in passage 51a will act on closure member 130 to move the closure member 130 away from its fluid blocking position with respect to branch passage 52a and will open fluid passage 51a to return through passage 125. At this time the electric motor has time to attain operational r.p.m. while the fluid pressure is increasing. As the pressure begins to build up in passage 51a it is admitted through restricted passage 131 into the interior of tube 126. Fluid pressure thus flows through tube 126 and out port 132 into the bore 120 on the lower side of the piston 121. As this pressure then accumulates and builds up in the bore 120 on the lower side of piston 121 the piston 121 will begin to move up as illustrated in FIG- URE 4. Piston 121 will increase the spring load due to s ring 137 on the closure member 130 and thus cause the pressure in passage 52a to increase.

It will be apparent that the operation of valve 17a is similar to that of valve 17 of FIGURE 2 in that the electric motor is allowed to attain operational r.p.m. before being placed under load and the load is imposed gradually as the relief setting is increased. Valve 17a likewise is adjustable in operation, by means of a screw driver slot 117 to increase the spring loading on the closure member 130, to provide various operational characteristics desired.

From the above it will be apparent that a new and novel control system has been provided which in the described fluid pump and electric motor combination allows use of less powerful and more economical electric motors than heretofore used since the motor is not under full load when it initially begins to operate the pump.

Various features of the invention have been particularly shown and described; however, it should be obvious to one skilled in the art that various modifications may be made therein without departing from the scope of the invention.

We claim:

1. In a system for supplying fluid pressure including a fluid pump; a control system connected to said pump comprising a manual by-pass valve and a pressure relief valve, said pressure relief valve including a piston and a pilot member, an output conduit connected to said pump, a first branch passage connecting said output conduit to said manual valve, a first return passage connecting said manual valve to the input of said pump, said manual valve control-ling fluid flow between said first branch passage and said first return passage, a second branch passage connecting said output conduit to said relief valve, a second return passage connecting said relief valve to the input of said pump, said piston having passage means to conduct fluid therethrough to establish fluid communication between said second branch passage and said second return passage, said pilot member being resiliently urged to block flow through said passage means and to interrupt said communication, fluid pressure in said second branch passage urging said pilot member to establish said communication, said piston being further movable toward said pilot member to interrupt said communication upon pressure increases in said second branch passage, whereby pressure in said second branch passage urges said pilot member to a position establishing said communication and as said pressure increases said piston moves toward said pilot member to interrupt said communication thereby allowing said communication upon initial pump operation and gradual interruption of said communication as said pump attains operational rpm. and is placed under load.

2. A system as claimedin claim 1 further including damping means in said relief valve to retard movement of said piston.

3. A system as claimed in claim 2 wherein said damping means comprises a fluid chamber partially defined by said piston and a restricted passage connecting said chamher to said fluid conducting passage means in said piston.

References Cited UNITED STATES PATENTS 2,026,938 1/1936 Eiserer -97 2,280,291 4/1942 Joseph 103-42 2,544,990 3/ 1951 Harrington et al. 103-136 X 2,759,423 8/1956 Keel 103-5 2,925,786 2/1960 Hill 103-42 X 2,970,818 2/1961 Kish et al 103-25 X 3,054,354 9/1962 Granbery 103-42 3,066,610 12/1962 Swanson 103-42 X 3,092,037 6/ 1963 Rhodes 103-42 X 3,096,927 7/1963 Wahl 230-31 X 3,193,184 7/1965 Hopper 230-31 DONLEY J. TOCKING, Primary Examiner.

' w. J. KRAU 5, Assistant Examiner.

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