Fluid motor throttle valve means responsive to motor exhaust pressure

April 3, 1962 w. e. herr 3,027,902

FLUID MOTOR THROTTLE VALVE MEANS RESPONSIVE TO MOTOR EXHAUST PRESSURE

Filed March 31, 1960

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ATTORNEY

3,027,902

Patented Apr. 3, 1962

United States Patent Office

3,027,902

FLUID MOTOR THROTTLE VALVE MEANS RESPONSIVE TO MOTOR EXHAUST PRESSURE

Warren E. Herr, Hasbrouck Heights, N.J., assignor to Specialties Development Corporation, Belleville, N.J., a corporation of New Jersey

Filed Mar. 31, 1960, Ser. No. 18,974

Claims. (Cl. 137—37)

The present invention relates to compressors, and, more particularly, to improvements in compressor systems including an air compressor and a hydraulic motor for driving the compressor.

In multi-stage air compressors of the type disclosed in United States Patent No. 2,827,227, the first stage piston is positively driven by an eccentric on a shaft powered ‘ by a rotary hydraulic motor and the subsequent stages are driven by cam faces on the eccentric which engage floating pistons. Such compressors are operated to maintain ? a volume of air at a given pressure within a reservoir, ' and when the air in the reservoir reaches that pressure the compressor may be stopped by interrupting flow of hydraulic fluid to the hydraulic motor. Also, the flow of hydraulic fluid may be interrupted for other reasons thereby causing the compressor to stop.

Since the hydraulic fluid is pressurized by a pump which usually is driven from a main drive shaft of an engine operated at variable speeds, a regulating valve is provided for controlling the rate of flow of the hydraulic fluid to the hydraulic motor to maintain the motor and compressor speed practically constant. Such valves must be opened more as the rate of flow of the fluid from the pump decreases, whereby when flow is interrupted completely the regulating valve has moved to an excessive fully open position. Thus, should fluid flow at a high rate be reestablished, the hydraulic motor and the compressor are restarted at a high speed.

It has been found, that, when the compressor is subjected to high starting inertia, the eccentric, the cams and the elements associated therewith are subjected to severe strains and stresses which ultimately shorten the useful life of the compressor by the breakage of parts on which excessive forces have been exerted for a number of times.

Accordingly, an object of the present invention is to provide an improved compressor system which is not subject to the foregoing objections and disadvantages.

Another object is to provide such a system wherein excessive opening of the regulating valve is prevented after the supply of hydraulic fluid to the motor has been interrupted.

A further object is to accomplish the foregoing in a simple, practical and economical manner.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been • chosen for purposes of illustration and description, and is i shown in the accompanying drawing, forming a part of the specification, wherein:

t' The single FIGURE is a schematic view, partly in secf tion, of a system in accordance with the present invention.

Referring to the drawing in detail, there is shown a compressor system which generally comprises an air compressor 10 such as disclosed in Patent 2,827,227, a rotary hydraulic motor 11 having a shaft 12 for driving the compressor, a valve 14 for regulating the rate of flow of hydraulic fluid to the motor, a rotary pump 15 having a shaft 16 driven by a variable or fixed speed engine (not shown) for pressurizing the hydraulic fluid, and a reservoir 17 for the hydraulic fluid connected to the input side of the pump 15. In a practical system, various 5 valves and controls are included in the system, but these are not shown because they would not further the understanding of the present invention.

The valve 14 comprises a body 18 having a cylinder 19 at one end, a bore 20 extending from the cylinder to 10 the other end of the body, a valve port 21 between the ends of the bore, an inlet 22 to the bore between the cylinder 19 and the valve port 21 connected to the output side of the pump 15, a passageway 24 connecting the valve port to the inlet of the hydraulic motor, a bore 25 15 connected at one end to the outlet of the hydraulic motor and at the other end to the reservoir, a passageway 26 connecting the bore 25 to an opening 27 at one end of the cylinder 19, a passageway 28 connecting the bore 25 to an opening 29 at the other end of the cylinder, and a 20 fluid flow restriction 39 in the bore 25 between the passageways 26 and 28.

The valve 14 further comprises a rod-like valve member 31 having enlarged end portions 32 and 33 slidably fitted in the bore 20 and having a reduced intermediate 25 section 35 provided with a tapered zone 36 at the end portion 32 for cooperating with the port 21 to meter the hydraulic fluid, a piston 37 slidably mounted in the cylinder 19 and connected at one side to the valve member end portion 33, and a spring 38 in the cylinder between 30 its end wall adjacent the opening 29 and the other side of the piston for biasing the valve member 31 in a direction to move the reduced section 35 thereof through the port 21. A passageway 39 extends through the valve member 31 and the piston 37.

In order to prevent the valve member 31 from being moved to a fully open position by the spring 38 when the flow of fluid from the pump 15 is interrupted, a stop member 40 is secured into the end of the bore 20 at the end opposite the cylinder 19 which is adapted to be engaged 40 by the valve member portion 32 to limit the movement of the valve member whereby the tapered zone 36 is still within the valve port 21.

As shown herein, the stop member 40 is threaded into the bore to adjust the position thereof, and is formed 40 with a screw driver receiving slot 41 or other suitable formation for engagement by a tool to facilitate making the desired adjustment. A lock nut 42 is threaded onto the stop member to retain the same in its adjusted position.

g0 Preferably, the stop member 40 is adjusted so that, when the valve is in a restricted fully open position and the pump 15 is operated at its maximum capacity with the shaft 16 at maximum speed, the flow rate of the fluid delivered to motor 11 is of a value to restart the motor g5 with an inertia surge which the compressor can safely withstand.

While the system is in normal operation with the pump 15 operating at about its maximum flow rate capacity, hydraulic fluid enters the inlet of the motor 11 by way of go the inlet 22, the bore 20, the valve port 21 and the passageway 24 and hydraulic fluid flows from the outlet of the motor to the reservoir 17 by the bore 25. Also, the cylinder 19 contains hydraulic fluid at both sides of the piston 37, and the space 43 in the bore 20 between the 65 end portion 32 of the valve member and the inner end of the stop member 40 has hydraulic fluid therein by reason of the passageway 39 in communication with the end of the cylinder to the right of the piston.

With such an arrangement, the left side of the piston ₇₀ 37 senses the pressure of the fluid in the bore 25 through the passageway 26 and the opening 27, and the right side of the piston senses the force of the spring 38 and the

3,027,902 pressure of the fluid which has been reduced by the restriction 30 through the passageway 28 and the opening 29. Thus, when the pump is operating at about its maximum capacity, the forces acting on the respective sides of the piston are equal and in balance whereby the piston and the valve member 31 assume a position to meter the hydraulic fluid at a rate to drive the motor and the compressor at the speed which enables the air compressor to produce the pressure and capacity output for which it is rated, for example, 4.4 c.f.m. of air at 3000 p.s.i.

In the event the speed of the pump 15 is reduced, the pressure of the hydraulic fluid in the bore 25 is likewise reduced and the combined force of the spring 38 and the fluid at the right side of the piston exceeds the force of the fluid at the left side of the piston, whereby the piston and the valve member 31 move towards the left and assume a position to increase the effective opening area of the valve port 21 about the tapered zone 36 to supply fluid to the motor at an increased rate and thereby maintain the desired motor and compressor speed. Should the speed of the pump be restored to or approach its former value, the force of the fluid at the left of the piston exceeds the combined force of the spring and the fluid at the right side of the piston, whereby the piston and the valve member move towards the left to decrease the effective opening area of valve port about the tapered zone 36 to reduce the flow rate of the fluid supplied to the motor. The piston and valve member assembly can move in either direction because fluid can flow back and forth between the cylinder 19 and the space 43 through the passageway 39 to maintain the pressure of the fluid equal at both ends of the valve member and piston assembly but such movement is damped as the fluid is transferred through the passageway 39.

In the event the flow of fluid to the motor is interrupted, the fluid does not exert any force on either side of the piston 37, and the spring 38 is effective to move the piston and valve member towards the left until the end portion 32 engages the stop member 48. When the flow of fluid to the motor is resumed the valve will be in its tolerable or restricted fully open position and the inertia surge acting on the compressor by the motor as it starts rapidly will not cause any damage. As the pressure of the fluid in the bore 25 builds up again, the piston and the valve member are moved towards the right into their desired flow regulating position.

From the foregoing description, it will be seen that the present invention provides an improved air compressor system which prevents damage to parts of a multi-stage, cam-type actuated compressor by minimizing inertia surges.

As various changes may be made in the form, construction and arrangement of the parts herein, without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense.