US2916879A - Combination hydraulic power unit - Google Patents

Description

' Dec. 15, 1959 ,1' GONDEK 2,916,879

COMBINATION HYDRAULIC POWER UNIT Filed April 4, 1956 2 Sheets-Sheet .1

60/7 7. Gonae/r BY a) yATTORNEY INVENTOR United States Patent Office 2,916,879 Patented Dec. 15, 1959 2,916,879 COMBINATION HYDRAULIC POWER UNIT John T. Gondek, Minneapolis, Minn. Application April 4, 1956, Serial No. 576,173 1 Claim. (Cl. 60-52) The invention relates to an improvement in combination power unit and deals particularly with a fluid system capable of producing power.

An object of the present invention resides in the provision of a reversible fluid power source capable of acting through a valve for introducing pressure into a cylinder or the like for moving a piston therein. The valve functions automatically depending upon the direction of movement of the power supply to direct hydraulic fluid to a selected end of the cylinder.

A feature of the present invention resides in the provision of a hydraulic system controlled by an automatic valve which includes means for locating the piston of the valve when the fluid supply is cut off. When fluid ceases to flow through the hydraulic system from the power supply, the valve returns to a neutral position automatically. As a result the system is at any time in readiness for operation in either direction.

A further feature of the present invention resides in the provision of a valve incorporating a piston provided with resilient means biasing the valve toward neutral position. The system is so arranged that the resilient means will return the valve to neutral position when the power source is stopped.

An added feature of the present invention resides in the provision of a fluid system including a valve which may function to lock the driven member in a fixed position when the power is cut off. If desired, the valve piston is so arranged as to close the fluid connections to and from the driven piston cylinder so as to retain the piston in a desired position.

A further feature of this invention lies in the fact that, if desired, the valve centering springs may be omitted so that a reversal of the fluid pressure is required to actuate the valve. Such an arrangement is desirable for use in conditions where it is neither necessary to lock the work cylinder from movement, or to leave it free to move.

A feature of a modified form of construction of the power unit lies in the provision of a system which will permit movement of the driven piston when the power supply is cut off. The arrangement may be such that the driven piston may move in either direction when the pressure from the pump ceases.

A further feature of the present invention lies in the provision of a fluid system in which the fluid from the driven piston cylinder returns to a reservoir before it may be drawn into the pump. As a result any foreign material in the fluid may be removed from the fluid within the reservoir.

A further feature of the present invention lies in the provision of a system which prevents overhauling of the driven piston. When the pump has moved the valve to allow oil from the discharge side of the piston to return to the reservoir, any tendency for the piston to move faster than the flow of oil into the driven piston cylinder from the gear pump would normally cause it to move causes a reduction in pressure on the discharge side of the gear pump. This reduction in pressure causes the centering springs to move the valve toward center position, thus throttling the flow from the discharge side of the piston. Thus when the load tries to move the piston faster than it should be moved by the pump, the discharge flow will be throttled to prevent this faster movement.

A further feature of the present invention lies in the fact that the power unit, including the reservoir, pump, and valve cylinder together with the connections described are in a single compact unit which may be attached to any work cylinder and plugged into any suitable current source.

In the drawings forming a part of the specification, Figure l'is a diagrammatical view of a combination hydraulic power unit showing the control valve in central position. a

Figure 2 is a view similar to Figure 1 but showing the control valve in one extreme position.

Figure 3 is a diagrammatical view of a modified form of hydraulic power unit, showing the control valve in centered position.

Figure 4 is a view similar to Figure 3 showing the control valve in one extreme position.

In View of the fact that the details of the controlled systems are not of utmost importance to the system as a whole, the drawings show the construction diagrammatically. The parts which are diagrammatically shown are believed already understandable as they are well known in the art.

Numeral 10 indicates in general a gear pump of any suitable form, the pump including oppositely movable meshed gears 11 and 12. The gears 11 and '12 are driven by any suitable source of power such as electric motor or the like, the motor being of a reversible type or equipped with a reversing clutch. It is a purpose of the invention that the gear pump be reversible so as to force hydraulic fluid in either direction. The gear pump 10 is provided with inlet-outlet lines 13 and |1 4 either of which may serve as the inlet line while the other serves as the outlet line. The conduit 13 is connected to conduit 15 leading through a check valve 1 6 to a reservoir or tank 17. The check valve 16 permits fluid to be drawn from the tank 17 past the check valve but does not permit a return flow through conduit 15.

The conduit 14 is similarly connected through a check valve 119 and conduit 20 to the tank 17. The check valve 19 permits fluid to be drawn from the reservoir past the check valve 19 and into the line 14 but does not permit a reverse flow of fluid.

The conduit 13 also leads to a conduit 21 extending from the reservoir 17 to a point near one end of a valve cylinder 22. The conduit 14 also is connected to a conduit 23 leading from the reservoir 17 to the end of the valve cylinder 22 opposite that to which the conduit 21 extends. A pressure relief valve 24 is transposed between the conduit 13 and the reservoir and a similar pressure relief valve 745 is provided between the conduit 14 and the'resenvoir. These pressure relief valves are capable of opening under abnormal pressure to permit a bypass of fluid to the reservoir. However, under normal conditions of operation, the relief valves remain closed.

The valve cylinder 22 is provided with closed ends and slidably supports a piston valve 26. The valve 26 is provided with a central portion 27 of reduced diameter past which fluid may flow when the valve is moved out of center position. A center port 29 is communicated by a conduit 30 to the reservoir 17 so that fluid can flow to this reservoir. A conduit 31 leads from a port 32 at a point spaced to one side of the center of the cylinder 22 to communicate with the conduit 13 and contains a check valve 33 which permits the flow of fluid from the pump to the port 32 but does not permit a reverse flow of fluid. A port '34 is aligned with the port 32 or is arranged on substantially the same plane normal to the axis of the valve. The port 34 is connected by a conduit 35 to a pressure cylinder 36 containing a piston 37. The piston 37 includes a piston rod 39 extending from the cylinder for the actuation of some driven object or apparatus.

Ports '40 and 41 are provided on the opposite side of the center of the valve from the ports 32 and 34. The port 40 is connected by a conduit 42- containing a ch ck valve 43 to the conduit 14. The check valve 43 is arranged to permit a flow of fluid from the gear pump 10 to the port 40 but does not provide a return flow of fluid.

The port 41 is connected by a conduit 44 to the end of the cylinder 36 opposite to that to which the conduit 35 is connected. Thus, when fluid under pressure flows from the pump 10 in one direction the piston 3'7 may move in one direction. Rotation of the pump 10 in the opposite direction will move the piston 37 in a reverse direction.

The reduced diameter portion 27 of the piston 26 is of suflicient length to span the space between the center port 29 and the side ports 32 and 34 on one side of center and the ports 40 and 41 on the opposite side of center. Thus, when the valve piston 26 is forced to one side or the other, it provides a connection between the center port 29 leading to the reservoir and a corresponding end of the cylinder 36.

The valve piston 26 is provided at opposite ends with sockets 45 and 46 which have hollow bosses 47 and 49 projecting in opposite directions from the bases of the respective sockets. The hollow boss 47 is thimble shaped having an outwardly directed flange 50 at its open end. A valve rod 51 extends through the outwardly projecting end of the boss 47 and is provided with a enlarged head 52 at its outer extremity. A spring 53 is transposed between the head 52 and the flange 50 of the boss. 47 to hold the boss in proper position and to urge the valve head 52 toward extended position.

The boss 49 is similarly provided with a marginal flange 54 which bears against the base of the socket 46. A valve rod 55 is slidably supported in the boss 49 projecting from the outer end thereof. A spring 56 is transposed between the enlarged head 57 on the valve rod 55 and the flange 54 of the boss 49 holding the boss in proper position and urging the head 57 against the right-hand end of the cylinder 22 in the drawing illustrated. Having now described in general, the construction of the combination hydraulic power unit, the operation of the system will now be described. I

The valve piston 26 is normally held in centered position by the engagement of the valve push rods 51 and 55 with the ends of the cylinder 22. In other words, the springs 53 and 56 are of substantially equal strength and act to push the valve toward a centered position. In this position the reduced diameter portion 27 of the valve is not in communication with either of the ports 32 and 34 on one side of center of the valve cylinder or the ports 40 and 41 on opposite sides of the center. As a result, the fluid within the cylinder 36 is prevented from escaping and the piston 37 is locked in a fixed position.

When it is desired to move the piston 37 in one direction, the pump 10 is rotated in a proper direction to force fluid to a desired end of the cylinder 36. For example, if the gears 11 and 12 are rotated in the direction of the arrows in Figure 2 of the fluid is carried from the reservoir 17 through conduit past check valve 16 and into the conduit 13 leading to the pump 10. This fluid is forced by the pump 10 through the conduit 14 and into the conduit 42, flowing past the check valve 43. If the ports 40 and 41 are connected through the body of the cylinder 22, the fluid may flow into the cylinder 36 4 to the right of piston 37 tending to move the piston 37 to the left.

Movement of the piston 37 to the left tends to force fluid through the conduit 35 to port 34 which is connected through the body of the cylinder by a circular groove or the like to the port 32. However, if the check valve 33 is seated, the fluid cannot escape and pressure is built up in the pressure line. As the pressure builds up, it is communicated to the right side of the valve piston 26 through the conduit 23. As a result, the piston 26 is forced to the left, fluid leaving the left side of the cylinder flowing through conduit 21 to the intake of the pump. Movement of the valve piston 26 continues until the reduced diameter portion 27 forms a connection between the center port 29 and the side ports 32, 34 as indicated in Figure 2 of the drawings. This action compresses the spring 53 to some extent but the pressure is suflicient to maintain the valve in a position where the fluid can escape from the cylinder 36. Any tendency of the spring 53 to expand and urge the piston 26 to the right cuts off the escape of fluid from the cylinder 36 and again builds up pressure suflicient to move the piston 26 to the left.

As soon as the pump 10 stops operation, the piston 26 returns to its center position and the piston 37 will be locked in a fixed position. If it is desired to move the piston 37 in a reverse direction, the direction of rotation of the pump is reversed and the system will function in a reverse manner to accomplish this result.

When the pump 10 is operated in a reverse direction, fluid is drawn to the pump from the reservoir through conduits 20 and 14 past the check valve 19. This fluid is forced past the check valve 33 through conduits 15 and 31 to the conduit 35 leading to the left end of the cylinder. This tends to force the piston 37 to the right. However, if fluid is trapped to the right of the piston 37 pressure builds up on the left side of the valve piston 26 forcing this valve to the right until the reduced diameter portion forms a connection between the port 29 and the ports 40, 41. At this time liquid is permitted to drain to the reservoir and the pressure to the left of piston 37 will force it to the right.

In Figures 3 and 4 of the drawings, a modified form of construction is illustrated which has many of the features previously described but which is employed when it is not desired to lock the operating piston in fixed position. In this form of construction a pump 60 which is reversible and which is connected to a suitable source of power supply is provided with inlet- outlet conduits 61 and 62, one conduit acting as the inlet while the other acts as the outlet. The conduit 61 is connected to a conduit 63 leading from the reservoir 64 to the valve cylinder 65 at a point near one end thereof. The conduit 63 includes a check valve 66 between the conduit 61 and the reservoir so that liquid may be drawn past the check valve toward the pump but cannot travel in a reverse direction.

The conduit 62 is connected to a conduit 67 leading from the reservoir 64 to the end of the valve cylinder 65 opposite that to which the conduit 63 is connected. The conduit 67 includes a check valve 69 positioned to permit fluid to flow from the reservoir to the pump but not in an opposite direction. A valve piston 70 is slidably supported in the cylinder 65. A central drain conduit 71 communicates with a central port 72 in the cylinder 65. Side ports 73 and 74 on opposite sides of the central port 72 communicate with conduits 75 and 76 leading to opposite ends of a hydraulic cylinder 77. A piston 79 is slidable in the cylinder '77 and is connected to a valve rod 80 connected to a suitable driven member. The apparatus is designed to control the movement of the piston and valve rod 80. The piston 70 is provided with two spaced central lobes 81 and 82 which are of proper diameter to snugly fit within the bore of the cylinder 65. These lobes 81 and 82 are spaced to provide a reduced diameter central piston portion 83 and reduced diameter and piston portions 84 and 85. The spacing is such that when the valve piston 70 is in a center position both ends of the cylinder 77 are connected through the reduced diameter piston portion 83 to the drain conduit 71. In other words, fluid may reach both ends of the cylinder 77 or at least is free to flow from the cylinder 77.

The ends of the valve piston 70 are provided with axial sockets 86 and 87 which are designed to accommodate springs 89 and 90 respectively. A central boss is provided at the center of each socket, each boss comprising a thimble like guide member 91, 92 having an outwardly extending flange 93, 94- at its inner end. Each boss 9lr--92 slidably supports a push rod 95, 96 which extends through the outer end of the boss. The spring 89 is transposed between the flange 93 of the boss 91 and the head 97 of the push rod 95, the spring tending to push the push rods outwardly and to hold the boss in place.

The spring 90 is similarly transposed between the flange 94 and the head 99 of the push rod 96. This spring acts in a similar capacity to the spring 89 and the two springs normally urge the valve piston 70 into central position.

The operation of the apparatus is simple. When the pump 66 is rotated in one direction as checked in Figure 4, fluid under pressure is forced through the conduits 62 and 67 to the right end of the cylinder 65 acting to force the piston 70 to the left as viewed in the figure.

Fluid from the opposite end of the cylinder can flowv through conduit 63 to conduit 61 through which fluid is being drawn toward the pump 60. The check valve 66 opens to permit fluid to be drawn from the reservoir 64.

Movement of the p ston 7i? to the left continues until the lobe S2 uncovers the port 74 connected to the conduit 76 leading to the right end of the cylinder 77. This action causes fluid under pressure to force the piston 79 and its piston rod 80 to the left.

When the piston valve 70 is in the position shown in Figure 4 the lobe 81 has passed the port 73 connected by conduit '75 to the right end of cylinder 77. As a result fluid may flow through conduits 75 and 71 to the reservoir 64.

When the movement of the pump 60 is stopped the valve piston 70 is urged by its springs into center po sition. However, in this case, the connections to both ends of the cylinder 77 communicate with the drain passage 71 and any drain is connected to the reservoir.

It will be noted that fluid is trapped to the right of the valve piston 70 after the valve piston has moved to the location shown in Figure 4. Thus, if no provision for the leakage of fluid was made the valve would remain in this position. The pump 60 normally provides some leakage when the gears or lobes are not in rota tion. Accordingly, when the pump is stopped, the 'valve piston will return to center position at a rate of speed independent upon the extent of speed of leakage past the pump.

The system described is simple but extremely eflective for certain installations. With the arrangement shown in Figures 1 and 2 of the drawings, the piston 37 may be locked in any desired position as soon as the motion of the pump is stopped as the centering valve piston acts to seal the outlets of cylinder 36. With the arrangement shown in Figures 3 and 4 the piston 79 is free to move as soon as the valve piston has returned to centered position and the time required for this action may be regulated to some extent by regulating the leakage through the pump.

In both systems the return flow of fluid from the driven cylinder 36 or 77 is directed to the reservoir. This is important as it permits any impurities in the fluid to settie out during periods while the apparatus is at rest. In other words, while the device is in many respects similar to a closed circuit operation, the fluid from the driven cylinder is not returned directly to the pump but flows through the reservoir.

Certain short cuts have been taken in the drawings and description to simplify the same. For example, no modification has been illustrated in which the centering springs are omitted, although they may be in installations where the locking of the piston or the free movement of the piston is not required. The purpose of the thimble-shaped sockets is to limit the expansion of the centering springs, this type of spring arrangement being commonly referred to as a bottle spring. Furthermore, while the description mentions reduced diameter portions in the valve piston, the actual units include connected slots in the valve piston surface, or other such connected passages. No seals have been shown, either on the driven piston or on the valve piston. It is obvious that such seals would normally be necessary if the valve is to lock the driven piston in fixed position.

In accordance with the patent statutes, I have described the principles of construction and operat on of my combination hydraulic power unit and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that changes may be made within the scope of the following claim without departing from the spirit of my invention.

1 claim:

A combination power unitincluding a reservoir, a pair of connections leading from said reservoir, said connections including check valves permitting a flow of fluid from said reservoir but preventing reverse flow to said reservoir, a reversible source of fluid power connected to said connections and capable of withdrawing fluid from one connection and forcing it toward the other, a valve cylinder, a reciprocable valve piston in said valve cylinder, passage means connecting said connections at respective locations intermediate said check valves and said fluid power source to said valve cylinder near opposite ends thereof, a return connection directly to said reservoir intermediate the ends of said vaive cylinder and communicating with the interior thereof, a pair of ports on opposite sides of said return connection, a work cylinder, means connecting opposite ends of said work cylinder to said ports, a piston reciprocable within said work cylinder, said valve piston having means therein selectively connecting each of said ports to said connections, and a check valve in each said passage means permitting a flow of fluid from said source of fluid power to said ports and directly to said work cylinder, but preventing a reverse flow from said work cylinder to said power source.

References Cited in the file of this patent UNITED STATES PATENTS

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