US2333530A - Hydraulic system - Google Patents

Description

Nov. 2, 1943. w, R T 2,333,530

HYDRAULIC SYSTEM Filed Ap ril 25. 1942 2 Sheets-Sheet 1 mvzn'ron WALTER ERNST BY- j ATTORNEY Nov. 2; 1943. w. ERNST HYDRAULIC SYSTEM Filed April 25, 1942 2 Sheets-Sheet 2 ATTORNEY for instance, a variable delivery pump,

Patented Nov. 2, 1943 HYDRAULIC SYSTEM Walter Ernst, Mount G The Hydraulic Develo .ilcad, Ohio, assignor to pment Corporation, Inc.,

- Wilmington, Del., a corporation of Delaware Application April 25, 1942, Serial No. 440,526

(Cl. Bil -97) 6 Claims.

This invention relates to hydraulic machinery and, in particular, to hydraulic'systems including a plurality of fluid operable motors and a pressure fluid source of variable delivery, which is common to said motors, for'supplying pressure fluid thereto, and has associated therewith a control device adapted, in response .to a predetermined pressure acting on said control device, to

reduce the delivery of the fluid source.

Heretofore, when trying to operate two or more hydraulic motors in a hydraulic system of the above mentioned type, it was always necessary to set the control device for the maximum pressure required in any of the hydraulic motors. In other words, even when the fluid pressure source, was idling, it continuously had to maintain the highest pressure required in the hydraulic system, which caused rapid wear of the pump.

Accordingly, it is an object of this invention to provide a hydraulic system with a plurality of hydraulic motors and a pressure fluid source common thereto, which will overcome the drawback outlined above.

It is another object of the invention to provide a hydraulic system including a plurality of hydraulic motors and a pressure fluid source of variable delivery with a control device for varying the delivery, in which the control device may .be set so that the pressure fluid source, when idling, operates only at the lower rather than the higher pressure required in the hydraulic system.

Still another object of the invention consists in the provision of a hydraulic system including a plurality of hydraulic motors and a variable delivery pump with servomotor means, in which the servomotor means may be'set so that the pump may selectively be shifted to and held in substantially neutral or no delivery po'sitionin response to the lowest pressure required in the system.

It is a still further object of the invention to provide a hydraulic system with at least three hydraulic motors adapted respectively to be operated at difierent pressures by a common variable delivery pump with servomotor means, in which the pump may be held in idling position at the lowest pressure required in the hydraulic system.

These and other objects and advantages of the invention will appear more clearly in connection with the accompanying drawings, in which:

Figure 1 diagrammatically illustrates a first embodiment of the invention. I

Figures 2, 3 and 4 show various positions of a valve used in connection with the hydraulic system of Figure 1.

Figure 5 is a further embodiment of the invention.

General arrangement According to the present invention, the variable delivery pump, adapted to supply pressure fluid to a plurality of hydraulic motors at different pressures, is provided with differential control plunger means, the largest area of which is continuously connected with the pressure side of the pump, while a smaller opposing area may selectively be connected with the pressure side of the pump when the latter supplies pressure fluid to a motor in the system which requires the maxi-' I mum pressure obtainable in the hydraulic system. Structural arrangement Referring now to the drawings and Figure 1 thereof in particular, the hydraulic system shown therein comprises a high pressure motor, generally designated l and two low pressure motors, generally designated 2, 3. The motor I includes a cylinder 4 having reciprocably mounted therein a piston 5 with piston rod 6. The motors I, 2 and 3 are adapted to be supplied with pressure fluid from a variable delivery pump 1, of any standard design, having a flow-control member 8, the position of which controls the delivery .of the pump.

The pump 1 includes a casing 9 housing a spring In, one end of which abuts a spring disc H adjustable by means of an adjusting screw l2. The other end of the spring I0 engages a head l3 of a control rod I4 which, in its turn, engages the flow-control member 8. The spring I0 continuously urges the flow-control member 8 into position for placing the pump 1 on full delivery stroke. The pump 1 has associated therewith a control mechanism, generally designated I5, which includes a casing l6 connected to the pump casing in any convenient manner. The casing l6 comprises a, cylinder bore I 1 and a chamber l8.

The cylinder bore H has reciprocably mounted therein a differential piston IS with an extension 20 adapted to engage the flow-control member 8 and, in response to a. predetermined pressure in the bore IT, to shift the flow-control member 8- against the thrust of the spring l0 toward the left, thereby shifting the pump 1 into substantially neutral or no delivery position. The outer end of the cylinder bore I1 is closed by a closure 2| connected to the casing IS in any convenient manner, and provided with, a bore 22 which, in

NT- optics" its turn, communicates with a conduit 23. The conduit 23 leads to a conduit 24 which communicates with the pressure side of the pump 1, while allow fluid communication between the upper portionof the valve casing 28 with the conduit 33. The valve member 29 also has a longitudinal bore 34 therethrough and is provided with an actuating shaft or handle 35, having a transverse bore 36 therethrough.

The conduit 33 communicates with a conduit 31 leading to the upper portion of the cylinder 4 pertaining to the motor I, while the lower portion of the cylinder 4 communicates with a conduit 38 leading to the lower portion of the fourway valve 21. The lowermost end of the fourway valve 21 furthermore communicates with a conduit 39 leading to the conduit 25. Communicating with the conduit 31 is a pilot line 40 which leads to the chamber l8 of the control mechanism l5.

Communicating with the pressure line 24 is a conduit leading to a conduit 42, which communicates with the four- way valves 43 and 44. These valves, in their turn, control the supply of pressure fluid to the motors 2 and 3 respectively. The valves 43 and 44 are four-way valves of any standard design with a neutral or intermediate position, in which no fluid is admitted to nor exhausted from the motors 2 and 3. If desired, the four- way valves 43 and 44 may be of the same construction as the four-way valve 21.

Connected to-the four-way valve 43 are two conduits 45 and 46 respectively leading to the upper and lower portion of the cylinder 41 pertaining to the motor 2 which, in its fundamental structure, may be similar to the motor I. Similarly, two conduits 48 and 49 connected to the four-way valve 44 lead to the cylinder 50 pertaining to the motor 3, which corresponds to the motor 2. A conduit interconnecting the valves 43 and 44, constitutes an exhaust line and leads to the tank 26.

The various positions of the valve 21 are shown in Figures 2, 3 and 4, and will be discussed in connection with the operation of the device.

It may be assumed that it is now desired to operate the high pressure motor I without operating the motors 2 and 3, which are cut off from the conduit 4| by placing the valves 43 and 44 in neutral position.

It may further be assumed that the pump 1 is idling. To effect operation of the motor I, the operator shifts the actuating shaft or handle 35 upwardly into the position of Figure 3, thereby causing a pressure drop in the pilot line 23 so that the spring l0 moves the pump 1 on full delivery stroke. The fluid expelled from the upper portion of the valve casing 28, during the upward shifting. movement of the handle 35, passes through bores 36 and 34 into the exhaust line 39. When the valve member 29 has thus been shifted, it will be clear that pressure fluid from the pump sure prevailing in the conduit 31 is also conveyed through the pilot line 40 to the chamber ll of the control mechanism I5. The piston 5 now performs its working stroke. 1

When, at the end or during any point of this workingstroke, a predetermined maximum pressure has been built up in the upper portion of the press cylinder 4, this pressure acts through the pilot line 49 on the annular area 52 of the differential piston l9, while the same pressure position.

acts through pilot line 23 on the larger differential area 53 of the piston l9. This diflerenti'al pressure then causes the piston l9 to move into the position shown in Figure 1, thereby shifting the pump to substantially neutral or no delivery In other words, the pump 1 is now idling at the maximum pressure required in the hydraulic system.

If, at this time, it is not required'to hold the piston 5 under its maximum pressure, the valve member 29 may be moved into intermediate or neutral position, in which instance the chamber |8 will be connected to the exhaust line 25 through the pilot line 40. conduit 33, slots 32, bores 36 and 34 and th conduit 39. quently, the pressure actinin the bore I1 of the control device l5 will not Lir' opposed by pressure in the chamber l8 so that tne pump 1 will be held in its idling position at a low pressure.

If it is desired to retract the piston 5, the operator shifts the shaft or handle 35 into the position of Figure 4, thereby again creating a pressure drop in the pilot line 2 so that the pump 1 is again moved into full delivery position by the spring Hi. Pressure fluid from the pump 1 then passes through the conduits 24 and 38 into the lower portion of the cylinder 4, while the upper portion of the cylinder 4 is connected through the conduits 31 and 33, the bores35 and 34 and the conduit 39 with the suction line 25.

1 passes through conduit 24 into the conduit 33,

and from there through conduit 31 into the upper Consequently, the piston 5 moves upwardly.

When the piston 5 has reached the end of its retraction stroke, namely, the position shown in Figure 1, and is halted, the pressure in conduits 38 and 24 acts through pilot line 23 on the differential area 53 of the piston l9 so as to shift the pump 1 to neutral or no delivery position against the thrust of the spring ID. The

operator may then shift the valve member 29 back into its neutral position, as shown in Figure 1. The hydraulic system is then again in its initial or idling position, shown in Fgure 1. It will be noted that, in this position, pressure acts on'the larger differential area 53 only and not on 1 the smaller differential area 52, so that the pump 1 is held in its idling position at the lowest pressure required in the system.

If it is now desired to operate the low pressure motors 2 and 3, the operator shifts the valves 43 and 44 so as to establish fluid connection between the conduits 45 and 43 with the conduit 4|, while simultaneously connecting the conduits 46 and 49 with the exhaust line 5|. This causes a pressure drop in the pilot line 23 so that the spring I0 again shifts the pump 1 into full delivery position. Fluid pressure, therefore, passes through conduits 24 and 4| and the conduits 45 and 48 to the motors 2 and 3 respectively, while fluid expelled therefrom is exhausted through conduits 46 and 49 to the tank '26.

The fluid pressure prevailing in conduit 4| is conveyed through the pilot line 23 to the larger differential area 53 of the differential piston l9,

Consewhile the conduit 46 communicates through the conduit 33, slots 32,.bores-3'6 and 34 and conduit the conduits 45' and 48, which maximum pressure is lower than the required maximum pressure in the motor I, the pressure in conduits 45 and 48 acts through pilot line 23 upon the larger area 53 of the difierential piston l9 so as to cause movement of the pump 1 into substantially neutral or no delivery position.

To return the motors 2 and 3 to their initial position, the operator reverses the position of the valves 43 and 44, thereby again causing a pressure drop in the pilot line 23 so that the spring l again moves the pump 1 intofull delivery position. Fluid pressure from the pump 1 then passes through conduits 4|, 46 and 49 into the lower portion of the cylinders 41 and 5!) respectively, thereby bringing about a retraction stroke of the motors 2 and 3. 7

When, at he close of this retraction stroke, a predetermined pressure has built up in the conduit 4|, this pressure acts through the pilot line 23 on the larger difierential area 53 of the dif ferential piston l9 again, and returns the pump 1 to its neutral or no delivery po ition in the manner previously described. The valves 43 and the motors I 2 and 3 could be operated at the maximum pressure required in the system by shifting the three four- way valves 21, 43 and 44.

Referring now to the embodiment of Figure 5, the system shown therein is similar to that shown in Figure 1, and similar parts are, therefore, designatedwith the same reference numerals as in the system of Figure 1, however, with the additional letter a. I

The system of Figure 5 differs from that of Figure 1 primarily in that the motors la, 2a and pressure motor, and the motor 311 is a low pressure motor. Furthermore, the control mechanism l5 of Figure 1 is replaced by a control mechanism 54, which comprises a casing with three chambers 56, 51 and 58. Reciprocably mounted in the chamber 56 is a differential piston 59 having a larger differential area 60 and a smaller diii'erential area 6|. The piston 59 is furthermore connected with a control rod 62 for shifting the flow-control member 8a. of thepump Ia. A sleeve-like floating plunger 63 is adapted to be acted upon by pressure fluid in the chamber 58, and to slide on the rod 62 so as to engage the piston 59.

The conduit system connecting thepump la with the high pressure motor Ia and low pressure motor 3a corresponds to that of Figure 1. The

, conduit-system pertaining to the medium pressure motor 211 comprises a conduit 64 leading from the chamber 58 in the control mechanism by a branch line 65 with-theupperportion of the cylinder 41a. The rest of the conduit system pertaining to the medium pressure motor 2a corresponds to the low pressure motor 2 of Figure 1.

The operation of the maximum pressure motor la in Figure 5 corresponds to that of the maximum pressure motor I' of Figure 1. To ef-' feet a downward stroke of the piston 5a, the operator shifts the valve handle 35a upwardly, thereby causing a pressure 'drop in the pilot line. 23a so that the pump-1a moves on full delivery stroke and delivers pressure fluid into the upper portion of the cylinder 4a, while fluid expelled from the lower portion of the cylinder 4a is exhausted into the tank 26a. When a predetermined maximum pressure has been established in the upper portion of the cylinder 4a, this pressure, which is conveyed through the pilot line 40a into the chamber 51 to act on the smaller difierential area BI and is also conveyed through the pilot line 23a to the chamber 56 to act on the larger differential area 60, causes the differential piston 59 to move the pump 1a into substantially neutral or' no delivery position, as shown in Figure 5.

To reverse the movement of the piston 5a, the operator reverses the position of the valve handle 35a, thereby again bringing about a pressure drop in the pilot line 23a and causing the pump 1a to return to its full delivery stroke position. Pressure fluid from the pump 1a is then conveyed into the lower portion of the cylinder 4a, while fluid from the upper portion of the cylinder 4a is exhausted into the tank 26a. When a predetermined pressure, lower than the maximum pres-; sure obtained during the downward stroke of the motor la, has been established, this pressure acts through pilot line 23a on the piston 59, so as to move the pump 1a to substantially neutral or no delivery position. It will be noted that the pilot line 40a is now connected to an exhaust or the tank 26a. The pump 1a, therefore, now idles at the lowest pressure required in the hydraulic system. The operator may now return the valve member 29a to its neutral position, as shown in Figure 5.

To operate the medium pressure motor 2a, the operator shifts the valve member pertaining to the valve 43a into its uppermost position so that a pressure drop occurs in the pilot line 23a, and the spring Illa. returns the pump la, to full delivery position. Pressure fluid thenflows through the conduit 24a and the conduit 65 into the upper portion of the cylinder 41a, while fluid expelled from the lower portion of the cylinder 41a is exhausted through conduits 5la and 39a into the tank 2611. It will be clear from the drawings that the pressure prevailing in the,

conduits 24a and 65 is conveyed through the pilot line 64 into the chamber 58 .and through pilot line 230. into the chamber 56. Consequently, the

toward the left, thereby shifting the pump la into substantially neutral or no delivery position. The pump is now idling at a medium pressure. If the motor 2a is not to be held under pressure,

the valve 43a may be shifted into its neutral position so that the chamber 58 will be connected through conduit 64 and the slots 32a, the bores 35a and 34a and the conduit 5la with the tank 16a so that the pressure acting in the chamber 56 is not opposed by pressure in the chamber 58, with the result that the pump la will idle at the lowest pressure required in the hydraulic system. To reverse the medium motor 2a, the operator shifts the valve 43a into its lowermost position, thereby again creating a pressure drop in the pilot line 23a so that the spring I0a returns the pump Ia to full delivery position. The conduits GI .and 65 are then connected to the tank 26a, while pressure fluid flows to the lower portion of the cylinder 41a through the conduit 46a. The motor 211 then returns to its upper position. When, at the end of this return stroke, a predeterminedlow pressure has been established, this pressure acts through the pilot line 23a on the piston 59 and moves the pump To to substantially neutral or no delivery position. The pump then idles-at low pressure. The valve 4311 may then be returned to its neutral position.

The operation of the motor 3a fully corresponds to the operation of the motor 3, so that no further description is required. When, the predeterminedmaximum pressure required for the motor 3a has been established therein, which maximum pressure is lower than the required maximum pressure of the motor Ia and the motor 2a, the pump la is 'shifted to substantially neutral or no delivery position and then idles at low pressure.

From the above, it will be clear that the hydraulic system according to the present invention enables the operation of a plurality of motors at difierent maximum pressures respectively required for these motors without having to idle the pump at the highest required maximum pressure. On the contrary, the pump may idle at the lowest maximum pressure required, thereby saving considerably in power and materially increasing the life of the pump.

' It will be understood that I desire to comprehend within my invention such modifications as come within the scope .of the claims.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:-

1. In a hydraulic system, a high pressure motor, a low pressure motor, each of said motors including a reciprocable plunger and fluid operable advancing and; retracting means for actuating .s aid'plungena variable delivery pump for supplying pressure fluid selectively to said ad vancing or retracting means, means for continuously urging said pump into fulldelivery stroke position, pump control means for opposing the action of said urging means and including a difierential piston with a larger area and a smaller 'opposed area, first conduit means continuously establishing fluid connection between the pressure side of said pump andsaid larger area, seco'nd conduit means continuously establishing fluid connection between said smaller diiferential area and the advancing means pertaining to said high -pressure"motor, and separate valve means for controlling the supply or fluid from said pump to each of said motors. i

- 2. In a hydraulic system; a high pressure motor, a-lowpressure motor, each of said motors having associated therewith fluid operable advancing and retracting means for causing said. motor to eflect an advancing and a retracting advancing means of said high pressure motor,

and separate valve means respectively associated with said high pressure and said low pressure motors for controlling the supply of fluid between said source and each of said motors.

3. In a. hydraulic system, a high pressure motor, a low pressure motor, each of said motors hav n associated therewith fluid operable advancing and retracting means for actuating said motors, a pressure fluid source for selectively supplying pressure fluid .to said advancing or retracting means of either of said motors, control means associated with said fluid source for varying the delivery thereof, means for continuously urging said control means into position to bring about maximum delivery of said fluid source, fluid pressure responsive mechanism operable to'counteract said control means for reducing the delivery of said fluid source, said mechanism comprising a difierential plunger with a larger area continuously connected to said fluid pressure source, and also comprising a smaller area opposed to the larger area and continuously connected with the advancing means pertaining to said high pressure motor, and separate valve means respectively lic motors, each requiring a difierent maximum operating pressure, each of said motors having associated therewith fluid operable advancing and retracting means for actuating the respective motor, a fluid source common to said motors for supplying pressure fluid thereto, control means associated with said fluid source for varying the delivery thereof, means for continuously urging said control means to bring about maximum delivery of said 'fluid source, pressure responsive mechanism for actuating said control means to reduce the delivery of said fluid source, said mechanism including a differential plunger having its largest effective area continuously connected to saidpressure'fluid source, and having a smaller efiective area opposed to the largest area and communicating with the advancing means of one of said motors, and separate valve means for each mot controlling the flow of fluid between said source ..nd each of LJ-id motors.

5. In a hydraulic system, a plurality of hydraulic motors, each requiring a difierent maximum operating pressure, each of said motors having associated therewith fluid operable advancing fluid source, and having a smaller efiective area opposed to-the larger area communicating with the advancing means of one of said motors, means for continuously urging said control means to bring about maximum delivery of said fluid source, and a plurality of control valves respectively associated with said motors for controlling the flow of fluid to and from said motors, each of said control valves comprising a balanced valve member with a longitudinal bore therethrough hydraulically connected at one end with passageways on said valve member and connected at the other end with an exhaust.

6. In a hydraulic system, three motors respectively requiring three difierent maximum operating pressures, each of said motors including fluid operable advancing and retracting means for actuating said motors, a variable delivery pump common to said motors for selectively supplying pressure fluid to said advancing or retracting means,

means for continuously urging said pump into full delivery position, pressure-responsive means associated with said pump andincluding difierential plunger means with three difierent effective areas, first conduit means continuously connecting the largest of said areas with the pressure side of said pump, second conduit means continuously connecting the second largest of said areas with the advancing means pertaining to the motor requiring the highest operating pressure, third conduit means continuously connecting the smallest of said efr'ectiveareas with the advancing means pertaining to the motor requiring the second highest maximum pressure, said second and third areas being opposed'to said first area and separate valve means for controlling the supply of

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