US3740167A - Hydraulic system - Google Patents

Abstract

A hydraulic system employing a pressure compensated variable displacement pump in which the pressure and volume control of the pump are interconnected for simultaneous adjustment within a range in a predetermined relationship.

Description

United States Patent 1 1 1111 3,740,167 Albrecht June 19, 1973 HYDRAULIC SYSTEM 2,835,228 5/1958 Park et a1. 417/222 3,588,286 6 1971 Skinner 91/506 [75] Inventor. Davld Eugene Albrecht, Blue Bell, 1,748,606 2,1930 lngoldbym 417/222 3,163,115 12/1964 Nerf et al 417 222 Assignees: David E. Albrecht, Blue 3,250,227 KOUl'lS 417/222 Ra mond H Jensen Plymouth 3,302,585 2/l967 Adams et al 417/222 Meyeting 3,489,094 1/1970 Vaughan et a1] 417/222 22 H J 19;) FOREIGN PATENTS 0R APPLICATIONS I 1 2,017,656 4 1970 Germany 417 222 Appl. No.: 49,134

52 US. Cl. 417/218 51 Int. Cl. F0lb49/00 [58] Field of Search 417 213, 218,222;

[56] 1 References Cited 7 UNITED sTATEs PATENTS 2,283,321 5/1942 D08 et al. 60/52 us 2,298,358 10/1942 Ernst 60/52 us Primary Examiner-William L. Freeh Attorney-Busser, Smith & Harding 57 ABSTRACT A hydraulic system employing a pressure compensated variable displacement pump in which the pressure and volume control of the pump are interconnected for simultaneous adjustment within a :range in a predetermined relationship.

5 Claims, 4 Drawing Figures Patented June 19, 1973 3,740,167

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ATTORNEYS Patented June 19, 1973 3,740,167

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I I 23 A T W f E l INVENTOR 4; DAVID EUGENE ALBRECHT ATTORNEYS HYDRAULIC SYSTEM BACKGROUND OF THE INVENTION This invention relates to hydraulic systems and particularly to a hydraulic system employing a pressure compensated variable displacement pump to deliver a volume of fluid under pressure to a work load.

In a hydraulic system the work done per unit time (horsepower) is directly proportional to the volume delivered and the delivery pressure. Most hydraulic systems employ a hydraulic cylinder or fluid motor to perform the work on a machine. A cylinder imparts linear motion whereas a fluid motor imparts rotary motion.

With respect to a cylinder, it will be apparent that the higher the hydraulic pressure, the greater is the force capability of the cylinder, and the higher the flow to the cylinder, the higher will be the speed at which the cylinder will operate. Likewise, with respect to a fluid motor, the higher the hydraulic pressure the greater will be the torque capability of the motor, and the higher the flow volume to the motor, the higher the speed at which the motor will rotate.

Typically, a hydraulic pumping system of the prior art is set for the maximum volume and the maximum pressure for which the system is designed. However, these two factors in the maximum condition may not be required simultaneously. It is desirable in such a system, to be able to vary infinitely the flow volume delivered and the delivery pressure in relation to one another in such a manner as would permit the system to deliver the optimum system requirement throughout the flow and pressure ranges. An example of such a de-' sired application is a spindle drive that requires a constant horsepower output. In a typical hydraulic systemof the prior art wherein the flow volume and pressure are set at maximum system limits, the horsepower available at the spindle is directly proportional to the spindle speed. This results in less than optimum utilization of the horsepower input.

SUMMARY OF THE INVENTION It is the general object of the invention to provide a hydraulic pumping system which is controlled so that the desirable flow/pressure condition can be obtained by employing a pressure compensated variable displacement pump which is controlled to produce this re sult.

Briefly stated, the control system in accordance with the invention is employed in a hydraulic system for delivering fluid to a work load and comprises a pressure compensated variable displacement pump adapted to have the maximum delivery volume and its maximum delivery pressure varied infinitely within a range. This pump also has means for setting the pressure and the volume to any desired setting within the pressure and volume ranges. The essence of the invention is the provision of a control means which interconnects said volume setting means and said pressure setting means for simultaneously varying said pressure and volume settings in a predetermined relationship.

In the pumps of the indicated type the operation is such that the pump will always deliver its maximum set flow rate unless the system pressure gets as highas the maximum pressure setting on the pump, in which case the pump will only deliver enough flow to maintain this system pressure. Also with this type of pump, means are provided for setting the pumps displacement from zero (no flow) to maximum pump delivery. The pump is also adapted to permit the maximum pressure setting to be adjusted infinitely within the pressure limits of the pump. In accordance with the invention there is provided a control system which interconnects the volume adjustment and the pressure adjustment of the pump in a manner such that said volume setting means and said pressure setting means can be simultaneously varied in A more specific application of the control system in accordance with the invention is the provision of a constant horsepower drive system where the control can be set to give a constant horsepower over a range of operation in which as the flow setting decreases, the pressure setting may be simultaneously increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic showing of the hydraulic system employing the control means in accordance with the invention;

' FIG. 2 is a detailed showing of the control means employed in the hydraulic system in accordance with the invention;

FIG. 3 is a diagrammatic illustration of the control means as viewed on lines 33 of FIG. 2; and

FIG. 4 is a graph illustrating an application of the hydraulic system in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1 his noted that this Figure '7 shows a typical circuit schematic for the hydraulic system employing the invention. This system includes a conventional pressure compensated variable displacement pump 10 which receives the hydraulic fluid from a reservoir 12 by means of a line 14 and delivers the same to a suitable work load 16 by way of line 18, the return line from the work load being indicated at20. The pressure control for the pump 10 is indicated at 22 and the volume control for thepump 10 is indicated at 24. The pressure control 22 and the volume control 24 are operated by the novel control means in accordance with the invention indicated generally at 26. Variable displacement pumps of the indicated type are conventional, one such pump being made by the Delavan Manufacturing Co. of West Des Moines, Ia. and being disclosed in this companys Manual No. 1211A wherein such a pump is designated as Model No. PV320 and described as a pressure compensator variable displacement pump. This pump is a positivedisplacement axial piston pump. in which a cylinder is rotated so pistons are driven back and forth in their cylinders in the direction parallel to the pump shaft. The basic construction of such a pump is disclosed in U.S. Pat. Nos. Re. 26,519, 3,221,660, and 3,350,881.

1n the operation of this type of pump, a cylinder rotor with its pistons is rotated on a shaft so that the pistons are driven back and forth in their cylinders in a direction parallel to the shaft, liquid being forced into the cylinders by pressure differences while the pistons are moving outwardly and liquid being forced out of the pistons while the pistons are moving inwardly. The pump is provided with means whereby the distance the pistons will move back and forth is set by the tilting of a cam reaction plate so that the angle of the cam reaction plate determines the piston stroke and accordingly the pump displacement.

The pump is provided with a volume limit adjustment whereby the maximum volume desired to be pumped can be set, such means comprising an adjustment screw which limits the maximum angle of the cam reaction plate. The pump is also provided with an adjustment means which sets the desired pressure of the pump, such means comprising an adjustment screw which operates on a pressure compensating spring of a pressure control valve which controls a pair of pistons which control the position of the cam reaction plate to limit the discharge pressure of the valve to the set amount.

It is to be noted that the hydraulic system in accordance with the invention may utilize various of the pressure compensated variable displacement pumps known in the art and is not limited to the particular type described above. Since these pumps are conventional and well known in the art, further description thereof is not deemed necessary.

Referring to FIG. 2 there is shown the pump which comprises the pressure control 22, which includes an adjustment screw indicated at 32, and the volume limit control 24, which includes an adjustment screw indicated at 34. As viewed from the right in FIG. 2, the pressure adjustment screw 32 is turned in a clockwise direction to increase the pressure and in a counter-clockwise direction to decrease the pressure whereas the volume adjustment screw 34 is turned in a clockwise direction to decrease the volume and in a counter-clockwise direction to increase the volume.

The control means 26 comprises a sprocket 40 mounted on a shaft 41 drivingly connected to pressure adjustment screw 32 by way of a coupling 42 and a sprocket 44 mounted on a shaft 45 drivingly connected to the adjustment screw 34 by way of a coupling 46. There is also provided a control shaft 50 which carries a control knob 52 on one end thereof. Shaft 45 is journalled in a bearing support 47 mounted on the pump or a supporting frame. Mounted on the control shaft 50 is a sprocket 54 which carries a drive chain 56 which is connected to the sprocket 40 on the pressure adjustment shaft 41. There is also provided another sprocket 58 on the control shaft 50 which is interconnected with the sprocket 44 on the volume adjustment shaft 45 by means ofa chain 59 as shown in the drawing. By means of this arrangement the pressure adjustment and the volume adjustment of the pump 10 are are interconnected by means of the control means 26 so that they may be simultaneously adjusted. Moreover, it will be apparent that this adjustment is designed so that the pressure adjustment and the volume adjustment may be varied in a predetermined relationship which depends upon the size and arrangement of the various interconnecting parts (i.e. sprockets and chains).

From a consideration of FIGS. 2 and 3, it will be noted that the rotation of the control knob 52 in a clockwise direction will cause a corresponding clockwise rotation of shafts 50, 41 and 45, and by reason of the connection through couplings 42 and 46, there will also be imparted a clockwise rotation to the pressure adjusting screw 32 and the volume adjusting screw 34 (the rotation of the control means 26 being indicated by the arrows in FIG. 3). As was discussed above, the clockwise rotation of the pressure adjusting screw 32 will cause an increase in the pressure adjustment of the pump and by reason of the clockwise rotation of volume adjustment screw 34, this will cause a decrease in the volume adjustment of the pump. Moreover, it will be apparent that by reason of the connection by way of the sprockets shown in FIG. 3, the increase in the pressure adjustment will be in a predetermined relation with the decrease in the volume adjustment. On the other hand when the control knob 52 is turned in the counter-clockwise direction, the effect on the pressure and volume settings will be the reverse, namely there will be a decrease in the pressure adjustment and an increase in the volume adjustment, and, again, these adjustments will be in a predetermined relationship.

It will be apparent that by a simple mechanical rearrangement of the parts, such as a criss-crossing of one of the belts 56 or 59, it is possible to reverse the abovediscussed control relationships. This is simply a matter of choice in design and is related to the results desired.

Moreover, it will also be apparent that although the disclosed arrangement shows the two controls mechanically innerconnected by a chain and sprocket means, a similar control action can be achieved with various mechanical connections such as gears, a rack and pin ion arrangement, etc., and may also be achieved by other means, such as electrical, pneumatic or hydraulic means, etc.

One important specific application of the hydraulic control system in accordance with the invention is the provision of a constant horsepower drive system where the control would be set to produce a constant horsepower over a range of operation. This would be achieved by setting the volume control so that as its setting is progressively decreased linearly, the pressure is progressively increased linearly so as to maintain a constant horsepower relationship throughout the range of operation. This arrangement is illustrated graphically in FIG. 4. It is noted that the control arrangement shown in FIG. 3 is specifically designed to achieve a constant horsepower output for a pump of the indicated type. However, it would be obvious that the characteristics of the pump and the adjustment means provided thereon will require the adaption of the control means in order to achieve the linear relationship which will produce the constant horsepower output discussed above.

It will also be apparent that by determining the particular relationship between the volume and pressure settings, it is possible to achieve various relationships to produce various horsepower conditions in addition to the constant horsepower condition discussed above.

It will be evident that changes may be made in the construction and arrangement of parts without departing from the scope of the invention. Accordingly, it is not desired to be limited except as set forth by the following claims.

I claim:

1. In a hydraulic system for delivering fluid to a work load, a pressure compensated variable displacement pump adapted to have the maximum delivery volume thereof set within an infinitely variable flow range and the maximum delivery pressure thereof set within an infinitely variable pressure range, means for setting the maximum delivery volume of said pump to a desired setting within said flow range, means for setting the maximum delivery pressure of said pump to a desired setting within said pressure range, said pump being constructed and arranged to deliver the maximum set volume of flow until the system pressure reaches the maximum set pressure whereupon the pump will only deliver enough flow to maintain the system pressure, and control means for simultaneously varying said pressure and volume settings in a predetermined relationship, said control means including means interconnecting said volume setting means and said pressure setting means for adjusting one setting to a predetermined desired setting as the other setting is adjusted to a corresponding predetermined desired setting.

2. In a hydraulic system according to claim 1 wherein said control means is arranged to simultaneously adjust said pressure setting means and said volume setting means to increase the pressure setting andidecrease the volume setting and vice versa.

3. In a hydraulic system according to claim 1 wherein said volume setting means includes an adjustable screw, said pressure setting means includes an adjustable screw, and said control means includes an adjustable member and means interconnecting said adjust able member with each of said adjusting screws.

4. In a hydraulic system according to claim 3 wherein said control means is arranged to simultaneously adjust said pressure setting means and said volume setting means to increase the pressure setting and decrease the volume setting and vice versa.

5. A hydraulic system according to claim 2 wherein said control means is constructed and arranged so that said pressure setting is varied in a linear relationship relative to said volume setting.

Claims (5)

1. In a hydraulic system for delivering fluid to a work load, a pressure compensated variable displacement pump adapted to have the maximum delivery volume thereof set within an infinitely variable flow range and the maximum delivery pressure thereof set within an infinitely variable pressure range, means for setting the maximum delivery volume of said pump to a desired setting within said flow range, means for setting the maximum delivery pressure of said pump to a desired setting within said pressure range, said pump being constructed and arranged to deliver the maximum set volume of flow until the system pressure reaches the maximum set pressure whereupon the pump will only deliver enough flow to maintain the system pressure, and control means for simultaneously varying said pressure and volume settings in a predetermined relationship, said control means including means interconnecting said volume setting means and said pressure setting means for adjusting one setting to a predetermined desired setting as the other setting is adjusted to a corresponding predetermined desired setting.

2. In a hydraulic system according to claim 1 wherein said control means is arranged to simultaneously adjust said pressure setting means and said volume setting means to increase the pressure setting and decrease the volume setting and vice versa.

3. In a hydraulic system according to claim 1 wherein said volume setting means includes an adjustable screw, said pressure setting means includes an adjustable screw, and said control means includes an adjustable member and means interconnecting said adjustable member with each of Said adjusting screws.

4. In a hydraulic system according to claim 3 wherein said control means is arranged to simultaneously adjust said pressure setting means and said volume setting means to increase the pressure setting and decrease the volume setting and vice versa.

5. A hydraulic system according to claim 2 wherein said control means is constructed and arranged so that said pressure setting is varied in a linear relationship relative to said volume setting.

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