Hydraulic-drive system for an intermittent-demand load
First Claim
1. An energy-efficient hydraulic drive system for interposition between a prime-mover source of rotary power and a hydraulic motor for an intermittently driven load, said system comprising:
- first and second pumps connected to the rotary-power output of the prime-mover source;
a hydraulic accumulator and a sump;
said first pump being of fixed-rate variety and connected to draw hydraulic fluid from said sump and to deliver the same to said accumulator via a first check valve oriented to prevent reverse flow, with relief-valve discharge to sump upon achievement of a predetermined high pressure of accumulated charge;
said second pump being of variable-rate variety and having substantially greater flow capacity than said first pump;
a fluid-delivery line from said accumulator to said motor via said second pump;
a fluid-return line from said motor to said accumulator via a second check valve oriented to prevent reversal of fluid-return flow; and
a dumping valve interposed between said motor and said second check valve for transient diversion of return flow to sump, whereby to transiently enable enhanced load-accelerating torque from said motor;
further whereby motor-running speed may be selectively determined by said second pump, and, upon reducing the flow-rate setting of said second pump, reflected load momentum causes said motor to pump return fluid in partial recharge of said accumulator.
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Accused Products
Abstract
A prime-mover driven variable-rate pump of relatively great flow capacity is in delivery and return-circuit connection to an intermittently loaded hydraulic motor. A fixed-rate pump of substantially less capacity is continuously driven by the prime-mover, to charge a hydraulic accumulator, there being a safety relief to sump when a predetermined high-pressure threshold is reached. The accumulator is exclusively connected to the inlet of the variable-rate pump, being isolated by check valves from delivering any reverse flow to the fixed-rate pump and from delivering any reverse flow to the return portion of the motor-driving circuit. In said return portion, and between its check valve and the motor, a "dump" valve is operable for transient diversion of return flow to sump, thereby transiently enabling enhanced load-accelerating torque from the motor; this valve is preferably pressure-operated to "dump" position upon a load-reflecting pressure rise in the supply line from the variable-rate pump to the motor. Normal motor-running speeds are selectively determined by the variable-rate pump; and load-reflected angular momentum causes the motor to pump return fluid at elevated pressure, in partial recharge of the accumulator, thus assisting in braking the angular momentum while aiding in a recharge of the accumulator.
37 Citations
12 Claims
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1. An energy-efficient hydraulic drive system for interposition between a prime-mover source of rotary power and a hydraulic motor for an intermittently driven load, said system comprising:
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first and second pumps connected to the rotary-power output of the prime-mover source; a hydraulic accumulator and a sump; said first pump being of fixed-rate variety and connected to draw hydraulic fluid from said sump and to deliver the same to said accumulator via a first check valve oriented to prevent reverse flow, with relief-valve discharge to sump upon achievement of a predetermined high pressure of accumulated charge; said second pump being of variable-rate variety and having substantially greater flow capacity than said first pump; a fluid-delivery line from said accumulator to said motor via said second pump; a fluid-return line from said motor to said accumulator via a second check valve oriented to prevent reversal of fluid-return flow; and a dumping valve interposed between said motor and said second check valve for transient diversion of return flow to sump, whereby to transiently enable enhanced load-accelerating torque from said motor; further whereby motor-running speed may be selectively determined by said second pump, and, upon reducing the flow-rate setting of said second pump, reflected load momentum causes said motor to pump return fluid in partial recharge of said accumulator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 9, 10, 11, 12)
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8. An energy-efficient drive system for interposition between a prime-mover source of rotary power and a hydraulic motor for an intermittently driven load, said system comprising:
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first, second and third pumps connected to the rotary-power output of the prime-mover source; a hydraulic accumulator and a sump; said first and third pumps being of variable-rate variety and of greatest capacity, said third pump being of lowest capacity, and said first pump being of capacity intermediate the respective capacities of said second and third pumps; said first pump being connected to draw hydraulic fluid from said sump and to deliver the same to said accumulator via a first check valve oriented to prevent reverse flow, with relief-valve discharge to sump upon achievement of a predetermined high pressure of accumulator charge; a fluid-delivery line from said accumulator to said motor via said second and third pumps in separate parallel branches, the branch for said third pump including a check valve oriented to prevent reverse flow and a second relief valve with discharge to sump; a fluid-return line from said motor to said accumulator via an on-off distributor valve and a second check valve, said second check valve being interposed between said on-off valve and said accumulator and oriented to prevent reverse flow; and means for selectively operating said on-off valve from a position of fluid return from said motor to said accumulator, to a position in which said fluid return is transiently diverted to sump.
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Specification