US4135121A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable-speed drive system with hydrostatic transmission and electric shunt motor
Assignee: Linde GmbH
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Filing: 1977-05-16
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Granted: 1979-01-16
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Expires: 1997-05-16
Abstract
Abstract A drive system for a utility vehicle, such as a fork-lift truck, comprises a hydrostatic transmission whose pump is driven by an electric shunt-wound motor having a field winding so energized, under the control of a potentiometer responsive to the fluid pressure in the transmission, that the field current varies inversely with transmitted torque over at least a portion of the speed range of the vehicle. The automatic potentiometer control exerted by the fluid pressure may be overridden by a manually operable lever. The same potentiometer can be used to vary the motor speed in response to the output pressure of another pump which is driven by the electric motor and coupled with the fork-lifting mechanism of the vehicle.
Inventors
- 👤 Hans W. Stuhr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 17:41
CPC Classifications
H; H02; H02P; H02P23/00; H02P23/16; Y; Y10; Y10S; Y10S388/00; Y10S388/923; Y10S388/929
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
197 words
A system for driving a load, comprising: a source of electric current; an electric motor having an armature and a field winding connected in parallel across said source; a transmission with a continuously variable ratio of input and output velocities, said transmission including a hydrostatic pump unit mechanically connected with said armature, a hydrostatic motor unit coupled with said load and conduit means interlinking said hydrostatic units for hydraulic power transfer therebetween, whereby a torque is applied by said hydrostatic motor unit to said load; manual setting means connected to at least one of said hydrostatic units for selectively varying said ratio over a predetermined adjustment range; torque-sensing means connected to said transmission; and current-control means in circuit with said field winding connected to said torque-sensing means for varying the energization of said field winding generally inversely with said torque over at least a part of a range of output velocities whereby the input velocity of said transmission varies generally in proportion to torque throughout said part of said range of output velocities, said current-control means being coupled with said setting means only through the intermediary of said torque-sensing means throughout substantially all of said adjustment range.
Claim 2
Independent Claim
197 words
A system for driving a load, comprising: a source of electric current; an electric motor having an armature and a field winding connected in parallel across said source; a transmission with a continuously variable ratio of input and output velocities, said transmission including a hydrostatic pump unit mechanically connected with said armature, a hydrostatic motor unit coupled with said load and conduit means interlinking said hydrostatic units for hydraulic power transfer therebetween, whereby a torque is applied by said hydrostatic motor unit to said load; manual setting means connected to at least one of said hydrostatic units for selectively varying said ratio over a predetermined adjustment range; torque-sensing means connected to said transmission; and current-control means in circuit with said field winding connected to said torque-sensing means for varying the energization of said field winding generally inversely with said torque over at least a part of a range of output velocities whereby the input velocity of said transmission varies generally in proportion to torque throughout said part of said range of output velocities, said current-control means being coupled with said setting means only through the intermediary of said torque-sensing means throughout substantially all of said adjustment range.
Claim 3
Dependent Claim
26 words
A system as defined in claim 1, further comprising manual actuating means linked with said current-control means for optionally overriding the effect of said torque-sensing means.
Claim 4
Dependent Claim
41 words
A system as defined in claim 1, further comprising a lost-motion coupling between said actuating means and said setting means for making said torque-sensing means ineffectual in a maximum-speed-ratio position of said setting means representing an end of said adjustment range.
Claim 5
Dependent Claim
36 words
A system as defined in claim 1 wherein said torque-sensing means comprises a hydraulic cylinder fluidically connected to said conduit means and a spring-loaded piston in said cylinder displaceable by fluid pressure in said conduit means.
Claim 6
Dependent Claim
57 words
A system as defined in claim 4 wherein said load comprises a traction wheel of a vehicle equipped with a cargo-lifting mechanism, said mechanism including a hydraulic pump driven by said electric motor, said cylinder being provided with a branch connection to a discharge port of said hydraulic pump for controlling the speed of said electric motor.
Claim 7
Dependent Claim
46 words
A system as defined in claim 5 wherein said cylinder has a first inlet communicating with said conduit means and a second inlet communicating with said branch connection, said piston having a small-area face confronting said first inlet and a large-area face confronting said second inlet.
Claim 8
Dependent Claim
28 words
A system as defined in claim 4 wherein said current-control means comprises a potentiometer in series with said field winding having a slider mechanically linked with said piston.
Claim 9
Dependent Claim
25 words
A system as defined in claim 4, further comprising manual actuating means linked with said piston for optionally overriding the effect of said fluid pressure.
Claim 10
Dependent Claim
46 words
A system as defined in claim 4 wherein said conduit means comprises a pair of conduits carrying hydraulic fluid at different pressures, the fluidical connection between said conduit means and said cylinder including a pressure discriminator transmitting only the higher of said pressures to said cylinder.
Claim 11
Dependent Claim
16 words
A system as defined in claim 9 wherein said pressure discriminator is a double check valve.
Claim 12
Dependent Claim
56 words
A system as defined in claim 4 wherein said setting means is connected to said hydrostatic motor, further comprising a coupling between said setting means and said current-control means for modifying the effect of said fluid pressure upon the energization of said field winding to compensate for changes in the fluid-absorption rate of said hydrostatic motor.
Claim 13
Independent Claim
107 words
A system for driving a load, comprising: a source of electric current; an electric motor having an armature and a field winding connected in parallel across said source; a generator of hydraulic pressure fluidically linked with a load and driven by said motor; pressure-sensing means in the output of said generator; and current-control means in circuit with said field winding connected to said pressure-sensing means for varying the energization of said field winding generally inversely with load over at least a part of a range of output velocities whereby the input velocity of said generator varies generally in proportion to load throughout said part of said range.
Claim 14
Independent Claim
107 words
A system for driving a load, comprising: a source of electric current; an electric motor having an armature and a field winding connected in parallel across said source; a generator of hydraulic pressure fluidically linked with a load and driven by said motor; pressure-sensing means in the output of said generator; and current-control means in circuit with said field winding connected to said pressure-sensing means for varying the energization of said field winding generally inversely with load over at least a part of a range of output velocities whereby the input velocity of said generator varies generally in proportion to load throughout said part of said range.
Claim 15
Dependent Claim
31 words
A system as defined in claim 12, further comprising manual actuating means linked with said current-control means for optionally overriding said pressure-sensing means to establish high output velocities independently of load.
Claim 16
Dependent Claim
148 words
A system as defined in claim 12, further comprising a transmission with a continuously variable ration of input and output velocities including a hydrostatic pump unit mechanically connected with said armature in parallel with said generator, a hydrostatic motor unit coupled with a second load, conduit means interlinking said hydrostatic units for hydraulic transfer therebetween whereby a torque depending on said second load and on said ratio is applied by said hydrostatic motor unit to said second load, and manual setting means connected to at least one of said hydrostatic units for selectively varying said ratio over a predetermined adjustment range, said pressure-sensing means being further connected to said conduit means for making the energization of said field winding additionally dependent upon said torque, said current-control means being coupled with said setting means only through the intermediary of said torque-sensing means throughout substantially all of said adjustment range.
Claim 17
Dependent Claim
47 words
A system as defined in claim 8, further comprising a unidirectionally yieldable spring coupling inserted between said actuating means and said piston, said current-control means being connected with said actuating means ahead of said spring coupling for positive entrainment in the yielding direction of said spring coupling.
References Cited (Backward Citations)
US2590022A
Cited
US3885204A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-01-15 | 1982-07-17 | 1983-01-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-01-15 | 1986-07-17 | 1987-01-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-01-15 | 1990-07-17 | 1991-01-16 | $7700.00 | Window Closed / Lapsed |