US3916625A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydrostatic propulsion system
Assignee: Doosan Bobcat North America Inc
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Filing: 1974-09-23
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Granted: 1975-11-04
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Expires: 1994-09-23
Abstract
Abstract A closed recirculating hydrostatic transmission system suitable for driving a traction vehicle. The system includes a pair of hydrostatic engine driven variable displacement pumps either of different displacements or engine driven at different speed ratios and each pump being operative to drive hydrostatic motors at the various wheels and in separate closed loop drive circuits such that accurate flow division as between the circuits is effected for driving the vehicle in four-wheel drive or, at the operator''s selection, for driving the motors in the one closed loop circuit at a higher speed in two-wheel drive by means of the pump of larger discharge volume. An operator''s control operates both pumps together with the limits of the smaller discharge pump in four-wheel drive, and operates the larger discharge pump within the limits thereof while rendering ineffective the smaller discharge pump in two-wheel drive. The operator''s control includes a magnetizable linkage which, at the operator''s election, may function as a rigid link to operate both pumps together or as a collapsible or expansible link which may operate the larger pump within its limits of displacement while returning the smaller pump to zero displacement. Valve means enables smooth transition and shifting between two and four-wheel drive at any time. Flow divider-combiner means in each closed loop circuit adjusts fluid flow to each motor as a function of steering angle to assure positive traction at each driven wheel in either forward or reverse drive under all surface conditions, and to differentiate, as required, wheel speeds during vehicle steering operations.
Inventors
- 👤 Donald A Holtkamp
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 12:19
CPC Classifications
F; F16; F16H; F16H61/00; F16H61/38; F16H61/40; F16H61/44; F16H61/456; B; B60; B60K; B60K17/00; B60K17/34; B60K17/356; B60T; B60T1/00; B60T1/02; B60T1/08; F16H61/42
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
115 words
In a hydrostatic drive system for a vehicle having first and second traction means, first and second hydraulic motor means for driving respective ones of said traction means and a prime mover means, first and second variable displacement hydraulic pump means driven by the prime mover means for driving the first and second motor means, respectively, said first pump means having a fluid discharge capability greater than said second pump means, and means controlling the fluid discharge of said first and second pump means including magnetic link means and means limiting the fluid discharge of said first pump means substantially to the fluid discharge of said second pump means in a first vehicle operating condition.
Claim 2
Dependent Claim
115 words
In a hydrostatic drive system for a vehicle having first and second traction means, first and second hydraulic motor means for driving respective ones of said traction means and a prime mover means, first and second variable displacement hydraulic pump means driven by the prime mover means for driving the first and second motor means, respectively, said first pump means having a fluid discharge capability greater than said second pump means, and means controlling the fluid discharge of said first and second pump means including magnetic link means and means limiting the fluid discharge of said first pump means substantially to the fluid discharge of said second pump means in a first vehicle operating condition.
Claim 3
Dependent Claim
34 words
A vehicle dRive system as claimed in claim 1 wherein said first and second pump means are operated at the same rpm, each pump means driving its respective motor means in a closed loop.
Claim 4
Dependent Claim
33 words
A vehicle drive system as claimed in claim 1 wherein said first and second pump means are operated at different rpm''s, each pump means driving its respective motor means in a closed loop.
Claim 5
Dependent Claim
48 words
A vehicle drive system as claimed in claim 1 wherein in a second operating condition said magnetic link means is demagnetized to permit said first pump means to operate at said greater fluid discharge and to permit said second pump means to operate at substantially zero fluid discharge.
Claim 6
Dependent Claim
36 words
A vehicle drive system as claimed in claim 4 wherein said first operating condition comprises driving said first and second motor means and said second operating condition comprises driving said first only of said motor means.
Claim 7
Dependent Claim
68 words
A vehicle drive system as claimed in claim 1 wherein said prime mover means drives said first and second pump means, each of said pump means operating with its respective motor means in a closed loop, and steering control means in each closed loop operable to effect differential wheel speed under traction as between each of two pairs of wheels driven by said first and second motor means.
Claim 8
Dependent Claim
118 words
A hydrostatic drive system for a vehicle having first and second traction means, first and second hydraulic motor means for driving respective ones of said traction means and a prime mover means, first and second variable displacement hydraulic pump means driven by the prime mover means for driving the first and second means, respectively, said first pump means having a fluid discharge capability greater than said second pump means, and control means operatively connected to said first and second pump means for operating said second pump means at substantially zero fluid discharge when said first pump means is operating at said greater fluid discharge, said control means including a link means and means for demagnetizing said link means.
Claim 9
Dependent Claim
118 words
A hydrostatic drive system for a vehicle having first and second traction means, first and second hydraulic motor means for driving respective ones of said traction means and a prime mover means, first and second variable displacement hydraulic pump means driven by the prime mover means for driving the first and second means, respectively, said first pump means having a fluid discharge capability greater than said second pump means, and control means operatively connected to said first and second pump means for operating said second pump means at substantially zero fluid discharge when said first pump means is operating at said greater fluid discharge, said control means including a link means and means for demagnetizing said link means.
Claim 10
Dependent Claim
41 words
A vehicle drive system as claimed in claim 7 wherein said control means operates to communicate in parallel the circuit of said second pump means and second motor means when said first pump means is operating at said greater fluid discharge.
Claim 11
Dependent Claim
157 words
A hydrostatic drive system for a vehicle having first and second traction means, first and second hydraulic motor means for driving respective ones of said traction means and a prime mover means, first and second variable displacement hydraulic pump means driven by the prime mover means for driving the first and second motor means, respectively, said first pump means having a fluid discharge capability greater than said second pump means, a control means connected to both said first and second pump means for maintaining under first operating conditions substantially equal fluid discharges thereof during operation within a fluid discharge capability limited by said second pump means and under second operating conditions enabling said first pump means to be operated at a fluid discharge greater than the fluid discharge capability of said second pump means, said control means including link means magnetizable and demagnetizable at the operator''s election to enable operation at said first or second operation condition.
Claim 12
Dependent Claim
157 words
A hydrostatic drive system for a vehicle having first and second traction means, first and second hydraulic motor means for driving respective ones of said traction means and a prime mover means, first and second variable displacement hydraulic pump means driven by the prime mover means for driving the first and second motor means, respectively, said first pump means having a fluid discharge capability greater than said second pump means, a control means connected to both said first and second pump means for maintaining under first operating conditions substantially equal fluid discharges thereof during operation within a fluid discharge capability limited by said second pump means and under second operating conditions enabling said first pump means to be operated at a fluid discharge greater than the fluid discharge capability of said second pump means, said control means including link means magnetizable and demagnetizable at the operator''s election to enable operation at said first or second operation condition.
Claim 13
Dependent Claim
59 words
A vehicle system as claimed in claim 9 wherein said link means when magnetized functions as a rigid link connected to both said first and second pump means and when demagnetized functions as a collapsible link enabling the first pump means to be operated at a fluid discharge greater than the fluid discharge capability of said second pump means.
Claim 14
Dependent Claim
75 words
A vehicle drive system as claimed in claim 9 wherein said control means also includes an operator''s control operatively connected to said first and second pump means by said link means, and means coordinated with said link means for limiting the range of control of said operator control means to a first range in said first operating condition and for limitIng the range of control thereof to a second range in said second operating condition.
Claim 15
Dependent Claim
49 words
A vehicle drive system as claimed in claim 9 wherein said link means includes a cylindrical member operatively connected to one of said pump means, a permanent magnet movable axially of said cylindrical member operatively connected to the other pump means, and electrical means for demagnetizing said permanent magnet.
Claim 16
Dependent Claim
31 words
A vehicle drive system as claimed in claim 12 wherein said electrical means is de-energized to effect said first opening condition and is electrically energized to effect said second operating condition.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-03 | 1979-05-05 | 1979-11-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-03 | 1983-05-05 | 1983-11-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-03 | 1987-05-05 | 1987-11-04 | $7700.00 | Window Closed / Lapsed |