Patent US4200008A successfully refreshed from Google Patents.
US4200008A
Expired / Lapsed
US
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Hydraulic actuating system for a pair of concurrently operating friction devices for the selection of speeds of a load-shiftable transmission
Assignee: ZF Friedrichshafen AG
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Filing: 1977-12-28
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Granted: 1980-04-29
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Expires: 1997-12-28
Abstract
Abstract A hydraulic control system of the type disclosed in U.S. Pat. No. 3,938,410 is improved by providing a 2-3 shift valve which connects a direct passage and a throttle-containing passage to the control valve for the second clutch or brake (second-friction device) while the pressure in the first clutch or brake (first friction device) is applied to one side of the second control valve, a restoring spring acting upon the opposite side of this second control valve. This valve establishes a threshold for the pressure in the first friction device such that the direct passage is connected to the second friction device below the threshold while the throttle-containing passage is connected to the second friction device at or above this threshold.
Inventors
- 👤 Hansjorg Dach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 23:29
CPC Classifications
F; F16; F16H; F16H61/00; F16H61/04; F16H61/06; F16H61/065; F16H61/067
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
310 words
In a hydraulic control system for a multispeed transmission shiftable under load and having two friction devices hydraulically actuatable concurrently in a predetermined speed condition of the transmission through a 2-3 shift valve, a first of said friction devices remaining actuated in a neighboring speed condition and being connected to a first control valve having a valve slider which acts against a spring in a first phase of pressure build-up in said first friction device and acted upon by a direct abutment formed by a piston of a first damper connected to the first friction device, a second control valve connected to a second of said friction devices and to a second damper having a piston acting upon a restoring spring with a fixed seat, and wherein the hydraulic lines to both said friction devices are connected in the concurrently actuated state there of, the improvement wherein: in said predetermined speed condition of the transmission with concurrent actuation of said first and second friction devices, a first hydraulic line feeding the first friction device is connected by the 2-3 shift valve to a direct passage and to a throttle-containing passage communicating via the second control valve selectively with a second hydraulic line feeding the second friction device; and the second control valve has a slider to one end surface of which is applied the pressure of the first friction device while a restoring spring bears in the opposite direction upon said slider of said second control valve so that at a pressure in the first friction device below a threshold value said second control valve connects said direct passage to said second hydraulic line and blocks the throttle-containing passage and upon the pressure in said first friction drive attaining said threshold value, said second control valve blocking said direct passage and connecting said throttle-containing passage to said second hydraulic line.
Claim 2
Dependent Claim
310 words
In a hydraulic control system for a multispeed transmission shiftable under load and having two friction devices hydraulically actuatable concurrently in a predetermined speed condition of the transmission through a 2-3 shift valve, a first of said friction devices remaining actuated in a neighboring speed condition and being connected to a first control valve having a valve slider which acts against a spring in a first phase of pressure build-up in said first friction device and acted upon by a direct abutment formed by a piston of a first damper connected to the first friction device, a second control valve connected to a second of said friction devices and to a second damper having a piston acting upon a restoring spring with a fixed seat, and wherein the hydraulic lines to both said friction devices are connected in the concurrently actuated state there of, the improvement wherein: in said predetermined speed condition of the transmission with concurrent actuation of said first and second friction devices, a first hydraulic line feeding the first friction device is connected by the 2-3 shift valve to a direct passage and to a throttle-containing passage communicating via the second control valve selectively with a second hydraulic line feeding the second friction device; and the second control valve has a slider to one end surface of which is applied the pressure of the first friction device while a restoring spring bears in the opposite direction upon said slider of said second control valve so that at a pressure in the first friction device below a threshold value said second control valve connects said direct passage to said second hydraulic line and blocks the throttle-containing passage and upon the pressure in said first friction drive attaining said threshold value, said second control valve blocking said direct passage and connecting said throttle-containing passage to said second hydraulic line.
Claim 3
Dependent Claim
53 words
The improvement defined in claim 1 wherein said first damper and said spring of said second control valve are dimensioned such that said second valve connects said throttle-containing passage to said second hydraulic line substantially upon direct abutment between said piston of said first damper and said slider of said first control valve.
Claim 4
Dependent Claim
38 words
The improvement defined in claim 2, further comprising means for applying load-modulated pressure to said slider of said second valve in a direction identical to that in which said restoring spring of said second valve is effective thereon.
Claim 5
Dependent Claim
30 words
The improvement defined in claim 3 wherein said throttle-containing passage is provided with a check valve opening upon the draining of said second hydraulic line to discharge fluid unimpeded therefrom.
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) | 1983-04-29 | 1983-10-29 | 1984-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-04-29 | 1987-10-29 | 1988-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-04-29 | 1991-10-29 | 1992-04-29 | $7700.00 | Window Closed / Lapsed |