US3809501A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydraulic load sensitive system
Assignee: SPX Technologies Inc
•
Filing: 1973-01-08
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Granted: 1974-05-07
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Expires: 1993-01-08
Abstract
Abstract A hydraulic load sensitive system is provided having a variable delivery pump, the output of which is controlled by an opencenter control valve. Load sensitive control apparatus is provided including a control cylinder having a piston for operating a control cam of the variable delivery pump. First and second feedback circuits are provided to govern operation of the control cylinder alternately, the first feedback circuit including an open-center position of the control valve and the second feedback circuit including a circuit through a pressure differential valve.
Inventors
- 👤 C Weisenbach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 13:51
CPC Classifications
F; F04; F04B; F04B49/00; F04B49/002; E; E02; E02F; E02F9/00; E02F9/20; E02F9/22; E02F9/2221; E02F9/2232; E02F9/2278; E02F9/2296; F15; F15B; F15B11/00; F15B11/02; F15B11/04; F15B11/05; F15B11/055; F15B2211/00; F15B2211/20; F15B2211/205; F15B2211/2053; F15B2211/20546; F15B2211/20553; F15B2211/25; F15B2211/253; F15B2211/30; F15B2211/305; F15B2211/30525; F15B2211/31; F15B2211/3105; F15B2211/3116; F15B2211/355
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
135 words
A hydraulic load sensitive system comprising a variable delivery hydraulic pump, an open-center control valve, and load sensitive control means wherein improved load sensitive control means comprises: a. a control cylinder containing a piston having a shaft for actuating a control cam of the variable delivery pump, b. a first feedback circuit from output of the pump to the control cylinder through an open-center circuit of the control valve for limiting pressure output of the pump, c. a pressure differential valve for comparing pump delivery pressure with load pressure, d. a second feedback circuit from output of the pump to the control cylinder through the pressure differential valve for limiting pressure output of the pump and e. means for rendering the first and second feedback circuits effective alternately for limiting output pressure of the pump.
Claim 2
Dependent Claim
135 words
A hydraulic load sensitive system comprising a variable delivery hydraulic pump, an open-center control valve, and load sensitive control means wherein improved load sensitive control means comprises: a. a control cylinder containing a piston having a shaft for actuating a control cam of the variable delivery pump, b. a first feedback circuit from output of the pump to the control cylinder through an open-center circuit of the control valve for limiting pressure output of the pump, c. a pressure differential valve for comparing pump delivery pressure with load pressure, d. a second feedback circuit from output of the pump to the control cylinder through the pressure differential valve for limiting pressure output of the pump and e. means for rendering the first and second feedback circuits effective alternately for limiting output pressure of the pump.
Claim 3
Dependent Claim
34 words
A hydraulic load sensitive system according to claim 1 wherein another open-center circuit through the control valve provides a restrictive circulation of fluid through the pump when the valve is in an open-center position.
Claim 4
Dependent Claim
10 words
a spring for biasing the spool in one direction, and
Claim 5
Dependent Claim
10 words
a spring for biasing the spool in one direction, and
Claim 6
Dependent Claim
22 words
means including a balanced piston for operating the spool selectively in opposiTe directions in accordance with different relative pump and load pressures.
Claim 7
Dependent Claim
22 words
means including a balanced piston for operating the spool selectively in opposiTe directions in accordance with different relative pump and load pressures.
Claim 8
Dependent Claim
42 words
A hydraulic load sensitive system according to claim 1 wherein inputs to the control cylinder in the first and second feedback circuits include a pressure sensitive shuttle valve which selects input from the first or second feedback circuit having the highest pressure.
Claim 9
Dependent Claim
29 words
A hydraulic load sensitive system according to claim 1 wherein the pressure differential valve has pressure supply, lap, and exhaust positions for governing respective connections to the control cylinder.
Claim 10
Dependent Claim
36 words
A hydraulic load sensitive system according to claim 4 wherein connections from ports of the differential valve are applied to the control cylinder at opposite sides of the piston for governing output pressure of the pump.
Claim 11
Dependent Claim
21 words
A hydraulic load sensitive system according to claim 4 wherein a pressure reducer valve is included in the second feedback circuit.
Claim 12
Dependent Claim
27 words
A hydraulic load sensitive system according to claim 6 wherein the pressure reducer valve is connected between output of the pump and input to the differential valve.
Claim 13
Dependent Claim
14 words
A hydraulic load sensitive system according to claim 4 wherein the differential valve comprises;
Claim 14
Dependent Claim
22 words
A hydraulic load sensitive system according to claim 8 wherein load pressure is applied to the differential valve through a restricting orifice.
Claim 15
Dependent Claim
25 words
A hydraulic load sensitive system according to claim 9 wherein load pressure applied to the differential valve is also applied to a pressure regulator valve.
Claim 16
Dependent Claim
37 words
A hydraulic load sensitive system according to claim 1 wherein the open-center valve has an open-center exhaust chamber separate from an exhaust manifold used when the open-center valve has one of its plungers in an actuated position.
Claim 17
Dependent Claim
27 words
A hydraulic load sensitive system according to claim 11 wherein the open-center valve has two exhaust ports when in its open-center position, one of which is restricted.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-06 | 1977-11-05 | 1978-05-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-06 | 1981-11-05 | 1982-05-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-06 | 1985-11-05 | 1986-05-07 | $7700.00 | Window Closed / Lapsed |