US4186909A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fail-to-neutral module
Assignee: Dynex Rivett Inc
•
Filing: 1978-05-23
•
Granted: 1980-02-05
•
Expires: 1998-05-23
Abstract
Abstract Disclosed is an improved hydraulic control comprising a fail-to-neutral module. As is conventional, the hydraulic control comprises a main spool and a fluid flow path comprising a bridge circuit including a driver stage. The fail-to-neutral module comprises means defining a fail-to-neutral orifice which (a) is located in the fluid flow path upstream of the bridge circuit and (b) has a relatively large flow area but a maximum dimension smaller than the smallest orifice in the pilot stage. Preferably the means comprise a pin positioned through a hole, the pin and the hole both being circular in cross-section and coaxial, and the fail-to-neutral orifice is the clearance between the pin and the boundary of the hole.
Inventors
- 👤 Kishor Patel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 07:20
CPC Classifications
F; F15; F15B; F15B13/00; F15B13/02; Y; Y10; Y10T; Y10T137/00; Y10T137/794; Y10T137/8593; Y10T137/86493; Y10T137/86574; Y10T137/86582; Y10T137/8659
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
139 words
A hydraulic control comprising: (a) a main spool; (b) a fluid flow path operatively connected to said main spool and comprising a bridge circuit containing a plurality of orifices at least one of which is a variable orifice; and (c) means defining a fail-to-neutral orifice which (i) has a flow area large enough so that it does not cause an appreciable pressure drop but a maximum dimension smaller than the smallest orifices in the bridge circuit, said maximum dimension being small enough so that the fail-to-neutral orifice serves as a filter for contaminants in fluid passing through said fluid flow path, and (ii) is located in said fluid flow path upstream of the bridge circuit, said means comprising a pin positioned through a hole, the fail-to-neutral orifice being the clearance between the pin and the boundary of the hole.
Claim 2
Dependent Claim
139 words
A hydraulic control comprising: (a) a main spool; (b) a fluid flow path operatively connected to said main spool and comprising a bridge circuit containing a plurality of orifices at least one of which is a variable orifice; and (c) means defining a fail-to-neutral orifice which (i) has a flow area large enough so that it does not cause an appreciable pressure drop but a maximum dimension smaller than the smallest orifices in the bridge circuit, said maximum dimension being small enough so that the fail-to-neutral orifice serves as a filter for contaminants in fluid passing through said fluid flow path, and (ii) is located in said fluid flow path upstream of the bridge circuit, said means comprising a pin positioned through a hole, the fail-to-neutral orifice being the clearance between the pin and the boundary of the hole.
Claim 3
Dependent Claim
27 words
A hydraulic control as recited in claim 1 wherein the maximum dimension of the fail-to-neutral orifice is much smaller than the smallest orifice in the bridge circuit.
Claim 4
Dependent Claim
21 words
A hydraulic control as recited in claim 1 wherein the pin and the hole are both circular in cross-section and coaxial.
Claim 5
Dependent Claim
54 words
A hydraulic control as recited in claim 1 wherein said means further comprise a member surrounding said pin, said member being sloped radially inwardly to an axially short annular land surrounding said pin, the fail-to-neutral orifice being the clearance between said pin and said land, the sloping portion serving to radially position said pin.
Claim 6
Dependent Claim
69 words
A hydraulic control as recited in claim 4 wherein: (a) said pin has a peripheral groove and (b) said means further comprise: (i) a retaining ring which has a radial slot sized to allow said pin to be slipped into said retaining ring at the peripheral groove in said pin and and a central aperture sized to receive said pin and (ii) means for axially positioning said retaining ring.
Claim 7
Dependent Claim
22 words
A hydraulic control as recited in claim 5 wherein said pin and said annular land are both circular in cross-section and coaxial.
Claim 8
Dependent Claim
22 words
A hydraulic control as recited in claim 4 wherein said pin and said annular land are both circular in cross-section and coaxial.
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) | 1983-02-04 | 1983-08-06 | 1984-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-02-04 | 1987-08-06 | 1988-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-02-04 | 1991-08-06 | 1992-02-05 | $7700.00 | Window Closed / Lapsed |