Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-03-17
2001-02-27
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C091S433000, C137S596140
Reexamination Certificate
active
06192936
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to hydraulic control means and more especially to a hydraulic remote control (HRC) valve. The invention has particular, but not exclusive, application to the control of hydraulic clutches employed on tracked vehicles such as earth-working equipment (bulldozers, etc) and military tanks.
As is well known, a tracked vehicle is steered by reducing or fully interrupting the drive to one or other of the two tracks, according to the change in direction required. This is achieved by reducing or interrupting the hydraulic supply to one or other of the clutches associated with tracks. Typically, this control of the hydraulic supply to the clutches is effected directly by the operation of levers acting on hydraulic valves but the torque involved is relatively high, thus requiring considerable manual effort on the part of the vehicle driver.
BRIEF SUMMARY OF THE INVENTION
There is a growing requirement for easing the effort required to operate tracked and other vehicles/machinery, especially having regard to the now recognised repetitive strain syndrome. The object of the present invention is to provide a hydraulic control valve requiring low-torque operation.
The present invention is defined in the appended claims and may provide a hydraulic control valve comprising a main hydraulic valve and a pilot pressure control valve operable manually to control the output of the main valve, the pilot valve being arranged such that when in operation the operating pressure of the pilot valve is increased, the output pressure of the main valve is decreased.
The pilot control valve may be, for example, a pressure-relief valve or a pressure-reducing valve and if the former, may be in the form of a poppet valve.
The operating pressure of the pressure-relief valve may be controlled by a manually-operable piston acting on a spring engaging the closure member of the poppet valve, the piston having a return spring, the rate of the return spring being such as to ensure that there is always a net force operable to urge the poppet valve to the open position.
The main valve may be a spool valve.
The output of the main valve may be fed back to the first end of the spool of that valve over a first portion of the overall cross-section of the spool, wherein pressure fluid controlled by the pilot valve is applied to a second portion of the overall cross-section of the spool at the first end, the forces generated by these pressures being balanced by a spring force acting on a second end of the spool.
A spring having a low, and substantially constant rate may act upon the second end of the spool of the main valve.
The pressure fluid may be applied to the first end of the spool of the main valve through restrictor means which may comprise two restrictors, one affecting the signal from the output, the other affecting the signal from the pilot valve.
In the application of the invention to the control of the two hydraulic clutches of a tracked vehicle, two control valves referred to above may be provided in a common housing and having independent controls. In view of the fact that in each control valve only a pilot valve is being manually controlled involving very small forces, mere finger-tip control has to be applied by the operator to the manually-operable means controlling that valve.
The present invention may also provide a method of controlling pressurised fluid comprising the steps of:
i) providing a main hydraulic valve;
ii) providing a pilot pressure control valve operable manually to control output of the main valve; and
iii) arranging the main valve such that an increase in the operating pressure of the pilot valve results in a decrease in the output pressure of the main valve.
The present invention may also provide a method of controlling hydraulic clutches associated with respective tracks of a tracked vehicle, comprising the steps of:
i) providing for each clutch a main hydraulic valve;
ii) providing for each main valve a pilot pressure control valve manually operable to control the associated main valve;
iii) providing independent manual controls for the pilot valves; and
iv) arranging the main valves such that an increase in the operating pressure of either pilot valve results in a decrease in the output pressure of the associated main valve.
This method may comprise the further step of providing the two main valves and two pilot valves in a common housing.
The step of providing a common housing may further comprise providing a block of material and drilling that block to provide valve bodies and fluid flow passages.
REFERENCES:
patent: 2913005 (1959-11-01), Grant et al.
patent: 3055383 (1962-09-01), Paine
patent: 4015619 (1977-04-01), Shore et al.
patent: 4281676 (1981-08-01), Morris
patent: 4469011 (1984-09-01), Loffler
patent: 4535809 (1985-08-01), Andersson
patent: 4537220 (1985-08-01), Anderson
patent: 4685748 (1987-08-01), Zoerb
patent: 5042832 (1991-08-01), Takahashi et al.
patent: 0314653 (1989-05-01), None
patent: 1479692 (1977-07-01), None
Aeroquip-Vickers Limited
Dinsmore & Shohl LLP
Michalsky Gerald A.
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