Motors: expansible chamber type – With motive fluid valve – Relatively movable serial valves
Patent
1985-01-14
1988-02-02
Look, Edward K.
Motors: expansible chamber type
With motive fluid valve
Relatively movable serial valves
91468, F15B 1108
Patent
active
047222620
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a fluid pressure system and hydraulic valves for automatically redirecting flow of pressure fluid from one side of the hydraulic motor, such as the hydraulic cylinder to the other for the purpose of reversing the hydraulic motor.
The invention provides for a signal reversal of the motor during one cycle of its operation without having to operate manually the normal main control valve for the actuator.
The currently known automatic valves of this type effect the redirection of flow either directly by means of mechanical or electric mechanical stops or triggers moved by the end of stroke movement of the piston or indirectly by means of pressure sensitive elements which switch over the reversing valve in response to predetermined pressure drops. The mechanical stops or triggers have the disadvantage in certain applications and particularly when used on turn-over plough mechanisms that they must be accurately designed, manufactured and adjusted and if used in a hard working environment must be readjusted because of the wear and deformations of individual parts. Furthermore they require extra space for installation and are of relatively high cost because a relatively larger number of parts are required.
A major disadvantage of indirect switching systems which rely on pressure is that because the turn-over plough or other mechanism may be carried by one of many makes of agricultural tractor the system pressure available from the tractor may vary considerably both between makes of tractor and between models of the same make, consequently the pressure at which the automatic valve on the plough operates must either be adjusted to match the tractor or it must be adjusted to respond to the lowest of all the tractor system pressures available. In the latter case the plough may be carrying a hydraulic cylinder which is far too large and expensive for a tractor which can supply a higher system pressure. The further disadvantage of indirect systems which rely on large pressure drops is that the actuator may reach the geometric end of its stroke before or after the pressure has built up to the pre-determined pressure differential so that the transition to the second part of the cycle is accompanied by a shock. Yet a further disadvantage of the system which rely on pressure and which are protected by a "kick-out" type of main control valve is that the pump delivery volume may also be high and internal throttling gives rise to a high dynamic or transient pressure during or at the end of the cylinder movement so that the tractor driver has to operate the main control valve lever a second time or keep his hand on it until the cycle is complete.
The objective of the invention is to mitigate the foregoing disadvantages and provide an automatic reversing valve which operates at the correct geometric position and which achieves a smooth transition with minimal delay and is independent of both the pressure of the system to which it is connected and the volume of delivery of the system pump.
According to the present invention there is provided a fluid pressure motor and fluid pressure valve means connected to said motor wherein the valve means includes a switching means for redirecting flow of pressure fluid to the motor and sensing means responsive to a predetermined state of the system and adapted to cause said switching means to operate.
Preferaby the sensing means is constituted by a sensing valve capable of taking up a stable operating position or a switch initiating position and adapted to become hydraulically balanced and on becoming so balanced of moving from the stable operating position to the switch initiating position and the application of a small force thereto.
The sensing valve preferably becomes balanced when the flow to the motor is zero and the small force may be derived from a spring or hydraulically from the motor itself or another part of the system.
According also to the present invention there is provided fluid pressure valve means adatped to be connected to a fluid pressure motor, an
REFERENCES:
patent: 4206685 (1980-06-01), Pusch
Look Edward K.
Massey-Ferguson Services N.V.
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