Fluid handling – Line condition change responsive valves – Pilot or servo controlled
Patent
1998-09-21
2000-05-30
Michalsky, Gerald A.
Fluid handling
Line condition change responsive valves
Pilot or servo controlled
137501, G05D 700
Patent
active
060680210
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to a directional control valve and to pressure reducing valves and flow control valves provided with a like directional control valve.
In FIG. 1 an embodiment of such a directional control valve is represented, which is designed as a 2-way fitted valve 2. It comprises a valve bush 4 wherein a main piston 6 is guided such as to be axially displaceable. The valve bush 4 may be secured in a control block in a known manner and thus form part of a hydraulic circuit which shall be explained in more detail hereinbelow.
The valve bush 4 comprises two ports A and B, with port B customarily being the inlet port and having the form of a radially or laterally branching port. Outlet port A is arranged coaxially with the main piston 6. At the peripheral wall of the main piston 6, radial bores 8 are provided whereby port B may be connected with port A in the case of a flow through the main piston 6. In the shown embodiment, port B and the radial bores 8 are each designed as a bore star. In the home position represented in FIG. 1, the main piston 6 is biased by means of a spring 10 towards a stop position wherein the connection from B via the main piston 6 to the outlet port A is open. I.e., in the home position of the main piston 6 the hydraulic fluid enters in a radial direction through port B, enters through the radial bores 8 into the main piston 6, and is deflected by approx. 90.degree. towards the port A.
By a suitable design of the control block and of the valve cover (not shown) it is possible to supply a control pressure to the spring side of the main piston 6, whereby the latter is additionally biased in the direction towards its home position. This control pressure may, for example, be applied by way of a control pressure line branching off from outlet port A.
The like valve arrangements in 2/2-directional control valve design belong to the category of the so-called logic components utilised as a main stage, e.g. for pressure reducing valves, pressure control valves, pressure switching valves etc. This main stage may be associated with pilot control valves which way, for example, be integrated on the valve cover, in the valve cover, or arranged in another location of a control block.
In FIG. 3 an exemplary switching circuit is represented wherein the fitted valve 2 represents a component of a pilot operated pressure reducing valve 12. The latter essentially consists of the fitted valve 2 and a direct operated pilot valve 14 designed as a pressure reducing valve. The flow direction at the fitted valve 2 is from port B towards port A, with a free flow being insured in the home position in accordance with the representation of FIG. 1.
The pressure at the outlet port A is tapped via a control line 16 and supplied via two nozzles 18 and 20 arranged in series towards the spring side of the main piston 8. The desired output pressure at the outlet port A may be adjusted through the spring of the pilot valve 14. This output pressure acts on the bottom side of the main piston 6 and is supplied via the control line 16 and the nozzles 18 and 20 to the spring side of the main piston 6. As long as the pressure at the outlet port A is lower than the input pressure adjusted at the pilot valve 14, the main piston 6 will, due to the spring 10, remain in its home position wherein the connection between A and B is controlled fully open. When the pressure at the outlet port A--and thus the one prevailing between the two nozzles 18 and 20--exceeds the preset value, the pilot valve 14 is opened, so that control fluid flows via the pilot valve 14 towards a tank T.
Due to the resulting flow of control fluid, a pressure gradient is created at the nozzle 18, so that due to the control fluid pressure difference between the bottom side of the piston and the spring side, the main piston 6 is displaced upwardly (view of FIG. 1) from its home position against the tension of spring 10, and the connection from B to A is controlled closed until a pressure equilibrium occurs. In this condition only such an amoun
REFERENCES:
patent: 2594626 (1952-04-01), Earle
patent: 3439696 (1969-04-01), Valentine
patent: 4368872 (1983-01-01), Machat
patent: 4791950 (1988-12-01), Pedersen
patent: 4809746 (1989-03-01), Wolfges
Mannesmann Rexroth AG
Michalsky Gerald A.
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