Servo-control device for controlling reduce pressure in an reduce pressure-line system, in particular for milking machines

摘要

The subject of the present invention is a servo-controlled control valve which keeps the reduce pressure, which is required for milking (or for other purposes), constant within very narrow limits and independently of the air requirement of the loads. The control valve consists essentially of a reduce pressure chamber (10) with an actuation spring (15), a control housing (24) with a control piston (1), a servo chamber (7) with diaphragm (11) and a working valve (12) with spring (14) in accordance with the attached drawing. The most important aspect of this invention is that a stable intersection point between the dynamic force-path characteristic of the pneumatic and mechanical forces (spring 14) acting downwards on the working piston (12) and the, also dynamic, force-path characteristic of the pneumatic forces acting upwards on the diaphragms (11) is obtained. This is achieved by means of a suitable selection of the spring constants of the springs (14) and (15) by means of a diabolo-shaped turned groove in the control piston (1) and by means of the damping piston (17) which terminates the damping chamber (18) with a small degree of running play. This running play ensures that, on average, atmospheric pressure prevails in the damping chamber (18), which is absolutely necessary to control a reduce pressure which is constant within very narrow limits. The working valve (12) can be constructed as a conical valve or as a slide valve. <IMAGE>