Valves and valve actuation – Fluid actuated or retarded – Pilot or servo type motor
Patent
1997-09-22
1999-09-07
Michalsky, Gerald A.
Valves and valve actuation
Fluid actuated or retarded
Pilot or servo type motor
251 63, 251368, F16K 31383
Patent
active
059474416
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a two-way seat-type valve having a valve seat which is arranged between a first and a second connection, and having a closure element which co-operates with the valve seat, is arranged in a guide so as to be movable towards the valve seat or away from the valve seat, and is subjected to a control pressure prevailing in a pressure chamber on the side, remote from the valve seat, of the closure element.
Valves of this type are used as hydraulic valves for controlling fluid flow and fluid pressures. They function without any problem, as long as oil, especially a synthetic hydraulic oil, is used as hydraulic fluid.
For some time, however, attempts have been made to replace the hydraulic oils, especially the synthetic hydraulic oils, by means of water, because of their somewhat questionable properties, from the environmental point of view, and especially of their toxicity. However, water has practically no lubricating properties, and, moreover, in many cases leads to corrosion damage, so that valves of this type wear out relatively quickly, or even seize up, so that they can no longer fulfil their function or can no longer do so to a satisfactory degree.
In the case of a valve of the type mentioned initially (DE 36 37 208 C2), it was therefore proposed to prevent the closure element from coming into contact with the guide by guiding the closure element in the guide by means of guide rings. The gap thereby produced between the closure element and the guide is closed by an additionally provided sealing element. A construction of this type, however, has the drawback that the opening and closing times become longer. The reaction characteristics of the valve therefore become poorer. This excludes the use of such a valve in applications in which it is a question of similar reaction times to those occurring when using oil as hydraulic fluid.
SUMMARY OF THE INVENTION
The problem underlying the invention is that of providing a hydraulic valve, suitable for water, which has good reaction characteristics.
This problem is solved in a valve of the type mentioned initially in that the closure element is guided seal-lessly in the guide.
By this means, a certain leakage is allowed past the closure element in the direction of the pressure chamber. This does indeed entail certain losses, which are relatively small. However, this makes it possible for a fluid layer or a fluid film to build up between the guide and the closure element, which in many cases allows the closure element to slide with low friction in the guide. Moreover, with a construction without seals, improved and more uniform operating behaviour is obtained. In the case of a construction with one or more sealing rings, the opening and closing times may differ from valve to valve. This is attributable on the one hand to scarcely avoidable tolerances with corresponding variations in stresses between the closure element and the guide, and on the other hand to differing wear. Moreover, seals have only a limited service life and change the dynamic characteristics in the course of time, owing to wear. If no seals are used, the dynamic characteristics remain the same over a longer period. This is of importance especially when several valves are connected together in such a way, for example in a bridge, that in the case of a too rapid opening movement or a too slow closing movement of one valve a short-circuit can occur between the pressure source and the pressure sink. Without seals, the speeds once set up can be maintained over a relatively long period.
Preferably, the pressure chamber is connected to a control pressure line by way of a non-return valve opening away from the pressure chamber. When sealing between the closure element and the guide is omitted and a certain leakage is thus allowed past the closure element, this naturally results in certain problems if the two-way seat-type valve is connected to a common control pressure line with other correspondingly constructed valves. In this case, a pressure incre
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Nielsen Jens J.o slashed.rgen
Plauborg Erik
Zenker Siegfried
Danfoss A/S
Michalsky Gerald A.
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