Fluid handling – Systems – Multi-way valve unit
Patent
1996-02-26
1997-09-23
Michalsky, Gerald A.
Fluid handling
Systems
Multi-way valve unit
13762565, 25112906, F15B 13044, F16K 3102
Patent
active
056694164
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates generally to servo-valves, and more particularly to a servo-valve with a tongue-like piezo-ceramic flexible transducer, which is firmly clamped at one end and can be moved at the other end by the application of an electric voltage. The movement of the flexible transducer moves the transducer from a position blocking an air inlet nozzle of the servo-valve into one that blocks an air outlet nozzle. The movement of the flexible transducer is opposed by a resetting spring.
An article in "Fluid" journal, April 1989, pages 34 and 37, discloses a servo-valve of this type, in which the flexible transducer is housed in an enclosure which has, besides an air inlet nozzle and an air outlet nozzle, an outlet to an actuating element of a main valve. In the enclosure of the known servo-valve, driver electronic circuitry is also provided, which provides an electric voltage to the flexible transducer in response to a switching pulse. The flexible transducer of the known servo-valve consists of two polarized layers joined to one another, which bend when an electric voltage is applied because the materials of these layers are chosen such that different deformations occur due to the piezoelectric effect. The flexible transducer of the known servo-valve is, in mechanical terms, a bending bar that is firmly clamped at one end, which can block the air inlet nozzle or the air outlet nozzle of the servo-valve with its other free end depending on how it is driven.
The tongue-like flexible transducer of the known servo-valve is subject not only to the risk of a permanent pre-bending in the rest state due to the constant loading on the transducer by the resetting spring, but is also affected by temperature. These influences can be so intense that the flexible transducer under some circumstances no longer works properly after a certain period of time. Accordingly, in a specific embodiment of the known servo-valve, the flexible transducer is not clamped absolutely firmly at one end but rather so as to allow readjustment of the flexible transducer in the area of its clamped end.
The present invention is therefore directed to the problem of developing a servo-valve having a tongue-like piezo-ceramic flexible transducer, in which mechanical and thermal influences on the bending behavior of the flexible transducer are automatically compensated.
SUMMARY OF THE INVENTION
The present invention solves this problem by providing that, in a servo-valve of the type specified in the introduction, one end of the tongue-like flexible transducer is firmly secured to a spindle that extends transversely to the flexible transducer. The spindle is provided with a controllable securing device that is released once the voltage is no longer being applied during the return movement of the free end of the flexible transducer towards the air inlet nozzle.
The essential advantage of the servo-valve according to the present invention consists in that the controllable securing device makes it possible for the flexible transducer to move with its free end to the air inlet nozzle under the influence of the resetting spring despite any possible internal stresses in each case after the application of an electric voltage, in that during this return movement of the free end of the flexible transducer, a rotating motion about the spindle occurs. The flexible transducer thus lies down with its free end against the air inlet nozzle once the electric voltage is no longer being applied and is not influenced by any internal pre-stresses solely under the action of the resetting spring, with a repositioning of the flexible transducer taking place in this manner each time. Afterwards, due to appropriate driving of the securing device, the spindle is secured by the securing device in the position assumed in each case upon termination of the return movement of the free end of the flexible transducer. From this position, a movement of the free end of the flexible transducer to the air outlet nozzle then takes place due
REFERENCES:
patent: 3638973 (1972-02-01), Poletti
patent: 5163463 (1992-11-01), Gassman et al.
Fluid, (Hydraulik Pneumatik Elektronik) Apr. 1989, pp. 34 & 37: Der Piezo-Pillen-Knick.
Michalsky Gerald A.
Siemens Aktiengesellschaft
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