Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Patent
1980-07-24
1982-10-19
Maslousky, Paul E.
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
92130D, 92136, 92155, F01B 702, F01B 3110, F01B 900
Patent
active
043544240
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to pneumatic operating devices, e.g. devices for regulating valves, of the kind which include a cylinder having a piston arranged for movement therein. The piston has an axially extending rack portion having teeth which engage teeth on an operating element mounted for rotation in at least one cylinder wall transversely of the axial direction of the piston. The piston passes through the cylinder wall and forms a seal therewith. The piston is located on the side of the cylinder wall opposite the rack portion and has a recess for accommodating a part of a return spring for the return movement of the piston.
Different kinds of such operating devices are known to the art, e.g. for opening and closing such valves as ball valves. Examples of such known devices are described in Swedish lay-open-prints 337,746 and 361,712, German Offenlegungsschrifts 2,647,385 and 2,430,268 and French Pat. No. 2,121,444.
With one such known operating device, springs are used for the return stroke of the piston, the springs being short and encircling rod-like elements for guiding the piston during movement thereof. The short springs produce only a small returning force and the return force varies widely over the length of the piston stroke. The arrangement of guide elements for guiding piston movement creates the disadvantage of an increase in the number of elements in the operating device and enhances the risk of the piston sticking in the cylinder.
A particular problem encountered with such operating devices is connected with the fact that their function is often such that the valve or the like operated by the device is held open when the piston is acted upon by air under pressure. When the pressure ceases, the valve is closed by the spring. If, however, the spring exerts only a small force or if the spring force varies in a manner such that only a slight force is exerted on the piston in the final stage of its closing movement, there is a risk that the valve will not be completely closed, which, as will readily be understood, can result in serious consequences.
An object of the present invention is to provide an operating device with which the aforementioned disadvantages are avoided. An operating device according to the invention is mainly characterized in that the recess for accommodating the spring extends a substantial distance into the rack portion of the piston, so that one end of the spring inserted in the recess, even when the piston is in the position in which the spring is compressed to its maximum, extends axially approximately up to or beyond a radial line through the center of rotation of the operating element.
An operating device according to the invention is distinguished by the fact that its operating element delivers a strong force with minor variations during its movement, and is thus more reliable than known operating devices. The spring operating the piston may also be comparatively strongly tensioned in one limit position of the piston, the spring tension being further increased upon movement of the piston as a result of the air pressure acting thereon. Thus, the piston will be returned by the spring in a much more positive and distinct manner than with known operating devices. Among one of the advantages afforded by the invention is that the same operating device can be used to operate larger valves than has hitherto been possible.
Practical tests have shown that with all conditions equal, an operating device according to the invention can use springs which deliver work which is four times greater in kilopound-meters than the operating devices previously known in the art.
The cylinder may in practice have a separate end wall which is removably connected to the cylinder by means of screws. The end wall may have a hole by means of which the cylinder can be connected to an air line. Further, the cylinder wall may have an axial bore which extends at right angles to the end wall and which together with the hole forms an air-supply passage to the cylinder interior.
The outer end wall
REFERENCES:
patent: 941999 (1909-11-01), Lewis
patent: 1031323 (1912-07-01), Christensen
patent: 2053720 (1936-09-01), Huck
patent: 2817562 (1957-12-01), Fleming et al.
patent: 3054136 (1962-09-01), Schlage et al.
patent: 4087074 (1978-05-01), Massey
Maslousky Paul E.
Wire Matic Regler AB
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