Valves and valve actuation – With snap action
Patent
1989-01-31
1990-05-08
Michalsky, Gerald A.
Valves and valve actuation
With snap action
91346, 13762566, F16K 3156
Patent
active
049231685
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a spool type switching valve device to be used for switching operation of a diaphragm pump or similar apparatus.
BACKGROUND ART
An example of conventional switching devices for diaphragm pumps is described in Japanese Utility Model Publication No. 35748/1986 which calls for providing a detent mechanism at the end of a spool used for switching the operations of a diaphragm pump in order to prevent the spool from standing still at the neutral point.
Such a conventional detent mechanism calls for convexes around the shaft at the end of the spool and propelling balls by spring pressure to the surface of the shaft at the end of the spool by means of compressed coil springs. And when the spool moves in an axial direction, the spring pressure in the direction of the radius of each ball works upon the slope of each of said convex, pushing the spool shaft towards one end of the shaft with the neutral point at the center so that the spool does not stop at the neutral point.
As the detent mechanism of a conventional device comprises convexes and compresses coils springs, when the pressure of the compressed coil springs is strong, frictional resistance between the convexes and the balls becomes strong, causing abrasion. As a result, problems lowering durability are evident. When such abrasion appears, there will be further problems in that the spool, which is fitted inside the sleeve so as to be able to rotate, becomes unable to rotate so that the abrasion continues at the convexes over only a limited portion of the balls.
On the other hand, if the pushing pressure of the coil springs is weak, the force from the balls upon the convexes becomes insufficient and thus, the switching operation of the spool becomes unreliable.
The objective of the present invention is to ensure both prevention of the detent mechanism's abrasion and the thorough switching operation of the spool.
DISCLOSURE OF INVENTION
The present invention relates to a spool type switching valve device having spool 31 fitted inside sleeve 46 so as to be able to move in the axial direction; and detent mechanism 51 provided at one end of said spool 31 in order to prevent spool 31 from standing still at the neutral point, wherein said detent mechanism comprises spool operator 57 fitted around shaft 55 incorporated at the end of spool 31 as one body; spring holder 53 provided at the end of sleeve 46 as one body; and C-shaped wire springs 58 with a circular cross section fitting between said spring holder 53. As spool 31 is moved and approaches the neutral point, wire springs 58 are rotated, with each side held by spring holder 53 as the respective center, and compressed between the spring holder and spool operator 57. When spool 31 has passed the neutral point, the repellent force stored in wire springs 58 is immediately released so that spool 31 is instantaneously switched by a snap action of wire springs 58.
The advantage of the present invention is that, as C-shaped wire springs with a circular cross section are used for the detent mechanism to apply a snap action directly to the spool operator, unlike conventional detent mechanisms using balls, it is free from the problem of wear due to abrasion and thus has better durability. The present invention has the further benefit of a smooth switching of the spool due to the rotating of the wire springs so the sufficient force in the axial direction is ensured and thus switching of the spool is done smoothly.
Further, according to the present invention, the spool operator of said refined spool type switching valve device is fitted around the shaft of the device with short clearances within which the spool operator is able to move in the direction of the shaft. As clearances 63 and 64 are thus provided, the movement of spool operator 57 is light so that wire springs 58 do not have to be strong, and that the air pressure required for switching operation of spool 31 may be made lower.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic section view of a s
REFERENCES:
patent: 4540349 (1985-09-01), Du
German Abstract Corresponding to: 52-038723 of Japan Above.
Murata Minoru
Yamada Kazumasa
501 Yamada Yuki Seizo Co., Ltd.
Michalsky Gerald A.
Morrison Thomas R.
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