Valves and valve actuation – Fluid actuated or retarded – With mechanical movement between actuator and valve
Patent
1984-09-19
1986-01-14
Yeung, James C.
Valves and valve actuation
Fluid actuated or retarded
With mechanical movement between actuator and valve
251 634, 92138, F16K 31163
Patent
active
045641692
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a fluid actuator for the stepwise regulation of valves between at least three different positions, such as between 0.degree., 90.degree. and 180.degree. and back in a ball valve, cock valve or the like, said fluid actuator comprising a cylinder which is defined by two end-walls and in which two pistons are arranged for movement towards and away from one another, each of said pistons having arranged axially therealong a gear-rack having teeth which mesh with a toothed wheel mounted on an actuating member which is journalled for rotation in and passes sealingly through at least one cylinder wall, so as to extend transversely to the direction of movement of the pistons. At least three fluid supply and discharge passages are provided, of which a first opens out between the pistons, a second opens out in one end-wall of the cylinder opposite the first piston, and a third opens out in the second end-wall of the cylinder opposite the second piston.
Fluid actuators of this kind have been found particularly useful for regulating valves for industrial purposes. Although the working medium preferred is pressurized air, other working media, such as hydraulic fluids, can also be used.
The actuator is particularly useful, primarily because of its compactness and also because it is able to transfer large regulating forces, despite its small dimensions. The actuator is also particularly reliable in operation.
BACKGROUND ART
An actuator of the aforedescribed kind may be used to execute regulating movements between three or more different and distinct operating positions. Thus, when regulating a valve it is often desired to adjust the valve reliably in both its half-open position, corresponding to a 90.degree. rotation of the valve spindle, and a fully-open position, corresponding to 180.degree. rotation of said spindle. Many hitherto known actuators are not able to satisfy this requirement, since they will only permit the valve to be regulated between a zero or closed position and an end position corresponding to a position in which the valve is fully open or in which the valve spindle has been rotated through 180.degree.. U.S. Pat. No. 4,087,074 (Massey et al) describes an example of a known valve of this kind, which has a return spring coupled to an independent fluid actuated piston to assist in spring compression on the forward stroke.
German Pat. No. 2,405,297 (Kurten) describes an actuator having four pistons in symmetrical arrangements, which is a rather complicated and expensive design.
German Pat. No. 2,508,683 (Yazaki) describes an actuator having, like Massey et al, a spring actuated additional piston, also providing a manually operated wheel for adjusting the end positions.
Consequently, when wishing to make intermediate adjustments, it has either been necessary to make such adjustments manually or to employ other, more complicated solutions, in which mutually different actuators are placed one upon the other, or the like. In certain cases it has been necessary to ignore fluid actuators of the kind described and to employ totally different solutions, for example solutions which require the use of electricity and which in practice greatly increase the costs entailed.
OBJECT OF INVENTION
An object of the present invention is to provide a fluid actuator with which the aforesaid disadvantages are obviated while retaining the reliability of the actuator without drastically increasing the costs.
BRIEF DESCRIPTION OF INVENTION
Accordingly, in its widest aspect, a fluid actuator according to the invention is mainly characterized in that extending through one end-wall of the cylinder is the piston rod of a third piston which is arranged in an adjacent, second cylinder chamber and the area of which exceeds the sum of the areas of the first and second pistons, the length of stroke of the piston rod of the third piston corresponding to half the length of stroke of the first and the second pistons.
By using such an auxiliary cylinder with its associated piston and
REFERENCES:
patent: 4029290 (1977-06-01), Karpenko
patent: 4087074 (1978-05-01), Massey et al.
patent: 4467833 (1984-08-01), Satterwhite et al.
WM Regler AB
Yeung James C.
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