Expansible chamber devices – With support or frame
Patent
1995-08-18
1997-05-13
Nguyen, Hoang
Expansible chamber devices
With support or frame
92DIG1, F01B 2900
Patent
active
056282389
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a hydraulic actuator for isolators, in particular for diverter valves or flap isolators (herein both referred to as isolators) used for isolating gases under severe operating conditions of high temperature and/or high pressure.
BACKGROUND OF THE INVENTION
For many diverter valve or flap isolator applications it is necessary or desirable to use hydraulic actuation systems.
Conventional hydraulic actuation systems usually consist of a hydraulic ram operating a lever which is connected to a shaft to be rotated, to which a valve closure plate is attached. The base end of the ram is pin jointed to an anchor bracket which is normally rigidly fixed to some point of the damper or isolator frame. The disadvantage of this arrangement is that differences in temperature between the isolator frame (hot) and the hydraulic ram (cold) causes the effective length of the ram link system and hence the position of the blade to change.
PCT patent application no. PCT/GB89/00593 (publication no. WO 89/11612) corresponding to U.S. Pat. No. 5,109,883 describes and claims an improved hydraulic actuator for overcoming such disadvantages. Specifically, the invention disclosed in the said WO 89/11612 provides a hydraulic actuator for an isolator, comprising a hydraulic ram one end of which is connected to a lever which is in turn connected to a shaft for a valve plate or other closure, the actuator having a casing which flange mounts on the isolator, and the other end of the said ram being attached to the end of the casing remote from the said flange.
The increasing size of gas turbines creates the need for larger diverter valves for directing the flow of products of combustion to boiler or by pass for combined cycle plant. Larger diverter valves require greater torque. One method of providing this torque is by means of the hydraulic actuator which is the subject of the above-mentioned WO 89/11612 and its corresponding U.S. patent.
The operating thrust for this particular actuator is provided by a single hydraulic ram. By the very nature of this arrangement the ram not only transmits the desired torque, but imposes on the overhung shaft a bending moment and also a corresponding radial load upon the bearing.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides a hydraulic actuator for an isolator such as a diverter valve, the actuator comprising a hydraulic ram one end of which is connected to a lever which is in turn connected to a shaft for a valve plate or other closure, wherein the end of the actuator frame remote from the shaft is connected to the isolator frame by means of a torque arm reaction anchor so as to prevent the actuator rotating with the shaft.
The actuator according to the present invention significantly overcomes the disadvantages of the above-mentioned known actuator according to WO 89/11612, of large bending moment on the overhung shaft and corresponding radial load upon the bearing.
In the present invention the actuator is shaft mounted and the torque reaction is taken up by the torque arm anchor. In comparison with the actuator of WO 89/11612, for a given torque the bending moment transmitted to the shaft and radial load transmitted to the bearings are reduced by about 80%. This is due to the fact that in the system of the present invention the torque reaction forces are reacted at a much greater effective lever arm length than they are in the case of the actuator of WO 89/11612, as will be described in more detail below with reference to the accompanying drawings.
The general construction of the actuator according to the present invention is similar to that of the actuator of WO 89/11612, but does not have a mounting flange. Instead the end of the casing opposite to the shaft has a torque arm reaction anchor.
In one embodiment of the actuator according to the present invention, the torque arm reaction is taken by sliding members which are free to slide over a tongue of a bracket, which tongue is to be mounted on the diverter valve frame via the torque arm anchor.
In a
REFERENCES:
patent: 3096077 (1963-07-01), Forsyth
patent: 3967539 (1976-07-01), Williamson
patent: 4039419 (1977-08-01), Buse
patent: 4453455 (1984-06-01), Bergstrand
patent: 4550571 (1985-11-01), Bertsch
patent: 5109883 (1992-05-01), Squirrell
patent: 5429153 (1995-07-01), Squirrell
Nguyen Hoang
WES Technology Inc.
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