Fluid handling – With lock or seal
Reexamination Certificate
2000-11-01
2001-08-14
Chambers, A. Michael (Department: 3753)
Fluid handling
With lock or seal
C137S098000, C137S111000
Reexamination Certificate
active
06273125
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gate valves for controlling material flow along a flowpath. More particularly, the invention relates to an adjustable lockout device using one or more compression keys to securely lock the gate valve in a desired operating position.
2. Description of the Prior Art
Those ordinarily skilled in the art will appreciate that it is often necessary or desirable to securely lock a flow control or gate valve in a particular operating position, typically either fully open or fully closed. This is true, for example, where the valve or associated downstream components are being repaired such that a change in actuation or flow state could be damaging to the valve or components or injurious to a worker. Locking the valve in a particular position is commonly accomplished using a lockout device fitted to the gate valve.
A number of conventional valves are not designed to be locked out, and must therefore be retrofitted with structure for selectively locking the valve. Those ordinarily skilled in the art will appreciate that it is virtually impossible to precisely retrofit a valve such that it can be reliably and accurately locked in a fully open, fully closed, or other exact position. Even where the effects of component tolerances can be minimized, subsequent wearing can result in a significant amount of “play” or movement of the valve even when locked.
Existing lockout devices include mounting (e.g., welding) a locking element to the valve assembly, the element having a hole which is aligned with some part of the valve. A pin is then inserted into the hole and engages the valve to prevent movement thereof. Unfortunately, actuation forces applied to the valve translate into shearing forces on the pin. Thus, the ability of such a lockout device to prevent movement is limited to the shear strength of the pin, which is typically 66% to 70% of its yield.
Furthermore, a number of existing lockout devices are not tamperproof, and consequently may be removed by unauthorized personnel or workers having no knowledge that the valve should remain locked out.
SUMMARY OF THE INVENTION
The present invention solves the above-described and other problems and provides a distinct advance in the art of gate valve lockout devices. More particularly, the present invention provides an adjustable lockout device using a key or wedge to securely lock the valve in a desired operating position.
The preferred lockout device comprises two lock couplings, two lock plates, and two keys. Each lock coupling presents tapered first contact surfaces and is threadably positioned upon and secured by a set screw to a valve actuator shaft portion of the gate valve at shaft locations corresponding, respectively, to valve open and valve closed positions. Each lock plate presents second contact surfaces and is stationarily secured relative to the shaft, operable to allow the shaft to slidably pass therethrough, and operable to receive a corresponding lock coupling. The keys are substantially wedge-shaped and held parallel to one another by a spacer. The keys are inserted to compressively engage the first and second contact surfaces when the lock coupling is received within and aligned with the lock plate, thereby preventing movement of the actuator shaft and lock coupling relative to the stationary lock plate. The keys may be subsequently withdrawn to allow the shaft to resume movement.
Because it is adjustable, the inventive lockout device provides for a greater range of lockout positions as well as for compensatory adjustments over time as parts wear and tolerances change. Another advantage of the present device is that actuation forces applied to the valve translate into compressive forces rather than shearing forces. Because the strength of a material in compression is equal to 100% of its yield, the lockout device of the present invention has improved ability to prevent movement of the valve. Furthermore, a lock attachment point is provided on each key whereby a padlock, cotter pin, or other locking means can be attached to prevent unauthorized or accidental removal of the key and disengagement of the lockout device.
These and other novel features of the present invention are described in more detail in the section entitled DESCRIPTION OF A PREFERRED EMBODIMENT, below.
REFERENCES:
patent: 5394715 (1995-03-01), Guerette
patent: 5560233 (1996-10-01), Watkins
patent: 6044860 (2000-04-01), Neu
Blenkush Robert A.
Warzecka Keith V.
Chambers A. Michael
McShane Thomas L.
Pepper Hamilton LLP
SPX Corporation
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