Abstract:
A locking device for a butterfly type valve is provided with an actuating shaft extending through a bore provided in a conduit in which the valve is located; the inner end of the shaft carries a locking arm that is movable upon rotation of the shaft between a locking and unlocking position relative to the valve.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to apparatus for positively locking a butterfly valve disk in a closed position to assure safe conduit maintenance downstream of the valve.  
         BACKGROUND OF THE INVENTION  
         [0002]    Butterfly valves have enjoyed widespread use in a large number of industrial applications in view of their reliability, operational ease and relatively low-cost. Typically, a butterfly valve comprises a circular plate that is mounted for rotation about a diameter of the plate either on a pivot rod that extends through a bore formed in the plate or the plate may be formed with lugs extending outwardly from the periphery, again, along a diameter. At least one end of the pivot rod or the lug will be connected to a valve actuating device which, when operated, will rotate the plate on the pivot rod or the lugs to effect opening and closing of the valve. Where maintenance on the conduit downstream of the valve is being carried out, it is necessary that the valve be maintained in its closed position for economic and safety reasons particularly in large valve installations were workers enter the conduit to perform work internally.  
           [0003]    In the past, it has been the practice to use one or more site employees to monitor the valve position and verify closure while downstream work takes place. Typically, positive closure relies entirely upon the resistance provided by the actuating device. Such precautions are not only costly but do not in all cases effectively guard against failure and leakage past the valve. In the case of toxic or similar fluids, should the valve fail, those monitoring the valve must act quickly to manually override the actuator to minimize any damage or injury.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an operator with a mechanical means to ensure that a butterfly valve disk or plate is positively locked while in the closed position. In many, if not all butterfly valve installations, the annular seal mounted in the conduit with which the valve plate cooperates, allows rotation of the plate in a prescribed direction relative to the higher pressure side of the valve installation. Thus, in one form of the invention, the valve locking mechanism of this invention will be a mounted to operate through the conduit wall on the lower pressure side of the butterfly valve, adjacent to the valve. The device includes a circular headpiece securely mounted on the end of a shaft which has a threaded portion that cooperates with a hand wheel to effect raising and lowering of the shaft by rotation about its longitudinal axis whereby the external threads of the shaft cooperate with the internal threads on the hand wheel. A restraining mechanism is provided to prevent rotation of the shaft while the hand wheel is rotated to move the shaft relative to the valve housing. With this arrangement, operation of the hand wheel extends the threaded shaft into the conduit to bring the headpiece to a proper radial position in the conduit so that after positioning of the shaft relative to the valve plate, the headpiece can be rotated by means of the shaft to bring it into contact with a side of the butterfly valve plate to thereby prevent opening of the valve plate. With this arrangement, effective locking and unlocking can be quickly and simply carried out.  
           [0005]    The foregoing and other advantages of the present invention will become apparent as consideration is given to the following detailed description taken in conjunction with the accompanying drawings, in which: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 is a side, sectional view in elevation of the locking device of the present invention in its unlocked position, and  
         [0007]    [0007]FIG. 2 is a view similar to FIG. 1 but showing the locking device in its locked position. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0008]    Referring to the drawings, wherein like numerals designate corresponding parts throughout the views, there is shown in FIG. 1, the locking device  5  of the present invention in its retracted, unengaged condition. As shown, the locking device  5  is mounted on a conduit  20  in which is mounted the plate  3  of a butterfly valve which, on one face, is provided with a strike plate portion  4  for cooperating with the locking device, as explained below. As is conventional with butterfly valves, the plate  3  will be mounted for rotation about a pivot axis that extends typically through its diameter from its illustrated closed position in the direction of arrow A to an open position. It will be noted that the periphery of the plate  3  extends at an angle to the direction of flow through the conduit  20  which will be from the right to the left as shown in FIG. 1. An annular sealing ring  22  is mounted in a groove  24  as is conventional and projects a small amount into the conduit  20  to provide a secure and resilient sealing for the plate  3  of the butterfly valve. The structure and operation of the butterfly valve is conventional and forms no part of the present invention and will therefore not be further described.  
         [0009]    Preferably, a recess is provided in the conduit wall  1  and a corrosion resistant plate  2  is disposed in the recess and on which rests the circular head  5 A when the locking device  5  is unengaged. One end  5 B of a shaft is secured as by welding to one side of the circular head  5 A adjacent to a periphery of the circular head  5 A to provide an extended body to serve as the locking member. Between the middle and lower end  5 C of the shaft, external threads are provided over at least a portion of its length to engage with internal threads provided in the neck or collar  12 C of hand wheel  12  and through which the shaft extends, as shown. The hand wheel  12  is secured to the shaft by means of a key  13 . When key  13  is inserted after raising the locking device  5 , rotation of the hand wheel will effect rotation of the shaft about its longitudinal axis and movement of the circular head  5 A into and out of its locking position. Installation of pin or set screw  15 , fixing the relative positions of the coupling  11  and collar  12 C, will prevent further rotation of the shaft  5 B and head  5 A.  
         [0010]    Two O-ring lip seals  7  are provided to resist internal fluid pressure from the conduit. These seals are held in place by a plate and spring assembly composed of three plates  8  and two stacks of  3  wave springs  17 . The plate and spring assembly is secured by a packing gland retainer  9  which is fixed in place by a larger retaining plate  10 . This retaining plate and the hand wheel coupling  11  are bolted to the body protrusion by cap screws  14 .  
         [0011]    As described above, when the hand wheel is rotated, in one direction, the shaft ( 5 B and  5 C) will move axially relative to the collar  12 C to raise the circular plate  5  from its recess to a height sufficient so that upon subsequent rotation of the shaft, as explained below, the edge  5 D remote from the shaft  5 B of the circular plate  5 A will come into contact with the strike plate  4  provided on the face of the valve plate  3 . Rotation of the shaft while operating the hand wheel can be prevented by providing rectangularly extending flats at the end  5 G of the shaft to allow ease of attachment of a tool such as a wrench to hold the shaft while moving the circular plate  5 A between its locking and disengaged positions. With the circular plate  5 A raised to the appropriate height whereby the hand wheel groove  12 A is aligned with the shaft opening  5 E, a key  13  is inserted into the opening  5 E provided in the shaft lower end. The edge  5 F of the circular plate  5 A can then be rotated into position by the hand wheel  12  so that edge  5 F is in contact with the strike plate  4 . The set screw  15  is provided to pin the hand wheel  12  to the coupling  11  at the hand wheel collar  12 C and to prevent the head  5 A from rotating away from the strike plate  4 .  
         [0012]    As will be apparent to those skilled in this art, other techniques for raising the shaft  5 B may be employed such as a hydraulic system, a mechanical jacking device or similar devices.  
         [0013]    Having described the invention, it will be apparent to those skilled in this art that various modifications may be made thereto without departing from the spirit and scope of the invention.