ANTI-STATIC DEVICE FOR BALL VALVES

Abstract: An anti-static device for ball valves or other rotary or "quarter-term" type valves. A hole (24) is bored in the stem (15) and a contact assembly incorporating a pair of spring-steel arms (26) is secured in the hole (24) by a tube (29) which is an interference fit in the hole (24). The tube (29) prevents longitudinal and rotational movement of the spring means (25) in the hole (24). The spring arms (26) engage the floor (31) and/or walls (32) in the socket (16) in the valve ball (14) to maintain an electrical path between the stem (15) and valve ball (14).

Description: TITLE: "ANTI-STATIC DEVICE FOR BALL VALVES" BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an anti-static device for ball valves. 2. Description of the Prior Art Most bal balves, e.g. used in the petro-chemical and plastics industries, must conform with British Standard 5351 ensuring electrical continuity between the ball, stem and body to prevent flashing. One requirement of B.S. 5351 is that the maximum electrical resistance between the ball, stem and body is 10 ohms, i.e. maximum „ne Λ w + 10 A . To date, many valves have incorporated anti-static devices between the ball stem, and between the stem and body respectively, comprising a small metal ball which is spring-loaded and retained in a drilled hole in the stem and gauged to protrude slightly from the stem to engage the ball or the body respectively. Experience has shown, particularly in the plastics and petroleum refining industries, that the medium passing through the valve can force itself between the metal ball i the stem and the valve ball, breaking the electrical path therebetween, the flow pressure of the medium retaining the metal ball in the stem out of contact with the valve ball. Therefore, while such valves conform with B.S. 5351 when new, this standard of performance cannot be maintained throughout the working life of the valve. SUMMARY OF THE PRESENT INVENTION It is, therefore, an object of the present invent- ion to provide a method of maintaining electrical contact between the ball and the stem in all operating conditions. It is a preferred object to provide a simple and inexpensive contact assembly for effecting the method. It is a further preferred object to provide such a contact assembly which operates to remove any medium which OMPI may come between the ball and the stem. Other preferred objects of the present invention will become apparent from the following description. In one aspect, the present invention resides in a ball valve of the type having a body, a valve ball in the body and a stem operatively connected to the valve ball to rotate the valve ball to open or close the valve, said stem being received in a socket in the valve ball, characterized by: an electrical contact assembly including: a hole in the stem; and spring means securely fixed in the hole and engag¬ ing the floor and/or the walls of the socket in the valve ball to provide an electrical path between the stem and the valve ball. Throughout the description and claims, the term "ball valve" shall be used to include other types of • rotary or "quarter-term" valves, e.g. plug or butterfly valves, and the term "valve ball" shall be used to include corresponding valve members, e.g. valve plugs or butterflies. Preferably the spring means is formed from a length of spring-steel wire bent to shape to form at least one spring arm extending substantially laterally from the drilled hole. Preferably there are two spring arms, each one engaging a portion of the floor and/or a wall of the socket. Preferably the spring means is retained in the hole by a tube which is an interference fit in the hole. Preferably the tube is swaged in position. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS To enable the invention to be fully understood, a preferred embodiment will now be described with reference to the accompanying drawings, in which: FIG. 1 is a side sectional view of a known ball valve; FIG. 2 is a side, part-sectional, view of the stem and contact assembly of the present invention prior to assembly; FIG. 3 is an end view corresponding to FIG. 2; FIG. 4 is a side, part-sectional, view intermediate assembly step; FIG. 5 is the completed stem corresponding to FIG. 4; and FIG. 6 is a side, part-sectional, view showing the engagement between the stem and the valve ball. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, the known ball valve has a body 10 with inlet passage 11 into, and outlet passage 12 from, a ball chamber 13 fitted with a valve ball 14. A stem 15, rotatably mounted in the body 10, has its lower end engaged in a socket 16 formed in the valve ball 14, the stem 15 being rotated by an operating handle 17. The valve ball 14 is sealed to the body 10 by suitable seat rings 18. An insert 19 screwthreadably mounted in the body 10 retains the valve ball 14 and seat rings 18 in their operating positions. Anti-static devices 20 are provided between the stem 15 and valve ball 14, and between the stem 15 and body 10. Each anti-static device 20 has a hole 21 drilled in the stem to receive a small metal ball 22 backed by a spring 23. A ring (not shown) is fitted at the mouth of the hole to retain the ball in the hole while allowing a portion of the ball 22 to engage the adjacent wall of the socket 16 or body 10. In the present invention the anti-static device 20 between the stem 15 and body 10 is retained. The present invention replaces the device 20 between the stem 15 and the valve ball 14. Referring to FIGS. 2 to 6, a hole 24 is drilled in the lower end of the stem 15. A length of spring wire 25 is cut from a roll and bent to the substantially U-shape shown in FIG. 2, the wire having a pair of spring arms 26 joined by an enlarged diameter head 27 to form a pair of shoulders 28. The locking tube 29 has an outer diameter selected to be an interference fit in the hole 24 and its length is approximately one-half to two-thirds the depth of the hole. A pair of aligned slots 30 are formed at the upper end of the tube. The contact assembly is assembled in the following manner. The spring arms 26 are passed through the tube 29 until the shoulders 28 on the wire engage the base walls of the slots 30, the enlarged head 27 preventing the wire from passing completely through the tube. The wire/tube assembly is pressed into the hole 24 in the stem, the tube 29 forming an interference fit with the hole. The head 27 engages the end wall of the hole 24 and is trapped between said end wall and the tube 29 to prevent longitudinal or rotational movement of the head in the hole. A swaging tool (not shown) is used on the free end of the tube 29 to securely lock the tube in the hole. The free portions of the spring arms are bent outwardly to lie substantially transversely to the axis of the hole 24 (see FIG. 5) . When the stem 15 is fitted to the ball valve (see FIG. 6), the free ends of the spring arms 26 engage the floor 31 and/or walls 32 of the socket 16 in the valve ball 14. This engagement causes deformation or bending of the spring arms which is opposed by the resilience of the wire and so firm contact is ensured between the spring arms 26 and the socket 16. In any relative movement between the stem and the valve ball, e.g. when the stem is rotated or when the valve ball is rocked in the ball chamber, the free ends of the spring arms will scrape the floor and/or walls of the socket, preventing the medium from breaking the electrical contact therebetween. This action provides a self- cleaning contact between the stem and the ball, ensuring electrical continuity therebetween. The above embodiment of the present invention ■ provides a simple, effective and self-cleaning electrical contact between the stem and the ball which overcomes the problems of the prior valves discussed above. As the wire 25 is securely held in position by the tube 29, the valve can be disassembled and reassembled, e.g. for maintenance, in the knowledge that the electrical continuity between the stem and valve ball will be restored and that the parts of the contact assembly cannot be lost or misassembled. Various changes and modifications may be made to the arrangement described without departing from the scope of the present invention. For example, the spring wire 25 may be secured in a plug which is screwthreadably mounted in the hole 24. O PI

Claims: AMENDED CLAIMS (received by t he International Bureau on 18 January 1982 ( 18.01.82 > (amended) 1- A ball valve of the type having a body (10), a valve ball (14) in the body (10) a d a stem (15) operatively connected to the valve ball (14) to rotate the valve ball (14) to open or close the valve, said stem (15) being received in a socket (16) in the valve ball (14) , characterized by: an electrical contact assembly including: an axial bore (24) in the end of the stem (15) adjacent the socket (16); and spring means (25) securely fixed in the bore (24) , said spring means (25) comprising: a length of spring-steel wire bent to form at least one spring arm (26) extending substantially laterally from the bore (24) engaging the floor (31) and/ or walls (32) of the socket (16) in the valve ball (14) to provide an electrical path between the stem (15) and the valve ball (14) . (amended) 2. A ball valve as claimed in Claim 1 and further characterized in that: two spring arms (26) extend laterally in opposite directions from the bore (24) , each spring arm (26) engaging a respective portion of the floor (31) and/or walls (32) of the socket (16) . (amended) 3. A ball valve as claimed in Claim 1 or Claim 2 and further characterized in that: the spring means (25) is retained in the bore (24) by a tube (29) which is an interference fit in the bore (24) , the head (27) of the spring means (25) being clamped between the tube (29) and the closed end wall of the bore (24). (amended) 4. A ball valve as claimed in Claim 3 and further characterized in that: a pair of slots are formed at the upper end of the tube (29) ; and shoulders (28) on the spring means (25) are engage in the slots to prevent rotation of the spring means (25) in the bore (24) . (amended) 5. A ball valve as claimed in Claim 3 or Claim 4 and further characterized in that: the tube (29) is swaged in position in the bore (24). ( amen d e d) *•> • A Da * L *'- valve as claimed in Claim 1 or Claim 2 and further characterized in that: the spring means (25) are fixed in a plug screwthreadably mounted in the bore (24) . (amended) 7. A ball valve as claimed in Claim 1 or Claim 2 and further characterized in that: when relative movement occurs between the stem (15) and the valve ball (14) , the spring arm or arms (26) scrape the floor (31) and/or walls (32) of the socket (16) in the valve ball (14) , to provide a self-cleaning electrical contact between the stem (15) and the valve ball (14) . (amended) 8. A ball valve as claimed in Claim 7 and further characterized in that: the spring arm or arms (26) prevent the build-up, in the socket (16) , of the medium passing through the valve.

Inventors: RICHARDS C
Applicants: RICHARDS & CO B C, RICHARDS C, B C RICHARDS & CO PTY LTD
Application year: 1981
Main classification: F16K5
IPC codes: F16K5