GB2062809A - A ball valve assembly - Google Patents

Abstract

A ball valve assembly 1 includes a bal valve member 2 made of a plastics resin material, preferably polyvinyl chloride, and movably mounted in a valve cavity 7 formed in a valve body A again made of a plastics resin material, preferably polyvinyl chloride. The valve body A consists of two body elements a, b coupled in a male-and-female connection with each other and rigidly and permanently united together thereat. Thus, the ball valve member 2 is confined in the valve cavity 7 in an unseparable way, and co-operates by direct and resilient contact with a pair of seat rings 4, 4' made of an elastomer or elastic rubber. These seat rings 4, 4' are so shaped and arranged when seen in an axial section of the valve assembly that they represent four limited contacting areas a, e, f and g, with the ball valve member 2 exerting sealing and supporting pressures against the ball valve 2 all directed substantially towards the centre of the member 2. <IMAGE>

Description

SPECIFICATION Ball valve assembly This invention relates to a ball valve assembly made from synthetic plastics material.

Plastics-made ball valves are nowadays broadly used in piping systems. The ball valve assembly comprises a bored and rotatable valve member, the main working part or valve proper being mounted in a valve cavity of a valve body made again of a plastics material. The plastics material for the valve member as well as the valve body is preferably polyvinyl chloride. The valve body is formed with fluid inlet and outlet bore passages arranged in line with each other and kept in direct fluid connection with the valve cavity at its opposite sides, repectively. At these junction area and around the respective bore passages, annular recesses are formed on the valve body for receiving and holding therein a seat ring adapted for tight and slidable cooperation with the valve member.As the material for these seat rings, polytetrafluoroethylene, hereinafter described briefly as "PTFE", have been used practically exclusively. However, since this material PTFE lacks of necessary sufficient elasticity it is liable to appreciable deformation upon repeated valvings, resulting in a loss of fluid tightness. With use of the ball valve fitted with PTFE-seat rings, it is thus necessary to provide means for adjusting the bati- seat contact pressure during an extended use of the ball valve assembly. As an example, such structure has been employed as to occasionally increase the ball seat contact pressure. As a further example, the PTFE-seat ring is backed up with an elastic member so as to compensate the eventual loss of the contact pressure.

The ball valve assembly of the above type is rather complicated in its structure and has numerous structural members. In addition the precision needed in the fabrication of these constituent parts is high.

Still a further defect in the hitherto known plastics-made valves resides in a heavier valvemanipulating torques caused by heavier valveseating pressure. This defect appears more apparent with increase of valve size or dimensions.

It is, therefore, the main object of the invention to provide a plastic-made valve assembly having a lighter and rather flat valve-manipulating characteristic irrespective of smaller and larger valve sizes.

Another object is to provide a simplified structure of plastics-made ball valve assembly, dispensing with means for after-adjustment of the ball-seat contact pressure.

The present invention provides a ball valve assembly comprising a ball valve member made of a plastics resin material, preferably polyvinyl chloride, and movably mounted in a valve cavity formed in a valve body also made of a plastics resin material, preferably polyvinvyl chloride, the valve body comprising two body elements coupled in a male-and-female connection with each other and rigidly and permanently united together to mounted the ball valve member permanently in a valve cavity, the ball valve member being supported in a floating condition within said valve cavity by direct and resilient contact with a pair of seat rings made of an elastomer or elastic rubber, said seat rings being so shaped and arranged when seen in an axial section of the valve assembly that the seat ring having four limited contacting areas with the ball valve exerting sealing and floating pressures against the ball valve directing all substantially towards the centre of the latter.

Even in the large, say 4-inch valve, the light floating condition is kept in existence by holding a valve stem coupled with the ball valve member by holding the stem with one and single O-ring.

More specifically, in the improved ball valve assembly, the seat rings are made of elastic rubber or elastomer having a proper hardness range as will be described later. The valve body or casing is made into one rigid body by uniting two mating, injection-moulded valve body halves rigidly and permanently together, for completely, yet rotatably encasing the valve member proper. No means for later adjustment of the ball-seat contact pressure are provided, thereby decreasing substantially the number of sealing rings.

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein Fig. 1 is a longitudinal section of a preferred embodiment of valve assembly of the present invention; Fig. 2 is an axial section of a seat ring and part of several related constituents employed in the assembly show in Fig. 1; Fig. 3 is a comparative chart showing how the valve-manipulating effort is smaller than conventionally.

Fig. 4 is a section view of part of the valve assembly, embodying modifications to the valve seat ring; and Fig. 5 is a view similar to that of Fig. 4, showing, however, a further modification of the valve seat ring.

In the following, referred to Figs. 1 to 3, a preferred embodiment of the invention will be described in detail.

A valve body "A" is composed originally of a male element b having a concentric stepped bore 10 for providing part of a fluid passage. This male element b is provided with outside male threads 11 adapted for screw connection with a femalethreaded end of a fluid piping, not shown. In the similar way, the valve body "A" includes originally a female element a which is similarly formed with a stepped bore 12 and outer male threads 13. The conjointing male-female non-threaded surfaces, only shown by single dotted lines c, of these both elements a and b, are rigidly united together at the final stage of the valve assembly job, as will be later more fully described. The unification of these valve body elements is made so rigid that they can not be separated from each other without destroying the valve body configuration.For this unification, an application of adhesive is most recommendable. However, fusion, welding or thermal conjointing may be employed if desired.

These two valve body elements a and b have been made of a common snythetic resin, preferably polyvinyl chloride, by injection moulding.

Valve body elements a and b are formed opposite and concentric annular grooves 8 and 8', respectively each of the latter having nearly the rectangular sectional form and receiving therein snugly a seat ring 4 or 4' made of elastic rubber or elastomer. The concentricity is made naturally relative to the fluid passage bore elements 10 and 12, respectively.

Seat rings 4 and 4' made of elastic rubber or elastomer are inserted in position in recesses 8 and 8' of the body elements a and b, respectively, before the assembly of the body elements a and b which are so shaped that a cavity or valve chamber 7 is formed at the central portion of the valve body A upon completion of the assembly. In this valve chamber 7, is formed at the central portion of the valve body A upon completion of the assembly. In this valve chamber 7, the valve memberper se or the working portion of the valve member 2 is totally encased or positioned rotatabiy, before the execution of the said valve body assembly job.

The valve body A is formed with a vertical stem-like projection 1 5 having a vertical bore 1 6 formed at right angles to fluid passage bore elements 10; 12 and in communication with the valve cavity 7.

A valve stem 3 passes through vertical bore 16 and mechanically connected at its inner end with the valve member in a conventional tongue-and groove mode. This mechanical connection is executed naturally before valve body assembly A ring assures a positive seal between stem 3 and bore 16. At the top end of the stem, an operating handle 6 is detachably attached..

As seen, the valve member is kept in direct and sealing contact with valve seat rings 4, 4' at four limited small areas as at d, e, fand g, when seen in any axial section of the valve assembly A, as may be well supposed from Fig. 1. At these contacting areas, substantially centrally and inwardly-acting valve-holding and sealing pressures are exerted upon the valve member. The provision of small annular spaces as at 40 provided behind the seat rings serves for increasing the elasticity thereof.

These four pressures are substantially balanced out practically relative to the centre of the valve member. In this way, the latter is kept in nearly floating condition. Thus, even in the large size valve, say of 4-inches, the valve stem 3 together with its handle 6 and valve member, can be easily and lightly operated. In fact, this light valve operating characteristic is substantially flat, as shown in Fig. 3 at II relative to I, the latter showing the valve operating efforts met with conventional and comparative valve assemblies.

Recommendable shore hardness of the seat rings may preferably extend from 60 to 95. As the material for these seats, natural or synthetic rubber can be used. As the latter, chloroprene rubber and ethylene propylene terpolymer rubber are most suitable. For increasing the lubricating performance of the seat rings, molybdenum disulfide may be compounded together.

It should be noted that if the valve body elements are made detachably, the aforementioned floating characteristic may be occasionally be lost upon reconnection thereof.

The curve II shown in Fig. 3 was obtained with conventional valves using PTFE-seat rings.

In the modification shown in Fig. 4, the seat ring is shown at 34 which is held fixedly in a receiving annular recess formed on the valve body as a modification from the groove 8 provided in the foregoing. The ring 34 is positioned in a fixed state by the provision of two annular sealing surfaces 38 and 39 positioned perpendicular to each other. By this means, the seat ring cannot be subject to alteration in its delicate and floating, yet sufficiently leak-preventing mating condition of valve member and valve seats.

A further slightly modified structure of the valve assembly is shown in Fig. 5. In this modification, the seat ring 24 is formed with an annular recess 26 in which an auxiiiary ring 18 is inserted. The latter ring 18 is attached to both the main ring 24 as well as the wall of the recess 26 and thus the valve body. In this way, otherwise possible postional change between valve ball and seat ring and valve body is positively prevented. The main ring 24 is formed with sealing ring projection 1 9 adapted for coaching with the radial wall surface of the receiving recess. In this way, a double sealing effect can be assured. The material of auxiliary ring 1 8 may be synthetic resin, rubber or even metal.

The distance "1" shown in Fig. 3 denotes the distance between the both valve seat rings as measure in their practically mounted position and between the outermost parts thereof.

Claims (2)

1. A ball valve assembly comprising a ball valve member made of a plastics resin material, preferably polyvinyl chloride, and movably mounted in a valve cavity formed in a valve body also made of a plastics resin material, preferably polyvinyl chloride, the valve body comprising two body elements coupled in a male-and-female connection with each other and rigidly and permanently united together to mount the ball valve member permanently in a valve cavity, the ball valve member being supported in a floating condition within said valve cavity by direct and resilient contact with a pair of seat rings being so shaped and arranged when seen in an axial section of the valve assembly that the seat rings having four limited contacting areas with the ball valve exerting sealing and floating pressures against the ball valve directing all substantially towards the centre of the latter.

2. A ball valve assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.