FR2469629A1 - Plastics pref. polyvinyl chloride ball valve - with elastomeric sealing rings supporting ball with floating action - Google Patents

Abstract

Plastics, pref. PVC valve has a ball movable in a body of two parts (a,b) with male-female coupling and permanently joined together. The ball is held by direct resilient contact with a pair of rings (4,4') shaped to have four limited contact areas with the ball when viewed axially of the valve. The rings exert sealing and floating pressures against the ball all towards the ball centre. The rings are e.g. of natural rubber, polychloroprene or ethylene-propylene terpolymer, optionally compounded with MoS2. The arrangement provides a lighter flat manipulation characteristic. The body parts are joined with adhesive or by welding, as if made detachable the floating characteristic may be lost on reconnection.

Description

The present invention relates to a valve or tap comprising a spherical valve in a synthetic material, preferably a polyvinyl chloride, mounted in a plug also in synthetic material, preferably, a polyvinyl chloride. According to the invention, in this valve, the valve body is composed of two elements made integral with one another by an assembly of the interlocking type of a male part in a female part and assembled permanently so as not to form only one piece. Thus, the spherical shutter is locked in the plug definitively and is kept practically floating in the plug by the direct and elastic contact of a pair of seals made of rubber or an elastomer. These seals are shaped and arranged, when '' we look at them in an axial section of the valve, so as to present four limited contact surfaces with the spherical shutter, exerting sealing and holding pressures on the spherical shutter, substantially towards the center of these this.

It is known that ball valve is currently widely used in pumping systems. Known spherical shutter valves include a shutter mounted in the plug made of synthetic material
The preferred synthetic material for both the valve body and the plug is polyvinyl chloride.

The valve body has fluid inlet and outlet passages aligned with each other and maintained in direct communication with the plug, respectively on two opposite sides thereof. At these junction points and around the respective inlet and outlet passages, annular housings are provided in the valve body to receive and maintain seat seals adapted to cooperate in leaktight and sliding manner with the obturator. So far, these seat seals have been produced almost entirely from polytetrafluoroethylene (PTFE). However, since the
PTFE does not have sufficient elasticity and is subject to deformation after several valve commands, this results in leaks. When using PTFE seat seals, it is therefore necessary to provide means of 'adjustment of the contact pressure with the ball valve, if one wishes to make a prolonged use of the valve. Such a structure has been used to occasionally increase the contact pressure of the spherical seat. Alternatively, in known valves, the PTFE seal can be used by an elastic element so as to compensate for the occasional loss of contact pressure.

Such known valves, of the type mentioned above, are relatively complicated with regard to their structure and have a relatively large number of elements. In addition, it is necessary to manufacture the various components precisely.

Another drawback of valves of this type known up to now, made of synthetic material, lies in high operating torques due to the very high pressure of the valve seat on the valve member. This defect is all the more apparent as
the dimensions of the valve are larger.

The object of the present invention is therefore a valve made of synthetic material which is easy to operate, whatever its size.

Another object is to provide a simplified structure avoiding the means for adjusting the contact pressure on the spherical obturator.

To this end, according to the invention, a ball valve comprising a ball valve in a synthetic material, preferably polyvinyl chloride, mounted in a ball valve formed in a valve body also in synthetic material, preferably polyvinyl chloride , is characterized in that said valve body is formed of two elements secured by a male and female assembly and definitively connected to each other, said ball valve being therefore trapped in the ball valve in a non-removable manner and being maintained practically floating in said plug by direct and elastic contact with a pair of seat seals made of an elastomeric or elastic material, said seat seals being shaped and arranged so that, in axial section of the valve, said seat seals have four surfaces of limited contact with the spherical obturator exerting sealing and float-keeping pressures on said obturator ator, these pressures being substantially directed towards the center of said shutter.

Even in the case of a large valve (for example of the order of 10 cm), the condition of maintenance with gentle friction is ensured, and, for the operation, a rod is provided coupled to the spherical obturator and associated with one or more seals.

More particularly, in the ball valve according to the invention, the seat seals are made of an elastic material or an elastomer having a specific hardness within the range indicated below. The one-piece valve body is produced by assembling two body halves obtained by injection molding, and permanently assembled so that the plug can rotate in the valve body. No means of adjusting the contact pressure of the seat on the ball valve is provided, so that a high number of seals is eliminated.

The figures of the appended drawing will make it clear how the invention can be implemented.

Figure 1 is an axial section of a preferred embodiment of the valve according to the invention.

Figure 2 is an enlarged and partial axial section showing a seat gasket and part of several components used in the valve of Figure 1.

Figure 3 is a comparative diagram illustrating the ease of operation of the valve according to the invention, compared to known valves.

Figure 4 is a sectional view concerning an alternative embodiment of the seat seals.

Figure 5 is a view similar to Figure 4 showing another variant of seat seals.

The preferred embodiment of the invention, illustrated in FIGS. 1 to 3, comprises a valve body A composed initially of a male element b having a concentric bore 10 with shoulders and capable of partially constituting a fluid passage . This male element b has an external male thread 11 capable of being connected to a threaded female end of a pipe, not shown. Similarly, the valve body A comprises a female element a which similarly comprises a shoulder 12 with a shoulder and an external male threading 13. The male-female surfaces not threaded (only represented by a dotted line c) of these two elements a and b are made integral with one another at the time of the final assembly of the valve as will be described below. The joining of these valve body elements is such that they can no longer be separated from each other later without destroying the valve body itself. For this joining, it is preferable to use an adhesive. However, it is also possible to carry out a process of fusion, welding or thermal joining if desired.

These two elements a and b are made from the same synthetic resin, preferably polyvinyl chloride, and are obtained by an injection molding technique.

The elements a and b comprise concentric and opposite grooves 8 and 8 'respectively, each of these grooves having a section of substantially rectangular shape and receiving a seat seal 4 or 4' of an elastic material or an elastomer. These seals are arranged concentrically with respect to the bores 10 and 12 for the passage of fluid, respectively.

The seat joints 4 and 4 ′ made of an elastic material or of elastomer are placed in position in the grooves 8 and 8 ′ of the body elements a and b, respectively, before the assembly of the body elements a and b which are shaped so as to delimit a ball valve 7 is formed in the central part of the valve body A, at the time of production of the assembly. In this chamber 7, the spherical shutter is completely enclosed and arranged in a rotary manner before the joining of said elements a and b.

The valve body A has a projection 15 pierced with a vertical bore 16 perpendicular to the bores 10 and 12 and in communication with the ball valve 7. A control rod 3 passes through the vertical hole 16 and is mechanically connected at its end inside, to the shutter by means of a dovetail device. This mechanical connection is obviously made before the assembly of the valve body.

Reference 17 designates a seal ensuring the seal between the rod 3 and the bore 16. At the upper end of the rod 3 is provided a removable operating handle 6.

As can be seen, the spherical shutter is kept in tight and direct contact by the seat rings by four small areas designated by d, e, f and g, when looking at an axial section of the body A, such that Figure 1. At the location of these contact areas are exerted on the shutter substantially central and sealing pressures and directed inward. Small annular spaces 40 are provided behind the seat seals and serve to increase the elasticity thereof. These four pressures are substantially balanced with respect to the center line of the shutter. In this way, the latter is maintained substantially in floating. Thus, even in the case of a large valve, the valve stem integral with the handle 10 and the shutter can be easily actuated. Indeed, the opening characteristic of the valve is substantially linear, as shown by curve II of FIG. 3 relative to curve I, the latter showing the operating forces relating to a known valve.

Preferably, the Shore hardness of the seat rings can be between 60 and 95. The material of these seals can be natural or synthetic rubber. As synthetic rubber, it is advantageous to use chloroprene, and the terpolemere of ethylene propylene. To increase the sliding performance of these seats, molybdenum disulfide can be incorporated into it.

It will be noted that if the body A was removable, the friction characteristic could be occasionally lost.

Curve I in Figure 3 was obtained with valves using PTFE seals.

In the variant embodiment shown in FIG. 4, the seat ring is shown at 34 and it is held in a receiving groove different from the groove 8 described above.

The ring 34 is held in position by surfaces 38 and 39 orthogonal to one another. By this means, the position of the seat ring cannot be changed, which avoids any leakage at the valve seats.

According to another alternative embodiment shown in Figure 5, the seat ring 24 has an annular groove 26 in which is inserted a ring 18. This ring 18 is integral with both the main ring 24 and the wall of the recess 26 and therefore of the valve body. In this way, the position variation between the ball valve and the seat ring as well as between the seat ring and the valve body is avoided.

The main ring 28 has a sealing tongue 19 adapted to cooperate with the radial wall of the receiving groove. In this way, we obtain a kind of double effect.

sealing. The material of the auxiliary ring 18 can be a synthetic resin, rubber or even a metal.

The distance "1" shown in FIG. 3 designates the distance between the outer faces of the two valve seat rings, in the mounted position. This distance "1" is indicated (in mm) on the abscissa, while on the ordinate the operating torque has been plotted (in kg.cm).

Claims (1)

 CLAIM Ball valve comprising a ball valve made of a synthetic material and moving in a plug formed in a valve body also in synthetic material, characterized in that said valve body is formed by two body elements assembled by a male type connection and female to each other and permanently secured, the spherical shutter being enclosed in said plug in a non-removable manner and being kept floating in said plug by direct and elastic contact with a pair of seals in an elastomer or an elastic rubber, said seat seals being shaped and arranged to present, in axial section of the valve, four limited contact surfaces with said spherical valve, exerting sealing pressures and maintaining float on said valve, directed substantially towards the center of it.