GB2301874A - Cartridge valves - Google Patents

Abstract

A cartridge valve assembly for a ball valve comprises a two-piece plastics cartridge 32, 34 having integral annular valve seats 36, 38 to co-operate with the ball 12 and held captive at one end by the housing top plate 18. An integral valve stem 26 actuates the ball. A circlip 42 optionally holds the cartridge portions in co-operating relationship with the ball even when disassembled from the valve housing.

Description

CARTRIDGE VALVES This invention relates to cartridge valves. An example of a cartridge valve is a ball valve assembly in which provision is made to enable the ball and its associated pair of annular seats to be assembled and disassembled from the associated valve housing in a simple manner, and usually as a one piece assembly.

For this purpose the usual arrangement is to provide a cartridge structure which serves to mount the ball and its associated pair of seats as a single assembly, and which allows this assembly to be inserted into and removed from the valve housing as a unitary structure as mentioned above. Such arrangements exist both for ball valves and other plug valves, and at least in relation to ball valves such arrangements have been known for at least ten and probably twenty or more years.

The conventional mode of construction for a cartridge valve is to provide it in the form of a metallic assembly with the plastics material of the annular seats trapped between the metallic structures of the ball and the cartridge.

Shortcomings of this conventional construction have existed likewise for many years, these including the relatively complex nature of the ball, cartridge and seats assembly, the need to provide means for ensuring a proper relationship between the cartridge, the ball and its seats, and an associated requirement concerning carry-over. Carry-over relates to the volume of fluid within the valve housing which carries over and is transmitted downstream when the valve is re-opened after closure. The minimisation of carryover is an important factor in many plug valve applications, particularly in the nuclear and chemical industries.

Examples of previously proposed cartridge valve assemblies are GB 936,686 GB 1,318,252 GB 970,176 We are aware of a prior proposal, in the name of Xomox, aimed, presumably, at meeting some or all of the above requirements in the form of a plug valve having a tapered or frusto-conical valve body which is insertable into a one-piece plastics cartridge. The cartridge has a corresponding tapering or frustoconical inner and outer form. The cartridge is formed with integral seating means to co-operate with the tapering form of the plug valve member on opposite sides thereof and in surrounding relation to the through-flow passage provided in the ball and the housing.

Because the cartridge member is formed in one piece, which is indeed possible in the case of a plug valve having a tapering valve member, the plastics cartridge is able to form a corresponding one-piece enclosure for the valve member which thereby holds the valve seat portions of the cartridge in their proper relationship to the valve member.

Such an arrangement is not possible in the case of a ball valve due to geometrical considerations, and an object of the present invention is to provide a cartridge valve assembly providing one or more improvements in this regard, or improvements generally.

We have discovered that, in the case of a ball valve, it is possible to provide a cartridge arrangement in which a cartridge of plastics material provides integral annular valve seats for co-operation with the ball-type valve member on opposite sides thereof and in surrounding relation to the throughflow passage, in the valve-open position. The assembly is characterised by the feature that the cartridge member comprises two separable pieces adapted to be mounted in surrounding relation to the ball valve member. There is provided, in addition to the cartridge member, and located at the exterior thereof in use, a releasable locating structure which, in its non-released condition, locates the separable cartridge portions in their oppositely-disposed positions in relation to the ball.

By providing the combination of a cartridge member of plastics material having integral annular seats and comprising two separable portions, together with a releasable locating structure for those portions, the embodiments enable the simplifying advantages of the above-mentioned prior proposal in the name of Xomox to be achieved in relation to ball valves while solving the geometrical problem. Whereas in the Xomox proposal, the relative disposition of the cartridge member to the tapering plug valve member is maintained by the very form and one-piece construction of the cartridge member, in the embodiments of the present invention this relationship is achieved despite the use of two separable cartridge portions, by means of the releasable locating structure.

In accordance with the invention there is provided a cartridge valve assembly as defined in the accompanying claims. The invention also provides a cartridge valve assembly wherein a cartridge member comprising plastics material comprises two separable portions and a releasable locating structure is provided which is adapted to locate the separable portions in relation to a ball valve member on opposite sides thereof.

In an embodiment, the arrangement of the two separable cartridge portions in relation to the ball valve member and the releasable locating structure is such that, for assembly and disassembly purposes, the cartridge portions are located in relation to the ball only on one side of the ball, being the side at which the ball is actuated, and the opposite side of the valve is, prior to assembly into the valve housing, not provided with any means for locating the cartridge members in relation to the ball. On insertion of the assembly into the valve housing, co-operation of the cartridge members with the valve housing provides a progressive inward locating effect on the cartridge members whereby they, and the associated annular valve seat facilities become held in proper positional and properly-loaded relation to the ball.

In this particular embodiment, the releasable locating structure for the cartridge member portions is thus provided mainly by the structure at the top of the assembly which holds the ball and the cartridge member portions together. The usual arrangement for cartridge valve assembly is for downward insertion into the valve housing, but the invention is by no means limited to this arrangement, and all other optional attitudes for insertion and removal are equally applicable.

In one particular embodiment, the ball member is provided with an integral operating stem and the cartridge portions are held captive in relation to the stem and the ball by a suitable locating member, such as a collar. No locating means is provided, in this embodiment, on the opposite side of the ball, and thus the plastics cartridge member portions tend slightly to splay open prior to insertion into the valve housing. However, the latter is of inwardly-tapering form and insertion of the assembly therein has the desired supplementary locating and loading effect in relation to the cartridge member portions and their dispositions in relation to the ball.

In the embodiments, it is found that the simplicity of construction resulting from the abovedescribed general form of the assembly enables the significant advantage of reduced carry-over to be obtained so that volumetric carry-over is within the 0 to 5% volume range (in relation to the internal volume of the valve housing, not including the ports), and indeed it is relatively straightforward to achieve a carry-over volume as low as 1% or less. This is a very significant advance in relation to the longconventional multi-piece metallic cartridge valve assembly.

Moreover, this advantage and the advantages of simplicity of construction provided by the embodiment described below are achieved in such a relatively straightforward way, eliminating the need for precision metallic machining operations in relation to the cartridge member, and otherwise simplifying the original equipment costs, that this ease of production, and the use of relatively unsophisticated materials represents another significant advantage.

In the embodiments, the plastics material employed for the cartridge member may be the relatively conventional PTFE material known for use in relation to valve seats. However, alternative plastics materials, whether polymers or co-polymers, with or without fillers, extenders and other materials may be employed for particular purposes.

By providing the cartridge in the form of a moulding of plastics or polymeric material, it can be conveniently shaped and proportioned to be a close and sliding face-to-face fit within the relevant surfaces of the valve housing. As a result, there is no need to provide the conventional feature used in metallic cartridge valve assemblies of an O-ring seal between the cartridge and the housing, which inevitably results in carry-over of fluid. Therefore, in the embodiments, the free space within the valve assembly in which carry-over of liquid and/or suspended solid matter is possible, is significantly reduced.

Obviously, it cannot be entirely eliminated but a significant reduction is of practical importance in terms of the quoted specifications of valve assemblies. In the embodiments, the numerical expression of this carry-over factor can be defined in terms of a) The internal volume of the housing for the cartridge, not including the volume of the throughflow passages connected thereto; b) The actual volume of the material of the cartridge itself; and c) The external volume of the ball valve member including its through-flow passage.

With a view to minimising carry-over, the relevant expression is A - (B + C) is not greater than 5% A and preferably is not greater than 1% A.

With a view to minimising carry-over, it will be clear from the above that the volume (B) of the actual material of the cartridge should be as large as possible, within the available parameters.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which Fig 1 shows a section taken on the axis of the stem of a ball valve, through a cartridge assembly including the ball valve; Fig 2 shows the cartridge assembly of Fig 1 inserted in and assembled with a valve housing and an operating handle for the stem of the valve member; Fig 3 shows an end elevation view of the cartridge assembly of Fig 1; and Fig 4 shows the cross-sectional view of Fig 1 on a larger scale.

As shown in the drawings, a cartridge valve assembly (10) comprises a plug-type valve member in the form of a ball valve member (12) and a cartridge (14).

Cartridge valve assembly (10) is shown in Fig 1 and is adapted to be inserted into a housing (16) for the cartridge valve assembly which housing includes a top plate (18). Top plate (18) co-operates with cartridge (14) in a manner to be more fully described below.

Ball valve member (12) is formed with a throughflow passage (20) which, in the valve-open position shown in the drawings is aligned with the through-flow axis (22) of the entire cartridge valve and housing assembly (24).

Ball valve member (12) is formed integrally with a valve stem (26) defining a valve-opening and valveclosing axis (28) about which the ball valve (12) is turned by means of a manually operable handle (30).

Ball valve member (12) is itself of generally conventional construction, comprising stainless steel, or other alloy material, depending upon the particular application for which it is intended.

Cartridge (14) comprises two separable cartridge portions (32) and (34), each formed as a moulding of plastics material. In this embodiment, the plastics material is PTFE. In Figs 1, 2 and 4 of the drawings the individual cartridge portions can be seen. Each of these is formed with a respective valve seat (36) and (38) of annular form and integral with the cartridge portions (32) and (34) respectively. The annular valve seats are adapted to co-operate with the adjacent spherical surfaces of the ball (12) on opposite sides thereof. The cartridge portions (32) and (34) are separable by virtue of their construction as separable portions and the plane on which the dividing line passes between them is, as seen in Fig 4, a vertical plane generally at right angles to the plane of the paper in Fig 4 and extending through the valve axis (28).The valve seats (36) and (38) are annular in form and moulded integrally with the remainder of the cartridge portions.

Releasable locating structure (40) is provided to releasably locate the cartridge portions (32) and (34) on opposite sides of the ball (12). The releasable locating structure comprises top plate (18) and a circlip (42). Top plate (18) co-operates with an upstanding locating collar (44) defined in part by each of the cartridge portions (32) and (34).

Likewise, a lower locating collar (46) is defined in part by each of the cartridge portions and is adapted to receive circlip (42) for assembly purposes.

In this embodiment, cartridge (14) is formed as a plastics moulding and with a minimum of surfaces requiring any machining operations. Indeed, in this embodiment, no such operations are required.

Upper locating collar (44) is adapted to be received in a complementary annular recess (48) formed in top plate (18) so as to be a captive fit therein.

This captive fit, together with the circlip (42) serves to releasably locate the two cartridge portions in relation to ball valve member (12). For release purposes, the circlip is removed and the cartridge portions (32, 34) can then be released from top plate (18) by forcibly disengaging collar (44) from recess (48).

Housing (16) of the cartridge valve and housing assembly (24) is formed as a metallic casting defining an inwardly-tapering opening (50), of which the inwardly-tapering opening (50), of which the inwardly tapering surfaces serve to exert a defined inward loading on the cartridge portions (32, 34) to achieve the required sealing loads on valve seats (36) and (38) for the valve application in question. Valve housing (16) defines through-flow passages (52, 54) disposed coaxially with through-flow axis (22) and adapted at their ends to co-operate with fluid flow conduits (not shown).

Top plate (18) is formed with a threaded opening (56) to receive a stop bolt (58) to define the limit of travel of handle (30). Valve stem (26) is journaled in top plate (18) for angular movement by means of packing rings (60) and a gland nut (62).

In use, cartridge portions (32) and (34) are assembled in relation to ball valve member (12) by locating upper collar (44) within recess (48) in top plate (18) and mounting circlip (42) in its recess or groove at the inner end of locating collar (46). The cartridge valve assembly (10) can then be assembled by insertion into the inwardly tapering opening (50) in housing (16), whereupon valve seats (36) and (38) are suitably loaded against ball (12).

Disassembly is effected by a reverse sequence of operations.

While in the above embodiment the valve has been described and illustrated in terms of the upright attitude shown in the drawings for top-insertion of the cartridge assembly, it will of course be understood that any other desired attitude may be adopted, including the inverse attitude with upwards insertion of the cartridge assembly.

Claims (10)

CLAIMS :

1 A cartridge valve assembly comprising a) a plug valve member; b) a cartridge for said plug valve member, said cartridge comprising a plastics material; c) said cartridge itself providing integral sealing means adapted to co-operate with said plug valve member and to provide a seal between said plug valve member and a housing therefor; characterised by d) said plug valve member being in the form of a ball valve member; e) said cartridge comprising two separable cartridge portions each providing an annular valve seat formed integrally with its cartridge portion and adapted to cooperate with said ball on one side thereof and opposed to the other cartridge portion; and f) said ball valve member being removable from said cartridge by separation of said cartridge portions; and g) a releasable locating structure adapted to releasably locate said cartridge portions on said opposite sides of said ball.

2 A cartridge valve assembly for a ball valve characterised by a plastics cartridge member comprising two separable cartridge portions each providing a valve seat to co-operate with the valve member.

3 A cartridge valve assembly according to claim 1 or claim 2 characterised by said cartridge portions being of inwardlytapering form and adapted to co-operate with a complementary inwardly-tapering opening defined by said housing.

4 A cartridge valve assembly according to claim 3 characterised by said cartridge portions defining respective inlet and outlet duct portions adapted to be aligned with the through-flow opening of said ball valve member.

5 A cartridge valve assembly according to claim 4 characterised by said annular valve seat on each cartridge portion being formed at the inner end of its respective duct portion.

6 A cartridge valve assembly according to any one of preceding claims characterised by said releasable locating structure comprising a locating collar defined in part by each of said cartridge portions, said collar being adapted to cooperate with a mounting plate of said valve housing.

7 A cartridge valve assembly according to claim 6 characterised by said collar being adapted to be held releasbly captive by said mounting plate.

8 A cartridge valve assembly according to any one of the preceding claims characterised by said ball valve member being provided with a stem defining the axis of turning of the ball valve member and extending through said locating structure.

9 A cartridge valve assembly according to any one of the preceding claims characterised by said releasable locating structure comprising a collar defined in part by each of said cartridge portions to co-operate with a releasable locating member at the inner end of said assembly.

10 A cartridge valve assembly according to claim 9 characterised by said releasable retaining member comprising a circlip.