This invention relates to a valve.

Much, use is made in laboratories of tubing fabricated from borosilicate glass. Such tubing is most suitable for laboratory use, as it is both chemically inert and heat-resist The major disadvantage of such tubing is that it is breakable. It is accordingly desirable that any ancillary equipment, such as valves which operate to close off and. open various portions of tubing, cannot be operated in such a way that they exert a force on the glass which is sufficient to cause a breakage. It is an object of this invention to provide an improved valve for glass tubing.

The invention provides a valve for use with glass tubin characterized in that a valve member (100) is connected to an element (128) , such' that the movement of the element (128) normally moves the valve member (100) relative to a vlave region (16) , there being means provided to prevent said valve member (100) exerting a force upon said tubing sufficient to break said tubing.

Preferably said means prevents said element (128) from exerting force on said valve member (100) after said valve member has reached a. predetermined position.

Preferably, said means includes a shaft (120) secured t said valve member, said shaft extending through an aperture in said element (128) , there being a spring (126) located between said valve member (100) and said cap (128) , such that when sai valve member (100) reaches said predetermined position, furthe movement of said element (128) is relative to said valve member (100) against the force of said spring (126) .

Alternatively, said element (128) is a cap with interna screwthreading (130,210) to enable it to be screwed onto external screwthreads on said tubing, and in that the screw¬ threading comprises a portion of reduced profile (210) .

In the drawings:

Fig. 1 is a section through a T-shaped section, of glass tubing, showing one form of valve according to the invention, in place thereon;

Fig. 2 is a section through an identical T-shaped section of glass tubing, showing another form of valve accordi

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to the invention, in place thereon;

Fig. 3 is an exploded perspective view of the valve of Fig. 1; and .

Fig. 4 is an exploded perspective view of part of the valve of Fig. 2.

Dealing initially with Fig. 1, there is shown, partial cut away, a T-shaped section 10 of borosilicate glass tubing. The section has a first tube portion 12 and a second tube por 14, with a valve region 16 therebetween. The first tube 12 i shown to have a wider bore 18 than the bore 20 of tube 14, bu this is simply one example of the many tubing arrangements fo which the invention is suitable.

The valve region 16 has an opening 22, and the tube ha an external screw thread 24 in the area of the opening. Regio 16 narrows into tube 12, and in this narrowing is created a valve seat 26.

Referring now to Figs. 1 and 3, the valve has a valve member 100, which is generally cylindrical. Valve member 100 has a solid end portion 102 with an internally threaded bore 104 therein. The remaining portion of the member 100 is holl (106) with an opening 108 at the other end thereof. An annul flange 110 is located around the opening 108. The member 100 is preferably formed from polytetraflouroethene (PTFE) .

A sealing member 112 consists of a sealing ring 114, preferably formed from rubber, fitted in a 'pulley' shaped - supprt member 116, having an aperture 118 therein. Member 116 is preferably formed from a plastics material, and sealing ri 114 may be formed from an elastomeric material.

An actuating shaft 120 is generally of a narrow cylindrical shape, and has a reduced diameter portion 122 wi an external screwthread 124, which screwthread is adapted to co-operate with internal screwthread 104 on shaft 100. Shaf 120 is preferably formed from a plastics material. There is a helical compression spring 126, the length of which approxi the length of member 120. The spring is preferably metalli Open-ended cap 128 is three-lobed, for easy manual actuation, is internally screwthreaded (130) , which screwthr co-operates with screwthreads 24 on glass tubing section 10.

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The cap 128 has an axial aperture 132 in the top thereof. Th cap 128 is preferably formed from a plastics material.

Actuating member 134 has a handle portion 136 adapted to be gripped between the fingers, a bifurcated portion 138 with an aperture 140 passing through both legs of the bifurca and a camming profile 146. The aperture is adapted to receive an axle 142 therein. The member 134 is preferably formed from a plastics material and the axle 142 is preferabl metallic. The valve is assembled as follows. The sealing member 112 is pushed into hollow portion 106 of valve member 100 by the annular shoulder 144 between the main body of shaft 120 and the reduced diameter portion 122. The reduced diameter portion 122 is adapted to pass through aperture 118 in member 112. Shaft 120 is screwed into member 100, by virtue of screw threads 124 and ^" 104.

Spring 126 is pushed over shaft 120 within the hollow portion 106, and one end rests on member 112. Near the other end a diametric aperture 141 is formed, for the receipt, afte that end is pushed through aperture 132, of axle 142. The en of shaft 120 is located within the bifurcated portion 138 of member 134, and retained therein by axle 142, which, in the final assembly is located in aperture 140 and in the aperture created near the end of shaft 120. In use, the assembled valve is located on T-shaped tubi section 10, by cap 134 being screwedonto threads 24. Member 100 enters valve region 16, and the presence of member 112 within member 100 radially deforms the walls of the hollow portion to enable a seal to be made with the wall of region 16.

Normally, the valve would be screwed into a position where end portion 102 seats onto valve seat 26; the valve arrangement is then in the 'closed' position, in which fluid is prevented from flowing from tube 12 to tube 14 or vice versa. To open the valve, actuating member 134 is rotated 180 about axle 142. The camming profile 146 acts to displace shaft 120 and valve member 100 along the region 16, and the actuating member operates in an Over-centre' manner

lock into the 'open' position, wherein fluid can flow between the tubing sections 12 and 14.

By adjustment of cap 128 when the valve is in the 'ope position, flow rates can be adjusted, and spring 126 insures that when the valve is returned to the 'closed' position, member 100 is held against valve seat 26.

For small fluid flows, such as to provide single drops to a beaker or the like, the handle 136 of actuating member 134 may be depressed towards cap 128, which thereby displaces the valve member 100 a short distance from the valve seat 26, to allow small amounts of fluid to pass from one tube to another.

Figs. 2 and 4 disclose an embodiment of the invention which has many features in common with the embodiment of Figs 1 and 3, and these features are denoted by the same reference numerals.

The arrangement of Figs. 2 and 3 includes an externall threaded retaining ring 200, which has two radial slots 202 for co-operating with a tool (not shown) to screw the ring into the screwthreaded portion 130 of cap 128. The ring also has an aperture 204 which allows the passage of the main body portion of valve member 100 to pass therethrough. The ring 200 is preferably formed from a plastics material. A helical compression spring 206 is also adapted to fit over member 100 The spring is preferably metallic.

A tubular support member 208 is adapted to fit within the hollow portion of member 100. It is preferably formed from a plastics material.

Finally, in this embodiment, there is no aperture in t top of cap 128. There is also.a section 210 of screwthread 130, which section is of reduced profile, allowing the cap t be screwed fully onto, for example, screw threads 24 of tubin section 10, when no force in the direction of the tubing is applied to the cap, but prevents the further screwing of the cap when such a force, of sufficient magnitude, is applied to the cap.

The valve is assembled as follows. Sealing member 112 is pushed into valve member 100 by tubular member 208. Sprin 206 is slid over the main body portion of member 100 unti_

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rests on the shoulder formed by flange 110. Member 100 is then pushed, in the direction of the arrow, into cap 128, and ring 200 is screwed into the cap, retaining the member 100 therein. In use, the valve is screwed onto a piece of equipment, such as tubing section 10, in a manner similar to that describ in relation to the embodiment of Figs. 1 and 3. With this embodiment the valve is opened and closed by screwing and unscrewing cap 128, which operation also enable continuous adjustment and flow-rate determination to take place. In addition, the cap cannot be tightened on the tube once the 'close' position of the valve has been reached, as spring 206 exerts a force against cap 128 to. the left in Fig. 3, whic causes the threads 24 to override those in the section 210 until they contact the normal profile threads at 130.

As stressed hereinbefore, the invention may be used in various applications. For example, the valve may be arranged with a panel between the actuating member 134 and/or cap 128 and the tubing 10. In such a case in intermediate member coul be provided in an aperture in the panel, which would screw ont tubing section 10, and onto which one of the valve arrangements would, be screwed.

The sealing between member 100 and the walls of a regio such as 16 may be enhanced by the provision of a circumferenti ridge or ridges in the area of the seal. Other types of seali members 112 may also be used within the hollow portion of memb 100.

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