FIELD OF THE INVENTION

This invention relates to valves for the inflation o tubeless pneumatic tyres for motor vehicles and othe wheeled equipment. Such valves are currently available i two configurations, known respectively as "snap-in" an

"clamp-in" valves.

Both types comprise a central valve core, which itsel comprises a valve body incorporating a seat and a spring loaded valve element co-acting with that seat, screwed as plug into a tubular core holder.

In the case of snap-in valves the core holder is bonded to an elastomeric outer base so shaped that, o insertion into the valve aperture in the rim of conventional vehicle wheel, its retention in, and airtigh seal with the rim, is effected. In the case of the clamp in type, the core holder is flanged at its lower end, threaded externally and by means of a rubber grommet, rubber and metal washers and clamping nut, may be secured airtightly in the rim's valve aperture. In each case the core holder and associated components referred to, except for the core, are known as a valve stem.

It is well known that tyre life and vehicle safety depend largely on tyres being maintained at the recommended inflation pressure, which varies with the vehicle-tyre combination, tyre location on the vehicle and operating conditions.

Thus gauges are available which may be applied to the open upper end of the core holder of a tyre valve which, by iln rnππinG the spring-loaded valve element of the vnlvo cor e , b e c om e pr e s sur i s ed and ind i c at e th e pr e s s ur e obtaining in the tyre .

SUBSTITUTE SHEET

It is also well known that such gauges often becom inaccurate with use, that motorists frequently take a ris on their tyre pressures being correct rather than go to t trouble of finding and using a gauge, and that occasional a sealed valve commences to leak following the disturban caused by use of a gauge.

DESCRIPTION OF THE PRIOR ART

Thus various proposals have been suggested for t provision of valve stems, or screw-on caps therefor, whi include built-in devices for indicating whether or not t tyre is correctly inflated. For the most part such pri proposals have included spring loaded pistons sliding cylinders exposed to the air pressure within the tyre. T correctness or otherwise of the pressure is then indicat by the position of the piston working against the effect the loading spring. Those proposals have be unsatifactory because the components additional to those a standard non-indicating stem, for example, the loadi spring, have increased the manufacturing and assembly cos and the tendency for seals either to leak or to seize has caused them to be unreliable. The indicating valve U.S. Patent 3906988 overcomes the sealing problem utilising a pliable or flexible diaphragm instead of cylinder but still incorporates a loading spring. Oth prior art disclosures known to applicant but thought to less relevant are U.S. patent specifications 4-31001 10354-9 and 4-606391.

SUMMARY OF THE INVENTION

The present invention was devised to provide continuous, visible, reliable indication of the correctne or otherwise of a tyre's inflation pressure by particular simple means, incurring very little additional materi cost by comparison with a standard non-indicating stem a Powor nπficϊinbly αlc α In manufacbure by comparison wi known indicating stems. The invention achieves that obje by utilising a moulded elastomeric support for a moveab

valve core holder which functions as both the seal between the holder and the wheel rim and the means providing a yieldable restraining force on the holder.

The invention consists in a pneumatic tyre inflation valve stem of the kind comprising a tubular, rigid valve core holder, a rigid mounting sleeve in which said holder is telescopically slidable, affixture means fixedly supporting said mounting sleeve and adapted to be secured airtightly within the valve aperture of a wheel rim, sealing means providing an airtight connection between said affixture means and said holder and loading means elastically restraining the movement of said holder, characterised in that said sealing means comprise a yieldable elastomeric diaphragm of sufficient stiffness to provide all of the elastic restraint on said holder.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a quarter-sectioned side elevation of a tubeless, pneumatic tyre valve stem according to the invention, drawn to an enlarged scale.

Figure 2 is a view similar to figure 1 of a second valve stem according to the invention.

Figure 3 is a view similar to figure 1 of a third valve stem according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The valve stem illustrated by fig. 1 is of the "snap- in" type. It comprises a resilient rubber affixture means 1 of conventional shape, including a cylindrical neck 2' wliich fits tightly through a clearance hole in a wheel rim and a retaining head 3-

The affixture means 1 is surmounted by a rigid plastics or metal tapered mounting sleeve 4- in which a

^S UBSTITUTESHEET

rigid valve core holder 5 is able to move axially up and down.

The core holder 5 is attached at its lower end to the interior of the rubber affixture means 1 by sealing means comprising an annular, yieldable elastomeric diaphragm 6 integral with the affixture means 1 and bonded to the core holder 5 _*

An air passage 7 through the centre of the affixture means 1 connects with a central passage of the holder 5 which is machined to take a standard valve core (no shown) .

As pressure varies in the tyre and hence in the ai passage 7 the diaphragm 6 elastically yields, permittin the holder 5 to rise or fall relative to the rim 8 o sleeve 4- as the pressure within the tyre changes.

Three colour coded rings 9 _» recessed in the holder where it protrudes from the sleeve 4- _> indicate whether th tyre is under-inflated, correctly inflated (to the nomina pressure for this embodiment) or over-inflated, dependin on which coloured ring is level with the rim of th sleeve «

The fig. 2 embodiment is similar to the fig. 1 embodiment and comprises affixture means 10, core holde

11, and sleeve 13 all corresponding in function to th affixture means 1 , holder 5 and sleeve 4- of the fig. 1 embodiment.

In this instance, however, the sealing means compris an annular end wall 14. of the affixture means 10 bonded t an extended end portion 15 of the core holder 11. The en wall 1/, in more floxible than the diaphragm 6 of the fig. embodiment to provide greater movement of the holder 11.

Furthermore the sleeve 13 is furnished with a ring-nu 16 which may be advanced or retracted to provide fo adjustment of the effective length of the sleeve 13•

The core holder 11 may be furnished with an indicato ring 17.

At an initial inflation of the tyre to its correc pressure, the ring-nut may be positioned so that its ri coincides with the ring 17. Thereafter any change i pressure will be indicated by the departure of the ring 1 from its coincidence with the rim of the nut 16. Thus thi embodiment may be adjusted to suit a range of nomina pressures instead of the one set pressure of the fig. embodiment.

The fig. 3 embodiment is a "clamp-in" valve stem. T that end its affixture means comprise a radially projectin flange 18 on a mounting sleeve 19, an elastomeric sealin washer 20, a rigid clamping washer 21 and a clamp nut 22.

The mounting sleeve 19 has a ring-nut 23 correspondin to the ring-nut 16 of the fig. 2 embodiment.

In this embodiment the sealing means between th sleeve 19 and core holder 23 is a resilient, elastomeric generally tubular boot 25-

One end margin 25A of the boot 25 is clamped betwee flange 18 and a wheel rim 26 and is thereby air-tightl held to the affixture means, of which, indeed, i constitutes a component.

SUBSTITUTESHEET

The other end margin 25B of the boot 25 is sealed t the core holder 23. It is clamped between a hat washer 2 and a plain washer 28 and held therewith as a fixe assembly by a swaged over rim 29 on the adjacent end of t core holder 23.