This indention relates to valve assemblies for pneumatic tyres: and to valve care sub-assemblies and cap sub-assemblies of said assemblies providing an automatic self-indicating facility to show, in operation, whether the associated tyre is under-inflated and/or providing protection against pressure loss and for more convenient inflation of the associated tyre in use.

It is important that tyres are kept inflated at the correct working pressure for the type of tyre, the service conditions, and the type of vehicle. Incorrect pressure, eg uπder-inflation will increase tyre tread ωear, can cause other damage to the tyre, affects safety in that the braking and handling of the vehicle are degraded, and causes inefficient operation e.g. increased fuel consumption. Early detection of under-inflation may lead to otherwise unsuspected damage to a tyre being detected in good time so that sudden and total failure is avoided and, possibly, a safe repair can be made which would not otherwise be possible.

Known methods of checking pressure of tyres fitted with the most common standard patterns of tyre valve assembly are not always convenient or accurate, most commonly a pressure gauge has to be used which is applied to each tyre valve in turn involving some effort time and trouble. Not all drivers carry or use a pressure gauge and many rely on infrequent checking e.g. when visiting service stations (where the pressure gauges are not always accurate), coupled with intermittent and often casual visual inspection of the tyres.

The protective caps fitted as part of the standard tyre valve assemblies have to be screwed off and on each time pressure is to be checked, and for inflation to be effected. The caps are often lost or omitted so that

grit or dirt can enter the main part of the valve wnich may cause leakage and the form of cap often supplied, usually a very basic plastics moulding, is ineffective i providing a secondary barrier against pressure loss tnrou-j the valve.

Proposals have been made to fit valve assemblies to tyres which are constructed to provide a built-in self- indicating facility, usually by including an indicator plunger or flag which changes condition to provide a visible warning of under inflation and some examples of such devices are described in G3-A-2GS2734 - Gα-A-1455301 GB-A-13S5C45: ΞP-A-01 4721 ' US-A-4133295 : and US-A- 4073591.

The known proposals have not proved generally acceptable in practice and have not come into widespread us .

The object of the present invention is to provide a tyre valve assembly, and/or sub-assemblies for use in said assemblies, which are economical to provide and instal; durable and reliable in use, and which may readily be in forms fully compatible and interchangeable with the standard patterns of tyre valve, or with sub- assemblies thereof, which are already in general use.

According to the invention in its various aspects there is provided a tyre inflation valve assembly and/or cap or core sub-assembly as defined by any of the appended claims.

Examples of the invention are now more particularly described with reference to the accompanying drawings wherein :

Figure 1 is a longitudinal sectional view of a tyre inflation valve assembly ,

Figure 2 is an elevation of a main body of said assembly ,

Figure 3 is an enlarged detail of Figure 1 showing diaphragm arrangement,

Figure 4 is an elevation of a cap sub-assembly

thereof ,

Figure 5 is a view on line 5-5 of Figure 4, and Figure B is a longitudinal sectional view of a second embodiment

Referring firstly to Figure 1 , a pneumatic tyre valve assembly 1G comprises a standard pattern main body 12 having the shape, dimensions, and screw threading standard to the most commonly used tyre valve assembly. Body 12 is fitted to a wheel rim (in the case of a tubeless tyre) or to the inner tube of a tyre in known manner, its externally threaded outer end portion 14, in standard practice, mounting a simple screw-on cap which would be removed for reception of a standard inflation appliance connector or the application of a standard tyre gauge for inflation and/or checking the correct tyre pressure in known manner.

A core sub-assembly (hereinafter referred to as the core) 16 screws into the connector duct defined by body

12 in the same way as the valve cores of the known standard valve assemblies so that it is readily interchangeable therewith. Core 16 comprises a core body

13 which screws down onto the standard taper seating within main body 12 so that its periphery is in airtight engagement therewith. Core body 18 has a stepped coaxial through bore 20 and the inner end of said body forms an annular valve seating 22.

Core 16 further includes a plunger-type valve element 24 having a headed stem 25 guided for longitudinal movement in bore 20, its inner end carrying a valve head 28 mounting an 0-ring main sealing element 30 which coacts with seating 22. In use the internal pressure of the fully inflated tyre forces valve element 24 outwardly so that sealing element 30 is in pressure- tight engagement with the seating 22 but element 24 is displaceable in the opposite direction by external pressure e.g. from an inflation line, or by depression of the outwardly projecting headed end 27 of stem 26 e.g. to check the tyre pressure or to release air if over- inflation has taken place.

The standard pattern of valve core includes a compression spring acting on the plunger rod to urge th valve element to the closed position, i.e. to supplemen tne tyre internal pressure exerted thereon. In the present arrangement core 15 includes a calibrated compression spring 32 located on stem 25 within bore 2ϋ acting between an abutment within core body 18 and the valve head 28. Thus spring 32 is urging valve element opεratively inwardly in opposition to the internal pressure of tne tyre i.e. the spring is tending to unse the valve element.

The spring loading is carefully preselected by calibration at the time of manufacture of the core 15 t De related to a given correct inflation pressure of the tyre, only if said pressure drops below the proper leve will the force exerted by spring 32 exceed the outward pressure loading on valve element 24 to cause it to be unseated so that pressurised air from the tyre enters a outer part of valve assembly 10 as referred to in great detail hereafter.

It is contemplated that a selection of cores 15 wi be manufactured calibrated to respective tyre pressures, they will be suitably colour coded or otherwise identifiable so that the appropriate core can be insert in a valve main body 12, e.g. when a tyre is fitted, suitable to the correct inflation pressure for the respective wheel of the vehicle concerned.

However, it is also contemplated that provision fo adjustment of the spring loading could be ^,: built-in ^' to the core 16, e.g. provision for screw adjustment of the longitudinal positioning of the spring abutment, enabli adjustment to be made to a particular core to suit the desired working pressure. Adjustment and/calibration m also be effected by adding a light return spring 33 acting between headed end 27 and the core body 18 in opposition to spring 32.

Valve assembly 10 further comprises an indicating

cap sub-assembly (hereinafter called ' ^" the cap ^" ) 40 which is screwed onto outer end portion 14 of body 12 instead of a standard cap.

Cap 40 comprises a tubular cap body 42 which, when fully screwed home onto end portion 14 of main body 12 forms a pressure tight seal therewith, the integrity of the joints so formed being further assured by the inclusion of joint sealing rings 44.

Indicating cap 40 incorporates sensing and read-out means in the form of an indicating element, in this example an indicating plunger 45 provided with a brightly coloured, e.g. red, or otherwise readily seen head 48 at its outer end, the plunger being guided coaxially in cap body 42 so that said outer end can be extended from or retracted into a recess 50 at the outer end of body 42.

In Figure 1 plunger 46 is shown at its "ready" position with head 48 flush with the outer end of body 42. A rod portion 52 of said plunger is guided for longitudinal sliding movement within body 42, the innermost end part 54 thereof being spaced just clear of headed end 27 with valve element 24 seated and with plunger 46 at said "ready" position.

An intermediate part of rod portion 52 includes an increased diameter piston formation 56 shown in detail in Figure 3. The periphery of the latter is provided with longitudinal grooves so that air can pass to either side of it.

The inner radial face of formation 56 carries an annular sealing diaphragm 58 formed from thin flexible rubber or like material so that it provides little resistance to axial displacement of the plunger 45 and it acts as a one-way valve, allowing air to pass inwardly past formation 56 but preventing passage of air in the other direction. The outer rim of diaphragm 58 is provided with a small inwardly directed lip or rim 53 (Figure 3) tapering to a fine edge for effective sealing against the inner wall of the cap body 42 when outward

air pressure is applied thereto without causing any substantial frictional resistance to longitudinal displacement of plunger 46.

The interior of the chamber 60 defined within cap body 42 in conjunction with the outer end portion 14 of main boαy 12 has a slight step 52 forming a very small reduction in internal diameter toward the outer end, the rim 59 of diaphragm 58 resting against this step when plunger 45 is at the "ready" position.

An 0-ring 54 is carried as a loose sliding fit on rod portion 52 between the outer radial face of piston formation 56 and the outer end of chamber 50 to serve as a backup seal further assuring that there is no escape of pressurised air from said chamber when the plunger 45 is shifted outwardly so that head 48 projects from recess 50.

This latter condition will occur if the tyre pressure drops below the correct level for which the particular core 16 is calibrated. When this occurs spring 32 unseats valve element 24 and pressurised air from the tyre passes into chamber 60 to act on the indicating plunger 46. The outward force is sufficient to urge the diaphragm 58 beyond the step 62 within the cap body 42 while preventing any substantial leakage of air past piston formation 56. The plunger is displaced to its outer position at which the outer face of formation 56 abuts the 0-ring 64 so that if air does pass piston 56 along its peripheral grooves it will not leak past the outer part of rod portion 52 into recess 50. Thus, even though the main sealing valve (i.e. element 24) of the valve assembly 10 is noω open leakage through the valve assembly as a whole is reliably prevented. For some applications a light return spring 65 acting on plunger 46, eg between head 48 and body 42 within recess 50, may be provided to assist in biasing the plunger outwards towards the "ready" and/or extended positions or holding it at one or other of said positions. In some cases this may be desirable to prevent any leakage past plunger 46 in circumstances where little pressure

differential exists between the interior of chamber 5G and the exterior of the assembly as when a ^" blow out or other major deflation of the tyre has occurred.

The extension of the head 48 of the plunger 45 jives a readily noticed visual indication that the tyre needs attention .

A protective outer cap 55 formed of transparent material such as plastics is removably snap-fitted or screwed onto the outer end of cap body 42 providing sufficient clearance for unobstructeo extension of the plunger head but preventing ingress of grit or dirt.

The external diameter of said part of the cap body 42 which receives the outer cap 65 is substantially equivalent to that of the externally threaded outer end portion 14 of the standard valve main body 12. Thus, with outer cap 66 removed, a standard inflation connector can be coupled to said outer part. Said connectors are normally provided with a central pin which depresses the stem of the valve element of the standard valve core to open the valve to facilitate inflation and monitoring of the tyre pressure.

With the present arrangement said pin will depress indicating plunger 46 inwardly beyond the "ready' position so that it bears on headed end 27 of stem 25 to open the main valve against the internal pressure of the tyre. At the same time the one-way arrangement of the diaphragm 58 allows its rim 59 to flex inwardly away from piston formation 56 so that the pressurised inflation air can flow past the latter formation through chamber 50 and into the tyre.

When inflation has been completed and the inflation connector is removed valve element 24 will snap closed against spring 32 (assuming that the tyre is now at the correct pressure) and at the same time a small reservoir of pressurised air will remain trapped within chamber 60 on the inner side of diaphragm 58 tending to cause the plunger 46 to be urged outwardly, possibly beyond the

''ready ¹ ' position .

In the preferred form the assembly is provided wit means for selectively venting said pressure from chambe 60. In the example shown in Figures 1 to 5 said means comprises a groove or grooves or other passages defined between the mating portions of the outer or distal end portion 14 of body 12 and the cap body 42 whicn may be provided in various ways, said grooves or passages being opened to vent the pressure from chamber 50 by unscrewi the indicating cap 40 by, say, a quarter or half a turn from its fully tightened position which will also unseat the sealing rings 44. Said passages or grooves may be defined wholly in the main body end portion 14, some alternative being indicated on Figure 2. Thus, a longitudinal channel 70a may be provided in and along th full length of the external screwthreads of portions 14 or possibly a pair of channels as indicated in Figure 1.

Alternatively a passage in the form of a slot or aperture as indicated in 70b or 70c in Figure 2 may be provided through the threaded wall of portion 14 to communicate directly with the chamber 60 and being unsealed or uncovered by unscrewing the cap as referred to above.

Providing passages of the latter form involves specially forming the end portion 14 of main body 12. I will usually be desirable to use a standard pattern of main body as already in bulk production without modification both for economy, and to enable core and ca assemblies as described to be used to adapt existing standard valve bodies to incorporate the invention in a speedy and simple way. Thus it may be preferable to provide said passages by forming one or more internal longitudinal channels in the internally threaded walls o the cap body 42 as indicated in Figure 5 at 72.

In an alternative construction the indicating cap i engaged on main body 12 by a bayonet type formation or some other kind of formation permitting angular and/or longitudinal displacement to a limited extent for openin

and closing vent passages or channels.

It is not normally necessary to remove tne cap completely once assembled, however, to avoid possible loss it may be linked to main body 12 by a flexible banc 74 e.g. of plastics as indicated in Figure 3 and the cap may further include a coloured or other mark 75 on its exterior to facilitate a check of its angular position i.e. whether it has been turned to the fully sealed position.

It is to be understood that, in some applications of the invention, said means for venting the chamber could be a selectively operable valve formed and actuated separately from the mounting of a cap as referred to above, e.g. if the chamber was defined in a body consisting of a single component, i.e. in effect having the cap integral with the main body, or if the cap was permanently bonded or sealed onto the main body on initial assembly.

Release of the pressure remaining in chamber 50 as referred to above following inflation allows plunger 46 to be pressed inwards manually to the "ready" position. If the tyre is still under-inflated valve element 24 will not have closed due to spring 32, pressurised air will continue to pass into the chamber and this will force the plunger out again, thus the operative will know that further attention is required.

In a contemplated alternative construction of indicating cap sub-assembly there is no facility for venting chamber 60. Thus again the indicating cap 40 can remain permanently in place in use and its cap body may, therefore, be bonded onto the end portion 14 of the main body 12 e.g. by the use of an adhesive. In this case resetting of the indicating plunger 46 would be effected by the residual pressure in chamber 50 as an inflation connector is removed being sufficient to urge diaphragm 58 closed and shift the plunger outwards until the diaphragm rim 59 abuts step 62, so repositioning it automatically at the "ready" position. If the plunger

should pass this position it can be reset manually.

If the primary valve constituted by valve element 2 is unseated in service plunger 46 will oe extended but the construction of the assembly is such that there will be no leakage and loss of air from the tyre, the cap is sealed onto the main body and the construction of the plunger and its diaphragm 53 coupled with the "back-up of the additional sealing ring 54 provides positive secondary sealing preventing any escape of air via chamber 60. Said extension of the plunger will provide visual signal that something is wrong and a check is needed.

If plunger 46 is extended and returns to the extended position on being pressed inwardly after ventin the user will know that the cause is under-inflation of the tyre.

It will be appreciated that other forms of one-way valve arrangement could be incorporated in an indicating cap as described above to permit inflation without necessitating its removal but to ensure against loss of tyre pressure if the main valve of the core 16 has opened, for example a spring loaded or other flap or bal valve might be employed or some other kind of spool or poppet valve might be incorporated in the indicating cap

In other applications the one-way valve arrangement within the indicating cap could be dispensed with entirely and a simple indicating plunger be employed which is sealed against the passage of air in either direction at all positions, said cap being removable for effecting inflation or pressure checking as with conventional tyre valve caps. In this case the central pin of the standard inflation connector or tyre gauge would cαact directly with headed end 27 of stem 26.

It will further be appreciated that other forms of pressure readout means could be incorporated in the indicating cap 40 either in place of or in addition to the visible indication provided by displacement of the

plunger head 48, for example a rotary disc or cylinder showing a colour change, e.g. from green to red, in a window or aperture of the cap: and/or possibly electronic or other sensing devices for remote read-out.

The outer cap 66 will be a non-airtight fit on body 42 and/or may be provided with a small venting aperture to ensure that there is no vacuum or back pressure therein which might inhibit operation of the plunger 50.

The head 48 is conveniently screwed onto the main part of rod portion 52 to facilitate assembly and to enable interchangeable heads to be provided e.g. of different colours, for example they might be colour coded and/or include figures indicating the appropriate correct inflation pressure for the particular tyre corresponding to the calibration of the associated core 16. Such figures may also or alternatively be marked on the outer cap 65, and/or on the exterior of cap 40 and/or of main body 12.

The interchangeability of the core and cap sub- assemblies with standard valve components enables one or other said sub-assembly to be used independently and it is anticipated that their design is such that, utilising volume mass production techniques, their price could compare favourably with the cost of existing components. Apart from the need to calibrate the springs, the number of parts, materials needed, and complexity of manufacture of a core 16 will be little different from the cost of a standard core and they might be used without the indicating cap.

Similarly while the indicating cap 40 is admittedly more complex and costly than the very cheap plastic caps normally supplied as standard, even if their indicating facility is not made use of, they do provide an effective leak-proof seal forming a second line of defence against accidental deflation if the valve element of the core should fail or leak, coupled with the facility for inflation or pressure checking without having to remove the main cap, thus it is contemplated that they might be

used without the core arrangement of the invention. ^'

The preferred interchangeability also means that valve core and indicating cap sub-assemblies embodying tne invention can readily be fitted to existing standard valve bodies so that any vehicle tyres can be retro¬ fitted with this checking facility readily at minimal cost. It is normal practice to recommend replacement of the entire valve assembly when a new tyre is fitted and a complete valve assembly according to the invention can be use on such replacement very readily and economically .

Another embodiment of the invention is illustrated diagrammatically in Figure 5. Here a valve assembly 310 has a specially shaped main body 312 defining a twin branched duct 313. An inner end part of body 312 is press fitted into the valve aperture of a wheel rim 309 (shown only in part) carrying a tubeless tyre (not shown ) .

A first branch of duct 313 is angled into a laterally extending portion of body 312 and is shaped to receive a core sub-assembly 316 (shown diagrammatically) of the same type core sub-assembly 16 described above, while the outer end of the branch accommodates an indicating cap sub-assembly 340 as described above, again shown only diagrammatically.

In this construction the indicating cap 340 has a read-out function only in that it is not adapted for inward passage of air from an inflation connector or the application of a pressure gauge, indeed the cap assembly may be permanently bonded onto body 312 so that its indicating plunger (not shown) and the core 316 are wholly protected against contamination or tampering.

The other branch of duct 313, which in this example is coaxial with the common opening into the tyre has its outer end formed as a conventional tyre valve main body and accommodates a standard valve core 341 (again shown only diagrammatically) and is provided with a removable

cap 343 of standard type at its outer end.

The latter duct branch is used for inflation and/or application of a pressure gauge in conventional manner.

As no inward air pressure is applied to the indicating cap 340, with this arrangement provision will be made for manual resetting of the indicating plunger t the ready position.

It is also contemplated that where the indicating cap also serves for inflation i.e. inward passage of air instead of providing an automatic one-way valve arrangement as referred to above, e.g. utilising diaphragm 53 (Figs.1 and 3) a manually operable inlet valve might be employed, possibly combined with the indicating plunger. For example such a plunger might be provided with a twist-lock or bayonet arrangement of interengaging formations whereby it can be fully depressed and retained at an innermost position at which the core valve element is held open for inflation. On releasing said engagement to free the plunger it would return automatically or be otherwise re-settable to the "ready" position, possibly with the assistance of a return spring. The plunger might incorporate helical camming formations for displacing it angularly in increments on successive inward movements between locked (valve open) and unlocked (valve closed) conditions. When unlocked the plunger would be free for outward displacement to show under-inflation as described above.