GB2334584A

GB2334584A - Valve cap tyre pressure indicator

Info

Publication number: GB2334584A
Application number: GB9725194A
Authority: GB
Inventors: John Russell Robinson
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-11-29
Filing date: 1997-11-29
Publication date: 1999-08-25
Also published as: GB9725194D0

Abstract

A valve cap tyre pressure indicator for a pneumatic tyre valve, the indicator comprising a pressure chamber 9, a manually operable actuator 7 arranged to permit a momentary opening of the tyre valve effective to cause a pressure increase in the chamber 9, an over pressure release valve 14 connected to the chamber, the valve (14) being normally closed but being arranged to open when a predetermined air pressure value is exceeded, and indication means 19 arranged to emit an audible signal when the release valve opens. This gives an indicator of simple construction that provides an audible signal output rather than requiring a visual inspection. Other embodiments are disclosed.

Description

VALVE CAP TYRE PRESSURE INDICATOR This invention relates to a valve cap tyre pressure indicator. It is particularly suited to being attached to a tyre valve of a motor vehicle where it can replace the tyre valve dust cap which is the normal external seal provided for the valve parts.

The need to maintain the correct air pressure value, as specified by the tyre manufacturer, within a vehicle pneumatic tyre is well-known and it is always recommended that the tyre pressures are checked frequently so any pressure loss can be corrected. However, it can be a somewhat tedious task to have to remove the fitted valve dust cap, check the tyre pressure with a manual gauge and then replace the valve dust cap. There have therefore been proposals to replace the valve dust cap with a fitted miniature pressure gauge which would remain semi permanently on the valve stem while the vehicle was in daily use. The means of indicating the tyre air pressure on such a miniature gauge generally relies on a visual inspection such that the movement of a marker with respect to a scale or the flexing of a bistable diaphragm relative to an observation window can be detected. Since the wheel and its tyre valve are operating in a rather harsh environment, it is likely that the gauge parts and any viewing window will get dirty quickly so that obtaining a clearly correct reading of the pressure gauge indication can cause a difficulty for the user.

I have now discovered a different way of obtaining an air pressure indication from a miniature pressure gauge where the need to make a close visual inspection of a movable part of the gauge is avoided.

According to the invention, there is provided a valve cap tyre pressure indicator for a pneumatic tyre valve, the indicator comprising a pressure chamber, a manually operable actuator arranged to permit a momentary opening of the tyre valve effective to cause a pressure increase in the chamber, an over pressure release valve connected to the chamber, the release valve being normally closed but being arranged to open when a predetermined value for the air pressure in the chamber is exceeded, and indication means arranged to emit an audible signal when the release valve opens.

In one embodiment, the over pressure release valve has a movable member including a ball which is supported by a spring against an aperture in a valve seat member.

In another embodiment, the over pressure release valve has a movable member including a piston which is movable within a cylinder, a spring serving to push the piston against a valve seat member. The piston may act to cover or uncover vent openings in a side wall of the cylinder according to the piston position within the cylinder.

In a further embodiment, the over pressure release valve has a movable member including an audible signal sounder which is movable within a cylinder, a spring serving to locate the movable member within a valve seat member. The position of the movable member may act to open or close vent openings in the sides of the sounder according to the position of the movable member within the cylinder.

The spring serving to retain the release valve movable member may be supported against a stop which is capable of being adjusted to vary the spring pressure on the movable member.

The indication means may be an audible signal sounder such as a whistle, reed, oscillator or other audible means which is powered by the air flow passing through the release valve. The pressure indicator may include two or more whistles which are arranged, when actuated, to produce signals of different pitches.

By way of example, some particular embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a first embodiment of a valve cap tyre pressure indicator in an axial cross-sectional view.

Figure 2 is a similar view of a second embodiment, Figures 3 and 4 are respectively cross-sectional views taken on the lines III-III and IV-IV of Figure 2, Figures 5, 6 and 7 are partial cross-sectional views of a third embodiment, Figures 8 and 9 are partial cross-sectional views of a fourth embodiment, and, Figures 10 and 11 are respectively cross-sectional views taken on the lines X-X and XI-XI of Figure 8.

As depicted in Figure 1, the valve cap tyre pressure indicator 1 is mounted on the stem 2 of a conventional motor vehicle tyre valve. The valve also has a valve pin 3 which is supported in a bridge 4 and the pin 3 is able to be pushed axially a short distance through the bridge when it is required to release air under pressure from the vehicle tyre.

The valve cap tyre pressure indicator 1 comprises a body 6 which has an internal screw thread arranged so that the indicator may be screwed onto the valve stem 2 in place of the dust cap that is normally located on the stem. The indicator 1 also has a pad 7 made of a resilient material which supports an actuator 8 positioned so that it will be able to push down the valve pin 3 relative to the bridge 4 when the pad 7 is depressed by a user's finger. The space below the pad 7 thus constitutes a stem void 9 which is capable of being filled with a pressurised volume of air whenever the user depresses the pad to push the actuator 8 into contact with the valve pin The tyre pressure indicator 1 also includes an over pressure release valve 11 which is connected to the stem void 9 by means of a duct 12. The release valve 11 comprises a valve seating 13 against which a ball 14 is supported by means of a spring 16. A lower end of the spring 16 is in contact with an adjuster 17 which is capable of being moved cn a screw thread to permit adjustment of the effective length of the spring 16.

The ball 14 supported by the spring 16 against the valve seating 13 thus constitutes a normally closed valve arrangement. The presence of an air pressure which exceeded a predetermined value in the space above the seating will tend to push the ball 14 away from the seating and cause a flow of the pressurised air to stream past the ball. Below the ball 14, the valve 11 has an outlet 18 which connects with a whistle 1S. The whistle 19 includes an edge 21 against which the outflowing air stream is directed to produce an audible sound.

In operation of the valve cap tyre pressure indicator, the indicator will be fitted on the valve stem 2 of a vehicle tyre after the valve dust cap which is originally fitted has been removed. The tyre pressure indicator 1 thus serves to eep dirt out of the valve stem 2 and it can be removed just as easily as the conventional dust cap when it is required to put further air into the vehicle tyre. A user of the vehicle intendin to chec the air pressure in the tyre will then depress the pad 7 of the indicator with a finger momentarily and this action will move the actuator t; to push down the pin 3 and permit pressurised air to flow from tile tyre into the stem void 9 so this void attains the same pressure as that of tile tyre. If te stem void 9 has reached a higher pressure than that at which the release valve 11 has been set, the ball 14 will be pushed away fron the seating 1s end air will flow past the ball 14, through the outlet 18 and into the whistle 19 causing an audible signal to be generated.

The particular pressure at which the release valve 11 will open to permit air to escape is adjustable by movement of the adjuster 17 and the setting of this component may either be effected and then fixed in position during the manufc.cture of the tyre pressure indicator, or it may be adjusted by the user.

Usually, the set air pressure will be that specified by the tyre manufecturer so that a failure to obtain any sound from the whistle 19 w1en the pad 7 is depressed will mean that the tyre pressure has fallen toc low. The user of the indicator will thus be made aware that the vehicle tyre needs to be pumped up se the correct pressure will be attained.

Figure 2 shows a different embodiment of tyre pressure indicato; 1 here the over pressure release valve 11 has a movable member in which the ball has been replaced by a piston 22 which is movable within a cylinder 23. In its uppermost position, the piston 22 closes against a seating 13 but when the piston is moved away from the seating, the piston uncovers a first vent opening in the side wall of the cylinder to allow the air flow to pass into an outlet 18 and from there into a whistle 19. In this embodiment, the cylinder side wall also includes a second vent opening 24 which is connected to a second whistle 26. Therefore, if the air pressure in the stem void 9 is so high that the piston will be moved the maximum possible distance away from the seating, both the first and second vent openings in the cylinder will be opened and both whistles 19,26 will sound. This will thus give a clear warning to the user of the indicator that excess air pressure is present in the tyre. The relative air pressures at which the two whistles will sound and the pitches of the audible signals generated will of course be set in manufacture during the construction of the tyre pressure indicator device.

Figure 2 shows the pad 7 of the indicator in the depressed condition as if the pad was being pushed down by a user's finger Thus, the actuator 8 has pushed down the valve pin 3 and an air flow 27 has entered the stem void 9 and passed through the passages leading to the whistles 19,26.

Figure 3 is a cross-sectional view taken on the line III-III of Figure 2 and Figure 4 is a similar view taken on the line IV-IV. In these cross-sectional views, the positions of the whistles 19,26 have been rearranged slightly from what might be expected from Figure 2 in order to show a more practical constructional arrangement.

In use of the embodiment of Figure 2, one of the whistles 19,26 may be set to sound when the target tyre pressure has been reached and the second whistle may be arranged to sound if a tyre over-pressure condition is present. It is not essential, however, that the two whistles whould be capable of sounding together at any time and in yet a further embodiment, the piston may be arranged to open and then close a first cylinder outlet and then open the second outlet.

This modified piston arrangement is depicted in the partial cross-sectional views of Figures 5, 6 and 7. For this embodiment, the piston 22 is provided with an orifice 28 on its upper surface which leads to a port 25 in a side wall of the piston 22. The port can thus be made to pass across the openings in the cylinder wall as the piston is moved down within the cylinder.

Figure 5 depicts the piston 22 with its orifice 28 in the uppermost position of the piston within the cylinder 23. The piston is at rest against its seating 13 and both of the cylinder openings are closed off. In Figure 6, the pad 7 has been depressed and air under pressure has entered the stem void causing the piston 22 to be pushed down within the cylinder 23 and the first cylinder opening to be aligned relative to tiie port 25 in the piston side wall. The pressurised air 27 from the stem void thus passes through the piston and out of the cylinder by way of the whistle 19. An audible warning is therefore produced for the attention of the indicator user.

In Figure 7, the air pressure within t.le stem. void has caused the piston to be pushed down to its full extent within the cylinder and the piston port has becone aligned with the second opening 24 in the cylinder wall. The pressurised air from the stem void therefore passes through this second opening and the second whistle 26 is made to sound. This second whistle 26 is made to produce a different sound output to that of the first whistle and the indicator user is able to easily recognise the difference between these two whistles and to understand the meanings of these sounds as indications of the pressure conditions within the vehicle tyre.

In the embodiment of figures 5, 6 and 7, the cylinder 23 is seen to be provided with a step 29 located at a point about half way along the length of tie cylinder. This step 29 serves a a stop to limit the allowable downward movement of the piston 22 in the cylinder by ensuring alignnent of port 25 with opaniri 24 if an overpressure condition persists.

Figures 8 and 9 show a different embodiment of tyre pressure indicator where the release valve 11 has a cylindrical hollow inner member 31 which is movable within an outer cylinder 32. The inner member 31 has an external upper flange 33, a sounder 34, in the present embodiment this is a reed, which generates an audiole sound when air is blown through it, and a closed lower end with a lateral vent opening 36.

The closed lower end of the inner member has a lower flange 37 which effects z seal with a valve seat 33 at the lower end of thn outer cylinder when no tyre over pressure condition is indicated. The lower face of tie inner member 31 is provided with a slot 39 perMitting it to be turned by use of a screwdriver to adjust the pressure at which the valve opens.

A spring 41 is located concentrically between t;ie outer cylinder 32 and the inner member 31. An upper end of the spring 41 locates against tile upper flange 33. whilst z lower end of the spring locates on a hollow adjuster ring 42 which is supported on screw threads 43 at an internally threaded lower end of t;ie outer cylinder 32. When rotated clockwise, the adjuster ring 42 tends to compress the spring 41, pushing the inner member 31 upwards and pressing the lower flange 37 onto tie valve seat 33, thereby effecting a seal The cross-sections of t;1e internal opening in tlie adjuster ring 42 and the inner member 31 may each be other than circular in shape so that the inner member slides freely through the adjuster ring 42 when the sections are aligned. However, when the inner member 31 is rotated by using a screwdriver to turn the slot 39 in the lower face, the i inner member 31 and adjuster ring 42 interfere, causing the adjuster ring to be rotated ard moved on its thread 43, this movement serves to change the pre-compression state of the spring 41 which alters the pressure at which the over pressure vindication takes place.

In its uppermost position, the lower flange 37 effects a seal with the lower end of the outer cylinder, but when the lower flange is moved away from the valve seet 38 by the pressure exerted on it, the vent opening 36 in the side wall of the inner member is exposed to allow the air flow to pass through the inner member 31 thus causing an audible signal to be generated.

Figure 9 shows the pad 7 of the indicator in the depressed condition as if the pad was being pushed down by a user's finger. Thus, the actuator has pushed down the valve pin and an air flow has passed through the passage leading to the inner member 31. The inner member 31 has been displaced downward by the air pressure, opening the valve, exposing the vent opening 3@, allowing air to be blown through the sounder 34 and the audible signal to be generated.

In use of the valve cap tyre pressure indicator device of the invention, it has been found to be inexpensive to construct and it forms a convenient replacement for the conventional vehicle tyre dust cap. By the user pressing on the ped 7, a rapid indication of the tyre pressure conditions can be given and this can be done easily in most weather conditions and whatever the location of the tyre valve stem might be in relation to the rotational position or stearing alignment of the vehicle wheel. The pressure indication may be obtained in poor light levels since it is so longer necessary to make a visual instection of the procedure indicator. Additionally, the pressure indication may be obtained repeatably, without a need for repair, replacement or frequent adjustment of valve cap components. The device is capable of being constructed in a mechanically robust form and it is resistant to the entry of road dirt and water.

The foregoing description of embodiments of the invention has been given by way of example only and a number of modifications may be made without departing from the scope of the invention as defined in the appended claims. For instance, the lower flange 37 may be provided with a knurled periphery so that it is capable of being easily adjusted by hand.

Claims

CLAIMS 1 A valve cap tyre pressure indicator for a pneumatic tyre valve, the indicator comprising a pressure chamber, a manually operable actuator arranged to permit a momentary opening of the tyre valve effective to cause a pressure increase in the chamber, an over pressure release valve connected to the chamber, the release valve being normally closed but being arranged to open when a predetermined value for the air pressure in the chamber is exceeded, and indication means arranged to emit an audible signal when the release valve is opened.
2 A pressure indicator as claimed in Claim 1, in which the over pressure release valve has a movable member including a ball which is supported by a spring against an aperture in a valve seat member.
3 A pressure indicator as claimed in Claim 1, in which the over pressure release valve has a movable member including a piston which is movable within a cylinder, a spring serving to push the piston against a valve seat member.
4 A pressure indicator as claimed in Claim 3, in which the piston acts to cover a vent opening in the side wall of the cylinder according to the piston position within the cylinder.
5 A pressure indicator as claimed in Claim 1, in which the over pressure release valve includes a sounder supported on a movable member which is movable within a cylinder, a spring serving to push the movable member against a valve seat member.
6 A pressure indicator as claimed in Claim 5, in which the movable member has a side wall including a normally closed vent opening arranged such that when the member is displaced from the valve seat, the vent opening will allow the passage of air therethrough.
7 A pressure indicator as claimed in any one of Claims 2 to 6, in which the spring supporting the release valve movable member is retained against an adjustable stop.
8 A pressure indicator as claimed in any one of Claims 1 to 7, in which the indication means is one or more audible signals.
9 A valve cap tyre pressure indicator, substantially as hereinbefore described with reference to any one of the accompanying drawings.