Tyre pressure control apparatus

Abstract: Apparatus for use in co-operation with a conventional tyre inflation valve which enables the pressure in the tyre to be reduced to a pre-determined value in a one step process. A movable pressure regulator member, for example pin and slot means, co-operates with a valve regulating spring to close a valve member, once the pressure in the tyre has reached the required value.

Description: This invention relates to pressure control apparatus for use with vehicle tyres and particularly to a pressure regulator which can be set to control the pressure in the vehicle tyre by adjusting the biasing force of a spring which urges a valve member to close an inlet port from a pressure source. It is known to provide a valve mechanism wherein a spring, which normally biases a closure member towards a valve seating, is adjustable to control the pressure passing into the valve through an air inlet port. Such adjustment may be made by means of a screw threaded into part of the valve housing and acting on one end of the spring. Rotation of the screw in one direction or another thus increases or decreases the biasing force of the spring. Such pressure regulators are disclosed in British patent specifications numbers 1567402, 138694, 336624, 384760, 1580240 and US patents 2690757, 2987071, 4869306 and 4883107. It is also known from British patent specification 8172/1910 to provide a spring biased pressure relief valve wherein the spring is located between a bridging member and the valve head, and where the biasing force of the spring is adjustable by moving the bridge member upwardly or downwardly with respect to the spring. The bridging member locates in slots in the valve housing and is secured in its desired position by means of nuts. British patent specification 2215438-A shows a spring biased relief valve wherein a pin extends transversely form a plunger which is in engagement with the spring and the pin is engaged by a rotary camming face formed in part of the valve housing. Rotation of the plunger causes a camming action on the plunger to adjust the biasing force of the spring. In all the above patent specifications the adjustment of the tyre pressure is a slow operation. There is, however, a need particularly in the case of military vehicles, eg. personnel carriers operating in desert conditions or other soft or boggy terrain to be able to adjust the tyre pressure downwardly with a great degree of urgency and accuracy. In some circumstances a vehicle may suddenly arrive at an area of such difficult terrain and it is important to be able to either advance or withdraw without undue delay. Thus, in order to combat the effect of the ground conditions, there is a need to quickly lower the tyre pressure in order to provide a "footprint" of larger area to increase the traction of the vehicle. There is disclosed in French Patent No. 683,406 tyre pressure control apparatus according to the pre-characterising portion of claim 1. An object of the invention is to provide improvements in one or more of these respects, or generally. According to the invention there is provided tyre pressure control apparatus as claimed in the accompanying claims. In an embodiment of the invention there is provided tyre pressure control apparatus for use in co-operation with a vehicle tyre inflation valve wherein a movable pressure regulator member is adapted to cooperate with a valve-regulating spring member to provide at least two spaced positions of said pressure regulator member corresponding to respective differing pressures in the tyre, between which positions said pressure regulator member can be shifted in one step. The pressure regulator member comprises adjustable pin and slot means which enables variation of compression of the valve-regulating spring member. The pin means is located on the pressure regulator member and the slot means is located on hte cooperating sleeve means. The use of pin and slot means enables adjustment of the tyre pressure between two pre-determined values to be effected both quickly and accurately. In an embodiment the pin means are rotatable about an axis parallel to the longitudinal axis of the vehicle tyre inflation valve. In a further embodiment of the invention there is provided tyre pressure control apparatus including a screw plug affixed within a bore at the second end of the inner sleeve member and adapted to be screwed on to a stem of a conventional vehicle tyre valve. A stationary plug having passageways formed thereon or therethrough is affixed within the bore in the second end of the inner member, the stationary plug having a tyre valve stem depressing nipple depending axially therefrom. The above object and features of the invention will become clear from the following description which is given by way of example only with reference to the accompanying drawings in which :- Fig 1 is a side elevation with part shown in section of tyre pressure control apparatus according to an embodiment the invention, Fig 2 is a longitudinal section view through the control apparatus of Fig 1, and Fig 3 is an exploded perspective view of the component parts of the apparatus. Referring to the drawings a control apparatus V comprises a cylindrical housing or outer sleeve 2 having a first portion 4 and a second portion of reduced diameter 6. A knurled head 8 is provided at one end of the housing. The portion 4 is formed with a bore 10 and the portion 6 is formed with a bore 12. An inner sleeve 14, formed with longitudinal slots 16 is freely rotatable within the housing 2. The housing 2 is provided at its periphery with a pair of diametrically opposed helical slots 18, and a number of short recesses 20A, 20B, 20C and 20D extend from the helical slots in the direction parallel to the axis of the housing. Slidably located within a bore 22 formed in the inner sleeve 14 are a first spring seat 24 forming a pressure inlet valve and a second spring seat 26 forming a pressure regulator member, compression spring 28 is fitted between those spring seats around spigots 30, 32. The spring seat 24 is formed at its lower end with a further short spigot 34 which is grooved to retain an O-ring 36, and passageways 37 are provided on its periphery. The spring seat 26 has a cylindrical extension 38 which terminates as a head 40, and a pin 42 extends radially from the spring seat 26 to pass freely through each of the slots 16 and into the helical grooves 18 and/or one of the recesses 20A, 20B, 20C or 20D. A rubber boot 44 envelopes part of the housing 2 in order to preclude ingress of foreign material eg road grime, sand or water. The lower end portion of the inner sleeve 14 is formed with a bore 46 and a valve seat 48 against which the O-ring 36 locates during sealing operation of the valve. A plug 50 having passageways 52 formed therein is shrink fitted into the bore 46 and has an axially projecting nipple 54 which extends into a screw threaded hole 56 in a further plug 58 which is also a tight fit in the lower portion of the bore 46. In use, a vehicle tyre is first inflated to its maximum pressure after which the control apparatus V is secured thereto by screwing the plug 58 on to the valve stem 60 of the road wheels so that the nipple 54 depresses the conventional tyre pressure relief valve rod 62 to allow the air within the tyre to escape through the valve stem 60. The air passes under pressure through the passages 52 in the plug 50 and acts on the lower face of the spring seat 24 to urge that seat against the biasing effect of the spring 28. Clearly, when the biasing force of the spring is equivalent to the pressure within the tyre the spring seat will remain in its operative position with the O-ring firmly compressed against the seat 48. When the pressure in the tyre exceeds the biasing force of the spring then the spring seat and its O-ring is lifted off of the valve seat 48 so that air under pressure escapes through passageways 37 and thence through the bore 22, slots 16 in the inner sleeve and helical slots 18 and recesses 20 to finally pass between the boot 44 and its contact points with the housing body 2 of the control apparatus. In order to maintain the tyre at its normal maximum recommended pressure the spring 28 is selected to provide a biasing force at least equal to the effect of that pressure. Initially the head 40 is manually depressed in order to move the pin 42 out of its engaging recess 20 and into the helical slot 18. The head 40 is then rotated in an anti-clockwise direction to move the pin 42 along the slots 18 until it reaches the limit of the extent of the slot when manual pressure on the head is relaxed to enable the pin to be located in the lowermost recess 20D. The biasing force of the spring is then at its greatest and the vehicle is used in the normal manner whilst it operates under normal road surface conditions. When the surface conditions change such that a rapid increases in the size of the "footprint" of the tyre is needed to allow the vehicle to have sufficient traction and low enough ground pressure to continue proceeding, the vehicle is preferably, but not necessarily stopped and then each of the units V is adjusted rapidly to allow air to escape from the respective tyres. Thus, the head 40 of each unit in turn is depressed to move the ends of the pin 42 from its engaging recess 20D into the helical slot 18 and then the head is rotated anticlockwise until the pin aligns with the recess 20C, 20B, 20A as required to reduce the air pressure in the tyres to the equivalent of the biasing force of the spring, so adjusted. It is found that such adjustment can be rapidly and accurately effected by the use of the valve of the invention. The vehicle may remain stationary to allow the tyre pressure to stabilise, or may be driven whilst the pressure reduces towards the stabilised level selected. In a further embodiment (not shown) the pressure inlet valve means are provided by a ball valve, engagable with a generally cup-shaped valve seat. In order that loss of tyre pressure does not occur due to the effect of an unduly bumpy road surface or terrain, the unit V may be unscrewed and removed from the Schraeder valves on the road wheels. Thus, sudden jolts which would otherwise have temporarily increased the tyre pressures above that preset by the spring are made ineffective. The units would of course be replaced when their use again becomes expedient.

Claims: A tyre pressure control apparatus (V) comprising a housing (2) having a first end portion (4) and a second end portion (6), pressure inlet valve means (24) having passageways (37) capable of connecting a pressure inlet port with atmosphere, a spring member (28) adapted to urge the pressure inlet valve means (24) into sealing relationship with a seating (48) formed on the pressure inlet port, the spring member (28) locating at one end with the pressure valve means (24) and at the other end with a pressure regulator member (26), the housing (2) being formed with regulating helical slots (18) at its periphery and a plurality of recesses (20A,20B,20C,20D) connecting with the helical slots (18), for defining a plurality of discrete fixed positions of adjustment in the regulator member (26) corresponding to respective differing pressures in a tyre, the pressure regulator member (26) having a radially extending pin (42) projecting into the helical slot (18) for co-operating with said recesses (20A,20B,20C,20D) to releasably retain the regulator member (26) in a desired one of the positions of adjustment, whereby the biasing force of the spring (28) may be adjusted by locating the radially extending pin (42) in the pressure regulator member (26) in a desired one of the discrete fixed positions of adjustment, characterized in that an inner sleeve member (14) is located within a pair of axial bores (10,12) formed in the housing (2), the valve means (24), the spring member (28) and the pressure regulator member (26) being axially movable within an axial bore (22) formed in the inner sleeve member (14), the inner sleeve member (14) extending axially between a first end and a second end and having a pressure chamber in communication with the pressure inlet port, the inner sleeve member (14) being further provided with longitudinally extending slots (16), the radially extending pin (42) of the pressure regulator member (26) also passing through the longitudinally extending slots (16) in the inner sleeve member (14), means (58) for releasably securing said pressure control apparatus (V) to an associated valve stem (60) on a tyre with said valve stem in communication with inlet passageway (52) and means for maintaining the pressure relief valve rod in the valve stem (60) depressed to allow air within the tyre to escape through the valve stem (60) and into the inlet passageway (52). Apparatus according to claim 1 wherein said means for securing said pressure control apparatus (V) to said valve stem (60) comprises a screw plug (58) affixed within a bore at the second end of the inner sleeve member (14) and adapted to be screwed on to a stem (60) of a conventional vehicle tyre valve; and there is further provided a stationary plug (50) having passageways (52) formed thereon or therethrough and affixed within the bore in the second end of the inner member (14), the stationary plug (50) having a tyre valve stem depressing nipple (54) depending axially therefrom. Apparatus according to claim 1, characterised in that said pin means is rotatable about an axis parallel to the longitudinal axis of the vehicle tyre inflation valve. Tyre pressure control apparatus according to claim 1, characterised in that said pressure inlet valve means comprises a ball valve. A tyre pressure control apparatus according to claim 1 in combination with a valved tyre. A method of controlling the pressure in a tyre using an apparatus according to claim 1, characterised by the step of moving said pressure regulator member between said spaced positions in one step.

Inventors: SAWYER CHRISTOPHER JOHN, STREET BRIAN ROY, SAWYER, CHRISTOPHER JOHN, STREET, BRIAN ROY
Applicants: SAWYER CHRISTOPHER JOHN, STREET BRIAN ROY, SAWYER, CHRISTOPHER JOHN, STREET, BRIAN ROY
Application year: 1993
Main classification: B60C23
IPC codes: B60C23