GB2055204A - A deflation warning device for a pneumatic tyre - Google Patents
A deflation warning device for a pneumatic tyre Download PDFInfo
- Publication number
- GB2055204A GB2055204A GB8025490A GB8025490A GB2055204A GB 2055204 A GB2055204 A GB 2055204A GB 8025490 A GB8025490 A GB 8025490A GB 8025490 A GB8025490 A GB 8025490A GB 2055204 A GB2055204 A GB 2055204A
- Authority
- GB
- United Kingdom
- Prior art keywords
- piston
- housing
- tyre
- seal
- port
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000000007 visual effect Effects 0.000 claims description 13
- 230000006835 compression Effects 0.000 claims description 8
- 238000007906 compression Methods 0.000 claims description 8
- 238000007789 sealing Methods 0.000 claims description 8
- 239000012780 transparent material Substances 0.000 claims 2
- 239000002184 metal Substances 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 239000013536 elastomeric material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
- B60C23/02—Signalling devices actuated by tyre pressure
- B60C23/04—Signalling devices actuated by tyre pressure mounted on the wheel or tyre
- B60C23/0491—Constructional details of means for attaching the control device
- B60C23/0496—Valve stem attachments positioned outside of the tyre chamber
Abstract
A deflation warning device for a pneumatic tyre indicates a predetermined pressure loss by the exposure of a brightly coloured element (29) within a transparent dome (11). An opaque shield (30) is mounted on a piston (26) which is biassed by a spring (27) to unmask element (29) when pressure falls but which is normally displaced by tyre pressure acting on its surface (25) to mask it. Piston (26) may be located between the inner and outer parts (19A and 19B) of a second piston (19) which is in turn responsive to tyre pressure acting on its surface (18). Alternatively the element may be integral with the piston and normally visible, becoming invisible through movement of the piston when tyre pressure falls. <IMAGE>
Description
SPECIFICATION
A deflation warning device for a pneumatic tyre
This invention relates to a deflation warning device for a pneumatic tyre and more particularly to a small and compact device which can be mounted on a wheel and tyre assembly so as to be in communication with the air chamber of the tyre, e.g. by being screwed onto the tyre inflation valve or into a bore in the wheel rim, and when so positioned will give a visual indication of the prevailing pressure condition of the tyre.
More particularly, the device of the invention is intended to give a clear visual indication of a dangerous, low pressure condition. Such a device is of course useful for all pneumatic tyres, but whereas a visual warning of low pressure of a tyre may not be considered essential on a motor vehicle it is highly desirable on an aircraft tyre where partial deflation of one of a large number of tyres may have the most dangerous consequences during take off and landing. Checking each individual tyre with a pressure gauge is a laborious and time consuming operation during which it is easy for one of a number of tyres to be overlooked.
Furthermore the partially deflated condition of a single tyre may not be noticed if it is masked by adjacent tyres on a multi-wheel bogie.
There is presently available a device in the form of an individual pressure gauge which can be mounted onthe inflation valve of a tyre to give a constant reading of tyre pressure, but of necessity the gauge is small and not easily read from a distance. Reading the gauge requires observing the position of a needle on a scale and an untrained or careless operator could easily misread or overlook a dial showing too low a reading.
Various proposals have been made in the past for giving audible, electronic or visual warnings of the low pressure state of a tyre but all have suffered drawbacks which it is the object of the present invention to avoid. Most prior art devices have been costly and cumbersome and those which rely on a simple, mechanical actuation of an indicator have not been adequately protected against deterioration, over a period of use, due to the ingress of dirt or corrosion causing them to be unreliable in operation.
A principal object of the present invention is to provide a cheap, small, compact device which will reliably give a clear visual signal over a prolonged period of use, its moving parts being enclosed within a housing which at all times protects them from dirt and corrosion.
In its simplest form the device of the invention comprises a housing adapted to be placed in communication with the air chamber of a pneumatic tyre, a piston reciprocable in the housing, the piston being biased in one direction and movable against said bias by tyre air pressure and a visual indicator enclosed within the housing which is visible therein through a transparent portion of the housing when the piston is in a first position but is masked from view when the piston is in a second position.
As described in the previous paragraph the visual indicator, fdr example a brightly coloured element, might be masked by an opaque portion of the piston so long as tyre pressure remains at a given value and becomes visible if tyre pressure falls below that value, causing the piston to move under its bias to a position where the element becomes visible through the housing window.
Alternatively the brightly coloured element might be integral and movable with the piston, being visible through a window of the housing so long as tyre pressure remains at a given value and becoming invisible through descent of the piston under its bias if tyre pressure falls below that value.
Such arrangements depending on movement of a single piston, for example biased by a spring, would be useful in giving a coarse measurement of tyre pressure but it is desirable that the device should respond positively to variation of pressure within a narrow range so that a dangerous low pressure condition of a tyre is clearly and accurately indicated, avoiding the danger that operators would come to ignore an indicator known to give an imprecise reading.
An object of a preferred embodiment of the invention is to provide a device which will respond positively to a pressure variation within a narrow range so that operators will be confident that a warning indication by the device accurately reflects a predetermined pressure condition of the tyre.
In accordance with a preferred embodiment of the invention, therefore, communication of the said first-mentioned piston with tyre air pressure to displace the same from its first to its second position is controlled by a second piston reciprocable in the housing, the second piston being biased in one direction and movable against said bias by tyre air pressure, the second piston controlling valve means which alternativley communicates the first piston with tyre air pressure, when the latter has displaced the second piston against its bias, or with atmosphere when the second piston is moved in said one direction by its bias.
The said valve means preferably comprises at least one port in the second piston movable therewith to opposite sides of a seal stationary with respect to the housing, on one side of the seal the port communicating with a passageway in the housing communicable with tyre air pressure and on the other side of the seal the port communicating with an air vent route through the housing.
The port is preferably formed in an annular wall of the second piston which surrounds a tubular portion of the housing defining said passageway and having said seal recessed into its outer periphery, said annular wall having a closed end defining a chamber for pressurised air acting on the second piston, which chamber is communicable via the port with the first piston when the port is on said one side of the seal.
Said annular wall of the second piston
preferably has, at a position spaced from said
closed end thereof, an outwardly extending flange
engaged by one end of a compression spring the
other end of which reacts against a fixed part of
the housing.
Said annular wall of the second piston is
preferably of enlarged internal diameter at a
position spaced from the port and on the side
thereof remote from said closed end, the
arrangement being such that if the second piston
is sufficiently displaced against its bias the
enlarged internal diameter portion of the second
piston will provide a path whereby pressurised air
in the chambers of the first and second pistons
may by-pass said seal on said tubular portion to
escape from the housing via said air vent route.
Sealing means may be arranged to close said
air vent route when the second piston reaches limit position thereof under the influence of its
biasing means, and said sealing means may comprise a second seal recessed into the outer
periphery of said tubular portion at a position
spaced from first-mentioned seal and arranged to
be engaged by the open end of the annular wall
when the second piston reaches a limit position
under the influence of the biasing means.
The first piston preferably has an annular wall
surrounding the second piston and a closed end
which defines a chamber for pressurised air
admitted thereto through the port and sealing
means is preferably provided between the first and
second pistons at a position spaced from said
closed end of the first piston to prevent the escape of pressurised air from said first piston chamber between the pistons.
The first piston is preferably reciprocably
located between inner and outer parts of the
second piston and the first piston is preferably biassed by a compression spring which reacts
between respective shoulders of the first piston and of the outer part of the second piston.
Preferred embodiments of the invention will
now be described with reference to the
accompanying drawings, in which Figures 1 and 2 are sectional elevations of two devices in
accordance with the invention.
The device illustrated in Figure 1 comprises a cylindrical metal housing 10 having at its upper
end a transparent dome 11 e.g. of a transparent
plastics material. The lower end of the housing 10
is plugged by a body 12 which is internally screwthreaded at 13' to receive a ring 12' which in turn has an internal thread 13 to enable the device to be mounted on the external screw threads of the inflation valve (not shown) of a pneumatic tyre.In the stepped, internal bore of the body 12 is a tubular metal insert 14 arranged to contact and depress the pip of the inflation valve, the insert 14 being surrounded by a seal 1 5 of rubber or the like elastomeric material which is engaged between the step 16 of the bore in the body 12 and a frusto-conical surface 17 of the insert 14, the arrangement being such that the metal insert 1 4 will only depress the pip of the tyre inflation valve
if the device has been screwed onto the inflation valve sufficiently to deform the seal 1 5 so that the insert 14 is extruded from the narrower diameter part of the bore of the body 12 toward the pipe of the inflation valve, thereby placing the interior of the device in communication with the air chamber of the tyre.The arrangement of the metal insert 14 and rubber seal 1 5 ensures that the tyre valve will not be opened until it is in sealing engagement with the seal 15.
When the device is fully screwed onto the inflation valve of a pneumatic tyre air pressure within the tyre acts on the under surface 1 8 of a piston 1 9 which is biassed by a compression spring 20 to the position shown. The piston 19 comprises outer and inner parts 1 9A and 1 9B between which an annular space accommodates a piston 26.One or more small bores 23 in the piston 19 are so positioned that they are below a sealing ring 24 recessed into the body 12 when the lower end of the piston assembly 1 9 rests on the top of the body 12 under the influence of the spring 20, but when air pressure from the tyre acting on the surface 1 8 of the piston 1 9 is great enough to raise the piston 1 9 against the action of the spring 20 sufficiently to raise the bore 23 above the seal 24 the air pressure of the tyre is communicated via the bore 23 with the underside 25 of a piston 26, which is guided for movement on the inner portion 1 9B of the piston 1 9 and biassed toward the plug 12 by a second compression spring 27 which reacts between the outer portion 1 9A of the piston and a step 21 of the piston 26.The setting of the second spring 27 is much lighter than that of the first spring 20 and as soon as the piston 26 is communicated with compressed air from the tyre by the bore 23 rising above the seal 24 air pressure in the chamber defined by the underside 25 of the piston 26 and a seal 28 recessed into the piston 26 and rubbing against the inner part 1 9B of the piston 1 9 the piston 26 is caused to rise relative to the piston 19 against the bias of the spring 27.
Located inside the cap or dome 11 is a brightly coloured element 29 which gives a visual indication or warning when it is visible through the transparent dome 11. The element 29 may be of brightly coloured metal or a plastics material.
When the second piston 26 rises from the piston shown it carries with it an annular shield 30 which, when it reaches the top of the dome 11, fully masks the element 29-from view.
The drawing shows the positions of the parts before the device is mounted on an inflation valve or if the tyre pressure is too low to raise the piston 1 9 sufficiently for the bore 23 to be above the seal 24. The tyre pressure at which this will occur is determined with accuracy by the setting of the spring 20.Whenever the bore 23 is above the seal 24 the piston 26 is raised so that the element 29 is fully masked by the shield 30 but as soon as tyre pressure falls below the value predetermined by the setting of the spring 20 so that the bore 23 passes below the seal 24 compressed air is dumped from the chamber defined by the
underside 25 of the piston 26 and seal 28 through
the bore 23 and, by-passing the seal 24 is allowed
to escape to atmosphere e.g. through the screw
threads 22 by which the body 12 is held in the
housing 10, or through a suitable escape hole (not
shown) in the housing 1 0. As the underside 25 of
the piston 26 becomes subject only to
atmospheric pressure the spring 27 rapidly returns
it to the position shown where the element 29 is
unmasked by the shield 30 giving a clear, visual
warning.
The device illustrated in Figure 2 resembles
that of Figure 1, and like parts have like reference
numerals. The device differs, however, in that the
bottom end of the housing 10 is closed by a plug
32 which is externally threaded at 33 to be
screwed into a hole tapped in a wheel rim (not
shown) so that a coaxial passageway 34 in the
plug 32 will communicate the air chamber of a
pneumatic tyre mounted on the rim with the
underside 1 8 of the piston 19.
The device of Figure 2 is further modified in
three other respects;
Air vent apertures 35 are provided for the
exhaust of compressed air from the housing 10
when the chamber defined by the underside 25 of
the piston 26 and the part 1 9B of the piston 19 is
communicated with the interior of the housing by
the bore or bores 23 passing below the seal 24.
Further the device of Figure 2 has means to
prevent over-inflation of an associated tyre and
means to prevent complete deflation of the tyre
via the device if its seal 24 should fail. The means
to prevent over-inflation comprises an annular
recess 36 in the inner periphery of the part 1 9B of
the piston 1 9 so positioned that it will come into
alignment with the seal 24 when the spring 20 is
sufficiently compressed. This sets an upper limit to
the inflation pressure of the tyre because when the
recess is aligned with the seal 24 it provides a path for air in the bore 34 to by-pass the seal 24 and discharge to atmosphere through the openings 35.
On the other handi an additional seal 37 recessed into the plug 32 is so positioned that it will co-operate with the slightly flared bottom end
38 of the part 1 9B of the piston 1 9 when pressure
acting on the surface 1 8 is so low that the spring
20 is able fully to extend within the limits imposed
upon downward displacement of the piston 19.
When the surface 38 is in contact with the seal 37
it cuts off the air escape route between the bore
34 and the openings 35.
Among the advantages of the devices
described and illustrated are that:
a) All moving parts of the device are enclosed
within the housing 10 and dome 11 and thus protected from corrosion and the ingress of dirt.
b) The dual piston arrangement, the piston 26
being subject to its own biassing spring 27,
ensures that the visual indicator 29 is either fully
masked or fully unmasked in response to a
pressure change within a narrow pressure range
so that the indication given by the device is not
progressive over a broad pressure range but gives a clear and positive indication that tyre pressure has fallen below a predetermined, safe value, and
c) The friction ot the seals 24 and 28 is compensated by the spring 27 which need be only a light spring with limited extensibility since it moves with the piston 1 9 and whatever the position of the latter the only work required of the spring 27 is to control the postion of the piston 26 relative to the piston 19. Upward movement of the piston 19, and therefore maximum compression of the spring 20, is limited by abutment of the outer piston part 1 9A with the base of the dome 11, while upward movement of the piston 26 is limited by the shield 30 contacting the top of the dome 11 , where a gasket 31 is provided. It will be appreciated that such upward movement of the piston 26, with consequent compression of spring 27, only occurs after it has already been raised jointly with the piston 19.
Claims (14)
1. A deflation warning device for a pneumatic tyre comprising a housing adapted to be placed in communication with the air chamber of a pnuematic tyre, a piston reciprocable in the housing, the piston being biassed in one direction and movable against said bias by tyre air pressure, and a visual indicator enclosed within the housing which is visible therein through a transparent portion of the housing when the piston is in a first position but is masked from view when the piston is in a second position.
2. A device as claimed in claim 1, wherein the visual indicator is a brightly coloured element fixed within a portion of the housing having a window of transparent material, and wherein an annular, opaque mask is movable with the piston to move into or out of said housing portion to conceal or reveal the coloured element.
3. A device as claimed in claim 1, wherein the visual indicator is a brightly coloured element movable with the piston to move into or out of a portion of the housing having a window of transparent material.
4. A device as claimed in claim 2 or claim 3, wherein the said housing portion is a transparent dome at an end of the housing remote from that adapted for communication with the air chamber of a pneumatic tyre.
5. A device as claimed in any one of the preceding claims, wherein communication of the said first-mentioned piston with tyre air pressure to displace the same from its first to its second position is controlled by a second piston reciprocable in the housing, the second piston being biassed in one direction and movable against said bias by tyre air pressure, the second piston controliing valve means which alternatively communicates the first piston with tyre air pressure, when the latter has displaced the second piston against its bias, or with atmosphere when the second piston is moved in said one direction by its bias.
6. A device as claimed in claim 5, wherein the said valve means comprises at least one port in the second piston movable therewith to opposite sides of a seal stationary with respect to the housing, on one side of the seal the port communicating with a passageway in the housing communicable with tyre air pressure and on the other side of the seal the port communicating with an air vent route through the housing.
7. A device as claimed in claim 6, wherein the port is formed in an annular wall of the second piston which surrounds a tubular portion of the housing defining said passageway and having said seal recessed into its outer periphery, said annular wall having a closed end defining a chamber for pressurised air acting on the second piston, which chamber is communicable via the port with the first piston when the port is on said one side of the seal.
8. A device as claimed in claim 7, wherein said annular wall of the second piston has, at a position spaced from said closed end thereof, an outwardly extending flange engaged by one end of a compression spring the other end of which reacts against a fixed part of the housing
9. A device as claimed in claim 7 or claim 8 wherein said annular wall of the second piston is of enlarged internal diameter at a positon spaced from the port and on the side thereof remote from said closed end, the arrangement being such that if the second piston is sufficiently displaced against its bias the enlarged internal diameter portion of the second piston will provide a path whereby pressurised air in the chambers of the first and second pistons may by-pass said seal on said tubular portion to escape from the housing via said air vent route.
10. A device as claimed in any one of claims 6-9, wherein sealing means is arranged to close said air vent route when the second piston reaches a limit position thereof under the influence of its biassing means.
11. A device as claimed in claim 10 as appendent to claim 7,8 or 9 wherein said sealing means comprises a second seal recessed into the outer periphery of said tubular portion at a position spaced from said first-mentioned seal and arranged to be engaged by the open end of the annular wall when the second piston reaches a limit position under the influence of the biassing means.
12. A device as claimed in any one of claims 5-11 , wherein the first piston has an annular wall surrounding the second piston and a closed end which defines a chamber for pressurised air admitted thereto through the port and wherein sealing means is provided between the first and second pistons'at a position spaced from said closed end of the first piston to prevent the escape of pressurised air from said first piston chamber between the pistons.
13. A device as claimed in any one of claims 5-12 wherein the first piston is reciprocably located between inner and outer parts of the second piston and wherein the first piston is biassed by a compression spring which reacts between respective shoulders of the first piston and of the outer part of the second piston.
14. A deflation warning device substantially as herein described with reference to and as illustrated in Figure 1 or Figure 2 of the accompanying drawings.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8025490A GB2055204A (en) | 1979-08-15 | 1980-08-05 | A deflation warning device for a pneumatic tyre |
IT24181/80A IT1150043B (en) | 1979-08-15 | 1980-08-14 | DEFLATION SIGNALING DEVICE FOR A TIRE |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB7928393 | 1979-08-15 | ||
GB8025490A GB2055204A (en) | 1979-08-15 | 1980-08-05 | A deflation warning device for a pneumatic tyre |
Publications (1)
Publication Number | Publication Date |
---|---|
GB2055204A true GB2055204A (en) | 1981-02-25 |
Family
ID=26272569
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB8025490A Withdrawn GB2055204A (en) | 1979-08-15 | 1980-08-05 | A deflation warning device for a pneumatic tyre |
Country Status (2)
Country | Link |
---|---|
GB (1) | GB2055204A (en) |
IT (1) | IT1150043B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2479465A1 (en) * | 1980-03-29 | 1981-10-02 | Festo Maschf Stoll G | OPTICAL INDICATOR DEVICE, PARTICULARLY FOR PNEUMATIC OPERATION |
EP0444398A2 (en) * | 1990-02-24 | 1991-09-04 | WABCO Vermögensverwaltungs-GmbH | Monitoring device for the pressure of a mesure chamber subjected to the pressure of a vehicle tyre |
-
1980
- 1980-08-05 GB GB8025490A patent/GB2055204A/en not_active Withdrawn
- 1980-08-14 IT IT24181/80A patent/IT1150043B/en active
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2479465A1 (en) * | 1980-03-29 | 1981-10-02 | Festo Maschf Stoll G | OPTICAL INDICATOR DEVICE, PARTICULARLY FOR PNEUMATIC OPERATION |
EP0444398A2 (en) * | 1990-02-24 | 1991-09-04 | WABCO Vermögensverwaltungs-GmbH | Monitoring device for the pressure of a mesure chamber subjected to the pressure of a vehicle tyre |
EP0444398A3 (en) * | 1990-02-24 | 1992-02-12 | Wabco Westinghouse Fahrzeugbremsen Gmbh | Monitoring device for the pressure of a mesure chamber subjected to the pressure of a vehicle tyre |
Also Published As
Publication number | Publication date |
---|---|
IT1150043B (en) | 1986-12-10 |
IT8024181A0 (en) | 1980-08-14 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |