Signal device for pneumatic tire

The invention provides a combined cap and signal device to be attached to a tire after the tire is inflated. The device includes an electric alarming unit mounted in a cap-like casing which incorporates an adaptor to be threadedly connected to an inflating valve of the tire. A resilient disc is disposed in the adaptor to be forced by air so that the disc causes the circuit of the electric alarming unit to be opened when the tire is not deflated.

BACKGROUND OF THE INVENTION 
This invention relates to a signal device for a pneumatic tire and 
particularly to a signalling cap for the inflating valve of a pneumatic 
tire which has an electrical sound producing unit for the purpose of 
alarming when the tire is deflated to a pressure below a predetermined 
proper pressure. 
Signal devices for pneumatic tires are known in the art. Some of them are 
of the type which is used during inflation of the tire for the purpose of 
alarming when the pressure in the tire exceeds a predetermined required 
pressure. Some of them are used as a cap for the inflating valve of a tire 
as well as a signal device to signal when the pressure in the tire is 
seriously deflated. U.S. Pat. No. 2,334,095 discloses a signal device of 
the latter type which includes a cap-like casing in which is mounted a 
valve that permit air to enter the casing from the tire to which the 
casing is connected when the tire is deflated to a predetermined pressure. 
The casing also contains a sound making unit which has an air-tight hood 
member that explodes when air enters the casing. U.S. Pat. No. 1,626,294 
discloses a signal device which is mounted on the inflating valve of a 
tire after the tire is inflated and which includes a spring loaded thimble 
to be used as an indicator to show the deflated pressure in the tire. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide an improved combined cap and 
signal device which includes an electric sound producing unit which will 
alarm when the tire to which the device is attached is seriously deflated. 
Another object of the invention is to provide a combined cap and signal 
device which has a simpler construction for actuating a sound producing 
unit than the other similar conventional signal devices. 
The invention provides a combined cap and signal device which comprises a 
cap-like casing and a hollow adaptor threadedly coupled together. The 
hollow adaptor has a stepped portion defining an annular shoulder and an 
internal thread formation adjacent to the annular shoulder. A transverse 
partition member is formed in the adaptor and having a central finger 
piece axially projecting therefrom to open the inflating valve of the tire 
and air inlet openings. 
A disc member which is made of a resilient material is secured to the 
annular shoulder with its annular flange. The disc member cooperates with 
the partition member to confine an air chamber communicated with the air 
inlet openings of the partition member. The disc member has a projection 
axially extending in a direction opposite to the finger piece. A 
conductive hollow screw member is inserted in the adaptor to clamp the 
peripheral flange of the disc member against the annular shoulder. The 
screw member has an external thread engaged with the internal thread of 
the adaptor. 
An electric alarming unit is mounted in the caplike casing and has a cell 
means which is in contact with a coil spring which in turn is connected to 
a conductive plate to urge the conductive plate to contact said conductive 
hollow screw. The projection of the disc member pushes the conductive 
plate to move away from the hollow screw member when the tire is not 
deflated. The spring urges the conductive plate to be in contact with the 
hollow screw member when the tire is deflated to a predetermined reduced 
pressure. 
The exemplary preferred embodiment will be described in detail with 
reference to the accompanying drawings, in which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings, a signal device according to the present 
invention is shown, having a cap-like casing 1 and a hollow adaptor 7 
which are made of an electric insulating material and which are threadedly 
coupled together. The cap-like casing 1 has a round closed end and an open 
end with an internal thread 11. The hollow adaptor 7 has an open end 71 
which has an internal thread 711 to be connected threadedly to an 
inflating valve of a tire. Another open end of the hollow adaptor 7 has an 
external thread 77 which engages the thread 11 of the cap-like casing 1. 
Adjacent to the open end 71 of the hollow adaptor 7 is a transverse 
partition plate 76 which has a central axially extending finger piece 72 
to push the inflating valve of the tire to an open position when the 
adaptor 7 is mounted on the inflating valve. The partition plate 76 is 
further provided with air inlet openings 74. A gasket 73 is press fitted 
in the adaptor member and abuts with the partition plate 76. The wall of 
the hollow adaptor member 7 is stepped to form an annular shoulder 78 and 
has an internal thread 79. 
In the hollow adaptor 7 is a disc member 6 which is made of a rubber 
material and has a peripheral flange 61 clamped by a hollow screw member 
53 against the annular shoulder 78. The hollow screw member 53 is made of 
a conductive metal and engages with the internal thread 79 of the adaptor 
member 7, thereby firmly holding the disc member 6 in the adaptor 7. The 
disc member 6 further has a projection 62 extending axially therefrom in a 
direction opposite to the finger piece 72 of the partition member 76. The 
disc member 6 and the partition member 78 cooperate to confine an air 
chamber 75 which will be communicated with the interior of the tire 
through the inflating valve of the tire and air inlet openings 74. 
An electric alarming unit is disposed adjacent to the closed end of the 
cap-like casing 1. It includes a buzzer 31 and a substantially circular 
printed circuit board 32 bearing a sound producing integrated circuit 33. 
The buzzer 31 includes a casing which is seated against shoulder 
formations 13 and 14 which are formed at the inner side of the cap-like 
casing 1. The printed circuit board 32 is seated on an annular shoulder 36 
and is clamped thereat by a sleeve 43 which is made of an insulating 
material and which is inserted into the casing 1. The sleeve 43 and the 
board 32 confines a chamber for accommodating batteries 42. The closed end 
of the casing 1 is provided with openings 12 for the outlet of sound. 
Conductors 34 and 35 are provided to electrically interconnect the 
integrated circuit 33 and the buzzer 31. 
The printer circuit board 32 further has a terminal 321 to be in contact 
with a positively charged terminal of the battery. A conductive coil 
spring 51 is provided to be in contact with a negatively charged terminal 
of the battery. The coil spring 51 is connected to a conductive plate 52 
to urge the plate to contact the end of the hollow screw member 53. The 
hollow screw member 53 is in turn connected to another terminal of the 
printed circuit board 32. 
When the signal device of the present invention is attached to the 
inflating valve of an inflated tire, the valve of the tire is opened by 
the finger piece 72 and the disc member 6 is pushed upward as is shown in 
FIG. 2. The projection 62 of the disc member 6 pushes the conductive plate 
52 against the force of the spring 51 and thereby separates the conductive 
plate 52 and the hollow screw member 53, placing the alarming unit in an 
OFF position. When the tire is deflated to a predetermined reduced 
pressure, the conductive plate 52 is pushed by the spring 51 to be in 
contact with the hollow screw member 53. In this situation, the sound 
producing circuit 33 produces an alarming sound. 
With the invention thus explained, it is apparent that numerous 
modifications and variations can be made without departing from the scope 
of the invention. It is therefore intended that the invention be limited 
as indicated in the appended claims.