Tire air pressure warning apparatus

• US 5,754,101 A
• Filed: 09/08/1995
• Issued: 05/19/1998
• Est. Priority Date: 12/22/1994
• Status: Expired due to Fees

• Current Assignee: Pacific Industrial Company Limited
• Original Assignee: Pacific Industrial Company Limited
• Inventors: Yamada, Hideo, Tsunetomi, Seishi
• Primary Examiner(s): Swarthout, Brent A.
• Assistant Examiner(s): TRIEU, VAN THANH
• Application Number:
  US08/525,824
• Time in Patent Office: 984 Days
• Field of Search: 340/442, 340/445, 340/447, 340/448, 340/539, 340/626, 73/146.3, 73/146.5, 73/146.8, 73/146.4, 116/34 R, 200/61.25
• US Class Current: 340/442
• CPC Class Codes: B60C 23/0496 Valve stem attachments positioned outside of the tyre chamber

Abstract

A signal transmitter mounted on a wheel of a vehicle is disclosed. The transmitter includes a stem member and a cap member being arranged to be detachably mounted on the stem member. The stem member serves as a tire valve when the cap member is detached from the stem member. The stem member detects an tire air pressure smaller than a predetermined level when the cap member is attached to the stem member. The cap member transmits a warning wave signal based on the detection of the stem member. The stem member has an air passage extending in the accommodating member from the open end to the closed end. An electrical conductor is disposed in the air passage to be electrically connected to the cap member when the cap member is mounted on the stem member. A pressure chamber is separated by a partition form the air passage. A tire air introducing passage communicates with the air passage and the tire at a point closer to the open end than the pressure chamber. A bore is formed in the partition to allow a communication of pressure chamber with the introducing passage. A diaphragm expands in the pressure chamber in accordance with pressure lower than a predetermined level flown into the pressure chamber through the introducing passage and the connecting means. An instructing member is secured to the diaphragm for the integral movement and outputs an instruction signal to the cap member through the conductor.

Claims

1. A signal transmitter, mounted on a wheel of a vehicle, including a stem member and a cap member being arranged to be detachably mounted on said stem member, wherein said stem member serves as a tire valve when said cap member is detached from said stem member and said stem member detects a tire air pressure smaller than a predetermined level when said cap member is attached to said stem member, and wherein said cap member transmits a warning wave signal based on the detection by said stem member, said stem member comprising:

a hollow accommodating member having a first closed end and a second open end, said accommodating member having an outer air passage extending from said second end to said first end;

a hollow guide received in said outer air passage of said hollow accommodating member, said hollow guide having an outer wall defining an interior air passage extending between opposite third and fourth ends of said guide, said outer wall closing said first air passage between said first closed end and said second open end, said third end being provided with an axially extending guide surface fabricated from electrically insulating material;

electrical conducting means disposed in said interior air passage, said electrical conducting means being slidably received in said axially extending guide surface and electrically insulated from said hollow accommodating member by said guide surface for electrical connection to said cap member when said cap member is mounted on said stem member;

a pressure chamber next to said outer air passage in the vicinity of said first closed end in said accommodating member;

a tire air introducing passage communicating with said outer air passage and the tire at a point closer to said second open end than said pressure chamber;

connecting means for connecting said pressure chamber to said introducing passage;

deforming means for selectively expanding and shrinking in the pressure chamber in accordance with the pressure of the tire air introduced into the pressure chamber through said introducing passage and said connecting means; and

instructing means for outputting an instruction signal to said cap member through said electrical conducting means, said instructing means being arranged to move together with said deforming means and contact said electrical conducting means when said deforming means is expanded.

2. The transmitter as set forth in claim 1, wherein said cap member includes:

an electric source;

a circuit electrically connected with said electric source;

contacting means for contacting said electrical conducting means when said cap member is mounted on said stem member, said contacting means being permanently connected with said circuit; and

an antenna for outputting a wave signal when said contacting means is brought into contact with said electrical conducting means, said antenna being actuated by said circuit based on the instruction signal.

3. The transmitter as set forth in claim 1 further comprising:

a partition for separating said outer air passage from said pressure chamber; and

said connecting means being defined by a bore formed in said partition.

4. The transmitter as set forth in claim 1, wherein said deforming means includes a diaphragm which is expandable according to the tire air pressure lower than a predetermined value in said pressure chamber.

5. The transmitter as set forth in claim 4, further comprising:

said electrical conducting means supporting a tire valve seal for engagement with said fourth end of said hollow guide to releasably seal said interior passage from said outer air passage;

said instructing means further comprising;

a movable terminal secured to said diaphragm;

a fixed terminal opposed to said movable terminal, said fixed terminal being contacted by said movable terminal shifted based on the expansion of said diaphragm; and

an electrical conducting spring connecting said fixed terminal and said electrical conducting means, said spring biasing said tire valve seal into said engagement with said fourth end of said guide.

6. A signal transmitter, mounted on the wheel of a vehicle, including a stem member having a longitudinal axis and a cap member being arranged to be detachably mounted on said stem member, wherein said stem member serves as a releasable tire valve when said cap member is detached from said stem member, and wherein said stem member serves as a closed tire valve and detects tire air pressure smaller than a predetermined level when said cap member is attached to said stem member, and wherein said cap member transmits a warning wave signal based on the detection by said stem member, said stem member comprising:

a hollow accommodating member having a first closed end and a second open end;

a first air passage extending in said accommodating member from said second end to said first end;

an electrically conductive path comprising an electrical conductor having an outer end electrically connected to said cap member when said cap member is mounted on said stem member, said conductor having an inner end carrying said tire valve;

an electrical insulating guide received in said first air passage and defining a second passage extending from said second open end to a tire valve end of said guide, said guide enclosing said electrical conductor and being provided with a hollow head portion adjacent to said second open end for engaging and guiding said electrical conductor for movement along said longitudinal axis;

a pressure chamber next to said air passage in the vicinity of said first closed end in said accommodating member;

a partition for separating said first air passage and said pressure chamber;

a tire air introducing passage communicating with said first air passage and the tire at a point closer to said second open end than said pressure chamber;

said partition including a bore for connecting said pressure chamber to said introducing passage;

connecting means for connecting said pressure chamber to said introducing passage;

a diaphragm positioned in said pressure chamber in accordance with pressure relative to a predetermined value, said pressure being the pressure of air introduced into said pressure chamber through said introducing passage and said bore;

said electrically conductive path further comprising a fixed terminal and an electrically conductive resilient member mounted between said partition and said tire valve for urging said tire valve against said tire valve end of said guide to close said second passage when said cap member is attached to said stem member; and

instructing means for outputting an instruction signal to said cap member through said electrically conductive path, said instructing means being secured to said diaphragm to contact said terminal.

7. The transmitter as set forth in claim 6, wherein said cap member includes:

an electric source;

a circuit electrically connected with said electric source;

contacting means for contacting said conductor when said cap member is mounted on said stem member, said contacting means being permanently connected with said circuit; and

an antenna for outputting a wave signal when said contacting means is brought into contact with said electrical conductor, said antenna being actuated by said circuit based on the instruction signal.

8. The transmitter as set forth in claim 7, said instructing means further comprising:

a movable terminal secured to said diaphragm;

opposed to said fixed terminal, said fixed terminal being contacted by said movable terminal shifted based on the position of said diaphragm.

9. A signal transmitter, mounted on a wheel of a vehicle, including a stem member having a longitudinal axis and a cap member being arranged to be detachably mounted on said stem member, wherein said stem member serves as a tire valve when said cap member is detached from said stem member, and wherein said stem member serves as a closed tire valve and detects tire air pressure smaller than a predetermined level when said cap member is attached to said stem member, and wherein said cap member transmits a warning wave signal based on the detection by said stem member of the smaller pressure, said stem member comprising:

an electrically conductive accommodating member having a first closed end and a second open end, said accommodating member having a first

air passage extending from said second end to said first end;

an electrically insulating sleeve member fixed within said first air passage and being hollow to define an inner air passage within said first air passage, said sleeve member having a third open end adjacent to said first closed end and a head portion adjacent to said second open end, said head portion having an inlet;

an electrically conductive rod disposed in said sleeve member, said rod having an outer end outside of said sleeve member to be electrically connected to said cap member when said cap member is mounted on said stem member, said electrically conductive rod having an inner end supporting said tire valve, said electrically conductive rod having a slide section received in said inlet for movement along said longitudinal axis to position said tire valve relative to said third open end;

a pressure chamber next to said first air passage in the vicinity of said first closed end in said accommodating member;

a partition for separating said first air passage and said pressure chamber;

a tire air introducing passage communicating with said first air passage and the tire at a point closer to said second open end than said pressure chamber;

said partition including a bore for connecting said pressure chamber to said introducing passage;

connecting means for connecting said pressure chamber to said introducing passage;

a diaphragm capable of expanding in said pressure chamber in accordance with pressure lower than a predetermined value existing in said pressure chamber and said introducing passage and said connecting means;

a movable terminal secured to said diaphragm;

a fixed terminal opposed to said movable terminal, said fixed terminal being contacted by said movable terminal shifted based on the expansion of said diaphragm;

a resilient, electrically conductive member for urging said tire valve against said third open end to close said inner air passage, said resilient member being connected to said fixed terminal; and

instructing means for outputting an instruction signal to said cap member through said fixed terminal, said resilient member, said tire valve and said rod, said instructing means being secured to said diaphragm for movement therewith to move said movable terminal into contact with said fixed terminal.

10. The transmitter as set forth in claim 9, wherein said cap member includes:

an electric source;

a circuit electrically connected with said electric source;

contacting means for contacting said rod when said cap member is mounted on said stem member, said

contacting means being permanently connected with said circuit; and

an antenna for outputting a wave signal when said contacting means is brought into contact with said rod, said antenna being actuated by said circuit based on said instruction signal.