Vehicle tire pressure sensing device

• US 3,938,076 A
• Filed: 03/05/1974
• Issued: 02/10/1976
• Est. Priority Date: 03/06/1973
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Hayashi, Tadashi
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Nowicki, Joseph E.
• Application Number:
  US05/448,519
• Time in Patent Office: 707 Days
• Field of Search: 340/58, 340/60, 340/240, 340/57, 200/61.25, 200/83 A, 200/83 J, 200/83 N, 200/83 Q, 200/83 P, 200/83 S, 73/146.3, 73/146.5, 73/146.8
• US Class Current: 340/448
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver

Abstract

A casing is disposed in an air pressure chamber of a pneumatic tubeless tire and carries therein a switch cooperating with an alarm to produce an alarm signal upon a fall in the air pressure in the tire below a predetermined value. The switch is controlled by a leaf spring which is deformable by the movements, in one direction, of a flexible diaphragm deformable in response to variations in the air pressure in the tire. The leaf spring is returnable by its resilient force upon the movements, in another direction, of the diaphragm. The casing is fixedly mounted on a wheel rim through a projection extending outwardly of the tire from the casing through the rim.

Claims

1. A tire pressure sensing device adapted to sense a fall in the pressure in a tire below a predetermined value, comprising a casing disposed in a pressure chamber of said tire and fixedly mounted on a wheel rim cooperating with said tire, a flexible diaphragm dividing said casing into an atmospheric chamber vented to the atmosphere and a pressure chamber communicating with said pressure chamber of said tire, said diaphragm being deformable in response to the pressures in said pressure chamber of said casing, a stationary contact disposed in said pressure chamber of said casing, a leaf spring disposed in said pressure chamber of said casing and supported by said casing, said leaf spring being deformable in response to movements of said diaphragm, a movable contact fixedly mounted on said leaf spring and engageable with said stationary contact, in which said casing has formed on one end thereof a projection extending outwardly of said pressure chamber of said tire through said rim and is fixedly mounted on said rim through said projection, said projection having a passage for communicating said atmospheric chamber with the atmosphere, in which said leaf spring comprises a flat section rockably supported by said casing and a curved section connected at one end thereof to said flat section and supported at the other end thereof by said casing, said curved section engaging said diaphragm through a bracket, said movable contact being mounted on said flat section, in which said flat section of said leaf spring comprises two members made of materials having different coefficients of thermal expansion.

2. A tire pressure sensing device adapted to sense a fall in the pressure in a tire below a predetermined value, comprising a casing disposed in a pressure chamber of said tire and fixedly mounted on a wheel rim cooperating with said tire, a flexible diaphragm dividing said casing into an atmospheric chamber vented to the atmosphere and a pressure chamber communicating with said pressure chamber of said tire, said diaphragm being deformable in response to the pressures in said pressure chamber of said casing, a stationary contact disposed in said pressure chamber of said casing, a leaf spring disposed in said pressure chamber of said casing and supported by said casing, said leaf spring being deformable in response to movements of said diaphragm, a movable contact fixedly mounted on said leaf spring and engageable with said stationary contact, in which said casing has formed on one end thereof a projection extending outwardly of said pressure chamber of said tire through said rim and is fixedly mounted on said rim through said projection, said projection having a passage for communicating said atmospheric chamber with the atmosphere, in which said leaf spring comprises a flat section rockably supported by said casing and a curved section connected at one end thereof to said flat section and supported at the other end thereof by said casing, said curved section engaging said diaphragm through a bracket, said movable contact being mounted on said flat section, further comprising a cover plate fixedly secured to said casing to close an opening formed at the other end thereof, said cover plate having formed therethrough a hole for communicating said pressure chamber of said casing with said pressure chamber of said tire, and in which said flat and curved sections of said leaf spring are carried by said cover plate through first and second posts, respectively, further comprising an electrically conductive rod extending through said projection and electrically insulated from said casing and said projection, said passage of said projection being formed through said rod, a movable coil disposed exteriorly of said pressure chamber of said tire and fixedly mounted on said rim, said movable coil being electrically connected to said stationary contact through said rim and said casing and to said movable contact through a conducting wire, said rod, said bracket and said leaf spring, a stationary coil fixedly mounted on a stationary part of a vehicle body and opposite to said movable coil, and alarm means connected to said stationary coil, in which said alarm means produces an alarm signal when said movable contact is disengaged from said stationary contact, in which said flat section of said leaf spring has a free end and said movable contact is fixedly carried on said free end of said flat section, said movable contact engaging said stationary contact when the pressure in said tire is higher than a predetermined value, in which said flat section of said leaf spring comprises first and second members overlapping one another, said first member being positioned adjacent to said cover plate, said second member being positioned adjacent to said daiphragm and having a coefficient of thermal expansion lesser than that of said first member.

3. A tire pressure sensing device for sensing a fall in the pressure in a tire below a predetermined value, comprising a casing disposed in an air chamber of the tire and fixedly mounted on a wheel rim on which the tire is mounted, a pressure sensitive member dividing the interior of said casing into a pressure chamber communicating with said air chamber of the tire and an atmospheric chamber vented to the outside atmosphere, said pressure sensitive member being movable in response to variations in the pressure in said pressure chamber, a leaf spring disposed in said pressure chamber, said pressure sensitive member being connected to said leaf spring to cause said leaf spring to move in accordance with movement of said pressure sensitive member, switch means actuated by movement of said leaf spring to produce an electric signal when the pressure in said pressure chamber falls below a predetermined value, said leaf spring having a portion made of two members which overlap one another and which have respectively coefficients of thermal expansion different from each other to deform said leaf spring to cause said leaf spring to actuate said switch means to produce an electric signal when the temperature of the pressure chamber exceeds a predetermined level.

4. A tire pressure sensing device as claimed in claim 3, further comprising a member connecting said pressure sensitive member and said leaf spring to cause said leaf spring to move in accordance with movement of said pressure sensitive member, in which said connecting member having a weight which produces a centrifugal force to move said pressure sensitive member to cause said leaf spring to actuate said switch means to produce an electric signal when the speed of the vehicle exceeds a predetermined level.