Device for indicating abnormal pressure conditions in a tire on a motor vehicle in motion

• US 4,694,273 A
• Filed: 10/24/1985
• Issued: 09/15/1987
• Est. Priority Date: 11/05/1984
• Status: Expired due to Fees

• Current Assignee: GREG Di S Greganti & CSAS
• Original Assignee: Domenico Franchino
• Inventors: Franchino, Domenico
• Primary Examiner(s): Rowland, James L.
• Assistant Examiner(s): Tumm, Brian R.
• Application Number:
  US06/790,827
• Time in Patent Office: 691 Days
• Field of Search: 340/58, 340/626, 200/61.25, 200/83 J, 73/146.3, 73/146.4, 73/146.5, 73/146.8, 73/745
• US Class Current: 340/447
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: B60C 23/0433 Radio signals
• CPC Class Codes: H01H 35/38 actuated by piston and cylinder

Abstract

The device is applied to the wheel of a motor vehicle and includes a component that is sensitive to the pressure inside the tire and has a conductive, sliding element. When this element reaches the extreme limits of its travel it closes an electrical contact and activates a radio transmitter whose signals, picked up by a receiver located in the passenger compartment, activate a visual and/or acoustic alarm.

Claims

1. Device for indicating abnormal pressure conditions in a tire on a motor vehicle in motion, consisting of:

a pressure sensor having a movable element and opposing spring which closes a transmitter circuit when it reaches one of two limit positions correspolnding to an upper and lower limit in a range of normal pressure values, and a receiver that picks up the transmitter signals and activates a visual and/or acoustic alarm, characterized in that the aforesaid sensor is composed of a substantially cylindrical case with its internal cavity divided into two parts, the first of which houses the movable element, in permanent electrical contact with one of the transmitter'"'"'s terminals, and is closed by a first adjustable ring nut that determines one of the limit positions, while the other part is divided into two chambers, that communicate with the first part and the inside of the tire respectively, by means of a flexible membrane whose edges are held with a seal ring between a bush made of conductive material, that determines the second limit position, and a second ring nut screwed into a fixed position in the cavity in the case;

in that both the bush and the second ring nut have axial cavities that house a first and a second piston, of which the first piston is held between the membrane and the movable element, and the second piston rests one end against the membrane and has the other end free and exposed to the tire pressure, these pistons keeping the movable element half way between the two limit positions as long as the pressure remains within a range of values that has been defined normal; and

in that the aforesaid receiver has logic outputs for connection with a tachograph and/or on-board computer.

2. Device according to claim 1, characterized in that the aforesaid bush is permanently connected electrically to a conductor for connection to the transmitter for closing the transmitter circuit in the second of the aforesaid limit positions.

3. Device according to claim 1, characterized in that the aforesaid first ring nut has a circular groove in its inner surface which houses the end of a conductor for connection to the transmitter, and one end of the opposing spring that establishes the permanent electrical contact between the conductor and the movable element.

4. Device according to claim 3, characterized in that the aforesaid ring nut has a plug protruding into the sensor case cavity, connected to a second conductor for connection to the transmitter and intended to come into contact with a protruding part of the movable element so as to close the transmitter circuit in the first limit position.

5. Device according to claim 1, characterized in that the transmitter and the sensor are placed in a common container fixed to the wheel, and the sensor'"'"'s internal cavity communicates with the inside of the tire by means of a flexible tube fixed on one side to the aforesaid second ring nut and on the other side to the tire'"'"'s inflation valve.

6. Device according to claim 2, characterized in that the transmitter has an antenna consisting of a wire placed inside the aforesaid tube and connected, via the second ring nut, to a transmitter antenna wire.

7. Device according to claim 1, characterized in that the transmitter and the receiver operate in frequency modulation, and in that the receiver includes equipment that is capable of recognizing whether the modulation frequency of a received signal is the modulation frequency used in the transmitter, and that if so, generates logic signals which activate the alarm devices and which cause the alarm to be recorded by at tachograph and/or stored by an on-board computer.

8. Device according to claim 7, characterized in that the recognizing equipment is connected to a memory device that maintains the logic signals until a manual reset device is operated to reset the receiver.

9. A device for indicating a pressure condition in a tire of a motor vehicle in motion, which pressure condition is outside of a normal range between an upper and a lower limit, comprising a transmitter having first, second and third conductors connected thereto, said transmitter being activatable to transmit a signal when said first conductor is electrically connected to one of said second and third conductors, a receiver for receiving the signal from said transmitter, alarm means connected to said receiver for producing an alarm when said receiver receives the signal from said transmitter, and a pressure sensor connected to said first, second and third conductors and operatively connected to receive pressure from the tire, said pressure sensor operating to electrically connect said first conductor with said second conductor when the tire pressure rises above the upper limit, and to electrically connect the first conductor to the third conductor when the pressure falls below the lower limit, said pressure sensor comprising a hollow body having an internal cavity and including opposite open ends, a first ring nut adjustable connected into one of said opposite open ends and carrying said first conductor, an electrically conductive hollow bush fixed to said hollow body and disposed in said internal cavity, said second conductor being electrically connected to said bush, said bush being spaced away from said first ring nut and defining a first cavity portion of said internal cavity, an electrically conductive movable element movably mounted in said first cavity portion between said bush and said first ring nut, said movable element being engageable against said bush for establishing electrical connection with said second conductor and being engageable against said first conductor for establishing electrical connection therewith when said movable element is in a position adjacent said first ring nut, a spring engaged against said movable element for biasing said movable element against said bush, said third conductor being electrically connected to said spring for establishing electrical connection wth said movable element, a first piston movable mounted in said bush for movement against said movable element to move said movable element away from said bush, a second ring nut connected in said opposite open end of said hollow body, said second ring nut having an axial cavity therein for communicating with the tire pressure, a second piston movably mounted in said axial cavity, said second piston having a first side for communication with the tire pressure and an opposite side, a flexible membrane fixed in said hollow body for separating said axial cavity from an interior space of said bush and from said first cavity portion, a gasket engaged between said second ring nut and said flexible membrane for sealing said flexible membrane to said hollow body, said opposite end of said second piston being engaged against said flexible membrane and said first piston being engaged against said flexible membrane whereby the tire pressure acting upon said second piston is capable of moving said second piston to move said first piston through said flexible membrane to move said movable element, said first ring nut being adjusted to a location with respect to said hollow body whereby the tire pressure between the upper and lower limits moves said second piston into a position to hold said second movable element in an intermediate location between said bush and said first ring nut, whereby a change of the tire pressure above said upper limit causes said movable element to be moved into electrical contact with said first conductor, and a change of the tire pressure below said lower limit causes said movable element to be engaged with said bush.