GB1344002A - Tyre pressure indication system - Google Patents

Abstract

1344002 Tyre pressure indication system U SIGIYAMA 19 April 1971 [3 March 1970 (2) 6 April 1970 4 Nov 1970] 21491/71 Heading B7C A tyre pressure indication system includes a pressure sensitive unit having a diaphragm type pressure switch mounted for rotation and communication with the tyre, a signal transmission unit comprising a magnet, also mounted for rotation with the tyre, and a reed switch arranged adjacent to the rotational path of the magnet, on a non-rotatable part of the vehicle on which the tyre is attached, and an alarm indication unit incorporating an alarm indicating means and an electric circuit having a thyristor, said alarm indication unit being connected to the reed switch so that when the reed switch is closed by the magnet in response to the actuation of the pressure sensitive unit on. fall of tyre pressure below a predetermined value the thyristor is operated to energize the alarm indication means. The diaphragm type pressure switch is contained within the inflatable tyre or to be arranged in gaseous communication with an inflation valve of the tyre. In one embodiment, Fig. 1, an pressure sensitive unit 1 is housed within the tyre and is connected via a contact 16, Fig. 4, operable to close by centrifugal force, to an electromagnet 8 mounted on a wheel hub. When there is a pressure drop contacts 5 of the unit 1 close and the magnet 8 is activated to close a reed switch 9 to trigger a thyristor 25 and thus operate buzzer 24 to cause an alarm signal to be sounded. In a second embodiment, Figs. 6 and 8, a pressure sensitive unit B is mounted on a hub 35 and communicates with the tyre by means of a conduit pipe 36, bleed element 34 and tyre valve 33. A pressure drop in the tyre causes a diaphragm 41 of unit B to move a spring blade 48 carrying a permanent magnet 49 to position the magnet 49 into an operative relationship with a reed switch 50 which is caused to close and the alarm signal sounded as before. In a third embodiment, Fig. 10, a pressure sensitive; unit 59 is mounted within the tyre and is associated with a permanent magnet 70 outside the tyre, the magnet being biased to its operative position by a spring 71 and retained in its inoperative position by a pin 66 attached to a diaphragm 65, which pin engages a groove 69 in the side of the shaft 68 on which the magnet is mounted. A reed switch 55 is mounted adjacent the magnet on a bracket 56, Fig. 9 (not shown), secured to a wheel backplate 58. In all embodiments the pressure sensitive units of all the wheels on each respective side of the vehicle may be connected to a respective common alarm circuit.