This patent relates to the field of devices for indicating loss of pressure and imminent failure of pneumatic tires in vehicles.
U.S. Pat. No. 2,686,493 shows, mounted to the fixed axle portion of the vehicle, at the axle-leaf spring connection, a sounding wire, consisting of a curved wire extending vertically downward to make a resonant sound through the frame of the vehicle upon contact to the wire with the ground.
This is extended by U.S. Pat. No. 2,794,411, which improves this concept by providing a resonator, a metal cup and an adjustment mechanism for varying and fixing the length of the contact wire.
Another ground contact detector is a sound generating device which is wheel mounted. Reeder U.S. Pat. No. 1,601,604 to Reeder shows an attachment in the hubcap of the vehicle in which a single striker mechanism is depended radially outward along the wheel of the vehicle. Contact with the ground causes it to strike and ring an internal bell mechanism.
U.S. Pat. No. 1,785,614 is typical of the majority of patents for tire pressure loss detectors in that it utilizes a mechanism physically mounted upon the wheel which responds to the outward expansion of a tire carcass during deflation. All such patents, of course, represent mechanisms whose behavior cannot be predicted in the event of a sudden failure, such as a blowout, with the attended collapse of the tire structure. Boyer shows a spring supported mechanism which is triggered from an inner to an outer position, if the tire wall extends to an outward point. The outward motion is not visually detectable but is rather used to trigger a microswitch creating an electrical signal for an electric signaling circuit.
U.S. Pat. No. 902,693 is an earlier mechanism for responding to the outward expansion of the tire. A spring loaded arm swings to an outward position to create a sound signal by striking against a vibrating member located on the frame of the vehicle.
U.S. Pat. No. 1,947,760 is a frame rather than wheel mounted deflection indicator of this basic type; the outward deflection of the tire pulls a cable mechanism which then triggers a mechanical sensor. This device is mounted upon the fixed portion of a brake drum of a car, and it would appear to be subject to high failure rate in the event of a strike by road debris and the like.
U.S. Pat. No. 2,917,020 shows an alternate form: a hubcap mounted sound alarm in which spring wires within a hubcap are set so that they will strike the ground during deflation, creating a ringing effect on the hubcap. An apparently unpatentable version is shown in FIGS. 8 through 9, which appear to be a duplicate of an earlier patent to Neiswanger.
U.S. Pat. No. 3,937,542 shows an electric low pressure sensor with indicator in which an electric pressure sensor is mounted within the valve stem of a tire and coupled to a motor vehicle indicator mounted through an insulated slip spring and brush mechanism on the frame of a car.
Perry U.S. Pat. No. 3,742,896 discloses a pneumatically actuated signal flag mounted upon the axle hub of a vehicle and responsive to the pneumatic pressure to indicate a low pressure condition in a vehicle tire.