Patent ID: 7437919

Claim:
A tire valve cap for mounting on a valve stem of a tire for indicating a safe pressure condition or a low pressure warning, comprising: a pressure indicator assembly including: a piston having a safe pressure indicator, and an internal bore; a warning indicator which is seated within said internal bore of said piston; and a biasing spring which is fitted between said warning indicator and said safe pressure indicator, and acts to urge them apart, such that said warning indicator is displayed when low pressure is applied to said piston, and when a safe level of air pressure is applied to said piston, said piston is moved against the force of said biasing spring to surround said warning indicator, and said safe pressure indicator is displayed: a main housing, having a transparent portion through which said warning indicator and said safe pressure indicator are displayed, wherein pressure to be monitored is applied to a bottom plate of said piston, and a safe level of air pressure will move said piston upward into said transparent portion of said main housing against the urging of said biasing spring; and an internal housing having an inner bore into which said piston is seated; wherein said internal housing includes an air nozzle having a contact plate which engages a valve core pin of a tire valve stem to allow flow of pressurized air into and out of the tire and said air nozzle includes an air passage which conveys pressurized air to contact a bottom plate of said piston which is seated in said inner bore of said internal housing, wherein said contact plate includes a slot which forms a horizontal air passage for air to flow between said tire valve stem and said air passage of said air nozzle and wherein said inner bore of said internal housing includes an enlarged diameter inner bore portion wherein said piston fits within said internal housing inner bore, and includes a lipped O-ring which forms an air tight seal with said internal housing inner bore when sufficient pressure has displaced said piston upwards a sufficient amount, but which does not contact said inner bore of said internal housing when insufficient pressure exists to displace said piston upwards, and thus passage of air is allowed.