Pressure drop indicating valve cap for pneumatic tires

A pressure drop indicating valve cap for a pneumatic tire equipped with a valve having a valve tube, the valve cap comprising:

• a housing including a wall, threaded means for mounting the housing to the valve tube, a closed end portion having a transparent section, and an open end portion, the housing wall and the closed end portion defining an interior of the housing;
• a sealing element for sealing the valve tube to the open end portion of the housing;
• an actuator for opening the tire valve;
• a deflectable indicator diaphragm which separates the housing interior into a first chamber adjacent to the transparent section of the closed end portion of the housing and a second chamber adjacent to the housing wall, said first chamber being in flow connection with the tire valve via at least one permanently open flow path recessed in the housing and said second chamber being in flow connection with the tire valve via a port in the housing wall;
• and
• sealing means for hermetically sealing said port whereby with the initial tire pressure being permanently maintained in the second chamber, a reduction of the actual tire pressure relative to the initial tire pressure causes the diaphragm to deflect closer to the transparent housing portion and become visible through said transparent section of the closed end portion of the housing.