Master cylinder reservoir diaphragm venting arrangement

摘要

A brake master cylinder reservoir diaphragm has a vent slit therein to operate as a vent valve to equalize air pressure when a pressure differential is impressed across the diaphragm as the brake fluid level in the reservoir changes. The vent slit has an omega or bell curve shape so that the movable valve member is the tongue-like part formed on the inner curvilinear part of the curved vent slit. The tongue valve member acts as a cantilever supported valve which bends at its base to open in either direction under a differential pressure acting on one side or the other of the diaphragm. The opening and closing action of the tongue valve member can be fine tuned by modifying the bending resistance of the base of that member. Such modifications can include a partial base slit extending only part way into the thickness of the base to form a groove in alignment with the straight ends of the omega slit and located between them. Such a groove may be provided on one or both sides of the base, and the depth and length of any such groove can be controlled to fine tune the bending characteristics of the base. The base slit may also be formed entirely through the diaphragm material. The length of the straight ends of the omega slit may also be changed to have a modifying effect on the base bending characteristics.