Air brake relay valve

An air brake relay valve comprising:

• a top housing unit defining an upper accommodating space and a lower accommodating space that are spaced apart along a first axis which extends in an up-down direction;
• a bottom housing unit defining an operating space that opens upward, and an air guiding space that opens toward said lower accommodating space and that fluidly communicates with said operating space, said bottom housing unit being formed with a first valve opening that fluidly communicates with said operating space and that is adapted to be connected to a pressurized air supply, and at least one second valve opening that fluidly communicates with said air guiding space and that is adapted to be connected to at least one brake chamber;
• an air guide unit including
• a base seat that is disposed in said operating space, and that has a base portion and a protruding portion protruding upward from said base portion,
• a ring plate member that is disposed in said operating space above said base seat and that is formed with an extension hole,
• a movable set that is disposed on said base seat, that is movable along the first axis, and that has an extension portion having an outer contour smaller than said extension hole for insertion into said extension hole, and a seal portion connected to a bottom end of said extension portion, sleeved on said protruding portion of said base seat, and having an outer contour larger than said extension hole, and
• a first resilient member that is connected between said base portion of said base seat and said seal portion of said movable set so as to bias said seal portion away from said base portion,
• wherein said movable set is movable between a communicating position, where said movable set is pushed so that said seal portion of said movable set is spaced apart from said ring plate member against a biasing force of said first resilient member, and so that a portion of said operating space which is adjacent to said first valve opening fluidly communicates with another portion of said operating space which is adjacent to said air guiding space through said extension hole to thereby permit fluid communication between said first and second valve openings, and a non-communicating position, where said movable set is biased by said first resilient member so that said seal portion sealingly contacts said ring plate member and cooperates with said extension portion to sealingly cover said extension hole, and so that said portion of said operating space which is adjacent to said first valve opening is isolated from said another portion of said operating space which is adjacent to said air guiding space to thereby prevent fluid communication between said first and second valve openings;
• a drive unit including a worm shaft that extends along a second axis transverse to the up-down direction and that extends into said upper accommodating space, and a motor that is for driving said worm shaft to rotate about the second axis;
• and
• a cam unit including
• a transmission member that has a worm gear portion meshing with said worm shaft and driven by said worm shaft to rotate about a third axis which is transverse to the first and second axes, and a cam portion co-rotatable with said worm gear portion,
• a driven member that is movable along the first axis, that has a cam follower portion disposed under and in contact with said cam portion of said transmission member, and a stem portion extending downward from said cam follower portion toward said extension portion of said movable set for pushing the extension portion downward;
• and
• a second resilient member that is disposed on said driven member to bias said cam follower portion toward said transmission member;
• wherein, during a brake action, said motor rotates by a predetermined angle to rotate said worm shaft to drive rotation of said transmission member, so that said cam portion of said transmission member is rotated to push said driven member downward to thereby push said movable set to move to the communicating position;
• and
• wherein, when the brake action is released, said motor rotates reversely by the predetermined angle to move said cam portion of said transmission member away from said driven member, so that said driven member is moved upward by a biasing force of said second resilient member away from said movable set and that said movable set returns to the non-communicating position without being applied with additional force.