Normally-closed diaphragm check valve

An air-operated spring brake actuator for actuating and releasing a brake in response to the introduction or exhaustion of pressurized air, comprising:

• a housing having a top wall and a bottom wall, connected by a peripheral side wall to define a spring brake chamber;
• a moveable member provided in the housing and fluidly separating the spring brake chamber into a first spring brake chamber and a second spring brake chamber, which is adapted for the introduction and exhaustion of pressurized air;
• a spring having a first end and a second end and positioned between the housing top wall and the moveable member such that the first end of the spring abuts the housing top wall and the second end of the spring abuts the moveable member;
• an actuator shaft having a proximal end and a distal end, the proximal being connected to the pressure plate, and the distal end passing through an opening in the housing bottom wall;
• and
• a normally closed check valve defining a fluid conduit extending through moveable member to establish and control fluid communication between the first spring brake chamber to the second spring brake chamber, the check valve comprising:
• a moveable valve element having a back side and a front side, the valve element being moveable from a normally closed position where the valve element substantially prohibits fluid flow through the fluid conduit and an open position where the valve element does not block fluid flow through the fluid conduit, and the front side of the valve element being in fluid communication with the second spring brake chamber;
• a fluid reservoir in fluid communication with the moveable valve element back side;
• and
• a flow restrictor fluidly connecting the second spring brake chamber to the fluid reservoir;
• whereby upon the exhaustion of pressurized air from the second spring brake chamber, the spring moves the pressure plate and diaphragm toward the bottom wall to extend the actuator shaft, increase the volume of the first spring brake chamber, and create a pressure differential across the front and rear face of the moveable valve element because of the slower depressurization of the fluid reservoir through the flow restrictor than the depressurization of the second spring brake chamber to thereby move the moveable valve element from the normally closed position to the open position and permit air flow between the first and second spring brake chambers to reduce the likelihood of the creation of a vacuum in the first spring brake chamber.

An air-operated brake actuator for actuating and releasing a brake in response to the introduction or exhaustion of pressurized air, comprising:

• a housing defining an interior chamber adapted to hold pressurized air;
• a movable member mounted within the housing and dividing the interior chamber into a first brake chamber and a second brake chamber, one of which is adapted to normally receive pressurized air to urge the movable member to move in a first direction, the movable member having a fluid conduit therethrough to establish fluid communication between the first brake chamber and the second brake chamber;
• force means to urge the movable member in a second direction opposite the first direction;
• an actuator shaft having a proximal end and a distal end, the proximal end being operatively connected to the moveable member, and the distal end extending through an opening in the housing for connection to a brake;
• and
• a check valve mounted to the movable member at the fluid conduit,
• with a moveable valve element having a back side and a front side, the valve element being moveable from a normally closed position where the valve element substantially prohibits fluid flow through the fluid conduit and an open position where fluid flow through the fluid conduit is enabled, and the front side of the valve element being in fluid communication with the pressurized brake chamber;
• a reservoir in fluid communication with the moveable valve element back side;
• and
• a flow restrictor fluidly connecting the pressurized brake chamber to the reservoir;
• whereby when pressurized air from the pressurized brake chamber begins to be exhausted and the force means urges the movable member in one of the first and second directions, thereby increasing the volume of the non-pressurized brake chamber, a pressure differential across the front and rear sides of the moveable valve element is created because of the slower depressurization of the reservoir through the flow restrictor than the depressurization of the pressurized brake chamber, thereby urging the moveable valve element from the normally closed position to the open position to permit air flow between the first and second brake chambers, reducing vacuum retardation in the non-pressurized chamber.