Flexible dust boot for automotive brake cylinder
A dust boot sealing system for automotive brake cylinders, is arranged for dust protection between a linear actuation member and a housing of the brake cylinder. The boot comprises flexible bellows between two concentrical interface portions, and the both interface portions rest radially outwards from their respective counterpart seats in circumferential grooves on housing and actuation member. The boot is provided with pressure relief valve and with integrated pressure relief valve function which automatically and temporarily changes into open status under a pressure gradient decline in direction from interior to exterior, with respect to the boot.
1. A drum brake system comprising:
a housing for the brake cylinder defining a cylinder bore and at least two first interface seats having at least two first grooves thereon;
a first actuation member of a linear actuator disposed in the cylinder bore and moveable relative to the housing, wherein the linear actuator defines a second interface seat having a second groove thereon;
a second actuation member disposed in the cylinder bore and moveable relative to the housing, wherein the linear actuator defines a third interface seat having a third groove thereon wherein the second actuation member acts in an opposing direction from the first actuation member;
a compression spring member interposed axially between the first and second actuation members so that the first and second actuation members are flexibly spread apart from each other thus safeguarding the nominal hydraulic chamber volume when the brake system remains driveless under brake release condition, whereby the ends of the compression spring member are allocated in opposed blind bores of the first and second actuation members;
a first flexible dust boot for the first actuation member;
a second flexible dust boot for the second actuation member;
a first interface on each of the first and the second boots having an annular shape and which is attachable to the housing at a respective one of the at least first interface seats, and wherein the first interface is located radially outward from the at least two first interface seats;
a second interface on each of the first and second boots having an annular shape with a different diameter than the first interface, wherein the second interface is attachable to one of the first and the second actuation members at a respective one of the second and third interface seats, wherein the second interface is located radially outward from the second and the third interface seats respectively; and
flexible bellows of the on each of the first and the second boots connecting the first interface and the second interface, such that an internal chamber is at least partially formed when the first interface is secured to the housing and the second interface is mounted to one the of the first and second linear actuators respectively such that the first and the second boots protect against ingress of foreign substance in to a first and a second interior chamber while allowing for relative movement between the housing and the first and second linear actuators; and
at least one pressure relief valve on each of the first and second boots which is at least one flange proximate to at least one of the first interface and the second interface and facing one of the first interface seat and one of the second and third interface seats, wherein the at least one pressure relief valve is normally closed and automatically actuates to an open position when a pressure of the respective first and second interior chamber increases to a predetermined pressure differential than a pressure of an exterior pressure;
wherein the at least one pressure relief valve integrates relief valve spring elasticity in the respective first and second flexible boot, and wherein the first interface or the second interface of the boot integrates a relief valve body, and a part of the radially grooved counterpart first, second or third seat integrates a relief valve seat of the at least one relief valve and wherein the relief valve seat is the same surface as the radially grooved counterpart first, second or third seat;
wherein the pressure relief valve body integrates a separate recessed portion, and wherein the recessed portion is fluidly connected with the respective first and second interior chamber and separated from the exterior;
wherein the recessed portion is a longitudinal slot which is arranged in one of parallel and antiparallel with respect of the linear displacement direction of the respective first and second actuation member;
wherein the recessed portion is separated from the exterior via an end wall, and wherein the end wall is arranged orthogonally with respect to the linear displacement direction of the respective first and second actuation members.
2. The drum brake as recited in claim 1 , wherein the internal chamber is fluidly sealed and hermetically closed to the exterior.
3. The drum brake as recited in claim 1 , wherein the at least one pressure relief valve is in the normally closed position when pressure in the respective first and second interior chamber is equal to the exterior pressure.
4. The drum brake as recited in claim 1 , wherein the at least one pressure relief valve is automatically self-actuated when the predetermined pressure differential is reached.
5. The drum brake as recited in claim 4 , wherein the at least one relief valve is actuated in currentless manner.
6. The drum brake as recited in claim 1 , wherein the end wall is provided with a predetermined resilience that corresponds with the predetermined pressure differential that actuates the at least one relief valve.
7. The drum brake as recited in claim 1 , wherein the end wall has reduced wall thickness compared to an average wall thickness of the rest of the respective first and second boot.
8. The drum brake as recited in claim 1 , wherein at least one of the first or second interface portion integrates multiple recessed portions.
9. The drum brake as recited in claim 8 , wherein the multiple recessed portions are equidistant from one another and in circumferential direction in equal angle to each other neighboring recessed portion.
10. The drum brake as recited in claim 1 , wherein at least one pressure relief valve is integrated only in the first interface portion, integrated only in the second interface portion, or alternatively integrated in the both interface portions of each boot.
11. The drum brake as recited in claim 1 , wherein the pressure relief valve is integrated at least partly in both interface portions.
12. The drum brake as recited in claim 1 , wherein the first interface portion of the boot is elastically snapped in the grooved counterpart first seat of an outer face of the housing, and the second interface portion of the boot is elastically snapped in grooved counterpart second or third seat that is arranged on an outer face of the actuating member.
13. The drum brake as recited in claim 1 , wherein the pressure relief valve is normally hermetically closed.