Spring brake actuator for a vehicle, in particular parking or emergency brake actuator for use in a commercial vehicle

1. A spring brake actuator ( 1 ) for a vehicle, the spring brake actuator ( 1 ) comprising:

a cylinder housing ( 2 ) having a cylinder housing base ( 5 ) and a spring seat ( 7 ) disposed on the base,

a spring brake piston ( 9 ) located in the cylinder housing ( 5 ) for applying a braking force,

a compression spring ( 11 ) arranged between the spring seat ( 7 ) and the spring brake piston ( 9 ), the compression spring providing a spring bias to push the spring brake piston ( 9 ) away from the base ( 5 ) and the spring seat ( 7 ),

wherein the cylinder housing ( 2 ) is divided into a spring chamber ( 12 ) and a pressure chamber ( 14 ), the compression spring ( 11 ) being arranged in the spring chamber ( 12 ) and the pressure chamber ( 14 ) being supplied with pressurized fluid,

wherein the cylinder housing ( 2 ) includes an elastically deformable diaphragm ( 15 ) disposed within the cylinder housing, the diaphragm having an annular flange ( 17 ) which is sealingly mounted to the cylinder housing ( 2 ) and an inner periphery ( 18 ) which is sealingly mounted to the spring brake piston ( 9 ) such that the pressure chamber ( 14 ) is fluid-tightly isolated from the spring chamber ( 12 );

wherein the diaphragm ( 15 ) comprises an inner annular insert ( 19 ) that is sealingly connected to an elastically deformable base body ( 16 ) of the diaphragm ( 15 ) by at least one of:

material joining, adhesive bonding, thermal bonding, or vulcanization, or threaded fastening.

2. The spring brake actuator ( 1 ) of claim 1 , wherein the cylinder housing ( 2 ) comprises a first housing part ( 3 ) and a second housing part ( 13 ) mounted to the first housing part ( 3 ), and the diaphragm ( 15 ) is mechanically fastened between the first and second housing parts ( 3 , 13 ).

3. The spring brake actuator ( 1 ) of claim 1 , wherein the diaphragm ( 15 ) is connected to the spring brake piston ( 9 ) by at least one of:

press fitting,

threaded fastening,

material joining, i adhesive bonding, thermal bonding, or vulcanizing,

shrink fitting,

wobble riveting.

4. The spring brake actuator ( 1 ) of claim 1 , wherein the spring brake piston ( 9 ) comprises a piston tube ( 20 ) that extends through the diaphragm ( 15 ) and is configured to reciprocate between a recessed position and an extended position, wherein in the extended position, the piston tube ( 20 ) extends out from the first housing part ( 3 ) to transmit brake force.

5. The spring brake actuator ( 1 ) of claim 4 , wherein a release bolt ( 23 ) is mounted at least partially inside the cylinder housing ( 2 ), the release bolt ( 23 ) extending at least partially into the piston tube ( 20 ), and

wherein the release bolt ( 23 ) comprises one or more engagement members ( 27 ) arranged inside the piston tube ( 2 ) the engagement members ( 27 ) configured to engage a stop shoulder ( 29 ) provided on the spring brake piston ( 9 ), wherein upon rotation of the release bolt ( 23 ) the piston tube ( 20 ) moves against the force exerted by the compression spring ( 11 ).

6. The spring brake actuator ( 1 ) of claim 5 , wherein the release bolt ( 23 ) is in threaded engagement with a static nut ( 25 ) permanently mounted to the cylinder housing base ( 5 ).

7. The spring brake actuator ( 1 ) of claim 1 ,

wherein the insert ( 19 ) is sealingly connected to the spring brake piston ( 9 ) by at least one of:

press fitting,

threaded fastening,

material joining, adhesive bonding, thermal bonding, or vulcanizing,

shrink fitting, or

wobble riveting.

8. The spring brake actuator ( 1 ) of claim 4 , further comprising an internal breather valve ( 22 ) fitted into the piston tube ( 20 ).

9. The spring brake actuator ( 1 ) of claim 8 , further comprising:

a third housing part ( 31 ) mounted to the second housing part ( 33 ) opposite the first housing part ( 3 ), the third housing part ( 31 ) containing a second diaphragm ( 33 ) which defines a service brake chamber ( 39 ) inside the third housing part ( 31 ), and

a push rod ( 35 ) located in the third housing part ( 31 ),

wherein the spring brake piston ( 9 ), is configured to act upon the second diaphragm ( 33 ) to transmit brake force onto the push rod ( 35 ).

10. The spring brake actuator ( 1 ) of claim 9 , wherein the second diaphragm ( 33 ) defines a working chamber ( 37 ) between the second diaphragm ( 33 ) and the second housing part ( 13 ), wherein the spring brake chamber ( 12 ) and the working chamber ( 37 ) are in fluid communication through the internal breather valve ( 22 ) and the piston tube ( 20 ).

11. The spring brake actuator ( 1 ) of claim 6 , wherein the static nut ( 25 ) closes the cylinder housing along with the release bolt ( 23 ) such that the cylinder housing ( 2 ) is always closed and dust or other dirt cannot enter the cylinder housing ( 2 ).

12. The spring brake actuator ( 1 ) of claim 6 , wherein the release bolt ( 23 ) is axially coupled to the piston tube ( 20 ), wherein rotation of the release bolt ( 23 ) relative to the static nut ( 25 ) causes axial movement of the piston ( 20 ).

13. The spring brake actuator of claim 2 , wherein the diaphragm ( 15 ) defines a fluid-tight seal between the first housing part ( 3 ) and the diaphragm ( 15 ) on one side and the second housing part ( 13 ) and the diaphragm ( 15 ) on the other side.

14. The spring brake actuator of claim 13 , wherein the diaphragm ( 15 ) includes an annular flange ( 17 ) that is deformed between the first housing part ( 3 ) and the second housing part ( 13 ) to define the fluid-tight seal.

15. The spring brake of claim 1 , wherein the diaphragm ( 15 ) includes an elastically deformable cup-shaped base body ( 16 ).

16. A spring brake actuator ( 1 ) for a vehicle, the spring brake actuator ( 1 ) comprising:

a cylinder housing ( 2 ) having a cylinder housing base ( 5 ) and a spring seat ( 7 ) disposed on the base,

a spring brake piston ( 9 ) located in the cylinder housing ( 5 ) for applying a braking force,

a piston tube ( 20 ) mounted to the spring brake piston ( 9 )

a compression spring ( 11 ) arranged between the spring seat ( 7 ) and the spring brake piston ( 9 ), the compression spring providing a spring bias to push the spring brake piston ( 9 ) away from the base ( 5 ) and the spring seat ( 7 ),

wherein the cylinder housing ( 2 ) is divided into a spring chamber ( 12 ) and a pressure chamber ( 14 ), the compression spring ( 11 ) being arranged in the spring chamber ( 12 ) and the pressure chamber ( 14 ) being supplied with pressurized fluid,

wherein the cylinder housing ( 2 ) includes an elastically deformable diaphragm ( 15 ) disposed within the cylinder housing, the diaphragm having an elastically deformable base body ( 16 ) with an annular flange ( 17 ) which is sealingly mounted to the cylinder housing ( 2 ) and an annular insert ( 19 ) separately formed from the base body and sealingly attached to the base body at an inner periphery ( 18 ) of the base body, wherein the annular insert ( 19 ) seals the base body ( 16 ) to the spring brake piston ( 9 ) such that the pressure chamber ( 14 ) is fluid-tightly isolated from the spring chamber ( 12 ).

17. The spring brake actuator of claim 16 , wherein the diaphragm is radially spaced apart from the piston tube ( 20 ), and wherein the annular insert is radially spaced apart from the piston tube ( 20 ).

18. The spring brake actuator of claim 16 , wherein the annular insert ( 19 ) and the spring brake piston ( 9 ) define a piston sealing interface therebetween, wherein the annular insert ( 19 ) and the spring brake piston ( 9 ) are fixed at the piston sealing interface and are free from relative movement at the piston sealing interface.

19. The spring brake actuator of claim 18 , wherein the base body ( 16 ) and the annular insert ( 19 ) define a base body sealing interface therebetween and are fixed at the base body sealing interface and free from relative movement at the base body sealing interface.

20. The spring brake actuator ( 1 ) of claim 1 ,

wherein the spring brake piston ( 9 ) comprises a piston tube ( 20 ) that extends through the diaphragm ( 15 ) and the inner annular insert ( 19 ) and is configured to reciprocate between a recessed position and an extended position,

wherein the inner annular insert ( 19 ) is spaced away from the piston tube ( 20 ) and does not contact the piston tube ( 20 ).