DEVICE FOR RETRACTING A PISTON

• US 20140231190A1
• Filed: 09/25/2012
• Published: 08/21/2014
• Est. Priority Date: 09/27/2011
• Status: Active Grant

• Current Assignee: Brembo SPA (Nuova Fourb Srl)
• Original Assignee: Freni Brembo S.P.A.
• Inventors: Cesani, Paolo, Crippa, Cristian
• Granted Patent: US 9,388,870 B2
• Time in Patent Office: Days
• US Class Current: 188/72.3
• CPC Class Codes: F16D 2121/02 Fluid pressure
• CPC Class Codes: F16D 2127/02 Release mechanisms
• CPC Class Codes: F16D 65/16 arranged in or on the brake
• CPC Class Codes: F16D 65/18 adapted for drawing members together , e.g. for disc brakes

Abstract

A device (1) for retracting a piston (2) for a brake caliper, said device comprising an annular seat (26) coaxial with the piston seat, said annular seat having an axial abutment surface (40) perpendicular to said axial direction and arranged in the direction of output of the piston (2), and a radial bottom surface (28) arranged facing said side surface (11) of the piston, at least one elastic element (12) arranged in said annular seat (26), with a first radial surface thereof (13) in contact with force against said side surface of the piston, and with a second radial surface thereof (14) in contact with force against said radial bottom surface (28) of the annular seat (26), at least one elastic ring (21) housed in said annular seat (26) and axially arranged between said at least one elastic element (12) and said axial abutment surface (40), on the opposite side to the brake fluid, said ring (21) having an inner perimeter surface (41) and an outer perimeter surface (42), between said inner perimeter surface (41) and said side surface (11) of the piston forming a first annular chamber (18) open towards the side surface (11) of the piston and towards the elastic element (12), a second chamber (20) facing said outer perimeter surface (42) and arranged between said outer perimeter surface (42) and a portion (30) of said radial bottom surface (28) of the seat (26), said second chamber (20) is suitable for allowing the deformation of the ring (21) up to its dilated configuration, said second chamber (20) is substantially continuous and annular; said ring (21) is radially elastically deformable varying between a rest configuration and a dilated configuration.

Claims

1. device for retracting a piston for a brake caliper, said brake caliper comprising a caliper body arranged astride of a brake disc having friction surfaces perpendicular to a rotation axis defining an axial direction, and opposite pads received in said caliper body so as to be able to slide in the axial direction to the brake disc to act respectively on said opposite friction surfaces, said caliper body also comprising at least one piston seat suitable for receiving the piston equipped with a side surface suitable for sliding in said piston seat so as to be able to be biased by a brake fluid coming out from said seat to influence at least one of said pads against said friction surfaces of the brake disc, wherein said device comprises:

an annular seat coaxial with said piston seat, said annular seat having an axial abutment surface perpendicular to said axial direction and arranged in the direction of output of the piston, and a radial bottom surface arranged facing said side surface of the piston;

at least one elastic element arranged in said annular seat, with a first radial surface thereof in contact with force against said side surface of the piston and with a second radial surface thereof in contact with force against said radial bottom surface of the annular seat;

at least one elastic ring housed in said annular seat and axially arranged between said at least one elastic element and said axial abutment surface, on the opposite side to the brake fluid, said ring having an inner perimeter surface and an outer perimeter surface, between said inner perimeter surface and said side surface of the piston forming a first annular chamber open towards the side surface of the piston and towards the elastic element;

a second chamber facing said outer perimeter surface and arranged between said outer perimeter surface and a portion of said radial bottom surface of the seat, Characterized in that

said ring being radially elastically deformable varying between a rest configuration and a dilated configuration, and wherein

said second chamber is suitable for allowing the deformation of the ring up to its dilated configuration,

said second chamber is substantially continuous and annular,

wherein

Said ring comprises lightening means suitable for facilitating the radial deformation of the ring when biased

And

Said lightening means are alternatively selected from the group consisting of;

said lightening means comprise a plurality of recesses or holes passing through axially, each said through recess or hole being arranged in a respective tooth

Or

said lightening means comprise at least one circumferential channel made along said ring

Or

said lightening means comprise at least one axially open inner radial recess

Or

said ring comprises a plurality of inner recesses and a plurality of outer recesses

Or

said ring has a radial thickness of between 0.6 and 0.8 mm.

2. device for retracting, according to claim 1, wherein said ring is selected so that the deformation index, as a ratio between rigidity of the ring and rigidity of the caliper body with pads, is between 13 and 14.

3. device for retracting, according to claim 1, wherein said lightening means comprise at least one axially open inner radial recess or at least one axially open outer radial recess.

4. device for retracting, according to claim 1, wherein each pair of adjacent inner or outer radial recesses defines an interposed tooth.

5. device for retracting, according to claim 1, wherein said lightening means comprise at least one recess or hole passing axially straight through the elastic ring.

6. device for retracting, according to claim 1, wherein said lightening means comprise a plurality of recesses or holes passing through axially, each said through recess or hole being preferably arranged in a respective tooth.

7. device for retracting, according to claim 1, wherein said lightening means comprise at least one circumferential channel made along said ring.

8. device for retracting, according to claim 3, wherein said ring comprises a plurality of said inner recesses and a plurality of said outer recesses, in particular equally spaced apart.

9. device for retracting, according to claim 8, wherein said inner recesses and said outer recesses are made in equal number or wherein said inner recesses and said outer recesses are arranged alternating with one another, said ring in particular having a coil shape.

10. device for retracting, according to claim 1, wherein said ring comprises thermoplastic resin, or Teflon®

, or a perfluoroalkoxy copolymer PFA.

11. device for retracting, according to claim 1, wherein said ring has a minimum radial thickness of between 0.6 and 0.8 mm.

12. device for retracting, according to claim 1, wherein said ring has a bevel between said inner perimeter surface and a base surface of the ring facing towards said elastic element, said bevel being suitable for facilitating the deformation of the elastic element in the direction of output of the piston.

13. method for retracting a piston for a brake caliper by means of a device for drawing back a piston for a brake caliper according to the characteristics of at least one of the previous claims, comprising the steps of:

influencing a portion of the elastic element on a third axial surface opposite to the direction of output of the piston, through the pressure of the brake fluid;

elastically deforming, in the direction of output of the piston, a portion of the elastic element in contact with side surface of the piston, said portion acting on the ring through a force depending on said deformation of the portion and on the pressure of the fluid and said force being suitable for being decomposed into a radial component and an axial component, said elastic element accumulating a first amount of elastic deformation energy;

elastically dilating the ring in the radial direction towards the outside through said radial component of said force, accumulating a second amount of elastic deformation energy.

14. method for retracting a piston for a brake caliper, according to claim 13, comprising the steps of:

removing the pressure of the brake fluid;

allowing the elastic return of the ring, said ring releasing said second amount of elastic deformation energy acting inwardly in the radial direction on said deformed portion of the elastic element, said elastic element partially drawing back and axially pulling the piston along a first roll-back section;

allowing the elastic return of the deformed portion of the elastic element, said elastic element releasing said first amount of elastic deformation energy pulling the piston axially along a second roll-back section.