Master cylinder lever for a hydraulic disc brake having on the fly dead-band adjustment

• US 20030121262A1
• Filed: 12/10/2002
• Published: 07/03/2003
• Est. Priority Date: 12/28/2001
• Status: Active Grant

• Current Assignee: SRAM LLC (SRAM International Corp.)
• Original Assignee: Avid, Incorporated
• Inventors: Lumpkin, Wayne R.
• Granted Patent: US 6,804,961 B2
• Time in Patent Office: Days
• US Class Current: 60/594
• CPC Class Codes: B60T 11/22 characterised by being integral with reservoir
• CPC Class Codes: B62L 3/023 acting on fluid pressure systems
• CPC Class Codes: Y10T 74/20438 Single rotatable lever [e.g., for bicycle brake or derailleur]
• CPC Class Codes: Y10T 74/20624 Adjustable

Abstract

A master cylinder for a bicycle hydraulic disc brake includes a cylinder having a port in fluid communication with a hydraulic fluid reservoir. The port opens to the cylinder between first and second ends of the cylinder. A piston within the cylinder is movable between a select starting position with the seal between the first end of the cylinder and the port opening with the piston a select distance from the port opening and a pressurized position with the seal between the port opening and the second end of the cylinder. A dead-band adjustment structure is operatively associated with the piston for moving the select starting position to adjust the select distance between the port opening and the seal. A lever is pivotably attached to the housing and is operatively associated with the piston to move the piston between the select starting position and the pressurized position as the lever is pivoted between a rest position and a fully-actuated position. A compensating structure operatively associated with the dead-band adjustment structure and the lever maintains the lever in a select rest position as the dead-band adjustment structure is actuated to move the select starting position.

Claims

1. A master cylinder for a bicycle hydraulic disc brake, the master cylinder comprising:

a housing defining a cylinder, the cylinder having a first and a second end;

a hydraulic fluid reservoir;

a port between the hydraulic fluid reservoir and the cylinder providing fluid communication between the hydraulic fluid reservoir and the cylinder, the port having a port opening located between the first and second ends of the cylinder;

a piston received in the cylinder having a radial seal, the piston being movable between a select starting position with the seal between the first end and the port opening with the seal a select distance from the port opening and a pressurized position with the seal between the port opening and the second end, the radial seal preventing fluid flow between the cylinder and the reservoir when positioned between the port opening and the second end to pressurize the second end;

dead band adjustment means operatively associated with the piston for moving the select starting position to adjust the select distance between the port opening and the seal;

a lever pivotably attached to the housing, the lever being operatively associated with the piston to move the piston between the select starting position and the pressurized position as the lever is pivoted between a rest position and a fully actuated position; and

compensating means operatively associated with the dead band adjustment means and the lever to maintain the lever in a select rest position as the dead band adjustment means is actuated to move the select starting position.

2. The master cylinder of claim 1 further comprising a push rod having a second end operatively associated with the piston and a first end operatively associated with the lever to translate pivotal movement of the lever to axial movement of the piston within the cylinder, the dead band adjustment means comprising a threaded member threadably engaging the housing axially of the first end of the cylinder, the threaded member having an axial bore receiving the push rod, the push rod and threaded member being configured so that axial rotation of the threaded member in a first direction moves the push rod toward the second end of the cylinder and axial rotation of the threaded member in a second direction moves the push rod away from the second end of the cylinder.

3. The master cylinder of claim 1 further comprising reach adjustment means operatively associated with the lever for varying the rest position to adjust the reach of the lever independent of movement of the select starting position of the piston.

4. The master cylinder of claim 3 wherein the reach adjustment means comprises a push rod and a cross dowel, the push rod having a second end operatively associated with the piston and an axially threaded first end, the cross dowel being received in the lever for pivoting about a cross dowel axis transverse the axis of the cylinder, the cross dowel having an internally treaded bore transverse the cross dowel axis, the internally threaded bore threadably receiving the axially threaded first end of the push rod, whereby axial rotation of the push rod moves the cross dowel axially of the push rod to pivot the lever about its pivot to move its rest position to adjust the reach.

5. The master cylinder of claim 4 wherein an axis of internally threaded bore of the cross dowel does not intersect the cross dowel axis.

6. The master cylinder of claim 2 further comprising means for operatively disassociating the second end of the push rod from the piston as the lever is pivoted from the select rest position in a direction away from the fully actuated position.

7. A master cylinder lever for a bicycle hydraulic disc brake, the master cylinder lever comprising:

a housing defining a cylinder, the cylinder having a first end and a second end along a cylinder axis;

a hydraulic fluid reservoir;

a port between the hydraulic fluid reservoir and the cylinder providing fluid flow therebetween, the port having a port opening located between the first and second ends of the cylinder;

a piston received in the cylinder, the piston having a seal and being movable between a select starting position with the seal between the port opening and the first end of the cylinder and a pressurized position with the seal between the port opening and the second end, the seal preventing fluid flow between the reservoir and the second end of the cylinder when positioned between the port opening and the second end to pressurize the second end;

a lever pivotably connected to the housing to pivot about an axis transverse the cylinder axis between a rest position and a fully actuated position;

a push rod having a first end and a second end, the push rod having a threaded portion near the first end with a threaded connection between the threaded portion and the lever and the second end operatively associated with the piston so that as the lever is pivoted between the rest position and the fully actuated position the piston is moved between the starting position and the pressurized position;

an externally threaded insert threadably received in the housing along the cylinder axis, the externally threaded insert being operatively associated with the push rod to move the second end of the push rod along the cylinder axis toward the second end of the cylinder as the externally threaded insert is rotated in a first direction within the housing and to move the second end of the push rod away from the second end of the cylinder as the externally threaded insert is rotated in a second direction within the housing, whereby the select starting position of the piston may be selected by a user; and

the threaded connection between the threaded portion of the push rod and the lever being configured to maintain the lever in a select rest position relative to the housing as the externally threaded insert and thereby the push rod are rotated in either of the first and second directions to vary the select start position of the piston.

8. The master cylinder of claim 7 further comprising a spring axially received in the cylinder between the second end of the cylinder and the piston, the spring biasing the piston toward the first end of the cylinder and into operative association with the second end of the push rod.

9. The master cylinder of claim 8 further comprising first means for maintaining the push rod fixed against rotation relative to the threaded insert as the threaded insert is rotated.

10. The master cylinder of claim 9 wherein the second end of the push rod has an enlarged head with a leading end abutting the piston, the first means comprising the enlarged head having a number of radial ribs extending axially opposite the leading end from the enlarged bead configured to engage with complimentary axially extending teeth in the externally threaded insert, the spring bias on the piston biasing the radially extending ribs into engagement with the axially extending teeth.

11. The master cylinder of claim 10 wherein the push rod is configured to be rotated independent of the threaded insert and the radial ribs and axially extending teeth are configured to disengage against the bias of the spring as the push rod is rotated relative to the threaded insert, whereby the rest position of the lever may be varied by axial rotation of the push rod independent of movement of the start position of the piston.

12. The master cylinder of claim 7 wherein the externally threaded insert includes a first externally threaded axial portion threadably engaged with the housing and a second axial portion having radially extending gear teeth inclined axially and configured to engage with a worm gear, the worm gear having a knob attached thereto and the worm gear being attached to the housing for rotation by the knob about an axis transverse the cylinder axis, whereby as the worm gear is rotated by the knob the externally threaded insert is rotated relative to the housing to thereby move the starting position of the piston.

13. The master cylinder of claim 7 wherein the externally threaded insert has an axial bore receiving the push rod, the axial bore having conical side walls configured to allow pivoting of the push rod relative to the treaded insert as the lever is actuated.

14. The master cylinder of claim 7 wherein the threaded connection between the threaded portion of the push rod and the lever comprises a cross dowel pivotably received by the lever for pivoting about a dowel axis parallel to the lever pivot axis, the cross dowel having an internally threaded bore transverse the dowel axis threadably receiving the treaded portion of the push rod.

15. The master cylinder of claim 14 wherein the internally treaded bore has an axis that does not intersect with the dowel axis.