HYDRAULIC RIM BRAKE

Abstract

The present invention provides a bicycle having front and rear wheels, a frame supported by the wheels, and a brake system. The brake system includes a caliper arm pivotally coupled to the frame at a pivot point, a pad secured to the caliper arm at a location spaced from the pivot point by a first distance, and an actuator (e.g., a hydraulic piston) positioned to apply a force to the caliper arm at a location that is spaced from the pivot point by a second distance less than the first distance. Preferably, the actuating location is positioned between the pivot axis and the pad. In addition, it is preferred to have a ratio of the first distance to the second distance be at least 4.0, preferably at least 6.0, and more preferably about 8.0.

Description

BACKGROUND

The present invention relates generally to the field of bicycles and specifically to brake systems for bicycles.

Bicycles commonly employ braking systems having brake pads that act on the rims of the bicycle wheels, commonly called a rim brake. The pads are typically moved into contact with the rim by a cable-actuated caliper.

Recently, bikes have been equipped with disc brake systems that have a brake disc mounted to the wheel and a caliper mounted to the bicycle frame. The caliper includes brake pads that are squeezed onto the disc to slow the bicycle. Disc brake calipers are typically actuated by a cable or by hydraulics.

SUMMARY

The present invention provides a bicycle having front and rear wheels, a frame supported by the wheels, and a brake system. The brake system includes a caliper arm pivotally coupled to the frame at a pivot point, a pad secured to the caliper arm at a location spaced from the pivot point by a first distance, and an actuator (e.g., a hydraulic piston) positioned to apply a force to the caliper arm at a location that is spaced from the pivot point by a second distance less than the first distance. Preferably, the actuating location is positioned between the pivot axis and the pad. In addition, it is preferred to have a ratio of the first distance to the second distance be at least 4.0, preferably at least 6.0, and more preferably about 8.0.

In one embodiment, the frame includes a front fork, and the caliper arm and pad are mounted on the front fork. In another embodiment, the frame includes a rear stay, and the caliper arm and pad are mounted on the rear stay (e.g., a seatstay). The actuator preferably has an actuating centerline that is positioned rearward of a side centerline of the portion of the frame to which it is mounted. In addition, it is preferred to have the pad positioned rearward of the portion of the frame to which the caliper is mounted.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a bicycle embodying the present invention.

FIG. 2 is perspective view in partial section of a portion of a fork of the bicycle of FIG. 1.

FIG. 3 is an enlarged upper front view of a caliper of the brake system of FIG. 2.

FIG. 4 is an enlarged upper rear perspective view of the caliper of FIG. 3.

FIG. 5 is lower perspective view of the caliper of FIG. 3.

FIG. 6 is a bottom view of the caliper of FIG. 3.

FIG. 7 is a side view of an alternative embodiment of the present invention.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

FIGS. 1-3 illustrates a bicycle 8 including front and rear wheels 9, a frame including a front fork 10, rear stays (including both seat stays 11 and chain stays 13), and a brake system 12 mounted on each of the front fork 10 and the seat stays 11. Instead of the seat stays 11, the brake system 12 could be mounted on the chain stays 13. FIGS. 2-4 illustrate half of the front fork 10 and one half of the brake system 12 embodying the present invention. It should be understood that the other half of the fork 10 and brake system 12 are essentially a mirror image of that shown in FIGS. 2-4. In addition, the brake system 12 illustrated in FIGS. 2-4 is substantially the same as the brake system mounted on the rear stays.

The illustrated fork 10 includes a steerer tube 14, a fork crown 16, and a fork blade 18. The fork 10 would also include a fork tip that would be coupled to a front wheel having a rim 20. A handlebar 22 is coupled to the fork 10 by a stem 24.

The illustrated brake system 12 includes a hydraulic brake lever 26 mounted on the handlebar 22. Upon actuation by a user's hand, the brake lever 26 applies force to a master cylinder (not shown) to provide pressurized brake fluid through a hydraulic line 28 routed through the handlebar 22, stem 24, steerer tube 14, crown 16, and blade 18. The other end of the hydraulic line 28 is connected to a brake caliper 30 mounted on the fork blade 18.

Referring to FIGS. 3-6, the illustrated caliper 30 includes a caliper base 32 secured to the fork blade 18, a caliper arm 34 pivotally coupled to the base 32, and a brake pad 36 secured to the end of the arm 34 and positioned rearward of the fork blade 18. The pad 36 is angled to match the surface of the wheel rim 20. The arm 34 and pad 36 are pivotable at a pivot axis 38 relative to the base 32 between a static position (with the pad 36 not contacting the rim 20) and an actuated position (with the pad 36 contacting the rim 20). In the illustrated embodiment, the distance D1 from the pivot axis 38 to the center of the pad 36 is about 75 mm. The arm 34 is biased toward its static position by a return spring (not shown).

Movement of the arm 34 is accomplished by an actuator in the form of a hydraulic piston 40 mounted for movement in a cylinder defined in the base 32. The piston 40 is coupled to the end of the hydraulic line 28 so that squeezing of the lever 26 causes the piston 40 to move toward the centerline of the bicycle. The piston 40 contacts the arm 34 such that inward movement of the piston 40 causes inward pivoting movement of the arm 34 and pad 36, resulting in the pad 36 contacting the wheel rim 20. The piston 40 is positioned to press on a crossbar 41 at a pressing point 42 that is a distance D2 of about 9.37 mm from the pivot axis 38. In light of this positioning, it can be seen that the caliper 30 achieves a 1:8 multiplier from the piston 40 to the pad 36.

As shown in FIG. 1, the brake caliper 30 is mounted to a mounting portion 43 of the frame (e.g., on either the front fork or the rear stays). When viewed from the side, the mounting portion 43 defines a centerline 45, and it can be seen that the hydraulic piston 40 has a center 47 that is offset rearward from the centerline 45.

A square seal 44 covers the piston in order to protect the piston and also to provide a return force to the face of the piston. Upon release of the lever 26, the square seal 44 will press on the face of the piston 40 and retract the piston about 0.25 mm (away from the centerline of the bicycle). Such retraction of the piston 40 will allow the arm 34 and pad 36 to pivot away from the rim 20 (due to the force provided by the return springs keeping the arm 34 in contact with the piston). In the illustrated design, the retraction of the piston 40 will result in a return of the pad 36 by about 2 mm, due to the 1:8 ratio described above. This return of the pad 36 is desired in order to inhibit the pad from rubbing on the rim 20.

Referring to FIG. 7, in an alternate embodiment, a master cylinder 50 can be positioned inside the steerer tube 52. The master cylinder 50 includes a master piston 54 movable longitudinally inside the steerer tube 52 to provide pressure to a hydraulic line 56 that is coupled to the caliper 58. The caliper 58 of this embodiment is aligned with the centerline 59 of the mounting portion 43 of the frame. Actuation of the master cylinder 50 can be accomplished via a cable 60 that is actuated by the brake lever on the handlebar.

Various features of the invention are set forth in the following claims.

Claims

1. A bicycle comprising: front and rear wheels;a frame supported by the wheels; anda brake system including: a caliper arm pivotally coupled to the frame at a pivot point;a pad secured to the caliper arm at a location spaced from the pivot point by a first distance; andan actuator positioned to apply a force to the caliper arm at a location that is spaced from the pivot point by a second distance less than the first distance.

2. A bicycle as claimed in claim 1, wherein the brake system further comprises a brake lever for actuating the actuator.

3. A bicycle as claimed in claim 1, wherein the frame includes a front fork, and wherein the caliper arm and pad are mounted on the front fork.

4. A bicycle as claimed in claim 1, wherein the frame includes a rear stay, and wherein the caliper arm and pad are mounted on the rear stay.

5. A bicycle as claimed in claim 4, wherein the rear stay is a seatstay.

6. A bicycle as claimed in claim 1, wherein the actuator is mounted to the frame at a mounting portion having a side centerline, and wherein the actuator defines an actuating center offset from the side centerline.

7. A bicycle as claimed in claim 1, wherein the actuator is mounted to the frame at a mounting portion, and wherein the pad is positioned rearward of the mounting portion.

8. A bicycle as claimed in claim 1, wherein a ratio of the first distance to the second distance is at least 4.0.

9. A bicycle as claimed in claim 1, wherein a ratio of the first distance to the second distance is at least 6.0.

10. A bicycle as claimed in claim 1, wherein a ratio of the first distance to the second distance is about 8.0.

11. A bicycle as claimed in claim 1, wherein the actuator comprises a hydraulic piston.

12. A bicycle as claimed in claim 1, wherein the brake system further comprises a hydraulic line and hydraulic fluid for transmitting force to the actuator.