WO2008012521B1

WO2008012521B1 - Bicycle pedal crank drive unit

Info

Publication number: WO2008012521B1
Application number: PCT/GB2007/002810
Authority: WO
Inventors: Andrew James Smith
Original assignee: Andrew James Smith
Priority date: 2006-07-26
Filing date: 2007-07-24
Publication date: 2008-03-13
Also published as: WO2008012521A1

Abstract

An improved bicycle pedal crank assembly that allows a longer lever arm between the foot pedal and the crank assembly bottom bracket centre line during the power stroke; on the return stroke the lever arm distance is shortened. A linear bearing or similar device is mounted onto the end of the bottom bracket assembly, the crank itself reciprocating in and out of said bearing. Cams that optimize the pedal motion are located at both ends of the bottom bracket housing.

Claims

AMENDED CLAIMS received by the International Bureau on 15 January 2008 (15.01.08),+ STATEMENT

1 . A bicycle pedal crank drive unit comprising:

(a) a cam unit whose profile predetermines the pedal motion about the bottom bracket centre line (6); and

(b) a system for varying the length of the crank shaft to enable a longer crank arm on the power stroke; characterized in that said pedal crank drive unit incorporates a 'no chain' drive connectable to the rear wheel of a bicycle, said 'no chain' drive being either shaft- (10) or hydraulically-driven.

2. A bicycle pedal crank drive unit according to claim 1 , which has a cam unit (2) whose profile creates a pedal orbit (14) which is non circular about said bottom bracket centre line (6)

3. A bicycle pedal crank drive unit according to claim 2, wherein said pedal orbit (14) has an effective crank length at the power stroke, comprised between 1 50 and 380 mm, and wherein said effective crank length at the power stroke is defined as the horizontal distance between the pedal centre line (1) and said bottom bracket centre line (6) with the crank shaft (7) fully extended.

4. A bicycle pedal crank drive unit according to claim 2, where the return pedal orbit (14), which is defined as the pedal orbit path opposite the power stroke and which is for the left leg example between the 6 to 12 o'clock positions about said bottom bracket centre line (6) and in an anti-clockwise direction, is comprised between 20 and 190 mm from said bottom bracket centre line (6).

5. A bicycle pedal crank drive unit according to claim 1 , which further comprises cam followers (9), and wherein said cam followers (9) are mounted at the end of said crank shaft (7).

6. A bicycle pedal crank drive unit according to claim 5, which comprises a crank arrangement whereby said cam followers (9) are mounted between the bottom bracket centre line (6) and the pedal centre line (1 ), wherein a sliding sleeve (24), guided by linear guiding means, is mounted over a fixed crank shaft (25); and wherein said sliding sleeve (24) is subsequently connected to said cam followers (9) which follow the cam unit's (23) profile and consequently guide the reciprocating motion of said sliding sleeve (24) and therefore pedal position as said crank shaft (7) rotates.

7. A bicycle pedal crank drive unit according to claim 1 , which comprises a low friction crank shaft reciprocating guide unit (8) to guide the reciprocating crank shaft motion, wherein said crank shaft reciprocating guide unit (8) is mounted directly onto the 11 bottom bracket axle (5) thereby rotating and reciprocating in a fixed orbit path about said bottom bracket centre line (6).

8. A bicycle pedal crank drive unit according to claim 7 wherein said crank shaft reciprocating guide unit (8) comprises a linear bearing and/or is of the bush and shaft type.

9. A bicycle pedal crank drive unit according to claim 5, which on the power stroke has said cam follower's (9) centre line positioned as close as possible to said bottom bracket centre line (6), and in a range comprised between 20 and 100 mm from said bottom bracket centre line (6), wherein said cam follower(s) (9) are secured to said crank shaft (7) and positioned at the opposite end of said crank shaft (7) to the power stroke; consequently the physical centre of said guide unit is offset from that of said bottom bracket centre line (6) and in a direction toward the pedal (1).

10. A bicycle pedal crank drive unit according to claim 1 , which has a plurality of cam units (2) mounted in a given position effectively at either end of the bottom bracket housing (4) and fixed in a manner so as not to rotate.

1 1 . A bicycle pedal crank drive unit according to claim 5, which comprises an inner (2a) and outer (2b) cam profile face with corresponding cam followers (9).

12. A bicycle pedal crank drive unit according to claim 1 1 , which incorporates a removable segment (1 5) either in the inner (2a) or outer (2b) cam unit profiles so as to allow said cam follower (9) to be fitted into said cam profile track.

1 3. A bicycle pedal crank drive unit according to claim 1 , which comprises a male cam (27), wherein said male cam (27) comprises a varying width cross section and a plurality of cam followers (9) mounted at the end of said crank shaft (7) and at the opposite end from said pedal orbit (14).

14. A bicycle pedal crank drive unit according to claim 1 , which comprises a horizontal linear distance between the 3 o'clock and 9 o'clock positions of the pedal orbit that is comprised between 1 70 and 400 mm.

1 5. A bicycle comprising a bicycle pedal crank drive unit according to any of the preceding claims.

16. A bicycle according to claim 1 5, wherein the height to which the leg thigh raises during the cranks rotational movement is lower than that obtained with a normal 165/1 75 mm cranks.

1 7. A bicycle according to claim 1 5, comprising a shaft-driven drive connected to the rear wheel which incorporates an internally geared rear hub.