GB2501540A - Rising, lowering or variable rate lever or piston - Google Patents

Abstract

A lever or piston which when mounted securely will provide rising, lowering or variable rate output force and distance movement for a given input. The lever is preferably a brake or clutch lever. This may be achieved in different ways, including cam and followers (fig 1), mechanical piston (fig 2), off-set or oval cogs (fig 3), or an hydraulic stepped piston (fig 4). The mechanisms may be built into a brake or clutch lever. The mechanisms may also involve additional springs to aid feel, to return the mechanism to a start position and/or to eliminate cable slack.

Description

Varying rate lever mechanism and piston This relates to risint or lowering variable rate lever and or piston concept.

Background

The problem with bicycle brake levers and many levers and mechanisms in general have the amount of movement at the out point, (the cable nipple on a bike brake lever) is directly fixed in the relation to the amount of movement at the in point, (where your fingers touch a bike brake lever).

This can lead to a smaller than ideal range of movement at the out poInt and rcstrict cable movement in a compromise to achieve enough leverage, especially childrens bikes. On a standard bike brake lever and generic braking steup tht brake pads may drag a little on the braking surface wasting energy as the lever may not allow endugh movement of cable to both lock the wheel and adequately clear the braking surface. This is particularly true with any kind of rim brakes as bicycle wheels rarely stay completely straight and true.

These issues are often true in hydraulic brakes and hydraulics in general.

Statement of invention

To overcome this my inventibn proposes one of many possible mechanisms using cams, pivots, bearings, linkages, springs, sub levers, pistons, sliding bearings, cogs, pulleys, cable, chain, rope (see drawings) incorporated into the lever that would cause the lever's out point to move a lot in relation to the levers in point initially then reduce, adding more power but reducing out point travel as the in point moves through its travel.

The hydraulic version compromises of one piston inside another working inside a suitably stepped chamber. The pistons may be linked by a spring and the fluid or gas from each part of the chamber controlled by reed, shim stack or other types of valve.

Also the two methods may be combined and either of the above may be reversed to suit applications where small initial response that becomes larger is required. The result would be a lever that gives the perfect rate of response in relation to out point movement throughout its travcl. The rate of force increase or decrease may be automatic.

Advantages At least one of these lever designs will be of use in any situation a regular lever does not achieve a satisfactory combination of out point travel and leverage or force on the thing the lever is attatched to in relation to in point movement.

On a bike this could mean the very common problem of energy wasting brake drag is eliminated as the brake pads could initially be spaced further from the braking surface, before the leverage ratio increases as the brake pads touch the braking surface. The mechanism could be tailored to any application.

Detailed description and drawings

I would like to introduce drawings 1, mechanical cam, 2, mechanical piston 3, offset and/or oval cogs, which show some ways of achieving a rising rate lever mechanism. 4, hydraulic stepped piston.

Mechanical cam description, relates to drawing 1.

Using a cam action this could be made using a lever acting on a shaped aim to give a cam effect, the advantage of that design being easy to tune to accurate characteristics by altering the cam size, position and shape. Although not essential, springs at the end of the cam arm could hold the cable outer and compensate for cable stretch and wear and by moving the pivot points and inner and outer cable attatch points in relation to the arms. The arm itself could be flexible to achieve the same effect. The pivot points and lever arm measurements can be altered in any way to give whatever characteristics are desired and the design is limitlessly scaleable.

Drawing 1 guide: Drawing is not to scale 1 bmke lever 2 cam ann 3 main body housing that the brake lever (1) and cam arm (2) mount to 4 cable adjuster and outer cable end stop handlebar A beginning of the cable, known as the cable nipple.

B bearing pivot allowing the brake lever to pivot in relation to the assemblys body and the cam arm.

C bearing to allow easy smooth operation as the bottom left corner of the brake lever (1) slides against the cam arm (2). The mechanism could function without this bearing Mechanical piston description, relates to drawing 2.

Another way of achieving a variable rate could be a sprung piston as part of the actuating arm with a bearing on the end which would act on a cable. This would allow higher cable movement until the higher cable resistance is met, at which point the cable tension would force the piston back into its bore compressing the spring which would reduce the effective length of the actuating arm increasing torque and cable pull. The mechanism is fully automatic and would automatically compensate for cable stretch, pad wear etc. Exact characteristics can be altered by the spring strength and or the springs rising rate or linear characteristics as well as by moving the pivot points and orientation of the moving parts and lever arm measurements can be altered to give whatever characteristics are desired, the design is limitlessly scaleable.

Drawing 2 shows how this design might look.

Drawing 2 guide: Drawing is not to scale A: Handlebar B: Brake lever C: Pivot points D: Piston extension spring E: (Circular in brake lever) Brake cable nipple F: Brake cable outer G: Brake cable outer stop aft actched to pivot to allow for change of brake cable inner angle H: Piston with cable roller on the end The "B" brake lever is fixed to or has the pistons bore as one peice. It pivots "C" on the pivot nearest the handlebar "A". The brake cable is stretched round the pivot on the piston "H" fixed at point "B" and running through "G" the endstop for the outer cable.

Offset or oval cogs description, relates to drawing 3.

This shows how a pair of eccentically mounted cogs, an oval and round pair, or a pair of oval cogs may be used to give a simalar rising or lowering rate effect to the above methods. The cogs either acting on eachother or linked by chain, belt, rope etc would be mounted on a sprung sliding bearing or other suitable platform that would allow for thier mounting points being forced closer or further during use. the sliding bearing or simalar would be sprung in order to keep the cogs under constant mesh or keep a chain or simalar taut during reduction / increase in slack as the cogs move. One cog would be attatched to the input eg: brake lever and the other attatched to the output eg: Brake ilmer cable. This arrangement would give a changing rate of speed and torque output for a given input movement, Drawing 3 guide: Drawing is not to scale.

Sliding bearing platform shown for clarity but any suitable design of cog mount could be used.

Springs "B" can be mounted on one or both ends or in between the axles of the cogs so long as they are pulling or pushing the right way to maintain mesh on the cogs. For brake lever application ideally one cogs axle would be fixed in position.

A: cogs B: springs mounted on sliding bearing to ensure cogs stay in mesh Hydraulic stepped piston description, relates to drawizw 4.

This shows how a hydraulic version or a rising or lowering rate mechanism could consist of a stepped bore with evenly spaced holes feeding reed or other one way valves inside pipes on the back / outside of the larger bore face. One small plain hole or a reed valve allowing a small amount of back flow would also be needed for fluid return to the large donut piston to prevent it hydraulic locking against the end of its bore in use. The pipes from the reed valves would join up with the pipe from the smaller sized piston via unions.

The pistons would consist of conventional piston but have a donut shaped larger piston around it.

The pistons, one inside the other, would have a simple and shallow slot and end stop interface machined into them to eliminate the possibility of them becoming seperated. The pistons would be linked by a spring to keep the pistons in the ideal position when pressure is not being applied.

Drawing 4 is not to scale and shows only the new parts. Piston seals would be conventional and are not shown for clarity Either a conventional lever or any other design above could act on either "B" or "C" piston.

A: Piston stepped bore (female) B: Larger donut piston C: Central piston D: Spring linking pistons together F: Reed valve inside pipe Drawing 4 shown on page