Brakes – Operators – Fluid pressure
Patent
1994-08-24
1996-07-09
Butler, Douglas C.
Brakes
Operators
Fluid pressure
188 2422, 188 26, 188 2412, B60T 1100
Patent
active
055335993
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a bicycle brake with at least one master cylinder connected with a hand lever and at least one wheel cylinder or brake cylinder and, connecting the cylinders, a hydraulic fluid brake line opening at both ends into a hollow body of variable volume whereas it is possible to reduce the volume in the master cylinder by means of an organ operated by the hand lever a against an accumulator.
Actuation of the master cylinder presses hydraulic fluid out of it and into two brake cylinders in opposite position and so the pistons with brake shoes attached on the piston rods are pushed in direction of the wheel rim edge. Contact between brake shoes and rim edge leads within the master cylinder or the brake cylinder to building up of hydrostatic pressure, transformed by means of the brake shoes to braking force and friction.
By decreasing the force exerted by hand, or loosening the hand lever, the spring positioned in the master cylinder and acting as a force accumulator pushes the piston back to its starting position, thus leaving the system without any transferable or braking force.
To have minimum maintenance and optimal braking conditions the inventor decided for applying a closed and therefore leakproof hydraulic pressure system.
SUMMARY OF THE INVENTION
To make the piston exert the maximum force onto the wheel rim edge and to preserve a leakproof system, the inventor decided for a hollow body consisting of an elastic, in its cylindrical part well deformable material as casing whereas a solid, not easily deformable material is foreseen for the front or bottom region. These two, totally different materials will, depending on the application as master cylinder or brake cylinder, be adequately formed and connected making them hydraulically impermeable.
In contrast to a common known pot-like diaphragm seal where forces and also interior pressure act upon the cylindrical and bottom region of the elastic material as well, the solution following the invention, existing maximum forces in axial direction here are exerted upon the hard solid material i.e. there are hardly any transverse loads or bending moments, increasing thus service durability or service life compared to known pot-like diaphragm seals.
Maximum tensions existing at the bottom of the piston, especially in the center thereof, are again unimportant compared to the potlike diaphragm seal for there isn't at this place any elastic or soft material to be crushed or torn by fluid pressure and a hard piston.
For a common known pot-like diaphragm seal moving axially without the possibility to unwind, the loads as described can be compared to loads existing during deep-drawing of steel or aluminum.
Both frontal ring areas of the elastic casing of the master cylinder are connected hydraulically tight with the bottom,of the guiding flange and with the back of the master piston. By moving the piston directly connected with the piston rod, having an outer diameter equal to the inner diameter of the hollow body, in direction of the cylinder bottom which has an opening connected with a fluid line, a volume reduction in the master cylinder will be created and so a rise of hydrostatic pressure. The elastic casing will, solidly fixed to the bottom of the guiding flange as well as to the back of the piston, be extended by axial displacement and pressed against the outer diameter of the piston rod by fluid pressure in the cylinder.
The hydraulic fluid, displaced in the master cylinder, flows into the brake cylinder by use of the fluid line.
Both frontal ring areas of the elastic casing are tightly connected with the bottom of the piston and the bottom of the brake cylinder where this latter has an opening connected with the fluid line.
The entering fluid acting onto the bottom of the piston and piston rod with brake shoe fixed on its fore-end presses the piston forward towards the wheel rim edge or another body of the braking stem as e.g. a brake disc connected with the bicycle wheel.
By this increase of volume and after th
REFERENCES:
patent: 4036328 (1977-07-01), Hoffman
patent: 4062427 (1977-12-01), Klaue
patent: 4391353 (1983-07-01), Mathauser
patent: 4865164 (1989-09-01), Kaneda
patent: 4896753 (1990-01-01), Sule
patent: 5050381 (1991-09-01), Matsuno
patent: 5082093 (1992-01-01), Sule
Bartz C. T.
Butler Douglas C.
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