Disc Brake for Heavies
Page 86
If you've noticed an error in this article please click here to report it so we can fix it.
nRAKING a heavy vehicle can be too
arduous a duty for a single disc. and for-this reason brakes are now being made having-two dits per wheel. This results in increased width. Which•May be difficult to accommodate in the design, and patent -No. 782,716 suggests a way in which the width rnaV be kept to a minimum. (Societe d'Inventions Aeronautiques Cl Mecaniques S.I.A.M., 1 route des Alpes. Fribourg, Switzerland.) •
A fixed splined tube (1) carries the brake assembly and wheel bearings. It also encloses the driving axle (2). Mounted on the wheel is a drum (3) to which are attached rings (4 and 5) Forming the brake discs. A fixed plate (6) occupies the space between. This plate contains six hydraulic expanders (7), whilst the left-hand plate (8) is also provided with another six (9). The right-hand plate functions only as an abutment.
During normal braking, only four sets of opposed expanders are used; these press interleaved friction segments on to the discs. The remaining two sets of expanders are separately piped to the control member and are used for additional emergency action or for a parking brake.
A HYDRAULIC PRESSURE SYSTEM
VE1-11CLE servo-mechanisms may need hydraulic pressure for various duties such as braking, steering and power-operated gear-changing. Usually these auxiliaries call for a special oil-pump or other means for creating the pressure. Patent No. 782,732 shows an ingenious method of using the movement of the suspension system for generating the required pressure. (R. Bishop, R. -Johnston and 0. Whitchurch. 28 Marlborough Road, Luton, Beds.) Each road wheel is fitted with a telescopic shock absorber, and these are modified to act as pumps, delivering oil into conduits (1) and drawing it from a reservoir through pipe 2. Thehighpressure oil is stored in a reservoir (3) in which an air-bag (4) acts as a spring. Excess pressure unseats a safety valve (5) and blows off into the low-pressure section. The unit (6) represents a pressure-consuming unit such as powered steering.
Although a small pump (7) is included in the system, it is intended only for priming after a vehicle has been stationary for some time.
A MAGNETIC-CUM-MECHANICAL CLUTCH
AN emergency method of mechanically engaging a. magnetic clutch is shown in patent No. 782,495. It may be used if the electric current should fail, or when it is required to leave the vehicle in gear while stationary. (S.A. Francaise Du Ferodo, 64 Avenue de la Grande Arme..e. Paris.)
The clutch is normally operated by energizing the coils (I): these attract an armature disc (2) which carries with it an outer clutch-plate (3). The latter compresses thedriven disc (4) on to a plate (5) carried by the flywheel.
To engage the clutch without electric energy, a lever (6) can he moved to the right, where it is held by the force of spring 7. The lever exerts a force on the thrust block (8) which is transmitted to the pressure plate.
SURFACE TREATMENT FOR RINGS
TTREATMENT for the wearing surfaces of piston rings is the subject of patent No. 782,340. (Sulzer Freres S.A.; Winterthur, Switzerland.) The patent mentions the use of a chromium layer, but asserts that the hardness of this metal prolongs the running-in period. It is proposed to use a very soft metal which will soon adapt itself to the cylinder shape.
The wearing surface of the ring is V-grooved as indicated in the drawing;
cutting a screw-thread along it is a-convenient method. The grooves are then electro-plated with a soft metal, copper for preference, as represented by the thick line (1).
The theory is, that although the copper rapidly wears from the tips, in doing so it is smeared over the iron surface and creates a durable thin film. Actual dimensions are, depth of plating, 0.004-0.008 in. and grooves spaced at about 25 to the inch.
A POWER-BRAKING SYSTEM
PATENT No. 782,755 refers to I power-assisted hydraulic brakes in which a continuously running fluid circuit is interrupted to generate a working pressure. (Alfred Teves Maschinenund Armaturenfabrik K.G., 41/53 Rebstockerstrasse, Frankfurt/ Main, Germany.)
Referring to the drawing, the brake pedal pivots on the boss 1, and when depressed moves the plunger 2 downwards. Circulating liquid enters at 3 and passes under the open end of the plunger to return via the central bore. a duct (4) and an outlet (5). The masterpiston (6) operates the braking system in the usual way through connection 7.
In operation, when the pedal depresses the plunger, the liquid path is closed and a pressure is created on the top of the master piston; this then applies the brakes. Increased braking demands a follow-up action of the pedal, so that an indicative reaction is given of the force applied. Liquid failure would not make the brakes ineffective because the central plunger would still be able to operate the master piston.
When at rest, a pressure balance on