Brakes – Wheel – Axially movable brake element or housing therefor
Patent
1999-05-11
2000-10-17
Butler, Douglas C.
Brakes
Wheel
Axially movable brake element or housing therefor
188196R, F16D 5540, F16D 6554
Patent
active
061317055
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a friction brake adjuster, comprising an elongated fastener means with a first end and a second end, said fastener means being arranged in a bore in a brake piston, which is displaceable relative to a brake housing surrounding the friction brake to a braking position and to a retracted position, the brake piston being displaceable to the retracted position by means of a spring member.
Such an adjuster is known through the document WO,A1,9004115, which maintains a constant play between the surfaces of the friction discs in a friction brake when the brake piston is in its retracted position, regardless of how much the friction discs have been worn down. An annular brake piston is provided with axial bores, which are aligned with corresponding holes in the wall of a housing surrounding the friction brake. Elongated fastener means provided with bolt heads are screwed into one or more of the bores in the brake piston. The fastener means extends into the corresponding aligned bore in the wall of the brake housing. The fastener means has at that end two flanges. A resilient clamp element is clamped in the bore in the housing wall. The clamp element is disposed between the flanges of the fastener means and thus limits the movement of the fastener means and thereby also the axial movement of the brake piston.
The brake piston is displaceable to a braking position by means of hydraulic fluid under pressure, supplied to a space behind the brake piston. Cylindrical helical springs are disposed in the bores which are not provided with fastener members. The helical springs are pretensioned and urge the brake piston to its retracted position. As the friction discs are gradually worn down, the brake piston is displaced further towards the brake discs, which means that the clamping element will be pulled by the fastener means. However, the force required to displace the clamping element in the bore is greater than the combined force of the spring acting on the clamping element when the brake piston is in its retracted position. This means that the brake piston will be in a new starting position in the retracted position, which means, in turn, that during braking, the brake piston will always be displaced the same distance regardless of how much the friction discs have been worn down. Thus, a constant hydraulic fluid volume can be supplied for each braking operation.
A disadvantage with the adjuster according to WO,A1,9004115 is that the more the friction discs are worn down, the more the springs will be tensioned since the anchoring point of each spring in the housing wall is not moved as the clamping element is displaced. This means that more force must be overcome during braking, and the risk of spring breakage also increases, thus shortening the life of the friction brake.
One purpose of the present invention is to achieve an adjuster of the type described by way of introduction, which keeps the resilient element under a constant pretension in the retracted position regardless of how much the frictional surfaces of the discs have been worn down.
Another purpose of the present invention is to achieve an adjuster of the type described by way of introduction which has a compact design and which thereby requires very little space in a friction brake.
This is achieved according to the invention by virtue of the fact second abutments away from each other, against the first abutment, and against the brake housing.
Such an adjuster makes it possible, firstly, to maintain a constant clearance between the frictional surfaces in a friction brake and, secondly, to maintain a constant pretension in the spring when the brake piston is in its retracted position, regardless of how worn the frictional surfaces are.
The invention will be described in more detail below with reference to examples shown in the accompanying drawing, where
FIG. 1 shows a sectional partial view of an adjuster for a friction brake in accordance with the invention.
The reference number 1 in FIG. 1 designates a friction brake, whi
REFERENCES:
patent: 3958670 (1976-05-01), Anderson
patent: 3990547 (1976-11-01), Plaat
patent: 3995721 (1976-12-01), Chambers
patent: 4010828 (1977-03-01), Ditlinger
Dahlen Tord
Strandberg Jonny
Butler Douglas C.
Volvo Wheel Loaders AB
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