Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
2000-06-05
2002-03-12
Butler, Douglas C. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S072700, C188S071800, C188S10600P, C188S072900
Reexamination Certificate
active
06354407
ABSTRACT:
The present invention relates to a disc brake for use on a motor vehicle.
More particularly, the present invention relates to a disc brake which comprises a fixed torque taking or carrier member which straddles a rotatable disc and carries both a directly and an indirectly actuated friction pad assembly. A brake housing overlies the torque taking member and is guided for sliding movement towards and away from the disc by guide pins which are fixed to the torque taking member and which are slidable in openings arranged in the brake housing in a conventional manner. The brake housing comprises a main body portion which contains an actuator mechanism, and a bridge section integral therewith ie. the bridge section is bolted to the main body portion or integrally cast therewith so as to be of unitary construction. The bridge section has an opening arranged radially of the disc, through which the friction pad assemblies can be inserted and removed from the torque taking member.
The present invention relates more specifically to a disc brake wherein the actuator mechanism comprises at least one, but preferably two tappets which are axially movable towards the brake disc to engage and press the directly actuated friction pad assembly against one side of the braking disc, the brake housing reacting and sliding on the said guide pins to apply the indirectly actuated friction pad assembly to the other side of the braking disc. Actuation of the brake is by way of a lever and eccentric arrangement wherein the eccentric arrangement engages the said tappets, pivotal movement of the lever causing the eccentric arrangement to move the tappets towards the braking disc.
In the above described type of disc brake certain problems occur in known constructions and it is the aim of the present invention to seek to overcome these problems to improve performance, life and ease of manufacture.
One such problem relates to the support of the adjustable tappets. In known constructions the adjustable tappets are supported in bearings in the brake housing. However, appreciating that each such tappet is an elongate assembly, it is usual for the bearing length to be less than optimum. As a result and noting the fact that the geometry of the brake actuator is such that the eccentric arrangement which engages the tappets exerts a side load on each of the tappets when the brake is actuated, the tappets will, in certain circumstances, experience side forces such as to cause them to tilt. This tilting may be accentuated by a combination of the tappets extending as a result of lining wear and also as a result of the clearances which exist between the outer wall of the tappet and its respective bearings. Tilting of the tappets may result in unwanted taper wear of the friction pads, and in addition, undesirable wear on the related components of the tappets, supporting bearings and adjacent mechanisms.
The aim of this aspect of the present invention it to produce a new brake design which minimises if not overcomes, the above problem.
According to a first aspect of the present invention there is provided a disc brake comprising a brake housing which, in use, straddles a braking disc and is slidably mounted on a torque taking member, so as to be movable towards and away from the braking disc, the brake housing incorporating a brake actuator mechanism located on one side of the braking disc and arranged to directly engage a friction pad assembly carried by the torque taking member on one side of the braking disc, another friction pad assembly being likewise carried by the torque taking member on the other side of the braking disc, the brake actuator mechanism comprising at least one adjustable tappet assembly which can be engaged with the directly actuated friction pad assembly under the action of a lever and eccentric arrangement, the actuator assembly being located within a recess in the brake housing, which recess is open towards the braking disc, and closed by a cover plate secured to the brake housing, the tappet extending through a bearing aperture in the cover plate, which bearing aperture extends as the inside wall of a cylindrical projection integrally formed with the cover plate, the cylindrical projection extending into the said recess of the brake housing for the major portion of the length of said tappet.
Thus, by virtue of this axially extended bearing the or each tappet is better supported along its length, this improved support resisting tilting of the tappet, and improving actuation efficiency and adjuster control.
In a preferred embodiment the brake comprises two adjustable tappet assemblies, each tappet being basically a two part assembly, one part being a female part which is generally cylindrical with an enlarged diameter head at one end region thereof, this enlarged diameter head engaging, in use, the directly actuated friction pad assembly. Extending from the other end of the said female part, through said female part, is an axially extending blind bore within which one end region of the other part of the tappet assembly ie. the male part, is threadedly engaged, the male part likewise having an enlarged head region which is, in use, engaged and acted upon by the said eccentric arrangement. This enlarged head forms a bearing surface which engages a wall of the axially extending cylindrical projection integrally formed with the cover plate.
Thus, appreciating that the major portion of the outer surface of the female part of each tappet assembly is supported along its length by the inner wall of a said cylindrical projections, thus resisting tilting of the tappet assembly, the engagement of the said bearing surface of the enlarged head of the said male part, with said cylindrical projection further improves tappet support and resists any possibility of tilting under the action of the eccentric arrangement.
Preferably this enlarged head has at its radially outer edge region, an axially extending lip which extends towards the threaded end region of the said male part and forms a cylindrical inner bearing surface which engages around the outer wall formed by the said axially extending cylindrical projection which is integrally formed with the cover plate. Alternatively the free end region of the said cylindrical projection has an enlarged internal diameter section which engages around the outer peripheral bearing surface of the said enlarged head of the said male part.
Whilst the cylindrical projections or extensions of the cover plate may be cast with the cover plate to thus form a unitary construction, the cylindrical extensions may alternatively be at least partially formed by cylindrical bearing sleeves which are secured to the cover plate. Thus the cylindrical bearing sleeves and cover plate may be made from different materials ie. the bearing sleeves may be made of a more suitable and probably more expensive bearing material such as a sintered bearing material and may be cast into the cover plate which can itself be formed as a die casting, thus optimising the construction.
Further, whilst the axially extending lip of the head reigon of the preferred form of said male part of each tappet assembly may be integrally formed with the said male part to thus form a unitary construction, the axially extending lip may alternatively be formed by an appropriately dimensioned hollow cylindrical member in the form of an annulus, which can be secured to the outer surface of the head region of the said male part.
Located between the two tappets is preferably an adjuster mechanism which is preferably secured in position in a further cylindrical projection of the cover plate, which further cylindrical projection is preferably cast with the cover plate to form a unitary construction. This adjuster mechanism incorporates a gear wheel which meshes with teeth provided on the respective heads of the respective male parts of said tappets so that rotation of the gear wheel adjusts both tappets—rotation of the male parts causing the said female parts which are keyed in the cylindrical bearing projections, to move axially
Heinlein Carl Edward
Jackson Jonathan Leslie Christopher
Trott Philip Leonard
Butler Douglas C.
Carlson Gaskey & Olds P.C.
Meritor Automotive Inc.
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