Brakes – Elements – Brake wheels
Reexamination Certificate
2002-12-05
2004-10-26
Graham, Matthew C. (Department: 3683)
Brakes
Elements
Brake wheels
C301S006800, C192S200000
Reexamination Certificate
active
06808050
ABSTRACT:
TECHNICAL FIELD
The invention relates to a brake disc for a disc brake, in particular for rail vehicles. This contains a hub body with a radially outwardly extending hub flange with axially parallel openings in which screws may be arranged in order to connect a brake ring flange of a brake ring to the hub body, said brake ring flange being arranged radially overlapping and axially adjacent the hub body. It further relates to a brake ring for a disc brake, in particular for rail vehicles containing a radially extending brake ring flange with axially parallel openings in which screws may be arranged in order to connect a hub flange of a hub body to the brake ring, said hub flange being arranged radially overlapping and axially adjacent the brake ring flange.
STATE OF THE ART
Disc brakes of the above mentioned type are for example known from DE 26 20 623 A1 (FIGS.
1
and
2
). They consist of a hub body which is arranged in a rotationally fixed manner on the shaft of the axle of a vehicle, as well as a brake ring connected to the hub body. The brake ring on at least one outer side comprises a friction surface on which brake shoes engage and by way of a suitable pressure on the friction surface may exert the desired braking effect. The connection between the hub body and the brake ring is effected via a screwing of the hub flange with the brake ring flange. The mentioned flanges are radially distant from the hub body or brake ring, overlap in the radial direction and are arranged axially adjacent one another. The details “radial” and “axial” or “axially parallel” relate to the rotational axis of the brake disc (the same as the axis of the shaft on which the brake disc is attached), which as a rule is also an axis of symmetry of the brake disc. Furthermore the flanges may be designed peripherally in a continuous manner as well as peripherally in a wave-like manner, wherein in the latter case they consist of adjacent lugs. The screws for fastening the brake ring on the hub body pass through openings in the hub flange and in the brake ring flange, these openings being essentially aligned to one another.
It is known that with disc brakes of the mentioned type, with braking procedures the brake ring expands on account of the occuring heating, whereas the hub body does not experience any comparable expansion. A multitude of designs are known for accommodating or for compensating the thermal expansions occuring between the hub flange and the brake ring flange.
Thus for example DE-B 10 31 337 shows a disc brake of the above mentioned type with which the screwing between the hub flange and the brake ring flange is designed such that a radial relative movement between both bodies is possible. In particular there are provided radial slots in the brake ring flange distanced equally over the circumference in which the screws which pass through it may travel radially. However with such a design there exists the danger that with thermal expansions the screws may lose their parallel position to the axis of the disc brake. Thus for example the screw heads may retain their position relative to the hub flange on which they rest, whilst the screw section lies in the brake ring flange and is displaced radially outwards by this on thermal expansion. This leads to considerable bending stresses of the screws which may lead to an increased wear, premature fatigue and in the worst case to a failure of the screws.
For reducing the mentioned bending stresses of the screws, in DE-A 28 28 137 it is known in a disc brake of the initially mentioned type to mount the screw heads as well as nuts in spherical bearing shells, by which means the screws may be pivoted out of their axially parallel bearings essentially without bending and shear stresses. This embodiment form however is very complicated and thus expensive and with thermal expansions leads to undesired changes in the pretension of the screws.
From DE 34 32 501 C2 there is further known a disc brake of the initially mentioned type with which the brake ring flange is arranged movable with thermal expansion between the hub flange and a separate tension ring, wherein the screws axially tension the hub flange against the tension ring. The respective ends of the screws are thus mounted in the hub flange or in the tension ring and thus in two elements which as a rule are not subjected to a relative movement on thermal expansion. It is however disadvantageous that additional means for torque transmission mentioned type to mount the screw heads as well as nuts in spherical bearing shells, by which means the screws may be pivoted out of their axially parallel bearings essentially without bending and shear stresses. This embodiment form however is very complicated and thus expensive and with thermal expansions leads to undesired changes in the pretension of the screws.
From DE 34 32 501 C2 there is further known a disc brake of the initially mentioned type with which the brake ring flange is arranged movable with thermal expansion between the hub flange and a separate tension ring, wherein the screws axially tension the hub flange against the tension ring. The respective ends of the screws are thus mounted in the hub flange or in the tension ring and thus in two elements which as a rule are not subjected to a relative movement on thermal expansion. It is however disadvantageous that additional means for torque transmission must be provided between the hub body and the tension ring so that no bending stresses of the screws occur perpendicular to the radial direction. On account of these means the constructional effort is increased and the assembly is made more difficult. With disc brakes ventilated at the inside, the tension ring may considerably handicap the supply of cooling air to the brake disc. Furthermore there also exists the possibility that with thermal expansion, the forces on the tension ring occur assymetrically with respect to the rotational axis of the disc brake and that on account of this the undesired bending stresses indeed do arise.
From DE-OS 20 60 352 there is known a multi-part brake disc with which on a hub there are provided radially outwardly extending lugs which have axially parallel openings in order to fasten an overlappingly arranged lug of a brake ring by way of corresponding screws, wherein in each case two lugs distanced from one another are in each case provided with an opening through which the ends of the screw may be held. At the same time one envisages designing the fastening screws for the brake ring consisting of brake ring elements as fitting bolts. In order to design the screw connection such that it is axially free of play, may be readjusted in limits and additionally is tensionally locked, at the same time each lug is tensioned against the end face of the hub via bushings.
DESCRIPTION OF THE INVENTION, OBJECT, SOLUTION, ADVANTAGES
Against this background it was the object of the present invention to improve a hub body, a brake ring and a brake disc of the initially mentioned type with simple design means in a manner such that with thermal expansions of the brake the axial parallelity of the screws which connect to brake ring flange to the hub flange is ensured. arranged a retaining element with all, but at least with three openings arranged distributed over the circumference.
With the brake disc according to the invention thus both ends of the screws which connect the hub flange to the brake ring flange are fixed relative to the hub body. The first end of the screw which may for example be the screw head, is mounted in an opening on the hub flange. The screw then passes through the brake ring flange, and its second end is held in the retaining element which is fixed on the hub body and transmits this fixation onto the end of the screw. By way of the radial fixing of the screws at both ends their axially parallel position is ensured even with thermal expansions of the brake ring. This is also the case with the use of several retaining elements if the forces should not occur symmetrically with respect to the rotational axis
Gronemann Manfred
Lehmann Wolfgang
Ruppert Helmut
Watson John
Graham Matthew C.
Kelly Lowry & Kelley LLP
Nguyen Xuan Lan
SAB Wabco BSI Verkehrstechnik Produtcs, GmbH
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