Patent Application
20050000764
The present invention relates to a shoe brake assembly according to the preamble of Claim 1.
From European Patent Document EP 0 665 154 B1, a shoe brake assembly for a rail vehicle is known which comprises a brake shoe which can be pressed against the tread of a rail wheel by means of an application device. For operating the shoe brake, a suspension system is provided which permits the brake shoe to carry out a certain lateral movement along with the wheels. By means of corresponding pressure or tension members of the suspension, the brake shoes are pressed against the wheel treads for generating a frictional force. The resulting high stressing of the wheel treads is disadvantageous because the service life of the wheel is shortened and a roughening or corrugation of the wheel tread is produced. The roughening or corrugation of the wheel tread leads to a high running noise during the rolling operation of the wheel, which is why, in the case of modern rail vehicles, separate disk brakes are frequently provided which, however, are comparatively expensive. In addition, the one-sided braking load of the wheel results in high thermal stress.
In order to avoid these disadvantages, an elastic brake body is disclosed in German Patent Document DE 19840065, in the case of which a bearing body is provided with recesses into which the friction material elements are inserted. These friction material elements form a joint friction surface and are carried in an elastic manner. Although these elastic brake bodies, to a certain extent, permit a compressing and rebounding of the friction material elements when these are pressed onto the tread of the rail wheel and thereby avoid the formation of hot spots, a roughening and corrugation on the tread is not completely avoided.
It is therefore an object of the present invention to provide a shoe brake assembly of the initially mentioned type which, while the construction is simple and high braking forces are generated, largely or completely avoids a stressing of the treads of the wheel.
This object is achieved by means of a shoe brake assembly having the characteristics of Claim 1.
If, in the case of the shoe brake assembly, for generating a braking force, at least one brake shoe can be placed against a surface of the wheel facing radially toward the interior, the tread of the wheel is not stressed by this brake shoe. As a result, on the one hand, temperature-caused tensions are avoided during the braking operation and, on the other hand, the above-mentioned roughening of the wheel tread by the brake shoe is also avoided. The development of noise during the rolling operation of the wheel can thereby be reduced. In addition, by means of the arrangement of the brake shoe on an inward-facing surface of the wheel, the contact pattern between the brake shoe and the wheel tread can be improved.
According to a preferred embodiment of the invention, the at least one brake shoe can be moved by way of a pendulum suspension essentially radially toward the outside against a surface of the wheel. The pendulum suspension permits a compensation of vertical movements between the bogie and the wheel, which are generated, for example, by the loading or unloading of the vehicle.
If at least two brake shoes are provided, which are applied to the wheel at opposite sides of the wheel web, no momentum is generated at the wheel web as a result of the introduction of force since, because of the one-sided application of forces, the wheel web is only under tension. For an effective introduction of force, each brake shoe is preferably linked to two tension bows (bars? translator) which are mutually connected in an articulated manner by way of transverse lugs and can thus be displaced with respect to one another in the manner of a parallelogram. This type of suspension permits the adapting of the position of the brake shoe to the frictional surface of the wheel during the compressing or rebounding of the wheel. In this case, the tension bow can be connected with the bogie in an articulated manner by way of one or several holding lugs.
According to a preferred embodiment, a holding lug is linked to a tension bow in the direct proximity of the brake shoe. As a result, the frictional force of the shoe can be diverted at the site of its origin directly by way of the holding lug, in which case the stiffer linkage of the brake shoe results in lower braking noises. In this case, the holding lug adjacent to the brake shoe can be linked to a single tension bow as well as to one of two tension bows. In addition, the holding lug can be disposed on a pressure piece which acts upon the brake shoe during the braking operation.
If a second brake shoe is provided at the suspension of the shoe brake assembly, which brake shoe can be moved against the tread of the wheel, a particularly high braking force can be generated. This double shoe arrangement with brake shoes situated on the outside and inside is particularly suitable for heavy rail vehicles, such as locomotives. As a result of the two-sided arrangement of brake shoes, a more uniform warming-up of the wheel is also caused.
If the block brake assembly comprises two brake shoes, which can be placed on one radially inward-facing surface of two adjacent wheels respectively, a caliper can be provided between the wheels for generating the force.
According to another preferred embodiment of the invention, the surface of the wheel and the opposite surface of the brake shoe are constructed to be slightly sloped toward a wheel web, so that the brake shoe is pressed to the interior toward the wheel web as a result of the slope of the braking surface during a movement radially toward the outside. By generating a braking force at a section of the wheel web as well as at the radially inward-facing surface, thermal tensions can be reduced between the wheel flange and the wheel web because a more uniform warming-up of the wheel takes place. The slope of the braking surface has the additional advantage that the brake shoes are centered and a clear assignment of the wheel surface and the frictional surface of the shoe exists even when axle displacements occur. In this case, the slope is, for example, in a range between 3 and 30°.
In the following, the invention will be explained in detail by means of several embodiments with reference to the attached drawings.
The shoe brake assembly illustrated in FIGS. 1 to 3 comprises a wheel 4 which is mounted on an axle 1 of a rail vehicle, a wheel hub 3 being fixed on the axle 1. A thinly constructed wheel web 2, which leads into a flange 5 of the wheel 4, extends away from the wheel hub 3 in the radial direction. On the outward-facing side, a tread 6 is constructed which has a slight diagonal slope with respect to the horizontal line. On the radially inward-facing side of the wheel flange 5, surfaces 7 are constructed on both sides of the wheel web 2, against which surfaces 7 a brake shoe 8 can be placed. The brake shoes 8 are each received on a holder 9 which has a bent construction and is fixed to an arm 10 of a tension bow 11. In
The suspension of the brake shoes 8 comprises two tension bows 11 which are each connected at a vertical distance by way of articulations 13 with the holder 9 of a brake shoe 8. In this case, the tension bows 11 are mutually connected by way of a first transverse lug 15 and a second transverse lug 18. The two axes 14 of the transverse lug 15 as well as the axes 17 of the transverse lug 18 form a rectangle, which is why the tension bows 11 can be displaced in a parallelogram-type manner. A tension rod 16 is mounted on the transverse lug 15 in an articulated manner, by way of which tension rod 16 an operating force F can be introduced in order to press the brake shoes 8 onto the braking surface 7.
The upper tension bow 11 is connected by way of two holding lugs 19 and 21 with the bogie of the rail vehicle. In this case, the holding lug 19 is mounted in an articulated manner on a suspension 20, and the holding lug 21 is mounted in an articulated manner on a suspension 22. In the loading case illustrated in
In the loading case illustrated in
For initiating the braking operation, a tension force F is applied by way of a caliper, which is not shown, which tension force presses the brake shoe 8 onto the surface 7 by way of the suspension, in order to generate the desired braking torque. As a result of the introduction of the tension force F in the center of the transverse lug 15, it is achieved that the two tension bows 11 can be mutually displaced when this is required by a change of the slope of the brake shoe 8 or in the case of a vertical movement of the wheel 4. As a result of a frictionally engaged prestressing at the articulations 14 and 17, it can be achieved in this case that, after the release of the brake, the slope of the brake shoe 8 is maintained and changes only when another angle of slope is defined by a compression change of the wheel 4. The force applied to the brake shoe 8 during the braking engagement will then result in an angular change between the tension bows 11 and the transverse lugs 15 and 18, in which case the frictionally engaged prestressing is then overcome.
Sintered, plastic as well as gray cast iron shoes can be used for the brake shoe 8. It is also conceivable to use so-called elastic brake shoes which are formed of several individual friction material elements which are prestressed toward the braking surface. Concerning the possible construction of the brake shoes, reference is made to the disclosure of German Patent Document DE 19840065.
In the embodiment illustrated in
The brake shoes 8′ have a friction surface which, like the surface 7′ on the wheel flange 5′, is constructed to be slightly sloped with respect to the wheel web 2′, so that, when a force F is introduced by way of the tension bows 11 and 12, a normal force FN is generated which is slightly sloped with respect to the vertical line and presses the brake shoe 8′ toward the wheel web 2′. As a result, the brake shoe 8′ rubs not only on the surface 7′ but also on a section 25′ of the wheel web 2′ to which the braking force Fax is applied. Therefore, during a braking operation, in addition, also the section 25′ of the wheel web 2′ is heated up, which reduces the thermal tensions within the wheel 4′. In addition, as a result of the sloped construction of the surface 7′, a centering of the brake shoes 8′ is caused toward the center. Since brake shoes 8′ are provided on both sides of the wheel web 2′, occurring axial forces are compensated.
In the embodiment illustrated in
In the embodiment illustrated in
In
In the embodiment illustrated in
The illustrated embodiments can also be combined with one another in order to create the shoe brake assembly according to the invention. For example, the sloped arrangement of the braking surfaces can also be used in the embodiments of
| Number | Date | Country | Kind |
|---|---|---|---|
| 101 41 253.3 | Aug 2001 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP02/09032 | 8/12/2002 | WO |
