The present invention relates to a bogie brake assembly, comprising

two brake beams to be suspended from a rail vehicle bogie and being provided with brake block heads at their respective ends,

two knee levers pivotally connected to the first brake beam,

a pushing brake unit arranged between a respective first arm of each of the two knee levers, and

push rods being connected to a respective second arm of each of the two knee levers and to the second brake beam in the vicinity of their brake block heads, wherein each push rod is pivotally connected to the second brake beam by means of a vertical bolt in a push rod end ear.

Background of the Invention

Bogie brake assemblies, intended for simultaneously applying several brake blocks to their respective treads of typically four wheels in a rail vehicle bogie, can be of several constructive types.

A typical example of a prior assembly of the type defined above is shown in

US 5 947 236. This assembly comprises, as is most clearly shown in its Fig 1, two brake beams 14 and 16, a pushing brake unit 20 at the first brake beam 14, and push rods 18 connected to the second brake beam 16. The push force from the brake unit 20 is transferred to the two push rods 18 via knee levers 70, Fig 2.

In this type the two brake beams and the two push rods form a parallelogram. If this parallelogram becomes warped or askew, or in other words if the two push rods do not form right angles with the second brake beam during brake application (and there is nothing in the construction to prevent that from happening), undue wear of the wheel flanges at the wheel treads can occur.

On the other hand, however, during brake application each push rod does not move exactly axially due to its connection to the rotating knee lever, causing a certain pitch.

The main object of the invention is to minimize the movability of the push rods in their planes, while allowing the angular movements due to the pitch. The Invention

This is according to the invention attained by a spring means between the second brake beam and each push rod arrangement to bias the push rod into a neutral position substantially perpendicular to the second brake beam.

In a practical embodiment, the push rod is surrounded by a sleeve attached to the beam and containing a rubber ring.

This rubber ring in its sleeve will allow the push rod to pivot to the very small extent necessary to accommodate the pitch during brake application and will also bias the push rod back to its neutral position.

In practice the second brake beam may be provided with a push bracket for each push rod, the bracket being provided with the sleeve.

In the bogie brake assembly so far described, there is nothing to distribute the slack between the brake blocks and the wheel treads at the right and left side of the bogie, which means that the entire slack can occur at one side. In order to accomplish an even distribution of the slack, a friction device can be arranged between each knee lever and the first brake beam.

In a practical embodiment, a friction bolt device comprising a bolt, two friction material washers and at least one cup spring may be arranged in an arc-shaped slot of a plate attached to the first brake beam at each knee lever, the friction material washers being biased into friction engagement with the knee lever and the plate.

In a conventional bogie brake assembly, for example as shown in US

5 947 236, the comparatively heavy brake unit hangs in the two knee levers and will accordingly expose them to considerable vertical forces and torque, which may be detrimental.

According to the invention this may be obviated in that the brake unit is laterally guided by plate profiles of the first brake beam, so that the brake beam carries the weight of the brake unit and the knee levers are not exposed to any vertical forces.

Brief Description of the Drawings

The invention will be described in further detail below under reference to the accompanying drawings, in which

Fig 1 is an isometric, overall view of a bogie brake assembly according to the invention,

Fig 2 is an isometric view of a portion to the right of the fore brake beam in Fig

1, Fig 3 is a view corresponding to Fig 2, but the brake beam is seen from below, and

Fig 4 is an isometric view, partly sectioned, of a portion to the right of the rear brake beam in Fig 1.

Detailed Description of the Invention

Fig 1 is an overall view of a bogie brake assembly according to the invention to be used in a railway vehicle bogie, as is well known to any person skilled in the art. In practice, two generally parallel brake beams 1 and 2 are built up of interconnected plate profiles 1 A, IB and 2A, 2B. Each brake beam is towards its ends provided with brake block holders 3 and replaceable brake blocks 4 for braking engagement with a respective tread of a wheel (not shown). A railway vehicle bogie may be provided with two wheels sets, each comprising two wheels on a common axle, the latter being journaled in side-frames of the bogie. The bogie brake assembly is mounted between the two wheel sets and is carried by the bogie, either by hanging links or - as shown - by guide feet 5 to be received in slots of the bogie side-frames.

The brake force for the shown bogie brake assembly or the force pressing the two brake beams 1 and 2 apart for braking engagement of the brake blocks 4 with the wheel treads is generated by a brake unit 6 placed between the two plate profiles 1 A, IB of the brake beam 1. The force therefrom is transferred to two knee levers 7 pivotally attached to the brake beam 1 and further to the second brake beam 2 by two push rods 8, preferably placed close to the brake beams ends.

The preferably pneumatically actuated brake unit 6 is preferably provided with a built-in slack adjuster for compensating for the wear of the brake blocks 4. The brake unit 6 will move laterally between the plate profiles 1 A, IB at brake actuation and are guided thereby so as to obviate gravity and shock induced transverse forces on the two knee levers 7. In the shown case the rod 9 to the right of the brake unit 6 may be a fixed rod, whereas the rod 10 to the left of the brake unit 6 is extended at brake actuation. The connection between the respective knee lever 7 and rod 9 or 10 is pivotal.

Each knee lever 7 is of a double-layered construction (with the rods 8, 9 and 10 pivotally attached between the layers) in order to provide a stable and sturdy

construction, which is able to transfer the brake forces. It has a stub axle 11 for its pivotal attachment between the plate profiles 1 A, IB at screw connections 12 (Figs 2 and 3).

In order to distribute the slack between the respective brake blocks 4 and the wheel treads in an appropriate way, each knee lever 7 may be provided with a friction device 13-16 for controlling its respective motion under the influence of the force from the brake unit 6, as is most clearly depicted in Figs 2 and 3. A plate 13 is attached to the underside of the upper plate profile 1 A (but may alternatively be attached to the lower plate profile IB). This plate 13 is provided with an arc-shaped slot 13 ^' . Extending through a hole in the wall of the knee lever 7 neighboring the plate 13 and through the slot 13 ^' is a friction bolt device 14-16, comprising a bolt 14, two friction material washers 15, engaging the knee lever 7 and the plate 13, and at least one cup spring (but preferably two cup springs) 16 for biasing the washers 15 into friction engagement with the knee lever 7 and the plate 13, respectively. Alternatively, other types of springs than cup springs may of course be used. The purpose of these friction devices is to evenly distribute the slack at the brake blocks 4. In order not to lose any force from the brake unit 6 to the brake blocks 4, the hole in the wall of the knee lever 7 is so formed as to accommodate the friction bolt device 14-16 to move only when there is a need to pick up slack due to wear of brake blocks and/or wheels.

The connection between each of the push rods 8 and the second brake beam 2 has the following construction with reference to Fig 4. A push bracket 17 is attached to the two plate profiles 2A, 2B constituting the second brake beam 2. An ear 8 ^' of the push rod 8 is pivotally attached to the push bracket 17 by means of a bolt 18. The push bracket 17 is provided with a sleeve 17 ^' surrounding the push rod. A spring means in the form of a rubber ring 19 is arranged between the push rod 8 and the push bracket sleeve 17 ^' .

The purpose of the arrangement is to provide a generally stiff connection between the push rod 8 and the brake beam 2 while allowing for compensation for the pitch of the knee lever 7, i e a very limited pivotal motion of the push rod 8. The rubber ring 19 will provide a bias back to a neutral position of the push rod 8.

Modifications are possible within the limit of the appended claims.