A device of this kind, a so-called"cat", is known from Swedish patent application no. 466490, among others. This construction is based on two centrifugal weights that are located on traction wheels and cause the traction wheels to stop in the event of overspeed. In regard to such devices, there have been attempts to provide braking arrangements that are in compliance with European safety requirements for suspended scaffolds (EN-1808). The problem with the known constructions is that the cat in some cases does not stop at overspeed because the wheels start to slide against the rail due to loss of friction. one solution to this problem is a separate catching device of the type illus- trated in Fig. 1. This catching device can either be pulled after or pushed in front of the cat. In case of overspeed, centrifugal weights in the catching device initiate a mechanism that locks the catching device to the rail. The sensor that releases the catching device is arranged sepa- rately from the cat. The problems with the known separate catching device are among others that it has difficulties going through sharp turns and the fact that it does not function as well in both directions.

It is the purpose of the present invention to provide a cat that complies with the European safety requirements for suspended scaffolds (EN-1808), which also generally is ap- plicable to other climbing arrangement where conveyance substantially is based on friction between the traction wheels and the rail.

Another purpose of the present invention is to provide a cat with a catching device that is not only based on fric- tion, but also a mechanical gripping of the rail, in order to prevent the cat from uncontrollable skidding or sliding

along the rail, in the event of frictional loss or some other system fault.

A third purpose is to provide a cat that is capable of go- ing through sharp turns and up steep grades.

A fourth purpose is to provide a device in which the cat and the catching device constitute an integrated unit.

The abovementioned purposes are fulfilled by a device ac- cording to the present invention, characterised by the fea- tures indicated in claim 1. Further advantageous aspects and characteristics are indicated in the dependent claims.

The present invention is described in further detail with reference to the enclosed figures, where Fig. 1 illustrates a view of a prior art cat comprising a separately arranged catching device, Fig. 2a-d illustrate various perspectives and details of a cat according to the present invention, Fig. 3a-b illustrate a wedging arrangement according to the present invention in the free and jammed position, respec- tively, Fig. 4a-b illustrate a second embodiment of the present in- vention viewed from two different angles, and Fig. 5 illustrates how the cat according to the present in- vention is capable of moving along a rail of any angle.

Fig. 2a illustrates a cat comprising two traction wheels 1, 10 abutting a rail 9. In normal circumstances, the friction between the traction wheels 1,10 and the rail 9 is large enough to enable the cat to move back and forth on the trail with the desired speed and without skidding or slid-

ing. If the traction wheels of the cat lose grip of the rail or in other ways move along the trail at speeds that are too high, a sensing device will detect this and release a wedge 2 which, when it contacts the rail 9, is pulled in and jammed between the traction wheel 1 and the rail 9 in a self locking manner.

In one particular embodiment of the brake wedge 2, the power from the wedge will cause a deformation of the rail 9. The wedge 2 might for instance be arranged with claws (not shown) that"dig"into the rail. In another embodi- ment, the rail material is so soft that the wedge 2 digs itself into the rail irrespective of if it comprises claws or not.

In any case, the design of the wedge 2 insures that there never will be a sudden stop. This results in a softer brak- ing and makes it possible to control the load on the vari- ous components, such as any shafts, bearings, cradles or other burdened parts. Due to the design of the wedge 2, there will always be a controlled braking over a predeter- mined distance. This distance is dependent of the angle of the wedge 2; a smaller angle of the wedge gives a longer the braking distance. In addition, at least one of the wheels 1,10 may possibly be divided into two parts 10,11, the two parts 10,11 being pushed together by means of one or more springs 12. During the braking action, the wheels 10, 11 are squeezed outwards, this further providing a smooth and controlled braking action.

Fig. 2c discloses a preferred embodiment of the wedge 2 ac- cording to the present invention. It is formed in an eccen- tric manner and works in both directions. The wedge 2 is designed to be located on and enveloping the traction wheel 1. One important characteristic of the wedge 2 according to the preferred embodiment is that it forms an overspeed brake that exerts its braking forces on an imagined line x- x (fig. 2b) between the two traction wheels 1,10. This

provides a safe, compact and efficient catching device, which forms an integrated part of the cat and its elements.

Fig. 4 illustrates an alternative embodiment of the catch- ing device 2. In this alternative embodiment, the wedge 2 is arranged sideways and independently of the traction . wheels 1,10, but nevertheless grabs and digs into the rail 9 between the traction wheels 1,10.

The advantage of the present invention, in which the catch- ing device 2 is integrated with the actual cat and performs its braking action on the rail 9 in between the traction wheels 1,10, is that the cat obtains a smoother and thus a safer course through sharp curves, regardless of angle or direction (see Fig. 5). The cat will also obtain a less complicated construction and include fewer elements. These factors together contribute to a safer and more feasible cat.

In one preferred embodiment the sensing element may include a separate wheel 3, which is located on the same line x-x as the traction wheels 1,10. This is illustrated in Fig.

2a-b, in which the wheel 3 suspended in a cradle 5 and pushed against a separate roller path of the rail 9 by means of a spring element 4. The wheel 3 may for instance include centrifugal weights 6 and rotates freely and inde- pendently in regard to the speed and direction of the trac- tion wheels 1,10. If a set speed is exceeded, the cen- trifugal weights are hurled outwards and cause a trigger mechanism 7 to initiate the braking action.

It is understood that the wheel 3 can be designed in any desired way, for instance like a toothed wheel, an ordinary wheel or the like, and has a surface that provides the de- sired level of friction and safety.