The invention relates to a friction disc for torque transmission in a brake or clutch, in particular in a clutch of a winch or similar transporting appliance, in particular in a forestry winch or forestry ropeway. Such inventions according to the International Patent Classification belong to machinery, namely machine parts suitable for transmission of rotation, and in particular to brake or clutch friction discs, and therefore to the class F16D 13/64.

In this, the invention is rest to a problem of improving efficiency and reliability, when compared with known solutions as known from the prior art, namely on the one hand of reliability of attachment of the friction lining for providing each required friction coefficient onto each metallic bearing material of a brake or clutch with each required mechanical properties, which enable transmission of each loads via said brake or clutch, and on the other hand also maintaining of appropriate conditions on the friction surface as such, despite to unavoidable wear thereof or also to exposure thereof to various influences from the surrounding.

A friction disc is disclosed in GB 2 341 901 B and comprises an axially symmetric disc-shaped base part, which is in its central region furnished with attaching means suitable for establishing appropriate interconnection thereof with each corresponding shaft, from which the torque is transferred on said disc. Said base part consists of metal and is therefore adapted for transmission of essential dynamic loadings, to which a brake or clutch is exposed, in which said disc is used. On one of its front surface said disc is furnished with a friction lining, which consists of different material having substantially worse mechanical properties, but much higher friction coefficient. Said friction lining consist of a plate-like material, which is however cut out in annular shape and attached to said front surface of the base part. Said friction lining is arranged on a radially peripheral area of the base part, so that each generated friction forces may act at a sufficient lever in order to produce or take-over as high as possible torque, which is transmitted via the brake or clutch. The central area of the front surface of the friction lining is free and is merely intended for forming a driving collar, which serves for connecting the disc with a shaft.

Such friction disc is somehow functional. As soon as the base part is placed on a shaft, by displacing it towards the opposite surface said friction lining is brought in contact with a corresponding opposite surface, so that due to friction between both surfaces the torque can be transferred to said base part or there-from. Said friction however results not only in the possibility of transmission of torque but also in heat generating and wearing, wherein also substantial shearing forces occur between said base part and said friction lining. Due to said exposure to the shearing forces, reliability of attachment of the friction lining into the base part is crucially important for reliability of operation of the brake or clutch as a whole. Said friction lining is usually attached to the base part by means of adhesive and may be in addition to that also mechanically secured, e.g. by means of rivets. To this aim, round bores may be foreseen in the friction lining and the base part, and each rivet is loosely by maintaining a sufficient gap therebetween inserted into each corresponding bore and then secured against removal by means of plastically deforming thereof. However, positioning of rivets on said cylindrical inner surfaces of such bores is pretty undefined, in particular when taking into account said gap in combination with possible and unavoidable variations of temperature during operation of the brake or clutch, so that transmission of said shearing forces from said inner surface of each bore in the friction lining towards the body of the rivet and thereafter towards the surface of the base part is always questionable. On the other hand, the opposite surface, with which the friction lining is engaged, is by operation of the brake or clutch exposed to substantial wearing, which results in removal of particles there-from. Said particles and possible other impurities, which can be brought from outside into the gap between the friction lining and each opposite surface, result in essentially reducing if engagement between the friction lining and the opposite surface, which results in decreasing of friction coefficient and efficiency of torque transmission. For such purpose known clutches or brakes are furnished with cleaning grooves, which are arranged on a friction lining and extend radially outwards, or at least essentially radially outwards. Such grooves are, when observed in circumferential direction, equidistantly spaced apart from each other, and are intended for collecting and retaining said particles and impurities, which should upon establishing contact between the friction lining and each opposite surface move into said grooves. However, due to presence of said grooves, on the one hand the effective friction surface may be essentially reduced and on the other hand also scrubbing of impurities from the friction surfaces in the area of edges of said grooves does not appear to be really efficient. Theoretically, friction between two bodies should not depend on extent of each contact surface between such bodies, however, a person skilled in the art will nevertheless understand that in the practice a sufficient large contact surface between the friction lining and the opposite surface must be available for the purposes of transmission of a pre-determined torque. Moreover, said person skulled in the art will understand that impurities may be removed from a surface by means of scrubbing i.e. by sliding an appropriately sharp edge along said surface. However, contrary to metallic base part, the friction lining consists of material, the hardness of which is essentially smaller, so that initially sharp edges around each grooves formed therein shortly after the beginning of operation of the brake or clutch become rounded or even smoothly rounded and completely inefficient for the purpose of scrubbing of particles of impurities from the surface of the friction lining or the opposite surface. In this, said change of the shape of edges may also generate certain amount of additionally removed particles, which may also have certain impact in the view of each friction coefficient established.

The present invention refers to a friction disc for torque transmission in a brake or clutch, wherein such disc comprises a base part, which is arranged axially symmetrically with respect to a central axis and rotatably around it, as well as a circular front surface and a centrally arranged driving collar, which is suitable for transmission of torque, and also an annular friction lining. Said friction lining is attached in a radially outward area of said front surface of the base part and is secured against rotation relatively to said base part by means of at least two mechanical securing members, at least one of which is adapted to be rest on the one hand on the material of said base part and on the other hand on the material of said friction lining. In addition to that, said friction disc is also furnished with a plurality of cleaning grooves, which are in the circumferential direction of the disc equidistantly spaced apart from each other and extend each per se in a direction from the central axis of said driving collar towards the circumference of the disc. The invention provides that said plurality of cleaning grooves which are each per se surrounded with a sharp edge, is arranged in the area of said base part, namely in the intermediate area between said driving collar and said friction lining, while the effective surface of the friction lining is planar and smooth. Each of said securing members is essentially cylindrical, but the cross-section thereof in the plane of said front surface on the base part is shaped in the form of letter D, so that each securing member is on its side, where due the torque transmission and friction on said friction lining as well as due to the tendency of its displacing relatively to said base part, said friction lining, said base part and said securing member are rest thereon, is furnished with a planar cutoff. The shape of the friction lining and shape of the base part are correspondingly adjusted to such shape of said securing member.

In general, each of said cleaning grooves is linear and extends radially, or can also be available in some different shape. Namely, in accordance with another embodiment of the invention, each of said cleaning grooves can also extend inclined with respect to radial direction, wherein all disposable grooves are along the circumference oriented in the same direction. In a further embodiment, all disposable cleaning grooves are along the circumference oriented in such manner, that they extend apart from the driving collar outwards and inclined towards those sides of said securing members, where said cutoffs are located.

Still further, each of said cleaning grooves can also be nonlinear, however it should be available in the form of a mathematically pre-defined curve, and in accordance with a still further embodiment certain number of said cleaning grooves can be linear and certain number of said cleaning grooves can be nonlinear and should be available in the form of a mathematically pre-defined curve, wherein all cleaning grooves are in circumferential direction arranged regularly and symmetrically with respect to the central axis.

The invention will also be described on the basis of an embodiment, which is shown in the attached drawing, and Fig. 1 represents said embodiment of a friction disc for torque transmission in a brake or clutch in a front view.

As shown in Fig. 1 , a friction disc, which is improved according to the invention and is suitable for torque transmission in a brake or clutch, comprises a base part 1 , which is arranged axially symmetrically with respect to a central axis 100 and rotatably around it, as well as a circular front surface 1 1 and a centrally arranged driving collar 12, which is suitable for transmission of torque, and in addition to that, said friction disc is also furnished with an annular friction lining 2.

Said friction lining 2 is attached in a radially outward area of said front surface 1 1 of the base part 1 and is secured against rotation relatively to said base part 1 by means of at least two mechanical securing members 3. Each of said securing members 3 is adapted to be rest on the one hand on the material of said base part 1 and on the other hand on the material of said friction lining 2. Moreover, said friction disc is also furnished with a plurality of cleaning grooves 4, which are in the circumferential direction of the disc equidistantly spaced apart from each other and extend each per se in a direction from the central axis of said driving collar 12 towards the circumference of the disc. Each of said cleaning grooves 4 is surrounded with a sharp, uninterrupted rectangular edge 41. Said plurality of cleaning grooves 4 is arranged in the area of said base part 1 , namely in an intermediate area 13 between said driving collar 12 and the friction lining 2, while the effective surface 21 of the friction lining 2 is planar and smooth.

Each of said securing members 3 is essentially cylindrical, but the cross-section thereof in the plane of said front surface 1 1 of the base part 1 is shaped in the form of letter D, so that each securing member 3 is on its side, on which due to torque transmission and friction on said friction lining as well as due to the tendency of its displacing relatively to said base part 1 said friction lining 2, said base part 1 and said securing member 3 are rest thereon, is furnished with a planar cutoff 31. As evident in Fig. 1 , the shape of the friction lining 2 and the base part 1 is adjusted to such shape of each securing member 3.

In the embodiment according to Fig. 1 each of said cleaning grooves 4 is linear.

In this, each of said cleaning grooves 4 extends inclined with respect to radial direction, wherein all disposable grooves 4 are along the circumference oriented in the same direction. As evident in Fig. 1 , all disposable cleaning grooves 4 are along the circumference oriented in such manner, that they extend apart from the driving collar 12 outwards and inclined towards those sides of said securing members 3, where said cutoffs 31 are located.

In a further embodiment of the invention, which is not shown in said drawing, each of said cleaning grooves 4 extends radially. In a still further embodiment of the invention, which is not shown in said drawing, each of said cleaning grooves 4 is nonlinear, however is available in the form of a mathematically pre-defined curve. In such case it usually makes sense, if certain number each of said cleaning grooves 4 is linear and certain number of said cleaning grooves 4 is nonlinear and is available in the form of a mathematically pre-defined curve, wherein all cleaning grooves 4 are in circumferential direction arranged regularly and symmetrically with respect to the central axis 10.

Prior to, or during to bringing said friction surface 21 in contact with each opposite surface, thanks to such smooth and planar friction surface 21 each wear particles or impurities are slided towards the intermediate area 12 on the base part 1 , from where they are thereupon scrubbed by means of sharp edges 41 , by which said cleaning grooves 4 are surrounded, and are then collected within said grooves 4. On the other hand, due to such described concept of said securing members 3, the resistance of said friction lining 2 against each potential displacement thereof relative to the base part 1 is essentially improved, which no doubt leads to improved reliability of the complete brake or clutch assembly.