AN IMPROVEMENT IN BRAKES OR CLUTCHES

Abstract: A device comprising relatively rotative elements (2, 3) and friction material to be applied between said elements. The friction material contains a fiber structure and particulate magnetic material bound together by a binder. In order to catch fibers detached from the friction material magnetic means (10) are provided adjacent the friction material (3) to attract magnetic particles adhered or nested to the detached fibers or clusters thereof.

Description: An improvement in brakes or clutches Technical Field This invention relates to a device, such as a fric¬ tion-type brake or clutch, comprising relatively rotative elements and friction material to be applied between said elements, said friction material contain¬ ing a fiber structure such as asbestos fibers and particulate magnetic metal or metal oxide material bound together with the fiber structure by a binder. Background Art It is very well known that asbestos provides environ¬ mental danger and therefore should not be used in the working life. Accordingly, efforts have been made to re¬ place asbestos with other materials providing less danger as to the health of people working therewith. In industrialized countries the use of asbestos to a great extent is prohibited by law or regulations and rigorous measures must be taken when asbestos or materials con¬ taining asbestos are being handled or worked. One field wherein it has not been possible so far to replace asbestos material by another less risky material is the automobile industry where friction linings for brakes and clutches normally contain asbestos fibers. Usually, the material of such linings comprises asbestos fibers as friction and reinforcing material, and fric¬ tion-modifying materials such as metal powders, metal oxides, organic friction dust and carbon, especially graphite, the fibers and the friction-modifying materials being held together by a binder system comprising a thermosetting plastics material such as phenolic resins and synthetic rubber. The content of asbestos fibers in friction linings may comprise as much as 60 to 70 per cent by weight. In order to protect people handling new linings for brakes and clutches in equipment shops and automobile repair workshops against the injuries associated v/ith asbestos products it is common to have a coating on such linings, which prevents detachment of the asbestos fibers therefrom. However, when repairs have to be made on brakes and clutches wherein dust containing asbestos fibers has been collected, people performing such repair are facing a considerable danger of inhaling air contain ing such fibers, particularly when repairs are made on trucks, buses and other large vehicles. It is therefore necessary to use breathing protection when such repairs are made or to bind the dust and the fibers entrained therein by means of water. The asbestos fibers detached from the friction linin in a brake or clutch due to abrasion of such lining when the brake is engaged or slipping occurs in the clutch, are not all of them collected in the brake or clutch. Although it has been maintained by manufacturers of brake and clutch linings that the asbestos fibers are converte by the heat developed in the brake or clutch into a modi fied form which is not injurious to health when inhaled, investigations made have shown that the air around big traffic routes in towns has a high content of asbestos fibers emanating from the vehicles passing on the traffi route. Disclosure of Invention The purpose of the invention is to eliminate the environmental danger to the health associated with the use of friction linings containing asbestos. For this purpose, a device of the kind initially referred to is characterized, according to the invention in that magnetic means are provided adjacent the fric¬ tion material to catch fibers detached therefrom, by magnetic attraction of magnetic metal or metal oxide particles adhered or nested to the detached fibers or clusters thereof. The invention is based on the observation that particles of the metal or metal oxide material in¬ cluded into the friction material adhere or nest to the asbestos fibers. Particularly, it has been found that the fibers are not usually detached from the fric¬ tion material as individual fibers; they are in most cases clogged or twisted together to form clusters of fibers wherein the metal or metal oxide particles are nested or caught between the individual fibers of the fiber cluster. Preferably, means are provided to direct an air flow adjacent the friction material and then along the magnetic means. It is also preferred that the magnetic means com- prises electromagnets which are energized in order to attract and catch the detached fibers scattered from the friction material, the electromagnets being de- energized to release the caught material for collection in a collector arranged below the magnetic means. Brief Description of the Drawing • The invention will be described in more detail below with reference to the accompanying drawing in which the only figure therein is a diagrammatic side view of a vehicle wheel with a brake arranged accord- ing to the invention. Description of the Preferred Embodiment In the drawing, there is shown a vehicle wheel 1 having a brake disc 2 and a pair of hydraulically operated shoes 3 comprising a friction material and supported by back plates in the manner which is cus¬ tomary in connection with disc-type automotive wheel brakes. The rotational direction of the wheel 1 is in¬ dicated by an arrow 4. Above the shoes 3 there is provided according to the invention an air tunnel 5 having an inlet opening 6 C?. r ?I catching the ram air when the vehicle is moving with the wheel rotating according to arrow 4. A butterfly valve 7 is provided at opening 6 for closing off said opening and this valve may be automatically operated so as to keep opening 6 normally closed and to uncover said opening when the brake is engaged. A downwardly extending stud 8 is provided on the tunnel 5 above each shoe 3 to collect fiber and other material detached from the shoes when the brake is engaged. In the tunnel 5 there is provided at the other, open end 9 thereof, opposite to opening 6, a system of grids 10, a collector box 11 being detachably mounted to the tunnel 5 below the grids and communicating with the interior of the tunnel through an opening 12. The grids can form part of an electromagnet or each grid may be provided with one or more coils for magnetizing by D.C. or A.C. current. When the brake is engaged on the moving vehicle the butterfly valve 7 being opened, air is forced into the tunnel 5 through the opening 6 and carries along fibers and particulate material emanating from the friction material of the shoes 3 and scattered into the tunnel or sucked thereinto through the stud 8 by in¬ jector action provided by the air flow through the tun- nel 5. The material thus entrained in the air is trans¬ ported by the air flow to the system of grids 10. The grids being magnetized will catch the material entraine in the air, .by magnetic attraction and as explained above, this will be true not only for magnetic metal or metal oxide material but also for the non-magnetic fiber material (asbestos fibers) because the magnetic material adheres or nests to the fibers or fiber clusters detached and scattered from the friction ma¬ terial. Thus, cleaned air without dangerous constitu- ents entrained therein will be discharged from the tun¬ nel 5 at the open end 9. The energization of the electromagnet or coils may be controlled over the brakes of the vehicle so that the electromagnet or coils are de-energized when the brake is disengaged, e.g. by connecting the electro- magnet or coils to the brake light circuit to which may also be connected an electromagnet operating the valve 7 so that the valve is opened when the brake is en¬ gaged and is closed when the brake is disengaged. Then, a major part of the material adhered to the grids 10 will fall down into the collector box 11 through opening 12. This box can be emptied from time to time under safe conditions or may be provided with closure means closing off the collector box when removed from the tunnel 5, the collector box then preferably being of the disposable type. Alternatively, the valve 7 and the electromagnet or coils may be controlled from the speedometer or the hand brake, so that the valve 7 is closed and the electro-magnet or coils are de-energized when the speed indicated by the speedometer is zero or close to zero and the hand brake is engaged, respectively. If it is desired not to rely upon particulate magnetic material adhering or being nested to the fibers so that the fibers can be attracted to the magnetic grids, the fibers can be specifically treated so as to secure under all circumstances that they can be attracted to the magnetic grids. This can be obtained by providing a thin layer or coating of magnetic material such as iron on the individual fibers forming a constituent of the friction material. Such a layer or coating can be applied to the surface of the fibers to be included in the friction material, by a vacuum deposition process according to a technology that is well known. The invention can also be applied if other fibers than asbestos fibers are used in the friction material if it is considered that such fibers should not be scattered to the environment when the brake or clutch is engaged. Particularly, if such other fibers are of a kind which does not form clusters retaining particle of magnetic material between the individual fibers, it is advantageous to apply to the fibers a layer or coating of magnetic material as mentioned above. The embodiment of the invention as described here in can be modified within the scope of the following claims. Several modifications have already been men- tioned and further modifications present themselves to a man skilled in in the art as far as the construc¬ tive details of the means for collecting and retaining the particles detached from the friction material are concerned. In case of electrically driven vehicles running on rails, collecting of the particles detached from the friction material of the brakes may be advantageous also from the point of view that such material other¬ wise may be deposited on electrical equipment on the vehicle and along the track for the vehicle and if it is electrically conducting may cause flash-overs in such equipment. This is a secondary advantage obtained by the invention. C "

Claims: CLAIMS : 1. A device, such as a friction-type brake or clutch, comprising relatively rotative elements (2, 3) and fric¬ tion material to be applied between .said elements, said friction material containing a fiber structure such as asbestos fibers and particulate magnetic metal or metal oxide material bound together with the fiber structure by a binder, characterized in that magnetic means (10) are provided adjacent the fric¬ tion material to catch fibers detached therefrom, by magnetic attraction of magnetic metal or metal oxide parti¬ cles adhered or nested to the detached fibers or clusters thereof. 2. A device according to claim 1, characterized in that means (5, 8) are provided to direct an air flow adjacent the friction material (3) and then along the magnetic means (10) . 3. A device according to, claim 1 or 2, characterized in that the magnetic means (10) comprise electromagnetic means, 4. A device according to claim 3, characterized in that a collector (11) for material attracted by the magnetic means (10) is arranged below such means.

Inventors: LARSSON H, LARSSON K
Applicants: LARSSON H, LARSSON K, PARTCOLL HANDELSBOLAG
Application year: 1981
Main classification: B03C1
IPC codes: B03C1, B08B15, B60T17, F16D13, F16D65