Solid anti-friction devices – materials therefor – lubricant or se – Solid anti-friction device – article or material therefor
Reexamination Certificate
1998-11-03
2001-07-24
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Solid anti-friction device, article or material therefor
Reexamination Certificate
active
06265356
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to granules suitable for manufacturing friction material used for brakes and clutches incorporated into various vehicles and industrial machines. Also, the present invention relates to a method of manufacturing the granules.
2. Description of the Related Art
Friction material widely used for brake pads, brake linings and clutch facings incorporated into various vehicles and industrial machines is manufactured as follows. Starting raw material containing raw material fiber such as heat-resistant organic fiber, inorganic fiber and metal fiber, and also containing raw material powder such as inorganic and organic filler, friction modifier and thermosetting resin binder is formed at a room temperature by a predetermined pressure (preforming) and then heat-formed at a predetermined temperature. Then it is cured (after-cure) and finished.
In the process in which the starting raw material is mixed and measured and then the measured material is charged into a die for heat-forming, powder (mixture) is handled, the shape of which is changeable. In many cases, raw material powder comprises fine particles, the diameters of which are several tens &mgr;m, for the reasons of ensuring the frictional characteristic of the frictional material. Therefore, each process tends to be dusty when the material is handled. Accordingly, it is necessary to take countermeasure to prevent dust from rising, for example, it is necessary to arrange a shielding plate in each process. When the countermeasure is taken as described above, the manufacturing cost is increased. Further, the raw material powder is composed of fine particles, the specific surface of which is large. Therefore, the raw material powder tends to adhere onto an inner surface of the forming die. Accordingly, it becomes difficult to charge the starting raw material into the forming die uniformly.
In order to solve the above problems, the starting raw material is granulated. That is, various raw material powder and raw material fiber, which are the starting raw material, are rolled while binder is being added to them, so that granules, the diameter of which are 2 to 5 mm, can be obtained, and these granules are used as material for manufacturing friction material.
When raw material powder is granulated, it is possible to solve the above problem of dust which rises in the process of handling and it is also possible to solve the above problem of adhesion of raw material powder onto the inner surfaces of the forming die.
Raw material fiber is originally added for enhancing the mechanical strength of friction material when the raw material fiber is dispersed entirely and uniformly and entangled with each other. However, according to a method by which material is granulated, raw material fiber is involved in the granules and divided for each granule. Therefore, it is impossible for the raw material fiber to get entangled with each other. As a result, the reinforcement effect, which is the most important, is decreased, and it becomes impossible to provide the reinforcement effect in some cases.
Usually, granules are substantially spherical. When granules charged into a forming die are heat-formed at a predetermined temperature and pressure, it is difficult for each granule to be broken in the initial stage of heat-forming. Accordingly, there is a possibility that raw material of the friction material contained in granules is not sufficiently mixed with each other. As a result, uniformity of the friction material is deteriorated.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above circumstances. It is an object of the present invention to provide granules of raw material preferably used for manufacturing friction material handily at low cost without using a special apparatus.
The above object of the present invention can be accomplished by the granules of raw material used for manufacturing friction material described in the following item (1) and the method of manufacturing granules of raw material used for manufacturing friction material described in the following item (2).
(1) Granules of raw material used for manufacturing friction material obtained by crushing primary granules made by the granulation of starting raw material containing raw material fiber, raw material powder and binder for friction material.
(2) A method of manufacturing granules of raw material used for manufacturing friction material comprising the steps of: granulating starting raw material containing raw material fiber, raw material powder and binder for friction material so as to obtain primary granules; and crushing the primary granules.
In the granules of raw material used for manufacturing friction material obtained when the primary granules are crushed, which will be referred to as the secondary granules in this specification hereinafter, raw material powder is fixed onto the surface of raw material fiber by the binder and physical adsorption. Therefore, no raw material powder is disconnected from the surface of raw material fiber. On the other hand, the tensile strength of raw material fiber itself is high. Therefore, raw material fiber is seldom cut off even if it is given an external force, the intensity of which is sufficiently high to crush the primary granules. Accordingly, these secondary granules are obtained in such a changeable form that the raw material fiber holds the raw material powder and is exposed from the surface of the raw material powder.
When these secondary granules are used, it is possible to enhance the mechanical strength of the obtained friction material because the fiber material exposed from the surface of the raw material powder gets entangled with the raw material fiber of the adjacent secondary granules. In the secondary granules, a large number of protrusions of acute angles are formed in the process of crushing. Therefore, the secondary granules are easily broken in the initial stage of heat-forming, and the friction material is mixed with each other. As a result, it is possible to obtain friction material in which the raw material of friction material is uniformly dispersed. Further, shapes of the secondary granules are changeable and the sizes are changed variously. Accordingly, the forming die can be tightly filled with the secondary granules. Therefore, compared with a conventional case in which spherical granules are used, it is possible to obtain friction material of high density.
In the manufacturing process of the secondary granules, a series of processes including mixing, granulating and crushing of raw material can be conducted by the same mixer. Accordingly, no additional devices are required, and no cost is raised.
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Akebono Brake Industry, Co., LTD
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Medley Margaret
Toomer Cephia D.
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