Title of Invention

METHOD FOR PRODUCTION OF A MULTI-LAYER CARBOBN BRUSH .

Abstract

Method for producing a multi-layer carbon brush (10) consisting of at least two electrically conductive functional layers (12, 14, 16) made of carbon material and at least one insulating layer (18) made of electrically insulating material, running between successive functional layers, characterized in that the carbon material or material containing it as filler and the electrically insulating material are added layer-by-layer in powder form in a mold (28) in the sequence corresponding to the layer sequence of the multi-layer carbon brush (10) to be produced are then pressed and subsequently heat-treated.

Full Text

Description Method for Producing a Multy-layer carbon Brush The invention relates to a rnethod fo producing a multi-layer carbon brush consisting of at least two electrically conductive functional layers made of carbon material and at least one insulating layer made of electrically insulating material and continuously running between the successive first functional layes. Multi-layer carbon brushes, which consist of carbon bars and insulating layers extending between them, are frequently used for smaller reversibe motors such as those found in washing machines. The insulating layer can consist of a film, an insulating adhesive, synthetic resin, or one or more powoer resins Due to the higher transverse resistance the current flowing between the two dirks of a commutator covered by the carbon brush is reduced, thereby improving commutation. The familiar multi-layer carbon brushes of the type described above are generally produced by aligning initially heat-treated carbon plates with each other in such a manner that allows a film to be inserted between them. The products are then machined and shaped before the ropes or cords are finally inserted. We are also aware of carbon brushes described as multi-layer carbon brushes in which the layers are all electrically conjuctive yet wherein each layer can each exhibit different mechanical properties. A carbon brush of this type is described in DE 91 06 977 U1. Being of different material competition, the various layers - also referred to as zones -can be formed by successively placing two starting layers of different material composition in a mold prior to pressing the carbon brushes and then by pressing said layers together. This method can thereby allow one zone 1o have a higher copper content than the other. As described in DE 44 30 7A5 a carbon brush referred to as a multi-layer sliding contact is comprised of layers each for sisting of a conductive powder To produce the multi-layer sliding contact, two conductive powders are simultaneously poured into a mold in which a heat treatment process is performed following compression Not only does this method allow the formation of layers through the :.imultaneous addition of powder to a mold, but it also facilitates the formation of adc itional layers through the successive placement of electrically conductive powder into the mold. DE-C-835 428 describes a highly-pohshed hard coal molded body as an applied arts object and a method for its production. To acomplish this, carbon is added to a mold, pressed, and then pre-sintered before being machined in order to cost or impregnate the body with oil-containing pastes prior to final sintering. DE-C-636 540 describes a method for producing mult-layer carbon brushes. Finished carbon layers are first smoothed. Viscous resin with an insulating material is then placed between the two finished carton layers. The carbon layers are then clamped into a special pressing tool to facilitate drying in a furnace. A method for producing a laminated material made of carbon is described in DE 33 07 090 A1. To achieve the desired end product, films made of thermoplastic resin are placed through pressing and heat-treatment between carbon layers such as carbon felt layers that can be stacked on top of each other, and the stack is then subjected to the desired pressure and temperature levels. DE 199 02 938 A1 relates to a carbon brush that is composed of sections having different material compositions. In th s case, the carbon brush is produced through a pressing process. The object of the present invention is to develop a process for producing a multi-layer carbon brush consisting of at least two electrically conductive functional layers and an insulating layer running between successive functional layers in such a manner that constitutes both an improvement and simplification of the current process and also allows for the easy integration of the insulating layer with he application area of the multi-layer carbon brush The adjustment of material properies such as porosity or fnction values shall also be facilitated without difficulty. Moreover, easy individual adjustment of the thickness levels of the functional layers shall be enabled without requiring complex machining measures The invention demonstrates that the problem can be essentially resolved by applying layers of the carbon material or canon-containing material as filler and the electrically insulating -material - in powder form - into a moid following a sequence that corresponds to the layer sequence of the multi-layer carbon brush to be produced, before pressing and finally subjecting the product to hea -treatment. When doing so, the insulating material should be added into the mold with an appropriate layer height so that the insulating layer in the finished multi-layer carbon brush has s thickness d of preferably 100 pm The invention is particularly characterized by a method for producing multilayer carbon brushes consisting of at least two electrically conductive functional layers made of carbon material and at least one insulating layer made of elecincally insulating material running between successive functional layers and comprises the fo lowing procedural steps - creation of a plate by filling a mold with layers of carbon material or a carbon-containing material in powder form and electrically insulating material in powder form or in the form of a film corresponding to the multi-layer carbon brush to be produced, pressing of the layers present in the mold to form the plate heat treatment of the plate, and - division of plates into sizes corresponding to the multi-layer carbon brushes or their final contours. Shaping and the insertion of the cord or rope shall be performed according 1:0 the current art. The invention teaches that the manufacture of a mass-produced laminate carbon brush only requires a heat-treating step :o facilate the production of a quantity of multi-layer carbon brushes. By contrast, according to the state of the art the plates made from carbon are either produced separately from each other, or carbon brushes consisting of several layers with electrically conductive properties are produced individually, when the stalling materials are initially added to a mold. The invention specifically sug jests for use as the electrically insulating material a synthetic resin powder, organic or inorganic insulating film such as AI2O3 film, one or more powder resins such as phenol or epoxy resins, tissue film, fiber mat, self-adhesive or adhesive-activgted films or combinations thereof. Below are the specifications of the preferred material composition for the multi-layer carbon brushes to be produced or the plates from which they are to be made. About 50% by weight .natural graphite, about 50% by weight synthetic graphite, about 25% by weight phenol or epoxy or thermoplastic resin in powder form, up to about 40% by weight hard coal tar pitch, wherein tne latter relates to 100% by weight filler, i.e. natural graphite and synthetic graphite. The desired quantity of the specified material composition is thus placed in powdered form into a pressing mold layer-by-!ayer and separated by the electrically insulating material. After the pressing process, it is either heat-treated, e.g. over a period of about 15h up to a temperature T1 of about 200°C, or anrealed up to an end temperature T2 of about 600°C. Further details, benefits and features of the invention are described not only in the claims, the features disclosed in said claims - either alone and/or in combination -, but also in the following description of preferred exemplary embodiments shown in the drawing. Shown are: Fi9- 1 a schematic illustration of a multi-layer carbon brush with three functional layers, -Fig. 2 a part of the carton brush from Fig. 1, Fig. 3 a schematic illus :ration of a mold used to produce plates, and Fig. 4 multi-layer plates used to produce multi-layer carbon brushes The invention relates to a nnethod fo producing a multi-layer carbon bush In this context, multi-layer carbon brushes shall be defined as brushes in which an insulating layer runs between functional layers consisting of electrically conducive material made of carbon material or carbon-containing material - also referred to a carbon bars. The invention describes a process for manufacturing multi-layer carbon brushes with two or more functional layers. Fig. 1 shows a basic sketch o1 a multi-layer carbon brush 10 with three carbon bars 12, 14, 16, which are insulated from each other by means of insulating layers 18. The carbon bars 12, 14, 16 as well as the insulating layers 18 extend perpendicularly to the running surface 20 of the carbon brush. A stamping contact 24 with rope or cord 26 extends from the surface 22 opposite the running surface 20 Regarding this feature, however, reference shall be made to already known designs of multi-layer carbon brushes of the type described above. The invention proposes the production of multi-layer carbon brushes through the successive addition of the materials forming the individual layers XZ, 14, 16, 18 in the desired layer sequence into a die 28 of a pressing device 30. In the die 28 a stamp 32 is arranged adjustably to allow the die 28 to be filled with the various materials in the desired quantity. After the material for a respective layer has been placed in the die, excess material is removed by means of a slide: 34. After the desired materials made of carbon and those composed of electrically insulating material have been pla;ed in the die 28 layer-by-layer, the layers are pressed into form b/ means of a stamp 36. It is provided pursuant to the invention that the cross-section of the the 28 is selected such that it leads to a multi-layer plate 38, which upon removal from the die 28 and upon heat-treating can be divided in the familiar fashion into sections 40, 42, 44, the dimensions of which correspond to the multi-layer carbon brushes to be produced. Sh.aping of the sections 40, 42, 44 and insertion of the rope are performed in the familiar fashion. The plate 38 shown in Fig. 4 composes the functional layers 46, 48 consisting of carbon material, between which the layer 50 consisting of electrically insulating material runs. If the insulating layer 18, 30 s obtained preferably through a pressing process involving powdered materials, then filrr made from electrically insulating material can be placed between the individual layers consisting of carbon material, which can then be pressed in a die 28 with the carbon mater al or carbon containing material in the die 28. The following types of films can be used: inorganic or organic films such as e.g. AI2O3 film, tissue films or fiber mats, self-adhesive or adhesive-activated films can oe used The films may have to be activated. The invention teaches that it is possible to produce mult -layer carbon brushes in a simple manner, wherein said brushes have insulating layers with desired levels of thickness. In this case, it is therefore only necessary to fill the pressing mold 30 with the desired quantity of insulating material. However, insulating material should be added in such a quantity to allow for an insulating layer thickness of between 100 urn anc 500 mm following the pressing of materials. Independent thereof, desired mate-rial properties of the individual layers, such as porosity, can be easily modified by adjusting, for example, fill levels or pressing parameters,. WE CLAIM: 1. Method for producing a multi-layer carbon brush (10) consisting of at least two electrically conductive functional layers (12, 14, 16) made of carbon material and at least one insulating layer (18) made of electrically insulating material, running between successive functional layers, characterized in that the carbon material or material containing it as filler and the electrically insulating material are added layer-by-layer in powder form in a mold (28) in the sequence corresponding to the layer sequence of the multi-layer carbon brush (10) to be produced are then pressed and subsequently heat-treated. 2. Method as claimed in claim 1 wherein the insulating material is placed in the mold (28) at an appropriate layer thickness so that the insulating layer in the finished multi-layer carbon brush (10) has a thickness d of preferably 100um 500 urn. 3. Method for producing multi-layer carbon brushes consisting of at least two electrically conductive functional layers (46, 49) made of carbon material and at least one insulating layer (50) made of electrically insulating material, running between successive first functional layers, wherein the following procedural steps: - production of a plate (38) by placing layers, which correspond to the multi-layer carbon brush to be produced, of carbon material 01 carbon-containing material as filler in powder form and electrically insulating material in powder form or in the form of a film into a mold (28), - pressing of the layers present in the mold to form the plate (38), - heat treatment of the plate (38), and - division of the plate into sizes corresponding to the multi-layer carbon brushes or their final contours. 4. Method as claimed in claim 3, wherein a synthetic resin powder, organic or inorganic insulating film such as AI2O3 film, one or more powder resins such as phenol or epoxy resins, tissue film, fiber mat, self-adhesive or adhesive-activated films or combinations thereof are used as the electrically insulating material. 5. Method as claimed in claim 1, wherein natural graphite, synthetic graphite as well as resin such as phenol resin and/or pitch are used as electrically conductive starting material for the electrically conductive functional layer. 6. Method as claimed in one of the claims 3-5, wherein about 50% by weight natural graphite and about 50% by weight synthetic graphite as well as about 25% by weight resin such as phenol resin or about 40% by weight pitch are used as the starting material, wherein the resin and/or pitch shall correspond to 100% by weight of the filler in the form of natural graphite and synthetic graphite. Method for producing a multi-layer carbon brush (10) consisting of at least two electrically conductive functional layers (12, 14, 16) made of carbon material and at least one insulating layer (18) made of electrically insulating material, running between successive functional layers, characterized in that the carbon material or material containing it as filler and the electrically insulating material are added layer-by-layer in powder form in a mold (28) in the sequence corresponding to the layer sequence of the multi-layer carbon brush (10) to be produced are then pressed and subsequently heat-treated.

Documents:

1427-kolnp-2004-granted-abstract.pdf

1427-kolnp-2004-granted-claims.pdf

1427-kolnp-2004-granted-correspondence.pdf

1427-kolnp-2004-granted-description (complete).pdf

1427-kolnp-2004-granted-drawings.pdf

1427-kolnp-2004-granted-examination report.pdf

1427-kolnp-2004-granted-form 1.pdf

1427-kolnp-2004-granted-form 18.pdf

1427-kolnp-2004-granted-form 2.pdf

1427-kolnp-2004-granted-form 26.pdf

1427-kolnp-2004-granted-form 3.pdf

1427-kolnp-2004-granted-form 5.pdf

1427-kolnp-2004-granted-reply to examination report.pdf

1427-kolnp-2004-granted-specification.pdf

1427-kolnp-2004-granted-translated copy of priority document.pdf