Abstract:
A powder leveling method and apparatus capable of leveling to a uniform thickness a thin layer of powder containing fiber so as to form friction material having a multi-layered structure. A cavity of predetermined shape having an opening in a flat surface is filled with powder containing fiber so that the powder overflows the opening of the cavity in the flat surface. A cylindrical leveling device is moved in a first direction across the cavity and then in a second direction intersecting to the first direction at a speed greater than the speed with which the leveling device moves in the first direction, so as to trim away the excess powder and make it flush with the flat surface.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a leveling apparatus that measures a predetermined amount of powder, and more particularly, to a measurement method and a leveling apparatus suitable for powder used in a method for manufacturing friction material such as disc pads, brake linings, and clutch facings.  
         [0003]     2. Description of the Related Art  
         [0004]     Brake linings, clutch facings and the like are affixed to a brake shoe and a clutch disc, respectively, by an adhesive agent, rivets, or the like. Of these, some, like a disc pad, are made by attaching a metal plate called a back plate to the friction material by thermocompression molding.  
         [0005]     The friction material is formed by filling a thermocompression mold with powdered friction raw material, composed of a mixture of fiber, filler, binder and the like and heating and compressing it with a press machine (hereinafter “press”). There are two such methods of forming the friction material. One method involves directly filling the thermocompression mold with the powdered friction raw material and molding it by pressing it with a press. The other method involves filling the thermocompression mold with the powdered friction raw material and compressing it with a press without heating to form a preform. The preformis then put into a separate thermocompression mold and heated and pressed with a press. In a disc pad, the back plate overlays the powdered friction raw material and is heated and pressed so as to mold the back plate to the friction material.  
         [0006]     Although the above-described friction material may be a single layer composed of a single composition, it is not uncommon for the friction material to be of two- or a multi-layer construction. In disk pads in particular, in order to obtain adequate strength of adhesion and shearing strength between the back plate and the friction material, as well as both adequate heat insulation to retard the propagation of heat from the friction surface of the friction material to the back plate and adequate vibration absorption in order to prevent the occurrence of screeching, an intermediate layer composed of a material that behaves differently from the friction layer is often provided between the friction layer that acts as a brake and the back plate.  
         [0007]     In the conventional multi-layer friction material structure having two or more layers, the weight of both the raw material for the substantially powdered friction layer and the raw material for the substantially powdered intermediate layer, respectively, is measured, and as an initial step the raw material for the intermediate layer is spread to a uniform thickness inside a compression mold, after which the raw material for the friction layer is spread atop the raw material for the intermediate layer. The layers are then compressed with a press to form a preform. Where the step of creating a preformis not taken, a thermocompression mold is filled with the friction layer raw material and the intermediate layer raw material, the back plate is directly contacted against the material and the whole is heated and compressed by the press to form a finished product.  
         [0008]     However, with the above-described conventional method, because the powdered raw material for forming the intermediate layer is measured by weight and a given weight is either manually or mechanically spread to a uniform thickness inside the mold, it is easy for the thickness of the layer to be or become uneven. Typically, in contrast to the thickness of the friction material, which is approximately 10 mm, the thickness of the intermediate layer is approximately 1-2 mm. Given such thinness, any unevenness in the thickness of the intermediate layer can produce local deficiencies in that thickness, which in turn can give rise to insufficient adhesive strength, shearing strength, heat insulation, and vibration absorption. Consequently, conventionally, in part because it had been impossible to give the intermediate layer a uniform thickness, the intermediate layer has been made extra thick, so that, even if local thinness dose arise, there is no loss of the adhesive strength, shearing strength, heat insulation and vibration absorption properties described above.  
         [0009]     However, such an approach, while solving the problem of too little intermediate layer material, leads to the opposite problem of localized thickness of the intermediate layer, in other words, too much material. Where too thick, the intermediate layer becomes exposed extremely quickly once the friction material wears away, leading to localized deterioration in friction performance such as degradation of the coefficient of friction, of wear, and of fade resistance.  
         [0010]     Thus, as described above, where the friction material consists of a multi-layer structure, it is very difficult to make the thickness of the layers uniform.  
         [0011]     In order to overcome this drawback, Japanese Laid-Open Patent Publication No. 11-226979 proposes a friction material manufacturing apparatus like that shown in  FIG. 14 . That is, in  FIG. 14 , a slide plate  3  having a cavity  3   a  of a uniform depth is disposed so as to be horizontally slidable between a plunger  2  and a fixed mold  5  and a hopper  6  for intermediate layer raw material is provided near a frame  1 , with an exit aperture  6   a  contacting the slide plate  3 .  
         [0012]     The slide plate  3  itself is disposed so as to contact a bottom edge  1   b  of the frame  1 . A cavity  3   a  of the same shape as the friction material is provided in the shape of an aperture penetrating the slide plate  3 , with the bottom of the hole covered by a bottom plate  4 . Both the slide plate  3  and the bottom plate  4  can be moved in the horizontal direction. When the cavity  3   a  is positioned directly beneath the frame  1 , the bottom plate  4  rests atop the fixed mold  5 . A small cavity  4   a  corresponding to the boss of a preform is formed in the bottom plate  4 . The slide plate  3  and the bottom plate  4  break apart into two parts along an imaginary line that passes through the center of the small cavity  4   a.    
         [0013]     When the slide plate  3  moves horizontally and the cavity  3   a  comes under the hopper  6 , the cavity  3   a  and the small cavity  4   a  are filled with intermediate layer raw material  8 . When the slide plate  3  returns to its position beneath the frame  1 , the surface of the bottom edge  6   b  of the hopper  6  becomes a leveling plate that makes the thickness of the intermediate layer raw material  8  uniform. When the cavity  3   a  returns to a position beneath a cavity la in the frame  1 , a certain amount of friction layer raw material  9  enters the empty space la from above and is made a uniform thickness, after which the plunger  2  descends and compresses the layers of material to form a structure. By using multiple slide plates  3  and filing a different hopper with more powdered intermediate layer raw material, a multi-layered structure can be obtained.  
         [0014]     It is desirable that as much fibrous material as possible be mixed into the intermediate layer in order to increase the strength of adhesion and shearing strength between the back plate and the friction material. However, with the apparatus described in Japanese Laid-Open Patent Publication No. 11-226979, there is a limit to the amount of fiber that can be mixed into the intermediate layer. The intermediate layer has a thickness of approximately 1 mm when formed by thermocompression and the cavity  3   a  has a depth of approximately only several millimeters. If a large amount of fibrous material is mixed into the intermediate layer raw material, then when leveled by the surface of the bottom edge  6   b  of the hopper  6  as shown in  FIG. 14  the intermediate layer raw material cannot be leveled cleanly because the fibers that contact the surface of the bottom edge  6   b  of the hopper  6  are pulled along by the edge of the surface of the bottom edge  6   b  when pushed and moved by the surface of the bottom edge  6   b,  which in turn appears to cause a substantial amount of powdered raw material to be pulled along therewith. As a result, when leveling is finished, in some areas there is absolutely no powdered raw material at all, the leveled surface is not flush, and there are bumps and depressions. If the structure is exposed to thermocompression molding in this state, the result will be an uneven intermediate layer and/or friction material with no intermediate layer backing.  
       SUMMARY OF THE INVENTION  
       [0015]     Accordingly, the present invention is conceived as a solution to the above-described situation, and has as its object to provide a powder leveling method and apparatus that can trim a thin layer of powder containing fiber to a uniform thickness, and is capable of forming friction material into a multi-layer structure.  
         [0016]     To achieve the above-described object of the present invention, there is provided a powder leveling method comprising the steps of: 
        filling a cavity of predetermined shape with an opening in a flat surface with powder containing fiber so that the powder overflows the opening of the empty space in the flat surface;     leveling a heap of powder by moving a leveling means of which at least an edge portion of a bottom edge surface thereof is roughened in a first direction of movement over the empty space; and     leveling the powder by moving the leveling means in a second direction of movement intersecting to the first direction of movement, at a speed greater than a speed with which the leveling means moves in the first direction of movement.        
 
         [0020]     In addition, to achieve the above-described object of the present invention, there is also provided a powder leveling apparatus comprising: 
        a frame enclosing a cavity of a predetermined shape with an opening in a flat surface of the frame so that the powder overflows the opening of the empty space in the flat surface;     leveling means of which at least an edge portion of a bottom edge surface thereof is roughened so as to trim flush with the flat surface the powder filled into the empty space by moving the leveling means relative to the frame;     first movement means for leveling the powder by moving the leveling means or the frame in a first direction of movement over the empty space; and     second movement means for leveling the powder by moving the leveling means or the frame in a second direction of movement intersecting to the first direction of movement, at a speed greater than a speed with which the leveling means or the frame move in the first direction of movement.        
 
         [0025]     According to the invention described above, when the empty space is filled to overflowing with powder and is leveled by the leveling means, since the leveling means having a roughness on at least an edge portion of a lower edge surface thereof moves in a first direction as well as more quickly in a second direction intersecting to the first direction, when fibrous material caught on the edge portion of the bottom edge surface attempts to drag powdered raw material, the leveling means can trim while cutting through the fibrous material and stopping the dragging of the powdered raw material. Therefore, the powdered raw material is not dragged by the fiber and the powder can be leveledsmoothly, that is, without unevenness, and flush with the flat surface.  
         [0026]     Preferably, the leveling means is provided with a cylinder having a central axis perpendicular to the flat surface; 
        a bottom edge surface of the cylinder slides over the flat surface; and     the second direction of movement is rotation of the cylinder about its axis.        
 
         [0029]     According to the invention described above, a cylinder is used in the leveling means, and therefore movement in a second direction can be added simply by rotating the cylinder to enable leveling away of excess powder with ease.  
         [0030]     Preferably, the inner diameter of the cylinder is greater than the empty space.  
         [0031]     According to the invention described above, making the inner diameter of the cylinder greater than the empty space enables leveling to commence when the empty space enters the cylinder. As a result, excess powder can be held within the cylinder, without scattering, thus making collection unnecessary.  
         [0032]     Preferably, the vibrator is provided on the leveling means and the second direction of movement is a reciprocal sliding of the vibrator over the flat surface.  
         [0033]     Preferably, the leveling means is provided with a continuous belt, such that by rotation of the continuous belt one edge of the belt slides over the flat surface to achieve the second direction of movement.  
         [0034]     Preferably, the leveling means is a continuous line wound continuously between two separated pulleys and the second direction of movement involves rotating the continuous line about a hypothetical line connecting centers of the two pulleys while sliding the continuous line over the flat surface by rotating the two pulleys.  
         [0035]     According to the invention described above, a vibrator, belt or line can be used as the leveling means, such that scattering of the powder can be reduced.  
         [0036]     Preferably, the leveling means comprises a cylinder having a central axis perpendicular to the flat surface and a disk inside the cylinder having an eccentric aperture therein, the disk sliding over the flat surface, the disk rotatable with the cylinder and movable within the cylinder a predetermined distance along the central axis of the cylinder.  
         [0037]     According to the invention described above, by providing the cylinder with an axis of rotation perpendicular to the flat surface and a disk disposed within the cylinder that slides over the flat surface and in which is formed an eccentric aperture, the disk can be made to rotate together with the cylinder and to move a predetermined distance in the direction of the axis of rotation inside the cylinder, and thus excess powder can be swept away by the periphery of the eccentric aperture and held within the cylinder, making collection unnecessary.  
         [0038]     Preferably, the central axis of the cylinder and the axis of rotation of the motor are eccentric.  
         [0039]     According to the invention described above, by making the central axis of the cylinder and the axis of rotation of the motor eccentric, the direction of the second direction of movement is changed periodically, enabling powder to be leveled efficiently.  
         [0040]     Preferably, the frame comprises press molding apparatus frame molds and a lower mold movable between and relative to the frame molds, with the depth of the empty space being adjustable by changing the relative height of the frame molds and the lower mold.  
         [0041]     According to the structure described above, the leveling apparatus of the present invention can be easily adapted to a press molding apparatus used to form friction material, thereby enabling the manufacture with ease of friction material having a multi-layer structure in which the layers are of uniform thickness.  
         [0042]     Other features, objects and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
         [0044]      FIG. 1  is a diagram showing a longitudinal cross-sectional view of a press apparatus, in which a powder leveling apparatus is adapted to a press device as a machine for the manufacture of friction material, according to a first embodiment of the present invention;  
         [0045]      FIG. 2  is a diagram showing a plan view of the apparatus shown in  FIG. 1 , with the upper mold removed;  
         [0046]      FIG. 3  is a diagram showing a state in which the empty space is filled with a heap of powder for forming an intermediate layer;  
         [0047]      FIG. 4  is a diagram showing a state in which the powder in the empty space is leveled flush;  
         [0048]      FIG. 5  is a diagram illustrating a method for overlaying the powder of the intermediate layer with powder of a friction layer to a predetermined depth and leveling the friction layer flush;  
         [0049]      FIG. 6  is a diagram showing illustrating a method for overlaying the powder of the intermediate layer with powder of a friction layer to a predetermined depth and leveling the friction layer flush;  
         [0050]      FIG. 7  is a diagram showing a powder leveling apparatus according to a second embodiment of the present invention, which prevents peripheral scattering of the powder by a rotating body during leveling of the powder;  
         [0051]      FIGS. 8A and 8B  are diagrams showing a powder leveling apparatus according to a third embodiment of the present invention, in which  FIG. 8A  shows a plan view thereof and  FIG. 8B  shows a cross-section view thereof along a line B-B;  
         [0052]      FIG. 9  is a diagram showing a longitudinal cross-sectional view of a powder leveling apparatus according to a fourth embodiment of the present invention;  
         [0053]      FIG. 10  is a diagram showing a plan view of the apparatus shown in  FIG. 9 , with the upper mold removed;  
         [0054]      FIG. 11  is a diagram showing a longitudinal cross-sectional view of a powder leveling apparatus according to a fifth embodiment of the present invention;  
         [0055]      FIG. 12  is a diagram showing a plan view of the powder leveling apparatus according to the fifth embodiment;  
         [0056]      FIG. 13  is a diagram showing a perspective view of a powder leveling apparatus according to a sixth embodiment of the present invention; and  
         [0057]      FIG. 14  is a diagram showing a conventional apparatus for production of friction material. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0058]     Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.  
         [0059]      FIG. 1  is a diagram showing a longitudinal cross-sectional view of a press apparatus, in which a powder leveling apparatus is adapted to a press device as a machine for the manufacture of friction material, according to a first embodiment of the present invention.  FIG. 2  is a diagram showing a plan view of the apparatus shown in  FIG. 1 , with the upper mold removed. A press  10  forms a preform of friction material.  
         [0060]     In the diagrams, the frame molds  11 , which act as a frame, are provided with an empty space  11   b  in the center of a flat top surface  11   a  thereof. As shown in  FIG. 2 , the empty space  11   b  has the same shape as the preform.  
         [0061]     Inside the frame molds  11  there is a lower mold  12 . The lower mold  12  can ascend and descend within and relative to the frame molds  11 , and can be stopped at any position within the empty space  11   b.    
         [0062]     Above the frame molds  11  there is an upper mold  13 . The upper mold  13  can also ascend and descend within and relative to the frame molds  11 . Inside the empty space  11   b  in the frame molds  11 , and between the lower mold  12  and the upper mold  13 , pressure is applied to powdered friction material to form a preform.  
         [0063]     Up to this point, the friction material production apparatus is the same as the conventional art. What is distinctive about the present invention is the addition of a leveling means  15 .  
         [0064]     The leveling means  15  is slidably disposed atop the flat top surface  11   a  of the frame molds  11 . A hollow cylinder  15   a  thereof is rotated in a direction indicated by arrow b in  FIG. 2  by a motor  15   b.  The cylinder  15   a  is provided with a rough edge on at least a surface of a bottom edge  15   c  thereof. In other words, either the entire surface of the bottom edge  15   c  is a rough surface or the surface of the bottom edge  15   c  is smooth and only the edge thereof is rough. The cylinder  15   a  may be made of any material used in buffing having a rough surface of, for example, hard foamed polyurethane.  
         [0065]     As can be understood by those of ordinary skill in the art, although in the embodiment shown in the diagram the cylinder  15   a  of the leveling means  15  is hollow, the cylinder  15   a  is not limited to such a construction and therefore may, alternatively, be solid. However, a solid construction increases the surface area that contact the powder, and therefore a hollow costruction can be said to be preferable. If the outer diameter D of the cylinder  15   a  is made greater than the minor axis W of the empty space  11   b,  then the leveling means  15  will not fall into the empty space  11   b  even if the leveling means  15  is smaller than the major axis L of the empty space  11   b.    
         [0066]     The cylinder  15   a  and the motor  15   b  are coupled to each other by a moving means  15   d  fixedly mounted on the frame molds  11 , for example, and by a rod  15   e.  The exact structure of the coupling is not fixed, and thus, for example, a screw shaft may be used, or a rack and pinion arrangement, or a-pneumatic cylinder or hydraulic cylinder.  
         [0067]     In the above-described construction and in the following description, the direction indicated by arrow a is a first direction, the moving means  15   d  is a first-direction moving means, the direction indicated by arrow b is a second direction, and the motor  15   b  is a second-direction moving means.  
         [0068]     Next, a description will be given of a method of measuring powder A by the press  10 , such powder A being the raw material for the friction material.  FIG. 3  is a diagram showing a state in which the empty space  11   b  is filled with the powder A for forming the intermediate layer.  FIG. 4  is a diagram showing a state in which the powder A in the empty space  11   b  isleveled.  
         [0069]     As shown in  FIG. 3 , the lower mold  12  is stopped at an upper part of the empty space  11   b.  The depth H 1  of the empty space  11   b  is several millimeters. In the present invention, the depth is 6 mm. Moreover, as shown in  FIG. 2 , the empty space  11   b  has a length L of 100 mm and a width W of 50 mm, and the cylinder  15   a  has a diameter D of 200 mm and a thickness of 10 mm. As can be appreciated by those of ordinary skill in the art, these dimensions are purely illustrative and constitute merely one embodiment, and accordingly, the present invention is not limited thereto.  
         [0070]     The empty space  11   b  is filled with the powder A so as to overflow the space, as shown in  FIG. 3 . The powder A forms the intermediate layer of the friction material. In order to increase the strength of the adhesion and the shearing strength between the friction material and the back plate, the powder A that will become the intermediate layer contains at least 4 percent by volume fiber having a length of at least 500 μm. The fiber may be organic fiber, inorganic fiber, or metallic fiber. Any variety of synthetic fiber may be used for the organic fiber. For the inorganic fiber, glass fiber, rock wool and the like may be used. Steel, copper or the like may be used for the metallic fiber.  
         [0071]     Once the empty space  11   b  is filled with the powder A so as to overflow the space, the cylinder  15   a  of the leveling means  15  is rotated at 300 rpm, and slid over the flat surface  11   a  in the first direction a shown in  FIG. 4  at a speed of 30 mm/sec so as to pass over the empty space  11   b  and thus trim the heap of powder A flush with the flat surface  11   a.  The linear speed of the cylinder  15   a  is approximately 3100 mm/sec in a second direction b substantially perpendicular to the first direction a, or at least 100 times the 30 mm/sec speed of the cylinder  15   a  in the first direction a.  
         [0072]     It should be noted that although in the present embodiment the second direction b is substantially perpendicular to the first direction a, the invention is not limited to such an arrangement and there is no particular limitation on the angle at which the second direction b intersects the first direction a.  
         [0073]     Since at least the edge of the surface of the bottom edge  15   c  is a rough surface, and since the cylinder  15   a  is moving in the second direction b at a speed greater than the speed with which it moves in the first direction a due to the rotation described above, when the edge of the bottom edge surface  15   c  pushes against and tries to drag the fiber material contained in the powder A, such dragging can be broken off, thus eliminating the dragging of the powdered raw material, and the cylinder  15  can pass over the empty space  11   b  and trim the powder A flush with the flat surface  11   a.  Thereafter, excess powder A is collected by a vacuum device, not shown, and reused.  
         [0074]     Initially, the lower mold  12  is lowered a distance H 2  (shown in  FIG. 5 ) from the position shown in  FIG. 4 . The distance H 2  is greater than the depth H 1 , being approximately 30-40 mm. The empty space  11   b  thus formed is then filled to overflowing with the powder B that will become the friction layer. The powder B is a composition designed to maintain performance as a friction layer.  
         [0075]     Once the empty space  11   b  is filled to make a heap of the powder B, the cylinder  15   a  of the leveling means  15  is rotated/moved at the same rotation speed and velocity as with powder A, and passed over the empty space  11   b  so as to trim the powder B flush with the flat surface  11   a.  If the leveling means  15  used to trim powder B is different from that used for leveling powder A, then mixing of powder B with powder A can be prevented. Thereafter, though not shown in the drawings, the upper mold  13  is lowered into the empty space  11   b  and powders A and B are compressed to form a preform consisting of two layers, an intermediate layer and a friction layer.  
         [0076]     Although the foregoing description pertains to a two-layer construction, it applies equally well to a structure consisting of three or more layers. In addition, although in the embodiment shown the cylinder  15   a  rotates about a central axis, alternatively, the cylinder  15   a  may be given an eccentric rotation, and further, the axis of rotation may itself be circular, imparting a double rotation to the cylinder  15   a.    
         [0077]      FIG. 7  shows a second embodiment of the present invention, which prevents peripheral scattering of the powder when leveled by a rotating body. The leveling means  16  is provided with a hollow cylinder  16   a  and a motor  16   b.  The hollow cylinder  16   a  has an inner diameter sufficiently large to cover the empty space  11   b.  As shown in  FIG. 3 , the empty space  11   b  is filled to overflowing with powder A and the hollow cylinder  16   a  covers the powder A from the outside. When in such state the hollow cylinder  16   a  is then rotated and moved in the direction indicated by arrow a, the excess powder A is moved away from the empty space  11   b  on the flat surface  11   a  in a state in which the excess powder A remains inside the hollow cylinder  16   a,  without scattering outside the hollow cylinder  16   a.  Thereafter, the excess powder A removed from the empty space  11   b  on the flat surface  11   a  is collected by a vacuum or the like. Although not shown, the first-direction moving means  15   d  can be mounted as necessary.  
         [0078]      FIGS. 8A and 8B  are diagrams showing a powder leveling apparatus according to a third embodiment of the present invention, in which  FIG. 8A  shows a plan view thereof and  FIG. 8B  shows a cross-section view thereof along a line B-B. The leveling means  20  of this embodiment is comprised of a cylinder  21 , a disk  22  contained within the cylinder  21  that rotates with the cylinder  21 , a flange  23  provided along the outside of the cylinder near a top edge thereof, four driving means  24  that support the flange  23  from below, and four guide rollers  25  that guide the rotation of the cylinder  21 . The disk  22  is provided with an eccentric aperture  22   a  formed therein and a projection  22   b  extending therefrom. The projection  22   b  engages a groove formed in the cylinder  21  to stop the rotation of the disk. In addition, the projection  22   b  moves within the groove in the cylinder  21  so as to allow the disk  22  to move in an axial direction (that is, vertically in the diagram). With such a structure, although the disk  22  rotates with the cylinder  21 , the disk ascends and descends inside the cylinder  21 . At the same time, since the cylinder  21  itself does not trim, it is preferable that a slight gap be maintained between it and the flat surface  11   a.    
         [0079]     Although not shown, the leveling means  20  is provided with first-direction moving means  15   d  like the first embodiment shown in  FIG. 1 , and is similarly coupled thereto by the rod  15   e.  The driving means  24  are provided with second-direction moving means in the form of four motors  24   a,  one motor for each driving means. When the motors  24   a  rotate, a drive roller  24   b  also rotates and the flange  23  rotates in the second direction b, rotating the cylinder  21  and the disk  22  inside the cylinder  21 . Since the aperture  22   a  formed in the disk  22  is eccentric, the powder is cut by rubbing, between an edge of the aperture  22   a  and a bottom surface of the disk  22 . At the same time, the leveling means  20  moves in the first direction, and therefore can cut by rubbing the entire top surface of the empty space  11   b.  Moreover, it should be noted that although four motors  24   a  are shown, alternatively, one motor is sufficient and may be used instead of four.  
         [0080]      FIG. 9  and  FIG. 10  are diagrams showing a powder leveling apparatus according to a fourth embodiment of the present invention, with  FIG. 9  showing a longitudinal cross-sectional view thereof and  FIG. 10  showing a plan view thereof from which the upper mold has been eliminated for the sake of clarity.  
         [0081]     As described with reference to the second embodiment shown in  FIG. 7  as well, the leveling means  15  shown in  FIG. 1  cuts by rubbing along the outer periphery of the cylinder  15   a,  and consequently scatters powders A, B widely, creating the problem of lengthy collection time. The fourth embodiment solves this problem by using a reciprocating vibrator.  
         [0082]     In other words, in  FIGS. 9 and 10 , the leveling apparatus  10  is comprised of leveling means  28 , a vibrator  28   a  and driving means  28   b.  An object having an uneven, saw-toothed forward edge surface  28   c  may be used as the vibrator  28   a.  Alternatively, instead of a saw, the forward edge surface  28   c  may be a brush or a comb.  
         [0083]     Although the driving means  28   b  may be a vibrator, preferably the driving means  28   b  may be like an air cylinder, that is, has a large stroke of several cm. In the present embodiment, the amplitude of the stroke in the second direction b is 30 mm, the cycle is 5 strokes/second, and the speed of leveling in the first direction a is 10 mm/sec, which nevertheless can trim to a flat surface without unevenness in the leveled surface. In this instance, the speed in the second direction b is 300 mm/second, or 30 times the speed of 10 mm/second in the first direction a.  
         [0084]     It should be noted that although the vibrator  28   a  is a plane, and in the embodiment shown in  FIGS. 9 and 10  is disposed at an angle to the flat surface  11   a,  alternatively the vibrator  28   a  may be disposed parallel to the flat surface  11   a.  In the latter case, however, the excess powder A can only be carried away with difficulty, and therefore in such a case it is preferable that the vibrator  28   a  be shaped into the form of an L in cross-section, with the long vertical line thereof disposed perpendicular to the flat surface  11   a,  so as to carry away the excess powder A.  
         [0085]     When the leveling means  28  moves in a first direction, it combines with the reciprocal movement in the second direction perpendicular to the movement in the first direction, and therefore it is possible that the leveling means  28  might lack sufficient power to remove any excess powder A, B from atop the empty space  11   b.  In such an instance, a c-direction swinging centered on the driving means  28   b  side of the leveling means  28  may be added, and can be accomplished by swinging the driving means  28   b  by a separate swinging movement means.  
         [0086]      FIG. 11  and  FIG. 12  are diagrams showing a fifth embodiment of the present invention, in which  FIG. 11  shows a longitudinal cross-sectional view and  FIG. 12  shows a plan view thereof. The leveling means  30  of the present embodiment is comprised of a continuous belt  30   a  stretched between two pulleys, with a motor  30   b  mounted on one of the pulleys as a second-direction driving means. An edge of a bottom side of the continuous belt  30   a  contacts the flat surface  11   a.  Although not shown, by mounting the first direction driving means  15   d  and the rod  15   e  shown in  FIG. 1  on the motor  30   b,  the leveling means  30  can be driven in the first direction indicated by arrow a. Of course, the first-direction driving means is not limited to such an arrangement.  
         [0087]     When the empty space  11   b  is filled to overflowing with powder A and the motor  30   b  is rotated, the continuous belt  30   a  rotates in the second direction b. In such a state, driving the leveling means  30  in the first direction a with the first-direction driving means  15   d  causes the bottom of the continuous belt  30   a  to slide along the flat surface  11   a  so as to remove excess powder from atop the empty space  11   b.    
         [0088]      FIG. 13  is a diagram showing a perspective view of a sixth embodiment of the present invention. The leveling means  35  of this embodiment is comprised of a continuous line  35   a  wound between two pulleys  35   b,    35   c.  When the motor  35   d  rotates, the continuous line  35   a  slides over the flat surface  11   a  so as to trim powder from atop the empty space  11   b.  It is preferable that the surface of the line  35   a  be rough, and may be rope made of twisted fiber.  
         [0089]     Furthermore, in the present embodiment, additionally, a motor  35   e  rotates a frame that supports the two pulleys  35   b,    35   c  so as to rotate the line  35   a  about a hypothetical line X connecting the centers of the two pulleys  35   b,    35   c  (the line X being identical to the axis of rotation of the motor  35   e ). In the present embodiment, the motor  35   d  and the motor  35   e  together comprise the second-direction moving means. By adding rotation in the direction indicated by arrow c in  FIG. 13 , excess powder can be removed from atop the empty space  11   b.    
         [0090]     As described above, the powder leveling method and leveling apparatus of the present invention is suitable for the manufacture of brake, clutch or other friction material used in automobiles and other vehicles, and in particular to the production of multi-layered friction material consisting of multiple thin layers.  
         [0091]     As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific preferred embodiments described above thereof except as defined in the claims.