Patent Publication Number: US-6981303-B2

Title: Blank feeding method

Description:
TECHNICAL FIELD 
     The present invention relates to a blank feeding method in which a billet for use in plastic working is cut into blanks of a predetermined thickness and the cut blanks are fed to a press molding device. 
     BACKGROUND ART 
     A method of cutting a billet into blanks is disclosed in, for example, {circle around (1)} Japanese Patent Laid-Open Publication No. 2001-321871, “Method of Press Molding Aluminum-based-composite Disc-like Parts.” A method of feeding blanks heated to a predetermined temperature is disclosed in, for example, {circle around (2)} Japanese Patent Laid-Open Publication No. HEI-6-198413, “Solid-liquid-coexisting-range Die Casting Method.” 
     The press molding method of the conventional art {circle around (1)} will be described below with reference to  FIG. 12 . 
     First, alumina (Al 2 O 3 ) powder is formed into a predetermined shape in advance, being a porous alumina compact. Then, the compact is reduced and a molten aluminum alloy is infiltrated into the reduced porous structure, producing an aluminum-based-composite billet  101 . 
     The aluminum-based-composite billet  101  is successively cut by a cutter  102  to a predetermined thickness t, forming a blank material  103  of the aluminum-based composite. Then, the blank material  103  is placed on a metal mold for molding. 
     In the cutting method of the conventional art {circle around (1)}, however, the cutter  102  cuts the aluminum-based-composite billet  101  with the blade of the cutter  102  wearing away soon, increasing the frequency of replacement of the cutter  102 , and increasing production cost. The increased frequency of replacement of the worn-out cutter  102  lengthens the stop time of the cutting machine, resulting in poor productivity. Further, a machining allowance corresponding to the width dimension of the cutter  102  is required, reducing the yield of the expensive aluminum-based composite. 
     The die casting method of the conventional art {circle around (2)} comprises the following steps: 
     (a) first, a round bar is cut at a predetermined length, and a cut material is put into a metal container with its internal surface coated in advance with a mold release agent; 
     (b) then, the material put in the container is heated in a heating furnace to a solid-liquid coexisting temperature range of the material. After the heating, the container containing the material is put out from the furnace and is carried to a sleeve insertion opening; and 
     (c) finally, the container is upset (inverted 180°), letting only the material fall into the sleeve, thus injecting the heated material into a mold cavity. 
     The use of the die casting method, however, requires the step of inverting the container after heating the container to let the material fall from the container, taking time for handling the material, and resulting in poor productivity. Further, the cutting work of cutting the round bar to a predetermined length of materials, producing a plurality of materials from the single round bar takes time. Especially with a round bar of a hard-to-cut material, the work takes time, increasing production cost. 
     DISCLOSURE OF THE INVENTION 
     It is an object of the present invention is to provide a blank feeding method which allows increased productivity and thus allows reduced production cost. 
     According to the present invention, there is provided a method of feeding a blank by cutting a billet for plastic working, which comprises the steps of: superimposing a plurality of annular members having a coefficient of linear expansion smaller than that of the billet and an inside diameter slightly greater than the outside diameter of the billet on one another to assemble a tubular jig; inserting the billet into the assembled jig; heating the billet and the jig to a temperature at which the billet is half-molten; and cutting the billet into at least one blank by moving the annular members adjacent to one another in opposite directions. 
     The billet expands by heating, eliminating clearance, contacting at its outer peripheral surface to the inner surface of the jig, and causing a compressive force on the billet. With the compressive force, the jig holds the billet so as to prevent its moving inside the jig, causing no sliding in the axis direction, and facilitating the cutting in the subsequent step. Heating the billet to a half-melting temperature together with the jig reduces the shearing resistance of the billet. As a result, the cutting of the billet in the following step is facilitated. 
     In the step of cutting the billet into the blank, the billet is cut by half-melting the billet and moving the adjacent annular members in the opposite directions, which eliminates the need for a cutting tool such as a cutter. As a result, there occurs no wear of blades caused by using a cutting tool such as a cutter, incurring no purchase cost of cutting tools. 
     Since the billet is half-melt and the adjacent annular members are moved in the opposite directions, thereby to cut the billet, there is no need to provide a machining allowance for cutting. As a result, yields of the billet are increased, reducing production cost. 
     Further, since the billet is half-melt and the adjacent annular members are moved in the opposite directions, thereby to cut the billet, the jig can cut the billet into a plurality of blanks at a time, increasing productivity. 
     In the step of disposing the blank on a press molding device, the blank, being fitted in the annular member, is carried to the press molding device, so that the blank can be disposed on the press molding device before the temperature of the blank decreases, eliminating the need for reheating the blank before molding. 
     In addition, since the blank, being fitted in the annular member, is fed to the press molding device, a locating portion of the annular member can be brought to a locating portion of the press molding device, setting the blank in a predetermined position, and facilitating the positioning of the half-molten blank. 
     In a preferred embodiment of the present invention, the blank feeding method further comprises the step of disposing the blank, being fitted in the annular member, on the press molding device. 
     The press molding device preferably has a mold half having fitting holes for receiving the plurality of annular members with the blanks fitted therein, and the blank disposing step comprises fitting the plurality of annular members into the fitting holes. 
     In another preferred embodiment of the present invention, the annular member has a grip protruding outward of an outer peripheral surface, and the blank disposing step includes carrying the annular member to the press molding device by holding the grip. 
     The heating may be performed by an induction heating method. With this, the heating time of the billet is shortened and the cycle time of the heating step is shortened. 
     The billet is preferably formed with an aluminum-based composite. The aluminum-based composite is cut by inserting the aluminum-based composite into the jig and moving the adjacent annular members in the opposite directions, which eliminates the need for a cutting tool for cutting the aluminum-based composite. As a result, no cost occurs for purchasing cutting tools to be subjected to severe wear for the aluminum-based composite. Further, since the aluminum-based composite is cut by moving the adjacent annular members in the opposite directions, no cutting tool is necessary for cutting the aluminum-based composite. As a result, there is no need to provide a machining allowance for cutting, increasing the yield of the expensive aluminum-based composite. 
     The jig is preferably formed with austenitic stainless steel. With this, an induction heating method can inductively heat only the billet without inductively heating the austenitic stainless steel, enlarging the expansion difference, and increasing the compressive stress of the billet. As a result, the cutting in the subsequent step is facilitated. The use of the austenitic stainless steel can apply a compressive force to the aluminum-based composite inside the jig by the thermal expansion difference because the coefficient of linear expansion of the austenitic stainless steel is smaller than the coefficient of linear expansion of the aluminum-based composite. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a flowchart of a blank feeding method according to the present invention; 
         FIG. 2  is a schematic perspective view illustrating an assembling step of a jig used for cutting a billet and a billet inserting step; 
         FIG. 3  is a plan view illustrating the billet inserting step; 
         FIG. 4  is a schematic diagram illustrating the step of heating the billet to a half-melting temperature; 
         FIGS. 5A to 5C  are schematic side views illustrating the step of cutting the billet into blanks; 
         FIG. 6  is a partial schematic diagram of the blank fitted in an annular member before being fed to a press molding device; 
         FIG. 7  is a schematic cross-sectional view illustrating the blank, being fitted in the annular member, disposed on a lower mold half of the press molding device; 
         FIG. 8A  is a schematic cross-sectional view illustrating the molding of the half-molten blank disposed on the lower mold half in  FIG. 7 ; 
         FIG. 8B  is a schematic diagram of a molded part resulting from the molding of the half-molten blank in  FIG. 8A ; 
         FIG. 9A  is a schematic perspective view illustrating the way of disposing blanks on another lower mold half of the press molding device; 
         FIG. 9B  is a schematic cross-sectional view of the blanks disposed on the lower mold half in  FIG. 9A ; 
         FIG. 10A  is a schematic side view illustrating partially in cross-section the molding of the blanks in  FIG. 9B ; 
         FIG. 10B  is a schematic diagram illustrating molded parts resulting from the molding in  FIG. 10A ; 
         FIG. 11A  is a schematic perspective view illustrating an annular member according to a modification, with a blank fitted therein; 
         FIG. 11B  is a schematic perspective view illustrating the way of disposing the annular member in  FIG. 11A  on a lower mold half according to another modification; and 
         FIG. 12  is a schematic perspective view illustrating the conventional billet cutting method. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A blank feeding method according to the present invention will be described with reference to  FIGS. 1 and 2 . In  FIG. 1 , ST denotes a step. 
     First, annular members  15  to  18  having a coefficient of linear expansion smaller than that of a billet  11  are superimposed on one another, assembling a tubular jig  12  (ST 01 ). Then, the billet  11  is inserted into the tubular jig  12  (ST 01 ). Thereafter, the billet  11  and the jig  12  are heated to a temperature at which the billet  11  is half-molten (ST 03 ). Successively, the adjacent annular members  15  to  18  are moved in opposite directions, thereby cutting the billet  11  into blanks  31  of a predetermined dimension (ST 04 ). Finally, the blanks  31 , being fitted in the annular members  15  to  18 , are disposed on a press molding device  32  (ST 05 ). 
     Now ST 01  to ST 05  will be described in more detail especially with reference to  FIG. 2 . 
     First, the jig  12  used for cutting the billet  11  is assembled. Specifically, the jig  12  consists of circular press plates  13  and  14  provided at its opposite ends for holding the opposite ends of the billet, the first annular member  15 , the second annular member  16 , the third annular member  17  and the fourth annular member  18  arranged in a superimposing manner between the press plates  13  and  14 , and bolts  21  and  22  for uniting those annular members. The first to fourth annular members  15  to  18  are superimposed on the press plate  14  and the bolts are fastened, thereby assembling the tubular jig  12 . 
     The first annular member  15  has an inner peripheral portion  15   a  of an inside diameter Di slightly greater than the outside diameter Db of the billet  11 . An outer peripheral portion  15   b  outside the inner peripheral portion  15   a  is provided with a grip  15   c  of a width W. The grip  15   c  has a hole  15   d.    
     The first annular member  15  is formed with a material such as austenitic stainless steel (e.g., JIS SUS304) having a coefficient of linear expansion smaller than that of the billet  11 . The second to fourth annular members  16  to  18  are each identical with the first annular member  15  and will not be described. Reference signs  16   c  to  18   c  denote grips of the second to fourth annular members  16  to  18 , and  16   d  to  18   d  denote holes of the annular members  16  to  18 . 
     The billet  11  is formed with an aluminum-based composite, for example. 
     The aluminum-based composite is made, for example, by forming in advance alumina (Al 2 O 3 ) powder into a porous alumina compact of a predetermined shape, reducing the alumina compact under an atmosphere of magnesium nitride, exposing the metal for good wettability, and infiltrating a molten aluminum alloy into the porous structure. The aluminum-based composite thus has good formability with the aluminum and the reinforcing material firmly combined at an interface threrebetween by chemical contact. 
     The billet  11  is successively inserted into the tubular jig  12  as shown by arrow {circle around (1)}. 
     After the insertion of the billet  11  into the jig, the press plate  13  is placed on the first annular member  15  and the bolts  21  and  22  are fastened as shown in  FIG. 3 . 
     The billet  11  is disposed with a clearance C equally provided between the outer peripheral surface of the billet  11  and the inner peripheral surface of the jig  12 . The billet  11  may be disposed to partially contact the jig  12 . 
     As has already been mentioned, the jig  12  is provided with the inside diameter Di slightly greater than the outside diameter Db of the billet  11  so as to provide the predetermined radial clearance C between the tubular jig  12  and the billet  11 . Specifically, with the coefficient of linear expansion of the billet  11  as β, with the coefficient of linear expansion of the jig  12  as α, with the temperature of the jig  12  and the billet  11  at room temperature as T 1 , and with the heating temperature as T 2 , the clearance C is 2×C&lt;(Db×β−Di×α)×(T 2 −T 1 ). 
     The coefficient of linear expansion a of the jig  12  is α&lt;β. 
     To meet those conditions, an aluminum-based composite is used as the material of the billet  11  and austenitic stainless steel as the material of the jig  12 . Since the coefficient of linear expansion of the austenitic stainless steel is smaller than the coefficient of linear expansion of the aluminum-based composite, the difference in thermal expansion allows the application of a compressive force to the aluminum-based composite inside the jig  12 . 
     The coefficient of linear expansion of the aluminum-based composite is 19.3×10 −6 /°C., and the coefficient of linear expansion of the austenitic stainless steel (JIS SUS304) is 18×10 −6 /°C. 
     In  FIG. 4 , the billet  11  and the jig  12  are heated with an induction heating means  23  to a temperature half-melting the billet  11 . Reference numeral  24  denotes a mount for mounting the jig  12 . 
     In the heating process, when the billet  11  and the jig  12  are heated to a temperature half-melting the billet  11 , the billet  11  thermally expands, the difference in expansion from that of the jig  12  brings the outer peripheral surface of the billet  11  into contact with the inner peripheral surface of the jig  12 , and the confinement of the jig  12  causes a compressive force on the billet  11 . As a result, no sliding in the axis direction occurs in the subsequent cutting step, facilitating the cutting. 
     Further, since the billet  11  and the jig  12  are heated to a temperature half-melting the billet  11  in the heating step, shearing resistance is reduced in the subsequent cutting step, facilitating the cutting of the billet  11 . 
     In the heating step, the adoption of the induction heating method can shorten the time of heating the billet  11  and also shorten the cycle time of the heating step. Thus provided is an increase in productivity. 
     The adoption of the induction heating method and the use of austenitic stainless steel as the material of the jig  12  allow the induction heating of only the billet  11  without inductively heating the austenitic stainless steel, providing greater expansion difference, and increasing the compressive stress of the billet  11 . As a result, cutting in the following step is facilitated. 
     Successively, when the billet  11  reaches the half-melting temperature, the induction heating means  23  is removed from the jig  12 . 
     Now, with reference to  FIGS. 5A ,  5 B and  5 C, the step of cutting a billet into blanks according to the present invention will be described. 
     As shown in  FIG. 5A , the jig  12  is used for starting cutting. More specifically, the bolts are removed to fit a pulling jig  25  in the open holes  16   d  and  18   d  and fit a pulling jig  26  in the holes  15   d  and  17   d . The press plates  13  and  14  on the opposite ends are pressed via a pressure-applying device  27  known by one of ordinary skill in the art to the extent that the press plates  13  and  14  are not tilted when the pulling jigs  25  and  26  are pulled in opposite directions as shown by arrows {circle around (2)} and {circle around (3)}. 
     Then, as shown in  FIG. 5B , the pulling jigs  25  and  26  are moved in the opposite directions as shown by arrows {circle around (2)} and {circle around (3)}, applying shearing forces to the billet  11  with the jig  12 , and cutting the billet  11  into four pieces at a time. 
     The cut billet  11  provides blanks  31  fitted in the first to fourth annular members  15  to  18  as shown in  FIG. 5C . 
     In this manner, in the process of cutting the billet  11  into the blanks  31 , the second and fourth annular members  16  and  18  are pulled leftward (In the direction of arrow {circle around (2)}) and the first and third annular members  15  and  17  adjacent to the second and fourth annular members  16  and  18  are pulled rightward (in the direction of arrow {circle around (3)}), the second and fourth annular members  16  and  18  and the adjacent first and third annular members  15  and  17  being moved in the opposite directions, thereby cutting the billet  11 . As a result, the billet  11  can be cut into four pieces at a time, allowing increased productivity. 
     The second and fourth annular members  16  and  18  and the adjacent first and third annular members  15  and  17  are moved in the opposite directions, thereby cutting the billet  11 . As a result, the billet  11  can be cut without using a cutting tool such as a cutter, reducing production cost. 
     When the material of the blank  31  is an aluminum-based composite, supply cost of cutting tools to be subjected to severe wear for the aluminum-based composite can be eliminated. Thus production cost can be reduced. 
     Further, since the second and fourth annular members  16  and  18  and the adjacent first and third annular members  15  and  17  are moved in the opposite directions to cut the billet  11 , there is no need to provide the billet  11  with a machining allowance for cutting, increasing the yield of the expensive aluminum-based composite, and reducing production cost. 
     Now with reference to  FIGS. 6 and 7 , the step of disposing a blank on a press molding device  32  will be described. 
     The blank  31  is, as shown in  FIG. 6 , fitted in the first annular member  15  by thermal expansion. With this state, by holding the grip  15   c  of the first annular member  15 , the blank  31 , together with the first annular member  15 , is carried to the press molding device  32 . 
     Similarly, by holding the grips  16   c ,  17   c  and  18   c  of the second to fourth annular members  16  to  18  (see  FIG. 5C ), the blanks  31 , together with the respective second to fourth annular members  16  to  18 , are sequentially carried to the press molding device. The first to fourth annular members  15  to  18  may be carried by holding portions other than the grips. 
     As shown in  FIG. 7 , the press molding device  32  includes a mold  33  consisting of an upper mold half  34  and a lower mold half  35 . A fitting hole  36  is formed in the lower mold half  35 . In the hole  36 , the first annular member  15  is fitted. Although the figure only shows the one mold  33 , the press molding device  32  has as many molds  33  as the second to fourth annular members with the blanks  31  fitted therein, for receiving them. Since the blanks  31 , being fitted in the first to fourth annular members  15 , are carried to the press molding device  32  for disposition, cooling time for taking the blanks  31  out of the first to fourth annular members  15  can be eliminated, resulting in increased productivity. 
     Since the blanks  31 , being fitted in the first to fourth annular members  15 , are fed to the press molding device  32 , time between cutting and feeding is shortened. The temperature of the blanks  31  thus hardly decreases, eliminating the need for reheating the blanks  31  before molding. This allows an increase in productivity. 
     Successively, as shown in  FIG. 8A , the upper mold half  34  is lowered for press, forming the blank  31  into a molded part  37  of a desired shape. Then the upper mold half  34  is moved upward to take the first to fourth annular members  15  and the molded parts  37  out of the lower mold half  35 . Finally, the molded parts  37  as shown in  FIG. 8B  are taken out of the press molding device. The molded parts  37  are pulley components in this embodiment. 
     Now with reference to  FIGS. 9A to 10B , the way of disposing annular members with blanks fitted therein on another mold of the press molding device will be described. 
     As shown in  FIG. 9A , the press molding device  32  has a plurality of lower mold halves  41  of a flat shape each having locating portions  42  and fitting holes  42   a . The blank  31 , being fitted in the first annular member  15 , is fed to the press molding device  32 , and is then positioned with the grip  15   c  inserted in the locating portion  42  as shown by arrow {circle around (4)}, and the first annular member  15  is fitted in the fitting hole  42   a  as shown by arrows {circle around (5)}. Similarly, the second annular member  16  is positioned with the grip  16   c  and fitted in the locating portion  42  and the fitting hole  42   a , and the third annular member  17  is positioned with the grip  17   c  and fitted. As a result, the first to third annular members  15  to  17  with the blanks  31 ,  31  and  31  fitted therein are disposed on the lower mold half  41  as shown in  FIG. 9B . 
     In this manner, the blanks  31 , being fitted in the first to third annular members  15 ,  16  and  17 , are fed to the press molding device  32 , and then the grips  15   c ,  16   c  and  17   c  are inserted into the locating portions  42  of the lower mold half  41 , which facilitates the positioning of the blanks  31 . As a result, the precision of molded parts can be increased without effort, and variation in dimension between molded parts can be prevented, providing stable molding. 
     In the case of simultaneously molding a plurality of pieces as shown in  FIG. 9A , the jig  12  (see  FIG. 5B ) is used to cut the billet  11  into four pieces at a time as previously described, and then the blanks  31 ,  31  and  31 , being fitted in the first to third annular members  15  to  17 , are fed to the press molding device  32 , so that the three blanks  31  can be fed substantially at the same time, preventing variation in temperature between the blanks  31 . 
     Successively, as shown in  FIG. 10A , an upper mold half  43  corresponding to the lower mold half  41  is lowered thereby forming the blanks  31  into molded parts  44 . Thereafter, the completed molded parts  44  as shown in  FIG. 10B  are taken out of the press molding device. The shape of the molded parts  44  is only an example. 
     Now, with reference to  FIGS. 11A and 11B , the way of disposing an annular member in a modification on still another mold of the press molding device will be described. Components identical to those in the embodiment of  FIGS. 2 to 6  are affixed the same reference numerals, and will not be described. 
     As will be clear from  FIG. 11A , a billet  11 B is cut to obtain a blank  31 B fitted in a first annular member  15 B. The material of the billet  11 B is identical to that of the billet  11 . The billet  11 B has a plane surface  51  formed by cutting off a part of the circle. The material of the first annular member  15 B is identical to that of the first annular member  15 . The first annular member  15 B has a flat portion  52  formed at an inner peripheral portion  15   a  and a locating portion  53  protruding outward of an outer peripheral portion  15   b.    
     As shown in  FIG. 11B , a press molding device  32  has a lower mold half  54 . The lower mold half  54  has two locating pins  55  and  56  extending upward from the top surface. The blank  31 B, being fitted in the first annular member  15 B, is carried to the press molding device  32 , and then a grip  15   c  of the annular member  15 B is fitted onto the locating pin  55  of the lower mold half  54  as shown by arrow {circle around (6)}, and the locating portion  53  of the annular member  15 B is fitted onto the locating pin  56  of the lower mold half  54  as shown by arrow {circle around (7)}. Thereafter, the blank  31 B fitted in the annular member  15 B is molded into a desired shape in a manner as described above. 
     The positioning of the blank  31 B in this modification also provides effects similar to those in the above-described embodiment. 
     The configuration of the induction heating means  23  in  FIG. 4  is an example. A special furnace, for example, may be used. 
     The composition of the aluminum-based composite can be any, and may be made by dispersing alumina (Al 2 O 3 ) powder in a molten aluminum alloy. 
     The first to fourth annular members  15  to  18  are superimposed on one another to assemble the tubular jig  12 . The number of the annular members is not limited to four and can be any. 
     The billet  11  is cut into four pieces with the jig  12  at a time. The number of cut pieces can be any. 
     The shape of the first to fourth annular members  15  to  18  can be any. For example, the inner periphery formed with the inside diameter Di may be formed in a polygon, and the outer periphery may be formed in a polygon. 
     The configuration of the mold  33  in  FIG. 7  is an example. The shape of the fitting hole  36  formed in the lower mold half  35  is an example. 
     INDUSTRIAL APPLICABILITY 
     As will be apparent from the above, the blank feeding method according to the present invention eliminates the need for a cutting tool for cutting a billet, causing no wear of blades, and thus allowing reduced production cost of blanks for producing parts, and also feeds a plurality of blanks at a time without the need for reheating, thus allowing increased productivity of blanks. The present invention is thus beneficial to parts-producing fields.