Patent Publication Number: US-8984927-B2

Title: Die for machine press

Description:
TECHNICAL FIELD 
     The present invention relates to a die for a machine press. 
     BACKGROUND ART 
     Many improvements for dies for a machine press have been proposed. For example, a die in which a plurality of links is connected in a mesh shape is proposed in Patent Document 1. In this die, a mesh surface forms a design surface. In this die, the shape of the mesh, i.e., the design surface, can be changed in various ways by changing the connecting angle of the links. Here, in the present specification, “design surface” means a surface that makes contact with a work plate, is formed in a target shape, and transfers this target shape to the work plate. Below, in order to simplify the description, the “die for a machine press” is simply called the “die”. 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: Japanese Patent Application Publication No. H6-210351 (1994-210351) 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     In general, a die is utilized as a part of a pair. One of the dies is attached to a bolster of a press machine, and the other of the dies is attached to a slider. After a work plate has been positioned between the pair of dies, the slider descends, a load is applied to the work plate, and the dies are pressed against the work plate. The work plate deforms along the design surface of the die, transferring the target shape to the work plate. 
     When press processing is performed, a high load is applied to the die. Consequently, the die requires high rigidity. On the other hand, when work is to be formed by a pair of dies, the positioning of the pair of dies is also important. For positioning, each of the pair of dies usually has a guide pin and a guide bush. At the time of pressing, as one die approaches the other die, the guide pin provided on the one die fits with the guide bush provided on the other die, thus allowing the two to be positioned accurately. That is, the die has a part having the design surface and a part for positioning. When the pair of dies has been positioned accurately by using the guide pin and the guide bush, the position of the design surface of both of the pair of dies is also strictly determined. Here, since the rigidity of the die is high and the position of the design surface is firmly fixed, the load may be concentrated on a particular part of the design surface. Concentration of the load may cause local damage to the design surface. Alternatively, the entire die may be inclined by the concentration of the load, thus the processing accuracy of the work may be reduced. On the other hand, if the rigidity of the die is low, the design surface itself may deform, thus processing accuracy may be reduced. For example, since the technique of Patent Document 1 utilizes the mesh-shaped links as the design surface, high rigidity cannot be expected in the design surface, and the technique is not suitable for pressing a comparatively hard work plate. The present specification presents a technique which gives adequate flexibility to the entire die while maintaining the rigidity of the design surface. 
     Solution to the Technical Problem 
     In one aspect of a novel die taught in the present specification, the die comprises a framework, a design block, and a positioning block. The framework is assembled from a plurality of rods. The framework is assembled from the plurality of rods so as to have a Rahmen structure, a truss structure, or a combination of the Rahmen and the truss structures. The Rahmen structure and the truss structure are technical terms used in the field of structural mechanics or architecture. A “truss structure” means a structure that is assembled from rods, and is a structure in which only force in an axial direction is applied to the rods, and bending moment is not applied thereto. A “Rahmen structure” means a structure that is assembled from rods, and is a structure in which both force in the axial direction and the bending moment are applied to the rods. 
     Any of the rods, the design block, and the positioning block may typically be made from steel, cast iron, or another metal. 
     The design block is a block having a design surface for transferring a target shape to a work plate. The positioning block is a block for positioning the die relative to a counterpart die attached to a press machine, and typically is a block having a guide pin or a block having a guide bush. It should be noted that the component used for positioning is not limited to a pin or a bush. 
     Both the design block and the positioning block are fixed to the framework. However, the design block and the positioning block are fixed to the framework at positions separate from one another. In other words, this die has a shape in which the design block and the positioning block are connected by the plurality of rods, and the plurality of rods is assembled into the truss structure, the Rahmen structure, or the framework structure in which the truss and the Rahmen structures are combined. Below, to simplify the description, a “structure configured of a plurality of rods and having the truss structure, the Rahmen structure, or the structure in which the truss and the Rahmen structures are combined” is simply called a “framework structure”. That is, the aforementioned die comprises the framework having the framework structure. 
     Since the design surface is provided on the design block, the design surface has high rigidity. The guide pin or the guide bush is provided on the positioning block, and the rigidity of the positioning block itself is high. On the other hand, since the design block and the positioning block are connected by the rods, the design block has adequate flexibility relative to the positioning block. In particular, in the framework in which the rods are assembled in the framework structure, the rigidity of each part is easily predicted, and consequently the desired rigidity is easily achieved. This is a major factor in achieving appropriate rigidity between the positioning block and the design block. Describing this die from another perspective, the framework has a rigidity that is lower than the rigidity of the positioning block, and that is lower than the rigidity of the design block. 
     In another aspect of the die taught in the present specification, it is preferred that the design block is surrounded by the plurality of rods in a plan view of the die, and that the positioning block is disposed at a periphery of the die (at a periphery of the framework). Here, a “plan view of the die” is equivalent to “viewed from the front of the design surface”. It is preferable for the positioning block to be disposed at the periphery of the die so as to accurately determine the position of the design block located near the center of the framework. 
     Further, the design block is disposed opposite to the design surface of the contraposed die (counterpart die), with the work plate sandwiched therebetween, and the design block receives the load. It is preferred that, upon receiving the load, the design surface of the design block and the design surface of the counterpart die become parallel. For this purpose, four sides of the design block may respectively be supported uniformly by the rods. 
     In another preferred aspect of the die taught in the present specification, is the framework has a vertical rod that supports a backside of the die. This is because supporting the backside of the die is preferred so as to withstand the load when pressing. 
     Not only the design block, but also a block for supporting a tool for machining the work plate may be fixed to the framework. Various tools utilizing the pressing load may be attached to the die for a machine press. For example, there is a tool that converts the pressing load in a direction perpendicular to the pressing direction and creates a hole in the work plate. Alternatively, there is a tool that converts the pressing load in the direction perpendicular to the pressing direction and bends the work plate. It is preferred that, like the design block, this type of block for supporting the tool also has high rigidity and relative flexibility with respect to the positioning block. Consequently, it is preferred that the block for supporting the tool is fixed to the framework at a position separate from the design block and the positioning block. 
     The novel die taught in the present specification is suitable for use in casting. In particular, the die is suitable for a full-mold casting process using an evaporative pattern. In other words, in another aspect of the die taught in the present specification, the design block, the positioning block and the plurality of rods are formed integrally by casting in the full-mold casting process using the evaporative pattern. The advantage of the die taught in the present specification being suitable for the full-mold casting process using the evaporative pattern will be described in the embodiment. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a plan view of a die of the embodiment. 
         FIG. 2  shows a schematic side view of a press machine. 
         FIG. 3  shows an example of a tool utilizing a pressing load. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The figure at an upper side of  FIG. 1  shows a plan view of a die  2  of the embodiment, and a figure at a lower side of  FIG. 1  shows a side view of the die  2 . The virtual line shows a contraposed die  102 . Below, the contraposed die  102  is called a counterpart die  102 . The dies  2  and  102  are dies for a machine press and, as shown in  FIG. 2 , are used by being attached to a press machine  50 . The die  2  is fixed to a bolster  51 , and the counterpart die  102  is fixed to a slider  52 . The slider  52  is moved up and down by an actuator  55  while being guided by a support  53 . 
     The die  2  has a design block  20 , positioning blocks  24 , and a support block  30 . The design block  20  has a design surface  20   a  for transferring a target shape to a work plate. The die  2  of this embodiment is a die for press forming a fender of an automobile. The design surface  20   a  is formed in a shape of the fender, Moreover, the positioning blocks  24  are disposed at the four corners of the die  2 . It should be noted that the reference number  24  has been appended to only one of the positioning blocks, and the reference number has been omitted on the other positioning blocks. 
     A work plate W deforms to a shape of the design surface  20   a  when the work plate W is sandwiched between the design block  20  of the die  2  and a design block  120  of the counterpart die  102 , and the actuator  55  lowers the slider  52 , applying load to the work plate W. That is, the shape of the design surface  20   a  is transferred to the work plate W. 
     When the die  2  and the counterpart die  102  are to be fitted together, guide pins  25  of the die  2  fit into guide bushes  125  of the counterpart die  102 , allowing the die  2  and the counterpart die  102  to be positioned relative to one another. That is, the design surface  20   a  of the die  2  and a design surface  120   a  of the counterpart die  102  can be positioned relative to one another. The guide pin  25  is formed on the positioning block  24 . As shown in  FIG. 1 , the positioning blocks  24  are located at the four corners of the die  2  so as to surround the design block  20 . By locating the positioning blocks  24  at the four corners of the design block  20 , the relative position of the design surface  20   a  of the die  2  and the design surface  120   a  of the counterpart die  102  can be determined accurately. 
     The support block  30  is a block to which a variety of tools utilizing a pressing load is attached. The support block  30  will be described later. 
     The design block  20 , the positioning blocks  24  and the support block  30  are mutually connected by a plurality of rods  12 . The rods are connected by joints  14 . The plurality of rods  12  is assembled vertically, horizontally and obliquely to form a framework  10 . The plurality of rods  12  constituting the framework  10  is classified into several types. That is, the plurality of rods  12  is classified into longitudinal rods  12   a , transverse rods  12   b , oblique rods  12   c , and vertical rods  12   d . When assembled, the longitudinal rods  12   a  and the transverse rods  12   b  form a lattice in a horizontal plane. The vertical rods  12   d  are disposed in a vertical plane. Several longitudinal rods  12   a , transverse rods  12   b  and vertical rods  12   d  constitute a rectangular parallelepiped. The oblique rods  12   c  are disposed on diagonals of the lattice. The entire framework  10  also forms a rectangular parallelepiped. Moreover, it should be noted that the reference numbers have been omitted for part of the rods in the figure. 
     A portion where the latticed window is rectangular constitutes a Rahmen structure. A portion, including the oblique rods  12   c , where the latticed window is triangular constitutes a truss structure (provided there is a pin connection between the rods). That is, the framework  10  has the framework structure described above. Moreover, the truss structure means a framework structure in which only axial force acts on the rods and moment does not act thereon, and the Rahmen structure means a framework structure in which both axial force and moment act on the rods. Both the Rahmen structure and the truss structure are configured only of rods, and consequently, while having a high strength, have adequate flexibility as a whole. 
     As shown in  FIG. 1 , seen from the plan view, the design block  20  is supported at four sides by the rods  12  (the longitudinal rods  12   a  and the transverse rods  12   b ). Further, the design block  20  is also supported from the backside by the vertical rods  12   d . Due to being supported from the four sides and the backside by the rods  12 , upon receiving the load, the design block  20  can move flexibly, although by a small amount. That is, when a biased pressing load has been applied, the design block  20  moves slightly so that the pressing load is distributed uniformly. This slight movement solves the bias of the pressing load. The position of the entirety of the die  2  relative to the counterpart die  102  is determined accurately by the positioning blocks  24 . On the other hand, due to being supported from the four sides and the backside by the rods  12 , the design block  20  moves slightly to solve the bias of the pressing load. Since the biased pressing load is not concentrated on the design surface  20   a , wear of the die can be suppressed, and high work molding precision is maintained. 
     The rigidity of the design block  20  is greater than the rigidity of the framework  10  assembled from the rods  12 . Further, the rigidity of the positioning blocks  24  is also greater than the rigidity of the framework  10 . Consequently, when the pressing load is acted, the design block  20  and the positioning blocks  24  undergo less deformation than the framework  10 . That is, the entire framework  10  deforms, whereas the deformation of the design block  20  and the positioning blocks  24  is suppressed. Since the deformation of the design block  20  itself is suppressed, high work molding precision can be maintained. 
     The support block  30 , and the tools utilizing the pressing load will be described.  FIG. 3  is a figure for describing a tool  60  for making a hole in a side surface of the work plate W. An upper surface of the support block  30  is flat, and the tool  60  is attached to this upper surface. A punch  60   a  is attached to a side of the tool  60 . An upper surface of the tool  60  is inclined. A counterpart tool  160  is attached to the counterpart die  102  above the tool  60 . A lower surface of the counterpart tool  160  is parallel to the inclined upper surface of the tool  60 . When the counterpart tool  160  is lowered, the inclined upper surface of the tool  60  makes contact with the inclined lower surface of the counterpart tool  160 . When the counterpart tool  160  is lowered further, the tool  60  is moved toward the right of  FIG. 3  (in a horizontal direction) by the pressing load acted to the inclined upper surface. That is, the pressing load is converted to a direction perpendicular to the pressing direction. When the tool  60  moves, the punch  60   a  at a tip thereof makes a hole in the side surface of the work plate W. Thus, the tool  60  moves horizontally employing the pressing load of the press machine, making a hole in the side surface of the work plate W. 
     The pressing load is also acted to the tool  60 . At this occasion, the support block  30  that supports the tool  60  is supported at the four sides and the backside by the rods  12   a ,  12   d  and, as with the design block  20 , the support block  30  shifts slightly to reduce the bias of the pressing load. 
     Summarized, the advantages of the die  2  are as follows. In the die  2 , the design block  20 , the positioning blocks  24 , and the support block  30  are connected by the plurality of rods. The position relative to the counterpart die  102  is adjusted accurately by the positioning blocks  24 . On the other hand, the design block  20  and the support block  30  are supported from the backside and the four sides in a horizontal plane by the rods  12 , and consequently move slightly to disperse a biased pressing load. Since concentration of the pressing load is mitigated, local wearing of the design surface does not occur and, further, high molding precision of the work can be achieved. Further, the framework  10  that is assembled from the plurality of rods has many latticed windows, and is consequently well ventilated. As a result, it also has the advantage that dust, etc. does not adhere readily. 
     The die  2  having the framework structure described above is suitable for being formed integrally by casting in a full-mold casting process using an evaporative die. The reason therefore is as follows. First, since the latticed windows surrounded by the rods are large, there is an advantage that it is easy to pack sand densely. Further, in the casting process, the cast product thermally contracts at the time of cooling and the dimensions change. However, the thermal contraction of rods is easy to predict, and consequently the dimensions of the framework are easily controlled. Further, the framework assembled from the plurality of rods cools in a relatively short time after casting. For example, a die for an automobile body is extremely large. When an extremely large die is cast, a long time is required for cooling. However, the framework assembled from the plurality of rods cools rapidly even if the die is extremely large, and consequently the manufacturing time can be reduced. 
     Next, points concerning the technique taught in the present specification will be given. The lattice surrounded by the rods is not restricted to being square or triangular. The lattice surrounded by the rods may be trapezoid or polygonal. That is, the framework may be assembled such that the rods are arranged irregularly. Further, the cross-sectional shape of the rods may be round, rectangular, or another polygonal shape. Further, a framework in which a plate such as a nameplate, dustproof plate, etc. is attached to the framework is also included in the scope of the technique taught in the present specification. The reason is that the nameplate or dustproof plate is not a member that contributes to the strength of the framework. 
     The die  2  of the embodiment has the positioning blocks  24  at the four corners. The number of positioning blocks of the die is not restricted to four. The technique taught in the present specification can also be applied, for example, to a die having two positioning blocks. For example, the die may have positioning blocks at only two corners on a diagonal line. The die may have more than four positioning blocks. Further, the position of the positioning blocks is not restricted to the corners of the die. The technique taught in the present specification can also be applied, for example, to a die having positioning blocks at each of a pair of opposing sides of a die. In a plan view of the die, the positioning blocks may be arranged at an inner side of a periphery of a framework. The technique taught in the present specification can also be applied to such a die. 
     A fastening member such as a pin, bolt, rivet, etc. may join the rods together, or may join the rods with the blocks. Instead, welding may join the rods together, or may join the rods with the blocks. As described earlier, the plurality of rods and the blocks may be formed integrally by casting. 
     Further, the connection between the rods may be either a pin junction or a rigid junction. Moreover, in case the rods are assembled such that the latticed window forms a triangle, and each of the rods forms a pin junction, the framework becomes a truss structure. In case the design block, the positioning blocks and the rods are all formed integrally by casting, the junction portion of the rods forms a rigid junction, and consequently the framework  10  has a Rahmen structure. 
     Upon the press processing, a cushion ring may be used in combination with the die  2 . A cushion ring is a component for pressing the work plate, and is disposed so as to surround the design block. 
     Specific examples of the present invention are described above in detail, but these examples are merely illustrative and place no limitation on the scope of the patent claims. The technology described in the patent claims also encompasses various changes and modifications to the specific examples described above. The technical elements explained in the present specification or drawings provide technical utility either independently or through various combinations. The present invention is not limited to the combinations described at the time the claims are filed. Further, the purpose of the examples illustrated by the present specification or drawings is to satisfy multiple objectives simultaneously, and satisfying any one of those objectives gives technical utility to the present invention. 
     LIST OF REFERENCE SIGNS 
       2 : Die,  10 : Framework,  12 : Rod,  12   a : Longitudinal Rod,  12   b : Transverse Rod,  12   c : Oblique Rod,  12   d : Vertical Rod,  20 : Design Block,  20   a : Design Surface,  24 : Positioning Block,  25 : Guide Pin,  30 : Support Block,  50 : Press Machine,  51 : Bolster,  52 : Slider,  53 : Support,  55 : Actuator,  60 : Tool,  60   a : Punch,  102 : Counterpart Die