Patent Publication Number: US-2002011322-A1

Title: Structure of a casting die

Description:
BACKGROUND OF INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a structure of casting die in which a melt metallic material or a melt alloy material is die cast to form a product. In particular, the invention is directed to a structure of casting die which permits for forming a die-cast product having holes therein, such as spring securing holes adapted to allow the ends of support springs or resilient support elements to be respectively engaged therein.  
       [0003] 2. Description of Prior Art  
       [0004] Among various sorts of seat frames or frameworks of automotive seats, there has been known a framework formed by die casting from a light alloy material such as magnesium alloy or aluminum alloy. For instance, the U.S. Pat. No. 5,897,168 discloses a magnesium die-cast backrest framework.  
       [0005] This die-cast seat frame has a pair of lateral frame portions, and, as well known, a plurality of sinuous or S springs are extended therebetween for giving a comfortable resilient support to the back or buttocks portion of a seat occupant. For that purpose, plural securing holes are formed in those two lateral frame portions in mutually facing relations with one another so that the two ends of each spring may be securely engaged in the corresponding mutually faced pair of securing holes, respectively.  
       [0006] Conventionally, each of the two lateral frame portions has been manually perforated by a drill to form those spring securing holes therein, as a result of which, the assembly of seat frame has been time-consuming and troublesome, and further, it has been difficult for a worker to manipulate the drill to precisely form each of the securing holes in a given point of the lateral frame portion. This problem has also been found in forming other holes than such spring securing holes in the seat frame.  
       [0007] To address the problem, plural rod-like slides are incorporated in a casting die to form the plural spring securing holes or other holes. Those sorts of slide elements are movable in the casting die in a direction laterally thereof, and therefore, after having moved the slides laterally into the inside of the casting die, a melt mass of alloy material is die cast in the die into a predetermined shape of seat frame, while simultaneously, by way of the slides, a plurality of holes are defined precisely in the predetermined points of each of the two lateral frame portions or other points thereof in the resulting die-cast seat frame.  
       [0008] However, the provision of such slide die elements has been found defective in that they must be formed singly and separately from the casting die, which means undesired increase of die elements and complicated structure of the casting die itself, thus resulting in high raise of costs involved.  
       SUMMARY OF THE INVENTION  
       [0009] In view of the above-stated drawbacks, it is a primary purpose of the present invention to provide an improved casting die capable of directly forming holes in a die-cast product without resort to drilling and separate die elements.  
       [0010] In order to achieve the purpose, a casting die in accordance with the present invention is basically comprised of:  
       [0011] a first die means including a first sloped die surface area defined therein,  
       [0012] at least one first projection defined on the first sloped die surface area such as to diverge in one direction therefrom; said at least one first projection having a surface;  
       [0013] a second die means including a second sloped die surface area defined therein at a point corresponding to the first sloped die surface area of lower die means;  
       [0014] at least one second projection defined on said second sloped die surface area such as to converge therefrom in another direction opposite to the afore-said one direction associated with the first projection, which second projection has a surface to be neatly contacted with the surface of first projection; and  
       [0015] the surface of each of the first and second projections being oriented in a direction along which the first and second die means are engaged with and disengaged apart from each other,  
       [0016] with such an arrangement that, when the first and second die means are engaged together, the first and second projections are matched and aligned with each other to form one die element by which the hole is to be defined in the die-cast framework.  
       [0017] Accordingly, during die-casting process, the mutually matched two projections causes a hole or a plurality of holes to be formed in the die-cast product, and further, the structure of this casting die allows the first and second die means to be smoothly removed apart from each other without interference with the adjacent portions of resulting die-cast product.  
       [0018] Other various advantages and features of the present invention will become apparent from reading of the descriptions hereinafter with reference to the annexed drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0019]FIG. 1 is a partially schematic perspective view partly in section, which shows a casting die of the present invention and a die-cast seat back frame formed thereby;  
     [0020]FIG. 2 is a sectional view taken along the plane II-II in FIG. 1;  
     [0021]FIG. 3 is a sectional view similar to FIG. 2, which only shows the state where upper and lower dies are engaged together, with a die casting cavity defined therebetween;  
     [0022]FIG. 4 is a schematic sectional view which explanatorily shows the upper and lower dies as being removed apart from each other to take out a resulting die-cast seat back frame therefrom;  
     [0023]FIG. 5 is a fragmentary sectional view showing first and second projections as being matched and contacted with each other;  
     [0024]FIG. 6 is a fragmentary sectional view which particularly shows a hole formed in the lateral frame portion of resulting die-cast seat back frame;  
     [0025]FIG. 7 is a partly broken schematic perspective view showing the first projection formed in the sloped die surface of lower die; and  
     [0026]FIG. 8 is a partly broken schematic perspective view showing the second projection formed in the sloped die surface of upper die. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION  
     [0027] Referring to FIGS. 1 through 7, there is illustrated one exemplary mode of casting die device (A) in accordance with the present invention. Designation (F) denotes a seat back frame to be formed by the casting die device (A) from a light alloy material such as magnesium or aluminum alloy. It should be understood that the casting die device (A) is not confined to forming the seat back frame ( 3 ), but may be modified to form another kinds of seat frames, like a seat cushion frame, within the gist and scopes of the present invention.  
     [0028] As shown, the casting die device (A) is basically comprised of an upper die ( 2 ) and a lower die ( 1 ). A schematic whole configuration of those upper and lower dies ( 2 ) ( 1 ) can be comprehended from FIG. 1 which illustrates both of them in the combination of one-dot chain and solid lines, and partly in cross-section. Generally stated, as understandable from FIGS. 1, 2 and  3 , the lower die ( 1 ) has a recessed die surface whereas the upper die ( 2 ) has a generally downward protuberant die surface to be mated in that recessed die surface of lower die ( 1 ) such as to define a die-casting cavity ( 4 ) therebetween. Of course, though not shown in detail, such cavity ( 4 ) determines a given whole shape of the seat back frame (F) to be die cast therein. The resulting seat back frame (F) cast by the die device (A) is shown in FIG. 1 as having a pair of lateral frame portions ( 3 ) ( 3 ) each formed with a plurality of spring securing holes ( 30 H) therein. Those two lateral frame portions ( 3 ) each comprises a longitudinal main body ( 30 ) which is somewhat slant in a direction inwardly of the frame (F) and two flange portions ( 31 ) ( 32 ) extending horizontally from the main body ( 30 ) in the direction opposite to each other.  
     [0029] The illustrations of FIGS.  2  to  7  give an exemplary mode where both die surfaces of upper and lower dies ( 2 ) ( 1 ) are formed with projected portions adapted to form the plural spring securing holes ( 30 H) in each of the two lateral frame portions ( 3 ) of resulting seat frame (F). Now, particular reference is made to FIG. 4 in conjunction with FIG. 3. Basically, the die surfaces of upper die ( 2 ) includes, defined therein, a horizontal region ( 2 A) and a downward protuberant region ( 2 B) of a generally inverted trapezoidal cross-section. The horizontal region ( 2 A) provides a horizontal base die surface. On the other hand, the downward protuberant region ( 2 B) assumes a generally truncated pyramid shape (shown in an inverted state in the figures) as viewed three-dimensionally, which is suited for forming a whole generally rectangular configuration of seat back frame (F) having inwardly sloped lateral frame portions. In other words, it is to be understood that the protuberant region ( 2 B) has four lateral die surfaces ( 21 ) and a flat end die surface ( 24 ). In particular, the two lateral die surfaces ( 21 ), effective in die casting the respective two lateral frame portions ( 3 ) ( 3 ), are both in an inwardly sloped state; that is, they are sloped in a direction inwardly of the upper die ( 2 ) proper, converging toward each other as they proceed down to the flat end die surface ( 24 ). Such inwardly sloped lateral die surfaces ( 21 ) are also each formed with a plurality of projections ( 2 P) therein which are adapted to form the plural spring securing holes ( 30 H), respectively, in each of the two lateral frame portions ( 3 ) of resulting die-cast seat back frame (F). In this respect, one exemplary specific mode of the projection ( 2 P) is shown in FIG. 8, according to which, an inverted-wedge-like shape of projection ( 2 P) is suggested and it has: a sloped base area ( 2 P- 3 ) integrally fixed on the inwardly sloped lateral die surface ( 21 ); a vertical planar surface ( 2 P- 1 ) extending downwards away from the sloped lateral die surface ( 21 ) in a direction perpendicular to a horizontal plane where the flat end die surface ( 24 ) lies; and a horizontal bottom side ( 2 P- 2 ) defined between the sloped base area ( 2 P- 3 ) and vertical planar surface ( 2 P- 1 ). Hence, the projection ( 2 P) per se diverges or enlarges its mass downwards with respect to the sloped die surface ( 21 ) while keeping the perpendicularity of its vertical planar surface ( 2 P- 1 ).  
     [0030] Further defined in each of the two lateral die surfaces ( 21 ) are an upper local die surface area ( 22 ) thereabove and a lower local die surface area ( 23 ) therebelow. The lower local die surface area ( 23 ) is recessed from and lower than the end die surface ( 24 ). Those upper and lower die surface areas ( 22 ) ( 23 ) are adapted to form the abovementioned two flange portions ( 31 ) ( 32 ), respectively, in a resulting lateral frame portion ( 3 ).  
     [0031] On the other hand, with regard to the lower die ( 1 ), turning back to FIGS. 4 and 3, it includes a recessed die region ( 1 B) of a generally inverted trapezoidal cross-section and a working die region ( 1 A) surrounding the recessed die region ( 1 B). The recessed region ( 1 B) is roughly similar in shape to the afore-said protuberant region ( 2 B) of upper die ( 2 ), thus assuming a generally truncated pyramid shape (shown in an inverted state), but relatively larger in dimensions than the latter for the purpose of creating the die casting cavity ( 4 ) therebetween to cast and form a generally rectangular whole configuration of seat back frame (F) in the cavity ( 4 ). Given such dimensions of recessed region ( 1 B), the working die region (IA) defined therearound has four lateral die surfaces ( 11 ) and a flat bottom die surface ( 13 ). In particular, the two lateral die surfaces ( 11 ), which are adapted to die cast the respective two lateral frame portions ( 3 ), are so sloped as to diverge outwardly from the bottom die surface ( 13 ) by the same inclination angle as that of the two sloped lateral die surfaces ( 21 ) of upper die ( 2 ). Such sloped lateral die surfaces ( 11 ) are also each formed integrally with a plurality of projections ( 1 P) which are to cooperate with the respective plural projections ( 2 P), as explained later, to form the plural spring securing holes ( 30 H) in each of the two lateral frame portions ( 3 ) of resulting die-cast seat back frame (F). One exemplary specific mode of the projection ( 1 P) is shown in FIG. 7, wherein, as opposed to the inverted-wedge-like shape of previously stated projection ( 2 P), there is suggested a normal wedge-like shape of projection ( 1 P) which has: a sloped base area ( 1 P- 3 ) integrally fixed on the sloped lateral wall ( 11 ); a vertical planar surface ( 1 P- 1 ) extending upwards from the sloped lateral die surface ( 11 ) along a line perpendicular to a horizontal plane where the bottom die surface ( 13 ) lies; and a horizontal top side ( 1 P- 2 ) defined between the sloped base area ( 1 P- 3 ) and vertical planar surface ( 1 P- 1 ). Further defined in each of the two lateral die surfaces ( 11 ) is an upper local die surface area ( 12 ) thereabove. The upper local die surface area ( 12 ) is recessed from and lower than the top wall of lower die ( 1 ) as best seen from FIG. 4, serving to form the flange portion ( 31 ) in a resulting lateral frame portion ( 3 ).  
     [0032] It is noted that both vertical planar surfaces ( 1 P- 1 ) ( 2 P- 1 ) respectively of the two projections ( 1 P) ( 2 P) are identical in geometry and area to each other so that, as explained later, they will be precisely matched for complete alignment and engagement with each other, to thereby neatly form one bridge-like inner die element, as generally designated by (B), between the mutually opposed two lateral die surfaces ( 11 ) ( 12 ), which directly acts to form each spring securing hole ( 30 H) mentioned above during die casting. Hereinafter, the projection ( 1 P) shall be referred to as “first projection”, and the projection ( 2 P) referred to as “second projection”. As understandable from FIG. 5, the horizontal top wall ( 1 P- 2 ) of each first projection ( 1 P) has a width (W 1 ) which is equal to the width (W 2 ) of the horizontal bottom wall ( 2 P- 2 ) of each second projection ( 2 P), which is therefore a factor to determine a thickness of the resulting main frame body ( 30 ) as well as a thickness of the spring securing hole ( 30 H).  
     [0033] From FIGS. 1, 7 and  8 , it is to be understood that a plurality of the first and second projections ( 1 P) ( 2 P) are disposed on the respective lateral surfaces ( 11 ) and ( 12 ) in mutually spaced-apart or equidistant relationship along the longitudinal direction thereof so as to form a series of spaced-apart or equidistant spring securing holes ( 30 H) in each of the resulting two lateral frame portions ( 3 ) ( 3 ). It is to be, of course, understood that such disposition of first and second projections ( 1 P) ( 2 P) must be such that, when the upper and lower dies ( 2 ) ( 1 ) are mated with each other as in FIG. 3, all the vertical surfaces ( 1 P- 1 ) of first projections ( 1 P) are respectively brought in a precise alignment and contact with those ( 2 P- 1 ) of second projections ( 2 P) to establish the corresponding plural bridge-like inner die element (B) between the first and second dies ( 1 ) ( 2 ).  
     [0034] In operation, the upper and lower dies ( 2 ) ( 1 ) are put together while insuring that all the vertical planar surfaces ( 1 P- 1 ) of first projections ( 1 P) and all the corresponding vertical planar surfaces ( 2 P- 1 ) of second projections ( 2 P) are brought in contact with and slid on one another in a relative movement manner. Upon the two dies ( 2 ) ( 1 ) having been completely engaged together as in FIG. 3, all the first and second projections ( 1 P) ( 2 P) are precisely matched and in alignment with one another to define plural bridge-like die elements (B) between the two sloped lateral die surfaces ( 11 ) and ( 21 ). Then, a melt light alloy material (e.g. magnesium or aluminum) is poured in and left cold in the die casting cavities ( 4 ) created between the two dies. Subsequent thereto, as shown in FIG. 4, the two dies ( 2 ) ( 1 ) are disengaged apart from each other, during which, it is readily appreciated that both first and second projections ( 1 P) ( 2 P) are smoothly slid away from one another without any interference with the adjacent portions (at  30 ) of resulting die-cast product, owing to the fact that, as seen from FIG. 4, the die casting cavities ( 4 ) for forming the lateral fame portions ( 3  and  30 ) are inclined at a certain angle away from the vertical or perpendicular line along which a sliding relative movement occurs between the first and second projections ( 1 P) ( 2 P) at their respective vertical surfaces ( 1 P- 1 ) ( 2 P- 1 ). Resultingly, there is obtained a die-cast seat back frame (F) with a plurality of spring securing holes ( 30 H) formed in both lateral frame portions ( 3 ) thereof.  
     [0035] The projections (e.g.  1 P and  2 P) are not limited to the illustrated wedge-like shape, but may be changed in shape and dimensions, depending on any desired shapes of holes (such as circular holes) to be formed in a resulting die-cast product.  
     [0036] In accordance with the present invention, the structure of casting dies is much simplified, requiring no separate die element, such as slide dies, in order to form holes in a resulting die-cast product, and therefore eliminating the steps for die casting processes and reducing the assembling costs involved.  
     [0037] It should be finally understood that the present invention is not limited to the illustrated embodiments, but any other modifications, replacements and additions may be structurally applied thereto without departing from the scopes of the appended claims.