Drawing and coining die for manufacturing metal containers and the like

Abstract: A drawing and coining die for manufacturing metal containers and the like, comprising: a matrix (1), which is connected to a lower base (4) adapted to be associated with a footing of a press and is provided with means (5) for centering a disk (6) that constitutes the material to be processed; and a male element (8), which is connected to an upper base (9) adapted to be associated with a movable slider of the press and is shaped so as to make contact with an edge of the resulting container.

Description: The invention relates to a drawing and coining die for manufacturing metal containers as described in the preamble of claim 1. Such a die is disclosed in GB-A-609907. It is known that metal containers, such as a for example pans in their many constructive shapes, and similar items, are manufactured by means of dies which are associated with a press. The finished product is obtained starting from a metal disk which is first drawn by the action of a male element combined with a matrix, assuming the intended shape without substantial variations in thickness, with a final coining to obtain a shape which has a modulated thickness. Conventional dies suffer some drawbacks, one of which is the fact that products obtained with such dies entail the presence of burr which forces to perform one or more finishing passes, considerably increasing the manufacturing costs. GB-A-609907 discloses a punch (1) and die (2) whose shapes are such that in their closed position as seen in Fig. 3 the blank (3) is completely surrounded by the surfaces of such punch (1) and die (2). The aim of the present invention is to provide a die which has improved characteristics with respect to conventional dies and in particular allows to manufacture metal containers and the like without burr thereon. In accordance with the invention, there is provided a drawing and coining die for manufacturing metal containers comprising: a matrix, which is connected to a lower base adapted to be associated with a footing of a press and is provided with means for centering a disk that constitutes the material to be processed; a male element, which is connected to an upper base adapted to be associated with a movable slider of the press and which comprises a peripheral contact region shaped so as to make contact with an edge of the resulting container interposed between said matrix and said male element in a fully closed configuration of said die; and a blank holder which extends about said male element and which is connected to said upper base through means which allow their mutual distances to vary and with elastic elements interposed, said blank holder and said male element and said matrix being mutually configured such that in said fully closed configuration of said die a bottom surface of said blank holder makes contact with the matrix. Further characteristics and advantages of the present invention will become apparent from the following detailed description of some preferred but not exclusive embodiments thereof, illustrated by way of nonlimitative example in the accompanying drawings, wherein: Figure 1 is a sectional view of the die in the open condition; Figures 2 and 3 are sectional views of successive steps of the closure of the die; Figure 4 is a sectional view of the closed die with the finished product; Figure 5 is a sectional view of the die in an opening step; Figures 6 and 7 are enlarged-scale sectional views of details of the circled regions of Figure 4; Figure 8 is a sectional view of a first embodiment of the invention, during the closure thereof; Figure 9 is a sectional view of a second embodiment of the invention, during the closure thereof. With reference to the above Figures 1 to 7, 1 designates a matrix, which is connected, by means of screws 2 and with a spacer 3 interposed, to a lower base 4, which is adapted to be associated with a footing of a press (not shown). The matrix is provided with a ring 5, which is detachably fixed by means of screws 5a, for centering a disk 6 to be processed, shown in Figures 1 and 2, while Figure 3 illustrates a step 6a of the modification of said disk for approaching a final configuration 6b shown in Figures 4, 5, 6 and 7. The disk 5 comprises a region, designated by the reference numeral 5b, which allows the passage of the finished product. In the matrix 1, at the bottom thereof, a plate 7 is provided, which is equipped with movement means comprising a shaft 7a which protrudes from the footing of the press and is managed by a fluid-actuated system with which the press is provided. The reference numeral 8 designates a male element which is connected, by means of screws 8a, to an upper base 9, adapted to be associated with the movable slider of the press. A blank holder 10 is also connected to the base 9 through sliding traction elements 10a and with the interposition of springs 10b. The blank holder 10 includes a duct formed by two portions 11a, 11b for feeding air under pressure into an interspace 12, which is shown in Figure 7 and is formed between the male element 8 and the blank holder 10, as explained hereinafter. The male element 8 is shaped so as to make contact at the region 8b with an upper edge of the resulting product 6b, with the only exception of a band which is located in the outer peripheral region and whereon the blank holder 10 acts (figure 7). Said blank holder rests on the matrix 1 and has a band 10c which protrudes onto the impression formed in the matrix so as to form a shape which is complementary to the shape of the container to be obtained. Another preferred characteristic of the invention which will also be described hereinafter and is shown in Figure 6 is the fact that the plate 7 is slightly larger than the end cross-section of the male element 8. The operation of the invention is now described starting from the condition in which the die is open, as shown in Figure 1. The upper base 9 descends and the male element 8, starting from the position of first contact with the disk 6 shown in Figure 2, draws said disk, which is supported so as to allow yielding by the plate 7, which reacts with a force which is adjusted by the fluid-actuated system for managing the shaft 7a. Figure 3 illustrates the intermediate step of the drawing, during which the blank holder 10 has made contact with the matrix 1. The further descent of the upper base 9 from the position of Figure 3 occurs thanks to the sliding of the traction elements 10a in the base 9 and with a compression of the springs 10b, and ends the drawing operation, which is followed, during the last moments of the descent of the male element 8, by coining with compression of the product so as to produce a migration of material within the impression so as to give to the product the configuration 6b which has a modulated thickness, shown in Figures 4 to 7. Figure 4 illustrates the condition in which the die is closed and the product is perfectly formed. The characteristics shown by Figures 6 and 7 perform their function during the coining step, because the material that migrates inside the impression between the male element 8 and the matrix 1 reaches the regions where there is the clearance, in said impression, between the matrix 1 and the disk 7, as shown in Figure 6, and there is the gap 12 shown in Figure 7, when the migration is ending, and therefore the transfer of material into said spaces which would cause burr does not occur. The product that leaves the die according to the invention therefore requires no finishing pass. The blank holder 10 which, in the described embodiment, actually has not performed the function implied by its name, but rather has completed, with the region 10c, the matrix 1 in forming the impression meant to be filled by the material being processed, is also highly important during the first steps of the opening of the die to remove the finished product from the male element 8. When the upper base 9 rises, pulling the male element 8 with it, the blank holder 10 remains, thanks to the action of springs 10b, in the position reached earlier, so as to lock the finished product 6b in the matrix 1 thanks to its contact in the region 10c. The danger is thus avoided of the finished product remaining attached to the male element 8, which would interrupt the automatic continuous operation of the die. An additional safety against the occurrence of this circumstance is constituted by the pressurized air jet that is sent through the ducts 11a, 11b into the interspace 12 during the first moments of the ascent of the male element 8. The base 9 therefore rises and subsequent steps of the opening of the die occur, such as the one shown in Figure 5, which shows that the finished product 6b is guided out of the matrix 1 by the action of the plate 7, which is conveniently moved by the shaft 7a according to the adjustment of the fluid-actuated system for managing said shaft, until it can be received by an extraction arm through the region 5b of the centering disk 5. The blank holder 13 performs the function implied by its name in the embodiment shown in Figure 8, in which the traction elements 13a are longer than the traction elements 10a of the first described embodiment and also determine, at the very first contact between the male element 14 and the disk 6 to be processed, the contact of the blank holder 13 with the disk 6. The typical function of the blank holder 13 is therefore provided during the first drawing steps; thereafter, at a certain moment said blank holder releases the disk being processed and makes contact with the matrix 1. In this embodiment, the male element 14 is shaped so as to make contact with the edge of the resulting container as a whole, and therefore the blank holder 13 no longer has any band that is located at the inner peripheral region and protrudes onto the recess formed in the matrix 1 so as to form a shape which is complementary to the shape of the container, renouncing the functions of matrix completion and of extractor for removing the finished part from the male element 8 presented in the previously described embodiment. A further embodiment is described in Figure 9, in which a matrix 15 is provided, which does not have a plate that follows the finished product as it leaves the die and therefore this function is assigned to different means, such as for example suckers; as regards the rest, the die has the previously described characteristics. The present invention is susceptible of numerous other modifications and variations within the scope of the claims: thus, for example, the plate 7 might be moved by means of underlying elastic means. In the practical embodiment of the invention and within the scope of the claims, all the details may be replaced with other technically equivalent elements; the materials employed, as well as the shapes and the dimensions, may be any according to requirements. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims: A drawing and coining die for manufacturing metal containers comprising: a matrix (1;15), which is connected to a lower base (4) adapted to be associated with a footing of a press and is provided with means (5) for centering a disk (6) that constitutes the material to be processed; a male element (8;14), which is connected to an upper base (9) adapted to be associated with a movable slider of the press and which comprises a peripheral contact region (8b) shaped so as to make contact with an edge (6b) of the resulting container interposed between said matrix (1;15) and said male element (8;14) in a fully closed configuration of said die; characterised in a blank holder (10;13) which extends about said male element (8;14) and which is connected to said upper base (9) through means (10a;13a) which allow their mutual distances to vary and with elastic elements (10b) interposed, said blank holder (10;13) and said male element (8;14) and said matrix (1;15) being mutually configured such that in said fully closed configuration of said die a bottom surface of said blank holder (10;13) makes contact with the matrix (1;15). The die according to claim 1, characterized in that the male element (8) is shaped so as to make contact with the edge (6b) of the resulting container, with the only exception of a band which is located in an outer peripheral region of said edge, the blank holder (10) adapted to make contact with the matrix having a band (10c) which is located at an inner peripheral region and protrudes onto a recess formed in said matrix (1) so as to form a shape which is complementary to the shape of the container. The die according to claim 1, characterized in that the male element (14) is shaped so as to make contact with the edge of the resulting container as a whole. The die according to one claim 1, characterized in that the matrix (1;15) is provided with a disk centering ring (5) which is detachably fixed thereto and comprises a region (5b) which allows the passage of the resulting container. The die according to claim 1, characterized in that the blank holder (10;13) is connected to the upper base (9) by virtue of sliding traction elements (10a,13a) and with springs (10b) interposed. The die according to claim 2, characterized in that , within the blank holder (10;13), a duct (11a,b) is provided for feeding compressed air, during the first steps of the opening of the die, into an interspace (12) defined between said blank holder (10;13) and the male element (8;14). The die according to claim 1, characterized in that a plate (7) provided with movement means (7a) is arranged within the matrix (1) at a bottom of said matrix, said plate being slightly larger than the dimensions of an end cross-section of the male element (8). The die according to claim 7, characterized in that the movement means for moving the plate (7) comprise an underlying shaft (7a) which protrudes from the footing of the press and is controlled by a fluid-driven system with which said press is equipped. The die according to claim 7, characterized in that said movement means (7a) comprise underlying elastic means.

Inventors: MARIN VISINO, MARIN, VISINO
Applicants: ATTREZZERIA MV & C SNC, ATTREZZERIA M.V. DI MARIN VISINO & C. S.N.C.
Application year: 1998
Main classification: B21D22
IPC codes: B21D45, B21D22