MULTI-FUNCTION MOULD FOR PROCESSING A STEEL STRIP AND METHOD FOR PRODUCING A WASHING MACHINE DRUM

Abstract

A mould for processing a metal panel by means of a hydraulic press includes a forming punch and a forming die, provided on their operating surfaces with corresponding hole patterns, a set of tubular deep-drawing punches disposed in the forming punch and movable relative thereto to protrude through its holes, a set of tubular deep-drawing dies disposed in the forming die in correspondence with its holes, and a set of blanking punches sized to be smoothly guided along the axial holes of the deep-drawing tools. The relative method of operation involves sequentially closing the mould, lowering the deep-drawing punches, lowering the blanking punches, raising the deep-drawing punches, raising the blanking punches and opening the mould.

Claims

1. A mould for a hydraulic press comprising: a movable upper part provided with means for coupling to a ram of said hydraulic press; a fixed lower part provided with means for coupling to a base of said hydraulic press; a first element of a moulding tool fixed to said movable upper part and provided in its operating surface with a hole pattern; a second element of a moulding tool fixed to said stationary lower part and provided in its operating surface with a hole pattern corresponding to said hole pattern of said first element; a first set of tools arranged at least partially in the first element of the moulding tool and movable with respect thereto to protrude through its holes; a second set of tools disposed in said second element of the moulding tool in correspondence with its holes; and mechanisms for operating said first set of tools between a working position, wherein said tools protrude inferiorly from the first element, and a rest position, wherein said tools do not protrude inferiorly from the first element; the first set of tools consisting of blanking comprising deep-drawing punches having a tubular structure and provided with a bottom end shaped to obtain a specific deep-drawing profile; the second set of tools comprising deep-drawing dies having a tubular structure with a top entrance hole and provided with a flat top or a top shaped to be complementary to said bottom end of the deep-drawing punches; the mould further comprising a third set of tools disposed at least partially in the first element of the moulding tool and movable with respect thereto to protrude through its holes, said third set of tools comprising blanking punches dimensioned to be smoothly guided along the axial holes of the tools of the first and second sets of tools, mechanisms for operating the third set of tools between a working position, wherein the tools protrude inferiorly from the first element of the moulding tool and the deep-drawing punches, and a rest position, wherein the tools do not protrude inferiorly from the first element of the moulding tool and the deep-drawing punches, said first element of the moulding tool being a forming punch and said second element of the moulding tool being a forming die.

2. The mould according to claim 1, wherein the bottom end of the deep-drawing punches has a shape chosen from hemisphere, truncated cone and circular paraboloid.

3. The mould according to claim 1, wherein the blanking punches have an upper portion having a larger diameter, which corresponds substantially to the inner diameter of the deep-drawing punches, and a lower portion having a smaller diameter, which corresponds substantially to the diameter of the entrance hole of the deep-drawing dies. The mould according to claim 2, wherein the blanking punches have an upper portion having a larger diameter, which corresponds substantially to the inner diameter of the deep-drawing punches, and a lower portion having a smaller diameter, which corresponds substantially to the diameter of the entrance hole of the deep-drawing dies.

Description

[0012] Further advantages and features of the mould and its method of operation according to the present invention will be apparent to those skilled in the art from the following detailed description of an embodiment thereof with reference to the accompanying drawings, in which:

[0013] FIG. 1 is a perspective view from above of a processing bench with a single moulding station comprising a mould according to the present invention;

[0014] FIG. 2 is a perspective view from below of the forming punch of the above-mentioned mould;

[0015] FIG. 3 is a perspective view from above of the forming die of the above-mentioned mould;

[0016] FIG. 4 is a perspective view from above of the three sets of tools contained in the mould for performing deep-drawing and blanking operations, with an enlarged detail in exploded view;

[0017] FIG. 5 is a sectional view of the closed mould with the tools in their final operating position at the end of the three processing stages, with an enlarged detail;

[0018] FIG. 6 is an exploded schematic side view of the open mould before starting the panel processing;

[0019] FIG. 7 is a view similar to the previous one showing the first forming stage;

[0020] FIG. 8 is a view similar to the previous one showing the second deep-drawing stage; and

[0021] FIG. 9 is a view similar to the previous one showing the third blanking stage.

[0022] Referring to FIG. 1, it can be seen that a processing bench 1 traditionally comprises a frame structure 2 which carries a plurality of tools and devices, including an hydraulic press 3, for processing a stainless steel strip inserted through inlet 4 by unwinding it from a reel via a decoiler (not shown) which pushes the strip towards bench 1. Here, a panel is cut from the strip and sequentially subjected to the forming, drawing and blanking steps in the single station comprising press 3, which carries a mould 10 according to the present invention as described below.

[0023] Once these operations have been completed, the panel is sent through outlet 5 to the next stages of processing into a finished washing machine drum. It should be noted that the panel extends almost the entire length of bench 1 between inlet 4 and outlet 5, so that its complete processing over its entire length requires multiple processing sequences in press 3 on the various portions of the panel being advanced, typically three or four sequences.

[0024] The perspective views in FIGS. 2 and 3 show forming punch 11 and forming die 12, which are part of the movable upper part and fixed lower part of mould 10 respectively. If forming punch 11 and forming die 12 were simple traditional forming tools, they would imprint the aesthetic geometry on the sheet without allowing any further processing.

[0025] A first novel aspect of the mould according to the present invention is to comprise three sets of tools contained within it and arranged to interact with each other via two hole patterns 13, 14 formed at corresponding positions in the opposing operating surfaces of punch 11 and die 12 respectively. More specifically, as shown in FIGS. 4 and 5, mould 10 comprises a set of blanking punches 15, a set of deep-drawing punches 16 and a set of deep-drawing dies 17, which also cooperate with the blanking punches 15.

[0026] In fact, both punches 16 and dies 17 have a substantially tubular structure, and punches 15 are sized to be smoothly guided along the axial holes of said tools. In particular, punches 15 preferably have an upper portion 15a having a larger diameter that substantially corresponds to the inner diameter of punches 16 (with adequate clearance), and a lower portion 15b having a smaller diameter that substantially corresponds to the diameter of the entrance bore 17a of dies 17 (with adequate clearance). In this way, the blanking punches 15 are stronger and more durable as they are not limited in their diameter by the diameter of holes 17a but can have a larger diameter, taking advantage of the larger diameter of the deep-drawing punches 16.

[0027] In practice, the die set 17 accommodates the deep-drawing punches 16 and the blanking punches 15 within the forming die 12 in the lower half of mould 10 (note that the sheet metal panel arranged in mould 10 is not shown in FIGS. 5-9). The top of die 17 can be complementary to the shape of end 16a of the deep-drawing punch 16, or it can be flat to simply act as an end stop in the deep-drawing phase. Said end 16a preferably has a hemispherical shape, but may have other shapes such as a truncated cone, a circular paraboloid or the like.

[0028] While dies 17 are fixed inside the forming die 12, punches 15 and 16 move together with the forming punch 11, which is mounted on the upper part of mould 10, and are at least partially housed inside it. In addition, punches 15 and 16 are progressively engaged and actuated in order to make them protrude inferiorly from the forming punch 11 through holes 13, so as to perform their respective processes in a given sequence. Note that the hydraulic mechanisms used to actuate punches 15, 16 are standard and therefore need not be described.

[0029] The simple and effective operation of the mould according to the present invention is immediately apparent from the above description, with the aid of FIGS. 6-9 schematically illustrating its operation with reference only to the punches and dies.

[0030] In the initial position of FIG. 6 with the die open, punches 15 and 16 are schematically shown outside forming punch 11, while dies 17 are not visible as they are inside forming die 12. In the first forming stage of the panel (not shown), the mould is closed by bringing forming punch 11 against forming die 12, with punches 15, 16 moving together with punch 11 but not relative to it (FIG. 7).

[0031] In the second deep-drawing stage illustrated in FIG. 8, the first set of drawing punches 16 are lowered so as to protrude from the forming punch 11 and act on the panel until it is pushed against the drawing dies 17. Subsequently, in the third blanking phase of FIG. 9, the second set of punches 15 is engaged and, passing through the deep-drawing punches 16 and entering dies 17, shears a circular section concentric to the deep-drawing geometry, completing the processing with the drainage holes.

[0032] The mould-opening sequence is reversed from the processing sequence described above, i.e. first the blanking punches 15 are lifted, then the deep-drawing punches 16 are lifted, and then the forming punch 11 is lifted, so that the processed panel can be advanced to outlet 5 of the moulding station.

[0033] It should be noted that the forming punch 11 could theoretically also perform deep-drawing so as to reduce the process to just two steps, dispensing with the deep-drawing punches 16, but in reality it is more advantageous to use the mould and process according to the present invention. In fact, deep-drawing requires a stronger localised action than forming, which implies a higher wear of the punch in the deep-drawing areas, so that there would be an accelerated wear of punch 11 in the deep-drawing areas. This would involve replacing the entire punch 11 even if it was still effective for the forming operation, otherwise the entire punch 11 would have to be made of a stronger, more expensive and heavier material to avoid localised wear, with obvious cost disadvantages. Note that the same problem would occur in the case of using forming die 12 for deep-drawing as well, to dispense with drawing dies 17.

[0034] Conversely, having separate tools 11, 12 for the forming phase and 16, 17 for the deep-drawing phase allows only the tools affected by wear to be changed, and possibly even the deep-drawing profile to be changed independently without changing the forming and vice versa.

[0035] It is clear that the above-described and illustrated embodiment of the mould according to the invention is only an example susceptible to numerous variations. In particular, the shape, size and mode of coupling of punches 11, 15, 16 and dies 12, 17 may vary freely according to constructional requirements, as may the drive mechanisms of punches 15, 16. For example, punches 15 might have a single diameter along the shank, or a different clearance to punches 16 than to dies 17.

[0036] The innovative method of producing a semi-finished panel for a washing machine drum by means of a hydraulic press 3 equipped with a mould 10 according to the invention can thus be summarised in the following steps: [0037] a) closing of mould 10 to perform an initial forming phase using the forming punch 11 and forming die 12; [0038] b) lowering the deep-drawing punches 16 until the metal panel comes into contact with the deep-drawing dies 17, in order to perform a second deep-drawing phase; [0039] c) lowering the blanking punches 15 until they enter holes 17a of the deep-drawing dies 17, in order to perform a third blanking phase; [0040] d) lifting of the blanking punches 15; [0041] e) lifting of the deep-drawing punches 16; [0042] f) opening of mould 10.

[0043] As mentioned above, it is clear that this method can be applied to the production of a semi-finished metal panel for other types of products, other than a washing machine drum, as long as the processing of such a panel involves the same forming, deep-drawing and blanking steps.