The invention relates to a press tool for the stamping of an undercut sheet metal.
Embossing is a shaping operation of a thin sheet which is commonly used in industry, particularly in the automotive industry to form including cladding panels, such as a hood of a motor vehicle. The stamping is carried out in press by means of a stamping tool 10 comprising a lower support frame and an upper movable drawing frame. The support frame carries a punch which delimits a stamping face of the sheet. Complementarily, the support frame comprises at least one counter-shape which delimits an undercutting portion of the sheet designed to cooperate with the punch. The edge of the sheet bent undercut has the disadvantage of being able to oppose the removal of the sheet on the punch and make the cutting of the sheet difficult or impossible. To overcome this drawback, the counter-form is slidably mounted on the support frame in a first direction, between a stamping position in which the counter-form is able to cooperate with the sheet, and a retracted position in which the counter-form allows the removal of the stamped sheet. The counter-form is driven in displacement by a drive means which is generally arranged in a housing formed in the punch or below the punch, as described and shown in US-A-7,243,524. Such an arrangement of the driving means of the counter-form 30 is often achieved to the detriment of the robustness of the punch. Indeed, the punch is generally partially hollowed out to provide the housing of the drive means so that the punch is weakened mechanically, particularly in the vicinity of the portion of the punch which cooperates with the drawing portion of the counter-form, this portion of the punch 35 may have a large cantilever.
In addition, this type of arrangement of the drive means makes the drive means little or not accessible. The invention aims to overcome these drawbacks in particular by providing a stamping tool which allows to drive the counter-form in displacement without weakening the punch. For this purpose, the invention proposes a press tool for stamping a sheet, of the type comprising: a support frame, a punch which is mounted on the support frame and which delimits a face of stamping the sheet, at least one against-shape which delimits a stamping portion of the undercut sheet adapted to cooperate with the punch, and which is mounted movably on the support frame in a first direction, between a drawing position in which the counter-form is adapted to cooperate with the sheet metal, and a retracted position in which the counter-form allows the withdrawal of the stamped sheet, a drive means in displacement of the counter-form - A movable frame which is movable relative to the support frame, characterized in that the drive means drives the counter-form into its drawing position by pulling the counter-form outwardly of the punch. Thus, the invention allows to arrange the drive means beyond the punch, that is to say outside the space occupied by the punch. According to another characteristic, the counter-form is slidably mounted on the support frame in the first direction, between its retracted position and its stamping position. In addition, the counter-form extends in said first direction, the counter-form comprising: a first end section which forms said stamping portion and which cooperates with the punch; a second end section; opposite which forms a sliding drive portion of the against-shape and which is arranged beyond the punch, and - an intermediate section which connects the drawing portion and the drive portion.
Also, the drive means cooperates with the driving portion of the counterform to pull the counterform from its retracted position to its drawing position. This characteristic makes it possible to arrange the drive means 5 beyond the punch. In addition, the drive means comprises: - a cam which is carried by the movable frame, - a plug which is slidably mounted on the support frame in a second direction and which drives the counterform in displacement, - a counter-cam which is carried by the plug, the cam and the cam follower being designed to cause the counterform to move from its retracted position to its drawing position. Similarly, the cam and the cam follower are interposed between the drive portion of the counterform and the punch. According to another characteristic, the tool comprises a first resilient return means of the counterform to its retracted position. This feature allows the counterform to be automatically recalled to its retracted position. In addition, the tool comprises a press member which is slidably mounted on the mobile frame, between a rest position and a working position in which the press member cooperates with the counter-form to stamp the sheet against and, which cooperates with synchronization and sliding means designed to drive the press member in its working position under the action of the movable frame, when the againstform 25 is in its drawing position. Complementarily, the tool comprises a second elastic return means of the press member to its rest position. Finally, the movable frame carries a presser which is designed to press and hold the sheet against the punch. Other features and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: FIG. 1 is a cross-sectional view, which illustrates a tool stamping machine having a counterform in the retracted position and a press member in the rest position according to the invention; FIG. 2 is a cross-sectional view similar to FIG. 1, which illustrates the counter form of the tool of FIG. 1 in a stamping position; Figure 3 is a cross-sectional view similar to Figure 1, illustrating the counter shape of the tool of Figure 1 in a stamping position and the press member in a work position; - Figure 4 is a cross-sectional view similar to Figure 1, which illustrates the counter form of the tool of Figure 1 in its retracted position and the sheet pressed against undercut. In the description and the claims, the terms "upper", "lower" and "low", "high" will be used in a nonlimiting manner with reference to the upper part and the lower part respectively of FIGS. 1 to 4. In order to clarify the description and the claims, the longitudinal, vertical and transverse terminology with reference to the L, V, T trihedron shown in the figures will be adopted without limitation. In addition, we will use the terms "before" marked AV in the figures, with reference to the right portion of the figures, and "rear" marked AR in the figures, with reference to the left side of the figures. FIG. 1 shows a press tool 10 for stamping a metal sheet 12 of the type which comprises a lower support frame 14 and a mobile frame 16 which is upper. The movable frame 16 is designed to approach and move in translation away from the support frame 14, in a direction V supposed vertical, and 25 respectively during the closing and opening cycles of the tool 10. A punch 18 is mounted on the support frame 14, the punch 18 delimiting an upper stamping face 20 of the sheet 12 on which the sheet 12 is extended, as partially shown in FIG. 1. In a complementary manner, the tool 10 is equipped with a counter-form 22 which delimits a drawing portion 24 designed to cooperate with the punch 18 to stamp the sheet 12 against undercut. As shown in FIG. 1, the stamping portion 24 formed by the counter-form 22 is arranged beneath a projecting portion of the punch 18. The counterform 22 extends in a first direction A, the counter-form 22 -form 22 comprising a first front end section which forms the drawing portion 24 and which cooperates with the punch 18, a second opposite rear end section which forms a sliding drive portion 26, and an intermediate section 28 which connects the drawing portion 24 and the drive portion 26 between them.
The sliding drive portion 26 of the counter-form 22 is here arranged beyond, or outside, the punch 18, that is to say that it is not necessary to reserve a space in, or under, the punch 18 for arranging the drive portion 26. In addition, the counter-form 22 is slidably mounted on the support frame 14 by means of a first sliding connection 29. More particularly, the counter -form 22 is sliding back and forth, in the first direction A, between a stamping position shown in Figures 2 and 3, wherein the counter-form 22 is adapted to cooperate with the sheet 12 to stamp it, and a retracted position 15 shown in Figures 1 and 4, wherein the counter-form 22 allows the removal of the sheet 12 stamped from above, for example by means of a robotic arm (not shown). For this purpose, the tool 10 comprises a drive means for moving the counterform 22, which is designed to drive the counterform 22 into its drawing position by pulling the counter-form 22 towards the outside the punch 18, that is to say from front to back. The term "pull" is opposed here to the term "push" which would imply that the drive means is arranged in front of the counterform 22, for example below the counterform 22. The means drive of the counterform 22 comprises a cam 30a which is carried by the mobile frame 16 and which delimits a first working profile 32a inclined relative to the vertical direction V. In addition, the drive means comprises a bushel 34 which is slidably mounted on the support frame 14 from front to back in a second transverse direction T substantially inclined with respect to the first sliding direction A of the counter-form 22. The plug 34 comprises a transverse plate 36, which is slidably connected to the support frame 14 by means of a second slide connection 35, and a drive finger 38 which extends vertically upwards from the plate 36.
As shown in Figure 1, the drive finger 38 delimits a vertical rear face 40 which is equipped with a sliding plate 42. The sliding plate 42 is arranged in a transversal support against a complementary sliding plate 44 which is mounted on the drive portion 26 of the counterform 22. In addition, the driving finger 38 delimits a vertical front face 46. which is equipped with a cam follower 30b. The counter-cam 30b delimits a second working profile 32b which extends against the first profile 32a and parallel to the first profile 32a of the cam 32a. Thus, the vertical movement of the movable frame 16 downwardly drives the plug 34 towards the rear via the cam 32a and cam follower 32b provided for this purpose, the plug 34 acting simultaneously on the portion of drive 26 of the counterform 22 to drive the counterform 22 from its retracted position to its drawing position. Complementarily, the tool 10 comprises a first resilient return means 48 which cooperates with the first slide link 29 and resiliently removes the againstform 22 forward towards its retracted position when the mobile frame 16 is driven upwards. As shown in FIGS. 1 to 4, the cam 30a and the cam follower 30b are interposed transversely between the drive portion 26 of the counterform 22 and the punch 18. In another aspect, the tool 10 comprises a press member 50 which delimits a drawing portion 51 which is adapted to cooperate with the drawing portion 24 of the counter-form 22 to stamp the sheet 12 against undercut. The press member 50 has a double ramp and is equipped with a first upper sliding plate 52a cooperating with a sliding plate 54a complementary to the movable frame 16 and a second lower sliding plate 52b cooperating with a sliding plate 54b complementary to the mobile frame 16. The press member 50 is slidably mounted on the mobile frame 16 in the first direction A, by means of a slide connection (not shown), between a rest position and a working position in The press member 50 cooperates with the stamping portion 24 of the counter-form 22 to stamp the sheet 12 against undercut, as shown in FIG. 3. The sliding plates 52a, 54a, 52b, 54b forming synchronizing and sliding means which are designed to drive the press member 50 into its working position when the moving frame 16 is lowered, when the counter-form 22 occupies its position. stamping osition. For this purpose, according to FIGS. 2 and 3, the cam 30a delimits a third vertical working profile 32c and the cam follower 32a delimits a fourth vertical working profile 32d, the third profile 32c and the fourth profile 32d being arranged and designed to allow the vertical descent of the frame 16 following the driving of the counter-form 22 in its stamping position. Complementarily, the tool 10 comprises a second elastic restoring means 56 of the jack type, which is designed to return the press member 50 towards the rear, towards its rest position, when the mobile frame 16 goes back towards the the top. Finally, the mobile frame 16 carries a presser 58 which is designed to press and hold the sheet 12 against the punch 18 during stamping of the sheet by the action of the press member on the stamping portion 24 20. The operation of the drawing tool 10 is described in the following description, starting with the closing cycle and ending with the opening cycle. Initially, the tool 10 is open, the movable frame 16 is at the top of the stroke, the counter-form 22 occupies its retracted position and the press member 50 occupies its rest position, as shown in FIG. a first downward travel portion of the movable frame 16, the first profile of the cam 30a cooperates with the second profile 32b of the cam follower 30b so as to drive the against-shape 22 in its drawing position 30, by the intermediate of the plug 34 associated, according to Figure 2. In a second downward stroke portion of the movable frame 16, the slide plates 52a, 54a, 52b, 54b forming means of synchronization and sliding cause the press member 50 in its working position, so that the sheet 12 undercut against, as shown in Figure 3.
Conversely, in a first upward stroke portion of the movable frame 16, the press member 50 is returned to its rest position by the second elastic return means 56 provided for this purpose. Finally, in a second upward stroke portion of the movable frame 16, the against-shape 22 is returned to its retracted position by the first elastic return means 48 provided for this purpose, as shown in FIG. 4. Thus, the The invention makes it possible, in particular, to arrange the means for driving the counterform 22 outside or beyond the punch 18, 10 so as to avoid mechanically weakening the punch 18. Moreover, only the portion stamping 24 of the counterform 22 is arranged below the punch 18.