Swaging tool for forming stamps and related stamping methods - Patents.com

Abstract

To provide such a swage tool that can readily form a final part.SOLUTION: In a swage tool, an upper-side die (26) intended to swage a metal blank in a proper position in a housing (10) of a lower-side unit is installed to an upper-side unit, where the upper-side die (26) is fitted so as to be movable along an axis of motion; and a plier (14) including two arms (16A2, 16B2) fitted so as to be movable between an open position and a closed position at a plane perpendicular to the axis of motion is installed to the lower-side unit, where an opening (18) between part of the housing (10) for receiving the metal blank and the two arms is defined and a dimension of the opening is smaller than a dimension corresponding to an upper-side part (12A) and a lower-side part of the metal blank (12).SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to the field of swaging tools, also known as stamps, intended to swage against a metal blank and to plastically deform this blank.

[0002] The present invention therefore relates to such a swaging tool for forming a stamp, and to a stamping method associated therewith, which is intended, for example, in particular for forming a relief pattern, in particular a logo, on the upper main surface of a timepiece crown head, in particular a winding crown head of a portable timepiece (e.g. wristwatch, pocket watch). [Background technology]

[0003] Industrial stamping involves the plastic deformation (so that it does not return to its original shape) of a metal object using a "die" with a hydraulic, mechanical, screw press, or a forging hammer, which together form the swage tool (also called stamp). This forging process, which is carried out hot or at ambient temperature, can be carried out in several operations. The first operation is called "blanking" and the last operation is called "finishing". The blank allows the metal to be spread, which most often starts with a cylindrical or parallelepiped shape, and takes a shape close to the finish. The final blank is larger in vertical dimensions and smaller in horizontal dimensions than the finish, by up to a few millimeters, which allows for forging without energy losses due to friction at the walls of the figure. The blank usually has rounded corners compared to the finish. In fact, filling the corners is the most difficult part in forging.

[0004] The main advantage of stamping is that the internal structure of the steel is formed, enhancing the material properties of the final part, resulting in superior mechanical properties.

[0005] A stamp usually consists of two units, a lower unit and an upper unit, which respectively contain a lower die and an upper die (also used as a term to include lower half die and upper half die). The lower die is the stationary part, and the upper die is typically a movable drop hammer, which stamps and deforms the part.

[0006] Finishing completes the transformation of the material. The result includes the rough part and the burrs. The latter are excess material throughout the part that ensures the image fills correctly. The burrs are then separated from the rough part by a forging process called trimming.

[0007] However, such trimming operations are tedious, time consuming, and add to the overall cost of the entire part formation process. The additional steps of finishing the part are tedious and can result in the formation of certain corners in the final part (e.g., with several iterations), the need to modify the part's contour, the formation of undercuts, etc. Summary of the Invention [Problem to be solved by the invention]

[0008] In this situation, the present invention aims to solve the problems of the prior art by providing a swaging tool (forming a stamp) for performing a low-cost stamping method, which can easily form the final part, with little or substantially no need to remove burrs or modify the part's contour, and where finishing of the part is simple and low-cost. [Means for solving the problem]

[0009] To this end, the invention relates to a swaging tool for forming a stamp for a metal blank, comprising a lower unit and an upper unit, the lower unit being adapted to form a housing intended to receive said metal blank, the upper unit having an upper die intended to stamp said metal blank in a suitable position in the housing of the lower unit, the upper die being mounted movable along a movement axis, the lower unit having pliers formed by two arms mounted movable between an open position and a closed position in a plane perpendicular to said movement axis, the two arms of the pliers being spaced apart in said open position between which a metal blank can be placed, and in said closed position the two arms of the pliers are brought close together, defining along said movement axis upper and lower areas of the housing separated by an opening, the dimensions of which are smaller than the corresponding dimensions of the lower area of ​​the housing and the corresponding dimensions of the upper area of ​​the housing, the two arms in the closed position forming a lower die for said metal blank at least in said upper area of ​​the housing.

[0010] Thanks to the presence of the pliers thus configured, the swaging tool according to the invention makes it possible to give the metal blank substantially its final shape, in particular with grooves on its edges, this swaging with little or substantially no need to remove burrs and without the need to modify the contour of the part. In fact, thanks to the two arms of the pliers forming part of the housing for receiving the metal blank and the opening between them, their dimensions being smaller than the corresponding dimensions of the upper and lower parts of the metal blank, the swaging by the upper die on the metal blank is not hindered and the forming of the shape of the upper part can be carried out by the swaging tool without degrading the outer surface of this lower part, in particular the surface of the longitudinal grooves. The final part therefore requires only minor emptying and grinding, possibly at the end of the process, again after it has been stamped (but no modification of the contour of the part is necessary). In particular, a groove separating the upper and lower parts can be formed on the periphery of the metal blank, the upper wall of this groove being completed by swaging, if necessary.

[0011] In one advantageous embodiment of the invention, the corresponding parts of the two arms that define the upper part of the housing form a lower die for the metal blank. Such a lower die thus allows partially giving the metal blank its final shape. In this embodiment, the metal blank does not in fact have the same initial shape as the final shape for the part of the metal blank that is located in the upper part of the housing, and the swaging of the metal blank by the upper die thus induces a deformation of the upper part (also known as the head) of the blank, in particular of at least one upper part of the void middle part. It is to be noted that the term "housing for receiving a metal blank" is not to be understood as having the same shape as the initial shape of the metal blank, but as a defined space for receiving this metal blank that at least partially defines the final shape of the part obtained after swaging.

[0012] The swaging tool further includes an actuator configured to close the pliers arms prior to swaging.

[0013] According to a particular technical feature of the invention, the upper unit is mounted for movement relative to the lower unit along the axis of movement, and preferably the actuator is mounted on the upper unit and configured to move the arms of the pliers closer to their closed position.

[0014] Preferably, the actuator attached to the upper unit is a first actuator and the lower unit comprises a second actuator formed by a spring, in particular a straight extension spring, connecting the two shanks of the pliers.

[0015] According to an advantageous technical feature of the invention, the travel of the movement of the upper unit relative to the lower unit and the shape of the first actuator, the flared zone and the cylindrical zone of the pliers, respectively, are synchronized with the swaging by the upper unit against the metal blank, such that the movement of the two arms of the pliers intended to partially receive the metal blank towards each other causes these two arms to reach a closed position to form the part of the housing before swaging is performed.

[0016] According to a particular feature, the pliers have two branches formed by a hinge connection of two arms and two shanks, the two branches not crossing each other but hinged at a joint located between the two arms and the two shanks, the two shanks each forming a flared zone on the upper side followed by a cylindrical zone on the bottom side, the two flared zones and the two cylindrical zones of the pliers being arranged facing each other, the first actuator is shaped so as to be able to press the two flared zones of the pliers first when the upper unit approaches the lower unit, moving the two shanks apart and bringing the two arms of the pliers closer together to a closed position, thereby defining the portion of the housing for receiving the metal blank, and then finishing the movement of the pliers between the two cylindrical zones while keeping the two arms in the closed position.

[0017] Another aspect of the invention relates to a method of stamping using the swaging tool, the pliers being initially in an open position with the two arms of the pliers spaced apart, the method comprising: Providing a metal blank having an upper portion and a lower portion; placing the metal blank between two of the arms of the pliers; thereafter, moving the two arms of the pliers together to a closed position of the pliers to form a portion of the housing for receiving the metal blank, with upper and lower portions of the metal blank positioned on either side of the opening formed between the two arms along the axis of motion; moving the upper unit along the axis of motion toward the lower unit to swage the metal blank with the upper die; separating the two arms of the pliers to place the pliers in an open position; and ejecting from the lower unit the final part obtained after swaging the metal blank.

[0018] Such stamping methods are simplified compared to prior art processes, contributing to time savings by requiring little or no burr removal or modification of the contour of the final part, which has a groove around its periphery and, optionally, a fluted lower portion below the groove, which, after being stamped, may require only minor re-emption and polishing at the end of the process (but no modification of the contour of the part is required).

[0019] Preferably, the stamping process is carried out at ambient temperature.

[0020] According to an advantageous technical feature of the invention, the step of swaging the metal blank with the upper die is performed synchronously, and therefore at least partially simultaneously, with the closing of the two arms of the pliers, which reach their closed position, defining the upper and lower areas of the housing, after the upper unit has started its movement along the movement axis and before swaging. This advantageous variant is preferred. However, in another variant, the closing of the pliers, i.e. the closing of its two arms, can be performed before the swaging step, i.e. before the upper unit moves continuously towards the blank to swage this blank.

[0021] According to one embodiment example of the invention, during the step of swaging the metal blank with the upper die, a relief pattern, in particular a logo, is formed on the upper main surface of the head of the metal blank, the final shape of the upper main surface of this head being determined during the swaging.

[0022] Preferably, the metal blank is a timepiece crown blank, and the upper portion of the metal blank forms a crown head blank.

[0023] In a particular embodiment, the metal blank is generally cylindrical with rotational symmetry, and the upper portion of the metal blank forms a substantially circular blank head, the radius of the upper portion being less than the radius, about the axis of rotation, defined by the bottom of each flute in the fluted lower portion of the metal blank, such that the flutes can be easily formed in the lower portion of the metal blank, in particular by linear milling or drawing, without degrading the head of the metal blank, and the head of the final part can be given its final shape by stamping.

[0024] One of the parts advantageously obtained by this stamping method using the swaging tool according to the invention is a timepiece crown, the metal blank being a timepiece crown blank, the upper part of the metal blank forming the crown head.

[0025] Advantageously, the metal blank has a voided intermediate portion separating a lower portion and an upper portion of the metal blank, the lower portion of the metal blank being formed with a fluted portion having a plurality of flutes extending around a periphery of the metal blank, and the intermediate portion being grooved around a periphery of the metal blank.

[0026] In particular, the groove has a transverse profile in the shape of an inclined "V" about the axis of motion of the upper unit, the lower surface of the groove, in particular its angle with respect to the horizontal plane, being substantially determined during machining of the metal blank, and the upper surface of the "V" on the side of the upper part of the metal blank being finally determined during swaging of the metal blank by an upper die.

[0027] In this document, the terms "horizontal", "vertical", "transverse", "lower", "upper", "top", "lower" and "side" are defined with respect to the orientation of the swaging tool according to the invention. In particular, in this application, the term "vertical" refers to a direction along the axis of motion of the upper unit of the swaging tool, and the term "horizontal" refers to a direction or plane perpendicular to this axis of motion.

[0028] The objects, advantages and features of the swaging tool and the associated stamping method according to the invention will become more apparent on reading the following description of various embodiments illustrated in the drawings. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a perspective view of a swaging tool according to one embodiment of the present invention, the swaging tool including two-armed pliers that are mounted for movement between a pliers open position and a pliers closed position. [Diagram 2] FIG. 2 is a top view of the swaging tool of FIG. 1. [Diagram 3] FIG. 2 is a side view of the swaging tool of FIG. 1. [Figure 4] FIG. 2 is a front view of the swaging tool of FIG. 1, which has an upper unit with an upper die and a lower unit intended to receive a metal blank. [Diagram 5] 4 is a cross-sectional view of the swaging tool of FIG. 3 along vertical section VV with the pliers in an open position. [Figure 6] FIG. 6 is an enlarged view showing details of one embodiment of the swaging tool of FIG. [Figure 7] FIG. 7 is a cross-sectional view of the swaging tool of FIG. 4 along vertical section VII-VII, with the pliers in an open position. [Figure 8] 8 is a cross-sectional view along horizontal section VIII-VIII of the swaging tool of FIG. 5, the swaging tool comprising a first actuator and a second actuator; [Figure 9] 4 is a cross-sectional view of the swaging tool of FIG. 3 along vertical section VV with the pliers in a closed position. [Figure 10] FIG. 10 is an enlarged view showing details of one embodiment of the swaging tool of FIG. [Figure 11] FIG. 7 is a cross-sectional view of the swaging tool of FIG. 4 along vertical section VII-VII, with the pliers in a closed position. [Figure 12] FIG. 10 is a cross-sectional view of the swaging tool of FIG. 9 taken along horizontal section XII-XII. [Figure 13] FIG. 2 is a perspective view of a first arm of the pliers of FIG. 1. [Figure 14] FIG. 2 is a perspective view of a second arm of the pliers of FIG. 1. [Figure 15] FIG. 9 is a perspective view of the first actuator of FIG. 8 as seen from below. [Figure 16] 16 is a cross-sectional view taken along the vertical cross section XVI-XVI of the first actuator of FIG. 15. [Figure 17] FIG. 5 is a perspective view of the upper die of FIG. [Figure 18] FIG. 18 is a cross-sectional view of the upper die of FIG. 17 along vertical section XVIII-XVIII. [Figure 19] FIG. 19 is an enlarged view showing details of one embodiment of the upper die of FIG. [Figure 20] 5 is a perspective view of the metal blank of FIG. 4 prior to stamping with a swage tool according to an example embodiment. [Figure 21] FIG. 21 is a cross-sectional view of the metal blank of FIG. 20 along vertical section XXI-XXI. [Figure 22] FIG. 5 is a perspective view of the metal blank of FIG. 4 after stamping with a swaging tool to form a final part according to an example embodiment. [Diagram 23] FIG. 23 is a cross-sectional view of the final part of FIG. 22 along vertical section XXIII-XXIII. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] 1-12 show a swaging tool 1 for forming a stamp according to a particular embodiment of the present invention. The swaging tool 1 comprises a lower unit 2, an upper unit 4, a first actuator 6 and a second actuator 8.

[0031] As shown in figures 5 to 12, the lower unit 2 is adapted to form a housing 10 for receiving a metal blank 12. Figures 20 and 21 show an example of such a blank 12. According to this particular example, the metal blank 12 is a blank for a crown for a timepiece, with an upper part 12A forming the crown head, a fluted lower part 12C and an intermediate part 12B separating the upper part 12A from the lower part 12C. The lower part 12C of the blank 12 thus has several flutes 13 formed on the outer circumference of the blank 12 and equally distributed angularly on said circumference. The lower part 12C of the blank 12 forms, for example, a hollow cylindrical body, which has been hollowed out beforehand. The intermediate part 12B of the blank 12 has a groove (also known as an "undercut") formed on the outer circumference of the blank 12. The grooves 12B preformed in the metal blank 12 have a contour with a longitudinal cutout, specifically an asymmetrical "V" shape inclined to the vertical. As shown in FIG. 21, the angle α1 formed by the lateral "V" faces of the fluted lower portion 12C of the blank 12 with respect to the horizontal is preferably less than 45°, for example of the order of 32°. The angle α2 formed by the lateral "V" faces of the upper portion 12A of the blank 12 with respect to the horizontal is greater than 45°, for example of the order of 76°. The head 12A of the blank has a substantially dome-shaped upper main surface 15, the edges of which are slightly rounded.

[0032] 20 and 21, the metal blank 12 is generally cylindrical in shape forming a rotational symmetry, with the upper surface 15 of the upper portion 12A of the metal blank 12 forming a substantially circular head, the radius R1 of the upper portion 12A about the axis of rotation A-A' of the blank 12 being smaller than the radius R2 defined by the depth of each of the longitudinal grooves 13. The metal blank 12 is made, for example, of steel, typically DIN 1.4441 steel.

[0033] The lower unit 2 includes pliers 14 with two branches 16A, 16B. Preferably, the lower unit 2 also includes a support rod 17 and an outer guide 19 for angular positioning of the metal blank 12 and / or for holding the metal blank 12 in a radial position, as shown in Figures 5-7 and 9-11. The two branches 16A, 16B of the pliers 14 are mounted so as to be movable in a horizontal plane between an open position of the pliers 14 shown in Figures 5-8 and a closed position of the pliers shown in Figures 9-12. In the open position of the pliers 14, the two arms 16A2, 16B2 are spaced apart, so that the metal blank 12 can be placed between these two arms 16A2, 16B2. 10, in the closed position of the pliers 14, the two arms 16A2, 16B2 are close to each other, defining an opening 18 between the upper part of the housing 10 and the two arms 16A2, 16B2 for receiving the metal blank 12. The dimensions of the opening 18 are smaller than the corresponding dimensions of the upper and lower parts 12A, 12C of the metal blank 12, which are located on either side of the opening 18 along the vertical direction, when the metal blank 12 is placed in the lower unit 2 and the pliers 14 are in the closed position. The term "housing for receiving a metal blank" should not be understood as having the same shape as the initial shape of the blank 12, but as a defined space for receiving the blank 12.

[0034] In the particular embodiment shown in Figures 8, 12, 13 and 14, the two branches 16A, 16B of the pliers 14 have a shank 16A1, 16B1 and an arm 16A2, 16B2, respectively. However, the two branches 16A, 16B of the pliers are hinged at a connection 20 located between the two shanks 16A1, 16B1 and the two arms 16A2, 16B2, but the two branches 16A, 16B do not intersect. As shown in Figures 13 and 14, the first shank 16A1, 16B1 of each of the pliers branches 16A, 16B respectively defines a flared zone 22A, 22B on its upper surface, which extends downwards into a substantially cylindrical zone 24A, 24B. Each arm 16A2, 16B2 of each branch 16A, 16B of the pliers 14 defines, in a recess 25A, 25B of the arm, a part of the housing 10 and a part of the opening 18 for receiving the metal blank 12. The two flared zones 22A, 22B and the two cylindrical zones 24A, 24B of the pliers 14 are arranged opposite each other. As will be explained in detail below, the first actuator 6 has a shape suitable for being able to actuate the pliers. Each recess 25A, 25B belonging to one of the arms 16A2, 16B2 of each branch 16A, 16B of the pliers 14 has an upper part 27A, 27B and a lower part 29A, 29B, the latter of which is formed by a semicircular annulus (intended to partially form the final groove or undercut 11B of the blank). The two lower portions 29A, 29B of the arms 16A2, 16B2 define the opening 18 and thus the portion of the housing 10 for receiving the metal blank 12 when the pliers 14 are in their closed position, and the two lower portions 29A, 29B of the two arms 16A2, 16B2 form a lower die for the blank 12.

[0035] The support rods 17 are mounted for vertical movement and are connected to ejectors 21 (shown in Figures 5, 7, 9 and 11). The support rods 17, on which the metal blank 12 is initially placed, form inner guides for placing the metal blank 12 and are configured to allow ejection of the metal blank 12 of the lower unit 2 after swaging against the metal blank 12.

[0036] The lower unit 2 (apart from the pliers 14) consists, for example, of hard metal. The pliers 14 consist, for example, of tool steel.

[0037] The upper unit 4 includes an upper die 26 and is mounted to be movable along a vertical axis of movement B-B' relative to the lower unit 2. For this purpose, the upper unit 4 is mounted to the lower unit 2, for example, via two vertical ball cages 31 (shown in Figures 1, 2, 4, 5 and 9), which allow a vertical translational movement of the upper unit 4. The upper die 26, which is rigidly connected to the upper unit 4, is thus mounted to be movable along this vertical axis of movement B-B' and is configured to swage the metal blank 12 (specifically its head 12A) at a suitable position in the housing 10 of the lower unit 2.

[0038] As shown in Figures 10 and 17-19, the upper die 26 is, for example, in the form of a drop ram with a substantially frustoconical body 28, which has an end portion 30 intended to come into contact with the head 12A of the blank during swaging. The end portion 30 has a hollowed-out inner die 32 bounded by an annular rim 34 (here circular). A relief pattern image 36, in particular a logo image, is formed, for example, in the recess of the hollowed-out inner die 32. The upper die 26 is thus configured to form a relief pattern 38 (shown in Figure 22), in particular a logo, on the upper main surface 15 of the head 12A of the blank. The upper die 26 is also configured to define the final shape of this upper main surface 15 during swaging of the upper die 26 against the metal blank 12. Specifically, as shown in Fig. 10, the end portion 30 of the upper die 26 is configured to slide within the upper portions 27A, 27B of the two arms 16A2, 16B2 of the pliers 14 when the pliers 14 are in their closed position. The end portion 30 of the upper die 26 then extends above the portion of the housing 10 for receiving the metal blank 12, which is defined by the two arms 16A, 16B of the pliers 14. The annular rim 34, together with the hollow inner die 32, gives the metal blank 12 a portion of its final shape. The upper die 26 is made of, for example, tool steel.

[0039] The first actuator 6 is attached to the upper block 4 and is configured to close the arms 16A2, 16B2 of the pliers 14. In particular, as shown in Figures 8, 12, 15 and 16, the first actuator 6 has a shape complementary to the shape of the flared zones 22A, 22B and the substantially cylindrical zones 24A, 24B of the pliers 14. The first actuator 6 has a shape configured such that when the upper unit 4 approaches the lower unit 2, the first actuator 6 can first press the flared zones 22A, 22B of the pliers 14. This causes the two shanks 16A1 and 16B1 to move apart, thus bringing the two arms 16A2, 16B2 of the pliers closer to the closed position to form the portion of the housing for receiving the metal blank, and then finishing the movement between the two cylindrical zones 24A, 24B of the pliers 14. This is done while keeping the two arms in the closed position until the upper die 26 performs the envisaged swage. Thus, when the upper unit 4 moves downwards along the axis B-B' towards the lower unit 2 so that the upper die 26 performs the swage on the metal blank 12, the first actuator 6 simultaneously moves downwards towards the upper surface of the two shanks 16A1, 16B1 of the pliers 14 and is gradually inserted into the flared zones 22A, 22B, separating the two shanks thanks to the radial forces resulting from the transverse contours of the flared zones and the actuator 6. The shape of the actuator is then such that, during the final phase of the movement of the upper unit before swaging, it can slide freely between the cylindrical zones 24A, 24B, while keeping the two arms 16A2 and 16B2 in the closed position. 15 and 16, the first actuator 6 has a shape such that there is an inflection point P1 in the profile of the first actuator in a vertical cross section along the continuous outer surface 40. Thanks to this, the closing movement of the two opposing arms 16A2, 16B2 of the pliers 14 intended to partially receive the metal blank 12 is facilitated by allowing a gradual closing of the two arms 16A2, 16B2.

[0040] Preferably, the travel of the movement of the upper unit 4 relative to the lower unit 2 and the shape of the first actuator 6, the flared zones 22A, 22B and the cylindrical zones 24A, 24B of the pliers 14 are such that, before the swaging takes place, the closing movement of the two arms 16A2, 16B2 of the pliers 14 intended to partially receive the metal blank 12 is synchronized with the swaging by the upper die 26 against the metal blank 12, such that these two arms 16A2, 16B2 reach a closed position and press against each other to form the upper part of the housing 10 for receiving the metal blank 12. In this way, as the upper unit moves downwards along the axis B-B' towards the lower unit 2 and the upper die 26 approaches the metal blank 12, the first actuator 6 acts on the two shanks 16A1, 16B1 of the pliers 14 to gradually close the two arms 16A2, 16B2, one opposite the other, until they reach a closed position just before the swage. Thus, the closing of the two arms 16A2, 16B2 of the pliers 14 is synchronized with the swage of the upper die 26 against the metal blank 12.

[0041] 2, 8 and 12, the second actuator 8 is a spring that connects and provides a resilient return force to the two shanks 16A1, 16B1 of the pliers 14. This spring 8 is typically a straight extension spring.

[0042] The stamping method according to the invention, which is carried out by the swaging tool 1, will now be described with reference to Figures 4 to 12. The pliers 14 are initially in an open position, shown in Figures 4 to 8, in which the two arms 16A2, 16B2 of the pliers 14 are separated from each other. The upper unit 4 is separated from the lower unit 2. As a result, the upper die 26 is at a certain distance from the metal blank 12 and the first actuator 6 is separated from the two shanks 16A1, 16B1 of the pliers 14.

[0043] This stamping method comprises an initial step shown in Fig. 8, during which the metal blank 12 is placed in the lower part of the housing 10 and the pliers are in an initial open position (i.e. the two arms 16A2 and 16B2 are in the open position). In particular, the (hollow) lower part 12C of the metal blank 12 is placed on the one hand inside the outer guide 19 and on the other hand in contact with the support rod 17 so as to surround the end of the support rod 17. As shown in Fig. 6, the upper part 12A and the middle part 12B of the metal blank 12 protrude from the lower part of the housing 10 formed by the outer guide 19 and are placed between the two arms 16A2, 16B2 of the pliers 14, in particular in the lower area of ​​these two arms intended to form the opening 18.

[0044] The stamping method then comprises a step of vertically moving the upper unit 4 towards the lower unit 2 along the vertical axis B-B'. In so doing, the first actuator 6 is gradually inserted into the flare zones 22A, 22B of the pliers 14, thus acting on the two shanks 16A1, 16B1 against the elastic return force provided by the second actuator 8, gradually closing the two arms 16A2, 16B2 of the pliers 14. These two arms then approach each other until the closed position of the pliers 14 forms the upper part of the housing 10 and the above-mentioned opening 18 for receiving the metal blank 12. In this state, the upper and lower parts 12A and 12C of the metal blank 12 are located on either side of the opening 18 along the motion axis B-B'. When the pliers 14 are in the closed position, the first actuator 6 is free to terminate the movement of the pliers 14 between the cylindrical zones 24A, 24B while holding the pliers 14 in the closed position.

[0045] In parallel with this step, and synchronous with the lowering of the first actuator 6 (and therefore with the closing of the two arms 16A2, 16B2), the upper die 26 moves along the vertical axis B-B', approaching the metal blank 12. As shown in FIG. 10, when the pliers 14 are in the closed position, the end portion 30 of the upper die 26 slides on the upper portions 27A, 27B of the two arms 16A2, 16B2 of the pliers 14. Then, as shown in FIGS. 9-12, the end portion 30 of the upper die 26 swages against the metal blank 12 in a later step of the process. The annular rim 34 of the end portion 30 together with the hollow inner die 32 gives part of its final shape to the metal die 12, i.e. the final shape of the upper portion 12A (crown head). Thus, the space jointly defined by the two lower parts 29A, 29B of the arms 16A2, 16B2 of the pliers 14, the annular rim 34 of the end part 30 of the upper die 26 and the hollow inner die 32 forms the upper part of the housing 10 for receiving the metal blank 12 when the pliers 14 are in the closed position. Preferably, the upper die 26 forms a relief pattern (in particular a logo) on the upper main surface 15 of the head 12A of the blank during this swaging step, thanks to its image 36 shown in Figure 19. The upper die 26 also determines the final shape of this upper main surface 15 during the swaging of the metal blank 12.

[0046] The stamping method comprises a subsequent step of vertically separating the upper unit 4 from the lower unit 2, whereby the first actuator 6 gradually moves up from the cylindrical zones 24A, 24B of the pliers 14 towards and out of the flared zones 22A, 22B thereof, and the shanks 16A1, 16B1 of the pliers 14 approach each other due to the elastic return force provided by the second actuator 8, which triggers the separation of the two arms 16A2, 16B2 from each other into the open position of the pliers 14, specifically the two arms.

[0047] The stamping method comprises a final step in which the final part 11 (obtained after stamping the blank 12) is ejected from the lower unit 2 by actuating the ejector 21 to move the support rod 17 vertically upwards, triggering the ejection of the final part 11.

[0048] 22 and 23 show an example of such a final part 11 obtained after stamping a metal blank 12. According to this particular example, the final part 11 is a timepiece crown with a crown head 11A, a fluted lower part 11C and an intermediate part 11B separating the upper and lower parts 11A, 11B. The intermediate part 11B of this part 11 forms a groove or "undercut" at the edge of the part 11. In contrast to the initial groove 12B, this final groove 11B formed after stamping has a more voided longitudinal profile, in particular an asymmetrical "V" shaped longitudinal profile with a smaller internal angle, this asymmetrical "V" profile being inclined at 90° to the vertical. As shown in FIG. 23, the angle α1 formed by the inner surface of the "V" groove on the side of the fluted lower part 11C of the part 11 with respect to the horizontal plane is preferably less than 45°, this angle α1 remaining substantially equal to the corresponding angle of the metal blank 12. The angle α3 formed by the upper surface of the "V" groove on the side of the crown head 11A with respect to the horizontal plane is preferably greater than 45°, for example of the order of 50°, advantageously less than the corresponding angle α2 of the metal blank. In fact, during the swaging of the head 12A by the upper die 26, this swage widens the head 12A and at the same time slightly reduces its height, so that the final radius R3 of this head is greater than its initial radius R1 (as shown in FIG. 21). The final radius R3 of the crown head 11A is therefore greater than the radius R2 defined by the innermost part of each of the fluted grooves 13 around the rotation axis A-A' of the final part 11. The final crown head 11A has a slightly domed upper main surface 15 which is terminated by a rounded annular bulge 42. Thanks to the annular rim 34 of the end portion 30 of the upper die 26, as shown in Figure 19, it is possible to form the radius of the upper part of the end bulge 42 to a radius R4, which is, for example, substantially 0.25 mm, while the lower part of the rounded annular bulge 42 is formed by the two lower parts 29A, 29B of the arms 16A2, 16B2 of the pliers 14 which form the lower die of the stamping tool.The hollow inner die 32 of the end portion 30 of the upper die 26 defines a curved shape adapted to form the slightly domed upper main surface 15 of the crown head 11A. This curved shape of the hollow inner die 32 has a radius at its center R5, e.g., substantially 20 mm, which radius R5 is advantageously larger than the corresponding radius of the blank 12.

[0049] In the particular embodiment shown in Figures 22 and 23, the final part 11 is formed with a relief pattern 38, in particular a logo, on the upper main face 15 of the crown head 11A. [Explanation of symbols]

[0050] 1 Swaging tool 2 Lower unit 4 Upper unit 6 First Actuator 8 Second Actuator 10. Housing 11 Final parts 12 Metal Blanks 12A upper part 12B middle part 12C lower part 13 Vertical groove 14 Pliers 15 Upper main surface Branch 16A, 16B 16A1, 16B1 shank 16A2, 16B2 Arm 17 Support rod 18 Aperture 19 Guide 20 Connection part 22A, 22B flare zone 24A, 24B Cylindrical Zone 26 Upper Die 27A, 27B upper part 29A, 29B lower part 32 Inner die with hole 34 Annular Rim 38 Relief Pattern

Claims

1. A swaging tool (1) for forming a stamp for a metal blank, comprising: The device comprises a lower unit (2) and an upper unit (4), said lower unit being adapted to form a housing (10) intended to receive said metal blank (12); The upper unit has an upper die (26) intended to swage the metal blank at a suitable location in the housing (10) of the lower unit (2); said upper die (26) is mounted for movement along an axis of movement (B-B'); The lower unit (2) has pliers (14) formed by two arms (16A2, 16B2) mounted for movement between an open position and a closed position in a plane perpendicular to the axis of movement (B-B'), In the open position, the two arms of the pliers are spaced apart between which a metal blank can be placed, and in the closed position, the two arms (16A2, 16B2) of the pliers are brought together to define, along the axis of movement (B-B'), an upper region and a lower region of the housing (10) separated by an opening (18), a dimension of the opening (18) is smaller than a corresponding dimension of the lower region and a corresponding dimension of the upper region of the housing; The two arms in the closed position form a lower die for the metal blank at least in the upper region of the housing. A swaging tool (1).

2. and an actuator (6) configured to move the two arms (16A2, 16B2) of the pliers (14) toward each other to the closed position before the upper die (26) swages the metal blank at the appropriate position in the housing (10). Swaging tool (1) according to claim 1 .

3. The upper unit (4) is attached to the lower unit (2) so as to be movable along the axis of movement (B-B'); The upper unit (4) is provided with the actuator Swaging tool (1) according to claim 2.

4. The actuator is a first actuator (6), the lower unit (2) comprises a second actuator (8) adapted to open the two arms (16A2, 16B2) of the pliers (14) when the first actuator is not acting on the pliers, This holds the two arms in the open position while the first actuator is not actuated. Swaging tool (1) according to claim 3.

5. The pliers (14) have two branches (16A, 16B) hingedly formed by two arms (16A2, 16B2) and two shanks (16A1, 16B1); The two branches are hinged at a connection (20) located between the two arms and the two shanks without crossing each other, The two shanks each have a flare zone (22A, 22B) formed on the upper side, The flared zone (22A, 22B) is followed at the bottom by a cylindrical zone (24A, 24B), The two flared zones and the two cylindrical zones of the pliers (14) are arranged opposite each other; the first actuator (6) is configured to first press the two flare zones of the pliers (14) when the upper unit (4) approaches the lower unit (2); At this time, the two shanks (16A1, 16B1) are separated and the two arms (16A2, 16B2) of the pliers (14) are brought closer together and moved to a closed position; This defines the upper and lower areas of the housing (10) for receiving the metal blank (12), after which the pliers (14) complete their movement between the two cylindrical zones (24A, 24B) while holding the two arms in a closed position. Swaging tool (1) according to claim 4.

6. The travel of the movement of the upper unit (4) relative to the lower unit (2) and the shape of the first actuator (6), the two flared zones (22A, 22B) and the two cylindrical zones (24A, 24B) of the pliers (14) respectively, are synchronized with the travel of the movement of the upper unit such that the movement of the two arms (16A2, 16B2) of the pliers (14) approaching each other reaches a closed position to form the upper and lower areas of the housing before swaging is performed. Swaging tool (1) according to claim 5.

7. one portion (30) of the upper die (26) is configured to be slidable on the upper portions (27A, 27B) of the two arms (16A2, 16B2) when the two arms (16A2, 16B2) are in a closed position; The upper portion (27A, 27B) extends above the upper region of the housing (10).

7. The swaging tool of claim 6.

8. The lower unit (2) further comprises a support rod (17) configured to support the metal blank (12) and to at least initially position the metal blank axially; The support rod is mounted for movement along the axis of movement (B-B'), This allows the final part (11) consisting of the swaged metal blank (12) to be ejected from the lower unit (2) after swaging by the upper die (26). A swaging tool according to any one of claims 1 to 7.

9. The lower unit (2) further comprises guides (19) for angular positioning of the metal blank (12) and / or for radially holding the metal blank (12). A swaging tool according to any one of claims 1 to 7.

10. The upper die (26) is configured to form a relief pattern (38), in particular a logo, on the upper main surface (15) of the metal blank (12) when the metal blank (12) is swaged by the upper die (26), thereby determining the final shape of the upper main surface (15). A swaging tool according to any one of claims 1 to 7.

11. A stamping method for making a stamp of a metal blank using a swaging tool (1) according to any one of claims 1 to 7, comprising the steps of: The pliers (14) are initially in an open position in which the two arms (16A2, 16B2) of the pliers (14) are spaced apart; The method comprises: Providing a metal blank (12) having an upper portion (12A) and a lower portion (12C); placing the metal blank (12) between the two arms (16A2, 16B2) of the pliers (14); thereafter, moving the two arms (16A2, 16B2) of the pliers (14) closer together to a closed position of the pliers (14) to define upper and lower areas of the housing (10) for receiving the metal blank (12) and the opening (18) between these upper and lower areas, wherein the upper and lower parts (12A) and (12C) of the metal blank (12) are respectively located on either side of the opening (18) along the axis of motion (B-B') and are therefore respectively located in the upper and lower areas; moving the upper unit along the axis of motion (B-B') towards the lower unit to swage the metal blank (12) with the upper die (26); moving the two arms of the pliers apart to place the pliers in an open position; and ejecting from the lower unit (2) the final part (11) obtained after swaging the metal blank. A method comprising:

12. The step of swaging the metal blank (12) with the upper die (26) is performed in synchronization with the closing of the two arms (16A2, 16B2) of the pliers (14), The two arms of the pliers reach a closed position that defines the upper and lower areas of the housing (10) after the upper unit starts its movement along the axis of movement (B-B') and before swaging.

12. The method of claim 11 .

13. Using the swage tool according to claim 10, forming a relief pattern (38), in particular a logo, on the upper main surface (15) of the metal blank (12) during the step of swaging the metal blank (12) with the upper die (26); The final shape of the upper main surface of the final part obtained by this stamping method is determined during this swaging.

12. The method of claim 11 .

14. The metal blank (12) is a blank for a timepiece crown, The upper part (12A) of the metal blank (12) is intended to form the crown head.

12. The method of claim 11 .

15. The metal blank (12) is a blank for a timepiece crown, The upper part (12A) of the metal blank (12) is intended to form the crown head.

14. The method of claim 13.

16. The metal blank (12) has a middle portion (12B) separating the lower portion (12C) and the upper portion (12A) of the metal blank (12); the lower portion of the metal blank forms a fluted portion having a plurality of longitudinal flutes (13); The flutes (13) are formed on the outer periphery of the metal blank and are machined prior to swaging; The intermediate portion (12B) has a groove formed on the outer periphery of the metal blank (12).

12. The method of claim 11 .

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