ARRANGEMENT CONSISTING OF A BRACKET, A CIRCUIT BOARD AND FASTENINGS, ESPECIALLY FOR A CLOCK

Description

Technical field of the invention

[0001] The present invention relates to the field of assemblies comprising a support, a plate and fixing means, in particular a watch movement support and a motor plate of a timepiece. Technical background of the invention

[0002] In the techniques of assembling a module and a support, for example a watch movement support and a motor plate of a timepiece, it is known, in the field of watches, to use self-tapping screws as fixing means. This type of screw is inserted into a housing having a smooth wall, and in which they carve a thread, when they are screwed into the housing.

[0003] There figure 1shows an example of a self-tapping screw 1 of the prior art. The screw 1 comprises an enlarged head 2 and a longitudinal body 3, of which a first section 4 arranged opposite the head 2 is smooth, and a second section 5 extending from the head 2 to the first section 4 is surrounded by a spiral thread 6. The first section 4 is narrower than the second section 5, and has a diameter close to that of the housing. The first section allows the screw to be positioned in the housing to keep it straight. When the screw 1 is screwed into the housing, the thread 6 gradually sinks into the wall of the housing, because the diameter of the second section with the thread 6 is wider than that of the housing.

[0004] FR 1 234 518 A (FELDMAN) October 18, 1960 (1960-10-18) discloses the assembly of an upper plate 2 and a lower plate 1, the lower plate 1 comprising pillars 5 with holes in which self-tapping screws 5A are screwed into the housing receiving the screws. The body of the screw 5A has a conical shape and includes a thread.

[0005] These screws are, for example, useful for assembling a watch movement support to a motor plate of a timepiece. Indeed, housings are preformed without tapping, the support is positioned on the plate, and the screws are screwed into the housings. One of the two elements, for example the plate, is fitted with the housing(s), preferably made of a softer material than the metal screw, for example plastic. Thus, each screw taps a housing and assembles the two elements together.

[0006] However, a first disadvantage of such a screw is that it is necessary to screw for a fairly long time to tap the housing and fix the screw there. Indeed, the tapping is done little by little, because only a part of the thread at the end of the second section forms the thread. Thus, each screw requires a certain number of turns of the screw, and consequently a substantial handling time, whereas assembly must generally be quick.

[0007] Another disadvantage is related to the pre-positioning of the screw in the housing before screwing. Indeed, the first section serves only as a guide and does not tap the housing so that part of the housing receiving the first section does not have the function of fixing the screw in the housing. Thus, the first section is quite short to avoid losing too much space, because the element must not be too thick, and take up too much space, which would be annoying for example in a watch case. Since the first section is short, the screw does not hold well in the housing before screwing, and risks easily coming out of the housing. Summary of the invention

[0008] The present invention aims in particular to overcome the various drawbacks of the devices known from the prior art.

[0009] More specifically, an objective of the invention is to provide an assembly that is easy and quick to assemble and which guarantees good retention of the support on the plate.

[0010] The invention also aims to provide an assembly that is robust and inexpensive.

[0011] For this purpose, the invention relates to an assembly comprising a support and a plate, in particular a watch movement support and a motor plate of a timepiece, as well as means for fixing the support to the plate, the fixing means comprising: a self-tapping screw configured to form a thread when screwed in, the screw comprising a head and a longitudinal body, the body comprising an end opposite the head and a thread arranged around the body, the body having a diameter varying along the first axis of the body, which is wider at the head to a smaller diameter at the end, a first hole passing through the support or the plate, a housing arranged respectively in the plate or the support according to the arrangement of the first hole, the housing having a shape defined by a wall and an opening for receiving the body of the screw, such that, with the body of the screw passing through the first hole, the shape of the housing is tapped, when the screw is screwed into the housing, the body of the screw being cylindrical and comprising at least two cylindrical sections, a first section at the end of the body and a second section upstream of the first section, the second section being wider than the first section, and the housing comprising at least two cylindrical sections, a first section extending from the opening of the housing and a second section deeper into the housing, the first section being wider than the second section.

[0012] The device is remarkable in that the predefined shape of the housing has a variable width, which is wider at the opening to a smaller diameter at the bottom of the housing, the shape corresponding to that of the screw body.

[0013] Thus, the housing being wider at the opening than at the bottom of the housing, it adapts to the shape of the screw on several levels. On the one hand, a larger part of the screw can be inserted into the housing prior to screwing. The screw is better held in the housing, in a direction corresponding to that of screwing. This feature facilitates screwing, because there is no need to hold the screw by hand or with an instrument to screw it, the screw is guided by the housing, without risk of coming out of the housing.

[0014] On the other hand, since the screw body and the housing have a substantially identical shape, the screw thread is more quickly in contact with the wall over the entire height of the screw body. Consequently, the screwing requires fewer turns to achieve complete screwing of the screw into the housing.

[0015] According to a particular embodiment of the invention, the thread is arranged along the entire length of the body. Thus, the entire body of the screw serves for fixing. There is no part of the body of the screw in the housing without having the function of fixing to the housing, as in the state of the art described previously.

[0016] According to a particular embodiment of the invention, the body of the screw and the housing each have a cone shape, a base of one cone being arranged at the head for the screw, and a base of another cone being formed by the opening for the housing.

[0017] According to a particular embodiment of the invention, the housing is closed at the bottom opposite the opening.

[0018] According to a particular embodiment of the invention, the housing is extended by a retaining collar arranged beyond a second hole passing through the stator and the core of the motor, when the plate comprises the housing.

[0019] According to a particular embodiment of the invention, the collar is wider than the second hole, so that the stator and the core are held to the plate.

[0020] According to a particular embodiment of the invention, the housing is formed from a deformable material, for example plastic, such as polyethersulfone or polypropylene, possibly reinforced with glass fibers.

[0021] According to a particular embodiment of the invention, the screw is made of metal.

[0022] According to a particular embodiment of the invention, the body of the screw has a length substantially equal to the length of the housing and that of the first hole.

[0023] According to a particular embodiment of the invention, the head is wider than the first hole.

[0024] According to a particular embodiment of the invention, the head is wider than the first hole.

[0025] According to a particular embodiment of the invention, the assembly comprises a motor module provided with the plate and a motor configured to move the clockwork movement carried by the support, the motor being provided with a coil core, a stator, and a motor activation circuit held by the plate. Brief description of the figures

[0026] Other characteristics and advantages of the invention will appear more clearly on reading the following detailed description of an exemplary embodiment of the invention, this example being given purely for illustrative and non-limiting purposes, in conjunction with the appended drawing in which: there figure 1is a sectional view of a self-tapping screw according to an embodiment known from the state of the art, and the figure 2 is a schematic sectional view of an assembly according to the invention, when the screw is held in the housing before screwing, and the figure 3 a schematic sectional view of an assembly according to the invention, when the screw is inserted into the housing after screwing. Detailed description of the invention

[0027] On the Figure 2 and 3, the assembly 10 comprises a support 30 for a watch movement of a timepiece, such as a wristwatch. The movement, which is not shown in the figures, generally makes it possible to move hands on a dial of the timepiece. The assembly comprises a motor module provided with a plate 20 and a motor 31 configured to move the watch movement carried by the support 30. The motor 31 is provided with a stator 33 and a coil core 32 for activating a rotor, not shown in the figures, as well as an electronic control circuit 36 ​​for the motor 31, and an activation circuit 35 for the coil for activating the rotation of the rotor. The stator 33, the core 32 and the activation circuit 35 are held under the plate 20, while the electronic control circuit 36 ​​is arranged between the plate 20 and the support 30, when the plate 20 and the support 30 are assembled to each other.A spring 34 provides a connection between the control circuit 36 ​​and the activation circuit 35, to transmit an electric current and enable the activation of the coil. The spring 34 is disposed in a passage 37 through the plate to connect the two circuits.

[0028] The assembly 10 further comprises means for fixing the support 30 to the plate 20. Thus, the two elements are fixed to each other to be placed in the timepiece. The fixing means comprise a self-tapping screw 11 and a housing 21 arranged in the plate 20, as well as a first hole 16 passing through the support 30.

[0029] The screw 11 comprises a head 12 and a longitudinal body 15 about a first axis, the body 15 comprising an end 19 opposite the head 12 and a thread 9 arranged around the body 15. The head 12 comprises a plate 14 provided with a slot 13 allowing the screw to be rotated using a screwdriver. The slot 13 is straight in the figures, but it could also be cruciform or of another usual shape for a screw. The end 19 is here flat, but could also be pointed. The thread 9 has a helical shape with a predetermined pitch and width. The pitch of the thread has for example a value of 0.25 mm.

[0030] The housing 21 is formed in the plate 20 of the motor around a second longitudinal axis. The housing 21 has a predefined shape comprising an inner wall 8 delimiting the shape, as well as an opening 7 for the passage of the screw 11. The housing 21 is preferably closed at the bottom 24 opposite the opening 7. The housing 21 is extended by a retaining collar 25 arranged beyond a second hole 26 made through the stator 33, the activation circuit 35 and the core 32 of the motor 31. The wall 8 of the housing 21 passes through the second hole 26, the bottom 24 of the housing 21 being formed in part by the collar 25. The collar 25 is wider than the second hole 26, so as to retain the stator 33, the activation circuit 35 and the core 32 against the plate.

[0031] When the screw 11 is screwed into the housing 21, the body 15 passes through the first hole 16, while the plate 14 of the head 12 being wider than the first hole 16, the latter 12 remains blocked on the support 30, outside the first hole 16. The first and second axes are substantially collinear after screwing, as well as prior to screwing, when the screw is partly positioned in the housing.

[0032] Preferably, the body 15 of the screw 11 has a length substantially equal to the length of the housing 21 and that of the first hole 16. This prevents the assembly from being too thick and taking up too much space, for example in a watch case.

[0033] The screw 11 is configured to form a thread in the housing 21 when it is screwed into the interior thereof. For this purpose, the thread 9 is configured to sink into the wall 8 of the housing 21 during screwing. The body 15 and the thread 9 of the screw 11 are preferably made of a hard material while the wall 8 of the housing 21 is made of a softer material than that of the screw 11. Thus, the thread 9 of the screw 11 easily taps the wall 8 of the housing 21. The screw 11 is for example made of metal, preferably turned steel. The housing 21 is formed of a deformable material, for example a plastic material, such as polyethersulfone or polypropylene, possibly reinforced with glass fibers.

[0034] The body 15 of the screw 11 has a variable diameter along the first axis of the body, the body 15 being wider under the head 12 to a smaller diameter at the end 19.

[0035] According to the invention, the predefined shape of the housing 21 has a variable width corresponding to that of the body 15, so that the predefined shape of the housing 21 and the body 15 of the screw 11 cooperate so that the body 15 of the screw 11 is held by the housing 21 over the entire height of the body 15 after screwing. Furthermore, the width of the screw 11 comprising the body 15 and the thread 9 is greater than that of the housing 21 at the same height, when the screw is screwed into the housing. Thus the thread 9 taps the housing 21, whatever its height on the body 15.

[0036] According to the invention, shown in the Figures 2 and 3, the body 15 of the screw 11 is cylindrical and comprises at least two cylindrical sections 17, 18, a first section 17 extending from the end 19 of the body 15, and a second section 18 extending upstream of the first section 17, for example from the head 12 of the screw 11 to the first section 17. The second section 18 being wider than the first section.

[0037] Thus, according to the invention, the shape of the housing 21 comprises at least two cylindrical sections, a first section 23 starting from the opening 7 of the housing, and a second section 22 deeper in the housing 21, the first section 23 being wider than the second section 22.

[0038] According to different variants of a first embodiment, not shown in the figures, the body of the screw and the housing may have three or four sections, or even more depending on the length of the screw.

[0039] Thanks to the invention, the variation of the width of the body 15 and the corresponding shape of the housing 21 allows a large part of the thread 9 to tap the housing 21 simultaneously. Thus, screwing is faster than with a conventional screw which taps the housing little by little with only one part of the thread. Time is saved because the screw requires less handling, that is to say fewer turns of the screw. For example, for a screw of the same length and the same pitch, a conventional self-tapping screw requires up to six turns of the screw, whereas a screw according to the invention requires only three turns.

[0040] Furthermore, as can be seen on the figure 2, the screw 11 is well held by the housing 21 before screwing, thanks to the corresponding shapes of the screw 11 and that of the housing 21 according to the invention. Indeed, a part of the body of the screw starting from the end, can be inserted into a first part of the housing 21 to be held vertically before screwing. In this embodiment, the first section 17 extending from the end 19 of the body 15 is inserted into the first section 23 starting from the opening 7 of the housing 21 without the thread tapping the wall 8. Excellent holding of the screw in a good direction is obtained before screwing, in order to avoid any risk of the screw falling or being guided in a bad direction.

[0041] Advantageously, the width of the screw at the level of the first section 17 of the body 15 of the screw 11 with the thread 9, is substantially equal to the width of the first section 23 of the housing 21.

[0042] Preferably, the thread 9 is arranged along the entire length of the body 15. Thus, the entire body 15 of the screw 11 serves to tap the housing 21 and to fix the support 30 and the plate 20 together. In the first embodiment, the thread 9 is therefore arranged on the two cylindrical sections 17, 18 of the body 15. As shown in figure 3 after screwing, the first section 17 of the body 15 tapped the second section 22 of the housing 21, while the second section 18 of the body 15 tapped the first section 22 of the housing 21. The two tappings occurred simultaneously, which requires a fewer number of screw turns.

[0043] In the embodiment with an even larger number of sections, screwing is even faster, because the threads in each section of the housing are made simultaneously.

[0044] In an example not forming part of the claimed invention, not shown in the figures, the body of the screw and the housing each have a cone shape. The first cone of the body of the screw has a base arranged under the head for the screw, while the apex is arranged at the end of the body. The second cone formed by the housing has a base formed by the opening, the apex being formed by the bottom of the housing. The thread is preferably arranged over the entire height of the first cone. The same advantages are found as those of the first embodiment. In particular, screwing is even more time-consuming, because the conical shape means that a large part of the thread taps the housing simultaneously over the entire height of the body.

[0045] It goes without saying that the present invention is not limited to the embodiments which have just been described and that various modifications and simple variants of the invention can be envisaged by those skilled in the art without departing from the scope of the invention as defined by the appended claims. In particular, according to a variant not shown in the figures, the first hole is arranged in the plate and the housing is arranged in the support.

Claims

1. Assembly (10) comprising a support (30) of a horological movement and a motor (31) plate (20) of a timepiece, in addition to means for fastening the support (30) to the plate (20), the fastening means comprising: - a self-tapping screw (11) configured to form a tapping when screwed, the screw (11) comprising a head (12) and a longitudinal body (15), the body (15) comprising an end (19) opposite the head (12) and a threading (9) arranged around the body (15), the body having a diameter that varies along the first axis of the body (15), which is wider at the head (12) and extends to a smaller diameter at the end (19), - a first hole (16) passing through the support (30) or the plate (20), - a recess (21) respectively arranged in the plate (20) or the support (30) according to the arrangement of the first hole (16), the recess (21) having a shape defined by a wall (8) and an opening (7) for receiving the body (15) of the screw (11), characterised in that the shape of the recess (21) having a variable width, which is wider at the opening (7) extending to a smaller diameter at the bottom (24) of the recess (21), the shape corresponding to that of the body (15) of the screw (11), such that, with the body (15) of the screw (11) passing through the first hole (16), the predefined shape of the recess (21) is tapped when the screw is screwed into the recess, the body (15) of the screw (11) being cylindrical and comprising at least two cylindrical sections, a first section (17) at the end (19) of the body (15) and a second section (18) upstream of the first section (17), the second section (18) being wider than the first section (17), and the recess (21) comprising at least two cylindrical sections, a first section (23) extending from the opening (7) of the recess (21), and a second section (22) located deeper inside the recess (21), the first section (23) being wider than the second section (22).

2. Assembly according to claim 1, characterised in that the threading (9) is arranged along the entire length of the body (15).

3. Assembly according to claim 1 or 2, characterised in that the bottom (24) of the recess (21) opposite the opening (7) thereof is closed.

4. Assembly according to any one of the preceding claims, characterised in that the recess (21) is extended by a retaining flange (25) arranged beyond a second hole (26) passing through the stator (33) and the core (32) of a motor, when the plate (20) includes the recess (21).

5. Assembly according to claim 4, characterised in that the flange (25) is wider than the second hole (26), such that the stator (33) and the core (32) are held against the plate (20).

6. Assembly according to any one of the preceding claims, characterised in that the recess (21) is made of a deformable material, for example plastic, such as polyethersulphone or polypropylene, potentially with glass fibre reinforcement.

7. Assembly according to any one of the preceding claims, characterised in that the screw (11) is made of metal.

8. Assembly according to any one of the preceding claims, characterised in that the body (15) of the screw (11) has a length that is substantially equal to the length of the recess (21) and that of the first hole (16).

9. Assembly according to any one of the preceding claims, characterised in that the head (12) is wider than the first hole (16).

10. Assembly according to any one of the preceding claims, characterised in that it comprises a motor module provided with the plate (20) and with a motor (31) configured so as to move the horological movement borne by the support (20), the motor (31) being provided with a coil core (32), a stator (33) and a circuit (35) for actuating the motor (31), which are held by the plate (20).