Device for fastening a back to a clock case frame

Description

Field of invention

[0001] The invention relates to a device for fixing a back to a caseband of a watch.

[0002] The invention also relates to a timepiece, in particular a watch, comprising such a device. Background of the invention

[0003] The exterior of watches and similar devices is subject to numerous constraints, in particular water resistance, robustness and appearance, and must be carried out in such a way as to prevent any involuntary disassembly which would inevitably result in after-sales intervention for the replacement of seals, cleaning, lubrication or even repair.

[0004] Some trim or control components must also be angularly indexed relative to each other, for reference position markings of origin, rest, or actuation, or to facilitate the reading of indications or graduations, or to ensure the continuity of left surfaces and / or decorations. This angular indexing is often difficult to achieve properly, in combination with good tightening of the components and perfect sealing of the joints.

[0005] EP2874022 A1 discloses a device for attaching a back to a caseband of a watch. Summary of the invention

[0006] The invention proposes to produce a watertight and secure assembly of cladding components with easy-to-achieve angular indexing.

[0007] To this end, the invention relates to a device for fixing a back to a caseband of a watch, the backband having a shoulder forming a cover arranged to cover all or part of the caseband and a body arranged to rest in the caseband, said device comprising a ring mounted between the backband and the caseband and secured to the latter, and at least one pin secured to the backband and arranged to cooperate with the ring and the caseband.

[0008] According to the invention, said ring comprises at least one groove arranged to cooperate with the pin, said pin being able to slide in the groove between a first position, called the insertion position in which the back is free, and a second position called the locking position in which the back is locked and positioned angularly relative to the caseband, and in that said groove comprises at least one bump to form a hard point and increase the torque when the pin passes at the level of the bump. The groove extends along a radius of the ring and is through so that the pin slides through the groove.

[0009] According to other advantageous variants of the invention: the pin is mounted on the bottom, said pin having a body, a head and a foot, the body and the foot having a diameter smaller than the diameter of the head; the middle comprises a shoulder for receiving the ring, said shoulder having at least one hole so as to secure the ring to the middle via fixing means; the middle comprises at least one recess arranged to cooperate with the head of the pin, the head of the pin sliding in the recess; the ring is made of an elastically deformable material, such as polyoxymethylene, polyurethane, a polymer-based material, or an elastomer material; the pin is made of metal or metal alloy; the groove, a first and a second end, and two walls, the distance between the two walls being equivalent to the diameter of the body of the pin so as to guide the pin and hold it axially;the first end forms a space for the insertion of the pin, and the second end forms a stop and holds the pin in position; the first end has dimensions similar to the head of the pin, and the second end has dimensions similar to the body of the pin; the bump is formed on one of the two walls of the groove; the groove comprises several bumps, the distance between each bump being identical; the groove comprises several bumps, the distance between each bump being decreasing; the device comprises at least three pins distributed angularly on the bottom and arranged at regular intervals.

[0010] The invention also relates to a timepiece comprising such a fixing device. Summary description of the drawings

[0011] Other characteristics and advantages of the invention will appear more clearly on reading the following description of a particular embodiment of the invention, given as a simple illustrative and non-limiting example, and the appended figures, among which: there Figure 1 is an exploded perspective view of a fixing device according to the invention; Figures 2a and 2b are respectively a perspective view of a base and a middle of a fixing device according to the invention; Figures 3a to 3b are respectively a perspective view of a ring and a pin of a fixing device according to the invention Figure 3c illustrates a sectional view of a fixing device according to the invention. Detailed Description of Preferred Embodiments

[0012] The invention proposes to produce a watertight and secure assembly of cladding components with easy-to-achieve angular indexing, and in a guaranteed position, and this with a minimal number of components.

[0013] THE Figures 1 to 3c illustrate the non-limiting example of the assembly and angular indexing of a back in relation to a watch case.

[0014] The invention relates to a device 100 for fixing a back 2 to a caseband 1 of a watch comprising a ring 3 mounted in the caseband, at least one pin 4 secured to the back and arranged to cooperate with the ring 3, and a seal mounted on the back 2. The reverse mounting is obviously possible, and the pin 4 can be mounted on the caseband 1 while the ring 3 is mounted on the back 2 which can be solid or transparent.

[0015] The bottom 2 is arranged to move from a first disassembled insertion position to a second assembled and locked position. As illustrated in Figure 2a , the bottom 2 has a shoulder 21, slightly raised relative to the cover and forming a groove 20 at the periphery of the bottom. The bottom 2 is arranged to cover all or part of the middle 1 and comprises a body 22 arranged to rest in the empty space 14 of the middle 1.

[0016] According to the invention, this fixing device comprises at least one pin 4, which is arranged to be inserted axially between the back 2 and the middle 1, fixed in rotation relative to one of them, and which slides in a groove 5 of the ring 3.

[0017] This pin 4 comprises a head 40 provided with a slot 41, a body 42 and a foot 43, the pin 4 being screwed into the bottom 2 so as to make it integral with the latter. As illustrated, the body 42, the head 40 and the foot 43 are cylindrical in shape, the head 40 having a diameter greater than the diameters of the body 42 and the foot 43. The pin 4 is screwed onto the bottom 2, the bottom 2 comprising for this purpose at least one threaded hole to receive the foot 43 of the pin 4. The pin 4 is preferably made of a metallic material or a metallic alloy such as steel. Of course, other shapes than a slot could be used to fix the pin, such as a star or a cross for example.

[0018] As can be observed on the Figure 3a, the ring 3 is formed by a ring 30 and comprises at least one groove 5 arranged to cooperate with the pin 4, the pin 4 being arranged to slide in the groove 5 between a first position, called the insertion position in which the bottom 2 is free, and a second position called the locking position in which the bottom 2 is locked and positioned angularly relative to the middle 1, the groove 5 comprising at least one bump 55 to form a hard point and increase the torque when the pin 4 passes at the level of the bump 55. Such an arrangement also ensures safety against loosening and consequently loss of sealing.

[0019] In order to make the portion of the ring receiving the groove 5 more rigid, this portion has a greater width than the rest of the ring so that the ring 5 is compressed between the bottom 2 and the middle 1 at the level of this wider portion.

[0020] The ring 3 can be made of a material chosen from: polyoxymethylene, polyurethane, a polymer-based material, or even an elastomer, for example, asutane ® or hytrel ®. The material chosen, the geometry of interference with the pin and the material of the pin make it possible to determine the maximum tightening torque. The advantage of such a ring 3, preferably in an elastic polymer or similar material, is its ease of manufacture and replacement in the event of breakage or wear.

[0021] The ring 3 is fixed to the middle 1 via screws 6 passing through the ring 3 via holes 31 and screwing into holes 13 of the middle 1. Advantageously, the heads of the screws 6 rest in a counterbore formed at the holes 31 and on the surface of the ring 3. The ring 3 rests against the bottom 12 and the wall 11 of a shoulder 10 of the middle 1, the shoulder having dimensions similar to the ring so that the surface of the ring 3 is flush with the edges of the middle 1. Advantageously, the bottom 12 of the shoulder 10 has at least one recess 15 extending along a radius of the middle, the position of the recess 15 corresponding to the position of the groove 5 of the ring once it is mounted.The width of the recess 15 is provided to be greater than the width of the groove 5, the width of the groove is equivalent to the dimensions of the body 42 of the pin 4 and the width of the recess 15 is at least equivalent to the width of the head 40 of the pin 4 so that the pin 4 can move in the recess 15 and maintain it axially in the groove 5. It should be noted that the length of the recess 15 defines the stroke length of the pin 4.

[0022] In the first disassembled insertion position, the case 1 and the back 2 have a first angular orientation relative to each other.

[0023] According to the invention, the back cover 2 comprises radial sealing means, such as an O-ring seal (not shown in the figures), at the interface between the middle part 1 and the back cover 2, the seal resting in the groove 20 of the cover and thus filling the space formed by the shoulder 21 at the periphery of the back cover. The transition from the first disassembled insertion position to the second assembled and locked position is carried out under the action of forces exerted by an operator: an axial force to overcome the resisting force of the O-ring seal and assemble the back cover 2 and the middle part 1, and a torque to bring them into an angular indexing position.

[0024] In the second assembled and locked position, the caseband 1 and the back cover 2 have a second angular orientation relative to each other that is different from the first angular orientation. The back cover 2 and the caseband 1 are held axially by means of a bayonet fit.

[0025] Advantageously, the joining of the back 2 and the middle 1 by bayonet adjustment, in particular around an axial direction D, is reversible, and allows their disassembly. In a manner specific to the invention, this disassembly requires from an operator forces similar to those exerted during assembly, this disassembly preferably requires the use of a special tool, cooperating for example with peripheral holes or notches arranged on the visible face of the back 2. Such an assembly makes it possible to avoid disassembly of the back by the wearer, or disassembly following clumsiness or an impact.

[0026] The body 42 of the pin is arranged to cooperate with at least one complementary relief, such as a boss 55, which the groove 5 of the ring 3 comprises. As illustrated in Figure 3a, the ring 3 comprises at least one groove 5 which extends along a radius of the ring 3 and has a width of dimension equivalent to the diameter of the body 42 of the pin 4 so that the pin 4 slides within the groove 5. The groove 5 comprises a first end 51 and a second end 52, and two walls 53.

[0027] Thus, any passage of the pin 4 over the boss 55 in the groove 5 generates a resistive torque which tends to oppose the relative rotational movement between the caseband 1 and the back 2.

[0028] According to a preferred embodiment, the groove 5 comprises a plurality of bosses 55, which are arranged to oppose successive resistance when the pin 4 passes. According to the invention, in the same groove 5, the angular distance between the successive bosses 55 decreases so as to oppose increasing resistance, during a rotation between the back 2 and the middle 1. The angular distance between the successive bosses 55 can also be provided to be constant so as to oppose a constant resisting torque.

[0029] Several configurations for the arrangement of the bosses are possible. According to a first embodiment, one or more bosses 55 are present on a single side wall of the groove 5. According to a second embodiment, one or more bosses 55 are arranged on the two side walls of the groove 5, the bosses 55 of each wall being arranged opposite each other. According to a third embodiment, one or more bosses 55 are arranged on the two side walls of the groove 5, the bosses 55 of each wall being offset from each other. Similarly, the distance between bosses 55 positioned opposite each other can vary so as to provide a progressive resistive torque.

[0030] The first end 51 of the groove 5 forms a space for the introduction of the head 40 of the pin 4, and the second end 52 forms a stop and holds the pin 4 in position in the groove 5. To do this, the first end 51 has dimensions slightly larger than the head 40 of the pin 4, and the second end 52 has dimensions similar (within the manufacturing tolerance) to the body 42 of the pin 4.

[0031] It is understood that the resisting force is all the greater as the number of grooves 5, bosses 55, the dimensions of the bosses, and complementary pins 4 in cooperation is high. It is therefore possible to play on the number of successive bosses 55, and / or on the number of pins and grooves. According to a preferred embodiment of the invention, the ring 3 comprises three grooves 5 distributed angularly in a regular manner, and the bottom 2 comprises three complementary pins 4.

[0032] Naturally, the configuration can be reversed, with a ring 3 attached to the bottom 2 and a pin 4 attached to the middle 1.

[0033] We could imagine removing the six fixing screws 6 and putting three additional pins 4 fixed on the middle 1. This would add three additional grooves and would also offer resistance to disassembly on the D axis, via this double bayonet.

[0034] We could also imagine having two pins on the case and two pins on the bottom to only have four grooves to make.

[0035] During assembly, the operator places the back 2 on the middle 1 so as to match the head 40 of the pin(s) 4 with the first end 51 of the groove(s) 5 so that the pins 4 are inserted therein when the operator gives a translational movement along the axis D to the back 2 to place the cover 20 of the back 2 near the lower edge 16 of the middle 1, until the pin comes into abutment against the bottom of the recess 15 and thus ensures sealing thanks to the seal. The friction of the o-ring seal makes it possible to provide an initial resistance. Pin 4 has a height very slightly greater than the distance between the bottom of recess 15 and bottom 2, which makes it possible to avoid contact between bottom 2 and caseband 1, and a clearance of 0.02mm to 0.04mm is present between the bottom and the caseband.

[0036] Then the operator applies a progressive torque to apply the relative rotation between the case 1 and the back 2. During this rotation, the operator carrying out the assembly encounters a second resistance when the body 42 of the pin 4 engages with the first bump 55 of the groove 5. Thus, the resistive torque increases during the complete passage of the bump 55.

[0037] In a first case, the first boss 55 cooperating with the pin 4 is unique. In a second case, the groove 5 comprises several bosses 55 so that the operator provides a jerky force during rotation, the cumulative resistive torque peak increasing during each passage of a hard point, to reach, at the indexing angle, the maximum value. The operator thus encounters a sensation of increasing resistance due to the bosses and the “pin-boss” interference which is stronger as the box is closed by turning the bottom.

[0038] As illustrated in Figure 1 And Figure 3a , the ring 3 comprises three grooves 5, distributed at 120°, each of the grooves 5 being arranged to cooperate with a pin 4 complementary to the groove 5. The base 2 thus comprises three pins 4 distributed at 120°, and the operator feels a single hard point passage when the three pins 4 at 120° pass a bump 55 simultaneously.

[0039] The seal exists as soon as the back 2 is placed on the case 1, and the mechanism according to the invention is arranged so that, as in the previous case of a single boss, the sealing of the joint is secured as soon as the back is introduced into the case, and then no loosening can occur without voluntary action by an operator.

[0040] In practice, very good results are obtained with at least two, and preferably three, or even four, successive bumps, so as to provide sufficient elementary angular travel for the passage of each bump.

[0041] The invention requires, during assembly, the successive crossing of several bumps so as to form an increasing resistance, but also during disassembly, because, from the final indexed position, in particular on the mechanical stop, any application of a sudden force results, in the worst case, in the crossing of a single bump 55, without total disassembly, with a visual shift, and above all without loss of watertightness or risk of pollution of the interior of the watch. In the example illustrated, even when the operator successively crosses three thresholds, visible optically due to the shift, the watertightness is still ensured. To have a loss of watertightness, the operator must partially remove the back 2 so that the gasket is no longer compressed.

[0042] According to one embodiment, the distance between each bump 55 is identical, and its passage opposes the same resistant torque.

[0043] In an advantageous variant, the distance between each bump is decreasing, and the operator must apply increasing torque.

[0044] The invention is advantageous because it is perfectly compatible with watch dimensions, while having a capacity for high resistant force, which can reach 1.2Nm ± 0.2Nm depending on the watch diameters.

[0045] Moreover, in the case where the timepiece is subjected to particular constraints of great magnitude, the dismantling of the mechanism according to the invention requires the continued application of a possible force of accidental origin during a significant angular travel, from 5 to 10° for crossing a single bump in the example illustrated, safety still remaining assured if several bumps follow one another.

[0046] According to the invention, the angular indexing is guaranteed by the second end 52 which forms a travel limiting stop.

[0047] The invention thus makes it possible to prevent any unexpected and involuntary disassembly of the case back, for example under the effect of vibrations, successive expansion cycles, by inadvertent use by the wearer, or otherwise.

[0048] Preferably, disassembly requires a special non-commercial tool, which ensures that maintenance is carried out by after-sales personnel with the required qualifications.

[0049] The invention lends itself well to cases where the caseband and the back are made of different materials, with different coefficients of expansion, or fragile or hard materials (ceramic, sapphire), which do not allow standard attachment methods. Classic configurations include the assembly of a gold caseband with a sapphire back, or a case entirely made of ceramic, a metal-ceramic combination, or the like.

[0050] An important advantage of the invention is to eliminate any contact / friction between the bottom and the caseband and thus prevent the appearance of residues due to friction and the addition of grease to trap them as is the case in the prior art.

[0051] Another important advantage of the invention is to provide increased security when opening thanks to the successive passage of several notches and the obligation to at least partially remove the bottom before any loss of sealing.

[0052] The invention also relates to a timepiece or watch comprising such a fixing device.

[0053] In short, the invention provides a fixing device with a compact design, ensuring that the watch remains watertight and protected against accidental disassembly.

[0054] The invention also makes it possible to ensure the perfect orientation of a component held locked in its service position.

[0055] The invention provides many advantages: from a first relative angular position, between the back and the caseband, where the sealing function is ensured, for example as soon as the compression of a sealing gasket is carried out, there exists, in the mechanism according to the invention, an extended range of relative angular values ​​between the back and the caseband, in which the sealing remains guaranteed, for example of several tens of degrees, which is important in comparison with for example a standard screwed back in the case of a caseband-back subassembly, where unscrewing by only a few degrees results in loss of sealing and the need for cleaning and a new gasket, whereas according to the invention it is only after passing the very last notch during disassembly that loss of sealing becomes possible if rotation is continued and the back 2 is started to be extracted from the caseband 1 (which corresponds to the detachment of the bayonet);a closure by succession of notches which presents a largely dimensioned closing torque of the bottom, both sufficient and acceptable for such an assembly, thanks in particular to the multiplication of the number of bumps distributed in the groove, with, for the operator, a sensation of screwing in stages of increase of the closing torque until the desired position, deemed to be the closed position, which is also clearly perceptible; an opening safety, which is increased by two factors: the need for the operator to provide significant positive energy to pass a notch, and the successive passage of several notches prior to any loss of sealing.;

Claims

1. Device for fastening (100) a back on a middle of a watch, the back (2) having a shoulder (20) forming a cover (21) arranged to cover totally or partially with the middle (1) and a body (22) arranged to rest in the middle (1), said device comprising a ring (3) mounted between the back (2) and the middle (1) and integral with the latter, and at least one pin (4) integral with the back and arranged to cooperate with the ring and the middle, characterised in that said ring (3) comprises at least one recess (5) arranged to cooperate with the pin (4), said pin (4) being capable of sliding in the recess (5) between a first position, referred to as insertion position wherein the back (2) is free, and a second position referred to as locking position wherein the back (2) is locked and angularly positioned in relation to the middle (1), and in that said recess (5) comprises at least one bump (55) to form a hard spot and increase the torque during the passage of the pin (4) at the bump (55), and in that the recess (5) extends according to a radius of the ring (3) and is passing through in such a way that the pin (4) slides through the recess (5).

2. Device for fastening (100) a back (2) on a middle (1) of a watch according to claim 1, characterised in that the pin (4) is mounted on the back (2), said pin (4) having a body (42), a head (41) and a foot (43), the body and the foot having a diameter smaller than the diameter of the head.

3. Device for fastening (100) a back (2) on a middle (1) of a watch according to claim 1 or 2, characterised in that the middle (1) comprises a shoulder (10) for receiving the ring (3), said shoulder (10) having at least one hole (13) in such a way as to secure the ring to the middle via fastening means.

4. Device for fastening (100) a back (2) on a middle (1) of a watch according to claim 2, characterised in that the middle (1) comprises at least one hollow (15) arranged to cooperate with the head (41) of the pin, the head (41) of the pin (4) sliding in the hollow (15).

5. Device for fastening (100) a back (2) on a middle (1) of a watch according to one of the preceding claims, characterised in that the ring (3) is made of an elastically deformable material, such as polyoxymethylene, polyurethane, a polymer-based material, or also an elastomer material.

6. Device for fastening (100) a back on a middle of a watch according to one of claims 1 to 5, wherein the pin (4) is made of metal or metal alloy.

7. Fastening device (100) according to one of claims 2 to 6, characterised in that the recess (5) comprises a first and a second end (51, 52), and two walls (53), the distance between the two walls (53) being equivalent to the diameter of the body (42) of the pin in such a way as to guide the pin and hold it axially.

8. Fastening device (100) according to claim 7, characterised in that the first end (51) forms a space for inserting the pin (4), and the second end (52) forms a stop and holds the pin in position.

9. Fastening device (100) according to claim 7 or 8, characterised in that the first end (51) has dimensions similar to the head of the pin (4), and the second end (52) has dimensions similar to the body (40) of the pin.

10. Fastening device (100) according to one of claims 7 to 9, characterised in that the bump (55) is formed on one of the two walls (53) of the recess (5).

11. Fastening device (100) according to one of claims 1 to 10, characterised in that the recess (5) comprises a plurality of bumps (55), the distance between each bump (55) being identical.

12. Fastening device (100) according to one of claims 1 to 10, characterised in that the recess (5) comprises a plurality of bumps (55), the distance between each bump (55) being decreasing.

13. Fastening device (100) according to one of claims 1 to 12, characterised in that the device comprises at least three pins (4) angularly distributed on the back and disposed at regular intervals.

14. Timepiece characterised in that it comprises a fastening device (100) according to one of claims 1 to 13.