Patent Application
20160368093
This application claims priority from European Patent Application No. 15172344.2 filed Jun. 16, 2015, the entire disclosure of which is hereby incorporated by reference.
The invention relates to a method for fabrication of a face intended to be welded and, more specifically, a face of this type having improved surface flatness.
It is known from WO Publication No. 2015/185423 how to form a timepiece component from a part comprising a silicon-based or ceramic-based material which is welded by electromagnetic radiation directly onto another part, such as, for example, a metal or a metal alloy.
In the context of this development, it transpired that it was important for the gap between the parts not to exceed 0.5 micrometre, otherwise they could not be welded.
It is an object of the present invention to overcome all of part of aforecited drawbacks by proposing a new fabrication method with at least one contact surface having improved flatness that enables parts to be assembled by welding.
To this end, according to a first embodiment, the invention relates to a method for fabrication of a timepiece component including the following steps:
According to the first embodiment, the fabrication method can advantageously provide a face with a reduced welding surface, or limit it to a line of contact, to diminish the gap between the parts to a value that ensures the welding thereof.
Further, according to a second embodiment, the invention relates to a method for fabrication of a timepiece component including the following steps:
According to the second embodiment, the fabrication method advantageously ensures an isostatic configuration of the fitting of the part, to diminish the fitting gap between the parts to a value that ensures the welding thereof.
In accordance with other advantageous variants of the invention:
Other features and advantages will appear clearly from the following description, given by way of non-limiting illustration, with reference to the annexed drawings, in which:
The invention relates to a component formed using a material having no usable plastic range i.e. with a very limited plastic range, with another part comprising the same type of material or a different type of material.
This component was devised for applications in the field of horology and is rendered necessary by the increasing part played by fragile, brittle materials, such as silicon-based or ceramic-based materials. It is possible, for example, to envisage forming a case, a dial, a flange, a crystal, a bezel, a push-button, a crown, a case back, a hand, a bracelet or strap, a balance spring, a balance wheel, a pallets, a bridge or bar, an oscillating weight or even a wheel, such as an escape wheel, entirely or partially from fragile or brittle materials.
Preferably, the silicon-based material used to make the compensated balance spring may be single crystal silicon, regardless of its crystal orientation, doped single crystal silicon, regardless of its crystal orientation, amorphous silicon, porous silicon, polycrystalline silicon, silicon nitride, silicon carbide, quartz, regardless of its crystal orientation, or silicon oxide. Of course, other materials may be envisaged, such as glass, ceramics, cermets, metals or metal alloys. Further, the first silicon-based part may also optionally include at least one partial coating of silicon oxide, silicon nitride, silicon carbide or an allotrope of carbon, depending upon the intended applications of the timepiece component.
As explained above, the other part may include the same type of material or another type of material. Therefore, preferably, the other part is metal-based and may include an iron alloy, a copper alloy, nickel or an alloy thereof, titanium or an alloy thereof, gold or an alloy thereof, silver or an alloy thereof, platinum or an alloy thereof, ruthenium or an alloy thereof, rhodium or an alloy thereof, or palladium or an alloy thereof.
For the sake of simplicity, the explanation below will concern an assembly between a balance spring and a balance staff.
A compensating balance spring 15 is shown more clearly in
A staff 27 is illustrated more clearly in
As illustrated in
However, within the context of developing the teaching of WO Publication No. 2015/185423, it very soon became clear that the gap between the parts must not exceed 0.5 micrometre, otherwise they cannot be welded together.
According to a first embodiment, the fabrication method includes a first step intended to profile-turn the shoulder of the staff in order to provide a reduced welding surface, or to limit the contact to a line, to diminish the gap to a value less than or equal to 0.5 micrometre.
The method according to the first embodiment of the invention therefore includes a first step comprising a first phase of taking a bar able to withstand profile-turning. As the example relates to an assembly between a balance spring and a balance staff, the bar may be made from a metal or from a metal alloy.
The second phase is intended to profile-turn the various diameter portions required to form balance staff 47 and particularly diameter portion 42 for receiving collet 17 or balance spring 15. As seen in
Of course, according to a variant illustrated in
According to an alternative of the first embodiment illustrated in
It is thus understood that, after optional finishing phases comprising, for example, a burnishing phase and possibly a deburring phase, the staff 47, 47′, 57 obtained offers a reduced welding surface 43, or limits the contact to a line 43′, 53, to diminish the gap to a value less than or equal to 0.5 micrometre.
The method continues, according to the first embodiment, with a step in which collet 17 is fitted onto diameter portion 42, 42′ or 52, i.e. between the surface of shaft 41, 41′ or 51 and surface 43, 43′ or 53. Finally, in a final welding step, the collet 17 is laser welded with the assurance that the lower face 18 and/or the inner face 20 of the balance spring 15 and staff 47, 47′ or 57 are joined to each other.
According to a second embodiment, the fabrication method includes a first step intended to profile-turn the shaft of the staff in order to ensure an isostatic configuration of the fitting of the collet on the staff. It is understood that it is desired that the inner surface of the collet be able to adapt to the geometry of the shoulder, i.e. to follow the geometry of the shoulder with greater degree of freedom, in order to diminish the gap to a value less than or equal to 0.5 micrometre.
The method according to the second embodiment of the invention thus includes a first step comprising a first phase of taking a bar able to withstand profile-turning. As the example relates to an assembly between a balance spring and a balance staff, the bar may be made from a metal or from a metal alloy.
The second phase is intended to profile-turn the various diameter portions required to form balance staff 67 and particularly diameter portion 62 for receiving collet 17 or balance spring 15. As seen in
Of course, according to a variant that is not illustrated, the second profile-turning phase could even be deliberately intended to form an undercut starting from shoulder 63 of the cutting tool towards shaft 61 forming a line of contact instead of the more limited surface 61 illustrated in
It is thus understood that after optional finishing phases which include, for example, a burnishing phase and possible a deburring phase, the staff 67 obtained enables the inner surface 18 of collet 17 to adapt to the geometry of shoulder 63, i.e. to follow the geometry of shoulder 63 with greater degree of freedom, in order to diminish the gap to a value less than or equal to 0.5 micrometre.
The method continues, according to the second embodiment, with a step in which collet 17 is fitted onto diameter portion 62, i.e. the surface of shaft 61 and surface 63. Finally, in a final welding step, the collet 17 is laser welded with the assurance that the lower face 18 and/or the inner face 20 of the balance spring 15 and staff 67 are joined to each other.
Of course, this invention is not limited to the illustrated example but is capable of various variants and modifications which will appear to those skilled in the art. In particular, the first and second embodiments may be combined to take advantage of their combined effects.
Thus, as seen in
It is thus noted that staff 77 advantageously offers a face 73 with a reduced welding surface to ensure the welding thereof but also a contact face 71 with a reduced surface ensuring an isostatic configuration of the fitting of staff 77 onto diameter portion 72, in order to further diminish the fitting gap thereby further improving the welding with the lower face 18 and/or the inner face 20 of the balance spring 15.
| Number | Date | Country | Kind |
|---|---|---|---|
| 15172344.2 | Jun 2015 | EP | regional |
