Abstract:
The invention relates to a method ( 1 ) of fabricating a micro-mechanical component that includes the following step:
       a) forming ( 3 ) at least one plate that includes a frame connected by at least one bridge of material to a part of said component, wherein said part has a hole.       
 
     According to the invention, the method ( 1 ) also includes the following steps:
       b) stacking ( 5 ) said at least one plate against a support;   c) securing ( 7 ) a pin in the hole of said at least one stacked part so as to form the component;   d) releasing ( 9 ) the component formed from each plate.       
 
     The invention concerns the field of watchmaking.

Description:
[0001]    This is a National Phase Application in the United States of International Patent Application PCT/EP2009/064639 filed Nov. 4, 2009, which claims priority on European Patent Application No. 08169687.4 of Nov. 21, 2008. The entire disclosures of the above patent applications are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a method of fabricating a micro-mechanical component and, more specifically, a method of this type for assembling micro-machined and/or electroformed components. 
       BACKGROUND OF THE INVENTION 
       [0003]    It is advantageous in the watchmaking industry to fabricate components or parts of components by using a micro-machining process, for example photolithography then deep reactive ion etching, or electroplating, for example photolithography then galvanic growth. These processes make fabrication with improved precision possible, compared to conventional techniques. 
         [0004]    However, it is difficult to form components from several parts. Thus, in the case of electroformed components, a laser weld between two parts and, for example, an arbour, is liable to deform the parts and arbour so that the very high level of precision resulting from the electroplating process is lost. Moreover, whatever the process, it is very difficult to obtain assembly precision between two components and, for example, a pivoting arbour. 
       SUMMARY OF THE INVENTION 
       [0005]    It is an object of the present invention to overcome all or part of the aforementioned drawbacks by proposing a method of fabricating a micro-mechanical component that includes, for example, at least three parts, wherein the precision of said processes is not altered by the assembly precision of the parts. 
         [0006]    The invention therefore relates to a method of fabricating a micro-mechanical component with several levels includes the following steps:
       a) forming at least two plates that each include a frame connected by at least one bridge of material to one part of said component;
 
characterized in that it further includes the following steps:
   b) stacking said at least two plates against a support so as to stack at least two of said parts;   c) securing a pin in a hole of each of said at least two stacked parts so as to form the component with a single pin protruding from at least one of the stacked plates so as to use it as gripping means;   d) releasing the formed component from said at least two plates.       
 
         [0011]    Advantageously according to the invention, it is possible to fabricate a part from any process (micro-machining, electroforming, electroerosion, stamping) without handling the part itself, but only said frame and said pin, prior to final assembly of said part. Moreover, the support is used as a guide for fabricating the final component in a more precise manner while still maintaining the precision of the process (micro-machining, electroforming, electroerosion, stamping) used to make each part during step a). 
         [0012]    According to other advantageous features of the invention:
       for each plate, step b) includes the following steps: e): guiding said plate using alignment means to orient said plate reliably relative to the support, and f): sliding said plate against at least one arbour secured to the support until it abuts against a shoulder of said arbour so that said plate is placed reliably relative to the support;   each of said alignment means includes at least one bevelled ring, which is mounted in the extension of said at least one arbour of the support, and which cooperates with a recess made in each of said at least two plates during step a);   at least two alignment means are used in step e) to improve guiding reliability;   each recess is made in the frame of said at least two plates or consists of a space between the frame and the part of each of said at least two plates;   each at least one bridge of material includes a narrow section at the end connected to said part of the component so as to create a weak area that can facilitate step d);   several parts are formed on each plate so as to form several components in step c);   the pin is extended at each of its ends by a pivot-shank that includes a pivot so as to form a pivoting arbour;   the pin includes a coaxial ring used as a stop member for limiting the penetration of said pin into said holes;   said coaxial ring has a toothing so as to form a pinion;   at least one of said plates is formed in step a) using an electroplating and/or micro-machining process;   at least one sub-part can be mounted on at least one of said parts laterally relative to said plate prior to, during or after step b).       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Other features and advantages will appear more clearly from the following description, given by way of non-limiting illustration, with reference to the annexed drawings, in which: 
           [0025]      FIG. 1  is a schematic diagram of two plates according to the invention; 
           [0026]      FIGS. 2 to 4  are schematic diagrams of successive steps of the method of the invention; 
           [0027]      FIGS. 5 to 7  are schematic diagrams of micro-mechanical components that can be made via the method of the invention; 
           [0028]      FIG. 8  is a flow chart of the method according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    As illustrated in  FIG. 8 , the invention relates to a method  1  of fabricating a micro-mechanical component  31 ,  41 ,  51 . Method  1  is for securely assembling at least two distinct parts  19 ,  21  by stacking them using a pin  29 . Method  1  includes a step  3  of making parts  19 ,  21  of the final component  31 ,  41 ,  51 , a step  5  of stacking the plates  11 ,  13  that include said parts, a step  7  of securing said parts, then a step  9  of releasing the component  31 ,  41 ,  51  thereby formed from plates  11 ,  13 . 
         [0030]    Advantageously according to the invention, the first step  3  of making parts  19 ,  21  of component  31 ,  41 ,  51  can be performed using a micro-machining and/or electroplating process. A micro-machining process, i.e. a process with machining precision approximately equal to or less than a micron, may comprise, for example, photolithography, to form a protective mask on a plate of micro-machinable material, then an etch of the unprotected parts of said plate, for example, deep reactive ion etching. A micro-machinable material may thus consist, for example, of a silicon, crystallised silica or crystallised alumina based material. Of course, other materials may be used. 
         [0031]    An electroplating process may include, for example, photolithography, to form a mould in which galvanic growth is carried out. A galvanic growth material may thus consist, for example, of a metal material like pure nickel or nickel-phosphorus. Of course other materials may be used. 
         [0032]    Manufacturing step  3  includes at least two distinct formation phases  2 ,  4 . Each phase  2 ,  4  using said micro-machining and/or electroplating processes is for forming a respective plate  11 ,  13  as illustrated in  FIG. 1 . Each plate  11 ,  13  includes a frame  15 ,  17  connected by at least one bridge of material  12 ,  14  to a part  19 ,  21  to be used for fabricating the final component  31 ,  41 ,  51 . As is visible in  FIG. 1 , each part  19 ,  21  preferably includes a through hole  16 ,  18 . 
         [0033]    It is thus clear that the final component  31 ,  41 ,  51  can be made, either from the same process, or from several different processes. Of course, processes other than micro-machining and/or electroplating, capable of fabricating these plates  11 ,  13 , etc., can be used, such as electroerosion or stamping. 
         [0034]    According to the invention, method  1  includes a second step  5  for stacking plates  11 ,  13  against a support  23 . In the example illustrated in  FIGS. 2 to 4 , support  23  includes at least one arbour  22  for cooperating with an associated recess  20 ,  26 , which is made in the plate  13 ,  11  to be stacked. This assembly of arbour  22 -recess  20 ,  26  enables plate  13 ,  11  to be precisely positioned relative to support  23 . 
         [0035]    Preferably, according to the invention, each arbour  22  has a shoulder  24  to make the distance between plate  13 ,  11  and support  23  more accurate. Support  23  preferably also includes alignment means  25  for reliably orienting plate  13 ,  11  relative to support  23 . In the example illustrated in  FIGS. 2 to 4 , alignment means  25  include a bevelled ring mounted in the extension of each arbour  22  for cooperating with one of recesses  20 ,  26  made in plate  13 ,  11 . 
         [0036]    In a first phase  6  of second step  5  illustrated in  FIG. 2 , a first plate  13  is mounted against support  23 . First of all, plate  13  is moved closer to support  23  along direction A. Secondly, plate  13 , illustrated by dotted lines, meets alignment means  25  which guide it along direction B. Alignment means  25  and recesses  20  orient plate  13  accurately so that recesses  20  are placed plumb with each arbour  22  of support  23 . Thirdly, plate  13  is slid along direction A by means of its recesses  20  against their arbour  22  until it comes into contact, finally, with shoulders  24  of each arbour  22 , as illustrated in  FIG. 2 . It is thus clear that plate  13  is very precisely positioned relative to support  23 . 
         [0037]    In a second phase  8  of second step  5  illustrated in  FIG. 3 , a second plate  11  is mounted against support  23 , by being stacked relative to first plate  13 . First of all, plate  11  is moved closer to support  23  along direction A′. Secondly, plate  11 , illustrated by dotted lines, meets alignment means  25  which guide it along direction B′. Alignment means  25  and recesses  26  orient plate  11  accurately so that recesses  26  are placed plumb with each arbour  22  of support  23 . Next, plate  11  is slid along direction A′ by means of its recesses  26  against their arbour  22  until it comes into contact, finally, with the top of first plate  13 , as illustrated in  FIG. 3 . 
         [0038]    It is thus clear that plates  11  and  13  are very precisely positioned relative to support  23 , and, incidentally, in relation to each other. It will also be noted that part  21  of plate  13  is located underneath and in contact with part  19  of plate  11 . Finally, it can also be seen that, in the example illustrated in  FIG. 3 , holes  16  and  18  are approximately aligned plumb with each other. 
         [0039]    Of course, first and second steps  3  and  5  are not limited to making and stacking two single plates  11  and  13 . Indeed, method  1  advantageously enables more or fewer than two plates to be made in step  3  so as to fabricate a component  31 ,  41 ,  51  from more or fewer than two stacked parts on support  23  in step  5 . It is also clear that more or fewer phases  2 ,  4  are necessary in step  3  and more or fewer phases  6 ,  8  are necessary in step  5 . 
         [0040]    According to the invention, method  1  includes a third step  7  for securing each of the stacked parts  19 ,  21  to form micro-mechanical component  31 ,  41 ,  51 . Preferably, according to the invention, securing step  7  is achieved by mounting a pin  29  in holes  16 ,  18  of each part  19 ,  21 . Thus support  23  preferably also includes a post  27  with a hollow top portion  28  to prevent any relative movement between parts  19 ,  21  and their plates  11 ,  13  when pin  29  is inserted into their respective holes  16 ,  18 . Indeed, any such relative movement would involve a risk of breaking bridges of material  12 ,  14  that is undesirable in this third step  7  of method  1 . 
         [0041]    Depending upon the nature of the materials used to make plates  11 ,  13 , etc., several embodiments of third step  7  could be envisaged. Thus, according to the invention, the preferred embodiments are driving in, welding and bonding. Of course, if one of plates  11 ,  13 , etc., is made of a material with no or very limited plastic deformation domain, it will be difficult to perform a driving in operation. 
         [0042]    In a first, embodiment, related to driving, in the example illustrated in  FIG. 4 , first of all in third step  7 , pin  29  is moved closer along direction C to each of stacked holes  16 ,  18 . Secondly, pin  29  is forcibly driven into holes  16  then  18  of plates  11  and  13 . Advantageously, the driving in force can be adjusted using an automaton. Each part  19 ,  21  is thus secured to pin  29  and forms the final component  31 ,  41 ,  51 . 
         [0043]    In a second weld-related embodiment, in the example illustrated in  FIG. 4 , first of all in third step  7 , pin  29  is coated with a solder. Secondly, pin  29  is moved closer along direction C to each of the stacked holes  16 ,  18 . Next, pin  29  is inserted into holes  16 , then  18  of plates  11  and  13 . Advantageously, the accuracy of direction C can be improved by using an automaton. Subsequently, the solder is solidified, for example, using a heat treatment. Each part  19  and  21  is thus secured to pin  29  and forms the final component  31 ,  41 ,  51 . 
         [0044]    In a third bonding-related embodiment, in the example illustrated in  FIG. 4 , first of all, in third step  7 , pin  29  is coated with an adhesive material, for example a polymer adhesive. Secondly, pin  29  is moved closer along direction C to each of the stacked holes  16 ,  18 . Next, pin  29  is inserted into holes  16 , then  18  of plates  11  and  13 . Advantageously, the accuracy of direction C can be improved by using an automaton. Subsequently, the adhesive material is activated, for example, by being heated. Each part  19  and  21  is thus secured to pin  29  and forms the final component  31 ,  41 ,  51 . 
         [0045]    According to the invention, method  1  includes a fourth step  9  of releasing the micro-mechanical component  31 ,  41 ,  51  formed from each of the plates  19 ,  21 , etc. stacked in second step  5 . Step  9  is preferably achieved by exerting a force capable of breaking bridges of material  12 ,  14 . 
         [0046]    Preferably, for all of the embodiments of third step  7 , pin  29  is secured so that it projects from at least one of the stacked plates and can be used as gripping means, i.e. so that parts  19 ,  21 , etc. of each plate  11 ,  13 , etc. do not have to be handled. Advantageously, method  1  thus makes high surface quality possible for each of the parts. It is also clear that the top hollow part  28  of post  27 , mounted on support  23 , enables pin  29  to go beyond the bottom of plate  13  and/or limits the extent to which the pin is driven into holes  16 ,  18 , etc. 
         [0047]    According to a first variant of the invention, pin  29  has a ring  30  that forms a stop member on said projecting part so as to limit how far pin  29  penetrates the holes in the parts. Ring  30  thus provides an improvement in manufacturing quality. Moreover, ring  30  which can be integral with pin  29  may also, advantageously, comprise a toothing that can form a pinion as explained below. 
         [0048]    According to a second variant of the invention, in addition to ring  30 , pin  29  can also be extended at each of its ends by a pivot-shank that includes a pivot so as to form a pivoting arbour. Advantageously, according to the invention, it is thus clear that it is possible, in third step  7 , to secure a multitude of elements in the holes of the stacked parts, which may vary from a simple pin  29  to a pivoting arbour fitted with at least one pinion. 
         [0049]    Upon reading method  1 , it is clear that it is possible to form several identical, or non-identical parts  19 ,  21 , etc. on each plate  11 ,  13 , etc. so as to mass produce identical or non-identical final components  31 ,  41 ,  51 . It is also clear that, after third step  7 , plates  11 ,  13 , etc. can be delivered straight to the production lines, of, for example, timepiece movements before fourth step  9  is carried out. The advantage of this is that it is only the frames  15 ,  17 , etc. of plates  11 ,  13 , etc. of many final components that are handled at the same time, without any risk of said stacked parts  19 ,  21 , etc. being damaged by handling. 
         [0050]    Advantageously, method  1  thus provides improved fabrication precision, the possibility of fabricating high quality composite components in a flexible manner, i.e. components including several different materials of high quality without having to manipulate the parts of the final component in a very simple manner and with a multitude of plates. It is thus clear that method  1  may be entirely automated, for example, using a multi-station production line. 
         [0051]    Micro-mechanical component fabrication examples in accordance with method  1  will now be presented with reference to  FIGS. 5 to 7 . In the example illustrated in  FIG. 5 , a timepiece wheel set  31  is shown including a pivoting arbour  33 , a pinion  35  and a toothed wheel  37 . Method  1  can, for example, allow pinion  35  to be a part of a plate obtained via an electroplating process and wheel  37  to be part of a plate obtained by a micro-machining process. 
         [0052]    In the example illustrated in  FIG. 6 , a timepiece wheel set  41  is shown including a pivoting arbour  43 , a pinion  45  and two toothed wheels  47 ,  49 . Method  1  may, for example, allow pinion  45  to be a part of a plate obtained by an electroplating process and wheels  47 ,  49  to be parts of plates obtained by a micro-machining process. 
         [0053]    Advantageously, according to the first variant explained above, pinions  35 ,  45  may also be integral with arbours  33 ,  43  respectively and thus form assemblies that can secure the final components  31 ,  41  in the third step  7  of method  1 . 
         [0054]    It is thus clear that a multitude of micro-mechanical components could be fabricated depending upon the materials used, the embodiments used and/or the variants chosen. Thus, by way of example, as illustrated in  FIG. 7 , one could also envisage fabricating a timepiece pallet assembly  51  that includes a pivoting arbour  53 , a top arm  55 , a main body  57 , but also a guard-pin  55 ′ and possibly a pin  53 ′. 
         [0055]    Method  1  may, for example, allow pallet assembly  51  to be obtained using silicon-based parts alone. Pallet assembly  51  could be obtained from two plates made by a micro-machining process in step  3 , stacked in step  5  on a support  23 , with top arm  55  and guard-pin  55 ′ being secured to main body  57  respectively by means of an arbour  53  and a pin  53 ′ by bonding in step  7 , pallet assembly  51  then being released from said plates by exerting a force on arbour  53  in final step  9 . 
         [0056]    Of course, the present invention is not limited to the illustrated example but may be subject to various variants and alterations, which will be apparent to those skilled in the art. In particular, in step  5  could include, as illustrated in  FIG. 8  in double lines, an intermediate step  10  of depositing an adhesive material between each stacked plate  11 ,  13 , etc., and/or ring  30 . This adhesive material improves the local join between at two elements of the final component if necessary. The adhesive material may be deposited by a screen printing process, which allows deposition of a precise thickness and surface area. 
         [0057]    Moreover, in order to provide the place where breakage occurs in step  9 , as illustrated in  FIG. 1 , each bridge of material  12 ,  14  may include a narrow section at the end connected to its associated part  19 ,  21 . 
         [0058]    There may also be more or fewer arbour  22 -recess  20 ,  26  assemblies. Further, these recesses  20 ,  26  may be replaced by recesses that already exist between frame  15 ,  17  and parts  19 ,  21  of plates  11 ,  13 . 
         [0059]    Finally, all of the components in the above explanation are mounted approximately vertically in each step purely to facilitate understanding of the invention. In fact, the direction of assembly of the components is not limited to directions A, A′ or C. For example, in the case of fabrication of a pallet assembly  51 , one could envisage mounting the pallet stones, before, during or after step  5  via a pierced side of frame  15 ,  17  of plate  11 ,  13 , etc. used to form part  57  and/or top arm  55 . Indeed, as the positioning of the pallet stones is very important, assembly against support  23  in phases  6 ,  8 , etc. of step  5  may be used to mount the pallet stones very precisely in an approximately perpendicular direction to direction A, A′, C. More generally, it is clear that at least one sub-part can be mounted on at least one of said parts laterally relative to said plate, before, during or after step  5 .