Abstract:
A process for adjusting a device including a first piece and at least one second piece, wherein the at least one second piece is fixed to the first piece by a joint made from a first material arranged between the first and second piece. The first material is an at least partially amorphous metal alloy. The process further includes: heating at least the joint to a heating temperature in a range of between a glass transition temperature and a crystallisation temperature of the first material; modifying a position of the at least one second piece until a desired determined position is obtained; cooling at least the joint so that it retains its at least partially amorphous state.

Description:
[0001]    The present invention relates to a process for adjusting a device. The device comprises a first piece and at least one second piece, wherein said at least one second piece is fixed to the first piece by means of a joint arranged between said first and second pieces. 
         [0002]    The technical field of the invention is the field of mechanics. 
       TECHNOLOGICAL BACKGROUND 
       [0003]    There are numerous devices that after production require a step of adjustment in order to be perfectly compliant. This need for high precision exists in fields of microtechnology such as watchmaking, for example. In fact, the world of watchmaking works with dimensions from the millimetre to hundredth of a millimetre range. Examples of devices where precision is important include wheel trains or also the escapement. In actual fact, the escapement is formed from an anchor and an escape wheel cooperating with one another. The rotation of the latter is controlled by the anchor of the escapement system, the pulses of which are supplied by a spring balance. Thus, the escapement system comprises an anchor mounted to pivot on an axis. This anchor comprises a lever fitted on a first end with a fork intended to cooperate with a pin mounted on a disc and fitted on a second end with arms intended to receive pallets in order to cooperate with the escape wheel. During its operation the anchor pivots on its axis in such a manner that the pallets of the arms come into contact with the teeth of the escape wheel in order to control the rotation of the wheel trains. Now, if the pallets of the anchor are not positioned properly, the pulses between the pallets of the anchor and the escape wheel are not perfect and losses occur, thus affecting the efficiency of the escapement and therefore the precision of the watch. Currently, the assembly of the pallets on an anchor is achieved using a gum lacquer, which is a natural product with properties similar to those of thermoplastic materials. These properties allow the pallets to be repositioned relative to the anchor by locally heating the anchor. However, the quality of gum lacquer fluctuates greatly from one batch to another, which makes repositioning a delicate operation. Moreover, since the viscosity of gum lacquer is difficult to control and as it is difficult to control the volume of glue deposited, an overflow of the gum often occurs, which results in possibly unacceptable aesthetic flaws. Moreover, since gum lacquer is an organic material, it is subject to aging and consequently the fixture of the pallet can be weakened. 
         [0004]    Another possibility would be to use brazing or soldering. However, these two solutions are also problematic, since to have any chance of soldering a ceramic or silicon or mineral material, it is necessary to use reactive brazing/soldering, which must be conducted at a relatively high temperature (generally above 700° C.) and in a neutral atmosphere or in high vacuum. This results in very long assembly cycles and risks of breakage/cracking of the material are possible. 
       SUMMARY OF THE INVENTION 
       [0005]    The aim of the invention is to overcome the disadvantages of the prior art by proposing to provide a simple, reliable and precise adjustment process. 
         [0006]    For this purpose, the invention relates to the aforementioned adjustment process, which is characterised in that the first material is an at least partially amorphous metal alloy, and in that said process additionally comprises the following steps: 
         [0007]    heating at least said joint to a heating temperature in the range of between the glass transition temperature and the crystallisation temperature of the first material; 
         [0008]    modifying the position of said at least one second piece until the desired determined position is obtained; 
         [0009]    cooling at least said joint so that it retains its at least partially amorphous state. 
         [0010]    A first advantage of the present invention is to enable a controlled adjustment of the position of the second piece in relation to the first piece. In fact, at least partially amorphous materials such as amorphous metals have the ability to soften significantly when they are heated to a temperature in the range of between their glass transition temperature and their crystallisation temperature. In this temperature range, amorphous metals have a viscosity that decreases significantly, wherein the decrease in viscosity is dependent on the temperature: the higher the temperature, the greater the decrease in viscosity. This decreasing viscosity thus allows the fixture to be loosened in such a way that the second piece can be displaced to modify its position and give it a desired precise position. The viscosity can then be adjusted so as to simplify said adjustment process. 
         [0011]    Another advantage of this process is that it is reproducible in the sense that once the amorphous metal is cooled to be solid, it is possible to reheat it to a temperature in the range of between its glass transition temperature and its crystallisation temperature to modify the position of the second piece in relation to the first if this was not perfect. 
         [0012]    Advantageous embodiments of this process are the subject of the dependent claims. 
         [0013]    In a first advantageous embodiment said first material is completely amorphous. 
         [0014]    In a second advantageous embodiment said metal alloy comprises at least one precious metal element selected from the group formed by gold, platinum, palladium, rhenium, ruthenium, rhodium, silver, iridium or osmium. 
         [0015]    In a third advantageous embodiment, in the heating step the heating temperature is selected to obtain a determined viscosity of the first material. 
         [0016]    In another advantageous embodiment the process additionally comprises a step of crystallisation of said first material consisting of heating said first material to a temperature in the range of between its glass transition temperature and its melting temperature, holding said material at this temperature for a certain period and cooling it. 
         [0017]    In another advantageous embodiment the temperature and holding time of said first material is selected in order to reach a determined crystallisation rate. 
         [0018]    In another advantageous embodiment the joint and the first piece only form a single piece made from the first material. 
         [0019]    In another advantageous embodiment the first piece is an anchor and the at least one second piece is a pallet. 
         [0020]    One of the advantages of these embodiments is to allow the adjustment to hold by crystallising the amorphous metal joint. In fact, crystallising an amorphous material takes away its ability to be changed into a viscous state by heating it to a temperature in the range of between its glass transition temperature and its crystallisation temperature. Thus, returning the joint to amorphous form requires changing it into liquid form and rapidly cooling it, and thus destroying the device. 
         [0021]    The invention also proposes to provide a device comprising a first piece and at least one second piece, wherein said at least one second piece is fixed to the first piece by means of a joint arranged between said first and second pieces. Said device is characterised in that said joint is made from an at least partially amorphous metal alloy. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0022]    The aims, advantages and characteristics of the process according to the present invention will become clearer from the following detailed description of at least one embodiment of the invention given solely as a non-restrictive example and illustrated in the attached drawings, wherein: 
           [0023]      FIG. 1  schematically shows an anchor before the production process; 
           [0024]      FIG. 2  schematically shows an anchor at the end of the production process; 
           [0025]      FIG. 3  schematically shows an anchor during the adjustment process according to the present invention; 
           [0026]      FIG. 4  schematically shows an anchor after having undergone the adjustment process according to the present invention; and 
           [0027]      FIG. 5  schematically shows a variant of the anchor undergoing the adjustment process according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIGS. 1 and 2  show a device  1  comprising a first piece  2  and at least one second piece  3 . This device  1  can be a part of an escapement of a timepiece, for example. This escapement  1  is formed from an anchor and an escape wheel that cooperate with one another. The rotation of the latter is adjusted by the anchor of the escapement system, the pulses of which are supplied by a spring balance. Thus, the escapement system comprises an anchor mounted to pivot on an axis. This anchor  2  represents the first piece and is provided in the form of a lever  20  fitted on a first end with a fork  21  intended to cooperate with a pin mounted on a disc and fitted on a second end with at least two arms  22 . This anchor  2  is intended to receive at least one second piece  3 , i.e. pallets, in order to cooperate with the escape wheel. During its operation the anchor  2  pivots on its axis in such a manner that the pallets  3  come into contact with the teeth of the escape wheel in order to control the rotation of the wheel trains. 
         [0029]    The pallets  3  are fixed to the lever  20  of the anchor  2  at seats  23  arranged on each of the two arms  22 . These seats  23  have dimensions calculated to allow for an interstice or space  24  to be created between said arm  22  and said pallet  3  when the latter is inserted into the seat  23 . This interstice  24  is used so that a joint  4  made of a first material can be arranged between said arm  22  of the anchor  2  and said pallet  3 . 
         [0030]    In a first embodiment of the present invention the joint  4  is made of a first material, which is an at least partially amorphous material comprising at least one metallic element. This first material can be an at least partially amorphous metal alloy. This metallic element can be a precious metal element such as gold, platinum, palladium, rhenium, ruthenium, rhodium, silver, iridium or osmium. An at least partially amorphous material is understood to be a material that is able to solidify at least partially in amorphous phase. Said first material is preferably completely amorphous. 
         [0031]    The assembly of the pallets  3  on the anchor  2  by means of the joint  4  precedes this adjustment step and can be achieved by different methods. 
         [0032]    The property of amorphous materials that allows these to have a viscosity that decreases considerably in a given temperature range for each material while remaining amorphous is made use of to modify the position of the pallets  3  of the anchor  2 . 
         [0033]    The first step of this adjustment process consists of providing said anchor  1 , to which the pallets  3  are fixed. 
         [0034]    The second step consists of increasing the temperature of at least one part of the anchor  1 . Advantageously, the joints  4  are subjected to said increase in temperature. In fact, the joints  4  hold the pallets  3  fixed to the anchor  2  and an adjustment is made possible by acting on these joint  4 . The joints  4  are heated to a temperature in the range of between the glass transition temperature Tg and the crystallisation temperature Tx of the first material. This increase in temperature results in a decrease in viscosity of the first material forming the joints  4 . 
         [0035]    The third step consists of displacing at least one of the pallets  3  to place it in a desired position as visible in  FIG. 3 . This displacement is possible because the first material is an amorphous metal alloy with a very low viscosity when it is heated to a temperature in the range of between its glass transition temperature Tg and its crystallisation temperature Tx. This low viscosity enables the pallet or pallets  3  to be displaced without deterioration or breakage of the joint or joints  4 . To optimise the procedure it would be possible to adapt the temperature at which the joints  4  are heated to obtain a determined viscosity. In fact, the viscosity is dependent on the temperature, i.e. the higher the temperature, the lower the viscosity will be and vice versa. Now, if the viscosity is too low, the displacements of the pallet  3  will be difficult because the pallet or pallets  3  will be displaced too easily and therefore there will be a loss of precision in the adjustment. In contrast, if the viscosity is too high, more force must be applied to displace the pallet or pallets  3  and risks of breakage can arise. 
         [0036]    Once the pallets  3  are placed in the desired position, a fourth step consists of cooling the joints  4  of amorphous metal so that they remain at least partially amorphous and hold the position of said pallets  3  as in  FIG. 4 . The advantage of said process is thus to prevent any degassing of the material while assuring a very high strength of the fixture of the pallet at the anchor  2 . The advantage is that the joints  4  are always in an amorphous state, which allows the position of the pallets  3  to be modified once again as required. 
         [0037]    In a first variant there is provided an additional or fifth step, in which the amorphous metal joints  4  are crystallised. This crystallisation is conducted by heating these joints  4  to a temperature in the range of between the glass transition temperature Tg and the crystallisation temperature Tx of the material forming the joints. The first material is then cooled slowly to allow the atoms to arrange themselves in a crystalline structure. This crystallisation enables the position of the pallets to be held since after this crystallisation step it is no longer possible to modify the position of pallets  3  by heating the joints  4  between the glass transition temperature Tg and the crystallisation temperature Tx of the material. 
         [0038]    Moreover, this crystallisation can in some cases cause an increase in volume of the material, which changes from an amorphous state to a crystallised state. The consequence of this increase in volume is an increase in stress applied by said joints  4  on said anchor  2  and on the pallets  3 . These pallets  3  are thus held under force and there is therefore no risk of them being displaced in the event of impacts with the teeth of the escape wheel. 
         [0039]    In a second embodiment of the present invention shown in  FIG. 5 , the joint  4  and the anchor  2  form only one single piece. It is thus understood that the anchor  2  is made of the said first material and therefore of an amorphous metal. The anchor  2  thus acts as joint  4 . 
         [0040]    The anchor  2  can be made by hot or cold forming. The anchor  2  is thus formed at the same time as the pallets  3  are fixed to said anchor  2 . 
         [0041]    Once the anchor  2  has been formed, it is possible to adjust the position of the pallets  3  if these are not placed correctly. 
         [0042]    The first step of this adjustment process therefore consists of providing said anchor  2 , to which the pallets  3  are fixed. 
         [0043]    The second step consists of increasing the temperature of at least one zone of the anchor  2 . The increase in temperature must be conducted locally at the fixture zones between the first piece  2  and the second piece  3 . In the case of an anchor  2 , these zones are the zones of the seats of the arms  22  where the pallets  3  are inserted. These zones are heated to a temperature in the range of between the glass transition temperature Tg and the crystallisation temperature Tx of the amorphous metal. This temperature increase causes a decrease in the viscosity of the amorphous metal without this losing its amorphous state. 
         [0044]    The third step is similar to the third step of the first embodiment and thus consists of the displacement in three axes: length, width and height, of at least one of the pallets  3  to place it in a desired position. To optimise the procedure it would be possible to adapt the temperature at which the joints  4  are heated to obtain a desired viscosity. 
         [0045]    Once the pallets  3  are placed in the desired position, a fourth step consists of cooling the amorphous metal zones so that they remain at least partially amorphous and hold the position of said pallets  3 . The advantage of said process is thus to prevent any degassing of the material while assuring a very high strength of the fixture of the pallet at the anchor. 
         [0046]    It is understood that this adjustment process can be conducted once again if the adjustments performed are not yet perfect or in the case of a later modification of the position of the pallets  3 . 
         [0047]    A fifth optional step can be performed. This step consists of an at least partial crystallisation of the zones at the level where the pallets  3  are fixed. This step is performed by increasing the temperature of the zones at the level where the pallets  3  are fixed. The temperature is increased to reach a temperature in the range of between the glass transition temperature Tg and the crystallisation or temperature Tx or melting temperature of the amorphous metal. The latter decreases in viscosity while remaining amorphous. These heated zones are then held at this temperature and are then cooled slowly so that they form a crystalline structure. The cooling temperature and period and the holding time of the metal at this temperature are parameters that allow the crystallisation rate to be fixed. This crystallisation is used to hold adjustments made beforehand. In fact, when a material is in crystalline form, it cannot undergo the adjustment process according to the invention. The only way would be to change it to amorphous form, i.e. to heat it to above its melting temperature to make said material liquid and then cool it rapidly to below its glass transition temperature so that it is amorphous. Now, with respect to a joint  4  between a pallet  3  and an anchor  2 , the melting of the joint causes at least a deterioration in the joint  4  or even destruction of the device  1 , making an adjustment impossible. 
         [0048]    In a variant of this second embodiment it can be provided that the pallets  3  are also made from amorphous metal. The amorphous metal used for the pallets  3  will preferably be different from that used for the anchor  2  so that when the amorphous metal of the anchor  2  is heated to reach a temperature in the range of between its glass transition temperature Tg and its crystallisation temperature Tx, the amorphous metal of the pallets does not become viscous like the amorphous metal of said anchor  2 . 
         [0049]    It will be understood that various modifications and/or improvements and/or combinations evident to the person skilled in the art can be applied to the different embodiments of the invention discussed above without departing from the framework of the invention defined by the attached claims. 
         [0050]    It is naturally understood that this adjustment process is not restricted to the adjustment of the position of the pallets  3  and an anchor  2 . This process can be used with respect to other devices. The devices using this adjustment process are, for example, a device comprising a wheel driven onto an axis, wherein said device comprises a joint positioned between said axis and said wheel. The position of the wheel can then be adjusted by applying the adjustment process to said joint. Adjustment can be performed along the axis or angularly.