EP3825782B1 - Reinforced timepiece component - Google Patents

Description

The present invention relates to a watch component comprising a composite part comprising an upper face, a lower face and an edge, made of a first material and coated with a second material to increase its mechanical resistance, a part of its edge being devoid of this coating. The present invention also relates to a method of manufacturing such a component.

PRIOR ART

Silicon is a material of choice for the production of watch components due to its low density, its elasticity, its non-magnetism and its ability to be machined using engraving techniques. However, in the raw state, its mechanical strength, in particular its impact resistance, is relatively low because, on the one hand, silicon does not deform plastically and, on the other hand, the beginnings of rupture propagate very easily along its crystalline planes.

There are solutions for mechanically strengthening silicon parts. For example, the patent application WO 2007/000271 proposes for this to produce a coating in a thick amorphous material, such as silicon oxide, nitride or carbide, titanium nitride or carbide, silicon oxide being the preferred material and its thickness being, in in this case, at least five times greater than the thickness of the silicon oxide formed naturally on the surface of the silicon in contact with the ambient air. Watch components comprising a silicon structure covered with a reinforcing layer of silicon oxide are also described in the patent application WO 2008/135817 of the present plaintiff.

The micro-etching techniques used for the manufacture of silicon parts allow the simultaneous production of a batch of parts from the same silicon wafer. Thus, during engraving, silicon parts are left to constitute attachments or bridges holding each of the parts attached to the rest of the plate. These fasteners will later be broken to release the parts from the plate.

As indicated in the aforementioned patent application WO 2008/135817 , the fasteners may only be broken at the end of the manufacturing process, which implies that the reinforcement layer is formed, after etching, on the entire silicon wafer, including the parts and fasteners. In practice, after releasing the parts from the plate, if there are any attachment parts remaining on the parts, they are often removed by machining or abrasion, for aesthetic reasons. The areas of the surface of the final parts where the fasteners were located are made of silicon, that is to say they are not covered by the reinforcing layer (for example in silicon oxide) since this layer was formed before the breakage of the attachments. These zones therefore constitute areas of fragility which will allow possible ruptures resulting from shocks to propagate inside the part and cause it to rupture. In addition, the fragility of these areas is aggravated by the fact that their surface condition is generally less good than that of the rest of the part and that they can present micro-cracks as soon as they form.

The patent application EP 2 503 404 describes a manufacturing process making it possible to limit the impact of such fragile zones on the solidity of the component. For this, it is proposed, contrary to the practice which consists of eliminating by machining or abrasion the possible remainder of the attachment parts on the parts once separated from the plate, to detach the part from the plate so as to that at least part of at least one fastener is left on the final component ready to be mounted in the mechanism. The clip is typically laser cut so that its length is at least equal to its width and/or its thickness. Leaving at least part of at least one fastener on the final component makes it possible to significantly increase the mechanical strength of the component. In fact, the fasteners or fastening parts left distance the uncoated surfaces created by the detachment of the structure from the rest of the exterior surface of the component, which limits the propagation of the beginnings of rupture. This solution is however not entirely satisfactory insofar as, even if the fasteners or parts of fasteners limit the propagation of the beginnings of rupture in the event of an indirect impact, a direct impact on the weakened zone can lead to an impact on the residue. attachment.

The invention relates to a watch component comprising a composite part comprising an upper face, a lower face and an edge, made of a first material and coated with a second material to increase its mechanical resistance, at least part of its edge being devoid of of this coating, typically following the breakage of one or more fasteners resulting from its manufacturing process. The part or parts of the edge of the part devoid of this coating constitute areas of fragility of the component.

An aim of the present invention is to provide such a component whose risk of rupture or damage in the event of impact, typically direct, on the or one of said fragile zones is reduced.

BRIEF STATEMENT OF THE INVENTION

To this end, the invention proposes a watch component comprising a composite part comprising an upper face, a lower face and a edge, made of a first material and coated with a second material to increase its mechanical resistance, at least part of its edge being devoid of this coating, typically following the breakage of one or more fasteners resulting from its manufacturing process, said watch component being characterized in that it comprises a protective member which, in top view or in bottom view , extends outside the edge of the part at said part devoid of coating, covering at least partially, and preferably completely, said part.

Said protective member makes it possible to limit the possibility of direct impacts on the part of the edge of the composite part devoid of coating with which it is associated and thus has, as its name indicates, a protective function.

Preferably, in addition to its protective function, said protective member has another function such as, for example, an adjustment function, a weighting function, or a tribological function, preferably, an adjustment function.

As a protective member having an adjustment function, we can for example cite a weight for adjusting the inertia of a balance wheel, an eccentric allowing, by being pivoted, to adjust a rest or function position of a component with which it cooperates or well to adjust the stroke of a component with which it cooperates.

In an advantageous embodiment of the invention, the watch component is characterized in that said at least part of the edge of its composite part devoid of coating is located recessed in the component, typically in a notch in the edge of said composite part. This is thus doubly protected against direct impacts, by the protective member and by the rest of the edge of the composite part.

The composite part of the component according to the invention may comprise several parts of its edge devoid of coating. It then typically has at least as many protective organs as said parts so that each of said parts devoid of coating is associated with a distinct protective organ. In this case, in top view or bottom view, each of the protective members associated with a part of the edge of the composite part devoid of coating extends outside the edge of this part at the level of this part by covering this part at least partially.

When a protective member is an adjusting member, it extends outside the edge of the part at the level of the part devoid of coating with which it is associated, covering at least partially and preferably completely this part and this regardless of its adjustment position.

The invention also proposes a watch mechanism comprising a first watch component according to the invention and a second watch component intended to cooperate directly with said first watch component during operation of the mechanism, characterized in that the second watch component cannot reach the first watch component only on a part of the edge of its composite part carrying the coating or on a protective member and this regardless of the adjustment position of the adjustable protective member(s) if there are any.

The invention also relates to a timepiece such as a wristwatch, a pocket watch, a clock or a clock comprising such a watch mechanism.

1. a. graver une pièce ayant une forme souhaitée pour le composant dans une plaque d'un premier matériau en laissant au moins une attache entre la pièce et le reste de la plaque, ladite pièce comprenant une face supérieure, une face inférieure et une tranche,
2. b. revêtir la plaque d'un deuxième matériau destiné à augmenter la résistance mécanique de la structure et couvrant ainsi la pièce et la ou les attache(s),
3. c. détacher la pièce de la plaque en sectionnant la ou les attache(s), puis, optionnellement, éliminer les portions d'attache(s) restantes, une ou plusieurs partie(s) de la tranche de la pièce étant alors dépourvue(s) dudit revêtement, et
4. d. fixer au moins un organe protecteur sur la pièce, de manière à ce que, en vue de dessus ou en vue de dessous, ledit organe protecteur s'étende à l'extérieur de sa tranche au niveau de la partie ou d'une des parties de sa tranche dépourvue(s) de revêtement en couvrant au moins partiellement ladite partie,

les étapes c) et d) pouvant être interverties.Finally, the invention relates to a method of manufacturing a watch component ready to be mounted in a watch mechanism comprising the following steps:

1. has. engrave a part having a desired shape for the component in a plate of a first material leaving at least one attachment between the part and the rest of the plate, said part comprising an upper face, a lower face and a edge,
2. b. coat the plate with a second material intended to increase the mechanical resistance of the structure and thus covering the part and the fastener(s),
3. vs. detach the part from the plate by cutting the fastener(s), then, optionally, eliminate the remaining portions of fastener(s), one or more part(s) of the edge of the part then being devoid(s) of said covering, and
4. d. fix at least one protective member on the part, so that, in view from above or in view from below, said protective member extends outside its edge at the level of the part or one of the parts of its edge devoid of coating by covering at least partially said part,

steps c) and d) can be interchanged.

Step a) of the manufacturing process according to the invention is typically carried out using the deep reactive ion etching technique DRIE (Deep Reactive Ion Etching).

Step c) of the manufacturing process according to the invention is preferably implemented by cutting the fasteners by machining means, for example by laser. It can also be implemented by making a break, for example by making two beginnings of breakage then applying a force on the fastener to break it.

1. a. une longueur au moins égale à sa largeur,
2. b. une longueur au moins égale à son épaisseur,
3. c. une longueur au moins égale à la moitié de la longueur qu'avait l'attache avant l'étape de détachement

comme cela est décrit dans la demande EP 2 503 404 , de manière à diminuer d'avantage le risque de rupture ou d'endommagement du composant consécutivement à des chocs.Preferably, during step c) at least part of at least one fastener is left on the final component ready to be mounted in the mechanism, said at least part of at least one fastener projecting on the slice of the final component and having at least one of the following characteristics:

1. has. a length at least equal to its width,
2. b. a length at least equal to its thickness,
3. vs. a length at least equal to half the length that the fastener had before the detachment step

as described in the application EP 2 503 404 , so as to further reduce the risk of breakage or damage to the component following shocks.

The first material according to the invention is typically a “fragile” material, that is to say one which is not capable of plastic deformation (at room temperature, i.e. at 25°C). This is typically silicon. In this case, silicon can be monocrystalline, polycrystalline or amorphous, and have different crystalline orientations. It may also be doped or not.

The second material according to the invention is for example silicon oxide, carbide or nitride, titanium nitride or carbide or diamond, silicon oxide being preferred.

The protective member according to the invention is typically made from a metal base, for example a copper-beryllium or nickel phosphorus alloy, gold, platinum, steel or nickel. Alternatively, it could also be made of wood, ceramic, polymer or rigid foam.

The watch component according to the invention has reinforced mechanical resistance, in particular to direct shocks. The arrangement of its protective member(s) makes it less likely to suffer damage or even break in the event of an impact, for example during storage, transport, assembly or assembly. use within a watch mechanism.

The component according to the invention also has the advantage of being able to be manufactured precisely and in batches, a large number of components being able to be produced simultaneously from the same plate.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1 est une vue en perspective de dessus d'un balancier selon un mode de réalisation particulier de l'invention ;
• la figure 2 est une vue de dessus d'une partie d'un mécanisme horloger selon un mode de réalisation particulier de l'invention, ledit mécanisme comprenant le balancier illustré à la figure 1 et un stop-balancier ;
• la figure 3 est vue de dessus en transparence illustrant une partie du balancier et du stop-balancier illustrés à la figure 2 ;
• la figure 4a est une vue de profil coupée selon l'axe I-I du balancier et du stop-balancier illustrés à la figure 1 ; la figure 4b est une vue de profil coupée selon l'axe II-II, du balancier et du stop-balancier illustrés à la figure 2 ;
• la figure 5 est une vue de dessus en transparence d'un balancier selon un autre mode de réalisation de l'invention.

Other characteristics and advantages of the present invention will appear on reading the following detailed description given with reference to the appended drawings in which:

• there figure 1 is a top perspective view of a balance according to a particular embodiment of the invention;
• there figure 2 is a top view of a part of a watch mechanism according to a particular embodiment of the invention, said mechanism comprising the balance wheel illustrated in figure 1 and a balance stop;
• there Figure 3 is seen from above in transparency illustrating part of the balance and the stop-balance illustrated in the figure 2 ;
• there figure 4a is a profile view cut along axis II of the balance wheel and the balance stop illustrated in figure 1 ; there figure 4b is a profile view cut along axis II-II, of the balance wheel and the balance stop illustrated in figure 2 ;
• there Figure 5 is a transparent top view of a balance wheel according to another embodiment of the invention.

DETAILED DESCRIPTION

With reference to figures 1 to 4b , a balance 1 for a regulating member of the sprung balance type of a mechanical watch movement comprises, according to a particular embodiment of the invention, a composite structure 2 of low density carrying at its periphery metal parts 3 having a high density and inertia adjustment weights 11.

The balance wheel 1 and its structure 2 typically extend in a plane. Structure 2 has an upper face 2.1 and a lower face 2.2 delimiting its section 2.3. By “slice” we mean the slice defining the exterior contour of the structure 2 of balance 1. This therefore excludes the interior contours of the openings 2.4 which are optional.

Structure 2 comprises a board 4 of thickness e, typically constant. The board 4 has an annular central part 5 through which the shaft on which the balance 1 is intended to be mounted can pass, a rim, for example comprising two parts 6a and 6b in the form of diametrically opposed arcs of a circle, arm 7 connecting the central part 5 to the two parts 6a, 6b of the serge and, in each of the parts 6a, 6b of the serge, cavities 8 in which the metal parts 3 are located. The structure 2 comprises also edges 9 projecting from the upper surface of the board 4. These edges 9 extend in height the wall of the cavities 8, allowing the cavities 8 and therefore the metal parts 3 which fill them to have a greater height or thickness than the thickness e of the board 4. Each of the cavities 8 and the metal parts 3 has an elongated and curved shape which follows the arcuate contour of the part 6a or 6b of the serge in which it is located. The number and dimensions of the metal parts 3 may vary. Their function is to weigh down the serge in order to increase the moment of inertia to mass ratio of the balance 1.

Finally, the structure 2 comprises four pins 10 each carrying a weight 11, said weights 11 allowing the adjustment of the moment of inertia of the balance 1. These weights 11 are typically held on the pins 10 by elastic tightening. The elastic tightening is such that each of them is able to pivot around the pin which carries it for adjusting the inertia of the balance 1.

With the exception of the metal parts 3 and the weights 11 which are attached, the balance 1 can be entirely monolithic. Structure 2 is therefore typically monolithic. It is made of a base material 12, for example silicon, covered with a coating 13 intended to increase the mechanical resistance of the balance 1, in particular its resistance to shocks. The coating 13 is, for example, a layer of silicon oxide.

The balance wheel 1 is manufactured using a process similar to that described in the patent application WO 2008/135817 of the present plaintiff. Thus, a plate of the base material 12 is etched, preferably by DRIE deep reactive ion etching, to form a batch of parts each having the shape of the structure 2, each of these parts being attached to the rest of the plate by fasteners or bridges of material left during engraving. Then the coating 13 is formed on all surfaces of the plate, including the surfaces of parts and fasteners. Then the metal parts 3 are formed in cavities defined by the coated parts, namely the cavities 8, typically by electroforming (galvanic growth). Finally, the parts are detached from the plate and the adjustment weights 11 are mounted on the balance 1.

In the case of a coating 13 of silicon oxide on a base material 12 consisting of silicon, the coating 13 can be formed by applying a heat treatment to the plate to oxidize its surfaces, as in the patent application WO 2008/135817 . In other cases, the coating 13 can be formed for example by chemical vapor deposition or physical vapor deposition.

The detachment of the parts from the plate creates fragile end surfaces 15, devoid of the coating 13. In the context of the invention, the detachment is typically carried out in a manner which leaves attachment parts 14 on the parts in order to to limit the propagation of the beginnings of rupture which could occur on these “fragile” surfaces, as described in the request EP 2 503 404 . Thus, as shown in figures 1 to 4a , said attachment parts 14 project onto edge 2.3 of each part. Each of them is covered by the coating 13 except on the part of its edge 2.3 corresponding to its end surface 15 created by the detachment of the parts from the plate ( figure 4a ). The length of the attachment parts 14 is typically greater than or equal to its width and/or its thickness measured at the level of the end surface 15, as described in the application EP 2 503 404 .

In the present invention, the position of the pins 10 and the dimensions of the weights 11 are such that, in top view, each of the weights 11 extends outside the section 2.3 of the structure 2 at the level of a part separate attachment 14 by at least partially covering the part 15 of the edge of this attachment 14 devoid of covering 13. The whole is arranged so that this is the case whatever the adjustment position of the weight 11 considered.

Each adjustment weight 11 thus plays a protective role by limiting the possibility of direct shocks on the “fragile” parts 15 of section 2.3 of the balance 1 which could occur during its storage, transport or assembly in a watch mechanism or after said assembly, during the normal operation of said watch mechanism.

There figure 2 illustrates part of a watch mechanism comprising, among other things, a plate 16 on which the balance 1 is mounted and a balance stop mechanism 20, also called “stop-second” or “stop-balance”. The balance stop 20 comprises an elastic arm 21 actuable by the time setting rod (not shown) of the mechanism and whose end is intended to cooperate directly with the periphery of the balance 1 to stop its oscillation by friction, and this regardless of its position. It is possible that it hits it directly next to one of its attachments 14 presenting a fragile zone 15.

As we can see in figures 4a and 4b , the arm 21 of the balance stop 20 generally has a thickness or height h corresponding to the sum of the thickness e of the board 4 and the thickness e' of its flyweight and is arranged so that if it hits the balance 1 at the level of a fragile part 15 of its edge 2.3, the impact is on the flyweight 11 and not on said fragile part 15. In other positions of the balance 1, the arm 21 would typically strike directly on a part of section 2.3 carrying the covering 13 or on another of the four weights 11.

The height h of the balance arm 21 could be different from the moment the protection function is ensured. Typically, the arm 21 is arranged so that, once mounted in the watch mechanism, it is horizontally facing both at least part of the section 2.3 of the board 4 of the balance 1 and at least one part weights 11.

In addition to its protective role limiting the possibility of direct impacts on the “fragile” parts 15 of section 2.3 of the balance 1 which could occur from its manufacture and until its assembly in a watch mechanism, the weights 11 have a protective role with respect to impacts against the arm 21 of the balance stop 20. In this way, the risk of breakage or major damage to the balance 1 during actuation of the balance stop 20 is significantly reduced.

In view of the above, the weights 11 therefore have a dual role, they serve both as a protective member or mechanical “shield” of the balance 1 against shocks which may be unpredictable (transport, assembly, etc.) or predictable. (repeated impacts against a balance stop for example) and inertia adjustment member.

To satisfy their dual role, the weights 11 must have a high density to provide inertia to the balance 1 and preferably high mechanical resistance. If they are typically made of a copper - beryllium alloy, other materials traditionally used for the production of adjustment weights, such as gold, platinum, steel, nickel or a nickel-phosphorus alloy are quite suitable in the scope of the invention.

As a variant, it is possible to produce a balance wheel 1 according to the invention whose attachment parts 14 would have been completely eliminated, typically by abrasion, the fragile parts 15 of section 2.3 not covered with coating 13 would then be flush with the rest of section 2.3. In this case, the position of the pins 10 and the dimensions of the weights 11 would be such that, in top view, each of the weights 11 would extend outside the section 2.3 of the structure 2 at the level of one of its parts 15 devoid of distinct coating, by at least partially covering said part 15, the whole being arranged so that this is the case whatever the adjustment position of the weight 11 considered.

In a variant of the method of manufacturing the balance 1 according to the invention, the adjustment weights 11 could be mounted on the pins 10 before the fasteners break.

In the example illustrated in figures 1 to 4b , the structure 2 comprises four fragile parts 15 and four pins 10 each carrying an adjustment weight 11, each of said weights 11 protecting one of said fragile parts 15. It is clear that the structure 2 could comprise a different number of fragile parts 15 and weights and that only certain fragile parts 15 could be protected by weights or that only certain weights 11 protect a fragile part 15.

In another embodiment, the component according to the invention is a watchmaking hammer and its adjustment member is an eccentric allowing the adjustment of its rest position against a stop.

In reference to the Figure 5 , in yet another embodiment, the component according to the invention is a balance wheel 100 comprising a composite structure 102, typically made of silicon covered with silicon oxide, comprising an upper face, a lower face and a edge. A so-called fragile part 115 of this slice, corresponding to the surface created by the breakage of a manufacturing fastener 114, is devoid of coating. The structure 102 comprises pins 110 carrying inertia washers, one of which 111 is positioned so that, in top view, it extends outside the edge of the structure at the level of said fragile part 115 by completely covering said part. This inertia washer has a dual role, both protective in that it limits the possibility of direct shocks on the fragile part 115 and both weighting to increase the inertia of the balance 100. Advantageously, the part fragile 115 of the edge of the structure 102 is set back in this structure, in a notch in its edge, so as to further limit the possibility of direct impacts on the fragile part 115.

In addition to its high precision, linked to the precision of its engraving step (a), the manufacturing process according to the invention makes it possible to produce a large number of components simultaneously from the same wafer.

Although the invention was described above for silicon parts coated with silicon oxide, it could be applied to other composite materials such as tempered glass.

Whatever the watch component produced, it is possible to engrave the base part of this component so that the part of the edge of this part devoid of coating at the end of the manufacturing process is recessed in the component, typically in a notch of said slice, as in the case of the balance 100 illustrated in figure 5 . Thus, said part devoid of coating is doubly protected, by the adjustment member and by the rest of the edge of its base part.

In addition to the numerous advantages mentioned above, in the preferred case where attachment parts are left on the final component, the watch component according to the invention has an aesthetic advantage in that it allows these attachment parts to be hidden. .

Claims (15)

1. Timepiece component (1; 100) comprising a composite piece (2; 102) comprising an upper face (2.1), a lower face (2.2) and an edge (2.3), and being made from a first material (12) and coated with a second material (13) to increase the mechanical strength thereof, at least one part (15; 115) of its edge (2.3) being free of this coating (13), said timepiece component (1; 100) being characterised in that it comprises a protective member (11; 111) which, as seen from above or from below, extends outside of the edge (2.3) of the piece at said part (15; 115), at least partially covering said part (15; 115).
2. Timepiece component (1; 100) as claimed in claim 1, characterised in that, as seen from above or from below, said protective member (11; 111) extends outside of the edge (2.3) of the piece (2; 102) at said part (15, 115), completely covering said part (15; 115).
3. Timepiece component (1; 100) as claimed in claim 1 or 2, characterised in that, in addition to limiting the possibility of direct impacts on said part (15; 115), said protective member (11; 111) has a function such as a weighing-down function, a setting function or a modifying function for the tribological properties of said composite piece.
4. Timepiece component (1) as claimed in claim 3, characterised in that said protective member (11) is a setting member, and in that, as seen from above or from below, it extends outside of the edge (2.3) of the piece (2) at said part (15), at least partially covering said part (15), regardless of its setting position.
5. Timepiece component (1; 100) as claimed in any one of the preceding claims, characterised in that said first material (12) is made of silicon.
6. Timepiece component (1; 100) as claimed in any one of the preceding claims, characterised in that said second material (13) is selected from silicon dioxide, carbide or nitride, titanium nitride or carbide, or diamond, preferably silicon dioxide.
7. Timepiece component (1; 100) as claimed in any one of the preceding claims, characterised in that said protective member (11; 111) is produced based on metal, preferably from a nickel-phosphorous or copper-beryllium alloy, from gold, from platinum, from steel or from nickel.
8. Timepiece component (1) as claimed in any one of claims 1 to 7, characterised in that it is a balance, and in that said protective member (11) comprises an inertia-block for setting the inertia of the balance.
9. Timepiece component (100) as claimed in any one of the preceding claims, characterised in that said part (115) of the edge free of coating is recessed in the component, typically in a notch in the edge of said composite piece (102).
10. Timepiece component (1) as claimed in any one of the preceding claims, characterised in that said composite piece comprises several parts (15) of its edge (2.3) which are free of coating (13) and at least as many protective members (11) as said parts (15), the whole being arranged such that a separate protective member (11) is associated with each of said parts (15) free of coating.
11. Timepiece mechanism comprising a first timepiece component (1) as claimed in any one of claims 1 to 10 and a second timepiece component (20) intended to cooperate directly with said first timepiece component (1) when said mechanism is operating, characterised in that the second timepiece component (20) can contact the first timepiece component (1) only via one part of its edge (2.3) bearing the coating (13) or via a protective member (11), regardless of the setting position of the settable protective member(s) (11) if present.
12. Timepiece mechanism as claimed in claim 11, characterised in that the part of said second timepiece component (20) intended to cooperate directly with said first timepiece component (1) is horizontally facing both at least one part of the edge (2.3) of said first component (1) and at least one part of the or each protective member.
13. Timepiece mechanism as claimed in claim 11 or 12 when dependent on claim 8, characterised in that said second timepiece component comprises a balance stopping mechanism (20).
14. Timepiece such as a wristwatch, a pocket-watch, a clock or a miniature clock comprising a timepiece mechanism as claimed in any one of claims 11 to 13.
15. Method for manufacturing a timepiece component (1) ready to be mounted in a timepiece mechanism, comprising the following steps:

    a. etching a piece having a desired shape for the component (1) in a plate of a first material (12), leaving at least one tie between the piece and the rest of the plate, said piece comprising an upper face (2.1), a lower face (2.2) and an edge (2.3),

    b. coating the plate with a second material (13) intended to increase the mechanical strength of the piece and thereby covering the part and the tie(s),

    c. detaching the piece from the plate by separating the tie(s), then optionally removing the remaining tie portion(s) (14), one or more parts (15) of the edge (2.3) of the piece thus being free of said coating (13),

    d. attaching at least one protective member (11) to the piece (2) such that, as seen from above or from below, said protective member (11) extends outside of the edge (2.3) of the piece (2) at the part (15) or one of the parts (15) of its edge (2.3) which is or are free of coating (13), at least partially covering said part (15),

    wherein steps c) and d) can be inverted.

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