EP1248164B1 - Clockwork - Google Patents

Description

The present invention relates to a movement for a timepiece comprising a plate, a needle display device, a gear train connecting training means to said needles, said train comprising a wheel drive at least indirectly with said drive means and secured to a pivoting roadway on a tenon mounted in a gear train, a barrel wheel disposed on the roadway, the drive wheel and the barrel wheel extending on either side of said platen. Such a movement is described by example by the document FR 2 433 194.

This type of movement for timepieces is common and known since long time. However, it can be noted that the movements of the prior art have certain drawbacks, which the present invention makes it possible to remedy.

Figure 1 schematically shows part of a movement with second in the center as described in the prior art. This figure 1 lets appear the relative positions of the time display mobiles. In particular, we distinguish a second mobile 101 pivotally mounted in a stone 102, itself driven in a gear train 103. The axle 104 of the second gear is arranged in a center tube 105, said center tube 105 being driven through a plate 106. The second axis 104 comprises, in its median part, an annular bulge 107 having a diameter substantially equal to the inner diameter of the center tube 105. Said center tube 105 thus fulfills the function of radial guide for the axis of second 104. The roadway 108 is rotatably mounted on said center tube 105, the base of the floor 108 resting on the top of the plate 106. It may be noted that the center tube 105 also performs a radial guide function for the floor 108. The pinion of the roadway 109 meshes with a timer wheel 110, secured to a timer pinion 111 which meshes with a gun wheel 112. Said gun wheel 112 is rotatably mounted on the roadway 108 which serves it therefore radial guide.

A first disadvantage presented by such a type of movement appears from Figure 1 and relates to manufacturers of movements of timepieces, in particularly when they deliver these movements to customers who then follow them in watch boxes of their choice. Indeed, in a conventional way, while that all the wheels of the movement are enclosed between a platinum and bridges, the barrel wheel is disposed on said platen, so outside the movement. Moreover, since the said shotgun must be free to turn around the pavement, it is typically simply "threaded" on said pavement, and therefore free axially. Therefore, the gun wheel is likely to come off its taken with the timer gear during transport from the manufacturer of movement at his client's. Specifically, during the assembly process of the timepiece, the dial is usually pressed on the movement. If, when this step, the barrel wheel is not properly engaged with the sprocket timer, the teeth of the gun wheel can become deformed due to their pressure against the timer gear. In the case of cheap movements, the wheel barrel is sometimes made of plastic and his teeth may then become break when laying the dial, if the toothing of the gun wheel is not engaged correct with that of the timer gear. The customer is obliged, before the installation of the dial, to carry out an automatic or manual control of the correct positioning of the gun wheel if he does not want to risk malfunctions of the piece watchmaking, following damage to the movement. This control step inevitable result in an increase in the duration and cost of the manufacture of the final product.

Similarly, the cannon wheel can be released entirely from the roadway and lose during transport movements to the casing post, which also generates additional production costs.

A known solution of the prior art to remedy this problem consists in add a washer on the pavement tube once the barrel wheel is put into place, so as to block the latter axially. This solution, however, a disadvantage in that it requires the manufacture of an additional piece, typically a washer, and the implementation of an additional step in the method of mounting the movement, for laying said washer.

The present invention therefore has the main purpose of overcoming the disadvantages of the aforementioned prior art by providing a movement for a timepiece, allowing in particular to ensure a hold in the grip of the gun wheel with the Timer gear during transport movements before operation casing.

For this purpose, the subject of the invention is a movement for a timepiece according to the object defined by claim 1 of the patent.

The structure according to the invention makes it possible to prevent the cannon wheel from escaping from the roadway during the transport stage and therefore be lost or damaged during the setting of the dial, while suppressing the mentioned control step previously.

An additional advantage of the invention stems from the fact that the means of retaining the barrel wheel on the pavement tube are integral parts of these two elements. The realization of the retaining means therefore does not require the setting implementation of an additional step, as such, in the manufacturing process some movement.

According to a particular embodiment of the invention, said means for restraint are of the type notch. They may include a bead and a complementary grooves respectively on the tube of the barrel wheel and on the pavement tube, for example.

An additional advantage of the present invention is that said bead is made by an extra thickness of material on the tube of the wheel to barrel, said overthickness being located substantially at the level where the needle of hours is then hunted. Indeed, the hunting of a needle usually gives instead of a creep of material on its support that can increase with time. This phenomenon can cause a game of the needle relative to its support, or even the detachment of the needle from its support. Thanks to the structure of the tube of the wheel barrel according to the invention, in particular by virtue of said oversize, material creep on the tube is limited and a good hold of the hour hand is ensured in the time.

Another disadvantage presented by the movements of the prior art such that shown in Figure 1 relates to the manufacturing tolerances to be taken in account for the realization of the different parts composing the movement. More particularly here, the tolerances on the radial dimensions of the second mobile 101, the center tube 105, the roadway 108 and the cannon wheel 112 have a great importance. Indeed, these different parts must both be free from rotate relative to one another and act as a radial guide for each other. The disadvantage of such a structure is that uncertainties about the dimensions in one piece, directly related to tolerances allowed by the manufacturer, are add to the radial uncertainties that exist on the next piece, and so on. Overall, the sum of all these uncertainties can lead to a finished product having a poor quality of manufacture, due to a significant radial clearance of the axis of rotation of the hour hand for example.

An obvious solution to this problem is to reduce tolerances allowed in the manufacture of movement parts, which has consequence of limiting the radial uncertainties and therefore the final play of the axis of the hour hand. However a limitation of the tolerances, even weak, generates significant additional production costs, which is not suitable for the production of cheap movements.

The present invention therefore also aims to overcome the disadvantages of the aforementioned prior art by providing a movement for timepiece having an acceptable manufacturing quality at a low cost price.

For this purpose, the subject of the invention is also a movement for a workpiece of the type mentioned above, characterized by the fact that it does not include of center tube and that there is provided an annular shoulder on the plate of the movement serving as radial guide to the barrel wheel. In this way the uncertainty overall radial is strongly lowered compared to that of art movements prior to insofar as a coin, and therefore the uncertainty that accompanies it, have been deleted. It is worth recalling here the economic importance of simply remove a part in a movement, especially when this is a cheap move made to at least several hundred thousand even several million copies.

In addition, the various uncertainties mentioned above were partly dissociated to the extent that the roadway no longer fulfills the radial guide function for the cannon wheel. As a result, the radial clearance existing at the level of the impeller does not absolutely does not depend on the radial uncertainties inherent in mobile manufacturing second and floor. Thus, the radial clearance of the axis of rotation of the needle of hours can be properly controlled, regardless of the uncertainties at the level of the second mobile and the roadway.

• la figure 2 est une vue de dessus d'un mode de réalisation particulier de la roue à canon selon l'invention;
• la figure 3 est une vue en coupe transversale d'une partie du mouvement pour pièce d'horlogerie selon la ligne III-III de la figure 2.

The invention will be better understood with the aid of the following description of an exemplary embodiment with reference to the appended drawings in which:

• Figure 2 is a top view of a particular embodiment of the gun wheel according to the invention;
• FIG. 3 is a cross-sectional view of a part of the movement for a timepiece along the line III-III of FIG. 2.

As shown in FIG. 2, the barrel wheel 1 has a structure conventional. Three radial extensions 2 connect the toothed wheel 3 to the barrel 4. In the particular embodiment shown in FIG. 2, it can be seen that three arms 5, substantially in the form of arcs of circle, each extend from one of said radial extensions 2. These arms 5 have the function of regulating axial positioning relative to the cannon wheel 1 and the roadway (not shown in this figure) thus eliminating the need for a foil spring, usually used to ensure this function.

Figure 2 also reveals the particular characteristics of the gun wheel 1, namely the fact that the inside of its barrel 4 has a bead ring 6.

FIG. 3 makes it possible to better understand the interest of said bead 6 since it is represented in its service position, that is to say when the gun wheel 1 is arranged on the floor 7.

The movement for a timepiece visible in part in this figure is type with center second. We distinguish in particular a bridge of cogwheel 8 and a platinum 9 defining a cage in which is the essence of the movement. The trolley bridge 8 carries stones 10, in which are pivotally mounted mobile. We distinguish in particular a second mobile 11 in the center and a mobile Timer 12. The second mobile 11 is driven by an exhaust pinion (not shown) through the second wheel 13. The second gear 14 meshes with a medium wheel (not shown) integral with a pinion average (not shown) being engaged with the drive wheel 15 mounted to friction on the pavement 7. The pavement 7, arranged directly on the mobile of second 11, then transmits its rotational movement to the timer 12 via the wheel Timer 16. The radial guide of the roadway 7 is made directly by the movable second 11, via two annular beads 17 formed on the axis of second 18. The timer gear 19, passing through an orifice 20 formed through the plate 9, is engaged with the barrel wheel 1, disposed on the top of said cage, and communicates to him his rotational movement.

It is clearly seen in FIG. 3 that said gun wheel 1 is mounted free to rotate on the roadway 7. The cannon wheel 1 and the roadway 7 comprise respectively complementary means for axially retaining said wheel cannon 1 on the floor 7, especially during the transport stages. Said means complementary are of type notch, specifically, the tube 21 has opposite the bead 6 of the gun wheel 1 an annular groove 22 of complementary form.

The outer face of the plate 9 further comprises an annular shoulder 23 acting as a radial positioning guide to said cannon wheel 1.

It is understood that the gun wheel 1 is placed on the roadway 7 by "clipping", that is to say by elastic deformation of material. Indeed, the cannon wheel 1 is first threaded on the roadway 7 until the bead 6 of the wheel barrel abuts on a bead 23 located immediately above the groove 22 of the 21. At this stage, a slight pressure on the barrel wheel 1 causes the elastic deformation of the barrel 4, allowing the bead 6 to cross said bead 23 and to be housed in the groove 22, which ensures the establishment of said barrel wheel 1 on the plate 9. This has the consequence that said wheel with cannon 1 can not stand alone from its location during transport. It may be noted that the step of setting up the cannon wheel 1 on the floor 7 does not requires no modification of the conventional assembly process, because of the simplicity and ingenuity of the retaining means 6, 22.

An additional detail of the structure of the gun wheel 1 can be noted. As has been pointed out previously, the annular bead 6 formed in the tube 4 of the barrel wheel 1 is constituted by an overthickness of material and not simply by deformation. This characteristic has the important consequence material creep that takes place when the hour hand is set (no represented), is located at the level of said overthickness. The deformation suffered by the gun wheel 1 during this assembly step is therefore limited to this region. Of more, once the needle is in place, material creep continues slowly during time and the existence of said overthickness, disposed at the same level as the needle, gives the positioning of the needle better durability over time than in the case of a conventional barrel wheel tube.

It is also possible, according to an alternative embodiment, to reverse said fastening structure notch by leaving the bead 6 on the floor 7 and the throat 22 on the gun wheel 1, although this alternative is less advantageous than the described above. Indeed, in this case, the advantage, described above, from the existence of an excess material on the tube 4 of the wheel to canon 1 is lost, which results in a decrease in the good maintenance of the hour hand over time.

According to a particular embodiment, the timer mobile 12 is preferentially made of steel, brass or plastic, while the roadway 7 is made of steel or brass and that the gun wheel 1 is made of material plastic, such as polyoxymethylene or polyacetal. These examples of materials are, of course, not limiting and the person skilled in the art can use any other material capable of performing the same functions.

It should be noted also that the particular characteristics of the movement for timepiece according to the invention, also visible in the figure 3. It can first be noted that due to the lack of center tube, the uncertainty on the radial dimensions related to this piece is removed compared to prior art movements having a center tube. Having a room less compared to the movements of the prior art also constitutes a economic advantage in that it contributes to lowering the price of returns from the movement. This economy has two aspects, since on the one hand manufacturer must manufacture one piece less than usual and that on the other hand the Mounting process involves one step less.

In addition, as described above, the gun wheel 1 is guided radially by an annular shoulder 23 formed on the top of the plate 9 and nor by the roadway 7, as is typically the case in the prior art. The have significant uncertainties about the radial dimensions of the axis of second 18 and the pavement tube 21 no longer has any influence on the free rotation of the cannon wheel 1 thanks to the structure according to the invention, visible in FIG. particularity allows the manufacturer to be content with relatively high tolerances as regards the radial dimensions of the second axis 18, of the tube of 21 and tube 4 of the gun wheel 1. This technical advantage contributes also to lower the cost price of the movement according to the invention and allows thus to achieve cheap movements.

The foregoing description corresponds to preferred embodiments of the invention and can in no way be regarded as limiting as regards more particularly relates to the nature of the materials used.

In addition, the movement described here is of the type with second in the center but can obviously adapt the structure according to the invention to a movement without second in the center, where the second mobile is simply replaced by a central tenon.

It will be understood that the invention is in no way limited to this alone realization and that it can advantageously be applied to any timepiece electronic or electromechanical having at least one display of the type analog.

Claims (8)

1. Timepiece movement including a plate (9), a display device with hands, a gear train connecting drive means (1, 7, 11, 12) to said hands, said train including a drive wheel (15) meshed at least indirectly with said drive means and secured to a cannon-pinion (7) pivoting on a post (18) mounted in a gear train bar (8), an hour wheel (1) arranged around the cannon-pinion (7), the drive wheel (15) and the hour wheel extending on either side of said plate (9), characterized in that the hour wheel (1) is pivoted on the plate (9), in that the hour wheel (1) and the cannon-pinion (7) respectively include complementary means (6, 22) for holding the hour wheel (1) axially on the cannon-pinion (7), the hour wheel (1) being free to rotate with respect to the cannon-pinion (7).
2. Timepiece movement according to claim 1, characterized in that said holding means (6, 22) are of the snap-fitting type.
3. Timepiece movement according to claim 2, characterized in that said holding means include complementary annular bulge (6) and groove (22) one of which is arranged on the cannon-pinion (7) and the other on the hour wheel (1).
4. Timepiece movement according to claim 3, characterized in that said bulge (6) and said groove (22) are respectively arranged on the hour wheel (1) and the cannon-pinion (7).
5. Timepiece movement according to claim 3 or 4, characterized in that said annular bulge (6) is formed of an over-thickness of material of the hour wheel (1).
6. Timepiece movement according to any one of the preceding claims, characterized in said the plate (9) includes an annular shoulder (23) acting as a radial guide for the hour wheel (1).
7. Timepiece movement according to any one of the preceding claims, characterized in that the hour wheel (1) is made of plastic material.
8. Timepiece movement according to any of the preceding claims, characterized in that it further includes a seconds wheel set (11) and in that said post is the arbour (18) of said seconds wheel set (11).

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