Title of Invention: Automatic pawl winding mechanism
Abstract: An automatic pawl winding mechanism for a watch movement has a rotor solidly attached to a rotor wheel and oscillating about the axis of a rotor pivot, a pawl wheel to which an oscillating motion of rotor is transmitted by the rotor wheel being pivoted about the axis of a pawl wheel shaft, at least one pawl being eccentrically attached to the pawl wheel shaft, and an automatic wheel cooperating with the pawl or pawls. The oscillating motion of the rotor wheel is thus transformed into a unidirectional rotary motion of the automatic wheel, and this rotary motion is transmitted to a ratchet wheel via a transformation gear train. The rotor, the gear train from the rotor with rotor wheel to the pawl wheel with the pawl or pawls is mounted on an independent rotor bridge while no other organ of the mechanism is mounted on this bridge.
Detailed Description: Part general_description_paragraphs: The object of the present invention is an automatic pawl winding mechanism for a movement that comprises an oscillating weight or rotor solidly attached to a rotor wheel and oscillating about the axis of a rotor pivot, a pawl wheel articulated rotatably about the axis of a pawl wheel shaft to which an oscillating motion of the rotor is transmitted, at least one pawl mounted eccentrically about the axis of this pawl wheel shaft, and an automatic wheel cooperating with the pawl or pawls in such a manner that the oscillating motion of the rotor wheel is transformed to a unidirectional rotary motion of the automatic wheel, and transmitting this rotary motion via a gear train to a pawl wheel.
Devices of this type have basically been known for a long time in different embodiments. In the document EP 1 041 458, for instance, an automatic pawl winding device of this kind is presented in which the different elements of the device are more particularly arranged between several supporting structures which in part also serve to attach other parts of the movement to them. Such a conventional construction is relatively complicated and entails difficulties in assembly, possibly as well a specific setting between the different parts, and it may also complicate maintenance of the watch, since access to one part of the watch may require disassembly of another part.
The invention further relates to a support acting as a shock absorber for the rotor or generally for the parts attached to this support, this support being useful in general for the most diverse applications within watches.
In watches, it is in fact desirable in particular applications that such a support has elastic properties in a plane, such that the spring constant of the support has the same value independently of the direction of motion of the support in this plane. The term “same value” is used in the text below for a spring constant in the sense that a maximum departure of about ±20% from the average value of the spring constant is accepted. Furthermore, the support should have the largest possible rigidity in a direction normal to this plane in order to limit motions of the support along this axis.
It is the aim of the present invention to obviate the disadvantages mentioned above and to realise the features cited above, by proposing a particular automatic pawl winding mechanism.
Notably, the rotor as well as the gear train of the proposed automatic pawl winding mechanism from the rotor with the rotor wheel to the pawl wheel with the pawl or pawls are mounted on an independent rotor bridge, these parts thus constituting an independent module in the sense that no other element of the mechanism is attached to this independent rotor bridge.
On the other hand, an independent rotor support or independent rotor bridge is proposed in the present invention which can be designed such as to constitute a support that will act as a shock absorber for the rotor or all parts that are mounted on this bridge that latter having the properties mentioned above due to the fact of having a special geometric shape. This support is useful generally and independently for applications of the most diverse kind in watches where a support is needed that simultaneously constitutes a shock absorber, for instance for attenuation of the pivoting of a mobile.
The invention will now be described in detail while referring to the attached drawings illustrating by way of example an embodiment of the invention.
Referring to FIGS. 1 and 2 it should at first be pointed out that the automatic pawl winding mechanism according to the present invention is intended for easy integration into a watch movement. As in the ordinary case of such mechanisms, it comprises a rotor 1 solidly attached to a rotor wheel 2 oscillating about the geometric axis of a rotor pivot 3. A pawl wheel 4 is articulated rotatably about the geometric axis of a pawl wheel shaft 7. The oscillating motion of rotor 1 is transmitted to this pawl wheel 4, at least via the rotor wheel 2. The mechanism further comprises at least one, preferably two pawls 5a, 5b mounted eccentrically and in a pivoting manner about the axis of pawl wheel shaft 7, as well as an automatic wheel 11 cooperating with the pawl or pawls 5a, 5b in such a manner that the oscillating motion of rotor wheel 2 is transformed in known fashion into a unidirectional rotary motion of the automatic wheel 11 in the direction of winding of the movement. This rotary motion is then transmitted via a transformation gear train 12 to a ratchet wheel 13 in order to wind the movement. For the sake of simplicity, the automatic wheel 11 preferably is solidly connected with an automatic pinion 12 directly engaged with ratchet wheel 13 that is placed on a barrel shaft (not shown), such that the automatic pinion 12 represents the transformation gear train mentioned above. The gear ratio can be modified depending on the size of the torque required to wind the barrel, by adding one or several transmission wheels to that shown in FIG. 2 to explicitly constitute a gear designated as transformation gear train 12.
In the example represented in the drawings, the automatic pinion 12 is pivoted between a base bridge 17, here the barrel bridge, and an automatic bridge 15 attached to the base bridge with two screws 16a and 16b. The barrel shaft which is indicated in the figures with its geometric axis 14 is attached between the barrel bridge 17 and a base plate (not shown). The elements of the mechanism from the automatic wheel 11 to the automatic pinion 12 which can be seen in the left-hand part of FIG. 1 thus constitute a separate unit attached between base bridge 17 and automatic bridge 15.
For a more detailed description of the elements represented in the right-hand part of FIG. 1, it should first be remarked that the rotor 1 as well as the gear train from the rotor 1 with rotor wheel 2 to the pawl wheel 4 with the pawl or pawls 5a, 5b are mounted solely on an independent rotor bridge 9, without that the rotor or this gear train have any point of attachment to another support structure, and whilst no other element of the mechanism is mounted on this independent rotor bridge 9. Thus, bridge 9 and the elements 1 to 8 that are mounted on this bridge constitute an independent module of the mechanism.
Preferably, the oscillating motion of rotor 1 is transmitted directly from the rotor wheel 2 to the pawl wheel 4, the latter being directly engaged with the rotor wheel 2, rather than providing further intermediate wheels forming a more complicated gear train, which would be another possibility. In fact, it can be seen from FIG. 2 that rotor 1 is attached as an overhanging projection to the rotor pivot 3, which also holds the rotor wheel 2. As an alternative, the rotor pivot could be replaced by a ball bearing, for instance, inasmuch as only the oscillation of rotor 1 and rotor wheel 2 about their geometric axis is important. In the embodiment represented in the figures, pawl wheel 4 is attached to pawl wheel shaft 7 which in turn is rotatably attached between the independent rotor bridge 9 and a pawl wheel bridge 8. The latter is attached solely to the independent rotor bridge 9 and thus constitutes a part of bridge 9, hence does not detract from the independence of bridge 9 relative to the remaining mechanism. Again, since it is only the oscillation of pawl wheel 4 about its geometric axis which is important, it would be possible as well to mount the pawl wheel 4 as an overhanging projection on a pawl pivot attached to the independent rotor bridge 9, while for instance the eccentrics determining the movement of pawl(s) 5a, 5b would be attached to pawl wheel 4.
Pawl(s) 5a, 5b are mounted in the conventional way, that is, freely rotatable, each about an eccentric 6a, 6b which in the embodiment shown in the figures is placed on pawl wheel shaft 7. As indicated in the attached drawings, and notably in FIGS. 10a and 10b, the pawl wheel shaft 7 preferably has two pawls 5a, 5b while the axes of the corresponding eccentrics 6a, 6b are mutually offset in order to increase the efficiency of the mechanism, the pawls being arranged in such a manner that the first pawl 5a actuates the automatic wheel 11 while the second pawl 5b is at a dead angle where it has little or no effect on this wheel, and vice versa.
As to the operating principle of the mechanism, which corresponds to that of known devices, for instance as described in patent documents CH 284 841, DE 882 227, and CH 254 578 assigned to the International Watch Corporation (IWC), the section through the complete automatic mechanism including rotor 1 as shown in FIG. 2 nicely illustrates the cinematic chain from rotor 1 to the barrel. An oscillating motion of rotor 1 is first transmitted to pawl wheel 4 by rotor wheel 2. The motions of the pawls about the eccentrics 6a, 6b sitting on the axis of pawl wheel 4 give rise, either via the end 5e of one of the pawls 5 to a pull acting on the automatic wheel 11, or via the end 5f to a push acting on the automatic wheel 11, see FIG. 10a. Whatever the direction of rotation of rotor 1, the direction of rotation of the automatic wheel 11 will always be the same and match the direction of winding of the movement. The rotary motion of automatic wheel 11 is then transmitted to the ratchet wheel 13 and to the barrel shaft by automatic pinion 12.
In its preferred embodiment shown in the drawings, and notably in FIGS. 3 to 5b, the independent rotor bridge 9 is attached to the base bridge 17, solely with one of its ends 9a. The other end of bridge 9 is free, in this case, and comprises a segment 9e serving as a point of attachment for the rotor pivot 3 and pawl wheel shaft 7. A part of bridge 9 which connects end 9a with the free end 9e acts like a spring, in such a manner that the independent rotor bridge 9 constitutes a shock absorber for parts 1, 2, 3, 4, 5, 6, 7, 8 mounted on this bridge 9. The bridge thus comprises a flexible section and is attached in such a manner that it is partially capable of carrying out a movement, rather than being rigid and being rigidly mounted.
The independent rotor bridge 9 or, generally, a support according to the invention has a special geometric shape shown in detail in FIGS. 5a and 5b and includes a number of functional segments in order to obtain the elastic properties more particularly mentioned in the introduction and notably the same values of the spring constant in a given plane. Firstly, it comprises a first rigid segment 9a representing the end attached to the base bridge 17, here the barrel bridge, the attachment being realised for instance with the aid of two screws 10a and 10b, as illustrated in FIGS. 1 and 6. It then comprises a section acting as a spring and including a first elastic segment 9b attached to the first rigid segment 9a as well as a second elastic segment 9d, the two elastic segments 9b and 9d being inter-connected by a second rigid segment 9c. The bridge finally comprises a third rigid segment 9e attached to the second elastic segment 9d, and constituting the free end of the independent rotor bridge 9. At least the two elastic segments 9b and 9d lie in one plane and procure spring constants having the same value in all directions of this plane to the independent rotor bridge 9.
In addition, the orientations of the straight-line main segments of the neutral axes of the two elastic segments 9b, 9d of the independent rotor bridge 9 which are hatched in FIG. 5a subtend an angle of about 90°, such that spring constants having the same values in all directions of the plane mentioned above are achieved, a situation illustrated in FIG. 5a. This property is in fact necessary when the two elastic segments 9b, 9d have identical elastic properties. If this is not the case, then the orientations of these two segments 9b, 9d can be selected alternatively in such a manner that the differences in their elastic properties are compensated, such that bridge 9 as a whole still is provided with spring constants having the same values in all directions in its plane. By varying the width b as well as the length of the elastic arms, see FIG. 5a, it is possible to modify the constant of elasticity of an elastic segment or of the elastic section of the support.
In the preferred embodiment of an independent rotor bridge or support according to the present invention, the distances d1 and d2 between the geometric centres c1, c2 of the two elastic segments 9b, 9d of the independent rotor bridge 9 and the centre of rotation R of rotor 1 are close to d1=d2=D/√2. These values are indicated schematically in FIG. 5b, where D=b1+b2 is the sum of the distances b1 and b2 between the geometric centres c1, c2 of the two elastic segments 9b, 9d and a line perpendicular to these distances and passing through the centre of rotation of rotor 1.
Thus, independent rotor bridge 9 not only constitutes an independent module together with the elements 1 to 8 attached to it, but also acts as a shock absorber for these elements, and notably for rotor 1. The hatched region in FIG. 4 is the section that can move during shocks. The distance e between the axes can vary without detriment to the function of the automatic mechanism, since the connection between pawl wheel 4 and automatic wheel 11 is secured by pawls 5, and hence is not rigid.
The movement of the free end 9e of the independent rotor bridge 9 in a direction perpendicular to the plane of construction of bridge 9 can be limited by a height-limiting screw 10c as illustrated in FIGS. 1 and 7.
The movements of the free end 9e of the independent rotor bridge 9 can be limited in the directions within the plane of construction of bridge 9e by a rigid element of the watch case that lies in the same plane as the rotor 1, or by any other adequate means, in order not the exceed the admissible strain of the support material. In FIG. 8, the space p remaining between rotor 1 and the element of the case serving as a stop is indicated.
Advantageously, each free end of a pawl 5a, 5b has an extension forming a support and release finger 5g, see FIG. 9a. These extensions 5g have two main functions, as is evident from the name. Firstly, in the case of shocks in a direction perpendicular to the plane of bridge 9 the support and release finger 5g contacts the automatic bridge 15, thus avoiding that pawl 5 slides beyond the automatic wheel 15, which would put the mechanism out of operation. Second, with the aid of suitable tools it is possible to push these elements 5g apart simultaneously, and to release the pawls 5 from the automatic wheel 11. This is of interest during assembly when the mechanism must be disengaged.
Detail E in FIG. 9b shows a pressure point which is a raised point on each arm of pawl 5b, and which in the preferred case of using two pawls 5a, 5b allows to maintain a distance. This serves to reduce possible friction between pawls 5a, 5b. FIG. 10a is a perspective view showing the superposition of the two pawls 5a, 5b mounted on their axis, that is, on pawl wheel shaft 7.
After this detailed description, the advantages of the present invention will be clear.
Integrating the pawl wheel with its axis and the pawl (or pawls), the whole being held for instance by a pawl wheel bridge, into an independent rotor support is advantageous inasmuch as the mechanism thus forms a modular system comprising more particularly the rotor module sitting on the rotor bridge. On the other hand, the automatic wheel with its pinion sitting on the automatic bridge can be regarded as a further independent unit.
Considering the non-rigid connection between these two units that is provided by the pawls, this arrangement moreover will not detract from the functioning of the automatic mechanism.
Assembly of such a mechanism is rapid and simple, and requires no particular setting.
Using a flexible support in accordance with the present invention which acts as a shock absorber, values of the spring constant are provided for the support which are almost identical in all directions of motion of the support in its plane of construction, but at the same time a strong rigidity in a direction perpendicular to this plane is provided.
When used as a support for a rotor, this elastic property reduces the loads acting on the rotor pivot, and thus makes it possible to reduce the diameter of the pivot and thus the frictional losses.
It is further possible by this elastic property to noticeably reduce the transmission of vibrations produced by the rotary motions of the rotor. The characteristic frequency of a rotor is between 3 and 6 Hz and resembles the oscillating frequency of the regulating organ situated between 2.5 and 5 Hz. With a support rigidly attached to the basic movement, interfering effects may have a negative influence on the isochronism of this organ, while this situation can be improved by a support according to the present invention.
The combination of a flexible rotor support with an automatic pawl winding mechanism according to the present invention has further advantages.
A movement of the flexible section of the independent rotor bridge which occurs under the influence of shocks does not detract from the functions of the automatic mechanism. It is even likely that part of the shock energy is transmitted to the automatic winding mechanism, and adds to the energy provided by the rotor. In fact, a movement equal to the amplitude of the eccentric of the pawl wheel axis in the flexible region of the independent rotor bridge in the direction from the axis of the pawl wheel shaft to the axis of the automatic pivot corresponds to approximately half a turn of the rotor.
In any case, shocks are absorbed by the support and possibly by part of the casing or the height-limiting screw.
The spring constant of the support can be selected such that the deformation of the pawl is compensated when it is acting upon the automatic wheel. In fact, the pawl is deformed when the section of the pawl working in traction pulls a tooth of the automatic wheel, and the system's geometry is not optimal in case of rigid supports, thus an inferior efficiency is possible. The support proposed here, to the contrary, moves under the effect of the same force in the direction of the automatic wheel and compensates the pawl's deformation. The same compensating effect is present at the other segment of the pawl that works in compression.
It should be noted that for the combination of a flexible support with a pawl winding mechanism the particular number of pawls is irrelevant. The version involving two pawls has only been described here for reasons of the system's efficiency.
Lastly, the flexible support according to the invention is not necessarily the point of attachment for rotor and pawl wheel but may more generally be used in any application in watches requiring characteristics similar to the ones described above.


{'bibliographic_information': "{'country': 'US', 'doc-number': '11320954', 'kind': 'B2', 'date': '20051230', 'extension': '82', 'invention_title': 'Automatic pawl winding mechanism'}", 'source_file': './grant/2008/ipg080325.xml', 'source_data': 'USPTO-Grant'}