The invention relates to a wristwatch comprising a body, in particular a watch movement , that is provided with an energy storage device with a frame , said energy storage device compri sing a shaft and one or more leaf springs that provide a driving force to put the shaft and/or the frame in motion with reference to each other, wherein the energy storage device comprises a drive portion, said drive portion connecting the one or more springs with the shaft . The invention also relates to a separate energy storage device which is tailored to be mounted in such a wristwatch .

It is known that a mechanical watch comprises a winding mechanism, an energy storage device for storing winding energy, and a gear train for trans ferring energy from the energy storage device to an escapement and oscillator mechanism that are eventual ly used for moving the hands of the wristwatch .

DE 145 729 and EP 3 483 660 , each show a mechanism employing springs that are bent for storing and release of energy .

The invention aims to improve the performance of the energy storage device of a mechanical wristwatch according to the preamble , primarily to increase the amount of energy that can be stored, without notably increasing the dimensions of the energy storage device . In other words , the aim is to improve the ratio of the amount of energy that can be stored per unit of volume ; i . e . to improve the energy density .

To promote the obj ectives of the invention, a wristwatch and energy storage device for such a wristwatch are proposed having the features of one or more of the appended claims . A feature that is common to the wristwatch and energy storage device of the invention is that the one or more springs are equipped for storing and release of energy by tensioning of the springs. By tensioning of the springs, it is meant that the forces applied on the spring result in tensioning or tensile stress, so that the spring is loaded in tension. It has been found that storing and release of energy by tensioning of the springs rather than by bending or buckling provides an improved energy density, i.e. the amount of energy that can be stored and released in a certain volume is higher. Accordingly the displacements for the storing and release of energy are lower than with bending or buckling of the springs, which renders it advantageous that the drive portion that connects to the energy storage device comprising the one or more springs has a transmission ratio higher that 1:1, preferably at least 5:1, even more preferable at least 10:1, so as to arrange that relaxing of the one or more springs provides a motion that the drive portion magnifies into a corresponding larger motion of the shaft with reference to the frame. In all embodiments according to the invention the transmission ratio should therefore be higher than 1:1. The shaft should at least rotate multiple times (in general about 7-10 times) , and the drive portion in most embodiments can rotate 180 degrees at the most. Accordingly it is preferred that the transmission ratio is higher than 5:1, preferably higher than 10:1.

Within the scope of the invention there are several options to implement the wristwatch of the invention. In a first option the frame is rotationally motionless with reference to the body of the wristwatch so as to arrange that the shaft is rotatable with reference to the body of the wristwatch. In another option the shaft is rotationally motionless with reference to the body of the wristwatch so as to arrange that the frame is rotatable with reference to the body of the wristwatch .

As already mentioned a mechanical wristwatch is conventionally embodied with an oscillator . In a preferred aspect of the invention the energy storage device is embodied as a barrel which is arranged to maintain oscillations of said oscillator .

Advantageously the barrel drives the oscil lator through a gear train .

It is essential that for storing and release of energy the springs are tensioned, with optionally additional bending and/or compression of the springs .

A notable feature is further that in use the drive portion converts a translational motion into a rotational motion . More speci fically, the drive portion converts a translational motion of the spring or springs into a rotational motion of the shaft .

Another notable feature is further that in use the drive portion converts energy from a deformation into an energy embodied in a rotational kinetic motion .

It has been found preferable that the drive portion comprises a rack and pinion drive . This feature may form the backbone of many embodiments .

In one embodiment the pinion is mounted on the shaft and the rack is loaded with the one or more springs .

It is preferred that the rack has a neutral position and displacement of the rack away from the neutral position tensions the one or more springs . Another preferred feature is that the one or more springs connect the rack with the frame so as to provide that movement of the rack in a first direction tensions the one or more springs , and movement of the rack in a second direction opposite to the first direction relaxes the one or more springs .

There are embodiments in which the rack is embodied with a body shaped as a segment of a circle , which body has an outer surface with a partly circular contour that i s in contact with the pinion on the output shaft .

Preferably the rack is embodied with two or more separate bodies , each body shaped as a segment of a circle , and each body being provided with an outer surface with a partly circular contour that is in contact with the pinion on the output shaft .

In a suitable arrangement the bodies of the rack are positioned circumferentially around the pinion on the output shaft .

Advantageously each body of the rack is loaded with at least one spring that is connected to the frame .

In another embodiment the feature is applied that for each body of the rack the at least one spring of such body i s connected to a base portion that is rotatably connected to such body of the rack .

It is preferred that for each body of the rack there are plural springs connecting to first and second mutually orthogonal base portions that are rotatably connected to such body of the rack . In still another embodiment the rack is embodied as a body with a central open segment provided with an inwardly directed continuous contour that is in contact with the output shaft .

Notably in this embodiment the body connects with flexures and with the springs to the frame .

The invention will hereinafter be further explained with reference to the drawing of example embodiments of a wristwatch and energy storage devices according to the invention that are not limiting the appended claims .

In the drawing : figure 1 shows a schematic drawing of a wri stwatch of the invention; and figure 2 , 3 and 4 show schematic drawings of di f ferent embodiments of an energy storage device to be used in a wristwatch according to the invention .

Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts .

Figure 1 schematically shows a mechanical wristwatch 1 comprising a movement or body 2 that is provided with an energy storage device 3 . The energy storage device has features to store energy, and these features can be charged by a user through a winding stem 5 reaching from outside to inside the body 2 of the wristwatch 1 . Alternatively, these features can be loaded by an energy winding system such as an automatic winding module in a manner known by the person skilled in the art .

The above-mentioned features for storing of energy will be further detailed hereinafter . For clarity it is however first shown with reference to figure 1 that the energy storage device 3 drives a gear train 6 for trans ferring energy from the energy storage device 3 to an escapement 7 and oscillator 8 that are eventually used for moving the (not shown ) hands of the wristwatch 1 . Usually the energy storage device 3 is embodied as a barrel which is arranged to maintain oscillations of the oscillator 8 through the gear train 6 .

In the following, di f ferent embodiments of the energy storage device 3 will be discussed with reference to figures 2-4 . Common in all these embodiments is that the energy storage device 3 comprises a shaft 10 and one or more springs 11 that provide a driving force to put the shaft 10 in motion with reference to the frame 4 of the energy storage device 3 . Accordingly the energy storage device 3 of the invention compri ses a drive portion 12 , said drive portion 12 connecting the one or more springs 11 with the shaft 10 .

Generally speaking the energy storage device 3 can be operated in several ways in the body 2 of the wristwatch 1 . In one possible operation the frame 4 of the energy storage device 3 is rotational ly motionless with re ference to the body 2 of the wristwatch 1 so as to arrange that the shaft 10 is rotatable with reference to the body 2 of the wristwatch 1 . In another possible operation the shaft 10 is rotationally motionless with reference to the body 2 of the wristwatch 1 so as to arrange that the frame 4 is rotatable with reference to the body 2 of the wristwatch 1 .

The two options discussed in the previous paragraph can be implemented together in the same energy storage device 3 while being active during di f ferent times or simultaneously . For example , one of the two options can be active during operation of the winding mechanism, while the other of the two options can be active when a driving torque or driving energy is trans ferred through the gear train 6 to the escapement 7 and oscillator 8 mechanism of the watch 1 .

Alternatively, the function of frame 4 and shaft 10 can be reversed, the shaft 10 serving then as the input from the winding mechanism to store additional energy in the energy storage device 3 , and the frame 4 serving as the output , keeping the gear train 6 under tens ion to drive the hands and the oscillator 8 of the watch movement 2 . Indeed, in a usual watch movement , the barrel or energy storage device 3 unwinds through the frame 4 ( through the outer gearing of the barrel drum, for example ) , while the energy storage device 3 can be simultaneously wound up ( through a manually actuated winding stem 5 or through the automatic module ) through the shaft 10 .

With reference now to a first embodiment of the energy storage device 3 as shown in figure 2 , this embodiment comprises a drive portion 12 in the form of two rotational bodies 13 that are rotatable relatively to the fixed frame 4 . The shaft 10 , which has a small radius , is linked with the rotational bodies 13 at a relatively large distance from the rotational axis of the bodies 13 . Tensile springs 11 are connected at a small di stance to the rotational center of the rotational bodies 13 . The springs 11 are equipped for storing and release of energy by tensioning, and optionally in addition compression of the springs 11 . This combination results in a large motion ampli fication, enabling a small translational motion of the springs 11 to convert into a large rotation of the shaft 10 . Correspondingly the energy storage springs 11 can be elongated with a very limited extension while the rotational bodies 13 undergo a large rotation, which results in turn in multiple rotations of the shaft 10 . The drive portion 12 embodied with the rotational bodies 13 thus converts a translational motion into a rotational motion, wherein the drive portion 12 preferably has a transmission ratio higher that 1 : 1 so as to arrange that relaxing of the one or more springs 11 provides a motion that the drive portion 12 magni fies into a corresponding larger motion of the shaft 10 with reference to the frame 4 . A plurality of such mechanisms can be placed in parallel around a central driveshaft to balance forces acting on such driveshaft . A plurality of such mechanisms can also be stacked and connected in series or in parallel , preferably around a central driveshaft , to provide larger energy storage capacity .

Essentially what figure 2 shows is that the drive portion 12 comprises a rack and pinion drive , wherein the pinion is provided on the shaft 10 , and the rack is formed by the rotational bodies 13 . In accordance with the invention the rack formed by the rotational bodies 13 i s loaded with the one or more springs 11 . It will be clear for the skilled person that the embodiment as discussed with reference to figure 2 has the feature that the rack formed by the rotational bodies 13 has a neutral position, and that displacement of the rack away from the neutral position tensions the one or more springs 11 . It will be clear for the skilled person that the one or more springs 11 connect the rack formed by the rotational bodies 13 with the frame 4 so as to provide that movement of the rack in a first direction tensions the one or more springs 11 , and movement of the rack 12 in a second direction opposite to the first direction relaxes the one or more springs 11 .

It is further clear from the embodiment of figure 2 that the rack formed by the rotational bodies 13 are shaped as a segment of a circle , wherein each body has an outer surface 13 ' with a partly circular contour that i s in contact with the pinion on the shaft 10 . Actually in the embodiment o f figure 2 the rack is embodied with two separate bodies 13 , each being shaped as a segment of a circle , and each being provided with an outer surface 13 ' with a partly circular contour that is in contact with the pinion on the shaft 10 . The number of bodies 13 that are actually applied is not essential ; there can be only one but there can also be two or more . The embodiment of figure 2 is merely one example . Further the bodies 13 of the rack are positioned circumferentially around the pinion on the shaft 10 , and each body 13 of the rack is loaded with at least one spring 11 that is connected to the frame 4 of the energy storage device 3 . In this embodiment , as in the other rack- and-pinion embodiments disclosed herein, the connection between rack and pinion can be implemented by a gear comprising meshing teeth on the rack and pinion . Alternatively, the driving contact between rack and pinion can be implemented by friction between the surfaces of the rack and pinion .

Figure 3 depicts a second embodiment of the energy storage device 3 of the invention, in which each of the rotational bodies 13 cooperates with two translational base portions 14 ' , 14 ' ' . The translational base portions 14 ' , 14 ' ’ can assume a linear translational motion with respect to the fixed frame 4 in y- and x-direction, respectively . The translational motion is enabled by flexible springs 11 connecting the translational base portions 14 ' , 14 ' ’ to the frame 4 . The springs 11 are equipped for storing and release of energy by tensioning, and optionally additional bending of the springs 11 . The rotational bodies 13 are suspended by the translational base portions 14 ' , 14 ' ’ and are not directly connected to the frame 4 . There is a rotational j oint at the connections of the translational base portions 14 ' , 14 ' ’ with the rotational bodies 13 . This construction has a single degree of freedom . While the translational base portion 14 ' translates in y- direction, the other translational base portion 14 ' ’ translates in x-direction and the rotational body 13 rotates correspondingly over an angle determined by the extent of translation of the translational base portions 14 ' , 14 ' ' . When translational base portion 14 ' translates along its ful l stroke in y-direction, this motion is converted to a 180 ° rotation of rotational body 13 , thus driving shaft 10 . The energy storage springs 11 are tensioned and optionally additionally bent with a translational deflection when the rotational bodies 13 rotate , which results in multiple rotations of the shaft 10 . Again a plurality of these mechanisms according to the embodiment of figure 3 can be placed in parallel around a driveshaft to balance forces acting on such driveshaft . As with other embodiments , a plural ity of such mechanisms can also be stacked and connected in series or in parallel , preferably around a driveshaft , to provide larger energy storage capacity .

Essentially what figure 3 shows is that the drive portion 12 in this embodiment also comprises a rack and pinion drive , wherein the pinion is provided on the shaft 10 , and the rack is formed by the rotational bodies 13 . In accordance with the invention the rack formed by the rotational bodies 13 is loaded via the intermediate translational base portions 14 ' , 14 ' ’ with the one or more springs 11 . It will be clear for the skilled person that the embodiment as discussed with reference to figure 3 has the feature that the rack formed by the rotational bodies 13 has a neutral position, and that displacement of the rack away from the neutral position tensions the one or more springs 11 . It is shown that the one or more springs 11 connect the rack formed by the rotational bodies 13 through the translational base portions 14 ' , 14 ' ’ with the frame 4 so as to provide that movement of the rack in a first direction tensions the one or more springs 11 , and movement of the rack 12 in a second direction opposite to the first direction relaxes the one or more springs 11 .

It is further clear from the embodiment of figure 3 that the rack formed by the rotational bodies 13 are shaped as a segment of a circle , wherein each body has an outer surface 13 ' with a partly circular contour that is in contact with the pinion on the shaft 10 . Actually in the embodiment o f figure 3 the rack is embodied with two separate bodies 13 , each being shaped as a segment of a circle , and each being provided with an outer surface 13 ' with a partly circular contour that is in contact with the pinion on the shaft 10 . Further the bodies 13 of the rack are positioned circumferentially around the pinion on the shaft 10 , and each body 13 of the rack is loaded with plural springs 11 that are connected to the frame 4 of the energy storage device 3 .

A di f ferentiating feature o f the second embodiment o f figure 3 in relation to what is shown with reference to the embodiment of figure 2 , is that for each body 13 of the rack the at least one spring 11 of such body 13 is connected to a translational base portion 14 ' , 14 ' ’ that is/ are rotatably connected to such rotational body 13 o f the rack . It is further clearly shown in figure 3 that for each body 13 of the rack there are plural springs 11 connecting to first and second mutually orthogonal base portions 14 ' , 14 ' ’ that are rotatably connected to such body 13 of the rack .

Corresponding features as are discussed with reference to the embodiments of figure 2 and figure 3 are also present in the third embodiment shown in figure 4 . The third embodiment of figure 4 di f ferentiates from the other embodiments in that the rack i s embodied as a body 13 with a central open segment 13 ' ’ provided with an inwardly directed continuous contour surface 13 ' . The body 13 connects with flexures 15 and with springs 11 to the frame 4 .

The springs in the various embodiments are preferably leaf springs , meaning that they comprise at least one blade or strip of material , having a generally rectangular cross section .

Although the invention has been discussed in the foregoing with reference to exemplary embodiments of a wristwatch and energy storage device of the invention, the invention is not restricted to these particular embodiments which can be varied and combined in many ways without departing from the invention . The discussed exemplary embodiments shall therefore not be used to construe the appended claims strictly in accordance therewith . On the contrary the embodiments are merely intended to explain the wording of the appended claims without intent to limit the claims to these exemplary embodiments . The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using these exemplary embodiments .