Spring motor device

Abstract

A spring-driven device, particularly suitable for making mechanical watches, comprises: a circular gear wheel 3 installed inside the barrel and directly meshed with the internal circular ring gear 2 of the drum 1, to roll with a constant transmission ratio around a central axis orthogonal to a plane of rotation of the circular gear wheel 3 and substantially parallel to the central axis of the barrel, so that the second central axis B rotates around the axis of the barrel with a fixed eccentricity greater than zero; a shaft 4 constrained to the circular gear wheel 3, longitudinally directed along the central axis of rotation of the circular gear wheel 3; at least one rotatable rigid body 4 configured to rotate about the central axis of the barrel and connected to the circular gear wheel 3 so as to maintain it permanently in contact against the internal circular ring gear 2 and to be driven into rotation when the circular gear wheel 3 rolls in the internal circular ring gear 2; a spring 6 having a first end 7 connected to the drum 1 and a second end 8, opposite to the first, fixed directly to the tube 5 of the circular gear wheel 3 so as to rotate eccentrically around the central axis of the drum 1, so that the spring 6 is loaded or unloaded when the toothed wheel is rolled relative to the barrel, depending on the direction of rotation. A mechanical spring-driven watch is also disclosed.

Description

[0001] SPRING MOTOR DEVICE TECHNICAL FIELD

[0002] This invention generally relates to mechanical watches that use a spring to provide energy for operation. More specifically, the present invention is a spring-driven motor device without planetary gears and with a high transmission ratio, suitable for use in a mechanical watch.

[0003] BACKGROUND

[0004] In spring-driven mechanical watches, energy for operating the watch is provided by a spring 6 that is part of a barrel. By barrel is meant the entire assembly of components comprising, as depicted in Figure 1, a drum 1 containing a constant-force torsion spring 6, a central shaft 12, and a closing cap 13. The spring 6 has a first end 7 connected to the drum 1 and a second end 8 fixed to the shaft of the barrel, so that it can be wound by rotating the shaft while holding the barrel stationary, or vice versa, typically for a very limited number of turns. In place of the constant-force torsion spring shown in Figure 2a, it is also possible to use the S-spring shown in Figure 2b, connecting one end to the barrel and the other end to the central shaft 12. Once the spring 6 has been wound, the barrel can rotate while holding the central shaft 12 stationary.

[0005] Figure 3 shows a classic gear train in a mechanical watch. The barrel, which contains the wound spring 6, has external teeth 10 meshing with a fixed-axle gear train to move the minute hand wheel 14. The gear train multiplies the barrel rotation, so that the wheel carrying the minute hand 14 can complete numerous revolutions before the spring 6 of the barrel is completely unloaded. Also shown in the figure are the escape wheel 15 and an anchor 16, as well as a balance wheel 17, which, as it oscillates, oscillates the anchor escapement 16, which, in turn, moves the escape wheel 15 in steps.

[0006] Since the spring 6 can be fully wound with just a few revolutions of the barrel or its central shaft 12, a classic mechanical watch uses a gear train like the one illustrated. This is relatively bulky because it requires several parts to ensure a high transmission ratio. Another drawback of using a gear train like the one shown is that energy loss increases with the number of gears meshing with their respective pinions. Furthermore, as is well known, the losses due to contact between the teeth of a gear and a pinion are greater the lower the number of teeth of the pinion and the higher the transmitted torque. It would be desirable to create a device usable in mechanical watches that would both avoid the use of pinions and reduce the number of components used to multiply the rotations of the barrel, without having to increase the size of the barrel itself compared to watches that use a traditional multiplying gear train.

[0007] SUMMARY

[0008] Studies conducted by the Applicant have demonstrated that it is possible to avoid the use of a gear train while still achieving high transmission ratios and reduced energy losses. This excellent result was achieved using a spring-driven motor device, particularly suitable for mechanical watches, which uses a gear train without planetary gears and a spring that compensates, thanks to its elasticity, for eccentricity greater than zero of the gear train axes without the use of articulated arms or drive pins typical of cycloidal gearboxes.

[0009] This excellent result was achieved using a spring-driven motor device as defined in claim 1, which has a circular gear installed inside the barrel and meshed directly with the internal circular ring gear of the barrel, for rotating with a constant transmission ratio around a central axis orthogonal to a plane of rotation of the circular gear wheel and substantially parallel to the central axis of the barrel, so that the second central axis B rotates around the axis of the barrel with a fixed eccentricity greater than zero.

[0010] In this context, to say that the respective rotation axes of the barrel and the gear wheel are "substantially" parallel means that they may not be perfectly parallel but may converge, forming a small angle between them, typically less than 10°.

[0011] The spring motor device also comprises: a tube (5) constrained to the gear wheel, longitudinally directed along the wheel's central axis of rotation; at least one rotatable rigid body configured to rotate around the barrel's central axis and connected to the tube (5) of the gear wheel so as to keep the gear wheel permanently in contact with the internally geared gear wheel of the barrel and to be driven into rotation when the gear wheel rolls, meshing with the internally geared ring of the barrel; a spring having a first end connected to the barrel drum and a second end, opposite to the first, attached directly to the tube (5) of the circular gear wheel so as to rotate with an eccentricity greater than zero around the central axis of the barrel, so that the spring is loaded or unloaded when the gear wheel is rolled relative to the internal circular ring gear of the barrel, depending on the direction of rotation.

[0012] A spring-driven mechanical watch having a spring-driven device according to the present disclosure is also disclosed.

[0013] Further embodiments are defined in the appended claims.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 shows a barrel suitable for mechanical watches, including a constant-force torsion spring 6.

[0016] Figures 2a and 2b show two different types of constant-force torsion springs.

[0017] Figure 3 shows a fixed-axis gear train of a mechanical watch, which multiplies the rotation imparted by the external teeth 10 of the barrel of Figure 1 to move the minute hand wheel.

[0018] Figure 4 is a plan view of a spring-driven motor device according to one aspect of the present disclosure.

[0019] Figure 5 is a sectional view of the spring motor device of Figure 4.

[0020] Figure 6 is a constant-force torsion spring 6 used in the spring motor device of Figure 4. Figure 7 shows a drive gear usable in the spring motor device according to the present disclosure, comprising a circular gear wheel 3 directly meshed with an internal circular ring gear 2 of a drum 1 of a barrel, both having teeth arranged with equal pitch.

[0021] Figure 8 shows a drive gear, usable in the spring motor device according to the present disclosure, similar to that of Figure 7, in which the circular gear 3 has teeth with a pitch that is an integer multiple of the pitch of the teeth of the internal circular ring gear 2.

[0022] Figure 9 is a sectional view of a spring motor device according to one aspect of this disclosure, in which the drum 1 of the barrel has external teeth 10 concentric with the internal circular ring gear 2.

[0023] Figure 10 is a simplified plan view of the spring motor device of Figure 9, in which the barrel is shown, with the external gear 10 concentric with the internal circular ring gear 2, and the circular gear wheel 3 meshing directly with the internal circular ring gear 2.

[0024] Figure 11 is a sectional view of a spring-driven device according to one aspect of this disclosure, wherein the drum 1 of the barrel has external gear 10 concentric with the internal circular ring gear 2 and wherein the rigid body that eccentrically rotates the tube 5 of the circular gear wheel 3 is itself a gear wheel.

[0025] Figure 12 shows a gear train of a mechanical watch that uses the spring-driven device of Figure 9 to move the minute hand wheel.

[0026] DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0027] The present invention will be illustrated with reference to the accompanying figures 4 through 12, which show various views of working embodiments of a spring-driven motor device according to the present disclosure. These figures are purely illustrative and also include technical features that are not essential to the operation of the invention, but which may be useful in particular conditions of use of the device, depending on where the load to be moved is attached. Furthermore, the figures depict some technical features with shapes specifically designed for a specific type of embodiment, but these features may be omitted or shaped differently if the device is manufactured using another technique, such as plastic injection, molding, or milling and turning of the mechanical components of the device of the invention.

[0028] As in a classic spring-driven motor device of the type used for mechanical watches, the spring-driven motor device of the present disclosure also comprises a drum 1 containing a spring 6 that must be wound. In contrast, in the spring-driven motor device of this disclosure, the drum 1 has an internal circular ring gear 2 and a circular gear wheel 3 installed inside the barrel and meshed directly with the internal circular ring gear 2, i.e., without the use of planet gears, as is the case in many epicyclic gear trains. As illustrated in particular in Figures 7, 8, and 10, the gear wheel 3 is configured to rotate while always keeping at least one tooth engaged with the internal circular ring gear 2, so as to define a constant transmission ratio.

[0029] The circular gear wheel 3 is configured to rotate around its central axis of rotation B, which is orthogonal to a plane of rotation X of the circular gear wheel 3 and which is substantially parallel to the central axis A of rotation of the barrel.

[0030] When the gear wheel rolls in mesh with the internal circular ring gear 2 of the barrel, the tube 5 of the gear wheel 3, directed along the central axis B of the gear wheel 3, rotates around the axis A of the internal circular ring gear 2 (the axis A of the barrel) with a fixed eccentricity greater than zero. A rotatable rigid body 4 is configured so that it may rotate around the axis A of the internal circular ring gear 2, being driven into rotation by the tube 5 of the gear wheel 3 as the latter rolls in contact with the internal circular ring gear

[0031] 2 of the barrel. The rotational motion generated by the driving device can be transmitted outward through the rotatable rigid body 4 while holding the drum 1 still, or by the drum 1 itself equipped with an external gear wheel 10 while holding the rotatable rigid body 4 still.

[0032] A spring 6 is installed in the drive device, with one end connected directly to the drum 1 and the other end attached directly to the tube 5 of the circular gear 3. As the circular gear

[0033] 3 rotates relative to the internal circular ring gear 2, the spring 6 is loaded or unloaded depending on the direction of motion of the gear 3 relative to the drum 1. Thanks to its elasticity, it automatically compensates for the oscillations caused by the eccentricity greater than zero of the tube 5 of the circular gear 3 relative to the axis of the drum 1.

[0034] In one aspect, the spring 6 is connected to the drum 1 and the tube 5 of the circular gear 3 by engaging in respective slots. Alternatively, one or both ends of the spring 6 may be connected in other ways, for example, by fastening means such as screws or joints.

[0035] By appropriately determining the dimensions of the internal circular ring gear 2 and the circular gear wheel 3 as well as the respective number of teeth, high transmission ratios my be obtained, so that the drive device of this disclosure allows for a reduction in the number of gears that in a mechanical watch are necessary for multiplying the rotation of the barrel. For example, the Applicant has succeeded in obtaining transmission ratios of even 40: 1 by making the circular gear 3 with a radius of its pitch circle close to the radius of the pitch circle of the internal circular ring gear 2, reducing the eccentricity of the motion of the tube 5 of the circular gear 3 and therefore greatly reducing the resulting torques that stress the bearings of the tube 5 of the circular gear 3. Furthermore, since the number of teeth of the circular gear 3 is close to that of the internal circular ring gear 2, an instantaneous transmission ratio is obtained that is practically constant during the entire rolling period of the circular gear 3.

[0036] The figures, and in particular Figures 7 and 10, show a circular gear 3 with teeth distributed with the same pitch as the internal circular ring gear 2. However, it is possible to create a circular gear 3 with a tooth pitch that is a multiple of that of the teeth of the internal circular ring gear 2, as illustrated in Figure 8. In fact, to ensure the correct rotation of the gear 3 in the internal circular ring gear 2, it is sufficient that at least one tooth at a time engages in the internal circular ring gear 2, thus ensuring a constant transmission ratio.

[0037] Secondly, the circular gear 3 is sized so that exactly one tooth engages in the internal circular ring gear 2 at a time, thus preventing energy dissipation due to radial friction while maintaining a constant transmission ratio.

[0038] The figures show a torsion spring 6, in particular of the constant force type as illustrated in figure 6, but nothing prevents the use of a different type of spring 6, for example a spiral spring 6, a cylindrical or conical spring 6 used for torsion, or any type of contrast spring 6, provided that it is loaded or unloaded by rotating the tube 5 of the circular gear wheel 3 with respect to the drum 1 and fulfills the eccentricity compensation condition at least in the angular sector of operation foreseen for the barrel, which may be less than one complete turn. In this last non-multi-turn case, the internal circular ring gear 2 and the circular gear wheel 3 could be partially toothed.

[0039] The figures also show an optional annular plate 9, installed between the spring 6 and the circular gear wheel 3, to conveniently protect the teeth of the internal circular ring gear 2 from possible contact with the spring 6. In cases where the design includes dry gears, this annular plate 9 prevents the grease of the spring 6 from ending up between the teeth of the internal circular ring gear 2.

[0040] Thanks to the spring motor device, it is possible to create a mechanical clock with fewer fixed-axle wheels transmitting motion to the hand wheels, for example as shown in Figure 12.

[0041] The spring motor device of this disclosure may also be used, for example but not limited to, in spring-wound toys, in which the spring 6 may be wound by turning a key, rotating the rigid rotatable body 5, or by reverse-winding, rotating the drum 1.

Claims

CLAIMS1. A spring motor device (11), applicable in mechanical watches, including: a drum (I) having an internal circular ring gear (2), defining a first central axis (A) of the drum (1); a circular gear wheel (3) installed inside said drum (1) and directly meshed in said internal circular ring gear (2), said circular gear wheel (3) being configured to roll in contact with said drum (1) with at least one tooth at a time meshed in the internal circular ring gear (2) so as to have a constant transmission ratio, wherein said circular gear wheel (3) is configured so as to rotate around a second central axis (B) which is orthogonal to a rotation plane (X) of the circular gear wheel (3) and is substantially parallel to said first central axis (A) so that said second central axis (B) rotates around said first central axis (A) with a fixed eccentricity greater than zero when the circular gear wheel (3) rolls meshed in the internal circular ring gear (2) of the drum (1); a tube (5) connected to said circular gear wheel (3), longitudinally directed along said second central axis (B); at least one rotatable rigid body (4) configured to rotate around said first axis so as to keep the circular gear wheel (3) permanently in contact against the drum (1), and to be dragged into rotation when the circular gear wheel (3) rolls in said internal circular ring gear (2); a spring (6) having a first end (7) connected directly to the drum (1) and a second end (8), opposite to said first end (7), fixed directly to said tube (5), wherein said second end (8) is configured to rotate with said eccentricity around the first central axis (A), said spring (6) being configured to load when the circular gear wheel (3) is rolled with respect to the drum (1) in a first direction and to discharge when the circular gear wheel (3) is rolled with respect to the drum (1) in a second direction opposite to the first direction.

2. The device according to claim 1, wherein said spring (6) is a torsion spring.

3. The device of claim 2 wherein said torsion spring is a constant force type spring.

4. The device according to one of the previous claims, in which said circular gear wheel (3) has dimensions and number of teeth determined so as to roll in said internal circular ring gear (2) keeping only one of its teeth at a time in contact with the internal circular ring gear (2).

5. The device according to one of the previous claims, further comprising an annular plate (9) installed between the spring (6) and the internal circular ring gear (2) so as to cover the teeth of the internal circular ring gear (2), to avoid that, any lubricant of the spring (6) may fall between the teeth.

6. The device according to one of the previous claims, wherein: said drum (I) integrates a respective fixing means to retain said first end (7) of the spring (6); said tube (5 ) of the circular gear wheel (3) integrates a respective fixing means configured to retain said second end (8) of the spring (6).

7. The device according to one of the previous claims, wherein said drum (1) has an external gear (10) concentric with said internal circular ring gear (2).

8. A mechanical device, including: a spring motor device (11) according to one of the previous claims; a train of gears coupled to the spring motor device to transmit to the mechanical device a force imparted by a component chosen from: the circular gear wheel (3), the internal circular ring gear (2), the rotatable rigid body (4), an external gear (10) of the drum (1).

9. The mechanical device according to claim 8, wherein said mechanical device is a mechanical watch.

Images