WO2021023768A1

WO2021023768A1 - Compensator train

Info

Publication number: WO2021023768A1
Application number: PCT/EP2020/071985
Authority: WO
Inventors: Morten Beyer
Original assignee: Montre Liquide Ag
Priority date: 2019-08-07
Filing date: 2020-08-05
Publication date: 2021-02-11

Abstract

The invention concerns a compensator train for a device driven by a spring, especially a windable spring such as the main spring of a timepiece like a clock or watch, said compensator train comprising at least two different compensators which are connected for common compensation movement.

Description

COMPENSATOR TRAIN

DESCRIPTION

The invention relates to a compensator train for a mechanically driven device, especially a device driven by a windable spring such as the main spring of a timepiece like a clock or watch.

By contrast to electronic or electric devices, a mechanically driven device derives the driving force from a mechanical source. In preferred embodiments of this invention, the source is a windable spring such as the main spring of a timepiece like a clock or watch.

The invention will hereinafter be described by reference to such preferred embodiments, but is not presently intended to be limited to specific embodiments.

A windable spring is an example for a mechanical energy storage means. It stores this energy by elastic deformation, i. e. winding, and can then release this energy by returning to its initial, e. g. unwound state in which it is less deformed or even undeformed. The unwinding process can be used to drive the device, e. g. a gearing such as a clockwork. Generally, this driving process is controlled or regulated to proceed at a specific speed, e. g. by the escapement of a clock or watch.

The release of energy during the unwinding of a spring, especially a coiled spring such as the main spring of a clock or watch, does not proceed in a completely linear fashion. Especially near the end points, when the spring is fully wound or fully unwound, the energy that released by the spring is markedly different from the energy that can be released when the spring is inbetween its fully wound and fully unwound states, sufficiently apart from these endpoints. In this inbetween or intermediate range, the energy released as the spring unwinds is markedly more independent from the degree to which the spring has unwound, than when the spring is dose to the endpoints.

However, even in the intermediate range of unwinding, the energy release is not completely linear. The more the spring unwinds, the lower is the energy release. This may affect the functioning of the device. E.g., a watch would then run faster in the initial part of the intermediate range, and progressively slow down as the spring unwinds. Since the running of the device should, however, be as even as possible (i. e. isochronous) , this is undesirable.

It is known to counteract this non-linearity by a variety of measures. It is generally helpful to limit the intermediate unwinding range actually used for driving the device to only a few turns of the mainspring axle. In timepieces, isochrony was historically improved by the use of a fugee wheel. This is thus an early example of a spring torque compensator. In more modern timepieces and similar devices using an escapement, isochrony has been improved by adjusting the torque of the escapement or balance spring. This option is of course limited to devices with an escapement incorporating a balance spring.

Another problem in achieving an even and constant running of the device, e. g. isochrony in a timepiece, is caused by temperature changes, which may affect the mechanical parameters of the device. Overcoming these problems requires a temperature compensator. E. g. in timepieces, it is known to counteract this temperature effect by using materials which compensate such influences, such as bimetallic components. Such temperature compensators e. g. include a bimetallic element, the dimensions of which change with temperature. Where a rise in temperature leads to undesired elongation of a mechanical element, the element may be coupled to a bimetallic element which effectively shortens as the temperature increases and thus compensates the elongation.

In many modern timepieces, balance springs and escapement parts are made from Invar Nivarox or Glucydur, which are less sensitive to temperature changes. Again, this option would not be available in a device that has no conventional escapement, or where the temperature change is so great that it affects even such materials.

Where sufficient compensation is not achievable just by the choice of material, as in some of the above examples, structural compensation means must be selected.

It is therefore quite common for devices of the kind discussed here, to have separate structural compensator means for spring load deviations, temperature effects and other factors influencing the desired even functioning, which then require separate setting and adjusting of said compensator means. In case, these structural means may be provided alongside of compensator means based on material selection, such as bi-metallics.

This use of separate structural compensator means is, however, not generally desireable, since it is difficult to set all these means correctly, since they are mutually dependent. Setting one first compensator and then setting a second one may require the first compensator to be readjusted. This again may require the setting of the second compensator to be readjusted, and so on.

This problem is at least partly alleviated by the invention, which in a first aspect comprises arranging two or more compensator means in a train, such that the first compensator in the train acts directly on the following compensators. In preferred embodiments comprising a spring torque compensator and a temperature compensator, the spring torque compensator is operatively connected to the temperature compensator E. g., where the spring torque compensator comprises a mechanical setting element moved to achieve the compensation, the temperature compensator is connected to said element for common movement. The temperature compensator may thus e. g. be a part of the setting element. In a highly preferred embodiment, the spring torque compensator comprises a mechanical setting element and the temperature compensator comprises a bimetallic element integrated in the setting element, so that the bimetallic acts to change at least one effective dimension, especially the effective length, of the setting element.

By such a preferred arrangement, the length of the spring torque compensator’s setting element automatically adapts to temperature changes, and no separate adjustment is required. The invention is especially useful for devices which do not include a balance wheel escapement or other regulating functionality incorporating a separate spring other than the main spring.

It is specifically useful in the context of timepieces without a conventional (balance wheel) escapement, e. g. as disclosed in our earlier application PCT/EP2019/051047, the complete disclosure of which is incorporated herein by reference.

We will now further define and explain the invention using the timepiece of PCT/EP2019/051047 as a preferred embodiment example.

The timepiece according to PCT/EP2019/051047 does not incoporate a conventional escapement, and thus does not incorporate a balance spring. The above-described compensator means which act on the balance spring of a conventional escapement therefore cannot be used.

Instead, the timepiece has an escapement based on resistance to the flow of a fluid, comprising a pump arranged for continuously and uninterruptedly pumping said fluid. The said pump is a mechanical pump, preferably a gear pump, a piston pump, a membrane pump or a bellows pump.

The timepiece has a, preferably adjustable, flow control device arranged to limit the flow of the fluid therethrough. This flow control device actually determines the unwinding speed of the timepiece’s main spring, and thus its timekeeping function.

The flow control device is preferably a valve arranged for adjustable throughput of fluid, and most preferred it is a needle valve with adjustable aperture.

As in all conventional needle valves, the valve aperture is set and adjusted by moving the valve needle into, or out of, the valve housing, which narrows, or widens, the aperture between the needle and the housing. Generally, this requires a linear movement of the needle which is therefore connected to a setting means, which permits the setting of the needle position, preferably from the outside of the timepiece. Two major factors influence the isochroncity of the timepiece, i. e. actual spring torque and temperature. The actual spring torque will not be constant as the main spring unwinds, which would affect the power available to drive the pump. Changes in temperature would affect the geometry of the needle valve, since e. g. the needle may contract or expand. Both these effects need to be compensated.

By the invention, it is advantageous to use a compensator train for this function. In preferred embodiments, the spring torque compensator and the temperature compensator are therefore integrated in a common compensating arrangement for the valve needle. The compensating arrangement then does not only move the needle with respect to the valve housing, to compensate for spring torque change, but at the same time it moves the temperature compensator. This forms a compensator train within the meaning of the invention. The effects of both compensators in the compensator train thus add up to an overall compensation.

In a presently highly preferred embodiment, the spring torque compensator bases on the power reserve indicator functionality of the timepiece.

It is generally desirable for the user to know how much the spring has already unwound and thus, whether it needs winding. It is known to indicate this power reserve of the spring based on counting the number of turns which the spring axle has performed in unwinding, and to automatically indicate the corresponding power reserve based on this count. Generally, this is done using a planetary gear which moves an indicator pointer or disc, the position of which shows the power reserve. An alternative way of indicating the power reserve could be based on detecting the actual power of the main spring, e. g. through the force exerted by the main spring on the winding means, e. g. the ratchet preventing the main spring from spontaneously uncoiling.

In the most preferred embodiment, the power reserve indicator corresponds to the planetary gear arrangement used in conventional mechanical watches. The planetary gear is driven by the main spring and e. g. provides 1/10 of a full rotation of its indicator wheel for every 8 rotations of the main spring arbor. The indicator wheel carries a cam which moves the valve needle to slightly open the needle valve, thus compensating for declining pump driving power as the main spring unwinds.

This arrangement resets when the main spring is rewound.

As already indicated, the timepiece is further provided with a temperature compensation feature, to ensure that the flow rate of the liquid through the flow control device is independent of the liquid’s temperature. Said temperature compensation is preferably based on selecting at least one material with a thermal expansion performance that compensates for changes in the liquid’s temperature, and especially based on selecting a homogenous material, e. g. a polymeric material, or a non-homogenous material, e. g. a bimetallic material, with said characteristics. In the most preferred embodiments, the material is a bimetallic material. A part of the compensator train is formed from this bimetallic material, e. g. a part of a rod or other mechanical component which connects the indicator wheel cam to the needle valve. Thus, temperature compensation by the bimetallic material automatically adds to the spring torque compensation.

In preferred embodiments, further compensation is added, which however is not directly connected to the above-described compensator train.

Thus, the timepiece movement is enclosed by a housing and a compensation device is arranged to compensate for thermal expansion and contraction of the housing, said compensation device preferably comprising a membrane or bellows arranged to expose its outer surface to the interior of the housing, while its interior surface is comiected to the ambient exterior of the housing. This is relevant, since in the preferred embodiments, the timepiece is provided with a housing enclosing the movement, wherein the housing is internally completely filled with the fluid, especially the liquid, pumped through the needle valve by the main spring driven pump.

Claims

1. A compensator train for a device driven by a spring, especially a windable spring such as the main spring of a timepiece like a clock or watch, said compensator train comprising at least two different compensators which are connected for common compensation movement.

2. The compensator train of claim 1 , said compensators comprising a spring torque compensator for changes in spring torque, especially such caused by the unwinding of said spring, and a temperature compensator compensating for a dimensional change of a mechanical element of the device, caused by a temperature change.

3. The compensator train of claim 1 or 2, wherein the compensation movement of said spring torque compensator changes the position of the temperature compensator, or the compensation movement of the temperature compensator changes the position of the spring torque compensator, said position being the position relative to the other elements of the device.

4. The compensator train of any preceding claim, said device being a mechanical timepiece.

5. A timepiece comprising the compensator train of any one of claims 1 to 4.

6. The timepiece of claim 5, which has an escapement based on resistance to the flow of a fluid, comprising a mechanical pump arranged for continuously and uninterruptedly pumping said fluid, preferably a gear pump, a piston pump, a membrane pump or a bellows pump.

7. The timepiece of claim 5 or 6, provided with a, preferably adjustable, flow control device arranged to limit the flow of the fluid from the pump therethrough, preferably comprising a valve arranged for adjustable throughput of fluid, most preferred a needle valve with adjustable aperture.

8. The timepiece of claim 7, provided with a needle valve, wherein the valve needle is connected to a setting means, which permits the setting of the needle position, preferably from the outside of the timepiece.

9. The timepiece of claim 8, comprising a spring torque compensator and a temperature compensator integrated in a common compensator train for the valve needle, and especially integrated in the setting means for the valve needle.

10. The timepiece of any preceding claim, said timepiece being provided with a power reserve indicator functionality, and said spring torque compensator being operatively connected to said power reserve indicator functionality of the timepiece.

11. The timepiece of claim 10, wherein the power reserve indicator corresponds to a planetary gear and indicator wheel or disc arrangement and the indicator wheel or disc carries a cam which moves the valve needle to open the needle valve, thus compensating for declining pump driving power as the main spring unwinds.

12. The timepiece of any preceding claim, further provided with a temperature compensation feature, to ensure that the flow rate of the liquid through the flow control device, especially the needle valve, is independent of the liquid’s temperature.

13. The timepiece of claim 12, said temperature compensation being based on selecting at least one material with a thermal expansion performance that compensates for changes in the liquid’s temperature, and especially based on selecting a homogenous material, e. g. a polymeric material, or a non-homogenous material, e. g. a bimetallic material, with said characteristics.

14. The timepiece of claim 13, wherein the material is a bimetallic material, and part of the compensator train is formed from this bimetallic material, e. g. a part of a rod or other mechanical component which connects the indicator wheel cam to the needle valve.