The invention relates to monolithic timepiece regulators, to timepiece movements and timepieces having such regulators.
Document US2013176829A1 discloses a monolithic timepiece regulator made in a single plate, comprising:
This oscillating mechanism has two separate internal rigid elements, each connected to the external rigid element by elastic suspensions. One problem of such design is that when fixing the two internal elements on a common support, deformations and stresses are created in the elastic suspensions, thus modifying the characteristics of the oscillator and in particular its frequency or its rotation axis, which is not suitable.
One objective of the present invention is to at least mitigate this drawback.
To this end, according to an embodiment of the invention, the internal rigid element comprises a plurality of arms which are rigid with one another, said arms being distributed on 360 deg. and leaving between them free angular spaces which are radially external to the internal rigid element, and the elastic suspensions are respectively located in said free angular spaces.
In various embodiments of the mechanism according to the invention, one may possibly have recourse in addition to one and/or other of the following arrangements:
Besides, the invention also concerns a timepiece movement having a monolithic timepiece regulator as defined above.
In various embodiments of the timepiece movement according to the invention, one may possibly have recourse in addition to one and/or other of the following arrangements:
Further, the invention also concerns timepieces having a timepiece movement as defined above.
Other features and advantages of the invention appear from the following detailed description of one embodiment thereof, given by way of non-limiting example, and with reference to the accompanying drawings.
In the drawings:
In the Figures, the same references denote identical or similar elements.
The mechanical energy storage 2 is usually a spring, for instance a spiral shaped spring usually called mainspring. This spring may be wound manually through a winding stem and/or automatically through an automatic winding powered by the movements of the user.
The transmission 3 usually is a gear comprising a series of gear wheels (not shown) meshing with one another and connecting an input shaft to an output shaft (not shown). The input shaft is powered by the mechanical energy storage 2 and the output shaft is connected to the energy distribution wheel. Some of the gear wheels are connected to the watch hands or other time indicators 4.
The energy distribution wheel 5 may be for instance an escape wheel and the blocking mechanism may be for instance pallets as known in the art, e.g. a set of Swiss pallets or detent pallets cooperating with the escape wheel in the usual way. This example is of course not limitative.
The transmission 3 is designed so that the energy distribution wheel rotates much more quickly than the input shaft (with a speed ratio which may be for instance of the order of 3000).
The regulator 7 will be described in more details below. It is designed to oscillate with a constant frequency, thus ensuring the timepiece's precision. The oscillation of the regulator is sustained by regular transfers of mechanical energy from the energy distribution wheel 5, for instance through the blocking mechanism 6.
The mechanical energy storage 2, a transmission 3, energy distribution wheel 5, blocking mechanism 6 and regulator 7 form together a timepiece movement 8.
According to the invention, the regulator 7 is monolithic and made in a single plate 9, as shown for instance in
The plate 9 may have a small thickness, e.g. about 0.1 to about 0.6 mm, depending of the material thereof.
The plate 9 may have transversal dimensions, in the plane of said plate (e.g. width and length, or diameter), comprised between about 15 mm and 40 mm.
The plate 9 may be manufactured in any suitable material, preferably having a relatively high Young modulus to exhibit good elastic properties. Examples of materials usable for plate 9 are: silicon, nickel, steel, titanium. In the case of silicon, the thickness of plate 9 may be for instance comprised between 0.5 and 0.6 mm.
The various members of the regulator 7, which will be detailed hereafter, are formed by making cutouts in plate 9. These cutouts may be formed by any manufacturing method known in micromechanics, in particular for the manufacture of MEMS.
In the case of a silicon plate 9, plate 9 may be locally hollowed out for instance by Deep Reactive Ion Etching (DRIE), or in some cases by solid state laser cutting (in particular for prototyping or small series).
In the case of a nickel plate 9, regulator 7 may be obtained for instance by LIGA.
In the case of a steel or titanium plate 9, plate 9 may be locally hollowed out for instance by Wire Electric Discharge Machining (WEDM).
The constituting parts of regulator 7, each formed portions of plate 9, by will now be described in details.
In all embodiments, regulator 7 comprises:
The external rigid element 10 may have an annular shape, i.e. a closed shape surrounding a hollow space, either substantially circular or other. In possible variants, external rigid element 10 may surround internal rigid element 11 only partially, i.e. not on 360 deg.
The difference between so-called rigid parts and so-called elastic parts is their rigidity in the plane of plate 9, due to their shape and in particular to their slenderness. Slenderness may be measured for instance by the slenderness ratio (ratio of length of the part on width of the part). Parts of high slenderness are elastic (i.e. elastically deformable) and parts of low slenderness are rigid. For instance, so-called rigid parts may have a rigidity in the plane of plate 9, which is at least about 1000 times higher than the rigidity of so-called elastic parts in the plane of plate 9.
The internal rigid element 11 comprises a plurality of rigid arms 13 which are rigidly connected with one another.
The arms 13 are distributed on 360 deg. and leave between them free angular spaces 14 which are radially external to the internal rigid element 11.
For instance, the internal rigid element 11 may also include a rigid central hub 15 formed in one piece with the arms 13. The arms 13 may extend substantially radially outwardly from the central hub 15.
In the example of
The arms 13 may be wider at their radially outer end compared to their radially inner end. More specifically, in the example of
It should be noted that the configuration of the regulator may be reversed, with the rigid internal element being fixed and the rigid external element being pivoting in oscillations.
The radially outer end of the arm 13 may be extended laterally, by two opposite lateral extensions 18, so that each arm 13 is T-shaped, the outer end of the arm 13, including the lateral extensions, forming an outer head extending in a substantially angular direction relative to the axis of rotation Z.
The inside rim of the rigid external element 10 is preferably circular and centered on the axis of rotation Z, and the outer rim of each arm 13, including possible lateral extensions 18, are also circular and centered on the axis of rotation Z. A small clearance is left between the outer rim of each arm 13 and the inner rim of the rigid external element 10, for instance of the order of 0.1 mm.
The rigid external element 10 may possibly include protrusions 19 extending radially inwardly from the inner rim of said rigid external element 10. These protrusions 19 may serve as stop members cooperating with the lateral extensions 18 to limit the angular oscillations of the rigid external element 10 relative to the rigid inner element 11. In the example shown in
The elastic suspensions 12 are respectively located in said free angular spaces 14 between the arms 13.
Preferably, each elastic suspension 12 includes a plurality of elastic branches which are disposed substantially radially with regard to the axis of rotation and which extend each between an inner end and an outer end, said elastic branches being connected together either at their respective inner ends, or at their respective outer ends.
In the example of
The length of elastic branches 20, 21 may be comprised between for instance 8 and 13 mm.
The width of elastic branches 20, 21 may be comprised between 0.02 and 0.03 mm, for instance around 0.025 mm.
The same order of magnitude of lengths and widths may apply to other elastic branches of the elastic suspensions 12, in other embodiments.
The elastic suspension 12 may include two first elastic branches 20.
The outer ends of the first elastic branches 20 may be connected to the protrusions of the rigid external element 10.
The outer ends of the second elastic branches 21 may be connected respectively to the free ends of the lateral extensions 18, which avoids interference between said elastic branches 21 and arms 13.
The intermediate rigid elements 22 may be shaped as arcs of circle centered on the axis of rotation Z and disposed around the rigid hub 15, which may also have a circular shape. The clearance between rigid elements 22 and hub 15 may be small, e.g. about 0.1 mm.
The above regulator may have an oscillation frequency of e.g. about 15 to 30 Hz when made out of silicon.
The amplitude of oscillation may be up to around 20 deg. while keeping good properties of linearity and thus good precision in time measurement. In particular, the amplitude of oscillation may be up to 13 deg. while keeping excellent time precision, with maximum time deviation per day of less than 6 s.
In a particular example of the embodiment of
The above described regulator has a number of advantages over the prior art and in particular over US2013176829A1:
As shown schematically in
The embodiments of
The embodiment of
The first elastic branches 20 have an outer end connected to the external rigid element 10 and for instance to one of the protrusions 19, and an inner end connected to a first rigid intermediate element 22 separate from the internal rigid element and similar to the above described rigid intermediate element 22.
The two second elastic branches 21 having inner ends connected to said first intermediate rigid element 22 and outer ends connected respectively to two outer arms of a V-shaped second rigid intermediate element 27.
Said second rigid intermediate element 27 is separate from the internal rigid element 11 and from the first rigid intermediate element 22.
Said second rigid intermediate element 27 has a base 28 disposed between the first rigid intermediate element 22 and the axis of rotation Z and two outwardly diverging rigid V-shaped arms 29 rigidly connected to the base 28. The V-shaped arms 29 may be hollowed out in their center, to reduce the mass of internal rigid element 11.
Each arm 29 may have a head 30 close to the inner rim of the external rigid element 10. The head 30 may have opposed lateral extensions 31 which extend respectively toward the adjacent protrusion 19 and the adjacent lateral extension 18.
The two third elastic branches 32 have outer ends connected to said second intermediate rigid element 27, for instance to the lateral extension 31 close to the adjacent lateral extension 18. The two third elastic branches 32 also have inner ends connected respectively to a third rigid intermediate element 33. Said third rigid intermediate element 33 is separate from the internal rigid element 11 and from the first rigid intermediate elements 22 and second rigid intermediate element 27.
The third rigid intermediate element 33 is disposed between the basis 28 of the second rigid intermediate element 27 and the axis of rotation Z. The third rigid intermediate element 33 is disposed close to the outer rim of hub 15.
The two fourth elastic branches 34 have inner ends connected to said third intermediate rigid element 3 and outer ends connected respectively to adjacent arms 13 of the internal rigid element. The outer ends of the two fourth elastic branches 34 may in particular be connected to the lateral extensions 18 of arms 13.
In a particular example of the embodiment of
The embodiment of
In case a blocking mechanism 6 similar to that of
In the above-described embodiments, the monolithic timepiece regulator 7 has three elastic suspensions 12 regularly distributed angularly at 120° from each other around the axis of rotation Z. More generally, the monolithic timepiece regulator 7 may have at least three elastic suspensions 12 regularly distributed angularly at 120° from each other around the axis of rotation Z. This disposition is particularly advantageous to reduce the off-axis drift in all directions in the plane of plate 9, so that the centre of mass of the moving portion (either external rigid element 10, or internal rigid element 11) will remain substantially the same during rotation. It causes the system to become “force balanced” for a rotational motion. This is particularly useful because, for purposes of enhancing linearity of the oscillating system, the elastic suspensions 12 are usually individually soft, but the overall off-axis stiffness (i.e. stiffness with respect to shifting movements in the plane of plate 9) is relatively high, thus making the design of regulator 7 more robust against acceleration, gravity influences and shocks. Besides, having 3 elastic suspensions enables to have a large amplitude of rotational oscillations.
Generally, regulator 7 may have an off-axis stiffness koa of at least 60 N/m, preferably about 65 N/m or more.
Also, regulator 7 may generally have a rotational stiffness kr of at most 5 10−4 Nm/rad, preferably less than 2 10−4 Nm/rad and even more preferably less than 1.5 10−4 Nm/rad.
In all embodiments, the energy P per stroke of the regulator mechanism 7 is preferably at least 20 10−6 W (20 micro Watt), preferably at least 40 10−6 W. This energy per stroke P is calculated as follows:
P=E·f, where E is the total potential energy of the regulator mechanism 7 and f is the frequancy of oscillation;
E=0.5·kr·θ2, where θ is the amplitude of oscillation.
Number | Date | Country | Kind |
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14193516.3 | Nov 2014 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2015/076716 | 11/16/2015 | WO | 00 |