EP1710637A2 - Analog time display device - Google Patents

Abstract

The instrument has an index comprising an articulated system movable relative to a dial. The system is a deformable assembly comprising movable units connected between themselves by four articulations (a). One of the articulations coincides with a center of rotation (P). The opposite articulation has a tip (I) of the index. The orientations of the two articulated units with respect to the dial are imposed by mechanical connections with the rest of the instrument. Two of the articulated units have an off center circular toothed wheel and a non circular toothed wheel, respectively.

Description

For centuries the analog display of time has been achieved by indicating the time by the position of hands on a dial. The first clocks iron about dating from the ^13th century had a needle for hours. The need for precision quickly led to the addition of a needle for minutes. The movement of these needles is naturally circular uniform. The dial is usually circular, the drawing of the rail minute follows the path of the end of the minute hand, giving it naturally a circular shape.

Since the 18 ^th century non-circular dials have appeared to give additional indications concerning the time, the position of the planets (planetary clocks) etc. At the beginning of the twentieth century very varied forms of dials were created and marketed especially for watches bracelets, for reasons of aesthetic research or fashion. This search for aesthetics or originality generally leads to a significant loss of readability of the minute scale. This readability is paradoxically worse in areas where the graduation is the most distant, ie where it could be the best. This loss of legibility minutes is easily accepted by users who do not really need the precision of the minute and who favor the aesthetic aspect compared to the utility function. For those who are attached to the analog time display, the circular minute rail is still today the only way to display minutes accurately.

In contemporary culture models of men's wristwatches must be of sufficient size to give them a virile character. But from an ergonomic point of view the width of the bracelet and especially the transversal size of the case of a wristwatch and its crown are always a hindrance during certain movements of the hand and wrist, especially when the crown comes sinking into the folds of the skin caused by the raising of the hand relative to the forearm. In addition, the elongated dials fit better in the continuity of the bracelet than dials and circular boxes (see Figures 3 / b and 3 / c). This explains why many noncircular dials are still made despite their legibility or accuracy handicap.

Since the ^18th century, to ensure better readability along non-circular graduations, some clocks have used variable length needles to the time display as for astronomical indications associated with elliptical paths. This variation in length as a function of the position of the needle was achieved mechanically by associating a slidably deformable needle with a cam-probe device. This principle, which involves not only important but also irregular friction (for example due to the return spring associated with the feeler), could easily be accepted in the clocks in view of the motive force available therein.

It should be noted here that, while the expression "sliding deformable needle" is understandable, it is very unsuitable because the term "needle" in principle designates rigid, indeformable object. It would be more correct to speak of "deformable index", a timepiece being a particular type of index.

The word index is unfortunately used by watchmakers sometimes in the direction of fixed mark marked on a dial, sometimes in the sense of an animated object indicating a value on a graduation or division in the manner of the index of the hand. FIG. 11 illustrates a watch in which the time is displayed by means of fixed indexes (a) linked to the dial (A), and indexes (b) and (c) marked on the mobile discs (B). ) and (C) respectively. The object constituted by such a mobile disk (B) its index (b) is itself a mobile index. Similar ambiguities arise when we speak of a dial or even the measurement of time.

It is necessary to specify some terms.

The measurement of time is generally expressed in several simultaneous units, so it is generally composed of several values. The hour for example is usually expressed by two numerical values: a number of hours and a number of fractions of an hour (quarter of an hour, half hour, minute). This requires two needles (or index). But we use many other units: year, month, day in the month, week, day in the week, lunar month ... The months and days of the week have names, ie alphanumeric values. The phases of the moon can not be represented by graphic symbols, that is to say by symbolic values.

In the present text, the generic term "dial" covers both classical watch dials and dials of physical instruments, as well as refined dials which do not include explicit graduation, but only a few markers or even no markers, on which the eye is able to situate the positions of the hours mentally. Transparent dials are sometimes used to reveal the mechanism or objects behind it.

By way of example, FIG. 3 / a illustrates a dial reduced to a simple plane without any marking: the midday position is implicitly vertical to the axis of rotation of the hands, the eye is capable of content. In the example of Figure 3 / b the midday position is marked by the single digit XII. Figure 3 / c illustrates the very common case where the circumference is divided into quarters.

In this text, an index is an object that indicates a value, numeric, alphanumeric or symbolic on a dial.

An hour hand (small hand) is an index of hours, and a minute hand (large hand) is an index of minutes. The whole hour hand and the minute hand of a watch do not constitute an index because it indicates two values. The word index can also refer to a cursor. It may also have an eyecup (or other type of marker) rather than a tip. It can be rigid or deformable. A "deformable needle by sliding" is a particular deformable index: a telescopic index.

Deformable indexes have not been used in wristwatch watches for lack of sufficient motive power. But curiously, it is precisely in this application that the needles with variable length can bring a considerable advantage from the ergonomic point of view, by improving the physical comfort without harming the quality of readability.

To meet this need, it is necessary to design (FIG. 2) a deformable index with precision (I), capable of following a desired path (R) serving as a reference, and consuming a weak and acceptable driving force by the associated clockwork movement. so as not to disturb his indispensable chronometry. In other words, avoiding the friction related to the telescopic index and cam-probe system which has just given the disadvantages.

The invention consists in using an articulated deformable index, the shape of this articulated index being defined by its links with the rest of the system of which it is part. This is to be compared to the way in which the position and shape of an articulated puppet are defined by the puppeteer's drawn threads (Figure 4). Such an index can follow all kinds of graduation paths.

But here again, it is necessary to specify some terms.

In the present text an articulated system is a deformable assembly consisting of movable elements interconnected by means of articulations.

Many common objects are articulated systems. Examples include folding objects in general, objects with a flip top, a bicycle chain, the hands of a clock (Figure 5), a Swiss army knife, a pair of scissors, the skeleton of a fan, an articulated bus, a crank-handle system.

An articulated system element may be a single part (elements (C) and (D) of FIG. 6), or result from the assembly of several parts by rigid links (elements (A) and (B) of FIGS. and 6).

An articulated assembly deforms with very low friction, and with very good accuracy when its elements are rigid. One or more articulations of an articulated system may be fixed, but the elements of an articulated system are movable.

In the present text, an articulation is a non-rigid link between two elements, allowing rotational movements of one with respect to the other.

Here are some canonical examples of the minutes swiveling inside the clock of a clock (Figure 5), articulation with a screw in range. But there are also flexible joints: back of a sugar tong, spire of a safety pin, leather link of a flail, localized flexible zones of a piece of molding, flexible kneecap of windsurfing mat. In the present text, a crank is a rotating part comprising an eccentric crankpin relative to the axis of rotation thereof, and on which is articulated a connecting rod.

In the present text, a crank-crank system is the combination of a crank and an articulated rod on its crank pin. This system transforms a rotational movement into reciprocating rectilinear movement or not.

A crank-rod is an articulated system.

Figures 5, 6, 7 / a, 7 / b, illustrate deformable systems of articulated elements. Figure 7 / a shows an index consisting of an articulated parallelogram. It has four joints (a), one of them coincides with the center of rotation (P) of two of its elements. The opposite hinge is the tip ( I ) of the index. FIG. 7 / b represents an index consisting of two articulated elements (A) and (B), its single articulation (a) is movable and rotates around the center of pivoting (P). Element B comprises an eyelet (O) of center (I).

The exploded figure shows a set of hour hand and minute hand of a conventional time display device. The minute hand (a1) is driven on its barrel (a2), itself secured to the wheel (a3); these three pieces together constitute the element (A). Similarly, the hour hand (b1) is driven on its barrel (b2), itself secured to its wheel (b3); these three pieces together constitute the element (B). The elements (A) and (B) can rotate relative to each other about the common axis of their respective guns which constitutes an articulation. The elements (A) and (B) constitute a system of two articulated elements.

The exploded figure 6 derives from FIG. 5. The elements (C) and (D) are added to the elements (A) and (B). The elements (C) and (D) are connected to each other and to the elements (A) and (B) by articulations defined by the axes (I1), (12) and (13). The elements (A), (B), (C) and (D) constitute a set of four articulated elements.

The shape of a system of articulated elements can be defined by imposing the values of one or more angles of the figure defined by its articulations, for example the angles θ of FIGS. 7 / a and 7 / b.

As has been described above in FIG. 5, the assembly formed by a conventional rigid timepiece, its barrel and the toothed wheel driven on it, is an example of such an element (FIG. 5). It is clear that part of this element, the wheel (a3) and its barrel (a2), is usually hidden behind the dial.

It can be seen in FIG. 6 that the elements (A) and (B) each comprise a toothed wheel (respectively (a3) and (b3)) which imposes on it a proper orientation angle, these being the "constrained elements". On the other hand, in Figure 5, the set of hour and minute hands of a traditional clock or watch - and parts each of which is integral - is an example of a set of constrained articulated elements and variable geometry, but their association does not constitute an index.

Figures 9 / a to 9 / c illustrate rotational constraints imposed on two elements of the articulated system to cause its deformation when moving. The angle α defines the orientation of the element (A) and The angle β defines the orientation of the element (B). In these figures the angle β is a function of the angle α, β = f (α). For the articulated system to deform when it moves, it is necessary and sufficient that the difference of these angles of orientation α and β is not constant. In other words, the derivative of the orientation angle on the dial of one with respect to the orientation angle of the other, dα / dβ, must not be zero, or the angular velocities snapshots of the elements relative to the dial, that is to say the derivatives of the angles α and β with respect to time, dα / dt and dβ / dt, must be different.

When it comes to measuring time, especially hours or minutes, the hands periodically go to the same points on the dial. These angles of orientation relative to the dial, as the rotational speeds with respect to the dial, are therefore periodic functions of time.

1. 1) l'engrenage à rapport de transmission variable qui à partir d'un mouvement rotatif uniforme génère un mouvement rotatif périodique à vitesse variable, par exemple en associant des roues excentrées ou non circulaires (figure 10). De multiples autres profils d'engrenages ont été conçus dans le passé.
2. 2) le système bielle-manivelle qui à partir d'un mouvement circulaire, uniforme ou non, génère un mouvement alternatif linéaire ou angulaire (figures 9/c et 10).

The means that can be used to generate these periodic angular velocities while limiting the friction as much as possible can come under two very different principles:

1. 1) the gear with variable transmission ratio which from a uniform rotary motion generates a periodic rotary motion at variable speed, for example by associating eccentric or non-circular wheels (Figure 10). Many other gear profiles have been designed in the past.
2. 2) the rod-crank system which from a circular motion, uniform or not, generates linear or angular reciprocating motion (Figures 9 / c and 10).

These systems can be integrated or coupled to a watch movement.

In the rest of the talk we will talk about the speed of rotation of the index. This definition is not entirely obvious in the case of an index with variable geometry: each element has its own speed of rotation relative to the dial and each point has its own linear speed. On the other hand, apart from the cranks of the crank-and-crank systems possibly integrated in the device, they all have the same average rotational speed with respect to the dial. The average angular velocity is that of any element of the index, except cranks apart.

Figures 11 / a and 11 / b illustrate the first principle of animation of a variable index geometry with articulated elements, of the type of Figure 9 / a, by means of gearing variable ratios. The variable speed gear train has two eccentric wheels and two oval wheels. The two oval wheels (A) and (B) are free and rotate each with its barrel around the same geometric axis (F). The wheel (A) is integral with the segment (a) of the index and the wheel (B) is integral with the segment (b). The two eccentric wheels (C) and (D) are driven on the same axis (E) and diametrically opposed, they constitute the same element (S) which rotates around the geometric axis of (E). They drive the oval wheels. Each of these last (A) and (B) is integral with a segment of the index articulated through its barrel. The gear ratio of the eccentric wheel to the oval wheel is two to one.

In Figure 11 / a, the hinged index is in the short position, the two oval wheels are shifted by about 50 °. In Figure 6 / b, the index is in long position, they have shifted by 80 ° and the two eccentric wheels have traveled around their axis, in the retro-clockwise direction, an angle of 180 °, on the other hand, the two oval wheels have traveled around their barrel, clockwise, different angles of rotation: the oval wheel (A) has traveled an angle of about 50 ° while the oval wheel (B) has traveled an angle of about 130 °. This angular variation of (B) on (A), caused a rotation of the barrel of the oval wheel (B) on the barrel of the oval wheel (A) and as a result, decreased (or closed) the angle of first segments of the articulated index, and therefore caused it to vary in length.

FIG. 12 illustrates a use of the crank-handle system,

In FIG. 12, the constrained element (A) of the index, oriented α and driven in uniform rotation by the clockwork movement, carries the satellite wheel (B), which is oriented β with respect to the dial, who rolls on the fixed wheel. (R). It is connected to the adjacent segments by two rods pivoting around two crank pins offset by 180 °.

If the articulated system incorporates a crank-crank system, the periodicity of the deformations of the index depends on the ratio of the speed of rotation of the crank (s) to the average angular speed of the index. The ratio 3 is particularly suitable for an elongated dial, oblong or polygonal, or rectangular. The ratio is suitable for a square, 1/2 or 3/2 dial at an hour index describing a closed curve at two turns in 24 hours. Figure 13 shows such a graduation path with an index of hours in two positions, 15 hours and 22 hours. FIG. 8 gives an example of an index according to the invention, with ten articulated elements, with a speed ratio of 3. It can be seen in several positions (0, 15, and 35 minutes ...). The segment (S) links the two pinions carried by the satellite wheel (not shown) itself carried by the element (A), the rods (B) cause the elements (C). The deformation of the index is caused by the rotation of the segment (S) with respect to the element (A). Surprisingly, we see that the associated graduation has a fairly regular linear pitch, much more than the natural graduation that would result from a constant angular step (6 ° per minute). In this example, the readability gained is not only for the 12-hour and 6-hour regions, where the index can follow exactly the graduation, but also for the 3-hour and 9-hour regions, where the graduation is significantly larger than graduation with constant angular steps.

Likewise, the profile of the variable ratio gears can be chosen so that the graduation described by the end of the index is more regular.

It is obviously possible to combine the various principles described above, Figure 10 illustrates the use of a simple connecting rod crank associated with the non-circular wheel (A) of a variable ratio gear. This could be used to further improve the regularity of the graduation.

It is advantageous to design the device so that it can be mounted simply on the barrels of a series movement without any modification. Figures 14 and 15 show the principle of such a device assigned to the display of minutes, the hour hand being rigid. This is a dual-link crank system that fits on a conventional timer train of a series movement (B) in front of or behind its dial (C). It is a principle to use the speed difference between the hour and minute guns to vary the length of the minute index. The deformation of the index of minutes is induced by the difference in speed of rotation between the guns of minutes and hours of the clockwork movement (12-1). The gear ratio "satellite of the index of minutes" / "integral wheel of the hours gun" is 3 + 3/12, ie 13/4 (instead of 3 in figure 8), in order to integrate the effect of the rotation of the hours barrel relative to the dial.

The hour hand (D), integral with the wheel (A), flushes, as usual, on the barrel of the hour wheel. On the gun of minutes is driven a bracket (1) where pivots a satellite pinion (H) and its plate (G). On this plate pivot the two connecting rods (E). In the example of Figure 14 the contour of the minute index (F) consists of four segments. It may be noted that in this figure none of the joints of the articulated system constituting the minute index coincides with the center of pivoting of the element (1).

It is easy to derive a variant of this solution in which the double crank system and the differential gear are placed behind the dial, and are therefore invisible.

Claims (20)

Measuring or display instrument comprising a fixed reference system, for example a dial, and characterized in that it comprises an index constituted, at least in part, of an articulated system movable relative to the reference system. Instrument according to claim 1 characterized in that the orientations relative to the dial of at least two articulated elements of one of its indexes are imposed by mechanical links with the rest of the measuring instrument of which it is part. Instrument according to one of the preceding claims, characterized in that two articulated elements of one of its indexes each comprise a toothed wheel. Instrument according to Claim 3, characterized in that at least one of the articulated elements of one of its indexes comprises an eccentric circular toothed wheel. Instrument according to Claim 4, characterized in that at least one of the articulated elements of one of its indexes comprises a non-circular toothed wheel. Instrument according to one of the preceding claims, characterized in that at least one articulated element of one of its indexes is connected to a crank via a connecting rod. Instrument according to Claim 6, characterized in that at least two of the articulated elements of one of its indexes are each connected to a crank via a connecting rod. Instrument according to claim 1 characterized in that the articulated system of one of its indexes comprises at least one crank-crank system. Instrument according to claim 8 characterized in that the articulated system of one of its indexes comprises at least two crank-crank systems. Instrument according to one of the preceding claims characterized in that the deformation of the hinged system of one of its indexes changes the appearance, for example by release or closure of empty parts, appearance or disappearance of colored parts, evolution of graphics. Instrument according to one of the preceding claims, characterized in that an articulated index follows a non-circular graduation. Instrument according to one of the preceding claims, characterized in that the graduation associated with one of its articulated indexes is more regular than that which would result from a constant angular step. Instrument according to one of the preceding claims, characterized in that a point of one of its articulated indexes describes a closed curve with several turns. Instrument according to one of the preceding claims, characterized in that one of its articulated indexes comprises at least one deformable part. Instrument according to one of the preceding claims, characterized in that one of its articulated indexes comprises at least one sliding guide. Instrument according to one of the preceding claims, characterized in that one of its articulated indexes comprises a cam-probe system. Instrument according to Claim 1, characterized in that the value indicated by an articulated index is one of the values of the measurement of time. Instrument according to one of the preceding claims, characterized in that an articulated index is used for displaying the minutes. Instrument according to Claim 17, characterized in that this index at. is driven by a traditional watch movement, b. and comprises a crank driven by a wheel meshing, directly or indirectly, with a wheel secured to the gun hours of this movement. Clock, pendulum or wristwatch according to one of the preceding claims.

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