HK1038620B - Watch equipped with means for determining a location longitude - Google Patents

Description

The present invention relates to a clock designed to determine the longitude of a place. Such clocks are well known to the trade. One of them is described in patent CH 184 338. It has three hands moving each in front of a graduated circular dial. The hands and dials are concentric. The first dial carries a scale with each division corresponding to 1° of arc, placed in front of a needle making a turn in 40 minutes. The second dial carries a graduation of 36 divisions each corresponding to 10° of an arc and placed in front of a needle making a turn in 24 hours.The third dial has a graduation of 60 divisions corresponding to one minute of arc and is placed in front of a hand that makes a turn in four minutes of time. The watch also has a ring to change the position of the hands to allow correction relative to the time equation. It was, for example, intended for airmen to allow them to know their position. It allows a precise determination of longitude, but is hardly conducive to reading the time.

Patent FR 852 214 relates to a watch with two discs showing the time and minute.

A third disc, a concentric disc, allows longitude to be determined, since the exact time of the place is known.

Documents DE 25 104 84 and US 2 560.618 describe devices for determining the longitude and latitude of a place.

Finally, patent FR 460 311 describes an astronomical instrument for making an assessment, for monitoring a star, etc.

Today, the GPS system allows the position of a place to be defined with a much greater precision than that achieved with a conventional watch. People who need to know their position accurately can therefore use this system without any problem. However, there is no simple way to explain and understand what longitude is and how it can be determined in reference to time, and the movement of the Sun relative to the Earth. To perform these functions, it is necessary to have a simple object of ordinary use, involving manipulations and easily understandable and easy to read.

The present invention relates to a common timepiece, which has a 12-hour turn-by-turn clock and hour hand, a one-hour turn-by-turn clock and minute hand, and a dial. Its main purpose is to enable easy reading of time and to determine longitude of a place in a simple and easily understandable manner.

This is achieved by the fact that the watch of the invention has a rotating ring for reading longitude, bearing a reference and, from this, a scale in degrees covering an angle of 180° on its entire circumference and that the dial is equipped with a circular scale for selecting the time zone, with a midpoint corresponding to the top of the dial and a graduation covering 12 hours on its entire circumference, the value of the scale graduation in degrees being equal to 15 times the value of the hour scale graduation for the values facing each other, when the marker coincides with the midpoint.

The advantage is that the scale of the ring, expressed in degrees, extends from 0° to 90° on either side of the reference line, and the circular scale, carried by the dial and intended for selecting a time zone, has a graduation from 0 to + 6 hours or - 6 hours from the midpoint, depending on the direction of rotation.

Since longitude is measured with a single hour hand, the scale must be as large as possible. In a watch, however, this hand is usually the shortest. To overcome this disadvantage, the ring surrounds the dial so that it has the largest possible scale, and the hour hand is extended by an arrow to the ring's neighborhood, its length being longer than that of the minute hand. Thus, longitude can be read with good accuracy.

To be able to define longitude with some precision, it is necessary to take into account the difference between the mean time and true solar time, called the time equation. To this end, in a particular way of making, the watch has a display surface in polar coordinates, with an angular indication of the months and days of the year and a radial indication in the form of a curve relative to the time equation, and a mobile mounted index rotating with respect to the display surface and carrying a reading scale to determine the time equation.

To define longitude, it is necessary to know the angular shift of the Sun in its course from the time difference corresponding to the equation of time. To simplify reading, the index has two arms, diametrically opposed, one of which carries a scale in degrees of angles and the other a scale in minutes of time.

The accuracy of the longitude reading depends on the accuracy of the correction required by the time equation, and for this purpose the ring has indexes defining fractions of degrees for values between ± 5° on either side of the reference line.

The accuracy of the longitude reading can be improved by using the vernier principle, whereby the dial and the ring on the one hand, the ring and the hour hand on the other hand each carry a scale to define two verniers, respectively, to introduce correction of the time equation and read the longitude more accurately.

Longitude determination requires knowledge of the orientation of the meridian plane, which can be given, at least approximately, by a sun-compass clock with a disc that rotates in 24 hours, in sync with the hour hand, and that contains information about the cardinal points.

The definition of the passage of the Sun at the meridian is difficult without a compass. However, the information given by a solar compass can only be approximate, as long as the longitude of the place is not known. The addition of a magnetic compass takes up a lot of space and is not precise, because of the difference between the magnetic pole and the geographic pole. To overcome this difficulty, the present invention also relates to a device for determining the height of the Sun on the horizon. Indeed, by definition, the passage of the Sun at the meridian corresponds to its greatest height on the horizon.

One solution is to use the gnomon principle, i.e. to arrange a rod vertically and define when the shadow is shortest. This method is uncertain, because if the rod is not perfectly vertical, it can result in a large difference between the time when the shadow is shortest and the actual passage to the meridian.

The present invention also aims to enable the height of the Sun from the horizon to be determined by means of inexpensive, small-sized and even integrated into a watch. To this end, the watch according to the present invention is equipped with a device comprising a diaphragm to define a light ray of small section and a stripped surface on which the ray is projected.

In a particular mode of manufacture, the device has a body of transparent material, of a considerably prismatic shape, with two opposite, considerably parallel faces and an oblique face connecting the two opposite faces and which has a transparent opening, considerably central and intended to let a ray of light enter the body, surrounded by an opaque surface, in which the opposite faces are arranged in such a way as to reflect the ray. In this device, one of the opposite faces has a stripped surface and a scale in view of the surface, to assess the movement of the Sun on the horizon.

Such a device associated with a watch could be quickly scratched depending on the material used, a problem that could be avoided by making it from tempered glass or sapphire.

In order for the device to perform its function fully, it is desirable that it be permanently coupled to the watch and be used simultaneously with the reading of the dial.

Other advantages and features of the invention will be shown in the following description, made in conjunction with the attached drawing, in which: Figures 1 and 2 show, in the plan, a watch of the invention, showing two different states,Figure 3 is a partial view, in cut-out, of the watch of Figures 1 and 2,Figure 4 shows, in the plan, the bottom of the watch of Figures 1 to 3, and Figure 5 illustrates a device for measuring the height of the sun on the horizon.

As can be seen particularly in Figure 3, the watch of the invention has a box 10, containing a movement 12 of a quite conventional design and equipped with movements 14, 16, 18 and 20, schematically represented and making one turn in 24 hours, 12 hours, 60 minutes and 60 seconds respectively.

Each of these mobiles carries a display organ, in particular, the 14th mobile carries a disc 22 with diametrically opposed N - S indications (Figures 1 and 2) which has the function of a solar compass, as will be explained below.

The 16th mobile carries a 24-hour hand which normally makes two turns a day; the 24th mobile carries a 26th arrow, the use of which will be explained below; the 18th and 20th mobile carries 28 minutes and 30 seconds hands respectively.

The movement 12 also has a dial 32 with a dial 33 and a disc of quantium 34 visible through this dial.

The dial 32 has a dial 35 with the letters GMT at noon and the numbers 1 to 6 on both sides, in a half circle, with the + sign in the clockwise and - sign in the counterclockwise direction (Figures 1 and 2).

Indication 35 allows the time shown to be specified in which time zone.

Box 10 is fitted, in the traditional manner, with a 36-carr, a 38-ice, a bottom consisting of two parts 39 and 40 connected by a 41-hinged hinge and a 42-hour timing rod. It also has a 44-rotating ring and a 46-rotating ring control crown.

In all cases, the ring 44 has a scale covering an angle of 180° on its entire circumference and the dial 33 has a graduation covering 12 hours on its entire circumference, the graduation of the scale in degrees being equal to 15 times the graduation of the scale in hours for the values facing each other, when the reference 47 coincides with the midpoint 35.

As can be seen schematically in Figure 4, the bottom 40 part bears an index 48, mounted on a friction pivot, and a curve 50, inscribed, corresponding to the time equation represented in polar coordinates.

To access this information, the user must open the bottom by lifting the part 40. This can be done advantageously by means of a so-called secret system, such as that used in Lépine watches.

The clock, as described and represented, allows several functions complementary to the classical hour functions, namely the approximate determination of the meridian plane, the definition of longitude and the definition of the time equation.

The meridian plane, which is a vertical plane passing through the North-South axis at a given location, is indicated approximately by the N-S indications carried by the disk 22 when the 24-hour hand is pointed towards the Sun.

To determine the meridian plane accurately, the clock would have to display the local solar time and take into account the equation of time.

The device shown in Figure 5 allows the apogee of the Sun to be determined with a precision comparable to that obtained in the determination of longitude.

The oblique face 66 is partially covered by an opaque layer 68, defining a significantly central slit 70 with a diaphragm function. This slit 70 is intended to let through a 72-ray light ray from the Sun. The opposite faces 62 and 64 are arranged to reflect the 72-ray. They bear, for example, layers of metal 74 and 76. The upper face 62 is only partially covered. It has a 78-polarized surface at its opposite end to the side 66, through which the 72-ray protrudes from the body 60 and forms an image at a point at the height of the Sun 79 on the horizon.

By sizing the above device so that it is 3 mm thick for a length of about 20 mm, with a tilt of 45 degrees to the near side 66 a change in the height of the Sun of 1 degree corresponds substantially to a displacement of 1 mm of image 79.

The device will, however, include at least a diaphragm to define a light ray of adequate cross section, a stripped surface on which the ray is projected and a reference to assess the displacement of the Sun. The presence of a reflective surface in the path between the diaphragm and the stripped surface allows for a more compact structure.

Before explaining how longitude is determined, it is necessary to understand what the equation of time is. It is known that the time between two passes of the Sun in the meridian plane varies from day to day. The difference with respect to the mean time as measured by a clock is called the equation of time. This difference corresponds to the curve 50 and can be read by means of the graduated scale 52.

Longitude is the angle formed by two planes passing through the poles, one through Greenwich, the other through the place under consideration. Knowing that the relative motion of the Sun and the Earth has a periodicity of 24 hours, it is sufficient to know the passage of the Sun at the meridian of the place under consideration, expressed in Greenwich time, and then to transform this time into an angle - 24 hours corresponding to 360 degrees - to define longitude. To do this, however, it is necessary to know to which time zone the time indicated by the watch refers. This information is entered by moving the ring 44 by means of the crown 46, so that the origin 47 is in front of the value of the graduated scale 52 hours corresponding to the time shown by the watch.

The time equation is determined by the index 48 which is placed against the current day, and the value of the correction to be made, given by the intersection of index 48 with curve 50, is read on the graduated scale 52 and the correction is then introduced by moving the rotating ring 44 so that the index is offset from the time zone, to a value corresponding to the time equation.

The orientation of the meridian plane, and in particular the direction of the south, is defined in an approximate manner. When the observer wants to determine the longitude of a place in which he is, he must also have a means of determining the height of the sun from the horizon, so as to know when it is at its greatest, which corresponds to the passage to the meridian.

This can be done by placing the watch with the device as shown in Figure 5 on a relatively flat surface and facing the Sun. The observer can then see the image 79 moving on the unfolded surface 78. The meridian pass corresponds to the moment when the image stops and changes direction.

The position of the various components of the watch corresponds to a longitude reading in New York City. This city is in a time zone 5 hours behind Greenwich. The user places the dial 44 so that the index 47 is in front of the -5 of the 33 scale carried by the dial 32. The current date is 18 July. He opens the bottom of his watch and places the index 48 in front of this date t so that he can read the time equation which corresponds to a correction of 1.5°. The user then places this correction on the ring 44, so that the index of the scale 33 -5 is in front of 1.5° of the 44 scale.

In this position, the user places the watch on a flat surface, so that the device in Figure 5 is oriented towards the Sun. The image 79 then appears on the unpolished surface 78. As the Sun rises on the horizon, the image moves away from the oblique surface 66. When the Sun has reached its apogee, the image stops. At this point, the user can read the longitude value, which corresponds to the indication on the 45th scale, in relation to the 26th arrow of the hour hand, which is 24 hours, 72 degrees west longitude.

In a variant, not shown in the drawing, the dial carries a scale opposite the 45 scale, whose steps are in a ratio of 9 to 10, to set a vernier to improve accuracy in the introduction of the time equation.

As explained above, the longitude scale carried by the 44th ring is limited to 180°. This is because the hour hand makes two turns per day. The clock thus described allows the longitude to be measured between 90° West and 90° East. However, it is also easy to know the longitude for the other half of the Earth by taking the meridian passing through the Greenwich antipod as a reference and adding 180° to the measured value, the longitudes being considered as negative.

Claims (15)

1. Watch intended for defining a location longitude, including a wheel (16) completing one revolution in 12 hours and carrying an hour hand (24), a wheel completing one revolution in one hour and carrying a minute hand (28), and a dial (32), characterised in that it further includes a rotating ring (44) for reading longitude, bearing an index mark (47) and, therefrom, a scale (45) in degrees covering an angle of 180° over the whole of its periphery, in that the dial (32) is equipped with a circular scale (33) for selecting a time zone, with a median point (35) corresponding to the top point of the dial and a graduation covering 12 hours over the whole of its periphery, the value of the graduation of the scale in degrees being equal to 15 times the value of the graduation of the hour scale for the values located opposite each other, when said index mark (47) coincides with said median point (35).
2. Watch according to claim 1, characterised in that the scale (45) in degrees, extends from 0° to 90° on either side of said index mark and in that the circular scale (33) for selecting a time zone bears a graduation going from 0 to +6 hours or -6 hours from the median point (35), depending on the direction of rotation.
3. Watch according to claim 1 or 2, characterised in that said ring (44) encircles the dial (32) and in that the hour hand (24) is extended by an arrow (26) up to the vicinity of the ring (44), which is of greater length than the minute hand.
4. Watch according to any of claims 1 to 3, characterised in that it further includes a display surface (54) in polar co-ordinates, with an angular indication of the months and days of the year and a radial indication in the shape of a curve (50) relative to the equation of time, and an index (48) mounted to move in rotation opposite the display surface and bearing a reading scale (52) for determining the equation of time.
5. Watch according to claim 4, characterised in that said index (48) includes two diametrically opposite arms, bearing a scale relative to the equation of time, on one in degrees of angle and on the other in minutes of time.
6. Watch according to claim 4 or 5, of the type including a case (10) with a back cover (40), characterised in that said index (48) is mounted so as to move on the back cover of said case.
7. Watch according to any of claims 4 to 6, characterised in that the scale (45) borne by the ring (44) includes indices defining fractions of a degree for values comprised between +5° on either side of said index mark, to facilitate adjustment of the equation of time.
8. Watch according to any of claims 1 to 7, characterised in that the dial (32) and the ring (44) each bear a scale defining a vernier, to improve the equation of time adjustment precision.
9. Watch according to claim 8, characterised in that the hour hand (24) and said ring (34) each bear a scale defining a vernier to improve longitude reading precision.
10. Watch according to any of claims 1 to 9, characterised in that it further includes a disc (22) completing one revolution in 24 hours, in synchronism with the hour hand (24) and bearing data relative to the cardinal points.
11. Watch according to any of claims 1 to 10, characterised in that it further includes a device for determining the sun's altitude above the horizon including a diaphragm (70) for defining a light ray of small section, a frosted surface (78) onto which said ray is projected.
12. Watch according to claim 11, characterised in that said device includes a body (60) made of transparent material, of substantially prismatic shape, with two opposite substantially parallel faces (62, 64) and an oblique face (66) connecting the two opposite faces and which includes a transparent substantially central opening (70), intended to let a sun ray penetrate said body and surrounded by an opaque layer (68), wherein said opposite faces (62, 64) have surfaces arranged so as to reflect said ray (74, 76), and wherein one of said faces (74) includes a frosted surface (78) on which an image (79) of the opening (70) appears, which moves as a function of the sun's altitude.
13. Watch according to claim 12, characterised in that said device further includes a scale (80) opposite said surface (78), for facilitating the evaluation of the sun's altitude.
14. Watch according to claim 12 or 13, characterised in that said device is made of tempered plate glass or sapphire.
15. Watch according to any of the claims 11 to 14, characterised in that it further includes a case and a wristband and in that said device is associated with said wristband.