FR2765977A1 - Portable adjustable direct reading sundial - Google Patents

Abstract

The sundial has a base plate (H) and side pieces (Vw,Ve). The baseplate (H) has a fixed foot (Pn) and two adjustable feet (Pe,Pn) which allow a single design to be used throughout a large area. A pyramidal stylus (S) is screwed to the base plate (H). The sundial is read from lines drawn on inserts (Th,Te,Tw) attached to the base plate and side pieces (H,Ve,Vw) and these inserts are reversed at the winter and summer solstices which allows a simpler layout and easier reading. The lines on the inserts are drawn from computer calculations for every fifteen days which take all the significant astronomical factors into account.

Description

The present invention relates to the production in industrial series of sundials
portable allowing a direct reading (with an accuracy of the order of a minute) of the hour
GMT whatever it is between sunrise and sunset and throughout the year
(i.e. the legal time to an integer number of units varying according to the time of the year). This type of dial also allows a good appreciation of the current date (to one or two days). I1
also indicates the time and direction of sunrise and sunset at the geographic location for which it was calculated. Finally, an adjustment device makes it easy to position it on
any horizontal surface Up to several hundred kilometers around this geographic location without affecting the accuracy of reading the time and date.

 Old sundials generally indicate local solar time. Such information, sufficient for the mentalities of the past, is of less interest today.

The more modern dials take into account the offset in longitude from the Greenwich meridian. They often contain a curve intended to allow the reading correction due to the "time equation". Remember that this means that the angular position of the sun around the Earth's axis does not repeat itself perfectly from one day to the next as if it were traveling exactly and regularly 360 degrees in 24 hours (which is not true that on average over a year); in reality there can be up to a quarter of an hour or so ahead or a quarter of an hour behind this average schedule. Reading the time on these dials therefore requires three phases:
- reading the time from the time lines (straight lines from the anchor point of the
base of the dial rod, rod called style).

- reading on the ad hoc curve, (in the shape of an eight), and according to the current date,
of the algebraic value of the correction
- mental calculation of the real time (identical to that of the watch, one or two
whole hours) by adding the two previous values
Sundials are often incomplete, that is, they cannot "see" the sun throughout the day, at least between the spring and fall equinoxes.

Finally, the dials, in their greatest number, are fixed. When they are not,
repositioning and adjustment systems are either non-existent or relatively complex and
does not remedy the reading difficulty described above.

The present invention indicates GMT hours by directly taking into account the equation
time. It makes it easier to read by distinguishing a usable path from the winter solstice to
summer solstice and another usable the rest of the time, ie from summer to winter solstice.

Reversible plates bear these traces, one on the front, the other on the back. The arrangement of these plates is such that the time can be read at any time of the day and throughout the year
(as soon as there is sufficient sunshine), including at sunrise and sunset. This last
point allows to read a priori time and direction of sunrises and sunsets at any
time of year.

As a variant, the semiannual traces can be placed on concave surfaces in particular
on hemispheres. In this case, provision must also be made for the semi-annual exchange of areas
used, which can be done by simply inverting part of the dial as in the
case of plates.

The present invention, as well as its variants, is equipped with feet of adjustable length which
which allows it to tilt a few degrees from the horizontal plane. This allows,
after an adjustment which will be defined below, to validly use it up to a few degrees of
longitude and / or latitude away from the place for which the plots were calculated Otherwise
said, a dial of the same manufacture can be used with the same precision on an area
geographic whose dimensions are expressed in hundreds of kilometers.

 Figure 1 shows in perspective a realization of the present invention.

This particular but non-limiting achievement (the plans receiving the routes could
be variously inclined) includes:
- a structure called "carrier",
- the style of the dial,
- three removable flat parts receiving on the front and back the lines of the dial,
- an adjustable support system, (here three feet two of which are long
adjustable).

The U-shaped support structure consists of a horizontal part H and two vertical parts Vw and Ve. The assembly must be positioned so that Vw is on the side
West and Ve on the East side. We therefore see Figure 1 from the Southwest. The tracks of
dials are made according to the latitude and longitude of a defined geometrical place qualified as a reference place and according to the dimensions of the device. We can recommend a
distance between Vw and Ve of at least one decimeter in order to preserve the overall legibility
and at most four or five decimeters to facilitate portability.

The part H presented in FIG. 2 has a projection in its northern part and another in its
southern part to ensure precise positioning of the Th plate. This plate must be able to
place it on both of its faces which requires symmetry along the North-South axis.

The part Ve presented in FIG. 3 must be able to receive and maintain the plate Te
(or the Tw plate). Two g grooves have been provided for this purpose.

 The part Vw is symmetrical with the part Ve with respect to a vertical North-South plane.

The style of the dial consists of a pyramidal piece presented in Figure 4. Its height
is the only important dimension; it must be identical to that of parts Vw and Ve.

The style of the dial, Ve and Vw are screwed by their bases above the plate H respectively in its middle part, on its East edge and on its West edge as shown
the six assembly holes provided for this purpose.

Three flat removable plates Th, Tw and Te, (see figures 1 and 5) are placed on
each of the three parts H, Vw and Ve. They are engraved on the front and back as it will be
indicated below. A set of asymmetrical notches d authorizes the association of only two
predefined configurations; the reversal of Th requires the permutation of Te and Tw. We
note that Th fits above the pyramid style through the triangular orifice o.

The support is provided by 3 feet Pw, Pe and Pn intended to rest on a horizontal surface
(see figure 1). These feet end in a spherical part to maintain the same quality of contact for a slightly oblique positioning. Indeed, while Pn is of
fixed length, Pw and Pe can slide in their housing (see figure 6) and be locked (screws
b) over longer or shorter lengths than that of Pn. By construction
the length of the rod of Pn is half the height of Vw and Ve while those of Pw and
Pe can slide the same length more (down) or less (up). This device allows a correction of the horizontality of the device when its place of use is
distant from that used for the calculation of the tracks engraved on the front and back of Th, Tw and Te,
while staying in the intended area of use.

Alternatively, the adjustable feet instead of being fitted with locking screws b can be fitted
any other device allowing a fixed length to be kept after adjustment. (for example:
screwed feet with locking key per turn or fraction of a turn)
The plots result from calculations carried out according to the rules of the art, it being understood that it is necessary for
each calculated value take into account the "equation of time". On the other hand this is the point
corresponding to the shadow of the tip of the style on the surface concerned which constitutes the point
current of the plot and consequently of the reading.

In practice, software calculates for each hour and half an hour, the first and the fifteen of
each month of the year, the coordinates of the point to place on the projection surface. We also get the sunrise and sunset times and directions
corresponding. The calculation takes into account the eccentricity of the Earth's orbit, the inclination of
the axis of the earth on the ecliptic plane, the precession of the equinoxes, the advancement of the perigee and finally, the refraction of the sun's rays in the atmosphere suitably modeled. To note
that, due to the precession of the equinoxes and the advancement of the perigee, it should be specified
the year of the calculation. This parameter inducing only very small variations over a few centuries,
we can remember, for example, the year 2000. We can obviously refine as much as the
legibility of time and calendar divisions.

The set of results makes it possible to draw (see Figure 7) 1 hour time lines and
monthly lines Im. Because the time lines have a well-known figure-eight shape, the
reading according to the position of the current point p would be difficult. She is considerably
improved by the present invention. Indeed, as it was said previously, one side of the
plates Th, Tw and Te receives the trace relating to the rise of the sun from the winter solstice to the summer solstice (Figure 8a) during winter and spring, while the other side corresponds to its
descent from the summer solstice to the winter solstice (Figure 8b) during summer and fall. A
sufficient overlap can be provided between the two sides so as to leave a period of
a few days to proceed with the bi-annual reversal of the three plates.

The daily operation is therefore as follows:
- time and direction of the sunrise readable at the top of the plate placed to the west on Vw, at
know Tw or Te depending on the semester.

- time tracking by examining the position of the shadow of the tip of the style along a daily line consistent with the layout of the monthly lines (therefore interpolable
visually between two monthly lines). The time is legible from sunrise on the
plate placed to the west (Tw or Te), then on Th, finally until sunset on the
plate placed to the east (Te or Tw).

 - time and direction of sunset readable at the top of the plate placed to the east on Ve.

Correct operation requires correct positioning. This one is almost
immediately when the device is used in or near geographic location (up to a few
kilometers) from the geographic location for which the plaques were engraved. (We will qualify this
place of "place of reference"). Otherwise, adjust the "correction
horizontality ".

Positioning at the reference location is based on the fact that the dial gives both the time
(to the nearest minute) and the date (to one or two days). It is enough, after having posed
the device on a flat surface whose horizontality has been checked, to orient it by sliding
turning so that it indicates the known time by means of a watch. We must then check
that the date appreciated by interpolation is correct. In summary: set the time and check the date. The opposite approach (setting the date and checking the time) is also possible, but at
usage, less precise. In the position thus defined, the dial then remains indefinitely at
time and date, with details given, during the current semester.

The relevance of this positioning procedure, which is not obvious, can be explained
by the following reasoning. Or a sundial calculated to rest on a horizontal plane in a defined place, with a precise orientation (North-South for example). Having such
dial placed on the horizontal plane at the defined location but in any orientation, this
dial has no reason to give the current time or date (which are assumed to be known).

However one can, by rotation while remaining posed on the horizontal plane, seek and
find an orientation for which he gives the time in question (or the date). If it is indeed correct, one must also read the current date (or time) for this orientation. In
in addition, it must keep the current time and date over time. If this is the case, it is because
exact; or vice versa, if it is correct, this will be the case. In other words, an exact dial correctly
positioned at a given instant remains so later (with very slow modifications:
precession of the equinoxes, advancement of the perigee ...).

The dial being correctly oriented at the place of reference one can imagine that a
observer of the Sun-Earth system transports it from this place to another place of use in
retaining its orientation in space. This amounts to saying that, perpendicular to the vertical
from the place of reference, it is no longer that of the place of use. Given the distances
in play, any movement on the surface of the earth remains sufficiently small (seen from the sun, the
earth is comparable to a point) so that the dial having kept the same orientation, it keeps
also the same indications for both the time and the date. A horizontal correction at
place of use therefore allows the dial to give in this place the same information as
point for which it was calculated
The correction of horizontality in a "place of use" far from the reference place leads to
adjust the lengths of feet Pw and Pe according to the different latitudes and longitudes of
these two geographic points. The algebraic length of a foot is counted from a
position 0 identified when the length of this foot is equal to that of the fixed foot Pn. She
will be positive when the foot is longer and measured, for example, relative to the base of the
plate H. The lengths are to be read on an abacus calculated for the device and supplied with it. This
abacus can be engraved on one of the free surfaces of the device as well as the latitude and the
longitude of the place of reference that is precious to know. Figure 9a, relating to the foot
Pw, illustrates this type of abacus. The first step is to locate the latitude and longitude of the place of use. After having identified (or interpolated) the corresponding latitude curve lt, ItO
being that of the reference place, we read directly the positive or negative elongation of the foot Pw
for the abscissa of the difference in longitude towards East or West.

A second abacus perhaps dedicated to the length of the foot Pe (Figure 9b). Can also
note that, the apparatus being symmetrical, the elongation of Pe is readable on the abacus of figure 9a by simple inversion of the sign of the offset in longitude: read Pe on the East side if Pw has been
read from the West side and vice versa.

The adjustment of Pw and Pe having been carried out for a place of use, the positioning on
a flat surface in this place is done as simply as explained above: sliding sliding
for setting the time and checking the date (or less precise reverse approach).

In summary, the present invention is a sundial to be placed on a horizontal surface
(hence the qualifier of a sundial of a transportable living room or garden), with traces
calculated according to the rules of gnomonic art but taking into account J "equation of time"
for each point and by dividing the lines between Winter-Spring and Summer-Autumn, lines which
will alternately be visible after turning (direct reading of GMT time). This
dial is structured so as to receive the shadow of the tip of the style at all times of the
day whatever the period in the year (complete device). It is fitted with a
modification of the horizontality which allows the correction to be read on one (or more) abacus (s)
supplied (sY of the device and parameterized according to the latitude and longitude of the place
of utilìsioll (adjustable device).

Note that the present invention is not limited to flat surfaces; Figures 10 and
11 present two variants based on receptor hemispheres. These variants can be
considered to be a modernization of scaphes from the Roman era.

 Variant 1 (Figure 10) is composed of a cylindrical part Cy and a support part Sp.

Each end of the Cy part carries a hollow hemisphere. The hour lines Ih and
monthly lines Im drawn there at one end (Eh) for winter and spring and at
the other end (Ee) for summer and fall. The end Eh is exposed while Ee rests on the support Sp in the groove g provided for this purpose. The following semester we reverse the
extremities. It is imperative that the angular orientation of Cy with respect to Sp is exactly
determined; this can be done by sparing the keying notches d. The Sp part is
equipped with three feet Pn, Pw and Pe whose definition and operation are identical to
those of figure 1. The end of the style here is a small sphere S (or S 'depending on the semester).

Variant 2 (Figure 11) consists of a parallelepiped part Pp in which are
inscribed the two hemispheres carrying the lines with the two corresponding styles S and S '. PP
is returnable in the Sp part which constitutes the support. A hollow d in Sp avoids everything
incorrect positioning of Pp. Sp has four feet Pnw, Pne, Psw and Pse, all of
adjustable length. Indeed, although a three-leg arrangement as in FIGS. 1 and 10 is possible, it is preferable for obvious aesthetic reasons to provide four legs. In this
In this case, any of them can be chosen as a pivot-reference. The abacuses of
adjustment will give the lengths of each of the other two closest feet. The length
the farthest (on the diagonal) is obtained immediately since it is the sum of the two
other. In practice, in order to have only to consider increases in the length of the feet, it is recommended to take as pivot the one which is closest to the reference point of the
dial. For example if the dial is used in the South-East direction from the place of
reference, we will take Pnw as the pivot, we will read the elongation on the one hand from Pne and
on the other hand from Psw. Finally, the elongation of Pwe is calculated by adding the two preceding ones.

The structures offered in variants 1 and 2 have the advantage of being valid whatever
the area of latitudes considered. It suffices to modify the traces in the
hemispheres as well as the setting charts.

The present invention authorizes the industrial production of sundials whose interest for
amateurs is to be really functional (because sufficiently precise and
complete) and transportable. Their structure in one or more materials to select during production (wood, stainless steel, brass, precious metal, plastic, etc.) allows them to be
embellish decorative elements as is customary. A single production can cover
several degrees in both latitude and longitude, that is to say in fact the whole of a
territory like France. The extension of the covered area depends on the extent of the setting
possible for foot length. The same production can also see its field extended simply by providing a few variants for the traces on the three plates Th, Tw
and Te, (or on the hemispheres of Figures 10 and 11) and for the adjustment charts
feet lengths ..

An example of sizing covering the whole of France, the North of Spain and
Italy and part of Central Europe is given below. This model, called
"Fréhel-Aubusson", corresponds to the main configuration presented above, namely:
- U-shaped structure with three retoumables plates
- support by three feet, two of which are adjustable in length
Sizing is done for the following reference location:
Latitude: 46 North
Longitude 2 "East
(i.e. a place near the city of Aubusson)
The year 2000 is the year used for the calculation.

 Note: the projections provided on the structure H for positioning the plate Th are not necessarily present. This simplification is legitimate since the plate Th is retained both by the style on which it fits and, laterally, by Te (or Tw) and Ve in the East and Tw (or Te) and Vw in the West .

 Figures 12 and 13 give the essential dimensions of the device.

 Th plate length: 32 cm., Useful width (excluding keys): 24 cm. , thickness I cm.

 Tw and Te plates: length 32 cm., Useful height (excluding keys) 5.5 cm., Thickness 1 cm.

 Stvle - Useful height: 5.5 cm.

(ie actual height of 6.5 cm. taking into account the thickness of Th)
(a triangular base of 2 x 5.31 cm at the level of Th corresponds to an edge
of the style in traditional position, ie parallel to the terrestrial axis)
- Position: point vertically from the origin of the axes, i.e. on the North-South axis of the
Th plate and at 10 cm. from its lower edge (edge intended for the South)
Feet:
West foot Pw and East foot Pe, positioned at 14 cm on either side of the axis
North-South, in the Vw and Ve structures, and 3.5 cm from the bottom edge
(ridge for the South), 6.5 cm from the origin of the axes.

North foot Pn, positioned on the North-South axis, and 13 cm north side of the origin of the
axes. Fixed length of 3 cm. from the bottom surface of the
structure H
There is therefore 19.5 cm between the axis of Pn and the straight line joining the axes of Pw and Pe.

The lengths of Pw and Pe will be adjustable by 2.7 cm. more and less, either
0.3 to 5.7 cm.

In winter and spring, the plots given in Figures 14a, 15a and 16a are put in place.
(note that the wide keys are then to the East)
In summer and autumn, the plots given in Figures 14b, 15b, and 16b are put in place.

(note that the wide keys are then to the West)
Important note The last six figures indicated above, from 14a to 16b, have
been plotted on a 1/2 scale. A division is worth one cm.

For the repositioning of the West foot Pw, use figure 17a
For the repositioning of the East Pe foot, use figure 17b
Given the planned adjustment range (+ or - 2.7 cm) the area of use extends between the following four geographic points:
38 0 Lat. North; 2 Long. East (South of the Balearic Islands)
46 0 Lat. North.; 12 Long. West (West of the Bay of Biscay)
54 "Lat. North; 2 Long. East (North Sea near North Holland)
46 "Lat North .; 16 Long. East (roughly Zagreb)

Claims (8)

 1) Sundial (Figure 1) characterized by the presence of plates that can be turned over every six months, allowing direct reading of the G.M.T. and the date (Figures 8a and 8b), at any time between sunrise and sunset, throughout the year, and by the presence of feet of adjustable length to position the device on a horizontal surface its point of use which can be very far (up to several hundred kilometers) from the point for which it was calculated.  2) Sundial according to claim 1 characterized in that each of the faces of the constituent plates only carries the outline of a semester (winter-spring or summer-autumn), the time lines being calculated taking into account in particular the correction of 1 '"equation  time".  3) Sundial according to claim 1 characterized in that the reversible plates are provided with keying pins (Figure 1: d and Figure 5: d) allowing only two configurations, one showing the layout of the dial relative to winter and spring (Figure 8a), the other for summer and fall (Figure 8b).  4) Sundial according to claim 1 characterized in that the support feet  (figure 1: Pn, Pe, Pw) are, with the possible exception of one of them, of adjustable length (figure 1: Pe, Pw and figure 6) so as to bring the necessary horizontal correction when this sundial is placed on a horizontal surface at a location far from the reference location for which it was calculated. The variants of claim 1 also bear  feet of adjustable length (figure 10: Pn, Pw, Pe; figure 11: Pnw, Pne, Psw, Pse)  5) Sundial according to claims 1 and 4 characterized in that  - graduations are marked on the support legs of adjustable length (fig. 6)  - the zero corresponds to the position for which the feet are all of equal length (fig. 6),  - the algebraic elongation values are read on charts provided with the device and preferably engraved on its structure (Figures 9a and 9b). These charts are calculated for  the device and set according to the latitude and longitude of the place of use.  possible and may be necessary in other latitudes than the middle latitudes.  variants with inclination of the parts with respect to the horizontal and / or vertical are  so that, in medium latitudes, the shadow of the S-style point always impacts this structure whatever the time of the day and the year (Figures 1, 2 and 3). Of  horizontal H and two vertical parts Vw and Ve arranged one on the West side and the other on the East side Sundial according to claim 1 characterized in that it is structured in one part  7) Sundial according to all the preceding claims, designed as a variant (FIG. 10) and  characterized in that the half-yearly plots are placed on two hemispheres at the ends  of a cylindrical part Cy resting on a support structure Sp whose possible correction  horizontality is ensured by feet of adjustable length (Pw, Pe) and also characterized in that the semi-annual exchange of traces is ensured by simple reversal of Cy,  a. groove g and a notch ensuring its correct positioning on Sp.  8) Sundial according to all the preceding claims, designed as a variant (Figure 11)  and characterized in that the half-yearly plots are placed on two hemispheres arranged  symmetrically side by side in a parrallelipipedic volume Pp itself inserted in a  receiving support structure Sp, the possible horizontal correction of which is ensured by  feet of adjustable length (Pnw, Pne, Psw and Pse) and also characterized in that  the semi-annual exchange of traces is ensured by simple reversal of Pp in Sp, a trough d  in Sp avoiding incorrect positioning.