A SUNDIAL

Abstract: A sundial comprises a strip-shaped body (1) with surfaces substantially in the form of helicoidal surfaces (2a, 2b). The body (1) is optionally made of a very thin material. At least one of the helicoidal surfaces (2a, 2b) is graduated. As a result, the sundial is very simple to manufacture, and in addition it is very easy to set up. Moreover, it is very easy to read the time even at a relatively long distance.

Description: Title: A Sundial Technical Field The invention relates to a sundial. Background Art A sundial has been known for a long time, said sundial comprising an inclining bar, which in sunny weather casts a shadow on a curved scale member provided with indications of the time. As a result, the time can be directly read from the spot where the shadow falls. The manuf cturing of such a sundial involves a good many working steps, and furthermore the parts of the sundial must be assembled rather exactly. In addition, it is difficult to read the time at a long distance, such as for instance a few meters, because the shadow cast by the bar on the scale member is relatively small. Disclosure of the Invention The object of the invention is to provide a sundial which is very simple to manufacture and to set up, and which furthermore allows an easy reading of the time even at a relatively long distance. The sundial according to the invention is charac erised in that it comprises a strip-shaped body with surfaces substantially in form of helicoidal surfaces, said body optionally being made of a very thin material, and at least one of the helicoidal surfaces being graduated. In this manner the manufacture of the sundial is very simple because the sundial comprises only one part, said part being easy to mount in a holder. When the sundial is in use, i.e. when the sun is shining, the strip-shaped body casts a relatively wide, very clear shadow on itself, and as the sun travels about said body, the shadow travels upwards or downwards the helicoidal surface. The time indicated by the sundial is read at the graduation/time on the helicoidal surface which the front rim of the shadow has reached. When the sundial is set up, care should be taken that the body is correctly inclining relative to the path of the sun, i.e. in such a manner that the longi¬ tudinal axis of the body is parallel to the earth's axis of rotation, or in other words that said longitudinal axis is pointing towards the north star. According to the invention the strip-shaped body may be a flat bar twisted for instance 360° about its longitudinal axis, whereby a particularly simple manufacturing of the sundial is obtained. In addition according to the invention the helicoidal surfaces of the strip-shaped body may advantageously be helicoids . According to the invention it is preferred that the gra¬ duation is equidistant and placed along the centre line of the helicoidal surface on which the shadow of the sun can fall when the sundial is in use. Moreover according to the invention a graduation may exist on both sides of the strip-shaped body, whereby the sundial is particularly easy to read because it is no longer necessary to move particularly far for finding a good reading position. The two graduations oppose one another. According to the invention the ratio of the thickness to the width of the strip-shaped body may be in the range of 0.01 to 0.1, whereby the sundial is provided with a suit- able strength and is rather easy to read. Furthermore according to the invention the ratio of the width to the length of the strip-shaped body may be in the range 0.02 to 0.2, whereby the resulting shadow is of such a width that it is easy to find and read for an observer standing rather far from the sundial. An embodiment of the sundial comprises a holder, such as in the form of a circularly curved bar preferably of an arc of measure of at least 180°, and a standard, said sundial being characterised in that the strip-shaped body is placed along a diameter of the holder, the axis of the strip-shaped body being adjustable parallel to the earth's axis of rotation. The resulting sundial is very easy to adjust . Moreover according to the invention the holder may be an inclining bar, and the strip-shaped body may be arranged in extension thereof, whereby an extremely simple con¬ struction of the sundial is obtained. According to the invention the strip-shaped body is ad¬ vantageously made of a weatherproof material, such as bronze or stainless steel. Finally according to the invention a releasable connection, such as a connection by way of a locking screw, may be provided between the curved bar and the standard, whereby the inclination of the strip-shaped body is particularly easily adjustable. Brief Description of the Drawing The invention is described in greater detail below with reference to the accompanying drawing, in which Fig. 1 is a side view of an embodiment of the sundial according to the invention, Fig. 2 is an end view of the embodiment of Fig. 1, Fig. 3 illustrates a portion of the strip-shaped body, where the graduation appears clearly and the sun casts a shadow, and Fig. 4 illustrates an embodiment of the sundial, where the holder is a single inclining bar on a base. Best Mode for Carrying Out the Invention The sundial of Figs. 1 and 2 comprises a strip-shaped body 1 with surfaces 2a., 2b. substantially in the form of helicoidal surfaces. A graduation 4 is provided on the helicoidal surface 2a_, said graduation allowing a reading of the time by means of the shadow cast by the sundial on itself, cf. the more detailed explanation below. The body 1 may be mounted on a holder 5, which, as illustrated, can be a circularly curved bar preferably of an arc of measure of at least 180° . In addition a standard 5a. is provided, which is secured to a base 6. When the sundial is to be set up, the body 1 is arranged in such a manner that its longitudinal axis 8 is parallel to the earth's axis of rotation, i.e. said axis is pointing towards the north star. The helicoidal surfaces 2a. and 2b. incline preferably constantly and are preferably helicoids. In the specification and claims "helicoidal surface" means a surface produced by screwing a curve, whereby the points of the curve pass through helices of the same helical pitch. The expression "helicoid" means a helicoidal surface formed by the principals of a helical line. The strip-shaped body 1 may as indicated be made of a flat bar, which has been twisted for instance 360° about its longitudinal axis 8. As illustrated in Fig. 3, the graduation 4 is usually equidistant and placed along the centre line of the heli¬ coidal surface 2a., on which the shadow 10 cast by the sun can fall when the sundial is in use. The front rim 10a. of the shadow 10 indicates the time. A graduation may optionally exist both on the helicoidal surface 2a. and the helicoidal surface 2b., only one gradua¬ tion 4 being shown in the drawing for the sake of clarity. The ratio of the thickness t. to the width b. of the strip- shaped body 1, cf. Fig. 3, is preferably in the range 0.01 to 0.1, whereas the ratio of the width b. to the length 1. of the strip-shaped body 1, cf. Fig. 1, is preferably in the range 0.02 to 0.2. As illustrated in Fig. 1, the strip-shaped body 1 may be placed along a diameter of the circularly curved bar 5. It is also possible to vary the point on the bar 5 to which the standard 5a is secured in such a manner, that the body 1 can be caused to incline more or less. The connection between the bar 5 and the standard 5a is prefer¬ ably a releasable connection, such as for instance a connection by way of a locking screw, but it may be shaped in many other ways. Fig. 4 illustrates how the holder can be an inclining bar 5' provided with a base 5", where the strip-shaped body 1 is arranged in immediate extension of the bar 5' . The strip-shaped body may be made of a weatherproof mate- rial, such as bronze or stainless steel, but many other materials may be used, such as for instance plastics, ceramics or glass. The invention may be modified in many ways without thereby deviating from the scope thereof. Thus each helicoidal surface on the strip-shaped body may disclose a varying pitch, in which case the graduation is non-equidistant . As to the indications of the graduation, said indications may for instance be small elevations or recesses on and in the helicoidal surfaces. The elevations may optionally be situated at the rim of the strip-shaped body with the result that said elevations are particularly evident when seen against the sky. A sundial set up at about 10 m above level comprises suitably a strip-shaped body 1 of a length of about 4 m, a width of about 40 cm, and a thickness of about 1 cm. It should be observed that the helicoidal surfaces 2a, 2b. need not literally be helicoidal surfaces, but may deviate therefrom for instance by disclosing deformations, such as waves, projections etc. at more or less regular inter- vals. The helicoidal surfaces may be twisted to the right or to the left according to desire. In the latter two cases corresponding shadows move in opposite directions. The strip-shaped body, such as the flat bar, may be of a varying width, such as for instance uniformly decreasing from total width at one end of the body to half width at the opposite end. The strip-shaped body of small sundials may be of a thickess of a very few mm.

Claims: Claims . 1. A sundial, c h a r a c t e r i s e d in that it comprises a strip-shaped body (1) with surfaces substan¬ tially in form of helicoidal surfaces (2a., 2b_) , said body optionally being made of a very thin material, and that at least one of the helicoidal surfaces (2a., 2b.) is gra¬ duated. 2. A sundial as claimed in claim 1, c h a r a c t e r¬ i s e d in that the strip-shaped body (1) is a flat bar twisted for instance 360° about its longitudinal axis (8) . 3. A sundial as claimed in claim 1 or 2, c a r a c¬ t e r i s e d in that the helicoidal surfaces (2a, 2b.) of the strip-shaped body are helicoids. 4. A sundial as claimed in claim 1, 2 or 3, c h a r - a c t e r i s e d in that the graduation is equidistant and placed along the centre line of the helicoidal surface (2a.) on which the shadow (10) caused by the sun can fall when the sundial is in use. 5. A sundial as claimed in claim 1, 2 or 3, c h a r - a c t e r i s e d in that the graduation is non-equidis¬ tant. 6. A sundial as claimed in one or more of the claims 1 to 5, c h a r a c t e r i s e d in that a graduation exists on both sides of the strip-shaped body (1) . 7. A sundial as claimed in one or more of the claims 1 to 5, c h a r a c t e r i s e d in that the ratio of the thickness (t to the width (b_) of the strip-shaped body (1) is in the range 0.01 to 0.1. A sundial as claimed in one or more of the claims 1 to 7, c h a r a c t e r i s e d in that the ratio of the width (b.) to the length (1.) of the strip-shaped body (1) is in the range 0.02 to 0.2. 9. A sundial as claimed in one or more of the claims 1 to 8 and comprising a holder, such as in the form of a circularly curved bar preferably of an arc of measure of at least 180° , and a standard, c h a r a c t e r i s e d in that the strip-shaped body (1) is placed along a diame¬ ter of the holder (5) , and that the axis (8) of the strip- shaped body is adjustable parallel to the earth's axis of rotation. 10. A sundial as claimed in one or more of the claims 1 to 9, c h a r a c t e r i s e d in that the holder is an inclining bar (5'), and that the strip-shaped body (1) is arranged in extension of said bar. 11. A sundial as claimed in one or more of the claims 1 to 10, c h a r a c t e r i s e d in that the strip-shaped body (1) is made of a weatherproof material, such as bronze or stainless steel. 12. A sundial as claimed in claim 8, c h a r a c t e r¬ i s e d in that a releasable connection (14) , such as a connection by way of a locking screw, is provided between the curved bar (5) and the standard (6).

Inventors: HEIN PIET, HEIN, PIET
Applicants: HEIN PIET, HEIN, PIET
Application year: 1990
Main classification: G04B49
IPC codes: G04B49