US2101339A - Luminous clock - Google Patents

Description

Dec. 7, 1937. F. E. MONTROY 2,101,339

LUMINOUS CLOCK Filed May 4, 1936 2 Sheets-Sheet l /N VENTOR F. E. MONTROY LUMINOUS CLOCK Dec. 7, 1937.

2 Sheets-Sheet 2 Filed May 4, 1936 Patented Dec. 7, i937 UNITED STATES PATENT OFFICE LUMINOUS cLocx Frank Edward Montroy, Los Angeles, Calif.

Application May 4, 1938, Serial N0. 77,677

3 Claims. 01. 240-21) This invention relates to an illuminated clock and has for its object the provision of means to illuminate the dial and hands of a clock uniformly and brightly by means of a tubular light 5 positioned around the edge of the dial.

It is now common practice to illuminate clock dials designed for display or public convenience purposes by disposing a tubular light around the edge of the dial and a sheet of glass in front of the clock face a little distance in front of the dial and hands. The glass sheet serves as a mechanical protection for the hands and also functions to distribute the light across the face of the clock.

Various types of clocks are now to be seen with the tube light in diflerent positions with respect to the dial. In some the light is between a plane dial and the glass, casting light directly between them. In others the light is positioned in the plane of the dial or is set back beyond the plane of the dial and casting the light in part or in whole by reflection between the dial and glass.

In some clocks the dial is dark with light numerals and light hands, and in others this arrangement is reversed. In general the dials are fln- 2s ished with glossy surfaces so that they reflect light incident on them at sharp angles back toward the glass to be rereflected to the dial by the glass. In a few types the dials are of dull finish and dependence is placed on reflection from the glass direct to the dial and hands.

All of the devices of the prior art I have observed suffer from the common defect of being brighter around the edge than at the center. This invention is directed to correcting this defeet by providing a zone of increased concentration of light around the inner edge of the character circle. As the characters constitute the major display feature of the clock any unevenness of the light over the characters mitigates heavily against the appearance of the clock.

Likewise a correction of the light over the characters does more to improve the general appearance of the clock than an absolute increase in the intensity. It is more important in fact to provide uniformity of illumination over the characters than to increase the unit intensity of light on the hands. As will be shown later on, the appearance of the hands can be improved very effectively without resorting to heightened illumination, at least to that degree necessary to bring the characters up to their proper display value.

It is an object of the invention to provide for a general balance-of attraction value between the characters and the hands by a more scientific distribution of the light over the characters, thus increasing the readability without an increase in the illumination.

Other objects of the invention will be apparent from the following specification and the drawings. The invention is illustrated in certain preferred 5 embodiments in the accompanying drawings. It

is to be understood, however, that it may be variously embodied within the purview of the claims and may be applied to any of the various types of illuminated clocks described above, as well'as to 1 combination types in which the hands are light on a dark background with dark characters on a light ground, or vice versa.

Figure 1 is a face view of a clock made according to this invention having light hands and 1 characters on a dark field.

Figure 2 is a sectional view of the same through the section indicated by 2-2, Figure 1.

Figure 3 is a perspective view of a hand showing the conformation thereof. 20

Figure 4 is a cross section on one half of a clock made according to this invention with a tube positioned to cast light directly between the dial and the glass.

Figure 5 is a similar view of a clock with the a tube positioned in an annular recess around the dial.

Figure 6 is a similar view of clock provided with a glass cover conformed to selectively distribute the light over the dial.

Figure 7 is a comparison diagram of radiation illustrative-of the operation of the device shown in Figure 6.

' The notations in Figures 1 and 2 are the same. Numeral I indicates a clock in which 2 indicates 5 the dial, 3 the glass face,'4 the clock mechanism, and 5 and 6 the hands. The housing I is spun with a recess 8 in which the glass is set. Theglass is held in place by a ring 9. The dial iscomposed of a flat center portion 10, correspond- 49 ing to the area swept over by the hands, the backwardly beveled radial portion I 2, corresponding to the characters, and the reflecting rim i3, rolled over to flt into the reflecting portion I 5 of the housing. a

The hands 5 and 6 move in the space between the dial and the glass. Preferably they should be located closer to the dial than the glass in order to catch the light reflected from. the glass. The hands are shown with beveled edges designed so to intercept rays traveling parallel to the glass. Since the light comes into this area from" all directions, beveled hands are well lighted without shadows and catch more light than flat hands.

The tubular light I8 is disposed in the space as 2 around the edge of the structure so formed. It

is concealed from direct view by the reflecting portion ll of the housing. The terminals of the tube extend backwardthrough the dial at the points indicated by 20 and 2| and are connected to a transformer indicated by the dotted lines at 22.

It is to be understood that, insofar as the improvements in this invention are concemed, the

light can be exposed to view if desired.

The details of the illuminated elements of the device are shown enlarged in Figure 4. The same notations apply as in the previous views. It will be noted that a certain portion of the radiation is cast directly into the region around the hands. Some will fall directly onto the hands, while some of the'rays will be reflected from the glass onto the hands, and some will be reflected from the background to the glass and then to the hands.

That portion of the radiation which strikes'thc dial in-the region of thecharacters and the glass over the characters is, however, the most important. It is to be understood, of course; that at each reflection from the glass a portion of the light goes through the glass and a portion is refiected. In spite of the direct loss through the glass, it is this reflected light which is responsible for the attractive displays produced with clocks of this general type.

In clocks of the prior art the dial and glass are parallel. Consequently each ray of confined light is reflected between the dial and the glass at the same angle each time. This will be seen in Figure 7 where the paths of three rays are traced. It is to be expected that the characters will be much more brightly lighted near the tube than near the hands. This, of course. is the case. I have found that this unevenness of illumination may be reduced to a very low value by beveling the dial backward toward the rim. The beveled portion inmost instances should include only the character portion of the dial, although there are certain types of clocks in which it might be carried farther in.

In Figure 5 I have shown a clock with the tube light positioned backward of the surface of the dial. The light may be positioned thus or in the relative location shown in Figure 4 as desired.

' The general effect will be virtually the same in either case. I have traced the paths of two rays to show the manner in which the radiation is concentrated toward the inner edge of the characters. The ray A is reflected from the glass at a and strikes the dial at b. It is reflected from the dial to the glass at c and reaches the dial again at d just at the edge of the character section. It follows that all rays striking the glass outside of the circle defined by a will be reflected at least twice onto the dial. By comparison, now,.I have shown a dotted line from b" which is the direction the rays would take from a surface parallel to the glass. It will be seen that the converging of the surfaces tends to bring the rays to a concentration near the inner edge of the characters. However, that is only the case with rays that strike the dial at least once. The long slanting rays that strike the glass once and are reflected into the hand region are not changed in this construction.

Another ray B is reflected twice at the rim and strikes the dial at f. It is reflected to the glass at g and back to the dial at h at the of the outer edge of the characters, which is as it should be.

In Figure 6 I have shown an alternative construction in which the glass is beveled and the dial is flat. The light in this case is positioned in the plane of the dial, although the location oi the light may be below the dial or in front of it -as desired without materially changing the effect. Here the paths of three rays 0", D and "E" are traced. Ray 0" strikes the dial first atlc" and secondly at "l". The corresponding points "12 and l are indicated in the view in Figure 7 illustrative of a corresponding device tothat of Figure 8 but with a flat glass. It will be seen that the effect of the beveling of the glass was to send the ray outward on its first striking of the dial and inward on the second.

Ray D strikes the dial first at "m" and secondly at "n. In Figure 'I it will be seen that the ray strikes the dial only once and closer in the tube. The efl'ect of the divergence of the reflecting surface is thus to lower the concentration of light near the tube and increase it toward the inner edge of the characters. Ray "E" strikes the dial at "0 at that point where the advantage is about canceled out and it goes on into the hand region in its next reflection from the glass. It is to be understood that these diagrams are merely illustrative of general effects. The light does not follow this course strictly but is 'partially dispersed at eachcontactwith a surface. Wherever it strikes a portion of the dial which has been treated to represent a character it will be entirely dispersed and scattered to leave through the glass in all directions.

The length of the hands is subject to considerable variation according to the practice of the art. So far as the purposes of this invention are concerned, the hands may extend over the characters. In such cases, the remarks above apply to the regions of the hands within the inner edge of the characters. Part of the light reflected from the outer portions of the hands is used at the expense of the characters immediately underneath thereof, which is a matter of no practical consequence.

The term "clock" as used in the claims is to be understood as including any indicating instrumentality whether used for indicating time or any other quantity.

The invention may be practiced in the construction of clocks of any desired shape other than round. For instance, oblong, square and hexagonal shapes are included within the meaning of my terms. In particular, it is to be understood that the term "annular" is so qualified.

The term luminous tube" includes any and all types of tubular lights.

In general it is preferred to finish the dial with a glossy surface to facilitate the reflections.

However, with the construction shown in Figure 6 the advantages of the invention may be realized even with a dull finished dial. It is to be understood that the invention is not limited to the particular embodiments thereof shown but may be variously embodied within the purview of the claims. The tube may be located in any of the various positions shown or even exposed directly to view.

Having thus described my invention, whatI' claim is:

1. In an illuminated clock, a dial, a transparent plate positioned in front of and a short distance from said dial, hands between said dial and said plate, and a luminous tube around the edge of the assembly so formed and disposed to radiate light between said dial and said plate, said dial being provided with characters annularly disposed therearound, the annular portion thereof including said characters being beveled away from said plate from the central region of said dial toward said tube.

2. In an illuminated clock, a. dial, a transparent plate positioned in front of and a short distance from said dial, hands between said dial and said plate, and a luminous tube around the edge of the assembly so formed and disposed to radiate light between said dial and said plate, said dial being provided with characters annularly arranged thereon, the near surfaces of said dial and said plate diverging from each other over the region of said characters from the central regions of said dial and said plate toward said tube.

3. In an illuminated clock, a dial having characters annularly disposed therearound, a transparent plate positioned in front of and a short distance from said dial, hands between said dial and said plate, and a luminous tube around the edge of the assembly so formed and disposed to radiate light between said dial and said plate, said plate diverging from said dial from the central region of said plate toward said tube over the region of said characters.

FRANK EDWARD MONTROY.

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