US2068805A - Cover glass - Google Patents

Description

Jan. 26, 1937*. s. l.. LEBBY v2,068,805

COVER GLASS INVENTOR. 'f/l 716.5 FE 537 A TTORNE YS.

Jan. 26, 1937. l s L, EBBY 2,068,805 I COVER GLASS Filed Feb. 4,1935 '2 sheets-sheet 2 IN V EN TOR. 57.475.5/2 549? ATTORNEYS. V

Patented Jan. 26, 1937 UNITED STATES 'COVER' GLASS States Lee Lebby, Corning, N. Y., assignor to Corning Glass Works, Corning, N. Y., a corporation of New York Application February 4, 1935, Serial No. 4,922

4 Claims.

This invention relates to cover glasses, and more particularly to a cover glass having certain refractive characteristics that render it especially adapted for use in signalling.

In signalling equipment, such as railway and trafc signals, it is customary to utilize cover glasses placed in front of the light projecting System to shield it and also to modify the direction of the beam of light coming therefrom. Inasmuch as there are times when a signal is lighted and therefore intended to serve as an indication,

and there are other times when it is unlighted and is not intended to serve as an indication, it is necessary that the signal .be such that there will be no uncertainty as to Whether it is lighted or not.

In many previous signalsv it has been noticed that when the rays of the sun or the light from an approaching vehicle enter the signal and fall upon portions of' its projecting system, it will appear to be lighted when in fact it is not, so that a person approaching the Signal will misconstrue the state of facts of which thev condition of the 'signal is supposed to be an indication, often with disastrous results. Y

`Such lfalse' signal indications, which are in reality reflex indications and are often referred to as phantom indications, usually appear as a small spot of light and,`inasmuch as the close-up indications of previous signals have generally api peared as a, similar spot of light, confusion has often resulted.

It is an object of this invention to produce a new and improved type of Signal indication.

Another object isto project a primary beamr ofE substantially parallel lig'ht of high intensity and a secondary asymmetric beam of light which in Aone plane spreads through a relatively Wide angle and progressively decreases in intensity as the angle from which it is viewed recedes from the axis of the main beam while in a plane at right angles to the first plane, it is spread symmetrically with relation to and slightly in excess of the main beam with similar ldiminishing intensity.

A further object is to so intermingle the primary andV secondary beams at their source that the cover glass will always present the appearance of a filled aspect when viewed from any position within the primary orsecondary beams.

The above and other objects may be accomplished by employing my invention which embodies among its features a concavo-convextransparent .plate having distributed over its con'cave surface aplurality of transparent light cleflecting members, each, having three sides, one of which is contiguous with 'the concave face of the plate while the other two sides converge to form a ridge lying along a line which intersects the the concave face of the plate at two spaced (ci. rrr-329)' points. One of the faces of each member simply Serves as a riser while the other onactive face is of cylindrical contour as it recedes from the ridge.

Other features embody the symmetrical distribution of the light deflecting members in spaced rows over the concave face of the plate and so proportioning them with relation to the plate that they will intercept only a limited portion of the light projected upon the plate when it is employed as the cover glass of a projecting system.

In the drawings:

Fig. 1 is a diagrammatic View illustrating the paths of the primary and secondary beams produced by my cover glass when it is used in conjunction with a traliic signal;

Fig. 2 is a graph upon which is plotted a` curve Showing the varying intensity inone type of secondary asymmetric beam which my cover glass is capablevof producing;

Fig. 3 is an elevation of the inside of a cover glass embodying my invention:

Fig. 4 is a vertical transverse section on the line 4-4 of Fig. 3 illustrating the cover glass in use with a conventional type of light projector;

Fig. 5 is a horizontal transverse section on the line 5 5 of Fig. 3;

Fig. 6 is an enlarged sectional View of a fragment of my improvedA cover glass showing the light deflecting members in detail;

Fig. '7 is an enlarged vertical View similar to Fig. 4 of a fragment of my cover glass showinglof the light deflecting members;

Fig. 9 is a view similar to Fig. 8 of a modified form of light deecting member, and Fig. 10 is a fragmentary sectional view through a cover glass showing the light distribution therethrough when it is equipped with light derlecting members of the type shown in Fig. 9.

Referring to the drawings in detail, my lmproved cover glass consists of a transparent plate designated generally I0 having a convex outer face I I, a concave inner face I2 of a curvature equal to that ofthe'outer face, and a circumferential flange I3. The plate is preferably of glass pressed to form with light deflecting members to' be more fully hereinafter described formed integral therewith, though of course in some instances the latter may be separately formed and attached to the plate I0 by a suitable transparent cement.

Distributed symmetrically over the inner concave face I2 of the cover glass and so proportioned with relation thereto as to interrupt but a limited amount of parallel light passing theregenerally I4 which, as shown, are preferably arranged in uniformly spaced` parallel rows with those in one row staggered with relation to those in the next adjacent row. This arrangement causes the secondary beam to emanate from the signal unit from a plurality of uniformly distributed and spaced portions of the cover glass so that when the latter is viewed from any position within the secondary beam, it will cooperate with the function of the eye of an observer known as the persistence of vision so as to produce the appearance of being illuminated over its entire surface and effect what is commonly called a filled aspect.

From the fact that approximately seventy-flve or more per cent ofthe light falling upon the cover glass I0 passes directly through a plurality of uniformly distributed surfaces of equal curvature and is unrefracted,.it is evident that the cover glass, when viewed from any position within the main beam, will appear in full aspect.

In order to obtain the desired distribution of light intensity in the secondary beam and to simultaneously secure a symmetrical spread thereof in a plane perpendicular to the plane in which it is deflected, the light deflecting members each have three sides I5, I6, and II. The side I5 of each light deecting member is contiguous with the inner face I2 of the cover glass I0 and hence is of spherical contour and produces no refraction at its junction with the concave face I2 while the sides I6 and I1 converge to form a ridge I8 which lies along a line which intersects the concave face I2 of the cover glass at two spaced points. The side I 6 of the light deflecting member forms a riser which is preferably so shaped and positioned with relation to the light passing through the cover glass as to produce no refraction nor interference with any refracted ray while the side I'I is of cylindrical contour as it recedes from the ridge and conse' quently produces an asymmetrically deflected beam which, upon emergence through the convex face II of the cover glass, is spread symmetrically to a slight degree in a plane prependicular to the deection produced by the side II of the light deflecting member. Due to the fact that the side I'I is cylindrical in form and that the side I 5 is of spherical contour, it becomes evident that the active sides I5 and I1 of the light deflecting members I4 progressively diminish in area as the ends of the deflecting members are approached and as a result the long range portions of the secondary asymmetric beams, i. e., those closest to the axis of the primary beam, will be of greater intensity than those portions further away from the axis of the primary beam so as to produce a light distribution in the secondary beam which follows intensities illustrated by the curve plotted in Fig. 2.

As shown in Fig. 4, I illustrate my cover glass in use with a conventional type of light projector for producing a primary beam of parallel light. In this embodiment the projector consists of a projection mirror I9 in which a suitable light source, such as an electric bulb 20, is mounted. The cover glass I0 is shown mounted in front of the open side of the reflector in such a position that the light deflecting members I4 will interrupt the primary beam at uniformly spaced intervals and deflect a predetermined limited portion of the primary beam into an asymmetric secondary beam which spreads through a relatively wide angle in one direction but possesses but limited spread in a direction at right angles thereto. Obviously other suitable types of projectors for producing a primary beam of substantially parallel light may be employed without 'in any way departing from the spirit and scope of my invention.

This application is a continuation in part of my forfeited application Serial Number 231,140, filed November 4, 1927, and allowed April 4, 1934.

I claim:

1. The combination with a cover glass having a convex outer face and a concave inner face of a plurality of light deflecting members on the inner face of the cover glass, each light deflecting member comprising a transparent body having three sides, one of which is contiguous with the inner face of the cover glass While the other two sides converge and form a ridge which lies along a line which intersects two spaced points on the concave face of the cover glass, the ridges of the light deflecting members being parallel, one of said converging sides of each light deecting member being an active face of cylindrical contour as it recedes from the ridge, the active faces of the light deflecting members being on the same sides of the ridges.

2. The combination with a cover glass having a convex outer face and a concave inner face of a. plurality of light deflecting members on the inner face of the cover glass, each light deflecting member comprising a transparent body having three sides, one of which is contiguous with the inner face of the cover glass While the other two sides converge to form a ridge which lies along a chord of the curve dening the concave face of the cover glass, the ridges of the light deflecting members being parallel and one of the converging sides of each light deflecting member being an active face and cylindrical, the active faces of the light deflecting members being on the same sides of the ridges.

3. The combination with a cover glass having a convex outer face and a concave inner face of a plurality of light deecting members on the inner face of the cover glass, each light deflecting member comprising a transparent body having three sides, one of which is contiguous with the inner face of the cover glass while the other two sides converge and form a ridge which lies along a line which intersects two spaced points on the concave face of the cover glass, the ridges of the light deflecting members being parallel, one of said converging sides of each light deflecting member being an active face of concave cylindrlcal contour as it recedes from the ridge, the active faces of the light deflecting members being on the said sides of the ridges.

4. The combination with a cover glass having a convex outer face and a concave inner face of a plurality of light deflecting members on the inner face of the cover glass, each light deflecting member comprising a transparent body having three sides, one of which'is contiguous with the inner face of the cover glass while the other two sides converge to form a ridge which lies along a chord of the curve defining the concave face of the cover glass, the ridges of the light deflecting members being parallel and one of the converging sides of each light deecting member being of concave cylindrical contour. the active faces of the light deflecting members being on the same sides of the ridges.

STATES LEE LEBBY.

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