US 1478680 A
Description (OCR text may contain errors)
Dem 255 19233 J. SQDERBERG HEADLIGHT GLASS OR LENE Filed Feb. 8.
FEEJL- FBE E.
INVENTOR Patented Dee. 25, 1123.
JACOB SODER-BERG, OF PITTSBURGH; PENNSYLVANIA, ASSIGNOR TO PITTSBURGH PLATE GLASS COMPANY, A CORPORATION OF PENNSYLVANIA.
HEADLIGHT GLASS OR LENS.
Application filed- Eebruary 8, 1921.
To (ZZZ whom-it may concern."
Be it known. that LJAOOB I citizenof the United States, and a. resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have made a- 443362, of even date herewith, being par-.
ticularly designed for automobile lamps. The present lens constitutes a modification of that. showninsaid applicationand difrefracting fers therefrom in that the prisms are in part placed upon one side of the glass and in part upon the other side, instead of having all of the retracting elements-on the one side. The principle or theory of light distribution upon which the two lenses are constructed is similar and the result secured substantially the same. The annular prisms on the one side, tend to spread or bend the parallel rays so thatany upward glare is avoided. One embodiment of the invention is illustrated in the accompanying drawings, wherein:
Figure 1 is a rear. elevation of thelens; Fig. 2 is a horizontal section on the line IIII of Fig. 1; and'Fig. 3 is a vertical section on the line.IIIIII- of Fig. 1.
It will be understood that the lens is designed tobe used in the usualway with the parabolic reflector which reflects the light. therefrom theoretically in substantially horizontal rays. However, due to the fact that the filament of the lamp employed cannot beconcentrated atthe focus ofthe lens and extends forward and backwardof such focus, a part of the reflected light is more or less divergent from the axisofthe parabola, such divergence being greatest with respect to those rays which are reflected from those portions of the reflector nearest its center. into consideration in the design of the lens, the angles of thehorizontal prisms nearest the center of the lens being accentuated to give a greater bending down eifect as com-' SODERBERG, a
This condition istaken Serial No. 443,361..
pared with the prisms adjacent the upper and lower edges of: the'lens.
The concentric diflusing ridges or prisms on-the rear face ofthe lens are so designed that the light will be spread laterally, that is in a horizontal plane, to'just the amount necessary; to give the degree of side light-- ing required. The horizontal prismson the front face of the lens arethen so designed that the diverging transmitted light is bent downward, so that thegreater portion of thelight is thrownupon the roadway: at the desired distance forward of the lens, the light passing through the extreme upper edgeof the lens'beingbent downwardly so that it is either horizontal or very nearly so; the'purpose being to fulfill the requirements of the law for protectingthe occupants of approaching vehicles from glare due to up wardly. directed beams of light.
Referring ,now to the drawings, 1 isthe edge portion of the lens adapted to be'fitted in the rim of the lamp; 2, 3, 4-, 5and Gare concentric ridges or prisms-upon the rear face ofthe lens, and 7 te l? are horizontal prisms ext-ending across'the front face of the lens. The prisms 2vto 6 areof such angle that the parallel rays from the para bolic reflectorpassin'g therethrough are bent outwardly? from" the axisA of the reflector, the. amount'of the bending being determinedby the amount'of side lighting desired The prisms 7- to-17 bend this diverging lightdownwardly to the" desired extent with respect to the area upon the ground infront of the lens-which it is de sired to. illuminate. Therays passing throughthe upper portion of the lens must. of course,,bebent downwardly more than those passing through the lower portion since the rays fromthe upper'portion of the lens are bentupward by-th'e prisms on the inside of the lens, while those on the: lower portion are bent downwardly by such prisms. The angles of these horizontal prisms may be varied in order to secure just the amount of downward bending de sired, and it will be understood that the illustration is not by any means exact, the
angles of the prisms being greatly eXagcalled for if the light from the filament of the'lamp were concentrated at the focus of the lens as heretofore referred to. The rays reflected from the central portion of the reflector, due to this condition,have a greater degree of divergence than those from the outer portion of the reflector, so that the angles of the central transverse prisms are made relatively heavier than would otherwise be the case. The angles of the other transverse prisms above the axis of the lens are so designed that very little, if any, of
the light transmitted passes above a hori-' zontal plane, the objectionable glare which would otherwise occur, being thus avoided.
With respect to the angle of theprisms below the axis of the lens, this is made to suit requirements and given just the desired amount of illumination in the area'of roadway ahead of the car to which the lens is applied,.the angles of the prisms: on'the front of the lens and those on the back being carefully designed to avoid dark lines in the area illuminated and a uniform shading off of intensity from the center of the field of illumination to the outer edges thereof. The curved faces on the concentric prisms assist in securing this effect as the light passing therethrough is dilfused so that the light from the various concentric zones overlaps and blends. The transverse ridges also tend to break up any tendency to produce the appearance of concentric bands in the field of illumination incident to the use of the concentric prisms. 7 One oreat advantage of this lens is that the molds may be machined, therebeing no requirement for hand chipping such as is the case in the molds used for the formation of lenses in'which the prisms are not continuous. Such molds are not only expensive to makebecause' of the hand work required, but are correspondingly hard to re-surface after a certain amount of use. The face of the mold whichproducesthe concentric ridges of the applicants lens may be machined in a lathe while the plunger which forms the transverse prisms may be machined in a planer or milling machine. VV-hen the mold members need to be refinished, this can be quickly and cheaply done following the method by which the mold members were originally machined. Because of this'possibility of machining the mold members may also be made of exceedingly hard, durable material, such as nichrome or stellite. This material may be machined or ground but could not possibly be used in molds which require hand work, so that if desired, the applicant may-produce his molds from material which may be used almost indefinitely before requiring re-surfacing and which will give a better surface on the glass than cast iron or other molds of relatively soft material.
front side of'the lens. It is necessary'and i most desirable that the light passing through the upper half of the lens be bent downwardly so that the'uppermost rays are horizontal'or approximately so in order to avoid glare and avoid wasting a portion of the illumination, but this is not so essential in the lower portion of the lens in which the light isffor the most part bent downwardly by the annular prisms on the rear face of the lens. The degree of additional bending downward of the rays by 'the horizontal prisms is more or less a matter of discretion, such rays being bent down little or. much, depending upon the lifghting' de sired.' Similarly as to the variation in angle of the prisms in the upper half of the lens, the angle preferably increasing upward from the center as illustrated, for the reasons heretofore stated, but this is not necessarily the case and the degree of angle may be considerably changed. It is, however, quite important that the light transmitted through the lower part should be bent downwardly somewhat inorder to give the proper illumination immediately in front of the car. Also that that portion of the light transmitted just below the center of the lens should be bent down more than that transmitted further down, as the lateral diver- V gence of'such light is. so great as to be of littleuse for side lighting when bent down sharply; however, this light is brought close enough to the car and to the center of the field of illumination to be of value.
What I claim is: 7 r 1. In combination in a headlight lens or cover glass for use with a parabolic reflector,
a plate'of glass provided on one side with a series of complete annular prisms substantially symmetricalthroughout their circumference adapted to bend substantially all of the parallel rays from the reflector away from the axis thereof and provided on the other side witha plurality of transversely extending prisms adapted to bend the rays downwardly, the angles of those transverse prisms nearest the center being reater than those above and below.
2; In combination in a headlight lens or cover glass for use with a parabolic reflector, a plate of glass provided on one side with a,
series of complete annular prisms substandownwardly, the angles of those transverse tially symmetrical throughout their circumprisms nearest the center being greater than ference adapted to bend substantially all of those below the center. 10 the parallel rays from the reflector away in testimony whereof, I have hereunto I from the axis thereof and provided on the subscribed my name this 2nd day of Feb other side With a plurality of transversely ruary, 1921. extending prisms adapted to bend the rays JACOB SODERBERG.