US 2263953 A
Description (OCR text may contain errors)
Patented Nov. 25, 15941 ,MOLDEH) REFLECTOR BUTTON Thomas Il. Morcom, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,
Application September 30, 193'8, Serial No. 232,559
The present invention relates, in general, to luminous signs for use along the wayside of rail- (Icl. ss-sz) ways, highways, and the like, and has more parp ticular reference to reector buttons of the unit molded type, for use in such signs.
In the manufacture of luminous signs employing reflector buttons which receive light` from an outside source, and reflect the light back to the source, it is desirable to provide buttons which are economical to manufacture and which are brilliant and durable and long lived.
With the above and other considerations in mind, it is proposed. in accordance with this invention, to provide a 'reflector button which is molded in a single operation from a transparent material, with the reflector molded into the button so as to be embedded therein. In producing such buttons it is apparent that the molded material constituting the body of the button must be of a character which can be worked at a low enough temperature to avoid injuring the reecting surface of the embedded reector.
More specically, it is proposed, in accordance with this invention, to employ a reflector of steel, or the like, having a reflecting surface of nickel, chromium, silver, or other suitable material, and to mold this reflector in a transparent material which can be molded at a low enough temperature to avoid tarnishing, or in any way harming, the reflecting qualities of the reecting surface.
Further objects, purposes and characteristic A.features of the present invention will appear as the description progresses, reference being made to the accompanying drawing, showing, wholly in a diagrammatic form, and in no manner whatso-A `ever in a limiting sense, two forms of the invention. In the drawing:
Fig. 1 is a fragmentary plan view of a reflecting sign, in accordance with this invention.
Fig. 2 is a sectional view, with parts shown-in elevation, online 2-2 of Fig. '1, and viewed in the direction of the arrows. f
Fig. 3 is a sectional view, with parts. shown in elevation, and parts broken away, of a mold and its contained button, for producing the button.
Fig. 4 is a sectional view, on line 4-4 of Fig. 3, and viewed in the direction of the arrows.
Fig. 5 is a longitudinal sectional view, on line 5 5 of Fig. 4, and viewed in the direction of the arrows, and with the mold omitted, and to an enlarged scale, of a reflector button, in accordance with this invention. e
' Fig. 6 is a view,`similar to Fig. 3,
. of a modied forni of the invention.
Referring' now to the drawing, and first to Fig. 1, there is here shown a portion of a luminous or reecting sign, constituted byia support, or back ground, plate l, of metal or other summe material, on the face of which are depicted characters 2, outlined in any suitable manner. These characters' receive reflector buttons B, whereby to make the characters stand out in a luminous manner when light from an approaching vehicle,
either a locomotive headlight, or an automobile headlight, or the like, shines upon the buttons B.
The buttons, as shown in section in Fig. 5, are formed with shoulders 3, which bear against the front of support plate I, and with an annular groove 4 which is spaced the thickness of plate I from the shoulder 3, so as to lie to the back of the plate when the reflector button is in place in the plate. This groove 4 is adapted to receive a U-shaped metal clip 5 functioning as a retaining member, which is sprung into place in groove l,
and which is circular in cross section, whereby to project beyond the groove and form a retaining shoulder bearing against the back of plate l.
The reflector button, a's best shown -in Fig. 5, has a frontrefracting surface FS, and a back or innerreecting surface BS, these two surfaces being suitably spaced from each other so as to produce a button which can be characterized as `reiiex reflecting. or, in other words, autocollimating. In other words, the button is so formed that light from an external source which is received' parallel to the longitudinal. axis 6 thereof, or from any direction included within an angle tol either side of the axis 6 of about 30, is'refracted by the front surface FS and reected from the back surfacesBS, to return toward the source of light in a line parallel to the Ventering beam, al-
though, in some cases, slightly displaced there-- from. This is indicated diagrammatically, by
the entering pencil of vrays 1, which, after being refracted by the surface FS is reflected fromthe surface BS- and emerges at 8 in a direction parallel to the entering beam 1. Allntherlight beams V'striking the 'button substantially within the limits referred to above, emerge in a like manner..
The reflecting surface BS is spherical in form and is constituted by a. coating 9, ofnickel. silver, A
chromium, aluminum, or any other suitable material, placed on the inner face of a reecting plate I0, which is relatively thin and steel, or the like.
'Referring to lthe refracting surface surface FS, this surface is formed as a surface of rotation about the axis 6, ofthe curve as -shown in Fig. 5. lThis curve 'is constituted by a central is made of.
or front and at each side of curve portion I3, is a circular portion Il and I5, which connects to the portion I3 where the curves become tangent, so that they vmerge into eachother and produce no abrupt changedn curvature. These portions M and I5 are portions of circles, having centers at I6 and I1 and having radii of lengths of .367 inch. The centers of the curves I4 and Liare placed to opposite sides of the axis 6, as shown in Fig. 5, and are placed rearwardly along the axis 6 with respect to the center I2 for the central curve I3.
'I'he complete curve, formed as described just above, and constituted by the portions Il, Il and I 5, upon being rotated about the axis 0, forms the front aspherical refracting surface FS, constituting an essential part of this reecting button.
'I'he axial distance between the reflecting surface BS. and the refracting surface FS, is so chosen as to make the button reflex reflecting for the material employed, and in accordance with the index of refraction of the material employed.
With the material to be described below, and having an index of refraction of 1.49, the spacing of these two surfaces, is as shown in the drawing,
. approximately three times the radius Il of the front central portion I3 of the front surface FS. To state it mathematically exactly the distance is equal to '760/255 of this radius II, or approximately 2.98 times radius I I. Furthermore, it can be noted that the radius for the spherical reflecting surface is appron'mately two and one-half times the radius." for the .central portion of the refracting surface and that the centers of curvature of these two surfaces-are overlapped to an extent of about one-half the length of radius Il. With this arrangement and proportioning of parts a very perfect autocollimatingbutton is obtained. I
In the production of the buttons in accordance with this invention, a mold is employed which can be of the form as shown in Fig. 3, for example. This mold comprises a top portion I8 and a bottom portion constituted by two separate side members I9 and 2l, joining along the line 2i, A
and a separate support insert vmember 22 for the reflector I 0.,The top member 'I8 carries-pins 23,
receivable in openings 24 in the bottom members, for holding the parts in proper position for the molding process.
With the mold as described just above, the reflector is first placed in the mold inthe position shown in 3, and is accurately centered therein by thel projecting ilngers 25, which are here shown as being three in number and extending outwardly so as to contact with the inner cylindrical side of the mold. The 'eflector is supported on the portion 22 so as to hold it in position and carry it on a broad enough base to avoid any deformation of the reflector during the mol process. Y
Materialemployed in forming the button can be any suitable thermo-plastic material, of a transparent character, which can be molded at a low enough temperature to avoid tarnishing or otherwise harming lthe reflecting qualities of the reflecting surface 9 or deforming the body I0 -of the reflector. While many materials may be produced which are suitable for this purpose, at the present time it has been found that for various reasons, many of the commercially available plastics now on the market are quite unsuited, due to lack of transparency, high working temperatures, poor ageing.-.uualitiesl etc. One material mold, and then the mold isclosed under a pressure varying from 2000 to 4000 pounds per square inch, while being subjected to a temperature of from 300 to 360 Fahrenheit. With such hish pressures employed, it is very essential that the relatively thin reector Il. be securely supported against displacement in the mold, and against deformation of its contour, and the mold, as de-P scribed above, performs these functions most satisfactorily.
Also, with material which can be successfully molded at as low a temperature as 360 Fahrenheit, the reflecting surface of the reflector is not tarnished or harmed in any manner whatsoever. While the. temperature may vary over the range indicated, it has been found that very satisfactory results have been obtained with the employment of a temperature of 330 Fahrenheit, and with a pressure of 3000 pounds per square inch.
It can be noted that the molded material can pass down beyond the body of the reector, between the ngers 25, and cover the rear side of theretlector I0 to an extent` determined by the portion 22 of the `mold, and this portion can be varied in area to some extent, although it must be suiilcient to adequately support the refiector against deformation.
After the material has been molded into place, the mold can be taken apart and the button in its complete form, is ready for use. The reflector is embedded in the molded material and oompletely shielded against any mechanical or chemical change taking place in the reflector, such as deformation. or oxidation in the front face.- o1:V
the like. 'I'he button is thereforevery durable and rugged, and secure against, harm and destruction, and still is very economical to produce since the entire button is produced by a single molding operation of a very simple nature.
One of the main features which makes possible the production of the buttons in accordance with this invention, is the employment of a plastic material which can be molded at a low temperature so as not to harm or destroy the reflector or the reflecting surface. Another feature which makes the production of this button possible is the employment of a mold so cooperatingwith the reilector as to permit the reflector to be accurately positioned in thel mold without any great dimculty and to permit supporting the reilectorso as to avoid deformation under the very high pressures necessarily. employed in the in the button during the molding process, is subsequently machined therein. l
The mold oi Fig; 6 is comprisedof a top member 26, carrying pins 21, iitting into openings 28, in a bottom member -29; The member 2 0 has ansupport portion 30, as described above, i'or the reflector Il, and in this case there-is provided an opening Il, for .receiving a suitable tool for pushing the button out oi the lower portion 2l aiter the top of the mold has'beenv removed. The button 'is then machined to form the, groove.
A button formed same as that described above in connectionV with the other iigures, but under certain conditions it may be more economical to produce the button in this last described manner.
summarizing some ofthe features of the present invention, it can be seen that a button has been produced which is very economical to manufacture and which is very rugged and durable in use. The reector is embedded within the transparent material forming' the body o! the as in W1h'm.8, 1n its nished fOlm, is exactly the.
times theradius o! the central portion of the reltildlnalaxls.
button, and this is made possible by the employment oi a mold which suitably suPPOlf-S the reflector, and the employment o! a material which can be worked-at a sumciently low temperature to avoid any harm to 'the reecting surface or practice, without departing from the scope or the spirit o! the present invention, except insof farasitislimitedbytheappendedciaims.
l. A reilector button comprising an elongatai bodyo'i molded transparent thermo-plasticmateria! moldable at not more than 350 F., and having an index of reiractionot about 1.49, an aspherical refracting -face o n the front oi the button having a central spherical portion, a spherical forwardly directed reilectins member molded inthe body near fthe-rear oi the button,
the radius of the reiiecting face being about 2% iracting face, the radii of said two spherical portions having their inner ends on the same'lonltudinal axis and overlapped about $5 the length oi the shorter radius, said asphericai tace 'being a surface of rotation of a curve about said longitudinal axis, said curve having a central circu-v lar portion the radius of which is said shorter radius, and two end portions, each comprised of a circular arc connected tansentially atone end to' one end of the portion and with radii longer than said shorter radius and with their inner ends at opposite sides of said longi- -2. A reiiector button col'nprising` an elongated body of molded transparent thermo-plastic ma terial having an index of 'refraction o t about 1.49, an aspherieal reiracting face on the iront of the button having a central spherical portion,
a spherical forwardly directed reiiecting member V moldedinthebodyneartherearofthebutton,
theradiusofthereiiectingiacebeingaboutzttimeatheradiusottbecentralportiootthe .refracting face, the radii of said two spherical portions having theirinner ends on'th samelongitudinal axis and overlapped abou the length of the shorter radius, said aspherical tace being a surfaceoi rotation of a curve about .said longitudinal axis, said curve having a central-A -cimularporuontnemamsofwmcmssaidsmrier radius, and two end-portions, each comprised' foi' a circulararc connected tangentiall'y at one` end to one end of the central portion and with radiilongertbansaid shorter radius and with,
Y their inner ends at opposite sides oi said 'longitudinalaxis.'