US1285901A - Reflector and method of making same. - Google Patents

Description

KING SAME.

G N Dn ELA AMA. HFI. CWOH D,D .0D CHE Tn.. UNEF HMN CDM SNT. UAM ARH BOP .TP .CA WF. L F LL on Patented N ov; 26, 1918.

INVENTRS .Y K Md ATTRNEY 'UNITED STATES PAT l1i t OFFICE.

WILLIAM BAUSCH, OF ROCHESTER, AND CARL GUSTAV HAERING, OF BRIGHTON, NEW YORK, ASSIGNORS TO BAUSCH & LOMB OPTICAL COMPANY, OF ROCHESTER, NEW

YORK, A CORPORATION 0F NEW YORK.

Specicaton of Letters Patent.

Patented Nov. 2c, isis.

Application led December 14, 1916. SerialNo. 137,065.

I invention, reference being had to the accompanying drawings, forming a part of this specification, and to the figures and letters of reference marked thereon.

Our invention relates to the structure of optical reflectors which commonly consist of a glass support provided with a reiecting surface. More particularly, our invention relates to re-inforced optical reiectors.

One application of optical reflectors in which the structure of the reflector is seriously taxed is in the use of reflectors for search lights. For this purpose a glass shell, usually of spherical or parabolic form, polished on its front and back surfaces, and silvered on the latter surface, is used. vThis reflector is mounted in a search light projector with its focus co-incident with the light source, which is usually an electric arc lamp. The heat to which this reiector is normally subjected is quite high, as high sometimes as 600 degrees Fahrenheit, and the stresses to which the glass is oftentimes subjected by temperature changes such as are induced after striking and after extinguishing the arc, and by variations in the action of the arc, are tremendous and have often resulted Ain racturing the reflector. When the fracture was a mere crack the reflector mav have remained intact, but fractures from this cause have sometimes resulted in total disintegration of the reflector. l

As applied to Search lights for military use the reectors are subjected to 'still greater abuse, for added to the stresses im posed on the reflector by the expansion and contraction of the material of the reiector by the heat of the light source, are stresses imposed by the transportation-of the search light projector from place to place and by gun fire designed to destroy the search light. The effect of transportation on the reflector is much the same as that caused by the hea-t of the lamp, the effect of gun ire,'however, l

is more.violent, a single shot sometimes sufiicing to shatterand wholly destroy a large reflector.

It has been found that if the fracture of a reflector could be localized by absorbing as much of the shock as is possible and if the pieces or segments into which the refiector has been divided after fracture can be held together in their original positions, the reflector will still be capable of useful work, for, although the optical eiiicie'ncy of the reflector will have been aected and reduced by the fracture, its effectiveness for use in a searchlight will have been impaired merely, and not destroyed.

One object of this invention .is to provide a reflector having an improved reinforcing backing Which is comparatively light in weight, and which also preserves substantially the original forni of the reflector thus assuring its practical optical eficiency should it be cracked by the heat of the light source,4

or during transportation, or should it be pierced by gun il'e.

A further object of the invention is to provide a. reflector having a backing which, during or after application tothe reflecting surface support, will not distort the support from its initially ground or finished contour thus preserving while unin'ured its originally intended optical quali cations and efciency.

A further Eobject of the invention is to avoid the risks of distortion and self-breakage to which reector supports are liable when they are subjected to stress and strains of compression heretofore used to prevent total disintegration. of a cracked or pierced reflector.

A still further obj ect of the invention is to provide a reflector backing which may with our invention, showing steps in the process of making the reflector; Fig. is a vcross sectional view of the finishedreflecto'r.

Throughout the-drawings, llke characters of'reference indicate the same elements and for the sake of clearness, the proportions of the various layers of material have been eX- aggerated and the materials have been conventionally shown.

In carryin out this invention there is applied to a re ector shell A, such as shown in Fig. l and usually made of glass, the usual silver lm B, also shown in Fig. 1, and over the silver lm B is preferably deposited, usually in a plating tank, a protecting and strengthening layer of metal such as copper C, as shown in Fig. 2. To the outer surface of the copper layer C, is preferably applied a coating or layer D, of any suitable adhesive cement orA varnish which on drying will form a protective coating for the metallic layers B. C. as shown in Fig. 3. In practice, it is preferred to form the layer D by applyingone or more coatings of black varnish or lacquer composed preferably of linseed oil, a coal tar derivative such as asphaltum, and lamp-black, in suitable proportions. These coatings are preferably baked on for a period of labout twelve hours. Over the baked varnish layer D, is then preferably applied a coating or layer E, of pigmented varnish as shown in Fig. il, and which may consist of an adhesive resinous spar varnish such as Valspar varnish,.to which has been added suhcient zinc oxid to give the mass the consistency of a thick paint, and this applied pigmented varnish layer E is preferably then baked for about four hours. A layer of any suitable reinforcing material, preferably metallic and porous, such as metal gauze F, which may be a copper wire gauze of about twenty mesh, is then smoothly laid over the outer surface of the baked pigmented vari nish layer E, as shown in Fig. 5. This gauze F, constitutes the inner re-inforcin material of the reflector backing. One met od of applying the preferred copper wire gauze F, 1s to ay the partly finished reflector face down on a suitable support and after placing the gauze, (which may or may not previously have been formed to lit the contour of the mirror) lupon the baked pigmented varnish layer E, the gauze is spread smoothly over and is temporarily held in intimate contact with the layer E. The layer E prevents the auze from' abrading or otherwise marring t e reflecting surface. While the gauze is thus smoothly held to the reflector support a comparatively thick la er G of a plastic adhesive or paste is app ied to the gauze covered varnish layer E, in such a manner as to permeate and embed the gauze F and to tenaciously adhere to the baked varnish layer E whlch itself tenaciously adheres to the outer surface of the baked var-` nish layer D, as shown in Fig. 6. The comand an adhesive resinous spar varnish such as the well known Valspar varnish. `This composition layer Gr, is dried atmospherically or by applied'heat until it is hard and then it cooperates with the embedded wire gauze layer F and the baked varnish layer E to form the preferred main foundation or re-inforcing framework of the reflector backing. After the composition layer G has hardened, the protruding peripheral portions of the gauze are trimmed olf about even with the periphery of the layers E, G. After scraping or otherwise clearing o any superuous material from the layer G, there is applied to the outer face of said layer and also over the edges of all of the layers G, F, E, D, C, B, and the eripheral edge of the reflector glass or shel A, a layer H of coating material' as shown in Fig. 7. For this layer H, it is preferred to use two coats of a suitable varnish or paste such as is commonly used for covering the silvered backs of mirrors, and composed of klinseed oil, resinous varnish and a red iron oxid pigment. This layer H may be baked for two hours, and then a final layer I of a liquid coating material is preferably applied over the layer I-I, as shown in Fig. 8. For this back finishing layer I it is preferred to use a single coat of resinous spar varnish which may be atmospherically dried but is preferably baked for two hours. Either or both layers H, I, especially obviates possible tendency to curling or stripping of edge portions of the backing from the reflector support.

The nature of the reector shell backing layers and the manner in which they are applied results in a composite re-inforcing shell backing consisting of a plurality of layers as described, each layer being practically integral with the contiguous substance or substances whereby the reflector and its backing are in molecular contact. With this reflector structure, a glass reflector will prove less liable to breakage from concussion since the peculiar backing serves to absorb stress creating vibrations. In the event ofy local stress being applied to the material of the shell proper, such as is caused by the 1mpact of a projectile, the backing serves to limit the extent of the fracture from the point of impact to a relatively small area. At the same time the backing holds any separated segments or parts formed by the f racture substantially in their original positions, thus efectuallypreventing optical distortion or'4 shattering of the reflector shell.

A reflector constructed in accordance with this invention is thus more durable than the usual form of reector since it not only withstands ordinary shocks and stresses without even evidencing` theirfexistence by cracking, but eventhough the reflector be subjected to treatment which makes fracture of the shell inevitable, the extent of the fracture is igreatly reduced and optical distortion or shattering of the reflector shell is prevented. Instead, the individual fragments of the shell are constrained, thus causing the shell to retain substantiall its original form. Another feature pecu iar to this reflector backing structure is that it is suitable for plano and convex reflectors as Well as concave reflectors, and for any form of reflector the backing enables -the reflector to Withstand shockorstress'applied from any direction. Y

It is obvious that the number and relative arrangement of the backing layers lying between the reflecting surface and the einbedded reinforcement may be varied, as for instance, the pigmented varnish layer E, or the baked varnish layer D, may be omitted, but both layers D, E, are preferably used because of the better protection they afford the reflecting surface and of the increased strength they impart to the vfinished reflector structure.

In contradistinction to the hereinabove named prior reflector structure and method involving a constant compressive stress upon the backed reflector support radially inward from or outward toward its periphery, our invention may be practically carried out by first providing a flat sheet of any suitable plastic material which then would be the practical equivalent of the above named pigmented varnish layer E, and laying a suitable re-inforce such 'as a metallic gauze layer F, upon said sheet, and overlaying said re-inforce and gauze by a second layer of composition such as Gr, and then rolling the layers together intimately into a single reinforced sheet from which a backing of proper size may be cutand when used for curved reflectors Will be pressed into shape to fit the silvered back of the reflector to which it will be later applied and secured. by an interposed adhesive coating; or only the layers F, G, of re-inforcing and plastic material may be intimately rolled together in a sheet and a backing cut from it and afterward shaped to fit the silvered surface of any reflector support and be cemented thereto or to a protective varnish coating such as D, first applied to the silvered back of the support.

Having thus described our invention, What We claim is:

1. The combination With a fracturable optical reflector including a support provided with a reflecting surface, of a backing comprising a layer of tenacious material in adhesive contact with the back of the reflector and a layer of tough reinforcing material embedded Within said layer of tenacious material, .for preventing the entire disintegration of the reflector and minimizing the distortion thereof in eventof its fracture.

2. The combination With a fracturable'optical reflector including a support provided with a reflecting surface, of a backing com- 'prising a layer of tenacious material in adhesive contactl with the back of the reflector and a reinforcing layer of porous tough metal adhesively7 embedded Within said layer of tenacious material, for preventing the entire disintegration ofthe reflector and minimizing the distortion thereof in event of its fracture.

3. The combination With la fracturable optical reflector including a support provided with a reflecting surface, of a backing comprising 4a layer of tenacious solidified plastic material in adhesive contact with the back of the reflector, and a reinforcing layer of tough porous fabric adhesively embedded Within said plastic material in close proximity to the reflecting surface, for preventing the entire disintegration of the reflector and minimizing the distortion thereof in event of its fracture.

4. The combination With a fracturable optical reflector including a support provided with a reflecting surface, of a backing comprising a plurality of mutually adhering layers of tenacious solidified plastic material in adhesive contact With the back of the reflector, and a reinforcing layer of tough porous fabric adhesively embedded in said solidified plastic material, for preventing the entire disintegration of the reflector and minimizing the distortion thereof in event of its fracture.

5. In a reflector, the combination With a transparent support having a reflecting surface at its rear face, of an adhesive protecting and strengthening coating applied backA of said .reflecting surface, a layer of porous reinforcing material overlying said protecting coating, and a layer of strengthening plastic material overlying and adheringl to the porous reinforce and the protecting coating and hardened thereon and holding the porous reinforce securely in place.'

6. In a reflector, the combination with `a transparent support having a reflecting me dium at its rear face, 0f an adhesive protecting and strengthening coating applied back of said reflecting medium, a porous metal reinforcing layer overlying said' protecting coating, and a layer of strengthening plastic material overlying and adhering to the ,porous metal reinforcing layer and the protecting coating and hardened thereon ailid holdigthe porous reinforce securely in p ace.

7. In a reflector, the combination With a transparent glass support having a convex rear l 2 5 face, of a reflecting lm on said face, one or more protecting and strengthening layers of varnish applied backof said reflecting film,

a Wire gauze reinforce overlying sai varnish, and a layer of strengthening plastic material-overlying said Wire gauze reinforce and the subjacent protecting varnish and tenaciously adhering to and hardened upon them and holding the Wire gauze reinforce securely in place. i

8. In a reflector, the combination With a transparent glass support provided With a silver reflecting surface, of a protective metal coating deposited upon the silver, one or more protecting and strengthening layers of varnish applied back of the deposited coating, a Wire gauze reinforce overlying said varnish, and a layer of strengthening plastic material overlying said Wire gauze reinforce and the subjacent protecting varnish and tenaciously adhering to and hardened upon them and holding the Wire gauze reinforce securely in place.

. 9. The combination with a fracturable optical reflector, of a backing for preventing the entire disintegration of the reflector and minimizing the distortion thereof in event of its fracture, comprising a layer of solidified coating material adhering at the back of the support, a layer of tough metallic gauze overlying the outer surface of said layer of coating material, a layer of tenacious adhesive plastic material permeating and adhesively embedding the gauze and adhering to the layer of coating material, and a protective finishing coating applied over the outer surface of said layer of plastic material.

10. In an opticall reflector, the combination With a fracturable support having a refleeting surface, of a backing for preventing the entire disintegration of the reflector and minimizing the distortion thereof in event of its fracture, embodying a protective coating applied to theiback of said support, a layer of tough metallic gauze overlying the outer surface of said coating, a layer of pigmented varnish permeating and adhesively embedding said gauze and solidified and adhering to the protective coating, a layer of coating composition spread over the outer surface of said solidified pigmented varnish,

and a finishing layer of varnish applied over said coating composition.

11. rlhe combination with a fracturable optical reflector, of a backing' for preventing the entire disintegration of the reflector and minimizing the distortion thereof in event of its fracture, comprising a layer of solidified coating material adheringat the back of 'the support, a layer of tough metallic gauze overlying the outer surface of said layer of coating material, a layer of tenacious adhesive plastic material permeating and adhesively embedding the gauze and adhering to the layer of coating material, and a protective binding and finishing coating applied over the outer surface and peripheral edge of the backing and the peripheral edge of the support to prevent curling orvstripping of edge portions of the backing from the reflector support.

l2. The method of backing a fracturable optical reflector to prevent its entire disintegration and minimize distortion thereof in the event of its fracture, consisting in covering the back of the reector With a protective layer, smoothly and closely overlaying the back of the reflector thus protected with a layer of porous re-infcrcing material, and applying to the latter a layer of adhesive material which is Worked into the re-inforcing material to cover it and cause said material to adhere to the underlying protecting layer.

1B. The method of backing a fracturable' optical reflector to prevent its entire disintegration and minimize distortion thereof in event of its fracture, consisting in embedding a tough re-inforcing material in a slab of tenacious plastic material, forming the backing to the contour of the back of the reflector support and securing the correspending surfaces of the reflector support 9@ and the backing together.

WILLAM BAUSCH. CARL GUSTAV HAERNG.

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