US 2103538 A
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. Dec. 28, 1937. F. P.'KOLB 2,163,538
REFLECTOR Filed Nov 22, 1934 6 SILVER 7 COPPER FRANK P. KOLB' INVENTOR ATTORNEY Patented Doc. 28, 1937 UNITED STATES- PATENT OFFICE.
.REFLECTOR Frank P. Kolb, Rochester, N. Y., assignor to 'Bausch & Lomb Optical Company, Rochester, N. Y., acorporation of New York Application November 22, 1934, Serial No. 754,317
2 Claims. (Cl. 88105) coating takes up moisture when cool, losing it' when heated and shrinking as the moisture is '15 driven off. As the coating is relatively thick,
strong and closely adherent to the backing, this shrinking process causes it to destroy the backing and even to destroy the surface of the glass body. Thus the life of these'reflectors was relatively short and repairing them required regrinding and repolishing the glass as well as resilvering.
One of the objects of the present invention is to provide a new and improved reflector having a relatively long life and being easy and simple to repair. Another object is to provide a reflector having a protective coating which is impervious to moisture and eflicient in heat radiation.
' A further object is to provide a reflector having a protective coating including glycerol phthalate and aluminum powder. These and other objects and advantages reside in certainnovel features of construction, arrangement and combinations of elements as will hereinafter be more fully set .forth and pointed out in the appended claims.
. In the drawing: 1
Fig. 1 is a. face view of a reflector embodying my invention.
Fig. 2 is a section taken on'line 2-2 of Fig. 1. My invention is illustrated in the drawing wherein 5 indicates'a' concavo convex glass body which is ground and polished on both surfaces and a reflective layer 6 of silver is chemically deposited on the convex surface. A layer 1 of cop- 45 per is electrolytically superimposed upon the silver in the usual manner. Reflectors having a glass body, a layer of silver and a layer of copper is also essential that the coating 8 be free from excessive expansion and contraction and it must be incapable of tearing out pieces of the glass body when it does expand or contract. The synthetic resins combine these properties and glyceral phthalate, sold under the trade name of Glyptal has been found to serve very well.- Such a substance can be spread'onto the refiector in a very thin coat which is moisture proof, yet of insufficient strength to pit the glass surface regardless of the amount of expansion or contraction.
A metallic pigment, preferably aluminum pow- I v der, is incorporated in the resinous coating to radiate the heat from the reflector. Other pigments can be used but metallic pigments are ;preferred because of their radiating powers and because the flatness of metallic. flakes permits the use of a thinner coating.
Silver and copper backed reflectors should not be subjected to temperatures above 600 degrees'F. Another advantage from the use of glycerol phthalate is the factthat it deteriorates at this temperature. This affords an indicator'showing whether or not the reflector has been subjected to excessive heating.
In the event thatthe reflecting backing ofthe reflector is destroyed or damaged, it is necessary only to resilver, recopper and recoat the glass body portion. Failure of the backing does not destroy the surface of the glass and hence it is not necessary to re at the costly steps of regrinding and repolishing't e glass body portion. The reflecting backing alone can be replaced at relatively small cost.
From the foregoing it is apparent that I am able to attain the objects of my invention and provide a new and improved reflector having a long life and being easy and inexpensive to repair. Various modifications can, of course, be made without departing from the spirit .of my inven tion.
l. A reflector comprising a glass body, a reflective layer of silver on said body, a layer of copper on said silver and a protective coating, said coating being composed principally of glycerol phthalate and containing a metallic pigment.
2. A reflector comprising a glass body, a reflective layer of silver on said body, a layer of copper on said silver and a protective coating, said coating being composed principally of glycerol phthalate and containing an aluminum powder.
FRANK P. KOLB. I