US2043913A - Photographic lamp - Google Patents

Description

June 9, 1936- R. w. WENGEL 2,043,913

PHOTOGRAPHIC LAMP Filed Aug. 9, 1934 gmvntov Rdymnnd W, Wen E1 dbtomwga Patented June 9, 19,36

UNITED STATES PATENT OFFICE to Eastman Kodak C ompany, Rochester, N. Y.,

a corporation of New York Application August 9, 1934, Serial No. 739,111 1 Claim. (Cl. 176-26) My invention relates to electric lamps and particularly to lamps for use in taking photographs where it is desired to operate them at very high intensity'for short periods of time.

Lamps for this purpose are generally referred to as photoflood lamps and in use are operated at normal or relatively low intensities during the time consumed in making preliminary arrangements and are then overloaded for a very short period of time during which an exposure may be made. This overloading has been accomplished in many ways, usually with the aid of an external rheostat or by switching two or more lamps from series to parallel relation in a circuit.

The use of a rheostat entails expense in construction, .adds weight to the apparatus and over long periods wastes much current. A switching arrangement involving two or more lamps often is awkward in application, as for instance, in the lamp house of an enlarger. Also, two photoflood lamps in series produce considerably less light than might be obtained, without materially reducing the filament life, by a more suitable adjustment of filament voltage.

It is an object of the present invention to provide a photoflood lamp whereby the brilliance of a single lamp may be altered from normal to photoflood brilliance without the aid of external resistances or transformers, i. e. the voltage impressed on the lamp is the same in each instance.

Another object of the invention is to provide a photoflood lamp whereby an operator by means of a simple external switch may select either normal incandescent lamp intensity or photoflood intensity.

Other objects and advantages of my invention will be understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claim While my invention may assume any one of several forms, I have illustrated, by way of example, in the single figure of the drawing one suitable form as comprising a glass bulb or envelope l0 having a suitable base ll of insulating -material through which pass lead in wires l2,

l3 and M to three star connected filaments IS, IS and I! having a common terminal l8. The base H is provided with three electrically separated terminals I9, 20 and 2|, to which are connected the lead in wires l2, l2 and I4 respectively.

The filaments i5 and I! are preferably identical so that the voltage drops across them are equal when the line voltage is impressed across the terminals l9 and 2|, and their resistances are so chosen that this voltage produces normal brilliance or, of course, any other desired brilliance. The third filament I6 is given a resist,- ance value which is less than that of either the filaments I5 and I! so that when one side of the line is connected to terminal 2|! and the other side to both the terminals I9 and 2|, the filaments l6 and I! will be in parallel in series with the filament I 6 and the voltage drops across the filaments l5 and II will be more than half the line voltage. Thus the three filaments will be energized above normal brilliance any desired amount depending upon the magnitude of the resistance of the third filament I6.

The lamp may be mounted in any well known triple contact socket which is here represented by three contacts 22, 23 and 24 adapted to engage the lamp terminals IB, 20, and 2|, respectively. The two filaments l5 and I! are shown connected to an electric current source 25 through lines 26, two blades 21 of a double throwknife switch, leads 28 and 29 and the contacts 22 and 24. When thus connected, the two filaments l5 and I! are in series across the lines 26 and the lamp operates at normal intensity.

When it is desired to energize the lamp to photoflood intensity the switch is thrown to'its other closed position in which one of the blades 21 connects one side of the line 23 to the contact 23 through a lead 30. The other blade 27 is forked as shown and connects the other side of the line 26 to both of the contacts 22 and 24 through the leads 28 and 29. When thus connected, the two filaments l5 and I! are in parallel in series with the filament l6 and the lamp operates at photoflood intensity.

In order to adapt the lamp for use as an ordinary photoflood lamp utilizing an ordinary house socket, a strip of conducting material may be impermanently secured across the lamp terminals i9 and 2|. This strip may be removed by any user having available a triple contact socket.

It will be noted that no external resistances or transformers are employed and that the third filament l6 emits light when the lamp is operating. at photoflood intensity. In this connection it hardly needs to be pointed out that, if desired, the third filament l8 may consist of a simple reslstance in which event the energy consumed thereby would not add to the light intensity.

The form of my invention which I have shown and described is merely illustrative and various modifications may be made without departing from the spirit and scope of myinvention. which end of each oi the others; andan' individual lead modifications I am to cover by the appended from the free end ofeach filament to a separate claim. 1 a v external contact, the maa'nitude of the individual 7 What I claim as new and desire to secure by resistances of two of said filaments being equal 5 Letters Patent 0! the United States, is: and substantially greater than the magnitude of 5 An electric lamp having a translucent enthe resistance of the third of said filaments.

velope and a base, three filaments within the envelope each having one end connected to one RAYMOND W. WENGEL."

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