US3496451A - Heat dissipating lamp dimmer of the screw-in type - Google Patents

Description

5.1: DUNCAN HEAT DISSIPAI'ING LAMP DIHMER OF THE SCREW-IN TYPE Filed D190. 9. 1966 INVEN OR. M J. Jm

United States Patent US. Cl. 32316 7 Claims ABSTRACT OF THE DISCLOSURE A lamp dimmer includes a male screw shell at one end for screwing into the socket of a conventional lamp and a female socket at the other end for receiving the base of a conventional light bulb. An electronic circuit including a silicon controlled rectifier and a potentiometer-switch unit are mounted within the male screw shell, the potentiometer-switch being controlled by an external knob to control the power supply to the light bulb. The silicon controlled rectifier is mounted in such a manner that it is electrically insulated from the screw shell but is in heat conductive relationship therewith. Thus, the lamp or fixture into which the dimmer is screwed serves as a heat sink without requiring a special heat sink within the dimmer itself.

This invention relates to a lamp dimmer, and more particularly, to such a dimmer arranged for insertion into a standard lamp socket.

In my copending US. patent application Ser. No. 258,255, filed Feb. 13, 1963, now Patent No. 3,300,711, there is disclosed and claimed a novel lamp dimmer which is enclosed within a standard incandescent lamp socket. As pointed out in that application, a number of prior attempts have been made to produce commercially successful dimmers for home light dimming. However, the prior art devices have faced a number of difliculties, most of them relating to the large sizes required, the high power consumption, the large amount of heat generated and the high temperatures created. These diificulties are not limited to dimmers employing potentiometers, saturated reactors, etc., but are also true of the newer solid state dimming devices, primarily because of the amount of heat generated by the solid state components, such as silicon controlled rectifiers, which are used in such circuits. In 7 my copending application the problem of disposing of the heat generated by the solid state components was solved by means of a novel heat sink.

It is an object of the present invention to further improve the heat-dissipating characteristics of a miniature lamp dimmer. In particular, it is an object of the present invention to dispense with the necessity for a special heat sink in a lamp dimmer socket. Other objects are to decrease the mechanical complexity of a lamp dimmer; to provide a lamp dimmer especially adapted to insertion into a standard lamp socket; and to provide a lamp dimmer constructed to transmit its generated heat directly into the lamp socket with which it is used. The manner in which these objects are achieved will be more apparent from the following description, the appended claims, and the figures of the attached drawings, wherein:

FIG.1 is an elevational view of the dimmer socket D of this invention;

FIG. 2 is a plan view of the apparatus of the invention shown partially cut away;

.FIG. 3 is a cross sectional view taken along the line 3 3 of FIG. 2;

FIG. 4 is a cross sectional view taken along the line 44 of FIG. 3; and

FIG. 5 is a schematic diagram of a circuit usable in this invention.

FIG. 1 illustrates the manner in which a dimmer D of this invention may be installed in a lamp socket S and how it is adapted to receive an incandescent lamp L. The construction of dimmer D will be more apparent from the illustration of FIGS. 2, 3 and 4. The dimmer of the invention includes a generally cylindrical plastic shell 10 having a transverse wall 12 integral therewith. Wall 12 divides the cylindrical shell 10 into two chambers. The upper chamber 14 includes a screw shell 16 of standard design for receiving the base of lamp L. The lower portion of the screw shell 16 is bifurcated to present a pair of opposed semi-cylindrical edge portions 18, 20, each terminating at its lower end in a planar foot 22, 24, each of which is secured to the transverse wall 12 by means of a suitable rivet 26, 28. A centrally located springing lamp contact 30 is positioned between and spaced from the feet 22, 24 and is electrically and mechanically connected by means of rivet 32 through the wall 12 to provide an electrical connection into the lower chamber 34.

The lower chamber 34 of the lamp dimmer D provides space for some of the solid state electronic components employed in the circuit of this invention and the wall of the plastic shell 10 also provides mechanical support for the potentiometer 36 which is secured by means of a nut 38 screwed onto threaded stud 40. The threaded stud 40 encircles a potentiometer shaft 42 and a suitable control knob 44 is positioned on the end of the shaft externally of the dimmer. The lower edge of the plastic shell 10 is provided with an annular shoulder 46 and a flange 48. A screw shell 50 of the type used as incandescent lamp bases has an upper flange 52 which fits against shoulder 46. The inner side of flange 48 is grooved to receive a metallic snap ring 54- which locks the screw shell into position against the end of cylindrical shell 10. The lower end of the screw shell 50 terminates in a planar base 56 which includes a central opening for mounting the solid state controlled rectifier 58. Rectifier 58 is one of the major sources of heat in the circuit of the invention and its proper mounting is important to this invention. A cylindrical nylon bushing 60 encircles the stud 62 of the rectifier 58 and lies within the opening in base 56 to provide electrical isolation between the stud and the screw shell. A mica washer 64 also encircles the nylon bushing 60 and lies between the rectifier 58 and the base 56. The mica provides electrical isolation, but at the same time is a relatively good heat conductor so that heat generated by the rectifier 58 flows easily into the screw shell 50. The stud 62 of the rectifier is drilled, as at 66, and is externally threaded. A conical and centrally tapped element 68 of an electrically insulating material, such as Micarta, is screwed over stud 62 and against base 56 so as to hold the stud 62 in place. The end of stud 62 is then rolled as illustrated in FIG. 3 to provide a suitable permanent riveted connection. The various circuit ele ments are all contained within the enclosure 34 and the screw shell 50.

An understanding of the component utilized in this invention may be best achieved by reference to the schematic diagram of FIG. 5. In FIG. 5 there is illustrated a lamp L whose supply voltage is controlled by a silicon controlled rectifier 58 which is fired by a unijunction transistor firing circuit. The firing circuit includes a unijunction transistor 70'having its base two and emitter timing circuit supplied through dropping resistor 72. The emitter of the unijunction transistor is connected to a potentiometer 74 and a capacitor 76. The voltage across the capacitor 76 rises to a value which is determined by the time constant of the circuit. When it reaches the peak point voltage the unijunction transistor 70 will fire and this, in turn, triggers the silicon controlled rectifier 58 into the conducting state.

Mechanically connected to the potentiometer 74 are ice a pair of electrical switches 78, 80. These switches are integrally connected with the potentiometer 74 and are alternately actuated as the potentiometer control reaches either end of its travel. Switch 78 is connected in series with the load and functions as an on-oif switch for both the lamp and the dimmer circuit. As the potentiometer control knob (44, FIG. 3) is turned clockwise from its olf position this switch first closes. The potentiometer then gradually increases the timing constant of the timing circuit, causing the silicon controlled rectifier 58 to conduct through a greater and greater portion of its conducting half cycle. As the potentiometer reaches the point of maximum clockwise rotation, switch 80 closes, bypassing the entire dimming circuit and placing the lamp L directly across the line voltage for 100 percent illumination. It will be readily understood that the circuit illustrated in FIG. 5 is a half wave rectification circuit. Accordingly, the maximum brightness achieved by the dimming circuit alone is a function of the half wave power. In one embodiment of this invention, dimming is achieved throughout the region of 0 to 38 percent of the lamp wattage. As the 38 percent point is reached, the switch 80 closes and places the lamp across the load for 100 percent operation. The result is that the brightness of a 150 watt lamp may be set at a controlled level anywhere between 0 and approximately 60 watts. The higher illumination level switch 80 closes and places the lamp directly across the line for 150 watt illumination.

As has been pointed out, the silicon controlled rectifier 58 is a heat-producing device. Accordingly, the protection of closely spaced electronic components including such a rectifier is difiicult. However, in the present invention this difficulty has been overcome by a novel arrangement whereby the entire lamp stand or other fixture into which the dimmer is screwed functions as a heat sink. This results from placing the silicon controlled rectifier in direct heat-conducting relationship to the external screw shell. Heat conduction may be further enhanced by applying a silicone grease between the rectifier 58, the washer 64 and the base 56. By means of the apparatus of this invention the heat flow from the rectifier passes outwardly into the screw shell and from there into the lamp stand or other fixture into which the dimmer is screwed. Accordingly, a simple, compact lamp dimmer is provided which is simple to construct, lightweight, and in which the heat problem is essentially overcome. If desired, the components contained within the lower chamber 34 may be encapsulated by a suitable plastic, such as a resin.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A lamp dimmer which comprises: amain body member having a female first end arranged to receive 3. The dimmer of claim 2 wherein said body member includes a transverse wall therein, said wall dividing the interior of said body member into a first and a second chamber.

4. The dimmer of claim 3 wherein said first chamber terminates at said first end and includes a female metallic screw shell therein and said second chamber terminates in a circular edge at said second end, said male screw shell being substantially cup-shaped and having a circular rim abutting and secured to said circular edge.

5. A lamp dimmer which comprises: a substantially cylindrical body member of an electrically insulating material having first and second ends and a transverse dividing wall therebetween; an electrically conductive screw shell liner positioned within said first end and adjacent a first side of said wall to receive an incandescent lamp base; center contact means within and insulated from said liner; a cup-shaped male metallic screw shell secured to said body member and including a circular rim adjoining the second end of said body member, said body member and said screw shell defining an enclosed wiring space between the closed end of said screw shell and said transverse dividing wall; a solid state controlled rectifier mounted within said wiring space and against the closed end of said screw shell, a portion of said rectifier exte'nding through said closed end forming a central contact thereon; heat conductive and electrically insulating means between said rectifier and said closed end whereby heat means supported by said body member and extending the base of an incandescent lamp bulb and a second therethrough in actuating relationship with said circuit parameter varying means.

'6. The dimmer of claim 5 wherein said circuit parameter varying means comprises a unijunction transistor having an emitter timing circuit with a variable time constant adjustable from said knob means.

7. The dimmer of claim 6 wherein said knob means is connected in actuating relationship to a potentiometer.

References Cited UNITED STATES PATENTS 1,658,787 2/1928 Levy 33871 X 3,163,768 12/1964 Bernheim 2.40153 X 3,331,013 7/1967 Cunningham. 3,372,302 3/1968 Fasola 315-2.72

OTHER REFERENCES General Electric SCR Manual, third edition, 1964, pp. 269, 272, 274, 275.

LEE T. HIX, Primary Examiner A. D. PELLINEN, Assistant Examiner U.S. Cl. X.R.

Images