US3009071A

US3009071A - Electrical switching device

Info

Publication number: US3009071A
Application number: US851065A
Authority: US
Inventors: Robert C Morton
Original assignee: California Computer Products Inc
Current assignee: California Computer Products Inc
Priority date: 1959-11-05
Filing date: 1959-11-05
Publication date: 1961-11-14
Anticipated expiration: 1978-11-14

Description

Nov. 14, 1961- R. c. MORTON 3,009,071

ELECTRICAL SWITCHING DEVICE Filed. Nov. 5. 1959 FIG. I

BRIGHT- DIM CONTROL 4 FIG. 3

ROBERT C. MORTON INVENTOR.

CONTROL SUPPLY BY W 730% 5 ATTORNEY Patented Nov. 14, 1961 fornia Filed Nov. 5, 1959, Ser. No. 851,065 Claims. ((1 307-146) This invention relates to switching devices for electric lamps and the like, and in particular relates to an improved construction useful in connection with a switching device of the type providing two illumination levels from electric lamps.

In my United States Patent No. 2,896,125 there is described an electric lamp switching mechanism of the type useful in providing two controllably different illumination levels for homes-the brighter illumination level is provided by connecting the electric lamp directly to an alternating current source, while the dimmer of the two illumination levels is provided by inserting a rectifier in series with the lamp so as to energize the lamp with pulsating direct current.

Switches of the type useful in residential and similar environments are typically manufactured in a variety of sizes and styles. Since such switches are commonly available at a relatively low cost, it is desirable to provide a means for converting any of these switches to the dual intensity control arrangement referred to by the addition of a series connectable rectifier structure, the conversion to be made by the home owner or electrical contractor. However, most fire and safety codes prohibit the use of residential switching arrangements that are capable of careless installation in a manner exposing current carrying parts to possible short circuiting to outlet boxes or similar metallic enclosures in the walls or ceilings of houses. These restrictions commonly take the form of prohibiting the use of switch attachments capable of flexible in-wall mounting, or .in-wall mounting in a manner exposing current carrying back surfaces. Consequently, it has been found that most conventionally available light switches could not heretofore be used by the average home owner or electrician for dual light intensity control purposes since the manner of installation of the rectifier could not always be predicted.

Furthermore, these same codes usually also specify an upper temperature limit that the switching arrangement cannot exceed during normal operation of the arrangement. This latter consideration has precluded residential use of series resistance light dimming arrangements. The same consideration, however, limits the maximum size rectifier that can be tolerated in a residential type outlet box even though rectifier type light dimming operation does not generate an appreciable amount of heat. The maximum size of a rectifier that can be used for light dimming is limited by the heat dissipation characteristics of the arrangement. The greater the amount of heat that can be radiated from the switching arrangement to the outlet box without raising the temperature of any part of the switch beyond the maximum code temperature limitation, the greater the light dimming control capacity of the arrangement. Thus, while one type of silicon diode rectifier that has been used is structurally capable of handling appreciably more than 250 watts of power, the temperature of the diode reaches higher than code permitted temperatures when a load of more than 250 watts is applied to the switching arrangement. While heat radiation surfaces would normally increase the rating of the diode, the heat radiating surfaces must be thermally connected to the diode; this thermal connection implies an electrical connection. But the exposure of large current carrying surfaces is limited by the aforementioned code requirements. Consequently, the use of rectifier arrangements has heretofore been limited to relatively low load environments of the order of 250 watts or less.

Accordingly, one of the objects of this invention is to provide a rectifier mounting arrangement useful in connection with commonly available home-type control switches for converting such switches to dual light intensity control with an assurance that the resulting conversion would be free from hazardous combinations.

The foregoing and related objects are realized in accordance with the invention by the provision of an encapsulated rectifier structure so constructed that it may be mounted on conventionally available home switches in only a predetermined safe manner.

In the drawing, wherein like reference characters refer to like parts:

FIG. 1 is a perspective view of a switching device module useful in practicing the invention;

FIG. 2 is a plan view of a light dimming switching arrangement of the kind typically used in residences, and used in combination with the structure of FIG. 1;

FIG. 3 is a schematic illustration of an incandescent lamp control circuit using the arrangement shown in FIG. 2;

FIG. 4 is an illustration of a modification of the device of FIG. 1; and

FIG. 5 is a schematic illustration of a modification of the arrangement of FIG. 3 as applied to a motor speed control switching arrangement.

FIG. 1 illustrates a structure capable of use in combination with many residential type wall switches, and which incorporates a thermal conduction and radiation system that permits the control of relatively large lighting loads while still meeting the aforementioned code requirements.

The structure of FIG. 1 includes a half-wave rectifier 10, which may for example be any of the conventionally available hermetically sealed silicon diodes, mounted within a nonconductive encapsulation holder 12' The rectifier 10 is electrically connected to two sheet metal lead-in

members

14 and 16. These

members

14 and 16 serve four purposes: (a) they provide electrical access to the rectifier '10, (b) they serve as heat conduction and radiation elements for controlling heat flow from the rectifier, (0) they serve as electrical connection means for interconnecting the two

electrical switches

18 and 20 to be described in connection with FIGS. 2 and 3, and (d) they serve to fix the position of the rectifier in relation to the rest of the switch arrangement in which they are used and thus assure mounting of the rectifier in only a predetermined safe manner.

One of the lead-in members 14 is connected to one electrical side of the rectifier 10 and is integral with two apertured terminal elements or

ears

22 and 24. The other lead-in member 16 is connected to the other side of the rectifier 10 and has a single apertured ear 26. As explained in connection with FIG. 2, each ear is oriented so that its aperture is positioned to register with a threaded aperture 28 (FIG. 2) of standard residental

type wall switches

18 and 20. Each of the lead-in

members

16 and 18 is also provided with an apperciable surface area both within and without the encapsulation holder 12 in order to reduce the temperature gradient within the holder to maximize heat collection (by the members) by conduction within the holder, and to maximize heat dissipation by radiation outside of the holder. To this end the

members

16 and 18 are preferably made of a good heat conductor, such as copper or aluminum, and have relatively large surface areas.

The encapsulation holder 12. is made of an electrically nonconductive material such as a resin that is solidifiable, in situ. While a number of different materials have proven satisfactory, the use of a self-extinguishing, flame retarding, encapsulating material is preferred. The most favorable formulation for such material consists substantially 10 parts by weight polyester resin 100 parts by weight powdered silica 15 parts by weight powdered chlorinated parafiin (for example, a non toxic, resinous, chlorinated paraffin known in the trade as chlorowax 70) 15 parts by weight antimony trioxide 1 to 2 parts 60% methyl ethyl keytone peroxide in dimethyl phthalate The relatively high percentages of the chlorinated paraffin and antimony trioxide render the material highly flame resistant. The chlorinated paraffin decomposes when heated to flame temperatures, giving oil free chlorine in an amount sufficient to extinguish the burning material within a few seconds after an externally applied flame is removed from it.

In order to maintain the encapsulation material in position prior to its solidification, the region to be filled with the encapsulated material is in part bounded by a flame resistant container 30 made of a nonconductive material, such as a rigid vinyl (polyvinyl chloride).

The structure of FIG. 1 will now be discussed in greater detail in connection with FIG. 2.

A complete switching arrangement, incorporating the module of FIG. 1, is principally comprised of the two single-pole, single-throw switches 18 and Zti. In order to distinguish the functions of the switch, the on-otf switch 18 may take the form of one of the conventional toggle type switches, while the other switch, the bright-dim switch 20, may take the form of a push type switch. The two switches are mounted on a standard three opening mounting strap 32. The on-off switch 18 is mounted and positioned by virtue of one opening 34 in the mounting strap 32, and other switch 20 is mounted and positioned relative to the first switch by virtue of the opening 36 on the end of the mounting strap 32 remote from the first opening 34. The encapsulated diode structure 12 is located in the space defined between the two switches 18 and 2t), and is fixed in position by virtue of three

bolts

38, 40, and 42 that lock the structure 12 to the switches. Connection of the entire switching arrangement for incandescent lamp control is provided by connections to two

bolts

42 and 44. In order to avoid possible consumer error in connecting the switching arrangement to the house wiring, the other two

bolts

38 and 40 are preferably of a non-removable type.

Operation of the switch of FIG. 2 will now be discussed in connection with FIG. 3. The switching arrangement is indicated schematically within the dash lines 46. It is noted from the circuit diagram of FIG. 3 that when the on-oii switch 18 is at its illustrated off position, the single-element incandescent lamp 48 to be controlled in illumination level is tie-energized. However, when the switch is moved to its on position, electric current from the alternating current power supply is able to flow through the switch 18, through the rectifier and then through the lamp 48 energizing it at approximately one-half its normal illumination level.

If, now, the bright-dim switch 20 is changed from the open position illustrated to a closed position, current flow to the lamp 4 8 is able to by-pass the rectifier 10, energizing the lamp for illumination at its full, normal power value. Thus, the switching arrangement enables the control of a standard single-element incandescent bulb to two appreciably different illumination levels through the use of, for the most part, conventional switching apparatus.

FIG. 4 illustrates a module similar to the one of FIG. 1, but incorporating a modification of the device of FIG. 1. In order to even further increase the rigidity of the overall arrangement described in connection with FIG. 2, the module 12a may desirably include an extra, dummy lead-in member 50. This member 50, like the other lead-in

members

14 and 16, has an integral appertured terminal element or ear 52 for making a thermally conductive connection to the first switch 18 (FIG. 2) by means of the other bolt 44 of the first switch 18. The increased rigidity of the assembly thus effected assures that the module 12a will be mounted by the uninitiated in only the desired, predetermined, safe manner and also assures even greater conduction from the encapsulated rectifier to portions of the arrangement remote from the rectifier. In the device of FIG. 4, a relatively large portion of the circuit areas of the lead-in

elements

14 and 16 is embedded in the encapsulated material and thus provides a lesser amount of thermal radiation from. the unit. However, adjacent surface portions of the encapsulated material reduce the exposed area of electrically conductive elements at the expense of only a relatively small reduction in thermal radiation. (The thermal radiation from the device is not appreciably reduced since heat conducted from the rectifier to the lead-in element surfaces is only a very short distance to the outer surface of the encapsulated material.)

In order to even further increase the thermal radiation efliciency of the portions of the device exposed to the ambient, the exposed device portions are preferably provided with a black matte surface. Thus, the lead-in

elements

14 and 16 of the device of FIG. 1 are there desirably provided with a black radiating surface, while in the device of FIG. 4 the surface portions of the encapsulating material adjacent to the lead-in members are provided with the blackened coating in this latter device.

FIG. 5 illustrates schematically a modification of the arrangement of FIG. 3 as applied to a motor speed control switching arrangement. While the discussion of the switching arrangement has, for convenience of explanation, been confined to the control over the illumination level of lamps, it is appreciated that the speed of an A.C.- D.C. type motor may also be controlled by the arrangement. In such an arrangement it is often desirable, when operating a motor at the reduced speed, to provide a continuous indication of this fact. Further, since neon pilot lamps are relatively inexpensive and convenient for such indication, it is desirable to use a neon bulb for the purpose. This has not heretofore been practicable in conventional resistance type motor speed control switches since haltf motor speed usually implies half voltage, or about 55 volts operation-and neon bulbs will not operate at such low voltages. Since speed control by means of the insertion of a rectifier in series with a motor results in the application of full voltage half the time (instead of half of the voltage full time, in the case of the usual resistance speed control), the neon lamp will operate when subjected to such half speed energization.

As illustrated in FIG. 5, an A.C.-D.C. type motor 62 is connected for control by the switching arrangement. A neon bulb 60 is connected in parallel with the rectifier 10. The rest of the circuit of FIG. 5 is generally the same as the circuit of FIG. 3.

When the speed control switch 20 allows full AC. voltage to pass to the motor 62, no voltage drop is experienced across the rectifier 10 or the neon lamp 60. Hence, the lamp 60 remains dark. However, when the speed control switch 20 is opened, to allow the motor 62 to run at approximately half speed, full voltage appears across the lamp 66 during each half cycle during which current flow to the motor is blocked by the rectifier 10. Thus, the neon lamp 6 glows during the operation of the motor 62 at reduced speed, providing an automatic continuous reminder of this (fact. The neon lamp 60 in such an arrangement is preferably encapsulated with the rectifier, but in a position protruding from the encapsulation so that its light is visible to an operator of the switch.

From the foregoing it is apparent that the mounting arrangement of the invention proves useful in combination with commonly available residential type switches for converting such switches to dual light intensity control by the uninitiated, and with the assurance that the resulting conversion will be substantially free of hazardous combinations.

What is claimed is:

1. Dual energization level control structure assembly, comprising: three terminal elements, two spaced-apart heat radiating members, and a half-wave rectifier, two of said terminal elements and one of said heat radiating members being integral, and the third of said terminal elements and the second of said heat radiating members being integral; and said rectifier being electrically connected between said two heat radiating members and in thermally conductive heat transfer relationship with respect to said members.

2. A dual intensity incandescent light dimming switch structure assembly of the kind capable of selectively energizing the light by alternating current and by direct current, from a single source of alternating current, comprising the combination of a half-wave diode and a generally rectangularly shaped enclosure therefor, said enclosure including at least two substantially parallel sidewall heat radiating members of the kind that exhibit a relatively high thermal conductivity, said diode being mounted between said two heat radiating members, with said members being mounted in thermally conductive contact with the ambient, whereby said enclosure is adapted to provide mechanical support for said diode and at the same time regulate the overall temperature of said enclosure and diode for limiting the maximum temperature of all portions of said structure during normal operation thereof.

3. Structural assembly of the kind adapted for mounting on a residential type light control switch, comprising: three terminal elements; two spaced apart, sheet metal heat radiating members; a half-wave rectifier; and rectifier encapsulation means; two of said terminal elements and one of said heat radiating members being integral, with one of the two terminal elements being adapted to be connected to a first single-pole, single-throw switch, and the second of the two terminal elements being adapted to be connected to a first terminal of a second single-pole, singlethrow switch; the third of said terminal elements and the second of said heat radiating members being integral, with said third terminal element being adapted to be connected to a second terminal of the first single-pole, single-throw switch; said half-wave rectifier being electrically connected between said two heat radiating members and in thermally conductive heat transfer relationship with respect to said members, said heat radiating members having generally parallel and oppositely facing heat radiating surfaces; said encapsulation means substantially completely filling the region defined between said heat radiating members and substantially completely encapsulating said rectifier; at least a portion of each of said heat radiating members having heat radiating surfaces in directions substantially perpendicular to other heat radiating surfaces thereof.

4. Dual intensity light controlling structural assembly of the kind adapted for mounting on a residential type light control switch, comprising: four terminal elements; three spaced apart, sheet metal heat radiating members; a half-wave rectifier; and rectifier encapsulation means; two of said terminal elements and one of said heat radiating members being integral, with one of the two terminal elements being adapted to be connected to a first singlepole, single-throw switch, and the second of the two terminal elements being adapted to be connected to a first terminal of a second singlepole, single-throw switch; a third of said terminal elements and a second of said heat radiating members being integral, with said third terminal element being adapted to be connected to a second terminal of the first single-pole, single-throw switch; and the fourth of said terminal elements and the third of said heat radiating members being integral, with said fourth terminal element being adapted to be connected to a second terminal of the second single-pole, single-throw switch; said half-wave rectifier being electrically connected between two of said heat radiating members and in thermally conductive heat transfer relationship with respect to said two members, said two heat radiating members having generally parallel and oppositely facing heat radiating surfaces; said encapsulation means substantially completely filling the region defined between all three of said heat radiating members and substantially completely encapsulating said rectifier; at least a portion of each of said heat radiating members having heat radiating surfaces in directions substantially perpendicular to other heat radiating surfaces thereof.

5. Dual intensity light controlling structural assembly of the kind adapted for mounting on a residential type light control switch, comprising: three terminal elements, two spaced apart, sheet metal heat radiating members, a diode, and recitifer encapsulation means; two of said terminal elements and one of said heat radiating members being integral, with one of the two terminal elements being adapted to be connected to a first single pole, single throw switch, and the second of the two terminal elements being adapted to be connected to a first terminal of a second single pole, single throw switch; the third of said terminal elements and the second of said heat radiating members being integral, with said third terminal element being adapted to be connected to a second terminal of the first single pole, single throw switch; said diode being electrically connected between said two heat radiating members and in thermally conductive heat transfer relationship with respect to said members, said heat radiating members having generally parallel and oppositely facing heat radiating surfaces in thermally conductive contact with the ambient; said encapsulation means substantially completely filling the region defined between said heat radiating members and substantially completely encapsulating said diode.

6. The structural assembly claimed in claim 5, wherein said encapsulation comprises a solidified in situ material consisting substantially of one hundred parts by weight polyester resin, one hundred parts by weight powdered silica, fifteen parts by Weight powdered chlorinated paraffin, fifteen parts by weight powdered antimony trioxide, and from one to two parts by weight sixty percent methyl ethyl keytone peroxide in dimethyl phthalate.

7. In combination: two single-pole, single-throw switches, each having two screw type terminals; a mounting bracket constructed to receive said switches in spacedapart, side by side relationship with respect to each other; and a light dimming structure removably mountable in a region between said two switches and mountable for support substantially only by at least one of the screw terminals of each of said switches; said structure including three terminal elements, two spaced-apart, sheet metal heat radiating members, a half-wave rectifier, and rectifier encapsulation means; two of said terminal elements and one of said heat radiating members being integral, with one of the two terminal elements being adapted to be connected to a terminal of the first of the single-pole, single-throw switches, and the second of the two terminal elements being adapted to be connected to a terminal of a second of the single-pole, single-throw switches; the third of said terminal elements and the second of said heat radiating members being integral, with said third terminal element being adapted to be connected to a second terminal of the first single-pole, single-throw switch; said rectifier being electrically connected between said two heat radiating members and in thermally conducted heat transfer relationship with respect to said members; said heat radiating members having generally parallel and oppositely facing heat radiating surfaces; said encapsulation means substantially completely filling the region defined between the said heat radiating mem bers and completely encapsulating said rectifier; at least a portion of each of said heat radiating members having heat radiating surfaces in direction substantially per-pendicular to other heat radiating surfaces thereof.

8. Dual energization level control structure, comprising: three terminal elements, two spaced-apart, sheet metal heat radiating members, a diode, gas discharge indicating means, and rectifier encapsulation means; two of said terminal elements and one of said heat radiating members being integral, with one of the two terminal elements being adapted to be connected to a first single-pole, single-throw switch, and the second of the two terminal elements being adapted to be connected to a first terminal of a second single-pole, single-throw switch; the third of said terminal elements and the second of sau'd heat radiating members being integral, with said third terminal element being adapted to be connected to a second terminal of the first single-pole, single-throw switch; said diode being electrically connected between said two heat radiating members and in thermally conductive heat transfer relationship with respect to said members, said heat radiating members having generally parallel and oppositely facing heat radiating surfaces in thermally conductive contact with the ambient; said indicating means being electrically connected between said heat radiating members and at least partially encapsulated by said encapsulating means; and said encapsulation means substantially completely filling the region defined between said heat radiating members and substantially completely encapsulating said diode.

9. Dual energization level control structure, comprising: three terminal elements, two spaced apart heat radiating members, gas discharge indicating means, and a halfwave rectifier, two of said terminal elements and one of said heat radiating members being integral, and the third of said terminal elements and the second of said heat radiating members being integral; said indicating means being electrically connected between said members, and said rectifier being electrically connected between said two heat radiating members and in thermally conductive heat transfer relationship with respect to said members.

10. Stntctural assembly useful in dual intensity incandescent light dimming switch assemblies, comprising a generally flat support bracket of the kind mountable within residential type metal lic wall outlet boxes; an electrical switch assembly mounted on said bracket; a crystal diode electrically connected to said switch assembly to enable said assembly to selectively provide alternating current and pulsating direct current therefrom; and a combined support and heat regulating enclosure for said diode; said enclosure being of a material exhibiting a relatively high thermal conductivity and having a black matte outer surface portion, with said portion facing said generally fiat support bracket for effecting radiative heat transfer from said enclosure to said bracket; said diode mounted in a snug fit against said enclosure for effecting a high thermal conductivity path between said diode and enclosure; whereby said enclosure is adapted to provide mechanical support for said diode and at the same time regulate the overall temperature of said enclosure and diode by the distribution of diode originated heat along said enclosure surface and along said generally flat support bracket and thereby limit the maximum temperature over all portions of said structure during normal operation thereof.

References Cited in the file of this patent UNITED STATES PATENTS 502,444 Moore Aug. 1, 1893 2,815,487 Kaufman Dec. 3, 1957 2,896,125 Morton July 21, 1959