US2162098A

US2162098A - Electric switch

Info

Publication number: US2162098A
Application number: US124982A
Authority: US
Inventors: Ira E Mccabe
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-06-10
Filing date: 1937-02-10
Publication date: 1939-06-13
Anticipated expiration: 1956-06-13

Description

June 13, 1939. l. E. M CABE ELECTRIC SWITCH Filed Feb. 10, 1937 INVENTOR IRA E. MCABE BYK A TTORNE Y.

Patented June 13, 1939 UNITED STATES PATENT OFFICE memo swrrcn Ira E. McCabe, Chicago, Ill. Application February 10, 1931, Serial No. 124,982

15 Claims. (01. zoo-13s This invention relates to improvements in electric switches, and more particularly to a switch so constructed that, while unaffected by changes in ambient temperature, it is responsive to the action of radiant energy emanating from a. source of light to open or close, and is a further development or continuation of the invention disclosed in the applicant's prior copending application Serial No. 94,352, filed August5, 1936.

It is an object to provide a. switch of the character described with a single thermal actuating element so constructed as to be unaflected by ambient temperature, and to provide means for concentrating the rays of light upon a portion of the thermal element.

The advantages of this improved construction over that disclosed in said prior copending application are obvious. The mass of material in the thermal element is reduced to a minimum and thereby reduces the amount of radiant energy required to operate the switch. When employed as a part of a fluid fuel burning device, the switch may be focused upon a bright spot of the flame and be unaffected by normal fluctuation in the flame. Also, the rays of light emanating from sources other than that upon which the switch is focused will be deflected from the thermal element.

With these and other objects in view reference is made to the accompanying sheet of drawings which illustrates preferred embodiments of this invention, with the understanding that minor changes may be made without departing from the scope thereof.

85 In the drawing:

Figure 1 is a view in side elevation of one form of this improved switch with parts broken away and partly 'in section.

Figure 2 is an enlarged view in transverse ver- 40 tlcal section taken on the line 2-2, Figure 1,

looking in the direction of the arrow.

Figure 3 is an enlarged detail view of the operating members of Figure 1 shown partly in top plan and partly in section.

Figure 4 is a view similar to Figure 2 of another form of this invention.

Figure 5 is an enlarged expanded detail fragmentary view of one form of thermal member.

Figure 6 is a similar view of another form of thermal member.

Figure 7 is a schematic view showing the wiring diagram of an oil burner control employing this improved switch.

Figure 8 is a view in vertical central section of another form of this invention, with parts shown in elevation.

Figure 9 is a detail plan view of a modifled form of coiled thermal member.

The preferred form of this improved switch is 5 shown in Figures 1, 2, 3 and 'l and includes a sealed container l preferably of glass having a well 2 at the unobstructed end thereof and two

electrodes

3 and 4 sealed in the opposite end thereof. The electrode 3 is arranged to nor- 10 mally enter and remain in contact with a glcbule of mercury 5 or other electrical conducting fluid contained in the well 2 when the switch is in the position shown in Figure 1. The electrode I is so formed that its free end extends in the axis 15 of the container l, as shown in Figure 3, and mounts thereon a concave reflector 8 and by an extension 1 from the free end a coiled thermal member 8, the termination of the outer convolution thereof carries a contact piece 9 adapted to 20 be engaged and withdrawn from the mercury 5 to make and break the circuit through the switch.

The thermal member 8 is in the form of a coil of bi-metallic or thermal metal, and, as shown in Figure 5, is so constructed that at approxi- 25 mately the middle of the coil the metals I 0 and II are relatively reversed, so that when subjected to changes in ambient temperature one section of the coil expands while the other section contracts, with the result that since the 30 inner convolution of the coil is secured upon the stationary or immovable extension I the relative position of the contact 9 upon the free end of the outer convolution remains unaffected by changes in ambient temperature. If desired to prevent the heat absorbed in one section being transmitted to the adjacent section, material I 2 of low heat transmission may be inserted between the two sections as shown in Figure 6.

The extension I from the electrode 4 supports the thermal coil I axially of the end of said electrode and of the container I with the entire inner section of the coil, before the change in the relations of the bi-metallic metals l0 and II, supported within the fleld of the rays reflected from the concave reflector 8. as shown in Figure 3. When the axis of the container l is in line with a source of light, the direct rays strike the entire surface of the coil 0 adjacent the source. so that one section will expand and the other contract as when affected by changes in ambient temperature with no operation of the switch. but the rays reflected by the concave reflector 6 upon the side of the coil I most distant from the source of light are concentrated upon the innermost section of the coil 8 and will cause the coil to expand or contract in accordance with the 'nature of the thermal material employed to open or close the circuit by the movement imparted to the contact 9. In the construction shown in Figures 1, 2 and 3, the coil 8 is so constructed as to expand and open the circuit as a result of the presence of a source of light when aligned therewith. Should a source of light be estabiished at an angle to the axis of the container I, such rays will not be concentrated upon the inner section of the coil but will be reflected by the concave reflector 8 either upon both sections with the same result as changes in ambient tem- 'perature or so as not to fall upon the coil.

In the switch shown in Figure 4, the contact 9 normally closes the circuit. The coil 8 is constructed as above described, but the sections employ metals offering different resistance to the passage of the electric current, whereby the continued passage of an electric current will cause a greater increase in temperature in the outer section of the coil to open the switch. The presence of a source of light in line with the axis of the container l before the opening of the circuit will concentrate the rays from the concave redoctor 6 upon the inner section of the coil to increase its temperature to that of the outer section and the circuit will continue to pass through the switch. If desired, an external magnetic force M may be employed to enact with an armature of magnetic metal l mounted upon the contact 9 so positioned that upon the opening of the switch the armature I0 is brought within the field of the magnetic force M and the resistance of the magnetic force must be overcome before the switch will close, so that the normal closing of the switch will be prevented, thereby necessitating a manual resetting such as the removal momentarily of the magnetic force M from the armature ID.

A practical application of this improved switch is illustrated in Figure '7 wherein a commercial form of the pressure type of oil burner O is shown installed with a commercial type of a domestic heating furnace F with the electrical control connection shown in diagram. The relay R, main switch MS and safety switch SS are preferably constructed and operated as disclosed in this applicant's prior Patent No. 2,024,697, dated December 1'7, 1935. When the burner O is idle the circuit from the commercial source is completed from wire L through the commercial boiler control B, safety switch SS and primary windings of the relay R to wire L. When the room: thermostat T, a commercial article, closes the circuit through the secondary winding of the relay R, it not only operates the relay to close the main switch MS to the burner motor, but it also closes the circuit through the heating element H of the safety switch, which will at the end of a predetermined time open the safety switch unless this part of the circuit is shunted out.

The form of this improved switch illustrated-in Figures 1, 2 and 3 is shown mounted in the draft pipe P of the oil burner with the axis of its container l in line with the burner flame and the switch is shown connected in the secondary circuit to shunt out the safety switch if the burner fluid is ignited within the said predetermined time. The switch in container I is normally open so that when the room thermostat T calls for heat by closing, the establishment of the burner flame creates a source of light which acts upon the improved switch to close its circuit and Shunt the heating element as long as the flame burns. The increase or decrease of ambient temperature within the draft pipe P within which the switch I is mounted does not affect its operation.

The form of this improved switch illustrated in Figure 4 is a further development of the employment of operating members oil'ering different electrical resistance to the passage of an electric current therethrough, as disclosed in this applicants prior co-pending application executed Decamber 30, 1936, Serial No. 118,719, flled January 2, 1937.

It is to be understood that in the form shown in Figure 2 while the thermal operating coil 8 includes two continuous sections, both sections are of material offering the same electrical resistance to the passage of an electrical current through the coil when the switch is closed but the response of the sections is reversed upon changes in temperature, that is, one contracts while the other expands and, as this invention contemplates constructing each section of similar materialshaving the same coefficient of expansion, the relation of the contact 9 to the mercury 5 will not be changed until the temperature of one section of the thermal coil 8 is affected by a change in temperature not imparted to the other section, as by concentrating the rays of light by the reflector 6 upon the inner section, as shown in Figure 3. The thermal coil 8 in the form shown in Figure 4 is formed of two sections of reverse responsiveness to changes in temperature and of materials having the same coefficient of expansion, but as this invention contemplates that the normal position of the switch is closed when the circuit is closed thereto and that the sections of the coil 8 offer different electrical resistance to the current passing therethrough when the circuit is established, it is desirable to place the greater electrical resistance in the outermost section of the coil so that the passage of the current will-increase the temperature of the outer section to a greater degree than that of the inner section to cause the switch to open unless the temperature of the inner section of the coil'8 is correspondingly increased, as by concentrating the rays of light by the reflector 6 upon the inner section.

Figure 8 illustrates the application of this invention to a different type of container than that shown in Figures 1 and 7. In this type of switch the axis of the container lies in a vertical plane when the switch is in operative position and the rays of visible light emanating from the source of light pass through the opposite walls of the bulb and are concentrated upon the thermal coil by the reflector 6a which is arranged upon the exterior of the side of the switch opposite the source of light. It is preferable to employ a container in which the contour of the bulb may be adapted to support the means for concentrating the rays of light and the reflector 6a may be a metal disc, as shown, formed to follow the curvature of the container or consist in coating the surface of the bulb with paint or metal leaf to form the concave reflector 811;

It has been found that the type of heating element shown in Figure 9 may be most advantageously employed in such a device wherein the rays of visible light are concentrated'thereon to normally fall upon the inner or central section of the coil. This improved coil 80 is composed of two equal lengths of thermal metal arranged to be oppositely responsive to changes in temperature which are joined to each other by overlapping the adjacent ends to oifset the inner convolution of the outer coil and space it apart from theadjacent inner convolution, as shown. This construction makes the heating element more sensitive in operation and does not require the same precision in mounting the coil 8 shown in Figures 2, 3 and 4, because such reflected rays as may overlap the inner coil will fall in the space between the sections and not affect the outer section.

It has also been proven by actual test that coils such as 8a may be constructed of thermal metal that in weight need not exceed one onethousandth of an ounce. These switches, because of the small mass of, material to be afiected by the reflected rays, may be made highly sensitive and responsive to small sources of light,- such as that emanating from a gas burner pilot flame. Furthermore, switches of this construction have been found to operate satisfactorily at distances from the light source greater than possible with switches constructed in accordance with the applicants prior co-pending application Serial No. 94,352, filed August 5, 1936.

The use of light sensitive switches, particularly in control systems for the automatic control of fluid fuel burners is well known to the applicant, as will be evident from the disclosure made in his prior Patent No. 1,745,178, granted January 28, 1930, upon an application flied December 6, 1926.

The switch of the type shown in this aforementioned patent requires a larger space and a greater amount-of energy for operation, although operating from light, than does the switch disclosed in this invention. It is also more expensive to build and more fragile than this The adaptation of this improved switch to the applicant's previous invention will greatly increase its usefulness and scope.

It is also to be understood that the use of this invention is not restricted to a fluid fuel burner control herein disclosed, as this disclosure is but one of many uses. It is obvious that this improved switch niay be employed wherever it is desirable to use a switch responsive to radiant energy without being afl'ected by changes in ambient temperature.

What I claim is:

1. A thermally actuated switch responsive to the radiant energy of light including a stationary electrode, a movable electrode, a thermal operating coil forming a part of the movable electrode for making and breaking contactwith the flxed electrode, said operating coil being formed in two uninterrupted continuous sections oppositely responsive to temperature changes whereby the relation between the electrodes is unaffected by changes in ambient temperature, and means for concentrating rays of light upon one section to operate the switch.

2. The structure of claim 1 wherein the switch is mounted within a transparent container having the portion of the movable electrode supporting the thermal coil and the thermal coil arranged axially of the container.

3. The structure of claim 1 wherein the switch is mounted within a transparent container having the portion of the movable electrode supporting the thermal coil and the thermal coil arranged axially of the container, and the means for concentrating the rays of light including a concave reflector.

4. The structure of claim 1 wherein the switch is mounted within a transparent container having the portion of the movable electrode supporting'the thermal coil and the thermal coil arranged axially of the container, and the means for concentrating the rays of light including a. concave reflector and wherein said reflector is mounted upon the axial portion of the movable electrode. v

5. The structure of claim 1 wherein the switch is mounted within a transparent container having the portion of the movable electrode supporting the thermal coilv and the thermal coil arranged axially of the container, and the means for concentrating the rays of light including a concave reflector and wherein said reflector is mounted upon the axial portion of the movable electrode and so arranged that only one section of the oppositely responsive thermal sections lies wholly within the held of the rays of light reflected by the concave reflector.

6. In a light responsive switch, an operating member therefor including a coil of bi-metallic or-thermally responsive metal formed in two uninterrupted continuous sections which are oppositely responsive to changes in temperature and Y each possesses the same coefllcient of expansion whereby the operationis unaflected by changes in ambient temperature.

7. The structure of claim 6 wherein the sections of the coil oifer diiferent electrical resistance to the passage of an electrical current therethrough, whereby upon establishment of the circuit through the switch the section of the coil oil'ering the greatest resistance will respond to the difference in temperature between the two sections to operate the switch.

8. In a light responsive switch, an operating rim switchrmember therefor including a coil of bi-metalllc or thefmallyresponsivemetal formed in two uninterrupted continuous sections which are oppositely responsive to changes in temperature and each s the same coeflicient of expansion whereby the operation is unaflected by changes in ambient temperature, wherein the sections of the coil offer different electrical resistance to the passage of an electrical current therethrough, whereby upon establishment of the circuit through the switch the section of the coil offering the greatest resistance will respond to the difference in temperature between the two sections to operate the switch, and means for concentrating rays of light upon the section of the coil offering the least electrical resistance to the passage of an electrical current therethrough whereby its temperature is raised to equal that of the other section and cause the thermal coil to remain in'inoperative relation to the switch.

9. The structure of claim 8 wherein said last named means includes a concave reflector axial-- 1y arranged in relation to the thermal coil and upon the side thereof most distant from the source of light.

10. The structure of claim 8 wherein an armature is mounted upon a part of said operating means and a magnetic force arranged exterior ,of said switch adapted to hold said armature concave reflector supported upon the electrode carrying the thermal coil.

14. The structure of claim 11 wherein the means to concentrate the rays of light includes a concave reflector supported exteriorly of the container.

15. The structure of claim 11 wherein the means to concentrate the rays of light includes a concave reflector supported exteriorly of the container and supported upon the wall thereof. 10

IRA E. MCCABE.