US2190303A - Electric switch - Google Patents

Description

Feb. 13, 1940. c. WANTZ ELECTRIC SWITCH Original Filed July 5, 1934 Izwzwiia Cmmzzw @121? I By fi/uzwu,

Patented F eb. 13, 1940 UNITED STATES ELECTRIC SWITCH Clarence Wantz, Milwaukee, Wis., assignor to Milwaukee Gas Specialty Company, Milwaukee, Wis., a corporation of Wisconsin Original application July 5, 1934, Serial No.

733,722. 1936, Serial No. 83,481

7 Claims.

This invention relates to thermo-electric safety switches, and more particularly to thermally operated electric switches for controlling the flow of fuel to a burner or heater.

The present invention is a division of my copending application, Serial No. 733,722, filed July 5, 1934, and is directed particularly to the electric switch construction for controlling the operation of the burner.

In the ordinary type of heater, the fuel supplied to the burner is controlled by a valve which is operable to vary the quantity of fuel flowing to the line in accordance with the temperature sensings of a thermostat disposed in the room or enclosure being heated. In order to prevent escape of unburned fuel when the thermostat opens the valve in the fuel supply line at times when the pilot burner is not ignited, it has become customary to provide some means responsive to the heat of the pilot flame for mechanically closing the valve, or opening the circuit between the room thermostat and the valve to provide for release of the valve to closed position.

The present invention, in its preferred embodiment, is directed to a structure wherein the fuel supply valve is of the normally closed solenoid type, and is electrically connected to a room thermostat,'being controlled thereby. The pilot lgniter for the heater burner is provided with means for supporting a thermocouple, whereby during ignition ofthe pilot burner an electric current is generated in the thermocouple circuit, which circuit is utilized to maintain the fuel supply valve circuit operable. Upon extinguishment of the pilot flame, the thermocouple circuit juncture at the pilot flame igniter immediately cools and current ceases to flow in this circuit. This failure of current in the thermocouple circuit operates a suitably constructed thermoelectric switch to open the fuel supply valve circuit and the fuel supply valve closes, or remains closed, preventing the escape of unburned fuel at the main burner.

A primary object attained by the present invention is the provision of electrical means for controlling the operating circuit of a fuel supply valve, which requires no power to maintain it in operation, and which is substantially immediately responsive to extinguishment of the pilot flame for opening the operating circuit of the fuel supply valve.

Another object of the present invention is the provision of a compact switch structure for use in connection with the control of the operating circuit of the fuel supply valve by the pilot flame.

sition within a room or other enclosure that may Divided and this application June 4,

A further advantage of the present invention is the adaptability of the present construction to heating installations now in use, since it can be readily incorporated in such installationswith little or no change.

Another feature of the present invention is the provision of a thermo-electric safety switch structure which is simple in design, readily assembled, and which can be installed in any position adjacent the burner or fuel supply valve structure, thereby eliminating any mechanical or structural restrictions to its use, which is not the case when mechanical connections or the like are employed.

Other objects and advantages of the present invention will appear more fully from the following detailed description, which, taken in conjunction with the accompanying drawing, will disclose to those skilled in the art the construction and operaion of a preferred form of the present invention.

In the drawing:

Figure 1 is a diagrammatic elevational view of a thermo-electric safety switch and associated structure employed in connection with a heating burner or the like;

Figure 2 is a sectional elevational view through a side wall of the thermo-electric switch housing, illustrating the details of the switch structure;

Figure 3 is a front elevational view of the switch or relay housing;

Figure 4 is a view of the switch mechanism with the cover to the housing removed; and

Figure 5 is a perspective view of the armature and its associated contact spring.

Referring now in detail to the drawing, in Figure 1 I have shown a main burner, indicated at "I, which is provided with fuel by means of the fuel supply manifold l2. A normally closed solenoid actuated fuel control valve 13 is interposed in the fuel supply line, preferably anterior to a manually controlled gas cock I 4, which is adapted to remain open during normal operation of the burner. The burner I0 is mounted within a housing l5 which is preferably inserted into the base of the furnace or other heating appliance to which the burner is applied, and is provided with a pilot flame burner indicated generally at 86 which is supplied with fuel through conduit I! connected through a regulating valve 48' to the gas manifold l2 at It.

The solenoid actuated valve I3 is connected through conductors 20 and 22 to a thermostat 23, of any desired type, which is mounted in nobe remotely disposed with respect to the heating appliance, and which is being heated by the burner I0. The source of power for the conductors 20 and 22 comes from the line conductors 24, which, are connected to, the primary 25 of transformer 26. The secondary 21 of the transformer is connected, at one side, to the conductor 22, and at its opopsite side is connected, through conductor 28, to the terminal 30 of a thermo-electric switch structure indicated generally at 32.

The burner I8 is provided with a thermocouple indicated at 33, the burner I8 being supported by brackets 34 upon the top of the box I5. A pair of conduits lead from the thermocouple within the conductor flexible cable 35 to the switch housing 32. r This switch housing 32 may be mounted in any desired position adjacent to the burner I0 or the solenoid valve I3, and because of the flexible conductors 35, 28 and the conductor 36, which leads from the switch housing 32 to the opposite terminal of the valve I3, there are no mechanical or structural limitations as to the particular disposition of this switch housing.

Referring now in detail to the thermo-electric switch shown in Figures 2 to 5, inclusive, the housing 32 is substantially cup-shaped in form, and is provided with integral ear portions I0 and 12, which, as shown in Figure 2, are adapted to receive suitable bolts I3 for securing the housing to a supporting wall I4 or the like. The housing 32 is shown as formed of insulating material and is provided with a cover member I5 carrying the terminals 30, 18 and TI. The cover is secured to the housing 32 by means of a pair of screw members 18, which thread into suitably tapped openings I9 formed in offset portions of the housing 32.

Mounted within the housing 32 and supported by the cover I5, is a bracket member 82,heldin position by means of the terminal member "and a bracket supporting screw 83. Supported on the inner extending portion of the bracket 82 is a U-shaped magnetic frame 84, held in position by means of a second bracket 85 secured in position upon the bracket 82 by means of bolts 88.

Mounted upon each of the arms of the U-shaped magnetic frame 84 is a-coil 81, the coils thereof being connected, through suitable conductors, to the junction of the thermocouple circuit. Thus, when this thermocouple junction is heated by the pilot flame I 9, current will pass through the conductors, energizing the coils 81 and producing a magnetic flux at the ends of the legs of frame 84. A suitable bracket member, indicated at 90, is

- mounted upon the bracket 82, preferably formed integral with the bracket 85, and carries a pivot 92 adapted to support a reversely rolled bearing portion 93- of a keeper or armature frame 94 which supports the armature bar 95, the bar 95 being movable into position over the ends of the U-shaped frame 84 to close or shorten the magnetic circuit. Mounted upon the armature frame 94 is a contact spring member, indicated in its entirety at 96, and having a contact arm 91 extending therefrom and provided with a contact point 98 at the free end thereof, and aspring arm 99 extending parallel thereto and bent downwardly with respect to the arm 91, the arm 99 being provided on its lower surface withan insulate ing block member I00.

The coils 81, together with the pivoted arm 95, provide a conventional relay of a very sensitive type, operable upon an electrical potential of less than five milli'volts. This extreme sensitivity, in the present instance, is obtained by using Perm aloy, "Hypernic, or other similar materials of a very low magnetic reluctance for the magnetic frame 84 and the magnetic keeper or armature 85-, with the faces thereof ground so that there is a minimum air gap therebetween. However, inas- 5 much as the conductors are of a very low resistance from the thermocouple to the switch, and the frame is of low magnetic reluctance, a relatively intense magnetic field is set up therein when the thermocouple junction is heated by the pilot flame I9.

The contact I8, shown in Figure 2, is provided with an extending portion I02, which is threaded to receive an adjustable contact I03, positioned above the contact arm 91'. Similarly the contact 30 is provided with an extending portion I04 having the adjustable contact I05 threaded therein, and also provided with an adjustable stop I08 which is adapted to have engagement with the insulating plate I00 carried by the spring member 99. The contact members I03 and I05 have contact portions selectively engageable by the contact stud 98 carried by the arm 91.

In normal open position of the switch, the contact arm 9'! is in the position shown in Figure 3, with the contact stud 98 engaging the contact I03 due to the spring tension of the arm 99 bearing against the top of the adjustable stud I06. Since the terminal I6 is not connected in the electrical circuit shown in Figure 1, there is no circuit extending through the solenoid valve I3, and the valve is thereby rendered inoperative. This position of the switch occurs whenever the pilot flame is unignited or accidentally extinguished.

Upon ignition of the pilot flame, the heating of 35 the welded junction at the thermocouple produces current flow through suitable conductors which energize the coils 81. Energization of these coils creates a relatively intense magnetic field in the frame 84, and draws the magnetic bar 95 downwardly into engagement with the ends thereof, depending upon the adjustment of the contact I05. This downward movement results in move-. ment of the contact stud 98 away from the contact I03 and into engagementwith the contact I05. Inasmuch as the terminal 11 is connected to the bracket 82 supporting the magnetic frame, a circuit is completed extending from the terminal 11 through the frame 84 and keeper 95 to the contact arm 96, and thence through contact stud 98 to contact terminal I05 and thence to terminal 30.

This closes the circuit through the secondary 21 of the transformer 28 and induces current flow through the, thermostat 23 and the solenoid valve I3 to control the valve. Thus the valve, during energization of the coils 81 by reason of the heat of the flame I9 upon the welded junction of the thermocouple, is directly responsive to the temperature sensings of the thermostat 28, and is controlled thereby, thus varying the quantity of fuel admitted to the burner I 0 in accordance with the temperature within the room in which the thermostat23 is disposed.

However, if the flame I9 is accidentally extinguished, the thermocouple junction rapidly cools": and current flow through the conductors decreases to an extent whereby the spring member 99 is sufiicient to move the keeper 95 away from the frame 84, and consequently to disengage contact stud 98 from contact I05, opening the circuit for the valve I3, and allowing the valve to close under influence of a spring or the like. If de- .sired, the contact I6 may be employed when it is practical to use a multiplicity of contacts in order to control much more complicated circuits than in the present instance. In such cases the engagement of the contact stud 98 with the contact I03 would effect closing of another circuit as the first circuit was opened. It is thus apparent that I have provided a thermo-electric safety switch which will serve to keep the circuit through the fuel supply valve closed whenever the pilot flame is burning, but immediately upon extinguishment of the pilot flame will open the relay to break the circuit through the fuel supply valve and to effect closing of the valve.

It is apparent that the underlying principles of the present invention may be varied considerably in scope and the present construction is intended to serve only as an illustration of a preferredembodiment of the invention. I do not intend to be limited to the construction disclosed, except as defined by the scope and spirit of the appended claims.

I claim:

1. A magnetic switch structure comprising a switch housing, a U-shaped frame in said housing, energizing coils mounted on the legs of said frame, an armature pivoted adjacent the end of one of said legs and extending across the top of said frame, a resilient forked extending contact member secured to said armature, a contact at the end of one fork of said member, an insulating pad at the end of the other fork of said member, said last-named fork being bent downwardly below the plane of the contact-carrying fork, and stop means engaged by said pad for normally holding said contact out of operative position I when said coils are unenergized.

2. A. magnetic switch structure including a pair of spaced, contacts, a stop member having one surface lying in the plane of the contact surface of one of said contacts, a magnetic coil, 8. pivoted armature extending across the end of said coil and carrying a bifurcated plate member having the ends thereof extending into the space between said contacts, one of said ends being disposed in a lower plane than the other of said ends and engaging said stop surface to hold the other of said ends out of engagement with said coplanar contact surface when said armature is in unattracted position.

3. In combination, a U-shaped frame having parallel extending legs, energizing coils about each of said less, an armature pivoted at one side of said frame and extending over the ends of said legs, a plate member secured to the upper surface of said armature and having two parallel extending resilient tongue portions, a contact carried at the end of one of said tongue portions, a terminal adapted to be engaged by said contact when said armature is in attracted position on the ends of said legs, and stop means engaged by the end of the other tongue portion whereby upon deenergizatlon of said coils said other tongue portion raises said armature out of attracted position and disengages said contact from said terminal.

4. In combination, a relay comprising an electromagnetic frame, an armature pivoted at one side thereof, a bifurcated arm on said armature, one end of said arm carrying a contact, the other end of said arm being bent out of the plane of said first end and carrying an insulated pad, and stop means engaged by said pad for normally holding said armature away from said frame.

5. In combination, a magnetic frame, a pivoted armature movable towards and away from one end of said frame, a keeper for said armature having a resilient projecting bifurcated portion, one end thereof carrying a contact and the adjacent end thereof carrying insulating stop means, an adjustable contact adapted to be engaged by said keeper contact when said armature is in attracted position, and a stop engaged by said stop means for resiliently urging said contacts out of engagement when said armature is deenergized.

6. An armature for a relay of the class described comprising a pivoted keeper member having a rolled end hinge portion and having normally extending tabs for retaining an armature block in fixed position on the under surface thereof, and a. bifurcated contact arm secured to the upper surface of said keeper and extending laterally thereof, oneflend of said arm carrying a fixed contact and the other end of said arm being bent out of the plane of said first end and carrying an insulated stop pad.

7. In combination, in a switch housing, a magnet frame having laterally spaced pole faces, energizing means therefor, an armature extending transversely over both said faces and hinged at one side of said frame, a bracket extending normal to said armature and spaced laterally of said frame on the side thereof opposite the armature hinge, a contact and an adjustable stop spaced laterally on said bracket and disposed substantially coplanar with said pole faces, a pair of laterally spaced arms on said armature, one carrying a contact adapted to engage. said bracket contact upon energization of said armature, and the other being vertically oflset and carrying insulated stop engaging means normally holding said contact out of engagement.

: CLARENCE WANTZ.

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