US2292178A - Electric switch - Google Patents

Description

Aug. 4, 1942. F. H. TRAVERS I ELECTRIC SWITCH 2 Sheets-Sheet l Filed June '7, 1939 Aug. 4, 1942. RH. TRAVERS 2,292,178

ELECTRIC SWITCH Filed June 7, 1939 2 Sheets-Sheet 2 Invent, or: Fred |'l. Travers.

His Attornlg.

Patented Aug. 4, 1942 ELECTRIC SWITCH Fred H. Travers, New Britain, Conn., assignor to General Electric Company, a corporation of New York Application June 7, 1939, Serial No. 277,824

5 Claims.

The present invention relates to electric switches, and more particularly to an improved construction and arrangement in electric switches of the type used for controlling the heat output of multiple element heater units.

It is an object of this invention to provide a switch construction having a simplied contact arrangement for controlling the connections of a multiple element heater unit with a power supply to provide a plurality of different heat outputs and to completely isolate the heater unit from the power supply when the switch is in open circuit position.

Another object of this invention is to provide an improved circuit controller including interconnected switches for controlling the energization of a plurality of heater units and for limiting the maximum power which may be consumed by the heater units associated with the interconnected switches.

Further objects and advantages of the present invention will become apparent as the following description proceeds, reference being had to the accompanying drawings, in which Fig. l is a plan view of a circuit controller embodying the invention; Fig. 2 is an elevational view, partially broken away, of the controller of Fig. 1; Fig. 3 is an exploded view in perspective showing one of the positioning and actuating mechanisms employed in the controller of Fig. l; Fig. 4 is a sectional view taken along the lines 4 4 of Fig. 2, but with the rotatable contact structure displaced 90 degrees in a clockwise direction as viewed in Fig. l, and Figs. 5 to 13 are schematic diagrams showing the circuit controller of Figs.

l to 4 in a number of its operative positions and illustrating the condition of the heater circuits associated therewith.

In the drawings I have shown a circuit controller embodying my invention as comprising f the base by suitable bolts I6. Since both of the switches I and Il are of identical construction only one will be described and corresponding parts will be designated by the same numerals.

An operating spindle Il passes through an The strap is secured to 1 Cil opening in the mounting strap I and has its lower end received in a suitable bearing sleeve I5 secured to the base at the center of the recess I3. The spindle is provided at its outer end with an operating knob I9 which is secured thereto in any suitable manner. The movable contacts of the switch are secured to a disk of insulating material which is assembled on a langed sleeve 2I with an insulating washer 22, a metal spacing washer 22a and a driving member 23. This disk assembly is mounted on the spindle for rotation relative thereto.

In the drawings I have shown a positioning means for the disk assembly as comprising a member 24 secured to the lower face of the mounting strap and having four equally spaced projections 25. A specially shaped pawl member 26 surrounds the spindle and has an eccentric portion arranged to lie between a pair of the projections 25. The pawl 26 has a depending lug 2l which is received in an elongated opening 28 in the disk driving member 23, so that the disk is retained against rotation with respect to the switch body as long as the pawl member 26 engages one of the projections of the member 24.. In order to release the pawl, a cam member 29 fixed eccentrically to the spindle engages the walls of an opening in the pawl 26, so that rotation of the spindle is effective to move the pawl transversely of the axis of the spindle and release it from the projections 25.

The driving connection between the disk assembly and the spindle is accomplished by a double helical spring 30 which is retained between a pair of metal plates 3l and 32 xed to the spindle. A bearing washer 3Ia of insulating material is assembled on the spindle between the upper surface of the plates 3l and the disk 20 and a metal spacing washer 32a is placed on the spindle between the plate 32 and the upper ange of the bearing sleeve I8 to properly position the spindle assembly relative to the body and stationary contacts. A pair of axially extending arms 33 and 34, formed integrally with the plate 3l and the driving member 23 respectively, are positioned :between a pair of spaced laterally extending spring arms 35 formed on the opposite ends of the helical spring. With this construction it is seen that the arm 33 is secured to the spindle and the arm 34 to the disk assembly with the spring 30 forming the driving connection between these arms. The member 23 is positioned on the opposite side of the disk 32 from the plate 3l so that the arm 34 passes through an opening 36 in the disk and engages the walls thereof to form a driving connection with the disk. When the spindle is rotated the arm 33 moves one arm of the spring while the other arm of the spring is retained by the depending arm 34 on the driving member 23. When the spindle has been moved the required amount, which in the present case is approximately 90 degrees, the pawl 28 is released from the projections 25 and the driving member and disk are free to rotate under the influence of the spring arm having engagement with the arm 34 until the pawl 26 engages the next projection on the member 24.

With the construction thus far described, it is apparent that the disk 20 may be moved with a snap action to four different equally spaced positions by rotation of the operating knob I9. In accordance with the present invention a novel arrangement of iixed and movable contacts is also provided for accomplishing the desired electrical connections between the heater units and the supply lines. Each switch is provided with two sets of fixed contacts, one of which is arranged to engage the upper surface of the disk and the other of which is arranged to engage the lower surface. In the construction illustrated the upper set includes three contacts 31, 33 and 38 and the lower set includes four contacts designated by the numerals 40-43, inclusive. Each contact is provided with a terminal portion which is secured to the face of the switch body by a flanged internally threaded sleeve 44 which receives a binding screw 45 for securing circuit wires thereto. Openings 46 formed in the base l2 adjacent the terminal portions of the fixed contacts permit top wiring of the switches; keep the wires within the contines of the base and provide a strain relief for the connections. The upper surface of the disk is provided with arcuate contacts 41 and 48 and the lower surface of the disk is provided with arcuate contacts 49 and 50. The spacing of the fixed contacts and the angular extent and spacing of the arcuate contacts which are important features of the present invention can best be explained in connection with a heater circuit with which the controller of the present invention may be used to particular advantage. This circuit is shown with the switches l and in various circuit-controlling positions in the schematic diagrams of Figs. to 13, inclusive. In order to simplify these iigures the arcuate contacts secured to the lower face of the disk have been shown on a separate disk 20a, and the portions of the circuit which carry current in each of these diagrams are shown in heavier lines, so that the circuit changes accomplished by the switches are readily observed by an inspection of the drawings.

In the diagrams the switches l!! and 2| of the circuit controller are shown connected to control the energization of a pair of heater units designated generally by numerals 5| and 52 from a pair of supply lines 53 and 54. Each of the heater units comprises a pair of resistance elements 55 and 56 having a common terminal at one end and separate terminals at the other end. Heater units of this type may be energized to supply a high, a medium or a low heat output by selectively connecting the heater terminals to a single supply voltage. In the drawings I have shown the heater unit 5| and the heater unit 52 connected to the switches |53 and respectively, in the following manner: The common terminal is connected to contact 31 of the upper set of iixed contacts, one of the separate terminals is connected to the contact 39 of the upper set and to contact 43 of the lower set, and the other separate terminal is connected to contact 42 of the lower set. The contact 40 of the lower set of fixed contacts of the switch I0 is connected directly to the supply line 54, while the contact 40 of switch is connected directly to supply line 53. The contact 38 of the upper set of fixed contacts of each switch is connected by conductor 51 to the fixed Contact 4| of the lower set of xed contacts of the other switch. The fixed contact 4| is positioned adjacent the contacts 40 and may be connected thereto by one of the arcuate contacts 48 or 50 in all but the high heat position of the switch so that power from one of the supply lines is supplied to each switch through a pair of angularly spaced contacts on the other switch except when the other switch is in its high heat position. The advantage of this arrangement will become apparent as the description of the circuit proceeds.

In Fig. 5 both of the switches are in their oi" position and both of the heating units 5| and 52 are completely isolated from the supply lines. In Fig. 6 the switch has been rotated 90 degrees in a clockwise direction to its high heat position. With the switches in this position, a circuit is completed from supply line 53 to iixed contact 38 of switch through fixed contact 40 of switch arcuate contact 49, the fixed terminals 42 and 43, the resistor elements 55 and 55 of heater unit 52, xed Contact 31, and arcuate contact 48 to ixed terminals 38 of the switch A circuit is completed from contact 38 to the other supply line 54 through conductor 51, angularly spaced fixed contacts 40 and 4| and the arcuate contact 50 of the switch I0. With the switch in its high heat position, as shown in this figure, it is seen that it would be impossible to energize the heating unit 5| associated with the switch I0 since the fixed contact 4| of the switch is insulated from the fixed contact 4|) of that switch which is the only contact of the two switches connected directly to the supply line 53. In Fig. 7 the switch has been rotated 90 degrees in a clockwise direction to its medium heat position. In this position the element 56 of heater unit 52 is energized through a circuit which is apparent from the drawings. In Fig. 8 the switch has been given another degrees turn in a clockwise direction to its low heat position in which the elements 55 and 56 of its associated heater elements 52 are connected in series across the supply lines 53 and 54. From the preceding description it is seen that the fixed contact 38 which supplies power selectivity to the upper contacts 31 and 39 through the arcuate contacts 41 and 48 is positioned between contacts 31 and 39 and nearer to the contact 31 so that power may be supplied to the common terminal of the heater unit in two positions of the switchy namely, the high and medium heat positions, while the fixed contact 39 is connected to the contact 38 only in the low heat position of the switch.

In Fig. 9 the switch 0 has been rotated 90 degrees in a clockwise direction to its high heat position and switch has been rotated in a counterclockwise direction to its medium heat position. With the switches in this posiiton it is seen that the elements of the unit 5| are con nected to the line through a circuit including the spaced contacts 40 and 4| of switch which are bridged in the medium heat position of the switch by arcuate Contact 49. With the switch ID in its high heat position, however, the heater unit 52 is not energized even though the switch Il is in its medium heat position since, as previously pointed out, only one power supply line is connected directly to each switch andthe other power supply line is connected thereto through a pair of spaced contacts on the other switch. In this case, the spaced contacts 40 and 4I of the switch ID are not bridged by either` of the arcuate contacts 49 or 50. In Fig. 10 the switch I is in its low heat position and the switch Il in its off position. Here the condition of the heater units 5| and 52 is exactly the reverse of that described in connection with Fig. 7. In Fig. 11 both switches are in the medium heat position and both heater units are energized, the circuit for each one being completed through the angularly spaced contacts 40 and 4I of the switch controlling the other heater unit; the fixed contacts being bridged by arcuate contact 49. Fig. 12 shows the switch Il) in its high heat position and the switch Il in its open circuit position, which is the opposite of that shown in Fig. 6. Fig. 13 shows both switches in their high heat positions and as is clear from this diagram neither of the heater units is energized since the spaced contacts 40 and 4I of both switches are insulated from each other, so as to disable the heater unit associated with the other switch.

In the preceding description the switches have been described as having two arcuate contacts 41 and 48 on the upper face of the disk 20. However, it is clear from an inspection of the diagram that the switches are operative if this contact is made in one piece. With a single arcuate contact `on the upper face of the disk there is a tendency for the leading edge of the arcuate contact on the upper surface of the disk to make contact with the fixed contact 39 before the arc is extinguished between the arcuate contact 49 and the xed contact 40 when the switch is rotated from medium to low heat position; thus resulting in a momentary short circuit. To avoid this the upper arcuate contact is made in two sections 41 and 48 of unequal length so that the power supply line 54 which is indirectly connected to the xed terminal 38 of the switch Il is not connected to the arcuate contact 48 in the medium" heat position of the switch Il and xed contact 39 is offset slightly in a counterclockwise direction to engage the arcuate contact 41 in the low heat position of the switch.

While in the preceding description I have disclosed a circuit controller comprising two interconnected switches for controlling a pair of plural element heater units, it is apparent that the simplied construction of the switches may also be used to advantage for controlling a single three-heat unit. For example, if switch l0 were to be used for controlling a single unit, the interconnecting conductors 51 would `be omitted and the fixed contact 38 would be connected directly to the other supply line 53. In this case the xed contact 4| and the arcuate contact 50 would not be used.

With the circuit controller of the present invention the switch structures employed are simple and easily manufactured using fixed contacts of uniform construction and arcuate contacts positioned on the disk to provide the selective connection to the heater units with the power supply lines. The separate arcuate contact 50 provides means for energizing one of the interconnected switches when the other is in its off position, and the larrangement of the fixed contacts is such that the heater unit is completely isolated from the power supply line when the switch with which it is associated is in its open circuit position. The spaced contacts of one switch which usually supply power from one of the supply lines to the other switch are open circuited when the one switch is in its high heat position so that it is impossible to draw more than a predetermined maximum amount of power from the supply lines even though the switches of both units are in the closed circuit position. This feature is particularly desirable in control- 1ers designed for use with hot plates which are plugged into convenience outlets of house wiring systems.

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

1. An electric circuit controller for controlling the energization of a pair of two element heater units from a pair of supply lines, comprising an electric switch having an open circuit position and three closed circuit positions associated with each of the heater units for controlling the heat output thereof, each of said switches having a rotatable contact structure including a support of insulating material having arcuate contact means mounted on one face thereof and a pair of arcuate contacts of different angular extent mounted in insulated relation on the other face thereof, a rst stationary contact on one of said switches connected to one power supply line and arranged to engage the arcuate contact of greater angular extent on said other face of said supporti in the three closed circuit positions thereof, a second stationary contact of said one switch having engagement with the arcuate contact means on said one face of said support in the three closed circuit positions of said one switch, said second stationary contact being connected to the other supply line through a pair of angularly spaced stationary contacts of the other of said switches, said angularly spaced stationary contacts being electrically connected by the arcuate Contact of lesser extent of said other switch in the open circuit position of said other switch and being electrically connected by the other of the pair of arcuate contacts of said other switch in all but one closed circuit position of said other switch whereby the heating unit with which said one switch is associated may be energized only through cooperating contacts of said other switch when said other switch is in any but said one closed circuit position.

2. A circuit controlling device for controlling the energization of a pair of two element heater units having a plurality of terminals from a pair of supply lines, comprising an electric switch associated with each of the heater units for controlling the heat output thereof, each of said switches having a rst fixed Contact for direct connection with a different one of the power supply lines, a second xed contact and a third xed contact, the third fixed contact of each of said switches being electrically connected to the second Xed contact of the other of said switches, other xed contacts on each of said switches for connection with the terminals of its associated heater unit, each of said switches having a rotatable contact structure including a plurality of arcuate shaped contacts for connecting selectively said other xed contacts with said rst and third xed contacts, and a separate arcuate contact on each of said switches for bridging said first and second fixed contacts when said switches are in their open circuit positions whereby the heater unit associated with either switch may be energized when the other switch is in its open circuit position.

3. A circuit controlling device for controlling the energization of a pair of two element heater units having a plurality of terminals from a pair of supply lines, comprising an electric switch including a rotatable contact structure having a plurality of circuit controlling positions associated with each of the heater units for connecting the elements thereof to the supply lines for different heat outputs, one of said switches having a plurality of xed contacts connected to the terminals of its associated heater unit, a fixed contact connected directly to one power supply line and another xed contact connected to the other of the supply lines through a pair of angularly spaced xed contacts on the other of said switches, the rotatable contact structure of said one switch including a plurality of arcuate contacts for connecting selectively the fixed contacts connected to the terminals of its associated heater unit with the fixed contacts connected to the power supply lines, the rotatable contact structure of the other of said switch having a plurality of arcuate contacts of such angular extent and spacing as to bridge said pair of angularly spaced xed contacts in all but the high heat position of said other switch whereby the heater unit associated with said one switch may be energized when the rotatable contact structure of said other switch is in any but its high heat position.

4. A circuit controlling device for controlling the energization of a pair of two element heater units having a plurality of terminals from a pair of supply lines, comprising a multi-position electric switch associated with each of the heater units for controlling the heat outputs thereof, each of said switches having a first fixed contact for direct connection with a different one of the power supply lines, a second xed contact and a third fixed contact, the third xed contact of each of said switches being electrically connected to the second xed contact of the other of said switches, other xed contacts on each of said switches for connection with the terminals of its associated heater unit, each of said switches having a rotatable contact structure including a plurality of arcuate contacts for connecting selectively said other fixed contacts with said first and third fixed contacts and for bridging said first and second contacts in the medium and low heat positions of said switches, and a separate contact on the rotatable contact structure of each of said switches for bridging said first and second contacts thereof when said switches are in their open circuit position, the spacing of said xed contacts and the arcuate length and spacing of said arcuate contacts being such as to completely isolate the heater unit from the supply lines when the movable contact structure of the switch with which it is associated is in its open circuit position.

5. A circuit controlling device for controlling the energization of a pair of two element heater units having a plurality of terminals from a pair of supply lines, comprising a multi-position electric switch associated with each of the heater units for controlling the heat output thereof, each of said switches having a plurality of xed contacts arranged in two sets lying in different planes, a first fixed contact in one set for direct connection with a different one of the power supply lines, a second fixed contact in the other set and a third fixed contact in said one set, the third fixed contact of each of said switches being electrically connected to the second xed contact of the other of said switches, other xed contacts in each set of each of said switches for connection with the terminals of its associated heater unit, each of said switches having a rotatable contact structure including a plurality of arcuate contacts arranged in two different planes for connecting selectively said other fixed contacts with said first and second fixed contacts and for bridging said rst and third contacts in the medium and low heat positions of said switch and a separate arcuate contact on the rotatable Contact structure of each of said switches for bridging the first and third contacts thereof when said switches are in their open circuit position whereby the heater unit associated with either of said switches may be energized when the other switch is in any but its high heat position.

FRED H. TRAVERS.

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