US2474189A - Electric switch - Google Patents

Description

June 21, 1949. PORTER 2,474,189

ELECTRIC SWITCH Filed March 15, 1946 IN VEN TOR.

Patented June 21, 1949 ELECTRIC SWITCH Malcolm E. Porter, Middleboro,

to The Lobl Manufacturing Company,

Mass, assignor Middleboro, Mass., a corporation of Massachusetts Application March 15, 1946, Serial No. 654,643

5 Claims.

This invention relates to improvements in electric switches. More particularly it provides a compact and eflicient switch which may be produced economically and which is especially adapted for effective control of a heatin element of an electrical unit so that the electrical unit may be operated selectively with the heating element maintained below any of a plurality of predetermined temperatures. The invention may be used for the control of electric heating pads, for example, with provision for selection between a plurality of operating temperatures for the pad.

It is among the objects of the invention to provide an electric switch having a plurality of depressible switch buttons of which one button is depressible to open the main circuit through the switch and of which at least two other buttons are selectively depressible to close a parallel circuit through the switch respectively with and without a resistance connected in the parallel circuit.

Another object is to provide an electric switch having a plurality of depre'ssible buttons of which one button is depressible to open the main circuit through the switch, and having a lamp within the switch casing connected in parallel in the main circuit for illuminating the switch whenever said main circuit is closed, there being means for latching a depressed button in depressed condition and for releasing any particular depressed button when any other of the plurality of buttons is depressed. Still another object is to provide a plural button switch wherein all of the make-andbreak contacts are made of strip metal stock which may be economically stamped out of sheet stock and be quickly formed to desired shapes.

Yet another object is to provide a plural button switch wherein all of the make-and-break contact elements and the main electrical connections therebetween are economically made of strip metal stock including bendable ears for clamping electrical connection to conductor terminals.

It is, moreover, my purpose and object generally to improve the structure and operation of plural button electric switches.

In the accompanying drawings:

Fig. l is a face view of an electric switch embodying features of the invention;

Fig. 2 is a View of the switch of Fig. l with the button-carrying cover section of the casing removed;

Fig. 2a is a. fragmentary view of the grooved partition wall with the strip contacts omitted;

Fig. 3 is a cross-sectional view on line 3-3 of Fig. 2;

Fig. i is a view looking at the interior of the button-carrying cover section of the casing;

Fig. 5 is a cross-sectional view on line 5-5 of Fig. 4;

Fig. 6 is a fragmentary view showing the latch plate in its intermediate cammed position just prior to the final movement of a button which is being depressed;

Fig. '7 is a cross-sectional view on line 'I-l of Fig. 4, on a larger scale;

Fig. 8 is a cross-sectional view on line 88 of Fig. 6, on a larger scale;

Fig. 9 is a cross-sectional view similar to Fig. 8 but showing the button latched in depressed position;

Fig. 10 is a fragmentary cross-sectional view on line lil-l0 of Fig. 2, on a larger scale; and

Fig. 11 is a diagrammatic view of the switch as it may be connected for control of an electric heating pad.

Referring to the drawings, the switch casing as shown comprises the body section II] and the cover section I2 which may be secured together in any conventional manner as by the screws l4 whose heads preferably will be seated below the surface of the casing and whose threaded ends each has a nut threaded thereon which also preferably will be seated below the surface of the casing.

The casing body section H! has the side flanges l6 extending from end to end thereof and, at one side, has the flange lB spaced inward from flange 16 to provide a narrow channel 20 extending approximately from end to end of the section, between the flanges. At the other side a similar but shorter flange 22 is spaced inward from the side flange It to provide a narrow channel 24 extending along the side of the section at its lower half as viewed in Fig. 2. A relatively thick partition wall 26 extends across the section between the inner flanges I8, 22 at a mid-location along the section and has three shallow parallel grooves 28 extending across it inspaced relation. Another and longer shallow groove 30 extends along the partition wall, crossing the grooves 28.

Three strips 32, 34 and 36 of spring metal constitute spring contacts of the switch and each is seated in one of the grooves 28 with the groove walls maintaining them in parallelism. A metal strip 38 is seated in the crossing groove 39 and is pinned as at 40 to each strip 32, 34 and 36 with each pin extending into the partition wall 26 for securing the strips to the wall. As represented, the strip 38 has length for extending substantially beyond one end of its groove 30, and this extending part is bent adjacent the end of the groove and extends along a side flange I6 of the casing within the short channel 24 to a location toward one end of the casing section where it is connected as at 42 to a flexible conductor 44 extending into the casing section at one end thereof.

The parallel strips 32, 34 and 36 have equal substantial extent toward one end of the casing section from their points of anchorage on partition wall 26. Strips 32 and 36 have no appreciable extent on the opposite side of wall 26. Strip 34, however, has substantial extent as at 34' on this opposite side of wall 26 for yieldingly engaging under the elevated terminal part 46 of a metal strip 48 which is pinned at 56 to the bottom wall of body section I9 of the casing. Strip 40, adjacent its pin 50, has a tab of the strip stock bent as at 52 into clamping relation to the end of a flexible conductor 54 extending into the casing section at this end thereof. Another flexible conductor 56 entering the casing section at this end is connected at 58 to a metal strip 69 which extends along the side flange I6 of the body section, in the channel 20, at the side opposite the location of the bent portion of strip 38. Strip 60 extends to a location adjacent the other end of the section where it is connected as at 62 to a flexible-conductor 64 entering at this end of the casing section.

The extension 34 of strip 34 normally resiliently engages the terminal part 46 of strip 48. Hence, assuming conductors 54, 56 to be connected to a source of electrical energy, and assuming the conductors 44, 64 to be connected through a heating element of an electrical unit, such as the heater resistance 66 of Fig. 11, the extension 34' constitutes a main switch closing the main circuit through the heating element 66 whenever it is in engagement with terminal part 46 of strip 48. However, means to be described, provides for depressing extension 34' to open the main circuit. Also, means is provided for depressing the strips 32, 34 and 36 selectively for a purpose now to be explained.

Control of an electrical unit having selective operating temperatures customarily is effected by adding or subtracting resistance in the circuit to the unit. My present invention provides simple and effective means for accomplishing such control by selectively depressing one or another of the resilient strips 32, 34, 36 thereby to decrease the resistance in an auxiliary circuit which selectively may be connected in parallel with the main circuit or may be disconnected from the main circuit.

In the diagrammatic showing of Fig. 11, my improved switch is illustrated connected for control of an electric heating pad having the main resistance heater element 66 with the associated thermostatic bi-metal switch element 68 responsive for opening and closing the heater circuit automatically in response to temperature conditions of the heating pad. An auxiliary heater ll! is located adjacent the bi-metal element 68 and, when the auxiliary heater is energized, it

4 hastens the warping of the bi-metal and thus causes the main heater circuit to open more quickly than it would open if the main heater alone affects ambient temperature at the bimetal element. Hence, the main heater in such case will operate at a lower temperature.

The auxiliary heater ID is shown connected in a parallel circuit 12 which normally is open at the resilient strips 32, 34. The auxiliary circuit I2 has a terminal 14 spaced directly under the strip 32 and has another terminal 16 spaced directly under the strip 34 with a resistance I8 connected between the terminals 74, I6. Hence, assuming the main circuit to be closed through the main heater 66 of the pad, depression of strip 34 into contact with terminal 16 connects the auxiliary heater 10 in parallel with the main heater 66 and the resistance 18 also is in the parallel circuit reducing current flow through the auxiliary heater and thus delaying its temperature rise. As a result the main heater 66 will reach a higher temperature before the thermostat opens the circuit as compared with the condition if the resistance I8 was not in the parallel circuit 12. Depression of strip 32 into contact with terminal 14 connects the auxiliary heater 779 in parallel with the main heater 66 without resistance I8 in the parallel circuit.

Referring to Figs. 1-5, selective depression of the strip extension 34 and strips 32, 34 and 36 is effected by the buttons 80, 82, 84 and 86 which project exteriorly of the cover section I2 for convenient actuation by a finger of the operator of the switch. Preferably the buttons project into suitable depressions or recesses 88, 90 exteriorly of the cover section so that, in their pro- J'ected positions, they will not extend appreciably beyond the face of the cover section.

Each button has the general shape as shown in Figs. 7-9, including an annular latching groove 92 inward of which is the camming surface portion 94 extending between the groove 92 and the inner finger-engaging head 96. A latch plate 98 is pivoted at I00 interiorly of the cover section and has four holes I 02 therethrough for reception of the respective buttons 80, 82, 84 and 86. Each hole I92 is substantially larger than the diameter of the button therein and the latch plate is constantly biased by spring I04 in one direction about its pivot I00 so that a side wall of each hole I02 is yieldably urged against its button. When a button is in projected position the wall of its hole in plate 98 yieldingly presses against the camming portion 94 of the button. As the button is depressed, the camming portion 94 rotates the latch plate a little about its pivot against the bias of spring I04 until the wall of the hole comes opposite the annular groove 92 of the button, at which time the Wall of a hole I 62 snaps into the groove 92 to latch the button in depressed condition. The slight rotation of the latch plate during depression of a button is suflicient to release any button which previously may have been depressed and latched.

In use of the switch for control of the heating pad represented in Fig. 11, the button will be latched in its depressed condition when the pad is not in use. This causes the contact finger 34 to be depressed out of engagement with terminal 46 of strip 48 and the main circuit to the pad consequently will be open.

When it is desired to operate the heating pad at its maximum temperature, button 82 will be depressed. The only effect of depressing button 82 is to cause unlatching of the button 86 thereby to permit finger 34" to contact terminal and close the main circuit through the heater element 66 of the pad. Neither the auxiliary heater 10 nor the resistance 18 will be in the circuit when button 82 is depressed and the heater element 66 in consequence will heat up until element 65 itself creates ambient temperature at the thermostatic element 68 suflicient to cause opening of the circuit. I

When a lower operating temperature for the pad is desired, button 84 may be depressed thereby to connect the auxiliary heater 10 and resistance T8 in parallel with the main circuit. This results in the auxiliary heater Ill hastening the opening of the thermostat and the heater element 66 does not have an opportunity to get as hot as in the previously described case. However, the resistance I8 is a limiting factor as regards the amount of current flowing to the auxiliary heater l and the auxiliary heater does not influence the thermostat as quickly as when resistance 18 is eliminated. Hence the low temperature operation of the pad is attained when button 86 is depressed which cuts out resistance 18 leaving auxiliary heater l0 free to exert its maximum effect on the thermostat.

It is desirable in many cases to have means for visual indication in the dark that the switch is on. I attain such an indication by providing a lamp I06 within the casing permanently electrically connected between the strip 38 and the strip 60 with a suitable protective resistance H38 in the connection. An opening H0 in the cover section 12 of the casing permits light from the lamp to show exteriorly to indicate that the main circuit is closed.

I claim as my invention:

1. In an electric switch having a casing comprising a recessed body section and a cover see tion, a partition extending across the recess of the body section, a plurality of resiliently depressible contact fingers anchored on said partition and projecting in spaced relation at one side of the partition, one of said fingers having extent also at the other side of the partition and constituting there a resilient depressible contact finger, a fixed terminal member overlying the free end of the latter said finger in position for said finger normally to resiliently engage the overlying terminal, a fixed terminal below the free end of one of the said fingers at the other side of the partition and in position to be engaged by said finger when the latter is depressed, a button for each said projecting through the cover section of the casing and having its inner end engaging a said finger, and means interiorly of the cover section for automatically latching any said button in depressed position in response to a finger depression of any said button, said means being responsive for releasing a previously depressed and latched button whenever another said button subsequently is depressed.

2. In an electric switch having a housing, a pair of conductors leading into the housing, three conductors leading out of the housing, means interiorly oi the housing permanently electrically connecting one of said incoming and one of said outgoing conductors, a plurality of resiliently depressible contact fingers anchored within the housing, means within the housing permanently electrically connecting a second one of said outgoing conductors with each of said fingers, means within the housing overlying the free end of one of said fingers and permamently connected to the second of said incoming conductors, said overlying means being normally engaged resilientlyby the underlying finger thereby to electrically connect said second incoming and outgoing conductors, a fixed terminal underlying the free end of a second one of said fingers and permanently electrically connected to the third one of said outgoing conductors, said underlying terminal being normally out of contact with the overlying fingen-a button for each finger for depressing the fingers selectively, and means for latching any depressed button in its depressed condition, the latter said means being responsive to depression of any button for releasing a previously depressed and latched button.

3. In an electric switch having a housing, a pair of conductors leading into the housing, three conductors leading out of the housing, means interiorly of the housing permanently electrically connecting one of said incoming and one of said outgoing conductors, a plurality of resiliently depressible contact fingers anchored within the housing, means within the housing permanently electrically connecting a second one of said outgoing conductors with each of said fingers, means within the housing overlying the free end of one of said fingers and permanently connected to the second of said incoming conductors, said overlying means being normally engaged resiliently by the underlying finger thereby to electrically connect said second incoming and outgoing conductors, a fixed terminal underlying the free end of a second one of said fingers and permanently electrically connected to the third one of said outgoing conductors, a fixed terminal underlying the free end of a third one of said fingers and permanently electrically connected through resistance means with the other fixed and underlying terminal, both said underlying terminals being normally out of contact with the overlying fingers, a button associated with each finger for depressing the fingers selectively, and means for latching any button in its depressed condition and responsive to depression of any button for releasing a previously depressed and latched button.

4. In a multi make-and-brealr. switch, a series of depressible contact fingers each comprising a strip-metal stamping, a stamped metal connecting strip electrically connecting all of the fingers, a support for said fingers and connecting strip having shallow grooves in spaced parallelism, in. each of which grooves a said finger is seated with the groove walls maintaining the lingers in parallelism, and having a groove extending across the parallel grooves in which crossing groove said connecting strip is positioned with the walls of the groove maintaining said strip in fixed crossing relation to said fingers, and a pin at the juncture of each finger with the connecting strip securing the fingers and connecting strip together and to the support.

5. An electric switch comprising a housing, a series of depressible contact fingers and a series of fixed terminals for coactiori with the fingers Within the housing, each said finger and terminal comprising a strip-metal stamping, a stamped metal connecting strip electrically connecting all of the fingers, a support for said fingers and connecting strip within the housing having shallow grooves in which said fingers and connecting strip are seated, a pin at each juncture of a finger with the connecting strip securing the fingers and connecting strip together and nently connected to the second of said incoming conductors, and means for depressing the fingers selectively.

MALCOLM E. PORTER.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,607,270 Smith Nov. 10, 1926 1,859,515 Kageyama May 24, 1932

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