US3320384A

US3320384A - Snap acting switch mechanism

Info

Publication number: US3320384A
Application number: US291117A
Authority: US
Inventors: Charles C Gambill; Richard S Gaugler
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1963-06-27
Filing date: 1963-06-27
Publication date: 1967-05-16
Anticipated expiration: 1984-05-16

Description

May w, WWI c. GAMBILL ETAL 3,a2@,384

SNAP ACTING SWITCH MECHANISM 2 Sheets-Sheet 1 Filed June 27, 1963 INVENTORS (HA/WEE 6. 6A MB lF/ffi/ARD 5. GAUGLER BY ATTORNEY May 16, 1967 (3. c. GAMBILL ETAL 3,

SNAP ACTING SWITCH MECHANISM Filed June 27, 1963 2 Sheets-Sheet INVENTORS CHARL E5 C. GA MB/L L R/CHARD 5. GA UGL ER BY ATTORNEY United States Patent Ofifice 3,320,384 Patented May 16, 1967 3,320,384 SNAP ACTING SWITCH MECHANISM Charles C. Gambill, Tipp City, and Richard S. Gaugler,

Dayton, Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 27, 1963, Ser. No. 291,117 3 Claims. (Cl. 200-122) This invention relates to control systems for electrical devices and more particularly to an improved controller for the electrical surface heater of a kitchen range or the like.

Many electrical control systems have circuit breaking contacts connected across relatively high voltage sources in the range of 115 to 230 volts which tend to weld together during the controlling operation. It is therefore desirable to provide contact actuating means which separate the contacts by a snap action as they are moved into their open position upon the occurrence of a predetermined event or condition. In many applications it is desirable that such contact actuating means have a selectively variable effect on the circuit breaking contacts in order to produce a modulated control of an electrical device associated therewith.

An object of the present invention, therefore, is to improve electrical control systems having circuit breaking contacts by including improved means therein for positively separating the circuit breaking contacts and moving them into an open position.

Another object is to improve electrical controllers having a pair of circuit controlling contacts by the provision of a thermally responsive element having a predetermined transition temperature at which the element initially expands a predetermined amount to open the controlling contacts for carrying out a given control function.

A further object of the invention is to improve an electrical controller actuated by such a thermally responsive element by the provision of means for regulating the rate of temperature increase of the thermally responsive element for modulating the controlling action thereof.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

' In the drawings: 7 FIGURE 1 is a view in perspective of a portion of an electrical range including the present invention;

FIGURE 2 is a schematic view of the controller of the present invention;

FIGURE 3 is a view in front elevation of a structural embodiment of the improved controller with the front cover and control knob thereof removed;

FIGURE 4 is a view in horizontal section taken along the line 44 of FIGURE 3 with the front cover and control knob shown;

FIGURE 5 is a view in vertical section taken along the line 55 of FIGURE 3;

FIGURE 6 is a view in horizontal section taken along the line 66 of FIGURE 3;

FIGURE 7 is a view in vertical section taken along the line 7-7 of FIGURE 3;

FIGURE 8 is a view in vertical section taken along the line 8-8 of FIGURE 3; and

FIGURE 9 is a schematic view of another embodiment of the invention.

Referring now to FIGURE 1, an electrical range 10 is illustrated as having an electrical resistance coil or surface heater unit 12 representing a typical electrical device regulated by a controller 14 constructed in accordance with certain of the principles of the invention. In FIGURE 2 the controller 14 is shown associated in an electrical system including a suitable source of power 16 such as a residential electrical system of volt power connected to

lines

18, 20. Line 18 is electrically connected to a fixed contact 21 adapted to engage a movable contact 22 supported by and electrically connected to one end of a cantilevered spring arm 24 of conductive material biased into engagement with the outer periphery 25 of a rotatable cam 26 having a notched portion 28 therein for receiving an offset portion 30 of the arm 24 when the

contacts

21, 22 are in an open position as shown. The spring arm 24 is rigidly secured at its other end to a suitable fixed support 31. The

contacts

21, 22 serve as an on-off switch for the improved controller as will be discussed.

The cam 26 is supported on a shaft 32 connected to a manually rotatable temperature control knob 34 having a suitable scale 36 thereon movable relative to an indicator 37 for selecting a predetermined operating temperature or other desired condition of operation for the electrical heater or range surface heating element 12.

When the control knob 34 is moved from its off position, the cam 26 will bias the arm 24 to close the

contacts

21, 22 to thereby complete a circuit through a conductor 38 electrically connected between the arm 24 and the heater 12 and thence through a conductor 39 electrically connected between the heater 12 and a thermally responsive conductive element 40, a conductor 42, a cantilevered spring arm 44 of conductive material having one end thereof supporting a movable contact 46 which is biased thereby against a fixed contact 48 electrically connected to the line 20. The opposite end of arm 44 is anchored on a suitable fixed support 49.

The thermally responsive conductive element 40 has one end thereof rigidly secured to a suitable fixed support 50 and the opposite end thereof in contact with the spring arm 44. Intermediate the ends of the element 40 is a channel-shaped member 52 spring biased by means of a spring element 54 against a curve-d surface 56 on the cam 26. The channel-shaped element 52 is movable by the cam surface 56 relative to the conductive element 40 so that a greater or lesser portion of

arms

58, 59 on either side thereof are located in overlapping relationship with the element 40.

In accordance with certain of the principles of the pres ent invention, the conductive element 40 is a thermally responsive material having a predetermined transition temperature at which it will expand a predetermined amount to operate the

contacts

46, 48 to thereby terminate energization of the heater 12. One example of a material having such expansion characteristics is Mn Cr Sb. This material has little or no linear expansion below a predetermined transition temperature which is dependent on the quantity (x) in the above-described formula but when the temperature of the element 40 reaches a predetermined transition temperature, it will suddenly expand a-predetermined amount sufficient to deflect the spring arm 44 upwardly to cause a snap action opening of

contacts

46, 48. In the above-described improved control arrangement the element 40 is in cluded as a conductor portion of the electrical heater circuit and accordingly when the

contacts

21, 22 and

contacts

46, 48 are closed current flow through the element 40 will cause it to self-heat to thereby increase the temperature thereof to the predetermined transition temperature at which it will expand to produce the abovedescribed contact opening action.

In order to modulate the heat ouput of the surface heater 12 the control knob 34 is rotated to a predetermined temperature setting to cause the cam 26 to shift the channelshaped element 52 into a greater or lesser overlapping relationship with the element 40. The channel-shaped element 52 is made from a material having good thermal conductive properties and hence serves as a variable heat sink to thereby produce a greater or lesser heat transfer from the element 40 during the periods in which it is heated. For example, when the element 52 is in its greatest overlapping relationship with the element 40, a

relatively great amount of heat is conducted thereby from the element 40 to delay the time required to reach the above discussed predetermined transition temperature at which the element will expand. Accordingly, the surface heater '12 remains energized for a relatively long duration before the element 40 will reach the transition temperature at which it initially expands to open

contacts

46, 48.

Following opening of the

contacts

46, 48, the element 40 cools below the transition temperature thereof and consequently contracts to again allow the spring arm 44 to close the

contacts

46, 48. The element 40 will continue to pulsatingly regulate the length of time that power is supplied to the heater 12 at the above-described duration of energization until the control knob 34 is moved into another position, for example, to -a position where the element 52 will barely overlie the element 40. In this case, there is lesser thermal conduction to element 52 from the element 40 and it will, accordingly, reach the transition temperature through self-heating at an earlier point in time to open the

contacts

46, 48. The element 40 will again cool and reheat to the transition temperature at an increased rate to reduce the average power input to the surface unit and hence reduce the heat output therefrom in a selected fashion. Hence, the heat sink element 52 serves to selectively regulate the rate of temperature increase in element 40 for modulating the contact controlling action thereof.

One feature of the present invention is that the operative parts thereof can be associated in an extremely compact manner. This is best illustrated in FIGURES 3-8 where a structural embodiment of the invention illustrated in FIGURE 2 is shown with like elements in the schematic view of FIGURE 2 and the structural views being designated with the same reference numerals. In the structural arrangement, the control mechanism is enclosed in a housing 60 having a front cover 62 with an opening wherein for receiving the shaft 32 which has one end thereof supported by the rear wall of the housing 60 at 64 for rotation relative thereto. A snap ring 65 is secured to the shaft 32 at the end thereof to prevent axial movement thereof relative to housing 60. The cam 26 is secured on the shaft 32 between the rear wall of the housing 60 and the front cover '62 thereof for rotation relative thereto by the knob 34 which is secured to the end of the shaft 32 outwardly of the cover 62 for movement relative to the indicator 37 mounted on the outer face of the cover 62. The fixed contact 21 of the on-otf switch is secured by means of a suitable fastener to a rib 66 located at one side of the housing 60- where a terminal 67 electrically connected thereto is adapted to be connected to a suitable source of power such as line 20 in FIGURE 2. The spring arm 24 is secured to the same side wall of the housing 60 by means of a rivet 68 which also secures a terminal 70 in electrical contact with the arm 24 with the terminal 70 being adapted to be connected to a conductor such as 38 in FIGURE 2 leading to a surface heater unit such as 12.

The thermally responsive element 40 is secured at one end thereof on the opposite side of the cam 26 by a clip 72 secured to the housing 60 adjacent the base thereof and is directed generally vertically of the housing 60 upwardly from the clip 72 where a beveled upper end portion 73 thereof contacts the cantilevered spring arm 44 adjacent one end thereof anchored to the housing 60 by means of a clip 74 secured thereto at 75.

In certain structural embodiments of the invention the physical dimensions of element 40 reduce the electrical resistance thereof to a point where it will not self-heat sufficiently to produce the transition temperature necessary for

opening contacts

46, 48. In such cases an electrical heater 76 is wound in heat transfer relationship with the element 40 leaving one end thereof connected to a terminal 77 adapted to be electrically connected to a conductor such as 39 in circuit with the device to be controlled. The opposite end of heater 76 is connected to the spring arm 44 at 7-5 to complete an energizing circuit for the heater 76 when

contacts

46, 48 are closed.

One feature of the structural arrangement is that when the knob 34 is in an off position, as shown, the cam 26 is positioned so that a protuberance 79 on the upper portion thereof will contact an offset cam follower 80 secured to the underside of the spring arm 44 to position the

contacts

46, 48 in an open position so that there will be no tendency for pressure welding these controlling contacts when the controller is turned off. When the cam 26 is moved from its off position the protuberance 79 will move away from the follower 80 to allow the spring arm 44 to bias the contact 46 into engagement with the contact 48. When the cam 26 is moved in this manner, it will also force the spring arm 24 in a direction to cause the

contacts

21, 22 of the on-otf switch to close to produce the above-discussed self-heating of the element 40 and the consequent pulsating control of the

contacts

46, 48 to regulate the energization of an electrical device associated with the controller.

It should be noted that in structural arrangement of FIGURES 3-8 the length of the spring arm 44 between the point at which the beveled end 73 of the element 40 is in contact therewith and the contact carrying end thereof is substantially equal to the full width of the controller housing 60. This substantial length of the arm 44 in accordance with certain of the principles of the present invention, produces an amplification of the expansion movement of element 40 at the transition temperature thereof suflicient to produce a desired spacing of the

contacts

46, 48 when they are in an open position to prevent arcing therebetween.

It should be further noted that the contact 48 is secured to a screw element 82 threadably engaged in a C-shaped internally threaded base 84 to allow adjustment of the contact 48 relative to the contact 46 by insertion of a suitable tool through an opening 85 in the housing 60 to provide a predetermined adjustment of the spacing between the

contacts

46, 48 to calibrate the controller. The base 84 is secured to housing 60 by a rivet 86 which also supports a terminal 87 in electrical contact through base 84 and screw 82 with contact 48. The terminal 87 is adapted to connect to another line of a power source such as line 18 in FIGURE 2.

Another feature of the illustrated structural embodiment of the invention of FIGURE 2 is the manner in which the channel-shaped heat sink element 52 is supported for adjustment relative to the thermal responsive element 40. It will be noted that in the structural embodiment the spring 54 is illustrated as a flat spring having the ends thereof in engagement with the arm 58 of the heat sink 52 and a central portion thereof secured to a rib 89 of the housing by means of a'clip 88 so that the spring 54 will bias the heat sink element 52 against the camming surface 56 on the cam 20 to provide for smooth sliding movement of heat sink element 52 relative to the element 40.

In the embodiment of the invention illustrated in FIG- URE 9 a suitable source of power is connected to

lines

100, 102 for energizing a surface heater 104 under the control of a thermally responsive element 106 like the element 40 in the embodiment of FIGURE 2. In this arrangement a control knob 108 having a suitable scale 110 thereon is manually rotatable relative to an indicator 112 for rotating a shaft 114 to move a cam 116 relative to a cantilevered spring arm 118 of conductive material that is biased against the outer periphery of cam 116 and fixed at one end thereof to a fixed support 119. This causes an offset of arm 118 to be moved from a notch 122 in the outer periphery of the cam 116 so as to move a contact l24 secu'red to the end of the spring arm 118 in electrical contact therewith into engagement with a fixed contact 126 connected to line 102 to thereby close a circuit from the line 102 through the contacts 124, 126, the arm 118, a conductor 128, the surface heater 104, a conductor 130, a cantilevered spring arm 132 of conductive material having one end thereof fixed at support 133 and having a contact 134 secured on the free end thereof spring biased into engagement with a fired contact 136 electrically connected to the line 100.

Concurrently with energization of the heater 104, current passes through a conductor 138 electrically connected to the conductor 128 and thence through an electrical heater element 148 in heat transfer contact with the element 106 representatively illustrated as an insulated wire wound in heat transfer relationship therewith, and thence through a resistance element 150 of a potentiometer, its contact carrying rotatable arm 154, a conductor 156, conductor 130, the spring arm 132 of conductive material and line 100. The heater 148 serves to increase the temperature of the thermally responsive element 106 until it reaches the transition temperature thereof to cause an expansion therein sufiicient to open the

contacts

134, 136 to thereby de-energize the heater 104.

In this embodiment of the invention the controlling action of the element 106 is modulated by rotating the potentiometer arm 154 through the control knob 108. More particularly, the contact carrying arm 154 of the potentiometer is operatively associated with the shaft 114 connected to the knob 108 so that when the knob 108 is rotated to a preselected temperature the contact carrying arm 154 is moved relative to the resistance element 150 to include a greater or lesser portion thereof in circuit with the heater 148 for varying the current flow therethrough to thereby vary the manner in which the element 106 is heated.

When it is desired to regulate the hater 104 to produce a relatively high heat output therefrom, the knob 108 is rotated in a direction to cause a greater portion of the resistance 150 to be serially connected in circuit with the heater 148. This reduces the current flow through the heater 148 to reduce the heat output therefrom so that it will take a longer period for the element 106 to reach the transition temperature at which it will expand to open the

contacts

134, 136. Accordingly, the element 106 will heat and cool to produce a greater percentage of energization of the heater 104. When the knob 108 is rotated in a direction to include less of the resistance 150 in circuit with the heater 148, a greater current will flow therethrough to produce a more rapid heating of the element 106 to thereby cause it to reach its transition temperature quicker. Thus, the percentage of energization of the heater 104 is reduced along with the heat output therefrom. The potentiometer thereby serves as a customer control since it will determine the length of time that power is supplied to the heater 104 and also the length of time that power is removed from the heater 104. In other Words, it will provide a means for controlling the average power input to the surface unit 104.

While the embodiments of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An electrical control device associable with a power source for regulating the energization of an electrical device comprising, means including a pair of contacts for interrupting current flow from the power source to the controlled device, a thermally responsive element having a predetermined transition temperature at which it abruptly expands, means for heating said thermally responsive element to said predetermined transition temperature, means for connecting said thermally responsive element to one of said pair of contacts for moving said contacts to an open position when said thermally responsive element reaches said predetermined transition temperature for controlling the energization of the controlled device, an element of thermal conductive material serving as a heat sink, means for supporting said element of thermal conductive material in heat transfer relationship with said thermally responsive element, and means varying the heat transfer relationship between said thermal conductive element and said thermally responsive element to vary the heat sink capacity of said thermal conductive element for varying the rate of temperature increase of said thermally responsive element to modulate the contact controlling action thereof.

2. An electrical controller comprising a housing, a temperature responsive element having a predetermined transition temperature at which it abruptly expands, said thermally responsive element having one end portion fixed to said housing and another end portion free to expand relative thereto, means for heating said thermally responsive element to said predetermined transition temperature, a fixed contact, a movable contact, a cantilevered spring arm of conductive material secured to said movable contact for biasing it into engagement with said fixed contact, said cantilevered spring arm extending across the width of said housing, means for electrically connecting said cantilevered spring arm and said fixed contact in circuit with an electrical device energized by a power source controlled by said fixed and movable contacts, another end of said thermally responsive element engaging said cantilevered spring arm adjacent the anchored end thereof a substantial distance from the contact carrying end thereof, said thermally responsive element upon sensing a predetermined temperature abruptly expanding to move said cantilevered spring arm for separating said movable contact from said fixed contact to control the energization of the electrical device an element of thermal conductive material having portions thereof overlapping said thermally responsive element in heat transfer relationship therewith to serve as a heat sink, a cam element engaging said heat conductive element, means for resiliently biasing said thermal conductive element against said cam, means for rotating said cam relative to said thermal conductive element for causing movement thereof relative to said thermally responsive element to vary the heat sink capacity of said thermal conductive element for regulating the rate of temperature increase of said thermally responsive element to thereby modulate the contact controlling action thereof.

3. A controller comprising a housing, a temperature responsive element having a predetermined transition temperature at which it abruptly expands, said thermally responsive element having one end portion fixed to said housing and another end portion free to expand relative thereto, means for heating said thermally responsive element to said predetermined transition temperature including an electrical heater located in heat transfer relationship with said thermally responsive element, a fixed contact, a movable contact, a cantilevered spring arm of conductive material secured to said movable contact for biasing it into engagement with said fixed contact, said cantilevered spring arm extending across the width of said housing, means for electrically connecting said cantilevered spring arm and said fixed contact in circuit with an electrical device energized by a power source controlled by said fixed and movable contacts, said another end of said thermally responsive element engaging said cantilevered spring arm adjacent the anchored end thereof a substantial distance from the contact carrying end thereof, said thermally responsive element upon sensing a predetermined temperature abruptly expanding to directly move said cantilevered spring arm for separating said movable contact from said fixed contact to control the energization of the electrical device when said thermally responsive element reaches said predetermined transition temperature with the expansion of said thermally responsive element being amplified through the cantilevered spring arm for maintaining a desired separation 7 between said fixed and movable contacts when they are in their opened position, and means for varying the heat out put of said heater for regulating the rate of temperature increase of said thermally responsive element to thereby modulate the contact controlling action thereof.

References Cited by the Examiner UNITED STATES PATENTS 8 3,078,361 2/1963 Mason et al. 200-122 3,254,180 5/1966 Flanagan 200-113 FOREIGN PATENTS 461,166 10/1913 France.

OTHER REFERENCES Hansen, Max: Constitution of Binary Alloys, New York, McGraw-Hill, Inc., 1958.

1,642,485 10/ 1927 Chace.

2,162,343 6/ 1939 Brace 200-122 X 10 BERNARD A. GILHEANY, Primary Examiner. 2,315,565 4/1943 Waltenberm 2,814,694 11/1957 Moodie f 200-137 H. A. LEWITTER, L. A. WRIGHT, Asszstant Examiners.