US2623137A

US2623137A - Electric switch

Info

Publication number: US2623137A
Application number: US157932A
Authority: US
Inventors: Walter H Vogelsberg
Original assignee: Proctor Electric Co
Current assignee: Proctor Electric Co
Priority date: 1950-04-25
Filing date: 1950-04-25
Publication date: 1952-12-23
Anticipated expiration: 1969-12-23

Description

Dec. 23, 1952 w. H. V OGELSBERG ELECTRIC SWITCH 3 Sheets-Sheet 2 Filed April 25, 1950 Dec. 23, 1952 w. H. VOGELSBERG ELEICTRIC SWITCH 3 Sheets-Sheet 35 Filed April 25, 1950 the contacts I and II are engaged, a clrcuit is established from the supply line 2, through adjustable blade I2 contacts I0 and II, through heater B to the heating load I and thence to line 2. When the contacts I0 and II are separated, the heating load is deenergized. A control knob I3 er some other suitable manual adjusting means is provided on the oontrol device 4 for selecting the desired input to the heating load. The adjustment is efiected by the manipulation of the flexible blade I2 through a screw memher I4.

The operation of this partieular thermostatic clevice can be explained by follovving a typical cyole of closing and opening of the contacts I0 and II. Assume that the contacts I0 and II are separated and that the thermomotive means 4 is cooling. In this oondition, the free end of the thermomotive member 4 moves to the right. Upon engagement of contacts I0 and II, current fiowing through the heater leg 6 will cause it to heat rapidly, expand longitudinally and force the free end of the thermomotive member 4 farther I:=o the right. As the leg B continues to heat, the bimetal leg 5 will receive heat therefrom and Will begin to flex and move the contact I0 towarcl the left. This motion will continue until the contacts separate, thereby deenergizing the heating load and diseontinuing the current supply to the leg 6. Immediately upon separation of the oontacts I0 and II, the leg 6 will quickly cool, contraot and so force the thermomotive member 4 farther to the left. Furthercooling of the thermomotive member 4 Will cause the bimetallic leg 5 to return toward its unflexed position, permit the oontacts I0 and II to be reengagecl and thus start another cycle of operation.

It Will be observed that both the bimetal 5 and heater 6 contribute to the thermoinotive aotion of the swltch but that the thermomotive effeot of the primary element 5 is always arranged to supersede the effeot of the secondary element That is to say, the 1orimary element 5 is the more -active er more efiective in that it always ultimately dominates the action of the secondary element 6 in effeoting opening and olosing of the switch contaots on heatin and cooling respectively. The effect of the additional thermomotive aetion offered by the heater 6 is to provicle a differential between the opening and olosing temperatures of the bimetal 5 which in turn efiects a greatly inoreased cycle length. The length of the time cycle is now made up of the undershoot and overshoot of the bimetal plus the increased cycle length due to the aetion of the heater. It

should be noted that i-f the heater were not mechanically connected with the bimetal, no differential would exist and the entire cycle would consist; of the time necessary for the bimetal to overshoot and undershoot.

The utilization 015 the the1moh1otive aotion offei*ed by the heater is considered of maximum importance in the application of this device, and particularly when this device is to be used in conjunction with the fiashing or the overenergizing of an electric heating unit so that lt can attain its operating temperature quickly. In my copending application, Serial N0. 81,938, filed March 17, 1949, systems and devices are shown which utilize a Single thermal Wattage controller to control the length of the overenergization period and also to control the input during normal energization by cyclically opening and C1OSillg of the oircuit to the electric heating unit. A wattage oontr0ller so adapted must meet many severe requirements. First, it must possess those feaw tures so essential in the application of the device as an ordinary wattage oontroller; it must be reliable, simple to manufacture, etc., and it must have moderately long cycles. Secondly, to meet the requirement of adaptability to a. flashing system as above mentioned, it must heat and cool at substantially the same rateas the heating unit it is controlling. Thus lt must be a thermal prototype of the eleetrical load (i. e the heatlng unit) it is controlling. In these fiashing systems. the heater for the wattage controller has an energization rate proportional to that of the beatin unit. Dlllil'lg the overenergization interval. the wattage oontroller acts to time the duration of the overenergization. When the controller attains a temperature proportional to the desired operating temperature -of the heating unit, the contacts open and terminate the flash interval. Thereafter the controller, having a reduced energization rate proportional to the reduced energization rate of the heating unit aets to control the wattage input level to said unit by cyelically opening and closing the circuit thereto. The ability of the wattage controller to track the heating unit thus permits it to act as a safety device if a refiashis attr'empted, for the temperature which the controller must attain is reduced an amount 'oorresponding to the temperature of the heating unit at the tlme a reflash is attempted, thereby preventing sueoessive reflashing for extended perlods of time which might result in dangerous overheating of the heating unit. 3

A unique problem is presented when it is desired to provide a thermal c-ontroller that will give long cycles as well as have the ability to track the heating unit, without resorting to snapaotion switohes. T0 obtain moderately long. oycles in the past lt was necessary increase the thermal mass of the switch, thereb inore'asing the undershoot and ovefShoot of the associated thermal element in a manner well known in the art. To cause the controller to tra.ck the heating unit, it is necessary that the thermal capacity and the thermal dissipative capacity of the thermal element of the controller be of the proper magnitudes. These two requirements are not consistent with one another, it being only a fortuitous combination of circumstances or severe comprom'ises that would permit previous arrangements to be used. However, by using the present invention wherein the thermomotive action of the heater 6 is used to obtain the long cycle independent of the heat storage capacity of the mass associated With the thermal element, wide latitude is permitted in designing a controller with the correct prototype characteristics.

A physical embodiment of the above described form, adapted to a control device of the character disclosed in my oopendin applieation Seria1 N0. 157,933 filed April 25, 1950, is shown in Figs. 2 to 9. Only that part cf the device involving the present invention need be described.

In these figures, there is shown a control device comprising a control box or oasing I5 onto which is flxed-a cover member I6 by means of screws I'I. A control knob I8 serves to control the position of an adjustable bl'ade I0 through a oontrol cam 20 carried by a shaft 2I whioh is rotatably supported by cover I6 and the rear of the casing I5 in a pil-ot hole 22. The adjustable blade I0, a relatively heavy metallic member. has affixed to its free end a contact 23 which cooperthe adjustable controiIblagle I9 argWelgled-foblade 32 through an ins ula} tin g b1t1qgn 33. mounted thereon to isolatge ohe cor 1 tml blade electrically and thermally from said compgansator, Near the center of the a;djustaeblade I9 is'a landed projectiom 34 whichcoactswith the su 1& face of the control cam2il.

The construction and the arrangement of the masses as shown for the component ;partsof the adjustable blade and mounting l9,25 haveproven quite satisfactcry in eliminating excessive vibra tion prevalent in -devices that have extremely flexible contact support members. Tl1e cqnstruction is also advantageousbecause 117 permits a very convenient way cf institutirgg the comp epn sating action and in addition the -factory adjustment, which Will be explainedhereinaftern It should be mentioned that-the details of the cam are describ-ed at length inthe -aforementioned copending application.; Of :parti cular interest is thecam program -that provi'des a, comtinuous selection of inputs from some 10W value to a-ful1 100% input-position. In that applicaticn the circuit in which the wattage controller is used does not require that the contacts 2'31a11d carry the continuous 100% 1oad;an auxiliary pathbeing provideid therefojrv Thepresentinvention is capa'ble of application tothistype of circuit o1 an arrangement whera 1hewontacts are -maintained clo-sed by the cam throW to' give" the* 100% input. The cam =is further provid'ed With 2 recessed. offpositionatfi0a; insufing a gene1ouselectrical clearance at this partilcular switch conditioning:

The thermomotive means 25 (see Fi gs. 6 to 8) consists of a substantially"straight' control bimetal 35 and aheater element 35 cf ;hightemperature material, such as a, nickel chrome a11oy, having a narrow sec tion '31.Whi0hf8Xtlld3 a greater portion of its length; Thebimetal 35, the heater element- 35, and the electrical c'ontact 24. .are Welded together using a; stee1 .button 391 th Cyclic heating anti coolling pf the; thermonio-- tiye n1eans 25.

35 than with the bimetal 35, anc'f that;ah air a trminal meinbe r 50, Ehe loweiy part of the oigher. It will be noted that 2zr; i- 1113501 Strip 52 is interpcised"betvveenfthejheald" of thriiretj 2ind formed in the casing 'to pxqvgrlxtfthethiarmpe is maintained subStantially coristetht1egardles's of changesin ambitaixt*temperatures* tcr=which the device is eXposed.:-The bilrnalrcompensator is disposed Witt 1 its high expangionsidenward; i.e. toward the leit; as -viewed ir 1 Figs.; *2 a1 1d 6:

7 surface of control cam 20 and so rotates the free end of the control blade toward the 1eft.

The compensator 32 is prevented from movement other than that to achieve the compensating action. A recess 51 provided in the casing, a projeotion 58 adjacent the fixed pivot or fulcrum 54 and a pin 54b through a hole 32a in the compensator 32 locate oho compensator in the 1ower portion of the casing. The adjusting screw 55 permits oontrol of the controller calibration by varying the position of the lower end. of the control blade I9. Thus if the inputs to the heating unit are in excess of what they should be for a particular setting of the control knob I8, it wou1d be necessary decrease the temperature or deflection ab whioh the

contro1 contacts

23 and 24 separate. This wou1d means that the Initial position of contact- 23 would have to be disposed farther oo the right, as viewed in Figs. 2 and 6, which can be achieved by backing ofl the adjusting screw 55 thus allowing the compensator to pivot clockwise (Fig. 5) about fulcrum 54, displacing the 1ower end of the control blade I9 toward the 1eft.

The electrical and thermal operation of this device is similar to that shown diagrammatically in Fig. 1. The :urrent path is through the termina1 member 28, through the rivet; 21, through ehe mounting spring 26, the control blade I9, contact 23 and contact 24, through the heater 36, rivet 40 and out through the terminal member 50. The meohanical operation can be followed in Fig. 2. Rotation of the control knob 18 to 0ne of the on positions will cause translation of the adjustable Made toward the left with consequent estab- 1ishment of the circuit through

contacts

23 and 24. The adjustable b1ade is manipulated through the lanced portion 34 and engages at its upper end the contact 24 of the thermomotive means 25, whi1e at its lower end it engages the insu1ating button 33 of the compensator. During the heating cyole of the thermomotive means 25 the adjustable blade through contact 23 follows the motion of oontact 24 until separation is efiected. Under this condition and throughout; the ofi portion of the cyc1e the blade takes up an equilibrium position as determined by the cam 20, the compensator 32 and the positioning efiect 015 the mounting spring 26.

Of importance in the design of the thermomotive means 25 is the ofiset 59 provided on ehe heater 36. It has been found that this feature constitutes (a) a convenient means for preventing overstress in the heater during its expansion and contraction; (b) a means to vary the amount of mechanioal infiuence of the heater on the bimetal Which in turn effects the length of ehe time cyc1e; e. g. increasing the offset while still maintaining the spacing between tne heater and bimetal the same will decrease the length of the cyc1e; (c) a means of preventing overstressing of the top fibres cf the g1ass cord wrapping by reducing the lateral foroe during compression of. the heater.

In one particular structural embodiment of this invention, the bimetallic member 35 was made from a material having a high expansion side of 72% manganese, 18% copper, and 10% nickel, whi1e the low expanding side was =of Invar. A third layer of nicke1 was provided between the high and low expansion sides to give a desired low electrical resistance to the entire bimetal. The length from the center 1ine of the mounting rivet 43 to the top 013 the bimetal was approximately 8 2%", ehe width along the major portion of the 1ength at .218" while the thickness was .030".

The heaoer 36 was maae from a material composed of nickel and 20% chromium which was annealed after being formed into the shape shown in Fig. 6. The width a1ong the greater part of its 1ength was .096" with a thickness of .005", the effective length of this necked-down portion measuring 1%,". a as shown in Fig. 6 Was %4. The thickness of the insulating medium was .034" for the as-- bestos strip 4l and .001" for the mica strip 42.. The asbestos was selected from a 1ong fibre stock of .042" in thickness which was subsequently compressed to the aforementioned thickness.

The particular 1oad used with this wattase coutroller was such as to pass approximately 5 amperes through the heater.

The compensator bimetal 32 was selected from a material having the high expansion side o1 72% manganese, 18% copper and 10% nickel, whi1e the low expanding side was of Invar. Its Width at the widest point was .340 having a thickness of .022" with an effective length of approximately 1 with the fulcrum at the widest point looated about 1 from the center of the button 33.

A modified form of the invention is shown in Figs. 10 to 12 to comp1ise a thermomotive member 60 and an adjustable member 61 having cooperating

contacts

62 and 63 mounted thereon. The thermomotive member of this embodiment comprises two parallel

bimetallic members

64 and 65 hold in spaced relation and placed with their low expansion sides facing each other. An insulating and separating member 66 is disposed between these bimetallic members and a g1ass cord wrapping 67 is provided around these mombers to maintai1mthe mechanical and thermal rel-ation so one another. Electrical connection is ensured between the tops of

bimetals

64 and 65 by means of the flexible conductor 68 hold under the contaot 52 on bimetal 65 and through a rivet 69 to bimetal 64. Aside from the modifications shown the device is similar to the previously described form.

The operation of the thermomotive member 60 is substantially the same as the above-described device, for as the contacts first make, the bimetal 64 which also acts as the heater forces the free end of the primary bimetal 65 farther to the right. The thermomotive action 01 the bimetal 64, however, results from the flexing due to its regular bimetallio action rather than from a change in its overall length. As heating coutinues, the bimetal 65 will flex to -tloe leih, over coming the force exerted by the heater bimetal 64, and eventually efiect Separation of ehe nontacts 62 and 63. Upon first separacion of the contacts the heater bimetal will cool rapidly, exerting a force toward the leih through the glass cord wrapping thereby substantially augmenting the oontact separation. Hera as in the previous embodiment the thermomotive efieot of the secondary or heater element is arranged to be superseded by that of the primary olement.

In a physical embodimen, the material for bimetal member 65 was similar that used for bimetallic member 35 having the same general dimensions, while the secondary bimetallic member 64 was of .020" thick material of the same composition as the compensator bimetal 32. The narrowed section of the secondary member 64 had an approximate efiective 1ength of 1fg" and a width of 1%"- The insulating medium 56 was The offset dimension between said members, the less active member having an offset to prevent overstressing thereof ancl t control the diiferential between the temperatures of the more active member at opening and. closing of said electrical connections, the initial heating of said less active member ca1ising a rapid thermomotive action in opposition to the thermomotive action of said more active member on heating, and the initial cooling 013 said less active member causing rapid movement in opposition to the movement of said more active member an cooling.

7. In an input control switch, thermomotive means having a free end and a fixed end, said means comprising two thermomotive members of thermomotively dissimilar materials disposed in substantially parallel spaced relation, with rigid mechanical connections between said members at two points, thermal insulating means disposed between said members, electrical connections including contacts cyclically operable by the free end of said thermomotive means for supplying energy 130 the less active of the two members to rapidly heat the same during each cycle, the more active member receiving heat from the less active member, and means for holding said members and the associated therma1 insulating means in close constant association with one another, ehe initial heating of said less active member causing a rapid thermomotive action in opposition to the thermomotive action of said more active member on heating, and the initial cooling of said less active member causing rapid movement in opposition t;o the movement; of said more active member on cooling.

8. In an input contro1 switch, a thermomotive means having a free end and a fixed end, said means comprising two thermomotive members of thermomotively dissimilar materials disposed in substantially parallel spaced relation, with rigid mechanical connections between saiol members at two points, thermal insulating means disposed between saicl members, electrical comnections including contacts cyclically operable by the free end of said thermomotive means for supplying energy 120 the less active of the two members to rapiclly heat the same during each cycle, the more active member receiving heat from the less active member, the latter member being relatively thin so as to have W mass and high electrical resistivity, and means associated with the latter member 130 prevent buckling thereof, the initial heating of said less active member causing a rapid thermomotive action in opposition to the thermomotive action of said more active member on heating, and the initial cooling of said less active member causing rapid movement in opposition to the movement of said more active member on cooling.

9. In an input control switch, thermomotive means having a free end and a fixed end, said means comprising two thermomotive members of thermomotively dissimilar material dlsposed in substantially parallel spaced relation with rigid mechanical connections between said members ab two points, thermal insulating means disposed between said members, electrlcal connections including contacts cyclically operable by the free end of said thermomotive means for supplying energy to the less active of Ehe two members 1:0 rapidly heat the same during each cycle, the more active member receiving heat from the less active member, means for holding said members and the associated thermal insulating means in means to facilitate relative motion between the less active member and said thermal insulating means, the initial heating of said less active member causlng a rapid thermomotive action in opposition 110 the thermomotive action of said more active membefon heating, and the initial cooling of said less active member causing rapid movement in opposition to the movement 0f said more active member on cooling.

10. In an input control switch, thermomotive means comprising a pair of oppositely-acting bimetallic heat-expansibe members having different degrees cf heat expansivity, said members being disposed in substantially parallel spaced relation and being rigidly connected together ab one end, means securing said members together along substantially their entire length while permitting relative sliding therebetween, currentcontrolling contacts controlled by said thermomotive means and adapted when closed to effect; current heating of the member having the lower heai: expansiyity. the member having the higer heat expansivity receiving heat from the member having the lower heat expansivity, and said coutacts being con trolled by conjolnt action of said members.

11. In an input control switch, thermomotive means comprlsing a palr of thermomotively dissimilar members, sa1d members being disposed in substantially parallel spaced relation, with mechanical connectiong between said members adjacent the fixed ends am). at least at one point along the lengths of said members, a contact carried by said thermomotive means and electrically connected to the member having the lower heat expansivity, a manually-adjustable contact arranged cooperatively with said first contact, said contacts when closed efiecting currenc heating of the member having the lower heat ex pansiVity, the member having the higher heat expansivity receiving heat from the member having the lower heat expansivity, and said (3011- tacts being controlled by conjoint action of said members, the lnitial heating o1 said less active member causing a rapid thermomotive action in opposition to the thermomotive action of said more actiVe member on heating, and the initial cooling cf said less active member causing rapid movement in opposition to the movement of said more active member on cooling.

12. In an input control switch, thermomotive means comprising a pair of thermomotively dissimilar members, said members being disposed in substantially parallel spaced relation, witl1 ms chanical connections between said members ad jacent the fixed ends and at least ab one point along the lengths of said members, a contac carried by said thermomotive means and electrically connected to the member having the lower heat expansivity, a manually-adjustable contact arranged cooperatively with said first contact means including a compensator element for positioning Said second contact according to ambient temperatyre, said contacts when closed eflecting current liea'ting of the member having the lower heat expaiisivity. the member having tne higher heat expahsivity receiving heat from ehe member having the lower heat expansivity, and said contacts being controlled by conjoint; action of said members, the initial heating of said less active member causing a rapid thermomotive action in opposition to the thermomotive action of said more active member on heating, and the c1ose constant association with one anqther, and initial cppling of said less act1ve member sausing rapid movement in opposition to the movement f said more active member on cooling.

13. An input control switch according to claim 12, including means f01 efiectin initial adjustment of said compensator elemenu.

14. An input control switch ac-eording t-o claim 12, including a spring supporu f01 said second contact an adjusting arm connected 120 said support and movable loy said compensaoor element, and a manually-adjustable eam engaging said arm.

15. An input svvitch according 50 claim 14- wherein said compensator is disposed ab a 1ight angle to the adjusting arm.

16. An input control1er for supplying a predetermined average wattage input 170 a remotely connected heating load, comprising: ci1cuit Controlling, connections including contacts adapted to be cyclically closed and opened, the relative lengths 01 the c1ose and open intervals deterd mining the average wattage input to said load; means for initially efiecting Closure of said comtacts to starb an input control function; thermomotive means operative 120 cyclically open and close said contacts, said thermomotive means comprising a primary thermal-responsive memher having a relatively high thermomotive characteristic and a re1atively high eifective thermal mass operable upon heating to effect opening of said contacts and operable upon cooling 110 effect closing of said. contacos, and an oppositely-acting secondary thermal-responsive member haVing a relatively lower efiective thermomotive characteristic and a relatively lower efiective thermal mass mechanicaliy coupled to said primary memleer for conjoint thermomotive action of the two members and for transfer of heat therebetween; said circuit controlling connections being ar- 1anged to effect heating of said secondary memher when the contacts are closed, thereby to effeet an initially rapid thermomotive action of said secondary member tending 120 maintaiu said contaccs closed and lengthen the on cye1e, and subsequent greater thermomotive action 01 said primary member, in response to heat transferred thereto from said secondary member, effective to open said contacts, whereupon the heating ef said secondary member is interrupted and. the latter cools rapidly efiecting augmented opening cf said connectiong and lengthening of the 011 cycle.

17. An input controller according 110 claim 16, wherein said thermomotive means comprises a bimetal primary member naving a movable portion, and a rapidly expansible and contractlble currenc-conclucting secondary membey having one end fixed said movab1e pertien, said secondary member serving, by its rapid expansion and contraction, to efiect the desirecl secondary thermomotive action.

18. In an input control switch, a thermomotive means having a free end and a fixed end, said meang comprising two thermomosively dissimilar members disposed in substantially parallel spaced relation, said member5 being rigidly connected together ab two points, therrnal insulating means disposed between said members, electrical C011- nections including contacts cyclically operable by the free end of said thermomotive means for supplying energy to the less active of the two members to rapidly heat the same during each cycle, the more active member receiving heat from the less active member, the latter member being relatively thin so as have 10W mass ancl high electrical resistivity and having a rectangular cross-sectien With the broader surface thereof disposed parallel 120 said more active member, and means securing said less active member to said. more active member along their entire length between said two points to prevent buckling of said less active member and to maintain a c1ose constant association between said members while permitting relative sliding motion between said members, the initial heating of said less active member causing a rapid thermomotive acaion in opposition the thermomotive action of said more active member on heating, and the initia1 cooling of said less active member causing rapid movement in opposition to the movement of said more active member on cooling, the thermomotive action of said more active member 011 heating and cooling ultimately dominating the thermomotive action of said lass -active member on heating and cooling respectively.

WALTER I-I. VOGELSBERG.

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

UNI'IED STATES PATENTS Number Name Date 908,679 Kelley Jan. 5, 1909 1684,709 Lowenstein Sept. 18, 1928 1,924647 McGregor Aug. 29, 1933