US2685636A - Electric heating unit control - Google Patents

Description

Aug. 3, 1954 w. H. VOGELSBE ELECTRIC HEATING UNIT CONTROL Filed 001;. 8 1951 5 Sheets Sheet l F/c j.

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3, 1954 w. HQVOGELSBERG 2,685,636

ELECTRIC HEATING UNIT CONTROL Filed Oct. 8, 1951 3 Sheets-Sheet 2 3, 1954 w. H. VOGELSBERG 2,685,636

ELECTRIC HEATING UNIT CONTROL Filed Oct. 8. 1951 5 Sheets-Sheet 5 Patented Aug. 3, 1954 UNITED STATES iATENT OFFICE ELECTRIC HEATING UNIT CONTROL Application October 8, 1951, Serial No. 250,326

1 9 Claims.

The present invention relates to wattage controllers for use with electric range surface heating units and more particularly to a controller for use in effecting initial rapid heating of the surface unit to bring said unit to its operating temperature quickly.

Electric ranges currently being manufactured are equipped with four surface heating units. These usually comprise two heating units approximately 6 in diameter and of approximately 1200 watts capacity, adeep well cooker having a heating unit or" approximately 1200 watts capacity, and an 8 heatin unit having approximately 2169 watt capacity. This latter unit gives the housewife a large amount of available heat for use with the larger cooking pots or oversize pans, pressure cookers, etc. The present invention relates to an improved controller and electrical system that is particularly useful with this large surface heating unit.

To eifect rapid heating of the surface heating units by first using a high wattage or over-energizing and subsequently reducing that wattage to some lower normal value, has been generally known as flashing. In flashing, the 1200 watt 6 units are operated at 4800 watts for approximately 3c seconds, and then the wattage is reduced to 1206 watts after the unit has reached the desired operating temperature. This l-to-l energization ratio between flash and normal operation can he obtained by a series parallel arrangement of two approximately equal resistance coils. It is also possible to obtain this in the smaller units by switching from a 236 volt to a 118 volt line. A similar two-coil series-parallel approach on the larger 8 units would give approximately 8409 watts durin the flash interval. This wattage is considered excessive and is, therefore, avoided in the design of present day electric ranges. One approach to flashing the larger 8 units without overloading the supply lines to an electric range is shown in the Patent No. 2,419,083, issued April 15, 1947, to J. W. Myers. The patent arrangement, however, requires a three-coil heating unit and only a portion of the unit flashes to its full operating temperature While the remainder i not energized until the flash interval is completed.

A prime object of this invention is to provide a system for flashing an electric range surface unit such that toe heating unit will heat initially and simultaneously over its entire surface in attaining its operating temperature, and thereafter will operate at this temperature throughout the entire surface of the heating unit.

A further object is to provide a system and controller therefor that will not overload the supply line to an electric range and will show economies over previous arrangements.

In my copending application Serial No. 157,933, filed April 25, 1959, a flasher switch construction system is provided for use with a 6 heating unit. ihat device employs a single thermostatic control member both to time the hash operation and to control the normal operation. Further, iu makes use of a direct connection of a heating unit across the line to obtain high or input in order to insure continuous energization of the heating unit. Moreover, the system 8.1. ploys a thermostat which has a memory or history characteristic which operates to prevent damage to the system on repeated attempts at reiiashing by the user.

Another object of this invention is to provide an 8 flasher system and switch construction which utilizes these features, and which is easily adapted to fit the general framework of the 6" flasher witch mentioned above.

Briefly, the present invention contemplates the provision of an 8 surface unit comprising two coils, on having twice the resistance of the other, in combination with a 3-wire electrical supply system such that during the flash period the smaller resistance coil is energized oy a line voltage E, e. g. 118 volts, while the double resistance coil is energized by a line voltage 2E of twice the first voltage, c. g. 236 volts. During normal oporation, the resistance coils are serially connected across the 236-volt line. By such an arrangemerit, a flash wattage in the vicinity of 4808 watts is supplied for approximately one minute, while during run the energization is approximately 2161'. watts. This, of course, is the situation for a high heat condition. Lower heats are pro-- vided by reducing the time that the 4890 watts is supplied and during normal or run operation by cyclically making and breaking the 2100 watt circuit at a predetermined average rate.

Referring now to the accompanying drawings,

1 is a diagrammatic illustration of the systern in its oil condition;

Figs. 2 to 5 show the conditioning of the various switch elements during the various operating conditions;

Fig. 6 is a rear view of the controller with its various connections;

Fig. '7 is an elevational section taken along line l'! of Fig. 6;

S is a fragmentary elevational section taken along line 3-8 of Fig. 6;

Fig. 9 is a face View of two of the switch members and their cooperatin cam;

Figs. 10 to 13 are similar views t lien along line l 3is of Fig. 9, showing various positionings of the switch parts of Fig. 9 during difierent conditionings of the controller;

Fig. 14 is a front face View of the controller with the cover and cam removed; and

Fig. 15 is a sectional view along line li5 of Fig. 14 with the cover and in place.

The system for flashing, as shown diagrammatically in Fig. 1, includes a 3-wire supply designated at L1, N, and L2, and a control device generally designated as it under the control of the user through a manual adjusting knob H for controlling energization of an electric range surface unit l2 comprising heating elements or coils ifia and i213. To obtain approximately 4800 watts energization (4725 watts, to be exact) during the flash and approximately 2100 watts en ergization during normal conditioning, heating element lid is chosen at 8.8% ohms while heating element 92b is selected at 17.58 ohms. These resistances are chosen for a nominal line voltage (i. e. L1 to L2) of 236 volts with a nominal voltage from line to neutral (N) of 118 volts. ing coils, if of the rod type, are of equal cross" sections and are designed to give the same watt age per lineal inch of coil during normal or run operation. Fig. 1 shows a load is, under control of switch it, which may be considered to be the oven heating unit or any other load in the same range and on the same range circuits. The con trol device it, during the overenergization period of heatin unit 92, deenergizes load 25 to avoid exceeding the overall rating of the range during that interval. This is termed load dropping and is well known in the art.

The control device it is generally similar to that shown in my above-mentioned application but differs therefrom in certain respects as hereinafter described. For the purpose of this application, it sufiices to illustrate and describe the control device only to the extent necessary for a clear understanding of this invention. In Fig. 1, the dotted lines represent mechanical connections or engagement of parts in operation.

Control device i 3 includes a manually operated on-off switch blade "2.9 and its cooperating relatively stationary contacts 2! and 22, two latch controlled blades 25 and 26 and their cooperating relatively stationary contacts 21, 28 29 and 353, a manually operated switch blade 33, a switch blade 35 which is either manually operated or latch controlled, and a continuously adjustable ambient compensated thermostat control switch 38. Manual control knob i l, operating through shaft it, controls the following: the movement of cam 4!, which can manipulate lade 2% from an off position where it engages contact 23 to an on position, where it engages contact 22; cam d2 which can manipulate blades 33 and 35; cam is which controls thermostatic switch 38 by forcing an adjustable blade 44 with its contact 45 into engagement with a thermostatic member 56 thru its contact ll to thereby p eselect the various input levels; and cam 458 to actuate a latch member 58 which is pivoted about axis 5! for actuating blades 25 and 2%, respectively, through extension arms 52 and 53. though the various cam members are shown as individual peripheral cams operated from the same shaft, it is preferred to incorporate the cam races into a single molded member having a plurality of face cam surfaces. This single cam is The heat-- shown in Figs. '7 and 15 as member 53. This cam is rotated through shaft to by means of control knob H or its equivalent. Control knob l is marked with suitable indicia (not shown), permitting the user to select a full range of inputs from some low or simmer heat to the high or 100% energization, i. e. 2190 watts.

The latch 58 is provided with latching surface it which is engageable by a U-shaped self-heating bimetallic prop member 5?. Blades and 25 are spring biased, preferably by their own resilience, toward the right as viewed in Fig. 1, and are held in engagement with contacts 28 and 39, respectively, by latch 55. In the off position the lobe of cam holds the latch 56 in this conditioning, while at other positions of the control knob ii prop 5? is used to hold blades 25 and 26 in engagement with contacts 28 and 3-8 during the dash interval.

The thermomotive member it comprises bimetal 58 and heater 59 insulated from one another. On heating, the thermomctive member moves generally toward the left causing separation of contacts ll and iii. With the heater 59 deenergized, the thermomotive member cools and flexes generally back toward the right, with an eventual reestablishment of the circuit by engageinent of contact ll with at. This thermostatic device is generally of the type disclosed and claimed in my coopending application Serial No. 157,932, filed April 25, 1950, now Patent 2,623,137. The usefulness of this device in a flasher is set forth in that application.

The switch members described thus far are generally similar to those shown in my firstmentioned application No. 157,933. The constr' ction of blades 33 and does differ and this can best be explained by reference to Figs. 9 and 10. Switch blade is in the form of a bent strip fixed to the switch casing at as and has a reverse bend at El and an extending portion 52 which carries an electrical contact so. The blade is self-biased toward the cam 12 and. is provided with a raised portion at for actuation by the lobe of said cam. The self-biasin movement of said blade is determined by engagement of raised portion E i with the flat of said cam. The switch case is recessed at to accommodate the extension '32, and a hole 56 provided in said switch case accommodates a finger extension ii? of said blade for angularly positioning the switch blade with respect to the axis of the cam.

Switch blade is in the form of a strip riveted to the switch case at 58 and is self-biased toward cam 22 which it is adapted to engage through an extension 59. An insulating button it, held by fingers ii onto said blade, is adapted to engage the latch controlled blade 26. Blade 35 can, therefore, receive motion from either the latch controlled blade 26 or the lobe on cam A12.

Blade 35 affixed to the switch case at 53 connects through a special bus 12 (Figs. 6 and 7) to the base of bimetal 5-8 of the thermostat. This bus runs along the back of the switch case, makin a degree bend out of this plane at 12c and then is bent to lay under the bimetal (Fig. 8). The rivet connection at 68 is insulated from surrounding members at the switch case rear by an insulating barrier 73. An insulating barrier is also molded into the switch case at M to isolate the rivet connection from stationary contact 30 and blade 28.

Referring now to the mode of operation of the present invention, in the off position (Fig. 1) of the switch, heating unit I2 is disconnected from lines L1 and L2 of the power supply. One end of heating element it, however, is connected through blade 26 and contact as to the neutral connection, preferably grounded, of the power supply. Continuity of electrical supply is maintained to the heating load through line L1, blade 2@, contact 2i and switch it.

Assume first that the control knob ll is rotated to one of the operating heats less than high (Fig. 2). Cam all forces blade 2 into engagement with contact 22, and cam i2 is moved out of the way of blade 33 permitting it to engage blade 35. The lobe of cam 68 is also moved out of the way of the latch member 59, permitting the prop member 51 to hold the blades 25, 2t and 35 into their overenerg'ization position, while earn 43 forces blade 45 into engagement wi h therrccmotive member 46 and pre-stresses it in amount depending upon the desired heat. Under this conditioning, the heating unit [2 is overenergized, for coil I20. is placed across the 118 volt line, i. e., lines L1 and N, while coil i2?) is placed across the 236 volt line, i. e., lines L1 and L2. The circuit be traced as follows: Starting from L1 current flowing to the heating unit proceeds through blade contact 22, blade contact 23, to the junction of coils iiia and I213. One portion of current then travels through coil 52a to blade 23, contact and thence to line N. Another portion of the current flows through coil [2b, thermostat contacts 45 and ii, heater E53 and thence to line L2. Engagement of blades 35 and 33 places the bimetallic prop in shunt across contacts 45 and 4'. of thermostatic switch 38. However, the low resistance path provided by these contacts does not permit sufiicient current to flow through the shunt path of the prop 5! for actuation of the latter. The overenergization or flash period of heating unit i2 is determined by the thermostatic switch 33 can be varied according to the setting of said thermostat through cam 43 and knob l l. The len th of the overenergization period is thus synchronized with the particular selected heat of the heating unit so that the heating unit heats rapidly to a preselected temperature. The length of the overenergization period is also determined by the residual heat in thermornotive member 4% so that the heating unit will not be dangerously overenergized. This is known as the history heater eirect. Suincient mass is usually associated with the thermomotive s to give it a time constant commensurate with that of the heating used. During the flash interval the circuit to load is deenergized for none of contacts 29, or ii are energized at L1 potential.

Upon attainment of a. predetermined conditioning of thermostatic switch contacts es and 4'! of said switch separate, causing the current, which had been flowing from heating element 52 through said contacts to line L2, to travel through prop latch 5?, blades biuietal 533, heater 59, and thence to line L2. The eifect of this "m to cause flexing o the upper end of birnetal prop toward the left to thereby release latch 5t under the bias of blades causing blade to engage contact 22', blade 25 to engage contact 29 and blade to bear surface 420 of earn The control device i is now in its normal run condition (Fig. 3) for the selected heat less than high. Under this conditioning, heating elements its and 521: are serially con nected across the volt line, i. e. L1 and L2, and the selected heat is maintained by cyclically opening and closing of contacts 45 and 4'! of thermostatic switch 38.

The circuit for the normal energiza-tion for heats less than high may be traced from L1, to blade 2;], contact 22, blade 25, contact .2! to contact 29, blade 25, coil lZa through coil 21) to adjustable blade 45 of thermostatic switch 38, contacts 45 and 41, heater 59, and then to line L2. During this normal energization of the heat ing unit, the electrical supply is restored to the load it through L1, blade 251, contact 22, blade 25, contact 2'; and switch H5. Under continuous enerthe serially connected coils Ma and i213 across the 236 volt line, a total of 2100 watts will be consumed. At heats less than full, the serially connected heating coils are cyclically energize and deenergized by thermostat 33 to give varying percentages of the 2100 watt load, depending upon the thermostat setting.

Full energization of the heating unit l2, i. e. high heat, is obtained by connecting heating unit sections 52aand I2?) serially across L1 and L2 independently of the thermostat switch contacts. The circuit for this connection may be traced from line L2 through heater El bimetal closed contact blades 33 and 35 (Fig. 5), prop latch 51, heating elements i222 and 12a in series, and thence through blade 25, contact 29, contact 2?, blade contact 22, blade it, to line L1. In the high heat position of control knob l l, lobe holds blade 35 in engagement with blade 33, as shown in Figs. 4 and 5. The overenergization conditioning of the heating unit at high heat is similar to that during overenergization at heats less than full, except that the lobe 201 of cam 42 is used to effect engagement of blades 35 and 3-3. This is in addition to the action of blade 26 which forces blade 35 into engagement with blade 33 through protection it, when blade 26 is latchheld in engagement with contact 3.). Thus, regardless of whether blades 25 and 25 are latchheld in contact with contacts 23 and 35 or are in a released position wherein they engage contacts 21 and 29, blade engages blade 33. The overenergization period is terminated upon 0 ening of contacts Q5 and 43 of thermostatic switch permitting the overenergization cur rent to flow throu h prop latch 5?, blades 33, 35 and biineta-l 53. The flexing of prop it] releases latch 55], permitting blades 25 and 2% to engage contacts 2'5 and 29 respectively, to institute serial connection of coils 12c, and I217. During the series connection in the high heat position, contacts and i? of thermostatic switch 33 normally maintained separated for heater 59 is continuously energized. The advantages of the shunting of the thermostatic contacts at the high heat positions in flasher systems has been brought out in my first-mentioned copending application No. 157,933.

From the foregoing description it will be seen that the control device iii shown diagrammatically in Fig. 1 has been bodied (Figs. 5 to 15) in a switch structure similar to that disclosed in my aforementioned application No. 157,933. It will be noted that the particular system shown in. Fig. '1 requires that minimum changes be made in the switch structure of that application for adaptation therein.

Fig. 6 shows the manner in which the switch connects the heating unit [2 to the electrical supply lines. The terminal connections can best be understood by a comparison of Fig. 6 and Fig. l. A terminal as which is connected to the base of blade 26 is used for a connection to line L1. A terminal 8| attached to stationary contact 28 connects to the junction of coils lZa and I211. A terminal 82, which is connected to bus 93 carrying contacts 2 I, 2? and 29, connects to the load i 5. A terminal 83 connects stationary contact 30 to the neutral side of the line. A terminal 8 attached to blade 25 connects to one side of coil 2a. A terminal 85 attached to the base of prop latch 51 connects to one side of heating unit 521), while a terminal 86 secured electrically and mechanically to the base of heater es of thermostat 38 connects to L2.

It should be pointed out that the release bimetal 51 is placed under conditions different from those of the prop latches of the earlier, smaller heating unit flashers. At the termination of overenergization, release bimetal 5? receives 13% amperes, while during run at the high heat position where it is continually energized, it receives 8.9 amps. With the 6"-2-coil flasher or the aforementioned application No. 157,933, the current of termination of overenergization is 21.2 amps, while the current during high heat on run is only 5.3 amps. The material used for the release bimetal in the present device is known to the trade as High-Heat 4'7, and is .025 thick. The inactive section of the bimetal that is directly under the latch is of substantial lengthto improve the efficiency and the dissipation characteristics of the latch prop. Further the initial bias on the release bimetal when cold is The thermostat 38 is essentially the same as that of the aforementioned application except that a new material is selected for heater es. watts dissipated by the thermomotive member substantially the same as the device of the previ ous disclosure.

In switching from the overenergization condi-- tion of the heating unit to the normal run condition, as described above, the latch 50, on release, permits blades and 25 to move from contacts '28 and to contacts 21 and 20, respectively. During this switching, blade 25 is maintained at L1 potential while stationary contact 3%} is maintained at neutral potential. To avoid the possibility of drawing an are through the medium of moving blade 26 between stationary contact 30 and contact 25) which assumes an L1 potential as blade 25 engages contact Z'i, latch 55 is damped. The damping of latch 52 slows down the movement of blades 26 and 25 to such an extent that any are established between contact 3t and blade 26 will be extinguished before the arc-over can occur. The damped latch construction is disclosed and claimed in an application to John J. Lawser, Serial No. 254,037, filed October 31, 1951. Briefly, latch (Figs. '7 and 9) is provided with a hole 88 into which is inserted an absorbent, resilient pad 90 such as sponge rubber or felt. The latch rides between lands 9! and 92 on the switch case. The space between these lands is approximately and pad 39 before insertion between the lands is approximately Before insertion the pad is impregnated with a special fluid to cooperate therewith and to provide damping action. It has been determined that a fluid such as Dow-Germ ing DC 200 having a viscosity of 60,000 cstks. provides an effective and satisfactory damping action.

While the present invention is particularly intended for use in the manner described, it is intended that the invention shall be applicable to This resistance is chosen so as to keep the 8 any use to which it may be applied by those skilled in the art.

I claim:

1. A device for effecting difierent modes of energization of an electrical heating unit having a first element of predetermined resistance and a second element of substantially twice the resistance of the first element, from a three-wire supply line having two main conductors and a neutral conductor supplying one voltage between a main conductor and the neutral conductor and a second voltage between the main conductors substantially twice the value of the first voltage, said device comprising: three load terminals, one for connection to an end of each of said elements and the other two for connection respectively to the other ends of said elements; three input terminals, one for connection to said neutral conductor and the other two for connection respectively to said main conductors; two-position switch means; circuit means controlled by said switch means in one position thereof for connecting said first element between a main conductor and the neutral conductor and for simultaneously connecting said second element between the two main conductors, circuit means controlled by said switch means in the other position thereof for connecting both of said elements in series between said main conductors; means for initially establishing the first position of said switch means, thereby to efiect relatively high wattage input to the two-element heating unit and rapid heating of the same to a desired temperature; and means for establishing the second position of said switch means upon attainment by said heating unit of said temperature, thereby to reduce the Wattage input to the heating unit for normal operation of the same.

2. A device accordin to claim 1, further characterized in that said switch means is biased toward its second position, and further including latch means for initially retaining said switch means in its first position, and means for effecting release of said latch means upon attainment by the heating unit of the desired temperature.

3. A device according to claim 2, wherein said latch means includes a current-operable thermomotive release element included in said circuit connections, and said release effecting means comprises current-operable thermostatic switch means also included in said circuit connections and having contacts in shunt relation with said release element.

4. A device according to claim 3, wherein said thermostatic switch means is adjustable for selection of different temperatures of said heating unit, and said thermostatic switch means serves to control the normal operation of the heating unit for selected temperatures less than the highest selectable temperature, the device further including means for effecting continuous energization of the heating unit during operation at the highest selectable temperature.

5. A device according to claim 1, including means for preventing energization of loads subsequent to said heating unit on the same supply line during the supply of high wattage to said heating unit.

6. In a system for effecting overenergization of an electrical heating unit, and for effecting subsequent normal energization of the heating unit, from a three-wire supply line having two main conductors and a neutral conductor supplying one voltage between a main conductor and the neutral conductor and a second voltage between the main conductors substantially tiwce the value of the first voltage, a heating unit comprising a first heating element having a predetermined resistance and a second heating element having a resistance substantially twice that of the first element, two position switch means, ch'cuit means controlled by said switch means in one position thereof for connecting said. first element between a main conductor and the neutral conductor and for simultaneously connecting said second element between the main conductors, circuit means controlled by said switch means in the other position thereof for connecting both of said elements in series between said main conductors, means controlled according to the temperature condition of said heating unit for effecting actuation of said switch means from said first position to said second position upon attainment of a desired operating temperature of the heating unit, a switch for interrupting supply of current to loads subsequent to said heating unit on the same supply line during the first-mentioned connections of said elements, and a common bus carrying contacts of said switch means and said switch serving to effect circuit continuity to subsequent loads during the last-mentioned connections of said elements and during the off condition of the system.

.7. In a system for efiecting overenergization of an electrical heating unit, and for effecting subsequent normal energiaation of the heating unit, from a three-wire supply line having two main conductors and a neutral conductor supplying one Voltage between a main conductor and the neutral conductor and a second voltage between the main conductors substantially twice the value of the first voltage, a heating unit comprising a first heating element having a predetermined resistance and a second heating element having a resistance substantially twice that of the first element, two position switch means, circuit means controlled by said switch means in one position thereof for connecting said first element between a main conductor and the neutral conductor and for simultaneously connecting said second element between the main conductors, circuit means controlled by said switch means in the other position thereof for connecting both of said elements in series between said main conductors, said switch means being biased toward said second position, latch means for initially retaining said switch means in said first position, and means for effecting release or said latch means upon attainment of a desired temperature of the heating unit, whereby to effect movement of said switch means from said first position to said second position.

8. In a system according to claim '7, wherein said latch means includes a current-operable thermoinotive release element, and said release effecting means comprises current-operable therniostatic switch means having contacts in shunt relation with said release element.

9. In a system according to claim 8, wherein said thermostatic switch means is adjustable for selection of different temperatures of said heating unit, and said thermostatic switch means serves to control the normal operation of the heating unit for selected temperatures less than the high est selectable temperature, the system further including means for effecting continuous energization of the heating unit during operation at the highest selectable temperature.

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