US3610887A

US3610887A - Control arrangement for heating unit in an electric range or the like

Info

Publication number: US3610887A
Application number: US4523A
Authority: US
Inventors: Cloyd L Betzer
Original assignee: Roper Corp
Current assignee: RGE Corp A CORP OF
Priority date: 1970-01-21
Filing date: 1970-01-21
Publication date: 1971-10-05
Anticipated expiration: 1988-10-05

Abstract

A control device for a heating unit in an electric range in the form of a low-power resistor and switch in a tubular capsule recessed in a convenient position near the unit. The capsule has a presented wall which is flexible so that a portion of the resistor therein may be shorted out to change the resistance value simply by pressing at a desired point along the length of the capsule. The capsule is sealed and contains a fluid so that when the capsule is pressed at a second point, for example, at the end of the capsule, pressure is developed resulting in release at the first point. The resistor is controllingly included in the input of a solid-state circuit having the heating unit in the output.

Description

United States Patent [72] Inventor Cloyd L. Betzer Kankakee, Ill. [21] Appl. No. 4,523 [22] Filed Jan. 21, 1970 [4S] Patented Oct. 5, 1971 [73] Assignee Roper Corporation Kankakee, Ill.

[54] CONTROL ARRANGEMENT FOR HEATING UNIT IN AN ELECTRIC RANGE OR THE LIKE 17 Claims, 9 Drawing Figs.

[52] US. Cl 219/501, 338/47, 338/96 [51] Int. Cl 1-105b 1/02 [50] Field of Search 29/448, 482, 501; 338/92, 96, 99,125, 47 [56] References Cited UNITED STATES PATENTS 3,418,850 12/1968 Goddin 338/47 3,428,785 2/1969 Welch Primary Examiner-Bernard A. Gilheany Assistant Exam iner-F E. Bell Attorney-Wolfe, Hubbard, Leydig, Voit & Osann ABSTRACT: A control device for a heating unit in an electric range in the form of a low-power resistor and switch in a tubular capsule recessed in a convenient position near the unit. The capsule has a presented wall which is flexible so that a portion of the resistor therein may be shorted out to change the resistance value simply by pressing at a desired point along the length of the capsule. The capsule is sealed and contains a fluid so that when the capsule is pressed at a second point, for example, at the end of the capsule, pressure is developed resulting in release at the first point. The resistor is controllingly included in the input of a solid-state circuit having the heating unit in the output.

CONTROL ARRANGEMENT FOR HEATING UNIT IN AN ELECTRIC RANGE OR THE LIKE It is an object of the present invention to provide a control arrangement for an electric range that is distinctly different in appearance and function from that used in conventional ranges and in which the rate of generation of heat may be controlled conveniently by touching with the fingertip. It is another object to provide a control arrangement which utilizes a longitudinally extending resistor in a flexibly walled tubular capsule which retains a resistance setting corresponding to the point on the capsule which is pressed but which cancels such resistance setting to change the rate of heat generation automatically when the device is pressed at a second point along its length.

It is a general object of the invention to provide a control device for heating unit in which the user need not be concerned with adjustment of a calibrated knob or the like and in which the rate of generation of heat is immediately responsive to the user's wish, with pressure applied halfway along the device corresponding approximately to 50 percent heat output, and so on, without exercising of care or attention and with the heat output being reduced to minimum, or increased to maximum, by pressing near the respective ends of the device. Positive shutoff is assured by an integral switch contained at one end of the device.

It is another object of the present invention to provide a control device for an electric range which not only constitutes ultimate simplification in control, but which imparts a distinctive appearance to the range and which, on the practical side, facilitates cleaning with no necessity for wiping around or under control knobs of conventional type. Furthermore, the device described can be used for both oven and surface unit control.

It is yet another object of the present invention to provide a control device for a heating unit in an electric range or the like, which is long lived, capable of outlasting the range with which it is used, and which is inherently simple and inexpensive, pennitting continuous infinite variation of heat output at a cost no greater than that required for other types of solidstate controls.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawing in which:

FIG. 1 is a fragmentary view showing a heating unit, or burner, and a portion of the backsplash panel of an electric range embodying the present invention;

FIG. la shows that approximate heat rate versus resistance characteristic;

FIG. 2 is a solid-state control circuit of a type which may be used with the control device shown in the remaining figures;

FIG. 3 is an enlarged elevational view, in partial section, of the control device following application of finger pressure;

FIG. 3a is a fragment showing the nature of a flexible conductor;

FIG. 4 is a cross-sectional view taken along line 44 in FIG.

FIG. 5 is a cross-sectional view at the point of pressure application, taken along the line 5-5 in FIG. 3;

FIG. 6 is a view similar to FIG. 3 but showing application of fingertip pressure at the end of the capsule for turning off the heating unit; and

FIG. 7 is an enlarged section showing an alternative construction.

While the invention has been described in connection with a preferred embodiment, it will be understood that I do not intend to be limited to the particular embodiment shown, but intend, on the contrary, to cover the various alternative and equivalent constructions which are included within the scope of the invention.

Turning now to the drawing there is shown in FIG la portion of an electric range top having a heating unit 11 and a control device 12 which is mounted in a control panel 13. The control device, as will be seen, serves to control the rate of heat liberated at the heating unit as well as providing positive shutoff. The control device 12 includes a variable control resistor 15 (FIGS. 2 and 3) made up of conducting elements l6, 17. It will suffice for the moment, to state that means are provided for establishing a predetermined, but variable, resistance across the output terminals indicated at 18 and I9.

The control resistor 15 is connected in series with a capacitor 20 across the regular domestic AC line providing, in efiect, a potentiometer having a variable voltage control terminal 19. Also connected across the AC line is a series circuit formed by the heating unit 11 connected in series with a thyristor" solid-state device 25, the heating unit being in series with the main, or output,

terminals

26 and 27 of the solid-state device. For controlling conduction in the solid-state device 25, the gate, or input, terminal 28 thereof is connected to the control terminal 19 via a voltage responsive triggering element 29 having a predetermined threshold voltage for conduction, for

example, a diode of the type known as a DIAC." A neon lamp having a predetermined firing voltage may also be used.

In a practical case where the r.m.s. line voltage is on the order of 240 volts, the variable control resistor 15 may have a maximum resistance on the order of 370,000 ohms. The capacitor 20, which is in series with it, may have a capacitance of 0.1 microfarad. In operation, the capacitor charges at atime rate proportional to the selected value of the variable resistor 15. When the resistance is small, the capacitor charges quickly, almost instantaneously, at the beginning of each half cycle of the AC voltage wave, and when the resistance is large, the capacitor will require almost a full half-cycle to reach the desired voltage at 19. As is understood by those skilled in the art, when the capacitor has charged for sufficient time to reach the desired firing voltage of the trigger device 29 (for example, 35 volts with a DIAC"), the capacitor discharges through the trigger device into the gate of the thyristor" I8, which triggers it on to conduct for the remainder of the half cycle AC voltage wave. Hence, the heating unit ll conducts successive pulses of current with the length of the pulses being dependent upon the set value of control resistor 15.

The heating unit 11, commonly used for top burner purposes, may have a nominal current rating in the range of 5-14 amperes. The thyristor" solid-state device 25 may have a maximum rating of 15 amperes, and may be of the TRIAC Type GEXIZ, manufactured by General Electric Co., or QUADRAC," which differs only in having an integral trigger device and which is manufactured by Electronic Control Corp. Under the conditions set forth above, varying the resistor 15 throughout its range produces a corresponding variation of the heat output rate of a 15 ampere heating unit over a range of approximately B.t.u. per hour to approximately 10,00 B.t.u. per hour.

In accordance with the present invention, the resistance control device 12 is in the form of an elongated hollow capsule or tube having a longitudinal resistor element with a com panion conductor extending parallel to it, so arranged, and with the presented wall of the capsule being formed of such flexible material that when fingertip pressure is applied at a selected point along the'length of the capsule the resistance element is brought into local contact with the conductor so that a corresponding selected value of resistance exists across the terminals.

Further in accordance with the invention, means are provided for maintaining persistent contact at the selected point and for later turning the heating unit off at the end of the cooking operation.

Thus, referring to FIGS. 3 and 4, the control device I2 is in the form of a capsule 30 having a terminal end 31 and having a remote end 32. The capsule having an upper wall 33 to which fingertip pressure is applied and a lower wall 34. Extending longitudinally within the capsule are the conducting

elements

16 and 17. Both of the conducting elements may be in the form of a resistance element or, alternatively, one of the elements may exhibit resistance, while the other simply serves as a return conductor. In any event, the element 16 is so arranged'that when fingertip pressure is applied at a selected point, for example, point 35 along the length of the capsule 30, the

elements

16 and 17 are brought into bridging engagement thereby to determine the amount of resistance existing between the

output terminals

18 and 19. To both provide the necessary flexibility and to achieve the necessary resistance the elements 16, l7-in particular l6are preferably fonned as a small diameter, continuous helix of wire having successive, closely spaced convolutions as shown in FIG. 3a. It will be understood, however, that the invention is not limited thereto and that other flexible forms of resistance element may be employed, such as "ribbon resistors.

Further in accordance with the invention means are provided for holding the walls of the capsule together to obtain persistent contact between the resistor elements after fingertip pressure has been removed and for subsequently separating the walls. Referring to FIGS. 4 and 5 the capsule has a central longitudinal space 40, with means on the upper and lower walls for mutual clinging engagement. In the preferred embodiment, the interengaging means is in the form of a tongue and groove connection, with the tongue indicated at 41 integrally formed on the upper wall 33 of the capsule, and with a,

registering groove, indicated at 42, integrally formed on the lower wall 34, the width of the tongue being slightly greater than the width of the groove to provide a mild interfering fit, sufficient to keep the tongue captive, and contact maintained, at the region of pressing, but nevertheless capable of easy separation when fluid pressure within the space 40 is slightly increased.

The flexible material of which the capsule is made is preferably soft and pliable plastic, which may either be molded or extruded in continuous length, and of sufficiently thin section so that the upper wall is locally defonnable as shown in FIG. 3, yet sufficiently elastic so that when the tongue and groove engagement illustrated in FIG. 5 is released, the capsule tends to return to is original cross-sectional, in this case circular, shape. A number of different plastic materials may be employed which meet the qualifications, for example, vinyl plastic having a durometer rating of approximately 50.

In the construction shown in FIGS. 4 and 5, the conducting, i.e., resistance, elements are preferably spaced away from the tongue and groove connection in order to permit slight overtravel of the tongue so that the slight springback" which occurs upon fingertip release will not have the effect of breaking the contact. However, to insure contact in the face of springback" the arrangement shown in cross section in FIG. 7 may be employed. Here the resistance element indicated at 16a, is in contact with a longitudinal conductor 17a which may have substantially zero resistance. The resistor 16a is embedded in the side of the tongue, indicated as 41a, and the conductor is in the form of a metallic angle having a vertical leg extending down into the groove 42a. Because of the vertical extent of conductor 17a, contact is insured regardless of small amounts of springback." In addition, if desired, a detent may be provided in the form of a longitudinal ridge on the tongue cooperating with longitudinal recess formed in the wall of the groove.

In accordance with one of the important aspects of the present invention, the capsule is sealed and contains a body of fluid and means are provided for increasing the pressure of such fluid for the purpose of breaking contact between the conducting elements and for restoring the body of the capsule to its initial cross section. As a result when the capsule is pressed as a new point, fluid pressure is built up within the capsule causing pressure to be applied against the upper wall 33. This is effective to pop out the pressed in upper wall in the previously pressed region 35 so that the cross section is restored from that shown in FIG. 5 to the normal cross section shown in FIG. 4.

For the purpose of turning the heating unit completely off, I propose two schemes. The first and simplest is to terminate one of the

resistance elements

16, 17, or both of them, short of the end of the capsule so that when the capsule is pressed in the end position there is no contact between them and have no conduction in the thyristor" 25. I prefer, however, to include within the capsule an isolation switch which is in series with the main AC supply line. Such switch, indicated at 50, in series with the upper line, has a fixed contact 51 and a moveable contact 52. The fixed contact may be mounted, as shown, on the capsule end wall, while the moveable contact is secured to a small bracket mounted on the deformable wall of the capsule adjacent the high end of the

elements

16, 17. This provides an "off position beyond the high" position.

When the capsule is in its temperature control mode, the contacts are in engagement and the control circuit is connected to the supply line. When the capsule is pressed in its "off position, as shown in FIG. 6, contact 52 is separated from the contact 51 and held in the separated condition by the tongue and groove engagement. The circuit, being isolated in the off condition, is unaffected by line transients.

Subsequently pressing of the capsule at a selected point, by increasing the internal pressure, releases the moveable contact for movement into engagement with the fixed contact.

For indicating that the burner is on, a simple neon lamp 55, having a series resistor 56 may be shunted across the heating unit 11, or if desired an incandescent lamp may be employed, the brightness signifying the degree of energization.

While it is preferred to provide means at the proposed interfaces of the

walls

33, 34 for holding them persistently together after fingertip pressure is applied, it is one of the features of the present invention that a persistent dimple may be achieved at the point of pressing, with maintenance of contact, by dispensing with the clinging tongue and groove connection, or the like, and by employing instead, an inert and noncompressible liquid such as transfonner oil completely filling the inner space 40, but having a total volume which is less than the normal expanded volume of the space 40. The shortage of the liquid should be approximately equal to the reduction in internal volume which results from applying fingertip pressure at a concentrated point along the length of the capsule. Under such circumstances, the capsule will maintain a persistent dimple" since, because of the shortage of the liquid fill, the capsule will never be able to expand fully all the way along its length. When using such means for achieving persistent contact, there will be more tendency toward springback" than where frictional holding, or detenting is employed. Thus it is preferred to employ a contacting arrangement, between the

conductors

16, 17 along lines of that shown in FIG. 7 which is immune to the effects of relatively large amounts of springback."

It will be apparent to one skilled in the art that minor modifications may be made in the cross sectional configuration for the purpose of optimizing performance; for example, the cross-sectional wall thickness of the upper wall 33 of the capsule and the length of the tongue may be reduced as desired to improve local flexibility and to produce a more localized and well-defined dimple" at the region of pressing.

With respect to manufacture, the capsule may, if desired, be extruded in the form of circular or noncircular tubing, cut into lengths, following which the conducting elements and switch may be installed and the ends may be sealed, for example, by fusing of the plastic material. The capsule may be as large or as small as desired since the resistance elements serve to control only the triggering current drawn by the gate 28 of the thyristor, so that very little power dissipation is required, notwithstanding the fact that the controlled heating unit may draw 10 to 15 amperes at full load.

It will be apparent that the capsule need not be made wholly of flexible plastic material, provided that the top wall 33 is sufficiently flexible to form a dimple" upon application of normal fingertip pressure.

It is one of the features of the construction that the control device 12 may be placed in the backsplash panel or in the cook top as shown in FIG. 1. Conveniently the capsule may have a pair of grooves 61, 62 which receive the metal edges of a slot formed in the supporting surface.

The presence of the control devices need not affect the smooth uninterrupted and easily cleaned nature of the cooking top or control panel areas. in the event of spillage or soil deposit, a damp cloth may be used to wipe directly over the control devices, particularly if they are recessed approximately half-way into the surface as shown in FIG. 4. Conventional knobs, which have long characterized electric ranges in both appearance and in function, are totally eliminated and an entirely new look," having asthetic and functional merit, is achieved. The present mode of control is psychologically desirable, as one wishing to operate a heating unit at one-half of its maximum rate will instinctively press at the middle of the longitudinal scale, with all of the other settings being in proportion. Linearity of heat rate as a function of the setting of the control resistor may be achieved to the extent desired by using tapered"

resistance elements

16, 17.

The control system is easily installed in a range with economy in assembly since the solid-state device 25 may be located near the heating unit, thereby to minimize the length of current carrying runs. The remainder of the control circuit may be either nearby or remote and connected by light control wir- While the invention has been described in connection with the control of a heating unit in an electric range, including the control of an oven, it will be understood that the invention is not necessarily limited thereto, and that the control device 12 and associated solid-state circuit may be employed with equal advantage to control heaters in other environments, or indeed, to control other appliances where an efficient, neat-appearing and easy-to-clean variable control is desired.

I claim as my invention:

1. In a control arrangement for a heating unit in an electric range or the like, the combination comprising an elongated hollow capsule adapted to be mounted at an accessible surface, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals respectively connected to the resistor element and conductor, the presented wall of the capsule being formed of flexible material so that when fingertip pressure isapplied at selected different points along the length of the capsule the resistance element is brought into contact with the conductor at corresponding different points so that a corresponding value of resistance exists across the terminals, mean for maintaining persistent contact at the point pressure is applied even though the pressure is released, a solid-state control circuit having an input and an output and so arranged that the value of resistance at the input controls the amount of current at the output, means for connecting the terminals to the input, and means for connecting the output in series with the heating unit to control energization thereof.

2. In a control arrangement for a heating unit in an electric range or the like, the combination comprising an elongated hollow capsule adapted to be mounted at an accessible surface, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals connected to the resistance element and conductor, the top and sidewalls of the capsule being formed of flexible material so that when fingertip pressure is applied at a selected point along the length of the capsule the resistor element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, means for maintaining persistent contact at the selected point, means actuated by pressing the capsule at one end thereof for breaking contact, a solid-state control circuit having an input and an output and so arranged that the value of resistance at the input controls the amount of current at the output, means for connecting the terminals to the input, and means for connecting the output in series with the heating unit so that heat is developed therein at the desired rate until contact is broken by pressing of the capsule at the end thereof.

3. In a control arrangement for a heating unit in an electric range or the like, the combination comprising a tubular capsule, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals connected to the resistance element and conductor, the presented wall of the capsule being formed of flexible material so that when fingertip pressure is locally applied at a selected point along the length of the capsule, the resistor element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, means for maintaining persistent contact at the selected point, means actuated by pressing the capsule at one end thereof for breaking contact, a solid-state control circuit having an input and an output and so arranged that the value of resistance at the input controls the amount of current at the output, means for connecting the terminals to the input, and means for connecting the output in series with the heating unit so that heat is developed therein at the desired rate until contact is broken by pressing of the capsule at the end thereof, the range having a panel including a registering recess associated with the heating unit for nesting the capsule to provide an easily cleaned substantially continuous surface.

4. in a control arrangement for a heating unit in an electric range or the like, the combination comprising an elongated hollow capsule adapted to be mounted at an accessible surface, the capsule having opposed upper and lower walls extending parallel to one another, an elongated resistor element extending along one of the walls and a conductor extending along the other, terminals on the capsule connected to the resistor element and conductor, the presented upper wall of the capsule being formed of flexible material so that when fingertip pressure is applied at a selected point along the length of the capsule the resistor element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, the upper and lower walls being formed to cling to one another for maintaining persistent contact, means actuated by pressing the capsule at one end thereof for breaking the contact, a solid-state control circuit having an input and an output and so arranged that the value of resistance at the input controls the amount of current at the output, means for connecting the terminals to the input, and means for connecting the output in series with the heating unit so that heat is developed thereon at the desired rate until contact is broken by pressing the capsule at the end thereof.

5. In a control arrangement for a heating unit in an electric range or the like, the combination comprising an elongated hollow capsule adapted to be mounted at an accefiible surface, a resistor element longitudinally disposed inthe capsule and having a companion conductor extending parallel thereto, terminals on the capsule connected to the resistor element and conductor, the presented upper wall of the capsule being formed of flexible material so that when fingertip pressure is applied at a selected point along the length of the capsule the resistor element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, means in the capsule for engaging the upper wall of the capsule for maintaining it in its pressed state, a solid-state control circuit having an input and an output and so arranged that the value of resistance at the input controls the amount of current at the output, means for connecting the terminals to the input, means for connecting the output in series with the heating unit so that heat is developed therein at a rate corresponding to the selected value of resistance, the capsule being sealed and filled with fluid so that pressing the capsule at the end thereof develops pressure in the capsule for restoring the upper wall of the capsule to its normal state accompanied by breaking of the contact and deenergization of the heating unit.

6. The combination as claimed in claim 5 in which the upper wall of the capsule and lower wall of the capsule are formed for mutual engagement at the selected point to hold the upper wall in its pressed state.

7. The combination as claimed in claim 5 in which the upper wall of the capsule and lower wall of the capsule are formed to provide between them a longitudinally extending tongue and groove connection with the tongue being temporarily held captive in the groove at the point of pressing until the holding force is overcome by pressing the capsule at its end.

8. The combination as claimed in claim in which the capsule is formed of flexible plastic material in which one of the upper and lower walls is formed with a longitudinally extending tongue and in which the other of the walls is formed with a complementary groove for snug reception of the tongue and holding thereof at the point of pressing, the resistance element and conductor being disposed in parallel relation along the opposed walls adjacent the tongue and groove.

9. The combination as claimed in claim 5 in which the upper wall of the capsule and lower wall of the capsule are formed to provide between them a longitudinally extending tongue and groove connection with the tongue being temporarily held captive in the groove at the point of pressing until the holding force is overcome by pressing the capsule at its end, the conductor associated with the upper wall being formed of closely spaced helical convolutions to provide a high degree of flexi' bility in the face of locally applied finger pressure.

10. In a resistance control device for controlling the heating unit in a range or the like, equipped with a solid-state control circuit, the combination comprising an elongated hollow capsule adapted to be mounted at an accessible surface, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals on the capsule connected to the resistor element and conductor, the presented upper wall of the capsule being formed of flexible material so that when fingertip pressure is applied at a selected point along the length of the capsule the resistor element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, means for'maintaining the upper wall in its pressed state to produce a persistent value of resistance at the terminals, the capsule being sealed and filled with fluid, and means for subsequently increasing the pressure of the fluid so that the upper wall is restored to its normal state accompanied by breaking of the contact.

11. The combination as claimed in claim 10 in which a series switch is included in one end of the capsule responsive to fingertip pressure and so arranged that pressing upon the upper wall at such end pressurizes that fluid in the capsule for restoring the upper wall to its initial state separating the resistor element and conductor from one another.

12. The combination as claimed in claim 10 in which the fluid is in the form of relatively inert gas.

13. The combination as claimed in claim 10 in which fluid is in the form of a substantially incompressible inert liquid.

14. In a resistance control device for controlling a heating unit in a range or the like equipped with a solid-state control circuit, the combination comprising a hollow tubular capsule of flexible plastic material sealed at the ends, means for mounting the capsule on an accessible surface to define opposed intemal walls, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals connected to the element and conductor and extending through one end thereof, the resistor element and conductor being so disposed that when fingertip pressure is applied at a first selected point along the length of the capsule the resistor element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, the walls being so formed that they cling together at the pressed point along the length thereof for maintaining persistent contact, the capsule being substantially filled with fluid so that upon application of fingertip pressure at a second selected point contact is made at the second point to change the value of resistance across the terminals accompanied by development of fluid pressure within the capsule restoring the wall at the first point to it ini tial condition.

15. In a resistance control device for controlling a heating unit in a range or the like equipped with a solid-state control circuit, the combination comprising a tubular capsule of flexible material, means for mounting on an accessible surface thereby to define upper and lower walls, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals for the element and conductor, the presented walls of the capsule being sufiiciently thick as to tend to maintain a generally tubular shape and sufficiently thin as to permit the walls to be pressed together upon application of fingertip pressure at a selected point so that the resistor contacts the conductor thereby to establish a desired value of resistance across the terminals, said capsule being sealed and filled with inert liquid, the quantity of the liquid being somewhat less than the normal internal volume of the capsule so that when the capsule is locally pressed at a point along its length it tends to remain in pressed condition for persistent contact, and switch means at the end of the capsule for turning off of the heating element.

16. In a control arrangement for a heating unit in an electric range or the like for connection to an AC supply line, the combination comprising an elongated hollow capsule adapted to be mounted at an accessible surface, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals respectively connected to the resistor element and conductor, the presented wall of the capsule being formed of flexible materials so that when fingertip pressure is applied at a selected point along the length of the capsule the resistance element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, means for maintaining persistent contact at the selected point, a solid-state control circuit having an input and an output and so arranged that the value of resistance at the input controls the amount of current at the output, means for connecting the terminals to the input, means for connecting the output in series with the heating unit to control energization thereof, and switch at the end of the capsule in series with the AC supply line so that when the capsule is pressed at the end the switch is opened to isolate the control arrangement and heating unit from the AC supply line.

17. The combination as claimed in claim 16 in which the switch has a fixed contact and a moveable contact and in which the moveable contact is connected to the presented wall of the capsule for holding open when the end of the capsule is pressed.

Claims

1. In a control arrangement for a heating unit in an electric range or the like, the combination comprising an elongated hollow capsule adapted to be mounted at an accessible surface, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals respectively connected to the resistor element and conductor, the presented wall of the capsule being formed of flexible material so that when fingertip pressure is applied at selected different points along the length of the capsule the resistance element is brought into contact with the conductor at corresponding different points so that a corresponding value of resistance exists across the terminals, mean for maintaining persistent contact at the point pressure is applied even though the pressure is released, a solid-state control circuit having an input and an output and so arranged that the value of resistance at the input controls the amount of current at the output, means for connecting the terminals to the input, and means for connecting the output in series with the heating unit to control energization thereof.

5. In a control arrangement for a heating unit in an electric range or the like, the combination comprising an elongated hollow capsule adapted to be mounted at an accessible surface, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals on the capsule connected to the resistor element and conductor, the presented upper wall of the capsule being formed of flexible material so that when fingertip pressure is applied at a selected point along the length of the capsule the resistor element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, means in the capsule for engaging the upper wall of the capsule for maintaining it in its pressed state, a solid-state control circuit having an input and an output and so arranged that the value of resistance at the input controls the amount of current at the output, means for connecting the terminals to the input, means for connecting the output in series with the heating unit so that heat is developed therein at a rate corresponding to the selected value of resistance, the capsule being sealed and filled with fluid so that pressing the capsule at the end thereof develops pressure in the capsule for restoring the upper wall of the capsule to its normal state accompanied by breaking of the contact and deenergization of the heating unit.

8. The combination as claimed in claim 5 in which the capsule is formed of flexible plastic material in which one of the upper and lower walls is formed with a longitudinally extending tongue and in which the other of the walls is formed with a complementary groove for snug reception of the tongue and holding thereof at the point of pressing, the resistance element and conductor being disposed in parallel relation along the opposed walls adjacent the tongue and groove.

9. The combination as claimed in claim 5 in which the upper wall of the capsule and lower wall of the capsule are formed to provide between them a longitudinally extending tongue and groove connection with the tongue being temporariLy held captive in the groove at the point of pressing until the holding force is overcome by pressing the capsule at its end, the conductor associated with the upper wall being formed of closely spaced helical convolutions to provide a high degree of flexibility in the face of locally applied finger pressure.

10. In a resistance control device for controlling the heating unit in a range or the like, equipped with a solid-state control circuit, the combination comprising an elongated hollow capsule adapted to be mounted at an accessible surface, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals on the capsule connected to the resistor element and conductor, the presented upper wall of the capsule being formed of flexible material so that when fingertip pressure is applied at a selected point along the length of the capsule the resistor element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, means for maintaining the upper wall in its pressed state to produce a persistent value of resistance at the terminals, the capsule being sealed and filled with fluid, and means for subsequently increasing the pressure of the fluid so that the upper wall is restored to its normal state accompanied by breaking of the contact.

14. In a resistance control device for controlling a heating unit in a range or the like equipped with a solid-state control circuit, the combination comprising a hollow tubular capsule of flexible plastic material sealed at the ends, means for mounting the capsule on an accessible surface to define opposed internal walls, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals connected to the element and conductor and extending through one end thereof, the resistor element and conductor being so disposed that when fingertip pressure is applied at a first selected point along the length of the capsule the resistor element is brought into contact with the conductor so that a corresponding selected value of resistance exists across the terminals, the walls being so formed that they cling together at the pressed point along the length thereof for maintaining persistent contact, the capsule being substantially filled with fluid so that upon application of fingertip pressure at a second selected point contact is made at the second point to change the value of resistance across the terminals accompanied by development of fluid pressure within the capsule restoring the wall at the first point to it initial condition.

15. In a resistance control device for controlling a heating unit in a range or the like equipped with a solid-state control circuit, the combination comprising a tubular capsule of flexible material, means for mounting on an accessible surface thereby to define upper and lower walls, a resistor element longitudinally disposed in the capsule and having a companion conductor extending parallel thereto, terminals for the element and conductor, the presented walls of the capsule being sufficiently thick as to tend to maintain a generally tubular shape and sufficiently thin as to permit the walls to be pressed together upon application of fingertip pressure at a selected point so that the resistor contacts the conductor thereby to establish a desired Value of resistance across the terminals, said capsule being sealed and filled with inert liquid, the quantity of the liquid being somewhat less than the normal internal volume of the capsule so that when the capsule is locally pressed at a point along its length it tends to remain in pressed condition for persistent contact, and switch means at the end of the capsule for turning off of the heating element.