US2418867A - Heat responsive device having separate minimum flame and normal flame responsive elements - Google Patents

Description

2,418,867 HAVING SEPARATE unuuuu IENTS Apz'ii 15, 1947. L. w. BURCH um'r masrousrva nnvxcs Imus AND nomm. FLAME zmsrousxvm ELE Original Filed Sept. 25, 1940 INVENTOR Z ynaon A! 80/66 ATTORNEYS Patented Apr. 15, 1947 HEAT RESPONSIVE DEVICE HAVING SEPA- RATE MINIMUM FLAME AND NORMAL FLAME RESPONSIVE ELEMENTS Lyndon W. Burch, Pelham, N. Y., assignor to The Wilcolator Company, Newark, N. J a corporation of Delaware Original application Se No. 358,224. March 15,

13 Claims.

Thi invention relates to. heat responsive apparatus and more particularly to a novel apparatus of this character whch operates as the result of an uneven distribution of heat therein due, for example, to radiation of heat on only a part of the device. The new apparatus is sensitive' in operation and may bearranged to provide a positive actuation in one direction when it is subjected to radiant heat, and to provide a positive actuation in the opposite direction when the source of radiant heat is cut off.

This application is a division of pending application of Lyndon W. Burch, Serial No. 358,224, flied September 25, 1940, for Control system for ovens" which became Patent No. 2,361,530 on (Jet. 81, 1944.

For illustrative purposes, the invention will be described in connection with a system for indi cating the condition of an oven burner in a gas rangegalthough it will be understood that the invention is not limited to this use but isapplicable to furnaces and other heat appliances as well.

Gas ranges as commonly made at the present time are so well insulated and the oven burner is so completely enclosed that there is little or no evidence that the oven burner is ignited. Accordingly, it sometimes happens that the burner is left in operation unintentionally after the cooking is completed, with the result that a considerable quantity of gas is wasted. Also, in gas ranges having means for automatically lighting the oven burner when the burner is turned on, the operator usually cannot determine whether or not the automatic lighter has actually ignited the burner, except by opening the oven door and looking through a vent hole.

It has been proposed heretofore to reduce this hazard by providing adjacent the burner a thermostatic device which, when the burner is extinguished, closes a valve in the supply line to the burner or operates an indicating device outside the oven. However, the thermostat cannot be of the ordinary type which operates only on temperature change in the oven, because a well insulated oven may remain at a relatively high ptember Z5, 1940, Serial Divided and this application 1944, Serial No. 526,523

2 circuit. When the burner is ignited, the ceramic element is heated to a temperature at which it becomes an electrical conductor so that the circuit is closed, but when the burner is extinguished and the element cools, it no longer conducts current, whereby the circuit is opened. These thermostats are objectionable for various reasons among which are their poor response, their tendency to break down under the intense heat from the burner, and the fact that they cannot provide a positive motion without auxiliary apparatus.

Another form of thermostat previously employed includesa U-shaped member which is inverted overthe flame and provided with a row of holes extending through it near its inner edge, as disclosed in a patent to O. .W. Hahn, No. 2,064,909. The holes serve to reduce the heat conducted to the outer edge of the U-shaped member so that the flame maintains the inner edge at a higher temperature and causes the member to assume an expanded-position. When the flame is extinguished, the two edges cool to the same temperature so that the, sides of the member move together. While this form 01' thermostatic element provides a positive movement, it is bulky and relatively expensive to manufacture. Moreover, its response is not sufficientlyrapid for some purposes.

Still another form ot thermostatic device heretofore described by Gordon et al., Patent No. 2,185,436; is formed of a single piece of flat 4 strip metal, such as steel, which is bent at its middle so that the two halves are approximately parallel to each other. The ends of the bent strip are welded together and the two halves are separated between the bend and the weld by a small air space or. by a layer of asbestos. This thermostat is mounted directly over a pilot burner flame so that half of the strip is heated while the other is 'shielded, the shielded half being cooled by a current of air. Thermostats of this form are not uniform in character because of the bending and welding operations, which also make for structural failures and imperfections. They arealso relatively expensive to make because temperature for a long time. after the burner is extinguished. In order to provide a quick response to igniting and extinguishing of the burner, it is desirable that the thermostat operof the number of operations involved in their manufacture.

The primary feature or the present invention, therefore,. resides in the provision of a novel thermostat or heat responsive apparatus or device which is simple to make and duplicate uniformly on a mass-production basis. According to the disclosure of the above-mentioned appli-- cation, the improved thermostat is not of the cients of expansion,

responds to temperature changes in the oven, but is of a type which responds only to radiant heat from the burner. A thermostat of this type is comprised of two metallic elements having substantially equal coeffithe elements being connected together at their ends but separated intermediate their ends by a medium which is a poor conductor of heat, the thermostat being mounted in the oven so that one of the metallic elements shields the other from direct radiation from the burner. A preferred form of the thermostatic apparatus of the present invention comprises a tubular metal member having a pair of diametrically opposed slots terminating short of the ends of the member, the slots being so disposed that they divide a section of the metal tube into two opposed substantially parallel elements. Another preferred form of the improved apparatus of the present invention comprises a pair of such tubular members mounted adjacent a burner in the manner described hereinafter. When a tubular thermostatic device of this character, in which the elements have substantially equal coefficients of expansion and are connected together at their ends but separated intermediate their ends by a medium which is a poor conductor of heat, is mounted in an oven so that one end is free and one of the elements shields the other from direct radiation from the burner, a positive actuation will be eilected. For example, when the oven burner is ignited, the metallic element subjected to direct radiation is heated to a higher temperature than the shielded element, and expands relative to the latter so as to move the free end of the member in one direction. On the other hand, when the oven burner is extinguished, the two elements quickly assume the same temperature, that is, the temperature in the oven, and the free end of the member moves back to its original position.

The pending application referred to above discloses an indicating system for positively indicating to the operator when an oven burner is actually lighted, so as to afford an indication equivalent to that usually provided on electric ranges by the pilot light. This system makes use of a thermostat or heat responsive apparatus of the type of that of the present invention mounted in the oven adjacent the oven burner. so that it receives direct radiation from the burner flame. The movable and of the heat responsive member is connected toa contact which is movable by the member relative to a fixed contact. These two contacts comprise a switch which may be included in the circuit of an indicating device, such as a lamp bulb, mounted outside the oven where it is visible to the operator. Preferably, the system is used with a range of the type in which the oven burner is throttled to provide a low maintaining flame when the desired temperature is reached, and the contacts are arranged so that they are normally open to de-energize the indicator when the burner is not operating. Accordingly, when the burner is ignited, the contacts are closed by the radiant heat thermostat to energize the indicator, and 'the operator will therefore know that the burner is operating as called for by the position of the adjustment handle of the usual thermostatic valve. Should the burner be accidentally extinguished for any reason, the radiant heat thermostat will quickly open the contacts and tie-energize the indicator, so that the operator will be warned to turn the adjustment handle to its "of!" position or ordinary type which relight the burner. If the burner should fail to ignite when the adjustment handle is turned to one of its on" positions, the contacts will remain open and the indicator de-energized, thereby warning the operator. The radiant heat thermostat operates independently of the oven temperature and causes the indicator to remain energized even when the oven burner is operating with a minimum maintaining flame.

The pending application also discloses an indicating system in which the apparatus of the present invention may also be employed for indicating when the oven burner has heated the oven to the temperature for which the adjustment handle of the usual thermostatic regulating valve is set. In this system a radiant heat responsive member of the type of that of the present invention is mounted in the oven adjacent the oven burner, but is so positioned with respect to the burner that it'operates only when the burner provides a substantial amount of radiant heat; that is, the radiant heat responsive member returns to its initial position whenever the oven burner is operating with a minimum temperature maintenance or by-pass flame, or whenever the burner is extinguished. The radiant heat thermostat also preferably operates a pair of contacts in circuit with an indicator, so that when the oven burner is turned on and ignited, the indicator is energized, but when the desired temperature is obtained and the thermostatic valve throttles the burner, the radiant heat therefrom is not sufiicient to hold the radiant heat thermostat in its actuated position, whereby the indicator is de-energized,

If desired, the indicating system according to said application may include two radiant heat thermostats, one operating on both minimum maintenance and normal burner flame and the other on only a normal flame, and each thermostat may operate an indicating device so that the operator is informed whether the burner is ignited or extinguished and is also informed when the desired temperature is attained.

Other features, objects and advantages of the present invention will be explained more in detail in connection with the accompanying drawings. in which:

Fig. 1 is a broken view partly in horizontal section, showing one form of the new heat responsive apparatus or thermostatic device applied to the oven of a gas range.

Fig. 2 is an enlarged vertical sectional view of the apparatus taken on the line 2-2 of Fig. i.

The new heat responsive apparatus or thermostatic device as shown, is applied to a gas range including an oven in having a main gas burner ii mounted therein, the burner being provided with suitable jets Ila. Gas for the oven burner ii may be supplied in the usual way through a conventional regulator (not shown) which may be connected to a thermostat (not shown) responsive to temperature changes in the oven. In systems of this type, the oven thermostat actuates the regulating valve to supply more or less gas in accordance with variations in the oven temperature, to counteract any temperature variation.

Mounted in the oven i0 adjacent the main burner Ii are two similar heat responsive members or thermostats 3B and 31 which are responsive only to direct radiation from the main burner i i. The thermostats 36 and 31 may take any desired form but preferably they comprise tubular members as and 38a, respectively, made of metal,

and each having a pair of diametrically opposed slots as and "a, respectively. extending lengthwise oi the tube but terminating short 01 the ends of the tube, the slots being so disposed that they divide a section of each tube into two opposed elements one of which faces the burner and the other of which is shielded by the ilrst element. At their inner ends. the tubular members are mounted in a hollow metal casing 40 so that the tubes communicate with the interior oi the casing. Fitted closely in the free ends oi the tubes are metal collars 4i and Ma, respectively. supporting rods 42 and 42a. respectively, which extend inwardly through the tubes in spaced relation thereto and proiect into the casing 40. The free ends of the rods 42 and 42a coact with fixed contacts 48 and 43a, respectively, mounted on suitable insulating supports 44, the fixed contacts and their corresponding rods forming separate control means ior a purpose to be described presently. 1

The side of the casing 40 opposite the tubular members 38 and 38a is provided with a hollow boss 48 having a generally spherical portion 41 intermediate its ends. A metal bracket 48 has a circular opening therein for receiving one end of the spherical portion 41 and is connected by bolts 48 to a plate 50 having a similar opening for receiving the other end of the spherical portion. Thus. the spherical portion 41 and the coacting bracket 48 and plate 50 provide a universal mounting for the housing so that the latter may be adjusted to position the tubular members 48 and "a relative to the Jets of the oven burner. The bracket 48 is preferably connected to the adiacent side wall oi the oven 10 so that it is grounded, as shown as 5|. Threaded on the outer end of the hollow boss 48 is a compression fitting ll engaging an enlargement B4 on the end of ametal tube 58 which extends through the adjacent wall of the oven. The fitting 53 is screwed tightly on the boss so as to clamp the enlargement 54 against the outer end of the boss.

The fixed contact 43 has a wire 51 connected thereto which leads from the interior of the easing through the boss 46 and tube ill to the out side of the oven where it is connected to one terminal oi a suitable indicating device such as an incandescent lamp. Similarly, the nxcd contact 43a has a wire 60 connected thereto, leading through the boss 48 and tube 5! to one terminal of a second suitable indicating device, such as an incandescent lamp. The other terminals of the indicating devices or incandescent lamps may be connected to a source of electrical power which would be grounded to the stove or connected to the ground lead II, to form a complete circuit.

In operation, the rods 42 and 42a disengage their corresponding contacts when the oven burner I I is extinguished, thus de-energizing the indicating devices. When gas is turned on in the oven and the burner ii ignites. as for example, by a suitable pilot, the resulting radiant heat from the burner flame strikes the adjacent thermostat 38 and heats the adjacent side oi this thermostat to a higher temperature than the remote side, with the result that the adjacent side expands relative to the remote side and causes the free end of the thermostat to move away from the burner and tilt the rod 42 in a counter-clockwise direction, thereby causing the inner end of the rod to engage its fixed contact 43. A circuit is then established through the indicating device. such as a lamp, from the round or other connection II, through bracket 48, casing 40, tube II,

6 collar 4i. rod 42, contact 43, wire 87, and back to the indicating device or lamp which is connected through a source oi electric power to the range or to connection H. The external indicating dc vice is thus energized and informs the operator that the main burner is ignited.

Similarly, the thermostat 31 is subjected on one side to direct radiation from the main burner ll, although the radiant heat on this thermostat is not as intense as it is on the thermostat 38, due to the fact that the thermostat 31 is located at a greater distance from the main burner ii and is partly shielded therefrom by the thermostat I6. However, when the main burner is operated with a normal name, as when it is heating the oven up to the desired temperature or which the regulator is set. the radiant heat on the side of the thermostat 3'! adjacent the burner Ii is sufficient to cause this side to expand relative to the opposite side, so that the free end of the thermostat 81 moves away from the burner and causes its rod 42a. to engage the corresponding fixed contact 48a. A circuit is thus established irom the ground connection ll through bracket 48, casing 40. tube 88a. collar 4la, rod 420. fixed contact 43a. wire 60. the indicating device. and back through a source of electrical energy to a ground connection to the range, or directly to the wire of the ground 8|.

when the temperature-in the oven has reached that for which the oven regulator was set, the gas supply isthrottled to give a minimum or maintaining flame on the burner H. The radiant heat from this minimum ilame is sui'ilcient to maintain the required temperature differential between the opposed sides of the thermostat 38 to cause the latter to hold its rod 42 in engagement with contact 43. and thus energize the indicating device. However. radiant heat from the minimum llama is not sufiicient to maintain the required temperature differential in the thermostat 81. and the opposed sides or the latter tend to approach a uniform temperature so that the tube 380 rcturns toward its normaliposition and discnaagcs its rod 42a. from the fixed contact 48a. As a result. the circuit through the indicator or lamp is broken and the latter dc-encrgized. thereby indicating to the operator that the desired tempera-- ture has been reached in the oven.

Ii ior any reason the oven burner H should be extinguished, the opposed sides oi the thermostat 38 will quickly assume a uniform tempcrature and cause the free end of the thermostat to move toward the burner and disengage the rod 42 from its fixed contact 43. The circuit from this thermostat is then broken and the indicator or lamp deencrgized to indicate to the operator that the main burner is not operating.

The new heat responsive apparatus is of simple construction and is readily installed in a range. The operator may determine by a glance at the indicators operated through control means by the thermostats I4 and 31, whether the oven is actually operating, as called for by the oven regulator, and whether the oven has been heated to the temperature for which the regulator is set. In the event that the burner H tails to operate when the gas is turned on, the operator is immediately and positively informed at the dangerous condition by the absence of illumination from the lamp or other indicator connected to the thermostat 38. I! the current for cncraizihg the indicators should be interrupted, they to function, the operator is warned that either the burner is not ignited or that the indicating system has not responded. Since the switches 42, 43 and 42a, 43a, for controlling the indicators, are housed by the casing 40 and the slotted tubes, they are protected against damage by food inserted in the oven, grease, etc. Also, by reason of the universal mounting for the casing 40, the latter may be readily adjusted to place the tubes 38 and 38a in their proper positions relative to the adjacent burner jets Ila, and when the adjustment is completed, the bolts 49 may be tightened to hold the parts securely in position. It will be apparent to those skilled in the art that the slotted members may be made inexpensively and uniformly by a simple slot cutting operation on standard tube stock or on equivalent stock of similar shape.

With the use of the improved heat responsive apparatus, it is unlikely that the operator will accidentally leave the burner turned on after the food is removed from the oven, because the lamp or other indicator associated with the thermostat 36 remains illuminated or active as long as the burner is operating, even with a minimum flame. While in the illustrated form of my invention the thermostats of heat responsive members 36 and 31 energize the indicators only when they are actuated by radiant heat, it will be understood that the parts may be arranged so as to energize the indicators whenever the radiant heat thermostats return to their normal positions and to de-energize the indicators when their respective thermostats are actuated by the radiant heat. With the latter arrangement, the indicators would be de-ener gized automatically when the oven regulator is provided with a switch in the indicator circuits, which is opened when the regulator is turned to its off position.

I claim:

1. A heat responsive apparatus comprising an elongated tubular-shaped metal member having a section intermediate its ends slotted lengthwise of the member to form a pair of opposed substantially parallel segments, one end of said member being rigidly mounted and the other end being free and deflectable from its normal position with respect to the other end of the member by the unequal heating and expansion of said segments when said member is disposed with one or said segments shielding the other from direct radiation from a source of heat.

2. A thermal responsive device comprising a metal rod having a longitudinal slot therethrough forming two parallel members, means i or mounting the rod adjacent a source of radiant heat with one of said members shielding the other from the source of heat, whereby flexure will result from a difference in temperature between the two said members, said slot extending through a portion only of the rod length and leaving unslotted a substantial portion thereof.

to said burner so that it is responsive to a mini- 4. In a heat responsive apparatus for a burner,

two elongated metal flexing heat responsive members each having a substantial section intermediate its ends slotted through to provide two substantially parallel segments opposite each other, means for mounting one end of each of said members near the burner with one of the segments of each member shielding the other segment thereof from direct heat radiation from the burner, whereby flexure of each member will result from a diiference in temperature between the two segments thereof, one of said members being mounted with respect to saidburner so that it is responsive to a minimum and to a normal flame thereon, the second of said members being mounted a greater distance from said burner than the other member and partly shielded from the burner flame by said other member so that it is responsive to a normal flame but not responsive to a minimum flame on the burner, and means for utilizing the flexure of each of said members to operate a control device.

5. In a heat responsive apparatus, an elongated tube having a section intermediate its ends slotted lengthwise of the tube to form a pair of opposed substantially parallel segments, one end of said tube being rigidly mounted in a casing and opening thereinto while the other end oi the tube is free and deflectable irom its normal position with respect to the fixed end of the tube by the unequal heating and expansion of said segments when said tube is disposed with one of said segments shielding the other from radiation from a source of heat, and control means in the casing operable by the deflection or the free end oi the tube.

6. In a heat responsive apparatus, an elon gated metal tube having a section intermediate its ends slotted lengthwise of the tube to form a pair of opposed substantially parallel elongated segments, one end of said tube being rigidly mounted in a housing and opening thereinto while the other end of the tube is free and deflectable from its normal position with respect to the rigidly mounted end of the tube by the unequal heating and expansion of said segments when said tube is disposed with one of said segments shielding the other from radiation from a source of heat, a movable contact in the housing connected electrically to the free end of the tube and operable by deflection thereof, and a flxed contact in the housing coacting with the movable contact and insulated from the housing.

'7. In a heat responsive apparatus, an elongated metal tube having a section intermediate its ends slotted lengthwise of the tube to form a pair of opposed substantially parallel elongated sag ments, one end of said tube being rigidly mounted in a casing and opening thereinto while the other end of the tube projects from the casing and is free and deflectable from its normal position with respect to the fixed end of the tube by the unequal heating and expansion of said segments when said tube is disposed with one of said segments shielding the other from radiation from a source of heat, a metal rod connected tel the projecting free end of the tube and extending through the tube into the casing in spaced relation to the tube wall, a movable contact in the casing mounted on the free end of the rod and operable by the deflection of the tube and rod, and a fixed contact in the casing coacting with the movable contact and insulated from the cas- 8. A heat responsive apparatus comprising an e gated metal tube having a. longitudinal slot the ,ethrough forming two parallel members, means for mounting the tube by one end only with the other end, free adjacent a source of radiant heat with one of said members shielding the other from the source of heat, whereby flexure will result from a difierence in temperature between the two said members, said slot extending through a portion only of the length of the tube and leaving unslotted the end portions thereof, and'a control device operatively connected to the free end of the .tube and responsive to the fiexure thereof.

9. A heat responsive device comprising an elongated thermo-responsive member including a pair of elongated substantially parallel thermoexpansible elements of equal coefflcients of expansion connected together at their respective ends and separated from each other by a, slot through a substantial portion of their lengths, means for rigidly mounting said member by one end only with th other end free adjacent a source of radiant heat with'one of said elements shielding the other from the source of radiant heat, whereby flexure of said member will result from a difference in temperature between the two said elements, a rod connected in fixed position between said elements at the free end of said member and extending between the elements with a clearance, and a control device operated by the rod in response to the flexure of the member.

10. A thermal responsive device comprising a metal rod of round cross section having a longitudinal slot therethrough forming two parallel members, means for mounting the rod adjacent a source of radiant heat with one of said members shielding the other from the source of heat, whereby flexure will result from a diil'erence in temperature between the two said members.

11. A heat responsive device comprising an elongated metal member of round cross section having a longitudinal slot therethrough intermediate its ends, said slot forming two substantially parallel segments, and means for rigidly mounting said member adjacent a source or radiant heatby one end only while the other end is free, said member being mounted with one of said segments exposed to radiation from said source and shielding the other segment therefrom, whereby flexure of the member will result from a difference in temperature between the two segments.

12. A heat responsive apparatus comprising an elongated metal tube having a longitudinal slot therethrough forming two parallel members, means for mounting the tube with one end free adjacent a source of radiant heat with one of said members shielding the other from the source of heat, whereby flexure of the tube will result from a difference in temperature between the two said members, said slot extending through a portion only of the length of the tube and leaving unslotted the end portions thereof, a control device, and means within said tube for transmitting movement caused by the deflection of the tube to the control device.

13. In a heat responsive apparatus, an elongated metal tube having a section intermediate its ends slotted lengthwise of the tube to form a pair of opposed substantially parallel elongated segments, one end of said tube being rigidly mounted in a casing and opening thereinto while the other end of the tube is free and deflectable from its normal position with respect to the fixed end of the tube by the unequal heating and expansion of said segments when said tube is disposed with one of said segments shielding the other from radiation from a source of heat, a rod of substantially smaller cross-section than that of said tube fixed to and rigidly mounted in the free end of the tube and extending through the tube into the casing, and a control means in the casing operable by the rod in response to a deflection of the free end of the tube.

LYNDON W. BURCH.

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

UNITED STATES PATENTS

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