Electric heater.

Application filed Inly 9, 1910.

Serial No. 571,235.

To dll whom it may concern:

Be it known that I, Ctt arles P. Madsen, a citizen of the United States, and resident of Chicago, Cook county, Illinois, have in5 vented certain new and useful Improvements in Electric Heaters, of which the following is a full, true, clear, and exact description, such as will enable others skilled· in the art to which it appertains to make 10 and use the same.

My invention relates to that class of electrically heated devices known as bread toasters, meat broilers, air warmers and the like.

The object of my invention is to provide an electric heating device of this character in which· the heat generated by the heating element will be imparted or transmitted to the object or'material to be heated radiantly through the atmosphere surrounding and containing the heating element, and in which the heat imparted will be confined upon an area where it will be most effective and will not become dissipated in other parts of the 25 device, thereby increasing the effective heating capacity and the heating speed of the heater for a given current consumption.

A further object of my invention contem. plates the provision of an electric heater 30 having a heating element or heat generator which will be independent of its containing case or receptacle and removable therefrom as a tmit, and which will be comparatively inexpensive to manufacture whereby the 35 heating element may be conveniently removed and renewed at slight cost by the user of the device, should it become damaged or injured in any manner.

Further and more particular objects of 40 my invention are to provide a heater which will be compact and neat in appearance; which will be portable and which will have means for quickly and effectively making and breaking electrical connection with the 45 heating element; and which will be particu. larly adapted for toasting bread and for broiling or frying meats and other food products.

I will explain my invention further by ref50 erence to’ the accompanying drawings in which: Figure 1 is a top plan view of an electric heater structure embodying my invention; Fig. 2 is a longitudinal sectional view on line 2—2 of Fig. 1; Fig. 3 is a view 55 in side elevation showing an invertible pan or tray used in conjunction with my electric heater for rendering it adaptable for frying meats, griddle cakes and other food’ products ; Fig. 4 is a view in end elevation showing the plug socket and the terminals for 60 the heating element; Fig. 5 is a view in section on line 5—5 of Fig. 1; Fig. 6 is a top plan view of the unit heating element removed from its containing casing or receptacle; Fig. 7 is a view of the under side of 65 said heating element showing the connecting plug in relative position; Fig. 8 is anenlarged, transverse, sectional view showing the relation of the food grid, the heating element and the heat reflector; Figs. 9 and 70 10 are enlarged detail sectional views-showing the means of securing the food-grid and the unit heating element in position; and Figs. 11, 12, 13 and 14 are detail views of the connection plug for connecting^ the 75 heater to an electric circuit.

I have discovered by extensive experiment that, in a certain class of heaters, if the heating element is maintained out of mechanical contact with the object or material to 80 be heated and with any other object and instead is arranged so that it imparts its generated heat to the object or material to be heated by radiation through the medium of the atmosphere surrounding the heating ele- 85 ment, the efficiency and effective heating capacity of the heating element will be greatly increased for a given current consumption. The difficulties which are presented in a heating devcie of this sort lie in arranging 90 the heating element so that it will impart or transmit all of its generated heat to the external object, and preventing the loss or dissipation of heat at points where it will not be effective in heating the external ob- 95 ject or material. I have discovered that· the highest efficiency, the most effective heating capacity and the maximum heating speed can be attained by disposing the external. object to be heated at a given distance 100 from a heating element of a given temperature. I have accordingly provided an electric heater having a heating element which is arranged to lie in one plane and. by arranging the heating element in this man- 105 ner it may be spaced at a given distance from the external object, the distance being uniform at all points throughout the heated area. The heating element, however, being disposed in one plane radiates heat there- 110

1,007,126 from on both sides thereof, and in a practical structure it is preferable that the external object or material to be heated be disposed on one side of‘the heating element. 5 To prevent the heat radiated from the heating element on the' other side thereof from being dissipated into the atmosphere or the supporting structure and thereby being wasted so far as the external object is con10 corned, I have provided a heat reflecting device disposed in a plane-substantially parallel with the plane of the heating element and spaced therefrom at a given distance. This device reflects the heat radiated from 15 the unused side of the heating element and cumulatively adds it to the heat radiated from the side of the heating element on which the external object is disposed. In this manner substantially all of the heat 20 generated by the heating element is confined over an area where it is completely effective to heat the external object.

The electric heater which I have shown in the drawings and in which my invention is 25 embodied, is especially adapted for toasting bread or for broiling meats. I have found by experiment that the most effective heating capacity and the highest efficiency are obtained by disposing the food product to be 30 heated, the heating element and the reflector in parallel planes and by spacing the food products at about one-half the distance from the heating element as the heat reflector is spaced therefrom. These proportions may 35 vary within the range of one to one and one to two without material detriment to the efficiency of the device. In this structure the heating element preferably comprises an electrical conductor 1 of suitable resistance 40 to produce the desired temperature with a given quantity of current and of suitable characteristics, to withstand the temperature to which it is subjected without fusing or without deteriorating. The conductor is 45 preferably a round wire for the reason that it is the least expensive, but it will be understood, however, that a wire or rod of any desired cross section may be used. This conductor is preferably wound in a reflex or 50 zigzag manner and is disposed in one plane.

It is retained in position by a base member of refractory insulating material 2 through the medium of L-shaped spring members 3 disposed in parallel rows on each side of the 55 flanges 4 carried on the edges of said base member. One of these L-shaped springs is preferably provided for each bend or bight in the conductor 1. They are anchored at the lower edges 5 of the outer face of the 60 flanges 4 and extend vertically for a distance adjacent the outer faces of the flanges and then horizontally through suitable slots 6 provided in the upper edges of said flanges. At the inner ends of these springs 65 are hooks 7 into which the conductor 1 is looped. These springs automatically compensate for the expansion and contraction of the conductor 1 due to changes in temperature thereof and thereby maintain the several portions of wire taut at all times so ₇₀that they will not become displaced out of a horizontal plane. By arranging the springs in this manner they are protected by the flanges 4 so that they lie almost wholly outside of the influence of the heat and in con- 75 sequence their temper will not be impaired. The conductor 1, in the structure shown, is wound to form a rectangle but, of course, it may be wound or otherwise arranged in a single plane of any geometric figure. Fur- so thermore the tension members or openings may be disposed in any suitable relation to the conductor to maintain it in its given plane. . Of course if a conductor of sufficient rigidity to be self-maintaining were 85 used, the tension members may be dispensed with.

The insulating base 2 is supported in the proper horizontal position within a suitable containing case or receptacle 10 by means of 90 two plates 11 secured to the bottom of the receptacle 10 and extending vertically upward . The upper edges of these plates lie adjacent the shoulders 12 on the underside of the base member and are intended to prevent 95 said base member from shifting laterally. ΤΑθ base member is clamped securely in position on the upper edges of these plates by the bolts 13, which also clamp the food grid in position, as will be hereinafter described, lot The space below the insulating base is preferably filled with magnesia or some other· loose, refractory heat insulating material (as shown in Figs. 2 and 5) to prevent the heat from reaching the casing and rendering it 10c too hot for comfortable handling. It will be noted that the heating conductor and the insulating support thereof comprise a unit heating element structure which is independent from the casing and the rest of the 110 apparatus and which is easily removable therefrom. This is a desirable feature, since the heating element can be manufactured comparatively cheap, and in the event that it should become burned out or otherwise 115 damaged it can be conveniently removed from the receptacle and a new unit substituted at. a. slight cost. This unit heating element is insulated from the rest of the apparatus and the base thereof is in metallic 120 contact with the casing receptacle only at its points of support at the upper edges of the supporting plates 11. It is thus separate from the casing by an air space, consequently an almost negligible quantity of the heat 125 generated by the heating element will be dissipated in the casing.

Disposed upon the upper face of the insulating base 2, and lying substantially paraHell with the plane of the heating elo ISO

1,007,128 ment, is the heat reflector 15. This preferably comprises a flat, rectangular, metallic plate loosely slidable in side grooves formed by overhanging portions· 16 of the flanges 4 5 on the insulating base. One end of this reflector projects through a slot 17 in the end of the casing and has an upturned flange which substantially closes said opening and which carries a small knob or handle 18 by 10 which the reflector may be conveniently removed or placed in position. The heat reflector serves the additional purpose of a removable crumb tray or dripping tray.

The casing or receptacle 10 is open at its IB top. Spanning this opening and disposed at a given relative distance above the heating element: and in a parallel plane thereto is the food holder or food grid. This grid is a flat, open-work structure comprising a rim 20 20 fitting the upper edge of the casing and having a number of bars or rods 21 spaced apart and arranged transversely of said rim. The rods are secured to a depending flange 22 so that they will lie substantially flush 25 with the upper face of the rim 20. The food grid thus presents a substantially flat foodsupporting surface upon which bread, meat or other food products may be laid. One end of this flange is continued downward to 30 a point very close to the bottom.ofthe receptacle and serves not only to assist in spacing the insulating base from the end thereof, but it also serves to prevent food crumbs or grease drippings from falling into the 35 lower part of the receptacle. As before mentioned, the food grid is clamped in position by the bolts 13 which pass through the lugs 24. The structure which I have just described is particularly designed as a bread 40 toaster and will conveniently accommodate two slices of bread. The heating element is in a sense divided into two divisions and oach division is substantially covered by a slice of bread. One of the reflex portions 45 of the conductor is omitted to provide a gap between these two divisions, this being left in order that the temperature will not become too great at the center of the device and scorch the adjacent.edges of the two 50 slices of bread. The upper faces 25 of the flanges are arranged to diverge or flare outwardly so as to increase the heat area of the device. It is desirable, though not necessary, in the use of this device that the object or 55 article to be heated cover substantially the entire heated area since it is evident that all of the heat generated by the heating element will then be utilized. 'The casing or receptacle 10 is preferably formed up from sheet 60 metal and is made to present a neat appearance. It is provided with suitable legs 10' .and with handles 20² on the ends by which it can be conveniently carried from place to place.

Referring now to Fig. 3 Ί- have shown a tray or pan 27 having a handle 28 on each end and having a flat bottom which covers the entire upper area of the receptacle. This pan may be used in two positions, (as will be seen by the full and dotted lines in γθ said figure) either as a fry pan, when it is in its normal position with its sides upturned, or as a griddle plate when in an inverted position.

Depending from the under face of the 75 insulating base 2, near one end thereof, is a block of insulating material 30 to which are secured two plates 31 serving as terminals for the heating element, the ends of the conductor 1 being connected by suitable go leads 32 lying on the under face of the insulating base and extending to the terminal plates 31. These terminal plates 31 extend through the opening in the bottom of the casing 10 and lie within a plug socket or re- 85 ceptacle 33 which is secured to the bottom of the casing 10 and which has lateral guide flanges 34 to maintain the connecting plug in connection with the terminal plates 31. The connecting plug is composed of two 90 parts 35 of insulating material clamped together by bolts 36 and having registering depressions 37 in their adjacent faces in which depressions the contact terminals 38 are arranged, their binding posts 39 being 95 inclosed between the two parts of the plug. The forward end of this plug is provided with two slots 40 which permit the terminal plates 31 to enter and make contact with the contact terminals 38 of the plug, and 10 the rear end of the plug is provided with a single opening 41 through which the electric conductors 42, representing the source of electric current, enter the plug. Surrounding these conductors 42 is a spiral 10 spring 43, anchored at one of its ends 44 to the plug and freely extensible along the conductors in a direction away from the plug. This spring has secured to it about midway of its length a suitable knob 45. 11 The purpose of this arrangement is to permit the plug to be removed from its socket and the circuit to be quickly broken in order to prevent undue burning of the contacts. The plug, as will be noticed, is in- U serted almost wholly within its socket and is held therein by friction. When it is desired to disconnect the heater, from the source of current the spring 43 is extended by pulling upon the knob 45. This places 1! a tension upon the plug and as soon as this tension overcomes the friction between the · plug and its socket the plug will fly out of its socket with a quick movement and the circuit will be quickly broken thereby pre- T· venting to a great extent the burning of contacts.

My novel heater as herein shown and .described is capable of considerable modification without departing from the spirit of 1

1,007,125 my invention. For example, it is obvious that windings of the conductor may be permanently secured at one side of the insulating base and held in tension by a single 5 movable element or comb at the other side of the base. It will also be understood that the heating elements may be arranged either singly or in pairs and supported in inclined or vertical positions and the means 10 for supporting and protecting the heating element may be modified according to the uses to which the device is to be put. Still other modifications may be made and employed within the scope of ,my invention, 15 and for the reasons here stated I desire it to be understood that my invention is not limited or confined to the specific structure herein shown and described.