US2235091A - Heating unit for electrical cooking devices - Google Patents

Description

March 18, 1941. s s, VINEBERG 23.235,091

HEATING UNIT FOR ELECTRICAL COKG DEVICES Filed Sept. l2, 1936 Q Inv-enfra? SAMUEL S. VrNEBERQ Planted Mu. 1s, 1941 Samuel S. Vlneberg, Malo, N. Y.

Application September 12. i938, Serial No. 100,507

2 Claims. (Cl. 201-63) Hy invention relates in general to heating units, and more particularly to that typeoi unit used in connection with electrical stoves, and the like.`

5 It is well known tc'those skilled in the art that the heating elements used in units o! the type to which my invention applies are usually made in-one or two pieces, oi .considerable length, and laid in long, continuous grooves oi spiral iorm. In this present day form, the inner ends oi the coil extend through suitable aperturesnear the centeroi the unit' and the outer ends extend through apertures near the periphery oi the. unit. Eachoisuchinwardlyextendingendsissecure'd to suitable terminals located under the unit and, whenrepairsaretobemade,itisnecessa`ryto remove the entire unit from the stove beiore a new coil can be inserted.4 Furthermore. suchl coils must be threaded into the grooves and usually beneath retaining lugs and, unless great care is exercised, even by an experienced workman, the coil is easily stretched or otherwise mutilated during such threading process. Furthermore, when the heating element is in one clontinuous length, and one portion thereof becomes burned out, the entire element must be discarded and replaced by a new one.

The general objects oi my invention have beenY to overcome thedisadvantages above pointed out. 3o Another principal object has been to provide a Iheating unit having a heating element made up oi a number oi relatively short segments instead of a relatively long, continuous coil.

Another object has been to provide heating elements having each o! their terminals tlxed to an eyelet, such an eyelet containing sufdcient metal to reduce its electrical resistance to a point where there shall be no danger of its becoming fused or welded to the connecting terminals. A further object is to provide a plurality of terminal sleeves permanently fixed in the porcelain body of the heating unit, each sleeve being provided with means, accessible from the upper surface of the plate, for receiving a fasteningA screw to secure the element terminals in place.

Another object has been to provide a heating element having non-expansible means connecting the ends thereoil so as to deilnitely determine the length oi' the coil when being assembled in the unit, such means being carbonized and thereby removed from the element when the same is ilrst heated.

Furthermore, my unit is so designed that there is less waste on the heating surface than in la whole.

of my unit, showing the formation of the bottoni present day designs, thereby assuring maximum heat transmission at a given temperature.

Moreover, it has been an object to so design the heating elements that all sharp turns in the element shall beeliminated, thereby preventing 5 hot spots in the coil which cause the coil to `burn out.

Another object im been to provide the unit with grooves, eachso iormed'at the bottom as to v allow circulation oi air under the element and l0 alsoY to prevent hot spots in the element caused by the accumulation of liquids or melted solids. A further object has been to provide heating elements which lhall bcliormed in substantially ellipticalsliapesoastomakepossible theuseoi l5 ,a greater length oi wire tor a given wattage, and thereby increase'the lite oi the element, or make possible an increase o! wattage of the element in a given space. The use o! my element, therelore. makes it possible to minimize the Awaste 20 Asurface on the heating unit by reducing the width o! the porcelain shoulder between adjacent element grooves, which thereby increases the heat transmission eillciency oi the unit as .Another object ci. my invention has been to place the elliptically-shapcd coils of my elements with .their major lateral axes perpendicular to the surface being heated, thereby making it possible to use a maximum amount oi wire under a 30 given surface.

The above objects and advantages have been accomplished by the device shown in the accompanying drawing, of which:

Fig. l is a plan view of my heating element. 3f

Fig. 2 is a reduced, diagrammatic, bottom, plan view showing the'connections between the various coils.

Fig. 3 is a side, fragmentary, sectional elevation taken through the unit on line 3--3 of Fig. l.

Fig. 4 is a fragmentary, perspective view oi one ci my complete heating elements.

Fig. 5 is a cross-sectional view oi a unit, showing the elliptical form ci the coil- Fig. 6 is a reduced, fragmentary, sectional-view of one of the grooves, and is taken on line 6 6 of Fig. l.

My unit comprises the customary base or plate i0 which is usually 0i porcelain or like material/50 Instead of one or two spirally-formed grooves, as is customary in heating units oi' the present day art, I form in my plate a plurality of short. camshaped grooves il, i2, il, it, Il, it, il, and i0. As shown in Fig. i, these grooves are curved ings Segments-25,26, 21, q28, 29, 30, 3|, and.32 are mounted, Frespectively, in grooves il' to I8, in-

clusive. At veach end of each of the grooves there is provided a terminal sleeve each of which,'for convenience, will be given separate numbers, the sleeve which is arranged at the outer end of the groove il being numbered 35. The sleeve 35, as

well as each of the other sleeves,1is providedwith a body 36 formed with an integral shoulder 31 at the upper end thereof. The body part and shoulder of the sleeve are set into the base i@ with the ktop surface of the shoulder preferably flush with the bottom of the groove-as shown in Fig. 3. The'zbody of the sleeve or the shoulder 'thereof may be so formed as to prevent rotations -withinthe base ofthe'unit. The lower end 38 of lthe body -'is extended below the bottom surface of the base lil where it is screwthreaded for the reception oi' two nuts Se. These nuts provide '-'means forpermanently securing the sleeve in place'within the base l as `well as for permanently attaching a lead thereto, as shown by the lead 60 which is connected to the terminal sleeve Each of the sleeves is provided witha centrally arranged and screwthreaded aperture i -with which a terminal screw i2l is engageable. This screwthreaded aperture is' formed at the lower end of the body and is, therefore, located as far as possible from thatpart of the sleeve which has the highest temperature. The body of the sleeve is preferably provided with a counterbore e3 which is somewhat larger than the diameter of the body of the screw 42. The screw i2 is preferably formed with a central aperture 4&3 therethrough. The counterbore i3 in the body of the sleeve and the aperture it of the screw are formed so as to provide air spaces to aid in keeping the terminal sleeve and screw as cool as possible. As hereinbefore stated, the terminal sleeve 35 is arranged at the outer end of the groove ii.

A similar sleeve 4E is arranged at the inner end of the groove i i. In like manner, the grooves i2 to it, inclusive, are each provided with outer terminal sleeves il to 53, respectively, and with inner terminal sleeves 5-5 to t@ respectively. As shown in the drawing, my device, therefore, may comprise eight segmental heating elements, thereby dividing the single heating elements of the present art, which are usually approximately thirty-six inches in length, into a number of short, segmental elements. Each of these segmental elements can be easily installed and, when burned out, replaced irrespective of the others. Each of these elements, as shown in Fig. 4 cornprises a coil of resistance wire preferably wound in substantially elliptical form, as shown also in Fig. 5, having each of its ends permanently attached to an eylet 6l. These eyelets are so designed and proportioned that the resistance offered to the passage o1" the current will not heat them sufficiently so as to cause fusing or Welding thereof to the terminal sleeve. They are preferably grooved, as shown in Figs. 3 and 4;, and the engaging end of the element is securely wound Y The eyelet, as shown in Fig. 3, isclamped in position on top of the respective terminal sleeve by means of a terminal screw 42. By making the coil elliptical in cross-section, it is possible to increase the wattage of an element on a surface heating unit without increasing the area of the surface under the cooking utensil. This is. because each turn of the coil of my element, due to its substantially elliptical form, is of greater length than the oustomary cylindrical form of coil for a given width of groove and, therefore, the total length of my element will be greater than the ordinary cylindrical coil for a given length of element and pitch of winding. This makes it possible to use a larger gauge wire in my element because 'of such increased length of wire, thereby bringing the emisvsivity rate within predetermined, safe limits. lBy

reason of the elliptical form of my element, it may be designed to consume the same wattage as the present day units of finer wire, but the resistance of the wire of my new element will naturally be less than that of an element made of nner wire. The' larger wire, therefore, reduces the burning temperature and emissivity rate, and thereby the life of the element is increased.

Therefore, owing to .the use of an element of elliptical cross-section, placed as shown in the drawing, having its maior, lateral axis perpendicular to the surface being heated, I can employ larger gauge element wire which permits the winding of element coils having greater width, thereby reducing the length of the element and consequently the length of the insulating ridges between adjacent elements. Since the top faces of the ridges are waste surfaces, from the standpoint of heat transmission, it is obvious that by reducing this waste area I can, as a result of my invention, increase the exposed space above the heatingA elements for heat transmission to the surface being heated. Therefore, by means of my invention I may either increase the capacity of the unit or reduce its burning temperature. Each of the segmental elements is provided with' a cord d2 of cotton or other suitable material which will not stretch and which is, therefore, lengthconfining when in place, thereby definitely spac- .ing the two eylets i of each heating element. This prevents the stretching of the coil beyond its normal length, and thereby makes it possible for any one, even though unskilled, to properly place the element in position. Obviously, the material used in the cord is such that when the element is first heated, it will carbonize and thereby remove itself from the element.

As shown in Fig. 6, the bottom of each of the grooves H to i3, respectively, is provided with two upstanding, interspaced ridges 55. These ridges are preferably il-shaped in forni, thereby providing line contact with the bottoms of the heating elements, and thus holding the elements in. spaced relation with the bottoms of the grooves and thereby allowing air to circulate under the coil. This is particularly valuable when water or other liquids have boiled over a cooking utensil or have been accidentally dropped upon the heating unit. This construction thus obviates the hot spotswhich are occasioned by the presence of such liquids in the bottoms of the grooves of the ordinary, presentday units. A number of holes d6 are preferably provided through the base It, terminating in the bottoms of the grooves, through which such liquid may be drained. l

In Fig. 2, I have shown a. preferable arrangement of heating elements whereby either the entire number may be heated or only every alternate one. I show four contact points 10, 1i, 12, and 1I. These contact points are supplied with current from a suitable source through a switch by which only a number of they coils may be heated, or all o! them heated. 'I'his A switch is a standard article of manufacture and is, therefore, not shown or described. The contact points 10 and 1i are designed to energize one group of segmental heating elements, and contact points 12 and 13 are designed to energize the other group of heating elements, each group oi' elements being preferably formed by alternately arranged elements. Contact point 10 is connected to the outer terminal sleeve 48 by means of a lead 1l. Current is conducted from this terminal through the heating element 21 to the inner terminal sleeve 55. This terminal sleeve is connected to the inner terminal sleeve 51 by means of a lead 15. From terminal sleeve 81, the current is conducted through heating element 29 to the outer terminal sleeve 50 of that element. This last mentioned sleeve is connected to the outer sleeve 52 by means oi lead 18. Current will ilow from sleeve 52 through element Il to the inner sleeve 59, which is connected to the`inner sleeve 46 of the element 25 by means of a lead 11. Current passes from terminal sleeve 46 through the heating element Il to the outer terminal sleeve 35 and thence through lead 40 to the terminal 1l. Thus when current is applied across the terminals 1G and 1I, heating elements 21, 29, 3|, and 25 will be energized and heated. Terminal 12 is, vin like manner, connected to the outside terminal sleeve 53 by means of a terminal 83 and current, when applied to said terminal, passes through the element 32 to the inner terminal sleeve 60 of that element. Sleeve 60 is connected to the sleeve 54 at the inner end o! the element 28 by means of a lead 18. The sleeve 41 at the outside ot the element 26 is connected to the sleeve 49 at the outside of the element 28 by means of a lead 19. The inner sleeve I8 of the element 2B is connected to the inner sleeve 58 of element 30 by means ot a lead 80. The outer lead 5I of element 30 is connected to the lead 13 by means of a lead 8|. Obviously, current applied across leads 12 and 13 will cause heating elements 32, 26, 28, and 30, to be energized and heated. It is also obvious that when current is applied across both groups of terminals 10 and 1|, and 12 and 13, all of the heating elements will be energized and the unit will be giving its maxi mum heat.

As hereinbefore stated, each of the segmental heating elements is secured in place by means o! two terminal screws I2. Each of these screws passes through the eyelet 6I at each end of the element and through the counterbore 43 of the terminal sleeve and into the screwthreaded opening Il at the bottom thereof. The propor tions oi the terminal sleeve and the terminal screws 42, as well as the eyelets GI, as hereinbefore pointed out, are such that the electrical resistance offered by them to the current passing therethrough will not be sufficient to cause them to become heated and thus oxidize or burn the parts. They are so proportioned that they remain relatively cool, with the result that a good connection between the eyelets and the terminal sleeve is always assured. Each of the terminal screws is, of course, provided with a head which is accessible from the top side o1' the vheating unit. When the screws are released, the element is completely detached from the unit and may, therefore, be easily removed. When a burned out element is to be replaced by a new element, the new element with its spacing cord 62 is placed in the groove and the terminal screws 42Y are passedthrough the eyelets I o! 1 the new element and into the `respective terminal sleeves, thereby securing the element in place.

' It willv be obvious that all the connectionsjjust abovev described `between kthegouter v and inner terminal sleeves are of a permanent nature and the leads are secured to their respective terminals by means of one of the nuts 39 provided on the lower end of each of the terminal sleeves. These nuts are all located on the bottom of the unit where they are concealed and since such connections are permanent they are not touched when any of the heating elements of my unit are to be replaced.

While I have shown and described a segmental element providedwith eyelets 6l and a nonstretching cord 62, which element is securable from the top of the unit, it is obvious that these novel features are also applicable to a heating element'oi the usual single-piece length oi' either circular or substantially elliptical cross-section.

Furthermore, the terminal means carried by the `o! radiation of heat from the screw head, the

thickness of the head'may also .be increased to increase the surface presented to the air. These and other modifications of the details herein shown and described may be made without departing from the spirit of my invention or the scope of the appended claims, and I do not. therefore, wish to be limited to the exact embodiment herein shown and described, the form shown being merely a preferred embodiment thereof.

rHaving thus described my invention, what I claim is:

1. A replaceable heating element adapted to be flexed for insertion in an open facial groove of an electric heating unit, comprising as an entiretyan open, coreless coil of resistance Wire adapted to be iiexed upon insertion, and a single, flexible combustible cord in the coil reduceable to ash upon initial heating of the said coil and being anchored only at its opposite ends tothe ends of the coil for limiting the maximum dis tortion of the latter prior to placement in the heating unit, said cord passing unattached through the coil for permitting universal flexing oi' the coil to conform the latter to a groove in an associated heating unit.

2. A replaceable heating element adapted for insertion in an open facial groove in the body 4 e 2,935,091 and near the bose thereof, each eyele; having its mail,A and positioning and anchoring means passaxis arranged suhetantismy parallel to the maior in: throum the eyelets for fastening the elealla ot the ellipse. a flexible cord Bassins unatment in sn associated heating yunit ln predeterthro'uzh the ooll and secured at its ends mined position. 5 only to ma 'memrins eyelets. nid eord bein: smimns. vmxnma. 5 to loeh upon initial o! the

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