US3217279A - Electric resistance heater - Google Patents

Description

Nov. 9, 19635 A, c. BOGGS ELECTRIC 'RESISTANCE HEATER 2 Sheets-Sheet l Filed Feb. 19, 1962 NV ENTOR. ALEEN G, BOC-SGS @wf/5w Afm/ma vm w) y m Rv mwmww.

Nov. 9, 1965 A. c. BOGGS ELECTRIC RESISTANCE HEATER 2 Sheets-Sheet 2 Filed Feb. 19, 1962 I N VENTOR.

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NN SX@ .www NN United States Patent O ice 3,217,279 ELECTRIC RESISTANCE HEATER Alben C. Boggs, Pittsburgh, Pa., assigner to Edwin L. Wiegand Company, Pittsburgh, Pa. Filed Feb. 19, 1962, Ser. No. 174,019 Claims. (Cl. 338-239) The present invention relates to electric heaters, more particularly to electric resistance heaters and to methods of making the same, and the principal object of the infvention is to provide new and improved heaters and methods of this character. y

Whi-le an electric resistance heating element having selectively energizable portions is not broadly new, prior art elements of this character were complicated and expensive to manufacture. Hence, their selling price was relatively high thus seriously limiting their use in many applications. The present invention, however, provides for the manufacture of such heaters at relatively low cost thus making their use feasible in applications in which they were heretofore too costly. These and other advantages will readily become apparent from a study of the following description and from the drawings appended hereto.

In the drawings accompanying this speci'cation and forming a part of this application, there is shown, for purpose of illustration an embodiment which the invention may assume, and in these drawings:

FIGURE 1 is a view in longitudinal section through a preferred embodiment of the invention,

FIGURE 2 is a broken elevational view of an assembly seen in FIGURE 1,

FIGURE 3 is an exploded perspective View of certain details seen in FIGURE 1,

FIGURE 4 is a schematic wiring diagram illustrating a preferred arrangement for controlling energization of the heater seen in FIGURE 1, t

FIGURES 5, 6 and 7 are reduced size elevational views illustrating a preferred method of assembling the heater seen in FIGURE 1,

FIGURE 8 is a perspective view of a modied detail seen in FIGURE 1,

FIGURE 9 is a View similar to FIGURE 1 but showing the heater after further manufacturing operations,

FIGURE 10 is a reduced size elevational View similar to FIGURE 1 but with the sheath omitted in the interest of clarity and of a modified structure, and

FIGURE 11 is a View similar to FIGURE 4 but illus- 'trating a preferred arrangement for controlling energization of the heater seen in FIGURE 10.

With reference to FIGURE 1, there is illustrated a pair of heater sections A and B in end-to-end relation shown within a tubular metallic sheath 10. With reference also to FIGURE 2, heater section A in this embodiment comprises an elongated cylindrical body 11 of a suitable dielectric, heat-resistant material such as, for exa-mple, magnesium oxide powder held together with a suitable binder. The outer diameter of body l11 is somewhat smaller than the internal diameter of the sheath 10 to insure adequate radial space therebetween for a purpose to appear.

Helically wound upon the exterior of 4body 1=1 is a resistor wire `i12 which is anchored to the body exterior by the following means. lReferring especially to FIGURE 3, body 1l has a pair of openings 13, 14 extending longitudinally therethrough in side-by-side, parallel relation. Opening 13 has a rounded portion 113 adjacent the axis of the body to closely receive a later to be described pin and a portion 213 adjacent the *body periphery to closely receive a later to be described metal strip 15. Opening 14 is identical to 13 and has respective portions 1114, 214-.

3,217,279 Patented Nov. 9, 1965 As best seen in FIGURE 3, the previously mentioned metal strip '15 has a U-shaped configuration with a long leg for fitting within opening portion 213 -at one end of the body and a short -leg 215 for overlying the periphery of the body at such body end. An identical metal strip 116 (FIGURE 2) is disposed at the opposite end of body 11 with its long leg 116 disposed in opening portion 214 and its short leg 216 overlying the body periphery. The previously mentioned wire 12 wound upon the ybody `111 has one end welded or otherwise secured to strip leg 21S and its other end similarly secured to strip leg 216 to thereby retain the wire assembled upon the body.

Turning now to heater section B, such section preferably comprises a body identical to 11 and identified by the same reference character but with the suix .1 added. Also similar to body 11, body 11.1 has a resistor Wire 12.#1 wound thereon and anchored to strips 15.11, '1611 which are preferably identical to those previously described. Other corresponding parts of the heater section B are identified by t-he same reference characters as lused in the description of heater section A but with the suffix .1 added. As herein shown, wire 12.1 has fewer turns than wire 12 so that it has a lower electrical resistance for a purpose to appear; however, it is to be understood that this is illustrative only and that wire 12.1 Icould also have a different cross-sectional area from wire 1.2 or be made of a different material to provide the different electrical resistance. Also, while it is presently desirable to provide the wires 12, 12:1 with diiterent electrical resistances, it is contemplated that there may be applications where it is desired to provide such wires with the same electrical resistance.

At the present time, it is preferable to maintain the bodies 11, 1:1.1 in predetermined spaced relation by means of a disk-like spacer 17 interposed therebetween. Such spacer may be formed of the same material as bodies 11, 11.1 and as viewed in FIGURES 1 and 3, is of a diameter to closely t within the sheath 10 and has apertures 118 for registry with respective body openings 13, 14, 13.1 and 14.1. Similar disk-like members 17.1 and 17.2 having apertures 18.1, 18.2 respectively are disposed at respective outer ends of the bodies 11, 11.1 as seen in FIGURE t1.

Still referring to` FIGURE 1, a `generally rigid, current conductor pin 19 of metal or the like extends through the aligned openings 13, 13.1 of respective bodies 11, 11.1 and through aligned apertures 18, 18.1 and 18.2 of respective spacer members 117, 17.1 and 17.2. As herein disclosed, pin 19 is of a length to project beyond respective sheath ends; however, it may, if desired, be shortened to project beyond only one sheath end.

Similarly, a generally rigid current conductor pin 20 extends through the body opening 14.1 and part way into the body opening 14. While pin 20 projects beyond the sheath end adjacent Ibody 11:1, it is important that it project into the body 1x1 only far enough to maintain the bodies 11, 11.1 in alignment but not Yfar enough to engage the long leg of strip 16. A third current conductor pin 21 ext-ends into body opening 14 and projects beyond the sheath end adjacent the body 11, such pin being spaced axially of the pin 20 to insure electrical isolation there- `'between Ifor a purpose to appear.

It is to be understod that with the parts positioned as seen in FIGURE l, pin 19 is in tight frictional engagement with the elongated legs of strips 15, .15.1 to establish electrical connections between this pin and the resistor wire ends secured to such strips. Similarly, pin 20 is in tight frictional engagement with the elongated leg of strip 16.1 while the pin 21 is in tight frictional engagement with the elongated leg of strip 16.

The structure thus far disclosed provides an electric resistance heating element having selectively energizable portions and, as diagrammatically seen in FIGURE 4, pin 19 may be connected to a source of electrical energy such as a power line L-1. Pin 2t) may be connected to a power line L-2 through normally open contacts 22 of a switch mechanism 23 while pin 21 may be connected to a power line L-2 through normally open contacts 24 of such switch mechanism. If contacts 22 are bridged, current will tlow through and energize resistor wire 12.1 of heater section B to thus energize the latter. On the other hand, if contacts 2d are bridged, current will flow through and energize resistor wire 12 of heater section A. Similarly, if contacts 22 and 24 are bridged, both heater sections A and B will be energized as will be evident.

Returning now to FIGURE and assuming that the bodies 11, 11.1 have been wound with respective resistor wires and the latter have been anchored in position by being secured to respective strips disposed as previously described in respective body openings, assembly of the heater seen in FIGURE l will preferably be as follows:

Conductor pin 19 will first .be inserted into opening 13 of body 11 in the direction indicated by the arrow. Spacer 17 will next be positioned adjacent the right end of body 11 as shown in FIGURE 6 with the pin 19 projecting through one of the spacer apertures 18. Pin 19 will now be inserted into body opening 13.1 of body 11.1 in the direction indicated by the arrow until body 11.1 abuts spacer 17 which in turn abuts body 11. Finally, and with reference to FIGURE 7, pins 20 and 21 will be inserted into body openings 14.1 and 14 respectively and in the direction of the arrows until such pins are positioned as seen in FIGURE l. Thereafter, spacers 17.1 and 17.2 may be assembled over the pins and the entire assembly then inserted into the sheath 10. It should be understood, however, that for certain uses, the sheath as well as the spacers 17, 17.1 and 17.2 may be omitted. Also, while not shown, suitable plugs or the like may be inserted into the sheath ends and/or the ends of the sheath turned radially inwardly to retain the parts assembled.

While the assembly seen in FIGURE yl is complete, it is sometimes desirable to subject the assembly to further manufacturing processes to improve its eiiiciency. This is commonly done by iilling the sheath 10 with iinely divided mate-rial, such as powdered magnesium oxide, and then transversely reducing the sheath by a swaging operation or the like to compact the material to a rocklike hardness.

To permit introduction of the finely divided material into the sheath, spacer member 17 must be modied somewhat. As illustrated in FIGURE 8, spacer member 17a is similar to spacer member 17 except that its periphery is provided with a plurality of notches 25.

In the manufacture of the modified structure, the parts will be assembled as previously described, using, of course, the spacer 17a rather than the spacer 17 and also substituting for one of the end spacers, such as 17.2, a spacer identical to 17a. The assembly will then be illed with the powdered magnesium oxide by a vibratory process or the like, the peripherally notched spacers permitting the magnesium oxide to completely inltrate the interior of the sheath.

After tiling as above described, the sheath ends may be closed by any suitable plugs to prevent escape of the powdered magnesium oxide and the unit then subjected to a rolling, swaging, pressing, or other operation to transversely reduce the size of the sheath. The transverse reduction of the sheath fragments the bodies upon which the resistors are wound together with the spacers to a homogeneous, rock-hard mass with the powdered magnesium oxide as illustrated in FIGURE 9.

Following transverse reduction of the sheath, the previously mentioned end plugs may be removed, if desired,

and the voids thus left in the sheath ends iilled with a suitable, paste-like cementitious material 26 which hardens in situ to form permanent, dielectric closures for the sheath ends. It is to be understood, however, that under certain conditions, the previously mentioned plugs may be left in place with or without the use of the cementitious material 26.

While in the construction thus far disclosed there has been illustrated the use of but two bodies 11, 11.1 each having a resistor wound thereon, the invention contemplates the use of a greater number of resistor-wound bodies to form a heater having sections A and B.

By way of illustration, there is shown in FIGURE l0 (the sheath being omitted in the interest of clarity) a heater formed of resistor-wound bodies 111, 211 which form heater section A and resistor-wound bodies 111.1, 211.1 and 311.1 which form the heater section B. These bodies may, of course, be similar to those previously described and may be separated by spacers 117, 217, 317 and 417 with spacers 117.1 and 117.2 at respective ends of the assembly. As in the earlier described embodiment, terminal pins 119, 120 and 121, respectively corresponding to terminal pins 19, 20 and 21 are disposed within respective body openings to maintain the bodies in axially aligned relation and to form electrical connections with the resistors carried thereby. As will be understood, pin 119 is electrically connected to one end of each of the resistors wound upon the bodies 111, 211, 111.1, 211.1 and 311.1. Pin 120, on the other hand, is electrically connected to the opposite end of the resistors wound upon the bodies 111.1, 211.1 and 3111.1 while pin 121 is electrically connected to the opposite end of the resistors wound upon the bodies 111, 211.

With reference now to FIGURE l1 wherein the heater seen in FIGURE 10 is diagrammatically illustrated, pin 119 may be connected to a power line L-1 while pin 120 may be connected to the power line lf2 through the normally open contacts 27 of a switch mechanism 28. Pin 121 may also be connected to the power line L-2 but through the normally open contacts 29 of the switch mechanism.

In manner similar to FIGURE 4, closing of the contacts 27 will cause current to iiow through the resistors in the B section of the heater; that is, through those resistors wound upon the bodies 111.1, 211.1 and 311.1. Alternatively, it contacts 29 are closed, current will liow through the resistors in the A section of the heater; that is, through those resistors wound upon bodies 111, 211. Obviously, closing of both contacts 27, 29 will cause all resistors to be simultaneously energized.

Although not shown, it will be understood that the heater seen in FIGURE l0 may be enclosed in a tubular sheath if desired and may further be subjected to additional operations as described in connection with FIG- URE 9.

While the long leg of metal strip 15 (and the corresponding leg of strip 16 since the strips are identical) have previously been shown to be rectangular in transverse section, it is to be understood that it may be preferably to transversely curve such leg to closely fit with the exterior of the terminal pins. Furthermore, in such case, opening portions 213, 214 of the body 11 would be moditied from the shape shown in FIGURE 3 to closely it with such transversely curved strip legs.

In view of the foregoing, it will be apparent to those skilled in the art that I have accomplished at least the principal object of my invention and it will also be apparent to those skilled in the art that the embodiments herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described; hence it will be appreciated that the herein disclosed embodiments are illustrative only, and that my invention is not limited thereto.

I claim:

1. An electric resistance heating element, comprising a pair o'f elongated dielectric bodies, each having a resistance conductor on the surface thereof and each having a pair of openings extending longitudinally therethrough in parallel relation, a terminal of said resistance conductor of each body disposed within one opening at one end of such body and another terminal of said resistance disposed within the other opening at the opposite end of such body, said bodies being disposed in endto-end relation with the openings in axially aligned relationship and with the resistance conductor termi-nals of one pair of aligned openings in adjoining relation and the resistance conductor terminals of the other pair of aligned openings at lopposite ends of the end-to-end bodies, a first conductor pin extending entirely through said one pair of openings to maintain the latter aligned and hold said bodies in end-to-end relation and to electrically connect said adjoining resistance conductor terminals, and second and third conductor pins extending inwardly from opposite ends of said end-to-end bodies and electrically connected to respective ones of said resistance conductor terminals at such ends.

2. The construction of claim 1 wherein said second conductor pin extends entirely through one body and partially through the other body but out of electrical engagement with the resistance conductor terminal of the latter, said second conductor pin holding said bodies against rotation about said rst conductor pin and assisting the latter `in holding said bodies in end-to-end relation.

3. An electric heating element, comprising a pair of pre-formed resistor elements, each including the assembly `of a core of electric insulating material and a resistance wire coiled thereon substantially from end-to-end thereof, each core having a pair of spaced longitudinally extending openings therethrough and the terminal portions of each resistance wire conducting current from one end of the wire to within an adjoining end o'f one opening and from the other end of the wire to within an adjoining end of the other opening, and electrical connection means comprising three conductor pins upon which the preformed resistor elements are disposed with said pins fitting into the core openings of said elements in skewer relation, one conductor pin being in electrical enga-gement with a terminal end of each resistance wire and the other two pins being in electrical engagement with respective ones of the remaining of said terminal ends, said pins being adapted `for electrical connection to switch means for selectively energizing said resistance wires in various electrical relationships.

4. The construction according to claim 3 wherein the electrical engagement with the terminal ends of said resistance wire is automatically made when said pins are moved to proper position within respective longitudinal openings.

5. The construction according to claim 4 wherein each terminal end is formed as a U-shaped metal clip having a leg within a respective core opening for engagement with a respective conductor pin and having another leg electrically connected to the respective end of the coiled resistance wire.

References Cited by the Examiner UNITED STATES PATENTS 2,058,769 10/ 36 Brown 338-295 2,861,162 11/58 Van Inthoudt 29-15565 2,879,361 3/59 Haynman 338-325 2,933,805 4/60 McOrlly 29-155.65 2,993,186 7/61 Hay 338--261 3,051,923 8/62 Julie 338-273 RICHARD M. WOOD, Primary Examiner.

Claims (1)

1. AN ELECTRIC RESISTANCE HEATING ELEMENT, COMPRISING A PAIR OF ELONGATED DIELECTRIC BODIES, EACH HAVING A RESISTANCE CONDUCTOR ON THE SURFACE THEREOF AND EACH HAVING A PAIR OF OPENINGS EXTENDING LONGITUDINALLY THERETHROUGH IN PARALLEL RELATION, A TERMINAL OF SAID RESISTANCE CONDUCTOR OF EACH BODY DISPOSED WITHIN ONE OPENING AT ONE END OF SUCH BODY AND ANOTHER TERMINAL OF SAID RESISTANCE DISPOSED WITHIN THE OTHER OPENING AT THE OPPOSITE END OF SUCH BODY, SAID BODIES BEING DISPOSED IN ENDTO-END RELATION WITH THE OPENINGS IN AXIALLY ALIGNED RELATIONSHIP AND WITH THE RESISTANCE CONDUCTOR TERMINALS OF ONE PAIR OF ALIGNED OPENINGS IN ADJOINING RELATION AND THE RESISTANCE CONDUCTOR TERMINALS OF THE OTHER PAIR OF ALIGNED OPENINGS AT OPPOSITE ENDS OF THE END-TO-END BODIES, A FIRST CONDUCTOR PIN EXTENDING ENTIRELY THROUGH SAID ONE PAIR OF OPENINGS TO MAINTAIN THE LATTER ALIGNED AND HOLD SAID BODIES IN END-TO-END RELATION AND TO ELECTRICALLY CONNECT SAID ADJOINING RESISTANCE CONDUCTOR TERMINALS, AND SECOND AND THIRD CONDUCTOR PINS EXTENDING INWARDLY FROM OPPOSITE ENDS OF SAID END-TO-END BODIES AND ELECTRICALLY CONNECTED TO RESPECTIVE ONES OF SAID RESISTANCE CONDUCTOR TERMINALS AT SUCH ENDS.

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