US3736405A

US3736405A - Electric heaters

Info

Publication number: US3736405A
Application number: US00201753A
Authority: US
Inventors: C Bryson; G Barton
Original assignee: Emerson Electric Co
Current assignee: Emerson Electric Co
Priority date: 1971-11-24
Filing date: 1971-11-24
Publication date: 1973-05-29
Anticipated expiration: 1990-05-29

Abstract

A sheathed electric heater, particularly of the charcoal lighter type, having a resistor within the sheath, terminal pins electrically connected to the ends of the resistor, and an insulated power supply cord having a pair of current conductors electrically connected to respective terminal pins, the improvement comprising a handle for the heating element which is formed of electric insulating material and molded around adjoining parts of the sheath and cord and extending unbroken therebetween to completely encapsulate such parts, the terminal pins extending from the sheath and the electrical connection between the terminal pins and the current conductors.

Description

United States Patent 91 Bryson, Jr. et al.

1 1 3,736,405 1 51 May 29, 1973 [541 ELECTRIC HEATERS [75] Inventors: Charles E. Bryson, Jr.; Gary I. Barton, both of Murfreesboro, Tenn.

[22] Filed: Nov. 24, 1971 21 Appl.No.: 201,753

[52] US. (:1 ..219/270, 174/76, 110/28 D, 219/523, 219/541, 317/98 51 lnt.-Cl ..F23q 7/22 [58] Field of Search ..219/260, 261, 267, 219/270, 521, 523, 541, 544; 110/1 F, 8 E,

3,238,355 3/1966 Van Eeck ..219/528 2,917,615 12/1959 Raines ..219/267 2,922,016 1/1960 Persinger.... .....219/261 3,334,214 8/1961 Davidson.... ..219/261 3,387,364 6/1968 Boggs ..219/523 X 3,593,002 7/1971 Herbert ..219/541 Primary Examiner-Volodymyr Y. Mayewsky Attorney-Michael Williams [57] ABSTRACT A sheathed electric heater, particularly of the charcoal lighter type, having a resistor within the sheath, terminal pins electrically connected to the ends of the resistor, and an insulated power supply cord having a pair of current conductors electrically connected to respective terminal pins, the improvement comprising a handle for the heating element which is formed of electric insulating material and molded around adjoining parts of the sheath and cord and extending unbroken therebetween to completely encapsulate such parts, the terminal pins extending from the sheath and the electrical connection between the terminal pins and the current conductors.

2 Claims, 5 Drawing Figures Patented May 29, 1973 3,736,405

2 Sheets-Sheet 1 PRK R ART mvamons al GART L BARTON A We RN: 7

CHARLES: E- Bm'scmdn- Patented May 29, 1973 2 Sheets-Sheet 2 R v MM m wm NRA BB LL b M k M W C ELECTRIC HEATERS BACKGROUND AND SUMMARY Heretofore, inso far as applicants are aware, handles, such as for charcoal lighters, were formed in sections and held assembled with the sheath of the heater by suitable clamping means, such as screws. Currently, handles are being made in two mating portions, each molded of a phenolic material. The portions are held assembled with each other and with the sheath by screws passing through holes in one portion and threaded into corresponding holes in the other portion. In order to provide for proper disposition of the heater sheath within the cavities'of the handle portions, and in order to provide strain relief for the power cord, the cavities of the handle portions required intricate matching surfaces and thus required expensive molds to produce the same. Also, expensive construction was required to guard against current leakage and against moisture penetration of electrical connections.

Through use of our invention, all of the foregoing disadvantages are eliminated, and a superior handle is produced at lower cost.

DESCRIPTION OF THE DRAWINGS In the drawing accompanying this description and forming a part of this specification, there is shown, for purpose of illustration, an embodiment which our invention may assume, and in these drawings:

FIG. ,1 is a perspective view of a charcoal lighter illustrating an embodiment of our invention,

FIG. 2 is a separated, perspective view of a sectional handle of the prior art, showing a part of the sheath of an electric charcoal lighter in position for assembly,

FIG. 3- is a top plan view of the lower portion of a mold used in the production of our improved handle, showing adjoining parts of the heater sheath and power cord disposed within the mold cavity,

FIG. 4 is a section corresponding to the line 44 of FIG. 3, showing upper and lower portions of the mold 'in section and in separated relation, and

FIG. 5 is a sectional view of the handle portion of our improved heater.

DESCRIPTION OF PREFERRED EMBODIMENT In the disclosed embodiment, the apparatus shown is adapted for molding a handle for and onto an electriccharcoal lighter. As'seen in FIG. 1, such lighter comprises a metal-sheathed tubular heater which may be formed in conventional manner. Briefly, the metal sheath 11 of the heater is initially rectilinear, and a coiled wire resistor 12 is disposed within the sheath. Suitable granular refractory material 14 is disposed within the sheath to electrically insulate the resistor from the sheath and conduct heat from the resistor to the sheath. Terminal pins 15 (see FIGS. 2 and 3) extend outwardly from respective ends of the sheath, each terminal pin being mechanically and electrically connected to an end of the'resistor. The sheath is subjected to a rolling or side pressing operation to compact the granular refractory, and then is bent to form a loop 16 and legs 17,17 with end portions of the latter in closely spaced side-by-side manner.

A sheet-metal bracket or shield 18 is then slipped over the ends of the legs 17,17, such bracket having openings 19 and 20 to freely pass the legs. In such assembly, the bracket 18 has limited movement longitudinally of the legs 17, movement toward the loop being limited by abutment of the marginal surface of the openings 19 with the diverging portions of the legs 17, and movement in the opposite direction being limited by abutment with the adjoining surface of the handle 21.

A conductor cord 22 is electrically connected to the terminal pins, this cord being of suitable length and having a male plug (not shown) at its free end for insertion into a socket of a conventional electrical outlet. The inner end of the cord 22 is separated into respective leads 23 (see FIG. 3) and each lead has its conductor wire electrically connected to a respective terminal pin 15 by a conventional metal crimp connector 24. The conductor cord 22 may also carry a ground lead 25 which has a crimp connector 26 soldered to a leg 17 of the metal sheath 11.

All of the foregoing is in the prior art except that formerly the handle 21 was molded in two hollow parts 26,27 (see FIG. 2) which required a partition 28 to cradle the ends of the legs 17, and strain relief portions 29 into which a portion of the cord is disposed in sinuous fashion to relieve the crimp connections 24 of any pulling strain. Further, prior constructions required a positioning bar 30 (see FIG. 2) to be welded across the legs 17. This bar was adapted to abut the wall 31 of handle half 26 to define the position of the legs 17 lengthwise within the handle half. Also, prior construction required that the handle half 26 be formed with threaded holes 32 and the handle half 27 be formed with matching holes for passing the shanks of connecting screws. Further, in order to provide electrical safety, insulating sleeves (not shown) were shrunk around the end of each sheath leg 17, the crimp connector 24 and the adjoining end of the cord insulation. By use of our invention, all of the foregoing is no longer required. How ever, FIG. 2 is shown for the purpose of illustrating the complicated and detailed structure necessary heretofore to produce an electrically safe charcoal lighter handle, and suggests the expensive molds required to produce the same.

Our invention comprises the molding of a handle about the sheath legs 17, the adjoining end of the conductor cord 22, and the electrical connections therebetween, to firmly anchor all parts in proper position and in approved electrically insulated manner. A polyurethane molding compound is used and a commercially available compound is sold by PPG Industries under the trademark Selectrofoam. Chemically, such polyurethane molding compounds are a thermoset, cellular urethane plastic. The thermoset property provides that conventional wood or paint finishes may be applied to the molding for attractive finishes; that the moldings will resist warpage when exposed to moisture or heat, thus making them ideal from an electrical standpoint; and that the molded parts may be machined, if necessary. In addition, the exceptional dimensional stability of urethane polymers minimizes the need for shrinkage allowances.

Polyurethane molding compounds presently available are supplied in two components and during processing the components are mixed and poured into the mold. By using different master batches, the density of the molding may be controlled between about 2 and 50 pounds per cubic foot and it is presently preferred to use a density generally in the order of 20 pounds per cubic foot. The low pressure characteristic of molding with polyurethane permits the use of inexpensive molds. Referring to FIGS. 3 and 4, the mold herein disclosed comprises upper and

lower halves

35,36, respectively, each of which may be formed of a wood or metal frame F and a plaster of Paris or high density urethane foam filler P. The mold halves, when closed, form a cavity which will produce the desired shape of the handle to be molded. In conventional manner, each mold half is provided with a silicone rubber lining 37. The ends 38 of the mold halves are formed with matching openings 39 so that marginal surfaces thereof closely fit around respective sheath legs 17. The ends 40 of the mold halves are also formed with matching openings 41 to closely fit around the conductor cord 22.

In accordance with our invention, the assembled parts including the heater l and cord 22 with crimp connections 24 made, are disposed in the lower mold half 36, with the legs 17 cradled within respective recesses 39 and the cord cradled within the recess 41. The bracket 18 is disposed outside of the mold and its depending part 42 is adapted to bear against the mold end 38 to generally determine the amount of extension of the sheath legs 17 within the mold. No special attention need be given to support of the cord 22 within the mold since this part of the cord may sag a little without any detrimental effect.

The components of the polyurethane molding. may be mixed and placed in a dispensing container 45 (shown in small scale) having a pouring tube 46, or the components may be placed in the container 45 and mixed by stirring blades or the like contained therein, and the temperature of the mix may also be controlled within the container in any suitable manner.

Before the polyurethane is poured into the mold, the mold surfaces defining the cavity are sprayed with a barrier coating to provide for ready release of the mold halves from the molded handle. Suitable release agents are paraffin, toluene, or a product sold by Miller- Stephenson Company under the trademark Polylease."

With the heater parts disposed in the barrier-coated mold half 36, a suitable amount of polyurethane foam is poured into this mold half to substantially fill it. The barrier-coated mold half 35 is then positioned over the half 36 and the two halves are clamped against separation in any suitable manner. The temperature of the clamped molds is controlled in the order of about 160 F for about to minutes (the time varying with the particular composition of the mix.) The controlled temperature of the mold will cause the polyurethane foam to rise or expand to completely fill the mold and encapsulate all parts within the mold cavity.

After a suitable time (such as the 5 to 10 minutes above mentioned), the mold halves may be unclamped and separated, and the handle thus molded on the heating element and conductor cord may be removed.

After removal of the handle from the mold, any flash may be trimmed and the handle may be stained for a wood finish appearance, or it may be painted. If stained, the stain may be sprayed thereon and hand or machine rubbed, after which a lacquer finish may be sprayed over the stain.

We claim:

1. An electric heating element, such as a charcoal lighter and the like, comprising a metal sheath having an intermediate bight portion and legs in closely spaced side-by-side relation, a resistor within said sheath, terminal pins electrically connected to respective ends of said resistor and each terminal pin extending outwardly from a respective sheath end, compacted refractory material within said sheath to electrically insulate said resistor and said terminal pins from said sheath and to conduct heat generated by said resistor to said sheath, and an insulated power cord having a pair of current conductors which are electrically connected to respective terminal pins, said cord being adapted to be connected to a source of electrical energy to cause said resistor to generate heat, the improvement comprising:

a handle for said heating element comprising an encapsulation of the ends of said sheath legs and the space therebetween and said terminal pins and their connection to said power cord and the end of the power cord adjacent to said connection, the encapsulation consisting of a cellular urethane plastic which in uncured state occupies only a part of a mold closed about the parts above mentioned and which expands upon application of heat to completely fill the mold and surround and adhere to said parts, the plastic upon subsequent cooling and removal from said mold forming a one-piece rigid handle of cellular cross-section, said handle forming a rigid electrically insulating member by which said heating element may be safely handled, and through adherence to said power cord end forms a strain relief for the electrical connections between said terminal pins and said power cord conductors, the density of the cellular urethane plastic is in the general order of 20 pounds per cubic foot.

2. An electric heating element, such as a charcoal lighter and the like, comprising a metal sheath having an intermediate bight portion and legs in closely spaced parallel relation and diverge toward said bight portion, a resistor within said sheath, tenninal pins electrically connected to respective ends of said resistor and each terminal pin extending outwardly from a respective sheath end, compacted refractory material within said sheath to electrically insulate said resistor and said terminal pins from said sheath and to conduct heat generated by said resistor to said sheath, and an insulated power cord having a pair of current conductors which are electrically connected to respective terminal pins, said cord being adapted to be connected to a source of electrical energy to cause said resistor to generate heat, the improvement comprising: a handle for said heating element comprising an encapsulation of the ends of said sheath legs and the space therebetween and said terminal pins and their connection to said power cord and the end of the power cord adjacent to said connection, the encapsulation consisting of a cellular urethane plastic which in uncured state occupies only a part of a mold closed about the parts above mentioned and which expands upon application of heat to completely fill the mold and surround and adhere to said parts, the plastic upon subsequent cooling and removal from said mold forming a one-piece rigid handle of cellular crosssection, said handle forming a rigid electrically insulating member by which said heating element may be safely handled, and through adherence to said power cord end forms a strain relief for the electrical connections between said terminal pins and said power cord conductors, and a sheet-metal shield including a body portion overlying the legs of said heating element and having opposite ends bent in the same direction from said body portion, each end having a pair of openings which closely but slidably receive parallel parts of said legs, movement of said shield in a direction toward the bight portion of said sheath being limited by wedging action of the defining surfaces of the openings in the 6 posed close to the adjacent portion of the handle and adapted to be disposed outside of the mold and engageable with an exterior mold surface to longitudinally poend of the shield nearest the bight portion with the di- 5 Sitio" Parts Within the moldverging legs, the opposite end of said shield being dis-

Claims

1. An electric heating element, such as a charcoal lighter and the like, comprising a metal sheath having an intermediate bight portion and legs in closely spaced side-by-side relation, a resistor within said sheath, terminal pins electrically connected to respective ends of said resistor and each terminal pin extending outwardly from a respective sheath end, compacted refractory material within said sheath to electrically insulate said resistor and said terminal pins from said sheath and to conduct heat generated by said resistor to said sheath, and an insulated power cord having a pair of current conductors which are electrically connected to respective terminal pins, said cord being adapted to be connected to a source of electrical energy to cause said resistor to generate heat, the improvement comprising: a handle for said heating element comprising an encapsulation of the ends of said sheath legs and the space therebetween and said terminal pins and their connection to said power cord and the end of the power cord adjacent to said connection, the encapsulation consisting of a cellular urethane plastic which in uncured state occupies only a part of a mold closed about the parts above mentioned and which expands upon application of heat to completely fill the mold and surround and adhere to said parts, the plastic upon subsequent cooling and removal from said mold forming a one-piece rigid handle of cellular cross-section, said handle forming a rigid electrically insulating member by which said heating element may be safely handled, and through adherence to said power cord end forms a strain relief for the electrical connections between said terminal pins and said power cord conductors, the density of the cellular urethane plastic is in the general order of 20 pounds per cubic foot.

2. An electric heating element, such as a charcoal lighter and the like, comprising a metal sheath having an intermediate bight portion and legs in closely spaced parallel relation and diverge toward said bight portion, a resistor within said sheath, terminal pins electrically connected to respective ends of said resistor and each terminal pin extending outwardly from a respective sheath end, compacted refractory material within said sheath to electrically insulate said resistor and said terminal pins from said sheath and to conduct heat generated by said resistor to said sheath, and an insulated power cord having a pair of current conductors which are electrically connected to respective terminal pins, said cord being adapted to be connected to a source of electrical energy to cause said resistor to generate heat, the improvement comprising: a handle for said heating element comprising an encapsulation of the ends of said sheath legs and the space therebetween and said terminal pins and their connection to said power cord and the end of the power cord adjacent to said connection, the encapsulation consisting of a cellular urethane plastic which in uncured state occupies only a part of a mold closed about the parts above mentioned and which expands upon application of heat to completely fill the mold and surround and adhere to said parts, the plastic upon subsequent cooling and removal from said mold forming a one-piece rigid handle of cellular cross-section, said handle forming a rigid electrically insulating member by which said heating element may be safely handled, and through adherence to said power cord end forms a strain relief for the electrical connections between said terminal pins and said power cord conductors, and a sheet-metal shield including a body portion overlying the legs of said heating element and having opposite ends bent in the same direction from said body portion, each end having a pair of openings which closely but slidably receive parallel parts of said legs, movement of said shield in a direction toward the bight portion of said sheath being limited by wedging action of the defining surfaces of the openings in the end of the shield nearest the bight portion with the diverging legs, the opposite end of said shield being disposed close to the adjacent portion of the handle and adapted to be disposed outside of the mold and engageable with an exterior mold surface to longitudinally position parts within the mold.