US3617703A

US3617703A - Surface-type electric heating treatment elements

Info

Publication number: US3617703A
Application number: US62995A
Authority: US
Inventors: William A Ewart Jr
Original assignee: Emerson Electric Co
Current assignee: Emerson Electric Co
Priority date: 1970-08-11
Filing date: 1970-08-11
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02

Abstract

A surface-type electric heating element with terminal pins disposed within opposite ends of a tubular metal sheath and connected to respective ends of the heating resistance within the sheath, compacted refractory material electrically insulating the resistance and terminal pins from the sheath and holding them in position therewithin, each terminal pin extending outwardly from a sheath end and terminating in a loop, the compacted refractory material adequately supporting each terminal pin so that the latter may be twisted along its longitudinal axis whereby the loops may be disposed in selected angular relation to adapt for use with either a plug-in type socket or a screw-type socket. Each terminal pin, at least in the portion subjected to the twisting action, has a Rockwell hardness of about B38 to B55.

Description

United States Patent [72] Inventor William A. Ewart, Jr.

Pittsburgh, Pa. [21] Appl. No. 62,995 [22] Filed Aug. 11,1970 [45] Patented Nov. 2, 1971 [73] Assignee Emerson Electric Co.

St. Louis, Mo. Continuation-impart of application Ser. No. 791,480, Jan. 15, 1969, now abandoned.

[54] SURFACE-TYPE ELECTRIC HEATING TREATMENT ELEMENTS 10 Claims, 4 Drawing Figs. [52] U.S .Cl 219/451, 219/467, 219/541, 338/241 [51] Int. Cl 1105b 3/68 [50] Field 01 Search 219/541, 451, 455, 458, 463, 467, 452; 338/239-241, 273-74, 316; 339/192 [56] References Cited UNITED STATES PATENTS 2,888,656 5/1959 Bremer ABSTRACT: A surface-type electric heating element with terminal pins disposed within opposite ends of a tubular metal sheath and connected to respective ends of the heating resistance within the sheath, compacted refractory material electrically insulating the resistance and terminal pins from the sheath and holding them in position therewithin, each terminal pin extending outwardly from a sheath end and terminating in a loop, the compacted refractory material adequately supporting each terminal pin so that the latter may be twisted along its longitudinal axis whereby the loops may be disposed in selected angular relation to adapt for use with either a plug-in type socket or a screw-type socket. Each terminal pin, at least in the portion subjected to the twisting action, has a Rockwell hardness ofabout B38 to B55.

PATENTEUuuv 2 ISTI INVENTOR. W\ LLAAM A. EWAR'QJn Aa/ %M A T TORNEXS SURFACE-TYPE ELECTRIC HEATING TREATMENT ELEMENTS This application is a continuation in-part of application Ser. No. 791,480, now abandoned, of the same title and assigned to the same assignee.

BACKGROUND AND SUMMARY Surface-type electric heating elements usually, comprise an elongated tubular metal sheath containing a heating resistance which is electricallyinsulated from and held in position within the sheath by compacted refractory material and has terminal pins at the opposite ends of the sheath, the sheath being in the form of a flat winding and having its opposite end portions disposed below the flat winding and extending laterally therefrom, the terminal pins extending from opposite ends of the sheath.

Surface-type elements as above described had their terminal pins connected to a source of electrical energy. in vari+ ous manner, such as by plugging the terminal ends into a dielectric socket for contact with spring contacts within the socket, the latter having: lead wires connected thereto, or as by connecting the terminal ends with screw connections to lead wires, the screw connections being carried by a dielectric socket or terminal block.

Each of the above-mentioned twotypes of connections have many variations, and thus a service man had to stock many dif= ferent types of surface heating elements and terminalblocks in order to be in position to adequately service different types of electric stoves. It is the object of the present invention to provide electric heating elements which will enable a service man to stock only one type of surface unit and only two types of terminal blocks in order to service amajority of electric stoves now in use.

lncopending patentapplication of G. E. Ammerman et. al.

Ser. No. 592,484, filed Nov. 7 1966, now U.S. Pat. No.

material adequately supportsthe inner portion of the terminal.

pin so that the latter may be twisted about its longitudinal axis. to dispose the loop end in any desired. angular relation, without impairing electrical insulation of the pin from the sheath, and this permitsadaptation of the surface-type unit for selective connection to plug-in or screw-type sockets.

DESCRIPTION OF DRAWING In the drawing accompanying this specification and forming a part of this application, there is shown, for purposes of illustration, an embodiment which my inventiommay assume, and in this drawing.

FIG. 1 is a fragmentary, separated perspective view illustrating the embodiment of the invention adapted for plug-inpurposes,

FIG. 2 is a fragmentary, separated perspective view of the embodiment of the invention adapted for screw-type electrical connection,

FIG. 3 is an enlarged, fragmentary sectional view of the terminal pin portion of the heater, and

FIG. 4 is an enlarged, fragmentary sectional view showing the screw-type connection.

DESCRIPTION OF THE PREFERRED EMBODIMENT The usual surface-type electric heater comprises a tubular metal sheath containing a heating resistance 11 which is electrically insulated from and held in position within the sheath by compacted refractory material 12. The sheath is in the form of a flat winding and has its opposite end portions 14-14 disposed below the flat winding and extending laterally thereof. Oppositeends of the heating resistance are mechanically and electrically connected to terminal pine 15, each of which has a portion disposed within an end portion of the sheath and a portion extendingoutwardly of. the sheath and terminating in a loop 16 of generally button-hook shape. A dielectric bushing 17 may bev disposed within the end of each endportion, as seen in FIG. 3.

1n the. process of forming the surface elements, the sheath is reduced in cross-sectional size, as by side pressing, rollingor swaging, to densify the refractory material to a hard, rocklike condition and it has been found that: this dense condition (aided perhaps by the fact that the terminal pin within the sheath is bent to follow the contour of the sheath end portion, as shown in FIG. 3) will adequately support the terminal pin so that it may be twisted about its longitudinal axiswithout affecting thesupport or insulation of thepin. Thus, each pin may be twistedto dispose its loop in any desired angular relation to match the loop with the type, of electricalconnection required. Twisting thepin may be accomplished by use of an ordinary pair of pliers and may bedone while on a service call.

It is important that the terminal pins do not fracture or break duringthe twisting action since otherwise the utility of this invention would be impaired. The terminal pinsv are usually formed of stainless steel and it has been found that if such pins, at least in the portion subjected to the twisting action, have a Rockwell hardness of about B38 to 855, the pins will be hard enough to withstand electrical connection with the contacts in the terminal block, yet aresoft enough to be easily twisted without fracturing. To effect this feature, terminalpins having a Rockwell hardness higher than the range above-mentioned may be used, and the pins spot annealed, after assembly, in the twisting portion. Or, .the terminal pins, in their entirety, may be of a Rockwell hardness in the range above-mentioned prior to assembly.

Usually, a metal strip 18' is connected across the terminal portions 14- l4.of the sheath, as shownin FIG. 1, the purpose for this beingto. hold the portions in definite spaced relation. One terminalportion of the sheath is firmlyheld by the strap and the other may have a sliding fit through an openingin the strap to provide. for expansion and contraction of the sheath without lateral deformation of the flat winding. Detailed construction' for accomplishing this purpose is shown in US. Pat. No. 3,350,674.

For use with a plug-in type socket or terminal block asillustrated at 19 in. FIG. I, the loops 16l6. are disposed in spaced, parallel. vertical planes, although this is merely a present choice of construction and thesocket 19 may be formed torequire other angular dispositionlof the loops.

The block 19is provided with a pair of elongated openings, 2040 throughwhich the loops are respectively projected. The block has internal cavities communicating with the openings and housing contact member 2121 which resiliently engage flatwise with the loops to provide maximum surface ihterengagement. Each contact member is electrically connected toa leadwire 22 which in turn is adapted to beconnected in circuit with a source of electrical energy.

In a plug-in type, surface unit, it is desirable that the unit be automatically. grounded, at or just prior to the time, its terminals are plugged into electrical engagement with the eontacts 21 of the terminal block, and this may be accomplished in a manner shown in US. Pat. No. 3,246,123. Briefly, metal contact spring strips 23 may be disposed on opposite sidesof the terminal block 19 and connected to a ground, such as the frame of the range. As the loops 16 are projected through the openings 20, the spring contacts 23 engage. opposed edges of the strap 18 to ground the surface unit.

As an additional feature and to assist in preventing the unit from turning relative to its adapter ring or stove top opening, a finger 24 may be welded in upright position to the strap 18 for frictional engagement with a defining surface of the opening or ring. When the unit is used for plug-in purposes, the finger 24 is broken off since it is not required. However, since the unit is adapted for use with either plug-in or screw-type terminal blocks, it should be welded to the strap at the time the unit is manufactured since it is an easy matter for the serviceman to break it off, whereas it would require special tools for the serviceman to properly add it to the strap.

when the surface unit shown in FIG. 1 is to be used with a screw-type tenninal block 25 shown in FIG. 2, the finger 24 is not broken off. To properly orient the loops 16-16 for disposition within the horizontal openings 26-26 of the terminal block, the serviceman twists the respective terminal pins to dispose each loop in the horizontal position shown in FIG. 2. This twisting may be easily accomplished by use of a pair of pliers so it is evident that the heating unit may be readily adapted in the field for use with a screw-type terminal block.

Several forms of screw-type connections are herein illustrated. In one form, the lead conductor 27 may have its insulation stripped from an end and the exposed wire end crimpconnected with a connector 28 that provides a flat, washerlike portion 29. To electrically connect a terminal pin 15 to a conductor 27, the loop 16 is inserted into one end of the terminal block 25 and a connector 23, with conductor crimped thereto, is inserted into the opposite end of the block. A machine screw S is passed through aligned openings in the loop 16 and the portion 29 and threaded into a nut 30 to insure good electrical connection. In some cases, the nut 30 may be omitted and a self threading screw employed to thread into the metal surrounding the loop opening.

The nut 30 is herein shown formed with a spade portion 31 so that it may also be used to electrically connect with a separable female member 32, the spade slidably but frictionally fitting within the member 32 in well known manner. As shown, a conductor 33 may have crimp connection with the member 32. In the event the electrical connection is made by connecting the member 32 to the spade 31, it will be appreciated that the crimp connector 28 will be omitted.

in order to ground the heating element when electrical connection is made in either manner shown in FIG. 2, a clamp strap 34 is firmly connected to an end portion 14 of the heating element, a conductor leading from the strap to a suitable ground.

claim: Claim:

1. A surface-type electric heating element assembly, comprising an elongated tubular sheath containing a heating resistance which is electrically insulated from and held in position within the sheath by compacted refractory material and has terminals at the opposite ends of the sheath, said sheath being in the form of a flat winding and having its opposite end portions disposed below said flat winding and extending laterally therefrom, each of said terminals comprising a terminal pin having one end within said sheath and connected to an end of said heating resistance and its other end disposed outside of said sheath and terminating in a loop, said assembly further comprising a terminal block having a pair of openings for receiving respective loops, a terminal member within each block opening, each member having a threaded opening for receiving a threaded terminal screw which projects through a respective loop, the member and screw forming clamping means for electrically connecting an electrical lead wire to said loop.

2. The construction according to claim 1 wherein each terminal member has an extending portion which combines with a complementary member to form a separable electrical connection.

3. The construction of claim 2 wherein a spade portion extends from each terminal member and combines with a female connector to form a separable electrical connection, each female connector being connected to a lead wire which is adapted to be connected to a source of electrical energy.

4. A surface-type electric heating element assembly, comprising an elongated tubular metal sheath containing a heating resistance which is electrically insulated from and held in position within the sheath by compacted refractory material and has terminals at the opposite ends of said sheath, said sheath being in the form of a flat winding and having its opposite end portions disposed below said flat winding and extending laterally therefrom, each of said terminals comprising a terminal pin having one end within said sheath and connected to an end of said heating resistance and its other end disposed outside of said sheath and terminating in a loop, a dielectric terminal block having openings in one end through which the loops of said terminal pins extend for disposition within a cavity in said terminal block, a screw passing through a loop and a nut engaged by said screw, said nut having a spade extension.

5. The construction according to claim 4 wherein a female connector has separable connection with said spade extension, said female connector being adapted for connection to a power circuit.

6. The construction according to claim 5 wherein a crimptype connector is adapted for connection to a power circuit, said connector having an extension which is tightly clamped to a terminal pin loop by said screw and nut.

7. An electric heating element assembly, comprising a tubular sheath containing a heating resistor which is electrically insulated from and held in position within said sheath and has terminals for connection to a source of electrical energy, at least one terminal comprising a terminal pin extending outwardly of an end of said sheath and having a loop at the outer end, a dielectric block having at least one opening through which said loop is inserted to the interior of said block, a terminal member within said terminal block, and a self-threading screw having a head bearing against said terminal member and a shank threaded into said terminal pin loop to clamp said terminal member against said loop.

8. An electric heating element assembly, comprising a tubular sheath containing a heating resistor which is electrically insulated from and held in position within said sheath and has terminals for connection to a source of electrical energy, at least one terminal comprising a terminal pin extending outwardly of an end of said sheath and having a loop at the outer end, a dielectric block having at least one opening through which said loop is inserted to the interior of said block, a terminal member within said terminal block, a screw having a threaded shank passing through said terminal pin loop, and a nut threaded on the end of said shank, the head of said screw and said nut clamping said loop and said terminal member therebetween for good electrical connection.

9. An electric heating element assembly, comprising a tubular sheath containing a heating resistor which is electrically insulated from and held in position within said sheath and has terminals for connection to a source of electrical energy, at least one terminal comprising a terminal pin extending outwardly of an end of said sheath and having a loop at the outer end, a dielectric block having at least one opening through which said loop is inserted to the interior of said block, a terminal member within said dielectric block having a flat portion with an opening and a crimp connection with an electrical conductor which extends outwardly of said dielectric block, said flat portion and said loop being disposed in flatwise relation, a screw having a threaded shank passing through said terminal pin loop and the opening in the flat portion of said terminal member, and a nut threaded on the end of said shank, the head of said screw and the nut clamping said flat portion and said loop therebetween for good electrical connection.

10. A surface-type electric heating element, comprising an elongated tubular metal sheath containing a heating resistance which is electrically insulated from and held in position within the sheath by compacted refractory material and has terminals at the opposite ends of the sheath, said sheath being in the form of a flat winding and having its opposite end portions disposed below said flat winding and extending laterally therefrom, each of said terminals comprising a terminal pin having one end within said sheath and connected to an end of said heating resistance and its other end disposed outside of said sheath and terminating in a loop, said refractory material being compacted about at least a part of the inner portion of adapted for use with terminal blocks of the plug-in type having slots in one direction to pass said loops, and of the screw-type having slots in a direction transverse to said one direction to pass said loops, the twistable nature of said terminal pins providing for disposition of said loops for a selected type terminal block.

Claims

6. The construction according to claim 5 wherein a crimp-type connector is adapted for connection to a power circuit, said connector having an extension which is tightly clamped to a terminal pin loop by said screw and nut.

10. A surface-type electric heating element, comprising an elongated tubular metal sheath containing a heating resistance which is electrically insulated from and held in position within the sheath by compacted refractory material and has terminals at the opposite ends of the sheath, said sheath being in the form of a flat winding and having its opposite end portions disposed below said flat winding and extending laterally therefrom, each of said terminals comprising a terminal pin having one end within said sheath and connected to an end of said heating resistance and its other end disposed outside of said sheath and terminating in a loop, said refractory material being compacted about at least a part of the inner portion of each terminal pin and adequately locking the latter so that its end outside of said sheath is twistable about its longitudinal axis, each terminal pin at least in the portion subjected to twisting action having a Rockwell harness of about B38 to B55 so as to be soft enough to withstand twisting without fracture and yet being hard enough to withstand electrical connection with contacts of terminal blocks, said heating element being adapted for use with terminal blocks of the plug-in type having slots in one direction to pass said loops, and of the screw-type having slots in a direction transverse to said one direction to pass said loops, the twistable nature of said terminal pins providing for disposition of said loops for a selected type terminal block.