US3670143A

US3670143A - Electric heating unit for clothes dryers

Info

Publication number: US3670143A
Application number: US29388A
Authority: US
Inventors: Fred J Zenz
Original assignee: Whirlpool Corp
Current assignee: Whirlpool Corp
Priority date: 1970-04-17
Filing date: 1970-04-17
Publication date: 1972-06-13
Anticipated expiration: 1989-06-13

Abstract

A heater box assembly for an electrically heated clothes dryer has a pair of spaced insulators with a wire heating element wound around the two insulators and with adjacent turns spaced apart. The support for the heating unit includes at least one spring acting on at least one insulator to apply a tension on the wire heating element to compensate for the change in length of the wire element due to thermal expansion. The box-like support is snugly received in a flanged opening of a wall of the dryer to form the heated air inlet for the dryer and mounting means including one or more tabs on the box for insertion into one or more corresponding slots in the flanged opening and a single fastener for securing the box at a side removed from the position of the slot or slots.

Description

United States Patent Zenz [54] ELECTRIC HEATING UNIT FOR CLOTHES DRYERS [72] Inventor: Fred J. Zenz, Berrien Springs, Mich.

[73] Assignee: Whirlpool Corporation, Benton Harbor,

Mich.

[22] Filed: April 17, 1970 [21] Appl.No.: 29,388

Weingardt Kempston et al.

[15] 3,670,143 1451 June 13,1972

FOREIGN PATENTS OR APPLICATIONS 208,7l4 1/1956 Australia ..34/ l 33 Primary ExaminerR. F. Staubly Attorney-James S. Nettleton, Thomas E. Turcotte, Burton H. Baker. Donald W. Thomas, Gene A. Heth, Franklin C. Harter, Anthony Niewyk, Robert L. Judd and Hill, Sherman, Meroni, Gross & Simpson [57] ABSTRACT A heater box assembly for an electrically heated clothes dryer has a pair of spaced insulators with a wire heating element wound around the two insulators and with adjacent turns spaced apart. The support for the heating unit includes at least one spring acting on at least one insulator to apply a tension on the wire heating element to compensate for the change in length of the wire element due to thermal expansion. The boxlike' support is snugly received in a flanged opening of a wall of the dryer to form the heated air inlet for the dryer and mounting means including one or more tabs on the box for insertion into one or more corresponding slots in the flanged opening and a single fastener for securing the box at a side removed from the position of the slot or slots.

12 Claims, 12 Drawing Figures FATENTEU R1 m2 7 (3)670, 143

sum 1 or s INVENTOR FQ JZ6ZZZ By f @Wgmmms PA'TENTEDM 13 1912 3. e70. 143

SHEET 2 0f 5 [N VENTOR.

ffi ed J Z9122 BY WATTORNEYS P'A'TENTEDJM 1-3 1972 3. 670, 143

' sum 3 or 5 5 INVENTOR.

ffiedJZez Z BY 4 ATTORNEYS PKTENTED N 1 3 2 3.670 143 I 1 6112 2 22 2 an" q b %vomtys BACKGROUND OF THE INVENTION being expensive to manufacture and expensive to install it in an appliance such as a dryer. Many of the heating units used in dryers are disposed with the length of the wire of the heating unit running substantially parallel or at a slight angle to the direction of the air flow so that various sections of the heating element are in contact with air of different temperatures and the unit develops hot spots which cause premature failure.

SUMMARY OF THE INVENTION The present invention provides a heater box assembly of a box having means of mounting a heating unit therein. Preferably the heating unit comprises a wire element wound between a pair of spaced insulators and mounting means, which biases the insulator apart to compensate for thermal expansion, positioning the heating wire with the wire element extending transverse to the air flow to prevent unequal cooling of the wire element. In the preferred embodiment the box is formed in sections which when secured together provide the mounting means for holding one of the insulators in a substantially rigid position and the other insulator being free for relative movement thereto. The mounting means include springs disposed on the outside of the box for biasing the other insulator away from the one insulator. The present invention also provides an expedient manner for attaching the heater box assembly to an appliance utilizing one or more coacting tabs and slots and a single retaining means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a rear view of a clothes dryer with portions broken away for, purposes of illustration showing the heater box assembly of the present invention mounted therein;

FIG. 2 is a front view of a rear bulkhead of a dryer apparatus having the heater box assembly of the present invention mounted thereon;

FIG. 3 is an enlarged view of the heater box assembly of the present invention mounted on the back surface of a bulkhead with portions broken away for purposes of illustration;

FIG. 4 is a cross section taken along lines IVIV of FIG. 3;

FIG. 5, which is located on the sheet with FIG. 1, is an enlarged view of a resilient mounting means used in the heater box assembly of FIGS. 3 and 4;

FIG. 6 is an enlarged cross-sectional view of a tab and slot arrangement illustrated in the circle identified by VI in FIG. 4;

FIG. 7 is a view similar to FIG. 3 of an embodiment of the heater box assembly of the present invention;

FIG. 8 is a crosssectional view taken along lines VIIIVIII of FIG. 7;

FIG. 9 is a view similar to FIG. 3 of a third embodiment of a heater box assembly of the present invention;

FIG. 10 is a cross-sectional view taken along lines XI-XI of FIG. 10;

FIG. 11, which is located on the sheet with FIG. 1, is a crosssectional view of an embodiment of an insulator of the present invention; and

FIG. 12 is a side view of the insulator of FIG. 11 with portions removed for purposes of illustration.

assembly 2 DESCRIPTION OF THE PREFERRED EMBODIMENT Although the principles of the present invention can be utilized in a heater box assembly for any apparatus, they are particularly useful in a heater box assembly generally indicated at 15 attached to a laundry device such as an electrically heated dryer generally indicated at 16 in FIG. 1. The electrically heated dryer 16 has an outer casing 17 made up of a back panel 18, a pair of

side panels

19, 20 and a front panel not illustrated. Extending between the side panels Hand 20 and extending parallel to the back panel 18 is a wall or bulkhead 21, which, as best illustrated in FIG. 2, has an annular beaded embossment 22 formed thereon to receive a sealing means attached to the rear end of a rotatable dryer drum (not shown). The bulkhead 21 is provided with an exhaust or outlet opening 23 which is covered by a grill and an oval opening 24 having a peripheral flange 25 defining an inlet opening for a heating chamber defined by the front surface of the bulkhead and the rotatable drum. The heater box assembly 15 is mounted on the bulkhead 21 at the opening 24 to heat air entering the drying chamber. Disposed on the rear side or surface of the bulkhead 21 is an air duct 26 (FIG. 1) in communication with the exhaust opening 23 and extending to a blower housing 27 which has an exhaust outlet 28. During the drying operation a blower mounted in the blower mounting 27 creates a suction causing air to enter the drying chamber by passing through the heater box 15 through the inlet opening 24 following the path of the arrows through the heating chamber to be withdrawn through the exhaust opening 23. After leaving the heating chamber through the exhaust opening 23, the air is pulled through the duct 26 to the blower housing 27 and expelled through the exhaust outlet 28 of the blower housing. An example of a laundry dryer and a description of its complete structure and operation is set forth in US. Pat. No. 3,398,465 which is assigned to the assignee of this application.

Referring to FIGS. 3 and 4, the heater box assembly 15 is made up of a pair of

metal members

30 and 31 each of which has deformed portions so that when the two members are attached together they define a heating chamber 32. Both the

members

30 and 31 are preferably formed of sheet metal by a metal stamping process which provides a peripheral edge or

flange

33 and 34 respectively, which are used for securing the two members together in a conventional manner such as by fastening means 35.

The member 30, which has a dished or concave portion 36, has a series of parallel louvers 37 extending across the bottom of portion 36, which louvers define inlet means for admitting air into the chamber 32. The member 30 is also provided with an aperture 38 for receiving a temperature sensing means such as a thermostatic control of a conventional design.

The member 31 has a depressed portion of a cup shape with a bottom 40 which has been further shaped to provide a projecting portion 41 with a reversely bulged or indented bottom 42 which is provided with a pattern of perforations 43 to define an air inlet for the drying chamber of dryer 16. The projecting portion 41 has side walls 44 and has an oval configuration complementary to the opening 24 in the bulkhead 21. The size of the projecting portion 41 is selected so that the side walls 44 are received in the peripheral flange 25 in a snug engagement.

As best illustrated in FIG. 6, the side wall 44 is provided with a bend 45 which abuts against an edge 46 of the peripheral flange 25 to limit insertion of the portion 41 into opening 24. The side wall 44 is also provided with a tab 47 which is inserted into slot 48 formed in the peripheral flange 25. The slot 48 and the tab 47 coact as shown in FIGS. 4 and 6, to attach the lower end of the projecting portion 41 to the peripheral flange 25 of the bulkhead 21.

To complete the mounting or attachment of the heater box 15 in the opening 24, a retaining means generally indicated at 50 (FIG. 3) comprising a strap 51 which is attached at one end to the member 31 and at the other end carries a fastening means such as a screw 52 for securing the strap to the bulkhead 21. Thus, by engagement of the coacting slot 47 and tab 48 and the single fastening means of the retainer 50, the box assembly is secured in the opening 24. It is to be realized that the coacting tab or tabs and slot or slots can be at other locations on the side wall 44 such as one side. The

retaining means 50 would be mounted opposite to the coact-- ing tab and slot retainer regardless of which portion of side wall 44 is utilized.

Disposed in the chamber 32 of the heater box assembly 15 is a heating unit generally indicated at 53 including a pair of spaced elongated or

bar insulators

54 and 55 and a wire heating element 56 which is wound or looped around the pair of

insulators

54 and 55 to provide wire loops or turns 57. Adjacent turns are spaced apart by axial spaced fins 58 on each of the

insulators

54 and 55. To anchor the wire heating element, the end turns 59 are passed by the upper insulator 54 on the opposite side relative to the other turns 57 to form the cross wire configuration illustrated in FIG. 4. Each of the ends of the element 56 are then passed through the box assembly 15 by extending through a hollow insulator 60 and is then connected to a source of electrical energy. Alternately, terminals may be welded or crimped to the ends of element 56 with said terminals being retained by the hollow insulators 60.

To mount the

insulators

54 and 55 of theheating unit 53 the

members

30 and 31 are provided with coacting mounting means which receive end portion 61 of the

insulators

54 and 55, which end portions 61 have a reduced diameter and a circumferential-groove 62. As illustrated, each of the

members

30 and 31 are provided with a pair of aligned semi-circular cutout portions on the peripheral edge to form a pair of circular apertures or openings'63 to receive each of the end portions 61 of the upper insulator 54 which end portions protrude from the heater box assembly 15. The openings 63 maintain the upper insulator 54 in a substantially fixed position with respect to the heater box assembly 15. The lower insulator 55 has its reduced end portion 61 protruding from the heating chamber 32 and being received in

elongated cutout portions

65 and 66 formed respectively in the

members

30 and 31 which

cutout portions

65 and 66 form an elongated aperture enabling relative movement of the insulator 55 when mounted.

The

flanges

33 and 34 have portions removed at the respective cutout portions to provide clearance for the end portions 61 of the insulators. It should be realized that

insulators

54 and 55 could be provided with rectangular end portions rather than reduced diameter portions61. In the event that rectangular end portions be provided, the

members

30 and 31 would be provided with appropriately dimensioned cutouts to receive the modified insulators.

To compensate for thermal expansion in the wire heating element 56, while in use, bearing means such as a pair of springs 69 are provided to maintain a tensioning force on the loops 57 of the wire element 56 by urging the lower insulator 55 away from the upper insulator 54. As best illustrated in FIGS. 3 and 5, each of the springs 69 has an end 70 received by a notch on the exterior of the heater box assembly 15 and the other end has a hook or loop 71 which is received in the groove 62 of the end portion 61.

In operation, air drawn into the dryer chamber by the blower in the blower housing 27, is drawn through the louvers 37, which forms the inlet means of the heater box assembly 15, into the chamber 32. As theair moves across. the loops 57 of the wire heating element, it is heated and then passes through the perforations 43 into the dryer chamber of the dryer 16. Since a tensioning force is applied to the loops 57 of the wire element 56 by the springs 69 pulling the lower insulator 55 away from the upper insulator,,any slack in the loop 57 of the wire element 56, which slack is the result of a change in length due to thermal expansion, is removed by the tension applied by the springs 69. By placing the springs on the exterior of the box assembly 15, the deleterious effect of the heat emitted by the heating 1 element 56 on the spring characteristics is minimized.

In FIGS. 8 and 9, an embodiment of the heater box assembly is generally indicated at 15a which comprises a pair of members 300 and 31a attached together to define a box means having a heating chamber 32a.

Members

30a and 31a are substantially similar to the

corresponding members

30 and 3 1 of the previously described'embodiment except they do not have cutout portions on their. peripheral edges for providing support means for mounting the insulators of a heating unit.

Disposed in the chamber 32a is a heating unit 53a which comprises an upper insulator 54a and a lower insulator 55a which are substantially similar to the previously described insulators except their length is such that the reduced end portions 61a are disposed in the chamber 32a. As in the previously described heating unit 53, a wire heating element 56a is wound between the two spaced insulators 54a and 55a with turns or loops 57a which are spaced apart by fins 58a on each of the pair of insulators. The primary difference in the structure of the heater box assembly 150 over the previously described embodimentis the mounting means for mounting the heating unit 53a in the chamber 32a. The mounting means comprises a pair of resilient members 74 which are attached by fastening means 75 to one of the

members

30a or 31a and as illustrated to the member 30a. The resilient members 74 are provided with eye means 76 at each end to engage a groove 62a formed in each of the reduced end portions 61a. The members 74 are of a spring character so that they bias both the insulators 54a and 55a apart to maintain the desired tension on the loops 57a of the wire heating element 56a.

As in the previously described embodiment, air enters through the louvers 37a formed in the member 30a and flows substantially perpendicular to the plane formed by the wire loops 57 across the heater element 56a and then passes through the perforated bottom 42a of theprojecting portion of the member 31a into the drying chamber formed by the bulkhead 21 and the tumbling drum of the laundry dryer 16.

A third embodiment of the heater box assembly is generally indicated at 15b and illustrated in FIGS. l0 and 11. The heater box assembly 15b is made up of a pair of members 30b and 31b which are interconnected at the peripheral edge in a manner similar to the previously described embodiments to form a box structure having a heater chamber 32b. The member 30b is provided with louvers 37b to admit air into the heating chamber 32b and the member 31b is provided with a projecting portion 41b having a perforated indented bottom 42b which is complementary in shape and size to be snugly received in a peripheral flange 25 of the opening 24 of the bulkhead 21. As in the previously described embodiment of FIGS. 8 and 9, a heating unit generally indicated at 53b comprising an upper cylindrical insulator 54b and a lower cylindrical insulator 55b with the wire heating element 56b wound into turns or loops 57b thereon and between. As in the embodiment of FIGS. 8 and 9, the insulators 54b and 55b are of a length so that they are completely contained within the heating chamber 32b.

To mount the heating unit 53b in the chamber 32b, two pairs of

brackets

80,80, 81,81, respectively, are attached to one of the members and as illustrated attached to the member 30b. Each of the brackets 80 has a slot 82 opening in the upward direction towards a top of the heater box assembly 15b. The lower pair of brackets 81 have a slot 83 opening in a direction opposite to the slot 82 and opening at a direction towards the bottom of the heater box 15b. As illustrated, the upper insulating 54b is supported in the pair of brackets 80 with its reduced end portions 61b received in the slots 82. The lower insulator 55b has reduced end portions 61b which are received in the slots 83. The reduced end portions 61b of both insulators 54b and 55b are provided with grooves 62b which prevent axial shifting of the insulators in the brackets.

' To bias the pair of insulators 54b and 55b away from each other, a resilient spring 86 is anchored to an eye 87 attached to the interior of the chamber 32b and as is illustrated is attached to a lowerwall 88 of the member 30b. The other end 89 of the resilient spring 86 is attached to a wire loop 90 which is received in a groove 91 formed at the center of the insulator 55b. The spring means 86 applies a tension to the loops 57b to maintain the upper insulator 54b in abutting relation with the bottom of the slots 82 and to maintain a desired tension on the wire element 56b to compensate for the expansion during heating of the heating unit.

In each embodiment, the heating unit 53, 53a or 53b can be formed by winding the wire element around the two spaced insulators. Then the unit is installed in the box structure with a minimum amount of labor. It is contemplated that a disposable spacer can be utilized to hold the two insulators such as 54 and 55 the desired distance apart to prevent any entanglement of the wire loops of the heating element. In the embodiments of FIGS. and 11 one pair of brackets which can be the brackets 80 or the brackets 81 will need to be assembled onto the member 30b after the other pair has received its respective insulator.

In each of the embodiments the air enters the louvers on the

member

30, 30a or 30b and passes in a direction substantially perpendicular to the direction of the wires 56 and out through the perforated bottom 42 into the drying chamber. By having the air flow in this manner, each of the wire elements is contacted by air of substantially the same temperature so that the desired cooling is obtained throughout the heating element to eliminate the occurrence of any hot spots thereon. Such cooling enables the use of wires of alloys such as iron base alloys to operate at a lower heating temperature and therefore enables the construction of the heating unit 53 using a material which is more economical and available than used in prior heating elements which are typically nickel based wire alloys. Since the two

insulators

54 and 55 are mounted with a means biasing them apart to maintain the desired tension on the wire element 56, the element can be a straight wire instead of the helically turned wire of the previous heating units and the tensioning prevents sagging or buckling of the wire during a heating operation and eliminates the possibility of shorting between turns or loops due to buckling or sagging of the wire.

An alternate embodiment of the insulator generally indicated at 93 is illustrated in FIGS. 12 and 13. The insulator 93 is provided with fins 94 which are axially spacedalong its length to maintain wire loops 95 in spaced relationship to prevent their accidentally contacting or shorting. In between each of the fins 94 the insulator 93 has a passageway 96 toenable a flow of air to cool the insulator. As illustrated in FIG. 13, a portion of each wire loop 95 overlies the passageway 96 to receive the effect of the cooling air. In the design of the insulator 93, only a small portion 98 of each wire loop 95 is in contact with the solid portion of the insulator 93. Thus, the

wire loops 95 receive additional cooling to prevent the creation of hot spots thereon during a heating operation.

Each of the embodiments such as the units 15, a and 15b are provided with a tab for acting with a coacting slot on the flange of the opening in the bulkhead 21 and the retainer means 50. Thus the unit or

heater box assembly

15, 15a or 15b can be easily assembled onto the bulkhead 21 of the dryer device 16. The present structure of the unit not only simplifies the manufacturing of the heating elements 53 and its assembly into the box formed by the members and 31, but also simplifies the installation of the heating box assembly 15 onto' the bulkhead 21 whether during initial installation or in a subsequent removal and installation of repair parts.

Although minor modifications might be suggested by those skilled in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

l. A heater box assembly for a laundry appliance such as an electrically heated clothes dryer, comprising:

a first member having means for forming an air inlet for the laundry appliance; I

a second member attached to said first member to provide a box means having an enclosed heating chamber, said second member having means for forming an air inlet to the chamber;

a heating means including a pair of insulators and a wire heating element wound about the insulators with adjacent turns being spaced from each other; and

means for mounting said heating means in the heating chamber with a pair of insulators in spaced relationship and with the ends of each insulator protruding therefrom including biasing means for urging the pair of insulators away from each other thereby applying a tension on the wire to compensate for the thermal expansion of the wire;

said mounting means including aligned cutout portions in each of said first and second members coacting together as the members are assembled to provide an aligned pair of apertures to receive the protruding ends of each of said pair of insulators with one of the pair of apertures maintaining one of the pair of insulators substantially rigid in said chamber and the other pair of apertures being shaped to enable relative movement of said other insulators away from the one insulator under the urging of said biasing means to maintain the wire heating element under tension.

2. A heater box assembly in accordance with claim 1, wherein the wire heating element is of a material of an iron base.

3. A heater box assembly according to claim 1, wherein said biasing means comprises a pair of springs disposed on the outside of the heating chamber, each of said springs being anchored to the box means formed by said first and second members and attached to a protruding end of said other insulator so that said springs are removed from the heat generated by the wire heating element to prevent the deleterious effect of the heat thereon.

4. A heater box assembly according to claim 1, wherein said bias means comprises a resilient spring anchored to said box means and attached to the other of said pair of insulators.

5. A heater box assembly for a laundry appliance such as an electrically heated clothes dryer comprising:

a first member having means for forming an air inlet for the laundry appliance; v

a second member attached to said first member to provide a box means having an enclosed heating chamber. said second member having means for forming an air inlet to the chamber;

means for mounting said heating means in the heating chamber with a pair of insulators in spaced relationship including biasing means comprising a resilient spring anchored to said box means and attached to one of said pair of insulators for urging the pair of insulators away from each other thereby applying a tension on the wire to compensate for the thermal expansion of the wire, said means for-mounting said pair of insulators comprising brackets attached to one of said first and second members, each of said brackets having a slot for receiving an end of said insulators, said brackets being arranged in pairs with the slots of one pair opening in a direction opposite to the slots of the other pair so that the resilient spring holds the other of said pair of insulators against the base of the slots of the one pair of brackets while the one insulator is urged away from the base of its slots of the other pair of brackets.

6 A heater box assembly according to claim 1, wherein each of the insulators of said pair are cylindrical members provided with axially spaced fins to maintain separation between adjacent turns of the wire heating element thereon.

7. A heater box assembly according to claim 6, wherein each of said insulators has passageways extending between each of the axially spaced fins to enable the passage of air therethrough for cooling of said insulator.

8. A heater box assembly according to claim 1, wherein the means forming the inlet-in the first member has a shape complementary to an opening in a wall of the laundry device and is adapted to snugly fit therein; and further including means for mounting the heater assembly in said opening comprising a tab disposed on said first member coacting with a slot adjacent the opening in the wall, and a fastening means disposed on said box a substantial distance from the coacting tab and slot whereby the heater box assembly is mounted in the opening by engaging the tab in the slot and then securing the fastening member to the wall of the laundry device.

9. A heater box assembly for a laundry appliance such an electrical heated clothes dryer, comprising:

a first member having means for forming an air inlet for the laundry appliance;

a second member attached to the said first member to provide abox means having an enclosed heating chamber,

,said second member having means for forming an inlet to the chamber;

a heating means including a pair of insulators and a wire heating element wound about the insulator with adjacent turns being spaced from each other; and

means for mounting said heating means in the heating chamber with the pair of insulators in spaced relationship, said means for mounting including biasing means for urging both of the insulators of said pair in a direction away from each other thereby applying a tension on the wire to compensate for the thermal expansion of the wire.

10. A heater box assembly in accordance with claim 9, wherein said mounting means comprises resilient spring means attached to one of said first and second members and resiliently mounting each of said pair of insulators in the heating chamber.

11. A heater box assembly according to claim 1, wherein said mounting means disposes said heating means in the heating chamber with the flow of air substantially perpendicular to the direction of the wire heating element thereby eliminating hot spots on the heating element.

12. A heater box assembly for a laundry appliance such as an electrically heated clothes dryer, comprising:

a first member having means for forming an air inlet for the laundry appliance;

a second member attached to said first member to provide a box means having a heating chamber, said second member having means for forming an air inlet to the chamber;

a heating means including a pair of insulators and a wire heating element of an iron base material wound about the insulators with adjacent turns being spaced from each other;

each of said pair of insulators being a cylindrical member having axially spaced fins to maintain separation between adjacent turns of the wire heating element and each'insulater having passageways extending between each of the spaced fins to enable passage of air therethrough for cooling the insulator; and

means for mounting said heating means in the heating chamber with the .pair of insulators in spaced relationship including biasing means for urging the pair of insulators away from each other thereby applying a tension on the wire to compensate for the thermal expansion of the wire; said mounting means comprising means defining cutout portions in both of said first and second members, said cutout portions being arranged in aligned pairs so that the attachment of said first and second member forms pairs of aligned apertures to assemble said pair of insulators in the desired position in the heating chamber, one pair of said pairs of apertures receiving the endsof one of said pair of insulators and maintaining said one insulator in a substantially fixed position relative to said heating chamber, the other of said pair of apertures each having an elongated configuration to receive the ends of the other insulator of said pair of insulators and enabling relative movement of the other insulator away from the one insulator and relative to said heating chamber; and

said biasingmeans comprising a pair of springs disposed on the outside of the heating chamber, each of said springs being anchored to the box means formed by said first and second members and attached to a protruding end of said other insulator so that said springs are removed from the heat generated by the wire heating element to prevent the deleterious effect of the heat thereon.

Claims

1. A heater box assembly for a laundry appliance such as an electrically heated clothes dryer, comprising: a first member having means for forming an air inlet for the laundry appliance; a second member attached to said first member to provide a box means having an enclosed heating chamber, said second member having means for forming an air inlet to the chamber; a heating means including a pair of insulators and a wire heating element wound about the insulators with adjacent turns being spaced from each other; and means for mounting said heating means in the heating chamber with a pair of insulators in spaced relationship and with the ends of each insulator protruding therefrom including biasing means for urging the pair of insulators away from each other thereby applying a tension on the wire to compensate for the thermal expansion of the wire; said mounting means including aligned cutout portions in each of said first and second members coacting together as the members are assembled to provide an aligned pair of apertures to receive the protruding ends of each of said pair of insulators with one of the pair of apertures maintaining one of the pair of insulators substantially rigid in said chamber and the other pair of apertures being shaped to enable relative movement of said other insulators away from the one insulator under the urging of said biasing means to maintain the wire heating element under tension.

5. A heater box assembly for a laundry appliance such as an electrically heated clothes dryer comprising: a first member having means for forming an air inlet for the laundry appliance; a second member attached to said first member to provide a box means having an enclosed heating chamber, said second member having means for forming an air inlet to the chamber; a heating means including a pair of insulators and a wire heating element wound about the insulators with adjacent turns being spaced from each other; and means for mounting said heating means in the heating chamber with a pair of insulators in spaced relationship including biasing means comprising a resilient spring anchored to said box means and attached to one of said pair of insulators for urging the pair of insulators away from each other thereby applying a tension on the wire to compensate for the thermal expansion of the wire, said means for mounting said pair of insulators comprising brackets attached to one of said first and second members, each of said brackets having a slot for receiving an end of said insulators, said brackets being arranged in pairs with the slots of one pair opening in a direction opposite to the slots of the other pair so that the resilient spring holds the other of said pair of insulators against the base of the slots of the one pair of brackets while the one insulator is urged away from the base of its slots of the other pair of brackets.

6. A heater box assembly according to claim 1, wherein each of the insulators of said pair are cylindrical members provided with axially spaced fins to maintain separation between adjacent turns of the wire heating element thereon.

8. A heater box assembly according to claim 1, wherein the means forming the inlet in the first member has a shape complementary to an opening in a wall of the laundry device and is adapted to snugly fit therein; and further including means for mounting the heater assembly in said opening comprising a tab disposed on said first member coacting with a slot adjacent the opening in the wall, and a fastening means disposed on said box a substantial distance from the coacting tab and slot whereby the heater box assembly is mounted in the opening by engaging the tab in the slot and then securing the fastening member to the wall of the laundry device.

9. A heater box assembly for a laundry appliance such an electrical heated clothes dryer, comprising: a first member having means for forming an air inlet for the laundry appliance; a second member attached to the said first member to provide a box means having an enclosed heating chamber, said second member having means for forming an inlet to the chamber; a heating means including a pair of insulators and a wire heating element wound about the insulator with adjacent turns being spaced from each other; and means for mounting said heating means in the heating chamber with the pair of insulators in spaced relationship, said means for mounting including biasing means for urging both of the insulators of said paiR in a direction away from each other thereby applying a tension on the wire to compensate for the thermal expansion of the wire.

12. A heater box assembly for a laundry appliance such as an electrically heated clothes dryer, comprising: a first member having means for forming an air inlet for the laundry appliance; a second member attached to said first member to provide a box means having a heating chamber, said second member having means for forming an air inlet to the chamber; a heating means including a pair of insulators and a wire heating element of an iron base material wound about the insulators with adjacent turns being spaced from each other; each of said pair of insulators being a cylindrical member having axially spaced fins to maintain separation between adjacent turns of the wire heating element and each insulator having passageways extending between each of the spaced fins to enable passage of air therethrough for cooling the insulator; and means for mounting said heating means in the heating chamber with the pair of insulators in spaced relationship including biasing means for urging the pair of insulators away from each other thereby applying a tension on the wire to compensate for the thermal expansion of the wire; said mounting means comprising means defining cutout portions in both of said first and second members, said cutout portions being arranged in aligned pairs so that the attachment of said first and second member forms pairs of aligned apertures to assemble said pair of insulators in the desired position in the heating chamber, one pair of said pairs of apertures receiving the ends of one of said pair of insulators and maintaining said one insulator in a substantially fixed position relative to said heating chamber, the other of said pair of apertures each having an elongated configuration to receive the ends of the other insulator of said pair of insulators and enabling relative movement of the other insulator away from the one insulator and relative to said heating chamber; and said biasing means comprising a pair of springs disposed on the outside of the heating chamber, each of said springs being anchored to the box means formed by said first and second members and attached to a protruding end of said other insulator so that said springs are removed from the heat generated by the wire heating element to prevent the deleterious effect of the heat thereon.