US3632981A

US3632981A - Radiant heater with means for reducing sag of the electrical heating element

Info

Publication number: US3632981A
Application number: US54103A
Authority: US
Inventors: Bernardas Gasparaitis
Original assignee: Sunbeam Corp
Current assignee: Sunbeam Corp
Priority date: 1970-07-13
Filing date: 1970-07-13
Publication date: 1972-01-04
Anticipated expiration: 1989-01-04

Abstract

A radiant heater is provided in which a housing section and a grille section enclose a removable reflector assembly. The reflector assembly includes a support assembly for providing a substantially constant amount of tension to the heating element to minimize sag of the heating element during operation of the heater. The support assembly includes a number of insulator assemblies each of which consist of a cylindrical retaining cup having an outwardly extending rim, an insulator which extends through an opening in a closed portion of the retaining cup to receive a loop of the heating element and a helically coiled spring which is compressibly disposed around the periphery of the associated retaining cup between its rim and an exterior surface of the reflector assembly.

Description

United States Patent [72] Inventor Bernardas Gasparaitis Chicago, Ill.

[211 App]. No. 54,103

[22] Filed July 13, 1970 [45] Patented Jan. 4, 1972 [73] Assignee Sunbeam Corporation Chicago, Ill.

[54] RADIANT HEATER WITH MEANS FOR REDUCING SAG OF THE ELECTRICAL HEATING ELEMENT 6'Claims, 6 Drawing Figs.

52 US. Cl 219/377,

- 174/128 J, 174/158 R,2l9/355,219/532, 219/542, 338/316 [51] Int. Cl F24h 3/02, 1-105b 3/32 [50] Field of Search 174/138 J, 152.2, 158; 219/339-358, 375, 376, 377, 532; 338/279, 280, 281, 283, 315, 316, 318, 319, 321

[56] References Cited UNITED STATES PATENTS 1,628,858 5/1927 Shawk 174/1522 X Primary ExaminerR. F. Staubly Attorney-George R. Clark ABSTRACT: A radiant heater is provided in which a housing section and a grille section enclose a removable reflector assembly. The reflector assembly includes a support assembly for providing a substantially constant amount of tension to the heating element to minimize sag of the heating element during operation of the heater. The support assembly includes a number of insulator assemblies each of which consist of a cylindrical retaining cup having an outwardly extending rim, an insulator which extends through an opening in a closed portion of the retaining cup to receive a loop of the heating element and a helically coiled spring which is compressibly disposed around the periphery of the associated retaining cup between its rim and an exterior surface of the reflector assembly.

RADIANT HEATER WITH MEANS FOR REDUCING SAG OF THE ELECTRICAL HEATING ELEMENT BACKGROUND OF THE INVENTION This invention relates to electrical space heaters and more particularly to radiant space heaters that employ a straight resistance wire or a flat ribbon as a heating element in which the heating element is supported in front of a radiation reflecting plate which preferably has a parabolic shape.

Radiant heaters may be'constructed with either coil-type heating wires, with straight resistance wires or with flat resistance ribbons. The springlike construction of a coiled heating wire compensates for the contraction and the expansion of the heating element so as to minimize sagging of the heating element during operation of the heater. The coiled heater wire, however, is not as efficient as the straight or ribbon resistance wires for radiant heating elements because of the considerably smaller portionof the surface area of a coiled heater wire that is capable of directing heat rays to the radiant reflector plate.

When a straight resistance wire or ribbon is employed as a heating element in a radiant heater, it is desirable to provide a support assembly which compensates for the sag of the heating element as the wire contracts and expands due to temperature changes to prevent shorting of the heating wire against itself. Radiant heaters having difierent exterior appearances may be inexpensively manufactured if different housing and grille sections may be employed to enclose the same basic reflector assembly. It is desirable, therefore, that the reflector assembly be designed so that it is easily removable from the heater and so that the heating element support assembly and the parabolic reflector plate remain secured to the frame of the reflector assembly in their proper locations when the reflector assembly frame is removed from the heater.

It is an object of the present invention to provide a new and improved heating element support assembly for a radiant heater wherein the support assembly is constructed so as to compensate for heat-induced physical changes in the heating element of the heater.

It is a further object of the present invention to provide a radiant reflector assembly for an electric radiant heater that may be utilized with a variety of housings and grilles of different appearances and colors wherein the radiant heat reflector assembly is removable from the heater as a unit and contains a reflector plate which preferably has a parabolic shape; and a heating element support assembly is employed for supporting a resistance element in front of the reflector plate with a minimum of sag of the heating element during operation of the heater; and wherein a series resistance element for low range operation is preferably employed and mounted behind the reflector plate.

It is an additional object of the present invention to provide an electric heater in which a radiant heating wire support assembly is constructed of two types of insulators, one type of which is constructed to provide support for a male electrical connector for removable connection with a female connector and the other type of which is employed in an insulator support assembly that uses a resilient member to reduce sag of an associated heating element as it changes size during operation of the heater.

It is another object of the present invention to provide an insulator assembly of novel construction for use in a radiant reflector assembly wherein the insulator assembly is constructed using a retaining cap, an insulator and a resilient spring member and the retaining cap is preferably made of a material such that it provides a low-friction bearing surface with the wall of the radiant reflector assembly.

It is another object of the present invention to provide an improved electric radiant heater in which a straight heating wire or flat ribbon is employed along with a means to compensate for the expansion and the contraction of the wire or ribbon and wherein an inexpensive insulator is employed which may be easily replaced in the event that it is cracked.

Further objects and advantages will become apparent from the following description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front perspective view of an electric radiant space heater which embodies the present invention.

FIG. 2 is a cross-sectional view of the heater of FIG. 1 which is taken along the lines 2-2 of FIG. 1.

FIG. 3 is a cross-sectional fragmented view of the heater which is taken along the lines 3-3 of FIG. 2.

FIG. 4 is a cross-sectional view which is taken along the lines 4-4 of FIG. 3.

FIG. 5 is a cross-sectional view which is taken along the lines 5-5 of FIG. 3.

FIG. 6 is a plan, partially sectionalized view of the handle portion of the heater viewed along the lines 6--6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, an electrical radiant heater that embodies the present invention is generally shown at 10 of FIG. 1. The heater 10 as illustrated includes a generally U- shaped outer housing 11, a grille l2 and a reflector assembly 13. The housing 11 provides support for the reflector assembly 13 and the grille 12. The housing 11 and the grille 12 may be supplied in a number of different finishes and colors so that the heater 10 may be manufactured to suit the tastes of a large number of people.

The reflector assembly 13 supports a flexible reflector plate 14 which has a highly reflective surface that faces the grille 12. The reflector plate 14 is preferably made of aluminum or other lightweight metal and preferably has a parabolic shape. The reflector assembly 13 consists of sidewalls l5 and 16, a top section 17, and a bottom section 18. The plate 14 is bent as it is inserted into the reflector assembly 13, and it is held in the desired flexed position by inserting

tabs

19 and 20 which extend from its outer edges through holes in the top section 17 and the bottom section 18 of the reflector assembly 13, respectively.

The sidewalls l5 and 16 of the reflector assembly 13 are of a relatively heavy gauge sheet metal which may be steel, for example. The

sidewalls

15 and 16 are secured to the top and

bottom sections

17 and 18 of the reflector assembly by metal tabs, such as the

tabs

21, 22 and 81. The sidewalls l5 and 16 also receive the insulators of the support assembly which are employed to support the heating element 23 in front of the reflecting surface of the reflector plate 14. The heater wire is preferably a straight wire or a flat ribbon wire of nickelchrome, or other suitable resistive material.

In order to provide for selective control of heat, the heater is provided with a control unit 24. The control unit 24 contains a conventional thermostatic switch (not shown) which is controlled by the control knob 25 to achieve the desired heating effect, and a conventional protective switch (not shown) which shuts off the unit in case it is tipped over. The control unit 24 also contains a power indicator 26, an on/ofi switch (not shown) which is controlled by the control button 27, a low-range control button 28 and a high-range control button 29. The

range control buttons

28 and 29 are mechanically interlocked so that when one of these buttons is depressed, the other is released. Depression of the low-range button 28 inserts the coiled series resistance wire 30 in series with the heating element 23 in order to reduce the power dissipated in the heating element 23. When the high-range button 29 is depressed, the heating element 23 is connected directly across the line voltage which is supplied to the heater 10 through the line cord 31 that passes through the plastic grommet 32 in the rear wall of the housing 1 l, as shown in FIG. 2.

The series resistance wire 30 is preferably a coiled wire which is positioned behind the reflecting surface of the reflector plate 14. Employment of a coiled wire reduces sag of the wire, and sag of the series resistance wire 30 is further reduced by the manner in which the wire is mounted. To provide electrical connection, the series resistance wire 30 has male connectors 33 and 34 on its ends which extend through openings in the

insulators

35 and 36 which in turn extend through holes in the sidewall 16. The

tabs

37 and 38 that are formed when the holes for these insulators are punched are bent over the ends of the

insulators

35 and 36 to hold them in place.

The series resistance wire 30 extends in a loop through a number of insulators 39 which are retained in metal mounting brackets 82 that are secured to the reflector assembly 13 by the rivets 83. A flange 40 is provided on the insulators 39 which extends outwardly from two sides of the base 41 of the insulators 39. The mounting brackets 82 are formed with a rectangular slot of such dimensions that the flange 40 can pass through the slot when the insulator 39 is turned with its longitudinal dimension running parallel to the longitudinal dimension of the slot and so that the slot prevents the flange 40 from passing through it when the insulator 39 is turned transversely, as shown in FIGS. 2 and 4.

The center hole in the

insulators

35 and 36 does not line up with the center holes of the insulators 39. The reason for this is to provide tension on the series resistance wire 30 to minimize its sagging during low-range operation. The male connectors 33 and 34 which extend through the

insulators

35 and 36 are flat, and the coiled series resistance wire 30 is cylindrical. Connection to the ends of the series resistance wire 30 is made by pulling the ends of this wire away from the positions that they tend to assume due to the location of the insulators 39 and toward the connectors 33 and 34 which extend through the

insulators

35 and 36 where they are welded or secured by other appropriate means.

Cooling of the housing 11 to minimize the danger of heat damage to objects or structures which are placed near to the heater 10 is provided by the fan 42. The motor 43 of the fan 42 shown in FIG. 2 has a laminated field structure 44 which is surrounded by an energizing coil 45. Energization of the motor 43 is achieved through the energizing coil 45 which is wrapped around the supporting brackets 46 that are secured to the rear wall of the housing 11 by rivets 47. The fan 42 is mounted on the right-hand side of the heater 10 between the sidewall 16 of the reflector assembly 13 and the end cap 48, as shown in FIG. 1. The end cap 48 is provided to seal off the right hand end of the heater and the end cap 49 seals off the left hand end of the heater l and the end caps 48 and 49 are secured to the housing 11 and to the grille 12 by screws, such as the screws 50. Air supplied by the fan 42 passes through the upper portion of the grille 12, the lower portion 52 of the grille 12 and between the air channel produced between the top section 17 of the reflector assembly 13 and the top wall 1 la of the housing 11. Air is also provided to cool the housing 11 through the cut out portion 53 of the sidewall 15 to the rear wall 116 of the housing 1 1.

To support the heater 10, a pair of legs 54 are secured to the bottom wall 11 of the housing 110 by screws 55. Foot grips 56, which are formed of rubber or other suitable material, are secured to the bottom of the legs 54 to provide a friction grip with the surface on which the heater l0 rests. Support for the bottom of the reflector assembly 13 is provided by the bottom wall 11c of the housing 11. The grille 12 is supported by the housing 11, by the upper and lower retaining

lips

86 and 87 into which the ends 88 and 89 are wedged, respectively, thereby securing the grille 12 to the housing 11. Sheet steel is a suitable metal for both the housing 1 1 and the grille 12, but a lighter gauge is preferred for the grille 12.

In order that the heater may be carried from one location to another, a handle 57, as shown in FIG. 6, is provided. The handle 57 is formed of a U-shaped metallic rod which is springable and is insertable into the handle receptacles 58 by compression of the sides of the handle 57.

The support assembly for the heating element 23 is best illustrated in FIG. 3 which has a broken-away central portion. The right-hand wall 16 of the reflector assembly 13 supports two different types of insulators. One type of insulator is shown at 59 and 60 and the other type is shown at 61. A

passageway is provided through the

insulators

59 and 60 for the flat

male connectors

62 and 63, respectively. The

male connectors

62 and 63 are secured to the ends of the heating element 23 by welding or other suitable methods. To prevent passage of the

end connectors

62, 63 through the central openings of their respective insulators, flanges such as the flange 64 of the insulator 60 are provided.

The

metal tabs

66 and 67 are bent over the ends of the insulators 59 and 61, respectively, to hold them in place and are formed when the elliptically shaped openings for these insulators are punched from the wall 16.

Insulators

59 and 60 are formed of front circular cylinder sections 59a and 60b, and of rear elliptical cylinder sections 59 b and 60b, respectively. Simplification of the assembly is achieved due to the fact that the

insulators

35 and 36 which support the end connectors 33 and 34 for the series resistance wire 30 are the same type of insulators as the

insulators

59 and 60.

Support for the two insulator assemblies 68 and 69 is provided by the left-hand wall 15. The insulator assemblies 68 and 69 provide compensation for sag of the heating element 23 during expansion and contraction of the heating element 23 by maintaining a substantially constant tension on it during operation of the heater 10. Construction details of the insulator assemblies 68 and 69 are best shown in the cross-sectional view of FIG. 5. The

insulators

70 and 71 which are used in the insulator assemblies 68, 69 are the same type of insulators as is the insulator 61 which is rigidly mounted in the right-hand wall 16. The

insulators

61, 70, and 71 are constructed to support a loop of the heating element 23 which is formed of two strands of the heating element, such as the strands 23a and 23b, which are supported by the leg 72 of the insulator 71. A ridge 85 is provided on the upper end of the leg 72 to prevent the strands 23a, 23b from slipping off over the top of the leg 72. The insulator 71, for example, is inserted into the retaining cup 73 which is a hollow cylinder with a cylindrically extended rim portion 74 around the top edge of the cylinder. A rectangular slot 76 is cut into the closed portion of the retaining cup 73 which allows all of the insulator 71 except for the outwardly extending flange 77 to pass therethrough. The retaining cup is preferably formed of aluminum or other metal which forms a low friction bearing surface when it rubs against the edge of the aperture in the steel wall 15 through which it extends. I Substantially constant tension is provided on the heating element 23 by the springs 78 which are compressed between the rim 74 of an associated insulator assembly and the wall 15. The spring 78 is preferably a helically coiled spring which is constructed of a metal such as stainless steel so that it will not lose its resiliency after many expansions and contractions. Electrical connections are made from the control unit 24 and the line cord 21 to the appropriate flat male connectors, such as the

connectors

33, 34, 62, and 63, by conventional flat pressure-fit female connectors, such as the connectors 79 and 80 of FIG. 2.

It is evident that the disclosed support assembly provides a low cost and efficient way of minimizing sagging of a heating element in an electric radiant heater. Cracked or broken insulators in the insulator assemblies 68 and 69 may be removed simply by lifting the appropriate heating wire strands off of the damaged insulator and by pulling the associated retaining cup away from the wall 15. In addition, the support assembly of the present invention takes up very little space in front of the reflector plate 14 and, therefore, the surface of the reflector plate is efficiently utilized for reflection of heat rays from the heating element 23.

While a preferred embodiment of the invention has been described, other modifications within the scope of the present invention may occur to those skilled in the art, and it is intended that the appended claims cover all such modifications that are in accordance with the spirit and the scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An electric radiant heater comprising a housing having a front, a reflector assembly mounted in said housing, said reflector assembly comprising a frame portion including a first sidewall, a second sidewall, a top section and a bottom section and a reflector plate having a heat-ray reflecting surface, said reflector assembly being secured to said frame portion of said reflector assembly such that said reflector surface faces said front of said housing, a first insulator and a second insulator of a first type, each having an aperture therein, said first insulator and said second insulator being mounted in said first wall of said reflector assembly, a plurality of insulator assemblies mounted in said second wall, a retaining cup for each of said insulator assemblies which are mounted in said second sidewall, each of said retaining cups having a slotted end and open end and an extending rim around said open end and each of said retaining cups extending partially through an associated opening in said second sidewall with the slotted end of said associated retaining cup extending into said reflector assembly, a plurality of resilient spring means each compressibly disposed around the periphery of a retaining cup between the rim of said associated retaining cup and a surface of said second sidewall, a plurality of insulators of a second type each having a leg portion and each extending partially through the slot in its associated retaining cup and an electrically resistant heating element having electrical conductor segments on each of its ends, each conductor segment extending through one of said apertures in said first and second insulators, said heating element passing in front of said reflecting surface and being supported by said leg portions of said insulators of said second type as said heating element proceeds in a path from said first insulator to said second insulator of said first type.

2. The electrical radiant heater of claim 1 wherein at least one insulator of said second type is mounted in said first sidewall in a position intermediate said insulators of said first type such that said resilient heating element is supported by the leg portion of said insulators of said second type in said first wall.

3. The electrical radiant heater of claim 1 wherein said retaining cups and said associated resilient spring means are constructed of materials which provide a low-friction bearing surface.

4. The electrical radiant heater of claim 3 wherein at least one insulator of said second type is mounted in said first sidewall in a position intermediate said insulators of said first type such that said resilient heating element is supported by the leg portion of said insulators of said second type in said first wall.

5. An electric heater comprising a housing having a wall with an exterior surface, an interior surface and apertures therein at selected locations, a reflector, a continuous strip electrical heating element passing in front of said reflector, means for supporting said heating element in front of said reflector comprising a plurality of retaining cups each inserted into one of said apertures in said wall, each of said retaining cups comprising a rim portion which is larger than its associated aperture, a slotted end and an open end, said slotted end of said retaining cups being inserted into its associated aperture in said wall, said open end of said retaining cup being surrounded by said rim, an electrical insulator for supporting said heating element and for providing tension on said heating element associated with each of said retaining cups and a resilient spring means compressibly disposed around the periphery of each of said retaining cups between said rim and said exterior surface of said wall, each of said insulators having a support portion for supporting the heating element and a flange portion which is larger than the slot in said slotted end of said associated retaining cup, said insulators thereby being biased by said associated resilient spring means for providing a temperature-variable tension on said heating element.

6. The electrical radiant heater of claim 1 wherein said retaining cups and said associated resilient spring means are constructed of materials which provide a low-friction bearing surface.