Patent Publication Number: US-4149065-A

Title: Electric space heater unit

Description:
U.S. Pat. No. 2,944,138 issued July 5, 1960 to James E. Goff for an Electric Space Heater and Method of Manufacture describes the construction of an elongated electric space heater unit that extends horizontally and is mounted directly on a wall. That heater unit includes a resistance heater conductor clamped directly to a single elongated heat radiating fin. The latter is mounted to an elongated wall box in position spaced from the walls of the box to permit free upward circulation of air over both the front and rear of the heat radiating fin. A baffle is disposed in front of the radiating fin to enhance circulation and a cover is disposed in front of the baffle to protect users from coming in contact with very hot portions of the heater unit. 
     Pursuant to the instant invention a heater unit is constructed of a wall box and a single subassembly. The latter includes an elongated housing having top and bottom ventilating openings, a resistance heater element extending longitudinally through the housing, and a plurality of transverse radiating fins in heat conducting relationship with the heater conductor. In addition, the assembly includes thermal cutout means secured to the rear of the subassembly housing and connected in parallel with the resistance heater by low impedance conductor means having loop sections formed at opposite ends thereof. The latter extend into terminal boxes at opposite ends of the housing for connection to an energizing circuit. 
     Accordingly, a primary object of the instant invention is to provide a novel construction for an electric space heater unit which is relatively economical to produce. 
     Another object is to provide a space heater unit of this type which is relatively compact. 
     A further object is to provide a space heater unit of this type that is readily installable at a building site. 
     Still another object is to provide a space heater unit of this type constructed so that the likelihood of damaging the heater element during installation is minimized. 
    
    
     These objects as well as other objects of this invention shall become readily apparent after reading the following description of the accompanying drawings in which: 
     FIG. 1 is an exploded perspective of an electric space heater unit constructed in accordance with teachings of the instant invention. 
     FIG. 2 is a cross-section of the heater unit of FIG. 1 taken through a vertical plane near the center of the heater unit. 
     FIG. 3 is a fragmentary front elevation of the heater subassembly looking in the direction of arrows 3--3 of FIG. 2 with the front cover of the subassembly removed. 
     FIG. 4 is a plan view, partly sectioned of the elements shown in FIG. 3. 
     FIG. 5 is an electrical schematic of the space heater unit of FIG. 1. 
    
    
     Now referring to the drawings. The electric space heater unit of the instant invention is an elongated device adapted to be mounted with its longitudinal axis extending horizontally and its rear surface 11 (FIG. 2) abutting a vertical wall (not shown). Screws or nails (not shown), which extend through rear wall 25 near its upper edge, are used for mounting wall box 12. 
     The space heater unit consists of wall box 12 and heater subassembly 14 secured to wall box 12 by sheet metal screws 15, 16 which extend through clearance apertures 17, 18 at opposite ends of subassembly 14 and are received by threaded apertures 21, 22 in flanges 91, 92 bent from the respective transverse walls 93, 94 of wall box 12. The latter is an elongated trough-like structure having terminal boxes 23, 24 at opposite ends thereof partially bounded by the respective walls 93, 94. The main central portion of wall box 12 includes rear wall 25, lower inclined wall 26 extending downward and forward from the lower edge of rear wall 25, and upper inclined wall 27 extending forward and upward from the upper edge of rear wall 25. Top flange 28, positioned in a horizontal plane, extends rearward from upper inclined wall 27 with the rear edge of flange 28 terminating in downwardly extending lip 29 that is coplanar with rear wall 25. Elongated stiffening member 31, of modified U-shaped cross-section, extends between the lower surface of flange 28 and the rear surface of upper inclined wall 27, being secured to the latter by a plurality of screws 32. In addition, stiffening member 31 provides a cover for wireway 33 formed between flange 28 and wall 27. 
     An individual grounding screw 34 is provided in the rear boundary wall for each of the junction boxes 23, 24. Each of the boxes 23, 24 is provided with a removable cover 19 formed with a pair of tabs 36, 37 that extend behind section 38, which joins the forward edges of wall 27 and flange 28, to position the upper edge of cover 19. Sheet metal screw 39 extends through clearance aperture 41 in forwardly extending flange 40 along the lower edge of cover 19 and is received by threaded aperture 42 of wall box 12 to fasten cover 19 in closed position. 
     Heater subassembly 14 includes an elongated housing of generally rectangular cross-section constructed of rear member 43 and U-shaped member 44 having the free ends of its U-arms fastened by sheet metal screws 45 to rear member 43 along opposite edges thereof. When subassembly 14 is mounted to wall box 12, the inner surface of the web of U-shaped member 44 abuts flanges 91, 92. 
     Extending longitudinally generally through the center of housing 43, 44, is a heating element comprising resistance wire heater 50 surrounded by aluminum tube 49 and insulated therefrom by a relatively good heat conducting insulator 48, such as magnesium oxide. The heating element 48, 49, 50 is positioned by end brackets 51, 52 and central bracket 53 all of which are secured to rear wall 43 and extend forward therefrom. Screw 54 is threadably mounted to central bracket 53 and engages the outer surface of tube 49 to prevent longitudinal movement of heater wire 50. Each end of tube 49 extends through a plastic bushing 55 secured to end brackets 51, 52 by individual push nut 56. The position of tube 49 is further stabilized by V-shaped spring wire retainers 57 which extend around tube 49. Each retainer 57 is provided with reversely bent ends which extend through spaced holes 88 in rear member 43 and engage portions of rear member 43. Spaced along the length of tube 49, and secured thereto in heat conducting relationship, are a plurality of rectangular fins 58 disposed in generally vertical planes so that air circulating through top and bottom ventilating openings 61 of housing member 44 flows across the major surfaces of heat radiating fins 58. 
     Each end of wire heater 50 is provided with a terminal 63 welded thereto. Clamping screws 64 threadably mounted to terminals 63 connect relatively low resistance insulated conductor means 65 to each end of resistance wire heater 50. The sections of low resistance conductor 65 connect three thermal cutouts 66 in a series combination. The end portions of low resistance conductor are formed into loops 73, 74 which connect opposite ends of the series connected cutouts 66 to opposite ends of resistance wire heater 50 when heater unit 12, 14 is shipped from the factory (FIG. 5). Thermal cutouts 66 are spaced along the length of rear member 43 being secured to the rear surface thereof by individual clamps 67 (FIG. 4). Loops 73, 74 which are entered into the respective junction boxes 23, 24 through side openings 79. The particular junction boxes 23, 24 used for connecting resistance wire heater 50 to an energizing circuit is a matter of convenience for the installer. If junction box 23 is chosen then conductor 65 is cut at loop 73 and splicing is done at the cut ends in a manner such that the series combination of thermal cutouts 66 is in series with resistance wire heater 50. When junction box 24 is chosen for wiring then conductor 65 is cut at loop 74. 
     Thus, it is seen that the instant invention provides a simplified construction for an electric space heater unit in which heater subassembly 14 is readily mounted by utilizing the two screws 15, 16 so that wall box 12 may be secured in position without taking any precautions to protect the electrical parts. 
     Although a preferred embodiment of this invention has been described, many variations and modifications will now be apparent to those skilled in the art, and it is therefore preferred that the instant invention be limited not by the specific disclosure herein but only by the appended claims.