US 3883721 A
An open coil electric heater assembly for use in various heating applications. The heating element is usually a helically coiled resistance wire or ribbon which generates heat when an electric current is passed therethrough. The heating coil is carried by a metal framework which includes a plurality of metal supports having openings therein. Insulating bushings fit within respective openings and the coil passes through the bushings and thus is insulated from the metal supports.
Description (OCR text may contain errors)
United States Patent [191 Paulson et a1.
(451 May 13, 1975 1 OPEN COIL ELECTRIC HEATER ASSEMBLY  Inventors: Donald W. Paulson, Esmond; Dennis J. Hamish, Rockford, both of I11.
 US. Cl 219/532; 174/138 J; 174/153 G; 219/536; 338/317; 339/126 R; 339/131  Int. Cl. H05b 3/06  Field of Search 219/532, 536, 537, 552; 338/299, 317; 339/126 R, 131; 174/138 J, 152 G, 153 G  References Cited UNITED STATES PATENTS 684,909 10/1901 Cole 174/153 G 913,024 2/1909 Meacham 174/153 G 1,809,864 6/1931 Pearson 339/131 1,813,767 7/1931 Reichart 219/536 1,838,245 12/1931 Amon 174/152 G 2,352,126 6/1944 Schmitt 339/126 R 2,680,840 6/1954 O'Neill 339/126 R 2,856,500 10/1958 Hartman 219/536 3,092,705 6/1963 Roussan, Jr. et a1. 338/317 X 3,315,215 4/1967 Kulka 339/126 R 3,472,154 10/1969 Dokos et a1 3,632,981 1/1972 Gasparaitis 219/532 X 3,641,312 2/1972 Ammerman et a1. 219/532 FOREIGN PATENTS OR APPLICATIONS 122,781 9/1948 Sweden 174/153 G Primary Examiner-Volodymyr Y. Mayewsky Attorney, Agent, or Firm-Michael Williams  ABSTRACT An open coil electric heater assembly for use in various heating applications. The heating element is usually a helically coiled resistance wire or ribbon which generates heat when an electric current is passed therethrough. The heating coil is carried by a metal framework which includes a plurality of metal supports having openings therein. Insulating bushings fit within respective openings and the coil passes through the bushings and thus is insulated from the metal supports.
3 Claims, 4 Drawing Figures OPEN COIL ELECTRIC HEATER ASSEMBLY Our invention relates to an improved connection of an insulating bushing to a metal support wherein each of the holes in the support has a plurality of tongues extending radially inwardly. A bushing is pressed into the hole to displace the tongues radially so that in final assembly the tongues grip a tubular portion of the bushing to firmly lock it in place.
BACKGROUND AND SUMMARY Coiled resistor wires and ribbons have long been sup ported from metal supports by insulator bushings. However, the prior constructions have either required holding strips in conjunction with the metal support between which a portion of the insulator bushing was clamped, or complicated bushing design for locking a bushing in place. An early U.S. Pat, No. 1,813,767, discloses tongues margining in opening in a metal support, adjoining tongues being displaced from opposite side surfaces of the support, with a peripheral flange on the insulator clamped between the tongues. However, this construction necessitated the bending of tongues on one side surface of the support to receive the bushing peripheral flange, and the subsequent re-bending to the tongues to clamp the flange, or a special coordinating design of tongues and bushing flange.
Our invention simplifies the construction of both the support and the bushing and effects proper assembly with a minimum of labor. The bushing is tubular, with a flange at one end. The support, which is normally a thin metal plate, has a plurality of holes punched therethrough, with each hole having a plurality of tongues extending radially inwardly. The tubular portion of the bushing need only be pressed into a respective hole from one side surface of the support until its end flange abuts such side surface, the tongues being displaced to firmly grip the tubular portion of the bushing and thus maintain the assembly of the bushing and support.
DESCRIPTION OF THE DRAWING In the drawing accompanying this specification and forming a part of this application, there is shown, for purpose of illustration, an embodiment which our invention may assume, and in this drawing:
FIG. 1 is a plan view of one type of heater construction in which our invention may be incorporated,
FIG. 2 is a side view of the construction shown in FIG. 1,
FIG. 3 is an enlarged, separated perspective view of parts shown in FIGS. 1 and 2, and
FIG. 4 is an enlarged fragmentary sectional view corresponding to the line 44 of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 illustrate one type of heater construction in which our invention may be used and this construction may be disposed within ducts for heating air moving therein. The construction is varied in accordance with requirements and the form herein disclosed should not be considered limiting in nature.
As shown in FIGS. 1 and 2, the construction comprises a metal base member which may be of channel cross section, and adapted to be secured to a portion of the interior of a duct or the like. A pair of rigid metal arms ll, 11 are secured to the base member,
such as by spot welding a foot portion I2 of each to the web of the channel,
A plurality of support members 14 extend crosswise of the arms. Each support member is formed as a thin metal strip having a foot 15 which is spot welded to the arms 11, 11 to form a fairly rigid frame. The members support an open coil heating element 16 having a plurality of reaches extending between the support members. Opposite ends of the heating element are connected to respective terminals 17, 17 which are carried by insulators 18 connected to the web of channel base 10.
The reaches of the open coil heating element are insulated from the support members by insulating bushings 20 and our invention is directed to the manner in which the bushings are connected to the support members. As best seen in FIG. 3, the thin wall of each support member I4 has a plurality of holes 21 punched therein, the marginal surface defining each hole being serrated to provide a plurality of tongues 22.
Each insulating bushing 20 is preferably a molded ceramic body having a tubular portion 23, and a flange 24 at one end forming a shoulder 25 with the tubular portion. The tubular portion is of an external diameter which is only slightly larger than a hole 21. but somewhat larger than the opening defined by the inner ends of the tongues 22. Thus, the tubular end of a bushing may be pressed into a hole 21 an amount limited by abutment of the bushing shoulder 25 with one side surface of the support member I4, and this action bends the tongues from a position substantially in the plane of the support member to a position shown in FIG. 4, wherein the tongues extend at an angle from the opposite side surface of the support member and firmly grip peripherally spaced parts of the tubular portion 23. Thus, the flange 24 and the bent tongues 22 firmly lock the bushing 20 against axial movement.
The described construction enables all bushings on a support member to be pressed in place at one time in a suitable press, and the support members, with bushings assembled thereon, may then be welded crosswise of and to the arms 11, ll. Thereafter, the open coil heating element is threaded through the bushings to the position shown in FIG. 1, and opposite ends of the coil connected to respective terminals 17, 17.
1. An electric heater assembly for supporting a plurality of reaches of a sinuously formed helical resistance element, comprising:
a heat resistant base,
a thin metal plate secured to said base forming a rigid assembly therewith, said thin plate constituting the sole support for said element reaches adjacent thereto,
said plate having a plurality of apertures therethrough and through which said reaches extend,
said plate at the periphery of said apertures having a serrated configuration to define a plurality of tongues in circumferentially spaced relation extending radially inwardly of said apertures,
said tongues when unstressed being disposed in the plane of said plate,
and a plurality of rigid tubular heat resistant insulating bushings, each having a radial flange thereon, one surrounding each reach where the latter extends through a plate aperture thereby to insulate the reach from said plate,
with said bushing constituting the sole support of said bushing in said plate, thereby providing an effective, simple and stable support for said electric element reaches in said heater assembly.
2. The electric heater assembly of claim 1 wherein said insulating bushing is formed from ceramic material.
3. The electric heater assembly of claim 1 wherein said heat resistant base includes a pair of spaced arms and wherein said metal plate extends between and interconnects said arms.