US 2763763 A
Description (OCR text may contain errors)
p 1956 D. M. CUNNINGHAM ETAL 2,763,763
ELECTRIC HEATERS Filed May 6, 1955 INVENTORS DONALD M. CUNNINGHAM b LESTL'R 0. DRU ND Y BYZ m AtZornqy United States Patent Ofiice 2,763,763 Patented Sept. 18, 1956 ELECTRIC HEATERS Donald M. Cunningham and Lester D. Drugmand, Pittsburgh, Pa., assignors to Edwin L. Wiegand Company, Plttsourgh, Pa., a corporation of Pennsylvania Application May 6, 1955, Serial No. 506,467 Claims. (Cl. 219-38) The present invention relates to electric heaters, more particularly to electric heaters having elongated sheathed heating elements supported in cantilever fashion and, therefore, being prone to damage by vibration, and the principal object of our invention is to provide new and improved electric heaters of such character.
ln shipping electric water heaters of the type in which a sheathed, electric resistance heating element is positioned inside the heater tank and is supported in cantilever fashion by a wall thereof, it has been found that many water heaters reached the consumer with their heating elements fractured. These fractures generally occurred in the heating elements adjacent the point where they were supported and were caused by vibration of the elements in the empty tanks during shipment.
In prior art water heaters, this situation was not too serious since the electric heating elements were rather small and few, if any, heaters were damaged in shipment; however, since present practice is to utilize longer heating elements in order to increase heat output, these longer elements are much more prone to damage.
The present invention provides cantilever supported, elongated heating elements of considerable length for high heat output but which are highly resistant to damage caused by vibration. This advantage and others will readily become apparent from a study of the following description and from the drawing appended hereto.
In the drawing accompanying this specification and forming a part of this application, there are shown, for purpose of illustration, embodiments which the invention may assume, and in this drawing:
Figure 1 is a perspective view of an electric heater adapted for use in a domestic water heater and illustrating a preferred embodiment of the invention,
Figure 2 is an enlarged, fragmentary sectional view generally corresponding to the line-2-2 of Figure 1, and
Figures 3 and 4 are views similar to Figure 2 but of a modified construction.
As best seen in Figure 1, the present electric heater comprises a mounting flange which is adapted to overlie an opening in the wall of the water heater (not shown) and is adapted to be secured in position by means of belts or the like which pass through apertures 11 in the flange. A suitable gasket 12 may be interposed between the mounting flange and the wall of the water heater to insure against leakage.
Secured to flange 10 and extending therefrom in cantilever fashion to project into the interior of the water heater tank is a conventional sheathed embedded electric resistance heating element 1.3. In the embodiment herein disclosed, heating element 13 is of considerable length and is formed to hairpin shape to provide spaced legs 14 having terminal portions 15 at one end and an integral connecting bight portion 16 at the other end. The terminal portions 15 of the element are adapted to be secured to the flange by any suitable means and, as is usual, terminal portions 15 extend through the flange and are accessible from the exterior of the water heater to provide for making the necessary electrical connections to the embedded resistor.
Legs 14, 14 are doubled back at 17 to position bight portion 16 adjacent terminal leg portions 15. The bight portion end of the element is adapted to be rigidly connected to the spaced terminal leg portions 15 in manner wherein bight portion 16 will act as a strut between the terminal leg portions to strengthen the element and increase its resistance to vibration. In the embodiment shown in Figures 1 and 2, the bight portion end of the element is adapted to be fused to terminal leg portions 15 by welding, brazing or the like as indicated at 18. This construction, it will be appreciated, greatly strengthens the heating element without materially adding to its manufacturing cost. Indeed, laboratory tests show that while a conventional electric heater will fracture after being subjected to a vibrating machine for about fifteen minutes, an electric heater constructed in accordance with the present invention has been vibrated more than forty hours before damage occurred.
The construction illustrated in Figure 3 is similar to that heretofore disclosed; accordingly, similar parts have been identified by the same reference characters but with the sufiix a added. In the construction shown in Figure 3, the bight portion end of the heating element is not fused to the terminal leg portions 15a but instead, clamps 19 are employed for this purpose. Each clamp 19 comprises a band which is adapted to be tightly wrapped about the adjoining element portions and held in position by suitable fastening means such as a screw 20 and a nut 21. It is to be understood, however, that the clamps herein shown are illustratii e only and that any other suitable clamp may be utilized for rigidly securing the adjoining element portions together.
In the construction shown in Figure 4, the bight portion 16b of the heating element, as in the construction shown in Figure 3, is mechanically connected to the terminal leg portions 15b. In this embodiment, a loop is placed transversely around adjacent parts of the bight portion and leg portions and is held in place by a threaded member 26.
The loop may be formed of sheet metal and may be an endless band, as shown, with holes pierced in opposite reaches to receive the fastening member 26. The fastening member may be a self-tapping screw, as shown, or may be a screw and bolt connection.
Instead of an endless band, the loop may be formed of a strip of metal bent to loop form with ends lapping and formed with apertures to pass the threaded member 26.
The loop 25 is preferably positioned close to the bight portion so that the threaded member 26 is abuttable with the bight to restrict movement of the loop in a direction toward the flange 19. As the threaded member 26 is tightened, it will be appreciated that opposite reaches of the loop will be drawn toward each other, as seen in Figure 4. Since the leg portions 15b and leg extensions of the bight portion 16b diverge in a direction toward the doubled back portion (designated 17 in Figure 1), the loop is prevented from moving in such direction and, accordingly, is firmly anchored in place.
The electric heater of our invention is particularly suitable for heating the contents of a receptacle, such as a water tank as shown in Greer Patent No. 2,423,184. The heating element 13 is inserted to position within the tank through an opening in the tank wall and bolts are disposed through apertures in the flange and gasket and are threaded into corresponding threaded openings in the tank. It will be appreciated that the insertion and removal of the heating element 13 through the relatively small opening in the water tank is greatly facilitated since the bight portion is held closely to and against movement away from the leg portions 15 and therefore cannot catch on the marginal surface defining the tank opening.
In view of the foregoing it will be apparent to those skilled in theart that we have accomplishedat least the principal object of our. invention and it will also be apparent to those skilled in the art that the embodiments herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described, hence it will be appreciated that the herein disclosed embodiments are illustrative only, and that our invention is not limited thereto.
1. An electric heater having an active heating portion of considerable length for high heat output and securable to a member which is subject to vibration, comprising support means adapted to be secured to said member, a hairpin-type sheathed heating element supported in cantilever fashion by said support means and providing spaced legs having terminal portions at one end and a connecting bight portion at the other end, said terminal portions being connected to said support means and said legs being doubled back upon themselves to position the bight portion end adjacent to the supported terminal portions,
and a. metal loop disposed transversely about adjacent parts of said bight portion and said terminal portions and drawn into tight engagement therewith to increase rigidity of said heating element and to thereby reduce the danger of breakage caused by vibration of said member.
2. An electric heater having an active heating portion of considerable length for high heat output and securable to a member which is subject to vibration, comprising a metallic flange plate adapted to be rigidly secured to said member, a hairpin-type sheathed heating element supported in cantilever fashion by said flange plate and providing spaced legs having terminal portions at one end and a connecting bight portion at the other end, said terminal portions being rigidly connected to said flange plate and said legs being doubled back upon themselves and angling toward said terminal portions to position said bight portion in relation overlying said terminal portions a metal loop disposed transversely about adjacent parts of said bight portion and said terminal portions, and a threaded member passing through opposite reaches of said loop and having an intermediate portion extending through the space between said legs, said threaded member abutting said bight portion to restrain movement of said loop in one direction and the angled disposition of said legs forming a Wedge surface restraining movement of said loop in an opposite direction, said threaded member rigidly clamping said loop about said bight portion and said terminal portions to increase rigidity of said heating element and to thereby reduce the danger of breakage caused by vibration of said member.
3. An electric immersion heater having an active heating portion of considerable length for high heat output and insertable through an opening in the wall of a tank for position to heat the contents of said tank, comprising a metallic flange plate adapted to be connected to the tank wall in position spanning the opening in said tank, a hairpin-type sheathed heating element supported in cantilever fashion by said flange plate and extending into said tank when said flange is secured thereto, said heating element providing spaced legs having terminal portions at one end and a connecting bight portion at the other end, said terminal portions being rigidly connected to said flange plate and said legs being doubled back upon themselves to position said bight portion end adjacent to said terminal portions, and means rigidly connecting said bight portion end with the adjacent parts of said legs.
4. An electric heater having an active heating portion of considerable length for high heat output and securable to a member which is subject to vibration, comprising support means securable to the vibration subject member, and an elongated sheathed heating element supported in cantilever fashion by said support and formed of a pair of legs each having one end portion terminating in a connecting bight portion, the other end portion of each leg being securable to said support means to position such other end portions in adjoining, spaced-apart relation and said legs being doubled back on themselves to position said bight portion adjacent said other end portions of said legs, said bight portion extending between said spaced, other end portions of said legs and being rigidly connected between such leg portions to provide a reenforcing strut which increases the rigidity of said heating element and thereby reduces the danger of damage to said element caused by vibration.
5. A construction in accordance with claim 4 wherein said bight portion is connected between such leg portions by means of a fused metallic connection therebetween.
References Cited in the file of this patent UNITED STATES PATENTS 1,823,925 Woodson Sept. 22, 1931 2,274,930 Newton Mar. 3, 1942 2,606,271 Morris Aug. 5, 1952