US 3116401 A
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Description (OCR text may contain errors)
United States Patent O 3,116,401 ELECTREC HEATERS Lester D. BrugmanF Pittsburgh, Pa., assigner to Edwin L. Wiegand Company, Pittsburgh, Pa. Filed .lune 22, i966, Ser. No. 38,033 3 Claims. (ill. 22m-38) My invention relates to electric heaters, more particularly to an improved heater construction and mounting, and method of making me same, for protecting against corrosive valvanic action, and the principal object is to provide new and improved products and methods of the character described.
rlibe patents to Boggs et al., No. 2,723,340, and to Dicorne, No. 2,816,815 adequately discuss the need for protection of an electric heater against the damaging effects of galvanic current generated in a Water heater and therefore no further discussion will be made in this application.
rl`he present invention is an improvement over the con structions disclosed in the aforementioned patents and the advantages of the present invention w-ill become apparent from a reading of the following speciiication in connection with the accompanying drawing.
ln the drawing accompanying this speciiication and forming a part of this application, there is shown, for purpose of illustration, several forms which my invention may assume, and in this drawing:
`FlGURE 1 is a plan view of an electric heater showing on-e embodiment of my invention.
`FEGURES 2 and 3 are similar enlarged sectional views, FIGURE 3 being fragmentary and corresponding to the line 3--3 of FiGURE l and showing heater construction after a certain pressing operation, and FIGURE 2 illustrating the heater construction prior to a pressing operation, the press dies being fragmentarily shown.
FIGURES 4 and 5 are enlarged fragmentary sectional views corresponding respectively to the lines 4 4 and Sw of FlGURE l.
FlGURE 6 is a plan view of another embodiment of my invention, and
FGURE 7 is an enlarged fragmentary sectional View corresponding generally to the line "i-7 oi FIGURE 6.
Referring to ElGURES l through 5 of the drawings, the embodiment therein disclosed comprises a mounting member id, here shown to have a flat flange portion lll and a slightly conical inwardly dished portieri i2 providing a ilat bottom wall lll.
The flange portion lll is preferably rectangular (square) in plan and provided with holes l5 at its corners to pass fastening bolts (not shown) which secure the mounting member lill to a tank wall. Attention is directed to the aforementioned Boggs and Dicome patents for details oi `mounting the heater to the water tank wall.
rEhe mounting member `il@ may be formed of any suit able material and at the present time it is preferred to make this member as a brass forging. The bottom wall ld is formed with a pair of openings i6, le, each margined at its opposite ends by collars 17, i7 which are integral with the wall lle and extend from opposite sides thereof.
The two legs d8, `1d of a hairpin type electric heating element l@ are disposed through respective `openings i6, as shown in FIGURE 2. Generally, the heating element comprises a metal sheath 2li enclosing a resistor 2l, the latter being embedded within compacted, powdered refractory material 22., such as magnesium oxide, to electrically insulate the resistor from the sheath and to conduct heat from the resistor to the sheath. Terminal pins 23 are electrically and mechanically connected to opposite ends of the resistor 2l and extend outwardly of respective legs i8. A suitable end seal, not shown, may be disposed within the terminal ends of the heating element.
lliulhl Patented Bec. 3l, 1953 ice insulating sleeves 2d are disposed between adjoining surfaces of the openings i6 and sheath legs lil. rEhe material from which the sleeves are made should possess good electrical insulating qualities and at the same time should embody a limited degree of resiliency for a purpose later to appear. Sleeves made of nylon have been used with good eiiect.
rThe sleeves Z4 are preferably a little longer than the length of the openings iti through 4which they pass, as seen in FIGURES 2 and 3, and have a fairly close lit with the adjoining surfaces of the openings lli-i and sheath legs l. A proper assembly may be effected by cementing the sleeves to the adjoining parts, or by iilling the recess of the dished portion 1?; to a level, as indicated by the dotted line 25 in FIGURE 3, with a suitable epoxy resin.
However, to insure against any leakage which may be caused by vibration, or otherwise, it is preferred to effect a mechanically tight engagement between the sleeves 2d and adjoining parts. One manner in which such engagement may be effected is shown in FEGURE 2, wherein lower and upper dies 27 and Z8 are disposed on opposite sides of the mounting member and are relatively movable to close upon such member.
The dies Z7, 2d are formed with conical openings 29, the inner smaller diameter of which is just slightly larger than the outer diameter' of the nylon sleeves 2d. When the dies 27, 2S are closed upon the mounting members, the surface of the openings 29 peripherally engage about the terminal ends of the collars and deiorm such collars radially inwardly to exert a high pressure against the sleeves and the sheath and thereby iirmly support the electric heating element i9 from the mounting plate lll. The pressure exerted by deformation of the collars will compress and deform the sleeves and the sheath legs ld, but no attempt to show such compression or deformation has been made in `FlGURE 3. rfhe sleeves being somewhat resilient, suitably seal the openings lle, le against leakage of liquid from the tank. Also, the resiliency of the sleeves will insure that vibration will not loosen the heater assembly or cause leakage through the openings i6.
in order to insure a predetermined amount of galvanic current ilow between the mounting member il@ and the sheath of the heating element i9, a resistor 3d is interposed therebetween. Tne resistor may be of any suitable commercially available type, and preferably is of the radio type, comprising a cylindrical body with current conducting leads 3l., ft2 extending from its opposite ends.
rlne method of assembly herein before disclosed lends itself well to inclusion of the resistor assembly since it is only necessary to insert the lead 3d between the exterior surface of the sleeve 2d and the adjoining surface of the opening liti (see FIGURE 4) to insert the lead 32 between the interior surface of the other bushing 2d# (see FiGURE 5) and the adjoining surface of the heater sheath. When the collars i7 are inwardly deformed, the resulting inward directed pressure will insure good electrical engagement between the leads 3l, and the respective adjoining surface. Since the sleeves 2d are somewhat resilient, the leads 3l, 32 will be adequately surrounded toi prevent leakage `of liquid through the openings le.
Because of space limitations, the resistor Btl, as seen in FIGURE 1 is disposed to one side of a line drawn through the longitudinal axes of the heater legs i8, and the upper die 2S is formed with a recess (not shown) which provides clearance for the resistor.
Many parts of the embodiment shown in FIGURES 6 and 7 are similar to parts hereinbefore described and therefore such similar parts will be identified with the same reference numerals with the sufx a added.
In the embodiment of FIGURES 6 and 7, a llat plate 3 35 may be used as the mounting member. The plate 35 may be formed by a stamping operation and boit holes and inner holes 16u, 16:1 may be formed in the same operation.
The leads 31a, 32a, as before, are interposed between the sleeves 2da and the adjoining parts of the mounting member and heater sheath. Since the plate 35 is i'lat, no collars (such as collars 17, 117) are provided. ln this case, the dies (similarto dies 27, 23) may be formed with an almost closed circular projection (not shown) which is il-shaped in cross-section so that when the dies are closed upon the opposite sides of the mounting plate, il-shaped grooves 36, are formed in the opposite sides. The grooves 36 on tr e top of the plate 35 are circular and almost closed, as seen in Fi 6, clearance being provided to avoid injury to the resistor leads 31m, 31a, or to the resistor The grooves 36 on the bottom of the plate 35 may be circular and entirely closed, as suggested in FlGURE 7, to insure that a goed luid seal is made.
The tf-shaped grooves Slt? crowd the metal of the mounting plate surrounding the openings 16a, 16a inwardly toward the aXis of each opening to eiect the assembly and sealing pressure hereinbefore mentioned, Since each top groove 36 is almost a completely closed circle, the slight interruption therein will not affect the assembly and sealing pressure exerted, especially when the lower grooves 36 are completely closed circles.
ln view of the foregoing, it will be apparent to those skilled in the art that l have accomplished at least the principal object of my 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 my invention is not limited thereto.
1. An electric heater assembly, comprising a metallic mounting member having a pair of openings therein, a dielectric sleeve closely ttting within each of said openings, an electric heating element having a metallic sheath, portions of the latter closely tting within and extending into respective ones of said sleeves and being lirmly connected to said mounting member, means for regulating flow of electric current between said sheath and said mounting member and having a pair of electrical `connection leads, one of said leads being disposed between and in contact with the defining wall of one of said openings and the adjoining outer surface of the corresponding sleeve to place said one lead in electrical contact with said defining wall and thus in electrical Contact with said mounting member, and the other of said leads being disposed between and in Contact with the exterior surface of the sheath portion and the interior surface of the sleeve at the other of said openings to place said other lead in electrical contact with said sheath.
2. The construction according to claim 1 wherein metal of said mounting plate adjoining said openings is deformed radially inward to exert an inward pressure against respective sleeves and sheath portions to seal the openings against leakage of liquid therethrough and to effect good electrical contact at said leads.
3. The construction according to claim 1 wherein said mounting plate has integral collars extending therefrom and margining said openings, and wherein said collars are deformed radially inwardly to exert an inward pressure against respective sleeves and sheath portions to seal the mounting plate openings against leakage of liquid therethrough and to eiect good electrical contact at said leads.
References @Cited in the le of this patent UNITED STATES PATENTS 2,550,751 Adams May l, 1951 2,670,529 rThomas Mar. 2, 1954 2,723,340 Boggs et al. Nov. 8, 1955 2,769,891 Harrison Nov. 6, 1956 2,785,270 Burger i Mar. 12, 1957 2,810,815 Dicome Oct. 22, 1957 2,824,944 Ammerrnan Feb. 25, 1958 2,947,846 Fox Aug. 2, 1960 3,074,159 Baldwin et al. lan. 22, 1963