US2861162A

US2861162A - Methods of constructing sheathed electric heaters

Info

Publication number: US2861162A
Application number: US585578A
Authority: US
Inventors: John Van Inthoudt
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-05-17
Filing date: 1956-05-17
Publication date: 1958-11-18
Anticipated expiration: 1975-11-18

Description

Nov. 18, 1958 J. VAN IN1-HOUDT 2,861,162.

METHODS 0F' CONSTRUCTING SIIEATI-EIDl ELECTRIC HEATERS Original-.Filled June 23, 1951 s 1 Sax l /l' United States Patent METHODS OF CONSTRUCTING SHEATHED ELECTRIC HEATERS John Van Inthoudt, Milwaukee, Wis.

Continuation of application Serial No. 233,196, June 23, 515.78 This application May 17, 1956, Serial No.

5 Claims. (Cl. 201-67) This invention relates to methods of constructing sheathed electric heaters. This is a continuation of my application Serial No. 233,196, now abandoned, tiled June 23, 1951.

A primary object of the invention is to provide improved forms of non-breakable, moisture impervious end seals for heaters of the aforementioned type.

Another object is to provide simplified methods of s sealing the ends of such heaters.

A more specilic object is to provide a method of assembly whereby closure means affording permanent sheath end seals also serve to close the sheath ends during assembly, thus eliminating the need for temporary closure devices during assembly, and

Another specific object is to effect permanent sealing of the sheath ends as an in'cident to contraction of the sheath during swaging of the latter for compaction of the insulating ll.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate preferred embodiments of the invention which will now be described, it being understood that such embodiments are susceptible of modification in respect of details without departing from the scope of the appended claims. Y

In the drawings: Y

Figure l is a view in longitudinal section of a portion of a tubular sheath heater following insertion' of the heating element therein but prior to the insertion of an end plug therein;

Fig 2 is like Fig. l but shows the heater at a later stage in its construction;

Fig. 3 is like Fig.' l, but shows the heater at a still later stage in its construction; Y

Fig. 4 is like Fig. 3 but shows a modified form of en'd seal, and v Fig. 5 is like Fig. 3 but shows still another modied form of end seal.

One preferred method of assembly of a tubular sheathed electric heater initially comprises threading through the bore of atubular sheath 10, a heating element, having a helical resistor 11 and end terminal members 12, so that one such terminal member extends in part beyond the end of the sheath as shown in Fig. 1. Then a silicone rubber plug 13 of elastic character, in its normal incompressed state, and having a central longitudinal perforation 13a is slipped over such terminal member and inserted into the end of the sheath. As shown in Fig. 1, the sheath preferably has its bore enlarged adjacent the ends thereof to provide end recesses 10e, and the plug 13 is adapted to seat against the inner sheath wall surrounding a recess 10et when inserted therein. The length of the plug 13 is preferably somewhat in excess of the l depth of the recess 10a, and such plug is preferably externally formed to match the cross sectional form of such recess, but with slightly greater dimensions so that it will initially seat in bottle stopper fashion. With the plug 13 so seated, the portion of the sheath adjacent said ice plug is swaged to a limited degree (Fig. 2) to insure that said plug will lirmly grip the portion of a terminal, 12 projecting therethrough and provide for anchoring of the latter against displacement axially of the sheath bore during the subsequent filling operations. When tubular sheaths with enlarged end portions are used, this auxiliary swaging operation reduces one enlarged end, containing a plug 13, to the same dimensions as the center or main body portion of the sheath.

It may now be assumed that the thus far assembled unit is placed in one of the well known types of loading machines which are adapted to effect filling of the sheath with a suitable granular refractory insulating material, such as magnesium oxide. The assembly is positioned in the loading machine vertically with the end containing the plug 13 lowermost. The upper terminalmember (not shown) of the heating element is suitably positioned centrally of the bore of the sheath and extends the proper distance outwardly of the upper end of the sheath. Granular insulating material is then introduced into the sheath bore, accompanied by intermittent compacting of such material within the sheath in a well known manner. Sheath 10 is preferably lled with such compacted granular insulating material to the bottom of the other, or upper, recess (not shown) in the other end of the sheath and then removed from the loading machine. A plug, like plug 13, is then slipped over the upper terminal member and seated within the upper recess, like 10a, as aforedescribed.

The assembly is then subjected to well known swaging operations over its entire length to effect further compaction' of insulating material 14 and consequent further contraction of the sheath in cross section. During such swaging operations the aforementioned plugs prevent displacement of the insulating material out of the ends of sheath itl. The end portions of the sheath surrounding the plugs are contracted to the same cross sectional dimensions as the other portion of the sheath, and consequently the plugs are compressed in place laterally by contraction of the sheath and are extended axially to some extent, as shown' in Fig. 2. As best shown in Fig. 3, such lateral compression and axial extension of the plugs results in tightly fitting and intimate endwise. engagement of the plugs with the compacted insulating material 14, with the portions of the terminal members 12 which they surround, an'd with the portions of the inner sheath wall surrounding the plugs. The plugs will be securely anchored within the ends of the sheath against withdrawal axially; and the same thus afford permanent end seals for the sheath of moisture impervious and non-breakable character.

Provision' of the enlarged recesses 10a, as shown in Fig. l, preparatory to assembly is not necessary. Such recesses permit some latitude in respect of the initial cross sectional dimensions of the silicone rubber plugs, while insuring following swaging and contraction of the sheath that the desired sealing action by the plugs will be had.

If annealing of the sheath is required, then emplacement of the silicone rubber end plugs would be deferred until following annealing of the sheath. In such case temporary end plugs, preferably of the type disclosed in the Charbonneau Patent No. 2,652.622, granted September 22, 1953, would be used in the sheath ends during the filling, swaging and annealing steps, and then the silicone rubber plugs would thereafter be inserted into recessed ends of the sheath, laterally compressed and anchored in place.

Fig. 4 depicts a modified form of construction for end sealing of a sheathed heater, employing a silicone rubber plug 15 having a frusto-conical tapered portion 15a extending beyond the sheath ends. Fig. 5 depicts another aeeinea modied form of construction for end sealing of a sheathed heater, employing silicone rubber plugs 16, which are initially short in length and inserted wholly Within the sheath ends so that in iinal sealed state a recess is provided in the sheath ends, in which auxiliary sealing materials or devices may be inserted if desired.

Any of the assemblies shown in Figs. 3, 4 and 5 may have any desired form of terminal device secured to their terminal members to facilitate connection of electrical conductors therewith.

While not li-mited thereto, the sheath end seal construction and the methods of making the same aforedescribed have proved to be particularly advantageous for heaters used in defrost service of refrigeration equipment where high moisture conditions prevail.

I claim:

1. The method of making a sheathed electric heater wherein a resistor with a terminal end portion is surrounded by a tubular metal sheath containing granular refractory insulation in which said resistor is embedded, cornprising inserting into an end of said sheath prior to tilling the same with granular insulating material a plug formed of elastic heat resistant material which is perforated to receive a terminal end portion of the resistor, then filling said sheath to a point adjacent its other end with granular refractory insulating material, and then contracting said sheath laterally over its entire length for compaction of said insulatingmaterial and for lateral compression of said elastic plug to anchor the same against axial displacement and to effect permanent sealing thereof with the compacted insulating material, with the peripheral surface o-f said terminal end portion, and with the inner Wall of said sheath.

2. The method of making a sheathed electric heater, which comprises inserting a resistor with terminal end portions into a tubular metal sheath, then inserting into an end of said sheath a plug formed of elastic heat resistant material, perforated to receive a terminal end portion of the resistor, then filling said sheath to a point adjacent its other end with granular insulating material, and

then contracting said sheath laterally over its entire length for compaction of said insulating material and compressive anchoring of said elastic plug against axial displacement and permanent sealing thereof with the compacted insulating material, with the peripheral surface of said terminal end portion of the resistor, and with the inner wall of the sheath.

3. The method of making a sheathed electric heater, which comprises inserting a resistor with terminal end portions into a tubular metal sheath, then inserting into an end of said sheath a plug formed of elastic heat resistant material, perforated to receive a terminal end portion of the resistor, then lling said sheath to a point adjacent its other end with granular insulating material, then inserting another like elastic heat resistant plug in the latter end of said sheath, and then contracting said sheath laterally over its entire length for compaction of said insulating material and compressive anchoring of said elastic plugs against axial displacement and to effect permanent sealing thereof with the compacted insulating material, with the peripheral surfaces of the terminal end portions of said resistor, and with the inner wall of said sheath.

4. The method of making a sheathed electric heater, which comprises inserting a resistor with termin-al end portions into a tubular metal sheath, then inserting into an end of said sheath a silicone rubber plug of elastic heat resistant character, perforated to receive a terminal end portion of the resistor, then filling said sheath to a point adjacent its other end with granular insulating material, and then inserting another like elastic heat resistant silicone rubber plug in the latter end of said sheath, and then contracting said sheath laterally over its entire length for compaction of said insulating material and compressive anchoring of said elastic heat resistant silicone rubber plugs against axial displacement and to effect sealing thereof with the compacted insulating material, with the peripheral surface of said terminal end portion of the resistor, and with the inner Wall of said sheath.

5. The method of sealing the end of a tubular metal sheathed heater having a resistor with a terminal element projecting beyond the end of the sheath and compacted refractory insulating material in which said resistor and said terminal element in' part are embedded in spaced relation to the inner sheath wall, comprising inserting into the end of the metal sheath at a selected stage in the assembly of the heater an elastic heat resistant silicone rubber plug, perforated to receive said terminal element, and after assembly contracting said metal sheath to laterally compress said elastic heat resistant plug for permanently anchoring the latter against axial displacement and to effect sealing thereof with the peripheral surface of said terminal element and with the inner peripheral surface of said metal sheath.

References Cited in the iile of this patent UNITED STATES PATENTS Re. 23,679 Charbonneau et al July 7, 1953 1,157,916 Wentworth Oct. 26, 1915 1,298,609 Wentworth Mar. 25, 1919 1,359,400 Lightfoot Nov. 16, 1920 2,375,058 Wiegand May 1, 1942 2,448,756 Agens sept. 7, 1948 2,460,795 Warrick Feb. 1, 1949 2,475,756 Peulet July 12, 1949 2,480,903 Charbonneau Sept. 6, 1949 2,538,808 Swiss Ian. 23, 1951 2,617,001 Hasley NOV. 4, 1952 2,624,829 Dzaack Ian. 6, 1953 2,635,163 Temple Apr. 14, 1953 2,652,622 Charbonneau June 7, 1953 2,659,795 Boggs Nov. 17, 1953 FOREIGN PATENTS 546,150 Great Britain June 30, 1942 624,422 Great Britain June 8, 1949 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent Noa 2,861,162 November 18, l958 John Van lnthoudt It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected'below,

yIn the grant, lines l, 2 and 3, for l'John Van lnthoudt, of Milwaukee, Wisconsin,H read John Van lnthoudt, of Milwaukee, Wisconsin, assignor to Cutler-Hammer, Inc., of Milwaukee, Wisconsin, a corporation of Delaware,-m; line l2, for HJohn Van lnthoudt, his heirs" read Cutlerldammer, Incu its successors in the heading to the printed specification, line 4, for nJohn Van lnthoudt, Milwaukee, Wis,H read John Van lnthoudt, Milwaukee, Wis., assignor to Cutler-Hamer, Inc., Milwaukee, Wiso a corporation of Delaware u; column 2, line '7, for "one enlarged end," read n one enlarged end portion,

Signed and sealed this 31st day of March 1959,

(SEAL) Attest:

KARL H AXLNE i ROBERT C. wAIsoN Attestng Officer i Conmssioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2,861,162 November 18, 1958 JOhn Van lnthoudt lt is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as cor-1 rected'belowel 1n the grant, lines l, 2 and 3, for HJohn Van lnthoudt, of Milwaukee, Wisconsin,H read John Van lnthcudt, of Milwaukee, Wisconsin, assigner to Cutler-Hammer, Inc., of Milwaukee, Wisconsin, a corporation oi Delawarefm; line l2, for "John Van lnthoudt, his heirsH read CutlerI-Iamner, lnco its successors in the heading to the printed specification, line 1, for "John Van lnthoudt, Milwaukee, Wis,H read John Van lnthoudt, Milwaukee, Wis, assignor to Cutler-Hammer, lncu Milwaukee, Wis., a corporation of Delaware column 2, line 7, for none enlarged end," read w one enlarged end portion,

Signed and sealed this 31st day of March 1959,

(SEAL) Attest:

KARL H., AXLINE ROBERT C. WATSON Attesting Officer Conmssioner of Patents