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Патент USA US3080554

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March 5, 1963
A. c. BOGGS
3,080,543
ELECTRIC HEATERS
Filed Nov. 22, 1960
2 Sheets~$heet 2
INVENTOR
)"1 ‘a; ALBEN C‘. 50665
United States
T6
1
fiddiih?dg
Patented Mar. 5, 1963
2
spective strips 14 and is in tight engagement therewith to
provide a low-resistance, electrical connection therebe
tween. The interior of the sheath is ?lled with a suitable,
3,089,543
ELECTRIC HEATERS
Alben C. Boggs, Pittsburgh, Pa., assignor to Edwin L.
Wiegand Company, Pittsburgh, Pa.
highly compacted, electric-insulating, heat-conductive ma
Filed Nov. 22, 1960, Ser. No. 71,082
1 Claim. (Cl. 338-273)
terial 17 such as magnesium oxide which immobilizes the
various parts above described. A thin, flexible washer
The present invention relates to electric heaters, more
particularly to electric heaters of the type known as car
18 of, for example, mica or the like may abut the ma
terial 17 at the open end of the sheath to prevent loss of
such material through the open sheath end. If desired,
tridge heaters, and the principal object of the invention is
the pocket shown at the open end of the sheath may be
filled with a suitable cement or the like in the well-known
manner to further close such sheath open end.
Referring now to FiGURE 2 wherein the heater thus
to provide new and improved heaters of the character
. described.
Cartridge heaters of the type wherein a tubular sheath
encloses a resistor coil embedded in compacted electric
far described is shown during a preliminary stage of
assembly, it will he noted that the sheath in at this stage
is shorter and larger in diameter than is shown in FIG
URE 1. Disk 11, at this time, but loosely closes the left
end of the sheath, the disk being seated against a radially
inwardly turned sheath end portion 19.
insulating, heat-conductive material and wherein a pair
of terminal conductors project outwardly of an end of the
sheath and are connected to respective coil ends have long
been known. Such heaters are highly ef?cient and have
enjoyed wide usage; however, traditionally constructed
heater-s of this type have been rather expensive to manu
facture, especially when the resistor coil is of ?ne wire. 20
In an attempt to reduce manufacturing costs, it has
been proposed that the usual swaging or pressing oper
ation, which operation reduces the transverse size of the
Lheater to compact the contained material about the re
sistor coil and the terminal conductors, be employed to
effectuate certain electrical connections within the sheath.
While this proposal has been meritorious, in practice the
prior art constructions have not been satisfactory since
consistently good electrical connections have been diffi
cult to achieve.
The present invention advantageously utilizes the swag
}ing' operation, or other equivalent mode of compacting
The resistor coil 12 is wound upon the periphery of a
frangible, dielectric body 20 formed, for example, of
magnesium oxide powder held together by means of a
suitable binder. The outside diameter of this body is
somewhat smaller than the interior of the sheath so that
the resistor coil on the body exterior will be spaced from
the sheath interior. Extending from end to end of the
body 20 are openings 21 in spaced, side-by~side relation.
As illustrated, such openings provide for the reception
of respective terminal pins 16 and legs 15 of respective
strips 14.
An important feature of the present invention is the
cross-sectional configuration of the body openings 21
~the electric-insulating, heat-conductive material within the
and that of the strip legs 15. As best seen in FIGURE
FIGURE 2 is a vview similar to FIGURE 1 but at a
be assembled by inserting one of the strips 14 in one end
of a body opening 21 so that the strip leg 13 overlies the
sheath, to provide suitable electrical connections there .35 3, pins 16 are round in cross-section while strip leg 15
is arcuate in cross-section to closely ?t with the pin and
.within which are consistently satisfactory. Other advan
partially embrace the latter. Openings 21 are formed
tages will readily become apparent from a study of the
to closely ?t about the pins and the strip legs 15 and to
following description and from the drawings appended
this end, each opening (see especially FIGURE 4) has
.hereto.
a relatively large, arcuate de?ning margin 22 for closely
In the drawings accompanying this speci?cation and
receiving a respective strip leg 15 and an opposed, rela
forming a part of this application there is shown, for pur
tively small, arcuate de?ning margin 23 for closely re
pose of illustration, embodiments which the invention may
ceiving a respective terminal pin 16. The importance
assume, and in these drawings:
of so forming the strip legs and the body openings will
FIGURE 1 is~a view in longitudinal section through
hereinafter appear.
-a cartridge heating element constructed in accordance
The construction thus far disclosed may conveniently
‘with the present invention,
preliminary stage of manufacture,
periphery of the body at one end of the latter. The re
FIGURE 3 is an enlarged, exploded fragmentary per
spective view of certain details seen in FIGURE 2,
50 sistor 12, one end of which was preferably welded or
otherwise secured to the leg 13 of the aforesaid strip 14
FIGURE 4 is an enlarged, fragmentary transverse sec- '
prior to its insertion in the body opening, may then be
tional view of one of the details seen in FIGURE 3, and
wound to coil form on the exterior of the body 2th from
FIGURE 5 is a reduced‘ size view similar to FIGURE 2
said one end to the other. The other strip 14 may then
but of a modi?ed structure.
With reference to FIGURE 1, there is illustrated a car 55 be inserted into the other body opening from the opposite
tridge heater in substantially ?nal form constructed in
accordance with the present invention. Such heater is
herein shown to comprise a tubular metal sheath Ill closed
at the left end by an inwardly dished, metallic disk 11.
Disposed within the sheath and in radially spaced rela
tion with the interior thereof is a coiled resistor 12. Re—
spective ends of the resistor coil ‘are welded or otherwise
connected to the short leg 13 of respective U-shaped,
electrically-conductive metal strips 14. The long leg 15
of each strip 14 is disposed within the resistor coil and
extends longitudinally thereof for a purpose to appear.
Also disposed within the resistor coil in spaced, side
by-side relation are a pair of terminal conductor pins 16
which project outwardly of the right, or open end of the
sheath for connection to a source of electrical energy.
Each terminal pin is coextensive with the leg 15 of re
end of the body with its leg 13 overlying the body periph
ery. The adjoining end of the resistor may then be
welded or otherwise secured to such strip leg 13 to retain
the resistor coil assembled with the body. It will be
understood, of course, that each strip leg 15 Will be dis
posed in the portion 22 of its opening 21.
Terminal pins 16 may then be inserted into body open
ings 21 to close ?tting engagement with respective strips
14. Note that the considerable length of strip leg por- .
tions 15 insures an adequate area of contact between the
strips and the pins as does the pin-embracing, cross-sec
tional con?guration of such legs. For reasons to appear,
pins 16 are so inserted into the body openings that their
ends 116 project beyond the body a slight amount.
With the resistor 12, the pins 16 and the strips 14 as
sembled with the body 2%} as above described, such as
sembly may be inserted into the open end or" the sheath
350391.543
3
with the 'body end containing the terminal pin portions
116 foremost. Prior to such ‘insertion of the body, a
member 24, preferably of the same frangible material as
body 20, will be disposed for interposition between the
disk 11 and the body 20, Such member presently has an
4
continuity between the pins and the resistor. With the
present construction, however, wherein the strips-‘1V4 par
tially embrace the pins, fragmented pieces of the body
cannot ‘wedge the pins and the strips apart thus causing
such continuity loss.
An important advantage in forming: heaters in accord
ance with the present invention is that merely by em
ploying longer terminal pins and a longer sheath, a series
the body for closely receiving respective terminal pin
of bodies may be strung upon. the pins to. provide heaters
ends 116.
greater heatoutput. Thus, as ‘shown in FIGURE 5,
Following disposition of the assembled body 20 within 10 of
two bodies 20a (similar in all respects to body 20) may
the sheath 10‘ (as seen in FIGURE 2‘) with the member
outside diameter closely ?tting the sheath interior and has
a pair of recesses 25, see FIGURE 3, in the face adjacent
'24 interposed-between thebody vand the disk 11‘, a second
member 26 (see also FIGURE 3) will be disposed
be disposed'in end to end relation'with terminal pins 16a
extending through their aligned‘ openings. As will be
obvious, ‘the resistors 12;: carried lbyprespective bodies 20;:
against that end, of the body- adjacent the open end of
will
‘be connected together in- parallel so that a failure
15
the sheath. This member also is preferably formed of
of
one
resistor will notatfect operation of the other; vNote
the same frangible material as body 720 and has a pair
that a second member 26a is interposed between the two
(if-through apertures 27 for passing respective terminal
pins. Member 26 is similar to 24 in that it too is pro
bodies‘ZOa to insure concentricity of the bodies with the
sheath interior. While FIGURE 5' illustrates a ‘heater
portioned to closely ?t within the sheath; however, a plu
rality of notches 28 are provided in its periphery for. a 20 employing but’ two bodies, there is- no vlimit to the num
ber that could be employed by following the above teach
purpose ‘to appear;
7
I
>
With the parts assembled‘ as seen in FIGURE 2, it will
be noted that the body’ 20‘ is maintained‘ centered within
the sheath by means of the interengagernent. of the mem
bers 24, 26' with the sheath interior and‘ their interengage
ment with the terminal, pins 16 extending through the
‘body. Accordingly, the sheath may now be ?lled with
,lIlgS.
In view- of vthe foregoing it- will {be apparent to those
‘skilled ‘in the art that'l have'accomplishedv at least the
principal object: of,v my invention and it will‘ also be ap
parent to those skilled in the art that the embodiments
‘herein described may- be variously changed and xmodi?ed,
powdered material, such as magnesium oxide, through its
without departing from the spirit of the invention, and
29 and ‘the members 24, 26 and ‘to pack the powdered
~le'g- coextensive with and‘contacting said pin over a con
that the invention is capable of uses and has advantages
open end. Note that the notches 23 in the periphery of
30 not herein speci?cally described; hence it- will‘ be ap
the member- 26 permit entrance of such material._
preciated that the herein disclosed embodiments are illus
If desired, member 24' may also be formed with 'pe
trative only, and that my invention is- not limited: thereto.
ri‘pheral notches (not shown) similar to those, formed in
I claim:
,
7'
the member 26 to perm-it the powdered material‘ to ?ll
An electric lheatingelement, comprising a metal sheath
the voids between the member 24 and the disk '11,.
substantially?lled with'electric insulating material, a. re
After the sheath has been ?lled to the level of the
sistor and a terminal pin embedded_ within said insulating
member 26, the mica washer 18 may be installedv to pre
material, and a low- resistance conductor of strip- metal
vent escape of the powdered material. The unit will next
electrically connected to said resistor- and also embedded‘
be subjected vto a swaglng or other operation which re,
within said insulating material, said-conductor havin'g'a
duces its transverse size an amount to ‘fragment the body
material‘, together with that which is fragmented, to a
gsiderable‘ length thereof, said‘leg beingofj'a cross-sectional
shape and’ size complementary to the shape and‘ size or.
generally homogenous mass of rock-like hardness in which
‘the
contacted portion ofsaid terminal pin whereby ‘con
the resistor, the strips and the terminal pins are'embed-ded'.
siderable surface inte‘rengagement is effected ‘the'rebé
In accordance with well-known practice,’ removable 45 ‘tween,
and saidleg being held in tight engagement with
‘plugs may be inserted in one or both ends of the sheath
said pin- portion and mechanically ‘and ‘electrically vcon.
during this compacting operation to insure against loss
nected thereto solely by permanent inward deformation
of any of the contained material. As a’result- of this com.
of said sheath which exerts inward‘ pressure against the
pacting operation, the sheath will berreduced‘in transverse
electric insulating material disposed between theinterior
size and also elongated as may be seen by a vcomparison 50 of said sheath and said leg to in turn pressr'said‘ileg; against
of FIGURESv 1 and‘ 2. Also, as a result of‘ this opera
said pin.
'
tion, the dished disk 11 will be tightly crimped in the left
References‘ Cited. in the ?l'erof» this patent
end' of the sheathto close the latter.
It ‘is to be understood that the vibration of the. swaging
UNITED STATES'VPATENTS
operation together with the fragmentation of the body 20 55
' 2.008.288
my 16.1935
tends to cause a slight shifting of the terminal pins and
2,527,026
Mucher _
ovate-4,, ‘1950
theother parts within the sheath. In some prior art con,
Shaw ..__.._
_ ,“LMay 22,1954
structions this sometimes resulted, in a- loss of electrical
2,553,875
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