Note: Descriptions are shown in the official language in which they were submitted.
w 200 357 5
- 1 -
BACKGROUND OF THE INVENTION
This invention relates generally to the field of
hand held soldering/desoldering tools and, more particularly,
to such instruments which utilize a stream of gas to convey
heat from its source along at least a portion of the path to
the soldering point, the term "hand held" being intended to
include robotic or robot-like applications. The term "gas" as
used here usually means ambient air, but may include inert or
relatively inert gases such, for example, as carbon dioxide or
nitrogen or the noble gases or the like as when oxidation,
corrosive reactions, or other undesired chemical action is to
be minimized.
The advantages of hot gas soldering have become
known and understood in recent years. It suffices here to
point out that hot gas soldering by a stream of very hot gas
with a very small cross section can apply precisely the
desired quantity of heat at precisely the desired work point
without deleteriously heating other adjoining or contiguous
material or objects. In addition, the gas stream presents to
the work point a substantially constant temperature heat
source - unlike a conventional soldering tip the temperature
of which inherently varies somewhat as varying amounts of heat
are drawn therefrom and then replenished along a metal
conduction path. A related advantage is that the gas may be
heated instantly as it flows across, in heat exchange
relation, the heat source and is instantly applied to the work
24101-253
2003575
- la -
point while a conventional soldering tool, exhibiting a
significantly greater degree of thermal inertia, requires that
heat be
24101-253
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~_.~,"..'~ ~," ~, ~.. I;~v ,r,~", ~~~'~'~~-"'.' ~'
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l
i~~~a~J~S
- 2 -
conducted through the solid components of the tool until
the tip,. inherently at some distance from the source,
reaches a temperature adequate for working.
It may also be pointed out that by hot gas techniques,
a thin-walled, low inertia soldering tip may be heated
on its inside by an internally directed stream of hot
gas providing most of the above advantages. In addition,
although the soldAring action is more like conventional
soldering, the tip may be very desirably of iron composition
since copper is not needed for its high thermal conductivity.
Tnusly avoided are the weight and expense of copper and
its plating as well as its high vulnerability to decay
by chemical reactions aggravated by its intense thermal
environment.
These and other advant~g~s of t-~t gas soldering
have not been achieved in the prior art because of the
difficulty of generating the gas stream, satisfactorily
heating it, and providing means for shaping it and directing
it upon the work point.
It is accordingly an object of the present invention
to provide an improved hot gas soldering system.
2003575
- 3 -
SUMMARY OF THE INVENTION
The present invention may be broadly characterized
as hot gas soldering system comprising: base housing body;
electric power supply means carried therein for energizing a
soldering gas heater; electronically remotely controlled
temperature control circuit carried by said housing body; gas
supply flow control means carried by said housing body;
soldering tool holding means carried by said housing body; hot
gas soldering tool having handle portion; electric heating
element carried by said handle portion and coupled to said
electric power supply and said temperature control circuit;
gas heating means connected to said gas supply control means
for transferring heat from said heating element to said gas;
soldering gas jet forming means coupled to said gas heating
means for causing the heated gas to impinge upon and heat a
predetermined soldering point; and combination hose and
electric conductors means connecting said housing body and
said handle portion, the conductors being disposed within said
hose, and said hose also constituting a carrier of said gas
from said housing body to said hot gas soldering tool, said
hot gas tool further including: a hollow metal tubular sheath
carried by said handle portion and extending forwardly
therefrom; a hollow ceramic cylindrical heating element
support tube upon the outer surface of the forward end of
which is disposed said electric heating element; said heating
element support tube being carried within and radially spaced
from said metal tubular sheath to form a first heating chamber
24101-253
2003575
- 3a -
component of said gas heating means; an inner, gas circulator
tube carried by the forward end of said metal tubular sheath
and extending rearwardly therefrom for approximately the
length of said electric heating element and being disposed
within and radially spaced from said hollow ceramic support
tube to form thereby a second heating chamber component of
said gas heating means; and gas flow means connecting to the
interior of said handle portion for carrying gas from said
combination hose means, through the interior of said handle
portion, forwardly along the length of said first heating
chamber, radially inwardly over the forward end of said
ceramic heating element support tube, rearwardly along the
length of said second heating chamber, radially inwardly over
the rear end of said circulator tube, and forwardly toward
said soldering work point.
24101-253
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20035'~S
- 4 -
DESCRIPTIVE LISTING OF DRAWING FIGURES
Embodiments of the present invention will now be
described, by way of example, with reference to the
accompanying drawings, in which
FIGURE 1 is a perspective view of an example of a hot
gas soldering system constructed in accordance
with the principles of the present invention;
FIGURE 2 is a partially exploded perspective view of
the 'base unit thereof;
FIGURE 3 is rear elevational view of the base unit;
FIGURE 4 is a view, partially in longitudinal section,
of the handle and supply cord thereof;
FIGURE 5 is a longitudinal sectional view of the
soldering tip end thereof;
FIGURE 6 is a longitudinal sectional view of portions
of the handle and heater thereof with an
alternate soldering tip;
FIGURE 7 is a cross sectional view of the structure shown
in FIGURE 6 taken along the reference lines
7-7 thereof;
FIGURE 8 is a cross sectional view of the structure shown
in FIGURE 6 taken along the reference lines
8-8 thereof;
FIGURE 9 is a cross sectional view of the structure shown
in FIGURE 6 taken along the reference lines
9-9 thereof;
... _ . ..,. _ ._....~~. _;.::d:.~~~,......~ ,. _... _... .u_
~-.u.~. :~._w:.:;~:.:~r- .:~~ _ ' .. .'_" , ' ' : . '".'.'.' _ .. '. ' ' .' .
_ . _. ~ '
_.. ~r~Oa~J~J
FIGURE 10 is a cross sectional view of the structure shown
in FIGURE 6 taken along the reference lines
10-10 thereof;
FIGURE 11 is a cross sectional view of the structure shown
5 in FIGURE 6 taken along the reference lines
1 1-1 1 thereof ;
FIGURE 12 is an exploded, perspective view of a portion
of the apparatus shown in FIGURE 5.
FIGURE 13 is a similar view of two alternative tip arrange-
ments of the invention.
FIGURES 14, 15 and 16 are similar views of further
alternative tip arrangements all in accord with
the principles of the present invention; and
FIGURE 17 is a view like FIGURE 1 illustrating additional
and a-tern~.tive features of the invention.
20035"~S
- 6 -
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
The example of the invention illustrated in FIGURES 1, 2) and 3
includes a base unit 10) a hand held soldering instrument 12 having a hot
gas tip 14, and an interconnecting supply line 16 for carrying electrical
leads and gas to the instrument 12. A removeable insulated and protec-
tive holder 18 for the instrument 12 is shown attached to the base
housing 20 by the central one of three mating slip-on brackets 22, 23,
24. Alternatively, a pair, not shown, of instruments may be held by the
base housing by utilizing a pair of holders 18 and the two outside
brackets 22, 24.
The housing 20 also carries an electrical power inlet terminal 26,
an auxilliary parallel power outlet terminal 2E, a gas supply inlet
terminal 30 which may be connected to an air compressor, not shown, or
other source o; pressurized gas, a gas supply outlet terminal 32, and an
electrical outlet terminal 34, the latter two terminals being connected,
as shown in FIGURE 1 to the common cord/hose tube of the supply line 16
which in turn is connected to the handle 36 of the soldering instrument
12.
Contained within the housing 20 is a pressure regulator unit 38 for
controlling the flow of gas to the soldering instru~ent 12. The unit 38
includes an on-off valve 40, a regulator control 42, and an output
pressure meter 43.
An electronic circuit board 44 receives power from an external
source via terminal 26 and a pair of internal leads 46, 48. An associ-
ated ground lead 50 connects the terminal 26, the circuit board 44, the
__.__ ,._~._. __.._...,~._...~... . .,. . . . . , , _ ,_ . :. . _ .-., ...
...':'~~~:.*'''_~~v~'"'
20035'5
output terminal 34, and, ultimately, the exposed metal portions of the
soldering instrument 12 to the ground of the external electric power
source. The reference numeral 50 or 50' is used consistently throughout
this description to indicate a lead connecting between articles grounded
or to be grounded.
The electronic circuit of the board 44 is, in this example, of the
character to control remotely the temperature of the heating element of
the soldering instrument 12 by using for a very short portion of the
period of each cycle, including an inflection point, of the applied
alternating current to effect a resistance measurement of the electrical
heating element, the magnitude of that electrical resistance being a
function of its temperature. A signal representative of the instan-
taneous value of the resistance is generated which is used in a feedback
sense to control the current flow to the heating element to cause it to
main'.alr 3 prE.ietermined desired temperature. Thusly, without a separate
sensor in the soldering tip and without separate leads being used for a
temperature feedback signal, essentially full wave power is continuously
impressed on the heater. This technique and its application as hereir is
described in U.S. Patent No. 4,507,546 issued March 26, 1985, and U.S.
Patent No. 4,734,559 issued March 29, 1988, both to William S. Fortune
and Wayne A. Murray. A single control 52 is used for on-off and solder-
ing tip temperature setting. A pilot lamp 54 is shown for indicating
when the circuit is energized and when power is actually being supplied
to the heater element, the different "on" modes being distinguished, for
example, by a constant versus an alternating illumination of the lamp
54.
20035'~S
_8_
To complete the description of the base unit 10 and housing 20) it
may be noted that a tip cleaning sponge 56 moistened by a water, or other
cleaning fluid) reservoir 58 is shown at its forward end. A small tool
tray 60 may be provided, as shown, for holding items such as extra tips,
a tip wrench, or the like. The base unit is molded of a relatively high
density, impact resistant plastic and is preferably carbon loaded or
otherwise made adequately conductive to preclude any build-up of static
charge.
Referring to FIGURE 4, the composite supply line 16 is shown to
include a cable connector 34' for mating with the housing terminal 34 and
carrying four leads: two power leads 62, 64, a fibre optic lead 66, and a
bare ground wire 50' along a connector cord 68 to a Y junction fitting 70
with a gas supply tube 72 for connection by a coupler 74 to the gas
outlet terminal 32. The cord 68 is blocked with respect to passage of
Grey of the gas therethrough. The fitting 70 couples the gas supply tube
72 to the composite supply line 16 whereby gas from the regulator unit 38
is carried through the hollow interior of the line 16 to the interior of
the handle 36 of the soldering instrument 12. An enlarged diameter
retainer bushing 76 is forced within the end of the line 16 inside the
handle 36 to lock the tube to the soldering instrurr~nt. The four leads,
electrical and optic are also carried within the line 16 which may read-
ily be of the character to be appropriately insulative, flexible, and
mechanically protective of the leads. In addition, the material of the
line 16 may be sufficiently loaded or coated to prevent static charge
build-up.
,. . . . . . .,~. . ~ - ~' ,.. .~. , _.,_.-~i _N.r~.n W.L:...,~... _.... ..
......
2G035'~5
- 9 -
It is important to note two effects within the supply 16 as the gas
flows therethrough: 1) static electricity which may otherwise accumulate
because of the gas flow over the dieletric materials therein and cause a
high and deleterious potential is effectively conducted away by the bare
ground lead 50'; and 2) the supply is somewhat preheated by its flow
over the current carrying leads 62, 64 which are warmed due to their
inherent IZR losses.
Surrounding the forward portion of the handle 36 is disposed a
finger guard 78 which includes a large diameter forward flange portion 80
having a central opening through which the base end plug body 82 of the
heater assembly 84 passes. A skirt portion 86 formed integrally and
concentrically with the flange portion 80 extends rearwardly therefrom
over the forward portion of the handle 36. An annular gap is provided
between the skirt portion and the handle's outer surface to insulate the
finger guard and to provide further cooling for operator comfort by the
forced flow therethrough of the pressurized gas from the plenum of the
interior of the handle 36. The actual flow path is shown in detail in
subsequent figures.
The plug body 82 has an enlarged diameter retaining shoulder 88
disposed within the finger guard; and an elastameric o-ring 90 is shown
disposed compressively between the rear of the flange portion 80 and the
retaining shoulder 88. The plug body 82 behind the retaining shoulder 88
is disposed within the forward end of the handle 36 except for a pair of
rotation resisting, mating tabs 92 and notches 94 on these respective
elements. The assembly is held together by a diametrically opposed pair
of locking tabs 96 molded on the exterior of the handle 36 and a matching
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20035"5
- 10 -
set of slots 98 formed on the inner surface of the skirt portion 86.
With the sets of tabs 92 and notches 94 in line, the handle 36 is pushed '
forwardly against the rear of the retaining shoulder 88 which in turn
compresses the o-ring 90 against the flange 80 until the tabs 96 pop into
their respective slots 98. The assembly may be taken apart by pressing
the plastic, deformable skirt portion 86 radially inwardly at a pair of
diametrically opposed points thereon disposed angularly 90° from the
slots 98.
Other elements of the heater assembly 84 illustrated in FIGURE 4 are
the utility threads 100 for affixing special tips and accessories to the
instrument, a portion of its metal sheath 102 with its grounding lug 1~3,
the rear end of the ceramic heater cylinder 104 with one of its electric
terminals 62', 64') and some silastic potting material 106 to plug the
end of the cylinder against airflow therethrough and to retain the fiber
optic lead 66.
Referring to FIGURE 5, the forward end of the heater assembly of
this example of the invention is shown to include the metal sheath 102
terminated at its forward end by a reduced diameter portion formed with
pressed threads 108 manifest on both its inner and outer surfaces. A
retainer bushing 110 is threaded into the inner of the threads 108 until
its forward larger diameter portion 112 is tight against the end of the
metal sheath 102. A central bore 114 retains the forward enlarged
diameter end 116 of a gas circulator tube 118. A threaded nozzle tip
120, as an example of the tip 14 shown in FIGURE 1, is shown screwed onto
the outer of the threads 108 to retain the flanged tube 118 tightly
against and within the retainer bushing 110.
2G035"~5
- - » -
Most of the length of the circulator tube 118 is wrapped with a heat
exchange enhancing filamentary element in the form of a metallic spring
121 wound snugly about its outer surface. This portion of the circulator
tube is disposed within the forward end of the ceramic heater tube 104
axially contiguously to the actual heating element 122 which is deposited
on the ceramic tube 104 then glazed over with a very thin glass or
ceramic insulative coating and may be of the type obtained from, for
example) Kyocera in Kyoto, Japan, Model No. F1495.
Wrapped around the ceramic heater the 104 contiguously to the
heating element 122 is a second heat exchange enhancing filamentary
element in the form of a m eal tape 124 wound snugly over the outer
surface of the ceramic cylinder.
The metallic sheath 102 surrounds the ceramic tube and is spaced
therefrom to form a cylindrical annular heating chamber 125 and path for
the soldering gas. As indicated by the gas flow arrows 126, ga=. from the
handle plenum, as described below, is fed along the annular chamber 125
over the wound tape 124 for enhanced heat pick-up, thence around the end
128 of th;: ceramic tube 104, tack along the inner annular chamber 129
over the spring like element 121 for more turbulence and heat pick-up
from the ceramic heater tube, then forwardly again through the interior
of the collector tube 118, and finally forwardly out through the bore 130
of the nozzle tip 120.
Referring to FIGURE 6, a more detailed view of the interior of the
handle 36 and heater assembly 84 is shown with, however, an alternative
tip arrangement. The full length of the ceramic heater tube 104 is
shown, with one of its electric terminals 62', and silastic material plug
_ .. . __...., ." n , . ._..": , r _ . :':'t.':'- . .. '".~ y...... . . v.J-
_'~~... .. ' T~..., .
''''v 20035"5
- 12 -
106 at its rear, base end. The fibre optic and electric leads 66) 62) 64
are shown schematically) along,with the ground lead 50') extending rear-
wardly from the ceramic tube. An annual spacer ring 132 centers the
ceramic tube 104 within the plug body 82 and a second quantity of
silastic material forms a retaining plug 134 to seal the ceramic tube 104
to the plug body 82. The metal sheath 102 is press fitted into the
forward portion of the plug body and is securely retained therein by its
flared end 136. Gaz flow communication between the annular space 125 and
the plenum interior of the handle 3c is provided by radially extending
bores 138 in the wall of the plug body 82. Gas flow between the plenum
and the annular space between the skirt portion 86 of the finger guard 78
and the outer surface of the handle 36 is provided by the axial annular
gap 140 between the retaining shoulder 88 of the plug body 82 and the
forward end of the handle 36 which is maintained by the contact of the
extra length of locking tab 92 in the shorter notch 94 of the h~~dle 36
(see FIGURE 4).
The fibre optic lead 66 which extends from, in this example, a light
so~r,:e 66' on the circuit board 44 is shown terminated in a lens 142 for
projecting light forwardly along the central bore of the soldering
instrument whereby a beam of light normally illuminates the work point
for the operator and shows him where the hot gas will impinge upon the
work piece. This feature may be understood by considering the basic hot
gas nozzle tip arrangement of FIGURE 5 since in the alternative arrange-
ment of FIGURE 6, the central bore is optically blocked by a solid tip
144 which is held in place by a retainer nut 146 threaded onto the outer
of the threads 108 of the metal sheath 102. An inwardly extending
. ..,.. .w...._ wy. . ..."...a .. _.~.....vLiC.._..r.... .. ._...~ ._ . ..
.........~..~. . u...~ J.._. :.... ... . , . .. .... ~ ' _ . ~ .. . . . _ ..
,. .. . . . . . . . . . .., ..... ~! a ... ,: ~ J' ~.w" . ~. . ~ ~' Y .. .-
20035'5
_ 13 _
retaining shoulder 148 of the nut 146 engages an outwardly extending
shoulder 150 on the body. of the tip '144. The nut 146 is turned onto the
threads 108 until the base end of the tip is compressed tightly against a
fixed collar 152 on an elongated gas circulator tube 154 which extends
well into the heater portion of the ceramic tube 104 and forwardly con-
centrically into an oversized central bore 156 in the tip 144. The bore
extends axially forwardly of the end of the circulator tube whereby the
hot gas flowing through the long, central bore 155 of the circulator tube
154 passes out of its forward end and impinges upon the forward bottom of
the bore 156 of the tip 144 and returns along the annular gap 158 between
the tube 154 a-v the bore 156 and exhausts through radially directed
ports 160. It may be noted that the forward inner surface 147 of the nut
146 is conically shaped for turning the exhausted gas forwardly toward
the work point. This feature not only provides a means for blowing
overly noxious fumes from the work area but may, when desired, be used to
preheat gently the general area of the work point.
In this form of the invention, the tip functions much as a conven-
tional soldering tip but with the advantage that it heats very quickly
since the heat is carried by fast flowing hot gas and not by conduction
through a high inertia metal path. Accordingly, the tip materials can be
of iron instead of copper and iron plated copper thus avoiding the highly
undesireable plating process and its expense as well as the weight and
corrosion vulnerability of copper. It should be noted that aat IIPatP(I
tips according to this invention may be considerably thinner walled than
implied by the geometry of the tip 144 as illustrated.
I~r~oa.~J~J
- 19 -
FIGURE 7 is an enlarged cross section view taken through the tip 144
showing its solid iron body, the circulator tube 154, the central gas
f low path of the bore 155, and the return path of the annul ar gap 158
between the tip and the inner tube.
FIGURE 8 is similar view taken further rearwardly and showing the
exhaust bores 160 and the gas directing conical forward surface 147 of
the retainer nut 146.
FIGURE 9 is a crops sectional view taken further rearwardly and
shows the ceramic heater tube 104 with its deposited heater element 122
and wrapped by the flat metal tape 124 heat exchange enhancer. Concen-
trica Os disposed within the ceramic heater tube is the gas circulator
tube 154 similarly wrapped by the spring-like 121 heat exchange enhancer.
This view illustrates the three concentric, in-cascade hot gas flow
paths: the annular gap 125 over the tape 124 and between the outer metal
sheath 102, the annular gap 129 over the spring 121 and between the
ceramic tube 104 and the inner tube 154 and finally the inner bore 155
thereof.
Referring to FIGURE 10, the essentially concentric geometry of the
handle portion of the soldering instrument 12 is shown to include the
outer handle portion 36 circumscribed by the skirt portion 86 of the
finger guard 78. The locking tabs 96 and slots 98 thereof arP ~hnwn in
elevation and dashed lines, respectively. The angular locking tabs 92
and notches 94 of the plug body 82 and handle portion 36, respectively,
are also illustrated in this view. Immediately radially inwardly of the
plug body 82 is shown the metal sheath 102 just forwardly of its flared
rear end 136. This view also shows its groundirj lug 103 extending
.y..~...~...... .... . .~ - ' - ~ . . ,. .. w... .. - , - ..- . ~~......., v .
.~..,~.,.s~v ~ y'r. , -~'~-=.. ~,~y:,lY~~ ~ ~yL~~i~l:..~ 7s r.
20035"~S
- 1s -
rearwardly from the metal sheath 102. In turn, within the metal sheath
is disposed the ceramic tube 104 and the fiber optic lead 66.
The similar view of FIGURE 11 taken just rearwardly of the previous
figure shows again the outer skirt portion 86 of the finger guard 78, the
handle portion 36 and the locking tabs 96 and slots 98 thereof, the rear
portion of plug body 82 filled with the silastic potting material 134,
the rear portion of the ceramic heater tube 104, and the inner fiber
optic lead 66.
In FIGURES .2) 13, 14, 15, and 16, a series of alternative hot gas
soldering tips and their respective circulator tubes are shown.
The combination of FIGURE 12 is essentially like that shown in
FIGURE 5 except that the retainer bushing 110' is fabricated integrally
with the circulator tube 118' and is not threaded. The bushing 110' -
tube 118' and heat exchange enhancer spring 121 are retained within the
end of the sl eeve 102 by screw i ng the thre4 ied nozzl a ti p 120 onto the
threads 108 of the forward end of the sleeve 102.
In FIGURE 13, two examples are shown which are similar to that of
FIGURE 6 except that the elongated gas circulator tube 154 is used to
direct a well defined stream of hot gas directly onto the work point
instead of to heat the rear, inner surface of a tip 144; that is, the tip
144 is simply removed from behind the retainer nut 146 so that the
forward end of the circulator tube 154 may direct the hot gas directly to
the work point. The other example of FIGURE 13 combines the circulator
tube 118' of the structure shown in FIGURE 12 with a finer, smaller
diameter forward extension tube 164 having a central retaining collar 165
and the rear port i on 166 of wh i ch f i is w i t!~ i n the c i rcul ator
tube 118'
20035"~S
- 16 -
and forward portion 168 of which extends beyond the retainer nut 146 for
use, when a particularly fine and precise jet of soldering gas is desired.
In FI6URE 14) the example shown is essentially like that of FIGURE 6
shown in an exploded form without the retainer bushing 110, for simplic-
ity, and with a spade, or chisel shaped tip 114'.
Referring to FIGURE 15, the forward end structure of FIGURE 12 is
repeated except that the threaded nozzle tip 120 is shown replaced by a
heavy duty, internally threaded tip 170.
FIGU'_ 16 illustrates the same structure again except that the
special, internally threaded tip 172 in this case is in the form of a
rectangular oven over the peripheral edges 174 of which the hot gas flows
when placed closely over a surface mounted circuit board device. With
such a tip all the soldering terminals of such a surface mounted device
may be melted at one time for ease of soldering or desoldering it with
respect to the circuit board.
Referring to FIGURE 17, the basic structure shown in FIGURE 1 is
illustrated showing, however, a number of additional or alternative
features of a hot gas soldering system which may be considered to be
essentially self contained. To this end a compact electric compressor
180 is mounted within the base housing 20 with its associated control
unit 182. The compressor may be controlled with respect to its on or off
modes by the toggle switch 40, by a foot switch 184, or by a contact
switch 186 which is activated by withdraw al of the soldering unit 12 from
its holder 18. Either of the latter type of controls may be used on a
"momentary contact" basis whereby the compressor operates and supplies
air flow only when actually desired thus minimizing power consumption,
) .... . _ .: . , . ..°:'. .._.
2GU35'~S
- 17 -
wear on the compressor's mechanical parts, and noise in the environment
of the tool. Further in the latter regard a filter-muffler unit 188 may
be carried by the housing 20 further to quiet the operation of the com-
pressor.
Utilizing the input to the compressor as a vacuum source is a major
feature of this example of the invention. A vacuur~ hose 190 terminated
in a vacuum nozzle 192 may be used for noxious soldering fumes removal at
the workpiece and/or for desoldering when desired. For utilization in
such mode, the nozzle 192 preferably contains a removeable filter system
consisting of a steel wool cartridge 191 for collection of course pieces
of solder and a felt disc 193 for collecting smaller bits of solder and
solidified resin and the like.
The base housing 20 may also carry a transformer 194 to convert high
voltage line power to, for example, 12 or 24 volts for energizing the
compressor, the heater, the fiber optics, and all control functions.
There have th~~s beer. jisclosed and described here a number of
examples of a hot gas soldering system which achieves the objects and
exhibits the various advantages discussed above.
