Dual intermittent microflame system for discrete point soldering

A dual intermittent microflame system for discrete point soldering comprising first and second gas valves which are each connected to a source of combustible gas and a source of non-combustible gas. A flashback arrestor is imposed between each of the gas valves and the sources of combustible gas. A pair of gas lines connect the gas outlets of the first and second gas valves to first and second microflame nozzle tips which have ignition electrodes position adjacent thereto for igniting the nozzle tips. A workpiece holder is positioned adjacent the nozzle tips for positioning a workpiece adjacent thereto so that the tips are able to solder a pair of solder points.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a dual intermittent microflame system for 
discrete point soldering and more particularly to a dual intermittent 
microflame system for discrete point soldering including a positive flow 
purge system to prevent flashback of combustible gas and oxygen. 
2. Description of the Prior Art 
Microflame soldering is well-known in the art and the requirements and 
technology therefore are disclosed in U.S. Pat. No. 5,169,053. In 
addition, see also U.S. Pat. Nos. 3,957,618; 4,113,601; 4,206,029; and 
4,336,122. Generally speaking, many microflame systems such as illustrated 
in FIG. 1 include a generator which generates combustible gas which is 
delivered to a booster system for lowering the flame temperature, with the 
booster being connected to one or more torches. Most microflame soldering 
systems utilize a combustible gas mixture of hydrogen and oxygen. The 
mixture of hydrogen and oxygen will burn within the supply hoses if 
ignited. Normally, the flame at the nozzle tip does not ignite the 
combustible gas within the supply hoses because the combustible gas 
pressure is maintained by its supply, thereby preventing the flame from 
travelling back from the flame nozzle tip into the gas supply hose. 
Flashback is initiated from the flame nozzle tip when the external flame 
travels back into the gas supply hose when the gas pressure lowers as it 
exits the open flame nozzle tip. 
The requirements in technology for high speed discrete point soldering, as 
disclosed in U.S. Pat. No. 5,169,053, have been established since the 
middle 1980s. The constraints of this technology have also been 
established with respect to cost, physical size and space required for the 
flame tip to swing into position, variability in heating and operator 
setup. With respect to cost, a conventional rotary microflame system 
generally consists of a gas supply, electrical gas valve, control system, 
flashback protection device, pneumatic rotary actuator, pneumatic pressure 
regulator, pneumatic flow controls, electronic pneumatic actuation valve, 
a pair of rotary travel stops, a pair of electrical rotary position 
sensors, timing belt drive, housing, rotary flame tip holder, and flame 
tip nozzle. 
The physical size of the conventional rotary microflame housing is 
determined by the size of the rotary flame tip and is rotary actuated. The 
relatively large actuator size can prohibit access to some of the 
components to be soldered. In addition, other adjacent components are 
sometimes sensitive to the heat of the microflame as it is rotated into 
position to heat the parts to be soldered. 
Heating of the parts to be soldered is affected by the actual time the 
flame is directed at the part. The pneumatic rotary actuator is affected 
by air pressure, air lubrication, pneumatic flow control, and the 
condition of the rotary actuator. 
Control of the pneumatic rotary actuator of the prior art is critical 
because of the significant time it takes to apply heat to (400 
milliseconds) and redirect heat (400 milliseconds) from the point to be 
soldered compared to the relatively short overall cycle time (900 
milliseconds). With this rapid cycle time, the operator usually makes the 
corrections on a trial and test basis. 
In the closed loop temperature based prior art systems, after the cycle is 
initiated, the gas valve is energized to feed gas to the nozzle tip, the 
electronic ignition creates a spark to the nozzle tip to ignite the gas, 
thereby causing a flame, the flame heats the part to the required 
temperature as determined by the temperature sensor, and the gas valve is 
then de-energized to shut off the flame. 
SUMMARY OF THE INVENTION 
A dual intermittent microflame system for discrete point soldering is 
disclosed comprising a source of combustible gas, a source of 
non-combustible gas, a first gas valve having first and second gas inlets 
and a gas outlet, a second gas valve having first and second gas inlets, 
and a gas outlet. Each of gas valves are movable between "off" and "on" 
positions. First and second gas lines connect the source of combustible 
gas to the first gas inlets of the first and second gas valves, 
respectively. A flashback arrestor is imposed in each of the first and 
second gas lines. Third and fourth gas lines connect the source of 
non-combustible gas to the second gas inlets of the first and second gas 
valves, respectively. The system includes a pair of spaced-apart first and 
second microflame nozzle tips with fifth and sixth gas lines connecting 
the gas outlets of the first and second gas valves to the first and second 
microflame nozzle tips, respectively. An ignition electrode is positioned 
adjacent each of the microflame nozzle tips for igniting the microflame 
nozzle tips. A workpiece holding apparatus is provided for positioning a 
workpiece adjacent the microflame nozzle tips whereby the tips are able to 
solder a pair of solder points. 
A principal object of the invention is to provide a dual intermittent 
microflame system for discrete point soldering which lowers gas 
consumption as the flame and its gas flow are required only for the actual 
time the flame is heating the part. 
Still another object of the invention is to provide a dual intermittent 
microflame system for discrete point soldering which has a lower 
acquisition cost as the system requires approximately 75% less components 
than the conventional rotary actuator systems. 
Still another object of the invention is to provide a dual intermittent 
microflame system for discrete point soldering which has lower operating 
costs than the prior art devices and which is more reliable and accurate 
than the conventional rotary actuator systems of the prior art. 
Yet another object of the invention is to provide a dual intermittent 
microflame system for discrete point soldering which provides improved 
part production quality as the closed loop IMF system controls the process 
based on the actual heat of the part, not the time that it should have 
taken to achieve the optimal temperature, thereby eliminating the 
variability caused by ambient conditions, part size and fit variations, 
machine fixture conditions, operator setup, etc. 
Still another object of the invention is to provide a dual intermittent 
microflame system which provides improved safety due to the elimination of 
the flashback condition when the electrical gas valve is de-energized to 
cut off the combustible gas supply to the microflame nozzle tip to 
extinguish the flame. 
Still another object of the invention is to provide a compact and portable 
dual intermittent microflame system for discrete point soldering. 
These and other objects will be apparent to those skilled in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 and 2 illustrate prior art devices. In FIG. 1, the numeral 10 
refers to a combustible gas generator having a combustible gas supply line 
12 extending therefrom to one or more canisters 14 having a fuel supply 
line 16 extending therefrom to a torch handle 18 having a flame nozzle tip 
20. Normally, a flashback arrestor 22 is provided in the supply line which 
extends from gas valve 24 which is in communication with the canisters 14. 
Flashback is a problem with the configuration illustrated in FIG. 2 when 
the electrical gas valve 24 is de-energized to shut off the gas supply and 
extinguish the flame. This causes the loss of gas pressure as it exits the 
open flame nozzle tip 20. The flashback is initiated from the flame nozzle 
tip 20 when the external flame travels back into the gas supply hose 16. 
The flashback is arrested by the flashback protection device 22 to prevent 
ignition of the combustible gas supply. However, the noise of the 
explosion, similar to a small caliber gunshot, and the reassembly of the 
gas supply hose 16 is an annoyance. In addition, the flashback protection 
device 22 must be periodically replaced, as the flashback explosions can 
damage the same. A further problem with the configuration of FIG. 2 is 
that the electrical gas valve 24 is located between the combustible gas 
supply 14 and the flashback protection device 22 inasmuch as the 
electrical gas valve 24 is a potential ignition source of the combustible 
gas supply and there is nothing to prevent the flashback to reach the 
combustible gas supply. 
The positive flow purge system for use with the dual intermittent 
microflame system of this invention is illustrated in FIGS. 3, 4A and 4B. 
The positive flow purge system of FIGS. 1-4 is also described in my 
co-pending patent application entitled "POSITIVE FLOW PURGE SYSTEM FOR 
MICROFLAME TORCH". In FIG. 3, the numeral 30 refers to a two-position, 
three-port, electrical gas control valve having gas inlets 32 and 34 and 
gas outlet 36. Supply line 38 extends from gas outlet 36 to the flame 
nozzle tip 40. The numeral 42 refers to a conventional flashback 
protection device or arrestor, such as illustrated in FIG. 2, but which is 
positioned at the upstream side of the gas control valve 30 and which is 
connected to the gas inlet 34 by supply hose 44. The inlet end of 
flashback protection device 42 is connected to the canisters 14 which are 
connected in series and which are connected to the combustible gas 
generator by hose 46. Gas inlet 32 is connected to a source of low 
pressure, noncombustible gas such as compressed air by means of supply 
hose 48. 
FIGS. 4A and 4B schematically represent the "on" and "off" positions of the 
valve 30. When the valve 38 is in the "on" position, as illustrated in 
FIG. 4A, the combustible gas is supplied to the flame nozzle tip 40 by 
means of the hose or supply line 38. When in the position of FIG. 4A, the 
non-combustible gas is routed to the flame tip by the open valve port 
which permits the non-combustible gas to flow continuously to the flame 
nozzle tip 40 which is connected to the exit port of the valve, thereby 
causing the flame to be extinguished when the gas valve is de-energized so 
that flashback into the supply hose 38 is prevented, due to the flow of 
non-combustible gas through the flame nozzle tip 40. The positive flow 
purge system of this invention eliminates flashbacks within the gas supply 
hoses and its potential ignition of the combustible gas supply by 
maintaining the pressure within the gas supply hoses with a 
non-combustible gas, thereby preventing flashback within the gas supply 
hoses when the gas valve is de-energized to extinguish the flame. The 
positive flow purge system of this invention improves the safety of 
microflame technology and its commercial application by reducing the risk 
of flashbacks. 
FIGS. 5-8 illustrate a dual intermittent microflame system for discretely 
soldering a pair of solder points such as is required on a vehicle back 
glass 50 having heating wires 52 embedded therein or placed thereon. As 
seen in FIG. 9, a pair of terminals 54 are provided at opposite ends of 
the back glass 50 with each of the terminals 54 having a pair of 
connectors which are soldered to a pair of leads or wires, respectively. 
The dual intermittent microflame system of this invention is suited for 
soldering the terminals 54 to the back glass 50. In FIGS. 5-8, the numeral 
14' refers to a canister, such as illustrated in FIGS. 1 and 2, and having 
fuel line 46' extending therefrom to the flashback protection device or 
flashback arrestor 42'. Flashback protective device 42' is provided with a 
T-connector 56 having gas hoses 44' and 44" extending therefrom to the gas 
inlets 34' and 34" on the gas valves 30' and 30", respectively. Gas line 
48' is connected to the source of non-combustible fuel and has a 
T-connector 58 connected thereto from which extends gas lines 60 and 62. 
Gas lines 60 and 62 are connected to the gas inlets 32' and 32", 
respectively. Gas lines 38' and 38" extend from gas outlets 36' and 36" to 
the microflame nozzle tips 40' and 40". Conventional igniter electrodes 62 
and 64 are provided for igniting the flame tips. The numeral 66 refers 
generally to a workpiece holding apparatus for supporting the back glass 
50 thereon below the terminal holding apparatus 68, which is adapted to 
receive and support the terminal 54 therein so that the terminal contacts 
70 and 72 of the terminal 54 are positioned above the back glass 50, as 
illustrated in FIG. 7. After the back glass 50 has been positioned on the 
workpiece holding apparatus 66 in the manner illustrated in FIG. 7, the 
workpiece holding apparatus 66 is moved vertically with respect to the 
terminal contacts 70 and 72 to bring the terminal contacts 70 and 72 into 
contact with a pair of wires or heating elements at one end of the back 
glass 50. The control system for the apparatus is then operated to ignite 
the flame nozzle tips 40' and 40" to solder the terminal contacts 70 and 
72 to the wires or heating elements at one end of the back glass 50. When 
the soldering operation has been performed, the flames at the tips 40' and 
40" are extinguished and the workpiece holding apparatus 66 is lowered 
with the terminal 54 being pulled from the holding apparatus 68. The back 
glass 50 is then manipulated so that the other end of the back glass is 
properly positioned on the workpiece holding apparatus 66. A second 
terminal 54 is the inserted into the holding apparatus 68 and the 
procedure is repeated. 
Although the system of this invention is ideally suited for dual discrete 
point soldering, the system is well-suited for single discrete point 
soldering or multiple discrete points soldering. Further, the system of 
this invention could also be used with only combustible gas, however, the 
use of both combustible and non-combustible gases is preferred. 
Thus it can be seen that the invention accomplishes at least all of its 
stated objectives.