An automatic dross removal apparatus (10) is disclosed for removing dross from the surface of a solder bath (22) in an automated electric component handling system. A rotatable wiper blade (14) is positioned adjacent the solder bath (22) which skims the dross off of the surface prior to the dipping of a robot conveyed component into the bath. An electronic control circuit (34) causes a motor (32) to rotate the wiper arm (14) one full rotational cycle each time a pulse is received from a robot controller (44) as a component approaches the solder bath (22)

Webb, Winston S.

NASA Technical Reports Server

US005087356A 
United States Patent 1191 [ i l l  Patent Number: 5,087,356 
Webb [45] Date of Patent: Feb. 11, 1992 
[54] SOLDER DROSS REMOVAL APPARATUS 
[75] Inventor: Winston S. Webb, Duaedin, Fla. 
4,332,373 6/1982 Huppunen et al. ................. 266/228 
4,509,670 4/1985 Cammarata ........................ 22W56.2 
4,705,998 1/1987 Millerd et al. ................... 1V250.17 
Primary Examiner-Robert A. Dawson 
by Of Assistant Examiner-David Reifsnyder 
Attorney, Agent, or Firm-Robert L. Broad, Jr.; Jerry L. 
Seemann 
[73] Assignee: The United States of America as 
the Aeronautics 
Administration, Washington, D.C. 
Appl. No.: 524,110 
Filed: Mny 16,1990 
Int. C l . 5  ......................... BOlD 21/30, B23K 1/00 
US.  Cl. .................................... 210/143; 210/523; 
210/525; 2 10/528; 266/78; 266/92; 266/228; 
228/34; 22W56.2; 15/250.17 
Field of Servch ............... 210/143, 523, 525, 528, 
210/531, 923; 266/78, 228, 92; 15/250.17; 
228/56.2, 34; 318/444 
[571 ABSTRAtX 
An automatic dross removal apparatus (10) is disclosed 
for removing dross from the surface of a solder bath 
(22) in an automated electric component handling sys- 
tem. A rotatable wiper blade (14) is positioned adjacent 
the solder bath (22) which skims the dross off of the 
surface prior to the dipping of a robot conveyed compo- 
nent into the bath. An electronic control circuit (34) 
causes a motor (32) to rotate the wber  arm (14) one full 
. I  . ,  
[561 References Cited rotational cycle each time a pulse is received from a 
robot controller (44) as a component approaches the 
solder bath (22). 
U.S. PATENT DOCUMENTS 
3,941,360 3/1976 Blank ................................... 266/228 
3,980,219 9/1976 Schmid ................................. 228/34 
4,007,119 2/1977 Antonevich ........................ 210/523 6 Claims, 2 Drawing Sheets 
22 
44 34 
https://ntrs.nasa.gov/search.jsp?R=20080004351 2019-08-30T02:33:18+00:00Z
U.S. Patent Feb. 11, 1992 Sheet 1 of 2 5,087,356 
44 34 
U.S. Patent Feb. 11, 1992 Sheet 2 of 2 
INPUT 
FROM 
ROBOT 
C 0 N TR OUER 
44 
5,087,356 
34 
FIG.3 
FIG.4 
1 
SOLDER DROSS REMOVAL APPARATUS 
5,087,356 
2 
BEST MODE FOR CARRYING OUT THE 
INVENTION 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
&t to the provisions Of Section 305 Of the National 
Aeronautics and Space Act of 1958, as amended, (42 
USC 2457). 
Turning now to a more detailed consideration of the 
5 present invention, a solder dross removal apparatus is 
illustrated in FIG. generally at which includes a 
rotatable shaft and arm assembly 12 having a wiper 
blade 14 attached to a free end 16 thereof. The appara- 
tus 10 is attached by means of a support bracket 18 to 
10 the side of an electric solder heater pot 20 which con- 
tains a molten solder bath 22 for use in tinning the leads 
of electrical components. A circular cam wheel 24 is 
attached to the support bracket 18 by means of a plural- 
ity of support arms 25 which guides the arm 12 as it 
15 rotates on a teflon slide bearing 26. As illustrated in 
FIG. 1, the cam wheel 24 is disposed at an inclined 
angle relative to the surface of the solder bath 22 so that 
1. Technical Field 
The present invention relates in general to a solder 
dross removal apparatus for removing dross and burnt 
flux from a static solder pot in an automated electronic 
component preparation system. 
2. Background Art 
ln electronic component preparation sys- 
w, the components me typically assembled to printed 
wiring boards or after having their leads tinned 
as the be dipped 
into the solder bath 22 and then raised IIboVe the bath SO 
12 rotates, the wiper blade l4 
20 that it will clear the edge of the pot 20. This action 
cBuses the wiper blade 14 to skim the top of the 
illustrated by the dash lines in FIG. 2. The dross and 
burnt flux that is removed from the clean area 28 is 
in a molten solder bath. Wave soldering machines have 
is agitated so that the solder rises in waves against the 
component leads as the conveyed 
ing machines is that the waves are unsteady and hard to 
control which makes positioning Of the Components 
relative to the soldering machine difficult. The use of a 
static solder pot remedies this problem, however, a top To control the intermittent rotation of the shaft and 
kyer of dross and burnt flux which adversely affects the 30 arm assembly 12, an electric gear motor 32 of conven- 
quality of the solder process quickly builds up if the tional design is attached thereto which is operated by 
solder is not agitated. signals from a motor control circuit 34 that is electri- 
cally connected to the motor 32 via a line 36. The motor 
DISCLOSURE OF INVENTION 32 rotates the shaft and arm assembly 12 so that the 
It is therefore the object of the present invention to 35 wiper blade 14 travels at a suitable Speed, such as aP- 
provide an apparatus for removing dross from a static ProfimatelY 3.5 inches per second. A 
solder pot in an automated electronic component prepa- actuated switch 38 is attached to the cam 
bly 12 will contact it and cause switch 38 to close as the are achieved through provision of an automatic dross 4o arm cOntaCtS switch 38. The switch 38 is electrically 
removing apparatus which includes a rotatable wiper connected via a line 4o to the 
blade that skims across the top surface of a solder bath which in turn is connected via a he 42 to a robot con- 
in a pot and moves the dross to one side so that a clean troller &. 
solder surface is provided each t h e  a component is ne =hematic for the motor control circuit 34 is 
dipped into the bath by a robot arm. The wiper is ro- 45 illustrated in FIG. 3 and essentially comprises a transis- 
to control signals from a robot controller so that the motor 32 and is controlled by the output of an OR gate 
wiper sweeps the dross just before the robot arm dips a 52 connected to a base 53 of the transistor switch 50. 
component into the solder bath. In this manner, the The OR gate 52 has two inputs, a first input from the 
cleanest possible solder surface will be provided for 50 robot controller 44 which generates a pulse in response 
each component before it is dipped into the solder bath. to the approach of a component to be dipped in the 
solder bath 22 on a robot arm, and a second input from 
BRIEF DESCRIPTION OF DRAWINGS ground through the switch 38. A five volt DC source is 
The foregoing and additional objects, features and connected though a Pair of Pull-up resistors 5) to the 
d v a t a g e s  ofthe p r a n t  invention will become appar- 55 inputs of the OR gate 52. In this manner, whenever 
from the following detailed dtscription thereof, either the switch 38 is open circuited or a pulse is gener- 
ated by the robot controller 44, the output of the OR 
gate 52 will be high so that the transistor switch 50 will taken in conjunction with the accompanying drawings 
complete the circuit to the motor 32 and the motor 32 in which: FIG. 1 is a side view of a preferred embodiment of d l  be to thereby rotate shaft and arm 
the present invention, showing a solder pot in cross assembly 
Kction; The timing diagram for the motor control circuit 34 is 
FIG. 2 is a top view of a preferred embodiment of the illustrated in FIG. 4. the robot arm approaches the 
present invention; solder bath with a component to be dipped therein, a 
FIG. 3 is a schematic circuit diagram Of a motor 65 short pulse of approfimately 100 &]iwconds appears 
control circuit for a preferred embodiment of the pres- on the input from the robot controller. 44 and the OR 
mt invention; and, gate 52 generates a high output so that the motor 32 is 
FIG. 4 is a timing diagram for the circuit of FIG. 3. actuated and rotates the arm assembly 12. AS this hap- 
ken used for this Purpose and a bath that =]der bath 22 and form a clean =ea of solder 28 as 
above the bath. A difficulty with these types of solder- 25 moved to one side of the solder pot 20 as illustrated 
at 30. Preferably, the arm assembly is 
tioned so that the wiper blade 14 skims the top approxi- 
mately 0.150 microns of the solder bath 22. 
ration system. This and other objects of the invention 24 such a position that the arm 
control circuit 
Wed by motor that is intermittently driven in response tor switch 50 that is placed in a ground h e  51 for the 
5.087.356 
3 
pens, the switch 38 will open so that the output of the 
OR gate 52 will remain high and the arm assembly 12 
will continue to rotate through one full rotation cycle 
until the arm closes the switch 38 once again and the 
motor 32 stops. This cycle repeats each time a pulse is 
sent by the robot controller 44 to the OR gate 52. 
In the above manner, the present invention provides 
an apparatus for sweeping dross off the surface of a 
molten solder bath that is automatically operated in 
response to a trigger pulse each time a component to be 
dipped into the solder bath approaches the bath on a 
robot arm. The invention thereby enables the use of a 
static solder pot which ensures accurate positioning of 
the solder bath relative to the components to be dipped 
therein and eliminates dross build up problems that are 
normally associated with such static solder pots. 
Although the invention has been disclosed in terms of 
a preferred embodiment, it should be understood that 
numerous modifications and variations could be made 
thereto without departing from the true spirit and scope 
thereof as defrned by the following claims. 
I claim: 
1. Apparatus for removal of dross from a top surface 
a) a pot containing a bath; 
b) a rotatable wiper means positioned adjacent said 
pot so that said wiper means will skim the surface 
of said bath as the wiper means rotates; 
c) motor means attached to said rotatable wiper 
means to rotate the same; 
d) switch means disposed adjacent said rotatable 
wiper means and operable by said rotatable wiper 
means to disconnect power to said motor means 
once every revolution of said wiper means; and 
e) means to override said switch means and supply 
power to said motor means in response to an ele- 
ment approaching said pot to be dipped therein. 
2. The apparatus of claim 1 wherein said means to 
override further comprises: 
a transistor switch disposed in a ground line for said 
motor means; and, 
an OR gate having an output connected to a base of 
said transistor switch, a first input connected to an 
output of said switch means disposed adjacent said 
rotatable wiper means, and a second input con- 
of a bath comprising: 
4 
nected to a means for generating a pulse in response 
to an element approaching said pot to be dipped 
therein. 
3. The apparatus of claim 2 wherein said bath is a said 
5 solder bath and said means to override operates in re- 
sponse to an electronic component approaching said pot 
to be dipped therein by an automated component han- 
dling system. 
4. An apparatus for removal of dross from a top sur- 
a) a pot containing a solder bath; 
b) a rotatable wiper means positioned adjacent said 
pot to skim the surface of said bath as the wiper 
means rotates; 
c)  motor means attached to said rotatable wiper 
means to rotate the same; and, 
d) a motor control circuit for said motor means in- 
cluding; 
i) means to actuate said motor means in response to 
a signal pulse received from a robot controller 
indicating that an electrical component to be 
dipped in said solder bath is approaching said 
solder bath; and 
ii) means to deactuate said motor means automati- 
cally after said rotatable wiper means has 
skimmed the surface of said bath once. 
5. The apparatus of claim 4 wherein said means to 
switch means disposed adjacent said rotatable wiper 
means and operable by said rotatable wiper means 
to disconnect power to said motor means once 
every revolution of said wiper means. 
6. The apparatus of claim 5 wherein said means to 
a transistor switch disposed in a power line for said 
motor means; and, 
an OR gate having an output connected to a base of 
said transistor switch, a first input connected to an 
output of said switch means disposed adjacent said 
rotatable wiper means, and a second input con- 
nected to said robot controller for receiving a sig- 
nal pulse in response to an electronic component 
approaching said solder bath to be dipped therein. 
lo  face of a solder bath comprising: 
l5 
20 
25 
deactuate said motor means comprises: 
30 
35 actuate said motor means comprises: 
40 
* * * * *  45 
55 
65 


Solder dross removal apparatus

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