Universal pneumatic parts locating system

A printer table including a series of angled jets for sources of air and for sources of vacuum and also including a set of locating pins. The combination enables the use of the directed jets to move a substrate into position for processing and to hold the substrate in position once located by the locating pins with the use of a vacuum. Because the substrates are very thin and the locating pins are very short, the combined use of the vacuum and directing jets effectively permit the substrate to float on air in close proximity to the table surface while not overriding the locating pins.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed to the mechanical locating of circuit 
substrates during the manufacturing process; and more particularly to a 
work or printer table arrangement for use in locating alumina substrates 
for laser scribing during thick film circuit pattern printing. 
2. Background Art 
In previous arrangements, substrates were typically pushed manually against 
the locating pins of the printer table and then fixed in position by a 
vacuum actuated by an operator's footswitch. This particular method was 
slow and inconsistent in alignment as well as inconsistent in loading 
force often resulting in damage to the substrates. 
Upon automation of the thick film printers, the substrates were positioned 
by a mechanical locating mechanism. The mechanism in one particular 
example consisted of six spring-loaded linkages driven by a linear cam 
with a vacuum, actuated by a limit switch fixing the substrate position 
after locating was complete. 
In this particular system, four major problems developed. The first of 
these was positioning and timing of the linkages which was difficult and 
time consuming; second, the linkages would often wear out over time 
requiring replacement; third, the linkages had to be adjusted each time 
the substrate thickness or pattern orientation was changed; and fourth, 
the system could only handle rectangular substrates within a plus or minus 
one percent size specification. 
Another variation of this system utilized air cylinders and limit switches 
to actuate the linkages instead of springs and cams. The system decreased 
the number of required linkages but was rough on the substrates, often 
causing damage. Also, as with the previously outlined system, it required 
adjustment depending on the substrate thicknesses and pattern orientation 
and could not be used for oddly-sized or shaped parts. 
In addition, due to the space requirements of both these systems, they were 
only applicable to the printing machinery and could not be utilized in 
laser scribing and laser trimming operations. These functions remained 
manual operations. 
SUMMARY OF THE INVENTION 
In the process of printing thick film circuits on thin alumina substrates, 
consistent and repeatable substrate location is of primary importance. 
Registration of plus or minus 0.001 inch must be maintained during 
possibly fifteen different operations on fifteen different machines and on 
both sides of the substrate. A pattern of three locating pins is repeated 
on all machinery for this purpose. 
For automation purposes, placement of substrates against the locating pins 
had to be done without manual labor. In the past, mechanical devices such 
as linkages and air cylinders were used with varying success. Typical 
problems encountered were mechanical wear, alignment loss, inconsistent 
location and inflexibility. 
To improve on current "moving parts" methods of substrate locating, it was 
decided that the parts should be moved by directional air to simulate a 
frictionless surface similar to that used on an air hockey table. Properly 
aimed air jets would float a substrate against the pins and hold it there 
as long as the table surface was level and stationery to eliminate 
additional forces. The system was not susceptible to external forces such 
as gravity due to the virtually frictionless surface provided over which 
the chips could be moved. 
The most difficult application for the air jet system is in the printing 
process. The printing process is difficult because the requirement that 
the locating pins remain below the surface of a 0.025 inch thick 
substrate. The method had to be established to maintain a minimum air gap 
so that the parts would not float over the very short locating pins. It 
was soon discovered that air sufficient to move the substrates could 
overcome the vacuum used to fix substrate location during the actual 
printing cycle. By allowing the vacuum to stay on during locating 
concurrently with the air jets, a gap of 0.010 inch was achieved. The 
vacuum had the added advantage of lessening the bouncing of the substrates 
against the pins. 
The successful use of the air jet locating system has solved many of the 
major problems inherent to the mechanical and manual techniques previously 
found. Since the air system has no moving parts to wear out, replace or 
realign, most maintenance requirements are thus eliminated. The air 
arrangement works faster than previous methods and puts virtually no 
compression forces onto the substrate, therefore eliminating the breaking 
or cracking of the brittle alumina. 
The greatest improvement, however, is provided in the flexibility of the 
air locating system. With the mechanical system, snugger pins as well as 
the locating pins which contacted the substrate had to be raised and 
lowered for changing substrate thicknesses. An entire linkage are had to 
be moved when the printed surface changed from the front to the back of 
the substrate. If a differently shaped precise substrate was used, the 
mechanical system was of no use and manual loading had to be used to 
replace it. 
With the present air jet system, the same height pins can be used for both 
0.025 inch and 0.035 inch thick substrates since the air gap remains under 
0.010 inch. The low number of air holes and air pressure required allow 
tooling to be oriented to the left or right at the turn of a valve and 
thus, it is possible to handle the rectangular-shaped substrates within a 
plus or minus fifteen percent tolerance. The substrates do not have to be 
rectangular as long as there are three flat surfaces to contact the 
locating pins. 
The elimination of moving parts and associated hardware also allows the air 
jet system to be used in laser scribing and laser trimming operations as 
well as in the printing process.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, a printer table embodying the pneumatic parts 
locating system of the present invention is shown partially cut away. The 
upper table 1 shows in position thereon a substrate 2 in position against 
locating pins 3, 4 and 5. Should the orientation be for a right 
positioning rather than a left positioning, a locating pin would be 
positioned in opening 6' instead of including locating pin 3, at which 
point contact would be made to the locating pins 4, 5 and locating pin 6 
which would be in the opening 6'. Positioned through the table are a 
number of openings 11 through which air jets and/or vacuum are made 
available for utilization in the present system. It can be readily seen 
that compressed air coming out of some of the holes 11 acts as a cushion 
facilitating the moving of the substrate into location against the 
locating pins (such as 3, 4, 5, etc.). At the same time, a vacuum through 
other holes helps to retain the substrate in close proximity to the top of 
printer table section 1. Located underneath the upper table portion 1 is 
lower section 10 which includes connections 8 and 9 (see FIG. 2) to air 
and/or vacuum sources. Locating pins 3, 4 and 5 are also shown in location 
on upper portion 1 and retaining substrate 2 in the appropriate location 
for left orientation. 
Referring now to FIG. 3, channels 12 and 13 are shown which meld into the 
surface of the lower portion of the printer table 10 and which, as may be 
seen by reference to sectional views of FIGS. 4 and 5, are connected, with 
the channel 12 being connected to air source connection 9 and channel 13 
being connected to vacuum source connection 8. 
If the orientation of the substrate is to be to the left, compressed air 
will be introduced through connection 8 to channel 13 with vacuum then 
connected through opening 9 to channel 12. If the orientation for 
substrate location is to be the reverse, that is to the right with 
locating pins being in positions 4, 5 and 6', then it will be arranged 
with compressed air applied to connection 9 with vacuum at location 8. 
Referring to FIG. 6, the multiplicity of openings 11 which are connected to 
the channels 12 and 13 are evident as are the pin locating openings 3', 
4', 5' and 6', as well as the locations for the fasteners or bolts through 
opening 7 which provide connection between the upper and lower portions of 
the printer table. Reference is made briefly to sectional view of FIG. 7, 
wherein the opening 6' for pin locator 6 (not shown) and opening 7 for the 
fastener by which the upper and lower portions are connected are shown. 
As noted previously, the arrangement in accordance with the present 
invention provides two different three-pin locating layouts by means of a 
four-pin locating arrangement. As anticipated in the present invention, 
both bottom pins are used on all operations, while which of the two side 
pins 3 or 6 are utilized would depend on which side of the substrate is 
being processed. 
In the present arrangement, the compressed air required for moving the 
substrate is brought underneath the part from a source through channels 
which meld into the bottom portion 10 and connected to the top portion 1 
by bolts and sealed by gasket material. The block or bottom portion 10 
contains two channels 12 and 13, one for moving the part to the lower left 
and one for moving the part to the lower right. That passage not used for 
location serves as the vacuum channel for securing the substrate in 
position once properly located. The compressed air comes up from the 
bottom portion 10, channels 12 or 13, underneath the substrate to angle 
holes 11 drilled between the top and bottom surfaces of the top planar 
portion 1. 
During a print cycle using the air jet tooling in accordance with the 
present invention, a substrate 2 is dropped onto the tooling nest formed 
by the four-pin area by an automatic loader normally with a plus or minus 
0.125 inch accuracy. The air and vacuum are both on as the substrate lands 
in the nest area. Upon contact with the upper portion 1, the air jets 
float the substrate 2 against the locating pins and hold it there. The 
table is then moved by a pneumatic piston toward the printing location 
while the air jets 11 hold the part 2 against the pins, such as 3, 4 and 
5. During table motion and prior to arrival at the printing station, a 
limit switch (not shown) is encountered which closes the air valve 
allowing the vacuum to secure the part in position for printing. 
After printing is completed, the table of the present invention begins to 
be cycled back to the original loading station. While the table is in 
motion, a second limit switch (not shown) closes the vacuum valve and 
activates a rake-off mechanism which clears the freshly printed substrate 
from the tooling nest. Finally, when the table reaches the original 
loading position, another limit switch (not shown) opens the air and 
vacuum valves and another substrate is dropped onto the tooling nest 
portion of the upper plate 1. 
On those thick film printers presently available, substrate locating is 
done either by methods described in the background art section of this 
application or by optically driven mechanisms. In optically driven 
mechanisms, the substrate is placed and immediately secured on the tooling 
nest. An optical system then senses the current substrate orientation in 
relation to the desired orientation. A microprocessor in conjunction with 
the optical system then activates several motors to reorient the entire 
tooling nest to the proper location, providing much more complex 
arrangement than that shown in the present invention, where simplification 
is secured by means of the aforementioned mechanisms as outlined. 
While but a single embodiment of the present invention is shown, it will be 
obvious to those skilled in the art that numerous modifications may be 
made without departing from the spirit of the invention which shall be 
limited only by the scope of the claims appended hereto.