Method and apparatus for inverting printed circuit boards

The device flips substrates or passes them through without flipping, selectively, and the substrate can enter either end and exit either end of the device, as desired depending on how it is assembled. The spacing between channels which restrain opposite edges of the substrate is adjustable so as to accommodate different widths. The channels are separate from, but cooperable with, feed wheels which extend into the channels and engage the board when the channels are not moved out of alignment with the feed plane, e.g., when the flipping action is not taking place. During flipping, one end of each channel is raised above the feed plane, while the other end is moved substantially parallel to the feed plane so as to eliminate interference with an undercarriage or anything else below the feed plane of the device.

FIELD OF THE INVENTION 
The field of the invention generally deals with substrate handling, such as 
selective manipulation of printed circuit boards during automated transfer 
of the boards between various work stations such as component mounting and 
soldering stations. The invention is applicable to handling individual 
circuit boards or sheets of multiple boards prior to separation of each 
sheet into individual boards. For that matter, the inventive concept is 
applicable to any industry involving manipulation of a substrate. 
BACKGROUND OF THE INVENTION 
In the industry involving high speed automated handling of printed circuit 
board substrates, the boards typically are moved from station to station 
for step-wise performance of functions such as mounting components on 
opposite sides of the board, testing the components, wave soldering, 
reflow soldering, and the like. Sometimes, it is required to flip the 
substrate so as to operate on the top surface thereof at one station and 
on the bottom surface thereof at the next station. 
Heretofore, a device has been provided for receiving and flipping printed 
circuit boards and, alternatively, transporting the boards through the 
device without flipping them. During such flipping, the board retaining 
mechanism of this device passes below a feed plane, generally defined as 
the plane of the board prior to flipping, so as to require greater 
undercarriage clearance and thus limit the length of the board according 
to that clearance. Further, the prior art device requires recycling 
thereof after flipping a board in order to position the same end of the 
flipping mechanism for receiving the next board to be handled. 
Thus, it is an objective of the invention to flip or not flip a printed 
circuit board, selectively and under command of a programmable computer or 
other form of controller, so as to present the appropriate surface of the 
board for work at a work station, while keeping the board substantially on 
one side of the feed plane during such flipping. 
Additionally, it is an objective of the invention to provide for flipping 
boards which are lesser or greater in length than the edge restraining 
channels of the device, without interference with any undercarriage of the 
device. 
Further, it is an objective of the invention to provide for easy adjustment 
of spacing between the board restraining channels so as to accommodate 
boards of different widths. 
Still further, it is an objective of the invention to provide that the 
device does not require recycling in order to receive the next substrate 
to be handled. 
Moreover, it is an objective of the invention to provide that the 
substrates may enter either end and exit either end of the device, as 
desired, with revision of a few parts in assembly of the device. 
BRIEF SUMMARY OF THE INVENTION 
The device flips substrates or passes them through without flipping, 
selectively, and the substrate can enter either end and exit either end of 
the device, depending on how it is assembled. The spacing between channels 
which restrain opposite edges of the substrate is adjustable so as to 
accommodate different widths. The channels are separate from, but 
cooperable with, feed wheels which extend into the channels and engage the 
board when the channels are not moved out of alignment with the feed 
plane, e.g., when the flipping action is not taking place. During 
flipping, one end of each channel is raised above the feed plane, while 
the other end is moved substantially parallel to the feed plane so as to 
eliminate interference with an undercarriage or anything else below the 
feed plane of the device.

DETAILED DESCRIPTION OF THE INVENTION 
Flipping of a circuit board is accomplished by flipping or inverting two 
channels 70 which are spaced apart sufficiently to receive opposite edges 
of the substrate or circuit board. As seen in FIGS. 5 and 8-10, these 
channels are generally U-shaped in cross section. Referring to FIGS. 2 and 
11, it may be seen that sides gaps are milled in both side of the "U" of 
each channel so that the outer periphery of each drive wheel 60 (FIG. 10) 
can protrude through either side of the "U" and into the corresponding gap 
72 to engage the edge of the circuit board 2 for frictional feed thereof. 
Steel strips 74 are attached to, but could be integral with, each channel 
70 in order to close each gap 72 and thus keep the front end of a warped 
printed circuit board from getting caught on a gap when feeding or driving 
the circuit board into or out of a respective channel 70. 
Opposite ends of each channel 70 have follower wheels 76, 78 so that either 
end of the channels may follow a horizontal guide 64 FIGS. 1 and 8-10 
during inversion of the channel 70. Each channel also has a channel 
blocker 80 pivotally attached at each end of the channel, with the free 
end of the blocker being spring biased to a "blocking position" so as to 
prevent egress of a circuit board from the channel 70 unless the blocker 
80 is held open against the bias of tension spring 86. 
As best seen in FIGS. 6-10, each channel blocker 80 has pins 82 protruding 
therefrom and extending through corresponding slots or oversized holes 84 
in a channel 70. These pins 82 are adapted to cooperate with camming 
surface 66 (FIGS. 8 and 9) so as to move the channel blocker 80 from the 
phantom line position of FIG. 7 to the solid line position thereof against 
the bias of the corresponding spring 86. 
Referring to FIGS. 1-5 and 11, each channel 70 has a central pivot point 88 
at which it is pivotally connected to a slide 16 which moves up and down 
in vertical guide 14 of a vertical bar 12 which, in turn, is mounted on 
horizontal mounting block 10. Integral with slide 16 is a rack 18 (FIGS. 
1,4, and 11); and a pinion 32 meshes with rack 18 and a spur gear 34 which 
is rotated by reversible motor 30 via timing belt 36. A switch 19 detects 
when rack 18 is in the "down" position. 
Reversible motor 50 drives frictional drive belt 56 via timing belt 52, 
gear arrangement 54, and belt tensioner 58. Frictional drive belt 56, in 
turn, frictionally engages the outer periphery of feed wheels 60. A 
back-up platen 62 is situated on the opposite side of drive belt 56 from 
the feed wheels 60; and an arcuate relief 63 is provided in the back-up 62 
opposite of each feed wheel so as to allow a greater tolerance in the 
outer diameters of the feed wheels 60. 
Baffles 40 and 44 are provided at opposite ends of the horizontal mounting 
block 10 for the purpose of controlling the direction in which a channel 
70 can flip during raising and lowering of rack 18. Baffle 40 is spring 
biased to the position of FIG. 4 by tension spring 42, and baffle 44 is 
spring biased to the position of FIG. 4 by spring 46. As seen in FIG. 1, 
movement of baffle 40 is sensed by a switch 43. 
FIG. 12 shows the orientation of parts when used in a right to left board 
travel configuration. FIG. 13 shows it when the board travel is left to 
right. Baffles 40, 44 and 20 along with their holding blocks and switches 
would be reversed. Also cams 100, 101, 102, 103, 104 and 105 would be 
reversed. 
OPERATION OF THE DEVICE DURING FLIPPING 
Referring to the Figures, particularly FIG. 12, a circuit board 2 is fed or 
inserted sufficiently into the device such that at least one drive wheel 
60 engages it at each edge (as illustrated in FIG. 10) so that the circuit 
board side edges can be driven by wheels 60 into the corresponding 
channels 70 until the leading edge of the circuit board interrupts a laser 
beam switch or the like (not shown) to provide an indication that the 
circuit board is within the channel sufficiently for flipping thereof. 
When the channels are located in the position of FIG. 4, pins 82 engage 
camming surfaces 66 and move channel blockers 80 to the position of FIG. 8 
so that the channels 70 are open for reception of the circuit board. 
Having driven a circuit board sufficiently into the channels 70, the 
leading edge is sensed and the information is transmitted to a controller 
which, in turn, controls halting of feed motor 50 and commencement of 
motor 30 in one direction so as to raise rack 18 and the center pivot 88 
of each channel 70. When raising the center of a channel 70, baffle 44 
allows one end 76 of the channel 70 to be raised (FIG. 12) while baffle 40 
ensures that the follower wheel 78 at the opposite end of the channel 
follows horizontal guide 64. At or near the upper limit of raising rack 
18, follower wheel 76 of channel 70 will depress and pass over top baffle 
20 against the bias of spring 24 so as to ensure inversion of the channel 
70 with downward movement of rack 18 during reversing of motor 30. Switch 
22 (FIG. 1) is actuated when follower 76 depresses top baffle 20 against 
the bias of spring 24, so that a controller will know when to reverse the 
rack driving motor 30. 
Once the inversion of channel 70 has been completed from the orientation 
illustrated in FIG. 4 to one in which the ends of channel 70 are opposite 
that illustrated in FIG. 4, the pins 82 of channel blockers 80 will have 
engaged camming surface 66 so as to allow the circuit board to be fed out 
of the channel by actuation of feed motor 50. Feed motor 50 may be driven 
in either direction so that the boards may be loaded into the channels 
from either end and may be unloaded from the channels out of either end 
thereof. FIG. 9 illustrates the position follower 78 in one of the 
intermediate positions of FIG. 12 such that the follower is riding on a 
raised portion of horizontal guide 64 prior to the dropoff 65 (FIG. 6) of 
horizontal guide 64. 
As may be seen from the drawings, each side of the board inverter is 
substantially a mirror image of the other side, with the left side as 
viewed in FIG. 3, having support rods 94 affixed thereto and the right 
side of the device being moveable toward and away from the left side on 
support rods 94. Such an arrangement allows for adjusting the device to 
substrates or circuit boards of various widths. Square drive rods 90 
insure channel inversion on both sides of the device according to whatever 
spacing is provided between the sides, and bellows members 92 cover the 
outer ends of square rods 90 and accommodate these widths adjustments. 
As may be appreciated by reference to the drawings, the edge restraining 
channels are cooperable with but separate from the frictional feed wheels 
60 providing for simplicity and minimizing the weight of that portion of 
the device which actually inverts with the circuit board. The simple, yet 
elegant, design of the device also allows substrate entrance into the 
device from either direction and exit of the substrate out of the device 
in either direction, selectively. It is also to be noted that the 
orientation of the overall device does not matter in order to invert or 
flip a substrate, as long as the length of the substrate is wholly within 
the channels along the edges thereof. Further, on the occasions that the 
circuit board or substrate may have a length longer than that of the 
channels, the inversion or flipping of the substrate can still be 
accomplished on one side of the feed plane without interference with 
anything located on the other side of the feed plan; and the orientation 
of the overall device during flipping is only limited to those which would 
prevent the oversized circuit board from falling out of a channel during 
such inversion. 
Typically, the device is microprocessor controlled using a printed circuit 
board control module of Universal Instruments Corporation, part no. 
43000401. 
The following claims are intended to cover all of the generic and specific 
features of the invention herein described and all statements of the scope 
of the invention which, as a matter of language, might be said to fall 
therebetween. 
Now that the invention has been described,