Material handling and inspection apparatus and method

According to the present invention, a material handling system for transporting a device to or from a radiation chamber in which the device is inspected is provided. The system includes a shuttle carriage having a base and two opposing walls, a conveyor mounted between the two opposing walls of the shuttle carriage, and means for moving the shuttle carriage along a path between a loading position and an unloading position. The system also includes a housing that encloses the shuttle carriage and the moving means. The housing has an internal cavity that is fitted to the two opposing walls. The housing also has a first opening coincident with the loading position and a second opening coincident with the unloading position. Further, a drive mechanism is provided for extending the conveyor partially through the first opening and the second opening.

BACKGROUND OF THE INVENTION 
The present invention relates to a material handling and inspection 
apparatus and method, and more particularly, to an apparatus and method 
for handling and inspecting a series of devices carried by a moving 
conveyor. 
In the production environment, it is becoming increasingly difficult to 
achieve satisfactory process control using visual inspection techniques. 
This is particularly true when the devices being produced are of a size or 
complexity that makes visual inspection time consuming, and cost 
prohibitive if not impossible. For example, printed circuit boards having 
thousands of electrical connections are now commonplace. Frequently, many 
of these electrical connections cannot be visually inspected because they 
are located below components attached to the printed circuit board. Even 
if all the electrical connections could be visually inspected, time and 
cost constraints may require that only sample printed circuit boards be 
inspected, rather than each printed circuit board. However, sample 
inspections may be insufficient to achieve satisfactory process control. 
Inspection time for complex devices, such as printed circuit boards, may be 
greatly reduced through automated inspection. An automated apparatus for 
determining the quality of solder connections on printed circuit boards is 
shown in U.S. Pat. No. 4,809,308. This apparatus utilizes x-rays to 
inspect solder quality on circuit boards that are loaded onto a motion 
table. Because an operator may load the printed circuit boards, the 
apparatus includes safety interlocks to prevent leakage of radiation. 
Although the automated apparatus greatly reduces inspection time compared 
to visual inspection, it is desirable to minimize inspection time, while 
maintaining safety, so that the inspection can be performed at production 
line rates, even for complex devices. 
Accordingly, it could be desirable to have an improved material handling 
and inspection apparatus. 
SUMMARY OF THE INVENTION 
According to a first aspect of the invention, a material handling system 
for transporting a device to or from a radiation chamber in which the 
device is inspected is provided. The system includes a shuttle carriage 
having a base and two opposing walls, a conveyor mounted between the two 
opposing walls of the shuttle carriage, and means for moving the shuttle 
carriage along a path between a loading position and an unloading 
position. The system also includes a housing that encloses the shuttle 
carriage and the moving means. The housing has an internal cavity that is 
shaped to mate with the two opposing walls. The housing also has a first 
opening coincident with the loading position and a second opening 
coincident with the unloading position. 
According to a second aspect of the invention, a method of inspecting a 
series of devices is provided. The method includes the steps of conveying 
a first device with a first conveyor to an input shuttle assembly 
positioned adjacent to the first conveyor, shuttling the first device with 
the input shuttle assembly through a housing to an inspection apparatus, 
loading the first device from the input shuttle assembly to the inspection 
apparatus, and simultaneously inspecting the first device and returning 
the input shuttle assembly to the position adjacent to the first conveyor. 
The method further includes the steps of conveying a second device with 
the first conveyor to the input shuttle assembly, shuttling the second 
device with the input shuttle assembly to the inspection apparatus, 
unloading the first device from the inspection apparatus to an output 
shuttle assembly, loading the second device from the input shuttle 
assembly to the inspection apparatus, and simultaneously inspecting the 
second device and returning the input shuttle assembly to the position 
adjacent to the first conveyor. Next, the method includes the steps of 
shuttling the first device with the output shuttle assembly to a second 
conveyor. 
According to a third aspect of the invention, a material handling system 
for transporting a device through an inspection apparatus is provided. The 
material handling system includes a first conveyor, and an input shuttle 
assembly positioned between the first conveyor and the inspection device. 
The input shuttle assembly transfers the device from the first conveyor to 
the inspection apparatus. The system also includes a second conveyor, and 
an output shuttle assembly positioned between the inspection apparatus and 
the second conveyor. The output shuttle assembly transfers the device from 
the inspection apparatus to the second conveyor.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT 
Reference is now made to FIGS. 1 through 7 in which like elements are 
referred to by like numerals. FIG. 1 is a schematic diagram of a material 
handling and inspection apparatus in accordance with the present 
invention. An input conveyor 10 is shown carrying a device 12 to be 
inspected. An input shuttle assembly 14 is located adjacent to an end of 
the input conveyor 10. The input shuttle assembly 14 has a shuttle 
carriage 16 that is slidably mounted upon a linear beating assembly 18 
within a housing 20. An inspection apparatus 22 is attached to the input 
shuttle assembly 14. An output shuttle assembly 14', which has like 
components to the input shuttle assembly 14, is attached to the opposite 
side of the inspection apparatus 22 from input shuttle assembly 14. The 
components of the output shuttle assembly 14' are designated with a prime 
following the corresponding numeral from the input shuttle assembly 14 in 
order to distinguish the components of the output shuttle assembly 14' 
from the components of the input shuttle assembly 14. An output conveyor 
26 is located adjacent to the output shuttle assembly 14'. 
The inspection apparatus 22 is preferably an automated, real-time x-ray 
imaging apparatus, which includes an x-ray source 28, an x-y table 30, and 
an inspection conveyor 31 mounted to the x-y table 30, such as the models 
MV6000 and CXI-3600 manufactured by IRT Corporation of San Diego, Calif. 
for performing circuit board solder quality inspection. Alternatively, the 
inspection apparatus 22 may be any type of inspection device that utilizes 
a source of penetrating radiation. An appropriate clamping mechanism is 
provided to secure the device 12 for movement about the x-y table 30 as 
the x-y table 30 moves during inspections. Preferably, the clamping 
mechanism is pneumatically controlled to project into the conveyor belt, 
whereby the device 12 will be clamped between the conveyor belt and a 
rigid material block. Each of the conveyors 38, 38' and 31 may be motor 
driven. 
As shown in FIG. 1, the shuttle carriage 16 has a base 32 and two opposing 
walls 34 and 36. A shuttle conveyor 38 is mounted to the base 32 between 
the opposing walls 34 and 36. The shuttle conveyor 38 is preferably 
mounted to the base 32 in a manner that allows the shuttle conveyor 38 to 
be partially extended from the shuttle carriage 16 between the opposing 
walls 34 and 36, as is further described below. 
FIG. 2 is a cut-away, isometric view of the input shuttle assembly 14 shown 
in FIG. 1. The housing 20 of the input shuttle assembly 14 has a first 
opening 42 and a second opening 44. The first opening 42 and the second 
opening 44 in the housing 20 are large enough to pass the shuttle conveyor 
38 and the device 12. However, the length of the openings 42 and 44 is 
shorter than the distance between the opposing walls 34 and 36 of the 
shuttle carriage 16. 
Preferably, the walls 34 and 36 and the housing 20 are constructed from 
sheet steel. In addition, those portions of the inspection apparatus 22 
and the housing 20 that are within the direct line-of-sight of the x-ray 
source 28 are preferably lined with 3/16" thick lead sheets. The inner 
surface of the shuttle carriage 16 is also preferably lined with 1/16" 
thick lead. Although it is not necessary that the periphery of the walls 
34 and 36 contact the inner surface of the housing 20, any gap between the 
walls 34 and 36 and the housing 20 is preferably small enough to eliminate 
all direct paths between the x-ray source 28 and the exterior of the 
housing 20. 
As shown in FIG. 3, the shuttle conveyors 38 and 38' are preferably mounted 
to the bases 32 and 32' of the shuttle carriages 16 and 16' in a manner 
that allows the shuttle conveyors 38 and 38' to be extended partially 
through the first openings 42, 42' and the second openings 44, 44'. In 
FIG. 3, the shuttle conveyors 38 and 38' are illustrated extended through 
the second openings 44 and 44'. In this position, the devices 12A and 12B 
may be transferred simultaneously to the inspection conveyor 31 and to the 
output shuttle conveyor 38', respectively. 
FIG. 5A is a sectional view of the output shuttle carriage 16' in which the 
base 32' and the output shuttle conveyor 38' have been removed. The 
corresponding elements of the input shuttle carriage 16 are arranged as 
the mirror image of FIG. 5A. A linear bearing assembly 60', including two 
linear trackways 61' and four linear bearing blocks 62', is mounted within 
the shuttle carriage 16'. Preferably, a pneumatic rodless cylinder 64' is 
arranged to drive the shuttle conveyor 38' in the directions of the double 
arrow 66'. A source 70 of compressed gas is coupled to a fitting 67' at 
each end of the cylinder 64' through a pneumatic valve 90. 
A suitable commercially available pneumatic cylinder for this application 
is the Ultran rodless cylinder from Bimba of Monee, Ill., which is shown 
in FIG. 5B. The Ultran rodless cylinder has a section of stainless steel 
tubing 48' that contains a piston 50'. A number of magnets 52' are located 
on the piston 50'. A cylinder carriage 54' is slidably mounted on the 
tubing 48', and a number of magnets 56' are also located on the cylinder 
carriage 54'. The magnets 52' and the magnets 56' magnetically couple the 
piston 50' to the cylinder carriage 54'. 
Returning to FIG. 5A, the cylinder carriage 54' and the four linear bearing 
blocks 62' are attached to the base 32' (not shown in FIG. 5A) so that the 
travel of the shuttle conveyor 38' may be driven by the pneumatic rodless 
cylinder 64'. Preferably, three mechanical stops, a left stop 74', a home 
stop 76', and a right stop 78', are attached to the shuttle carriage 16' 
to limit the travel of the shuttle conveyor 38'. At the home stop 76' 
position, the shuttle conveyor 38' is contained within the shuttle 
carriage 16' so that the shuttle carriage 16' may move between the first 
opening 42' and the second opening 44'. At the left stop 74' position, the 
shuttle conveyor 38' is extended to the left partially through the first 
opening 42'. At the right stop 78' position, the shuttle conveyor is 
extended to the right partially through the second opening 44'. 
As shown in FIG. 5A, the mechanical stops 74', 76' and 78' are preferably 
horizontally mounted hydraulic shock absorbers fitted with stop collars 
75', 77' and 79', respectively. Appropriate contact blocks may be attached 
to the bottom side of the base 32' to define the left and right stop 
positions. In addition, a pneumatic cylinder 86' coupled to a source 70 of 
compressed gas by a pneumatic valve 92, as shown in FIG. 5C, may be 
mounted to the left contact block so that, when the rod of the pneumatic 
cylinder 86' is extended by the application of the compressed gas, the rod 
will strike the home stop 76' defining the home position. 
Alternative stop arrangements may be employed without departing from the 
scope of the present invention. For example, the left stop 74' and the 
right stop 78' may be replaced by shock absorbing blocks mounted on or 
near the rodless cylinder 64' to directly limit the travel of the cylinder 
carriage 54'. Alternatively, optical or electronic sensors may be used to 
control the application of the compressed gas to the cylinder 64' to 
thereby stop the cylinder carriage 54' at the appropriate position. 
As shown in FIG. 5A, the shuttle carriage 16' includes three proximity 
sensors 80', which may be positioned to sense the position of the cylinder 
carriage 54'. More particularly, the proximity sensors 80' may sense that 
the cylinder carriage 54', and therefore the shuttle conveyor 38', has 
reached its left, home or right position. A suitable proximity sensor for 
this application is manufactured by Omron under the part no. 
TL-X1R5C2-P1E, which is available from Western Switches & Controls, Inc. 
of San Diego, Calif. The proximity sensors are coupled to a system 
controller 88. 
Referring now to FIG. 6, a sectional view of the output shuttle assembly 
14' is shown to illustrate the drive mechanism for the shuttle carriage 
16' (not shown). The linear bearing assembly 18' includes two linear 
trackways 19' and four linear bearing blocks 58'. Mounted between the two 
linear trackways 19' is a rodless pneumatic cylinder 46', which drives a 
cylinder carriage 82'. Preferably, the rodless pneumatic cylinder 46' is 
an Ultran rodless cylinder as shown in FIG. 5B and described above. A 
source 70 of compressed gas is coupled to each end of the rodless cylinder 
46' by fittings 84'. The shuttle carriage 16' (not shown) is mounted to 
the four linear bearings 58' and the cylinder carriage 82' for guided 
travel along the direction of the double arrow 40. 
The rodless pneumatic cylinders 46' and 64' and the pneumatic cylinder 86' 
of the output shuttle assembly 14' may be controlled as shown in FIG. 5C. 
The source 70 of compressed gas is coupled to three pneumatic valves 90, 
92 and 94 mounted on a manifold. Each of the valves has a single pressure 
regulator 96, 98 and 100 respectively, and a speed control 102, 104 and 
106 respectively, which permits control of the speed of the piston of 
cylinders 64', 86' and 46' by throttling exhaust air. Preferably, the 
valves are solenoid actuated. A suitable commercially available valve for 
this application is sold under the MARK 3 name by Numatics as model number 
031SA4. A suitable commercially available pressure regulator for this 
application is sold under the MARK 3 name by Numatics as model number 
031RS7020. A suitable commercially available speed control for this 
application is sold under the MARK 3 name by Numatics as kit no. 229-527A. 
The valves 90, 92 and 94 may be controlled by the system controller 88. The 
source 70 of compressed gas is selectively coupled through the valves 90, 
92 and 94 each end of the pneumatic cylinders 64', 46' and 86', as shown 
in FIG. 5C. Thus, the piston 50 and the cylinder carriage 54 may be driven 
in either direction along the tubing 48 by coupling the compressed gas to 
the appropriate end of the tubing 48. A like three valve assembly, coupled 
to the system controller 88, controls the three pneumatic cylinders for 
the input shuttle assembly 14. 
Alternatively, the shuttle carriage 16 may be driven by a conventional 
pneumatic cylinder having a piston and a rod, although such an arrangement 
would require a longer pneumatic cylinder to achieve the same travel 
stroke as the rodless cylinder described above. In addition, the shuttle 
carriage 16 may alternatively be driven by a motor-driven lead screw. 
Furthermore, the shuttle carriage 16 may be propelled by other known 
devices, such as a motor-driven chain, cable, or belt. 
Each of the shuttle conveyors 38 and 38' and the inspection conveyor 31 is 
fitted with a device stop mechanism 108, as shown in FIG. 5E, which stops 
the conveyor when the device 12 has reached the desired location on the 
conveyor. Preferably, the device stop mechanism 108 is pneumatically 
controlled, although other electrical or optical sensors, or mechanical 
stops, could alternatively be used. 
FIG. 5D is a schematic diagram of the pneumatically controlled stop 
mechanism 108. The stop mechanism 108 includes a rotary actuator 110. The 
rotary actuator 110 is coupled to a valve 112. The valve 112 is controlled 
by the system controller 88. The stop mechanism 108, as shown in FIG. 5E, 
is axially mounted to the rotary actuator 110. When the system controller 
88 determines that the conveyor 38, 38' or 31 is ready to receive the 
device 12, the system controller 88 provides a signal to the valve 112 to 
change the state of the rotary actuator 110, rotating a finger 114 of the 
stop mechanism 108 into the path of the device 12. The conveyor 38, 38' or 
31 may be started by the system controller 88 simultaneously with or after 
signalling the valve 112. A photodetector 116 is positioned above the 
finger 114. When the device 12 reaches the finger 114, the photodetector 
116 provides a signal to the system controller 88 to stop the conveyor 38, 
38' or 31. 
The preferred operation of the material handling and inspection system will 
now be described with reference to FIGS. 1 and 4 for a series of devices 
12. Initially, the shuttle conveyor 38 of the input shuttle assembly 14 is 
extended partially through the first opening 42, where the shuttle 
conveyor 38 docks with the input conveyor 10. A first device 12A is loaded 
from the input conveyor 10 to the shuttle conveyor 38. The shuttle 
conveyor 38 is retracted into the shuttle carriage 16, which then travels 
through the housing 20 to the second opening 44. At the second opening 44, 
the shuttle conveyor 38 is extended into the inspection apparatus 22, 
where the shuttle conveyor 38 docks with the inspection conveyor 31. Next, 
the device 12A is loaded from the shuttle conveyor 38 to the inspection 
conveyor 31. The shuttle conveyor 38 is then retracted into the shuttle 
carriage 16 and the shuttle carriage 16 returns to the first opening 42 to 
dock with the input conveyor 10 as the device 12A is inspected. 
As the inspection of the device 12A continues, a device 12B is loaded from 
the input conveyor 10 to the extended shuttle conveyor 38, which then 
retracts into the shuttle carriage 16. The shuttle carriage 16 and the 
shuttle carriage 16' then travel to the second openings 44 and 44', 
respectively. Upon completion of the inspection of the device 12A, the 
shuttle conveyors 38 and 38' dock with the inspection conveyor 31, and the 
device 12A is loaded from the inspection conveyor 31 to the shuttle 
conveyor 38' simultaneously with the loading of the device 12B from the 
shuttle conveyor 38 to the inspection conveyor 31. The shuttle conveyors 
38 and 38' are then retracted into the respective shuttle carriages 16 and 
16' and the shuttle carriages 16 and 16' return to the first openings 42 
and 42' to dock with the input conveyor 10 and the output conveyor 26, 
respectively, as the device 12B is inspected. 
As the inspection of the device 12B continues, a device 12C is loaded from 
the input conveyor 10 to the extended shuttle conveyor 38 and the device 
12A is unloaded from the shuttle conveyor 38' to the output conveyor 26. 
When interacting with the input conveyor 10 and the output conveyor 26, it 
is not necessary that the shuttle carriages 16 and 16' move 
simultaneously. Next, the shuttle conveyors 38 and 38' retract and the 
shuttle carriages 16 and 16' return to the second openings 44 and 44', 
respectively. Upon completion of the inspection of the device 12B, the 
shuttle conveyors 38 and 38' dock with the inspection conveyor 31. The 
device 12B is then loaded from the inspection conveyor 31 to the shuttle 
conveyor 38' while the device 12C is simultaneously loaded from the 
shuttle conveyor 38 to the inspection conveyor 31. The shuttle conveyors 
38 and 38' are then retracted into the shuttle carriages 16 and 16', which 
then return to the first openings 42 and 42' to dock with the input 
conveyor 10 and the output conveyor 26, respectively. The operation of the 
material handling and inspection system will continue in like sequence 
until the last of the series of devices 12 is loaded onto the output 
conveyor 26. 
In an alternative operational mode, more than one device 12 is carried by 
the shuttle carriages 16 and 16' and the inspection conveyor 31, and is 
inspected within the inspection apparatus 22 at any one time. For example, 
as shown in FIG. 7, the shuttle carriage 16 may transport three devices 
12B simultaneously and the inspection apparatus 22 may inspect three 
devices 12A simultaneously. Upon the completion of the inspection routine, 
the three devices 12A are unloaded onto the shuttle carriage 16' and the 
three devices 12B are loaded into the inspection apparatus 22. By using 
three stop mechanisms 108 on each of the shuttle conveyors 38 and 38' and 
the inspection conveyor 31, and three clamping mechanisms on the 
inspection conveyor 31, the devices 12 may be loaded into or unloaded from 
the inspection apparatus 22 one at a time as shown in FIG. 7. 
Alternatively, once the shuttle conveyors 38 and 38' and the inspection 
conveyor 31 are aligned, multiple devices may be simultaneously unloaded 
from and loaded to the inspection conveyor. Where multiple devices are 
transported simultaneously, one stop mechanism 108 may be used, rather 
than three, by locating the stop mechanism 108 to stop the first of the 
devices 12. 
As a further alternative, the stop mechanisms 108 could be replaced by 
photodetectors. However, at present, the stop mechanism 108 described 
herein provides a more accurate stop position, which reduces inspection 
time. 
Throughout the operation of the inspection sequence, the travel of the 
shuttle carriage 16 within the housing 20 is preferably limited so that at 
least one of the two opposing walls 34 and 36 is located between the first 
opening 42 and the second opening 44 regardless of the position of the 
shuttle carriage 16. The opposing walls 34 and 36 are fitted within the 
inner surface of the housing 20 to prevent leakage of radiation from the 
x-ray source 28 out of the housing 20. The opposing walls also provide a 
physical barrier to prevent insertion of any part of the human body 
through the housing 20 and into the primary x-ray beam from the x-ray 
source 28. Because of the arrangement of the opposing walls 34 and 36, the 
need for redundant interlocks is eliminated. 
Although the operation of the conveyors 10, 38, 38' and 26 has been 
described to produce a flow of devices 12 from right to left through the 
apparatus of FIG. 1, the flow may be reversed, in which case the devices 
12 would be loaded from the conveyor 26 and unloaded with the conveyor 10. 
In addition, the shuttle conveyors 38 and 38' and the inspection conveyor 
31 are preferably adjustable in width so that they may accommodate devices 
12 of various sizes. 
It is intended that the foregoing detailed description be regarded as 
illustrative rather than limiting and that it is understood that the 
following claims including all equivalents, are intended to define the 
scope of the invention.