Sheet material flaw detector

Apparatus is disclosed for detecting flaws in sheet material of the character which increase the surface height of the sheet material. The apparatus includes a pair of horizontally parallel driven lower rolls and three upper rolls each mounted on a corresponding pivotal bracket. Two of the upper rolls are associated with one of the lower rolls and are axially spaced apart therealong, and the third upper roll is associated with the other lower roll and positioned therealong to span the space between the other two upper rolls. Each of the upper rolls is rotatably supported by the corresponding bracket for pivotal movement toward and away from the lower roll. Each upper roll bracket is provided with a pair of adjustable stop screws, one adjacent each of the opposite ends of the corresponding upper roll, and each adjustable stop screw carries a switch actuator screw which is adjustable relative to the stop screw. The apparatus frame carries a pair of microswitches for each roll actuated by a corresponding one of the actuator screws through a pivotal switch lever. Each bracket and thus the corresponding upper roll is biased toward the corresponding lower roll, and the spacing between the upper and lower roll is adjusted by the pair of stop screws. An increase in surface height of a sheet passing between the rolls causes the upper roll to be deflected upwardly to actuate one or the other or both of the microswitches.

BACKGROUND OF THE INVENTION 
This invention relates to the art of flaw detectors for moving sheet 
material and, more particularly, to apparatus for mechanically detecting 
an increase in surface height of a moving sheet of material. 
In the art of producing thin walled seamless metallic can bodies of steel 
or aluminum, a shallow cup-shaped blank is first produced from a flat 
metal sheet and is thereafter deep drawn to produce an elongated can body 
blank. In order to be economically competitive with other container 
constructions in the market place, seamless can body production must be 
achieved at high output rates. In order to avoid excessive equipment 
requirements and/or size, the production machinery must therefore operate 
at high speeds. Furthermore, in order to avoid machinery jams and/or the 
production of defective or unacceptable can bodies while maintaining a 
desirable high speed operation and output, accuracy between mechanically 
cooperative parts is extremely important. Likewise, in connection with the 
foregoing operating parameters, it is important to preliminarily eliminate 
any initial flat metal sheet having a defect or flaw of the character 
which might cause such apparatus jams and/or the production of 
unacceptable can bodies. In this respect, it will be appreciated that the 
initial flat metal sheets from which the cup-shaped can body blanks are 
initially produced are either delivered in stacks from which the sheets 
are individually removed and transported to the cupping press, or are 
delivered in rolls from which appropriate lengths are cut for delivery to 
the cupping press. In either case, defects often occur in the flat sheet 
material during production, cutting and stacking, coiling, or 
transportation to a point of use. Such defects may, for example, include 
an increase in the sheet material thickness, or a lump, kink, bend, crease 
or inclusion in the sheet material. Any such defect in the sheet material 
can cause the undesired jamming of the apparatus and/or the production of 
unacceptable can body blanks and, moreover, can be damaging to the press 
apparatus and necessitate undesirable down time for replacement or repair 
of component parts thereof. Still further, where the initial flat blank is 
a sheet delivered to the cupping press from a stack, it is possible to 
have two sheets delivered simultaneously toward the cupping press. This is 
obviously undesirable in that the press parts are designed and set to 
handle a particular material thickness which, if doubled, can seriously 
damage the press parts. 
From the foregoing, it will be appreciated that the detection of flaws in 
the initial flat material blank is of considerable importance. It will be 
further appreciated that the high speed operation of the production 
equipment for seamless can bodies, and the accuracy required with regard 
to the cooperating dies and the like to achieve such high speed operation, 
make it desirable to optimize the detection of any flaw in the initial 
sheet material which might ultimately cause a break down or jamming of the 
can body producing equipment and/or the production of unacceptable can 
bodies. This is achieved in accordance with the present invention by 
passing the sheet material between fixed and displaceable roll members 
such that a defect which increases the surface height of the sheet 
material deflects the displaceable roll to actuate a detecting device 
which thus indicates the flaw and/or causes displacement of the defective 
sheet from the feed line. 
Roll type sheet material gauging and flaw detecting arrangements have been 
provided heretofore, but none of the prior arrangements has provided the 
ability to achieve the accuracy of detection achieved in accordance with 
the present invention. In this respect, for example, detection in certain 
prior art arrangements is predicated upon differential displacement of two 
rolls between which the material passes and an electrical signal produced 
as a result of such differential displacement. With such arrangements, 
roll displacement can have a cancelling effect which allows a flaw to 
escape detection. Other opposed roll type detecting apparatus include an 
upper roll spanning the full width of the material being inspected and a 
roll deflection detector component at only one end of the upper roll. Due 
to the length of the roll and/or roll deflection as a result of the weight 
of the roll, a defect at or toward the end of the upper roll opposite the 
end having the detector component can escape detection. 
SUMMARY OF THE INVENTION 
The flaw detector apparatus in accordance with the present invention 
overcomes the foregoing and other disadvantages of previous devices. In 
this respect, the arrangement according to the present invention includes 
fixed and displaceable rolls and provides for the displaceable roll to be 
pivotally supported for displacement toward and away from the fixed roll 
and to include adjustable stop members adjacent the opposite ends of the 
roll to enable accurate adjustment of the preliminary spacing between the 
two rolls. The initial spacing is with respect to the thickness of the 
sheet material to be inspected and advantageously provides for optimizing 
the accuracy of the spacing of the displaceable roll relative to the fixed 
roll along the length of the displaceable roll. Additionally, a roll 
displacement detector arrangement is provided at each end of the 
displaceable roll to optimize detection of a flaw which might otherwise 
escape detection as a result of the length of the displaceable roll or 
roll deflection between the ends thereof. Preferably, the detector 
arrangement at each end of the displaceable roll includes an adjustable 
actuator cooperative with a pivotal switch operating lever, whereby actual 
displacement of the displaceable roll is multiplied to increase the 
sensitivity of the detector arrangement. Still further, in the preferred 
arrangement the displaceable roll is mounted on a bracket pivotal about an 
axis laterally spaced from the roll axis in the direction opposite that of 
the adjustable stop members and detector arrangements, thus to 
additionally multiply the actual displacement of the roll at its point of 
contact with the sheet of material being inspected. 
In accordance with another aspect of the invention, the detector apparatus 
includes a pair of fixed rolls and three displaceable rolls associated 
therewith in axially staggered and overlapping relationship to cover the 
entire width of a sheet of material passing therebetween. Each of the 
displaceable rolls is individually pivotally supported as described above 
and provided with corresponding adjustable stop members and corresponding 
deflection detector arrangements as described. This arrangement 
advantageously enables adjusting each of the three displaceable rolls 
relative to the corresponding fixed roll to obtain accurate spacing 
therebetween with respect to the thickness of the sheet material being 
inspected. This minimizes spacing problems encountered with a single 
displaceable roll due to roll deflection resulting from the length 
thereof, and the individuality of the supports, adjusting and detecting 
arrangements for each of the displaceable rolls optimizes efficiency of 
the unit with respect to detecting flaws at any location along the width 
of the sheet material being inspected. 
The provision of adjustment capability and roll deflection detectors at the 
opposite ends of the displaceable roll also enables detection of 
deflection at one end of the roll which might not be sufficient to cause 
deflection of the entire roll along its length about the pivot axis for 
the roll supporting bracket. In this respect, for example, a deflection 
encountered centrally of the displaceable roll with respect to its 
opposite ends would ideally be expected to uniformly displace the roll 
away from the fixed roll and about the bracket pivot axis. Likewise, a 
large enough flaw at either end of the displaceable roll would ideally be 
expected to so displace the displaceable roll. Under such ideal 
conditions, a single detector at either end or centrally of the 
displaceable roll would be sufficient. However, manufacturing tolerances 
with respect to the detector components as well as wear of the moving 
parts thereof can, at least eventually, create a condition where a flaw 
will result in deflection at one end of a roll relative to its support 
structure and relative to the opposite end of the roll. Such a deflection 
might not be detected if the detector arrangement were at the opposite end 
of the roll or in the center thereof. Accordingly, considerably improved 
accuracy is achieved by detector arrangements at the opposite ends of the 
displaceable roll, and the adjustable stop arrangement at each end 
together with the adjustable actuator arrangement advantageously enables 
maintaining the desired accuracy by adjustments to compensate for 
manufacturing tolerances and wear. 
It is accordingly an outstanding object of the present invention to provide 
an improved apparatus for detecting increases in surface height of moving 
sheet material. 
Another object is the provision of apparatus of the foregoing character 
having improved sensitivity with respect to the detection of flaws which 
increase surface height of the material being inspected. 
Still another object is the provision of apparatus of the foregoing 
character including fixed and displaceable rolls and in which the 
displaceable roll is more accurately adjustable relative to the fixed roll 
than heretofore provided. 
A further object is the provision of apparatus of the foregoing character 
having improved sensitivity for detecting deflection of the displaceable 
roll relative to the fixed roll. 
Still a further object is the provision of apparatus of the foregoing 
character in which the displaceable roll is pivotally supported relative 
to the fixed roll and is provided at its opposite ends with arrangements 
for adjusting the spacing thereof relative to the fixed roll and for 
detecting deflection thereof relative to the fixed roll. 
Yet another object is the provision of apparatus of the foregoing character 
including a plurality of displaceable rolls associated with fixed rolls in 
axially staggered and overlapping relationship therewith and in which the 
displaceable rolls are individually pivotal relative to the corresponding 
fixed roll, individually adjustable at the opposite ends thereof relative 
to the corresponding fixed roll, and provided adjacent the opposite ends 
thereof with corresponding deflection detector arrangements operable 
independent of one another and independent of the other displaceable rolls 
.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring now in greater detail to the drawings wherein the showings are 
for the purpose of illustrating a preferred embodiment of the invention 
only and not for the purpose of limiting the invention, flaw detector 
apparatus 10 is shown in FIGS. 1 and 2 of the drawing in association with 
a source of sheet material 12 and a cupping press 14. In the embodiment 
shown, source 12 provides a stack of metal sheets and a feeding 
arrangement for delivering the sheets one by one to flaw detector 10 in 
the direction toward cupping press 14. Source 12 and cupping press 14 do 
not form a part of the present invention and are shown merely to 
illustrate the structural association of the flaw detecting apparatus of 
the present invention in connection with one possible use thereof. In 
connection with such use, it will be appreciated that a sheet of material 
S is delivered to flaw detector 10 from source 12 and between lower and 
upper rolls of the flaw detector, as explained more fully hereinafter, and 
thence onto a conveyor portion 16 leading toward cupping press 14. The 
sheet material is held against the conveyor by hold down fingers 18 and, 
if no flaws are detected, the sheet is delivered onto a sheet feeder 
portion 20 leading to the press. A plurality of sheet deflecting fingers 
22 are disposed at the discharge end of conveyor 16 and are adapted to be 
actuated by a solenoid motor 24 from the horizontal position shown in FIG. 
1 to an elevated position in which a sheet of material on conveyor 16 is 
directed upwardly between a pair of reject rolls designated generally by 
the numeral 26. Such actuation of the fingers 22 by solenoid motor 24 is 
in response to the detection of a flaw by detector 10 and results in the 
defective sheet being directed onto a reject tray 28 so that the sheet is 
not delivered to the press. 
The structure and operation of flaw detector 10 will be best understood 
with reference to FIGS. 3-9 of the drawing. In this respect, the detector 
10 includes a frame assembly comprising a first or lower frame portion 30 
of box-like construction including spaced apart sidewalls 32 rotatably 
supporting a pair of horizontal parallel lower rolls 34 and 36. The frame 
assembly further includes a second or upper frame portion 38 in the form 
of a plate covering lower frame portion 30 and mounted thereon for hinged 
pivotal movement about an axis 40 parallel to the axes of rolls 34 and 36, 
for the purpose set forth hereinafter. In the embodiment shown, the hinge 
arrangement is provided adjacent the input end of the detector, and the 
opposite end of the frame assembly is provided with a pair of pivotal 
latch bolts 42 and corresponding latch nuts 44 to releaseably hold frame 
plate 38 in its closed position with respect to frame portion 30. Lower 
rolls 34 and 36 are adapted to be driven together to achieve the feeding 
of a sheet through the detector apparatus and, for this purpose, are 
provided at one end thereof with corresponding sprocket wheels 46 and 48 
driven by a suitable motor 50 through a sprocket chain or the like 52. 
In the preferred embodiment shown, a pair of upper rolls 54 and 56 are 
supported in overlying relationship with respect to lower roll 34 and an 
upper roll 58 is supported in overlying relationship with respect to lower 
roll 36. Upper rolls 54 and 56 are vertically aligned with lower roll 34 
and are axially spaced apart from one another with respect to lower roll 
34 so that each has an outer end adjacent the corresponding outer end of 
the lower roll. Upper roll 58 is vertically aligned with lower roll 36 and 
is axially positioned centrally thereof so as to span the axial space 
between rolls 54 and 56. Thus, the three upper rolls collectively cover 
the width of the lower rolls and thus the width of a sheet passing through 
the detector. In accordance with the present invention, each of the upper 
rolls 54, 56 and 58 is individually supported relative to the 
corresponding lower roll, is individually adjustable relative to the 
corresponding lower roll, and is individually displaceable relative to the 
corresponding lower roll in connection with the detection of a flaw in a 
sheet of material passing through the detector assembly. The structural 
arrangements for the three upper rolls by which these characteristics are 
achieved are identical. Accordingly, it will be appreciated that the 
following description of the support arrangement for upper roll 54 is 
applicable to the support arrangements for upper rolls 56 and 58. 
With reference in particular to FIGS. 7-9 of the drawing, upper roll 54 is 
supported relative to lower roll 34 by means of a bracket member 60 
extending between the opposite ends of roll 54. Bracket member 60 is 
provided at its opposite ends with depending roll mounting blocks 62 
welded or otherwise secured to the bracket, and a corresponding shaft 
clamping block 64 is bolted or otherwise secured to each mounting block 
62. Preferably, upper roll 54 includes a shaft 66 tightly clamped at its 
opposite ends between mounting blocks 62 and clamping blocks 64 against 
rotation relative thereto, and a hollow roller body 68 supported at its 
opposite ends for rotation relative to shaft 66 by bearing assemblies 70. 
Bracket 60 is mounted on upper frame plate 38 for pivotal movement toward 
and away from lower roll 34 about an axis parallel to and laterally spaced 
from the axis of upper roll 54. More particularly, bracket 60 is provided 
adjacent its axially opposite ends with laterally extending hinge fingers 
72 to which depending hinge blocks 74 are suitably secured such as by 
welding. Further, frame plate 38 is provided with a pair of pivot blocks 
76 secured thereto such as by bolts 78, and blocks 74 and 76 are provided 
with aligned openings receiving corresponding hinge pins 80 which provide 
a pivot axis for the bracket parallel to and laterally spaced from the 
axis of upper roll 54. 
Upper roll 54 is adapted to be positioned in spaced relationship with 
respect to lower roll 34 in accordance with the thickness of the sheet 
material passing therebetween. In accordance with the present invention, 
such positioning is achieved by adjustable stop arrangements 82 at the 
axially opposite ends of upper roll 54 and laterally spaced from the roll 
axis in the direction opposite that of the hinge axis of the bracket as 
defined by pins 80. In the embodiment shown, the axially opposite ends of 
bracket 60 are provided with fingers 84 extending laterally of the bracket 
in the direction opposite that of hinge fingers 72, and each of the 
fingers 84 supports a corresponding one of the stop arrangements 82. Each 
stop arrangement includes a rod 86 having a lower end threadedly 
interengaged with finger 84 for displacement with bracket 60 and locked 
against rotative displacement relative to the bracket by means of a jam 
nut 88. Rod 86 extends vertically upwardly from bracket 60 through an 
opening 90 in frame plate 38, and the upper end of rod 86 is threaded to 
receive an adjustable stop nut 92. Accordingly, it will be appreciated 
that stop nuts 92 at the axially opposite ends of bracket 60 can be 
rotated in opposite directions relative to the corresponding rod 86 to 
adjust the position of the opposite ends of bracket 60 and thus the 
opposite ends of roll 54 relative to lower roll 34. This advantageously 
enables an accurate adjustment of the space between rolls 54 and 34 along 
the length of roll 54. It will be further appreciated that openings 90 
through frame plate 38 permit displacement of bracket 60 upwardly relative 
to frame plate 38 in response to a flaw increasing the surface height of a 
sheet of material passing between the rolls. 
Bracket 60, and thus roll 54, is biased toward lower roll 34 by means of a 
pair of coil springs 94 disposed between frame plate 38 and bracket 60. 
More particularly, frame plate 38 is provided adjacent the axially 
opposite ends of bracket 60 with spring retainer assemblies each including 
a sleeve 96 welded or otherwise secured to frame plate 38 and internally 
threaded to receive a spring adjusting nut 98. Frame plate 38 is provided 
with apertures 100 therethrough for sleeves 96, and the upper surface of 
bracket 60 is suitably recessed to receive and locate the lower ends of 
springs 94. Nuts 98 are adapted to be rotated relative to sleeves 96 to 
vary the spring force acting against bracket 60. Preferably, each of the 
springs 94 is vertically aligned with the axes of rolls 54 and 34 and is 
aligned laterally of the roll axes with the stop rod 86 at the 
corresponding end of bracket 60. Accordingly, the spring pressure is 
applied at the opposite ends of roll 54 and directly over the rolls to 
optimize accuracy of upper roll adjustment and accuracy in detecting 
flaws, as set forth more fully hereinafter. 
Further in accordance with the present invention, a roll deflection 
detecting arrangement is provided for each of the axially opposite ends of 
upper roll 54. In the embodiment shown, each such detecting arrangement 
includes an actuator rod 102 at each of the axially opposite ends of 
bracket 60 and displaceable therewith in response to pivotal movement of 
the bracket about its pivot axis. In the preferred embodiment, each 
actuator rod 102 is in the form of a headed bolt coaxial with stop rod 86 
at the corresponding end of the bracket and having a shank of smaller 
diameter than that of the stop rod. The upper end of each stop rod 86 is 
internally threaded for interengagement with the threaded lower end of the 
actuator rod, and the latter is provided with a lock nut 104 by which the 
actuator rod can be locked in an adjusted position relative to the stop 
rod. Each of the roll deflection detecting arrangements further includes a 
microswitch 106 mounted on frame plate 38 between the axially opposite 
ends of upper roll 54, and a corresponding switch operating lever 108. 
Each lever 108 has its opposite ends engaging the upper end of the 
corresponding actuator rod 102 and a switch button 110 of the 
corresponding microswitch. Each lever 108 is mounted on frame plate 38 by 
means of a suitable bracket 112 for pivotal displacement about an axis 114 
transverse to the axis of roll 54. 
It will be appreciated from the foregoing description that each of the 
axially opposite ends of upper roll 54 can be independently adjusted 
relative to lower roll 34 by means of the corresponding adjustable stop 
rod 86 and stop nut 92 and in accordance with the thickness of the sheet 
material to be inspected. It will be further appreciated that the position 
of each actuator rod 102 can be adjusted relative to the corresponding 
stop rod 86 to control the extent of roll and bracket displacement 
required to cause actuation of the corresponding microswitch 106. In 
connection with operation of the device during movement of sheet material 
between upper roll 54 and lower roll 34, a sheet of material of uniform 
thickness having no flaws therein of the type which elevate the surface 
height of the sheet will pass between rolls 34 and 54 without displacing 
or deflecting roll 54 and thus bracket 60 relative to lower roll 34. 
Should a sheet of material include a flaw of the type which increases the 
surface height thereof, the flaw will cause upper roll 54 and thus bracket 
60 to be deflected upwardly from roll 34 against the bias of the springs 
94 and about the pivot axis of the bracket. This upward deflection causes 
upward movement of one or both stop rods 86 and the corresponding actuator 
rod 102, thus pivoting one or both switch levers 108 about lever axis 114 
to operate one or both switches 106. It will be appreciated that the 
positioning of stop rods 86 and the corresponding actuator rods 102 on the 
opposite side of the axis of roll 54 from the pivot axis of the bracket 
multiplies the vertical displacement of roll 54, and that the pivotal 
displacement of switch levers 108 multiplies the vertical displacement of 
actuator rods 102. Thus, through adjustments of stop rods 86 and actuator 
rods 102, switches 106 can be actuated in response to very minute 
increases in the surface height of the material being inspected. 
Furthermore, the adjustment capability of each of the opposite ends of the 
upper roll enable compensation for errors in manufacturing tolerances as 
well as wear of the component parts to enable maintaining the capability 
to detect such minute flaws. 
It will be appreciated that the provision of three upper rolls oriented 
relative to lower rolls 34 and 36 as described hereinabove and each of 
which upper rolls is independently structurally associated with frame 
plate 38 in the manner described herein with regard to upper roll 54 
provides for optimizing the detection of a flaw or flaws over the entire 
width of the sheet material being inspected and minimizes the likelihood 
of a flaw passing through the apparatus undetected. Furthermore, it will 
be appreciated that switches 106 can perform a number of functions in 
connection with the detecting apparatus and detecting procedure. In this 
respect, for example, with reference again to FIGS. 1, 2 and 3 it will be 
appreciated that each of the switches 106 can be connected in an 
electrical circuit to control the operation of solenoid motor 24 such that 
detecting fingers 22 are elevated when any flaw is detected so that the 
corresponding sheet is displaced onto reject tray 28. Additionally, each 
of the switches can be provided with an indicator light 116 which, for 
example, is normally on and which goes off when a flaw is detected. Such a 
light facilitates adjusting the corresponding actuator rod 102 so that the 
switch is actuated in response to a predetermined vertical displacement of 
the actuating rod, and this advantageously enables very fine adjustment to 
be made in this respect. Additionally, when the light goes off during 
operation of the apparatus a workman in attendance at the apparatus can 
visually determine that the apparatus functions properly to displace a 
defective sheet onto the reject tray. Further, should the light go out and 
remain out, the workman is aware that the apparatus is in need of 
adjustment for proper functioning, or that a bulb is burned out and needs 
to be replaced to facilitate such visual surveillance. 
As mentioned hereinabove, biasing springs 94 are preferably vertically 
aligned with the axis of the corresponding upper roll and are positioned 
adjacent the axially opposite ends of the upper roll. Such positioning of 
the biasing springs is preferred in that it avoids roll or bracket 
deflection which could occur if the springs were otherwise positioned 
between the bracket and frame plate 38 and which deflection would cause a 
flaw to pass through the apparatus undetected. In this respect, if the 
springs were for example located in alignment with stop rods 86, bracket 
60 could flex in the area above the corresponding roll in response to a 
flaw passing between the upper and lower rolls, whereby bracket 60 would 
not be pivoted about its end axis or would not be pivoted sufficiently to 
displace actuator rods 102 to the extent necessary to actuate the 
corresponding switch 106. With the biasing springs disposed directly over 
the axis of the upper roll, such flexure of the bracket is advantageously 
avoided thus increasing the sensitivity of the apparatus. Furthermore, the 
location of springs 94 at the opposite ends of the upper roll from the 
lower roll along the length of the upper roll, and achieving and 
maintaining such accuracy to avoid potential errors resulting from 
manufacturing tolerances and/or wear of parts. In this respect, each 
spring provides a considerable biasing force against the bracket, 
preferbly a force of up to six hundred pounds. The magnitude of such force 
biases the bracket relative to frame plate 38 at each of the hinge 
connections between the bracket and frame plate. This tightly interengages 
the hinge components to eliminate free play therebetween resulting from 
manufacturing tolerances and wear. Such spring force also biases the 
bracket ends and thus the roll ends relative to the hinge connections 
enabling the opposite ends of the roll to be accurately adjusted for the 
roll to be uniformly and accurately spaced from the lower roll. 
The provision of the hinged connection between frame plate 38 and lower 
frame portion 30, and releasable clamping nuts 42 at the opposite end of 
the frame assembly as discussed herein, advantageously enables upper rolls 
54, 56 and 58 and the corresponding brackets, biasing springs, stop 
arrangements and roll deflection detector assemblies to be pivoted 
upwardly as a unit about hinge axis 40 and away from lower rolls 34 and 36 
to facilitate maintenance and replacement operations. 
While considerable emphasis has been placed herein on the particular 
structure of the component parts of the detector apparatus and the 
structural interrelationships between the component parts, it will be 
appreciated that many embodiments of the invention can be made and many 
changes can be made in the preferred embodiment without departing from the 
principles of the present invention. Accordingly, it is to be distinctly 
understood that the foregoing descriptive matter is to be interpreted 
merely as illustrative of the present invention and not as a limitation.