Skew control mechanism for sheet material

A skew control mechanism for sheet material. Sheet material, such as corrugated paperboard, is slit into strips of various widths and the slit strips are then cut transversely into lengths by a cut-off machine. The cut sections are conveyed by an endless belt conveyor to a stacking mechanism, and to prevent skewing of the cut sections on the conveyor, a skew control mechanism is mounted for movement on the frame of the machine. The skew control mechanism includes a series of carriages located along each side of the machine and the carriages at each side are connected together by links, while transverse shafts are pivoted to carriages at opposide sides of the machine. A plurality of wheels are mounted for floating vertical movement about each shaft and the wheels ride on the upper surfaces of the cut sections. An adjusting mechanism is incorporated which enables the shafts to be pivoted with respect to the carriages so that the axes of the wheels can be adjusted with respect to the machine direction and thereby steer the cut sections into proper machine direction alignment.

BACKGROUND OF THE INVENTION 
In the manufacture of corrugated paperboard, paper sheets are bonded with 
an adhesive to opposite faces of a corrugated core, and the laminated 
sheet is then passed through a slitter which slits the sheets into a 
series of strips of various predetermined widths. The slit strips are then 
passed through cut-off knives which cut the slit strip into lengths. As it 
is often desired to cut the strips into different lengths, multiple 
cut-off units are used, with certain of the strips being directed to one 
cut-off knife, and other groups of strips being directed to a second 
cut-off knife. 
Following the cutting of the strips, the cut lengths or sections are 
conveyed to a stacking mechanism, as described in U.S. Pat. No. 3,905,595, 
which serves to stack the cut sections and convey the stacks to a given 
site. 
It is important that the cut sections be maintained in proper machine 
direction orientation on the conveyor approaching the stacking machine, 
for if the cut sections are skewed, interleaving of the sections will 
occur during the stacking with the result that the stacks cannot be 
properly separated from one another. 
Attempts have been made in the past to prevent skewing or misalignment of 
the cut sections on the conveyor leading to the stacking machine. In the 
past, canvas drapes have been employed which were adapted to ride on the 
cut sections in an attempt to prevent skewing. However, the draped canvas 
would not correct skewing which may have occurred at the cut-off knife and 
would, at most, control skewing on the conveyor. Furthermore, the use of 
the draped canvas had certain distinct disadvantages in that after a 
period of use the canvas became ragged or worn, and the draped canvas also 
restricted access to the conveyor in the event of a jam-up. 
Attempts have also been made in the past to control skewing of the cut 
sections on the conveyor by use of sandwich belts in which the cut 
sections were held between the cooperating endless belts. The use of the 
cooperating belts, at most, controlled skewing on the conveyor and did not 
correct skewing which had occurred at the cut-off knives. Furthermore, the 
gap or spacing between the cooperating belts was set for a given thickness 
of paperboard, and during normal daily operation, it was common for 
various thicknesses of paperboard to be run through the machine. With the 
gap set for the thickest paperboard, the unit would not give proper 
control when running paperboard of lesser thickness. 
Pivoted floation rolls have also been used in the past in an attempt to 
control skewing on the conveyors. In this type of system, one or more 
transverse rolls were mounted to ride against the upper surfaces of the 
cut sections and the resulting pressure would provide some measure of 
control against skewing. However, the use of the pivoted flotation rolls 
would not correct skewing which had occurred at the cut-off knife. 
Moreover, if the cut sections were located only along one side edge of the 
conveyor, the flotation roll would tend to tilt, with the result that a 
differential in pressure would be applied transversely across the cut 
sections, causing the sections to skew, so that under certain conditions, 
the flotation rolls accentuated, rather than controlled skewing. 
SUMMARY OF THE INVENTION 
The invention relates to a skew control mechanism to prevent skewing of cut 
pieces or sections of sheet material as they exit from the cut-off 
machine. In accordance with the invention, the skew control mechanism 
includes a supporting structure or frame having carriages which are 
mounted for movement on guideways on the cut-off machine so that the 
mechanism can be installed or removed from the cut-off machine as an 
integral unit. The carriages along each side of the frame are pivotally 
connected together by longitudinal arms, while shafts extend transversely 
of the frame and are pivoted to carriages at opposite sides of the frame. 
Pivotally mounted on each shaft is a group of individual wheels which are 
adapted to ride on the cut sections of sheet material being conveyed by 
the endless belt conveyor. The wheels provide segmented floation and act 
to apply substantially uniform pressure to all of the cut sections 
regardless of their position on the conveyor. The use of the individual 
wheels will not accentuate skewing as can occur with the use of a single 
transverse floating roll, as used in the past. 
An adjustment feature is incorporated with the skew control mechanism which 
enables skewed sections to be steered or directed back into machine 
direction alignment. To provide this adjustment, adjusting studs are 
connected to the carriages at each side of the frame and by adjustment of 
the studs, the shafts and wheels can be shifted relative to the machine 
direction. By proper shifting of the axis of the wheels, the cut sections 
can be steered back into machine direction orientation to thereby 
compensate for any skewing produced by the cut-off knives. 
As a further advantage, the entire skew control mechanism can be readily 
removed from the machine for purposes of servicing the cut-off knives or 
for removing any jam-ups that may have occurred. 
The skew control mechanism incorporates a sufficient number of transverse 
shafts which carry the flotation wheels to insure that even the shortest 
lengths of cut sections are always in flotation control. It is preferred 
to have at least two wheels in contact with each cut section at all times. 
The flotation wheels are equipped with low pressure pneumatic tires which 
provide a shock absorbing action. 
Other objects and advantages will appear in the course of the following 
description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a cut-off machine 1 for cutting previously slit strips 
of corrugated paperboard into lengths. The cut-off machine includes a 
housing 2 having a pair of side walls 3 and a top wall 4 which is 
connected between the central portions of the side walls 3. A lower 
cut-off unit 5 and an upper cut-off unit 6 are located within the housing 
2, and each cut-off unit serves to cut one or more of the slit strips 
transversely into lengths or sections. The use of the two cut-off units 5 
and 6 enables the strips to be selectively cut to two different lengths, 
as opposed to a machine incorporating a single cut-off unit in which all 
of the slit strips would be cut to the same length. 
The lower cut-off unit 5 is of conventional construction and includes a 
pair of cooperating cut-off rolls 7 and 8. The slit strips 9 are fed to 
the cut-off rolls 7 and 8 on a feed plate 10, and the cut sections or 
lengths 11 are conveyed by a conveyor unit 12 to an automatic stacking 
machine, not shown, but which can be of the type described in U.S. Pat. 
No. 3,905,595. In accordance with the invention a skew control mechanism 
indicated generally by 13, is associated with the conveyor unit 12 to 
prevent skewing of the cut sections 11 on the conveyor and to steer any 
previously skewed sections into machine direction alignment. 
The upper cut-off unit 6 is similar to the lower cut-off unit 5 and 
includes a pair of cooperating cut-off rolls 14 and 15. The slit strips 9 
are fed to the cut-off rolls 14 and 15 on a feed plate 16, and the cut 
sections 11 are conveyed on the conveyors unit 17 to the stacking machine. 
A skew control mechanism 18, similar to skew control mechanism 13, is 
associated with the upper conveyor unit 17. 
The cut-off rolls 7, 8, 14 and 15 are of conventional contruction, and the 
upper rolls 7 and 14 each include one or more generally helical or spiral 
blades 19 which cooperate with a spiral groove 20 in the lower rolls 8 and 
15 to cut the strips 9 as they pass between the rolls. 
The conveyor unit 12 includes an endless conveyor belt 21 which travels 
over a drive roll 22 and idler roll 23. The drive roll 22 can be driven by 
any conventional drive mechanism to thereby move the belt 21 in its 
endless conveying path. 
The skew control mechanism 13 includes a series of groups of wheels 24 
which ride on the cut section 11 being conveyed on belt 21, and the wheels 
of each group are spaced transversely across the machine. As shown in FIG. 
1, there are four groups of wheels 24a-24d, but the number of groups and 
the spacing between groups can vary depending on the length of the cut 
sections 11. The longitudinal spacing between adjacent groups of wheels is 
designed so that the wheels of at least one group will be in contact with 
each of the cut sections 11 at all times to thereby provide proper control 
for the cut lengths or sections 11. 
While the drawings show 10 wheels in each group, the number can vary 
depending on the width of the machine and the width of the cut strips 9. 
Each of the wheels 24 includes a pneumatic tire 25 which is mounted on a 
hub 26 that is journalled on axle 27. The pressure within the tires is 
generally maintained at a relative low value in the range of 2 to 5 psig, 
so that the tires riding on the cut sections 11 will provide a soft 
cushioning action. 
As best illustrated in FIG. 3, each axle 27 is cantileverd from an arm 28 
that is secured to a sleeve 29, and sleeves 29 are mounted for rotation on 
a transverse shaft 30 which extends across the machine. With this 
construction, the wheels 24 are free to pivot or float in a vertical plane 
and, thereby apply constant downward pressure on the cut sections 11 which 
are moving along the conveyor belt 21. 
It is preferred to partially counterbalance the wheels to reduce the 
downward pressure being applied to the cut sections 11. In this regard, an 
arm 32 is connected to each of the arms 28 and extends forwardly to the 
opposite side of the shaft 30 from the arm 28. A counterweight 33 is 
adjustably connected to the forward end of each arm 32. As shown in FIGS. 
3 and 5, the counterweight 33 is provided with a pair of upwardly 
extending lugs 34 which are connected to the forward end of the arm 32 by 
a bolt 35. Each bolt extends through a slot in the end of the arm 32, and 
the slotted connection provides a means of adjusting the position of the 
counterweight in the machine direction to thereby vary the magnitude of 
the counterbalance force. As previously noted, the wheels 24, and the 
pivotal connection of the wheels 24 to shaft 30, along with the 
counterweight 33 provides a soft floating action which will control the 
cut lengths and prevent skewing as they move along the conveyor, without 
adversely loading the conveyor drive mechanism. 
As illustrated in FIG. 6, the ends of each shaft 30 are provided with 
collars 36 and lugs 37 extend outwardly from the collars. The lug at each 
end of the shaft is pivotally connected to clevis 38 on carriage 39 by pin 
40. The pins 40 extend through elongated slots in the lugs 37. The 
carriages 39 located along each side of the machine are pivotally 
connected together by longitudinal arms 41. The carriages 39, connecting 
arms 41, shafts 30 and wheels 24 thus comprise an integral unit or 
structure. To facilitate installation of the skew control mechanism 13 on 
the machine 1, each carriage 39 is provided with a pair of rollers 42 that 
are adapted to ride on tracks 43 secured to the side walls 3 of the 
machine and as shown in FIG. 6, each track 43 is mounted on a bar 44 which 
is connected to vertical plate 45 that is mounted through channels 46 to 
the respective side wall 3 of the machine. 
With this construction the entire skew control mechanism 13 can be removed 
as a unit from the cut-off machine by merely sliding the carriages 39 
outwardly along the track 43. This greatly facilitates the servicing of 
the cut-off knives, as well as removing jam-ups of the cut sections that 
may have occurred at the cut-off knives. 
In accordance with a feature of the invention, an adjusting unit, indicated 
generally by 48, as best shown in FIGS. 3 and 4, is associated with each 
side of the skew control mechanism 3 to shift the angularity of the shafts 
30 with respect to the machine direction to thereby correspondingly shift 
the axes of wheels 24 and steer skewed sections 11 into machine direction 
orientation. Each adjusting unit 48 comprises a horizontal bar 49 which is 
secured to the rearmost carriage 39. The rear end of the bar 49 is 
connected by pin 50 to the lower end of a vertical bar 51, and a bolt 52 
has an outer threaded end 53, which is threaded within an opening in 
bracket 54, and has an inner end which extends freely through an opening 
in the upper end of vertical bar 51. Mounted centrally on bolt 52 is a 
stop collar 55. As bolt 52 is turned clockwise, stop collar 55 moves 
vertical bar 51, arm 49 and the corresponding carriages in a direction 
toward the cut-off knife. Lock nut 56 serves to retain the bolt 52 in 
position. 
The carriages 39 along each side of the machine will be forced rearwardly 
against the respective adjusting bolt 52 by the force of the cut sections 
11 passing through the machine. By threading the bolt 52 at one side of 
the machine inwardly, the carriages along that side of the machine will be 
moved forwardly relative to the carriages on the opposite side of the 
machine to thereby pivot the shafts 30 relative to the machine direction. 
Pivoting or shifting of the shaft will cause the axes of the wheels 24 to 
correspondingly shift. In operation, if the operator observes that the cut 
sections 11 are being discharged from the cut-off knives in a skewed 
manner, the operator, through adjustment of the bolts 52, can steer the 
cut sections 11 back into machine direction alignment. On the other hand, 
if the cut lengths 11 are being discharged from the cut-off knives with 
the proper machine direction orientation, no adjustment is necessary and 
the wheels 24 will provide pressurized floatation on the cut sections to 
prevent skewing as the sections move along the conveyor. 
The skew control mechanism 18 associated with the upper cut-off unit 6 is 
similar in construction and function to skew control mechanism 13 and 
comprises a series of groups of wheels 57. As shown in FIG. 1, the 
conveyor 17, which is similar in construction and function to conveyor 12, 
has a shorter length than conveyor 12, so that only two groups of wheels 
57a and 57b are utilized. As shown in FIG. 2, the wheels 57 of each group 
are spaced transversely across the machine. 
Each of the wheels 57 is similar in construction to wheels 24 and is 
supported from an arm 58 that is secured to a sleeve 59 journalled on 
transverse shaft 60. Spacers 61 are located between the sleeves. 
As in the case of the skew control mechanism 13, the weight of the wheels 
57 is partially counterbalanced by a counterweight 62 which is adjustably 
mounted on the end of an arm 62 which extends forwardly from the 
corresponding arm 58. 
The ends of the shafts 60 carry collars 64, and a slotted lug 65 which is 
secured to each collar is pivotally connected to clevis 66 on carriage 67 
by pin 68. As in the case of the lower skew mechanism control- 13, the 
carriages 67 along each side of the machine are pivotally connected 
together by connecting arms 69. 
Each carriage 67 includes a pair of rollers 70 that ride on track 71 which 
is supported on bar 72. Each bar 72 is connected through vertical plate 73 
and channel 74 to the side wall 3 of the machine. 
As in the case of the lower skew control mechanism 13, an adjusting 
mechanism 75 is associated with each side of the upper skew control 
mechanism 18 to pivot or shift the shafts 60 relative to the machine 
direction to thereby steer skewed cut sections 11 back into a machine 
direction orientation. Each adjusting mechanism 75 includes a bolt 76 
which is threaded within an opening in a bracket 77 secured to the 
rearmost channel 74. The forward end of each bolt engages the rear end of 
the rearmost carriage 67 and the bolts can be locked in position through 
lock nuts 78. 
The pressure of the cut sections 11 moving along the conveyor 17 forces the 
carriages at each side of the machine into engagement with the respective 
bolts 76. By threaded adjustment of the bolts 76, the shafts 60 can be 
pivoted relative to the carriages 67 to thereby move the axes of the 
wheels 57 relative to the machine direction. As previously described, if 
it is observed that the cut sections 11 are skewed as they are discharged 
from the cut-off knive, the axes of the wheels can be shifted relative to 
the machine direction by adjustment of bolts 76 to steer the cut sections 
toward the machine direction. 
The apparatus of the invention not only prevents skewing of the cut 
sections on the conveyor leading to the stacking machine, but is also 
capable of correcting a skewed condition by steering the skewed sections 
into machine direction orientation. 
Through the use of individual wheels attached to each transverse shaft, 
segmental floatation is achieved as opposed to entire width flotation as 
used in prior art machines. The segmental floatation insures that 
substantially uniform pressure is applied to the cut sections 11 and 
prevents skewing in the event that the cut sections are located only along 
one side of the machine. 
As the entire skew control mechanism can be readily removed from the 
machine, servicing of the cut-off knives is facilitated and jam ups can be 
readily corrected. 
The groups of wheels are preferably arranged so that wheels of at least one 
group are in contact with each cut section at all times, thereby insuring 
that even the shortest cut section is fully controlled to prevent skewing. 
Various modes of carrying out the invention are contemplated as being 
within the scope of the following claims particularly pointing out and 
distinctly claiming the subject matter which is regarded as the invention.