Method for adjustment of slitter blades

A pair of cooperating circular slitter blades are adjusted by locking a first of these blades in a selected axial position on its drive shaft and moving the second of these blades along its drive shaft into engagement with the first blade. Prior to locking the second blade in an axial position on its drive shaft, the latter together with the second blade are turned slowly through at least one revolution for axial runout of the second blade. Thereafter the second blade is locked in axial position.

This invention relates to rotary slitters in general and more particularly 
relates to a method for setting the operative relationship between 
cooperating circular slitting blades. 
Shortly after a relatively wide web of corrugated board issues from a 
so-called double backer, the wide web is slit longitudinally into a 
plurality of narrower webs. Typically, each of the longitudinal cuts or 
slits is made by a pair of cooperating rotating slitter blades which must 
be set with precision in order to obtain an accurate cut and to prevent 
excessive wearing of the slitter blades. 
In the prior art, positioning of the slitter blades was usually 
accomplished by accurately positioning one of the blades and locking it in 
adjusted position. Thereafter, the other blade was brought into engagement 
with the fixed blade and then the other blade was locked in axial 
position. Even though the contact pressure between the blades was not 
particularly great for the angular positions of the blades at the time the 
last of these blades was locked in axial position, as the blades rotated 
excessive forces developed between the blades leading to excessive blade 
wear. More particularly, high contact forces resulted from so-called axial 
runout, a condition which exists because some points of the engaging blade 
surfaces lie outside of a single plane of engagement lying perpendicular 
to the shafts for the slitter blades. 
In order to eliminate excessive wear due to axial runout, the prior art has 
provided means for axially biasing one of the slitter blades toward the 
other cooperating slitter blade. This type of arrangement is disclosed in 
U.S. Pat. No. 4,026,176 issued May 31, 1977 to G. Weiskopf for Means For 
Setting Slitting Heads. In order to be effective, the springs of the prior 
art arrangement must exert sufficient force so that the blade being biased 
is not easily deflected yet the force must not be so great that there is 
excessive blade wear. 
In order to overcome the aforesaid difficulty encountered by the prior art, 
the instant invention provides an arrangement wherein both of the 
cooperating slitter blades are locked in fixed positions on their 
respective shafts. However, because of a novel set-up method, blade wear 
is reduced substantially over that resulting from prior art arrangements. 
In particular, according to the instant invention the first slitter blade 
of the pair is locked in a selected axial position, the second slitter 
blade is moved axially into engagement with the first slitter blade, both 
shafts are then rotated slowly, and then the second slitter blade is 
locked in axial position. With this set-up arrangement, the blades make 
only line-to-line contact at the point of closest approach between the 
blades. Axial runout causes only a small clearance between the blades. 
Typically, such clearance is in the order of 0.003" which, in the case of 
sharp blades, will cause no problems in cutting. Since there is no 
negative clearance or interference between blades, excessive blade wear is 
avoided. 
Accordingly, the primary object of the instant invention is to provide a 
novel method for setting the operative relationship between rotating 
slitter blades. 
Another object is to provide a method of this type which results in 
substantially reduced blade wear. 
A further object is to provide a method of this type which is utilized with 
cooperating slitter blades, both of which are locked in axially fixed 
positions.

Now referring to the Figures and more particularly to FIG. 1 which 
illustrates slitter 10 for longitudinally cutting a web of corrugated 
board (not shown) or the like which moves between and parallel to slitter 
shafts 11, 12 in a plane perpendicular to the plane of the drawings. 
Cooperating circular slitter knives 15, 16 are mounted on respective 
shafts 11, 12 as are knives 17, 18 of another set of cooperating slitter 
knives. According to the prior art, slitter knives 15-18 are moved to and 
locked in their respective cutting positions by initially moving blades 15 
and 17 to selected axial positions where they are locked against axial 
movement. Thereafter, blade 16 is moved axially along shaft 12 until blade 
16 engages blade 15 and then blade 16 is locked in axial position. 
Similarly, blade 18 is moved axially along shaft 12 until blade 18 engages 
blade 17 after which blade 18 is locked in axial position. Utilizing the 
aforesaid set-up procedure of the prior art, axial runout, as shown in 
FIG. 2, results in extremely high forces acting between blades 15, 16 
leading to excessive blade wear. Axial runout comes about because the 
engaging blade surfaces are not parallel to one another for all rotational 
positions of shafts 11, 12. 
Pursuant to the instant invention, blade set up takes place by initially 
moving one of the blades in each set, say blade 17, to a selected axial 
position along upper shaft 12 and then locking blade 17 in this position. 
Blade 18 is then moved axially along shaft 12 into engagement with locked 
blade 17. Prior to locking blade 18 in axial position, shafts 11, 12, and 
blades 17, 18 keyed thereto are rotated slowly through at least one 
complete revolution. Now the axial runout of blade 18 causes the latter to 
be realigned and assume the position shown in FIG. 3. This results in only 
line-to-line contact between blades 17, 18 at the point of closest 
approach between them. This runout causes only a small positive clearance 
between blades 17, 18. With sharp blades 17, 18, as much as 0.003" of 
clearance causes no problems in cutting, and without negative clearance or 
interference, excessive loading between blades 17, 18 is avoided. After 
runout, blade 18 is locked in axial position. 
In FIG. 4 both of the blades 16, 18 on lower shaft 12 have, according to 
the instant invention, been locked in their respective axial positions 
after axial runout. Preferably, to obtain the arrangement of FIG. 4 both 
of the blades 15, 17 are locked in their respective axial positions on 
upper shaft 11. Blades 16 and 18 are then moved axially on shaft 12 into 
contact with the respective blades 15 and 17. However, prior to locking 
blades 16 and 18 in these axial positions both shafts 11 and 12 are 
rotated slowly to rotate blades 15-18 through at least one complete 
revolution whereby blades 16 and 18 assume runout positions in which they 
are locked axially to shaft 12. 
It is noted that for purposes of illustration only, the proportions between 
the slitter blades and their shafts is not accurate. That is, these 
proportions have been exaggerated in order to accentuate the condition 
resulting from axial runout. 
Although a preferred embodiment of this invention has been described, many 
variations and modifications will now be apparent to those skilled in the 
art, and it is therefore preferred that the instant invention be limited 
not by the specific disclosure herein, but only by the appending claims.