Rotary cutting apparatus

A rotary cutting apparatus for forming serially connected envelope blanks from a longitudinally advancing web of sheet material is provided with two rotary knives, both of which rotate into cutting relationship with the same stationary knife but at different times. The web of sheet material is advanced over the stationary knife so that at least one side of the web is positioned between the stationary knife and each of the rotary knives to remove a section at the side of the web. With two sets of rotary and stationary knives operating respectively on the two sides of the web, a series of interconnected envelope blanks can be formed by feeding the web through the cutting apparatus at a speed coordinated with the rotations of the knives. By adjusting the angular relationship of the two rotary knives with respect to one another about the axis of rotation, the section of sheet material removed from the advancing web can be varied correspondingly. Such adjustment in conjunction with a change in the feed rate of the web permits envelope blanks, and resulting envelopes, of different sizes to be formed with the same cutting apparatus.

BACKGROUND OF THE INVENTION 
The present invention relates to a rotary cutting apparatus for cutting an 
advancing web of sheet material. More particularly, the present invention 
is related to an adjustable rotary cutting apparatus for cutting serially 
connected envelope blanks from a web of sheet material advancing 
longitudinally through the cutting apparatus. 
It is a common practice to manufacture envelopes by cutting envelope blanks 
in serially connected relationship from a web of sheet material, usually a 
high quality paper. The web is pulled from a spool and advanced or fed 
longitudinally through a cutting machine which removes corresponding 
sections from each side of the web. The knives in the cutting apparatus of 
the machine are so shaped that the material remaining in the web defines a 
series of interconnected envelope blanks, each blank having a front panel, 
two side flaps, a rear panel and a closing flap. The serially connected 
blanks are subsequently severed from one another by a cut-off knife. Each 
blank is then folded, pasted and gummed in addition to any other special 
processing required to form a finished envelope. 
The cutting apparatus used in the past at each side of the advancing web of 
sheet material to form the serially connected envelope blanks has 
generally included a rotary knife cyclically engaging a stationary knife 
to shear a section conforming generally to one side flap and portions of 
the closing flap and the rear panel of the envelope. The cutting edges of 
the knives would, accordingly, have profiles corresponding precisely with 
the section of sheet material to be removed from one side of the web. If 
the size of the envelope was changed in such a manner that it necessitated 
a change in the shape of the envelope blank along a dimension extending 
parallel to the direction in which the web was fed through the cutting 
apparatus, it was necessary to change the rotary knife and stationary 
knife as well as the advancement of the web through the cutting apparatus 
during each knife rotation. 
To cut different sized envelopes, therefore, it was necessary to have pairs 
of stationary and rotary knives of different sizes. Both sets of knives at 
each side of the web were replaced in their entirety whenever a different 
size of envelope was run. 
It is an object of the present invention to disclose a new rotary cutting 
apparatus in which a single set of knives can be adjusted to cut envelopes 
of many different sizes. 
SUMMARY OF THE INVENTION 
The present invention resides in a rotary cutting apparatus for forming 
serially connected envelope blanks from a longitudinally advancing web of 
sheet material. The cutting apparatus includes one stationary knife over 
which at least one side of the advancing web of sheet material passes in a 
cutting operation. The stationary knife has a cutting edge determining the 
contours of a section of sheet material to be removed from the one side of 
the web but the shape of the section to be removed and the cutting edge do 
not have exactly the same profile. 
A first rotary knife having a cutting edge corresponding to at least part 
of the cutting edge on the stationary knife is supported for rotation 
about an axis bringing the cutting edges of the first rotary knife and the 
stationary knife into cutting relationship with the web of sheet material 
at the one side. The first rotary knife in its preferred form has a 
cutting edge coextensive with the cutting edge on the stationary knife so 
that a portion of the section to be removed is entirely severed from the 
web of sheet material by the first rotary knife. To this extent, the 
cutting apparatus in the preferred form is similar to the prior art 
cutting apparatus. 
A second rotary knife having a cutting edge corresponding to at least part 
of the cutting edge on the stationary knife is supported for rotation 
about the rotational axis of the first knife to also bring the cutting 
edges of the second knife and the stationary knife into cutting 
relationship with the web of sheet material. The second rotary knife, 
however, is held in spaced relationship to the first knife about the 
rotational axis so that the time interval between the engagement of the 
web by the first rotary knife and the engagement by the second rotary 
knife permits at least a segment of the web to advance through the cutting 
apparatus. The second rotary knife, therefore, operates upon a segment of 
the web material different from that operated upon by the first rotary 
knife. By adjusting the spaced relationship of the two rotary knives, the 
segment of the web operated upon by the second knife can be varied along 
with the size of the section removed. Coordinating the feed rate of the 
web and the spacing of the two rotary knives to change the size of the 
section removed permits envelopes of different sizes to be produced by the 
same cutting apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows portions of an envelope forming machine which produce envelope 
blanks from a web of sheet material that is fed longitudinally, as 
indicated by the arrow a, from a storage roll (not shown) into the 
machine. The envelope blank B shown at the right-hand side of FIG. 1 has 
been severed from the web W by a cut-off knife (not shown) and will be 
recognized as a blank for forming an envelope by the front panel f defined 
by the dotted fold lines, a rear panel or bottom flap r, two side flaps s 
and a closing or sealing flap c. The completed envelope is subsequently 
formed by folding the side flaps over the front panel, folding the rear 
panel over the front panel, pasting the side flaps and rear panel together 
and gumming the peripheral edge of the closing flap. 
In accordance with well-known practice, the envelope blanks B are formed 
from the web of sheet material by cutting out corresponding sections at 
each side of the web to form notches as shown in FIG. 1. A series of 
interconnected blanks is formed. The machine which forms the envelope 
blanks has at one side of the web W a rotary cutting apparatus, generally 
designated 10, embodying the present invention. A corresponding apparatus 
11, forming a mirror image of the apparatus 10, is located on the other 
side of the web. A pair of feed rollers 12 (only one visible) engage the 
top and bottom surfaces of the web at the input to the cutting apparatuses 
and another pair of rollers 14 (only one visible) engage the web at the 
output to cause the web W to advance through the cutting apparatus at a 
selected speed. The rollers 12 and 14 are connected by a variable ratio 
transmission 16 to a drive motor 18. 
The rotary cutting apparatus 10 has a set of knives or blades which operate 
on one side of the web W to cut out a section and thereby define portions 
of adjacent blanks B in the web. It will be noted that since the envelope 
blanks themselves are symmetric about the longitudinal axis of the web, 
the sections removed by the cutting apparatuses are also symmetric with 
respect to the same axis. Also, each time a section is removed, part of a 
side flap and closing flap of one blank and part of the side flap and rear 
panel of the adjacent blank are formed. 
The sets of rotary knives which remove sections from the web W are driven 
rotatably about axes extending parallel to the longitudinal axis of the 
web by means of the transmission 16 and motor 18. A cross drive 22 
interconnects the sets of knives at each side of the web to insure that 
the knives are driven in synchronism with one another and that they 
thereby remove sections from laterally opposed stations along each side of 
the web. The rotary knives make one complete revolution as the material 
needed to form a single envelope blank advances through the cutting 
apparatuses 10 and 11. A synchronized relationship of the knife rotations 
and web feed is maintained by the variable ratio transmission 16. A 
transmission with variable ratios is used so that the relationship between 
the feed rate and the rotational speed can be changed whenever it is 
desired to change the size of the envelope blank. 
FIGS. 2-4 show the detailed construction of the rotary cutting apparatus 10 
utilized at one side of the web W. The cutting apparatus 10 has a 
stationary knife or fixed blade 30 over which one side of the web W 
advances during a cutting operation. The stationary knife 30 has at its 
midsection a cut-out defined by a shearing or knife edge 32. The edge 32 
has curved portions and straight portions which determine the contours of 
the section to be removed from the one side of the web. It should be 
understood that the profile of the cutting edge is not exactly the same as 
the profile of the entire section removed from the web due to the 
operation of the cutting apparatus which is described in greater detail 
below. 
A large rotary knife or leading blade 34, shown separately in FIG. 5, and 
another small rotary knife or trailing blade 36, shown separately in FIG. 
6, are precisely mounted on an arbor shaft 38 and rotate about a 
rotational axis 40 of the shaft relative to the stationary knife 30. The 
arbor shaft 38 is supported in journal bearings 42, 44 and two upright 
sections of a frame 46 to which the stationary knife 30 is fixed by cap 
screws 48. The rotary knife 34 has a cutting edge 50 corresponding in 
shape to the cutting edge 32 of the stationary knife 30 and the knife 34 
is mounted on the arbor shaft 38 so that the cutting edges 32 and 50 are 
brought into cutting relationship with the web each time the knife 34 is 
rotated past the stationary knife 30. In a similar manner, the rotary 
knife 36 has a cutting edge 52 which corresponds in shape to a part of the 
cutting edge 32 over which the one side of the web first passes when the 
web is fed in the direction indicated by the arrows a in FIGS. 1, 2 and 3. 
The knife 36 is also precisely mounted on the shaft 38 so the cutting 
edges 32 and 52 are brought into cutting relationship with the web of 
sheet material during each revolution of the shaft 38. 
The rotary knife 34 is supported from the shaft 38 by means of a clamp or 
blade holder 58 including split members 60 and 62, shown most clearly in 
FIG. 4. The member 60 is held fixedly in position on the arbor shaft 38 by 
means of a key 64 and cap screws 66. A base plate 68 is mounted in 
cantilever fashion from the projecting end of the member 60 by means of 
cap screws 70. The rotary cutting knife 34 is held on the base plate 68 by 
means of cap screws 70 and 72. Two wedges 74 (only one shown) are engaged 
respectively by two of the cap screws which hold the knife 34 and are 
interposed between the knife 34 and a tang 76 at the rear of the base 
plate 68 to hold the knife 34 precisely in its radially projecting 
position with respect to the shaft 38. 
The small rotary knife 36 is mounted on the arbor shaft 38 by means of an 
adjustable clamp or blade holder 80 including split members 82 and 84. 
Unlike the clamp 58, the clamp 80 is not keyed to the shaft 38 but instead 
is capable of being adjusted to different angular positions about the 
shaft. Cap screws 86 hold the members 82 and 84 in clamping relationship 
with the shaft 38. The cap screws at the projecting end of the clamp 80 
also secure the knife 36 to the clamp and a pair of wedges 88 precisely 
position the knife 36 in a radially projecting position when the cap 
screws 86 are tightened. Of course, the positions in which the rotary 
knives 34 and 36 are held bring the cutting edges 50, 52 of the knives 
into shearing or cutting relationship with the edge 32 on the stationary 
knife 30 as shown for example, by the knives 30 and 34 in FIG. 4. 
The bushings 90 and 92 hold the clamps 58 and 80 in an axially fixed 
position along the arbor shaft 38. 
OPERATION 
The operation of the cutting apparatus 10 at the one side of the web W is 
best described in connection with FIGS. 3 and 4. As the web advances 
through the cutting apparatus in the direction of the arrow a, the arbor 
shaft 38 is rotated as indicated by the arrow b (also shown in FIG. 1). 
When the cutting edges of the rotary knife 34 and stationary knife 30 come 
together on the web, a portion of the section to be removed to form an 
envelope blank is cut from the one side of the web. The portion removed by 
the knife 34 has the same profile as the cutting edges 32, 50 on the 
knives 30 and 34. 
The web W continues to advance after the knife 34 rotates downwardly 
through the cut-out in the stationary knife 30. When the second or small 
rotary knife 36 rotates downwardly onto the web W in cutting relationship 
with the knife 30, a longitudinal segment of the web W represented in FIG. 
3 by the dimension d will have moved over the stationary knife 30 and the 
remaining, generally trapezoidal portion of the section to be removed is 
cut by the knife 36. It will be readily apparent that by adjusting the 
clamp 80 and varying the angle between the rotating knives 34 and 36, the 
size of the section removed by the cutting apparatus 10 is changed. 
To set up the machine and adjust the cutting apparatus 10 for an envelope 
blank of a given size, the feed rate of the web W and the rotational speed 
of the cutting knives 34 and 36 are adjusted relative to one another by 
means of the variable ratio transmission 16 in FIG. 1. The relationship of 
the rotational speed and the feed rate is selected so tht the rotary knife 
34 makes one complete revolution with the arbor shaft 38 while the web of 
sheet material advances by an amount equal to the cut-off length of an 
envelope blank, the longitudinal length of the web between corresponding 
points on serially adjacent envelope blanks. 
The angular relationship between the rotary knife 34 and the rotary knife 
36 is then determined from the incremental portion which is to be cut 
solely by the small knife 36 from the section forming the blank of given 
size. Such portion has a length equal to the distance the web advances 
after the knife 34 cuts the web and until the knife 36 cuts the web. The 
distance is represented in FIG. 3 by the dimension d. Establishing a ratio 
in which the numerator is d and the denominator is the cut-off length, and 
multiplying the ratio by 360.degree. determines the angle .alpha. defining 
the spaced relationship of the two rotary knives. By adjusting the angular 
relationship of the knives to the determined angle, the desired section 
will be removed from the web during each revolution of the arbor shaft 38. 
It will be understood that normally part of the cutting edge 52 on the 
knife 36 will partially duplicate or overlap upon the longitudinally 
extending cut produced by a part of the cutting edge 50 on the knife 34. 
The amount of the overlap along the longitudinal cut depends upon the 
angular adjustment of the knives 34 and 36. The angular spacing of the 
knives 34 and 36 reaches an upper limit at a point where the overlap 
disappears so that the longitudinally extending parts of the cutting edges 
50 and 52 produce longitudinally "contiguous" cuts. "Contiguous" here 
means in actual contact and non-overlapping. 
It will thus be seen that the disclosed rotary cutting apparatus can be 
adjusted to cut envelope blanks of different sizes with the same set of 
stationary and rotating knives. It is no longer necessary to maintain many 
sets of knives for many different blanks. Substantial savings can be 
realized with the cutting apparatus because the knives have one basic 
design. 
While the present invention has been described in a preferred embodiment, 
it should be understood that still other modifications and substitutions 
can be had without departing from the spirit of the invention. Although 
the rotary knife 34 has a cutting edge 50 corresponding substantially to 
the entire cutting edge 32 of the stationary knife 30 and the edge 52 on 
knife 36 is shorter, it is possible to utilize two shorter rotary knives 
having cutting edges which correspond in shape to overlapping parts of the 
cutting edge 32 on the stationary knife. For example, if the knife edge 50 
on the rotary knife 34 terminated without having a portion mating with the 
diagonally extending part 32a, (FIG. 3) of the edge 32, the rotary cutting 
apparatus, nevertheless, would operate successfully and remove a section 
at the side of the web in substantially the same manner as described 
above. The only difference in operation that could be observed would be 
that the entire section cut from the web would be removed in one piece 
rather than in two pieces. It is merely necessary that the cuts produced 
by the two shorter rotary blades intersect, preferably in overlapping 
relationship, so that a section is completely severed from the one side of 
the web. The particular construction of the clamping members, can, of 
course, be varied in order to permit one or both of the knives to be 
angularly adjusted about the arbor shaft 38. It is, however, preferable to 
have the rotary knife which forms a portion of the closing flap keyed to 
the shaft since the shaft and the cut-off knife are drivingly 
interconnected, and the cut-off knife and the rotary knife forming the 
closing flap must operate upon the advancing web at precisely related 
positions. While the present invention has been disclosed with two rotary 
knives adjustable relative to one another about the arbor shaft, it is 
possible that additional adjustable rotary knives must be added to operate 
in conjunction with the stationary knife 30 upon successive segments of 
the advancing web. Accordingly, the present invention has been described 
in a preferred embodiment by way of illustration rather than limitation.