Paper web perforating machine

A machine for performing certain operations in the production of endless business forms has a plurality of cross-perforating knife blades for perforating the endless paper webs at predetermined increments, whereby the perforating knife blades are mounted in slots in the surface of rotating cylindrical bodies and are cutting through the paper webs with their spaced apart perforating knife edges against a rotating "anvil" cylinder which has a hardened, smooth surface. The cyclic impacts of the perforating blades on the anvil cylinder can become resonant with critical frequencies of the anvil cylinder at certain speeds of the latter and with a certain number of inserted perforating blades causing the destruction of the cutting edges of the former, and therefore the structure of the anvil must be such that no resonances will occur between the cyclic impacts of multiple perforating blades at high speed production operations of the machine. Similarly the structure of the knife blade cylinder may be such that resonance will not occur and the combined anvil cylinder and knife blade cylinder may be so structured to shift or reduce resonant frequency problems.

BACKGROUND OF THE INVENTION 
A. Field of the Invention 
The invention relates generally to paper cutting devices and particularly 
to paper web perforating devices having rotatable anvils against which 
multiple perforating knives mounted in spaced distances on the surface of 
rotating cylinders operate. 
B. Description of the Prior Art 
Machines and devices for perforating paper webs in the longitudinal and in 
the transverse direction are known in the art. Such devices have discs 
with perforating tools operating against die rings correspondingly having 
female discs and having further one or two cross perforating cylinders 
carrying one or more axially extending perforating knife blades arranged 
in slots in the surface of the cylinders, which operate against an anvil 
cylinder having a smooth, hardened surface. The perforating blades are 
adjusted in their slots in the perforating cylinders in such manner, that 
their cutting knife edges touch the hardened, smooth surface of the anvil 
cylinder without breaking or bending the cutting knife edges, thus cutting 
cleanly through the paper webs, which are fed over the anvil cylinder. 
However it has become known that machines of this kind could only be 
operated at relatively slow speed when more than 2 perforating blades had 
been set 180.degree. C apart from another in the perforating cylinder. The 
problem was that difficulties started mounting with increased speed of the 
machine or when 4, 6 or 8 blades had been arranged at spaced 
circumferential distances on the periphery of the perforating cylinder. 
These difficulties resulted from vibrations of the anvil cylinder under 
the rythmic impacts of the perforating blades which inexplicably got bent 
and blunted knife edges from the periodical hammering at the hardened 
surface of the anvil, thus rendering a perforation impossible after a 
short operation, particularly in the center portion of the paper webs. By 
making the journal ends of the otherwise solid anvil cylinder stronger 
and/or by increasing and prestressing the cylinder bearings the adverse 
condition did not improve and that problem is now solved by the 
applicant's invention. The word "webs" should be understood to include the 
singular "web" as well as the plural. 
The most relevant prior art are U.S. Pat. Nos. 1,018,155, 1,098,060, 
1,714,583 issued to Bengoush, Spiller and Anthony respectively. None of 
these show an anvil cylinder or a knife blade cylinder like that taught in 
this application. 
SUMMARY 
The invention consists in the novel parts, construction arrangements and 
improvements herein shown and described. The invention is direction toward 
the novel structure of the anvil cylinder and the knife blade cylinder (or 
either of them) (in the transverse perforation part of the paper webs 
perforation machine) against which the perforating blades of the 
perforating cylinders operate. The conventional anvil cylinder consists of 
a heavy piece of solid steel which has a substantial stiffness and 
resistance to deflection in bending. However a rotating body of this kind 
has a basic natural frequency of vibration (resonant frequency) and thus 
has a basic critical speed with respect to critical tolerances of adjacent 
parts. Multiples of this basic first order critical speed occur, and when 
load impacts are applied to the rotating body at the same frequency of 
vibration of the cylinder at one of the critical speeds, a harmonic 
resonance will occur, resulting in substantial deflections and vibrations 
of the rotating cylinder. Such deflections and vibrations cause the 
perforating blades to hammer hard on the surface of the anvil cylinder, 
and their cutting knife edges are bent and damaged. A typical example of 
the range of these critical speeds is shown in the table: 
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order of critical 
speed 1 2 3 4 5 6 7 
number of cylinder 
revol./min. 775 675 720 600 540 440 480 
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indicating also the order of intensity of damage to the knife edges of the 
blades. The worst conditions had been found when 6 and 8 perforating 
blades had been inserted in the perforating cylinders. 
By changing the structure of the anvil cylinder the natural frequency and 
the range of the subsequent multiples thereof is changed to such an 
extent, that the critical speeds and the deflections and vibrations are no 
longer in the range of the rythmic impacts of the perforating actions of 
the blades. The gist of the invention is to make either or both the anvil 
cylinder and the knife blade cylinder partly hollow or filled with a 
different material whereby the moment of inertia of the cross sections of 
the partly hollow or partially filled cylinder varies over the length of 
the cylinder between the bearing supports thereof without sacrificing the 
degree of stiffness of the cylinder. It is at the same time an advantage 
to reduce the weight of the cylinder or cylinders whereby the deflection 
thereof in the center under its own weight between the supporting bearings 
is reduced. 
Objects and advantages of the invention will be set forth in part hereafter 
and in part will be obvious herefrom or may be learned by practicing the 
invention the same being realized and attained by means of the 
instrumentalities and combinations pointed out in the appended claims. 
It is an object of the invention to provide an improved anvil cylinder 
and/or perforating cylinder for a high speed multiple blade paper webs 
perforating machine. 
A further object of the invention is to provide an anvil cylinder and/or a 
perforating cylinder for a high speed paper webs perforating machine which 
has a partly hollow structure. 
Furthermore it is an object of the invention to provide a novel anvil 
cylinder and/or perforating cylinder in a high speed multiple blade paper 
webs perforating machine by which the production speed of the latter is 
substantially improved. 
Various further and more specific purposes, features and advantages will 
clearly appear from the detailed description given below taken in 
connection with the accompanying drawing which forms part of the 
specification and illustrates merely by way of example one embodiment of 
the device of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now in detail to the drawing illustrating a preferred embodiment 
by which the invention may be realized; there is a perforating machine 10 
shown, which has a frame 11 in which two driven "hole punching" cylinders 
12, 13 are rotatably located in adequate bearings for punching holes 
through the paper webs W or webs in successive order. Paper web W is 
further led over an idler roller 14 to a driven slitter roller 15 where it 
is longitudinally slit into ribbons of page width. The ribbons are then 
fed over further idler rollers to a driven "impression" or "anvil" 
cylinder 16. Propeller rollers 17 are arranged to hold the ribbons in 
tight contact with the surface of anvil cylinder 16. Two perforating 
cylinders 18, 19 which are driven in unison with anvil cylinder 16, are 
located adjacent to anvil cylinder 16. It is obvious that also a single 
perforating cylinder 18 can be arranged, if so desired. Each one of the 
two shown perforating cylinders 18, 19 has a plurality of axially 
extending slots or grooves 20 in the surface thereof, in which the 
perforating knife blades 21 are adjustably clamped by means of bars 22. 
Knife blades 21 are set to touch the surface of anvil cylinder 16 so that 
they will cut cleanly through the ribbons of paper webs across the width 
thereof but without hitting hard at the hardened surface of anvil cylinder 
16. The cut is obviously an interrupted one since blade 21 consists of a 
plurality of small knife edges 23 which are separated from one another by 
a narrow gap 24. Thus the cut across the width of the ribbons of paper 
webs W is actually a "line" perforation. 
Anvil cylinder 16 consists of a tubular steel sleeve 25 having a smooth, 
hardened surface. End plugs 26, 27 are pressed into steel sleeve 25 and 
are welded to the latter. Plug 26 has further extensions 28, 29 for 
accommodating the seats for the roller bearing 30 and for the drive gear 
31, respectively, whereas plug 27 has only the extension for the seat 32 
for the bearing 33. Plugs 26, 27 have cone-shaped inner cavities 34, 35 
extending from the inside of the inner end of the plugs to a certain 
predetermined depth, and the total pressed-in length of the plugs 26, 27 
is predetermined at a certain proportion of the total length of the body 
of anvil cylinder 16. Plug 27 further has an axially extending central 
bore 36 through which sound absorbing material 37, such as for example a 
polyurethane foam, may be filled into the inner cavity of anvil cylinder 
16. 
In another embodiment of the present invention, a perforating cylinder 
(Show in FIG. 5) 116 consists of a tubular steel sleeve 125 having a 
smooth hardened surface. End plugs 126, 127 pressed into the sleeve 125 
and welded thereto. Plugs 126, 127 have extensions 128, 129 for 
accommodating the sets of roller bearings. Plugs 126, 127 have cone-shaped 
inner cavities 134, 135 extending from the inner end of the plugs to a 
predetermined length and the total pressed in length of the plugs 126, 127 
is determined in proportion to the total length of the perforating 
cylinder 116. Plug 127 has an axially extending bore 136 through which 
sound absorbing material 137 may be placed. Axially extending slots 120 
have perforating knife blades 121 are adjustable, clamped by means of bars 
122. Tubular sleeves 25, 125 have radially inwardly depending edges 40, 
140 forming stops for the end caps 26, 27, 126, 127 and a discontinuity in 
the inner surfaces 25A, 125A of the sleeves 25, 125. The end caps 26, 27, 
126, 127 may be formed from a material having a different density than 
that of the sleeve members 25, 125. 
The natural frequency and the critical speed of this structure, as well as 
the harmonic multiples of the first critical speed is now out of the range 
of any resonance at the high production speed of the machine. Thereby no 
further hammering of the knife edges of the perforating blades against the 
hardened surface of anvil cylinder 16 can occur and the knife edges 23 of 
the perforating blades 21 remain sharp and undamaged. 
While the invention has been described and illustrated with respect to a 
certain preferred example which gives satisfactory results, it will be 
understood by those skilled in the art after understanding the principle 
of the invention, that various other changes and modifications may be made 
without departing from the spirit and scope of the invention, as it is 
expressed in the appended claims.