US3916744A

US3916744A - Rotary web perforating apparatus

Info

Publication number: US3916744A
Authority: US
Inventors: Henry L West
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-05-02
Filing date: 1973-05-02
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04
Also published as: FR2227933B1; FR2227933A1

Abstract

A rotary web perforating apparatus for making perforations in one or both side edges of a web such as a photographic film. The web perforating apparatus comprises a rotary, variable width, web supporting drum having a plurality of individual, hinged perforator assemblies of improved design mounted on the drum periphery and movable therewith for perforating the web at speeds of 1,500 feet per minute or more.

Description

[451 Nov. 4, 1975 United States Patent [191 West U.S. Patent Nov. 4, 1975 sheet 1 of 6 3,916,744

U.S. Patent Nov.4, 1975 sheet 2 @f6 3,916,744

, 1975 Sheet 3 0f 6 U.S. Patent Nov, 4

U.S. Patent N0v.4, 1975 sheen @f6 3,916,744

U.S. Patent N0v.4, 1975 sheetof 3,916,744

ROTARY WEB PERFORATING APPARATUS i BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates generally to perforating apparatus, and more specifically to an improved rotary web perforating apparatus.

2. Description of the Prior Art Rotary web perforating apparatus for making edge perforations in a web such as a photographic film are generally old in the art, as exemplified by U.S. Pat. Nos. 2,760,576 and 3,661,044. In such rotary web perforators, a rotary drum is provided with a plurality of individual, hinged perforator assemblies rotatable therewith, and movable by stationary cam means from a retracted position to a perforating position upon rotational movement of the drum. When such rotary perforators are used to perforate webs at a high rate of speed, such as 200 feet per minute or more, portions of the perforator assemblies, such as the rocker arm and punch assembly, are subjected to repetitive, reciprocal movement at a high rate of speed, resulting in a high degree of wear at the bearings and other load points. Since web perforating, particularly the perforation of photographic film, is necessarily a precise operation requiring the maintenance of close tolerances so that the perforations exactly match and engage the teeth of drive sprocket wheels, any undue wear in the perforator assemblies cannot be tolerated. Although the aforementioned rotary web perforators operated satisfactorily, some of the shortcomings or disadvantages of such perforators is their inability to perforate at high rates of speed such as l,500 feet per minute or more. In addition, the apparatus is not capable of precise, repetitive, reciprocal action at the higher rates of speed without excessive wear and breakdown. Also, such prior art rotary web perforators are designed to handle webs of a predetermined width, and cannot be readily modified to handle webs of varying widths.

SUMMARY OF THE INVENTION In accordance with a preferred embodiment of the invention, a rotary web perforating apparatus is disclosed comprising a shaft journaled for rotation in a support member, and a web supporting drum secured `to the shaft and mounted on bearings interposed between the support member and drum for concentric rotation and transport of the web. A plurality of individual, hinged web perforating means are mounted on the drum in circumferentially spaced relation for rotation therewith, and are movable upon rotation of the drum between a retracted position displaced from the web,

and a perforating position for perforating the web. Cam

means are mounted on a cylindrical surface of the sup- `port membereccentric to the shaft, and ring means are is provided with a tunnel connected to a vacuum source for removing web chips produced during a perforating operation. Chip deflection means are provided rotatably supported at one end of the shaft for continuously deflecting the web chips into the hollow shaft during rotation thereof. In another modification, the web perforating means is connected to the ring means by an actuating link having a spherical bearing at each end thereof. In another modification, the web perforating means is hinged, and is provided with an adjusting means, such as an eccentric, to adjust the position of the hinged rocker arm. In another modification, the web perforating apparatus is provided with a pair of coaxial drums, and coupling means, such as a cylindrical spacer, for drivingly coupling the drums together, and for axially spacing the first and second drums apart to vary the distance between the web perforating means for accommodating webs of varying width. In another modification, each of the perforating assemblies is provided with a punch holder for supporting a plurality of i parallel, spaced apart punches cooperating with corresponding die openings in a die assembly. The groups of punches and corresponding die openings on each side of a plane parallel to the punches and extending through the center of the holder and die assembly are substantially identical and reverse images of one another. In each group, the punches and corresponding die openings are spaced apart different distances, and are of different width in the circumferential direction. Consequently, the web perforations produced by the punches and dies in a curved web all have substantially the same effective width and pitch when the relaxed web is flattened or pressed on a plane surface. ln still another modification, means are provided to hold web tension at a preselected value within a predetermined range while in contact with the rotary perforator mechanism. Such tension mechanisms are well known in the art and are physically located ahead and/or after the rotary section. Such preselected tension values keep the perforation to perforation pitch constant on a relaxed flattened-out web, even though the circumference of the webs on the rotary perforator varies during a perforating operation. This system requires that relationship of punch spacing and the drum diameter be carefully chosenl based on the range of tension, thickness and modulus of elasticity of webs to be handled by the perforator. In still another modification, each of the web perforating assemblies is provided with a preloaded hinge means for pivotally coupling the rocker arm to the base of the perforator assembly to provide axial and rotational rigidity to the rocker arm for maintaining precise alignment of the punches and die openings diiring cyclic operation at a high rate of speed. In still another modification, a stripper comprising a leaf spring is provided for each perforating assembly for stripping the web chips from the punches. The stripper is designed, constructed and mounted such that the leaf spring provides mounting accuracy for the stripper, and a coil spring is used to select adequate stripping force andhigh resonant frequency for reducing the bouncing of the leaf spring during high speed stripping operation.

The primary object and advantage of the rotary web perforating apparatus of this invention is to perforate webs of varying width at a high rate of speed on the order of substantially 1,500 feet per minute or more in a highly precise manner with a minimum of maintenance and repair.

The invention and its objects and advantages will become more apparent from the detailed descriptionof the preferred embodiment presented below.

BRIEF DESCRIPTION OF THE DRAWINGS In the detailed description of the preferred embodiment of the invention presented below, reference is made to the accompanying drawings, in which:

FIG. lV is a perspective view with por'tions thereof broken away, illustrating a preferred embodiment of the rotary web perforating apparatus of this invention;

FIG. 2 is an enlarged, segmental side elevational view in section of the left side portion of the web perforating apparatus of FIG. l;

FIG. 3 is an enlarged fragmentary view taken substantially along line 3-3 of FIG. 2; illustrating the mechanism for the eccentric punch activating ring;

FIG. 4 is an elevational view of the perforating apparatus of FIG. 2 taken substantially from line 4-4, and illustrating the position of the actuating link at various degrees of rotation of the ring and drum;

FIG. 5 is an elevational view of FIG. 2 taken substantially from line 5 5;

FIG. 6 is a side elevational view, illustrating one of the individual perforating assemblies;

FIG. 7 is a section view taken substantially along line 7-7 of FIG. 6;

FIG. 8 is a side elevational view of a punch assembly for the perforating assembly;

FIG. 9 is a top plan view of the punch assembly of FIG. 8;

FIG. l0 is a top plan view of a die assembly for the perforating assembly;

FIG. 1l is a section view taken substantially along line ll-ll of FIG. 10;

FIG. l2 is a segmental view partially in section and in exaggerated form of a web on the drum after it has been perforated FIG. 13 is a view of the web of FIG. l2 lying in a plane; in which the effective width of each perforation and the effective pitch between perforations are substantially constant throughout the web length.

FIG. 14 is a view of the web lying in a horizontal plane after it has been perforated by an alternate arrangement of punches.

DESCRIPTION OF THE PREFERRED EMBODIMENT Because rotary web perforators are well known, the present description will be directed in particular to ele- -ments forming part of or cooperating more directly with, apparatus in accordance with the present invention. Rotary web perforator elements not specifically shown or described herein should be understood to be selectable from those known in the art.

With reference to FIG. l of the drawings, a rotary web perforator is illustrated in which a web 16 is fed by conventional means, not shown, around a lay on" guide roller 18 such as a porous air roller and onto a ro`- tatable drum 20, then over substantially 300 ofthe drum circumference during which the web is perfo` rated, and then around a take-away roller 22 to-any suitable takeup device, not shown. Tension-is applied to the web by any suitable tension adjusting mechanism as is well known in the art. The web perforator comprises left and right hand perforating mechanisms 24 for perforating each of the edges of web 16 with perforations of any desired pitch up to a limit of one perforation per revolution of the drum. Sincesuch perforating mechanisms are substantially identical, only one will be described in detail.

Each perforating mechanism 24 as best seen in FIG. 2 comprises a stationary frame 26 having a laterally extending integral cylindrical support member 28 for rotatably supporting a shaft 30 on bearings 32. The shaft 30 has an axially extending tunnel 34 therethrough, and a drive wheel or sprocket 36 secured to one end thereof drivingly connected to any suitable drive means, not shown, for rotatably driving the shaft. The opposite end of shaft 30 has a plate 38 integral therewith, and a cy- Iindrical web supporting drum '40 secured thereto by any suitable means. The drum 40 is further supported for rotation along with shaft 30 on bearings 42 interposed between drum 40 and support member 28. One face of drum 40 is provided with a pair of drive blocks 44 (FIG. 3) secured thereto, for engaging and driving rollers 46 secured by brackets 48 to an actuating ring S0 (FIG. 2) for driving the ring in either direction of rotation, depending upon the direction of rotation of shaft 30 and drum 40. The ring S0 is mounted for rotation on a cylindrical cam surface 52 on support member 28 which is eccentric to shaft 30 and drum 40 axis O. To facilitate rotation of ring 50, bearings 54 are interposed between ring 50 and stationary cam surface 52. The drum 40 has a polygonal periphery forming races 56 (FIG. 5) thereon for supporting a plurality of individual, hinged perforating assemblies 58, as best illustrated in FIG. 6, for perforating the web along one or both edges thereof at one of many desired pitches depending on the number of perforating assemblies used up to a maximum pitch obtained by one assembly of one perforation per drurn revolution.

Each of the perforating assemblies 58 comprises a base 60 precisely positioned on a corresponding drum face 56 by cooperating dowel pins 62 and openings, and rigidly secured thereto by any suitable bolts 64. The base 60 has an upstanding substantially semicircular boss 66 (FIG. 7) for supporting a shaft 68 onto which a pair of preferably tapered roller bearings 70 are mounted with one face of each bearing in engagement with one face of boss 66. A substantially V- shaped rocker arm 72 has a recess 74 for receiving boss 66, and is further provided with partially circular journals 76 adjacent each side of recess 74 for receiving the outer race of tapered bearings 70. The bearings 70 are preloaded by providing caps 78 secured to rocker arm 72 by screws 80 and bearing against the outer race of bearings 70. Accordingly, rocker arm 72 is provided with a preloaded hinge bearing to provide precise pivotal movement of the rocker arm without lateral movement.

A punch assembly (FIGS. 6, 8 and 9) comprises a block 82 secured to one end ofl rocker arm 72 by screws 84 or the like. The punch block 82 is provided with a plurality of parallel plates86 secured together by a bolt 88 for releasably holding spaced apart punches a, b and c corresponding to` and cooperating with complementary die openings in a die assembly to be described hereinafter upony rocking movement of rocker arm 72 to sever a web 16-interposed therebetween. Web perforations 90 formed by the conventional parallel, equally spaced punchv elements of a predetermined width penetrating a web 16 mounted on a curved support surface will appear substantially as shown in FIG.

12. Accordingly, when the film is relaxed and flattened or placed in a horizontal plane, as seen in FIG. 13, the effective widths W and W1 of the perforations and the effective pitches P and P, between the surfaces of adjacent perforations adapted to be engaged by a drive sprocket are not all equal due to the slant of some of the perforations. Where three or more of such punches are used, the variation in perforation width and pitch is not acceptable for applications of the type in which the web is driven by a drive sprocket. This problem has been solved by customizing the width of the punches a, b and c, and the space therebetween such that the relaxed web 16 when laid or flattened in a horizontal plane, as seen in FIG. 14, has effective perforation widths W and normal pitches P that are substantially equal throughout the length of the web. Accordingly, as illustrated in FIG. 8, the punches a, b and c on one side of a plane P parallel to and passing between inner punches a and through the center of block 82 are mirror images of the punches on the opposite side. In one specific application, the inner punches a both have the same width d of 0.07792 inches, the center punches b have a slightly greater width d' of 0.078 l5 inch, and the outer punches c have the greatest width d" of 0.07840 inches. Also, the space between punches a is 0.10912 inches, the space between punches a and b is slightly less at 0.10901 inch, and the space between punches b and c is the least at 0.10877 inches.

In addition to customizing the width of the punches and the space therebetween to compensate for perforation slant, certain other factors that affect the pitch must be taken into account, such as web thickness, web modulus of elasticity, and the tension to which the web is subjected. Such factors result in web elongation during the perforating operation, and a resulting reduction in pitch when the web is removed and relaxed in a plane. If the perforator is to handle webs varying in thickness from 2 to 8 mils with a modulus from E 4.5 X 105 psi to E 8 X 105 psi at a tension level ranging from 0.25 to 1 lb. per inch width, it is possible to compute the change in elongation or length ofa web on the drum due to the above factors, and to obtain a pitch correction change for use in calculating a precise final drum diameter which will take into account the above factors. Accordingly, by selecting the proper tension within the aforementioned range for a web of a predetermined thickness and modulus of elasticity, the normal pitch of each of such webs when removed from the drum and placed in a plane in a relaxed state will be substantially equal and of the correct desired pitch.

One end of base 60 is provided with a die assembly 92 which is precisely located on base 60 by means of dowels and dowel openings and is secured thereto by screws. The die assemblies 92, as best seen in FIGS. 5, and 11, each have a curved upper web supporting surface 94 and slanted sides 96 which cooperate when the perforating assemblies 92 are mounted on drum 40, to form an uninterrupted cylindrical web supporting surface. Each die assembly 92 comprises an upper block 97 having a plurality of parallel, spaced apart die openings 98 connected to enlarged openings 100, an intermediate spacer 102 having an opening 104 connected to openings 100, and a lower block 106 having an opening 108 connected to opening 104.

The'blocks j

97, 106 and spacer 102 are secured together and to base 60 by screws or the like. Base 60 has an opening 110 (FIG. 2) connected to opening 106, and drum 40 has an opening 112 connected to opening 110 which connects to a cylindrical chamber 114 formed between shaft plate 38 and closure plate 116 secured to the outer end of drum 40. The chamber 114 is in turn connected to the open end of tunnel 34 which is connected to any suitable source of vacuum, not shown. Accordingly, any web or lm chip severed by the cooperative action of the punches a, b and c and dies 98 is drawn by the vacuum through

openings

100, 104, 108, 110, and 112, chamber 114 and tunnel 34 to any suitable waste bin or the like not shown.

To facilitate' movement of the severed web chips from chamber 114 into tunnel 34, a V-shaped tapered chip scoop 118 (FIGS. 2 and 5) is provided having a laterally extending, annular journal 120 supported by a bearing 122 interposed between journal 120 and a portion of shaft 30. Accordingly, chip scoop 118 is nonrotating, and under the influence of gravity maintains a vertically oriented deflecting position at all times. The chip scoop 118 is positioned below the upper portion of the drum circumference in which the web perforating occurs.

A stripper 124 (FIG. 6) is provided for stripping the web chips from the punches when the punches are retracted following a perforating operation. The stripper 124 comprises a leaf spring 126 having one end secured to rocker arm 72 by screws 128 or the like, and its op posite end provided with a soft facing to protect the web and openings, not shown, through which the punches a, b and c extend. To modify the resonant frequency of spring 126, and hence the tendency of the spring to bounce at high speeds, a helical spring is interposed between rocker arm 72 and substantially the mid-portion of spring 126. The helical spring 130 is mounted on a pin 132 depending from and secured to rocker arm 72 by a bolt 134, and extending through an opening in leaf spring 126. A head 136 is provided on I the free end of pin 132 for limiting the downward deflection of spring 126.

The rocker arm 72 is further provided on its end opposite the punch and die assemblies with a pair of spaced apart journals 138 (FIGS. 4 and 6) for receiving a cylindrical member 140 supporting an eccentrically mounted shaft 142 between the spaced journals. An actuating link 144 has a spherical bearing 146 at one end mounted on shaft 142, and a spherical bearing 148 on its oppositeend mounted on a shaft 150 supported by a bifurcated mounting bracket 152. The bracket 152 is secured to ring 50 by any suitable means, such as screws. The purpose of

spherical bearings

146, 148 at each end of actuating link 144 is to provide relative movement between the eccentrically mounted ring 50 and the concentrically mounted drum 40 and rocker arm 72. Since ring 50 is rotating about an axis O which is different than the axis O about which drum 40 and rocker arm 72 rotate, (FIG. 4) the ring bracket 152 and rocker arm journals 138 are out of alignment in each of the 90 and 270 positions of the ring and drum. Such nonalignment of ring bracket 152 and rocker arm journals 138 is compensated for by the tilting movement of actuating link 144 permitted by

spherical bearings

146, 148.

An adjusting means is provided on rocker arm 72 for varying the distance the punches a, b and c are allowed to enter die openings 9,8. The adjusting means (FIG. 6) comprises a worm gear segment 154 on cylindrical member 140 cooperating with a rotatable worm 156 carried by rocker arm 72. By rotating worm 156, the cylindrical member 140 is rotated, moving the eccentric shaft 142 and spherical bearing 146. Such movement pivots rocker arm 72 for varying the space between the punches a, b, and c and die openings 98.

The web perforator of this invention is versatile in that it is capable of perforating a web 16 of any width along one edge only by a single perforating mechanism 24 of the type described, or along both edges by a pair of perforating mechanisms 24 in a manner now to be described. This is accomplished by providing another perforating mechanism 24 as illustrated in FIG. l comprising a stationary support member 26 and a shaft and drum 40 substantially identical to the aforementioned described elements. The perforating mechanisms 24 are coaxially mounted and can be drivingly coupled together by any suitable means such as bolts or interengaging fingers and notches extending laterally from the peripheral end surface of one drum 40 coacting with corresponding fingers and notches on the other drum. Accordingly, rotation of shaft 30 and drum 40 of the first mechanism 24 is drivingly coupled to the drum and shaft of the second mechanism for rotating it. Accordingly, a drive pulley on the shaft of the second mechanism is not required. In such an embodiment, the perforating assemblies 58 and drums 40 are preferably constructed such that when the drums are coupled together, the distance between the punches a, b and c on the perforating assemblies of the two drums is precisely correct for the narrowest desired width of web 16 to be perforated. The die blocks 97 are preferably provided with upstanding tabs 157 (FIGS. 2 and 6), for guiding the edges of the web over the perforating drums 40. In order to perforate webs 16 of varying widths, cylindrical spacers 158 (FIGS. l and 2) can be provided interposable between the perforating mechanisms 24 by slidably mounting one of the perforating mechanisms relative to the other by any suitable means such as slotted guide ways and cooperating slide rails, not shown. Each of the cylindrical spacers 158 is preferably provided with annular depending wall portions 160 at the ends thereof, each adapted to be bolted to the adjacent drum 40 or provided with complimentary fingers and notches, not shown, along one edge thereof for engaging fingers and notches on the adjacent drum. Wall portions 160 each have an annular lip 162 insertable within the corresponding drum end for maintaining the drums 40 and spacer 158 in axial alignment. The outer periphery of spacer 158 is of a diameter substantially equal to the diameter of the outer surface of the die assemblies 92 on drum 40 to provide a substantially uninterrupted surface for supporting the web to be perforated. For safety purposes, a cylindrical housing 164 (FIG. 2) encircles the perforating assemblies 24 on each of the drums 40 and is secured to the stationary member 26 by any suitable means.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove.

I claim:

l. In a rotary web perforating apparatus, the combination comprising:

a support member;

a shaft extending through and journaled for rotation within said support member;

a web supporting drum secured to said shaft and mounted on bearings interposed between said support member and said drum for concentric rotation and transport of said web;

web perforating means mounted on said drum for rotation therewith and movable between a retracted position displaced from said web and a perforating position for perforating said web;

cam means on said support member eccentric to said shaft; and

ring means encircling said cam means and mounted for rotation thereon, and secured to said web perforating means for moving said web perforating means between said retracted and perforating positions upon rotation of said shaft for continuously perforating said web transported on said drum.

2. The invention according to claim 1 wherein said drum has a polygonal periphery forming faces for receiving said web perforating means.

3. The invention according to claim l wherein said drum has a polygonal periphery forming faces for receiving said web perforating means, and dowel means are provided between each face and corresponding web perforating means for precisely positioning said web perforating means on said face.

4. The invention according to claim l wherein said web perforating means is hingedly mounted on said drum, and has an actuating link, a spherical bearing at one end of said link for connecting said end to said web perforating means, and a spherical bearing at the opposite end of said link for connecting said link to said ring means.

5. The invention according to claim l wherein said web perforating means comprises a rocker arm hingedly mounted on said drum, an eccentric rotatably supported by said rocker arm, an activating link having one end connected to said eccentric by a spherical bearing, and its opposite end connected to said ring means by a spherical bearing.

6. The invention according to claim 5 wherein adjusting means is provided for said eccentric to adjust the position of said rocker arm on its hinge.

7. The invention according to claim 6 wherein said adjusting means comprises a worm gear on said eccentric and a cooperating worm on said rocker arm.

8. In a rotary web perforating apparatus, the combination comprising;

a first support member;

a first shaft extending through and journaled for rotation within said first support member;

a first web supporting drum secured to said first shaft and mounted on bearings interposed between said first support member and said first drum for concentric rotation and transport of said web upon rotation of said first drum;

a second support member;

a second shaft coaxial with said first shaft and extending through and journaled for rotation within Said second support member;

a second web supporting drum secured to said second shaft and mounted on bearings interposed between said second support member and said seconddrum for concentric rotation and axial movement;

means for drivingly coupling said first and second drums;

web perforating means mounted on each of said first and second drums for rotation therewith; and

cam means on said first and second support members eccentric to said first and second shafts for actuating said web perforating means upon rotation of said shafts and drums for continuously perforating said web transported on said drums.

9. The invention according to claim 8 wherein said coupling means comprises means for axially spacing said first and second drums to vary the distance between said web perforating means for accommodating webs of different width.

10. The invention according to claim 8 wherein said coupling means comprises a cylindrical spacer member interposed between said first and second drums, and interengaging means between each end of said spacer member and a corresponding end of one of said first and second drums.

11. The invention according to claim 8 wherein each of said drums has a polygonal periphery forming faces for receiving said web perforating means.

12. The invention according to claim l1 wherein dowel means are provided between said faces and said web perforating means for precisely positioning said web perforating means on said faces. l

13. In a web perforating assembly for a rotary perforator having a drum provided with a plurality of circumferentially spaced, cylindrically-shaped die assemblies, each having substantially radially extending parallel die openings, the combination comprising;

a punch'holder for each die assembly for supporting a plurality of parallel, spaced apart punches mounted for reciprocal movement causing said punches to enter and retract from corresponding die openings in said die assembly to perforate a web transported over said drum;

each first pair of said punches and corresponding die openings on each side of a plane parallel to and passing between an innermost pair of said punches and through the center of said holder and die assembly respectively being spaced apart a different distance and being of different widths in the circumferential direction than a remaining second pair whereby the web perforations produced thereby all have substantially the same effective width and pitch when the web is removed from said drum and laid in a plane.

14. The invention according to claim 13, and further comprising means for subjecting webs of varying thickness and circumferential length transported over said drum to preselected tensions within a predetermined range whereby said webs when removed from the drum and placed in a plane ina relaxed state all have a substantially uniform normal pitch.

15. The invention according to claim 13 wherein the diameter of D of said drum is computed by the formula where P is the normal perforation pitch plus a correction factor taking into account the thickness, modulus of elasticity and tension, n is the number of punches in a circumference, and t is the web thickness.

is k il if UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE 0F CORRECTION PATENT No. 3 ,916 ,7M

DATED Novembera LI, 1975 lN\/|ENTOR(S) I-Ienry L. West It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The assignee was omitted from the cover sheet which should be amended as follows:

Eastman Kodak Company Rochester, New York Signed and ,Sealed this Twenty-third I Day 0f November 1976 RUTH C. MASON Anesling Offirer C. MARSHALL DANN Commissioner ofParenrs and Trademarks

Claims

1. In a rotary web perforating apparatus, the combination comprising: a support member; a shaft extending through and journaled for rotation within said support member; a web supporting drum secured to said shaft and mounted on bearings interposed between said support member and said drum for concentric rotation and transport of said web; web perforating means mounted on said drum for rotation therewith and movable between a retracted position displaced from said web and a perforating position for perforating said web; cam means on said support member eccentric to said shaft; and ring means encircling said cam means and mounted for rotation thereon, and secured to said web perforating means for moving said web perforating means between said retracted and perforating positions upon rotation of said shaft for continuously perforating said web transported on said drum.

3. The invention according to claim 1 wherein said drum has a polygonal periphery forming faces for receiving said web perforating means, and dowel means are provided between each face and corresponding web perforating means for precisely positioning said web perforating means on said face.

4. The invention according to claim 1 wherein said web perforating means is hingedly mounted on said drum, and has an actuating link, a spherical bearing at one end of said link for connecting said end to said web perforating means, and a spherical bearing at the opposite end of said link for connecting said link to said ring means.

5. The invention according to claim 1 wherein said web perforating means comprises a rocker arm hingedly mounted on said drum, an eccentric rotatably supported by said rocker arm, an activating link having one end connected to said eccentric by a spherical bearing, and its opposite end connected to said ring means by a spherical bearing.

8. In a rotary web perforating apparatus, the combination comprising; a first support member; a first shaft extending through and journaled for rotation within said first support member; a first web supporting drum secured to said first shaft and mounted on bearings interposed between said first support member and said first drum for concentric rotation and transport of said web upon rotation of said first drum; a second support member; a second shaft coaxial with said first shaft and extending through and journaled for rotation within said second support membEr; a second web supporting drum secured to said second shaft and mounted on bearings interposed between said second support member and said second drum for concentric rotation and axial movement; means for drivingly coupling said first and second drums; web perforating means mounted on each of said first and second drums for rotation therewith; and cam means on said first and second support members eccentric to said first and second shafts for actuating said web perforating means upon rotation of said shafts and drums for continuously perforating said web transported on said drums.

12. The invention according to claim 11 wherein dowel means are provided between said faces and said web perforating means for precisely positioning said web perforating means on said faces.

13. In a web perforating assembly for a rotary perforator having a drum provided with a plurality of circumferentially spaced, cylindrically-shaped die assemblies, each having substantially radially extending parallel die openings, the combination comprising; a punch holder for each die assembly for supporting a plurality of parallel, spaced apart punches mounted for reciprocal movement causing said punches to enter and retract from corresponding die openings in said die assembly to perforate a web transported over said drum; each first pair of said punches and corresponding die openings on each side of a plane parallel to and passing between an innermost pair of said punches and through the center of said holder and die assembly respectively being spaced apart a different distance and being of different widths in the circumferential direction than a remaining second pair whereby the web perforations produced thereby all have substantially the same effective width and pitch when the web is removed from said drum and laid in a plane.

14. The invention according to claim 13, and further comprising means for subjecting webs of varying thickness and circumferential length transported over said drum to preselected tensions within a predetermined range whereby said webs when removed from the drum and placed in a plane in a relaxed state all have a substantially uniform normal pitch.

15. The invention according to claim 13 wherein the diameter of D of said drum is computed by the formula D P X n/ pi - t where P is the normal perforation pitch plus a correction factor taking into account the thickness, modulus of elasticity and tension, n is the number of punches in a circumference, and t is the web thickness.