CA1184112A - Cutter for making arcuate cuts in travelling webs - Google Patents
Cutter for making arcuate cuts in travelling websInfo
- Publication number
- CA1184112A CA1184112A CA000410006A CA410006A CA1184112A CA 1184112 A CA1184112 A CA 1184112A CA 000410006 A CA000410006 A CA 000410006A CA 410006 A CA410006 A CA 410006A CA 1184112 A CA1184112 A CA 1184112A
- Authority
- CA
- Canada
- Prior art keywords
- axis
- shaft
- roller
- knife blade
- longitudinal axis
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B26—HAND CUTTING TOOLS; CUTTING; SEVERING
- B26D—CUTTING; DETAILS COMMON TO MACHINES FOR PERFORATING, PUNCHING, CUTTING-OUT, STAMPING-OUT OR SEVERING
- B26D1/00—Cutting through work characterised by the nature or movement of the cutting member or particular materials not otherwise provided for; Apparatus or machines therefor; Cutting members therefor
- B26D1/01—Cutting through work characterised by the nature or movement of the cutting member or particular materials not otherwise provided for; Apparatus or machines therefor; Cutting members therefor involving a cutting member which does not travel with the work
- B26D1/12—Cutting through work characterised by the nature or movement of the cutting member or particular materials not otherwise provided for; Apparatus or machines therefor; Cutting members therefor involving a cutting member which does not travel with the work having a cutting member moving about an axis
- B26D1/25—Cutting through work characterised by the nature or movement of the cutting member or particular materials not otherwise provided for; Apparatus or machines therefor; Cutting members therefor involving a cutting member which does not travel with the work having a cutting member moving about an axis with a non-circular cutting member
- B26D1/34—Cutting through work characterised by the nature or movement of the cutting member or particular materials not otherwise provided for; Apparatus or machines therefor; Cutting members therefor involving a cutting member which does not travel with the work having a cutting member moving about an axis with a non-circular cutting member moving about an axis parallel to the line of cut
- B26D1/42—Cutting through work characterised by the nature or movement of the cutting member or particular materials not otherwise provided for; Apparatus or machines therefor; Cutting members therefor involving a cutting member which does not travel with the work having a cutting member moving about an axis with a non-circular cutting member moving about an axis parallel to the line of cut and slidably mounted in a rotary member
- B26D1/425—Cutting through work characterised by the nature or movement of the cutting member or particular materials not otherwise provided for; Apparatus or machines therefor; Cutting members therefor involving a cutting member which does not travel with the work having a cutting member moving about an axis with a non-circular cutting member moving about an axis parallel to the line of cut and slidably mounted in a rotary member for thin material, e.g. for sheets, strips or the like
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B26—HAND CUTTING TOOLS; CUTTING; SEVERING
- B26D—CUTTING; DETAILS COMMON TO MACHINES FOR PERFORATING, PUNCHING, CUTTING-OUT, STAMPING-OUT OR SEVERING
- B26D3/00—Cutting work characterised by the nature of the cut made; Apparatus therefor
- B26D3/10—Making cuts of other than simple rectilinear form
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B26—HAND CUTTING TOOLS; CUTTING; SEVERING
- B26F—PERFORATING; PUNCHING; CUTTING-OUT; STAMPING-OUT; SEVERING BY MEANS OTHER THAN CUTTING
- B26F1/00—Perforating; Punching; Cutting-out; Stamping-out; Apparatus therefor
- B26F1/18—Perforating by slitting, i.e. forming cuts closed at their ends without removal of material
- B26F1/22—Perforating by slitting, i.e. forming cuts closed at their ends without removal of material to form non-rectilinear cuts, e.g. for tabs
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- Life Sciences & Earth Sciences (AREA)
- Forests & Forestry (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Making Paper Articles (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A cutter for making arcuate cuts in a travelling web of film is disclosed. The cutter comprises a rotating means, a shaft and a knife blade wherein the shaft is adapt-ed to be rotated about a longitudinal axis and the knife blade is attached to one end of the shaft, offset from the longitudinal axis such that the knife blade is parallel to the longitudinal axis and the sharp edge of the knife points tangentially about a circle whose centre is coaxial with the longitudinal axis and about a second axis. The shaft's longitudinal axis is spaced apart from the second axis and is substantially perpendicular to a plane passing through the second axis.
A cutter for making arcuate cuts in a travelling web of film is disclosed. The cutter comprises a rotating means, a shaft and a knife blade wherein the shaft is adapt-ed to be rotated about a longitudinal axis and the knife blade is attached to one end of the shaft, offset from the longitudinal axis such that the knife blade is parallel to the longitudinal axis and the sharp edge of the knife points tangentially about a circle whose centre is coaxial with the longitudinal axis and about a second axis. The shaft's longitudinal axis is spaced apart from the second axis and is substantially perpendicular to a plane passing through the second axis.
Description
f~
CUTTER FOR MAKING ARCUATE CUTS IN TRAVELLING WEBS
_ The present inven-tion relates to an appara-tus for cutting arcuate slits in a travelling web of mater:iall particularly a web of a thermoplastic polymer material. The present invention is particularly useful in bag-making oper-ations for making, at intervals, small arcuate cuts in a portion of a tubular film prior to transversely cutting the tubular film close to -the arcuate cut. Such a transversely cut tube forms, on one side of the cut, a protruding tab at one end of the cut tube which is useful for gripping the tube in subsequent operations in bag-making. On the o.her side of the cut an indented scallop is formed in the end of the cut tube which is useful for aiding separation of the walls of a flattened tube or bag. The present invention may also be used for making large arcuate cuts in tubular film to form, for example, an opening in a wall of a bag that is suitable for use as a handle. Other uses include the making of a plurality of arcuate cuts, to form valve-like flaps, in plastic films e.g. in aquatic weed barrier as disclosed in copending patent application No. 398 464 of E.L. Fletcher, filed 1~8~ March 16.
Heretofore arcuate cuts in a thin web of material have been accomplished by punching an arcuate knife blade through the webO Depending on the nature of the material being cut, it may be necessary to have a back-up pad or die against which the arcuate knife blade is pressed during such punching. Inclusion of the back-up pad is desirable for webs made of materials which are li~ely to stretch e.g.
polyethylene film.
A preferred method for cutting plastic materials is by slicing the material, for e~ample by moving a knife through the plastic material. The term "plastic" used here-in refers to synthetic thermoplastic polymers capable of melt extrusion and forming films, ~hose synthetic thermo-setting polymers which are capable of mel-t extrusion and forming films, mixtures of said polymers, and foamable composi-tions comprising any of said polymers or mixtures.
An apparatus adapted to perform a combination of sliciny a~tions for cutting heat sealable materials is disclosed in U.S. Patent 3 188 7~1 which issued 1965 June 15 to Aquarlus et al.
The aforementioned method and apparatus of the prior art are not well adapted to orm arcuate cuts in a travelling web of material.
It has now been found that an arcuate cut may be made in a travelling web by a knife which is caused to rotate about a first axis, and a second axis, the first axis being spaced apart from the second axis, said first axis also being perpendicular ~o a plane passing through said second axis, said second axis being parallel to the plane in which the travelling web travels.
Accordingly the present invention provides a cutter comprising rotating means, a shaft and a knife blade having at least one sharp edge, wherein the shaft is adapted to be rotated about a longitudinal axis and the knife blade is attached to one end of the shaft and offset from the longitudinal axis such that the knife blade is parallel to the longitudinal axis and a sharp edge of the knife points tangentially about a circle whose centre is coaxial with the longitudinal axis of the shaft, and wherein the rotating means is adapted to rotate the shaft and the knife about said longitudinal axis and about a second axis, the longitu-dinal axis of the shaft being spaced apart from the secondaxis and substantially perpendicular to a plane passing through the second axis.
The present invention also provides a cutter comprising a roller, first and second shafts and a knife blade wherein:
a) the roller has first and second cavities therein, and is adapted to be rotated about a longitudinal axis, the first cavity being coaxial with said longitudinal axis, extending at least part-way into the roller and being open at one end of the roller, said first cavity being adapted to receive the first shaft and allow the irst shaft to rotate therein about the longitudinal axis; one end, the first end, of the second cavity being open at the ex~:erior surface of the roller, and the other, second, end of the second cavity extending into the roller such that the longi-tudinal axis of the second cavity is spaced apart from the longitudinal axis of the roller and is perpendicular to a plane passing throuyh the longitudinal axis of the roller, said second end being on the opposite side of said plane to the first end, the second cavity being adapted to receive the second shaft and allow the second shaft to rotate about the longitudinal axis of the second cavity, said first and second cavities being in communicating relationship;
b) the first shaft is encased in the first cavity of the roller, said first shaft being adapted to be rotated about the longitudinal axis of the roller, and being further adapted to be driven independently of the roller and -to drive the second shaft;
c) the second shaft is encased in the second cavity of the roller and i.s adapted to rotate about the longitudinal axis of the second cavity of the roller and is in driven relationship with the first shaft, and d) the knife blade is attached to the end of the second shaft closest to the first end of the second cavity such that when the second shaft rotates, the motion of the knife blade circumscribing a circle having its centre coax-ial with the longitudinal axis of the second shaft, said ~5 knife blade being sufficiently long to enable a tip thereof to protrude beyond the exterior surface of said roller during at least a portion of said motion, said kni:Ee blade having a sharp edge which faces the direction of rotation of the knife blade.
The present invention also provides a process for making an arcuate cut in a travelling web comprisi.ng:
a) pulling the web longitudinally along a path b~ cutting the web a-t intervals with a knife blade having a cutting edge, said knife blade being rotated about a first axis such that the cutting edge of -the knife blade is in a line parallel -to khe first axis and faces -the direction of rotation of the knife blade, said first axis being rotated about a second axis, the second axis being spaced apart from the first axis and the firs-t axis being /
substantially perpendicular to a plane passing through the second axis' said second axis being spaced apart from the path through which the web is pulled by a clistance marginal-ly less -than the maximum distance between the second axis and the point of the knife.
In a preferred embodiment the direction of rota-tion of the fixst axis about the second axis i9 such that the direction of travel of the first axis, in a path paral-lel to the path through which the web -travels, when between the second axis and the web, is in the direction of travel of the web.
In another embodiment the web is a film of a thermoplastic polymer, preferably a homopolymer of ethylene or a copolymer of ethylene and a C4 - C10 ~-olefin and more preferably a homopolymer of ethylene or a copolymer of ethylene and a C4 - Clo ~-olefin having a density of from 0.9~5 to 0.970 g/cm3. In another embodiment the web of film is oriented.
The invention may be illustrated by reference to the drawings in which:
; Figure 1 shows, schematically and partially cut-away an apparatus of the present invention;
Figure 2 shows a schematic cross-section of an apparatus of the present invention being used in the cutting of a travelling web, and Figure 3, which is placed between Figures 1 and 2, shows a schematic cross section of a fur-ther embodiment of apparatus of the present invention being used in cutting a travelling web.
In Figure 1 a cylindrical roller 10 has an axial cylindrical hole 11 extencling from one end of the roller to the other. In addition roller 10 has a cylindrical cavi-ty 12. The longitudinal axis of cavity 12 is perpendicular to a plane passing through the longitudinal axis of roller 10, and displaced therefrom. Hole 11 and cavity 12 are in communicating relationshipO Roller 10 is journalled in journal means (not shown) and is adapted to be rotated about its longitudinal axis by rotating means (not shown).
, Drive shaf-t 13, within hole 11, has a helical gear 15 machined thereon or attached thereto such that the heli-cal gear 15 extends into the communicating passageway be-tween hole 11 and cavity 12. Drive shaft 13 is journalled by means (not s'nown) and adapted to be rotated by rotating means (not shown) about -the longitudinal axis of roller 10.
In addition drive shaft 13 is maintained in its position in hole 11 by known means e.g. retaining rings (not shown).
The rotating means for roller 10 and drive shaft 13 may be independent o-f one another or may, more usually, be synchro-nously driven at different angular speeds.
Shaft 14 is inserted into cavi-ty 12. One end of shaft 14 has an a~ially disposed helical cog 16, while the other end has a knife blade 18. The cogged end of shaft 14 is inside roller 10 and is journalled in the closed end 19 of cavity 12. ~le position of cog 16 on sha~t 14 is such that the teeth of cog 16 engage, through the communicating passageway between hole 11 and cavity 12, with helical gear 15. Shaft 14 protrudes from cavity 12, through aperture 17 in the periphery of roller 10. Knife blade 18 is triangu lar, with the base of the triangle tangentially mounted on the periphery of the end of shaft 14. The txiangle is in a plane parallel to the longitudinal axis of shaft 14. One of the edges of the knife blade is sharpened.
Figure 2 shows the assembly of one arc cutter according to the present invention in more detail. Roller 10 has a longi-tudinal hole 11 in which is situated shaft 13 having helical gear 15 thereon. A cavity, 12, has a longi-tudinal axis perpendicular to a plane passing through the longitudinal axis of roller 10. Cavity 12 passes completely through roller 10. Cavity 12 comprises a shaft guide cavity 32 adjacent to a gear cavity 25. Shaft guide cavity 32 has a cutter head cavity 21 at the end opposite to the gear cavity 25. ~ear cavity 25 has a large plug retaining cavity 23 at the end opposite to sha~t guide cavity 32~ Cavity 12 is adapted such that a cutter assembly and a plug 2~ may be inserted -therein. The cutter assembly comprises a cutter head 22 having a knife blade 1~ attached thereto, a shaft 1 and a bevelled cog 16.
The cutter head cavity 21 is adapted to receive cutter head ~2 to which knife blade 18 is attached. The plug retaining cavity 23 is adapted to receive and retain plug 24. Gear cavity 25, adjacent to and in communicating relationship with hole 11 is adapted to enclose and receive helical cog 16. Shaft guide cavity 32 is adapted to enclose the portion of shaft 1~ which joins the cutter head 22 and the helical cog 16.
Cutter head 22 is attached to one end of shaEt 1~, the other end of shaft 14 being machined to form a bearing surface 26. Bearing surfac~ 26 is adapted to turn within and bear against bearing 27 i.nserted in of plug 24. Helical cog 16 is attached to shaft 1~. Plug 24 is held in place in plug retaining cavity 23 by bolts 28 and ~9 which key into threaded holes 30 and 31 respectively in roll&r 10.
The operation of the arcuate cutter may be illustrated by further reference to Figure 2.
A web of material W is caused to travel in a plane in a direction indicated by the arrow. The arcuate cutter 2Q is disposed in relation to the plane through which the web travels such that the distance between the longitudinal axis of roller 10 to the plane of the web is marginally less than the maximum distance between the longitudinal axis of roller 10 and the sweep of the tip of knife blade 18. The path o:E
the tip of blade 18, when viewed from an end of roller 10 is shown by dotted line 20. The relative rates of rotation o roller 10 and shaft 13 and the gear ratio of helical gear 15 and cog 16 determine the number of revolutions of knife blade 18 about shaft 1~ for ea~h revolution of roller 10.
In the embod.iment shown knife blade 18 rotates four times for each revolution of roller 10. The rate of travel of web W, the rate and direction of rotation of roller 10 and the rate of rotation of knife blade 18 all affect the nature of the arcuate cut in web W. The number of revolutions of the knife blade 18 should be an inte~ral number of times of the number of revolutions of roller l0 in order to ensure that successive arcuate cuts are the same shape.
It will be unders-tood by those skilled in the art that the rate of rotation of the knife blade 18 may be altered by using helical gears of various pitches or by using worm and cog gears or other types of gear arrangements known in those skilled in the ar-t.
It will also be apparent that the web can be in contact with the roller either tangentially or over an arc.
When the web is in contact with the roller over an arc and the cut has an angle of sweep of less than 2~ radians, it may be necessary that the tip of the blade for part of each of its revolutions be hidden within the roller as shown in Figure 3. As will be apparent the knife blade -tip will be hidden within roller 10 as it sweeps through area A and thus will not be able to cut web W.
A Xnife blade suitable for cutting plastic films may be made of tool steel and made integrally with the cutter head.
The apparatus of the present invention is particu-larly useful for making arcuate cuts in one face of a gus-setted tube preparatory to transversely cutting the tubesuch that a tab is formed by the arcuate cut and the trans-verse cut, as described with more par-ticularity hereafter.
In one embodiment of the present invention, a flat web of high density polyethylene film, e.g. having a densi-ty of from 0.955 to 0.970 g/cm3, is folded longitudinally and formed into a flattened gussetted tube by a method known in the art. The gussetted tube is pulled over the top of a table in a direction perpendicular to a line parallel to and displaced from the longitudinal axis of roller 10. The gussetted portions o the tube are separated by an internal plate. The table has a hole therein, below which is posi-tioned the cutting device of the present invention. The cutting device is so situated that, upon rotation, the knife blade 18 may cut the portion of the gusse-tted tube which travels be~ween the table and the internal plate. The roll~
er 10 is rotated so that ~he periphery of -the roller closest to the gussetted tube moves in the same direction as the gussetted tube. The knife blade is caused to rotate e.g~
5-10 times for every revolution of the roller. Semicircular or arcua-te cuts may be made at intervals thereby, in the part of the tube closest to the table. The flattened cut tube is then pulled over the table towards a ripping station situated at an edge o~ the ~able. The arc of the cut is closer to the ripping station than is the base of the arcuate cut.
Two longitudinal slits, inset from the longitudi-nal edges of the tube, are made with razor blades, in the upper portion of the tube e~tending from a transverse line t'hrough the base of the arcuate cut, and on the opposit~
side of the transverse line to the arcuate cut.
The tuba is then advanced past the table edge, across a gap and fed between a pair of rotating nip rollers.
The ripping station is situated in the gap and comprises a striker bar adapted to move rapidly across the path of travel of the tube, and a stationary ripping~bar. The tube is ripped by the force exerted on the tube by the motion of the striker bar and the restraint to movement of the tube caused by the ripping bar and the nip rollers. The tube is ripped transversely on both sid2s of the arcuate cut across a line extending through the base of the arcuate cut.
Movement of the leading edge of the cut -tube across the gap and into the throat of the nip roller may be aided by jets of hig'h velocity air b]own from inside the tube towards the throat of the nip rollers as more fully described in copending Canadian patent application of O.H. Vogt, filed the same date as the present application (Case DC-0121).
Cut lengths of tube are then transported to an apparatus adapted to form the bottom of a self-opening square bag as is known in the art.
Under the above conditions the tubes may be formed, cut and made into self-opening square bags at a rate of about 150 bags/minute. The present invention is a useful modification for a Model 83 Potdevin* paper self-opening square (SOS) bag making machine to enable plastic SOS bags to be made therewith.
*denotes trade mark.
D ription of Reference Numerals Roller 11 Cylindrical hole 12 Cylindrical cavity 13 Drive shaft 14 Shaft Helical gear 1~ Cog 17 Aperture 18 Knife blade 19 Closed end of cavity 12 Path o:E knife tip 21 Cutter head cavity 22 Cutter head 23 Plug retaining cavity 24 Plug Gear cavity Z6 Bearing surface 27 Bearing 28 Bolt 29 Bolt Threaded hole 31 Threaded hole 32 Shaft guide cavity W Web A Area inside cavity 21 where knife blade is hidden
CUTTER FOR MAKING ARCUATE CUTS IN TRAVELLING WEBS
_ The present inven-tion relates to an appara-tus for cutting arcuate slits in a travelling web of mater:iall particularly a web of a thermoplastic polymer material. The present invention is particularly useful in bag-making oper-ations for making, at intervals, small arcuate cuts in a portion of a tubular film prior to transversely cutting the tubular film close to -the arcuate cut. Such a transversely cut tube forms, on one side of the cut, a protruding tab at one end of the cut tube which is useful for gripping the tube in subsequent operations in bag-making. On the o.her side of the cut an indented scallop is formed in the end of the cut tube which is useful for aiding separation of the walls of a flattened tube or bag. The present invention may also be used for making large arcuate cuts in tubular film to form, for example, an opening in a wall of a bag that is suitable for use as a handle. Other uses include the making of a plurality of arcuate cuts, to form valve-like flaps, in plastic films e.g. in aquatic weed barrier as disclosed in copending patent application No. 398 464 of E.L. Fletcher, filed 1~8~ March 16.
Heretofore arcuate cuts in a thin web of material have been accomplished by punching an arcuate knife blade through the webO Depending on the nature of the material being cut, it may be necessary to have a back-up pad or die against which the arcuate knife blade is pressed during such punching. Inclusion of the back-up pad is desirable for webs made of materials which are li~ely to stretch e.g.
polyethylene film.
A preferred method for cutting plastic materials is by slicing the material, for e~ample by moving a knife through the plastic material. The term "plastic" used here-in refers to synthetic thermoplastic polymers capable of melt extrusion and forming films, ~hose synthetic thermo-setting polymers which are capable of mel-t extrusion and forming films, mixtures of said polymers, and foamable composi-tions comprising any of said polymers or mixtures.
An apparatus adapted to perform a combination of sliciny a~tions for cutting heat sealable materials is disclosed in U.S. Patent 3 188 7~1 which issued 1965 June 15 to Aquarlus et al.
The aforementioned method and apparatus of the prior art are not well adapted to orm arcuate cuts in a travelling web of material.
It has now been found that an arcuate cut may be made in a travelling web by a knife which is caused to rotate about a first axis, and a second axis, the first axis being spaced apart from the second axis, said first axis also being perpendicular ~o a plane passing through said second axis, said second axis being parallel to the plane in which the travelling web travels.
Accordingly the present invention provides a cutter comprising rotating means, a shaft and a knife blade having at least one sharp edge, wherein the shaft is adapted to be rotated about a longitudinal axis and the knife blade is attached to one end of the shaft and offset from the longitudinal axis such that the knife blade is parallel to the longitudinal axis and a sharp edge of the knife points tangentially about a circle whose centre is coaxial with the longitudinal axis of the shaft, and wherein the rotating means is adapted to rotate the shaft and the knife about said longitudinal axis and about a second axis, the longitu-dinal axis of the shaft being spaced apart from the secondaxis and substantially perpendicular to a plane passing through the second axis.
The present invention also provides a cutter comprising a roller, first and second shafts and a knife blade wherein:
a) the roller has first and second cavities therein, and is adapted to be rotated about a longitudinal axis, the first cavity being coaxial with said longitudinal axis, extending at least part-way into the roller and being open at one end of the roller, said first cavity being adapted to receive the first shaft and allow the irst shaft to rotate therein about the longitudinal axis; one end, the first end, of the second cavity being open at the ex~:erior surface of the roller, and the other, second, end of the second cavity extending into the roller such that the longi-tudinal axis of the second cavity is spaced apart from the longitudinal axis of the roller and is perpendicular to a plane passing throuyh the longitudinal axis of the roller, said second end being on the opposite side of said plane to the first end, the second cavity being adapted to receive the second shaft and allow the second shaft to rotate about the longitudinal axis of the second cavity, said first and second cavities being in communicating relationship;
b) the first shaft is encased in the first cavity of the roller, said first shaft being adapted to be rotated about the longitudinal axis of the roller, and being further adapted to be driven independently of the roller and -to drive the second shaft;
c) the second shaft is encased in the second cavity of the roller and i.s adapted to rotate about the longitudinal axis of the second cavity of the roller and is in driven relationship with the first shaft, and d) the knife blade is attached to the end of the second shaft closest to the first end of the second cavity such that when the second shaft rotates, the motion of the knife blade circumscribing a circle having its centre coax-ial with the longitudinal axis of the second shaft, said ~5 knife blade being sufficiently long to enable a tip thereof to protrude beyond the exterior surface of said roller during at least a portion of said motion, said kni:Ee blade having a sharp edge which faces the direction of rotation of the knife blade.
The present invention also provides a process for making an arcuate cut in a travelling web comprisi.ng:
a) pulling the web longitudinally along a path b~ cutting the web a-t intervals with a knife blade having a cutting edge, said knife blade being rotated about a first axis such that the cutting edge of -the knife blade is in a line parallel -to khe first axis and faces -the direction of rotation of the knife blade, said first axis being rotated about a second axis, the second axis being spaced apart from the first axis and the firs-t axis being /
substantially perpendicular to a plane passing through the second axis' said second axis being spaced apart from the path through which the web is pulled by a clistance marginal-ly less -than the maximum distance between the second axis and the point of the knife.
In a preferred embodiment the direction of rota-tion of the fixst axis about the second axis i9 such that the direction of travel of the first axis, in a path paral-lel to the path through which the web -travels, when between the second axis and the web, is in the direction of travel of the web.
In another embodiment the web is a film of a thermoplastic polymer, preferably a homopolymer of ethylene or a copolymer of ethylene and a C4 - C10 ~-olefin and more preferably a homopolymer of ethylene or a copolymer of ethylene and a C4 - Clo ~-olefin having a density of from 0.9~5 to 0.970 g/cm3. In another embodiment the web of film is oriented.
The invention may be illustrated by reference to the drawings in which:
; Figure 1 shows, schematically and partially cut-away an apparatus of the present invention;
Figure 2 shows a schematic cross-section of an apparatus of the present invention being used in the cutting of a travelling web, and Figure 3, which is placed between Figures 1 and 2, shows a schematic cross section of a fur-ther embodiment of apparatus of the present invention being used in cutting a travelling web.
In Figure 1 a cylindrical roller 10 has an axial cylindrical hole 11 extencling from one end of the roller to the other. In addition roller 10 has a cylindrical cavi-ty 12. The longitudinal axis of cavity 12 is perpendicular to a plane passing through the longitudinal axis of roller 10, and displaced therefrom. Hole 11 and cavity 12 are in communicating relationshipO Roller 10 is journalled in journal means (not shown) and is adapted to be rotated about its longitudinal axis by rotating means (not shown).
, Drive shaf-t 13, within hole 11, has a helical gear 15 machined thereon or attached thereto such that the heli-cal gear 15 extends into the communicating passageway be-tween hole 11 and cavity 12. Drive shaft 13 is journalled by means (not s'nown) and adapted to be rotated by rotating means (not shown) about -the longitudinal axis of roller 10.
In addition drive shaft 13 is maintained in its position in hole 11 by known means e.g. retaining rings (not shown).
The rotating means for roller 10 and drive shaft 13 may be independent o-f one another or may, more usually, be synchro-nously driven at different angular speeds.
Shaft 14 is inserted into cavi-ty 12. One end of shaft 14 has an a~ially disposed helical cog 16, while the other end has a knife blade 18. The cogged end of shaft 14 is inside roller 10 and is journalled in the closed end 19 of cavity 12. ~le position of cog 16 on sha~t 14 is such that the teeth of cog 16 engage, through the communicating passageway between hole 11 and cavity 12, with helical gear 15. Shaft 14 protrudes from cavity 12, through aperture 17 in the periphery of roller 10. Knife blade 18 is triangu lar, with the base of the triangle tangentially mounted on the periphery of the end of shaft 14. The txiangle is in a plane parallel to the longitudinal axis of shaft 14. One of the edges of the knife blade is sharpened.
Figure 2 shows the assembly of one arc cutter according to the present invention in more detail. Roller 10 has a longi-tudinal hole 11 in which is situated shaft 13 having helical gear 15 thereon. A cavity, 12, has a longi-tudinal axis perpendicular to a plane passing through the longitudinal axis of roller 10. Cavity 12 passes completely through roller 10. Cavity 12 comprises a shaft guide cavity 32 adjacent to a gear cavity 25. Shaft guide cavity 32 has a cutter head cavity 21 at the end opposite to the gear cavity 25. ~ear cavity 25 has a large plug retaining cavity 23 at the end opposite to sha~t guide cavity 32~ Cavity 12 is adapted such that a cutter assembly and a plug 2~ may be inserted -therein. The cutter assembly comprises a cutter head 22 having a knife blade 1~ attached thereto, a shaft 1 and a bevelled cog 16.
The cutter head cavity 21 is adapted to receive cutter head ~2 to which knife blade 18 is attached. The plug retaining cavity 23 is adapted to receive and retain plug 24. Gear cavity 25, adjacent to and in communicating relationship with hole 11 is adapted to enclose and receive helical cog 16. Shaft guide cavity 32 is adapted to enclose the portion of shaft 1~ which joins the cutter head 22 and the helical cog 16.
Cutter head 22 is attached to one end of shaEt 1~, the other end of shaft 14 being machined to form a bearing surface 26. Bearing surfac~ 26 is adapted to turn within and bear against bearing 27 i.nserted in of plug 24. Helical cog 16 is attached to shaft 1~. Plug 24 is held in place in plug retaining cavity 23 by bolts 28 and ~9 which key into threaded holes 30 and 31 respectively in roll&r 10.
The operation of the arcuate cutter may be illustrated by further reference to Figure 2.
A web of material W is caused to travel in a plane in a direction indicated by the arrow. The arcuate cutter 2Q is disposed in relation to the plane through which the web travels such that the distance between the longitudinal axis of roller 10 to the plane of the web is marginally less than the maximum distance between the longitudinal axis of roller 10 and the sweep of the tip of knife blade 18. The path o:E
the tip of blade 18, when viewed from an end of roller 10 is shown by dotted line 20. The relative rates of rotation o roller 10 and shaft 13 and the gear ratio of helical gear 15 and cog 16 determine the number of revolutions of knife blade 18 about shaft 1~ for ea~h revolution of roller 10.
In the embod.iment shown knife blade 18 rotates four times for each revolution of roller 10. The rate of travel of web W, the rate and direction of rotation of roller 10 and the rate of rotation of knife blade 18 all affect the nature of the arcuate cut in web W. The number of revolutions of the knife blade 18 should be an inte~ral number of times of the number of revolutions of roller l0 in order to ensure that successive arcuate cuts are the same shape.
It will be unders-tood by those skilled in the art that the rate of rotation of the knife blade 18 may be altered by using helical gears of various pitches or by using worm and cog gears or other types of gear arrangements known in those skilled in the ar-t.
It will also be apparent that the web can be in contact with the roller either tangentially or over an arc.
When the web is in contact with the roller over an arc and the cut has an angle of sweep of less than 2~ radians, it may be necessary that the tip of the blade for part of each of its revolutions be hidden within the roller as shown in Figure 3. As will be apparent the knife blade -tip will be hidden within roller 10 as it sweeps through area A and thus will not be able to cut web W.
A Xnife blade suitable for cutting plastic films may be made of tool steel and made integrally with the cutter head.
The apparatus of the present invention is particu-larly useful for making arcuate cuts in one face of a gus-setted tube preparatory to transversely cutting the tubesuch that a tab is formed by the arcuate cut and the trans-verse cut, as described with more par-ticularity hereafter.
In one embodiment of the present invention, a flat web of high density polyethylene film, e.g. having a densi-ty of from 0.955 to 0.970 g/cm3, is folded longitudinally and formed into a flattened gussetted tube by a method known in the art. The gussetted tube is pulled over the top of a table in a direction perpendicular to a line parallel to and displaced from the longitudinal axis of roller 10. The gussetted portions o the tube are separated by an internal plate. The table has a hole therein, below which is posi-tioned the cutting device of the present invention. The cutting device is so situated that, upon rotation, the knife blade 18 may cut the portion of the gusse-tted tube which travels be~ween the table and the internal plate. The roll~
er 10 is rotated so that ~he periphery of -the roller closest to the gussetted tube moves in the same direction as the gussetted tube. The knife blade is caused to rotate e.g~
5-10 times for every revolution of the roller. Semicircular or arcua-te cuts may be made at intervals thereby, in the part of the tube closest to the table. The flattened cut tube is then pulled over the table towards a ripping station situated at an edge o~ the ~able. The arc of the cut is closer to the ripping station than is the base of the arcuate cut.
Two longitudinal slits, inset from the longitudi-nal edges of the tube, are made with razor blades, in the upper portion of the tube e~tending from a transverse line t'hrough the base of the arcuate cut, and on the opposit~
side of the transverse line to the arcuate cut.
The tuba is then advanced past the table edge, across a gap and fed between a pair of rotating nip rollers.
The ripping station is situated in the gap and comprises a striker bar adapted to move rapidly across the path of travel of the tube, and a stationary ripping~bar. The tube is ripped by the force exerted on the tube by the motion of the striker bar and the restraint to movement of the tube caused by the ripping bar and the nip rollers. The tube is ripped transversely on both sid2s of the arcuate cut across a line extending through the base of the arcuate cut.
Movement of the leading edge of the cut -tube across the gap and into the throat of the nip roller may be aided by jets of hig'h velocity air b]own from inside the tube towards the throat of the nip rollers as more fully described in copending Canadian patent application of O.H. Vogt, filed the same date as the present application (Case DC-0121).
Cut lengths of tube are then transported to an apparatus adapted to form the bottom of a self-opening square bag as is known in the art.
Under the above conditions the tubes may be formed, cut and made into self-opening square bags at a rate of about 150 bags/minute. The present invention is a useful modification for a Model 83 Potdevin* paper self-opening square (SOS) bag making machine to enable plastic SOS bags to be made therewith.
*denotes trade mark.
D ription of Reference Numerals Roller 11 Cylindrical hole 12 Cylindrical cavity 13 Drive shaft 14 Shaft Helical gear 1~ Cog 17 Aperture 18 Knife blade 19 Closed end of cavity 12 Path o:E knife tip 21 Cutter head cavity 22 Cutter head 23 Plug retaining cavity 24 Plug Gear cavity Z6 Bearing surface 27 Bearing 28 Bolt 29 Bolt Threaded hole 31 Threaded hole 32 Shaft guide cavity W Web A Area inside cavity 21 where knife blade is hidden
Claims (9)
1. A cutter comprising rotating means, a shaft and a knife blade having at least one sharp edge, wherein the shaft is adapted to be rotated about a longitudinal axis and the knife blade is attached to one end of the shaft and offset from the longitudinal axis such that the knife blade is parallel to the longitudinal axis and the sharp knife edge points tangentially about a circle whose centre is coaxial with the longitudinal axis of the shaft, and wherein the rotating means is adapted to rotate the shaft and the knife about said longitudinal axis and a second axis, the longitudinal axis of the shaft being spaced apart from the second axis and substantially perpendicular to a plane pass-ing through the second axis.
2. A cutter comprising a roller, first and second shafts and a knife blade wherein, a) the roller has first and second cavities therein, and is adapted to be rotated about a longitudinal axis, the first cavity being coaxial with said longitudinal axis, extending at least partly into the roller and being open at one end of the roller, said first cavity being adapted to receive the first shaft and allow the first shaft to rotate therein about the longitudinal axis; one end, the first end, of the second cavity being open at the exterior surface of the roller, the other, second, end of the second cavity extending into the roller such that the longitudinal axis of the second cavity is spaced apart from the longitu-dinal axis of the roller and is perpendicular to a plane passing through the longitudinal axis of the roller, said second end being on the opposite side of said plane to the first end, the second cavity being adapted to receive the second shaft and allow the second shaft to rotate about the longitudinal axis of the second cavity, said first and second cavities being in communicating relationship;
b) the first shaft is encased in the first cavity of the roller, said first shaft being adapted to be rotated about the longitudinal axis of the roller, and being further adapted to be driven independently of the roller and to drive the second shaft;
c) the second shaft is encased in the second cavity of the roller and is adapted to rotate about the longitudinal axis of the second cavity of the roller and is in driven relationship with the first shaft, and d) the knife blade is attached to the end of the second shaft closest to the open end of the second cavity such that when the second shaft rotates, the motion of the knife blade circumscribing a circle having its centre coax-ial with the longitudinal axis of the second shaft, said knife blade being sufficiently long to enable a tip thereof to protrude beyond the exterior surface of said roller during at least a portion of said motion, said knife blade having a sharp edge which faces the direction of rotation of the knife blade.
b) the first shaft is encased in the first cavity of the roller, said first shaft being adapted to be rotated about the longitudinal axis of the roller, and being further adapted to be driven independently of the roller and to drive the second shaft;
c) the second shaft is encased in the second cavity of the roller and is adapted to rotate about the longitudinal axis of the second cavity of the roller and is in driven relationship with the first shaft, and d) the knife blade is attached to the end of the second shaft closest to the open end of the second cavity such that when the second shaft rotates, the motion of the knife blade circumscribing a circle having its centre coax-ial with the longitudinal axis of the second shaft, said knife blade being sufficiently long to enable a tip thereof to protrude beyond the exterior surface of said roller during at least a portion of said motion, said knife blade having a sharp edge which faces the direction of rotation of the knife blade.
3. A cutter according to claim 2 wherein the radius of the circle is less than the shortest distance be-tween the longitudinal axes of the roller and second shaft.
4. An apparatus for making an arcuate cut in a web of material, comprising a) a cutter according to Claim 1, and b) a web conveying means adapted to convey the web along a tangent of a circle, the centre of which is the second axis, the radius of the circle being less than the distance between the second axis and the pointed end of the knife blade and greater than the distance between the second axis and the point of attachment of the knife blade to the shaft;
said rotating means and web conveying means being synchronised such that the linear speed of a point on the cutter and on the circle is an integral number of times the speed of the web.
said rotating means and web conveying means being synchronised such that the linear speed of a point on the cutter and on the circle is an integral number of times the speed of the web.
5. A process for making an arcuate cut in a travelling web comprising a) pulling the web longitudinally along a path, and b) cutting the web at intervals with a pointed knife blade having a cutting edge, said knife blade being rotated about a first axis, such that the cutting edge of the knife blade is in a line parallel to the first axis, and faces the direction of rotation of the knife blade, said first axis being rotated about a second axis, the second axis being spaced apart from the first axis and the first axis being substantially perpendicular to a plane passing through the second axis, said second axis being spaced apart from the path through which the web is pulled by a distance marginally less than the maximum distance between the second axis and the point of the knife.
6. A method according to Claim 5 wherein the direction of rotation of the first axis about the second axis is such that the direction of travel of the first axis, in a path parallel to the path through which the web travels, when between the second axis and the web, is in the direction of travel of the web.
7. A process accordng to Claim 6 wherein the web is a film of a thermoplastic polymer.
8. A process according to Claim 7 wherein the thermoplastic polymer is a homopolymer of ethylene or a copolymer of ethylene and a C4 - C10 .alpha.-olefin.
9. A process according to Claim 8 wherein the thermoplastic polymer has a density of from 0.945 to 0.970 g/cm3.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000410006A CA1184112A (en) | 1982-08-24 | 1982-08-24 | Cutter for making arcuate cuts in travelling webs |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000410006A CA1184112A (en) | 1982-08-24 | 1982-08-24 | Cutter for making arcuate cuts in travelling webs |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1184112A true CA1184112A (en) | 1985-03-19 |
Family
ID=4123472
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000410006A Expired CA1184112A (en) | 1982-08-24 | 1982-08-24 | Cutter for making arcuate cuts in travelling webs |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1184112A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1190821A2 (en) * | 2000-09-22 | 2002-03-27 | Windmöller & Hölscher KG | Oscillating single bladed knives and method of cutting with such knives |
-
1982
- 1982-08-24 CA CA000410006A patent/CA1184112A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1190821A2 (en) * | 2000-09-22 | 2002-03-27 | Windmöller & Hölscher KG | Oscillating single bladed knives and method of cutting with such knives |
| EP1190821A3 (en) * | 2000-09-22 | 2004-11-03 | Windmöller & Hölscher KG | Oscillating single bladed knives and method of cutting with such knives |
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