Method and apparatus for removing waste windows from web carton material

Abstract

 A method and apparatus are provided for removing waste die-cut windows from continuously moving carton board web material. A paid of juxtaposed parallel cylinders (12, 16) with their axes disposed transverse to the direction of web movement accept the moving web and knock-out the die-cut windows by virtue of a protuberance (20) on one cylinder mating with a recess (22) on the other, the protuberances and recesses matching each other and also matching the position of the die-cut window. In a variant, the non-male cylinder has an outer layer of substantially uniform thickness and is made of resilient polymeric material adapted to be elastically distorted sufficiently to receive the outward protrusion along with the waste window.

Description

[0001] This invention relates generally to a rotary mechanism that is used to remove waste sections of die-cut material that are retained within a continuously moving web of carton board material.

[0002] Rotary window stripping is a widely used method for removing die-cut waste sections from carton board web. In a conventional web fed carton press, web is unwound, fed through a series of print heads, die-cut, stripped, separated and finally, stacked. This invention pertains specifically to the stripping function of the overall board converting process.

[0003] Window stripping of die-cut board stock is done in order to remove the waste die-cut apertures from the web. The waste window pieces are retained in the die-cut web by means of 'nicks' that tie the window to its adjacent web. Each nick is like a minute bridge of material linking the window and the web, and forms as the result of a small discontinuity in the cutting edge of the die rule. Each window can have several nicks. The 'window' knockouts are typically used as hook holes or viewing windows in a carton box. If used as an actual window, then the aperture is typically later covered by an adhesive-applied transparent plastic panel.

[0004] There are two main methods of window stripping: flat and rotary. The flat method consists of a reciprocating platen that contains suitably located knockout tooling and moves perpendicular to the direction of web motion. This type of stripper requires that the web be momentarily stopped in order that the tool set can penetrate the web without ripping it. Rotary strippers, on the other hand, are used with continuously moving webs and thus are able to operate at higher line speeds than flat strippers. Conventional rotary strippers are often referred to as 'rotary pin strippers' because of the unique pin shaped tooling they use to spear the window scrap.

[0005] In the proposed invention instead of using pins, a meshing set of raised image plates (typically, though not necessarily, of flexible photopolymer construction), one male, the other female, is engaged in a rotary manner so as to eject the scrap material. Each plate is mounted on the surface of a separate cylinder such that the resulting composite circumference matches that of the print repeat of the parts being stripped. The two cylinders are positioned relative to each other and to the web by the stripping mechanism so as to achieve synchronized registry of the raised images with the window parts to be removed from the die-cut web.

[0006] According to a first embodiment of the proposed system, a continuous die-cut web replete with nicked waste parts (windows) is passed between the mating set of imaged plates carried on two cylinders. The male and female plate images match the shapes of the waste parts to be removed from the cartons, except that they are slightly mis-sized so as to allow for mis-registration, clearance and draft angles on the shoulders of the mating plate images. Typically, the male plate is mounted on the cylinder above the web and the female beneath, with possible vacuum assist being coupled into the female plate to permit a boost to the extraction process. Nicks linking the window waste to the parts must be broken and the meshing action of engaging imaged plates provides the positional action to do this. By this process, waste parts are knocked out of the moving web and held in the cavities of the female plate until such time as the cylinder on which the female plate is mounted rotates to a position where the waste parts can fall out of, or be ejected from, the female plate cavities. Waste parts thus deposited can be gathered and removed from the stripper mechanism by a suitable means, e.g. conveyor, air stream or vacuum apparatus.

[0007] In accordance with a second embodiment of the proposed system, the male plate is unchanged but the female plate, instead of providing defined apertures in registry with raised portions of the male plate, has an outer layer of substantially uniform thickness made of resilient polymeric material, which is adapted, when the raised male portion pushes out a waste window, to be elastically distorted sufficiently to receive at least part of the outwardly protruding part of the male plate, along with the waste window.

[0008] Benefits of the proposed system relative to existing methods may include:

• the required tooling for the system (drums, plates, etc.) is less expensive than the tooling required for either conventional flat or rotary stripping systems;
• can operate at a higher speed than the flat system;
• less change-over time required between jobs;
• takes up less space than conventional systems;
• less time required to fabricate the tooling, therefore, lead times can be reduced. Similarly, changes/repairs to the tooling can be done faster and at less cost.
• more positive means of stripping than pins - window parts are positively displaced as opposed to being speared.
• on-the-fly tool-to-tool registration, both lateral and longitudinal.

[0009] In the proposed design, the rotary stripper unit can be powered and registered to the main press by any number of types of mechanical/electrical/servo systems.

[0010] More particularly, this invention provides a method of removing waste die-cut windows from continuously moving carton board web material, comprising the steps:

providing a pair of juxtaposed parallel cylinders with their axes transverse to the direction of web movement,

passing the web material between the cylinders,

using radially outwardly protruding means on one cylinder to push against and dislodge said waste windows in the direction toward the other cylinder, and

receiving the waste windows in the outer layer of the said other cylinder.

[0011] Further, this invention provides an apparatus for removing waste die-cut windows from continuously moving carton board web material, the apparatus comprising:

a pair of juxtaposed parallel cylinders with their axes disposed transverse to the direction of web movement,

guide means for passing the web material between the cylinders,

one of said cylinders having outwardly protruding means for pushing against and dislodging said waste windows in the direction toward the other cylinder, and

means in the outer layer of the other cylinder adapted for receiving the waste windows.

[0012] One embodiment of this invention is illustrated in the accompanying drawings, by way of example only, in which like numerals denote like parts throughout the several views, and in which:

[0013] Figure 1 is a perspective view showing the components of a typical die-cut carton web.

[0014] Figures 2 and 2A are perspective and side elevational views, respectively, of the first embodiment of this invention, consisting of an upper cylinder plate with its raised image area matching the window/scrap sections of the carton. The lower cylinder has a female plate with recesses that mate with the male upper cylinder plate.

[0015] Figures 3 and 3A are perspective and side elevational views, respectively, of a variant of the first embodiment, consisting of an upper cylinder plate with its raised image area matching the window/scrap sections of the carton and the scrap matrix. The lower cylinder has a plate with raised image areas that match the shape of the carton. Recesses (or lower washed-out elevations) in each plate mate with the male areas of the other mating plate.

[0016] Figures 4 and 4A are perspective and side elevational views, respectively, of the second embodiment of this invention, consisting of an upper cylinder plate with its raised image area matching the window/scrap sections of the carton. The lower cylinder has an elastic, continuous polymeric coating.

[0017] As previously pointed out, the purpose of the device herein disclosed is to remove the scrap window areas from a die-cut web.

[0018] Figure 1 shows a typical die-cut carton 2, still retained in its host web 4. The window sections 6 are shown still retained in the web. Item 8 is a waste window after it has been removed from the web. The continuous longitudinal and short lateral pieces of scrap web 10 are referred to as matrix, and are typically removed from the individual cartons at a station subsequent to the rotary stripper. The overall shape of the matrix is typically that of a ladder.

[0019] Figure 2 shows a first embodiment of this invention, in which an upper cylinder 12 with an attached raised image plate (male) 14 engages with a lower cylinder 16 having an attached raised image plate (female) 18. The two plates are formed such that their raised image surfaces and recessed pockets are complementary. This allows meshing of the two surfaces without interference. In the case where photopolymer plates are utilized, attachment of the plates to their respective cylinders is accomplished by using double-sided tape (referred to in the printing trade as 'sticky back'). The raised images 20 on the upper plate 14 are shaped to match the waste window areas to be removed from the cartons. Similarly, the pockets 22 on the lower plate 18 are shaped to match the waste windows. The pockets are typically sized to allow some edge clearance with the mating male images. At the beginning of the operation, the upper and lower cylinders, 12 and 16, are indexed apart from each other in order to allow free passage of the die-cut web 24. Once the two cylinders are synchronized with each other, and registered as a pair to the web images, they are then brought into engagement with each other such that the raised (male) images 20 located on the upper cylinder penetrate the web line and drive the waste window pieces 26 into the matched recessed pockets 22 located in the lower plate 18. Each stripped (removed) window 26 is retained in a lower plate pocket until its position on the lower cylinder has rotated through approximately half a revolution. At this point, the waste window is removed from the pocket either by gravity and/or air jet stream. Being rotary, this process of sequential waste window removal continues uninterrupted. After leaving their pockets, parts can be extracted by a vacuum system or dropped into a bin/conveyor.

[0020] The window-stripping plates can be made of any suitable material, e.g. steel, aluminum, polymer, etc. However, there will be a real advantage in using UV-exposed photopolymer plates, since the exposure and development techniques for these materials are common to the printing industry. In fact, the same materials used for the printing plates would be used for window-stripping.

[0021] Subsequent to window stripping, the matrix, complete with retained cartons, continues in a straight path to a pair of driven nips, specifically top nip 28 and bottom nip 30, at which point the matrix 32 is pulled down over the lower nip and drawn into a shredding device. The individual cartons are simultaneously drawn ahead by a conveying mechanism (not shown) that serves to:

a) provide tension to the cartons to break the nicks retaining the cartons within the matrix, and

b) convey the separated cartons 34 to the next stage of processing, typically conveying/spreading/stacking.

[0022] The post-stripping nip pair 28 and 30 is preferably driven, and the plane between the longitudinal axes of the two nips can be rotated +/- through an arc in order to facilitate the stripping of the cartons from the matrix. It is believed that the "kicking" action resulting from tilting the nip set will aid stripping. It is expected that the ability to vary the speed of the stripping nip set relative to the speed of the window stripping cylinders will be of advantage.

[0023] Alternatively, the matrix may be stripped directly off the lower stripping cylinder, as shown by dashed line 36 (in Figure 2).

[0024] Figure 3 illustrates an alternative arrangement whereby the profile of the lower female plate is such as not only to receive the stripped-out windows, but as well to serve to 'kick-up' the cartons while the matrix is being stripped off the lower cylinder. Thus two actions simultaneously result from the stripping action of the plates:

a) removal of the waste windows from the cartons, and

b) stripping of the cartons from the matrix.

[0025] As a result, no secondary nipping set is required to achieve matrix stripping. In effect, the lower plate acts as both a female and male, depending on the nature (i.e. window/carton/matrix) of a specific area of the web. In this arrangement, the matrix is stripped off the female cylinder at the same diametral depth as the recessed pocket base; whereas in the assembly shown in Figure 2, the matrix, if stripped from the lower cylinder, is removed from the outer diameter of the plate, i.e. the non-recessed area. Disposal of the waste windows is the same as for the arrangement shown in Figure 2.

[0026] Figure 4 shows a second embodiment of this invention, in which the upper cylinder with its attached male plate acts against a lower cylinder having an elastic continuous polymer coating 38 in place of a female plate. In this instance, the raised image areas 20 of the upper plate 14 act to depress the window areas into the soft polymer surface of the lower cylinder. Non-window areas in the web are not acted upon by the male plate and are supported by the polymer surface of the lower cylinder. This results in a displacing action in which the window nicks are broken and the window pieces 26 are separated from their host carton pieces. Upon exiting from the stripping line between the two cylinders, the window waste tends to adhere to the polymer surface of the lower cylinder through static attraction. These pieces can then be removed from the lower cylinder surface by any number of means, for example, utilizing an anti-static bar and air jet, or using an annularly grooved profile for the lower cylinder surface in conjunction with a comb whose teeth track through the annular grooves (without touching them) and scrape off the window pieces.

[0027] In this embodiment, the matrix 32 can be stripped from the cartons at a separate nip set, or directly from the lower cylinder, as previously described.

[0028] With this embodiment, several advantages relative to the previously described versions are realized:

a) the variable cost of a lower (female) plate is eliminated. In addition, the polymer-coated lower cylinder can be used for all print repeats, unlike the plated version which requires a different diameter cylinder for each print repeat. Tooling costs are greatly reduced.

b) because the lower cylinder is smooth, it need not be lowered so as to be disengaged from the upper cylinder male plate. Equipment for positioning the lower cylinder is thus greatly simplified and lower in cost.

c) because of the action of the male raised images on the polymer surface of the lower cylinder, it is not necessary to drive the lower cylinder in synch with the upper cylinder; in fact, the lower cylinder can be an idler. If desired, it can also be driven. Again, cost reduction is realized.

d) window waste is more easily removed from a smooth cylinder surface than from the recessed pockets in a lower female plate as used in the arrangements depicted in Figures 2 and 3.

[0029] Although the foregoing disclosure describes a window-stripping arrangement in which the window pieces are stripped out against a lower cylinder mounted beneath the web, it is expected that stripping could also occur against the upper cylinder, but such an arrangement is not expected to be of great benefit, since the position of the waste parts would be acting against gravity.

[0030] One possible material for the outer layer carried on the lower cylinder is Nitrile, although it is expected that some wear resistance benefit will be gained from using polymers such as polyurethane. The Nitrile used has a hardness of 35 Shore A.

[0031] Experimental plates of various durometers and thicknesses were utilized on the upper cylinder in developing this invention. Specifically, plate thicknesses between 0.067" to 0.125" were tried, with success. It is expected, however, that the plate thickness could be outside this range. During these trials, plate durometers of 45 to 90 Shore A+ were utilized.

[0032] It is of advantage to be able to vary the depth of engagement between the two window-stripping plates during operation, in order to achieve optimum performance. For example, too much engagement (i.e. interference) can result in the entire web being trapped between the two cylinders with the result that the window stripping cylinder acts has a nip. This can cause misregistration and web breakage. The objective is to have the male images "poke out" the windows from the web.

[0033] While several embodiments of this invention have been described hereinabove and illustrated in the accompanying drawings, it will be evident to those skilled in the art that changes and modifications may be made therein, without departing from the essence of this invention, as set forth in the appended claims.

Claims

1. A method of removing waste die-cut windows from continuously moving carton board web material, comprising the steps:

providing a pair of juxtaposed parallel cylinders with their axes transverse to the direction of web movement,
passing the web material between the cylinders,

using radially outwardly protruding means on one cylinder to push against and dislodge said waste windows in the direction toward the other cylinder, and

receiving the waste windows in the outer layer of the said other cylinder.

2. The method claimed in claim 1, in which the receiving of the waste windows is accomplished by virtue of outwardly open recess means in said outer layer sized and adapted to accept at least part of said outwardly protruding means along with the waste windows.

3. The method claimed in claim 1, in which the receiving of the waste windows is accomplished by distortion of the outer layer, which is made of resilient material.

4. An apparatus for removing waste die-cut windows from continuously moving carton board web material, the apparatus comprising:

a pair of juxtaposed parallel cylinders with their axes disposed transverse to the direction of web movement,

guide means for passing the web material between the cylinders,

one of said cylinders having outwardly protruding means for pushing against and dislodging said waste windows in the direction toward the other cylinder, and

means in the outer layer of the other cylinder adapted for receiving the waste windows.

5. The apparatus claimed in claim 4, in which said means for receiving waste windows is constituted by outwardly open recess means in said outer layer sized and adapted to accept at least part of said outwardly protruding means along with corresponding waste windows.

6. The apparatus claimed in claim 4, in which said outer layer of the other cylinder is of substantially uniform thickness and is made of resilient material adapted, when said protruding means pushes out a waste window, to be elastically distorted sufficiently to receive at least part of said outwardly protruding means along with the waste window.

7. The apparatus claimed in claim 6, in which said resilient material is a polymeric material with a hardness of about 35 Shore A.

8. The apparatus claimed in claim 6 or claim 7, in which the polymeric material is selected from the group consisting of: Nitrile, polyurethane.

9. The apparatus claimed in claim 4, in which an external cylindrical plate is secured to said one of said cylinders, and in which said outwardly protruding means includes at least one radially outward projection fixed with respect to said cylindrical plate.

10. The apparatus claimed in claim 9, in which said means for receiving waste windows is constituted by outwardly open recess means in said outer layer sized and adapted to accept at least part of said outwardly protruding means along with corresponding waste windows.

11. The apparatus claimed in claim 9 or claim 10, in which said outer layer of the other cylinder is of substantially uniform width and is made of resilient polymeric material adapted, when said protruding means pushes out a waste window, to be elastically distorted sufficiently to receive at least part of said outwardly protruding means along with the waste window, in which said polymeric material has a hardness of about 35 Shore A, and in which the polymeric material is selected from the group consisting of: Nitrile, polyurethane.

12. The apparatus claimed in claim 4, 9, 10 or 11 including adjustment means for varying the distance between the axes of the cylinders.

Drawing