WO2014188009A1

WO2014188009A1 - Double rotor shear and method for driving the same, cardboard cutter and system for automatically forming packaging boxes comprising said double rotor shear

Info

Publication number: WO2014188009A1
Application number: PCT/EP2014/060871
Authority: WO
Inventors: Herman Sytema
Original assignee: Neopost Technologies
Priority date: 2013-05-24
Filing date: 2014-05-26
Publication date: 2014-11-27
Also published as: EP3003658B1; EP3003658A1

Abstract

Double rotor shear, comprising a first rotor (1) comprising at least one first cutting edge (3a), a second rotor (2) comprising at least one second cutting edge (3b), a driving mechanism (10, 12) for rotatably driving the first rotor (1), wherein said first and second rotors (1, 2) are arranged on axes for moving the cutting edges into and out of a travelling plane of a sheet between said first and second rotors (1, 2), said at least one first cutting edge of the first rotor (1) and said at least one second cutting edge of second rotor (2) forming at least one pair of cutting edges adapted for cutting a sheet between the cutting edges forming said pair, wherein the second rotor (2) is rotatably driven by said at least one first cutting edge (3a) pushing directly or indirectly against said at least one second cutting edge (3b).

Description

DOUBLE ROTOR SHEAR AND METHOD FOR DRIVING THE SAME,

CARDBOARD CUTTER AND SYSTEM FOR AUTOMATICALLY FORMING PACKAGING BOXES COMPRISING SAID DOUBLE ROTOR SHEAR

TECHNICAL FIELD OF THE I NVENTION

The invention relates to a double rotor shear and a method for driving the same. The invention also relates to a cardboard cutter and a system for automatically forming packaging boxes comprising the double rotor shear. Particular fields of the invention are shredding of cardboard waste, cardboard cutting and cardboard packaging machines.

BACKGROUND OF THE I NVENTION

In recent years, mail ordering has become increasingly common. In order to cope with the increased need for packaging mail ordered items, different systems and methods for automatically forming packaging boxes have been proposed. US 2008/0020916 A1 discloses a box-making machine, which executes creasing and cutting steps to obtain a cardboard blank, which is then folded to obtain a packaging box from the blank. The invention may be advantageously used in this type and similar types of machines. For making cardboard blanks to be used in box-making machines, usually a long web of cardboard is fed to such machine either from a roll of corrugated cardboard or from a stack, in which the web is zigzag folded into panels. The cardboard is then cut to form the blank. In a machine that cuts cardboard to desired size and shape, cardboard waste is generated. This cardboard must be removed without disturbing the process of cutting the cardboard to a desired shape and size. Furthermore, it is desired to limit the size of this cardboard waste, to ease further transport and/or processing of the material, and to limit the volume of the waste material when gathered, with or without compressing it.

US 2002/0184985 A1 discloses a double rotor cutoff apparatus, comprising

a first rotor comprising a cutting edge on a radial skin surface thereof, a second rotor comprising a cutting edge on a radial skin surface thereof, wherein

said first and second rotors are arranged on parallel axes for moving the cutting edges into and out of a travelling plane of a sheet between said first and second rotors,

a pair of cutting edges consisting of said cutting edges of the first and second rotors is adapted for nipping the sheet via cooperation of said first and second cutting edges for shearing the sheet,

the a double rotor shear further comprising

a driving mechanism of the first rotor for adapting a rotation of the first rotor to a travelling movement of the sheet.

In this prior art, rotating knives are helical and a precise distance between the cutting surfaces is conceived via synchronized driving mechanisms for the first and second rotors.

For sheet material with a significant thickness like cardboard, often a pair of knives is used whereby the cutting surfaces do not touch each other. However, for example due to wear, the distance between the cutting surfaces may change over time and/or play in a drive chain may deteriorate the cutting function.

A precise control between two drives in such a context in order to manage a precise distance or force between the cutting parts is shown in US 2009/0188360 A1. US 4,493,235 shows compensating for a play in a special gearing to prevent backlash.

US 4,034,637 shows a double rotor shear, comprising

a first rotor comprising a cutting edge on a radial skin surface thereof, a second rotor comprising a cutting edge on a radial skin surface thereof, wherein said first and second rotors are arranged on parallel axes for moving the cutting edges into and out of a travelling plane of a sheet between said first and second rotors,

wherein a pair of cutting edges consisting of said cutting edges of the first and second rotors is adapted for cutting the sheet via cooperation of said first and second cutting edges for shearing the sheet,

the double rotor shear further comprising

a drive mechanism of the first rotor for adapting a rotation of the first rotor to a travelling movement of the sheet and a complex system of gears for

synchronizing the movement of the first and the second rotor.

It has turned out that synchronizing the movements of the first and second rotors in the known double rotor shears is not trivial, in particular when the cutting edges wear out and should in fact be brought closer together than initially, when the cutting edges are new. With synchronizing mechanisms using gears, the rotors will always move synchronously, but over time without necessarily bringing the cutting edges into contact so that proper shearing of a sheet to be cut is not guaranteed.

DISCLOSURE OF THE I NVENTION

It is an object of the invention to enable a cutting device for a cardboard with cutting edges on a pair of rotors which allows reliable operation even when the cutting edges show some wear.

It is a further object of the invention to enable a cutting device for a cardboard that needs only one drive for the rotors. Among further objects of the invention are enabling an automatic compensation for play between two knives forming a pair of cutting edges, allowing automatic compensation for wear without need of adjustment over time, allowing employing a self-sharpening mechanism and/or allowing a simple and cost efficient construction. These objects are solved by a double rotor shear comprising a first rotor comprising at least one first cutting edge, a second rotor comprising at least one second cutting edge, a driving mechanism for rotatably driving the first rotor, wherein said first and second rotors are arranged on axes for moving the cutting edges into and out of a travelling plane of a sheet between said first and second rotors, said at least one first cutting edge of the first rotor and said at least one second cutting edge of the second rotor forming at least one pair of cutting edges adapted for cutting a sheet between the cutting edges forming said pair, wherein the second rotor is rotatably driven by said at least one first cutting edge pushing directly or indirectly against said at least one second cutting edge.

The invention provides an automatic synchronization of the rotors without any gears or other complex synchronization mechanisms and ensures that the cutting edges come into close contact and reliably shear a sheet to be cut even when the cutting edges show some wear.

It should be noted that the cutting edge(s) provided on the first rotor push either directly, i.e. in direct physical contact and without a sheet of paper or cardboard in between them against the cutting edge(s) on the second roller, or indirectly with a sheet to be cut in between them, which is then sheared off when the cutting edges make contact.

It should also be noted that the term "sheet" refers to the typical item being cut with this type of double rotor shears but does in practice not need to be a single sheet like a standard A4 sheet or the like, but can for example be a short or a long strip of cardboard to be shredded. Obviously, multiple strips or sheets can be fed to the double rotor shear at the same time, depending on the capacity of the shear and its drive. Hence, when the claims refer to "a sheet" this is only to make the claims concise and to clearly define the invention, but is not limiting the scope of protection to certain applications.

Preferably, the second rotor can move freely on its axis, restricted only when the cutting edge(s) provided on the rotor abut against the cutting edge(s) provided on the first rotor. In one embodiment, the double rotor shear comprises a first rotor comprising a cutting edge on a radial skin surface thereof, a second rotor comprising a cutting edge on a radial skin surface thereof, wherein said first and second rotors are arranged on parallel axes for moving the cutting edges into and out of a travelling plane of a sheet between said first and second rotors, wherein a pair of cutting edges consisting of said cutting edges of the first and second rotors is adapted for cutting the sheet via cooperation of said first and second cutting edges for shearing the sheet, and wherein the a double rotor shear further comprises a driving mechanism for driving the first rotor for adapting a rotation of the first rotor to a travelling movement of the sheet, while the second rotor is only driven by its cutting edge coming into contact with the cutting edge of the first rotor.

The rotors may have the shape of a circular cylinder or a prism.

The invention's double rotor shear is specifically advantageous in case of a double rotor shear with cutting edges of helical knifes on said first and second rotors. Then each helical knife has less than one, one or multiple revolutions around the radial skin surface on which it is arranged.

In one embodiment, the double rotor shear has a plurality of said pair of cutting edges provided on said first and second rotors, wherein the cutting edges of each rotor define sectors of equal size of said rotor.

A pair of entrance rollers, preferably flexible in radial direction, may be arranged on parallel axes. These rollers may define a gap which is intersected by said travelling plane of the sheet.

The driving force on the sheet, which may be made of cardboard, may be limited, so that the transfer speed in the cutting elements having the cutting edges may be a bit higher than the transfer speed in the entrance rollers so that the cardboard can slip between the entrance rollers. The entrance rollers may also contain a one way clutch mechanism.

The invention's double rotor shear is preferably used in a cardboard cutter. To solve the aforementioned and similar problems, the invention also proposes a method as defined in claim 16, a cardboard cutter as defined in claim 17 and a system for automatically forming packaging boxes from cardboard as defined in claim 18.

Further aspects of the invention will become apparent from the following description of a preferred embodiment together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

Figs. 1 A to 1 F show very schematically a profile of certain parts of a double rotor shear according to a first embodiment of the invention in different rotational positions of the rotors.

Fig. 2 shows very schematically a view onto a cut of certain parts of the double rotor shear shown in Fig. 1.

Fig, 3 shows very schematically a perspective view of major parts of a double rotor shear according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS A cardboard cutter according to the invention comprises a double rotor shear as very schematically shown in Figs. 1 A to 1 F, which illustrate the movement in particular of the rotors 1 , 2 chronologically. The rotors 1 , 2 have cylindrical bodies mounted on parallel axes. The illustrated parts include entrance rollers 4, 5. A pair of cutting edges 3 consisting of cutting edges of the first and second rotors 1 ,

2 is adapted for cutting a sheet via cooperation of said first and second cutting edges for shearing the sheet. Only one of the corresponding rotating cutting surfaces is driven, and in operation drives the other by direct or indirect (i.e. with a sheet to be cut in between them) physical contact of the cutting edges. This also implies there is no need to adapt for the thickness of the material being cut.

Specifically, Figs. 1A to 1 F illustrate a first rotor 1 comprising a cutting edge on a radial skin surface thereof and a second rotor 2 comprising a cutting edge on a radial skin surface thereof.

A pair of entrance rollers 4, 5, which may be flexible in radial direction, is arranged on parallel axes and defines a gap which is intersected by said travelling plane of the sheet.

A driving mechanism of the first rotor 1 is provided, which is known per se and not shown here. Such driving mechanism may involve gears with toothed wheels on shafts of the first rotor 1 and maybe also on entrance roller 4. A further toothed wheel on a further shaft 6 may synchronize the movement of entrance roller 4 and rotor 1 . In this embodiment, the entrance roller 4 is arranged on the same side with respect to said travelling plane of the sheet and driven with the same rotational direction and speed as said first rotor 1. A one way clutch can be arranged for driving entrance roller 4. The driving mechanism of the first rotor 1 can adapt a rotation of the first rotor to a travelling movement of the sheet. The second rotor 2 is only driven via the cutting edges of the first and the second rotor.

In the embodiment shown, the first rotor 1 has a protrusion forming a cutting edge 3. The protrusion is tapered towards its free end. Said second rotor 2 also has a tapered protrusion forming the cutting edge. The cut parts/protrusions on the first and second rotors 1 , 2 do not have a rectangular, but rather a rhombic shape in side cut.

The illustrated parts are arranged in a housing, which is stabilized by rods 7, which are arranged parallel to the axes of said first and second rotors and of said entrance rollers 4, 5. The rollers are flexible in radial direction, so that sheet material with varying thickness can be pulled into the shredding unit. As illustrated in Fig. 2 the cutting edges 3 are cutting edges of helical knifes on said first and second rotors 1 , 2. The corresponding helical cutting surface of each helical knife comprises one complete revolution (a single helix), so that the one drives the other continuously.

As shown in Fig. 2 a funnel 8 for inserting a sheet and into an opening of the funnel 8 consists of two curved plates and is arranged in said travelling plane of the sheet in front of said entrance rollers 4, 5 with respect to a travelling direction of the sheet upon cutting.

The funnel 8 forms an entrance for a cardboard directing the cardboard sheet material into the entrance rollers 4, 5, which are mounted on parallel axes that are fixed in the construction, so that the distance between these axes is fixed. In the illustrated embodiment, only one of the entrance rollers needs to be driven and for use with a cardboard a small gap is between both entrance rollers, so that the non-driven roller only rotates when there is a cardboard between the rollers.

Fig. 3 is a schematic perspective view of the major parts of another embodiment of a double rotor shear. A first rotor 1 is provided with a first helical knife providing a first cutting edge 3a, a second rotor 2 is provided with a second helical knife providing a second cutting edge 3b.

A motor (not shown) drives gear 10, which meshes with gear 12 provided on the shaft of rotor 1 for rotatably driving rotor 1. Rotor 2 can turn freely about its shaft up to the points, where its helical knife, respectively its cutting edge 3b, abuts against helical knife, respectively its cutting edge 3a. In operation, rotor 2 is driven by rotor 1 , whose cutting edge 3a directly or indirectly contacts cutting edge 3b.

In this embodiment, rotor 2 is provided with a gear 14, which meshes with gear 16 to drive gear 18 provided on entrance roller 5. Hence, by driving rotor 1 , automatically the movements of rotor 2 and of entrance roller 5 are synchronized and in the embodiment shown, rotor 1 indirectly, namely via rotor 2 and gear 16, drives entrance roller 5. Moreover, wear on the cutting edges 3a and 3b does not automatically lead to deterioration of the cutting results as still the cuttings edges will contact each other to shear material feed between them.

The entrance rollers 4 and 5 are mounted on parallel axes that are fixed in the construction, so that the distance between these axes is fixed. The rollers can be flexible in radial direction, so that material with varying thickness can be pulled into the shredding unit formed with the double rotor shear. Only one of the entrance rollers needs to be driven. For use with cardboard, there can be a small gap between both rollers 4, 5, so that the non-driven roller 4 only rotates when there is cardboard between the rollers. Furthermore, the driving force on the cardboard may be limited, so that the transfer speed in the cutting elements may be a bit higher than the transfer speed in the entrance rollers 4, 5, so that the cardboard can slip between the entrance rollers. Alternatively, the entrance rollers may contain a one way clutch.

Plates 8a and 8b form a funnel for introducing material to be cut in the shredding unit formed with the double rotor shear.

Advantages of the invention:

- only one drive needed

no need for exact control of two different drives

no complex gearing required to compensate for play between two knives, possibility of automatic compensation for wear without need of adjustment over time.

- possibility of employing a self-sharpening mechanism.

possibility of a simple and cost efficient construction.

Claims

1. Double rotor shear, comprising

a first rotor (1 ) comprising at least one first cutting edge,

a second rotor (2) comprising at least one second cutting edge,

a driving mechanism for rotatably driving the first rotor (1 ),

wherein said first and second rotors (1 , 2) are arranged on axes for moving the cutting edges into and out of a travelling plane of a sheet between said first and second rotors (1 , 2),

said at least one first cutting edge of the first rotor (1 ) and said at least one second cutting edge of second rotor (2) forming at least one pair (3) of cutting edges adapted for cutting a sheet between the cutting edges forming said pair (3), characterized in that

the second rotor (2) is rotatably driven by said at least one first cutting edge pushing directly or indirectly against said at least one second cutting edge.

2. Double rotor shear according to claim 1 , characterized in that the second rotor (2) can move freely on its axis, restricted only when the cutting edge(s) provided on the second rotor (2) abut against the cutting edge(s) provided on the first rotor (1 ).

3. Double rotor shear according to claim 1 or 2, wherein said cutting edges are cutting edges of helical knifes on said first and second rotors (1 , 2).

4. Double rotor shear according to claim 3, wherein each helical knife has multiple revolutions around the radial skin surface of the rotor (1 , 2) on which it is arranged.

5. Double rotor shear according to any of the preceding claims having a plurality of pairs of cutting edges formed by multiple first and second cutting edges on said first and second rotors.

6. Double rotor shear according to any of the preceding claims having a pair of entrance rollers (4, 5) arranged on parallel axes.

7. Double rotor shear according to claim 6, wherein said entrance rollers (4, 5) are flexible in radial direction.

8. Double rotor shear according to claim 6 or 7, wherein at least one of said entrance rollers (4) is driven.

9. Double rotor shear according to claim 8, wherein said at least one driven entrance roller (5) is directly or indirectly driven by the first rotor (1 ).

10. Double rotor shear according to claim 8 or 9, wherein said at least one driven entrance roller is driven with a lower rotational speed than said first rotor.

1 1. Double rotor shear according to one of claims 8 to 10, wherein a one way clutch is arranged for driving said at least one driven entrance roller.

12. Double rotor shear according to one of claims 1 to 1 1 , comprising a funnel (8) for directing a sheet to be cut into said travelling plane.

13. Double rotor shear according to any of the preceding claims, wherein at least one of said first and second cutting edges is formed by a protrusion on the respective rotor, said protrusion being tapered towards its free end.

14. Double rotor shear according to any of the preceding claims, wherein each rotor (1 , 2) has the shape of a cylinder, in particular of a circular cylinder or of a prism.

15. Double rotor shear according to claim 14, wherein the cutting edges are provided on the radial skin surfaces of said circular cylinder(s) or of said prism(s).

16. Method for driving a double rotor shear having

a first rotor comprising at least one first cutting edge,

a second rotor comprising at least one second cutting edge, wherein said first and second rotors are arranged on axes for moving the cutting edges into and out of a travelling plane of a sheet between said first and second rotors,

said at least one first cutting edge of the first rotor and said at least one second cutting edge of second rotor forming at least one pair of cutting edges adapted for cutting a sheet between the cutting edges forming said pair,

characterized in that

the second rotor is rotatably driven only by said at least one first cutting edge pushing directly or indirectly against said at least one second cutting edge.

17. Cardboard cutter comprising the double rotor shear according to one of claims 1 to 15.

18. System for automatically forming packaging boxes from cardboard comprising a cutting station having a double rotor shear according to one of claims 1 to 15.