Wire feeding device in a rotary stapling machine

Abstract

 A wire advancement device (90) and a method in a rotary stapling machine which wire advancement device comprises a wire source (91, 92), an advancement system (93, 94) and a driving motor (95) arranged so that wire (T) from the wire source is continuously advanced via the advancement system to a first and a second wire introduction assembly (41, 42) mounted in a staple pick-up zone (31) in the rotary stapling machine, and that the wire introduction assemblies are provided with cutting edges that co-operate with the corresponding cutting edges of stapling forks (21, 21'), the cutting edges being arranged to cut off a length of wire advanced to the wire introduction assemblies (41) and forming a staple blank at each revolution the stapling fork (21) passes the wire introduction assembly (41), as well as that guide means (43, 44) are arranged to allow that the first wire introduction assembly (41) only delivers staple blanks to one of the stapling forks (21) and to allow the second wire introduction assembly (42) to only deliver staple blanks to the other one of the stapling forks (21') by the guide means (43, 44) providing a displacement of the respective wire introduction assembly (41, 42) in the direction away from the stapling cylinder to allow free passage of a stapling fork (21, 21').

Description

Technical Field

[0001] The present invention relates to the area of rotary staplers intended for stapling printed matter, e.g., newspapers and brochures, the pages of which come from a printing press on a double-sided printed running paper web. Each double-sided printed paper web is collected and synchronised to each other, whereupon the collected paper webs define continuous product parts that after stapling are cut off into finished products. Alternatively, the collected paper webs are cut off into product units, which after that are led into the rotary stapler and there are stapled together into finished products. Particularly, the invention relates to wire advancement and wire pick-up in such a machine.

Background of the Invention

[0002] From the printing presses, one or more paper webs run, usually in so-called broadsheet format, at a constant speed on each other, which paper webs together form a continuous row of product parts in the form of printed matter. The paper webs with the product parts run past a rotary stapler that staples together the paper webs, the paper webs after that being cut off halfway between the stapling points and forming separate products. In doing so, the products constitute finished printed matter after folding has been effected along the staplings.

[0003] The paper webs in broadsheet format will be folded only once along the web. Usually, these products will not become stapled at all since the wire staples have to be inserted in the longitudinal direction. However, so-called tabloid products are folded twice. First along the web, at the same time as the web becomes cut lengthwise, and next transverse to the direction of motion. Thereby, the wire staples have to be inserted transverse to the web in the second folding line. The stapling can be effected before as well as after the paper web has been cut off transverse to the direction of motion, by means of a web-breaking roller. This technique of stapling tabloids in the fold is well-known since before.

[0004] Smaller products, so-called quarter-folded products, are folded three times. After a tabloid product has been produced by two foldings, it has to be folded a third time along the direction of motion again. Therefore, the stapling in the third folding line has also to be carried out along the direction of motion. These products will usually be stapled outside the folding machine on a so-called saddle stapler.

[0005] Further backgrounds of rotary staplers are seen, e.g., in the Swedish patents 9300536-1 (506 107) and 9300537-9 (506 108), which correspond to the US patents US 5,474,221 and US 5,690,266. Also the US patent specification US 3,762,622 presents the background of rotary staplers. The rotary staplers are mounted in direct connection to the printing presses in spaces especially adapted to the rotary staplers.

[0006] By the patent specification EP 981450, a device for longitudinal stapling of multi-paged printed products over a saddle is previously known. The patent specification discloses a device having a stapling fork that is turned from a staple forming position into a stapling position as well as is turned to align the stapling fork to be parallel to the material web during the stapling stage. Also the die of the device in the die cylinder thereof is turned to align also this one into a position parallel to the material web. Accordingly, both the stapling fork and the die are held parallel to each other as well as to the material web during the stapling stage. The device comprises also a staple bending device that is formed with two parts each one of which is turnable around a separate axis. A device according to this patent specification is adapted to stapling over a saddle and that is clearly shown in Figures 1 and 2 thereof. Accordingly, it cannot be used for linear stapling in the fold, before the last folding (quarter-fold) is made.

[0007] As for the wire advancement to the stapling forks for conventional rotary staplers, a continuous advancement of the wire is used. This way of advancing the wire has been used for staplers that have a symmetrical construction of the stapling cylinder.

[0008] When stapling by a conventional symmetrical stapler in so-called "collect mode", i.e., when two products are collected above each other on a collecting cylinder and only every second product is stapled, a problem arises since a length of wire is only needed every second machine revolution. Therefore, the feeding of wire has to stop for a while and then be accelerated and braked rapidly. Different solutions to staple in the "collect mode" have been established. A first solution is that the wire advancement is carried out by a stepping motor having a control system, which is a very variable solution that is adaptable to many operational cases, however the speed is very limited since the motor and the wire have certain inertia and it is not possible to accelerate and brake arbitrary fast. A second solution that is the simplest solution, which is used in so-called double round machines, i.e., machines where the stapling cylinder rotates two revolutions for each cut-off length, is to remove only one of the two symmetrically placed stapling forks and feed the wire at half speed, which is a simple solution, however having the disadvantage that a mechanical conversion between the two operation cases is required. A third solution is shown in DE 10 2004 040 851, which solution for the wire advancement uses two motors in the proper "feeder housing". In the "collect mode", the first motor drives continuously at half speed on the wire coil and advances wire in a storage. A second motor that is closer to the machine advances at full speed, intermittently, at intervals, wire into the machine. This solution decreases the inertia and friction of the wire for the proper feeding motor since it operates with only a small wire loop. However, the solution is complicated since a complicated control system including two motors is required.

The Object of the Invention

[0009] The present invention aims at providing an improved continuous wire advancement device for a rotary stapling or stitching machine.

[0010] A further object of the invention is to provide a continuous wire advancement for an unsymmetrical rotary stapler, where the stapling forks accordingly are placed after each other.

[0011] Yet an object of the invention is to provide a continuous wire advancement for an unsymmetrical linear stapling machine.

Summary of the Invention

[0012] By the present invention such as the same is defined in the independent claims, the above-mentioned objects are met. Suitable embodiments of the invention are defined in the dependent claims.

[0013] The invention concerns a wire advancement device in a rotary stapling machine, preferably a linear stapling machine, which wire advancement device comprises a wire source, an advancement system and a driving motor arranged so that wire from the wire source is continuously advanced via the advancement system to a first wire introduction assembly mounted in a staple pick-up zone in a rotary stapling machine. The wire introduction assembly is provided with a cutting edge that co-operates with a corresponding cutting edge of a stapling fork in turn mounted in a stapling cylinder rotating around a first axis, the cutting edges being arranged to cut off a length of wire advanced to the wire introduction assembly and forming a staple blank at each revolution the stapling fork passes the wire introduction assembly. The wire advancement device is provided with a second wire introduction assembly co-operating with a second stapling fork placed in the same axial position on the stapling cylinder as the first stapling fork in order to cut off a second continuously advanced length of wire forming a staple blank. Furthermore, guide means are arranged to allow that the first wire introduction assembly only delivers staple blanks to one of the stapling forks and to allow the second wire introduction assembly to only deliver staple blanks to the other one of the stapling forks. This is effected by the guide means providing a displacement of the respective wire introduction assembly in the direction away from the stapling cylinder to allow free passage of a stapling fork.

[0014] In one embodiment of the invention, the two stapling forks are placed after each other in the stapling cylinder, which means that they are in the staple pick-up zone simultaneously.

[0015] In one embodiment of the invention, the guide means comprises cam followers mounted one to each wire introduction assembly and cam curves mounted to the stapling cylinder and that are formed to change the positions of the cam followers in directions perpendicular to the first axis.

[0016] In one embodiment of the invention, a primary cam follower of the first wire introduction assembly is arranged to be displaced by a primary cam curve situated at the second stapling fork, so that the second stapling fork clears the first wire introduction assembly. Also a secondary cam follower of the second wire introduction assembly is arranged to be displaced by a secondary cam curve situated at the first stapling fork, so that the first stapling fork clears the second wire introduction assembly.

[0017] In one embodiment of the invention, the cam curves of the guide means are rotatable together with the stapling forks around the first axis.

[0018] In one embodiment of the invention, a staple forming device, preferably in the form of a forming wheel comprising a forming roller, is mounted in the staple pick-up zone after the two wire introduction assemblies in respect of the direction of motion of the stapling fork.

[0019] In one embodiment of the invention, the staple forming device is arranged to form staples picked up by both stapling forks.

[0020] In addition, the invention concerns a method for wire advancement in a rotary stapler in which one motor continuously advances wire from a wire source to a wire introduction assembly, one motor continuously advancing wire from a second wire source to a second wire introduction assembly, a first stapling fork in a stapling cylinder cutting off and picking up a staple blank from only one of the wire introduction assemblies while a second stapling fork in the stapling cylinder cutting off and picking up a staple blank from only the other one of the wire introduction assemblies.

[0021] In one embodiment of the invention according to the method, the first stapling fork and the second stapling fork are trailing each other, the same accordingly being in the staple pick-up zone simultaneously.

[0022] In one embodiment of the invention according to the method, the wire advancement to the two wire introduction assemblies is driven by one and the same motor.

[0023] In one embodiment of the invention according to the method, each stapling fork carries the respective staple blank to a forming wheel that forms the staple blank into a staple.

[0024] In one embodiment of the invention according to the method, guide means displace, on one hand, the second wire introduction assembly or the first stapling fork away from the wire pick-up position thereof, and on the other hand the first wire introduction assembly or the second stapling fork away from the wire pick-up position thereof.

[0025] In one embodiment of the invention according to the method, the wire advancements are effected at a constant speed.

[0026] The invention concerns a wire advancement device according to the above that is intended for a rotary stapler, which by a stapling module placed in a rotating stapling cylinder applies wire staples provided with penetrating branches through the plurality of material layers of a printed product. The wire staples are formed by wire being advanced to a cutting assembly where a stapling fork cuts off a length of wire that after that is formed into a staple, which upon the stapling is pressed by a punch mounted in the stapling fork in the stapling module through the material layers, whereupon the branches of the wire staples are formed against a die in a die cylinder counter-rotating in relation to the stapling cylinder,

[0027] Furthermore, a stapler is disclosed for which a wire advancement device according to the invention is extraordinarily suitable, which stapler is to be mounted in the proper folding part of a printing press, the products becoming stapled before the last folding is carried out, so-called quarter fold. The stapling is effected against a cylinder surface that requires a non-linear motion of the stapling head. In contrast to prior art, the present stapler is adapted to be integrated in the folding assembly in the printing press in order to allow the stapling to be effected before the last folding is carried out. In the present invention, a pivoting is provided of only the stapling head against a cylinder so that the stapling head follows the cylinder surface. Accordingly, this motion is not linear. The die may be made passive, the same being possible to mount on already existing cylinders.

[0028] A wire advancement device is suitable for a linear stapling machine that is provided with a stapling fork rotating around a first axis as well as with a die counter-rotating around a second. The axes are placed in such a way and are arranged to be rotated so that the stapling fork and the die roll off against each other at some instant of time so that the branches of a wire staple that is carried by the stapling fork can be forced through a plurality of layers of a product part running through the rotary stapler and thereby be formed against the die. A first guide means is arranged to turn the stapling fork by 90" during its motion to as well as during its motion from a staple pick-up zone, which is defined as a zone having an extension that corresponds to 1/4 to 1/3 of a stapling cylinder circumference, in relation to a stapling zone so that the orientation of the stapling fork is parallel to the first axis in the staple pick-up zone, but that the stapling fork is perpendicular to the first axis in the stapling zone. The staple pick-up zone and the stapling zone are defined in the stapler shown and described here as the respective distances along which the stapling fork is not turned during a cylinder revolution. Upon stapling through the product part, the wire staple will then be essentially parallel to the direction of motion of the product part, and upon picking-up, be essentially perpendicular to the direction of motion of the product part. Furthermore, at least one second stapling fork rotating around the first axis and trailing the first stapling fork is arranged to roll off against a corresponding second die counter-rotating around the second axis so that the branches of a wire staple that is carried by the second stapling fork can be forced through a plurality of layers of the same product part running through the rotary stapler and thereby be formed against the second die. In this connection, the first guide means is arranged to turn the second stapling fork by 90° to and from the staple pick-up zone in relation to the stapling zone so that the orientation of the second stapling fork is parallel to the first axis in the staple pick-up zone and perpendicular to the first axis in the stapling zone. Upon stapling through the product part, the wire staple is in this connection essentially parallel to the direction of motion of the product part. In addition, a base plate is arranged in which a stapling cylinder is rotatably mounted for rotation around the first axis, the stapling cylinder supporting the stapling forks. By virtue of this construction of a linear stapling machine, a product part or product unit can be completely stapled by only one stapling cylinder during one revolution before the last folding.

[0029] In one embodiment of such a linear stapling machine, a cutting assembly is mounted at the staple pick-up zone and provided with a first wire introduction assembly and a second wire introduction assembly, as well as that third guide means are arranged to allow that the first wire introduction assembly only delivers staple blanks to one of the stapling forks and that the second wire introduction assembly only delivers staple blanks to the other one of the stapling forks by a pushing-away of the respective wire introduction assembly. It is also possible that the pushing-away actuates the stapling fork instead of the wire introduction assembly.

[0030] In one embodiment, the third guide means comprises third cam followers mounted one to each wire introduction assembly and third cam curves that are formed to change the positions of the third cam followers in directions perpendicular to the first axis.

[0031] In one embodiment, a primary third cam follower of the first wire introduction assembly is arranged to be displaced by a cam curve situated at the first stapling fork, so that the first stapling fork clears the first wire introduction assembly, and a secondary third cam follower of the second wire introduction assembly is arranged to be displaced by a cam curve situated at the second stapling fork, so that the second stapling fork clears the second wire introduction assembly.

[0032] In one embodiment, the cam curves of the third guide means are rotatable together with the stapling forks around the first axis.

[0033] In one embodiment, the cutting assembly is fixedly mounted to the base plate of such a linear stapling machine.

[0034] In one embodiment, a staple forming device, preferably in the form of a forming wheel, is mounted in the staple pick-up zone after the two wire directing assemblies in respect of the direction of motion of the stapling fork. In this connection, it is required that the forming of the staple is effected after the staple pick-up has been effected but before the stapling fork with the staple begins to be turned.

[0035] In one embodiment, the staple forming device is arranged to form staples picked up by both stapling forks.

[0036] In one embodiment, the stapling forks are mounted in a stapling cylinder that is arranged to rotate around the first axis.

[0037] The embodiment examples that will be described relate to a so-called "single round" linear stapling machine, which means that for each revolution the stapling cylinder rotates, a product part/product unit will be stapled. However, also a "double round", a "triple round", etc., linear stapling machine can be comprised within the scope of the invention. In this connection, two, three, etc., product parts/product units will be stapled during each revolution. For all these types of machines, it applies however that the stapling forks are placed in pairs "trailing" each other in order to finally staple together one and the same product part or product unit during the same revolution of the stapling cylinder.

[0038] The wire advancement to the two wire directing assemblies can be effected by one and the same motor at a constant speed, which is an advantage of this type of wire advancement system since no acceleration and retardation of the wire advancement is needed.

[0039] The holding of the staple in the stapling fork at its carriage from the staple pick-up zone to the stapling zone is effected either by a damping mechanism having grooves/notches and integrated in the stapling fork or by a magnet action arranged in the stapling fork. However, the holding of the staple has to be integrated in the stapling fork since this is turned during the rotation of the stapling cylinder.

Brief Description of the Drawings

[0040] The invention will now be described in more detail by means of embodiment examples, reference being made to the accompanying drawings, in which

Figure 1

shows a side view of linear stapling machine according to the present invention,

Figure 2

shows a part in perspective from Figure 1 with a staple drawn,

Figure 3

shows a perspective view of a part of the linear stapling machine according to Figure 1,

Figure 4

shows a perspective view according to Figure 3 with the stapling cylinder dismounted but with stapling heads and stapling forks,

Figure 5

shows a perspective view without cutting assembly and with stapling heads and stapling forks situated in a position half a revolution later in relation to the position according to Figure 4,

Figure 6

shows in planar view stapling heads and stapling forks in the same position as in Figure 5,

Figure 7

shows in planar view the second cam curve according to the invention,

Figure 8

shows a perspective view of a stapling head having a stapling fork mounted according to the invention,

Figure 9

shows a schematic view of the cam follower control at the staple pick-up zone,

Figure 10

shows a length-time diagram of the wire feeding.

Description of the Invention

[0041] To start with, a linear stapling machine will be described that is particularly suitable for a wire advancement device according to the present invention.

[0042] Figure 1 shows a linear stapling machine 10 of rotary type provided with a stapling cylinder 11 in which two stapling modules 12, 12' situated in pairs after each other are mounted at the circumference of the stapling cylinder. The stapling cylinder is rotatably mounted to a base plate 45 for rotation around a first axis 13 around which the stapling cylinder is driven by driving means (not shown). The stapling cylinder 11 is furthermore parallel mounted in relation to a die cylinder 14, which is rotatable around a second axis 13' and against which the stapling cylinder rolls off. By "roll off', it is meant a co-operation between the cylinders 11, 14 where they have the same circumference speed in a stapling zone. Contact between the cylinders is not required. In this connection, the stapling modules 12, 12' roll off against two dies 15, 15' mounted in the die cylinder 14 for final forming of a wire staple 25, Figure 2. Between the stapling cylinder 11 and the die cylinder 14, the printed product parts 16 run consisting of a plurality of paper layers that are to be stapled together into finished products. The product parts 16 that are to be stapled together consist either of a continuous material web that is cut off into finished products after stapling of the continuous product parts or of separate, already cut-off product units that are stapled into finished products in the stapler. In case the product parts consist of a continuous material web, this can pass through the stapler at different degrees of enclosure of either cylinder. In case the product units consist of already cut-off product units, these entirely follow the surface of the die cylinder and are held on the surface of the die cylinder by pliers elements or pins. In this connection, the stapling is intended to be effected when the stapling modules 12, 12' roll off against the dies 15, 15', which in the shown position in the figure occurs at the first stapling module 12. The figure shows further that the stapling modules 12, 12' are provided with a respective stapling fork 21, 21' that carries a ready-formed wire staple 25, see Figure 2, from a staple forming device 22, in the figure shown as a forming wheel, to the position when the wire staple, via a punch S mounted in the stapling cylinder 11, see Figure 2, is forced through the material web 16 and finally formed against the die 15. Accordingly, the stapling is effected against the dies 15, 15' at the surface of the die cylinder. In the way the initial foldings have been made in a contemplated application for quarter-folded products according to Figure 1 it is already cut-off product units, indicated by the arrow 16 on the cylinder surface, which are held by pliers elements on the die cylinder and which become stapled in the position shown in Figure 1. Accordingly, the cutting into product units has already been carried out on a collecting cylinder by means of a web-breaking roller. However, the last folding into finished product is made after the stapling. The figure also shows the directions of rotation of the stapling cylinder 11 and the die cylinder 14 as well as the direction of motion of the product parts 16. Both the stapling cylinder 11 and the die cylinder 14 rotate at a constant number of revolutions that corresponds to a circumference speed that is equal to the speed of the material web 16. Furthermore, a cutting assembly 40 is mounted adjacent to the stapling cylinder 11, which is provided with a first wire introduction assembly 41 and a second wire introduction assembly 42 that is arranged to advance wire 23 to a staple pick-up position. In this connection, the zone for picking-up of staples is defined as a staple pick-up zone 31, which in the present type of stapler extends from the position when the stapling fork is aligned for picking-up of a staple until the stapling fork is altered for an alignment into a stapling position. In addition, there is defined a stapling zone 32 situated essentially at a displacement of half a revolution in relation to the staple pick-up zone. Said zones apply to the distance when no turning of the stapling fork is allowed. The stapling cylinder 11 with the stapling forks 21, 21' and the cutting assembly 40 thereof are mounted to the base plate 45.

[0043] Figure 2 shows a stapling fork 21 that holds a wire staple 25 that has been bent by the forming wheel 22 upon the passage of the stapling fork into a U-shape having two branches 26 and a web 27. In this connection, the wire staple is arranged to be forced through the material web by a punch S in the stapling fork. A corresponding wire staple for the second stapling fork has been analogously designated by a second wire staple 25', a second pair of branches 26', and a second web 27'.

[0044] The forming of each wire staple is made by wire 23, from a coil of wire not shown, being advanced to a cutting position, whereupon cutting, picking-up and forming of the wire staple are effected when the stapling fork 21, 21' passes the cutting assembly 40 with the staple forming device 22 thereof, see Figure 1. Next, the wire staple is carried by the stapling fork 21 approximately half a revolution so as to encounter the die 15, the wire staple via the punch being forced through the product part 16 and formed against the die 15.

[0045] Figure 3 shows in perspective the linear stapling machine 10 with the stapling cylinder 11 rotatable around the first axis 13. The stapling cylinder comprises the stapling modules 12, 12' that are identically constructed and therefore we only describe the first stapling module 12, the indexed numbered reference referring to the parts of the second stapling module 12'. The stapling module 12, 12' comprises a stapling head 50, 50' that is turnably mounted around a stapling main axis 35, 35'. The stapling head is provided with a stapling fork 21, 21' that is rotatably mounted in the stapling head 50, 50' around a stapling fork axis 61, 61' that is perpendicularly orientated in relation to the stapling main axis 35, 35'. The stapling fork is arranged with a cylindrical body 36, 36' rotatably in a corresponding cylindrical space in the stapling head. The cylindrical body is provided with a first guide means 37 by which the stapling fork 21, 21' can be turned around the stapling fork axis 61, 61' in the stapling head 50, 50'. The stapling head is further provided with a second guide means 38, 38' by which the stapling head together with the stapling fork can be turned in the stapling cylinder around the stapling main axis 35, 35'. The stapling cylinder 11 comprises a cam disc 39 provided with a primary third guide means 43 and a secondary third guide means 44, which third guide means are mounted adjacent to a respective stapling fork. Said third guide means 43, 44 are placed at each stapling fork but axially displaced to each other so that the primary third guide means 43 pushes away one of the wire introduction assemblies from the first stapling fork 21 and the other wire introduction assembly from the second stapling fork 21' when the stapling forks pass the cutting assembly 40. In doing so, one of the stapling forks always picks up staple blanks from one of the wire introduction assemblies but never from the other one, while the other stapling fork always picks up staple blanks from the other wire introduction assembly but never from the one of them. By this design of a cutting assembly having two wire introduction assemblies, the wire advancement can be kept constant and also be driven by only one motor.

[0046] Figure 4 shows the corresponding view as in Figure 3 but with the stapling cylinder parts removed. The first guide means 37 of the cylindrical body 36, 36' comprises a first cam follower 46 mounted to a first turning arm 47, which cam follower 46 co-operates in the rotation of the stapling cylinder with a first cam curve 48 for a turning of the stapling fork 21 in the stapling head. In doing so, the first guide means 37 provides a turning of the stapling fork by 90° during its motion to respective from the cutting assembly 40 outside the stapling zone and outside the staple pick-up zone so that the stapling fork before stapling in the stapling zone holds the wire staple with the web 27 thereof essentially parallel to the direction of motion of the product parts 16 and perpendicular in relation to the first axis 13. Accordingly, the first cam curve 48 is formed to change the position of the first cam follower 46 in directions parallel to the first axis 13 upon rotation around the first axis 13. When the stapling fork has delivered up the staple in the stapling zone, the stapling fork is turned back so that the stapling fork can fetch a new staple blank from the cutting assembly 40 in the staple pick-up zone. The staple blank is formed when it passes the forming wheel 22 whereupon a new turning of the stapling fork by 90° is effected when the same has left the staple pick-up zone and a new stapling cycle commences.

[0047] The second guide means 38. 38' comprises a second cam follower 56, 56' mounted to a second turning arm 57, 57' connected to the stapling head 50, 50'. The cam follower runs guided by force in a second cam curve 58 that is formed to change the position of the second cam follower 56, 56' in directions perpendicular to the first axis 13.

[0048] In Figure 5, the first stapling head 50 is shown in a position for picking-up of a staple blank in the form of a cut-off length of wire, while the trailing second stapling head 50' has not yet reached this position. Figure 5 shows more clearly the first cam curve 48 that in the shown position, via the first cam follower, has turned the stapling fork by 90° in relation to the position of the stapling fork 21 that is shown in Figure 4. Also the second cam curve 58 that guides the turning of the stapling head 50 is clearly shown in the figure. Both the first cam curve 48 and the second cam curve 58 are fixedly mounted to the base plate 45. As furthermore is seen in the figure, the second cam curve 58 is formed to guide the second cam follower 56 by force in both directions, while the first cam curve 48 guides the first cam follower by force in both directions during a part of a revolution, while during the rest of the revolution, the first cam follower is spring actuated for the return into a rest position that is shown for the first cam follower 46 in Figure 4.

[0049] Figure 6 shows in planar view the position according to Figure 5, the first stapling fork 21 having been turned to one end position thereof by the first cam curve 48 having actuated the first turning arm 47 with the cam follower thereof for the turning of the stapling fork 21. The figure also shows that the second stapling fork 21' has been turned approximately halfway toward the position of the first stapling fork. The cam followers 56, 56' of the two stapling heads 50, 50' follow all the time the second cam curve.

[0050] Figure 7 shows the second cam curve 58 that during approximately half a revolution, where the stapling forks are in an initial stapling stage 71, a stapling stage 72, and a final stapling stage 73, is formed so that the stapling head with the stapling fork is aligned during the initial stapling stage 71 so that the web of the wire staple during the stapling stage 72 is held parallel to the die in the die cylinder and accordingly is turned in the stitching zone in order to allow the punch to force the wire staple at a right angle through the material web and in that connection simultaneously form the branches of the staple against the die. Accordingly, the stapling fork will be radially directed toward the die cylinder and the die during the stapling stage. By virtue of this motion, the die can be fixedly formed in the die cylinder, which means a very simple and functional design of the die. During the rest of the revolution, the second cam curve 58 is circularly formed during a staple pick-up and staple forming stage 74.

[0051] Figure 8 shows the stapling head 50 provided with the second turning arm 57 with the second cam follower 56 mounted. During the motions of the second cam follower, the stapling head will be turned around the stapling main axis 35. In the stapling head, the stapling fork 21 is with the cylindrical body 36 thereof turnably arranged around the stapling fork axis 61 by the first turning arm 47 being fixedly arranged on the cylindrical body 36 and movable when the first cam follower 46 is guided by the first cam curve.

[0052] Figure 9 shows a wire advancement device 90 including the two stapling forks 21', 21 that are placed after each other in the stapling cylinder 11, the stapling forks being in the staple pick-up zone 31 simultaneously and accordingly being aligned to pick up a length of wire and form the same into a staple. Adjacent to the first stapling fork 21, labelled "1", the primary third guide means 43 is mounted to the stapling cylinder 11, and adjacent to the second stapling fork 21', labelled "2", the secondary third guide means 44 is mounted, also this one to the stapling cylinder 11. Said third guide means 43, 44 are slightly displaced axially along the first axis 13 to each other, which also is seen in Figure 3, so that the primary third guide means 43, by a secondary cam curve 431, lifts the second wire introduction assembly 42 via actuation of the secondary cam follower 421 thereof, so that the first stapling fork 21 can pass freely past the same and only cut and pick up staple wire from the first wire introduction assembly 41. Furthermore, by a primary cam curve 441, the secondary third guide means 44 lifts the first wire introduction assembly 41 via actuation of the primary cam follower 411 thereof and accordingly only allows the second stapling fork 21' to cut and pick up staple wire from the second wire introduction assembly 42. In the figure, also the difference between a wire pick-up position 97, indicated by the circular arc, and a wire passage position 98, indicated by the corresponding circular arc, is seen. After the stapling forks have passed the two wire introduction assemblies 41, 42, the stapling forks pass the forming roller 99 of the forming wheel 22 that is driven by being fixedly mounted to the forming wheel, which in turn abuts against and thereby is driven by the stapling cylinder 11 when the same rotates in the direction of the arrow around the first axis 13.

[0053] The wire advancement to the two wire introduction assemblies 41, 42 is shown schematically in the figure by a motor 95 running out wire T from two wire magazines 91, 92 via two advancement systems 93, 94. As is seen in the figure, are interconnected to be able to be driven by only one motor, but separate systems driven from two synchronized motors are also feasible within the scope of the invention.

[0054] Figure 10 shows a diagram of the length "d" in millimetre of the wire feeding-out versus the time "t" in seconds, the wire length of a staple according to the diagram being 28 mm. Naturally, other wire lengths are feasible within the scope of the invention. Just after the first stapling fork has cut a fully fed-out wire length at time zero, the wire of the second stapling fork is almost entirely fed out. Next, the second stapling fork cuts the entirely fed-out wire length thereof. After each cut, the wire feeding-out proceeds continuously from 0 mm up to 28 mm where the wire is cut, whereupon additional wire for a new staple is advanced. Numerals "1" and "2" in the diagram designate the first and the second wire introduction assembly. Accordingly, a cut is effected at each revolution by both stapling forks, and in a particular rate of production, each revolution takes 0,08 s. Other production rates and wire advancement speeds are feasible within the scope of the invention. Accordingly, the continuous speed of wire feeding to each wire introduction assembly is 35 cm/s. The cut of the first revolution at the first wire introduction assembly is effected after 0,08 s, and the cut of the second revolution at the first wire introduction assembly is effected after 0,16 s according to the diagram.

Claims

1. Wire advancement device (90) in a rotary stapling machine, preferably a linear stapling machine, which wire advancement device comprises a wire source (91, 92), an advancement system (93, 94) and a driving motor (95) arranged so that wire (T) from the wire source is continuously advanced via the advancement system to a first wire introduction assembly (41) mounted in a staple pick-up zone (31) in a rotary stapling machine, and that the wire introduction assembly is provided with a cutting edge that co-operates with a corresponding cutting edge of a stapling fork (21) in turn mounted in a stapling cylinder (11) rotating around a first axis (13), the cutting edges being arranged to cut off a length of wire advanced to the wire introduction assembly (41) and forming a staple blank at each revolution the stapling fork (21) passes the wire introduction assembly (41), characterized in that the wire advancement device is provided with a second wire introduction assembly (42) co-operating with a second stapling fork (21') placed in the same axial position on the stapling cylinder as the first stapling fork (21) in order to cut off a second continuously advanced length of wire forming a staple blank, as well as that guide means (43, 44) are arranged to allow that the first wire introduction assembly (41) only delivers staple blanks to one of the stapling forks (21) and to allow the second wire introduction assembly (42) to only deliver staple blanks to the other one of the stapling forks (21 ') by the guide means (43, 44) providing a displacement of the respective wire introduction assembly (41, 42) in the direction away from the stapling cylinder to allow free passage of a stapling fork (21, 21').

2. Wire advancement device according to claim 1, characterized in that the two stapling forks (21, 21') are placed after each other in the stapling cylinder (11), and accordingly are in the staple pick-up zone (31) simultaneously.

3. Wire advancement device according to any one of claims 1-2, characterized in that the guide means (43, 44) comprises cam followers (411, 421) mounted one to each wire introduction assembly (41, 42) and cam curves (431, 441) mounted to the stapling cylinder (11) and that are formed to change the positions of the cam followers in directions perpendicular to the first axis (13).

4. Wire advancement device according to claim 3, characterized in that a primary cam follower (411) of the first wire introduction assembly (41) is arranged to be displaced by a primary cam curve (441) situated at the second stapling fork (21'), so that the second stapling fork (21 ') clears the first wire introduction assembly (41), and that a secondary cam follower (421) of the second wire introduction assembly (42) is arranged to be displaced by a secondary cam curve (431) situated at the first stapling fork (21), so that the first stapling fork (21) clears the second wire introduction assembly (42).

5. Wire advancement device according to any one of claims 3-4, characterized in that the cam curves (431, 441) of the guide means (43, 44) are rotatable together with the stapling forks (21, 21') around the first axis (13).

6. Wire advancement device according to any one of claims 1-5, characterized in that a staple forming device, preferably in the form of a forming wheel (22) comprising a forming roller (99), is mounted in the staple pick-up zone (31) after the two wire introduction assemblies (41, 42) in respect of the direction of motion of the stapling fork.

7. Wire advancement device according to claim 6, characterized in that the staple forming device (43) is arranged to form staples picked up by both stapling forks (21, 21').

8. Method for wire advancement in a rotary stapler in which one motor (95) continuously advances wire (T) from a wire source (91, 92) to a wire introduction assembly (41, 42), characterized in that one motor continuously advances wire (T) from a second wire source (92) to a second wire introduction assembly (42), a first stapling fork (21) in a stapling cylinder (11) cutting off and picking up a staple blank from only one of the wire introduction assemblies (41) while a second stapling fork (21') in the stapling cylinder (11) cutting off and picking up a staple blank from only the other one of the wire introduction assemblies (42).

9. Method according to claim 8, characterized in that the first stapling fork (21) and the second stapling fork (21 ') are trailing each other, and accordingly are in the staple pick-up zone (31) simultaneously.

10. Method according to any one of claims 8-9, characterized in that the wire advancement to the two wire introduction assemblies (41, 42) is driven by one and the same motor (95).

11. Method according to any one of claims 8-10, characterized in that each stapling fork carries the respective staple blank to a forming wheel (22) that forms the staple blank into a staple.

12. Method according to any one of claims 8-11, characterized in that guide means (43, 44), on one hand, displace the second wire introduction assembly (42) or the first stapling fork (21) away from the wire pick-up position (97) thereof, and on the other hand displace the first wire introduction assembly (41) or the second stapling fork (21') away from the wire pick-up position (97) thereof.

13. Method according to any one of claims 8-12, characterized in that the wire advancements are effected at a constant speed.

Drawing