The subject matter of the invention is a system for positioning a tool on a shaft, used in particular for positioning rotary slitting tools on rotary shafts employed, inter alia, in devices for slitting a web of material to slit a continuous web of material into narrower strips of material of a specified width. The subject matter of the invention is also a web slitting device comprising the system for positioning a tool on a shaft. The subject matters of the invention are applicable in the slitting of a continuously translocating web of material, such as paper, plastic or sheet metal.

Slitter knives are typically used in devices for slitting a web of material to slit the web along the direction of its transfer to obtain several narrower fragments or to cut the side margins. The web is slit between a circular blade of a knife and a so- called stone against which the knife is pressed. The knives and stones rotate on two pneumatic expansion shafts which hold their position when the air pressure is activated. There may be several pairs of knives and stones in the system depending on the number of slits needed. The slitting width is set by translocating the blades and stones manually or automatically. In a system with a manual mechanism for translocating blades and stones, there are usually no expansion shafts, while knives and stones are bolted on the shaft by hand tightening the assembling clamps. In the practical implementation of automatic knife/stone positioning systems, in order to translocate knives and stones on the expansion shaft, certain pressure is maintained (lower than the pressure securing the knives and stones rigidly) so that knives/stones do not displace on the expansion shaft after their dynamic movement due to their inertia.

In the current solutions with the automatic slitter knife positioning system, the knife blade is positioned with a gripper with a lateral drive realised by an electric motor coupled to a lead screw or toothed belt which convert the rotational movement of the motor shaft into a linear movement of the gripper. The current position of the gripper is defined indirectly by calculating the angle of rotation of the motor shaft multiplied by the gear ratio. In addition to the lateral drive, the gripper also has a drive to be displaced towards and away from the shaft with the knives/stones to ensure free movement without displacing the knife/stone. Because the knife engages with the stone, the drive shafts of the knives and stones have a drive that enables them to be displaced away from each other and disengage, which enables the knives to freely move in relation to the stones.

From Polish patent PL175379B1 a mechanism is known to adjust the locating of tools on the rotating rollers of a device for processing boards of cardboard or the like. The device consists of at least two pairs of rotary working rollers between which the processed board is fed. At least one roller of each pair is fitted with tool heads, at least part of which is slidable. The device comprises a mechanism for setting the longitudinal dimensions of the performed operations based on a chain with drive wheels of the rollers. The mechanism for determining the longitudinal dimensions for one or several pairs of rollers is composed of two adjusting intermediate wheels permanently located on a common member, which is mounted slidably in the gear. The device comprises a mechanism for setting the lateral dimensions of the sections of the processed plate, comprising lead screws for slidable tool heads, driven by the gears from the drive to form a mechanism a planetary gear.

US patent US4252044A discloses an automatic cutter positioning device in a gang slitter. The gang slitter has a frame assembly comprising an upper frame including rails, a lower frame including rails and side frames. Cutter heads are slidably mounted to the upper and lower rails. The cutter heads can be located in the desired position by rotation of ball screws which are driven by motors fixed to the frame. Each head has one ball screw which is loosely fitted with adequate clearance to the head so that the screw does not engage with the head. Further, a mechanism is provided that transmits rotation of the external power source via a coupling to cutter shafts by spline shafts which pass through each head.

An apparatus for automatically controlling the position of a plurality of slitters for slitting a moving web is known from US patent US4607552A. The slitting apparatus including the apparatus for automatically controlling the position of a plurality of slitters comprises a first rail disposed adjacent to a first face of the web and a second rail disposed adjacent to a second, opposite face of the web. Housing members are movably connected to the rails, the housing members moving transversely relative to the web. A slitter blade is rotatably secured to the first housing member, the member movably disposed on the first rail, while a slitter band is secured to the second housing member, the member movably disposed on the second rail, for cooperating with the slitter blade for slitting the web. Both housing members comprise independent driving means for moving the housing members along the rails transversely relative to the web, the driving means being stepping motors coupled to the gearbox via a clutch. The gearboxes of each of the driving means cooperate with an indexing rack disposed along each of the rails.

The technical problem faced by the present invention is to develop such a system for positioning a tool on a shaft that will be suitable for use in web slitting devices and will provide increased positioning accuracy while maintaining a relatively high speed of positioning tools. Furthermore, it is desirable to provide a system for positioning a tool on a shaft, which will be characterized by lower noise emission and will at the same time guarantee increased reliability of operation and greater efficiency of work. The first subject matter of the invention is a system for positioning a tool on a shaft, the system comprising a shaft with at least one tool being slidably disposed on said shaft, characterized in that it comprises a longitudinal body extending substantially parallel to the shaft, wherein a carriage is slidably attached to the body and at least one gripper extends from said carriage towards the shaft to cooperate with the corresponding tool, wherein the gripper is attached to an actuating device to ensure the gripper translocates towards and away from the shaft, wherein a stator of a linear drive is disposed on the outer surface of the body, and a corresponding coil of the linear drive is disposed on the rear wall of the carriage, the coil arranged in close proximity to the stator of the linear drive.

In a preferred embodiment of the invention, the body is a U-shaped profile.

In a further preferred embodiment of the invention, the stator of the linear drive is disposed on the inner surface of the cavity of the U-shaped body and the corresponding coil of the linear drive is disposed in the cavity of the U-shaped body.

In the next preferred embodiment of the invention, a linear guide is disposed on the face of the shelf of the U-shaped body with the carriage being slidably mounted on said linear guide.

Preferably, the carriage has two grippers attached to two actuating devices disposed in the extreme side positions of the carriage.

Equally preferably, the actuating devices are controlled independently.

Even more preferably, the tool is a circular knife and/or a circular stone.

In a preferred embodiment of the invention, the gripper has a gripping part being an arcuate cutout fitted to the circumference of the corresponding tool. In a preferred embodiment of the invention, the actuating device is a pneumatic actuator. In a further preferred embodiment of the invention, the stator of the linear drive is a series of permanent bar magnets disposed in series, one next to the other, the bar magnets contacting each other with the edges of opposite poles.

In a further preferred embodiment of the invention, the carriage comprises a position measuring head cooperating with a measuring ruler disposed on the body.

Preferably, the shaft is a pneumatic expansion shaft.

The second subject matter of the invention is a device for slitting a web of material, comprising a frame with side plates, characterized in that the system for positioning a tool on a shaft, as defined in the first subject matter of the invention, is disposed between said side plates.

In a preferred embodiment, the device for slitting a web of material has a shaft with at least one circular knife slidably disposed on said shaft and a shaft with at least one circular stone slidably disposed on said shaft, the shafts being disposed parallel to each other at a distance ensuring direct contact of the surface of the circular knife with the surface of the circular stone, and comprises two independently controlled systems for positioning a tool on a shaft, i.e. a system for positioning the circular knife on the shaft and a system for positioning the circular stone on the shaft, respectively.

In a further preferred embodiment of the invention, the shaft has a gear at its end, the gear coupled to the gear at the end of the shaft.

The system for positioning a tool on a shaft according to the present invention, due to the use of a direct drive of the carriage with grippers, realised by means of a linear motor, has enabled it to eliminate a transmission changing the rotational movement of the motor to a linear movement of the carriage (gripper) and any additional gears and clutches. This enabled it to eliminate any clearances, which resulted in increased accuracy of locating the tool on the shaft. In addition, the absolute measurement of the position of the carriage with the gripper is a more accurate measure in relation to calculating the position by converting encoder pulses from classic electric motors used in solutions known in the art.

Furthermore, due to the use of a direct drive of the carriage with the grippers realised by means of a linear motor, it is possible forthe carriage to move at higher speeds and accelerations compared to the currently used drives with similar power by eliminating additional moving elements of the drive, which negatively affect the dynamics of movement. In addition, due to the use of absolute measurement of the position of the carriage and the gripper itself, it is now not required to periodically locate the tools in the end position (so-called zeroing), which was normally required to eliminate the accumulation of the position error resulting from the conversion of the position from the angle of rotation of the motor. Moreover, the use of the gripper with the gripping portion in the form of an arcuate cutout fitted to the circumference of the corresponding tool (knife or stone) enables the cutting tools to be disposed very close next to each other with the rigidity of the gripper being at the same time maintained. In addition, the asymmetry of this arcuate cutout has a beneficial effect on the economy of the gripper manufacturing process by machining one deeper relief from one direction versus two smaller reliefs from different sides.

What is important, the linear drive realised by means of the linear motor and used in the system for positioning a tool on a shaft according to the present invention enables it to eliminate the noise coming from motor bearings and any transmissions used in solutions known in the art. Additionally, the relatively simple construction of the system for positioning a tool on a shaft according to the present invention enables it to reduce the number of mechanical elements, such as bearings, drive screws and toothed belts, said elements wearing out over time and degrading the mechanical properties of solutions known in the art. The solution according to the invention is presented in the following embodiment and is illustrated in the drawing, in which Fig. 1 shows an axonometric view of the device for slitting a web of material comprising the system for positioning a tool on a shaft according to the embodiment of the present invention, Fig. 2 shows a side view of the device for slitting a web of material of Fig. 1, Fig. 3 shows a cross- sectional view of the device for slitting a web of material made along A-A plane marked in Fig. 1, Fig. 4 shows an axonometric view of the system for positioning a tool on a shaft according to the embodiment of the present invention, Fig. 5 shows a side view of the system for positioning a tool on a shaft of Fig. 4, Fig. 6 shows a front view of the system for positioning a tool on a shaft of Fig. 4, Fig. 7 shows the first axonometric view of the carriage of the system for positioning a tool on a shaft according to the embodiment of the present invention, Fig. 8 shows the second axonometric view of the carriage of Fig. 7, Fig. 9 shows a side view of the carriage of Fig. 7, while Fig. 10 shows a front view of the carriage of Fig. 7. Example

Fig. 1 - 3 show the device for slitting a web of material in which the system for positioning a tool on a shaft according to the embodiment of the present invention is included. The device for slitting a web of material comprises a frame on which all the components necessary for continuous feeding of the tape of material to be slit are mounted. The device for slitting a web of material illustrated in the present embodiment employs the system wherein the web is slit between the circular blade of the knife 2 and the stone 3 against which the knife 2 is pressed. The general construction of the device for slitting a web of material is known in the art, which is why its standard construction elements will not be described in the present embodiment for the sake of clarity of the disclosure.

The frame of the device for slitting a web of material comprises side plates 1 to which the systems for positioning a tool on a shaft are attached. In the present embodiment, due to the use of tools in the form of a plurality of circular knives 2 disposed on the first expansion shaft 4 and a plurality of circular stones 3 disposed on the second expansion shaft 5 located at a short distance from the first expansion shaft 4 such that during operation the outer surface of the plurality of circular knives 2 contacts the outer surface of the corresponding plurality of circular stones 3, the device for slitting a web of material comprises two systems for positioning a tool, i.e. the system for positioning the knife and the system for positioning the stone, respectively. In the embodiment, seven circular knives 2 are disposed on the expansion shaft 4 and seven circular stones 6 are disposed on the expansion shaft 5. The number and type of tools used on the expansion shafts 4, 5 are not a limitation to the present invention and in alternative embodiments, it is possible to introduce a greater or smaller number of tools, not necessarily in the form of circular knives 2 and corresponding circular stones 3. The operations of both systems for positioning a tool on a shaft are independent of each other. A single first system for positioning a tool on a shaft is shown in more detail in Fig. 4 - 6. The second system for positioning a tool on a shaft has a structure analogous to the one of the first system for positioning a tool on a shaft, which is why, for the sake of clarity of the disclosure, it will not be described in more detail.

For the purpose of ensuring proper operation of the device for slitting a web of material according to the present embodiment of the invention, the device is additionally provided with a drive pressing circular knives 2 against circular stones 3. The expansion shaft 5 with circular stones 3 is axially stationary in relation to the frame of the device, while the expansion shaft 4 with circular knives 2 is able to move axially (for example, in the range of approx. 2 mm). With the circular knives 2 and the circular stones 3 having been located in the desired working positions (with a gap between their working surfaces maintained), the expansion shafts 4, 5 are first brought closer to each other to engage, which is followed by an axial shift on the expansion shaft 4 with the circular knives 2 for the circular knives 2 to be contacted with the circular stones 3 and for exerting pressure between them. This pressure depends on the size of the gap and the smaller the gap is, the greater the pressure. The circular knife 2 has some flexibility in axial direction. For example, the gap equal to the range of axial motion, i.e. 2 mm, results in zero pressure between the circular knife 2 and the circular stone 3. However, the gap of 1.5 mm, after axial movement of 2 mm, results in a deformation of the circular knife 2 of 0.5 mm, which results in a certain pressure force between the circular knife 2 and the stone 3.

The system for positioning a tool on a shaft, as shown in Fig. 4 - 6, comprises a body 6, being a substantially U-shaped profile, which is attached by its side surfaces to side plates 1 of the frame of the web slitting device. On the outer surfaces of the shelves of the U-shaped body 6, two linear guides 7 are attached, which on the side surfaces are equipped with guiding grooves. A stator 8 of the linear drive is disposed on the inner surface of the web of the U-shaped body 6, said stator in the present embodiment being a series of permanent bar magnets disposed in series, one next to the other, the bar magnets contacting each other with the edges of opposite poles. The system for positioning a tool on a shaft also comprises a carriage 9 which is slidingly mounted on linearguides 7, which ensures said carriage can freely translocate along the direction of the length of the body 6 (perpendicular to the direction of movement of the web being fed). The detailed structure of the carriage 9 is shown in Fig. 7- 10. Two grippers 10 extend from the carriage 9 towards the first expansion shaft 4, said grippers being connected to the corresponding pneumatic actuators 11, which are drives for the grippers displacing them towards the circular knives 2. The grippers 10 are disposed in the extreme side positions of the carriage 9 and have a fixed distance between each other in the longitudinal direction of the body 6. Each pneumatic actuator 11 comprises a piston 12 which is connected to the gripper 10 to translocate the gripper towards and away from the corresponding expansion shaft 4, 5. The control of the carriages 9, comprising translocating them along the body 6 and independently displacing each gripper 10 towards and away from the corresponding expansion shaft 4, 5, is realised from the control system (not shown) of the system for positioning a tool. The carriage 9 also comprises a coil 13 of the linear drive disposed from the rear side of the carriage 9, wherein the coil 13 of the linear drive is dimensioned to correspond to the cavity shape of the U- shaped body 6 and when the carriage 9 is installed on the body 6 the coil is inserted into the cavity of the U-shaped body 6 and is located at a short distance from the stator 8 of the linear drive, in this example at a distance of 0.7 mm, as best illustrated in Fig. 5.

The carriage 9 also comprises a position measuring head 14 for absolutely measuring the position of the carriage 9 on the body 6 and thus of the corresponding grippers 10. The position measuring head 14 protrudes from the carriage 9 towards the body 6 and cooperates with a measuring ruler 16 disposed on the outer surface of the shelf of the U-shaped body 6, opposite to the corresponding expansion shaft 4, 5. In the present embodiment, the position measuring head 14 and the measuring ruler 16 form an optical measuring system, but the type of the measuring system used is not a limitation to the present invention and in alternative solutions, it is possible to provide a mechanical, magnetic or piezoelectric measuring system provided that an accurate measurement of the position of the grippers 10 on the expansion shaft 4, 5 is provided. The gripping part 15 of each gripper 10, said part cooperating with the corresponding circular knife 2 or stone 3, is an arcuate cutout fitted to the circumference of the corresponding tool, i.e. the circular knife 2 or stone 3.

The shafts 4, 5, which are used in the web slitting device and the system for positioning a tool and on which tools in the form of circular knives 2 or stones 3 are attached, are expansion, pneumatic shafts, which in the tool positioning state have a diameter that is slightly smaller than the internal diameter of the corresponding tool arranged on the shaft 4, 5 so that a free movement of the tool on the shaft 4, 5 along its longitudinal axis is ensured. After the tool has been properly positioned on the expansion shaft 4, 5, an adequate air pressure is set, which causes expansion of the outer surfaces of the shaft 4, 5 and stable attachment of the tool in a defined position. The expansion shafts 4, 5 are rotary shafts which are rotated via a suitable toothed mechanism with a transmission, the mechanism functionally connected to the driving motor. The expansion shafts 4, 5 at one end have suitable gears 17 which are engaged with each other to provide synchronous rotation in opposite rotational directions.

In the present embodiment of the invention, the linear drive responsible for translocating the carriage 9 comprises a stationary stator 8 of the linear drive and a movable coil 13 of the linear drive, i.e. translocating together with the carriage 9. The coil 13 of the linear drive is arranged on the carriage 9 moving on the linear guides 7 just above the surface of the stator 8 of the linear drive. As a result of the coil 13 of the linear drive being supplied by an appropriate controller, a transverse force is generated which displaces the coil 13 of the linear drive together with the carriage 9 attached to it. A position measuring head 14 is also attached to the carriage 9, said head indicating the current exact position of said carriage without the need to convert the position from the rotations of the motor and transmission, as was the case in solutions known in the art.

The procedure for locating tools (circular knives 2 and circular stones 3) in the web slitting device using the system for positioning a tool on a shaft according to the embodiment of the present invention is as follows. In the first step, the surface of the knives 2 is displaced away from the stones 3 by axial movement of the expansion shaft 4 (on which the circular knives 2 are attached). In the next step, the pneumatic shafts 4, 5 are displaced away from each other to disengage the surface of the knives 2 and stones 3 and from the slit material making it possible for the knives 2 and stones 3 to be displaced. In the further step, the pressure in the expansion shafts 4, 5 is reduced to a level enabling it to easily displace the knives 2 and stones 3. In the next step, the tools are positioned by relocating the knives 2 and stones 3 to the new required work positions. Afterwards, the expansion shafts 4, 5 are displaced towards each other for engagement. In the final step, the surface of the knives 2 is displaced towards the stones 3 and pressure is exerted between them. List of reference signs:

1 - side plate of the frame

2 - circular knife

3 - circular stone

4 - expansion shaft of the knife 5 - expansion shaft of the stone

6 - body 7 - linearguide

8 - stator of the linear drive

9 - carriage 10 -gripper

11 - actuating device (pneumatic actuator)

12 - piston of the actuating device

13 - coil of the linear drive 14- position measuring head 15 -gripping part of the gripper

16 - measuring ruler

17 -gear