The invention relates to a differential shaft configured to support at least two different reels of material to be wound on or wound off the respective reels, and to enable differential winding or unwinding of the at least two different reels, wherein the differential shaft comprises an interior arrangement and an exterior arrangement, the exterior arrangement comprises a row of rings which are arranged in a side-by-side positioning in longitudinal direction of the differential shaft and which are independently rotatable on the interior arrangement, and the interior arrangement is configured to support the row of rings.

The invention also relates to a device configured to handle and process webs of material, comprising: at least one differential shaft as mentioned here before, a transport system configured to transport webs of the material of the reels to be supported by the differential shaft through the device, a sensor arrangement configured to detect at least one of: at least one parameter of the respective reels and at least one parameter of the respective webs of material, and a processing unit configured to process input from the sensor arrangement and to thereby determine aspects of operation of the at least one differential shaft.

In a very general sense, the invention is applicable to the field of winding material on a reel and winding material off a reel. In a more specific sense, the invention is applicable to the field of supporting and rotating on a single shaft at least two different reels of material to be wound on or wound off the respective reels. In this field, it is known to use differential shafts to thereby realize differential winding or unwinding of the at least two different reels, differential winding or unwinding being a process of clutching adjustment which allows tension to equalize from one reel to a next on the same shaft, wherein each of the reels is allowed to rotate at a speed as appropriate for each of the reels. Even when a master unwind reel is slit and then rewound, thickness variations across the width of the material cause a different rewind torque requirement for each separate reel across the rewind shaft. By using differential winding, it is possible to build at least two reels which differ from each other in width and/or diameter, for example, and still support those reels on a single shaft without introducing problems following from at least one of the reels getting too tight and/or at least one of the reels getting too loose, thereby avoiding tension control difficulties and quality issues in subsequent unwinding operations involving the reels thus obtained, or even avoiding breakage of the material or crushing of a reel core in a case of at least one tightly wound reel or the reel falling apart in a case of at least one loosely wound reel.

In a known design, a differential shaft comprises an interior arrangement and an exterior arrangement, wherein the exterior arrangement comprises a row of rings which are arranged in a side-by-side positioning in longitudinal direction of the differential shaft and which are independently rotatable on the interior arrangement, and wherein the interior arrangement is configured to support the row of rings. During operation of the differential shaft, the rings consistently slip like a clutch around the interior arrangement, which usually comprises a pneumatic shaft which is rotated at overspeed or underspeed during operation and which includes an air bladder which is controlled to be inflated and deflated so as to increase and decrease the amount of slip of the rings on the pneumatic shaft. Generally, as reels build, air pressure is increased to continually deliver the proper winding torque. Because respective reels require different winding torques, the respective reels will slip differently on the pneumatic shaft, as a result of which the proper tension is maintained for each of the reels.

Usually, for the purpose of enabling the pneumatic shaft to engage on a reel, each of the rings comprises at least two coupling elements arranged in the ring, wherein the respective coupling elements are movable between a radially retracted position in which they are at most flush with an exterior surface of the ring and a radially extended position in which they project from the exterior surface of the ring. Such coupling elements are usually ball-shaped or barrel-shaped. The coupling elements can be made to move between the radially retracted position and the radially extend position in any suitable way, such as by using a structure having ramps for each of the coupling elements and a mechanism for forcing the coupling elements up and down the ramps, or by simply using a structure having compressible mounting springs for each of the coupling elements.

In the art of differential winding and unwinding, various ways of web tension control are known. For example, assuming that a differential shaft including a pneumatic shaft is used, it is possible to apply open loop tension control by sensing at least one aspect of a relevant reel, such as the diameter of the reel, by means of an ultrasonic sensor or another suitable sensor, and to set pressure to the differential shaft based on the sensor input and a desired tension in the web of material of the reel. On the other hand, it is possible to apply closed loop tension control by directly sensing the actual web tension, by means of a load cell on a relevant shaft or another suitable sensor, and to set pressure to the differential shaft based on the sensor input and a desired tension in the web of material of the reel. In both cases, sensor input representing the at least one aspect of the reel, such as the diameter of the reel, can be used for controlling the rotational speed of the motor driving the pneumatic shaft.

It is an object of the invention to provide a differential shaft which is of such design and which functions such that processes of winding material on a reel and winding material off a reel are enabled at high accuracy, especially in a context in which at least two reels are arranged on the differential shaft. It is further advantageous if the differential shaft according to the invention is of such design and functions such that slip between the rings of the differential shaft and an interior surface of the respective reels is avoided. In this respect, it is noted that reels usually include a cardboard core, and that slip between the reel core and the rings of the differential shaft causes tiny bits of cardboard to be scraped off the reel core, as a result of which contamination of the differential shaft takes place and functioning of the differential shaft is affected.

In view of the foregoing, the invention provides a differential shaft configured to support at least two different reels of material to be wound on or wound off the respective reels, and to enable differential winding or unwinding of the at least two different reels, wherein the differential shaft comprises an interior arrangement and an exterior arrangement, the exterior arrangement comprises a row of rings which are arranged in a side-by-side positioning in longitudinal direction of the differential shaft and which are independently rotatable on the interior arrangement, the interior arrangement is configured to support the row of rings, the respective ring comprise at least two piston-shaped coupling elements arranged in the rings, wherein the respective coupling elements are movable between a radially retracted position in which they are at most flush with exterior surfaces of the rings and a radially extended position in which they project from the exterior surfaces of the rings, and the respective rings comprise a pneumatic ejecting mechanism configured to cause the respective coupling elements to shoot from the radially retracted position to the radially extended position, wherein the respective rings comprise a hollow ring- shaped peripheral chamber inside of the exterior surface and a hollow ring-shaped air chamber inside of the peripheral chamber, wherein the respective coupling elements extend radially through the peripheral chamber of the respective rings, and wherein the respective coupling elements are configured to disable air communication between the air chamber and the peripheral chamber in the radially retracted position, and to enable air communication between the air chamber and the peripheral chamber in the radially extended position.

It follows from the foregoing definition of the differential shaft according to the invention that the respective rings of the differential shaft comprise at least two piston-shaped coupling elements arranged in the rings, and that the coupling elements are movable between a radially retracted position in which they are at most flush with exterior surfaces of the rings and a radially extended position in which they project from the exterior surfaces of the rings. On the basis of the presence of the coupling elements in the respective rings, the respective rings are enabled to engage on the respective reels. In order to avoid slipping of an interior surface of a reel relative to one or more rings on which the reel is arranged, under all circumstances including speeding up and slowing down, a design of the differential shaft is envisaged in which the respective rings comprise a pneumatic ejecting mechanism configured to cause the respective coupling elements to shoot from the radially retracted position to the radially extended position. By having the ejecting mechanism as mentioned, it can be achieved that the rings can have a firm grip on the reels through the coupling elements, wherein it may even be so that the coupling elements are shot towards the interior surfaces of the reels at such force that the coupling elements penetrate the interior surfaces of the reels to some extent.

The respective rings comprise a hollow ring-shaped peripheral chamber inside of the exterior surface and a hollow ring-shaped air chamber inside of the peripheral chamber, the respective coupling elements extend radially through the peripheral chamber of the respective rings, and the respective coupling elements are configured to disable air communication between the air chamber and the peripheral chamber in the radially retracted position, and to enable air communication between the air chamber and the peripheral chamber in the radially extended position. In this configuration, causing the coupling elements to shoot from the radially retracted position to the radially extended position is done for all coupling elements of a ring in one go by increasing air pressure in the air chamber.

Advantageously, the interior arrangement of the differential shaft comprises a slip setting mechanism configured to set an extent to which the respective rings are allowed to slip relative to the interior arrangement, and the slip setting mechanism comprises slip setting units which are assigned to respective individual rings and/or subgroups of the total amount of rings and which are independently controllable to set the extent to which the respective rings are allowed to slip relative to the interior arrangement per individual ring and/or subgroup of the total amount of rings. Having the slip setting mechanism enables setting the extent to which the respective rings of the differential shaft are allowed to slip relative to the interior arrangement per individual ring and/or subgroup of the total amount of rings. This means that the braking force necessary for proper unwinding or rewinding of reels arranged on the differential shaft can be put to an optimal value for each of the reels, without a need for complex measures, as will be further explained in the following.

It is practical if the respective rings comprise a medium situated at interior surfaces of the rings, and the respective slip setting units are configured to act on the medium to thereby vary an extent to which the medium is allowed to couple the interior surfaces of the respective rings to exterior surfaces of the respective slip setting units. In particular, the invention covers a possibility that the medium as mentioned is magnetic powder and that the respective slip setting units comprise an electric coil. Thus, optimal control of web tension can be achieved through individual and optimal slip control involving magnetic powder clutching techniques. One feasible way of realizing a functional configuration of the differential shaft designed to apply magnetic powder clutching techniques comprises providing a core shaft and arranging the respective electric coils of the slip setting units in row-like fashion on the core shaft in longitudinal direction of the core shaft.

The invention further relates to a device configured to handle and process webs of material, comprising: at least one differential shaft of which the interior arrangement comprises the slip setting mechanism as mentioned here before, a transport system configured to transport webs of the material of the reels to be supported by the differential shaft through the device, a sensor arrangement configured to detect at least one of: at least one parameter of the respective reels and at least one parameter of the respective webs of material, and a processing unit configured to process input from the sensor arrangement and to thereby determine control settings of the slip setting mechanism of the at least one differential shaft. A practical example of the at least one parameter of the respective reels is an actual diameter of the respective reels, and a practical example of the at least one parameter of the respective webs of material is actual web tension of the respective webs in the transport system. In a practical embodiment, the device further comprises a drive mechanism configured to drive the interior arrangement of the at least one differential shaft, in which case it is advantageous if the processing unit is also configured to determine control settings of the drive mechanism on the basis of the input from the sensor arrangement.

The invention covers various types of the device as mentioned here before. According to one feasible option, the device may be of the type which is configured to handle and process webs of foil for use in a printing process during which transfer portions of a layer of the foil are transferred to a substrate to be printed, and may be intended for arrangement at a printing press having a printing area adapted to let such a printing process take place during operation of the printing press. One practical example of the printing process is a cold transfer printing process. The printing process may involve the use of at least one of various materials including metal materials, polypropylene (PP), polyethylene terephthalate (PET), and woven materials such as carbon materials or cotton materials. According to another feasible option, the device may be of the type which is configured to handle and process webs chosen from a group comprising paper, metal foil and fabric.

The present invention will be further explained on the basis of the following description, wherein reference will be made to the drawing, in which equal reference signs indicate equal or similar components, and in which: figure 1 diagrammatically shows a differential shaft according to an embodiment of the invention; figures 2-4 illustrate the constructional set-up of the differential shaft; figure 5 diagrammatically shows a perspective view of a ring of the differential shaft; figure 6 diagrammatically shows a sectional view of the ring; figures 7 and 8 diagrammatically show another sectional view of the ring, for two different positions of coupling elements of the ring; and figure 9 diagrammatically shows a foil handling device according to an embodiment of the invention and a portion of a printing press.

Figure 1 diagrammatically shows a differential shaft 1 according to an embodiment of the invention, and figures 2-4 illustrate the constructional set-up of the differential shaft 1 . The differential shaft 1 is intended to be used in a process of differential winding or unwinding of at least two different reels. In this respect, reference is made to figure 9, in which the differential shaft 1 is shown once again, and in which it is shown how the differential shaft 1 can be used for supporting and rewinding four reels 2.

Basically, the differential shaft 1 comprises an interior arrangement 10 and an exterior arrangement 20, wherein the exterior arrangement 20 comprises a row of rings 21 which are arranged in a side-by-side positioning in longitudinal direction of the differential shaft 1 and which are independently rotatable on the interior arrangement 10. Each of the rings 21 is equipped with a number of coupling elements 22 by means of which the rings 21 are capable of firmly engaging on the reels 2, as will be explained later in more detail. In the present embodiment, the number of coupling elements 22 per ring 21 is three, which does not alter the fact that the number may as well be less or more than three. The coupling elements 22 are preferably equally distributed along the periphery of the rings 21 . In the view on the differential shaft 1 in figure 1 , one coupling element 22 can be seen on each ring 21.

The row of rings 21 is supported on the interior arrangement 10 of the differential shaft 1 , as can be seen best in figure 4. In the present embodiment, the interior arrangement 10 comprises a carbon shaft 11 as can be seen in figure 2, head pieces 12 arranged on the ends of the carbon shaft 11 , and electric coils 13 arranged on the carbon shaft 11 as can be seen in figures 3 and 4. The number of electric coils 13 is the same as the number of rings 21 , and the longitudinal positioning of the electric coils 13 corresponds to the longitudinal positioning of the rings 21 , such that each of the electric coils 13 is exactly associated with one of the rings 21 . The design of the head pieces 12 shown in the figures represents just one of many feasible possibilities covered by the invention. Generally speaking, the head pieces 12 are functional to support the differential shaft 1 in a frame of a device in which the differential shaft 1 is applied, and also to enable coupling of the interior arrangement 10 to a mechanism of the device for driving the interior arrangement 10. Further, in the present embodiment, the head pieces 12 are functional to enable coupling of the electric coils 13 to a source of electric power, such as by allowing electric wiring to pass through. Similarly, the head pieces 12 may also be used for allowing wiring which is suitable to convey signals to pass through. It is to be noted that it is not necessary that the interior arrangement 10 comprises a carbon shaft 11 . Another type of shaft comprising at least one other type of material than carbon is possible as well.

The reels 2 are normally arranged on the differential shaft 1 with some space between them in longitudinal direction. Hence, it is possible that one or more rings 21 are left open between two successive reels 2. During operation of the differential shaft 1 , the interior arrangement 10 is rotated, and the rings 21 are rotated along with the interior arrangement 10, in a slipping fashion. Due to the segmented set-up of the exterior arrangement 20 with the rings 21 , differential winding of the respective reels 2 can take place as intended. In the present embodiment, the interior arrangement 10 of the differential shaft 1 comprises a slip setting mechanism 30 configured to set an extent to which the respective rings 21 are allowed to slip relative to the interior arrangement 10. Generally speaking, the slip setting mechanism 30 comprises slip setting units which are assigned to respective individual rings 21 and/or subgroups of the total amount of rings 21 and which are independently controllable to set the extent to which the respective rings 21 are allowed to slip relative to the interior arrangement 10 per individual ring 21 and/or subgroup of the total amount of rings 21 . In the present embodiment, the slip setting units as mentioned comprise the electric coils 13. Further, as can be seen in figures 7 and 8, in the present embodiment, each of the rings 21 is provided with magnetic powder 24 situated at an interior surface 23 of the ring 21. This means that when an electric coil 13 associated with a ring 21 is provided with electric power and an electromagnetic field is formed, a force acting to couple the interior surface 23 of the ring 21 to an exterior surface 14 of the electric coil 13 is generated. The extent to which the magnetic powder 24 is allowed to couple the interior surface 23 of the ring 21 to the exterior surface 14 of the electric coil 13 increases when the supply of electric power to the electric coil 13 is increased, and decreases when the supply of electric power to the electric coil 13 is decreased. Thus, the extent to which the ring 21 slips on the rotating interior arrangement 10 during operation of the differential shaft 1 is controlled by setting the supply of electric power to the electric coil 13.

It follows from the foregoing that the differential shaft 1 is equipped with a segmented magnetic powder clutch as it where, by means of which the rotational speed of each of the rings 21 can be controlled such that an optimal braking force can be applied on each of the reels 2 supported on the differential shaft 1 . This means that the web tension of a web 4 of material of each of the reels 2 can be controlled separately from the web tension of a web 4 of material of the at least one other reel 2, i.e. of the three other reels 2 in the example illustrated in figure 9. All it takes is detecting one or more relevant parameters per reel 2 and calculating an appropriate value of electric power to be supplied to the electric coil 13 or electric coils 13 associated with the ring 21 or rings 21 on which the reel 2 is positioned, i.e. a value of electric power which is appropriate for maintaining a desired web tension. To this end, a suitable detector arrangement and a processing unit configured to process input from the sensor arrangement and to thereby determine control settings of the slip setting mechanism 30 can be used in a device comprising the differential shaft 1 . The processing unit can also be used to determine control settings of the drive mechanism of the device, to thereby set an appropriate value of the rotational speed of the interior arrangement 10.

Figure 9 shows an example of a device as mentioned here before, namely a foil handling device 3 which is used at a printing press 5 of which a portion is shown in the figure as well. In figure 9, the drive mechanism of the foil handling device 3 is indicated by means of reference numeral 40, and the detector arrangement and the processing unit are depicted as respective boxes 50 and 60 in dashed lining. The detector arrangement 60 may comprise any suitable type of sensor, such as a load cell for detecting load on the differential shaft 1 and/or a sensor for detecting the actual diameter of a reel 2 arranged on the differential shaft 1. The foil handling device 3 shown in figure 9 may particularly be used to handle foil which is suitable to be used in a cold transfer printing process. In the present example, the foil is supplied to the printing press 5 in four parallel webs 4 taken from four supply reels 6. Each of the webs 4 extends from the supply reels 6 to the reels 2 which are arranged on the differential shaft 1 and which function as rewind reels. The foil handling device 3 comprises a transport system 70 for transporting the webs 4 through the device 3. As mentioned earlier, each of the rings 21 of the differential shaft 1 is equipped with a number of coupling elements 22 by means of which the rings 21 are capable of firmly engaging on the reels 2. In the present example, as can be seen in figures 5, 7 and 8, the coupling elements 22 are piston-shaped. The fact is that the coupling elements 22 are movable between a radially retracted position in which they are at most flush with exterior surfaces 25 of the rings 21 and a radially extended position in which they project from the exterior surfaces 25 of the rings 21 . When the coupling elements 22 of a ring 21 are in the radially retracted position, it is possible to slide a reel 2 over the ring 21 . It is practical if the inner diameter of the reels 2 to be arranged is chosen so as to be only slightly larger than the outer diameter of the rings 21 , so that the coupling elements 22 only need to bridge a small distance in the radially extended position.

Advantageously, the coupling elements 22 of each of the rings 21 are arranged so as to be shot from the radially retracted position to the radially extended position when it is intended to establish a coupling between a reel 2 and the differential shaft 1 . To that end, any suitable ejecting mechanism configured to cause the respective coupling elements to shoot from the radially retracted position to the radially extended position can be used. By shooting the coupling elements 22 radially outward, it is achieved that such a tight grip of the coupling elements 22 on an interior surface of a reel 2 is obtained that slipping of the reel 2 on the ring 21 or rings 21 which is/are covered by the reel 2 and the disadvantages associated therewith are avoided under all circumstances.

In the present example, the ejecting mechanism as mentioned here before is of a pneumatic nature. As can be seen in figures 5, 7 and 8, the respective rings 21 comprise a hollow ring-shaped peripheral chamber 26 inside of the exterior surface 25 and a hollow ring-shaped air chamber 27 inside of the peripheral chamber 26, wherein the respective coupling elements 22 extend radially through the peripheral chamber 26 of the respective rings 21 . Further, it follows from a comparison of figures 7 and 8 that the respective coupling elements 22 are configured to disable air communication between the air chamber 27 and the peripheral chamber 26 in the radially retracted position, as illustrated in figure 7, and to enable air communication between the air chamber 27 and the peripheral chamber 26 in the radially extended position, as illustrated in figure 8. In this configuration, shooting the coupling elements 22 of a ring 21 from the radially retracted position to the radially extended position is done by increasing air pressure in the air chamber 27. In figures 5 and 6, it can be seen that the air chamber 27 is provided with air holes 28 through which the air chamber 27 is connectable to a source of pressurized air, for example. In figures 5, 7 and 8, a practical option of using 0 rings 29 for sealing various ring-shaped components of the ring 21 against each other is illustrated.

It will be clear to a person skilled in the art that the scope of the present invention is not limited to the examples discussed in the foregoing, but that several amendments and modifications thereof are possible without deviating from the scope of the invention as defined in the attached claims.

The invention can be summarized as follows. In the field of differential winding and unwinding, a differential shaft 1 is provided for supporting at least two different reels 2 of material to be wound on or wound off the respective reels 2. An exterior arrangement 20 of the differential shaft 1 comprises a row of rings 21 which are independently rotatable on an interior arrangement 10 of the differential shaft 1 . The respective rings 21 comprise at least two piston-shaped coupling elements 22 arranged in the rings 21 so as to be movable between a radially retracted position and a radially extended position, wherein the respective rings 21 comprise a pneumatic ejecting mechanism for the respective coupling elements 22. The respective rings 21 comprise a combination of an outer hollow ring-shaped peripheral chamber 26 and an inner hollow ring-shaped air chamber 27, wherein the respective coupling elements 22 extend radially through the peripheral chamber 26 of the respective rings 21.