"Rewinder for the Production of Rolls of Strip Material with a Device for the Temporary Acceleration of one of the Winding Rollers"

Technical Field

The invention relates to a rewinder for the production of rolls of wound strip material, of the type comprising a first winding roller, a second winding roller and a third winding roller, rotating in the same direction, which, during the winding, are in contact with the roll being formed, and in which at least one of the rollers is driven at a rotation speed which is temporarily and cyclically variable during each winding cycle, in other words during the winding of each individual roll.

Background Art

A rewinder of this type is known, for example from EP-A-0524158, which describes a rewinder in which the third winding roller, with a movable shaft to follow the winding of the roll being formed, is temporarily accelerated at the end of the winding to permit the breaking of the strip material and the start of the winding of the next roll.. The acceleration of the third winding roller must be sufficiently rapid and sufficiently great to permit correct tensioning, at the proper time, of the strip material (typically paper for the formation of rolls of toilet paper, kitchen paper and similar) . This is achieved, according to a possible embodiment illustrated in EP-A-0524158, by means of an epicyclic differential gear whose cage or frame is rotated at a speed proportional to the speed of feeding of the strip material, with an output axle which drives the movable winding roller and an input axle which receives the motion from a correcting motor. This correcting motor is rotated temporarily during the phase of acceleration

and subsequent deceleration of the roller. The variation of angular velocity of the winding roller is therefore achieved by taking the sum of two rotary motions imparted to a differential disposed on one side of the machine.

Rewinders of this type have a width of two or three metres, corresponding to the width of the reel of strip material supplied from the paper mill. The winding rollers have an axial length substantially equal to the width of the rewinder.

At the present time, there is a tendency to increase this width, and consequently the front of the machine and the axial length of the winding rollers, to increase production. This may cause difficulties in respect of dynamics on the rollers subject to acceleration and deceleration during the winding, especially when these variations of angular velocity are large and very rapid.

Disclosure of the Invention

The present invention proposes a particular configuration of the actuating means which drive one of the winding rollers at variable speed, by means of which it is possible to obtain high accelerations and decelerations in very short times even in rollers of considerable length, typically more than 3.5 metres.

Essentially, the invention provides that the winding roller driven at variable speed is associated with two actuators synchronized with each other, both of which simultaneously produce the acceleration and deceleration of the roller. This makes it possible to use to actuators of lower power to cause the acceleration of the roller, instead of a single actuator of considerable power, with consequent improvement of operation owing to the fact that two actuators of lower power have much lower inertia that a single actuator of greater power. Consequently, more accurately timed accelerations and decelerations are obtained.

In a particularly advantageous embodiment,

the two actuators are disposed at the two opposite ends of the roller. This provides the further advantage of a symmetrical force on the roller. However, it is possible for the two actuators to be disposed on the same side of the machine and both connected (preferably with a single common belt) to the same end of the roller.

In a preferred embodiment, two epicyclic differential gears with two corresponding synchronized correcting motors are associated with the two ends of the winding roller rotating at variable speed. In this way, the rotary motion in the normal operating phase is taken directly from the principal transmission of the rewinder, in a way similar to that described in EP-A-0524158. This permits optimal synchronization of the phases of acceleration and deceleration of the winding roller with respect to the angular position of the remaining winding rollers.

It is also possible for the winding roller driven at variable speed to be rotated by two independent actuators. In this case, the acceleration and deceleration are obtained by increasing or reducing the angular velocity of the two actuators which, in normal operating conditions, rotate at a speed proportional to the speed of feeding of the strip material.

Brief Description of the Drawings

The drawing shows non-restrictive possible embodiments of the invention, and, in particular,

Fig. 1 is a diagram of a rewinder in which the acceleration and deceleration device according to the present invention may be used;

Figs. 2 and 3 are longitudinal sections through the movable winding roller, provided with acceleration and deceleration devices according to the present invention in two embodiments;

Figs. 4 and 5 show in a highly schematic way the disposition of the actuators on one side only.

Best Mode for Carrying out the Invention

The rewinder illustrated in Fig. 1 is a continuous automatic peripheral rewinder, in which the strip material N, unwound from a supply reel which is not illustrated, is fed at a substantially constant speed so that it can be wound, according to the principle of peripheral winding, on a tubular core A made of cardboard or the like. Continuous automatic peripheral rewinders are known in themselves and in this document only the principal elements will be described, this description being necessary for a proper understanding of the invention. The rewinder comprises a first winding roller 1 and a second winding roller 3, which are disposed to provide a nip 5 between them through which the strip material N is fed and into which the tubular cores A are inserted successively for the winding of the individual rolls R. The rolls R are completed in a winding space 9 defined between the winding rollers 1 and 3 and a third winding roller 7.

The individual tubular cores A are introduced into the nip by an inserter 11 oscillating about an axis B, operated in a way known in itself. The cores A are fed to the rewinder by means of a conveyor 13 which advances as shown by the arrow Z. The tubular cores A fed by the conveyor 13 may be provided with glue distributed in annular stripes or in a longitudinal stripe by methods which are known in themselves.

The strip material N may be provided with perforation lines made by a perforator 17 disposed before the winding area 9.

The movable winding roller 7 must be accelerated at the end of a winding cycle, in other words when the roll R has been completed, to bring about the tensioning of the strip material before or during the introduction of a new core A, in order to break the strip material and discharge the roll R on to a chute 19, from

which the said roll is then fed to the subsequent processing stages.

Fig. 2 shows the device which enables the roller 7 to be accelerated and decelerated at the proper time, even when the roller has a particularly large longitudinal dimension, typically of the order of 3-5 metres and above.

The roller 7 is supported by a pair of arms 21 pivoted about an axis C to enable an actuator 23 to oscillate the roller 7 by means of an arm 25 and a cylinder and piston system 27 acting as a pneumatic spring.

It is also possible to provide two actuators 23 and two arms 25 at the two ends of the roller.

With reference to Fig. 2, an epicyclic differential gear is mounted on each side 29 of the machine, as indicated by 31A and 3IB. The two cages of the differentials 31A and 3IB are associated with corresponding pulleys 33A and 33B, which may be toothed. Belts 35A and 35B (which may be toothed) take the motion from any one of the rollers of the rewinder, rotating at a speed which is constantly proportional to the speed of feeding of the strip material N, for example the roller of the perforator 17 or preferably the winding roller 1.

First axles 37A and 37B of the differentials 31A and 3IB respectively are connected (through joints 39A, 39B) no auxiliary motors 41A and 41B respectively. The motors 41A, 4IB may advantageously be brushless or vectorial low inertia types, provided with suitable position encoders and connected to the central control unit of the machine.

Pulleys 43A and 43B are keyed to the output axles 42A and 42B of the differentials 31A and 3IB respectively. Belts 45A and 45B, which provide the motion to pulleys 47A, 47B keyed to the shaft of the roller 7, are run around the pulleys 43A and 43B respectively.

The operation of the device illustrated herein is as follows. During the winding of the roll R, the winding roller 7 rotates with a peripheral velocity substantially equal to the peripheral velocity of the winding rollers 1 and 3. This rotary motion is provided by the belts 35A, 35B through the epicyclic differential gears 31A, 3IB. In this phase, the correcting motors 41A and 4IB are halted or, preferably, rotate at a very low predetermined speed, so that there is a very precise and specific transmission ratio between the cylinder from which the belts 35A and 35B take their motion and the movable winding roller 7. When the latter has to be accelerated, the correcting motors 41A and 4IB are operated or accelerated in synchronization to impart to the corresponding differentials 31A, 3IB a motion which is added to the motion provided by the belts 35A and 35B, with consequent simultaneous acceleration of the pulleys 47A and 47B and, therefore, ultimately of the winding roller 7. A subsequent synchronized deceleration (to a halt if necessary) of the motors 1A and 4IB returns the winding roller with movable axis 7 to the normal operating conditions.

In certain special cases, it may be sufficient to operate the winding roller with the movable shaft 7 by means of two independent variable-speed motors, which directly rotate the winding roller 7 and cause it to accelerate or decelerate directly by altering the number of revolutions. This solution is illustrated in Fig. 3. The number 29 again indicates the sides of the machine and 21 indicates the supporting arms of the winding roller 7 with the movable shaft, oscillating about the axis C. In this case, two independent motors 51A and 51B, with output shafts 55A and 55B, on which are keyed toothed pulleys 53A and 53B respectively, are mounted on the sides 29. The pulleys 53A and 53B transmit the motion through toothed belts 57A and 57B respectively, running around toothed pulleys 59A and 59B keyed to the shaft of the movable

winding roller 7. In this case, as mentioned previously, the motors 51A and 51B rotate at a speed proportional to the speed of feeding of the strip material N for the whole winding cycle, and are simultaneously accelerated at the time of the replacement of the finished roll R with a new tubular core A on which the next winding is to be commenced.

In the preceding text, reference has always been made to the application of the device to the winding roller 7 with the movable shaft, since this is subject to high accelerations in particular types of peripheral rewinder. However, it is possible for the said double actuator device controlling the acceleration and deceleration of the roller to be associated with another of the winding rollers 1, 3 and 7, or with two winding rollers simultaneously, for example with the winding roller 3 and with the winding roller 7 with the movable shaft. This depends on the design of the machine and the methods by which it carries out the breaking of the strip material, the discharge of the roll, and the insertion of a new tubular core A.

In the examples of embodiments described hitherto, reference was made to solutions in which the two actuators are disposed on the two sides of the rewinder. This enables the best results to be obtained, since the dynamic forces on the roller are balanced.

However, the advantages in terms of the correct timing of the acceleration, and consequently the functional improvement of the rewinder, are also obtained by disposing the two actuators on the same side.

Fig. 4 shows in a highly schematic way one side of the rewinder, showing, for the sake of simplicity, only the elements of the transmission to the roller 7, in an embodiment corresponding to that in Fig. 3. Identical numbers indicate equivalent parts. The two actuators 51A, 51B drive two pulleys 53A, 53B which lie in the same vertical plane, and around which a common belt 57 runs.

This belt transmits the motion to the pulley 59 which is keyed to the shaft of the roller 7.

Fig. 5 shows a solution equivalent to that in Fig. 2, with the differential mechanisms on one side only. In this case also, parts having functions equivalent to those in Fig. 2 are indicated by the same reference numbers. A single common belt 35 transmits the motion from the principal drive to the two pulleys 33A, 33B which are integral with the cages of two corresponding epicyclic gears. The first input axle of each of the gears takes its motion from a corresponding correcting motor 41A, 4IB and the corresponding pulleys 43A, 43B are keyed to the second axle. A common belt 45 which provides the motion to the pulley 47 keyed on the axle of the shaft 7 runs around the pulleys 43A, 43B.

It is to be understood that the drawing shows only an example provided solely as a practical demonstration of the invention, and that this invention may be varied in its forms and dispositions without departure from the scope of the guiding concept of the invention. In particular, the same inventive concept may be applied in various types of peripheral rewinders, including rewinders which produce rolls without central- cores, such as that described in EP appl.n.93830312.0, published under n. 0 580 561 (or in the corresponding US ^' Pat. Appl. n. 08/090,519, or in JP Pat. Appl. N. 178.288/93), the contents of which are incorporated in the present description. The presence of reference numbers in the claims has the purpose of facilitating the reading of the claims, but does not limit the scope of protection thereof.