GB2294033A - Web unwinding. - Google Patents

Abstract

A roll of web 1 may need clockwise or anti-clockwise rotation to unwind web to nip 3. A motor 6 is thus selectively operable in forward or reverse directions to drive a belt 8 in one or the other direction depending upon whether unwinding is to be from the top or the bottom of the roll. Irrespective of motor direction, nip 3 is driven in one and the same direction, by way of oppositely acting clutches 12, 13 and belts 14, 15, belt 15 passing around an additional idler pulley 17. <IMAGE>

Description

"Web Unwind Control System" This invention is concerned with apparatus for unwinding a continuous web of paper from a reel to form the supply for a printing machine, burster, guillotine or similar piece of processing equipment. Process machines of these types demand the web to be supplied in a tensionless fashion.

The web of paper is fed between a pair of nip rollers which are also driven and then allowed to fall into a loop from which the parent machine can draw material as and when necessary for processing. This loop of material is sensed for position of height and this signal is then used to modulate the drive motor which provides rotational force, since as the parent draws off the material, the loop shortens causing the loop signal to change and requiring the drive motor to increase in speed. The converse is true in that, as the parent machine demands less web than the unwind is providing, the loop fills and the loop signal alters to slow the drive motor causing less material to be available.

Reversing of the unwinding direction might be necessary as the reel of paper may be coated or pre-printed. Normally reversal of the unwind direction requires the utilisation of separate drive motors for unwinding and for driving the nip rollers and significant alteration of the machine settings, which holds up production.

According to the present invention there is provided a web unwind control system incorporating a rotatable drive member for acting against a roll of the web to unwind the web from the roll, a nip roller assembly for drawing off the unwound web and a speed control motor for driving both the nip roller assembly and the drive member at predetermined relative speeds, the drive connections from the motor being such that the drive member can be driven in forward or reverse directions depending upon the desired direction of unwinding of the roll, whilst ensuring that the nip roller assembly is driven in the same direction regardless of the direction of rotation of the drive member.

Ideally the drive member will be a drive belt whose face is intended to engage the outer face of the roll, the belt assembly being pivoted at one end and biassed in a direction to engage the roll. One common motor is used to drive both this surface drive belt and the nip rollers.

However the nip rollers must always rotate in the same direction to fill the loop. This is achieved by the incorporation into the drive path to the nip roll of a system such as freewheeling clutches. More particularly the device is ideally formed with a drive connection from the motor to the drive member comprising a unidirectional drive connection, whilst the drive connection to the nip roller assembly will be reversed when the motor drive direction is reversed.

The nip roll drive can consist of a pair of power transmitting belts. These belts can be driven by pulleys mounted upon freewheels set in opposing directions upon one driving shaft coupled to the driving motor. When the motor shaft is rotating in one direction one clutch idles whilst the other is transmitting power and upon the reversal of the motor the clutch which was idling then drives a second belt which is arranged to rotate the nip rolls in the same original direction even though the driving shaft is now travelling in an opposing direction. This can be achieved by an assembly wherein two separate drive connections are provided from the motor to the nip roller assembly, each connection incorporating a one-way clutch which freewheels in the reverse direction, the two clutches being set to operate in mutually opposite directions.

The nip roll system should be arranged so that the surface speed of the nip rolls is equal to, or in excess of the paper feed speed, so that the web is always tight between the unwinding reel and nip rolls. The web is then allowed to slip within the nip rolls to maintain a constant pull on the paper as it leaves the reel.

The mechanism of reversed freewheels contained within the nip drive path could of course be performed in other fashions. For example, the machine operator could carry out a mechanical task such as engaging an alternative set of driving gears or changing the path of a single driving belt by means of twisting and refitting the belt. The drive path could also incorporate a particle or magnetic clutch to avoid the web slipping in the nip section.

The drive motor mounted upon the main machine framework can be coupled to any other features requiring power with ease.

The unwind stand could be used for the unwinding of not only a paper substrate but any continuous material which has to be supplied to a parent processing machine in a loose tensionless fashion.

The invention may be performed in various ways and a preferred embodiment thereof will now be described, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side view of a basic tensionless unwinding machine showing only the basic features of the web path, whilst unwinding from the top of the reel; Figure 2 is similar view to Figure 1 but showing, unwinding from the under side of the reel; Figure 3 shows a machine of the invention having a surface driving belt resting upon the reel of paper; Figure 4 illustrates a preferred arrangement for two power transmitting belts, freewheels and idling pulleys for driving the nip section of the machine of Figure 3; Figure 5 is a composite side elevation of the machine incorporating all the features of Figures 3 and 4; and Figure 6 is an end view of the machine of Figures 3 to 5 showing relative positions of driving features across the machine width.

The unwind stand as illustrated in Figures 1 and 2 supports a roll of paper 1 about its central axis such that if the roll is rotated the paper web 2 will unwind from above. The unwinding paper passes from the roll across to a nip section 3 from where it is allowed to feed into a loop 4, passing upward and over an exit roller or bar 5. The web 2 can then be pulled by a parent machine to be processed in any suitable fashion as dictated by the required product.

Movement of the loop of paper is sensed by a control system of the unwind machine which alters the rotational speed of the roll of paper 1, feeding more of less paper into the loop 4 to replace that removed by the process machine. As the parent machine demands paper, the loop shortens causing the control system to increase the speed of the unwind roll 1. Conversely, when the parent machine then demands less material than is filling the loop 4 from the reel the loop fills and the control system then reduces the speed of rotation of the reel of paper 1.

In the device of Figure 3 the reel of paper 1 is rotated by power from an electric motor 6 being transmitted via a belt 7 to a flat surface drive belt 8 passing around pulleys 9,10 mounted in a framework which is pivoted at one end 9. The free end of the belt 8 is held against the roll of paper 1 and allowed to follow the reel diameter as it decreases due to the unwinding process. The motor effort hence causes the reel to rotate at a speed in proportion to that of the motor and the associated drive ratios.

The drive from the motor 6 to the nip system 3 is shown in the Figure 4. The motor is directly connected to a shaft 11 upon which are mounted two pulleys 12 and 13 supported in line on the shaft on freewheels (see Figure 6). These freewheels are set in opposing directions as sprag clutches.

On the external surface of each pulley 12,13 a drive belt 14 or 15 respectively runs to carry power to a common upper driven pulley 16, mounted on one shaft of the nip roller system 2. The belts are arranged to pass around different sides of the respective drive pulleys 12,13, the belt 15 (shown by dashed lines) passing around an idling pulley -17 to complete the drive path. The arrangement is such that when the motor drive shaft 11 rotates in one given direction only one freewheel transmits power to its associated belt 14 and hence on to the driven pulley 16 mounted upon the nip roller shaft, while the other pulley 13 is isolated by its freewheel which is then idling. Upon a reversal of the drive motor direction, the previously idling freewheel now carries the power to its pulley 13 which is caused to rotate in the opposite direction. However the belt 15 carried by this pulley has already been set to run in a contra direction around the idler pulley 17, thus correcting the reversal of direction and ensuring the nip system continues to turn in the previously set discharge direction.

Figure 5 is a composite view of the unwind stand incorporating all the features of Figures 3 and 4. Figure 6 represents a rear of the unit to demonstrate the relative positions of the components across the width of the unwind stand.

Claims (7)

1. A web unwind control system incorporating a rotatable drive member for acting against a roll of the web to unwind the web from the roll, a nip roller assembly for drawing off the unwound web and a speed control motor for driving both the nip roller assembly and the drive member at predetermined relative speeds, the drive connections from the motor being such that the drive member can be driven in forward or reverse directions depending upon the desired direction of unwinding of the roll, whilst ensuring that the nip roller assembly is driven in the same direction regardless of the direction of rotation of the drive member.

2. A system according to Claim 1, wherein the drive member is a drive belt whose face is intended to engage the outer face of the roll, the belt assembly being pivoted at one end and biassed in a direction to engage the roll.

3. A system according to Claim 1 or Claim 2, wherein the drive connection from the motor to the drive member comprises a unidirectional drive connection, whilst the drive connection to the nip roller assembly will be reversed when the motor drive direction is reversed.

4. A system according to Claim 3, wherein two separate drive connections are provided from the motor to the nip roller assembly, each connection incorporating a one-way clutch which freewheels in the reverse direction, the two clutches being set to operate in mutually opposite directions.

5. A system according to Claim 3 or Claim 4, wherein the drive connections comprise belt and pulley drives.

6. A web unwind control system substantially as herein described with reference to the accompanying drawings.

7. Any novel combination of feature of a web unwind control system as described herein and/or illustrated in the accompanying drawings.