GB2087362A - Winding web at constant winding density - Google Patents

Abstract

Rider-roll pressure is controlled using a microprocessor so that the total weight of the rider-roll and the reel wound web, and hence the winding density, remains constant throughout a winding operation. The reel bears against a carrier drum during winding. The rate at which web is unwound from an unwind reel is monitored either by length using an optical encoder or by weight using load cells in the web unwinding stand. The microprocessor continually calculates the required rider-roll pressure from the monitored rate and from operator input parameters relating to the width desired total length and the density of the wound reel web, and increments the rider roll pressure accordingly. The rider roll can be driven. A VDU can be used to continually display the final weight of the reel being wound, the instantaneous weight of the reel and the instantaneous weight of the rider roll.

Description

SPECIFICATION Apparatus for winding web material The present invention relates to apparatus for winding web material such as paper and particularly to controlling the pressure exerted on a web during winding to control the winding density.

In a paper winding machine paper is wound from a parent reel onto a winding reel to form a paper reel which may be of smaller width and shorter length. The winding reel is usually provided with rotational drive by frictional contact with at least one carrier drum on which the winding reel rests. The paper is gripped between the carrier drum and the winding reel by a pressure known as nip pressure. It is this nip pressure combined with the tension with which the web is introduced to the reel (draw) which controls the winding density of the wound reel. The weight of the winding reel increases as more paper is wound onto it. Hence the nip pressure (and therefore the reel density) will increase correspondingly throughout the wind unless effective compensation is used.A rider-roll is usually used to rest on the winding reel so as to increase the effective weight of the winding reel during the first part of the winding operation. Ideally the rider-roll should be controlled so that the effective weight of the winding reel and the rider-roll remains constant. This has not hitherto been possible with any reasonable accuracy.

According to the present invention there is provided a method for use in a web winding operation which method comprises winding a web onto a reel via a carrier drum against which the reel bears to regulate the winding density, continually monitoring the quantity of web wound on the reel, generating in response to the monitored quantity a signal representing the weight of web wound on the reel and continually changing the pressure exerted between the reel and the carrier drum in inverse relationship to the wound web weight signal to maintain the winding density substantially constant.

According to a second aspect of the present invention there is provided apparatus for winding web material, comprising a reel onto which web is wound, a carrier drum on which the reel bears, means for regulating the bearing pressure to regulate winding density, means for generating a signal indicative of the rate of winding of the web, and processing means arranged (a) to receive said signal as well as operator input parameters defining characteristics of the web which enable the processing means to calculate the final weight and length of the web which will be wound on to the reel, (b) to continually calculate from said signal an indication of the instantaneous weight of the reel, and (c) to control the regulating means in dependence upon the calculated instantaneous weight to maintain the bearing pressure substantially constant.

According to a preferred embodiment of the second aspect the web is conveniently supplied from a parent reel, the regulating means is a rider-roll, and an optical encoder is used to generate a signal indicative of the length of web being unwound from the parent reel. The processing means may be a microprocessor.

For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made by way of example to the accompanying drawings in which: Figures 1 and 2 show diagrammatically two possible arrangements of a rider-roll in a pa per winding machine; Figures 3 and 4 indicate in outline how the rider-rollers of Figs. 1 and 2 respectively may be controlled; Figure 5 is a block diagram of a control system for the arrangements of Figs. 1 to 4; Figure 6 is a block circuit diagram of part of the circuit of Fig. 5.

Fig. 1 shows a paper reel 1 supported on two carrier drums 2 and 3 and fed with a continuous paper web 4. A rider-roll 5 rests on the paper reel 1 to an extent variable by moving the rider-roll 5 in a vertical plane 6 by sliding the ends of the rider-roll 5, carried in journal blocks 7, within vertical guides 8. The web 4 is unwound from a parent reel 9 and passes over rollers 1 2 and a slitter 1 3. The slitter 1 3 reduces the width of the final reel 1 as required. A rejector arm 14 is shown in Fig. 1 which moves the wound reel off the winding stand when the winding operation is complete.

Fig. 3 shows journal block 7, movable in vertical guides 8 connected to one vertical run of a loop of chain 20 carried by sprockets 21 and 22 placed one directly above the other.

The other vertical run of chain 20 is connected to a ram 23 of a pneumatic cylinder 24. Air under pressure may be applied to port 26 or port 27 of cylinder 24 to raise or lower rider-roll 5 respectively.

In Fig. 2 like parts are indicated by like reference numerals. In Fig. 2 the parent reel 9 is not shown and the reel 1 is shown at the commencement of a winding operation, i.e.

just the core of reel 1 is shown. Fig. 1 shows the reel 1 towards the completion of a winding operation: the initial position of the reel 1 is indicated by the broken line. Fig. 2 illustrates a different method to Fig. 1 of adjusting the pressure of rider-roll 5 on reel 1. This is effected in Fig. 2 by pivoting rider-roll 5 about point 10 so that it is movable along arc 11 which does not depart greatly from the vertical plane 6.

In Fig. 4 the rider-roll 5 is mounted for pivotal movement as is required for the ar rangement of Fig. 2. The rider-roll 5 is carried between two support bars 30 (only one of which is shown in Fig. 4). Rider-roll 5 is journalled at one end of each bar 30 and part way along the length of the bar a lug 31 carries a pivotal connection to the ram 33 of a pneumatic cylinder 34. The other ends of both bars 30 are secured to a common pivot shaft 35 so that the bars 30 are maintained in alignment. Air under pressure may be applied to either port 36 or port 37 of cylinder 34 to raise or lower the rider-roll 5 respectively.

Rider-roll 5 may be driven in both embodi ments.

In operation of the arrangement of Fig. 1 (or Fig. 2) the carrier drums 2 and 3 are rotatably driven, in this example in a clockwise direction. The paper web 4 feeds around a part of the circumference of carrier drum 2 then around the circumference of paper reel 1 which itself is driven in an anticlockwise direction by the frictional drive provided by carrier drums 2 and 3 where they rest against the paper reel 1. The paper web 4 is nipped at these rest points. The carrier drum 3 is generally driven at a slightly greater speed than is drum 2 so as to impart a tension to the web 4 as it is wound on the reel 1. This tensioning, known as draw, is only effective if the weight, supported by the two carrier drums 2 and 3 at the nip points with reel 1, produces sufficient frictional traction between each of the drums and the web.

The paper reel 1 obviously does not have a constant weight throughout the winding operation: it starts off light and becomes heavier.

It is therefore desirable to provide means for compensating for this weight variation and the rider-roll performs this function. In order to control the pressure exerted by the rider-roll 5 on paper reel 1 (and hence on carrier drums 2 and 3) in accordance with the present invention the control system illustrated in Figs. 5 and 6 may be used.

Fig. 5 shows a microprocessor 40, which may be a Nascom-2, with a keyboard input 41 and a video display 42. The Nascom-2 microprocessor is a Z-80 based microprocessor with a 1 6 bit peripheral input/output port.

An optical encoder 43 which is connected to monitor the rate at which the parent paper reel is unwound provides a one bit input to microprocessor 40 on line 44. A 1 2 bit output on lines designated 45 is converted to an analogue signal in digital-to-analogue converter 46 and amplified in amplifier 47 before passing via a transducer valve 48 to the riderroll pressure controller, e.g. to control the flow of air into either port 26 or port 27 of pneumatic cylinder 24 (Fig. 3).

In operation of the system of Fig. 5, an operator will enter details, via keyboard 41, of the density of the paper being wound, the length of the final wound reel, and the width of the final wound reel. Both the length and the width of the final wound reel may be different to the length and the width of the parent reel, the width being altered by a slitting device interposed between the parent and the winding reel. The reel width is preferably measured in millimetres to obtain the required accuracy, though the reel lengths may be measured in decametres as this is of sufficient accuracy (1% for a 1000m reel).

From these details the microprocessor calculates the final wound weight of the winding reel and uses this to calculate an appropriate value for and to set the initial rider-roll pressure so that the nip pressure between the winding reel 1 and the carrier drums 2 and 3 will intially be equal to the final nip pressure when the winding reel reaches its final weight.

The microprocessor multiplies the paper density, the reel length and the reel width to obtain a value of the weight of the final reel.

The microprocessor is programmed with scaling factors to ensure that at each stage of the multiplication overflow does not occur and that the result is in the correct range. The central processor unit has 1 6 bit registers and hence can calculate simply numerical values up to 65536 (216) without register overflow.

The digital-to-analogue converter 46 is a 1 2 bit converter and hence the maximum weight of the final reel (i.e. the maximum weight of the rider-roll) must be expressed by a number below 4096 (212). The error in calculation of the weight is found to be around 0.3%, which is negligible.

The optical encoder employed in the system of Fig. 5 is a series 35 OP made by Moore Reed. This is capable of producing 1,000 pulses per revolution and being geared to give one revolution per metre. For the present application 100 pulses per metre is more suitable because with machines operating at up to 2,000 metres per minute, the period of pulses generated at 1,000 per metre would be too small to give the microprocessor sufficient time to perform other functions. A divider circuit may be employed to obtain 100 pulses per metre. A maximum error of 2.8% is introduced using the encoder producing 100 pulses per metre. This error is tolerable.

The microprocessor calculates the number of encoder pulses per increment of the digital-toanalogue converter.

Consider paper having a density of 500 g/m2 which is to be wound into a reel having a length of 1,000m and a width of 2m.

The mass of the final wound reel is: 500 X 1,000 X 2 = 1,000,0009.

A rider-roll with no support has an effective dead (maximum) mass of one imperial ton, i.e. 1,016,9609. This is chosen to be equivalent to 4096. Hence in this example the mass of the final reel is 98.3% of the maximum rider roll mass. The maximum rider-roll mass therefore is set to be equivalent to 4026 which is equivalent to 1,000,0009. The weight of the rider-roll must be decremented 4026 times in 1,000m, hence it is decremented every 0.247m. For an optical encoder producing 100 pulses per metre the digital-toanalogue converter is decremented every 24 pulses.

Fig. 6 shows the input/output interface for the microprocessor in more detail. The optical encoder 43 (Fig. 5) is linked to input 49 to supply pulses to connection A7 of the microprocessor 40. Transistor T1 produces unipolar pulses from the bipolar output of the encoder.

These are fed to a decade divider IC6 so that 100 pulses per metre are fed via buffer IC7 to terminal A7 rather than 1,000 pulses per metre which is what the optical encoder generates.

Buffer IC7 converts the 15V logic level of the decade divider IC6 to the 5V logic level of the interface of the microprocessor.

ICI and lC2 are 8 bit input/output ports of the Intel 8212 type. Terminals AO to A3 of microprocessor 40 are output to IC1 and terminals B0 to B7 are output to IC2. The output ports IC1 and IC2 are connected to a digital-to-analogue converter IC3 which may be of the type AD 563K. An output signal is applied from terminal A4 of microprocessor 40 to both IC1 and IC2 to latch these output ports so that the digital-to-analogue converter IC3 receives all 1 2 bits simultaneously. This is necessary because the input/output controller of the microprocessor 40 can only output one port at a time.BO to B7 are putputted first, then AO to A3 with A4 being the last output.

The analogue signal from IC3 is applied to an operational amplifier IC4 which may be of the type 741 and which will usually form an integral part of the digital-to-analogue converter. The amplified signal is then applied to operational amplifier IC5 which operates as a voltage follower in conjunction with a VMOS FET device. The voltage across R4 is equal to the voltage across resistor R8 and hence the current through transducer valve 48 is proportional to the voltage across resistor R8. A potentiometer VR2 connected between the amplifiers IC4 and IC5 allows for adjustment of gain.

A visual display unit may be used to continually display: a) The final weight of the reel being wound.

b) The instantaneous weight of the reel.

c) The instantaneous weight of the rider-roll.

These results are most easily interpreted if they are displayed as a bar chart. The microprocessor can be programmed to calculate a suitable axis for the bar chart and to display titles.

The display information is stored in the microprocessor memory as ASCII code. The display programme transfers sections of this information to the relevant memory locations in the video display memory. A video display containing only 1 6 vertical locations may be used. Only 11 of these locations will exist in the space available for the bar chart, but the graphics capability of the Nascom-rnicropro cessor allows each location to be divided into three, giving a vertical resolution of 33. In fact a resolution of 32 is most convenient in the present application since this divides into 4096 (the number which would be used to represent the final weight of the reel being wound).

In an alternative embodiment of the invention the optical encoder could be replaced with load cells on the unwind stand which could weigh continuously the parent reel. The weight of the wound reel at any instant could easily and accurately be known from this as it would be equal to the loss of weight from the parent reel. Of course, if the paper is reduced in width as it is being wound this must be taken into account. This could be effected by a simple programme in the microprocessor if the original width and the final width of the paper is known. In this embodiment the initial weight of the rider-roll cannot be calculated because the final weight of the reel being wound is not known. In this case the rider-roll may initially be set at its maximum weight or the operator may set the initial weight according to his experience of the paper being wound.Alternatively the microprocessor could be used to calculate the initial weight of the rider-roll if values of the desity of the paper, the length and the width are fed into it.

In any case the microprocessor will ensure that the combined weight of the reel and the rider-roll remain substantially constant throughout the winding operation so as to maintain a consistent reel density. The actual reel density will depend on which method is adopted. With suitable programming, the actual reel density could be chosen by the operator. The microprocessor would then calculate the combined weight of the rider-roll and reel needed to achieve the required density and set the initial rider-roll weight accordingly.

Results obtained using the system of the present invention indicate that much greater uniformity than was previously possible may be obtained in the density of the reel as the diameter varies. A microprocessor controlled rider-roll produced a density variation across the diameter of the reel to within 7% of its maximum value. A conventional rider-roll controller shows a density variation across the diameter of the reel of 50% of the maximum value.

Claims (5)

1. A method for use in a web winding operation which method comprises winding a web onto a reel via a carrier drum against which the reel bears to regulate the winding density, continually monitoring the quantity of web wound on the reel, generating in re sponse to the monitored quantity a signal representing the weight of web wound on the reel and continually changing the pressure exerted between the reel and the carrier drum in inverse relation-ship to the wound web weight signal to maintain the winding density substantially constant.

2. Apparatus for winding web material, comprising a reel onto which web is wound, a carrier drum on which the reel bears, means for regulating the bearing pressure to regulate winding density, means for generating a signal indicative of the rate of winding of the web, and processing means arranged (a) to receive said signal as well as operator input parameters defining characteristics of the web which enable the processing means to calculate the final weight and length of the web which will be wound on to the reel, (b) to continually calculate from said signal an indication of the instantaneous weight of the reel, and (c) to control the regulating means in dependence upon the calculated instantaneous weight to maintain the bearing pressure substantially constant.

3. Apparatus as claimed in claim 2 in which said web is supplied from a parent reel and said regulating means is a rider-roll, and further comprising an optical encoder to generate a signal indicative of the length of web being unwound from said parent reel.

4. A method for use in a web winding operation substantially as described herein with reference to the accompanying drawings.

5. Apparatus for winding web material substantially as described herein with reference to the accompanying drawings.