GB2072378A - Automatic speed control of a rewinder - Google Patents

Abstract

A web finishing system includes a web rewinder which produces logs from a parent roll (10), an accumulator (64) used to store the logs temporarily a log saw (80) and means for automatically controlling the speed of the rewinder (10) based on the status of equipment in the system, eg the number of empty spaces in the accumulator, parent roll size, efficiency of the log saw, efficiency of the rewinder, the number of times the rewinder is inoperative in a certain time and the rate of production of reject logs. <IMAGE>

Description

SPECIFICATION Automatic speed control of a rewinder This invention relates generally to paper finishing systems which include a rewinding machine for converting large parent rolls of paper into smaller diameter rolls, or logs, an accumulator which provides temporary storage of the logs, and a saw for cutting the logs into rolls having a length suitable for use by the consumer. This invention is specifically directed to an apparatus for automatically controlled the rewinding speed based on the status of the various machines in the finishing system.

In early paper finishing systems it was generally customary to manually set the speed of each machine so that it produced work pieces at a slightly lower rate than could be handled by the next machine in the line. Thus, a paper finishing system that included a rewinding machine for converting large parent rolls of paper into smaller diameter rolls, or logs, a saw for cutting the logs into lengths used by the consumer, and a wrapper for wrapping the rolls, the log saw speed would be set so that it could cut logs at a faster rate than could be produced by the rewinder, and the wrapper speed would be set so that it could wrap rolls at a faster rate than could be produced by the log saw. When a parent roll has been exhausted the rewinder must be shut down so that a new parent roll can be installed.In such a system, while the rewinder is down for a parent roll change, the flow of logs to the log saw is stopped and the log saw and the wrapper become idle.

It was recognized that the production rate of the finishing system could be increased by incorporating a temporary storage device, called a log accumulator, between the rewinder and the log saw. Such a finishing system is shown and described in U.S. Patent 3,016,780 issued to D. W. Mosen on January 16, 1 962. One advantage of having an accumulator is that the rewinder can continue to produce logs even when the log saw is not operating, as the excess logs are stored in the accumulator. Another advantage is that the speed of the rewinder can be set so that it produces logs at a faster rate than can normally be handled by the log saw.If the speed of the rewinder is set properly, when the parent roll is exhausted, there will be a sufficient number of logs stored in the accumulator to allow continued operation of the log saw and wrapper while a new parent roller is placed on the rewinder.

In finishing systems that have an accumulator, there are occasions when the accumulator becomes almost full or full. This could happen, for example, if the saw were shut down for a period of time and the rewinder continued to produce logs. If the rewinder is set to produce logs at a faster rate than can be handled by the log saw, and the accumulator is almost full when the log saw comes back on line, it is possible to jam either the accumulator or the log saw and the rewinder will shut down which'usually results in waste. If the rewinder shuts down several times during a relatively short period of time, there is a tendency for the finishing line operator to lower the rewinder speed thereby lowering the probability that the finishing system will ever reach a point where the rewinder can produce more logs than can be instantaneously handled by the accumulator and the log saw.

Over the long term, this reduction in speed, although slight, can represent a significant reduction of the average flow rate of product through the finishing system.

It is, therefore, desirable to automatically control the speed of the rewinder to maintain a high flow rate of product through the finishing system. It is also desirable to take into account the status of the rewinder, accumulator and saw when automatically controlling the speed of the rewinder.

It is quite common for a finishing line operator to be responsible for operating two web rewinders. One responsibility of the operator is to replace an exhausted parent roll with a new parent roll. If it should happen that both parent rolls are exhausted at the same time, the first rewinder will be shut down for the time required to change the parent roll, but the second rewinder will be down for the time required to change two parent rolls.

Thus, if it appears that both parent rolls will be exhausted at the same time, it would be desirable to automatically control the speed of the rewinders so that the parent rolls will not become exhausted at the same time.

In one aspect of this invention there is provided a web finishing system including a web rewinder for making logs from a parent roll and means for automatically controlling the speed of the rewinder in response to a signal based on one or more parameters of the system.

Examples of the parameters include: (i) the number of empty spaces in the accumulator; (ii) the parent roll size; (iii) the status or efficiency of a log saw; (iv) the status or efficiency of the rewinder; (v) the number of times the rewinder is shut down over a predetermined interval of time; (vi) the rate the rewinder makes reject logs.

In accordance with this invention, a web finishing system that includes a web rewinder and an accumulator includes means for automatically controlling the speed of the rewinder as a function of the status of the accumulator, one measure of which is the number of empty storage spaces in the accumulator. In another aspect of this invention, means are provided for automatically controlling the speed of the rewinder based on the status or efficiency of the rewinder. One example of a measure of the status of efficiency of the rewinder is the number of times the rewinder is shut down over a predetermined interval of time. Another example of a measure of the status or efficiency of the rewinder is the rate that it makes reject logs. Rewinder speed can also be used as a measure of the status of efficiency of the rewinder.

In another aspect of the invention, means are provided for measuring the diameter of the parent roll in the rewinder and the speed of the rewinder is automatically controlled based on the size of the parent roll and the number of empty storage spaces in the accumulator. In one described embodiment of the invention, the finishing system includes a second rewinder. Means are provided for also measuring the diameter of the parent roll in the second rewinder. The size of the parent rolls in both rewinders are monitored and the winding speed of at least one rewinder is automatically controlled to prevent both parent rolls from being exhausted at the same time.

In another aspect of the invention, the finishing system includes a log saw and means for monitoring the status of the log saw. The log saw status is a parameter that is also used to automatically control the speed of the rewinder.

The invention will now be further described by reference to the following description of a preferred embodiment when read in conjunction with the accompanying drawings in which: Figure 1 is a block diagram of the equipment and sensors that are used in an embodiment of the finishing system; Figure 2 is a block diagram of the equipment for controlling the finishing equipment shown in Fig. 1; Figure 3 is a flow diagram showing the logic performed by the control equipment depicted in Fig. 2; Figure 4 is a flow diagram showing the logic performed by the control equipment of Fig. 2 to determine the efficiency of the rewinder shown in Fig. 1; and Figure 5 is a flow diagram showing the logic performed by the control equipment of Fig. 2 for keeping track of the storage capacity of the accumulator shown in Fig. 1.

Referring now to the drawings, Figs. 1 and 2 together comprise a block diagram of a finishing system in which'the speed, of a rewinder 10 is automatically controlled in accordance with this invention. The finishing equipment and sensors are shown in Fig. 1 and the rewinder 10 speed control equipment is shown in Fig. 2. Only those elements of rewinder 10 necessary for an understanding of the invention have been depicted in Fig. 1.

A complete description of one type of rewinder 10 that can be automatically controlled in accordance with this invention is found in U.S. Patent No. 2,769,600, issued November 6, 1 956 to E. M. Kwitek, et al. which is hereby incorporated by reference into this application. The rewinder 10 is a machine that converts a large parent roll 1 2 of a web material, such as toilet tissue or paper towels, into rolls 40, commonly referred to as logs, having a diameter that is suitable for use by a consumer. The parent roll 1 2 is rotatably mounted within a support stand 14. During the rewinding process, the web 16 from parent roll 1 2 is threaded over a bed roll 1 8 mounted on axle 20.Bed roll 18 is rotatably driven from motor 22 through appropriate belts and gears represented schematically by dashed line 24. The speed of rewinding the web 1 6 is determined by the angular velocity of the bed roll 1 8 which can be controlled by applying a suitable voltage to the input 30, designated REWINDER COMMAND SPEED, for motor 22. A REWINDER RUN/STOP signal 32 appears at an output of the rewinder 10. This REWINDER RUN/STOP signal 32 can be provided through a switch or relay closure that is activated by the on-off switch of rewinder 10. A shaft position encoder 26 is mechanically coupled to the axle 20 of bed roll 18.The output signal 34 of encoder 26 is a series of pulses wherein each pulse represents a fixed angle of rotation of the bed roll 1 8. As will be described later, these pulses can be processed to provide an indication of the actual speed of rewinder 10. A sensor, or transducer 36, provides an analog signal 38, designated ROLL Al SIZE, that is representative of the diameter of parent roll 1 2. In one embodiment of the invention, the transducer 36 was a sonar gauge, model 3500D, manufactured by Stevens International, Inc., however, one skilled in the art will readily appreciate that mechanical, optical or other types of sensors or transducers can also provide the required indication of the diameter of parent roll 12.

The finishing system can include a second rewinder 11. Rewinder 11 can have its own automatic speed control equipment (not shown) which is identical to the automatic speed control equipment associated with rewinder 10 shown in Figs. 1 and 2. Whether or not rewinder 11 has its own automatic speed control equipment, in one aspect of the invention, a second sensor, or transducer 37, provides an analog signal 39, designated ROLL A2 SIZE, that is representative of the diameter of the parent roll in rewinder 11 and which can be used to control the speed of rewinder 10.

Logs 40 that have been produced by rewinder 10 are transported by a conveyor 42 toward an accumulator 64. While the logs 40 are en route to the accumulator 64, improperly made logs 62, or rejects, are manually or automatically removed from the finishing system. Thus, when hinged member 44 is in the horizontal position, a properly made log 40 is allowed to proceed toward the accumulator 64, but when hinged member 44 swings downward to the position indicated by dashed line 45, a rejected log 62 falls into a waste bin 60. As a rejected log 62 falls into the waste bin 60, it trips a sensor 54 and circuit means 56 connected to sensor 54 provides an electric signal 58, designated REJECT LOG, indicating the production of a rejected log 62.

Properly made logs 40 continue to the input 46 of accumulator 64. As log 40 enters accumulator 64, it operates sensor 51 and circuit means 50 connected to sensor 51 provides an electrical signal 52, designated LOAD ACC, indicating that a log 40 has been loaded into the accumulator 64.

A detailed construction of log accumulator 64 is not shown as their construction is well known in the art, as represented, for example, by U.S. Patent 4,142,626, issued March 6, 1979, to John J. Bradley. Although the log accumulators depicted in Fig. 1 and described in the Bradley patent are first in, first out accumulators, the rewinder speed control equipment of this invention will work equally well with a last in, first out accumulator.

Although not absolutely necessary, it has been found desirable to provide sensors in the accumulator 64 which provide a first signal 66, designated ACC FULL, indicating that the accumulator 64 is full and a second signal 68, indicating that some predetermined number of logs have been stored in accumulator 64. In the described embodiment, the signal 68, designated ACC HALF FULL, indicates that the accumulator 64 is half full. When a log 72 is discharged from the accumulator 64, it is transported by a conveyor 70 to a log saw 80 which cuts the logs into rolls having a length suitable for use by a consumer. As a log 72 is discharged from the accumulator 64, it operates a sensor 74 which is connected to circuit means 76 which provides a signal 78, designated DISCHARGE ACC, indicating that a log has been discharged from the accumulator 64.The saw 80 is a model 1 25, manufactured by Paper Converting Machine Company. A detailed description of the saw is not provided because it is not necessary for a description of this invention. The saw 80 has been modified to provide a saw status signal 82, designated SAW RUN. In one embodiment of the invention, the saw status signal 82 is an indication that the saw is running which can be provided by a switch or relay closure that is activated by the on-off switch of the saw 80. Examples of other signals representative of the status of saw 80 which can be used to control the speed of rewinder 10 are log saw waste and log saw cutting rate.

The individual rolls 86 produced by the saw 80 are transported by means of a conveyor 84 to either a wrapping machine (not shown) or to a packing machine (not shown).

Fig. 2 is a block diagram of the equipment that accepts the finishing system sensor signals and machine status signals and automatically controls the speed of rewinder 10. The analog signal 39, ROLL A2 SIZE, is converted into a digital number, A2, by an analog-todigital converter 91. The digital number A2 is applied to an input 142 of a programmable controller 140. Programmable controller 140 is a Modicon 384 available from Gould, Inc.

Similarly, the analog signal 38, ROLL Al SIZE, is converted to a digital number, Al, by an analog -to-digital converter 90. The digital number, Al, is applied to an input 144 of programmable controller 140. The LOAD ACC signal 52 is applied as a digital signal, F, to an input 146 of programmable controller 140. The accumulator status signal 66, ACC FULL, is applied as a digital input, G, to an input 148 of programmable controller 140.

The accumulator status signal 68, ACC HALF FULL, is applied as a digital signal, H, to an input 1 50 of programmable controller 140.

The accumulator status signal 78, DIS CHARGE ACC, is applied as a digital signal, 1, to an input 1 52 of programmable controller 140. The saw status signal 82, SAW RUN, is applied as a digital signal, J, to an input 1 53 of programmable controller 140.

The counter and gates circuitry 96 and counter 102 convert the ANGLE CHANGE signal 34 from encoder 26 into a digital number that is proportional to the actual speed of the rewinder 10. As shown in the figure, the counter portion of circuit 96 counts at a 1 megahertz rate. The gate portion of circuit 96 provides a gating signal 98 that has a predetermined time duration. This gating signal 98 is applied to a gate input 106 of counter 102. The ANGLE CHANGE pulses 34 from encoder 26 are applied to a count input 104 of counter 102.When counter 102 counts the number of ANGLE CHANGE pulses that occur over a predetermined period of time, the resultant count will be a digital number directly proportional to the actual speed of rewinder 1 0. If the duration of gate signal 98 is appropriately selected, the digital number in counter 102 will be a convenient multiple of either meters or feet per second.

Since the programmable controller 140 may want to look at the number, Y, representing rewinder 10 speed while the number in counter 102 is changing, it has been found desirable to employ a buffer register 11 8. The digital output 110 of counter 102 is applied to a data input 11 2 of buffer register 11 8.

The gate signal 98 of circuit 96 is applied to a set input 11 6 of buffer register 11 8. At the end of the predetermined count period for counter 102, as designated by the trailing edge of gate signal 98, the digital number determined by counter 102 is transferred into buffer register 11 8. The output 1 20 of buffer register 11 8 is a digital number, Y, represent ing the actual speed of rewinder 10 and is applied to input 154 of programmable controller 140. The counter in circuit 96 and counter 102 are both reset by a timing signal.

which in one embodiment occurs every 2 minutes. This timing signal is provided at an output 162 of the programmable controller 140. The resetting of buffer register 11 8 occurs every 2 minutes and is also accom plished by a timing signal provided at an output 1 64 of programmable controller 140.

The WINDER RUN/STOP signal 32 is ap plied to a count input 1 24 of a counter 1 22 and is also applied as a digital signal, B, to an input 1 56 of programmable controller 140.

The output of counter 1 22 is a digital number, V, that is applied to an input 1 58 of programmable controller 140. Counter 1 22 is reset once every minute by a timing signal provided at an output 166 of programmable controller 140. If rewinder 10 is running well, the number V in counter 1 22 will be either zero or one. If the rewinder 10 is running poorly and has been shut down several times in a short period of time, the number V in counter 1 22 can be a number greater than one. Thus, the number V is an indication of the status or efficiency of rewinder 10.

The REJECT LOG signal 58 is applied to the count input 1 32 of a counter 1 30. The output 1 36 of counter 1 30 is a digital number, W, that is applied to an input 1 60 of programmable controller 140. Counter 1 30 is reset every minute by a timing signal provided at an output 1 68 of programmable controller 140. The number W in counter 1 30 is a measure of the reject rate and is, therefore, an indication of the status or efficiency of rewinder 10.

The programmable controller 140 processes the sensor and status information it receives and generates three signals 170, 172, 174, designated N 1, N2 and N3 respectively, representing a digital command speed for the rewinder 10. If the rewinder 10 is commanded to run at normal speed, the programmable controller 140 will cause a logical 1 to appear at output 1 72.If the rewinder 10 is commanded to run at low speed, which typically is in the range of 10 to 15% less than normal speed, but which could be as much as 25 to 35% less than normal speed, the programmable controller 140 causes a logical 1 to appear at output 1 7Q. If the rewinder 10 is commanded to run at high speed, typically 5 to 15% higher than normal speed, but which could be as much as 20 to 35% higher than normal speed, programmable controller 140 causes a logic 1 to appear at output 174. The N1, N2 and N3 signals are applied to a motor control circuit 1 76 which generates the proper analog REWINDER COM MAND SPEED signal 30.The motor control circuit 1 76 includes three voltage sources 1 78, 180, and 182, designated V1, V2 and V3 respectively. The negative terminals of voltage sources V1, V2 and V3 are connected to ground 1 98. The positive terminal of voltage source 1 78 is connected to node 1 96, representing the REWINDER COMMAND SPEED signal 30, through normally open relay contacts 186.Similarly. the positive terminal of voltage source 180 is connected to node 1 96 through normally open relay contacts 190, and the positive terminal of voltage source 182 is connected to node 1 96 through normally open relay contacts 1 94. The motor control circuit 1 76 includes circuitry, represented by dashed line 1 84, which causes relay contacts 186 to close when a logical 1 signal appears at output 1 70 of programmable controller 140.Similarly, motor control circuit 1 76 includes circuitry, indicated by dashed line 188, which closes relay contacts 1 90 when a logical 1 signal appears at output 1 72 of programmable controller 140, and circuitry, as indicated by dashed line 192, which closes relay contacts 1 94 when a logical 1 signal appears at output 1 74 of programmable controller 140. It is contemplated that voltage sources V1, V2 and V3 can be adjusted manually by the operator. The adjustment of voltage source V2 gives the operator control of the normal, or approximately the average, speed of the rewinder 10.Although programmable controller 140 has been described as providing three levels of commanded rewinder speed, it will be appreciated by those skilled in the art that the sensor and status information can be processed by programmable controller 140 in a manner that provides many more levels of rewinder speed command, in which case, a suitable motor control circuit 1 76 would be provided to generate the analog, REWINDER COMMAND SPEED signal 30. Furthermore, the functions performed by programmable controller 140 could be performed by a digital computer or by special purpose circuitry.

Figs. 3,4 and 5 are flow diagrams illustrating the logic performed by programmable controller 140 while processing the sensor and status information in order to select the normal, low or high speed command signals for motor control circuit 1 76.

In the discussion that follows, X represents the number of empty spaces available in accumulator 64. The numbers Xl, X2 and X3 depend on system parameters such as accumulator size, etc. and in the described embodiment have the values 30, 60 and 20 respectively. The number X4 is that number of rolls that can be finished from a parent roll that has a diameter equal to A.

Fig. 3 is the flow chart of the main control routine for programmable controller 140. This control routine is executed about 10 to 1 5 times every second. The start of the routine is indicated by block 200.

Upon entering the main routine, a check is made as indicated by decision block 202, to see if the rewinder 10 is running. If the rewinder 10 is not running, the programmable controller 140 waits until the REWINDER RUN/STOP signal, B, indicates that the rewinder has been turned on. If the rewinder 10 is running, a rewinder status bit, M, is checked as indicated by decision block 204.

If the rewinder status bit, M, is a logical one, indicating that rewinder 10 is not running well, blocks 206 and 208 command the rewinder 10 to operate at normal speed.

Thus, the speed of the rewinder 10 is automatically controlled by the status or efficiency of the rewinder 10. If the rewinder status bit, M, is a logical zero indicating that the rewinder 10 is running well, programmable controller 140 performs decision block 210. The logic of decision blocks 21 0, 21 2 and 214 controls the speed of rewinder 10 so that the parent roll 1 2 in rewinder 10 does not become exhausted at the same time as the parent roll in rewinder 11. Thus, if the diameters of both parent rolls are less than A, block 224 is performed which commands rewinder 10 to run at low speed.If the diameter of parent roll 1 2 in rewinder 10 is less than A, and the diameter of the parent roll in rewinder 11 is greater than A, block 216 will command rewinder 10 to run at high speed if there are enough empty spaces in the accumulator 64 to accept the rolls, as determined by decision block 214, and will be operated at low speed if there are not enough empty spaces in the accumulator 64.

Decision blocks 218, 220 226 and 228 select the speed of rewinder 10 based on the status or efficiency of the saw and the status, or number of empty spaces availabe in accumulator 64, when the diameter of the parent roll 1 2 in rewinder 10 is greater than A. If the saw 80 is running, the rewinder 10 is commanded to wind at low speed if there are fewer than 21 empty spaces available in the accumulator 64, is commanded to wind at normal speed if there are between 21 and 60 empty spaces available in accumulator 64, or is commanded to wind at high speed if there are more than 60 empty spaces available in the accumulator 64.If the diameter of parent roll 1 2 in rewinder 10 is greater than A, and the saw 12 is not running, the rewinder 10 is commanded to wind at low speed if there are fewer than 30 empty spaces available in accumulator 64, is commanded to wind at normal speed if there are between 31 and 60 empty spaces available in accumulator 64, or is commanded to wind at high speed if there are more than 60 empty spaces available in accumulator 64.

Referring now to Fig. 4 there is shown a flow diagram of the subroutine for keeping track of the status of efficiency of rewinder 10. If the rewinder 10 is running well, the rewinder status bit, M, will be equal to a logical 0, and if rewinder 10 is running poorly, the rewinder status bit, M, will be set to a logic 1. As indicated by decision block 242, a check is made to see if rewinder 10 has been shut down more than twice during the past one minute. If it has been shut down an excessive number of times, this is an indication that the rewinder 10 is operating poorly and block 250 causes the rewinder status bit, M, to be set to a logical 1. If the rewinder 10 has not been shut down an excessive number of times, that is an indication that the rewinder is running properly and block 246 causes the rewinder status bit, M, to be set to a logic 0 and then proceeds to decision block 248.Block 248 checks the reject rate of rewinder 1 0. If more than two logs have been rejected since the start of a one minute interval, the rewinder is not performing well and the rewinder status bit, M, is set to a logical 1. If fewer than two logs have been rejected since the start of the last one minute interval, the rewinder 10 is considered to be running well and the rewinder status bit, M, is left equal to a logic 0.

Fig. 5 is a flow chart showing the subroutine that keeps track of the number of empty spaces in the accumulator 64. The start of the subroutine is indicated at block 260. As mentioned above, the variable X represents the number of empty spaces in the accumulator 64. Blocks 262 and 264 recognize the presence of the LOAD ACC signal, F, indicating that a log is being stored in the accumulator 64, and subtracts one from the number of empty spaces, X, in accumulator 64. Blocks 266 and 268 respond to the ACC FULL signal, G, and sets X equal to zero which means that there are no spaces available in accumulator 64. Blocks 270 and 272 respond to the ACC HALF FULL signal, H, the sets X equal to 70 which is one-half the storage capacity of accumulator 64. Blocks 274 and 276 respond to the DISCHARGE ACC signal, 1, by adding one to the number of empty spaces, X, in the accumulator 64.It is to be noted that blocks 266, 268, 270 and 272 are not absolutely necessary for programmable controller 140 to keep track of the number of empty spaces in accumulator 64.

The logic represented by blocks 266-272 acts as a check on the value of the variable X in the event the programmable controller 140 fails to properly keep track of the number of empty spaces in the accumulator 64. It will also be appreciated that while the ACC FULL and ACC HALF FULL signals are convenient for the accumulator employed in the described system, any other convenient checkpoints could be employed.

Thus, a finishing system has been described that can include a web rewinder 10, an accu mulator 64 and a saw 80. A programmable controller 140 automatically controls the speed of rewinder 10 based on the status of the system or on the status of the equipments that make up the system. Among the parameters that can control the speed of rewinder 10 are: the status of the rewinder 10, the efficiency of the rewinder 10, the status of the accumulator 64, the status of the saw 80, the size of the parent roll 1 2 in the rewinder 10 being controlled by programmable controller 140, and the size of the parent roll in a rewinder 11 that is adjacent to the controlled rewinder 10. Although the operator can establish the normal speed, which approximates the average speed, of the rewinder 10, the programmable controller 140 controls the instantaneous speed of the rewinder 10 to optimize the productivity of the entire finishing system.

While the present invention has been described with reference to a specific enbodiment thereof, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention in its broader aspects.

Claims (22)

1. A web finishing system comprising a web rewinder for making logs from a parent roll and an accumulator for temporarily storing logs, first means for generating a signal representing the number of empty storage spaces in the accumulator, and circuit means responsive to the first means signals for automatically controlling the speed of the rewinder.

2. A web finishing system as claimed in claim 1 additionally comprising second means for generating a signal representative of parent roll size wherein the circuit means is also responsive to the second means signal.

3. A web finishing system as claimed in claim 1 or 2 wherein the web finishing system additionally comprises a log saw, and means for generating a signal indicating the status or efficiency of the log saw and wherein the circuit means is also responsive to said log saw signal.

4. A web finishing system comprising a first web rewinder for making logs from a first parent roll, a second rewinder for making logs from a second parent roll and an accumulator for temporarily storing logs, first means for generating a signal representing the size of the first parent roll, second means for generating a signal representing the size of the second parent roll, third means for generating a signal representing the number of empty storage spaces in the accumulator, and circuit means responsive to the first, second and third means signals for automatically controlling the speed of the first rewinder thereby controlling when both parent rolls run out.

5. A web rewinder for making logs from a parent roll comprising first circuit means for generating a signal representative or the efficiency of the rewinder; and second circuit means responsive to the first circuit means signal for automatically controlling the speed of the rewinder.

6. A web rewinder as claimed in claim 5 wherein the first circuit means signal represents the rate rejected logs are made by the rewinder.

7. A web rewinder as claimed in claim 5 wherein the first circuit means signal is the number of times the rewinder is shut down during a predetermined period of time.

8. A web finishing system comprising a web rewinder for making logs from a parent roll and an accumulator for temporarily storing logs, first means for generating a signal representative of the status of the rewinder, second means for generating a signal representing the status of the accumulator, and circuit means responsive to the first and second means signals for automatically controlling the speed of the rewinder.

9. A web finishing system as claimed in claim 8 additionally comprising third means for generating a signal representative of parent roll size wherein the circuit means is also responsive to the third means signal.

10. A web finishing system as claimed in claim 8 or 9 wherein the web finishing system additionally comprises a log saw, and fourth means for generating a signal indicating the status of efficiency of the log saw and wherein the circuit means is also responsive to said log saw status signal.

11. A web finishing system as claimed in claim 10 wherein the first circuit means signal represents the rate rejected logs are made by the rewinder.

12. A web finishing system as claimed in claim 10 wherein the first circuit means signal is the number of times the rewinder is shut down during a predetermined period of time.

1 3. A web finishing system as claimed in claim 10, wherein the web finishing system additionally comprises a second web rewinder for making logs from another parent roll, and fifth means for generating a signal representative of said other parent roll size and wherein the circuit means is responsive to the fifth means signal and controls the speed of the first rewinder thereby controlling when both parent rolls run out.

14. A web finishing system including a web rewinder for making logs from a parent roll and means for automatically controlling the speed of the rewinder in response to a signal based on one or more parameters of the system.

1 5. A web finishing system as claimed in claim 14, wherein a said parameter is the number of empty spaces in an accumulator in the system.

1 6. A web finishing system as claimed in claim 14 or 15, wherein a said parameter is the parent roll size.

1 7. A web finishing system as claimed in claim 14, 15 or 16, wherein a said parameter is the status or efficiency of a log saw.

1 8. A web finishing system as claimed in one of claims 14 to 17, wherein a said parameter is the status or efficiency of the rewinder.

1 9. A web finishing system as claimed in one of claims 14 to 18, wherein a said parameter is the number of times the rewinder is shut down over a predetermined interval of time.

20. A web finishing system as claimed in one of claims 1 4 to 1 9 wherein a said parameter is the rate the rewinder makes reject logs.

21. A web finishing system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

22. A web rewinder substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.