GB2156108A - Processing machine for strip material - Google Patents

Abstract

A processing machine for strip material comprises a pair of rolls 12 driven by a main motor 13 and further pairs of rolls 16, 19 driven by further motors 17, 20. The speeds of the rolls 12, 16, 19 are measured using sensors which produce pulse signals which are fed to a digital control system. The control system controls the speeds of the motors 17, 20 relative to the main motor. A rotary cutter arm 22 can be actuated to divide the strip leaving the machine into the desired length. <IMAGE>

Description

SPECIFICATION Processing machine for strip material This invention relates to a processing machine primarily for strip material, which includes a number of rotary strip engaging members for example rollers which engage the strip at different positions along the length of the strip, throughout its movement through the processing machine.

An example of such a machine is a printing press and in which it is necessary to keep the various rollers and drums in strict synchronism to firstly ensure that the paper is not stretched and secondly to ensure that where multiple printing is being carried out, the differently coloured impressions are in the correct position. Another example of the processing machine is one for the production of convoluted strip material for use for example in heat exchangers.

In the past the various shafts mounting the rollers or drums or in the case of the machine for producing convoluted strip material, the rolls which bend and pierce the material, have been interconnected by a transmission system including gear trains or chains and driven by a single motor. The transmission system adds considerably to the bulk of the machine and has to be carefully designed and manufactured to minimise backlash. In addition, depending upon the size of the machine considerable power loss takes place in the transmission system.

Moreover, in some machines notably those for producing convoluted strip material, it may be necessary to alter the drive ratio between one or more of the shafts when it is required that the machine should produce another type of convoluted strip. In the case where gear trains are utilised it is necessary to change the gears of the gear trains and this is a time consuming operation. It is known to use instead of the gear trains variable speed drive mechanisms which facilitate a change of drive ratio but which in themselves are expensive and bulky.

In order to overcome the disadvantages set out above it is proposed to provide each shaft with a drive motor and to control the speeds of the motors electronically relative to one motor. In this manner the transmission systems discussed above can be eliminated and furthermore, it is possible to alter the speed of one or more of the shafts relative to the shaft driven by the one motor, by adjustment of the electronic control circuit. This adjustment can be made in seconds whereas the time required to adjust the variable speed drive can be reckoned in minutes and the time required to alter the gear trains can be reckoned in hours.Very accurate control of the motor speeds is required and this is best achieved using digital techniques, each shaft having mounted thereon, a toothed wheel which has a sensor associated therewith which is responsive to the passage of the teeth as the disc rotates and supplies a series of pulses to the control system. The toothed wheels can be mounted on the motor shafts. The pulse trains from the different sensors are compared in the control system and the speeds of the motors controlled in accordance with the speed of the one or main motor so that the individual shafts rotate at the desired speed.

According to the invention a processing machine for strip material comprises a plurality of rotary strip engaging members engageable with the strip at different positions as it passes through the machine, a main drive motor for driving at least one of said members, further drive motors for driving the remaining ones of said members respectively and electronic means for controlling the speeds of said further drive motors relative to said main motor, said electronic means including sensors for producing pulse signals representative of the speeds of said members respectively, difference counters associated with said further drive motors respectively, each difference counter comparing the pulse signal produced by the sensor driven by the respective motor and the pulse signal produced by or a division thereof, the sensor driven by the main motor, the outputs of said difference counters being used to control the speeds of the respective further drive motors.

According to another aspect of the invention a processing machine for producing finned strip material comprises a pair of driven fin producing rolls, means for feeding plain strip material between said rolls, at least a further pair of driven rolls which receive the finned strip material produced by said first mentioned rolls, a rotary cutting arm mounted for rotation about an axis generally parallel to the direction of movement of the finned strip material through the machine, and a drive mechanism operable to rotate said cutting arm so as to sever the finned strip material leaving the machine in a direction transverse to its movement.

In an example of a machine for producing finned strip material, the raw material in the form of flat aluminium strip is fed from a coil through a de-tensioning device 10 driven by a DC electric motor. The de-tensioning device comprises a pair of nip-rolls driven by the motor and which draw the strip from a reel.

After passing through the nip-rolls the strip passes into a slack box and from the box the strip passes into a guide tunnel 11 which extends substantially the whole length of the machine. As it moves along the tunnel it passes between a pair of shaping rolls 12.

The rolls are positioned on opposite sides of the tunnel and the tunnel is provided with openings through which the rolls extend. The shaping rolls are provided with intermeshing teeth between which the strip passes and during such movement the strip is be# to convoluted form and at the same time portions of the strip are pierced and deformed.

The section of the strip after it has passed from between the rolls 12 is essentially a continuous zigzag. The rolls are interconnected by gearing and are driven by a main drive motor 13 through a reduction gearbox not shown. An indication of the speed at which the shaping rolls rotate, is provided by a toothed wheel 14 with which is associated a sensor.

After passing from the shaping rolls, the convoluted strip passes between a further pair of toothed rolls 15 which are driven in synchronism with the shaping rolls 12, through gearing from the motor 13. The convoluted strip then passes along the tunnel and between a first pair of rubber rolls 16. These rolls are interconnected by gearing and are driven by a separate DC drive motor 17. A signal indicative of the speed of rotation of the rolls 16 is provided by a toothed disc 18 which has a sensor associated therewith. The speed of rotation of the rolls 16 is carefully controlled so that as the strip passes between the rolls 15 and 16, the convolutions of the strip are closed up to a degree more than is required in the finished strip.

The tightly packed strip then passes between a second pair of rubber rolls 19 which again are interconnected by gearing and which are driven by a further DC drive motor 20. A signal indicative of the speed of rotation of the rolls 19 is provided by a toothed disc 21 and it is arranged that the rolls 19 rotate at a slightly higher speed than the rolls 16. The effect of this speed difference is to stretch slightly the convoluted strip as it passes between the rolls 16 and 19 and this means that the convolutions are no longer packed so tightly.

The strip as it leaves the rolls 11 passes to the end of the tunnel 11 where there is positioned a rotary cutting arm 22. The arm is movable by means of a suitable drive mechanism, transversely to the direction of movement of the strip so that it can sever the strip into appropriate lengths. Conveniently the drive mechanism comprises a constant speed motor 26 which drives the arm 22 through an electrically controlled brake/clutch 27. In this manner severing of the strip can be achieved very quickly and at a high repitition rate. The strip as it leaves the tunnel 11 moves onto a belt conveyor 23 which is itself driven by a DC drive motor (not shown). The speed of the belt can be cyclically varied so as to achieve separation of the cut strips along the length of the belt 13.

The lengths of the strips supplied to the conveyor belt 23 are precisely controlled us ing a measuring device in the form of a rotatable scroll 24 which has a helical thread formation on its peripheral surface which engages with the fins of the strip. The axis of rotation of the scroll is parallel to but spaced from the axis of movement of the strip and the scroll is coupled to a toothed disc 25 which is provided with a sensor. The pulse signals provided by the sensor are counted in an adjustable counter to determine the length of the strip passing beneath the scroll and when the set count value is achieved the clutch is energised to actuate the cutting arm 22. The scroll can have a single start thread on its periphery but it is more convenient to have a multi-start thread and the scroll is driven through appropriate gearing from the main motor.The scroll is conveniently positioned to enable it to be changed when a change in the pitch of the convolutions is required.

It is essential that the strip should be fed to the shaping rolls 12 in an untensioned state and therefore the speed of the drive motor which drives the de-tensioning device 10 is controlled in accordance with the speed of the main motor 13. In order to facilitate the installation of a fresh roll of strip material, it is possible to speed up the motor which is driving the de-tensioning device prior to slowing it so as to provide within the machine itself a supply of tape sufficient to allow the machine to continue to operate while a new roll of tape is placed in position and spliced to the end of the existing tape. If desired and in order to allow more time to achieve the splicing, the main motor may be slowed down.

The control system has facilities for adjusting the speed of the main motor 13 and for controlling its acceleration and deceleration.

The speed of the rolls 12 and hence the main motor 13 is used as the reference for control ling the speeds of the motors 17, 20 and the motor which drives the detensioning device 10. The pulse signals obtained from the sensor associated with the disc 14 form the reference. Each of the motors 17. 20 and the motor for the detensioning device 10 is provided with a variable ratio divider, a difference counter, an analogue/digital converter and a summation circuit, the signal from the latter being supplied to a power control circuit for the respective motor. The pulse signal from the sensor associated with the disc 14 is divided by the variable ratio divider and sup plied to one input of the difference counter.

The other input to the difference counter is obtained from the sensor associated with the particular motor. The difference signal is sup plied to the digital/analogue converter and from the converter to the summation circuit.

The other input to the summation circuit is an analogue signal representing the speed of the main motor 13 and the mathematical sum of the two signals is used to control the speed of the particular motor. By altering the settings of the variable ratio dividers the relative speeds of the various pairs of rolls relative to the rolls 12 and 15 can be altered.

The signal which is obtained from the sensor associated with the disc 25 is supplied to an adjustable counter which when the predetermined count value is achieved, energises the clutch 27 forming part of the drive mechanism of the cutting arm. The count value of the counter can be readily altered to alter the lengths of the severed strips. The signal which energises the clutch can also be used to effect a temporary increase in the speed of the conveyor 23 to achieve separation of the cut strips on the conveyor.

Claims (11)

1. A processing machine for strip material comprising a plurality of rotary strip engaging members engageable with the strip at different positions as it passes through the machine, a main drive motor for driving at least one of said members, further drive motors for driving the remaining ones of said members respectively and electronic means for controlling the speeds of said further drive motors relative to said main motor, said electronic means including sensors for producing pulse signals representative of the speeds of said members respectively, difference counters associated with said further drive motors respectively, each difference counter comparing the pulse signal produced by the sensor driven by the respective motor and the pulse signal produced by or a division thereof, the sensor driven by the main motor, the outputs of said difference counters being used to control the speeds of the respective further drive motors.

2. A processing machine according to Claim 1 including variable ratio divider circuits the outputs of which are counted to the difference counters respectively whereby the relative speeds of said further members relative to said one member can be varied.

3. A processing machine according to Claim 2 including digital/analogue converters for converting the output signals of said difference counters into analogue signals which are supplied to motor control circuits for said further drive motors.

4. A processing machine according to Claim 2 in which one of said further drive motors controls the delivery of strip to the member or members driven by said main drive motor, the control circuit of said one further drive motor including means whereby the speed of the motor can be increased to cause an accumulation of strip between the members driven by the one further and main drive motor, prior to slowing the motor.

5. A processing machine according to Claim 1 including a cutter mechanism operable to sever the strip leaving the machine, means for measuring the strip leaving the machine and a control circuit responsive to the signal provided by the measuring means for operating said cutter when a predetermined length of strip has passed from the machine.

6. A processing machine according to Claim 5 in which said control circuit is adjustable so that the length of the severed strip can be varied.

7. A processing machine for producing finned strip material comprising a pair of driven fin producing rolls, means for feeding plain strip material between said rolls, at least a further pair of driven rolls which receive the finned strip material produced by said first mentioned rolls, a rotary cutting arm mounted for rotation about an axis generally parallel to the direction of movement of the finned strip material through the machine, a drive mechanism operable to rotate said cutting arm so as to sever the finned strip material leaving the machine in a direction transverse to its movement.

8. A processing machine according to Claim 7 in which the drive mechanism for the cutting arm includes a rotary drive shaft and a clutch operable to couple said drive shaft to the cutter arm to effect rotation thereof.

9. A processing machine according to Claim 8 including means for driving said drive shaft at a substantially constant speed.

10. A processing machine according to Claim 1 including a rotatable scroll having a helical thread formation on its peripheral surface said thread formation being engaged with the fins of the finned strip material, a sensor for providing pulse signals as the scroll rotates, an adjustable counter for counting said pulse signals said counter effecting operation of said clutch after a predetermined number of revolutions of the scroll.

11. A processing machine for producing finned strip material substantially as hereinbefore described with reference to the accompanying drawing.