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(11) | EP 0 235 093 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Apparatus for automatically controlling the tension of fabric on the barrel of a carding and napping machine |
| (57) Automatic control apparatus for controlling the tension of a fabric as it passes
over the barrel of a carding and napping machine has a first electronic unit (10)
forcontrolling the speed of a first variable speed drive (3, 13) which feeds the fabric
onto the barrel and a second electronic unit (20) for controlling the torque of a
second variable speed drive (4, 24) which draws the fabric from the barrel. The two
variable speed drives (3, 13; 4, 24) are electrically interconnected in such a way
that the second variable speed drive is governed in speed in dependence on the speed
of the first variable speed drive by means of a tachometric generator (16) driven
to rotate by the said first variable speed drive (3, 13). |
[0001] The present invention relates to automatic apparatus for controlling the tension of fabric on the barrel of a carding and napping machine.
[0002] A problem which currently creates limitations and conditions on the carding and napping action which can be effected by carding and napping machines is that caused by variations in the tension of the fabric which is not easily controllable.
[0003] In fact, in conventional carding and napping machines, which are controlled by mechanical variators, the right tension on the fabric is only obtained when the right compromise between the speed of rotation of an input cylinder, the speed of rotation of an output cylinder, the speed of rotation of the carding cylinders working with the nap and the speed of rotation of carding cylinders working against the nap has been found. These operations are currently performed by trial and error techniques, with response times which are rather lengthy and which can consequently cause the production of sections of fabric damaged by operating with an incorrect setting.
[0004] Another disadvantage which can be encountered with prior art carding and napping machines is constituted by the fact that an incorrect tension of the fabric on the barrel can cause the metal gaskets of the carding rollers to be squashed with consequent damage and the necessity of frequent replacement.
[0005] A further disadvantage is constituted by the fact that the fabric is not infrequently caught by the carding cylinders, with the possibility of breakage of the fabric which often happens and which involves serious and troublesome downtime.
[0006] The object of the present invention is that of eliminating the above indicated disadvantages by providing apparatus for the automatic, continuous and constant control of the tension of the fabric on the barrel of a carding and napping machine, which makes it possible to vary the carding effect with or against the nap by maintaining the tension of the fabric constant between arrival at and departure from the barrel, so that a wider range of working options are available whilst the fabric is on the barrel.
[0007] According to the present invention there is provided apparatus for automatic control of the tension of the fabric on the barrel of a napping and carding machine, characterised by the fact that it comprises a first electronic control unit for controlling the speed of a variable speed drive for supplying the fabric onto the barrel, a second electronic control unit for controlling the torque of an output variable speed drive for drawing the fabric off the barrel, the said two variable speed drives being electrically connected together with the speed of the output variable speed drive being governed by the input variable speed drive by means of a tachometric generator driven to rotate by the input variable speed drive.
[0008] A particular advantage of the present invention is that it provides apparatus which is capable of adjustment and variation with rapid response times to all the variations of the carding parameters, with consequent considerable economic advantages for the user.
[0009] Another advantage of the present invention is that it provides apparatus which, whilst having considerably improved characteristics, is mechanically simplified. The apparatus of the present invention thus makes it possible to avoid damage to the. fabric during adjustment or variation and reduces, in a significant manner, the wear on the gaskets of the carding cylinders.
[0010] Another advantage of the present invention is that it provides apparatus which will give the possibility of synchronising composite lines of several machines, thereby making the installation simpler and more functional.
[0011] One embodiment of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a schematic side view of a carding and napping machine of the type to which the apparatus according to the invention is applied;
Figure 2 is a schematic block diagram of the electrical arrangement of the apparatus of the invention;
Figure 3 is a side view of the mechanical arrangement of parts for controlling the tension of the fabric;
Figure 4 is a side view similar to Figure 3, showing the disposition of the fabric in the case of excessive working of the nap;
Figure 5 is a side view similar to Figure 3, showing the disposition of the fabric in the case of excessive working against the nap;
Figure 6 is a side view similar to Figure 3, showing the disposition of the fabric if the tension becomes too low and it becomes retained between the carding cylinders;
Figure 7 further illustrates the control unit for the carding cylinders; and
Figure 8 schematically represents the machine showing the regulation potentiometers.
[0012] With reference now to the drawings which are schematic views only and from which component parts not relating directly to the invention have been omitted, the carding machine has a barrel 1 supporting, in a known way, a plurality of carding cylinders 60, over which passes a fabric 2 delivered to the barrel by an input cylinder 3 and drawn off it by an output cylinder 4, which introduces the fabric to an upper cylinder 5 from which the fabric then passes to a folding cylinder 6.
[0013] The apparatus for monitoring and controlling the operation of the carding machine is shown schematically in Figure 2 and includes an electronic unit 10 for controlling the speed of the input cylinder, which is driven by a variable speed drive, in order to control the speed at which the fabric is supplied to the barrel. The control unit 10 has a central unit 11, connected to a first potentiometer 12, which controls the motor 13 of the variable speed drive to determine the speed at which the fabric is supplied to the barrel 1; this supply speed is detected by a digital instrument 14 (Figure 8). The output of a tachometric generator 15, mounted for rotation with the axis of the barrel 1, is connected to the central unit 1 for synchronisation as will be described below. Another tachometric generator 16 is connected for rotation with the motor 13 of the variable speed drive, and its output is also fed to the first central unit 11.
[0014] Electrically connected to the said first electronic control unit 10 there is a second electronic control unit 20 which acts to control the torque of an output variable speed drive 24 which drives the output cylinder 4. This second control unit 20 has a second central unit 21 connected to a second potentiometer 22 by means of which the maximum working tension detectable by a digital instrument 23 to be set in such a way as to set the maximum torque provided by a motor 24 driving the output variable speed drive which is connected. A further tachometric generator 25 is connected for rotation with the motor 24 and its output is fed to the central unit 21.
[0015] The variable speed drive motors 13 and 24, which are connected to the input cylinder 3 and to the output cylinder 4, respectively, are connected together electrically. The speed of the variable speed drive motor 24 is piloted by the variable speed drive motor 13 by means of the tachometric generator 16 which is incorporated in the variable speed drive itself, and which controls the tension of the fabric by increasing or reducing its speed of rotation. This automatically compensates for elongation of the fabric, governed by the fabric itself, as a function of the set percentage tension by making use of the characteristics of the constant torque variable speed drive.
[0016] To put into practice the above stated effect it is necessary that the variable speed drive motor 13, the speed of which is set by the potentiometer 12, is not driven by the variable speed motor 24 which works under torque. For this reason the variable speeo drive motors are provided with electronically controlled brakes which, in the specific embodiment, prevent the variable speed drive motor 13 from being able to rotate at a speed greater than the set speed.
[0017] The apparatus further includes a third electronic unit 30 for controlling the upper cylinder 5, which is constituted by a third central unit 31 generated by a third potentiometer 32 which performs the actuation and governing of a variable speed drive motor 33 which drives the upper cylinder 35, and the speed of which in turn is governed by a third tachometric generator 34 mounted for rotation therewith.
[0018] A fourth electronic unit 40 is also provided, this being constituted by a fourth central unit 40 which is governed by a fourth potentiometer 42 which controls a fourth variable speed drive motor 43 for control of the folding cylinder 6, which motor is also governed by a fourth tachometric generator 44 mounted for rotation with the motor 43 itself.
[0019] At the electrical junction between the first electronic unit 10 and the second electronic unit 20 there is connected a control unit for controlling the rotation of the carding cylinders 60. This is constituted by three separate central units, namely a first carding control unit 50 which will be referred to hereinafter as a "no-carding" control unit, an electronic regulator 51 for controlling the speed of the carding cylinders which work with the nap (that is they rotate so that they brush the fabric in the direction of the nap), which is controlled by a potentiometer 52 for setting the desired speed of these cylinders, which controls a variable speed drive 53 which, as schematically illustrated in Figure 7, drives those cylinders 60 of the drum which rotate in the direction of the nap. The variable speed drive 53 drives a tachometric generator 54 (Figure 2) the output of which is fed to the control unit 51 as a feedback signal. The unit 51 thus controls the electrical feed to the motor 53 in dependence on the input signals received from the potentiometer 52, the control unit 50 and the central unit 11, and the feedback signal from the tachogenerator 54.
[0020] There is, further, provided an electronic regulator 55 which controls the speed of a motor 57 which drives the carding cylinders working against the nap; the demand speed of this motor 57 is set by a potentiometer 56 and it drives a tachogenerator 58 the electrical output from which is fed to the control unit 55.
[0021] In practice, the fabric 2 is caused to move around the barrel by the motion of the carding cylinders 60, as well as the fabric transport cylinders 3 and 4, and the carding cylinders 60 may all rotate in the same direction (those working against the nap merely being driven at a slower speed) or the carding cylinders 60 working against the nap may even be rotated in the opposite direction from those working with the nap.
[0022] The variable speed input drive cylinder 13 sometimes acts as a drive, whilst at other times it serves as a brake, maintaining the fabric always perfectly stretched over the barrel.
[0023] When the carding or napping parameters of a given article have been determined the apparatus according to the invention makes it possible to be able to perform optimum working automatically without any necessity for monitoring or intervention by the operator. In fact, the operator need only set the potentiometers for determining the nominal settings of the motors driving the carding cylinders working with and against the nap and the carding will proceed without the possibility of error, seeing that the tensions on the barrel at the output and input will be automatically compensated. The control of the tension effected by means of the tachometric generators avoids slackening of the fabric and prevents it from becoming hooked up.
[0024] With particular reference to Figure 4, if it is desired to be able to obtain a determined effect on a certain article, it may be desired for example to work with the nap. In a conventional carder where there is no separate control of the fabric tension, it is necessary to increase the action of the carding cylinders working against the nap; this intervention on the fabric will, however, largely cancel out the effect obtained by working with the nap, or else it will change the tension, causing a further elongation of the fabric. With the apparatus of the present invention on the other hand it is possible to vary the carding effect at will without having to balance the effects of the carding cylinders working with and against the nap, in that the control of the tension of the fabric takes place automatically.
[0025] With reference to Figure 5, it can be seen that if a strong counter-nap working is desired, to obtain a certain effect on the fabric, there inevitably forms an excess of fabric at the input; to eliminate this and balance the fabric tension it would be necessary in prior art carders to adjust the speed of the cylinders working with the nap, thereby nullifying at least in part the effect which it is sought to achieve by working against the nap. In the present invention the fabric tension is automatically adjusted without it being necessary to adjust the speed of the carding cylinders working against the nap.
[0026] In mesh fabrics, elongation of the fabric whilst carding is sometimes unthinkable and it is necessary continuously to correct the fabric tension in order to prevent the above described problems from occurring. In the apparatus of the present invention such tension adjustment takes place automatically.
[0027] Another advantage which the apparatus according to the invention offers is the possibility of obtaining a napped result by brushing in only one direction, even on a carder having carder cylinders mounted so as to work with the nap and against the nap. This is achieved by the fact that it is possible to drive only the carder cylinders which work against the nap whilst the cylinders which work in the direction of the nap are allowed to be freely rotatable on the barrel. In other words, the carder cylinders working in the direction of the nap can be driven by the fabric itself, conferring thereto a particularly effective treatment and degree of filling of the down on the fabric, which thus avoids the need for clipping. In the same way, the carder cylinders working against the nap can be allowed to rotate freely and work can proceed only with the carder cylinders which work in the direction of the nap. This result is only possible, however, because of the constant tension control exerted of the fabric on the carder barrel by the feed and draw-off rollers 3 and 4.
[0028] As can be seen in Figure 7, the variable speed drive motors 53 and 57 which drive the carding cylinders working with and against the nap work at a constant torque and can be made freely rotatable. The motor 53 drives a belt 70 passing over a pulley 71 of a transmission unit 73 the output pulley 72 from which drives a belt 74 passing over a pulley 75 which is fixed to a pulley 82 which drives a belt 76 engaging all the cylinders 60 which work with the nap. A similar drive train from the motor 57 leads via a belt 77, a pulley 78 of a transmission unit 80 to a pulley 79 driving a belt 81. This belt drives a pulley (not shown) coaxial with the pulley 75 and obscured by it in Figure 7, which in turn drives a pulley corresponding to the pulley 82 to drive a further belt (not shown) like the belt 76 which engages all the cylinders 60 which work against the nap.
[0029] The intervention times necessary to put the carding cylinders working with the nap or against the nap into their freely rotatable state, or else to put all the cylinders, both those working with the nap and those working aginst the nap into their freely rotatable state, can be effected in real time with response times of less than a tenth of a second.
[0030] Moreover, having the possibility of controlling the torque of the variable speed drive which controls the carding cylinders working with the nap and those working against the nap makes it possible always to work under optimum conditions, considerably extending the life of the gaskets, and eliminating those disadvantages typical of conventional carders which, because of errors in operation or evaluation of the settings of the carding parameters, lead to an excessive wear and, in extreme cases, damage to the gaskets of these carder cylinder claddings. These latter, upon losing their mechanical characteristics, have to be replaced with a not insignificant cost and with the machine stopped for rather a long time.
[0031] Moreover, the use of variable speed drives having electronic controls allows apparatus for control of the working with the nap and against the nap to be obtained which gives the possibility of interrupting the carding effect instantaneously, putting the variable speed drives 53 and 57 which control the carding cylinders working with and against the nap, into a freely rotatable condition and renewing the carding, again instantly, without having to stop the machine.
1. Apparatus for automatic control of the tension of the fabric on the barrel of a
napping and carding machine, characterised by the fact that it comprises a first electronic
control unit (10) for controlling the speed of a variable speed drive (13) for supplying
the fabric (2) onto the barrel, a second electronic control unit (20) for controlling
the torque of an output variable speed drive (24) for drawing the fabric off the barrel,
the said two variable speed drives (13, 24) being electrically connected together
with the speed of the output variable speed drive (24) being governed by the input
variable speed drive (13) by means of a tachometric generator (16) driven to rotate
by the input variable speed drive (13).
2. Control apparatus according to Claim 1, characterised in that the first electronic
unit (10) has a central unit (11) piloted by a first potentiometer (12) for controlling
the variable speed drive (13) driving a fabric input roller (3), a first tachometric
generator (16) being connected to the said input variable speed drive (13), an auxiliary
tachometric generator (15) being provided for synchronisation of the starting of the
drive motor (13).
3. Control apparatus according to Claim 1 or Claim 2, characterised in that the said
second electronic unit (20) for controlling the torque of the output variable speed
drive (24) has a second central unit (21) to which is connected a second potentiometer
(22) for determining the nominal speed of the output variable speed drive (24), and
a second tachometric generator (25) driven to rotate with the output variable speed
drive.
4. Control apparatus according to one or more of the preceding Claims, characterised
in that it includes a third electronic unit (30) for controlling an upper fabric take-off
cylinder (5), the said third electronic unit (30) having a third central unit (31)
receiving an input from a third potentiometer (32) for controlling the speed of a
variable speed drive (33) of the upper cylinder (5), a third tachometric generator
(34) being driven to rotate with the upper cylinder variable speed drive (33).
5. Control apparatus according to any preceding Claim, characterised in that it includes
a fourth electronic unit (40) having a fourth central unit (41) receiving an input
signal from a fourth potentiometer (42) for controlling a variable speed drive (43)
of a folding cylinder (6), a fourth tachometric generator being driven to rotate with
the folding cylinder drive (43).
6. Control apparatus according to any preceding Claim, characterised by the fact that
between the first and the second electronic control units (10, 20) there is connected
a unit (50, 51, 55) controlling the speed of rotation of the carding cylinders (60)
working with and against the nap.
7. Control apparatus according to Claim 6, characterised in that the said electronic
control unit (50, 51, 55) for the carding cylinders working with and against the nap
includes an automatic zero carding regulator (50).
8. Control apparatus according to Claim 6 or Claim 7, characterised in that the electronic
control unit (50, 51, 55) for the carding cylinders includes a central electronic
regulator (51) for controlling the speed of the carding cylinders working with the
nap and a potentiometer (52) for determining the nominal speed of the carding cylinders
working with the nap, the said central electronic regulator (51) controlling the speed
of a variable speed drive (53) for the carding cylinders working with the nap, in
dependence on the setting of the potentiometer (52) and on a feedback signal from
a tachometric generator (54) connected for rotation with the said variable speed drive
for controlling the carding cylinders working with the nap.
9. control apparatus according to any preceding Claims, characterised in that the
electronic control unit (50, 51, 55) for the carding cylinders includes a further
electronic regulator (55) for controlling the speed of the carding cylinders working
against the nap and a potentiometer (56) for determining the nominal speed of the
carding cylinders working against the nap, the said further electronic regulator (55)
controlling the speed of a further variable speed drive (57) driving the carding cylinders
working against the nap in dependence on the setting of the potentiometer (56) and
on a feedback signal from a tachometric generator (58) connected for rotation with
the said further variable speed drive (57) for controlling the carding cylinders working
against the nap.