Regulating method and system for producing a uniform sliver in a carding machine

A regulating apparatus for obtaining a uniform sliver delivered by a carding machine includes an rpm setter connected to a roller drive of the carding machine for determining an operational speed for the drive, a signal generator for producing a first signal as a function of actual properties of the sliver and a PI-regulator having a component determining a regulating time constant. The PI-regulator is connected to the signal generator for receiving the first signal and for generating a second, regulating signal. Further, the PI-regulator is connected to the drive for applying the second signal thereto. A regulating time constant setter is operatively connected to the component which determines a regulating time constant. The rpm setter and the regulating time constant setter cooperate for adjusting the regulating time constant setter as a function of adjustments of the rpm setter, whereby the regulating time constant of the PI-regulator is varied as a function of the rpm of the fiber-engaging roller.

BACKGROUND OF THE INVENTION 
This invention relates to a regulating method and a regulating system for 
producing a uniform sliver in a carding machine, wherein a deviation of 
actual values from desired values is determined and a signal, representing 
the deviation is, with the intermediary of a regulator, applied to a drive 
which varies the rpm of at least one carding roller as a function of the 
signal magnitude. 
In known processes of the above-outlined type the difficulty has been 
encountered that in case the operational speed of the carding machine is 
altered, that is, the rpm of the rollers is increased or decreased, the 
time behavior of the regulated system also varies. In particular, the 
delay of response of the regulating circuit is speed-dependent. By 
changing the speed of the carding machine, the speed of the fiber material 
supplied to, and/or the speed of the fiber material delivered by the 
carding machine changes to that the uniformity (cross section and weight) 
of the sliver delivered by the carding machine has been adversely 
affected. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an improved method and system 
of the above-outlined type from which the discussed disadvantages are 
eliminated and which, even in case of machine speed variations ensures the 
production of an optimally uniform sliver. 
This object and others to become apparent as the specification progresses, 
are accomplished by the invention, according to which, briefly stated, the 
carding machine uses a PI-regulator (proportional/integral regulator) in 
which the regulating time constant of the regulator is varied as a 
function of the output speed and/or the input speed of the fiber material. 
By changing the regulating time constants of the regulator upon changing 
the carding speed, the time behavior of the regulated system can be 
adapted to the changed machine speed. This ensures an optimally uniform 
sliver irrespective of an increase or decrease of the rpm of the carding 
rollers. 
In the regulating system according to the invention the rpm setter (rpm 
pre-selection for the basic rpm of a roller in the carding machine) 
cooperates with a setter which sets the regulating time constants of the 
PI-regulator. The rpm setter is preferably a potentiometer having linear 
characteristics. The time constant setter is preferably a potentiometer 
with non-linear, for example, logarithmic characteristics. 
According to a preferred embodiment of the invention, the rpm setter and 
the regulating time constant setter are coupled to one another, for 
example, mechanically (by means of gears or frictional wheels), 
electrically or electronically. 
According to a further feature of the invention, the rpm setter is a 
tachogenerator which is associated with the drive motor for one of the 
carding rollers and to the output of which a transducer is preferably 
connected. According to a particularly advantageous feature of the 
invention, the time constant setter varies the I-part (integral part) of 
the PI-regulator by varying the resistance of an RC-component which 
determines the regulating time constant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to FIG. 1, there is schematically shown a carding machine 
having a feed roller 1, a lickerin 2, a carding cylinder 3, a doffer 4, a 
take-off roller 5, squeezing rollers 6 and 7, a trumpet 8 and calender 
rollers 9 and 10. With the trumpet 8 there is associated a sensor which 
pneumatically measures, in a known manner, properties of the cross section 
of the sliver passing through the trumpet 8. The pressure oscillations 
resulting from such sensing operation are converted by a transducer 11 
(actual value transducer) into electric signals which are applied to a 
PI-regulator 12 (continuous regulator) which, as shown in FIG. 2, has an 
I-part 12a and a P-part 12b. To the output of the PI-regulator 12 there is 
connected an rpm regulator 13 such as a SIMOREG model to which, in turn, 
there is connected a drive motor 4a for the doffer 4. Outputs of a setting 
device 14 are connected to the PI-regulator 12 and the rpm regulator 13. 
FNT *)manufactured by SIEMENS AG, Munich (W. Germany)*) 
Turning now to FIG. 3, the setting device 14 comprises an rpm setter 15 
which may be, for example, a linear potentiometer electrically connected 
with the rpm regulator 13. The setting device 14 further has a setter 16 
which may be a potentiometer with logarithmic characteristics and which is 
electrically connected with the I-portion 12a of the PI-regulator 12. The 
I-portion 12a has an RC component comprising a capacitor 12d and a 
resistor 12c. The latter is connected to the setter (potentiometer) 16. 
The potentiometer 15 has a shaft 15a which carries a gear 15b as well as a 
setting knob 15c. The potentiometer 16 has a shaft 16a on which there is 
mounted a gear 16b. The gears 15b and 16b are in a meshing relationship 
with one another so that, as a result, the potentiometers 15 and 16 are 
mechanically coupled to one another. In this manner the rpm setter 15 
cooperates with the setter 16 whereby the latter sets the I-part 12a of 
the PI-regulator 12 and thus adjusts the regulating time constant as the 
rpm setting is changed. Thus, the potentiometer 15 serves for setting the 
machine speed, while with the aid of the potentiometer 16 the regulating 
time constant is varied by changing the resistance of the RC component. 
Since, as noted before, the potentiometer 15 for setting the rpm is a 
linear potentiometer, the resistance values change in direct proportion to 
the angular displacement of the shaft 15a. Further, the resistance values 
depend, in a good approximation, linearly from the rpm. The logarithm of 
the time constants is inversely proportional to the machine rpm. The same 
relationship prevails in the logarithmic potentiometer 16 between the 
angle of rotation of the shaft 16a and the set resistance values. 
In order to maintain the desired dependence of the time constants from the 
sliver speed, the linear potentiometer 15 is coupled with the logarithmic 
potentiometer 16 whereby the linear potentiometer 15 serves for the 
setting of the sliver speed. Expediently, only a predetermined part of the 
setting angle of the logarithmic potentiometer 16 is utilized. For setting 
the time constants, the appropriate range of angular adjustment is to be 
set by selecting a certain transmission ratio between the potentiometers 
15 and 16 and by setting the starting angle of rotation of the two 
potentiometers 15 and 16 with respect to one another. The selection of the 
total resistance range of the potentiometer determines the required 
capacitor in order to achieve the desired time constants for all speeds. 
Turning now to FIG. 4, to the output of the PI-regulator 12 there is 
connected, similarly to FIG. 1, an rpm regulator 13 which, in turn, is 
coupled with an rpm setter 15 such as a potentiometer. The rpm setter 15 
varies the rpm of the drive motor 17 for the feed roller 1. A 
tachogenerator 18 is coupled with the drive motor 17 to sense the rpm 
thereof. Signals from the tachogenerator 18 are applied to a transducer 
19, whose electric signals, in turn, are applied to the I-part 12b of the 
PI-regulator 12. 
Turning now to FIG. 5, in the graph shown therein, curve a represents the 
time constant T as a function of the traveling speed of the fiber material 
and curve b represents the resistance of the rpm potentiometer as a 
function of the traveling speed of the fiber material. 
Instead of measuring devices incorporated in the trumpet 18, there may be 
used other measuring instruments such as measuring rollers or the like. As 
a setting member, as an alternative to the doffer 4 or the feed roller 1, 
a feeding device (not shown) arranged upstream of the card may be used. 
Such setting member thus may be the drive for the delivery rollers in a 
feed chute of a fiber tuft feeding device supplying a fiber lap to the 
carding machine. Such a drive and delivery rollers are, for the purposes 
of the regulating system according to the invention, considered as forming 
part of the carding machine. 
In case the starting speed of the carding machine is determined by an 
external fixed resistor rather than by the base rpm setter, then for the 
starting speed an external I-value with fixed magnitude is to be applied. 
It will be understood that the above description of the present invention 
is susceptible to various modifications, changes and adaptations, and the 
same are intended to be comprehended within the meaning and range of 
equivalents of the appended claims.