Textiles: spinning – twisting – and twining – Apparatus and processes – Piecing up
Reexamination Certificate
2001-11-27
2004-07-13
Calvert, John J. (Department: 3765)
Textiles: spinning, twisting, and twining
Apparatus and processes
Piecing up
C057S264000
Reexamination Certificate
active
06761022
ABSTRACT:
BACKGROUND
The invention relates to a process and an apparatus to monitor a yarn piecing joint on a spinning machine with a plurality of spinning stations to which a piecing robot equipped with a yarn piecing apparatus with adjustable yarn piecing speed can be presented, with each spinning station or the piecing robot having a yarn monitoring apparatus to monitor yarn quality.
In a known yarn or thread cleaner for an open-end spinning machine (German patent 39 28 417 A1) respective thickness tolerance thresholds for different length ranges are entered to monitor the yarn quality of the spun yarn. When the yarn thickness tolerance is exceeded, the affected segment of the yarn is cut out and the yarn is pieced anew. The quality criteria essentially depend on the length and the diameter of the spun yarn, so that the length of the measured yarn must be known precisely to judge whether the quality criterion for the corresponding length class has been met or not. The length is here measured by entering the yarn production speed of the spinning machine which is constant once the nominal yarn production speed has been reached, and by measuring the time. The yarn length then results by multiplying the time with the yarn draw-off speed. During the piecing phase the yarn is however accelerated from the yarn draw-off speed to the nominal production speed, so that here no constant yarn draw-off speed is determined. It is therefore not possible to classify yarn defects during the piecing phase, since the yarn cleaner is lacking information concerning yarn length.
In a known apparatus of this type to monitor a yarn piecing joint on a spinning machine (German patent 40 30 100 A1), a yarn-monitoring device is installed at each spinning station to monitor yarn thickness during running production. During the piecing of the yarn by a piecing robot that can be presented to a spinning station, the yarn thickness is monitored by means of a second yarn-monitoring device that is built into the automatic spinning unit. On the one hand quality control with respect to yarn thickness is carried out using the results of the second yarn monitoring apparatus, and on the other hand statistical data is collected to optimize the piecing process of the piecing robot. In both instances, measuring data is used that is taken several centimeters upstream and downstream on the yarn from the yarn-piecing joint. The start and the end of measuring is determined by the start of the rotor run-up and the rotor acceleration. However, an additional measurement of the rotor speed is necessary for this. It is however not possible in that case to take into account the exact yarn position of the piecing joint of the current speed of the yarn to determine the yarn defect per length unit.
In a known method to monitor yarn quality of a yarn piecing joint (German patent 196 49 314 A1) the thickness profile of the yarn is also measured a few centimeters before and after a yarn piecing joint, and the measurement is then evaluated based and the precise position of the yarn piecing joint is determined on basis of that evaluation and the quality of the yarn piecing joint is judged by different criteria. In the evaluation it is assumed that the distance between two measuring points measured by the yarn monitoring device along the yarn can be associated with a predetermined measuring resolution without taking into account that the yarn length between two measuring points changes due to the acceleration in the acceleration phase during piecing. The subsequent finding of a yarn-piecing joint based on several measuring points is very time sensitive and therefore results in a delayed recognition of a defect on the yarn-piecing joint or in the adjoining yarn areas. Furthermore, because of the imprecise tarn length assignment to the measuring points, an exact determination of the yarn length defects is not possible.
SUMMARY
It is therefore a principal object of the invention to provide a method and an apparatus to monitor a yarn piecing joint on a spinning machine by means of which simple and precise establishment of the relationship between tarn piecing joint and measuring time or measured value and a precise classification of length and thickness defects in the yarn are possible. Additional objects and advantages of the invention will be set forth in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In an embodiment of the apparatus to monitor a yarn-piecing joint according to the invention, a yarn monitoring apparatus to monitor the yarn quality is installed on a piecing robot or at every spinning station of the spinning machine. Following a yarn breakage or for a bobbin replacement at a spinning station, the piecing robot can be presented to the spinning station, this piecing unit carrying out piecing of the yarn at the piecing station in a known manner.
Based on the piecing values set and optimizable on the piecing robot, the evolution of speed, over time, of the yarn draw-off, i.e. the velocity profile, is calculated in advance from the machine parameters of the piecing robot. Thanks to the transmission of piecing parameters of the piecing robot via a communication system to the yarn monitoring apparatus, the latter receives information concerning the progression of the yarn draw-off during piecing. The piecing parameters can in that case be transmitted continuously in the piecing phase from the piecing robot to the yarn monitoring apparatus, either before the beginning of piecing or at the beginning of piecing.
The piecing parameters may comprise a complete time profile of velocity or only individual acceleration, speed and/or time data from which a velocity-time profile or a yarn position-time profile is calculated first in the yarn monitoring apparatus. Based on the distance from the yarn piecing point to the yarn monitoring apparatus and on the velocity profile, the time can be calculated when the yarn piecing joint runs through the yarn monitoring apparatus. Thereby the characteristic yarn data obtained by the yarn monitoring apparatus can be assigned to the yarn-piecing joint, to the upper yarn of the yarn used for piecing and to the yarn segment following the piecing joint. Derived magnitudes, such as a length-dependent yarn thickness defect, can therefore be calculated exactly.
Additional piecing parameters to be taken into account in the evaluation can be the length of the piecing joint that depends among other things on the drawing-off speed and the rotor diameter at the spinning station. From the starting point and/or the end point of the yarn piecing joint or some other reference value, the yarn monitoring apparatus can then assign the measured values to the yarn-piecing joint via the directly received yarn piecing length or from the calculated yarn piecing length.
The yarn monitoring apparatus to monitor the yarn quality during piecing can in this case be provided at the piecing robot, at the spinning station, or at both. In the latter case, quality monitoring can be carried out at will with either of the two yarn-monitoring apparatuses.
If a yarn monitoring apparatus is provided only at the spinning station, it is used to measure the yarn piecing joint as well as the running yarn. Therefore the manufacturing costs of the spinning machine are reduced and the control expenditure for the spinning machine is simplified considerably since no control device or communication line is necessary for a yarn monitoring apparatus at the automatic spinning unit.
The yarn quality monitored by the yarn monitoring apparatus is in this case preferably the yarn thickness which can be determined e.g. optically. Additional quality parameters that can be monitored alternatively or in addition by the yarn monitoring apparatus are the yarn mass per yarn length that can be determined capacitively for example, spectral properties in order to detect e.g. foreign matters in the yarn, the surface aspect, e.g. as a measure of the emergence of fiber ends from the yarn, which is measured
Calvert John J.
Dority & Manning
Hurley Shaun R
Rieter Ingolstadt Spinnereimaschinenbau AG
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