Textiles: spinning – twisting – and twining – Apparatus and processes – Monitor and control
Reexamination Certificate
2000-11-20
2002-01-22
Calvert, John J. (Department: 3765)
Textiles: spinning, twisting, and twining
Apparatus and processes
Monitor and control
C057S022000, C057S023000, C057S261000, C057S262000, C057S263000, C057S265000, C057S400000, C057S404000, C057S405000
Reexamination Certificate
active
06339921
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a textile yarn piecing device with an evaluation arrangement for determining parameters of an automatic yarn piecing process, and more particularly to such a piecing device having at least one sensor device for measuring the yarn diameter and for detecting the position of a respective measuring point in relation to the yarn piecing created.
BACKGROUND OF THE INVENTION
As demands have been increasingly made on the yarn production process, continuously higher demands are being made on the creation of yarn piecings formed in the yarn production process. Following yarn breaks, the process of creating piecings and the subsequent re-start of the spinning process is usually performed at the individual spinning stations of the open-end rotor spinning frames by a piecing device, often referred to as a piecing cart, which travels along the spinning frames.
For example, following a yarn break, which triggers the piecing process, the time before spinning is re-started again at the spinning station is of varying length. The delivery of sliver is deactuated when the yarn break occurs. However, the opening roller continues running and continues to separate fibers from the sliver previously fed. In order to produce uniform conditions for the spinning re-start, the fiber feed from the sliver is equalized before every spinning start to achieve as uniform as possible a pre-feeding amount of sliver. Spinning starts with the start of rotation of the rotor. A control device, for example a microprocessor, calculates the acceleration required for the rotor to reach operating speed from pulses detected as a function of the number of rotor revolutions, so that a preset number of revolutions of the rotor for the spinning start is reached after a constant amount of time, and determines the time of starting the pre-feeding of sliver based upon the acceleration. Fibers are again combed out of the sliver and are aspirated over the edge of the stopped rotor during the time following the equalization of the fiber presented from the sliver and the time of re-actuation of the delivery device for the operational fiber feed. This causes a certain delay in achieving the required fiber flow and possibly a thinner extent of yarn downstream of the yarn piecing during the acceleration of the fiber delivery device to its delivery speed. Pre-feeding of fiber takes place during a predetermined time and is deactuated thereafter. In the course thereof, it is also possible to control the amount of delivered fibers by setting the delivery speed, besides the length of pre-feeding. Following the deactuation of fiber pre-feeding and the return of the trailing end of the broken yarn, i.e., the so-called upper yarn, the fiber delivery is turned on again shortly prior to the start of the fiber withdrawal in order to compensate for the delay. The amount of fibers now fed into the rotor is placed on top of the previously delivered amount of fibers in the rotor. Starting of the fiber withdrawal takes place after a defined amount of dwell time of the yarn in the rotor groove, during which the end of the upper yarn to be connected has time to break open the ring of fibers in the rotor and to become connected with the delivered fibers. The yarn withdrawal speed is set to a value corresponding to the instantaneous number of rotor revolutions while maintaining the desired yarn twist. Up to the point at which the operating number of rotor revolutions is achieved, the yarn withdrawal speed follows the increase in the number of rotor revolutions. Besides the continued running of the fiber flow after the delivery has been deactuated, and the delayed actuation of the delivery, the flow of fibers can also react with a delay during the increase of the delivery speed. This can lead to the yarn becoming too thin while the rotor is being accelerated. In particular, this occurs distinctively at low delivery speeds.
To prevent this undesired deviation from the desired yarn thickness, it is possible to perform a supplementary delivery of additional fiber. In the course thereof, the delivery speed of the fiber feed device is increased over a set value in order that the respectively required amount of fibers arrives in the rotor. A thinner extent in the yarn can also still occur even with the performance of a supplementary delivery of additional fiber, if the latter is performed to an insufficient extent. If the supplementary delivery of additional fiber is of too large a size, a thick place is caused in the yarn, which is also undesired. Efforts are therefore made to make the amount of the supplementary delivery of additional fiber as accurate as possible from the start. With the increasing feed path of the sliver, the addition is reduced. The supplementary delivery of additional fiber is terminated after a delivery length, which corresponds to the staple length, has been achieved. Starting at this time, the amount of fiber is delivered without any supplementary delivery of additional fiber. Such supplementary delivery of additional fiber during the start of spinning have been described, for example, in German Patent Publication DE 40 30 100 A1, or in the publication by Raasch et al., entitled: “Automatisches Anspinnen beim OE-Rotorspinnen” [Automatic Piecing in Open-End Rotor Spinning], in MELLIAND Textilberichte [Textile Reports], April/1989, pp. 251 to 256.
The demands made on the accuracy of the lengths of such additional deliveries of fiber have been noticeably increased because of the increasing requirements made on yarn quality, and in particular with the demands for greater spin drafting and smaller rotors. With a draft of 100 times, an error of 0.5 mm in determining the length of the supplementary delivery of additional fiber causes an error in relation to the yarn of 50 mm in length. With 350-times the draft, this error affects a length of 175 mm of the yarn. These examples clearly illustrate how great the demands made on accuracy are when determining the length of a supplementary delivery of additional fiber.
In accordance with the above mentioned prior art, the first piecing is already created with a supplementary delivery of additional fiber. In this manner, it is intended to prevent thinner extents, along with the danger of yarn breaks and interruptions during the spinning start connected with this supplementary delivery of additional fiber. To determine the supplementary delivery of additional fiber, an empirical value is employed, which is a function of the average staple length of the fibers used. While the staple length of synthetic yarn is known, the staple length of cotton or mixed yarns can only be determined with sufficient accuracy by means of extensive laboratory tests. Since the staple length is proportionally a part of the determination of the length of the supplementary delivery of additional fiber, deviations between the staple length used for the calculations and the actual staple length lead to errors in the determination of the length of the supplementary delivery of additional fiber, which has the above described results and in particular have a special effect in case of long drafts.
Further criteria, for example the clothing of the opening roller, the number of revolutions of the opening roller and the rotor acceleration time (with its effects on the comb-out time), have an effect on the required extent of the supplementary delivery of additional fiber. However, this effect can only be determined empirically, by means of generating and evaluating a large number of further piecings. Thus, a sufficiently exact size of the supplementary delivery of additional fiber for a qualitatively satisfactory piecing can only be determined following a relatively elaborate, and in particular time-consuming, optimization phase. The optimization requires the manual intervention of the operators. The quality of the results is definitely dependent on the experience of the operators.
OBJECT AND SUMMARY OF THE INVENTION
It is accordingly an object of the present inv
Lassmann Manfred
Mertens Heribert
Calvert John J.
Hurley Shaun R.
Kennedy Covington Lobdell & Hickman LLP
W. Schlafhorst AG & Co.
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