Textiles: fiber preparation – Working – Drafting
Reexamination Certificate
1999-03-08
2001-01-09
Calvert, John J. (Department: 3741)
Textiles: fiber preparation
Working
Drafting
C019S0650CR, C019S150000, C226S188000, C492S010000, C492S016000
Reexamination Certificate
active
06170125
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application No. 198 09 875.8 filed Mar. 7, 1998, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to an apparatus for feeding slivers to a drawing unit of a fiber processing machine, particularly a draw frame in which the slivers are pulled from coiler cans by a withdrawing roll pair after they run through a plurality of supply rolls which are mounted on a sliver intake table and which have different circumferential speeds.
The slivers which are, by means of the roll pairs (supply roll and pressure roll) of the intake table, guided to a sliver drawing unit, enter the nip of the withdrawing roll pair in a state stretched about 1.05 times after they run on rider rolls. The intake draft equals the ratio of the circumferential speed of the rider rolls to that of the withdrawing rolls. In practice, the intake draft is set such that each sliver runs between the intake rolls and the rider rolls at the smallest possible tension, but without any snag.
In conventional arrangements the supply rolls have been driven, via transmission mechanisms (belts, sprockets, and the like) by the drive of the draw frame, that is, the motor which forms part of the drive for the drawing unit. In such arrangements the supply rolls have, as a rule, identical circumferential speeds. The slivers may often run at unlike tensions, for example, because of different distances between the supply rolls, on the one hand, and the intake roll pair, on the other hand. Since, however, the slivers which are only slightly twisted, are composed of loosely interconnected fibers, they are coherent only by virtue of the friction between the fibers and are not able to take up any mechanical tension stress without undergoing, at the stressed locations, an undesired elongation which may adversely affect successive processing steps.
It is a further disadvantage of the above-outlined prior art arrangement that while all the coiler cans at the intake table initially contain sliver quantities of equal length, often residual sliver quantities remain in some of the coiler cans, while others have already been emptied. In their travel path from the coiler can to the intake of the draw frame the slivers have to change direction several times. Since the locations of reorientation involve friction, forces are generated during the sliver travel which lead to unintended drafts as a function of the properties of the material and the free path lengths of the sliver between the coiler can and the machine. Such parasite drafts have a stationary and a non-stationary draft component. The stationary draft component leads to the above-noted non-simultaneous emptying of the coiler cans since the fiber processing machine pulls the slivers with a constant sliver speed rather than with a constant mass flow. The non-stationary component which is generated by the own dynamic properties of the sliver during the withdrawal process, leads to fluctuations in the number of the inputted sliver.
German Auslegeschrift (application published after examination) 1,115,624 discloses an arrangement in which the supply rolls, dependent on their distance from the drawing unit, have different diameters and, accordingly, different circumferential speeds. The different circumferential speeds decrease as the distance from the drawing unit increases so that a slippage between the slivers and the supply rolls as well as a sagging of the sliver between successive supply rolls is compensated for and thus the slivers, upon entry into the withdrawing roll pair of the drawing unit have, with a good approximation, identical tensions. In this arrangement the supply rolls which are closest to the drawing unit have—assuming an identical rpm for all supply rolls—larger diameters than the more remote supply rolls. All the supply rolls are driven by a common drive shaft. It is a disadvantage of such a prior art arrangement that an adaptation of the intake tension between successive supply rolls is not possible as the operational conditions change. It is a further drawback that the slivers have only approximately the same tension.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved apparatus of the above-outlined type from which the discussed disadvantages are eliminated and which, in particular, makes possible an adjustment of the intake tension of the slivers in case of changed operational conditions and further permits an evening of such intake tensions.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the sliver supplying apparatus for simultaneously feeding a plurality of slivers to a draw frame includes an intake table; a plurality of supply rolls supported in a series by the intake table for guiding the slivers from the coiler cans to the draw frame; and an rpm-setting device for individually setting a circumferential speed of the supply rolls. The rpm-setting device includes a roll drive independent from the drive of the draw frame.
By virtue of the fact that for the supply rolls a driving assembly is provided which is independent from the driving assembly of the drawing unit and which, in particular, comprises individual, adjustable drives, the circumferential speed of at least one supply roll may be adjusted and adapted to the intake tension in a simple manner in case of changes in operational conditions. In this manner, an evening of the intake tension of the slivers among themselves is possible in a particularly advantageous manner. The apparatus according to the invention counteracts undesired tensions by suitably adapted rpm's (circumferential speeds) of the supply rolls. In particular, the undesired tension of all introduced slivers may be made identical, and thus, as a result, the coiler cans are all simultaneously emptied.
The invention has the following additional advantageous features:
A separate, rpm-regulated electric motor, such as a servomotor is connected to each supply roll and is coupled with an electronic control and regulating device for setting predetermined rpm's.
The servomotor is a d.c. motor or a frequency controlled three-phase squirrel cage motor.
The rpm of the electric motor may be set in a stepless manner.
The electronic control and regulating device has a desired rpm setter which is connected with memories and/or measuring elements.
Data representing properties of fiber to be processed are applied to a memory.
At least one measuring element measures the speed of the slivers.
Between the drive motor and the supply roll a transmission element, such as a gearing is provided.
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Steinert Thomas
Temburg Josef
Calvert John J.
Kelemen Gabor J.
Tr{umlaut over (u)}tzschler GmbH & Co. KG
Venable
Welch Gary L.
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