Patent DE-19925271-A1 (DE)
Title: Sliver drawing unit has an electronic control to position the drawing rollers at a given rotary angle on a stoppage while maintaining the draft condition of the sliver
Inventor: HARTUNG REINHARD
IPC: D01H5/32
Filed: 1999-06-02
Abstract: The sliver drawing unit has an electronic control unit (26) which registers the rotary angle position and/or the direction of rotation of the drawing rollers at the drawing roller sections (I-III) while the drawing unit (2) is operating or at rest, from the signals received from the incremental rotary movement transmitter system. At least one roller section (I-III) is set into a given position, by control of the motors (19,20).  The electronic control (26) can set the draft of the sliver (5) in and/or in front of the drawing unit (2), by control of the motors (19,20) to give a specified drafting action. On a stoppage, the exit rollers (I) and the entry rollers (III), or the entry (III) and center (II) rollers, can be moved around a given and small rotary path in the working direction (A). The length of the rotary path is at least equal to the reverse roller rotation through relaxation of the sliver (5) on a stoppage. After the rollers (I-III) have been rotated by the specified movement path, their rotation is stopped. The rollers (I-II) are all braked until they stop, and then the center roller (II) is accelerated slightly in the working direction. To cut off the machine, after a stoppage, the main electromotor (20) is switched off and the control motor (19) is switched on and then off. The rotary speed of the main motor (20) is reduced from its working level to zero, and the speed of the control motor (19) is brought down from the working speed initially to a level above zero and then down to zero. When the drawing unit motors (19,20) are switched on, the positions of the roller sections (I-III) are set to a given drafting position, and any position deviations from their nominal settings are corrected by moving the actual rollers (11-14) into their proper settings and then they are accelerated to their working speeds. The entry rollers (III) or the entry (III) and center (II) rollers can be accelerated slightly on a reverse turning in the working direction (A). The set rotary path length is 0-4 mm, or it is zero and the reverse rotation is lifted by a slight acceleration in the working direction (A), or the rotary path is zero and the reverse rotation length matches the small movement path length in the working direction (A). The sliver path length in the working direction (A) is 0.1-4.0 mm. On a stoppage at the exit rollers (I,12,11), the sliver in the main drafting field can be accelerated by a slight rotation of the entry (III,14) rollers or the entry (III,14) and center (II,13) rollers. The incremental rotary path transmitter (31,32) has a high resolution, and can show the direction of roller rotation. It can be a magnetic incremental rotary path transmitter (31,32). The transmitter (31) is at the rollers operated by the first motor (19), and can show the rotary speed of the rollers and their rotary angle positions in addition to the rotating direction. The transmitter (31,32) is encapsulated, and is linked to the electronic control unit (26). The control unit (26) determines the roller rotary speeds, the rotary angle positions and/or the direction of rotation and, on a stoppage, can rotate all or some of the rollers (I-III) against the working direction by a given rotary path length.