A. Field
The invention relates to a method for operating a loom, having a first drive motor which drives a first element, such as a batten, and at least a second drive motor which drives a second element, such as a shedding mechanism.
B. Related Art
In looms, the motions of the individual elements must be chronologically adapted to one another. To achieve this chronological adaptation when independent drive motors are used, it is known to detect the rotational angle position of a main shaft, which in particular drives a batten, and to synchronize the drive motor or drive motors of the other elements with these rotational angle positions. This synchronization presents problems, since the main shaft rotational speed changes. Before the beating-up of an inserted weft yarn, the rotational speed of the main shaft decreases. When the batten with the weaving reed reaches the rearward position, the rotational speed of the main shaft increases. If it is a goal to synchronize the drive motor of a shedding mechanism, for instance, with the main drive motor that drives the batten, then the drive motor of the shedding mechanism must likewise perform the nonuniform motion. As a result, the shedding mechanism drive motor, which is already subjected to a heavy load, and the shedding mechanism itself are both subjected to further loads, which are intrinsically not necessary.
To reduce the energy expenditure required for fully synchronous operation, it is known (European Patent Disclosure EP 0893535 A1) to embody the control and regulating device such that a switchover can be made between hard and soft regulation. In hard regulation, which is employed during the starting of the loom, the drive motor of the shedding mechanism follows the main drive motor with very precise synchronization. During normal weaving operation, a switchover to soft regulation is then made, in which mode the drive motor of the shedding mechanism is allowed to lead or trail the main drive motor with slight deviations from synchronized operation.
It is also known (European Patent Disclosure EP 0946801 B1) to control a selvedge tuck-in device of a loom independently of the main drive motor, in accordance with a program. In the process, monitoring is done as to whether desynchronization beyond an allowable value is occurring. If this desynchronization occurs, a correction is made in accordance with a correction program.
It is known to drive all the elements of a loom by means of one common main drive motor. To make it possible to search for a weft yarn if a weft yarn has broken, it is also known (European Patent Disclosure EP 0161012 B1) to provide an additional motor for the search for the weft yarn and for slow motion. In a search for the weft yarn the main drive motor is decoupled, so that by means of the additional motor, either only the shedding means, or the loom, can be moved at low speed.
It is also known (European Patent Disclosure EP 0726345 A1) to design the loom drive such that the same functions, that is, normal weaving operation, searching for a weft yarn, and the slow motion, can all be performed with only a single main drive motor.
It is also known (French Patent Disclosure FR 2660672 A1) to provide a drive motor for the shedding means, in particular a Jacquard mechanism, and a further drive motor for all the other elements of the loom. The two drive motors are connected to one another via an electronic comparator. The electronic comparator constantly compares the information from two pickups, namely one pickup that detects the rotation position of the main shaft of the loom and one pickup that detects the rotation position of the drive motor for the shedding means, and in this way assures that the two motors operate synchronously.
It is the object of the invention to operate a loom of the type defined at the outset such that if at all possible no unnecessary loads have to be overcome by the drive motors for elements.