Device for the rotational drive of a weft prefeed and measurement apparatus in a shuttle-less weaving machine

Claim 1

In a device for the rotational drive of weft prefeed and measurement devices, in a shuttle-less weaving machine which comprises a weft selector enabling a selected one of a plurality of weft threads supplied from respective lateral weft stores to be inserted at will, with a respective prefeed and measurement device having a rotary finger which stores a predetermined length of weft thread in a cyclical manner disposed in the path of each weft thread, the improvement which comprises: for each weft prefeed and measurement device, an electric motor having a controlled angular position having its output shaft coupled to the shaft of the prefeed and measurement device; a control assembly comprised of electronic power circuits associated with said electric motors; means for detecting the angular position of the main shaft of the weaving machine and for translating this position into electrical signals; and means which can be switched by a weft selection control of the machine and adapted to process the electrical signals supplied by said detecting means, by supplying them to the power circuits associated with the electric motor of the selected prefeed and measurement device, the means for detecting the angular position of the main shaft of the weaving machine and for translating this position into electrical signals comprising a coder wheel which is rotationally coupled to the said main shaft and comprises three concentric circular tracks, with a first track comprising unequally spaced divisions and provided such that each angular interval between two successive divisions corresponds to a basic rotation of a motor during an acceleration stage of the prefeed device associated therewith, with a second track comprising equally spaced divisions for the control of the rotation at a constant speed of a prefeed device and with a third track comprising unequally spaced divisions and provided such that each angular interval between two successive divisions corresponds to a basic rotation of a motor during a deceleration stage of the prefeed device associated therewith, the signals produced by these three tracks being transmitted to the means which may be switched from the weft selection control and are designed to supply the signals to the power circuits.