Patent GB-483816-A (GB)
Title: Improvements in electric drives for loom shuttles
IPC: H02K41/025
Filed: 1936-07-25
Abstract: 483,816. Loom picking-motions. EISSELT, G. July 25, 1936, No. 20613. [Class 142 (iii)] [Also in Group XXXV] The invention relates to an electric loom shuttle-drive of the type comprising a travelling field motor in which a stator core 2 wound with polyphase windings extends from end to end of the shuttle race and actuates the shuttle asynchronously, the shuttle 3 having an iron armature 1 with a short-circuited winding. According to the invention, in order to obtain high acceleration and speed, the weight of the shuttle is kept low by making the pole pitch at most equal to half the length of the shuttle and reducing the cross-section of the armature iron at places 5 where the flux has a low value, the frequency applied to the stator winding being a multiple of the normal fifty periods to compensate for the reduction in speed which would otherwise result from the small polepitch employed. It is explained in the Specification that the voltage applied to the stator winding can be resolved into two components namely, the operating voltage due to that part of the stator covered by the armature, and a component due to the impedance of the winding in the uncovered part of the stator. To reduce undesirable effects resulting from the change in relative values of the two voltage components, the windings 12, Fig. 2, of a wide loom may be connected to the supply through an automatically acting induction regulator 8 which increases the voltage applied to the stator windings 12 at starting. Series capacity 6 may be provided to reduce the inductance of the windings. In a modification, Fig. 4, the windings are divided into three sections, viz. : starting and retarding sections 13, 15 and a middle section 14 over which the shuttle travels at maximum speed. The number of turns of the section 14 is made large to reduce the magnetizing current. The change of connections is effected by a switch drum such as 7, Fig. 2, operated by the loom, and the winding of a section is switched in only after entrance of the armature into that section and is disconnected before the armature leaves the section. In the case of a narrow loom, there is no section over which the armature travels at uniform speed and the accelerating and retarding sections each extend over half the width of the loom. In order to make the resistances &c. of all the phases equal, two of the phases in a three phase system may have alternately long and short end connections in successive groups of windings. Mechanical means may be employed for starting the shuttle at each end of the race. As shown in Fig. 7, the shuttle on entering the box 22 compresses a spring 21 between the picker 24 and the wall 26 of the slay, and is held by the swell 25. When the swell is released by a member 27 movable from the slay, the shuttle is given an impulse by the spring. A tension spring may replace the compression spring. To hold the spring in the loaded condition a trigger pivoted to the slay may engage the picker and is releasable by an adjustable wedge secured to the wall of the loom. The spring may be tensioned by means of a warp protector connected to the picker and driven by the slay motion.