the shed 20 i e between the foremost heald devices 1 and the abutment point 19 of the reed 11 the lower warp thread layers 22 and 24 lie at least approximately in the same plane correspondingly also the upper warp thread layers 21 23 and 25 lie at least approximately in the same plane in the region of the shed 20 this deflection of the warp threads is attained thereby due to different displacements of different heald devices vertical rods 31 are fastened to the upper frame limbs of the heald devices 1 2 3 4 and 5 these are guided to be vertically displaceable above the warp threads in schematically illustrated guides 33 fastened to the frame of the loom furthermore only schematically illustrated tension springs 35 are shown which at one end are fastened to the frame part 37 and at the other end engage at the rods 31 and pull the heald devices upwardly a heald device driving means comprises a shaft 53 which is rotatably journalled by means of bearings 51 in the frame of the loom and which extends at right angles to the planes containing the heald devices a cam disc 55 for each heald device is fastened rotationally fast on shaft 53 cams 57 can be mounted on cam disc 55 at points uniformly distributed around the disc circumference the cams can for example be mounted at circumferential points which are spaced from.