rockers 5 which in turn rest by a pivot shaft 4 on support brackets 2 each free arm of the two rockers 5 is biased by a compression spring 7 supported by a rest 8 on one of the support brackets 2 so as to be pivotable about a spindle 9 the compression spring 7 is connected to arm 5 by a tip 10 which fits within a notch 11 of the arm 6 of the rocker 5 the compression spring can be pivoted in such manner about the pivot shaft 9 that the tip 10 also can also be caused to fit within other notches 13 and thus provide an adjustable bias force each of the two support brackets 2 can be affixed in height adjustable manner at the end faces of lateral parts 16 of the frame of the weaving machine a vertical and undercut groove having edges 34 is present in the region of the end face of the lateral part 16 the groove guiding a guide fitting 19 of the support bracket 2 guide fitting 19 is in the shape of a hammer head the hammer head shaped fitting 19 rests by guide surfaces 32 facing the support bracket 2 on the matching surfaces 33 of the edges 34 of the undercut groove and includes a thread engaged by an adjustment screw 17 within the groove the head of the screw 17 resting on a plate 18 which forms an upper boundary of the groove and is affixed to the lateral part 16 by rotating respective adjustment screws 17 the height position of each of support brackets 2 and hence that of the deflecting roller 3 may be adjusted the weight of the support brackets 2 and of.