order to be able to open the yarn clamp of the associated rapier with very reduced vibration in order not to damage the weft yarn the lever 61 is aligned parallel to the warp yarns of the shed not shown the head part with the pressing part 610 must be narrow so as to be pivotable as indicated by a double arrow s into the shed between the warp yarns without damaging the same the operative position 61 39 of the lever 61 is shown in chain dotted lines in fig7 by means of a small downwards pivoting movement the lever 61 when in the operative position 61 39 can press the lever actuating the rapier yarn clamp the clamp opener 6 according to the invention can be constructed to take up less space than the known clamp openers de os 3 224 708 this is very important since the physical conditions in a loom below the cloth path are usually difficult and do not allow the known devices to be used an even more compact clamp opener can be devised if an intermediate transmission for the tape wheel drive is abandoned as already suggested for the servomotor the circumstances shown in.