Abstract: A clamp is disclosed to be mounted on a yarn spinning machine and, if a roving of the yarn should break, serves to clamp the roving preventing it from further unravelling. The clamp comprises a housing body including a member for defining a passage guide for the roving and a blocking element mounted by the housing body to be moved by a biasing spring from a detained position to a roving clamping position. A sensor is provided to sense the breakage of the roving for actuating an electromagnet for releasing a lever that normally engages and holds the blocking member in its retained position, whereby the blocking element is moved by the spring to it's clamping position to thereby retain and clamp the roving against the member. A guide channel is attached to the housing body and further supports a fastening mechanism for mounting the clamp to the spinning machine.