Constant speed and tension beam let:off motion - adjusts to tension via infinitely variable pulleys and gears

An arrangement for maintaining the unwinding of the warp threads from the beam in a loom at constant speed and tension, includes a train of intermeshing and easily interchanged gear wheels together with a pair of split, "V"-belt pulleys forming a variable transmission. The firt variable speed pulley is driven from the loom main shaft, and the variation of the transmission ratio of the belt pulleys is effected bya system of connecting rods and levers responding to the tension on the warp threads. The gear train is formed by two pairs of wheels linked by a worm to the beam. One of the gears is keyed on the worm shaft, and the worm engages with a worm wheel attached coaxially to a gear wheel engaging with another on the beam shaft. The linkage responding to the warp yarn tension includes a rocker with a cylinder at one end over which the warp ends run, and a vertical connecting rod at the other which joins a horizontal lever with a counterweight. This is connected to the levers altering the widths of the variable speed "V"-belt pulleys. The arrangement improves the working conditions of the variable speed belt transmission so that it works accurately and reliably at very low speeds. The variable speeds pulleys are driven continuously by the loom main shaft turning at the same high speed so that they are not dependent upon the transmission through a train of gears. The speed of the beam cna thus be accurately adjusted. Dans le dispositif de l'invention, on règle la vitesse de rotation de l'ensouple 2 en fonction de la tension des fils de chaîne 3 au moyen d'une paire de poulies 24, 29 à diamètre variable dont le diamètre est réglé par un système de bielles et de leviers 15, 21, 32 qui est asservi à la tension des fils de chaîne.