a weft accumulating method and assembly of a weaving loom for accumulating a lenght of weft thread to be inserted into a shed by a pick insertion assembly of the loom in which the accumulator comprises a weft supply ; includes a drawing off device off a predetermined length of weft thread from the supply ; at least one perforated cylindrical tube ; a fluid blowing device to blow the drawn off weft through the tube ; and a clamping device to open and close the end of the tube to accumulate weft thread in the tube when the device is closed and to supply the weft thread to the pick insertion assembly when the device is open .