Abstract: There is described a device for unwindng thread by means of which the bobbin can easily rotate about the pin when a pull is exerted on the thread, but which stops the bobbin very rapidly when said pull on the thread stops, in such a way that the thread is thus no more unwound. The cross-section of the pin when considered at a right angle to the lenthwise direction thereof and the inner cross-section of the bobbin sleeve, also as considered at a right angle to the lengthwise direction thereof, at least where the sleeve and the pin engage one another, are so selected as to make possible a sidewise movement of the bobbin relating to the pin and at least where the sleeve and the pin engage one another, the one cross-section is circular while the other cross-section has a shape which is substantially different from a circular shape.