guides. There is a continuing development of new techniques to improve weft control or conditions during the weft-transfer operation, and four quite different strategies may be noted. First, the yarn clamps in the rapier heads can be positively actuated at the transfer (in addition to any positive actuation at weft pick-up and release) as on the Dornier and Iwer K2-330 100ms.Second, control of rapier location (perpendicular to the. weft direction) during the transfer can be improved. Note the guidance of the rapier head by the reed and race board on some rigid rapier loom such as the MAV, and the use of electromagnets in the central zone of the race board on the Meteor loom, for instance.

Third, the rapier displacement-timing characteristic may be elaborated with the aim of giving more favorable conditions in the transfer region. As an example, we may note the varying pitch along the screw-cam on the Vamatex Propeller loom. Fourth, there is the use of indirect transfer. That is, problems of yarn handing during transfer are avoided, by transferring the yarn clamp from one rapier to the other than the weft yarn itself, which remains gripped by the same clamp throughout (Fig.1 e.)

If indirect transfer is used to insert weft from only one side of the loom, a given yarn clamp will have to be returned empty o the supply side ,after use, and different methods of doing so are encountered on the two currently available looms. On the Acutis loom there are several yarn clamps, and these are returned empty to the supply side by a conveyor running under the weaving zone, in a manner reminiscent of the Sulzer machine. On the Mintiss each rapier enters the shed carrying a clamp, and these are exchanged at transfer, one bringing yarn from the supply side, the other returning empty.

The ability to insert single pick is usually required, to give the normal range of weaves, but some weaves can be produced most efficiently if in addition, when required, picks of more than one yarn can be inserted together in a single-loom cycle. It is only possible for given yarns to be inserted dither together in this way or separately, as required, on shuttle-less looms, and this facility has been provided on some rapier looms eg Dornier Iwer.

(The possibility of simultaneously inserted picks twisting needs to be considered though.)

Finally, it may be remarked that now a days rapier looms almost always insert weft from one side of the loom only. Apart from avoiding the need to duplicate the weft supply and selection systems, each rapier has then to perform only one role, that of giver or taker, and can be designed specifically for that role. Insertion from both sides was common, since it can readily be used together with loop transfer to produce semi-conventional selvedges.

Types of Rapiers

The rapiers used for weft insertion usually take the form either of rigid rods or of flexible metal or plastic tapes or bands. Both rigid and flexible rapiers have long been used on comparable numbers of makes of loom. Rigid 'rods can, of through the shed from outside the working width. In some cases, though, guidance within the working width is provided at the shed boundary by a board, possibly aided by the upper warp sheet or reed, or both, presumably to facilitate control over rapier location at weft transfer. In contrast, rapiers consisting of flexible tapes must always be guided within the working width. In some cases the rapiers are guided at the shed boundary as described, but more often guide plates mounted on the slay at short intervals across the width are used. The motion given to the plates is such that they enter the shed through the bottom warp sheet as the sley moves back, and leaves by the same route prior to beat-up.

Rigid-rapier method lends itself to simultaneously inserting weft in two sheds one above the other, using a separate pair of rapiers for each shed, Rapier looms of this kind have been found to have advantages for the face to face weaving of warp-pile fabrics, and such looms are also available for weaving two separate fabrics without pile, one above the other.