A third type of rapier has recently come into use . Like the rig i d rapier this has lateral rigidity, but consists of two or three 'telescopic' components. One component is connected directly to the rapier drive, and its weft-way position determines that of the second component, by means of a mechanism such as, the rapier thus becomes fully extended when' inserted in to the shed, and the components telescope together when it is withdrawn.

Rapier Mounting

The form of slay motion used on a rapier loom is affected by where the rapiers are mounted. Thus, the warp-way position of the rapier, relative to the fell, has to be such that the shed formed with the given heald motion is big enough for them. In addition, it is essential that the rapier be kept out of the way of the reed, even though a large part of the cycle (typically about two thirds) is normally used for weft insertion on rapier looms. Two mounting arrangements have to be distinguished, In the first, the rapier are mounted on the slay and so share is warp way movement. This means there is no question of collision between reed and rapier, and the rapier can be guided within the working width. The slay motion can be continuous, and the slay can have a simple crank drive. The slay can have a simple crank drive, the slay mass is, however, increased by having to carry the. Rapier, and the rapier-driving mechanism has to be one able to transmit motion from a fixed driving shaft to the moving slay.

The alternative arrangement is to mount the rapier in a fixed location on the loom frame, which simplifies the problem of transmitting motion to them. However, with a fixed mounting rapier guidance cannot be provided by a continuously moving slay, either inside the shed or at its boundaries. Moreover, a continuously moving reed would have to move much further away from the fell than the rapier. With rapiers mounted on the loom frame, therefore, the sley is normally cam driven and dwells virtually throughout the rapiers' motion in the reed path.

Nevertheless, in a few cases a continuously moving crank-actuated sley is used in conjunction with rapiers which are mounted on the loom frame. The rapiers may enter the shed nearer the fell than is usual and the sley moves back well beyond the rapier path. If the rapiers are in the shed for the usual fraction of the cycle, the distance from fell to rapier path has to be substantially less than the range of sley motion, and reducing the fell to rapier distance helps to keep this range down to an acceptable level. A smell shed size at the point of rapier entry is a disadvantage with warps liable to fail to form a clear shed. However. Such looms have established themselves and combine avoidance of the expense of a cam-driven sley with a simplification of the problem of actuating the rapiers.

In the former case the rapiers have to move further out beyond the selvedges than is necessary for weft insertion, to reconcile their continuous motion with the need to keep them clear of the working width until the weft-insertion stage of the cycle recurs. This has the disadvantage that the rapier reaches the point at which the weft is to be picked up having already attained a substantial fraction of its maximum velocity. On being picked up by such a rapier the weft velocity picked up by such rapier the weft velocity is abruptly increased from zero to a high value. Against this, the rapier drive can be a simple robust and relatively inexpensive crank-actuated mechanism.

A rapier displacement timing curve for a rapier whose path length is confined to that needed for weft insertion. This displacement has therefore to be confined to the appropriate part of the loom cycle too, and such motion is readily obtained from a cam actuated mechanism. During rapier displacement the forms of the two curves in Fig. 4 are the same, and it is clear that the velocity at which the weft is picked up is lower for the intermittent motion. the pickup velocity may still be appreciable though, as rapier velocity can increase very rapidly near the beginning of the displacement. During a Sino soidal displacement for example, a rapier would reach 0.4 of its maximum velocity within the first 5 percent of its range of motion.

Continuity of Rapier Motion

A distinctive feature of most rapier looms is that the weft'is attached to the insertion element, the rapier in this case, at a point near the entrance to the shed, rather than at the point from which it begins its motion - as on the Sulzer for example, or permanently -as on the shuttle loom (this enables multicolor weft devices to be particularly simple on rapier looms). Consequently weft insertion begins at whatever velocity has been attained by the rapier when weft is to be picked up.