GB2099862A - Weft insertion in shuttleless looms - Google Patents

Abstract

A drive wheel 10 for engagement with a weft inserter 4 is mounted on a shaft 40 driven by a pinion 42 meshing with a toothed sector 46 which is pivoted at 48 and is connected to a reciprocatory drive comprising a connecting rod 54 extending from a rotary crank 50. The connection between the connecting rod 54 and the sector 46 is made through a pin 56 capable of sliding in a radial slot 58 under the control of a lever 60 pivoted at a point 62 which is offset from the straight line extending from the pivot 48 along the axis of the pinion 42. As a result, the connection point on the pin 56 is located further from the pivot 48 at the reversal points of the oscillating movement than at the mid-point of this movement, thus leading to an enhanced reduction of speed at the reversal points. <IMAGE>

Description

SPECIFICATION Weft insertion in shuttleless looms This invention relates to shuttleless looms, that is to say looms in which the weft is inserted into the warp shed by means of a weft inserter which is reciprocated into and out of the shed. The weft inserter includes a weft carrier supported by a member which may be either rigid, e.g. in the form of a spear or rapier or flexible, that is to say in the form of a band or tape. With either type the weft inserter may carry the weft along the whole length of the shed or along only part of the shed, e.g. one half. With this later arrangement the weft may be carried along the remainder of the length of the shed by, for example, a second weft carrier which is caused to reciprocate from the other side of the loom and to which the weft is transferred at an intermediate change-over point.

Whether the weft inserter is rigid or flexible, the drive may be basically the same in that it is transmitted through a driving wheel engaging with the weft inserter, the wheel normally being toothed to engage with a corresponding row of teeth on the weft inserter, which teeth, in the case of a band or tape are defined by the spaces between a row of perforations. In order to reduce the required reciprocation the driving wheel must turn through a few revolutions first in one direction and then the other and one common form of mechanism for producing this result comprises a relatively small pinion which is fixed to the same shaft as the driving wheel and which meshes with a pivoted toothed sector which is caused to reciprocate about its pivot.The sector may reciprocate through an angle in the region of ninety degrees, producing several revolutions of the pinion for each stroke, thus leading to a corresponding number of revolutions of the driving wheel and corresponding reciprocatory stroke of the weft inserter.

The reciprocation of the toothed sector may, in its turn, be produced by a rotary crank or eccentric having a connecting rod of which the other end is pivotally connected to the toothed sector. Each revolution of the crank or eccentric thus produces a cycle of reciprocation of the sector. This form of drive is particularly suitable for the purpose because the rotary motion of the crank or eccentric causes the connecting rod and hence the toothed sector to decelerate towards the end of each stroke, to dweil instantaneously at the reversal point and then to accelerate again up to its maximum velocity at mid-stroke. This reduction in velocity at the reversal points is most useful since it greatly facilitates the pick-up of the weft at the beginning of the insertion stroke and the release of the weft at the end of the stroke.

Particularly if the weft is to be transferred to a second weft carrier at an intermediate point across the shed, this is an extremely critical operation which is facilitated by the reduction of speed.

A toothed sector represents only one example, although the commonest, of a toothed member by means of which the reciprocatory drive is transmitted to the driving wheel. Better mechanical balance can be obtained if a complete wheel is used Instead of just a sector, although only a proportion of its toothed circumference is operative in transmitting the drive. Another possibility is that the toothed member should be in the form of a rack which is guided so as to remain in mesh with the pinion and which is pivotally connected at one end to a pivoted lever arm which, in its turn, is caused to rock to and fro by a .connecting rod as already described. Such an arrangement is the direct mechanical equivalent of a toothed sector in that exactly the same degree of deceleration and acceleration is obtained at each of the reversal points.For the purposes of the present specification, the part driven by the connecting rod will be referred to as the pivoted member.

According to the present invention the connection between the connecting rod and the pivoted member is made by way of a member capable of movement in relation to the pivoted member so that the connection point moves along a path extending generally radially to the pivotal axis of the pivoted member, (preferably in the general plane of the pivoted member) the position of the connection point along the path being varied by means of a pivoted control lever connected to the movable member and the pivot of which is located at a point offset from the straight line extending from the pivot of the pivoted member along the axis of the meshing pinion and so related to the pivot of the pivoted member that the connection point on the movable member at the reversal points of the oscillating movement than at the mid-point of this movement.

As a consequence of this the drive to the pivoted member is transmitted to it at a distance from its pivotal axis which increases in the vicinity of the two reversal points and thus augments the reduction in speed at these points which is inherent in a drive of this type.

Preferably the pivot of the control lever is located on the same side of the pivot of the pivoted member as the meshing pinion. As a result, the drive is transmitted to the pivoted member at a distance from its pivotal axis which is still further increased in the vicinity of the two reversal points, as will be described in more detail later.

The principle involved can best be described by reference to the accompanying diagrammatic drawings, in which: Figure 1 shows the driving mechanism for a weft inserter on a shuttleless loom; Figure 2 is a view to a reduced scale showing part of a loom incorporating the drive mechanism of Figure 1; and, Figure 3 is a view of an alternative construction for part of the driving mechanism of Figure 1.

Turning first to Figure 2, a weft inserter comprises a weft carrier 2 and a flexible tape 4 having one end fixed to the weft carrier 2. The tape 4 has pitched perforations which mesh with the teeth 8 (better seen in Figure 1) of a driving wheel 10. While travelling through the warp shed the tape 4 and carrier 2 are supported by a low friction surface 12 on the sley 14, passing between spaced guides which control lateral movement. In the position shown, in which the weft carrier 2 is outside the shed, the tape 4 is supported by a continuous arcuate guide 6 carried by the end frame 18 of the loom. The sley shaft is shown as 20 and carries both the sley 14 and reed 24. As so far described, the arrangement is quite standard and the weft inserter 2 can operate in any of the different ways previously described.

The driving wheel 10 is mounted on a shaft 40, best seen in Figure 1 and it is with the drive mechanism to this shaft that the present invention is concerned. At the end remote from the driving wheel 10, the shaft 40 carries a bevel pinion 42 the teeth of which mesh with teeth 44 along the edge of one face of a sector 46 pivoted at 48 and constituting one example of the pivoted member referred to previously. In the position shown, the sector 46 is in the middle of its stroke and it is caused to reciprocate so that the pinion 42 rotates first in one direction and then the other, making a total of approximately two revolutions as the sector 46 moves through a complete stroke in one direction, the driving wheel 10 making a corresponding number of revolutions and thus serving to drive the weft inserter in one direction or the other along the length of its travel.The sector 46 is caused to reciprocate by an eccentric 50 turning about an axis 52 and having a connecting rod 54 which is connected at its further end to a pin 56. In previous constructions of mechanism of this type, the pin 56 has generally been fixed to the sector 46 so that rotation of the eccentric 50 produces reciprocation of the sector 46 with a reduction of velocity and an instantaneous dwell at each reversal point corresponding to the two limits of travel of the carrier 2.

in the construction in accordance with the present invention, as illustrated in Figure 1, the pin 56, instead of being fixed to the sector 46 is capable of sliding movement along a slot 58, being controlled for movement along this slot by a control lever 60 which is pivoted to the pin 56 at one end and is able to rock about a fixed pivot 62 at the opposite end which, as can be seen, is offset from the straight line extending from the pivot 48 along the axis of the pinion 42.If the pin 56 were fixed to the sector 46 it would move along the circular arc indicated by the dotted line B which is centered around the pivot 48. instead, owing to the presence of the control lever 60 and the slot 58, the pin 56 follows the arc indicated as A which is centered about the pivot 62, the pin thus moving outwardly along the slot 58 as the sector moves towards either of the two reversal points. The extent of movement of the pin 56 along the slot 58 is represented by the separation between the two arcs A and B at the reversal points and it will therefore be understood that since the distance of the pin 56 from the pivot 48 has been increased in the ratio of the separation of the radius of the arc B, the velocity of the sector 46 is decreased in the same ratio.This leads to a corresponding reduction in the speed of the inserter 2 so that the natural variation in speed which is inherent in the type of drive using an eccentric and connecting rod is augmented at any point by the separation between the two arcs A and B, being zero at mid-stroke (i.e. as illustrated in Figure 1) and a maximum at each reversal point.

Various characteristics illustrated in Figure 1, although typical are nevertheless not essential. As has been previously described, the sector 46 may be replaced by a complete wheel in order to improve the mechanical balance, although only the same range of teeth would be used as on the sector 46. Again, the sector could be replaced by the combination of a pivoted arm and a linear rack pivoted to the end of the arm and held in mesh with the pinion 42.

As illustrated, the pivot 62 is located on the same side of the pivot 48 as the pinion 42. In other words, the pivots 48 and 62 are on opposite sides of the pin 56 so that the curvatures of the arcs A and B are in different directions, thus enhancing the separation between them. The pivot 62 is shown as lying on a continuation of the line joining the pivot 48 to the pin 56, but if displaced slightly to either side of this line, the result is to make the separations between the two arcs on opposite sides of the pin asymmetrical so that the speed reduction is different at the two reversal points. This feature may be useful if a lower speed for the inserter is required at one end of its travel than at the other end.A greater separation between the arcs A and B can be obtained by the use of a shorter control lever 60 with consequent movement of the pivot 62 to the right, thus increasing the curvature of the arc A.

A similar result, but ieading to a reduced separation between the two arcs can be obtained if the control lever 60 extends to the right hand side of the pin 56 with its pivot located to the right of the pivot 48. If, for example, the pivot 62 is located at a point shown as 62' this leads to an arc shown as A' of which the curvature is in the same direction as that of the arc B and the separation is produced solely as a result of the different radii of the two arcs. As shown, the point 62' is located on the straight line joining the pin 56 and the pivot 48, but if it is displaced from this line to one side or the other, an asymmetrical result is achieved in the same way as previously described.

As shown, the slot 58 is straight and parallel with the radius drawn from the pivot 48 to the pin 56. Neither of these two features is strictly essential and minor departures may be made both in the straightness of the slot and its parallelism with the radius, but anything more than minor departures lead to risk of the mechanism jamming. The slot 58 can, however, be formed along any radius of the sector 46 provided that the position of the eccentric 50 and the connecting rod 54 are adjusted accordingly. Generally speaking, the connecting rod 54 needs to be approximately at right angles to the radius through the slot 58 for the mid-stroke position as illustrated, but again minor departures from this are possible, leading to slight asymmetry of the strokes in the two opposite directions.

In the construction illustrated the pin 56 constitutes the movable member referred to originally and the slot 58 constitutes the radial path. Although a pin has been illustrated for simplicity, better mechanical results are obtained by use of a parallel-sided block sliding in the slot 58. Instead of sliding, the movable member can be mounted to rotate so that its point of connection to the connecting rod 54 and to the control lever 60 follows an arcuate path along the same general line as the slot 58.

As mentioned previously, the slot 58 can lie along any radius of the sector 46 and since, as already mentioned, the sector 46 can be replaced by a complete wheel, it follows that the slot 58 can lie along any radius of the complete circle provided once again that the positions of the eccentric 50 and the connecting rod 54 are adjusted accordingly. One such variation is shown in Figure 3 in which only the sector itself shown as 46', the connecting rod shown as 54' and the control lever shown as 60' are included. In this modification the slot shown as 58' lies along a radius of a complete circle of which the sector 46 forms part, an extension 70 being provided for this purpose, and again the connecting rod 54' is shown as being substantially at right angles to the line joining the pin 56' and the pivot 48'.In this Figure, the arc which would be followed by the pin 56' if fixed to the sector 46' is shown as C and the arc which it follows under the control of the lever 60' as D. These two arcs have opposite curvatures, thus producing a relatively large separation at the two reversal points. As explained in relation to Figure 1, the two arcs could have their curvatures in the same direction but of different radii.

It will be understood from the foregoing that various of the features illustrated in Figure 1 are capable of variation and will lead to variation in the separation of the two arcs A and B and hence in the conditions at the two reversal points of the inserter 2. These conditions need to be chosen in accordance with the precise operating characteristics of the loom as a whole and other components of the loom such as the weft supply and (if the weft is to be transferred to a second weft carrier at an intermediate point across the shed) the characteristics of the second weft carrier. Generally speaking, the transfer of the weft at an intermediate point of the shed is more critical than the pick-up of the weft at the end of the shed and the mechanism will generally be designed to give optimum conditions at the former even to the detriment of the latter.

Claims (4)

1. A weft inserter drive mechanism for a shuttleless loom comprising a drive wheel for engagement with the weft inserter mounted on a shaft driven by a pinion meshing with a pivoted toothed member which is connected to a reciprocatory drive comprising a connecting rod extending from a rotary crank or eccentric, the connection between the connecting rod and the pivoted member being by way of a member capable of movement in relation to the pivoted member so that the connection point moves along a path extending generally radially to the pivotal axis of the pivoted member, the position of the connection point along the path being varied by means of a pivoted control lever connected to the movable member and the pivot of which is located at a point offset from the straight line extending from the pivot of the pivoted member along the axis of the meshing pinion and so related to the pivot of the pivoted member that the connection point on the movable member is located further from the pivot of the pivoted member at the reversal points of the oscillating movement than at the mid-point of this movement

2. A weft inserter drive mechanism according to claim 1 in which the pivot of the control lever is located on the same side of the pivot of the pivoted member as the meshing pinion.

3. A weft inserter drive mechanism according to claim 1 in which the pivot of the control lever is located on the opposite side of the pivot of the pivoted member to the meshing pinion and the connecting rod is connected to an extension of the pivoted member on that side of the pivot of the pivoted member.

4. A weft inserter drive mechanism according to any one of the preceding claims in which the pivot of the control lever is located on a continuation of the straight line joining the pivot of the pivoted member to the connection point between the pivoted member and the control lever.