Textiles: weaving – Weft manipulation – Weaving with stationary weft supply
Reexamination Certificate
1999-11-29
2001-03-13
Falik, Andy (Department: 3741)
Textiles: weaving
Weft manipulation
Weaving with stationary weft supply
C139S194000, C242S365400
Reexamination Certificate
active
06199598
ABSTRACT:
This invention relates to a measuring feeding device for a jet weaving maching having a stationary storage body for storing yarn in windings, from which yarn store the yarn can be withdrawn generally overhead of the storage body.
In the measuring feeding device according to U.S. Pat. No. 4,372,498 two moveable stop elements are provided and are placed offset from one another in the axial direction of the storage body. In winding direction ahead of the circumferential position of both stop elements a brake shoe is provided which is pressed onto the windings in the yarn store when the stop element at the withdrawal side has moved into the release position. The brake shoe is affecting the yarn store in the final phase of the insertion earlier than the yarn is caught at the stop element when same is brought into its stop position. By this measure the stretching beat (whiplash effect) in the withdrawn yarn ought to be damped. At the end of the insertion the brake shoe has to be returned into its rest position to not obstruct the further forward motion of the yarn store towards the withdrawal side of the storage body.
In the measuring feeding device according to EP 0 599 930 B1 a yarn clamp is associated with the stop element. Said yarn clamp clamps against the storage body the yarn as caught by the stop element in its stop position and in the direct vicinity of the stop element. As soon as the stop element is moved back into the release position the yarn clamp also opens.
In the measuring feeding device according to U.S. Pat. No. 4,781,225, the stop element is formed by a cyclically moveable yarn clamp consisting of a pawl movably suspended in the storage body and of a stationary counterfort provided outside of the storage body.
Measuring feeding devices are used in jet weaving machines in order to measure the inserted weft yarn length by means of the stop element, because the insertion device of the jet weaving machine operating with a nozzle system is unable to precisely define the inserted weft yarn length. In case of an operation fault, e.g. a yarn breakage downstream of the measuring feeding device or within the weaving shed or caused by other reasons, at least the jet weaving machine is switched off to allow mending of the fault. During or after a switch-off-action the yarn caught at the stop element in its stop position may contain significant yarn tension. If then said yarn tension is abruptly set free, then the at least last yarn windings in the yarn store on the storage body at the withdrawal side are loosened causing the formation of free loops and entangling of the yarn at components of the measuring feeding device. Said effect is particularly disadvantageous with highly twisted yarns and is very difficult to repair. Said yarn tension may be set free for example when the stop element manually is moved from its stop position into the release position in order to be able to further draw-off yarn by hand to mend the operation fault. The tension in the yarn can also be set free if the yarn is released from a gripper (water jet weaving machine) or from an optionally provided, controlled yarn clamping, braking or tensioning device (air jet weaving machine) upstream of the insertion nozzle. Loops, entanglements, fallen off or occasionally caught windings occurring due to the relaxation of the yarn back into the yarn store on the storage body might undesirably prolong the time needed to repair the resulting operation fault.
It is an object of the invention to improve a measuring feeding device of the type as mentioned above such that operation faults of the kind as mentioned above can be repaired quickly and without excessive waste of yarn material.
The brake shoe clamps the yarn store onto the storage body in the winding direction behind the circumferential position of the stop element even after the stroke of the stop element into its release position or in case of a sudden yarn relaxation downstream of the measuring feeding device and hinders the yarn windings on the yarn store against loosening, falling off or being caught elsewhere. The yarn store remains essentially correctly in the condition which it had when the operation fault occurred. This reduces the time for repairing the operation fault. Since the brake shoe is affecting the yarn store in a clamping fashion it is at any time possible to further manually pull-off a yarn length as necessary to mend the operation fault, since the braking effect of the brake shoe can be adjusted such that the yarn can be withdrawn by hand without breaking. Furthermore, the braking effect of the brake shoe is adjusted such that, particularly during the stroke of the stop element into its release position, the tension acting in the yarn is dissipated slowly.
The yarn clamping device serves to assure a proper yarn store during and after operation faults or during the repair of operation faults, respectively. For such cases, the brake shoe can be adjusted into its yarn clamping position and can be held there. It is further possible to move the brake shoe after each insertion cycle into the yarn clamping position in order to attenuate the influence of the stretching beat (whiplash effect) of the yarn in the yarn store at the end of an insertion cycle. As a result the operational performance of the measuring feeding device can be improved for normal operation, since then the yarn store and the free yarn end both are stabilised.
The brake shoe is pressed onto the yarn store in response to actuation of the release means moving the stop element into its release position. During a subsequent movement of the stop element into its release position, e.g. for repairing an operation fault or during the abrupt relaxation of the yam, no disordered condition of the yarn store can occur. If the brake shoe is already in its yarn clamping position when the stop element moves into its release position, the brake shoe further on will be held in the yarn clamping position. In the other case the brake shoe reaches its yarn clamping position with the movement of the stop element into its release position, optionally even earlier, and will then be held in its yarn clamping position.
The brake shoe is moved each time from its rest position into the yarn clamping position, when the operation-stop-switch responds and switches off the jet weaving machine and occasionally also the measuring feeding device.
The brake shoe may be returned into its rest position by hand or by means of a control command as soon as the operation fault is repaired or where there is no further danger for the yarn store.
The brake shoe automatically is returned in the rest position if the operation fault-switch is deactivated in order to restart normal operation.
For a desired safety function that the brake shoe in its yarn clamping position acts onto a partial section of at least the last yarn winding at the withdrawal side, which partial section extends from the yarn store to the yarn stop element.
The brake shoe in its yarn clamping position is positioned a circumferential distance behind the stop element and extends in the axial direction of the storage body. The brake shoe thus brakes at least the partial section of the last winding, seen in withdrawal direction, which partial section extends from the yarn store to the stop element, but advantageously also brakes additional windings of the yarn store at the withdrawal side. Thanks to the circumferential distance between the brake shoe and the stop element a short part of the yarn between the brake shoe and the stop element remains free to move during the stroke of the stop element into its release position, while the brake shoe solely hinders a further movement of the yarn on the storage body.
The brake shoe is longer in the axial direction than in the circumferential direction and in one embodiment, the brake shoe can be configured finger-like.
In one embodiment, the brake shoe defines a yarn clamping surface having a cross-section which substantially matches with the peripheral curvature of the storage body. As such, the braked yarn
Falik Andy
Flynn ,Thiel, Boutell & Tanis, P.C.
Iro AB
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