Field of the invention.

This invention concerns the perfecting of a thread accumulator-feeder for textile machines, used for knitted goods, hosiery and similar.

State of the art.

There already exist thread accumulator-feeders for the above-mentioned use, which usually have a spinning cylinder on which is accumulated, ready for use and in the form of a loop, a certain regulated quantity of thread which is supplied to a textile machine to the degree and/or tension previously established. However, these known accumulator-feeders are not without their drawbacks. In fact, the thread which accumulates upon them, because of

the air resistance, the centrifugal force and the inertia to which it is subjected, tends to detach itself from the spinning cylinder and, consequently, suffers from tugging and changes in tension, which may compromise the regularity of feeding to the textile machine and the quality of the material, namely, the knitted goods in question. This also happens, as in some well-known cases, when the accumulator is equipped with instruments, such as a sley or disk, for guiding the thread which is accumulated and destined for use. In fact, these instruments are ill-suited for ensuring the adherence of the thread to the cylinder, forcing the thread into compulsory and tortuous paths that have a negative effect on the tension and if there are knots or size anomalies they may cause the thread to break. The situation is even worse if the threads are ver fine microfibres and fed at high speed.

The invention.

The aim of this invention is to avoid the above-mentioned problems and drawbacks, using a perfected thread accumulator-feeder, consisting of a spinning cylinder around which loops of thread are wound and which is enclosed within a protective container, the latter rotating together with the cylinder and designed to keep the thread tight to the cylinder, thereby preventing it becoming detached and subject to tugging, whatever the force or the

resistance that the thread may undergo as a consequence of the rotation, stopping and restarting of the cylinder.

The protective element may take the form of a cap or a ring, and can be made to rotate in various ways. Ideally, the cylinder will be conical in order to favour a parallel arrangement and the feeding of the thread loops until the thread leaves the device.

There is a circular opening between the cylinder and the protective element through which the thread can pass without touching the adjacent surfaces and with a negligible winding tension. This has the avantage of removing all obstacles to the thread flow while not affecting the supply and tension of the thread directe towards the machine, particularly at high speeds and/or with delicate threads such as microfibres. The device may also be equipped with a micro-switch for controlling the stop and restart of the cylinder, according to the quantity of thread accumulated ; the micro-switch being located inside the cylinder itself.

Brief description of the drawings.

Further details of the invention will become clearer from the following description, made with reference to the enclosed drawings, in which : Fig. 1 shows a cross-section of one version of the device, with a cap-type protection element according to the invention;

Fig. 2 shows a cross-section of a version of the device with a ring-type protection element; Fig. 3 shows a cross-section of the device with the favoured method of control of the protective element rotation; and Fig. 4 shows a partial cross-section, according to the arrows IV-IV in Fig. 3.

Detailed description of the invention.

An accumulator-feeder of the type shown is intended to receive a thread 10 from a reel upstream, to be gathered in loops and then fed to a machine downstream, according to the arrow 11, following the demand for thread made by the machine itself.

The accumulator includes a spinning cylinder 12 with a shaft 12', driven by a motor 12". This cylinder may consist of numerous columns 13, which may be cylindrical or otherwise and which extend between two flanges or 14,15, one at the back which may be rotating (functioning as a control means for a switch that stops the cylinder) and one at the front, in the direction of the thread feeding. Ideally, the columns are laid out according to the surface of a truncated cone, with the larger diameter at the level of the rear flange or head 14. In this way, the cylinder has a conical movement from the rear flange or head 14 forwards to the front flange or head 15, favouring the parallel

arrangement and feeding of the thread loops onto the cylinder. The front flange or head 15 has at least one border rim 16 over which the thread passes when it leaves the cylinder in the direction of the user machine.

According to the invention, mounted concentrically around the cylinder 12 and the front flange 15, there is a protective element 17, which has no contact with any part of the cylinder and, together with the latter, defines a circular opening 18 for letting through the thread which is directed towards the user machine. The thread may be conducted through a guide bushing 19 either on board the device or distant from it, on the user machine, but still on the same axis as the cylinder.

Ideally, the protective element 17 is made from transparent material, in the form of a cap 17a, as in Fig. 1, or in the form of a ring 17b, as in Figs 2 and 3.

When it has the cap shape 17a, the protective element 17 is held by a support 117, guided and movable axially with respect to the fixed body 20, so as to unsheathe and give access to the cylinder 12.

When it has the ring shape 17b, the protective element 17 is supported at the edges by means of rollers 20', which, in their turn, are mounted on and supported by the fixed body 20 of the device. In either case, whether the protective element 17 is of the cap-type 17a or ring-type 17b, it rotates

together with the cylinder 12. Its rotation may be activated by a shaft from the transmission that drives the cylinder or autonomously by its own motor, which is not shown.

Better still, as shown in Figs 3 and 4, the protective element 17 may be activated by means of permanent or temporary magnetic elements, mounted facing each other on the cylinder, for example at the height of the front flange 15 and, opposite, on the protective element 17. In this way, the magnetic field created by the magnets 21,22 means that the rotation of the cylinder 12 induces the protective element 17 to follow it, although there is no physical link between the two components.

The protective element 17 allows the thread to pass through a circular opening 18 towards the user machine, according to the arrow 11, but, at the same time, prevents the thread and its loops from becoming detached from the cylinder, thereby eliminating the possibility of tugging and unwanted changes in tension when the device stops and restarts and the thread is requested by the user machine.

Finally, it should be noted khat the device, in place of or in addition to the rotating flange 14, may be equipped with a means for stopping the cylinder when sufficient thread has been accumulated on it and for restarting it when the quantity of thread has been reduced to the pre-established minimum. This means is best achieved by use of a micro-

switch 23 located inside the spinning cylinder 1. 2-Fig. 3- and a movable contact 24, which protrudes radially from the cylinder through the columns.

This movable contact is pressed by the thread loops, opening the electrical circuit and stopping the device once sufficient thread has been accumulated. When there is no thread, the movable contact opens, closing the circuit and restarting the device.