GB2088921A - Stranding machine - Google Patents

Abstract

In a stranding machine, a double-twist unit (12) is fed with strands twisted by a twister (11) rotated at a speed which is substantially twice the speed of a flyer (33) of the double-twist unit. The twister produces substantially all of the final twist in the strands, and is preceded by a strand straightener (10). <IMAGE>

Description

SPECIFICATION Improved stranding machine As is known, double-twist machines are currently used for making strands of steel wire and, more frequently, wires of non-ferrous and threads of non-metallic materials.

The double-twisting machines are fed by hanks or reels which pay off the wire from supporting members resting on a floor or secured thereto. The wires are introduced in the double-twisting machine wherein they are set into strands and a pitch is obtained which is one half that which would be expected as a function of the number of revolutions made by the double-twisting machine.

As a matter of fact, every individual strand receives a first twist as it enters the machine, and has a second twist at the place where it is collected by fixed members.

The strands so produced are collected on bobbins which are rotated about their axes, which are fixed in space in the interior of the doubletwisting machine.

The stranding pitches are impressed to the strand by acting on the speed of advance of the strand after that it has received both the first and second twist, that which is a characteristic of the machines referred to above.

This processing way pulls out of the feeding hanks or reels, wire lengths which geometrically correspond to the formation of a strand having a pitch twice the actual final pitch: the latter, conversely, is obtained just by duplicating the twisting step.

An object of the invention is to provide a machine wherein the strand is not exposed to a detrimental unravelling, which is often experienced in the conventional machines, but, rather, takes the exact geometrical configuration which is expected on the basis of the ratio between the feeding speed of the wires and the speed of rotation of the twisting machine.

In order that this result may be achieved, a machine has been envisaged, which comprises a wire feeding set, a rotary set which receives said wires therefrom and subjects them to twisting so as to make up a strand having the required final pitch, and sends the so-formed strand to an arcuate guiding race which is rotated at a speed equal to about one half the speed of the rotary set, the stand being fed back by a pulley or an equivalent member which rotates integrally with the guiding race, towards a takeup drum underlying said stationary-axis guiding race.

The objects of the invention, as well as the essential structural features of the machine according to the invention, will be best understood from the ensuring description of an exemplary embodiment thereof, illustrated in the accompanying drawings, the single Figure of which diagrammatically shows the machine according to the invention.

As shown in the drawings, the machine shown therein is composed of three sets in alignment, namely: a straightening unit 10, a rotary tackle 11, and a finishing twisting unit 12.

The units 10 and 11 are mounted on bearings 14, so as to be rotated integrally with one another as driven to rotation by the drive transfer mechanism 1 6 receiving its drive by a shaft 1 7 actuated by a motor 1 8.

Both the unit 10 and the set 11 are conventional as themselves, as the former provides to straighten out the wires it receives from a feeding unit symbolically shown at 1 9.

The device 11, also conventional as itself, consists of a tackle 20-21 on which the strand being formed is guided. The pulleys 20-21 are driven by a gear 1 3 which receives its drive from a gear train 1 5, so as to pull in the strand being formed at a preselected speed which, combined with the speed of rotation of the whole unit, impresses a definite twist to the strand.

The rotary tackle is integrated by all those conventional devices which ensure a correct arrangement of the wires which are united to make up a strand.

The set 12 comprises two rotary hubs 30 positioned at the ends and connected by drivetransfer mechanisms 31 to the shaft 17, said hubs 30 being borne at 32.

Between the two hubs 30, an arcuate guiding race 33, is installed, on which keepers 34 through which the strand is led. The strand route proceeds towards the pulley 35 which feeds it back towards a dragging unit 36 upstream of a takeup drum 37.

The dragging unit 36 and the takeup drum 37 are both placed in a cradle 38, the latter being supported for rotation by the hubs 30 aforementioned, so as to remain at stillstand as the latter are rotated. It deserves attention to note that the kinematic drive transfer ratios between the motor unit 18 and the sets 10-11 1 and 12 are such that the former are rotated at a speed which is substantially twice that of the latter.

In actual practice, in the embodiment shown herein, the drive-transfer set 1 6 has a transmission ratio which is twice that of the set 31.

The operation of the machine is therefore as follows.

From 19, the stranding machine receives wires along a direction, A, which is shown in dash and dot lines to mark the route followed by the stranded wires. The wires are straightened at 10 and stranded at 1 1, as pulled by the tackles of the relevant unit. From the latter, the stranded wires energe with a pitch and a geometrical configuration which are just the final ones.

The strand is then fed onto the guiding race 33, wherein the strands, in theory, would undergo a first twist at the intake and a second twist between the pulley 35 and the take up drum 37, the axis of the latter being stationary.

Inasmuch as the guiding race 33 is rotated at a speed which is one half the speed of the set 11, it could be surmised that the strand may lose one half of its twist: however, this fact does not take place with the machine according to this invention because the strand takes on the guiding race the expected correct configuration by virtue of the centrifugal action it undergoes, without any pressure or forced push against the keepers 34 or on the guiding race, so that it is allowed to be rotated about its own axis while retaining the pitch imparted thereto by the set 11: at the most, the pitch could be only slightly increased, but without unravelling in any case.

As it exit the pulley 35, the strand is, anyhow, subjected to an additional twist because it is forwarded to the stationary unit 36, and the strand is exactly blocked again at the twist impressed thereto by the unit 11, provided that the speed of the unit 12 is one half that of the sets 10-11.

It is apparent that slight deviations from such a speed ratio for the units in not critical, because, if the speed of the twisting set 12 is slightly greater or smaller than one half the speed of the upstream unit, the strand shall merely undergo a slight additional twisting or untwisting action, but its geometrical configuration shall not be modified in the slightest.

By the machine according to the invention, since the stranding to the final pitch is carried out in correspondence with a single unit and in a single stage, it becomes possible, by properly controlling the positions of the wires, to obtain a strand having an exceptionally accurate fidelity to the expected geometric configuration and without irregularities in its shape.

It is apparent that, should the wires be directly fed to the twisting unit 12, they would undergo a first half-twist at their inlet and, under these conditions, they would be fed back by the pulley 25 to receive the the second half twist. However, it has been ascertained in practice that in a strand which has been only half-twisted, unravellings are experienced to many instances and they cannot be taken up by the subsequent final twisting step, so that an unsatisfactory product is the result.

In the light of the principles of this invention as hereinbefore defined, it is apparent that a number of modifications can be introduced in the machine, which has been described hereinbefore by way of example only.

The configuration of each individual component unit is not particularly critical, inasmuch as each unit carries out a processing step which is technically conventional: thus, the straightening device 10, which is advantageous but not essential, can both be fixed and rotary.

The rotary unit 11 which forms the strand can have any conventionally known configuration, inasmuch as it is only supposed to apply to the wires a strand-forming twist having an accurately defined pitch and configuration, to feed the twisting unit 12.

The twisting and winding unit 12 can also be equipped with all the ancilliary and complementary apparatus of known make in order correctly to collect the strand: it is of utmost importance, more particularly, that the guiding properties thereof from the inlet to the feed back for the second twist are such as not to entrain the strand into rotation so as substantially to unravel it, but, rather, the strand must be set free to be rotated about its own axis as far as practicable in correspondence with the guiding race 33, so as to retain the twist impressed thereto by the previous twisting unit 11 unaltered.

The machine according to the invention is adapted to strand wires or non metallic threads, both bare and lined, for example those having plastics material linings.

Claims (5)

1. A stranding machine comprising a wirefeeding unit, a rotary set receiving said wires and subjecting them to twisting so as to form a strand having the final expected pitch, and sending the thusly formed strand to an arcuate guiding race, rotated at a speed one half the speed of the rotary set, the strand being fed back at the end of the guiding race by an idler the axis of which is rotated together with the guiding race towards a takeup drum which underlies said guiding race and has a stationary axis.

2. A machine according to Claim 1, characterized in that said rotary set comprises means for dragging the wires at a sliding speed which is in a preselected ratio relative to the speed of rotation of the set, to define the twisting pitch.

3. A machine according to Claim 1, characterized in that said rotary set forming the strand is associated to a unit for straightening the wires fed to form the strand.

4. A machine according to Claim 1, characterized in that the strand is retained on said guiding race so as to be free to be rotated about its own axis.

5. A machine according to any of the preceding Claims, substantially as hereinbefore described and illustrated in the accompanying drawings.