Improvements in and relating to stranding machines

Abstract: In a stranding machine in which a strand or cable is led through a cradle or flyer (11), twisting of the strand or cable due to friction against guide means during its planetary or orbital motion about the axis of the cradle or flyer is prevented by causing the guide means (32,36) to be driven to rotate relatively to the flyer in such a manner that they remain stationary relatively to the strand or cable. The guide means preferably comprise articulated members (33,32,34;36,37) that extend along the path of the strand or cable.

Description: This invention concerns improvements in and relating to stranding machines and more especially to such a machine for production of cable which is of complex section and/or large dimension at higher speed than has hitherto been possible. In the manufacture of stranded cables or wire ropes, two systems can be used: the "monotorsion" and the "double twist". In the first system, the elements of the cable or rope can be fed from separate supply bobbins to a stranding head at which they are laid up to form the cable or rope, a twist or "lay" being imparted to the cable or rope by the rotation of an appropriate haul-off device. The fact that the cable leaving the haul-off device is rotating about its longitudinal axis requires that the final storage bobbin or reel upon which the cable or rope is to be wound must be rotated at the same speed. This system has the advantage that a perfectly formed cable can be produced. It has the corresponding disadvantage, however, that owing to the mass of the components that must be rotated at the same speed of rotation as the cable or rope, the stresses generated by centrifugal force correspondingly limit the maximum speed at which the cable or rope itself can be rotated, thus limiting the production speed of the complete installation. In the second system, the so-called "double-twist" stranding machine, the path of the cable is led along a rotary flyer carrying the cable to a winding bobbin which is inside the envelope of the rotating flyer. This bobbin is rotated only about its own axis for winding, but is otherwise stationary and thus does not cause the above mentioned stresses and limitations due to the rotating masses. However, such double-twist stranding machine is not applicable to the production of cables of high quality and/or of complex section, because the second twist disorders the sectional shape of the cable that has been formed in the first. There is also known, see DE-A-2118967, a method and apparatus for the production of a stranded element having the features of the precharacterising clause of Claim 1 or 2. Such a known arrangement, however, is primarily intended for the production of relatively fine thread or wire, and would not be applicable to the production of cable of complex section or large dimension, of the kind initially referred to. Moreover, to the knowledge of the present applicants, no machine having the features of the prior document referred to has been put into successful commercial production, and thus the features of such a machine are not well known in the art. It is accordingly an object of the present invention to provide an improved stranding machine that is particularly applicable to the production of cable or wire rope of complex section or large dimension at higher speed than has hitherto been possible in practice. It is also an object of the invention to provide for an improvement in the quality of the lay of such cable or wire rope. In accordance with the invention these objects are achieved by the characterising features of Claim 1 and Claim 2. Further preferred features and advantages of the invention will become apparent from the subordinate claims taken in conjunction with the following description and drawings. The invention is illustrated by way of example in the accompanying drawings in which; Fig.1 is a diagrammatic elevation of part of a cable stranding installation incorporating a device in accordance with the invention, Fig.2 is an elevation shown partly in section of the double-twist section of Fig.1, Fig.3 is a view similar to Fig.1 illustrating the drive transmission to the various stages of the device. Fig.4 is a sectional view of a detail of Fig.2, Fig.5 is a section on the line V-V of Fig.4, and Fig.6 is an elevation in diagrammatic form of the rotating haul-off section of Fig. 1. Referring to Fig.1 of the drawings, a stranding installation, for example for the laying up of wire rope comprises a rotating haul-off device indicated generally at 1, which comprises, in known manner, a pair of driven capstans 2 and 3, which draw the finished rope from a stranding head at the left hand end of the drawing and discharge the rope along an axial path 4 in the direction of the arrow 5 towards a take-up device indicated generally at 6. As will be well understood by one skilled in the art the haul-off device 1 is driven to rotate about the axis of the path 4 at a rotary speed to which the linear speed of the finished rope must be related in such a manner as to introduce into the rope the desired length of lay. The device 6 incorporates a storage bobbin or reel indicated diagrammatically at 7 which is arranged to rotate about its own axis 8 as required to take up the finished rope, but is otherwise stationary. The finished rope passes from its axial path 4, along which it leaves the rotating haul-off device 1, to the reel 7 along a path indicated diagrammatically at 9, proceeding in the direction indicated by the arrow heads 10. The rope passes through a flyer indicated diagrammatically at 11 in Fig.1, held by supports 23 and 24 arranged to rotate in mountings indicated at 12 in Fig.1. Considering the path 9 of the rope it will be seen that as the rope passes through the flyer 11 it is diverted from its linear path 4 at the point 9A, passes through the flyer along a part 9B of the path 9 radially spaced from the rotational axis of the flyer 11 and is then turned through 180° in a region 9C before exiting from the flyer 11 at a point 9D. At this point all of the rotation of the rope caused by the haul-off device 1 is effectively cancelled. From that point on there is no rotation of the rope about its own axis as the rope is fed onto the take-up bobbin or reel 7. The rope can now be fed from the point 9D along a fixed path to a point 9E from which the rope can be layered onto the take-up bobbin or reel 7 in a conventional manner. Although the reel 7 and the path of the rope thereto is shown only diagrammatically in Fig.1, it will be appreciated that the bobbin 7 and an associated means for guiding and layering the rope onto the bobbin or reel can be supported by appropriate means 11 in such a manner that the flyer 11 can rotate around the bobbin or reel 7 whilst the latter and the associated guide means remain stationary. Referring now to Fig.2, the flyer 11 and the associated means for guiding the rope will be described in more detail. The flyer 11 is of the so-called "bow" type. That is to say that the portion of the flyer carrying the rope is formed as a flexible strap or bow 20, ends 21 and 22 of which are anchored to hubs 23 and 24 that are mounted for rotation in bearings 26 of the mountings 12. The bow 20 carries on its internal surface a series of ball races 27 within which are mounted tubes 28 for supporting guide rollers 29 for receiving the rope. The tubes 28 and the guide rollers 29 may be free to rotate with the rope, or may be driven by means not shown to rotate at the same speed as the rope. The bow 20 is counterbalanced by a matching bow 30 carrying balancing weights 31 having a mass corresponding to that of the elements 27, 28, 29 of the bow 20. The hub 23 at the left hand end of the flyer in Fig. 2 carries a first guide means 32 for the rope in the form of a shaft the left hand end 33 of which is mounted coaxially within the hub 23 and the right hand end 34 of which is linked to the hub 23 at a point adjacent the bow 20 in such a manner as to allow rotation of the shaft about its own axis. The first guide means 32 is articulated by means of universal joints in such a manner that the whole first guide means can be driven for rotation from its left hand end, in order to transmit corresponding rotation to the rope sliding within the shaft via rollers 35 carried in the segments of the first guide means. The right hand hub 24 of the flyer 11 likewise carries second guides means in the form of a hollow shaft that is articulated in a similar manner to the first guide means 32 and which also has a series of rollers. The second guide means 36, like the first guide means 32, is mounted in the hub 24 so that it can rotate relatively thereto about its own axis, but its extremity 37 is nevertheless fixed to the stationary support of the take up bobbin 7 and cannot rotate. The rope passes from the first guide means 36 to the take up bobbin along the path shown in Fig 1. Referring now to Fig.3, the drive to the various elements of the device includes a main drive motor 40 which is arranged to drive the haul-off device 1, the first guide means 32 and the hubs 23 and 24 of the flyer 6 from a common shaft via gear trains 41, 42 and 43 respectively, the ratio of the trains 42 and 43 being one half of that of the train 41 so that the flyer 6 is rotated at the appropriate speed. A motor 45 drives the capstans 2 and 3 in known manner. Motors 46 and 47 of a common take-up unit, not illustrated in detail and held stationary on bearings coaxial with the bearings of the flyer 6 by means of a counterweight, serve to rotate the bobbin 7 and to drive a traverse for layering the cable on to the bobbin. In fig. 4. three separate elements of the articulated guide means are shown, in a sectional view on a plane containing aforesaid guide means axis. The expert will appreciate that they are shaped in a way so that they can be connected by consecutive cardan universal joints, as at 48 and 49. Each element internally contains sets of rollers 50 and 51, having axes lying in planes orthogonal to the axis of the respective element. As shown in Fig. 5. the sets of rollers are composed of couples, with the axes of consecutive sets alternately rotated through 90 with respect to one another so as to offer to the cable a continued support during rotation of the articulated shaft. In Fig.6. is shown furthermore how the tendency of the cable to leave the haul-off capstan, due to the centrifugal force, can be prevented. A set of rollers or a pre-tensioned continous belt 52 press the cable against the capstan; sets of rollers 53, 54 prevent the cable moving away from the right path. Whilst one embodiment of the invention has been described in detail above, it will be appreciated that various modifications may be made thereto without departing from the scope of the invention as defined in the appended claims. Thus although in the above arrangement the relative speeds of the flyer 11 and the first guide means 32 are such that there is substantially no twist imparted to the finished rope, these relative speeds could be so related as to allow a slight twist to be imparted to the rope as it passes through the cradel, for the purpose of tightening the lay of the cable before it is wound onto the bobbin 7. Also, although three separate means 32, 28, and 36, are described for guiding the rotating rope through the cradel 11, it would in principle, be possible to use only a single guide means. For example either the first guide means 32 could be extended over the full axial length of the cradle to point 37 and fixed at that extremity with respect to the bobbin or the second guide means 36 could be extended to point 33 and, at that point, be left free to rotate. Furthermore the advantage of avoiding or reducing twist on an element passing through a rotating cradle or bow can be obtained with machines of other types than that described. For example in the case of a so called "skip strander" the same principle can be used top prevent twisting of an element fed rom a supply bobbin and through a rotating bow, in order to improve "detorsion" of the strand as required in these machines. Also the use of any or all of the means 32, 28 and 36 on the bow of a normal double twist stranded will greatly improve the quality of the cable produced, even if reducing its productivity.

Claims: A method for the production of a stranded element such as a cable or wire rope wherein stranded cable is fed through a driven member coaxial with an axial end of a rotating flyer (11), is guided around the periphery of the flyer and is turned within the flyer through 180° relatively to the axis (4) of the latter, passing through an elongate flexible guide means (36) of which one end is fixed relatively to a stationary axis of a take up reel (7) within the flyer and the other end is guided within the periphery of the flyer so that it is driven to undergo a planetary motion with the stranded element guided thereby, characterised in that the stranded element is laid up and is driven to rotate by means located externally of said driven member, that said driven member also comprises an elongate flexible guide means (32) extending from said axial end of the flyer (11) to the periphery thereof and guided in said periphery for planetary motion relatively to the axis (4) of the flyer, and that the said driven member and the said flyer are driven at such relative speeds that a slight twist is imparted to the stranded element during its passage from said driven member to the elongate guide means (36) associated with the take up reel (7) in order to tighten the lay of the stranded element. A stranding apparatus comprising a flyer (11) arranged to rotate about a predetermined axis (4), a first guide means (32) coaxial with one end of the flyer (11) and through which a stranded element can be guided to a periphery (20) of the flyer (11), means for driving said first guide means (32) and said flyer (11) to rotate relatively to one another, a second guide means (36) comprising an elongate flexible guide member of which one end is held stationary within the flyer adjacent a take up means (7) for the stranded element and the other end is guided within the periphery of the flyer so that it is driven to undergo planetary motion relatively thereto, the arrangement being such that a stranded element can be guided within the flyer (11) to said take up means (7) by said first and second guide means (32,36) whilst passing through 180° relatively to the axis of the flyer (11), characterised in that said first guide means (32) is arranged to receive a stranded element laid up and driven to rotate externally of the flyer (11), that said first guide means (32) comprises a flexible elongate member extending from said axial end of the flyer to the periphery (20) thereof and guided in said periphery for planetary motion relatively to the axis of the flyer (11) and that the said first guide means (32) and said flyer (11) are arranged to be driven at such relative speeds that, in use, a slight twist is imparted to the stranded element during its passage from said first guide means (32) to said second guide means (36) in order to tighten the lay of the stranded element. An apparatus according to Claim 2, characterised in that one or both of said guide means (32,36) comprises a universally jointed articulated guide member having a plurality of linked sections (48,49) each of which is mounted for rotation about an axis and which comprises opposed guide rollers (50,51) for engaging said stranded element in order to centre the axis of the latter upon the axis of rotation of the respective section of said guide means. An apparatus according to Claim 3, characterised in that each said section (48,49) comprises two adjacent pairs of guide rollers (50,51) of which the roller axes are located in planes orthogonal to the rotary axis of said section and are relatively displaced by 90° with respect to one another. An apparatus as claimed in any one of Claims 1-4, characterised in that there is arranged externally of said flyer (11) a rotating means (1) comprising a haul-off device for drawing a rotating wire rope from a stranding head, and that said take up means (7) is a take up reel onto which the wire rope is to be layered.

Inventors: CORTINOVIS SERGIO, WITHERDEN ALAN, CORTINOVIS, SERGIO, WITHERDEN, ALAN
Applicants: CORTINOVIS SPA, CORTINOVIS S.P.A.
Application year: 1991
Main classification: D07B7
IPC codes: D07B7, D07B3