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

[0001] 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.

[0002] 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.

[0003] 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.

[0004] The present invention is based on the concept that it would be desirable to combine the features of the two systems referred to, so that the cable section and lay is formed by a rotating haul-off die, as in the single twist machine, with the haul-off providing the pulling force required in the stranding operation, and an in-line double twist -machine serving solely as a means for taking up the cable onto a stationary winding bobbin.

[0005] The present invention is further based upon the appreciation by the present applicants that in order to effect a practical combination of such devices, some means must be provided to enable the flyer of the double twist machine to rotate at substantially one half the speed of the haul-off device without the normal cable guides thereof exerting a back-twist on the cable, so that the cable can continue to rotate at the speed of the haul-off device without the lay thereof tending to become disturbed by the tangential friction between the cable and the guides of the flyer.

[0006] It is accordingly an object of the invention to provide a solution to this problem and thus, inter alia, to enable the production of an installation of the kind envisaged above.

[0007] In accordance with one aspect of the invention there is provided a method of transporting an elongate element through a flyer arranged to rotate about an axis coinciding with a longitudinal path of said element externally of the flyer, characterised in that the said element is driven to rotate about its own axis relatively to the flyer, at at least one point on its path within said flyer, in order substantially to maintain that section of said element guided within the flyer at the same relative angular position about its own axis as a section thereof that is located on said longitudinal path.

[0008] According to one embodiment of the invention, the said flyer is arranged to rotate around a bobbin or reel onto which said element is to be wound and the path of the said element is turned through 180° within said flyer, whereby rotation of said element on said longitudinal path is cancelled at the point at which it is led to the bobbin or reel.

[0009] The invention further provides an apparatus for carrying out the method of the invention, comprising a flyer arranged to rotate around about a predetermined axis, guide means extending within said flyer and arranged to guide an elongate element along a path therein and means for driving said guide means to rotate relatively to the flyer in order to cause corresponding rotation of said element.

[0010] According to one embodiment of the invention the arrangement is such that said element is transported via said flyer from an axial path externally of said flyer and about which it is arranged to rotate, to a bobbin or reel located within said flyer, along a path extending therein through an angle of 180°, the said guide means and the flyer being arranged to rotate at such relative speeds that the rotation of the element is cancelled at the point at which it is led from the flyer to the bobbin.

[0011] 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 a 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] The hub 23 at the left hand end of the flyer in Fig. 2 carries a rope guide means in the form of a shaft 32 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 hollow shaft 32 is articulated by means of universal joints in such a manner that the whole shaft 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 shaft.

[0019] The right hand hub 24 of the flyer 11 likewise carries a hollow shaft 36 that is articulated in a similar manner to the shaft 32 and which also has a series of rollers. The shaft 36, like the shaft 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 shaft 36 to the take up bobbin along the path shown in Fig 1.

[0020] 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 shaft 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.

[0021] In fig. 4. three separate elements of the articulated hollow shaft are shown, in a sectional view on a plane containing aforesaid shaft 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.

[0022] 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.

[0023] 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.

[0024] Thus although in the above arrangement the relative speeds of the flyer 11 and the shaft 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.

[0025] 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 shaft 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 shaft 36 could be extended to point 33 and, at that point, be left free to rotate.

[0026] 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

1. A method of transporting an elongate element through a flyer arranged to rotate about an axis coinciding with a longitudinal path of said element externally of the flyer, characterised in that the said element is driven to rotate about its own axis relatively to the flyer, at at least one point on its path within said flyer, in order substantially to maintain that section of said element guided within the flyer at the same relative angular position about its own axis as a section thereof that is located on said longitudinal path.

2. A method according to claim 1, characterised in that the said flyer is arranged to rotate around a bobbin or reel onto which said element is to be wound and the path of the said element is turned through 180° within said flyer, whereby rotation of said element on said longitudinal path is cancelled at the point at which it is led to the bobbin or reel.

3. A stranding apparatus comprising a flyer (11) arranged to rotate around about a predetermined axis (4), and guide means (32,36) extending within said flyer and arranged to guide an elongate element along a path therein characterised in that it comprises means (33,37) for driving said guide means to rotate relatively to the flyer in order to cause corresponding rotation of said element.

4. A stranding apparatus according to claim 3, characterised in that it further comprises means (1) for rotating said element about its own axis at a point externally of said flyer, and means (7), arranged to remain stationary within said flyer (11), for taking up said element from said rotating means (1), that guide means (35,28,36) guide said element along a path extending through 180°within said flyer, and that said guide means (35,36) and said flyer are arranged to be driven at speeds so related to the speed of said rotary means (1) that the rotary speed of the element is cancelled as it approaches said take up means (7).

5. An apparatus according to claim 3 or 4, characterised in that said guide means (32) comprises a universally jointed articulated guide member one end of which is mounted coaxially with an axial end of said flyer (11) and the other end of which extends within the flyer along the path of said element said guide member being rotatable relatively to the flyer (11) and means (42) being provided for driving said one end of said guide member to rotate relatively to said flyer.

6. An apparatus according to any one of claims 3-5, characterised in that said guide means (36) comprises a universally jointed articulated guide member one end of which is mounted coaxially with an axial end of said flyer (11) and the other end of which extends within the flyer along the path of said element, said guide member being rotatable relatively to the flyer (11) and means (37) being provided for holding said one end of said guide member stationary whilst said flyer rotates relatively thereto.

7. An apparatus as claimed in claim 4 or claim 5 or 6 as appended thereto, characterised in that said rotating means (1) is a haul-off device for drawing a rotating wire rope from a a stranding head, that said take up means (7) is a take up reel onto which the wire rope is to be layered, and that the arrangement is such that the relative speeds of the rotating means (1), the flyer (11) and the guide means (32,36) are, in use, so related that substantially no twist occurs in the wire rope in its path between the haul-off means (1) and the take up reel(7).

8. An apparatus according to claim 7, characterised in that the said relative speeds are so modified as to cause controlled tightening of the lay of the wire rope.

Drawing