Cyril
Henry
Cyril
Henry
| 1. | A method of manufacturing a stranded assembly of flexible elements in which the lay of the elements is repeatedly reversed along the length of the assembly, which comprises: (i) assembling the elements together to form an initial assembly in which the elements extend substantially parallel to the axis of the assembly; (ii) feeding the initial assembly into one end of a guide arrangement, the guide arrangement having an upstream region in which the assembly is allowed to move at least to a limited extent in a circumferential direction with respect to the guide arrangement but which limits radial movement of the assembly, and a downstream region of the guide arrangement which is of generally circular crosssection; and (iii) removing the assembly from the other end of the guide arrangement; the assembly being fed into the guide arrangement at a higher speed than it is removed therefrom so that, in the upstream region of the guide arrangement, it is forced into a serpentine configuration (in the circumferential direction) and in the downstream region it is forced into a substantially straight assembly in which the lay of elements is repeatedly reversed. |
| 2. | A method as claimed in claim 1, wherein the guide arrangement is generally conical or part conical having a radius that reduces in the direction of travel of the assembly. |
| 3. | A method as claimed in claim 1 or claim 2, wherein the elements are retained together as an assembly within the guide arrangement by the guide arrangement itself. |
| 4. | A method as claimed in any one of claims 1 to 3, wherein the guide arrangement includes a guide through which the assembly passes, the guide retaining the elements together and moving circumferentially about the axis of the arrangement. |
| 5. | A method as claimed in claim 4, wherein the guide comprises a flexible tube. |
| 6. | A method as claimed in claim 4, wherein the guide comprises a plurality of discrete guide elements each of which is constrained to move in a circumferential direction. |
| 7. | A method as claimed in claim 6, wherein the guide elements include rollers that are arranged to form a guiding surface for the assembly. |
| 8. | A method as claimed in claim 6 or claim 7, wherein the guide arrangement includes a plurality of series of guide elements, each of which series is associated with a different stranded assembly, and a plurality of stranded assemblies are simultaneously fed through the different series of guide elements. |
| 9. | A method as claimed in claim 1 or claim 2, wherein the initial assembly is taped before it is fed into the guide arrangement in order to retain the elements together. |
| 10. | Apparatus for manufacturing a stranded assembly of flexible elements in which the lay of the elements is repeatedly reversed along the length of the assembly, which comprises: (i) a guide arrangement through which the assembly can pass, the guide arrangement having an upstream region in which the assembly can move at least to a limited extent in a circumferential direction with respect to the guide arrangement but which limits radial movement of the assembly, and a downstream region of the guide arrangement which is of generally circular crosssection; (ii) a feedin device for feeding an assembly of elements into the guide arrangement; and (iii) a takeup device for taking up the assembly from the downstream part of the device; the feedin device and takeup device being arranged to that an assembly will be fed into the guide arrangement at a higher speed than it is removed therefrom with the result that in the upstream region of the guide arrangement it will be forced into a serpentine configuration (in the circumferential direction) and in the downstream region it is forced into a substantially straight assembly in which the lay of the elements is repeatedly reversed. |
This invention relates to the manufacture of an assembly of separately formed elongate elements in which the direction of lay of the elements along the length of the assembly is reversed at regular intervals.
It is common practice in the manufacture of a stranded or "layed-up" assembly of separately formed flexible elongate elements, such as a multi-core electric power or communication cable, a multi-core optical cable, a steel hawser, pipes and tubes for hydraulic or pneumatic purposes, to "lay-up" or helically wind separately formed flexible elongate elements in a layer or where the stranded assembly comprises two or more layers of such helically wound elongate elements, it is also common practice, although not always, for the direction of lay of adjacent layers to be of opposite hand. In the case of flexible small elements a "bunch" of elements is twisted in one direction to give a general helical assembly without identifiable layers.
With a view to improving manufacture output it is sometimes practice to wind the separately formed flexible elongate elements of a layer helically in such a way that the elements are wound a plurality of times in one direction of lay and are then wound a like plurality of times in the reverse direction of lay, this cycle being repeated throughout manufacture of the stranded assembly.
One form of cable has been proposed in British Patent Specification No.2,241,374 in which the direction of lay is reversed relatively rapidly e.g. as the elements have made in the region of one revolution around the assembly or less.
Such a form of cable has the advantage for example that it can be formed in indefinite lengths since it is not necessary to spool the elements on to bobbins before laying up, which restricts the length of the elements and prevents tandem operation of machines before and or after the laying up process. In the method described in the above British Patent Specification the elements are formed into a ribbon which is wavy in the same plane as the ribbon and the ribbon is bent into a cylindrical geometry.
An improved method of manufacture of such an assembly is described in international application No.PCT/GB94/01124. In essence the individual elements in straight flat formation are inserted into a cone/trumpet shaped guide and extracted from this guide at a lesser controlled speed so that the elements are initially waved then closed about themselves such as to form an assembly of reversed lay at the output of the guide.
Although the method described in the international application provides a particularly simple and elegant way of forming such cables, it suffers from the disadvantage that it cannot be employed for assemblies in which the diameter of the elements differ widely. In addition, it may be difficult to employ the method with elements of non-circular cross section.
According to the present invention, there is provided a method of manufacturing a stranded assembly of flexible elements in which the lay of the elements is repeatedly
reversed along the length of the assembly, which comprises:
(i) assembling the elements together to form an initial assembly in which the elements extend substantially parallel to the axis of the assembly; (ϋ) feeding the initial assembly into one end of a guide arrangement, the guide arrangement having an upstream region in which the assembly is allowed to move at least to a limited extent in a circumferential direction with respect to the guide arrangement but which limits radial movement of the assembly, and a downstream region of the guide arrangement which is of generally circular cross-section; and (iii) removing the assembly from the other end of the guide arrangement;
the assembly being fed into the guide arrangement at a higher speed than it is removed therefrom so that, in the upstream region of the guide arrangement, it is forced into a serpentine configuration (in the circumferential direction) and in the downstream region it is forced into a substantially straight assembly in which the lay of elements is repeatedly reversed.
Essentially the guide arrangement is similar to the guide described in the international application and indeed it is possible to employ a guide of the international application provided that means are employed to prevent the elements of the assembly separating from one another in the guide arrangement. In the simplest form of the invention, this may be achieved by taping the elements together before the assembly is fed into the guide arrangement. Alternatively, the elements may be retained together within the guide arrangement by the guide arrangement itself. Thus, the guide arrangement may, for example, include a guide through which the assembly of elements passes, the guide retaining the elements together and moving circumferentially about the axis of the arrangement.
One form of guide arrangement that may be employed in the method according to the invention employs a flexible tube as the guide. The end of the tube through which
O 96/15311 PC17GB95/02562
4 the assembly enters the tube may be constrained so that it cannot move in the direction of travel of the assembly but so that it can move laterally in the circumferential direction, and the tube may be longer than the shortest path between the inlet and the outlet of the guide arrangement thereby enabling the assembly to adopt a serpentine configuration (in the circumferential direction).
An alternative form of guide assembly that may be employed comprises a plurality of discrete guide elements, each of which is constrained to move in a circumferential direction. For example, the guide elements may be rotatable to a limited extent about a common axis, and each element arranged to provide a guiding surface that is separated from the common axis so that the guide, which is constituted by the sum of the guiding surfaces of the elements can move in a "ripple" along the length of the guide arrangement. This form of guide arrangement may include more than one series of guide elements, each of which series is associated with a different stranded assembly, so that a plurality of different stranded assemblies can be simultaneously fed through the different series of guide elements.
In certain arrangements where elements of non-circular cross-section are employed in the assembly, the assembly may be held together by the elements themselves even without the need for taping.
Any elements that are normally employed to form electric cables, optical cables, assemblies containing pneumatic or hydraulic tubes or electro-magnetic waveguides may be used in the process, for example: solid or stranded circular or shaped conductor or bunched fine wire electric cables, optical fibres and cables and the like. The elements may be unitary in construction, or different sizes or shapes and composite elements may be employed such as for example twisted pairs of wires etc.
The production of a reversed lay assembly proceeds as described in the international application but in the case of this invention the closure of the elements has taken place before entry into the guide system and the guide imparts first a twist of the
elements, can with benefit, have a larger amplitude of oscillation and can have a shorter wavelength than is ultimately required in the final assembly. The process is best understood by considering a helical spring which is stretched or elongated so as to form a straight rod element. In straightening the spring, the rod forming the spring initially, is twisted. The invention carries out such a process on a continuous manner with an effective "spring" being formed within the guide first in one direction followed by a "spring" of opposite lay. As the elements approach the exit of the guide they are first twisted in one direction and then the other to form an assembly. The difference between the input and output speeds determines the ultimate lay of the assembly and prevents the untwisting of one section into its neighbour of opposite lay.
Other details of the method may be obtained from the international application No. PCT/GB94/01124, the disclosure of which is incorporated herein by reference.
According to another aspect, the invention provides apparatus for manufacturing a stranded assembly of flexible elements in which the lay of the elements is repeatedly reversed along the length of the assembly, which comprises:
(i) a guide arrangement through which the assembly can pass, the guide arrangement having an upstream region in which the assembly can move at least to a limited extent in a circumferential direction with respect to the guide arrangement but which limits radial movement of the assembly, and a downstream region of the guide arrangement which is of generally circular cross-section;
(ϋ) a feed-in device for feeding an assembly of elements into the guide arrangement; and
(iii) a take-up device for taking up the assembly from the downstream part of the device;
the feed-in device and take-up device being arranged so that an assembly will be fed into the guide arrangement at a higher speed than it is removed therefrom with the result that
the feed-in device and take-up device being arranged so that an assembly will be fed into the guide arrangement at a higher speed than it is removed therefrom with the result that in the upstream region of the guide arrangement it will be forced into a serpentine configuration (in the circumferential direction) and in the downstream region it is forced into a substantially straight assembly in which the lay of the elements is repeatedly reversed.
Several methods in accordance with the present invention will now be described by way of example, with reference to the accompanying drawings, in which:
Figure 1 shows various examples of assemblies employing non-circular element that may be employed in the invention;
Figure 2 shows one form of guide arrangement that may be used in the invention; and Figure 3 shows an alternative form of guide arrangement that may be used in the invention.
Referring to the accompanying drawings, figure 1 shows various forms of assemblies of elements that may be employed in the process according to the invention. In figure 3a a three-core assembly comprises three identical cores, each of which has the cross-section of a 120° sector. This form of assembly has the advantage that shear forces exerted on opposite sides of the assembly during the method will not cause the elements to separate since the plane of contact of any two elements does not extend through the entire assembly.
In contrast, an unsuitable four-core assembly is shown in figure lb. As shown, it is possible for two segments in this assembly to slide laterally with respect to the other two due to shear forces on the assembly with the result that the elements may separate. This problem may be overcome in a number of ways. For example, the individual elements of the assembly may be shaped as shown in figures lc and Id so that there is no single plane of contact that extends through the assembly with the result that the assembly is more stable. Alternatively, the assembly may be taped together as shown in
figure le.
One form of guide arrangement that may be employed in the method according to the invention and which will hold the elements of the assembly together during the method is shown in figure 2a to c. This guide arrangement has the same general configuration as that described in international application No.PCT/GB93/01124, and comprises an internal generally conical guide core H and an external generally conical guide block G located coaxially about core H to define a circumferentially extending slot N therebetween. The guide core H has a raised part I extending over part of its circumference in the upstream part of the arrangement which fills the gap between core H and block G. The raised part I tapers so that the slot N extends over an increasing arc as the diameter of the guide core H and block G decreases until, in the downstream part of the arrangement, the slot N extends 360° around the guide core H. The slot N thus has an arcuate inlet extending approximately 180° around the guide core H, and has a generally circular outlet at the other end of the assembly.
A guide for the assembly E of elements in the form of a flexible tube P extends from the inlet of the slot N to its outlet. The flexible tube P has a diameter that is slightly larger than that of the assembly, and a length that is greater than the shortest distance between the inlet and outlet of the flexible tube P is held at the entry of the slot N by means of a sliding plate L that is rotatable about a shaft M along the axis of the guide core H and includes bearings K that enable the plate L to slide along the arcuate inlet of slot N without being able to move axially along the guide arrangement.
The flexible tube P may be formed in any of a number of ways as shown in figure 2c. For example it may be formed from a material having a number of annular corrugations as shown in A, or it may be made up of a number of annular elements that are interlocked together to form an annularly corrugated structure as shown in B.
Alternatively, the tube may be in the form of a braid as shown in C or in the form of a long metal helix as shown in D.
whereupon the element is forced into a serpentine configuration within the guide arrangement. The lateral dimensions of the slot N enable the assembly to adopt such a configuration, while the tube P prevents the elements from separating. At the outlet J of the guide arrangement the assembly as a whole is forced into a straight configuration, and the reduction in the take-up speed of the assembly at the outlet J is accommodated by the elements of the assembly adopting a reverse lay configuration.
An alternative form of guide arrangement is shown in figure 3, which operates on the same general principle as the arrangement shown in figure 2. This arrangement comprises a central shaft A along which are fitted free running bearings B to which are attached support arms C. At the opposite end of each arm to the bearings B is attached a roller support F which is so constructed with rollers G as to allow the straight assembled elements to pass through smoothly and easily and also by means of the pin support and bearing H to change the angle at which the elements actually pass through the roller. As the elements are forced into the guidance system, by means of suitable driven rollers, caterpillar drives, capstans or similar devices, they bend, as a strut fails under compressive forces, to initially take up a sinusoidal or similar formation but contained within an imaginary conical space envelope as defined by the length of the arms which reduces from the longest arm at the point of entry of the element to the shortest arm at point J near the exit of the elements. From the initial entry arm to point I the arms are restricted in their rotational orbit by stops D which are so placed that the circumferential length moved by the individual rollers F and the elements passing through them is the same although the pitch circle diameter reduces as the elements pass through the guide system. This ensures that the straight assembled elements take up an approximate sinusoidal formation between their entry and point I. From point I to point J the arms continue to reduce in length but are now free to rotate in a complete circle of 360 degrees without any stops present. This arrangement ensures, after the initial setting up, when the elements are forced into he system without exit, that all the arms from entry to point I are up against their stops and are bent in excess of that ultimately required. From point I to J the elements experience a stretching as the amplitude of the wave is reduced and the wavelength or lay is increased. At point J the shaft A is
from entry to point I are up against their stops and are bent in excess of that ultimately required. From point I to J the elements experience a stretching as the amplitude of the wave is reduced and the wavelength or lay is increased. At point J the shaft A is terminated and from J to the final exit there are rollers or similar devices, K coaxial with the line of the shaft A which finally complete the unbending of the assembly and the twisting of the elements first in one direction and then in the opposite direction. Most of the twisting takes place between point I and point J as the elements, bent and formed from entry to I, are straightened. It is necessary to have the arms C spaced sufficiently close together to support the elements and prevent them from a strut type of failure in an uncontrolled manner between the roller supports.
There will be reactions to the force applied to the elements and an additional support to the arms C can be provided if required by the installation of reaction plates L which are firmly anchored and allow rollers M attached to the arms C to roll along the plates L to provide support and reduce the forces being applied to the bearings B. In order to reduce further these forces and those forces applied by input and output devices the bending of the elements can be induced by actuators attached to each of the arms. These actuators may be hydraulic, pneumatic, electro-magnetic or similarly operated and arranged to operate with pre-determined force on the arms according to a pre¬ determined pattern such as produced from a computer program or robotic program The reaction plates and arms can be combined with advantage to form a circular plate or wheel supported by a central shaft resting on rollers about its circumference and its periphery by rollers on the side of the plate to provide reaction forces. These circular plates can incorporate a toothed circumference engaging with a gear wheel to provide drive in either direction if required.
As with the description described in international application
No.PCT/GB94/01124, the axial speed of the elements' entry and the speed of the axis of the assembly's exit is not the same. The ratio of the higher input speed to the output speed determines the length of lay and it is essentially controlled to remain constant irrespective of any output speed if a consistent lay strength is required.
This example of a laying-up machine can be extended to include several untwisted assemblies to be fed into the similar number of roller supports F at the end of each arm C so that 2, 3, 4 or more assemblies can be laid up simultaneously to give twice, three times, four times or more output rates.