Patent Application
20210001390
This application relates to a stranding machine for producing a cord from a plurality of wires, preferably metallic wires. For example, in such a stranding machine, a plurality of such wires are stranded together by twisting, i.e. processed to form a cord, and the wires are preferably made of a copper alloy, particularly preferably a copper-magnesium or copper-tin alloy, for example with a content of 0.2 or 0.3% of magnesium or tin, or, equally preferably, of a copper-silver alloy.
A stranding machine of the type described in this application includes a stranding device for stranding the wires.
The stranding device preferably has a revolving rotor which comprises an elongated flyer bow that is curved radially outwards and is rotatably supported at both of its ends. The plurality of wires is fed to the rotor and guided over the flyer bow, as a result of which the wires are twisted at one or more stranding points.
The stranding machine preferably includes a rotatably mounted draw-off (or drawing) disc for drawing the cord off from the stranding device. The draw-off disc is preferably driven to generate the required tensile stress for drawing off the cord.
After the cord has been drawn off from the stranding device, the cord is preferably wound onto a bobbin with the aid of a suitable winding device, or is directly further processed. If the cord is wound onto a bobbin, the latter generally comprises a cylindrical spool core for winding the cord onto and, at the two ends of the spool core, one disc-shaped flange, respectively, to prevent the windings from slipping off the spool core. During the winding with the cord, the bobbin rotates generally around the longitudinal axis of the spool core (hereinafter referred to as “bobbin axis”).
In particular, in the case of stranding machines of the above-described type, having a flyer bow, which are operated as double twist stranding machines, the drawing-off disc, if applicable, and, if applicable, also the winding device and the bobbin for winding the cord, are preferably arranged within the rotational volume of the flyer bow, i.e. within the space around which the flyer bow rotates. Therefore, only limited space is available for the drawing-off disc, the winding device and/or the bobbin. The bobbin axis can be arranged substantially orthogonally to the rotor axis, substantially parallel to the rotor axis or else in a different angular position relative to the rotor axis. The cord preferably emerges from the rotor along the rotor axis.
In respect to the cord as produced, one problem arises that the cord may have a twist. In addition, in the unloaded state, the cord tends to bend, tends to “curl” or tends to display “rollovers”, i.e. loop formations.
This is problematic in the further processing of the cord, in particular during the winding onto a bobbin, during assembly and during crimping, i.e. when connectors are clamped onto the cord.
In addition, the process of extrusion, i.e. the casting of a plastic insulation around the cord in an extrusion process, is made more difficult as a result. In particular, the phenomena mentioned above impede the use of so-called “bag discharges” during extrusion, which operate continuously, instead of rotating tangential discharges which do not operate continuously and only permit a significantly smaller feed speed of the cord.
Finally, the twist and the tendency of the cord to “curl” reduce the number of alternating bending cycles achievable, i.e. the number of alternating bending cycles which can be carried out without material fatigue or failure.
It would therefore be desirable to provide a stranding machine and a process for producing a cord, such that the cord produced has, at most, a low twist and a low tendency to “curl.”
To address these and other problems with conventional designs as identified above, a stranding machine and a process for producing a cord are provided in accordance with embodiments of the present invention.
Embodiments of the invention are based on the observation that the twist and the tendency of the cord to “curl” can be reduced by a movement in the direction of the torsion of the cord resulting from the twisting, referred to below as “twisting torsion”, preferably in conjunction with a stretch forming of the cord, i.e. a stretching which leads to a plastic deformation of the cord.
In the stranding machine according to embodiments of the invention, and in the method according to embodiments of the invention for producing a cord, at least one measure is therefore implemented which takes into account this observation.
A stranding machine according to embodiments of the invention includes at least one rotatably mounted deflecting roller for deflecting the cord and at least one guiding device for guiding the cord. The guiding device is arranged in such a way that the cord can be guided, on a straight line, from the guiding device to the deflecting roller, in such a way that the cord is pressed against a first flank of the deflecting roller.
The deflecting roller is of a conventional design, wherein the running surface for the cord (on the end face of the deflecting roller) has a wedge-shaped recess, in respect to its cross-section. The wedge-shaped recess has a first flank and a second flank that is directed obliquely inwards towards the central plane of the deflecting roller. The area near the inner edges of the two flanks, in which the radius of the running surface is smallest, is referred to as the roller base.
During the deflection by the deflecting roller, the cord moves on its way from the point of entry to the point of exit from the first flank of the deflecting roller into the roller base. To provide an illustrative description, the cord “slips” down along the first flank into the roller base. Thereby, the cord is subjected to a movement that is in conjunction with or against the twisting torsion. By selecting the first flank out of the two flanks of the running surface of the deflecting roller accordingly, it can be achieved that the movement of the cord takes place in conjunction with the twisting torsion, as a result of which the tendency of the cord to “curl” is reduced.
In one embodiment of the invention, additionally, a pulling device is arranged behind the deflecting roller in the direction of movement of the cord, wherein said pulling device is suitable for exerting a tensile force on the cord running off the deflecting roller. This results in a stretch forming of the cord, i.e. a stretching which leads to a plastic deformation of the cord, as a result of which the tendency of the cord to “curl” is likewise reduced.
The pulling device is preferably a winding device. Such a winding device is already provided in many stranding machines anyway, in order to wind up the cord as produced. The winding device allows to exert the desired tensile force onto the cord as the same is running off the deflecting roller, in particular by a driven bobbin axis in the winding device.
In a further embodiment of the invention, a contact point of the cord on the guiding device, from which the cord can be guided on a straight line to the deflecting roller in such a way that the cord is pressed against the first flank of the deflecting roller, is offset with respect to the central plane of the deflecting roller. As a result, the cord runs off-center onto the deflecting roller and, in this way, is pressed by itself against the first flank of the deflecting roller, without the need of a further pressing device.
In a further embodiment of the invention, the guiding device is arranged in such a way that the cord can be guided on a straight line from the guiding device to the deflecting roller in such a way that the cord is pressed against a second flank of the deflecting roller, which second flank is different from the first flank. The cord can thus selectively be pressed against the first or against the second flank of the deflecting roller. This selection can be carried out depending on the lay of the cord, i.e. depending on the direction in which the individual wires are twisted together during the stranding and from which direction also the twisting torsion depends. In this respect, a distinction is made between the so-called S-stranding, in which the wires are wound around one another in a counterclockwise direction, and the so-called Z-stranding, in which the wires are wound around one another in a clockwise direction, this property being invariant with respect to the direction in which the cord is viewed.
The guiding device is preferably movable relative to the deflecting roller, in particular movable substantially orthogonally to the central plane of the deflecting roller. In this way, the contact point of the cord on the guiding device can be fine-tuned relative to the deflecting roller. Further preferably, the flank of the deflecting roller against which the cord is to be pressed can also be selected in this way.
Additionally or alternatively, the selection of the flank of the deflecting roller against which the cord is to be pressed can also be made by guiding the cord along different sides of the guiding device.
In a further embodiment of the invention, the guiding device is a rotatably supported guiding roller. As a result, the friction of the cord relative to the guiding device can be reduced.
In other embodiments, a process is provided for producing a cord from a plurality of wires, preferably metallic wires, where the process is to be carried out on a stranding machine according to the description herein. In the process, the wires are stranded in the stranding device, the cord is guided from the stranding device to the guiding device, the cord is guided on a straight line from the guiding device to the deflecting roller, in such a way that the cord is pressed against the first flank of the deflecting roller, the cord is deflected by the deflecting roller, and the cord is guided away from the deflecting roller.
During the deflecting by the deflecting roller, the cord preferably moves from the first flank into the roller base of the deflecting roller.
As a result of guiding the cord in that manner, the twist and the tendency of the cord to “curl” are reduced, based on the above-described mechanisms.
The accompanying drawing, which is incorporated in and constitutes a part of this specification, illustrates one or more embodiments of the invention and, together with the general description given above and the detailed description given below, explains the one or more embodiments of the invention.
The cord 1 runs through an opening 3 in the housing 2 to a draw-off disc 4, which is driven and which draws the cord 1 off the stranding device by way of exerting tensile stress. The draw-off disc 4 and a lift-off roller 5 arranged above the draw-off disc 4 and parallel to the latter each comprise a plurality of running grooves, through which the cord 1 is alternatingly guided, so that the cord 1 passes through the draw-off disc 4 and the lift-off roller 5, alternatingly and altogether multiple times. The draw-off disc 4 and the lift-off roller 5 function as a first torsion lock.
The cord 1 then passes through two deflecting rollers 6 and 7 and is thereby deflected overall by 270 degrees. In this case, the deflecting roller 7 is slightly slanted so that the cord running off from the deflecting roller 7 does not collide with the cord running onto the deflecting roller 6.
Thereafter, the cord 1 runs along one side—in the exemplary embodiment along the left side—of a rotatable guiding roller 8, the axis of which extends approximately vertically. The guiding roller 8 has the effect that the cord 1 is deflected slightly out of its path and does not run centrally onto the following deflecting roller 9, but is pressed against a flank of the deflecting roller 9, in the exemplary embodiment against the left flank 9a as seen in the running direction of the cord 1. The position of the guiding roller 8 relative to the deflecting roller 9 can be fine-tuned by a vernier 12. With the aid of the vernier 12, the axis of the guiding roller 8 can be moved back and forth substantially orthogonally to the center plane of the deflecting roller 9.
The cord 1 wraps around the deflecting roller 9 by slightly less than 180 degrees. On its path from the point of entry onto the deflecting roller 9 on the left flank 9a to the point of exit, the cord 1 moves from the flank 9a into the roller base 9b. In doing so, the cord 1 moves in conjunction with the twisting torsion, as a result of which the above-described tendency of the cord to “curl” is reduced.
The stranding machine also comprises a traverse mechanism 16 having further deflecting rollers 10 and 11, which can be moved along a traverse axis on a spindle (not shown). The spindle is supported in two bearings 13, 14 (shown in a sectional cut in
The cord 1 runs off from the deflecting roller 9 parallel to the spindle of the traverse mechanism 16 and thus runs onto the deflecting roller 10 of the traverse mechanism 16 always at the same angle, irrespective of the displacement position of the traverse mechanism 16. By the deflecting rollers 10 and 11, the cord 1 is again deflected in order to finally be guided to a winding device and to be wound onto a winding bobbin (both not shown) at the axial position of the winding bobbin predetermined by the displacement position of the traverse mechanism 16.
Therein, the driven winding bobbin exerts a tensile force onto the cord 1, as a result of which the cord 1 is pressed against the deflecting roller 9, preferably with a high pressing force, and is thus slightly stretch formed between the deflecting roller 9 and the winding bobbin, typically by 2% to 3%. In this way, the helical structure which is imposed on the cord due to the twisting is further minimized or even completely removed. Insofar, the deflecting roller 9 functions as a (second) torsion barrier.
The embodiments described above are only descriptions of preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Various variations and modifications can be made to the technical solution of the present invention by those of ordinary skill in the art without departing from the design and spirit of the present invention. The variations and modifications should all fall within the claimed scope defined by the claims of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 205 566.1 | Apr 2018 | DE | national |
This application is a national phase entry of, and claims priority to, International Application No. PCT/EP2019/058164, filed Apr. 1, 2019, which claims priority to DE 10 2018 205 566.1 filed Apr. 12, 2018. The above-mentioned patent applications are incorporated herein by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/058164 | 4/1/2019 | WO | 00 |
