| JP2008063703 | WIRE TWISTING MACHINE |
| WO/1988/009841 | MODULAR DOUBLEDECK TWISTING MACHINE/DOUBLING MACHINE |
| JP11302988 | TWISTING DEVICE |
| 1. | An annular or closed loop rotatable frame or "flyer" (1) , such as is used in a stranding machine of the type, in which two or more wires, fibres or strands are stranded to a cable, e.g. intended for telecommunication, the flyer being 5 arranged to rotate around one pr mqre_bobbins (10, 11), c h a r a c t e r i z e d in that the frame (1) is jour nalled in two diametrically opposite points (8, 22) and is prestressed at these two journal points in a direction per¬ pendicular to the centrifugal force produced by the rota 10 tion. |
| 2. | A frame according to claim 1, c h a r a c t e ¬ r i z e d in that it is made of fiber reinforced plastic (72) with continuous fibers (71) arranged circumferentially. |
| 3. | A frame according to claim 1, c h a r a c t e 15 r i z e d in that the two joumalling (3, 22) points are arranged on a frame (1) driving shaft (2) and on a socket (16) journalled (8) to the driving shaft. |
| 4. | A frame according to claim 1, c h a r a c t e ¬ r i z e d in that the frame is aerodynamically shaped 20 (Fig. 2) . |
| 5. | A frame according to claim 2, c h a r a c t e ¬ r i z e d in that it is made of carbon fibre (71) re¬ inforced expoxy resin (72) . |
| 6. | A frame according to claim 2 or 5, c h a r a c 25 t e r i z e d in that the fiber (71) is wound continously in a plurality fo turns along the frame (1) . |
TECHNICAL FIELD
The invention relates to an annular or closed loop rotatable frame or "flyer" such as is used in a stranding machine of the type, in which two or more wires, fibres or strands are stranded to a cable, e.g. intended for strandin insulated conductors e.g. for the production of cables for telecommunication, the flyer being arranged to rotate around one or more bobbins.
BACKGROUND ART
At a known stranding machine for stranding two or more wires or fibres a flyer is rotatable around a shaft and two or more wire bobbins are suspended within the orbit of the flyer on a suspension device rotatably supported by the flyer shaft and thus not taking part in the rotation of the flyer. From the bobbins the wires are passed down into the hollow shaft of the flyer, where they are stranded to a cable, which is further passed to a tape applicating ma¬ chine, or to a capstan. In order that the bobbins shall not take part in the rotation of the flyer, the suspension mean are constructed and loaded in such a way that their centre of gravity is outside the flyer shaft axis or its elonga¬ tion, which in addition diverges from the vertical.
Owing to the rotation the flyer is subjected to centri fugal forces that limit the stranding speed. In order to give the flyer better strength against these centrifugal forces, it has been tried to design the flyer as a pref¬ erably circular frame. But even for such a frame the rota¬ tion speed is limited, depending on the allowable stress of the material and depending on the air resistance of the rotating flyer.
DISCLOSURE OF THE INVENTION
According to the present invention the speed of a flyer constructed as an annular frame can be further increased by
ji
journalling the frame in two diametrically opposite points and prestressing the flyer by stretching it at these two points. It will then be prestressed by a bending moment in the plane of the flyer in a direction perpendicular to the 5 centrifugal force produced by the rotation of the flyer. Th prestressing force may at most produce the maximum accept¬ able bending moment in the flyer. When the. flyer rotates a bending moment in the opposite direction is developed and may thus be two times the bending moment that can be ac-
10 cepted without prestressing. It has been shown that for a circular flyer and a safety coefficient of 3.5 it is pos¬ sible to allow a speed of rotation which is 25% higher than without prestressing the flyer.
In order to gain the optimal speed the flyer according
15 to the invention ought to be made as thin as possible and aerodynamically shaped whereby the air resistance and noise decrease, but at the same time having high rigidity and low natural frequency. It is especially preferable to use rings of fibre reinforced plastics, e.g. carbon fibre re-
2o inforced epoxy resin with continuously wound fibres in tangential i.e. circumferential direction.
In order to produce the prestressing the flyer is mounted at diametrically opposite points in bearings, that can stand axial forces. Further advantages of the flyer are
25 achieved by embodiments given in the claims.
BRIEF DESCRIPTION OF THE DRAWING AND A PREFERRED EMBODIMENT OF THE INVENTION.
The invention is to be described in more detail re—
30 ferring to the attached drawing in which'Fig. 1 shows an embodiment with two bobbins inside the flyer. Figs. 2 and 3 show in cross section and longitudinal section respectively a flyer of the preferred material, carbon fibre placed in circumferential direction and bound with epoxy resin.
35 According to Fig. 1 an annular flyer 1 is fastened to a shaft 2 and journalled 3 in a rack 4. The other end of th shaft is equipped with a driving gear 5. Inside the flyer
3 the shaft is extended by a tube 6 on which a stand 9 for t bobbins 10, 11 is journalled, 7, 8. By eccentric suspensio of the bobbins or in any other way it is ensured that the centre of gravity of the stand always is below the incline centre line of the shaft. From the bobbins 10, 11 two wire 12, 13 are passed over pulleys 14, 15 mounted in a socket 16, projecting from the stand 9, to a wheel 17 attached to the tube 6, which is fixed to the shaft 2 of the flyer. Because this wheel 17 follows the flyer when it rotates th wires 12, 13 are twisted before the wheel. The twisted cab 18 is passed along the inside- of the flyer by pulleys 19 o nipples and leaves the flyer over a wheel 20. In order to prevent unbalance of the flyer also the other half of the flyer is equipped with pulleys 21 or appropriate counter- weights. When the flyer rotates the centrifugal force tends to give it an elliptic form. This causes bending stresses a the fastening points of the shaft 2. This flexural stress i counteracted by journalling 22 the flyer on the socket 16 projecting from the stand 9 at the intersection point be- tween the flyer and the extension of the centre line of the shaft.
According to the invention the flexural stress of the flyer can be further diminished by prestressing the flyer i the direction of the shaft. According to the embodiment shown this is performed with a screw 23 and a socket 24 by the help of which the flyer may be extended in the directio of the shaft. The bearings 3, 7, 8, 22 are constructed so that they can stand axial stresses arising at the prestres¬ sing. The extension of the flyer in the shaft direction pro duces a bending moment in a direction opposite to the ben¬ ding moment produced by the centrifugal force when the flye rotates. Consequently much higher centrifugal forces may be allowed before the bending moment in the fastening points o the flyer reaches an unallowable value. In Fig. 2 and 3 are shown a cross section and a longi¬ tudinal section respectively of a flyer of the preferred embodiment comprising monofil carbon fibres 71 bound by epoxy resin 72.
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