Background of the Invention
1. Field of the Invention
The invention relates to a coil of flexible material wound in a series of figure-8s with a radial hole into the axial opening for twistless payout through the hole.
2. The Prior Art
Coils of this sort are known for example from Taylor U.S. Pat. No. 2,634,722 and Newman U.S. Pat. No. 3,666,200.
Such coils are satisfactory where the wall thickness of the coil is not too great, particularly not greater than the radius of the mandrel on which the coils are wound. However, in winding thick-walled coils, particularly when these are paid out from a position in which the radial opening is arranged vertically, there is danger that the outer wall layers, when the inner layers have been withdrawn, will fall off downwardly, and will thus cause kinks or snarls which will prevent proper payout. This presents difficulties in producing coils of long length.
Summary of the Invention
The invention provides a method for producing a coil having means for preventing falloff of the walls of the outer layers during payout, and a coil produced by such a method.
According to the invention, the inner layers of the coil are wound in a normal manner, that is with a different gain from layer to layer, so that a compact structure is obtained. Attempts have been made to continue such a wind outwardly to a considerable wall thickness, and thereafter to insert pins into the side of the coil from the outside, for the purpose of preventing falloff. It has been found however that such pins, even when made of a relatively soft plastic material, may penetrate or deform the material of the coil, even a coil formed of wire. It appears that the forcing of the pins into the side wall therefore damages the coil and prevents proper payout.
According to the present invention, the inner portion of the coil is wound in a normal manner wth a variable gain from layer to layer, so that the cross-overs do not overlie each other and a relatively dense section is produced. On the other hand, after a certain point is reached, the gains are made equal in the different layers so that the cross-over substantially overlie each other from layer to layer. This provides a honeycomb section of low density, which of course is undesirable.
According to the invention, the pins which are to prevent fall-off are mounted slidably on a strip of metal and are pushed into the oustside face of the coil, the openings in the honeycomb permitting the pins to enter without breaking or bending the wound material. Thereafter, the sides of the end portions are compressed inwardly, that is, parallel to the axis of the axial opening in the coil, and the pins slide inwardly in their carrier. The density of the end portions is thus substantially increased, and the space required is thus reduced. At the same time, the pins extend into the walls of the coil from the outside and prevent the material from falling off undesirably during the latter part ot the withdrawal.
Brief Description of the Drawings
In the drawings:
FIG. 1 shows in cross-section the first step of producing a coil according to the invention;
FIG. 2 shows a pin carrier with the pins carried thereby;
FIG. 3 shows a completed package; and
FIG. 4 shows partly in cross-section a section of the arrangement of FIG. 2 .
Description of the Preferred Embodiments
Referring to FIG. 1, the material is wound in the manner described above, and particularly that described in Newman U.S. Pat. No. 3,666,200, on a rotating mandrel 2 having suitable end forms 4. These end forms are outwardly flared. During the first part of the wind, that is for example up to the point indicated by the line 6, the material is wound as described in the above Newman patent, that is, with varying gains from layer to layer, so that a relatively dense section is achieved.
The machine is not set to wind with equal angular gains, and thus forms a honeycomb structure in which the cross-overs in successive layers lie substantially on top of each other, in the portion indicated by the area 8, the width of the guide stroke being sufficient to lay the material across the increasing space between the end forms.
FIG. 2 shows a strip of metal 12 with a slot 14 therein. A plurality of pins 16 having heads 18 are slidably arranged in the slot, and have flanges 20 engaging the other wall of the piece 12 opposite the heads 18. These flanges may fit closely enough to give a frictional grip on the strip 12, so that undesirable sliding of the pins in the slot is prevented. The pins may be made of a relatively soft plastic material.
After the winding is completed, several of the pieces 12, angularly spaced around the periphery, are pushed against the outer periphery of the winding, and the pins enter into the openings in the honeycomb formation.
The package is now removed from the mandrel by taking off the end form and collapsing the mandrel if necessary. The package is then compressed in a direction parallel to the axis of the axial opening, as shown for example in FIG. 3. The pins slide down in the slot 14, and approach each other, and the layers are collapsed so that a dense outer section 8 is achieved.
The package may be enclosed in a covering material such as 22. The metal strip 12 may then have the ends bent as at 24 around the outside of the cover 22. This secures the strip in place and ensures holding of the pins firmly in the package.
During winding, in the manner described above, a radial opening 26 is formed from the outside of the package into the axial opening through which the inner end of the material can be led out.