Plastic bobbin and a method of manufacturing such a bobbin

IS 2 287 488 T3

DESCRIPTION

Plastic coil and a method of manufacturing such a coil.

Invention field

The present invention relates to a coil according to the preamble of claim 1.

Previous technique

The spools are used to wind, among others, cables, and can be manufactured in various shapes and from different materials. In small sizes, up to about 400 mm, in most cases they are made of plastic or paper. They can be manufactured in one piece or in several pieces that are then assembled.

A package of filamentary material is shown in US-A-1,437,954. This package is made from a sheet of paper, cardboard or other suitable flexible material. Cuts are made in the sheet to form a series of loops, which are then curved normal to the plane of the sheet and then rolled into a tubular shape. In order to be bendable, this sheet is made of a very thin material.

GB-1,303,063 discloses the manufacture of a coil by bending a plastic channel back over itself, so that its ends meet, and a cylinder with circumferential end fins is formed, after which the ends are joined by welding or gluing. The plastic channel is made by extrusion or hot forming of a plastic strip and is provided with transverse corrugations to allow it to be bent to form a cylinder.

The disadvantages of this manufacturing method are that it is time consuming since the manufacturing is carried out in several steps and different machines and tools are required at each step, and because the corrugation requires a large consumption of material. Summary of the invention

The object of the invention is to provide a method which makes it possible to simplify the manufacture of a coil of the above type and to reduce the consumption of material. A further object of the invention is to provide a reel which can be made of a small amount of material compared to the prior art reel of a corresponding size size and which further has the advantage that it can be transported and stored in a more rational way.

This object is achieved as regards the coil by means of a coil according to claim 1.

In order for the end fins of the coil to have sufficient strength, their fin elements have over their entire radial extension preferably an essentially constant length in the circumferential direction, the fin elements at each fin end having a total extension in the circumferential direction that it is essentially equal to the circumference of the cylinder.

In order to facilitate bending, the coil preferably has a plurality of grooves that are formed on the outer circumferential surface of the cylinder, each groove extending the entire length of the cylinder between a point between two contiguous fin elements of an end fin and a point between two contiguous fin elements of the other end fin.

Each fin element suitably has at its radial inner end a lug that extends past the inner circumferential surface of the cylinder and has a circumferential length that tapers radially inward. The U-shaped channel can be curved until each lug abuts an adjoining lug. In this way, the lugs make it easier to turn the U-shaped channel into a cylinder that retains its cylindrical shape and does not collapse when in use. In an alternative embodiment, the inner circumferential surface of the cylinder has a plurality of axial grooves, each groove extending the entire length of the cylinder between a point between two contiguous fin elements of an end fin and a point between two contiguous fin elements of the other extreme fin. The grooves on the inner circumferential surface of the cylinder are preferably located opposite the grooves on its outer circumferential surface and preferably have a wedge-shaped cross section.

Preferably, at least one fin element of one end fin has at its outer radial end an articulated projection which at its free end can engage the other end fin.

The above object is achieved as regards the method by means of the U-shaped channel that is made by injection molding and is shaped such that its side walls consist of a plurality of separate wall elements that are distributed along the length of the canal.

The ends of the channel are preferably connected to each other by protrusions, which are formed on a protrusion of the base of the channel, which protrusion protrudes at one end of the channel in the longitudinal direction of the channel, being inserted into holes that are formed at the base of the channel. channel at the other end of the channel.

In order to facilitate bending of the channel, during injection molding, internal transverse grooves are made at its base which extend over the entire width of the base between a point between two contiguous wall elements of a channel wall and a point between two contiguous wall elements of the other wall of the channel.

Preferably, each wall element during injection molding at its end is connected to the base provided with a lug that extends past the base and has a length that decreases in the longitudinal direction of the channel, away from the wall element, the curved channel until each lug comes into contact with an adjoining lug, the lugs forming stoppers that cause the channel to transform into a cylinder in connection with the bending. Alternatively, the base of the channel may be made during injection molding outer transverse grooves that extend the full width of the base between a point between two contiguous wall elements of a channel wall and a point between two elements of the channel. adjoining wall of the other canal wall.

Brief description of the drawings

The invention will now be described in more detail by means of a preferred but non-limiting embodiment and with reference to the accompanying drawings.

Figure 1 is a side view of a U-shaped channel used to make a coil in accordance with the invention.

IS 2 287 488 T3

Figure 2 is a sectional view along the line II-II of Figure 1 and shows a channel segment of the channel.

Figure 3A shows the channel segment in section along the line IIIA-IIIA of Figure 2.

Figure 3B shows the channel segment in section along the line IIIB-IIIB of Figure 2.

Figure 4 is an end view of a coil that is made of a curved channel according to Figures 1 and 2.

Figure 5 is a sectional view along the line VV of Figure 4 and shows the coil. Description of the preferred embodiments

The coil 1 according to the invention is made of plastic and has a cylinder 2 with a circumferential end fin 3 at each end of the cylinder. Each end fin 3 consists of a plurality of radial fin elements 4 which are perpendicular to the axis of the cylinder and are uniformly distributed along the circumference of the cylinder 2. In the preferred embodiment all the fin elements 4 have the same shape and size but could also have different shapes and / or sizes. The fin elements 4 are essentially in the shape of an elongated rectangle, each fin element being connected to the cylinder 2 on a short side of the rectangle. The total width of the fin elements 4 of each fin is approximately equal to the circumference of the cylinder 2. For greater strength, the fin elements 4 are internally provided with radial stiffeners 14, or have an arcuate straight section.

Each fin element 4 of one end fin 3 is arranged opposite a fin element 4 of the other end fin 3. Among the fin elements 4 in each pair of adjoining fin elements, the cylinder of each pair of fin elements contiguous, cylinder 2 has axial grooves 5 on its outer circumferential surface. The grooves 5 extend the entire length of the cylinder 2.

In an alternative embodiment (not shown), also the inner circumferential surface of the cylinder has axial grooves between the fin elements 4 in each pair of adjoining fin elements, the grooves of which extend the entire length of the cylinder 2 and have a straight section wedge-shaped.

Each cylinder portion 2 'between two adjoining grooves 5 has an outwardly arched straight section, as seen in Figure 3B, or an inwardly arched straight section. To provide a stiffer cylinder, these portions 2 'can be made with a more pointed cross section, as indicated by dashed lines in Figure 3B.

Each fin element 4 has at its inner radial end a lug 6 which extends past the inner circumferential surface of the cylinder 2 and has a circumferential length which tapers radially inward (see Figures 1 and 4). Each lug is tapered inward in such a way that, viewed in the axial direction, it has the shape of a radial outer part of a circle, whose radius is equal to the inner radius of cylinder 2 and whose acute angle is 360 ° / N , where N is equal to the number of fin elements of each end fin 3.

One or more fin elements 4 of one end fin are at their outer radial end provided with an articulated projection 7, the free end of which is to be hooked on a hook 19 on a fin element 4 of the other end fin, so that the protrusion 7 forms a transport cover for a cable wound on the spool.

The outer circumferential surface of the cylinder 2 has a hook 8 on which one end of a cable can be attached when a cable is wound on the spool.

According to the invention, coil 1 is formed by a U-shaped channel 9 which is injection molded from plastic and then is bent back on itself to form a cylinder 2 with an end fin 3 at each end of the cylinder. . The base 10 of the U-shaped channel 9 forms the cylinder 2 and its walls 11 form the end fins 3. To allow channel 9 to fold back on itself, its walls 11 consist of a plurality of essentially rectangular wall elements 12 which are spaced from one another and evenly distributed along the length of channel 9. When channel 9 is curved, the wall elements 12 are separated as seen in Figure 4.

The ends 13 of the channel are connected to each other by protrusions 15, which here are in the form of hooks, which are formed on a projection 17 of the base 10 of the channel, said projection projecting at one end 13 of the channel in the longitudinal direction of the channel 9, being inserted into the holes 16 that are formed in the base of the channel at the other end 13 of the channel (Figure 2). Of course, it is also possible to form the holes in the projection 17 at one end 13 of the channel and the protrusions at the other end 13 of the channel.

The boss 17 of the base arranged with the protrusions 15 at one end 13 of the channel also has an opening 18 through which the hook 8, which is formed at the other end 13 of the channel, is inserted when connecting the ends 13 of the channel. channel.

In an alternative embodiment (not shown), the ends of the channel are connected to each other by the protrusion at one end of the channel being inserted between two bearing elements extending in the longitudinal direction of the channel and having an essentially shaped cross section. of L, at the end of the channel opposite the projection. The first L-shaped legs of the support elements are attached to the base. The two second L-shaped free legs face each other and form support parts of the projection when the projection is inserted between the support elements by interconnecting the ends of the channel. A stopper heel is arranged at the base of the channel between the two support elements, the projection being formed with a hole into which the stopper heel is inserted once the ends of the channels are connected to each other. The support elements are preferably arranged outside the base of the channel, so that the finished coil has a smooth outer circumferential surface.

The base 10 of the channel 9 has internal transverse grooves 5 which make the channel easier to bend.

To facilitate the formation of a cylinder 2 by bending the channel 9 into a U-shape, and to prevent the cylinder from collapsing when using the coil 1, each wall element 12 is provided with a lug 6 that extends past the base 10 and having a decreasing length in the longitudinal direction of the channel 9, separated from the wall element. Channel 9 can be curved until each lug 6 abuts an adjoining lug 6. Alternatively, they last 3

ES 2 287 488 T3 In the injection molding of the base 10 the channel is made of external transverse grooves that extend over the entire width of the base between a point between two contiguous wall elements 12 of a wall 11 of the channel and a point between two contiguous wall elements 12 of the other wall 11 of the channel.

The spool according to the invention can be used not only for winding cable but also for winding, for example, ropes, ropes, hoses, emery cloth, and the like. The coil can also serve as a separating or insulating element in cylinders or large pipes with wires inserted into the tube that is formed in the coil cylinder.