EP0697991B1 - Cable reel and a method for manufacturing it - Google Patents

Abstract

The object of the invention is a cable reel, which includes a drum (2) made from sheet steel and ends (1) i.e. flanges attached to both sides. Curved tabs (4) are formed in the ends (1) of the drum (2) and extending in an axial direction through the ends (1), to which tabs corresponding curved slots (11) are formed. The parts of the tabs (4) extending from these slots (11) beyond the ends (1) are bent onto the external surface of the ends (1). The length and width of the tabs (4) in the direction of the circumference are so great taking into account the thickness of the sheet steel of the drum (2) and the diameter of the drum that the deformation work involved in bending the tabs due to the curved tabs is many times greater than compared to the bending of a straight tab. The invention is also concerned with a method for manufacturing the cable reel.

Description

• The object of the invention is a cable reel, which includes a drum and ends i.e. flanges attached to both sides, and in which curved tabs formed in the ends of the drum and extending in an axial direction through the ends are used in the attachment of the drum and the ends, in which corresponding curved slots are formed and the parts of the tabs extending beyond the ends are bent onto the external surface of the ends. The invention is also concerned with a method for manufacturing a cable reel.
• Known cable reels are generally made from wood strips and thicker wood. The end disks are manufactured from sheets of wood strips laid crosswise. The drum is typically made from slightly conical strips, from which a cylindrical component is formed. The above manufacturing technique for large drums is time-consuming and the drums have a considerable weight. This invention is mainly concerned with cable reels in which the drum diameter is 150 mm or greater. Small cable reels are manufactured as one piece by either moulding or spray-pressing from plastic, but this method is not suitable for large reels.
• US publication 3,544,032 presents a cable reel of the type referred to in the introduction. The tabs of the drum are fed through openings in the ends and bent. Here the tabs are very narrow and their protrusion is small. It does not require a very great force to bend them, especially if the opening is in the form of a triangle or rectangle. On the other hand, the publication does not show means for bending larger tabs.
• The intention of this invention is a stronger cable reel than previously, the manufacture of which is simple. The characteristic features of the invention are presented in the accompanying Claims. The invention is to a great extent based on the realization that essentially in bending each curved sheet-metal part deformation work must be carried out, which on the other hand the load would have to do in reverse in order to separate the end from the drum. The deformation of the tabs locks them effectively in place. The optimal deformation requires a precise shape for the curved opening. Due to the great deformation work it is advantageous and often essential to use a machine tool for bending. This sweeps a local formation over the entire length of the tab.
• Other advantages and forms of application of the invention appear in connection with the later examples of application. In what follows the invention is illustrated by reference to the accompanying Figures, which show various cable reels in accordance with the invention, as well as their components.

Figure 1

shows a drum and end before they are attached to one another.

Figure 2

shows a finished cable reel.

Figure 3

shows a detail of the cable reel in partial cross-section.

Figure 4

shows a cross-section of the construction of an end.

Figure 5

shows a cross-section of the seam of the drum.

Figure 6

shows the mechanical bending of the tabs.

Figure 7

shows the manufacture of an end by die-cutting.

• The principal components of a cable reel are here two ends 1 and 2 and the drum 3 between them. The drum is most advantageously manufactured from galvanized sheet steel, with a thickness of 0,3 - 2 mm, corresponding to drum sizes of 160 - 1200 mm. The ends are most advantageously made from birch or mixed plywood, but other strong boards, such as particle board or chipboard, may be considered. The manufacture of the cable reel begins by cutting an essentially rectangularly shaped piece of sheet steel, on both edges of which indentation are cut in order to make tabs 4. The bends to be made for seam 10 appear later. The drum in accordance with Figure 1 is bent from the sheet and the seam 10 is secured. At the same time disc 1 is made from birch plywood in which the curved openings 11 are formed. Manufacture takes place most advantageously by die-cutting in accordance with Figure 7, which is dealt with later in detail.
• Alternatively holes are drilled at the start of the curves and the required curves are cut with a fretsaw with the aid of a jig. After this the end 1 and the drum are joined together, the tabs 4 are pushed through the curved openings 11, and the ends are pressed against the drum, after which the ends of the tabs 4 are pressed against the outside of the end 1 by means of a hydraulic press. Figure 6 shows the tool 15 and the method of operation, by means of which the ends 14 of the tabs 4 are bent. The head of the tool 15 that forms the tabs has a wing shape, when the bending takes place gradually during the rotation of the tool. Compared with bending that takes place at once less force is required, because the forming is limited at each moment locally to a quite small area.
• Figure 2 shows a finished drum, in which the fold 14 of the tab 4 onto the outer surface of the end 1 can be seen. In addition., the Figure shows in broken lines a support disc 3, which, if addition strength is required, can be attached to the end disc 1, before the drum 2 is attached to it. In accordance with Figure 3 the support disc 3 carries the drum over its entire circumference and thus provides the construction with addition breaking strength.
• Figure 4 shows the joint between the drum 2 and the end 1 in detail. Here too the support disc 3 is visible. The tab 4 has been pushed through the curved opening 11 of the drum and its end has been turned, when the folds 14 can be seen against the end 1.
• The cable reel with its cable can be advantageously protected by means of a sheet metal cover 8, in each edge of which a groove 9 is formed. This is made from an essentially rectangular piece of sheet metal, which is formed into a cylindrical cover around the drum. By means of the groove in the edges the cover stays firmly in place. The ends include suitable locking devices, e.g. foldable tabs, by means of which the sheet is made to remain on top of the drum.
• The tabs of the drum extend advantageously 9 - 12 mm from the end. In any event the protrusion is between 7 - 20 mm. In general tabs longer than 12 mm remain "grinning" above the surface of the end, because the stress created during the bending does not really extend beyond 10 mm. Forming carried out by means of device in accordance with Figure 6 pulls the tabs outwards, in which case the curved parts of the drum 2 between the tabs bit into the inside surface of the ends. It is possible to make small curved grooves for them if it is desired to increase the load- bearing capacity in this area. In any case the curved parts cut more or less into the inner surface of the ends, creating a support for the drum over the entire circumference.
• The seam 10 of the drum 2 is formed by overlapping the ends of the metal sheet in such a way that bend 5 is formed in the sheet that remains underneath, by means of which places itself easily under the opposite end of the sheet in accordance with Figure 5. The ends of the sheet are secured to one another by point welding 6, when a strong and even seam 10 is obtained.
• In some manufactured cable reels dimensions of the following type were used. A cable reel with a diameter os 500 mm, in which a 240 mm drum was used was manufactured as follows. 0,7 mm thick galvanized steel sheet was used in the drum and 15 mm thick birch plywood in the ends. There were four tabs and they had a length of 100 mm (curved dimension). A 1500 mm diameter end was manufactured from 25 mm thick birch plywood and the 1100 mm drum in it was made from 1,25 mm galvanized sheet steel. There were eight tabs and these had a length of 100 mm.
• In a drum of diameter of 150 - 1500 mm galvanized sheet steel, with a thickness of 0,3 - 2 mm is used, adapted in such a way that the thickness s of the sheet of the drum 2, the width l of the tab 4, and the diameter D of the drum 2 fill the following conditions: $$\text{3,5}\frac{\text{1}}{{\mathit{\text{<figure-callout id="2" label="mm" filenames="imgf0001.png,imgf0002.png" state="{{state}}">mm</figure-callout>}}}^{\text{2}}}\text{<}\frac{\mathit{\text{D}}}{{\mathit{\text{s}}}^{\text{2}}\mathit{\text{l}}}\text{< 9}\frac{\text{1}}{{\mathit{\text{<figure-callout id="2" label="mm" filenames="imgf0001.png,imgf0002.png" state="{{state}}">mm</figure-callout>}}}^{\text{2}}}$$

  
• The protrusion of the tab is the abovementioned 9 - 12 mm. In cable reels in accordance with this the curve of the tabs causes a considerable deformation requirement. On the other hand, the finished bend resists considerably larger loadings than previously.
• Compared with the bending of a flat sheet, the bending force required to bend the entire tab at one time increases many times, to become at least 15 times greater. In general the force required would be still greater than this, for which reason it is better to bend the tab by means of local forming, which is carried out by means of sweeping over the tab in the manner shown in Figure 6.
• Inner discs are used in drums with a diameter of 600 mm or greater, though it is possible to replace them by increasing the material thickness in both the drum and end boards. In these too an inner drum can be used, if it is desired to further strengthen the construction.
• In the method of making the end in Figure 7 a longitudinal blank 22 is moved through die 16, which cuts the ready end boards 1 from it. The die 16 consists of a fixed lower section and upper part that strikes against it, of which only the cutting blades are drawn visibly. Openings for the tabs are formed by striking the upper curved blade 18 against the curved opening blade 17 of the lower part. A thin curved piece is removed through the lower blade 17. At the time the entire end disc can be die-cut from a blank board by means of blade 19. If required a centre opening 21 can be formed by the same strike with blade 20.

Claims (8)

1. A cable reel, which consists of a drum (2) with a diameter of 150 - 1500 mm and made from galvanized sheet steel with a thickness of 0,3 - 2 mm, ends (1) i.e. flanges attached to both sides, and in which curved tabs (4) are formed in the ends (1) of the drum (2), extending in an axial direction through the ends (1), to which tabs corresponding curved slots (11) are formed, the parts of the tabs (4) extending from these slots (11) beyond the ends (1) being bent outwards onto she external surface of the ends (1),
   characterized in that the part of the tab protruding from the end, i.e. the part to be bent is in length 7 - 20 mm, most advantageously 9 - 12 mm, and that in the drum (2) sheet steel is applied in such a way that the thickness s of the drum (2) sheet, the width l of the tab (4), and the diameter D of the drum (2) fill the following condition: $$\text{3,5}\frac{\text{1}}{{\mathit{\text{mm}}}^{\text{2}}}\text{<}\frac{\mathit{\text{D}}}{{\mathit{\text{s}}}^{\text{2}}\mathit{\text{l}}}\text{< 9}\frac{\text{1}}{{\mathit{\text{mm}}}^{\text{2}}}$$

   

   in which case the length and width of the tabs (4) in he direction of the circumference are so great, taking into account the thickness of the sheet steel of the drum (2) and the diameter of the drum, that the deformation work involved in bending the tabs due to the curved tabs is many times greater when compared to the bending of a straight tab.
2. A cable reel in accordance with Patent Claims 1 or 2, characterized in that the material of the end (1) is one of the following: birch plywood, mixed plywood, particle board, chipboard.
3. A cable reel in accordance with Patent Claim 1 or 2, characterized in that inside the drum (2) there is a support disc (3) attached to the ends (1), which carries the drum (2) over its entire circumference.
4. A cable reel in accordance with one of Patent Claims 1 - 3, characterized in that the curved part of the drum (2) between the tabs (4) that protrude through the ends (1) penetrates the inner surface of the end (1).
5. A cable reel in accordance with one of Patent Claims 1 - 4, characterized in that the thickness of the ends (1) is 6 - 30 mm in a reel in which the diameter of the drum (2) is 150 - 1500 mm.
6. A cable reel in accordance with one of Patent Claims 1 - 5, characterized in that inside the drum (2) that is actually intended for the cable there is an internal support drum, which is also made from sheet metal and is attached to the ends by means of tabs in its ends.
7. A method for manufacturing a cable reel in accordance with Patent Claim 1, in which method a drum (2) manufactured from sheet steel with tabs (4) formed in its ends according to claim 1, and ends (1) manufactured from board in the circumference of which curved openings (11) corresponding to the tabs (4) of the drum (2), are joined to one another by pushing the tabs (4) through the openings (11) in the ends (1) and by bending the protrusions (14) against the surface of the end (1), whereby the bending of each protrusion (14) is carried out by a wing-shaped member (16), which is rotated over the circumference in the same direction as it.
8. A method for manufacturing a cable reel in accordance with Patent Claim 1, in which method a drum (2) manufactured from sheet steel with tabs (4) formed in its ends according to claim 1, and ends (1) manufactured from board in the circumference of which curved openings (11) corresponding to the tabs (4) of the drum (2), are joined to one another by pushing the tabs (4) through the openings (11) in the ends (1) and by bending the protrusions (14) against the surface of the end (1), whereby the curved opening (11) in the end (1) are formed by die-cutting a thin curved piece out of the board.

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