WO1993015992A1

WO1993015992A1 - Method of manufacturing disposable drums

Info

Publication number: WO1993015992A1
Application number: PCT/SE1993/000124
Authority: WO
Inventors: Ulf Lindstrand
Original assignee: Ulvator Ab
Priority date: 1992-02-18
Filing date: 1993-02-17
Publication date: 1993-08-19

Abstract

A method of manufacturing a metal-free disposable drum for cable and line, for instance, and consisting of a sleeve (1) of cardboard and two end pieces (2, 3) of compressed wood chip material or plywood, each end piece being produced in situ of a support ring (11) and a central ring (12) with conical peripheral surface (18). According to the invention the support ring (11) is applied on the end part (4, 5) of the sleeve free from play so that it is retained in a starting position, after which the central ring (12) is inserted a limited distance into the sleeve (1), this distance being less than the thickness of the central ring (12). The disposable drum thus pre-assembled is then placed between two press members having parallel pressure surfaces facing each other, the pressure surfaces being brought into abutment with the end surfaces (6, 7) of the sleeve and at the same time the rings (11, 12) being pressed in so that their outer sides (13, 16) are located in a plane coinciding with the end surface (6, 7) of the sleeve for forming a wedge joint.

Description

Method of manufacturing disposable drums

The present invention relates to a method of manufacturing metal-free disposable drums intended for a continuous flexible object and having a diameter within the range of 500-900 mm, said drum consisting of a cylindrical form stable sleeve of cardboard with parallel end surfaces and two circular end pieces of compressed wood chip material or plywood joined firmly to the end parts of the sleeve by means of wedge joints and having a central aperture for shaft members for winding and unwinding the object, each end piece being produced in situ of a flat support ring for the object having a central aperture for the sleeve with a cylindrical wall surface, and a flat central ring with conical peripheral surface, said rings having parallel outer and inner sides.

It is known to use disposable drums with a size of 400 mm, this dimension referring to the diameter of the end pieces. Such disposable drums are described in US-A-2 881 986. The disposable drums are manufactured in such a manner and the joint between the end pieces and the sleeve forming the core is so constructed that they are not sufficiently strong to be used for larger sizes, from 500 mm to 900 mm. Wooden drums of conventional type are therefore still used for these sizes. However, these wooden drums are expensive and must therefore be re-used in order to make the handling of cable and line more economical as a whole. However, the return system functions most unsatisfactorily, thereby making the handling of cable and line less economical. Another drawback is that the end pieces of the wooden drums, made of planks nailed together, are easily damaged. Such damage in the timber may easily damage the cable or line as it is being uncoiled from the rotating wooden drum, particularly if the cable or line is running from the coil in a direction not perpendicular to the axis of rotation of the drum. The damage may be so serious that the entire coil or parts of the cable or line must be discarded. Interruptions may also occur, i.e. the work of laying cables or lines may be delayed. Another problem with said wooden drums is that the centre of rotation does not usually coincide with that of the sleeve and therefore not with the central axis of the coil either. This is extremely unsatisfactory and entirely unacceptable for opto-cable, for instance, which is very sensitive and may easily be damaged as a result of being off-centre during coiling or uncoiling. Deformation caused by the nature of the timber (not dead material) and faults or difficulties in manufacturing the wooden drums also contribute to this asymmetry. One suggestion for reducing this problem has been to replace the core formed of planks with a sleeve of iron. However, this suggestion does not solve all the problems and also creates new problems such as extra weight and increased cost.

It should also be possible to burn an inexpensively manufactured drum without any metal waste remaining. It has so far been impossible to satisfy this desire in the case of the sizes under consideration here, i.e. 500-

900 mm, since the drums are assembled using various metal parts such as nails and bolts.

Another problem is that a drum supplied is not utilised to its full capacity since customers may order smaller quantities of a cable, etc. than the drum can hold and there is usually no other suitably sized drum in the standard range, for the length ordered. It is therefore also desirable to be able to easily adjust the capacity of a disposable drum to the length of cable, etc. ordered, thereby enabling savings in material, as well as storage and transport space. In the disposable drum according to Figures 1-3 in said US-A-2 881 986 both the central ring and the support ring have conical surfaces and the conicity is so great that axial forces will be exerted on the central ring, with the risk of it being displaced out of the sleeve, particularly when uneven loading occurs on the support ring as may happen when uncoiling the cable, so that the wedge joint loosens at the diametrically opposite side of the support ring and central ring in relation to the point of load. Furthermore, it is difficult to assemble the disposable drum according to US-A-2 881 986 with uniform result during mass production, since a desired position of the support ring first placed on the sleeve may alter when the central ring is pushed in, and the central ring may easily, but unintentionally, be pressed in off centre so that the wedge joint becomes uneven all round. Furthermore, the pressed in length may differ from one disposable drum to another. US-A-2 881 986 neither reveals nor suggests simultaneous pushing in the support and central rings after they have been placed in a more clearly defined starting position in relation to the sleeve and employing very slight conicity on the peripheral surface of the central ring.

The object of the invention is to eliminate the problems mentioned above and manufacture a disposable drum that fulfils said desires in a simple and efficient manner resulting in such a strong wedge joint that larger disposable drums, namely sizes up to 900 mm, can be manufactured than has been possible before in situations where the conventional, inconvenient wooden drums have had to be used, and also ensuring that the end pieces are parallel to each other and that their outer sides coincide with the end surfaces of the sleeve, thereby ensuring uniform distance between the support rings all round (360°). The disposable drum according to the invention is manufactured by applying the support ring on the end part of the sleeve free from play so that, with a good fit to the sleeve it is retained in a starting position after having been pushed in a distance onto the end part shorter than the thickness of the support ring, after which the central ring, which is thicker than the support ring and has a peripheral surface with conicity of 1-5°, is inserted a limited distance into the end opening of the sleeve, this distance being less than the thickness of the central ring, said central ring at its inner side having a diameter somewhat less than the inner diameter of the sleeve so that said insertion can be performed manually, and at its outer side having a diameter somewhat larger than the inner diameter of the sleeve so that said limited insertion is ensured when an initial wedge engagement is achieved in cooperation with the inner side of the sleeve, after which the disposable drum thus pre-assembled is placed between two press members having parallel pressure surfaces facing each other, each of which covers the opposite end surface of the sleeve and at least a part of the support ring, the pressure surfaces of said press members being brought into abutment with the end surfaces of the sleeve and at the same time the support and central rings being pressed in so that their outer sides are located in a common plane coinciding with the respective end surfaces, each end piece thereby being joined to the sleeve by means of a permanent wedge joint thus formed.

The invention will be described further in the following with reference to the drawings.

Figure 1 is a longitudinal section through a disposable drum manufactured in accordance with the present invention. Figure 2 is a view in perspective of a sleeve and parts of an end piece to be anchored to the end of the sleeve by means of a wedge joint.

Figure 1 shows a longitudinal section through a disposable drum manufactured in accordance with the invention and consisting of a cylindrical sleeve 1 forming a form stable core, and two circular form stable end pieces 2, 3 joined firmly to the sleeve 1 at its two end parts 4, 5. The sleeve 1 has flat end surfaces 6, 7, located parallel to each other and perpendicular to the central axis 8 of the sleeve. The diameter of the end pieces 2, 3 is larger than that of the sleeve 1 so that, between them, they define a space 9 for a coil of a . continuous object comprising preferably cable or line, but also wire, wire cable, rope, cord, ribbon, hosing, chain or similar easily coiled, flexible object. Each end piece 2, 3 has a central aperture 10 to receive a shaft or two opposing shaft extensions of equipment for coiling or uncoiling the cable, etc. The sleeve consists of cardboard, manufactured from layers of cardboard glued together with waterproof adhesive, and has a constant predetermined wall thickness to ensure sufficient rigidity to carry said coil.

The size of the disposable drums manufactured according to the invention is within the range 500-900 mm, this size referring to the diameter of the end pieces.

Thanks to the invention it is easy to adjust the capacity of the drum to the quantity of cable, etc. desired by a customer for a certain purpose, by choosing a sleeve length which will ensure that the space between the end pieces will be utilised to the full for each individual order. The end pieces consist of wood chip material or plywood. According to the invention disposable drums are manufactured that are entirely free from metal objects and plastic. Each end piece comprises two separate parts, namely a flat support ring 11 for the cable, etc., and a flat central ring 12 with central aperture 10 for said shaft or shaft extensions. The outer and inner sides 13, 14 of the support ring 11 are parallel and the ring has a central aperture 15 with cylindrical wall surface and a diameter equal to or somewhat larger than the outer diameter of the sleeve 1 so that the support ring 11 can be applied on the end part of the sleeve 1 without any play appearing, i.e. the support ring 11 is fitted onto the sleeve with slight friction so that it is retained in a starting position. Application is suitably performed manually on a sleeve 1 placed horizontally on a conveying belt (not shown), the width of the belt corresponding to the length of the sleeve 1 less twice the thickness of the support ring 11, the belt acting as a support and preventing the support rings 11 from being pushed too far in on the end parts 4, 5 of the sleeve 1 during this initial manual assembly phase. Each support ring 11 is thus pushed onto the end part 4, 5 a distance equivalent to or preferably slightly less than the thickness of the support ring 11. The thickness of the support ring is 10- 25 mm depending, amongst other factors, on the size of the disposable drum.

The central ring 12 has parallel outer and inner sides 16, 17 and a conical peripheral surface 18 (see Figure 2), extending between the outer and inner sides 16, 17. The diameter of the central ring 12 is slightly smaller, e.g. 1-3 mm, on the inner side 17 than the inner diameter of the sleeve 1, and the diameter on its outer side 16 slightly larger, e.g. 2-5 mm, than the inner diameter of the sleeve 1 so that the central ring can be inserted a limited distance into the end opening 19 of the sleeve until an initial wedge engagement is achieved in cooperation with the inner side 20 of the sleeve. This limited distance is at most half and preferably at most one third of the thickness of the central ring 12. This insertion of the central rings 12 is suitably performed manually until said initial wedge engagement has been achieved so that the central rings 12 remain in their laterally, axially projecting positions. The thickness of the identical central rings 12 is greater than that of the identical support rings 11 and lies within the range 25-35 mm. It will be understood that the support rings 11 can be applied after the central rings 12 have been inserted into the sleeve in the initial positions described.

The disposable drum preassembled in this manner is than conveyed by the conveyor strip to a press station with two press members, spaced from each other, between which the disposable drum is placed. The press members have vertical, parallel pressure surfaces facing each other, these surfaces being larger than the cross-sectional area of the sleeve 1 and suitably so large that the whole end piece being formed is covered from each direction. The press members are moved towards each other until their pressure surfaces are brought into abutment with the end surfaces 6, 7 of the sleeve. During this process the central rings 12 are pressed into the end openings 19 of the sleeve 1 and the support rings 11 are adjusted to their correct positions so that their outer sides 13, 16 and the end surfaces 6, 7, respectively of the sleeve 1 are located in one and the same vertical plane. While the central rings 12 are being forced in in this way the wedge forces increase continuously and a sturdy, permanent wedge joint is achieved in the final position for each end piece, in which the sleeve 1 is clamped by radially outwardly directed wedge forces from the central ring 12 and radially inwardly directed forces from the support ring 11.

If desired a waterproof adhesive may be applied on the conical surface of the central ring and/or on the inner side of the sleeve in order to strengthen the wedge joint.

The central ring 12 has a conicity of 1-5°, depending amongst other factors, on the thickness of the central ring.

The method according to the invention thus means that no bolts or steel parts are required to assemble the drum, which in turn means that all material can be discarded or burned on site once the line or cable has been uncoiled, since all material is environmentally friendly.

Claims

C L A I M S

1. A method of manufacturing metal-free disposable drums intended for a continuous, flexible object and having a diameter within the range of 500-900 mm, said drum consisting of a cylindrical, form stable sleeve (1) of cardboard with parallel end surfaces (6, 7) and two circular end pieces (2, 3) of compressed wood chip material or plywood joined firmly to the end parts (4, 5) of the sleeve by means of wedge joints and having a central aperture (10) for shaft members for winding and unwinding the object, each end piece being produced in situ of a flat support ring (11) for the object, having a central aperture (15) for the sleeve (1) with a cylindrical wall surface, and a flat central ring (12) with conical peripheral surface (18), said rings (11, 12) having parallel outer and inner sides (13, 14; 16, 17), characterized in that the support ring (11) is applied on the end part (4, 5) of the sleeve free from play so that, with a good fit to the sleeve (1), it is retained in a starting position after having been pushed in a distance onto the end part (4, 5) shorter than the thickness of the support ring (11), after which the central ring (12), which is thicker than the support ring (11) and has a peripheral surface with conicity of 1-5° is inserted a limited distance into the end opening (19) of the sleeve (1), this distance being less than the thickness of the central ring (12), said central ring (12) at its inner side (17) having a diameter somewhat less than the inner diameter of the sleeve (1) so that said insertion can be performed manually and at its outer side (16) having a diameter somewhat larger than the inner diameter of the sleeve (1) so that said limited insertion is ensured when an initial wedge engagement is achieved in cooperation with the inner side (20) of the sleeve, after which the disposable drum thus preassembled is placed between two press members having parallel pressure surfaces facing each other, each of which covers the opposite end surface of the sleeve and at least a part of the support ring (11), the pressure surfaces of said press members being brought into abutment with the end surfaces (6, 7) of the sleeve and at the same time the support and central rings (11, 12) being pressed in so that their outer sides (13, 16) are located in a common plane coinciding with the respective end surfaces (6, 7) each end piece (11, 12) thereby being joined to the sleeve (1) by means of a permanent wedge joint thus formed.

2. A method as claimed in claim 1, characterized in that the support rings (11) have a thickness of 10-25 mm and the central rings (12) have a thickness of 25-35 mm.

3. A method as claimed in claim 1 or 2, characterized in that a waterproof glue is applied on the conical surface (18) of the central ring (12) and/or the inner side (20) of the sleeve (1) in order to strengthen the wedge joint.

4. A method as claimed in any of claims 1-3, characterized in that preassembly of the disposable drum is performed in conjunction with a conveying belt with a width corresponding to the length of the sleeve (1) less twice the thickness of one support ring (11), whereupon the sleeve (1) is placed horizontally and across the belt, and that the preassembled disposable drum is conveyed by the conveying belt to a subsequent press station with said press members arranged on either side of the conveying belt with their pressure surfaces vertically aligned.

5. A metal-free disposable drum intended for a continuous, flexible object and having a diameter within the range of 500-900 mm, said drum consisting of a cylindrical, form stable sleeve (1) of cardboard with parallel end surfaces (6, 7) and two circular end pieces (2, 3) of compressed wood chip material or plywood firmly joined to the sleeve at its end parts (4, 5) by means of wedge joints and having a central aperture (10) for shaft means for winding and unwinding the object, each end piece consisting of a flat support ring (11) for the object, said ring having a central aperture (15) for the sleeve (1) and a flat central ring (12) with a conical peripheral surface (18), characterized in that the central ring (12) is thicker than the support ring (11), that the outer sides (13, 16) of the support and central rings (11, 12) are located in a common plane coinciding with respective end surfaces (6,7) of the sleeve, and that the central ring (12) has a conicity of 1-5°.

6. A disposable drum as claimed in claim 5, characterized in that the support rings (11) have a thickness of 10-25 mm and the central rings (12) have a thickness of 25-35 mm.

7. A disposable drum as claimed in claim 5 or 6, characterized in that a waterproof glue is applied on the conical surface (18) of the central ring (12) and/or the inner side (20) of the sleeve (1) in order to strengthen the wedge joint.