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The present invention relates to a method for joining together a plurality of bobbin sections to provide a bobbin, and then particularly to a method of joining tubular first bobbin section of circular cross-section and made of wound paper or like material with an outer diameter which considerably exceeds the thickness of the material from which the bobbin section is formed to a corresponding second bobbin section in end-to-end relationship with the aid of an adhesive substance such as glue or an adhesive paste.

The invention also relates to plant for joining together a plurality of bobbin sections to form a bobbin of predeter¬ mined length.

The present invention obtains particular application when joining together bobbin sections which are comprised of tightly wound or coiled thin paper webs and which are used to roll-up a paper web which leaves a paper machine and which can be used as newsprint, writing paper, copying paper, etc.

The bobbin used in this regard is moved together with a rolled-up paper web to a station in which the paper web is unrolled for its intended purpose and the released bobbin can be reused to roll-up another paper web. However, the reuse of a bobbin for rolling-up a paper web requires the whole of the bobbin to be intact, and not even slight damage to the bobbin edges can be accepted.

SUBSTITUTE SHEET ISA/SE

BACKGRQVfl ART

Various methods of joining together bobbin sections with the sections placed end-to-end and with the aid of adhesive substances are known to the art. Plant machinery for carrying out such methods are also known.

There is known to the art a method and also a machine which enable bobbins and bobbin sections that have damaged end surfaces to be reused. To this end, there is used a unit which is functions to cut away the damaged section, together with a further length of the bobbin, normally 10 cm, such that the cut surface will form a right angle to the longitudinal axis of the bobbin section.

The thus formed right-angled end-surface, which with regard to surface extension is the smallest surface possible, is coated with a layer of adhesive and then pressed against a correspondingly shaped end-surface of another bobbin section.

During this severing and clean-cutting operation and while the adhesive takes effect, the bobbin sections rest against a number of section supporting rollers, normally two rollers, and the right-angled surfaces of the bobbin sections are pressed against one another as the adhesive effect develops, so that the adhesive substance can harden as the bobbin sections are pressed against one another.

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TECHNICAL PROBLEMS

When considering the earlier standpoint of techniques as described above, it will be seen that a technical problem resides in providing conditions which will enable each or

at least the majority of the severed sections of edge- damaged bobbins that are intended to be clean cut can be kept as small as possible.

Another technical problem associated with the application defined in the introduction is one of realizing the significance of increasing the surface extension of the surface to be coated with an adhesive substance in relation to the above related known technique, and to provide a sufficiently well-defined supportive edge which is able to take-up the pressure forces that are active while the adhesive becomes effective.

Another technical problem is one of realizing the signifi- cance of positioning the cut surfaces between mutually facing bobbin sections so as to enable these surfaces to adapt to the nature of the damage, at least on certain occasions and in the case of certain forms of damage.

Still another technical problem is one of realizing the significance of through the medium of a milling process using a larger adhesion surface extension than that afforded by cutting the bobbin sections at right angles and still provide conditions whereby mutually opposing bobbin sections can be pressed together while the adhesive takes effect, such as hardens, without the bobbin section sliding in relation to one another.

Another technical problem is one of realizing that the end- related and outer edge region of one bobbin section shall be worked to the shape of a frustum of a cone with the conical shape converging from the bobbin section.

Still another technical problem is one of realizing the significance of allowing the end-related and inner edge region of the bobbin section that can coact therewith to be worked, or machined, to a corresponding frusto-conical

shape with the cone shape converging inwardly in relation to said bobbin section.

Yet another technical problem is one of realizing the significance in allowing an outer and/or an inner section of respective edge regions to be provided with a narrow edge so orientated as to support one another when opposing bobbin sections are pressed against one another, subsequent to having applied adhesive, such as glue or adhesive paste to the worked surfaces.

It will also be seen that a technical problem resides in realizing the significance of choosing the cone forms and the angular value.

It will also be seen that another technical problem resides in realizing the significance of directing said edges at right angles, or generally at right angles, to a bobbin- section centre line, and to give the selected edge a width of normally less than 10 mm.

It will also be seen that a technical problem is one of providing plant which is preferably adapted for use in performing a jointing process which solves one or more of the aforesaid technical problems and which is able to provide conditions in different stations or units which will enable bobbins of predetermined lengths to be readily obtained from a number of bobbin sections of mutually different smaller lengths.

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With the intention of solving one or more of the aforesaid technical problems, there is provided in accordance with the present invention a method for joining together a plurality of bobbin sections to provide a bobbin, and then particularly to a method of joining tubular first bobbin

section of circular cross-section and made of wound paper or like material with an outer diameter which considerably exceeds the thickness of the material from which the bobbin section is formed to a corresponding second bobbin section in end-to-end relationship with the aid of an adhesive substance such as glue or adhesive paste.

It is now proposed in accordance with the invention that the end-related and outer edge region of one bobbin section is given the shape of the frustum of a cone, hereinafter referred to as a frusto-conical shape, which is convergent from said one bobbin section; that the end-related and inner edge region of the second bobbin section that coacts with the first bobbin section is given a corresponding conical shape which is convergent inwardly to said second bobbin section; that an outer and/or an inner part of respective edge regions is provided with respective edges which positioned for supportive coaction with one another when the bobbin sections are pressed against each other, subsequent to having provided one or both of the worked surfaces with a thin layer of adhesive substance.

According to proposed embodiments lying within the scope of the inventive concept, the cone will have a cone angle greater than 20° and smaller than 45°, normally about 30 ^β .

It is also suggested that the edge shall extend at right angles or generally at right angles to a bobbin-section centre line.

It is particularly proposed that the edge shall have a width of between 1 and 10 mm, preferably about 1-5 mm, particularly when the bobbin section has a wall thickness of between 10 and 20 mm.

The present invention also relates to plant machinery operative in forming a bobbin from a number of short bobbin

sections, preferably while applying a jointing method according to the aforegoing, said plant comprising

a) a unit for clean-cutting the end parts of damaged bobbin sections at right angles;

b) a unit for preparing and/or adjusting one and/or the other end-part of each clean-cut bobbin section, for joining the sections end-to-end;

c) a unit which is operative in working the bobbin- section end-surfaces that are to be joined together;

d) a unit for applying an adhesive substance, such as glue or an adhesive paste, to one or both of the mutually opposed jointing surfaces;

e) a unit which is operative in pressing the bobbin sections together while the adhesive takes effect; and

f) a unit which cuts the thus produced bobbins into predetermined lengths.

■ftPVAHTASES

Those advantages primarily afforded by an inventive method and an inventive plant reside in the provision of condi¬ tions in which not only is it possible to reduce the length to which a damaged bobbin section needs to be cut in order to provide cleanly-cut end-parts, but also that conditions are provided which enable a joint to be obtained between mutually adjacent bobbin sections that is sufficiently strong for the intended purpose.

The main characteristic features of an inventive method for jointing bobbin sections are set forth in the characteriz¬ ing clause of the following Claim 1, while the main characteristic features of an inventive plant are set forth in the following Claim 5.

BRIEF DESCRIPTION OF THE DRAWING

An exemplifying embodiment at present preferred of a method for jointing bobbin sections together end-to-end in accordance with the present invention, and associated plant will now be described in more detail with reference to the accompanying drawing, in which

Figure l illustrates a known method of end-joining short bobbin sections;

Figure 2 is a sectional view of the end-parts of two co- aligned bobbin sections which are intended to be joined together in accordance with the invention;

Figure 3 illustrates a first part of a plant located above a second part of the plant;

Figure 4 is a sectional view of the first plant;

Figure 5 is a sectional view of the second plant; and

Figure 6 is a side view of a milling head suitable for use when practicing the invention.

DESCRIPTION OF EMBODIMENTS AT PRESENT PREFERRED

Figure 1 illustrates a known method of joining a first tubular bobbin section 1 comprised of wound paper or like material and having a circular cross-section whose outer diameter "D" is much larger than the wall thickness "t" of the bobbin section, to a corresponding second bobbin section 2 in end-to-end relationship with the aid of an adhesive substance, such as glue or an adhesive paste.

The earlier known method involves clean-cutting the end- surface la of the first bobbin section l at right angles and providing the clean-cut surface with an adhesive layer and pressing this layer against an end-surface 2a of the second bobbin section.

The bobbin section is moved along guide rails (not shown) and the surfaces la and 2a are pressed together while the adhesive takes effect with the aid of press means not shown in the Figure.

Figure 2 illustrates features characteristic of the invention, wherein the end-related and outer edge-region la' (located uppermost in Figure l) of one bobbin section 1 are given a frusto-conical shape lb which converges away (to the left) from said one bobbin section 1.

The end-related and inner edge region 2a' of the second bobbin section 2 are worked or brought to a corresponding frusto-conical shape 2b, which is inwardly convergent (to the left) of the second bobbin section 2.

An outer and/or an inner part of the edge-region la' and the edge-region 2a' respectively is provided with a respective edge lc and 2c, these edges lc, 2c being orientated for mutual supportive coaction when the bobbin sections 1, 2 are pressed against one another, after having applied said adhesive substance to respective worked surfaces lb and lc.

The illustrated frusto-conical forms defined by the cone angle "a" in Figure 6 are chosen with a cone angle greater than 20° and smaller than 45°, normally about 30°.

The respective edges lc and 2c may be directed at right angles, or generally at right angles, to a bobbin-section centre line "C ^H .

When the thickness "t" (2t=D-d) lies between 12 and 15 mm of a bobbin section, the edge will conveniently have a width "b" of between 2-3 mm.

The principle of the invention enables a choice to be made between the size of the edge surfaces lc, 2c and the size of the surface extension lb, 2b.

The larger the edge, the greater the resistance to applied pressure. The smaller the cone angle, the larger the surface extension.

These parameters enable the person skilled in this art to readily evaluate required strength conditions.

In respect of this application, a thickness "t" of 17 mm and an outer diameter "D" which varies between 0.15 and 0.40 m enables an edge "b" of 2 mm and a cone angle "a" of 30 ^* to be chosen.

Plant for joining together a number of short bobbin sections to form a complete bobbin, preferably while applying the aforedescribed jointing method, will now be described in more detail with reference to Figure 3.

The plant includes to the aforesaid end a unit 10 in the form of a cutting blade li which is mounted for rotation about a rotary axle 12 and which can be moved in the direction of the arrow 13 by means not shown, to a position

in which the blade 11 can clean-cut end-parts 14a of damaged bobbin sections at right angles, as illustrated at 14.

Although not shown, the plant includes a unit by means of which an end-surface 34a is brought automatically or manually in line with a milling head 35 and thereafter the end-surface 34b in line with a milling head 37 and its rotational axle 38.

The plant also includes a unit 30 which functions to work one or both of the end-surfaces of bobbin sections.

This unit 30 is comprised of a wheel 31 which is driven by an axle 32 and which is pressed down against the bobbin section 34 in the direction of the arrow 33 by means not shown, so as to rotate the bobbin section. The milling head 35 is then lowered down onto the end-surface 34a of the bobbin section in the direction of arrow 36 by means not shown, so as to mill a surface extension lb having an edge lc.

The end-surface 34b of the bobbin section is then brought to another determined position and the milling head 37 is swung down about a rotary axle 38 for coaction with the end-part 34b, in the manner illustrated in Figure 3, therewith to form an extension surface 2b and an edge 2c.

Although not shown, there can be used, depending on the length of the bobbin section 34, sensors which bring the end-surface 34b to a predetermined position in relation to the milling head 37, and also the end-surface 34a to a predetermined other position in relation to the milling head 35.

It is necessary for the plant to include a unit 40 which functions to apply adhesive substance to one or both of the worked end-surfaces.

The unit 40 may have the form of a workman who manually applies an adhesive layer to a worked surface lb and lc, or may have the form of an automatically functioning device mounted in the proximity of the milling head 35 and functioning to apply the adhesive, either by spraying or some like process, after the surfaces have been worked.

The plant also includes a unit 50 which presses the short end-worked bobbin sections axially together while the adhesive takes effect and thereafter moves the bobbin away from other bobbin sections waiting to be joined.

The unit 50 includes matrix parts 51, 52 which can be raised and lowered by means not shown, and which can be moved in relation to one another by means not shown so as to press the bobbin sections 53, 54 together with suffi¬ cient force during the time taken for the adhesive to take effect.

Finally, the plant also includes a unit 60 which is operative in cutting the bobbin produced into predetermined lengths. Thus, the illustrated unit includes a stop position 61 for the end-surface 62b of the bobbin 62, and a cutting blade 63 which is rotatably mounted on a rotary axle 34 and which can be moved towards and away from the bobbin 62 by means not shown, so as to cut therefrom a bobbin 62 of lengths "1".

As will be seen from Figure 6, a milling head 37 is pivotally mounted on a pivot axle 38 (Figure 3) to enable the milling head to be brought to a position in which the surfaces 2c and 2b are formed by the milling head with the

aid of cutters 39 in a known manner, as the bobbin section is rotated.

Figures 4 and 5 are respective sectional views of the plant illustrated in Figure 3, and also show the bobbin sections resting against two rollers 70, 71.

It will be understood that the rollers 70, 71 may be more than two in number.

The surfaces lb and 2b and the edges lc and 2c will preferably be milled so as to produce edges of constant width "b" even though the outer diameter of the bobbin sections should vary.

It will be understood that the invention is not restricted to the aforedescribed and illustrated exemplifying embodi¬ ments thereof and that modifications can be made within the scope of the inventive concept as illustrated in the following Claims.