GB2377901A

GB2377901A - Improvements in and relating to the manufacture of wire binding elements

Info

Publication number: GB2377901A
Application number: GB0118028A
Authority: GB
Inventors: John Leighton; Robin Edward Trussler
Original assignee: James Burn International Ltd
Current assignee: James Burn International Ltd
Priority date: 2001-07-24
Filing date: 2001-07-24
Publication date: 2003-01-29
Anticipated expiration: 2021-07-24
Also published as: GB2377901B; GB0118028D0

Abstract

Apparatus for transforming a strip 10 of wire of zig-zag prong form to slotted tubular form ready for use as a binding element, comprising two rotary rollers 24,26, each having at least two parallel helical grooves 66,68 in which the tips and roots of the prongs engage for feeding the strip 10 by at least two prongs 12 at a time and for momentarily arresting the feed of the at least two prongs together at a shaping station. The apparatus further comprises means for clamping the at least two prongs at the shaping station and tools 70 for shaping the clamped prongs.

Description

This invention relates to the manufacture of wire binding elements for perforated sheets.

A well known method of binding perforated sheets uses binding elements which are lengths of wire bent so as to form curved prongs on which the sheets are impaled. The element is provided at the time of the impaling operation in the form of a tube having a longitudinal slot and the final stage in the binding process is to close the slot.

Such elements are generally manufactured by firstly converting a length of wire to the so-called'zig-zag'form, hereinafter referred to as a strip of wire of zig-zag prong form. As illustrated in Figure 1, in such a strip 10, the wire assumes the shape of a flat comb of indefinite length having prongs 12 which are closed at their tips 14 and open at their bases or roots 16 which are connected to their neighbours by aligned lengths of wire 18 forming the stock or spine of the comb so that the pitch of the prongs 12 corresponds to the pitch of the perforations in the sheets to be bound. A long length of such flat zig-zag wire is then brought to the slotted tubular form illustrated in Figure 2 by suitable bending of the prongs 12.

Perforated sheets are then impaled on the tips 14. That operation being performed, the binding is completed by bringing the tips 14 of the prongs into the roots or open ends 16, which operation is facilitated by an indentation 20 on either the convex or the concave surface of that part of each prong 12 which is midway between its tip and root.

The conversion of a strip of wire of zig-zag prong form to the slotted tubular form may be effected in several different ways. One machine which has been used has means for feeding the strip longitudinally, means for arresting the feed of each prong as it reaches a shaping station, means for clamping a portion of each prong at that station and means at the station for shaping each clamped prong into the desired configuration. Such a machine

will hereinafter be referred to as a'binding element forming machine of the type described'.

In such machines, the shaping is often effected by clamping the prongs of the strip of zig-zag wire on an anvil whose width is such that the roots and tips are unsupported. Hammers provided at the shaping station then strike the overhanging portions and cause them to conform to a shape determined by the anvil.

GB 1241807 discloses a binding element machine of the type described in which the feed means comprises rotary rollers having helical grooves in which the tips and roots of the prongs engage. A portion of each convolution of the helical grooves lies in a plane at right angles to its longitudinal axis and serves to arrest the feed of each prong as the prong is shaped.

In this known machine, the prongs are held stationary for a relatively short time. However, it was found that the positioning and forming of the prongs can be greatly improved if they are held stationary for a greater portion of each revolution of the feed means. Furthermore, this allows the prongs to be much more accurately clamped.

European Patent Application No. 0292271 discloses a binding element forming machine of the type described in which at least one eighth and preferably one quarter of each convolution of the helical grooves lies in a plane at right angles to its longitudinal axis and serves to arrest the feed of each prong for at least one eighth, preferably one quarter, of each revolution of the rotary rollers as the prong is shaped.

The machine has a shaping means which comprises two or more forming tools mounted on the rollers and an anvil on which each prong of the strip of zig-zag wire is clamped by clamping means such that its root and tip overhang the anvil. The forming tools are arranged to strike the overhanging

portions on either side of the clamped prong to cause them to conform to a shape determined by the anvil.

The machine of European Patent Application No. 0292271 has significant advantages, amongst which are that it allows more time for the prongs to be centralised at the first shaping station before they are clamped and shaped, which is the most difficult stage in shaping the zig-zag wire. In addition, shaping of the prongs is improved because heat created by the shaping process is permitted to dissipate over a longer period. Furthermore, it was seen as an advantage that the machine allowed the output speed to be increased by up to three times that possible with the apparatus of GB-A- 1251807.

The machine of European Patent Application 0292271 therefore constituted a significant advance in the art. It has been used with success by the Applicants for over ten years. However, it would be desirable to provide a still further improved binding element forming machine, in particular, in terms of productivity and quality.

In accordance with the invention there is provided an apparatus for transforming a strip of wire of zigzag prong form to slotted tubular form ready for use as a binding element comprising two rotary rollers each having a helical groove in which the tips and roots of the prongs engage for feeding the strip of zig-zag wire longitudinally and for momentarily arresting the feed of each prong of the wire strip as it reaches a shaping station, means for clamping each prong at that station and means for shaping each clamped prong, characterised in that each roller has at least two parallel, helical grooves for feeding the strip by at least two prongs at a time and for momentarily arresting the feed of at least two prongs together at the shaping station and in that the clamping means and the shaping means are arranged to, respectively, clamp and shape the at least two prongs together.

The replacement of the single helical groove of the rollers of known machines by at least two parallel helical grooves has significant advantages. The strip of wire is advanced through the apparatus by multiples of at least two prongs at a time. Taking the preferred case where there are two grooves per roller, the result is what might be termed "double progression", that is, advance and forming of the prongs, two by two. This allows a reduction in speed whilst still maintaining or even improving productivity. Reducing the speed reduces the heat generated and increases the life of the parts of the machine leading to lower maintenance costs and less machine downtime.

Reducing the generated heat also has the advantage that coatings on the wire are less affected. With prior machines it was found that generated heat was causing stripping of nylon coatings from the zig-zag wire. Double progression and the speed reduction which is therefore possible prevents nylon stripping.

Further advantages of a reduction in speed is that clamping can be carried out more efficiently and noise levels are cut.

Preferably the shaping means comprises forming tools mounted on the rollers at opposite positions and an anvil therebetween. The forming tools may, as in prior machines, be housed in the helical grooves of the rotary rollers. However, unlike known machines, the tools are provided in at least one set per roller, the tools of the or each set having essentially identical shaping contours and being mounted in corresponding positions in adjacent convolutions of the helical grooves. By providing the tools in this form, multiple prongs can be shaped at one time.

Each tool set may comprise a unitary body formed with the identical shaping contours. This facilitates manufacture of the tools and reduces cost.

Each tool body may be fitted in a cut-out in adjacent convolutions of the grooves, which includes a portion of the web (s) between the convolutions and

the tool body may include a projection which replaces the cut-out web portion (s). In this way a unitary tool body can be used and fitted in simple fashion whilst maintaining the helical grooves, including the webs therebetween, continuous.

Means may be provided for centering the at least two prongs at the shaping station such as to ensure that the prongs are properly engaged by the shaping contours of the set of forming tools. When the tools are provided as a unitary tool body the centering means may suitably comprise the projection (s) on the tool body.

A further advantage of the apparatus as described above is that the existing machines of the form of European Patent Application No. 0292271 can be easily retrofitted to provide for multiple prong progression by replacing the rollers, forming tools, clamp and anvil.

The invention will now be described by way of example with reference to the accompanying drawings in which :- Figure 1 shows a strip of zig-zag wire for use in a binding element forming machine of the type described; Figure 2 shows a length of slotted tube formed from the wire shown in Figure 1; Figure 3 is a part sectional side view of a binding element forming machine of the type described; Figure 4 is a plan view in the direction of arrows A-A of Figure 3; Figure 5 is a part sectional view taken in the direction of arrows B-B of Figure 4;

Figure 6 is a plan view showing the rollers and anvil of an apparatus in accordance with the invention; Figure 7 is a view taking the direction of arrow C of Figure 6 ; Figure 8 is a side view of one of the rollers of the apparatus of Figure 6; Figure 9 is a view of the other side of the roller of Figure 8; Figures 9A and 98 are sections taken along lines D-D and E-E of Figure 9; Figure 10 is a side view of the other roller of the apparatus of Figure 6; Figures 11 and 12 are, respectively, front and side views of a tool forming part of the apparatus of Figure 6, and, Figures 13 to 16 are sections taken through Figure 6 showing the steps of converting the zig-sag strip to the slotted tubular form.

Figures 3 to 5 and 13 to 16 show a binding element forming a machine of the type described. The machine is in the form disclosed in European Patent Application No. 0292271. Only those elements of the machine necessary for an understanding of the present apparatus will be described and reference should be made to the prior Application for a detailed description of the whole machine.

The machine has a feed table 22 along which the zig-zag strip 10 is longitudinally fed. It is thus presented to a pair of rollers 24,26 which have been omitted from Figures 3 to 5 for clarity but whose positions are shown in Figure 4. The rollers 24,26 will be described in detail below. They serve to advance the strip 10 and carry tools which shape the strip to transform the strip to the slotted tubular form.

The table 22 has an extension 28 between the rollers 24,26 which acts as an anvil. A guide 30 is provided along the feed table 22 to align the zigzag strip 10 accurately before it reaches the rollers 24,26.

The rollers 24,26 are driven from a main roller drive by means of drive shafts 32,34 and a roller drive gear 36.

The central parts of the prongs of the zig-zag strip 1 0 are clamped by a pressure pad 38 during forming of the strip. The pad 38 grips the strip 10 between itself and the anvil 28 when movement of the zig-zag strip 10 along the anvil 28 is arrested. Clamp actuation means is provided which as shown in Figure 5 comprises two double lobe cams 40 which act directly on two followers 42 connected to the pressure pad 38. The cams 40 are mounted on a cam shaft 44 which is driven from the main roller drive by means of an idler gear 46 which connects the roller drive gear 32 to a cam shaft drive gear 48.

The cams 40 cause the followers 42 and therefore the pressure pad 38, which is attached thereto, to move downwards. The followers 42 and pressure pad 38 are raised after the cams move past by action of a springs 50.

The pressure pad 38 has a projection 52, see Figure 16, which serves to put the indentation referred to above into the convex side of the prongs in the last stage of forming. An anvil extension 54 has a depression which matches the projection 52. The indentation may alternatively be formed by a cutting operation or may be produced before the zig-zag wire is converted to slotted tubular form.

Both the anvil 28 and the anvil extension 54 are split and may be raised or lowered to the action of wedges 56,58. The wedges can be adjusted manually or may be driven, for example, by a DC servo motor 60, 62. This allows the machine to be adjusted while operating rather than having to interrupt a production run and change the position of the pressure pad 38 by adjusting the followers 42.

A star wheel 54 is provided at the exit end of the machine to advance the wire out of the machine and to control and adjust the pitch of the wires to required dimensions.

The feed table 22, rollers 24,26, anvil 28 and anvil extension 54 of a binding element forming machine in accordance with the invention is shown in plan view in Figure 6. These elements may all be incorporated in a machine as disclosed in European Patent Application 0292271 and illustrated in Figures 3 to 5 and 13 to 16 and therefore, for ease of description, like reference numerals will be used for like parts.

The scroll 24 is shown in detail in Figures 8,9, 9A and 9B. It has two helical grooves, or scrolls, 66 the pitch of which is that of the prongs of the zig-zag strip 10. The width of the grooves 66 is slightly larger than the dimension P in Figure 1. The roller 26 is shown in more detail in Figure 10 and has similar grooves 68 of the same pitch but of opposite hand and the width of which is slightly larger than that of the tips 14 of the prongs 12 of the zig-zag strip 10. Rotation of the rollers 24,26 in opposite directions with strip 10 engaged in the groove 66,68 results in longitudinal movement of the strip 10 over the table 22 and the anvil 28.

The anvil 28 is dimensioned such that when a prong of the zig-zag strip 10 passes from the table 22 onto the anvil 28, its ends project beyond the edges of the anvil 28 and engage in the grooves 66,68 of the rollers 24,26.

Figures 9 and 10 show that for each convolution of the grooves 66,68, a sector which is about one quarter of a circle is straight, Le. lies in a plane at right angles to the longitudinal axis of the roller 24,26. When the zig-zag strip is engaged in that part of the grooves 66,68, its progression along the table 22 and anvil 28 is arrested. As a result, the zig-zag strip 20 moves along the table 22 and the anvil 28 in a series of steps. The provision of two grooves 66,68 on each roller 24,26 means that the stepped movement is two prongs

at a time. This double progression would be a treble progression if there were three grooves 66,68 or a quadruple progression if there were four grooves 66,68. However, the illustrated embodiment with two grooves has been found to be preferred as having the best balance between speed of movement and ease of manufacture of the rollers 24,26. Hereinafter the movement of the strip will therefore be referred to as double progression.

That double progression is halted each time the engaged prongs enter the straight sectors of the grooves 66,68. It is at this stage that shaping of the prongs is effected.

A pair of tools 70 is mounted on the straight sectors of the convolutions nearest the table 22, the tools 70 being located in corresponding positions in the two rollers 24,26, as illustrated by Figure 6. Tools 70 which take the form of hammers each strike the ends of the respective prong of the pair of prongs engaged in the sectors and cause them to bend to a shape determined by the anvil 28. In further adjacent convolutions there is a second pair of hammers 72 with shaping contours at a greater radial distance from the longitudinal axes of the rollers 24,26 which, on continued rotation of the rollers 24,26, cause the partially bent zig-zag strip to be further bent. The final tubular form is achieved by third hammers 74. During each forming step the prongs of the zig-zag strip 10 currently located on the anvil 28 are clamped by the pressure pad 38 which holds the prongs in position and ensures accurate shaping.

Immediately following the final shaping, the zig-zag strip 10 moves onto the anvil extension 54 and, as already discussed above, an indentation is made in the convex side of the prongs. As illustrated in Figure 7, this may be done by a diamond-shaped indenter 76.

Each pair of hammers 70,72, 74 may take the form of a unitary body.

The unitary body 78 forming the second pair of hammers 72 is illustrated in Figures 11 and 12. As shown there, the unitary body 78 has two identical

shaping contours 80 either side of a central projection 82. The body 78 is mounted in the roller 24,26 by forming an aperture across a portion of the straight sectors of the two adjacent convolutions, which involves removing part of the web between the grooves 66,68. The central projection 82 of the body 78 replaces the web and so ensures centering of the pair of prongs such that each is properly struck by the respective shaping contour 80.

Initial centering of the zig-zag strip is achieved by a pair of centralisers 84 mounted beside the first pair of hammers 70, as illustrated in Figure 9A.

The pair of centralisers 84 may, like the hammers 70,72, 74, take the form of a unitary body with a central projection.

As illustrated in Figure 6, the anvil 28 and anvil extension 54 can be joined by a tongue and groove form connector.

The form of the rollers 24,26 with the double helical grooves 66,68 means that the rate of progress of the zig-zag strip 20 between the rollers 24, 26 is doubled. As a result the speed at which the rollers 24,26 are rotated can be reduced by up to a half whilst still achieving the same output.

Reducing the speed means that there will be less maintenance problems caused by generated heat and that bearings, seals, etc. will last longer, leading to lower maintenance costs and less machine downtime which will, in turn, increase productivity. Reducing the generated heat also improves element quality, particularly if the wire is coated, as the coating will be less affected by heat. A further advantage of reducing the speed is that the recovery time for the springs 50 of the clamp mechanism is increased which has been found to reduce bounce of the pressure pad 38. Still further, noise levels are reduced.

In practice it has been found that optimum conditions result if the speed is reduced by about a third and the speed of the machine supplying the zigzag strip 10 increased by a third. The result is improvement in wire output of

Claims

1. Apparatus for transforming a strip of wire of zigzag prong form to slotted tubular form ready for use as a binding element comprising two rotary rollers each having a helical groove in which the tips and roots of the prongs engage for feeding the strip of zigzag wire longitudinally and for momentarily arresting the feed of each prong of the wire strip as it reaches a shaping station, means for clamping each prong at that station and means for shaping each clamped prong, characterised in that each roller has at least two parallel helical grooves for feeding the strip by at least two prongs at a time and for momentarily arresting the feed of at least two prongs together at the shaping station and in that the clamping means and the shaping means are arranged to, respectively, clamp and shape the at least two prongs together.

2. Apparatus as claimed in Claim 1 wherein each roller has two grooves.

3. Apparatus as claimed in either Claim 1 or Claim 2 wherein the shaping means comprises forming tools mounted on rollers at opposite positions and an anvil therebetween.

4. Apparatus as claimed in Claim 3 wherein the forming tools are housed in the helical grooves of the rotary rollers and wherein there is at least one set of forming tools per roller, each set including the same number of tools as there are grooves and the tools of the or each set having essentially identical

shaping contours and being mounted in corresponding positions in adjacent convolutions of the helical grooves.

5. Apparatus as claimed in Claim 4 wherein each tool set comprises a unitary body formed with the identical shaping contours.

6. Apparatus as claimed in Claim 5 wherein each tool body is fitted in a cut-out in adjacent convolutions of the helical grooves which includes a portion of the web (s) between the convolutions and wherein the tool body includes a projection which replaces the cut-out web portion (s).

7. Apparatus as claimed in any one of Claims 4 to 6 wherein means is provided for centering the at least two prongs at the shaping station such as to ensure that the prongs are properly engaged by the shaping contours of the set of forming tools.

8. Apparatus as claimed in Claim 7 as dependent on Claim 6 wherein the centering means comprise the projection (s).