GB2386366A

GB2386366A - Collapsible mandrel

Info

Publication number: GB2386366A
Application number: GB0303828A
Authority: GB
Inventors: John Michael Craig
Original assignee: CG AUTOMATION Ltd
Current assignee: CG AUTOMATION Ltd
Priority date: 2002-02-21
Filing date: 2003-02-20
Publication date: 2003-09-17
Anticipated expiration: 2023-02-20
Also published as: GB2386366B; GB0303828D0; GB0204085D0

Abstract

A collapsible mandrel 10 comprises a driven tube 12 and four outer leaves 14,16,18,20 mounted around the driven tube for movement between a winding and collapsed position. A cam shaft 22 is mounted inside and concentric with the driven tube 12, and is capable of axial movement relative to the driven tube 12. This axial movement causes roller cams 26 to act against the outer leaves 14,16 causing them to move radially outwards to the winding position, and subsequently the roller cams 32 to act against the outer leaves 18,20 causing them to move radially outwards also. The roller cams 26,32 act against the bias of return springs 36,37, which return the leaves to the collapsed position on reverse axial movement of the cam shaft 22. The surface of the leaves 14,16,18,20 is substantially smooth when the mandrel is in the winding position, enabling winding of a stretch film.

Description

Title: Collapsible Mandrel The present invention relates to a collapsible

mandrel and more particularly but not exclusively to a collapsible mandrel for winding a web of film, for example? stretch f lm used in packaging.

Currently in the manufacture of thin film such as stretch film, a web of film is wound onto a 5 cardboard, aluminium or plastics former or core. The film is wound under a controlled tension onto the core, which is mounted on a conventional mandrel of a winding machine. The film is elastic, and as it is wound, exerts a compressive force onto the core. Therefore, the core must have sufficient strength to withstand this compressive force both during winding, and when the core and film are removed from the mandrel.

10 It is known to wind paperproducts, for example wallpaper and wrapping paper, without a central core. The paper is wound directly onto a collapsible mandrel, having typically two or more outer leaves or segments. During winding, the leaves are radially spaced apart, and when it is desired to remove a roll of paper from the mandrel after winding, the leaves are moved towards each other, i.e. radially inwards. This method of winding is possible, because paper, unlike film, is substantially 15 inelastic, and therefore does not exert such a compressive load on the mandrel.

It has been found not practicable to wind film, for example stretch film, onto a known collapsible mandrel, since the inwardly directed compressive force which the film applies, causes wound film to extrude into the spaces between the leaves ofthe mandrel. This not onlyruins the wound film, but also obstructs the radial movement ofthe leaves, thus preventing removal of the roll of wound 20 film.

It is an object ofthe invention to provide a collapsible mandrel for wincing awed, especiallyofthin film, which substantiallyreduces the abovementionedproblems of winding film without a central core.

According to the present invention there is provided a collapsible mandrel for winding a web of film or the like comprising a driven tube and a plurality of leaves mounted around the driven tube, the leaves being radially moveable, in use, between a winding position in which the edges of adj acent leaves abut one another to form a substantially smooth cylinder, and a collapsed position in which S the leaves lie radially inwards oftheir winding position, thus providing the mandrel with a reduced diameter and enabling a web wound on the mandrel to be removed.

At least one ofthe leaves may move racially from itswindingpositionto its collapsedpositionprior to movement of the other leaves.

The mandrel may have at least three leaves. Preferably the mandrel has four leaves.

10 Preferably a first pair of diametrically opposed leaves are angularly offset relative to a second pair of diametrically opposed leaves. In use, the first and second pairs of diametrically opposed leaves move sequentially.

A cam shaft is preferably mounted inside and concentric with the driven tube. Roller cams mounted about and controlledbythecamshaftmayact against theinside ofthe leaves, through apertures 15 provided in the driventube. Axialmovement ofthe cam shaftrelativeto the driven tube may cause movement of the leaves between the winding and collapsed positions.

Preferably the leaves are spring loaded towards the collapsed position.

Drive screws may transfer drive from the driven tube to the leaves.

In an alternative arrangement, a pair of end caps may transfer drive from the driven tube to the 20 leaves.

The end caps and leaves may have mutually engaging formations.

l Preferablythe end caps are castleated, and have four circumferentially spaced radial slots, each slot engaging a key provided at the end of a leaf.

Each key may slide radially in and be guided by its respective slot of an end cap, facilitating the radial movement of the leaves between the winding position and collapsed position.

5 According to a further aspect of the present invention there is provided a method of winding a web onto a collapsible mandrel having a driven tube and a plurality of leaves mounted around the driven tube, the web beingwound onto the leaves in awinding position in which the edges of adjacent leaves abut one another to form a substantially smooth cylinder, and when winding is completed, the leaves being movedradiallyinwards to acollapsedposition, thus reducing the diameter ofthe 10 mandrel and enabling removal of the wound web from the mandrel.

According to a yet further aspect ofthepresentinvention there is provided a roil of film or the like, when wound without a core or formerusing a collapsible mandrel in accordance with the invention.

The invention will now be describedbywayofoxarnple onlywithreferenceto the accompanying drawings in which: 15 Fig 1 shows aschematiccrosssectionthroughafirstembodimentofamandrel, along its central axis, in accordance with the invention; Fig 2 shows a schematic cross section through the mandrel of Fig 1, along its central axis, the mandrel having been rotated through 90 ; Fig 3 shows an enlarged view of part of the cross section shown in Fig 1; 20 Fig 4 shows an enlarged view of part of the cross section shown in Fig 2;

Fig 5 shows a schematic cross sectional view through the mandrel of Figs l - 4, in a plane perpendicular to the central axis of the mandrel, with the mandrel in a winding position; Fig 6 shows a schematic cross sectional view through the mandrel of Figs 1 - 4, in a plane perpendicular to the central axis ofthe mandrel, with the mandrel in a collapsed position; S Fig 7 shows a schematic end view of the mandrel of Figs 1 - 6, including biassing springs; Fig 8 shows a similar view to that of Fig 1, with the mandrel in the collapsed position; Fig 9 shows a similar view to that of Fig 1, with the mandrel in the winding position; Fig 10 shows a schematic cross section through part of a second embodiment of amandrel, along its central axis, in accordance with the invention; and 10 Fig 11 shows a schematic cross section through the mandrel shown in Fig 10, along its central axis, the mandrel having been rotated through 90 .

Referring firstly to Fig 1, a first embodiment of a mandrel is indicated generally at 10. The mandrel 10 comprises a driven tube 12 and four outer leaves 14,16,18,20 which can be seen in Fig 5, mounted around the driven tube. A cam shaft 22 is mounted inside and concentric with the driven 15 tube 12, and is capable of axial movement relative to the driven tube as indicated by arrows A and B in Figs 8 and 9 respectively. Drive is transferred from the driven tube 12 to the outer leaves 14,16,18,20 by a plurality of drive screws 2, shown in Fig 7. The screws 2 each have a threaded portion 3, aplain bush portion 4 of larger diameter, and an enlarged head 5. Counter-bored holes 6 in the leaves 14,16,18,20, provided at spaced intervals along the leaves, see Figs 1 and 2, locate 20 the heads 5 ofthe drive screws 2, and the threaded portions 3 are engaged in threaded bores 7 in the driven tube 12. The plain bush portions 4 bridge the space between the outside ofthe driven tube 12 and the inside of the outer leaves 14,16,18,20.

A plurality of machined camming surfaces 24 are provided in diametrically opposite pairs spaced along the length ofthe cam shaft22. Referring also to Fig 3, pairs of rollercams 26, one pairof which is shown, bear against the camrning surfaces 24, and extend through apertures 28 provided in the driven tube 12. The roller cams 26 act on the outer leaves 14,16. Axial slots 27 are 5 machined on the inside surface of the outer leaves 14,16 in which the camming rollers 26 are received and guided.

A further set of machined camming surfaces 30, see Figs 2 and 4, also extend at spaced intervals along the length ofthe cam shaft 22, and are angularly offset through 90 from the camrning surfaces 24. Roller cams 32, one pair of which are shown in Figs 2 and 4, bear against the camming 10 surfaces 30, extend through aburther set ofapertures 34 in the driven tube 12, end act on the outer leaves 18,20. Axial slots 33 are machined on the inside surface ofthe outer leaves 18,20, in which the camming rollers 32 are received and guided.

The outer leaves 14,16,18,20 are wholly supported by the roller cams 26, 32 which are provided at intervals oftypically 0.3m apart, thus providing sufficient support to the outer leaves when under 15 a compressive load due to the tension applied in winding a resilient or elastic web, for example, stretch film.

Referring now in particular to Fig 5, the mandrel 10 is shown in a winding position, in which the outer leaves 14,16,18,20 are forced away from the cam shaft 22 by the roller cams 26,32. The edges of adj acent outer leaves abut one another to boron a substantially smooth cylinder onto which 20 a web can be wound. A first pair of return springs, indicated schematically at 36 in Fig 7, bias the leaves 14,16 radially inwards onto the roller cams 26, and a second pair of return springs 37 bias the leaves 18,20 radially inwards onto the roller cams 32. The return springs 36,37 are coil springs and are held in tension by fastening screws 48 between opposed leaves 14,16 and 18,20 respectively. The springs pass through channels 50,52 in the periphery ofthe driven tube 12, 25 shown in Figs 3 and 4.

l With reference also to Figs 8 and 9, on axial movement ofthe cam shaft 22 in the direction of arrow B. as showninFig9, firstlytherollercams 32 roll along the careening surfaces 30, opposite pairs of which become progressively closer together, thus causing the outer leaves 18,20 to move radially inwards under the bias ofthe return springs 36. The edges ofthe outer leaves 18,20 are 5 chamfered at 38 and engage adjacent chamfers40 ofthe outer leaves 14,16 inthewindingposition.

As the leaves 18,20 move radially inwards, the respective chamfers 38,40 serve to allow unimpeded passage of the outer leaves 18,20 inwards towards the driven tube 12.

The outer leaves 14,16 are provided with axial recesses 44 along their edges. Once the outer winding surfaces of the outer leaves 18,20 have passed the chamfers 40, they progressively move 10 into the axial recesses 44. On further axial movement ofthe cam shaft 22 in the direction of arrow B. the roller cams 26 roll along the camming surfaces 24, opposite pairs of which also become progressively closer together. Under the bias ofthe return springs 36,37 shown inFig 7, the outer leaves 14,16 also move radially inwards towards the driven tube 12.

As the outer leaves 14,16,18,20 move inwards, the leaves slide over the plain bush portions 4 and 15 heads 5 ofthe drive screws 2, which remain fixed relative to the driven tube 12. The screw heads 5 are wholly located within the counter-bored holes 6, and optionallythe counter-bored holes 6 can be filled with an epoxy filler or otherwise plugged to further enhance the smoothness ofthe cylinder. When the roller cams 26,32, reach their limit of movement, shown in Fig 8, the outer leaves 20 14,16, 18,20 are interlocked in a collapsed position, as shown in Fig 6. The diameter of the mandrel 10 across the outer leaves 14,16 and 18,20 is reduced in the collapsed position, thus enabling a rolled web (not shown) on the mandrel to be removed. The amount of radial movement is indicated by arrows C and D in Fig 6.

In order to return the mandrel from the collapsed position, as shown in Fig 6, to the winding 25 position, as shown in Fig 5, the cam shaft 22 is axiallymoved relative to the driven tube 12 in the direction of arrow A, as indicated in Fig 8. The roller cams 26 act against the outer leaves 14, 16

causing them to move radially outwards, and subsequently the roller cams 32 act against the outer leaves 18,20. The roller cams 26,32 act against the bias of the return springs 36, 37.

The mandrel 10 enables winding of a resilient and / or elastic web, for example, stretch film without the need for a roll core, because the periphery ofthe mandrel is substantially smooth. The mandrel 5 10 is also capable of radially inward movement at all ofthe points in its periphery, and can therefore release a wound web.

Referring now to Figs 10 and 11, a second embodiment of a mandrel is indicated at 110. The mandrel 110 comprises a driven tube 112, four outerleaves 114,116,118,120 and a cam shaft 122 mounted inside and concentric with the driven tube 112, in the same manner as the mandrel 10.

10 However, a pair of end caps 102 are provided, one of which is shown, with one attached to each end ofthe driven tube 112 Ofthe mandrel 110, fortransferringdrivefromthedriventube 112 to the leaves 114,116,118, 120bymeansofmutuallyengagingformations. More specifically, the end caps 102 are castleated, each having four circumferentially spaced radial slots 104. A key 106 is provided attheendofeachleafl 14,116,118, 120whichengages in a respective slot 104. Each 15 key 106 can slideradiallyin end tee guidedbyitsrespective slot 104 of an end cap 102, facilitating the radial movement of the leaves 114,116,118,120 between the winding position and collapsed position. In Figures 10 and 11, the mandrel 110 is shown in the collapsed position, held in this position by springs 136,137 shown partly in Fig 10. In this embodiment the springs 136,137 are held by 20 retention pins 108, rather than fastening screws as in the first embodiment described.

The operation ofthe mandrel l lOissimilartothatofthemandrel lO,but the mandrel l lOhas the advantage that the outer surface ofthe leaves 114,116, 118,120 is smoother than that ofthe leaves 14,16,18,20 ofthemandrel 10, due to the lack of counter-bored holes 6 in the leaves. If desired, the edges ofthe end caps 102 can be chamfered or rounded, which assists particularly in removal 25 of a wound web of film from the mandrel 110.

Claims

1. A collapsible mandrel for winding a web of film or the like comprising a driven tube and a plurality of leaves mounted around the driven tube, the leaves being radially moveable, in use, between awindingposition in which the edges of adjacent leaves abut one another 5 to form a substantially smooth cylinder, and a collapsed position in which the leaves lie radially inwards of their winding position, thus providing the mandrel with a reduced diameter and enabling a web wound on the mandrel to be removed.

2. A collapsible mandrel as claimed in claim 1 in which at least one ofthe leaves moves radially from its winding position to its collapsed position prior to movement of the other 1 0 leaves.

3. A collapsible mandrel as claimed in claim 1 or claim 2 in which the mandrel has at least three leaves.

4. A collapsible mandrel as claimed in anypreceding claim in which the mandrel has four leaves. 15

5. A collapsible mandrel as claimed in anypreceding claim in which a first pair of diametrically opposed leaves are angularly offset relative to a second pair of diametrically opposed leaves.

6. A collapsible mandrel as claimed in claim 5 in which, in use, the first and second pairs of diametrically opposed leaves move sequentially between the winding and collapsed 20 positions.

7. A collapsible mandrel as claimed in anypreceding claim in which a cam shaft is mounted inside and concentric with the driven tube, axial movement ofthe cam shaft relative to the driven tube causing movement ofthe leaves between the winding and collapsed positions.

8. A collapsible mandrel as claimed in claim 7 in which roller cams are mounted about the cam shaft and act against the inside of the leaves, through apertures provided in the driven tube.

9. A collapsible mandrel as claimed in any preceding claim in which the leaves are spring 5 loaded towards the collapsed position.

10. A collapsible mandrel as claimed in any preceding claim in which drive screws transfer drive from the driven tube to the leaves.

11. A collapsible mandrel as claimed in any one of claims 1 to 9 in which a pair of end caps transfers drive from the driven tube to the leaves.

10

12. A collapsible mandrel as claimed in claim 11 in which the end caps and leaves have mutually engaging formations.

13. A collapsible mandrel as claimed in claim 1 1 or claim 12 in which the end caps are castleated, and have four circumferentially spaced radial slots, each slot engaging a key provided at the end of a leaf.

15

14. A collapsible mandrel as claimed in claim 13 in which each key slides radiallyin and is guided by its respective slot of an end cap.

15. A method of winding a web onto a collapsible mandrel having a driven tube and a plurality of leaves mounted around the driven tube, the web being wound onto the leaves in a winding position in which the edges of adjacent leaves abut one another to form a 20 substantially smooth cylinder, and when winding is completed, the leaves being moved radially inwards to a collapsed position, thus reducing the diameter ofthe mandrel and enabling removal of the wound web from the mandrel.

r

16. A roll of film or the like, when wound without a core or former using a collapsible mandrel as claimed in any one of claims 1 to 14.

17. A roll of film or the like, when wound using the method as claimed in claim 15.

1 8. A collapsible mandrel substantially as described herein with reference to and as illustrated 5 in Figs 1 to 9 or Figs 10 and 11 ofthe accompanying drawings.

19. A method of winding a web onto a collapsible mandrel substantially as described herein with reference to and as illustratedin rigs 1 to 9 or rigs 10 and 11 ofthe accompanying drawings.