GB2058653A - Fibre extrusion die head - Google Patents

Abstract

A fibre extrusion die head comprises a spinneret plate 43 and a pumping arrangement 39 within the die head. In a preferred embodiment the fibre forming material supply duct passes from the top face of the die block to a cylindrical "family tree" distribution system located in a first bore in the die block and arranged to discharge material from its separated outlets to ducts which supply the material to a cylindrical pumping arrangement within the die block. The pumping arrangement presents a pump individual to each duct supplying material from the family tree and discharges to a plurality of ducts spaced apart in the length direction of the spinneret plate. The material supplied by the pump passes through a static mixer before passing to the spinneret plate. <IMAGE>

Description

SPECIFICATION Improvements in or relating to fibre extrusion apparatus This invention relates to fibre extrusion apparatus and more specifically to a die head for processing fibre material up to the spinneret plate.

In a conventional fibre extrusion die head fibre forming material is supplied continuously as a single feed to the die head, the single feed is directed to a so-called "family tree" which splits the single feed into a plurality of feeds by paths of equal length, the material flows from the plurality of outlets from the family tree paths to pumping means which individually pressurise each of the plurality of material flows, and each pressurised material flow discharges at a surface of the spinneret plate which has a group of apertures through which the pressurised material flow discharges to issue from the spinneret plate as continuous filaments. The groups of apertures in the spinneret plate are spaced apart and the filaments issuing from the plate generally pass downwardly before being deflected to processing apparatus, such as winders.

Although with this process each particle of fibre forming material should have substantially the same residence time and thermal history at the spinneret plate as all other particles delivered to the spinneret plate, the pumping is conventionally effected by pumps mounted externally of the die head block, the material must be directed from the outlets of the family tree to the pumps externally of the die head block and then returned to the die head block, and there is a danger that due to the shape of the die head block and the pump casings protruding therefrom, and the lengths of the material flow paths, the material flow passages and the material will be subjected to temperature differences and, accordingly, a constant and uniform thermal history for the material delivered to the spinneret plate cannot always be maintained.In the event that the material delivered to the spinneret plate is not of uniform consistancy and history the filaments will have different characteristics, which is undesirable in both the winding and subsequent processing of the fibres.

Further, provision of a separate pump for each family tree outlet greatly adds to the cost and maintenance of the conventional die head.

The present invention seeks to provide a fibre extrusion apparatus of simple construction and capable of affording flowable material of uniform characteristics at the spinneret plate.

According to one aspect of the present invention there is provided a fibre extrusion die head including a pumping arrangement within the die head block.

Preferably the pumping arrangement has a generally cylindrical form and locates in a cylindrical recess in the die head block.

Preferably the axis of the pumping arrangement lies in that plane passing through all the outlets of the family tree and through the longitudinal centre line of the spinneret plate.

Preferably the axis of the pumping arrangement lies parallel to the spinneret plate.

Preferably the pumping arrangement comprises a plurality of gear pumps, spaced apart in the axial direction of the pumping arrangement, with radial walls between the adjacent gear pumps preventing the flow of material between the pumps.

Preferably the gear pumps are driven by common drive means. In one embodiment of the invention all the gear pumps are driven by a single drive mechanism at one end of the die block head but, in a preferred embodiment, the pumping arrangement is split into two parts, in axial alignment, and each part is driven by a drive mechanism at its adjacent end of the die block.

According to á further aspect of the present invention there is provided a fibre extrusion apparatus comprising a die head including a spinneret plate, a pumping arrangement and a static mixer in the path of material flow to the spinneret plate.

Preferably the static mixer comprises a plurality of plates lying in planes parallel to the mean direction of flow to the spinneret plate, each plate has corrugations inclined to the mean direction of material flow to the spinneret plate, and preferably the corrugations on each plate are inclined to the corrugations of the plate or plates immediately adjacent thereto.

Preferably the corrugations of each plate are inclined at an angle of 450 to the mean direction of flow to the spinneret plate and whereby the corrugations on each plate lie at 90 to the corrugations on the adjacent plate or plates.

In an alternative embodiment a static mixer comprises a plate or body presenting two generally parallel major faces, intended to lie generally at right angles to the mean direction of flow through the head, one of said faces defining parallel channels, two rows of flow passages extending from each channel to the other major face of the plate or block, and the axes of at least some of said flow passages being inclined to the mean direction of material flow through the mixer.

Preferably all the flow passages in each row have their axes in a common plane inclined to the mean direction of flow towards the spinneret plate.

In one embodiment the common plane passing through the axes of one row of flow passages from a channel is inclined in opposite direction to the common plane passing through the axes of all the flow passages in the other row of flow passages from that channel.

In a preferred embodiment in accordance with the invention the die head comprises a die head block having two parallel major faces, parallel end faces, and parallel top and bottom faces, with two bores passing from end to end through the block with their axes lying on the mid-plane between the major faces and parallel to the top and bottom faces.The fibre forming material supply duct passes from the top face to the first of said bores, a cylindrical "family tree" is located at said first bore and arranged to discharge its material outlets to corresponding ducts between the first and second bores, said ducts having their axes on the mid-plane between the two major faces, and a cylindrical pump arrangement in the second bore receives the flowable material from said ducts and individually pumps the material discharge from each said duct to an outlet duct individual thereto and extending from the second bore to the bottom face of the block. The said ducts opening at said bottom face also have their axes in the mid-plane between said major faces.

Two opposite, flanged members are secured to the bottom face of the die block to support a spinneret plate, which has a plurality of groups of apertures spaced apart in the length direction thereof, and a static mixer is located between the spinneret plate and the discharge outlets opening at the bottom face of the die block.

The invention will now be described further by way of example with reference to the accompanying drawings in which: Fig. 1 shows a side view of a pumping arrangement for a fibre extrusion die head.

Fig. 2 shows a cross-section on the line 1111 in Fig. 1.

Fig. 3 shows a cross-section through a fibre extrusion die head including the pumping arrangement of Figs. 1 and 2, on the line 111111 in Fig. 4.

Fig. 4 shows a cross-section through the die head on the line IV IV in Fig. 3.

Fig. 5 shows, in perspective view, one corner region of a static mixer plate.

Fig. 6 shows a front view of a static mixer.

Fig. 7 shows a view of the mixer on the line V V in Fig. 6.

Fig. 8 shows a partially exploded end view of a die head shown in Figs. 3 and 4 illustrating the arrangement of the static mixer and, Fig. 9 shows an end view of an alternative mixer plate for a static mixer.

The pump arrangement as illustrated in Figs. 1 and 2 and generally indicated by numeral 11, comprises a plurality of disc shaped members 12, defining pump casings, separated by spacer discs 13, with location discs 14 and 1 5 at each end of the assembly. The disc shaped members 12 and 13 and location discs 14 and 15 lie on a common axis and have the same external diameter so as to present a cylindrical configuration and end caps 1 6 and 1 7 are located at the ends of the assembly and present radial flanges 1 6a and 1 7a respectively by which the pumping arrangement 11 is retainable in a fibre extrusion die head.

Each disc shaped member 12 defines a pump chamber 1 2a in which two conventional pump gear wheels 1 8 and 1 9 locate in meshing relationship. The gear wheel 18 of all the disc shaped members 12 are mounted on a shaft 20 and all the gear wheels 1 9 of the disc shaped members 12 are mounted on a shaft 21, the shafts 20 and 21 extending through bearings in all the spacer discs 13 and in the location discs 14.

Each disc shaped member 12 further includes an inlet duct 22 and an outlet duct 23, from the pump chamber 1 2a to the periphery of the disc shaped member, the ducts 22 and 23 are in axial alignment and the common axis of ducts 22 and 23 lies at right angles to the plane passing through the axes of shafts 20 and 21.Whilst the spacer discs 13 are angularly located by their bearings on shafts 20 and 21 and the gear wheels 18 and 1 9 will, to some degree, locate the disc shaped members 12 relative to shafts 20 and 21, the pump arrangement preferably includes pins 24, engaged in bores 25 in each of the disc shaped members 12, spacer discs 13 and location discs 14, 1 5. When assembled, the bores 25 lie parallel with the axis of the cylindrical pumping arrangement 11 and said pins 24, located in bores 25, maintain all the inlet ducts 22 and all the outlet ducts 23 in a common plane passing through the axis of the cylindrical pumping arrangement 11.

The shaft 20 further extends through the location disc 1 5 adjacent end cap 1 6 and through end cap 16 6 to project therefrom and a drive arrangement (not shown in Figs. 1 and 2) engages the shaft projecting axially from end cap 1 6 to impart drive to the shaft 20 and all the gear wheels 1 8 thereon, the gear wheels 1 8 in meshirig relationship with the gear wheels 1 9 serving to rotate gear wheels 1 9 at the same rotational speed as the shaft 20, the gear wheels 1 9 being secured on shaft 21 ensuring that all the gear wheels 1 9 rotate in unison.

The fibre extrusion die head illustrated in Figs. 3 and 4 comprise a die head block 26 with parallel major faces 27 and 28, a top face 29, and a bottom face 30. The block 27 has two bores 31 and 32 in spaced apart relationship, the axes of bores 31 and 32 lying on the mid-plane between major faces 27 and 28, and said axes lying parallel to the top face 29 and bottom face 30. A fibre material inlet duct 33 enters into the top face 29 of block 27 and a duct 34, in open communication with the duct 33, opens into bore 31 at a location mid-way between ends of bore 31 and in the midplane between major faces 27 and 28.

A cylindrical "family tree" structure 35, which may be identical with the cylindrical family tree construction described in our copending application "A" entitled "Improvements in or relating to Fibre Extrusion Apparatus", is located in bore 31 , bore 31 and the cylindrical exterior of family tree 35 being both finely ground to provide a relatively tight fit for the family tree 35 in bore 31.

As will be seen from Fig. 4 the "family tree" structure 35 provides longitudinal channels with connecting ducts by which a single feed to the channel 36 is split up to discharge at sixteen outlets 37, the material flow paths from all the outlet ducts 37, to the longitudinal duct 36 being of equal length.

It will also be observed that all the channels and ducts in the family tree construction 35 lie in a plane passing centrally through the axis of the construction 35 and, in operation, that plane lies on the mid-plane between major faces 27 and 28 of the die head block 26 so that the duct 34 discharges into longitudinal duct 36 of the family tree construction 35.

The die head block 26 includes ducts 38 extending between bores 31 and 32 on the midplane between major faces 27 and 28 and the ducts 38 are axially aligned with respective outlet ducts 37 from the family tree structure 35 so that material discharge from outlet ducts 37 is through ducts 38 to the bore 32.

A pumping arrangement 39 is located in bore 32 and is generally identical with the pumping arrangement 11 illustrated in Figs. 1 and 2 with the exception that it is split at its mid-plane to define two identical pumping arrangements 39a and 39b entered into the opposite ends of bore 32 until their respective end flanges 39c and 39d engage the adjacent end faces of block 26.

As the pumping arrangement 39 is, in effect, the pumping arrangement 11 split at its midplane, the inward end of each pumping arrangement comprises a spacer disc 1 3 of reduced thickness and the shafts 20 and 21 are split, the outboard end of each shaft 20 passing through its respective end flange 39c and 39dto a drive arrangement 40, 41 respectively and thus, the pumps of each pumping arrangement part 39a and 39b is driven independently but conveniently by "tuned" drives 40 and 41 to ensure identical rotation of the driving shafts 20 and the pumps throughout the length of the die head.

When assembled, and with the end caps 39c and 39dsecured to the end faces of the block 26 a disc shaped member 12 is aligned with each bore 38, the inlet bore 22 of each pumping arrangement is axially aligned with a bore 38 in the block 26 and the block 26 further includes outlet bores 42 extending from bore 32 to the bottom face 30 of the block and each axially aligned with the outlet 23 of a disc shaped member 12.

A spinneret plate 43 is clamped below the bottom face 30 of block 26 by clamping members 44 and 45 and, as illustrated, a static mixer 46 is located between the top face of spinneret plate 43 and the bottom face 30 of the block 26.

The die head block head illustrated in Figs. 3 and 4 operates with the drive means 40 and 41 rotating their respective shafts 20 at uniform speed and, with fibre forming material supplied continuously to duct 33, said material flows through duct 34 into the longitudinal duct 36 of the "family tree" construction 35, through the family tree channels and ducts, to discharge from outlets 37 and therefrom through ducts 38 and ducts 22 to their respective pumping arrangements, the discharge of which, under pressure, discharges via outlet ducts 23 to ducts 42 and from thence through the static mixer 46 and through the apertures in spinneret plate 43 from which the material extrudes as continuous filaments.It will be observed that with this construction the paths of the flowable material from inlet duct 33 to the duct 42 are identical in length and, as the pumps are operating uniformly, the residence time of each particle of fibre forming material passing through the static mixer 46 will be substantially identical with that of all other particles passing through the static mixer 46.

Further, as the family tree and the pumping arrangement are contained wholly within the rectangular die head block 26 and there are no protrusions, such as the pump casings of the prior art die heads, the die head block 26 and the family tree construction 35 and the pumping arrangements 39a and 39b can be maintained at a substantially uniform temperature and, thereby, a more uniform thermal history can be obtained than with the prior art constructions.

The static mixer 46 illustrated in Figs. 3 and 4 comprises a plurality of plates and, as will be seen from Fig. 5, each plate for the static mixer comprises a sheet 47, conveniently a metal sheet, with parallel corrugations 48 formed therein. The sheet is generally rectangular and the corrugations 48 are inclined to lie at an angle of 450 to the plane of the edges 47a of the sheet 47.

The static mixer 46 illustrated in Figs. 6 and 7 comprises five plates 49, 50, 51, 52 and 53, each identical with sheet 47 of Fig. 5, the plates 50 and 52 being arranged in identical manner to the plate 47 when viewed from the right in Fig. 5, whilst the plates 49, 51 and 53 are as illustrated in Fig. 5 but rotated through 1 800 about a vertical axis.

Thus, the corrugations 48 of the plates 49, 51 and 53 lie at 900 to the corrugations 48 of the plates 50 and 51 and the plates 49, 50, 51, 52 and 53 each makes contact with its adjacent plate or plates only at points where the respective corrugations 48 intersect.

The mixer construction illustrated in Figs. 6 and 7 presents, in the mean direction of material flow towards the spinneret plate 43 and which direction lies vertically downwards from the plane of the top 46a of the mixer 46, a succession of chambers, each receiving material equally from two preceding chambers and discharging equally into two succeeding chambers so that an effective "mixing" of the material flowing between each pair of adjacent plates 49, to 53 inclusive is obtained.

It should be noted that, in use, the mixer 46 is located within end walls 54, 55 and, preferably, side walls 56, 57 so that there is no transfer of material between any two adjacent plates 49 to 53 inclusive to the chambers between adjacent plates. When such transfer of material from the chambers between two plates to the chambers between other plates is desirable to assist mixing the plates 11 may include perforations and, in extreme cases, the sheets 11 may comprise sheets of perforated, expanded, or mesh material.

In the die head arrangement shown in Fig. 8 the static mixer 46 comprises five mixer units 46a, 46b, 46c, 46d and 46e, each identical to the static mixer illustrated in Figs. 6 and 7, in stacked relationship.

The plates 47 of the mixer units 46a, 46c and 46e run generally parallel with the mid-plane 58 whilst the general planes of the sheets 47 of the mixer units 46b and 46d lie generally at right angles to the mid-plane 58, and thereby at right angles to the general planes of the sheets in mixer units 46a, 46c and 46e.

With the static mixer units 46a to 46e arranged as described above the fibre forming material discharged from ducts 42 to mixer unit 46a is confined between the mixer plates 47 extending generally parallel to the plane 58 but, at the discharge from mixer unit 46a to mixer unit 46b, and wherein the plates 47 of unit 46b lie generally at right angles to the plane 58, a mixing of flowable material in the transverse direction is effected,-the chambers between each pair of adjacent plates 47 in mixer unit 46b receiving part of the material flow from each adjacent pair of plates 47 in the mixer unit 46a.

Thus, although in each mixing unit 46a to 46e the material flow between adjacent plates 47 is limited in the horizontal direction to the general plane of the plates 47 in the unit, a substantial and effective mixing in the opposite horizontal direction is obtained when the material passes to the succeeding mixing unit 46b, 46c, 46d or 46e and, thereby, an efficient mixing of the flowable material is effected, and material of uniform consistency is supplied to the top face of the spinneret plate 43.

To further assist mixing units 46a to 46e inclusive may be spaced apart vertically to permit horizontal flow of material between the adjacent units.

In the embodiment illustrated in Fig. 9 the mixer unit 58 has channels, each defined by inclined surfaces 59 and 60, in its upper plane 61 and channels defined by inclined surfaces 62 and 63 in its under plane 64, the direction of the channels in the under plane 64 extending at right angles to the direction of the channels in the upper plane 61.

Flow passages 65 and 66 extend respectively from inclined surfaces 59 and 60 to open at the inclined surfaces 62 and 63 in the under plane 64 of the unit and, the axis of each of the flow passages 65 or 66 lies at 90 to the plane of its respective surface 59 or 60.

It will be observed that material from each channel is positively split and transversely displaced by flow into and along passages 65 and 66 and further, as the flow passages 65 and 66 discharge into channels in the under plane 64 at right angles to the channels formed in the upper plane 61, each channel formed by surfaces 62 and 63 receives a discharge from each of the channels formed by surfaces 59 and 60 and whereby a positive mixing in both transverse directions is obtained.

The mixer unit illustrated in Fig. 9 can alone effect a mixing of flowable material towards the spinneret plate 43 but a greater mixing is achieved if a plurality of such blocks or plates for example five blocks as illustrated in Fig. 8, are arranged in a stack.

Claims (20)

1. A fibre extrusion die head including a spinneret plate and a pumping arrangement within the die head.

2. A fibre extrusion die head as claimed in claim 1 in which the pumping arrangement has a generally cylindrical form and locates in a cylindrical recess in the die head.

3. A fibre extrusion die head as claimed in claim 2 in which the axis of the pumping arrangement lies parallel to the spinneret plate.

4. Afibre extrusion die head as claimed in claim 1,2 or 3 in which the die head includes a family tree type distribution system, the outlets of which lie in a common plane and wherein the axis of the pumping arrangement lies in that plane passing through all the outlets of the family tree and through the longitudinal centre line of the spinneret plate.

5. A fibre extrusion'die head as claimed in claim 1, 2, 3 or 4 in which the pumping arrangement comprises a plurality of gear pumps, spaced apart in the axial direction of the pumping arrangement, and radial walls defining individual chambers for said gear pumps.

6. A'fibre extrusion die head as claimed in claim 5 in which the gear pumps are driven by common drive means.

7. A fibre extrusion die head as claimed in claim 5 or 6 in which all the gear pumps are driven by a single drive mechanism at one end of the pumping arrangement.

8. A fibre extrusion die head as claimed in claim 5 in which the pumping arrangement is split into two parts, in axial alignment, and each part is driven by a drive mechanism at its end remote from the other part.

9. Afibre extrusion die head as claimed in claim 5, 6, 7 or 8 in which the pumping arrangement presents a gear pump individual to each outlet from the family tree duct distribution system.

10. A fibre extrusion die head as claimed in any preceeding claim including a die body with two bores in spaced apart parallel relationship, a cylindrical body with a family tree type distribution therein locates in one of said bores and is arranged to present its outlets in a common plane, a single plastics material supply duct to the bore containing the said cylindrical body and aligned to supply material to the inlet to the family tree distribution system, a plurality of ducts between said two bores, there being a bore individual to each outlet from the family tree and aligned with its respective outlet from the family tree, a cylindrical pumping arrangement located in the other of said bores, and outlet ducts between the bore containing the pumping arrangement and that face of the die body adjacent a spinneret plate for the die head, there being an outlet duct aligned with each duct between the two-bores and said pumping arrangement being adapted to pump plastics material supplied from each duct between the two bores individually to the outlet duct individual thereto.

11. A fibre extrusion die head as claimed in claim 10 in which the axes of the said bores and the axes of all said ducts lie in a common plane.

1 2. A fibre extrusion die head as claimed in any preceeding claim including a static mixer in the path of material flow from the pumping arrangement to the spinneret plate.

13. A fibre extrusion die head as claimed in claim 1 2 in which the static mixer comprises a plurality of plates lying in planes parallel to the mean direction of flow to the spinneret plate and each plate has corrugations inclined to the mean direction of material flow towards the spinneret plate.

14. A fibre extrusion die head as claimed in claim 1 3 in which the corrugations on each plate are inclined to the corrugations of the plate or plates immediately adjacent thereto.

1 5. A fibre extrusion die head as claimed in claim 1 4 in which the corrugations of each plate are inclined at an angle of 450 to the mean direction of material flow to the spinneret plate and whereby the corrugations on each plate lie at 900 to the corrugations on the adjacent plate or plates.

16. A'fibre extrusion die head as claimed in claim 1 2 in which the mixer comprises a plate or body presenting two generally parallel major faces, intended to lie generally at right angles to the mean direction of flow towards the spinneret plate, one of said faces defining parallel channels with two rows of flow passages extending from each channel to the other major face of the plate or block, and wherein the axes of one row of flow passages are inclined to the mean direction of material flow towards said spinneret plate.

17. A fibre extrusion die head as claimed in claim 1 6 in which all the flow passages in each row have their axes in a common plane inclined to the mean direction of flow towards the spinneret plate.

1 8. A fibre extrusion die head as claimed in claim 1 7 in which the common plane passing through the axes of one row of flow passages from a channel is inclined in opposite direction to the common plane passing through the axes of all the flow passages in the other row of flow passages from that channel.

19. A fibre extrusion die head as claimed in any one of claims 12 to 18 inclusive including a plurality of static mixers in stacked relationship in the mean direction of flow towards the spinneret plate.

20. A fibre extrusion die head substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.