GB2055071A - Distributer block for fibre extrusion die head - Google Patents

Abstract

An insert, for a fibre extrusion die head, intended to distribute plastics material in the length direction of the die head by paths of equal length, comprises at least two plates in abutting relationship defining channels at the abutting faces one plate having a duct extending from the middle region of each channel back through the thickness of the plate and the other plate having a duct adjacent each end of each channel extending through the thickness of that plate. In a preferred embodiment the insert presents a cylindrical configuration and comprises three plates 11, 12, 13 in stacked relationship with channels 14 and 28-31 in the external surfaces of the first and third plates and channels 16, 19, 21 defined by the mating faces of the plates with ducts 15, 18, 20, 24-27 through the plates connecting the channels to form a "family tree" duct and channel distribution and whereby, from a single material supply inlet defined by the die head, the channels and ducts distribute the material uniformly to sixteen outlets defined by the die head via paths of equal length. <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 the fibre material up to the spinneret plate.

It is well known in the synthetic fibre art to process a fibre material from a single feed to the die head through passages in the die head to produce a plurality of material flows adjacent the spinneret plate, through which the material passes to issue as continuous filaments. The problems of processing the material through the die head are very well known in the art and it is essential that each and every part of the fibre material passing from the feed to the spinneret plate is subjected to the same thermal history.

The prior art method for ensuring a uniform thermal history for all parts of the material delivered to the spinneret plate is to pass the material along passages forming a so-called "family tree" and whereby, in the direction of material passage through the die head from the single feed towards the spinneret plate, the single feed duct opens into a first transverse channel, that channel feeds two ducts extending in the direction of the outlets, each of said two ducts feeds a transverse channel individual thereto and each of said channels feeds two ducts individual thereto in the direction of the spinneret and thus, by continuing the transverse channels and ducts, as described above, any even number of outlets from the single feed head towards the spinneret plate can be obtained.Further, by arranging each pair of outlet ducts from each channel equi-distant from the feed-in duct to that channel all the paths through the family tree are of equal length and, if the body of material defining the family tree is maintained at uniform temperature, the thermal history of each part of the material from the feed-in to the outlets of the family tree will be the same.

The difficulty with the manufacture of a family tree is that the cross sectional area of each transverse channel must be equal to one half of the cross sectional area of the duct feeding that channel and the cross sectional area of each outlet duct from a transverse channel must be exactly equal to one half of the cross sectional area of the inlet duct to that channel, so that the relative velocity histories of all parts of the material issuing from the outlets of the family tree will be the same. A further important factor is that the family tree must be completely free from "dead" areas where the material may lodge and thereby experience a different thermal and velocity history to the other parts of the material passing through the family tree.

To meet the above exacting parameters it has been the practice to cut the family tree into a face of a block df metal and to cover that face with a closure plate. Alternatively, but as may be expected more expensively, one half of the family tree (to one side of the mid-plane passing through all the channels and ducts) may be cut in one face of a metal block, the other half of the family tree cut into the face of a second block, and the two blocks assembled so that the two halves of the family tree are in exact alignment.

These prior art methods of construction present difficulties in machining the channels and ducts to the exact cross sectional area required and accurately machining and sealing the mating surfaces of the block and cover, or the block halves. Further, due to the rectangular form of the family tree block enforced by the prior art method of construction, problems are experienced in maintaining all parts of the metal adjacent the family tree at constant and uniform temperature.

The present invention seeks to provide a "family tree" construction which can meet the above defined parameters and which avoids many of the inherent and well known disadvantages of the prior art family tree constructions.

According to the present invention there is provided a family tree construction for a fibre extrusion die head comprising at least two plates in abutting relationship one, or the other, or both, plates defining channels at the abutting faces, one plate having a duct extending from the mid-length region of each channel back through the thickness of the plate and the other plate having a duct adjacent each end of each channel extending through the thickness of that plate and whereupon one of said plates has twice as many ducts as the other.

Preferably the family tree construction comprises three plates in stacked relationship, the mating surfaces of the three plates co-operating to define transverse channels, closed except for the ducts thereto.

Preferably the mating faces of the second and third plates in the stack define twice as many transverse channels as the mating faces of the first and second plates and each duct through the second plate opens to an end of a transverse channel defined by the first and second plates and to the mid-length region of a channel between the second and third plates.

Preferably all the channels and ducts have their axes in a common plane.

In a preferred embodiment in accordance with the invention the family tree construction comprises three plates in stacked relationship, the first plate of the stack has a transverse channel in its free surface remote from that surface abutting the second plate, two spaced apart transverse channels are defined by the abutting surfaces of the first and second plates and two ducts pass through the thickness of the first plate, one duct connecting the mid-length of one of said two transverse channels at the junction of the first and second plates with one end of the transverse channel in the free surface of the first plate and the other duct connecting the mid-length of the second duct at the junction of the first and second plates with the other end of the channel in the free surface of the first plate.

The second plate including ducts extending through its thickness from each end of each of the two transverse channels at the junction of the first and second plates to the mid-region of a transverse channel, individual to each duct, formed by the mating faces of the second and third plates. The third plate has ducts through its thickness, one to each end of each transverse duct between the second and third plates.

Preferably the longitudinal axes of the transverse channels are parallel to the axes of all the other channels.

Preferably the axes of all the ducts are parallel.

The term "transverse" channel when used in this specification is intended to define a channel extending at right angles to that direction from the single material inlet towards the spinneret plate and is thus not intended to describe the disposition of the channel relative to the external dimensions of the assembly of plates. Thus, in one embodiment in accordance with the invention, the "transverse" channels may extend parallel to the length direction of the assembly of plates.

Preferably the stack of plates presents a cylindrical external configuration with ducts all having their axes on a common plane passing through the centre of the cylindrical form, and the transverse channels all extend parallel to the direction of the axis of the cylindrical form and lie in said common plane.

Preferably the cylindrical form is imparted to the stack of plates after the transverse channels and ducts have been formed in said plates.

This invention also envisages a die head for receiving a family tree construction in accordance with the invention, said die head including a feed-in duct for supplying material to the family tree and a plurality of outlet ducts for receiving material from the outlet channels of the family tree.

The invention will now be described further by way of example with reference to the accompanying drawings in which: Figure 1 shows, in exploded view, a crosssection through a family tree construction on the line ll:ll in Fig. 2.

Figure 2 shows the left hand side of the family tree construction in assembled condition-on the line 111:111 in Fig. 1 and, Figure 3 shows, diagrammatically, a side view oF a fibre extrusion die head including the family tree construction illustrated in Figs.

1 and 2.

In the embodiment illustrated in Figs 1 and 2 the family tree construction comprises three plates 11, 1 2 and 13, the surface 11 a of plate 11 mating with the surface 1 2a of plate 12, the surface 1 2b of plate 1 2 mating with the surface 1 3a of plate 1 3 and the three plates, with their surfaces 11 a, 1 2a 1 2b and 1 3a in abutting relationship, define a cylindrical body.

The plate 11 has, in that surface remote from surface 11 a, a single channel 14 with a duct 1 5 at one end of channel 14 extending through the thickness of plate 11 to open in the mid-region of a channel 1 6 in surface 11 a. The channel 1 6 has a semi-circular cross-section and the surface 1 2a of plate 1 2 has a semi-circular groove 1 7 therein which co-operates with groove 1 6 to define a channel 16, 1 7 of circular cross-section.A duct 1 8 extends from one end of channel 16, 1 7 through the thickness of plate 1 2 to a channel 19 in the face 1 2b of plate 12 and a duct 20 extends from the other end of channel 16, 1 7 to the mid-region of channel 21 in face 12b, the channels 19 and 21 being of semi-circular cross-section. The surface 1 3a includes channels 22 and 23, of semi-circular cross-section, which respectively co-operate with channels 19 and 21 to define channels 19, 22 and 21, 23 of circular cross-section.

The plate 13 includes ducts 24, 25, 26 and 27 through its thickness, the ducts 24 and 25 extending from opposite ends of channel 19, 22 to the mid-length regions of channels 28, 29, 30 and 31 respectively in that surface of plate 1 3 remote from surface 13 a.

When assembled into a cylindrical bore 32 in die head 33 outlet ducts 34 and 35 in die body 33 open to opposite ends of channel 28, outlet ducts 36 and 37 in die body 33 open into opposite ends of channel 29, outlet ducts 38 and 39 in die body 33 open to opposite ends of channel 30 and outlet ducts 40 and 41 in die body 33 open into opposite ends of channel 31. An input duct 42 in die body 33 opens to the mid-length region of channel 14.

As will be evident from the drawings the cross-section through the family tree construction to the right of the centre line (line ll:ll in Fig. 2) is a mirror image of the cross-section shown to the left of the centre line in Fig. 2 so that to the right of centre line the channel 14 connects with a duct 15, duct 15 connects with a circular channel 1 6, 17, ducts 18 and 20 open the ends of channel 16, 1 7 to channels 19, 22 and 21, 23 respectively, ducts 24 and 25 connect channel 19, 22 to channels 28 and 29 and ducts 26 and'27 connect the ends of channel 21, 23 to channels 30 and 31, and outlets 34, 35 and 36, 37 and 38, 39 and 40, 41 in the die body 33 open to opposite ends of channels 28, 29, 30 and 31 respectively.Thus, from the single input duct 42 the material flows through the channels and ducts defined by the plates 11, 1 2 and 1 3 to sixteen output channels in the die body 33.

As the processing of the fibre material issuing from the outlets from the "family tree" forms no part of the present invention and may be effected in conventional manner, such subsequent processing will not be described herein.

It will be observed that the family tree proposed by the present invention having all its channels and ducts lying in a common plane and constructed from plates having mating surfaces at right angles to said common plane is far easier to construct than the prior art family tree cut into a flat face of a plate and the cylindrical configuration of the family tree, enterable into a bore in the die body, assists in retaining the plates so that effective sealing is readily obtained. Further, as the family tree has a cylindrical configuration and is housed within a block a more uniform temperature control of the family tree can be achieved.

Whilst the present invention has been described by way of example with reference to a specific embodiment the invention is not limited thereto and many modifications and variations, for example changes in the size, number and disposition of the channels and ducts and the number of plates, will be apparent to persons skilled in the art.

Claims (14)

1. An insert, for a fibre extrusion die head, comprising at least two plates in abutting relationship one, or the other, or both plates defining channels at the abutting faces, one plate having a duct extending from the mid-length region of each channel back through the thickness of the plate and the other plate having a duct adjacent each end of each channel extending through the thickness of that plate.

2. An insert as claimed in claim 1 comprising three plates in stacked relationship the mating faces of said three plates co-operating to define channels extending in the longitudinal direction of the insert and ducts passing through said plates to said channels.

3. An insert as claimed in claim 2 in which the mating faces of the second and third plates in the stack define twice as many transverse channels as the mating faces of the first and second plates and each duct through the second plate opens to an end of a transverse channel defined by the first and second plates and to the mid-length region of a channel between the second and third plates.

4. An insert as claimed in claim 1, 2 or 3 in which all the channels and ducts have their axes in a common plane.

5. An insert as claimed in any preceding claim comprising three plates in stacked relationship and wherein the first plate of the stack has a channel in its free surface remote from that surface abutting the second plate, two spaced apart channels are defined by the abutting faces of the first and second plates, four spaced apart channels are defined by the abutting faces of the second and third plates, two ducts pass through the thickness of the first plate, one duct connecting the mid-length of one of said two channels at the junction of the first and second plates with one end of the transverse channel in the free surface of the first plate and the other duct connecting the mid-length of the other of said channels at the junction of the first and second plates with the other end of the channel in the free surface of the first plate, four ducts pass through the second plate, each duct connecting the mid-length region of a channel between the second and third plates individual thereto with an end in a channel between the first and second plates individual thereto, and eight ducts pass through the third plate each said duct connecting an end of a channel between the second and third plates individual thereto to that face of the third plate remote from the mating face with the second plate.

6. An insert as claimed in claim 5 in which the third plate presents eight spaced apart channels in its surface remote from the abutting face with the second plate and each of the eight ducts in the third plate opens to the mid-length of one of said eight channels individual thereto.

7. An insert as claimed in claim 5 or 6 in which all the ducts and channels have their axes in a common plane parallel to the longitudinal axes of the insert.

8. An insert as claimed in claim 7 in which the axes of the ducts and channels lie in a common plane which passes through the longitudinal axes of the insert.

9. An insert as claimed in claim 5, 6, 7 or 8 in which the channels between the first and second plate are of equal length, and the channels between the second and third plate are of equal length.

1 0. An insert as claimed in claim 9 in which the channels defined by-said plates are equally spaced apart and whereby the arrangement of ducts and channels to one side of the central axis in the plane of said ducts and channels and passing centrally through the channel in the free surface of the first plate at right angles to the longitudinal axis of the insert is a mirror image of the arrangement of the ducts and channels to the other side of said central axis.

11. An insert as claimed in any preceding claim in which said stack of plates define a cylindrical external configuration and the axes of all the ducts and channels and the axis of the cylindrical insert lie in a common plane.

1 2. An insert as claimed in any preceding claim in combination with an extrustion die head presenting a recess for axially receiving the insert in close fitting relationship, said die head including a duct for delivering plastics material to the first plate for distribution through the duct and channels of the insert, and ducts for receiving flowable material from the outlets of the duct and channel flow paths through the insert.

1 3. In combination an extrusion die head and an insert as claimed in claim 1 2 when dependent upon claims 6 and 11 in which the recess in the die head is a cylindrical bore which snugly receives the cylindrical insert, the die head presents a single inlet duct and the insert is so axially located that said duct opens to the mid-length of the single channel in the external surface of the first plate and said die head presents sixteen ducts for receiving flowable material from the insert, said sixteen ducts being so arranged and spaced apart that each end of each of the eight channels in the exposed surface of the third plate has one of said sixteen ducts individually associated therewith and opening thereinto.

14. An insert for an extrusion die head substantially as hereinbefore described with reference to Figs. 1, 2 and 3 of the accompanying drawings.

1 5. An extrusion die head substantially as hereinbefore described with reference to and as illustrated in Fig. 1 of the accompanying drawings.