Melt spinning apparatus

A melt spinning apparatus is disclosed which is adapted for forming a plurality of synthetic filaments from a molten polymer. The apparatus comprises a spin block composed of a spin plate having a plurality of transverse ducts, a cover plate overlying the spin plate, and a cavity formed between the two plates and communicating with the ducts for receiving the molten polymer. A pair of side plates are disposed along respective opposite sides of the block, and the block and side plates include mating inclined contact surfaces whereby tightening of the side plates against the block causes the spin plate and cover plate to be pressed toward each other, whereby a seal is formed between the plates which prevents leakage of the molten plastic from the cavity.

The present invention relates to a melt spinning apparatus of the type 
adapted for dividing a molten polymer into a plurality of streams to form 
synthetic filaments or threads. 
A melt spinning apparatus is described in U.S. Pat. No. 3,762,854 and 
German OLS No. 2,117,130, which is composed of a rectangular block 
including a spin plate having multiple holes for extruding polymers into 
filaments, and a cover plate overlying the spin plate so as to form a 
cavity therebetween. Side plates are positioned along opposite sides of 
the block, and cooperating dovetail guides interconnect the sides of the 
block and the side plates. Further, a threaded interconnection is provided 
between the spin plate and cover plate so that the two plates may be moved 
apart to secure the dovetail interconnection, or moved together to release 
the interconnection and permit disassembly of the block. A band-like 
sealing ring is disposed about the periphery of the cavity to prevent the 
loss of the polymer melt when the spin plate and cover plate are moved 
apart by the threaded interconnection. 
In the extrusion of melts of high polymer plastics, very high pressures, on 
the order of 200 bars or more, are present in the plastic melt delivered 
to the spinning apparatus. As a result, a spin block of the type described 
in the above patents must be provided with a seal at the side plates which 
not only reliably withstands these high pressures, but also will continue 
to be absolutely tight during startup when the pressure is low, as well as 
during repeated changes of pressure which may for example occur from 
shutdowns of the operation. Also, the seal must meet further exacting 
requirements, such as resistance to high temperature since the extrusion 
temperature of many melts may reach about 300 degrees C. Further, it has 
been found that once a leak has occurred during the operation of the spin 
block, it can not readily be stopped. 
In the spinning assembly of the above described patents, such requirements 
are not fulfilled, because the holding arrangement for the spin plate and 
cover plate is not in a position to effect a seal for different loads at 
all operating conditions of the melt spinning apparatus. 
It is accordingly an object of the present invention to provide a melt 
spinning apparatus which avoids the above noted leakage problems 
associated with known apparatus of this type. 
It is a more particular object of the present invention to provide a melt 
spinning apparatus which includes a holding arrangement for the spin plate 
and cover plate which provides a permanent seal therebetween, and which 
remains tight under changing operating temperatures and pressures, to 
thereby avoid leakage. 
These and other objects and advantages of the present invention are 
achieved in the embodiments illustrated herein by the provision of a melt 
spinning apparatus which includes a generally rectangular spin block 
composed of a spin plate having a plurality of ducts extending 
therethrough, and an overlying cover plate. The spin plate and cover plate 
have opposing inner faces defining a transverse plane therebetween, and 
oppositely directed outer faces. The block further includes cavity means 
disposed between the opposing inner faces of the spin plate and cover 
plate, and communicating with the ducts in the spin plate, so as to be 
adapted for supplying a molten polymer or the like thereto. 
A pair of side plates are disposed along respective opposite sides of the 
spin block, and means are provided for mounting the side plates to the 
spin block such that the side plates may each be moved in a lateral 
direction toward or away from the associated side of the spin block. In 
addition, the apparatus includes cooperating surface means on the spin 
block and side plates for causing the spin plate and cover plate to be 
pressed toward each other upon the side plates being laterally moved in a 
tightening direction by the side plate mounting means, to thus oppose the 
tendency of the plates to separate by reason of the pressure of the molten 
polymer in the cavity means, and thereby avoid leakage. 
In the illustrated embodiments of the invention, the cooperating surface 
means takes the form of a side edge surface portion extending along each 
of the two outer side edges of each outer face of the block, with the two 
side edge surface portions of at least one of the outer faces being 
included in opposite directions and at substantially equal angles with 
respect to the transverse plane defined by the opposing inner faces of the 
spin plate and cover plate. Also, each of the side plates is provided with 
contact surfaces which overlie and conform to the inclination of 
respective ones of the side edge surface portions. 
In one preferred embodiment, the two side edge surface portions on both of 
the outer faces of the spin block are inclined in opposite directions with 
respect to the transverse plane, and the two side edge surface portions 
along each side of the block are inclined in opposite directions to define 
a wedge-like configuration in cross section. In another embodiment, the 
two side edge surface portions along each side of the block are inclined 
in the same direction, and the side plates are joined by at least one 
threaded member extending laterally between the plates and beyond one of 
the outer faces of the block. 
With regard to the degree inclination of the side edge surface portions of 
the spin block and the contact surfaces of the side plates, it is 
advantageous that an angle of inclination be selected which has a tangent 
not greater than the friction coefficient of the materials of the block 
and side plates. Preferably, the angle of inclination may be somewhat less 
so that its tangent is less than such friction coefficient. By this 
arrangement, a self-locking effect is achieved, which means that the 
tightening screws are not additionally loaded by the pressure forces of 
the melt. However, even if the tangent of the angle of inclination is 
greater than the friction coefficient of the materials of the block and 
side plates, only relatively small components of the melt pressure force 
become effective on the tightening screws. In any case, when choosing the 
angle of inclination, one should consider which tightening arrangement is 
required, so that there may be considered a compromise between the 
requirements for a small tightening force on the tightening screws 
resulting from the pressure of the melt on the one hand, and to the 
desired shortness of the tightening distance of the spin block and side 
plates on the other hand. Where the tangent of the angle is greater than 
the coefficient of friction of the materials of the spin block and side 
plates, it is preferable that an angle be selected which has a tangent not 
greater than 0.3. The effect of such an angle is that only a small part of 
the forces for tightening the spin block become effective on the screws 
and the screws may be dimensioned to accommodate only these smaller 
forces. 
The wedge-shaped inclination of the side edge surface portions of the 
block, and of the contact surface of the side plates, results in the side 
plates applying the high force needed for sealing the inner faces of the 
spin plate and cover plate, when the side plates are moved in the 
direction of tightening. There are several other constructional 
possibilities for the design of the cooperating surface means, as further 
described below.

Referring more specifically to the drawings, FIG. 1 illustrates a melt 
spinning apparatus 30 which embodies the features of the present 
invention. The apparatus 30 may be used, for example, in synthetic 
filament spinning operations, and it is preferably installed in groupings, 
called spin beams, to provide several spinning positions. In these 
operations, the polymer material is usually plasticized or melted in a 
screw-type extruder, discharged through a subsequent metering pump, such 
as a gear pump, and delivered to the spin beam in metered quantities 
through a heated melt distribution conduit to each individual spinning 
apparatus. The distribution conduit communicates with the conduit 5 of the 
apparatus as seen in FIG. 1. 
The apparatus 30 comprises a generally rectangular spin block 31 having two 
opposite sides 32, 33, with the block 31 being composed of a spin plate 1 
having a plurality of ducts 8 extending vertically therethrough, and a 
cover plate 2 overlying the spin plate. The spin plate and cover plate 
have opposing inner faces 36, 37 defining a transverse separating plane 6 
therebetween, and oppositely directed outer faces 38, 39 respectively. 
Cavity means in the form of a chamber 7 in the inner face of the spin 
block is disposed between the opposing faces, and communicates with the 
ducts so as to be adapted for supplying a molten polymer or the like 
thereto. The distribution conduit 5 also communicates with the chamber 7 
for delivering the molten polymer from the extruder. 
The vertical ducts 8 through the spin block proceed from the chamber 7 to 
the outer face 38 and communicate with the actual spinning holes 9. 
Spinning holes 9 may have different cross sectional configurations, hole 
diameters, and hole patterns. Several layers of wire screen 10 with a 
stepped mesh width serve to filter the plasticized molten material and 
prevent the spinning holes 9 from becoming clogged. 
The outer face 39 of the cover plate 2 includes a side edge surface portion 
11 extending along each of the two side edges thereof, and the outer face 
38 of the spin plate 1 includes two side edge surface portions 12 
extending along each of the two side edges thereof. The two side edge 
surface portions 11 are inclined in opposite directions and at equal 
angles (gamma) with respect to the transverse plane 6, and the two side 
edge surface portions 12 are also inclided in opposite directions and at 
equal angles with respect to the transverse plane. Further, the two side 
edge surface portions along each side of the block, e.g. the portions 11 
and 12 at side 33, are inclined in opposite directions to define a 
wedge-like configuration in cross section and as illustrated in FIG. 1. 
The spinning apparatus further includes a pair of side plates 3, 4 disposed 
along respective opposite sides 32, 33 of the spin block. Each of the side 
plates includes a pair of laterally extending shoulders 41, 42, and each 
shoulder has a contact surface 43, 44 overlying a respective side edge 
surface portion 11, 12 of the adjacent spin plate and cover plate. Thus 
for example, the contact surface 43 of the shoulder 41 overlies the side 
edge surface portion 11, and the contact surface 44 of the shoulder 42 
overlies the side edge surface portion 12. In addition, the contact 
surfaces 43, 44 of the shoulders conform to the inclination of the 
associated side edge surface portions 11, 12. 
The side plates 3, 4 are mounted to the spin block by an arrangement 
whereby the side plates may each be moved in a lateral direction toward or 
away from the associated side 32 or 33 of the block. Also, upon such 
lateral movement in a tightening direction, the inclined side edge surface 
portions 11, 12 and cooperating contact surfaces 43, 44 act to press the 
opposing inner faces 36, 37 of the spin plate and cover plate toward each 
other and thus oppose the tendency of the plates to separate by reason of 
the pressure of the molten polymer or the like in the chamber 7, and the 
thereby avoid leakage. 
In the embodiment of FIG. 1, the spin block 1 is pressed together by both 
shoulders 41, 42 of each side plate, and the side plates are secured to 
the cover plate 2 by several tightening screws 13. According to the 
invention, the two side edge surface portions 11 or 12 of at least one of 
outer faces 38 or 39, and the associated contact surfaces 43, 44 on the 
side plates, are inclined in opposite directions with respect to the 
transverse plane 6. Further, the wedge angle gamma, which is defined as 
the angle between the side edge surface portions and the transverse plane 
6, is selected so that its tangent is not greater than the friction 
coefficient of the materials of the spin plate 1 or cover plate 2 on the 
one hand, and the supporting shoulder 41 or 42 on the other hand, when 
these components are mated with each other. 
Referring again to the embodiment of FIG. 1, the two side edge surface 
portions 11, 12 along each side 32, 33 of the block are inclined in 
opposite directions to define a wedge-like configuration in cross section. 
Thus when the screws 13 are tightened, the spin block 31 is centered 
between the two side plates 3 and 4. In so locking the spin block 
together, there is present a distribution of forces wherein the supporting 
shoulders 41 and 42 first slide along the side edge surface portions 11, 
12 of the spin block, until the spacing of the members at the transverse 
plane 6 diminishes due to the force components effective in the vertical 
direction, and a continuous seal is formed at the transverse plane 6. It 
will be noted that a gap 14 is present between the side plates 3, 4 and 
the sides 32, 33 of the spin block, which permits the locking function to 
occur. 
FIG. 2 illustrates a melt spinning apparatus 30.1 which is generally 
similar to the embodiment of FIG. 1, but which includes a separate filter 
block 45 positioned between the spin plate 1.1 and cover plate 2.1. The 
filter block 45 includes the chamber 46 and a plurality of vertical ducts 
47, which communicate with a space 48 adjacent the inner face of the spin 
block 1.1. A first transverse separating plane 6.1 is thus formed between 
the cover plate 2.1 and the filter block 45, and a parallel second 
transverse separating plane 16 is formed between the block 45 and spin 
plate 1.1. Further, in this embodiment, the side edge surface portions 11, 
12, and the contact surfaces 43, 44 of the supporting shoulders 41, 42 
have a wedge-shaped inclination in the direction of tightening of the 
screws 13 and 17. It will be understood however that in all of the 
embodiments disclosed herein, the upper pair of side edge surface portions 
11, or the lower pair of side edge surface portions 12, and their 
respective mating contact surfaces on the shoulders, may be disposed 
parallel to the separating plane 6 (note FIG. 6), or be inclined in the 
same direction as the other pair of side edge surface portions and mating 
contact surfaces (note FIG. 5a). 
In the embodiment of FIG. 2, the cover plate 2.1 is locked together with 
side plates 3 and 4, upon tightening of the bolts 13, and as a result of 
the wedging effect of the upper supporting shoulders 41, the cover plate 2 
is pressed vertically against the filter block 45. Upon bolts 17 being 
tightened, the wedging effect of the lower supporting shoulders 42 causes 
the spin plate 1.1 to be pressed against the filter block 45, so that 
initially the structural members of the spin block are centered, and then 
the vertical force components become effective in both transverse 
separating planes 6.1 and 16 to prevent leakage in these separating 
planes. If desired, cooperating deformable seals (not shown) may be 
provided at each of the separating planes to facilitate the sealing 
function. 
The melt spinning apparatus 30.2 of FIG. 3 differs from the embodiment of 
FIG. 1 in that the spin plate 1.2 includes a cup-shaped recess 22 which is 
rectangular in cross section. This recess is enlarged so that it serves as 
a chamber for a sand filter 20 which is covered by several layers of wire 
screen 10 with a stepped mesh width. In order to adequately stabilize the 
walls of the chamber 22, a projecting tongue 21 extends about the chamber 
22 and upwardly beyond the separating plane 6. The outer side edge of the 
raised tongue 21 engages the inner side edge of a conforming recess 23 
provided in the cover plate 2.2 upon the inner faces being moved together, 
and this interengagement stabilizes the wall of the chamber 22 so that it 
cannot bulge laterally. A continuous seal 24 prevents leakage of the 
plasticized material from the chamber 22 when the inner faces are pressed 
together. 
The sand filter 20 preferably extends over the entire length of the 
rectangular spin plate 1.2, so that the circumferential tongue 21 is 
rectangular with rounded edges; however, it may be sufficient if the 
projecting tongue 21 only extends along the longitudinal side of the spin 
plate 1.2 for increasing the resistance against bending of the side walls 
of chamber 22 for the sand filter 20. With regard to the design of the 
side plates 3 and 4, and their supporting shoulders, as well as the 
locking and sealing of the members forming the spin block, reference is 
made to FIGS. 1 and 2. 
FIG. 4a shows a modification of the melt spinning apparatus of FIG. 3, by 
the addition of centering means formed between the spin plate 1.2 and 
cover plate 2.2. This additional centering means is provided by forming 
the mating lateral side edges of the tongue 21 and recess 23 to be 
correspondingly inclined in cross section in a wedge-shaped manner. Thus 
when the inner faces of the spin plate and cover plate are pressed 
together, the plates will become centered with respect to each other. The 
inclination of the engaging surfaces is preferably within the range of 
self-locking. 
The modification of FIG. 4b differs from the embodiment of FIG. 4a 
essentially insofar as the projecting tongue 21 has a recess 49 at that 
side which is adjacent the chamber 22 for the sand filter 20. Into this 
recess, a preferably closed annular sealing element 50 is inserted which 
abuts against the wall of the recess. Preferably, a preformed annular band 
made from a plastically deformable sealing material is utilized, which 
provides a self-adjusting seal with respect to the high pressure of the 
melt. 
The apparatus 30.3 illustrated in FIG. 5a is generally similar to the 
embodiment of FIG. 1, with the exception that the lower side edge surface 
portions 12.3 on the spin plate 1.3 are inclined in the opposite direction 
from that shown in FIG. 1. More particularly, in the embodiment of FIG. 5, 
the two side edge surface portions 11, 12.3 along each side of the block 
are inclined in the same direction. The cooperating contact surfaces of 
the supporting shoulders are correspondingly inclined, and the two side 
plates 3.3 and 4.3 are interconnected by at least one threaded member 26 
which extends laterally between the side plates and in spaced relation 
above the outer face of the cover plate 2.3. Since the contact surfaces of 
the upper supporting shoulders of the side plates are inclined in the 
tightening direction of the threaded member 26, the tightening of the 
member 26 results in a vertical force component being applied to the side 
edge surface portions 11, which acts to seal the chamber 7 between the 
spin plate 1.3 and cover plate 2.3. It should be noted that in this 
embodiment the side plates 3.3 and 4.3 lie against the two opposite sides 
32 and 33 of the spinning block without any gap 14. Thereby, a good heat 
transfer can additionally be attained for heating the spin block and 
especially the spin plate 1.3 with its plurality of ducts 8 and spinning 
holes 9. For achieving this effect, the seal 51 in the transverse plane 6, 
e.g. between the spin plate 1.3 and the cover plate 2.3, has been 
modified. 
With regard to the clamping of the spin block as shown in FIG. 5a, it 
should further be noted that it is desirable that the stress on the plates 
3.3 and 4.3 be applied so as not to bend the plates. This may be 
accomplished by coordinating the selected wedge angles gamma and the 
spacing of the bores 28 for the threaded members 26 above the spin block. 
It should further be noted that with the specified dimensioning of the 
wedge angle gamma on the side edge portions 11 and 12.3, a self-locking 
effect is achieved, and that when the operating pressure becomes 
effective, the initially stressed side plates are no longer able to slide 
from the corresponding side edge portions of the spin block, so that it is 
not necessary to increase the forces by retightening the screws 13, 17, or 
threaded member 26. This advantage applied to all embodiments. 
As seen in FIG. 5b, the distance between the side edge surface portion 11 
and the bores 28 in the side plates 3.3, 3.4 is chosen such that the line 
N, which is normal to the side edge surfaces 11, meets the center line of 
the tightening member 26 just where the nuts or heads of such members abut 
against the side plates for inducing the tensioning forces Z. The vertical 
component of N2 is D2, which force effects the compression of the spin 
block, and together with the opposite force D1 at the surface 12.3, 
results in the sealing of the spin block from leakage of the pressurized 
melt. 
In the embodiment of FIG. 6, the two side edge portions 11 on the outer 
face 39 are inclined in opposite directions with respect to the transverse 
plane 6, and the two side edge surface portions 12.4 on the outer face 38 
are substantially parallel to the transverse plane. Also, the sealing 
member 51 is of the type illustrated in FIG. 5a. 
In the drawings and specification, there have been set forth preferred 
embodiments of the invention, and although specific terms are employed, 
they are used in a generic and descriptive sense only and not for purposes 
of limitation.