BACKGROUND OF THE INVENTION
[0001] Significant strides have been made since man first began attempting to duplicate
the spinning of the silkworm early in this century. With first cellulosic fibers,
then later thermoplastic/setting resin fibers, man has significantly changed the world
in which he lives in terms of apparel, carpets, and other coverings.
[0002] The same basic system of the silkworm is still in use, however. Continuous filaments
are forced through capillaries, or small openings roughly the size of a human hair,
in an otherwise solid plate due to a force pressing upon the filament resin. The solid
plate -- part of an overall spinning assembly appropriate for the filamentary material
to be spun -- is commonly referred to as a spinneret in the same manner as the silk
spinning passages of the silkworm.
[0003] Spinnerets used in the manufacture of "artificial" filaments -- such as rayon, nylon,
polyester, acrylic, acetate, and the like -- will have from one to several thousand
capillaries, depending upon the particular use the filamentary product is to be put
to. The filament size will be determined by the spinning material and spinning conditions,
as well as the "size" of the capillary. Many capillaries are round in cross-section.
It has become increasingly prevalent, however, to have various shapes of capillaries
to impart different characteristics to the filamentary product.
[0004] Due to their small size, the spinneret capillaries can become "plugged" with foreign
matter in the spinning resin. When this occurs, the filament resulting will be smaller
in size or, in worst case, nonexistent. When a capillary plugging occurs, the spinneret
will be removed and the capillary cleaned.
[0005] Cleaning of capillaries, depending on the resin used, can be quite difficult. The
cleaning process also may damage the spinneret capillary beyond use. Having an additional
spinneret capillary "plugged" purposely, which can be called into service to replace
a plugged capillary, can be quite useful. Also, having additional capillaries available
in a spinneret will permit flexibility in the overall "size" or "weight" or other
characteristics of the resultant group of filaments. The weight is often referred
to as "denier" and is called by that name (nominally the weight in grams of 9,000
meters of the filaments) or by another convention -- decitex (10/9 denier). Further,
it is of benefit to have the capability of "marking" a filamentary product by having
a capillary different from others. The marking may be for temporary purposes, in which
case the different capillary would be sealed at times other than when the marking
should occur. There exist numerous instances, then, when it would be helpful to plug
or seal a capillary temporarily, but have the capillary fully usable otherwise.
[0006] The shape of the capillary for resinous materials may be varied, but usually consists
of two or more cavities in serial, usually concentric in nature. The lower section
(i.e., the last section through which polymer flows) or shaping section of the spinneret
capillary will be constructed to impart the final desired shape of the filament. The
lower section will usually be thin to reduce the cost of odd shaped filament construction.
Upper sections connecting to the lower section or "face" section will be larger and
usually cylindrical or tapering to the face section.
[0007] A typical capillary construction is found in U.S. Letters Patent 3,006,026. This
reference also shows one means of constructing removable inserts in the lower section
by having such insert constructed to press fit into a blank spinneret body.
[0008] Additionally, it is known to use a similar technique to plug a capillary by compressing
a soft aluminum rod into the upper capillary sections. The difficulty with inserting
such a rod is that it must bottom on the face section in order to be compressed outwardly
to seal the upper section, possibly damaging the face section.
[0009] Having a positive seal of a capillary without the potential of damaging the face
section would be of great benefit. Attempts were made to use threaded bolts and screws
in capillary openings to seal them. These attempts failed because the spinning environment
quickly corroded the screw/bolt threads. Further, the capillary openings were damaged
from the screw/bolt thread removal, affecting the flow characteristics and therefore
the spinning uniformity of the capillary.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
[0010] The present invention is to a method of sealing a capillary in a manner that positively
seals the capillary tube, but does not damage the capillary, especially the face section
of the capillary that forms the filament definition. The invention is a plug which
provides a positive seal, is inexpensive, and can be reused, if desired.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
Figure 1 is a schematic sectional side view of a spinneret capillary and a seal of
the invention.
Figure 2 is an exploded view depicting a typical spinneret and the plug used in the
present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0012] In the Figure 1, a cross-section of a typical spinneret plate 1 is shown, much in
the manner as that depicted in U.S. Letters Patent 3,006,026. A spinneret capillary
comprising a face section 2, an upper section 3, and an entrance section 4 is depicted.
[0013] The invention herein, a capillary seal 5 is shown inserted into the entrance 4 and
upper section 3. The total depth of the plug section 6 of the seal is less than the
combined depths of the entrance 4 and upper section 3. This depth limitation is to
prevent damage to the face section.
[0014] A slight interference fit between the plug section 6 and the wall 8 of the upper
section will retain the seal in place until pressure from a polymer extrusion source
(shown as arrows 9) is placed on the seal. The seal will normally be constructed of
a material softer than the capillary wall and capable of withstanding the extrusion
conditions above the spinneret plate. Aluminum alloys like 6061T6 are acceptable for
machinability and relative hardness. More permanent plugs may be constructed of type
316 stainless steel; however, copper based materials have a tendency to corrode in
a spinning environment.
[0015] The sealing element or cap section 7 formed on the upper end of the plug will have
a diameter larger than the entrance diameter in order to form a flat sealing surface
on the upper face 10 of the spinneret. While the interference fit of the plug 6 initially
retains the seal in place and contributes by maintaining the seal in position, the
downward force 9 on the cap section 7 forms an operationally tight seal of the capillary
at the contact section between cap section 7 and the spinneret plate 1 during spinning
conditions. When the spinning conditions are removed and the spinneret cleaned, the
seal 5 may be easily removed and the previously sealed capillary may be placed into
service.
1. A method of sealing a spinneret capillary, comprising inserting into said capillary
a plug seal consisting of a plug section 6 having an interference fit in the capillary,
said plug section being inserted to a depth less than the face section of the spinneret,
and further consisting of a cap section 7 having a diameter greater than the capillary,
said cap section conforming to the upper face of the spinneret surrounding the capillary;
and applying an extrusion force pressure to the upper face of the spinneret and plug
seal cap.
2. A spinneret plug seal comprising a plug section and a cap section, the plug section
forming a cylindrical rod shape of a length less than the depth of the capillary to
the capillary face section and diameter sufficient to form an interference fit with
said capillary; the cap section being formed to the plug section and having a diameter
greater than the entrance of the capillary, the upper face of the spinneret around
the capillary and the portion of the cap section of greater diameter than said capillary
forming a sealing section upon the application of an extrusion force to the spinneret.
3. A method of temporarily sealing at least one capillary in a spinneret, comprising
inserting into said capillary a plug seal consisting of a plug section and a cap section,
said plug section consisting of a cylindrical rod of length less than the capillary
upper section and diameter sufficient to form an interference fit with the wall of
the capillary; the cap section being formed to the plug section and having a diameter
greater than the capillary entrance; and applying a filamentary extrusion force to
the upper face of the spinneret and cap section.
4. A method of varying the characteristics of a filamentary product produced from
a spinneret having capillaries of varying forms and shapes comprising temporarily
sealing selected capillaries and melt spinning fibers from remaining capillaries exhibiting
the desired fiber forming characteristics.
5. A method of temporarily identifying a filamentary product from a spinning assembly
having at least one identifying spinneret hole having a temporary plug seal, comprising
removing the plug seal and spinning fibers through the spinneret openings including
the identifying spinneret hole.
6. A filamentary product spinning assembly containing a spinneret plate having a number
of spinneret openings of one selected type and at least one spinneret opening of a
second type and means for temporarily plugging the second type spinneret opening,
comprising a plug seal having a plug section and a cap section, the plug section forming
a cylindrical rod shape of a length less than the capillary depth in the spinneret
opening, the cap section of greater diameter than the spinneret opening.
7. In a spinneret for forming a determined number of filamentary products simultaneously,
the method of extending the useful life of the spinneret by forming at least one additional
spinneret opening in the spinneret and temporarily plugging the additional opening.