U.S. patent application number 17/719707 was filed with the patent office on 2022-07-28 for process for making a luggage shell from self-reinforced thermo-plastic material.
The applicant listed for this patent is Samsonite IP Holdings S.a r.l.. Invention is credited to Arno De Taeye, Rik Hillaert.
Application Number | 20220232935 17/719707 |
Document ID | / |
Family ID | 1000006259831 |
Filed Date | 2022-07-28 |
United States Patent
Application |
20220232935 |
Kind Code |
A1 |
De Taeye; Arno ; et
al. |
July 28, 2022 |
PROCESS FOR MAKING A LUGGAGE SHELL FROM SELF-REINFORCED
THERMO-PLASTIC MATERIAL
Abstract
Process of making a plastic component (1), in particular luggage
shell, from self-reinforced thermoplastic material, to a plastic
component (1) made of self-reinforced thermoplastic material and an
apparatus for making such a plastic component, in particular
luggage shell (7). The invention provides a new product and process
for manufacturing same on the basis of self-reinforced
thermoplastic material by means of the step of tensioning said
material (lamina), at least partially tensioning said lamina during
all follow-up component shaping and/or molding steps up to a
release of a component pre-form shape from the remainder lamina, to
form the component. The present invention allow the manufacturing
of an ultra-light weight luggage shell (7) on the basis of using
self-reinforced thermoplastic material, the manufacturing of same
can be further enhanced by permanently tensioning said material
during all manufacturing steps up to the final finishing of the
product.
Inventors: |
De Taeye; Arno; (Brakel,
BE) ; Hillaert; Rik; (Oudenaarde, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsonite IP Holdings S.a r.l. |
Luxembourg |
|
LU |
|
|
Family ID: |
1000006259831 |
Appl. No.: |
17/719707 |
Filed: |
April 13, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14185183 |
Feb 20, 2014 |
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17719707 |
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11629938 |
Apr 25, 2007 |
8663531 |
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PCT/EP2005/003899 |
Apr 13, 2005 |
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14185183 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 51/087 20130101;
B29C 51/262 20130101; B29C 51/085 20130101; B29C 2793/009 20130101;
B29C 70/56 20130101; B29C 51/46 20130101; B29C 35/08 20130101; B29C
70/541 20130101; B29C 51/34 20130101; B29C 51/082 20130101; B29K
2995/0041 20130101; B29C 51/145 20130101; A45C 5/02 20130101; B29L
2031/7418 20130101; B29K 2105/08 20130101; B29C 51/30 20130101;
B29C 51/32 20130101; B29K 2077/00 20130101; B29C 70/545 20130101;
B29C 70/04 20130101; B29K 2023/12 20130101 |
International
Class: |
A45C 5/02 20060101
A45C005/02; B29C 51/46 20060101 B29C051/46; B29C 51/08 20060101
B29C051/08; B29C 51/26 20060101 B29C051/26; B29C 51/30 20060101
B29C051/30; B29C 51/14 20060101 B29C051/14; B29C 51/34 20060101
B29C051/34; B29C 70/04 20060101 B29C070/04; B29C 70/54 20060101
B29C070/54; B29C 70/56 20060101 B29C070/56 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 18, 2004 |
DE |
102004029453.4 |
Claims
1. A luggage shell for a luggage case, having a base wall and
upstanding sidewalls and at least one corner region, the luggage
shell comprising a thermoplastic material selected from a
self-reinforcing thermoplastic resin of oriented pre-tensioned
strands surrounded by a matrix of substantially similar
thermoplastic material which is generally not oriented, the luggage
shell having a nominal thickness of between about 1 mm and about
2.5 mm, wherein the luggage shell has a three dimensional
stiffening pattern impressed into an outer main shell face of the
base wall so that the base wall has a repeating pattern of convex
and concave shapes molded thereinto, the overall thickness of the
base wall being substantially consistent among the convex shapes,
the concave shapes and the rest of the base wall.
2. The luggage shell according to claim 1, wherein the sidewalls
have a depth dimension and the base wall has a generally
rectangular wall shape having a length and width dimension, with
the width being no wider than the length dimension, the ratio of
the depth dimension to the width dimension being between about 0.1
and about 0.5.
3. The luggage shell according to claim 2, wherein a ratio of
length to width dimension is between 1 and about 2.
4. The luggage shell according to claim 3, wherein a ratio of
length to width dimension is between about 1 and about 1.40.
5. The luggage shell according to claim 1, wherein a radius of
curvature of the luggage shell in a corner region is about 80 mm or
smaller, in particular in the corner region connecting adjacent
sidewalls.
6. The luggage shell according to claim 1, wherein the
thermoplastic material is selected from a group consisting of
polypropylene, polyethylene, a semi-crystalline polymer and
combinations thereof.
7. The luggage shell according to claim 1, wherein the
thermoplastic material has an overall thickness of no more than
about 2 mm and has no more than about 20 layers of molecularly
oriented filaments.
8. The luggage shell according to claim 1, wherein the
thermoplastic material has at least one layer of polypropylene in
the form of molecularly oriented filaments and at least one layer
of substantially unoriented polypropylene.
9. The luggage shell according to claim 1, wherein the
thermoplastic material has at least one layer of polyethylene in
the form of molecularly oriented filaments and at least one layer
of substantially unoriented polyethylene.
10. The luggage shell according to claim 1, wherein the
thermoplastic material has at least one layer of high-density
polyethylene in the form of molecularly oriented filaments and at
least one layer of polyethylene having a lower density.
11. The luggage shell according to claim 1, wherein the
self-reinforced thermoplastic material comprises a substantially
monolithic structure.
12. The luggage shell according to claim 1, wherein the
self-reinforced thermoplastic material comprises oriented strands
of different orientation and said thermoplastic material comprises
multiple layers of molecularly oriented filaments with filaments of
different, in particular neighboring layers, being disposed angled
or crosswise.
13. The luggage shell according to claim 1, wherein the
thermoplastic material is laminated with a fabric, in particular
woven or melted fabric, preferably forming a lining.
14. The luggage shell according to claim 1, wherein a centerline of
a wall thickness along a cross section perpendicular to the
longitudinal dimension of the convex and concave shapes shows
troughs corresponding to the convex shapes and ridges corresponding
to the concave shapes, said troughs and ridges interconnected by
upstanding walls forming an angle to the main wall approximately
equal to a draft angle.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 14/185,183 filed on Feb. 20, 2014 and
entitled "Process For Making a Luggage Shell From Self-Reinforced
Thermo-Plastic Material", which application is a continuation
application of U.S. patent application Ser. No. 11/629,938 filed on
Apr. 25, 2007, now U.S. Pat. No. 8,663,531, and entitled "Process
For Making a Luggage Shell From Self-Reinforced Thermo-Plastic
Material", which application is the Section 371 of PCT
International patent application No. PCT/EP2005/003899 filed on
Apr. 13, 2005 and entitled "Process and Apparatus For Making a
Plastic Component From Self-Reinforced Thermo-Plastic Material and
Plastic Component Produced", which claims priority to German Patent
Application No. 10 2004 029 453.4 filed on Jun. 18, 2004 and
entitled "Process and Apparatus For Making a Plastic Component From
Self-Reinforced Thermo-Plastic Material and Plastic Component
Produced", which are all hereby incorporated by reference into the
present application in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to a process for producing a
plastic component, in particular luggage shell, from
self-reinforced thermoplastic material, a plastic component made of
self-reinforced thermoplastic material and an apparatus for
manufacturing such a plastic component, in particular luggage
shell.
BACKGROUND OF THE INVENTION
[0003] In the past, several attempts have been made to produce
plastic components having high physical strength and resistance
against breakage and distortion while rendering the component made
of such synthetic resin lightweight and easy to recycle. In
particular, in the luggage industry, there is a demand for
producing hard shell suitcases combining highest reliability and
resistancy against impacts from outside with distortion-free
behavior, favorable appearance and reduced weight to allow such
luggage to be handled with ease and convenience.
[0004] Also, a couple of composite materials comprising laminates
of synthetic resin such as thermoplastic resin and woven fabric
have been applied.
[0005] Accordingly, from U.S. Pat. No. 5,376,322 a process of
thermo-forming a cloth covered shape from a preform is known for
producing luggage shells by pressure laminating a layer of cloth
fabric to one surface of a thermoplastic substrate which
subsequently undergoes a press forming process in a mold press with
a specific focus on the forming of the corner areas. Still
difficulties occurred, however, to ensure smooth corner areas to be
produced, in particular when the radii of the corners or of the
intersections between main surfaces of the product are desirably
small. Moreover, further weight reduction in combination with
increased strength is desirable.
[0006] Moreover from U.S. Pat. No. 5,755,311 a method of making
hard side shells for luggage using a pressure differential molding
process and applying an integrally formed frame about a thin
thermoplastic hollow shell is known.
SUMMARY OF THE INVENTION
[0007] Based on the consideration that a high impact, low weight
sheet material made of synthetic resin such as thermoplastic
material can be produced on the basis of pre-stretched oriented
strands of polymeric fibers embedded in a matrix of softer material
of the same or similar type, EP 0 531 473 B1 provides a process and
material in which an assembly of oriented polymeric fibers is
maintained in intimate contact at an elevated temperature so that
outer areas of the oriented polymeric fibers melts and said fibers
are subsequently compressed so as to produce a coherent polymer
sheet. According to said method and material, the oriented
polymeric fibers, preferably comprising thermoplastic materials of
polyolefin and, in particular, polypropylene or other crystalline
or semi-crystalline materials and can be arranged as uni-axially
aligned bundles or twisted bundles of fibers or as a mat of
interwoven bundles depending on the later field of application.
[0008] A similar method for reinforcing an article by using tapes,
film or yarns of drawn thermoplastic material is known from WO
2004/028803 A1 using polyethylenes (PE) or polypropylenes (PP) in a
co-extrusion process, followed by stretching and cooling down.
Finally, the positive properties of self-reinforced polypropylene,
i.e. polypropylene reinforced with oriented polypropylene fibers
(so-called "all PP" composites) in terms of recyclability, strength
and stiffness are explained in greater detail in "Composite for
Recyclability" by John Peijs, Materials Today April 2003, pages 30
to 35.
[0009] Based on that existing knowledge of self-reinforced
thermoplastic material, in particular self-reinforced
polypropylene, it is an objective of the present invention to
overcome the difficulties to produce articles on the basis of
self-reinforced thermoplastic material having a high degree of form
change and comprise areas of high-grade deformation work, for
example deep luggage shells, which is normally difficult in view of
the high tensile strength and form change resistance of the
self-reinforced thermoplastic material containing that stretched
oriented strands or tapes, for example of PP or other crystalline
or semi-crystalline thermoplastic material which can be
pre-stretched prior to forming woven mats or other foil material
from such tapes, films or yarns.
[0010] Thus, it is an objective of the present invention to provide
a process of making a plastic component, in particular luggage
shell, from self-reinforced thermoplastic material allowing the
formation of highly durable but extremely lightweight components
such as specifically deep luggage shells in a cost efficient manner
paying particular attention to the smooth formation of corner
regions and intersection areas between main surfaces of the
component.
[0011] Moreover, it is an objective to provide such a plastic
component, in particular luggage shell, formed from self-reinforced
thermoplastic material allowing to considerably increase the ratio
of depths to the length and/or width of such a component so as to
be able to support high loads or weights with a minimal net weight
of the component, in particular luggage shell.
[0012] Moreover, it is an objective of the present invention to
provide an apparatus for making a plastic component, in particular
luggage shell, comprising areas of high degree of form change which
allows the production of three-dimensional plastic components
having a high ratio of depths to widths or lengths of the product
on the basis of machinery and tooling which has already been widely
used in conventional systems showing such apparatus to be designed
with ease and at relatively low costs, also with respect to the
operation of such apparatuses.
[0013] Regarding the process aspects, according to the present
invention, the afore-indicated objective is performed by a process
having the features of claim 1 or 11. Preferred embodiments of such
processes are laid down in the related dependent claims.
[0014] Accordingly, the present invention performs a process which
combines aspects of thermo-forming of polypropylene laminas with
that one of deep-drawing of metal, in particular light metal sheets
so as to develop a process which allows deep-drawing of
self-reinforced thermoplastic materials, in particular having
oriented strands of polypropylene or other crystalline or
semi-crystalline thermoplastic resin allowing the formation of
extremely lightweight components, such as luggage shells, having
areas of high-grade form change, in particular with respect to the
corner regions and intersection areas between main surfaces of such
components which, so far, due to the difficulties experienced in
press-forming self-reinforced thermoplastic mats or other sheets of
thermoplastic material could not be molded in practice.
[0015] Thus, components, in particular luggage shells with
substantial weight reduction compared to conventional hard side
cases can be manufactured. In particular, woven self-reinforced
polypropylene material will be used to manufacture such components,
in particular shells by means of a press forming technology
designated also as "compressed tech" technology.
[0016] An essential aspect of the present invention is the at least
partially tensioning of the self-reinforced composite of
thermoplastic material during all forming, in particular press
forming and shaping steps such as deep-drawing of said material so
as to be able to create components, in particular luggage shells
having a high depth to surface ratio. Accordingly, all "critical"
strands (tapes) and fibers, i.e. extending through areas of
high-grade deformation such as corner regions should be kept
tensioned during the entire process, irrespective of compression
forces to arise in such areas during the press forming process.
[0017] With respect to the plastic component, in particular luggage
shell, the above objective is performed by the features of claims
25 and 34 with preferred embodiments thereof being laid down in the
related dependent claims.
[0018] Prior to any shaping or molding process, preferably the
self-reinforced thermoplastic material (lamina) is lined with woven
or knitted fabric, preferably by heat-bonding in a continuous
inactive process with the further press-forming of the desired
plastic component.
[0019] There is also the option to dispose multiple layers of the
molecularly oriented strands contained in a respective layer of
self-reinforced thermoplastic material under a certain angle to
each other, in particular disposing neighboring layers crosswise
which leads to further improved unilateral strength and
quasi-anisotrop strength and bonding properties of the final
product.
[0020] It is also possible to form a composite body or component
such as shell comprising at least the self-reinforced thermoplastic
material combined with other lining or in a sandwich structure,
i.e. using a cell plastic or a lining made of dense cellular
plastic material which need not to be a thermoplastic.
[0021] Regarding the apparatus for making a plastic component, in
particular luggage shell, from a self-reinforced thermoplastic
material, the above objective, according to the present invention,
is performed by the features of claim 37, while preferred
embodiments of said apparatus are laid down in the further
dependent claims.
[0022] Accordingly, the present invention allows the manufacturing
of an extremely thin but durable, lightweight and
distortion-resistant component, in particular luggage shell, having
areas of high degree of form change such as relatively sharply bent
curves and bends including corner areas of relatively low radius
without wrinkles being produced.
[0023] This can lead to a new generation of ultra-lightweight
luggage based on synthetic resin.
[0024] By press forming, in particular deep-drawing of
self-reinforced thermoplastic composites (SRTC), a new type of
material is created which may be based on polypropylene as a base
material but also other crystalline or semi-crystalline material
such as nylon (which is a registered trademark) can be used.
Preferably, such self-reinforced thermoplastic composite materials
(SRTC) are made with either re-softened areas (by intermediate
heating) before press forming a laminate or under use of
(co-extruded polypropylene) tapes, these tapes, strings or yarns
are stretched and, after an in particular low temperature or cold
stretching process, comprise a highly oriented core with a thin
layer of same or similar material around the core having a lower
melting point.
[0025] Preferably, the tapes are woven into a fabric which can be
compacted or a multi-layer component can be combined therefrom
considering that at a certain temperature the outer film
surrounding the stretched core is melting and by pressure molding
the fabrics can be compacted to a plate or multi-layer lamina.
[0026] While polypropylene (PP) tapes are less stiff than organic
fibers and their visco-elastic behavior allows for more deformation
than plastic or thermoplastic composites such properties can
promote the deep-drawing of these materials.
[0027] In order to avoid the shortcomings of attempts of
deep-drawing SRTC with a considerable degree of form change, the
problem of heat shrinkage of the stretched tapes under elevated
temperature of more than 100.degree. C. has been solved considering
that a successful deep-drawing process would need to heat the SRTC
lamina up to about 170.degree. C.
[0028] The invention preferably keeps all critical tapes, i.e.
tapes at critical positions with respect to the high degree of form
change of the product during the deep-drawing or press forming
process under tension (creation of tensile force) during the entire
process. This tensioning may occur passive by fixing the
thermoplastic sheet material in its edge areas and proceeding to
subject same to a press-forming, such as deep-drawing process, so
that the lamina itself creates those tensile forces or may be an
actively controlled tensioning by introducing (steering) respective
tensile forces applied to the lamina (potentially additionally)
from outside.
[0029] According to the present invention, a sheet clamping device
is used which takes all tapes clamped around the entire
circumference and provides the opportunity to control and passively
or actively steer the tension in the tapes according to the desired
process. Said controlling or steering of the tensioning of the most
critical tapes can be force-driven, position-driven, or can be a
combination thereof.
[0030] Moreover, the present invention preferably avoids
compression forces in the corners of the product, in particular
luggage shell, to occur which would counteract or eliminate the
tension in the tapes, strings or yarns and could cause wrinkles in
the high degree form changed corner areas.
[0031] Accordingly, the present invention provides means that can
give an extra-controlled deformation at the corner areas to keep
all tapes under tension and/or guide potential wrinkles to avoid
them to slide into the final product. Preferably, this is done by
pre-stretching or steered stretching and tensioning during the
press forming, in particular deep-drawing process.
[0032] Preferably, the apparatus design of the respective machinery
may use the press of two independently moving mold halves (cavity
and core) or may apply an independent frame that holds auxiliary
mold surfaces or the like, operating through holes in the upper or
under gripping jaws. Also, a blow-forming step, i.e. a pre-stretch
prior to a deep-drawing activity by a blow-forming step beforehand
may be used.
[0033] Preferred embodiments are laid down in the further
subclaims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] In the following, the present invention is explained in
greater detail by means of several embodiments thereof explained
hereinafter in conjunction with the accompanying drawings,
wherein:
[0035] FIG. 1 a luggage shell according to a first embodiment of
the present invention in a perspective view from outside;
[0036] FIG. 2 a detail of the surface of the luggage shell of FIG.
1 ("detail C") to elucidate the surface pattern or surface design
of the luggage shell of FIG. 1;
[0037] FIG. 3 schematic cross-sectional views of the luggage shell
surface according to lines "A-A" and "B-B" of FIG. 2 which are
shown in FIG. 3 in a superimposed view to elucidate the surface
pattern;
[0038] FIG. 3.1 a plan view of an alternative stiffening pattern
for the base wall of a luggage shell;
[0039] FIG. 3.2 perspective, cross section scaled up to elucidate
the stiffening pattern of FIG. 3.1;
[0040] FIG. 3.3 a plan view of a further alternative stiffening
pattern similar to that shown in FIG. 3.1;
[0041] FIG. 4 a view along the length dimension of the luggage
shell of FIG. 1;
[0042] FIG. 5 a partial perspective view of a luggage case using
luggage shells according to the present invention in a view from a
lower corner of the luggage case;
[0043] FIG. 6 a detail (cross-section) of a zipper closure detail
of a luggage case, the schematic view;
[0044] FIG. 6.1 a detail according to FIG. 6 as schematic cross
sectional line drawing;
[0045] FIG. 7 a view similar to FIG. 5 but showing the interior
surface of that portion of a luggage case in schematic view;
[0046] FIG. 8 a production machinery for conventional luggage
shells as conventionally used, schematically;
[0047] FIG. 9 an embodiment of an apparatus for manufacturing
luggage shells according to the present invention;
[0048] FIGS. 10 to 15 the embodiment of the apparatus according to
FIG. 9 for different manufacturing steps and operational stages for
manufacturing a luggage shell according to FIG. 1;
[0049] FIG. 16 a lower mold tool (female tool) for making a luggage
shell according to the embodiment of the present invention
schematically;
[0050] FIG. 17 a lower mold tool (female tool) as shown in FIG. 16
positioned on a movable table;
[0051] FIG. 18 a lower mold tool (female tool) as shown in FIG. 16
and FIG. 17 with the movable table of FIG. 17 being in a raised
position while the auxiliary mold surfaces of the lower tool mold
retracted;
[0052] FIG. 19 a lower tool mold (female mold) similar to FIG. 16
for another embodiment with individual driven auxiliary mold
surfaces;
[0053] FIG. 20 the lower tool mold of FIG. 19 with the auxiliary
mold surfaces retracted;
[0054] FIG. 21 another embodiment of upper and lower mold halves
(male/female molds) wherein the auxiliary mold surfaces are
arranged to contact the sheet material from above, opposite to the
lower female mold;
[0055] FIG. 22 a gripping device of the press forming (deep-drawing
station) of the machinery of the apparatus of FIG. 9 in a schematic
prospective view from above and isolated from the remainder tooling
structure;
[0056] FIG. 23 one of the gripping bars of the gripping wreck of
FIG. 22 in a schematic prospective view, and
[0057] FIG. 24 a partial view of the gripping mechanism with the
gripping jaws removed.
[0058] FIG. 25 a sample lamina (unlined);
[0059] FIG. 26 another sample mold (modified deep-draw mold):
and
[0060] FIG. 27 a schematic cross-section of the mold of FIG.
26.
DETAILED DESCRIPTION
[0061] FIG. 1 shows a shell 1 according to the invention, in this
case a luggage shell. Here the edge around the perimeter of the
upstanding sidewalls 6 has been cut to remove the excess material,
or offal, left from the processing. The shell is deep drawn, that
is, the sidewalls 6 with respect to a base wall 5 have a depth
dimension that is quite large relative to previous shells made from
the preferred self-reinforcing thermoplastic sheet. More
particularly, this depth dimension is quite large relative to the
length or width dimension of the overall shell 1. This relationship
can best be express as a ratio of the smaller of either the length
or the width dimension. Preferably, the shell has a depth of up to
half of a width dimension of the shell with a preferred ratio being
in the range of about 0.2 to 0.3. The homogenous thickness of the
shell material preferably amounts to as low a 1 mm (or 0.8 mm) up
to 3 mm, preferably about 2.5 mm and should normally be in the
range of 1 to 2 mm. The preferred luggage shell is made from self
reinforcing plastic known commercially under the trademark "Curv"
from BP Amoco, although other thermoplastic materials having
similar physical, chemical, and thermo processing characteristics
will work as well, such as the Pure, available from Lankhorst. The
self-reinforcing thermoplastic material comprises, in particular
uni-aligned, twisted (in bundles) or woven tapes, strings or yarns
of preferably up to ten (potential more or less) layers containing
such molecularly oriented strands in conjunction with molecularly
unoriented thermoplastic or similar matrix material. By disposal in
predetermined patterns of subsequent layers or different layers
unidirectional strength properties can be assured with the
pre-tensioned strands extending inclined to each other in the same
or in different layers of the shell.
[0062] As shown in the figures, the shell's upstanding wall has a
dimension perpendicular to a base wall 5 of about 110 mm for a
typical 50 cm case. The ratio of length to width is preferably
between 1 and 2, in particular between 1 and 1.4. The shell has
integrally formed corner regions 7. The width of the shell for such
a luggage case thus would usually be around 36 cm. Such dimensions
result is a shell that, when paired with a similarly proportioned
shell by a simple frame or zipper closure at their mating edges,
provides a remarkably light luggage case with a substantial volume
in which to pack a traveler's needs. The upstanding wall 6 of each
such shell 1 should thus be as deep as possible, given the
difficulties in forming the self-reinforcing materials contemplated
by this invention. This perpendicular dimension for such a luggage
case could be as little as about 80 mm and still be considered
"deep drawn", especially where the radius of the self reinforcing
material in the corner regions is 60 mm or less.
[0063] The process and apparatus disclosed herein can make a range
of shell sizes, of course. But the most advantages of this
invention preferably occur for deep drawn shells where the ratio of
the perpendicular dimension discussed above to the smaller of the
width or length dimension is preferably less than about 0.3, for
shells with corner radiuses of preferably less than about 60
mm.
[0064] FIG. 2 is a close-up perspective view showing a small
section of the three dimensional stiffening pattern impressed into
the outer main shell face 1a of the base wall 5.
[0065] Self reinforcing plastics have remarkable strength, impact
and toughness characteristics which make them attractive for making
very lightweight structures, especially deep drawn shells of the
type described. Very thin sheet materials in the range of 12 to 15
mm thick provide excellent physical characteristics and light
weight. Unfortunately, a luggage shell should provide resistance to
distortion especially at its base wall to prevent crushing. A
thicker starting sheet would help, but at greater cost and
weight.
[0066] The base wall 5 of the inventive shell has a pattern of
alternating concave and convex areas 5a, 5b (see FIG. 3) to provide
remarkable structural stiffening by increasing the beam strength or
increasing the bending moment to resist bending in all planes
perpendicular to the base wall. Note that the figures show a
complex pattern of alternating concave and convex rectangular areas
extended in a two-dimensional surface plane of the base wall 5. Of
course, the concave/convex pattern is three-dimensional. These
areas are actually the visible result of impressing a series of
undulating strips into the base wall of the shell during deep
drawing. These strip patterns of continuous undulations are
substantially to one another, but in fact curve slightly as will be
detailed to that none form parallel edges to one another. Also,
adjacent undulations are offset from one another by about the
longitudinal dimension of one of the rectangular shapes or areas.
Of course, other, preferably regular alternating concave/convex
patterns, might be chosen.
[0067] FIG. 3 is a detail comparing the center line of general
cross sectional shape of the base wall at section AA with the
center line of the cross sectional shape of an adjacent Section BB
of FIG. 1.
[0068] This offset pattern of undulating shapes is not only
esthetically pleasing, it also results in remarkable stiffness or
resistance to bending forces that would tend to distort the shell's
base wall both parallel to its longitudinal dimension, that is
parallel to the longitudinal direction of the undulating strip
pattern, as well as perpendicular to its longitudinal dimension.
With regard to longitudinal stiffness, note that the lines AA and
BB of FIG. 3 each represent a line going down the center of the
self reinforcing material at the Section planes AA and BB of FIGS.
1 and 2. Although the edges of the undulating strip patterns appear
to be generally straight or, as will be detailed, gently and
smoothly curving lines, these edges in fact jog sidewise (i.e.,
displaced laterally) at each undulation. This is caused by the
draft angle "d" (that is the angle of a mold surface relative to
the direction of movement of the mold in a press) and the thus
corresponding molded edges used to form the lateral "walls" of each
rectangular shape in the pattern. This draft angle, even at the
relatively steep angle in the range of seven degrees, results in
multiple or repeating offsets of the slight distance shown enlarged
in FIG. 3. Clearly the rectangular indentations and protrusions
formed by this pattern move much of the self reinforcing material
away from the neutral axis, much like a series of ribs extending
across the width of the base wall would. But such ribs do nothing
to stiffen such a ribbed panel against bending parallel to such
ribs. Here however, the jogging or repeated offset created by the
draft angle as detailed above also places some self reinforcing
material away from the neutral axis parallel to the undulations,
tending to resist bending along these lines as well. Put another
way, the pattern detailed above creates a series of small walled
coffers with stiffening, upstanding walls despite the fact that
nowhere on the panel is the thickness of the self reinforcing sheet
thicker than its nominal starting dimension (mentioned above to be,
preferably in the range of 12 mm to 15 mm).
[0069] FIG. 3.1 shows and alternative form of stiffening pattern
formed in the base wall of the preferred luggage shell. Here
continuously curving edges are molded to define adjacent concave
and convex elongated grooves and ribs as can be seen in the scaled
up perspective section drawing FIG. 3.2. These edges visibly curve
continuously in a characteristic wavelength "w" in the general
plane of the base wall. The adjacent edges are offset to one
another in a longitudinal direction by a substantial portion of
this characteristic wavelength. In the example shown in here, this
offset is about 20% of the wavelength, thus giving a stiffening
effect to resist bending along the longitudinal direction (that is,
parallel to the grooves and ribs) while giving a softer,
potentially more esthetically pleasing pattern. FIG. 3.3 shows a
further variation. Here the longitudinal edges are shown in white
and the alternating grooves and ribs separated by these edges are
shown in black, and has a typical cross sectional shape similar to
that shown in FIG. 3.2. Each of these longitudinal edges curve
continuously in a very long characteristic wavelength "w", which in
this embodiment longer than the length dimension of the shell.
Adjacent edges are offset to one another about one half this very
long characteristic wavelength. While less pronounced, this pattern
can also provide some stiffening to resist bending along the
longitudinal dimension.
[0070] FIG. 4 is a view along the length dimension of the shell in
FIG. 1.
[0071] As mentioned above, the vertical lines visibly defining the
offset undulating strip patterns are, except for that at the
longitudinal center of the base wall, are all actually slightly
curving. This curve is small, that is the radius of curvature is
quite large, on the order of a few meters. Not only does this
curving help esthetically, but also prevents the series of small
upstanding jogged walls from forming "fold line", or line along
which the base wall can easily bend.
[0072] FIG. 5 is a partial perspective view of a luggage case using
shells according to the present invention, being a view from the
lower corner of the luggage case.
[0073] Here one can see that a luggage case can be made by mating
two similarly shaped, inventive shells. The adjacent edges are
selectively attached by a zipper 27 or slide opener track as will
be detailed. Note the caster wheel mounts 25 are at the shell
corners, in particular at the very corners giving stability much
like the casters on the ends of an office chair's legs (of course,
they can also be accommodated in recessed areas). As is derivable,
the shell halves can have quite different depths with the mating
area offset with respect to the corner/castor positions.
[0074] FIGS. 6, 6.1 is a cross-section of the zipper closure
detail.
[0075] One shell perimeter edge has a step 27a which goes
substantially all the way around its perimeter and is sized to just
engage or receive the corresponding perimeter edge of the other
shell 1. This step 27a is preferably formed with a draft angle
.alpha. approaching zero. The rest of the upstanding wall portions
are conveniently formed with a draft angle .beta. of about seven
degrees. Such a draft angle .beta. permits the opposed mold
surfaces of the male and female molds used to deep draft the shells
1 to apply sufficient molding pressure perpendicular to the shell
surfaces to properly pressurize the self reinforcing material and
keep it properly consolidated and provide a please surface finish.
For this stepped portion, a special female mold has a perimeter
portion 18 adjacent the mold edge which has almost no draft angle
(i.e., a draft angle of about zero degrees). Similarly, the
corresponding mold surface 19 of the male mold has almost no draft
angle. Compaction and shaping forces are provided by an elastomeric
element 20 in the male mold preferably made of a rugged,
temperature resistant silicone rubber or the like. This element
expands radially outwardly when it is squeezed between the male
mold support and the rest of the male mold, thus providing the
compressive pressure on the stepped edge portion of this shell (see
corresponding FIGS. 26, 27)).
[0076] The zipper tape 28 on the left of FIG. 6 is stitched at 28a
to this stepped edge, while the zipper tape 28 on the right is
stitched at 28a to the other shell edge such that when a zipper
slider 29 is operated to close the zipper 27, the shells 1 are
firmly held together in the telescoped position with their edges
firmly overlapping. Preferably, each zipper tape 28 has an extruded
flap 29a adhered along each outer edge thereof which can be pushed
out of the way by the sewing machine foot when the zipper tape 28
is being attached. This extrusion snaps back into place to both
hide the stitch line as well as help seal the resulting
perforations against precipitation. Associated zipper coils are
designated by 29c.
[0077] FIG. 7 is a view similar to FIG. 5 but showing the interior
surface of that portion of the luggage case.
[0078] The lower corner (when the case is erect on the attached
cast wheels) has a substantial indentation for receiving an
otherwise conventional wheel mount. Screw fasteners (not shown)
pass through holes drilled through the self-reinforcing polymer
sheet material in these indentations to fasten the wheel mount to
the shells. The luggage case shown, even including four wheels and
appropriate carry and wheeling handles, could way as little as 2.2.
Kg for a conventionally sized case of about 50 cm length.
[0079] FIG. 8 shows a conventional production machinery for making
a type of luggage shell.
[0080] This machinery is used to make basket weave textile covered
polypropylene luggage shells. I consists of (from left to right), a
heating station (pre-heating) 30 that warms the pre-laminated
textile and polymer sheet perform to proper processing temperature.
Next is a station 31 for placing a lining material such as a knit
fabric, on the next sheet to be pressure formed. The press section
32 to the right receives the polypropylene laminate and forms it
into a shell shape between matched mold forms. The component
removal station is designated with reference numeral 33.
[0081] FIG. 9 shows schematically the apparatus according to our
invention for making a shell 1 as in FIG. 1.
[0082] The FIGS. 10 to 15 show this apparatus of FIG. 9 in its
various operational stages: The apparatus includes, from left to
right, is a lining textile dispenser 22 which receives stacks of
knit textile cloth for placing on temperature conditioned sheets of
self reinforcing polymer, the press 23, and the radiant heater 24.
A supply of sheets of self-reinforcing polymer is behind the press.
The textile lines (not shown) are disposed on a tray 22a. The
deep-drawing press comprises upper and lower tables 23a, 23b which
are movable relative to each other, i.e. the upper table 23
supporting the upper or male mold 15 of the deep-drawing tooling 14
descends toward the lower or female mold 16 along and guided by
column frame 23c. Grippers 26 hold the corners of the lining fabric
or textile material to be bonded to a sheet (lamina) of
self-reinforced thermoplastic material to be supplied into the
press 23 from the back. A sheet gripping rack 12 (shown in more
detail in FIGS. 22 to 24) controllably holds or stretches each
warmed sheet from the sheet supply to a position between the upper
male shell mold tool 15 (shown with its support table removed for
clarity) and the lower, female mold 16. The radiant heater support
includes upper and lower radiant heater arrays 24. These arrays 24
slide simultaneously out of the support rack 12 to heat both sides
of the self-reinforcing polymer sheet while it is being gripped and
held or stretched by the gripping rack 12 between the shell mold
tools 14 (upper and lower deep-drawing molds 15, 16).
[0083] As shown in FIG. 10 the machinery is in the start position,
ready to receive the sheet polymer material and associated lining
textile for bonding same and for deep drawing both.
[0084] FIGS. 11 through 15 show the further operation of the
apparatus performing the process of making a luggage shell
according to this invention.
[0085] FIG. 11 shows the gripping rack 12 moved down ready to
receive a warmed sheet of polymer from the supply behind the press
23. The sheet moves to above the gripping jaws 31, 32 (see FIGS.
22/23) and drops onto the four support bars 12b and the lower jaws
32 of the four gripping bars or jaws 31, 32. Immediately the
radiant heaters 24 move quickly to above and below the thus gripped
polymer sheet to bring it to processing temperature (FIG. 12). The
gripping bars or jaws 31, 32 are hydraulically or pneumatically
driven to pull and/or move the gripped edges of the polymer sheet 4
during heating and/or deep drawing. Once the sheet has been heated,
the radiant heaters 24 move briskly back within their support rack
and out of the way and the mold surfaces move to contact and shape
the polymer sheet. Simultaneously with the heating and before
molding, a sheet of textile lining, usually a knit tricot, is
placed in position between the heater 24 and the upper mold tool
15.
[0086] In FIG. 13, the lining storage tray 22a is brought in an
elevated position and then the fabric lining is forwarded into the
press 23 (FIG. 14).
[0087] The lower mold, in this case the female deep draw mold 16
and auxiliary mold surfaces 13 move upwardly to contact the heated
and stretched sheet. The upper male mold 15 moves down to force the
sheet into contact with all the mold surfaces while simultaneously
shaping and adhering the lining material to the thermoformed
polymer sheet (FIG. 14.1, FIG. 15).
[0088] FIGS. 16 to 18 show the lower mold 16 (female mold tool)
isolated including auxiliary mold portions 13 disposed in the
corner areas which assist to apply additional tension to the
respective lamina or thermoplastic sheet (potentially lined with
fabric) and to help overcoming the compression forces arising in
that area. The auxiliary mold portions 13 are screwed to respective
carriers which are retractable and projectable so that the
auxiliary molds 13 themselves can be retracted into the lower mold
16 as shown in FIG. 18 or project therefrom (FIGS. 16, 17).
Additionally, as shown in FIGS. 16 and 17, the lower table 23b
itself can additionally be raised to adjust the respective
tensioning of the sheet material in conjunction with the fine
adjustment by the auxiliary mold portions 13.
[0089] Accordingly, the auxiliary mold surfaces and auxiliary mold
portions 13 help gather up excess material that would otherwise
accumulate at the corner regions and potentially wrinkle the molded
shell corners. As is shown in FIG. 19, each of the auxiliary mold
portions 13 may be individually driven by separate drives 13a which
allow fine tuning of the introduction of respective tensile forces
into the lamina and composite thermoplastic sheet material so that
the appropriate flow of material and permanent tensioning of the
molecularly oriented strands or fibers within the self-reinforced
thermoplastic material can be maintained and the development of
compression forces prevented reliably.
[0090] Thus, an embodiment as shown schematically in FIG. 19 would
be most preferred. In such a case, for example, keeping the
auxiliary mold portions and surfaces 13 at those corner regions
which are designed to exhibit the wheel receiving (castor housing
accommodating) concavities out of contact with the polymer sheet
could be beneficial to issue enough polymer material for these
concavities.
[0091] FIG. 20 shows the auxiliary mold portions or surfaces all in
a retracted position.
[0092] FIG. 21 discloses another embodiment of upper and lower mold
halves, wherein the auxiliary mold surfaces 13 are arranged to
contact the sheet material from above, opposite to the lower female
mold. They are disposed via a boss 13b supported at an upper mold
plate 15a, which also supports the male mold 15. Respective
recesses 13c are provided within the margin of the lower (female)
mold 16 for the auxiliary mold portions 13 to engage. Of course,
similarly as in the preceding embodiment, the precise position of
the auxiliary mold surfaces and auxiliary mold portions 13 can also
be fine-tuned by designing the support boss 13b to be telescopic or
otherwise adjustable. Of course, the boss 13b may also be supported
adjustably with respect to their length at the upper mold support
plate 15a.
[0093] FIGS. 22 to 24 show details of the gripping wreck mechanism
with FIG. 22 showing the gripping wreck 12 in a perspective view
from above showing the support rods 12b for supporting the sheet
material as well as the upper and lower gripping bars or gripping
jaws 31, 32. The jaw operating drive unit 33 which drive the upper
and lower gripping bars or jaws in response to a respective process
control via a linkage mechanism, for example toggle lever
mechanism, as shown in FIG. 24 may operate on an electrical,
pneumatical or hydraulic bases.
[0094] Preferably, the lower gripping bar or jaw is stationary and
the supporting rods 12b are affixed thereto while the upper
gripping bar or jaw is movable with respect to the lower one to
grip the material.
[0095] The tensioning control acting in this way on the sheet
during press forming, i.e. deep-drawing same, may either be a
passive one based on the molding process itself and clamping the
edges of the respective thermo-plastic (in particular lined)
material sheet or can also be actively performed, i.e. moving the
respective and potentially more individualized clamping areas of
the sheet actively to imply a certain tension to the reinforcing
strands within the sheet material during the molding process.
[0096] FIG. 24 shows the partially exploded view of the operating
assembly and gripping bar or jaw operators based on for example a
cylinder rod projecting from an operating cylinder 33 and
transferring an angular movement to an upper gripping bar or
gripping jaw support 33a to move under assistance of a cam control
groove 36 towards the lower gripping bar or jaw support via a
linkage 37.
[0097] Finally, FIG. 25 again embodies the lamina or base material
4 with a central portion 2, a field portion 3 and the respective
edges 8.
[0098] FIGS. 26 and 27 show an alternative embodiment of a
deep-drawing module having a matching upper (male) mold 15' and a
lower (female) mold 16' as another deep-drawing mold 14'. In that
case, the female mold portion 16' has a perimeter mold surface 18
near the trim line. That perimeter portion has almost no draft
angle. The male mold 15' comprising a perimeter mold surface 19 has
an elastomeric section 20, in particular a molded silicon plug
forming an expandable mold surface around the parameter so as to
provide a controlled and reliable molding force to avoid wrinkles
and any deformation, in particular in the corner areas of the
shell.
[0099] By the afore-indicated methods and apparatuses, an
ultra-light molded component implying at least in certain areas or
regions an extraordinarily high degree of form change, such as a
deep-drawn shell, in particular luggage shell, can be manufactured
having a high depth to width/length ratio and unrivaled mechanical
properties (i.e. strength, bending resistance, resistance against
distortion and breakage) combined with highest dimensional and
shaping accuracy and attractive appearance.
[0100] The invention provides a new product and process for
manufacturing same on the basis of self-reinforced thermoplastic
material by means of the step of tensioning said material (lamina),
at least partially tensioning said lamina during all follow-up
component shaping and/or molding steps up to a release of a
component pre-form shape from the remainder lamina, to form the
component.
[0101] The present invention allows the manufacturing of an
ultra-light weight luggage shell on the basis of using
self-reinforced thermoplastic material, the manufacturing of same
can be further enhanced by permanently tensioning said material
during all manufacturing steps up to the final finishing of the
product.
* * * * *