Note: Descriptions are shown in the official language in which they were submitted.
CA 02254687 2006-04-25
1
INSULATED CONTAINER AND LINER
Field of Invention
This invention relates to the field of soft sided insulated containers. In
particular
it relates to soft sided insulated containers having removable impermeable
liners for
discouraging or preventing the leakage of liquids.
Back,ground of the Invention
In recent times soft sided insulated containers have become popular for
carrying
either articles that may best be served cool, such as beverages or salads, or
warm, such
as appetizers, hot dogs, and so on. Such containers are frequently used to
carry liquids,
whether hot liquids, such as soup containers, coffee or tea, or cold liquids
such as beer
pop, juices and milk. The containers are typically made in a generally cube
like shape,
whether of sides of equal length or not, having a base, four upstanding walls,
and a top.
The top is generally a lid which opens to permit articles to be placed in, or
retrieved from,
the container.
By the nature of their use, it is advantageous for the containers to be water
tight.
That is, whether to hold melted run-off from ice cubes or to hold spilled
liquids, the
container must be sufficiently liquid tight that it does not leave a trail of
drips, or become
moist or sticky to the touch of a person carrying the container.
The present inventor has found it disadvantageous to try to seal the container
itself. The type of insulating wall used by the present inventor is generally
sewn at its
seams. Sewn seams have a tendency to leak at the stitches. Another approach is
to fold
the insulated blanket from which the container is made, to present an assembly
that,
through folding, has no seams. This is also disadvantageous, in the present
inventor's
view, because the insulated blanket used to form the container walls is
relatively thick.
CA 02254687 1998-11-25
2
The thick material does not fold well, in the inventor's view. It would be
preferable to
form an impermeable layer that has a relatively thin wall thickness so that
the resulting
product does not look bulky and cumbersome.
It is also advantageous to be able to clean the inside of the insulated
container.
Spilt liquids may not always have the most attractive air when allowed to dry,
and may
cause the inside of the container to become unsightly. It is possible to
provide a plastic
liner for soft sided insulated containers. A see through plastic liner can be
made of the
minimum amount of material by using only a single layer, and forming seams
where the
edges of the material meet. A common method of forming such a seam is to weld
two
adjacent edges together by heating. However, an existing liner of this type is
known to
have had a tendency for the heat welded seams to develop leaks over time. It
would be
advantageous to reduce or eliminate the number of heat welded seams formed in
areas of
the liner that may need to be water tight.
In general, manufacture of an assembly of this type emphasizes cost reduction.
One common source of cost savings is a reduction of the raw material used.
However,
the present inventor has observed, counter-intuitively, that the overall
benefit an increase
in raw material use can outweigh the cost saving that would otherwise be
achieved.
Unexpectedly, the use of a greater amount of material in a folded assembly has
been found
to be advantageous, and has eliminated the need to have a heat welding station
in
manufacture.
Summary of the Invention
In an aspect of the invention there is a soft-sided insulated container, and a
removable liner for placement inside the container. The liner is folded from a
monolithic
sheet of liner stock to define a chamber, capable of holding liquids. The
liner is free of
heat welded seams.
CA 02254687 1998-11-25
3
In another feature of that aspect of the invention the liner is made from a
water
impermeable plastic sheet. In an additional feature of that aspect of the
invention the liner
is made from a translucent static cling vinyl sheet. In another additional
feature of that
aspect of the invention the soft sided insulated container has a base, sides
and a top. The
liner has a base, sides for placement inside and adjacent to the base and
sides of the
container. The top of the container is moveable to an open position to permit
articles to
be placed in the chamber.
In still another additional feature of that aspect of the invention the
chamber has
an opening, the opening having a lip, and the liner is mated to the cooler
about the lip.
In yet another additional feature of that aspect of the invention the opening
has four sides,
the lip extends about the four sides opening and the liner is mated to the
container on the
four sides. In a further additional feature of that aspect of the invention
the liner has a
rectangular base and four sides extending from the base, each of the sides
having an edge
adjoining the base and a distal edge distant from the base. The chamber has an
opening
defined between the distal edges of the sides.
In a still further additional feature of that aspect of the invention one of
the sides
has a lid member extending therefrom, the lid member being moveable to close
the
opening of the liner. In yet another additional feature of that aspect of the
invention the
lid member is a flap formed integrally with the liner, the flap having four
lid edges, one
edge being a folded hinge edge adjoining one of the distal edges of the sides,
the
remaining three lid edges having a closure for mating with the remaining three
distal
edges.
In another aspect of the invention there is a removable liner for placement
inside
the container. The liner is formed from a water impermeable plastic sheet. The
sheet has
a periphery. The liner has a quadrilateral base and four sides extending from
the base to
define a chamber therebetween capable of holding water. Each of the sides are
joined to
the base at a base edge. Each of the sides has a pair of lateral edges each
meeting the base
CA 02254687 1998-11-25
4
edge at a corner. Each of the sides has an edge opposed to the base edge and
meets each
of the lateral edges at a corner. The sheet has corner portions defined
between adjacent
lateral edges of two of the sides and the periphery and the corner positions
are folded to
lie against the sides.
In a further additional feature of that aspect of the invention the base is a
rectangle
and two of the sides, joined to the base on opposite sides of the rectangle,
are trapezoidal.
In a still further additional feature of that aspect of the invention the
chamber has the
shape of an inverted, truncated rectangular based pyramid. In yet another
additional
feature of that aspect of the invention the container has an internal face
made from a
reflective material and the liner is transparent.
In another aspect of the invention there is a soft sided insulated container,
and a
removable liner for placement inside the container. The liner is formed from a
water
impermeable plastic sheet. The sheet has a periphery. The liner has a
rectangular base
and four sides extending from the base to form a chamber therebetween, each of
the sides
being joined to the base at a base edge. The sheet is folded on a first pair
of parallel fold
lines to define one pair of the base edges. The sheet is folded on a second
pair of fold
lines to define the remainder of the edges. The sheet has four corner portions
each
defined between an end portion of one of the first pair of fold lines, an
adjacent end
portion of one of the second pair of fold lines and the periphery, and the
corner portions
are folded to lie against the sides.
In an additional feature of that aspect of the invention the sides have an
inside face
and an outside face and the corner portions are folded to lie against the
outside faces. In
another additional feature of that aspect of the invention each of the corners
is folded to
form a triangular flap, and each of the flaps is folded to lie against one of
the sides. In still
another additional feature of that aspect of the invention one of the
triangular flaps is
folded to lie against each of the sides of the liner. In still yet another
additional feature of
that aspect of the invention two of the triangular flaps are folded to lie
against one side
CA 02254687 1998-11-25
of the liner. In a further additional feature of that aspect of the invention
two of the
triangular flaps are folded to lie against one side of the liner, and the
other two triangular
flaps are folded to lie against another side of the liner.
5 In still a further additional feature of that aspect of the invention each
of the sides
has a distal edge opposed to its respective base edge. The chamber has a lip
defined by
the distal edges. The corner portions are fastened to the sides adjacent the
lip. In still yet
a further additional feature of that aspect of the invention one of the sides
has a cover flap
formed integrally therewith, and joined thereto at a cover fold, the cover
flap mating with
the distal edges of the remaining sides of the liner. In an additional feature
of that aspect
of the invention the container has a reflective inner surface and the liner is
transparent.
Brief Description of the Drawings
These aspects and other features of the invention can be understood by with
the
aid of the following illustrations of a number of exemplary, and non-limiting,
embodiments
of the principles of the invention in which:
Figure 1 is a three quarter view, general arrangement drawing of an insulated
container and liner assembly according to the present invention;
Figure 2 is a view of the liner of Figure 1 taken on an opposite angle;
Figure 3 is a developed view of a liner for use in the assembly of Figure 1;
Figure 4 is a developed view of an alternative liner for an assembly analogous
to
the liner of assembly of Figure 1 in which two sides are tapered;
Figure 5 is a developed view of an alternative liner for an assembly analogous
to
the liner of assembly of Figure 1 in which four sides are tapered;
Figure 6 is a developed view of an alternative liner for an assembly analogous
to
the liner of assembly of Figure 1 in which the forward side of the assembly is
wider than
the rearward side;
Figure 7 is a front view of the assembly of Figure 1, in a collapsed position;
CA 02254687 1998-11-25
6
Figure 8 is a rear view of the assembly of Figure 1 in a collapsed position;
Figure 9 is a side view of the assembly of Figure 1 in a collapsed position;
Figure 10; is a section showing the wall construction of the assembly of
Figure 1
and
Figure 11 is a view of an alternative liner for the assembly of Figure 1.
Detailed Description of a Best Mode for Practicing the Invention
The description which follows, and the embodiments described therein, are
provided by way of illustration of an example of a particular embodiment, or
examples of
particular embodiments, of the principles of the present invention. These
examples are
provided for the purposes of explanation, and not of limitation, of those
principles and of
the invention. In the description which follows, like parts are marked
throughout the
specification and the drawings with the same respective reference numerals.
The drawings
are not necessarily to scale and in some instances proportions may have been
exaggerated
in order more clearly to depict certain features of the invention.
Referring to the general arrangement illustration of Figures 1 and 2, an
example
of a preferred embodiment of an insulated container and liner assembly
according to the
principles of the present invention is indicated generally as 20. It has two
major elements,
those being an outer casing in the nature of a soft-sided insulated container
22, and a
removable, impermeable liner 24 for placement inside container 22. An optional
moveable
bulkhead, or baflle, in the nature of a partition wall 25 seats within line 24
for dividing the
interior space into two sub-compartments 27 and 29.
Looking at these major elements in detail, it can be seen that container 22
has a
bottom 26, a front pane128, a rear panel 30, and a pair of left and right hand
side panels
32 and 34. In this preferred embodiment the choice of front and rear, left and
right,
orientations is arbitrary. Each of front panel 28, rear panel 30, and left and
right hand side
panels 32 and 34 is joined at sewn seams to bottom 26 at bottom vertices 36,
37, 38, or
CA 02254687 1998-11-25
7
39 respectively. Similarly, front panel 28 and side panels 32 and 34 have top
edges 40, 41
and 42, distant from their base edges. Rear pane130 is joined by a folded
hinge 44 at its
top edge to a top panel in the nature of a lid 46. Lid 46 has a closure member
in the
nature of a zipper 48 extending in a U-shape around the three free edge
portions of its
periphery to mate with the other portions of zipper 48 positioned about the
three top
edges 40, 41 and 42 of panels 28, 32 and 34. Lid 46 is moveable between a
closed
position, in which zipper 48 may be zipped closed, and an open position in
which lid 46
is folded back to permit entry and exit of objects to and from an internal
cavity 50 defined
between bottom 26 and panels 28, 30, 32 and 34. A generally rectangular
insulated
auxiliary pouch 52 is mounted to the front face of front panel 28.
In the preferred embodiment, lid 46 has an extent substantially equal to that
of
bottom panel 26. This need not be the case. Lid 26 could be a small opening
set in a
larger top panel, or could be an opening of half, or some other portion of the
panel. The
opening need not extend fully along three sides of lid 26, but could extend
along part of
one or two sides as may be found suitable in a particular use.
Top edges 40, 41, and 42 form the rim 54 of cavity 50. On the inside of rim 54
is a liner securing means, or liner attachment mounting, in the nature of a
zipper 56,
which, in the embodiment illustrated, includes portions 57, 58, and 59 mounted
respectively to panels 28, 32, and 34 near their upper margins, and a hook and
eye fabric
fastener strip 60 mounted to panel 30. Although this arrangement is preferred,
in an
alternative embodiment all of strip portions 57, 58, 59 and 60 (or some other
combination
of them) could be hook-and-eye fabric fasteners . Other types of mounting
could be used,
in addition to zippers, such as interlocking seal strips, snaps, clips,
grommets or other
means.
Container 22, with liner 24 installed, can be folded to a collapsed position,
as
shown in Figures 7, 8 and 9. In this collapsed, or storage position, side
panels 32 and 34
fold inward, and bottom 26 folds upward. This permits front panel 28 to move
toward
CA 02254687 1998-11-25
8
rear panel 30. Lid 46 is then drawn forward and downward in front of front
pane128 and
auxiliary pouch 52. Lid 46 has, on its inner face, spaced inwardly from zipper
48, a
retainer in the nature of another hook and eye fastener strip 62 that engages
a mating hook
and eye fastener strip 641ocated on a lower portion of the front face of
auxiliary pouch
52. In addition, left and right hand side retainers 66 and 68 mounted to the
left and right
hand edges of auxiliary pouch 52 of front panel 28 are drawn around to fasten
to fastening
strips 70 and 72 located on the outer, rearward face of rear pane130. (When
container 22
is in its open position, strips 66 and 68 engage storage strips 74 and
761ocated on side
panels 32 and 34 respectively).
Other features of container 22 are visible in Figures 1 and 2. Front and rear
canying handles 78 and 80 with reinforced bails are attached to both front
panel 28 and
rear panel 30 to permit two people to carry assembly 20 between them. In the
preferred
embodiment assembly 20 has a maximum capacity of 24 quarts. Smaller
embodiments,
include a twelve quart container. A single shoulder strap 79 is attached to
side panels 32
and 34. An elasticized retaining matrix 82 permits other materials, such as
cups, plates,
serving utensils or other objects to be carried on top of assembly 20. Above
strip 64,
auxiliary pouch 52 has a see-through mesh pocket 84, such as may be convenient
for
carrying knives, forks, spoons or other objects.
Figure 10 shows a cross section of front panel 28 with liner 24 in place. A
scab
section of panel 34 is also shown to reveal its layers of construction. With
the exception
of auxiliary pouch 52, this section is typical not only of front panel 28 but
also, generally,
of rear panel 30, side panels 32 and 34, bottom panel 26 and lid 46. The outer
facing
layer of front panel 28 is a canvas covering layer 88 for resisting abrasion.
It overlays a
closed cell foam insulation layer 90. The inner face of insulation layer 90 is
covered by
flexible plasticised metallic foil sheeting 92 that is shiny and reflective.
The material is
sold under the name Therma-Flect (T.M.). Liner 24 lies inside sheeting 92, and
is pressed
against it by the objects it contains. The inside of pouch 52 is lined with
white vinyl
sheeting, 93 on its forward and bottom sides.
CA 02254687 1998-11-25
9
Liner 24, is shown in Figures 2 and 3. It is made from a membrane, or web, in
the
nature of a sheet 100 of flexible, transparent plastic stock, in particular,
static cling vinyl.
The shiny, reflective surface of sheeting 92 is visible through liner 24 in
use. Liner 24 has
a base 102 and four sides, front, rear, left hand and right hand respectively,
104, 106,
108, and 110 extending upwardly from base 102. Each of sides 104, 106, 108 and
110
is joined to base 102 at a base edge, 112, 114, 116 or 118, as indicated, and
each has an
opposite, distal edge 120, 122, 124 or 126 distant from its respective base
edge. The
sides meet at respective upstanding corners 128, 130, 132 and 134. A chamber
136 is
defined between base 102 and sides 104, 106, 108 and 110. Chamber 136 has an
opening
138 defined by the peripheral lip 140 formed collectively by the distal edges
120, 122, 124
and 126 of sides 104, 106, 108 and 110. Immediately below lip 140 liner
support
fasteners, in the nature of hook and eye strips, are mounted to sheet 100.
This mounting
may be by heat welding or by use of a bonding agent or adhesive. In the
preferred
embodiment lip 140 is folded over to form a hem, and fasteners 141, 144, 143
are of the
nature of a continuous zipper around three sides of lip 140, and a fastener
142 in the
nature of a fabric hook-and-eye strip are sewn in place with stitching 145
that is at a
height relative to base 102 that is expected to be well above the liquid level
in liner 24.
In an alternate embodiment, fasteners 141, 142, and 143 are all fabric hook
and
eye fasteners each mounted on one side of lip 140, and which mate with
corresponding
hook-and-eye fastener strips mounted to container 22. These fastener strips
are
commonly sold under the name Velcro (T.M.). Optional partition 25 is variably
positionable. About the upper portion of its periphery it has a strip engaging
material 146
that catches on mating strips 147 and 148 located on the inner face of liner
24. These
strips can be hook and eye fastener strips. The range of the strips permits
the division of
sub compartments 27 and 29 of chamber 136 into equal, half-and half portions,
or into
some other portions, such as 1/4 to 3/4, 1/3 to 2/3, 2/5 to 3/5 and so forth
as may be
found desirable given the objects to be contained in chamber 136.
CA 02254687 1998-11-25
In Figure 3 sheet 100 is shown in developed view, as it would be before being
folded to form liner 24. A first pair of parallel fold lines 150 and 152
extend across sheet
100, and a second pair of parallel fold lines 154 and 156, perpendicular to
lines 150 and
152 extend along sheet 100, thus dividing it into nine portions within the
rectangular
5 periphery, 158, of sheet 100. It will also be noted that each of lines 150,
152, 154 and
156 has two intersections, and is thus divided into a central sector between
the parallel
lines it intersects, and a pair of end sectors between each of the parallel
lines it intersects
and the line's ternunation at periphery 158.
10 The central portion of sheet 100, bounded by the central sector of each of
lines
150, 152, 154 and 156, defines base 102, each of those sectors defining one of
base edges
112, 114, 116 and 118. Front side 104 is defined between the central sector
160 of line
150, two parallel forward end sectors 162 and 164 of lines 154 and 156, and a
mid-edge
sector 166 of periphery 158. Rear side 106 is defined by the central sector
168 of line
152, two parallel rearward end sectors 170 and 172 of lines 154 and 156, and a
mid edge
sector 174 of periphery 158. Left hand side 108 is defined by central sector
176 of line
154, two left end sectors 178 and 180 of lines 150 and 152, and a mid-edge
sector 182
of periphery 158. Right hand side 110 is defined by central sector 184 of line
156, two
right end sectors 186 and 188 of lines 150 and 152, and a mid-edge sector 190
of
periphery 158.
The remaining four portions of sheet 100 are corner portions 192, 194, 196 and
198 defined by a pair of adjacent end sectors of a pair of perpendicular
lines, and a corner
sector of periphery 158, indicated respectively as 202, 204, 206 and 208.
Corner portions
192, 194, 196 and 198 are bisected by diagonal bisectors 212, 214, 216 and 218
which
extend from the intersection of the respective perpendicular lines to
periphery 158.
Having thus defined the geometry of sheet 100, liner 24 is formed by folding
sides
104, 106, 108 and 110 upwardly such that sectors 162 and 178, 164 and 186, 170
and
180, and 172 and 186 lie adjacent to each other to form corners 128, 130, 132
and 134
CA 02254687 1998-11-25
11
respectively. This folding necessitates folding of corner portions 192, 194,
196 and 198,
and this is done along their respective diagonal bisectors.
When folded along bisectors 202, 204, 206, and 208 corner portions 192, 194,
196
and 198 form triangular flaps 220, 222, 224 and 226. In the preferred
embodiment flaps
220 and 222 are folded to lie against the outside face of front side 104, the
corner of flap
220 lying most distant from corner 128 overlapping the corner of flap 204
lying most
distant from corner 130. Similarly flaps 224 and 226 are folded to lie against
the outside
face of rear side 106 the most distant corner of flap 224 overlapping the most
distant
corner of flap 226. One edge of each flap lies roughly flush with lip 140,
which is folded
over and the entire periphery of opening of chamber 136 sewn as a hem 228
having a
double row of stitches. In this way liner 24 is formed from sheet 100 such
that it is not
only free of welded seams, but free of any seams below hem 228 of lip 140.
In the preferred embodiment the folding process is purely mechanical, and can
be
performed relatively quickly, in contradistinction to heat welding or adhesive
bonding
processes which require a time interval for heating and cooling or for
adhesive curing.
Inasmuch as the preferred embodiment uses a relatively thick static cling
vinyl, sheet 100
can be folded over a cube form of the desired dimensions, and held in place by
its own
clinging properties in preparation for the sewing of hem 228. The overlap of
the tips of
flaps 202 and 204, and flaps 206 and 208, and subsequent sewing makes it
doubly
improbable that liner 24 will unfold.
Liner 24 is formed from a single integral sheet, and, absent punctures of that
sheet
is not intended to leak below the level of the sewn seam at lip 140. The body
of base 102
and sides 104, 106, 108 and 110 is seamless, being free of heat welds or other
joints. In
general use the liquid level in chamber 136 is not expected to be greater than
one half of
the height of the sides, and still less commonly to be more than three
quarters of the
height. There are no seams below either of these levels, heat welded or
otherwise.
CA 02254687 1998-11-25
12
Liner 24 is also thin enough that it can be folded inside container 22 when
container 22 is compressed to its collapsed position as illustrated in Figures
7, 8, and 9.
Liner 24 need not be transparent, but could be translucent or opaque. A
transparent liner
is preferred since it permits the reflection of sheeting 92 to be seen.
In an optional embodiment, a liner 224 can have its own closure, or lid, 230,
to
provide a double closure with lid 46 of container 22 in Figure 11. As shown in
Figure 11,
optional lid 230 extends on a folding plastic hinge 232 that is an integral
part of sheet 234
from rear side 236 of sheet 234, and mates at front, left hand and right hand
side edges
238, 240 and 242 along a U-shaped closure interface such as may be held closed
by a
closure member in the nature of a seal, a zipper, a hook and eye fabric
fastener, or a
similar device. It is not necessary that the opening of the container, or the
liner, form a
parallel plane to the respective base or bottom sides. The opening could be in
a skewed
plane, or could be something other than a plane.
In alternative embodiments, one of each of corner flaps 220, 222, 224 and 226
can
be folded against each of sides 104, 106, 108 and 110, or a pair (220, 224)
can be folded
against left hand side 108 and another pair (222, 226) against. right hand
side 110, rather
than against front and rear sides 104 and 106 as illustrated in Figure 11. It
is not
necessary that the corner portions have one edge lying flush with lip 146.
However, if the
corner portions are cut down, the height at which a liquid tight barrier is
provided may not
necessarily be as high as shown in the preferred embodiment of Figure 1. It is
also not
necessary that corner portions 192, 194, 196, and 198 be folded against the
outside faces
of the sides, but could be folded to lie along the inside faces. It would also
be possible to
fold each flap to lie partially against one side and partially against another
side by using
more than one fold line and by cutting the periphery of the corner portions
differently.
There is simplicity in using a single fold and to fold the flaps against the
outside of one
side of the liner, as shown in the preferred embodiment of Figure 1.
CA 02254687 1998-11-25
13
As shown in the developed views of the alternate embodiments of Figures 4, 5,
and 6, the liner need not be a cube or cuboid, but could be a tapered,
trapezoidal, or
truncated pyramidal shape. In the embodiment of Figure 4 a developed sheet 300
has fold
lines for forming a liner having a pair of opposed trapezoidal sides 304 and
306 which rise
at right angles from a base 308, and a pair of opposed rectangular sides that
are folded
upward at an angle corresponding to the rake angle a of trapezoidal sides 304
and 306.
It can be seen that there is one pair of parallel fold lines 310 and 312, each
line having a
central sector 314, 316 and a pair of left and right end sectors 318, 320 or
322, 324.
There is also a pair of fold line sectors 326 and 328 which define the
remaining two sides
of base 308 (perpendicular to sectors 314 and 316). The intersections of
sectors 326, 314,
328, and 316 define the corners of base 308. Extending away from those corners
to
periphery 330 are left and right hand canted trapezoidal side sectors 332,
334, 336, and
338 to define the remaining vertices of trapezoidal sides 304 and 306. At the
angular
bisector of the included angle between adjacent pairs of rectangular side
lateral sectors
and trapezoidal side sectors, as, for example between sectors 318 and 332, are
corner
portion fold lines 340, 342, 344, and 346. Corner portions 348, 350, 352 and
354, each
defined between one trapezoidal side end sector, one rectangular side end
sector and
periphery 330, have been trimmed along periphery 330 to lie flush with the
resulting lip.
When sheet 300 is folded in a manner analogous to the folding of sheet 100, a
cradle
shaped liner will result, for mating use with a similarly cradle shaped
container analogous
to container 22.
In the embodiment of Figure 5 a developed sheet 400 has fold lines for forming
a liner 402 having a first pair of opposed trapezoidal sides 404 and 406 which
rise at a
non-perpendicular angle a from a base 408, and a second pair of opposed
trapezoidal
sides 410, 412 that are folded upward at an angle corresponding to the
vertical projection
of the rake angle P of the first pair of trapezoidal sides 404 and 406. It can
be seen that
there is one pair of fold line sector 414, 416 pairs of left and right hand
end sectors 418,
420 or 422, 424 and a perpendicular pair of fold line sectors 418 and 420
which define the
remaining two sides of base 408. The intersections of sectors 418, 414, 420,
and 416
CA 02254687 1998-11-25
14
define the corners of base 408. Extending away from those corners to periphery
430 are
left and right hand trapezoidal side lateral sectors 422, 424, 426 and 428.
Similarly, left
and right hand canted trapezoidal side sectors 432, 434, 436, and 438 extend
from those
intersections toward periphery 430 to define the remaining vertices of the
trapezoidal
sides. At the angular bisector of the included angle between adjacent pairs of
rectangular
side lateral sectors and trapezoidal side sectors, as, for example between
sectors 418 and
432, are cotner portion fold lines 440, 442, 444, and 446 of corner portions
448, 450, 452
and 454.
Sectors 422, 424, 426, 428, 432, 434, 436 and 438 all have the same true
length,
indicated as 1. The distance that sectors 422, 424, 426 and 428 are splayed
outward from
square is indicated as E. Similarly, the distance that sections 432, 434, 436
and 438 are
splayed outward from square is indicated as 8. Angle a satisfies the condition
that Sin a
_[E/(1Z-SZ)] '. Similarly Angle P satisfies the condition that Sin P =[S/(12-
52)] 1.
When folded in a manner analogous to the folding of sheet 100, sheet 400 will
form a truncated, inverted rectangular shaped pyramid. It should be noted that
the pairs
of opposed slanted pyramid sides need not rise at the same angle, but could be
at different
angles. In the most general case, each side could rise at a different angle,
and to a
different height. The upper edges of the sides need not be level, but could
have a slant,
or, alternatively, need not be linear but could be curved as may suit the
desired geometry.
However, it is expected that the sides will, most often, have straight and
level edges.
In the embodiment of Figure 6, a developed sheet 500 has fold lines for
forming
a liner 502 having a trapezoidal base 504 such as might be desired in a
knapsack having
a large rearward face for placement against a person's back, and a narrower
outer or
forward face. A pair of parallel lines of unequal length, being a short front
fold line 506
and a longer rear fold line 508, define the parallel sides of the trapezoidal
base 504. A pair
of left and right hand side fold lines 510 and 512 extend between lines 506
and 508 at
angles to define the splayed sides of trapezoidal base 504. Front side 514,
rear side 516,
CA 02254687 1998-11-25
left side 518 and right side 520 are all hinged along respective fold lines
506, 508, 510 and
512 to base 504. Corner portions 522, 524, 526 and 528 are defined between the
periphery 530 and respective pairs of side sectors 532 and 534, 536 and 538,
540 and 542,
and 544 and 546. Each of portions 522, 532, 526 and 528 has a fold line 548,
550, 552
5 or 554 on which the respective corner portion is folded, those portions
being trimmed
along their peripheral edges to lie flush with the peripheral edges of the
respective sides
against which they are folded, similar to the manner described above in
connection with
the preferred embodiment.
10 A preferred embodiment has been described in detail and a number of
alternatives
have been considered. As changes in or additions to the above described
embodiments
may be made without departing from the nature, spirit or scope of the
invention, the
invention is not to be limited by or to those details, but only by the
appended claims.
