U.S. patent application number 14/051988 was filed with the patent office on 2014-02-06 for synthetic resin container.
This patent application is currently assigned to TOYO SEIKAN KAISHA, LTD.. The applicant listed for this patent is Kazushi MATSUKIYO, Masaki MIURA. Invention is credited to Kazushi MATSUKIYO, Masaki MIURA.
Application Number | 20140034600 14/051988 |
Document ID | / |
Family ID | 41113620 |
Filed Date | 2014-02-06 |
United States Patent
Application |
20140034600 |
Kind Code |
A1 |
MIURA; Masaki ; et
al. |
February 6, 2014 |
SYNTHETIC RESIN CONTAINER
Abstract
A synthetic resin container includes a bottom part having a
bottom plate part present at the center of the bottom part and a
peripheral part positioned at the periphery of the bottom plate
part. The peripheral part includes a grounding part having an
inside slope rising outwardly of the container with the outer
peripheral edge of the bottom plate part being a start point, and
an outside slope continuing to the side surface of the bottom part.
When a load is applied in the axial direction in the state where
the container stands upright on the grounding surface, the shape of
the bottom part changes reversibly such that the bottom plate part
is depressed inwardly to the container. Thus, it is possible to
avoid deformation of the container into an unintended shape if a
load is applied to the container in the axial direction, and to
ensure the rigidity thereof.
Inventors: |
MIURA; Masaki;
(Yokohama-shi, JP) ; MATSUKIYO; Kazushi;
(Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MIURA; Masaki
MATSUKIYO; Kazushi |
Yokohama-shi
Yokohama-shi |
|
JP
JP |
|
|
Assignee: |
TOYO SEIKAN KAISHA, LTD.
Tokyo
JP
|
Family ID: |
41113620 |
Appl. No.: |
14/051988 |
Filed: |
October 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12736243 |
Sep 23, 2010 |
|
|
|
PCT/JP2009/055387 |
Mar 19, 2009 |
|
|
|
14051988 |
|
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Current U.S.
Class: |
215/383 |
Current CPC
Class: |
B65D 79/005 20130101;
B65D 1/44 20130101; B65D 1/0284 20130101 |
Class at
Publication: |
215/383 |
International
Class: |
B65D 1/44 20060101
B65D001/44 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 2008 |
JP |
2008-078897 |
Mar 28, 2008 |
JP |
2008-088398 |
Apr 7, 2008 |
JP |
2008-099106 |
Claims
1. A synthetic resin container comprising a mouth part, a trunk
part and a bottom part, wherein the bottom part includes a bottom
plate part which is present at a center of the bottom part and a
peripheral part which is positioned at a periphery of the bottom
plate part, the peripheral part includes a grounding part having an
inside slope which rises outwardly of the container with an outer
peripheral edge of the bottom plate part being a starting point,
and an outside slope which continues to a side surface of the
bottom part, the peripheral part includes a plurality of groove
parts which extends in a radial direction with the outer peripheral
edge of the bottom plate part being the starting point, to divide
the grounding part into a plurality of parts along a
circumferential direction at substantially equal angular intervals,
the container includes a first virtual surface including an axis of
the container or an axis of the bottom part and dividing the
grounding part into two parts in a circumferential direction, and a
second virtual surface including the axis of the container or the
axis of the bottom part and dividing the groove part into two parts
in the circumferential direction, in an overlapped virtual surface
wherein the first virtual surface and the second virtual surface
are rotated around the axis of the container or the axis of the
bottom part to overlap with each other, when the container is
placed upright on a grounding surface by defining an intersection
of the grounding part and a grounding surface as C, and when a line
CF connecting a point F on the groove part in the overlapped
virtual surface and the intersecting point C orthogonally crosses a
tangent for the groove part at the point F in the overlapped
virtual surface, an angle formed by the tangent and the grounding
surface is 3 to 20.degree., and when a load is applied in an axial
direction in a state where the container stands upright on the
grounding surface, a shape of the bottom part changes reversibly
such that the bottom plate part is depressed inwardly to the
container.
2. The synthetic resin container according to claim 1, wherein in
the overlapped virtual surface, when an intersection of the inside
slope of the grounding part and the groove part is taken as A, and
an intersection of the outside slope of the grounding part and the
groove part is taken as B, an angle formed by the intersections A,
C and B (<ACB) is obtuse.
3. The synthetic resin container according to claim 1, wherein in
the overlapped virtual surface, when an intersection of the outside
slope of the grounding part and the groove part is taken as B, when
a projection relative to the grounding surface of the intersection
B, which is parallel to the axial core of the container or the
axial core of the bottom part, is taken as E, and when an
intersection of the axial core of the container or the axial core
of the bottom part and the grounding surface is taken as O, a ratio
(OC/OE) of a length of a line OC relative to a length of a line OE
is 0.5 to 0.9.
4. The synthetic resin container according to claim 3, wherein a
ratio (2 OC/dmax) of a double of the length of the line OC relative
to a maximum trunk diameter (dmax) of the container is 0.5 to
0.9.
5. The synthetic resin container according to claim 1, wherein a
step part is provided concentrically with the bottom plate part at
a position nearer to the center than the outer peripheral edge of
the bottom plate part.
6. The synthetic resin container according to claim 1, wherein the
bottom plate part is formed to protrude inwardly of the container.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation application of U.S. patent
application Ser. No. 12/736,243 filed on Sep. 23, 2010.
TECHNICAL FIELD
[0002] The present invention relates to a synthetic resin container
molded in a shape of a bottle.
BACKGROUND ART
[0003] Conventionally, a synthetic resin container obtained by
forming a preform using a synthetic resin such as polyethylene
terephthalate, and molding this preform into the shape of a bottle
by stretch blow molding or the like is known as a container for
drinks which contains various drinks as its contents (see Patent
Document, or the like).
[0004] Further, for filling this type of a synthetic resin
container with contents, a method is known, as the filling sealing
method, in which the inside of the container is allowed to have a
positive pressure by adding a slight amount of liquid nitrogen (see
Patent Document 2, or the like).
[0005] Patent Document 1:JP-A-2006-103735
[0006] Patent Document 2:JP-A-2001-31010
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0007] Meanwhile, in recent years, a decrease in weight or a
reduction in cost by decreasing the amount of a resin used has been
strongly required for this type of synthetic resin container. Under
such circumstances, various attempts have been made to mold the
container as thin as possible. In Patent Document 1, an attempt is
made to allow the wall thickness of a container to be thin.
However, only by allowing a container to have a thin wall
thickness, the rigidity of a container is deteriorated due to such
a reduction in wall thickness.
[0008] Therefore, for example, after shipping containers which have
been filled with contents and sealed, containers may often be
stacked one upon another during the transportation or storage.
Therefore, there is a problem that when a load is applied in the
axial direction at this time, the containers may not withstand this
load, and may be deformed by buckling, whereby the commercial value
thereof is significantly deteriorated.
[0009] On the other hand, according to the invention of Patent
Document 2, advantageous effects such as a significant increase in
buckling resistance strength after the filling of contents, which
leads to an increase in the number of stacks, can be expected by
allowing the inside of the container to be positively pressurized
by adding liquid nitrogen.
[0010] However, in order to positively pressurize the inside of a
container by adding liquid nitrogen, the inside pressure of each
container may be varied unless the amount of liquid nitrogen to be
added is strictly adjusted. In addition, the height of the liquid
level in a head space may also be varied easily. In addition, since
a significant increase in pressure is expected by the vaporization
of liquid nitrogen, even in the case where non-carbonic drink is
filled as contents, the container shape is restricted to a shape
that can withstand such pressure.
[0011] The invention has been made in view of the above-mentioned
circumstances, and an object thereof is to provide a synthetic
resin container of which the rigidity can be ensured such that
deformation of a container in a shape which is not intended by
buckling deformation or the like can be prevented when a load is
applied in the axial direction
Means for Solving the Problems
[0012] The synthetic resin container according to the present
invention has a configuration in which it comprises a mouth part, a
trunk part and a bottom part, the bottom part having a bottom plate
part which is present at the center of the bottom part and a
peripheral part which is positioned at the periphery of the bottom
plate part, in the peripheral part, a grounding part having an
inside slope which rises outwardly of the container with the outer
peripheral edge of the bottom plate part being the start point and
an outside slope which continues to the side surface of the bottom
part are formed, and when a load is applied in the axial direction
in the state where the container stands upright on the grounding
surface, the shape of the bottom part changes reversibly such that
the bottom plate part is depressed inwardly to the container.
Advantageous Effects of the Invention
[0013] According to the synthetic resin container with the
above-mentioned configuration, when a load is applied in the axial
direction after a container is sealed or a container is filled with
contents and sealed, the shape of the bottom part changes
reversibly so that the bottom plate part thereof is depressed to
the container inwardly to raise the pressure in a container,
whereby a decrease in pressure in the container is suppressed or
the pressure of the container becomes positive. As a result, the
rigidity of a container against the external force is ensured and
hence it is possible to effectively avoid deformation of a
container into an unintended shape by buckling or the like even if
a load is applied to a container in the axial direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is an elevational view showing the example of the
synthetic resin container according to the present invention;
[0015] FIG. 2 is a cross-sectional view taken along line A-A in
FIG. 1;
[0016] FIG. 3 is a bottom plan view showing the example of the
synthetic resin container according to the present invention;
[0017] FIG. 4 is an explanatory view showing the relationship
between a groove part and a grounding part relative to a grounding
surface;
[0018] FIG. 5 is an explanatory view showing the state before and
after the shape of the bottom part changes reversibly; and
[0019] FIG. 6 is an explanatory view showing another example of the
synthetic resin container according to the present invention.
TABLE-US-00001 Explanation of Symbols 1 Container 2 Mouth part 3
Trunk part 4 Bottom part 41 Bottom plate part 411 Step part 42
Peripheral part 421 Groove part 422 Grounding part 422a Inside
slope 422b Outside slope X Axial core
BEST MODE FOR CARRYING OUT THE INVENTION
[0020] A preferred embodiment of the present invention will be
explained hereinbelow with reference to the drawings.
[0021] FIG. 1 is an elevational view showing one example of the
synthetic resin container according to this embodiment. FIG. 2 is a
cross-sectional view taken along line A-A shown in FIG. 1, and FIG.
3 is a bottom view of the container 1 shown in FIG. 1.
[0022] In this embodiment, for example, the container 1 can be
molded into a predetermined shape provided with a mouth part 2, a
trunk part 3 and a bottom part 4, as shown, by subjecting a
bottomed cylindrical preform formed of a thermoplastic resin which
is produced by known injection molding, compression molding or the
like to biaxial stretch blow molding, etc.
[0023] As a thermoplastic resin used for molding the container 1,
arbitrary resins can be used if stretch blow molding is possible.
As the specific examples thereof, thermoplastic polyesters, such as
polyethylene terephthalate, polybutylene terephthalate,
polyethylene naphthalate, polycarbonate, polyarylate, polylactic
acid or the copolymers thereof, or a blend of these resins or a
blend of these resins with other resins can be given. In
particular, ethylene terephthalate-based thermoplastic polyesters
such as polyethylene terephthalate are preferably used. In
addition, acrylonitrile resins, polypropylene, a propylene-ethylene
copolymer, polyethylene, etc. can also be used.
[0024] In the shown example, the mouth part 2 is formed in a
cylindrical shape. On the side surface of the mouth part 2 nearer
to the opening end, a thread for attaching a lid body (not shown)
is provided as a lid body attaching means. In this way, by
attaching the lid body to the mouth part 2 after the container is
filled with contents, the container 1 is sealed.
[0025] Moreover, a plurality of internal pressure adjustment panels
30 is formed on the side surface of a trunk part 4. The internal
pressure adjustment panel 30 mainly serves to offset a decrease in
internal pressure by its deformation when the pressure inside the
container is decreased by cooling after the container is filled
with contents and sealed at high temperatures or when air in the
head space of the container which is filled with contents is
dissolved in the contents, thereby to decrease the pressure inside.
In the shown example, eight vertical internal pressure adjustment
panels 30 are formed in the axial direction. As such internal
pressure adjustment panel 30, panels in various forms which have
conventionally been known can be used. However, in this embodiment,
it is preferred that a plurality of lateral grooves 31 be arranged
at almost equal intervals in the axial direction in the internal
pressure adjustment panel 30. A detailed explanation will be made
later on this matter.
[0026] Furthermore, as shown in FIGS. 2 and 3, the bottom part 4
has a bottom plate part 41 which is present at the center of the
bottom part and a peripheral part 42 which is positioned at the
periphery of the bottom plate part 41. In the peripheral part 42, a
grounding part 422 having an inside slope 422a which rises
outwardly of the container with the outer peripheral edge of the
bottom plate part 41 as a starting point and an outside slope 422b
which continues to the side surface of the bottom part 41 is
formed. As shown in FIG. 5, when a load is applied in the axial
direction to the container 1 which stands upright on a grounding
surface G, the shape of the bottom part 4 is reversibly changed
such that the bottom plate part 41 is depressed inwardly to the
container.
[0027] In addition, FIG. 5 is an explanatory view showing the state
before and after the shape of the bottom 4 changes reversibly, and
the bottom part 4 before deformation is shown by a chain line and
the bottom part after deformation is shown by a solid line.
[0028] In this way, when a load is applied to the container 1,
which has been filled with contents and sealed for shipping, in the
axial direction thereof by being stacked one upon another during
transportation or storage, as mentioned above, the shape of the
bottom part 4 changes reversibly to receive a load, and the volume
of the container 1 decreases by this deformation. The pressure
inside the container 1 increases with a decrease in the volume of
the container 1, and a pressure reduction inside the container is
suppressed, or the pressure inside the container becomes positive
to ensure the rigidity to withstand an external force. As a result,
even if a load in the axial direction is applied to the container
1, deformation of the container 1 into an unintended shape by
buckling or the like can be effectively avoided.
[0029] The amount of contents to be filled can be arbitral as long
as the container 1 is sealed. Similar effects can be obtained even
if the container 1 is empty. However, it is more effective to
reduce the head space within the container by increasing the amount
of contents to be filled.
[0030] That is, the pressure increase in the container 1 by
capacity reduction of the container 1 due to deformation of the
bottom part 4 largely depends on the volume decrease of the gas
which exists in the head space. Here, assuming that the gas which
exists in the head space is an ideal gas, and that the volume
decreases only by .DELTA.V and pressure increases only by .DELTA.P
from the state that the volume is V and the pressure is P under
circumstances where the temperature is fixed, the relationship
shown by the following formula (1) is established (Boyle's
law).
PV=(P+.DELTA.P)(V-.DELTA.V) (1)
[0031] If the formula (1) is solved for .DELTA.P, the following
formula (2) will be deduced.
.DELTA.P=P(.DELTA.V/(V-.DELTA.V)) (2)
[0032] From the formula (2), it can be understood that if the
amount of volume reduction .DELTA.V is the same, the pressure rises
in a greater amount if the original volume V is small. Therefore,
even if the absolute amount of a decrease of the volume of the
container 1 by the deformation of the bottom part 4 is small, the
pressure inside the container increases greatly if the volume of
gas present in the head space is small. Therefore, in filling the
container with contents, it is preferred that the amount of the
contents be increased to decrease the head space.
[0033] Moreover, as for the filling temperature of contents, it is
desirable to bring it closer to the temperature at the time of
distribution as much as possible, thereby to prevent the degree of
pressure reduction after filling from lowering. In particular, it
is preferred that the contents be filled at normal temperature such
that the pressure inside the container during distribution can be
kept almost the same as atmospheric pressure. If the pressure
inside the container during distribution can be kept almost the
same as atmospheric pressure, the pressure inside the container is
allowed to be positive easily by a decrease in volume of the
container 1 by deformation of the bottom part 4.
[0034] Here, as mentioned above, in this embodiment, in the inner
pressure adjustment panel 30 formed on the side surface of the
trunk part 3, it is preferred that a plurality of lateral grooves
31 be arranged at almost equal intervals in the axial direction.
The purpose of this arrangement is, when the pressure inside the
container is increased, to prevent the inner pressure adjustment
panel 30 from being deformed such that it expands outwardly of the
container and to prevent suppression of an increase in pressure
inside of the container. As mentioned above, in this embodiment, it
is preferred that an increase in pressure inside the container be
prevented from being suppressed by the deformation of the container
1 such that it expands outwardly of the container when the pressure
inside the container is increased.
[0035] Therefore, although the inner pressure adjustment panel 30
is formed on the side surface of the trunk part 3 in the shown
example, if the inner pressure adjustment panel 30 is omitted, only
a plurality of lateral grooves 31 may be arranged as a
reinforcement rib on the side surface of the trunk part 3. In
particular, when the trunk part 3 is formed in a polygonal
cylindrical shape, to form a reinforcement rib which extends in
such a manner that it orthogonally crosses the axial direction
irrespective of the presence of the inner pressure adjustment panel
30 is effective to prevent the side surface of the trunk part 3
outwardly of the container, thereby to cause the trunk part 3 to be
deformed in a cylindrical shape. As for such a reinforcement rib,
it may be one formed in the shape of a column or one formed in the
form of a ridgeline, and it may be formed such that it protrudes
outwardly of the container or protrudes inwardly of the container.
Further, the reinforcement rib may be one which is formed
circularly and continuously along the circumferential direction or
intermittently along the circumferential direction.
[0036] Moreover, when the pressure inside the container increases,
even if the bottom plate part 41 is deformed such that it expands
outwardly of the container, an increase in pressure inside the
container is suppressed to prevent the pressure inside the
container from being positive. Therefore, it is preferred that the
bottom plate part 41 have a shape which can be prevented from
expanding outwardly of the container, for example, have a shape
which protrudes inwardly of the container. In order to suppress the
bottom plate part 41 from expanding outwardly of the container, in
addition to allowing the bottom plate part 41 to protrude inwardly
of the container, a radial rib, a circular ridgeline, a circular
groove or the like may be provided in the bottom plate part 41.
[0037] When the shape of the bottom part 4 is changed as mentioned
above, while the height of the container 1 (the length along the
axial direction) is changed such that it is decreased according to
a load applied in the axial direction, the distance between the
bottom plate part 41 and the grounding surface G is changed such
that the bottom plate part 41 is away from the grounding surface G.
At this time, when the change amount in distance between the bottom
plate part 41 and the grounding surface G is larger relative to the
change amount in height of the container 1, the bottom part 4 is
deformed such that the bottom plate part 41 is depressed more
inwardly of the container. As a result, if the change amount in
height of the container 1 is relatively small, the inside of the
container is allowed to be positively pressurized easily, whereby
rigidity to withstand external force is improved. At this time, if
the container has a structure in which the change amount in
distance between the bottom plate part 41 and the grounding surface
G is increased by about several times relative to the change amount
in height of the container 1, the inside of the container can be
allowed to be positively pressurized easily without causing the
appearance of the container 1 to be significantly changed.
[0038] In addition, in changing the shape of the bottom part 4
reversibly as mentioned above, it is preferred that, in the
peripheral edge part 42, a plurality of groove parts 421, extending
towards the side surface of the bottom part 4 with the peripheral
edge of the bottom plate part 41 being the start point be formed
and that a grounding part 422 be divided into a plurality of parts
along the circumferential direction.
[0039] If the grounding part 422 is divided into a plurality of
parts by such groove part 421, when a load is applied to the
container 1 in the axial direction in the state where the container
stands upright on the grounding surface G, with the end point or
the vicinity of the groove portion 421 located on the side nearer
to the side surface of the bottom part 4 being the start point, the
entire peripheral part 42 is bent and deformed in such a manner
that it supports and rises the outer peripheral edge of the bottom
plate part 41. Simultaneously with this, the grounding parts 422
which are adjacent with each other through the groove part 421 are
narrowed and bent and deformed such that it further pushes up the
groove part 421. These actions are combined, whereby the shape of
the bottom part 4 can be changed such that the bottom plate pate 41
can be further depressed inwardly to the inside of the
container.
[0040] At this time, in order to ensure the above-mentioned change
in shape of the bottom part 4, as in the case of the shown example,
it is preferred that a plurality of groove parts 421, which is
extending radially with the outer peripheral edge of the bottom
plate part 41 being the start point, be formed in a radial
direction, and that the grounding part 422 be divided at almost
equal angular intervals along the circumferential direction by such
groove part 421. However, as for the position of the groove part
421, a plurality of groove parts 421 may be arranged helically or
adjacent groove parts 421 may be arranged in the shape of a wedge
or in the character of "V". As long as the predetermined object is
attained, the position of the groove part 421 is not limited to the
shown example.
[0041] In the shown example, with the outer peripheral edge of the
bottom plate part 41 being the starting point, the inside slope
422a of the grounding part 422 is allowed to rise, and at the same
time, the groove parts 421 are extended with the outer peripheral
edge of the bottom plate part 41 being the starting point. In this
way, the boundary between the bottom plate part 41 and the
peripheral edge part 42 becomes clear, and as a result, when the
shape of the bottom part 4 is changed reversibly such that the
bottom plate part 41 is depressed inwardly of the container, the
entire peripheral edge part 42 is easily bent and deformed such
that it supports the outer peripheral edge of the bottom plate part
41 to bring it up.
[0042] In the shown example, the bottom of the groove part 421 is
formed in a curved surface together with two parallel ridgelines
along the direction in which the groove parts 421 are extended. The
bottom of the groove part 421 may be formed linearly along a single
ridgeline. It is preferred that the bottom of the groove part be
formed together with two or more ridgelines formed along the
direction in which the groove parts 421 are extended. In this way,
the bottom of the groove part 421 is also bent and deformed between
the ridgelines, and, hence, the degree by which a bottom plate part
421a is depressed inwardly of the container can be larger. At this
time, the number of the ridgelines may be gradually increased or
decreased along the direction in which the groove part 421 is
extended, and the width between the ridgelines may be gradually
increased or decreased along the direction in which the groove part
421 is extended.
[0043] Further, in order to allow the shape of the bottom part 4 to
be reversibly changed with good reproducibility, it is preferred
that a plurality of groove parts 421 be radially formed along the
radial direction and that the relative relationship of the groove
part 421 and the grounding part 422 relative to the grounding
surface G.
[0044] First, a cross section which includes the axial core X of
the container 1 (preferably the axial core of the bottom part 4
when the axial core of the container 1 and the axial core of the
bottom part 4 are not in agreement with each other) and divides the
grounding part 422 into two parts in circumferential direction is
taken as a first virtual surface, and a cross section which
includes the axial core of the container 1 (preferably the axial
core of the bottom part 4 when the axial core of the container 1
and the axial core of the bottom part 4 are not in agreement with
each other) and divides the groove part 421 into two parts in
circumferential direction is taken as a second virtual surface. In
an overlapped virtual surface obtained by rotating the first
virtual surface and the second virtual surface around the axial
core X of the container 1 (preferably the axial core of the bottom
part 4 when the axial core of the container 1 and the axial core of
the bottom part 4 are not in agreement) to allow them to be
overlapped one on another, as shown in FIG. 4, the intersection of
the inside slope 422a of the grounding part 422 and the groove part
421 is taken as A, and the intersection of the outside slope 422b
of the grounding part 422 and the groove part 421 is taken as B,
the intersection of the grounding part 422 and the grounding
surface G is taken as C, and the projections relative to the
grounding surface of the intersections A and B of the container 1
which are parallel to the axial core X of the container 1
(preferably the axial core of the bottom part 4 when the axial core
of the container 1 and the axial core of the bottom part 4 are not
in agreement with each other) are taken as D and E.
[0045] In the overlapped virtual surface, when determining the
intersection A of the inside slope 422a of the grounding part 422
and the groove part 421, the intersection B of the outside slope
422 of the grounding part 422 and the groove part 421 and the
intersection C of the grounding part 422 and grounding surface G,
they are determined as intersections in the outermost profile of
the container 1 on the outer side of the container, without taking
into consideration of the wall thickness of the container 1.
[0046] Here, FIG. 4 is an explanatory view showing the relative
relationship of the groove part 421 and the grounding part 422
relative to the grounding surface G in the overlapped virtual
surface. In the shown example, ten grounding parts 422 are provided
radially at equal angular intervals. Therefore, a surface which is
obtained by rotating the first virtual surface and the second
virtual surface around the axial core X of the container 1
(preferably the axial core of the bottom part 4 when the axial core
of the container 1 and the axial core of the bottom part 4 are not
in agreement) by [18.+-.36.times.n].degree. is taken as an
overlapped virtual surface (n is an integer). In the example shown
in FIG. 4, the grounding part 422 is in point contact with the
grounding surface G, and hence, C is determined uniquely. However,
if a certain width of the contact part 422 is in contact with the
grounding surface G, as shown in FIG. 6, a part which is nearest to
the outer side of the container is taken as the intersection C of
the grounding part 422 and the grounding surface G in the
overlapped virtual surface.
[0047] When the points A, B, C, D and E are determined on the
overlapped virtual surface as mentioned above, it is preferred that
the ratio of the length of the line BE to the length of the line AD
(BE/AD) be 0.2 to 12, preferably 0.3 to 0.8 or 2 to 10, and the
ratio of the length of the line CE to the length of the line DC
(CE/DC) be 0.5 to 1.5.
[0048] In this way, the groove part 421 acts more effectively, and
the grounding part 422 and the groove part 421 can be bent easily
with the end point of the groove part 421 (a position corresponding
to the point B as defined above) or the vicinity thereof being the
supporting point. In particular, if a straight line AB connecting
the point A and the point B as defined above is inclined relative
to the grounding surface G, the grounding part and the groove part
can be bent more effectively.
[0049] Further, if the ratio of the length of the line AD to the
length of the line DC (AD/DC) exceeds 0 and is less than 1, and the
ratio of the length of the line BE to the length of the line CE
(BE/CE) exceeds 0 and is less than 1, the angle ACB with the
intersection C with the grounding surface G being the vertex
becomes obtuse, and at the same time, the inclination angle of the
bottom of the groove part 421 relative to the grounding surface G
along the direction in which the groove part 421 is extended
becomes relatively small. As a result, the grounding part 422 has a
shape (cross-sectional shape on the first virtual surface) which is
flat in the axial direction of the container 1. The grounding part
422 can be bent and deformed easily with the point B defined as
mentioned above or the vicinity thereof being the supporting point
while almost keeping its shape without being buckled by a load
applied in the axial direction. In particular, it is preferred that
the triangle which consists of the points A, B and C defined as
mentioned above becomes a triangle which approximates an isosceles
triangle with the angle ACB being an obtuse angle. As a result, the
grounding part 422 can fully withstand the load applied in the
axial direction, whereby deformation by buckling of the grounding
part 422 can be suppressed more effectively.
[0050] At this time, as for the angle of inclination of the bottom
of the groove part 421 relative to the grounding surface G along
the direction in which the groove part 421 is extended,
specifically, if the line CF connecting the point C defined as
mentioned above and an arbitral point F on the groove part 421 in
the overlapped virtual surface as shown in FIG. 4, orthogonally
crosses a tangent at the point F relative to the groove part 421 as
shown in FIG. 4, it is preferred that the angle .theta. formed by
the tangent and the grounding surface G be 3 to 20.degree. C., more
preferably 5 to 18.degree..
[0051] It is preferred that the length of the line CF be set to 2.5
to 3.5 mm since the groove part 421 can effectively act with this
length.
[0052] Moreover, the angle of inclination of the bottom of the
groove relative to the grounding surface G may be constant or may
be changed continuously or discontinuously. It is preferred that
the bottom of the groove part 421 at least contain a part which has
a fixed or variable inclination angle relative to the grounding
surface G along the direction in which the groove part 421 extends
in a range of 3 to 20.degree.. It is more preferred that it at
least contain a part which is fixed or variable in a range of the
inclination angle of 5 to 18.degree.. However, it is preferred that
the bottom of the groove part 421 be formed in a straight line or a
curved line in which no buckling part is present in the direction
in which the groove part 421 extends. As a result, the groove part
421 can be prevented from being bent by buckling and deformed,
whereby elastic, reversible deformation can be realized easily.
[0053] In order to prevent bending of the groove part 321 by
bucking, it is preferred that no bent part be present in a wide
area excluding the vicinity of the starting point of the groove
part 321 (the vicinity of a position corresponding to the point A
as defined above) and the vicinity of the end point of the groove
part 321 (the vicinity of a position corresponding to the point B
as defined above). Specifically, in the overlapped virtual surface
shown in FIG. 4, when the middle point of a section AB along the
groove part 321 which is defined by points A and B is taken as M,
and the point L is taken at a position which is separated from the
middle point M to the side nearer to the starting point (the side
nearer to the point A) of the groove part 321 along the groove part
421 by 45% of the length of the section AB, and the point N is
taken at a position which is separated from the middle point M to
the side nearer to the end point (the side nearer to the point B)
of the groove part 321 along the groove part 421 by 45% of the
length of the section AB, it is preferred that the section LN,
which is taken along the groove part 321 which is defined by the
points L and N, have a fixed or variable angle of inclination
relative to the grounding surface G in a range of 3 to 20.degree.,
more preferably 5 to 18.degree..
[0054] Meanwhile, for the convenience of drawing, the points L and
N are shown in FIG. 4 at approximate positions.
[0055] As a result, the bottom of the groove part 421 has a shape
of a straight line or a gently-sloped curve having no bent part in
a broad area along the direction in which the groove part 421 is
extended. Therefore, deformation by bending by buckling in the
middle of the bottom can be prevented further effectively.
[0056] As for the section AL formed along the groove part 321 which
is defined by the points A and L present in the vicinity of the
starting point of the groove part 321 (the vicinity of a portion to
be connected to the bottom plate part 41) and the section BN formed
along the groove part 321 which is defined by the points B and N
present in the vicinity of the end point of the groove part 321
(the vicinity of a portion to be connected to the side surface of
the bottom part 4), as in the case of the section LN, the angle of
inclination relative to the grounding surface G may be in a range
of 3 to 20.degree. or 5 to 18.degree.. In order to allow the groove
part 421 to be connected smoothly to the bottom plate part 41 and
the side surfaces of the bottom part 4, the inclination angles of
the sections AL and BN relative to the grounding surface G may be
outside the above-mentioned range if need arises.
[0057] In this embodiment, it is preferred that points C, D and E
be defined on the overlapped virtual surface as mentioned above and
that, when the intersection of the axial core X of the container 1
(if the axial core of the container 1 is not in agreement with the
axial core of the bottom part 4, preferably the axial core of the
bottom part 4) with the grounding surface G is taken as O, the
ratio of the length of the line OC to the line OE (OC/OE) be 0.5 to
0.9.
[0058] In this way, the contact point of the grounding part 422
relative to the grounding surface G is appropriately separated from
the end point of the groove part 421 which is positioned on the
side nearer to the side surface of the bottom part 4, and as a
result, the entire peripheral edge part 42 can be easily bent or
deformed with the end point or its vicinity being the supporting
point.
[0059] It is preferred that the ratio of the length of the line OD
to the line OE (OD/OE) be 0.2 to 0.8.
[0060] In this way, the start point of the groove part 421 which is
present on the outer periphery of the bottom plate part 41 is
appropriately separated from the end point of the groove part 421
which is positioned on the side nearer to the side surface of the
bottom part 4, and as a result, the entire peripheral edge part 42
can be prevented from being bent or deformed with the end point or
its vicinity being the supporting point without the fear that the
groove part 421 is stretched.
[0061] Further, it is preferred that the ratio of the double of the
line OC (2 OC/dmax) to the maximum trunk diameter (dmax) of the
container be 0.5 to 0.9.
[0062] In this way, the position of the contact point of the
grounding part 422 relative to the grounding surface G becomes a
position which is suitable for the maximum trunk diameter (dmax) of
the container, whereby the container 1 is hard to be toppled.
[0063] When the shape of the bottom part 4 changes reversibly, the
peripheral part 42 which is located around the bottom plate part 41
is deformed. If the wall thickness of this peripheral part 42 is
large, the bottom part 4 may be prevented from being deformed.
Therefore, in this embodiment, it is preferred that a step part 411
be formed concentrically with the bottom plate part 41 on a
position which is nearer to the center than the outer periphery of
the bottom plate part 41.
[0064] As mentioned above, the container 1 can be formed by
subjecting a bottomed cylindrical preform made of a thermoplastic
resin to biaxial stretch blowing, etc. At this time, by providing
the step part 411 as mentioned above, it is possible to keep the
resin to be used for forming the bottom part 4 to the side nearer
to the center than the step part 411 in blow molding, whereby the
wall thickness distribution of the bottom part 4 can be biased, and
the wall thickness of the peripheral part 42 relative to the bottom
plate part 41 is allowed to be relatively thin, whereby the shape
change of the bottom part 4 is not prevented.
[0065] In addition, by forming the step part 411, a circular
reinforcement part is formed between the outer peripheral part of
the bottom plate part 41 and step part 411. As a result, force
serves to support and lift the outer peripheral edge of the bottom
plate part 41 by the bending and deformation of the peripheral part
42 will act more surely through this circular reinforcing part.
[0066] The wall thickness of the peripheral edge 42 is preferably
set such that the position or its vicinity, which corresponds to
the above-mentioned point B and is present at least on the side
nearer to the outside slope 422b of the grounding part 422, becomes
0.2 to 0.3 mm. This wall thickness is preferable since the
grounding part 422 is easily bent at a position corresponding to
the point B or its vicinity, and the thermal resistance or the
piercing strength will be increased and insufficient molding (sink
marks) is prevented from occurring. Further, the wall thickness of
the step part 411 or the bottom plate part 41 is preferably set to
0.35 mm or more, whereby the strength which is sufficient enough to
withstand an increase in pressure inside the container can be
ensured.
[0067] The present invention is explained hereinabove with
reference to preferred embodiments. It is needless to say the
present invention is restricted to the above-mentioned embodiment,
and various modifications can be made within the scope of the
present invention.
INDUSTRIAL APPLICABILITY
[0068] The synthetic resin container according to the invention as
mentioned above can be applied to various synthetic resin
containers which are molded into the shape of a bottle.
* * * * *