U.S. patent application number 11/985236 was filed with the patent office on 2008-06-19 for heat-sealing apparatus.
This patent application is currently assigned to Toyo Jidoki Co., Ltd.. Invention is credited to Shoichi Koga, Shigeru Naoki.
Application Number | 20080142165 11/985236 |
Document ID | / |
Family ID | 39197291 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080142165 |
Kind Code |
A1 |
Naoki; Shigeru ; et
al. |
June 19, 2008 |
Heat-sealing apparatus
Abstract
A heat-sealing apparatus comprising a pair of opposed hot plates
and a pair of hot plate-mounting blocks to which said hot plates
are mounted, respectively. The hot plates respectively have
pressing surfaces adapted to be pressed against each other with
superimposed film sheets held therebetween during sealing; and
mounting surfaces formed at opposite sides to said pressing
surfaces. The hot plate-mounting blocks respectively have support
surfaces. The hot plates are mounted to said hot plate-mounting
blocks in such a manner that the mounting surfaces are pressed
against the support surfaces, and that the hot plates can thermally
expand and contract in a sealing direction without being restrained
by said hot plate-mounting blocks. In another aspect of the
invention, the mounting surfaces are formed on respective surfaces
extending substantially perpendicular to the pressing surfaces and
the hot plates are mounted on respective support surfaces formed on
the hot plate-mounting blocks.
Inventors: |
Naoki; Shigeru;
(Iwakuni-shi, JP) ; Koga; Shoichi; (Iwakuni-shi,
JP) |
Correspondence
Address: |
Daniel P. Burke, Esq.;DANIEL P. BURKE & ASSOCIATES, PLLC
Suite 131, 300 Rabro Drive
Hauppauge
NY
11788
US
|
Assignee: |
Toyo Jidoki Co., Ltd.
|
Family ID: |
39197291 |
Appl. No.: |
11/985236 |
Filed: |
November 14, 2007 |
Current U.S.
Class: |
156/583.9 |
Current CPC
Class: |
B29C 66/43121 20130101;
B29C 65/18 20130101; B29C 66/1122 20130101; B29C 66/8161 20130101;
B29C 66/81611 20130101; B29C 66/80 20130101; B29C 66/83221
20130101; B29C 66/81422 20130101; B29C 66/81423 20130101; B29C
66/849 20130101; B65B 51/30 20130101; B29L 2031/7128 20130101; B29C
66/81821 20130101; B29C 65/305 20130101 |
Class at
Publication: |
156/583.9 |
International
Class: |
B65B 51/10 20060101
B65B051/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2006 |
JP |
2006-341240 |
Claims
1. A heat-sealing apparatus comprising: a pair of opposed hot
plates; and a pair of hot plate-mounting blocks to which said hot
plates are mounted, respectively; wherein superimposed film sheets
are pressed between said hot plates to thermoweld them together;
said hot plates respectively comprising: pressing surfaces adapted
to be pressed against each other with said film sheets held
therebetween during sealing; and mounting surfaces formed at
opposite sides to said pressing surfaces; said hot plate-mounting
blocks respectively comprising support surfaces that retain said
mounting surfaces, respectively; wherein said hot plates are
mounted to said hot plate-mounting blocks in such a manner that
said mounting surfaces are pressed against said support surfaces,
and that said hot plates can thermally expand and contract in a
sealing direction without being restrained by said hot
plate-mounting blocks.
2. The heat-sealing apparatus of claim 1, wherein a constituent
material of said hot plates and a constituent material of said hot
plate-mounting blocks differ in thermal expansion coefficient from
each other.
3. The heat-sealing apparatus of claim 1, wherein said hot plates
are retained by said support surfaces at a part of said mounting
surfaces.
4. The heat-sealing apparatus of claim 1, wherein said hot plates
are formed so that said pressing surfaces are concavely or convexly
curved in a horizontal plane at an ordinary room temperature, and
said pressing surfaces become flat when said hot plates are heated
to a predetermined sealing temperature.
5. The heat-sealing apparatus according to claim 1, wherein said
hot plate-mounting blocks comprise guide portions that abut against
said hot plates to position said hot plates in a vertical
direction.
6. The heat-sealing apparatus according to claim 1, further
comprising: adjustment pins provided for said hot plate-mounting
blocks, respectively, said adjustment pins each comprising: a
mounting shank portion mounted to an associated one of said hot
plate-mounting blocks in such a manner that a position thereof in a
rotational direction is adjustable; and an eccentric shank portion
that is eccentric with respect to said mounting shank portion and
that extends toward an associated one of said hot plates; said
mounting surfaces of said hot plates comprising slots elongated in
the sealing direction, each of said slots being capable of
accommodating said eccentric shank portion.
7. The heat-sealing apparatus of claim 1, wherein said hot plates
are each secured to one end of each of a plurality of shaft-shaped
members spaced in the sealing direction and inserted through
respective holes formed in the associated one of said hot
plate-mounting blocks, said shaft-shaped members being urged by
urging members toward the other ends thereof, wherein at least all
but one of said shaft-shaped members are provided with clearances
in said holes at least in said sealing direction.
8. The heat-sealing apparatus of claim 7, further comprising:
fall-preventing plates that prevent movement of said shaft-shaped
members away from said hot plates.
9. The heat-sealing apparatus according to claim 1, wherein said
hot plates are each fixedly secured to an associated one of said
hot plate-mounting blocks at one portion thereof, said heat-sealing
apparatus further comprising: one or more shaft-shaped members
provided for each combination of each of said hot plates and an
associated one of said hot plate-mounting blocks, said one or more
shaft-shaped members being spaced in the sealing direction and each
mounted at one end thereof to either one of said hot plate and hot
plate-mounting block of said combination, the other end of each of
said one or more shaft-shaped members extending toward the other of
said hot plate and hot plate-mounting block of said combination and
inserted into a hole formed in said the other of said hot plate and
hot plate-mounting block of said combination with a clearance at
least in said sealing direction.
10. The heat-sealing apparatus of claim 9, wherein said one or more
shaft-shaped members are each mounted at said one end in such a
manner that a position thereof in a rotational direction is
adjustable, said the other end of each of said one or more
shaft-shaped members being eccentric with respect to said one end,
and said hole is a slot elongated in said sealing direction.
11. A heat-sealing apparatus comprising: a pair of opposed hot
plates; and a pair of hot plate-mounting blocks to which said hot
plates are mounted, respectively; wherein superimposed film sheets
are pressed between said hot plates to thermoweld them together;
said hot plates respectively comprising: pressing surfaces adapted
to be pressed against each other with said film sheets held
therebetween during sealing; and mounting surfaces formed on
respective surfaces extending substantially perpendicular to said
pressing surfaces; said hot plates being mounted on respective
support surfaces formed on said hot plate-mounting blocks.
12. The heat-sealing apparatus of claim 11, wherein a constituent
material of said hot plates and a constituent material of said hot
plate-mounting blocks differ in thermal expansion coefficient from
each other.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a heat-sealing apparatus
that seals together superimposed film sheets by pressing them
between a pair of opposed hot plates. More particularly, the
present invention relates to a heat-sealing apparatus that enables
hot plates to be readily mounted in correct position to hot
plate-retaining members, i.e. hot plate-mounting blocks.
[0003] 2. Discussion of Related Art
[0004] Conventionally, heat sealing has been performed for food
packaging bags, for example, in such a manner that a pair of hot
plates is pressed against seal portions of superimposed film sheets
from both sides thereof to seal together the seal portions of the
film sheets. Regarding the hot plates also, various improvements
have been proposed. In Japanese Utility Model Application
Publication No. Hei 4-128208, for example, shows in FIG. 3 thereof
a conventional support structure for hot plates and a basic
structure in which the hot plates are advanced and retracted
relative to each other, and also proposes a structure that prevents
drops of water from being sealed between seal surfaces. Japanese
Patent Application Publication No. Hei 11-91732 discloses a
structure in which heat seal teeth are detachably attached to
heater blocks so that it is possible to readily cope with various
widths of seal portions.
[0005] Usually, hot plates that directly press film sheets
therebetween are each integrally and fixedly secured to a hot
plate-mounting block with a thermal insulating plate interposed
therebetween by using bolts or the like. In the above-mentioned
Japanese Patent Application Publication No. Hei 11-91732, the
heater blocks that incorporate heaters therein are secured to
movable support members with bolts.
[0006] Generally, hot plates used in heat-sealing apparatus are
metallic and support members or hot plate-mounting blocks to which
the hot plates are secured are also metallic. In some cases, the
hot plates and the hot plate-mounting blocks are made of different
metallic materials. In such cases, the thermal expansion
coefficients of the materials are different from each other.
Therefore, when the heat-sealing apparatus is used with the hot
plates secured to the mounting blocks with bolts, heating of the
hot plates produces a difference in expansion between the hot
plates and the mounting blocks, causing deformation of the pressing
surfaces of the hot plates that are pressed against the film
sheets. Consequently, the pressing surfaces of the hot plates
cannot be brought into press contact with the whole seal portions
uniformly, resulting in a seal failure.
[0007] Even if the hot plates and the mounting blocks are made of
the same material, the following problem occurs. Usually, the
heaters are attached to the hot plates, and the hot plates are
secured to the mounting blocks with thermal insulating plates
interposed therebetween. Accordingly, during heating, a difference
in temperature is produced between the hot plates incorporating the
heaters and the mounting blocks, causing a difference in expansion.
Thus, the same problem as the above occurs although there is a
difference in the degree of seriousness of the problem. The
conventional practice for coping with such a problem is to dispose
a distortion correcting plate between each mounting block and the
associated thermal insulating plate and to bond liners to
appropriate positions on the distortion correcting plate to adjust
so that the pressing surface of each hot plate becomes flat when
the hot plate has been heated to a predetermined temperature.
[0008] To solve the above-described problem, the present inventor
inspected the deformation of hot plates and hot plate-mounting
blocks in a conventional hot plate-mounting structure. The results
of the inspection will be explained below with reference to FIGS.
13 to 16 with regard to an example of sealing the opening of a
packaging bag in automatic packaging of food products. In the
figures, reference numeral 41 denotes a packaging bag used in
automatic packaging of food products, and reference numerals 42 and
43 denote a pair of grippers that grip the laterally opposite side
edge portions of the bag 41. The figures show the bag 41 that has
moved to a sealing step after the completion of filling the bag 41
with the contents.
[0009] FIGS. 13 and 14 are a plan view and a sectional side view,
respectively, showing an essential part of a heat-sealing apparatus
1 according to a conventional related art. The heat-sealing
apparatus 1 has first and second advancing and retracting shafts 3
and 5 that are vertically spaced to extend in the same axial
direction and axially advanced and retracted in opposite directions
to each other by a driving device (not shown). A first hot
plate-mounting block (hereinafter referred to as "first block") 7
is secured to the distal end of the first advancing and retracting
shaft 3 by an appropriate securing device. The first block 7 is an
elongate member extending substantially perpendicular to the
longitudinal axis of the first advancing and retracting shaft 3 and
having a substantially square sectional configuration. The first
block 7 has a support surface 7a formed by one vertical surface
thereof (right-hand surface as viewed in the figures). A mounting
surface 9b of a first hot plate 9 is mounted to the support surface
7a of the first block 7, with a thin plate-shaped distortion
correcting plate 13 and a thermal insulating plate 11 interposed
therebetween. In this example, the first hot plate 9 is secured to
the first block 7 by using four bolts 15. The first hot plate 9 is
an elongate member having a substantially square sectional
configuration and substantially the same length as that of the
first block 7. A heater 17 is inserted and secured in a hole
longitudinally formed in the first hot plate 9.
[0010] The first block 7 and the distortion correcting plate 13 are
made of the same metallic material. The first hot plate 9 is made
of a metallic material different in thermal expansion coefficient
from the metallic material of the first block 7 and the distortion
correcting plate 13. The thermal insulating plate 11 is made of a
ceramic or other inorganic material, a heat-resistant resin, or a
composite material of them. It should be noted that metallic liners
(not shown) having an appropriate thickness are bonded to
appropriate positions on the side of the distortion correcting
plate 13 that faces the first block 7, as has been stated above, to
obtain a desired flatness of a pressing surface 9a of the first hot
plate 9.
[0011] A second hot plate-mounting block (hereinafter referred to
as "second block") 19 is secured to the distal end of the second
advancing and retracting shaft 5 by an appropriate securing device.
The second block 19 has a mounting portion 19a at the top thereof
and a body portion 19b integrally formed with the mounting portion
19a at the lower side thereof. The body portion 19b has the same
length as that of the first block 7 and extends parallel thereto.
The second block 19 is secured to the second advancing and
retracting shaft 5 at the mounting portion 19a. The second block 19
has a support surface 19c formed by one vertical surface (left-hand
surface as viewed in the figures) of the body portion 19b. A
mounting surface 21b of a second hot plate 21 is mounted to the
support surface 19c of the second block body portion 19b, with a
thin plate-shaped distortion correcting plate 25 and a thermal
insulating plate 23 interposed therebetween. The second hot plate
21 is secured to the second block 19 by using four bolts 27. The
second hot plate 21 is also an elongate member having a
substantially square sectional configuration and substantially the
same length as that of the body portion 19b of the second block 19.
A heater 29 is inserted and secured in a hole longitudinally formed
in the second hot plate 21. It should be noted that the constituent
materials of the second block 19 and other members described above
are the same as those of the foregoing first block 7 and other
corresponding members. Liners are appropriately bonded to the side
of the distortion correcting plate 25 that faces the second block
19 to obtain a desired flatness of a pressing surface 21a of the
second hot plate 21, as in the case of the above.
[0012] FIG. 15 shows a state where the first and second hot plates
9 and 21 have been heated to a desired sealing temperature by the
respective heaters 17 and 29. When the hot plates 9 and 21 have not
yet been heated and are at an ordinary room temperature before the
start of the operation, the pressing surfaces 9a and 21a of the hot
plates 9 and 21 are flat. However, as the temperature rises as a
result of heating, the pressing surfaces 9a and 21a are gradually
deformed concavely. Because the hot plates 9 and 21 are firmly
connected to the blocks 7 and 19 by the bolts 15 and 27, the
combinations of the hot plates 9 and 21 and the blocks 7 and 19 are
each deformed as one unit up to a certain temperature. When the
temperature rises beyond the certain temperature level, sliding
occurs between the hot plate 9 and the block 7 and between the hot
plate 21 and the block 19, so that the hot plates 9 and 21 will not
be curved any more.
[0013] When the heating is stopped to allow the sealing temperature
to lower gradually, the hot plate 9 and the block 7 are deformed in
the opposite direction to the above, and so are the hot plate 21
and the block 19. Consequently, the pressing surfaces 9a and 21a of
the hot plates 9 and 21 are curved convexly, as shown in FIG. 16,
after becoming somewhat flat, which is not so flat as in the
non-heating state. When the hot plates 9 and 21 are returned to the
ordinary room temperature, the pressing surfaces 9a and 21a remain
curved convexly. In other words, the pressing surfaces 9a and 21a
will not return to the flat state any longer because of the
sticking between the hot plate 9 and the block 7 and between the
hot plate 21 and the block 19 after the occurrence of sliding
therebetween during the rise of temperature. When the hot plates 9
and 21 are heated again, the pressing surfaces 9a and 21a are
curved concavely after becoming somewhat flat. At a certain point
of the heating, slide occurs again between the hot plate 9 and the
block 7 and between the hot plate 21 and the block 19, so that the
hot plates 9 and 21 will not be curved any more.
[0014] If the above-described distortion occurs, a gap is produced
between the pressing surfaces 9a and 21a of the hot plates 9 and 21
when pressed against each other. Accordingly, a satisfactory
sealing condition cannot be obtained. To cope with this problem,
conventionally, liners are bonded to appropriate positions on the
distortion correcting plates 13 and 25 and an adjustment is made so
that the pressing surfaces 9a and 21a of the hot plates 9 and 21
become flat when the hot plates 9 and 21 are heated to a
predetermined sealing temperature, as has been stated above.
However, the adjustment needs to be repeated many times until an
appropriate condition of the hot plates 9 and 21 is obtained. The
adjustment operation itself is very complicated and requires a high
level of skill. Even if the hot plates 9 and 21 have been set in
correct conditions successfully, it is necessary to make an
adjustment again at the time of reheating, changing the set
temperature, replacing the hot plates 9 and 21, and so forth. In
addition, the distortion condition may change with time. A
readjustment is needed every time the distortion condition changes.
Under these circumstances, we examined a measure to solve
drastically the problem caused by the distortion of the hot plates
9 and 21 in view of the overall deformation of the hot plates 9 and
21 and the mounting blocks 7 and 19, the details of which have been
clarified by the inspection conducted by the present inventor.
[0015] It should be noted that we discussed the overall structure
in which the hot plate 9 (21), the mounting block 7 (19) and the
distortion correcting plate 13 (25) are integrally secured to each
other with the bolts 15 (27). During our inspection, we also
examined the temperature difference between the pressing surface 9a
(21a) and the mounting surface 9b (21b) of the hot plate 9 (21)
when heated, and we found that the pressing surface 9a (21a) is
higher in temperature than the mounting surface 9b (21a).
Therefore, when the hot plate 9 (21) is considered as a single
element, it should be deformed so that the pressing surface 9a
(21a) becomes convex. Nevertheless, when heated, the overall
heat-sealing structure is deformed so that the pressing surface 9a
(21a) becomes concave as stated above. It is deemed from this fact
that the amount of deformation of the mounting block 7 (19) is so
large that the amount of deformation of the hot plate 9 (21) as a
single element is compensated for, and moreover, the pressing
surface 9a (21a) is made concave. The situation should differ if
the relationship in thermal expansion coefficient between the hot
plate 9 (21), the mounting block 7 (19), and so forth differs. Even
if the hot plate 9 (21) and the mounting block 7 (19) are formed
from the same material, if the mounting structure is the same as
the above, the condition of heat dissipation differs between the
pressing surface 9a (21a) and the mounting surface 9b (21b) of the
hot plate 9 (21), causing a temperature difference. Consequently,
the hot plate 9 (21) itself is deformed, so that the pressing
surface 9a (21a) of the hot plate 9 (21) fails to become flat,
although the distortion is not so large as stated above. There is
also a temperature difference between the hot plate 9 (21) and the
mounting block 7 (19), and a difference is produced in the amount
of expansion therebetween, as has been stated above. We performed
studies in view of these points in making the present
invention.
SUMMARY OF THE INVENTION
[0016] The present invention has been made in view of the
above-described problems associated with the related art.
[0017] Accordingly, an object of the present invention is to
provide a heat-sealing apparatus enabling the hot plate mounting
and adjusting operation to be performed easily, simply and
rapidly.
[0018] Another object of the present invention is to provide a
heat-sealing apparatus capable of minimizing the change of the
sealing condition.
[0019] The present invention is applied to a heat-sealing apparatus
having a pair of opposed hot plates and hot plate-mounting blocks
to which the hot plates are mounted, respectively, in which
superimposed film sheets are pressed between the hot plates to
thermoweld them together. According to a first aspect of the
present invention, the heat-sealing apparatus is arranged as
follows. The hot plates are respectively provided with pressing
surfaces adapted to be pressed against each other with the film
sheets held therebetween during sealing, and further provided with
mounting surfaces formed at the opposite sides to the pressing
surfaces. The hot plate-mounting blocks are respectively provided
with support surfaces that retain the mounting surfaces,
respectively. The hot plates are mounted to the hot plate-mounting
blocks in such a manner that the mounting surfaces are pressed
against the support surfaces, and that the hot plates can thermally
expand and contract in a sealing direction without being restrained
by the hot plate-mounting blocks. With this arrangement, the
desired flatness of the hot plates can be kept, and satisfactory
sealing can be performed.
[0020] In one embodiment, the constituent material of the hot
plates and the constituent material of the hot plate-mounting
blocks differ in thermal expansion coefficient from each other. In
this case also, the hot plates can thermally expand and contract in
the sealing direction without being restrained by the hot
plate-mounting blocks owing to employing the above-described
arrangement. Accordingly, the desired flatness of the hot plates
can be kept, and satisfactory sealing can be performed.
[0021] In one embodiment, the hot plates are each retained by the
support surface at a part of the mounting surface thereof. With
this arrangement, it is possible to reduce the difference in the
degree of exposure between the pressing surface and the mounting
surface of each hot plate and hence possible to reduce the
curvature of the hot plate itself. Thus, even more satisfactory
sealing can be performed.
[0022] In one embodiment, the hot plates have been formed in
advance so that the pressing surfaces are concavely or convexly
curved at an ordinary room temperature, allowing for an amount of
deformation when the hot plates are heated to a predetermined
sealing temperature. With this arrangement, a satisfactory flatness
of the pressing surfaces can be obtained during heating, and thus
satisfactory sealing can be performed.
[0023] In one embodiment, the hot plate-mounting blocks are
provided with guide portions that position the hot plates in the
vertical direction. With this arrangement, the hot plates are
positioned in the vertical direction to prevent relative positional
displacement between them and tilting thereof. Thus, it is possible
to perform sealing straight in the horizontal direction.
[0024] In one embodiment, the hot plate-mounting blocks are
equipped with adjustment pins capable of positional adjustment in
the rotational direction. Each adjustment pin has an eccentric
shank portion formed at an end thereof closer to the associated hot
plate. The eccentric shank portion of the adjustment pin is fitted
in a slot that is formed on the mounting surface of the hot plate
so as to be elongated in the sealing direction. Accordingly, the
mounting position of the hot plate can be readily adjusted by
properly rotating the adjustment pin.
[0025] In one embodiment, the hot plates are each secured to one
end of each of a plurality of shaft-shaped members spaced in the
sealing direction and inserted through respective holes formed in
the associated hot plate-mounting block. The shaft-shaped members
are urged by urging members toward the other ends thereof. All the
shaft-shaped members, except at most one of them, are provided with
clearances in the holes at least in the sealing direction. This
relatively simple arrangement enables the hot plates to thermally
expand and contract without being restrained by the hot
plate-mounting blocks as stated above.
[0026] In one embodiment, the heat-sealing apparatus further has
fall-preventing plates that prevent movement of the shaft-shaped
members away from the hot plates. This arrangement can prevent
loosening of the portions of the shaft-shaped members that are
fitted to the hot plates.
[0027] In one embodiment, the hot plates are each fixedly secured
to the associated hot plate-mounting block at one portion thereof,
and the heat-sealing apparatus further has one or more shaft-shaped
members provided for each combination of the hot plate and the hot
plate-mounting block. The shaft-shaped members are spaced in the
sealing direction and each mounted at one end thereof to either one
of the hot plate and the hot plate-mounting block. The other end of
each shaft-shaped member extends toward the other of the hot plate
and the hot plate-mounting block and is inserted into a hole formed
in the other of the hot plate and the hot plate-mounting block with
a clearance at least in the sealing direction. In this case also,
because each hot plate is fixedly secured at only one portion
thereof, the hot plate can thermally expand and contract without
being restrained by the hot plate-mounting block.
[0028] In one embodiment, the one or more shaft-shaped members are
each mounted at the one end in such a manner that the position
thereof in the rotational direction is adjustable. The other end of
each shaft-shaped member is eccentric with respect to the one end,
and the hole, in which the other end of the shaft-shaped member is
inserted, is a slot elongated in the sealing direction. This
arrangement enables adjustment of the mounting condition of the hot
plates by using the shaft-shaped members.
[0029] In addition, the present invention is applied to a
heat-sealing apparatus having a pair of opposed hot plates and hot
plate-mounting blocks to which the hot plates are mounted,
respectively, in which superimposed film sheets are pressed between
the hot plates to thermoweld them together. According to a second
aspect of the present invention, the heat-sealing apparatus is
arranged as follows. The hot plates are respectively provided with
pressing surfaces adapted to be pressed against each other with the
film sheets held therebetween during sealing, and further provided
with mounting surfaces formed on respective surfaces extending
substantially perpendicular to the pressing surfaces. The hot
plates are mounted on respective support surfaces formed on the hot
plate-mounting blocks. With this arrangement, even if each hot
plate and the associated hot plate-mounting block are curved as one
unit, the curvature will not influence the flatness of the pressing
surface of the hot plate. Therefore, satisfactory sealing can be
performed.
[0030] Thus, according to the first aspect of the present
invention, the hot plates can thermally expand and contract
independently of the hot plate-mounting blocks, without being
restrained by the hot plate-mounting blocks. Accordingly, it is
possible to minimize the distortion of the pressing surfaces of the
hot plates due to the influence of the hot plate-mounting blocks as
in the conventional apparatus. The hot plates can be mounted to the
hot plate-mounting blocks without the need to repeat adjustment
many times as in the past. The adjusting operation can be performed
easily, simply and rapidly.
[0031] Further, the curvature of the hot plates can be reduced to a
very small degree by reducing the difference in exposed area
between the pressing surface and the mounting surface of each hot
plate. Accordingly, sealing performance can be further
improved.
[0032] Further, a satisfactory flatness of the pressing surfaces
can be obtained during heating by forming the hot plates so that
the pressing surfaces thereof are concavely or convexly curved at
an ordinary room temperature, allowing for an amount of deformation
when the hot plates are heated to a predetermined sealing
temperature. Thus, a satisfactory flatness of the pressing surface
can be obtained during heating and satisfactory sealing can be
performed.
[0033] Further, the mounting position of each hot plate can be
readily adjusted by an arrangement in which the hot plate-mounting
blocks are provided with guide portions that position the hot
plates in the vertical direction, or an arrangement in which the
hot plate-mounting blocks are equipped with adjustment pins capable
of positional adjustment in the rotational direction, and eccentric
shank portions of the pins are fitted in slots formed in the hot
plates so as to be elongated in the sealing direction.
[0034] Further, the hot plates are allowed to thermally expand and
contract without being restrained by the hot plate-mounting blocks
by arranging such that the hot plates are each fixedly secured to
one end of each of a plurality of shaft-shaped members inserted
through respective holes formed in the hot plate-mounting blocks,
and the shaft-shaped members are urged by urging members toward the
other ends thereof and provided with clearances in the holes at
least in the sealing direction.
[0035] According to the second aspect of the present invention, the
distortion of the hot plates in the horizontal plane can be
minimized although they may be curved in the vertical direction.
Accordingly, satisfactory sealing can be performed. In addition,
the hot plates can be mounted to the hot plate-mounting blocks
without the need to repeat adjustment many times as in the past.
The adjusting operation can be performed easily, simply and
rapidly.
[0036] Other objects and advantages of the present invention will
become apparent from the following detailed description of
illustrated embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a plan view of an essential part of a heat-sealing
apparatus according to a first embodiment of the present
invention.
[0038] FIG. 2 is a sectional side view of the apparatus shown in
FIG. 1.
[0039] FIG. 3 is a plan view of the apparatus shown in FIG. 1,
illustrating a state where hot plates are pressed against each
other.
[0040] FIG. 4 is a sectional side view of the apparatus shown in
FIG. 3.
[0041] FIG. 5 is an explanatory view showing hot plates used in a
heat-sealing apparatus according to a second embodiment of the
present invention.
[0042] FIG. 6 is a plan view of an essential part of the
heat-sealing apparatus according to the second embodiment of the
present invention, illustrating a state where the hot plates are
separate from each other.
[0043] FIG. 7 is a sectional side view of the apparatus shown in
FIG. 6.
[0044] FIG. 8 is an explanatory view showing a mechanism for
adjusting the mounting position of a hot plate.
[0045] FIG. 9 is a plan view of an essential part of a heat-sealing
apparatus according to a third embodiment of the present invention,
illustrating a state where hot plates are separate from each
other.
[0046] FIG. 10 is a sectional side view of the apparatus shown in
FIG. 9.
[0047] FIG. 11 is a plan view of the apparatus shown in FIG. 9,
illustrating a state where the hot plates are pressed against each
other.
[0048] FIG. 12 is a sectional side view of the apparatus shown in
FIG. 11.
[0049] FIG. 13 is a plan view of a heat-sealing apparatus according
to a related art.
[0050] FIG. 14 is a sectional side view of the apparatus shown in
FIG. 13.
[0051] FIG. 15 is a plan view showing the way in which hot plates
of the apparatus in FIG. 13 are curved when the hot plates are
raised in temperature.
[0052] FIG. 16 is a plan view showing the way in which the hot
plates of the apparatus in FIG. 13 are curved when the hot plates
are lowered in temperature.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0053] Embodiments of the present invention will be described below
with reference to the accompanying drawings. It should be noted
that the following embodiments are for illustrative purposes only,
and that the scope of the present invention is not limited to these
embodiments.
[0054] FIGS. 1 to 4 show a heat-sealing apparatus 50 according to a
first embodiment of the present invention. FIGS. 1 and 2 are a plan
view and a sectional side view, respectively, showing the
heat-sealing apparatus 50 in a state where hot plates are separate
from each other. FIGS. 3 and 4 are a plan view and a sectional side
view, respectively, showing a state where the hot plates are
pressed against each other. In these figures, members corresponding
to those of the conventional related art shown in FIGS. 13 to 16
are denoted by using the same reference numerals as those in the
related art, and a detailed description thereof is omitted.
[0055] The heat-sealing apparatus 50 according to this embodiment
differs from the related art shown in FIGS. 13 to 16 in that first
and second hot plates 9 and 21 are not integrally and firmly
secured to first and second hot plate-mounting blocks (hereinafter
referred to simply as "blocks") 7 and 19, but mounted in such a
manner that the hot plates 9 and 21 can thermally expand and
contract freely independently of the blocks 7 and 19 without being
restrained by them. This prevents the pressing surfaces of the hot
plates 9 and 21 from being curved concavely or convexly as in the
past.
[0056] The first hot plate 9 is secured to the distal ends of bolts
15 that are disposed in parallel in the sealing direction and
inserted from the distal end sides thereof into holes 7b formed in
the block 7. The bolts 15 are urged leftward as viewed in the
figures by respective wave washers 51 provided as urging members
between the heads of the bolts 15 and a rear surface 7c of the
block 7. Thus, the first hot plate 9 is mounted to a support
surface 7a of the block 7 with a thermal insulating plate 11 and
liners 53 interposed therebetween. It should be noted that, unlike
the liners that is bonded to the distortion correcting plate to
obtain a flat surface in the related art, the liners 53 serves as a
spacer that makes the exposed areas of the pressing surface 9a and
the mounting surface 9b as close to each other as possible to
minimize the curvature of the hot plate 9 itself. Accordingly, the
liners 53 has a minimum necessary size. It should be noted that
each bolt 15 has a step between a portion thereof that is threaded
into the hot plate 9 and a shank portion above the threaded
portion, and the shank portions have the same length. Accordingly,
each bolt 15 can be set simply by screwing the threaded portion
into the hot plate 9 completely, without the need of any
adjustment.
[0057] A fall-preventing plate 55 is fixedly secured to a first
advancing and retracting shaft 3 to prevent the bolts 15 from
falling off. The bolts 15 do not firmly connect together the first
block 7 and the first hot plate 9, as has been stated above.
Therefore, the connection between the bolts 15 and the first hot
plate 9 may be loosened by vibration or the like. The
fall-preventing plate 55 retains the heads of the bolts 15 to
prevent movement thereof, thereby preventing loosening of the
connection between the bolts 15 and the first hot plate 9.
[0058] Regarding the relationship between the outer diameter of the
bolts 15 and the inner diameter of the holes 7b of the block 7, a
clearance is provided between each bolt 15 and the associated hole
7b at least in the longitudinal direction of the block 7, i.e. the
sealing direction (in the vertical direction in FIG. 1) to allow
the expansion and contraction of the hot plate 9 due to the
influence of heat. It should be noted, however, that no clearance
may be provided for at most one bolt 15. In this case also, the hot
plate 9 can thermally expand and contract without being restrained
by the block 7. Although in the above-described arrangement the
heads of all the bolts 15 are separate from the block 7, at most
one bolt 15 may integrally connect together the block 7 and the hot
plate 9 in the same way as in the related art. In this case also,
the hot plate 9 can thermally expand and contract without being
restrained by the block 7. In this case, it is possible to adopt an
arrangement in which the other bolts 15 are replaced with guide
pins that are mounted to the block 7, and the distal ends of the
guide pins are fitted in slots that are formed in the hot plate 9
so as to elongate in the sealing direction. The guide pins may be
arranged like adjustment pins 83 and 85 in a second embodiment
described later. In this case, slots corresponding to the
adjustment pins 83 and 85 are formed in the hot plate 9 so that the
mounting position of the hot plate 9 can be adjusted.
[0059] The first block 7 has plate-shaped guide portions 57 and 59
integrally formed thereon at the upper and lower sides thereof to
extend in the longitudinal direction of the block 7. The guide
portions 57 and 59 determine the positions of the upper and lower
surfaces of the first hot plate 9, thereby enabling the first hot
plate 9 to be positioned in the vertical direction even if there is
a clearance in the vertical direction between the bolts 15 and the
holes 7b.
[0060] The arrangement for mounting the second hot plate 21 to the
second block 19 is similar to the above. That is, the second block
19 has a mounting portion 19a and a body portion 19b formed with
holes 19d. The second hot plate 21 is secured to the distal ends of
bolts 27 inserted through the holes 19d. The bolts 27 are urged
rightward as viewed in the figures by wave washers 61 disposed
between the heads of the bolts 27 and a rear surface 19e of the
block 19, whereby the second hot plate 21 is retained at a mounting
surface 21b thereof by a support surface 19c of the second block 19
with a thermal insulating plate 23 and liners 63 interposed
therebetween. It should be noted that a fall-preventing plate 65
for preventing the bolts 27 from falling off is formed in an
L-shape and fixedly secured to the second block 19. Reference
numerals 67 and 69 denote guide portions for the second hot plate
21.
[0061] As will be clear from the above description, the bolts 15
and 27 used to mount the first and second hot plates 9 and 21 to
the blocks 7 and 19, respectively, do not integrally and firmly
connect together the hot plates 9 and 21 and the blocks 7 and 19.
Even if the hot plate 9 (21) and the block 7 (19) are firmly
connected by bolts 15 (27), the number of bolts 15 (27) used for
this purpose is at most one. Therefore, the hot plate 9 and 21 can
thermally expand and contract independently of the associated
blocks 7 and 19. Accordingly, there is no possibility that the hot
plate 9 (21) will be curved together with the block 7 (19) as one
unit owing to a difference in expansion coefficient therebetween or
a temperature difference during heating. Therefore, even if the
temperature is raised to a predetermined sealing temperature, the
flatness of the pressing surfaces 9a and 21a of the hot plates 9
and 21 is kept very satisfactorily, so that the pressing surfaces
9a and 21a closely contact the outer surfaces of the opposite walls
of a bag 41, as shown in FIGS. 3 and 4. Accordingly, no sealing
failure will occur. Further, the bolts 15 and 27 can be set in
position simply by screwing them into the associated hot plates 9
and 21 as far as predetermined portions thereof with the wave
washers 51 and 61 interposed between their heads and the rear
surfaces 7a and 21a of the blocks 7 and 21. There is no need to
perform flatness adjustment for the pressing surfaces 9a and 21a of
the hot plates 9 and 21 when mounted to the blocks 7 and 21. In
addition, the temperature difference between the pressing surfaces
9a and 21a and the mounting surfaces 9b and 21b can be reduced by
reducing the area of contact between the hot plates 9 and 21 and
the blocks 7 and 19 or the thermal insulating plates 11 and 23 by
using the liners 53 and 63. Consequently, the curvature of the hot
plates 9 and 21 themselves can be reduced to an extremely low
degree, and sealing can be performed even more reliably.
[0062] Next, a heat-sealing apparatus 81 according to a second
embodiment of the present invention will be explained with
reference to FIGS. 5 to 8. It should be noted that members
corresponding to the members in the first embodiment are denoted by
the same reference numerals as those used in the first embodiment,
and a detailed description thereof is omitted. The second
embodiment differs from the first embodiment in the configuration
of the hot plates 9 and 21 and the configuration of the liners 53
and 63, and in that the guide portions 57 and 59 for the first hot
plate 9 and the guide portions 67 and 69 for the second hot plate
21 are replaced with other adjusting members. The points in which
the second embodiment differs from the first embodiment will be
explained below.
[0063] First, hot plates 9 and 21 in the second embodiment will be
explained with reference to FIG. 5. The hot plates 9 and 21 are
formed so that pressing surfaces 9a and 21a thereof are slightly
curved concavely as shown in part (a) of FIG. 5 at an ordinary room
temperature. The degree of the curvature of the pressing surfaces
9a and 21a has been set in advance so that the pressing surfaces 9a
and 21a become flat as shown in part (b) of FIG. 5 when the hot
plates 9 and 21 are heated to a predetermined sealing temperature.
The degree of the curvature can be obtained experimentally. It
should be noted that the hot plates 9 and 21 may be formed so that
the pressing surfaces 9a and 21a are slightly curved convexly at an
ordinary room temperature if the hot plate-mounting structure or
other structure differs from that in this embodiment. Reference
numerals 9d and 21d denote threaded holes in which bolts 15 and 27
are engaged when the hot plates 9 and 21 are mounted to mounting
blocks 7 and 19, respectively, which have been explained in the
first embodiment. In this embodiment, two bolts 15 are used for the
first hot plate 9, and two bolts 27 are used for the second hot
plate 21. Two slots 9e are formed in a mounting surface 9b of the
first hot plate 9. The slots 9e are elongated in the sealing
direction and arranged between the threaded holes 9d at a
predetermined spacing in the sealing direction. Similarly, two
slots 21e are formed in a mounting surface 21b of the second hot
plate 21. The slots 21e are elongated in the sealing direction and
arranged between the threaded holes 21d at a predetermined spacing
in the sealing direction. The slots 9e and 21e will be explained
later in detail.
[0064] FIGS. 6 and 7, which correspond to FIGS. 1 and 2 showing the
first embodiment, are a plan view and a sectional side view,
respectively, showing the heat-sealing apparatus 81 according to
the second embodiment in a state where the hot plates 9 and 21 are
separate from each other. The liners 53 and 63 used in this
embodiment differ in configuration from those used in the first
embodiment, as has been stated above. The configuration of the
liners 53 and 63 have the same configuration as that of the
distortion correcting plates 13 and 25, which has been explained in
connection with the related art. The liners 53 and 63 and the
thermal insulating plates 11 and 23 have the same configuration as
that of the mounting surfaces 9b and 21b of the hot plates 9 and 21
and are respectively disposed between the blocks 7 and 19 on the
one hand and the thermal insulating plates 11 and 23 on the
other.
[0065] Next, the adjustment of the mounting positions of the hot
plates 9 and 21 will be explained. In this embodiment, the mounting
positions of the hot plates 9 and 21 are adjusted by using
adjustment pins 83 and 85. Each adjustment pin 83 has a mounting
shank portion 83a engaged with a threaded hole 7f formed in the
mounting block 7. The adjustment pin 83 further has an eccentric
shank portion 83b that is eccentric with respect to the mounting
shank portion 83a. The eccentric shank portion 83b is narrower than
the mounting shank portion 83a and fitted in a slot 9e (described
above) formed in the hot plate 9 at a position corresponding to the
adjustment pin 83 (see FIG. 8). The diameter of the eccentric shank
portion 83b is substantially equal to the vertical width of the
slot 9e. The same is the case with the adjustment pins 85 mounted
to the second mounting block 19. Accordingly, by rotating the
adjustment pins 83 and 85 appropriately, it is possible to adjust
the vertical positions and inclinations in a vertical plane of the
hot plates 9 and 21 when mounted and also possible to adjust the
height positions of the opposing pressing surfaces 9a and 21a of
the hot plates 9 and 21 to the same level. After the completion of
the adjustment, the adjustment pins 83 and 85 are fixed by using
nuts 84 and 86. Although in this embodiment spring washers 87 and
88 are used as urging members that urge the bolts 15 and 27,
compression coil springs may be used as the urging members.
Although the second embodiment does not use the fall-preventing
plates 55 and 65 for the bolts 15 and 27, which are used in the
first embodiment, the fall-preventing plates 55 and 65 may be used
if necessary.
[0066] It should be noted that the sealing condition in which the
hot plates 9 and 21 are pressed against each other will be clear
from the explanation made in connection with the first embodiment;
therefore, a redundant explanation thereof is omitted herein. In
this embodiment, the hot plates 9 and 21 have been curvedly formed
in advance, allowing for an amount of deformation due to heating,
and when deformed upon heating, the hot plates 9 and 21 are
prevented from being restrained by the mounting blocks 7 and 19.
Therefore, the pressing surfaces 9a and 21a of the hot plates 9 and
21 can keep a satisfactory flatness during heating. In addition,
the liners 53 and 63 are formed in the same configuration as that
of the mounting surfaces 9b and 21b of the hot plates 9 and 21.
Therefore, the difference in the temperature distribution in the
sealing direction of the hot plates 9 and 21 reduces. In addition,
because the adjustment pins 83 and 85, each having an eccentric
shank portion, are used for the adjustment of the positions of the
hot plates 9 and 21, the positional adjustment of the hot plates 9
and 21 can be performed very accurately.
[0067] Next, a heat-sealing apparatus 71 according to a third
embodiment of the present invention will be explained with
reference to FIGS. 9 to 12. FIGS. 9 and 10 are a plan view of a
sectional side view, respectively, showing the heat-sealing
apparatus 71 in a state where hot plates are separate from each
other. FIGS. 11 and 12 are a plan view and a sectional side view,
respectively, showing the heat-sealing apparatus 71 in a state
where the hot plates are pressed against each other. In the
figures, members corresponding to the members in the related art
shown in FIGS. 13 to 16 are denoted by using the same reference
numerals as those in the related art, and a detailed description
thereof is omitted herein.
[0068] The heat-sealing apparatus 71 differs from the related art
shown in FIGS. 13 to 16 in that the hot plates 9 and 21 are secured
to the blocks 7 and 19 at surfaces thereof that are substantially
perpendicular to the pressing surfaces 9a and 21a of the hot plates
9 and 21. In this embodiment, the hot plates 9 and 21 are secured
at the upper surfaces thereof to the blocks 7 and 19, specifically
to the lower surfaces thereof. With this arrangement, the hot
plates 9 and 21 will not be curved in a horizontal plane even if
they may be curved in a vertical plane, i.e. in a plane parallel to
the surfaces of the bag. Accordingly, although there is a
possibility of a sealed portion being formed such that its central
portion in the width direction is slightly curved upward convexly,
sealing itself can be performed satisfactorily.
[0069] That is, a support surface 7d is formed flat on the bottom
of the first block 7 secured to the distal end of a first advancing
and retracting shaft 3. The first hot plate 9 has a mounting
surface 9c formed on the upper surface thereof. The first hot plate
9 is secured at the mounting surface 9c to the support surface 7d
of the first block 7 with a thermal insulating plate 11 interposed
therebetween. The first hot plate 9 is integrally secured to the
block 7 by using bolts 15. Meanwhile, a support surface 19f is
formed flat on the bottom of a body portion 19b of the second block
19 secured to the distal end of a second advancing and retracting
shaft 5. The second hot plate 21 has a mounting surface 21c formed
on the upper surface thereof. The second hot plate 21 is secured at
the mounting surface 21c to the support surface 19f of the second
block 19 with a thermal insulating plate 23 interposed
therebetween. The second hot plate 21 is integrally secured to the
body portion 19b of the block 19 by using bolts 27.
[0070] As has been stated above, the blocks 7 and 19 and the hot
plates 9 and 21 are integrally connected, respectively, in the same
way as in the related art. Therefore, when the temperature of the
hot plates 9 and 21 rises or lowers, the hot plates 9 and 21 may be
curvedly deformed as in the case of the related art. However,
unlike in the related art, the curvature of the hot plates 9 and 21
occurs only in a plane extending vertically at right angles to the
plane of FIG. 9. Therefore, the pressing surfaces 9a and 21a of the
hot plates 9 and 21 are kept flat. Accordingly, when the hot plates
9 and 21 are pressed against each other, as shown in FIGS. 11 and
12, the pressing surfaces 9a and 21a closely contact each other
with a bag 41 held therebetween. Thus, sealing is performed
satisfactorily. Although in the above-described example the hot
plates 9 and 21 are secured to the respective lower sides of the
blocks 7 and 19, it is also possible to adopt an arrangement in
which the hot plates 9 and 21 are secured to the respective upper
sides of the blocks 7 and 19. In such a case, for example, the
second advancing and retracting shaft 5 is arranged so as to avoid
interference with the bag 41.
[0071] It should be noted that it is possible also in this
embodiment to adopt the arrangement used in the first embodiment to
mount the hot plates 9 and 21 to the blocks 7 and 19, respectively.
By doing so, the above-described curvature of the hot plates 9 and
21 in the plane perpendicular to the plane of FIG. 9 is also
prevented. Consequently, a seal is formed straight.
[0072] As has been stated above, this embodiment enables the
pressing surfaces 9a and 21a of the hot plates 9 and 21 to be kept
flat even if the hot plates 9 and 21 are curved. Therefore, sealing
can be performed satisfactorily. There is no need for any
complicated adjustment to obtain the desired flatness of the
pressing surfaces 9a and 21a as in the related art.
[0073] It should be noted that the present invention is not limited
to the foregoing embodiments but can be modified in a variety of
ways.
* * * * *