BACKGROUND OF THE INVENTION
[0001] The present invention relates to an air-tightly sealable container with a bell jar
covering provided with a sealing mechanism between the bell jar covering and the base
plate on which the bell jar covering is mounted to be used for storage and transportation
of various precision products to be kept absolutely free from contamination with atmospheric
dust particles such as semiconductor silicon wafers.
[0002] The routine delivery system of semiconductor silicon wafers is that the silicon wafers
as produced in the plant of a wafer producer are packaged in a specially designed
container for transportation and transported therein to the plant of a manufacturer
of semiconductor devices such as integrated circuits. Similar containers are used
also within the plant of the device manufacturers in-house for the purpose of transfer
of intermediate products from a line to a subsequent line for the next step of working.
[0003] Needless to say, a semiconductor silicon wafer is a product of extremely high purity
and must be kept away from any trace contamination on the base of which ultrafine
and extremely delicate electronic circuits are to be built so that the container therefor
must be provided with a very reliable sealing mechanism by means of which intrusion
of any trace amount of particulate foreign matters such as dust particles can be completely
prevented.
[0004] One of the most traditional way to obtain an air-tight sealing condition of the opening
in such a container is that a pressure-sensitive adhesive tape is attached along the
seam line of the container body and the covering all around or an elastic gasket member
is interposed between the open periphery of the container body and the periphery of
the covering under an appropriate compression so as to eliminate any smallest interstice
or gap, otherwise through which intrusion of dust particles may take place, to ensure
a hermetic sealing condition.
[0005] These conventional methods for sealing are each not free from difficult problems.
For example, adhesion of the pressure-sensitive adhesive tape to the surface of the
container is sometimes not perfect by the occurrence of creases or twisting of the
tape depending on the outer configuration of the container and the worker's skill
so that the hermetic sealing condition by this means is not always very reliable unless
an unduly long time is taken for the taping works if not to mention possible contamination
of the outer surface of the container with the adhesive. In addition, such a taping
work is hardly susceptible to automatization.
[0006] The sealing method by using a rubber gasket also requires a clamping mechanism by
which the container body and the covering are engaged and fastened each to the other
and an appropriate compressive force is applied to the elastic gasket member.
[0007] In the current trend toward full automation of various production lines, it is eagerly
desired to develop an air-tight sealing mechanism of a container with a bell jar covering
which can be operated by an automatic machine for closing and opening the container.
SUMMARY OF THE INVENTION
[0008] The present invention accordingly has an object to provide a novel air-tightly sealable
container with a sealing mechanism of a simple structure between a cylindrical bell
jar covering and the base plate, on which the bell jar covering is mounted, by means
of which mechanism a very reliable hermetic sealing condition can be ensured and which
mechanism can be operated by an automatic machine for closing and opening of the container.
[0009] Thus, the air-tightly sealable container with a sealing mechanism according to the
invention comprises:
(A) a cylindrical bell jar covering;
(B) a base plate having a laterally and downwardly opening groove therearound along
the outer side periphery, the dimensions of the base plate being smaller than the
inner dimensions of the bell jar covering;
(C) an elastic sealing member, such as an O-ring gasket of rubber, to fit the groove
of the base plate;
(D) a presser plate positioned below the base plate and for moving up and down to
press the elastic sealing member against the base plate in such a fashion that the
elastic sealoing member is elastically deformed and bulged out laterally to be brought
into contact with the inner wall of the bell jar covering surrounding the base plate;
and
(E) a mechanical means for pushing the presser plate against the base plate such as
a mechanism of cams and screws.
[0010] Needless to say, the above mentioned cylindrical bell jar covering as the part (A)
need not have a circular cross section but the horizontal cross section thereof can
be generally a square or rectangular form provided that each corner is rounded having
a sufficiently large radius of curvature so that the elastic sealing member as the
part (C) can fit the groove around the base plate as the part (B).
BRIEF DESCRIPTION OF THE DRAWING
[0011] Figures 1A and 1B each illustrate the bell jar container of the invention by an axial
cross sectional view in an open state and sealed state, respectively.
[0012] Figures 2A and 2B each illustrate the bell jar container of the invention in another
embodiment by an axial cross sectional view with the bell jar covering lifted above
the base plate and mounted on the base plate to establish a sealed state, respectively.
[0013] Figures 3A and 3B each illustrate the bell jar container (bell jar covering not shown)
of the invention in a further different embodiment showing an assembly of the base
plate and the pressing plate corresponding to an open and sealed states, respectively,
of the container by an axial cross sectional view.
[0014] Figure 4 is an axial cross sectional view of a still different embodiment of the
inventive container.
[0015] Figure 5 is an axial cross sectional view of the same container as shown in Figure
4 on use in an upside-down disposition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] As is described above, the air-tightly sealable bell jar container according to the
invention comprises, as the principal parts thereof, (A) a bell jar covering having,
for example, a circular cross section and mountable on a base plate, (B) a circular
base plate having a diameter smaller than the inner diameter of the bell jar covering
and provided with an annular groove open downwardly and laterally, (C) an elastic
sealing member such as an O-ring gasket of a rubbery material to fit the annular groove
in the base plate and (D) a presser plate which presses the elastic sealing member
against the base plate by (E) a mechanism such as cams or screw bolts and nuts to
such an extent that the elastic sealing member is compressed and laterally bulged
out to be brought into contact with the inner wall of the bell jar covering mounted
on the base plate to give an air-tight sealing condition between the base plate and
the inner wall of the bell jar covering.
[0017] It is assumed in the above given description that the materials to be contained in
the container are placed on the base plate and then the bell jar covering is mounted
thereon although it is optional that the materials are placed on the bottom of the
bell jar covering standing in an upside-down disposition and the assembly consisting
of the base plate and the presser plate is mounted on the upward opening of the bell
jar covering.
[0018] In the following, the air-tightly sealable bell jar container of the invention is
illustrated by making reference to the accompanying drawing. Although the following
description is given by assuming that the bell jar covering has a circular cross section,
about the same description is applicable even when the bell jar covering has a noncircular
cross section such as a generally rectangular cross section.
[0019] Figures 1A and 1B are each an axial cross sectional view of the inventive bell jar
container in an open and sealed state, respectively. The container comprises a circular
base plate 1, on which the materials to be contained are mounted, and a bell jar covering
2, of which the inner diameter is slightly larger than the diameter of the base plate
1, mountable on the base plate 1 in such a fashion that the base plate 1 is entirely
enveloped inside of the bell jar covering 2 mounted thereon leaving a small clearance
therebetween and a presser plate 5 below the base plate 1. The base plate 1 is provided
with an annular groove 3 along the outer periphery thereof in such a fashion that
the groove 3 is open laterally and downwardly. An O-ring gasket 4 of a rubber fits
the annular groove 3 with elastic resilience. It is not always necessary in the open
state of the container (Figure 1A) that the O-ring gasket 4 is in contact with the
inner wall of the bell jar covering 2. A presser plate 5 is provided below the base
plate 1 in such a fashion that the presser plate 5 is movable up and down by sliding
on the rods 6,6 downwardly extending from the lower surface of the base plate 1 by
operating the cams 7,7 pivotally supported on the rods 6,6 by means of the cam handles
8,8.
[0020] When the presser plate 5 is at the lowermost position as is illustrated in Figure
1A, the container is in an open state and the bell jar covering 2 can be freely removed
from the base plate 1. When the presser plate 5 is pushed up against the base plate
1 by turning the cams 7,7 in the direction indicated by the openwork arrows in Figure
1A, as is illustrated in Figure 1B, the O-ring gasket 4 in the annular groove 3 of
the base plate 1 is upwardly compressed by the presser plate 5 against the upper wall
of the annular groove 3 and is elastically deformed and bulged out laterally to have
an elliptic cross section and to be brought into contact with the inner wall of the
bell jar covering 2 so that an air-tight sealing condition is established between
the base plate 1 and the inner wall of the bell jar covering 2.
[0021] In Figure 1B, the base plate 1 and the presser plate 5 are fastened together by the
mechanism of cams 7,7. When the fastening force is released by turning the cams 7,7,
the base plate 1 is pushed up by the elastic resilience of the O-ring gasket which
regains the circular cross section as in Figure 1A.
[0022] Figures 2A and 2B are for the illustration of the inventive container in an embodiment
similar to that illustrated in Figures 1A and 1B. While the bell jar covering 2 illustrated
in Figures 1A and 1B has a smooth inner surface, the inner surface of the bell jar
covering 2' in Figures 2A and 2B is not smoothly cylindrical but has an annular groove
9 around the lower portion of the covering 2'. When the bell jar covering 2' is mounted
on the base plate 1 with an O-ring gasket 4 in the annular groove 3 of the base plate,
the groove 9 on the inner wall of the bell jar covering 2' comes to the same height
as the O-ring gasket 4 so that, when the presser plate 5 is pushed up against the
base plate 1, the O-ring gasket 4 is upwardly compressed and laterally bulged out
into the annular groove 9, as is illustrated in Figure 2B, so that engagement between
the base plate 1 and bell jar covering 2' can be improved as compared with the embodiment
illustrated in Figures 1A and 1B.
[0023] Although Figures 1A and 1B and Figures 2A and 2B show an O-ring gasket 4 which is
solid, i.e. not hollow, it is optional to use a hollow O-ring gasket 4' as is illustrated
in Figures 3A and 3B provided that a reliable air-tight sealing condition can be obtained
by the contact between the elastically deformed O-ring gasket 4' and the inner wall
of the bell jar covering (not shown in Figures 3A and 3B).
[0024] Figures 3A and 3B further illustrate an alternative mechanical means for fastening
the base plate 1 and the presser plate 5, in place of the mechanism of cams illustrated
in Figures 1A and 1B and Figures 2A and 2B, consisting of screw bolts 10,10 implanted
in and extending downwardly from the base plate 1 and screw nuts 11,11 movable on
the screw bolts 10,10. When the nuts 11,11 are at the lower positions, the O-ring
gasket 4' is in an uncompressed state, as is illustrated in Figure 3A, allowing free
mounting and removal of the ball jar covering on and from the base plate 1 while,
when the nuts are turned to push up the presser plate 5 against the base plate 1,
as is illustrated in Figure 3B, the O-ring gasket 4' is upwardly compressed and bulged
out laterally to be brought into contact with the inner wall of the bell jar covering.
[0025] In the above described embodiments of the inventive container, the presser plate
5 is assumed to have a diameter approximately equal to the diameter of the base plate
1 which is slightly smaller than the inner diameter of the bell jar covering 2. It
is, however, optional that the presser plate 5 has a diameter smaller or larger than
the diameter of the base plate 1. In particular, as is illustrated in Figure 4, the
diameter of the presser plate 5' can be larger than the inner diameter of the bell
jar covering 2 so that the bell jar covering 2 can rest at the lower periphery thereof
on the presser plate 5'.
[0026] The embodiment of the inventive container illustrated in Figure 4, in which the presser
plate 5' has a diameter larger than the inner diameter of the bell jar covering 2,
can be used as being turned upsidedown so that, while, in the other embodiments described
earlier, the materials to be contained in the container are placed on the base plate
1 and then the bell jar covering 2 is mounted thereon, the materials are first placed
on the bottom of the bell jar covering in an upsidedown disposition and then the assembly
of the base plate 1 and the presser plate 5 is mounted on the upper periphery of the
covering 2 without a trouble of falling down into the bell jar covering 2.
[0027] As is illustrated in Figure 5, the bell jar container of the invention shown, for
example, in Figure 4 can be used in an upside-down disposition. In this case, the
bell jar covering 2 in Figure 4 is now the container bottom 2 in Figure 5 standing
on the flat bottom and the presser plate 5 now serves as the covering. The material
contained in the container naturally rests on the bottom of the container body 2.
1. An air-tightly sealable bell jar container which comprises:
(A) a bell jar covering;
(B) a base plate having a laterally and downwardly opening groove along the outer
side periphery, the dimensions of the base plate being smaller than the inner dimensions
of the bell jar covering;
(C) an elastic sealing member to fit the groove of the base plate;
(D) a presser plate positioned below the base plate and for moving up and down to
press the elastic sealing member against the base plate in such a fashion that the
elastic sealing member is elastically deformed and bulged out laterally to be brought
into contact with the inner wall of the bell jar covering surrounding the base plate;
and
(E) a mechanism for pushing the presser plate against the base plate.
2. The air-tightly sealable bell jar container as claimed in claim 1 in which the mechanism
(E) for pushing the presser plate against the base plate is a means of cams each pivotally
supported on a rod downwardly extending from the lower surface of the base plate.
3. The air-tightly sealable bell jar container as claimed in claim 1 in which the mechanism
(E) for pushing the presser plate against the base plate is a means of screw bolts
each extending downwardly from the lower surface of the base plate and screw nuts
thereon.
4. The air-tightly sealable bell jar container as claimed in claim 1 in which the bell
jar covering is provided with a groove on the inner wall at such a height that, when
the bell jar covering is mounted on the base plate, the elastic sealing member in
the groove of the base plate is brought into contact with the groove on the inner
wall of the bell jar covering.
5. The air-tightly sealable bell jar container as claimed in claim 1 in which the presser
plate has dimensions larger than the inner dimensions of the bell jar covering.
6. The air-tightly sealable bell jar container as claimed in claim 1 in which the bell
jar covering has a circular cross section.
7. The air-tightly sealable bell jar container as claimed in claim 1 in which the bell
jar covering has a generally rectangular cross section having rounded corners.
8. The air-tightly sealable bell jar container as claimed in claim 1 in which the elastic
sealing member is an O-ring gasket made from a rubber.