Abstrict A desiccant canister comprised of a generally cylindrical body
portion, first and second end portions, and at least one gas permeable
disk-shaped member, wherein the body portion is generally impermeable
to liquids and gases, wherein at least one of the said end portions
is perforated, and wherein the disk-shaped member is secured to
the end portion of the canister containing perforations.
Claims We claim:
1. A desiccant canister comprising first and second end portions,
a body portion and at least one gas permeable, liquid impermeable
disk-shaped member, wherein the first end portion is secured to
the body portion, wherein the second end portion comprises an outer
wall and a top wall with perforations passing through the second
end portion, wherein said disk-shaped member is secured to the top
wall and the outer wall of the second end portion, wherein desiccant
material is placed within the desiccant canister between the disk-shaped
member and the first end portion and wherein the second end portion
with disk-shaped member secured thereto is secured to the body portion.
2. The desiccant canister of claim 1 wherein the first end portion
is formed as an integral element of the body portion.
3. The desiccant canister of claim 1 wherein the first end portion
is comprised of a gas impermeable material.
4. The desiccant canister of claim 1 wherein the first end portion
is perforated and a second disk-shaped member is secured to the
first end portion.
5. The desiccant canister of claim 1 wherein the body portion has
an outer wall with a recessed section, wherein a portion of the
outer wall of the second end portion fits in the recessed section
in the outer wall of the body portion.
6. The desiccant canister of claim 5 wherein the outer wall has
a rounded locking rib projecting outward to assist in the locking
of the second end portion to the body portion.
7. The desiccant canister of claim 1 wherein the top surface of
the second end portion contains reinforcing ribs extending across
the inner surface of the second end portion.
8. The desiccant canister of claim 1 wherein the perforations are
in the shape of a truncated square pyramid with smaller area ends
and larger area ends, wherein the smaller area ends are located
at the top surface and the larger area ends are located at the inner
surface of the second end portion.
9. The desiccant canister of claim 1 wherein the desiccant material
is selected from the group consisting of activated charcoal, crystalline
metal aluminosilicates, activated bentonites, silica gel, molecular
sieves and calcium sulfate is contained within the desiccant canister.
10. The desiccant canister of claim 1 wherein the disk-shaped member
is from about 0.2 to about 0.24 mm. in thickness.
11. The desiccant canister of claim 1 wherein the disk-shaped member
covers substantially all of the perforations in the second end portion.
12. The desiccant canister of claim 1 wherein the disk-shaped member
is secured to the second end portion of the desiccant canister by
ultrasonic welding.
Description BACKGROUND OF INVENTION
1. Field of Invention
This invention relates to a desiccant canister. More specifically,
this invention relates to a desiccant canister which permits gases
and vapors to enter the canister to be absorbed by desiccant material
contained therein without permitting the desiccant material to be
released from the desiccant canister.
2. Prior Art
A number of small desiccant canisters formed from gas and liquid
impermeable body portions with perforated end caps at one or both
ends have been disclosed. See for example U.S. Pat. Nos. 2852326
4093105 and 5191721. These canisters contain a desiccant material
which absorbs moisture from the air as the air flows through perforations
in the ends of the desiccant canister. However, some desiccant materials,
such as activated charcoal, form a fine powder, which powder may
pass through these perforations in the canisters. When desiccant
canisters of this type are used within containers for medicinal
tablets or capsules, this fine powder can be deposited on the tablets
or capsules. While this dust is generally harmless, as conventional
desiccant materials are generally non-toxic, the dusting action
is an undesirable feature of these canisters.
U.S. Pat. No. 4772300 discloses an absorbent cartridge which
attempts to address this problem. This cartridge is similar in design
to conventional desiccant canisters except elongated ribs are provided
on the outside surface of the canister. In addition, at least one
of the ends of the canister is prepared from a permeable, spun bonded
polyolefin which is gas permeable to permit water vapor to pass
therethrough. Difficulties in manufacture and use still exist with
this type of canister. For example, it has been discovered that
the use of such a polyolefinic material to form the end of an adsorbent
cartridge may be impractical as the polyolefin material cannot be
easily or economically secured to the body of the desiccant canister
to form an end of the canister. In addition, seals formed about
this material are frequently weak, thus allowing either the complete
discharge of the desiccant material from the canister or a gradual
loss of the desiccant material around the edges of the canister.
Other adsorbent cartridges for use in medicine pill containers
are disclosed, for example, in U.S. Pat. Nos. 3820309 2852326
and 2838795. See also U.S. Pat. No. 4093105 which discloses
a desiccant cartridge for use with drugs and chemicals. Adsorbent
packages formed from a spun bonded polyolefin are disclosed, for
example, in U.S. Pat. No. 3990872. See also U.S. Pat. No. 3309849.
While there have been several attempts to address the problem of
providing a desiccant canister for use with pharmaceutical products
which will absorb both water vapor and at the same time not create
the "dusting" problem that has been prevalent with prior
desiccant canisters, no completely workable canister has been developed.
Therefore, it is an object of this invention to provide a desiccant
canister for use with pharmaceutical products.
It is another object of this invention to provide a desiccant canister
which will efficiently and effectively absorb water vapor.
It is another object of this invention to provide a desiccant canister
which will efficiently absorb water vapor while at the same time
not permit the desiccant material contained within the canister
from spilling out of the canister in normal use.
It is a still further object of this invention to provide a desiccant
canister which will efficiently absorb water vapor while at the
same time eliminate the "dusting" problem present in certain
prior canisters.
These and other objects and features of the present invention will
become apparent to those skilled in the art from a consideration
of the following detailed description, drawings and claims. The
description, along with the accompanying drawings, provides a selected
example of construction of the product to illustrate the invention.
(c) SUMMARY OF INVENTION
In accordance with the present invention, there is provided a desiccant
canister comprised of a cylindrical body portion, first and second
end portions, and at least one disk-shaped, gas permeable member,
wherein the body portion is generally impermeable to liquids or
gases, wherein at least one of the said end portions is perforated
and wherein said disk-shaped, gas permeable member is secured to
the end portion of said canister containing perforations.
There is further disclosed a process for the forming of the desiccant
canister comprised of
(a) forming a cylindrical body portion open at both ends;
(b) closing one open end of the body portion with a gas impermeable,
first end portion;
(c) forming a second end portion from a gas impermeable material,
wherein said second end portion contains perforations therethrough;
(d) forming a gas permeable, disk-shaped member;
(e) securing the gas permeable, disk-like member to the second
end portion containing perforations;
(f) filling the body portion with a desiccant material; and
(g) securing the second end portion to the body portion to form
a desiccant canister.
(D) BRIEF DESCRIPTION OF THE DRAWINGS
This invention will now be described with reference to the accompanying
drawings in which
FIG. 1 is a cut-away side view of the desiccant canister showing
the gas permeable disk-like member.
FIG. 2 is a side view of the desiccant canister with the first
end portion secured in place but without the second end portion.
FIG. 3 is a cut-away side view of the end portion of the desiccant
canister containing the gas permeable disk-like member.
FIG. 4 is a cut-away section of FIG. 3 showing the side edge of
the desiccant canister containing the gas permeable disk-like member.
FIG. 5 is a cut-away end view of the second end portion showing
both the perforations in the end portion and the disk-shaped member.
(E) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Although the invention is adaptable to a wide variety of uses,
it is shown in the drawings for purpose of illustration as embodied
in a desiccant canister (10) comprised of a body portion (12) open
at each end, first (14) and second end (16) portions, at least one
of which contains perforations (18) and a gas permeable, disk-shaped
member (20) for securing to the end of the desiccant canister containing
perforations. See FIG. 1.
The canister body portion (12) is generally formed from gas impermeable,
plastic materials well known in the industry. It is generally cylindrical
in shape and open at each end. The outer wall (22) of the body portion
(12) has a recessed ring portion (24) around its outer surface,
near at least one of its ends. A rounded locking rib (26) projects
radially outward from this recessed ring portion (24). This locking
rib, which projects outward around the circumference of the outer
wall (22), is used for locking one of the end portions in place
to the body portion (12). See FIG. 2.
While the end portions of the desiccant canister can be formed
separately from the canister, in a preferred embodiment the first
end portion (14) is formed as an integral element of the body portion
(12). See FIG. 2. The first end portion (14) is generally formed
from gas impermeable plastic material well known in the industry,
similar to the material used to form the body portion. This first
end portion (14) preferably has a reinforcing rib or reinforcing
ribs (28) extending radially across the inner surface of the first
end portion to provide structural support for the first end portion.
The second end portion (16) is formed in the shape of a cap and
includes a cylindrical outer wall (30) and a flat top wall (32).
See FIG. 3. The outer diameter of the cylindrical outer wall (30)
preferably is equal to the outer diameter of the body portion (12).
The inner diameter of the outer wall of the second end portion is
equal to the diameter of the bottom surface (34) of the recessed
ring portion (24) of the outer wall (22) of the body portion (12).
The height of the outer wall is substantially equal to the depth
of the recess of the recessed ring portion (24) from the top of
the body portion. The outer wall of the second end portion has a
rounded recess (36) around its inner surface. Thus, the outer wall
(22) of the second end portion (16) can fit around the recessed
ring portion (24) of the outer wall of the body portion (12) with
the outer surface of the outer wall (22) of the second end portion
(16) being flush with the inner surface of the outer wall, with
the locking rib (26) snap fitting into the recess (36) in the outer
wall (22) to lock the second end portion (16) onto the body portion
(12). See FIGS. 1 and 4. The top wall (32) of the second end portion
(16) also has, preferably, a reinforcing rib or reinforcing ribs
(38) extending diametrically thereacross to provide structural security.
A plurality of small perforations (18) extend through the top wall
(32) in the area between the reinforcing ribs (38) and the outer
wall (22). See FIGS. 4 and 5. These perforations are preferably
in the shape of a truncated, square pyramids, having their small
area ends at the outer surface of the second end portion and their
larger area ends at the inner surface. The perforations can be as
small as about 0.007 inches at their small end and about 0.018 inches
at their larger end. There may be as many as 150 to 300 of these
holes in the second end portion.
The canister itself can be made as small as about 1/2 inch in height
and 17/32 inches in diameter, or even smaller, although different
shapes are within the coverage of the specifications.
The shape of the canister creates an open area within the body
portion to be filled with a desiccant material (not shown). In particular
the desiccant material is introduced into the canister before the
second end portion (16) is secured to the body portion (12). The
types of desiccant material are well known in the industry and include,
for example, activated charcoal, crystalline metal aluminosilicates,
activated bentonites, silica gel, molecular sieves, calcium sulfate
or any other suitable desiccant product or mixture thereof.
The disk-shaped member (20) to be used with the desiccant canister
is shaped to fit within the inside of the second end portion (16)
of the desiccant canister (10). See FIGS. 1 3 and 4. It is dimensioned
to fit tightly within the second end portion so that its edges fit
with close tolerance within the cylindrical outer wall (30) of the
second end portion of the canister. When this disk-shaped member
is secured in place, it will cover substantially all of the perforations
(18) in the second end portion.
This disk-shaped member (20) is formed from a material which is
gas permeable. In the preferred embodiment, this material is a spun
bonded polyolefin, and most preferably is formed of a TYVEK.RTM.
material. While there are various grades of the TYVEK.RTM. material
with different thicknesses, the exact thickness and material will
depend on the specific application of the desiccant canister. In
one preferred embodiment, the TYVEK.RTM. material for use is grade
1073B with a thickness of about 0.20-0.24 mm. As this disk-shaped
member does not have any perforations and as it covers substantially
all of the perforations of the second end portion (16), it will
assist in retaining the desiccant material (40) within the desiccant
canister (10). However, as the disk-shaped member is also gas permeable,
water vapor can pass through the disk-shaped member (20) and be
absorbed by the desiccant material (40). The disk-shaped member
is secured within the second end portion by friction fitting, ultrasonic
welding, adhesive sealing or any other method commonly used in the
industry, preferably ultrasonic welding.
Once the disk-shaped member (20) is secured within the second end
portion (16), the body portion is filled with the desiccant material.
The second end portion is then placed over the top edge of the body
portion (12) and snapped in place. The locking rib (26) of the body
portion (12) interacts with the recess (36) in the outer wall (22)
of the second end portion (16) to hold the second end portion securely
in place. Once the second end portion (16) is in place on the body
portion (12), a label can be secured around the cylindrical outer
wall (30) of the canister with the label extending across the junction
between the body portion (12) and the second end portion (16). Thus
the label of the printing serves both to disclose the contents of
the canister and, in addition, assist in preventing the second end
portion (16) from being accidentally dislodged from the body portion.
The shape of the canister permits ease of molding of the body portion
(12) and the second end portion (16) so that they can be formed
completely of plastic to provide greater rigidity of the canister.
The use of the gas permeable, but solid impermeable disk-shaped
member (20) prevents the desiccant material of the canister from
being discharged from the canister. However, gases and vapors can
pass through the disk-shaped member to enter the canister to be
absorbed by the desiccant material.
While the canister has been described with a single perforated
second end portion (16) and a single disk-shaped member, a second
perforated cap-like end and a second disk-shaped member can be secured
to the opposite end of the body portion to enhance the absorption
capability of the desiccant canister. If a second perforated end
portion is used, the desiccant material should fill the canister
after one of the end portions is secured in place against the body
portion (12). Alternatively, this second end portion can be formed
exclusively of a gas permeable material.
The process for the production of this desiccant canister begins
with the forming of the cylindrically-shaped body portion (12) which
is open at both ends. One end is closed by securing to that end,
preferably, an impermeable first end portion (14). In a preferred
embodiment the body portion and the impermeable first end portion
are formed as one integral element. See FIG. 1. Following the forming
of this body portion and first end portion (16), a second end portion
is formed in a cap shape with a number of perforations (18) passing
therethrough. A gas permeable, disk-shaped member (20) is next formed
and secured within the inside of the second end portion (16) covering
substantially all of the perforations of the second end portion.
The body portion is then filled with the desiccant material. Following
this filling, the second end portion (16) which contains the gas
permeable disk-shaped member (20) is then secured to the body portion
of the desiccant canister.
It will thus be seen that the objects set forth above, among those
made apparent from the preceding description, are efficiently attained
and, since certain changes may be made in the above articles without
departing from the scope of the invention, it is intended that all
matter contained in the above description or shown in the accompanying
drawings shall be interpreted as illustrative and not in a limiting
sense.
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