U.S. patent number 3,901,416 [Application Number 05/452,447] was granted by the patent office on 1975-08-26 for top-loaded pressure operated container for dispensing viscous products.
This patent grant is currently assigned to Robert S. Schultz. Invention is credited to Robert S. Schultz.
United States Patent |
3,901,416 |
Schultz |
* August 26, 1975 |
Top-loaded pressure operated container for dispensing viscous
products
Abstract
The invention contemplates a piston-operated pressurized
container adapted for top-loading with viscous foods or other
viscous products, the body of the piston having a substantially
smaller diameter than the diameter of the container. The outer
periphery of the piston is provided with a resilient flange member
that maintains a light sealing pressure on the interior surfaces of
the container, allowing the piston to move smoothly upwardly within
the container. The inventive method provides enhanced assurance
against product leakage and against propellant-contamination of
product, prior to selective product discharge as desired.
Inventors: |
Schultz; Robert S. (Old
Greenwich, CT) |
Assignee: |
Schultz; Robert S. (Old
Greenwich, CT)
|
[*] Notice: |
The portion of the term of this patent
subsequent to August 6, 1991 has been disclaimed. |
Family
ID: |
27390515 |
Appl.
No.: |
05/452,447 |
Filed: |
March 18, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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290977 |
Sep 21, 1972 |
3827607 |
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175253 |
Aug 26, 1971 |
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Current U.S.
Class: |
222/389;
92/243 |
Current CPC
Class: |
B65D
83/64 (20130101) |
Current International
Class: |
B65D
83/14 (20060101); B67d 001/04 () |
Field of
Search: |
;92/245,237,243,253,249
;222/386.5,389 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reeves; Robert B.
Assistant Examiner: Lane; Hadd
Attorney, Agent or Firm: Hopgood, Calimafde, Kalil,
Blaustein & Lieberman
Parent Case Text
This application is a continuation-in-part of my copending
application Ser. No. 290,977, filed Sept. 21, 1972, (now U.S. Pat.
No. 3,827,607) which copending application is a
continuation-in-part of my now-abandoned parent application Ser.
No. 175,253, filed Aug. 26, 1971.
Claims
What is claimed is:
1. A piston for a pressurized container having a viscous product
and provided with a dispensing valve, said piston comprising a
piston body portion of a generally tubular configuration and a
resilient annular elastomeric flange provided with an upstanding
skirt portion on the outer wall of said piston body portion, said
piston body portion being radially spaced from the inner wall of
said skirt portion, said upstanding skirt portion being for contact
with a container wall and being the only means of piston support,
said skirt portion being relatively thin with respect to the space
between said skirt portion and the piston body portion, said skirt
portion having a large surface area of substantial axial length;
whereby, when said piston is inserted in a suitable container and
when the space within said skirt portion and above said piston is
loaded with viscous product and the space beneath said skirt
portion and piston is subjected to a predetermined charge of gas
under pressure, said skirt portion will be pressure-loaded into
peripheral and axially continuous light sealing and stabilizing
contact with the container wall.
2. A piston as claimed in claim 1, wherein said piston body portion
includes reinforcement means whereby said piston body portion is
relatively stiff in relation to the resilience of said skirt
portion.
3. A piston as claimed in claim 1, wherein the thickness of said
skirt portion is in the range of 0.005 to 0.015 inch.
4. A piston as claimed in claim 1, wherein said skirt portion is
integrally formed with said piston body portion.
5. A piston as claimed in claim 1, wherein said piston body is
constituted of a plastic.
6. A piston as claimed in claim 1, wherein said resilient flange
projects radially outwardly and axially toward the head end of said
piston body portion.
7. A piston for a pressurized container having a viscous product
and provided with a dispensing valve, said piston comprising a
piston body portion of a generally tubular configuration, a first
resilient annular elastomeric flange provided with an upstanding
skirt portion on the outer wall of said piston body portion, a
second resilient annular elastomeric flange provided with a skirt
portion on the outer wall of said piston body portion and axially
beneath said first flange, said piston body portion being radially
spaced from the inner walls of said skirt portions, said skirt
portions being for contact with a container wall and being the only
means of piston support, said skirt portions being relatively thin
with respect to the space between said skirt portions and the
piston body portion, said skirt portions each having a large
surface area of substantial axial length; whereby, when said piston
is inserted in a suitable container and when the space within said
first skirt portion and above said piston is loaded with viscous
product and the space beneath said second skirt portion and piston
is subjected to a predetermined charge of gas under pressure, said
skirt portions will be pressure-loaded into peripheral and axially
continuous light sealing and stabilizing contact with the container
wall.
8. A piston as claimed in claim 7, wherein said second flange
projects axially downwardly and radially outwardly from said outer
wall to a location axially spaced from the location of said first
annular flange.
9. In combination, a pressure container comprising an elongate
cylindrical body with a closed upper end, dispensing-valve means in
said upper end, a piston having a closed upper end and integral
body structure extending downwardly within a cylinder spaced from
the container wall and united to the closed end of said piston, a
peripherally continuous axially upwardly directed flexible tubular
elastomeric flange carried by said piston within the annular space
between the piston body structure and the container wall and of
axial extent substantially less than that of said piston, said
flange being relatively thin with respect to the space between said
tubular flange and the piston body having a periphery of
substantially the inner wall-surface peripheral extent of the
container body, with a substantial axially extensive area of
circumferential flange-seal contact with the container wall by
reason of the tubular structure of said flange, said tubular flange
being the only means of piston suspension with respect to the
container wall, whereby a product chamber is defined in the
container space between the flanged piston and the valved end of
the container, a viscous product in said product chamber,
pressure-sealing means closing the lower end of said container to
define a pressure chamber beneath said piston, and a predetermined
charge of gas under pressure in the pressure chamber, whereby
viscous product pressure loads said tubular flange into peripheral
and axially continuous light sealing and stabilizing contact with
the container wall.
10. The combination of claim 9, in which said container body has a
top opening, said dispensing-valve means being assembled to said
body at the top opening after dispensable product is loaded through
the opening.
11. The combination of claim 9, in which the radial offset of said
tubular flange from said body structure is substantially ten
percent of the outer radius of said tubular flange.
12. The combination of claim 9, in which said closed upper end of
said container is a conical reduction from said cylindrical body to
a central valve-locating opening.
13. The combination of claim 12, in which said valve means
comprises a resilient bushing having a central body and an integral
conical flange generally conforming to the inner surface of the
conical reduction of the container and peripherally continuously
sealing said bushing to the container, and a headed
dispensing-valve member having a stem portion extending through
said bushing and located thereby.
14. The combination of claim 9, wherein said piston body and
tubular flange are parts of the same single injection-molded
plastic article, the wall thickness of the closed end of said
piston being substantially greater than that of said tubular
flange.
15. The combination of claim 14, wherein said piston body comprises
a cylindrical sheath with internal elongate stiffening ribs at
angularly spaced locations.
16. The combination of claim 9, wherein the upper wall-surface
contour of the closed end of said piston includes an outer
frusto-conical annulus of slope conforming to that of said conical
reduction.
17. The combination of claim 16, in which said tubular flange is
connected to said piston body near the upper end thereof, said
tubular flange being of effective axial length less than one half
the overall axial length of said piston, and the upper edge of said
flange being at substantially the elevation at which the
geometrical projection of the slope of the frusto-conical annulus
intersects the cylinder defined by the outer surface of said
tubular flange.
18. The combination of claim 9, wherein the portion of said valve
means exposed internally of said container is characterized by a
central convex spherical contour, and wherein the upper surface of
the closed end of said piston is characterized by a central
spherical concavity substantially matching the said convex
contour.
19. The combination of claim 9, in which the peripheral extent of
said tubular flange is slightly less than that of the adjacent
cylindrical container-body wall surface, the material of said
flange being sufficiently flexible to inflate into peripherally
continuous container-wall contact in response to piston-loading of
product by reason of super-atmospheric pressure in said pressure
chamber.
20. In combination, a pressure container comprising an elongate
cylindrical body with a closed upper end, dispensing-valve means in
said upper end, a piston having a closed upper end and integral
body structure extending downwardly within a cylinder spaced from
the container wall and united to the closed end of said piston, a
peripherally continuous axially upwardly directed flexible tubular
elastomeric flange carried by said piston within the annular space
between the piston body structure and the container wall, said
flange being relatively thin with respect to the space between said
piston body and the container wall and being the only means of
piston suspension with respect to the container wall, said flange
having a periphery of substantially the inner wall-surface
peripheral extent of the container body and being of substantial
axial extent which is substantially less than that of said piston
body structure, whereby a product chamber is defined in the
container space between the flanged piston and the valved end of
the container, a viscous product in said product chamber,
pressure-sealing means closing the lower end of said container to
define a pressure chamber beneath said piston, and a predetermined
charge of gas under pressure in the pressure chamber, whereby
viscous product pressure-loads said tubular flange into peripheral
and axially continuous light sealing and stabilizing contact with
the container wall.
21. A piston for a top-loaded pressurized container having above
said piston a viscous product and a dispensing valve, and a gaseous
propellant at super-atmospheric pressure beneath said piston, said
piston comprising a piston-body portion of generally tubular
configuration and a resilient annular elastomeric flange provided
with an upwardly directed skirt portion which projects upwardly and
outwardly relative to the outer vertical wall of the piston body,
said piston body being spaced from the inner wall of said container
and non-sealing therewith and said flange skirt portion being the
only means of piston-body suspension with respect to the inner wall
of said container, the included effective transverse sectional area
of said piston body substantially exceeding the included effective
transverse sectional area of said space between said piston body
and the inner wall of the container, said skirt portion having a
substantial axially extensive surface area and being of such a
length that substantially the total portion of said surface area
when the piston body is inserted in said container engages the
inner wall of said container with a light sealing pressure by the
force exerted by said gaseous propellant acting on the piston body
and thereby transmitting the predominant fraction of said force to
compressionally load the viscous product and, hence, said skirt
into radially outward sealing contact with the inner wall of said
container.
Description
The present invention relates to a top-loaded pressure packaging
system for viscous products, whereby the system is characterized by
improved operation.
It is an object of the invention to provide smoother discharge
flow, more precisely controlled valve action, and inherently
greater capacity in a given size container of the character
indicated.
A specific object is to achieve the foregoing objects in a
top-loaded valved pressure container having a piston operable
therein in which the viscous product is in the valved end of the
container and ahead of the piston while a gas, such as nitrogen, is
introduced under pressure behind the piston to urge the latter
against the product and expel the product through the valved
opening.
Another specific object is to provide in such a container a piston
and seal construction which permits the piston to operate smoothly
within the container in spite of any piston expansion, as may be
caused by piston absorption of oils present in the viscous product
to be dispensed.
A general object is to achieve the foregoing objects with a method
which inherently simplifies container assembly, which enables
smooth and reliable operation, and which also ensures (a) against
product-seepage past the piston and (b) against
propellant-contamination of product.
Other objects and various further features of novelty and invention
will be pointed out or will occur to those skilled in the art from
a reading of the following specification, in conjunction with the
accompanying drawings. In said drawings:
FIG. 1 is a longitudinal sectional view of a pressurized container
of the invention;
FIG. 2 is an enlarged fragmentary sectional view of the piston and
adjacent container wall of FIG. 1, and further illustrating a
modification;
FIGS. 3a and 3b are fragmentary sectional views to illustrate
another modification and showing a double-acting piston in the
container in both the unloaded (FIG. 3a) and loaded (FIG. 3b)
condition thereof;
FIG. 4 is an enlarged fragmentary sectional view of a portion of
FIG. 3;
FIG. 5 is a view similar to FIG. 1 to illustrate a further
embodiment of the invention;
FIG. 6 is an enlarged fragmentary sectional view of a parts
relationship for the structure of FIG. 5;
FIG. 7 is a similar view of a modified structure;
FIGS. 8 and 9 are similar enlarged fragmentary sectional views of
the FIG. 5 combination, to show detail of the relation of parts for
the uppermost position of the piston, in application to larger
(FIG. 8) and smaller (FIG. 9) container bore sizes;
FIGS. 10 and 11 are respectively perspective and longitudinal
sectional views of the piston in FIG. 8; and
FIG. 12 is a view similar to FIG. 11, but for the piston of FIG.
9.
Referring to FIG. 1, a pressurized container or can 10 is formed
with an integral conical top-end wall and provided with a valve,
referred to generally by the reference numeral 12. The valve 12 is
of the variety in which a valve stem 14 is pressed laterally in a
well-known manner in order to release the valve seal and permit the
viscous product 16, which is at super-atmospheric pressure, to be
expelled to the atmosphere. A generally tubular elastomeric hollow
piston 18, which may be constituted of a low-density polyethylene
or a polypropylene material, is used to drive product 16 through
the dispensing valve 12. Secured to or integral with the piston 18
is a relatively thin annular-shaped flange 20 provided with a
depending skirt portion. In fact, the thickness of the flange 20 is
less than half the thickness of the wall of tubular piston 18. In
this regard, the thickness of the flange 20 is in the order of
0.005 to 0.015 inches. Moreover, the flange 20 is provided with a
large surface area for dependable but light sealing contact with
the inner wall 10a of the container 10.
The container 10 is closed by a bottom wall 22 having a central
opening having a sealing grommet 24 through which a gas 26, such as
nitrogen, is introduced after the viscous product 16 and the piston
18 are inserted into the container. The gas 26 presses against the
interior surfaces of the top of piston 18 as well as in the space
A, beneath flange 20 and between the outer vertical walls of the
piston and the inner wall 10a of the container 10. It will be
apparent that the pressure of the gas 26 present in the space A
will force the thin resilient flange 20 into light sealing contact
with the inner wall 10a of the container 10.
The flange 20 may be separately secured or may be integral with the
vertical wall of the piston 18 at various selected locations on the
vertical wall of the piston; such a modified location of flange 20
is suggested by dashed outline in FIG. 2.
It will be noted that the space A, which permits the easy loading
and operation of piston 18 in container 10, functions to provide
room for the lateral expansion of the piston 18 especially when
oily-type or flavored products are loaded in the container, and the
piston expands due to the absorption of oils from the product. In
that event, the resilient flange 20 is even further flattened
against the inner wall 10a of the container 10; however, the light
sealing pressure created by the resilient flange continues to seal
the propellant from the product, but permits the piston 18 and
associated structure to move smoothly in the container 10.
FIGS. 3 and 4 show an alternate type of piston 28 which is
double-acting. This piston is provided with a thin resilient,
annular flange 30 provided with a depending skirt portion, as
already described in connection with FIGS. 1 and 2, as well as an
additional annular flange 32 provided with a depending skirt
portion, which is seen, in the left-hand fragmentary view of FIG.
3a in the unloaded state of the container 10, to be vertically
self-supporting. The loaded condition of the piston 18 in the
container 10 is depicted in the right-hand fragmentary view of FIG.
3b. Thus, when the loaded condition occurs, pressure of the product
on the flange 32 of the upwardly moving piston 28 causes the flange
to bend backwardly against the inner wall 10a of the container 10.
Consequently, the piston structure shown in FIGS. 3 and 4 results
in an arrangement which double-seals the piston flanges against the
container wall. Moreover, the vertical body wall of the piston 28
is provided with a reduced portion 19 at the top thereof which
permits substantially all of the product present to be dispensed
through the valve 12.
The nature of the thin resilient flanges 20-30-32 is to flex in and
out of any indentations and over any projections or other
imperfections that might be present on the interior wall surfaces
of the pressurized container.
FIGS. 5 and 6 show another modification of the present invention in
which like parts bear the same reference numerals applied to the
structure shown in FIGS. 1 and 2. In this embodiment, the container
10 is the type which is loaded with the product from the top of the
container since the bottom and sides of the container are integral,
the top panel 11 of the container being chime-connected to the
cylindrical body 10, as shown. As seen in FIG. 5, the entire top
unit with a valve assembly is inserted on the cylindrical can after
the product is loaded through the top of the can. It will be noted
that the upwardly projecting thin annular flange 20a provided with
a depending skirt portion is normally in a position adjacent to the
inner wall surface 10a which may include an actual light engagement
of this wall surface by the flange; flange 20a extends no further
upwardly than substantially to the geometrical projection of the
upper surface of the piston 18, as is apparent in FIG. 6.
Top-loading of the product 16 to be dispensed forces the upwardly
projecting thin annular flange 20 a against the inner wall surface
10a of the container 10; this sealing force and action are enhanced
upon closure of the top end 11 and subsequent pressurizing of the
container in the manner already described, so that a tight seal is
achieved between the piston 18 and the product 16 to be dispensed.
The propellant gas 26 present within the hollow piston 18 moves the
latter upwardly when the valve 12 is opened. Thus, as seen in FIG.
6, when the piston 18 reaches the end of its travel upwardly
against the conical top part 11 of the container 10, the flange 20a
is fully accommodated and remains sealingly engaged to the
cylindrical body 10; and substantially all of the product in the
container 10 is expelled therefrom. It will be understood that the
same result is achieved for the bottom-loaded configuration of FIG.
3 by eliminating the lower annular flange 30 from the FIG. 3
construction, and thereby relying on only the additional annular
flange 32 formed integral with the piston 18.
In the modification of FIG. 7, the cylindrical body of piston 18 is
slightly reduced, at 18', i.e., at overlap with flange 20a, to
provide a greater local radial clearance A' with flange 20a for
products of relatively high viscosity. The larger clearance of A'
will be understood to be readily fillable, without voids, for such
products.
FIG. 8 provides illustrative detail for the FIG. 5 organization
applied to a container of medium or relatively large diameter. The
conical end wall 11 is tapered, as in the range of 35.degree. to
55.degree. and, preferably, at approximately .pi./4 radian to the
container axis, terminating at a neck bead or shoulder 33 at the
central opening. Shoulder 33 serves to frictionally retain the
skirt of a removal nozzle-protecting closure cap 34, as will be
understood. An elastomeric grommet-like fitting or bushing 35 is
locked to the reduced central end of wall 11, and the dispensing
stem 14 of the valve is, in turn, locked to the fitting 35. More
specifically, the fitting 35 is held at a reduced circumferentially
continuous groove or waist 36, between an upper shoulder portion 37
and a lower conical flange portion 38, the latter including a
substantial downwardly and outwardly projecting region that is
relatively free of back-up connection to the central or main
generally cylindrical body portion 39. To facilitate longitudinal
assembly of fitting 35 via the interior of the container, the
shoulder 37 is upwardly tapered to a reduced nose-end diameter at
40, well within the diameter of the opening of wall 11, the taper
angle being less with respect to the central axis of the container
than the slope angle of the conical end wall 11.
To complete the description of valve structure, the stem 14 has a
central product-dispensing passage 41 which terminates at, but does
not extend through, an enlarged integral head 42. Head 42 and a
shoulder 43 define longitudinal limits of a reduced cylindrical
body 44 which is retained by the bore of fitting 35, and one or
more radial passages 45 open the lower end of passage 41 within the
bore of fitting 35 and adjacent head 42. Preferably, the lower
exposed surface of head 42 is spherical, as shown, about a center
which approximates the instantaneous center 53 of tilt displacement
of stem 14.
The closed end of the body of piston 18' (FIG. 8) is characterized
by a conical portion 46 conforming in slope to the taper of wall
11. A spherically dished central portion 47 conforms to the exposed
contour of head 42, and a flat radial annulus 48 integrally unites
the portions 46-47, in close proximity to the lower limit of flange
38. FIGS. 10 and 11 provide further detail, revealing the
cylindrical body of the piston as a relatively thin peripheral
shell or skirt 49, integrally reinforced at regular angular
spacings by thin elongate and radially inward stiffening ribs 50.
The juncture of the still thinner suspension and seal flange 20a
may be continuous with the shell 49, the upper edge of flange 20a
being substantially within the geometric projection of the outer
surface of the conical portion 46, as shown.
The arrangement of FIGS. 9 and 12 illustrates how precisely the
same dispensing valve and its supporting structure may be made to
serve containers of smaller diameter. For this reason, the same
reference numbers are used, where applicable. However, in view of
the smaller container diameter, the conical upper end wall 11' is
similarly limited, to the extent that flange 38 extends so near the
lower (outer) end of wall 11' that it is impractical to form a
conical portion in the closed end of piston 18". The end-wall
portions 47-48 are thus directly connected at a rounded corner 51
to the relatively thin cylindrical skirt 49', backed by ribs 50,
and the upper edge of the flange 20a lies substantially within the
geometrical projection of a cone sloped to match the slope of the
container end 11' and tangent to the piston corner 51.
In the carrying out of my invention, the axial extent of the waist
37 of fitting 35 preferably exceeds, as by 0.020 to 0.030 inch, the
corresponding axial extent of the bore of the can opening in which
it is retained, and the unstressed conical angle of flange 38
preferably slightly exceeds, as by 5.degree., the conical slope of
end wall 11; thus, for a wall 11 of 45.degree. slope from the
container axis, the unstressed slope of flange 38 is preferably
substantially 50.degree.. This relationship will be understood to
facilitate assembly of a stem 14 and its fitting 35 to the wall 11,
while assuring resiliently loaded, peripherally continuous
contour-adapting fit of flange 35 to adjacent lapped areas of wall
11.
Several important advantages will be seen to flow from the
described cone-to-cone fit at 38-11, quite aside from the assembly
feature just noted. For example, valve operation is more easily
controlled, and the precision of valve actuation is enhanced. In
operation, the fitting 35 serves as a resilient pivotal suspension,
stem 14 being tilted about an instantaneous center (suggested by
point 53 in FIGS. 8 and 9) within the waist region 36. Initial
tilting movement is not stiffly opposed, since the root end of
flange 38 is in slight clearance relation with the wall 11 near the
central opening thereof; furthermore, flange 38 can be said to have
a somewhat tangential connection to body 39 (in the sense about the
instantaneous pivot center 53) so that flange 38 is either locally
pulled down or pushed outward along wall 11, in the course of its
sliding adaptation to the magnitude of tilt actuation. Stated in
other words, for normal desired extents of valve-stem tilt, there
is no substantial shear-force development between body 39 and
flange 38. Additionally, the employment of a small-diameter
container (e.g., a 1 -inch diameter container, as in FIG. 9), or of
a larger-diameter container (e.g., a 1.5-inch or larger diameter
container, as in FIG. 8), both with conically tapered end walls 11
(11'), means greater facility for index-finger actuation of stem 14
while grasping the container body with the remaining fingers of the
same hand. Still further, the use of a conical end wall (11)
inherently provides more extensive area, within a given limiting
container diameter, to accomplish extensive resilient overlap of a
seal flange, such as the flange 38 of fitting 35.
As to the piston 18 (18'-18"), the employment of a conical tapering
portion (for the larger sizes), and the use of the particular
spherical-surface relationship described in connection with
42-47-53, means less axial draft in the formation of the piston end
wall, while achieving a contour which can assuredly expel virtually
all the viscous product. The seal skirt or flange 20a is initially
of preferably slightly less diameter (e.g., 0.002 to 0.005 inch)
than the container bore and has a length B.sub.1 in the order of
one third the piston length L (FIGS. 11 and 12), the axial extent
B.sub.2 of the portion in contact with the container wall being in
the order of one-quarter of the length L. The clearance C between
flange 20a and the piston body shell 49 is in the order of 0.040
inch, for the 1-inch and 1.5-inch sizes thus far mentioned, wherein
the ratio of overall piston length L to overall piston diameter D
is less than unity, being preferably approximately 3:4; stated in
other words, the radial offset of the tubular flange 20 from the
body structure or shell 49 is in the order of 5 to 15 percent of
the outer radius of flange 20, being preferably no greater than
substantially ten percent of this outer radius. In these
circumstances, the piston advances with uniform ease and
smoothness, even though it may have cause to tilt or slightly
misalign, in the course of its travel. The lower end of the piston
body shell (49) always provides a limit to the possible tilt, and
throughout the range of tilt angles, the seal flange 20a maintains
a smoothly continuous circumferential seal between the gas-pressure
region 26 and the viscous-contents region 16. Also, the spherical
conformity of the convex and concave surfaces 42-47 and their
relation to the instantaneous center 53 for stem (14) tilt will be
seen as assuring no interference with smooth control of tilt of
stem 14 (with related smooth control of discharged product flow)
upon approach to final discharge of the container, and regardless
of whether or not piston 18' (18") may have been slightly tilted in
the course of such approach.
Quite aside from the foregoing considerations, the top-fillable
embodiments of the invention (FIGS. 3 to 12) present the obvious
advantage of square supportability for the container bottom, and by
introducing product over the central region of the top of piston
18, the product must then flow radially outward, to fill the
clearance A' and to deflect flange 20a into assuredly sealed
relation with body wall 10a before the level of loaded product
rises above the top of flange 20a. Pressure loading of the
underside of the closed container immediately upwardly displaces
product and piston, to produce a much reduced pocket of compressed
air local to nozzle 12, and sealing contact with the container wall
is never jeopardized, thus assuring against product leakage into
the pressurized-gas region 26. Also, in the event that freon or
other gas-producing liquid is relied upon for propellant purposes
in region 26, the mere development of gas pressure is found to be
adequate to assure leakage of such propellant liquid into
contaminating contact with the product. Product quality,
dischargeable product volume, and gas pressure are thus found to be
maintainable for substantially increased shelf life of the filled
package, as compared with prior constructions and methods.
Quite aside from and in addition to the foregoing, it will be noted
that by reason of equilibrium between hydrostatic pressure in the
product region and gas pressure in the pressure region 26, in
conjunction with the convergent resilient conical annulus (e.g., at
38-39, in bushing 35) between the conical end wall 11 and the valve
stem 44, a residual pressure loading is automatically established
in the upward direction and over the inwardly exposed effective
area at 38-39-42, resulting in a strong axially upward wedging
force on bushing 35, such that substantially continuous and highly
effective seal action exists as between bushing 35 and container
end 11, and between bushing 35 and stem 44. This strong and
effective seal action is achieved as long as valve 12 is closed and
as long as product remains to be dispensed, and regardless of the
fractional extent to which product may have been dispensed; such
seal action is a direct result of the indicated geometry of
structural relation and of the indicated method steps which result
in pressure-loading of the product.
While the invention has been described in detail for preferred and
illustrative contexts, it will be understood that modifications may
be made without departure from the scope of the invention.
* * * * *