Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Container having COz compressed gas source and overpressure burst safeguard
Specification
The invention relates to a container that can be filled with liquid and closed
in pressure-tight condition, and from which liquid can be withdrawn. Examples
of such containers are drums, small drums (party kegs) or cans, in which C02-
containing liquids, especially beverages, are filled under pressure. In
particular, it relates to party beer kegs.
The prior-art container according to EP 1642861 Al has an insert, which can be
fixed sealingly in an opening of the container and which is provided with a
high-pressure CO2 cartridge, a pressure-regulating valve for discharging COZ
therefrom and an externally accessible control element, which can be actuated
to pierce the high-pressure COZ cartridge.
Commercial pierceable CO2 cartridges in a size suitable for pertinent
contairiers contain approximately 16 g CO2 under a pressure of approximately
60
bar. The pressure-regulating valve of EP 1642861 Al ensures reduction and
precise regulation of the pressure under which the COz discharged into the top
space of the container is maintained. The pressure is typically between 0.7
and 1.3 bar. It is equal to or slightly higher than the partial pressure of
the CO2 dissolved in the liquid.
The present invention addresses the inherently improbable accident that the
pressure-regulating valve according to EP 1642861 Al will ever fail for some
reason, since it is possible for a gradual or even very rapid uncontrolled
pressure rise to take place in the container. Tests show that a conventional
party beer keg withstands an internal pressure of up to approximately 6.5 bar.
At approximately 4 bar, the party keg begins to bulge; the top end plate
and/or bottom end plate of the party key swell outward. At approximately 6.5
bar the party keg splits, usually because a folded seam joint between the
shell and the top end plate or bottom end plate of the party keg comes undone.
The remaining COZ escapes. The party keg empties out, possibly with a vigorous
CONFIRMATION COPY
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fountain of beer. This does not pose any danger to persons but may cause
property damage, and laborious cleanup work is needed.
From EP 1688813 Al there is known a container with a built-in pressure system,
which is provided with a high-pressure CO2 cartridge, a pressure-regulating
valve for discharging COZ therefrom and an externally accessible control
element, which can be actuated to pierce the high-pressure COz cartridge. The
pressure system is provided with an overpressure safeguard, which in the event
of an undesired pressure rise in the container opens a flow path from the top
space thereof through the pressure system to the atmosphere.
The overpressure safeguard according to EP 1688813 Al is composed of an
overpressure valve, which has a valve element in the form of an overpressure
tubing section and which shuts off or opens a complicated flow path via a
plurality of openings, bores and ducts. The structural complexity and the cost
prices of such an overpressure safeguard are high.
The object of the invention is to provide a container of the said type with an
overpressure safeguard that has simple construction and is functionally
reliable, and that in the event of an accident signals the customer that
something is not right with the pressure system within the container.
The overpressure safeguard that achieves this object bursts after exceedance
of an internal pressure at which the container visibly bulges, but before
development of an internal pressure at which the container splits. The
bursting part of the overpressure safeguard is a diaphragm on the wall of a
housing with which the insert protrudes into the container.
After bursting of the overpressure safeguard, the remaining CO2 is blown off
from the top space of the container via a well-defined flow path. Thus liquid
or foam does not escape, or at least does not do so to a noteworthy extent. If
any impairments at all occur as a result, they remain within limits. The
visibly bulging container signals to the customer that something is not right
with the pressure system within the container.
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In a preferred embodiment, the flow path for blowing off the CO2 leads through
an unsealed zone of the control element. For this purpose it is possible to
take advantage of existing unsealed zones, such as those of the control
element on the insert according to EP 1642861 Al, only slight modifications in
the structural design thereof being needed.
In a preferred embodiment, the overpressure safeguard is inactive before the
high-pressure COZ cartridge is pierced. The overpressure safeguard is
activated by the piercing of the high-pressure CO2 cartridge. In this way it
is ensured that the overpressure safeguard functions only if it is actually
used, specifically in the event of failure of the pressure-regulating valve.
In a preferred embodiment, the overpressure safeguard bursts at an internal
pressure of between 4.0 bar and 9.0 bar, preferably 4.5 bar and 7.0 bar, more
preferably 5.0 and 6.0 bar.
In a preferred embodiment, the diaphragm is braced against the control element
before the high-pressure CO2 cartridge is pierced. As soon as the high-
pressure C0? cartridge is pierced, the diaphragm is released from the control
element.
In a preferred embodiment, the diaphragm is countersunk into the insert. In
this way it is protected from damage.
In a preferred embodiment, the diaphragm is composed of elastic plastic. In
the event of an uncontrolled rise of the internal pressure, the diaphragm
undergoes increasing elastic deformation, until it bursts.
The invention will be explained in more detail hereinafter on the basis of an
exemplary embodiment illustrated in the drawing, wherein:
Fig. 1 shows a COz compressed gas source in longitudinal section; and
Fig. 2 shows the elastic plastic component of a detail II of Fig. 1.
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The CO2 compressed gas source is constructed as an insert, which fits in the
bunghole of a container, extends into the container and tightly closes the
bunghole. The container is filled under pressure with COZ-containing liquid
through the bunghole, which is usually disposed at the middle of its top end
plate. Thereafter the bunghole is closed with the insert.
To withdraw the liquid, there can be used an integrated outlet tap, which is
disposed on the side wall of the container at the height of the bottom end
plate thereof. The liquid flows out under the action of internal pressure and
gravity, until a reduced pressure is reached in the top space of the container
above the liquid surface therein. To adjust this correctly and maintain it in
controlled manner, the CO2 compressed gas source is activated. The CO2
compressed gas source injects CO2 into the top space of the container under a
pressure that corresponds to the partial pressure of the COz dissolved in the
liquid or that slightly exceeds this partial pressure. Thereby steady emptying
of the container is ensured. No air is admitted into the top space of the
container. The CO2 content of the liquid remains constant.
The insert has slender elongated shape, and for the most part is radially
symmetric relative to a central axis. It is made largely of plastic. The two-
component plastic injection-molding technique can be used for manufacture.
When the insert is in installed condition, closing the bunghole of the
container, it projects with a housing 10 into the container.
At its inside end housing 10 has a chamber 12 for receiving a high-pressure
CO2 cartridge 14 in a snug fit. The head of cartridge 14, at the end face of
which it can be pierced, is proximal to the bunghole.
Housing 10 is supported externally with a circumferential collar 16 on the
beaded rim of the bunghole. On collar 16 there is molded a seal 18, with which
the insert seals the bunghole.
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A rotary knob 20 countersunk in housing 10 protrudes outwardly beyond collar
16, and can be actuated to pierce C0, cartridge 14. Rotary knob 20 has a steep
male thread 22, with which it is screwed into a complementary female thread of
housing 10.
To pierce CO2 cartridge 14 there is used a piercing needle 24, which is
structurally combined with the valve member of a pressure-regulating valve.
The valve member is mounted together with an elastic diaphragm 26 at the
center of the axis of housing 10. The tip of piercing needle 24 is disposed
only a short distance from the end face of COz cartridge 14.
During axial positioning movement of piercing needle 24 on COZ cartridge 14,
the valve member lifts from a valve seat 28 of the pressure-regulating valve.
Valve seat 28 is made from elastic sealing material and molded onto housing
10.
Piercing needle 24 is urged by a slide 30, which is disposed between rotary
knob 20 and piercing needle 24. Slide 30 is guided in longitudinal sliding
relationship in housing 10. Upon actuation, rotary knob 20 is screwed forward
against slide 30, which is axially adjusted in the process.
A helical compression spring 32 is clamped between rotary knob 20 and slide
30. Helical compression spring 32 braces slide 30 against piercing needle 24.
Diaphragm 26 bounds a working space downstream from valve seat 28 of the
pressure-regulating valve. The working space has a lateral outlet opening, in
front of which there is disposed an elastic 0-ring 34. 0-Ring 34 has the
function of a non-return valve. It prevents liquid from entering the insert.
To pierce COz cartridge 14, rotary knob 20 is turned by approximately 90 .
Slide 30 is moved axially inward by the screwing thrust of rotary knob 20.
Piercing needle 24 is driven axially inward under elastic deformation of
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diaphragm 26. The valve member lifts from valve seat 28. After piercing, a
very small valve space upstream from the head of CO2 cartridge 14 fills with
CO2 under high pressure.
After rotary knob 20 has turned a complete 90 or more, slide 30 springs
axially back outward under the force of helical compression spring 32. For
this purpose it is actuated by piercing needle 24, which is retracted axially
by the elastic return deformation of diaphragm 26. Helical compression spring
32 is compressed. The pressure-regulating valve is closed and a small amount
of CO2 under high pressure is admitted into the working space. The compressive
forces of the COz on diaphragm 26 contribute to the spring-back of slide 30
actuated by the piercing needle.
Further opening and closing of the pressure-regulating valve is determined by
an equilibrium of forces across diaphragm 26, established by the elastic
properties of diaphragm 26, the spring constant of helical compression spring
32 and the C0~ pressure in the working space. The determining factor for the
pressure of the discharged CO2 is the spring constant of helical compression
spring 32.
Usually the user will activate the CO2 compressed gas source when the internal
pressure in the container has dropped so much that the stream of liquid
emerging through the outlet tap is too weak. However, the C0, compressed gas
source can already be activated beforehand without difficulty even if the
internal pressure in the container is still high, very likely even when the
user first attempts to operate the container at all. Introduction of COz into
the top space of the container does not take place as long as the high
internal pressure is acting on 0-ring 34 in front of the outlet opening.
The COz compressed gas source is equipped with an overpressure safeguard,
which becomes active if the pressure-regulating valve fails and COZ enters the
top space of the container at uncontrolled high pressure.
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The overpressure safeguard is made by injection-molding thermoplastic
elastomer (TPE) onto the wall of housing 10 just in front of the bunghole,
such that its part having the smallest material thickness forms diaphragm 36
countersunk in the wall.
Diaphragm 36 is in flush contact with the outer shell of rotary knob 20, which
has not yet been activated to pierce CO2 cartridge 14. For this purpose it is
placed on rotary knob 20 between two adjacent thread flights of male thread
22.
When rotary knob 20 is turned by 90 to pierce COz cartridge 14, a window in
the shell of rotary knob 20 becomes positioned opposite diaphragm 36. In the
event of an uncontrolled rise of the internal pressure, diaphragm 36 is able
to expand elastically into this window, until it bursts at the location of
smallest material thickness at approximately 5.7 bar. Thereby a flow path is
opened from the top space of the container at the shell of rotary knob 20;
this path is not absolutely leaktight relative to collar 16, and so the C0, is
able to flow out of the top space of the container to the atmosphere.
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List of reference numerals
Housing
12 Chamber
14 High-pressure CO2 cartridge
16 Collar
18 Seal
Rotary knob
22 Male thread
24 Piercing needle
26 Diaphragm
28 Valve seat
Slide
32 Helical compression spring
34 0-ring
36 Diaphragm
