Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~32~7~
13 December 1988
12 640
Prof~ Dr. Wolfram Schiemann, Eugen-Nagel2-Str 17, 7140
Ludw;gsburg
PLASTIC-CANISTER SCREW CLOSURE
The invent;on relates to a device according to
the preamble of the ma;n Cla;m.
When a can;ster ;s emptied, sooner or later as
much air has to flow in as liquid flows out ~rom its
pour;ng nozzle. The most common canisters are 5 l canis~
ters, 10 ~ canisters and 20 l canisters. Of course,
these litre figures are only approximate and need not be
precisely correct. The 5 l and 1û l canisters of p~astic
are only available with screw closure, because a claw
c~osure would be too elaborate in this case, and for
other design reasons. xn the case of the 5 l canister,
often the chance of glugging is taken, ~hich disrupts
the pouring operation and is due to the fact that, when
there is sufficient negative pressure in the canister,
the air is sucked in through the pouring spout~ during
which time no liquid, or very little l;quid, can flow out
from the pouring nozzle.
There are a considerable number of pouring nozzles
for 5 l and 10 l can;sters ~h;ch have a;r return tubes
;nside. If no liqu;d is to pass through these, but air
;s to flow ;n, they must be at the top during pour;ng.
There are two approaches to how to accomplish th;s:
a) The manufacturer of the canister always produces the
external screw thread - and has done so for many years
- such that the start of the thread is a~ays ;n the
same p~ace. With such a can;ster he supplies a pour;ng
spout, the screw socket ~ith internal thread of wh;ch,
firmly connected to the spout, has such an ;nternal
thread that, with pouring spout tightened liquidt;ghtly,
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- 2 - ~ 3~1.77~
the air tube is at the top~ This has the disadvantage
that production has to be kept very a~curate. In add;-
tion, the pouring spout - even if it is ;njection-
moulded - is nevertheless ~o compL;ant ;n the thread
reg;on that the screwing movement cannot be stopped
exactly when the a;r tube is at the top. The angled-
off end region of the pour;ng spout then faces to the
side~ Such ;naccuracies in the screwing end stop may
also be due to the fact that the seal ~ears out, is
lost or the l;ke.
b) T~o-part pouring spouts in ~hich the screw ring is a
separate part are produced. Then the spout can in
fact be held firm in the correct position. The start
of the external thread is thus not critical in this
case. There is the disadvantage, ho~ever, that many
people are uninformed about f~ow cond;tions and, ;n
spite of the actually existing possibility of doing
it correctly, the air tube is not at the top. In
add;tion, a two-part des;gn, with all its disadvant-
2û ages such as seaLing points, stock keep;ng, lose-
ab;l;ty etc., suffers cons;derable disadvantages.
The two parts also have to be produced by different
technologies. The screw socket must be inject;on-
moulded, while the actual spout is usually blow-
moulded. Examples of the different pour;ng spouts
~hich can be screwed on to screw-on closures of p~as-
tic canisters are found, for exampLe, in West German
Utilitr Mode~ 1808610, in German Patent Spec;ficat;on
3508320, in German Patent Specif;cation 193û9û6.
In the case of 20 l canisters, the air return can
only be disregarded as far as lo~-grade canisters are con-
cerned. For industrial purposes, military purposes or
the purposes of emergency services, the canisters must
have an air tube which reaches ~rom the pouring nozzle
into the rear regions of the canister. The canister's
own ~ent;ng open~ out in the end face of the pouring
nozzle of the canister. If a claw closure is fitted on-
to the pouring nozzle, and if ~he pouring device like-
~ise has claws, the spatia~ relative arrangement of a
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certain place on the end face of the pouring nozzle and any air
tube there may be in the pouring spout is provided a~ a matter of
course. The air flowing in then reliably flows from the mouth of
the spout to the end of the canister's own air tube~
However, claw closures are expensive. Some people do
not understand their operation. They have more individual parts
than screw closures. A screw-on spout has, however, the
threading disadvantages mentioned above in relation to 5 litre
and 10 litre canisters and consequently it is not possible to
empty a screw-closure canister in a simple way. This is of much
greater disadvantage with 20 litre canisters than with 5 litre
and 10 litre canisterS~ because in the case of the former it
takes much longer until it is empty.
The object of the invention is to specify a device by
which such canisters as well can be emptied easily, the pouring
nozzles of which bear a screw closure with external thread.
Accordingly, in a broad aspect, the present invention
relates to a screw closure for a plastic canister, the plastic
canister having a pouring nozzle that bears an external screw
2~ thread and one air venting through hole in a wall of the pouring
nozzle, which opens into an end face of the pouring nozzle and
leads to inside the canister, the æcrew closure comprising a
sCrew closure shroud with an internal thread complementary to the
external screw thread on the plastic canister and coaxial to a
geometrical longitudinal axis of the screw closure; a screw
closure bottom substantially perpendicular to the geometrical
longitudinal axis; a coaxial annular wall having an outer wall
region, emerging from the bottom and extending distance shorter
than the shroud; a coaxial sealing ring with an inner region held
in defined contact by the outer wall region of the annular wall,
and defining a sealing plane for the pouring nozzle, the
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1 32~776
improvement wherein (a) the annular wall resists radial forces
from deforming the pouring nozzle, (b) on the far side Of the
sealing ring relative to the sealing plane, the screw closure
5 bottom has an annular channel that ls arranged coaxially, is open
away from the screw closure bottom and extends widthwise between
the annular wall and the shroud, (c) at least one through air
hole is provid~d in the screw closure bottom and is positioned
within the annular channel, (d~ a liquid outflow hole is provided
in the screw closure bottom within the annular wall, (e) down-
stream of the li~uid outflow hole, a flexible pouring spout is
connected in liquid-tight manner to the screw closure, (f) in a
screwed-on position the sealing ring engages with an inner
surface of the pouring nozzle, and (g) the annular channel is
1~ defined between an inner surface of the shroud and the outer wall
region of the annular wall and communicates with the air venting
through hole.
In another broad aspect, the present invention relates
to a screw closure for a plastic canister, the plastic canister
having a pouring nozzle that bears an external screw thread, the
screw closure comprising a screw closure shroud with an internal
thread complementary to the external screw thread on the plastic
canister and coaxial to a geometrical longitudinal axis of the
screw closure, a screw closure bottom substantially perpendicular
to the geometrical longitudinal axis; a coaxial annular wall
having an outer wall region, emerging from the bottom and
extending a distance shorter than the shroud, a coaxial sealing
ring with an inner region held in defined contact by the outer
wall region o the annular wall, and defining a sealing plane for
the pouring nozzle, the improvement whsrein (a) the annular wall
resists radial forces from deforming the pouring nozzle, (b) on
the far side of the sealing ring relative to the sealing plane,
the screw closure bottom has an annular channel that is arranged
coaxially, is open away from the screw closure bottom and extends
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widthwise between the annular wall and the shroud, (c) at least
one through air hole is provided in the screw closure bottom, one
end of which communicates with the annular channel, (d) a liquid
outflow hole is provided in the screw closure bottom within the
annular wall, (e) downstream of the liquid outflow hole, a
flexible pouring spout is conneGted in liquid-tight manner to the
screw closure, (f) the sealing ring has an outer wall region that
reaches at most up to the inner rim of the annular channel, and
(g) the sealing ring is an O-ring, the outer wall region of the
annular wall holds the o-ring is a coaxial annular groove, and
the O-ring lies in the annular groove under prestress.
In another aspect of the present invention the annular
wall does not yield to the pressure which occurs during screwing
of the device onto the pouring nozzle. It is then not necessary
to strengthen the annular wall in another way, for example by
inserted reinforcing rings or the like.
According to another aspect, it is easier for the
device to find its position relative to the screw closure.
Further features allow the sealing ring to be made
small and prevent it inadvertently covering the canister-side
vent opening and the air flow resistance remains sufficiently
small.
Other features keep the annular channel completely
clear.
According to additional features an optimum sealing
ring is provided, which is offered on the market as a standard
product, which is well-sealed with respect to the annular wall as
well, which is easy to keep and which, due to its round shape,
has a slide-on side, so that it adapts easily to different forms
of the inner, downstream coxner region of the pouring nozzle.
Other features reduce the risk that the O-ring slips
out of from its annular groove. In addition, the centring wall
centres in the pouring nozzle.
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-5a-
Aspects of the present invention make it easier to
produce the annular channel, all that is needed is a single air
hole, the air can flow to the air hole from both sides. This
solution is easier to provide than a plurality of annular channel
segments which do not intercommunicate, or only to a small
extent, and then to provide just as many air holes.
Features of the present invention allow the necessary
strainer to be accommodated easily and in a secure position.
Other features provide a buckling-resistant transition
from the screw-closure bottom to the pouring spout and a
sufficiently long distance to take care of liquidtightness and to
accommodate the strainer.
Other features of the present invention provide a very
stable device, which is much more stable than a multi-part
device. It is also easier to produce.
Other features make the device also mechanically
stronger, although it can also be blow-moulded for example.
Additional features allow on the one hand little
rethinking to be necessary in operation and on the other hand to
a great extent those designs for injection moulds or blow moulds
to be retained which are also used with the known screw closures,
so that mould making becomes easier. In the optimum case, there
is then little change in many respects from the hitherto usually
used sealing screw closures.
Also, features of the present invention allow these
advantages to be applied to 20 litre canister technology. Then
the pitch of the thread turns does not have to be recalculated,
the contact pressure conditions are known, as is the space
requirement of the canister with the device according to the
invention or else with a sealing screw closure, and it can be
assessed whether the injection moulding has constrictions or not
etc.
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-5b-
Further features lead to designs which have proved very
successful for a 20 litr~ canister without excessively weakening
the scr2w-closure bottom, without using too much material and
without excessively increasing the resistance to outflow.
~ he invention is now explained with reference to a
preferred exemplary embodiment.
In the drawings:
Figure 1 shows the side view of a three~handle
canister, partly broken away, and with a venting tube, but
without its screw-closure cover;
Figure 2 shows the plan view equivalent to Figure 1;
Figure 3 shows a representa~ion to scale of the device
according to the invention, partially in section and broken away,
before screwing onto the pouring nozzle of the canister, whi~h is
represented as partially broken away and in section.
A canister 11, blow-mGulded from plastic, has a nominal
capacity of 20 litres. It has three handles 12, which merge at
their rear end with a bulge 13. Their front end merges with a
~0 bevel 14, from which a pouring nozzle 16 emerges, which is
substantially rotationally symmetrical with respect to a
geometrical longitudinal axis 17. The pouring nozzle bears an
external screw thread 18, which is relatively course, and a finer
internal thread. The pouring nozzle 16 has an outside diameter
(without the height of the thread turns) of 82 mm and the clear
diameter in the region of the internal thread 19 is 56 mm. The
internal thread 19 reaches not quite up to the end face 21 of the
pouring nozzle 16. Rather, according to Figure 3, there is
between the end face 21 and the internal thread 19, a run-out 22
for the last turn o~ the internal thread 19, into which run-out
22 there also reach however the outermost helical regions of the
final internal thread turn. The run-out 22 is thus not a smooth,
level recess which is completely rotationally symmetrical with
respect to the longitudinal axis 17. In the about
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132 L77~
1 c~ thick wall 23 of the pouring nozzle 16 there is,
according to Figure 2, at about 12 o'clock a through hole
24, which opens out ;nto the end face 21 and continues on
the inside of the bevel 14 in a plug-on peg 26. F;tted
onto it is a r;g;d venting tube 27, the ;nner end 28 of
which oPens out in the region of the bulge 13, that is in
a region which, with a normally filled canister 11 tilted
for pouring, lies some~here in the residua~ air of the
canister 11. If such a canister is poured out, ~;quid
flo~s out of the opening 29 of the pouring nozzle 1~. At
the ~pening 31 of the pouring nozzle 16, air ;s sucked in,
which flows through the through hole 24, through the
~enting tube 27 to the end 28.
According to Figure 3, a dev;ce 32 has a shroud
33, uhich is coax;a~ to the geometrical longitudinal axis
17 and bears on its inside an internal thread 34, which
can be screwed onto the external thread 18 of the pouring
nozzle 16. In the left outer end region, the shroud 33
bears the usual protuberances 36, ~hich serve for the
better transference of force for the hand of a user. The
shroud 33 merges with a bottom 37, which is perpendicu~ar
to the ge~metrica~ longitudinal axis 17 and from which an
annular wal~ 38 emerges integrally to the right, accord-
;ng to Figure 3. All regions of the annular walL 38 are
2S coaxial to the longitudinal axis 17. An end face 39 is
a few millimetres wide and is perpendicular to the longit-
udinal axis 17. This is followed outwardly by a chamfer
41, which runs at 45 and merges on the outside ~ith a
circular-cylindricaL centring wall 42. This is fol~owed
30 to the ~eft by an annular groove 43, which receives in
about half of its inner circumference an 0-ring 44O The
outer cicumferential half projects outwards over the
centring ~all 42. Forcing away of the 0-r;ng 44 to the
~eft is guarded against by the inner surface 46 there of
the bottom 37, which forms a circular ring. The 0-ring
44 def;nes a seal;ng plane 47, ~hich lies some~hat to
the left or somewhat to the righ~ of ~he sealing plane
47 drawn ;n F;gure 3, depend;ng on the extent to ~hich
the said 0-ring is compressed~ To ~he left of the seal;ng
7 7 6
plane 47, no matter how far to the left the latter is even
in an extreme case, there is incorporated in the bottom
37 an annular channel 48, which merges with one side 49 ~ith
the inner surface 46, has a base 51 and reaches with its
outer side 52 up to the internal thread 34.
On the inside, the annular wal~ 38 is bounded by
a cy~;ndrica~ wall 53, which is coaxial to the longitu-
dinal axis 17 and merges by ~ 90 bend with the end face
39. The ~atter lies at about haLf the length of the
shroud 33. The diameter of the cylindrical wall 53 is
40 mm, wh;ch ;s st;ll quite considerably more than the
;nside d;ameter of a flex1ble spout 54, so that to this
extent the flow resistance is not reduced.
The ~aLl 53 tapers inwards by the same radius to
merge with the bottom 37, ~hich here has its original
thickness and loses about half of its thickness in the
region of the annular groove 43. Centrally and coaxially
to the longitudinaL axis 17, the bottom 37 has a through
hoLe 56 of about 22 mm diameter. To the left of this
lies a strainer 57, which is so fine-meshed that only liquid
wh;ch has the necessary degree of pur;ty can pass. Out-
s;de the rad;us of the through hole 56, there extends a
coaxial, circular-cylindrical holding socket 58. The
inner wall S of the latter holds the spout 54 liquid-
tightly. This is achieved by adhesive~ The insidediameter of the spout 54 corresponds approximately to
the diameter of the through hole 56. To the right, the
stra;nèr 57 cannot move out of place due to a step 61 and
to the Left the inner end face 62 of the spout 54 ;s in
the ~ay. The spout 54 is a protective tube of galvanised
steel, used for the Laying of eLectr;c cables, with PVC
sheathing and a cLear ~idth of 21.5 mm, as obtainabl~
under the designation SL-PVC from Messrs~ Albert Speck
~mbH & Co., of 7530 Pforzheim.
In order to be able to empty a canister 11, the
scre~ closure (not shown) is scre~ed off in the usual
~ay. Then the device shoun on the left ;n Figure 3 is
taken and scre~ed on in the same way as the closure cap
has previously been scre~ed off. During this operation,
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the device 32 already centres itself at about half way
along the internal thread 34 when screwing onto the
external screw thread 18, so that consequently the re-
quired position is already reached. In the event of pro-
duction inaccuracies, if the pouring nozzle 16 has becomecrushed or if there are any other inaccuracies of fit,
a precentring is obtained by the chamfer 41 at the run-
out 22 of the internal thread 19 and a complete centring
is obtained by the centring wall 42 On further screwing-
on, the O-ring 44 comes into contact with the upper region
of its inner surface 46, on the right according to Figure 3,
with the run-out 22 and is pressed increasingly against
the inner surface 46 until liquidtightness is established.
3epend;ng on the degree of screwing-on or the design, the
end face 21 then forms the continuation of the inner sur-
face 46 and terminates the annular groove 43 to the right.
The end 28 of the vent;ng tube 27 is then ;n connection,
;n terms of air, with the annular groove 43 and the latter
can suck air in via the through air hole 50. It is im-
material in this respect where the screwing movement ofthe dev;ce 32 ends, as the left end, according to Figure
3, of the through hole 2~ aLways opens out in the annular
groove 43.
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132~
SUPPLEMENTARY DI SCLOSURE
since the filing of the patent application to which the
supplementary disclosure relates, the applicant has developed
certain improvements to the invention, which shall be described and
claimed herein.
Canisters of the sort to which the applicants invention
relates are mass-produced articles and, owing to their method of
production, the manufacturing tolerances to be expected from them
are also not very high. They are used in widely differing
environments which, for example, can be at -40C to +75c. The
force with which the screw cap is tightened also varies widely.
When men are very tired and it is very cold, they have little
strength to spare. It is not always important that emptying of the
contents should proceed rapidly. Nevertheless, there are emergency
situations in which rapid emptying of the canister is important and
the ability to do this may be life-preserving. One need only
consider a situation in which, for example, fuel has to be
transferred from the canister to the tank on a swaying boat. If
this takes too long, even a strong man cannot hold the canister
balanced too long,. If the transfer takes too long, there is the
risk that the pouring spout will slip out of the inlet nozzle of
the tank and the fuel will miss, with all the danger~ that result
from this,,such as, for example the risk of explosion. Frequently,
it is also important to spill as little as possible, when the
canister is the last spare canister etc.
2~ A single through airhole 50 (see Figure 3) together with the
annular channel 48 is usually sufficient. However, if this through
airhole 50 is completely or partially blocked and\or if the annular
channel is completely or partially closed, the air no longer flows
back correctly and the abovementioned consequences can occur. For
various reasons, the cross-section of the annular channel 48 can
be reduced or completely closed in practice: ~or example enough
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il 32~7~
viscous fluid may get in-to it at very low temperatures; or i~ is
simply blocked; or its cross-section has been shut by some other
occurrence.
It iS the object of the improvement of this Supplementary
Di~closure to ensure good backflow of the air even in extreme
situations.
In a broad aspect, the improvement to the invention described
and claimed in the Applicant's application relates to a screw cap
for a device with an annular channel which opens away from the cap
base with at least one through airhole, which leads through the cap
base from the annular channel with an internal thread which matches
the external thread of a pouring nozzle of a canister, the screw
cap having a particular angular position relative to the pouring
nozzle at the end of the proces~ for screwing i~ on, and with a
through hole in the pouring nozzle characterized in that at least
two through airholes are pro~ided, which are arranged angularly
~ffset relative to one another.
Preferably, the angular spacing of the said through airholes
is between two and five airhole diameters. This allows optimum
~0 proximity between airholes 24 and 50 to be maintained, while
ensuring that the airholes in the cap are not so close ~ogether as
to weaken the cap and produce a predetermined breaking point on the
cap. Moreover, when they are sufficiently far apart, something
blocking one airhole does not necessarily block another. This is
2~ particularly the case when the airholes are spaced between two and
four diameters.
In a pra~erred embodiment, three through airholes are
provided. After screwing on of the cap, the central one will be
aligned with the through airhole in the canister. The other two
airholes in the cap come into effect in the event of extreme
tolerances in one direction or the other. This preferred
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132~7~1~
embodiment is accomplished by providing single start threads on the
cap and canister which, when tightened together align the middle
airhole on the cap with the through hole on the canister.
The improvement is now described with reference to an
illustrative embodiment. The drawings are on a scale of 1:1 and
values of interest may therefore be taken from it. In the
drawings:
Fig.4 shows the plan view of a screw cap without a pouring
spout, otherwise however being identical to the screw cap of the
main application;
~ig.5 shows a partially sectioned side view of the region of
the pouring nozzle of a canister.
A canister 11, blow-moulded from plastic, has a nominal volume
of 20 litres. It has a poring nozzle 16, which is essentiall~
rotationally symmetrical to a geometrical longitudinal axis 17.
The pouring nozzle bears an external screw thread 18 which is
relatively coarse. In the approximately 1 cm thick wall 23 of the
pouring nozzle 16 there is a through hole 24 which, during the
emptying of the canister 1l, is at the top, opens into the front
face 21 and, on the inside of a slope 14 of the canister 11,
continues in a mounting peg 26. Onto it is pushed a rigid vent
tube 27, the inner end of which opens in the volume which is
uppermost during the emptying of the canister. If such a canister
ll is emptied, liquid flows out of the opening 29 of the pouring
nozzle 16. Air is drawn in at the opening 31 of the pouring nozzle
16, said air flowing through the through hole 24, through the vent
tube 27 to the far end of the latter into the uppermost air volume
of the canister 11. On its lower side according to Fig.1, a screw
~.ap 32 has an annular channel 48 open towards the end ~ace 21 in
the use position. Into this there open three through airholes 50,
63, 64. Their diameter corresponds approximately to the width of
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~32~
the annular channel 48. Through airholes 63, 64 have an angular
spacing from airhole 50 of 30, as seen from the geometrical
longitudinal axis 17. Under normal conditions, i.e. in the central
range of the manufacturing tolerance, at normal temperatures and
in the case of normal screw-on forces, through airhole 50 is in
alignment with the opening 31. This is because an external thread
18, which is a single-start thread, has a thread start 66 which
coincides with the thread start 67 of an internal thread 19. The
internal thread 19 is likewise a single-start thread, with the
result that the through airholes 50, 63, 64 are always in the
region of the opening 31 with the screw cap 32 screwed on.
.
