Note: Descriptions are shown in the official language in which they were submitted.
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20434.2
Translation of PCT/EP02/06326 as filed on June 10, 2002
Dosing Device in a Tube Filling Machine
The invention concerns a tube filling machine dosing device having a
dosing chamber which is formed in a housing with an inlet opening and
an outlet opening for a medium to be dosed, at least one adjustable
dosing piston by means of which the volume of the dosing chamber can
be changed, and a control sleeve which is rotatably disposed in the
housing and has at least one connecting channel which, in a
predetermined rotated position of the control sleeve, connects the inlet
opening or the outlet opening with the dosing chamber, wherein the
control sleeve has a conical section which can be sealingly disposed on
a complementary conical section of the housing and can be lifted
therefrom.
A tube filling machine fills tubes with a predetermined dosed amount of
a product or fill medium, and usually has a conveyor device formed as
an endless belt or chain which carries a plurality of individual
receptacles for each tube. The empty tubes are inserted into the
receptacles of the conveyor device at a feed station and pass several
work stations, including, in particular, a filling station and a subsequent
closing station. The tubes are filled in the filling station via a filling
pipe
which is connected to a fill medium storage means via a dosing device.
The filled tube is transported to the closing station where the upper
tube end is closed.
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A dosing device of conventional structure (DE 36 36 804 C1) comprises
a housing which is connected to the fill medium storage means via an
inlet opening and to the filling pipe via an outlet opening. A control
sleeve is rotatably disposed in the housing, and a dosing chamber is
formed inside the sleeve which has an access opening alternately
connected to the inlet or outlet opening in dependence on the rotated
position of the control sleeve. A dosing piston is displaceably disposed
in the control sleeve and can draw a predetermined amount of the fill
medium through the inlet opening into the dosing chamber when the
outlet opening is closed and which can discharge it through the outlet
opening when the inlet opening is closed thereby introducing it into the
tube to be filled. The alternate opening and closing of the inlet and
outlet openings is effected through rotation of the control sleeve.
The control sleeve is sealed relative to the housing via annular seals,
and also has a conical section which abuts a complementary conical
section of the housing. The control sleeve is closed at its one axial end
and connected to an adjustment device through which it can be axially
adjusted to separate the two conical sections.
It is usually necessary to replace the dosing piston when the amount of
fill medium dose is to be changed, which is demanding and expensive
since the tube filling machine is inoperative during this time. It is even
more demanding when, after filling a i=Irst fill medium, change to
another fill medium is to take place, since, for hygienic reasons, the
filling unit and therefore also the dosing device must be completely
cleaned of residues from the first fill medium. In one conventional
solution to this problem, the dosing device is completely removed from
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the tube filling machine and cleaned by an operator, as a result of which
the cleanliness depends on the quality of the work of the operator.
Alternatively thereto, DE 36 36 801 CI suggests axial displacement of
the control sleeve through the adjustment device to such an extent that
the housing, the control sleeve, and the dosing piston are brought from
the normal working position to a cleaning position in which they are
separated from another to expose the seals coming in contact with the
fill medium being dosed. Through introduction of a cleaning liquid, the
components and seals can be cleaned from the residues of the
previously applied fill medium. The space required for the adjustment
device is very large and it has turned out that the seals are subjected to
great wear through the cleaning process and therefore must be
replaced frequently which is also time-consuming and expensive.
It is the underlying purpose of the invention to create a dosing device of
the above-mentioned type which is of compact construction and permits
product change in a simple fashion.
This object is achieved in accordance with the invention with a dosing
device of the above-mentioned type which has the characterizing
features of claim 1.
In the inventive dosing device, the seal between the control sleeve and
the housing is provided only or at least mainly through the sealing
abutment of the conical sections of these components. In this fashion, a
reliable and permanent seal between the control sleeve and the housing
can be obtained when the two conical sections are pressed together. To
release the two abutting conical sections, only the control sleeve must
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be slightly axially displaced thereby forming a gap between the conical
sections which can be rinsed with a cleaning liquid. The control sleeve is
subsequently displaced in the opposite direction until the two conical
sections of the control sleeve and of the housing once more abut in a
sealing fashion. In this manner, special elastic plastic seals can be
avoided thereby also eliminating the danger of excess wear and the
necessity of changing the seal.
A particularly compact design of the dosing device is obtained when the
control sleeve has an axial opening in which at least one dosing piston
is displaceably guided. A piston section of the dosing piston is received
with tight fit and thereby sealed in the axial opening such that no
special plastic seals are required.
At least portions of the dosing chamber are disposed to face the broader
end of the conical section of the control sleeve. When the fill medium
located in the dosing chamber is pressed via the dosing piston through
the outlet opening into the filling nozzle and thereby into the tube, the
pressure in the dosing chamber increases. In accordance with the
invention, this pressure is used to press together the two conical
sections of the control sleeve and the housing thereby ensuring the
sealing effect between the housing and the control sleeve while also
increasing the dosing accuracy for products of low viscosity.
Particularly good sealing properties can be obtained when the housing
and/or the control sleeve and/or the dosing pistons are made from a
ceramic material.
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In a further development of the invention, two coaxial dosing pistons
are provided of which the first dosing piston is formed as an annular
piston guided in the axial opening of the control sleeve and having an
axial bore in which the second dosing piston is displaceably guided.
This embodiment has the substantial advantage that the amount of fill
medium supplied to the tube via the outlet opening of the dosing
chamber can be changed in a simple fashion without changing the
dosing piston. When the two coaxial dosing pistons are displaced as a
unit, a relatively large amount of fill medium is supplied. When the
outer first dosing piston of annular cross-section is stationary and only
the inner second dosing piston is adjusted, a substantially smaller
amount of fill medium is discharged. Alternatively, the inner second
dosing piston may be stationary and only the outer annular first dosing
piston is adjusted thereby supplying another amount of fill medium
which is advantageously larger, preferably twice as much as the amount
of fill medium supplied by the inner second dosing piston only. Each
dosing piston preferably has its own drive, preferably in the form of a
servo motor.
A further development of the invention provides that a rinsing chamber
of an enlarged diameter is formed in the axial opening of the control
sleeve in which a piston section of the first dosing piston can be
received with play, wherein the rinsing liquid can be supplied to the
rinsing chamber via at (east one feed opening. In the cleaning position,
the annular first dosing piston is displaced within the axial opening of
the control sleeve such that its piston section is freely exposed in the
rinsing chamber. The inner second dosing piston thereby remains
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stationary and therefore projects freely from the displaced first dosing
piston such that it can also be cleaned upon introduction of a rinsing
liquid.
When the control sleeve is axially displaced, the two conical sections
come out of engagement and a gap is formed between the housing and
the control sleeve which can be rinsed with a rinsing liquid to clean the
dosing device. The rinsing liquid is preferably introduced through a
separate supply opening which is formed in the foot region of the
conical section of the housing.
In a possible embodiment of the invention, one end of the control
sleeve projects into the dosing chamber and the channel connecting the
dosing chamber to the inlet or outlet openings is formed in a
straightforward manner by an axial groove which terminates at the end
of the control sleeve.
Although one connecting channel or one axial groove is sufficient to
optionally connect the inlet opening or the outlet opening to the dosing
chamber, it is reasonable to provide at least two connecting channels or
axial grooves, to obtain as small and rapid adjustment motion of the
control sleeve as possible, the channels being disposed such that there
is no position in which both the inlet opening and the outlet opening are
simultaneously connected to the dosing chamber.
The conical section of the control sleeve is preferably formed on the
axial end projecting into the dosing chamber, wherein the axial grooves
are also provided in the conical section of the control sleeve.
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Further details and features of the invention can be extracted from the
following description of an embodiment with reference to the drawing:
Fig. 1 shows a vertical section through an inventive dosing device in
the initial position;
Fig. 2 shows a top view onto the dosing device in accordance with Fig.
1, with removed lid;
Fig. 3 shows the dosing device of Fig. 1 at the end of the suction cycle;
Fig. 4 shows a top view onto the dosing device of Fig. 3, with removed
lid;
Fig. 5 shows the dosing device of Fig. 1 at the end of the supply cycle,
Fig. 6 shows a top view onto the dosing device of Fig. 5, with removed
lid;
Fig. 7 shows the dosing device of Fig. 1 at the end of the suction cycle
in a first alternative operating mode;
Fig. 8 shows the dosing device of Fig. 1 at the end of the suction cycle
in a second alternative mode of operation; and
Fig. 9 shows the dosing device of Fig. 1 in the cleaning position.
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In accordance with Fig. 1, a dosing device 10 in a tube filing machine
has a housing 11 which is held on a support 17 (not shown in detail).
An axial bore 12 is formed in the housing 11 which extends in a smooth
conical manner in the upper region of the housing 11. The interior of
this conically extending section 12a of the axial bore 12 defines a
dosing chamber 13 which is sealingly closed at the upper end of the
housing 12 by a lid 16.
A radial inlet opening 14 is formed in the housing 11 in the central
region of the conical section 12a, through which a fill medium can be
introduced into the dosing chamber 13 (indicated by arrow M). A radial
outlet opening 15 is formed in the housing 11 diametrally opposite to
the inlet opening 14, through which the fill medium can be pressed from
the dosing chamber 18 to a filling nozzle (not shown in Fig. 5) as
indicated by arrow F. A radial bore ila is formed in the lower region of
the conical section 12a, i.e. in the transition region between the axial
bore 12 and the conical section 12a thereof, which is connected to a
supply of rinsing liquid (not shown).
A control sleeve 18 is inserted into the axial bore 12 of the housing 11,
which is seated with a lower circular cylindrical section with tight fit in
the axial bore 12, and has a conically extending section 18a at the
upper end which has the same slant angle as the conical section 12a of
the axial bore 12. The dosing chamber 13 is formed between the upper
end of the conical section 18a of the control sleeve 18 and the iid 16.
Fig. 1 shows the control sleeve 18 in its lower position, in which its
conical section 18a sealingly abuts the conical section 12a of the axial
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bore 12. The conical section 18a of the control sleeve 18 has two axial
grooves 18b and 18c which terminate at its upper front side (Fig. 2),
and whose width substantially corresponds to the width of the inlet
opening 14 and outlet opening 15 respectively and which extend to the
bottoms thereof. The two axial grooves 18b and 18c are offset in the
peripheral direction of the control sleeve by an angle of approximately
135°. When the control sleeve 18 is in the position shown in Figs. 1
and
2, in which the axial groove 18b connects the inlet opening 14 to the
dosing chamber 13, the connection between the dosing chamber 13 and
the outlet opening 15 is interrupted. When the control sleeve 18 is
turned from the position shown in Fig. 2 by an angle of approximately
45° in a clock-wise direction, the connection between the inlet opening
14 and the dosing chamber 13 is interrupted and the connection
between the dosing chamber 13 and the outlet opening 15 is opened.
A central axial opening 18d is formed in the control sleeve 18 which
widens in the lower section of the control sleeve 18 to a rinsing
chamber 18e having a larger diameter. The rinsing chamber 18e is
connected to a supply of rinsing liquid (not shown) through a radial
supply opening 21.
A first dosing piston 19 of annular cross-section is displaceably inserted
into the axial opening 18d of the control sleeve 18 and has a piston
section 19a at its upper end which seats with tight fit in that axial
opening 18d of the control sleeve 18. The width of the first dosing
piston 19 is reduced below the piston section 19a. The dosing piston 19
penetrates through the lower end of the control sleeve 18 at a bore 18f
and is guided therethrough.
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A central axial bore 19b of constant cross-section is formed in the first
dosing piston 19, in which a second dosing piston 20 is dispiaceably
disposed. The second dosing piston 20 has an upper piston section 20a,
which seats sealingly and with tight fit in the axial bore 19b of the first
dosing piston 19. The lower end of the piston section 20a of the second
dosing piston 20 joins to a piston rod section 20b which penetrates
through a lower guiding and cover plate 22 of the first dosing piston 19
in a sealing fashion, and is guided through same. The axial bore 19b of
the first dosing piston 19 has a supply opening 23 at its lower end
which is also connected to the supply of rinsing liquid.
The first dosing piston 19 can be displaced as a unit together with the
second dosing piston 20 in the axial bore 18d of the control sleeve 18.
It is, however, also possible to move each dosing piston 19 or 20
independently of the respective other dosing piston.
The function of the dosing device and its possible modes of operation
are exemplarily described below.
Figs. 1 and 2 show the initial position of a dosing process. The two
dosing pistons 19 and 20 and their piston sections 19a and 20a are
each in an upper end position and the control sleeve 18 is adjusted
within the housing 11 such that the inlet opening 14 is connected to the
dosing chamber 13 through the axial groove 18b. The connection
between the dosing chamber 13 and the outlet opening 15 is
interrupted. Departing from this position, the two dosing pistons 19 and
are downwardly displaced as a unit within the axial bore 18d of the
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control sleeve 18, thereby increasing the volume of the dosing chamber
13 (Fig. 3). The vacuum created thereby draws the fill medium through
the inlet opening 14 and the axial groove 18b into the dosing chamber
13. When the dosing pistons 19 and 20 have reached their lower end
position, the control sleeve 18 is turned by 45° thereby interrupting
the
connection between the inlet opening 14 and the dosing chamber 13
and producing a connection between the dosing chamber 13 and the
outlet opening 15 (Fig. 6). The two dosing pistons 19 and 20 are then
moved together in an upward direction thereby reducing the volume of
the dosing chamber 13 and forcing the fill medium out of the dosing
chamber 13 via the axial groove 18c through the outlet opening 15. The
associated pressure increase within the dosing chamber i3 also acts on
the control sleeve 18 and forces it downwards such that the conical
section 18a of the control sleeve 18 is pressed against the conical
section 12 of the axial bore I2 of the housing 11 thereby increasing the
sealing effect. At the end of the stroke of the dosing pistons 19 and 20,
they are again in their upper end position (Fig. 5) and the supply
process terminates. The control sleeve 18 is then turned by 45° in the
opposite direction to again reach the initial position of Fig. 1 from which
a new dosing process can be started.
When the amount of the fill medium dosed by the two dosing pistons 19
and 20 is too large, the dosing pistons 19 and 20 can also be adjusted
independently of each other. Fig. 7 shows a first example thereof.
Departing from the initial position of Fig. 1 in which the dosing chamber
13 is connected to the inlet opening 14 through the axial groove IBb,
only the outer annular first dosing piston 19 is downwardly displaced
rather than both dosing pistons 19 and 20, with the inner second dosing
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piston 20 remaining stationary. Supply medium is thereby drawn
through the inlet opening 14 and the axial groove 18b into the dosing
chamber 13, but the volume enlargement of the dosing chamber 13 is
less and the drawn amount of fill medium is accordingly reduced.
Turning of the control sleeve 18 and returning the outer annular first
dosing piston 19 into the initial position can force the fill medium
located in the dosing chamber 13 out through the axial groove 18c and
the outlet opening 19.
Fig. 8 shows an alternative mode of operation, with which the outer
annular first dosing piston 19 is stationary and only the inner second
dosing piston 20 is downwardly displaced to draw the fill medium into
the dosing chamber 13. The volume enlargement of the dosing chamber
13 thereby achieved is even less than in the above-mentioned example
in which only the outer first dosing piston 19 was displaced and even a
smaller fill medium amount is thereby dosed. In this case as well, the
fill medium is pressed out of the dosing chamber 13 after turning the
control sleeve 18 by returning the second dosing piston 20 to its initial
upper position.
When the fill medium to be dosed is changed, the dosing device 10
must be cleaned. Towards this end, the components can be moved to a
so-called cleaning position (see Fig. 9). The outer first dosing piston i9
is displaced within the axial opening 18d of the control sleeve 18 in a
downward direction until its piston section 19a is freely disposed in the
rinsing chamber 18e of the control sleeve 18. The piston section 20a of
the inner second dosing piston 20 projects upwardly out of the axial
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bore 19b of the first dosing piston 19 and lies freely within the axial
opening 18d of the control sleeve 18, which, in turn, is slightly upwardly
displaced relative to the housing 11 such that its conical section 18a is
separated from abutment with the conical section 12a of the axial bore
12 of the housing I1. Cleaning or rinsing liquid is introduced into the
rinsing chamber 18e through the supply opening 21 (indicated by arrow
C1), to rinse and thereby clean the piston section 19a of the outer first
dosing piston 19. Cleaning or rinsing liquid is also introduced through
the supply opening 23 into the axial bore 19b of the first dosing piston
19 as indicated by arrow C2 and flows through the axial bore 19b to exit
at the upper end and rinse the freely disposed piston section 20a of the
inner second dosing piston 20.
The axial displacement of the control sleeve 18 relative to the housing
11 forms an annular gap between the conical section 12a of the axial
bore 12 of the housing 11 and the conical section 18a of the control
sleeve 18, the lower end of which is connected to the opening 11a
through which the cleaning or rinsing liquid is introduced (indicated by
arrow C3). Cleaning and rinsing liquid can also be introduced through
the inlet opening 14 (arrow C4). The cleaning and rinsing liquid
introduced in this fashion can also be discharged through the outlet
opening 15 (indicated by arrow C5).
When the cleaning process is finished, the outer first dosing piston 19 is
upwardly displaced within the control sleeve 18 until its piston section
19a is sealingly disposed with tight fit in the axial opening 18d of the
control sleeve 18. Adjustment of the control sleeve 18 in an axial
direction brings the two conical sections 12a and 18a into sealing
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abutment such that the initial position shown in Fig. 1 is once more
obtained.
