Note: Descriptions are shown in the official language in which they were submitted.
CA 03005762 2018-05-18
INLET VALVE, MIXING DEVICE AND CONTROL METHOD FOR
INTRODUCING A POWDERY SUBSTANCE INTO A LIQUID
TECHNICAL FIELD
The invention relates to an inlet valve for introducing a powdery substance
into a
liquid that is present in a container of a mixing device according to the
preamble of
claim 1, a device for introducing a powdery substance into a liquid according
to
the preamble of claim 6, a method for controlling the introduction of a
powdery
substance according to the preamble of claim 7 and a method for introducing a
powdery substance into a liquid according to the preamble of claim 8.
PRIOR ART
Mixing devices are known, so-called vacuum mixers, that have a container with
a
stirring apparatus, in which a liquid is present that is mixed with a powdery
substance. The free surface of the liquid, which can have a fluid level with a
height
of 0.4 to 4 m in the container, for example, is subjected to a vacuum relative
to
atmospheric pressure of, for example, 0.2 to 0.8 bar, which is accordingly
associated with this height range, so that the liquid in particular in the
base region
of the container experiences a vacuum relative to atmospheric pressure under
all
operating conditions.
The container usually consists of a substantially cylindrical container jacket
and an
upper and a lower container bases. The lower container base can preferably be
conical, i.e. tapering downward, in particular configured as a cone. The
introduction of the powdery substance into the container occurs via an opening
in
the container wall, preferably either at the lowest point in the preferably
cylindrical
container jacket or, in a container base that tapers downward, preferably in
the
upper region of the container base. This opening continues in a tubular inlet
nozzle toward the outer side of the container, to which a pipe leading to a
powder
storage container is connected. The inlet nozzle and thus the pipe are
configured
such that they can be shut off so that, on the one hand, the mixing device can
be
1
CA 03005762 2018-05-18
closed off from its environment via this path and so that, on the other hand,
an
amount of the powdery substance present in the powder storage container can be
added to the liquid when required. As a rule, this is carried out in a so-
called batch
method, in which the amount of powder present is admixed into the amount of
liquid provided in the required mix ratio in the mixing device and, as a rule,
they
are mixed together by means of a stirring apparatus.
Heretofore, a disc or ball valve that functions as a check valve has been
arranged
in the inlet nozzle to control the supply of the powdery substance. Because of
the
design of a disc or ball valve, the valve seat is located at a more or less
large
distance from the internal wall of the container due to the respective closure
member configuration and kinematics, and so a dead space is formed in the
inlet
nozzle up to the respective valve seat as a result. Powder can build up in
this dead
space and remain there, causing a blockage that cannot or can only
insufficiently
be swept away by the action of the stirring apparatus. This risk arises in
particular
when the inlet nozzle is located in the downwardly tapering container base,
and this
arrangement may form a sump up to the valve seat of the respective valve.
Moreover, it is a disadvantage in disc and ball valves for the required seat
seals to
be arranged on the housing side and thus to be constantly exposed to the fully
developed pipe flow. As a result, the seat seals are subjected in an exposed
manner to the sometimes very abrasive powders, such as lactose, and are thus
liable to increased wear. A publication on the Internet by TYCO International
Ltd.,
Tyco Flow Control, Hygienic Products UPDATE, in conjunction with an F250
Powder SKI-JUMP Valve, for example, includes an indication of this
substantive
matter. A ramp ("ski jump") that is formed annularly around the valve housing
of
this disc valve and upstream of the seat seal in the flow direction of the
powder
channels the abrasive powder particles over the rubber seal, whereby abrasive
wear of the rubber seal should be reduced.
2
CA 03005762 2018-05-18
The two valve designs, the disc and ball valves, also have in common that,
when
the valve is closed, the powder is located upstream of the respective closure
member as viewed in the transport direction of the powder and can agglomerate
there and thus block the supply and the entry into the container. To be able
to
replace each worn-out seat seal, the valve has to be uninstalled from the pipe
in
which it is arranged. In the case of disc valves, it is also a disadvantage
that the
disc-shaped closure member is located in the flow path of the powder flow and
thus
represents an additional obstacle.
The object addressed by the present invention is that of developing at least
one
generic inlet valve for introducing a powdery substance into a liquid that is
present
in a container of a mixing device, or a generic device for introducing a
powdery
substance into a liquid, or a generic method for controlling the introduction
of a
powdery substance into a liquid, or a generic method for introducing a powdery
substance into a liquid such the formation of a dead space in the region of
the
internal wall of the container at the inlet point for the power as well as
agglomerations and blockages of the powder at the inlet point and in the inlet
valve
are avoided and such that a reliable and trouble-free introduction of the
powder into
the liquid and a simple adaptation to various powdery substances are ensured.
Moreover, an objective is to achieve a configuration of the inlet valve that
includes
a low-wear and easily exchanged arrangement of the seat seal.
SUMMARY OF THE INVENTION
With regard to the device, this object is solved by the inlet valve for
introducing a
powdery substance into a liquid with the features of claim 1 and by a device
for
introducing a powdery substance into a liquid with the features of claim 6.
Furthermore, the object is solved with regard to the method by the method for
controlling the introduction of a powdery substance into a liquid with the
features
of claim 7 and is solved with regard to the device and to the process by the
features of claim 8.
3
CA 03005762 2018-05-18
The invention proposes for the first time an inlet valve for introducing a
powdery
substance into a liquid that is present in a container of a mixing device,
said inlet
valve being configured as a globe valve, wherein the container consists of a
preferably cylindrical container jacket as well as an upper and lower
container base.
The lower container base preferably tapers downward and is preferably
configured
conically or cone-shaped and is joined seamlessly to the container jacket. A
valve
housing of the inlet valve is arranged with a valve closure member on the
container
jacket or the container base. Said valve housing has a valve seat, which
interacts
with a valve plate of the valve closure member. The valve seat forms a seat
opening, through which the powdery substance is introduced into the liquid. By
means of the valve plate, the seat opening can be adjusted between completely
closed and completely open, i.e. a closed position and a completely open
position
can be implemented. The seat opening is arranged in and in alignment with an
extension area of a wall of the container jacket or the container base.
Concretely,
this means that, to the greatest extent possible, the valve seat and thus the
seat
opening formed by it are flush with the internal wall of the container jacket
or the
downwardly tapering container base. A control apparatus, by means of which the
valve closure member can be shifted into the closed or the open position, is
associated with the inlet valve. The control apparatus has at least one signal
receiver, which is a measuring apparatus for the mixing parameters
= composition and consistency of the powdery substance,
= flow rate of the powdery substance in the inlet valve,
= pressure in the container of the mixing device in the region of the seat
opening,
= and/or the temperature of the liquid.
The aforementioned pressure can be measured indirectly in the head space of
the
container above the surface of the liquid or directly in the region of the
seat opening.
The closed or the open position of the inlet valve can be selected as a
function of
the mixing parameters during the introduction of the powdery substance.
4
CA 03005762 2018-05-18
For the seat opening to be as flush as possible with the internal wall of the
container
jacket or of the preferably downwardly tapering container base, a further
development of the inlet valve is proposed in which the container-side end of
the
seat opening is oriented perpendicular to the stroke direction of the inlet
valve and
is flush with the inner side of the wall of the container jacket or container
base. Here
the flush fit of the container-side end of the seat opening should be
understood to
mean that this end represents an integral part of the inner contour of the
container
wall in this region, wherein the contact surface between the seat opening and
the
associated seat seal in the valve closure member is disposed as close as
structurally possible to the end of the seat opening.
The aforementioned arrangement can also be executed with a valve seat in which
the valve seat and the valve closure member are sealed off from each other
without
a discrete seat seal. This can be a pairing of metal on metal or a metallic
valve seat
that interacts with a valve closure member with sealing properties (suitable
plastic).
What is essential here, too, is that the contact surface between the seat
opening
and an associated sealing surface on the valve closure member is disposed as
close as structurally possible to the end of the seat opening.
A further advantageous embodiment of the inlet valve provides that a part of
the
valve housing that accommodates the seat opening is surrounded radially
externally by a disc-shaped connecting element or expands into this connecting
element, wherein the connecting element extends in the plane of the seat
opening
and perpendicular to the stroke direction of the inlet valve. Thus the
connecting
element, on the one hand, is a radial external component of the valve housing,
in
which the seat opening is configured and, on the other hand, functions
advantageously as a weld-on part to be introduced into the wall of the
container
and thereby becomes an integral part of this wall.
Another further development of the connecting element provides that a front
surface
of the disc-shaped connecting element that faces the interior space of the
container
5
CA 03005762 2018-05-18
is flush and in alignment with the inner side of the wall of the container
jacket or the
container base. This container-internal-side closure and the orientation
aligned with
the internal wall prevents the formation of a dead space in this region, and
the valve
seat with its seat opening and the associated seat seal in the valve closure
member
is not only brought up close to the extension area of the wall but is
positioned in it,
to the extent that this is possible.
In order to ensure that there are no dead and hollow spaces in the valve
housing, it
is proposed that, at least in the region upon which the powder impinges, the
valve
closure member be configured as a cylindrical bar with the same diameter, on
which
the valve plate is molded with the same diameter. This means that the valve
plate
connects to the cylindrical bar seamlessly and with the same diameter. Based
on
this embodiment, when the inlet valve is in its fully open position, the valve
closure
member with its valve plate is moved as far as possible out of the fully
developed
flow of the powdery substance, and so it, on the one hand, does not constitute
an
obstacle to flow and, on the other hand, a seat seal, which is accommodated in
the
valve plate, is disposed near the wall of the valve housing and thus outside
of the
fully developed flow region of the pipe flow, and it is therefore at most
touched only
tangentially by the stagnating flow near the wall in this edge region.
According to the invention, the device for introducing a powdery substance
into a
liquid has an inlet valve with the features described above.
With regard to the process, the object is solved by the method according to
the
invention for controlling the introduction of a powdery substance into a
liquid. The
powdery substance is introduced into the liquid present in a container of a
mixing
device by means of an inlet valve. The powdery substance flowing through the
inlet
valve enters into the liquid via the seat opening. The closed or the open
position of
the inlet valve is adjusted during the introduction process as a function of
the mixing
parameters. The mixing parameters are understood to include the composition
and
the consistency of the powdery substance, the flow rate of the powdery
substance
6
CA 03005762 2018-05-18
in the inlet valve, the pressure in the container of the mixing device in the
region of
the seat opening and/or the temperature of the liquid.
The composition and the consistency of the powdery substance also determine
the
diameter of the seat opening and thus the nominal diameter of the inlet valve.
The
control of the inlet valve, especially the duration of its opening, is
determined by the
presence or absence of the powdery substance, in particular in the inlet
region of
the inlet valve. When a flow rate can no longer be detected here, the suction
of air
into the container via the inlet valve must be avoided, and the inlet valve
must be
shifted into its closed position by the control apparatus.
According to the invention, the method for introducing a powdery substance
into a
liquid is performed using a device according to the invention and with at
least one
of the stated method steps from claim 7.
All of the features and advantages disclosed for the inlet valve according to
the
invention and the device according to the invention similarly apply to the
method
according to claim 7 of the invention as well as its advantageous further
development according to claim 8.
Further features and advantages of the present invention arise from the
following
description in conjunction with the figures of the drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
A more comprehensive representation of the invention arises from the following
description and the included figures of the drawing as well as from the
claims. While
the invention is implemented in the most diverse embodiments, a preferred
exemplary embodiment of a mixing device for introducing a powdery substance
into
a liquid by means of an inlet valve according to the invention is described in
the
drawing. In addition, a method is indicated that can be performed with the
inlet valve
7
CA 03005762 2018-05-18
in conjunction with the mixing device. The following is shown:
Figure 1 in a schematic representation, a mixing device with an inlet
valve in
conjunction with a control apparatus;
Figure la in an enlarged representation, a section in the region of the
inlet
valve and the adjacent wall region of a container of the mixing
device, identified in Figure 1 with "A";
Figure lb in a further enlarged representation, a second section from the
first
section according to Figure la, identified in Figure la with "B";
Figure 2 in a perspective representation and in half-section, the inlet
valve
according to Figures 1 and la without a control head housing; and
Figure 3 in a perspective representation, the inlet valve according to
Figure
2, wherein, in contrast to Figure 2, the control head housing is
additionally shown.
A mixing device 1000 (Figure 1) includes, inter alia, a container 100, which
consists
of a preferably cylindrical container jacket 100.1 and an upper container
base, which
is not shown, and a lower container base 100.2. The lower container base 100.2
preferably tapers downwardly, usually in the shape of a cone or circular cone,
and
has an outlet 100.3 at the lower end. In the container 100, a liquid F is
present which
forms a free level N, above which a pressure p, usually a vacuum relative to
the
atmospheric pressure, normally prevails in the mixing device 1000 in question
(vacuum mixer). A valve housing 2 of an inlet valve 20 is arranged on the
container
jacket 100.1 or container base 100.2. A control device 30 is associated with
the inlet
valve 20, which serves to introduce a powdery substance P into the liquid F.
Disposed within the container 100 is a stirring apparatus 24, preferably
mechanical,
that extends down into the region of the lower container base 100.2. The
required
mixing effect can also be achieved by fluid-mechanical means, such as by
pumping
the liquid F through a circulation line and the tangential entry of the liquid
into the
container 100.
8
CA 03005762 2018-05-18
According to the invention, the inlet valve 20 is configured as a globe valve
(Figures 2 and 3). In its valve housing 2, it has a valve seat 2a and a valve
plate
8a that interacts with it and that is configured on a valve closure member 8.
As a
rule, the valve closure member 8 accommodates a seat seal 10, which brings
about the sealing effect in the closed position of the inlet valve 20 in
conjunction
with the valve seat 2a. Alternatively, it is also possible to implement seat
configurations without a seal, in which the pairing of metal on metal or metal
against a valve closure member 8 with sealing properties, such as a suitable
plastic, results in a sufficient seal.
The valve seat 2a has a seat opening 2b, through which the powdery substance P
is introduced into the liquid F. The liquid F, which is present above the
connection
point of the inlet valve 20 that is arranged in the wall of the container 100,
forms a
height h with its fluid column, and so the static pressure in the region of
the
connection point and thus of the seat opening 2b is composed of the vacuum p
and
the static pressure resulting from the height of the fluid column h. In a
vacuum mixer
having, for example, a vacuum of p = 0.2 to 0.8 bar and a height of the fluid
column
h = 0.2 to 4 m in accordance with this pressure range, there is always a
vacuum
relative to the atmospheric pressure in the region of the seat opening 2b, and
so
the seat opening 2b is suctioned out of the container 100.
The seat opening 2b can be adjusted by means of the valve plate 8a between
completely closed, i.e. the closed position, and completely open, i.e. the
open
position. According to the invention, the seat opening 2b is arranged in and
in
alignment with an extension area of a wall of the container jacket 100.1 or
the
container base 100.2 (Figures 1a, 1 b). The container-side end of the seat
opening
2b is oriented perpendicular to the stroke direction of the inlet valve 20
and, in the
best possible embodiment, which is not shown in Figure lb, is flush with the
inner
side of the wall of the container jacket 100.1 or the container base 100.2.
9
CA 03005762 2018-05-18
A part of the valve housing 2 that accommodates the seat opening 2b is
surrounded radially externally by a disc-shaped connecting element 2c that
extends in the plane of the seat opening 2b and perpendicular to the stroke
direction of the inlet valve 20 (Figures 1 b, 2,3 and 1). The connecting
element 2c
is arranged in a wall opening 100.4 of the container 100 and is preferably
materially bonded, preferably by welding, to its wall. A front surface of the
disc-
shaped connecting element 2c that faces the interior space of the container
100 is
flush and in alignment with the inner side of the wall of the container jacket
100.1
or the container base 100.2.
The valve closure member 8 can be shifted into the closed or the open position
by
means of the control apparatus 30. Said control apparatus 30 has at least one
signal
receiver 16 (Figure 1). The at least one signal receiver 16 is a measuring
apparatus
for the mixing parameters of composition and consistency of the powdery
substance P, flow rate of the powdery substance P in the inlet valve 20,
pressure
in the mixing device 1000 in the region of the seat opening 2b and/or the
temperature of the liquid F. A pipe connection 2d on the valve housing 2 is
connected via a supply line 18 to a powder storage container 26, in which an
appropriate amount is kept for a preferably batchwise introduction of the
powdery
substance P into the liquid F. The measuring apparatus 16 is located in the
supply
line 18, preferably in the immediate vicinity of the pipe connection 2d, and
here it
preferably detects the flow rate of the powdery substance P. The presence or
absence of the powdery substance P leads to a corresponding signal, which is
transmitted from the measuring apparatus 16 via a signal line 22 to the
control
apparatus 30. Depending upon the signal from the measuring apparatus 16, the
control apparatus 30 transmits a control command to a control head housing 14
of
the inlet valve 20 via a further signal line 22. During the introduction, the
closed or
the open position of the inlet valve 20 can be selected as a function of the
aforementioned signal from the measuring apparatus 16.
CA 03005762 2018-05-18
In a similar manner, further measuring apparatus can additionally or
alternatively
be provided to record the other mixing parameters so that it is also possible
to select
the closed or the open position of the inlet valve 20 using these mixing
parameters.
The valve housing 2 is connected to a drive housing 6 by a lamp housing 4 to
drive the valve closure member 8 (Figures 2 and 3). This is preferably a
spring/piston drive that is charged with pressurizing medium, wherein a return
spring 12 shifts the valve closure member 8 into its closed position when the
drive
is not charged with pressurizing medium, preferably pressurized air. A valve
rod
8b, which engages with the valve plate 8a of the valve closure member 8 and is
guided through the drive housing 6 and into the control head housing 14,
serves
to guide the valve closure member 8 axially on the drive side.
It is apparent from Figure 2 that, at least in the region upon which the
powder
impinges, the valve closure member 8 is configured as a cylindrical bar with
the
same diameter, on which the valve plate 8a is molded with the same diameter.
As
a result of this structural configuration, hollow and dead spaces in the valve
housing
2 are avoided in the movement area of the valve closure member 8, wherein the
valve closure member 8 with its end-side valve plate 8a and the associated
seat
seal 10 can be largely withdrawn from the region of the valve housing 2
through
which the substance is fully flowing.
The device, namely the mixing device 1000 described above, for introducing the
powdery substance P into the liquid F has the previously described inlet valve
20
with its likewise previously described further developments.
11
CA 03005762 2018-05-18
The method for controlling the introduction of the powdery substance P into
the
liquid F provides that the powdery substance P be introduced into the liquid F
that
is present in the container 100 of the mixing device 1000 by means of the
inlet valve
20 described above. In this way, the powdery substance P flowing through the
inlet
valve 20 enters the liquid F via the seat opening 2b, and the closed or the
open
position of the inlet valve 20 is adjusted during the introduction process as
a function
of the mixing parameters. The mixing parameters are understood to include the
composition and the consistency of the powdery substance P, the flow rate of
the
powdery substance P in the inlet valve 20, the pressure in the container 100
of the
mixing device 1000 in the region of the seat opening 2b and/or the temperature
of
the liquid F.
12
CA 03005762 2018-05-18
REFERENCE SIGN LIST FOR THE ABBREVIATIONS USED
20 Inlet valve
30 Control apparatus
1000 Mixing device
100 Container
100.1 Container jacket
100.2 Container base (conical; cone-shaped)
100.3 Outlet
100.4 Wall opening
2 Valve housing
2a Valve seat
2b Seat opening
2c Connecting element
2d Pipe connection
4 Lamp housing
6 Drive housing
8 Valve closure member
8a Valve plate
8b Valve rod
Seat seal
12 Return spring
14 Control head housing
16 Signal receiver
18 Supply line
22 Signal line
13
CA 03005762 2018-05-18
24 Stirring apparatus
26 Powder storage container
F Liquid
N Level
P Powdery substance
h Height of the fluid column
p Pressure above the fluid column
14
