Note: Descriptions are shown in the official language in which they were submitted.
CA 02679865 2009-09-02
MEMBRANE SUCTION PUMP UNIT
Technical Field
The invention relates to a membrane suction pump unit
according to the preamble of Claim 1.
State of the Art
A generic membrane pump unit as part of a breast pump
is known for example from US 4 964 851. The breast pump
has an electromotor, a piston rod powered by the motor,
and a connected pump membrane. The pump membrane is
held in a membrane frame and together with a membrane
cover forms a pump chamber. In the commercially
available pump, the membrane frame, pump membrane and
membrane cover are connected to one another by means of
a press connection, with three pins of the membrane
frame being held frictionally engaged in corresponding
openings in the membrane cover.
US 7 070 400 also discloses the same type of membrane
pump unit of a suction pump, where the membrane has a
membrane piston with rear depressions. The membrane
cover defines a space with a flat floor section and a
circular side wall widening conically outwards. This
space is covered by the membrane piston and forms the
pump chamber.
EP 0 744 180 likewise describes a membrane suction pump
which now however is suited for simultaneous use of two
suction connectors.
WO 2006/032156 also shows a membrane pump with three
housing parts which are interconnected by snap
elements.
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Description of the Invention
It is an object of the invention to provide a membrane
suction pump unit which has increased processing
stability.
This object is achieved by a membrane suction pump unit
having the features of Claim 1.
The inventive membrane suction pump unit has a
dimensionally stable membrane frame, a dimensionally
stable monobloc membrane cover, which has a pump chamber
with a floor region and a side wall encircling the floor
region and widening outwards away from the floor region,
and with a monobloc pump membrane which has a membrane
plate, a flexible membrane piston, at least one inlet
valve flap and at least one outlet valve flap, and a
monobloc pump membrane with a membrane plate, a flexible
membrane piston and with at least one inlet valve flap
and at least one outlet valve flap, the membrane plate
being arranged between the membrane frame and the
membrane cover, and membrane frame, pump membrane and
membrane cover being connected to one another by means of
connecting elements in a preset position. The membrane
piston passes through the membrane frame and, together
with the membrane cover, it forms a pump chamber or
covers the pump chamber. According to the invention,
there are more than three connecting elements, forming a
material and/or positive fit.
The connecting elements connect the membrane frame and
the membrane cover with each other and the pump
membrane is hold between membrane frame and membrane
cover. The connecting elements can penetrate the pump
membrane or the pump membrane can be hold between them.
The material and/or positive fit ensure that the
connection cannot be broken automatically or by
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vibrations. In the case of the previously used
frictional engagement, it is possible for the
connection between the individual parts, i.e. frame,
membrane and cover, to be broken, in particular if the
pump triggers vibrations in the range of the natural
oscillation of the device.
Assembly is also simplified. Assembly is usually
carried out manually. This proves easier in practice if
there are several connecting elements and thus
positions than when three corresponding positions have
to be manually brought into alignment. The danger of
jamming is hereby lessened.
Although using more than three connecting elements
would actually result in static uncertainty, it has
been shown that improved overall dimensional stability
is attained. The result of using more than three, in
particular from six to twelve, connecting elements is
thus greater stability and overall rigidity of the
device. As a result, membrane cover and membrane frame
can distort less, and the unit exhibits increased
tightness, or the danger of the unit becoming leaky due
to fluctuations in temperature, vibrations or material
fatigue is minimized. Preferably, nine connecting
elements are used, which are distributed around the
edge area.
The use of several connecting elements also increases
the characteristic frequency of the system. Acoustic
properties are improved, and the tendency to background
noise during the pumping procedure is reduced.
The connecting means are preferably pins which are
fixed in the seats. They can for example be bonded,
welded or riveted. Positive locking elements, for
example snap hooks, pine-tree snap locks and similar
means, can also be used in place of pins, however.
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It is also possible to use positive and material
locking, for example via welded pine-tree snap locks.
In a preferred embodiment, the membrane cover has over
its entire surface an approximately uniform thickness.
This also prevents warping and deformation and boosts
tightness.
The inventive suction pump unit can be manufactured
cost-effectively, in particular because it comprises
only three parts, of which the two dimensionally stable
parts, membrane frame and membrane cover, can be made
from plastic in an injection moulding process, and the
pump membrane can preferably be made from liquid
silicone in an injection moulding process.
This suction pump unit is preferably used in breast
pumps for expressing breast milk. However, it is also
suitable for other suction pumps, for example drainage
pumps.
Further advantageous embodiments will emerge from the
dependent claims.
Brief Description of the Drawings
The subject matter of the invention will be explained
hereinbelow by way of a preferred exemplary embodiment,
illustrated in the attached drawings in which:
Figure 1 shows a perspective exploded view of the
inventive membrane suction pump unit from above;
Figure 2 shows a perspective exploded view of the
membrane suction pump unit as per Figure 1 from below;
Figure 3 shows a perspective illustration of the
membrane frame;
Figure 4 shows a perspective illustration of the
membrane cover in a second embodiment;
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Figure 5 shows a perspective illustration of a
fastening pin;
Figure 6 shows a membrane frame with electromotor in
an exploded view, and
Figure 7 shows a perspective exploded view of the
membrane suction pump unit in a further embodiment.
Ways of Carrying Out the Invention
Direction particulars such as above and below are used
hereinafter. These refer solely to the arrangement of
the individual parts in the figures and do not refer to
the position of installation of the inventive membrane
suction pump unit in a suction pump.
The inventive membrane suction pump unit as per Figure
1 has a membrane frame 1, a pump membrane 2 and a
membrane cover 3. All these parts are preferably of
monobloc design. Membrane frame 1 and membrane cover 3
are dimensionally stable and preferably manufactured in
an injection moulding process from plastic, for example
thermoplastic, such as polyester. The pump membrane 2
is also monobloc and made in an injection moulding
process from liquid silicone.
The membrane frame 1 has a plane-parallel base plate 10
with a round through hole 11. Formed at one end of the
base plate 10 and vertical thereto is a stop plate 16.
This stop plate 16 has a pump unit seat 19, in which a
valve unit, not illustrated here, for example as
disclosed in US 4 964 851, is housed. In the seat 19
there is a suction opening 18 in the stop plate 16,
which merges into an air intake 18` on the rear side
visible in Figure 2.
On the side of the base plate opposite the stop plate
16 there is an electromotor 4, illustrated in Figure 6,
which is connected to the later described piston
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connector 26 of the pump membrane via a piston rod, not
illustrated.
As is evident from Figure 2, the stop plate 16 is
provided with an inlet opening 13, pointing to the pump
membrane 2. This inlet opening 13 is connected to the
exterior via a connecting channel 13" and an inlet
channel 13' connected to the latter. This is shown in
Figure 3.
The base plate 10, as is again now evident in Figure 1,
also has a channel 10' on its surface, which channel
terminates in the stop plate 16 in a through hole 10".
This serves to assemble a vacuum adjustment pin, not
illustrated here.
On the underside of the base plate 10, evident in
Figure 2, is a first circular sealing groove 12. It
encloses the through hole 11, the inlet opening 13 and
a groove forming an outlet channel 14. This outlet
channel is arranged on the side of the through hole 11
diametrically opposite the inlet opening 13 and
terminates on a side edge of the base plate 10. At this
end the base plate has an upper channel connection 17
in the form of a protruding nose having a U-shaped
longitudinal section.
On the base plate 10, connecting elements are formed
that project downwards to the pump membrane. In this
embodiment these connecting elements are substantially
cylindrical pins 15, 15', 15" , although other
connecting elements such as snap lock elements can be
present. In this case the snap lock elements are formed
preferably on the outer edges of the base plate. This
second embodiment is illustrated in Figure 7. Formed on
the membrane frame 1, on the circular front faces, are
hooks 151, and on the membrane cover 3 there are
matching snap-in shackles 152. The pump membrane 2
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needs no connecting elements, rather it is simply held
clamped between membrane cover 3 and membrane frame 1.
The pins 15, 15', 15" according to the first embodiment
are arranged preferably exclusively in the edge region
of the base plate 10 and outside the sealing groove 12,
distributed over the periphery. There are more than
three pins 15, 15', 15". In the illustrated example
there are nine pins, with preferably six to twelve pins
being used.
In a simplified embodiment, all pins are configured the
same length and same thickness. However, pins of
varying shape may also be used, as is the case here.
Some pins, preferably at least two opposing pins 15",
are designed as positioning pins and have a basic
cylindrical body and a tapering or tapered tip. Some
pins, here first pins 15, have a larger diameter than
second pins 15'. The pins 15, 15', 15" can also be
equipped with vertical ribs 150, as shown in Figure 5.
The length of the pins 15, 15', 15" is such that they
pass through the pump membrane 2 arranged behind and
project at least partially into the membrane cover 3 or
likewise pass preferably completely through this and
terminate at its opposite surface.
It is also possible that the pins are formed on the
membrane cover or that some of the pins are arranged on
the membrane frame and some on the membrane cover, as
illustrated in Figure 4.
The pump membrane 2 arranged beneath the base plate 10
has a likewise substantially plane-parallel membrane
plate 20. This membrane plate 20 has approximately the
same base surface as the base plate 10. In the middle
region of the membrane plate 20, the latter merges into
a membrane piston 21, which projects upwards of the
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membrane plate 20 to the base plate 10. The membrane
piston 21 is designed as a cap shape, and preferably
has annular circular recesses. Formed in the middle of
the membrane piston 20 is the piston seat 26 in the
form of a hollow cylinder. The piston can easily plug
into this seat 26 and is held therein positively and
non-positively.
Located on one side of the membrane piston 21 is a
horseshoe-shaped inlet valve flap 23. On the opposite
side of the membrane piston 21, the membrane plate 20
has two likewise substantially horseshoe-shaped outlet
valve flaps 24 arranged at a distance apart. There can
also be more than one or fewer than two valve flaps 23,
24.
The membrane plate 20 has an upper sealing lip 22
which, on the top side facing the base plate 10,
encloses the membrane piston 21 and the valve flaps 23,
24, and which is self-contained and projects upwards.
The membrane plate 20 similarly has on its underside
facing the membrane cover 3 a circular lower sealing
lip 28, which likewise encloses membrane piston 21 and
valve flaps 23, 24 and projects downwards. The two
sealing lips 22, 28 are preferably congruent.
It is however also possible that only one of the two
sealing lips is present, or that they are not
congruent. Instead of the sealing lips, sealing grooves
could also be in place, and the membrane cover and/or
the membrane frame are provided with a corresponding
sealing lip or edge.
Formed on a side edge of the membrane plate 20 is a
protruding nose 27 projecting over the edge, but
otherwise flush with the top side and underside of the
plate 20.
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Outside the sealing lips 22, 28 the membrane plate 20
is penetrated by first and second fastening holes 25,
25', the diameters of which preferably correspond to
the associated pins 15, 15', 15" of the base plate 10,
or are slightly larger.
The membrane cover 3 has a cover plate 30, the top side
of which pointing to the pump membrane 2 is likewise
designed substantially plane. Its underside on the
other hand is structured as is described hereinbelow.
Formed in the middle of the cover plate 30 is a pump
chamber 31, which has a floor region at the same level
as the surface of the remaining cover plate 30 and a
raised circular side wall 36, the side wall being
designed to incline upwards and outwards, so that the
opening widens out over the floor region. The side wall
36 can be designed straight oblique or, as shown here,
curved.
The side wall 36 is penetrated by at least one inlet
channel, here three inlet channels 33' running parallel
to one another. These channels 33 come from an inlet
basin 33, which is designed as a recess in the cover
plate 30 and terminate in the floor region at a
distance from the side wall 36. On the opposite side,
the side wall 36 is pierced by at least one, here two
outlet channels 34 running radially outwards and
terminating at a distance outside the side wall 36 in
the cover plate 30.
Pump chamber 31, inlet basin 33 and both inlet and
outlet channels 33', 34 are enclosed by a fully
circular second sealing groove 32.
Formed at one side edge of the cover plate 30 is a
protruding nose, which forms a lower channel connector
37 with upright side walls. This lower channel
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connector 37 forms the counterpart to the upper channel
connector 17 and thus preferably has a U-shaped
longitudinal section. The abovementioned protruding
nose 27 of the pump membrane 2 is of such a size that
it corresponds to the base area of the channel
connectors 17, 37 and is held therein.
Outside the second sealing groove 32 there are seat
openings 35, 35', 35" which take up the positioning and
fastening pins 15, 15', 15". These openings 35, 35',
35" are flush with the top side of the cover plate 30.
On the underside of same, however, they are formed as
uptake sockets and are connected to one another
preferably via reinforcing ribs 38. The sockets also
can be provided on the inside with vertical ribs or
have positioning aids. The sockets preferably have an
unround inner cross section and are preferably
polygonal. This again increases the stability of the
connection with the pins.
As is evident from Figure 2, the underside of the cover
plate 30 is designed structured as a negative to the
elements formed in the top side of the cover plate.
This means that the recesses of the top side are
designed extending downwards on the underside and the
elevations of the top side are correspondingly sunk in
the underside. Here the cover plate 30 has a thickness
approximately uniform over the entire base area or over
a large part of the base area. This does not however
apply at all points. By way of example, this does not
apply in the area of the reinforcing links between the
sockets or between other possible elevations in the
underside. This type of structured cover plate can also
be employed in suction pump units whose connecting
elements connect the individual parts frictionally
engaged or non-positively.
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When the inventive unit is in the assembled state, the
pump membrane 2 or its membrane plate 20 is now clamped
in between the base plate 10 of the membrane frame 1
and the cover plate 30 of the membrane plate 3. At the
same time the membrane piston 21 passes through the
through hole 11 and because of the motor can move up
and down. The membrane piston 21 covers the pump
chamber 31 and, since the outer diameter of the
membrane piston 21 is the same size as or greater than
the outer diameter of the side wall 36 of the pump
chamber 31, it seals the chamber 31 except for the
inlet and outlet channels 33', 34.
The fastening pins 15, 15', 15" pass through the
fastening holes 25, 25' of the pump membrane 2 and are
plugged positively into the uptake sockets 35, 35', 35"
of the membrane cover 3. In addition, they are stuck
therein by means of adhesive or are connected otherwise
to form a material or positive fit. By way of example,
they can be ultrasound-welded, vibration-welded, welded
at high frequency or ultrasound-riveted.
Due to this precise positioning of the three individual
parts, the inlet opening 13 lies above the inlet valve
flap 23 and the latter lies above the inlet basin 33.
The outlet channel 14 of the membrane frame 1 lies
above the outlet valve flaps 24 and the latter lie
above the outlet channels 34 of the membrane cover.
The upper and lower sealing lips 22, 28 lie in the
first and second sealing grooves 12, 32, respectively,
and thus seal the areas in each case enclosed thereby
to the exterior.
The side walls of the lower channel connector 37
resiliently enclose the side walls of the upper channel
connector 17 and thus form a tight positive and
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frictional connection. The nose 27 of the pump membrane
2 lies on the lower channel connector 37.
The membrane piston 21 passes through the through hole
11 of the base plate 10 when the unit is in the
assembled state.
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Legend
1 membrane frame
base plate
5 10' channel
10" through hole
11 through hole
12 first sealing groove
13 inlet opening
10 13' inlet channel
13" connection channel
14 outlet channel
first fastening pin
15' second fastening pin
15 15" positioning pin
150 vertical ribs
151 hook
152 snap-in shackle
16 stop plate
17 upper channel connector
18 suction opening
18' air intake
19 pump unit seat
2 pump membrane
20 membrane plate
21 membrane piston
22 upper sealing lip
23 inlet valve flap
24 outlet valve flap
25 first fastening hole
25' second fastening hole
26 piston connector
27 nose
28 lower sealing lip
3 membrane cover
30 cover plate
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31 pump chamber
32 second sealing groove
33 inlet basin
33' inlet channel
34 outlet channel
35 first seat opening
35' second seat opening
35" positioning hole
36 side wall
37 lower channel connector
38 reinforcing rib
4 electromotor
