Technical field
[0001] The invention relates to a membrane pump with leakage detection.
Background art
[0002] Today it is well known to use homogenizers within the food processing industry. For
instance, within the dairy industry homogenizers are used for dividing fat globules
into minor parts in order to obtain a stable fat emulsion against gravity separation.
In other words, by homogenizing milk one can avoid that a cream layer is formed on
top of the milk product. Other reasons for homogenizing food products are to achieve
a more appetizing colour, reduced sensitivity of fat oxidation, more full bodied flavor,
improved mouthfeel and better stability of cultured milk products.
[0003] Generally a homogenizer can be divided in two main parts, a high pressure pump forming
a high pressure and a homogenizing device providing a gap through which the product
is forced. Today, most often the high pressure pump is a piston pump with three to
five pistons. In order to make sure that unwanted microorganisms are not spread to
the product when the pistons are moving back and forth piston seals are used. A common
approach is to have at least two piston seals placed apart from each other such that
a barrier can be formed between the product, placed on a so-called hygienic side,
and non-hygienic parts of the homogenizer, such as crankcase and crankshaft using
hydraulic oil, placed on a so-called non-hygienic side.
[0004] For example, in non-aseptic homogenizers, i.e. homogenizers placed upstream a heat
treatment station, a common approach is to have double piston seals with water provided
between the seals to lubricate the pistons. In aseptic homogenizers, i.e. homogenizers
placed downstream a heat treatment station, a mixture of hot condensate and steam
may be supplied between the seals in order to prevent re-infection.
[0006] Since it is difficult to keep the hygienic side and the non-hygienic side apart when
the pistons are moving back and forth some food producers have decided to use only
food graded oils as a precautionary measure. By doing so they reduce the risk of causing
health issues, but if the oil finds its way to the product the product properties
are nevertheless negatively affected.
[0007] For the above mentioned reasons, it is today requested from food producers to make
sure that the oil does not end up with the product in order to avoid health issues
and product losses.
[0008] Further, apart from reducing the risk that oil does not end up with the product it
is important that the technical solution is cost efficient both from capital expenditure
perspective and operational performance expenditure. In other words, the technical
solution should require a reasonable investment cost for the food producer and when
running the technical solution the need for utilities should be kept at a low level,
and providing service should be possible without increasing operational costs significantly.
Summary of the invention
[0010] It is an object of the present invention to mitigate, alleviate or eliminate one
or more of the above-identified deficiencies in the art and disadvantages singly or
in any combination and solve at least the above mentioned problem.
[0011] According to the invention, these and other objects are achieved in full, or at least
in part, by a membrane pump comprising a first membrane, and a second membrane. A
membrane interior space with vacuum is formed between the first membrane and the second
membrane. The membrane interior space comprises a first element and a second element,
wherein the first element and the second element are separated and electrically insulated
by the vacuum in the interior space. The membrane pump further comprises a resistance
meter which is configured to detect a resistance between the first element and the
second element arising from a fluid leakage into the membrane interior space due to
rupture of the first membrane and/or the second membrane. Basically, if there is a
fluid leakage from one of the membranes, the fluid will put the first element and
the second element in communication with each other and a resistance will arise. The
resistance will be detected by the resistance meter and thus indicate that there is
a leakage from one or both of the membranes in the pump. The inventive membrane pump
will therefore provide a more immediate and robust indication of any membrane rupture
than any conventional membrane pump.
[0012] In a preferred embodiment, the first element and the second element, respectively,
comprises an annular element with protruding lips. The first element and the second
element may be attached to each other with some sort of separator between them so
that they will be in no contact between them unless there is a rupture of one or both
of the membranes and they are put in contact by means of a fluid entering into the
interior space. That is, the first element and the second element may be integrally
formed with a separator between them.
[0013] The membrane pump may further comprise a control unit which is connected to the resistance
meter and adapted to monitor the resistance between the first element and the second
element. The control unit may further be adapted to trigger an alarm when a resistance
between the first element and the second element arises due to rupture of the first
membrane and/or the second membrane.
[0014] The fluid entering into the interior space and breaking the vacuum may be a liquid
from a component in the filling machine but could also just be plain air from the
ambient.
[0015] According to a second aspect another membrane pump is described, comprising a first
membrane having a net of metal threads, and a second membrane having net of metal
threads. A membrane interior space is formed between the first membrane and the second
membrane. The membrane pump further comprises a detection device which is configured
to detect a change of an electrical property arising due to a rupture of at least
one of the metal threads. The same advantages as presented above also apply for the
membrane pump according to the second aspect. It should be further noted that this
is a simple yet very effective embodiment of the membrane pump.
[0016] The electrical property measured by means of the detection meter may be resistance
in which case a conventional resistance meter may be used as the detection device.
Another possibility is to energize the metal threads and instead measure voltage by
means of a voltage meter.
[0017] In one preferred embodiment of the second aspect, the net the first membrane may
comprise a first layer of metal threads and a second layer of metal threads, and net
of the second membrane may comprise a first layer of metal threads and a second layer
of metal threads. Here, the detection device is configured to detect a short circuit
between the first layer of metal threads and a second layer of metal threads in the
first membrane and/or in the second membrane.
[0018] The membrane pump may further comprise a control unit which is connected to the detection
device and adapted to monitor the information received from the same in order to detect
any potential change of the electrical property. The control unit may further be adapted
to trigger an alarm if a change of the electrical property is determined.
[0019] The membrane pump may further comprise a membrane ring connecting the first membrane
and the second membrane to each other in order to form the membrane interior space.
[0020] Generally, all terms used in the claims are to be interpreted according to their
ordinary meaning in the technical field, unless explicitly defined otherwise herein.
All references to "a/an/the [element, device, component, means, step, etc.]" are to
be interpreted openly as referring to at least one instance of the element, device,
component, means, step, etc., unless explicitly stated otherwise.
Brief description of the drawings
[0021] The above objects, as well as additional objects, features and advantages of the
present invention, will be more fully appreciated by reference to the following illustrative
and non-limiting detailed description of preferred embodiments of the present invention,
when taken in conjunction with the accompanying drawings, wherein:
Fig. 1 schematically illustrates a homogenizer.
Fig. 2 schematically illustrates a so-called wet end of the homogenizer of Fig. 1.
Fig. 3 schematically illustrates a wet end in a membrane equipped homogenizer.
Fig. 4 illustrates a number of different perspective views on a membrane.
Fig. 5a and 5b illustrate a membrane in a first mode and a second mode.
Fig. 6a, 6b and 6c illustrate the main components of a membrane pump.
Fig. 7 illustrates one exemplary embodiment of the membrane pump according to the
invention.
Fig. 8a and 8b illustrate further exemplary embodiments of the membrane pump according
to a second aspect.
Detailed description of preferred embodiments of the invention
[0022] Fig 1 generally illustrates a homogenizer 100, more particularly a homogenizer sold
under the name Tetra Alex™ by Tetra Pak. Generally, the homogenizer 100 comprises
two main parts, a high pressure pump and a homgenising device. The high pressure pump
forms a high pressure and the homogenising device provides one or several gaps through
which the product is forced with the effect that smaller fat globules are formed.
Further effects of homogenization is more appetizing colour, reduced sensitivity to
fat oxidation, more full-bodied flavour and better stability of cultured milk products.
[0023] In this example, the high pressure pump is a piston pump driven by a main drive motor
101 connected via a belt transmission 102 and a gearbox 103 to a crankshaft placed
in a crankcase 104. By using the crankshaft the rotary motion is converted to a reciprocating
motion driving pump pistons 105 back and forth. Today, it is common to have three
to five pump pistons.
[0024] The pump pistons 105 run in cavities formed in a pump block 106 made to withstand
the high pressure created by the pump pistons. Today it is common to increase the
pressure from 300 kPa (3 bar) to about 10 - 25 MPa (100 - 250 bar), but higher pressures
can be used as well.
[0025] Through cavities in the pump block 106 the product enters a first homogenizing device
107 and thereafter, in many cases, a second homogenizing device 108. As described
above, by forcing the product through one or several gaps the properties of the product
can be changed.
[0026] The reciprocating motion of the pump pistons 105 creates pulsations. To reduce the
pulsations it is common practice today to place an inlet damper 109 on an inlet of
the homogenizer. Further, in order to reduce vibrations and noise it is common practice
to place an outlet damper 110 on an outlet.
[0027] Fig 2 illustrates a so-called wet end of the homogenizer in greater detail. As can
be seen in this cross sectional view, the piston 105 is moving back and forth such
that a high pressure is formed in a product chamber 200 in the pump block 106. One
or several seals 202 are used for keeping a tight fitting between the piston 105 and
a piston receiving element 204. The one or several seals 202 also keep the product
in the product chamber 200 apart from the crankcase and other non-hygienic parts of
the homogenizer. In order to further make sure that unwanted microorganisms do not
end up in the product it is a common approach today to use steam barriers or the like
in combination with the piston seals 202.
[0028] In fig 3 a wet end 300 of a membrane equipped homogenizer is illustrated. As the
homogenizer illustrated in fig 1 and 2, the homogenizer is provided with a piston
302, or more correctly a number of pistons, although only one of them is illustrated
in this cross sectional view. Further, the piston 302 is forming a high pressure in
a pump block 304.
[0029] Unlike the homogenizer illustrated in fig 1 and 2, the wet end 300 is provided with
a first membrane 306 and a second membrane 308. The first membrane 306 can be arranged
such that a hydraulic oil chamber 310 and a membrane interior space 312, that is,
a space formed between the first membrane 306 and the second membrane 308, is kept
apart. The second membrane 308 can be arranged such that the membrane interior space
312 and a product chamber 314 are kept apart.
[0030] Further, a high pressure relief valve 316 can be connected to the hydraulic oil chamber
310 such that a pressure in the hydraulic oil chamber can be lowered by opening this
valve. Although not illustrated, when opening the high pressure relief valve 316 hydraulic
oil may be fed into a tank. This tank may also be connected to an inlet in the hydraulic
oil chamber via an inlet valve such that hydraulic oil can be fed into the hydraulic
oil chamber at a later stage. A positive effect of this set up is that the hydraulic
oil released via the high pressure relief valve 316 can be re-used. An example set
up is illustrated in fig 11.
[0031] The reason for having hydraulic oil is that this is used for forwarding the pressure
formed by the piston 302 via the first membrane 306 and the second membrane 308 to
the product chamber 314, but also for lubricating the seals and in that way extend
the life time of the seals. Hence, unlike the wet end illustrated in fig 2, the piston
is indirectly forming a pressure in the product chamber 314.
[0032] An advantage of having membranes separating the product chamber 314 from the piston
302, crankshaft, crankcase and other parts placed on the non-hygienic side is that
a well defined border is formed. An effect of this is that the risk that unwanted
microorganisms pass the membranes into the product chamber 314 is significantly lowered.
Even if the same degree of food safety may be achieved using for instance steam barriers,
the membranes solution has the benefit that no steam barriers are needed. The effect
of this in turn is that the operational costs for running the homogenizer can be significantly
reduced. Also from an environmental perspective, using less steam is of significant
value.
[0033] A risk with membrane equipped homogenizers is that the membranes break and that hydraulic
oil enters the product chamber. This may be a food safety hazard depending on the
hydraulic oil being used, but it will with a high likelihood result in product losses.
In order to overcome this risk, in the membrane interior space 312, that is, the space
formed between the first membrane 306 and the second membrane 308, a fluid may be
present. The aim of the fluid is to make it possible to detect a membrane rupture
in a reliable, fast and cost efficient way.
[0034] Fig 4 illustrates a number of different perspective views of a membrane 400 that
can be used as the first membrane 306 or the second membrane 308 in the wet end illustrated
in fig 3.
[0035] In order to receive the force created by the piston in a way such that the membrane
400 is not worn out only after a short period of time, the membrane 400 may be provided
with a raised section 402 placed between a periphery 404 of the membrane and a mid
section 406 making sure that the membrane can flex between a first mode, illustrated
in fig 5a, and a second mode, illustrated in fig 5b, without wearing out the material
of the membrane. Further, an advantage of having the raised section may also be greater
volume difference between the first mode and the second mode.
[0036] The mid section 406 may be strengthened by a strengthening portion 408, e.g. a metal
portion incorporated in the membrane, in order to avoid so-called "coining", i.e.
the membrane breaks such that a small portion of the mid section in the shape of a
coin is torn from the membrane.
[0037] In fig 5a the membrane is in the first mode in which no force is exerted on the membrane,
neither on a product chamber side (left side in fig 5a and 5b), nor on a hydraulic
oil chamber side (right side in fig 5a and 5b).
[0038] In fig 5b the membrane is in the second mode in which a force is exerted on the hydraulic
oil chamber side such that the mid section of the membrane is pushed towards the product
chamber side.
[0039] In order to make sure that the membrane can be cleaned properly and efficiently the
product chamber side of the membrane is preferably provided with properties such that
food residues can be easily removed. Further, the product chamber side should also
be able to withstand chemicals used when cleaning, e.g. lye and acid. The hydraulic
oil chamber side should on the other hand preferably have properties suited to work
well with the hydraulic oil. The membrane as a whole should be elastic such that the
pressure formed by the piston can be forwarded to the product chamber without wearing
out the membrane. Further, the membrane should also be elastic such that the membrane
can be small, e.g. a diameter of 10-30 cm. A small membrane namely has the effect
that the pump block can be made small, in turn implying that less material, e.g. stainless
steel, is needed, which directly affect the investment cost for the food producer.
[0040] Returning to fig 5a and 5b, it is illustrated a membrane 500 comprising a main body
502 made of a rubber material, such as an elastomer. In one particular example the
elastomer ethylenepropylenedienemonomer (EPDM) has been chosen, but since the choice
of material depends on the hydraulic oil used other material can be chosen as well.
Using a rubber material, such as an elastomer, for the main body, makes it possible
to reduce the size of the membrane to about 10-30 cm or lower while still being able
to forward the pressure from the piston satisfactorily.
[0041] In order to provide for that the product chamber side can be cleaned properly a coating
504 may be provided on this side. The coating 504 may be made of polytetrafluoroethylene
(PTFE), but other plastic material suitable for food processing and possible to be
coated can be used as well. Further, the coating can also protect the elastic material
against the cleaning agents used during cleaning and also against abrasive products.
[0042] In order to provide for that the elastic properties of the main body 502 is not lost
the coating 504 is preferably made thin, e.g. 0,5 mm. However, since different material
has different properties the thickness of the coating may differ for different material.
[0043] It should be noted that fig 5a and 5b are mainly for illustrative purposes. In real
applications, a difference between the first mode and the second mode may be less
significant.
[0044] Fig 6a, 6b illustrate the main components of a membrane pump 600 comprising a first
membrane 602, a second membrane 604, a membrane ring 606 and a sensor 608 in an exploded
view from two different perspectives. In Fig 6c, the first and second membranes are
attached to the membrane ring 606. As illustrated, both membranes may be of the kind
illustrated in fig 4, 5a and 5b. By connecting the first membrane 602 and the second
membrane 604 to each other in this way a closed space is formed, herein referred to
as the membrane interior space. In this closed space the fluid can be held, thereby
making it possible to easily replace one membrane module by another.
[0045] Fig. 7 illustrates one exemplary embodiment of the membrane pump 700 according to
the invention. The membrane pump 700 comprises a first membrane 701, and a second
membrane 702. A membrane interior space 704 with vacuum is formed between the first
membrane 701 and the second membrane 702. The membrane interior space 704 comprises
a first annular element 705 having lips 706 around its outer periphery, and a second
annular element 707 having lips 708 around its outer periphery. The lips 706 of the
first annular element 705 and the lips 708 of the second annular element 707 are separated
from each other and electrically insulated by the vacuum in the membrane interior
space 704. The membrane pump 700 further comprises a resistance meter 709 which is
configured to detect the resistance between the first annular 705 element and the
second annular element 707 that arises from a fluid leakage into the membrane interior
space 704 due to rupture of the first membrane 701 and/or the second membrane 702.
That is, when one or both of the first membrane 701 and the second membrane 702 is
ruptured, fluid will leak into the membrane interior space 704 and put the lips 706
of the first annular element 705 and the lips 708 of the second annular element 707
in communication with each other. Thus, a resistance can be detected by means of the
resistance meter 709.
[0046] In order to make the process completely automated, the membrane pump may further
comprise a control unit (not shown). The control unit is connected to the resistance
meter 709 and adapted to monitor the resistance detected by the same. When a resistance
between the first element 705 and the second element 707 arises due to rupture of
the first membrane 701 and/or the second membrane 702, the control unit will trigger
an alarm so that any appropriate action can be initiated.
[0047] In Fig. 8a and 8b, another embodiment of the membrane pump 800 is illustrated. The
membrane pump 800 comprises a first membrane 801 having a net of metal threads, and
a second membrane 802 having net of metal threads. A membrane interior space 803 is
formed between the first membrane 801 and the second membrane 802. The membrane pump
801 further comprises a detection device 804 configured to detect a change of an electrical
property that arises due to a rupture of at least one of the metal threads. The electrical
property measured by means of the detection device 804 may be resistance in which
case a conventional resistance meter may be used as the detection device 804. Another
possibility is to energize the metal threads and instead measure voltage by means
of a voltage meter.
[0048] In order to make the process completely automated, the membrane pump 800 may further
comprise a control unit (not shown). The control unit is connected to the detection
device 804 and adapted to monitor the information received from the same in order
to detect any potential change of the electrical property. When a change of the electrical
property is determined the control unit will trigger an alarm so that any appropriate
action can be initiated.
[0049] In one embodiment, the net of the first membrane 801 comprises a first layer of metal
threads and a second layer of metal threads, and the net of the second membrane 802
comprises a first layer of metal threads and a second layer of metal threads. Here,
the detection device 804 is configured to detect a short circuit between the first
layer of metal threads and the second layer of metal threads in the first membrane
801 and/or in the second membrane 802.
[0050] It is understood that other variations in the present invention are contemplated
and in some instances, some features of the invention can be employed without a corresponding
use of other features. Accordingly, it is appropriate that the appended claims be
construed broadly in a manner consistent with the scope of the invention.
1. Membranpumpe (700), umfassend
eine erste Membran (701),
eine zweite Membran (702),
einen zwischen der ersten Membran (701) und der zweiten Membran (702) ausgebildeten
Membraninnenraum (704), wobei der Membraninnenraum (704) ein erstes Element (705)
und ein zweites Element (707) umfasst, und
ein Widerstandsmessgerät (709), das ausgestaltet ist, einen Widerstand zwischen dem
ersten Element (705) und dem zweiten Element (707) zu messen, der aus einer Fluidleckage
in den Membraninnenraum (704) aufgrund eines Bruchs der ersten Membran (701) und/oder
der zweiten Membran (702) entsteht, dadurch gekennzeichnet, dass der Membraninnenraum (704) mit Unterdruck zwischen der ersten Membran (701) und der
zweiten Membran (702) ausgebildet ist, und
das erste Element (705) und das zweite Element (707) getrennt und durch den Unterdruck
elektrisch isoliert sind.
2. Membranpumpe (700) nach Anspruch 1, wobei das erste Element (705) bzw. das zweite
Element (707) ein ringförmiges Element mit hervorstehenden Lippen (706, 708) umfasst.
3. Membranpumpe (700) nach Anspruch 1 oder 2, ferner umfassend eine Steuereinheit, die
mit dem Widerstandsmessgerät (709) verbunden und ausgelegt ist, den Widerstand zwischen
dem ersten Element (705) und dem zweiten Element (707) zu überwachen.
4. Membranpumpe (700) nach Anspruch 3, wobei die Steuereinheit ausgelegt ist, einen Alarm
auszulösen, wenn ein Widerstand zwischen dem ersten Element (705) und dem zweiten
Element (707) aufgrund eines Bruchs der ersten Membran (701) und/oder der zweiten
Membran (702) entsteht.
5. Membranpumpe (800) nach einem der vorhergehenden Ansprüche, ferner umfassend einen
Membranring, der die erste Membran (701; 801) und die zweite Membran (702; 802) derart
miteinander verbindet, dass der Membraninnenraum gebildet wird (704; 803).
1. Pompe à membranes (700), comprenant
une première membrane (701),
une seconde membrane (702),
un espace intérieur de membrane (704) est formé entre ladite première membrane (701)
et ladite seconde membrane (702), ledit espace intérieur de membrane (704) comprenant
un premier élément (705) et un second élément (707), et
un dispositif de mesure de résistance (709) configuré pour détecter une résistance
entre ledit premier élément (705) et ledit second élément (707) résultant d'une fuite
de fluide dans ledit espace intérieur de membrane (704) en raison d'une rupture de
ladite première membrane (701) et/ou de ladite seconde membrane (702), caractérisée en ce que
l'espace intérieur de membrane (704) est formé avec un vide entre la première membrane
(701) et la seconde membrane (702), et
le premier élément (705) et le second élément (707) sont séparés et électriquement
insolés par ledit vide.
2. Pompe à membranes (700) selon la revendication 1, dans laquelle ledit premier élément
(705) et ledit second élément (707), respectivement, comprend un élément annulaire
avec des lèvres saillantes (706, 708).
3. Pompe à membranes (700) selon la revendication 1 ou 2, comprenant en outre une unité
de commande connectée au dispositif de mesure de résistance (709) et adaptée pour
surveiller la résistance entre le premier élément (705) et le second élément (707).
4. Pompe à membranes (700) selon la revendication 3, dans laquelle ladite unité de commande
est adaptée pour déclencher une alarme quand une résistance entre le premier élément
(705) et le second élément (707) se produit en raison de la rupture de la première
membrane (701) et/ou de la seconde membrane (702).
5. Pompe à membranes (800) selon l'une quelconque des revendications précédentes, comprenant
en outre un anneau de membrane raccordant ladite première membrane (701 ; 801) et
ladite seconde membrane (702 ; 802) l'une à l'autre de telle sorte que ledit espace
intérieur de membrane soit formé (704 ; 803).