WO2008039135A1

WO2008039135A1 - An arrangement determining a liquid level within a container

Info

Publication number: WO2008039135A1
Application number: PCT/SE2007/000846
Authority: WO
Inventors: Åke FORSSTRÖM
Original assignee: Forsstroem Aake
Priority date: 2006-09-29
Filing date: 2007-09-27
Publication date: 2008-04-03
Also published as: SE0602031L; SE531205C2

Abstract

The present invention encompasses an arrangement ('A') determining a liquid level (1) within a container (2) under the utilisation of, a pressure-sensitive and bottom-related sensor unit (3), in order with the aid of a hydraulic and/or pneumatic pressure to permit the evaluation of the height ('H2') of the liquid level above said sensor unit (3), a tube system (4) between the sensor unit (3) and a measurement unit (5), in order to distribute said pressure ('Pa') within the sensor unit (3) to said measurement unit (5) in order there, via circuits and functions (5), to generate a significative indication corresponding to a thus evaluated pressure value. Said sensor unit (3) is structured as an elastic blister or a membrane, for instance a rubber blister (3a), and with connected tube system (4) displays a pre-set pressure ('Pi'), where said pressure may correspond to a pressure value representative of the total container height ('Hl') or another selected pressure value. A pressure value propagated (7, 8) automatically via the measurement unit (5), such as an alarm value (Pmin; Pmax) is to be able to be accompanied by an identification of the transmitting arrangement ('A')

Description

TITLE OF THE INVENTION: An arrangement determining a liquid level within a container

TECHNICAL FIELD The present invention relates in general to an arrangement determining an actual liquid level within a container.

The present invention is based on the utilisation of a pressure-sensitive and bottom- related sensor unit, in order, with the aid of a hydraulic and/or pneumatic pressure, to evaluate the height of the liquid level above said sensor unit.

More particularly, use is made of a tube system (or a hose system) between the sensor unit and a measurement unit determining an instantaneous pressure level, in order to distribute said pressure within the sensor unit to said measurement unit in order there, via electronic circuits and/or functions, to permit the generation of a significative indication corresponding to a thus evaluated pressure value.

The present invention has for its object to obtain a specific application in level measurement of the liquid content in septic tanks, oil tanks and the like and is intended more specifically to be included in a system where the actual liquid levels for a large number of different such levels for selected tanks are coordinated via a wireless information transfer to a central unit in order there to be able to establish the need for emptying a thus indicated septic tank and/or replenishing a thus indicated oil tank.

BACKGROUND ART

Methods, arrangements and constructions related to the above-disclosed technical field and displaying a function and a nature which satisfy set requirements are previously known in the art in a plurality of different embodiments.

As one example of the state of the art and the technical field to which the present invention relates, mention might be made of an arrangement determining a liquid level within a container utilising a pressure-sensitive and bottom-related sensor unit, in order, with the aid of a prevailing hydraulic and/or pneumatic pressure, to evaluate the height of the liquid level above said sensor unit.

A tube system between the sensor unit and a measurement unit is provided so as to distribute said pressure within the sensor unit to said measurement unit in order there, via circuits and functions, to permit the generation of a significative indication corresponding to a thus evaluated pressure value.

Within this category of level-measuring arrangements are included the utilisation of a manually operated pump, which pressurises a tube system and which permits reading off of the prevailing static pressure within the tube system and permits conversion of this pressure to a level value and/or a prevailing volume.

One precondition for the function of this arrangement resides in the fact that the opening of the tube system is passed through the liquid to a region adjacent the bottom portion within the tank and is wholly open, which has not always proved to be the case in a level measurement of septic tanks, where there is then required an initial clean blowing of the pipe system with high air or water pressure before the actual level measurement under the utilisation of a static pressure with a pressure value representative of the height between the opening and the liquid surface.

A system of the related type is more closely illustrated and described in the Applicant's own Swedish Patent Application number 05 02132-4.

Taking into account the wireless and significative information transfer disclosed by the present invention from a measurement unit to a central unit, this information transfer may be put into effect with the aid of currently known systems, such as via the terrestrial telephone network, via Internet, via mobile telephone networks, via data networks and similar network structures. As then regards Patent Publication GB- 179 656- A, there is disclosed a meter of the liquid level within a container and where the principle is utilised that the pressure from the height of the liquid is sensed in a chamber provided with a membrane in the lower region of the container and under the utilisation of a pressure meter.

The chamber provided with membrane and the pressure meter communicate with one another by enclosing (enclosed = sealed) a selected quantity of air or gas.

In such instance, the meter is intended for measuring levels in tanks which contain a homogenous liquid, such as water, oil and the like.

Patent Publication EP-O 650 037-A1 shows and describes a starter device for an immersible pump with the aid of a sensor and under the utilisation of a bellows filled with a gaseous medium, where the bellows is given the possibility of being able to expand on increasing pressure and contract on reducing pressure.

Also here, it is a matter of an apparatus which, for its function, requires an application where liquid levels are to be evaluated for homogenous liquids, such as water, oil and the like.

As a summary of GB-179 656-A and EP-O 650 037-A1, the requirement on a homogenous liquid may be ascertained. A feature common to both of the cited arrangements is further that they are intended to operate under the utilisation of an instantaneously active atmospheric pressure and will thus int. al. be sensitive to variations of the atmospheric pressure with time.

SUMMARY OF THE PRESENT INVENTION TECHNICAL PROBLEM Taking into account the circumstance that the technical considerations which a person skilled within the relevant technical field must carry out in order to be able to offer a solution to one or more set technical problems is, on the one hand, initially a necessary insight into the measures and/or the sequence of measures to be adopted and, on the other hand, a necessary selection of the means required, in view hereof the following technical problems are likely to be relevant in the evolution of the subject matter of the present invention.

Taking into account the state of the art, as described above, it is probably therefore to be seen as a technical problem to be able to realise the importance of, the advantages associated with and/or the technical measures and considerations which will be required in order, in arrangement determining a liquid level within a container under the utilisation of a pressure-sensitive and bottom-related sensor unit to be able, with the aid of a hydraulic and/or pneumatic pressure, to evaluate height of the liquid level above said sensor unit and under the utilisation of a tube or hose system between the sensor unit and a metering or measurement unit in order to allow the distribution of said pressure within the sensor unit to said metering unit in order there, via electronic circuits and functions, to be able to generate a significative indication corresponding to a thus valued pressure level, to be able to utilise as a sensor unit an elastic blister or elastic membrane which is held expanded by means of an inner excess pressure within the tube system and the sensor unit and which is fixedly related to the lowermost point or bottom portion of the container.

There resides a technical problem in being able to realise the importance of, the advantages associated with and/or the technical measures and considerations which will be required in order to cause said sensor unit to be structured as a manifest elastic blister, such as thin rubber blister or a membrane, and that said elastic blister with connected tube system is to display a predetermined set pressure where said set pressure is to be able to correspond to a pressure value representative of a liquid quantity which fills out the total container height or a selected pressure value thereover.

There resides a technical problem in being able to realise the importance of, the advantages associated with and/or the technical measures and considerations which will be required in order to cause the set pressure to consist of a pneumatic pressure. There resides a technical problem in being able to realise the importance of, the advantages associated with and/or the technical measures and considerations which will be required in order to cause said measurement unit to display means and/or circuits in order to be able to carry out wireless transmission of said significative indication with a consequential identification of the pressure sensing arrangement.

There resides a technical problem in being able to realise the importance of, the advantages associated with and/or the technical measures and considerations which will be required in order to cause the measurement unit to encompass a central calculator unit which can be zeroised against a selected reference pressure.

There resides a technical problem in being able to realise the importance of, the advantages associated with and/or the technical measures and considerations which will be required in order with the aid of said hydraulic and/or pneumatic pressure and with the aid of constants allocated to a container to permit the evaluation, with the aid of circuits and functions within the measurement unit, of a value of the volume of the enclosed liquid.

There resides a technical problem in being able to realise the importance of, the advantages associated with and/or the technical measures and considerations which will be required in order, on an attained limit value stored in the measurement unit, to permit the generation and wireless transfer of an alarm signal, for example representative of a selected high liquid level and/or a selected low liquid level.

There resides a technical problem in being able to realise the importance of, the advantages associated with and/or the technical measures and considerations which will be required in order to cause such an alarm signal to be transferred automatically via a wire-linked or preferably wireless network to a centrally placed alarm unit or central unit via a pre-programmed telephone number or other identification allocated to the measurement unit. SOLUTION

In such instance, the present invention takes as its point of departure the prior art technology as disclosed above where an arrangement determining a liquid level within a container under the utilisation of a pressure-sensitive and bottom-related sensor unit in order, with the aid of a hydraulic and/or pneumatic pressure to cause the evaluation of the height of the liquid level above said sensor unit, as well as a tube system between the sensor unit and a measurement unit so as to distribute said pressure within the sensor unit to said measurement unit in order there, via circuits and functions, to generate a significative indication corresponding to a thus evaluated pressure value.

In order to be able to solve one or more of the above-disclosed technical problems, the present invention more specifically discloses that the prior art technology be complemented in that said sensor unit is to be structured as an elastic blister or a membrane, such as a rubber blister, and that said elastic blister with connected tube system is to display a preselected pressure value where said pressure value is to be able to correspond to a pressure value representative of the pressure value which corresponds to a liquid pressure valid for the total container height or a pressure value selected slightly thereabove.

As proposed embodiments, falling within the scope of the basic concept of the present invention, it is moreover disclosed that the set pressure value consist of a pneumatically caused pressure value.

Said measurement unit is advantageously to display means for being capable of the wireless transfer of said significative indication, ideally together with an identification of the relevant arrangement.

It also falls within the scope of the present invention that the measurement unit encompass a calculator unit which is zeroised against a selected static reference pressure. With the aid of said hydraulic and/or pneumatic pressure and with the aid of constants allocated to and related to a container, it will be possible with the aid of electronic circuits and functions to establish the instantaneous volume of the liquid, for instance an actual volume or a residual volume.

At a predetermined and attained limit value, stored in circuits or memories within the measurement unit, it lies within the scope of the present invention to be able to generate an alarm signal, for instance an alarm signal representative of a high liquid level and/or a low liquid level.

The alarm signal may then be transferred via a wire-linked or wireless network to an alarm unit, alarm centre or other central unit via a telephone number or the like entered and pre-programmed into the measurement unit where the alarm signal is to be able to accompanied by information identifying the arrangement.

ADVANTAGES

Those advantages which may principally be deemed to be characteristic of the present invention and the specific significative characterising features disclosed thereby is that there have hereby been created the preconditions in order, in an arrangement determining a liquid level within a container, under the utilisation of pressure-sensitive and bottom-related sensor unit for evaluating the height of the liquid level above said sensor unit and with the aid of a tube system, between the sensor unit and a measurement unit, to permit the distribution of said pressure within the sensor unit to said measurement unit in order there, via electronic circuits and functions, to permit the generation of a significative indication corresponding to a thus evaluated pressure value and offer a sensor unit, of a completely closed elastic material, and with a connected tube system create an initial pressure, which pressure will vary in response to an actual liquid level prevailing within the container.

The sensor unit may consist of a an elastic bellows or a membrane. That which may principally be deemed to be characteristic of the present invention is disclosed in the characterising clause of appended Claim 1.

BFIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

One currently proposed embodiment, displaying the significative characterising features associated with the present invention, will now be described in greater detail hereinbelow for purposes of exemplification and with reference to the accompanying

Drawings, where: Fig. 1 generally shows a level measuring arrangement applied on a septic tank, where the included parts and circuits are schematically illustrated;

Fig. 2 generally shows a measurement unit in block diagram form;

Fig. 3 is a side elevation of a sensor unit in the form of an elastic blister or bellows secured to the bottom portion of a container, and Fig. 4 is a side elevation of a sensor unit with a membrane.

DESCRIPTION OF CURRENTLY PROPOSED EMBODIMENT

It should then by way of introduction be emphasised that, in the following description of one currently proposed embodiment which displays the significative characterising features associated with the invention and which is clarified by means of the figures in the accompanying Drawings, we have selected terms and a specific terminology with the intention in such instance of principally clarifying the inventive concept.

However, in this context it should be observed that each expression selected here should not be seen as restrictive exclusively to the terms utilised and selected here, but it should be understood that each such selected term is to be interpreted so that in addition it encompass all technical equivalents which function in the same or substantially the same manner in order in such instance to be able to attain the same or substantially the same intention and/or technical effect. With reference to accompanying Figs. 1 to 4, there are thus shown schematically and in detail not only the basic preconditions of the present invention but moreover the significative properties associated with the present invention have been given concrete form as a result of the currently proposed embodiment which will now be described in greater detail hereinbelow.

Thus, Fig. 1 more generally shows an arrangement "A" determining a liquid level 1 within a container 2, under the utilisation of a pressure-sensitive and bottom portion- related sensor unit 3, more closely illustrated in Figs. 3 and 4, in order, with the aid of a (hydraulic) pneumatic pressure "Pa" to permit the evaluation of the height "H2" of the liquid level 1 above said sensor unit 3.

The pneumatic pressure value "Pa" will thus vary in response to the actual height of the liquid level "H2" with a higher height creating a higher pressure value and lower height creating a lower pressure value.

A tube system 4, adapted to extend between the sensor unit 3 and a measurement unit 5, where said measurement unit 5, more closely illustrated in Fig. 2, is adapted so as to be able to distribute an actual pressure value "Pa" within the sensor unit 3 to said measurement unit 5, where the pressure value is directly readable.

The measurement unit 5 is, according to Fig. 2, allocated a central unit or circuit 5' and a number of electronic circuits and/or functions 5a related thereto in order thereby to permit the generation of a significative indication in a circuit or memory 5b corresponding to a thus evaluated and actual pressure value "Pa".

Said sensor unit 3 is structured as an elastic blister, for instance a rubber blister 3a, more closely illustrated in Fig. 3.

According to the disclosures of the present invention, said elastic blister 3 a, with connected first end section 4a of the tube system 4, whose other end section 4b is connected to the measurement unit 5, be initially supplied with a pre-set pressure "Pi", which may then selected to be higher than each actual and measured pressure value "Pa".

The set value "Pi" is supplied through a valve 6 and where this pressure "Pi" is in any event to correspond to a pressure value which is representative of the total container height "Hl".

There is nothing to prevent the selection here of a pressure value which slightly exceeds said pressure value "Pi".

The set pressure "Pi" is here selected in the form of a pneumatic pressure.

Said measurement unit 5 in addition displays means 5c for wireless transfer of said evaluated significative indication to an alarm centre, not shown, or central unit, which is to be formed to be capable of receiving identified significative indications from a plurality of corresponding arrangements "A", which are not shown for reasons of simplicity.

The measurement unit 5 comprises a calculator unit 5d, which is adapted to be able to be zeroised against a selected reference pressure, such as the pressure value "Pi".

With the aid of said pneumatic pressure "Pa" and with the aid of constants allocated to the container, the volume "V" of the liquid is evaluated with the aid of electronic circuits and functions 5e.

At an attained limit value, "Vmax" or alternatively "Vmin" or any other stored limit value stored in a memory 5f in the measurement unit 5, an alarm signal 5g is generated via the central unit 5', representative of a selected, a high liquid level and/or a low liquid level 1. The alarm signal 5g is transferred via a wire-linked or wireless network 7 to an alarm centre, not shown, or central unit via a pre-programmed telephone number or other indication in a circuit 5h.

With reference to Fig. 3, there is there illustrated the utilisation of a rubber bellows 3a where this rubber bellows 3a displays a bottom plate 3b which is secured in a per se known manner to the bottom portion 2a of the container 2.

The sensor unit 3 also displays an upper plate 3c and a bellows arrangement 3d oriented between the bottom plate 3b and the upper plate 3c.

With an initial pressure value "Pi" within the bellows 3d and at low liquid height "H2", the sensor unit 3 is in a fully expanded state and is compressed only marginally by the compression force from a superjacent slight water column.

At an initial pressure value "Pi" within the bellows 3d and at a high liquid height "H2", the sensor unit 3 is in a fully compressed position and is compressed considerably by the compression force from a superjacent high water column "Pa" to "Pi + Pmax", where the latter value is approximately to correspond to "2 Pi".

The measurement unit 5 can thus evaluate and transform each increase of the pressure value "Pa" above "Pi" as an increase "H2" of the liquid level 1 and can then represent an increase of the liquid or water volume corresponding to the increase, or alternatively evaluate the actual volume "V".

The wireless communication network 7 may advantageously consist of an available GSM network 8.

With reference to Fig. 4, this figure shows an alternative embodiment of a sensor unit 3' in that an elastic membrane 3e' sealing the tube end is inserted in the open tube end 4a and this membrane 3e' is disposed to seal the tube end 4a'. A membrane, designated 3e", can be displaced a distance into the tube end 4a'.

Fig. 4 illustrates how a membrane 3e' is adapted to seal the tube end 4a' and, in a magnified partial view, it is illustrated that the membrane 3e' displays a convex cross section of the pneumatic or hydraulic pressure value "Pi" prevailing within the tube system 4 and displays a concave cross section of the pressure value ("Pi" + "Pa") prevailing within the tube system 4.

The membrane can naturally be formed as a non-return valve permitting a clean blowing at high pressure of the tube system 4 and in particular the tube end 4a, in order subsequently to close and permit a pressure increase corresponding to the position of the liquid level.

The present invention is naturally not restricted to the embodiment disclosed by way of example in the foregoing, but may undergo modifications without departing from the scope of the inventive concept as illustrated in the appended Claims.

In particular, it should be observed that every illustrated unit and/or circuit can be combined with every other illustrated unit and/or circuit within the scope in order to be able to attain the desired technical function.

Claims

1. An arrangement (A) determining a liquid level (1) within a container (2) under the utilisation of, a pressure-sensitive and bottom-related sensor unit (3), in order with the aid of a hydraulic and/or pneumatic pressure (Pa) to permit the evaluation of the height (H2) of the liquid level above said sensor unit (3), a tube system (4) between the sensor unit (3) and a measurement unit (5), in order to distribute said pressure within the sensor unit to said measurement unit in order there, via circuits and functions, to generate a significative indication corresponding to a thus evaluated pressure value, said sensor unit (3) being structured as an elastic blister and/or a membrane, for instance a rubber blister (3a), and where said elastic blister (3a) with connected tube system (4) displays a pre-set pressure value (Pi), characterised in that said pre-set pressure value (Pi) is adapted to in any event correspond to a pressure value representative of the total container height (Hl) or another selected higher pressure value (2Pi) and that the measurement unit (5) includes a calculator unit, which is adapted to be zeroised against a reference pressure (Pi).

2. The arrangement as claimed in Claim 1, characterised in that said measurement unit (5) displays means for the wireless transfer of a significative indication.

3. The arrangement as claimed in Claim 1, characterised in that at an attained level value, stored in the measurement unit, there is generated an alarm signal, for instance representative of a high liquid level and/or a low liquid level.

4. The arrangement as claimed in Claim 1, characterised in that a membrane is related to a tube end of the tube system allocated to the container and placed a distance in the tube.

5. The arrangement as claimed in Claim 1 or 4, characterised in that a membrane is related to the tube end of the tube system allocated to the container and placed in order to cover said tube end.

6. The arrangement as claimed in Claim 1 or 5, characterised in that said membrane is formed as a non-return valve in order to permit passage of fluid into the container, for clean blowing.