METHOD AND DEVICE FOR MONITORING A FLEXIBLE FLUID CONTAINER

Abstract: Method and device for monitoring a signal being generated in dependence of the extension of said bag and being transmitted to a recording unit (17) remotely of said bag (18). At least one electric resonant circuit (11) is provided at said stoma bag (18) and is driven to an oscillating condition at a resonant frequency significant to said resonant circuit (11) while transmitting to ether a signal comprising electromagnetic energy. The resonant frequency is varied in dependence of the extension/stretching of said stoma bag (18) and the variation of resonant frequency is recorded in a receiver (16) in said recording unit (17) to generate, at certain conditions, an alarm. Said electric resonant circuit (11) comprises a resonant frequency determining means (18) interacting with the extension of said stoma bag (18), and an exciting means (15) is provided for driving said electric resonant circuit (11) to resonance.

Description: .METHOD AND DEVICE FOR MONITORING A FLEXIBLE FLUID CONTAINER The invention relates to a method of monitoring stretching conditions in a fluid container, especially a stoma bag, and a monitoring device in a fluid container made of flexible material provided preferably for monitoring overloading of stoma bags (stoma bandages) . A problem experienced by many stoma patients is that the stoma bag is overloaded and comes loose which may occur during night time when the patient is asleep and has no control over the stoma bag. When the stoma bag comes loose parts of the content in the stoma bag may leak and cause uneasiness. Obviously there is a great demand for an efficient and reliable monitoring device indicating in one way or the other that the stoma bag is filled up to a level where it conveniently should be emptied. However, the invention can be used also in other areas, for instance as a drain alarm for infusion bags. When a container made of flexible material is filled up with a fluid the pressure against the wall of the container is increased. According to US-A-3,546,944 a device sensing such pressure is disclosed. According to said patent a means is arranged over a fold of the wall of the container and is attached thereto on both sides of said fold. When a predetermined pressure has been reached in said container said means is torn apart while folding out said fold by the pressure in the container. However, said means may also be flexible so as to indicate during stretching thereof the level of stretching on a non- flexible scale. The alarm, or rather indication, that can be achieved by such a device is not intended to make an alarm for instance when a stoma bag is overloaded during sleep or when the bag cannot be visually observed at all times. However, an alarm at overload condition is generated with a device according to W090/11501. Said document discloses a monitoring device for fluid containers made of flexible material, preferably for monitoring an overload of stoma bags, comprising a flexible means which extends over an extendable section of the container wall while being fixedly attached to the container wall in the ends thereof. Said flexible means comprises a flexible resistor element having an electric resistance that is changed by the extension of said means and having a terminal for the connection thereof to an alarm device responding to any change of resistance in said resistor element. The measurement of resistance as described above requires some kind of power supply for said resistor element, and also the transfer of the registered resistance value is made through a wire connection according to the document. Said stoma bag according to W090/11501 comprises terminal means for the connection of power supply and measurements. It should be easy for a user of said stoma bag to change the stoma bag and after that continuously be provided with correct measured signals, and therefore said terminal means have to be readily connected to said power supply and a sensing device. At such conditions it is hard to avoid that said terminal means become rather space requiring and hard to completely cover under clothings, which by the user of the stoma bag is experienced as a problem. A second problem existing at the measurement of resistance and the registering of measured values is that the unit required for the measurement and for the alarm function has to be provided rather closely to said stoma bag, the wiring otherwise having too large drawbacks. An object of the invention is to accomplish a device setting aside the above-mentioned problems and according to which a very small sensor for measuring the stretching of said stoma bag is provided on said bag. Said sensor is also very cheap and will allow a wireless remote registering of the stretching of said bag. The invention will now be described in more detail by means of a description, reference being made to the accompanying drawings in which FIG 1 schematically shows a stoma bag having a sensor according to the invention, and FIG 2 is a cross sectional view from line 2-2 of FIG 1. The device according to the invention comprises a sensor 10 attached to a stoma bag 18 or integrated in a wall of said stoma bag 18. .An alarm box 23 is provided at a distance of said sensor 10. Said sensor 10 is formed as an electric resonant circuit 11. According to the invention said electric resonant circuit 11 includes a means 12 determining the resonant frequency, said resonant frequency determining means including in a preferred embod-iment a strip made of magnetic material. Said resonant circuit 11 includes also an inductive element, and a capacitor 13 in parallel there¬ with. In a preferred embodiment said inductive element is a coil 14 which is magnetically coupled to said magnetic element. The characteristics of said capacitor 13 and said coil 14 according to the invention is maintained at a comparatively constant level, and the resonant frequency is determined by the magnetic properties of said magnetic element 12. In a specifically preferred embodiment said magnetic element is made of a strip or wire made of amor¬ phous material, the magnetic properties thereof varying to a very large extent when mechanically influenced, for instance if said strip is exposed to tractive forces or compressive forces in the longitudinal direction of said material. The function of the magnetic element is described in more detail below. As mentioned above the device according to the inven¬ tion comprises also an alarm box 23 provided with an alarm sensor 22. Said alarm sensor 22 transmits an acoustic and visual indication so as to warn the user of the stoma bag 18 that a certain level has been reached therein. Besides the types of indication shown above or as a complement to such types said alarm box 23 can be provided with a device generating an alarm in form of vibrations which transmitted from said alarm box are directed towards the skin of the stoma patient. For the excitation of said resonant circuit 11 said alarm box 23 is provided with an eletric excitation means 15. Said excitations means 15 comprises a not shown radio transmitter which is arranged to transmit electromagnetic energy driving said electric resonant circuit 11 into resonance. When said electric resonant circuit 11 oscillates electromagnetic energy is transmitted to the ether, and said energy is received by a receiver 16 which can be a conventional type radio receiver. Said receiver 16 and said excitation means 15 are operatively connected to a recording unit 17. The force sensing section of said sensor 10 accor¬ ding to the invention is constituted by said magnetic element 12. In a preferred embodiment it is made by a core or a strip made of amorphous material. The longitudinal direction of said strip determines the force sensing axis of said sensor. Therefore, said axis is directed along the direction along which the mechanical stress condition is to be recorded by the sensor. Said magnetic element 12 is magnetically coupled to a coil 14 which can be wound in a conventional way or formed as a printed conductive pattern. In an alternative embodiement said inductive element and said magnetic element are combined into a so called "cloth inductor" in which said elements are connected in a cloth¬ like structure. Such an embodiment will provide a very high magnetic coefficient of coupling between said magnetic element and said conductive element. Said embodiment is also appropriate if it is desireable to provide the sensor as a layer in form of a film of rubber or similar material. Such a film is inserted as a layer in said stoma bag 18 during production of said bag. One advantage with this embodiment is that an acurate geometry of said sensor is ensured in said bag 18, no directional corrections being necessary afterwards. When said magnetic element is exposed to mechanical strain, for instance as elongation the magnetic properties thereof are changed. As a result of the coupling to said coil 14 also the properties of the coil and the resonant frequency of said resonant circuit are changed. Thereby it is possible, by recording a change of resonant frequency around a nominal or center frequency, to record also elongation or extension of the bag material surrounding said sensor. Said recording unit 17 of said alarm box 23 is to this purpose provided with comparator means 20 comparing a frequency value of said recorded resonant frequency to a reference value. Said reference value is stored in a memory means 21 capable of storing a plurality of reference values if appropriate in certain applications. When the stoma bag is filled the wall thereof is exposed to an increasing internal pressure when the level of filling increases, thereby extending said amorphous element and changing the magnetic properties thereof as stated above. When the stoma bag is almost filled up said resonant frequency corresponds to the predetermined value required for an alarm to be generated in said alarm box so as to indicate to the user of the stoma bag that it is time to change the bag. Said alarm box can be formed to be carried on an appropriate place on the body of the stoma patient underneath his clothes or at an appropriate place within or on any article of clothing. It is appropriate if the material which the stoma bag is made of is extendable or elastic as such. It is also possible to provide said stoma bag with a fold or a section which is folded or wrinkled, said sensor 10 being mounted on said section. In that case the ends of said sensor can be attached directly on the wall of the bag over said folded or wrinkled section. The device described above can be used in a way corresponding to the use of alarms indicating emptying of infusion bags where said sensor is arranged on a lower part of the bag and will contract as the infusion bag is emptied. Thus, in this case said sensor is arranged to trig said alarm device at a resonant frequency existing when said sensor is contracted, said sensor contracting during the emptying from the bag from an initial condition deter¬ mined by said strip 12, ensuring that the resonance fre¬ quency trigging the alarm will be reached when the content in said infusion bag is running out.

Claims: CLAIMS 1. Method for monitoring stretching conditions in a fluid container, preferable a stoma bag (18), a signal being generated in dependence on an extension of said bag (18) when receiving material therein, and said signal being transmitted to a recording unit (17) distant from said bag (18) c h a r a c t e r i s e d in that at least one electric resonant circuit (11) is arranged at said stoma bag (18), that said electric resonant circuit (11) is driven into resonance at at resonant frequency characteristic of said resonant circuit (11) during transmission of a signal comprising electromagnetic energy to the ether, that said resonant frequency is varied in correspondence to an extension/stretching of said stoma bag (18) that a variation of said resonant frequency is recorded in said recording unit (17) by receiving said electromagnetic energy, and that said recorded resonant frequency is compared to a predetermined frequency value for generating an alarm when said recorded resonant frequency shows a predetermined correspondence with said predetermined frequency value. 2. Method according to claim 1, c h a r a c t e r i s e d in that said generated alarm is indicated as a vibration sensible by a person carrying said stoma bag (18). 3. Device for monitoring stretching conditions in a fluid container, preferably a stoma bag (18), comprising means (10) for generating and transmitting a signal in dependence on the extension of said bag (18) when said bag is receiving material, and a recording unit (17) arranged distant of said tire for receiving said transmitted signal, c h a r a c t e r i s e d in that at least one electric resonant circuit (11) having a characteristic resonant frequency is arranged in connection with said stoma bag (18) for transmitting electromagnetic energy to the ether, that said electric resonant circuit (11) comprises means (12) determining said resonant frequency in connection with the extension of said stoma bag (18), that excitation means (15) is arranged for driving said electric resonant circuit (11) into resonance, that said recording unit (17) is operatively connected to at least one receiver (16) for receiving electromagnetic energy indicating the resonant frequency of said resonant circuit (11), and that said recording unit (17) comprises means (20) for comparing a value corresponding to said received resonant frequency with at least one reference value stored in a storing means (21) and for transmitting an alarm signal when there is a predetermined correspondence between said value and said reference value. 4. Device according to cla.iιιι 3, c h a r a c t e r i s e d in that said means (12) for determining said resonant frequency is formed as a strip made of amorphous material. 5. Device according to cla.im 3, c h a r a c t e r i s e d in that said electric resonant circuit (11) comprises a coil (14) which is magnetically coupled to said resonant frequency determining means (12). 6. Device according to any of claims 3-5, c h a r a c ¬ t e r i s e d in that said sensor (10) is attached to a wall of said stoma bag (18) such that said resonant frequency determining means (12) engages said stoma bag (18), the length of said resonant frequency determining means (12) changing when said stoma bag (18) is extended/stretched. 7. Device according to any of cla.ims 3-6, c h a r a c t e r i s e d in that said resonant frequency determining means (12) is integrated in the wall of said stoma bag (18). 8. Device according to any of claiLm 3-6 c h a r a c ¬ t e r i s e d in that said resonant frequency determining means (12) is connected to the wall of said stoma bag (18) by an adhesive connection. 9. Device according to any of claims 3-6, c h a r a c ¬ t e r i s e d in that said resonant frequency determining means (12) is arranged to surround said stoma bag (18). 10. Device according to any of claims 3-8, c h a r a c ¬ t e r i s e d in that said resonant frequency determining means (12) is provided in said stoma bag (18) for sensing the extension/- stretching of said stoma bag (18) in a direction which is transverse to the extension/stretching of said stoma bag (18) which is caused by the weight of a material received in said stoma bag (18).

Inventors: LINDE OVE, TYREN CARL H, LINDE, OVE, TYREN, CARL, H.
Applicants: LINDE OVE, TYREN CARL, LINDE, OVE, TYREN, CARL, H.
Application year: 1993
Main classification: G01L9
IPC codes: A61F5, G01L9, G01L19