News Column

Researchers Submit Patent Application, "Medical Device Heaters and Methods", for Approval

July 18, 2014



By a News Reporter-Staff News Editor at Health & Medicine Week -- From Washington, D.C., NewsRx journalists report that a patent application by the inventors Hedmann, Frank L. (Volkach, DE); Sebesta, Sven (Schweinfurt, DE); Wernicke, Ulrich (Theres, DE), filed on February 13, 2014, was made available online on July 3, 2014 (see also Fresenius Medical Care Deutschland GmbH).

The patent's assignee is Fresenius Medical Care Deutschland GmbH.

News editors obtained the following quote from the background information supplied by the inventors: "In dialysis machines, heating of dialysis fluid is usually realized as an ohmic heating element to which a heating control applies mains voltage to switch the heating element on or to disconnect the heating element from the mains voltage in order to switch it off.

"The heating power can be set and adapted to the different rated voltages to split the heater into a plurality of heating elements or to control the heating elements via a phase angle control. Phase angle controls are, however, complicated and moreover have problems with electromagnetic irradiation. There is moreover a substantial power loss in the electronic system. The previously known division into a plurality of heating elements furthermore has the disadvantage that the devices have to be switched differently at different rated voltages of the mains power in order not to reach any unpermittedly high power consumption."

As a supplement to the background information on this patent application, NewsRx correspondents also obtained the inventors' summary information for this patent application: "In one aspect of the invention, a medical device (e.g. a dialysis machine) has a heater with at least one heating element as well as a heating control unit. The heating control unit applies mains voltage to the heating element. The heating control unit in this respect includes a monitoring arrangement and a switching arrangement. The monitoring arrangement can recognize the zero crossings of the mains voltage, and the switching arrangement can switch the at least one heating element on or off in the zero crossing.

"The heating control unit controls the power of the heating via the switching on and off of one or more half cycles of the mains voltage.

"Individual half cycles of the mains voltage can be switched on or off in this process. However, pulse packets can naturally also be connected with a plurality of half cycles or periods of the mains voltage. In this respect, the power is set via the ratio of the number of the half cycles with a switched on heating element to the number of the half cycles with a switched off heating element. In this respect, the irradiation, the number of components, and the power loss in the electronic system is considerably reduced with respect to a phase angle control.

"In an advantageous embodiment of the present invention, the monitoring arrangement detects the level of the mains voltage, and the heating control unit adapts the control of the at least one heating element to the detected level of the mains power supply. The medical device (e.g. dialysis machine) can be operated at different rated voltages of the mains voltage. The control of the power of the heating via the switching on and off of one or more half cycles of the mains voltage in particular allows an operation at different rated voltages of the mains power supply and/or allows an adaptation to fluctuating voltage levels of the mains power supply. The same maximum power of the heating at different mains AC voltages can in particular thus be provided. In this respect, the ratio of the number of the half cycles with a switched on heating element to the number of the half cycles with a switched off heating element is adapted to the detected level of the mains power supply, so that in each case the same maximum power of the heating is available independently of the level of the mains power supply.

"The medical device (e.g. dialysis machine) can furthermore have at least two heating elements which can be switched on and off independently of one another by the switching arrangement. The division into two heating elements in this respect permits an even more flexible control of the power of the heating.

"In this respect, with regard to the above-described control of the power of the heating via the number of the half cycles with a switched on heating element or with a switched off heating element, the number of the half cycles at which the first heating element is switched on and the number of half cycles at which the second heating element is switched on are advantageously added together, optionally while taking account of a factor for considering different rated powers of the two heating elements. The same applies to the number of the half cycles with a respective switched off first or second heating element.

"In this respect, the heating control unit advantageously has a first operating mode in which the two heating elements are operated partially or fully synchronously. The two heating elements in this respect in particular have rated voltage half cycles applied synchronously in part or in full. A correspondingly higher power can also be achieved with a low supply voltage due to the synchronous operation of the two heating elements. In this respect, both heating elements can be switched off synchronously for a corresponding number of half cycles. Alternatively, however, it is also conceivable only to switch off one of the two heating elements in each case to reduce the power.

"In some embodiments, the heating control unit has a second operating mode in which the at least two heating elements can be operated alternately. The two heating elements in this respect have a specific number of mains voltage half cycles applied alternately. In this second operating mode, for all mains voltage half-cycles in which the first heating element is switched on, the second heating element is switched off and vice versa. With this alternating operation, both heating elements can naturally also be switched off. The alternating operation of the two heating elements, in particular the operation of the two heating elements with one respective half cycle, makes it possible to maintain the amperage and/or power in a permitted range even at high supply voltages. The two heating elements are in this respect operated alternately with sequential half cycles.

"In some embodiments the heating control unit selects the first or second operating mode in dependence on the detected level of the mains power supply. It can thus be ensured that the same maximum heating power is provided despite different rated voltages of the mains power supply. Currents which would overload the mains power supply and/or the heating elements can furthermore be avoided by the second operating mode, even at high rated voltages.

"The heating control unit advantageously selects the first operating mode on detection of a mains AC voltage which is in a first, lower voltage range and the second operating mode on detection of a mains AC voltage in a second, higher voltage range. The first, lower region in this respect advantageously includes at least one mains AC voltage between 100 V and 120 V, (e.g., 100 V, 110 V or 120 V). The second higher range advantageously includes at least one mains AC voltage between 230 V and 250 V (e.g., 230 V or 240 V). In some embodiments, the first range includes the range between 90 V and 110 V. The first range can alternatively include the range between 80 V and 130 V or between 80 V and 160 V. The second range can advantageously include the range between 220 V and 240 V. The second range can alternatively include the range between 180 V and 250 V or between 160 V and 250 V.

"In an operation in the first and/or second operating modes, the ratio of the number of the half cycles with a switched on heating element to the number of the half cycles with a switched off heating element is advantageously set in dependence on the level of the detected mains AC voltage. With a mains AC voltage which lies within the respective voltage range in which an operation takes place in the first and/or second operating modes, the maximum power of the heating can be kept constant and/or a desired power can be set.

"The medical device can in this respect be operated in the first operating mode so that the two heating elements for setting the power are not acted on by all mains voltage half cycles, but are rather switched on and off synchronously or alternately for one or more mains voltage half cycles.

"In the second operating mode, not every half cycle is switched either to the one or to the other heating element, but a corresponding number of half cycles is not switched to any of the heating elements to reduce the power. The number of mains voltage half cycles which can act on the heating elements can be changed accordingly depending on the level of the mains AC voltage.

"The above described devices and methods can also be used with more than two heating elements. For the example, the above described devices and methods could be implemented with three or four heating elements, where the three or four heating elements each alternately have half cycles applied in the second operating mode, so that a half cycle is always as a maximum switched to one of the heating elements. The alternate operation can in this respect take place, for example, in that one or more half cycles are sequentially switched to the individual heating elements. The heating resistance of each individual heating element can hereby be increased and thus the maximum power consumption correspondingly reduced at a high mains voltage. At a low voltage, the heating elements can then be operated in parallel in the first operating mode. More than four heating elements are naturally also conceivable in this respect.

"In the above-described embodiments, the power of the heating was adapted to different levels of the mains power supply via the switching on and off of one or more half cycles of the mains voltage. The maximum power of the heating can thus be kept the same for different mains voltages. In addition, the occurrence of unpermittedly high currents can be avoided.

"The devices and methods described herein can, however, also be used to set the power of the heating to a value below the maximum power for purposes of temperature regulation. The present invention can, for example, be used to set the heating to a value between 0 and 10% of the maximum power. The currently output power can also here be set by the ratio of the number of the half cycles with a switched on heating element to the number of the half cycles with a switched off heating element.

"The medical device in this respect advantageously includes a temperature sensor, wherein the ratio of the number of the half cycles with a switched on heating element to the number of the half cycles with a switched off heating element can be set in dependence on a signal of the temperature sensor.

"Such a temperature regulation can in this respect also be used independently of the adaptation of the power of the heating to different mains voltages, in particular also with those devices which can only be used with a single mains voltage. Such a temperature regulation is, however, advantageously combined with an adaptation to the operating voltage of the mains power supply.

"In some embodiments, the heating control unit generates a control signal on the basis of the signal of the temperature sensor which is superimposed on the control signals for adapting the power to the detected level of the mains power supply. Different embodiments are conceivable for such a superimposition.

"In some embodiments, an envelope signal with a longer switching period in comparison with the mains voltage period can be generated using the signal of the temperature sensor. The envelope signal can be superimposed on the adaptation of the power to the detected level of the mains power supply working at one or more mains voltage half cycles. Alternatively, the ratio of the number of the half cycles with a switched on heating element to the number of the half cycles with a switched off heating element can be set directly smoothly in time in dependence on the signal of the temperature sensor and of the detected level of the mains power supply.

"In certain embodiments, one or more half cycles of the mains voltage are switched on and off. For example, individual mains voltage half cycles can be switched on and off. However, pulse packets of a plurality of half cycles of the mains voltage can also be switched on and off. For example, pulse packets of 1 to 100 mains voltage half cycles (e.g., 1 to 10 mains voltage half cycles) can be used.

"The heating element is in this respect relatively slow in its reaction so that the temperature of the heating element does not rise and fall in a relevant manner with the switching on and off of the half cycles on the use of a plurality of half cycles of the mains voltage, but rather is only determined via the mean ratio of the number of the half cycles switched on and off. To achieve a setting of the power which is as fine-grained as possible over a large power range and/or a large range of mains DC voltages, the smallest number of switchable half cycles used for the control are typically, kept relatively low (e.g., at 1 to 5 half cycles, at 1 to 3 half cycles).

"The ratio of the number of the half cycles with a switched on heating element to the number of the half cycles with a switched off heating element is in this respect advantageously determined for a specific time period or a specific number of half cycles and is used for the control. A typical time period in this respect can lie, for example, between 0.1 and 20 seconds (e.g., between 0.5 and 5 seconds).

"The heating control unit can switch the respective next half cycles on or off at any time so that the ratio remains at a desired value within the time period used for the determination.

"It is equally conceivable to redetermine the ratio required for the provision of the desired power of the number of the half cycles with a switched on heating element to the number of the half cycles with a switched off heating element after a fixed time period or after a fixed number of half cycles and then to carry out a corresponding control in the following time period or in the following fixed number of the half cycles. A typical time period can in this respect lie between 0.1 and 20 seconds (e.g., between 0.5 and 5 seconds). In this respect, the ratio is recalculated on the basis of the measured mains AC voltage and of the desired power.

"The devices and methods described herein can be used in a dialysis machine wherein the heater is used for heating a medical liquid, such as dialysate or blood. In some embodiments, the medical device is a peritoneal dialyzer having a heater for heating dialysate. The devices and methods described can equally be used in infusion devices, in particular for heating an infusion solution.

"The devices and methods can be used with any desired embodiments of dialysis machine heaters, including throughflow heaters, heating bag heaters, and heaters for heating a presentation or supply bag.

"A temperature sensor which directly measures the temperature of the heating element can be used as a temperature sensor for regulating the temperature. Alternatively or additionally, a temperature sensor can also be used to determine the temperature of the medium to be heated, such as the temperature of the dialysate used in a peritoneal dialysis device.

"In addition to the medical device with a heater, certain embodiments include a heating control unit for a medical device such as was described above. Such a heating control unit in this respect has the advantages such as were already described above.

"In another aspect, a method for operating a medical device having a heater with at least one heating element or for operating a heating control unit for such a device includes detecting the zero crossings of the mains voltage and switching the at least one heating element on and off in the zero crossing, wherein the power of the heating is controlled via the number of the half cycles of the mains voltage with a switched on heating element.

"The method advantageously takes place in this respect as was represented in more detail above with respect to the medical device. In this respect, the method can be a method for operating a medical device or a heating control unit of the type described above.

"The heating control units described herein can improve the heating methods of medical devices by providing simple and effective heating for such medical devices.

"The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

"FIGS. 1a-1c illustrate three diagrams which show typical developments of an automatic peritoneal dialysis treatment.

"FIG. 2 is a schematic diagram of a peritoneal dialysis system.

"FIG. 3 is a schematic diagram of the division of the peritoneal dialysis system into a dialysis machine and a fluid system.

"FIGS. 4a and 4b are perspective and plan views of a first embodiment of a cassette.

"FIG. 5 is a plan view of a second embodiment of a cassette.

"FIG. 6 is a perspective view of a first embodiment of a dialysis machine.

"FIG. 7 is a schematic fluid flowchart of a first embodiment of a peritoneal dialysis system.

"FIG. 8 is a perspective view of a second embodiment of a dialysis machine.

"FIG. 9 is a schematic fluid flowchart of a second embodiment of a peritoneal dialysis system.

"FIG. 10 illustrates the coupling of the cassette in the second embodiment of a peritoneal dialysis system.

"FIG. 11 illustrates a first embodiment of a pump actuator.

"FIGS. 12a and 12b illustrate the coupling of a pumping region of the cassette to a pump actuator.

"FIG. 13 is a schematic diagram of the design of an embodiment of a controller.

"FIG. 14 illustrates a first embodiment of a heater that includes two heating elements.

"FIGS. 15a and 15b are diagrams which show the mains voltage half cycles applied to the two heating elements of the heater shown in FIG. 14 in two different operating modes."

For additional information on this patent application, see: Hedmann, Frank L.; Sebesta, Sven; Wernicke, Ulrich. Medical Device Heaters and Methods. Filed February 13, 2014 and posted July 3, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=1838&p=37&f=G&l=50&d=PG01&S1=20140626.PD.&OS=PD/20140626&RS=PD/20140626

Keywords for this news article include: Fresenius Medical Care Deutschland GmbH.

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Source: Health & Medicine Week


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