DE3200556A1 - MICROWAVE HEATING DEVICE - Google Patents

Description

^:. * ^ PATENT ATTORNEYS DR KADOR & DR clunkers.

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K 13 889

Microwave heating device

This invention relates generally to microwave devices for safely heating a batch of various types Objects and in particular such a device for thawing the frozen parenteral Solution formed contents of plastic bags.

The addition of drugs to parenteral solutions is a widely accepted clinical practice. Although many intravenous supplements are currently manufactured in the patient wards by the nursing staff Increasingly, hospitals are demanding pharmacopoeic admixture programs to create to address the errors in medication and the risk of microbiological contamination ^ on reduce to a minimum. To minimize the use of available labor, have some pharmacies have used the practice to freeze additions.

Several antibiotics that are in clinical use are known to last for extended periods of time

remain stable when frozen in large volume parenteral solutions. Indeed, freezing antibiotic solutions can often extend stability and expose growth to essentially any microbiological contamination. Studies have shown that antibiotic admixtures remain unaffected for up to 30 days when frozen in container bags for 100 or 50 ml admixture. However, the hours of time it ^{takes to} thaw these units to room temperature often makes this technique unsuitable for the hospital setting. A certain improvement in the efficiency of the preparation or preparation can be achieved by thawing the bags in a warm water bath, a technique widely practiced in blood banks. Thawing in warm water, however, still takes considerable time, in addition to requiring labor intensive operations both to clean the baths to reduce the level of pollution and to prevent contact contamination during dispensing operations.

Microwave ovens have been proposed as a solution to these problems proposed as a medium for thawing frozen admixtures prior to intravenous administration. The resulting, rapid thawing would enable centralized admixture programs or drug programs to help one To operate 24-hour service without the need for a pharmacy to prepare the prescriptions to be ready anytime. Other characteristics include the opportunity to take advantage of efficiency, which is associated with large-scale manufacturing techniques. The possibility of a quality control would be particularly important produced batches to be sent before approval

³ ^ lead, which is currently not possible for prescriptions which are produced by conventional methods and for which the maximum permitted storage time in a refrigerated state is 24 hours.

Although microwave heating efficiency provides many benefits, previous microwave ovens have been satisfactory not all of the requirements for safe thawing of individually pouched units of parenteral substances on a scale required for practical applications. Even the most nuanced, time and temperature measuring controllers available with present microwave ovens cannot overheating of individual inputs under all conditions

jQ units during thawing of an entire filling or portion thereof prevent _T For example, an unfavorable combination of units in a predetermined section, which have substantially different volumes or chemical properties, which cause non-uniform temperature increases and a therefrom resulting overheating of special units. Similar consequences can result from accidentally adding a thawed or thawed bag to a completely frozen batch. In addition to the possibility of reducing the therapeutic effectiveness of its contents, overheating can also cause a special bag to burst. Under certain conditions, the explosive discharge from a ruptured bag can injure operating personnel, and in all cases the contents of that ruptured bag must be wiped off any equipment surface on which it accumulates.

The aim of this invention is therefore to provide a microwave heating device to provide what is safe, effective and at the same time removed from a frozen, parenteral Mixture formed contents of many plastic bags can thaw.

The invention is a microwave oven for selectively, quickly and safely raising the temperature of several separate objects. Basic components according to Subject matter of the invention are a housing, which a

Oven chamber delimited, a door, which gives access to it and a source of energy for introducing microwave energy into the chamber. Inside the chamber is one Arranged support arrangement, which defines a plurality of g heating stations, each of which is set up for this purpose is to pick up a separate object to be heated. A temperature sensor is in each of the stations arranged to measure the temperature of an object contained therein. Between microwave source and

A control circuit is coupled between the I Q temperature sensors and automatically deactivates the microwave source in response to the measurement of a temperature above a certain threshold value by any of the individual sensors. The arrangement of individual temperature sensors in each of several heating stations allows many objects to be heated up to a certain temperature level, while it is guaranteed that none of the individual objects will reach a temperature which is significantly above the certain height.

According to one feature of the invention, the sensors include a sensor located in an identifiable control station and a plurality of security sensors, which are each arranged in a different auxiliary station. The microwave source is de-energized by the control circuit, depending on either the measurement of a temperature above a given threshold by the control probe or by measurement by any of the Safety sensor for a temperature which is significantly above the specified threshold value. The control probe Automatically terminates a heating cycle when an item in the control station reaches a desired temperature has reached. At this time, all other items in the auxiliary stations will also be removed have reached temperatures within an acceptable temperature range. If, however

a special item in an auxiliary station already reaches a temperature prematurely which substantially exceeds that acceptable range, then causes it to do so a safety probe associated with this station automatically terminates the excitation of the Microwave source to prevent further heating.

According to another feature of the invention, each probe is enclosed by an elongated probe housing, formed from an electrically conductive material to provide shielding for microwave energy, and which has a length related to an antenna mismatched condition to the microwave transmission frequency of the source. The sensor housings prevent anything essential Microwave heating of the sensors, which therefore precisely reproduce the temperatures of the objects can be reached within each station in the chamber. 20th

According to yet another feature of the invention forms a rotatable base which is arranged in the chamber is an annular array of heating stations, each of which has a temperature responsive sensor records. The elongated probe housings which enclose the probes are centered in the chamber carried and extend radially into the stations. This temperature measuring system facilitates that Accurate temperature monitoring of a variety of different objects which are heated within the furnace chamber will.

According to another feature of the invention, each heating station includes a flat tray for carrying one object to be heated, and each probe housing includes an elongated, flat surface for engagement therewith. Each probe housing is arranged to be enclosed by a tray and an object

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and its flat surface is oriented substantially parallel to the tray. The flat housing surfaces promote heat transfer between the sensors and the heated objects.

According to yet another feature of the invention, the planar trays are oriented substantially vertically and include hooks for carrying the objects to be heated. The probe housings include vertical ones

, λ sections which are carried by the furnace housing, and horizontal sections, which are each arranged next to a central section of this tray, to which they are assigned. The trays equipped with hooks make it easier to warm up with one different sized substance-filled pouches, each of which in thermal engagement with the strategically arranged, horizontal housing sections can arrive.

According to another feature of the invention, a rotary joint comprises a stationary portion which is attached to the housing is mounted and has stationary contacts connected to the control circuit and a rotatable one Section which is attached to the rotatable base and has rotatable contacts which with the sensors are connected and in cleite engagement with the stationary contacts during the rotational movement of the rotatable base stand. The rotatable coupling facilitates the recovery of signal information from the temperature sensors, which move inside the microwave oven chamber.

Yet another feature of the invention is an electrical signal multiplexer that operates within the furnace chamber is attached and has an input connected to receive the output signals from all of the sensors and an output that is connected to the rotatable contacts and is set up to

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* consecutively all the output signals in a given Follow this to transfer. The multiplexer increases the signal capacity of the rotatable coupling assembly .

According to another feature of the invention, the multiplexer is housed in an electrically conductive box, of which an outer surface portion having both a dielectric coating material and a electrically conductive apron is covered adjacent to it. Microwave energy is used by the conductive Box and is dissipated by the capacitive block formed by the box, whereby the dielectric material and the conductive apron prevent interference with the multiplexer signals.

According to another feature of the invention, the rotatable coupling portion comprises an isolator column which extends through a wall portion of the housing and has an outer surface that supports the rotatable Carries contacts which comprise spaced apart rings, and the stationary coupling portion includes an insulator block carrying the stationary contacts and having a cylindrical opening which accommodates the isolator column. The stationary contacts comprise several spring contacts, which are arranged in pairs are, the spring contacts which form each pair, each a different one of the ring contacts grip around ■ and electrically connect 30

are bound. This arrangement provides an effective electrical coupling and the redundant pairs of the spring contacts prevent the loss of a signal depending on the accidental misalignment or the vibration of the various individual components.

In accordance with yet another feature of the invention, a turntable includes a centrally located column, a coaxial and displaceable wave picked up by it,

a device that produces a tongue and groove connection between the shaft and the column for mutual rotation, and a release mechanism which can be actuated to allow the relative axial movement between the column and the shaft.

After actuating the release mechanism, the isolator column can be extended from the isolator block, which the Removal of the entire turntable assembly from the furnace chamber allowed. The reassembly of the components is simplified by a conically shaped end section of the isolator column, which during the movement of the column into the isolator block engages the pairs of spring contacts.

The above and other objects and features of the invention will become even more apparent after studying the following description, which in connection with the attached drawings, in which:

Fig. 1 is a schematic perspective view of an inventive Fig. 2 is a schematic, partially cross-sectioned microwave oven. Fig. 1 is a front view of a single turntable heating station shown in Fig. 1;

FIG. 3 is a schematic, partially cross-sectional view of the heating station shown in FIG is,

Fig. 4 is a schematic cross-sectional view of a temperature sensor which is shown in Figs. 2 and 3,

Fig. 5 is a schematic view of a rotatable electric view Is the coupling shown in Fig. 1, Fig. 6 is a schematic view of a section,

taken along line 6-6 in Fig. 5,

Fig. 7 is a schematic view of a section,

which was made along line 7-7 in Fig. 6,

8 is a schematic view of a section through a center column of the one shown in FIGS. 5 to 7, rotatable coupling is,

Figure 9 is a schematic view showing details of the arrangement of the turntable and rotatable coupling which are shown in Fig. 1, and Fig. 10 is a schematic block diagram of an electric Control circuit for the microwave oven shown in FIG.

Fig. 1 illustrates a microwave heating device 11 made in accordance with the present invention is constructed. A housing 12 defines a furnace chamber 13, to which access is established by means of a door 14. Inside the chamber 13 is a rotatable Rotary disk assembly 14 for carrying items supported by a rotary drive mechanism 15 is coupled. A microwave source 16 transmits radiant energy to the oven chamber 13 for heating items contained herein. On a control panel of the housing 12 there is a display 18, several Oven control buttons 19 and a program card insertion slot

21. Between the control panel 17, the microwave source 16 and the drive mechanism 15 and a DC power supply 22 there is a printed circuit 23 for controlling the furnace. The above sections of the Microwave unit 11 are commercially available Microwave oven used.

The turntable 14 carries a control station 25 and several auxiliary stations distributed in the direction of the circular ring 26, which are each set up to accommodate an object to be heated in the chamber 13. Within the control station 25 is a temperature responsive control sensor 27 disposed while a temperature-responsive safety sensor 28 disposed in each of the auxiliary or auxiliary stations 26 is. A safety control circuit 31 is electrical with an alarm horn 32, an alarm light 33, a reset switch button 34 and an oven control circuit 23 coupled. Electrical signals from the sensors 27

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and 28 are from the chamber 13 of the furnace control circuit 23 and the safety control circuit 31 via the rotatable electrical clutch assembly 35 supplied. The heating stations 25, 26, the sensors 27, 28, the rotatable clutch assembly 35 and safety control circuit 31 are described in detail below.

Reference is now made to Figures 2 and 3; there is the control station 25 and the control probe in greater detail 27 shown. The secondary stations 26 and the safety sensors 28 are structurally identical to the Control station 25 and the control probe 27 and are therefore not further described. The control circuit is formed by a tablet 37, which is a lower Has end which is held in a base portion 36 of the turntable 14, and an upper end which is held by an upper portion 38 thereof. The control probe 27 comprises a horizontally oriented one End portion 41, which is arranged next to a central portion of the tray 37. From the top of the A hook 39 extends from trays 37 and carries an object 40 to be heated. With the preferred Use of the invention consists of the subject matter

40, for example, from a flexible plastic bag (as shown) containing an intravenous, contains freezing substance. When placed on bag 39, bag 40 overlies the end portion

41 of the sensor 27 and hereby comes into engagement,

to be in good thermal contact with it. As

^As shown in Fig. 3, the end portion 41 of the probe 27 is elongated in cross-section so that it provides a flat surface which is substantially parallel to and in close contact with the bag 40, the heat transfer therebetween being enhanced. As also shown in FIG. 3, the tray 37 is mounted at a small angle of, for example, 6 ° with respect to the vertical direction. This angle can be increased if there is increased heating rates for fewer stations

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are desired.

As shown in Figure 4, the control probe 27 comprises an elongated tube having a horizontal portion 41 and a vertical portion 42 which extends out of a sealed metal can 43 which also houses the safety probes 28 (Figure 5). A cable 44, which consists of a pair of insulated signal wires 45, 46, a braided, conductive shield 47 and an insulating cover 48, extends through the tube 41, 42. The outer ends of the signal wires 45, 46 are connected to the terminals of a thermistor 49, while the inner ends thereof are connected to an electrical circuit housed within the can 43, as will be described below. An electrical insulating tube 51 encloses the outer ends of the wires 45, 46 and the thermistor 49. The volume between the braided shield 4 7 and the horizontal pipe section 41 is filled with potting material such as silver epoxy, which has a high thermal conductivity, in order to produce good heat transfer between the pipe section 41 and the thermistor 49.

The heat transfer between the bag 40, (Fig. 2) and the thermistor 49 is due to the high thermal conductivity of the pipe section 41 and the potted connection 52 brought to the max. However, the direct heating by microwave energy at the sensor 27 brought to a minimum by the pipe 41, 42, which acts as a shield against microwave energy. Preferably, the tube 41, 42 is formed from a highly conductive material such as brass, and up to an extreme fine finish state with a material with coated with low resistance, such as with silver. In this way the conductivity is at the highest level brought and the microwave heating of the probe 27 to a minimum, because of the appearance

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the skin effect. In addition is the length of the probe 27 selected in such a way that it establishes a state of a non-tuned antenna for this purpose, at the microwave frequencies which are transmitted by the source 16. Such a mismatch further limits the microwave heating of the probe 27.

During the installation of the probe 27, the end of the braided shield 4 7 is pulled back around the ends of the signal wires 45, 46 attached to the opposite terminals of the thermistor 4 9 will. The insulator tube 51 is then placed over the thermistor 49 and with the portion previously withdrawn the braided shield 4 7 covered. After this preparation, the thermistor assembly is through the open end of the pipe section 4 2 is pushed in until it reaches the position inside the pipe section 41 achieved, which is shown in FIG. An electrically and thermally conductive potting compound 52 such as silver epoxy resin is then introduced through an opening 55 in order to completely fill the pipe section 41. Additionally to provide a mass for transferring heat between the bag 43 and the thermistor 4 9, the material 52 also seals the opening 55 in order to provide complete microwave shielding of the components manufacture inside the tube 41.

Reference is now made to Figures 5 through 8; there

are further details of the rotatable via assembly 35 shown. A cylindrical insulator block 57 is attached to a wall portion 58 of the housing 12, which closes the top of the furnace chamber 13. Axially extends through the cylindrical block 57 an opening 59 which receives a column arrangement 61, the lower end of which extends through the wall section 58 and is attached to the can 43. A plurality of spaced radial slots 62

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^ fir

Y penetrate a longitudinal surface portion of the block. A plurality of spaced-apart slots 63 extend radially into an opposite longitudinal surface section of the block 57. Although one of the slots 63 is shown in FIG. 6, it should be understood that the block 57 includes a plurality of slots, one of which is radially aligned with each of the slots 62. By means of a screw in each of the slots 62 there is a resilient, conductive one

2Q plate 64 held, which has an outer portion, which protrudes over the outer surface of the block 57, and an inner contact 65, which in the direction is spring-biased against the column 61. In a similar way Each of the slots 63 contains a resilient, guide 5 capable lamina 66 having an outer portion extending out of block 57 and an inner contact 67 which is spring biased towards the column 61. The sections of each on top of each other aligned pair of platelets 64,66 extending out of block 57 are electrical connected by insulated conductors 71. In addition, the outer end fitting portion of each of the wafers is connected to a different, insulated signal wire 72-76 (Fig. 5). Ground shields 77 for everyone Signal wires 72-76 are electrically connected to a collector wire 78 that extends longitudinally of the block extends and has opposite ends inserted into receiving openings therein.

Reference is now made to Figure 8; there details of the central column 61 are shown, which a plurality has identical, stacked insulating disks 81, which consists of a conically shaped insulator 82 and an elongated, cylindrical insulator 83 on one side are included. Circumferential recesses are along the top and bottom edges of the disks 81, a lower edge of the conically shaped insulator 82 and an upper edge of the elongated

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Isolator 83 is formed. Adjacent pairs of these recesses form annular channels, which each coincide with a ring contact 84 to 88 and accommodate this, and a metal cylinder 91 closes the lower portion of the elongated insulator 83. Each of the contact rings 84 to 88 is arranged in such a way that that it can be engaged with a different pair of the spring biased contacts 65,67. By the central openings in the disks 81 to 83 passing through an alignment rod 90 is pressed in, which is also extends through a top wall 89 of the can 43 and is attached thereto by means of a nut 90 '. In each of the Disks 81 to 83 also have a longitudinal slot formed with all of the slots on top of each other are aligned to produce a longitudinal channel 93 through the column assembly 61 therethrough. Through the Channel 93 and an opening 92 in wall section 89 extend a plurality of electrical lines 94 to 98 ', of which one is connected to each contact ring 84 to 88. Opposite ends of the lines 94 to 98 ' are connected to an electrical circuit in socket 43 as described below. So they are Lines 94 to 98 * individually each with the signal wires 72 to 76 (FIG. 5) via the ring contacts 84 to 88 and the contact plates 64, 66 connected.

It is returned to FIGS. 5 and 7; there the box 43 is shown in more detail, which, like described above, forms a housing for an electronic circuit, which between the sensors 27, 28 and the rotatable coupling 35 is connected. As shown, the can 43 is carried by a shaft 95 and in turn supports the central column 61. In order to restrict the entry of microwave energy, the Walls 96 of the can 43 are preferably formed from a material with good electrical conductivity, such as brass, for example A highly conductive material such as silver was subsequently finely revised to make it as small as possible

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Establish resistance. In addition, the side walls 96 of the can 4 3 are made of a dielectric material 97 covered, for example a -i.T.eflon tape, which is separated by a small air gap from a cylindrical metal sleeve 98 which is attached to the wall section 58 is fastened by means of screws 99. Together, the dielectric coating 9 7 and the encompassing, conductive one Cuff 98 as well as the side walls 96 form a capacitive block that serves to generate microwave energy to destroy and to prevent their entry into the can 43. Further insulation is provided by a ring-shaped, Energy absorbing disc. 101 is provided, which is arranged between the box 43 and the wall section 58 is, as well as an annular, energy absorbing disc 102, which is between the wall portion 58 and the rotatable coupling 3 5 is arranged. The disks 101 and 102 are made of a suitable microwave energy absorbent material such as Eccosorb (SFT-2.5) manufactured by Emmerson and Cummings in Canton, Massachusetts.

FIG. 9 shows the manner in which the can 43 and the components associated with it on the turntable 14 are carried inside the chamber 13. The hollow shaft 95 that supports the can 43 is above one Column 103 slidably received, which extends from the turntable 14 from the center. At the pillar and passing through a base portion of an L-shaped slot 104 in the shaft 95 is a pin 105

attached, which prevents the relative vertical movement between them. A second pin 106 is removable by means of of a hole in the column 103 and also extends through the base portion of the slot 104. When in position, pin 106 prevents relative rotational movement between the Shaft 95 and column 103 which align pin 105 with the upright portion of slot 104 would. After removing the pin 106, however, can

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such a relative movement take place, which allows the shaft 95 to follow the column 103 to move down when the pin 105 is received by the upright portion of the slot 104. The relative Vertical movement between column 103 and shaft 95 is sufficient to remove the supported can 43 and the Make column 61 of both the rotatable coupling assembly 35 and the sleeve part 98 (Fig. 7). Thus, these parts can be used together with the turntable

IQ 14 can be removed from the furnace chamber 13 through the door 14. During the reassembly, the conically shaped insulator 82 facilitates the centering of the column 61 during insertion into the coupling arrangement 35 and also causes the spring-loaded contacts 65 and 67 (FIG. 6) to be gently pushed apart when the column 61 enters the central opening 59 enters insulator block 57.

Fig. 10 shows in the form of a block diagram an 'electrics' Circuit 111 for controlling the operation of the microwave oven 11. In the control circuit 111 is a Multiplexer 112 and the safety control circuit 31 provided, which has a comparator section 114 and a section 115 with a device for processing the measured values and a latching switch. A variable resistor 116 provides an adjustable one Reference voltage for the comparator 114. The multiplexer 112 is housed in box 43 (FIGS. 5 and 7) and takes the exit on lines 45 and 46 of the control thermistor 49 in the control sensor 27. The outputs of the multiplexer 112 are also the Thermistors R .., R -... R added, which of the safety sensors 28 (Fig. 1) are kept ready. A connection between the multiplexer 112 and the safety circuit 31 establishes the rotatable coupling 35. The safety circuit 31 receives Power from the supply 22 and is connected to excite the horn 3 2 and the light 33 and from the

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self-holding state by a reset button switch 34 to be solved. Both from the section for the processing of measured values 115 and from the rotatable coupling 35 the furnace control circuit 23 receives signals and controls in turn the excitation of the microwave source 16.

Operation;

During the operation of the microwave unit 11, objects to be heated are arranged in the stations 25, 26 in the interior ¹ ^ of the oven chamber 13. In special cases of use, the objects consist of flexible plastic bags 40 which are filled with a frozen substance which, after thawing, is suitable for intravenous administration. Although any of the stations 26 may be left unoccupied by a frozen bag, there should always be a bag in the control station 25 prior to each thaw cycle. Because of this, the tax. station 25 clearly from the secondary stations 26 through a

Identification code 121 differentiated. In addition, 20

the filled volumes of all bags in a given run will be essentially the same, and their contents should have essentially similar thawing properties. After the turntable 14 with the number of required bag has been filled, door 14

closed, an appropriate program card is inserted into slot 21 and oven control buttons 19 are turned off operated in a conventional manner to energize the microwave source 16 and begin a thaw cycle. if

If the thawing process continues, the Thermis-30 will deliver

gate contained in each sensor 27, 28 of an occupied station, one for the temperature of the bag to which it is in thermal contact, proportional resistance. Conversely, the thermistors give that

in the sensors in the unoccupied stations

keep the ambient temperature in this station again. The signal indicating the temperature from the control sensor 27 on the lines 45, 46 is passed through the socket 43 directly into the lines 97 ^! ,

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passed on via the rotatable coupling 35 and the output lines 75, 76 to the furnace control circuit 23. The individual outputs of the safety sensors 28 are, however, received by the multiplexor 112, which constantly transmits these signals over the lines 94, 95 * in a specific sequence. The through the multiplexer Treated measured values are passed through the rotatable coupling 35 and via the output lines 72, 73 in the comparator section 114 entered. An equal supply

IQ voltage is obtained from the multiplexer 112 from the safety circuit 31 via the line 74, the rotatable coupling 35 and line 96 'added. Both for the DC power supply and the output of control probe 27 is through line 75, line 97 'and the rotatable Coupling 35 provided a common line.

The oven control circuit 23 is programmed in such a way that it monitors a defrosting activity and controls the excitation of the source 16 as a function of the measured value information from the control sensor 27. If this measured value information shows that essentially the entire contents of the bag in the control station 25 has reached a temperature threshold in the fully thawed state, for example 25 ^° C., then the oven circuit 23 ends the activities. At this point the bags contained in any of the slave stations 26 will have reached substantially the same temperature because of the even distribution of microwave energy produced by the rotating turntable 14. At the end of a defined cycle, the door 14 can be opened and the thawed bags can be removed and used as desired.

If, however, it is assumed that a bag in one of the secondary stations 26 inadvertently reaches a certain maximum safety ^{temperature threshold, for example 50 °} C., then temperature levels above this threshold can either damage the liquid contents of the bag or cause it to burst. Such a one

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Situation can arise from various circumstances, for example from the fact that a slave station 26 is already at the start of the thawing cycle contains a bag that has already been partially or fully defrosted, a bag with a smaller volume than that bag contained in the control station 25, or a bag that is filled with a substance that has a significantly different thermal characteristic compared to the Has the bag contained in the control station 25

After reaching the certain safety temperature or the temperature at which safety is no longer present, the safety measuring sensor 28, which is assigned to this bag, generates the rotatable coupling 35 and the output lines 72 via the multiplexer 112, the measuring wires 94, 95 ^s , 73 a signal voltage which is lower than a reference voltage which is produced by the adjustable resistor 116 in the comparator 114. The comparator section generates as a function of this

114 and the section on measured value processing and the latching switch 115 provides an output for the Oven control circuit 23 which causes the microwave source 16 to be de-energized. Additionally excites the section for measured value processing

115 the horn 32 and the light 33, which are both

provide audible as well as visual indication that the certain safety temperature limit has been exceeded became. Defrosting activities can only be resumed after the overheated object has been removed, the overheated probe will move below the The threshold has cooled down and the reset head 34 has been actuated by hand in order to cancel the self-holding state, which is present in the circuit section 115.

An essential feature of the invention prevents the security sensors 28 in unoccupied substations trying to reach a temperature that would cause the oven to shut down. This feature allows the oven unit 11 to be used with a

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Turntable 14 which is filled with less than full capacity. Reference is again made to FIG. 4; the mass, which is formed by the thermally conductive potting material 52, acts as a heat sink, which scatters or dissipates the limited amount of heat generated by microwave energy present on the surface of the shielding portion 41. As a result, the mass 52 in an unoccupied station 26 and the thermistor contained therein will not reach the shutdown temperature during normal operating conditions. Conversely, in the absence of a frozen bag in the control station 25, the mass 52 in the control probe 27 is selected so that it can be heated by microwave energy to a temperature above that required to normally end a thawing activity. Thus, in the event that there is no frozen bag in the control circuit 25, the control probe 27 will quickly obtain a temperature which will cause the oven control circuit 23 to respond as if a regular thaw cycle had been completed _{T on}

normal cycle can then continue after an operator discovered the problem and found a frozen - ~ - B-etrtel- in- ~ de-r -tuers tat ion -2-5-a-ngeoretoefc-hafe - * - ~~ -.— ~~

It will be apparent that many modifications and variations of the present invention can be made in light of the above teachings possible are. While a preferred application of the invention has been described, this description serves just as an example and it can be seen that the furnace

° Q can also be used to safely heat lots of objects other than those specifically mentioned. It is therefore pointed out that the invention can also be put into practice in other ways than this

specifically described.
35

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Claims (16)

^::. -PATENTANWÄLTE DR KADOR & DR clunkers. Baxter Travenol Laboratories, Inc. One Baxter Parkway DEERFIELD, Illinois 60015 USA K 13 889 Microwave heating device Expectations My furnace equipment, marked through the following features: - A housing device (12) which has an oven chamber (13) forms, - a door device (14) which provides access to the chamber, - An excitable device (16) for delivery and transmission of microwave energy into the chamber, - a pad (14) arranged in the chamber and forming a plurality of stations (25, 26), each of which are set up to accommodate a separate object to be heated, - A temperature sensor (27, 28) which is arranged in each of the stations and set up for this purpose is to measure the temperature of an object contained therein, and - A control circuit (31) which is coupled to the dispensing device and the measuring sensors and is set up for this purpose is, the delivery device automatically depending on the measurement of a temperature above - 2 to de-energize a certain threshold by any of the sensors. 2. Device according to claim 1, characterized in that that the sensors comprise a control sensor (27) which is located in an identifiable control station .. (25) is arranged, as well as a plurality of safety sensors (28), and that the control circuit (31) for this purpose is set up, the delivery device (16) as a function of either the measurement of a temperature above a predetermined threshold value by the control probe or by measuring a temperature de-energize any of the safety probes which have a second, from the first, threshold significantly exceeds the different threshold value. 3. Device according to claim 2, characterized by an elongated sensor housing (41) which each sensor (49) and is formed from an electrically conductive material to provide a shield against To form microwave energy, each housing having a length which for this purpose at the microwave transmission frequency the output device (16) produces the state of a non-tuned antenna. 4. Device according to one of claims 1 to 3, characterized characterized in that the base is a rotatable base (14) which is einaerichfcet for the movement of the stations (25, 26) to enable, and a drive device (15) which for moving the base is excitable. 5. Device according to one of claims 2 to 4, characterized in that the different, second threshold value is higher than the specified threshold. 6. Device according to one of claims 3 to 5, characterized in that each of the elongated probe housings (41) has an elongated, flat surface for engaging an object (40) located in the station (25, 26) which the probe occupies. 7. Device according to one of claims 4 to 6, characterized in that the rotatable base (14) has a flat support plate or a flat tray (37), which is set up to hold an object to be heated (40) to support, and that the sensor housing (41) are arranged and set up in such a way that they on both sides are enclosed by the tray and the items, the flat surface being substantially parallel runs to the tray. 8. Device according to one of claims 3 to 7, characterized characterized in that the sensors (27, 28) are centered in the Chamber (13) are carried and extend radially into the station (25, 26). 9. Device according to one of claims 4 to 8, characterized by a rotatable coupling arrangement (35), which provides an electrical connection between the circuit device (31) and the measuring sensor devices (27, 28) and comprises a stationary portion which is attached to the housing means (12) and has stationary contact devices (65, 67) which 30 are connected to the control circuit device, as well as a rotatable section (61) which is attached to the base (14) is attached and has rotatable contact means (84 to 88) which are connected to the sensors are and displaceable the excitation of the stationary contact devices during the rotational movement of the base allowed. 10. Device according to claim 9, characterized by a multiplexer device (112) which is attached to the base (14) is mounted inside the chamber (13) and has an input (R) for receiving output signals from all sensors (27, 28) is connected, the multiplexer having an output (94, 95 ') with the rotatable contact device (35) is connected and is set up to this successively all output signals in a specific Transfer order. 11. Device according to claim 10, characterized by an electrically conductive box (43) which completely including the multiplexer means (112) for providing microwave energy shielding therefor. 12. Device according to claim 11, characterized by a dielectric device (97) which has an outer Surface portion of the can (43) covers, as well as an electrically conductive sleeve device (98) which is arranged near the dielectric device, wherein the socket (43), the electrical device and the The cuff means form a capacitive block that dissipates the microwave energy emitted by the dispenser (16) is transmitted. 13. Device according to one of claims 10 to 12, characterized in that the rotatable contact device (61) comprises a plurality of electrically isolated, rotatable contacts (84 to 88), each with a different Output terminal of the multiplexer (112) are connected, and that the fixed contact device has a plurality electrically insulated, stationary contacts (65, 67), each with one of the rotatable contacts are in sliding engagement. 14. Device according to claim 13, characterized in that the rotatable portion is a cylindrical insulator column (61) extending through a wall portion of the housing (12) with an outer surface carries the rotatable contacts comprising longitudinally spaced annular contacts (84 to 88), and that the stationary section (35) has an insulator block which carries the stationary contacts (65, 67) and a cylindrical one Has opening which receives the isolator column. 15. Device according to claim 14, characterized in that the stationary contacts have a plurality of spring contacts (64, 66) have, which are arranged in pairs and each form a pair that is a different one of the ring contacts (84 to 88) and engages in this and electrically connected by a line device (71) is. 16. Device according to claim 15, characterized in that the rotatable base (14) has a centrally arranged Column (103), a shaft (95) received coaxially and displaceably by the column and a device (104, 105) comprises, which hereby fixes the shaft and column for rotary movement against each other, wherein a release device (106) is provided which is operable to allow the relative axial movement between the column and shaft to the removal of the column (61) from the isolator block allow.
30th