DE1565845C3 - Microwave oven - Google Patents

Description

40

The invention relates to a heating device with a work space for receiving food to be cooked, a electrical energy source and an ultra-high frequency generator connected to it, which an evacuated room, an electron gun, and electron trapping devices to form one Having electron beam within the evacuated space. '

Heaters of this type, commonly called microwave ovens are known. The known microwave ovens usually include one Variety of electronic components each performing different functions, most of which are arranged outside the furnace or work space. These known microwave ovens have in Depending on whether they are operated with direct current or alternating current, usually one complicated rectifiers, filters, a high voltage transformer and power lines. This equipment is necessary for the normal mains voltage to convert it into the high voltage necessary to excite a conventional magnetron tube. The Magrie- ■ arranged outside the work area tron tube is an essential component of the known microwave ovens. ' The magnetron is used to convert high voltage electrical energy into microwave energy; The magnetron tube is in operation consume a considerable amount of energy and generate a great deal of heat. Well-known types of ovens or stoves therefore require a fan to circulate the air or a pump to circulate the liquid in order to achieve the To be able to cool the magnetron tube.-Such devices are expensive, lead to electrical interference and increase the size of the known microwave ovens ioder ovens to such an extent that they are unsatisfactory for domestic or industrial use and have proven impractical.

The magnetron tube is usually attached to a shaft or oven in the known stoves or ovens. Waveguide connected, the dimensions of which are very precisely determined and worked so that through The microwave energy generated by the magnetron tube can be conducted to the furnace chamber. This waveguide generally ends at a stub or point source that opens at a small opening in a wall of the furnace chamber is arranged. Near this opening is a rotating or oscillating one Stirrer or fan arranged to distribute the radiated microwave energy evenly is used via the furnace chamber. Distribute these stirrers or fans of known microwave ovens the microwave energy in the oven is insufficient, so that the heating energy is not evenly distributed in the oven and hot or cold spots occur locally. In addition, such mechanical components increase the Cost and are relatively unreliable so that they hitherto in the way of the use of known microwave ovens stood.

In summary it can be said that the known microwave ovens or ovens have a complicated structure, are expensive and usually unsuitable for many uses because they take up a lot of space, and many electrical components located outside the cooker housing, as well as dangerous ones Have high voltage connections, so that they are unsuitable for household use.

The invention is based on the object of a heater of the type mentioned to create, which is due to its simpler and more compact Structure suitable for use in the household, can be produced easily and inexpensively can and gets by with significantly lower energy consumption than the known units.

'According to the invention, this object is achieved in a heating device of the type mentioned in the introduction, that the evacuated space is airtight by two oppositely arranged * at its peripheral edge interconnected, flat, dielectric plates are formed, which have a substantially flat, elongated evacuated space that limit to the flat surfaces of the opposite one another arranged dielectric plates facing the electron beam, electrostatic Focusing devices for focusing the electron beam in a flat fan in the space are printed between the dielectric plates and that on one of the dielectric plates, which at the same time forms at least part of a wall of the work space, an electromagnetic device is printed on is, which interacts with the moving electrons in the fan beam in such a way that its 'Electron transmission energy in micro-electrical energy is converted.

In the case of the microwave oven according to the invention, that is

actual heater arranged within the stove housing in such a way that it forms one side of the furnace space. The heater is a low-voltage unit that connects directly to the usual household mains voltage works and therefore does not require a magnetron or external cooling devices arranged outside the furnace. Almost all components of the heater according to the invention use printed circuits on dielectric plates, for example provide preferred embodiments of the invention that the components for generating and collecting of the electron beam, the device for bundling the electron beam, the microwave coupling device, the microwave radiators and the feedback circuits are printed circuit boards are. A variety of heating devices or microwave units for individual and different Operating frequencies can work side by side in a common vacuum jacket on one Wall of the work or furnace room to be heated, each unit has its own printed emitter. These radiators can be of any shape, with, when using several Radiators, either all of the same shape or of different shapes. The microwave signals of the different units are deliberately non-coherent, making the microwave energy uniform is radiated over the room to be heated and any mechanical circulation is superfluous will. The printed components provided according to the invention allow automatic production, so that the heater according to the invention not only a reduction in furnace dimensions and a Control of the operating voltage allowed, but also a reduction in manufacturing costs in comparison brings with it to the previously known microwave ovens.

Another advantage of the heater according to the invention can be seen if one considers that so far known devices of this type have relatively complex devices for measuring the voltage on the output line and need to feed back the measurement signals to the high voltage supply of the magnetron tube to keep it at a constant value. According to the invention, such complex circuits and additional facilities by using a simple and reliable control circuit avoided in a preferred embodiment. When the output power of the microwave unit changes, this power control circuit changes the coupling between the electron beam and a with this interacting device, so that a constant performance and constant operation of the microwave unit regardless of short or long-term changes in the power supply or decreasing electron emission is ensured due to aging phenomena. At a preferred embodiment, the control circuit comprises a differential deflection amplifier, the uses a certain part of the main electron beam as its amplifier beam. A printed microwave radiation meter forms part of a printed bridge circuit that separates voltages on opposite sides of the main electron beam arranged deflection electrodes are. These deflection voltages are of suitable polarity and Size in order to automatically transfer the electron beam to or from the coupling circuit away, thereby ensuring a constant microwave output power.

In summary, it can be stated that the heater according to the invention of a microwave oven known type, in which a klystron is used, is completely different. The difference is based essentially that the generator in the heater according to the invention has two dielectric plates has, which form an evacuated work or furnace space, in addition to both plates electrostatic focusing devices and an electromagnetic device for converting the Electron translation energy in microwave energy are printed. By using the dielectric panels Subject matter of the invention fulfill various functions, namely to form the work space once, as well but as a carrier for the imprinted beam focusing devices and also as a carrier for the imprinted electromagnetic device and other printed connections to serve as radiators or the like, the result is a completely new concept compared to the known microwave ovens. The inventive Heater is simple to manufacture and because of the simple structure of its components cheaper than a normal klystron, it also has a much lower energy requirement on.

Further advantages and details of the invention emerge from the exemplary description which follows on the basis of the drawing. In the drawing shows

F i g. Figure 1 is a perspective and partially broken away view of a one-piece microwave generating unit and radiating unit according to the invention,

F i g. 2 is a front perspective view of a furnace constructed in accordance with the invention, in which the upper furnace wall is formed by the microwave unit, wherein a plurality of microwave radiators is used,

F i g. 3 is a schematic circuit view of a voltage multiplier;

F i g. Figures 4A and 4B show plan views of printed circuit boards used as electrostatic focusing arrays or serve as coupling circuits,

F i g. 5 shows a top view of an additional form of printed coupling arrangement according to FIG the invention,

F i g. 6 shows a sectional perspective view of an alternative embodiment of the microwave unit according to the invention with an electron gun and electron collecting plates which are arranged disaxed from the major axis of the electron beam;
F i g. 7 schematically shows a power control circuit according to the invention and FIG

F i g. 7A is a graph of output power as a function of microwave oven operating time.

In Fig. 1 shows a microwave oven unit according to the invention, which is a compactly constructed one-piece Unit 15 for power conversion and for generating and radiating ultra-high frequencies Waves included. This unit 15 has a pair of dielectric plates arranged opposite to each other 10 and 11 on. These panels can be any suitable dielectric material, such as ceramic, glass, pyroceramic or another material which is suitable as a carrier for printed circuits. The ceramic floor plate, for example

te 11 is chosen to be shorter than the ceramic cover plate 10, to a sufficient extent to expose the plates 21 and 22 collecting the electron beam.

The ceramic plates 10 and 11 are supported by a plurality of metallic or ceramic supports with a space between them for the passage of the electron beam. Such a support 6 is shown in FIG. 1 shown broken away. The support 6 has a hollow cylinder with a microwave output line 73, which ^{is printed 1} on the inner surface and serves as a connection to the microwave radiation antenna 81. If necessary, electrical connections can be provided in a similar manner on the same or different supports, not shown.

The electron beam is generated in the chamber 12; she takes an electron gun 14, a heating coil 16 and a plurality of printed electrodes 18 which collect or collect the electrode beam. bundle up. The chamber 12 is followed by an elongated and flat chamber 20, which is also between the ceramic plates 10 and 11 is arranged. This shallow chamber 20 forms an area for guiding the Electron beam and has focusing circuits 23 and 23 printed on its upper and lower surfaces 24, which guide the electron beam 30 from the electron gun 14 into the chamber 26 in a flat bundle. The chamber 26 forms the area for collecting the electron beam and which receives the electron beam collecting plates 21 and 22 on. These beam-intercepting plates 21 and 22 are made of thin metal strips shaped, the surfaces of which are designed so that the strips have an effective heat dissipation through the glass cladding 25 which surrounds the entire furnace unit.

The glass cladding 25 also surrounds the ceramic plates 10 and 11 and is evacuated and on any known way hermetically sealed. Therefore, the chambers 12, 20 and 26 are between the ceramic Plates 10 and 11 are kept at a high vacuum as required to keep the electrons emit and bundle in the form of a flat strip.

The voltage conversion circuit 17 shall be described below on hand F i g. 3 to be described. The voltage multiplier 17 according to FIG. 3 sets the AC line voltage applied across terminals 45 into ripple voltage or DC voltage of any size depending on the number of diodes used. For example, if three pairs of diodes can be used, as in FIG. 3 shows a maximum DC voltage of 1000 volts with an AC input voltage of 220 volts. When the unit is at an input voltage is operated by 110 volts, 6 pairs of diodes are necessary, to generate a maximum DC voltage at the output of 1000 volts. Several different DC voltage levels are formed by each pair of diodes 31 to 36. For example, there are several Voltage levels at the outputs 60 to 63, which are designated as voltage levels Vb to V3. This DC voltage levels are used according to the invention in the present unit to generate the electron beam to create. She; are also used in various voltage combinations to the electron beam near a microwave interaction structure to focus and are also used in different tension combinations to Catch the electron beam as soon as it hits the microwave coupling device walked past.

In the voltage multiplier circuit 17 is in each case the anode of one diode is connected to the cathode of the other diode of a pair. As shown in FIG. 3 can be seen, the pairs are connected in series with one another. The voltage multiplier 17 according to FIG. 3 works in a known manner and, in addition to diodes 31 to 36, has capacitances 41 to 43 and capacitances 51 to 53 on.

One pole of all input capacitors 41 to 43 is connected to one of the input terminals 45 connected. The mains voltage on the input side is via a capacitance 41 to 43 each at a connection point between an anode and a cathode of the doubler diode pairs 31, 32 or 33, 34 or 35, 36 created. Each of the doubler circuits also includes output capacitors 51, 52 and 53, which are parallel to the Doubler diode pairs 31, 32 or 33, 34 or 35, 36 are connected.

The voltage multiplier unit 17 can either be inside or outside the microwave unit 15 can be arranged. When placed outside, the output lines 60-63 are through the glass jacket 25 carried out and connected to the corresponding components in the unit 17. the Diodes 31 to 36 are any conventional diode, e.g. B. hot cathode tubes or semiconductors.

Specific output voltages Vb to V3 as determined by the voltage conversion circuit 17 according to FIG F i g. 3 are connected to the heating coil 16 and the electron gun 14. You are further to the electron beam collecting electrodes 18, to the focusing electrodes 23 and 24, and on the electron beam intercepting plates 21 and 22 are applied. The electron gun used here is known per se; it is designed so that it emits an approximately strip-shaped electron beam can. For example, the electron gun 14 can consist of a stamped nickel strip onto which a emissive coating is sprayed so that the electrons are emitted from its concave surface can be when the heating coil 16 is energized. The heating coil 16 consists of a high wire Resistance, e.g. B. made of tungsten wire, and it is to the circuit 17 or to the AC mains voltage connected. The tungsten wire is wrapped around a ceramic rod that is secured in the chamber 12. The voltage heats the winding 16 in a known manner, which in turn heats the electron gun 14. A steady electron beam is emitted from the emissive coating of the heated electron gun 14 issued. The electrons emitted from the curved surface of an electron gun are bundled to a flat electron beam 30 by collecting electrodes 18. The high current density of the electron beam would cause the beam in region 20 due to the mutual repulsion of the electrons forming the beam 30 scatter and diverge. In this case, however, the beam becomes 30 in the form of a flat strip corresponding to the dashed lines in FIG. 1 through a pair of electrostatic Focusing rows 23, 24 held, each of which is one above and one below the electron beam 30 is arranged.

It will be understood that many different series of foci can be used. A possible execution

609520/168

Approximation form of the focusing row is partially in F i g. 1 and in FIG. 4A shown. The focus row according to F i g. 4A is in the form of two interlocking as double combs Circuits 23 and 24 carried out.

Each of the circuits 23 and 24 are different Voltage outputs of the voltage multiplier circuit 17 connected. The electron beam 30 has medium tension. The voltages of circuits 23 and 24 are above and below this mean voltage of the electron beam 30 selected.

The voltages at the electrodes 23 and 24 establish field gradients in the chamber 20, which alternatively attract and repel the electron beam 30 with respect to the focusing rows mounted on the two ceramic plates 10 and 11. The result of this developed field gradient is an inwardly directed electric field which keeps the electron beam 30 bundled approximately in the form of a flat strip. In order to achieve a stronger focus and a higher current density, a multi-voltage focusing array, as shown in Fig. 4B, can be used. The voltages Vo, Vi can be applied to the lower line windings 54 and 55 and the voltages Vi and Vz to the upper line windings 64 and 65.

As is known, the electron beam 30 represents considerable kinetic energy. This kinetic energy is caused by the acceleration of the electrons from the electron gun 14 to the collecting electrodes in the Area 26 generated. The kinetic energy of the electron beam 30 is converted into microwave energy within the unit 15 converted. To accomplish this conversion is a microwave coupling device 71 printed on the top of the ceramic plate 10. Various forms of microwave coupling devices are usable. The in F i g. 1 is a series of printed in parallel Wires 72 which are connected in the middle by a printed line 74 so that they are in the shape of a Form flat ring chain. This ring chain is arranged so that a microwave signal that the ring chain has the same axial velocity as the electron beam. The microwave fields are generated by the passage of the microwave signal through the ring chain 71 and extend through the ceramic plate 10 and interact (coupling) with the electron beam 30. This coupling between the signal in the ring chain 71 and the electron beam 30 leads to the generation the microwave power.

The generation of microwave power or energy from an electron beam is a typical conversion process in all microwave tubes using an electron beam. Such tubes can be traveling wave tubes or klystrons. Both types have microwave coupling circuits and cause a considerable gain. The difference between these two types of tubes lies in the type of coupling circuit or interaction circuit used. Two suitable embodiments a coupling circuit for both types are shown in FIGS. 4A and 5 shown. At the coupling circuit according to FIG. 4A is a series of parallel arranged wires 23 and 24 printed on a ceramic plate. The circuit arrangement is such that the conductor arrangements 23 and 24 receive a microwave signal propagate in the intended manner at the same speed as that of the electron beam.

In Fig. 4A are the two separated.parallel arranged rows 23 and 24 interlocked with one another and form a double ridge line.

F i g. 5 shows a coupling circuit or interaction circuit, which is suitable for developing the mode of operation of a klystron. Stand by a klystron the electrons only interact at certain intervals along the coupling circuit. These intervals and spaces, respectively, are sections of a chain of rings marked 56, 57, and 58 in F i g. 5 are designated. These sections are terminated by shorting straps 50. An interaction Via the shorting bar 50 between the sections 56 to 58 does not take place. In these short-circuited The electron beam drives over the sections without any interaction between it and the Coupling circuit according to FIG. 5 spread signal.

Returning to rows 23 and 24 of the

F i g. 4A, which is also a double comb-shaped line or represent a focus row, it must be noted that there is no interaction between a signal in the focusing row and the electron beam takes place, since the propagation speed in the focusing row is chosen to be significantly lower than the speed of the electron beam. If against it the in F i g. 4A serves as a coupling or interaction circuit, the speed of propagation in the double-comb shape equal to the speed of the electron beam chosen because this is an essential requirement for the operation either in the form of a traveling wave tube or a klystron. Separate the focusing rows 23 and 24 and the microwave wave coupling circuit 71 and arranges them on opposite sides of the ceramic plate 10 (FIG. 1), so can each of these circuits can be optimized independently of one another, resulting in a higher conversion efficiency and greater gain is achieved. If necessary, these circuits can also be in a single circuit can be combined.

Referring to FIG. 1 it must be emphasized that the microwave interaction is not self-exciting is. If self-excitation is not provided, then one is microwave energy for the microwave coupling circuit supplying source required. The need for an external source of microwave energy not applicable when using the printed feedback circuit as shown in the upper right corner F i g. 1 is shown. This feedback circuit has the printed one shown in the chain line Directional switch or the printed directional filter 75. This direction switch inductively probes you narrow range of the output-side microwave signal on the output line 73 of the ring chain.

This inductive coupling is achieved by a printed J-shaped stub 74 which is scanned Signal shown by arrows 46 is induced. This sample of the output signal becomes passed through the printed rectangular direction switches 77 and 78 and through another J-shaped one The printed branch line 79 and the line 80 are coupled back to the input of the ring chain 72. the printed rectangular directional switches 77 and 78 are designed so that they are a filter with create a very narrow pass frequency range. Accordingly, the entire microwave oven unit vibrates only at the pass frequency of the direction switch 75. For example, a typical pass frequency is

which is particularly suitable for a microwave oven, an oscillation frequency of 915 or 2450 MHz.

In Fig. 2 is an oven space 90 with four different ones randomly shaped antennas 81 to 84, which essentially form the top wall 91 of the oven space or the oven 90 form, shown. Usually several different microwave frequency modes are used in a typical Microwave oven provided. These different modes depend on the furnace chamber dimensions with the furnace chamber dimensions generally being a few wavelengths. The dimensions of the printed Radiators or antennas are chosen to provide the desired amount of microwave energy for everyone Modes is available, whereby uniform power and heating density is created in the furnace chamber. As in FIG. 2, in the microwave oven unit 15, a wide, flat electron beam be provided, the one with several coupling devices, each with associated radiators or antennas 81 to 84 is in interaction. Each coupling or interaction device can operate at a frequency that is different from the frequencies of the other coupling devices. It goes without saying that a plurality of separate microwave units can be used instead of one broad electron beam be provided. These different units can either be in separate housings or in a common vacuum housing 100, FIG. 2, be arranged.

The use of multiple radiators and multiple different frequencies can have various advantages entail, although such an arrangement does not give off coherent microwave energy. Different known constructions of traveling wave tubes sought coherence. However, the invention shows that a particular advantage lies in non-coherence. Due to the arrangement in many microwave radiator circuits next to each other, e.g. B. 81 to 84 in FIG. 2, a coherence is eliminated, but the energy coupling in the furnace chamber 90 optimized for many dishes. Through the use of antennas that are printed in random fashion the microwave energy is radiated from different points in the oven, and it even becomes one more even energy distribution achieved. In Fig. 1, the antenna 81 is on the bottom of the dielectric Plate 11 imprinted. The thickness of the dielectric plate is selected appropriately so that the focusing row 23 and 24 can form the necessary ground plane for the antenna. The antenna 81 radiates the microwave energy through the glass envelope 25. It should be noted that the radiators 81 to 84 are also on the underside of the Glass envelope or glass cladding 25 are printed on can then be connected to output line 73 (Fig. 1) by known techniques be able. It is also obvious that the antennas may be completely separate from the microwave unit can be arranged, the connecting lines in a known manner from the output the coupling circuit to the individual antennas.

In general it can be said that the generation of microwave energy consumes about half the kinetic energy of the electron beam 30. The coupling or mutual action process creates groups of electrons at different speeds. The various voltages Vi to Vi of the voltage multiplier circuit are each applied separately to collecting plates 21 and 22 in order to achieve the greatest possible efficiency. Slow electron groups are captured by those trapping plates that are at a higher voltage, and electrons at higher speeds travel to the trapping plates that are at a lower potential. ■

The following describes the collecting electrode in more detail with reference to F i g · 1: A plurality of electron beam deflector plates 85 to 87 are

ίο assigned to the collecting or collecting electrodes 21 and 22. These plates 85 to 87 are near the junction of the chambers 20 and 26 on the ceramic plates 10 and 11 are printed and connected to suitable voltages of the voltage multiplier circuit 17, around the electron beam 30 upwards in the direction of the disaxially arranged collecting plates 21 and 22 distract.

The electron gun 14 according to FIG. 1 is arranged approximately axially to the main axis of the electron beam 30. When the electron beam 30 is formed, small particles can hit the emitting surface emitted along with the electrons from the electron emitting surface of the electron gun 14 will. These tiny particles of emissive material can get between the electrodes of the Electron beam collecting and focusing rows 23 and 24 get stuck. Such deposits can short-circuit some of the electrodes guiding and shaping the electron beam and thus the service life of the tube and reduce the tube efficiency. This potential drawback is made possible by using an electron gun of a different design, such as that shown, for example, at 66 in FIG. 6 is avoided will. This electron gun 66 is constructed and supported in a manner similar to that of the electron gun 14 of Fig. 1, however, its electron-emitting electrode is with respect to the major axis of the electron beam 30 arranged disaxed.

The electron beam 30 is, as already in connection with FIG. 1 described, collected and additionally bent into the electron beam axis of the space 20. The bundling and turning as they are used to Guiding the jet in the shallow elongated jet guiding opening 20 is required achieved by a plurality of metallic electrodes, 95, 96, 97 and 98. These electrodes are hard soldered or otherwise connected to the ceramic plates 9 and 10 and are via suitable output lines of the printed voltage multiplier circuit 17 according to FIG. The The electron beam 30 is bent in the direction shown in FIG. 6 ensures that all emitted particles the emissive electrode are thrown against the underside of the ceramic plate 10 and cannot penetrate into the area 20 guiding the beam. This makes the possibility of one Electrode short-circuit is switched off with certainty, since the electron-emitting surface is inclined to the The main axis of the electron beam is arranged.

As already mentioned in the introduction to the description, the output power of known microwave units drops with the operating time of the tube, unless complicated voltage supply units are used to compensate for this change. In Fig. 7A, there is a diagram of the output power plotted over the tube operating time; this plot gives the curve 130, if an unregulated 220 volt AC input voltage is used.

From the power curve 130 it can be seen that the output power of a unit is initially 2000 watts but decreases with operating time. Such a reduction in output power has a corresponding effect Changing the cooking or baking time required for different dishes.

F i g. 7A also shows a regulated power curve 115. Curve 115 represents the output power of the microwave unit according to the invention at a constant value of 1000 watts, which in the case of the invention appropriate unit is available regardless of the operating time. This constant output represents a constant Cooking or baking time for any food to be cooked or baked despite the aging of the microwave unit secure.

The constant output power according to curve 115 is achieved by a novel power control circuit HO (Fig.7) reached. The control circuit 110 measures the Microwave output power of the tube corresponding to the heating effect achieved by the microwave power and converts this measured value into a deflection voltage that is surprisingly simple Coupling or interaction efficiency changes automatically to the heat, d. H. the loss of performance, too compensate. In the new microwave unit 15, the power control circuit sets the electron beam 30 first in the vicinity of the floor focusing row, as shown in FIG. 6 is shown. When the microwave unit or tube ages, the electron beam 30 moves up towards the coupling circuit 71, so that it interacts more closely with the coupling circuit and has a greater microwave output power is produced. The above applies to long-term reductions in benefits; temporary changes or fluctuations in the input voltage are controlled by the control circuit 110 according to the invention also compensated, as the following description will show.

The power control circuit 110, like most of the components used in the microwave unit 15, is advantageously a printed circuit. F i g. 7 shows the power control circuit for simplicity in a pictorial and circuit-like schematic view. The power control circuit 110 has the in Fig. 6, the beam deflection plates 104 and 105 shown on the flat ceramic plates 10 and 11 are arranged on opposite sides of the electron beam 30. These baffles 104 and 105 move the main electron beam 30 in the direction of the double arrow 106 (FIG. 7), that is to say perpendicularly to the major axis 107 of the electron beam. It goes without saying that the electron beam passes through the focusing electrodes 23, 24 (FIG. 6) when passing through the guide chamber 20 is held in the position in which it is at its entry into chamber 20 has been diverted. So when the electron beam 30 initially passes through the Deflection voltages on plates 104 and 105 have been deflected down onto the bottom focusing array is, it maintains this position when passing through the guide region 20, if not the deflection voltage on the plates 104 and 105, the initial position of the electron beam 30 changes.

F i g. Fig. 7 shows that in addition to baffles 104 and 105 that control the position of the electron beam with respect to of the microwave device 71, a Wheatstone resistance bridge 140 is provided one arm of which is formed by a microwave output measuring element 141. A Amplifier 150 surrounded by dashed lines is located between output terminals 143 and 145 of bridge 140 and the baffles 104 and 105. The component 141 measures any changes in the heating power of the unit 15. This component 141 can preferably be formed in a known manner by a resistor which changes in proportion to the temperature surrounding it. Component 141 may, for example, be a bolometer which measures the microwave power through its heating effect. As in Fig. 6, the bolometer 141 preferably arranged on a section of the output line 73 extending from the ring chain 72 and be designed as a printed variable resistor or as a thin tungsten wire. The microwave heating effects in the tungsten wire change the wire resistance, causing a voltage change the resistance bridge 140 results. Each resistor 146 of the resistor bridge 140 is a thermally compensated one Fixed resistance. The bolometer 141 of FIG. 6 has a resistance that changes accordingly the microwave power changes, as shown schematically by the dashed arrow in the one Arm of the bridge is indicated.

At curve 115 in FIG. 7A was believed to be a constant output power of the microwave unit would be 1000 watts. This output power corresponds to a predetermined initial resistance value in the bolometer 141 which, with reference to the Resistance values of the fixed resistors 146 was chosen so that the bridge circuit 140 initially is balanced. The input voltages Vo and V3 are applied to the circuit 140, and if the Bridge circuit 140 is balanced, no output signal occurs at the bridge output terminals 143 and 145 on.

The input voltages Vo and V3 also serve as voltages that are both the main electron beam 30 and the secondary electron beam 130. This secondary electron beam 130 can through a Outer edge of the main beam 30 or be formed by a completely separate electron beam. Both Electron beams 30 and 130 are assigned to beam-bundling and focusing electrodes 95 to 98. These collecting electrodes were referred to in connection with the discussion of the operation of the unit 15 (Fig. 6) so that a repetition is not necessary at this point. Their function is to provide the due to the voltage difference between the electron gun 66 and the anodes 97 and 98 Electrons give the flat, stripe-shaped focus and shape of electron beams 30 and 130.

The secondary electron beam 130 allows a differential amplifier 150 to be properly and economically can be incorporated into the microwave unit 15 as a one-piece component. It goes without saying that any suitable amplifier in place of a differential deflection amplifier 150 can be used. To the The output power correction voltages are applied to the baffles 104 and 105 however, deflection amplifier 150 is for feedback servo operation particularly favorable according to the present invention, since there are only slight changes in the output signal of the bridge circuit 140 can be boosted to a high differential correction voltage, the is independent of errors that usually occur in conventional amplifiers, especially when two ordinary amplifiers Amplifiers are to be used.

When the differential deflection amplifier 150 is operating

The electron beam 130 is evenly divided between the upper and lower collecting plates 151 and 152 when the bridge circuit 140 is balanced and therefore no output signal is applied to the lines 143 and 145. A resistor 155 is connected between the upper baffle 151 and the input voltage V3. The input voltage V3 is also applied to the deflector plate 105 of the main electron beam. The resistor 155 is selected such that its resistance value, which represents a predetermined voltage drop, is balanced with the bridge 140. The output lead 156 of the amplifier 150 connects the plate 151 directly to the baffle 104. This connection creates an initial voltage gradient between the plates 104 and 105, causing the electron beam 130 to move into the position shown in FIG. 6 position shown is deflected downwards.

For a further understanding of the operation of the control circuit 110, it is assumed that the through output power represented the resistance of the bolometer 141 either due to aging phenomena or a change in the input voltage the microwave oven unit sinks. The decreased output power results in a low temperature in the Bolometer 141, which has the effect of changing the resistance of the bolometer 141. Accordingly the bridge 140 is unbalanced, and there is an output signal on the lines 143 and 145, that results in a voltage gradient between deflection electrodes 147 and 148 of differential amplifier 150 leads. This voltage disturbs the normal division of electron beam 130 between plates 151 and 152, see above that the current through resistor 155 changes, thereby changing the voltage between the baffles 104 and 105 changes. This new voltage between plates 104 and 105 directs the entire electron beam 30 upwards, so that the degree of coupling between the electron beam 30 and the microwave coupling circuit 71 (Fig. 6) increases. Of course, increased coupling increases this Output power of the microwave unit 15, thereby also changing the resistance of the bolometer 141 so that the bridge circuit 140 is brought back into the balanced state.

The power control circuit 110 also compensates for a periodic increase in microwave output power by reducing the degree of coupling between electron beam 30 and the microwave coupling circuit 71 (Fig. 6). This working method does not need to be described in detail here, as it is clear from the above description ^ In short, changes, i.e. H. increases or decreases the Power control unit 110 determines the degree of coupling between the microwave device 71 and the electron beam 30 in such a way that a constant output power is ensured over the entire service life of the tube will.

It is evident that in the microwave unit 15 according to FIGS. 1 and 2 a plurality of staggered Beam intercepting plates as an alternative to stamped metal plates 21, 22 and 92-94 on either the upper one or the lower surface of the chamber 26 used to collect the jet may be printed. This Imprinted plates can also be connected to the output lines 60 by means of imprinted switching elements to 63 of the voltage multiplier (Fig. 3). When the electron beam 30 with the microwaving device 71 interacts, groups of electrons are accelerated differently generated in electron beam 30. Slower electrons are deflected earlier than faster electrons. All collecting plates have different areas and different potentials, so that these are different Groups of electrons are trapped by the plates, providing appropriate heat transfer produce. The heat generated by collecting the electron beam is conducted through the ceramic plate 10, by radiation and by natural convection of the glass jacket of the unit 15 destroyed.

For this purpose 3 sheets of drawings

Claims (1)

Patent claims: 1. Heater with a work space for receiving food to be cooked, an electrical energy source and an ultra-high frequency generator connected to it, which has an evacuated Room, an electron gun and electron capture devices for the formation of an electron beam having within the evacuated space, characterized in that the evacuated Space through two oppositely arranged, airtight to one another at their peripheral edge connected, flat, dielectric plates (9, 10, 11) is formed, which a substantially flat, elongated evacuated space that delimit the flat surfaces of each other oppositely arranged dielectric plates facing the electron beam, electrostatic focusing devices for focusing the electron beam in a flat fan are printed in the space between the dielectric plates and that on one of the dielectric plates Plates, which at the same time forms at least part of a wall (91) of the work space, one electromagnetic device is printed on it. which with the moving electrons in the Fan beam cooperates in such a way that its electron translational energy into microwave energy is converted. 2. Heater according to claim 1, characterized in that that the electromagnetic device in the wall (91) of the work space has an antenna, which is in communication with the electromagnetic device and on a dielectric board printed on this facility. 3. Heater according to claim 1 or 2, characterized by one with the electrical energy source connected voltage multiplier circuit for generating a number of voltage levels and connection lines provided within the evacuated space for connecting the electrostatic focusing means (23, 24) with the successive voltage levels for training and focusing the electron beam in a flat fan. 4. Heater according to one of the preceding claims, characterized in that the Focusing devices (23, 24) have a pair of electrostatic conductors (Fig.4A, 4B), one Conductor each pair onto one of the faces of the pair of dielectric plates that faces the electron beam is printed to keep the beam in a flat fan or plate shape. 5. Heater according to claim 4, characterized in that the electromagnetic device (71) comprises a microwave coupling conductor which extends onto one or both of the dielectric plates (10, 11) is printed on the surface that the Side of the plates (10, 11) opposite to which the bundling conductors (23,24) are applied. 6. Heater according to claim 5, characterized in that the radiation surface or antenna (81, 82, 83, 84) a plurality of juxtaposed, non-coherent microwave radiation are microwave radiators radiating into the furnace space (90). 7. Heater according to claim 6, characterized in that the dielectric carrying the radiators Component (10, 11) is of sufficient thickness to form an insulating support surface. 8. Heater according to claim 1, characterized in that the two dielectric plates (10, 11) have a raised peripheral edge, which forms a seal to form the evacuated working space is built in. 9. Heater according to claim 4, characterized in that the strip-shaped, flat bundled Electron beam is disaxed from its emission surface and that the focusing device has electron guide electrodes (95, 96,97, 98), which the electron beam in the space between the Lead pair of dielectric plates (10, 11). 10. Heater according to claim 1, characterized in that a control circuit (110, F i g. 7) is provided, which allows the position of the electron beam with respect to the electromagnetic device (71) to shift so that the implementation of the kinetic energy of the electrons in the electron beam in ultra-high frequency energy is stable at a constant value. 11. Heater according to claim 10, characterized in that that the control circuit (110) a signal-controlled beam deflection device (104, 105) for Adjusting the relative position of the electron beam with respect to the electromagnetic device (71), also a signal generator or controller (bridge 140, Fig. 7), which the deviations of the ultra-high frequency Encrgic emits proportional signals from a setpoint, and one between the signal generator and the beam deflection device comprises switched-on circuitry (143, 145, 150, 155, 160), which applies the signal supplied by the signal generator to the beam deflection device. 12. Heater according to claim 11, characterized in that that the beam deflector comprises a pair of deflector plates (104, 105), one of which on one side and the other on the opposite side of the flat, string-shaped Electron beam is arranged. 13. Heater according to claim I!, Characterized in that that the signal generator (bridge 140) a (c) ultra-high frequency energy responsive ^), in the connecting line between the electromagnetic device (71) and the radiator (81.82, 83, 84) switched on ^) measuring device or sensor (141), which or the for measuring the on the emitter output ultra-high frequency energy is used, and a balancing circuit (146) has to measured values of the measuring device in a deviation of the energy setpoint above the value Ultra-high frequency energy proportional first signal or one below the energy setpoint lying deviations to deliver a proportional second signal. 14. Heater according to claim 13, characterized in that the circuit arrangement (143, 145, 150, 155,156) from a differential amplifier (150) with an input (147, 148) and an output (151, 152) from the amplifier input with the signal generator (140) connecting lines (143, 145) and switching elements (155, 156) which the Connect the amplifier output to the deflection device (104, 105). 15. Heater according to claim 1, characterized in that the electromagnetic device has at least two different configurations, each for converting the electron translational energy in the electron beam in microwave energy are suitable, with each of the two configurations having different microwave frequencies result. 16. Heater according to claim 15, characterized by a plurality within the working space arranged radiators associated with the various configurations so that each the radiator emits at each of the different microwave frequencies through the work area 17. Heater according to claim or 3, characterized in that the beam-collecting plates consist of several separate plates (21, 22, 92, 93, 94), that a voltage multiplier circuit (17) connected to normal mains voltage is provided, the different output voltages ( Vo to 'Vi) supplies and that the outputs (Vo to Vi) lying at different voltages are each connected separately to one of the plates (21, 22, 92, 93, 94) in order to transfer the electrons moving at different speeds in the electron beam to different ones Collect collecting plates and thereby divert the thermal energy generated on the collecting plates in a controllable manner. 18. Heater according to claim 2 or 3, characterized by a feedback circuit (75; 76, 80) connected between an output and an input of the electromagnetic device (71) and is equipped with a filter (75) whose predetermined pass frequency is equal to Vibration frequency of the generator. 19. Heater according to claim 18, characterized in that that the filter (75) has a directional switch (74, 77, 78, 79).