Resonator housing for microwaves

p0001The invention relates to a of one strand of the tobacco processing industry permeated resonator made of metallic material, the microwaves in order to detect the mass and / or the humidity of the strip material are supplied.

p0002Under one strand of the tobacco processing industry is meant a covered or unumhüllter strand of rauchfähigem material such as cut tobacco, cigarillo tobacco, cigar tobacco or other rauchfähigem material; by this expression can also be a strand of a filter material such as cellulose acetate or paper to be understood.

p0003It is, eg., By the <patcit id="pcit0001" dnum="EP0791823A2"><text>EP 0791 823 A2</text></patcit>Known, (hereinafter referred to as "resonator") for detecting the mass and / or the moisture content of a tobacco rod, especially one from sheathed with cigarette paper cut tobacco existing cigarette rod, the strand through a measuring chamber made of metal to cause, in which it is acted upon by microwaves , Changes made to characteristic values ​​of the supplied microwaves at interspersed by a string resonator and at z. B. empty resonator can be concluded that the mass and / or moisture per unit length of the strand by special evaluation circuits.

p0004<patcit id="pcit0002" dnum="DE3407819"><text>DE 3407819</text></patcit> discloses a method for measuring the moisture of smoking materials, particularly ready-smokable products such as filter rods.

p0005The apparatus according to <patcit id="pcit0003" dnum="DE3407819"><text>DE 3407819</text></patcit> includes a microwave generator 12, a coaxial cable 22, and a coaxial cable 26 for a reference path and a coaxial cable 36 for a measurement range, the reference path a transition piece 28 and the measurement range, a transition piece 38 included.

p0006The the object underlying the invention is an improvement of Resonatorgehäusen according to the prior art in various ways in order to increase the accuracy and / or measurement sensitivity.

p0007The object is achieved by a method according to claim 1 and a resonator of claim 2.

p0008A particularly advantageous implementation of the invention is to provide an alloy as a material having a low coefficient of thermal expansion, which consists of approximately 64% iron and 36% nickel. The alloy components can vary but also to the values ​​mentioned around as long as the Temperaturausdehungskoeffizient is low enough that the mechanical deformations during temperature fluctuations are not so high that they falsify the measurement result invalid. Under this condition, other alloy components may be provided.

p0009According to the invention, the resonator comprises a temperature control arrangement, which keeps its working temperature is at least approximately constant. The temperature regulating arrangement comprises a sensor for the temperature of the resonator, which controls a transistor such that the loss of heat maintains the temperature of the housing at least approximately constant.

p0010The interior of the resonator has the shape of a symmetrical hollow body, preferably a hollow cylinder, which is closed by a removable closure element operatively. The shape of the inner space may vary from the exact form of a hollow cylinder. Also of advantage is then at least approximately symmetrical shape, eg. as a polygonal shape.

p0011In a further advantageous embodiment of the invention, the walls of the interior of the resonator are at least partially coated with a corrosion resistant material or consist of such material. Preferably, a metal is used, which is a good electrical conductor. Both requirements are met by gold, which can be either at least widely used neat or in a suitable alloy. Reingold suitable for coating the interior because already enough very thin layers for the aspired purpose of corrosion resistance and electrical conductivity. the outer walls of the resonator are provided with corrosion-resistant material is advantageous according to the invention, z. B. gold to disregard endure corrosion.

p0012In a further advantageous embodiment of the invention, a closed strand surrounding protective tube is provided. The protective tube is advantageously at least partially made of a plastic, in particular of the polyaryletherketone group (PEAK Group), in particular made of polyetheretherketone (PEEK). The protective tube can be expanded in the inlet area of ​​the strand.

p0013The resonator may continue according to the invention outside the interior (resonance chamber) outward toward the strand in order to prevent the escape of microwaves. The resonator can continue inward toward the strand is also within the interior space (resonance chamber).

p0014The resonator according to the invention is especially suitable for a measuring arrangement with a supply of the microwaves with at least two different frequencies from a generator to the resonator and a resonance frequency shifts by comparing the resonance curve influenced by the strand against the uninfluenced from the strand resonance curve as well as the damping detected by comparing the amplitudes of the affected and unaffected by the string resonance curves circuitry.

p0015A further advantageous development of the invention is that the resonator microwaves of two frequencies are supplied to both associated with a falling edge of the resonance curve.

Certain embodiments of the invention have numerous advantages:

p0016The resonator of material with an extremely low coefficient of thermal expansion changes shape with changing temperatures very little. To this end, the temperature control can contribute. The result is a very good constancy of the resonator, which the accuracy and consistency of measurement acquisition benefits.

p0017The use of corrosion-resistant material such as gold for the coating of the interior of the resonator and thereby prevents corrosion caused changes in the resonator. Due to the good electrical conductivity of this coating material negative influence of the so-called skin effect are largely eliminated maintained.

p0018The resonator is particularly suitable for the microwave feed and the conversion of the microwave signals in the measurement signals in accordance with the invention.

p0019The invention will be explained in more detail using an exemplary embodiment.

p0020A partially broken in the direction of arrow 5 moving cigarette rod 1, consisting of a filler 2 of cut tobacco and a wrapper 3 made of cigarette paper, through sets a resonator 4, the microwave in order to detect the mass and / or humidity of the filler are fed. The resonator 4 comprises a hollow body in the form of a hollow cylinder 6, whose interior space 7 is arranged symmetrically to the cigarette rod. 1 On it, a lid 8 is screwed to close. Both hollow cylinder 6 and the lid 8 are made of material with a very low Temperaturausdehungskoeffizienten. Suitable for this is an alloy that consists at least approximately of 64% iron and 36% nickel. Owing to the good stability of the geometry of the resonator 4 is also a good consistency of the measurement results can be achieved. For this purpose, yet contributes to a regulation of the temperature of the resonator, the temperature of which is detected by a temperature sensor. 9 The temperature sensor controls at least one heating transistor 11, z. B. the type BUZ 80 from. Siemens, whose waste heat heats the resonator above ambient temperature. The control by the temperature sensor is effected such that the temperature of the housing 4 is maintained at least substantially constant.

p0021The interior 7 of the resonator 6 is vapor-coated with a thin gold layer 12, reliably prevents a the Meßwertkonstanz impairing corrosion and at the same time as good electrical conductivity, preventing a damaging skin effect. Advantageously, the resonator is 4 gold from the outside to prevent corrosion and external.

p0022For mechanical completion of the interior 7 against the cigarette rod 1 and this may be promoted dirt, so the purpose of preventing pollution of the interior space 7, which would affect the measurement result, is a protective tube 13, which is advantageously made of a substance of the polyaryletherketone (PAEK) group, z. B. made of polyetheretherketone (PEEK). At one of its ends 13a, to which the train 1 enters the resonator 6, the protective tube 13 is flared.

p0023The resonator 4 extends outside of the interior space 7 a tubular shape (6a, 8a) on both sides in the direction of strand 1 to the outside in order to prevent the leakage of microwaves out of the resonator chamber. It may also be a tubular shape (6b, 8d) extend slightly inwards. For coupling the microwaves generated from a microwave generator is used an insulated by an insulating ring 14 from the metal housing 6 antenna 16 for coupling microwaves to be supplied to an evaluation circuit, not shown, is an isolated by insulation 17 antenna 18. An appropriate evaluation circuit is the German Patent application<patcit id="pcit0004" dnum="DE19734978"><text>197 34 978.1</text></patcit> refer to.