RU2566653C1 - Damper for magnetostrictive converter - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: invention relates to instrumentation, particularly, to damper for magnetostrictive converter. Claimed damper is composed by a cylinder fitted tightly on the waveguide in cylinder axis. Said cylinder of metal wire lengths wound to preset-length coil and subjected to stamping in cylinder-shaped dies. Said damper can be both solid and consist of several parts tightly pressed against each other, for example, of three or four parts, while its total length equals the ultrasound oscillation wavelength in magnetostrictive waveguide.

EFFECT: perfected design.

1 dwg

Description

The invention relates to measuring equipment, specifically to magnetostrictive transducers.

In the technique, magnetostrictive converters are widely used in delay lines (for example, described in the USSR AS No. 336770, M.cl. H03H 7/30), in displacement sensors (for example, described in the USSR AS No. 956965, M. class G01B 7/00), in displacement converters in code (for example, described in RF patent RU No. 2080559, M.cl. G01D 5/12) and level and density sensors (for example, described in RF patent RU No. 2285908, M incl. G01N 9/10).

Magnetostrictive transducers consist of the following main nodes: a waveguide through which an ultrasonic wave propagates (hereinafter referred to as ultrasound), an ultrasound forming device, an ultrasound receiving device, dampers (dampers).

The function of the damper is to extinguish the residual ultrasound in the waveguide (sound duct) after the operating cycle to a value that does not interfere with the reception of the operating ultrasound in the next operating cycle.

From the book Designing Delay Lines, Zakharyashchev LI, Sovetskoe Radio, 1972, p. 52, 53, it is known that “a gradual increase in the attenuation of a sound duct in an absorber is achieved by giving the body of the absorber an exponential shape”. The same source notes that “bitumen, BF-2 glue, and dried shellac have a high degree of absorption. The length of the absorbing load is selected by the wound 80-100 mm and the largest diameter of the pear-shaped load is 4-5 mm. The absence of reflections is ensured by imparting an exact pear-shaped shape to the load. ” It is also noted there that “absorbers made of hard wax or synthetic resin, saturated with minium or some other filler with a high specific gravity, for example, powdered silver, have somewhat better physicomechanical properties compared with the noted materials. In addition, it is recommended to use a thermoplastic mass such as gutta-percha based on, for example, acrylate. But since the latter material has a high adhesive ability, it is advisable to cover the absorber with a layer of varnish. The maximum absorptive effect of the absorber made of thermoplastic mastic is observed if the external axial section of the absorber has an exponential shape. ”

The known damper sound duct according to the patent of Czechoslovakia No. 106821, class. 21 a ⁴ , 74. 1963, in which the shape and material of the damper described above were patented, namely the pear-shaped form, hard wax and synthetic resins.

Known damper sound duct for AS USSR No. 801150, M.cl. H01L 41/06, in which the damper has a similar shape, but differs from that described in the Czechoslovakian patent No. 106821 in that it is multilayer, which increases the level of attenuation of the ultrasound.

However, all the dampers described above work well at temperatures above minus 10 ° C. At lower temperatures, the materials used become less elastic and the damper loses its properties and a weak attenuation of the reflected signals is observed.

Known damper for the delay line according to Japan patent No. 46-32138, class. 98/3 / A8, 1971. The damper comprises an elastic absorbing material, within which a sound duct is located. The disadvantage of this damper is also the weak attenuation of the ultrasonic vibrations at low temperatures.

Known damper described in US patent "Measuring system with a magnetostrictive transducer" US No. 5076100, M.cl. G01F 23/00, G01R 33/18, US C1, 73/290, consisting of two opposite elastic strips. The strips are fixed inside the sensor cavity in the upper housing of the support, downward they deviate from the waveguide, and their upper ends are pressed against the waveguide by the inner walls of the housing cavity. Due to the upward increase in the degree of interaction of the strips with the waveguide, the ultrasonic pulse traveling upward is absorbed by the strips without significant reflection of the pulse energy.

However, this design does not work well at low temperatures due to a decrease in the elasticity of the strip material.

Known composite material of an acoustic damper according to AS USSR SU No. 1043816, M.cl. H03H 9/12, which, in order to increase the stability of the damping properties, contains polydienurethane rubber. However, at low temperatures, this material also reduces elasticity, which significantly impairs its damping properties.

The known material of the acoustic damper according to the patent of the Russian Federation RU No. 2159503, M.cl. H09H 9/30, containing as an epoxy resin an epoxy low molecular weight Diane resin, and as a hardener a low molecular weight aliphatic polyamide. The specified material has good absorption properties of ultrasonic ultrasound, but like the dampers described above, it loses its properties at low temperatures.

The closest technical solution is the damper for the delay line A.S. USSR No. 628606, M.cl. H03H 7/30. The specified damper for the delay line contains three elements: two rubber tubes, one tube made with a smaller inner diameter, and the other with a larger one, and an elastic absorbing material, inside which the sound duct (waveguide) is located, while in order to increase the attenuation of the reflected signals between the sound duct and an elastic material placed a metal braid, which fits snugly with the inner side to the surface of the sound duct, and the outer one to the elastic absorbent material.

This design allows you to increase the attenuation of the ultrasonic ultrasound, but, like the previously described, it loses its properties at low temperatures due to a decrease in the elasticity of the rubber tubes and the elastic material inside which the metal braid is pressed, and, in addition, this design has a sufficiently large length (approximately 300 mm), which complicates the design of sensors with limited device dimensions.

The essence of the invention lies in the fact that the damper for the magnetostrictive transducer is made in the form of a cylinder tightly mounted on the waveguide along the axis of the cylinder and made of pieces of metal wire wound into a spiral of a given length and subjected to pressing in molds having the shape of a cylinder, and the damper can both to be continuous and to consist of several parts tightly pressed against each other, for example three or four, and its total length is equal to the wavelength of the ultrasonic vibration in the magnetostrictive wave Novode.

The aim of the invention is to improve the attenuation of the ultrasonic inspection while expanding the temperature range of operation of magnetostrictive sensors, especially when operating in the low temperature range.

The problem is achieved due to the fact that the damper for the magnetostrictive transducer is made in the form of a cylinder, tightly mounted on the waveguide along the axis of the cylinder, and is made of pieces of metal wire wound into a spiral of a given length and subjected to pressing in molds having the shape of a cylinder, moreover the damper can either be continuous or consist of several parts tightly pressed against each other, for example, three or four, and its total length is equal to the wavelength of the ultrasonic vibration in magnetostriction th waveguide.

The technical result is to obtain a damper for a magnetostrictive transducer having good suppression of a magnetostrictive ultrasonic signal in a wide range of operating temperatures from minus 100 ° C to plus 400 ° C.

The material from which the damper is made is known, it was first published in A.S. USSR No. 136608, cl. 47a, 8, in 1961 under the name "Elastic element for damping systems." The specified elastic element has found wide application in mechanical shock absorbers, for example, described in the copyright certificates: USSR No. 191280, class 47a, 16/10, a.s. USSR No. 194478, class 47a, 16/10, a.s. USSR No. 308254, M.cl. F16F 13/00, a.s. USSR No. 968538, M.cl. F16F 13/00, a.s. USSR No. 1281781, M.C. F16F 3/08, etc., as well as in patents: France FR 1440023 A, F16F, Great Britain GB 1079736 A, F16F, USA US 3844545 A, F16F 13/00, etc.

These shock absorbers have proven themselves when working in a wide range of temperatures, including low temperatures, and were used in mechanical shock absorbers, and depreciation was carried out by attaching the shock-absorbing device and the supporting base to different planes of the shock absorber. However, this material was not used to quench magnetostrictive ultrasonic waves.

It should be noted that in contrast to the classical mechanical shock absorber, which is rigidly fixed on one base with one plane and the other plane connected to the damped object, this damper is tightly mounted on the waveguide and is not fixed from the outside.

In contrast to the elastic element shown in the drawing for copyright certificate No. 136608, the proposed damper is made in the form of a cylinder, and a waveguide in the form of a wire is passed through its middle (the centerline of the cylinder), which contributes to good mechanical contact of the damper (elastic element) and the waveguide. To improve the manufacturability and assembly, the damping element can be made as a whole, or consist of several parts tightly pressed against each other, for example, three or four, and the total length of the damper is equal to the wavelength of ultrasonic vibrations in the waveguide.

It should be noted that in the manufacture of a damper from plastic and rubber materials with a change in temperature, the change in the length of the damper and the waveguide has different values. In this case, the optimal ratio L / γ = 1 is violated, where L is the damper length, γ is the wavelength. This leads to deterioration of the damper.

In the case of a volumetric wire damper, the material of the damper wire can be selected so that the linear temperature expansion of the damper and the waveguide is the same, for example, elinvar alloys are usually used for the waveguide, and 36NHTY alloy is suitable for the wire damper. This can significantly improve the stability of the damper in a wide temperature range.

The drawing shows a waveguide 1, at the end of which a damper 2 is attached. In the case shown in the drawing, the damper 2 consists of three parts, tightly pressed against each other. Damper 2 can be solid or composite, and the number of components is determined based on the manufacturability of the damper.

The damper works as follows. When magnetostrictive ultrasonic vibrations pass through the waveguide, these vibrations reach the damper, and due to scattering of the wave in different directions at the points of tangency of the damper and the waveguide, the energy of magnetostrictive ultrasonic vibrations is absorbed, which leads to attenuation of the pulses, and instead of them a small noise is observed, which is easily is filtered out. It should be noted that noise is observed on all types of dampers, but the danger for measurements is represented only by incompletely reflected reflection pulses.

It is important to note that elastic elements such as rubber, plastic, etc. after passing through magnetostrictive ultrasonic vibrations, they are deformed and tend to return to their original shape, which leads to vibrations of the “damper-waveguide” system and, ultimately, to poor damping. In the case of the inventive damper made of compressed wire material, this phenomenon is not observed.

It should be noted that dampers made of plastic materials and rubber quickly lose their properties due to aging of the material (3-4 years), especially when exposed to changes in ambient temperature. The damper made of pressed wire is more durable and lasts 12 years or more.

The company manufactured magnetostrictive sensors for measuring the level and density of liquid in a tank using the described damper; the length of the damper was 75 mm. These sensors confirm the improvement in the attenuation of the reflected ultrasonic signals while expanding the temperature range of operation of magnetostrictive sensors.

As studies have shown, this damper remains operational in the temperature range from minus 100 ° C to plus 400 ° C without impairing the extinction of the ultrasonic ultrasonic magnetostrictive waveguide.

Claims (1)

The damper for the magnetostrictive transducer, made in the form of a cylinder, tightly mounted on the waveguide along the axis of the cylinder, characterized in that the damper is made of pieces of metal wire wound into a spiral of a given length and subjected to pressing in molds having the shape of a cylinder, and the damper can be both continuous and consist of several parts tightly pressed against each other, for example three or four, and its total length is equal to the wavelength of ultrasonic vibrations in the magnetostrictive waveguide.