JP2020026973A - Ultrasonic flow meter measurement conduit body manufacturing method - Google Patents

Abstract

To manufacture a measurement conduit body integrally by a blow molding using a metallic mold even if the measurement conduit body has a complicated shape, and to achieve the measurement conduit body that is excellent in measurement accuracy.SOLUTION: A melting bag-like parison is arranged inside a metallic mold forming an outer shape of a measurement conduit body 10, and a blow molding is conducted by inflowing gas into the parison. By the blow molding, ultrasonic-wave input/output parts 14a and 14b as wall surfaces for attaching an ultrasonic transmission/reception element to the outside of both end parts of a measurement conduit part 11 are formed, a pipe-like inflow pipe part 12 and a pipe-like outflow pipe part 13 are formed in an orthogonal direction from an end part of the measurement conduit part 11, and the finished measurement conduit body 10 is taken out, and the end parts of the inflow pipe part 12 and the outflow pipe part 13 are cut.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method of manufacturing an ultrasonic flowmeter for detecting a flow rate by transmitting an ultrasonic beam through a fluid.

  In a general ultrasonic flowmeter, an ultrasonic beam is alternately propagated in a flow velocity direction and a counterflow velocity direction to a measurement fluid in a measurement pipe, and the propagation time is detected. Measure the flow rate.

  According to Patent Document 1, for example, as shown in FIG. The measuring pipe is of a type that is attached in a U-shape.

JP-A-60-115810

  Also in the case of Patent Document 1, it is preferable that the measuring pipe is inexpensive and inexpensive if it can be integrally manufactured by injection molding using a synthetic resin mold. However, since the internal structure of the measurement pipe is complicated, it is difficult to integrally manufacture the measurement pipe by injection molding.

  Therefore, when manufacturing a measurement pipe as shown in FIG. 6, it is necessary to divide it into several members and to perform injection molding, and these members are usually joined by welding or the like.

  However, in particular, when welding is performed at the center of the straight pipe portion 1, burrs and the like are generated inside the welded portion in the straight pipe portion 1 and become pipe resistance, disturbing the flow velocity distribution of the fluid, affecting measurement accuracy. Will be given. In addition, a welding process in several places is indispensable for manufacturing.

  In addition, when performing injection molding as in the past, since the inner surface of the tube is molded in contact with the mold, fine metal powder and metal ions that have been polished from the mold are melted into the tube. There is also a problem that these metal powders and metal ions are mixed in the fluid and adversely affect the fluid components.

  SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, and to form an integral body even in a complicated shape by forming the mold by blow molding using a mold. An object of the present invention is to provide a method of manufacturing a pipe body.

  In order to achieve the above object, a method for manufacturing a measurement pipe body of an ultrasonic flowmeter according to the present invention is characterized in that a propagation path through which an ultrasonic beam propagates between pipe ends of a straight tubular measurement pipe section, An ultrasonic input / output unit is formed in the mold, and has an inner mold for forming a measurement pipe body in which an inflow pipe section and an outflow pipe section are provided near both ends of the measurement pipe section. A method of manufacturing the measurement pipe body by blow molding, comprising: opening the mold and storing a cylindrical parison in which a synthetic resin material is soft-melted in the mold; and closing the mold. Injecting a gas into the parison, expanding the parison, and molding the outer surface of the parison by closely contacting the inner surface of the mold to form the measurement pipe body; and after cooling the parison, Opening the mold and removing the solidified measurement pipe body; Characterized in that a parts and cutting the ends of the outflow tube portion.

  According to the method of manufacturing the measurement pipe body of the ultrasonic flowmeter according to the present invention, even if the measurement pipe body has a complicated shape, it can be molded integrally and does not require welding. A good flow velocity distribution can be obtained without generating pipe resistance due to burrs on the inner surface of the road body.

  Also, since the parison is expanded by gas and blow-molded, the mold does not come into contact with the inner surface of the measurement pipe body, so that fine metal powder and metal ions from the mold do not adhere to the inner surface. Also, there is no adverse effect on the fluid components.

It is a perspective view of a measurement pipe body. It is sectional drawing. It is explanatory drawing of blow molding. It is sectional drawing of the measurement pipe body raw material manufactured by blow molding. FIG. 3 is a cross-sectional view of a measurement pipe body with an ultrasonic transmitting / receiving element attached. It is sectional drawing of the measuring pipe of a prior art example.

The present invention will be described in detail based on the embodiment shown in FIGS.
FIG. 1 is a perspective view of a measurement pipe body 10 of the embodiment, and FIG. 2 is a cross-sectional view. The measurement pipe body 10 of this embodiment is manufactured integrally by blow molding, and an inflow pipe section 12 and an outflow pipe section 13 are provided at both ends of a straight tubular measurement pipe section 11 with respect to the measurement pipe section 11, respectively. They are formed orthogonally. The two wall surfaces at the tube end in the longitudinal direction of the measurement tube unit 11 are ultrasonic input / output units 14a and 14b. Guide portions 15a and 15b having a circular cross section are formed on outer wall surfaces of the ultrasonic input / output portions 14a and 14b and serve as guides for attaching the ultrasonic transmitting / receiving element.

  The measurement pipe body 10 is manufactured by blow molding suitable for manufacturing a hollow synthetic resin molded product. That is, as shown in FIG. 3, the inflow pipe portion 12 of a space-like inner mold I of a symmetrical mold Ma, Mb (Mb not shown) divided into a plurality of pieces, for example, divided into two, is formed. Along with the inner die Ia, the inner die Ib for forming the measuring tube portion 11, and the inner die Ic for forming the outflow tube portion 13, a soft-melted cylindrical synthetic resin material, so-called parison P, is housed. Is sealed between the molds Ma and Mb to form a bag, and the molds Ma and Mb are closed.

  Next, a gas such as air is blown into the parison P through the air pipe A in the direction of the arrow, so that the parison P is expanded and its outer surface is brought into close contact with the inner mold I of the molds Ma and Mb. In this manner, blow molding of the measurement pipe body 10 having a thickness of, for example, about 2 mm is performed.

  Then, after the measurement pipe body 10 molded by the inner mold I is solidified and the molds Ma and Mb are opened and taken out, a material to be the measurement pipe body 10 as shown in FIG. 4 is obtained. Further, the closed end 12a of the inflow pipe 12 and the end 13a of the outflow pipe 13 are cut at the positions indicated by the dotted lines. Thereby, the measurement pipe body 10 shown in FIGS. 1 and 2 is obtained.

  When using the measurement pipe body 10 of the above-described embodiment, as shown in FIG. 5, an ultrasonic element which is a piezo element for transmitting and transmitting an ultrasonic beam to the outer wall surfaces of the ultrasonic input / output units 14a and 14b which are walls. The sound wave transmitting / receiving elements Sa and Sb are adhered via grease. Separate fluid conduits are connected to the inflow pipe section 12 and the outflow pipe section 13. The ultrasonic transmission / reception elements Sa and Sb are guided by the guide portions 15a and 15b, and can be mounted at accurate positions.

  Then, the fluid to be measured flows into the measuring tube portion 11, propagates through the propagation path W between the facing ultrasonic transmitting / receiving elements Sa and Sb, and the ultrasonic beams emitted alternately by the ultrasonic transmitting / receiving elements Sa and Sb are formed. The velocity of the fluid transmitted and received and flowing in the measurement pipe section 11 is obtained, and the flow rate is calculated by multiplying the cross-sectional area of the measurement pipe section 11. The velocity of the fluid is determined by a time difference method using an ultrasonic beam. However, since the principle of measuring the flow rate is well known, a description thereof will be omitted.

  As described above, according to the measurement pipe body 10 according to the present invention, since it is manufactured by blow molding, it can be integrally molded even in a complicated shape, and can be manufactured without the need for joining. A good flow velocity distribution can be obtained without generating burrs, which become pipe resistance, on the inner surface of the measurement pipe body 10.

  Although the directions of the inflow pipe section 12 and the outflow pipe section 13 with respect to the measurement pipe section 11 are aligned in one direction, they may be arranged in different directions. Also, the direction does not necessarily have to be a direction orthogonal to the measurement tube section 11.

  Since the measurement conduit 10 is formed by blowing a soft-melted synthetic resin parison P with gas to form an inner surface by blow molding, the mold is not used to form the inner surface of the measurement conduit 10, and the fineness of the mold is reduced. No metal powder or metal ions adhere and remain, and no metal powder or metal ions enter the fluid.

  Unlike the injection molding, the measurement pipe body 10 manufactured by the blow molding of the embodiment does not strictly regulate the inner surface shape and the wall thickness. For example, the thickness of the ultrasonic input / output units 14a and 14b and the measurement pipe unit It is conceivable that the inner diameter and the like of 11 vary, the characteristics of the individual measurement pipes 10 are different, and measurement errors occur.

  However, the accuracy of the flow rate measurement is ensured by calibrating the measurement pipe body 10 by flowing the actual flow rate individually and adding correction data. Also, in the case of rough flow measurement that does not require high-precision measurement, it can be used as it is without performing calibration.

Reference Signs List 10 Measurement pipe body 11 Measurement pipe section 12 Inflow pipe section 13 Outflow pipe section 14a, 14b Ultrasonic input / output section 15a, 15b Guide section I Inner type Ma, Mb Mold P Parison Sa, Sb Ultrasonic transmitting / receiving element W Propagation path

Claims (5)

An ultrasonic input / output section is formed at both ends of the straight pipe, and an inflow pipe section and an outflow pipe section are formed near both ends of the measurement pipe section. A method of manufacturing the measurement pipe body by blow molding using a mold that can be divided into a plurality of molds, the inner pipe forming a measurement pipe body provided with:
Opening the mold and storing a cylindrical parison in which the synthetic resin material has been soft-melted into the mold; closing the mold and injecting gas into the parison to expand the parison and expand the parison; Forming the measurement pipe body by closely contacting the outer surface of the mold with the inner mold of the mold, and taking out the solidified measurement pipe body by opening the mold after cooling the parison. Cutting the ends of the inflow pipe section and the outflow pipe section. A method of manufacturing a measurement pipe body of an ultrasonic flowmeter, comprising the steps of:   The measuring pipe body of the ultrasonic flowmeter according to claim 1, wherein the cylindrical parison is housed in the mold along the inflow pipe section, the measurement pipe section, and the outflow pipe section. Manufacturing method.   3. The method according to claim 1, wherein the gas into the parison is injected from at least one of the inflow pipe and the outflow pipe. 4.   The measurement pipe body of the ultrasonic flowmeter according to any one of claims 1 to 3, wherein the inflow pipe section and the outflow pipe section are formed in a direction orthogonal to the measurement pipe section. Manufacturing method.   The measuring pipe of the ultrasonic flowmeter according to any one of claims 1 to 4, wherein a guide part functioning as a guide part of an ultrasonic transmitting / receiving element is formed on an outer wall surface of the ultrasonic input / output part. How to make the body.

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