DE102007007512A1 - Measuring pipe has capillary tube for production of fluid connection between measuring device and fluid containing container, where capillary tube is attached to connection elements - Google Patents

Abstract

The invention relates to a measuring line with a capillary tube (1) for establishing a fluid connection between a measuring device and a container containing the fluid, wherein the capillary tube (1) has terminal elements (2, 3) attached terminally thereto. To improve the robustness and to agree on the production, it is proposed according to the invention that the capillary tube (1) by means of extrusion and the connecting elements (2, 3) are each made by injection molding of extrudable polyethylene.

Description

The The invention relates to a measuring line according to the preamble of the claim 1.

To It is known in the art to fill a fluid filled one Container, such as a hot water boiler, by means a measuring line with a measuring device, such as a temperature or pressure gauge to connect. The measuring line points a capillary tube for establishing fluid communication with the meter so that physical properties of the fluid are measured there can be.

Currently used as capillary tubes with thin copper cables an inner diameter of about 1 mm. Such copper capillary tubes can when exposed to an external force bend, bend or break easily. Apart from that, copper a high thermal conductivity, resulting in a rapid drop in the temperature of a recorded in the copper capillary Fluids and thus lead to a falsification of readings can. Finally, the manufacture is using the conventional copper capillaries consuming and increasingly expensive due to rising copper prices.

task The invention is to the disadvantages of the prior art remove. In particular, it should be as robust as possible Measuring line can be specified, which is simple and inexpensive can be produced. According to another object of the invention, the Measuring line as accurate as possible physical measurement Allow properties of a fluid funded therein.

These The object is achieved by the features of claims 1 and 12 solved. Advantageous embodiments of Invention will become apparent from the features of the claims 2 to 11 and 13 to 22.

To According to the invention, it is provided that the capillary tube by extrusion and the connection elements by means of injection molding, respectively are made of an extrudable polyethylene. - The proposed capillary deforms when exposed to an external Force elastic around its longitudinal axis. It points at the same time a high dimensional stability compared to a radial Deformation on. In the measuring line according to the invention are the connection elements in deviation from the prior art made of an extrudable polyethylene by injection molding. By the term "extrudable polyethylene" is meant a polyethylene understood, which has a relatively high viscosity and consequently by extrusion into moldings, in particular Pipes and the like, can be processed. Such a material will in the prior art - because of its high viscosity - not in Injection molding processed. The present invention has now been found that even extrudable polyethylene in a suitable Design of the injection mold processed by injection molding can be. The configuration of the injection mold has the circumstance To take into account that extrudable polyethylene is a special high viscosity. For example, there are more here To provide sprue points or larger sprue cross sections, than in a comparable injection mold for the processing of conventional injection moldable plastics.

The proposed production of the connection elements of extrudable Polyethylene has the advantage that it can be made by means of conventional Joining process particularly simple and reliable can be connected to the capillary tube.

To An advantageous embodiment of the invention are the capillary tube and the connecting elements of the same extrudable polyethylene as Prepared starting material. By only a single source material for the production of the capillary tube and the connection elements to Is the effort for Logistics and production kept very low.

To a particularly advantageous embodiment that is for the production the capillary tube used by an extrudable polyethylene Addition of carbon, advantageously carbon black, black inked. Conversely, the connecting elements are expediently transparent. This allows a connection the connection elements with the capillary tube by laser welding. To For this purpose, the connection elements on the ends the capillary tube attached and subsequently by laser welding be welded to the capillary tube.

To A further embodiment of the invention provides that the polyethylene is LLD polyethylene (LLDPE: Linear Low Density Polyethylene). The LLDPE may have side chains formed from hexene or octene. Also made of butene side chains are possible. To In another embodiment, the LLDPE is a metallocene catalyst polymerized. In particular, an LLDPE with the aforementioned Characteristics enables a particularly simple production the measuring line.

To In an alternative embodiment, the polyethylene can also be radiation-crosslinkable Polyethylene (PEX). In this case, the measuring line will be after the welding of the capillary tube with the connection elements by means of radiation, for example X-ray radiation, crosslinked.

To A further embodiment of the invention, the capillary tube a length of 20 cm to 300 cm and / or an inner diameter from 0.5 mm to 1.5 mm. A measuring line with such a capillary tube is flexible, robust and yet easy and inexpensive produced.

• a) Herstellen eines Kapillarrohrs mittels Extrusion aus extrudierbarem Polyethylen;
• b) Herstellung von Anschlusselementen mittels Spritzguss aus extrudierbarem Polyethylen und
• c) Herstellung einer fluiddichten Verbindung der Anschlusselemente mit den Enden des Kapillarrohrs.

According to another aspect of the invention, a method for producing the measuring line according to the invention is provided with the following steps:

• a) producing a capillary tube by extrusion from extrudable polyethylene;
• b) Production of connection elements by injection molding of extrudable polyethylene and
• c) producing a fluid-tight connection of the connection elements with the ends of the capillary tube.

By doing both the capillary tube and the connecting elements of extrudable Polyethylene can be made, because of the similarity or Identity of the material used is particularly simple reliable and permanent connection between the capillary tube and make the connection elements. Apart from that allows the proposed method to relatively simple and inexpensive Way of making a rugged measuring lead.

Because of the advantageous embodiments of the method is based on the Measurement lead described features and advantages referred to in the same Way for the procedure to apply.

following Embodiments of the invention with reference to the drawings explained in more detail. Show it:

1 a perspective view of a measuring line and

2 a schematic cross-sectional view through a capillary tube with a terminal plugged terminal thereon.

In 1 are at both ends of a capillary tube, preferably made of a metallocene catalyst-added LLDPE 1 each connection elements 2 and 3 intended. That for the production of the capillary tube 1 used LLDPE is colored dark by an addition of suitable pigments. In that regard, are suitable as pigments z. As carbon black or graphite. The LLDPE used is an extrudable LLDPE with an MFI (melt flow index) in the range of 0.5-2 g / 10 min (at 190 ° C and 2.16 kg). For the production of the capillary tube 1 the LLDPE is first melted, which is then provided with the black coloring additive. Then, from the melt by extrusion at about 200-250 ° C, the capillary tube 1 produced. The capillary tube produced is cut into sections of predetermined lengths, for example in the range of 20 cm to 300 cm.

For the production of connection elements 2 . 3 is also used as starting material, the above-described, preferably added with a metallocene catalyst, LLDPE. In this case, however, the material is not colored black by an additive. The extrudable LLDPE with an MFI of 0.5-2 g / 10 min (at 190 ° C, 2.16 kg) is injection molded using a specially adapted to the very high viscosity injection mold to the connection elements 2 . 3 processed. Because of the high viscosity of the extrudable LLDPE melt, compared to conventional injection molds, it is necessary to provide a gate with a significantly larger cross-section. The connection elements produced by injection molding 2 . 3 are transparent.

The production of a fluid-tight connection, ie a liquid-tight and / or gas-tight connection, between the connection elements 2 . 3 and the capillary tube 1 is in 2 shown. To make the connection is one of the connection elements 2 . 3 extending neck 4 positive fit on one end 5 of the capillary tube 1 plugged. Then the end 5 of the capillary tube 1 in with the neck 4 overlapping area welded by a laser transmission method. In this case, the transparent trained neck 4 irradiated with laser beams. The laser beams are essentially the black colored capillary tube 1 absorbed. As a result of the heat generated with it, the end will be 5 of the capillary tube 1 and the neck 4 partially melted and welded together.

According to a particularly advantageous embodiment, it is provided that the nozzle is not connected to the end by a laser beam guided around the end 5 of the capillary tube 2 is welded, but with a laser welding device, simultaneously irradiated with the entire circumference of the nozzle and thus at the same time over the entire circumference a connection can be made by welding. In 2 is with the reference numeral 6 a corresponding device for generating radially inwardly facing laser light shown. Such laser welding devices are known in the art. By way of example, reference is made to the following source: http: \\ www.leisterlaser.com

The LLDPE used for the preparation may also be modified. Instead of the matallocene catalyst, other suitable additives for the polymerization of the material may be included. Further, the LLDPE may be offset with butene, hexene or octene. Such additives can in egg be contained in a proportion of up to 19 wt.%. They lead to the formation of side chains.

Instead of the LLDPE, it is also possible to use radiation-crosslinkable polyethylene. In this case, however, it is necessary to connect the measuring line after making the connection between the connecting elements 2 . 3 and the capillary tube 1 a radiation crosslinking, for example, with X-rays to undergo.

1

capillary

2, 3

connection elements

4

Support

5

The End

6

Laser welding device

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• - http://www.leisterlaser.com [0022]

Claims (22)

Measuring line with a capillary tube ( 1 ) for establishing a fluid connection between a measuring device and a container containing the fluid, wherein the capillary tube ( 1 ) Terminally attached thereto terminal elements ( 2 . 3 ), characterized in that the capillary tube ( 1 ) by extrusion and the connection elements ( 2 . 3 ) are each made by injection molding of an extrudable polyethylene. Measuring line according to claim 1, wherein the capillary tube ( 1 ) and the connection elements ( 2 . 3 ) are made of the same extrudable polyethylene as the starting material. Measuring line according to one of the preceding claims, wherein the for the production of the capillary tube ( 1 ) extrudable polyethylene is darkened by the addition of pigments, preferably carbon, so that laser is absorbed. Measuring line according to one of the preceding claims, wherein the connection elements ( 2 . 3 ) are transparent to laser. Measuring line according to one of the preceding claims, wherein the connection elements ( 2 . 3 ) by laser welding with the capillary tube ( 1 ) are connected. Measuring line according to one of the preceding claims, wherein the polyethylene is LLD polyethylene (LLDPE). Measuring line according to one of the preceding claims, wherein the LLDPE has side chains formed from hexene or octene. Measuring line according to one of the preceding claims, wherein a metallocene catalyst is added to the LLDPE for polymerization is. Measuring line according to one of the preceding claims, wherein the polyethylene is radiation crosslinkable polyethylene (PEX). Measuring line according to one of the preceding claims, wherein the capillary tube ( 1 ) has a length of 20 cm to 300 cm. Measuring line according to one of the preceding claims, wherein the capillary tube ( 1 ) has an inner diameter of 0.5 mm to 1.5 mm. Method for producing a measuring line according to Claim 1, comprising the following steps: a) Production of a capillary tube ( 1 ) by extrusion from extrudable polyethylene; b) Production of connecting elements ( 2 . 3 ) by injection molding of extrudable polyethylene, and c) producing a fluid-tight connection of the connecting elements ( 2 . 3 ) with the ends ( 5 ) of the capillary tube ( 1 ). The method of claim 12, wherein the capillary tube ( 1 ) and the connection elements ( 2 . 3 ) are made from the same extrudable polyethylene as the starting material. Method according to one of claims 12 or 13, wherein the for the production of the capillary tube ( 1 ) used extruded polyethylene by pigments, preferably carbon, dark colored, so that laser is absorbed. Method according to one of claims 12 to 14, wherein the connection elements ( 2 . 3 ) are transparent to laser. Method according to one of claims 12 to 15, wherein the connection elements ( 2 . 3 ) by laser welding with the capillary tube ( 1 ) get connected. Method according to one of claims 12 to 16, wherein as polyethylene LLD polyethylene (LLDPE) is used. Method according to one of claims 12 to 17, wherein the LLDPE has side chains formed from hexene or octene. Method according to one of claims 12 to 18, wherein a metallocene catalyst is added to the LLDPE for polymerization is. Method according to one of claims 12 to 19, wherein polyethylene is used as radiation-crosslinkable polyethylene (PEX) becomes. Method according to one of claims 12 to 20, wherein the capillary tube ( 1 ) is produced in a length of 20 cm to 300 cm. Method according to one of claims 12 to 21, wherein the capillary tube ( 1 ) has an inner diameter of 0.5 mm to 1.5 mm.