WO1997032188A1

WO1997032188A1 - Temperature sensor

Info

Publication number: WO1997032188A1
Application number: PCT/SE1997/000348
Authority: WO
Inventors: Erland MÅRTENSSON
Original assignee: Ab Svensk Värmemätning Svm
Priority date: 1996-03-01
Filing date: 1997-02-28
Publication date: 1997-09-04
Also published as: SE9600810L; AU2110697A; SE9600810D0

Abstract

Method of manufacturing a temperature sensor with a measuring body (6) comprising a sensor (10) provided at one end of a rod-shaped insulator with line wires (9) arranged therein and connection means (3) at the other end of the rod-shaped insulator for connection of the sensor to recording equipment, e.g. intended for measuring of temperatures in a flowing medium, wherein line wires (9) are pre-tensioned in a mould, insulating material is injection moulded in the mould while at the same time the line wires are maintained pre-tensioned in the mould, whereupon the mould is removed when the material is hardened, and a temperature sensor manufactured with said method.

Description

"Temperature sensor"

Technical field

The present invention relates to a temperature sensor with a measuring body comprising a sensor at one end of a rod-shaped insulator with wires provided therein and connection means at the other end of the rod-shaped insulator for connection of the sensor to recording equipment, e.g. intended for measuring of temperatures in a flowing medium.

Background art

In district heating networks, the temperatures are supervised with the aid of temperature sensors. These compri¬ se a rod-shaped insulator with wires inside connected to a sensor at the outer end of the insulator. The insulator and the sensor are normally surrounded by a steel sleeve, which in turn is inserted into a diving tube. The insulator is made of ceramics and is provided with a number of channels passing there through corresponding to the desired number of wires, and often the rod is made of a number of shorter parts. A disadvantage with this construction is that from a strength point of view an outer steel shell has to be provided, which carries off heat. The manufacture is expensive as well as the device itself.

The invention

The object of the invention is to provide a more economic method for the manufacture of temperature sensors of the kind defined in the preamble, as well as a thermally insulated temperature sensor with a strength of its own, and manufac¬ tured with said method.

This is achieved with the method according to the present invention which is characterized in that wires are pre- tensioned in a mould, in that insulator mass is lnjection- moulded in the mould while the line wires are maintained in pre-tensioned condition in the mould, whereupon the mould is removed when the material is hardened.

After the removal from the mould the measuring body is made complete by mounting of sensors on the line wires, which are fixed, which facilitates the assembly. An electrical insulator is arranged over the connections, e.g. a Teflon® sleeve, and finally a metal sleeve is arranged over the lower part of the measuring body. According to a preferred embodiment of the invention phenylene sulphide PPS is injection moulded as the insulator material.

The temperature sensor according to the invention compri¬ ses a rod-shaped insulator of a high-strength, thermically and electrically insulating material with line wires moulded into the insulator. The insulator material is preferably PPS (phenylene sulphide) .

The substantial novelty of the invention compared to previous embodiments of temperature sensors of this kind is that the rod-shaped part, called the measuring body, is thermally as well as electrically insulating, and the strength is even higher than for previously known measuring bodies consisting of an outer metal sleeve with line wires running loosely therein inside an insulator. Also from a manufacturing point of view great advantages are achieved with the temperature sensor according to the invention, which can be manufactured in fewer steps and the manufacturing procedure can be automatized to a larger extent than previously.

Short description of the drawing

The invention will be described more in detail below with reference to the enclosed drawing on which

Fig. 1 shows a cross-sectional side view through one embodiment of the temperature sensor according to the invention,

Fig. 2 shows a cross-sectional view taken along the line II-II in fig. 1, and

Fig. 3 shows a partial view of the cross-section accor- ding to fig. 2 in an enlarged scale.

Description of preferred embodiments

In Fig. 1, one embodiment of the temperature sensor according to the invention is shown in a cross-sectional side view. In a housing 1 with a screw cap 2, plates 3 for electrical connections are arranged. A joint 4 is provided for inserting wires, and a joint 5 is provided for accommoda¬ tion of the measuring body 6, as well as for optional connec- tion to a diving tube, not shown, intended to be inserted into a flowing medium, e.g. in a district heating network. The housing with connections is conventional and, therefor, it will not be described further in this application.

The measuring body with its line wires is mounted with a sealing bushing 7 which is locked in the joint with a snap fitting 8. The measuring body 6 comprises a homogenous, injection moulded material with a strength per se. According to a preferred embodiment the material is phenylene sulphide PPS. At the manufacture of the measuring body line wires 9 are put under pre-tension in the mould and the pre-tension is maintained during the subsequent injection moulding process. In a subsequent step a sensor 10 is mounted on the ends of the line wires. In order to protect the sensor, a metal sleeve 11 is placed over the end of the measuring body. For this purpose e.g. 2 O-rings 12,13 are provided in grooves in the measuring body and in order to obtain maximum safety the metal sleeve is preferably also upset at 1 .

In Fig. 2 is shown a partial cross section through the measuring body, taken along the line II-II in fig. l, and in Fig. 3 an enlarged partial view of fig. 2 is shown. At the upper end of the measuring body a flange 15 is provided for fastening in the bushing 7 and in order to prevent extraction of the measuring body from the bushing. In the illustrated embodiment the measuring body 6 comprises to line wires 9', 9". The line wires are connected at 16,17 to the connections 18,19 of the sensor 10. A Teflon^® hose 20 or corresponding means is provided around the connec¬ tions of the sensor inside the sleeve while the sensor 10 extends down towards the bottom of the sleeve in the form of a T-film element 21 in heat conducting paste provided therein.

The design as well as the number of line wires may be varied without departing from the inventive thought.

Claims

1. Method of manufacturing a temperature sensor with a measuring body comprising a sensor at one end of a rod-shaped insulator with line wires provided therein and connection means at the other end of the rod-shaped insulator for con¬ nection of the sensor to recording equipment, e.g. intended for measuring of temperatures in a flowing medium, characte¬ rized in that line wires are pre-tensioned in a mould, in that insulator material is injection moulded m the mould while the line wires are maintained in pre-tensioned condi¬ tion in the mould, whereupon the mould is removed when the material is hardened.

2. A temperature sensor with a measuring body (6) comprising a sensor (10) provided at one end of a rod-shaped insulator with line wires provided therein and connection means (3) at the other end of the rod-shaped insulator for connection of the sensor to recording equipment, e.g. in¬ tended for measuring temperatures in a flowing medium, char¬ acterized in that the rod-shaped insulator comprises an injection moulded, high-strength, thermally and electrically insulating material, and m that the line wires in a pre- tensioned condition are moulded into the insulator.

3. A temperature sensor according to claim 2, charac¬ terized in that the injection material is phenylene sulphide PPS.