GB1598392A

GB1598392A - Temperature measuring device for non-contacting temperature measurement

Info

Publication number: GB1598392A
Application number: GB3957/78A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-02-10
Filing date: 1978-02-01
Publication date: 1981-09-16
Also published as: FR2380543A1; BR7800780A; FR2380543B1; BE863767A; DE2705520C3; DE2705520A1; DE2705520B2; ZA78781B

Description

(54) TEMPERATURE MEASURING DEVICE FOR NON-CONTACTING TEMPERATURE MEASUREMENT (71) I, HANS CLEMENS KUGLER, a German citizen of Bruchwiesen-Anlage 1, 6602 Saarbrticken-Dudweiler, Germany (Fed. Rep.) do hereby declare the invention, for which I pray that a Patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement: The invention relates to a temperature measuring device for non-contacting temperature measurement by means of a radiation pyrometer, which receives the temperature-dependent infrared radiation emitted by the object of measurement and converts it into an output voltage, which is supplied to an indicating instrument.Radiation pyrometers of this type are used mainly for measuring the temperature of objects which are not easily accessible or moving objects and cause no disturbance of the temperature field, as may occur when using heat sensors, which measure the temperature by way of a changing electrical resistance.

The invention deals with the problem of safety in areas subject to the danger of explosions and in underground operations, which is compromised by fire-damp. In these locations, explosions are caused easily due to overheating bearings, conveyor belts, brake drums and the like. Therefore, the new object of the invention is to increase safety in areas subject to the danger of explosions and in underground operations by using non-contacting temperature measurement.

According to the present invention there is provided a temperature measuring device for non-contacting temperature measurement comprising a radiation pyrometer, a pressure-resistant main housing in which the radiation pyrometer is located, pressuresealed openings in said housing for power cables, a wall of said housing located optically in front of the radiation pyrometer being provided with a radiation inlet with a window in the form of a germanium disc.

A temperature-measuring device is thus created with a construction which is resistant to explosions and firedamp, with whose assistance the temperature of machine parts, pipe lines etc. can be monitored, which could cause explosions due to inadmissible heating. As known, an additional intrinsically safe ancillary device could be associated with the radiation pyrometer, in order, upon the occurrence of inadmissibly high temperatures, to produce warning signals for example by way of monitoring limit values and remote control or even to switchoff machine devices automatically.Since a radiation pyrometer already responds to the thermal radiation of a human body, the temperature measuring device according to the invention can also be used as a barrier, so that in underground operations for example, miners are prevented from using the conveyor belts as transport means for themselves, which has already caused numerous accidents.

In contrast to a glass disc, a germanium disc in the radiation inlet has the advantage of substantially increased material density and also allows the infrared thermal radiation to pass virtually unhindered. In its seat in the insert, which is naturally likewise connected to the housing wall, for example the housing cover, associated therewith in a non-penetrable manner, the germanium disc is appropriately covered on both sides with sealing rings and housed by a screwthreaded thrust ring.

The pyrometer preferably includes an electrical output circuit having outlet terminals, said pyrometer output circuit being designed such that the short-circuit current intensity across said outlet terminals is limited to a maximum of 50 milli-amperes.

If a commercially available pressureresistant cast housing suitable for receiving the radiation pyrometer is selected as the main housing, as is available for housing indicators and switch-gear in a construction resistant to explosions and firedamp, the device preferably further comprises a nonpressure-resistant instrument housing attached to said main housing such that said pyrometer outlet terminals project into said instrument housing, and an indicator mounted within said instrument housing and having input terminals coupled to said pyrometer circuit outlet terminals. In view of the low short-circuit current intensity, the instrument housing does not need to be produced with a construction resistant to explosions and firedamp, since the formation of a spark is impossible with such a short-circuit current intensity.

When, as regards the pressure sealed openings for the inlet and outlet of leads, the main housing is not suitable for introducing the mains cables directly, the device preferably further comprises a pressureresistant mains junction box attached to said main housing and having pressure-sealed cable inlets and outlets.

One embodiment of a temperaturemeasuring device according to the invention is illustrated in the drawings and in particular Figure 1 is a front view of the device consisting of three housings Figure 2 is a front view according to figure 1 with the front walls cut partly away or with the front wall removed and Figure 3 is a section through the insert with the germanium disc on line III-III of Figure 1.

Figure 1 shows the central main housing 1 with the front cover 2 which comprises an opening, from which the insert 3 provided with a radiation inlet 4 projects. A germanium disc 5 is located in the radiation inlet 4 as a radiation window, which is covered with two sealing rings 6 and 7 and clamped in its seat by means of a screw-threaded thrust ring 8 (Figure 3). The free end face of the insert 3 is provided with four bores 9 for attaching a transparent dust-proof cover.

The insert 3 is screwed by its flange 3a to the rear side of the front wall 2 of the housing, with the interposition of a sealing ring 10. The inner seal 6 on the germanium disc 5 is appropriately a copper seal, whereas the seals 7 and 10 are metal-coated seals.

The clearance dimensions both of the screwthread of the thrust ring 8 as well as of the outer seals 7 and 10 correspond to the VDE specification (Association of German Electrical Engineers) 0170/0171 paragraph 16, 17d. According to the latter, the holder for the germanium disc is resistant to the penetration of sparks.

An instrument housing 11 of steel plate is attached to the top of the main housing 1, which housing 11 receives an indicator 12 and is provided with two cable outlets 13, in order to be able to connect ancillary apparatus to the indicator 12. Since the main housing 1 is a commercially available pressure-resistant housing, in this embodiment, a pressure-resistant mains connection box 14 is attached on the underside of the main housing, in which box the mains cable can be introduced through a tension-free cable inlet 15. The introduction (not shown) of the mains cable into the mains junction box 14 is constructed to be pressure-resistant or "intrinsically safe", in the same manner as the inlets in the main housing 1 for the cables coming from the connecting terminals 16 (Figure 2). To illustrate the terminals 16, the mains junction box 14 is illustrated without its cover in Figure 2.

Figure 2 shows the main housing 1 with its front cover 2 partly cut away and the inserted radiation pyrometer 18 with its optical system 18a. A plate 19 is attached to the radiation pyrometer 18, which plate supports the output circuit of the pyrometer consisting of wire-wound resistances and Zener diodes, which circuit is designed to limit the short-circuit current intensity of the commercially available radiation pyrometer 18 to a maximum of 50 milli-amperes. Due to this it is possible to attach the instrument housing 11 as a non-pressure-resistant construction on the upper side of the main housing 1. The signal leads 20 of the output circuit of the radiation pyrometer 18 are guided out of the main housing 1 in a pressure-resistant or intrinsically safe manner and terminate in connection terminals 21 inside the instrument housing 11.Since these terminals 21 carry a maximum shortcircuit current intensity of 50 milli-amperes, no sparks nor short-circuit heat can be produced in the instrument housing 11 which is not pressure-resistant, which sparks or heat could cause an explosion or firedamp. To illustrate the terminals 21, the cover 11a of the instrument housing 11 is shown partly cut away in Figure 2.

WHAT I CLAIM IS: 1. A temperature measuring device for non-contacting temperature measurement comprising a radiation pyrometer, a pressure-resistant main housing in which the radiation pyrometer is located, pressuresealed openings in said housing for power cables, a wall of said housing located optically in front of the radiation pyrometer being provided with a radiation inlet with a window in the form of a germanium disc.

2. A device according to claim 1, wherein the radiation inlet is provided in a removable insert in said front wall of the housing.

3. A device according to claim 2, wherein in its seat in the insert, the germanium disc is covered on both sides with sealing

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. main housing, as is available for housing indicators and switch-gear in a construction resistant to explosions and firedamp, the device preferably further comprises a nonpressure-resistant instrument housing attached to said main housing such that said pyrometer outlet terminals project into said instrument housing, and an indicator mounted within said instrument housing and having input terminals coupled to said pyrometer circuit outlet terminals. In view of the low short-circuit current intensity, the instrument housing does not need to be produced with a construction resistant to explosions and firedamp, since the formation of a spark is impossible with such a short-circuit current intensity. When, as regards the pressure sealed openings for the inlet and outlet of leads, the main housing is not suitable for introducing the mains cables directly, the device preferably further comprises a pressureresistant mains junction box attached to said main housing and having pressure-sealed cable inlets and outlets. One embodiment of a temperaturemeasuring device according to the invention is illustrated in the drawings and in particular Figure 1 is a front view of the device consisting of three housings Figure 2 is a front view according to figure 1 with the front walls cut partly away or with the front wall removed and Figure 3 is a section through the insert with the germanium disc on line III-III of Figure 1. Figure 1 shows the central main housing 1 with the front cover 2 which comprises an opening, from which the insert 3 provided with a radiation inlet 4 projects. A germanium disc 5 is located in the radiation inlet 4 as a radiation window, which is covered with two sealing rings 6 and 7 and clamped in its seat by means of a screw-threaded thrust ring 8 (Figure 3). The free end face of the insert 3 is provided with four bores 9 for attaching a transparent dust-proof cover. The insert 3 is screwed by its flange 3a to the rear side of the front wall 2 of the housing, with the interposition of a sealing ring 10. The inner seal 6 on the germanium disc 5 is appropriately a copper seal, whereas the seals 7 and 10 are metal-coated seals. The clearance dimensions both of the screwthread of the thrust ring 8 as well as of the outer seals 7 and 10 correspond to the VDE specification (Association of German Electrical Engineers) 0170/0171 paragraph 16, 17d. According to the latter, the holder for the germanium disc is resistant to the penetration of sparks. An instrument housing 11 of steel plate is attached to the top of the main housing 1, which housing 11 receives an indicator 12 and is provided with two cable outlets 13, in order to be able to connect ancillary apparatus to the indicator 12. Since the main housing 1 is a commercially available pressure-resistant housing, in this embodiment, a pressure-resistant mains connection box 14 is attached on the underside of the main housing, in which box the mains cable can be introduced through a tension-free cable inlet 15. The introduction (not shown) of the mains cable into the mains junction box 14 is constructed to be pressure-resistant or "intrinsically safe", in the same manner as the inlets in the main housing 1 for the cables coming from the connecting terminals 16 (Figure 2). To illustrate the terminals 16, the mains junction box 14 is illustrated without its cover in Figure 2. Figure 2 shows the main housing 1 with its front cover 2 partly cut away and the inserted radiation pyrometer 18 with its optical system 18a. A plate 19 is attached to the radiation pyrometer 18, which plate supports the output circuit of the pyrometer consisting of wire-wound resistances and Zener diodes, which circuit is designed to limit the short-circuit current intensity of the commercially available radiation pyrometer 18 to a maximum of 50 milli-amperes. Due to this it is possible to attach the instrument housing 11 as a non-pressure-resistant construction on the upper side of the main housing 1. The signal leads 20 of the output circuit of the radiation pyrometer 18 are guided out of the main housing 1 in a pressure-resistant or intrinsically safe manner and terminate in connection terminals 21 inside the instrument housing 11.Since these terminals 21 carry a maximum shortcircuit current intensity of 50 milli-amperes, no sparks nor short-circuit heat can be produced in the instrument housing 11 which is not pressure-resistant, which sparks or heat could cause an explosion or firedamp. To illustrate the terminals 21, the cover 11a of the instrument housing 11 is shown partly cut away in Figure 2. WHAT I CLAIM IS:

1. A temperature measuring device for non-contacting temperature measurement comprising a radiation pyrometer, a pressure-resistant main housing in which the radiation pyrometer is located, pressuresealed openings in said housing for power cables, a wall of said housing located optically in front of the radiation pyrometer being provided with a radiation inlet with a window in the form of a germanium disc.

rings and is held in position by a screwthreaded thrust ring.

4. A device according to any one of claims 1 to 3 wherein said pyrometer in- cludes an electric output circuit having outlet terminals, said pyrometer output circuit being designed such that the shortcircuit current intensity across said outlet terminals is limited to a maximum of 50 milli-amperes.

5. A device as claimed in claim 4, further comprising a non-pressure-resistant instrument housing attached to said main housing such that said pyrometer outlet terminals project into said instrument housing, and an indicator mounted within said instrument housing and having input terminals coupled to said pyrometer circuit outlet terminals.

6. A device as claimed in any one of the preceding claims, further comprising a pressure-resistant mains junction box attached to said main housing and having pressure-sealed cable inlets and outlets.

7. A temperature measuring device for non-contacting temperature measurement, substantially as herein described with reference to and as illustrated in the accompanying drawings.