Radiant energy – Photocells; circuits and apparatus – Housings
Patent
1993-11-15
1995-04-18
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Housings
250238, H01J 502
Patent
active
054080967
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an instrument for detecting the presence of a body, comprising a detector and a housing in which the detector is accommodated.
One known type of instrument is based on the principle of thermal radiation detection from a body. However, detection methods using other wave ranges are also known. Such a device comprises a housing provided with a least a transmission passage aimed in the direction of the body to be detected suitable for guiding to the detector one or more signals originating from the body. An instrument of this type is used in the practice of continuous casting. Applications in rolling mill installations are also known. Also applications in the field of measuring temperatures in hostile environments are known. Reference is made to U.S. Pat. No.5,000,580 and DE-C-895,161. U.S. Pat. No. 5,000,580 discloses a radiation pyrometer suitable for detecting the presence of a body, which basically comprises a detector (1) in a housing having a guide passage for transmission of radiation from the body to be detected, and is equiped with a gas purge system for directing cleansing gas (air) onto a lens and down the guide. At the distal end of the guide an additonal gas injection system is arranged of which one part defines a conduit about the end of said guide, and another part defines a slot from which gas (air) is discharged into the conduit away from the housing and about the guide passage.
A similar configuration is disclosed in DE-C-895,161. Whereas in U.S. Pat. No. 5,000,580 both puree and injection system are provided with pressurized gas, in DE-C-895,161 injection of gas takes place only via a separate inlet of the additonal injection system resulting in suction of gas through the purge system.
Further prior art (U.S. Pat. No. 4,738,528) shows a method of cleaning a pyrometer lens by directing purge aire spirally inward over the lens surface such that a vortex is formed by the spiral air flow to increase effectivity of the cleaning action.
U.S. Pat. No. 4,784,491 teaches the application of pitched grooves or screw threads in the walls of a gas channel to induce a swirling flow to protect optics against debris and moving particles in the air.
GB-A-1,114,682 proposes the application of a head for a detection instrument, including tangential gas inlet for supply of cleaning gas along the sight-way of the instrument.
In this application the instrument serves to detect the presence of a slab to be rolled out for purposes such as bringing the mill stands of the rolling mill up to the desired angular velocity on time and for making other setting adjustments. Instruments of the kind referred to in the preamble are also used in rolling mills provided with a reversing rolling unit. In a reversing rolling unit a slab is rolled out in a number of backward and forward motions into an intermediate product which is suitable for being rolled out to a desired finished rolling thickness in a finishing train. It is important in the use of such a reversing rolling unit to detect not only when the slab to be rolled is approaching the roller but also when it is leaving the roller. Valuable production time may be saved with this information, given that, for example, detecting the slab leaving the mill stand offers the opportunity of reversing the drive direction of that mill stand as early as possible.
There is a problem in the applications mentioned above in that the instrument has to work in highly contaminated surroundings which adversely affect the operation of the instrument especially in respect of the temperature conditions. Consequently, the known instrument requires a great deal of maintenance. These aggravating conditions include the continual presence of surrounding air saturated with moisture as a result of the cooling water sprayed onto the rollers and the high pressure descaling water for removing the scale from the slab to be rolled. In addition much dirt is present in the surrounding air in the form of iron oxide or oil. Also associated with this is the problem that, in terms of mea
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patent: 5317165 (1994-05-01), Montagna
De Visser Robert
Lea Richard W.
Hoogovens Groep B.V.
Nelms David C.
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