Optics: measuring and testing – Inspection of flaws or impurities – Bore inspection
Reexamination Certificate
2000-01-07
2003-10-28
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Bore inspection
C356S241500
Reexamination Certificate
active
06639664
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an endoscope for inspection of an observation cavity, in particular of an observation cavity in which a hot medium and/or infrared radiation is present, having a shaft in which an optical system is arranged, the shaft having an inner shaft and an outer shaft surrounding the latter at a distance, the optical system being arranged in the inner shaft, and the shaft being configured in the region of its distal end in such a way that it is substantially impermeable to electromagnetic radiation in the infrared spectral range.
An endoscope of this kind for technical applications is known from DE 44 38 229 C2.
An endoscope of this kind is generally used to observe dynamic processes in an observation cavity, for example a reaction chamber or a combustion chamber, directly through an eyepiece at the proximal end of the endoscope, or to transmit images, by way of a camera connected to the endoscope, into an image reproduction unit and there to display them.
A specific application for an endoscope of this kind is combustion research on piston engines on engine test stands. The endoscope can be used to visualize fuel injection, mixture distribution, and the process by which the combustion gases are combusted, while the engine is running.
Further applications for an endoscope of this kind are combustion research in gas turbines and jet engines, and on flames in oil burners, charge monitoring in furnaces, routine monitoring in incineration plants and blast furnaces, or the visualization of chemical reactions in chemical reactors.
A feature common to the aforesaid applications is the fact that a hot medium and/or infrared radiation, to which the endoscope is exposed during operation, can be present in the observation cavity being inspected.
In order to inspect an observation cavity with the endoscope, an orifice is made in a wall of the observation cavity, into which the distal end of the endoscope is introduced with the aid of a tubular insert that is open at both ends. To additionally allow the observation of non-self-illuminating processes, an illumination system is also used, introduced through a second orifice in the wall of the observation cavity.
During inspection of the observation cavity, the distal end of the endoscope introduced into the opening in the wall of the observation cavity, for example an engine, is exposed to the combustion chamber environment. In diesel engines, for example, average combustion cycle temperatures of up to approx. 1800° C. are present during operation. The system arranged in the shaft of the endoscope is designed, however, only for operating temperatures in the range between max. 100° C. to 200° C. The optical components themselves and also a mechanism present at the distal end of the endoscope would withstand even higher temperatures, but the optical cement and the adhesive joints that are used for assembly and installation of the optical system in the shaft would not.
The endoscope known from the aforesaid DE 44 38 229 C2 for observation of cavities that are under pressure and/or at high temperature has a pressure-tight encapsulation of the endoscope comprising a protective tube that surrounds the endoscope and that has, at the level of the endoscope objective, a pressure-resistant window made of quartz glass. The protective tube thus forms an external shaft, while the endoscope tube receives the optical system.
To prevent the distal end of the endoscope in the region of the objective from coming into direct contact with the hot medium, such endoscopes are generally used together with a test-tube-shaped glass shield that is inserted into the orifice in the wall of the observation cavity, and into which the distal end of the endoscope is introduced. While the glass shield does effect separation and isolation of the optical system of the endoscope from the hot medium present in the combustion chamber, it does not offer any protection against infrared radiation. It has been found that when a glass shield is used in a combustion chamber environment with combustion cycle temperatures of approximately 1800° C., temperatures in the range of 700° C. are still present behind the glass shield. Temperatures of that magnitude can result, however, in damage to the optical system of the endoscope.
The endoscope known from DE 44 38 229 C2 has a protective tube configured as a flow tube, although it is open at its distal end, such that it can be acted upon by a cooling and flushing medium, the cooling and flushing medium emerging into the observation cavity at the distal end of the flow tube, at the level of the distal end of the endoscope shaft.
Also known are endoscopes which have a cooling system that has a delivery and return for a cooling medium, for example a gas or a liquid, both a delivery line and a return line for the cooling line being integrated into the shaft of the endoscope. A cooling system of this kind, however, demands considerable space in the shaft of the endoscope, the result being that known endoscopes of this kind have a correspondingly large shaft cross section which makes the known endoscopes difficult to use for many applications, for example in modern multi-valve engines in which a small shaft diameter is necessary for structural reasons.
DE 33 16 167 C2 has furthermore disclosed a periscope for observation of a reaction chamber of a high-temperature reactor, having a periscope optical system that has a front lens, turned toward the reaction chamber, adjoining which is a conical hollow body whose smaller end surface is turned toward the reaction chamber and forms an aperture opening for the periscope optical system. The periscope optical system is surrounded coaxially by a tubular water-cooled jacket, thus forming an interstice that is open toward the reaction chamber and communicates with a source of a flushing gas whose supply pressure is greater than the operating pressure in the reaction chamber. A gap in the form of a conical envelope is present between the jacket and the conical hollow body. The interstice between the periscope optical system and the tubular jacket serves as a delivery cross section for the purging gas. The interstice is open at the distal end so that the purging gas emerges into the reaction space. The open distal end of this purging space is configured as an annular nozzle, by the fact that the conical hollow body, which together with the tubular jacket forms the annular nozzle at the distal end, is placed onto the front lens of the periscope optical system.
Also known, from DD 276 540 A1, is a heat shield for an endoscope for examining components in hot enclosed cavities, a decrease in the heat load in the region of the sensitive optical system being achieved by the fact that a replaceable casing equipped with a sight window, intended for the reception of a gaseous cooling medium, and adapted to the diameter of the endoscope—is arranged around the endoscope, further that adjoining the upper boundary of the casing is a receiving and distributing device for the cooling medium, and that the lower end of the casing is closed off by a plug.
Additionally known, from DE Published Application 26 41 594, is an endoscope for the observation of hot spaces that has inner and outer tubes which are arranged concentrically at a distance from one another and both extend into the observation cavity, as well as an annular cover plate that is mounted on the end of the outer tube inside the observation cavity and forms a viewing opening. The latter is equipped with a glass window, in front of which is arranged a transparent protective mica shield. A water cooling jacket is arranged around the inner tube, means being provided for circulating a coolant: through the jacket.
Lastly, DE Published Application 1 031 992 has disclosed an endoscope for observation of the combustion chambers and flue gas ducts of steam generators during operation, the endoscope being enclosed by a jacket for heat protection, and a coolant being directed through the interstice between the jacket and the
Haan Harald
Krattiger Beat
Kuster Manfred
Novak Pavel
Reling Jörg
Rosenberger Richard A.
St. Onge Steward Johnston & Reens LLC
Storz Endoskop GmbH
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