Illumination – Light fiber – rod – or pipe
Reexamination Certificate
2000-09-06
2003-04-01
O'Shea, Sandra (Department: 2875)
Illumination
Light fiber, rod, or pipe
C362S556000, C362S557000, C362S581000, C362S582000
Reexamination Certificate
active
06540389
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to a lighting system for illumination of an observation space, especially an observation space in which a pressurized and/or hot medium is contained.
A lighting system of this type is generally known. Lighting systems of the before-mentioned kind are used for illuminating an observation space, such as a reaction chamber or a combustion chamber in which chemical reactions, combustion processes or other physical or chemical processes take place, in order to display the development of the process outside the observation space, for example on a display unit.
A lighting system of this kind finds special application in the illumination of the combustion chamber of a combustion engine of a motor vehicle. In engine development and also in engine testing such lighting systems are used in combination with an observation system, for example a technical endoscope, for displaying the fuel injection process and the distribution of the mixture with the engine in running condition. As the observation system, i.e. the endoscope, normally works without a separate light supply, it is a requirement that the combustion chamber be illuminated with the aid of the lighting system in order to have the possibility to observe the mixture-forming processes taking place in the cylinder of the engine, which as such are not self-lighting.
To this end, an opening, i.e. a bore, is provided in the wall of the cylinder head, through which the front, i.e. the distal end of a lighting head of the lighting system is guided, whereafter the opening through which the lighting head has been introduced into the combustion chamber is sealed in a suitable way to prevent the escape of combustion gases. For observing the combustion chamber, being illuminated by the lighting system, the endoscope is introduced through a corresponding second bore provided in the cylinder head.
The lighting head is connected, via an optical-fiber cable, to a light source, for example a stroboscopic light source. The light generated by the light source is transmitted through an optical-fiber cable to the lighting head, where it emerges from the lighting head at the distal end, which latter has been introduced into the combustion chamber. For transmission of the light from the light source to the free end of the lighting head, the optical-fiber cable comprises optical fibers or optical fiber bundles.
In conventional lighting systems such optical fiber bundle is run to the distal end of the lighting head. At the distal end, the individual optical fibers are cemented together by an adhesive.
However, such a lighting system is connected with certain disadvantages. The optical fibers at the distal end of the lighting head must not get into contact with the combustion gases in the combustion chamber of the engine because the optical fibers as such, and their sealing compound as well, are resistant neither to pressure nor to high temperatures. But in the combustion chamber of an engine extremely high pressures of more than 100 bar and high temperatures, that may well exceed 200° Celsius, prevail in the running condition of the engine. In order to protect the optical fibers from the high temperatures and the high pressures, conventional lighting systems must, therefore, be used in combination with a cup-shaped protective glass that is inserted into the opening in the wall of the combustion chamber and into which the lighting head is introduced. The use of a protective glass necessitates a bore in the cylinder head of 14 mm diameter, for the installation of the protective glass. While an opening of such a diameter was no problem with older engines, applying a bore of such a diameter in the cylinder head is no longer possible with new multi-valve engines, due to space restraints that result from the particular structural conditions. Making the total arrangement, comprising the protective glass and the lighting head, smaller would of course be possible, but would considerably reduce the light-transmission capacity and make the illumination of the observation space less effective.
In addition to the use of a protective glass it is further necessary, with conventional lighting systems, to cool the distal end of the lighting head since the protective glass, while preventing direct contact between the optical fibers and the combustion gases, does not prevent the transmission of heat radiation. The heat radiation passing the protective glass subjects the distal end of the optical fibers to high temperatures, which cause damage to the fibers and in particular to their sealing compound. Conventional lighting systems therefore require an additional cooling circuit with supply and discharge systems in the lighting head, which occupy a large part of the cross-section of the lighting head so that only a small cross-section of approximately 3.5 mm diameter remains for the optical fibers while the effective outer diameter of the lighting head is approximately 7.5 mm so that the theoretical light-transmission capacity of the lighting head is poorly utilized. And there is further the risk that in case the cooling system should fail, the optical fibers at the distal end of the lighting head and, thus, the entire lighting system may be destroyed.
Now, it is the object of the present invention to improve a lighting system of the before-mentioned type so that the disadvantages described above are avoided and the lighting system can be used without a protective glass and without a cooling system, without the risk that extreme pressure or temperature influences may cause damage to the lighting head.
SUMMARY OF THE INVENTION
With respect to the lighting system described at the outset, the invention achieves this object by providing a lighting system, comprising
an optical-fiber cable having a first end which can be connected to a light source, and a second end;
a lighting head, which is connected to said second end of said optical-fiber cable and which can be introduced into said observation space,
wherein said lighting head comprises a light guide rod made from a material which is resistant to pressure and temperature.
In the lighting system according to the invention, the optical-fiber bundle of the optical-fiber cable, instead of being guided up to the distal end of the lighting head, is therefore replaced at the lighting head by a light guide rod made from a pressure and/or temperature-resistant material. The sensitive optical fibers are, thus, located outside the observation space and are no longer exposed to the damaging influences of pressure and temperature. The light guide rod provides the advantage that there are no glued joins or cemented areas at its distal end, which project into the observation space and which might deteriorate under the effect of pressure or high temperatures. By equipping the lighting head with a light guide rod made from a pressure and/or highly temperature-resistant material, the need for a protective glass and also for cooling of the lighting head is eliminated. The light guide rod may consist of a suitable transparent glass that may come in contact with the combustion gases in the combustion chamber of a combustion engine without being damaged thereby. Due to the fact that no protective glass is required any more as protection for the lighting head, the diameter of the opening in the wall of the observation space may be reduced, for example, to 10 mm so that the lighting system according to the invention can be used also with modern multi-valve engines where a bore of larger diameter cannot be applied. In order to permit the diameter of the opening to be reduced, no scaling-down of the lighting head, which would reduce its light-transmission capacity, is required with the lighting system according to the invention. While in conventional lighting systems, due to the cooling requirement, cooling channels are provided on the lighting head which heavily reduce the cross-section of the lighting head that can be used for light transmission, another advantage of the lighting sys
Haan Harald
Krattiger Beat
Kuster Manfred
Novak Pavel
O'Shea Sandra
St. Onge Steward Johnston & Reens LLC
Storz Endoskop GmbH
Ton Anabel
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