text: 1. Field of the Invention
  The present invention relates to an endoscope with a nozzle that is provided at the distal end of the endoscope and ejects gas and/or liquid.
  2. Description of the Related Art
  An endoscope system includes both the endoscope and a processor. The endoscope is inserted into the body of an examinee so that an internal image can be photographed. The processor is provided outside of the examinee and processes the photographed image. A distal end of the endoscope has an observation port that collects light reflected by an object under observation, and a nozzle that ejects gas or liquid toward the observed object. Gas or liquid ejected from the nozzle removes foreign matter that has adhered to the observation port.
  Nozzles that release fluids used for removing foreign matter that adhere to an observation port are disclosed. Japanese Patent No. 3493998 discloses a nozzle with a half-truncated cone-shaped pipe inside that can emit gas or liquid toward the distal end of an endoscope. Japanese Patent No. 3447577 discloses a compacted nozzle that has a tube connected to a fluid ejection port, and the thickness of the wall of the tube on the side of the fluid ejection port is increased. Japanese Patent Application Publication No. H09-201332 discloses a nozzle that moves back and forth so that it approaches an observation port at the moment when fluid is ejected. Japanese Patent No. 3845311 discloses an observation port that is raised from the distal end of an endoscope so as to form a truncated cone, so that fluid flows throughout the whole area of the observation port.
  The art disclosed in Japanese Patent No. 3493998, however, increases fluid flow at the center of the stream ejected from the nozzle. Concerning Japanese Patent No. 3447577, however, the diameter of the flow ejected from the nozzle is approximately the same as the diameter of the outlet of the nozzle. Therefore, the diameter of the outlet of the nozzle must be approximately the same as the diameter of the observation port so that the whole surface of the observation port can be cleaned. The nozzle is not compacted in such case, therefore downsizing of an endoscope is inhibited.
  Concerning Japanese Patent Application Publication No. H09-201332, however, the construction that allows the nozzle to move back and forth must be added to an endoscope, which inhibits downsizing of an endoscope.
  Concerning Japanese Patent No. 3845311, concavities and convexities are formed at the distal end of an endoscope when the observation port is raised from the distal end of the endoscope to form a truncated cone. The concavities and convexities may collect unwanted mucous and tissue residue.