A conventional extruder that kneads and mixes a material such as a rubber material and extrudes the material is disclosed in, for example, Japanese Utility Model Application Laid-Open No. 55-83331.
With reference to FIGS. 4A and 4B and FIG. 5, a conventional extruder will be described. FIGS. 4A and 4B are schematic diagrams for explaining the configuration of a conventional extruder. FIG. 4A is a schematic cross section of the extruder, and FIG. 4B is a cross section taken along line X-X of FIG. 4A. FIG. 5 is a diagram for explaining a foreign matter mixing mechanism and is a schematic perspective view of a scraper.
An extruder 100 has a housing 101 including a circular tube section 101a, a supply opening 101b provided on one of end sides of the circular tube section 101a, and an exhaust opening 101c provided on the end opposite to the supply opening 101b. A screw 102 is rotatably assembled in the circular tube section 101a. A feed roller 103 (FIG. 4B) is provided adjacent to and in parallel to a supply part 102a of the screw 102. The feed roller 103 is assembled in the housing 100 rotatably in a direction opposite to the rotation direction of the screw 102. A scraper 104 is attached on the side opposite to the supply opening 101b across the screw 102 and the feed roller 103.
The material such as a rubber material is supplied via the supply opening 101b of the housing 101 to the supply part 102a of the screw 102. The material supplied to the supply part 102a is fed to a material conveyance passage formed by the outer peripheral surface of the screw 102 and the inner peripheral surface of the circular tube section 101a by rotation of the screw 102 and the feed roller 103. The material fed to the material conveyance passage is kneaded by the rotation of the screw 102 and extruded from the exhaust opening 101c. 
The scraper 104 includes a scraping part 104a having a pointed shape in cross section and a guide surface 104b continued from the scraping part 104a to the inner peripheral surface of the circular tube section 101a. The scraper 104 is constructed to scrape the material from the surface of the feed roller 103 by the tip of the scraping part 104a. 
The scraper 104 is attached to an attachment face 101d provided on the side opposite to the supply opening 101b of the housing 101 by a fastener 105 such as a bolt.
Preferably, an attachment face 104c of the scraper 104 which is in contact with the attachment face 101d is attached tightly without a gap to the attachment face 101d in consideration of leakage of the material. In many cases, however, such an attachment face 101d is formed as a part of the housing 101. Due to limitation in processing accuracy, a gap is formed between the attachment face 101d of the housing 101 and the attachment face 104c of the scraper 104.
As shown in FIG. 5, a material 107a which enters the gap is fixed in the gap and is pushed out from the gap to the material conveyance passage side by a part 107b of the following material which is newly supplied and enters the gap. The pushed part 107c from the gap in the fixed material is mixed in the following material, so that the fixed material is mixed as a foreign matter in the following material pushed from the exhaust opening 101c (foreign matter mixture).
To prevent such foreign matter mixture, for each work, it is necessary to disassemble the extruder 100, detach the scraper 104, and do the cleaning. However, a not-shown flange provided at an end on the root side (the supply opening 101b side) of the circular tube section 101a is fixed by being fastened by a fastener such as a bolt to the side of a drive mechanism having a power source of the screw 102 and a reducer. The feed rotor 103 is also fixed by a fastener such as a bolt. Therefore, the work of disassembling the extruder 100 is very troublesome.
Further, the gap between the tip of the scraping part 104a of the scraper 104 and the surface of the feed roller 103 has to be adjusted to a small interval of about 0.05 mm. If such adjustment of the gap interval is performed for each cleaning, the work time becomes very long.
On the other hand, as a countermeasure against leakage of the material to the gap in the attachment face of the scraper 104, a method for sealing the contact faces of the scraper 104 and an attachment part 106 by a seal member such as an O-ring is considered. However, adhesion is not assured in the position of attachment of the seal member, so that the material enters.
There is also a method for making a rubber sheet packing, a metal sheet packing, or the like interposed on the contact face, applying a curable liquid gasket to the contact face, or the like. In the case of the rubber sheet packing, a piece of the deteriorated packing is mixed as a foreign matter. In the case of the metal sheet packing, a metal powder generated due to abrasion is mixed as a foreign matter. In the case of the liquid gasket, a piece of the deteriorated gasket is mixed as a foreign matter.
The present invention has been achieved to solve the drawback of the conventional techniques, and an object of the invention is to provide an extruder with improved efficiency of a cleaning work.