Rubber extruder

A rubber extruder comprising:

• a fixed cylindrical barrel adapted to receive a rubber material and having a die end and an opposite end opposite to said die end;
• an extrusion die mounted in said die end of said cylindrical barrel;
• a screw rod having an inner section that extends co-axially through said opposite end of said cylindrical barrel and into said cylindrical barrel and that has an abutting end adapted to abut against the rubber material, and an outer section that extends axially from said inner section and that is disposed outwardly of said cylindrical barrel, said screw rod being movable in an axial direction relative to said cylindrical barrel so as to extrude the rubber material through said extrusion die;
• a coupling unit including a threaded sleeve that is sleeved rotatably on and that engages threadedly said outer section of said screw rod;
• a fixed limiting member in constant engagement with said screw rod in such a manner that rotation of said threaded sleeve results in axial movement of said screw rod relative to said cylindrical barrel;
• a driving unit for rotating said threaded sleeve;
• a barrel support that is formed with a supporting hole;
• and
• a bearing that is mounted in said supporting hole;
• wherein said driving unit includes a motor with an output shaft, said coupling unit further including a bearing sleeve that is surrounded by and that contacts slidably said bearing and that is sleeved securely on said threaded sleeve, a driven gear that is sleeved securely on said bearing sleeve, and a driving gear that is secured to said output shaft;
• and
• wherein said outer section of said screw rod has a distal end that is distal from said inner section of said screw rod and that is formed with a limiting groove, said limiting member including an elongated limiting bar that is secured to said barrel support and that extends through said limiting groove in said axial direction so as to prevent said screw rod from rotating upon rotation of said threaded sleeve, thereby permitting axial movement of said screw rod.