Abstract: A mold clamping unit is provided.

Abstract: A mold adjustment device of an injection molding machine is required for movement of a rear template that moves depending on a size of a mold in a toggle clamp of the injection molding machine. At this time, a spherical bearing and/or a bushing is attached to an outer circumference of a nut of a tie bar gear that rotates along a tie bar and a tie bar screw enduring a clamping force of the toggle clamp so as to be contacted with the rear template. This mold adjustment device clears up any factor generating vibration or noise during the injection molding, thereby remarkably decreasing stoppage generated during the mold adjustment process and also relatively reducing vibration and noise.

Abstract: When an optical fiber preform is manufactured using MCVD (Modified Chemical Vapor Deposition), dehydration gas supplied into a tube on which soot particles are deposited is preheated at 600 to 1200° C. so that an internal temperature of the tube is kept over 500° C. in order to improve efficiency of the dehydration process for removing hydroxyl groups. At this time, a preheater for preheating is installed near a front end of the tube where the dehydration gas is introduced, or installed at a predetermined position of a gas supply line, or installed on a gas path in a main pillow. In addition, the preheater is capable of controlling thermal capacity, and a heatproof plate is installed around the preheater.