Length-adjustable film applicator

Abstract

A film applicator includes an outer tube, an inner tube in the outer tube, and an adjustment assembly in the inner tube. The adjustment assembly has a threaded shaft fixed in the inner tube, a retaining nut mounted around the threaded shaft, a turning knob rotatably mounted around the threaded shaft, and an adjustment ring threadedly provided around the threaded shaft. When at a first position, the adjustment ring pushes the turning knob against the retaining nut and allowing the threaded shaft to rotate the inner tube with respect to the outer tube, thereby adjusting the exposed length of and securing the inner tube. When at a second position, the adjustment ring does not push the turning knob, which therefore cannot drive the inner tube into rotation. The inner tube thus stays at the secured position.

What is claimed is: 
     
         1 . A length-adjustable film applicator, comprising:
 a stand having a supporting base and an outer tube, wherein the outer tube has an end provided at the supporting base;   an inner tube assembly having an inner tube, a positioning column, and a positioning sleeve, wherein the inner tube is rotatably and axially displaceably provided in the outer tube of the stand and has an operation end outside the outer tube and a positioning end in the outer tube, the positioning column is provided at the positioning end of the inner tube, and the positioning sleeve is threadedly connected to the positioning column such that, by rotating the inner tube, the positioning column is driven to either press the positioning sleeve tightly against the outer tube of the stand or loosen the positioning sleeve from the outer tube of the stand; and   an adjustment assembly having a threaded shaft, a retaining nut, a turning knob, and an adjustment ring, wherein the threaded shaft has an end fixed at the operation end of the inner tube, an opposite end threadedly connected with the retaining nut, and a flange; the turning knob has a collar between the retaining nut and the flange of the threaded shaft and is rotatably mounted around the threaded shaft via the collar; and the adjustment ring is threadedly provided around the threaded shaft and between the operation end of the inner tube and the turning knob and is displaceable between a first position, at which the adjustment ring pushes the collar of the turning knob against the retaining nut in order for the turning knob to rotate the inner tube with respect to the outer tube via the threaded shaft, and a second position, at which the adjustment ring is away from the collar of the turning knob and allows the turning knob to rotate freely without driving the inner tube into rotation.   
     
     
         2 . The length-adjustable film applicator of  claim 1 , wherein the adjustment ring has a recess, a flange groove, and a threaded hole; the recess has an end wall for pushing the collar of the turning knob when the adjustment ring is at the first position; the flange groove is coaxial, and in communication, with the recess and receives the flange of the threaded shaft; and the threaded hole is coaxial, and in communication, with the flange groove and is threadedly provided around the threaded shaft. 
     
     
         3 . The length-adjustable film applicator of  claim 1 , wherein the adjustment assembly further has a pressing plate detachably mounted around the threaded shaft in order to be pressed against a roll of film mounted around the inner tube and the outer tube. 
     
     
         4 . The length-adjustable film applicator of  claim 1 , wherein the positioning column has a conical portion and a threaded connection portion extending from the conical portion, the positioning sleeve has two opposing sleeve halves and a nut between the sleeve halves, each said sleeve half has a pressed portion, each said pressed portion has an outer periphery abutting against an inner periphery of the outer tube and also has an inner periphery, the inner peripheries of the two pressed portions form a wall of a conical groove, the wall of the conical groove abuts against the conical portion of the positioning column, and the nut is threadedly connected to the threaded connection portion of the positioning column.