FLUID FILLED BLADDER EXPANDING OF NEW RAW TUBES
Original Publication Date: 1995-Jun-30
Included in the Prior Art Database: 2004-Apr-07
Xerox Disclosure Journal
Electrophotographic printing machines frequently employ a photoconductive drum. The photoconductive drum has a photoconductive surface coated on an. aluminum tube. The aluminum tube must have its exterior circumferential surface precisely defined so as to enable a precise coating of photoconductive material thereon. Thus, the outside diameter tolerances of the photoconductive drum are very precise. At present, the ability to produce tightly controlled outside diameters on extruded aluminum tubing is a very non-exacting size. In order to reduce these outside diameter tolerances, a secondary operation is sometimes performed. This secondary operation normally use internal expanding cluster. The extruded aluminum tube is placed over the cluster and the cluster is expanded. However, since the extruded tube is unconstrained while it is being sized, shaped, expanded or rounded, it will yield at its weakest point which is usually the thinnest wall. Therefore, the tube is improved, at times, in roundness but is never truly considered round. To correct this problem, a series of clamps are added to the expand sections. These clamps will tightly hold the aluminum tubing to the expand sections and, therefore, apply a uniform support to the tubing being sized, shaped or rounded. In this manner the selective yielding or uncontrolled yielding is minimized or eliminated. In order to achieve this method, an oil or other fluid filled bladder or balloon may be utilized. This traps tubing against the outer die for a more accurate rounding, sizing or expanding. As the fluid fills the bladder, it enlarges until the cavity is filled. The bladder is also positioned against the outer housing and against the top and bottom of the extruded tubing within the cavity. As the fluid forces increase, the aluminum tubing first yields at the top and bottom locking itself against the outer walls. Further increases in pressure cause continued sizing, rounding or expanding of the part from the ends toward the center of the tube within the cavity.