A Hydrostatic Roller Bar for Veneer Lathes and Thick Slicing Studies

A discussion of the four conventional types of pressure bars used in veneer peeling is presented and the limitations of each are outlined. To overcome the major problem of excessive wear found with conventional double roller bars, a new roller bar design is presented which operates on the basis of hydrostatic lubrication. Four different roller bar prototypes were evaluated in a small laboratory lathe by peeling Douglas-fir disks, 4 inches long and 16 inches in diameter into veneer ranging in thickness from 1/16 to 1/2 inch. Water was used as a lubricant at supply pressures ranging between 200 and 400 psi. The housing for the role bar was subdivided into four pockets which were connected to the high-pressure water, supply through fine control needle valves which serve as restrictors. Pocket depths between 1/16 and 1/4 inch did not affect roller bar performance. However, for optimum results it was found desirable to align the upper and lower pockets symmetrically to the resultant force acting on the roller bar. The resultant force was found to act at an angle of approximately 15? with the horizontal. The main advantages of the design are significantly less wear of the roller, elimination of the drive mechanism for rotating the bar, and perfect synchronization with veneer velocity.

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