M. 1. Kaplan, R. E. Clocker,
and Herbert Sargent Richfield Oil Cor~oration Anaheim, California
II
A Teflon Bearing for Stirrers
W e have developed in our laboratories a stirrer bearing assembly which provides a good seal and has been used repeatedly a t speeds of 3000-5000 rpm for periods of several days with no added lubrication. The apparatus may be constructed from readily available materials. To make the bearing sleeve, Teflon tubing (10-mm o.d., ti-mm i.d.) is inserted in a Trubore type sleeve bearing (10-mm id.). The Teflon is not pushed to the bottom of the glass sleeve, to leave an area which will help keep liquids from creeping up the shaft. A tight fit is desirable so that rotation of the Teflon tubing is restricted. If there is some rotation, due to an imperfect match, the Teflon tubing may be wrapped with Teflon tape to increase effectively the diameter and thus to create a tight fit. The inner diameter of the Teflon tube is then widened a t the bottom (approximately 8-mm i.d.) with a drill to a depth of approximately 20 mm (see drawing). The stirrer shaft is made of ti-mm Pyrex rod. Because glass rods in a hatch are not uniform, we select those pieces which give a snug fit and yet allow easy turning when placed in the bushing. A bulge is fashioned in the rod by heating a small area and then pushing gently from both ends. The bulge should fit securely into the widened portion of the Teflon tube and seat up against the narrower portion.
To have a good seal during use, it is necessary to keep a slight pressure of the glass bulge against the Teflon seat. This can be accom~lishedby attaching the upper-end of the stirrer shaft to a motor with a piece of rubber tubing. By fixing the motor in such a position that it keeps a slight tautness on the 24/40 PYREX BEARING SLEEVE r u b b e r tubing, t h e Teflon-glass seal will he maintained. T E F L O N iUB(N6 A modification of ,,OMM 0.c.. this design for use in glassware without ground joints is possible. A glass tube placed in a rubber stopper may be subBULGED PORTION OF SHAFT stituted for the Trubore bearing sleeve. WlDENEO PORTIOH OF TEFLON Teflon tubing is available in many diameters and thus diferent sizes of stirrer 1.J shafts can be made. 6MM
(LO.,
Volume 38, Number 11, November 1961
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577
