摘要 |
<p>A non-reversible plate (91) which is rectangular in configuration and which has an irregular anti-reversal collar (93) beneath the plate portion. The collar (93) is elliptical in configuration and has a major axis at least seven milimeters longer than the minor axis. Another aspect of the invention is the utilization of a toggle actuated plate changing device (60) which swings in and out of position and can only be actuated when the plate (91) intended for insertion presents the proper length for insertion to the plate changing device (60).</p> |