| 摘要 |
A retainer of generally U-shape having slightly diverging legs detachably secures the proximal part of an excavating tooth within a complementary recess in its holder. The proximal end of the tooth has a generally rectangular cross-section with opposed outward extending ears and rearwardly thereof is formed with a spindle having a shoulder at the back. In the operative position of the retainer, a portion of the retainer straddles the spindle immediately in front of the shoulder. At least one leg of the retainer is formed with an upper offset leg portion and with oppositely offset lower leg portion with an interconnection there-between. The upper offset portion fits ahead of the shoulder to retain the tooth in place when the retainer is in operative position; but when the retainer is retracted to inoperative position, the upper offset portion of the leg clears the shoulder of the spindle of the tooth. The tooth holder is formed with an opening in which the retainer slides and the opening has an inward protuberance which engages the connecting portion to prevent unintentional complete withdrawal of the retainer so that it is not lost when it has been moved to retracted position. An improved distal tooth shape is disclosed wherein the blade has a body of substantially uniform thickness from front to rear with a central rib whereby the tooth remains sharp during its life. At the rear of the distal portion of the tooth is an abrupt shoulder which inhibits use of the tooth after its cutting life is exhausted and prevents excessive use from damaging the holder.
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