| 摘要 |
This invention relates to a fastener of a type having a core pin including a threaded shank portion, an enlarged head at one end thereof, and a torque tool engaging means on the opposite side of the core pin from the head. The fastener further has an expander means including the head with at least one recess in the outer surface at one end thereof and a tapered nose portion at the other end thereof. The expander means has a bore therethrough to receive the threaded shank portion of the core pin. Also, the fastener has sleeve means on the core pin between the nose portion of the expander means and the enlarged head of the core pin. An internally threaded drive nut is threadedly mounted on the core pin. The drive nut has a bearing surface facing towards the outer surface of the head of the expander means. The improvement in the fastener in accordance with this invention comprises the drive nut's bearing surface having at least one projecting portion adapted to engage in the recess in the outer surface of the head of the expander means without deformation of the projecting portion. The number of projecting portions can be equal to or less than the number of recesses. a:clms1376.wpf 16
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