| 摘要 |
A spearhead assembly ( 10 ) comprises a base ( 12 ) provided with a slot ( 14 ) at one end ( 16 ) which opens onto an outer surface ( 13 ) of the base ( 12 ). The outer surface ( 13 ) is composed of three contiguous surface portions ( 18, 20 and 22 ). A spearpoint ( 20 ) is pivotally coupled at its proximal end ( 26 ), which is disposed in the slot ( 14 ), to the base ( 12 ). A distal end ( 28 ) of the spearpoint ( 24 ) extends or projects beyond the slot ( 14 ) and the surface ( 13 ) of the base ( 12 ). A spearpoint positioning system ( 30 ) urges the spearpoint ( 24 ) toward one of three annually spaced positioned. These positions are characterised by the spearpoint ( 24 ) extending substantially perpendicular to parallel opposed edges of the slot ( 14 ) which open onto, or are flanked by, the surface portions ( 18 ), ( 20 and 22 ). Moving the spearpoint from one position to another requires the application of an external force. |
