| 摘要 |
<p>A pull gun (30) is used for pulling a mandrel (32, 232) through an expandable sleeve (240) positioned in a fastener hole (134, 136, 246, 248) having a countersink (138, 250). The mandrel (32, 232) expands the sleeve (126, 240) as it moves therethrough, causing the sleeve (126, 240), to put the metal which surrounds the hole (134, 136, 246, 248) and the countersink (138, 250) in a state of compression. The pull gun has an expandable countersink prestressing device (74, 162) having a generally central passageway (80, 182) through which the mandrel (32, 232) travels axially as it is being retracted into the pull gun. The prestressing device (74,162) has conical end surfaces (76, 190) to prestress the countersink (138, 250) as the mandrel (32, 232) is pulled through the hole (134, 136, 246, 248). The device (74, 162) has an axially split sleeve retainer (102, 214) extending therein so as to retain the sleeve within the fastener hole when the mandrel is being retracted. A solid film lubricant (127) is provided on the inner surface of the expandable sleeve (126, 240). The coefficient of friction of such lubricant (127) and the contact area (66) of the mandrel (32, 232) with the interior of the sleeve (126, 240) are controlled for the purpose of providing a reaction force which is sufficient to generate enough pressure between the conical insert (90, 190) and the walls of the countersink (138, 250) to adequately compress the metal bounding the countersink (138, 250).</p> |
