Expansion anchor with crack-arresting groove

An anchor comprising:

• a. an elongated stem having a longitudinal axis and a leading end and a trailing end;
• b. a tensioning head disposed at the leading end of the stem and connected to the leading end of the stem in such a manner that when the stem is moved along its longitudinal axis the tensioning head moves with the stem, the tensioning head having a leading end, a trailing end and an outer surface, the leading end of the tensioning head being wider than the trailing end of the tensioning head and the outer surface of the tensioning head flaring generally outwardly from the trailing end to the leading end of the tensioning head;
• c. an expansion sleeve having a longitudinal axis parallel to the longitudinal axis of the elongated stem, the expansion sleeve receiving the stem through a tunnel in the expansion sleeve in such a manner that the stem can move longitudinally with respect to the expansion sleeve when the expansion sleeve is held in a fixed position, the expansion sleeve further comprising:
• 1. a leading end and a trailing end and the expansion sleeve receives the stem in such a manner that the leading end of the expansion sleeve is disposed near the leading end of the stem and the trailing end of the expansion sleeve is closer to the trailing end of the stem than the leading end of the expansion sleeve;
• 2. a plurality of longitudinal slots formed in the expansion sleeve that extend from the leading end of the expansion sleeve toward the trailing end of the expansion sleeve and divide the portions of expansion sleeve toward the leading end of the expansion sleeve between the slots into anchoring segments;
• 3. a first weakening groove formed in each of the anchoring segments;
• 4. second grooves formed in the expansion sleeve at the end of each of the slots or between the ends of each of the slots and the trailing end of the expansion sleeve.