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US 4,068,879 AGranted
Concrete slab hoisting apparatus
AssigneeThe Burke Company
InventorsPhilip A. Torbet, Cyril Thomas Eager
Life of this patent
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AssigneeThe Burke Company
InventorsPhilip A. Torbet, Cyril Thomas Eager
Estimating the term…
A socket cavity formed in a concrete slab of the type poured horizontally and subsequently tilted up, which cavity affords engagement of hoisting equipment to the slab. The inner portion of the cavity is in the form of a frusto-conical wall surface communicating with the surface of the cavity through a cylindrical bore concentric with the frusto-conical surface. The cavity is formed by placing in the slab form an expendable flask-like hollow article formed of synthetic resin or the like which is left in the slab after erection thereof. Engaging apparatus cooperable with the cavity which has on the inner end thereof arms that are pivotally moveable between a retracted position and an extended position, the arms engaging the frusto-conical wall of the cavity when in the extended position. The apparatus includes mechanism at the outer end thereof for effecting retraction or extension of the arms, the mechanism being remotely operable so as to afford disengagement of the hoisting mechanism from the slab from a remote location after erection of the slab.
Apparatus for engaging a concrete slab to hoist the same, said slab having a generally planar surface, said apparatus comprising in combination:
Apparatus for engaging a concrete slab having a substantially planar surface and a symmetrical socket cavity having a cylindric portion normal to and opening onto said surface, said cavity having a frusto-conical portion communicating with and coaxial with said cylindric portion, said apparatus comprising a shaft having a diameter less than said cylindric portion and a length greater than the depth of said cavity, said shaft having an inner end and an outer end, a cylindrical enlargement on said inner end defining a bearing surface of substantially the same diameter as said cylindric portion and being coaxial with said shaft, means including at least three arms secured to said inner end at equal angularly spaced positions therearound for pivotal movement between a retracted position to afford insertion and removal of said shaft relative said cavity and an extended position for engaging said frusto-conical wall, and means accessible from the outer end of said shaft for controllably moving said arms between a retracted position and an extended position.
Dependencies are inferred from the claim text.