1. A sleeve anchor for use in a pre-drilled hole in concrete, brick, masonry and the like substrate materials, comprising a bolt threaded at one end for receiving a pressure member and including a shank providing at the other end a head of diameter greater than the shank, the head including a wedge-forming shoulder adjoining the shank, a sleeve disposed concentrically upon the bolt including an inner portion of petal-form configuration including three petals having distal ends presented for contacting the shoulder, the petals extending along the shank in closely-spaced side-by-side but separate relationship, the distal ends of the petals each defining in section a vee-shaped lobal prominence extending outwardly of the shank whereby the distal ends of the petals together form in section a figure of closed trilobular configuration, the sleeve being shiftable longitudinally upon the shank for setting in response to pressure upon the sleeve provided by the pressure member for causing the petal distal ends to ride up the shoulder for pressure engagement of substrate material interiorly of the hole for anchoring the sleeve anchor within the hole, the sleeve including pre-load structure for causing selective foreshortening of the sleeve to provide pre-loading of the sleeve anchor following setting in response to further pressure upon the sleeve provided by the pressure member, the pre-load structure comprising a collar of the sleeve disposed at its outer end and a plurality of rectilinear longitudinally extending pillars interconnecting the petals to the collar, the pillars being of narrow arcuate extent and between them windows of the sleeve of arcuate extent greater than the pillars, the collar including a collar-defining portion and each of the petals including a proximal end connected by a respective pillar to the collar-defining portion, each of the petals forming an ear disposed along a leading side edge of the petal for providing gripping antirotational engagement of interior surfaces of the hole, the pillars being torsionally deformed upon said further pressure for causing said foreshortening of the sleeve.

2. A sleeve anchor as set forth in claim 1 wherein each ear is constituted by an outwardly extending corner portion of the respective petal.

3. A sleeve anchor according to claim 1, wherein the arcuate extent of each of the pillars and windows is respectively substantially constant over a major portion of their respective longitudinal extents.

4. A sleeve anchor for use in a pre-drilled hole in concrete, brick, masonry and like substrate materials, comprising a bolt threaded at one end for receiving a pressure chamber and including a shank providing at the other end a head of diameter greater than the shank, the head including a wedge-forming shoulder adjoining the shank, a sleeve disposed concentrically upon the bolt including an inner portion of petalform configuration including petals having distal ends presented for contacting the shoulder, the sleeve being shiftable longitudinally upon the shank in response to pressure upon the sleeve provided by the pressure member for causing the petal distal ends to ride up the shoulder for pressure engagement of substrate material interiorly of the hole for anchoring the sleeve anchor within the hole, the sleeve including pre-load means for causing selective foreshortening of the sleeve in response to further pressure upon the sleeve provided by the pressure member, whereby to provide pre-loading of the sleeve anchor, the petals being three in number and extend along the shank in closely-spaced side-by-side but separate relationship to surround the shank, the distal ends of the petals each defining in section a vee-shaped lobal prominence extending outwardly of the shank whereby the distal ends of the petals togther form in section a closed figure of trilobular configuration the distal ends of the petals each forming in section a central arc and straight portions extending from opposite ends of the arc, the vee-shaped lobal prominence being of approximately 90° included angle whereby the petals together form in section an enhanced hexagon of trilobular configuration.

5. The sleeve anchor for use in a pre-drilled hole in concrete, masonry and the like, comprising:

a bolt including a threaded outer end for receiving an internally threaded pressure member and an inner end defining a shank extending from the outer end and terminating in a head of diameter greater than the shank, the head having a tapered wedge-forming shoulder adjoining the shank, the head constituting the leading end of the anchor for being inserted into the hole with the threaded outer end extending from the hole for receiving the pressure member to provide tightening by rotation thereof; and

a sleeve disposed concentrically upon the bolt, the sleeve including

a collar positioned concentrically around the bolt and extending along part of the bolt threaded portion at the upper end thereof, the collar being disposed for receiving longitudinal pressure toward the inner end of the bolt generated by tightening of the pressure member, and an inner portion of petalform configuration comprising three petals extending along the shank in closely-shaped side-by-side but separate relationship to surround the shank, the petals being jointed at proximal ends to the collar by respective pillars each of narrow arcuate extent to provide windows between the pillrs of arcuate extent greater than that of each pillar, the petals having distal ends contacting the shoulder whereby upon tightening of the pressure member the petals are caused to ride up the shoulder for radially outward expansion of the sleeve, the distal ends of the petals each forming in section a central arc and straight portions extending from opposite ends of the arc thereby to provide for each petal a vee-shaped lobal prominence of approximately 90° included angle, and whereby the distal ends of the petals together form in section an enhanced hexagon of trilobular configuration,

each petal forming at its proximal end a single ear disposed along a leading side edge thereof, each ear being constituted by an outwardly extending corner portion of the respective petal, the ears providing gripping antirotational engagement of interior surfaces of the hole upon insertion of the anchor into the hole,

the sleeve being formed of resilient but ultimately deformable metal to permit flexing of the ears and the distal ends of the petals to permit selective progressive torsional distortion of the pillars upon continued tightening of the pressure member caused by pressure between the opposite ends of the sleeve, whereby to cause pre-loading of the anchor with the hole.