Fixing devices for being driven into and anchored in material

Claim 1

A fixing device assembly for being driven already assembled into autoclaved aerated concrete and like low density constructional material, forming its own cavity thereby in said material; the fixing device assembly comprising: an elongate shank and a pilot member; the shank having a leading end and a rear end and comprising: a plurality of side-by-side part-tubular elongate sections forming in combination a substantially tubular leading end portion of the shank and extending from the leading end towards the rear end of the shank; means integrally, permanently and rigidly interconnecting rear ends of said sections; said sections being separated from each other forwardly of the rear ends of said sections by slits extending continuously from adjacent the rear ends of said sections between side edges of said sections along said leading end portion, said slits opening onto the leading end of the shank; said sections being adapted to be capable of being flexibly splayed apart from each other forwardly of their rear ends; the shank also comprising a head at its rear end; the shank forming an axial passage extending from the leading end of the shank and between said sections to the rear end of the shank and a tool portion-receiving opening through the head into the passage; the pilot member comprising a stem received in said passage between said sections of the shank and comprising a bit integral with the stem, said bit being positioned in front of the leading end of the shank; a rear end of the stem being positioned in the shank passage forward of the opening in the shank head; the bit comprising a rearward portion adjoining said stem and a wide part at the front of said rearward portion, said wide part being substantially the same width in cross-section as the external cross-section of the leading end portion of the shank, said rearward portion of the bit tapering rearwardly of said wide part towards said stem; the pilot member bit being characterised in that it comprises a forward portion adjoining said wide part and tapering forwardly of said wide part towards a narrow leading end of the pilot member bit, whereby the pilot member bit can punch a cavity passage in said constructional material both for the bit itself and for the shank when a tool portion is engaged through the opening in the shank head with the rear end of the pilot member stem and concussive drive is applied thereto, with the pilot member and shank already assembled together; the shank being forwardly drivable from an initial position relative to the bit for engagement of the shank sections by said rearwArd portion of the bit to cause splaying apart of said shank sections, subsequent to the punching of said cavity passage by the pilot member bit; the shank sections being adapted to individually penetrate the constructional material endwise after being splayed apart, thereby enlarging for themselves the cavity in the constructional material, and to grip the pilot member bit between their side edges; the pilot member stem being characterised by being sufficiently shorter than the shank so that the rear end of the stem will remain in the shank passage forward of the shank head after the assembly has been driven into the constructional material; whereby the pilot member can be protected by the shank from accidental direct impact tending to loosen the grip by the shank sections on the pilot member after said tool portion has been removed from the shank head opening.