Concrete screw
AssigneeYamashina Seiko-Sho, Ltd.
InventorWilliam D. Armstrong
Life of this patent
Estimating the term…
Abstract
A self-tapping screw for use on concrete and masonry structures is disclosed. The screw has a helically threaded shank of uniform diameter. The crest diameter of the helical thread on the shank has a taper which increases gradually from the tip or entering end of the shank for a predetermined distance along the shank and then has a uniform diameter over the remaining portion of the helical thread. The helical threads have a spacing of 5-8 threads per inch for screw sizes in the range of 1/2 to 3/16 inch. Thread cutting notches are formed in the threads over at least the tapered portion thereof. The screw is hardened to a Rockwell "C" hardness of 48 or greater.
Claims13
A self-tapping anchoring concrete screw in a pre-drilled bore in a concrete structure having individual concrete aggregate components comprising a driving head and a tip, a shank portion extending between said head and tip, said shank portion having a substantially constant diameter and only one spaced, helical thread formed thereon, said helical thread having an intermediate thread portion with a substantially constant thread crest diameter and a leading end portion extending from the tip axially toward the intermediate thread portion for a predetermined distance, said shank portion including a frusto-conical portion extending between said head and the intermediate thread portion, said frusto-conical portion having a greater diameter adjacent the head, the thread crest diameter of the leading end portion being approximately 0.250 inches and tapering from a first diameter at the tip to a second, greater diameter at said predetermined distance, said screw having 8 or less threads per inch, said helical thread having a plurality of thead cutting notches formed therein over at least said predetermined distance from said tip, said helical thread having a surface hardness of at least Rockwell "C" whereby damage to the helical thread by the individual concrete aggregate components is substantially prevented.
A self-tapping anchoring concrete screw in a pre-drilled bore in a concrete structure having individual concrete aggregate components comprising a driving head and a tip, a shank portion extending between said head and tip, said shank portion having a substantially constant diameter and only one spaced, helical thread formed thereon, said helical thread having an intermediate thread portion with a substantially constant thread crest diameter and a leading end portion extending from the tip axially toward the intermediate thread portion for a predetermined distance, said shank portion, the thread crest diameter of the leading end portion being approximately 0.250 inches and tapering from a first diameter at the tip to a second, greater diameter at said predetermined distance, said screw having 8 or less threads per inch.
Dependencies are inferred from the claim text.