Screws and threadforms
AssigneesHanstock Fasteners Pty Limited, Reid Construction Systems Pty Limited
InventorsFotios Papafotiou, David Ian Kershaw
Life of this patent
Estimating the term…
Abstract
A screw thread having a threadform including a ridge rising from root to crest with the crest having two peaks, separated by a trough the depth of which is less than the height of the ridge from root to crest. It has particular use as a screw for timber, and is especially suited to fixing railway rails to sleepers.
Claims14
A screw thread having a twin start helical thread configuration consisting of two ridges helically winding around a shank, each of the ridges having flanks rising from a root to a crest, and at least one of the crests having a pair of peaks, where in one of the ridges is higher than the other ridge.
A twin start screw thread for a fastener, the thread having a repeated threadform profile comprising:
- a first crest, having a first pair of peaks, rising from a first root and falling to a second root, and
- a second crest, having a second pair of peaks, rising from the second root and falling to the first root,
- wherein the first crest is higher than the second crest.
A railway track comprising:
- a timber sleeper;
- a rail fastened to the timber sleeper with a threaded fastener;
- the fastener comprising a screw thread having a threadform comprising two ridges rising from root to crest with at least one crest having two peaks separated by a trough the depth of which is less than the height of the ridge from root to crest, wherein one of the ridges is higher than the other ridge.
A method of rolling a helical screw thread onto a cylindrical shank of a metal workpiece comprising:
- rolling into the shank initial helical grooves by plastically deforming the metal into a hump immediately to either side of the grooves,
- subsequently deepening and widening the initial grooves by further rolling which increases the size of the humps and displaces the humps increasingly further from the initial grooves,
- further deepening and/or widening the grooves to press the two humps between adjacent grooves into each other until they produce a single ridge with a crest carrying a pair of peaks, and
- finish rolling the crest to more uniformly define the two peaks along the crest of the ridge.
A method of rolling a helical screw thread onto a cylindrical shank of a metal workpiece comprising:
- rolling into the shank initial helical grooves by plastically deforming the metal into a hump immediately to either side of the grooves,
- subsequently deepening and widening the initial grooves by further rolling which increases the size of the humps and displaces the humps increasingly further from the initial grooves,
- further deepening and/or widening the grooves to press the two humps between adjacent grooves into each other until they produce a single ridge with a crest carrying a pair of peaks, and
- finish rolling the crest to more uniformly define the two peaks along the crest of the ridge,
- wherein the height of each side pair of peaks, when measured from the bottom of a through between each pair, is between 10% and 40% of the height of their respective ridge.
Dependencies are inferred from the claim text.