Thread form and fastener system using the form
OwnerGeorge S. Winginventor
Life of this patent
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Abstract
A modified buttress thread has a root diameter equal to substantially .sqroot.0.7 of the core diameter with a pitch substantially equal to 1/6 of the core diameter. The thread root extends parallel to the axis of the fastener as a surface and transitions into the thread form at radii at both the load-bearing and trailing flank of the thread. The thread at its maximum diameter has a flat equal to about 0.16 of the pitch. In the fastener system the axial length along a thread form of the collar at radial locations corresponding to the locations on a mating pin are inversely proportional to the strength of the materials of the collar and the pin, for example, when the collar is aluminum and the pin is titanium the lengths are in the ratio of 60:40.
Claims20
In a threaded fastener with a buttress type thread which has a load bearing flank and a non-load-bearing flank, an improvement in the thread which comprises:
- (a) D.sub.R being substantially equal to .sqroot.0.7 D.sub.c,
- (b) P being substantially equal to 1/6 D.sub.c, and
- (c) the load-bearing-flank being at a maximum angle of inclination of about 7.degree. from the perpendicular to the axis of the fasteners, where
- D.sub.R =root diameter of the thread,
- D.sub.c =core diameter of the fastener, and
- P=the pitch of the thread.
In a threaded fastener combination of a male fastener and a female fastener both with a buttress type thread, an improvement in the thread form of both the male and female fasteners comprising substantially equal strength of both fasteners in resistance to failure in shear in the thread of each at the root diameter of each from loads in the axial direction by substantial equalization of the following relationship
- .tau..sub.m l.sub.m =T.sub.f l.sub.f
- where,
- .tau..sub.m =ultimate shear strength of the male thread fastener,
- l.sub.m =axial distance along the male thread at the diameter of its failure in shear in the axial direction,
- .tau..sub.f =ultimate shear strength of the female fastener thread, and
- l.sub.f =axial distance along the female thread at its diameter of failure in shear in the axial direction.
In a threaded fastener with a buttress type thread which has a load-bearing flank and a non-load-bearing flank, an improvement in the thread form comprising:
- (a) D.sub.R being substantially equal to .sqroot.0.7 D.sub.c,
- (b) P being substantially equal to 1/6 D.sub.c, and
- H=to about 0.9 P, where
- D.sub.R =root diameter of the thread,
- D.sub.c =core diameter of the fastener,
- P=the pitch of the thread, and
- H=the distance as seen in axial cross-section
- of a radius to the axis of the fastener from the intersection of lines drawn along the load-bearing and non-load-bearing flanks of an individual thread form to the intersection of lines drawn along the non-load-bearing flank of a preceeding thread form and the load-bearing flank of the individual thread form.
Dependencies are inferred from the claim text.