US3728750A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of fabricating screw fasteners
Assignee: Long Lok Fasteners Corp
•
Filing: 1971-03-03
•
Granted: 1973-04-24
•
Expires: 1991-03-03
Abstract
Abstract To fabricate a hollow-end screw having a thin circumferential wall with radial protuberances for self-locking action, the tendency for cracks to develop in one location is avoided in part by thickening the circumferential wall and in part by eliminating a sharp corner at an intermediate fabrication stage. The tendency for cracks to develop in a second location on the screw is avoided by eliminating a sharp corner in the final configuration of the screw.
Inventors
- 👤 D Stillman
- 👤 M Bagheri
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 07:40
CPC Classifications
B; B23; B23G; B23G9/00; Y; Y10; Y10S; Y10S411/00; Y10S411/924; Y10S411/929
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
206 words
A method of forminG an all-metal self-locking screw in which a longitudinal bore within the screw is selectively enlarged to form longitudinal protuberances in the threaded portion of the screw, said method comprising: forming a longitudinal blind preliminary bore in the leading end of the screw with said preliminary bore having a cylindrical portion having a given inner diameter, an entrance having a larger diameter than the diameter of the cylindrical portion, and a tapered entrance surface leading directly from the entrance to the cylindrical portion; expanding the preliminary bore of the screw by inserting a swaging punch into the preliminary bore with said swaging punch having circumferentially spaced lands which expand the portions of the preliminary bore that are contacted by the spaced lands to form longitudinal recesses in the wall of the preliminary bore and corresponding circumferentially spaced outer longitudinal protuberances in the threaded portion of the screw; said punch being inserted into the preliminary bore to make its initial contact with the bore by contacting the tapered entrance surface between the bore entrance and the cylindrical portion of the preliminary bore; and reboring the preliminary bore to form a final bore configuration by eliminating the longitudinal recesses in the wall of the bore.
Claim 2
Independent Claim
206 words
A method of forminG an all-metal self-locking screw in which a longitudinal bore within the screw is selectively enlarged to form longitudinal protuberances in the threaded portion of the screw, said method comprising: forming a longitudinal blind preliminary bore in the leading end of the screw with said preliminary bore having a cylindrical portion having a given inner diameter, an entrance having a larger diameter than the diameter of the cylindrical portion, and a tapered entrance surface leading directly from the entrance to the cylindrical portion; expanding the preliminary bore of the screw by inserting a swaging punch into the preliminary bore with said swaging punch having circumferentially spaced lands which expand the portions of the preliminary bore that are contacted by the spaced lands to form longitudinal recesses in the wall of the preliminary bore and corresponding circumferentially spaced outer longitudinal protuberances in the threaded portion of the screw; said punch being inserted into the preliminary bore to make its initial contact with the bore by contacting the tapered entrance surface between the bore entrance and the cylindrical portion of the preliminary bore; and reboring the preliminary bore to form a final bore configuration by eliminating the longitudinal recesses in the wall of the bore.
Claim 3
Dependent Claim
30 words
The method of claim 1 in which the longitudinal lands of the punch have leading end faces of the same taper as the tapered entrance surface of the preliminary bore.
Claim 4
Dependent Claim
62 words
The method of claim 1 in which the reboring of the screw to produce the final bore configuration is carried out by a boring tool having a rounded leading end to avoid forming a sharp corner at the bottom of the final bore configuration and to thereby eliminate the tendency for cracks to occur at the bottom of the final bore configuration.
Claim 5
Dependent Claim
35 words
The method of claim 3 in which said boring tool has a nose with a spherically curved shoulder to cause the final bore configuration to have a spherically curved annular surface at its bottom end.
Claim 6
Dependent Claim
58 words
The method of claim 4 in which the radius of curvature of the curved shoulder of the boring tool is substantially equal to the radius of the boring tool whereby the curvature of the spherically curved annular surface of the final bore conforms to the curvature of a sphere having the same diameter as the final bore configuration.
Claim 7
Dependent Claim
24 words
The method of claim 5 in which said spherically curved annular shoulder in a longitudinal cross section has an arcuate extent of approximately 30*.
Claim 8
Dependent Claim
88 words
The method of claim 1 where the inner diameter of the cylindrical portion of the preliminary bore is sufficiently small to provide a relatively thick wall between the preliminary bore and the threaded portion of the screw both at the juncture of the cylindrical portion of the bore with the tapered entrance surface and also in the region of the wall where the inner longitudinal recesses and outer longitudinal protuberances are formed, whereby the formation of cracks in the screw during enlargement of the preliminary bore is reduced.
Claim 9
Dependent Claim
63 words
The method of claim 7 in which the reboring of the screw to produce the final bore configuration is carried out with a boring tool having a rounded leading end to eliminate formation of a sharp corner at the bottom of the final bore configuration and to thereby eliminate the tendency for cracks to occur at the bottom of the final bore configuration.
Claim 10
Dependent Claim
37 words
The method of claim 8 in which said boring tool has a nose with a spherically curved shoulder to cause the final bore configuration to be formed with a spherically curved annular surface at its bottom end.
Claim 11
Dependent Claim
62 words
The method of claim 9 in which the radius of curvature of the curved shoulder of the boring tool is substantially equal to the radius of the boring tool whereby the curvature of the spherically curved annular surface of the final bore configuration has the spherical curvature of a sphere having the same diameter as the diameter of the final bore configuration.
References Cited (Backward Citations)
US2542023A
Cited
US2844830A
Cited
US2637361A
Cited
DE1028250B
Cited
CH334413A
Cited
US2856617A
Cited
US3245096A
Cited
US3227199A
Cited
US3419928A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-04-23 | 1976-10-23 | 1977-04-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-23 | 1980-10-23 | 1981-04-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-23 | 1984-10-23 | 1985-04-24 | $7700.00 | Window Closed / Lapsed |