Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Externally threaded fastener element – e.g. – bolt – screw – etc. – Head driving structure
Reexamination Certificate
1999-05-11
2001-04-24
Saether, Flemming (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Externally threaded fastener element, e.g., bolt, screw, etc.
Head driving structure
C411S419000, C411S393000, C470S008000
Reexamination Certificate
active
06220805
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a slotted screw and a method for making a slotted screw, more particularly to a slotted screw and method, and apparatus for forming a slot in an end surface of a semi-product of a screw prior to thread formation.
2. Description of the Related Art
Referring to
FIG. 1
, in a case where threads of a set screw
1
are formed prior to formation of a slot
10
(shown in slotted lines) in an upper end surface of the screw
1
by a lathe in a known manner, several tabs
11
(only one is shown) may be created on the screw
1
at positions adjacent to two end portions of the slot
10
. In this case, it is necessary for the screw
1
to undergo vibration processing in order to have the tabs
11
drop therefrom. To enable removal of the tabs
11
from the screw
1
by vibration, the screw
1
is made of high speed steel, thereby resulting in increased manufacturing costs. Because the slot
10
is formed by means of a lathe, the production efficiency is reduced, and a large amount of metal waste is created.
Referring to
FIG. 2
, in a case where a slot
10
′ is formed in an upper end surface of a screw
1
′ prior to formation of threads by a lathe in a known manner, several sharp projections
12
may be formed on the screw
1
′ in two end portions of the slot
10
′, thereby obstructing insertion of a wedge-shaped end of a screwdriver into the slot
10
′. As a result, this slot forming process is seldom adopted by manufacturers of slotted-screws.
SUMMARY OF THE INVENTION
The object of this invention is to provide a slotted screw and method, and apparatus for forming rapidly a slot in a semi-product of a screw prior to thread formation by forging so as to reduce the manufacturing costs of the screw and so as to minimize creation of metal waste.
According to this invention, an apparatus for forming a slot in a semi-product of a screw prior to thread formation includes a punch and a die mechanism. The die mechanism includes a tubular member, and an elongated die member formed integrally with a slot-forming plate which is located at a front end portion thereof and which has a uniform-thickness flat middle portion and two side portions that are wider than the middle portion. The semi-product can be compressed between the punch and the slot-forming plate of the die member in a central bore in a high-hardness block which is fixed in the tubular member, to form the slot. Accordingly, the slot has a uniform-width middle portion and two end portions which are wider than the uniform-width middle portion. When threads are formed on the semi-product by means of a lathe, no projections are created in the uniform-width middle portion of the slot, thereby permitting a wedge-shaped end of a screwdriver to engage fittingly the uniform-width middle portion of the slot.
REFERENCES:
patent: 2037066 (1936-04-01), Cook
patent: 2808087 (1957-10-01), Vaughn
patent: 2996093 (1961-08-01), Moore
patent: 3188849 (1965-06-01), Wisebaker et al.
patent: 3351966 (1967-11-01), Pelochino
patent: 3470786 (1969-10-01), Martins
patent: 4485510 (1984-12-01), Hatter
patent: 4538486 (1985-09-01), Lutrat
patent: 4805437 (1989-02-01), Heil, Jr. et al.
patent: 4932234 (1990-06-01), Adachi
patent: 5667443 (1997-09-01), Allen
Rodman & Rodman
Saether Flemming
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