Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Externally threaded fastener element – e.g. – bolt – screw – etc. – Pilot end having means enhancing fastening or installation
Patent
1999-01-25
2000-07-11
Saether, Flemming
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Externally threaded fastener element, e.g., bolt, screw, etc.
Pilot end having means enhancing fastening or installation
411424, F16B 2510
Patent
active
060863021
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Technical Field of the Invention
A self-tapping screw is known from EP 0 623 759 B1, in which the ratio which the major diameter bears to the minor diameter is approximately 1.25-1.5, the ratio which the major diameter bears to the pitch lead is approximately 1.5-1.6 and the flank angle of the thread is <50.degree. and >35.degree..
EP 0 433 484 B1 teaches a self-tapping screw, the thread of which is provided with cutting teeth of approximately bowed design, the central cutting edge being level with the crest of the thread and set negatively.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the invention to embody a self-tapping screw of the generic type such that it can be screwed especially easily in holes drilled in concrete or other materials such as brick or the like.
According to the invention, this object is attained by the features in the Surprisingly, it has been found that the parallel arrangement of the flanks, i.e. with a flank angle of approximately 0.degree., will make the screw especially easy-running when screwed in, in particular in the case of hole diameters that vary within the range of admissible tolerances. A reason may reside in that even with varying depths of cutting of the thread into the concrete or the other material, such as bricks, chip boards or hardwood, there is no pressing of the flanks towards the material into which the screw is screwed. The thread is cut over its full width into the material by the cutting notches. In particular one embodiment results in that the material cut out when the screw is screwed in can be delivered outwards without any pile-up.
Further features, advantages and details of the invention will become apparent from the description of exemplary embodiments, taken in conjunction with the drawing, in which
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an view of a concrete screw having a slightly tapered end to be inserted;
FIG. 2 is a plan view of a concrete screw having a strongly tapered end to be inserted;
FIG. 3 is a plan view of part of a concrete screw on an enlarged scale as compared to FIG. 1;
FIG. 4 is a cross-sectional view through the thread along the section line IV--IV in FIG. 3;
FIG. 5 is a lateral view of a thread in accordance with the arrow V in FIG. 3; and
FIG. 6 is an illustration, corresponding to FIG. 4, of a cross-section through a modified embodiment of the thread.
DETAILED DESCRIPTION OF THE INVENTION
The screw seen in FIG. 1 comprises a cylindrical core 1 having a slightly tapered section 3 in the vicinity of the end 2 to be inserted. A head 4 of arbitrary design is formed on the other end of the core. A thread 5 of web-type design is formed on the cylindrical core 1 inclusive of the tapered section 3, the major diameter D of which exceeds the nominal diameter of a drill hole into which to insert the screw by 1.0-2.5 mm. The nominal diameter of a drill hole is internationally standardized, amounting to 4, 5, 6, 8, 10, 12, 14, 16 . . . mm.
The amount by which the major diameter D exceeds the nominal diameter of the hole grows as the nominal diameter of the hole increases. At the end 2, to be inserted, of the tapered section 3, the major diameter D' of the thread 5 is less than the nominal diameter of the hole by an inferior amount of 0.1-0.2 mm for impeccable insertion not only of the end 2 of the screw, but also of the first flight or the first two flights into a hole to be possible. Subsequent to this first flight or the first two flights, one to two flights are provided as a transition to the thread 5 with the major diameter D. The thread 5 possesses this major diameter D over two to four flights. Subsequently, the major diameter D is again reduced by 0.1-0.2 mm to have a major diameter D", i.e. it still overshoots the nominal diameter of the drill hole. On the whole, the thread 5 is enveloped by an approximately crowned curve. A thread 5 need not forcibly be available in the area neighboring the screw head 4; this applies in particular to comparatively long screws.
In the embod
REFERENCES:
patent: 2140467 (1938-12-01), Cargile
patent: 2679744 (1954-06-01), MacDonald
patent: 3537288 (1970-11-01), Ansingh
patent: 4439077 (1984-03-01), Godsted
patent: 4842467 (1989-06-01), Armstrong
patent: 4850775 (1989-07-01), Lee et al.
patent: 5143498 (1992-09-01), Whitman
Saether Flemming
TOGE -- Dubel A. Gerhard KG
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