SELF-TAPPING THREADED BUSHINGS

• US 3,866,510 A
• Filed: 02/05/1973
• Issued: 02/18/1975
• Est. Priority Date: 06/05/1967
• Status: Expired due to Term

• Current Assignee: Carl-Herwig Eibes, Christian Eibes, Deceased Eibes, Nee Eibes Wagner
• Original Assignee: Carl-Herwig Eibes, Christian Eibes, Deceased Eibes, Nee Eibes Wagner
• Inventors: Eibes, deceased, Eibes, Christian, Eibes, Carl-Herwig, Wagner, nee Eibes
• Primary Examiner(s): Allen, Edward C.
• Application Number:
  US05/329,952
• Time in Patent Office: 743 Days
• Field of Search: 85/47,48
• US Class Current: 411/418
• CPC Class Codes: B21H 3/027 Rolling of self-tapping screws
• CPC Class Codes: B23G 7/00 Forming thread by means of tools similar both in form and in manner of use to thread-cutting tools, but without removing any material features of machines or devices not specially adapted to the particular mode of forming the thread B23G1/00
• CPC Class Codes: F16B 25/0031 the screw being designed to be screwed into different materials, e.g. a layered structure or through metallic and wooden parts
• CPC Class Codes: F16B 25/0052 the ridge having indentations, notches or the like in order to improve the cutting behaviour
• CPC Class Codes: F16B 37/122 Threaded inserts, e.g. "rampa bolts"

Abstract

The disclosure relates to a threaded bushing which, upon entering and turning in the initially smooth bore of the work piece, will form through its own male thread the corresponding internal thread within the wall of the work piece bore. The bushing is formed with one or more exterior bevels or grooves which extend axially over at least several threads and intersect such threads to form spoon or cup-shaped frontal areas where each bevel or groove merges into a respective thread.

Claims

1. A threaded self-tapping bushing adapted to be secured to a workpiece and comprising, an elongate member having helical male threads extending over at least a portion of its axial length said threads having crests, roots between said crEsts, and flanks extending from said crests to said roots on either side of said crests;

said member having at least one axially extending bevel intersecting a plurality of successive threads, the crests and flanks of each said male thread at their intersection with said bevel defining frontal areas on either side of said bevel which are concave both along the circumferential direction of each said male thread and transversely thereto along the axial direction of the bushing, each said bevel being approximately as deep as the roots between the crests to ensure that the roots between successive crests are essentially discontinuous at each bevelled portion, each said frontal area providing cutting edges along at least a part of its periphery as defined by said crest, flanks, and bevel, one of the two said frontal areas formed at the junction of each said male thread with said bevel having a greater curvature than the other.

2. The threaded bushing of claim 1 in which the leading frontal area in the direction of turning said bushing into said work piece has less curvature than the lagging frontal area.

3. The threaded bushing of claim 1 in which the beveled male thread profiles at at least one end of the bushing are conically tapered inwardly.