Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Threaded fastener locked to a discreet structure – Nut – and means to engage substructure on its opposite faces...
Reexamination Certificate
1999-12-06
2001-02-27
Saether, Flemming (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Threaded fastener locked to a discreet structure
Nut, and means to engage substructure on its opposite faces...
C411S082000, C411S456000
Reexamination Certificate
active
06193456
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a metal insert, in particular a threaded insert, adapted to be embedded into a receiving bore of a plastic part.
Such metal inserts generally are inserted into the receiving bore of the plastic part by pressing the insert into the plastic material softened by heat or ultrasonic energy (heat embedding, ultrasonic welding). Furthermore, it has become known to introduce the insert into the material of the plastic part by cold pressing or by injection molding. In order to prevent the insert from being withdrawn and from being rotated, the insert generally has its peripheral surface provided with surface irregularities such as undercuts, grooves, notches, indentations, toothings and the like. For example U.S. Pat. No. 4,046,181 discloses a sleeve-like insert having a peripheral surface comprising axial stepped conical portions which are provided with teeth and notches.
While such measures provide for increased resistance to withdrawal and rotation of the insert, it also increases to the insert's resistance to being inserted into the plastic part. Apparently, the requirements for maximal withdrawal and rotation resistance is somewhat in contrast to the requirements for minimal insertion resistance.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide a metal insert adapted to be embedded into a receiving bore of a plastics member, which insert possesses minimal insertion resistance and maximal withdrawal and rotation resistance.
The present invention provides a metal insert adapted to be embedded in a receiving bore of a plastic part, comprising a body member having a peripheral surface about a central axis, and at least one row of teeth projecting from said peripheral surface of the body member and being circumferentially spaced with respect to each other, each tooth being of a wedge-like shape diverging from a tooth front end in an axial direction towards a tooth terminal end, and having an end face extending at said tooth terminal end in a direction transverse to said axial direction such that there are gaps between the teeth, each gap tapering from said tooth front end in said axial direction towards said tooth terminal end while remaining open between said end surfaces of adjacent teeth.
Due to the design of the teeth provided on the peripheral surface of the body member of the insert the material of the plastic part may flow through the gaps between the teeth into the area downstream of the end faces of the teeth when the metal insert is being pressed into the plastic part. This results in a substantial decrease of the insert's resistance to being pressed into the plastic material. The area downstream of the end faces of the teeth provides for some kind of pockets which receive the plasticized plastic material so that it may expand and be cured in this area. This results in a substantial increase of the insert's withdrawal resistance. Simultaneously, the teeth radially projecting from the peripheral surface of the body member provide for a relatively high rotational resistance of the insert.
Preferably, each tooth has at its top a radially projecting, axially extending rib which substanially increases the insert's rotational resistance.
REFERENCES:
patent: 2949142 (1960-08-01), Sumerak
patent: 3403718 (1968-10-01), Hughes
patent: 4046181 (1977-09-01), Barnsdale
patent: 4842462 (1989-06-01), Tildesley
patent: 5131795 (1992-07-01), Kobusch
patent: 5391031 (1995-02-01), Medal
patent: 5634752 (1997-06-01), Haage
patent: 1978882 (1967-01-01), None
patent: 3143855A1 (1981-05-01), None
Borchard August
Jankowski Peter
Stumpf Michael
Bollhoff GmbH
Saether Flemming
Shaw Seyfarth
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