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...
Patent
1999-05-27
2000-11-14
Wilson, Neill
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...
411438, 4119291, F16B 3712
Patent
active
061460737
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a wire-type screw thread insert for insertion into a tapped hole of a workpiece consisting of a cylindrical body comprising a plurality of helically wound coils and an end coil which extends radially inwardly from the outer diameter of the cylindrical body and a use of such a wire-type screw insert in a tapped hole of a workpiece.
2. Description of the Related Art
Such wire-type screw thread inserts have become known, e.g. from U.S. Pat. No. 2,363,789, EP-A-140 812 and EP-A-157 715. Generally, the outer diameter of the cylindrical body is to be designed so as to exceed the outer diameter of the tapped hole in the workpiece so that the diameter of the wire coils is to be reduced when the insert is threaded into the tapped hole of the workpiece in order to provide for a tight grip of the screw thread coils in the tapped hole by resilient deformation of the wire coils. In order to facilitate threading of the wire-type screw thread insert into the tapped hole, half a coil at the end of the cylindrical body is deformed radially inwards in a manner known per se (EP-B1-0 228 981). The minimal outer diameter of the radially deformed portion should be substantially as large as or slightly larger than the associated outer diameter of the tapped hole. Furthermore, with this prior art wire-type screw thread insert the cross-section of the wire at the end thereof is reduced in a predetermined manner in order to facilitate insertion thereof and to avoid damaging the tapped hole. According to U.S. Pat. No. 2,152,681 the outer diameter of the reduced end portion is somewhat smaller than the outer diameter of the tapped hole. The circumferential angle of the reduced diameter portion again is 180.degree.. A similar wire-type screw thread insert has become known from U.S. Pat. No. 2,371,674 wherein, as may be seen in FIGS. 1 and 2 of that document, the end coil extends, following its diameter reducing portion, through a small angular range about a circumferential angle of somewhat more than 180.degree..
SUMMARY OF THE INVENTION
Nevertheless it is necessary with the prior art wire-type inserts to use a special tool comprising a preclamping cartridge and a spindle to be inserted initially into the wire-type screw thread insert in order to reduce the diameter of the insert before it is threaded into the tapped hole. Such an insertion tool has been described for example in U.S. Pat. No. 4,553,302. While it is possible to reduce the outer diameter in order to facilitate the threading operation, this however will weaken the tight grip, or specific regulations will not be met.
The problem to be solved by the invention is to design the wire-type thread insert such that insertion thereof into the tapped hole will be facilitated and in particular may be performed without a tool for reducing the diameter of the wire-type screw thread insert before insertion thereof
This problem is solved by the features of patent claim 1. Advantageous modifications thereof are defined in the subclaims.
In contrast to prior art wire-type screw thread inserts the invention provides for an insertion area consisting of the end coil (of a reduced and constant outer diameter) and the diameter reducing portion which together extend about a circumferential angle of preferably about 360.degree. and more. Even a circumferential angle of about 360.degree. facilitates substantially the insertion operation and above all allows to dispense with the so-called preclamping cartridge for reducing the outer diameter of the wire-type screw thread insert before insertion thereof. This allows to substantially simplify the insertion tool. The end coil with the reduced and constant outer diameter is concentric to the cylindrical body so that the wire-type screw thread inserts will not be misaligned when the insertion tool will be applied. This facilitates insertion of the insert into the tapped hole of the workpiece. Furthermore, the end coil is slightly overdimensioned with the reduced outer d
REFERENCES:
patent: 2152681 (1939-04-01), Caminez
patent: 2390514 (1945-12-01), Cram
patent: 2745457 (1956-05-01), Lang
patent: 2869224 (1959-01-01), Forster
patent: 2874741 (1959-02-01), Brancato
patent: 3272250 (1966-09-01), Hattan
patent: 3316795 (1967-05-01), Tann
patent: 4645398 (1987-02-01), Cosenza et al.
Bollhoff GmbH Verbindungs - und Montagetechnik
Wilson Neill
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