Double bevel prewinder mandrel

Details Double bevel prewinder mandrel Double bevel prewinder mandrel

1998-09-24

2001-11-27

Hail, III, Joseph J. (Department: 3723)

Metal working

Means to assemble or disassemble

By rotation of work part

C029S240000

Reexamination Certificate

active

06321433

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to tools for helically coiled wire inserts, and more particularly to prewinder mandrels and tools for installing tanged helically coiled wire inserts.
BACKGROUND
Helically coiled wire inserts are often used when fasteners are being fastened into relatively soft parent materials. For example, a wire insert may be introduced into a tapped hole in a relatively soft parent material, such as aluminum, to substantially reduce the risk of stripping the hole when a relatively hard fastener, such as a steel bolt, is received therein. Wire inserts are generally formed from a single length of wire that is wound into a helical shape, thereby defining a cylindrical channel including an internal and an external thread pattern. One end of the wire insert may include a tang, generally formed by bending one end of the length of wire substantially transversely across the cylindrical channel.
To install wire inserts, a prewinder tool may be used onto which a wire insert may be received prior to insertion into a tapped hole. For example,
FIGS. 1-2C
show a prewinder mandrel
10
for a prewinder tool (not shown) that includes a threaded lead end
12
terminating in a lead tip
14
. A slot
16
is provided across the lead tip
14
for receiving a tang from a wire insert (not shown) therein. The slot
16
divides the lead tip
14
into a first end portion
22
having a helical bevel
24
defined by the thread pattern
20
, and a second end portion
26
having an inclined ramp
28
and a leading edge
32
. The prewinder tool includes a threaded nozzle (not shown) through which the mandrel
10
may extend, and the nozzle and mandrel
10
may include cooperating thread patterns for driving the mandrel
10
at a predetermined pitch.
To wind a wire insert onto the mandrel
10
, the mandrel
10
is rotated about its longitudinal axis with respect to the wire insert, and the lead tip
14
is directed into the open end of the wire insert, through the cylindrical channel and towards the tang. The thread pattern of the lead end
12
substantially engages the internal thread pattern of the wire insert, generally compressing the wire insert radially as it is advanced over the lead end
12
. When the lead tip
14
passes through the cylindrical channel, the tang of the wire insert
10
(not shown) is engaged by the leading edge
32
of the lead tip
14
and enters the slot
16
, thereby fixing the wire insert on the lead end
12
.
The lead end
12
may then be introduced into a tapped hole (not shown), and the mandrel
10
rotated further to direct the wire insert into the tapped hole, the external thread pattern of the wire insert cooperating with a thread pattern of the tapped hole. Once the wire insert is fully received in the tapped hole, the rotation of the mandrel
10
may be reversed, the wire insert unwound from the lead end
12
, and the lead end
12
withdrawn from the tapped hole, leaving the wire insert therein. As the mandrel
10
is being rotated to unwind the wire insert, the tang may slide along the inclined ramp
28
and out of the slot
16
.
One of the problems often associated with conventional prewinder mandrels is improper seating of the tang within the slot as the wire insert is wound onto the lead end. During use, a force is generally applied tangentially between the mandrel and the wire insert, e.g., along their cooperating thread patterns, to wind the wire insert onto the lead end and to insert the wire insert into a tapped hole. The substantial loads transferred between the mandrel and the wire insert may create risks of damage to the nozzle of the tool, the mandrel, individual inserts, and/or the tapped hole unless precise tolerances are maintained.
In addition, because the leading edge is generally higher than the remaining portions of the lead end, it may result in the tang being picked up too early by the slot. This may cause the tang to bend outward, may distort the shape of the wire insert, may increase the diameter of the tang end and/or may even cause the tang to break, substantially increasing the risk of jamming or cross-threading in the nozzle and/or in the tapped hole.
Furthermore, the leading edge may result in single point contact between the tang and the lead tip. If the geometry of this contact is altered, for example, due to poor mandrel or tool manufacture, wear or damage to the mandrel or tool, variation in wire insert shape, variation in tapped hole geometry, and the like, the load transfer between the mandrel and the insert may be altered significantly, and problems similar to those described above may occur.
Accordingly, there is a need for improved prewinder mandrels and/or tools for installing helically coiled wire inserts.
SUMMARY OF THE INVENTION
The present invention is directed to mandrels and tools for installing helically coiled wire inserts, and to methods of installing wire inserts using such tools. Wire inserts are generally a helically wound length of wire defining a passage therethrough and including a tang extending substantially transversely across one end of the passage opposite an open end of the passage. Wire inserts generally include an outer thread for cooperating with a tapped hole and an inner thread for cooperating with a fastener being received in the tapped hole.
In one aspect of the present invention, a prewinder mandrel is provided that includes an elongate shaft defining a longitudinal axis and having a threaded first end and a second end. A slot extends substantially transversely across the first end, thereby dividing the first end into first and second end portions. A pair of opposing beveled edges are provided on the first end portion, the beveled edges sloping away from each other and towards the second end of the elongate shaft.
Preferably, the slot includes first and second drive edges for engaging a tang of a wire insert received on the first end, the first drive edge being located between the first and second beveled edges, the second drive edge being located on an outer edge of the second end portion. In addition, the first end portion may include an intermediate surface between the opposing beveled edges defining a plane substantially normal to the longitudinal axis of the elongate shaft.
The second end portion preferably defines first and second outer edges adjacent the slot, and preferably includes an inclined ramp extending between the first and second outer edges, the inclined ramp being inclined generally into the slot. The first outer edge preferably provides a drive edge for engaging a tang of a wire insert received on the first end, and the inclined ramp is preferably inclined from the first outer edge towards the second outer edge and towards the second end of the elongate shaft.
The mandrel may also include a drive head on the second end of the elongate shaft, and an enlarged, preferably threaded, region adjacent the threaded first end. The mandrel may also include a nozzle having an axial passage therethrough through which the shaft may extend. The axial passage preferably includes a threaded portion therein for cooperating with the threaded enlarged region of the elongate shaft for directing the elongate shaft axially with respect to the nozzle at a predetermined pitch.
The mandrel and nozzle may be included as part of a tool for inserting a wire insert, in accordance with another aspect of the present invention. The tool may include an elongate shaft having a first threaded end and defining a longitudinal axis, and a drive mechanism, preferably a pneumatic motor, for rotating the elongate shaft about the longitudinal axis. A slot may extend substantially transversely across the first end, thereby dividing the first end into first and second slot portions, and a pair of opposing beveled edges may be provided on the first slot portion. The beveled edges preferably slope away from each other and towards the second end of the elongate shaft, as described above for the prewinder mandrel.
In a preferred form, the elongate shaft is detachable from the drive

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