Method of inserting an insert in an opening of a plastic part

The method for inserting a screw or insert having a barbed or other irregular surface or barbed type insert includes the steps of providing a tool having an ultrasonic horn and a cavity for an insert; filling the cavity with plastic filler material and positioning the insert against the center of the filler material; thereafter, activating the horn to vibrate the insert to soften and penetrate the insert into the opening.

Balamuth U.S. Pat. No. 3,483,611 discloses the heading or staking of the 
portion of a rivet-like element extended through an aperture in a second 
element by subjecting same to high frequency vibratory energy, so as to 
cause the extended portion to overlap the edges of the aperture and 
thereby permanently join the two elements together. 
Soloff et al U.S. Pat. No. 3,440,117 discloses an ultrasonic method of 
inserting pins or other fastening elements into a thermoplastic block by 
applying the ultrasonic energy to the thermoplastic block and urging same 
onto the pins or other elements, thus causing the block to soften so that 
the pins penetrate same. No predrilling is required, although a small 
pilot hole may be provided. Such holes have been found particularly 
effective when driving plastic elements. 
DISCLOSURE OF THE INVENTION 
A general object of the invention is to provide an improved method of 
driving an insert into a new opening or a previously stripped opening in a 
thermoplastic part. 
Another object of the invention is to provide a method of driving an insert 
into a new drilled or molded opening or a previously stripped opening in a 
thermoplastic part by first filling the opening with a plastic filler 
material, urging the insert end against the filler material by adapting 
the distal end of the horn to receive the insert head and vibrating same 
to thereby soften the filler material while the insert penetrates same, 
with the filler material thereafter flowing around any insert threads or 
barbs to secure same. 
These and other objects of the invention will become more apparent when 
reference is made to the following drawings and the accompanying 
description.

BEST MODE OF CARRYING OUT THE INVENTION 
Referring now to the drawings in greater detail, FIG. 1 illustrates an 
ultrasonic tool 10 receiving alternating current energy from a generator 
11, and having a horn 12 with a recess 14 formed in the distal end thereof 
suitable for receiving the head 16 of an insert 18, such as a screw, for 
example. 
Either a new pilot hole 20 is formed in a first part, such as a 
thermoplastic part, represented at 22, or the part 22 contains a 
previously stripped hole A plastic filler material 24 is inserted in the 
hole 20 or the hole previously stripped hole becoming bonded to the 
surrounding plastic material. 
A second part 26 (FIG. 1) which is to be secured to the first part 22, 
includes an opening 28 formed therethrough. 
The horn 12 is activated so as to direct its high frequency energy against 
the head 16 of the insert 18, with the leading end 30 of the insert 
positioned through the opening 28 against the center of the exposed 
surface 32 of the filler material 24. The resultant vibration to which the 
insert 18 is subjected causes the filler material 24 to become softened 
such that the insert penetrates same until the second part 26 is tightly 
clamped against the first part 22. 
The insert 18 achieves a tight fit within the softened filler material 24 
by virtue of the latter flowing around any threads or barbs formed on the 
insert, and quickly hardening therearound (FIG. 2), rather than the normal 
process of requiring that threads, for example, rotate to cut away plastic 
in the surfaces of a new hole or stripped hole. 
Industrial Applicability 
It should be apparent that the invention provides an efficient, fast, and 
dependable method for inserting an insert in either of a new opening, or a 
previously stripped opening, in a thermoplastic part. 
Two general embodiments of the invention have been shown and described.