Heat staking head with radiant heat source

Details Heat staking head with radiant heat source Heat staking head with radiant heat source

2000-03-20

2001-10-02

Davis, Robert (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Preform assembly means and means for bonding of plural...

With treatment means other than assembling, bonding, shaping...

C264S249000, C264S481000, C425S112000, C425S174400, C425S392000

Reexamination Certificate

active

06296470

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to heat staking machines for joining parts together, and more particularly to a head for use on such a machine and having a radiant heat source to heat and thereby soften the part to be deformed.
BACKGROUND OF THE INVENTION
Heat staking is a process for permanently joining first and second parts at one or more discrete points. One of the parts to be joined includes a short plastic post or stud which is inserted through a hole or aperture of roughly equivalent size in other part. The plastic stud is then heated until it is plastically deformable and the end of the stud is flattened with a metal punch to form a rivet-like head which locks the two parts together.
It is possible to accomplish the heating and the flattening of the stud simultaneously by heating the punch prior to bringing into contact with the stud, the punch transferring its heat to the stud to soften it is being shaped. In such an operation, the punch is typically resistance heated by applying electrical current to the punch. Heat staking machines operating in this manner are disclosed in U.S. Pat. Nos. 4,767,298 and 5,227,173.
Another known heat staking technique is to heat the stud prior to it being contacted by the punch. In the past, this has been achieved by blowing hot air over the stud. U.S. Pat. No. 5,018,957 discloses a staking machine using electric heaters to generate the hot air and blowers to circulate the hot air over the stud. In some manufacturing operations, this pre-impact heating of the stud has been found to be advantageous in that it minimizes the amount of residual stress in the deformed stud after it has cooled. In the past, however, the apparatus necessary for the heating and circulation of air has resulted in a relatively large and mechanically complicated machine. Also, such a machine is relatively energy inefficient in that a large percentage of the heat generated to is not transferred to the stud but rather is wasted.
It is therefore desirable to provide a heat staking machine that is energy efficient and that is simple and compact in construction.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved heat staking head for use in a staking machine utilizes a radiant heat source and primary and secondary reflectors which combine to focus radiant energy onto the plastic stud to heat and soften stud prior to the staking punch impacting the stud.
In a first embodiment of the invention, the source of radiant energy is an infrared heat lamp mounted directly above and in coaxial alignment with the staking punch such that the lamp points downward toward the plastic stud. A generally parabolic primary reflector surrounds the lamp, and a punch is mounted for sliding movement along the axis of thereof. A secondary reflector has a central aperture at its vertex through which the stud projects, the reflector directing substantially all of the radiant energy emitted by the lamp radially inward onto the stud. When the stud has been sufficiently heated and softened, the punch is driven downwardly to impact and deform the stud. This provides a compact, mechanically simple and highly energy efficient staking apparatus.
In a second embodiment, multiple radiant energy sources are used, each with its own primary reflector. A single secondary reflector serves both primary reflectors.
In a still further embodiment a punch-head is disposed on a pivotal arm so as to be moveable in and out of an operative position relative to the heat source and the work piece.


REFERENCES:
patent: 3452376 (1969-07-01), Ito
patent: 4510005 (1985-04-01), Nijman
patent: 4767298 (1988-08-01), Bocchicchio et al.
patent: 5018957 (1991-05-01), Assink et al.
patent: 5227173 (1993-07-01), Sherwood
patent: 6099291 (2000-08-01), Lanser
Derwent Abstract of Research disclosure RD-419047A, Mar. 10, 1999.

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