CA1118978A

CA1118978A - Thermoplastic swaging

Info

Publication number: CA1118978A
Application number: CA000320758A
Authority: CA
Inventors: Isaac Revah
Original assignee: Northern Telecom Ltd
Current assignee: Nortel Networks Ltd
Priority date: 1979-02-02
Filing date: 1979-02-02
Publication date: 1982-03-02

Abstract

THERMOPLASTIC SWAGING
Abstract of the Disclosure An apparatus and a method for joining together two articles wherein one article has a stud protruding from its surface and the other article has an aperture for receiving the stud, and the stud is deformed by heat, once the two articles are juxtaposed, so as to maintain the two articles connected. The apparatus comprises a pressure pad both for pressing the two articles to be connected against a common base support, and for surrounding the stud to be deformed so as to form and to cool the deformed material. A heated die passes through an opening in the pressure pad to contact and to plasticize the free end portion of the stud sufficiently to cause its constituent material to deform.

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Description

This invention relates generally to swaging thermoplastic material and more particularly to heat swaging the ends of thermoplastic studs, for example when mounting components to a support piece.
It is well known in the prior art to mount a first article having a plastic stud to a second article by passing the stud portion of the first article through an aperture in the second article and then deforming the protruding portion of the studg by heat or by sonics, to form a retaining head to keep the two articles connected together. United States patent 3a900~714 dated August 19, 1975 to L.R. Beyer depicts a tool for heat deforming a plastic stud to achieve the aforementioned purpose of joining two articles. ~ !
United States patent 3,367,809 dated February 6, 1968 to R.S. Soloff and U.S. patent 3,483,611 dated December 16, 1969 to L. Balamuth and T. Parisi, both relate to a similar operation of deforming a plastic stud for the purpose of ioining or connecting two items, but rather than using heat as the deforming agent, ultrasonic energy is employed. These two patents describe some disadvantages that arise when heat is employed to perform the deforming operation.
~0 These disadvantages include loose joints caused by the plastic contracting upon cooling, difficulty in controlling the flow of the melted plastic, the fact that the heat may be detrimental to the items being joined (i.e. other than the studs), and the studs may become burned and charred so as to be commercially unacceptable.
Because of these disadvantages of employing heat, U.S. patents 3,367~809 and 3,483,611 use ultrasonic energy to perlorm the function of deforming the studs.
The aforementioned U.S. patent 3,900,714 specifically mentions the problem of the plastic of the studs sticking to the thermo-forming die at the temperature necessary for ~hermo-forming.

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U.S. patent 3,900,714 is directed to a tool for preventing this sticking problem by designing the tool so as to have the inherent quality of automatically cycling the temperature of the heat-applying portion of the tool~ This is achieved by providing a heat conduit, between the die itself and the source of heat for the die, that is more restrictive to heat transmission than is the die, thereby allowing the die to cool and allowing removal of the die from the stud without sticking.
The present invention is an apparatus, and a method, For joining two articles (or items) wherein one of the articles has a stud protruding from its surface and the other of the articles has an aperture for receiving the stud. The stud is deformed by heat, - once the two articles are juxtaposed, so as to maintain the two articles connected. The apparatus of the present invention comprises a pressure pad which surrounds the stud to be deformed, with a clearance fit, and which presses the two items to be connected against a common base. A heated cylinder (die) passes through an opening in the pressure pad to contact and to plasticize the exposed (or free ` end) portion of the stud sufficiently to cause its constituent material to deform. The pressure pad functions both to form and to cool the plasticized material of the stud.
Stated in other terms the present invention is an ; apparatus for performing a swaging operation on a thermoplastic stud, the apparatus comprising: a pressure means, both for surrounding a portion of the stud so as to define a cavity around the stud and for applying a force so as to hold an article, supportin!~ the stud, in a Fixed position; and a heated deforming means moveable through an opening in the pressure means so as to contact a free end of the stud and to cause the stud to deform and to flow into the cavity deFined by the pressure means.

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Stated in yet another way, the present invention is an apparatus for 'oining two items together wherein the first item includes a stud portion protruding from the surface ,thereof, and the second item includes an aperture for receiving the stud portion such that the stud portion protrudes beyond the second item and defines a free end of the stud, and wherein the apparatus performs a swaging operation on the free end of the stud, the apparatus comprising: a pressure means for applying pressure to force the two items into tight contact, one with the other; the pressure means including a flared portion which surrounds the free end of the stud while maintaining an access aperture aligned with the longitudinal axis e-~f c d of the stud, a~die means, for deforming the free end of the stud :
such that the stud forms a headed portion sufFiciently large to prevent it from passing through the aperture in the second item. -Stated in still other terms, the present invention is the method of swaging a thermoplastic stud wherein the stud is an integral part of a first item and the first item is situated relative to a second item such that the stud protrudes through an aperture in ; the second item, the portion of the stud extending beyond the second i~em referred to as the free end of the stud, the method comprising:
-Forcing the first and second items into close contact with one another, the force being applied along lines parallel to the longitudinal axis of the stud, applying adequate heat to the free end o~ the stud so : that the stud deforms sufficiently to fill any void between the stud ~:
and the second item, containing and cooling the thermoplastic material emanating from the stud so as to form an enlarged head on .
the stud, of larger diameter than the diameter of the aperture in the second item.
The invention will now be described ln more detail with reference to the accompanying drawing wherein:

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Figure 1 is a sectional view of the preferred embodiment of the invention.
One particular application of the invention is depicted in Figure 1 for purposes of exemplification, i.e. attaching a connector 12 to a printed circuit board 10. A printed circuit board (PCB) 10 is depicted having two circular apertures indicated at lla and llb. A connector 12 is shown adjacent PCB 10.
Connector 12 has two cylindrical studs 13a and 13b that protrude through apertures lla and llb respectively as shown in Figure 1.
Stud 13a is depicted in its unswaged state, and it can be seen from the Figure that there is a clearance fit between stud 13a and aperture lla and that the free end of stud 13a protrudes beyond PCB IO. Stud 13b is depicted in its swaged state; it can be seen that stud 13b has a shank portion 14 that completely fills the aperture llb, and a head portion 15 that has a diameter greater than the diameter of aperture llb so as to prevent the stud 13b from passing through aperture llb.
The device 16 for performing the swaging operation on studs 13a and 13b is shown in Figure 1 in the process of swaging stud 13b.
Device 16 comprises a pressure pad 17, a die 18, and a base 19. As can be seen from Figure 1, the connector 12 rests against base 19 and PCB 10 rests against the upper portion of connector 12 in such a manner that the studs 13a and 13b of connector 12 protrude through the aperture lla .~
and llb respectively, of PCB 10~ Pressure pad 17 fulfills several di~ferent functions. One function of pressure pad 17 is to apply force to PCB 10, along a line of application generally parallel to . the longitudinal axis of studs 13a and 13b to thereby force PCB 10 -~
and connector 12 together into a tight and non-moving contact between ;~ base 19 and pressure pad 17 itself.
Pressure pad 17 also serves the function of containing .
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i and forming the material from studs 13a and 13b when they are swaged.
Additionally pad 17 functions to cool the material from studs 13a and 13b immediately after forming~ The swaging process of the present invention includes the plasticizing of a substantial portion oF the stud;
sufficient to completely fill apertures lla and llb and to form head portion 15. To this end pressure pad 17 has at its extremity that engages PCB 10, a columnar opening for receiving studs 13a and 13b with a clearance fit. The columnar opening extends completely through pressure pad 17 so as to permit die 18 to pass through the columnar opening and to come into contact with studs 13a and 13b in order to plasticize them. The columnar opening in pressure pad 17 has a bevelled (or flared) mouth 20 at the end oF pad 17 that engages PCB 10.
The purpose of the bevelled mouth 20 is to form a cavity into which material, from the studs 13a and 13b, can flow so as to form the head portion 15. Once the studs 13a and 13b have cooled to the solid state, head portion 15 prevents the studs from pulling through apertures lla and llb of PCB 10.
Once the combination oF pressure pa~ 17 and base 19 have forced PCB 10 and connectnr 12 into immoveable contact, one with the other, die 18 (heated to a sufficiently high temperature to plasticize the material of which studs 13a and 13b are constructed)is brought into contact with stud 13b, through the columnar opening in pressure pad 17 along a line of movement approximately collinear with the longitudinal axis of stud 13b. The face of die 18 that comes into contact with stud 13b is preferably flat (although`other shapes can be used) and the diameter of the face of die 18 is approximately the same as that of the unswaged stud 13b.
After stud 13b has been deformed sufficiently to completely fill aperture llb and to form a head portion 15, die 18 is ; 30 retracted and the deformed (or swaged) stud 13b is allowed to cool.
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During this cooling process pressure pad 17 remains in intimate contact with PCB 10 to form the head portion 15 of stud 13b. Once stud 13b has cooled sufficiently, pressure pad 17 is removed from PCB 10.
This procedure is then repeated for stud 13a.
Variations can be made to the preferred embodiment of Figure 1. One variation would be to use a separate pressure pad 17 for each stud that is to be swaged, one die 18 could be used and applied to each stud in turn, or else a separate die 18 could be provided for each stud. Another variation would be to provide groups of pressure pads 17 and dies 18, e.g. if there are lour studs to be swaged, two pads 17 and t~o dies 18 could be used simultaneously to swage two studs at a time.
In one embodiment reduced to practice by the inventor the studs 13a and 13b were made of Noryl*ahd pressure pad 17 was made of steel.
The invention can of course be used to join together parts in various applications and is not limited solely to the eremplary case of a printed circuit board and a ccnnector.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An apparatus for performing a swaging operation on a thermoplastic stud, said apparatus comprising:
a pressure means, both for surrounding a portion of said stud so as to define a cavity around said stud and for applying a force so as to hold an article, supporting said stud, in a fixed position; and a heated deforming means moveable through an opening in said pressure means so as to contact a free end of said stud and to cause said stud to deform and to flow into the cavity defined by said pressure means.

2. An apparatus for joining two items together wherein the first item includes a stud portion protruding from the surface thereof, and the second item includes an aperture for receiving said stud portion such that said stud portion protrudes beyond said second item and defines a free end of said stud, and wherein said apparatus performs a swaging operation on said free end of said stud, said apparatus comprising:
a pressure means for applying pressure to force said two items into tight contact, one with the other;
said pressure means including a flared portion which surrounds the free end of said stud while maintaining an access aperture aligned with the longitudinal axis of said stud; and a heated die means, for deforming the free end of said stud such that said stud forms a headed portion sufficiently large to prevent it from passing through the aperture in said second item.

3. The apparatus of claim 2 wherein said die means is positioned for reciprocating motion, along an axis parallel to the longitudinal axis of said stud, through an opening in said pressure means.

4. An apparatus for performing a swaging operation on the free end of a thermoplastic stud, wherein said stud is part of a first item and said first item is in contact with a second item such that said stud protrudes through an aperture in said second item so as to define a free end of said stud, said apparatus comprising:
a base means for supporting said first and second items, a pressure pad, both for surrounding said stud with a clearance fit, and for forcing both said first object and said second object into immoveable contact against said base means;
a heated die for reciprocating movement through an opening in said pressure pad so as to contact said stud and to apply sufficient heat to said stud so as to cause said stud to deform and to flow into the cavity defined by said pressure pad, by said second item, and by said stud prior to deformation.

5. The apparatus of claim 4 wherein said pressure pad defines a larger zone of clearance from said stud, in the portion of the pressure pad closer to said second item, and wherein said pressure pad functions as a heat sink to aid in cooling the deformed material of said stud.

6. The method of swaging a thermoplastic stud wherein said stud is an integral part of a first item and said first item is situated relative to a second item such that said stud protrudes through an aperture in said second item, the portion of the stud extending beyond said second item referred to as the free end of said stud, said method comprising:
forcing said first and second items into close contact with one another, said force being applied along lines parallel to the longitudinal axis of said stud;
applying adequate heat to the free end of said stud so that said stud deforms sufficiently to fill any void between said stud and said second item;
containing and cooling the thermoplastic material emanating from said stud so as to form an enlarged head on said stud, of larger diameter than the diameter of said aperture in said second item.