Metal fusion bonding – Process – With clamping or holding
Reexamination Certificate
1998-10-13
2001-02-13
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Process
With clamping or holding
C228S044300, C269S287000
Reexamination Certificate
active
06186391
ABSTRACT:
The present invention relates to a fastener, which is weldable by arc welding at one of its end faces to a component, and has at least one longitudinal slit; the invention further relates to welding equipment for its welding on, and to an arrangement for the fastening of its assembly part to the fastener.
A fastener according to the heading of Patent claim
1
is known from Canadian Patent No. 887, 911, or GB Patent No. 1,275,799, in which a slitted cup is gripped in the interior of its central portion, by means of a bolt under resilient pressure, is pressed on to and welded to a component, whereupon the lateral portions are bent over. Such a method is not suitable for rationalised and above all for reliable production, as is required in the automotive industry.
The same applies to the element according to U.S. Pat. No. 3,996,446, which is in fact resilient in design, but must firstly be taken into its single possible correct position in order to be gripped internally and pressed on during welding.
Further fasteners are known, such as are frequently used in the automotive industry, in order to fasten, for example, car body components or electrical cables or the like. A common factor in all these previously-known weld-on fasteners is that they are manufactured as solid studs, which as a rule have a flange by means of which they are welded to the sheet metal, for example according to DE-A-32 18 886 or DE-U-79 25 469. Such a solid stud requires a flexible collet on a stud welding equipment. It is apparent from the drawings of the German publication that the gripping with the collet of the stud welding equipment, due to the rigid design of the stud, and in particular also by the flange with wider diameter, requires the use of expensive mechanical parts, which must operate reliably even at high operating frequencies.
A cylindrical welding stud is known from DE-A-25 32 311, having no flange, yet which does not substantially simplify the collet chuck of the stud welding equipment.
Moreover, problems arise due to the design of the previously-known studs relating to uniform weld quality of the fusion between the sheet metal part and the stud, for which special measures are necessary for the design of the welding surfaces of the stud. This applies also for the fasteners according to DE-B-2 227 384, in which either the threaded studs or the nuts must be welded on as fasteners. Both these illustrated fasteners cause high demands on the collet of the stud welding equipment, which must be specially designed for this purpose.
Moreover, when there is fatigue in the collet, electrical contact with the stud can no longer be guaranteed, which leads to scorched areas, reducing reliability, which is essential in assembly lines.
Finally, the previously known weld studs or fasteners have a defined welding surface, which must be accurately positioned in the welding equipment. This complicates the feeding, as these elements must be fed into the welding equipment pre-sorted.
Using this prior art as a starting point, one purpose of the present invention is to propose a weld-on fastener which on the one hand guarantees reliable welding on to a support and, even in its simplest embodiment, offers the possibility of fastening a variety of assembly parts thereon, while on the other hand simplifying the retaining portion of the welding equipment and its feeding system, ensuring an optimal flow of current between the collet and the fastener. Such a fastener is described in claim
1
.
With such a fastener, on the one hand the said fastener needs not be pre-sorted and accurately positioned in order to be fed into the rigid holder, and on the other hand the resilient force or push-on force is so high because of the formation of the longitudinal slit on the current-transferring holder, that an optimum transmission of current from the holder to the fastener is always ensured.
Whereas in one embodiment the conical funnels on both end faces of the fastener have a threaded shape, the fastener may also be provided with an external thread or with retaining claws. A common feature of all features is however that they are resilient in design, in order to ensure the flexibility necessary for the fastening technology, and guarantee good current conduct.
The previously-known studs for example are welded on with a welding equipment according to DE-A-32 18 886 or DE-U-79 25 469. Such a solid stud requires a flexible collet on the welding equipment. It is apparent from the drawings of the Disclosure Document that the holder with the collet of the welding equipment, constrained by the rigid execution of the stud and in particular also by the flange with its wider diameter, must comprise expensive mechanical parts, which must operate reliably even at high operating cycles.
In such welding equipments with known stud holders with a collet made from steel or beryllium copper, at the required flexibility the collet is subject to extreme wear, particularly when the contact and clamping surfaces of the collet bear against sharp thread zones of the stud.
In stud welding according to the drawn arc principle, 3-5000 A are transmitted through the small contact points, which, upon release of the clamping force of the collet, leads to scorched areas. This reduces the reliability, which is essential particularly in assembly lines.
Moreover, problems arise from the formation of the previously-known welding studs in terms of a uniform welding connection between the sheet metal part and the stud, so that special measures for shaping of the welding surfaces are necessary. This applies also to the fasteners according to DE-B-2 227 384, in which either threaded studs or nuts are welded on as fasteners. Both these illustrated fasteners make particularly stringent demands on the collet of the welding equipment, which for this purpose must be specially designed.
There is in addition known from EP-A-406 459 a stud welding gun requiring stud holder tubes with a differing diameters, as well as plastics washer inserts, whereby the retaining tubes being subject to relatively heavy wear.
Finally, the design of the previously-known weld studs with a defined welding surface requires an arrangement for accurately positioned feeding of the weld studs.
Starting from this point, a further purpose of the invention is to propose a welding equipment in which the feeding system and the retaining part for the fastener can be considerably simplified, and ensures an optimum current flow between the retaining part and the fastener during the welding process. A welding equipment fulfilling this purpose is described in claims
14
-
16
.
The welding equipment claimed is characterised in that its holder has, instead of a flexible collet, a rigid tube, in which the fastener, designed as a flexible sleeve, is guided and embraced over a large area. In this way a large number of the movable parts of the welding equipment, which are liable to malfunction, are eliminated.
In known arrangements, the internal wall of the fastening bore of the assembly part which is to be assembled, mostly made from plastic material, usually has webs, which are uniformly distributed as stiff ribs. Assembling such a part on to a solid weldstud, which may be profiled, demands high push-on forces requiring high energy consumption and a stiff design, particularly with semi-automatic and automatic assembly tools.
Assembly parts are also known with locking protections which engage in a profiled portion on the weld stud; in this case, however, only little pull and shear forces are transmitted from the assembly point to the stud.
In the case also of a cylindrical bore in the assembly part, the assembly forces are higher by a multiple than in the assembly part with webs, yet here also contact is only established at points between the stud and the internal wall of the bore of the assembly part.
Starting from this point, a further purpose of the invention is to propose an arrangement for attaching an assembly part to a weld-on fastener which gives rise to considerable simplification of the mounting of the ass
Foley & Lardner
Johns Jonathan
Ryan Patrick
Splitfast Technologies Limited
LandOfFree
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