Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Threaded fastener locked to a discreet structure – Nut – and means to engage substructure on its opposite faces...
Reexamination Certificate
1998-09-08
2001-07-10
Browne, Lynne H. (Department: 3628)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Threaded fastener locked to a discreet structure
Nut, and means to engage substructure on its opposite faces...
C411S179000, C411S180000, C411S181000
Reexamination Certificate
active
06257814
ABSTRACT:
BACKGROUND
The present invention relates to self-attaching fasteners, a die button for use with such fasteners, a method of attaching such fasteners to a plate-like component, and the assembly which results after carrying out the method and the method of forming the improved self-attaching fasteners.
Fasteners of the general type having a hollow body or bore, such as for example internally threaded nuts are known from EP-A-0 553 822 A1 or from the corresponding US-A-5 340 251. Similar elements having hollow bodies are moreover known from US-A-3 234 987, from US-A-3 648 747 or from US-A-3 253 631.
All these known embodiments have a so-called pilot portion. That is to say that the groove or recess at the end face projecting toward the panel or part is restricted at the radially inner side by a projecting cylindrical pilot portion which extends at least substantially up to the end face.
Such fasteners are typically nut elements; however, for example they could have a cylindrical bore for receiving a spigot or the like. These fasteners offer relatively high security against rotation so that on screwing in a bolt element the fasteners remain firmly anchored to the component, and moreover have a relatively high resistance to push-out.
It has however been found that in operation with changing loads the fasteners sometimes tear out of the plate-like component which is normally made of sheet metal. Moreover the manufacture of such elements or fasteners having hollow bodies is relatively costly and a problem exists that the contact surface is frequently not adequate. Furthermore. the radial dimensions of the part engaging surface of the fastener make it necessary to use a relatively large washer at the bolt side in order to transmit the forces in the desired manner.
The undercut in the sidewall of the fastener recess which is necessary to generate the required press-out resistance of the hollow body, is normally generated in such a way that the hollow element is subjected to a squeezing process at the outer peripheral jacket with the sidewall of the recess being brought from an initially axial parallel position into an inclined position. This results in the opening to the recess between the pilot part and the now inclined sidewall to be smaller in comparison to the base surface of the recess. Additionally, as a result of this squeezing movement, the hollow element also has an inclined surface at the outer jacket surface adjacent to the end face engaging the component. On attachment to the plate-like component, the wedge-shaped contact surface, facing the plate-like component, is frequently so deformed that it acts in a knife-like manner under load and a high surface pressure results between the component and the hollow element.
As a result of this high surface pressure the plate-like component yields after a few operating hours and no longer sits as tightly as designed, so that the danger of settlement and of reduction of the preload to zero exists, and thus the danger of failure of the threaded connection.
SUMMARY OF THE INVENTION
The present invention is based on the object of providing a fastener which can be manufactured economically and ensures good security against twist-out, a reliable seat after attachment to the plate-like component, and retains a firm seat even with changing loads without being torn out of the plate-like component and without loosening the bolt element that is used. Another advantage is that the contact surface can be smaller in diameter in comparison to prior solutions but nevertheless of adequate size area-wise so that an undesired high surface pressure does not arise at the plate-like component.
In order to satisfy this object, provision is made in accordance with the invention for the base surface of the fastener recess to extend up to the passage of the bore at least substantially preferably without a pilot portion.
The pilot portion which played a central role with the previously mentioned nut elements during the deformation of the plate-like component into the recess may be omitted in the disclosed embodiment of this invention. In this way, the radial dimensions of the nut element can be reduced approximately by the wall thickness dimensions of the customary pilot portion, whereby the inner diameter of the contact surface is made substantially smaller in diameter. This however also offers the possibility of dimensioning the outer diameter of the contact surface in comparison to the inner diameter in such a way that the radial width of the contact surface is larger. In this way an enlarged ring surface is present in comparison to the known hollow elements and the surface pressure can be reduced in operation. As a result of the changed dimensions the necessity of using a washer at the bolt side can be avoided.
In order to use this element with a hollow body, a modification of the die button and of the setting head is necessary to satisfy the functions previously satisfied by the pilot portion. In the prior art, the pilot portion serves on the one hand as a hole punch in order to punch out a slug from the sheet metal part in cooperation with a die button. This punching function is now achieved by means of a hole punch which is coaxially guided in the setting head relative to the hollow element and which, during the closing movement of the setting head, moves through the bore of the hollow element and in cooperation with the die button, serves to punch out a slug.
A hole punch of this kind is known, for example from the German patent 34 46 978 or from DE-OS 38 35 566.3; however, the hole punch is used there with a differently shaped hollow element which, so to say, also has a pilot portion in the form of a so-called rivetting section. Accordingly the use of a hole punch with a nut element without a pilot portion is not believed to be obvious.
Another function of the pilot portion in the hollow element of the prior art lies in forming the metal of the sheet metal component into the undercut in order to generate the security against push-out and additionally also the security against twist-out. This function is also taken on by the die button of the present invention and solved differently than before.
To generate the security against twist-out for the hollow element of the present invention, a number of end face recesses are pressed into the contact surface. The die button for the insertion of the nut element has a plurality of noses which ensure that the material of the plate-like component is pressed onto at least one of the end face recesses and preferably into a plurality of the recesses and generates a resistance against rotation. By way of example, eight recesses can be provided in the contact surfaces and six noses on the die button whereby, independently of the respective rotational position of the fastener, at least one of the noses lies opposite a recess.
Through the use of a recess in the contact surface, undercuts are formed at the sidewall of the recess in the hollow element simultaneously with the forming of the recesses by pressing and indeed in the form of local bead-like deformations or rib portions of the sidewall or outer wall of the fastener recess. During the attachment process the sheet metal is pressed into the so formed undercuts which additionally ensures the required resistance to push-out and on the other hand however also forms an additional resistance against rotation.
Since the undercuts arise during the formation of the recess in the contact surface of the hollow element, and do not have to be generated by a squeezing movement at the jacket surface of the hollow element, the hollow element lacks the pronounced chamfer which arises with hollow elements in accordance with the initially named EP-A-0 553 822. This is however of advantage because it is then possible to form the transition from the contact surface into the jacket surface of the hollow element with only a small radius, for example of less than 0.5 mm, whereby the available surface of the contact surface is increased in comparison to the prior art.
In a second preferr
Browne Lynne H.
Conley Fredrick
Howard & Howard
Profil Verbindungstechnik & Co.
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