Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Headed fastener element – Having plastically flowable or deflectable end – e.g. – rivet,...
Reexamination Certificate
1999-07-16
2002-01-15
Browne, Lynne H. (Department: 3726)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Headed fastener element
Having plastically flowable or deflectable end, e.g., rivet,...
C403S332000, C029S525060, C029S524100, C029S432200
Reexamination Certificate
active
06338601
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a punch rivet with a cutting edge which is arranged on the end face of its rivet shank and is formed in the cutting region by an outer face extending parallel to the axis and a conical inner face of the rivet shank.
The invention also relates to a riveted joint produced with such a punch rivet, a tool suitable for this purpose and to a method of producing a riveted joint.
A punch rivet of the type described above is described and illustrated in DE-OS 43 33 052 and has, on its side remote from the cutting edge, that is its back, a plate-like countersunk head which closes the punch rivet with a plane lid on this side, the rim of the lid passing conically or in a rounded fashion into the outer face of the rivet shank on its side facing the cutting edge. The plane outer face of the lid is suitable for application of a ram during the riveting process which presses the punch rivet through the components to be riveted, the components facing the cutting edge, that is the upper components, being pierced by the punch rivet and the component remote from the cutting edge, that is the bottom component, receiving the cutting edge due to the effect of a cone which, as a projection of a die, is directed toward the hollow interior of the punch rivet and widens the cutting edge radially outwardly when the cutting edge penetrates the bottom component without the bottom component being pierced.
DE-PS 39 42 482 describes a similar design with a head which is rounded in the manner of a tallow-drop screw. The known design dealt with above is also disclosed in DE-OS 44 31 769 which explains the requirements of the punch rivet material, which are that the punch rivet must have the necessary hardness in the cutting edge region for punching through the upper components, but be highly deformable in the shank region in order to widen the rivet shank radially outwardly within the bottom component in the cutting edge region and therefore to effect riveting. The state of the art showing punch rivets with a covering head is extensive.
DE-PS 28 39 838 describes a fundamentally different design of a punch rivet which consists of a round, axially symmetrical, solid body terminated on both sides by a plane radial end face. The corner which is right-angled in cross section and with which the radial end faces pass into a relatively narrow cylindrical annular face serves as a cutting edge in this punch rivet. To rivet two superimposed metal sheets, the punch rivet is pressed through the sheets, the two sheets being punched without the punch rivet being deformed. Riveting is effected in that, after punching, the sheets are pressed together by the punch rivet held in the punched holes, are deformed radially inwardly owing to an indentation formed between the end faces of the punch rivet and penetrate into the indentation, the punch rivet being held by the sheets and securing them with its indentation. Apart from the fact that this punch rivet is based on a fundamentally different principle from the punch rivet described at the outset, as it is not deformed during production of a riveted joint, the known solid punch rivet with its indentation can exert only relatively low holding forces on the two superimposed sheets as the punch rivet allows only a relatively slight, radially inwardly directed deformation of the sheets into the indentation, so a riveted joint withstanding considerable forces cannot be produced with this known punch rivet.
Reference is finally made to a riveted joint which is disclosed in PCT specification WO 93/10925 and is based on the principle of pressing two superimposed sheets together with a ram into a die such that a common material eyelet with outward radial widening is produced without the sheets being punched. The ram attenuates the sheet material which expands radially in the process, an undercut in the die ensuring that one sheet is pressed into the undercut, the other sheet following this undercut and therefore being riveted to the other sheet. A sleeve which surrounds the ram and presses the sheets into the die with the ram can remain in the hollowed eyelet in order to stabilise it. The sleeve has, on its back, a narrow head which is obviously to increase the strength of the riveted joint. As the above-described riveted joint is based on the riveting of the two plates at the base of the passage, so that production of the riveted joint is not dependent on genuine punching of at least one sheet and pronounced deformation of the punch rivet, this known method of producing a riveted joint does not provide any starting point for the design of a punch rivet with which genuine punching and deformation of the punch rivet are effected during riveting.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a punch rivet which has a particularly simple design eminently suitable for mass production and can advantageously be worked so as to produce stable, heavy-duty riveted joints.
The present invention provides a punch rivet with a cutting edge which is arranged on the end face of its rivet shank and is formed in the cutting region by an outer face extending parallel to the axis and a conical inner face of the rivet shank, characterised in that the outer face extends continuously parallel to the axis over the entire rivet shank and the punch rivet is provided with the same cutting edges on either side in an axially symmetrical design in the form of a tube.
The punch rivet according to the invention requires a smaller clinching force than a punch rivet having a lid-like head on the side remote from the cutting edge. This head prevents the respective side of the punch rivet from expanding when pressed onto the top component. For the punch rivet to act as a solid abutment with its head designed as a lid, it has to be pressed into the surface of the top component and this demands considerable forces. With the punch rivet according to the invention, on the other hand, which receives the punching pressure on its back, it is possible for the tubular punch rivet to expand radially on this side owing to the absence of a lid so it effectively claws in the top component and only has to be deformed by it to the extent of widening. Widening of the punch rivet on the side which receives the punching pressure is therefore particularly advantageous for processing of the punch rivet. During this widening of the back of the punch rivet, completely mutually adapted deformation of the respective part of the punch rivet and of the material of the top component occurs as the respective part of the punch rivet pushes the material of the top component forward to a certain extent during this deformation, producing an intimate connection between the respective part of the punch rivet and the top sheet metal part at this point. This considerably increases the strength of the riveted joint. The punch rivet is also distinguished in that, owing to its axially symmetrical design, its position does not have to be checked with respect to front and back, in particular during automatic supply to a processing station. During the riveting process, each side of the punch rivet can be used as its front, that is the side performing the punching process. This automatically also allows particularly simple production of the punch rivet as special features on either side do not have to be allowed for. Owing to its tubular symmetrical design, it can receive a punched out piece from either side. The design of the punch rivet with a cutting edge also on the back of the punch rivet where it is pressed against the components to be riveted by means of a tool affords the further advantage that the inner face which is also conical on this side of the punch rivet simplifies central introduction of a punching tool and simplifies the expansion thereof which occurs during the riveting process, owing to the material attenuation there. This part of the punch rivet is then placed on the material of the component to be riveted, smoothly with a uniform transition owing to the conicity of its
Mauer Dieter
Opper Reinhold
Volnhals Robert
Browne Lynne H.
Emhart Inc.
Malcolm Tomlyne A
Murphy Edward D.
LandOfFree
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