Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Having separate expander means – Frangible member
Reexamination Certificate
2000-06-01
2001-10-09
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Having separate expander means
Frangible member
C411S042000, C411S070000
Reexamination Certificate
active
06299398
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a blind rivet, and more particularly to an improvement in the so-called ‘peel’ type blind rivet specially adapted for use to fasten a relatively soft article to a hard support or the like.
2. Prior Art
The blind rivet of the peel type is composed of a rivet body and a mandrel with a head, wherein radial blades are formed in and integral with the lower surface of this head. The rivet body comprises a cylindrical part that has at one of its opposite ends a flange-shaped head. In use, the mandrel inserted in the cylindrical part of the rivet body will be pulled strongly to such an extent that the blades cut deep into the other open end of said cylindrical part. A petal-shaped flare, that will thus be formed at that other end, consists of a plurality of severed feet protruding centrifugally so that these feet cooperate with the flange-shaped head to fasten a soft article onto a hard support (see for example the Japanese Laid-Open Patent No. 2-26305, ibid. 10-274220 and the Laid-Open Utility Model No. 5-36115).
In each of the prior art blind rivets of the described type, the mandrel head is of a diameter substantially equal to or slightly smaller than outer diameter of the cylindrical part of the rivet body. Therefore, effective cutting area defined as the diameter of a circumcircle surrounding the blades in the lower surface of mandrel head is noticeably smaller than said outer diameter of the cylindrical part. As a result, those blades are likely to fail to cut full thickness of peripheral wall at the open end of said cylindrical part. Thus, it has been difficult to cut the end wall into severed feet, and even if this were possible, those feet have tended to form a distorted or irregular flare at said end.
In the blind rivet disclosed in the Laid-Open Utility Model No. 5-36115, grooves are formed in the inner periphery of the rivet body's cylindrical part, at the open end thereof These grooves extending longitudinally of said part are weakened zones where the peripheral wall is rendered easy to break. However, such grooves are not only difficult to form, but also make it necessary for the mandrel's blades to be aligned with the respective grooves in the rivet body. Misalignment of the blades with the grooves will give rise to another problem that the cylindrical part's open end becomes more difficult to cut.
In the other prior art blind rivet shown in the Laid-Open Patent No. 2-26305, the peripheral wall of the open end is thinned for easier cutting with the blades. A petal-shaped flare, that may be formed in use in such a weakened region, will however probably fail to provide a sufficient fastening strength.
It is almost impossible to apply those prior art structures to blind rivets whose rivet bodies are made of an ordinary steel or a stainless steel, even if feasible for blind rivets of a much softer material such as aluminum alloys easy to cut.
SUMMARY OF THE INVENTION
An object of the present invention made in view of these inconveniences inherent in the prior art is therefore to provide a novel blind rivet of the peel type comprising a mandrel and a rivet body such that blades formed in a lower surface of a head of the mandrel can cut and expand centrifugally a cylindrical part of the rivet body at an open end thereof opposite to a flange-shaped head of said body, in a reliable and uniform manner without necessity of forming in an inner periphery of the open end such grooves as would be required in use to be set in alignment with the blades.
In order to achieve this object, a peel type blind rivet of the present invention comprises a rivet body composed of a cylindrical part and a flange-shaped head formed integral with one of opposite ends of said cylindrical part. The rivet further comprises a mandrel composed of a mandrel body and an enlarged mandrel head formed at one of opposite ends of the mandrel body that is shaped for insertion in the cylindrical part. A plurality of radial blades are formed in and integral with a lower surface of the enlarged head of the mandrel such that the other open end of the cylindrical part will be cut into radially protruding and petal-like split feet when the mandrel body is pulled in use of the blind rivet. The blind rivet of the invention is characterized in that the mandrel head is of a maximum diameter noticeably greater than an outer diameter of the rivet body's cylindrical part. The rivet is further characterized in that the mandrel head's lower surface increases its diameter gradually and upwards from an outer periphery of the mandrel body towards the mandrel head's rim having the maximum diameter. Each of the blades is of a V shape in cross section and protrudes downwards from the mandrel head's lower surface such that a cutting edge of each blade extends upwards and obliquely from the outer periphery of the mandrel body towards the mandrel head's rim having the maximum diameter. It is important to the blind rivet of the invention that a circumcircle of outer ends of the cutting edges is of a diameter substantially equal to or slightly greater than the outer diameter of the rivet body's cylindrical part.
Thus, the blind rivet provided herein does comprise those blades whose cutting edges have effective outer ends that define the circumcircle equal to or a little greater than the cylindrical part outer diameter of the rivet body. By virtue of this feature, those blade edges can fully act on the cylindrical part even to its outer peripheral face. This part's open end will surely be severed to form split feet that are then guided along the mandrel head lower surface increasing its diameter gradually and upwards so as to protrude radially and outwards to assume a petal-like shape.
REFERENCES:
patent: 3515028 (1970-06-01), Patton
patent: 4736560 (1988-04-01), Murphy
patent: 4904133 (1990-02-01), Wright
patent: 4909687 (1990-03-01), Bradley et al.
patent: 4969785 (1990-11-01), Wright
Antonelli Terry Stout & Kraus LLP
Wilson Neill
Yugenkaisha Shinjo Seisakusho
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