High pulling force fastener with bowable head

Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Having separate expander means – Including sleeve and distinct tapered expander

Reexamination Certificate

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Details

C411S055000, C411S173000, C411S183000

Reexamination Certificate

active

06299399

ABSTRACT:

FIELD OF THE INVENTION
This invention pertains fasteners, and more particularly fasteners which have expandable legs and which attach one object to another object.
BACKGROUND OF THE INVENTION
In the original conventional technology of fasteners employed to securely attach one object to another, such as for example one part to another in the case of an automobile or an appliance, has utilized a nut on one of the two objects, usually welded or glued to the back of said object, and a bolt passing through a hole on the second object in a manner to be engaged by the nut, thereby securing the two objects together.
This arrangement presents many problems, among which, one of the most important is that in the case that one object is hollow, the nut has to be in place at the back of the hollow object before assembling the two objects together. If for any reason the nut is misplaced, and/or if it becomes desirable to introduce a new fastening connection between the two objects, the task of achieving such connection becomes very difficult if not impossible for all practical purposes.
The so-called “quick nuts” have also been used to connect two objects. In addition, vibration during the operation of a device, such as an automobile or appliance for example, containing the two objects results very often in loosening of the bolt or “quick nut” and in either full disassembling of the objects from each other, or in a vibration noise which is most annoying and often of unacceptable levels. Further, such connections are not water-resistant and water may be easily penetrate the connection point and be transferred from one side of one or both objects to the other side.
Recently, fasteners of the type described in U.S. Pat. No. 4,500,238 (Vassiliou) have been utilized to reduce considerably the potential of bolt or screw loosening and vibration. They have also eliminated the problem of having to place one member of the fastener at the back portion of the hollow object. These fasteners are placed through a slot from the front part of the hollow object. An expanding member, being usually a bolt or a screw, supports the second object by forcing the legs of the fastener (as described for example in U.S. Pat. No. 4,500,238) to open or expand, thereby securing the two objects together. The fasteners of this type have greatly improved the prevailing torque (as defined hereinbelow), as well as the pulling force (as also defined hereinbelow) of the system. The legs of the fastener are supported by a head having an upper side and a lower side joined by side bents.
In the fasteners of the above type, when an increasingly higher force is applied on the screw to pull it away from the fastener, there is reached a value of the force (pulling force) at which failure (separation of the expanding member from the fastener or breaking a part of the fastener) occurs. The failure usually occurs at the side bents which join the upper side of the head of the fastener with the lower side. This failure is quite abrupt as the head of the fastener splits all of a sudden.
One major object of the instant invention is to provide fasteners which are characterized by highly increased pulling force combined with more gradual failure, among other advantages.
SUMMARY OF THE INVENTION
In the text describing and claiming the instant invention, the following comments and definitions are appropriate:
The expanding member is preferably a screw having threads and a root on which the threads are supported.
Prevailing torque is the torque required to render a screw loose.
Pulling force is the pulling force applied on the screw to the point of failure (usually failure occurs an the side bents that join the upper side of the head and the lower side of the head).
Critical hardness regarding fasteners of the instant invention is a hardness at or over which failure occurs without substantial permanent bowing of the head of the fastener, while under which hardness failure occurs with substantial permanent bowing of the head of the fastener.
Engageable hole or region is an at least partial hole or region which can be engaged with a screw, or similar element.
Pitch of a screw is defined as the distance between two consecutive threads of the screw.
Gap in the vicinity of a bent is equal to the diameter of a circle with the same radius as the radius of curvature of the inside portion of the bent, as illustrated in
FIG. 7
, and explained in more detail hereunder.
This invention pertains a sheet metal fastener, the sheet metal fastener having a first hardness and characterized by a critical hardness higher than the first hardness, the sheet metal fastener comprising:
(a) a substantially flat head portion having an upper side, and a lower side, the two sides joined through side bents and being separated by a gap, the upper side having a first hole engageable to an expanding member;
(b) a neck having an opening and two side neck portions, the neck extending from the lower side of the substantially flat head portion at a substantially right angle with respect to the substantially flat head portion; and
(c) two substantially flat legs extending from the neck, each leg having an inner surface, the two inner surfaces of the two legs being at an initial proximity with each other, the legs having a funnel configuration at a region where the legs start extending from the neck, the legs being expandable in opposite directions upon engaging to the first hole and inserting into the funnel configuration the expansion member;
the first hardness being adequately low to allow the head to permanently bow upon application of a pulling force to failure on the expanding member away from the fastener, but not lower than a hardness at which the force to failure is lower than a force to failure of the same fastener having the critical hardness.
The instant invention also pertains a vehicle comprising two parts connected with a sheet metal fastener, the sheet metal fastener having a first hardness and characterized by a critical hardness higher than the first hardness, the sheet metal fastener comprising:
(a) a substantially flat head portion having an upper side, and a lower side, the two sides joined through side bents and being separated by a gap, the upper side having a first hole engageable to an expanding member;
(b) a neck having an opening and two side neck portions, the neck extending from the lower side of the substantially flat head portion at a substantially right angle with respect to the substantially flat head portion; and
(c) two substantially flat legs extending from the neck, each leg having an inner surface, the two inner surfaces of the two legs being at an initial proximity with each other, the legs having a funnel configuration at a region where the legs start extending from the neck, the legs being expandable in opposite directions upon engaging to the first hole and inserting into the funnel configuration the expansion member;
the first hardness being adequately low to allow the head to permanently bow upon application of a pulling force to failure on the expanding member away from the fastener, but not lower than a hardness at which the force to failure is lower than a force to failure of the same fastener having the critical hardness.
It is preferable that the first hardness is in the range of 32 to 37 in the Rockwell C scale, and/or the critical hardness is in the range of 40 to 45 in the Rockwell C scale.
The sheet metal has preferably a thickness in the range of 0.2 to 1.2 mm, and it is highly preferable that the gap in the vicinity of the bents is greater than the thickness of the sheet metal.
The first engageable hole may have a round or an oblong shape. Fasteners having a round hole are well known to the art. Fasteners having a hole with an oblong shape are described in the provisional application of Joseph W. Lowry and Eustathios Vassiliou, titled “Extensive Engagement Fastener”, Ser. No. 60/171,544, filed on Dec. 22, 1999, which provisional application is incorporated herein by reference.
The expanding member may comprise threads, a root, a

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