Title of Invention	" A CAPTIVE CLINCH NUT FOR ROTATABLE ATTACHMENT TO AN APERTURED SHEET"
Abstract	The invention relates to a captive clinch nut for rotatable attachment to an apertured sheet, comprising: a nut body (2) having an axial threaded bore (7); a first bearing surface (11) of reduced friction on a bottom side of said nut body (2); a displacer (5) unitary with said nut body (2) and located directly below said bearing surface (11), the displacer (5) having an outside diameter less than an outside diameter of said flange (3); a tubular flared shank (8) unitary with said nut body (2) and coaxially extending from said displacer (5); and characterized in that a neck of said shank (8) immediately adjacent said displacer (5) comprises an outside diameter less than the outside diameter of said displacer (5) forming an undercut area (6) between the outside of said shank (8) and an underside of said displacer (5) for receiving the cold flow of metal of a sheet (9).

Title of Invention

" A CAPTIVE CLINCH NUT FOR ROTATABLE ATTACHMENT TO AN APERTURED SHEET"

Abstract

The invention relates to a captive clinch nut for rotatable attachment to an apertured sheet, comprising: a nut body (2) having an axial threaded bore (7); a first bearing surface (11) of reduced friction on a bottom side of said nut body (2); a displacer (5) unitary with said nut body (2) and located directly below said bearing surface (11), the displacer (5) having an outside diameter less than an outside diameter of said flange (3); a tubular flared shank (8) unitary with said nut body (2) and coaxially extending from said displacer (5); and characterized in that a neck of said shank (8) immediately adjacent said displacer (5) comprises an outside diameter less than the outside diameter of said displacer (5) forming an undercut area (6) between the outside of said shank (8) and an underside of said displacer (5) for receiving the cold flow of metal of a sheet (9).

Full Text	FIELD OF THE INVENTION The present invention relates to fasteners which are captivated in a sheet of material yet are free to rotate so that they may engage another member. More specifically, it relates to a tool- rotatable captivated fastener which is captivated by a sheet of metal which is deformed during the clinch attachment process. BACKGROUND OF THE INVENTION There is a need in the fastening industry for a nut that is captive similar to existing clinch nuts, but may still be turned to engage a screw or bolt to provide a clamp load. In one case, this is needed so that a captive and stationary stud can be used in conjunction with a captive nut. This allows both mating components, the stud and the nut, to be captive in a sheet. The benefit of the captive components include elimination of loose hardware, reduction of BOM inventories, ease of manufacturing and assembly and cost reductions. It is known to provide a captive rotatable nut in a sheet by flaring the shank of the nut within a washer on the opposite side of the sheet as shown for example in U.S. Patent 6,866,456. This configuration, however, requires a specialized anvil to be located on the opposite side of the sheet and a clamp load cannot be applied directly to the back side of the sheet because of the presence of the washer. Also, simple stake nuts are known that include an extending shank which is deformed against the back side of the sheet. This also requires a second installation component, i.e. an anvil, and does not provide a flush attachment. The present invention solves the problems posed by these undesirable characteristics of the prior art. SUMMARY OF THE INVENTION The device is a clinching nut without an anti-torque feature unlike the prior art which includes sheet-gripping structures to provide rigid attachment. The shank of the clinch nut includes a displacer and an undercut, but no anti-torque features such as knurl-type serrations are included. In this regard, a smooth surfaced shank extends from a flange of the nut. The flange provides a bearing surface that is free of projections and irregularities that could impair the rotation of the nut or disturb the surface of the substrate. The head of the nut may be of any shape. A hex is recommended as a convenient nut shape because of the commonality of the design. A standard hex shape above the flange allows common wrenches and sockets to engage and turn the nut, however other shapes may also be applied. For example a circle with two flats, an acorn nut, or a more exotic shape could be utilized. The height of the head should be sufficient to provide the desired nut strength. Material choice of the nut is important for the design to function correctly. Because the part must clinch, the hardness of the part must be sufficient to cause yielding of the substrate panel. These issues are common with other clinching fasteners and should be apparent to one skilled in the art. More specifically, the applicant has devised a captive clinch nut for rotatable attachment to an apertured sheet comprising a nut body having an axial threaded bore, and a flange forming a base of the nut body. The flange includes a surface on a bottom side thereof preferably unitary therewith for providing a bearing surface of reduced friction against the sheet. A displacer unitary with the nut body is located directly below the flange and has an outside diameter less than an outside diameter of the flange. A tubular flared shank unitary with the nut body extends coaxially from the displacer, and includes a neck immediately adjacent the displacer with an outside diameter less than the outside diameter of the displacer forming an undercut area between the outside of the shank and an underside of the displacer for receiving the cold flow of metal of the sheet. The outer surfaces of the displacer and the shank are of reduced friction for providing a bearing surfaceof the nut against the inside wall of the aperture in the sheet. The side surface of the displacer is preferably tapered inwardly. The captive nut is used with a sheet wherein the displacer and shank of the nut body are located within the sheet and are coaxial with the aperture such that a portion of the sheet lies within an undercut area located between the bottom of the displacer and the outside surface of the shank. A space between the outside surfaces of the displacer and the flange and an inside wall of the sheet aperture is such that the nut is freely rotatable within the sheet while being secured against substantial axial displacement therefrom. Preferably, the width of the displacer and the length of the shank are less than the thickness of the sheet such that the shank does not extend beyond a back side surface of the sheet. The nut is used with a relatively ductile sheet material such that the flange remains relatively non-deformable and is composed of a material having a hardness substantially greater than that of the sheet. From the following drawings and description of the preferred embodiment, it will be appreciated by those of skill in the art that the objects of the invention have been achieved. While the present invention will be described with the reference to a specific embodiment, the following description is illustrative of the invention and is not to be construed as limiting the invention.Various modifications to the present invention can be made to the preferred embodiment by those skilled in the art without departing from the true spirit and scope of the invention. It will be noted here that for better understanding like components are designated by the reference numerals throughout the various figures of drawing which follow. DESCRIPTION OF THE DRAWINGS Figure 1 is a front view of the invention. Figure 2 is a bottom isometric view. Figure 3 is an elevation partial section view. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to Figure 1, the fastener of the invention is in the form of a nut including a head 1 which includes tool-engaging flats 2 for applying a rotational torque to the nut. A hexagonal configuration is preferred for the tool-engaging surfaces. The nut further includes a flange 3 which has a smooth bottom face 11 which serves as a first bearing surface against a sheet (shown in Figure 3) into which the nut is installed. The nut is installed by the clinch process in which a lower shank portion 8 is provided with a displacer 5 and an undercut 6. The displacer is tapered inwardly. The shank of the nut is placed through an aperture in the sheet, and when the nut is pressed into a sheet of sufficiently ductile material, the displacer forces a cold flow of sheet material into the undercut area 6, thus attaching the nut to the sheet. As shown in Figure 2, undercut feature 6 which begins at a neck of said shank lies immediately below said displacer 5. Internal threads of the nut 7 extend the entire length of the nut. Tubular shank 8 and the outer surface of displacer 5 are smooth surfaced and are of reduced friction to enhance their function as bearing surfaces in addition to the bottom face 11 of the nut flange 3. Referring now to Figure 3, the nut is installed in a sheet 9 which has an aperture diameter and thickness sized in relation to the dimensions of the nut shown in Figures 1 and 2 such that the cold flow of metal of the sheet is not tightly compressed against the outer surfaces of the displacer or the flange. Space 10 between the sheet and the nut enables the nut to freely rotate within the sheet 9 while providing significant pull-out resistance due to the cold flow of material of the sheet located within the undercut area between the flared shank 8 and the displacer 5. Bottom face 11 of flange 3 bears against the top surface of sheet 9 and surface 11 is a smooth surface of reduced friction to enhance its performance. It should be understood that there may be other modifications and changes to the present invention that will be obvious to those of skill in the art from the foregoing description, however, the present invention should be limited only by the following claims and their legal equivalents. WE CLAIM : 1. A captive clinch nut for rotatable attachment to an apertured sheet, comprising: - a nut body (2) having an axial threaded bore (7); - a first bearing surface (11) of reduced friction on a bottom side of said nut body (2); - a displacer (5) unitary with said nut body (2) and located directly below said bearing surface (11), the displacer (5) having an outside diameter less than an outside diameter of said flange (3); - a tubular flared shank (8) unitary with said nut body (2) and coaxially extending from said displacer (5); and - characterized that a neck of said shank (8) immediately adjacent said displacer (5) comprises an outside diameter less than the outside diameter of said displacer (5) forming an undercut area (6) between the outside of said shank (8) and an underside of said displacer (5) for receiving the cold flow of metal of a sheet (9). 2. The clinch nut as claimed in claim 1 comprising a flange (3) forming a base of said nut body. 3. The clinch nut as claimed in claim 2 comprising a head portion (1) having tool-engaging flats on its outer surface. 4. The clinch nut as claimed in claim 3 wherein said head (1) is of hexagonal cross- section. 5. The clinch nut as claimed in claim 4, wherein said threaded bore extends through the entire length of the nut (2). 6. The clinch nut as claimed in claim 1 wherein the outer surfaces of said displacer (5) and said shank (8) are of reduced friction for providing bearing surfaces (11,13) of said nut (2) against said sheet (9). 7. The clinch nut as claimed in claim 1 wherein said first bearing surface (11) is integral with said nut body (2). 8. The clinch nut as claimed claim 1 wherein the displacer (5) is tapered inwardly. 9. A tool rotatable device comprising a clinch nut having a flange, and a sheet (9) having an aperture formed therein, a displacer (5) and a shank (8) of said clinch nut being located within said sheet (9) and being coaxial with said aperture such that a portion of said sheet (9) lies within an undercut area (6) located between the bottom of said displacer (5) and the outside surface of said shank; (8) and a space (10) between outside surfaces of said displacer (5) and said flange (3) and an inside wall of said sheet aperture such that the nut (2) is freely rotatable within said sheet (9) while being secured against substantial axial displacement therefrom. 10. The device as claimed in claim 9, wherein the width of said displacer (5) and the length of said shank (8) are less than the said sheet (9) such that said shank (8) does not extend beyond a back side surface of said sheet.(9). 11. The device as claimed in claim 10 wherein said nut (1) is composed of a material having a hardness substantially greater than said sheet. 12. The device as claimed in claim 11 wherein said flange (3) is relatively non-deformable. 13. The device as claimed in claim 12 wherein the portion of said sheet (9) which lies within said undercut area (6) is received therein by the cold flow of metal of said sheet (9). The invention relates to a captive clinch nut for rotatable attachment to an apertured sheet, comprising: a nut body (2) having an axial threaded bore (7); a first bearing surface (11) of reduced friction on a bottom side of said nut body (2); a displacer (5) unitary with said nut body (2) and located directly below said bearing surface (11), the displacer (5) having an outside diameter less than an outside diameter of said flange (3); a tubular flared shank (8) unitary with said nut body (2) and coaxially extending from said displacer (5); and characterized in that a neck of said shank (8) immediately adjacent said displacer (5) comprises an outside diameter less than the outside diameter of said displacer (5) forming an undercut area (6) between the outside of said shank (8) and an underside of said displacer (5) for receiving the cold flow of metal of a sheet (9).

Full Text

FIELD OF THE INVENTION
The present invention relates to fasteners which are captivated in a sheet of
material yet are free to rotate so that they may engage another member. More
specifically, it relates to a tool- rotatable captivated fastener which is captivated
by a sheet of metal which is deformed during the clinch attachment process.
BACKGROUND OF THE INVENTION
There is a need in the fastening industry for a nut that is captive similar to
existing clinch nuts, but may still be turned to engage a screw or bolt to provide
a clamp load. In one case, this is needed so that a captive and stationary stud
can be used in conjunction with a captive nut. This allows both mating
components, the stud and the nut, to be captive in a sheet. The benefit of the
captive components include elimination of loose hardware, reduction of BOM
inventories, ease of manufacturing and assembly and cost reductions.
It is known to provide a captive rotatable nut in a sheet by flaring the shank of
the nut within a washer on the opposite side of the sheet as shown for example
in U.S. Patent 6,866,456. This configuration, however, requires a specialized
anvil to be located on the opposite side of the sheet and a clamp load cannot be
applied directly to the back side of the sheet because of the presence of the
washer. Also, simple stake nuts are known that include an extending shank
which is deformed against the back side of the sheet. This also requires a second
installation component, i.e. an anvil, and does not provide a flush attachment.
The present invention solves the problems posed by these undesirable
characteristics of the prior art.

SUMMARY OF THE INVENTION
The device is a clinching nut without an anti-torque feature unlike the prior art
which includes sheet-gripping structures to provide rigid attachment. The shank
of the clinch nut includes a displacer and an undercut, but no anti-torque
features such as knurl-type serrations are included. In this regard, a smooth
surfaced shank extends from a flange of the nut. The flange provides a bearing
surface that is free of projections and irregularities that could impair the rotation
of the nut or disturb the surface of the substrate. The head of the nut may be of
any shape. A hex is recommended as a convenient nut shape because of the
commonality of the design. A standard hex shape above the flange allows
common wrenches and sockets to engage and turn the nut, however other
shapes may also be applied. For example a circle with two flats, an acorn nut, or
a more exotic shape could be utilized. The height of the head should be
sufficient to provide the desired nut strength. Material choice of the nut is
important for the design to function correctly. Because the part must clinch, the
hardness of the part must be sufficient to cause yielding of the substrate panel.
These issues are common with other clinching fasteners and should be apparent
to one skilled in the art.
More specifically, the applicant has devised a captive clinch nut for
rotatable attachment to an apertured sheet comprising a nut body having an
axial threaded bore, and a flange forming a base of the nut body. The flange
includes a surface on a bottom side thereof preferably unitary therewith for
providing a bearing surface of reduced friction against the sheet. A displacer
unitary with the nut body is located directly below the flange and has an outside
diameter less than an outside diameter of the flange. A tubular flared shank
unitary with the nut body extends coaxially from the displacer, and includes a
neck immediately adjacent the displacer with an outside diameter less than the

outside diameter of the displacer forming an undercut area between the outside
of the shank and an underside of the displacer for receiving the cold flow of
metal of the sheet. The outer surfaces of the displacer and the shank are of
reduced friction for providing a bearing surfaceof the nut against the inside wall
of the aperture in the sheet. The side surface of the displacer is preferably
tapered inwardly. The captive nut is used with a sheet wherein the displacer and
shank of the nut body are located within the sheet and are coaxial with the
aperture such that a portion of the sheet lies within an undercut
area located between the bottom of the displacer and the outside surface of the
shank. A space between the outside surfaces of the displacer and the flange and
an inside wall of the sheet aperture is such that the nut is freely rotatable within
the sheet while being secured against substantial axial displacement therefrom.
Preferably, the width of the displacer and the length of the shank are less than
the thickness of the sheet such that the shank does not extend beyond a back
side surface of the sheet. The nut is used with a relatively ductile sheet material
such that the flange remains relatively non-deformable and is composed of a
material having a hardness substantially greater than that of the sheet. From
the following drawings and description of the preferred embodiment, it will be
appreciated by those of skill in the art that the objects of the invention have
been achieved. While the present invention will be described with the reference
to a specific embodiment, the following description is illustrative of the invention
and is not to be construed as limiting the invention.Various
modifications to the present invention can be made to the preferred embodiment
by those skilled in the art without departing from the true spirit and scope of the
invention. It will be noted here that for better understanding like components are
designated by the reference numerals throughout the various figures of drawing
which follow.

DESCRIPTION OF THE DRAWINGS
Figure 1 is a front view of the invention.
Figure 2 is a bottom isometric view.
Figure 3 is an elevation partial section view.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figure 1, the fastener of the invention is in the form of a nut
including a head 1 which includes tool-engaging flats 2 for applying a rotational
torque to the nut. A hexagonal configuration is preferred for the tool-engaging
surfaces. The nut further includes a flange 3 which has a smooth bottom face 11
which serves as a first bearing surface against a sheet (shown in Figure 3) into
which the nut is installed. The nut is installed by the clinch process in which a
lower shank portion 8 is provided with a displacer 5 and an undercut 6. The
displacer is tapered inwardly. The shank of the nut is placed through an aperture
in the sheet, and when the nut is pressed into a sheet of sufficiently ductile
material, the displacer forces a cold flow of sheet material into the undercut
area 6, thus attaching the nut to the sheet.
As shown in Figure 2, undercut feature 6 which begins at a neck of said shank
lies immediately below said displacer 5. Internal threads of the nut 7 extend the
entire length of the nut. Tubular shank 8 and the outer surface of displacer 5 are
smooth surfaced and are of reduced friction to enhance their function as bearing
surfaces in addition to the bottom face 11 of the nut flange 3.
Referring now to Figure 3, the nut is installed in a sheet 9 which has an aperture
diameter and thickness sized in relation to the dimensions of the nut shown in
Figures 1 and 2 such that the cold flow of metal of the sheet is not tightly

compressed against the outer surfaces of the displacer or the flange. Space 10
between the sheet and the nut enables the nut to freely rotate within the sheet 9
while providing significant pull-out resistance due to the cold flow of material of
the sheet located within the undercut area between the flared shank 8 and the
displacer 5. Bottom face 11 of flange 3 bears against the top surface of sheet 9
and surface 11 is a smooth surface of reduced friction to enhance its
performance.
It should be understood that there may be other modifications and changes to
the present invention that will be obvious to those of skill in the art from the
foregoing description, however, the present invention should be limited only by
the following claims and their legal equivalents.

WE CLAIM :
1. A captive clinch nut for rotatable attachment to an apertured sheet,
comprising:
- a nut body (2) having an axial threaded bore (7);
- a first bearing surface (11) of reduced friction on a bottom side of said
nut body (2);
- a displacer (5) unitary with said nut body (2) and located directly below
said bearing surface (11), the displacer (5) having an outside diameter
less than an outside diameter of said flange (3);
- a tubular flared shank (8) unitary with said nut body (2) and coaxially
extending from said displacer (5); and
- characterized that a neck of said shank (8) immediately adjacent said
displacer (5) comprises an outside diameter less than the outside
diameter of said displacer (5) forming an undercut area (6) between the
outside of said shank (8) and an underside of said displacer (5) for
receiving the cold flow of metal of a sheet (9).

2. The clinch nut as claimed in claim 1 comprising a flange (3) forming a
base of said nut body.
3. The clinch nut as claimed in claim 2 comprising a head portion (1) having
tool-engaging flats on its outer surface.

4. The clinch nut as claimed in claim 3 wherein said head (1) is of hexagonal
cross- section.
5. The clinch nut as claimed in claim 4, wherein said threaded bore extends
through the entire length of the nut (2).
6. The clinch nut as claimed in claim 1 wherein the outer surfaces of said
displacer (5) and said shank (8) are of reduced friction for providing
bearing surfaces (11,13) of said nut (2) against said sheet (9).
7. The clinch nut as claimed in claim 1 wherein said first bearing surface (11)
is integral with said nut body (2).
8. The clinch nut as claimed claim 1 wherein the displacer (5) is tapered
inwardly.
9. A tool rotatable device comprising a clinch nut having a flange, and a sheet
(9) having an aperture formed therein, a displacer (5) and a shank (8)
of said clinch nut being located within said sheet (9) and being coaxial with
said aperture such that a portion of said sheet (9) lies within an undercut
area (6) located between the bottom of said displacer (5) and the outside
surface of said shank; (8) and a space (10) between outside surfaces of
said displacer (5) and said flange (3) and an inside wall of said sheet
aperture such that the nut (2) is freely rotatable within
said sheet (9) while being secured against substantial axial displacement
therefrom.

10. The device as claimed in claim 9, wherein the width of said displacer (5)
and the length of said shank (8) are less than the said sheet (9) such that
said shank (8) does not extend beyond a back side surface of said sheet.(9).
11. The device as claimed in claim 10 wherein said nut (1) is composed of a
material having a hardness substantially greater than said sheet.
12. The device as claimed in claim 11 wherein said flange (3) is relatively
non-deformable.
13. The device as claimed in claim 12 wherein the portion of said sheet (9)
which lies within said undercut area (6) is received therein by the cold flow of
metal of said sheet (9).

The invention relates to a captive clinch nut for rotatable attachment to an
apertured sheet, comprising: a nut body (2) having an axial threaded bore (7);
a first bearing surface (11) of reduced friction on a bottom side of said nut body
(2); a displacer (5) unitary with said nut body (2) and located directly below said
bearing surface (11), the displacer (5) having an outside diameter less than an
outside diameter of said flange (3); a tubular flared shank (8) unitary with said
nut body (2) and coaxially extending from said displacer (5); and characterized
in that a neck of said shank (8) immediately adjacent said displacer (5)
comprises an outside diameter less than the outside diameter of said displacer
(5) forming an undercut area (6) between the outside of said shank (8) and an
underside of said displacer (5) for receiving the cold flow of metal of a sheet (9).

" A CAPTIVE CLINCH NUT FOR ROTATABLE ATTACHMENT TO AN APERTURED SHEET"

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