Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Including settable material
Reexamination Certificate
1999-10-26
2002-05-28
Saether, Flemming (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Including settable material
C411S172000, C052S708000, C052S787100
Reexamination Certificate
active
06394722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to an anti-distortion insert to provide threaded attachment to a panel. More specifically, the present invention is directed to an anti-distortion insert for threaded fastening of optical elements to a honeycomb panel.
2. Background Information
Elements of an optical system are often mounted together on a common flat panel. Threaded inserts are embedded in the panel at predetermined positions so that the optical elements may be bolted to the common flat panel in a straightforward manner.
Referring to
FIG. 1
, a cross-sectional view is shown of a threaded insert
10
that is bonded to a honeycomb panel
12
by epoxy resin
14
. The insert
10
is embedded all the way through the panel
12
. The threaded bore
16
of the insert
10
is useful for fastening elements of an optical system to the panel
12
.
Referring to
FIG. 2
, a cross-sectional view is shown of a threaded insert
18
that is embedded only partially through a honeycomb panel
20
. The insert
18
is bonded to the panel
20
by epoxy resin
22
. The threaded bore
24
of the insert
18
is useful for fastening elements of an optical system to the panel
20
.
Honeycomb panels (i.e., having a honeycomb core structure) have been developed that have very low thermal distortion properties in the lateral plane (i.e., the plane of the flat panel). As a result, the elements of the optical system that are affixed to a honeycomb panel maintain a consistent position and orientation in the lateral plane, despite temperature gradients that may develop across the honeycomb panel. However, thermal expansion and contraction in the transverse direction (i.e., perpendicular to the plane of the flat panel) remains a problem for honeycomb panels.
The amount of expansion or contraction of the panel per unit of temperature in the transverse direction is called the transverse (or “through-the-thickness”) Coefficient of Thermal Expansion. The transverse Coefficient of Thermal Expansion (CTE
TRANS
) of a honeycomb panel in the vicinity of a conventional bonded insert is primarily a function of the material forming the core of the panel, the material forming the insert, and the type and amount of the adhesive used to bond the insert to the panel. This may be expressed generally as
CTE
TRANS
~K
1
·CTE
PANEL
+K
2
·CTE
INSERT
+K
3
·CTE
BOND
(1)
where CTE
PANEL
is the coefficient of thermal expansion of the panel core material in the transverse direction, CTE
INSERT
is the coefficient of thermal expansion of the insert material, CTE
BOND
is the coefficient of thermal expansion of the material bonding the insert to the panel, and K
1
, K
2
, and K
3
are each constants.
For a conventional insert, the CTE
TRANS
at the insert can be substantial, causing the optical component mounted to the panel at that location to undergo an unacceptably high transverse deflection as a result of a temperature change.
To attempt to minimize CTE
TRANS
, it has been proposed to make the inserts of a material that has a low CTE and to increase the mass of the inserts. Although this would tend to lower the overall CTE
TRANS
, it is not an acceptable alternative for applications where minimizing weight is critical. The panel generally has dozens of inserts. Making substantial increases in the mass of each of the inserts would add up to a large mass increase in the aggregate. Such a large mass increase would be problematic, for example, in a spacecraft where mass must be minimized for launch.
It has also been proposed to manufacture the honeycomb panel using a graphite core with improved dimensional stability. However, this is not a satisfactory solution either, because (assuming a sufficiently stable graphite core could be discovered) the thermal dimension changes caused by the bonding material would still contribute to a CTE
TRANS
of substantial size.
Thus, what is needed is an insert, for use with honeycomb panels, which will isolate an optical component mounted thereon from thermal expansion and contraction of the honeycomb panel and any bonding material used to bond the insert to the panel.
Furthermore, even if an optical component could be perfectly isolated from the thermally induced dimension changes of the honeycomb panel and the bond material, this does not solve the entire problem. That is because the insert itself also expands and contracts as a function of temperature. Accordingly, the insert also contributes to CTE
TRANS
.
Thus, what is also needed is an insert that will compensate for its own thermal expansion and contraction, so as to minimize thermally-caused deflection of an optical component mounted thereon.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an interface point to a honeycomb panel that has a very low CTE
TRANS
irrespective of the CTE of the honeycomb panel in the transverse (through-the-thickness) direction.
It is also an object of the present invention to provide a honeycomb panel threaded insert that isolates an optical component mounted thereon from thermal expansion and contraction of the honeycomb panel and any bonding material used to bond the insert to the panel.
It is an additional object of the present invention to provide a threaded insert that compensates for its own thermal expansion and contraction, so as to minimize thermally-caused deflection of a component mounted thereon.
It is a further object of the present invention to provide a mounting panel for mounting components, wherein the attachment points for mounting have a very low CTE
TRANS
irrespective of the CTE of the mounting panel in the transverse (through-the-thickness) direction.
Some of the above objects are achieved by a fastener for providing isolation from thermal expansion and contraction. The fastener has a sleeve and a post. The sleeve has a positioning pad projecting from its interior surface. The post is attached to the inside of the sleeve and is axially positioned inside the sleeve by the positioning pad. The post is substantially isolated by the sleeve from thermal expansion and contraction external to the fastener.
Other of the above objects are accomplished by an insert for use with a honeycomb panel. The insert has a sleeve and a post. The sleeve has a positioning pad projecting from its interior surface. The post is attached to the inside of the sleeve and is axially positioned inside the sleeve by the positioning pad.
Another of the above objects is accomplished by mounting panel for mounting optical elements via threaded engagement. The mounting panel has a honeycomb panel with plural threaded inserts imbedded in the honeycomb panel at predetermined locations. The inserts each have a sleeve and a post. The sleeves each have a positioning pad projecting from their interior surfaces. The posts are attached to the inside of their respective sleeves and are axially positioned inside the sleeve by the positioning pad.
Some of the above objects of the present invention are also achieved by a one piece unitary insert for use with a honeycomb panel. The insert has a sleeve portion and a post portion. The post portion is surrounded by the sleeve portion and cantilevered with respect to the sleeve portion from a meeting point axially positioned inside the sleeve portion.
According to one embodiment of the present invention, the insert has two parts, a sleeve and a post that attaches to the inside of the sleeve. The exterior surface of the sleeve is bonded to the panel and has a positioning pad on its interior surface. The post has a threaded engagement with the sleeve, and is axially positioned inside the sleeve by the positioning pad.
According to another embodiment of the present invention, the insert is formed of a single piece having a sleeve portion and a post portion inside the sleeve portion. The exterior of the insert is bonded to the panel. The point at which the post portion and the sleeve portion meet is the meeting point. The meeting point location is selected so as to isolate the post portion from
Kunt Cengiz
Lee Chiachung
Roberts Abokhair and Mardula, LLC
Saether Flemming
Swales Aerospace
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