Patent Description:
Current installation of EME protection seal caps, which cover an end portion of a fastener extending from a surface within an aircraft, requires much time, labor and cost and experiences a high rate of defective installations. Defective installation of an EME protection seal cap requires re-installation of the defectively installed protection seal cap whether during fabrication of the aircraft or during in-service maintenance of the aircraft. Since select aircraft utilize potentially thousands of EME protection seal caps, savings on installation and improvement on quality installations are of high value.

Regardless of fabrication of the aircraft or in-service maintenance of the aircraft, the EME protection seal caps will be inspected and if determined to not meet specifications, the EME protection seal caps will be scraped off and replaced. The replacement of the protection seal caps for in-service maintenance, which occur in the field, will experience installation of the protection seal caps within confined space within the aircraft in contrast to a controlled environment of a factory at time of fabrication of the aircraft. The installation of the EME protection seal cap requires the installer to hold the protection seal cap in place on a structure of the aircraft for approximately a minute while sealant, used in the installation of the protection seal cap, decompresses under the protection seal cap.

Without holding the protection seal cap in place during decompression of the sealant, the decompression of the sealant will cause liftoff of the protection seal cap with respect to the surface of the structure to which the protection seal cap is being secured. Liftoff of the protection seal cap is unacceptable and requires re-installation of the protection seal cap resulting in additional labor and cost.

There is a need to improve on the time expended for installation of protection seal caps including reducing the number of quality defects, which require re-installation of the protection seal cap. There is also a need to reduce the effort expended by the installer with respect to holding the protection seal cap during application of sealant and during decompression of the sealant, particularly in confined locations and also where installation orientations provide gravity challenges with respect to maintaining the protection seal cap in a desired position. In addition, there is a need to install a protection seal cap at the time of in-service maintenance wherein removal of all of the old sealant from the fastener is not required.

<CIT> mentions, in its abstract, that "The present application relates to a cap for forming a sealed cavity around an end of a fastener protruding from a surface of a structure. In particular, the application relates to a spark prevention cap. The cap has an annular base with an annular base terminating at a base rim. The base rim surrounds an opening into a central cavity for receiving the end of the fastener. The base rim lies in a base rim plane around at least a majority of a circumference of the annular base. An annular skirt provides an annular pocket in which a sealant material is received. A biasing configuration is configured to positively bias the base rim against the surface of the structure".

<CIT> mentions, in its abstract, that "A cap is disclosed having a collar portion with three or more contact regions arranged to contact the end of a fastener around which the collar portion is provided, the collar portion having a lobed shape in cross-section such that an outwardly projecting lobe extends between each neighbouring pair of contact regions. An advantage of this lobed arrangement is that the cap can tolerate relatively large manufacturing tolerances at the fastener end. The cap may be for fitting over a nut or fastener head, with the contact regions of the cap being arranged to contact corresponding contact regions on a cylindrical collar base portion of the nut or fastener head. The diameter of this cylindrical collar portion may not be well controlled, so that the manufacturing tolerance is high. The lobed shape of the cap base ensures that the contact regions will always provide a good frictional engagement with the nut, whether the cylindrical collar is undersized, oversized, or at its nominal diameter".

<CIT> mentions, in its abstract, "A cap (<NUM>) and a method of installing the cap to form a sealed cavity (<NUM>)around an end of a fastener (<NUM>, <NUM>, <NUM>), which passes through a structure (<NUM>). The cap (<NUM>) comprises a body portion forming a central cavity (<NUM>) and a circular cylindrical base (<NUM>), and an annular flange (<NUM>) which extends outwardly from the body portion. The body portion is deformable between a first configuration in which the annular flange (<NUM>) is inclined upwardly, and a second configuration in which the annular flange (<NUM>) is inclined downwardly. The method comprises: applying a quantity of sealant (<NUM>) to the annular flange (<NUM>) in the first configuration; fitting the cap (<NUM>) over the end of the fastener so that the fastener is enclosed by the cap; and turning down the annular flange (<NUM>) such that the cap assumes the second configuration in which an annular pocket (<NUM>) is formed between the flange (<NUM>) and the base (<NUM>), and the sealant material (<NUM>) fills the annular pocket (<NUM>); and bonding the cap (<NUM>) to the structure (<NUM>) with the sealant material (<NUM>)".

<CIT> describes a cap for forming a sealed cavity around an end of a fastener. The cap has a cap body with an annular base terminating at an inner cap rim which surrounds an opening into a central cavity and lies in an inner cap plane around a majority of a circumference of the annular base. A skirt provides an annular pocket between the skirt and the annular base. The skirt has a first part which is integrally formed with the cap body from a first material and terminates at an edge, and a second part which is formed from a second material and extends from the edge of the first part of the skirt to a skirt rim which lies in or below the inner cap plane around a majority of a circumference of the skirt. The second part of the skirt is attached to the edge of the first part of the skirt by a joint comprising a male part received in an annular groove which runs round the circumference of the skirt. The first material has a first elastic modulus and the second material has a second elastic modulus which is lower than the first elastic modulus. An inlet hole in the skirt is in fluid communication with the annular pocket to permit a flow of sealing material through the skirt via the inlet hole into the annular pocket. The skirt forms a continuous annular wall with no holes through the annular skirt in fluid communication with the annular pocket other than the inlet hole. In one embodiment the second part of the skirt has a length between the edge of the first part and the skirt rim which varies around the circumference of the skirt.

In a first aspect there is provided a fastener which extends from a structure and a protection seal cap as defined in claim <NUM> of the appended claims. In a second aspect there is provided a method as defined in appended claim <NUM>.

In referring to <FIG> and <FIG>, protection seal cap <NUM>, for enclosing an end portion <NUM> of fastener <NUM> extending from structure <NUM> includes cap member <NUM>. Cap member <NUM> includes sidewall <NUM>, which defines interior space <NUM> within cap member <NUM>. Sidewall <NUM> forms continuous wall member <NUM>, as seen in <FIG>, which defines opening <NUM> providing access to interior space <NUM>. Continuous wall member <NUM> is configured to create an interference compression fit between end portion <NUM> of fastener <NUM> and continuous wall member <NUM>.

With respect to discussion related to continuous wall member <NUM>, continuous wall member is designated as <NUM> in a non-deformed condition, as seen in <FIG>, and will be referred to as <NUM>' with continuous wall member being in a deformed condition by way of an interference compression fit between the continuous wall member and end portion <NUM> of fastener <NUM>, as seen in <FIG>. With respect to continuous wall member <NUM>', sidewall <NUM>, as seen in <FIG>, has a width dimension D greater than first width dimension D1 of continuous wall member <NUM>'. Continuous wall member <NUM>' extends in direction <NUM> away from sidewall <NUM> of cap member <NUM>. Continuous wall member <NUM> has first end surface <NUM>, as seen in <FIG>. First end surface <NUM> of continuous wall member <NUM> is positioned within first plane P1, as seen in <FIG> wherein first plane P1 is shown as a line designated as P1 and is aligned along first end surface <NUM> representing first end surface <NUM> being in first plane P1.

End portion <NUM> of fastener <NUM>, in this example, includes a tool interface configuration <NUM>, as seen in <FIG>, for engaging fastener <NUM> with a compatible configuration of a tool so as to facilitate the tool gripping fastener <NUM> for tightening or loosening fastener <NUM> relative to structure <NUM>. Tool interface configuration <NUM> can take on various shapes so long as the shape is compatible with being gripped by a particular tool for tightening or loosening fastener <NUM>. In this example, end portion <NUM> of fastener <NUM>, also includes a cylindrical portion <NUM> positioned adjacent to tool interface configuration <NUM> on one side of cylindrical portion <NUM> and positioned to abut structure <NUM> on an opposing side of cylindrical portion <NUM>. In this example, a twelve point bolt head is the tool interface configuration <NUM> along with cylindrical portion <NUM> are known as a head portion of fastener <NUM>. Head portions of fasteners <NUM> can take on a wide variety of shapes and dimensions. In this example, when fastener <NUM> is tightened cylindrical portion <NUM> applies a compressive force against structure <NUM> along with a nut or a swaged collar (not shown) positioned on fastener <NUM> on an opposing side of structure <NUM>.

As mentioned above, a head portion of end portion <NUM> of fastener <NUM> can take on a wide variety of configurations and sizes. Similarly, end portion <NUM> of fastener <NUM> can be positioned on an opposing side of fastener <NUM> and can take on one of a variety of configurations and sizes which include, for example, a wide variety of nut(s) (not shown) or a wide variety of nut(s) and washer(s) (also not shown). In applying cap member <NUM> to end portion <NUM> of fastener <NUM>, cap member <NUM> can be used to engage either end portion <NUM> of fastener <NUM> as needed in fabrication or maintenance of an aircraft. Cap member <NUM> can be used to enclose end portion <NUM> of fastener <NUM> which includes the head portion of the fastener <NUM> as shown for example in <FIG> or to enclose end portion <NUM> of fastener <NUM> which includes the nut(s) or nut(s) and washer(s) portion of the fastener <NUM> on an opposing end of the fastener <NUM> which is not shown. In either application, continuous wall member <NUM> creates an interference compression fit with an end portion <NUM> of fastener <NUM> such that cap member <NUM> positioned against structure <NUM> holds position with respect to fastener <NUM> and encloses end portion <NUM> of fastener <NUM> within cap member <NUM> and structure <NUM>. In accomplishing this interference compression fit, opening <NUM> of cap member <NUM>, defined by continuous wall member <NUM> can be shaped and dimensioned by continuous wall member <NUM> so as to create the interference compression fit with end portion <NUM> of fastener <NUM> of either end portion of fastener <NUM>, as described above, as needed. For example, the interference compression fit would be made with the head portion of fastener <NUM>, as seen in the example shown in <FIG> and <FIG>, or with nut(s), nut(s) and washer(s) or a swaged collar of fastener <NUM> (not shown).

In the present example, opening <NUM>, as seen in <FIG>, formed by continuous wall member <NUM>, can take on one of a wide variety of shapes and sizes. So long as the shape and size of continuous wall member <NUM> allows continuous wall member <NUM> to encounter end portion <NUM> of fastener <NUM> such that end portion <NUM> of fastener <NUM> contacts and deforms continuous wall member <NUM>' and an interference compression fit is created between end portion <NUM> and continuous wall member <NUM>'.

As seen in <FIG>, continuous wall member <NUM>', in this example, is deformed by end portion <NUM> of fastener <NUM> at three spaced locations <NUM>, <NUM> and <NUM> of continuous wall member <NUM>'. Deformation of continuous wall member <NUM>', in this example, includes compressing portions of continuous wall member <NUM>' which contact cylinder portion <NUM> of end portion <NUM> of fastener <NUM>. The compression deformation of continuous wall member <NUM>' occurs, in this example, at each of the three locations <NUM>, <NUM> and <NUM>. At location <NUM> continuous wall member <NUM> has thickness "T" where cylinder portion <NUM> is in contact with continuous wall member <NUM>' in contrast to continuous wall member <NUM>' having a greater thickness "T1" between contact location <NUM> and contact location <NUM> where end portion <NUM> of fastener <NUM> is not in contact with continuous wall member <NUM>'. This deformation of continuous wall member <NUM>' occurs with cap member <NUM> being constructed of a thermoplastic or thermoset material which is less hard than metal construction, in this example, of end portion <NUM> of fastener <NUM>. The deformation of continuous wall member <NUM>' is seen in <FIG> at location <NUM> as deformation <NUM> and at location <NUM> as deformation <NUM> and similarly shown in <FIG> at location <NUM> as deformation <NUM>. Such deformation similarly occurs in this example at location <NUM>.

In this example, further deformation of continuous wall member <NUM>' occurs with deformation of the overall configuration or shape of continuous wall member <NUM>' which effects shape of opening <NUM> with end portion <NUM> of fastener <NUM> positioned within opening <NUM> surrounded by and in contact with continuous wall member <NUM>'. The shape of continuous wall member <NUM>' becomes distorted as seen in <FIG>. Continuous wall member <NUM>, in a non-deformed and undistorted state of <FIG> is shown in <FIG> in phantom and designated as continuous wall member <NUM>. Continuous wall member <NUM>', which is deformed and distorted by end portion <NUM> of fastener <NUM> is designated in <FIG> as continuous wall member <NUM>'.

With deformation of continuous wall member <NUM>' at locations <NUM>, <NUM> and <NUM> along with the distortion in shape of continuous wall member <NUM>', a compression interference fit is created between end portion <NUM> of fastener <NUM> and continuous wall member <NUM>' creating friction between continuous wall member <NUM>' and end portion <NUM> of fastener <NUM>. With cap member <NUM> positioned against structure <NUM>, the compression friction maintains cap member secured to fastener <NUM> and end portion <NUM> of fastener <NUM> enclosed within cap member <NUM>. With continuous wall member <NUM>' gripping end portion <NUM> of fastener <NUM> by way of the interference compression and resulting friction, cap member <NUM> can be positioned and secured into any orientation onto structure <NUM> within an aircraft regardless of gravitational forces operating on cap member <NUM>. This orientation can include extreme orientations of cap member <NUM> such as being positioned upside down on a surface, positioned on a vertical surface or positioned on an inclined surface without the individual installer needing to hold cap member <NUM> in place. The holding of cap member <NUM> in place, by way of the interference compression fit and maintaining end portion <NUM> of fastener <NUM> enclosed within cap member <NUM> and structure <NUM>, as will be described below, cap member <NUM> is in proper position during injecting of sealant within cap member <NUM> facilitating installation of cap member <NUM> and in proper position during decompression of sealant without any need for the installer to hold cap member <NUM> in place providing enhanced rate of quality installations.

Moreover, the compression fit capabilities of continuous wall member <NUM>' also provides installer the ability to not have to remove all sealant in an in-service maintenance of the aircraft. The compression interference fit will accommodate cap member <NUM> gripping end portion <NUM> of fastener <NUM> without all sealant being removed from the end portion <NUM> of fastener <NUM> and provide installer from needing to remove all sealant when installing of cap member <NUM>.

In referring to <FIG>, <FIG>, <FIG> and <FIG>, sidewall <NUM> forms wall member <NUM> positioned spaced apart from continuous wall member <NUM>, <NUM>'. Wall member <NUM> extends in direction <NUM> as seen in <FIG>, away from sidewall <NUM> of cap member <NUM> which defines interior space <NUM>. Wall member <NUM> has second end surface <NUM>. Second end surface <NUM> is configured such that second end surface <NUM> extends within a second plane P2, as seen in <FIG>, wherein second plane P2 is shown as a line designated as P2 and aligned along second end surface <NUM> representing second end surface <NUM> being in second plane P2. First and second planes P1 and P2 are not coplanar with one another but are parallel to one another. First end <NUM>, with cap member <NUM> positioned on structure <NUM>, is positioned slightly separated from the surface of structure <NUM> ensuring second end surface <NUM> to be in contact with the surface of structure <NUM>. This prevents sealant <NUM> from escaping channel <NUM> to outside <NUM> of cap member <NUM>, described below, and thereby prevents additional cleaning of sealant <NUM> from the surface of structure <NUM> versus sealant <NUM> escaping from channel <NUM> past first end <NUM> into interior space <NUM> which is acceptable.

In referring to <FIG>, <FIG>, <FIG> and <FIG>, channel <NUM>, defined by sidewall <NUM> of cap member <NUM>, is positioned extending about continuous wall member <NUM>, <NUM>' and positioned between continuous wall member <NUM>, <NUM>' and wall member <NUM>. Wall member <NUM> defines two ports <NUM>, <NUM> which extend through wall member <NUM> which are spaced from one another. Two ports <NUM>, <NUM> are each positioned on opposing sides <NUM>, <NUM> of cap member <NUM>. Each of the two ports <NUM>, <NUM> are in fluid communication with channel <NUM>. First flow path <NUM> extends from outside <NUM> of cap member <NUM> through, for example, port <NUM> of the two ports <NUM>, <NUM> and into the channel <NUM>. Second flow path <NUM> extends from inside <NUM> of channel <NUM> to port <NUM> of the two ports <NUM>, <NUM> and through port <NUM> of two ports <NUM>, <NUM> to outside <NUM> of cap member <NUM>. This configuration permits installer to inject sealant <NUM> through for example port <NUM> of two ports <NUM>, <NUM> with sealant <NUM> exiting port <NUM> of two ports <NUM>, <NUM>, as seen in <FIG>. With sealant moving out of port <NUM> in this example, the installer is provided an indication that sealant <NUM> has flowed through channel <NUM> and is present within channel <NUM>.

As earlier discussed, fastener <NUM> is constructed of a harder material than that of the material which constructs continuous wall member <NUM>, <NUM>' such that with a force applied by the end portion <NUM> of fastener <NUM> against continuous wall member <NUM> continuous wall member <NUM>' deforms. The deformation of continuous wall member <NUM>, <NUM>' provides the interference compression fit between continuous wall member <NUM>' and end portion <NUM> of fastener <NUM> properly holding cap member <NUM> in position for sealant <NUM> injection to be accomplished and for decompression of sealant <NUM> to occur without cap member <NUM> experiencing unwanted liftoff of cap member <NUM> from structure <NUM>.

In referring to <FIG>, method <NUM> is shown for holding protection seal cap <NUM> against structure <NUM> and enclosing end portion <NUM> of fastener <NUM> which extends from structure <NUM>. Method <NUM> includes positioning <NUM> cap member <NUM> of protection seal cap <NUM> over end portion <NUM> of fastener <NUM>. Cap member <NUM> includes sidewall <NUM> which defines interior space <NUM> within cap member <NUM>. Sidewall <NUM> forms continuous wall member <NUM> positioned within cap member <NUM>. Continuous wall member <NUM> defines opening <NUM> providing access to interior space <NUM>. Continuous wall member <NUM> is configured to create an interference compression fit between end portion <NUM> of fastener <NUM> and continuous wall member <NUM>. Method <NUM> further includes deforming <NUM> of continuous wall member <NUM>' creating an interference compression fit between continuous wall member <NUM>' and end portion <NUM> of fastener <NUM>.

Positioning <NUM> of cap member <NUM> further includes positioning cap member <NUM> against structure <NUM>. Sidewall <NUM> forms wall member <NUM> positioned spaced from continuous wall member <NUM>. Wall member <NUM> extends about continuous wall member <NUM> and channel <NUM> defined by sidewall <NUM> is positioned between wall member <NUM> and continuous wall member <NUM>. Wall member <NUM> defines two ports <NUM>, <NUM> which extend through wall member <NUM> and are in fluid communication with channel <NUM>. Method <NUM> further includes injecting sealant <NUM> into channel <NUM> through one of the two ports <NUM>, <NUM>.

Claim 1:
A fastener (<NUM>) which extends from a structure (<NUM>) and a protection seal cap (<NUM>) for enclosing an end portion (<NUM>) of the fastener (<NUM>), the protection seal cap (<NUM>) comprising:
a cap member (<NUM>) constructed of a thermoplastic or thermoset material and comprising a sidewall (<NUM>) that defines an interior space (<NUM>) within the cap member (<NUM>), wherein:
the sidewall (<NUM>) forms a continuous wall member (<NUM>, <NUM>') positioned within the cap member (<NUM>);
the continuous wall member (<NUM>, <NUM>') defines an opening (<NUM>) providing access to the interior space (<NUM>);
the continuous wall member (<NUM>, <NUM>') is shaped and sized such that the continuous wall member (<NUM>, <NUM>') can be contacted and deformed by an end portion (<NUM>) of a fastener (<NUM>) and an interference compression fit created between the end portion (<NUM>) of the fastener (<NUM>) and the continuous wall member (<NUM>);
wherein the fastener (<NUM>) is constructed of a harder material than that of a material which constructs the continuous wall member (<NUM>, <NUM>');
wherein a thickness (T1) of the continuous wall member (<NUM>, <NUM>') between contact locations (<NUM>, <NUM>, <NUM>) where the continuous wall member (<NUM>, <NUM>') is in contact with the end portion (<NUM>) of the fastener (<NUM>) is greater than a thickness (T) of the continuous wall member (<NUM>, <NUM>') at the contact locations (<NUM>, <NUM>, <NUM>);
the continuous wall member (<NUM>, <NUM>') extends in a direction (<NUM>) parallel to a central axis of the cap member (<NUM>) and away from the sidewall (<NUM>) of the cap member (<NUM>) which defines the interior space (<NUM>), and wherein the continuous wall member (<NUM>, <NUM>') has a first end surface (<NUM>) that is positioned within a first plane (P1);
the sidewall (<NUM>) forms a wall member (<NUM>) positioned spaced radially outward from the continuous wall member (<NUM>, <NUM>'), the wall member (<NUM>) extends in the direction (<NUM>), and the wall member (<NUM>) has a second end surface (<NUM>) configured such that the second end surface (<NUM>) extends within a second plane (P2), wherein the first plane (P1) and the second plane (P2) are parallel and non-coplanar, and when the cap member (<NUM>) is positioned on the structure (<NUM>), the first end surface (<NUM>) is separated from a surface of the structure (<NUM>) and the second end surface (<NUM>) is in contact with the surface of the structure (<NUM>).