Patent Description:
A variety of latches are used on aircraft to retain various components of the aircraft in a locked condition under circumstances such as flight and storage of the aircraft. During maintenance or repair periods the latches must operate to unlock the corresponding panel, cowling or other device from the aircraft. For example, upon a cowling the latch is disengaged to allow the cowling to be operated away from the engine components which it houses. The cowling, once opened, allows the aircraft maintenance professional to access the engine components. At the end of the repair event the cowling is closed. The latch is used to lock the cowling in the closed condition to retain the engine components in the housed condition.

As an additional matter, the maintenance professional may use a device to "clip" the latches closed to keep them from projecting out from the aircraft body or housing. The latches are clipped in a closed or lower profile position to prevent the latches from becoming bumped or from bumping the maintenance professional. Clipping the latches does not necessarily close or lock the latch but allows the latch to be maintained in a much lower profile against the aircraft housing or body. Since the latches are in a lower profile configuration, they reduce the chance of the maintenance professional bumping into them either with his body or with a piece of equipment. This can be useful to protect the latches as well as the maintenance professional. However, clipped latches can inadvertently appear to be locked and as such may fail to be locked. Additionally, even if the latches are operated to attempt to lock them a potential issue with the latch mechanism might interfere with complete locking and as such could inadvertently unlatch during operation. It would be desirable to develop a system and assembly to be used with a latch to help provide assurances that the latch will, in fact, be closed and locked in the proper position.

<CIT> discloses a lock cylinder having tumbler elements that are inserted into a cylinder core within the housing having a bearing cavity, and which are movable to release position by insertion of a key. The latching units are arranged within the bearing cavity to provide latching force to prevent axial displacement of the cylinder core in key insertion direction. The latching units are comprised such that the cylinder core is pressed against a stopper only after complete insertion of the key.

<CIT> discloses a lock and key combination including an axial split-pin tumbler-type lock having a lock cylinder and a barrel assembly secured within the cylinder. The barrel assembly includes a forwardly disposed rotatable operating part and a rearwardly disposed stationary part, which carry in longitudinal bores thereof spring-pressed tumblers having separate driver and follower elements, the driver elements of which extend forwardly out of the bores for engagement with the key. The operating part has a planar front face surrounding a forwardly extending key guide post adapted to resist application of lock-picking torque. The key has a shank provided with a socket adapted for receiving the guide post therein. Sittings on the outer periphery of the shank are adapted for engagement with the front ends of the driver elements to hold the tumblers in positions wherein a transverse interfacial plane between the operating and stationary parts coincides with the joints between the driver and follower elements to free the operating part for rotation. A drive tooth on the outer periphery of the key shank is adapted for sidewise engagement alternately with two of the driver elements, for driving the operating part alternately in opposite directions when the key is turned in such directions.

This background information is provided to provide some information believed by the applicant to be of possible relevance to the present invention. Other aims, objects, advantages and features of the invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

In accordance with the present invention there is provided a clevis-sensing lock mechanism as defined in claim <NUM>.

Optional or preferable features are set out in the dependent claims.

The present disclosure includes a clevis-sensing lock mechanism for use with a latching system. The clevis-sensing lock mechanism can be installed into the latching system and provides structures which function to prevent operation of the clevis in the unlocked position. A device such as a key or tool is used to unlock the latch and allow it to open. The structure and function of the clevis-sensing lock mechanism retains this device in the lock to prevent its removal unless the latch is in the fully closed position. Once in the fully closed position the lock can be closed and the device removed. Additionally, an indicator or flag can be added to the device to further enhance the visibility of the locked or unlocked condition of the latch. The lock provides structures which function to interfere with the operation of the clevis until the latch is in the desired closed and confirmed locked position. The clevis-sensing lock mechanism can be used with a specially designed latch or retrofitted to be used with a variety of latches. The variety of latches can be remanufactured to provide the same or substantially the same envelope of operation using virtually the same components but replacing portions of the trigger assembly with the lock assembly.

According to the present disclosure, a latch mechanism includes a hook-handle assembly, a clevis, and a clevis-sensing lock mechanism. The hook-handle assembly may include a hook member, a handle, and a linkage arrangement coupled between the hook member and handle. The clevis may include a hook-end receiver and a coupler portion spaced apart from the hook-end receiver to at least partially define an opening therebetween.

In illustrative embodiments, the hook-end receiver may be configured to engage with a hook end of the hook member as the handle moves from an open position extending away from the clevis toward a closed position extending toward the clevis.

The clevis-sensing lock mechanism may be coupled to the handle to move with the handle. The clevis-sensing lock mechanism comprises in particular a block, a lock cylinder received in the block and configured to rotate relative to the block, and an interference member coupled to the lock cylinder to rotate with the lock cylinder relative to the block.

The interference member may be configured to pass through the opening of the clevis and rotate relative to the block to engage an underside of the clevis and the lock cylinder may be configured to control rotation of the interference member.

The clevis-sensing lock mechanism further comprises a tumbler arrangement coupled between the lock cylinder and the block and configured to control rotation of the lock cylinder relative to the block.

In illustrative embodiments, the tumbler arrangement may include a detent spring, a detent pin positioned between the lock cylinder and the detent spring, and a tumbler pin positioned between the detent pin and the lock cylinder. The detent spring may be configured to bias the detent pin toward the tumbler pin. The detent pin may be configured to engage with the block and the lock cylinder to restrict rotation of the lock cylinder when an interface between the detent pin and the tumbler pin is misaligned from a lower surface of the lock cylinder.

The latch mechanism may further include a key configured to be received in the lock cylinder to engage with the tumbler pin and to align the interface between the detent pin and the tumbler pin with the lower surface of the lock cylinder.

In illustrative embodiments, the clevis-sensing lock mechanism may further include a key having a head and a shaft coupled to the head. The shaft may be configured to be received in the lock cylinder to engage with the tumbler arrangement to allow rotation of the lock cylinder and the head may be configured to extend away from the handle to provide an indication of an unlocked state of the clevis-sensing lock.

In illustrative embodiments, the key may further include a protrusion extending outward from the shaft and configured to engage with the handle to trap the shaft within the lock cylinder when the lock cylinder is rotated relative to the block.

The lock cylinder is formed to include an annular groove and an axial slot extending toward the interference member from the annular groove.

The clevis-sensing lock mechanism further comprises a cross-pin configured to slide in the annular groove and axial slot of the lock cylinder to control rotation of the lock cylinder.

The clevis may further include a fin extending from an upper surface clevis opposite the underside. The fin may be configured to move the cross-pin out of the axial slot and into the annular groove to allow rotation of the lock cylinder as the handle moves toward the closed position.

In illustrative embodiments, the lock cylinder may be formed to include a groove extending at least partially around a circumference of the lock cylinder. A fastener may extend through the handle and the block to couple the clevis-sensing lock to the handle and may be received in the groove of the lock cylinder.

The groove of the lock cylinder may be configured to limit rotation of the lock cylinder relative to the block.

In illustrative embodiments, the clevis-sensing lock mechanism may further include a fastener extending through the block. The lock cylinder may be formed to include a groove extending at least partially around a circumference of the lock cylinder. The fastener may be received in the groove of the lock cylinder. The groove of the lock cylinder may be configured to limit rotation of the lock cylinder relative to the block.

Other aims, objects, advantages and features of the invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

The present invention will be described hereafter with reference to the attached drawings which are given as a non-limiting example only, in which:.

The exemplification set out herein illustrates embodiments of the invention that are not to be construed as limiting the scope of the invention in any manner. Additional features of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the invention as presently perceived.

While the present invention may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, embodiments with the understanding that the present description is to be considered an exemplification of the principles of the invention. The invention is not limited in its application to the details of structure, function, construction, or the arrangement of components set forth in the following description or illustrated in the drawings. The use of various phrases and terms is meant to encompass the items or functions identified and equivalents thereof as well as additional items or functions. Unless limited otherwise, various phrases, terms, and variations thereof herein are used broadly and encompass all variations of such phrases and terms. Furthermore, and as described in subsequent paragraphs, the specific configurations illustrated in the drawings are intended to exemplify embodiments of the invention. However, other alternative structures, functions, and configurations are possible which are considered to be within the teachings of the present invention, in accordance with the appended claims. Furthermore, unless otherwise indicated, the term "or" is to be considered inclusive.

The foregoing terms as well as other terms should be broadly interpreted throughout this disclosure to include all known as well as all hereafter discovered versions, equivalents, variations and other forms of the abovementioned terms as well as other terms.

An engine assembly <NUM> for attachment with an aircraft is shown in <FIG>. Engine assembly <NUM> includes a nacelle or fan cowl <NUM> positioned to surround a gas turbine engine <NUM> supported by an engine-mounting bracket <NUM> for securing engine assembly <NUM> to the aircraft. Nacelle <NUM> includes a right-side panel <NUM> and a left-side panel <NUM> which are movable relative to engine <NUM> between a closed position, shown in <FIG>, and an open position extending away from engine <NUM>.

A latch mechanism <NUM> is coupled between panels <NUM>, <NUM> to secure panels <NUM>, <NUM> in the closed position at the selection of a user as suggested in <FIG>. One of the problems that can occur with such a latch mechanism is that the latch mechanism can be mislocked. In this regard, the latch mechanism can be closed under some circumstances and appear to be locked to the maintenance professional, when, in fact, it may not be fully engaged or fully locked. It is important to return the aircraft components, such as panels, doors, and cowlings, to the appropriate in-flight condition to seal and house the portions of the aircraft. It is also important to maintain the latch mechanism to retain these components in the closed locked condition. As such, it is important to provide a system to assure that the latch mechanism is, in fact, in the appropriate condition when locked.

As such, latch mechanism <NUM> includes a hook-handle assembly <NUM> coupled to one of panels <NUM>, <NUM> and a clevis <NUM> coupled to the other of panels <NUM>, <NUM> as suggested in <FIG>. A clevis-sensing lock mechanism <NUM> in accordance with the present invention is coupled to hook-handle assembly <NUM> and is configured to pass through and engage with clevis <NUM> to maintain latch mechanism <NUM> in a locked and closed position as suggested in <FIG>. It should be noted, that clevis-sensing lock mechanism <NUM> can be configured for use with a variety of latch mechanisms.

A key <NUM> is inserted into clevis-sensing lock mechanism <NUM> to unlock latch mechanism <NUM> as suggested in <FIG> and <FIG>. In the illustrative embodiment, a signal flag <NUM> is coupled to key <NUM> to indicate to an operator or user that latch mechanism <NUM> is unlocked as suggested in <FIG>. An enlarged head <NUM> of key <NUM> also provides such an indication if signal flag <NUM> is lost or removed inadvertently. Signal flag <NUM> and key <NUM> allow a user to inspect engine assembly <NUM> to ensure that latch mechanisms <NUM> are locked and closed to secure panels <NUM>, <NUM> in the closed position. For example, if no signal flag <NUM> or key <NUM> are visible, then there is an indication that latch mechanisms <NUM> are in the locked and closed position as suggested in <FIG>.

Hook-handle assembly <NUM> includes a handle <NUM> used to operate latch mechanism <NUM>, a hook member <NUM>, and a linkage arrangement <NUM> coupled between handle <NUM> and hook member <NUM> as suggested in <FIG> and <FIG>. Latch mechanism <NUM> is coupled to one of panels <NUM>, <NUM> by inserting a pin through a sleeve <NUM> of linkage arrangement <NUM>. Hook-handle assembly <NUM> moves relative to the pin inserted through sleeve <NUM> between the unlocked and open position, shown in <FIG>, and the locked and closed position, shown in <FIG>, and as suggested in <FIG>.

Clevis <NUM> includes a hook-end receiver <NUM> for engaging with a hook end <NUM> of hook member <NUM> and a coupler portion <NUM> coupled to a clevis retainer <NUM> as suggested in <FIG>. In the illustrative embodiment, coupler portion <NUM> is threaded. Clevis retainer <NUM> couples with the other of panels <NUM>, <NUM> opposite hook-handle assembly <NUM> and is configured to allow axial adjustment of clevis <NUM> by engaging with coupler portion <NUM>. Handle <NUM> is rotated toward clevis <NUM> to engage hook end <NUM> with hook-end receiver <NUM> and pass an interference member <NUM> of clevis-sensing lock <NUM> through an opening <NUM> of clevis <NUM>, and interference member <NUM> is rotated by key <NUM> to engage with flats <NUM> on an underside <NUM> of clevis <NUM> to secure panels <NUM>, <NUM> in the closed positon so that key <NUM> can be removed as suggested in <FIG>. Clevis <NUM> also includes fins <NUM> positioned on an upper surface <NUM> to engage with clevis-sensing lock <NUM> to allow rotation and removal of key <NUM> as suggested in <FIG>.

Clevis-sensing lock mechanism <NUM> includes a block <NUM> coupled to an underside surface <NUM> of handle <NUM> and a coupler shaft <NUM> configured to couple interference member <NUM> with block <NUM> as suggested in <FIG> and <FIG>. Block <NUM> is coupled to handle <NUM> by pins <NUM> and is configured to receive a tumbler assembly <NUM> to control rotation of interference member <NUM> as suggested in <FIG>. In some embodiments, pins <NUM> are in the form of a removable fastener or in the form of a rivet-type fastener. A lock cylinder <NUM> of tumbler assembly <NUM> is received in a bore <NUM> of block <NUM> and coupled to coupler shaft <NUM> to rotate with interference member <NUM> as suggested in <FIG>. A tumbler pin arrangement <NUM> of tumbler assembly <NUM> is positioned between lock cylinder <NUM> and block <NUM> to control movement of lock cylinder <NUM> as suggested in <FIG> and <FIG>. Lock cylinder <NUM> is formed to include a bore <NUM> configured to receive a shaft <NUM> of key <NUM> for rotation of lock cylinder <NUM> and interference member <NUM> as suggested in <FIG> and <FIG>.

To assemble clevis-sensing lock mechanism <NUM>, coupler shaft <NUM> is positioned within bore <NUM> of lock cylinder <NUM>, and a pin <NUM> is engaged with holes <NUM>, <NUM> of coupler lock cylinder <NUM> and coupler shaft <NUM>, respectively, as suggested in <FIG>. Tumbler pin arrangement <NUM> includes detent pins <NUM>, detent springs <NUM>, and discrete length tumbler pins <NUM>. In the illustrative embodiment, four of each of detent springs <NUM>, detent pins <NUM>, and tumbler pins <NUM> are shown. In some embodiments, more or less of each of detent springs <NUM>, detent pins <NUM>, and tumbler pins <NUM> are used. The unique arrangement of tumbler pins <NUM> between various latch mechanisms <NUM> provides a degree of selectivity to allow only certain keys <NUM> to work with each clevis-sensing lock mechanism <NUM>, thus providing a general security keying feature. While a uniform key could be used across all latching platforms, the additional security may enhance the use of the clevis-sensing lock mechanism <NUM> to provide security features as well as the above described and herein described benefits.

Tumbler pins <NUM> are inserted into corresponding bores within lock cylinder <NUM> and lock cylinder <NUM> is inserted into bore <NUM> of block <NUM> as suggested in <FIG>. Detent pins <NUM> are inserted into block <NUM> to engage with tumbler pins <NUM> and detent springs <NUM> are inserted into block <NUM> to engage with detent pins <NUM>. A retainer plate <NUM> is engaged with an underside of block <NUM> to retain tumbler pin arrangement <NUM> within block <NUM>. Coupler shaft <NUM> is inserted though interference member <NUM> and is coupled to coupler shaft <NUM> by a pin <NUM> extending through holes <NUM>, <NUM> of interference member <NUM> and coupler shaft <NUM>, respectively.

Guide pins <NUM> are received in cavities <NUM> of block <NUM> as suggested in <FIG>. Guide pins <NUM> include a head <NUM> and shaft <NUM> coupled to head <NUM>. A spring <NUM> is positioned to surround shaft <NUM>. Head <NUM> is formed to include a hole <NUM> for receiving a cross-pin <NUM>. Guide pins <NUM> and springs <NUM> are inserted into cavities <NUM> and cross-pins <NUM> are inserted through slots <NUM> formed in block <NUM> and holes <NUM> of heads <NUM> to retain guide pins <NUM> within cavities <NUM>. Block <NUM> is coupled to handle <NUM> by pins <NUM> such that an upper portion of cavities <NUM> and side portions of slots <NUM> are covered. As such, handle <NUM> retains springs <NUM> within cavities <NUM> and cross-pins <NUM> within slots <NUM>.

Interference member <NUM> includes protruding portions <NUM> and flats <NUM> extending between protruding portions <NUM> as shown in <FIG>. Protruding portions <NUM> are configured to engage with flats <NUM> of a narrowed portion <NUM> of clevis <NUM> to lock latch mechanism <NUM>. Key <NUM> is inserted through an aperture <NUM> in handle <NUM> to engage with clevis-sensing lock <NUM> as suggested in <FIG>. Key <NUM> is then rotated to rotate interference member <NUM> and align flats <NUM> with narrowed portion <NUM> such that protruding portions <NUM> are disengaged from flats <NUM> and interference member <NUM> is allowed to pass through opening <NUM> of clevis <NUM> as suggested in <FIG>.

Clevis-sensing lock mechanism <NUM>, as assembled, is shown in <FIG>. Coupler shaft <NUM> and lock cylinder <NUM> are aligned with aperture <NUM> of handle <NUM> to allow insertion of key <NUM> as suggested in <FIG>. Detent pins <NUM> are positioned to engage with lock cylinder <NUM> to block rotation of lock cylinder <NUM> until key <NUM> is inserted as suggested in <FIG>. In the illustrative embodiment, clevis-sensing lock mechanism <NUM> was assembled and attached to handle <NUM> such that clevis-sensing lock mechanism <NUM> is initially in the locked orientation as suggested in <FIG>. After key <NUM> is inserted and turned for the first time, clevis-sensing lock mechanism <NUM> will need to be engaged with clevis <NUM> in order to turn and remove key <NUM> as further detailed below.

Key <NUM> includes head <NUM> and shaft <NUM> coupled to head <NUM> as shown in <FIG>. Shaft <NUM> is hollow to define a cavity <NUM> sized to receive coupler shaft <NUM>. Lock cylinder <NUM> is formed to define a shoulder <NUM> as shown in <FIG>. A protrusion <NUM> extends radially from shaft <NUM> and aperture <NUM> of handle <NUM> is shaped to allow shaft <NUM> and protrusion <NUM> to pass therethrough as suggested in <FIG>.

In the locked orientation, an interface between tumbler pins <NUM> and detent pins <NUM> is misaligned from a bottom plane P of lock cylinder <NUM> such that detent pins <NUM> engage with lock cylinder <NUM> and block <NUM> to prevent rotation of lock cylinder <NUM> as suggested in <FIG>. A leading end <NUM> of key <NUM>, having mating portions <NUM> corresponding to tumbler pins <NUM>, extends into lock cylinder <NUM> to engage with tumbler pins <NUM> and align detent pins <NUM> with bottom plane P to allow rotation of lock cylinder <NUM> as suggested in <FIG>. Protrusion <NUM> of key <NUM> engages with shoulder <NUM> of lock cylinder <NUM> to limit insertion of key <NUM> and ensure proper alignment of detent pins <NUM> with bottom plane P.

As key <NUM> is rotated to unlock clevis-sensing lock mechanism <NUM>, protrusion <NUM> extends under handle <NUM> and becomes misaligned from aperture <NUM> as suggested in <FIG>. As such, key <NUM> is trapped inside clevis-sensing lock mechanism <NUM> until key <NUM> is turned to re-lock clevis-sensing lock mechanism <NUM>. This prevents key <NUM> and signal flag <NUM> from being removed before latch mechanism <NUM> is in the locked and closed position to ensure that panels <NUM>, <NUM> are properly secured in the closed position.

Lock cylinder <NUM> is formed to include a groove <NUM> as shown in <FIG>. One of pins <NUM> extends through block <NUM> to engage with groove <NUM>. Groove <NUM> only partially extends around lock cylinder <NUM> to control rotation of lock cylinder <NUM>. In the illustrative embodiment, lock cylinder <NUM> is limited to about <NUM> degrees of rotation. In some embodiments, that lock cylinder <NUM> rotates further than <NUM> degrees. Lock cylinder <NUM> is also formed to include an annular groove <NUM> with axial slots <NUM> extending downward therefrom as shown in <FIG>. Cross-pins <NUM> slide in annular groove <NUM> as lock cylinder <NUM> is rotated as suggested in <FIG>. Lock cylinder <NUM> is rotated until cross-pins <NUM> are aligned with axial slots <NUM>. Cross-pins <NUM> are forced into axial slots <NUM> by springs <NUM> to engage with lock cylinder <NUM> and block rotation of lock cylinder <NUM> as suggested in <FIG>.

Once clevis-sensing lock mechanism <NUM> is unlocked by key <NUM>, latch mechanism <NUM> can be opened as suggested in <FIG>. A handle release <NUM> is coupled to handle <NUM> and engages with hook member <NUM> when latch mechanism <NUM> is in a closed position as suggested in <FIG>. Handle release <NUM> is rotated to disengage from hook member <NUM>. Handle <NUM> is lifted to pass interference member <NUM> out of clevis <NUM> as suggested in <FIG>. Further rotation of handle <NUM> disengages hook end <NUM> from hook-end receiver <NUM> to allow movement of hook-handle assembly <NUM> relative to clevis <NUM> as suggested in <FIG>.

Fins <NUM> of clevis <NUM> are engaged with guide pins <NUM> to allow rotation and removal of key <NUM> as suggested in <FIG>. Clevis <NUM> is shown with fins <NUM> facing downward in <FIG>. As such, even though latch mechanism <NUM> is in a closed position, removal of key <NUM> is prevented by clevis-sensing lock <NUM>. Thus, latch mechanism <NUM> is prevented from being in an improper unlocked and closed position where panels <NUM>, <NUM> may inadvertently open during operation of the aircraft. With clevis <NUM> properly oriented, fins <NUM> engage with guide pins <NUM> during closure of latch mechanism <NUM> to move cross-pins <NUM> out of axial slots <NUM> and allow rotation of lock cylinder <NUM> as suggested in <FIG>.

A hook-handle assembly 32a incorporating an alternative clevis-sensing lock 50a in accordance with the present disclosure is shown in <FIG>. Similar to hook-handle assembly <NUM>, hook-handle assembly 32a includes a handle 42a, a hook member 40a, and a linkage arrangement 44a coupled between handle 42a and hook member 40a. A handle release 46a is coupled to handle 42a to engage with hook member 40a. Clevis-sensing lock 50a is coupled to an underside surface 116a of handle 42a. In the illustrative embodiment, hook-handle assembly 32a and clevis-sensing lock 50a are configured to cooperate with the same clevis <NUM> as hook-handle assembly <NUM> of latch mechanism <NUM>, described above. Hook-handle assembly 32a also operates in a similar fashion to hook-handle assembly <NUM>. As such, discussion of hook-handle assembly 32a will be limited for sake of brevity. As discussed herein, features of hook-handle assembly <NUM> can be incorporated into hook-handle assembly 32a, and vice versa, without departing from the present disclosure.

Clevis-sensing lock 50a includes a block 64a and a lock cylinder 102a configured to couple an interference member 56a with block 64a as suggested in <FIG> and <FIG>. Block 64a is coupled to handle 42a by pins 70a and is configured to receive a coupler shaft or key interface 68a to control rotation of interference member 56a coupled to lock cylinder 102a as suggested in <FIG>. Lock cylinder 102a is received in a bore 154a of block 64a and coupled to key interface 68a by a pin assembly 104a to rotate with interference member 56a. Pin assembly 104a moves relative to a notch 184a of block 64a to control movement of lock cylinder 102a as suggested in <FIG>.

Lock cylinder 102a is formed to include a bore 92a aligned with an aperture 82a of handle 42a and configured to receive a shaft 98a of a key 80a for rotation of lock cylinder 102a and interference member 56a as suggested in <FIG> and <FIG>. Key 80a includes a head 84a coupled to shaft 98a. Shaft 98a is formed to define a flat side 97a to orient key 80a during insertion. Key 80a also includes a grip tip 91a coupled to shaft 98a and configured to engage with key interface 68a as suggested in <FIG> and <FIG>.

To assemble clevis-sensing lock mechanism 50a, a tamper guard 186a, key interface 68a, a spring 136a, and a spacer 188a are inserted into lock cylinder 102a and retained therein by a retainer ring 189a as suggested in <FIG>. A pin 113a is inserted through a slot 107a of lock cylinder 102a and a hole 109a of key interface 68a. Pin 113a is secured by a sleeve 115a coupled to pin 113a to form pin assembly 104a. Spring 136a engages with spacer 188a to bias key interface 68a and pin assembly 104a toward an upper end of slot 107a.

Guide pins 110a are received in cavities 76a of block 64a as suggested in <FIG>. Guide pins 110a include a head 182a and shaft 111a coupled to head 182a. A spring 112a is positioned to surround shaft 111a. Head 182a is formed to include a hole 190a for receiving a cross-pin 114a. Guide pins 110a and springs 112a are inserted into cavities 76a and cross-pins 114a are inserted through slots 192a formed in block 64a and holes 190a of heads 182a to retain guide pins 110a within cavities 76a. Lock cylinder 102a is inserted into a bore 154a of block 64a and engaged by cross-pins 114a.

A ball detent assembly 172a is positioned within a ball detent receiver 178a as suggested in <FIG>. Ball detent assembly 172a includes a spring 174a and a ball bearing 176a. Spring 174a is configured to bias ball bearing 176a toward a detent recess 179a of lock cylinder 102a as suggested in <FIG>. Block 64a is coupled to handle 42a by pins 70a such that an upper portion of cavities 76a and ball detent receiver 178a, and side portions of slots 192a, are covered as suggested in <FIG>. As such, handle 42a retains springs 112a within cavities 76a, ball detent assembly 172a within ball detent receiver 178a, and cross-pins 114a within slots 192a.

Similar to interference member <NUM>, interference member 56a includes protruding portions 150a and flats 142a extending between protruding portions 150a as shown in <FIG>. Protruding portions 150a are configured to engage with clevis <NUM>. Flats 142a are configured to align with clevis <NUM> such that protruding portions 150a are disengaged from clevis <NUM> and interference member 56a is allowed to pass through opening <NUM> of clevis <NUM>.

Clevis-sensing lock mechanism 50a, as assembled, is shown in <FIG>. In the illustrative embodiment, clevis-sensing lock mechanism 50a was assembled and attached to handle 42a such that clevis-sensing lock mechanism 50a is initially in a locked orientation. After key <NUM> is inserted and turned for the first time, clevis-sensing lock mechanism <NUM> will need to be engaged with clevis <NUM> in order to turn and remove key 80a as further detailed below.

Key 80a is inserted into clevis-sensing lock mechanism 50a to move pin assembly 104a out of notch 184a as suggested in <FIG>. Shaft 98a of key 80a extends into lock cylinder 102a and grip tip 91a passes through tamper guard 186a to engage with key interface 68a as suggested in <FIG>. Key 80a is forced downward against the force of spring 136a to move pin assembly 104a as suggested in <FIG>. In the illustrative embodiment, grip tip 91a has a geometric shape, such as a triangle, which corresponds with a geometric shape of a tip receiver 69a of key interface 68a as suggested in <FIG>. Key interface 68a also includes a projecting portion 67a to engage with lock cylinder 102a. As such, grip tip 91a engages with tip receiver 69a to rotate key interface 68a, which in turn engages with lock cylinder 102a to rotate lock cylinder 102a with key 80a.

Shaft 98a of key 80a is formed to include a groove 95a as suggested in <FIG> and <FIG>. Side 97a of shaft 98a allows key 80a to pass by pin <NUM> and into lock cylinder 102a as suggested in <FIG>. Key 80a is allowed to turn to unlock clevis-sensing lock mechanism 50a when groove 95a aligns with pin 70a as suggested in <FIG> and <FIG>. Lock cylinder 102a also includes a groove 170a which cooperates with pin 70a to restrict rotation of lock cylinder 102a. Cross-pins 114a cooperate with a groove 158a and slot 180a of lock cylinder 102a to further control rotation of lock cylinder 102a, as suggested in <FIG> and <FIG>, similar to clevis-sensing lock mechanism <NUM>, described above.

Clevis-sensing lock mechanism 50a includes anti-tamper features as suggested in <FIG>. Tamper guard 186a minimizes the ability of a lock pick 99a, such as a screw driver or other tool, to enter clevis-sensing lock mechanism 50a and rotate lock cylinder 102a as suggested in <FIG>. Tamper guard 186a is configured to slide and rotate on key interface 68a without providing sufficient friction to turn lock cylinder 102a to disengage interference member 56a from clevis <NUM>. Ball detent assembly 172a engages with lock cylinder 102a to increase the force required to turn lock cylinder 102a as suggested in <FIG>. These features cooperate to prevent unlocking of clevis-sensing lock mechanism 50a without the use of key 80a.

In illustrative embodiments, the clevis-sensing lock mechanisms described herein can be configured for use with a specific latch design or configured to be used as a retrofit on a remanufactured latch. An existing latch assembly can reuse most of the parts with perhaps a modification to the handle to remove a pre-existing handle release and to accommodate a clevis-sensing lock mechanism. Additionally, the clevis can be replaced merely by disengaging the threaded portion of the old clevis and attaching a new clevis which will include the fins and other corresponding structures detailed above. This design is easy to operate, difficult to defeat, and provides a nearly fail-proof method of ensuring the latch has properly secured the latch cowl.

In illustrative embodiments, a clevis-sensing lock mechanism can be retained on a latch mechanism for preventing the latch mechanism from opening inadvertently. The clevis-sensing lock mechanism includes a tool, key, or other device which must be used to unlock the clevis-sensing lock mechanism to permit movement of the handle to disengage the latch mechanism. The key cannot be removed from the lock when the latch is open. Furthermore, the key includes a visual indicator such as a flag, streamer, or other device which provides a clear visual indicator that the key is retained in the lock. This visual indicator extends away from the aircraft to provide a clear visual indication of the unlatched condition. Since the key can only be removed from the lock when the latch is, in fact, in a proper closed position, the presence of such a visual indicator indicates that the latches are not secure for flight operations.

Engine cowls may sometimes appear to be in a latched closed position when they are not due to the low profile of the latches and low height from the ground of the engines of the aircraft. It is often times that technicians will clip the latches up tight against the cowling without latching them to prevent snags with clothing during operations on the engine. These situations can be problematic if an aircraft takes off while the latches are open, and may cause damage to the cowlings or engines while in flight.

In illustrative embodiments, a clevis sensing lock mechanism can be attached to any hook latch that engages with a clevis. The clevis sensing lock mechanism attaches to the handle of the hook latch, and passes through the clevis when the latch is closed. It requires a key or tool to unlock the latch and allow the latch to open. When the latch is open, the key cannot be removed from the handle. The key has a long flag or streamer attached to it so that anybody standing around the aircraft, not necessarily near the engine, can see that the cowls are not closed and latched. To unlatch the cowls, the operator inserts the key, with the long flag or streamer attached, into the latch, turns the key, then opens the latch.

In illustrative embodiments, the lock includes a block which holds all of the lock's internal parts to the handle of the hook latch. The block has a large hole for a lock cylinder, and some slots and holes for some pins, guides, and springs. Another pair of slots on the block allows fins that are attached to the clevis to fit into the block. The T-shaped lock cylinder, which fits into the block, has two large flats on one end, which allows it to fit through the clevis during handle opening and closing.

In illustrative embodiments, at the other end of the lock, there is a hole for a key to fit into. Near the open end of the hole, the lock cylinder has a retaining groove that protrudes into the hole, but only part way around the lock cylinder. This groove on the lock cylinder engages with a rivet that passes through the handle and through the block in such a way that the lock cylinder cannot come out of the lock, and in such a way that the lock cylinder can only turn a predetermined amount. The rivet protrudes into the hole of the lock such that the key has a corresponding flat on it that allows the key to pass by the rivet when the latch is closed. When the key is inserted into the lock, a groove on the key matches the groove on the lock cylinder that engages with the rivet that holds the lock cylinder in place. When the key is turned, the groove on the key engages with the rivet, which prevents the key from being removed.

In illustrative embodiments, the end of the key has a feature which grabs onto a mating component, sometimes called a plug, down in the bottom of the hole of the lock cylinder. The shape at the end of the key can be any shape that allows the key to grab the plug and turn it. The plug has a spring behind it, and a hole for a cross pin, which fits into a through slot on the lock cylinder. The cross pin limits the amount of axial movement in the lock cylinder and also ensures that the key, plug, and lock cylinder turn together. When the key is not inserted into the lock, the cross pin is pushed by the spring, via the plug, into a V-groove on the block, thereby preventing accidental rotation of the lock cylinder when the latch is closed. When the key is inserted into the lock, the cross pin is pushed out of the V-groove on the block, and the cylinder is allowed to turn. With this arrangement of the key, lock cylinder, and plug, they cannot be turned unless the key is fully inserted into the lock cylinder and engaged with the plug.

In illustrative embodiments, the lock cylinder also has a circular groove and two intersecting straight slots, which are parallel to the axis of the lock cylinder, that allow the ends of two locking pins to travel in them. The locking pins ride in a guide, inside the block. Each guide is pushed by a spring toward the clevis. The clevis has two fins which, in the latch closed position, engage with the guides, and push the guides and locking pins into the circular groove. When the locking pins are in the circular groove, the lock may be turned toward the unlock position. Once the lock cylinder is turned completely to the unlock position, the handle may be moved in the direction that opens the latch, and the engaging portion of the lock may pass through the clevis. The clevis has two fins which fit into some blind slots on the block, and push the guides and locking pins when the latch is closed. As the latch opens, and the handle moves away from the clevis, the fins on the clevis disengage from the guides and locking pins. The locking pins are then pushed down into the straight slots on the lock cylinder, which prevents the lock cylinder from turning toward the lock position and prevents the key from being removed.

Claim 1:
A clevis-sensing lock mechanism comprising:
a block (<NUM>) formed to include a cylinder-receiving first bore (<NUM>) extending into the block and a pin-receiving slot (<NUM>) extending into the block to intersect with the cylinder-receiving first bore (<NUM>);
a lock cylinder (<NUM>) configured to be received in the cylinder-receiving first bore of the block (<NUM>) and rotate relative to the block (<NUM>), the lock cylinder (<NUM>) including a first end and a second end spaced apart from the first end, the lock cylinder (<NUM>) formed to include an annular groove (<NUM>), an axial slot (<NUM>) extending toward the first end of the lock cylinder (<NUM>) from the annular groove (<NUM>), and a key-receiving second born (<NUM>) extending from the second end toward the first end;
a cross-pin (<NUM>) positioned within the pin-receiving slot (<NUM>) of the block (<NUM>) and configured to slide in the annular groove (<NUM>) and axial slot (<NUM>) of the lock cylinder (<NUM>) to control rotation of the lock cylinder (<NUM>);
a tumbler arrangement (<NUM>) coupled between the lock cylinder (<NUM>) and the block (<NUM>) and configured to control rotation of the lock cylinder (<NUM>);
a coupler shaft (<NUM>) positioned within the key-receiving second bore (<NUM>) and coupled with the lock cylinder (<NUM>) to rotate therewith; and
an interference member (<NUM>) coupled to the coupler shaft (<NUM>) at the first end of the lock cylinder (<NUM>) to rotate with the lock cylinder (<NUM>).