Hook latch for an engine cowling

An improved latch for securing together a pair of hinged cowlings surrounding an aircraft engine. The latch is characterized by having a safety lock for engaging a hook when the latch is in a locked or latched position and also for engaging the hook when the hook has been disengaged from a latch keeper thereby allowing the operator of the latch to engage and disengage the cowlings using only one hand.

BACKGROUND OF THE INVENTION 
This invention relates to an improved latch for securing together two 
members and more particularly but not by way of limitation to a latch for 
securing together a pair of hinged cowlings surrounding an aircraft 
engine. 
Prior to the subject invention a problem existed with some aircraft cowling 
latches in that maintenance personnel were required to use both hands when 
hooking up or unlocking the cowling latches. This is especially true with 
an overcenter hook type latch since this type of latch has an internal 
spring force acting against the latch handle and the latch hook, forcing 
the two apart usually toward an open direction thereby moving the hook 
away from the latch keeper. The latch keeper being attached to an opposing 
hinged cowling is usually an eye bolt, "U" bolt or standard bolt or a pin. 
For latching a standard overcenter hook latch, the sequence of operation 
required the two hinged cowlings to be brought together and aligned by 
some means and then latched. The operator then grasps the latch handle 
with one hand and with the other hand moves the latch hook into a position 
near the keeper. He then rotates the handle toward the closed position 
while holding the hook until it engages the keeper. The operator continues 
rotating the handle to its fully closed position to complete the latching 
cycle. By rotating the handle to the closed position the hook is moved 
overcenter or past a centerline through the keeper and the bolt securing 
the handle to the cowling and thereby increasing the latching force to a 
present amount. A safety lock on the latch is automatically engaged upon 
closing and prevents the latch from inadvertently opening due to the 
relaxing of the forces between the cowling halves. 
In unlatching the hook latch, the operator depresses the safety lock 
allowing the handle to rotate freely toward an open position. The free 
rotation of the handle gives the operator room to grasp the handle. The 
free rotation occurs after release of the safety lock but does not effect 
the hook-up forces. The handle is then rotated toward the open position 
which in turn moves the pivot of the hook overcenter releasing the 
latching forces. Further rotation causes the hook to be disengaged from 
the latch keeper. However, depending on the latch geometry, handle 
rotation and/or latch mounting position, the hook may or may not be free 
of the keeper. Therefore, the operator must use one hand to move the hook 
off of the keeper while the other hand moves the handle. The subject 
invention eliminates the above mentioned problem of the operator having to 
use both hands in securing or releasing the latch hook from the latch 
keeper. 
Heretofore there have been various types of latches such as those described 
in U.S. Pat. No. 2,712,955 to Andrews, U.S. Pat. No. 2,894,777 to Hogan, 
U.S. Pat. No. 2,927,812 to Smith et al, U.S. Pat. No. 3,259,412 to Wheeler 
and U.S. Pat. No. 4,318,557 to Bourne et al. None of the latches described 
in the above mentioned patents particularly point out the unique structure 
and features of the improved latch and the advantages of this latch as 
described herein. 
SUMMARY OF THE INVENTION 
The subject invention incorporates an improved latch which locks the handle 
and hook together either in a closed or opened position. This allows the 
operator to use only one hand to latch or unlatch the cowling halves. The 
one hand operation is beneficial to the operator when the operator has 
limited access or particularly no access in the latch keeper area. 
Also, the improved latch is beneficial when the operator must use his free 
hand to force the cowling halves together for latching. 
The improved latch for securing together a pair of cowlings surrounding an 
aircraft engine includes a latch keeper secured to one of the hinged 
cowlings. A hook is pivotally mounted on the other hinged cowling. A hook 
release handle is pivotally mounted on the hook and includes a safety lock 
attached to the handle. The safety lock has a first slot and a second 
slot. The first slot is received around a pin on the hook for securing the 
latch in a locked position. The second slot is received around the pin on 
the hook for securing the handle to the hook when the hook is in an 
unlocked position from the keeper. 
The advantages and objects of the invention will become evident from the 
following detailed description of the drawings when read in connection 
with the accompanying drawings which illustrate preferred embodiments of 
the invention.

DETAILED DESCRIPTION OF THE DRAWINGS 
In FIG. 1 the improved latch is shown in a latched and locked position and 
designated by general reference numeral 10. The latch 10 is used for 
securing together a pair of hinged cowlings surrounding an aircraft engine 
or the like. 
The improved latch includes a latch keeper 12 which is secured to one of 
the hinged cowlings to the left of the drawings. A hook is shown engaged 
to the keeper 12 and designated by reference numeral 14. The hook 14 is 
pivotally mounted on a hook pivot pin 16 which is attached to a bolt and 
pivot pin link 18 shown in dotted lines and connected to a latch mounting 
bolt 20. The bolt 20 is secured to a portion 21 of the other hinged 
cowling to the right of the drawings. Also pivotally mounted on the hook 
pivot pin 16 and bolt 20 is a hook release handle 22 having a first end 
portion 24 and a second end portion 26. 
It should be noted the improved latch 10 is an overcenter type latch 
wherein the hook pivot pin 16 when the latch 10 is in a latched and locked 
position is overcenter and past a centerline 30 through the center of the 
latch keeper 12 and the latch mounting bolt 20. Further the hook pivot pin 
16 is spring biased in a locked position by a handle torsion spring 32 
mounted around the pin 16 with one end engaging a mounting pin 34. 
To further insure the latch 10 is held in a latched and locked positon a 
safety lock 36 having a first end portion 38 and a second end portion 40 
is pivotally mounted to the handle 26 on a lock pivot pin 42. One end of a 
lock portion spring 44 is disposed around the pin 42 with the other end of 
the spring 44 engaging a mounting pin 46. The lock 36 is biased in a 
clockwise direction by the spring 44. The second end portion 40 includes a 
first slot 48 for engaging a hook pin 50 attached to the side of the hook 
14. The safety lock 36 insures the latch 10 stays in a latched and locked 
position should the forces holding the cowling halves together be relaxed 
during the operation of the aircraft engine. 
In FIG. 2 the first end portion 38 of the safety lock 36 had been pressed 
in a counter clockwise direction as indicated by arrow 52. At this time, 
the spring 44 is compressed with the safety lock 36 rotating on pin 42 in 
a counter clockwise direction as indicated by arrows 54 thereby releasing 
the first slot 48 from the pin 50. At this time, the safety lock has 
released the latch 10 so the latch may now be unlocked. 
In FIG. 3 the handle 22 has been rotated in a clockwise direction as 
indicated by arrow 56. At this time, the hook 14 moves to the left as 
indicated by arrow 58, releasing the end of the hook 14 from the keeper 
12. At the same time the safety lock 36 moves upwardly with the second end 
portion 40 riding against the side of the pin 50 until a second slot 59 
receives the pin 50 therein. In this position the latch 10 has become 
unlatched but the handle 22 is now locked to the hook 14 so the operator 
of the latch 10 is free to remove the hook 14 from the keeper 12 by merely 
rotating the handle 22 in a counter clockwise direction with one hand as 
shown by the arrow 60 shown in FIG. 4. 
In FIG. 5 the hook 14 and handle 22 can be seen released from a locked 
position to each other by pressing inwardly the first end portion 38 of 
the safety latch 36 as indicated by arrow 62. At this time the first end 
portion 38 of the safety lock 36 is rotated in a counter clockwise 
direction with the second slot 59 being moved away from the pin 50 so the 
hook 14 is released from the handle 26. 
In FIG. 6 a bottom view of the improved latch 10 is illustrated. In this 
view the hook 14 can be seen in a latched and locked position to the latch 
keeper 12 with the safety lock 36 engaging the pin 50 mounted on the side 
of the hook 14. Also in this view the latch mounting bolt 20 can be seen 
secured to a portion of the cowling 21 and extending through the sides of 
the handle 22. Also in this view, the first end portion 38 of the safety 
latch 36 can be seen through an insert 62 in the handle 22. Also shown in 
dotted lines are the hook pivot pin 16 and handle torsion spring 32. 
In operation the improved latch 10 provides a means for the operator of the 
latch to lock the handle 22 and hook 14 together either in a closed or 
opened position. This allows the operator to use only one hand to latch or 
unlatch the cowling halves. The one hand operation is very beneficial to 
the operator when there is limited access or practically no access to the 
area housing the latch keeper 12. Also it is beneficial when the operator 
must use his free hand to force together the cowling halves for securing 
the cowlings with the improved latch 10. 
On latching the cowlings together, the operator rotates the handle 22 and 
the hook 14 which are held together by the safety lock 36. He positions 
the hook 14 using the handle 22 near the latch keeper 12 and then 
depresses the first end portion 38 of the safety lock 36 thereby unlocking 
the hook 14 from the handle 22. At this time, the handle torsion spring 32 
forces the end of the hook 14 against the latch keeper 12. The operator 
then rotates the handle 22 in a counter clockwise direction toward a 
closed position causing the hook 14 to engage the keeper 12. Upon 
completion of the rotation, the hook pivot pin 16 passes the centerline 30 
and at the same time, the safety lock 36 engages the pin 50 in the first 
slot 48. The hook 14 and handle 22 are now securly locked together in a 
closed position to prevent the inadvertent unlatching of the improved 
latch 10. 
Upon unlatching the latch 10 the operator depresses the safety lock 36 
which releases the lock 36 from the pin 50. He then rotates the handle 22 
in a clockwise direction to an open position and the safety lock 26 then 
engages the pin 50 in the second slot 59 thereby again securing the handle 
22 to the hook 14. Upon further rotation of the handle 22 in a clockwise 
position, the hook 14 is moved away from the latch keeper 12 thereby 
completing the unlatching sequence and the cowling halves are now free to 
swing open. It can be appreciated from the above description of the 
operation of the improved latch 10, the operator is free to latch and 
unlatch the split cowlings surrounding an aircraft engine with only one 
hand. 
Changes may be made in the construction and arrangement of the parts or 
elements of the embodiments as described herein without departing from the 
spirit or scope of the invention defined in the following claims.