Toggle Link Latch
A latch with a unique nesting toggle linkage that extends and retracts a hook via movement of an actuation handle. The linkage links have U-shaped lateral cross sections with a central channel into which the respective links nest when the latch is closed to minimize the overall volume of the latch. The links fold toward each other while closing to reduce the latch's overall length when fully closed. The components of the latch are arranged so that the center of gravity of the latch is positioned in front of a mounting pin; therefore, in applications where the latch swings in the vertical plane, the hook will necessarily hang downwardly away from the keeper when the latch is open. Optionally, a keeper detector prevents the actuation handle from closing if the keeper has not been first captured in the mouth of the hook.
1 . A latch for applying a clinch load between a mounting pin and a keeper, comprising:
an elongate latch arm having a body portion slideably affixed to an upper toggle link by a transverse mounting pin received through a longitudinally extending slot in the latch arm at a first end thereof, and having a hook at a second end thereof opposite the first end for engaging the keeper;
a lower link hingedly connected to the latch arm at one end and hingedly connected to the upper link at an opposite end thereof, said upper and lower links providing a toggle linkage for extending and retracting the latch arm between an open and a closed position;
wherein the toggle linkage and latch arm are nested when the latch is in the closed position, said lower link being nested in a first channel in the upper link and a portion of said latch arm being nested within a second channel in the lower link.
2 . The latch of claim 1 further including a handle affixed to the lower link for actuating the latch between the open and closed positions, wherein the handle is moveable between locked and unlocked positions within a limited range of rotational motion with respect to the lower link.
3 . The latch of claim 2 further including a lock assembly including a trigger pivotably connected to the handle which releaseably holds the handle in the locked position.
4 . The latch of claim 3 wherein said trigger comprises a base and a pair of side arms fixed to and extending from opposed sides of said base, and said lock assembly includes a pair of catches extending from the latch arm that releasably engage said side arms to hold the handle in the locked position, wherein the base of said trigger lies substantially flush with the handle when the handle is held in the locked position.
5 . The latch of claim 4 wherein the handle includes bias means that urge the handle toward the unlocked position.
6 . The latch of claim 5 wherein said handle is substantially flush with the upper link when the handle is in the locked position.
7 . The latch of claim 1 wherein the joints of the links form an over-center position of the toggle linkage when the latch is closed whereby a portion of the load applied between the mounting pin and the latch arm forces the linkage toward the closed position.
8 . The latch of claim 7 wherein the trigger includes bias means that resiliently urge the trigger toward the locked position.
9 . The latch of claim 1 wherein the upper and lower links each have a U-shaped lateral cross section.
10 . The latch of claim 9 wherein the lower link includes bias means that urge the lower link in a direction away from said hook.
11 . The latch of claim 1 wherein the latch arm includes a keeper detector mechanism which prevents the handle from closing if the mouth of the hook is not occupied by the keeper.
12 . The latch of claim 11 wherein the keeper detector mechanism includes a rotatable lever having two arms, a first arm that contacts the handle and prevents it from closing when a second arm of the lever occupies the mouth of the hook indicating the absence of the keeper.
13 . The latch of claim 12 wherein the keeper mechanism includes bias means that urge the second lever arm toward the mouth of the hook.
14 . The latch of claim 1 wherein the toggle linkage is a toggle linkage in which the toggle links fold together as the handle moves toward the locked position.
15 . The latch of claim 14 wherein said mounting pin is constructed and arranged to connect the latch to a supporting structure.
16 . The latch of claim 15 wherein the latch is connected to a supporting structure.
17 . The latch of claim 16 wherein the supporting structure is a part of an aircraft.
18 . The latch of claim 2 wherein a portion of the handle is nested within said first channel of the upper link.
19 . The latch of claim 4 wherein said side arms have barbed ends that bear against said catches as the handle is moved to the locked position.