| 摘要 |
A simple, inexpensive ratchet type latch mechanism for maintaining a movable portion of an articulated structure in an elevated position relative to a stationary portion of the structure on which the movable portion is pivotably mounted. The latch mechanism includes a ratchet plate pivotally mounted at one end thereof to the stationary portion of the structure and has an elongate ratchet slot with a plurality of ratchet notches, an escapement plate slidably mounted to the ratchet plate for movement between a first position wherein the ratchet notches are exposed, and a second position wherein the ratchet notches are covered. A crank arm is pivotally connected at one end to the movable portion of the structure and has a pin at another end thereof which projects from the crank and through the slot in the ratchet and through the slot in the escapement plate. The pin is engagable with a cam surface at one end of the slot in the escapement plate to move the escapement plate to a set position wherein the ratchet notches are exposed. The pivotable portion can be raised to any of a plurality of discrete elevated positions wherein the clevis pin engages one of the ratchet notches to support the pivotable portion in a corresponding elevated position. When the clevis pin is moved passed the ratchet notches corresponding to the most elevated position in which the pivotable portion can be maintained by the mechanism, the pivot pin engages the cam surface at the end opposite of the first cam surface to cause the escapement plate to move to the reset position wherein the ratchet notches are covered by the escapement plate to allow the pivotable portion to be lowered unimpeded by the ratchet notches. As the pivotable portion is translated downwardly to its lowest position, the clevis pin again engages the first cam surface causing the escapement plate to move back to the set position wherein the ratchet notches are again exposed to reconfigure latch mechanism so that the pivotable portion can be again raised and held in an elevated position by the engagement of the pin with the ratchet notches.
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