Self-locking chock system for a jack-up rig unit

In a jack-up unit having a support leg (16) and with a rack (30) connected thereto and disposed generally along a portion of the leg, a platform (12) supported by the leg, and a chock system (32) carried by the platform to selectively lock the leg and the platform together for rigidification of the jack-up unit, a chock system improvement for the jack-up unit characterized by:

• (a) a plurality of cams (36,38,40,42) grouped in an unevenly spaced apart sequential alignment along the platform, each of said cams including:
• (1) a cam pivot axis (46) for each of said cams,
• (2) a cam profile portion (56) adapted to ride along the rack profile (58) where relative motion between the platform and the leg rack is in a first direction,
• (3) a cam pawl portion (52) adapted to selectively engage the rack profile when aligned in a desired locking engagement where relative motion in a second direction generally opposite to the first direction is restricted, and
• (4) a cam center-of-gravity (50) located to continuously urge both said cam profile portion and said cam pawl portion against the rack profile and into locking engagement, respectively, and
• (b) a cam unlocking means including:
• (1) a block-and-tackle cable (70) connected to each of said cams so that a cam in the desired locking engagement can be moved away from the rack profile by pivoting about said cam pivot axis against the continuous urging of said cam center-of-gravity developed force.