才（Adv.）+V "not until" 
   才 is used here to give the sense of "later than expected". It is usually preceded by an expression of time.
              
                 Subj.+ time expression +才+V
Examples:
1. 中国2001年才加入世贸。
China didn't join the World Trade Organization until 2001.
2. 美方代表要等公司总裁过目后才在合同草案上签字。
The American representative won't sign the contract until the CEO of his company has read the draft.

Substitutive drills: