沉重的传统观念成为了束缚他们自由的枷锁。

The heavy traditional beliefs became yokes that limited their freedom.

yokes 是名词 yoke 的复数形式。yoke 本义是"轭"，即套在牛马脖子上用来拉车或犁的工具，引申为"束缚、枷锁"的比喻意义。在句中指传统观念像枷锁一样限制人们的自由。