Ivy caching with travis ci

in travis.yml file I am using cache but look like it has no effect with ivy. each time when i run the travis ci build it keep downloading dependencies.

before_cache:
# Cleanup the cached directories to avoid unnecessary cache updates
- find “${HOME}”/.ivy2/cache -name “ivydata-*.properties” -print -delete
cache:
# Cache the following directories
directories:
- $HOME/.ivy2/cache

please suggest me .
Thanks,

Imprint