Applescript to purge backup copies

I need a script which will purge (remove) old backups from two internal drives. Since I already have an automated backup setup (using Chronosync) I'm thinking I can just have it run this script whenever it does its backup.

The first drive contains Adobe Lightroom catalogs. There are two backup folders on this drive:

/Volumes/Cache HD/Family/Backups/
and
/Volumes/Cache HD/Projects/Backups/

Within these folders you'll find an endless number of backup folders named with the date, such as:

2015-05-02 2214
2015-05-03 2329
2015-05-04 0049
2015-05-04 0645
2015-05-05 1441
2015-05-05 2119
2015-05-07 1756

At any time I'd like to keep no more than say the 4 most recent backups.


The second drive (incidently the Time Machine drive, using its root for this) consists of a folder with numerous media files (images, videos, audio files etc.) which are copied to here whenever I import anything new to Adobe Lightroom or via Adobe Photo-downloader, in addition to its main drive. This is just to ensure I have a backup from my memory cards in case the main drive goes down in the process etc.
The imported files are either placed directly in the backup folder (/Volumes/Time Machine/Media backups/) or in a sub-folder of it named something like "Imported on 2 May 2015". The folder naming depends on how I configure it in Lightroom so this might change.

I figure it might be best to purge according to the file's date, regardless of being in a sub-folder or not, so let's say I want to purge any file which is older than 3 weeks old, and if a sub-folder is purged so that it's empty that folder should also be deleted.

Are there any ready made scripts around which would be adapted for this use?