Imac and Probox 4 bay Hd enclosure

I'm running a Imac mid 2011; OS 10.9.5.. To it I have a Probox 4 HD enclosure connected via USB. System works great as I have been running this way for three years now. The problem is; that when my computer goes to sleep; the Probox disconnects completely and I get those notifications for each HD that they have been ejected improperly. I've gone into the Settings/ Energy Saver and have the following settings:
Computer Sleep - NEVER
Display Sleep - 1 hr
Put Hd to sleep - NEVER
Wake for Network Access - YES
Startup auto after power failure - Yes

Is there any way to set this computer up so that when it goes to sleep; the Hd's don't?

Thanks

Still waiting for some help on this. There must be some way; some setting that can be adjusted; so that this Probox does not disconnect every time my computer goes to sleep.