ability to obtain a patent on an existing item which patent has expired

[PSpiva]

I have an item that I'm looking to patent that is already in existance Patent expired but I have modified to work in another industry so the only thing I had to change was the way it mounts and the slides on the fixture it's self I already have a prototype that works and would like to get it to market but would like to patent if possible before doing so I feal certian it will be coppied if I put it out there without some kind of protection before doing so, please help I,m new to the patent world

[Brad]

Please send me an email or request a quote using this link:  https://patentfile.org/patent-estimate/

Thank you,
Brad