Getting high rankings takes time, so unfortunately there is no way to accomplish this "quickly".
Also, your question is very broad and there are no details. How long ago did you fully launch your website? What is your competitive edge (i.e. what sets your couplings apart from your competition)?
Finally, ranking for a generic keyword like "couplings" is a very time consuming and expensive process. When you start out, your goal should be to capitalize on some longer tail keywords that you can rank for in the short term (2-3 months) and work toward the shorter keywords as you progress. In other words, rather than limiting yourself to "couplings", perhaps you could work on ranking for "Jaw Flex Couplings" or "Jaw Flex Couplings L", etc... This focus may render substantially more profit in the next few months, as opposed to just "couplings".