Question On "Improvement Patents"

Firstly, in reality, there is no such thing as an improvement patent, and furthermore, the vast majority of patents are effectively "improvements" relative to what has been patented before - hence, the citing of "prior art" (prior patents) in office actions when your patent application is examined - the examiner is effectively telling you what has been previously been patented and that in his opinion, your invention is not in fact an improvement at all with respect to existing patents - it is then your job, or that of your patent attorney/agent to insert language into your claim(s) which render the claims patentable over the prior patents cited by examiner, and obviously you have done this which is why your patent issued.

As for filing your subsequent patent application in 2016 or 2017, you must cite your current patent to the Patent Office by means of an Information Disclosure Statement which effectively cites to the Patent Office all patents of which you are aware that are relevant to the invention disclosed within your patent application - since your new patent application will be an "improvement" over your existing patented method, your patent is obviously relevant and must be cited along with all of the prior art cited during the prosecution of the patent application which has now resulted in your patent. You have a duty to disclose to the Office all patents of which you are aware, and obviously, you are aware of all of the patents cited during the prosecution of your first patent application. Your job will then be to have something in the claim(s) of your new patent application which will patentably distinguish your invention not only from all of the prior art cited during the prosecution of your recently issued patent but also from your own patent. If you had filed your new application as a continuation-in-part (CIP), before your patent issued, as opposed to filing it in 2016/2017, your current patent disclosure could not be used against you for the disclosed matter common to the patent and your subsequent application, however, since you did not file a CIP, that subject matter, even though it is your own disclosure material, can be used against you because I am assuming that your current patent was previously published as a patent application publication which would probably have been published more than one year before the filing of your new patent application. If this is not the case, then you have effectively lucked out whereby your original disclosure material will not be able to be used against you.
See the new AIA provisions of 35 USC 102.

Such an 'improvement' patent application will be no more or no less than a normal patent application. The only difference is that there is a piece of prior art (your first patent) that may or may not be held against you. Further, your first patent may not only be regarded as prior art (if and how will depend on the publication data of the patent application and the filing data of your new application) but it will also prevent you to be allowed claims that overlap with the claims that have been granted already. This is called the prohibition of 'statutory type double patenting'. If claims would overlap, the solution would be to file a so-called terminal disclaimer in the newer patent which would set the expiry date of the ne patent equal to the expiry date of the earlier patent.