(1) Where a patent for an invention has been applied for or granted, and the applicant or patentee, as the case may be, applies for a further patent in respect of any improvement in or modification of the invention, he or she may, if he or she think fit, in his or her application for the further patent, request that the term limited in that patent for the duration thereof be the same as that of the original patent or so much of that term as is unexpired.