(1) Subject to the provisions contained in this section, where an application is made for a patent in respect of any improvement in or modification of an invention described or disclosed in the complete specification filed therefor (in this Act referred to as the "main invention") and the applicant also applies or has applied for a patent for that invention or is the patentee in respect thereof, the Controller may, if the applicant so requests, grant the patent for the improvement or modification as a patent of addition.
(2) Subject to the provisions contained in this section, where an invention, being an improvement in or modification of another invention, is the subject of an independent patent and the patentee in respect of that patent is also the patentee in respect of the patent for the main invention, the Controller may, if the patentee so requests, by order, revoke the patent for the improvement or modification and grant to the patentee a patent of addition in respect thereof, bearing the same date as the date of the patent so revoked.
(3) A patent shall not be granted as a patent of addition unless the date of filing of the [application] was the same as or later than the date of filing of the [application] in respect of the main invention.
[(4) A patent of addition shallnot be granted before grant of the patent for the main invention].