Patents of Addition

1A patent of addition is granted for an improvement or modification of an invention. (Patents Act 1970, ss 2(1)(q) and 54. See Terfenadin [1998] FSR 145, p 155.) As the term implies, a patent of addition is granted as an addition to a pre-existing invention described or disclosed in the complete specification. The invention so described or disclosed is known as the ‘main invention’. As a patent of addition can be granted only on the basis of an earlier application or in a granted patent, the grant of the patent of addition cannot precede the grant of the main invention. (Patents Act 1970, s 54(4).) For the same reason, the date of filing of the application for a patent of addition should be the same as or later than the date of filing of the application of the main invention. (Ibid, s 54(3).)

2The object to providing for patents of addition is to protect improvement and modification of an inventor which may be made in the course of working of his patent, which may, by itself, not be entitled for a separate patent. Such improvements and modifications are tagged along to the main invention and protected along with the main invention so long as the main invention exists. No additional renewal fee is required for such additions. However, the validity of a patent of addition is not affected by a revocation of the main invention.

3In Selfdot Technologies (OPC) v Controller General of Patents, Designs & Trade Marks (2023) the Madras High Court held that “a patent of addition is linked to the parent or main invention in multiple ways. By way of illustration, the application for grant of a patent of addition cannot be filed earlier than the date of filing of the application for grant of patent for the main invention; it cannot be granted before grant of the patent for the main invention; the term of the patent of addition shall not exceed that of the main invention, even if granted later than the main invention; and the complete specification of the main invention shall be taken into account to determine novelty of the claim for a patent of addition.” (para 11) It held that “The nature of a patent of addition, i.e. involving an improvement in or modification of the parent or main invention, would invariably require additional disclosures to those contained in the complete specification of the main invention.” (para 12)

4A patent of addition may be granted in lieu of an independent patent for an improvement or a modification of another invention. Where an invention, which is an improvement in or modification of another invention, is the subject of an independent patent held by the patentee who also holds the patent for the main invention, the patentee may request the Controller to revoke the independent patent (the patent for the improvement or modification) and grant a patent of addition in lieu of it, bearing the same date as the date of the patent so revoked. (Ibid, s 54(2).) If the Controller is satisfied that the provisions under the Patents Act have not been met, he will be bound to make an order of revocation. (See Aktiebolaget Celloplast’s Application (1978) RPC 239, p 243. The court held that if the Comptroller was satisfied upon the application of s 26(2) of the UK Patents Act 1949 [which corresponds to s 54(2) of the Patents Act 1970] that the provisions of the statute were met, then the Comptroller had no discretion and had to do what the statute required of him. The earlier decision in Van der Lely’s Application (1958) RPC 383 was not followed.)

5In Ravi Kamal Bali v Kala Tech (2008) the Bombay High Court brought out the distinction between a patent and a patent of addition. It held that “Sections 54 and 55 in terms establish the link between the main invention and the patent of addition. It posits that the patentee of the main invention and the patentee of the patent of addition, are the same. Section 54 permits the grant of a patent of addition only if the applicant thereof applies or has applied for a patent of the main invention in respect whereof the notification or improvement is claimed. It is obvious therefore that only the patentee of the main invention is entitled to improve or modify the main invention for otherwise it would permit anybody to benefit from it by exploiting the main invention. A stranger to the main invention cannot apply for a patent of addition in respect of any modification or improvement of the main intention.” (para 34) The Court held that “A view to the contrary would lead to the most incongruous results. A view to the contrary would dilute if not obliterate the rights of a patentee in respect of a main invention entirely.” (para 35)

6A specification in respect of a patent of addition under s 54 shall contain a specific reference to the number of the main patent, or the application for the main patent, as the case may be, and a definite statement that the invention comprises an improvement or modification over the invention claimed in the specification of the main patent granted or applied for. (Patents Rules 2003, r 13(3).) A patent of addition may be combined with an earlier patent of addition and preferred in one application. An ordinary application may also be converted into an application for a patent of addition pursuant to an opposition proceeding. (See Hauni-Werke Korber & Co KG’s Patent of Addition (1976) RPC 328, [1980] FSR 121.)

7Under s 54 of the Patents Act, an applicant must satisfy the following requirements: (Section 54 of the Patents Act 1970 in substance reproduces s 26 of the UK Patents Act 1949. For further details, see Justice N Rajagopala Ayyangar, Report on the Revision of the Patent Laws, September 1959, para 510 onwards.)

(a) the patent of addition must relate to an improvement in or modification of the main invention; (b) such improvement or modification should pertain to an invention described or disclosed in the complete specification of the main invention; (c) the patent of addition must show that the invention comes within the scope of an improvement or modification of the main invention, ie, it should not pertain to a improvement or modification not covered in the main invention; (d) the complete specification of the patent of addition must be filed on the same date or after the filing of the complete specification of the main invention.

8A patent of addition must relate to a single invention for which a patent has already been granted. It shall not be an addition to a series of invention for which separate patents subsist. A patent of addition must be fairly based on the main invention. (See Hughes Tool Co v Ingersoll-Rand Co Ltd [1977] FSR 406; Letraset Ltd v Rexel Ltd [1975] FSR 62, (1976) RPC 51 (CA).) In determining whether the patent of addition is fairly based on the main invention, the court has to look into the whole of the disclosure and not merely the claims. (See Kopat’s Patent (1965) RPC 404.)

9In determining whether an improvement or modification has been made to the main invention, a proper comparison should be made between the novel contributions made by the two specifications to the art. It will be necessary to consider both what has been changed and what has been retained. (See Buchanan v Alba Diagnostics Ltd (2000) RPC 367, p 383.) The meaning of the expressions ‘improvement’ and ‘modification’ are well-understood. In Elliott Brothers (London) Ltd’s Application, Lloyd- Jacob J said: ([1966] FSR 334, p 338, (1967) RPC 1. In this case, the application for patent of addition was refused as the improvement or modification claimed represented a radical departure from the novel features introduce by the main invention.)

The meaning of the words ‘modification’ and ‘improvement’ is clear enough. A modification is an alternation which does not involve a radical transformation and an improvement is a variation, whether by addition, omission, or alteration to secure a better performance, whilst retaining some characteristic part… What seems to be abundantly clear is that the mere presence of a number of elements common to both inventions if common also in the known art, is not sufficient to make one invention an improvement or addition to the other (See Sadgrove v Godfrey (1920) 37 RPC 7).

10It is important to note that s 54(1) of the Patents Act requires the improvement or modification to be described or disclosed in the complete specification of the main invention. It does not limit such improvement or modification to what is claimed in the earlier specification. (See Justice N Rajagopala Ayyangar, Report on the Revision of the Patent Laws, September 1959, para 510 onwards. See also Georgia Kaolin Co Ltd’s Application (1956) RPC 121; Welwyn Electrical Laboratories Ltd’s Application (1957) RPC 143.) In determining whether a patent of addition qualifies as an improvement or a modification, the court has to looking into the whole of the disclosure made in the main invention and not merely to the claims. (See Hughes Tool Co v Ingersoll-Rand Co Ltd [1977] FSR 406.) Thus, the mere claiming in a later application of a subject matter contained in the earlier specification which is not claimed therein, cannot qualify for a patent of addition as the purpose of such a claim would only be to rectify an omission to claim at the first instance. (See Welwyn Electrical Laboratories Ltd’s Application (1957) RPC 143, p 146.)

11The Patents Act allows for the making of an application for an improvement or modification independent of s 54. Under s 54, the improvement or modification of the invention described in the specification of the main invention which is required for qualifying for an application for a patent of addition need not be of such character as to qualify for an independent patent. (Justice N Rajagopala Ayyangar, Report on the Revision of the Patent Laws, September 1959, para 519.) In other words, a patent of addition will be granted for an improvement or a modification of an earlier invention provided such an invention is described or disclosed in the complete specification of the main invention. The inventive step mentioned in the main invention (earlier patent) shall be taken into account in determining the inventive step of the improvement as the same is based on the earlier patent and any publication or use of the invention in the complete specification of the main invention or the patent of addition cannot be a ground for its refusal or revocation. (Patents Act 1970, s 56.) For this reason, s 56(1) makes it clear that the validity of patent of addition shall not be questioned on the ground that the invention ought to have been the subject of an independent patent.

12The Patents Act also provides that a complete specification filed after a provisional specification may include claims in respect of developments or additions to the invention described in the provisional specification, if they are of such a nature that the applicant would be entitled to make a separate application for a patent under s 6 of the Patents Act. (Ibid, s 10(7).) It also provides for a similar provision for a convention application. (Ibid, s 136(2).)

13The test to determine whether an improvement or a modification will qualify for a separate patent, as opposed to a patent of addition under s 54, will involve:

(1) identifying whether the improvement or modification relates to a single invention or to a group of invention linked to form a single inventive concept as disclosed in the specification of the main invention; and (2) determining whether the improvement or modification is fairly based on the matter disclosed in the specification of the main invention.

If the above two steps are answered in the negative, the improvement or modification may qualify for a separate patent if it satisfies the conditions of patentability under the Patents Act.

14A patent of addition does not extend the term of the main invention. A patent of addition is granted for a term equal to that of the main invention or to such extent of the term that has not expired. As the patent of addition is based on the main invention (earlier patent), it shall remain in force during the term of the main invention or until the main invention is revoked, whichever is shorter. If the patent for the main invention is revoked by the court or the Controller, the patentee may make a request in the prescribed manner for the patent of addition to be treated as an independent patent for the remainder of the term of the patent.

15The advantage of claiming an improvement or a modification of an invention as a patent of addition is that no renewal fee is payable in respect of the patent of addition. The renewal fee paid with regard to the main invention will suffice. But, if the main invention is revoked and the patent of addition becomes an independent patent, then the same fee as that of the main invention shall be paid on the same dates as that of the main invention had that been valid. (Patents Act 1970, s 55(2).)

16A patent of addition is likely to raise contentious issues with regard to novelty and obviousness. The Patents Act states that the grant of a patent of addition shall not be refused or a patent of addition already granted shall not be revoked or invalidated on the ground only that the invention claimed in the complete specification does not involve any inventive step. In determining obviousness, the patent of addition shall not be regarded as obvious or lacking an inventive step by the fact of:

(a) any publication or use of the main invention described in its complete specification; or (b) any publication or use of any improvement in or modification of the main invention described in the complete specification of a patent of addition to the patent for the main invention or of an application for such a patent of addition.

17Such publication would include publication by the patentee as well as by third parties. (See Monsanto Co (Salyer’s) Application [1966] FSR 271, (1969) RPC 75.) The validity of a patent shall not be questioned on the ground that the invention ought to have been the subject of an independent patent. (Patents Act 1970, s 56(1).)

18In determining the novelty of the invention claimed in the complete specification of the patent of addition, the complete specification of the main invention shall be considered. (Ibid, s 56(2).) In other words, the complete specification of the main invention may be cited for anticipation by publication. The claim in a patent of addition must disclose a novel matter not disclosed in the complete specification of the main invention, though it need not involve any inventive step. (See Justice N Rajagopala Ayyangar, Report on the Revision of the Patent Laws, September 1959, para 519. See also P & S’ Application (1952) 69 RPC 249.)