In the United States, a patent application may be filed based on an earlier filed “parent” application.  Such applications include divisional applications and continuation applications.  Continuation application and divisional applications have the same specification as the parent application but normally have different claims.  Continuation-in-part (CIP) applications are also available in the United States.  However, CIPs include subject matter not originally disclosed in the parent application.  Of these types of applications available in the United States, only divisional applications are available in Canada.

Unity of invention and divisional applications are governed by section 36 of the Patent Act.  According to paragraph 36(1) of the Patent Act, a patent shall be granted for one invention only, but shall not be deemed invalid by reason only that it has been granted for more than one invention.

During the prosecution of the patent application, an Applicant may be faced with an opportunity to file a divisional application voluntarily or upon direction of the Commissioner of Patents to limit the claims to a single invention.  Divisional applications have the same filing date as the parent application and must be filed before the parent application issues to patent.

Voluntary Division:  According to paragraph 36(2) of the Patent Act, where a patent application discloses more than one invention, the Applicant may limit the claims to one invention only and any other invention disclosed may be made the subject of a divisional application.

Division on Direction by Commissioner: According to paragraph 36(2.1) of the Patent Act, where a patent application discloses and claims more than one invention, the Applicant shall on the direction of the Commissioner, limit the claims to one invention only, and any other invention disclosed may be made the subject of a divisional application.

In the case of voluntary division it is important to note that divisional applications may be filed for any other invention disclosed.  Accordingly, the additional invention does not necessarily need to be claimed in the parent application prior to the filing of the divisional application.

In the case of division on direction by the Commissioner, at least one additional invention must be claimed in an application in order for the divisional requirement to be raised.  This issue may arise, for example, in an Office Action where the Examiner has taken the position that the claims are directed to more than one invention.  In the objection, the Examiner will typically group certain claims together and indicate which claims may be allowable in a single application.  Once such a divisional objection has been applied, an Applicant may select the allowable claim group(s) for further prosecution.  The Applicant may then choose to file divisional applications for one or more of the other claim groups selected by the Examiner.  An Applicant may also choose to make submissions to the Examiner, arguing for the allowability of the claims in a single application or proposing different groups of claims than those presented by the Examiner.  However, if the Commissioner maintains the divisional requirement, the Applicant must limit the claims to one invention.

Although voluntary division is available, it is recommended practice to file your application with all of the desired claims and allow the Examiner to make the divisional requirement.  Where patents issue based on divisional applications filed on a voluntary basis, the Applicant runs the risk of being faced with a double patenting objection.  However, the Supreme Court of Canada has ruled in Consolboard v. MacMillan Bloedel (1981) that where patents issue based on divisional applications filed on direction by the Commissioner, then double patenting is inappropriate.

The Test for Unity of Invention in Canada

Assessing whether or not unity of invention exists amounts to determining whether or not a “single general inventive concept” links the claims.  Generally, two independent claims will share a general inventive concept if a set of essential elements which, in combination, are new and unobvious in view of the prior art is common to each claim.

Summary

A patent must be limited to a single invention.  However, during the prosecution, an Applicant may file divisional applications on a voluntary basis for any other invention disclosed in the application.  Where an application claims more than one invention, the Commissioner may require the Applicant to limit the claims to one invention.  The Applicant may then file one or more divisional applications to any other invention disclosed.  Recommended practice is to allow the Examiner to make the divisional requirement.  Filing divisional applications on a voluntary basis puts the Applicant at risk of being hit with a double patenting problem after the patents issue.