Background 

The doctrine of “file wrapper estoppel” (also called “prosecution history estoppel”) holds that submissions or amendments submitted by a patent owner to a court during patent enforcement proceedings should be rejected (i.e., estopped) by the court if they contradict or are inconsistent with earlier comments submitted to the patent office during prosecution of the patent in suit.  The recent decision in Bradken Resources Pty Ltd v Lynx Engineering Consultants Pty Ltd,[1] handed down by Nicholas J, has reiterated that in view of the considerable obstacles facing the application of file wrapper estoppel in Australia, it is unlikely to be applied in Australia in the foreseeable future.

The preliminary question that Nicholas J was required to determine in his decision was whether Bradken’s Iron Ore Wagon included an internal ridge that was integrally formed within a side wall. Bradken’s Iron Ore Wagon included an internal ridge that was welded onto the inside of the side wall. The preliminary question, to come to a determination on possible infringement, therefore turned on an issue of construction and whether the phrase “integrally formed” included welding.

As part of their submissions, Bradken attempted to rely upon a letter from Lynx’s patent attorney, to the Commissioner of Patents, that included the following statement during examination:

“The container of the present invention, unlike prior art, uses a reinforcing ridge or ridges that are formed from the flat plate that makes up the side walls. One plate only is required, as the ridge or ridges are achieved through bending and not through welding or any other connections or fasteners.”[2]

Lynx effectively invited the court to overlook this statement during the proceedings in favour of a far broader construction of “integrally formed”. In particular, Lynx submitted the word “integrally”, as used in the claimed invention, indicates that the internal ridge must be an integral or permanent part of the side wall that cannot be disassembled or removed from the wall by non-destructive methods. It submitted that a welded or riveted part of the side wall meets that definition.

In contrast, Bradken submitted that the phrase “integrally formed” is intended to be read in much the same way as it would be if the word “formed” was used in its technical sense and, therefore, this implies that the material has been pressed or bent into shape without the addition of material by (for instance) welding, riveting or bolting.

Nicholas J provided the following construction of the phrase “integrally formed” and, as part of his decision, addressed issues relating to the application of file wrapper estoppel in Australia. 

Construction – Integrally Formed 

Construction of patent claims under Australian law is ultimately a matter for the court.[3] This construction may be assisted by evidence from a person skilled in the art but it is for the court, not for any witness, to ultimately construe the claims of a specification.[4]

With the above principles in mind, and after considering the specification as a whole in addition to evidence presented during the proceedings, Nicholas J (unsurprisingly) concluded that, in his opinion, the phrase “integrally formed” refers to a piece of material that has been bent, pressed or moulded into shape from one piece of material. There were a number of considerations which lead Nicholas J to this conclusion including a comparison between the specification before and after amendment.[5]

In particular, claim 1 in its original form required that at least one side wall includes at least one ridge. Claim 1 in its amended form requires that there be an internal ridge integrally formed within the side wall. Nicholas J therefore outlined that the amendment to the claimed invention strongly suggests that the new wording is to be understood to convey something more than that the ridge must be integral in the sense of being a permanent, or permanently attached, part of the side wall.[6]In his view, “the amendment tends to confirm that, properly construed, claim 1 requires that the ridge and the side wall be “integrally formed” in the sense that they must be bent, pressed or moulded into shape from the one piece of material.”[7] Notably, this conclusion did not depend in any way upon the above statement made by Lynx’s patent attorney during examination of the application. 

File Wrapper Estoppel 

The above statement made by Lynx’s patent attorney during examination was clearly unfavourable to their case. However, in accordance with previous Australian authorities, Nicholas J did not think that this statement was admissible evidence as to the proper construction of the claimed invention.

Whilst Nicholas J agreed with Bradken that the applicability of the U.S. doctrine of file wrapper estoppel has not been settled in Australian law, the observations of Gummow J in Prestige highlight the considerable obstacles that are involved in applying the doctrine in this country.[8]  Indeed, “the scope of the monopoly depends upon the proper construction of the claims read in the context of the specification as a whole and in light of the common general knowledge.”[9] Under Australian law such construction is a matter for the court and, bearing in mind that there is no immediate counterpart for the doctrine of equivalents in Australia, authorities in this country have naturally refrained from recourse to extrinsic materials (such as correspondence between the patent applicant and the Commissioner) for the purpose of ascertaining the true scope of a claim.

Bradken was unable to point to any developments in the law since Prestige was decided that might suggest that these obstacles are now any less weighty than Gummow J’s reasons suggest them to be.[10] Nicholas J therefore decided the construction point in accordance with well-settled principles under Australian law, without giving regard to the above statement made by Lynx’s patent attorney during examination. 

Conclusion

Based on Nicholas J’s construction of “integrally formed”, the Bradken Iron Ore Wagon was found not to infringe the claims of Lynx’s patent. With this in mind, Nicholas J’s judgment reiterates the following practice points:

  1. Construction of patent claims under Australian law is ultimately a matter for the court.
  2. Construction of patent claims may be assisted by evidence from a person skilled in the art and recourse may be had to earlier versions of the patent specification, to assist interpretation.
  3. Whilst it needs to be borne in mind that foreign and domestic prosecution history may be used when interpreting the scope of U.S. patent claims,[11] there are considerable obstacles to applying the doctrine of file wrapper estoppel in Australia.
  4. In view of these considerable obstacles, it is highly unlikely that the doctrine of file wrapper estoppel will be applied in Australia in the foreseeable future.