Claim Categories

The requirement that the claims must be clear applies to individual claims, i.e. to independent and dependent claims alike, and also to the claims as a whole. The clarity of the claims is of the utmost importance in view of their function in defining the matter for which protection is sought. Therefore, the meaning of the terms of a claim must, as far as possible, be clear for the person skilled in the art from the wording of the claim alone (see also F‑IV, 4.2). In view of the differences in the scope of protection which may be attached to the various categories of claims, the division must ensure that the wording of a claim leaves no doubt as to its category.


source: EPO Guidelines for Examination: Part F - The European Patent Application; 4.1 Clarity


The EPC does not define or directly refer to the different categories of a claim. With respect to conciseness, the number of claims, and thus the number of independent claims per category should be reasonably small, so that the scope of protection is not blurred. The Guidelines refer to two basic claim categories, one kind of claims related to a physical entity and one kind of claims related to activities:

  • product claim / apparatus claim
  • process claim / use claim

Whilst independent claims of too many categories are not allowed for the same reason of clarity (article 84 EPC) the claims must define the category it belongs to.

In the second part of the fictious communication pursuant to Article 94(3) EPC (examination report) deficiencies of the first claim would be raised:

In relation to the first invention:

The application does not meet the requirement of Article 84 EPC, because claim 1 is not clear.

Claim 1 defines "Introducing into an enclosed space ...". Said term leaves the reader in doubt about the category of the claim.

The applicant is therefore requested to reformulate said claim in order to define it clearly either as an entity (i.e. apparatus or device) or activity (i.e. method).

Amendments to state a clear category

Mainly by using verbs the original claims of DE N° 532 claims 1 and 4 clearly relate to activities: "introducing", "expand", "sucking in", "compressing", "combustion", "generating", "exiting". Claim 5 clearly relates to a physical entity: a machine with a special construction. The category of claims 2 and 3 are referring to the property of the gas before combustion. As they are dependent on claim 1, a method claim, they should be also reformulated as a method claim. The original claims therefore should be reworded with respect to the lack of referring to a claim category the claims should be amended as follows:


  1. Method for introducing into an enclosed space combustible, with air mixed gases and air of a different kind prior to their combustion in such manner that at a point of an initiated combustion it [the combustion] slows down while [the combustion is] continuing from gas particle to gas particle, whereby the combustion products and the kind of air that envelopes them expand by the produced heat and thus release operational power.

  2. Method according to claim 1 wherein the gases until combustion have atmospheric pressure.

  3. Method according to claim 1 wherein the gases have before combustion more than atmospheric pressure.

  4. Method of operating a gas engine according to one of claims 1, 2, or 3 with a crank motion such that for two rotations of the crankshaft of one side of the piston the following effects are generated:

    1. Sucking in the gas types into the cylinder;

    2. Compression of those;

    3. Combustion and generating work of those;

    4. Exiting of those of the cylinder.

  5. A machine, constructed as described.


These amendments do not take into account other issues of lack of clarity that would be raised by the EPO examiner.

With article 123(2) EPC we are restricted to amendments that do not go beyond the original disclosure. The only disclosure why the pressure of the gases before combustion have atmospheric pressure or have a pressure greater than atmospheric pressure is actually a consequence whether the gases are compressed or are not compressed before combustion. Ideally claims 2 and 3 as real method claims should have been filed as:

2. Method according to claim 1 wherein the gases are not compressed before combustion.

3. Method according to claim 1 wherein the gases are compressed before compression.

and thus also refer to an activity ("compressing").



Clarity claim 1