4.13.2
Interpretation of means-plus-function features ("means for ... ") 

Means-plus-function features ("means for ...") are a type of functional feature and hence do not contravene the requirements of Art. 84.

Any prior art feature suitable for carrying out the function of a means-plus-function feature will anticipate the latter. For example, the feature "means for opening a door" is anticipated by both the door key and a crowbar.

An exception to this general principle of interpretation is where the function of the means-plus-function feature is carried out by a computer or similar apparatus. In this case the means-plus-function features are interpreted as means adapted to carry out the relevant steps/functions, rather than merely means suitable for carrying them out.

In practice this means that the following two formulations of a claim directed to an eyeglass lens grinding machine are equivalent, i.e. they claim the same subject-matter:Example:

"1. 
An eyeglass lens grinding machine for processing a lens such that the lens is fitted in an eyeglass frame, said machine comprising: 

at least a grinding wheel for bevelling the lens;

means for receiving frame configurational data on the eyeglass frame and layout data to be used in providing a layout of the lens relative to the eyeglass frame;

means for detecting an edge position of the lens on the basis of the received frame data and layout data;

means for determining a first bevel path by calculation based on the result of detection by said edge position detecting means;

means for determining a second bevel path obtained by tilting said first bevel path such that said second bevel path passes through a desired position on a lens edge; and

means for controlling the grinding wheel during the bevelling of the lens on the basis of said second bevel path."

"1. 
An eyeglass lens grinding machine for processing a lens such that the lens is fitted in an eyeglass frame, said machine comprising: 

at least a grinding wheel for bevelling the lens;

a computer adapted to:

– 
receive frame configurational data on the eyeglass frame and layout data to be used in providing a layout of the lens relative to the eyeglass frame; 
– 
detect an edge position of the lens on the basis of the received frame data and layout data; 
– 
determine a first bevel path by calculation based on the result of detection by said edge position detecting means; 
– 
determine a second bevel path that is obtained by tilting said first bevel path such that said second bevel path passes through a desired position on a lens edge; and 
– 
control the grinding wheel during the bevelling of the lens on the basis of said second bevel path." 

Each of these two claims is new over a prior art disclosing an eyeglass lens grinding machine comprising a grinding wheel and a computer for controlling the grinding wheel if the specific processing steps are not disclosed in the prior art. When "means for" refers to computer means, the processing steps being defined as "means for + function" (first claim) and "computer adapted to + function" (second claim) are to be interpreted as limiting. In order to anticipate these apparatus claims,Therefore, a prior-art document disclosingmust disclose an eyeglass lens grinding machine comprising at least a grinding wheel for bevelling the lens and a computer only anticipates these claims if the prior-art document also discloses that the computer is programmed to carrythat carries out the claimed steps, not merely an apparatus suitable for carrying out said steps.

For further information on claim formulations commonly used in computer-implemented inventions, see F‑IV, 3.9.

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