Chocolate teapots and nuclear bombs: Whole range sufficiency of mechanical inventions (T 0149/21)

A question that confuses discussions on sufficiency is whether certain sufficiency tests are applicable to only certain types of invention. However, according to the established case law of the EPO, the underlying test for sufficiency is consistent, regardless of the type of invention. The test is always whether there is substantiated doubt that a skilled person would be able to perform the invention in view of the disclosure of the application as filed and common general knowledge (CGK). A recent decision from the Boards of Appeal (T 0149/21) confirmed that "whole range sufficiency", i.e. that a skilled person should be able to perform the invention of the whole scope of the claim, should not be considered specific to the fields of chemistry and medical use. If there is doubt with regards to a broadly claimed feature, then more evidence is needed to overcome this doubt, regardless of the technical field. 

Basic Sufficiency 

Rolling mills

In order to be sufficiently disclosed under Article 83 EPC, a detailed description of at least one way of carrying out the invention must be given in the application (Rule 42(1)(e) EPC). An objection of insufficiency requires there to be serious doubts, substantiated by verifiable facts, that the skilled person would be able to work the invention. In many cases, the sufficiency bar is low and can be satisfied by providing a single example falling in the scope of the claim in the application as filed.

However, for certain types of invention there may be a higher level of underlying doubt about whether the invention can be worked by a skilled person. These inventions include those relating to therapeutic uses and those involving broadly claimed features, such as a broad range of parameter values, functional features, or a broad genus of compounds. In such cases, there may be a high level of underlying doubt that a skilled person would be able to work the invention across the full scope of the broadly claimed feature (CLBA, II-C 5.4) ("whole range sufficiency"). Additional evidence is therefore required to meet the sufficiency standard requirement for these types of invention. 

Taking account of unknown unknowns (T 0149/21)

The patent in question in T 0149/21 (EP2630545) claimed a method for reducing the energy consumption of a rolling mill. Claim 1 particularly claimed a method including the step of identifying a fault leading to an unplanned pause of the rolling mill. The fault is then communicated to a control device. The control device anticipates the duration of the unplanned pause in rolling, depending on the nature of the fault, and powers down certain components of the mill as appropriate in order to save energy. 

At Opposition, the Opposition Division was satisfied that the sufficiency requirement was met in view of the single example provided in the application as filed. Particularly, the application as filed described a control device that had a database of common faults (and their associated delays) that it could use to identify a fault and anticipate the expected duration of the pause in rolling. The application as filed provided an example whereby faults were identified and inputted into the control device by a user. 

However, the claim was not limited to the faults specified in the database of common faults, or to a method in which the faults were manually identified. The broad language of the claim covered automatic detection of all possible faults, including those which were unknown (the unknown unknowns). On appeal, the Opponent argued that the claim was not sufficiently disclosed over the whole scope of the claims, particularly with regards to these unknown faults. 

Whole range sufficiency and chocolate teapots

The first question for the Board of Appeal was whether "whole range sufficiency" was a test specific to the chemical field. The Board of Appeal noted a recent decision implying that "over the whole scope of the claim" did not necessarily apply to inventions outside of the chemistry field. Particularly, it was suggested in T 1983/19 that "whole range sufficiency" could not be transferred to the mechanical field because almost every mechanical claim could be said to cover any number of impractical and non-working embodiments. This argument recalls the "chocolate teapot" thought experiment discussed by Mr Justice Birss (as then was) in Illumina v MGI ([2021] EWHC 57 (Pat), IPKat), whereby a claim to a new teapot may be construed as including within its scope the impractical and non-working embodiment of a chocolate teapot. 

For the Board of Appeal, the chocolate teapot problem is easy to overcome if it is remembered that a skilled person will use the direction of the application as filed and their common general knowledge (CGK) to interpret and carry out the claimed invention and exclude non-working embodiments. A skilled person would already know from CGK that a chocolate teapot would not function as a teapot (EPO Guidelines for Examination, F-III, 5.1). Mr Justice Birss (as then was) solved the chocolate teapot problem by finding that the invention only needs to be disclosed over the whole scope of the claim with respect to features relevant to the core inventive concept of the claimed invention (IPKat). The Board of Appeal also noted that there were many cases outside the chemical field which had applied the "whole range sufficiency" test, including those in the fields of electrical engineering (T 1542/12T 2210/16T 1306/17), physics (T 2305/14,  T 1921/19, T 0222/17) and mechanics (T 1905/10T 2431/11).

Airplanes and nuclear bombs

The Patentee in the present case argued that it would be excessive to require the invention to be sufficiency disclosed with respect to all the unknown unknowns falling under the scope of the claim, and that it should be sufficient for one example to be provided in the application as filed. The Patentee argued that it would be absurd to require the application to show that the invention could be worked by a skilled person with respect to any kind of fault, e.g. a nuclear bomb or an airplane crashing into the rolling mill (equivalents to the "chocolate teapot" scenario). 

However, whilst the Board of Appeal agreed that in many cases one example may be sufficient, the bar might be higher for broadly claimed inventions. Particularly, it may be necessary to provide more evidence in cases of a broad claim in order to ensure the patent bargain was met (r. 3.6, T 0435/91). The Board of Appeal dismissed the Patentee's nuclear bomb argument, on the grounds that a skilled person would not consider these embodiments technically reasonable. The potential for the chocolate teapots is thus not an argument against a requirement of whole range sufficiency in the mechanical field.

With respect to the claim in question, the Board of Appeal also noted that there were many types of less extreme faults that would fall under the claim but for which the skilled person would not know how to work the invention. Furthermore, the claim covered within its scope automatic detection of faults, and from the disclosure of the application as filed, a skilled person would not know how to program the control device in order to facilitate this automatic detection. 

The Board of Appeal thus found that the claimed invention was not sufficiently disclosed, and that the patent as granted was invalid. 

Final thoughts

Attentive readers may have noticed that this post has not yet mentioned "plausibility". As demonstrated above, it is possible to discuss the issue of "sufficiency over the whole range of a claim" without having to use the term "plausibility" (IPKat). However, given that the whole range sufficiency test is equivalent to the whole range "plausibility" test, the present case can also be said to confirm that plausibility is relevant to the sufficiency of invention in the mechanical field. Furthermore, the Board of Appeal in the present case confirmed the established case law that whole range sufficiency may be applied to broadly claimed inventions in the mechanical field. Interestingly, the US Supreme Court in the recent decision on enablement in Amgen v Sanofi also took great pains to emphasise that the law of enablement of broadly claimed inventions was originally derived from, and continues to apply, to the mechanical field (IPKat). 

Further reading

Chocolate teapots and nuclear bombs: Whole range sufficiency of mechanical inventions (T 0149/21) Chocolate teapots and nuclear bombs: Whole range sufficiency of mechanical inventions (T 0149/21) Reviewed by Rose Hughes on Monday, July 31, 2023 Rating: 5


  1. "Enablement across the full scope of the claim" is legally unsound - it functions as a figleaf for an underlyihng sniff test by which a fact-finder sees whether it thinks the claim is overbroad. Self-evidently, claim to a torch comprising an electric light source operatively connected via a switch to a rechargeable battery is bad for lack of enablement over the full scope of the claim since neither light source nor battery technology has reached a zenith within which no further innovation is possible. What is often meant by "enablement across the full scope" is enablement of the features defining the inventive step, or contribution, relative to the state of the art, and then only weakly. But to admit that would be to require that Art. 83 be engaged only after Arts. 54 and 56 had been addressed, which is not the way that the EPO likes to do things!

  2. The reference to nuclear bombs triggered my Arthur Pedrick association reflex and his famous GB1426698 of 1974 titled: "Photon Push-Pull Radiation Detector For Use in Chromatically Selective Cat Flap Control And 1000 Megaton Earth-Orbital Peace-Keeping Bomb".

    The independent claim defines a spectrally selective photo-detector, using a version of Crooke's radiometer (the science toy with the black and white vane in a partially evacuated glass bulb). This probably was novel, as the skilled person of the day would have rather resorted to optoelectronics means.

    Claim 2 is for a feline-selective cat (kat?) flap incorporating the device of claim 1.

    Claim 3 is for an geosynchronous orbiting Strangelove-like doomsday device, also employing the detector of claim 1, designed to automatically zap any country foolish enough to launch an ICBM attack.

    Claim 1 thus potentially covers a huge range of applications.

    This patent should have asserted against Ronald Ray-Gun and his "Star Wars" SDI. (Edward Teller is mentioned BTW in the disclosure).

    1. As a former examiner at the UKIPO, Arthur Pedrick has filed numerous "interesting" applications.
      I remember a bingo hall established under the earth in the cavity created by an atomic bomb, whereby a beer pipe line was connected to the nearest brewery.
      I also remember the proposal of sending all the search documentation in orbit and accessing it remotely. At least this idea was not so far fetched as one can now realise with today's technology.

  3. Any independent claim is, in principle, the result of some generalisation.

    The mere fact that a feature is broad is not in itself a ground for considering a claimed subject-matter insufficiently disclosed, see T 219/18, Reasons 5.1.

    Coming up with very simple examples like here is not really helpful. The example given is actually useless as being over simplified.

    T 149/21 is interesting as it made clear, by analysing quite a few decisions, that mechanical inventions do not have a specific status when it comes to sufficiency. Problems of sufficiency occur mainly in chemistry/pharmacy/biotech, but it can also happen in electricity/physics and mechanics.

    T 149/21 is interesting as it also made clear that satisfying the description requirement under R 42(1,e), it is not necessarily sufficient to satisfy the requirement of Art 83.

    I was once confronted with a bidirectional line transmitting an alarm signal. In case of an alarm the bidirectional line was pulled to ground, which makes it impossible to transmit any signal. In one embodiment pulling the line to ground, triggered the discharge of a capacitor and set an alarm circuit on. Once limited to this embodiment, the patent could be maintained. During OP the opponent even made the comment that he now realised why the claimed invention did not work in all circumstances.

    One embodiment was disclosed under R 42(1,e), but the claim was not enabled in its whole breadth. This case is comparable to the present one.

    In the present case, the claim was simply too broad with respect of what was actually disclosed and could reasonably comprise other aspects which were not disclosed.

    For the same token, only “technically unreasonable” claim interpretations do not fall under the requirement of sufficiency.

    I have commented this decision in another blog.

  4. Addressing Rose's final paragraph on plausibility, it must remembered that this concept comes out of whether the relevant molecules have the promised 'properties', therapeutic, insecticidal, etc. It does not sit well with mechanical inventions or ICT inventions where one 'constructs' the invention, and we know what we have constructed.
    Sufficiency across the breadth also comes from a similar place. How many of the claimed molecules, embodiments, etc, will have the required properties, functionalities, etc? Again not immediately applicable to the mechanical and ICT fields.
    So talk of chocolate teapots, etc, is entertaining, but ignores the fact that the plausibility and 'across the breadth' tests were necessary in fixing a situation where applicants were not complying with their part of the bargain in having made a contribution commensurate to the claim scope they wanted. They are not the result of the EPO being unreasonable or going beyond the EPC, but are a fair way of judging and 'quantifying' in a sense what the applicant has invented. Unfortunately the case law cannot yet deal with looking at things in this way, and so we'll be talking about chocolate teapots for a while I believe


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