Invalidity of a Patent for Insufficiency of Description: The Case of a Sound Emitter

Imagine: you are in Billère, near Pau, and you have just bought a sound emitter for your security company. It promises to emit a powerful, reliable signal, in accordance with a patent. But after a few weeks, the sound weakens, distorts. You contact the manufacturer, who refers you to the patent: "everything is explained, it's your installation that is at fault." Yet, when you open the device, you notice that the surface area of an essential component does not correspond to any precise figure. How could a judge resolve such a dispute?

This is exactly the question raised in the judgment of the French Supreme Court of 16 October 1978 (No. 76-15.118). At the time, a company, Kla…on, had patented a sound emitter. But the court declared the patent invalid, considering that its description was too vague: a specialist (the "person skilled in the art") could not, from the patent alone, manufacture a functional device without resorting to empiricism, i.e., trial and error. The surface area of a key element was neither quantified nor limited to a range, and varied according to external phenomena.

This decision, rendered nearly half a century ago, remains a reference in patent law. It reminds us that filing a patent is not enough: the invention must be described in a sufficiently clear and complete manner to be reproduced. So, how can you avoid a patent being declared invalid? Follow the guide.

The facts: a story that happens every day

In Orthez, the company Kla…on specialised in manufacturing sound emitters. It had filed a patent for a device intended to improve the power and reliability of signals. But a competitor, or perhaps a dissatisfied customer, challenged the validity of this patent before the Paris High Court (tribunal de grande instance de Paris). The ground? Insufficiency of description.

The patent described an emitter in which a central element – say a membrane or resonance chamber – had to have a specific surface area. However, the patent gave neither the exact value of this surface area nor even a range of acceptable values. Worse still, this surface area could vary depending on external factors such as temperature or humidity, without the patent specifying how to compensate for these variations. For the person skilled in the art – an acoustic engineer, for example – it was impossible to manufacture a compliant emitter without conducting their own experiments, which the law calls "empiricism".

Kla…on lost at first instance and then on appeal. The Paris Court of Appeal, in a judgment of 24 June 1976, confirmed the invalidity of the patent. The company then appealed to the Supreme Court. But the Supreme Court dismissed its appeal on 16 October 1978. For the judges, the lower court judges (who examine the facts) may declare a patent invalid if the description is insufficient, and they had freely assessed that this was the case here.

The reasoning of the court — dissected

To understand, we must refer to Article L. 612-14 of the French Intellectual Property Code (in its version applicable at the time: Article 8 of the Law of 2 January 1968). This text requires the patent to disclose the invention "in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art." In other words, the patent is not a mere slogan or general idea: it must be a real instruction manual.

The judges analysed the patent in detail. They noted that the surface area of one of the elements, which was supposed to serve as a basis for calculating other dimensions, was not quantified. No number, no range, no equation. Moreover, this surface area was influenced by external phenomena (such as atmospheric pressure). Result: the person skilled in the art had to "resort to empiricism" – i.e., personal experiments – to manufacture a device. However, the patent must allow reproduction without additional inventive effort.

Kla…on argued that the person skilled in the art, by virtue of their general knowledge, could fill the gaps. But the Supreme Court replied: no, if the patent does not provide the necessary indications, the judges may declare it invalid. This is not a reversal of case law: it is a classic application of the principle of sufficiency of description. The decision confirms that the lower court judges have broad discretion to assess whether the description is sufficiently precise.

What this means for you — practically

Are you an inventor or patent applicant? This decision requires you to be extremely precise. Imagine you file a patent for a new type of solar panel. If you write "a suitable capture surface" without giving dimensions or a range, your patent risks being declared invalid. A competitor could challenge it, as in the sound emitter case.

Are you a manufacturer or patent exploiter? Check that your licences or patents are solid. An invalid patent means a lost exclusivity. In Orthez, a company that had invested in producing the Kla…on emitter would have found itself without protection.

Are you simply the owner of a patented product? If you find that the product does not work as advertised, invalidation of the patent can be a defence. For example, if a manufacturer sues you for infringement, you can argue that its patent is invalid due to insufficiency of description. This could save you from paying damages.

Concretely, if you are in this situation, you should: keep all documents describing the invention, check that the claims are precise, and consult a patent attorney before filing a patent. The time limits for bringing an invalidity action are five years from the grant of the patent (Article L. 613-25 of the CPI). An invalidity action may cost between €5,000 and €20,000 depending on the complexity.

Four tips to avoid this type of dispute

• Write a comprehensive description. Do not just describe the principle. Give numerical values, ranges, examples of implementation. The more precise your patent, the less vulnerable it will be.
• Engage a patent attorney. A professional knows what the person skilled in the art expects. They will help you avoid generalities. In Billère as in Paris, drafting errors are costly.
• Test your invention before filing. If you yourself cannot reproduce the invention from your own patent, that is a bad sign. Conduct a practical test.
• Anticipate challenges. If your patent is attacked, gather evidence that the person skilled in the art can carry it out without empiricism: technical notes, expert testimonies, etc.

Further information: related case law and developments

The 1978 decision is part of a consistent line of case law. As early as 1973, the Supreme Court had invalidated a patent for insufficiency of description in a chemical composition case (Civ. 3e, 13 March 1973). More recently, in 2015, the Court recalled that the requirement of sufficiency of description is assessed in light of the general knowledge of the person skilled in the art at the filing date (Com., 9 June 2015, No. 14-14.572). The trend is clear: judges are strict. A patent that is too vague is a stillborn patent.

This rigour was reinforced by European Directive 98/44/EC on biotechnological inventions, which requires an even more detailed description for genetic sequences. But the principle remains the same: the patent must be a tool for the transmission of knowledge, not a riddle.

Summary and next steps

FAQ:

• What is "insufficiency of description"? It is the fact that a patent does not describe the invention clearly enough for a specialist to reproduce it without inventing themselves.
• Who can request the invalidity of a patent? Any person with a legitimate interest (competitor, customer, etc.) can bring an invalidity action before the judicial court.
• What are the time limits? An invalidity action may be brought at any time during the life of the patent (20 years) and up to 5 years after its expiry.
• What are the risks if one's patent is invalidated? One loses all exclusive rights. One may also be ordered to pay damages if one has sued infringers on the basis of an invalid patent.
• Can I challenge a patent that hinders me? Yes, if you believe it is insufficiently described. Gather technical evidence and consult a specialised lawyer.

Are you in a similar situation? A first 30-minute consultation with Maître Zakine (€45) can save you months of proceedings — and often much more. Book an appointment →