The requirements for a patentable invention

01 Nov 2017

Somewhere in hangar in a Highveld town in South Africa dreams are being turned into reality. Jonker Sailplanes has its home in Potchefstroom, about 90 minutes’ drive south west of Johannesburg and is a manufacturer of world-class, high-performance gliders. It is here that the Jonker brothers are living their dream. The brothers started from modest roots and as such buying a high-performance glider was simply not an option. Instead of leaving their castle in the sky, they decided that if they cannot buy it, they will build it and one early morning in December 2006, their JS-1 Revelation had her maiden voyage. Shortly afterwards the JS-1 took home the trophy in the South African 18m/Open Class Nationals competition. It has since raked in top accolades at international glider competitions and is a favourite high-performance glider amongst glider pilots across the globe.

A glider (or sailplane) relies only on its wings to fly, sailing on the air currents. It is normally towed or catapulted into the air and, gliding on the wind, it slowly sails back to earth. The wings are shaped in the form of an airfoil, which is what enables and keeps the plane airborne.



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The shape of the airfoil creates a higher pressure below the wing than above the wing when air passes over it. This is called lift. In the case of gliders, the airfoil design is especially important, as the glider does not have an engine to help it create lift by way of forward thrust and its airfoil must be carefully designed so as to optimise the lifting effect of air streams.

The flow of air passing over the airfoil also creates drag. In engine-driven planes, the drag is easily overcome by the engine providing forward thrust. In the absence of an engine and in order to overcome this drag, the airfoil should create as little as possible drag to enable the glider to fly further and for longer periods of time.

In designing and optimising their glider, the Jonker brothers invented and patented a system for controlling the boundary layer and the nature of the airflow over the airfoil.

The Jonker brother obtained US Patent 8,251,319 (‘319 patent), through the North-West University, which provides an improved airfoil specifically for gliders to control at which point along the airfoil the laminar flow is converted to turbulent flow when air moves over the wing. The transition point where laminar flow changes to turbulent flow is known as the boundary layer and the position of the boundary layer along the airfoil determines how much drag is experienced by the wing. Generally, the further back the boundary layer is along the wing, the less drag is experienced by the wing.


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The Patents Act 57 of 1978 (‘the Act’) provides in section 25(1) that a patent may “…be granted for any new invention which involves an inventive step and which is capable of being used or applied in trade or industry or agriculture”. A new airfoil design must thus fulfil all three requirements in order to qualify for a valid patent.

Firstly, we need to assess the novelty inquiry. The Act provides in section 25(5) that “…an invention shall be deemed to be new if it does not form part of the state of the art immediately before the priority date of the invention…” The state of the art (more frequently referred to as ‘prior art’) to the airfoil invention of the ‘319 patent is, firstly, a conventional airfoil flap. The flap is movable and is mounted on the airfoil’s trailing edge, which changes the camber of the airfoil and effectively alters the shape of the airfoil thus influencing the boundary layer. However, the addition of a flap to the trailing edge of the airfoil introduces a flap gap, at the point where the flap moves relative to the airfoil. When the flap is deflected a flap kink forms at the point of deflection and the laminar flow is tripped to turbulent flow at the position of the flap gap. It is possible, but very difficult, to seal and smooth the flap gap so that the flow is not tripped to turbulent flow at that position. The flap provides a method of tripping the laminar flow at a fixed position. The prior art further disclosed the provision of holes along the airfoil to suck air into the holes to influence the boundary layer. This prior art did not overcome the unwanted tripping of the boundary layer when the flap is deflected. Other prior art disclosed a turbulator tape attached to the length of the airfoil, consisting of small, three-dimensional obstacles which trip the boundary layer from laminar to turbulent flow. The position of the turbulator tape is fixed and not manipulated in flight.

The 319’ patent describes a system with which a pilot is able to control the position of the boundary layer of an airfoil. It consists of a row of small holes provided along the airfoil and the flap through which air is blown or sucked and with which the pilot has full control of the boundary layer through all flight operations. In doing so, the pilot is able to selectively trip the air flow between laminar flow and turbulent flow, thus optimising the lift effect on the airfoil. The prior art makes no mention of the holes included in the flap or a method to consistently and selectively control the boundary layer of the airfoil, thus the invention is deemed to be new.


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Inventive step or obviousness means, according to section 25(10), “… an invention shall be deemed to involve an inventive step if it is not obvious to the person skilled in the art…” Inventiveness is subjective and is the area of patent law that usually takes up most of the Court’s time in patent litigation. In the judgement of Roman Roller CC and Another v Speedmark Holdings (Pty) Ltd 1996 (1) SA 405 (A), the court held that inventiveness “…must be judged by asking oneself whether, in the light of the state of the art at the time, the step forward taken by the invention would have been obvious to the skilled addressee.” The court attempts to provide an objective test, but determining what is and is not obvious will always be subjective to those judging the case of inventiveness. The fact that no one has found a way in which to selectively control the boundary layer and tripping the airflow over the airfoil between laminar and turbulent flow, before the ‘319 patent, indicates that the invention is sufficiently inventive to qualify for a valid patent.

Thirdly, we turn to industrial applicability. Having control of the boundary layer is undoubtedly useful in this industry. The judgement in Frank & Hirsch (Pty.Ltd. v. Rodi & Wienenberger Aktiengesellschaft, 1960 (3) S.A. 747 (A.D.) at p. 755C-D, describes this concept eloquently: “The word “useful” … also bears, not its ordinary meaning, but the specialised meaning of being operative or effective to produce the result or results aimed at by the invention as described in the specification.”

Therefore, extrinsically an invention must be new and useful, not obvious and capable of being used or applied in industry. It is important to keep in mind that, additionally, inventions cannot be granted for mere ideas; each patent application must thus contain a technical aspect to the invention and must disclose a method of obtaining the result of the invention.

The Jonker brothers have shown that great dreams may be realised from small beginnings as long as you find the motivation, focus and perseverance to explore the limits of imagination. Although it may be said that the Jonker brothers have achieved their lifetime goal, this did not stop them from improving the JS-1 into what is now available as the JS-3 and it is reasonable to expect them to continue developing improved gilders for many years to come.

See also: An infinite number of monkeys against novelty

(This article is provided for informational purposes only and not for the purpose of providing legal advice. For more information on the topic, please contact the author/s or the relevant provider.)
At van Rooy

At van Rooy is a Director and Patent Attorney at Kisch IP. His expertise includes: Patent litigation; Plant Breeders’ Rights and Plant Variety protection and litigation; Patent filing, prosecution and... Read more about At van Rooy

Christina Louw

Christina Louw is a Candidate Attorney at KISCH IP's Patent Department. Read more about Christina Louw


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