Patent tip: Stack your patents!

When an invention is selling or, better still, is selling profitable, then it may be wise to stack patents. Patent stacking is best explained by an example. This example is about kites for kite surfing.

Example: Kite patent stacking

Yearly estimated tube kites sold globally (blue line) and various patents on tube kites:
white the basic model tube kite, red the four lines improvement, green the bridle
improvement and yellow the bow kite.

This image shows the most relevant patents on tube kites, invented by Bruno and Dominique Legaignoux. The left hand side arrow indicates the filing date of patent applications for the specific technology, the right hand side arrow the expiry of the related patent protection. The first patent application on tube kites was filed in 1985, while the first product became commercially available only around 1995; a good ten years later. The Tube kite patents expired in 2006, while the market was still in its infancy.

In 1995 the Legaignoux brothers filed a patent application for a four line design, greatly improving maneuverability and safety of the kites. While the four lines kites were greatly improving some of the properties, the bridle type of leading edge connection further improved the maximum power and shape stability on the kites. The patent application for this technology was filed in 2000.

One of the most recent developments is the bow shape of the kite, which further improves aerodynamics of the kite.

So although the basic tube kite patent is now expired, and the four line patent is expiring soon, still protection on improvements stretches on till 2026.  So stacking patents and thus stretching protection is a very sensible thing to do, provided there exists a selling product or selling service underneath.

When to stack patents? 

So when is it sensible to stack patents this way?

Well if the diffusion of the invention is relative low, compared to the size of the market. Another quite illustrative example is the -relatively slow- development of the steam engine:

Here the patents of James Watt (first represented by white, the last represented by red arrows) covered less than 1 thousandth of the market. Because diffusion was so low, more patents could have been stacked. The estimated time till full saturation of the marked is about 235 years!

When not to stack patents? 

Well for those inventions that will not find any reasonable sales, patent stacking is a waste of time, money and resources. For inventions that diffuse so rapidly, that the market reaches saturation before expiry of the patent, stacking may be wise as well. In the following image the first iPhone design protection is indicated. The estimated time to reach full saturation of the market is about 12 years.

The iPhone design was granted a design patent in 2008 and will expire in 2022. In the S-curve fitted model, the expiry is when almost full saturation of the market will be reached. It is noted that this design is most relevant for the first generation iPhones, which was overtaken by newer designs:

So stacking is a very wise option, provided your technology has become commercially relevant.

I wish you happy inventing!

Hendrik de Lange
Dutch and European patent attorney
+31 (0) 6 481 74 686

Sources

About the patents on tube kites:
http://inflatablekite.com/siteinf/gb/InfPatent.html


Watts first steam engine patent (espacenet):
http://worldwide.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=176900913A&KC=A&FT=D&ND=3&DB=EPODOC&locale=en_EP


Patent on a steam engine with an improved equalizer (espacenet):
http://worldwide.espacenet.com/publicationDetails/originalDocument?DB=EPODOC&II=2&ND=3&adjacent=true&locale=en_EP&FT=D&date=17820704&CC=GB&NR=178201321A&KC=A


Watts steam engine with rotary motion patent (espacenet):
http://worldwide.espacenet.com/publicationDetails/originalDocument?DB=EPODOC&II=1&ND=3&adjacent=true&locale=en_EP&FT=D&date=17840825&CC=GB&NR=178401432A&KC=A