Patents: Battlekart Europe SA v Chaos Karts 1 Ltd

 

Jane Lambert

Intellectual Property Enterprise Court (HH Judge Hacon) Battlekart Europe SA v Chaos Karts 1 Ltd and others [2025] EWHC 1936 (IPEC) (25 July 2025)

This was an action by Battlekart Europe SA ("Battlekart") against Little Lion Entertainment Ltd ("Little Lion"), its subsidiaries, Chaos Karts Limited and The Ents Inc Limited and their director, Thomas Maguire for the infringement of European patent (UK) 3 304 522 B8 and a counterclaim by the defendants for revocation of the patent on grounds of obviousness, implausibility and added matter.  The action and counterclaim were tried by HH Judge Hacon between 17 and 19 June 2025.  By para [136] of his judgment in Battlekart Europe SA v Chaos Karts 1 Ltd and others [2025] EWHC 1936 (IPEC), which he handed down on 25 July 2025, the learned judge held that the patent was invalid for lack of an inventive step and added matter.

The Patent

EP3304522 B8 had been granted for a system for creating an immersive experience which combined driving a go-kart with the features of a video game about go-karts, such as "Mario Kart". The player drives a virtual kart around a virtual track, which is projected onto a floor. Obstacles on the track, such as banana skins, may be projected onto the track. If a kart's wheels hit a skin, the wheels spin uncontrollably.  The BattleKart: Beyond Reality!  YouTube video demonstrates the system to the public.

Judge Hacon described the invention by reference to the drawing labelled figure 2 above as follows:

"[12] Projectors 310 are in the ceiling of the room 900. A projection cone 611 emitted by each projector creates a partial image 610 on the floor 910 of the room. The partial images from the projectors combine to create an overall image, as shown a karting track 911. A 'mobile element' 200 as shown is a kart located on a projected track and for simplicity I will assume that the mobile element of the invention is a kart. There may be more than one kart.
[13] There is a locating system comprising sensors 110 in the ceiling, each of which has a 'capture zone' 121, corresponding to the zone perceived by the sensor. The area of the floor within a capture zone is the capture surface 120 of the sensor. Preferably the capture surfaces cover the whole image 600 so that the kart is always visible to the locating system. An administrator uses a management device 500 to select the form of track and the type of game to be played. A server (not shown) receives this input and determines the information to be sent to the projection system and to the kart (or karts). In effect, the server coordinates the projection system, the locating system and the information sent to the kart.
[14] Each kart has an emitter (not shown in Figure 2) so that its position may be detected by the locating system. The specification states (omitting reference numbers):

'The emitter preferably comprises at least one electromagnetic radiation source, which can be an infrared lamp. The emitter more preferably comprises at least two electromagnetic radiation sources. Having two sources enables one of the sources to always be active in the event of the other one failing. The emitter even more preferably comprises a first infrared lamp 211 and a second infrared lamp.'

[15] The electromagnetic radiation is detected by the sensor, which allows each sensor to perceive karts present in its capture zone. Where the preferred infrared lamp or lamps are used by the emitter on the kart:

'The sensor preferably comprises a filter, a camera and a data processing device. The filter is preferably a filter that lets the infrared pass through it. The camera is preferably a monochrome camera, capable of detecting the infrared radiation, and comprises, for example, a matrix of 128x96 pixels. The data processing device 115 is, for example, an FPGA.'

[16] An FPGA is a field-programmable gate array, a type of integrated circuit that can be reprogrammed after manufacture which allows flexibility of application by the user."

Claims

S.125 (1) of the Patents Act 1977 provides:

"For the purposes of this Act an invention for a patent for which an application has been made or for which a patent has been granted shall, unless the context otherwise requires, be taken to be that specified in a claim of the specification of the application or patent, as the case may be, as interpreted by the description and any drawings contained in that specification, and the extent of the protection conferred by a patent or application for a patent shall be determined accordingly."

S.14 (2) (b) requires every application for a patent to contain a specification with a claim or claims.  S.14 (5) states that the claims shall:

"(a)  define the matter for which the applicant seeks protection;

(b) be clear and concise;
(c) be supported by the description; and
(d) relate to one invention or to a group of inventions which are so linked as to form a single inventive concept."

Chaos Kart System

The defendants have developed their competing attraction called "Chaos Karts", which is described in the YouTube video " What is Chaos Karts".

Action

Battlekart alleged that the Chaos Karts infringed claims 1, 5, 6 and 11 of the patent.   The defendants admitted infringing claim 11.  That meant that they would have been liable for patent infringement had they been unable to revoke the patent.

Counterclaim

The judge turned to the counterclaim.

S.72 (1) of the Patents Act 1977 provides:

"Subject to the following provisions of this Act, the court or the comptroller may ... by order revoke a patent for an invention on the application of any person (including the proprietor of the patent)] on (but only on) any of the following grounds, that is to say—
(a)  the invention is not a patentable invention;
............................
(d) the matter disclosed in the specification of the patent extends beyond that disclosed in the application for the patent, as filed, or, if the patent was granted on a new application filed under section 8 (3), 12 or 37 (4) above or as mentioned in section 15 (9) above, in the earlier application, as filed;

......................"

An invention is patentable if it satisfies the conditions of s .1 (1) of the Patents Act 1977.  One of those conditions is that the invention involves an inventive step.

His Honour addressed the question of whether the patented invention involved an inventive step between para [30] and para [124].    He said at [125] that the defendants' argument that claim 11 neither disclosed nor rendered plausible any contribution to the art added nothing to their argument on inventive step. He considered added matter between [126] and [135]. 

Obviousness

S.3 of the Patents Act 1977 states that:

"An invention shall be taken to involve an inventive step if it is not obvious to a person skilled in the art, having regard to any matter which forms part of the state of the art by virtue only of section 2 (2) above (and disregarding section 2 (3) above)."

S.2 (2) provides:

"The state of the art in the case of an invention shall be taken to comprise all matter (whether a product, a process, information about either, or anything else) which has at any time before the priority date of that invention been made available to the public (whether in the United Kingdom or elsewhere) by written or oral description, by use or in any other way."

Lord Hodge referred to those provisions in para [58] of his judgment in Actavis Group PTC EHF and others v ICOS Corporation and another (2019) 167 BMLR 1, [2019] Bus LR 1318, [2019] RPC 9, [2020] 1 All ER 213, [2019] UKSC 15 and added:

"These statutory provisions mandate the court to assess whether an invention is obvious by having regard to the state of the art at the priority date of the invention. If the invention is not obvious to the skilled person at that date, section 3 deems the invention to involve an inventive step."

He said at para [60]:

"In addressing the statutory question of obviousness in section 3 of the 1977 Act it is common for English courts to adopt the so-called Windsurfing/Pozzoli structure, which asks these questions:

'(1) (a) Identify the notional ‘person skilled in the art’;
(b) Identify the relevant common general knowledge of that person;
(2) Identify the inventive concept of the claim in question, or if that cannot readily be done, construe it;
(3) Identify what, if any, differences exist between the matter cited as forming part of the ‘state of the art’ and the inventive concept of the claim or the claim as construed;
(4) Viewed without any knowledge of the alleged invention as claimed, do those differences constitute steps which would have been obvious to the person skilled in the art or do they require any degree of invention?”
(Pozzoli SPA v BDMO SA [2007] EWCA Civ 588; [2007] FSR 37, para 23 per Jacob LJ)."

Persons Skilled in the Art

Judge Hacon said at para [30] that it was not clear from the start from which technical field the skilled person should be drawn.   Nor was it clear at that stage which of the parties' experts came closest to the skilled addressee or team and therefore knew more about addressees' common general knowledge.  In para [64], the skilled addressees were identified as a team consisting of a systems engineer, a software engineer and a software engineer.  The judge decided at [79] that neither expert embodied the skilled addressee, but the defendants' expert came closer by some margin.

Common General Knowledge

It was common ground that the invention combined specially adapted go-karts, a tracking system, a server to interact with and coordinate the tracking system, projectors and the players' driving instructions and a projection system. It was agreed that there had been commercially available options for all those elements before the priority date, each of which would have been part of a skilled addressee's common general knowledge.  There was a dispute as to whether the BlackTrax tracking system, which Chaos Karts used and had existed for 3 years before the priority date, had been part of the skilled team's common general knowledge.  The judge found that the skilled team would not only have known about BlackTrax and two equivalent tracking systems at the priority date, but would also have believed that any one of them would prove useful in improving a karting experience. It would have tried using a tracking system of that kind, expecting it to be helpful.

Inventive Concept

Judge Hacon broke down claim 1 of the patent into the following integers:

"1A. System for creating an environment, the environment comprising at least one image arranged to be perceptible by at least one pilot of at least one mobile element, the system comprising:
1B. the at least one mobile element, which itself comprises an electronic interface and at least one actuating means connected to the electronic interface, and arranged to carry out a modification of characteristics of the mobile element based on a signal received from the electronic interface,
1C. a locating system arranged to determine a position of each mobile element present near the at least one image, and
1D. a server arranged to be connected to the electronic interface of each mobile element and to the locating system, the server being arranged to control said at least one actuating means based on the position of each mobile element received from the locating system,
1E. the system for creating an environment further comprising a projection system arranged to project the at least one image on at least one floor,
1F. the server being arranged to be connected to the projection system, the server is arranged to control the projection system based on the position of each mobile element received from the locating system,
1G. and in that each mobile element further comprises an emitter comprising at least two electromagnetic radiation sources comprising an infrared emitter, the emitter being arranged to transmit a signal enabling the mobile element to be located by the locating system."

All the other disputed claims were dependent on claim 1:

"5. System according to any one of the preceding claims, wherein the locating system comprises at least one microcontroller connected to the server and at least one sensor connected to the microcontroller.
6. A System according to the preceding claim, wherein each sensor comprises a camera arranged to take an image and capable of detecting infrared radiation.
11. System according to any one of the preceding claims, wherein the at least one mobile element is a kart, and the image comprises a karting track."

Prior Art

The judge listed the prior art in para [84] of his judgment:

"(1) The Battlekart Disclosure. This was a demonstration by Battlekart of the Battlekart system conducted in Mons before the priority date. Various documents and videos are relied on to demonstrate the detail of what was disclosed.
(2) The MIT Disclosure. This was a demonstration of a game based on Mario Kart created by three students at MIT evidenced by a document and videos.
(3) The Disney Application. This is a US patent application no. 2010/0144413 entitled 'System and method for providing a real-time interactive surface' owned by Disney Enterprises, Inc."

Applicable Principles

Before considering what, if any, differences existed between matter cited as forming part of the ‘state of the art’ and the inventive concept, the learned judge recalled his judgment in Claydon Yield-O-Meter Limited v Mzuri Limited [2021] EWHC 1007 (IPEC):

"[72] It was common ground in this case that in a prior user case in which it is said that the invention was made available to the public, even though nobody in fact took advantage of that availability, the information made available is that which would have been either noticed or inferred by a person skilled in the art who, hypothetically, had taken advantage of the access to the invention established on the evidence. I agree. In effect, the hypothesis concerns a skilled person as observer.
[73] Mr Nicholson made the further point that for the invention to be enabled, the skilled person need only have been able to discern details of the invention at the level of generality at which they appear in the claim. I agree.
[74] As appears from Folding Attic Stairs [Folding Attic Stairs Ltd v Loft Stairs Co Ltd [2009] EWHC 1221 (Pat)] it must be assumed that the skilled person's access was limited to that permitted in law; access by trespassing, for instance, is excluded from the hypothesis."

The Battlekart Disclosure

His Honour held at para [112] that skilled addressees attending the demonstration at Mons would have thought it obvious at the priority date to use BlackTrax as a tool to create an improved karting experience like the one in the demonstration.   It would also have been obvious to use 2 or 3 infrared light-emitting diodes on each vehicle.   It followed that claim 11 was obvious over the Battlekart disclosure.

The MIT Disclosure

The defendants' expert said that the skilled team would have introduced the features of the MIT game using BlackTrax or a similar tool and that this would have led to a system as claimed in the patent. He did not give much detail about the steps required to introduce the Mario Kart features of the MIT game into conventional karting but his evidence was preferred to that of the claimant's expert. In addition, his evidence was consistent with evidence that the Chaos Kart project started with a prototype of a size something like the MIT game and that it had been scaled up using BlackTrax. Accordingly, the judge found that claim 11 lacked an inventive step over the MIT disclosure.

The Disney Application

Leaving aside features that were not relevant, the differences between this application and claim 11 were (i) no tracking system, (ii) no two IR radiation emitters on the karts and (iii) no sensor in the form of a camera capable of detecting IR radiation. For the reasons he gave in relation to the Battlekart disclosure, the learned judge found that claim 11 lacked an inventive step over the Disney application.

Added Matter

The judge referred to paras [11] to [13] of Lord Justice Arnold's judgment in Generics (UK) Ltd v AstraZeneca AB [2025] EWCA Civ 903 for the reason why a patent can be revoked under s.72 (1) (d) of the Patents Act 1977 if the matter disclosed in the specification of the patent extends beyond that disclosed in the application for the patent:

"[11] So far as I am aware, all patent laws in the world now operate on the 'first to file' basis. (The USA used to be an exception, but that has ceased to be the case since the America Invents Act 2011). Without descending into detail, this essentially means that the first person to file an application to patent a particular invention is entitled to any resulting patent to the exclusion of any later applicant. Thus the date on which the application is filed, or the priority date if earlier, is critical. (The priority date is the date of an application by the same applicant in respect of the same invention filed up to one year earlier. The priority system enables an applicant to file an initial application in one country followed by multiple subsequent applications in other countries.) It is by reference to that date that issues of patentability are assessed. Thus it is by reference to the state of the art at that date that it is determined whether the claimed invention meets the core requirements of novelty, inventive step and industrial application. And it is by reference to the common general knowledge of the person skilled in the art at that date that the patent is interpreted, and that inventive step and sufficiency of disclosure are assessed. It is a cardinal principle of patent law that hindsight should, so far as is humanly possible, be excluded from these assessments. As has often been pointed out, it would be unfair to inventors if inventive step were to be assessed with hindsight, since many inventions appear obvious after the event.
[12] It can readily be seen that it would undermine this system if applicants for patents were permitted to add information (what patent lawyers call 'subject-matter') to the information that is contained in their applications after the application date or, where applicable, the priority date. For this reason, patent laws typically contain substantive rules which are designed to prevent this. In the case of the EPC, the key two rules are Article 87 (1), which provides that priority can only be claimed in respect of “the same invention”, and Article 123 (2), which provides that '[a] European patent application or a European patent may not be amended in such a way that it contains subject-matter which extends beyond the content of the application as filed.' These provisions are implemented in the UK by sections 5 (2) and 76 of the 1977 Act. The jurisprudence both of the Boards of Appeal and of national courts establishes that these rules are strict ones.
[13] It would also undermine this system if applicants were permitted to rely upon information (other than common general knowledge) that is not present in the application (or priority document) when filed as establishing the patentability of the invention. That would also be objectionable for another reason, namely that it would be contrary to the 'patent bargain' discussed by Lord Sumption in Generics (UK) Ltd v Warner-Lambert Co LLC [2018] UKSC 56, [2019] Bus LR 360 ('Warner-Lambert') at [17]. In short, this is the principle that the reward of a 20 year monopoly is bestowed on the proprietor of a patent in return for the disclosure of the invention to the public in the patent application."

The disclosure in the application as filed was as follows:

Integer G of claim 1 claimed:

"and in that each mobile element further comprises an emitter comprising at least two electromagnetic radiation sources comprising an infrared emitter, the emitter being arranged to transmit a signal enabling the mobile element to be located by the locating system."

The dispute turned on the meaning of the words "sources comprising" in claim 1 which meant "each source comprising" according to Battlekart.  It submitted that the emitter comprised at least two electromagnetic radiation sources each of which comprised an infrared emitter.  His Honour disagreed.  In his view, the words "sources comprising" meant what they said, namely that the words qualify "at least two electromagnetic radiation sources" and must collectively comprise at least one infrared emitter. There may be more than one infrared emitter but there need not be. The reader was therefore told that there may be at least 2 electromagnetic radiation sources of which only one was infrared.   For that reason, the patent was invalid for added matter.

Comment

This case shows the importance of appointing an expert witness with the appropriate practical experience. Battlekart's expert was a senior lecturer in the computer science department of a leading university with experience in plane cockpit simulators and software for training radiation therapists.  The defendants' had spent his career in lighting for TV shows and developing software and lighting systems for live productions, including creating an infrared location system for use in amusement parks and immersive entertainment.  As a result, the judge was more confident in accepting the defendants' evidence on the skilled addressees' common general knowledge and the differences between the prior art and the invention. 

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