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Heraeus Noblelight versus First Light Lamps

Interpretation of the scope of patent claims is, of course, central to the exploitation of patent rights. Developments in the understanding of patent claims have led to what is now, following Actavis vs Eli Lily effectively a doctrine of equivalence for patent claims. However, the previous dominant principle of claim construction, purposive construction, is still used to interpret specific terms in a patent claim. Accordingly, some claim features are not construed as narrowly as their literal wording might suggest. A recent example of this is the judgement by Mr Justice Zacaroli in Heraeus Noblelight Limited v First Light Lamps Limited [2023] EWHC 1950 (Pat), issued on 31 July 2023. 

This case relates to methods for manufacturing a quartz glass lamp. In particular the invention relates to forming the seal between the metal electrode and the quartz glass tube during the course of manufacture.  

Accordingly, the problem that this invention seeks to solve is to simplify the hitherto complex method of manufacture. The previous method of manufacture involved many stages and was still susceptible to producing a light bulb where the seal between electrode and the quartz class failed.  

The problem relating to reducing the differential amount of stress produced during the cooling of the seal of the light bulb was known. Similarly, a solution was perceived whereby the intermediate glass material between electrode and bulb has a thermal expansion co-efficient between that of the electrode and the quartz tube. However, manufacturing, even taking this into account, was complex.  

The present invention simplified the process by forming a direct seal using a bead formed on the electrode that was melted to fuse and join to the quartz tube.  A further step was that an internal pressure in the tube caused any edges to be smoothed out internally. This process is illustrated in the two pictures from the patent that are shown below.  

Quartz tube (1) prior to sealing to electrode (2,3) with bead (4)  

Quartz tube (1) after sealing to electrode (2,3) with bead (4) 

The first picture shows the components in position prior to fusing together and the second picture shows the electrode after the process of heating the bead and the electrode being rotated relative to the quartz tube. Thus the glass bead is sealed against the quartz tube and then the internal pressure applied to smooth out the internal joint, thus forming a smooth internal radius that by dint of its geometry reduces the chances of cracking on cooling.  

Turning to the claims of the patent, Claim 1 recites the following features, and we have picked out a particular feature and shown it in bold in the claim this is the particular feature that was analysed during this case according to the principles of purposive construction.  


      1. A method of forming a quartz glass laser lamp or quartz glass flash lamp containing electrodes (2) at opposite ends within a tube (1) of quartz glass, an end of said tube (1) having an internal diameter, an external diameter and an annulus, wherein said method comprises formation of a glass to metal seal at said one end of the quartz glass tube comprising the following steps:

    (1) the electrode (2) or its electrical feed through (3) is surrounded with a sealing glass (4) comprising a sheath and a bead, the bead being bigger than the internal diameter of the end of the tube (1) but not bigger than the external diameter of the end of the tube (1), 

    (2) heating the bead to a soft state while rotating it, 

    (3) inserting the bead into the annulus so as to form a seal, 

    (4) after the insertion, heating the seal so that the sealing glass (4) wets on and fuses with said one end of the tube (1), both internally and to the end of the tube (1), 

    (5) after said fusing of the sealing glass (4) with said quartz tube (1), applying an internal positive pressure while the sealing glass (4) is molten causing the sealing glass (4) inside the tube (1) to move back towards the end of the tube (1) so as to form an internal radius of sealing glass (4) which is directly sealed between the electrode or its electric feed through (3) and the tube (1) of quartz glass. 

It appears clear that the bead would have to be bigger than the diameter of the quartz tube otherwise a seal could never be made. The controversy arose over the feature that the bead was defined as being “not being bigger than the external diameter of the end of the tube.” This was important because the alleged infringing method involved using a bigger bead. However, the bead was bigger by approximately 0.1-0.3 millimetres. Otherwise the process of manufacture was the same.  

Thus the potential infringement would appear on a literal reading of the claim to lie outside the scope of the claim. However, Heraeus argued that in this context “not bigger” should be considered according to the principles of purposive construction as meaning “not bigger by reference to tolerances that formed part of the common general knowledge” furthermore Heraeus considered that 0.3 millimetres was within such tolerances. Similarly, the term should be interpreted as meaning “not bigger such that it impairs the strength or utility of the seal. Such an interpretation would thus also include oversized beads within the scope of the claim.  

Heraeus also stated that within the range of tolerances there would be literal infringement because some of the beads used by the defendant would be smaller than the diameter of the quartz tube.  

Following submissions from both sides and expert evidence Mr Justice Zacaroli found that the common general knowledge of the skilled person would include using beads of varying sizes, including oversized beads. Further the judge considered that the tolerances in question in here were not essential to produce the finished product. Accordingly the protection sought by the patent was not limited to a method in which the bead was exactly and no bigger than the outer diameter of the tube. On the contrary, variants in the size of the bead “which could have no material effect on the way in which the invention worked” (i.e. following Lord Diplock in Catnic).  

Accordingly, “not bigger” as recited in claim 1 also encompassed “bigger” versions that did not affect or impair the quality of the seal (i.e. strength or utility) and thus the claim covered any bead according to claim 1 that was made in concordance with the principle of the invention and within the tolerances of the common general knowledge of the skilled person.  

In the light of this construction the patent was found to valid over the cited documents and thus the patent was both valid and infringed.  

This case would appear to show that the scope of claims is arguable and that a close workaround produced by a rival might still fall within the scope of the claims. Thus the strength of the patent claims may be greater than it appears. However, this should be scant comfort because, from a commercial point of view, having to begin legal proceedings is not desirable to any company and is certainly not the objective of any patent attorney.  

Thus it also appears that the lesson to patent practitioners from this case would be to avoid terms that are too precise. Patent attorneys are proud of the precision of their language but in some cases language can be more precise than the engineering constraints on the invention and in the gap between these a savvy operator can perceive a work around.  

Thus this case would seem to be a lesson to patent practitioners as to the limits of precision vs the practical and commercial focus on how we draft our claims and conceive the scope of inventions.  

Link to PDF of Judgement 

Our articles are for general information only. They should not be considered specific legal advice, which is available upon request. All information in our articles is considered to be accurate at the date of publishing.


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