Heraeus Noblelight Limtied v First Light Lamps Ltd
| Jurisdiction | England & Wales |
| Judge | Mr Justice Zacaroli |
| Judgment Date | 31 July 2023 |
| Neutral Citation | [2023] EWHC 1950 (Pat) |
| Court | Chancery Division (Patents Court) |
| Docket Number | Case No: HP-2021-000032 |
[2023] EWHC 1950 (Pat)
Mr Justice Zacaroli
Case No: HP-2021-000032
IN THE HIGH COURT OF JUSTICE
BUSINESS AND PROPERTY COURTS IN ENGLAND AND WALES
INTELLECTUAL PROPERTY LIST (ChD)
PATENTS COURT
Rolls Building
Fetter Lane
London, EC4A 1NL
Geoffrey Pritchard and Charles Brabin (instructed by Mishcon de Reya LLP) for the Claimant
Christopher Hall (instructed by Mills & Reeve LLP) for the Defendant
Hearing dates: 21, 22, 23, 26, 27 & 28 June 2023
Introduction
The claimant, Hereaus Noblelight Limited (“Hereaus”) brings this action for infringement of its patent, EP (UK) 1 598 845 (the “Patent”).
The Patent, with a priority date of 19 May 2004, is a method for sealing the ends of quartz glass tubes used in the manufacture of arc lamps.
Quartz glass arc lamps generally consist of a hollow cylindrical tube filled with gas. Different lamps require the gas to be at different pressure levels. Inside the tube at each end is an electrode, fed by a wire (usually tungsten) which passes through the ends of the tube. When an electrical charge is passed through the gas, it forms a plasma and emits light.
Heraeus contends that the defendant, First Light Lamps Limited (“First Light”) has infringed the Patent in adopting a method for sealing the ends of the lamps that closely follows that taught in the Patent. First Light denies infringement, on the basis that its method involves a material change (explained at §23. below) from the method taught in the Patent.
First Light also counterclaims for a declaration of invalidity and the revocation of the Patent on the grounds of obviousness over two instances of prior art.
Quartz Arc Lamps
A quartz arc lamp must be hermetically sealed to keep the gas inside. This can be done in a variety of ways, depending on the type of lamp and its intended use. This case is concerned only with those lamps that use a “rod seal” method. This involves the electric current being carried by a tungsten rod inserted into each end of the lamp, around which is attached a thin sleeve of sealing glass, the middle section of which is worked up to form a “bead”. The bead is then fused with the outer glass tube of the lamp so as to form a hermetic seal. I will refer to the sealing glass as “GS10”, because that is the type of sealing glass used by Heraeus. The size of the bead is at the centre of the argument about infringement, as explained in detail below.
This carries with it a problem, arising from the fact that tungsten and quartz glass have different coefficients of expansion. In order to fuse quartz glass it must be heated to approximately 1600C. If tungsten is heated to that temperature in order to be fused with the quartz glass, then the rate at which it contracts during cooling can cause the quartz glass to fracture. There is also a (smaller) risk of cracking during the heating and cooling of the lamp during use.
The common method of solving that problem, prior to the method described in the Patent, was by using a form of indirect seal. Under this method an intermediate layer (or layers) of GS10 is (or are) introduced between the tube and the bead. This solved the problem because GS10 can be fused using a lower temperature (approx. 1200C). Accordingly, the intermediate layer of GS10 can first be fused to the quartz glass at 1600C, and subsequently fused to the tungsten rod at the lower temperature. This is referred to as the “GS10 Dome Method”, and involved the following steps:
(1) A stick of heated GS10 is brought into contact with the rotating tungsten rod to form a sleeve around it.
(2) The central region of the sleeve is then increased in thickness, whilst it is rotating, to form a “bead” of GS10.
(3) Next, one end of the quartz tube is rotated and heated, and the heated end is then closed by spinning a bead of molten GS10 into and over it.
(4) A smaller diameter tube of quartz glass is fused into the side of the main tube of the lamp, so as to extend radially from it. This is necessary to enable the internal pressure of the lamp tube to be varied during the assembly process. It is removed following assembly of the lamp, commonly leaving a small “bump” of up to a few tenths of a millimetre on the outside of the tube.
(5) The pressure inside the quartz tube is now increased so that the GS10 bead that was fused to one end (in step 3 above) balloons outwards and is punctured. The punctured end (whilst kept hot) is now made concentric with the lamp tube axis by use of a carbon tool, and enlarged so as to be capable of receiving the electrode. This results in a GS10 extension to the quartz tube (referred to as the “arms” of the tube).
(6) The electrode, with its integral sleeved tungsten rod is now introduced into the end of the arms. Both are reheated and, with the assistance of a carbon tool, the arms are worked down so as to fuse to the bead. Since this is a fusion of GS10 to GS10, it is carried out at 1200C.
It is an essential feature of the GS10 Dome Method that, by introducing the GS10 arms on the end of the quartz tube, it results in the indirect sealing of the tube and the rod. The following diagram illustrates the GS10 Dome Method immediately prior to fusion between the “arms” and the bead:
The Patent, on the other hand, teaches a method of direct sealing between the tube and the rod, as described in the next section.
The Patent in more detail
The invention, as described at [0001] of the Patent:
“refers to a mechanically strong and leak free sealing of bodies comprising a quartz glass tube and a high temperature material of an electrical feed through such as are used as flash lamps and laser lamps, and in particular to the construction of the ends of such lamps and a method of effecting the sealing of electrodes into the ends thereof.”
The difficulties caused by the different coefficients of expansion of the tungsten used for the electrodes and wires in the lamp and the fused silica/quartz are described at [0003].
The GS Dome method is described at [0005] of the Patent, and at [0008] the following is said:
“Lamps constructed in accordance with the above method have been found to possess a weakness in the end regions thereof where a GS to GS seal has been formed. Investigations have indicated possible reasons for this weakness and it is an object of the present invention to provide an improved method which reduces the chance of weakness being introduced into the structure by the manufacturing process.”
The invention is summarised at [0009] to [0015], which include the following material points:
(1) The problem which the invention is intended to address is referred to as “a high derivation [it is common ground that this is meant to say “deviation”] in seal quality”, and the object of the invention is described as “to increase the reliability of the seal by reducing the [deviation] … without a loss in quality of the seal.”
(2) The invention involves a “direct sealing” of the glass tube with the seal around the metal rod. The fact that a (GS10) dome does not need to be sealed to the tube is said to be surprising.
(3) Compared to the prior art, the method is “very simplified” so that it is “extraordinarily quick manually” and allows for an automated process “which moreover guarantees a further minimizing of quality tolerance”.
(4) It is pointed out that the beads used in the invention could have a “small deformation”, so its final shape could have a “small notch and a little asymmetry.”
(5) At [0013 to 0015] the key characteristic is identified in the fact that the glass tube and metal electrodes (and their feed) are “directly sealed with a sealing bead”, and the benefits are repeated as enabling “the production of high quality seal with a small quality tolerance” and a seal that is “mechanically strong and leak free”, in order to bring an electrical source into “any form” of lighting or discharge lamp.
At [0017] a preferred example of the invention is described as comprising the following steps:
“(1) A tungsten pin is coated with sealing glass comprising a sheath and bead the bead being bigger than the internal diameter of the quartz tube but no bigger than the external diameter of the quartz tube. The quartz tube is that which forms the lamp housing, of typically 0,5 mm wall thickness.
(2) The bead is heated to a soft state while rotating it on a lathe and inserted into the annulus of the lamp housing tube to form the seal.
(3) After the insertion the seal is then heated to allow the sealing glass to wet on and to fuse with the housing tube.
(4) After fusing the bead to the quartz both internally and to the end of the quartz tube and while the sealing glass is molten an internal positive pressure is applied causing the sealing glass inside the quartz tube to move back towards the previously open end to form a smooth internal radius. The process of applying pressure to move the sealing glass back towards the end of the quartz tube not only creates:
(4a) a smooth radius between electrode or the electrical feed through and the quartz tube.
(4b) an area on the internal diameter that now has a coating of sealing glass that transitions to the fused bead effectively creating an internal radius of sealing glass. This radius is critical to the seal.”
A further example is described at [0018], in which the “end of the quartz glass tube is molten and softly pressed to a heated bead. Pre-forming or tooling of the quartz tube is possible to create different starting positions for this process.” First Light places significant reliance on [0018] of the Patent in the context of its case on obviousness, and I will return to it in that context.
[0019] emphasises the benefits of the invention, as being much simpler than the appropriate methods in the state of...
To continue reading
Request your trial