Obviousness is a question of law – but the court will only pick up lines of attack that have been asserted

Case No. O2016_009 ¦ Decision of 18 December 2018 ¦ ‘Durchflussmessfühler’

Reading time: 18 minutes


Art. 226, 229 CPC
New facts, amendment of patent claims.

If in a patent infringement proceeding the plaintiff files before the instructional hearing a reply limited to the defense of the validity and no pleadings take place at the instructional hearing, the plaintiff may submit new allegations of fact, and therefore also amended patent claims, in the completed reply filed after the instructional hearing without having to meet the requirements of art. 229 para. 1 CPC.

Please find some background information about the subject-matter at stake on this Blog here, and a report about the main hearing of 29 October 2018 on this Blog here.

Vyaire logo

In brief, Hamilton Medical AG alleged infringement of its Swiss patent CH 701 755 B1 (see Swissreg for further bibliographic details) by some of imtmedical AG‘s iFlow sensors. Note that Vyaire has recently taken over imtmedical’s ventilator and related consumables business; see imtmedical’s press release here.

The only independent claim 1 of CH’755 as granted reads as follows:

Durchflussmessfühler (10) mit einem ein zylindrisches Gehäuse (10) definierenden Durchgang mit einer ersten Durchgangsöffnung (13) und einer zweiten Durchgangsöffnung (29); einem im Durchgang des Gehäuses angeordneten Strömungswiderstand (23), welcher das Gehäuse in einen ersten und einen zweiten Gehäuseteil (11 und 27) unterteilt; einer ersten Anschlussstelle (17) mit einer Verbindung zum Innern des ersten Gehäuseteils (11); und einer zweiten Anschlussstelle (19) mit einer Verbindung zum Innern des zweiten Gehäuseteils; dadurch gekennzeichnet, dass die ersten und zweiten Anschlussstellen (17, 19) in einem Abstand voneinander auf dem gleichen Gehäuseteil angeordnet sind.

Inofficially translated to English language:

Flow sensor (10) with a passage defining a cylindrical housing (10) with a first passage opening (13) and a second passage opening (29); a flow resistor (23) arranged in the passage of the housing which divides the housing into a first and a second housing part (11 and 27); a first terminal (17) having a connection to the interior of the first housing part (11); and a second terminal (19) having a connection to the interior of the second housing part; characterised in that the first and second terminals (17, 19) are spaced apart on the same housing part.

Fig. 1 of CH’755 surely helps to understand what the invention is about:

Fig. 1 of CH 701 755 B1

The defendant denied an infringement, and argued for nullity as a plea in defense.

The verbal limitation of the patent

This is what the hn is all about. Imagine a plaintiff / patentee in infringement proceedings who is confronted with a plea for nullity in defense: When is his last chance to formally assert his patent only to a more limited and presumably valid extent?

First, it is important to understand how the FPC conducts the proceedings. If the defendant raises a plea for nullity in his answer to plaintiff’s statement of claim in infringement proceedings, the FPC invites the plaintiff to file a reply which is strictly limited to only the nullity aspects of the case. What follows next is an instructional hearing. In preparation of that hearing, the limitation of plaintiff’s reply to only the nullity aspects is to assure that the court has a single exchange of opinions at hand for both infringement and nullity. If the case moves on after the instructional hearing, it is again up to the plaintiff to complete his reply. Thereafter, the defendant provides the rejoinder re both infringement and nullity. This is the end of the regular exchange of briefs in which the parties can present facts and arguments without the need to comply with Art. 229(1) CPC (novae). However, the plaintiff may of course comment on new allegations and facts presented by the defendant in his rejoinder — within a deadline set by the FPC (typically two weeks, extendable by one further week; see this Blog here), or under the unconditional right to be heard (within 10 days).

The below is an illustrative summary of this chain of events:

Plaintiff Defendant
Statement of Claim
re infringement
w nullity plea in defense
First reply
re alleged nullity only
Instructional hearing w/o pleadings
Second reply
re infringement and nullity
re infringement and nullity
on new factual allegations in the rejoinder, if any
Judge rapporteur’s expert opinion

Note the subtitle to the second reply in the above: The decision holds that the plaintiff may present arguments and facts in his second reply after the instructional hearing not only relating to infringement aspects, but rather also to the nullity aspects of the case.

In the defendant’s view, the plaintiff thus had three chances to deal with validity / nullity of the patent, i.e. in his initial statement of claim and both his replies. The FPC disagreed: There is no reason for a plaintiff to deal with nullity in the beginning. How would he even do so in the absence of any knowledge of the defendant’s potential arguments? Thus, the FPC held that both parties had exchanged their views on both aspects of the case for the first time only after plaintiff’s first reply (limited to nullity). With the second reply and the rejoinder, both without limitations re novae, the double exchange of briefs is concluded.

Undoubtedly, an amended claim is to be considered a new fact (decision 4A_543/2017 of the Supreme Court, ¶2.3); as such, it would be an inadmissible novum after the normal exchange of briefs.

The plaintiff ‘verbally limited’ the claim only in his second reply. The defendant argued that this second reply was limited to only infringement aspects; it should only complement the first reply that had already dealt with nullity. Defendant argued that this was established practice at the FPC. Again, the FPC disagreed: There was not an established practice of the FPC in that sense.

now, what?!

Interestingly, the former President Dieter Brändle had apparently indicated in the instructional hearing that the patent could not be asserted in a more limited form any more after the instructional hearing. Defendant argued that it is against good faith if the limitation was now accepted nevertheless. However, the decision holds that it is up to the whole panel of judges to finally rule on admissibility of new facts; Mr. Brändle only gave his personal, preliminary opinion on this issue at that time. When the defendant had been invited to provide his rejoinder, this came along with an explicit note to deal with plaintiff’s reply as a whole, and that the whole panel of judges would finally decide on admissibility of the limitation of the patent. Thus, the defendant had no procedural disadvantage.

On a sidenote, I am wondering what the last point of time would be for a patentee / plaintiff to limit the claim when faced with a full-fledged counterclaim for nullity, i.e. when there are two parallel tracks of claim and counterclaim:

Statement of Claim
(re infringement)
re claim
(re nullity)
re c’claim
Instructional hearing w/o pleadings
re claim
re claim
re c’claim
re c’claim
on new factual allegations in the rejoinder re c’claim, if any
Judge rapporteur’s expert opinion

Would the plaintiff’s reply after the instructional hearing then be limited to the infringement part, and the final chance to limit the claim be the rejoinder re c’claim? This remains to be seen in a case to come.

General remarks on claim construction

The decision summarises certain key aspects of claim construction in ¶25 (and, later on, in ¶47). I do readily agree with most of it, but stumbled upon the following:

When case-law refers to ‘broadest interpretation’ of claim features,15 the feature must still be capable of fulfilling its purpose in the context of the invention. This means that the claim must not be interpreted under its wording, but also not in such a way that embodiments are covered which do not achieve the inventive effect.

15 FPC, decision O2013_008 of 25 August 2015, ¶4.2 — ‘elektrostatische Pulversprühpistole’ [see this Blog here]

The decision cites ample case-law, but there is no fn in the last sentence. Now, where does that come from? The sentence somehow reminds me of hn 3 of the ‘Spannschraube’ decision of the German Federal Supreme Court, X ZR 85/96 of 2 March 1999. The German Supreme Court had held:

The scope of protection of a European patent cannot be extended to embodiments which wholly (or to an extent which is practically insignificant) waive the success sought by the patent.

However, the Swiss Supreme Court had to assess the same subject-matter shortly thereafter, and explicitly disagreed; 4C.348/1999 of 12 April 2001: What had been considered to be no infringement in Germany, was well an infringement in Switzerland!

The Swiss Supreme Court did not see any reason to deviate from the literal and technically plausible meaning of the feature — even though an explicit object of the patent that had been recited in the specification was not achieved by such embodiments, i.e.  the use of very short clamping screws (see EP 0 319 521 B1, col. 1, l. 54-57):

Der Erfindung liegt die Aufgabe zugrunde, eine Rohrschelle der eingangs genannten Art zu schaffen, die sich auch mit einer sehr kurzen Spannschraube gut handhaben und leicht schliessen lässt.

It remains to be seen whether the present decision might indicate a gradual departure from the old Spannschrauben approach of the Swiss Supreme Court.

Alleged nullity 

The claims at stake can be summarized as follows, structured into features:

a) Flow sensor (10) with
b) a passage defining a cylindrical housing (10) having a first through opening (13) and a second through opening (29);
c) a flow resistor (23) arranged in the passage of the housing, which divides the housing into a first and a second housing part (11 and 27);
d) a first connection point (17) having a connection to the interior of the first housing part (11);
e) a second connection point (19) having a connection to the interior of the second housing part;
f) the first and second connection points (17, 19) being arranged at a distance from one another on the same housing part;
i) claim 4 as granted:
wherein flanges are provided on the first housing part (11) and on the second housing part (27) for connecting the housing parts with flange pressure surfaces (15, 16, 31, 32) are formed;
j) first variant of claim 10 as granted:
wherein the connections run partly in the flange pressure surfaces,
k) second variant of claim 10 as granted:
[wherein the connections] exit through the flange pressure surface as openings on the sealing surface side (17, 19, 21, 33, 35, 37) .

Features a) – f) correspond to claim 1 as granted (marked in bold in the above); the whole set of features, i.e. a) – f) and j) – k), corresponds to the claim as limited with plaintiff’s second reply. Don’t get confused by the missing features g) and h): The parties referred to these features in their feature analysis; but they are irrelevant for the present decision since they only relate to dependent claims 2 and 3 which are not at stake.

The decision holds that claim 1 as granted lacks novelty over document E10, i.e. (JP S61-205023); see Fig. 1:

JP S61-205023, Fig. 1

Next, the decision assesses and acknowledges novelty of the more limited claim over E1 (US 6,585,662 B1) which lacks features j) and k). Defendant had also argued that a prior use of the device of E1 had occured (prior use ‘Jones’). However, the decision holds that this prior use does not need to be assessed any further: Defendant had argued that the prior use disclosed a device according to the teaching of E1. Thus, the decision holds that any such prior use would necessarily also have lacked features j) and k).

Novelty over E10 (JP S61-205023; see above), E11 (JP H02-55123) and E12 (JP H03-44627) is also acknowledged in the decision.

Moving on to the assessment of obviousness, the decision emphasizes that it is up to the party that alleges nullity of a patent to make the relevant allegations. The court only examines whether the grounds put forward lead to the invalidity of the patent. Even though obviousness is a question of law, the relevant factual assertions must be made by the party that asserts nullity. In the following, therefore, the decision only deals with the assessment of obviousness starting from document E2 that has been referred to as ‘closest prior art’ by the defendant, i.e. US 4,083,245.

Features f), j) and k) are missing in E2.

With E2 as closest prior art, the decision holds that documents E7 (DE 32 25 114 C1, erroneously referred to as DE 32 25 115 C1 in the decision), E8 (US 1,768,563 A) and E9 (JP H03-21735 U) fail to render the limited claim obvious — mainly because these devices are made from metal / intended for use in high pressure applications, contrary to flow sensors in the medical field which are typically made of plastic, using die casting methods.

In sum, the more limited claim that the plaintiff had submitted with his second reply was thus held to be valid.


Defendant most fiercely contested that the adult version of the flow sensors has flange pressure surfaces and, even if there were flange pressure surfaces, that the connections from the connection points to the inside of the first/second half of the housing run partially into or through the flange pressure surfaces. Defendant referred to the computer tomographic images that had been submitted by the plaintiff:

CT image of the flange of an attacked embodiment

The above figure shows a cross-section through the flanges of the two halves of the housing. The flow resistor which is clamped between the flanges is marked with 23. Identifiers 45 and 47 mark a groove and comb structure. Defendant argued that the gas-tight connection is made exclusively via the groove/comb structure. However, the flange surfaces would not touch each other (red arrows in the above figure); only the planes of the comb and groove that protrude perpendicularly from the flange surface would be in contact (white arrows in the above figure). Defendant argued that this is intentional because it allows flow resistors of different thicknesses to be used without the housing halves having to be designed differently, contrary to the teaching of the patent in suit. Since, by definition, flange pressure surfaces would have to lie against each other under pressure, flange pressure surfaces are missing in the adult version, in the defendant’s view. And even if the area in which the flow resistor is trapped by the flanges (marked with a yellow arrow in the figure above) were still called the ‘flange pressure surface’, no connections would occur there in any case. Defendant referred to the below figure in this respect (with the white squares / annotations added by the court):

Flange, annotated by the court

The above figure again shows a cross-section of an adult version of the flow sensor. The thin vertical line is the flow resistor; identifier 33 refers to one of the connections to a connection point which seems to end on the right because it runs diagonally in the Z plane. The decision holds that ‘flange pressure surface’ and ‘flange surface’ are used as synonyms in the patent. A flange pressure surface in the sense of the claim is the surface of a flange facing away from the body part to which the flange is attached and serving to connect the body part to another body part, whereby the connection need not necessarily be made over the entire surface.

Thus, the flange pressure surface of the attacked embodiment runs over the entire width of the flange, i.e. in the above figure from point a) to point b). Consequently, the decision holds that the connections from the connection points to the inside of the first/second housing parts also run through the flange pressure surfaces, as can be seen in the figure above.

The decision holds that the defendant may have improved the teaching of the patent in suit, and the improvement might even be patentable. This does not, however, lead out of the scope of protection of the earlier patent (cf. Art. 36 PatA). In sum, the decision holds that the version for adults is literally covered by the limited claim of the patent. Likewise, the version for children is also held to be literally covered by said claim.

Wording of the injunctive relief

The defendant objected to the wording of the request for injunctive relief, for that it is too indefinite and merely recites the wording of claim features that are under dispute between the parties (such as e.g. the term ‘flange pressure surface’). The decision holds that the features are defined in the reasons of the decision beyond any doubt, so that a mere factual check by the competent authorities is well sufficient. Thus, it is neither necessary nor helpful for each and every feature to be defined in the prayer for relief itself.

Again, this reminds me a bit of the German approach where the mere claim wording is typically used in prayers for injunctive relief, and the exact scope is then to be deduced from the reasons of the decision. I do have some symphathy for the FPC’s approach that keeps the verdict clean and simple, with all the potential ambiguities being resolved by way of definitions given in the reasons.

In sum, the defendant was ordered to abstain from further use of the infringing embodiments, and to provide information and accounting concerning the same.

The parties commented on the decision with the following press releases:

The decision is not yet final; an appeal is pending at the Supreme Court.

Reported by Martin WILMING


Case No. O2016_009 ¦ Decision of 18 December 2018 ¦ ‘Durchflussmessfühler’

Hamilton Medical AG
imtmedical AG

Panel of Judges:

  • Dr. Mark SCHWEIZER
  • Dr. Tobias BREMI
  • Dr. Lorenzo PARRINI


  • Dr. Tobias BREMI

Court Clerk:


Representative(s) of Plaintiff:

Representative(s) of Defendant:

  • Dr. Rudolf RENTSCH (IPrime)
  • Ernst BREM (IPrime)
  • Joachim KÜNSCH (PPR)


Fullscreen view (new tab)

CH 701 755 B1

Fullscreen view (new tab)


Enter your name and email address below to get notified of new posts by email.

Print Friendly, PDF & Email

5 Replies to “Obviousness is a question of law – but the court will only pick up lines of attack that have been asserted”

Leave a Reply

Your email address will not be published.