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England and Wales Court of Appeal (Civil Division) Decisions
You are here: BAILII >> Databases >> England and Wales Court of Appeal (Civil Division) Decisions >> Dyson Appliances Ltd v Hoover Ltd  EWCA Civ 1440 (4 October 2001)
Cite as: (2001) 24(12) IPD 24077,  ENPR 5,  EWCA Civ 1440,  RPC 22
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COURT OF APPEAL (CIVIL DIVISION)
ON APPEAL FROM CHANCERY DIVISION
MR R.M. FYSH Q.C.
London, WC2A 2LL
Thursday 4th October 2001
B e f o r e :
LORD JUSTICE SEDLEY
LADY JUSTICE ARDEN
| DYSON APPLIANCES LIMITED
|- and -
Smith Bernal Reporting Limited, 190 Fleet Street
London EC4A 2AG
Tel No: 020 7421 4040, Fax No: 020 7831 8838
Official Shorthand Writers to the Court)
David Kitchin QC and Guy Burkill (instructed by Olswang for the Respondent)
Crown Copyright ©
LORD JUSTICE ALDOUS:
"This invention relates to a vacuum suction cleaning appliance and in particular to an appliance of the kind described in the published EPC Specification no. 0018197, being prior art as defined in Art. 54(3) EPC."
"EPC specification no. 0018197 describes an appliance in which a cleaner head for contacting a dirty surface is connected to the interior of the casing in which an air flow is set up by a motor-driven fan. The casing contains two cyclone units in series operating successively to extract dirt particles (dust and other extraneous matter) from the air flow there through and to deposit the extracted dirt.
A cleaning appliance based on cyclone units has the advantage that dust bags are not required as dirt can be discharged from the appliance by removing and separating the cyclones from the surrounding casing. Other advantages are that the air discharged from the appliance is substantially dust-free and the use of filters as main cleaning elements is avoided.
In the appliance described in the said EPC patent application each of the two cyclone units has a body of substantially frusto-conical shape tapering away from the cyclone air inlet, this shape serving to maintain the velocity of the dirt particles swirling therein and hence render the cyclone capable of depositing fine particles of small diameter. Such tapered cyclone units with the means to maintain the velocity of the fine dirt particles will hereinafter be referred to as 'high efficiency' cyclones, efficiency being used in relation to the ability to deposit fine dust particles."
"The invention recognises that a vacuum cleaner incorporating only the higher efficiency cyclones necessary to deal with the fine particles does not operate entirely satisfactorily under normal domestic conditions when dirt particles of larger size and other extraneous objects are sucked into the appliance. These larger size particles tend to be retained either performing the spiral or circular motion in the cyclone or drifting to the cyclone central regions and are not deposited. This causes noise and interferes with the efficient operation of the cyclone.
Accordingly the present invention proposes incorporating into the air passage upstream, relatively to the inlet for dirty air, of the high efficiency cyclone unit a cyclone deliberately constructed to be of lower efficiency by omitting the frusto-conical taper and constructing the cyclone casing of cylindrical form or with a reverse taper or flare away from the inlet.
This 'lower efficiency' cyclone, though not ultimately capable of dealing effectively with the finest particles i.e. particles of 50 microns diameter or under, carries out a primary cleaning action of the dirty air flow by depositing all but some of these finer particles. The high efficiency cyclone with the taper is then left to function in its optimum conditions with comparatively clean air and only particles of very small size."
"1. A vacuum cleaning appliance including cyclone units of successively higher efficiency, in the capability of depositing fine dust, in series connection, the highest efficiency cyclone having a frusto-conical part (15) tapered away from its entry (18) and means for generating an air flow from a dirty air inlet sequentially through the cyclone units characterised in that a lower efficiency cyclone unit upstream of the highest efficiency unit has a body (13) without the taper away from the air entry, being either cylindrical or having a reverse taper.
2. A vacuum cleaning appliance according to claim 1 characterised by a casing (1) with a dirty air inlet, a generally cylindrical container (13) constituting the lower efficiency cyclone unit positioned within the casing and being connected to the dirty air inlet, the high efficiency cyclone being positioned within the lower efficiency cyclone unit.
4. A vacuum cleaning appliance according to any preceding claim capable of working in an upright mode on wheels (9) characterised by cleaning head (2) with rotatable brush (4) at the dirty air inlet, the means for generating the airflow being a motor-driven fan (3).
5. A vacuum cleaning appliance according to claim 4 characterised in that the motor of fan (3) also drives brush (4) through belt (5)."
"18. Section 125 of that Act provides that an invention shall be that specified in the claim "as interpreted by the description and any drawings ... shall be determined accordingly." The extent of protection is not only important when considering whether an alleged infringement falls within the claim, but also when considering validity. A patent will be invalid if the extent of protection includes within it the prior art or something which was obvious having regard to the prior art.
19. Section 125(3) requires the Protocol on Interpretation of Article 69 of the EPC to be applied. It states:
"Article 69 should not be interpreted in the sense that the extent of the protection conferred by a European Patent is to be understood as that defined by the strict, literal meaning of the wording used in the claims, the description and drawings being employed only for the purpose of resolving an ambiguity found in the claims. Neither should it be interpreted in the sense that the claims serve only as a guideline and that the actual protection conferred may extend to what, from a consideration of the description and drawings by a person skilled in the art, the patentee has contemplated. On the contrary, it is to be interpreted as defining a position between these extremes which combines a fair protection for the patentee with a reasonable degree of certainty for third parties."
The Protocol outlaws what can be termed strict literal and also liberal interpretation using the claims as a guideline. The correct approach is to achieve a position between those extremes "which combines a fair protection for the patentee with a reasonable degree of certainty for third parties.""
"55. In my judgment, the device described and claimed in the Patent is intended to clean a variety of surfaces or locations which have become dirty or covered with unwanted particles. It is not intended to function as an air purifier as such or as a dust extractor, though having performed its primary surface cleaning function, provision must obviously be made to retain the dirt within the device until the user wishes to discard it. The user of the device proposed in the Patent has only a secondary interest in the cleanliness of the air which is finally expelled from the device. Still less is the phrase to be understood to comprise devices such as a particle collector or particle agglomerator. The user of the appliance described and claimed in the Patent places no value whatever in what is extracted from the dirt-laden air; it is discarded. Thus, though the appliance claimed 'cleans' first a surface and thereafter the dirt-laden air sucked from that surface so as to rid it of unwanted dirt, its primary purpose is simply to clean surfaces.
56. However I agree with Hoover that the device claimed is not intended only for use in a domestic environment. Claims 1 and 2 are apt to cover a vacuum cleaning appliance for use in industrial and commercial establishments or in public buildings, schools or churches etc where machines of more robust and capacious construction may be required.
57. This construction of the opening words of claim 1 is not only in harmony with the rest of the specification but also with the dictionary definitions proposed by Dyson."
"A document takes away the novelty of any claimed subject-matter derivable directly or unambiguously from that document including any features implicit to a person skilled in the art in what is expressly maintained in the document."
"When the prior inventor's publication and the patentee's claim have respectively been construed by the court in the light of all properly admissible evidence as to technical matters, the meaning of words and expressions used in the art and so forth, the question whether the patentee's claim is new for the purposes of section 32(1)(e) falls to be decided as a question of fact. If the prior inventor's publication contains a clear description of, or clear instructions to do or make, something that would infringe the patentee's claim if carried out after the grant of the patentee's patent, the patentee's claim will have been shown to lack the necessary novelty, that is to say, it will have been anticipated. The prior inventor, however, and the patentee may have approached the same device from different starting points and may for this reason, or it may be for other reasons, have so described their devices that it cannot be immediately discerned from a reading of the language which they have respectively used that they have discovered in truth the same device; but if carrying out the directions contained in the prior inventor's publication will inevitably result in something being made or done which, if the patentee's patent were valid, would constitute an infringement of the patentee's claim, this circumstance demonstrates that the patentee's claim has in fact been anticipated.
If on the other hand, the prior publication contains a direction which is capable of being carried out in a manner which would infringe the patentee's claim, but would be at least as likely to be carried out in a way which would not do so, the patentee's claim will not have been anticipated, although it may fail on the ground of obviousness. To anticipate the patentee's claim the prior publication must contain clear and unmistakable directions to do what the patentee claims to have invented: Flour Oxidizing Co. Ltd v. Carr & Co Ltd. ((1908) 25 RPC 428 at 457 line 34, approved in B.T.H. Co. Ltd v Metropolitan Vickers Electrical Co. Ltd (1928) 45 RPC 1 at 24, line 1). A signpost, however clear, upon the road to the patentee's invention will not suffice. The prior inventor must be clearly shown to have planted his flag at the precise destination before the patentee."
"In using the device, a hose 7 conveys the laden fluid in the direction of the arrow to the interior of the separation chamber 2. The conduit or hose 7 may be coupled at one end to the wall of the separation chamber either radially of the chamber or tangentially thereof, as shown in the figure. When the connection is made in the tangential relation, the fluid is given an initial rotary motion as it enters the chamber and progresses upwardly to the tuyere which is indicated generally at 8. The other end of the hose of course receives the laden fluid from any suitable source such as a vacuum cleaner head, receivers for finely divided particles sprayed into a drying atmosphere such as dried milk or egg and other particles, and like apparatus."
"119. In my judgment, the reader of this document would appreciate that it is via the tuyere and within the central conical cyclone alone that the benefit of efficient separation and/or agglomeration takes place. Prof Syred agrees with this: Report, para 204. Hoover argued however that because the 'separation chamber' was so called, that indicated that at least some separation must be taking place therein, that is, around but outside the central conical cyclone. I reject this argument. The separation chamber (elsewhere called the 'receiving and separation chamber') is indeed where separation occurs- but within the central conical cyclone which is itself wholly within the separation chamber. The descriptive distinction is between the separation chamber (2) on the one hand and the discharge chamber (3) on the other: Col 2, ll 15-16. Note also that there is also no mention of 'dirt' in the Campbell patent. The skilled reader would I believe, understand this device to be an industrial proposition for the collection of all the particulate material in the single bin, that material being the wanted product. The agglomerating and the vacuum cleaning functions in Campbell are proposed on equal footing and are there to treat laden fluid passing through separator. As Prof Syred said "The obvious intention was to recover as much of the spray dried milk or egg material as possible" [Supplementary Report, para 15 (e). No cross-examination]. There is no suggestion of using Campbell to clean dirty surfaces, for example.
120. In order for Campbell's proposal to be an effective citation under lack of novelty, Hoover have of course first to establish that the walls of the cylindrical separation chamber act as a cyclone. Then they have to establish the lower efficiency of this unit with respect to the reverse flow cyclone - which is undoubtedly described. In my judgment, on the face of the document, Hoover have failed to do this. The possibility of cyclonic separation adjacent the walls of the separation chamber is neither described, illustrated nor, reading the patent as a whole, even contemplated. First, the swirl, a necessary pre-condition to cyclonic action, would only arise so it seems, when the tangential rather than the radial option on the inlet is exercised. Yet the machine one would be entitled to assume, works in just the same way using either option. Setting up a swirl within this outer chamber so as to effect separation would I believe, be if anything counter-indicated by reason of the presence of the unprotected mound of the (probably desirable) material under the flop-valve. In any event, Campbell's is a system which aims for 'high operating efficiency' of the central cyclone. This is literally the focus of the proposition. The presence of true swirl in the separating chamber (which is not I believe, the same as the 'initial rotary motion' described for the tangential option) would be likely to disturb this material, whether falling on the actuation of the flop- valve or in repose, leading to re-circulation into the cyclone via the tuyere, thus leading to inefficiency. Furthermore, if separation were to have already occurred to any significant extent in the separating chamber, this would also be likely to diminish the efficiency and purpose of the central cyclone. As a minor point, this view is further supported by the direction of a downward arrow in the diagram adjacent the bent inlet tube.
121. What then is the purpose of the separating chamber? There is some evidence on the point and in this matter, I prefer the evidence of Prof Syred to that of Prof Allen. It is more realistic and accords in my view, with a fair reading of Campbell. Prof Syred in his Report sees Campbell's separation chamber simply as a plenum chamber. As he put it (Supplementary Report, para 13):
" This ensures that the laden fluid is evenly distributed around the casing and therefore enters the tuyeres from all directions.""
Mr Hobbs rightly criticised the last sentence of paragraph 119 of the judgment. Although not prepared to accept the reasoning of the judge in those paragraphs, he concentrated on showing that it was inevitable that the Campbell apparatus would fall within claim 1 rather than establishing that that would be apparent to a skilled reader of Campbell. This was a case where it could not be immediately discerned that Campbell would have a lower efficiency cyclone as claimed, but that when carrying out the directions in Campbell it was inevitable that such a cyclone would be made.
"126. Details of the Dyson 're-build' are set out in Annexe I to Dyson's Notice. It is at once apparent that Dyson have built a device about half the height of a man. They have also chosen to deliver the particle-laden air not via a 'tangential' inlet of the sort depicted in the Campbell drawing but 'radially of the chamber'. This it will be recalled, is the alternative (col 2, lines 25-27) to the arrangement which Campbell has drawn. From the video recordings which were made, I could see the bits of paper and moulding chips falling apparently by gravity, to the bottom of the separating chamber. The chips fell directly down and the paper spiralled down, no doubt meeting some air resistance. Some R 10 dust also appeared to be deposited in the base of the outer chamber but far more was deposited on the outer walls of the separating chamber and within the conical separator. But as with Hoover's experiment, I could not observe (a). What I could see however, was a slowly rising serpentine coil of particulate material which was swirling just inside the walls of the separating chamber, but not substantially in contact with them. Hoover allege that even Dyson's model of Campbell anticipates claim 1 of the Patent."
"132. Prof Syred was also cross-examined at length as to how a visible layer of particulate matter ("a light coating") came to settle on the walls of the separation chamber of Dyson's model of Campbell: 3/300-308. Hoover alleged that this came about by cyclonic action. However, Professor Syred was of the view that electrostatic forces had been primarily responsible for this: 3/308. If there was any cyclonic effect, it was in his view "negligible". Prof Allen was of course more inclined to attribute this to a cyclonic phenomenon operating in the separation chamber. However this light coating was not deposited where the dust or agglomerate should have been deposited as a result of cyclonic action, that is at the bottom of the collecting pan. Then there is the issue as to whether the paper and moulding material dropped into the bottom of Dyson's version of the Campbell separation chamber by gravity ("an inertial separator or drop-out pot" : Syred Supplementary Report, para 35) or got there as a result of centrifugal separation. Professor Syred remained of the view under cross-examination that this was indeed a gravity separator. In fact Hoover agreed that the moulding chips did fall by gravity but they said, this was because they had been chosen so as to be too heavy to begin with. The evidence of both experts on this entire latter point is too speculative for me to come to a sure conclusion as to who is correct."
That was sufficient to reject the attack of lack of novelty. Hoover had not established that the Campbell disclosure inevitably led to construction of an apparatus that fell within claim 1.
"134. There is however another more fundamental reason for rejecting lack of novelty on the basis of Hoover's experiment. According to the evidence, what is the most significant practical parameter in this unit is the inlet velocity of the laden air as it enters the separation chamber. Both experts were agreed that this is of great importance: Prof Syred, Supplementary Report, para 10: "The important parameter is the inlet velocity to the outer chamber." Prof Allen in cross-examination 4/465 (see below for a fuller quotation). There was a significant difference between the inlet velocities as between the two devices even allowing for debate over exact figures: see Prof Syred, Supplementary Report, paras 33-34 and cross-examination 3/316 et seq. That however is not quite the point. The point is that changing the inlet velocity of the particle-laden air could significantly alter the mode of action of Campbell's separation chamber, both as regards what happens within the reverse cyclone and within the cylindrical chamber alone. At 3/300, Prof. Syred said:
"Q Once there is rotation of the airstream, there is going to be centrifugal separating force on the particles?
A It does depend on the velocity and as stated in the literature there are lower limits for that.
Q ..Once there is some rotation, there is some centrifugal force?
A There will be some centrifugal force inevitably. Yes, it depends on the magnitude of velocity.
At 4/564, Prof Allen said:
"Q one cannot say from any of the materials before the court that operated in the manner which I understand you to suggest, that one could operate Campbell [so] that the inner cyclone would be more efficient at separating finer particles because those particles would become re-entrained with the airflow if it jetted ?
A Again, it would depend on the inlet velocity and it would be possible to design a version of Campbell which had a low pressure drop in your terms which had a reasonable inlet velocity and which still collected better on the inlet .It is possible to design and make a better version of Campbell at a smaller scale at a reasonable pressure drop.
Q .It is equally possible, may I suggest to you, to design such a system, if not more possible, whereby that does not occur and one simply gets a gentle rising motion of the air in the outer chamber and the rapid centrifugal separation in the central chamber?
A It is possible to build that. I have not seen it.
Q I would suggest that not only is that possible but that is what Campbell is himself describing ?
A Campbell is describing something which is clearly aimed at the milk drying application and the vacuum cleaning within it .[Milk particles] are very friable, they break very easily. The spray drying process produces either highly porous particles which if you impact them hard into a surface will break down to much smaller particles which are difficult to collect.. My guess is that is designing a gentle outer vortex in order to stop the particles being broken up.
Q There is no suggestion of the 'hang up' problem..?
A It is not specifically mentioned. The object of the outer separating chamber in this one has, I suspect, more to do with any break up."'"
"135. It seems to me that there are evidently a number of ways of operating Campbell which will depend upon choice of the inlet velocity. Some may fall within a claim of the Patent, others may not. Following General Tire, that evidence alone is enough to dispose of the argument of 'inevitable result' and thus lack of novelty. Further, a fair reading of Campbell leads Professor Allen to conclude that it was intended for a particular application wherein separation in the outer part of the separation chamber was actually to be avoided because of break-up of the working particles. That is, that it is to be operated in a manner which would not fall within any of the claims of the Patent. It must be borne in mind that the criterion in lack of novelty is that of inevitability and not 'might'. Furthermore, the words of Jenkins LJ in Fomento v Mentmore  RPC 87 are particularly germane to this aspect of the case. At page 101 of that report, dealing with lack of novelty, he said:
" I do not think that the Plaintiff's patent is to be held invalid because a person working a prior specification in which, so far from being described or claimed, the relevant characteristic seems inferentially to have been excluded, might unwittingly produce it." (My emphasis)
There are therefore in my judgment, no 'clear and unmistakable directions' in the Campbell patent, no planting of the flag 'at the precise destination' and in addition, no 'inevitable result' in the light of Hoover's (or Dyson's) experiment with a Campbell 're-build'. The objection to the Patent on the basis of lack of novelty in the light of Campbell, accordingly fails."
"Q. Could I please just invite you to go back to the Campbell picture on page 4 of bundle 3, behind tab 2. When we saw that cyclonic action in the video of the Hoover model and one considers for a moment the impact that would have on fine dust, it is right to say, it is not, Prof., that swirling flow that we saw in the Hoover model would sweep up a pile of dust such as that we see depicted in Campbell?
A. Yes, there is going to be a lot of entrainment from the base of the pan. As I explained earlier, that entrainment will reach some kind of equilibrium level. The gas cannot carry on holding the particles up and eventually you will get to a certain concentration where they have dropped down. There will be an equilibrium established between that which is being picked up and dropped down.
Q. As a result, one simply cannot say from any of the materials before the court that operated in the manner which I understand you to suggest one could operate Campbell that the inner cyclone would be more efficient at separating finer particles because those particles would be become re-entrained with the airflow if it jetted in in the manner shown, for example, in the Hoover video?
A. Again, it would depend upon the inlet velocity and it would be possible to design a version of Campbell which had a low pressure drop in your terms which had a reasonable inlet velocity to the outer chamber and which still collected better on the inlet. I am afraid I did not quite get the relationship between the scaling on diameter pressure drop and flow rate quite right earlier on. It is possible to design and make a better version of Campbell at a smaller scale at a reasonable pressure drop.
Q. What I would suggest, Prof., is I understand what you are saying about it is possible to design such a system. It is equally possible, may I suggest to you, to design such a system, if not more possible, whereby that does not occur and one simply gets a gentle rising motion of the air in the outer chamber and the rapid centrifugal separation in the central chamber?
A. It is possible to build that. I have not seen it.
Q. Also I would suggest
THE DEPUTY JUDGE: But?
A. I have not seen it, in the sense of the outer chamber having no centrifugal action.
MR KITCHIN: I would also suggest to you that not only is that possible but that is what Campbell is himself describing?
A. Campbell is describing something which is clearly aimed at the milk spray drying application and I would suspect the vacuum cleaning within it. I mentioned earlier on that I went to a milk spray drying plant when I was very young and I was struck by how dirty it was. I suspect that given the timing of this, 1954, this was aimed as a vacuum cleaner for picking up milk particles. They are very friable, they break very easily. The spray drying process produces either highly porous particles which if you impact them hard into a surface will break down to much smaller particles which are difficult to collect or it will produce little hollow spheres for which the same is true. My guess is he was designing a gentle outer vortex in order to stop the particles being broken up.
Q. There is no suggestion in this document, is there, of any understanding of the dog hair or "hang up" problem that we have discussed and which Mr Dyson experienced?
A. It is not specifically mentioned. The object of the outer separating chamber in this one has, I suspect, more to do with any break-up.
Q. There are no
A. And preventing break up of the particles which are friable."
"156. Common general knowledge has both positive and negative aspects. I have so far considered under this topic, as is customary, only positive aspects of the knowledge with which the skilled addressee is to be imbued. In my view in certain cases (and I believe this to be one of them), negative aspects of knowledge must in approximation to reality, play their part. At the priority date of the Patent, I believe that such was the 'mindset' within the vacuum cleaner industry, no notional, right- thinking addressee would ever have considered the viability of purifying dirt-laden air from a vacuum cleaning operation, other than by means of using a bag or bag and final filter. For present purposes, the addressee is nonetheless deemed to have been presented with (in effect) three items of prior art wherein it is proposed to clean dirt-laden air by means not of bags but by cyclonic action alone. He is also assumed to take some interest in them however inimical the proposals may be to his likely way of thinking at the time. In terms of its impact on the issue of obviousness, I believe that this negative thinking which as Mr Kitchin suggested amounted to prejudice, would at least have caused the addressee to regard modification to any of these prior art proposals with considerable reserve if not overt scepticism. This likelihood must, I consider, be given due weight. In my view of the matter, I cannot think that any of the cited prior art would ex facie be likely to have lead the addressee at the relevant date with any enthusiasm to effect the often substantial changes which would bring these proposals within a claim of the Patent: see para 153. My view in this regard is bolstered (but not precipitated) by Mr Dyson's evidence of what actually happened when he tried to interest the industry in Dyson I."
"If the plea of obviousness is to succeed, the court has to be satisfied that it would have appeared to the hypothetical technician, skilled in the art but lacking in inventive capacity, worthwhile to coat the helix of a self-pulling corkscrew with a friction-reducing material for purpose (a) or purpose (b) above or both of them. As cases such as Technograph and Beecham show, he is not to be expected to take steps or try processes which he would not regard as worthwhile. In using the word "worthwhile", we mean worthwhile as a possible means of achieving or assisting in practice the objective which he has in view. This, we infer, was what the judge had in mind in saying that the word "obvious" in section 3 is directed to whether or not an advance is "technically or practically obvious". We do not think that the hypothetical technician must also be taken as applying his mind to the commercial consequences which might follow if the step or process in question were found in practice to achieve or assist the objective which he had in view. As Oliver L.J. said in the Windsurfing case,  R.P.C. 59 at 72, "What has to be determined is whether what is now claimed as invention would have been obvious, not whether it would have appeared commercially worthwhile to exploit it". We thus agree with the judge that the word "obvious" in section 3 is not directed to whether an advance is "commercially obvious". We do not think that he misdirected himself in the relevant passage of his judgment."
Since at least the Hallen case, it has been recognised that the patent system is not available to protect mere commercial improvements. The observation of Slade LJ were directed at that issue which is step four of the Windsurfing steps.
"154. There are, we think, four steps which require to be taken in answering the jury question. The first is to identify the inventive concept embodied in the patent in suit. Thereafter, the court has to assume the mantle of the normally skilled but unimaginative addressee in the art at the priority date and to impute to him what was, at that date, common general knowledge in the art in question. The third step is to identify what, if any, differences exist between the matter cited as [forming part of the state of the art] and the alleged invention. Finally, the court has to ask itself whether, viewed without any knowledge of the alleged invention, those differences constitute steps which would have been obvious to the skilled man or whether they require any degree of invention."
"172. I have already considered Campbell in some detail under lack of novelty and have held that to the notional addressee reading it at the priority date, the separation chamber (2) would not appear to be acting as a cyclone at all, even when the tangential entry option is chosen. A major portion of the Dyson claims are thus missing even assuming that this device is indeed a vacuum cleaning appliance as I have construed the phrase (which it is not).
173. On the evidence, it is difficult to assess what the likely reaction of the notional skilled addressee would be on being presented with Campbell at the priority date. Given its context in the food industry (or in so-called 'agri- business'), its essentially industrial context, its age and the prejudice in the industry in favour of bags, I sense that the addressee would spend little time with Campbell as a serious candidate for some wholly new development in the vacuum cleaner field. The preparation of spray-dried milk and eggs has never I would guess, been a bonus to those manufacturing vacuum cleaners. Hoover argue however that the scaling down of Campbell to 'domestic' proportions would have been well within the competence of the skilled man at the relevant time. Maybe so, but I can find no evidence which would motivate him to do so with a reasonable expectation of a dividend. Moreover at the same time, the skilled reader would need to work hard so as to arrange for the dirty air inlet velocity to be such that
(a) the separating chamber would always function as a cyclone separator, and
(b) that the conventional cyclone which Campbell has proposed would always be of higher separation efficiency as defined in the Patent with respect to the separating chamber
174. Even if the skilled man were to take an interest in Campbell, its teaching is a very long way away from anything claimed in the Patent. Professor Allen as one would expect, was cross-examined concerning the necessary modifications which would be required to bring Campbell within the claims: 4/567-568. His answers were however based on the belief that Campbell in fact disclosed all the features of claim 1 which I have held not to be so. As with other aspects of their obviousness case, Hoover were not helped by the absence of any witness who could speak with authority as to current thinking in the vacuum cleaner field in 1980. For reasons already given, I do not regard the evidence of either expert witness to be of primary assistance on this point. In summary, in my judgment, the Patent is not obvious in the light of Campbell."
Mr Hobbs rightly pointed out that the judge had wrongly concluded that Campbell did not disclose a vacuum cleaning appliance. However, for reasons I have given, I reject the criticism that he wrongly adopted the attitudes and prejudices of the skilled person.
At trial there was a dispute as to how the device operated. Therefore the judge had to make findings of fact. I can describe the Hoover device using those findings of fact.
"65. 'In series' is normally used in English in the sense of 'one after the other' or 'one thing following another'. This is of course a general usage and its contextual meaning must be assessed in the light of the purpose to be served by (in this case) the requirement that the cyclone units are to be arranged 'in series'. It is clear that from the functional point of view, the 'in series connection' of claim 1 requires that all the 'comparatively clean air' from the lower efficiency unit is delivered to the 'highest efficiency unit'. Dyson's submission was simply that that which is received by the latter must have been pre-cleaned. Hoover submitted that an important qualification had to be made to this in that all the cleaned air from the low efficiency unit should pass directly into the higher efficiency unit. In connection with this phrase, I was addressed by both parties on the analogy of electrical circuits (such as resistors) arranged 'in series' and 'in parallel' (which would no doubt have been familiar to the addressee). In my judgment however, the proper construction of the phrase 'in series' in context does not import the requirement that the output from the low efficiency unit must flow directly into the higher efficiency unit. The 'connection' does not have to be direct.
66. I have also checked the references to the use of the phrase 'in series' in the body of Patent for consistency with the above finding. The first is to Dyson I and I have already considered that: see para 27. The second is to be found in relation to the cited prior art patent to Davis (Col 1, ll 37-43) which, as previously noted, discloses a single first stage frusto-conical type separator unit for coarse dust removal which delivers its entire output to a multicyclone unit of six of smaller separators in parallel to remove the 'finer dirt'. The system is described as 'having first and second stages through which air serially flows ' (See Col 1, ll 30-31 of Davis). All of the air which is going into the high efficiency second stage unit has come from the first stage which is upstream of it. Hoover's argument on 'in series' would require that the output of the first stage should go through each of the six cyclones within the multicyclone - one after the other. But that is not the way Davis works. On the contrary, in my judgment the way Davis works would be taken into account on this point by the skilled reader.
94. I reject Hoover's submission that SU1 and SU3 are not 'in series connection'. First, ignoring for a moment re-circulation from SU3, it is agreed that dirt-laden air flows sequentially through the appliance from SU1 through SU2, on to SU3 and then out of the cleaned air exit in SU2 to the environment. Hoover have chosen to use SU2 to bleed off three-quarters of the pre-cleaned air from SU1, out to the surroundings. This air still contains some fine dirt and this is an inefficiency which is rendered acceptable by the subsequent use of filters. Nonetheless, there is a concentrated dirty air stream which must next be cleaned in SU3, albeit of less volume than that of the bleed off. But the significance of this dirty air cannot properly be measured merely in terms of volume; it must be looked at in my judgment, in terms of the overall purpose of the apparatus. This is in truth the functional sequence which is at the very heart of the vacuum cleaning appliance subject of the Patent. However, I have held that SU2 is not a 'cyclone unit' within the claim; it does not deposit dirt nor is it even capable of so doing. It is therefore not the 'highest efficiency unit' and so far as claim 1 is concerned, even if its presence is in some way beneficial. It does not 'count' so far as infringement is concerned. All dirt-laden air entering SU3 has first been pre-cleaned by SU1 which is upstream of SU3; SU3 alone is the relevant 'highest efficiency unit'. It matters not that such pre-cleaned air has come, slightly concentrated perhaps in dirt, through SU2 any more than it has passed through say, specially designed ducting from SU1. SU1 and SU3 are in series connection as called for in the claim. As noted, the fact that this concentrating action may be either an advantage or a disadvantage, is irrelevant if, as is the case, it does not affect the way the invention works: see col 1, ll 63 et seq. Furthermore, the presence of SU2 is not in my judgment, a 'variant'. In reaching this conclusion, I have taken into account the evidence of both Prof Syred and Prof Allen.
97. I next turn to the alternative way in which Dyson put the infringement argument which became available as a result of the amendment to which I have referred. They say that SU2 and SU3 may properly be regarded as a single 'cyclone unit' within the meaning of the claims. All the output of SU1 undoubtedly goes into such unit, it is undoubtedly in series connection with it even on Hoover's construction, from it dust is deposited and clean air is exhausted to the environment. I confess to having at first viewed this alternative argument with some suspicion as it so easily avoids the complex issues of bleed off and re-circulation upon which the parties devoted so much time in preparation for trial. On this view, the internal 'plumbing' in this part of HTV can in effect, be ignored. However having considered the evidence, I believe that Dyson's alternative argument is sound. There was some skirmishing between the experts as to whether this sort of 'block unit' approach was in theory (that is, from essentially the academic point of view) legitimate but I do not consider it profitable to approach the matter this way."
"101. The expression 'trumpet shaped' is itself not an exact descriptive phrase. Different sorts of trumpets have different profiles. Furthermore, the horn, which sounds an octave below the trumpet, is also visually in the same league and for my part I should have described the separating zone of HTV (see for example Annex III) as being more like a cut off English hunting (or beagle) horn. Certainly, both are tapered. The apparently trivial difference between a geometrically perfect frusto-conical profile and that of the relevant portion of the HTV was dramatically highlighted at trial by the drawing put forward by Dyson in chief as Document X-9. This was a blown- up photocopy of the relevant portion of a sectional drawing of the relevant part of the HTV appliance. Upon this, two geometrically correct frusto-conical profiles had been superimposed in red, showing a slightly different notional angle corresponding to the 'top' and 'bottom' of Hoover's 'trumpet'. I have held that properly construed, the phrase 'frusto-conical' does not demand such geometric exactitude since to do so would be to indulge in the sort of strict literal interpretation which is forbidden by the Protocol. For this reason alone, I would be hesitant to hold that the separating zone in SU3 is not in fact 'frusto-conical' within the proper meaning of the claim. And I feel sure that the skilled reader would so regard it."
LORD JUSTICE SEDLEY:
" what he must be supposed to have done is to try everything which would appear to him as giving any prospect of valuable results."
" By 'obvious modifications' are meant that which technically or practically would be obvious to the unimaginative skilled addressee in the art . He does not and should not have to look further and consider whether the step he is taking is obvious or not for commercial reasons. The prize for a good commercial decision or idea is a head start on the competition and not a monopoly for twenty years."
LORD JUSTICE ARDEN: