Weatherford Australia Pty. Limited v Lettela Pty. Ltd

OFFICIAL NOTICE
DECISION OF A DELEGATE OF THE COMMISSIONER OF PATENTS
Application : No. 700529 in the name of Weatherford Australia Pty Limited

Title: Screen Construction

Action: Opposition under section 59 of the Patents Act 1990 by Lettela Pty Ltd; hearing

Decision: Issued
Abstract

The invention relates to a vibratory screening panel. The panel is defined to have a particular arrangement of screen surface members and underlying supporting members. The panel is formed of a resilient plastics material, such as polyurethane. A defined feature of the panel is that each surface member is constructed so as to be able to twist over a fraction of its length.
The invention was found to be novel.
However the invention was found to lack an inventive step. This was on the basis that a skilled person in the art at the priority date would have considered forming a wedge wire style screening panel from polyurethane with the panel having some flexibility enabling the surface screening members to twist in localised regions of their length.
The invention was also found to be not for a manner of manufacture. This was on the basis following the Microcell case regarding the use of a known material in the manufacture of known articles for the purpose of which its known properties make that material suitable.
The application was refused.
PATENTS ACT 1990
DECISION OF A DELEGATE OF THE COMMISSIONER OF PATENTS
Re:Patent application No. 700529 by Weatherford Australia Pty Limited, and opposition under section 59 of the Patents Act 1990 by Lettela Pty Ltd.

BACKGROUND

Patent application 27228/95 was filed on 27 July 1995 by Hunter Wire Products Limited. The application claims priority from Australian provisional application PM 7130 dated 28 July 1994, and this date is the earliest priority date of the claims of the application. Application 27228/95 was advertised accepted on 7 January 1999 and assigned number 700529. In June 2002 interest in the application was recorded to Weatherford Australia Pty Limited ("Weatherford" hereafter).
A notice of opposition to the grant of a patent on the application was filed on 7 April 2000 by Lettela Pty Ltd ("Lettela" hereafter) and a statement of grounds and particulars followed on 7 July 2000. Evidence in support, answer and reply were duly filed.
On 7 February 2001, when completing service of its evidence in answer, Weatherford filed a request to amend the specification under s.104. This request was eventually allowed on 18 September 2001. The amendments had the effect of replacing the description and claims as accepted with amended text, claim 1 as accepted being extensively amended as a result. Subsequent reference is to that amended specification.
Lettela completed its evidence in reply on 8 October 2001. On the same date Lettela sought leave to amend its statement of grounds and particulars ("the Statement"), and this was allowed on 29 October 2001.
The Statement lists as grounds of opposition the non-compliance with the following provisions of the Patents Act 1990 ("the Act"): paragraph 18(1)(a) (manner of manufacture), paragraph 18(1)(b) (novelty and inventive step), and sections 40(2) and 40(3) (invention not fully described, and fair basis and clarity of the claims).
On 18 October 2001 Weatherford filed an application to serve further evidence. This was allowed and further evidence was duly filed. Lettela also filed evidence in response to the further evidence.
This matter was set for a hearing in Canberra on 20 March 2003. Weatherford was represented by Mr C Owens a patent attorney of F B Rice & Co. Lettela was represented by Mr B Caine, senior counsel, instructed by Mr G Cowin patent attorney of Phillips Ormonde & Fitzpatrick. Mr R Woodgate a representative of Lettela also attended.
Subsequent to the hearing the parties requested that a decision on the opposition be deferred pending negotiations between the parties to settle the opposition. When no settlement was reached the parties asked that the Commissioner proceed to determine the opposition.
THE SPECIFICATION
The invention is entitled " Screen Construction" and concerns industrial screening systems. The invention is said to provide a new screen construction with improved properties. The background to the invention is given as follows:
"Vibrating screens are used in a variety of industrial and mining applications to separate and size material being processed. Traditionally such screens were of woven wire construction, although more recently welded wedge wire screens have also become popular particularly for smaller sizing applications.
A drawback of metal screens has always been their rate of wear with screen elements having to be replaced frequently.
Even more recently, polyurethane screens have been designed which because of their resilient nature have exhibited better wear characteristics than traditional metal screens, however polyurethane screens typically have the drawback that they have a lower open area ratio than metal screens, which reduces throughput, and they can be prone to blinding with some process materials or alternatively they are too flexible and pass unacceptable levels of oversize material. Each of these drawbacks are partially or wholly because of the location of cross members flush with the upper surface of the screen to accurately maintain the aperture and provide structural strength."
The specification then summarises the invention in terms of a consistory statement corresponding to the terms of claim 1 and with reference to preferred forms. It is convenient to quote claim 1 at this point. I have paragraphed and labelled features to aid subsequent reference.
"1. (a) A vibratory screening panel for use in vibrating screening equipment,
the panel comprising
(b) a plurality of screen surface members running in a first direction and extending the length of the panel from a first edge to an opposite, substantially parallel edge thereof the surface members having substantially planar upper surfaces defining a screening surface of the panel
(c) and a plurality of underlying supporting members running substantially transversely of and connected to each of the surface members to locate the surface members relative to one another and to provide structural strength to the panel,
(d) each surface member being separated from its adjacent surface members by gaps, thereby forming open slots between adjacent pairs of the surface members, the gaps having a dimension defining the discriminating size of the screen panel,
(e) and each of the surface members protruding above the transverse members such that a plurality of open slots are provided at the surface of the panel,
(f) the slots extending through a bottom surface of the panel between the transverse members, each of the slots extending the length of the panel in said first direction and being open above the transverse members over said length of the panel and through said edges of the panel,
(g) and each of the surface members having a transverse profile which has a widest point adjacent its upper surface and sides which are non-divergent below the widest point,
(h) the screen panel being formed of a resilient plastics material
(i) and each of the surface members being constructed so as to be able to twist about a substantially longitudinal axis of the respective surface member, over a fraction of its length, relative to the support members and a remainder of the respective surface members."
The invention thus relates to a particular form of screening panel. It particularly concerns the arrangement of the screen surface members and underlying supporting members, the profile of the support members, the provision of the "slot" formed between surface members, and the twisting property of the surface members. The specification includes a detailed description of the invention with reference to 12 drawing figures. The figures show different screen arrangements and different profiles of both surface and supporting members.
As to the terms "slot" and "gap" the specification states:
"In the context of this specification the terms slot and gap are used interchangeably, with the term "slot" being used generally to define the 3-dimensional space between two surface members 11 and the term "gap" being used to describe the separation of the surface members and therefore the minimum dimension of the slots."
On page 5 there is description of the characteristics of the panel of the invention compared to prior panels. In particular it states:
"Referring to Figures 2 and 3 which are both end views of the surface members 11, it will be noted that the surface members 11 project a significant distance above the transverse members 12 in order to provide a surface having slots 13 which are substantially open or uninterrupted along their length. It has not previously been known to manufacture panels out of plastics material, and more specifically polyurethane, in such a configuration. Polyurethane panels in the past have typically been manufactured with both the longitudinal and transverse members extending to the top surface of the panel to provide rigidity and strength. Such a structure was considered necessary in polyurethane panels in order to maintain accurate sizing, because excessive flexibility would lead to oversized material passing through the screen. These prior art screens suffer from problems with blinding where material builds up against transverse members at the downstream ends of each slot, and eventually closes the entire slot. This problem is particularly severe in some operating environments and can lead to screens requiring cleaning several times a day, with significant loss of throughput resulting.
The screen of Figures 1-3 has several characteristics which enable it to overcome the blinding problems of prior art screens. First, because the transverse members 12 are located below the surface of the screen, the slots 13 are open along their entire length, thereby reducing the opportunity for buildup to occur. This feature can be enhanced if panels are manufactured in such a way that the slots 13 are open through the ends of the panel and slots from one panel line up with slots in the next panel.
The second feature of the panel of Figures 1-3 which enhances its performance is that the increased flexibility of the panel assists in keeeping the panel clear without any significant degradation of the sizing capability of the screen. …"
The profile of the surface members is described in these terms on page 6:
"The surface members in the preferred embodiment will have a substantially rectangular profile with a slight taper, in the range of 0⁰to 13⁰ in the bottom third of the member. In another embodiment, a slight taper in the range of 0° to 13° may be provided in the top two thirds of the member. The taper angle is selected to suit aperture size and the application of the screen. In at least one advantageous form of the invention the taper is approximately 6⁰."
These preferred profiles are the subject of claims 11 to 14.
There are 17 claims appended to the specification. Claims 2 to 16 append either directly or indirectly to claim 1. Claim 17 is an omnibus claim in the following terms:
"17. A screen panel substantially as hereinbefore described with reference to the accompanying drawings."
THE EVIDENCE FILED
Evidence in support
The evidence filed in support of the opposition comprises statutory declarations by the following persons:
·    Graham Cowin, patent attorney. (Declaration includes exhibits GLC-1 to GLC-12.)
·    Peter Bowden, sales manager of Elastomers Australia, a division of Lettela. (Declaration includes exhibits PB 1 to PB 7.)
·    Vernon Leith Murphy, retired manager (Murphy's 1^st). (Declaration includes exhibit LM 1.)
Evidence in answer
This comprises statutory declarations by:
·    Robert Johnstone, consultant. (Johnstone's 1^st). (Declaration includes exhibit RIJ 1.)
·    Robert Johnstone (Johnstone's 2^nd).
·    Robert Johnstone (Johnstone's 3^rd). (Declaration includes exhibit RIJ 2.)
·    Ron Johnson, R&D technical manager of USF Johnson Screens Pty Ltd (Johnson's 1^st). (Declaration includes exhibits RLJ 1 and RLJ 2.)
·    Colin McLean, a retired mechanical engineer.
·    Brandon McDougall, contracts manager of USF Johnson Screens Pty Ltd.
Evidence in reply
The evidence filed in reply comprises statutory declarations by:
·    Philip Gehrig, patent attorney. (Declaration includes exhibit PWG 1.)
·    Vernon Leith Murphy (Murphy's 2^nd). (Declaration includes exhibit LM 2.)
·    Vernon Leith Murphy (Murphy's 3^rd).
·    Raymond Woodgate, production manager of Elastomers Australia. (Declaration includes exhibits RMW 1 to RMW 4.)
Further Evidence filed by Weatherford
This evidence comprises statutory declarations by:
· Robert Johnstone (Johnstone's 4^th).
· Ron Johnson (Johnson's 2^nd). (Declaration includes exhibit RLJ 3.)
Response Evidence to Further Evidence filed by Lettela
This evidence comprises a statutory declaration by:
· Melvyn King, a director of Minspec Mineral Processing Equipment Pty Ltd of WA.
General comments about the declarants and evidence
Mr Caine submitted that the evidence of some of Weatherford's declarants needed to be treated with caution. In particular he drew attention to the evidence of Johnstone (his 1^st at clauses 20, 34, 35 and 43 and his 4^th at clauses 4-10) and Johnson (2^nd at clauses 9-12) where comments distinguishing the present invention from the prior art are made, but the comparison is with a product or prototype screen panel not with the claimed invention. He thus questioned the relevance of some of this evidence and the reliability of the declarants as technical witnesses in the matter. He added if there was a collision between the evidence of the parties, Lettela's declarants Murphy and King ought to be preferred to Johnstone and Johnson.
As to evidence generally, the Commissioner, while functioning as a Tribunal, is not bound by the rules of evidence but nevertheless must reach a decision on rationally probative material, ie. material which tends rationally to show the existence or non-existence of facts relevant to decision. It is for the Commissioner to determine the weight to be given to material of probative value. I will keep Mr Caine's comments in mind when drawing on the evidence in this matter.
DECISION
At the outset of the hearing Mr Caine indicated that the opponent would rely on the opposition grounds of lack of novelty, obviousness and not a manner of manufacture. Whilst he indicated there was no attack under s.40 grounds, there arose issues of construction going to the true scope of the invention claimed.
Construction issues
The main issues of construction surround the features of claim 1 that I have listed as (h) and (i). However before discussing those features some comments about other features are appropriate.
The subject of the claim is a screening panel for vibrating screening equipment. It thus relates to a panel suitable for use in such screening equipment. From features (b) and (c) the panel comprises a plurality of screen surface members and a plurality of underlying supporting members, the general orientation and extent of these members being stated. There is nothing to limit the screen surface members to being straight over the length of the panel, and given the definitions in claims 7-10, different forms are clearly included.
Feature (d) introduces the requirement for a separation between adjacent surface members by gaps to thereby form open slots between adjacent pairs of such members. The dimension of the gaps defines the discriminating size of the screen panel. It is implicit from this definition that the gaps must be uniform otherwise the screen panel will not have a discriminating size giving uniform size of screened product.
From feature (e) the definition requires each of the surface members to protrude above the transverse members. Further that definition and that of feature (f) make it clear that the slots are open through to the bottom surface of the panel between the supporting (transverse) members, and that the slots are open above the supporting members over the length of the panel and through to the edges. Thus above the supporting members the slots are open from edge to edge of the panel while below the panel the supporting members interupt the slots opening to below the panel.
Feature (g) defines the transverse profile of each surface member. The profile has a widest point
adjacent its upper surface and sides which are non-divergent below the widest point. It was accepted that this included rectangular profiles and other profiles where the sides of the members tapered inwardly over some of their height.
I now come to feature (h), which defines "the screen panel being formed of a resilient plastics material". The definition encompasses any material fitting a "resilient plastics material", not simply polyurethane which is claimed in claim 3. However several issues arose with this definition. It was said on behalf of Lettela that the definition did not make it clear whether the panel was made from only one plastics material and that it included no metal. Mr Owens seemed to concede that the claim possibly encompassed some additional material being in the panel, such as metal wires to control shrinkage when moulding the plastics material. In my view the claim definition by its wording and plain meaning limits the panel to be formed of "a", that is one, resilient plastics material. That "resilient plastics material" could be polyurethane or any other suitable material meeting the definition. I do not believe it is legitimate to interpret the wording in a way whereby the forming could involve multiple plastics materials - such a panel may be one of resilient plastics, but the wording identifies a singular "plastics material". As to whether the panel contains other than plastics material, it seems to me that the definition excludes it. Again the wording "being formed of a resilient plastics material" is precise and suggests exclusiveness in the material from which the screen is formed. It is stretching the point to, say, interpret "being formed of" as "being at least formed of", or that because the word "solely" does not appear the option for other materials is included.
Feature (i) also provoked discussion. It states:
"and each of the surface members being constructed so as to be able to twist about a substantially longitudinal axis of the respective surface member, over a fraction of its length, relative to the support members and a remainder of the respective surface members."
It was submitted for the opponent that the definition did not set out the nature and extent of the twisting. Mr Owens however submitted that by virtue of "over a fraction of its length", the definition indicated that there was localised twisting as against twisting over the entire length of the surface members. I am inclined to agree with Mr Owens. I think it is true that the definition lacks some precision in the manner of expressing the twisting, but it seems to me that the ability for the surface members to twist in localised regions of its length when needed is the only fair meaning to give to this feature. Thus at any time any twisting only affects the surface member over a fraction of its length.
It should be noted that in relation to feature (i) the claim does not relate the twisting characteristic to any purpose it may be intended to serve. From the description the feature is intended to characterise the flexibility inherent in the surface members which assists against problems with blinding of the screen, the twisting or flexing assisting in displacing material from the slots and clearing the panel. However any such in use aspect is not a limitation to the claims.
Novelty
For assessing the novelty of a claimed invention an accepted test is the so-called "reverse infringement test" as set out in Meyers Taylor Pty Ltd v Vicarr Industries Ltd (1977) 137 CLR 228 at 235. Under this test if a citation discloses all the essential features of a claim so that it would constitute an infringement of the claim if the claim were in a patent, the claim will lack novelty.

Following the amendment to the specification Lettela only relies on one document for its opposition ground of lack of novelty. That document is US patent 4374169, granted in 1983, and which was referred to as the UOP patent. Although Lettela placed in evidence some material concerning an alleged prior use before the priority date of a so-called JOHNATHANE panel, said to correspond to the invention disclosed in the UPO patent, none of that material was subsequently relied upon by Lettela in these proceedings because of doubts about the availability to the public of information of any such prior use. Thus although declarants from both sides have referred to the JOHNATHANE panel, I do not rely on it. Further, insofar as declarants Johnstone and Johnson have made an association between features of the JOHNATHANE panel and disclosure of the UOP patent, and not independently interpreted the disclosure of the patent document, I have not relied upon that evidence.
The UOP patent discloses a reinforced screen panel member suitable for vibrating screening equipment. The panel member has a first plurality of elongated, parallel surface wire members which are formed by extruding a resilient, abrasion resistant layer of elastomeric material around a core portion which is more rigid than the elastomeric layer. A second plurality of elongated, parallel support rod members are arranged transverse to the surface members and are formed by extruding a layer of elastomeric material around a more rigid core portion. Bonds are formed at intersection points of the surface and support members such as by melting the outer elastomeric layers. The spacing apart of the surface members provides the desired screen size corresponding to the size of the material to be screened. The "surface wire members" can have a steel core member but more typically have a core formed of a plastics material. Thus the core and outer layers of the surface members can both be formed of polyurethane by a co-extrusion process but the core can be formed from a more rigid polyurethane than the outer layer. As for the support rod members, these are described as "almost always provided with a core 24 of solid wire" about which is extruded an elastomeric material, such as polyurethane, to provide an outer layer. Although Murphy in Murphy's 2^nd doesn't suggest there is disclosure for other than a steel wire core for the support members, the wording quoted suggests to the contrary. In fact the description does not exclude the use of an elastomeric material for the core of these members also, like that for the surface members. There is an emphasis on the level of elasticity for the core portions of both the support and surface members, which according to claim 1 of the patent are at the same level, and it is only claim 7 which specifies a core portion of solid steel wire for the support members. Thus I believe to a skilled addressee there is disclosure that the support members can also consist of a core and outer layer of elastomeric material, such as polyurethane. As for other features, the drawings illustrate the surface members standing proud of the support members, and that the surface members have a profile with their sides tapering inwardly from a widest point adjacent the upper surface of the members.
Comparing the disclosure of the UOP patent with claim 1 it is clear that there is full disclosure of a screening panel having all features (a) to (g). As to feature (h), as the UOP patent discloses both surface and support members being formed using one resilient plastics material, such as polyurethane, without any steel core to the support members, this feature is disclosed. It does not matter that the members of the UOP patent have a composite form.
With regard to feature (i), there is no disclosure in the UOP patent to the effect that the surface members are so constructed so that they can twist in a localised manner as this feature defines.
Thus the UOP patent would not constitute an infringement of claim 1 if it were in a patent. Accordingly the claimed invention is novel.
Common general knowledge
In assessing issues such as whether the invention exhibits an inventive step the common general knowledge in the art needs to be identified. The following statement indicates the nature of common general knowledge:
"The notion of common general knowledge itself involves the use of that which is known or used by those in the relevant trade. It forms the background knowledge and experience which is available to all in the trade in considering the making of new products, or the making of improvements in old, and it must be treated as being used by an individual as a general body of knowledge." (per Aickin J. in Minnesota Mining & Manufacturing Co v Beiersdorf (Australia) Limited (1980) 144 CLR 253 at 292).
The evidence in this matter gives some indications rather than clear pronouncements about what may have formed part of the common general knowledge in the art. These indications arise from statements about matters being "common practice", "commonly used" or "well known" to certain individuals or workers before the priority date. I believe that evidence of Murphy, Bowden, Woodgate and King can all be considered because they all have had considerable involvement with the art in question, namely screening of materials. I will now refer to these matters.
Woven wire screens
The specification mentions screens of woven wire as a traditional screening form. These forms of screens were clearly part of the common general knowledge.
Perforated metal plate screens
Woodgate refers to such screens in clause 11 and exhibits a brochure from a manufacturer. Although there is little mention made of such screens in the evidence it appears such forms of screens have been used for many years and qualify as part of the common general knowledge.
Wedge wire screens
Wedge wire screens are mentioned in the background discussion in the specification. Murphy in Murphy's 3^rd at clause 3 says that panels of such screens have been commonly used in Australia for many years and certainly well before the priority date. King at clause 23 makes similar comments. There was no dispute from the applicant about these statements. It appears that wedge wire screens are typically made of stainless steel and have a shape and form of screening surface and underlying support members equivalent to that shown for embodiments of the screens for the present invention, such as shown in figures 1 and 10. I believe that wedge wire screens were common general knowledge in the art.
Polyurethane screening panels
Murphy states that screening panels composed of polyurethane have been manufactured in Australia since the "early 1980s" and widely or commonly used well before the priority date (see Murphy's 2^nd at clause 13 and 3^rd at clauses 5 and 8). Woodgate, in clauses 2-10, also refers to certain screens being made from polyurethane and marketed in Australia since 1980. Bowden's evidence also supports this. I note that Woodgate says that cross tensioned screens having polyurethane panels replaced in the early 1980s what was then conventional metal plate cross tensioned screens (clause 11). King also says that screening panels made from polyurethane were used in Australia for some time (clause 28). I believe that screening panels made of polyurethane were part of the common general knowledge.
King also states that properties associated with polyurethane, such as abrasion resistance and flexibility, were well known before the priority date (clauses 29-31). King also states that it was widely known in the industry before the priority date that the flexibility of the polyurethane could be controlled in screening panels by making the panels of different material compositions and also by varying the thickness and bulk of the panel members. Murphy in Murphy's 3^rd at clauses 6 and 8 also refers to these properties of polyurethane being well known. Accordingly I believe such matters also formed part of the common general knowledge in the trade at the earliest priority date.
Inventive step
From sections 7(2) and (3) of the Act a claimed invention will lack an inventive step when compared with the prior art base if it would have been obvious to a person skilled in the art in the light of:
(a)the common general knowledge existing in the art before the priority date considered alone; or
(b)the common general knowledge existing in the art before the priority date considered together with information in a single document or through doing a single act, provided that the skilled person could, before the priority date, be reasonably expected to have ascertained, understood and regarded the information as relevant to work in the relevant art in the patent area.
(The provisions of s. 7 applicable to the present application are those applying immediately prior to the amending act which came into effect in 2001.)
It is from the position of a non-inventive worker in the field equipped with the common general knowledge and together with any qualifying prior art information that the invention must be considered to assess the presence of an inventive step.
Lettela's arguments in support of a lack of an inventive step for the claimed invention relied upon the known use of polyurethane screens in the art together with the properties such as wear resistance and flexibility which polyurethane was known to exhibit. Thus there was reliance on these elements of the common general knowledge that I have discussed above.
The argument advanced to support a lack of inventive step was essentially this. Prior to the priority date wedge wire screens were commonly used for screening panels. At the priority date screening panels for various screening purposes and for use in certain screening equipment were being formed from polyurethane rather than metal, and some such panels had been used for some time before the priority date. Polyurethane was known to have elastomeric properties and to have a flexibility which could be dependent on actual composition and also on configuration and size of product formed. Thus it was argued that at the priority date there could be no inventive step required in seeking to form a traditional wedge wire screen out of polyurethane. Further for such a screen to possess some flexibility in the surface members would have been an inevitable consequence depending on precise material composition and configuration of surface members and panel formed.
In answer Weatherford submitted that it was not shown that the characteristics of polyurethane were useful for a vibrating screen as distinct from use in other screens such as aperture screens. It was submitted that at the priority date the flexibility of polyurethane was considered a barrier to a solution aimed at avoiding a blinding problem with polyurethane screens having a lower open area ratio than metal screens, but the applicant has come up with a solution. Thus the assertion that it was obvious or a design selection to make a vibrating screen panel of polyurethane or other plastics material with full length slots which avoided excessive flexibility but reduced blinding effects was disputed.
One way to approach the issue of the presence or otherwise of an inventive step is to consider "whether the hypothetical addressee faced with the same problem would have taken as a matter of routine whatever steps might have led from the prior art to the invention, whether they be the steps of the inventor or not" (Wellcome Foundation Ltd v V.R. Laboratories (Aust.) Pty Ltd (1981) 148 CLR 262 at 286).
The question in this case essentially seems to resolve to this: Would a skilled person in the art at the priority date in seeking to provide an alternative to the metal wedge wire screens have considered forming one using a resilient plastics material such as from polyurethane and with the surface members having some flexibility to twist? In order to assess that question I need to refer to some of the evidence.
Woodgate refers at some length to cross tensioned screens and how before the priority date those of conventional metal plate had been replaced by ones made from polyurethane. He refers to some advantages the polyurethane screens exhibited over the metal ones, such as wear characteristics, lighter and thus easier to handle, and that they were cost effective. He says that these advantages arose from characteristics of the polyurethane material, characteristics he says were commonly known in the industry for many years before the priority date.
Murphy, in Murphy's 3^rd, discusses screening panels composed of polyurethane. He says that such panels have been developed and used in mining operations in Australia for some years. He says polyurethane "has been favoured for many screening panel applications because of its better wear capabilities when compared with metal such as stainless steel" (clause 5). Murphy also says in clause 6 that:
"Polyurethane has an inherent flexibility. As a result, the surface members or "wires" defining the discriminating slots of polyurethane screening panels do tend to flex under loading of the material being screened and the vibratory stresses applied by the screening apparatus in which they are mounted. … Excessive flexing can lead to oversized material being received in the slots where it will either pass through the slots leading to inaccurate screening, or become wedged in the slots causing "blinding" of the screening panel."
In clause 10 he says that in view of the inherent resilient flexibility of polyurethane it has been well known before the priority date that "in screening panels formed of polyurethane the surface members will flex under normal use conditions."
In clauses 13 and 14 Murphy refers to factors that may affect the extent of twisting and flexing of surface members of screening panels. Then in clause 15 Murphy says this:
"Accordingly, an entirely expected consequence of forming a screening panel, having the configuration of the wedge wire screening panel sampled in Exhibit PB 1, of polyurethane is that the surface members or wires would be able and would tend to twist and flex. The polyurethane surface members or wires would protrude above the transverse support members, and therefore would not have a rigidity that would be achieved if those support members extended up flush with the screening surface of the panel. As a result, the surface members would tend to readily twist, and flex both horizontally and vertically under the action and influence of material loaded onto the screening surface and the vibratory forces of the screening apparatus. Such a result would not, in my opinion, have been at all surprising as at 28 July 1994. Indeed, in my opinion, the twisting and flexing of the surface members is an entirely expected outcome of using polyurethane to manufacture a screening panel having essentially the same configuration of previously well known stainless steel wedge wire screening panels."
Exhibit PB 1 is a portion of a stainless steel wedge wire screen.
Murphy further discusses the flexibility aspect in clause 16. That clause includes these paragraphs:
"Whether or not a screening panel having surface members protruding above the support members produces excessive flexibility in the surface members will depend on several factors related to the construction of the panel, including the dimensions (thickness and height) of the surface members, the height of the surface members above the support members, and the spacing of the underlying surface members. Those factors have been well recognised and understood by me for many years, and certainly well before the 28 July 1994. I also believe that they were widely understood within the Australian mining, quarrying and mineral processing industry well before that date.
I appreciated well before the 28 July 1994 that forming a polyurethane screening panel with surface members protruding above the support members would not necessarily result in surface members which are excessively flexible. That is because, flexibility in the surface members is not simply dependent on the relative height disposition of the surface and support members. Therefore, it would not have been at all surprising to me, as at 28 July 1994 that a screening panel with protruding surface members forming continuous or uninterrupted slots along the screening panel did not lead to the passing of oversized material due to excessive flexibility in the surface members. Moreover, I believe that such a situation would have been well appreciated by other members of the Australian mining, quarrying and mineral processing industry at that time."
In clause 17 Murphy states that it was well known within the mining, quarrying and mineral processing industry before the priority date that the continuous slots in the stainless steel wedge wire panels reduced material buildup against the support members and thus blinding of the slots.
Johnstone, in Johnstone's 4^th, in responding to Woodgate's evidence, points out that Woodgate is only discussing cross tensioned screens and that such screens do not have continuous full slot apertures running the length of the screens. His evidence thus implies caution is needed against extending knowledge about such screens to full slot screens.
In the same declaration Johnstone responds to Murphy. In clause 17 he suggests that Murphy, when discussing the aspects of the flexibility of polyurethane,
"assumes that flexibility was thought to be a good feature in a wedge wire style panel. Leith seems to jump to this conclusion because polyurethane panels have been used for aperture plates, however in making this leap he ignores the significant differences between wedge wire and aperture plates."
Then in relation to further comments by Murphy in his clauses 13 to 17 about flexibility and twisting he states in clause 18 that:
"Leith's analysis is after the fact and relies on the assumption that it was obvious to use polyurethane in a full slot wedge wire style screen. However, the basis of this assumption does not hold up and in fact it is history that no one successfully made a full slot polyurethane surface before 28 July 1994, and I believe that at that date the common thinking was that such a panel would suffer from oversizing."
Johnstone, in clause 26, completes his evidence thus:
"The opponents in this latest evidence have given only simple aperture plates as examples of the metal and polyurethane screens being interchangeable. They have conveniently avoided more complex screens but simply asserted that the same interchangeability holds true for wedge wire without support for their proposition. I say that at 28 July 1994, no one in the mining industry would have thought it possible to form a full slot wedge wire style screen in resilient plastics material without problems of premature failure and/or oversizing, and I say that this is supported by the fact that even in 1990 [sic, 1998], when Hunter trialed their prototypes that no one else had produced such a product."
Finally I refer to King's evidence. His evidence was filed after that of Johnstone just mentioned. In clauses 29 to 31 he refers to polyurethane and flexibility aspects thus:
"29. Polyurethane is an elastomer of synthetic rubber. It has elastomeric properties that suite [sic] ore screening applications. Elasticity of an elastomer is the property of recovering an original shape after deforming forces are removed. Resilience refers to the speed with which the material recovers its shape under screening conditions. Modulus is the material's ability to absorb energy and reduce flex fatigue. The material's abrasion resistance is a complex property which is determined by coefficient of friction, tear strength, and elasticity. The properties are used in a variety of configurations to produce polyurethane components that suitably resist wear, by bending, flexing and twisting. Those properties vary depending on the material composition of the elastomer. Different compositions will produce softer or harder polyurethane which, in turn, will affect its behaviour in use. That was well known in Australia long before 28 July 1994.
30. It was widely known within the Australian mining, quarrying and mineral processing industry prior to 28 July 1994 that this flexibility of the polyurethane could be controlled in screening panels by making the panels of different material compositions and also by varying the thickness or bulk of the panel members. Sometimes, parts of the panel were reinforced with metal pieces embedded within the polyurethane in order to provide structural strength. In this way, it was possible to select a combination of material composition, bulk of panel, extent of reinforcement, and size of openings that would achieve effective screening in a polyurethane screening panel.
31. The intention in selecting those parameters was not to eliminate the flexibility from polyurethane screening panels. Indeed, it was recognised at the time that the flexibility simply could not be eliminated because of the inherent characteristics of polyurethane and the forces to which the panels would be subjected in vibratory screening equipment. Rather, it was appreciated before 28 July 1994 that a degree of flexibility, often greater than that which occurs in metal screening panels, enhanced screening effectiveness. Too much flexibility was likely to result in oversized materials passing through the panels, and/or materials jamming easily in the panel openings causing "blinding" of the screening panel. However, some flexibility was known to actually deter blinding. That is, the right amount of flexing of the panel members defining the openings caused a degree of self cleaning of the openings, with particles initially lodged in the openings subsequently being dislodged following vibration and flexing of the panel. At the same time that flexibility did not lend to unacceptable screening of oversized particles."

In clauses 34 to 36 King further discusses matters surrounding the possible use of polyurethane for screening panels. He states:
"34. I was not aware as at 28 July 1994 of any screening panel composed of plastics material, such as polyurethane, and having the same general configuration of a stainless steel wedge wire screening panel. … However, there is nothing surprising to me about such a panel. That is, as at 28 July 1994 I would not have been surprised by the existence of a screening panel having the general configuration of a stainless steel wedge wire screening panel but being composed of polyurethane.
35. The materials of plastic such as polyurethane and metal such as stainless steel will not always be simply interchangeable in the manufacture of screening panels. A large number of factors will need to be taken into account in determining the preferred or most appropriate material of construction of such panels. In some situations there will clearly be a preference for the use of stainless steel, whilst in other situations the preference will be for polyurethane. That is true for screening panels originally made in one particular material, as well as any newly developed screening panel. Thus, with existing screening panels composed of, for example metal, there may be no practical or economic reason to manufacture such a panel in other material, such as polyurethane. On other occasions the characteristics of polyurethane may make a panel not previously composed of that material more suited for the intended panel application than a panel previously composed of metal. In some instances the same panel configuration may be composed of different materials to suit different applications for the panel.
36. What has been apparent to me, and to other members of the Australian mining, quarrying and mineral processing industry, since well before 28 July 1994 is that polyurethane is widely recognised as a suitable material for construction of screening panels. Polyurethane has a series of well identified characteristics, including resistance to wear and flexibility, that make it entirely appropriate for screening panels in certain circumstances and applications. As a result, since well before 28 July 1994, screen panel designers and manufacturers have had available to them polyurethane as a material of construction of screening panels. Up to that date, polyurethane could be considered as a viable alternative to previously used materials such as stainless steel. Moreover, having taken into account various factors those designers and manufacturers could, if polyurethane is assessed to be the preferred material, elect to use that material in the construction of the screening panel in question."
The evidence indicates that polyurethane had been used to form certain screening panels before the priority date, and that was part of the common general knowledge. Furthermore the evidence suggests to me that there would be nothing remarkable about forming a wedge wire style screening panel from polyurethane. Murphy and King point to the knowledge possessed by skilled persons about the characteristics of polyurethane and the use of polyurethane in certain screening panels for some time before the priority date. I note that King says that before the priority date polyurethane could be considered by screen designers and manufacturers as a viable alternative to previously used materials such as stainless steel for forming screen panels. I also note that King says that various factors and circumstances may influence the choice of material from which particular screen panels or surfaces are formed.
It seems to me that in seeking to provide an alternative to the metal wedge wire screens a skilled person at the priority date would have considered forming one using a resilient plastics material, such as polyurethane. In my view there is nothing in the evidence which clearly points to difficulties or problems in proceeding along that course. To the contrary, plastics material, in particular polyurethane, was already known and used at that time in making some particular screening panels, and the characteristics of polyurethane for use in such screens also known to those in the art. Furthermore I do not see that the skilled person would have had any difficulty in addressing any excessive flexibility issue arising with using polyurethane for such a screen because the evidence indicates that the degree of flexibility could have been something readily addressed by varying the composition used. In that regard it would require nothing more than routine steps by the skilled person to arrive at a screen panel having appropriate flexibility characteristics in order for the screen panel to meet its intended purpose.
Having considered the evidence it is my conclusion that the skilled person in the art at the priority date would have considered forming a wedge wire style screening panel from polyurethane with the panel having some flexibility enabling the surface screening members to twist in localised regions of their length. Thus I find that the claimed invention lacks an inventive step. That conclusion applies to all claims, since the dependent claims do not introduce any features that could be considered to require any exercise of inventive ingenuity given the known forms of metal wedge wire and known characteristics of polyurethane.
Manner of manufacture
The argument advanced by Lettela under this opposition ground was that the invention is not a manner of manufacture on the basis of what is said in Commissioner of Patents v Microcell Limited 102 CLR 232. Reliance was placed on various passages of that judgement, such as the following at 251, as being applicable to the situation in the present case:
"We have in truth nothing but a claim for the use of a known material in the manufacture of known articles for the purpose of which its known properties make that material suitable. A claim for nothing more than that cannot be subject matter for a patent, and the position cannot be affected either by the fact that nobody thought of doing the thing before, or by the fact that, when somebody did think of doing it, it was found to be a good thing to do."
In the present case Lettela submitted that polyurethane was known to be suitable for use in forming screening panels and used for forming such articles. The present invention did no more than use such material in forming an article for which its known properties made it suitable. Furthermore the specification does not point to any unknown or unsuspected property of the material to make it suitable for the particular use claimed, or otherwise point to some technical advance in the technique of production of the screen which may suggest some invention. It was submitted that the present situation was a clearer case than that in Microcell because here it had been previously known to use polyurethane to form particular screening panels unlike the situation in Microcell where the well-known material had not been previously used in similar articles to that of the alleged invention.
In reply submissions Weatherford disputed that the characteristics of polyurethane had been recognised as useful for making a vibratory screen as claimed, adding that it was not correct to equate what was known about aperture plate screens with vibratory screens of the type claimed.
Under the previous heading I have accepted the evidence of Murphy and King and what they say about what was known of polyurethane at the priority date in relation to its use for screening panels. There is no evidence which raises in my mind a doubt that the known material of polyurethane could not have been readily applied to form a vibratory screening panel as claimed. I agree with Lettela's submission that there is no suggestion that an unknown property of the material is being relied upon or that some new production technique is involved for utilising polyurethane in forming these types of screening panels. Thus in my view the claimed invention is of the type found wanting for manner of manufacture as found in the Microcell case.
Accordingly I find that the claimed invention is not for a manner of manufacture.
CONCLUSION
I have found that the claims do not lack novelty.
However I have found that the invention claimed in the claims lacks an inventive step and is not for a manner of manufacture.
Given my findings, I do not see any patentable subject matter in the specification. Accordingly I refuse the application.
COSTS
The usual practice is that costs should follow the event and the submissions for the parties were consistent with that approach. As I have found the opposition successful on the ground of lack of inventive step and not a manner of manufacture, costs should go against the patent applicant. Accordingly I award costs in this matter against Weatherford Australia Pty Limited.
Trevor Bruhn
Delegate of the Commissioner
Patent attorneys for the applicant: F B Rice & Co, Sydney
Patent attorneys for the opponent: Phillips Ormonde & Fitzpatrick, Melbourne

[2003] APO 51

14 November 2003