Labcyte Inc.

[2022] APO 73

IP AUSTRALIA

AUSTRALIAN PATENT OFFICE

Labcyte Inc. [2022] APO 73

Patent Application:             2019245278

Title:Fluid impermeable ultrasonic transducer

Patent Applicant:                Labcyte Inc.

Delegate:R Subbarayan

Decision Date:  18 November 2022

Hearing Date:  Written submissions filed on 28 April 2022

Catchwords:  PATENTS - examiner objections – whether claims lack inventive step – examiner’s objections are valid – all claims lack inventive step – opportunity to amend – final date for acceptance reset

Representation:                   Patent attorney for the applicant: Spruson & Ferguson

IP AUSTRALIA

AUSTRALIAN PATENT OFFICE

Patent Application:             2019245278

Title:Fluid impermeable ultrasonic transducer

Patent Applicant:                Labcyte Inc.

Date of Decision:                18 November 2022

DECISION

The examiner’s objections are valid, and I find that all the claims lack an inventive step.

I provide the applicant a period of 3 months from the date of this decision to overcome through amendment the adverse findings of this decision. Therefore, pursuant to sub-regulation 13.4(3), the final date to gain acceptance is set at three (3) months from the date of this decision.

REASONS FOR DECISION

BACKGROUND

1. Patent application AU2019245278 in the name of Labcyte Inc. (the ‘applicant’) was filed on 29 March 2019 as a PCT application and claims an earlier priority date of 30 March 2018. Examination of the application was requested on 29 September 2020.

1. On 23 February 2021 the applicant filed amendments that were to be considered during examination.

1. A first examination report was issued on 5 March 2021 objecting that all the claims lack novelty and/or inventive step.

1. On 23 July 2021 the applicant filed amendments that they submitted overcomes the objections raised.

1. A second examination report was issued on 19 August 2021 objecting that all the claims still lack novelty and/or inventive step.

1. On 17 January 2022 the applicant filed further amendments that they submitted overcomes the objections raised.

1. A third examination report was issued on 1 February 2022 objecting that all the claims still lack inventive step.

1. On 21 February 2022 the applicant filed further amendments that they submitted overcomes the objections raised.

1. A fourth examination report was issued on 28 February 2022 objecting that all the claims still lack inventive step.

10.  On 3 March 2022 the applicant filed a request to be heard in relation to the outstanding examiner’s objections.

11.  On 25 March 2022, the Office wrote to the applicant that the hearing would be done through written submissions and invited the applicant to file their submissions by 29 April 2022.

12.  The applicant filed their written submissions on 28 April 2022.

THE INVENTION

13.  The present invention relates to a fluid impermeable ultrasonic transducer. Ultrasonic transducers are employed in a number of fields including medical imaging, medical treatment, non-destructive testing and for ejection of fluid droplets in various processes.

14.  An ultrasonic transducer typically includes an actuator for producing acoustic energy in the form of ultrasonic vibrations and a focusing element for focusing and concentrating the acoustic energy to a small focal point. In applications involving droplet ejection, the transducer is immersed in an acoustically conductive fluid like water and the ultrasonic vibrations from the transducer will be transmitted through the fluid and then into a reservoir from which droplets are ejected. The focusing element may be a curved surface or a Fresnel lens. The specification notes that the focusing element is generally made of epoxy resin, ceramic or composite material as they can be “formed precisely to a focusing shape and that can readily transmit acoustic energy into the liquid medium”[1].

[1] Specification at page 2, lines 6-7

15.  A typical prior art transducer is described with reference to figure 1 that is reproduced below.

16.  FIG. 1 shows a transducer 100, having a casing 102 and a transducer head 104 with a focusing lens 106 that is inserted into the casing and joined thereto through an interface 108 that prevents liquid from entering the casing. The transducer head 104 is formed of a moulded epoxy resin, silicone, or other comparable material. An actuator 116 within the casing contacts the transducer head to impart vibrations through the transducer head.

17.  The specification notes that the materials like epoxy used in the prior art transducers can deteriorate when immersed in a liquid for long periods leading to deformation and a consequential shift in the transducer’s focusing characteristics and this can be a problem, particularly in acoustic droplet ejection applications, where consistency of focus is critical for device performance.

18.  According to the specification, there is therefore a need for immersion transducers that can perform “within a narrow range of focusing behavior and remain within that narrow range despite the transducer being immersed for long periods of time”[2].

[2] Specification at page 2, lines 21-22

19.  The present invention addresses this need by providing an ultrasonic transducer in which the transducer head with the focusing element and the transducer casing are both formed of one or more fluid-impermeable, non-absorbing solid materials such as a metal and are permanently connected to one another through a water-impermeable and non-absorbing joint.

20.  Preferred embodiments of the invention are then described with reference to various figures of which figure 3, which shows a side sectional view of the fluid impermeable transducer, is reproduced below.

21.  This figure shows a transducer 200 having a casing 202 and a transducer head 204 that are permanently joined together such as by welding, sintering, or brazing to form a fluid impermeable joint that prevents ingress of liquids into the casing. Both the casing and transducer head are made of a non-permeable material such as a metal or metal alloy. The examples given include aluminium, beryllium, cadmium, germanium, lead, silver, tin, titanium, zinc and stainless steel.

22.  A concave focusing lens 212 is formed on the front surface of the transducer head and this is bounded by a narrow transducer head rim 214. An actuator 222 comprising a piezoelectric disc is bonded or attached to the back surface 216 of the transducer head to impart vibrations through the transducer head 204. The figure also shows positive and negative electrodes 226, 228 of the piezoelectric disc, electrical connector 208 and a backing material 224 that serves to firmly hold the actuator in place against the transducer head back surface and to effectively deaden reverberations traveling back through the casing 202. The remaining space in the cavity 218 of the casing 202 can be filled with an inert sealant material, such as epoxy resin.

23.  In some embodiments, a matching acoustic layer is disposed on the focusing lens for improving the transmission of acoustic energy into the surrounding medium.

24.  While in the embodiment of figure 3, the casing and transducer head are formed as separate parts that are joined together permanently, the specification also notes that the casing and transducer head can be integrally formed as a single part. Figure 8 that is reproduced below shows an integrally formed casing and transducer head.

25.  The specification highlights the benefit of using metallic material for the transducer casing and transducer head.

“Suitable materials may include, e.g., aluminum, beryllium, cadmium, germanium, lead, silver, tin, titanium, zinc, zirconium, alloys of any of the above, or composites containing any of the above materials with or without sealants, dopants, or comparable means for mitigating corrosion, toxicity, or structural weaknesses. The material selection for the transducer head (or lens) contrasts with conventional epoxy lenses not only in fluid impermeability, but also in being relatively homogenous in mechanical properties. The transducer head (or lens) therefore remains mechanically homogenous when immersed, resulting in good beam symmetry that persists over the lifetime of the transducer”[3].

[3] Specification at page 3, lines 17-24

26.  The specification as filed included 65 claims, but these have been amended during examination. The specification as currently amended includes 19 claims of which the two independent claims, 1 and 19, are reproduced below. A full set of the claims is included as an Annex at the end of this decision.

1. A fluid impermeable transducer, comprising:

a fluid impermeable metal casing;

a fluid impermeable transducer head comprising a metal focusing lens, the transducer
head having a back surface and a front surface, the metal focusing lens being disposed on the front surface and configured to focus ultrasound towards a focal point, wherein at least a portion of the transducer head is disposed within the metal casing; and

an actuator bonded to the back surface of the transducer head and operable to generate
oscillatory mechanical vibration of the metal focusing lens so that ultrasound is emitted from the metal focusing lens towards the focal point, wherein the metal casing and transducer head are permanently connected in a fluid impermeable manner to prevent ingress of liquid into the casing.

19. A method of forming a fluid impermeable ultrasonic transducer, the method comprising:

forming a substantially hollow metal casing having an internal cavity and an open first
end;

forming a transducer head element from the fluid impermeable material, the transducer
head element being sized to connect with the open first end of the metal casing, wherein at least a portion of the transducer head is disposed within the metal casing;

forming a focusing lens on a front surface of the head element, the focus lens configured
to focus ultrasound towards a focal point;

joining the head element with the first end of the metal casing to form a fluid
impermeable joint, the head element positioned such that the focusing lens points away from the metal casing; and

bonding an actuator to a back surface of the transducer head opposite the front surface,
the actuator operable to generate oscillatory mechanical vibration of the focusing lens so that ultrasound is emitted from the focusing lens toward the focal point.

Differences between claim 1 and claim 19

27.  Before I discuss the prior art and the examiner’s objections, I will compare independent claims 1 and 19 to identify any significant differences in scope between these claims.

28.  The most obvious difference is that claim 1 is an apparatus claim whereas claim 19 is a method claim.

29.  While most of the integers that follow the preamble of each of these claims are similar in scope, there are differences that are not insignificant.

30.  Firstly, I note that while claim 1 defines the focusing lens as being made of metal, there is no such limitation in claim 19 other than the requirement that it be made of a fluid impermeable material.

31.  Secondly, I note that while claim 1 defines that the metal casing and transducer head are

permanently connected in a fluid impermeable manner, claim 19 only defines that the head element is joined with the first end of the metal casing to form a fluid impermeable joint. Claim 19 does not require a permanent connection between the head and the casing.

CLAIM CONSTRUCTION

32.  Before I discuss the ground of inventive step raised by the examiner, I will construe some important terms in the claims.

Fluid impermeable

33.  The plain English meaning of the term ‘impermeable’ is ‘not allowing fluid to pass through’ (Oxford English Dictionary). It is therefore clear that the plain meaning of the term ‘fluid impermeable’ is also the same.

34.  The specification does not appear to depart from this meaning other than to describe what are some of the fluids that are not allowed to pass through.

[0045] Fluid impermeable as described herein can include, e.g., impermeable to water or similarly viscous reactive and non-reactive solvents, or impermeable to penetration by common liquids and/or solvent systems including non-polar, polar protic and polar aprotic solvents and, in particular, water/aqueous-solutions (including salt water), DMSO, alcohols, alkanes, oils, surfactants and the like. In some embodiments, fluid impermeable also includes impermeable to vapor, e.g. solvent vapor, water vapor, air, or other comparable gas, at both conventional operating conditions and at elevated temperatures/pressures such as those used during sterilization procedures.

35.  As the claim itself does not specify any fluids, I will construe this term as not allowing any fluid to pass through.

36.  Hence the claims require that the transducer casing, the transducer head and the connection between these two components do not allow fluid to pass through under normal operating conditions of the transducer.

Permanently connected

37.  During examination, the applicant submitted that the term ‘permanently connected’ in claim 1 also includes within its scope the construction where the casing and the head are formed as an integral or single part, i.e. without having to be formed as two separate components that are then joined together permanently. This construction is also then specifically claimed in dependent claims 2 and 4. While I did have some reservations about adopting this construction, given the definition in claim 1 to having two discrete parts that are permanently joined together, I am prepared to do so as this construction was also eventually accepted by the examiner and also does not affect the outcome of this decision.

THE EXAMINER’S OBJECTION

38.  In the last examination report, the examiner maintained that the claimed invention does not involve an inventive step. The examiner’s objection reads as follows.

“I have carefully considered applicant’s submissions in their response but I am not persuaded by these. Claims 1-19 lack an inventive step over D1 when read in the view of common general knowledge for the reasons discussed below and the previous objection is maintained.

Inventive step
When considering inventive step an invention is taken to involve an inventive step when compared with the prior art base unless the invention would have been obvious to a person skilled in the relevant art in the light of the common general knowledge as it existed before the priority date of the relevant claim. I have considered issues relevant to inventive step as discussed under the following headings.

Problem to be solved
The specification indicates that the problem to be solved is to provide an ultrasonic transducer that is durable and maintains focussing behaviour when immersed for long periods of time (see paragraph [0004] of the present specification).

Person skilled in the art
I consider that the person skilled in the art would be an electromechanical engineer who would work to solve the problem described above.

Prior art information
I consider document D1 discloses most of the features of independent claims 1 and 19 as discussed in the previous examination report dated 1 February 2022.

As also discussed in the previous examination report, D1 differs from the invention of claims 1 and 19 in that it does not disclose wherein the metal casing and transducer head are connected in a fluid impermeable manner to prevent ingress of liquid into the casing. In D1 the casing comprises a seal between housing (12) and faceplate (14) (copper clad “V” seals) (col 2, lines 33-35). Liquid ingress into the casing occurs to the extent that liquid may pass between the housing (12) and faceplate (14) up to the point where the copper clad “V” seals are located (see figure 1).

The applicant has amended claim 1 to include that “the metal casing and transducer head are permanently connected in a fluid impermeable manner to prevent ingress of liquid into the casing”. D1 also does not disclose the transducer head and casing are permanently connected. In D1 the casing and transducer head are connected with a threaded connection comprising copper clad “V” seals (see figure 1).

Common general knowledge
An electromechanical engineer would have known that components of ultrasonic transducers are sealed in many possible ways. These include non-permanent methods such as the threaded housing combined with copper clad V seals of D1 and permanent methods such as soldering, welding and brazing (see for example D4 (col 3, lines 13-27)).

An electromechanical engineer would also be aware that soldered and brazed seals are the most reliable hermetic sealing methods when sealing electronic components. For example D4 teaches that the hermetic sealing methods, including welding and brazing, described in the embodiments improves reliability and longevity (col 9, lines 55-59). Paragraph [0046] of the present specification also teaches the well known advantages of hermetic sealing and laser welding where associated connectors can be sealed using "standard high pressure/temperature hermetic RF connector design and laser welding techniques to join that connector to the transducer casing"

Obviousness
D1 teaches that the “Copper clad “V” seals prevent entry of liquid sodium, though it should be understood that other hermetic seals can be employed such as Swagelok fittings” (col 2, lines 33-35). As indicated by the applicant in their response no seal is perfect “all seals are susceptible to failure and are required to be replaced after a certain period of use”.

A person skilled in the art who is an electromechanical engineer would in seeking to provide an ultrasonic transducer that is more durable when immersed for long periods of time be motivated to look for other types of hermetic seal that are less prone to failure. An electromechanical engineer would be aware that permanent seals such as those formed by welding, brazing or soldering are the most reliable methods of providing a hermetic seal. A person skilled in the art would therefore connect the metal casing and transducer head in such a manner as an obvious choice, requiring no inventive ingenuity to implement.

The specification describes no particular problem to be overcome which would act as a barrier in applying such a known alternative without an inventive solution, nor is such a solution described. Additionally the particular selection provides no new or surprising result. Therefore this is merely an obvious choice which the person skilled in the art would arrive at by a routine and non-inventive process.

Therefore the invention of claims 1 and 19 does not involve an inventive step over D1 when read in the view of common general knowledge”.

39.  In this objection, citation D1 refers to US 3989965 and citation D4 refers to US 5295120.

INVENTIVE STEP

40.  The statutory basis for inventive step is set out at s7(2) and s7(3) of the Patents Act, and is reproduced below:

“(2) For the purposes of this Act, an invention is to be taken to involve an inventive step when compared with the prior art base unless the invention would have been obvious to a person skilled in the relevant art in the light of the common general knowledge as it existed (whether in or out of the patent area) before the priority date of the relevant claim, whether that knowledge is considered separately or together with the information mentioned in subsection (3).

(3) The information for the purposes of subsection (2) is:

(a) any single piece of prior art information; or

(b) a combination of any 2 or more pieces of prior art information that the skilled person mentioned in subsection (2) could, before the priority date of the relevant claim, be reasonably expected to have combined”.

41.  The test for obviousness is whether it would have been a matter of routine to proceed to the claimed invention.

“The test is 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.” (Aicken J in Wellcome Foundation Ltd v VR Laboratories (Aust) Pty Ltd [1981] HCA 12 at [45]; (1981) 148 CLR 262 at 286)

42.  The High Court in Aktiebolaget Hässle v Alphapharm Pty Ltd [2002] HCA 59 at [51] - [53] also approved the approach taken in Olin Mathieson Chemical Corporation v Biorex Laboratories Ltd [1970] RPC 157 at 187 in which Graham J had posed the reformulated Cripp’s question:

“Would the notional research group at the relevant date in all the circumstances directly be led as a matter of course to try [the claimed invention] in the expectation that it might well produce a useful [desired result]?”

43.  In relation to what level of inventiveness is required to sustain a patent, the Full Federal Court in Garford Pty Ltd v Dywidag Systems International Pty Ltd [2015] FCAFC 6 stated as follows at [44]:

“The inventiveness required to sustain a patent for a claimed invention is quite small. A “scintilla” of inventiveness is all that is required: Alphapharm at [195]. However, there must still be “some difficulty overcome, some barrier crossed” (per Lockhart J in RD Werner & Co Inc v Bailey Aluminium Products Pty Ltd [1989] FCA 57; (1989) 25 FCR 565 at 574) or some contribution to the art “beyond the skill of the calling” (Allsop Inc v Bintang Ltd [1989] FCA 297; (1989) 15 IPR 686 at 701)”.

(D1) US 3989965

44.  D1 is titled “Acoustic Transducer with Damping Means” and describes a transducer that is suitable for high temperature applications such as a caustic liquid sodium environment. The construction of the transducer can be easily understood with reference to figure 1 and the corresponding description, both of which are reproduced below.

“The transducer of this invention is specifically suitable for high temperature applications in a reactive, caustic, sodium environment and includes as its basic element a piezoelectric active element encased in a housing 12 constructed of a material specifically compatible with sodium such as stainless steel. FIG. 1 shows the basic configuration. The active element 10, typically lead zirconate, lead titanate ceramic, is bonded to the backside of the transducer faceplate 14 coaxial with the transducer lens 16 formed as a concave cutaway portion in the lower side of the transducer faceplate. Electrical isolation is maintained between the side walls of the housing 12 and the piezoelectric active element 10 by a fitted ceramic annular washer 18 interposed between the housing side walls and the element. Copper clad “V” seals prevent entry of liquid sodium, though it should be understood that other hermetic seals can be employed such as swage lock fittings. A spring loaded electrical contactor 22 makes electrical contact with the back electrode of the crystal 10, and a polyimide or other high temperature, radiation resistant insulator 24 isolates the contactor from the housing. The spherical-shaped concave lens 16 machined into the transducer faceplate focuses the ultrasound at a point F determined by:

F = (R(n/(n-1)), 45
where R is the radius of curvature of the surface, and n the index of refraction for sound between the lens material and sodium.

This invention provides a novel backing member 26 interposed between the back side of the active element 10 and the electrode 22, which is specifically advantageous when employed in conjunction with thin active elements to maintain electrical continuity between the electrode 22 and the active element”[4].

[4] D1 at column 2, lines 18-54

45.  The description further discloses that the faceplate is also made of stainless steel[5]. Although not explicitly described, it is clear from figure 1 that the faceplate is attached to the housing by a threaded connection with a “V” seal 20 interposed between these two components to prevent fluid from entering the main cavity of the housing in which the active element and electrical contactor are located.

[5] D1 at column 4, line 37

46.  The focus of the invention disclosed in D1 relates not to the connection between the housing and the face plate but to the novel backing member 26 that is interposed between the back side of the active element 10 and the electrode 22, in order to maintain electrical continuity between the electrode 22 and the active element even if the active element were to be fractured due to the harsh environment in which the transducer is used. This novel backing layer comprises an elastomeric electrically conductive material that is impregnated with tungsten.

47.  It is clear from the above that D1 discloses a fluid impervious (hermetically sealed) transducer that comprises:

• a fluid impermeable metal casing 12,

• a fluid impermeable transducer head 14 comprising a metal focusing lens 16 disposed on the front surface and configured to focus ultrasound towards a focal point,

• wherein at least a portion of the transducer head (the threaded portion seen in figure 1) is disposed within the metal casing,

• an actuator (active element 10) bonded to the back surface of the transducer head and operable to generate oscillatory mechanical vibration of the metal focusing lens,

• wherein the metal casing and transducer head are connected in a fluid impermeable manner (through the “V” seal 20) to prevent ingress of liquid into the cavity of the casing 12 in which the active element 10 and the electrical contactor 22 are located.

DISCUSSION

48.  The examiner has adopted the problem solution approach in their assessment of inventive step in line with the authorities. For example in Ranbaxy Laboratories Ltd v AstraZeneca AB [2013] FCA 368 at [203], [218], Middleton J cited Jagot J's comments in Apotex Pty Ltd v AstraZeneca AB ( No. 4), [2012] FCA 162 with approval:

“In assessing obviousness, it is necessary first to determine the nature of the claimed invention and the inventive step described in the Patent.  This may involve ascertaining the ‘starting point’ of the inventive step, sometimes described in terms of an existing problem for which the inventor found a solution.  The obviousness of the invention as claimed is then assessed by reference to common general knowledge in Australia at the priority date”.

49.  I will also therefore adopt the same approach.

Problem to be solved

50.  The examiner has identified the problem to be solved as being to provide an ultrasonic transducer that is durable and maintains focussing behaviour when immersed for long periods of time.

51.  The applicant has submitted that “the objective technical problem to be solved can be considered to be the provision of an improved transducer for precision droplet ejection and suitable for long-term immersion”.

52.  Paragraph [0004] of the specification talks about the problems with known immersion transducers.

“[0004] A focusing immersion transducer employs a shaped active physical element that may include a curved face, for example, or that may employ a Fresnel lens or similar structure. In such cases, the face must be composed of a material that can be formed precisely to a focusing shape and that can readily transmit acoustic energy into the liquid medium. To this end, traditional focusing, immersion ultrasonic transducers employ a hard-set epoxy resin, ceramic, composite, or comparable material to form the focusing shape of the focusing lens. While such focusing lens materials can be formed by molding or another net-shape manufacturing method, and while generally waterproof up to a limited duration, it has been found that such materials are prone to degrade and, when exposed to water for a long duration, can tend to gradually take up water, leading to deformation, a shift in acoustic properties and ultimately to failure of the transducer. While such transducers may be suitable for short-term immersion applications, greater precision and durability are needed for applications that require long-term immersion. Typical immersion transducers, such as those used for conventional NDT procedures, have a relatively low duty cycle in liquid compared to droplet-ejecting transducers, and do not need to have a constant focal length over time. However, for acoustic droplet ejection applications, device performance is much more reliant on consistency of focus, particularly consistency over long immersion times. Hence, it is desirable to have a collection of transducers that perform within a narrow range of focusing behavior and remain within that narrow range despite the transducer being immersed for long periods of time”. (emphasis added)

53.  It is clear from this paragraph that the problem that the claimed invention seeks to address, is that prior art transducers that typically employ a hard-set epoxy resin, ceramic, composite, or comparable material to form the focusing lens are not suitable for long term immersion as these materials can degrade when immersed in water for long periods of time and can also absorb water and this can consequently lead to deformation of the acoustic lens and a shift in its acoustic properties.

54.  The problem identified by the applicant does not talk about the actual problem of distortion of the lens and the change in focussing characteristics. Furthermore, while paragraph [0004] does talk about droplet ejection applications, I note that there is nothing in the invention as claimed to suggest that the present invention is intended primarily for such applications. To therefore restrict the problem to such applications as submitted by the applicant is erroneous in my view.

55.  Therefore, the problem that the claimed invention seeks to address is to provide an immersion transducer in which the focussing lens does not degrade or distort and can maintain its focussing characteristics even when immersed in water for long periods of time.

Common General Knowledge

56.  The examiner has asserted that it was common general knowledge in the art that the casing and head of ultrasonic transducers could be hermetically sealed in many possible ways including permanent methods such as soldering, welding and brazing. The examiner has cited D4 as an example of hermetic sealing by welding and brazing and also points to paragraph [0046] of the present specification as an admission in the specification that laser welding is a well-known technique for providing a hermetic connection.

57.  The applicant has refuted this arguing that, although D4 discloses a welded connection between the casing and the head for providing a hermetic seal, the transducer of D4 is not meant for immersing in a liquid and there is no disclosure that the welded connection would be waterproof if the transducer were to be immersed for long periods of time. They have also argued that in any event, disclosure of a welding connection in a single prior art document is not evidence of this technique being common general knowledge in the art.

58.  It goes without saying that any transducer that is meant for immersion in liquids would need any external joints to be fluid tight so as to prevent ingress of liquid into the casing where sensitive components such as the electromechanical actuator and the electrical connectors are housed. There are a number of well-known options for joining two metal components in a fluid tight manner. These include reversible connections like threaded joints and permanent irreversible connections like welding, brazing, bonding and swaging. As a mechanical engineer with over 35 years of experience as a patent examiner in the mechanical technologies, I can confidently state that resistance seam welding and laser welding were well known techniques for hermetic sealing of electronic packages before the priority date. This is also evident from even a cursory search of the internet. Document D4 cited by the examiner is just one example in which this technique is used to provide a hermetic seal in transducers.

59.  In my view, the applicant’s submissions to the contrary are mere assertions without any basis. I also note that even in the description of the present application, there is nothing to suggest that providing a hermetic seal between the transducer casing and head was an issue with prior art transducers or that the use of welding or brazing in the present invention is an advance over prior art techniques.

60.  I am satisfied that providing a permanent joint between the transducer casing and transducer head by welding was common general knowledge in the art at the priority date.   

Inventive step in light of D1 and the common general knowledge

61.  The applicant has argued that D1 relates to the use of an electrically conductive backing member that ensures continued electrical continuity even in the event of a fracture of the active element and that the person skilled in the art would therefore not consider D1 as a good starting point for providing a solution to the problem being addressed by the present invention.  

62.  I beg to disagree. D1 discloses an immersion transducer that is for use in high temperature liquid sodium environments. While the focus of D1 may relate to the material of the backing layer of the active element within the transducer, it would be readily apparent to the person skilled in the art that a transducer that is capable of being immersed in caustic high temperature liquids may well be a reasonable starting point in providing a solution to the problem of identifying a transducer head material that will not deteriorate when immersed in water for long periods.

63.  D1 discloses that the transducer casing and the transducer head including the focussing lens are made of stainless steel. There is therefore a clear teaching in D1 that stainless steel is a suitable material for forming the focussing lens of an immersion ultrasound transducer. It is furthermore common general knowledge that stainless steel is impermeable to water and does not degrade in the presence of water even when immersed for long periods. The person skilled in the art would have been therefore directly led as a matter of course to try stainless steel as the material for both the casing and the head with the expectation that it may well provide a solution to the problem.

64.  The applicant has further argued that in D1 the threaded connection between the casing and the head with a “V” seal interposed between these two components to form a hermetic seal is not a permanent connection as required by the claimed invention and that a person skilled in the art would not have been led to alter it to a permanent connection as it would “significantly alter the design of the device and render the reversible nature of a threaded arrangement ineffective”[6].

[6] Applicant’s written submissions at page 3

65.  I do not find this argument persuasive. I accept that D1 appears to show a reversible threaded connection, with a hermetic seal “V” seal sandwiched between the casing and the head. While the transducer of D1 may call for a transducer that can be disassembled, where disassembly is not a requirement, as in the case of the present invention, then as asserted by the examiner, replacing the reversible fitting of D1 with an irreversible permanent connection such as welding or brazing of the two components in a hermetic manner is nothing more than the choice of well-known sealing techniques for metal components that I have found were part of the common general knowledge in the art.

66.  I note that the problem being addressed is the degradation of the epoxy material of the focussing lens in the prior art and D1 clearly provides the same solution as the present invention, i.e., the use of a metal (stainless steel) as the material for forming the transducer head and focussing lens. There is nothing in the specification to suggest that existing sealing arrangements were in any way deficient or that welding the casing and head to form a permanent connection is in any way an advance over prior art connections or that there were any practical difficulties that needed to be overcome in welding the head and the casing in a fluid tight manner. I agree with the examiner that the inclusion of the feature of a permanent connection between the casing and head does not make the claimed invention inventive over D1.

67.  The applicant has also argued that in D1 liquid can enter the space where the “V” seal is located, and this space is within the casing and D1 therefore does not disclose the feature of the seal preventing ingress of liquid into the casing. Although the examiner appears to have conceded to this argument, I do not accept that the ingress of fluid up to the “V” seal can be considered as liquid entering the casing. The “V” seal is at the heart of the fluid impermeable joint of D1, and it clearly prevents ingress of liquid into the main cavity of the casing where the actuator and electrical terminals are located. This is the critical main cavity of the casing that needs to be protected from ingress of liquids. While the “V” seal is located within the casing at one end of the casing and therefore ingress of liquid up to the “V” seal could be arguably considered as ingress of liquid into a portion of the casing, a person skilled in the art applying a sensible construction to this feature in claim 1 would only interpret this as preventing ingress of liquids into the main cavity of the casing that houses the liquid sensitive components such as the actuator and the electrical contacts. Clearly D1 satisfies this requirement of claim 1.

68.  In any event, this issue is now moot as any welding or brazing of the casing and the head to provide a permanent joint, which I have already found to be an obvious modification, would be externally of the casing at or around the interface of the casing and the head and hence there is no possibility of any ingress of liquid even into that portion of the casing that currently houses the “V” seal.

69.  In summary, I agree with the examiner’s objection that independent claims 1 and 19 lack an inventive step.

70.  The examiner has objected with appropriate reasoning that they consider dependent claims 2-17 also lack an inventive step as the relevant features of these claims are either disclosed in D1 or are common general knowledge in the art/mere design choices. The applicant has not rebutted the examiner’s reasoning or provided any other submissions in relation to the dependent claims.

71.  I am satisfied that the examiner’s objection to the dependent claims is well founded, and I therefore find that the dependent claims also lack an inventive step.

OTHER OBSERVATIONS

72.  Although the examiner has objected to independent claim 19 as lacking inventive step, as I have noted earlier, claim 19 does not require a permanent connection between the head and the casing. The “V” seal in D1 clearly provides a fluid impermeable joint, and as already discussed I also do not consider that ingress of fluid up to the seal is ingress of fluid into the casing. It would therefore appear that D1 discloses all the features of claim 19 making this claim lack novelty. However, as this objection has not been raised by the examiner in the fourth report and the applicant has not been provided an opportunity to make submissions in relation to this ground, I am not making any formal findings in relation to claim 19 under this ground.

73.  Also, during my deliberations, I conducted a quick search to get a better understanding of the state of the art and through that search I identified some prior art documents that are highly relevant to the claimed invention. Although I have not relied on these documents in arriving at my decision, I would still like to bring the following two documents to the applicant’s attention.

• US 3925692 (Leschek et al.) 9 December 1975 – This document discloses an immersion transducer in which the casing and head are made of stainless steel and are permanently joined by welding to form a fluid tight seal. (see column 2, lines 33-54 and figure 1)

• US 4945276 (Mylvaganam et al.) 31 July 1990 – This document discloses an immersion transducer in which the casing and head are integrally formed as a single part that is made of a metal such as titanium or stainless steel. (see column 2, lines 53-60, column 4, lines 19-22 and figure 1)

CONCLUSION

74.  The examiner’s objections are valid, and I find that all the claims lack an inventive step.

75.  It is possible that there may still be some subject matter within the specification that when included in the independent claims may make them novel and/or inventive. It is therefore appropriate that I provide the applicant a short period of 3 months from the date of this decision to overcome through amendment the adverse findings of this decision. Therefore, pursuant to sub-regulation 13.4(3), I reset the final date to gain acceptance as three (3) months from the date of this decision.

R Subbarayan

Delegate of the Commissioner of Patents

Annex – Amended Claims

1. A fluid impermeable transducer, comprising:
a fluid impermeable metal casing;
a fluid impermeable transducer head comprising a metal focusing lens, the transducer head having a back surface and a front surface, the metal focusing lens being disposed on the front surface and configured to focus ultrasound towards a focal point, wherein at least a portion
of the transducer head is disposed within the metal casing; and
an actuator bonded to the back surface of the transducer head and operable to generate oscillatory mechanical vibration of the metal focusing lens so that ultrasound is emitted from the metal focusing lens towards the focal point, wherein the metal casing and transducer head are permanently connected in a fluid impermeable manner to prevent ingress of liquid into the
casing.

2. The transducer of claim 1, wherein the casing comprises a metal casing connected to the metal focusing lens via a fluid impermeable joint or wherein the casing and the metal focusing lens are integrally formed.

3. The transducer of claim 2, wherein the metal casing is connected to the metal focusing lens by a welded, sintered, or brazed joint.

4. The transducer of claim 2, wherein the casing and the metal focusing lens are a common or
single part.

5. The transducer of any of the preceding claims, wherein the front surface of the transducer head comprises a peripheral portion surrounding the focusing lens, and further comprising an attenuation layer interfaced with the peripheral portion and configured to absorb ultrasonic energy emitted through the peripheral portion from the actuator.

6. The transducer of any of the preceding claims, further comprising a matching layer coupled to

the focusing lens to transmit ultrasound from the focusing lens to a medium, the matching layer

being configured to enhance transmission of ultrasound from the focusing lens to the medium as
compared to direct transmission of ultrasound from the focusing lens to the medium.

7. The transducer of claim 6, wherein the focusing lens has a first acoustic impedance, the medium has a second acoustic impedance different from the first acoustic impedance, and the
matching layer has a matching acoustic impedance between the first and second acoustic impedances.

8. The transducer of claim 7, wherein the matching acoustic impedance is within a range of about 4-10 Mrayl.

9. The transducer of claim 6, 7 or 8, wherein the matching layer has a thickness corresponding to an odd multiple of a quarter wavelength of an acoustic signal at a nominal frequency passing through the matching layer.

10. The transducer of claim 9, wherein the nominal frequency is in a range of 2 to 15 MHz.

11. The transducer of claim 1, further comprising a first matching layer disposed on the front
surface and a second matching layer disposed on the first matching layer, the first and second
matching layers configured to enhance transmission of ultrasound from the focusing lens to a medium as compared to direct transmission of ultrasound from the focusing lens to the medium,
wherein:
the focusing lens has a first acoustic impedance;
the medium has a second acoustic impedance different from the first acoustic impedance;
the first matching layer has a first matching acoustic impedance between the first and second acoustic impedances; and
the second matching layer has a second matching acoustic impedance between the first matching acoustic impedance and the second acoustic impedance.

12. The transducer of any of the preceding claims, wherein the transducer head and casing are
characterized by a liquid penetration depth and induced material loss of zero when immersed in
liquid.

13. The transducer of any of the preceding claims, wherein the transducer head and casing are
characterized by a material weight loss of less than 0.1% per year of contact with liquid.

14. The transducer of any of the preceding claims, further comprising a backing material configured to attenuate acoustic energy transmitted by the actuator, the actuator being positioned
between the backing material and the metal focusing lens.

15. The transducer of claim 14, wherein the backing material has acoustic impedance ranging from 13.5 to 16.5 Mrayl.

16. The transducer of any of the preceding claims, wherein a focal length of an acoustic beam
generated by the transducer is sufficiently stable that the focal length changes at a rate of less than 0.1% per year of contact with liquid.

17. The transducer of any of the preceding claims, wherein an eccentricity of an acoustic beam
generated by the transducer is sufficiently stable that the eccentricity changes at a rate of less than 0.1% per year of contact with liquid.

18. The transducer of any of the preceding claims, wherein the transducer is fluid impermeable and resilient against changes in performance when exposed to temperatures in excess of 130˚C at
more than 2 atmospheres.

19. A method of forming a fluid impermeable ultrasonic transducer, the method comprising:
forming a substantially hollow metal casing having an internal cavity and an open first end;
forming a transducer head element from the fluid impermeable material, the transducer head element being sized to connect with the open first end of the metal casing, wherein at least a portion of the transducer head is disposed within the metal casing;
forming a focusing lens on a front surface of the head element, the focus lens configured to focus ultrasound towards a focal point;
joining the head element with the first end of the metal casing to form a fluid impermeable joint, the head element positioned such that the focusing lens points away from the metal casing; and
bonding an actuator to a back surface of the transducer head opposite the front surface,
the actuator operable to generate oscillatory mechanical vibration of the focusing lens so that

ultrasound is emitted from the focusing lens toward the focal point.