Raymond Patrick Dunne v Thomas Campbell Loggie and Graham Hodge

[1983] APO 13

In the Matter of the Patents Act 1952

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In the Matter of Application No. 500350 for Letters Patent by RAYMOND PATRICK DUNNE

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In the Matter of Opposition thereto by THOMAS CAMPBELL LOGGIE and GRAHAM HODGE

DECISION OF A SUPERVISING EXAMINER OF PATENTS:
         This matter concerns an application for a patent in respect of an invention entitled "Force Measuring Device" by Raymond Patrick Dunne.   Acceptance of the application was advertised in the Official Journal on 17 May, 1979, and a Notice of Opposition to the grant of a patent on the application was lodged by Thomas Campbell Loggie and Graham Hodge on 21 October, 1979.
         Following service of evidence‑in‑support, ‑answer, and ‑reply, the opposition was set down for hearing in Sydney on 2 March, 1983.   However neither party wished to be heard, and accordingly I have to decide the matter in the light of the written evidence.
         According to the specification, the invention relates to force measuring devices of the vibrating filament type in which an applied force to be measured is transformed into an output which takes the form of a frequency or a time period.   When an axially loaded member has its ends terminated in a manner conducive to effective wave reflection, transverse vibrations can be induced and maintained by suitable means, giving rise to a standing wave.   The frequency of vibration is determined by the relationship

f = 1 (W) 1/2
          2L (m)

where     W represents the axial load in the resonating filament,
         m represents the mass per unit length of the filament at load W,
         f represents the resonant frequency of the filament at load W, and
         L represents the equivalent length between end reflectors at load W.
         Transposed, the above equation becomes
  W = 4f2L2m,
or, since under normal conditions the product Lm remains constant,
  W   f2L
         Vibrating filament devices generally possess no inherent stiffness, and consequently have to be pretensioned such that axial tensions near zero are not approached, even when the additional applied load opposes the pretension load.
         The specification indicates that various options are available in the choice of ratio of pretension load to applied load, and refers to prior art in which it is known to operate at 'high' pretension loads, i.e. where the pretension load is large in comparison with the applied loads.   Under such conditions the change in length L induced by the extra applied load becomes negligible, and hence
  W   f2
It is then sufficient to measure the vibration frequency or period, for example by digital means, to square that measurement, to invert if necessary, and to compare the result obtained for an applied load with the corresponding result for the pretension load alone in the absence of any applied load.   The difference gives a measure of the applied load, and the processing of the data can be performed using standard digital techniques.
         It is also known to operate at even higher values of pretension load. Under such conditions not only does length variation become even less significant, but also the incremental change in frequency or period caused by an applied load is sufficiently small so that squared terms can be ignored, with the result that the frequency or period change becomes linearly related to the applied load.   As a result the data processing is correspondingly simplified.
         According to the specification, a disadvantage of both these techniques is that they involve deriving the value of the load to be measured from the difference between measured frequencies or periods.   For high or very high pretensile loads, this involves a small residual obtained as the difference between two relatively large quantities which approach each other in magnitude.   The dangers and indeterminancies of such techniques are well known in all fields of metrology.
         Although not referred to in the specification, it is apparent from the evidence submitted that there is another type of prior art device in which the portion of length increment resulting from a load change is removed from the actively vibrating portion of the resonator.   For example at least one of the termination means can be constructed in such a manner as to permit the filament to slide through, or roll past the termination means in response to the applied load, with the result that the resonated length is maintained constant.   Such arrangements have their own advantages and disadvantages, and are mentioned here only to provide a more comprehensive picture of the prior art.
         The approach advocated by the specification is to operate at relatively low pretensioning load ratios.   This avoids the problem of amplified error effects in a small residual difference which characterises the higher pretension load techniques.   Filaments using low pretensioning loads can be designed, the specification states, to possess great stability of measurement.   The assumption, inherent in the higher pretension load operations, that in the equation
  W   f2L
L can be regarded as constant, is of course no longer justified, and if made in the low pretension load situation would give rise to significant error.   What the specification proposes, however, is the application of appropriate correct‑
ion means which accounts for the variation of length L with load.   Thus the invention is said to relate to the inclusion within the digital squaring and subtraction means, of automatic corrections designed to minimise the errors which would otherwise arise from the dependence of the equivalent length L upon the gross axial load.
         The specification goes on to show how the basic equation above can be combined with the well‑known equation for Hookes Law, and transposed to yield the resultant equation

1

It should be noted that in the specification the constant K appearing in this equation (equation 7 at page 15 lines 7 and 8) is erroneously shown as the same constant as appears in the Hookes Law equation (equation 4 at page 14 line 15). The applicant has admitted this error in his evidence‑in‑answer.   In fact the correct constant is the product of the constant in the Hookes Law equation and the constant of proportionality 4Lm from the basic standing wave equation shown earlier.   However this does not really affect the fundamental thrust of the relationship expressed above.
         Apart from references to techniques for zero and span adjustments which are described as conventional and well‑known to those skilled in the art, the remainder of the description relates to an example which allegedly illustrates the derivation and application of the factor K to a sample set of results.   The opponent in his evidence has criticised this aspect of the description in that it is not made clear how K is derived.   Having had the benefit of studying not only the specification but also the evidence, and in particular the applicant's answer to the opponent's specific criticism on this point, I must confess that, like the opponent, I am unable to determine whether the value of K in the described example has been obtained by calculation, direct measurement, successive approximations, or otherwise.   The most relevant passage in the description is at page 18 line 17 to page 19 line 6 where it is stated that:

The value of K can be obtained by direct calculation from the known characteristics of the system, but is also obtainable by direct measurement of the non‑linearity displayed by the system in the absence of the correction.  If further refinement is required, the value of K obtained by this measurement can be inserted into the system and a second direct non‑linearity measurement undertaken, and from this a second approximation to the value of K is obtained which is then inserted and so on.

The successive values of K thus obtained converge rapidly and in practice it is rarely found necessary to obtain more than the second approximation.   It is usually sufficient to measure the non‑linearity at only one point approximately midway between the values of W0 and W1.

The content of this passage does not adequately enable the reader to deduce how the specific numerical value of K of 533 333 333, appearing in column 7 of Table 2 of the specification, has been derived.   Paragraphs 11 and 12 of the applicant's declaration forming the evidence‑in‑support purportedly deal, at considerable length, with this and associated criticisms, but do not really answer the point.   It is not good enough to assert that "The method of obtaining the value of K by direct measurement is described to the extent required by a person familiar with the art." (Declaration page 6 lines 17 to 19), or that "The value of K used is easily calculable from the equations previously discussed and the numerical values given on page 16 for the example for which the Tables are derived is stated in column 6 of Table 2." (Declaration page 7 lines 25 to 28).   I suspect that what the applicant may be attempting to say is that, in the broadest context of the inventive concept, the precise method of obtaining K is not critical, which may well be so.  However in an example which is apparently intended to demonstrate the best method of performance which is known to the applicant, it is singularly remiss not to provide a clear indication of how the particular value of K used in that embodiment actually was derived, especially since the whole thrust of the invention centres on the application of this value and the benefits derived therefrom.
         The specification also contains a number of other errors and uncertainties.   It is not clear whether the squared output data in column 5 of both Tables 1 and 2 arise from actual measured values of time period or are typical, exemplary values only.   The values of length indicated in column 4 of the Tables do not correspond to the values calculated on page 16.   The basis for the derivation of the values shown in column 7 of the Tables is not as clear as it might be.   On page 16 the term 'strain' is apparently used in a different sense from its conventional meaning in physics and engineering.  I have already referred to the erroneous use of the same constant K in two different equations.
         Some of these points compound the difficulty the addressee has in comprehending fully the illustrated example, including the precise derivation of the value for K and an assessment of the effectiveness of the demonstrated technique.   Others do not pose serious problems in understanding although they may be indicative of errors in drafting.   For these reasons the applicant has not fully discharged his obligations under sub‑section 40(1)(a).
         The evidence on both sides also contained much argument about the terminology used in the derivation of the basic relationship

f = 1 (W)
   2L (m)

I consider this to be a matter of semantics only.   Regardless of which party may be strictly correct in its view on terminology, the simple fact is that the resultant equation is so well‑known and widely accepted that the addressee is not interested in the specification for the provision of a precise account of its basis.   For similar reasons I need not comment on the argument between the parties regarding whether the specification relates to improvements in linearity or correction of error.
         Turning now to the claims, the specification ends with six claims, as follows:

1.A force measuring device comprising, in combination, an axially loaded filament or beam adapted to vibrate trans‑

versely in response to an axial input force applied thereto, and output means adapted to detect the period of the resulting vibration, and means adapted to modify the output of said output means from a first value to a corrected value to compensate for those changes in the length of said filament or beam which result from the application of the force to be measured.

2.A force measuring device as claimed in claim 1, wherein said output means incorporated a squarer whose output is fed to an inverter via a correcting sub‑system adapted to modify the input to said inverter from a first value to a corrected value to compensate for those changes in the length of said filament or beam which result from the application of the force to be measured.

3.A force measuring device as claimed in claim 2, including a clock pulse generator and a counter which feeds said squarer, the counter being adapted to measure the number of reference clock pulses occurring between successive pulses from a control pulse generator, and the output period of said control pulse generator being determined by the vibration period of said filament or beam.

4.A force measuring device as claimed in any one of claims 1 to 3, including means adapted to produce an output signal representing a load which is additional to a pretensioning load in said filament or beam.

5.A force measuring device as claimed in claim 4, including means for producing signals representing final values of said additional load after effecting zeroing and spanning correction thereof.

6.A force measuring device substantially as described herein with reference to Figures 2 and 4 of the accompanying drawings.

The opponent has made no detailed criticism of the wording of these claims, in terms of non‑compliance with sub‑section 40(2).   Nevertheless I consider that in claim 1 the expressions "means adapted to modify the output of said output means from a first value to a corrected value to compensate for those changes in the length of said filament or beam which result from the application of the force to be measured" is broader than the disclosure warrants, limited as it is to the application of the constant K in the expression
  W
         In the formal Notice of Opposition the grounds listed are:

1.THAT the invention, so far as claimed in any claim, is the subject of a claim of earlier priority date contained in the complete specification of a patent;

2.THAT the invention, so far as claimed in any claim, was published in Australia before the priority date of that claim;

3.THAT the invention, so far as claimed in any claim, is not a manner of manufacture within the meaning of the Section Six of the Statute of Monopolies;

4.THAT the invention, so far as claimed in any claim, was obvious and did not involve an inventive step, having regard to what was known or used in Australia on or before the priority date of that claim;

5.THAT the invention, so far as claimed in any claim, was before the priority date of that claim, otherwise not novel in Australia; and

6.THAT the complete specification does not comply with the requirements of Section Forty of this Act.

No evidence has been lodged to support the ground of prior claiming. Since nothing suggestive of a prior claim has been brought to my attention, the opposition on this particular ground fails.
         Section 40 criticisms corresponding to the sixth of the listed grounds, have already been discussed at some length and I have indicated that at least some of these criticisms are justified.
         Apart from these issues, the main thrust of the opponent's attack is on two fronts.   Firstly, evidence has been submitted in the form of five US patent specifications, numbers 3540271, 3394587, 2618970, 2265786 and 2040874, together with extracts from various textbooks.   In each case there is support‑
ive evidence of publication and availability in Australia before the priority date of the claims.   In my view, and I do not believe that the opponent has seriously suggested otherwise, none of these documents constitutes a prior publication of the invention as claimed.
         US 3540271 relates to the measurement of stress applied to a moving cable on such devices as cranes or winches.   It acknowledges that "One known method of measuring the stress on static or moving cables incorporates the technique of vibrating a portion of cable positioned between two fixed points ... (using the basic formula) ...", but it goes on to state that "However such devices are of extremely limited capability as the resulting measurement is only correct for one predetermined cable diameter and length".   This specification utilises two sleeves mounted a fixed distance apart so that the cable forms a straight resonant stretch therebetween.   It is stated that "It can be seen that during all phases of operation the cable can be pulled throughout its operative length and resonant stretch 25 will maintain a consistent functional length".
         US 3394587 is concerned with tension measuring and control for a continuous web.   Again, there is a reference to the basic relationship which is said to serve "as the basis for the operation of this invention.  Where the length and the mass per unit length of the web are constant, the fundamental frequency of the web is related to tension.   These conditions are achieved in this invention by noting the following.   The distance between feed roll 10 and take up roll 11 represents L the length of the vibrating web 3 and this dimension remains constant.   The mass per unit length of a uniform web is a constant.   Therefore when the web is forced to vibrate its frequency provides a means of measuring its tension of the web".   Thus it provides a method of continuously measuring and controlling web tension in which the length L is maintained constant as the distance between rolls 10 and 11 while the web is wound therebetween.
         US 2618970 relates to the determination of tensile stresses in an elongated body of material while the body is travelling in a longitudinal direction, for example as in the drawing of metal wire or rolling of metal strip, where it is desired that the tension is known and controlled.   Again the basic formula is acknowledged.   It notes that the tensile stress is proportional to the square of the frequency and also the square of the length between supports, assuming mass per unit length is constant.   It goes on to describe embodiments in which the length is kept constant by permitting the wire or strip to move over supports which are maintained a fixed distance apart.
         US 2265786 deals with the testing of tension in wire ropes or the like.   It contains no explicit reference to the basic equation, but states that the tone or frequency will vary with the tension of the rope.   The wire under tension to be measured is clamped between two supports a fixed distance apart, and plucked to produce resonance at an audible frequency.   Mounted alongside is a musical string extending over a series of frets.   The fret which most accurately produces a tone matching that of the wire under test is then determined, and the wire tension is obtained from a scale calibrated against the frets.
         US 2040874 is particularly concerned with the measurement of stress in tie‑rods.   There is no explicit disclosure of the basic formula.   The tie‑rod under test has a portion of its length clamped between two supports.   The invention operates on the basis of changing the resonant frequency of the test section, to make it match that of a known audio frequency standard, by adjust‑
ing the effective length of the test section.   This is achieved by causing one of the supports to move along the clamped portion of the tie‑rod.   The position of the adjusted support is then measured against a scale calibrated in terms of tension.
         Thus each specification discloses the measurement of force or tension by utilising the relationship with, and measurement of, the resonant frequency. While the relationship with L is recognised, nowhere is it suggested that a correction factor be applied to compensate for variations in length L resulting from the applied load.
         Similarly the extracts from the various textbooks cited, "Waves" by Crawford, "Waves" by Coulson, "Wave Phenomena" by Towne, "Mechanics" by Symon, "Vibrations and Waves" by Sherman, "Vibrations and Waves" by Feather and "Physics of Waves: by Elmore and Heald, are all concerned with the derivation of the fundamental physical properties and relationships governing the motion of a vibrating string.   They discuss the factors involved and the effects of the various simplifying assumptions made.   But again there is no disclosure of a more accurate measurement of tension or load by correcting for length variations.

         All these citations were introduced, in paragraph 12 of the Declaration by Hodge in the evidence‑in‑support, as support for the proposition that "the use of vibrating filaments under load for measuring loads, and the recognition of changes in effective length of resonator causing inaccuracies in measurements of loads are well‑known".   While there is no doubt about the first half of this proposition, I am not entirely satisfied that the second has been established.   As already indicated the textbook extracts are concerned with the theoretical derivation of the fundamental formulae and contain no specific reference to load measurement as such.   The cited US specifications are concerned with load or tension measurements per se, but the role of the effective length L on the relationship is mentioned only in passing.   It could be claimed, however, that the applicant has in effect conceded the point in his specification where he discusses, as admitted prior art, the use of the higher pre‑tension load ratios in an attempt to minimise this effect.   Assuming that the proposition is established, then it represents the first step in a sequence which (paraphrasing from the Declarations of Schilling and Hodge in the evidence‑in‑reply) appears to continue thus:

(2)"It is well known in metrology that when a higher order of accuracy is required than is provided by utilising a formula based on simplifying assumptions, it is only necessary to take into consideration the significant factors which are the causes of errors and make appropriate allowance therefor".

(‑ this statement I believe can be accepted without further proof).

(3)"As a consequence of the above two propositions, it therefore follows that the means of compensation for errors introduced into force measurements utilising vibrating strings by force‑

induced variations in effective length was self‑evident, and thus the invention as claimed was obvious and did not involve an inventive step."

I do not believe that this final conclusion is a necessary consequence of what has gone before.   There is a substantial volume of evidence, embracing both the prior art admitted in the specification, the accuracy of which has not been challenged by the opponent, and also the US specifications cited by the opponent, which demonstrate various means of measuring force or tension by vibrational resonance which do not involve, and/or by their nature do not require, length correction.   For example the admitted prior art indicates alternatives such as choosing an operational area like the higher pretension load ratio situation where the length variation effect is minimised.   It seems to me that in the context of such a background of prior art the final conclusion is not an inevitable consequence of the earlier propositions.  Expressed another way, invention may reside in the idea itself, notwithstanding that once the idea has been conceived there may be no difficulty in carrying it into effect; Hickton's Patent Syndicate v. Patents and Machine Improvements Company Ltd. (1909) 26 RPC 339.   In the present case it may well be that once the idea of applying the length correction was conceived the means of implementation were self‑evident; but that does not, of itself, detract from the inventiveness of the idea.   Accordingly, since nothing in the evidence has convinced me otherwise, I am not satisfied that the grounds of obviousness or lack of inventive step have been established.
         The second major allegation made by the opponent is that apparatus, incorporating the invention claimed, was sold before the priority date to Australian Iron and Steel Pty. Ltd., (hereinafter referred to as A.I.S.), and possibly also to others, by Inflo Belt Weighers Pty. Limited, hereinafter referredto as IBW.   The precise nature of the relationship and degree of involvement between the applicant Dunne and IBW has been the subject of much discussion in the written evidence; for the purposes of this Decision it is sufficient that IBW was operating with at least the indirect authority of, and licence from, Dunne.   It is common ground that before the priority date of the claims, which has generally been accepted as 22 February, 1974 when the provisional specification was lodged, IBW brochure No. RF/4‑2 on Resometric Belt Weighing (exhibit GH‑9) was in circulation, and also that apparatus designated Model RF‑4 Belt Weigher had been ordered by AIS from IBW, by an order allegedly dated 2 November, 1973.
         There is no firm evidence as to when delivery of the ordered apparatus actually took place.   Although the order allegedly contained a reference to 6 weeks delivery, there is no indication that this promise, if indeed it can be interpreted as a promise, was in fact met.   Also exhibited as GH‑8 is a copy of IBW's invoice to AIS dated 26 April, 1974 for the supply of equipment to that order, but even if it can be assumed that delivery preceded the invoice, it does not assist in pinpointing the delivery date in relation to 22 February, 1974.   The dates in regard to sales and deliveries to other parties are equally indefinite.
         It is not suggested that brochure RF/4‑2 itself constitutes a disclosure or prior publication of the invention as claimed.   Clearly it does not.   The opponent's contention, as I understand it, is that the brochure by implication is referring to the claimed invention when it refers to model RF‑4, and that there was disclosure by sale to AIS and/or others, and possibly also disclosure during negotiations for said sales.   The inferences about what the brochure is allegedly describing are based on:

(a)reference in the brochure to "patented",

(b)the sensitivities and/or accuracies claimed in the brochure allegedly correspond to those revealed in the patent specification,

(c)the apparent absence of a later brochure extolling the merits of an improved model, which would have been expected with the advent of the invention corresponding to the patent specification.

Point (a) is explained by the applicant as an inaccurate reference to an earlier patent application accompanied by a provisional specification number 2949/73 which was in fact lodged on 10 April, 1973 by Dunne.   It is also true that the six‑digit number 294973 appears three times in the brochure in the guise of a numerical display.   I accept the applicant's explanation on this point.
         Both parties have had much to say on the various references in the brochure and in the patent specification, and comparisons therebetween, on matters of accuracy, linearity, sensitivity and stability, and also the surrounding background of events.   All of this is inconclusive and lacking in the firm facts necessary to sustain the opponent's argument.   I think also that some allowance must be made for the propensity of sales brochures to make exaggerated claims regarding the virtues of their product.   If the instance of the "patented" reference is any indication, the brochure RF/4‑2 has already been demonstrated to be somewhat lacking in accuracy.   It can also be noted that the opponent has exhibited copies of three IBW invoices:

No. 100/7  ‑ "resometric model RF4 continuous
  conveyor belt weigher"                  ‑ $4345

No. 100/8  ‑ "resometric model RF4 continuous
  conveyor belt weigher"                  ‑ $4885

No. 100/10 ‑ "model RF4 belt weigher complete with
  remote integrator"  ‑ $3940

The latter invoice also lists various extra items bringing the total invoice amount to $4545.   Presumably these differences in price are due to significant variations in the technical equipment supplied.   This supports the view that the code RF4 denotes, and brochure RF/4‑2 describes, a generic belt weigher system embracing various sub‑systems, the precise technical specifications for which are neither disclosed nor necessarily invariable.
         It appears that the opponent has had a fair amount of cooperation from AIS in providing his evidence on these matters.   One would think that if, in fact, the equipment supplied to AIS had been in accordance with the patent specification, and if delivery or other form of disclosure had occurred before 22 February, 1974, evidence to that effect would have been as readily forth‑
coming as the evidence actually submitted.   In fact the opponent Hodge, in paragraph 16 of his declaration in evidence‑in‑reply, appears to tacitly concede that the apparatus supplied to AIS did not have the claimed features by arguing that the apparatus did have such "means" by virtue of there being a point in the circuitry at which a signal corresponding to the value of K "could be" inserted.   I do not accept the proposition that an electrical circuit which has a capability of having an input signal connected at some point constitutes a disclosure of "means adapted to modify the output ...".
         For these reasons I conclude that the opponent's allegations have not been substantiated.
         The opposition succeeds insofar as non‑compliance with section 40 only.   However the defects under this heading are not insurmountable.   I shall allow the applicant an opportunity to seek leave to amend the specification within sixty days of this interim decision.   Costs are awarded against the applicant.

(G.R. BROWN)