T 0368/00 18-06-2003

Reasons for the Decision

1. The appeals are admissible.

Main request

2. Clarity

2.1. The action of the "isothermic block means" and the meaning of the expression "an ambient temperature" are of fundamental importance and these terms will be discussed first.

The Board takes the view that the "ambient temperature" is normally that prevailing about the apparatus at any given time, and clearly changes depending on the ambience, ie on whether the apparatus is in a standby condition prior to use, for example in a holder, or in the measuring condition in the proximity of the ear of a patient. In claim 1, however, this expression refers to the standby condition in which the apparatus has time to attain an isothermal state, and it is required of the isothermic block to hold the apparatus at this ambient temperature while a temperature reading is taken, even if thermal transients may tend to change this temperature. This interpretation of the wording of claim 1 is the only one consistent with the disclosure of the patent in suit as a whole, as discussed below.

The following passages of the original PCT application WO 90/02521 support the above conclusion: Claim 12 of the application states that the radiation detector means and the wave guide are held at or about an isothermic condition by said heat conducting block means at or about a temperature corresponding to the air temperature immediately adjacent to said heat conducting block means, and claim 14, which is dependent on claim 12, says that the block further is of sufficient mass to substantially maintain said isothermic condition of said wave guide and radiations sensor. Similar wording is found in claim 5 of the PCT application.

These claims define the two different functions of the block. Further, page 10, lines 20 to 24 says that the isothermic conditions among the various components in the sensor assembly are maintained even when the ambient temperature changes. This means that the block brings about thermal equilibrium amongst the different components, which condition is maintained even if the ambient temperature changes.

The appellant acknowledged, in its notice of opposition dated 21 May 1997, page 2, paragraph A.2, that the description meant that the isothermic block has sufficiently great thermal mass that it resists rapid temperature changes, ie is responsible for the stable temperature feature. This appellant now argues that the description only supports the view that the block is responsible for the same temperature feature. The Board prefers the former interpretation since this is not only consistent with the terminology used, but also means that the claims can be read in a manner consistent with the description, whereas the latter interpretation renders the claims at odds with the description, and should not be adopted, according to well established practice of the EPO, as stated in decision T 190/99 (see Catchwords).

2.2. The temperature measuring apparatus of the patent in suit comprises an infra red sensor within a housing and a waveguide that guides infra red radiation from the body of a patient (for example the tympanic membrane) to a thermopile type radiation detector which is provided with a thermistor for correcting temperature readings should the temperature of the detector drift. Precautions are taken to minimise errors in temperature measurement by configuring the detector part of the apparatus such that the detector, the cold junctions, and the thermistor are held at the same temperature by a heat conducting material. This is a normal precaution in the art, as exemplified by D1 (column 7, lines 29 to 31, 63 and 64), and D2 (column 5, lines 10 to 14).

The patent in suit describes a heat conductive block for this purpose, termed an "isothermic block means" in claim 1. The word "isothermic" suggests that the block maintains temperature equilibrium between these components at the ambient temperature, so that the arrangement corresponds to the prior art arrangement in that the detector, the cold junctions, and the thermistor are maintained at the same temperature by a material of good heat conductivity.

The claim also says that the block should have sufficient mass so that the infrared radiation detector means, the wave guide means and the detector temperature sensor means are held at substantially the same temperature, at or about an ambient temperature, even when the ambient temperature changes. The use of the terms "mass" and "block" carries the connotation that the block is relatively massive, and indeed is shown in the cross-sectional view of Figure 4 as being relatively massive compared to the waveguide and the detector assembly. The technical implication of this is that the block has a substantial thermal capacity.

Therefore, the block as defined in claim 1 has two different functions: (i) to cause temperature equilibrium amongst the elements in the block, and (ii) to resist temperature change of the block should the ambient temperature change. It is these that appellant I refers to as the "same temperature" and "stable temperature" features, respectively.

2.3. Appellant I sees a contradiction in the two requirements, that the block should be a good conductor so as to rapidly equalise temperature, and it should also have sufficient mass to prevent temperature changes. This apparent contradiction vanishes if the time scales involved are considered.

Before a temperature measurement of a patient is made the apparatus would be held or supported in a holder in the standby condition, somewhat in the manner of the apparatus of D1, in which state the detector, the cold junctions, and the thermistor would have a time of at least the order of minutes to come into temperature equilibrium with each other because of the good thermal conductivity of the block and despite the mass of the block. This equilibrium temperature is the ambient temperature in the standby condition, and is referred to in the claims. When a temperature reading is taken the apparatus is removed from its support and moved towards the ear of the patient, and the proximity of the waveguide with the ear, for example, could cause a thermal transient to be applied at the end of the waveguide. However, the time scale involved in taking a reading is about a second or two (patent in suit column 8, lines 52 to 55, D1, column 6, lines 55 to 59 or less, D2, column 1, lines 24 to 26), and in this short time block would have sufficient thermal capacity for the transient not to materially alter the temperature prevailing at the detector. Claim 1 states that the apparatus strives to maintain the ambient temperature at the detector, even if this changes, which is consistent with the above understanding of the description.

2.4. According to appellant I the above considerations are not based on the wording of the patent in suit. However, that the mass of the block is responsible for resisting rapid temperature changes is admitted by the appellant itself, in the notice of opposition, as is the fact of the time scale involved, since the above applies in the case of rapid temperature changes.

With the above interpretation of the expressions used in claim 1, and taking into consideration the effects involved, a self-consistent reading of the application, including the claims, is possible. The appellants' current interpretation of the term "ambient temperature" and the role of the isothermic block not only contradicts its initial interpretation in its notice of opposition, but also excludes a sensible reading of the claims, which is not permissible.

The Board is also satisfied that it is implicit from the context of claim 1 that the isothermic block means must be made of a good heat conducting material, even though this is not specified in the claim.

3. Article 100(c) EPC

The isothermic block means of the claimed apparatus is required to be a good conductor of heat so as to rapidly equalise temperature amongst the components, and also have sufficient mass to act as a heat sink of sufficient thermal capacity to absorb thermal transients during the relatively short period during which a temperature measurement is taken.

The person skilled in the art would be able, by simple calculation or trial and error, to determine what mass is "sufficient" for the purpose. This would depend on the configuration of the mass since its thermal conductance would depend on its shape, its thermal conductivity, the temperatures involved, the time scales involved, and the allowable error of the temperature reading. The last three factors would be known by the medical staff using the apparatus.

Assuming a substantially cylindrical configuration as shown in the particular embodiment, for example, and assuming a time scale of minutes in the standby condition and of seconds during a measurement, the person skilled in the art could estimate the mass of the block for a given material, also taking into consideration what measurement errors of body temperature are permissible, for example 0.1C. Alternatively, simple tests would determine whether the mass was sufficient to maintain the temperature of the assembly stable enough to achieve a medically acceptable accuracy of the temperature reading.

The person skilled in the art would also know how to position the block relative to the components to be stabilised in order to achieve the desired effect. In practice this would mean that the block should subtantially enclose and be in intimate contact with the components.

The Board, therefore, considers that the patent meets the requirement of Article 100(b) EPC.

4. Article 123 EPC

4.1. Article 123(2) EPC

Claim 1 of the main request combines the subject-matter of original claims 1, 4, 5, and 6, and additionally refers to a patient rather than an emissive target, and includes the phrase "even when the ambient temperature changes". These additions are supported by the application as originally filed and are allowable. Similar considerations apply to claim 9.

4.2. Article 123(3) EPC

The "cold reference junction" feature of claim 1 was removed at the opposition stage, but has now been re- instated, so an objection in this respect has been met.

5. Novelty

5.1. The isothermic block means of the claimed apparatus and method is a heat conducting material positioned proximate to the wave guide means and is of sufficient mass that not only the infrared radiation detector means and detector temperature sensor means, but also the wave guide means are held at substantially the same temperature, at or about an ambient temperature even when the ambient temperature changes. As discussed above this means that the mass must act as a heat sink of sufficient thermal capacity to absorb thermal transients during the short period during which a temperature measurement is taken. It is implicit that it must also have a certain physical relationship with the components to be able to act effectively in the required manner.

This implies an appreciable mass, considerably greater than the combined masses of the radiation detector, the wave guide, and the temperature sensor, and also that the mass substantially encloses these components, so that the temperature drift thereof owing to change of ambiance between the standby condition and the measurement position is kept sufficiently low so that the error in the temperature reading is also kept acceptably low, for example 0.1°C.

5.2. Bearing in mind that a prior art document must unambiguously disclose all the features of a claim for it to anticipate the claimed apparatus or method, none of the documents D1, D2, D6, or D7 discloses such an isothermic block means.

In document D1 the thermopile detector is embedded in a metal housing and good thermal conductivity is provided between them (column 7, lines 17 to 20 and 29 to 31). The thermal relationship between these components is also schematically illustrated in Figure 8a, where the block 20 includes the housing 94 holding these components in intimate thermal contact with each other. Moreover, the housing is heated by resistors to a precise temperature controlled by a circuit shown in Figure 9. This points to a housing having a low thermal capacity since the heat from the resistors must be dispersed quickly throughout the housing in order to follow changes set by the variable resistor R15 in a precise manner (column 7, lines 52 to 55). Moreover, the metal waveguide 96 has an end that is merely secured to the housing 94 (column 7, lines 19 and 20), so the housing is not clearly capable of resisting the effects of thermal transients, acting on the other end of the waveguide, during a measurement. Nor is there a statement in D1 that this would be useful.

The radiation detector of document D2 does not include a waveguide or a thermopile type detector, and for these reasons alone it does not anticipate the apparatus of claim 1 of the patent in suit.

The radiation detector of document D6 also does not include a thermopile type detector. The waveguide (barrel 14) of this apparatus is said to be interconnected to the pyroelectric sensor 18 so as to be in thermal equilibrium therewith, but it is not clear how this is achieved with an intervening shutter as shown in Figures 1 and 2. There is also no disclosure of an isothermic block means for resisting temperature changes in the waveguide. The appellant I equates the housing 164 in Figure 17 with the isothermic block means, but even this is no more than the arrangement of D1, since the housing is not so positioned proximate the waveguide that it is clearly capable of resisting the effects of thermal transients on the waveguide during a measurement. For these reasons D6 does not anticipate the apparatus of claim 1 of the patent in suit.

In D7 it is doubtful that the inner cylinder 3 may be regarded as a waveguide since a lens focuses the radiation onto a detector. Moreover, there is no disclosure of the cylinder being in contact with a block. Rather than resisting temperature changes, this arrangement is meant to have the opposite effect, that is any temperature variations are passed rapidly on to the case 9 of the detector and the temperature compensating element. The inner cylinder 3 is formed of a high conductivity metal and the intention is that the temperature of the case 9 should adapt promptly to the temperature of the cylinder 3 (page 5, lines 1 to 6). This points to the cylinder having a low thermal capacity. The important point, however, is that there is no mass that tends to resist temperature changes of the cylinder.

The appellants' arguments, that the housing 94 of D1 and the tube 3 of D7 would inevitably have a stable temperature function in addition to their same temperature function, is not accepted by the Board since the mass of the block and its physical relationship with the waveguide must be significant such as to cause the desired effect, as set out in point 2.1 above. The stable temperature function of the heat conducting parts of the cited prior art apparatus cannot be inferred in the absence of some explicit teaching to this effect, and the arguments of the appellants in this respect are based on an ex post facto analysis of the prior art.

For these reasons the claimed apparatus is novel, as is its use as defined in method claim 9.

6. Inventive step

6.1. Closest prior art: document D1 discloses a probe with a thermopile type infrared sensor for insertion into the ear canal and taking temperature measurements of the tympanic membrane (column 6, lines 55 to 59), and has all the features of claim 1 of the patent in suit, save that there is no mass of high heat capacity for resisting temperature changes, during a temperature reading, of the waveguide means.

6.2. The radiation detector of D2 is a fundamentally different type of detector in that a conical cup is used to gather radiation instead of a waveguide in order to negate the effects of emissivity of a surface, which is not a consideration in the case of the apparatus of the patent in suit. Since the apparatus of document D2 does not use a waveguide, there is obviously no teaching that temperature changes in a waveguide must be resisted. The potting material of this document is mentioned only in the context of measuring temperatures of about 500°F, and the Board understands the statement in column 5, lines 14 to 19, and in particularly the reference to "sufficient mass", only to mean that the potting material should transfer heat rapidly away from the sensor, not that temperature changes owing to thermal transients should be resisted, since there is no disclosure that significant transients would occur in this apparatus.

In D6 a shutter control mechanism 68 places a shutter 66. between the waveguide (barrel 14) and the radiation sensor 18, so it is not clear how thermal coupling between the two is achieved. However, assuming this coupling is achieved somehow, then this is equivalent to the arrangement of D1, where there is a block for maintaining the radiation detector and the detector temperature sensor at ambient temperature, but the block does not act on the waveguide.

In D7 the inner cylinder is not for resisting thermal transients, it is for rapidly equalising the temperature.

Thus, none of the prior art documents, taken singly or in combination, discloses the importance either of maintaining a waveguide in thermal equilibrium with the detector at ambient temperature, or the use of a conducting block for this purpose, as well as for the purpose of maintaining the radiation detector and the detector temperature sensor at the ambient temperature despite thermal transients. In particular there is no teaching in these documents that the means for achieving isothermal conditions between the radiation detector and the temperature sensor should additionally be configured with the intention of providing the stable temperature feature, especially for the waveguide. These features provide certain technical effects that are not envisaged in the prior art, and enable a passive temperature control system to be used instead of the active one of document D1. For these reasons the subject-matter of claim 1 involves an inventive step. Method claim 9 similarly involves an inventive step.

7. Therefore, the main request meets the requirements of the EPC.