“[2] The patent relates to disc brake calipers for motor vehicles. Although the claims of the granted patent are not so limited, the invention is particularly directed to brake calipers for racing cars. The parties are involved in designing and making calipers for racing cars. [3] Disc brakes are so called because they operate on a disc which rotates with the road wheels of the vehicle on a hub carried by the vehicle chassis. The caliper is the body into which brake pads are fitted and in which the brake pads can be actuated to make contact with the disc. When so actuated the pads slow down the disc and, with it, the road wheels. The caliper body straddles the disc at its periphery and can be thought of as comprising two limbs, one on each side of the disc. In the type of caliper with which this case is concerned the limbs are rigidly connected or of ‘monobloc’ construction. The parts which straddle the disc are called the bridging members. At least one piston is mounted within the caliper body and, when actuated, squeezes the pad against the disc. [4] Calipers are mounted on the fixed uprights. For ease of description, they have a mounting side and a non-mounting side which are on opposite sides of the disc. Rather than describe the forward and rearward parts of the caliper as such, it is conventional to refer to a leading and trailing edge of the caliper by reference to the edges where the disc enters and exits the caliper body respectively when the vehicle is moving forward. [5] When the brakes are actuated, the pistons apply pressure from each side via the pads onto the disc. When the vehicle is stationary this results in a reaction force which splays the two limbs of the caliper outwardly and away from each other. This is referred to as the ‘static’ or ‘pressure’ load case. It can be thought of as splaying the limbs from a ‘U’ shape into a ‘V’ shape. There is also a ‘dynamic’ or ‘torque’ load case which arises when the vehicle is moving. Because the caliper is mounted on only one side, braking makes the non-mounting side limb of the caliper turn or twist relative to the mounting side limb. If, looking from above, the caliper is seen as a rectangle, the torque or dynamic load will tend to deform it out of its rectangular shape. All this was well known to a disc brake designer at the priority date of the patent. [6] High performance brake calipers such as those used in motor racing need to be stiff and light. If the caliper is not stiff enough it will flex under load, and if it is heavy the performance of the car will suffer. The forces experienced by calipers in motor racing are particularly high.”
“[29] The way optimisation software is used is as follows. A general shape is defined. This may be the space envelope in which the component may fit or it could be a basic component shape. All the fixed points which must be included are given. For a caliper this would include things such as mounting points and pistons. The load scenarios which the component must withstand are given, along with the material properties. The software then carries out a finite element analysis and removes material where it is not needed. This is repeated iteratively until a target weight is achieved. The process produces a final shape. Very often using this technique the final shape is rather organic in appearance, no doubt because in some ways the process has similarities to evolution by natural selection. [30] The key difference between this technique and the conventional design process using CAD/CAM and FEM is that in the conventional process the designer designs the shape of the article and uses software, including FEM, to model its behaviour in various load cases. He or she then uses design and engineering skill and experience to adjust the design. The structural optimisation technique does not really start with a design: it might start simply with the volume in which the component will reside. The final shape arises from the iterative removal of material found to be unnecessary by the computer. [31] Nevertheless, although much of the design work is carried out by the computer, the shape produced by the structural optimisation technique will depend on decisions made by the engineers using it. Two obvious examples are the choices about which load scenarios to model, and about the starting shape and volume of material. The technique works by removing material from within the given volume. Looking ahead to the obviousness argument, structural optimisation software will not produce a design for a caliper with parts (say “peripheral stiffening bands”) which are located beyond the normal envelope of a caliper body unless the engineer decides in the first place to define a starting volume beyond the normal envelope of a caliper.”
“There is a need, therefore, for an improved disc brake caliper body which has increased structural rigidity or which can provide equivalent structural rigidity to that of conventional caliper bodies but using less material.”
“[45] … The patent then asserts that conventionally caliper bodies have been designed to resist the static load (i.e. the well-known pressure load) but have not taken into account the bending moment. In contrast the caliper according to the invention has been designed to take account of the bending moment generated by brake torque under dynamic braking loads. At p12 ln4–12 the patent states: In this regard, the peripheral stiffening bands 45, 55 are configured to resist the bending moment generated during braking. In tests, it has been found that the caliper body 30 exhibits increased stiffness when the body is subject to a bending moment under dynamic braking loads than when subject to static brake loads. Due to the presence of the stiffening bands, less material is required elsewhere in the caliper body 30 so that the overall weight of the caliper is reduced when compared with a conventional caliper body having an equivalent stiffness.”
“Because conventional caliper bodies are designed [to] cope with static braking forces they tend to have a generally symmetrical outer profile when viewed in plan. Of course conventional caliper bodies are not perfectly symmetrical because of the need to provide mountings and fluid connections but generally they have a largely symmetrical profile when viewed in plan. It will be noted that use of peripheral stiffening bands 45, 55 in the caliper body 30 and the removal of material elsewhere gives the body 30 a distinctly asymmetrical appearance when viewed in plan.”
“[50] From the perspective of a skilled person reading the patent, the invention is really quite simple. The distinctive asymmetrical appearance of the calipers is ultimately a consequence of the asymmetrical torque load they are designed to resist. The reason stiffness can be improved relative to weight is because these calipers extend over a larger area than a conventional caliper. The stiffening bands are on the periphery where they can do more good. As a result of material being moved to the outer periphery of the caliper, material from the interior can be taken away without compromising stiffness. So there are numerous openings in the structure. Also, instead of the cylinders simply looking like holes bored in a block, the material around the cylinders has been removed, making the shape of the cylinders visible from the outside and contributing to an organic, rather skeletal appearance.”
“Each of the limbs 31, 32 is profiled so as to form distinct housing portions 42 about each of the cylinders.”
“These arrangements result in a caliper profile that is highly asymmetrical when viewed in plan.”
“To save weight, the radially outer and inner faces (the upper and lower faces as shown) 22, 23 of the housing are sometimes machined to match the profile of the cylinders where this can be achieved without compromising the structural rigidity of the caliper. Where the upper and lower faces 22, 23 of the housing are machined in this way, the regions of the housing 24 surrounding the side walls of each cylinder extend generally parallel to the axis of the cylinder, except at the lateral inner and outer edges where they are radiused.”
“[57] … Mr Cuddigan pointed out that the part of the limb which numeral 11 happens to point to is a small rib of material ‘outboard’ the ends of the cylinders. He said that the skilled reader, seeking to understand what the patentee was using the words to mean, would not think that this rib was what the patentee meant by ‘peripheral stiffening band’ even if the rib could be said at some level to contribute a degree of stiffness to the structure. I do not think a skilled person would analyse figure 1 of the patent in this sort of detail but I do accept the general point Mr Cuddigan is making. The rib in figure 1 is a useful illustration of the argument. It has material which is probably within Mr Smith's definition but that material is not what the reader would understand the patentee to be talking about.”
“[58] A skilled person would understand ‘peripheral stiffening band’ in the patent in the following way. A peripheral stiffening band is plainly supposed to stiffen the caliper. It is a band of material and it is meant to be appreciably beyond and distinct from the limb material at the ends of cylinders. That is what the word ‘peripheral’ is getting at. I do not think a skilled person would understand the patent to be trying to include within this expression some relatively arbitrary outer portion of the thickness of the limb material on the ends of the cylinders simply because it contributes to stiffening.”
“[46] Mr Campbell attacked the judge's construction as being of uncertain scope, as failing to identify any criterion as to what is meant by ‘appreciably beyond’, as being unsupported by the description and as placing excessive reliance on Figure 1. He invited us to accept the alternative construction put forward by Mr Smith. [47] I was not persuaded by Mr Campbell's argument that the judge's approach to the meaning of ‘PSB’ was incorrect. According to the specification, Figure 1 is representative of the prior art. The patentee is proposing the addition of a peripheral stiffening band to the known construction. The judge was correct that the skilled person would not expect the patentee to be using the term to cover just the material at the margin of the ends of the pistons. The arguments as to the precise scope of what the judge meant by appreciably beyond do not seem to me to be material to the outcome of the appeal.”
“[59] … It is plain that although to a mathematician symmetry and asymmetry may be regarded as absolutes, to a skilled reader of the patent, the expressions are not absolute. This is clear from the passage quoted above from p12 ln26p13 ln5. Some minor asymmetry at a detailed level is acknowledged to be known and irrelevant.”
“[65] Thus although it is true that the patent never defines the precise location of ‘the’ lateral axis, there is no practical difficulty in either of the two embodiments depicted. The bands shown are all asymmetric about any lateral axis. I note that the claim uses the indefinite article: ‘a’ lateral axis. In my judgment, if a band is asymmetric about any lateral axis then it will fall within the claim. Conversely if there is a lateral axis about which the band is symmetrical, the band is not within the claim. [66] There was an argument that since the asymmetry is a consequence of the asymmetric torque load, to be relevant the asymmetry had to be enough to affect the torque response or the overall braking efficiency. I do not accept this. No criteria are laid down by the patent in order to make that sort of assessment. The specification is talking about an asymmetric appearance. A visual assessment is required. For the hockey stick shaped bands, the skilled person would have no difficulty seeing the asymmetry referred to and would not be puzzled by the reference to a lateral axis. Even for band 145, one can see that the band has an asymmetrical shape as a result of the offset of the hole towards one end and possibly also the angles of the outer edges. What may make the visual assessment difficult in some cases is that minor asymmetry is not relevant. This is not a practical problem for the caliper in figure 4, is harder but not insurmountable for the caliper in figure 9, but may be more difficult to deal with in other cases.”
“[68] I have found that four shapes infringe and one does not. Nonetheless, the issue of infringement is not easy to decide. I have not reached this view without some hesitation. There is no difficulty in relation to a lateral axis. The area of doubt concerns identifying what level of detail the asymmetry should relate to and, to some extent, which features should be regarded as part of the profile of the peripheral stiffening bands.”
“Several openings 47, 48, 49, 50, 51, 52 are formed through the band to reduce the weight of the material without compromising the structural rigidity of the body 30.”
“For at least part of its length, at least one peripheral stiffening band may comprise a laterally outer region connected with a cylinder housing portions [sic] by means of a web, the web having a reduced thickness when compared with the laterally outer region of the band.”
“Now, I think Mr Pumfrey must be right in principle. It is possible to imagine claims which simply have no meaning to the skilled man. A lie detector which had to be calibrated in Pinocchio units, no one knowing what these were, would be an example. But I have, not without some hesitation, come to the conclusion that the concept of normal use is clear enough for the skilled man.”
“[54] Feature 5 also refers to housing portions, these are the shaped parts of the limbs around each cylinder. The extent in the longitudinal direction is said to be ‘about and interconnecting’ the outer lateral end regions of the housing portions. This is referring to the peripheral stiffening band running along the outer ends of the housing portions, in effect joining them up (although they are not separate).”