"Background to the invention. 7. The invention is concerned with a machine for continuously packaging food products. A familiar example of the kind of package with which the patent is particularly concerned is the ubiquitous potato crisp packet. The package consists of a generally tubular bag which is heat sealed at each end. The tube is itself formed from a flat web of material, and the edges of the flat web are joined together with a continuous longitudinal seal. The machine that forms the bag, fills it and seals it is called a form, feed and seal or FFS machine. There are two classes of machines, horizontal (HFFS) and vertical (VFFS). The former are used for regularly shaped solid products, such as chocolate bars and the like. For loose confectionery and snack products, on the other hand, VFFS machines are used. In a VFFS machine the weighed product passes down the centre of a tubular former round which the web which will make the bag is wrapped. At this stage, the longitudinal seal is made in the web to form a cylinder. The product drops into the bottom of the web, which is sealed, and the upper seal is formed above the product, so forming the bag. 8. In the case of dense products (sweets, dried fruit, nuts and so on) there is no problem in getting the product into the tube and into the bag. With light products, such as potato crisps and other snackfoods, there is a problem getting the product into the bag in a reliable manner. Where the product is not dense, and has a propensity to float, the manufacturer must allow sufficient time, or take deliberate steps, to ensure that all the weighed product is in the bag before the top is sealed. It is most important to avoid what is called the "crisp in seal" problem. The main classes of product which exhibit this difficulty are potato crisps, tortilla-like products and various extruded products such as Hula Hoops and cheese puffs. I shall call these snackfood products. 9. By the priority date, it was known to use a technique called "stripping"
"A stripping and sealing assembly, for packaging apparatus, (1) said apparatus including a product delivery head and a drive assembly to pass tubular bag material (12) past said delivery head so that product delivered from said head is located within said tubular bag material (12), (2) said stripping and sealing assembly including a pair of opposing sealing and stripping means (14, 40, 41, 42) located on opposite sides of said bag material (12) at a position downstream from said delivery head relative to the direction of movement of said bag material (12) through said apparatus, (3) said sealing and stripping means (14, 40, 41, 42) being adapted to cooperate to sealingly close portions of said bag material (12) and strip same, (4) a first arm means (15, 45) supporting one of said sealing and stripping means (14, 40.41, 42) and a second arm means (15,45) supporting the other sealing and stripping means (14, 40, 41, 42), (5) a pair of generally parallel rotatably driven shafts (16.43.44) from each of which there extends radially outwardly therefrom one of the arm means (15, 45), (6) cutting means (27, 46) mounted so as to be adjacent the extremities of the arm means (15, 45) and adapted to cooperate to sever said sealed portions from said bag material (12) to thereby form discrete bags of said product and wherein (7) each sealing and stripping means (14, 40,41, 42) includes co-operating stripper bars (22, 49, 50) which strip the bag material (12); wherein the arm means (15, 45) via said shafts are rotatably driven continuously through complete revolutions in synchronism in opposite directions about spaced parallel fixed axes generally transverse of the direction of movement of the bag material (12) (8) so that prior to sealing said bag material (12) the sealing and stripping means (14, 40, 41, 42), are moved along said bag material (12) to cause the stripper bars (22,49, 50), to strip same, and wherein (9) each arm means (45) is provided with one of the stripper bars (22, 49, 50), and the assembly further includes pivotable supports (19, 20, 53. 55, 47, 48, 57) for each stripper bar (49, 50) pivotally mounting the stripper bars (49 50) relative to said arm means (15,45) so as to provide for relative movement therebetween."
"44. The arms rotate in a generally D-like locus. ….. When stripping is switched on, the movement is very D-like. This is the most general case ( Figure D ). Figure D – Stripping on In this Figure, the movement of one jaw only is shown by the heavy line (including the dotted portions CA and BD.) The jaw shown rotates anticlockwise. If one starts from point D: the arm, driven by the arm servo, rotates from D to C, and the axis remains stationary where X CD intersects the horizontal axis. From C to A the axis moves from X CD to X A [and accelerates]. The jaws move from A-F as the axis moves away from the film, from X A to X F . Then the jaws move together to seal, and between G and B the axes again move to keep the jaws in clamping relationship with the film. Then from B to D the jaws move towards the web [and the movement of axes decelerates]. During the whole of the cycle, the rotational speed of the jaws varies. In the parts of the cycle denoted by a thick line they move essentially at constant angular velocity, but CA and BD are regions of the cycle where there is [normally] angular acceleration [of the arm]."
"35. All rotary machines, on the evidence, permit one or both shafts a degree of movement to accommodate the fact that the surfaces of the jaws must touch through the web. The web is thin and high precision is not attainable, and so a degree of "give" must anyway be incorporated. But to apply pressure, the pitch circles of the jaws must be deliberately arranged to intersect, so that on contact one or both jaws recoils slightly. It is important not to exaggerate this effect, as the radii of curvature are comparatively large. A great deal of confusion was caused in the evidence by the suggestion that if the pitch circles marked out by the jaws intersect there will be a so-called D-shaped movement, so that the web is continuously pressed by the sealing jaws. Mr Taylor makes this suggestion in Appendix 5 to his report, where a contrast is made between a "point contact" arrangement and a spring loaded shaft. But there is no distinction as X3, put to Mr Taylor, makes clear. In fact what happens geometrically is that if the pitch circles of the jaws overlap, the jaws touch and remain just touching at the leading edge until horizontal dead centre is reached, when they roll past each other. The contact remains a rolling contact, but under higher pressure. Practically, the position is not so simple because at the leading edge the jaws are nipping the web, and beginning to form a seal, and the same happens at the trailing edge. In fact, the contact time of the web with the jaws is largely influenced by the profile of the surface of the jaws. But this is obvious, and all jaws for rotary machines appear on the evidence to have a generally wavy profile cut in them. To this extent paragraph 10.2 of Mr Taylor's report is not correct as a matter of geometrical fact. I should observe that Mr Taylor has conducted or is conducting litigation against Ishida in a number of jurisdictions. From time to time, particularly when giving evidence in relation to the disclosure of the patent, he stepped over the line and became an advocate. On the other hand, particularly when he was giving evidence in relation to the history of his development, and as to how, based on his observations, the Ishida machines operated, he was a satisfactory and reliable witness."
"36. It is convenient to deal with the question of flat-faced jaws at this stage. Flat-faced jaws (of the kind for example used in Zwight and Crawford) cannot be used in a purely rotary machine unless they are arranged to pivot, so that the faces of the jaws are parallel and move into positive engagement with the film as their support rotates. Such a movement is difficult to achieve mechanically (Crawford gets over it with his cam track for the heads and his barrel cam for varying the speed of rotation). With flat faced jaws, sealing time is directly measured. The position is different with jaws with a cylindrical surface. In the latter case, the relevant time is the time during which the softened, or molten, web material is in the nip between the jaws. Although the times are not directly comparable, Mr Taylor gave evidence that in fact the times were comparable, and he supported this contention by reference to his sketch X4. 37. Mr Taylor said that a machine with a "kissing" contact between the jaws would not work. He was adamant, under repeated cross-examination, that as a practical matter some give was absolutely necessary, and that it would be obvious to the skilled man that he could (within limits) increase the time during which the film was subjected to a sealing pressure by increasing the overlap of the pitch circles of cylindrical-faced jaws. So far as flat jaws are concerned, obviously they required substantial overlap of the pitch circles and (equally obviously) flat jaws were used to increase sealing time. On this question I accept Mr Taylor's evidence. The arguments to the contrary seem to me to turn excessively on a purely geometrical analysis of the problem (see for example X3) in which insufficient attention has been directed to the real dimensions of the components concerned and the realities of machinery rotating rapidly."
"38. In my view, if the axes move in a manner which is irrelevant to the basic requirements of the invention, such a movement is within the contemplation of the claim. I consider that a movement of the jaws normal to the web would be seen by the skilled man as inevitable if a seal was to be formed using cylindrical sealing faces and he would further appreciate that such a movement would be provided by the conventional spring guide arrangement shown in Figure 3 of the patent. I consider, therefore, that a movement normal to the web of the axis of rotation of one or both of the jaws the function of which is to ensure that the sealing jaws (a) follow the web as they rotate and (b) move so as to control the pressure or duration of the clamping action is within the claim. I think that this construction is really to put a sensible meaning on the word "fixed" in its context. It is certainly a variant on the acontextual meaning of the word, and it seems to me that the skilled man would both appreciate that it was a meaning which could have no effect on the way the invention worked—indeed, it is necessary for the invention to work practically—and it is certainly not excluded by the specification itself."
"67. Of course, Mr Poley's report is an actual rather than a conjectural series of steps, and it is right also that Mr Poley did not start with any particular end in view. In the present case I think that the sum of the steps which I have outlined above in considering Mr Poley's report is, cumulatively, indicative of invention, albeit not of the flash of inspiration variety. But to go from the start to the end was in my judgment inventive, and my conclusion is that the claim is not invalid for obviousness over the common general knowledge."
"62. The approach of Mr Poley's report is rigorously systematic, but in no sense merely mechanical. He is himself an inventor with a number of patents to his name. The development was investigated in advance of the availability of weigh feeders capable of supplying 120 bags per minute from a single head. Phase 1 of the investigation, which was a design study, was the only work done by Mr Poley. He is a good engineer introduced to a new art, and he approaches the problem which he was given with none of the preconceptions of prejudices of the workers in the art themselves. He considered that it was obvious to rotate the strippers on the jaws, and Mr James disagreed. 63. Mr Poley's report proceeds by successive refinement. He sets out with a set of logical options for phase 1. He investigates how potato crisps drop in tubes. He identifies the need to avoid high accelerations and heavy components. He looks at the physics of film sealing. The report refers to brainstorming sessions for generating innovative concepts without consideration of the prior art. The results of these sessions were presented to Wright's for discussion. The report in fact contains an excellent step by step analysis of the design of a machine. Mr Poley did not come to the idea of attaching the strippers to the arms carrying the sealing heads immediately: his figure 6.15 in the first part of the report does not contain this feature, and it was after he had investigated the locus of the jaws and the locus of the stripper blade that he concluded that selection of a rotary stripping mechanism would allow elimination of a separate strip drive motor. I should record that Mr Poley's evidence taken as a whole both in his report or under cross-examination left me with the clear impression that the invention was not obvious. Mr Kitchin identified I think seven successive distinct steps in Mr Poley's design: (1) the brainstorming sessions (2) the investigation of the drop characteristics of potato crisps (3) the production of a number of different design concepts, including a design with independently driven strippers and sealing jaws (4) selecting between the different approaches (5) investigation of the different approaches to stripping through the sealing zone, and identification of reciprocating, rotary and track strippers and sealers, but without any particularly driving means (6) analysis of kinematics of the stripping and sealing mechanisms (7) the final design. Mr Kitchin points to the fact that PA considered that at the step 6 stage they had made a significant development."