ROTOPLAS LTD.

[1983] APO 46

In the Matter of the Patents Act 1952

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In the Matter of Patent Application No. 45561/79 for Letters Patent in the Name of ROTOPLAS LTD.

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In the Matter of Examiner's Objections thereto.

DECISION OF A SUPERVISING EXAMINER OF PATENTS:
     This matter concerns an application for a patent entitled "IMPROVEMENTS IN ROTATIONALLY MOULDED CONTAINERS" lodged on 30 March 1979.  Examination of the application and complete specification has been in accordance with section 48.
     In his most recent report dated 11 October 1983, the Examiner has maintained an objection from earlier reports, namely that the proposed amended claims are not novel.  As the Examiner's first report issued on 8 March 1982, the time for acceptance as specified under section 54, including all extensions, expires on 8 December 1983.  The applicant requested a hearing which took place in Canberra on 10 November 1983 with Mr A.R. Smeeton, patent attorney, of Davies & Collison, Melbourne, appearing on behalf of the applicant.
        As proposed to be amended, the specification commences by stating that the "invention relates to rotationally moulded containers", particularly those of large size e.g. 1000 litres and more, and particularly to containers designed to contain "liquid foodstuff, specifically where the stored liquids are poured into the containers while hot, heremetically sealed and allowed to cool".

The specification then continues with the following paragraphs:

"In order to achieve sufficient mechanical strength, containers generally have to be of sufficient predetermined wall thickness.  It is also know that different portions of containers of the kind referred to are subject to different amounts of stresses, namely, the upper or top portion of such containers are subject to stresses generated by the formation of vacuum within the container, and therefore tend to buckle or belly inwardly.  Therefore, such container‑tops should have been made of wall thickness greater than the remaining portions of the container.  However, in rotationally moulding process the control of the wall thickness as different locations of containers is difficult and may only be achieved within small limits.  Consequently the overall wall thickness of the container must practically be equal to the wall thickness where the highest stresses are present.  This of course entails an actual waste of materials and increases the manufacturing costs.

One way of solving this problem was to provide the container at the maximum stressed portions thereof with upright strengthening ribs.  This solution is, however, unsuitable or at least undesirable where liquid foodstuff is concerned, since the formation of the ribbing resulted in complementary depressions at the inside of the containers.  Such depressions or recesses are difficult to clean, caused the accumulation of dirt and bacteria and therefore disqualified the containers for their desired purpose."

The specification continues with two consistory statements worded in terms identical to claims 1 and 3.  It is convenient at this point to set out the claims of the specification as currently proposed.  They read as follows:

"1.A rotationally moulded container characterized by integral solid strengthening ribs having a generally V‑shaped cross‑section wherein the projecting height  of each solid rib is less than or equal to 2.5 times the width b at the bottom of such rib.

2.The container as claimed in claim 1 wherein h equals 2.5 b for rotational moulding polyethylene having a Melt Index of between 3 and 10.

3.A method of rotationally moulding containers having integral solid strengthening ribs of generally V‑shaped cross‑section, comprising:

a.p roviding a mould characterized by V‑shaped cross‑sectional grooves or depressions for producing solid ribs on the container, wherein the projecting height h of each solid rib is less than or equal to 2.5 times the width b at the bottom of such rib,

b.moulding a polymer in said mould at elevated temperature while rotating the mould, thus causing the polymer to flow and coat the inside walls of the mould, for a sufficient amount of time to substantially fill‑in the grooves or depressions of the mould with the polymer,

c.cooling the mould, and

d.removing the container from the mould.

4.The method as claimed in claim 3 wherein the polymer is polyethylene having a Melt Index of between 3 and 10.

5.Rotationally moulded containers substantially as hereinbefore described with reference to figures 5 and 6 of the accompanying drawings.

6.A method of rotationally moulding containers substantially as hereinbefore described with reference to figures 5 and 6 of the accompanying drawings."

The detailed description of the invention in the specification is made with reference to 5 figures.  Figures 1 to 3 show containers and details thereof identified on the drawings as representing "prior art".  Figures 1 and 2 each show a cylindrical container with a frusto‑conical top portion T incorporating a small access opening.  Figure 1 shows in dash lines how the top portion can distort under certain conditions, whereas Figure 2 shows a container having a number of ribs R provided in the top portion T, the cross-­sectional profile of same being illustrated in Figures 3a and 3b as being U and V‑shaped, respectively.  When moulded into the top portion, the ribs are formed integrally with the container wall so as to present elongated recesses K which face the interior of the container.  The specification further discusses the prior art containers and the ribs of Figure 3 in these terms:

"While such ribs would in fact contribute to the mechanical strength of the container, the elongated recesses K formed within the rotationally moulded container would cause the gradual accumulation of dirt, being difficult to reach through the opening of the containers for cleaning purposes.

It has been found that the only feasible solution to the problem of having strengthening ribs but without substantial internal recesses or cavaties would be to form solid ribs P with a V‑shaped cross‑section, as schematically shown in Figure 4."

Figure 4 is a cross‑sectional representation of "a rib designed according to the principles of the present invention" and shows a portion of a container wall having an integral solid rib P projecting to one side thereof and a small shallow depression K' represented on the other side of the wall opposite the rib formation.
        The specification continues with a discussion about the formation of the solid ribs by a rotational moulding process.  The relevant paragraph is as follows:

"In order to prepare such solid ribs via a rotational moulding process, a certain relationship between width b at the base of the rib P, and the height H [h] thereof must be kept within certain limits, depending on the flow characteristics as measured by the Melt Index of the material used.  In the case of polyethylene, for example, were a resin of Melt Index greater than 10 is used, the height h relative to the width b must be smaller in order to avoid the formation of a cavity or recess K as shown in Fig. 3b.  If the Melt Index is smaller than 3 the height h may be increased, but the flow rate would be too slow to be practical for rotational moulding.  It has been found that the optimal relationship between h and b for polyethylene having a Melt Index between 3 and 10 would be h = 2.5 b.  This relationship will insure maximum mechanical strength of the container wall while still keeping a relatively smooth inner wall surface with only a small depression or meniscus K' formed at the base of the ribs, as shown in Fig. 4."

The description then concludes by stating that the strengthening ribbing of "the present invention is applicable to various kinds and sizes of containers" such as cylindrical containers or spherical containers (illustrated in Figure 5).
        As I understand the specification, the invention is concerned with producing containers incorporating solid integral V‑shaped strengthening ribs via a rotational moulding process (commonly called 'rotomoulding').  However, to produce such a container by rotomoulding so as to properly form the ribs and provide a relatively smooth inner wall surface on the container opposite the ribs, the described invention provides a method of moulding involving, inter alia;
         (i)  using a mould having particularly dimensioned grooves for forming the ribs, the dimension of the grooves being related to the flow characteristics of the mouldable material to be used,
        (ii)  performing the actual moulding in that mould under such conditions (e.g., quantity of material, time, mould temperature) whereby solid ribs and a relatively smooth inner container wall opposite each rib results.
        I turn now to a consideration of the proposed claims as listed earlier in this decision and firstly to claim 3.
        Claim 3 is directed to a method of rotationally moulding containers having integral solid strengthening ribs of generally V‑shaped cross‑section.  Para (a) defines the mould and the grooves formed in the mould for producing the solid ribs on the container during the rotomoulding step via that mould.  Para (b) refers to the step of "moulding a polymer in said mould ... for a sufficient amount of time to substantially fill‑in the grooves or depressions of the mould with the polymer".  Thus the precise extent of the method claimed is in effect limited to the container and ribs to be obtained.  I therefore need to consider whether the method claimed is necessarily limited to the method of the invention described.
        From my review of the specification, the method of the present invention is not only intended to fill‑in the grooves of the container-­producing mould so as to form integral solid ribs on the container but is also intended to result in the inner container wall being substantially smooth and without depression or cavity opposite each solid rib location (see the description on pages 4 and 5).  Furthermore, in my view it is apparent from the description that to successfully achieve the desired container and rib configuration, not only must the moulding time be sufficient but the ratio selected between rib height h and rib width b (and hence the rib‑producing groove dimensions) needs to be related to the specific polymer to be used and accordingly to its Melt Index.  As the method of claim 3 contains no requirement relating the rib dimensions to the polymer characteristics being used, nor is limited to producing a container having solid ribs and a substantially smooth inner wall surface opposite these ribs, I consider that claim 3 fails to adequately define the method of the present invention.
        Claim 1 is directed to a rotationally moulded container characterized only by having integral solid strengthening ribs which are

(a)generally V‑shaped in cross‑section, and

(b)have a rib height h "less than or equal to 2.5 times" the rib width b.

The claim therefore is quite broad encompassing a wide range of solid rib shapes and dimensions, and having no limitation as to the inner wall configuration of the container.  In view of the matters discussed earlier in relation to the method of the invention I conclude that claim 1 is an inadequate definition of the container the subject of the present invention and accordingly like claim 3 offends against section 40 of the Act.
        The main point of dispute between the Examiner and the applicant over a number of report stages has concerned the question of novelty of the proposed amended claims, and I will consider that question against the known state of the moulding art prior to the priority date of the claims.
        Containers with solid ribs made by a moulding process other than by rotomoulding are known, a point not disputed by the applicant.  Also, it is well accepted in the moulding art generally that the incorporation of ribs on a moulded article can increase the rigidity and strength of that article without it being necessary to increase the thickness of the article throughout.  In addition, the concept and practice of moulding articles by a rotational moulding process has been in existence for many years and such a process has been increasingly utilized in more recent years, e.g. since the 1960's, to produce containers of quite varying dimensions and shape.  Reference to such widely circulated publications as the monthly journal "Modern Plastics International" and the annual "Modern Plastics Encyclopaedia" issued prior to 1978 reveal numerous articles on the subject of rotational moulding.  Accordingly, prior to the priority date of the claims, a skilled addressee in the moulding art had access to all moulding processes then known and available including, for instance, injection moulding and rotational moulding, and consequently would have considered rotational moulding as a clear alternative to other forms of moulding for articles such as containers.
        As previously discussed, claim 1 is directed to a rotationally moulded container having integral solid ribs.  In view of the fact that moulded containers with solid ribs were known, and that in the moulding art ribs are incorporated into moulded articles for strengthening purposes, I consider there to be no novelty in the rotationally moulded container as defined by claim 1.
        As regards claim 3, this claim is directed to "a method of rotationally moulding containers" and while I feel that the Examiner's objection to this claim on the question of novelty has merit I consider it unnecessary to decide that issue at this stage since amendments to claim 3 to overcome section 40 deficiencies are necessarily required.  However I might add that in my opinion, it seems that any novelty which may exist in the present application primarily resides in the particular method of rotational moulding to form a container with solid ribs as has been described.
        Whilst I consider that the specification cannot be accepted in its present form, I believe the specification can be amended to overcome the section 40 deficiencies mentioned and result in claims free of objection on novelty grounds.  I therefore afford the applicant an opportunity to lodge a statement of proposed amendments to my satisfaction within the time remaining for acceptance.

(T.R. BRUHN)
Supervising Examiner of Patents