The present invention relates to a moulding apparatus, and to a method of moulding, and is particularly, though not exclusively, concerned with an apparatus and method for rotational moulding.

Rotational moulding consists of introducing a pre-weighed amount of plastic powder into a hollow mould. The mould is heated and rotated about two axes so that the plastic powder in the mould gradually adheres to and forms a uniform layer against the inner surface. The rotation continues during the cooling phase so that the plastic retains the shape as it solidifies. When the plastic is sufficiently rigid, the mould rotation is stopped to allow the removal of the plastic product. The process is distinguished from spin-casting or centrifugal casting by its relatively low rotational speeds, typically 4 - 20 revs/min.

Rotational moulding is a method for manufacturing hollow plastic products. It is well known for the manufacture of tanks, but many designers all over the world are using the process to manufacture many different types of plastic parts .

Some of the market sectors are:

□ medical products

□ Oil and water storage tanks

□ consumer products, planters, street furniture, grit bins, litter bins □ agricultural and garden equipment,

□ automotive and transportation components,

□ toys,

□ boats, kayaks and canoes

□ sporting equipment,

O furniture, for internal or external use

□ materials handling products, pallets, IBC's

□ Point-of-sale products. Generally, but not exclusively, the material used in rotational moulding is a thermoplastic resin which is fused to the internal surface of the mould as a result of heating the mould while the mould is rotated for a period of time at a sufficiently high temperature until the material has melted and formed a contiguous layer on the inside of the mould, at which point the heating process is terminated.

The subsequent phase of the process is to cool the mould and thus the layer of thermoplastic material whilst initially maintaining at least one of the rotation axes in motion until the formed layer has cooled sufficiently to allow all rotations to be stopped, and the mould accessed and opened so that the moulded part can be removed. The mould can then be reloaded with material and the moulding process can be repeated.

Most large commercial machines are of a "carousel" type design. In these machines the moulds are mounted on an arm which provides bi-axial rotation to the moulds and carries them sequentially into the oven, the cooler, and finally into the de-moulding/charging area. Typically, three arms are used so that heating, cooling, and servicing can be carried out simultaneously on three different sets of moulds. In some cases, the arms are on a fixed turret at 120° spacing. In others the arms are mounted on carriages and can be moved independently of each other so variable cycle parameters can be accommodated if needed.

Other variants of bi-axial machines include single station "clam-shell" machines and single or multiple shuttle machines .

Currently there are two main methods of conducting the moulding process. One method is known as the bi-axial method, in which moulds are mounted on a suitable platen, fixed to a face plate of a gear box mounted on a rotating arm. The 360° rotation of the arm is known as the primary axis and the 360° rotation of the platen is known as the secondary axis .

The relative speeds of the two rotations can be varied or fixed to ensure even material distribution around the inside of the moulds mounted on the platen. The bi-axial method is ideally suited to manufacture mouldings with complex geometry for example fuel tanks with filler necks and mounting fixtures moulded in.

The other method used is known as rock and roll method derived from the primary axis (the rock) which pivots through an arc of -45° to +45° above and below the horizontal plane and the secondary axis (the roll) which rotates through 360°, the centre of this rotation being perpendicular to the primary axis . The rock and roll method is ideally suited to the manufacture of long items such as canoes and kayaks. Machines applying these two principles are widely available either in bi-axial format or in rock and roll format only.

Embodiments of the present invention aim to provide a moulding apparatus and moulding method that can accommodate both types of moulding method.

The present invention is defined in the attached independent claims, to which reference should now be made. Further, preferred features may be found in the sub-claims appended thereto.

According to one aspect of the present invention, there is provided a moulding apparatus comprising one or more moulding stations located at a respective one or more moulding positions, the or each moulding station being arranged in use to perform a moulding operation, and a heating unit, moveable with respect to the or each moulding station position so as to engage with the or each moulding station .

The heating unit preferably comprises an oven, and may be arranged in use to engage with the or each individual moulding station. The heating unit is preferably arranged in use to move on a support structure, more preferably a gantry, located substantially above the moulding station positions. Preferably the heating unit is arranged in use to move in a first direction, preferably substantially horizontally on the support structure. The heating unit may be arranged to move in a second direction, substantially transverse to the first direction, and preferably substantially vertically, to engage with a moulding station.

One or more of the moulding stations may comprise a rotational moulding machine.

One or more of the moulding stations may comprise a biaxial moulding machine. One or more of the moulding stations may comprise a rock and roll moulding machine. More preferably the apparatus comprises a combination of bi-axial and rock and roll moulding machines. The moulding station may comprise other kinds of moulding machine and the moulding stations may be substantially interchangeable.

Advantageously, the apparatus may allow a modular moulding system, having a plurality of moulding stations which can be dedicated or interchangeable for use either as bi-axial process stations or rock and roll process stations.

The oven may be located in a canopy and may be mounted on a carriage. The support structure may operate both vertically and horizontally to engage and complete a heating phase of the process cycle.

Individual moulding stations may be engaged sequentially or non-sequentially by the heating unit. The heating unit may include a recirculation duct and preferably includes a fan. Preferably the duct is orientated so that a heated air stream impinges across individual moulds of the moulding stations as it flows, preferably horizontally, from one side of the heating unit to the opposite side. In a preferred arrangement, the heated air re-enters the recirculation duct, and is drawn over the heater by the fan and back into the heating unit.

According to another aspect of the present invention there is provided a method of moulding, the method comprising moving a heating unit with respect to one or more moulding stations located at a respective one or more moulding station positions, so as to engage with the moulding statio .

Preferably the method includes moving the heating unit on a support structure substantially above the or each moulding station. The method may include moving the heating unit in a first direction, preferably substantially horizontally on the support structure . The method may include moving the heating unit in a second direction, substantially transverse to the first direction, and preferably substantially vertically, to engage with a moulding statio .

The invention also comprises a program for causing a device to perform a method of moulding, the method comprising moving a heating unit with respect to one or more moulding stations located at a respective one or more moulding station positions, so as to engage with the moulding statio .

According to another aspect of the present invention, there is provided an apparatus comprising a processor and a memory having therein computer readable instructions, the processor being arranged in use to read the instructions to cause the performance of a method of moulding, the method comprising moving a heating unit with respect to one or more moulding stations located at a respective one or more moulding station positions, so as to engage with the moulding station.

The invention also includes a computer implemented method comprising moving a heating unit with respect to one or more moulding stations located at a respective one or more moulding station positions, so as to engage with the moulding station.

In a further aspect, the invention provides a computer program product on a non-transitory computer readable storage medium, comprising computer readable instructions that, when executed by a computer, cause the computer to perform a method of moulding, the method comprising moving a heating unit with respect to one or more moulding stations located at a respective one or more moulding station positions, so as to engage with the moulding statio .

The invention may include any combination of the features or limitations referred to herein, except such a combination of features as are mutually exclusive, or mutually inconsistent.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic perspective view of a three-station modular moulding machine configured with three rock and roll moulding stations with an oven canopy engaged with moulding station number 1;

Figure 2 is a schematic front perspective view of the machine of Figure 1;

Figure 3 is a schematic side perspective view of the machine of Figure 1;

Figure 4 is a schematic side perspective view of the machine of Figure 1 but with the oven canopy disengaged;

Figure 5 is a schematic front perspective view with the elevated oven canopy engaged with a full moulding station;

Figure 6 is a schematic perspective view showing a modular moulding machine with a bi-axial station added in place of a rock and roll station;

Figure 7 is a schematic sectional view of an oven canopy and recirculation duct showing the relative positions of the recirculation fan and the heater.

It is an aim of the present invention to provide a single moulding machine with the facility to manufacture from one or more moulding stations with either bi-axial processing capability or rock and roll processing capability or with a combination of both bi-axial stations and rock and roll stations all of which are interchangeable with each other and with additional stations of either type. For example, an initial configuration may have three stations all of which operate bi-axially, should the need arise to produce an item of a size and design which can only be moulded efficiently utilizing the rock and roll process then one of the bi-axial stations can be substituted with a rock and roll station and vice versa.

Referring to Figure 1, this shows a modular moulding machine generally at 100. The machine comprises a gantry 120 as a support structure, and a carriage 130 which supports an oven canopy 140 and a cradle 150. The carriage 130, canopy 140 and cradle 150 are arranged to move longitudinally on the gantry 120 between first, second and third mould stations 160, 170 and 180 respectively.

Figure 2 is a schematic front perspective view showing the oven canopy 140 attached to the cradle 150 which is shown positioned and engaged with the first mould station 160.

Figure 3 is a side perspective view of the machine 100 in the same configuration as that shown in Figure 2, in which the oven canopy 140 is engaged with the first mould station 160, with the gantry 120, carriage 130 and cradle 150 in their respective positions .

Figure 4 is a side perspective view of the machine 100 in which the oven canopy 140 and the cradle 150 are shown in a raised position.

Figure 5 is a front perspective view showing the oven canopy 140 engaged with the first mould station 160 illustrated in an elevated and tilted position with the gantry 120, carriage 130 and second and third mould stations 170 and 180 in their respective positions.

Figure 6 shows an alternative arrangement, in which the modular moulding machine 100, comprising a gantry 120, carriage 130, oven canopy 140 and cradle 150 is again arranged to move longitudinally between the mould stations 160-180. However, in this arrangement, whilst mould stations 160 and 170 are rock and roll stations, the third station, 180 is a bi-axial station. In addition, cooler units 190, 200 and 210 are also shown in their respective positions .

Referring to Figure 7, this is a schematic cross-sectional view of the oven canopy 140 showing a recirculation duct 220, a recirculation fan 230 and a heater unit 240. An airflow pattern is illustrated by the directional arrows A.

In the exemplary embodiments of the modular moulding machine the individual moulding stations are positioned in a linear pattern with sufficient spacing in between to provide adequate clearance. The oven canopy and support structure operate vertically and horizontally to engage and disengage with each of the moulding stations in turn. The moulding stations could be arranged in another geometry with suitable changes to the gantry.

To improve the efficiency of the machine it is possible to operate the moulding stations either sequentially for example station 160 then station 170 then station 180 and then returning to station 160 and thereafter repeating the sequence. However, there may be occasions when it is not possible to operate one of the stations, for example in the event of a breakdown on station 170, the machine will remain in operation utilizing stations 160 and 180 thus maintaining production allowing the problem to be rectified with minimal disruption to productivity.

In an exemplary embodiment of the modular moulding machine the oven canopy 140 comprises an insulated body and a heater 240 which may comprise a gas-fired burner positioned within an insulated duct with an in-line fan 230 providing sufficient air volume and velocity to develop an airstream entering into the oven cavity from the duct outlet, and exiting the oven cavity through a corresponding duct inlet on the opposite face of the oven. It is through this heated airstream that the moulds are rotated to allow the hot air to impinge against the external surfaces of the moulds so as to raise their temperatures sufficiently to transmit the heat through to the material inside the mould and thus form a skin.

Advantageously, the fact that the hot airstream enters the oven directly and does not for example need to heat up a primary chamber, from which the resulting hot air is drawn and returned, means that the moulds are brought up to working temperature quickly and efficiently, it also means that because there is no primary chamber the burner can be switched off completely between heating cycles thus saving energy.

When the heating cycle is complete the oven canopy 140 is disengaged from the moulding station, the cooling cycle can commence, and the canopy can traverse to the next available station to commence the heating cycle there.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and/or shown in the drawings, whether or not particular emphasis has been placed thereon.