It is known to form hollow articles such as disposable urine bottles, bed pans, bowls and the like from paper pulp by introducing paper pulp slurry into a mould having a water-permeable moulding surface (e. g. made from metal gauze) formed into the shape of the article to be produced. By application of vacuum to the rear face of the moulding surface or application of pressure into the interior of the mould, paper pulp is deposited on the moulding surface. The applied vacuum or pressure causes much of the water to pass through the permeable moulding surface, causing solid material to build up on the moulding surface in the desired shape. The mould is then opened to allow removal of the moulded article which is thereafter dried, for example in an oven. An example of such an apparatus is disclosed in GB-A- 2153740.

Typically and as disclosed in GB-A-2153740, the moulding apparatus comprises several banks of moulds which are mounted on an endless conveyor and indexed stepwise through a moulding cycle. The moulding cycle comprises closing the mould, immersing an entrance aperture of the mould in a paper pulp slurry, applying a vacuum to the mould to draw paper pulp fibres onto the moulding surface, moving the mould out of the paper pulp slurry while continuing to apply vacuum (or alternatively pressure) to extract water from the deposited paper pulp fibres. The mould is then opened to deposit the moulded article onto a conveyor for further

drying. The open mould is then sprayed with water jets to remove unwanted deposits from the moulding surface which would otherwise interfere with the moulding process.

After the cleaning step, the mould is then closed and moves round to the paper pulp slurry to repeat the cycle.

It is important that the moulding surface of the moulds be cleaned thoroughly before moving to the moulding step. Failure to do so can result in the cumulative build up of material on the moulding surface which can ultimately lead to malformation of further articles.

In the known apparatus, thorough flushing of the moulds has been ensured by spraying a large volume of water in a fixed spray pattern having a relatively wide angle. Whilst this arrangement can work successfully if set up correctly, it does involve the use of a great deal of flushing water to ensure that all of the moulding surfaces are adequately cleaned, with a consequential increase in cost. Moreover, if the spray is not adjusted correctly, it is possible for parts of the moulds to be inadequately flushed as a result of the distribution pattern of the spray, with a consequential build-up of material.

It is an object of the present invention to overcome or reduce the problems associated with the prior art.

In accordance with the present invention, there is provided a moulding apparatus comprising a mould for forming an article, spray means for spraying flushing fluid into the mould after discharge of a moulded article and spray control means for controlling the spray means to spray a non-constant distribution of flushing

fluid to the mould during spraying.

By spraying a non-constant distribution of flushing fluid to the mould, the likelihood of there being any regions which do not receive sufficient flushing fluid is greatly reduced.

In one embodiment, the spray means is displaced, e. g. angularly displaced, during spraying. The spray means may comprise a plurality of spray apertures.

The apparatus may comprise a plurality of moulds. Preferably, the moulds are displaced sequentially, e. g. indexed stepwise, to a position adjacent the spray means.

The apparatus may comprise a plurality of moulds which are sprayed simultaneously, a respective spray means being associated with each mould and being controlled by the spray control means. The spray means may comprise a pipe or tube having one or more spray apertures associated with each mould to be sprayed.

In one embodiment, there is provided a plurality of banks of moulds which are moved sequentially to a spray means, the spray means comprising an elongate tube or pipe into which flushing liquid is fed and a spray head associated with each mould in the bank, the tube or pipe being pivotable about its longitudinal axis during spraying to apply a non-constant spray profile to the moulds during spraying.

Preferably, the tube or pipe is adapted to pivot between predetermined angular orientations. There may be an air or an electric motor for pivoting the tube or pipe.

Preferably, there is an air motor for pivoting the tube or pipe.

The apparatus may further comprise at least one limit switch for controllinng the pivoting of the tube or pipe between predetermined angular orientations or a timer

device for controlling the pivoting of the tube or pipe between predetermined angular orientations in a predetermined time period.

The apparatus may also further comprise valve means for controlling the supply of flushing liquid to the tube or pipe. The valve means may be electrically actuated or actuated via means of an air motor and preferably is actuated to synchronise the supply of flushing liquid with the pivotal movement of the tube or pipe.

The present invention also includes a method of cleaning a moulding apparatus having a mould for forming an article, the method comprising spraying flushing fluid from a spray means into the mould after discharge of a moulded article and controlling the spray means to spray a non-constant distribution of flushing fluid to the mould during spraying.

Preferably, the method comprises displacing the spray means during spraying, for example angularly displacing the spray means during spraying.

The method may comprise angularly displacing the spray means between predetermined angular orientations during spraying.

The supply of flushing fluid to the spray means is preferably synchronised with the displacement of the spray means.

The method preferably comprises spraying the flushing fluid through a plurality of spray discharge apertures.

The moulding apparatus may comprise a plurality of moulds, the flushing fluid being sprayed into said plurality of moulds.

By way of example only, a specific embodiment of the present invention will now be described with reference to the accompanying drawings, in which : - Fig. 1 is a schematic side view of an embodiment of moulding apparatus in accordance with the present invention; Fig. 2 is a plan view of spray means forming part of the apparatus of Fig. 1 ; Fig. 3 is a longitudinal cross-section through the spray means illustrated in Fig. 2; and Fig. 4 is an end view of the spray means illustrated in Fig. 3.

Referring firstly to Fig. 1, an apparatus for vacuum forming hollow articles is generally as described in GB-A-2153740. In general terms, the apparatus comprises a mould transport apparatus 14 mounted for pivotal movement about an axis 16 by means of a hydraulic ram (not illustrated) which controls the pivotal movement of the transport apparatus in an oscillatory manner between first and second positions, as will be described.

A plurality of banks of two-piece moulds 20 are carried by the transport apparatus on an endless conveyor chain 22. Means is provided for applying suction to the moulds as the moulds are indexed stepwise to submerge an open end of each of the moulds into a vat of paper pulp slurry 24. This causes paper pulp to be drawn onto the moulding surface of the moulds and as the moulds are indexed stepwise out of the slurry 24 the suction is applied to withdraw additional water from the material deposited within the moulds.

Just beyond the uppermost point of their path, the moulds are opened and the moulded articles are discharged onto a conveyor apparatus (not illustrated), typically

in the form of a series of banks of upstanding pins, one pin being provided for each mould. The moulded articles are then generally conveyed through a drying oven to remove further water.

The open moulds are then indexed stepwise until at one point they are positioned adjacent to a spray means 26 which sprays water into each of the open moulds. The spray means is illustrated in more detail in Figs. 2 to 4.

As best seen in Fig. 2, the spray means comprises a horizontally-disposed rigid spray tube 30 having a plurality of groups of discharge apertures 32, each group of discharge apertures being positioned to correspond with the lateral position of one of the moulds 20 in each mould bank. The tube 30 is pivotable between first and second extreme angular positions by means of an air driven actuator 34 connected to one end of the tube. The opposite end of the tube 30 receives water from an inlet pipe 35 via a solenoid-actuated valve 36. The end of the tube 30 adjacent to the valve 36 is also pivotally mounted by means of a bearing 37 mounted on a support 38, the outlet of the solenoid valve 36 passing sealingly through the bearing 37 into the tube 30.

The air driven actuator 34 comprises a reversible air motor 40 supplied with air from air feed inlet 42 and having an air feed outlet (not illustrated). The direction of rotation of the motor 40 is controlled by two limit switches 46,48, which control the direction and passage of air to a control valve through which air is supplied to the motor 40. Each switch 46,48 is adapted to engage with a respective one of two lugs 50,52 projecting from a disc 54 which is secured to, and rotates with, the motor 40 and the tube 30. Alternatively, the motor 40 may be made to rotate several times

during each operation of the moulding machine by means of a timer in the control means 56 to control the number of rotations of the motor 40 by controlling the direction and the passage of air through a control valve to the motor 40 in a predetermined time period. The operation motor is also controlled by control means 56 which controls the apparatus as a whole, including the movement of the moulds, the opening and closing of the moulds and the application of suction to the moulds, as will be explained.

In use, as the open moulds 20 are indexed to the spraying station, the motor 40 and spray tube 30 will be in the position illustrated in Fig. 4, namely with one of the lugs 50 engaging the first limit switch 46. When the next bank of moulds 20 to be sprayed is in position at the spraying station, the controller 56 of the main apparatus controls the flow of compressed air in a first direction into the motor 40 which then causes the motor and the pipe to rotate in the clockwise direction as illustrated in Fig. 4. Simultaneously, the solenoid actuated valve 36 is opened by the controller 56 of the apparatus to allow pressurised water to flow into the pipe 30 and out of the discharge apertures 32 in the form of several sprays.

The motor 40 is actuated until the second lug 52 engages the second limit switch 48, whereupon the direction of the rotation of the motor 40 is reversed, with the solenoid actuated valve 36 still open. When the first lug 50 re-engages the first limit switch 46, a signal is sent to the controller 56 of the main apparatus which deactivates the motor 40 and closes the solenoid actuated valve 36. The lugs 50,52 and limit switches 46,48 are positioned to allow the tube 30 to pivot to and fro through the angle defined by the position of the lugs 50,52.

Thus, it can be seen that at the spraying station the profile of the spray received by the open moulds 20, and the distribution of water received by the moulds, is not constant, in view of the fact that the direction of spraying, and therefore the spray profile to which the moulds are subjected, changes during the spraying process.

As a result, the likelihood of any particular area within the open mould not being adequately flushed is significantly reduced. It has also been found that by adjusting the direction of the sprays during spraying, the moulds are cleaned more efficiently and that the amount of water required is reduced as compared with fixed sprays.

The invention is not restricted to the details of the foregoing embodiment. In particular, although the embodiment has been described with reference to vacuum forming of paper pulp articles, the invention is equally applicable to any mould which requires cleaning regularly during use.