WO2016070240A1

WO2016070240A1 - Method and apparatus for applying a mould release agent to a mould surface

Info

Publication number: WO2016070240A1
Application number: PCT/AU2015/000680
Authority: WO
Inventors: James Gilder Dixon; Peter Andrew DAVIES
Original assignee: Rocla Pty Limited
Priority date: 2014-11-08
Filing date: 2015-11-09
Publication date: 2016-05-12
Also published as: AU2015342735A1

Abstract

A method is disclosed for applying a mould release agent to a mould surface. The method comprises the steps of atomizing a liquid mould release agent into droplets, electrically charging the droplets, and spraying the charged droplets in a direction of a mould surface to form a film of mould release agent on the mould surface. An apparatus for applying a mould release agent to a mould surface according to the method is also disclosed.

Description

METHOD AND APPARATUS FOR APPLYING A MOULD RELEASE AGENT TO A

MOULD SURFACE

[0001] Field of the Invention

[0002] The present invention relates to a method and apparatus for applying a mould release agent to a mould surface.

[0003] The invention has been developed primarily for use in applying mould release agents to a concrete mould and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

[0004] Background of the Invention

[0005] Concrete manufacturing industries produce customer products by shaping freshly batched concrete in a variety of moulds and/or formers. An undesirable condition as a result of this process is contamination of the moulds with tenacious concrete, often referred to as "mould stick", which requires continual cleaning of the mould or former, and application of a mould release agent.

[0006] Mould release agents have commonly been sourced from waste mineral oil, petroleum distillates and lately organic oils such as canola, sunflower and lanolin. The traditional methods of applying these mould release agents to product moulds has been to pneumatically and mechanically spray said oil, creating an inhospitable workplace environment and up to a 60 to 70% wastage of valuable mould release agent.

[0007] The present invention seeks to provide a method and apparatus for applying a mould release agent to a mould surface, which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[0008] The above discussion of background art is included to explain the context of the present invention. It is not to be taken as an admission that any of the documents or other material referred to was published, known or part of the common general knowledge in Australia at the priority date of any one of the claims of this specification.

[0009] Summary of the Invention

[0010] According to a first aspect of the present invention, there is provided a method of applying a mould release agent to a mould surface, the method comprising the steps of: [0011] atomizing a liquid mould release agent into droplets;

[0012] electrically charging the droplets; and

[0013] spraying the charged droplets in a direction of a mould surface to form a film of mould release agent on the mould surface.

[0014] Preferably, the method further includes providing a mould release agent including a mixture of a mould release oil containing an additive for allowing the mould release agent to be ionised and thereby electrically charged.

[0015] Preferably, the step of electrically charging the droplets includes:

[0016] moving the droplets of mould release agent relative to at least one charged electrode.

[0017] Preferably, the method further includes, before the step of atomizing liquid mould release agent to form droplets, the step of:

[0018] moving an arm comprising an electrostatic spray head relative to a working position located adjacent to the mould surface.

[0019] Preferably, the mould is a hollow pipe mould and the mould surface is an internal surface of the hollow pipe mould, the arm being configured to locate substantially within the hollow pipe mould in the working position.

[0020] Preferably, the method includes:

[0021] moving the spray head between a retracted position in which the spray head is located substantially inboard within the arm and an extended position in which the spray head extends outboard from one end of the arm when the arm is located at the working position.

[0022] Preferably, the method includes:

[0023] moving the arm relative to the mould while spraying the charged droplets in a direction of the mould surface at a speed in a range of between about 2 metres per second and about 5 metres per second.

[0024] In one embodiment, the method includes:

[0025] moving the arm relative to the mould while spraying the charged droplets in a direction of the mould surface at a speed in a range of between about 3 metres per second and about 4.5 metres per second.

[0026] Preferably, the step of spraying the charged droplets includes: [0027] spraying the charged droplets along a trajectory incident on the mould surface at an angle of greater than about 90 degrees.

[0028] Preferably, the step of spraying the charged droplets includes:

[0029] spraying the charged droplets at a velocity in a range of between about 2 metres per second and about 5 metres per second.

[0030] In one embodiment, the method includes:

[0031] spraying the charged droplets at a velocity in a range of between about 3 metres per second and about 4.5 metres per second.

[0032] Preferably, the step of atomizing the liquid mould release agent to form droplets further includes the steps of:

[0033] heating the mould release agent; and

[0034] delivering the heated mould release agent through an atomising device.

[0035] According to a second aspect of the present invention, there is provided an apparatus for applying a mould release agent to a mould surface, the apparatus comprising:

[0036] a spray sub-assembly having a spray head for producing a spray of charged droplets of mould release agent; and

[0037] a positioning sub-assembly for selectively moving the spray sub-assembly relative to a working position adjacent a mould surface such that the charged droplets of mould release agent are drawn towards the mould surface to form a film of mould release agent on the mould surface.

[0038] Preferably, the spray head comprises a charged electrode and a mould release agent atomiser for producing the droplets of mould release agent adjacent to the electrode, wherein the electrode has an electrical potential applied thereto that is sufficient to electrically charge the droplets of mould release agent sprayed adjacent to the electrode.

[0039] Preferably, the positioning sub-assembly comprises an arm operable for moving the spray sub assembly relative to the working position adjacent the mould surface. [0040] Preferably, the positioning sub-assembly comprises a gantry crane with the arm operably coupled thereto, the spray sub assembly being at least partially housed within the arm.

[0041] Preferably, the mould is a hollow pipe mould and the mould surface corresponds to an internal surface of the hollow pipe mould adapted to form the external surface of a pipe moulded therein, the arm being locatable substantially within the hollow pipe mould in the working position.

[0042] Preferably, the spray sub-assembly comprises an actuator for selectively moving the spray head between a retracted position in which the spray head is located inboard of the arm and an extended position in which the spray head is located outboard of the arm.

[0043] Preferably, the actuator is a linear actuator.

[0044] Preferably, the apparatus further comprises a mould release agent reservoir and a supply line for fluidly communicating mould release agent from reservoir to the spray head.

[0045] Preferably, the apparatus further comprises a pump disposed in line within the supply line.

[0046] Preferably, the apparatus further comprises a pump controller for controlling the pump to selectively pump mould release agent from the reservoir.

[0047] Preferably, the apparatus further comprises at least one valve disposed in line within the supply line downstream of the pump for selectively preventing or allowing mould release agent to be supplied from the reservoir to the spray head.

[0048] Preferably, the apparatus further comprises a valve controller for selectively opening or closing the valve to selectively allow mould release agent to be supplied to the spray head.

[0049] Preferably, the apparatus further comprises a sensor for sensing a position of the spray head relative to the mould.

[0050] Preferably, the apparatus further comprises a control means for controlling the supply of mould release agent to the spray head in response to the spray head being located in the working position.

[0051] Preferably, the atomiser includes a rotary atomiser nozzle and a rotary drive motor operably coupled to the rotary atomiser nozzle to rotate the rotary atomiser nozzle about a central axis to generate droplets of mould release agent adjacent to the electrode.

[0052] Preferably, the atomiser includes a rotary atomiser nozzle and an air compressor in fluid communication with the rotary atomiser nozzle, the rotary atomiser nozzle being configured to rotate about a central axis in response to compressed air incident on the rotary atomiser nozzle to generate droplets of mould release agent adjacent to the electrode.

[0053] According to a third aspect of the present invention, there is provided a method of forming a moulded cementitious product such as a cementitious pipe, the method comprising the steps of:

[0054] providing a mould including a mould surface corresponding to an external surface of the moulded cementitious product;

[0055] applying a mould release agent to the mould surface including the steps of: a) atomizing a liquid mould release agent into droplets;

b) electrically charging the droplets, and

c) spraying the charged droplets in a direction of the mould surface to thereby provide a film of mould release agent on the mould surface,

[0056] placing cementitious material in the mould; and

[0057] removing the moulded cementitious product from within the mould after the cementitious material has at least partially cured.

[0058] Preferably, the method further includes providing a mould release agent including a mixture of a mould release oil containing an additive for allowing the mould release agent to be ionised and thereby electrically charged.

[0059] Preferably, applying a mould release agent to the mould surface includes moving an arm comprising an electrostatic spray head relative to the mould surface.

[0060] Preferably, removing the moulded cementitious product from within the mould includes moving the arm relative to the mould to support the moulded cementitious product and withdrawing the arm and the moulded cementitious product supported thereon from the mould. [0061] Preferably, the step of applying the mould release agent to the mould surface occurs as the arm is withdrawn from the mould with the moulded cementitious product supported thereon.

[0062] Preferably, the spray head is retracted with the spray head located substantially inboard within the arm as it is moved into the mould and is extended outboard of the arm as the arm is withdrawn from the mould.

[0063] Other aspects of the invention are also disclosed.

[0064] Brief Description of the Drawings

[0065] Notwithstanding any other forms which may fall within the scope of the present invention, a preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which :

[0066] Fig. 1 shows a schematic representation of an apparatus for applying a mould release agent to a mould surface in accordance with a preferred embodiment of the present invention;

[0067] Fig. 2 shows (i) an isometric view, (ii) a sectional side view and (iii) a bottom view of a spray sub assembly of the apparatus of Fig. 1 ;

[0068] Fig. 3 shows isometric views of the spray sub assembly of Fig. 2 in (i) an extended position, and (ii) a retracted position;

[0069] Fig. 4 shows an isometric view (in exploded form) of the spray sub assembly of Fig. 2; and

[0070] Fig. 5 shows a schematic representation of a method for applying a mould release agent to a mould surface according to another preferred embodiment of the present invention.

[0071] Detailed Description of Specific Embodiments

[0072] It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features.

[0073] The present invention is predicated on the finding of an apparatus and a method for applying a mould release agent to a mould surface. The method provides a convenient means by which to apply a thin film of electrostatically charged droplets of mould release agent or oil to a surface of a grounded (electrically) mould in a quick and efficient manner, thereby realising an accurate distribution of mould release agent over the surface of the grounded mould, while limiting overspray and subsequent wastage of the mould release agent, thereby making the workplace environment more hospitable for those involved.

[0074] As shown in Fig. 1 there is provided an apparatus 10 for applying a mould release agent to a mould surface according to a preferred embodiment of the present invention.

[0075] In its simplest form, the apparatus 10 comprises a spray sub-assembly 20 having an electrostatic spray head for producing a spray of negatively charged droplets of mould release agent, and a positioning sub-assembly 30 for selectively moving the spray sub-assembly 20 between a rest position, in which the spray head is located away from a mould to be sprayed, and a working position located adjacent to the mould, which is grounded to attract the negatively charged droplets of mould release agent when sprayed in the direction of the grounded mould to form a film of mould release agent on the mould surface.

[0076] It will become apparent from the description below that the working position of the spray sub-assembly 20 is not limited to simply being a static working position, in which mould release agent is sprayed while the spray head is stationary. Rather, the spray head may also apply mould release agent to the mould surface in a dynamic fashion such that the working position can be considered as a dynamic working position.

[0077] As shown in Fig. 1 , the spray head takes the form of an electrostatic spray head 22, comprising an electrode (not shown), an atomising device in the form of a rotary atomiser nozzle 24 or bell cup for forming and spraying droplets of mould release agent adjacent to the electrode, and a high voltage gun 25 mounted to a rear end portion of the spray head 22. The high voltage gun 25 is operably connected to a high voltage power supply 66 (housed within a cabinet 70) via a high voltage cable 67 for charging the electrode to an electrical potential of a magnitude sufficient to electrically charge the droplets of mould release agent sprayed adjacent thereto. The spray sub assembly 20 further comprises a rotary drive motor (not shown) operably coupled to the rotary atomiser nozzle 24 to rotate the rotary atomiser nozzle 24 about a central axis.

[0078] The spray head 22 uses the centrifugal force of the rotating atomiser 24 to drive the mould release agent toward the outer surface of the bell cup where primarily electrostatic forces produced by the electrode cause internal repulsion of the thinly sheeted film of mould release agent formed on the bell cup surface such that the charged mould release agent, which is now attracted to the grounded mould surface, breaks free of the bell cup surface into small atomized droplets, which are directed toward the surface of the grounded mould.

[0079] In a preferred form, but not limited thereto, the positioning sub-assembly 30 takes the form of a gantry crane comprising a universal beam 52 and a gantry arm 56 suspended below and operably coupled to the universal beam 52 by virtue of arms 54A, 54B. While not shown in Fig. 1 , it will be appreciated by those skilled in the relevant art that the gantry arm 56 is able to move relative to the universal beam 52, either manually or automatically, by conventional means. In this embodiment, and as shown in Fig. 1 , the movement of the gantry arm 56 is controlled by an electrical motor 60 that is operably connected to a control unit 65 (housed in the cabinet 70) via a control line 75. The gantry arm 56 is a generally elongate hollow body that is configured to house the spray sub assembly 20. Mounted at one end of the gantry arm 56 is a shroud 58. The shroud 58 comprises an opening 58A which is large enough to allow the rotary atomiser nozzle 24 of the spray head 22 to pass substantially therethrough.

[0080] As shown in Fig. 3, the spray head 22 is configured to be selectively transitioned between a retracted position (Fig. 3 (ii)), in which the spray head 22 is located inboard of the gantry arm 56, and an extended position (Fig. 3(i)), in which the spray head 22, and in particular, the rotary atomiser nozzle 24 extend externally from the shroud opening 58A at the end of the gantry arm 56 to locate outboard of the gantry arm 56. To this end, and as shown in Figs. 3 and 4, the spray head 22 is mounted to a support plate 26 by way of a U-shaped bracket 30A having threaded end portions for threaded engagement with a corresponding threaded bolt.

[0081] Referring specifically to Figs. 2 and 4, the spray sub assembly 20 comprises an elongate mounting bracket 29 having a generally C-shaped cross-section as defined by a generally rectangular shaped top plate 29A, and two side plates 29B, 29C extending downward from the longer edges of the top plate 29A. Mounted on a lower portion of the inner surface of each side plate 29B, 29C, and generally part way along the length of said side plates 29B, 29C, is an inwardly facing locating channel 27A, 27B. The support plate 26 comprises two pairs of nodules or bars 26C disposed on either side and at either end of the mounting plate 26, with each pair being configured to locate within a corresponding one of the two locating channels 27A, 27B to enable the support plate 26 to slide back and forth relative to the mounting bracket 29, as defined by the length of the locating channels 27A, 27B. The support plate 26 further comprises a pair of opposing flanges 26D, 26E extending generally perpendicularly from the plane of the support plate 26, thereby defining a cavity substantially therebetween for seating the spray head 22.

[0082] Referring specifically to Figs. 1 and 2(iii), the support plate 26 comprises an aperture drilled substantially therethrough for receiving a manifold 40 to operably connect the spray head 22 to a supply line 85 for receiving mould release agent from a mould release agent reservoir 80.

[0083] Referring specifically to Figs. 2 to 4, there is shown a linear actuator 28 mounted to the top plate 29A of the mounting bracket 29 at a rear portion thereof via a pair of U-shaped brackets 30B, 30C, each having threaded end portions for threaded engagement with a corresponding threaded bolt. The actuator 28 comprises a body 28A housing an electrical motor (not shown), which is operably connected via connector 28C to a power supply (not shown) via a cable (not shown) and a piston 28B that is configured to extend and retract from the body 28A of the actuator 28 when a current is applied. The piston 28B is operably coupled to the support plate 26 by way of a connection formed between a connector 28D located at the end of the piston 28B and each of the two perpendicular flanges 26D, 26E. In this respect, it will be appreciated that the spray head 22 can be selectively transitioned between the retracted position and the extended position relative to the gantry arm 56 when a current is applied.

[0084] As shown in Figs. 3 and 4, a packing plate 35 is located between the top plate 29A of the mounting bracket 29 and the actuator 28 to protect the actuator 28 from possible damage in use or in transit.

[0085] The spray sub assembly 20 is mounted within the gantry arm 56 by virtue of a plurality of bolts (not shown) through the side plates 29B, 29C of the mounting bracket 29.

[0086] As shown in Fig. 1 , the mould release agent is fluidly communicated from the mould release agent reservoir 80 to the manifold 40 of the spray head 22 via the supply line 85. The flow of mould release agent to the spray head 22 is controlled by a pump 90 disposed in line within the supply line 85, which is configurable between an ON status and an OFF status as required.

[0087] While not shown in Fig. 1 , it will be appreciated by those skilled in the relevant art that the apparatus 10 further comprises a pump controller (not shown) for controlling the pump 90 between the ON and OFF status as required in order to selectively pump mould release agent from the reservoir 80. A pressure regulator 92 is disposed in line within the supply line 85 and located slightly downstream of the pump 90 in order to regulate the pressure within the supply line 85 so as to maintain a constant flow of mould release agent.

[0088] As shown in Fig. 1 , the apparatus 10 further comprises two valves 94A, 94B disposed in line within the supply line 85. The first valve 94A is located at the reservoir 80 to act as an isolation valve to stem the flow of mould release agent from the reservoir 80 as required. The second valve 94B is a solenoid valve positioned downstream of the pump 90 and located within the body of the gantry arm 56.

[0089] While not shown in Fig. 1 , it will be appreciated by those skilled in the relevant art that the solenoid valve 94B is operably connected to a valve controller (not shown) for selectively opening and closing the solenoid valve 94B to selectively allow mould release agent to be supplied to the spray head 22. By virtue of this arrangement, it will be appreciated that mould release agent will only flow to the spray head 22 when it is required to be sprayed onto the surface of the mould.

[0090] While not shown in any of the figures, it will be appreciated by those skilled in the relevant art that in the case of an automated system, the apparatus 10 further comprises a controller (not shown) for controlling the supply of mould release agent to the spray head 22 in response to the spray head 22 being located in the working position and one or more sensors (not shown) in operable communication with the controller.

[0091] In a preferred form, the controller takes the form of a programmable logic control (PLC) controller, one of the sensors takes the form of a travel limit switch (not shown) configured to sense the position of the spray head 22 relative to the mould to determine whether the spray sub-assembly 20 and thus the spray head 22, is in the working position, and another of the sensors takes the form of a proximity switch configured to activate and deactivate the spray head 22 when the spray head 22 is in the working position, and thus within the confines of the target area, so as to control the electrostatic spray of charged droplets of mould release agent toward the surface of the grounded mould.

[0092] It will be appreciated by those skilled in the relevant art that the apparatus 10 may further comprise an additional travel limit switch (not shown) mounted, for example, within the body of the gantry arm 56, which is configured to sense the position of the spray head 22 relative to the gantry arm 56 as it is transitioned between the retracted position and the extended position, For instance, in use, when the spray head assembly 20, and thus the spray head 22, is in the working position, as determined by the travel limit switch, and just prior to activating the spray head 22 to produce the electrostatic spray, the controller sends a signal to the electric motor of the linear actuator 28 to transition the spray head 22 from the retracted position within the body of the gantry arm 56 to the extended position such that the rotary atomiser nozzle 24 is outside of the opening 58A of the shroud 58 in readiness for producing the electrostatic spray of charged droplets of mould release agent.

[0093] In addition, the valve controller for controlling the solenoid valve 94B may be a standalone controller operably coupled to the programmable logic control (PLC) controller described above, or may simply be the PLC controller itself. In the latter case, it will be appreciated by those skilled in the relevant art that the solenoid valve 94B is thus not simply limited to being in a fully open or fully closed position, but may instead be a valve that allows for a variable flow under full control of the PLC controller.

[0094] In essence, it will be appreciated by those skilled in the relevant art that a desirable outcome of the PLC logic is to control the flow of electrostatically sprayed droplets of mould release agent relative to the surface area of differently dimensioned moulds while maintaining functional extraction speeds.

[0095] Method

[0096] According to another preferred embodiment of the present invention, there is provided a method 100 of applying a mould release agent to a surface of a mould using the apparatus 10 described above.

[0097] As shown in Fig. 5, and for the purpose of illustrating the method 100, the following steps will be described in terms of applying a mould release agent onto an internal surface 205 of a grounded, generally cylindrical hollow pipe mould 200 for preparing cementitious pipes 300.

[0098] In addition, and referring specifically to Fig. 5(i), it will be appreciated by those skilled in the relevant art that the method 100 is not simply limited to forming a film of mould release agent on the internal surface 205 of the pipe mould 200 when the pipe mould 200 is empty. For instance, the method 100 also allows for situations in which a prefabricated cementitious pipe 300 already exists within the concrete pipe mould 200, and that a film of mould release agent may be applied to the internal surface 205 of the pipe mould 200 as the cementitious pipe 300 is withdrawn therefrom.

[0099] The method 100 comprises the following steps. [00100] According to a first step, as shown in Fig. 5(i), the gantry arm 56 is moved in a generally horizontal direction (as indicated by the arrow) by the gantry crane 52 (either manually or automatically) from a rest position in a direction toward the grounded pipe mould 200, whereupon the gantry arm 56, and the spray sub-assembly 20 housed therein, enters an opening 210 of the pipe mould 200 so as to be substantially located therein in a working position.

[00101] According to a second step, as shown in Fig. 5(ii), once inside the pipe mould 200, the gantry arm 56 is lifted by the gantry crane 52 such that the gantry arm 56 engages with an underside of the prefabricated concrete pipe 300. The concrete pipe 300 is then attached to the gantry arm 56 by virtue of attachment means (not shown).

[00102] The spray sub assembly 20 is then activated by the power supply such that the actuator piston 28B causes the spray head 22 to transition from the retracted position within the gantry arm 56 to the extended position such that the rotary atomiser nozzle 24 protrudes from the opening 56A of the shroud 56.

[00103] According to a third step, liquid mould release agent that has been supplied from the reservoir 80 under pressure from the pump 90 to the spray head 22 via the manifold 40, is driven by the centrifugal force associated with the rotating atomizer nozzle 24 to the outer surface of the rotating atomizer nozzle 24 where primarily electrostatic forces produced by the electrode cause internal repulsion of the thinly sheeted film of mould release agent formed on the bell cup surface to electrostatically charge the mould release agent.

[00104] It will be appreciated by those skilled in the relevant art that the step of electrostatically charging the droplets of mould release agent ionizes the droplets of mould release agent formed.

[00105] Good results have been obtained when droplets of native mould release agent such as a mineral oil, petroleum distillate or organic oil, or combination thereof, are charged by the electrode that has itself been charged by the high voltage gun 25 to an adequate electrical potential.

[00106] Thus, as shown in Fig. 5(iii), as the gantry arm 56 is withdrawn from the pipe mould 200 by the gantry crane 52 at a controlled rate, the attached concrete pipe 300 is simultaneously withdrawn thereby exposing the internal surface 205 of the grounded pipe mould 200. At the same time, the charged mould release agent, which is attracted to the internal surface 205 of the grounded pipe mould 200, breaks free of the bell cup surface thereby forming small charged atomized droplets, which are directed toward the internal surface 205 of the grounded pipe mould 200.

[00107] It will be appreciated by those skilled in the relevant art that the deposition of a uniformly thin film of mould release agent on the internal surface 205 of the pipe mould 200 is key to reducing "mould stick" and is dependent on several factors including the viscosity of the mould release agent, the degree and uniformity of charge on both the droplets of mould release agent and the internal surface 205, as well as the velocity and angle of deposition, the speed of the gantry arm 56 as it is withdrawn from the pipe mould while electrostatically spraying the charged droplets of mould release agent, and the size of the mould and thus the surface area to be sprayed.

[00108] In one embodiment, the charged droplets of mould release agent may be sprayed along a trajectory to impinge against the internal surface 205 of the grounded pipe mould 200.

[00109] Good results have been obtained when the charged droplets of native mould release agent such as a mineral oil, petroleum distillate or organic oil, or combination thereof, are sprayed at an angle of greater than 90 degrees relative to a plane of the internal surface 205.

[00110] Good results have been obtained for spray distances between the spray head 22 and the internal surface 205 of the grounded pipe mould 200 in the range of about 150 mm to about 600 mm, when the charged droplets of mould release agent are sprayed at a velocity preferably in a range of between 2 metres per second and 5 metres per second to cause the droplets to form a uniform distribution over the internal surface 205 of the grounded pipe mould 200, more preferably in a range of between 3 metres per second and 4.5 metres per second.

[00111] It will be appreciated by those skilled in the relevant art that the speed at which the gantry arm 56, and thus the spray head 22, is withdrawn from the pipe mould 200 whilst spraying mould release agent is important for depositing a uniformly thin film of mould release agent on the internal surface 205 of the grounded pipe mould 200.

[00112] Good results have been obtained for spray distances between the spray head 22 and the internal surface 205 of the grounded pipe mould 200 in the range of about 150 mm to about 600 mm when the gantry arm 56 is withdrawn from the pipe mould whilst spraying at a speed preferably in a range of between 2 metres per second and 5 metres per second, more preferably in a range of between 3 metres per second and 4.5 metres per second.

[00113] In one embodiment, the viscosity of the mould release agent may be reduced simply by heating the mould release agent to a desirable temperature using a heater (not shown), and then delivering the heated mould release agent to the rotary atomiser nozzle 24. It will be appreciated by those skilled in the relevant art that the temperature used to heat the mould release agent will largely depend on the type of mould release agent used.

[00114] Other factors may also influence the deposition of a uniformly thin film of mould release agent on the internal surface 205 of the pipe mould 200. For instance, in one embodiment, the mould release agent may be treated with a suitable additive to increase the conductivity of the mould release agent so as to assist in ionizing the droplets of mould release agent.

[00115] In essence, it will be appreciated by those skilled in the relevant art that the volume of mould release agent needed to form a uniformly thin film on the internal surface 205 of the pipe mould 200 will need to be calibrated according to various factors including those highlighted above.

[00116] According to a fourth step, and as shown in Fig. 5(iv), the cementitious pipe 300 has been fully withdrawn from the grounded pipe mould 200 and the internal surface 205 of the pipe mould 200 has now been completely sprayed with a uniformly thin film of mould release agent.

[00117] The rotary atomiser nozzle 24 is subsequently deactivated and the actuator piston 28B is then activated to cause the spray head 22 to transition from the extended position to the retracted position within the gantry arm 56 for protection.

[00118] It will be appreciated by those skilled in the relevant art that the method 100 is not limited to simply applying a uniformly thin film of mould release agent on the internal surface 205 of the pipe mould 200 as the gantry arm 56 is being withdrawn from the pipe mould 200. For instance, the pipe mould 200 may be empty, that is, no cementitious pipe 300, such that the mould release agent may be applied by the spray head 22 from the opening 210 of the pipe mould 200 to the opposite end of the pipe mould 200.

[00119] In either case, once a film of mould release agent has been applied to the internal surface 205 of the pipe mould 200, a generally cylindrical cage (not shown) of a smaller diameter than the pipe mould 200 but of an equivalent length, is then loaded into the pipe mould 200 so as to define a cavity between the internal surface 205 of the pipe mould 200 and an external surface of the cage. The opening 210 of the pipe mould 200 is sealed, and then a cementitious material of low moisture is loaded into the cavity. Once full, the pipe mould 200 is fully sealed and then mounted onto a mandrel where it is then spun at a suitable speed to compact the cementitious material. The pipe mould 200 is then placed inside a steam chamber at controlled temperature and moisture settings to partially cure the compacted cementitious material. The resulting partially cured cementitious pipe 300 is then ready for withdrawing from the pipe mould 200 and a further film of mould release agent applied to the internal surface 205 of the pipe mould 200 according to the above method 100 in readiness for forming the next cementitious pipe 300.

[00120] Advantages

[00121] An apparatus 10 for applying a film of mould release agent on a mould surface of the kind described above, and the method for achieving this, provides a convenient means by which to apply a thin film of electrostatically charged droplets of mould release agent to the surface of a grounded mould in a quick and efficient manner. This not only realises an accurate distribution of mould release agent over the surface of the mould to reduce "mould stick", it also limits overspray and subsequently avoids a significant wastage of the mould release agent in the process, thereby realising a more cost effective process compared to traditional spray methods, as well as making the workplace environment more hospitable for those involved, thereby satisfying occupational health and safety (OH&S) requirements.

[00122] Other Embodiments

[00123] In other embodiments, it will be appreciated that the spray sub assembly 20 is not limited to using a rotary drive motor to rotate the rotary atomiser nozzle 24 about the central axis to generate droplets of mould release agent adjacent to the electrode. For example, the spray sub assembly 20 may instead comprise an air compressor (not shown), which is in fluid communication with the rotary atomiser nozzle 24 to cause the rotary atomiser nozzle 24 to rotate about the central axis in response to receiving air produced by the air compressor.

[00124] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. [00125] Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group thereof.

[00126] Industrial Applicability

[00127] It is apparent from the above, that the arrangements described are applicable to the construction industry.

Claims

Claims The claims defining the invention are as follows:

1. A method of applying a mould release agent to a mould surface, the method comprising the steps of:

- atomizing a liquid mould release agent into droplets;

- electrically charging the droplets; and

- spraying the charged droplets in a direction of a mould surface to form a film of mould release agent on the mould surface.

2. A method according to claim 1 , further including providing a mould release agent including a mixture of a mould release oil containing an additive for allowing the mould release agent to be ionised and thereby electrically charged.

3. A method according to claim 2, wherein the step of electrically charging the droplets includes:

- moving the droplets of mould release agent relative to at least one charged electrode.

4. A method according to claim 1 , further including, before the step of atomizing a liquid mould release agent to form droplets, the step of:

- moving an arm comprising an electrostatic spray head relative to a working position located adjacent to the mould surface.

5. A method according to claim 4, wherein the mould is a hollow pipe mould and the mould surface is an internal surface of the hollow pipe mould, the arm being configured to locate substantially within the hollow pipe mould in the working position.

6. A method according to claim 4, including:

- moving the spray head between a retracted position in which the spray head is located substantially inboard within the arm and an extended position in which the spray head extends outboard from one end of the arm when the arm is located at the working position.

7. A method according to claim 4, including: - moving the arm relative to the mould while spraying the charged droplets in a direction of the mould surface at a speed in a range of between about 2 metres per second and about 5 metres per second.

8. A method according to claim 1 , wherein the step of spraying the charged droplets includes:

- spraying the charged droplets along a trajectory incident on the mould surface at an angle of greater than about 90 degrees.

9. A method according to claim 1 , wherein the step of spraying the charged droplets includes:

spraying the charged droplets at a velocity in a range of between about 2 metres per second and about 5 metres per second.

10. A method according to claim 1 , wherein the step of atomizing the liquid mould release agent to form droplets further includes the steps of:

heating the mould release agent; and

- delivering the heated mould release agent through an atomising device.

11. An apparatus for applying a mould release agent to a mould surface, the apparatus comprising:

- a spray sub-assembly having a spray head for producing a spray of charged droplets of mould release agent; and

- a positioning sub-assembly for moving the spray sub-assembly relative to a working position adjacent a mould surface such that the charged droplets of mould release agent are drawn towards the mould surface to form a film of mould release agent on the mould surface.

12. An apparatus according to claim 11 , wherein the spray head comprises a charged electrode and a mould release agent atomiser for producing the droplets of mould release agent adjacent to the electrode, wherein the electrode has an electrical potential applied thereto that is sufficient to electrically charge the droplets of mould release agent sprayed adjacent to the electrode.

13. An apparatus according to claim 11 , wherein the positioning sub-assembly comprises an arm operable for moving the spray sub-assembly relative to the working position adjacent the mould surface.

14. An apparatus according to claim 13, wherein the positioning sub-assembly comprises a gantry crane with the arm operably coupled thereto, the spray sub assembly being at least partially housed within the arm.

15. An apparatus according to claim 13 or 14, wherein the mould is a hollow pipe mould and the mould surface is an internal surface of the mould adapted to form the external surface of a pipe moulded therein, the arm being locatable substantially within the hollow pipe mould in the working position.

16. An apparatus according to claim 13, wherein the spray sub-assembly comprises an actuator for selectively moving the spray head between a retracted position in which the spray head is located inboard of the arm and an extended position in which the spray head is located outboard of the arm.

17. An apparatus according to claim 16, wherein the actuator is a linear actuator.

18. An apparatus according to claim 1 1 , further comprising a mould release agent reservoir and a supply line for fluidly communicating mould release agent from the reservoir to the spray head.

19. An apparatus according to claim 18, further including a pump disposed in line with the supply line.

20. An apparatus according to claim 19, further including a pump controller for controlling the pump to selectively pump mould release agent from the reservoir.

21. An apparatus according to claim 19 or 20, further including at least one valve disposed in line with the supply line downstream of the pump for selectively preventing or allowing mould release agent to be supplied from the reservoir to the spray head.

22. An apparatus according to claim 21 , further including a valve controller for selectively opening or closing the valve to selectively allow mould release agent to be supplied to the spray head.

23. An apparatus according to any one of claims 1 1 to 22, further including a sensor for sensing a position of the spray head relative to the mould.

24. An apparatus according to any one of claims 1 1 to 23, further including a control means for controlling the supply of mould release agent to the spray head in response to the spray head being located in the working position.

25. An apparatus according to any one of claims 1 1 to 24, wherein the atomiser includes a rotary atomiser nozzle and a rotary drive motor operably coupled to the rotary atomiser nozzle to rotate the rotary atomiser nozzle about a central axis to generate droplets of mould release agent adjacent to the electrode.

26. An apparatus according to any one of claims 1 1 to 24, wherein the atomiser includes a rotary atomiser nozzle and an air compressor in fluid communication with the rotary atomiser nozzle, the rotary atomiser nozzle being configured to rotate about a central axis in response to compressed air incident on the rotary atomiser nozzle to generate droplets of mould release agent adjacent to the electrode.

27. A method of forming a moulded cementitious product such as a cementitious pipe, the method comprising the steps of:

- providing a mould including a mould surface corresponding to an external surface of the moulded cementitious product;

- applying a mould release agent to the mould surface including the steps of:

a) atomizing a liquid mould release agent into droplets;

b) electrically charging the droplets, and

- placing cementitious material in the mould; and

- removing the moulded cementitious product from within the mould after the cementitious material has at least partially cured.

28. A method according to claim 27, further including providing a mould release agent including a mixture of a mould release oil containing an additive for allowing the mould release agent to be ionised and thereby electrically charged.

29. A method according to claim 27, wherein applying a mould release agent to the mould surface includes moving an arm comprising an electrostatic spray head relative to the mould surface.

30. A method according to claim 29, wherein removing the moulded cementitious product from within the mould includes moving the arm relative to the mould to support the moulded cementitious product and withdrawing the arm and the moulded cementitious product supported thereon from the mould.

31. A method according to claim 30, wherein the step of applying the mould release agent to the mould surface occurs as the arm is withdrawn from the mould with the moulded cementitious product supported thereon.

32. A method according to claim 30 or claim 31 , wherein the spray head is retracted with the spray head located substantially inboard within the arm as it is moved into the mould and is extended outboard of the arm as the arm is withdrawn from the mould.