THIS INVENTION relates to applying coatings to tubing interiors, and it has more particular reference to a novel method of and/or apparatus for applying coatings in instances requiring the lining of relatively small tubes or pipes with cured powder coatings, though it is not exclusively limited to small diameters.

BACKGROUND ART

It is common practice to apply a coating to the interior of a tube or pipe so that it can perform its liquid or gas flow function while being protected against corrosion, or for protection against chemicals reacting with the tube, and in particular so that the tube will be suitable for potable water. However, methods and apparatus currently used have failings when dealing with, for example, steel pipes from 12mm to 25mm, while particular difficulties can arise according to the type of coating material which it is desired to apply. Many attempts have been directed at overcoming these problems, and a comprehensive discussion on the prior art is to be found in U.S. Patent Specification No. 3,982,050 for example. However, none of the prior art overcomes satisfactorily the major problems which still exist.

Our present invention has been devised to overcome the aforesaid problems currently encountered in this field, and it has for its principal object the provision of a new method and/or apparatus whereby any powder coating can be applied successfully to tubes of as small a diameter as say 12mm and suitably up to 100mm, but without specific upper limits when engineered further with the appropriate design variations. The invention aims to provide a method and/or apparatus as aforementioned which will handle the applying of a wide range of present or future coatings such as "RILSON NYLON 11" and "BAYER LEVASINT" as well as fusion bonded epoxy and other powder coatings.

Another object of the invention is to provide a

vastly improved form of apparatus for use in applying coating to the tubing interiors, the apparatus being designed to cater for efficient and reliable operation and high output relative to the cost-effective nature thereof. Other objects and advantages of the invention will be apparent from the subsequent descriptions herein, and for convenience of description the word "pipe" will be used herein to embrace all types of tubes or pipes to which the invention is applicable.

DISCLOSURE OF THE INVENTION With the foregoing and other objects in view, the invention resides broadly, according to one aspect, in apparatus for use in applying a coating to the interior of a pipe, said apparatus being of the type having means defining a coating station contained within an oven, means for releasably supporting a selected length of pipe at the coating station rotatably and in horizontal disposition, means for causing rotation of the supported pipe at a predetermined rate of rotation, means whereby there may be drawn through the supported pipe from one end thereof to the other a predetermined quantity of coating powder entrained in a gas stream, and control means whereby oven heat applied to the rotating pipe will cause powder particles deposited on the interior surface of the pipe to be fused or cured to form a continuous lining film, characterised in that the means whereby the coating powder may be drawn through the supported pipe includes a powder supply line connected at one of its ends to an inlet manifold sealably and releasably connectible to the said one or powder-entry end of the pipe while the other end of the powder supply line is connected to a powder container for a fluidised bed thereof, the supply line having inlet means for air constituting said gas stream, means for adjustably varying the powder inlet to the supply line and means for adjustably varying the air inlet to the supply line, while at the other or powder-exit end of the pipe there

is provided an outlet manifold sealably and releasably connectible to the adjacent end of the pipe and having a powder discharge line connected to a vacuum pump and collector means for discharged powder; and further characterised in that the two said manifolds are each mounted to extend through a respective end wall of the oven so that each has a part thereof within the oven to engage the respective end of the pipe and a larger part outside the oven, each manifold having means whereby a cooling medium may be applied thereto so as to be effective for cooling both parts of the respective manifold both inside and outside the oven.

According to one practical embodiment of the aforedescribed invention, each manifold is tubular and elongate for axial alignment with and at the ends of the pipe to be treated, each manifold having an inner powder- carrying tube surrounded by a coaxial cooling jacket, and the means whereby a cooling medium may be applied to each manifold comprises a water inlet tube connected to an outer part of the cooling jacket and a water outlet tube connected to an inner part of the cooling jacket for the purpose of circulating a continuous supply of cooling water constituting the cooling medium.

Preferably in this form of apparatus, each manifold has its powder-carrying tube mounted for rotation in bearings within the respective cooling jacket whereby its inner end may be secured to the pipe for rotation therewith, its outer end being connected to the respective powder line via a split coupling to allow relative rotation in sealed relationship thereto. In that instance, suitably the powder-carrying tube at ^' a position thereon remote from the pipe connection is operatively connected to drive means adapted to be actuated to maintain its rotation in unison with the pipe regardless of the effectiveness of the connection between the end of the pipe and the adjacent or inner end of the powder-carrying tube.

In one practical form of apparatus as abovedescribed, preferably each manifold is mounted on a carriage for movement along frame means towards or away from the pipe substantially on the axis thereof for the purpose of causing engagement with or release from the pipe when the latter is in rotatable but otherwise fixed operative disposition. Suitably motor-actuated screw means are provided for causing advancement or retraction of each carriage and supported manifold, overload switch means being provided to coact with spring-compression means once the respective manifold achieves full engagement with the adjacent pipe end whereby the switch will be triggered to prevent further engagement action of the motor-actuated screw means.

It is further preferred that the carriage of each manifold is provided with height-adjustment means relative to the frame means whereby the height of the manifold may be adjustably varied to cater for assisting axial alignment obtained with different pipes of different diameters when said different pipes have the same mounting height arrangements when being treated. Suitably each manifold is so mounted on its carriage that it may be replaced when desired by a similar manifold of greater length so as to extend further towards the adjacent pipe end and so cater for pipes having lesser distances between ends.

With regard to the oven construction, it is preferred that the coating station is surrounded by or is within said oven having said end walls for mounting the manifolds and of substantially rectangular form, interconnected by substantially vertical longitudinal front and rear side walls and an overhead roof of substantially head height, the means for releasably supporting a selected length of pipe at the coating station rotatably and in horizontal disposition being so arranged that the supported pipe is about midway up the height of the oven and closer to one side wall than the

other. Suitably, the oven has hot air inlet ducts at the roof adjacent one side wall and air collection or retrieval duct means at the base of the oven adjacent the other side wall.

For continuous treatment of a series of pipes of the same predetermined length, the front and rear side walls of the oven have horizontal longitudinal slots to act as entry and exit slots respectively for pipes in parallel relationship to the operative horizontal disposition of each pipe being treated when the pipe is secured between manifolds, flexible heat-resistant cloth being arranged to depend within the oven at said slots to minimise heat loss through said slots while being flexible enough to move clear as a pipe is moved therethrough. Preferably also the entry slot has guide means for receiving pipes sequentially and in parallelism from a wheeled table or trolley when the latter is placed external of the oven, said guide means leading down within the oven for gravitational feed of pipes to an upwardly and inwardly inclined conveyor assembly for incremental advance in spaced series for delivery to the treatment position horizontally between said manifolds. Suitably, the exit slot is below the treatment position for each pipe, the latter being fed therefrom by an exit conveyor assembly operative to discharge treated pipes in series, pipe removal arm means being provided and arranged to be actuated to remove successive treated pipes for collection and discharge via the exit conveyor assembly and exit slot after each pipe has been subjected to predetermined treatment at the coating station.

According to another preferred feature, pipe-contact rollers are provided for supporting and rotating a pipe at the coating station, one set of rollers being fixed on a drive shaft adapted to be rotated through drive chain means by external motor controls, the other set acting as idlers and co-operating with respective driven rollers to support the pipe therebetween, there being a parallel

overhead shaft carrying clamping rollers adapted to be brought into engagement with the pipe being treated upon actuation of an external actuation means for the clamping rollers. Preferably, each pair of co-acting pipe-contact rollers forms part of a mounting assembly having a third axis and bearing parallel to those of the said pair whereby a wider spacing of axes is selectable to cater for pipes of a larger or maximum size to be treated. Preferably also, said mounting assembly has means whereby it may be secured to a longitudinal mounting beam within the oven at a selected one of a plurality of designated locations to cater for pipes of different lengths.

It will be appreciated that the invention therefore provides apparatus for use in applying a coating to the interior of a pipe as aforedescribed wherein the oven and its heating means are so made and arranged as to be capable of providing an operating temperature between 240°C and 280°C as required. A further feature is that the pipe holding and rotating means is so made and arranged as to be operable with pipes of diameters as small as 12mm or as large as 65mm, by way of stating a typical range.

The invention also embraces, according to another aspect thereof, a method of applying a coating to the interior of a pipe, comprising the steps of arranging in horizontal disposition at a coating station a length of pipe cleaned to the specification for treatment laid down by the supplier of the coating powder to be applied; providing a heated atmosphere or oven about said coating station to afford preheating of the pipe to specified temperature; causing rotation of said pipe at said coating station at a substantially constant predetermined rate of rotation; causing said pipe length to receive coating powder drawn therethrough from a receiving end by suction means at a delivery end; curing the powder and removing the length of the pipe from the oven at the coating station. Preferably said method includes

securing the ends of the pipe in releasably sealed manner in a powder flow line, the full length of pipe being heat treated for powder curing by connection of its ends via heat resistant sealing means to constantly cooled manifold means, the supply end of the powder flow line being connected via a powder inlet adjustment in a powder fluidised bed, with air inlet adjustment interposed in the powder inlet tube, while a vacuum pump is provided at the outlet end.

Other features of the invention will be hereinafter apparent from the ensuing drawings and descriptions. BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings wherein:-

Fig. 1 is a perspective view of apparatus in accordance with one practical embodiment of the invention, taken from the rear or pipe-exit side, the powder-entry end being at the left in the drawing and the vacuum pump at the right of the drawing at the suction end of the apparatus;

Fig. 2 is a further perspective view of the apparatus of Fig. 1 but showing the opposite side which is the front or pipe-entry side, and with the powder-entry end of the apparatus at the right in the drawing;

Fig. 3 shows diagrammatically in sectional side elevation the basic components of the apparatus, corresponding to Fig. 1 but with design parts omitted;

Fig. 4 shows diagrammatically in sectional end view the components for feeding pipes in at the pipe-entry side of the apparatus, at the left of the drawing, and for discharging treated pipes at the pipe-exit side;

Fig. 5 shows in fragmentary perspective view the pipe-supporting and drive arrangements at the

powder-entry end of the apparatus, including the inner end of the inlet manifold and an overhead pipe clamping roller;

Fig. 6 is similar to Fig. 5 but showing the powder-exit end of the pipe, as well as the outlet manifold;

Fig. 7 is a diagrammatic sectional side elevation, showing the manifold at the powder-entry end of the apparatus at the right side of the drawing;

Fig. 8 is a fragmentary plan view corresponding to Fig. 7 but showing the carriage for mounting the manifold, as well as the motor-operated screw- threaded advancement and retraction means for the manifold relative to the adjacent pipe end;

Fig. 9 corresponds to Fig. 8 but showing the clamping position of the manifold to which it has been moved by the screw-threaded means so as to trigger a switch to cause cessation of advancement;

Fig. 10 shows in fragmentary perspective view the components of Figs. 8 and 9, the carriage having a manifold of a first length thereon, while illustrated thereabove is a manifold of greater length to be substituted to cater for shorter pipes, and

Fig. 11 shows in fragmentary perspective view the selective mounting of a roller-mounting assembly at different locations to cater for shorter pipes, utilising telescopically-adjustable mounting or drive shafts.

As shown in the drawings, the coating apparatus indicated generally at 10 has a coating station 11 contained within an oven 12, a selected length of pipe 13 at the coating station 11 being mounted for rotation in a horizontal disposition and being supported by support means indicated generally at 14. Means indicated generally at 15 are provided for causing rotation of the

pipe 13 at a predetermined rate. The apparatus employs means whereby there may be drawn through the supported pipe 13 from one end thereof to the other a predetermined quantity of coating powder entrained in a gas stream, it being understood that this constitutes an "air or inert gas diluted powdery mixture" from which particles are deposited on the inner surface of the pipe and fused or cured to form a continuous lining film. Control means of basic types are provided in conjunction with electric drive motors as later described to ensure that operations are automatic where necessary and to the extent necessary for smooth and reliable operation.

The means whereby the coating powder 20 may be drawn through the supported pipe 13 includes a powder supply line 16 connected at its downstream end to an inlet manifold 17 sealably and releasably connectible to the powder-entry end 18 of the pipe 13 while the other or upstream end of the powder supply line 16 is connected to a powder container or hopper 19 for a fluidised bed thereof shown at 20a, said supply line 16 having air inlet means provided with adjustment means 21 for adjustably varying the air inlet to the supply line for said gas stream purposes. Adjustment means 22 are also provided for adjustably varying the powder inlet to the supply line 16. At the other or powder-exit end 23 of the pipe 13, there is provided an outlet manifold 24 sealably and releasably connectible to said end 23 of the pipe 13 and having a powder discharge line 25 connected to a vacuum pump 26 and collector means for discharged powder, a suitable cyclone being indicated at 27.

The two manifolds 17 and 24 are of elongate tubular form and so mounted as to extend through respective end walls 28 and 29 of the oven 12 so that each has an inner part 30 within the oven 12 to engage the respective end of the pipe 13 and a larger part 31 outside the oven. Each manifold 17 and 24 has water circulation pipes for cooling both parts ^* 30 and 31 of each manifold as later

described, the inlet pipes being indicated at 32 and the outlet pipes at 33. As shown best in Fig. 7, each manifold 17 or 24 is tubular and elongate for axial alignment with the axis of the tube 13 and connectable at the ends thereof, the illustrated manifold 17 being that at the entry end 18 of the pipe 13, there being shown an inner powder-carrying tube 34 surrounded by a coaxial cooling jacket 35, said water inlet pipe 32 being connected to an outer part of the cooling jacket 35 as illustrated, while the water outlet pipe 33 is connected to an inner part of the cooling jacket 35 so that a continuous supply of cooling water 36 may be circulated through the cooling jacket 35.

It will be seen from Fig. 7 that the powder-carrying tube 34 is mounted for rotation in bearings 37 whereby its inner end 38 may be secured to the pipe 13 for rotation therewith, being flared for wedging engagement thereover, the other or outer end portion 39 being connected to the powder line 16 via a split coupling 40 to allow relative rotation of the two coupling parts in sealed relationship. Although not shown in the drawings, we prefer to provide on the powder-carrying tube 34 at a position (such as that indicated at 41) remote from the end engaging the pipe 13 suitable motor-driven drive means for causing rotation of the tube 34 in unison with the pipe 13 as a positive drive regardless of the effectiveness of the connection of the pipe 13 to the adjacent end of tube 34. It will be appreciated that the bearings 37 in Fig. 7 are water resistant sealing bearings, while the inner end 38 of the tube 34 is suitably designed in any other respects to ensure that it attains sealed relationship with the powder-entry end 18 of the pipe 13.

As shown in Figs. 8, 9 and 10, each manifold 17 or 24, such as the inlet manifold 17 illustrated, is mounted on a carriage 42 for movement along horizontal frame means 43 towards or away from the pipe 13 substantially

on the axis of the pipe 13 for engagement or release purposes when the pipe is mounted rotatably but is otherwise fixed and not axially slidable. Mounted on the frame means 43 is a drive motor 44 driving through a dog clutch 54 to rotate a threaded screw 45 journalled in bearings 46. Of the apertures through which the screw 45 passes, only that of trigger-carrying block 47 in the carriage box 48 is tapped so that rotation of the screw 45 in the operative direction advances the block 47 to advance the carriage 42 on its wheels 49 and advance the supported manifold 17 to be urged against the end of the pipe 13 and so clamp the same. The compression spring 50 becomes compressed as illustrated in Fig. 9 to take up the load, overload being prevented by the trigger 51 on the trigger-carrying block 47 triggering the switch 52 which causes cessation of the motor-actuated screw means. The dotted lines at 53 in Fig. 9 indicate backing off of the trigger-carrying block 47 marginally after operation of the switch 52 so that the pipe 13 is clamped with the correct load and with only partial compression of the spring 50. Comparison of Figs. 8 and 9 will show that all components have been advanced to the left in Fig. 9 except for the frame member 43 and its fixed connections, namely the motor 44, bearings 46 and the rotatable but otherwise stationery threaded screw 45.

Also as shown in Fig. 10, the carriage 42 of the manifold 17 has at inner and outer locations adjustment screws 55 adapted to be adjusted to vary the height of the manifold 17 above the frame means and member 43 with which the carriage wheels 49 engage, thus ensuring that axial alignment can be obtained with different pipes of different diameters. As illustrated, the manifold 17 is so mounted on its carriage 42 that it may be replaced when desired by a similar manifold of greater length to cater for the handling of shorter pipes. According to the diameters of the pipes 13, the manifold 17 can also be replaced by one having a different size of end opening

to the powder-carrying tube 34. Fig. 10 also shows in perspective view the carriage box 48 and other components shown in plan view in Figs. 8 and 9.

Reverting to Figs. 1 to 4 in particular relative to the coating station 11 in the oven 12, the latter has its end wall 28 for mounting the inlet manifold 17 and its other end wall 29 for mounting the outlet manifold 24, the manifolds being secured to fire resistant membranes as indicated at 56 in Fig. 2, while the walls 28 and 29 are substantially rectangular and interconnected by vertical longitudinal front and rear side walls 57 and 58 respectively, and by an overhead roof 49 just above head height. It will be seen from Fig. 4 that the coating station 11 at which the pipe 13 is treated is about midway up the height of the oven 12 and closer to one side wall, namely the rear side wall 58, than the other side wall 57. The oven 12 has hot air inlet ducts 60 at the roof 59 adjacent one side wall 57 and air collection or retrieval duct means 61 at the base of the oven 12 adjacent the other side wall 58.

For continuous treatment of a series of pipes 13 of the same predetermined length, the front and rear side walls 57 and 58 of the oven 12 have horizontal longitudinal slots 62 and 63 respectively through which pipes can enter for treatment and exit after treatment. Each slot has a flexible heat-resistant cloth 64 within the oven to minimise heat loss but flexible enough to move clear when brushed aside by a pipe moved therethrough. As shown in Fig. 4, the entry slot 62 has guide means 65 for receiving pipes sequentially and in parallelism from a wheeled trolley or table 66 on which pipes are brought to the oven, the guide means 65 leading down within the oven 12 for gravitational feed of pipes in parallelism to an upwardly and inwardly inclined entry conveyor assembly 67 for incremental advance in spaced series for delivery to the treatment position where it is gripped between the two manifolds.

It will be seen that the exit slot 63 is below the treatment level for each pipe, the treated pipe being fed therefrom by an exit conveyor assembly 68 operative to discharge treated pipes sequentially in series. Pipe removal arm means are also provided as indicated at 69 and arranged to be actuated by pivoting about axis 70 to raise and remove successive treated pipes for collection and discharge via the exit conveyor assembly 68 and exit slot 63.

For supporting and rotating each pipe 13 to be treated, there are provided pipe-contact rollers arranged in pairs spaced along longitudinal axes to hold a pipe therebetween, main drive rollers 71 being fixed to driven shaft 72, while secondary rollers are denoted at 73. The driven shaft 72 passes through high temperature bearings and is rotated through drive chain means 74 and an external motor 76. The secondary rollers could be idler rollers but in this instance are fixed on a shaft driven in unison with the shaft 72 and in the same direction by virtue of the pulley and belt system 102 shown best in Figs. 4 and 5.

There is also a parallel overhead shaft 77 carrying clamping rollers 78 (of desired diameter and interchangeable) adapted to be brought into engagement over and against the pipe being treated upon actuation of an external actuation means 79 for firm gripping when subjected to friction drive for rotation of the pipe 13. As apparent from Figs. 5 and 6, each pair of co-acting pipe contact rollers 71 and 73 forms part of a mounting assembly 80 having a third axis and bearing at 81 parallel to the others whereby a wider spacing of axes can be selected to cater for larger diameter pipes. Also the mounting assembly 80 is releasably securable to a longitudinal mounting beam 82 within the oven at a selected one of a plurality of designated locations to cater for pipes of different lengths, the choice of mounting apertures 83 being clear from the drawings. As

shown in Fig. 11, when the mounting assembly 80 is moved to another location as indicated by the dotted lines 84, mounting and/or drive shafts can have telescoping parts 85 to be locked or keyed together by lock pins or nuts 86 after adjustment has been effected.

Apparatus as described and illustrated will be found effective for its purposes and for carrying out the methods broadly described and claimed. As each pipe is treated individually in the oven at the coating station, it is rotated to ensure uniform coating, with a specified temperature of preheating and controlled vacuum-induced flow of adjusted air and powder supply. These conditions will ensure that any selected powder can be applied in the appropriate thickness and cured to specification, thereby being usable if for example a high chemical resistance is being sought, including acid-resistance, at reasonable temperatures. By controlling the adjustments, a typical coating thickness of 700um might be achieved in 20 seconds of curing, by way of example.

Anti-corrosion coatings for steel can be effectively applied to very small diameters of pipes which by means of the invention will be rendered potable-approved, while such coatings can also be useful for making pipes fracture-resistant on bending. Curing in all instances will be effective for all desired thicknesses of coatings and for all materials as aforementioned, and with any practicable colour selections being available. The apparatus can easily handle pipes of 12mm to 25mm diameter in the range currently presenting difficulties, but a skilled engineer can adapt the disclosures to cater for larger pipes, such as up to 65mm or even larger, such as 100mm. The oven can be designed without difficulty to afford temperatures between 240°C and 280°C for adequate results as aforementioned.

The invention will be understood to embrace many modifications of constructional detail and design which will be readily apparent to persons skilled in the art.

while various minor details shown in the drawings have not been specifically described. For example. Fig. 1 shows a control box 87 for the operator adjacent the powder hopper or container 19 at the powder-entry end of the apparatus, while at the other end of the apparatus, the electrics are housed in a box 100 and the discharge line 25 to the vacuum pump 26, cyclone 27 and sump 101 is flexible to allow for advancement and retraction of the outlet manifold 24, its swivel joint or split coupling 40 being shown. Various valves will be provided as necessary such as the valve 89 and air inlet 90 shown in Fig. 1. Also, fan and heater units for the oven are shown at 88. In Fig. 2 the actuator for the pipe removal arm is shown at 91 while a worm gear drive unit for the manifold carriage is shown at 92. The actuator for advancing the feed or entry conveyor assembly 67 is shown at 93, and the actuator to advance the exit conveyor assembly 68 is shown at 94. An access door to the oven 12 is shown at 95. The invention is to be understood to embrace all variations and obvious design features as reside within the broad scope and ambit of the invention as defined by the appended claims.