SPRAYING APPARATUS

Abstract: Spraying apparatus arranged so that articles (48) to be sprayed are conveyed along an arcuate path (51) through a spraying zone (28) in a spray booth (10) whilst being sprayed with a material which is directed inwards towards the axis of the path, so that overspray material (i.e. material which misses the articles) and air is drawn inwards through the spraying zone; and so that means (13, 14) for rotating the articles and moving the articles along said path and moving the spray gun or guns are disposed clear of the spraying zone.

Description: SPRAYING APPARATUS This invention concerns spraying apparatus for spraying articles with fluent materials. There are many known types of spraying apparatus which comprise a booth which encloses or partially encloses a spraying zone; conveyor means for conveying articles through the spraying zone; and support means for supporting one or more spray guns or nozzles. In some of these types of apparatus the support means is adapted to move the spray gun or nozzle to automatically coat an article with material. However, these types of the apparatus have various disadvantages and give rise to many problems, such as obstructed or difficult access to the interior of the booth; complex and costly mechanical drives for the support means; faulty spraying or excessive paint consumption arising from poor synchronisation between the movement of the articles and the movement of the spray guns or nozzles; paint contamination of the conveyor means and support means; and the complexity and cost of the necessary precautions against fire and explosion. According to the present invention there is provided spraying apparatus, for spraying articles with fluent materials, comprising a booth, conveyor means for conveying articles through the booth, and support means for supporting at least one spray gun or nozzle; wherein the conveyor means comprises an endless conveyor; wherein the booth at least partially encloses a spraying zone within the booth; and wherein the support means comprises a gun or nozzle carrier in or extending into the spraying zone and a mechanism to support the carrier, and characterised in that: (a) the booth is provided with a static arcuate guide means arranged to constrain the endless conveyor to move in an arc, about an axis outside the spraying zone, as said conveyor traverses the spraying zone; and (b) the mechanism is disposed outside the spraying zone and is arranged to cause or allow the carrier to move arcuately about said axis, or about an axis alongside said axis, in synchronism with the movement of the conveyor. The disposition of said mechanism outside the spraying zone, in conjunction with the provision of a static arcuate guide means greatly reduces said disadvantages, and enables the booth, said mechanism and the means for driving the endless conveyor to be simplified to overcome said problems. In the known types of apparatus, said disadvantages are particularly severe in the case wherein the interior of the articles is to be sprayed; whereas the apparatus of the invention is inherently suitable for construction for such interior spraying, and may be constructed in various forms. For example, the endless conveyor is preferably provided with article carriers, and may be associated with carrier drive means, such as a belt or like drive to rotate article carriers for rotating the articles; or the endless conveyor may have carrier drive means comprising rollers which engage the static guide means to rotate the article carriers in the spraying zone. The conveyor may pass the bottom of the spraying zone or the top of the spraying zone, or the conveyor means may comprise a plurality of such conveyors, e.g. one above and one below the spraying zone. The spraying zone is preferably within a space bounded by a floor, a ceiling, a front, two side portions and, optionally, an internal member of the booth, the side portions being apertured for passage of the articles. The front is preferably apertured for access to the spray guns or nozzles, and the internal member is preferably a filter, liquid wash curtain or baffle arrangement at the rear of the spray zone. The booth is preferably arranged for extraction of booth purging air, material solvents andlor material overspray, via a duct, space or a chamber in the booth to the rear of the spraying zone. The side portions may extend rearwards beyond the spraying zone. The floor andlor ceiling is preferably slotted to allow the carriers or carrier supports to extend therethrough. Said mechanism preferably comprises a radius arm between said axis and the gun or nozzle carrier, and a shaft or bearing on which said arm is mounted. A power transmission may connect said shaft with the conveyor drive, and the shaft and transmission are preferably disposed at the rear of the booth. Alternatively, the gun carrier or a device attached to the radius arm may be adapted to engage the conveyor or the article carriers to move the gun carrier through an arcuate spraying or working stroke, and thereafter to disengage from the conveyor or article carriers so as to be movable through a return stroke by bias means acting on said radius arm. The mechanism and gun or nozzle carrier are preferably arranged to move a spray gun or nozzle through an arc having a radius the same as or greater than the radius of the arc through which the conveyor is constrained to move; and said axis is preferably disposed at or towards a rear of the booth, the booth providing an access opening at the front of or in front of the spraying zone. The length of said arc in the spraying zone is preferably less than 600 or less than twice the radius of the arc, and the length is most conveniently within the range of 100 to 400 or 0.2 to 1.5 times the radius. The conveyor means preferably extends within the booth beyond the spraying zone. The apertures may be disposed in or adjacent the rear of said side portions. The conveyor means preferably includes guides for the conveyor, said guides extending to the side portions of the booth, so that the conveyor has an approaching run tangential to one end of the arcuate guide means and a departing run tangential to the other end of said arcuate guide means. Said runs preferably extend, to the rear of the booth, to drive and idler wheels or sprockets of the conveyor means. The runs may be parallel, or may converge so that the angle between said runs is less than 1200 but more than 500, and is conveniently within the range of 900 to 600. The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings, wherein: FIGURES 1, 2 and 3 are front, side and plan diagrams of a first embodiment of apparatus of the invention; FIGURE 4 is a side diagram of a second embodiment of the invention; FIGURES 5 and 6 are plan and side diagrams of a third embodiment; and FIGURE 7 is an enlargement of part of FIGURE 6. Referring to FIGURES 1 to 6, the apparatus generally comprises a booth 10, conveyor means 11, an oven 12 (indicated in broken lines only in FIGURE 3), support means 13 and carrier drive means 14. In the first embodiment, the booth 10 has a raised cabin provided with a floor 20, ceiling 21, two side portions 22 and 23, a front 24 and a rear 25. A filter panel or baffle 26 divides the cabin into a rear extractor chamber 27 and a spraying zone 28 in front of the chamber 27. The support means 13 comprises a mechanism 17 having a vertical shaft 30 carrying a radius arm 31 above the cabin, and comprises a gun carrier 32 which depends from the arm 31 into the zone 28, through a slot 29 (FIGURE 2) in the ceiling 21, to support a spray gun 33. A further or alternative arm 34 with a gun carrier 37 may extend from the shaft 30, through a base 35 of the cabin and a slot 36 in the floor, into the zone 28 as indicated in FIGURE 2. The chamber 27 is connected to an extractor unit 38 for drawing air through the cabin via a front opening 39. The conveyor means 11, comprises an endless chain conveyor, indicated by a chain broken line 40 in FIGURE 3, which is supported by guides 41, 42 and 43, a conveyor drive 44 having a chain drive sprocket 45, and an idler sprocket 46. Article carriers 47 (only a few of which are shown) are rotatably mounted on the conveyor 40 so as to be regularly spaced apart (e.g. at 20cm intervals for small articles), and the carrier drive means is arranged to rotate the carriers 47 about their axes as they traverse the zone 28. The conveyor 40 is arranged to pass through the base 35 so that the carriers 47 extend into the zone 28 via a slot in the floor 20, and the side portions 22 and 23 extend to panels 122 at the sides of the booth, which panels 122 are provided with openings 50 for passage of the carriers 47 and articles 48 thereon. The booth is provided, within the base 35, with static arcuate guide means 15 comprising a fixed track 51 indicated in broken lines in FIGURE 3, which is engaged by the conveyor 40 so that the carriers 47 move through the cabin along an arcuate path centred on the axis of the shaft 30. The guides 41 and 42 are arranged so that the runs of the conveyor to and from the booth are substantially tangential to the ends of the track 51. The support means 13 includes a power transmission 52, indicated in broken lines in FIGURE 3, connecting the drive 44 to the shaft 30 to reciprocate the arm 31 or 34. The transmission 52 is adjustable to permit the stroke of the arm 31 or 34 and the speed of the return stroke to be varied, and is arranged so that the speed of the working stroke is synchronised with the speed of the conveyor, so that the reciprocations of the carrier 32 or 37 can be determined to suit the inter-carrier spacing of the carriers 47 for accurate spraying of the articles. The second embodiment of the invention is generally similar to the first embodiment except primarily in that the conveyor means 11 is inverted and is arranged as an overhead conveyor 53, as shown in FIGURE 4, so that the article carriers 47 depend through the ceiling 21, and the guide track 51 is disposed in the ceiling. Furthermore, the second embodiment employs the radius arm 34 and gun carrier 37. The features of the first and second embodiments may be employed in any suitable combination. For example, the inverted upper conveyor 53 and an upper guide track may be incorporated into the first embodiment, as indicated in broken lines in FIGURE 2, e.g. to operate in unison with the conveyor 40 to support the upper and lower ends of elongate articles such as the article 148. In all embodiments the carrier drive means 14 generally comprises a belt 60 which extends around a drive pulley 61, a tensioner pulley 62 and, optionally, a return idler pulley 63; and a detachable cover 64 which extends in front of and above the belt and pulleys. The cover 64 is inverted for use with the conveyor 53. The drive pulley 61 is driven by a motor 65 via shafts 66 and a gearbox 67. The drive and tensioner pulleys 61 and 62 are spaced apart so as to be separated by an arc which is greater than the maximum arcuate stroke of the arm or arms 31, 34, and are arranged so that one run of the belt extends between these pulleys 61 and 62, without requiring further support, to contact simultaneously a cylindrica part 54 of all the carriers 47 in the spraying zone and adjacent to the spraying zone, as indicated in FIGURES 3, 5 and 7. The single tensioner pulley 62 is biased by a spring 68 (or other bias ) to apply a predetermined, and preferably adjustable, tension to the belt. The third embodiment (FIGURES 5 to 7) is similar to the first embodiment in many respects, and differs primarily in that the radius arm 34 carries a device 70 to enage the conveyor 40 (instead of the shaft 30 being driven by a power transmission 52), as shown in detail in FIGURE 7. The device 70 comprises a member 71 pivotally mounted on the arm 34, and an actuator 72 (such as an electrical solenoid actuated ram, a hydraulic ram, or a pneumatic ram) carried by the arm 34 to move the member 71 in the radial plane of the arm 34 between a forwards position, clear of the conveyor, and a rearwards position (as shown) in which the member 71 engages the conveyor, so that the arm 34 is moved by the conveyor, in unison with the conveyor in said arc from the start to the end of a working stroke. At the end of the working stroke, the actuator 72 moves the member 71 forwards from the conveyor to enable a return device 73 (FIGURE 5) to return the arm rapidly to the start of the working stroke. In all embodiments, the gun carrier 37 (or 32) may be arranged to move the spray gun or nozzle relative to the arm 34 (or 31), e.g. as shown in FIGURE 6, in which the gun carrier 37 provides a gun mounting 74 which is vertically movable along guides 75 by a further actuator 76. The conveyor 40 and track 51 are also shown in more detail in FIGURE 7. Abutments 55 are provided by the conveyor vertically below the article carriers 47, for engagement by the member 71 below plates 56 of the conveyor which cover an arcuate slot 57 in the fixed track 51. The latter extends to form part of the floor 20, the remainder of which floor is not shown in FIGURE 6 and may be of any suitable form. The conveyor 53 is similar to the conveyor 40. The third embodiment incorporates further features, which may also be incorporated into the first and second embodiments. For example, the booth 20 has extended side portions 22 and 23 in which the track 51 extends arcuately towards the rear of the booth so that the guides 41 and 42 extend in parallel from rear openings 50, as shown in FIGURE 5. Optional internal partitions 76 having further openings 58 may be provided between the side portions 22 and 23 and a central portion of the booth, to facilitate use of the side portions for supplementatry processes, e.g. preheating and drying. For example the portion 22 may be provided with heaters for pre-heating the articles, and the portion 23 may have a forced air flow therein for drying the sprayed articles prior to inspection. The air from the portion 23 may be extracted by the extractor 38 via a passage 77 having a variable flow controller 78 preferably of non-return form, which passage 77 extends into the rear portion 27 or chamber of the booth to the rear of the central portion. Also a workspace 79 to the rear of the booth may be enclosed to protect the bearings, motors and like ancilliary equipment. The invention is not confined to the precise details of the foregoing examples, and many variations are possible within the scope of the invention as defined by the appended claims. In particular, the shape of the booth may be varied, e.g. the sides may converge, and may terminate at the rear at an extractor duct so that the booth is trapezoidal or approximately triangular in plan. The track 51 may extend beyond the sides, or the guides may extend beyond the sides, or the guides may extend into the booth. The various openings and the slots in the floor and ceiling may be restricted, and may be arranged so that air is drawn into the cabin therethrough. The apparatus enables the cabin to be constructed so that the surfaces adjacent the spraying zone are by flat and easy to clean, and so that the spraying zone is free from mechanisms which could be harmed by paint or other material. The apparatus has further advantages, in that the conveyor, being tensioned by the drive or a tensioner, follows the track accurately and the support means provides accurate support for the spray gun to give accurate spraying. Material feed, e.g. paint spraying, is preferably interrupted during the return strokes, and may be wholly interrupted when an unloaded article carrier enters the booth, e.g. by means of load sensors. The conveyor drive and the oven, together with other optional equipment, is disposed to the rear of the spraying zone, e.g. out of the prescribed safety area, so that the motors, etc, need not be of flameproof construction. The disposition of the conveyor runs to and from the booth also provides excellent working access for persons loading the articles well clear of any persons working at the front of the booth, in a relatively small floor area. The conveyor drive and idler gear is also simplified, and the usual need for a multiplicity of sprockets and rollers is avoided. Spray gun control sensors may be provided so that movement of the gun carrier at the start of the working stroke initiates spraying. Adjustable deflector means, e.g. a portion of the track or a protuberance or cam on the track, may be provided to move said member 71 out of engagement with the conveyor at the end of the maximum spraying or working stroke, e.g. to prevent damage if the actuator 72 should fail. The or each carrier may carry a plurality of spray guns or nozzles. In general, the invention provides apparatus arranged so that articles to be sprayed are conveyed along an arcuate path through a spraying zone in a spray booth whilst being sprayed with a material which is directed inwards towards the axis of the path, so that overspray material (i.e. material which misses the articles) and air is drawn inwards through the spraying zone; and so that means for rotating the articles and moving the articles along said path and moving the spray gun or guns are disposed clear of the spraying zone. The apparatus thus provides clear access to the spray guns and carriers, and to the carrier drive means and cover from peripherally outside (in front of) the spraying zone and conveyor, e.g. via the opening 39 or a openable closure; and the remainder of the mechanisms are easily accessible either in the protected lower part or base of the booth (e.g. via an openable closure at the front of the base), or at the rear of the booth.

Claims: CLAIMS 1. Spraying apparatus, for spraying articles with fluent materials, comprising a booth (10), conveyor means (11) for conveying articles through the booth, and support means (13) for supporting at least one spray gun (33) or nozzle; wherein the conveyor means (11) comprises an endless conveyor (40,53); wherein the booth (10) at least partially encloses a spraying zone (28) within the booth; and wherein the support means comprises a gun or nozzle carrier (32,37) in or extending into the spraying zone and a mechanism (17) to support the carrier, and characterised in that: (a) the booth is provided with a static arcuate guide means (15) arranged to constrain the endless conveyor (40,53) to move in an arc, about an axis outside the spraying zone, as said conveyor traverses the spraying zone; and (b) the mechanism (17) is disposed outside the spraying zone and is arranged to cause or allow the carrier (32,37) to move arcuately about said axis, or about an axis alongside said axis, in synchronism with the movement of the conveyor. 2. Spraying apparatus as claimed in Claim 1 wherein the mechanism and gun or nozzle carrier (32,37) are arranged to move a spray gun or nozzle through an arc having a radius greater than the radius of the arc through which the conveyor is constrained to move. 3. Spraying apparatus as claimed in Claim 1 or 2 wherein said axis is disposed at or towards a rear of the booth, the booth providing an access opening (39) at the front of or in front of the spraying zone (28). 4. Spraying apparatus as claimed in Claim 1, 2 or 3 and comprising article carriers (47) mounted on the conveyor means, and carrier drive means (14) to rotate the carriers as the latter transverse the spraying zone. 5. Spraying apparatus as claimed in Claim 1, 2, 3 or 4 wherein the conveyor means comprises said endless conveyor (40 or 53) and a further endless conveyor (53 or 40), one of said conveyors (53) passing above the spraying zone and the other of said conveyors (40) passing below the spraying zone. 6. Spraying apparatus as claimed in any preceding claim wherein said mechanism (17) comprises a radius arm (31,34) between said axis and the gun or nozzle carrier (32,37) and a shaft (30) or bearing on which said arm is mounted at the rear of the booth (10). 7. Spraying apparatus as claimed in any preceding claim wherein said conveyor means comprises guides (41,42) for the or each conveyor (40,53), which guides extend to the booth so that the or each conveyor has an aproaching run tangential to one end of the arcuate guide means(15) and a departing run tangential to the other end of the arcuate guide means. 8. Spraying apparatus as claimed in any preceding claim wherein the booth has side portions (22,23) which provide openings (50) for passage of articles into and out of the booth; and wherein the arcuate guide means (15) comprises a static guide track (51) extending into said side portions. 9. Spraying apparatus as claimed in Claim 8 wherein at least one of said side portions (22,23) extends rearwards to provide a pre-heating or drying zone. 10. Spraying apparatus as claimed in any preceding claim wherein said support means comprises a device (70) to engage the conveyor means (11) to move the gun or nozzle carrier (32,37) arcuately in a first direction, and to disengage from the conveyor means to allow the gun or nozzle carrier to be moved in the opposite direction by a further device (73).

Inventors: PRITCHARD, ALFRED MAURICE
Applicants: SPRAYMATIC COMPANY LIMITED
Application year: 1986
Main classification: B05B15
IPC codes: B05B13