Abstract:
A spray booth for providing a controlled environment for spraying of material comprises a roof portion ( 31 ), a side portion which extends from the roof portion to a floor, first and second end portions which extend from respective opposing ends of the roof portion to the floor, the roof portion, side portion and first and second end portions thereby defining a work space ( 21 ) having a substantially closed side, a pair of substantially closed ends, and a substantially open side, air input equipment ( 34 ) operable to provide an input airflow into the work space via the roof portion ( 31 ), and air extraction equipment ( 32,37,38,33 ) operable to produce an output airflow to extract air from the work space. In use, the volume flow rate of the input airflow is larger than the volume flow rate of the output airflow, creating an outpour of excess of input air acting as an air curtain ( 23 ) on the open side.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    A spray booth is a structure that provides a ventilated, air filtered and temperature controlled environment in which spraying activities such as painting and powder coating can take place. A spray booth is necessary for the safe execution of such activities, since the sprayed materials include solvents and particulate material that must not enter the atmosphere in large quantities. The particulate material that does not stick to the article being sprayed must be removed from the spraying area to ensure safe working conditions, and to manage environmental impact. 
         [0002]    A spray booth also provides a controlled supply of filtered air that aids the spraying process and leads to higher quality finishes. In addition, it is necessary to heat sprayed materials in order to dry them (in a process known as baking), and a spray booth typically provides a controlled temperature environment in which such baking can be undertaken. 
         [0003]    In the automotive sector, a body shop which repairs and repaints cars and other vehicles may have the need to prepare and spray small components, such as wheels. Using a spray booth designed for spraying of whole vehicles is wasteful in several respects; the energy requirements for the booth are high, relative to the objects being sprayed, the size of the booth significantly exceeds that required for the smaller objects, and the use of a full booth for smaller jobs creates organizational issues for the spray booth operator. 
         [0004]    Accordingly, it is desirable to provide a spray booth arrangement that is tailored for smaller objects, in order to enable higher efficiency in processing of those smaller objects, whilst providing the required controlled environments for spraying and finishing at a reasonable cost. 
       SUMMARY OF THE INVENTION 
       [0005]    According to a first aspect of the present invention, there is provided a spray booth for providing a controlled environment for spraying of material, the spray booth comprising a roof portion, a side portion which extends from the roof portion to a floor, first and second end portions which extend from respective opposing ends of the roof portion to the floor, the roof portion, side portion and first second end portions thereby defining a work space having a substantially closed side, a pair of substantially closed ends, and a substantially open side, air input equipment operable to provide an input airflow having an input volume flow rate into the work space via the roof portion, and air extraction equipment operable produce an output airflow having an output volume flow rate to extract air from the work space, wherein, in use, the input volume flow rate is larger than the output volume flow rate. 
         [0006]    In one example, the input volume flow rate is at least twice the output volume low rate. The roof portion may define a plenum into which the airflow is supplied. The air input equipment may comprise a fan unit mounted on the roof portion. 
         [0007]    The air extraction equipment comprises an extraction aperture located in the side portion, a fan unit located outside of the workspace, extraction ducting extending from the extraction aperture to the fan unit, and an extraction filter. An air outlet may be connected with the fan unit, and arranged for connection to an air outlet chimney. 
         [0008]    According to a second aspect of the present invention, there is provided a kit of parts for a spray booth in accordance with the first aspect of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic side view of a spray booth arrangement embodying aspects of the present invention; 
           [0010]      FIG. 2  is a schematic cross-sectional view of the spray booth arrangement of  FIG. 1 ; 
           [0011]      FIG. 3  is a schematic plan view of the spray booth arrangement of  FIG. 1 ; 
           [0012]      FIG. 4  is a schematic plan view of an oven component of the spray booth arrangement of  FIG. 1 ; 
           [0013]      FIG. 5  is a schematic cross-sectional side view of the oven component of  FIG. 4 ; 
           [0014]      FIG. 6  is a schematic cross-sectional view of the component of  FIGS. 4 and 5  in a closed configuration; 
           [0015]      FIG. 7  is a schematic cross-sectional view of the component of  FIGS. 4 and 5  in an open configuration; and 
           [0016]      FIGS. 8 to 14  are schematic views illustrating operation of the arrangement of  FIGS. 1 to 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]      FIG. 1  illustrates a spray booth arrangement embodying various aspects of the present invention. The arrangement  1  comprises a centrally located work space  2 , with first and second ovens  4  and to respective sides of the work space  2 . Air handling plant  3  provides clean air input into, and air extraction out of, the work space  2 . A workpiece transfer rail  6  extends between the work space  2  and the first and second ovens  4  and  5 , and is used to transfer a workpiece 
         [0000]    between those areas, as will be described in more detail below. 
         [0018]    The air handling plant  3  comprises an air inlet region  31 , which provides air  35  into the work space  2 , and an air extraction filter  32  through which air  36  is extracted from the spray booth zone  2 . 
         [0019]    The ovens  4  and  5  each incorporate a high temperature baking zone  41 ,  51 , and a lower temperature curing zone  42 ,  52 . Each oven  4 ,  5  is provided with a door  43 ,  53  to enable access to the curing zone  42 ,  52 . 
         [0020]      FIG. 2  is a schematic side cross sectional view of the spray booth zone  2  of the spray booth arrangement of  FIG. 1 . The work space  2  has two regions—a work zone  21  which extends in front of the two ovens  4  and  5 ), in which an operative is located during use of the booth, and a spraying region  22 , in which a workpiece  10  is located during spraying thereof. 
         [0021]    The work space  2  is provided with air handling plant  3  which is operable to provide clean air input into the work space  2 , and to extract contaminated air from the work space  2 , and in particular from the spraying region  22 . 
         [0022]    The air handling plant  3  comprises an inlet fan  34  which draws clean air in from outside of the spray booth and passes this clean air into an inlet plenum  31  which extends across the ceiling area of the spray booth work zone  21 . The inlet fan  34  preferably includes an air filter or filters in order that the air input into the work space  2  is cleaned to a required standard. 
         [0023]    An air extraction port  32  is provided in a side wall  25  of the spraying region  22 . An air extraction fan  37  draws air  36  through the extraction port  32 , through ducting  38 , and causes the air to be expelled from the spray booth arrangement  1  via a chimney  33 . The extraction port  32 , the extraction fan  37  and/or the ducting  38  preferably includes one or more filter elements for removal of contaminants from the extracted air before release from the arrangement  1 . In many installations it is required that the air being expelled from the arrangement has a significantly reduced level of contamination, and so suitable filtration may be provided in the extraction part of the air handling plant  3 . 
         [0024]    The transfer rail  6  extends through the spraying region  22 , such that a workpiece  10  can be sprayed and worked on in a filtered controlled air environment. A worker (not shown for clarity) is able to spray the workpiece  10  as it is suspended from the transfer rail  6  in the spraying region  22  from the work zone  21 . Any appropriate spraying process may be carried out in the spraying area, for example spraying of water or other liquid based paints, or powder coating in which dry particulate material is sprayed onto the workpiece  10 . 
         [0025]      FIG. 3  is a schematic plan view of the spray booth arrangement  1  of  FIGS. 1 and 2 . As can be seen more clearly from  FIG. 3 , the spray booth arrangement  1  is bounded by end walls  23  and  24 , and by a side wall  25 . A roof portion extends over the arrangement  1 . The work space  2  is located in a central region of the arrangement  1  and includes the work zone  21  and the spraying zone  22 . As described above, the work space  2  is bounded at each end by an oven  4 ,  5 . Each oven defines a self-contained volume, separated from rest of the spray booth arrangement  1  by way of insulated walls. Each oven includes a sliding door to enable a workpiece to be moved into and out of the oven from the spraying region  22  of the work space  2  using the rail  6 . In  FIG. 3 , the work piece  10  is shown in a spraying position (A), and can be moved to the first oven  4  (position B) or to the second oven  5  (position C). More detailed description of the ovens and the overall operation of the arrangement is set out below. 
         [0026]    The spray booth arrangement shown in  FIGS. 1, 2 and 3  has an open side opposite to the spraying zone  22  and ovens  4  and  5 . This open side enables work pieces to be transferred into and out of the spray booth arrangement  1  with ease and high efficiency. However, having such an open side may cause problems with the cleanliness of the air within the work space  2 . 
         [0027]    Accordingly, in an embodiment of one aspect of the present invention, the flow rate of clean air input to the work space  2  is higher than the rate of extraction of air from the spraying zone  22  of the work space  2 . In one preferred example, the flow of air into the work space  2  is approximately twice the flow rate of air extracted through the extraction port  32 . For example, the input flow rate may be approximately 30000 m 3 /hr with the extraction rate of approximately 15000 m 3 /hr. This difference in flow rates results in a flow of clean air out of the open side of the spray booth arrangement  1 , which provides an air curtain  28 . This air curtain  28  provides a barrier that serves to prevent ingress of contaminants from outside of the spray booth arrangement  1  through the open side thereof. The extraction flow rate is chosen such that all, or substantially all, of the contaminated air from the spraying region  22  is removed from the work space  2 , without reaching the work region  21 . In this way, any release of contaminated air can be closely controlled. 
         [0028]      FIGS. 4 and 5  are schematic cross sectional plan and end views respectively of the first oven  4 . It will be readily appreciated that the second oven  5  is preferably identical in construction and arrangement to the first oven  4 . 
         [0029]    In accordance with another aspect of the present invention, the oven  4  defines a high temperature baking zone  41 , and a lower temperature curing zone  42 . The baking zone  41  is arranged above the curing zone, and operates at a temperature higher than that of the curing zone. The transport rail  6  extends into the baking zone  41 . An opening in a side wall of the baking zone  41  is provided, and is positioned such that a workpiece  10  can be moved into and out of the baking zone  41  using the transport rail  6 . A sliding door  50  is used to selectively close the opening into the baking zone  41  of the oven  4 . 
         [0030]    In addition, the oven  4  is provided with a lower door  43  to enable access thereto from the work space  21 . The lower door  43  is combined with a workpiece support  44 , which is attached to the lower door  43 , and which extends into the curing zone  42  when the lower door  43  is closed. The workpiece support  44  may be provided with an upstand  45  on which a workpiece  11  is supported. Operation of the lower door  43  and workpiece support  44  will described below with reference to  FIGS. 6 and 7 . 
         [0031]      FIGS. 6 and 7  illustrate the curing zone of the oven  4 ,  5  in closed and open configurations respectively. The lower door  43  is rotatably attached to the oven structure by way of a pivotable hinge  46 . The workpiece support  44  is attached to the lower door  43  and extends into the curing zone  42  from the lower door  43 . 
         [0032]    The lower door is movable between the closed ( FIG. 6 ) configuration, and open ( FIG. 7 ) configuration by rotating the lower door  43  about the hinge  46 , as shown by arrow  47  in  FIGS. 6 and 7 . 
         [0033]    When the oven door is in the open position as shown in  FIG. 7 , the curing zone of the oven is closed, thereby reducing heat loss from the oven. In addition, the workpiece support  44  and upstand  45  are available to the operator for location or removal of the workpiece (not shown for clarity in  FIG. 7 ). 
         [0034]    Processing of workpieces will now be described with reference to the schematic views of  FIGS. 8 to 14 . At a first stage of the process, a number of workpieces  10 ,  10 A are delivered to the workspace, preferably on a wheeled trolley ( FIG. 8 ). In the present example, the workpieces are vehicle wheels, which are process in pairs. An important application of the arrangement and process described herein is to the refurbishment of wheels for cars, which are most commonly processed in two pairs. It will be readily appreciated that the principles of operation described herein are applicable to any type and number of workpieces. 
         [0035]    A first pair of wheels  10  is loaded onto a frame on the transport rail  6  in the spraying zone  22  ( FIG. 9 ). The frame may be provided as a removable part of the trolley on which the wheels  10  are delivered, or may be separate from the trolley. The trolley carrying the second pair of wheels  10 A is not shown in  FIG. 9  for the sake of clarity. The operator is then able to undertake a spraying operation, be that paint spraying or powder coating, while the wheels are in the spraying zone  22 . During this operation, the air handling equipment described above is providing a clean air environment in the work space  2 . 
         [0036]    Once the first pair of wheels  10  have been sprayed, they are moved into the baking zone of one of the ovens, in this case the first oven  4  ( FIG. 10 ). The upper door of the first oven  4  is opened and the frame carrying the wheels  10  is moved along the transport rail  6  so that the wheels  10  are located within the baking zone of the first oven  4 . The upper door is then closed and the first oven can be operated to bake the wheels  10  at the appropriate temperature for the appropriate time. 
         [0037]    Now that the spraying zone  22  is free, a second pair of wheels  10 A is loaded onto the transport rail  6  ( FIG. 11 ) in the spraying zone  22  for spraying and processing by the operator. During this processing, the first pair of wheels  10  is being baked in the first oven  4 . As such, the arrangement described enables different operations to be carried out in parallel with one another, thereby contributing to increased throughput and efficiency. Following completion of the spraying operation on the second pair of wheels  10 A, those wheels are moved along the transport rail  6  into the baking zone of the second oven  5 . The spraying zone  22  is then free, and the first pair of wheels  10  can be moved into that zone  22  when the baking operation in the first oven  4  is completed ( FIG. 12 ). 
         [0038]    Some finishing operations require a second spraying stage, and that can now be completed in the spraying zone  22  for the first pair of wheels  10 . The first pair of wheels may then be returned to the oven  4  for a further baking stage. Alternatively, the first pair of wheels  10  may require curing in the curing zone of the first oven  4  (the curing zone of the second oven  10  may be used), and so this first pair of wheels  10  is moved by the operator to that curing zone. 
         [0039]    Once the first pair of wheels  10  has been moved out of the spraying zone  22  into the curing zone of the first oven  4 , then the spraying zone  22  is again free for use. A third pair of wheels  10 B may then be placed in the spraying zone  22  for processing while the second pair of wheels  10 A are baked in the second oven  5 . Such a situation is illustrated in  FIG. 13 . Following spraying, the third pair of wheels  10 B are moved into the first oven for baking. The second pair of wheels  10 A can be removed from the second oven  5 , and then handled appropriately, for example being placed in the curing zone, thereby enabling a further pair of wheels to be processed and baked. 
         [0040]    As will be readily appreciated, the arrangement described above enables increases in efficiency in the processing of workpieces, such as wheels, by enabling the workpieces to be transported between processing locations easily, using the transport rail, and by enabling processing to be carried out in parallel. That is the baking and curing ovens are separate to the spraying zone, thereby enabling baking and curing to carry on in parallel with one another and with a spraying process on another workpiece.