Abstract:
An adjustable duct assembly for the collection of fumes, dust and the like comprises two duct sections connected end to end by a duct support system comprising two elongate arms pivotally connected, the arms attached to the adjacent ends of the ducts, externally. A counterbalance arm extends from the duct support of a lower or outer duct section beyond the pivot point of the elongate arms, to counterbalance the lower or outer arms. A filter arrangement may be associated with the duct assembly, consisting of a generally planar filter element within a housing. A travelling nozzle arrangement directs a stream of air in a direction countervailing the normal flow through the filter, for backwash cleaning of the filter. First and second drives propel the nozzle simultaneously across and along the filter, to provide full backwash cleaning coverage of the filter.

Description:
This application claims benefit of U.S. Provisional Application No. 60/104,730 filed Oct. 19, 1998. 
    
    
     FIELD OF INVENTION 
     This invention relates to the collection and removal of fumes, dust and similar material, and particularly, to a removal apparatus which is controllably movable. The invention further relates to a filter assembly with a backwash cleaning modality. 
     BACKGROUND OF THE INVENTION 
     The collection and removal of unwanted material, such as noxious fumes, dust and the like, can be obtained by the use of ducting having a collecting valve capable of being positioned adjacent to a source of unwanted material, the ducting connected to an abstraction system. Some of the uses of such removal devices include welding operations, grinding machines, laboratory operations which can produce fumes from chemical reactions, and surgical operations. Such devices typically comprise a duct assembly having a collecting mouth or inlet at one end, and a connection to an abstraction fan at the other. The assembly has some flexibility so that the collecting mouth or inlet can be stationed at any desired position. The assembly usually needs to be periodically repositioned and some form of support arrangement is required to retain the assembly in any given orientation and to permit easy movement and repositioning. Once repositioned the assembly should retain the new orientation and not be subject to undesirable movement. The mouth or inlet is normally movable in any direction in a plane and also movable in and out of such plane. 
     Various arrangements exist providing an adjustable assembly, including the provision of internal or external jointed frames which support the duct. Various devices such as lifting or position-balancing means, such as springs and other devices can be used, together with frictional means at joints. 
     Canadian Patent number 973,012 (Nederman) discloses a folding duct assembly having an internal duct support extending substantially the length of the duct. The duct support comprises a jointed arm having spring counterbalances to counter the weight of the duct. The joints of the duct support incorporate friction pads to retain the duct in a desired position. Jointed duct support structures are also shown in U.S. Pat. No. 5,527,217 (Engstrom) and U.S. Pat. No. 4,860,644 (Kohl et al). In the Kohl et al device, the joints incorporate friction pads to restrict their mobility, while the joints in Engstrom are linked to a retainer wire that in turn is held in place by a friction fit. 
     It is desirable, and in most cases essential, that there is provided means for holding the duct assembly in position during use, while still permitting easy movement to a new position. These conflicting requirements are difficult to satisfy with friction type joints. Wear at the joints will interfere with acceptable operation and regular adjustment will be required. If the support structure or frame is housed within the ducts of the assembly, such adjustment becomes very difficult. Also, the action of the friction joints can be adversely affected by the material being extracted through the ducts. 
     In a further aspect, the typical dust or contaminant removal apparatus includes a filter arrangement, whereby the contaminated air is purified before discharge from the apparatus. A typical filter comprises a hollow cylindrical structure having a folded paper filter element. This type of filter is characterized by inconsistent spacing between the filter pleats, resulting in difficulty in removing dust and dirt lodged within the filter. This reduces the life-span and efficiency of the filter. Accordingly, the use of a planar filter element is desirable. Further, it is desirable to provide a means whereby the filter may be automatically cleaned, without removal of the filter from the apparatus. A typical filter-cleaning arrangement is disclosed within U.S. Pat. No. 5,322,535 (Simms), relating to an apparatus for cleaning a hollow cylindrical air filter. The arrangement comprises a travelling nozzle, which both rotates and travels axially relative to the filter, thereby backwashing the filter with a narrowly directed stream of air moving in a countervailing direction to the normal direction of flow. This arrangement is limited for use with a hollow cylindrical filter, and is not capable of use with a planar filter arrangement. In general, it is desirable to provide a moving nozzle arrangement for directing a narrow air stream against the filter for backwash cleaning, rather than an air stream which covers the entire filter simultaneously, as a more efficient backwash cleaning means. 
     SUMMARY OF THE INVENTION 
     The present invention provides a ducting assembly for collection and removal of material, comprising an assembly comprising a plurality of duct sections and a duct support. A first duct has a collection inlet at an inlet end, an outlet end connected to an inlet end of a second duct. The outlet end of the first duct is connected to the inlet end of the second duct by the duct support. The duct support comprises at least two elongate arms, pivotally connected, a first arm attached to the first duct at the outlet end and the second arm attached to the second duct at the inlet end. Extending from the first arm beyond the pivot connection is a counterbalance arm weighted such as to counterbalance the first duct and any associated inlet device, such as a hood or the like. The adjacent ends of the ducts are connected in an air-tight manner by flexible ducting. The outlet end of the second duct is movably mounted by duct support means, which again can comprise two pivotally connected elongate arms. Counterbalancing of the duct assembly can be by an air piston or air spring assembly. 
     In a further aspect, the invention comprises a filter assembly having filter cleaning means. The assembly comprises a filter housing, at least one generally planar filter element, and a cleaning means for directing a gas flow against the filter element for backwash cleaning. In order to provide complete or substantially complete coverage of the filter, while still permitting a relatively forceful air blast, the cleaning means comprises a nozzle, linked to a compressed gas supply, directed at the filter. The nozzle is mounted for movement relative to the filter, along two axes within a plane parallel to the filter. First and second drive means propel the nozzle along the two axes. 
     Preferably, the filter is vertical, and the nozzle includes drive means to move the nozzle along vertical and horizontal axes, whereby the nozzle describes a generally zig-zag pattern as it shuttles simultaneously or sequentially along the horizontal and vertical axes. The drive means may alternatively move the nozzle in a spiral pattern. The nozzle maintains a constant distance from the filter throughout. 
     Preferably, dual spaced-apart parallel filter elements are provided, with the cleaning means comprising dual oppositely-facing nozzles mounted to a traveller. The traveller shuttles on a horizontal support, with the support in turn being mounted to and travelling vertically on one or more pillars. Drive means propel the traveller and horizontal support respectively, in reciprocating movement. 
     A controller controls the reciprocating movement of the traveller and permits an operator to activate the cleaning means on a periodic basis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation of one embodiment of the present invention; 
     FIG. 2 is a view in the same direction as FIG. 1, showing the movement of a collecting hood; 
     FIG. 3 is a view normal to that of FIG. 1, showing the collecting hood movement; 
     FIG. 4 is a side elevation of a filter sub-unit; 
     FIG. 5 is a second side elevation of the filter sub-unit; 
     FIG. 6 is a side elevation of another embodiment of the duct assembly; 
     FIG. 7 shows a portion of the duct assembly of FIG. 6, showing the pivotal movement of the inlet; and 
     FIG. 8 is a perspective view of another embodiment of the filter sub-unit, showing a portion of the assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The adjustable duct assembly illustrated in FIGS. 1 to  3  includes two duct sections comprising a first duct section  10  and a second duct section  12  in end-to-end relationship, and also includes a duct support comprising two elongate arms  14  and  16 , pivotally connected by a pivot joint at  18 . 
     The first duct section  10  has a collection inlet  20  attached to its inlet end  22  and is attached to arm  14  at the outlet end  24 . The second duct section  12  is attached at its inlet end  26  to arm  16  and at its outlet end  28  is attached to a mounting support  30 , in this example by a second pair of elongate arms  32  and  34  pivotally connected at  36 . 
     Rigidly attached to the arm  14  is an arm  40  which extends from the arm  14  beyond the pivot joint  18 . At the outer end of the arm  40  is a weight  42 . Extending between the arm  16  and the support  30  is a gas spring  44 , of known form. The gas spring  44  acts to hold the duct section  12  in any desired orientation but can be overridden to move the duct section. The weight  42  counterbalances the weight of the first duct section  10  and its associated parts, maintaining the duct section in a desired orientation but allowing easy movement of the duct section to any position. The weight  42  can be a localized weight mounted on the arm  40 , or the arm  40  can act as the weight as an entirety. 
     The suction inlet  20 , in the example in the form of a hood, is connected to the inlet end via flexible duct sections  50  extending from a tubular section  52  on the hood to the inlet end  22 . Similarly the outlet end  24  of the duct section  10  is connected to the inlet end  26  of duct section  12  by a flexible duct section  54  and a further flexible duct section  56  connects the outlet end of the duct section  12  to the support  30 . The suction inlet hood  20  can be swivelled around to any desired direction, as seen in FIGS. 2 and 3. Also, if desired, the mounting support  30  can be pivotally mounted to permit swivelling of the entire assembly. 
     The invention permits the positioning of a collection inlet in any desired position, being freely and easily moved but at the same time, being held firmly in any set position. No friction joints exist, with thus freedom from wear and other problems. No spring counterweights are used with the associated problems of their ineffectiveness. The support structures, the arms  14  and  16 , arms  32  and  34 , the counterweights  40  and  42  and gas spring  44  are all external of the duct sections and therefore do not interfere with the air flow. 
     The collected air and other material can be exhausted to the atmosphere, through a filter system for example, or can be filtered and treated, with the air recycled. 
     The above description and the drawings relate to a particular development which is capable of modification. For example, it is possible to insert a third duct section between the second duct section  12  and the support mounting  30 , with a pivotal connection between them as is between duct sections  10  and  12 , and with a further counterbalance weight as at  40  and  42 . 
     Referring to FIGS. 4 and 5, the filter portion of the apparatus comprises a housing  60 , having an opening  62  extending therethrough and communicating with the free end of the second duct section  12 . The housing features a second opening  64 , for discharge of cleaned exhaust gases. Within the housing, first and second spaced-apart planar filter elements  66   a  and  66   b  are retained in parallel relationship within an internal compartment  68 . The internal compartment includes apertures  70  whereby the air flow passing through the housing is directed inwardly through the filters towards an interior space between the filters, and this purified air is subsequently vented out of the compartment and filter housing. The filter elements may comprise any convenient substantially planar filters, and conveniently comprise a folded paper filter element  72 , retained within framework  74 . The filters are disposed in a generally vertical orientation. It will be understood that the apparatus may be positioned in any orientation, and it is simply for convenience of description that a vertical orientation of the filters is selected. 
     Disposed within the interior space between the filter elements is a filter cleaning means  76 , as shown in detail within FIG.  5 . 
     The filter cleaning means comprises a pair of spaced-apart, vertically disposed, elongate pillars  80 , each comprising a round bar. An air nozzle support  82  spans the pillars, and is slidably engaged thereto for vertical travel along substantially the length of the vertical bars. A first electric motor  84  is mounted to the air nozzle support and drives the air nozzle support in a vertical direction along the pillars  80 . The air nozzle support  82  comprises a pair of spaced-apart parallel bars  92 . An air nozzle traveller  94  is slidably engaged to the air nozzle support  82 , and is mounted for reciprocating horizontal movement along the air nozzle support. A second electric motor  96  mounted to the air nozzle support  82  propels the air nozzle traveller  94  along the air nozzle support  82 , by means of a belt  98  connected to the traveller and driven by the second motor  99 . The second motor is associated with a drive pulley  100  linked to the second belt  98 , with the opposed end of the belt threaded through guide bearings  102 . The first and second motors are geared to propel the traveller horizontally at a relatively high speed, and vertically at a relatively low speed. 
     The air nozzle support  82  is driven vertically relative to the vertical supports by means of a pulley  86  and belt  88  arrangement. In this arrangement, the belt  88  is journalled by an array of guide bearings  90 , with the pulley  86  being rotatably driven by the motor  84 . 
     An air nozzle  104  is mounted to the air nozzle traveller  94 . The nozzle features two opposed openings  106   a  and  106   b  for directing an air stream at the first and second filter elements  66   a  and  66   b  respectively. Air is supplied to the nozzle by means of an air hose  108  linked to a supply of compressed air. 
     The reciprocal horizontal shuttling of the nozzle, when combined with the relatively slow vertical movement thereof, results in a generally zig-zag pattern being described by the nozzle, relative to the filter elements. 
     A control means  110  controls operation of the filter cleaning means  76 , whereby the air nozzle traveller  94  travels in a reciprocating horizontal movement as the traveller  94  is simultaneously being driven in a reciprocating vertical direction, thereby providing fill coverage to backwash all portions of both of the filter elements. 
     FIGS. 6 and 7 illustrate a further embodiment of the duct assembly portion of the invention. In this version, the assembly is composed of first and second duct sections  210  and  212  as in the first embodiment. A collection inlet  220  forms the inlet end of the second duct section. As shown in FIG. 7, collection inlet  220  may be pivoted about an axis, within a range of approximately 180°. 
     In this embodiment, a third duct section  230  is provided at the outlet end of the duct assembly, and joined to the first duct section  210  by flexible duct connection means  232 . Also joining sections  230  and  210  is a hinged connection means  234 , which forms a pivotal hinge means between the two sections. Connection means  234  includes a plate like member  236 , fixedly mounted to third duct section  230 . 
     A gas spring  244 , and associated mount and support means  246  joins the first and third duct sections, one end of the mount means  246  being fastened to the plate like member  236 . 
     A counterweight  242  is engaged to the second duct section  212  in much the same manner as in the first embodiment. 
     Turning to FIG. 8, an alternative arrangement of the filter portion is shown. FIG. 8 illustrates the frame assembly  300 , which is supported within a housing, not shown, in much the same manner as in the first embodiment. Filter elements  302  are shown in outline form, and are mounted to opposing sides of the frame assembly  300 . A threaded pillar  304  extends the full height of the frame  300 , and supports one side of beam  308 . Beam  308  is moveable vertically within the assembly  300 . The second end of beam  308  abuts a column  310  within the assembly  300 . A coiled spring-biased tape assembly  312  suspends the beam  308  and permits vertical travel of the beam within the assembly. The wound-up portion of the tape supports the beam  308 . A tongue  313  extends upwardly from each end of the beam  308 . The respective tongues support an elongate rod  316  which extends parallel to the elongate axis of the beam, directly above the midline of the beam. Rod  316  slidably supports a traveller  318 , which is free to move lengthwise along the beam  318 , on rod  316 . 
     A pair of paddle-shaped nozzle members  320  extend outwardly from either side of the traveller  318 , and are directed towards the inside faces of the filter elements  302 . The nozzle members  320  are connected to a supply of pressurized gas, not shown, for directing a narrow stream of pressurized gas at the filter elements for backwash cleaning thereof. 
     A continuous cord loop  330  extends around the peripheral edge of the beam  308 , and is recessed into a groove within the beam  308 . The cord loop  330  is driven by a motor  332 , which is connected via a gear box  334  to the cord loop  330 . An upwardly extending fin  340  is fastened to the cord loop, for contacting an engaging one or the other of the nozzle member  320 . Upon engagement with a first nozzle member  320 , the fin moves the traveller  318  in a first direction, as the cord loop means is driven by the motor  332 . Upon reaching the end of the beam, the fin  340  reverses direction as the loop passes around the end of the beam, and the fin then contacts a second of the nozzle members  320 , thereby moving the traveller in the reverse direction towards the opposed end of beam  308 . In this fashion, traveller  318  and associated nozzle members  320  are shuttled in a reciprocal fashion along beam  308 . 
     Beam  308  is moved vertically within the frame assembly  300 , by means of a gearing arrangement within gear box  334  which engages the threaded post  304 . By this means, motor  332  drives both the traveller  318  in a reciprocating horizontal direction, and beam  308  in a vertical direction. Gear box  334  includes direction reversal means whereby when beam  308  reaches either the top or bottom of the frame assembly  300 , the rotational direction of the gearing within gear box  334  is reversed, in order to reverse the vertical direction of travel of beam  308 . 
     In an alternative arrangement, which is also shown in FIG. 8, post  304  is rotatable, and is journalled within rotary mounts  346  within frame assembly  300 . A motor  350 , associated with gear box  352 , rotatably drives the post  304 . In this version, beam  308  is provided with a threaded aperture which engages post  304 , for raising or lowering beam  308  as post  304  is rotated. A similar direction reversing means is provided within gear box  352 , in order to reverse the direction of rotation of post  304  when resistance is encountered upon the post contacting the bottom or top of frame assembly  300 . 
     It will be seen that in connection with both the first and second embodiments of the filter assembly, the assemblies have been illustrated and described in an orientation wherein the filter members are arranged essentially vertically. However, the assembly may be adapted for positioning in essentially any orientation, for example with the filter assemblies being on horizontal planes. All directional references are thus used only for convenience of description, and are not intended to limit the scope of the invention. 
     It will be further seen that in a further variant, a single filter element may be provided, with the filter compartment and nozzle arrangement being adapted accordingly.