Patent Publication Number: US-10327605-B2

Title: Air bar cleaning tool, system and method

Description:
This application claims priority of U.S. Provisional Application Ser. No. 62/093,815 filed Dec. 18, 2014 and titled “Air Bar Cleaning Tool and Method”, the disclosure of which is hereby incorporated by reference as if it was fully set forth herein in its entirety. 
    
    
     FIELD 
     Embodiments disclosed herein relate to an air bar or nozzle cleaning tool, and a system for and method of cleaning an air bar or nozzle using the same. 
     BACKGROUND 
     Air bars or nozzles are used to direct a jet of air to impinge on the surface of a material to carry out heat and/or mass transfer functions. As is known to those skilled in the art, a plurality of air nozzles may be arranged in an array or multiple arrays to direct air impingement over a large surface of a material in web form, either on one side of the web, or both sides simultaneously. Flotation air bars are a type of air nozzle used in industrial dryers and ovens to floatingly support and convey a continuous web to be processed by thermal treatment, which may include any combination of drying, heating, curing or cooling of the web. In many cases a coating is applied to the surface of the web or a volatile material is present within the base web material which must be dried and/or heated to a particular temperature so as to facilitate thermal curing of a polymer material in the coating. Web materials commonly processed in this manner include paper, plastic film, metal foils, woven and non-woven fabrics and mats, and porous membrane materials. In many processes the volatilized materials within the web or coating after being liberated from the web surface are carried away from that surface by the spent nozzle air and conducted by an air handling system to an exhaust path, or recirculated to the air nozzles via an air handling system. Within the air handling system, the recycled air is typically re-heated by a burner or other suitable air heating means and pressurized by a fan in order to supply the heated air to the air nozzles under sufficient pressure to deliver the supply air jets at the desired impingement velocity. In some cases the materials in the recycled air either condense or are chemically altered and produce solid, semi-solid or viscous liquid forms of the liberated material. Due to the recirculation of the air within the dryer air handling system, these solid, semi-solid or viscous liquid materials can accumulate as deposits on or inside the nozzles. When deposits block the flow of air reaching or passing through the apertures of the air nozzle, the heat transfer capability of the blocked nozzles is diminished, often resulting in reduced production capacity and economic loss. Cleaning of the nozzles typically requires shut down of the process and cooling of the oven apparatus to facilitate access for manual cleaning. Clearing of the material blocking the nozzle flow usually requires some combination of brushing, scraping, loosening with compressed air blast, and vacuuming. 
     Although it is desirous to clean air nozzles in situ, most nozzles are designed so as to be removable from the oven enclosure to facilitate access for thorough cleaning. Removal for cleaning and remounting of the air bars is known to be an arduous and time-consuming task which increases costs of maintenance and further negatively impacts the productivity of the production line. Various tools and devices intended to clean air nozzles in-situ such as scraper knives or brushes fastened to extension poles have been fashioned by maintenance personnel with limited cleaning effectiveness. In some cases, such devices have been known to damage the integrity of the nozzles by deforming the nozzle apertures, resulting in adverse effects in product quality such as drying defects, marking, or web breaks. 
     A particular family of processes wherein curable silicone coatings are applied to a web, such as in the production of release liners for pressure sensitive adhesive tapes, films and sheets, suffers from extensive generation of dust buildup within the nozzles and air handling systems of the drying and curing ovens used for this purpose. Many of these silicone release liner products are dried and cured in flotation ovens. In this type of oven, not only is heat transfer and drying capacity diminished when deposits block nozzle apertures, the conveyance function of the flotation dryer is also compromised, leading to web product defects. Known apparatus and methods used to attempt cleaning of flotation nozzles in situ are only minimally effective. Deposits inside of the air bar apertures and flow distribution elements within the body of the air bar cannot be reached effectively by most mechanical means when accessing the air bars in situ. Further, cleaning of the flotation air bars by improper mechanical methods can result in degradation and even permanent damage to the apertures adversely affecting the stable flotation conveyance of the web as well as adverse heat transfer and drying effects. 
     In most cases, thorough cleaning of air bars can be practically accomplished only by removal from the oven and careful washing and/or vacuuming steps requiring a significant amount of downtime. 
     It is therefore an aspect of embodiments disclosed herein to provide an apparatus (tool) which can effectively remove buildup within the flotation air nozzle while in situ. It is a further aspect of embodiments disclosed herein to ensure that the mechanical interaction of the cleaning tool with the air bars is not detrimental to the mechanical integrity of the nozzle apertures. Further, in certain embodiments, the sequence of cleaning steps provides for removal of dust/material from the nozzles so as to prevent re-accumulation of dust from deposits already freed from the internal surfaces of the air bars, thus extending the time between cleanings. 
     SUMMARY 
     In accordance with certain embodiments, cleaning air knife elements (two shown), such as those available from ExAir Corporation, Cincinnati, Ohio, are assembled in a parallel orientation inside a housing enclosing the air knife assembly and in fluid communication with a compressed air source. In certain embodiments, the air knife elements are spaced apart a distance that orients the cleaning air knife discharge slots directly parallel and in line with the slots of the air nozzle or bar to be cleaned. Air discharging from said air knife discharge slots passes through the discharge slots of the air bar to be cleaned, dislodging dust and friable solid buildup from the air bar slots. Additionally, the cleaning air jet enters the air bar body, further dislodging dust and friable solids from the internal passages of the air bar inside said air bar body. 
     One embodiment includes an air bar cleaning tool comprising a housing, one or more air knife elements in the housing, each air knife element having a discharge slot and a tab extending from the discharge slot, wherein the discharge slot and tab are adapted to be aligned with a slot in the air bar to be cleaned. A propelling assembly for propelling the tool along the length of the air bar being cleaned may be used, and may include a spring-loaded yoke for supporting the housing. 
     Another embodiment includes a system for cleaning an air nozzle or bar, comprising an air bar to be cleaned, the air bar having an air bar slot; a housing sealed to the air bar; an air knife element in the housing, the air knife element having a discharge slot and a tab extending from the discharge slot, wherein the discharge slot and tab are aligned with the air bar slot such that the tab is received in the air bar slot; and a source of compressed air in fluid communication with the air knife element. In certain embodiments, the housing includes two air knife elements, each having a discharge slot and a tab extending therefrom. 
     Yet another embodiment includes a method of cleaning an air nozzle or bar having at least one air bar discharge slot, comprising providing an air bar cleaning tool comprising a housing, at least one air knife element in the housing, each air knife element having a discharge slot and a tab extending from the discharge slot; aligning the housing with the air bar such that the air knife element discharge slot aligns with the air bar discharge slot and the tab enters the air bar discharge slot; introducing air through the air knife discharge slot and into the air bar discharge slot; and moving the housing along the length of the air bar. 
     In certain embodiments, the housing is moved along the length of the air nozzle with an actuator. In certain embodiments, the actuator is responsive to a controller. 
     These and other non-limiting aspects of the disclosure are more particularly described below. For a better understanding of the embodiments disclosed herein, reference is made the accompanying drawings and description forming a part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments disclosed herein may take form in various components and arrangements of components, and in various process operations and arrangements of process operations. The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting. This disclosure includes the following drawings. 
         FIG. 1A  is a schematic view of an air nozzle with a cleaning tool engaged therewith in accordance with certain embodiments; 
         FIG. 1B  is a side view of a cleaning tool in accordance with certain embodiments; 
         FIG. 1C  is a front view of a cleaning tool in accordance with certain embodiments; 
         FIG. 1D  is a top view of a cleaning tool in accordance with certain embodiments; 
         FIG. 2  is a schematic view of an air nozzle with a cleaning tool engaged therewith and supported on a yoke in accordance with certain embodiments; 
         FIG. 3  is a schematic diagram of an air nozzle and cleaning tool shown traversing the air nozzle in accordance with certain embodiments; 
         FIG. 4  is a schematic diagram of an air nozzle and cleaning tool shown traversing the air nozzle and including a linear actuator in accordance with certain embodiments; 
         FIG. 5  is a schematic diagram of an air nozzle and cleaning tool shown traversing the air nozzle and including a linear actuator and controller assembly in accordance with certain embodiments; and 
         FIG. 6  is a schematic diagram of an air nozzle and cleaning tool shown traversing the air nozzle and including a screw actuator in accordance with certain embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     A more complete understanding of the components, processes, systems, methods and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. The figures are merely schematic representations based on convenience and the ease of demonstrating the present disclosure, and is, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments. 
     Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function. 
     The singular forms “a,” “an,” and the include plural referents unless the context clearly dictates otherwise. 
     As used in the specification, various devices and parts may be described as “comprising” other components. The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional components. 
     All ranges disclosed herein are inclusive of the recited endpoint and independently combinable (for example, the range of “from 2 inches to 10 inches” is inclusive of the endpoints, 2 inches and 10 inches, and all the intermediate values). 
     As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially,” may not be limited to the precise value specified, in some cases. The modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression “from about 2 to about 4” also discloses the range “from 2 to 4.” 
     It should be noted that many of the terms used herein are relative terms. For example, the terms “upper” and “lower” are relative to each other in location, i.e. an upper component is located at a higher elevation than a lower component, and should not be construed as requiring a particular orientation or location of the structure. As a further example, the terms “inward”, and “outward” are relative to a center, and should not be construed as requiring a particular orientation or location of the structure. 
     Turning now to  FIGS. 1A through 1D , there is shown an air bar or nozzle  10  having an air nozzle or air bar body  12 . During operation, the air nozzle or bar  10  is in fluid communication with a gas source, such as a supply of air, for heating or cooling a web, and/or for floating the web. The air nozzle  10  has one or more nozzle slots or openings  14  (two shown) for discharging gas towards the web. In some embodiments, the nozzle slots can be Coanda slots. In certain embodiments, the air nozzle  10  can include an air bar vacuum withdrawal port or connection  15 . 
     A cleaning tool housing  20  is shown engaged with the air nozzle  10 . In certain embodiments, the housing  20  houses one or more (two shown) cleaning air knife elements  22 . In certain embodiments, the number of cleaning air knife elements  22  in a housing  20  corresponds to the number of slots in the air bar  10  to be cleaned. In certain embodiments, each cleaning air knife element  22  is 2 to 6 inches in length, most preferably 4 inches in length, and is assembled in a parallel orientation inside housing  20  enclosing the air knife assembly and in fluid communication with a compressed air source via a feed port  23 . In certain embodiments, the compressed air source is regulated to a pressure between 40 and 80 psig. 
     In certain embodiments, each air knife element  22  includes a housing  27  having an air knife discharge slot  26 , and the air knife elements  22  are spaced apart a distance that orients the cleaning air knife discharge slots  26  directly parallel and in line with the slots  14  of the air bar  10  to be cleaned. Air discharged from the air knife discharge slots  26  passes through the discharge slots  14  of the air nozzle  10  to be cleaned, dislodging dust and friable solid buildup from the air nozzle slots  14 . Additionally, the cleaning air jet enters the air nozzle body  12 , further dislodging dust and friable solids from the internal passages of the air nozzle inside the air nozzle body  12 . 
     In certain embodiments, the housing  20  supports the air knife elements  22  and encloses the air knife elements  22  and extends an additional to 2 inches, preferably 1 inch beyond each end of the air knife elements  22  to provide passages for vacuum air flow inside each end of the cleaning tool housing  20 . The housing  20  engages the air nozzle body  12  and is fitted with sliding seal elements  30  to create a seal between the housing  20  and the air nozzle body  12 . In certain embodiments, the sliding seal elements  30  may be made of brush material or preferably of low-friction solid materials such as Teflon® or Nylon. 
     An optional hose connection  32  may be connected to a vacuum source (not shown) through a vacuum hose, such as commonly available for shop utility vacuum appliances. The vacuum flow into the vacuum appliance is drawn from inside the air nozzle body  12  and carries dust and dislodged solid material away from the internal surfaces through the internal passages of the air bar, through the air bar discharge slots  14  and through the vacuum air flow passages inside the ends of the cleaning tool housing  20  to the hose connection port  32 . 
     In the embodiments shown, for example see  FIGS. 3 and 4 , the rod  60  extends towards an access opening  61  in the dryer housing  62 , allowing for manual traverse action of the rod  60  by an operator so that the housing  20  can be moved along the length of the air bar  10  to clean the discharge slots  14  along their entire length. 
     The tabs  40  (see for example  FIG. 1 ) may be made of rigid metal such as spring steel, preferably of a hardness greater than the material of the air nozzle body  12 . In certain embodiments, the tabs  40  may be formed with a beveled or curved profile to prevent catching in the air bar slots  14  or gouging the edges of the air bar slots  14  as the assembly is propelled along the air bar  10  to be cleaned. The tabs  40  provide a mechanical means of cleaning solids from the air bar discharge slots  14  in conjunction with the air knife jet cleaning action. In certain embodiments, the tabs  40  extend preferably 10 mm outward from the discharge slot  26  of the air knife element  22  in the jet flow direction and are 5 to 20 mm, preferably 10 mm, in width, extending along the air knife discharge slot  26  length direction from the ends of the air knife element inward toward the center of the discharge slot length. This tab spacing (preferably 80 to 100 mm apart) and arrangement having four tabs engaged, two per air knife discharge slot engaged with each side of the slot opening, provides a stable engagement with the air bar slots  14 , preventing mechanical damage from misalignment forces that would otherwise create a prying action on the air bar slot gap. Accordingly, in certain embodiments, the tabs  40  of each air knife element  22  are positioned to be received by and engage a respective discharge slot  14  of the air bar to be cleaned. Although preferably each air knife element has at least two spaced tabs  40 , an air knife element  22  having a single tab  40  can be used. 
     The housing  20  may be supported by the sliding seal elements  30  riding on the air bar  10  top surface in the case of air bars facing upward (lower air bar nozzles in the oven). 
     In the case of cleaning the downward facing air bars (upper air bar nozzles in the oven), the housing  20  may be supported by means of a yoke assembly ( FIG. 2 ) having spring-loaded rollers engaged and supported on moveable track bars or rails  51  attached to the upper air bar support frame. The rails  51  may be removable or permanently attached to the header  80 . In some embodiments, the yoke assembly may be attached to the housing  20  with suitable latch clamps  52 , such as quick spring latch clamps, and/or with engagement pins  90  as shown. Optionally, the movable rails  51  can be used to support the housing  20  for cleaning of the lower air bars by means of a spring-loaded yoke assembly, including gas springs  81  and yoke frame  92 , in a similar manner as for the upper air bars. 
     One advantage of the embodiments disclosed herein is the cleaning action is provided by high velocity air knife jet action in combination with the mechanical scraper action of the tabs  40  along with vacuum air flow which provides an enhanced sheering action at the ends of the air knife jets in conjunction with the vacuum air flow acting in the opposite direction. For effective in situ cleaning of air bars, the operator, after following safe lock-out procedures and utilizing all necessary personal protection equipment, engages the cleaning tool housing to the air bar  10  to be cleaned, such as with the support yoke. A compressed air source is connected to the cleaner tool assembly via feed port  23 ; preferably by quick connect/disconnect fittings with a local hand valve to shut off flow. A vacuum source (e.g., a conventional SHOP-VAC® vacuum) appliance is connected to the cleaner tool housing connection. Vacuum is started first, followed by opening the compressed air source such as with a valve (not shown). The cleaner is manually traversed over the entire length of the air bar  10 . Following full traverse, the vacuum may be optionally disengaged and attached to vacuum port  15  on the air nozzle body  12  of the air bar (if provided) and the cleaner tool again traversed with compressed air on to blow and vacuum loose material directly from inside the air bar body. The compressed air source valve is then closed and the vacuum source disconnected. The cleaner tool is disengaged from the cleaned air bar. The procedure may be repeated for each air bar to be cleaned. A suitable controller may be used to traverse the cleaner rather than manual traverse. 
     It is to be appreciated that in certain embodiments, the cleaning operation of air nozzles in a flotation oven requires portability of the cleaning apparatus to interact with a plurality of air nozzles inside said dryer (oven). Therefore the portability and ease of positioning the cleaning housing  20  in a repetitive fashion is desired. Portability and positioning of the housing  20  on a plurality of the air nozzles may be carried out manually by a human operator or include pneumatic or electric powered assistance. 
     With reference to  FIG. 3 , in certain embodiments, the housing  20  may be manually propelled along the length of the air nozzle body  12  with an articulating push/pull rod  60  coupled to the housing  20  by any suitable means, such as a flexible coupling  70  coupled to a housing attachment rod  71 , allowing free rotation of the housing  20  such that air knife elements  22  are held in line with the discharge slots  14  of the air bar  10  via tabs  40  which are received by and penetrate into respective air bar discharge slots  14  at each end of each air knife element and may assist in aligning the tool with the bar. The movement of the housing  20  may also be controlled by a suitable controller. In an optional embodiment ( FIG. 4 ), controlled movement of the housing  20  may be effected by mechanically connecting a linear actuator  105  to the attachment rod  71  and/or flexible coupling  70  in lieu of or in combination with rod  60 . The linear actuator  105  in mechanical connection to housing may be initially positioned manually by a human operator grasping rod handle  100  connected to rod  60  and additional motion imparted to housing  20  is effected by the linear actuator  105 . The range of the travel motion of housing  20  may be selected to cover a portion of the length of air nozzle body  12  or to extend along the entire length of the air nozzle body  12  by selection of stroke length  106   a  of actuator rod  106 , thus providing automated cleaning over the desired location along the length of the air nozzle body  12 . The linear actuator  105  is preferably of the pneumatic air cylinder type (as commercially available from suppliers such as Bimba Manufacturing Company, University Park, Ill.) and is responsive to the controller and operated by compressed air regulated with a suitable pressure regulator and connected through suitable valves, such as solenoid operated valves, to air connection ports  107   a  and  107   b  in order to control extension and retraction of actuator rod  106 . Piping and air regulation arrangements for extension and retraction motion control of the rod  106  are well known to those skilled in the art. 
     In certain embodiments, for example see  FIGS. 5 and 6 , the controllers  130 ,  130   a  may have a processing unit and a storage element. The processing unit may be a general purpose computing device such as a microprocessor. Alternatively, it may be a specialized processing device, such as a programmable logic controller (PLC). The storage element may utilize any memory technology, such as RAM, DRAM, ROM, Flash ROM, EEROM, NVRAM, magnetic media, or any other medium suitable to hold computer readable data and instructions. The instructions may be those necessary to operate the actuator. The controller may also include an input device, such as a touchscreen, keyboard, or other suitable device that allows the operator to input a set of parameters to be used by the controller. This input device may also be referred to as a human machine interface or HMI. The controller may have outputs adapted to control the actuator. These outputs may be analog or digital in nature, and may provide a binary output (i.e. either on or off), or may provide a range of possible outputs, such as an analog signal or a multi-bit digital output. 
     In the embodiment of  FIG. 5 , a source of compressed air  140  is piped through vented solenoid operated valves  131   a  and  131   b  to air connection ports  107   a  and  107   b . Controller  130  operates solenoid actuators  131  which position the valves  131   a  and  131   b  to supply air pressure effecting the desired extension and retraction movement of linear actuator rod  106  in order to move housing  20 . Linear actuator  105  with trunnion mount  108  on the actuator housing is mounted in yoke  116  which is attached to portable mounting bracket  115 . The stroke length of rod  106  is preferably selected to provide a travel length suitable to propel housing  20  over the full length of air nozzle body  12 . Portable mounting bracket  115  is preferably clamped to the dryer (oven) enclosure frame  110  with clamping hand screw  117  or other suitable means mechanically connecting linear actuator  105  to the dryer (oven) enclosure frame  110  in order to anchor the actuator housing and propel cleaner housing  20  along the length of air nozzle body  12  without need of manual force by a human operator. In certain embodiments, portable bracket  115  may be easily moved along the length of the dryer enclosure frame  110  by loosening hand screw  117  and sliding bracket  115  to a new position in alignment with the next air nozzle body  12  to be cleaned and then retightening hand screw  117 . 
     Turning to  FIG. 6 , in an alternative embodiment a reversible linear screw actuator  105   b  of the electric type (as available from Electric Automations, Richmond, British Columbia Calif.) may be used to propel housing  20 . Motor  109  drives an acme screw, ball screw or other suitable mechanical actuating rod  106   b  of suitable length to extend and retract over the desired length of air nozzle body  12 , the actuating rod  106   b  being in mechanical connection with attachment rod  71  and/or flexible coupling  70 . Directional power is applied to the drive motor by means of a suitable reversing motor control  130   a  in order to control extension and retraction of electric actuator rod  106   b  as is known to those skilled in the art. 
     In a preferred embodiment to effectively clean air nozzle  10 , control of the linear actuation imparts an oscillatory motion to housing  20  as in a vibratory “scrubbing” action by alternate positioning of the solenoid operated valves piped to the pneumatic cylinder by controller  130  of  FIG. 5 , or by switching of applied power to the reversible electric linear actuator  105   b  by controller  130   a  of  FIG. 6 . The switching frequency to effect the oscillatory motion is adjustable by the operator, preferably in the range of 0.5 to 10 Hz with stroke amplitudes in the range of 1 to 20 millimeters in order to effect the vibratory scrubbing action. In a preferred control sequence of operation of either of the arrangements shown in  FIG. 5  or  FIG. 6 , the actuating rod  106  or  106   b  of the linear actuator  105  or  105   b , respectively, begins the cleaning sequence in an extended position in order to position housing  20  over a beginning position on air nozzle  10  to be cleaned, and executes the vibratory motion for a preset desired period of time, typically 1 to 10 seconds. Following the period of time the actuator rod retracts over a travel distance [substantially] equal to the length of air knife  22  of  FIG. 1C , typically in the range of 2 to 6 inches. Following this retraction movement, the vibratory action is again initiated for a preset period of time. The sequence is repeated until the overall actuator rod retraction travel has moved housing  20  fully to the end of air nozzle  10  opposite the beginning position. 
     While various aspects and embodiments have been disclosed herein, other aspects, embodiments, modifications and alterations will be apparent to those skilled in the art upon reading and understanding the preceding detailed description. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting. It is intended that the present disclosure be construed as including all such aspects, embodiments, modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.