Glass sheet cleaning apparatus

Abstract: In stationary equipment including a system for successively conveying curved glass sheets (90) in a linear horizontal pathway through washing and rinsing zones, and then a drying zone, upper (106, 108, 110) and lower (100, 102, 104) air knife assemblies are utilized in the drying zone for simultaneously directing pressurized air streams on the opposite broad surfaces of the glass sheets (90) to effect drying action. Each air knife assembly comprises an elongated bendable casing (114) formed into a plenum (112) disposed transverse to the pathway, with each plenum having a longitudinally extending slot (120) serving as an orifice for emitting the air stream against the glass surface. The slot is defined by parallel spaced flexible strips (116, 118) sealed in longitudinal disposition on the casing (114). The strips, with the casing to which they are sealed, are adapted to be selectively adjustably shaped to generally conform to various glass sheet configurations. Conveying successive curved glass sheets through the drying zone is accomplished by continuously advancing spaced-apart cord-like belts (34, 36) supporting the sheets (90) for movement along the pathway and preferably between the upper and lower air knife assemblies.

Description: Background of the Invention This invention relates generally to the cleaning of glass sheets in apparatus wherein glass sheets are successively transported by a conveyor system through washing and drying zones, and it more particularly pertains to such apparatus particularly designed for cleaning bent or curved sheets or plates of glass. It is common industrial practice to clean substantially large sheets of glass by providing equipment including a conveyor system that continuously moves successive glass sheets first through an enclosed tunnel-like washing and rinsing zone and then through a drying zone. The degree of required cleanliness determines the complexity of the equipment utilized in the washing and rinsing operation. A relatively simple water flushing and brushing process may be used where the glass sheets need only be generally visibly clean. Absence of finger marks, streaks, or spots on the sheets may require more intensive brushing and use of a heated detergent solution prior to rinsing. Greater degrees of cleanliness may be required where the glass sheets are intended for insulating, laminating, silvering, or vacuum coating processes, and for such needs, chemical-free or even clinical cleanliness can be accomplished by the provision of specialized brushing equipment, repetition of steps in the washing process, and more thorough or repeated rinsing. It is typical, following the washing and rinsing steps, to convey the glass sheets through a drying zone where rinse water is removed such that the sheets are dispensed from the conveyor in a perfectly dry condition for packing or a subsequent manufacturing operation. In some relatively low-efficiency glass washer-dryer equipment, the glass sheets are dried by application of heated rinse water which is allowed to evaporate from the glass surface. This method typically results in water spotting and does not accomplish effective drying of the glass edges. More advanced systems virtually eliminate water spotting by accomplishing the drying operation through the use of a high-pressure air stream applied to the glass sheet surfaces. Each glass sheet, supported by the conveyor, is moved past an adjacent slot elongated to reach across the entire sheet, and the high-intensity blower-driven air stream is emitted close to the sheet surface at a predetermined angle to peel the water and any other impurities from the glass surface and blow them rearwardly as the glass sheet progresses forwardly on the conveyor. The structure which distributes the air stream against the glass, including the aforementioned slot, is referred to in the industry as an air knife. A plurality of spaced-apart air knives may be utilized whereby the glass sheet, as it progresses on the conveyor, may be subjected to successive high-intensity air stream applications to effect thorough drying of the sheet. The typical air knife assembly includes an elongated box-like enclosed chamber or plenum disposed to extend transverse to the pathway of the conveyor on which the successive glass sheets are supported. From a remote stationary heavy-duty blower, a continuous air flow is conducted into the plenum through an inter-connecting conduit, and the air flow is distributed from the plenum through a longitudinal slot as a high velocity curtain-like air stream striking the glass surface on a line extending entirely across the sheet. For the cleaning of curved glass sheets which present one concave surface and an opposite convex surface, it is common practice to provide a conveyor system adapted to support the sheets from beneath, for travel in a horizontal pathway, with the sheets oriented with the axis of their curvature parallel to the pathway. US-A-2671241 discloses a glass drying apparatus in which the sheets are supported in this way. For such specialized cleaning equipment, air knives have been developed where the structure defining the air stream distribution slot has a rigid sweeping curvature so that the slot is positioned closely parallel to the curved glass sheet surface conveyed past the slot during the drying operation. Such equipment has proven very effective for its desired purpose but is limited in its application to the cleaning only of curved glass sheets to which the air knives are shaped to conform. Such machinery has been adapted to permit conversion by substitution of appropriately shaped air knives consistent with the particular curvature of glass sheets to be subjected to a cleaning operation. Such conversion, however, necessitates the special construction of differently shaped air knives, each shape suitable only for drying glass sheets of a particular curvature. This involves high manufacturing costs and the additional operating expenses associated with extensive conversion down time. The present invention comprehends the provision of apparatus in the form of stationary equipment for cleaning curved glass sheets by conveying identical successive sheets through washing and rinsing zones and then through a drying zone where pressurised air streams are directed against the entire sheet to effect a thorough drying operation. The curved glass sheets are preferably conveyed through the successive cleaning zones in a linear horizontal pathway, with the sheets being supported on their underside by the conveyor and the sheets preferably being oriented such that their major symmetrical curvature is parallel to the direction of travel of the conveyor. It is a primary aim of the present invention to provide, in curved sheet glass cleaning apparatus, air knife structure capable of being reshaped to a plurality of curvatures without requiring its removal from its general operative disposition. According to the present invention there is provided apparatus for drying sheets of glass including conveyor means for moving a wet glass sheet, oriented with its broad surface facing generally vertically, in a linear pathway, at least one air knife assembly including an elongated plenum disposed adjacent the pathway and opened along its length, with the plenum having a pair of opposed edges defining the opening, a pair of opposed, elongated, parallel, spaced flexible strips with each strip secured to each respective edge, the securement of the strips to the edges constituting a longitudinal slot for emitting a continuous air stream against at least one broad surface of the sheet in a pattern transverse to the direction of sheet movement, each strip having an angled facing edge for effecting the direction of air stream emission, and the slot being adjustable to a plurality of predetermined curvatures, each generally conforming to the curved configuration of particular glass sheets. Separate upper and lower air knife assemblies may be utilised in the apparatus, each fixedly mounted and conformably curved relative to the adjacent glass surface against which its air stream is directed. For providing the air flow to the plenum and thence creating the air stream from the slot of the air knife, a remotely located stationary heavy-duty blower is utilised and its output side is connected to conduit means communicating with the plenum. In its preferred form, the conduit from the blower to the plenum is flexible tubing of the same general structure and diameter as the plenum body and constitutes two separate conduits coming from the output side of the blower with each extending to join the plenum at one of its ends whereby the longitudinal slot is the only available exit for the air flow and the rate of distribution along the length of the slot is thereby maintained uniformly constant. The air knife apparatus of the present invention may further include rigid slot bridging means substantially contained within the tubular member for maintaining the integrity of the assembly, and adjustable mounting means permitting reshaping of the air knife body, in accordance with a desired contour or curvature, and locking the air knife body in the reshaped orientation. The air knife is also preferably provided with means to enable it to be selectively tilted as a unit and means to shift it angularly as a unit on a vertical pivot line. In a preferred embodiment of the present invention there is also provided means for selectively adjusting the tilt of the air knife or the angle of its line of extension across the pathway in which glass sheets are conveyed for accomplishing a drying operation thereon. Other structural and functional features of the invention will become apparent from the ensuing detailed description of the presently preferred embodiment of the invention when read in reference to the accompanying drawings. Figure 1 is a side elevational view of structure constituting drying zone apparatus of the present invention; Figure 2 is a top plan view of the structure first shown in Figure 1 but, here, showing certain components repositioned relative to that which is shown in Figure 1; Figure 3 is an isometric view illustrating the output end of the drying zone apparatus of the present invention; Figure 4 is a view in vertical section taken generally along lines V-V of Figure 1; Figure 5 is a fragmentary enlarged view in vertical section taken from the structure first shown in Figure 1; Figure 6 is an isometric illustration of an element of the invention first shown in Figure 5 and shown enlarged as compared in Figure 5; Figure 7 is a fragmentary enlarged side elevational view of air knife structure in accordance with the present invention; and Figure 8 is a view in enlarged vertical section of a component of the air knife structure shown in Figure 7. Figure 1 illustrates structure utilised in a system for effecting a drying operation on substantially large glass sheets. The structure includes a support frame identified generally by the numeral 10, and a conveyor system 12. The components of the support frame 10 are best shown in Figures 1, 2 and 3. The support frame 10 has a rectilinear configuration with fixed vertically-extending pillars 14, 16, 18, and 20 interconnected by upper longitudinally-extending beams 22 and 24, intermediate longitudinally-extending beams 26 and 27, and floor-level beams 28 and 29. The rectilinear form of the support frame 10 further includes upper cross-beams 30 and 31, and floor-level cross-beams 32 and 33. In addition to the major fixed frame components of the support frame 10 heretofore described, there are other adjunct support members which will be mentioned as this description continues. The conveyor system 12 is positioned to extend longitudinally and centrally through the support frame 10. US-A-2312186, US-A-2671241, US-A-3679076 and US-A-4189047 disclose examples of conveyor systems. As illustrated in Figure 1, the apparatus of the present invention includes air knife means, preferably comprising separate air knife assemblies 100, 102, 104, 106, 108 and 110. The provisions of air knife means enables the use of a pressurised air stream to effectively "peel" rinse water from both broad surfaces and all the edges of prewashed and rinsed glass sheets whereby glass sheets conveyed through the drying zone established by the disclosed apparatus are delivered therefrom in a fully dried condition. The air knife assembly 110, shown in Figure 5, is generally representative of the other air knife assemblies in the apparatus, includes an air distribution plenum identified generally by numeral 112 having a casing 114 with a flat long side or face constituting a pair of strips 116 and 118 defining between them a slot 120. As shown in Figure 4, the plenum 112 is elongated whereby its casing 114 extends from one plenum end 122 to its other end 124. The strips 116 and 118 are also elongated, extending the full length of the casing 114. The plenum 112 is preferably formed by utilising, for the casing 114, a length of commercially available, corrugated, cord-reinforced tubing. Such tubing, having a vinyl exterior and ring-like corrugations 121 is similar to a corrugated plastic vacuum cleaner hose but of a significantly larger diameter (preferably 4-inch wide diameter). An appropriate length of the tubing is split along its length, as indicated in Figure 8, and the resulting edges defining the split are reformed outwardly to provide longitudinal flanges 126 and 128. The strips 116 and 118 are cut from a substantially thick sheet (preferably 25 inches) (63.5 cm) of semi-rigid flexible plastic material. Polyethylene having an ultra-high molecular weight has been successfully used for this purpose. The strips 116 and 118 are respectively sealably fixed, along one long edge thereof, to the underside of the respective flanges 126 and 128. A plurality of internal rigid abridgement members 130, one of which is shown separately in Figure 6, are equidistantly spaced within the casing 114, as shown in Figure 7. Each bridging member 130 has a central rigid U-shaped portion 132 (Figure 6) and integral oppositely-extending arms 134 and 136, terminating in respective upwardly turned end portions 138 and 140. As shown in Figure 5, the bridging member 130 bridges the slot 120, and its respective legs 134 and 136 are sealably captured between the respective strips 116 and 118 and the casing flanges 126 and 128. The ends 138 and 140 provide respective connecting points for a rigid support bracket member 142 and rod 144. The air knife assembly 110 further includes an angle iron member 146, shown in its full length in Figure 4, which serves as a mounting base for the plenum 112. The angle iron member 146 is connected, at each of its ends, to respective tiltable pedestals 148 and 149, adjustably fastened respectively to beams 26 and 27 (Figure 5). Along the length of the angle iron support member 146 (Figure 4), each of the rods 144, oriented vertically, is slidably secured by its own releasable clamp 152. At an intermediate point along its length, the plenum 112 has a fixed rigid mounting plate 154 (Figure 4) secured at one end to the angle iron member 146 and at its other end to the flanges of the casing 114 and the contiguous strip 118 (Figure 5). The plenum 112, at its end 122 and 124, is joined to conduit or tubing sections 160 and 162 (Figure 4), each of which is preferably the same type of tubing used in the formation of the casing 114. The conduits 160 and 162 may each be joined to the plenum casing by provision of an internal rigid collar which extends across the point of jointure and the provision of outer clamping bands 163 to complete the connection. Each of the conduits 160 and 162 has an end projecting outwardly from the support frame 10 which is connected to the output side of a heavy-duty blower assembly 164. Figures 3, 4 and 5, show the structure forming or relating to the air knife assembly 104 which is disposed directly beneath and coextensive with air knife assembly 110. The air knife assembly 104 includes a plenum 168 which is substantially identical in construction to the plenum 112 in the air knife assembly 110. The plenum 168 has its own set of support rods 172, identical in form and function to the rods 144. The rods 172 extend upwardly, as shown in Figure 4, from a rigid member 174 shaped as an inverted "V" and having opposite ends 176 and 178 fixedly secured to an angle iron member 180. At each of its ends, the angle iron member 180 is rigidly joined to upwardly-projecting arms 182 and 184 which are rigidly attached to respective hanger members 186 and 188 tiltably suspended from the respective beams 28 and 26. The plenum 168 is clamped in flow communication with flexible tubular members 190 and 192 by means of clamping bands 194. As shown in Figure 3, the conduits 190 and 192 are in flow communication with the output side of blower 164. The apparatus shown in Figure 1 constitutes the drying zone to which glass sheets are successively delivered in a wet condition from equipment (not shown) which thoroughly washes and rinses the sheets. The washing and rinsing equipment is provided with its own separate conveyor system having a horizontal bed at the same level as that of the conveyor system 12 whereby each wet sheet is smoothly transferred to the drying apparatus shown in Figure 1. Each sheet moves through the drying apparatus in a linear horizontal pathway, from left to right as viewed in Figure 1. As the sheet progresses through the drying zone established by the apparatus, it is subjected to high-intensity rearwardly-angled air streams emitted from the air knife assemblies spaced along its route of travel. The air stream impacting against the glass surface first creates a dynamic barrier which breaks the water film adherence to the surface and creates a curtain-like barrier to halt the forward progress of the water film. Then, the force of the rearwardly dissipating air stream imparts energy to the arrested water accumulation whereby the water is propelled rearwardly as the glass sheet continues its forward progression on the conveyor. Each air knife assembly of the present invention, in addition to being reshapable along its length to conformably curve the plenum face to a desired configuration, is also adapted for a limited tilting or rolling adjustment on an axis parallel to the plenum. Referring again to air knife assembly 110, it will be seen that this is accomplished by the manner in which the pedestals 148 and 149 and the hangers 186 and 188 are adjustably secured to the respective support frame beams 26 and 27. Moreover, the plenum may be selectively shifted a limited distance by shifting its angle of orientation relative to the pathway of conveyor travel. More specifically, the elongated plenum, whether above or below the conveyor travel pathway, always extends transversely, at an angle to a vertical plane taken centrally through the pathway. The mounting arrangement of the plenum includes means for a limited adjustment in the angular position of its extension relative to the described vertical plane. The present means of accomplishing such adjustment is shown in Figures 2, 3 and 5. As shown in Figures 3 and 5, the pedestal 148 is carried on a slidable plate member 150. The plate member 150 may be selectively repositioned along the beam 27. A similar slidable arrangement is provided for the hanger member 188. Figure 3 shows that the pedestal 149 and hanger member 186, are slidably arranged on the beam 27. Figure 2 shows that the plate member 150 is appropriately slotted to accommodate the repositioning of the angle iron support member 146 whereby the air knife assembly 110 can be angularly shifted relative to the conveyor pathway to a position, for example, as shown in Figure 2 for the air knife assembly 108 or that of the air knife assembly 106. With reference to the slidable arrangement for supporting the aforedescribed pedestals and hanger members as illustrated in Figure 5, and the slidable arrangement for the journal support frames of the pulleys 64, shown in Figure 3, the structure to accomplish the slidable function can be interlocking channel tracks which are commercially available and sold under the trade name "Unistrut". With reference to the selective reshaping of the plenum structure of an air knife assembly to conform it to a particular glass sheet configuration, it should be noted that the plenum structure of air knife 100 (which is representative of all other air knife assemblies shown) is reshaped first by appropriate loosening of the clamps 152 as shown in Figure 4, followed by proper manipulation of the rods 144 whereby the bending action occurs in the strips 116 and 118, with the flexible casing 114 flexibly conforming to the bending of the strips. The clamps 152 are then tightened to hold the rods 144 in their respective new positions. Imparting the bending action to the strips, rather than the centerline of the casing, assures that the resultant stress or strain maintains the strips in tension rather than compression to thereby avoid buckling or distortion of the strips which would destroy the continuity of the slot 120. Although the apparatus shown in Figure 1 utilises six separate air knife assemblies arranged in upper and lower pairs, the actual number required in any given installation depends upon such variables as the size and shape of the glass sheets being processed and the end use requirements of a particular installation. In some installations, only one set of upper and lower air knife assemblies may be required whereas a spacing of a plurality of air knife assemblies along the route of travel can assure absolute dryness of the emerging sheets with respect to both major surfaces and the edges as well. A glass sheet passing through the first set of upper and lower air knives loses the bulk of its rinse water coating but water droplets missed by the first air knife sweep, particularly along the sheet edges, will streak rearwardly over the upper and lower broad surfaces of the sheet and be picked up and "peeled" off by the next set of air knives disposed downstream in the sheet travel pathway. The effective operation of an air knife in achieving effective drying of glass sheets and glass cleaning equipment requires that the elongated orifice or slot through which the air stream is emitted be at a close uniform distance from the sheet's surface at any point across the sheet. Hence, the versatility of such equipment is significantly enhanced by the provision, in accordance with this invention, of an air knife assembly capable of preadjustment to conform the orientation of the air stream emitting slot to the configuration of glass sheets to be cleaned in a mass production operation. The adjustable air knife assembly is compatible for perfectly flat sheets while being also adaptable to curved glass sheets of the type now commonly used for vehicle windshields and rear windows. It is contemplated that the adjustable air knife assemblies of the present invention may be employed with known forms of sheet material conveyors, including conveyor systems having spaced rollers carried on rotating transversely-extending shafts, in which the sheet would be passed between upper and lower air knife assemblies without continuous sheet support in the area between the adjacent upper and lower air knife slots that is provided by the conveyor system 12. It is anticipated that modifications or variations may hereafter be made which depart from the specific structure illustrated with reference to the preferred embodiment in the accompanying drawings, and it is intended that all such modifications or equivalent variations be included within the scope of the appended claims.

Claims: Apparatus for drying sheets of glass including conveyor means for moving a wet glass sheet (90), oriented with its broad surface facing generally vertically, in a linear pathway, at least one air knife assembly (110) including an elongated plenum (112) disposed adjacent the pathway and opened along its length, with the plenum (112) having a pair of opposed edges defining the opening, a pair of opposed, elongated, parallel, spaced flexible strips (116, 118) with each strip (116, 118) secured to each respective edge, the securement of the strips (116, 118) to the edges constituting a longitudinal slot (120) for emitting a continuous air stream against at least one broad surface of the sheet (90) in a pattern transverse to the direction of sheet (90) movement, each strip (116, 118) having an angled facing edge for effecting the direction of air stream emission, and the slot (120) being adjustable to a plurality of predetermined curvatures, each generally conforming to the curved configuration of particular glass sheets (90). The apparatus of claim 1, characterised by the plenum (112) being formed from flexible tubing. The apparatus of claim 1 or 2, further characterised by the plenum (112) being at least partially arcuate in cross-section. The apparatus of any proceeding claim further characterised by the plenum (112) being in flow communication with a means (164) for generating a pressurised air flow. The apparatus of any of claims 1 to 3, further characterised by the plenum having a first end (122) and a second end (124) connected to receive a pressurised air flow. The apparatus of any preceding claim further characterised by the plenum (112) comprising flexible tubing (114) split along its length and rigid bridging means (130) contained within the tubing for maintaining the strips (116, 118) in relative parallel and spaced disposition to define the slot. The apparatus of claim 6 further characterised by the strips (116, 118) being sealed to and along the respective tubing edges (126, 128). The apparatus of any preceding claim further characterised by said one air knife assembly (110) being disposed above the pathway and a further air knife assembly being disposed below the pathway. The apparatus of any preceding claim further characterised by a plurality of rods (144) movably secured, in spaced relation to each other, from a frame member (146) the frame member (146) extending in a generally horizontal disposition transverse to the pathway, the plenum (112) disposed in spaced adjacency to the frame member (146) and each of the rods (144) connected to the plenum. The apparatus of claim 9 further characterised by the frame member (146) being adapted for limited tilting on an axis coextensive with the frame member. The apparatus of any one of claims 1 to 8, further characterised by means mounting the plenum (112) for selective limited tilting relative to an axis extending in the lengthwise direction of the plenum (112). The apparatus of any one of claims 1 to 8, further characterised by means (144) for selectively reshaping the plenum (112) by bending it on plural, spaced-apart and parallel axes which are transverse to the direction of the plenum's (112) elongation. The apparatus of any preceding claim, further characterised by the plenum (112) extending at an angle to a vertical plane taken centrally through the pathway, and means for selectively changing the angle of the plenum (112) relative to the vertical plane.

Inventors: SHANER DALE H, TRAUTMANN HUGH M, SHANER, DALE H., TRAUTMANN, HUGH M.
Applicants: BILLCO MFG CO, BILLCO MANUFACTURING COMPANY
Application year: 1990
Main classification: B08B11
IPC codes: B08B11, F26B21