Abstract:
A pneumatic handling and recoating apparatus for handling workpieces, such as glass, is provided. The apparatus utilizes a holding device operatively connected to a vacuum assembly. The holding device engages workpieces by vacuum and subsequently releases them by a burst of gas. The burst of gas also facilitates the application of a coating material, such as a stain-retardant agent, to a workpiece upon release from the holding device.

Description:
FIELD OF THE INVENTION 
   The present invention provides an apparatus for lifting and handling objects, such as glass, by utilizing a holding device operatively connected to a vacuum source. More specifically, the invention provides a holding device that engages objects by vacuum and subsequently releases them by a burst of gas that includes one or more protective materials that adhere to the surface of the object. 
   BACKGROUND OF THE INVENTION 
   It is a conventional feature of automatic machines for moving materials, particularly sheet-like materials, that the material is handled using suction devices connected to air lines of a pneumatic system. Systems of this nature, for example, are commonly used in moving glass sheets. In such operations, suction cups are typically connected to vacuum pumps and invested with translatory motion such that they can be made to approach and grip the outermost sheet of a stack. The outermost sheet, which may be at the top, bottom, front, or back of a stack, is then separated from the stack and translated toward the final destination by a distancing movement of the suction cups. 
   When the suction cups are to be detached from the sheet to allow further processing, the connection with the vacuum pumps is terminated, and the cups are vented to the atmosphere. Alternatively, the connection with the vacuum pumps can be terminated, and the cups subjected to a burst of compressed gas. The connections in question are controlled in most instances by means of pneumatically actuated valves, which are incorporated into the delivery system. For example, the use of three-way valves is conventional in this field. 
   In practice, these suction cups can leave traces of contact on the surface of a workpiece, which is typically a rigid sheet of material. For example, upon release of a suction device, suction cup shaped markings can be left on the handled surface. The suction device can also remove powders and/or other coatings that have been applied to the workpiece. Sheets of glass, for example, are often treated with protective powders (or “separators”), as discussed below. Removal of these powders by the suction device can have adverse effects on the glass. For example, the surface of the glass from which the powder is removed will subsequently be vulnerable to soiling, staining, and corrosion by water and/or other materials. 
   It is noted that moisture corrosion roughens the surface of glass. In fact, the longer water sits on a glass surface, the more the surface is typically affected. For example, as water sits on glass, alkali components are leached from the glass, thereby changing the pH of the water to alkaline. Thus, when water is allowed to remain on unprotected glass for a significant period of time, it tends to remove elements from the glass, particularly sodium ions. This process leaves a mark on the glass that, in some cases, can be so objectionable as to render the glass unsaleable. 
   As noted above, glass is typically treated with stain-retardants that prevent or minimize damage from moisture corrosion. For example, acidic buffers, such as adipic acid and maleic acid, are commonly sprayed onto the glass. These buffers are sometimes mixed into a powder which, as noted above, is generally referred to as a “separator”. The separator also provides protection during storage and transportation against abrasion between adjacent glass sheets in a stack. 
   As noted above, conventional pneumatic handling devices tend to remove some of the protective material from glass sheets during handling. For example, when glass is engaged by a pneumatic handling device, each suction cup acts somewhat like a vacuum cleaner. In effect, the protective material is vacuumed from the surface of the glass. Further, to effect disengagement of the suction cup from the glass, a short blast of pressurized air is sometimes applied. This blast of air can carry away even more of the protective powder. Finally, the portions of the suction cup that contact the glass tend to carry away protective material from the glass surface. 
   Often, it may not be immediately apparent that the protective powder has been displaced. In fact, suction cup marks may only appear after extended periods of storage. While these marks can be made visible by fogging the glass with steam, this procedure is so time-consuming as to be economically unfeasible. Even if no suction cup marks appear following storage, these marks may show up once the glass has been coated. To make matters worse, some suction cup marks only appear after the coated glass has been tempered. Of course, suction cup marks decrease the quality and value of glass. Moreover, depending on the severity of the marks, such damaged glass may be rejected in the marketplace. 
   It would be desirable to provide material handing devices and methods, particularly for glass sheets, which facilitate handling workpieces coated with protective material (e.g., powder) without removing such material during handling or replacing material upon release. 
   SUMMARY OF THE INVENTION 
   The present invention reduces the likelihood of corrosion and attendant marking caused by the handling and/or movement of a workpiece, by utilizing pneumatic holding devices that coat or recoat the surface of the workpiece that was contacted by the devices with a protective material. Accordingly, embodiments of the present invention provide a holding device that utilizes a vacuum system, which may temporarily remove the protective material during pneumatic holding, but subsequently replaces the protective material when the holding device is detached. Furthermore, embodiments of the present invention utilize a burst or blast of gas including a protective material, such as stain-retardant powder, to recoat the surface of a glass sheet upon detachment of the holding device from the glass. Thus, the adverse effects that can result from removal of such protective materials can be minimized by the reapplication of such material during the release procedure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic drawing depicting a pneumatic handling and recoating apparatus in accordance with one embodiment of the present invention; 
       FIG. 2  is a perspective view of a pneumatic handling and recoating apparatus which includes a holding device, vacuum assembly, and gas assembly; 
       FIG. 3  is a perspective view of a pneumatic handling and recoating apparatus which includes a holding device, vacuum assembly, and gas assembly; 
       FIG. 4  is a frontal perspective view of a holding device of a pneumatic handling and recoating apparatus; 
       FIG. 5  is a sectional view of a holding device in accordance with one embodiment of the present invention; 
       FIG. 6  is a top partially sectional view of a pneumatic handling and recoating apparatus that includes a holding device, a coating device, and vacuum and gas assemblies in accordance with another embodiment of the invention; 
       FIG. 7  is a top partially-sectional view of a pneumatic handling and recoating apparatus that includes a single unit vacuum/gas assembly, a coating assembly, and holding devices in accordance with still another embodiment of the invention; 
       FIG. 8  is a top partially-sectional view of a pneumatic handling and recoating apparatus that includes a single unit vacuum/gas assembly, a coating assembly, and holding devices in accordance with yet another embodiment of the invention; 
       FIG. 9  is a sectional view of a holding device, which is operably coupled with a single channel pneumatic system in accordance with one embodiment of the invention; and 
       FIG. 10  is a sectional view of a holding device, which is operably coupled with a single channel pneumatic system in accordance with another embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings, depicted in  FIG. 1  is an embodiment of a pneumatic handling and recoating apparatus  10  of the present invention for handling workpieces. The apparatus  10  is particularly useful for handling sheet-like workpieces (e.g., sheets of glass, metal, plastic, or any other types of panels, such as automotive panels). The illustrated pneumatic handling and recoating apparatus  10  generally includes a base frame  35  and a plurality of holding devices  40 . In this embodiment of the present invention, the base frame  35  is constructed of a plurality of retention beams (or “rods”)  45 , each adjoined to a main beam  50 . Each retention beam  45  is coupled to an adjacent retention beam  45  by one or more connectors  55  (e.g., bolts, hinges, rivets, welds, etc.). Each of the illustrated retention beams  45  are connected to the main beam  50 .  FIG. 1  also depicts holding devices  40  including optional spray grids  42  with their associated spray apertures  44 . Such holding devices  40  are described below in more detail. 
   The main beam  50  can be provided with a movement system  48  as depicted in  FIG. 2 , including a track or rail system  60 , which facilitates movement of the entire apparatus  10  as well as movement the retention beams  45  selectively closer to, or further away from, one another. Movement of the retention beams  45  allows the holding devices  40  to be positioned to accommodate objects of various sizes and shapes. In embodiments that facilitate such movement, the connectors  55  are desirably adapted to permit pivoting. Preferably, the movement system also facilitates moving the entire base frame  35  from place to place (e.g., along the track or rail). Other mechanisms known in the art can be incorporated to facilitate movement of the base frame  35  and/or movement of the beams  45  relative to one another. For example, various hydraulic or electrical assemblies can be utilized to facilitate such movement. 
   The retention beams  45  and main beam  50  can be formed of any material suitable for supporting the weight of the desired objects to be handled. For example, suitable materials include metals, alloys, fiberglass, rigid plastics, and any other materials used conventionally for structures of this nature. The holding devices  40  can be positioned upon the retention beams  45  at any desired locations. Preferably, holding devices  40  are generally uniformly spaced (as shown in  FIG. 1 ) to provide optimum engagement with sheet-like workpieces.  FIGS. 2–4  illustrate the spacing of suction cups on conventional pneumatic handling apparatuses. The holding devices  40  of the present invention can be spaced about the base frame  35  in much the same arrangement. 
     FIGS. 4 and 5  illustrate a preferred holding device  40  of the present invention. The holding device  40  (or “suction device”) includes a rim  65 , a bellows  70 , a cavity  75 , and an optional spray grid  42 . The rim  65  is preferably formed of an elastomer material that is adapted to provide a good seal between the holding device  40  and the surface of a workpiece (not shown). A flexible material is preferred, such as rubber or neoprene. A bellows  70  expands from the rim  65  of the holding device  40 . The bellows  70  is advantageously formed of a flexible material that permits contraction and expansion thereof according to the gas pressure within. The bellows  70  and inner walls of the rim  65  define boundaries of the cavity  75 . Finally, each holding device  40  optionally includes a spray grid  42 , located within the cavity  75 . If present, the spray grid  42  assists in dispersing coating onto the surface of a workpiece through the spray apertures  44 . It is noted that each holding device  40  of the invention can be provided in the form of a cup or pad in any desired size or shape. 
   With reference to the embodiment typified in  FIG. 6 , each holding device  40  can be operably connected, in a selective manner, to a vacuum assembly  80 , gas assembly  84 , and coating assembly  88 . In one embodiment of the present invention, the vacuum assembly  80 , gas assembly  84 , and coating assembly  88  can each be mounted, or located adjacent, to the main beam  50 . The vacuum assembly  80  is advantageously provided with a vacuum generator (not shown) operably connected to vacuum conduits  135 , such as vacuum hoses, which preferably lead in parallel to each of the holding devices  40 . If so desired, a single vacuum conduit  135  can alternatively be routed in series to each of the holding devices  40 . With continued reference to  FIG. 6 , each vacuum conduit  135  is adjoined, via a connection housing  100  on one of the holding devices  40 , to a vacuum channel  140  opening into the cavity  75  of that holding device  40 . Thus, when the holding devices are engaged with a workpiece (not shown), the vacuum generator can be operated to draw a vacuum in the cavity  75  of each holding device  40 , thereby sealingly attaching the holding devices  40  to the workpiece. 
   The pneumatic assembly  10  embodiment of  FIG. 6  is provided with a vacuum assembly  80  that is separate from the gas assembly  84 . The gas assembly  84  is advantageously provided with a gas compressor (not shown) operably connected to gas conduits  145 , such as gas hoses, which preferably lead in parallel to each of the holding devices  40 . If so desired, a single gas conduit  145  can alternatively be routed in series to each of the holding devices  40 . With continued reference to  FIG. 6 , each gas conduit  145  is adjoined, via a connection housing  100  on one of the holding devices  40 , to a gas channel  150  opening into the cavity  75  of that holding device  40 . In more detail, each illustrated gas conduit  145  opens into a coating reservoir  120 , from which extends a gas channel  150 . As discussed below, the optional coating reservoirs  120  are adapted to receive coating material from the coating assembly  88  (via coating conduits  155 ). 
   If provided, the coating reservoir  120  (or “chamber”) is preferably adapted to accommodate enough coating material to sufficiently coat or recoat the workpiece surface to which the holding device  40  is attached. The size of the chamber, of course, can be varied depending the amount of coating that is desirably applied to the workpiece. One or more reservoir valves (not shown) can be positioned within the coating reservoir  120  to control the injection, retention, and release of the coating. Such reservoir valves would allow entry of coating into the reservoir  120  at the desired time and also release coating from the reservoir  120  into the suction device  40  when desired. Reservoir valves can, of course, be utilized in this manner in any embodiment of the present invention. 
   The pneumatic assembly  10  also includes a coating assembly  88 . Generally speaking, the coating assembly  88  is a containing and injection system for retaining a supply of coating and delivering coating material to the holding devices  40 . The coating assembly  88  is advantageously provided with a coating injector (not shown) operably connected to coating conduits  155 , such as coating hoses, which preferably lead in parallel to each of the holding devices  40 . If so desired, a single coating conduit  155  can alternatively be routed in series to each of the holding devices  40 . With continued reference to  FIG. 6 , each coating conduit  155  is adjoined, via a connection housing  100  on one of the holding devices  40 , to a gas channel  150  opening into the cavity  75  of that holding device  40 . In more detail, each illustrated coating conduit  155  opens into to a coating reservoir  120  from which extends a gas channel  150 . If so desired, each coating conduit  155  can alternatively be adjoined at an intersection point to one of the gas conduits  145 , such that the coating conduit  155  opens into the gas conduit  145  at such intersection point. 
   With continued reference to  FIG. 6 , when the holding devices  40  are engaged to a workpiece (not shown), the vacuum generator (or “vacuum source”) can be utilized to create a vacuum in the cavity  75  of each holding device  40 , thereby sealingly attaching the holding devices  40  to the workpiece. When it is desired to detach the holding devices  40  from the workpiece, the gas  84  and coating assemblies  88  can be operated to deliver coating material to the coating reservoirs  120  and to deliver a burst of gas through the gas lines  145  so as to expel the coating material from the coating reservoirs  120 , through the gas channels  150 , and onto the workpiece. It is noted that in various embodiments of the present invention a series of injection nozzles may be operably adjoined to the coating reservoir  120  and extending through the apertures  44  to deliver the burst of gas and coating material to the surface of the workpiece. Preferably, the coating assemblies  88  and gas assemblies  84 , are operated in succession, although simultaneous operation is also envisioned. For example, the coating assembly  88  can be operated to deliver coating material to the gas conduits  145  or coating reservoirs  120  prior to detachment of the holding devices. Thereafter, the gas assembly  84  can be operated to deliver a burst of gas through the gas conduits  145 , thereby detaching the holding devices  40  and expelling coating material from the gas channels  150  onto the workpiece. 
     FIGS. 7 and 8  depict embodiments of the invention wherein a single unit provides emission of both gas and vacuum. As shown in  FIGS. 7 and 8 , an integrated compressor/vacuum assembly  90  can be mounted to the top of the main beam  50 . Alternatively, an integrated compressor/vacuum assembly  90  can be positioned in an area surrounding the pneumatic handling and recoating apparatus  10 . The mounting of this assembly  90  would, of course, be well within the purview of those skilled in the art. 
   With reference to  FIG. 7 , the compressor/vacuum assembly  90  advantageously includes a gas compressor (not shown) and a vacuum generator (not shown). In the illustrated embodiment, the compressor/vacuum assembly  90  is operably connected to multiple pneumatic conduits  175 , which lead to each of the holding devices  40 . If so desired, a single pneumatic conduit  175  can alternatively be routed in series to each of the holding devices  40 . In the illustrated embodiment, each pneumatic conduit  175  is adjoined, via a connection housing  100  on one of the holding devices  40 , to an outlet channel  190  opening into the cavity  75  of that holding device  40 . In one embodiment, each pneumatic conduit  175  opens into a coating reservoir (not shown), from which extends an outlet channel  190 . Likewise in this embodiment, a coating conduit  155  opens into each coating reservoir. In another embodiment, each coating conduit  155  is adjoined at an intersection point (not shown) to one of the pneumatic conduits  175 , such that the coating conduit  155  opens into the pneumatic conduit  175  at such intersection point. 
   With continued reference to  FIG. 7 , each pneumatic conduit  175  is adapted to emit both gas and vacuum. Thus, when the holding devices  40  are engaged to a workpiece (not shown), the vacuum generator can be utilized to create a vacuum in the cavity  75  of each holding device  40 . When it is desired to detach the holding devices  40  from the workpiece, the gas compressor and the coating assembly can be operated simultaneously to deliver coating material either to the intersection point of the pneumatic conduits  175  and coating conduits  155  or to the coating reservoirs  120 , whichever the case may be, and to deliver a burst of gas through the pneumatic conduits  175 . This expels the coating material through the outlet channels  190  and onto the workpiece. Alternatively, the coating assembly  88  and the compressor/vacuum assembly  90  can be operated in succession. For example, the coating assembly  88  can be operated to deliver coating material to the intersection points of the pneumatic conduits  175  and coating conduits  155  or to the coating reservoirs  120 , as the case may be, prior to detachment of the holding devices  40 . Thereafter, the gas compressors can be operated to deliver a burst of gas through the pneumatic conduits  175 , thereby detaching the holding devices  40  and expelling the coating material from the outlet channels  190  onto the workpiece. 
     FIG. 8  illustrates another embodiment of the invention involving an integrated compressor/vacuum system  90  capable of simultaneously providing both vacuum and gas at pressure. As with the embodiment of  FIG. 7 , the compressor/vacuum assembly  90  advantageously includes a gas compressor (not shown) and a vacuum generator (not shown). In the embodiment of  FIG. 8 , the vacuum generator (or “vacuum source”) within the integrated compressor/vacuum system  90  is operably connected to a single vacuum conduit  135  that is routed in series through each of the holding devices  40 . If so desired, the vacuum generator can alternatively be operably connected to multiple vacuum conduits (not shown) leading in parallel to each of the holding devices  40 . In the illustrated embodiment, the vacuum conduit  135  is in communication with a vacuum channel  110  in each of the holding devices  40 . The vacuum channel  10  in each holding device  40  opens into the cavity  75  of that holding device  40 . 
   With continued reference to  FIG. 8 , the gas compressor within the integrated compressor/vacuum system  90  is operably connected to multiple gas conduits  145 , which lead to each of the holding devices  40 . If so desired, a single gas conduit (not shown) can alternatively be routed in series to each of the holding devices. In the illustrated embodiment, each gas conduit  145  is adjoined, via a connection housing  100  on one of the holding devices  40 , to a coating channel  117  opening into the cavity  75  of that holding device  40 . In the embodiment of  FIG. 8 , each gas conduit  145  opens into a coating reservoir  120 , from which extends a coating channel  117 . These reservoirs  120  are operably connected to the coating assembly  88  via coating supply conduits  155 . A coating flow valve  125  system can be positioned within each coating reservoir  120  to control the retention and release of coating. The valves  125  can be of any conventional type that would allow entry of coating, via coating conduits  155 , into the reservoirs  120  at the desired time and also release coating from the reservoirs  120  into the holding devices  40  via the coating channels  117  when desired. Although valves of this nature are not illustrated in the embodiments of  FIGS. 6 and 7 , those skilled in the art would of course appreciate the benefits of their use in such pneumatic systems. 
     FIG. 9  illustrates an embodiment of the present invention involving a single outlet to the cavity  75  of a holding device  40 . This embodiment generally includes a spray passage  165 , a coating reservoir  120 , a coating conduit  155 , and a pneumatic conduit  175 . If so desired, the spray passage  165  can be provided with a conventional grid  42  at its outlet end to facilitate the dispersion of coating onto the surface of a workpiece (not shown). The spray passage  165  is adjoined to one end of the coating reservoir  120 . The coating reservoir  120  optionally includes a coating release valve  170 , which controls the release of coating into the spray conduit  165 . The coating conduit  155  and the pneumatic conduit  175  are attached to the coating reservoir  120  through a reservoir valve  180 . The reservoir valve  180  controls the release and retention of coating and gas into the reservoir  120  from the coating conduit  155  and the pneumatic conduit  175 , respectively. The pneumatic conduit  175  can be operably connected to a compressor/vacuum assembly (not shown), as depicted in previously discussed embodiments, which provides both a vacuum source and a gas source. It is noted that the compressor/vacuum assembly can be controlled by an automated or computerized system (not shown). Such automated system could be adapted to control the emission of vacuum and gas by the compressor/vacuum assembly, as well as control the intensity of such emissions. It could also be adapted to control the reservoir valve  180 , the coating release valve  170 , and any other valves provided within the system. 
     FIG. 10  depicts another embodiment of the invention involving a single outlet to the cavity  75  of a holding device  40 . A holding device  40  of this nature can be operably connected to a vacuum generator (not shown) that is separate from a gas compressor (not shown). The embodiment of  FIG. 10  includes a spray passage  165 , which is comparable to that depicted in  FIG. 9  except that it is not provided with a spray grid. The spray passage  165  is adjoined to a vacuum passage  190  and a coating reservoir  120  through a first valve  200 . Finally, the coating reservoir  120  is functionally connected to a coating conduit  155  and a gas conduit  205  through a second valve  210 . Those skilled in the present art would readily appreciate that many other variations on the connection schemes illustrated in  FIGS. 6–10  would be suitable for use with the present invention. 
   Referring back to  FIG. 1 , the pneumatic handling and recoating apparatus  10  of the invention can be employed to handle workpieces of various types and/or to move them from one location to another. In so doing, the pneumatic handling and recoating apparatus  10  is initially moved into a position adjacent to the workpiece to be handled. As presently contemplated, the invention is believed to be most valuable in handling glass sheets, although the invention is by no means limited to use with glass. As noted above, glass sheets are commonly stacked in a semi-upright position. When removing sheets from such a stack, the pneumatic handling and recoating apparatus  10  is moved into a position adjacent to a sheet at one end of the stack (i.e., an outermost sheet). Next, the base frame  35  is adjusted, by expansion or contraction, to position the holding devices  40  at desired locations to provide optimum handling of the workpiece (e.g., the outermost glass sheet). The base frame  35  is then moved toward the workpiece (e.g., toward the exposed major surface of the outermost glass sheet) until the holding devices  40  engage the workpiece, thereby defining a cavity  75  between each holding device  40  and the engaged surface of the workpiece. Next, a vacuum is drawn in each cavity  75  to sealingly attach the pneumatic devices  10  to the workpiece. The workpiece can then be lifted and/or moved to a desired location. When it is desired to release the workpiece for further processing, gas and coating material are expelled into the cavity  75  of each holding device  40  to detach the holding devices  40  and to apply or reapply coating to the workpiece. 
   As noted above, a single burst of gas and coating material can be employed to simultaneously detach the holding devices  40  and to apply coating to the workpiece. Alternatively, a delayed emission of coating can be provided, such that the coating is applied to the workpiece following detachment of the holding devices  40  from the workpiece. In such processes, detachment of the holding devices  40  preferably occurs just prior to emission of the coating. For example, a first burst of gas can be used to detach the holding devices  40  from the workpiece. Shortly thereafter, the coating material can be delivered to a coating reservoir  120  (or to an intersection point with each gas conduit) in each of the holding devices  40 . Then, a second burst of gas can be emitted to expel the coating through the suction device  40  and onto the workpiece. 
   The present invention can be used to apply any desired coating to a workpiece during handling of the workpiece. The invention has particular utility in the handling of workpieces that carry an existing coating prior to handling, which coating is intended to remain on the workpiece following handling. As noted above, it is anticipated that the invention will be most valuable in the handling of glass sheets, such as are commonly used in automotive glazings (e.g., windshields) and architectural glazings (e.g., windows in residential or commercial buildings). As is well known in the art, glass sheets of this nature are commonly treated with protective materials, such as stain-retarding material and/or acidic buffers. For example, adipic acid and maleic acid have been used in various forms (e.g., powders and aqueous solutions). As noted above, these coatings are sometimes removed when the coated surface is handled by conventional pneumatic suction devices. This removal of coating can, however, be compensated for via the coating function provided by the pneumatic handling and recoating apparatus of the present invention. 
   Generally, it is preferable to recoat the surface of a handled workpiece with the same coating material as that applied to the workpiece (assuming a pre-coated workpiece) prior to handling. For example, when glass sheets coated with an adipic acid-based material are handled, it is typically preferable to set the present pneumatic handling and recoating apparatus to recoat the handled glass surfaces with another adipic acid-based agent. Of course, the glass (or other workpiece) can alternatively be coated with a material different than that which was originally applied to the workpiece. Moreover, it is to be understood that the present invention is not limited to use with workpieces that are coated prior to handling. Rather, the invention would be beneficial in any case where it is desirable to apply a coating to the surface of a workpiece during a handling operation. 
   While preferred embodiments of the present invention have been described, it should be understood that a variety of changes, adaptations, and modifications can be made therein without departing from the spirit of the invention and the scope of the appended claims.