Abstract:
Apparatus and method for the automatic removal of a protective cover from a planar sheet. Air under pressure is directed angularly from an air nozzle system at the cover to partially dislodge same and to force a portion of the cover into contact with a rotating roll. The portion of the cover in contact with the roll is held thereby until presented to the force of suction at an entrance to a suction duct. The cover is carried away by air currents in the duct after the cover and is fully stripped from the sheet.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus and method for automatic stripping and removal of a protective film from a planar substrate and particularly from a polymer sheet such as plexiglass and the like. 
     Polymeric sheets, for example, have historically been utilized in fabrication of various and sundry structures. Typically, such sheets are provided to a fabricator as planar sheets of a certain size which must be cut to a predetermined size and shape as needed for a particular fabrication process. Exemplary of polymer sheets of the type being discussed herein are polymethylmethacrylate sheets which are sometimes referred to as plexiglass. During fabrication, the sheets may be cut, milled, shaped, drilled and otherwise manipulated to facilitate fabrication of an intended structure. After working the sheet(s), to the desired size and shape, these sheets are used in fabrication of the intended article. Just by way of example, and without limitation, many display supports of various and sundry sizes and shapes are fabricated from such polymeric sheets. Often in use of the structures fabricated from the polymeric sheets, smooth transparent surfaces add to the aesthetic or functional qualities of the structure. 
     Typically, the planar sheets of the polymeric materials have an optical quality of transparency. However, due to softness of the surfaces of the sheets, the sheets are easily scratched or otherwise deformed, detracting from the conventional optical qualities of the sheets, and ultimately therefor the aesthetics of the structures fabricated therefrom. Consequently, in order to protect the polymeric sheets against scratching and the like, a protective flexible film or cover is routinely secured along opposite sides of the sheet and normally remains in place until the sheet is used in fabrication of the intended structure, or even in some cases after the structure is produced and until the product is ready for its intended use. 
     In the past, though some machines have been developed to remove protective covers, there has been a general industry practice of manual removal of the protective covers from the sheets at the appropriate time. Manual removal of the protective covers from the polymeric sheets, as would be expected, is labor intensive, and therefore not desirable. 
     Similarly, in the electronics field, printed circuits, in some instances, have a protective film cover provided across one or both sides of the circuit being produced which must be stripped during or prior to the process for manufacture of the printed circuit board. Particularly in a process where a portion of the board is photographically processed to achieve a particular functional element of the circuit, protective covers are employed. In this industry, machines also have been previously developed for automatically removing the protective film cover from the printed circuit boards. 
     Exemplary of prior art efforts directed to removal of protective covers from planar substrates are U.S. Pat. Nos. 2,337,724; 4,274,676; 4,724,032; 4,770,733; 4,867,836; 5,358,591; and 5,662,762. 
     The present invention represents an improvement over the apparatus and processes described in the above prior art patents. Particularly, it is submitted that the present invention is patentable over the above listed prior art patents taken either alone or in combination. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide apparatus for the automatic removal of protective cover from polymeric or other sheets. 
     Another object of the present invention is to provide an improved apparatus for the automatic removal of a protective layer from a substrate. 
     Still another object of the present invention is to provide an improved apparatus for the automatic removal of an outer film layer from a planar polymeric substrate. 
     Still further another object of the present invention is to provide an improved method for the automatic removal of a protective film from a substrate. 
     Yet another object of the present invention is to provide an improved method for the removal of a flexible film layer from one or both sides of a polymeric sheet. 
     Generally speaking, apparatus according to the present invention comprises a conveyor arrangement for engaging and moving a sheet having a protective cover on one or both sides of same along a predetermined path; an air nozzle system located along a continuation of said path for said sheet and being disposed at a predetermined angular relationship with respect to a sheet passing along said path for directing gas under pressure against said protective cover adequate to partially dislodge said cover from said side of said sheet; a driven roll located proximate said air nozzle system and said path, said roll having a capability for receiving and holding a portion of protective cover dislodged from said surface for further removal of same as said sheet passes thereby; and a suction system located adjacent said roll for receiving said protective cover from said roll and transporting said protective cover away. 
     More specifically, apparatus according to a preferred embodiment of the present invention includes a pair of opposed driven belts that define a passageway therebetween, preferably adjustable, for a planar sheet and cooperate with the planar sheet therebetween to move same along said passageway which is an intended path of travel. A plurality of air jets are angularly disposed with respect to a continuation of the path followed by the sheet for directing air under pressure against the cover to initially and partially dislodge the cover so that the cover can be completely removed from said sheet. A suction duct is located along the path, adjacent the air nozzles with a driven roll in close proximity to the air nozzles for receiving a portion of the cover as it is dislodged from the sheet and transporting the dislodged portion of the cover and presenting same to the effects of suction in the suction duct so that when the cover is fully dislodged from the sheet the cover is carried away by the force of suction in the duct. A second conveyor may be provided for movement of the sheet away from the air jets. 
     Generally speaking, the method according to the present invention for removing a protective cover from a planar substrate comprises the steps of transporting a sheet with a protective cover thereon along an intended path of travel; directing air under pressure at a predetermined angle to said path against said cover to dislodge a portion of said cover from said sheet; engaging a portion of said cover dislodged from said sheet with a driven roll and continuing gradual removal of said cover; presenting said portion of said cover to the effects of a source of suction adequate to hold said portion and transport said cover away after said cover is completely removed from said sheet. 
     More specifically, according to a preferred embodiment of the present invention, a planar substrate having a protective film cover on opposite sides of same is fed under controlled conditions to a stripping station where air under pressure is directed at a predetermined angle with respect to the interface between the substrate and the protective cover and partially dislodges the film from the sheet. The partially dislodged film is forced by the air against a driven roll located closely proximate the nozzles and the sheet. The driven roll grabs and holds the cover and as the roll rotates continues to remove the cover from the sheet and present the cover to the effects of a source of suction. The removed cover is then transported away by the suction and the sheet, now stripped, is conveyed away from the stripping area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the remainder of the specification, which makes reference to the appended figures in which: 
     FIG. 1 is a top plan view of a portion of apparatus according to teachings of the present invention. 
     FIG. 2 is an enlarged top view of the film stripping area of apparatus according to the present invention as illustrated in FIG. 1; 
     FIG. 3 is a further detailed view in partial cross section of the stripping area according to a preferred embodiment of apparatus according to the present invention as illustrated in FIG. 1, shown in perspective and with protective film in the process of removal; 
     FIG. 4 is a partial frontal view of air nozzles according to the present invention. 
     FIG. 5 is a schematic diagram of a control system for apparatus according to the present invention. 
    
    
     Repeat use of reference characters throughout the present specification and appended drawings is intended to represent same or analogous features or elements of the invention. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Making reference to the Figures, preferred embodiments of the present invention will now be described in detail. 
     Referring to FIG. 1, apparatus according to teachings of the present invention includes a sheet feeding and controlling section generally indicated as  20  through which a substrate generally  10  is transported. Substrate  10  includes a base or sheet  12  to which a protective cover  14 , normally a film, is secured to one on both sides. Typically, according to the present invention, sheet  12  is a polymer sheet, exemplified by polymethylmethacrylate, with a polymeric film cover  14  provided over the entirety of both outer surfaces of same, leaving the peripheral edges of base  12  uncovered. Protective films  14  are generally secured to base  12  by a static or electrical attraction and removal of same is ultimately intended. 
     A substrate  10  being stripped of its protective film cover(s)  14  is fed from control feed section  20  to a film stripping section generally  50  where the protective film(s) or cover(s) are automatically removed from sheet  12 . From stripping section  50 , sheets  12  (now with cover(s)  14  removed) are received by an exit feed section generally  60  which transports sheets  12  away from stripping section  50 . 
     In the following description, a base or sheet  12  with a protective cover  14  on both sides of same is discussed by way of example only and not by way of limitation. 
     Control feed section  20  preferably includes a pair of opposing conveyor belts  21 ,  22  oriented face to face for frictional engagement with a substrate  10  passing therebetween. As illustrated in FIG. 1, belt  21  is received about two pulleys  23 ,  23 ′ with pulley  23  being driven and pulley  23 ′ being an idler pulley. Pulleys  23  and  23 ′ are journaled for rotation and supported by a frame work not shown. A pair of guides  24 ,  24 ′ are located between pulleys  23  and  23 ′ and define an intermediate pathway for belt  21 . As shown in FIG. 1, guide  24 ′ is springloaded by a pair of coil springs  25  and  25 ′ to be biased outwardly in a direction away from guide  24 . Though coil springs are shown, any other arrangement could be employed which applies an outward bias against guide  24 ′. In like fashion, pulley  231 ′ is springloaded by a coil spring  26  so as to be biased outwardly in a direction away from pulley  23  to maintain tension on belt  21 . Again, other biasing arrangements could be employed. 
     Belt  22  is received around pulleys  27 ,  27 ′ with a single intermediate guide structure  28  located therebetween and with opposite edges  28 ′ and  28 ″ serving as guide surfaces to define the intermediate pathway for belt  22 . Pulley  27 ′ is springloaded by a coil spring  29  so as to be biased outwardly away from pulley  27  to maintain tension on belt  22 . 
     With guide  24 ′ spring loaded in a direction towards guide  28 , the width of the passageway between belts  21  and  22  is variable. For example, a substrate  10  having a particular thickness passing between belts  21  and  22  will act against the biasing force of coil springs  25  and  25 ′ moving guide  24 ′ away from guide  28 . At the same time, tension is maintained on belt  21  by pulley  23 ′ and biasing force of springs  25  and  25 ′ will ensure proper frictional contact between belts  21 ,  22  and substrate  10 . As such, substrates varying in thickness may be driven by belts  21  and  22  for proper presentation to stripping section  50  to be described hereinafter. 
     Sheet  12  emerges from control feed section  20  and enters film stripping area or section  50 . In film stripping area  50  the present invention provides apparatus for removal of film from one or both sides of a sheet. Since films or covers are normally provided on both bottom and top surfaces of a sheet, the invention is described herein for such. In film stripping area  50 , there are air nozzle systems generally  30 ,  30 ′, driven rolls  47 ,  47 ′ and suction systems generally  45 ,  45 ′. Apparatus on one side of the sheet passageway through stripping area  50  is a mirror image of that on an opposite side of the passageway, wherefore only one side will be specifically described, with numbers bearing a prime representing the opposite structure. 
     Air nozzle system  30  which is best shown in FIGS. 3 and 4 includes an elongated nozzle housing  31  which forms a plurality of plenum chambers  39  separated by walls  38  and with each plenum chamber defining a plurality of nozzle openings  37 . Structurally, housing  31  includes a generally U-shaped top wall  32  with a bottom wall  33  secured thereto, and with end walls  34 . Bottom wall  33  includes a plurality of spaced protrusions  36  that define nozzle openings  37  therebetween. Each plenum chamber  39  has a coupling  40  for securement of an air hose or the like  42  thereto through which air is supplied to each plenum chamber  39 . Housing  31  is located to cause air exiting nozzles  37  to impinge on film covers  14  passing thereby at an angle α from about 35 to about 45 degrees, and preferably about 40 degrees. (See FIG.  2 ). Nozzle housing  31  is sufficient in length to act on the full width of a substrate  10  passing thereby. 
     Air is supplied to air hoses  42  at a predetermined pressure in a range of from about 75 to about 150 pounds per square inch, preferably about 100 pounds per square inch from a conventional source of pressurized air  44  (See FIG.  5 ). Controls  70  are associated with the air source  44  to cause same to operate for a predetermined duration at predetermined intervals. 
     Adjacent air nozzle system  30  is a suction system generally  45 . Suction system  45  includes an air duct  46 , the outer face end of which is positioned closely proximate to nozzles  37 . A source of suction such as a blower  47  (See FIG. 5) is operatively associated with duct  46  and generates suction therein for transport of film coverings  14  after they have been stripped from sheets  12 . 
     Located closely adjacent nozzle system  30  and duct  47  is a roll  48  which is journaled for rotation in a framework (not shown). Roll  48  is driven by a motor M, preferably a variable speed motor, which also preferably drives conveyors of conveyor assemblies  20 ,  60 . Though adjustable to accommodate different substrates, roll  48  in one arrangement is located about three-fourths inch from nozzles  37  and the entrance to duct  46 . Roll  48  is positioned to receive, hold and transport film covers  14  to duct  47  where film cover  14  comes under the influence of suction in duct  47  and is transported thereby as cover  14  leaves roll  48 . Roll  48  may be fully covered with friction surfaces with respect to film cover  14  such that film  14  becomes lightly attached to roll  48 . However, any other arrangement may be provided for the surface of roll  48  such as a plurality of bands, o-rings or the like which will hold film  14  for stripping and for presentation to suction duct  47 . Typically, a rubber type-surface will afford adequate holding power for removal of film  14  from substrate  12 , and for release of film  14  to the force of suction. Further, a pair of rolls may be used which define a nip therebetween through which film cover  14  passes and is held thereby. 
     Downstream of film stripping area  50  is discharge conveyor section  60  for transport of substrate  12  away from stripping area  50  after film(s)  14  has been removed. Conveyor section  60  may be like feed section  20  or otherwise so long as sheet  12  may be transported thereby. 
     Operation of apparatus according to the present invention will now be described in detail. A sheet  12  with a film cover  14  on both sides is supplied to the space between conveyor belts  21 ,  22 . Belts  21 ,  22  receive sheet  12  with belt  21  holding sheet  12  against belt  22  by the force of springs  25 ,  25 ′. Successive sheets  12  may then be fed to and handled by belts  21 ,  22 . 
     Sheet  12  exits belts  21 ,  22  continuing along the same path and comes under the influence of air knives or nozzles  30  that at least partially lift a leading edge portion of film  14  from the affected side of sheet  12 . Air under a pressure of about 75 to about 150 pounds per square inch impinges on film  14  at an angle and in a range of from about 35 to about 45 degrees. Preferably, air flow against sheet  10  is intermittent which conserves air, lessens noise and provides a series of sudden starts of a removal action. Preferably, air at about 100 pounds per square inch spurts in duration of about 2 seconds at about 5 second intervals against sheets  12  at an angle of about 40 degrees. The front leading edge portion of film  14  is thereby lifted from sheet  12  and forced against the outer surface of roll  48  which is rotating in a direction away from the path of travel for sheet  10  (clockwise). In a preferred arrangement, as noted above, roll  48  is located approximately equi-distant from duct  47  and nozzles  37 , in one setting about three-fourths inch from each. Film  14  frictionally adheres to the surface of roll  48 , and rotation of roll  48  thus assists in lifting film  14  from the moving sheet  12 . Air blasts continue against sheet  12  and film  14 , now generally at the junction, where film  14  and sheet  12  meet, also assisting in the stripping action. 
     As roll  48  rotates with film  14  in engagement therewith, film  14  is presented to the open end of suction duct  47  where the force of suction within duct  47  now lifts the leading edge of film  14  from roll  48 . As roll  48  continues to present film  14  to duct  47 , suction within duct  47  continues to act on film  14  continuously removing same from roll  48 . Once film  14  has been totally removed from sheet  12  and roll  48 , the now free film  14  is transported by the force of suction through duct  47  to a waste collector (not shown). 
     As sheet  12  passes through film stripping area  50 , and after film  14  has been removed, sheet  12  is received by discharge conveyor  60  and is transported away for use in fabrication as intended. 
     Using apparatus of the present invention for stripping film from a substrate in a most preferred arrangement, there is coordination between speed of movement of sheets  10 , the angle of air nozzles  30 , the duration and intervals of air blasts from nozzles  30  and the proximity of roll  48  and duct  47  to individual nozzles  37 . Proper control of these mentioned parameters permits efficient film removal. As shown in FIG. 5, a suitable, conventional program controller  70  is employed for controlling air pressure and supply to nozzles  30 . In a preferred arrangement, substrate  10  is transported by the conveyors in sections  20  and  60  at a common rate. Air is delivered from nozzle system  30  at an angle of about 40 degrees in 2 second blasts every 5 seconds at about 100 pounds per square inch. Film covers  14  are thereby separated partially from sheets  12  and are blown against roll  48  located about three-fourths inches away. Suction force within duct  47  is generated by an airblower  46  or the like. With this preferred arrangement, films  14  may be efficiently continuously removed from sheets  12 . 
     While particular embodiments of the invention have been described and shown, it will be understood by those of ordinary skill in the art that the present invention is not limited thereto since many modifications may be made. Therefore, it is contemplated by the present application to cover any and all such embodiments that may fall within the scope of the invention and the appended claims.