Universal edge strip assembly and carrier sheet assembly

Information

  • Patent Grant
  • 6318261
  • Patent Number
    6,318,261
  • Date Filed
    Wednesday, January 5, 2000
    24 years ago
  • Date Issued
    Tuesday, November 20, 2001
    22 years ago
Abstract
A universal edge strip is secured to both leading and trailing edges of a flexographic carrier sheet. A universal edge strip assembly includes the universal edge strip and a retaining clip. The universal edge strip includes a first pair of parallel walls connected to a center web which define a first deep slot or channel. The universal edge strip also includes a second pair of walls connected to the same center web which defines a second J-shaped shallow slot or channel. The first slot receives the carrier sheet which is secured to the universal edge strip by conventional means. One of the walls adjacent the second shallow slot includes a projection or J-shape which defines a throat adjacent the opposite wall. A U-shaped retaining clip is received within the second shallow slot in the universal edge strip at one end of the carrier sheet and is hooked to an undercut lip on the flexographic printing cylinder. As noted, both leading and trailing edges of the carrier sheet include a universal edge strip. Adjacent each edge strip is a plurality of slots. A plurality of elastic straps disposed in the slots secure the trailing edge of the carrier sheet to the cylinder.
Description




BACKGROUND OF THE INVENTION




The invention relates generally to devices for providing accurate and secure mounting of a flexographic carrier sheet to a printing cylinder and more specifically to a universal edge strip assembly for securing an end of a printing plate carrier sheet to a printing cylinder.




Flexographic printing, also known as flexography or aniline printing, is a generally preferred printing process for large areas such as containers and cardboard cartons, point of purchase displays and the like. Flexographic printing is relief, i.e., direct, printing utilizing large plates fastened to a rotating cylinder. It is capable of producing an image with exceptional clarity and contrast. A single inking roller supplied with aniline ink from rollers in the ink fountain provides ink to raised, image forming printing plates disposed on the rotating cylinder which print directly upon the product. The carrier sheet or mounting material which carries the printing plate or plates may be several inches on each side or several feet. The carrier sheet is mounted to the printing cylinder at one edge by cooperation between a lip on the lead edge of the carrier sheet and a complementarily configured channel and undercut lip on the cylinder. The opposite edge of the carrier sheet is secured to the printing cylinder by one, or typically a plurality of, elastic straps which retain the carrier sheet upon the printing cylinder and properly tension it.




Since the elastic mounting straps merely provide tension to the carrier sheet to retain it upon the printing cylinder, it is apparent that the location and the registration of the carrier sheet and thus of the printing plate disposed thereon is almost exclusively the result of cooperation between the lead edge strip of the carrier sheet and the complementary lip on the printing cylinder. Since the printing cylinder is most generally fabricated of metal, it may be considered dimensionally stable and may thus be virtually ruled out as a source of variability and error when installing and utilizing flexographic printing plates. However, since the carrier sheet and its mounting edge are relatively lightweight, correct mounting and stability are concerns with regard to same. Accordingly, significant attention has been directed to the mounting and components of carrier sheets and their details.




SUMMARY OF THE INVENTION




A universal edge strip assembly for a flexographic carrier sheet includes a universal edge strip and a retaining clip. The universal edge strip is secured to both leading and trailing edges of the flexographic carrier sheet. The universal edge strip includes a first pair of parallel walls connected to a center web which define a first deep slot or channel. The universal edge strip also includes a second pair of parallel walls connected to the same center web which defines a second shallow slot or channel. The first slot receives the carrier sheet which is secured to the universal edge strip by conventional means. One of the walls adjacent the second shallow slot includes a projection or J-shape which defines a throat adjacent the opposite wall. A U-shaped retaining clip is received within the second shallow slot in the universal edge strip at one end of the carrier sheet and is hooked to the undercut lip of a flexographic printing cylinder. As noted, both leading and trailing edges of the carrier sheet include a universal edge strip. Formed in the carrier sheet adjacent each edge strip is a plurality of slots. A plurality of elastic straps disposed in the slots secure the trailing edge of the carrier sheet to the cylinder in tension.




The universal edge strip assembly is preferably transparent as this facilitates mounting of the universal edge strip assembly and carrier sheet upon a printing cylinder. The universal edge strip assembly is preferably extruded polyvinyl chloride (PVC). The edge strip may be utilized in any application requiring a secure, engageable lip disposed along an edge of diverse sheet material.




Thus it is an object of the present invention to provide an engageable strip for securement to an edge of sheet material.




It is a further object of the present invention to provide a novel universal edge structure for a carrier sheet for flexographic printing.




It is a still further object of the present invention to provide a universal edge strip assembly which includes a pair of parallel walls to which a carrier sheet may be secured.




It is a still further object of the present invention to provide a universal edge strip assembly with improved strength and rigidity which facilitates positive securement of a carrier sheet to a flexographic printing cylinder.




It is a still further object of the present invention to provide a universal edge strip assembly which is transparent and thus facilitates proper disposition of an associated carrier sheet upon a flexographic printing cylinder.




It is a still further object of the present invention to provide a universal edge strip which may be mounted to both the leading and trailing edges of a carrier sheet such that the carrier sheet may be reversibly mounted upon a flexographic printing cylinder.




It is a still further object of the present invention to provide a universal edge strip which, when mounted to trailing edge of a carrier sheet, does not interfere with the flexographic printing process.




Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred embodiment and appended drawings wherein like reference numbers refer to the same component element or feature.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective view of a prior art lead edge strip attached to a carrier sheet;





FIG. 2

is a diagrammatic, perspective view of a flexographic printing cylinder having a carrier sheet secured thereto by a universal edge strip assembly according to the present invention;





FIG. 3

is a diagrammatic end view of a flexographic printing cylinder having a carrier sheet secured thereto by a universal edge strip assembly according to the present invention;





FIG. 4

is a perspective view of a flexographic carrier sheet having a universal edge strip according to the present invention secured at each end;





FIG. 5

is a greatly enlarged, end elevational view of a universal edge strip according to the present invention;





FIG. 6

is a greatly enlarged, end elevational view of a preferred embodiment retaining clip for a universal edge strip assembly according to the present invention; and





FIG. 7

is a greatly enlarged, end elevational view of a first alternate embodiment retaining clip for a universal edge strip assembly according to the present invention.











DESCRIPTION OF THE PREFERRED AND ALTERNATE EMBODIMENTS




Referring to

FIG. 1

, a prior art lead edge strip is illustrated and generally designated by the reference number


10


. The prior art lead edge strip


10


may be conveniently described as a “T” with serifs which is inverted in the illustration. The prior art lead edge strip


10


is symmetrical and defines a bottom portion


12


which is integrally formed with a centrally disposed web


14


which is perpendicular to the bottom portion


12


. Disposed parallel to the central web


14


and equally spaced therefrom are a pair of symmetrical ears


16


. Between each of the ears


16


and the central web


14


is a channel


18


having a width greater than the thickness of a carrier sheet


20


. The carrier sheet


20


is secured to the central web


14


by stitching or staples


22


. The prior art lead edge strip


10


is an extrusion of opaque plastic material.




Referring now to

FIGS. 2 and 3

, a flexographic printing cylinder


24


is diagrammatically illustrated. The printing cylinder


24


is disposed for clockwise rotation about a center axis


26


when viewed from the left end as illustrated in FIG.


2


. The flexographic printing cylinder


24


includes a C-shaped kerf or channel


28


which extends generally across its full width. One wall of the channel


28


and an outer surface


30


of the printing cylinder


24


define a first substantially undercut lip


32


. The channel


28


also defines a second, opposed undercut lip


34


spaced from and disposed parallel to the first undercut lip


32


.




Disposed about and conforming to the outer surface


30


of the printing cylinder


24


is a flexographic printing carrier sheet


36


. The carrier sheet


36


includes a printing plate


38


which is illustrative and representative of any and all types of text, diagrams, drawings and pictures, for example, which may be disposed upon and attached to the carrier sheet


36


. The trailing edge of the carrier sheet


36


may be secured to the printing cylinder


24


by a plurality of elastic straps


42


which extend from and are secured to the carrier sheet


36


in a plurality of slots


44


located adjacent a first universal edge strip


40


. The opposite ends of the elastic straps


42


are attached to the printing cylinder


24


by suitable flat hooks


46


and engage slots in the printing cylinder


24


. At the opposite (leading) edge of the carrier sheet


36


is a second universal edge strip


50


. It will be appreciated that the first universal edge strip


40


and the second universal edge strip


50


are identical in construction and configuration; the sole difference between them being their disposition at opposite edges of the carrier sheet


36


.




As especially well illustrated in the elastic straps


42


are secured to the printing cylinder


24


by flat hooks


46


as noted. The elastic straps


42


extend along the surface of the printing cylinder


24


and over the first universal edge strip


40


, thereby holding it against the surface of the printing cylinder


24


. The elastic straps


42


engage the slots


44


and are secured thereto. Nowhere do the outer surfaces of the elastic straps


42


extend into or interfere with the effective print radius


48


of the printing plate


38


. The carrier sheet


36


is held to the surface of the printing cylinder


24


by the tension supplied by the elastic straps


42


.




Disposed at the opposite (leading) end of the carrier sheet


36


, is the second universal edge strip


50


. Secured to the second universal edge strip


50


, is a retaining clip


60


. The retaining clip


60


engages the first undercut lip


32


of the C-shaped channel


28


. When properly engaged, the retaining clip


60


secures the second universal edge strip


50


to the printing cylinder


24


.




Referring to

FIG. 4

, the carrier sheet


36


is shown with the universal edge strips


40


and


50


and the retaining clip


60


installed. A universal edge strip assembly


70


is shown including the universal edge strip


50


and the retaining clip


60


disposed therein. The universal edge strips


40


and


50


extend essentially the full width of the carrier sheet


36


. Likewise, the retaining clip


60


extends essentially the full width of the second universal edge strip


50


. Both universal edge strips


40


and


50


are secured to the carrier sheet


36


by stitching or staples


52


or other means such as an adhesive or autogenous bonding achieved by the application of RF or IR radiation, heat or ultrasonic energy.




Referring to

FIG. 5

, the second universal edge strip


50


according to the present invention is shown. It will be appreciated that, as noted, the first universal edge strip


40


and the second universal edge strip


50


are, but for their opposed, mirror image disposition at opposite ends of the carrier sheet


36


, identical. Thus, only the second universal edge strip


50


will be described. The second universal edge strip


50


defines an asymmetric structure having a central web


54


which separates a first deep slot or channel


56


from a second shallow slot or channel


58


. A first pair of parallel walls


62


define the first deep slot


56


which receives the carrier sheet


36


. The first pair of parallel walls


62


are spaced from each other a distance substantially equal to or just slightly greater than the thickness of the carrier sheet


36


. Each of the parallel walls


62


define radiused, semi-circular terminal portions


63


and interior surfaces


65


. The bottom of the first deep slot


56


, that is, that portion immediately adjacent the central web


54


, defines a curved, semi-circular surface


64


. The semi-circular surface


64


serves to reduce stress concentrations and distributes forces acting on the universal edge strip


50


thereby inhibiting cracking and improving its service life. The carrier sheet


36


is received within the first slot


56


and is secured to the parallel walls


62


of the universal edge strip


50


as shown in FIG.


4


and as noted above. The lengths of the parallel walls


62


are preferably similar as illustrated. Alternatively, they may have different lengths as shown in U.S. Pat. No. 5,410,964, incorporated herein by reference. As illustrated in

FIG. 4

of the U.S. Pat. No. 5,410,964, unequal wall lengths provide a flat surface adjacent the end of the shorter wall which advantageously acts as a guide and facilitates insertion of the carrier sheet into the slot.




Returning to the present invention, the second, J-shaped shallow slot or channel


58


extends from the side of the central web


54


opposite the first deep slot or channel


56


. A shorter, thicker wall


66


extends from the central web


54


and terminates at radiused corners


72


and an oblique surface


74


. A longer, thinner wall


68


extends from the opposite end of the central web


54


parallel to the shorter, thicker wall


66


. At the end of the longer, thinner wall


68


, is J-shaped and includes oblique projection


76


extending toward the shorter, thicker wall


66


. The oblique projection


76


does not extend beyond the plane defined by an outer surface


78


of the shorter, thicker wall


66


. The projection


76


defines an overhanging hook or lip surface


82


at a right angle or a large acute angle with respect to the longer thinner wall


68


. The inside lip surface


82


is parallel to the oblique surface


74


. The projection


76


terminates at a rounded end


84


.




The second J-shaped shallow slot


58


is defined by the shorter, thicker wall


66


, the longer, thinner wall


68


, and the projection


76


. The radiused corners


72


and the rounded end


84


define an entrance or mouth of the shallow J-shaped slot


58


. The shallow slot


58


terminates at a semi-circular surface


86


of the central web


54


. The shallow slot


58


is generally complementary to and receives the U-shaped retaining clip


60


.




Referring now to

FIG. 6

, a retaining clip


60


is shown from an end. The retaining clip


60


is a skewed U-shaped channel with first and second parallel sidewalls,


92


and


94


, extending in the same direction from the ends of an oblique center section


96


. The center section


96


defines an inner surface


93


and an outer surface


95


. The first sidewall


92


extends away from one end of the center section


96


and forms an acute angle with the center section


96


. The first sidewall


92


terminates at semi-circular surface


98


and has an inner surface


102


.




On the opposite end of the center section


96


, the second sidewall


94


extends from the center section


96


and in the same direction. The second sidewall


94


, which is preferably slightly longer than the first sidewall


92


, forms an obtuse angle with respect to the center section


96


and terminates at a semi-circular surface


104


. An inner surface


106


of the second parallel sidewall


94


abuts the first undercut lip


32


of the printing cylinder


24


upon installation. The angle formed between the first sidewall


92


and the center section


96


is approximately the same angle as that formed between the longer, thinner wall


68


and the projection


76


of the universal edge strip


50


. Preferably, both parallel sidewalls


92


and


94


and the center section


96


have the same thickness and are joined with radiused inner and outer corners where the sidewalls


92


and


94


extend from the center section


96


to reduce bending stresses when loaded.




When assembled as shown in

FIG. 4

, the first sidewall


92


of the retaining clip


60


is inserted into the shallow slot


58


of the second universal edge strip


50


. When properly positioned, the semi-circular surface


98


of the first sidewall


92


abuts the semi-circular surface


86


at the end of the shallow slot


58


. The projection


76


flexes outward and away from radiused corners


72


during assembly.




As shown in

FIG. 3

, upon final assembly of the carrier sheet


36


to the printing cylinder


24


, the second sidewall


94


of the retaining clip


60


is inserted into the C-shaped channel


28


of the printing cylinder


24


. The second sidewall


94


is hooked under the first undercut lip


32


of the channel


28


such that the inner surface


106


of the second sidewall


94


abuts the first undercut lip


32


.




It will be appreciated that the two components of the universal edge strip assembly


70


cooperate to restrict the motion of the carrier sheet


36


in the direction of the tension force applied by its elastic straps


42


. When properly installed, the elastic straps


42


apply a tensioning force to the carrier sheet


36


. This tensioning force is resisted at the lead edge of the carrier sheet


36


by the securement means


52


. The securement means


52


secures the carrier sheet


36


to at least one surface


65


. The surface


65


of the universal edge strip


50


is connected to the inside surface


82


through the parallel wall


62


, central web


54


, longer thinner wall


68


, and projection


76


. Any combination of structural elements may be used to connect surfaces


65


and


82


. The important factor is the surface


82


must oppose any motion in the direction of the tensioning force. Abutted at surface


82


is the outer surface


95


of the retaining clip


60


. The surface


95


restricts the motion of the surface


82


in the direction of the tensioning force. The outer surface


95


is connected to the inner surface


93


through the center section


96


. The inner surface


93


abuts the corner of the first undercut lip


32


to restrict motion of the retainer clip


60


in the direction of the tensioning force. Alternatively, the outer surface


95


is connected to the semi-circular surface


104


through the center section


96


and the second parallel panel


94


. The semicircular surface


104


restricts the motion of the retaining clip in the direction of the tensioning force when it abuts the end of the first undercut lip


32


. Any structural element combination may be used to connect the surfaces, provided the orientation and positions of the surfaces remain essentially constant.




Referring now to

FIG. 7

, a first alternate embodiment retaining clip


100


is illustrated. The first alternate embodiment retaining clip


100


is similar in all respects to the preferred embodiment retaining clip


60


with the exception of the orientation of the oblique center section


96


. In the alternate embodiment retaining clip


100


, the center section


108


forms essentially right angles with respect to a first parallel sidewall


112


and a second parallel sidewall


114


. In a similar manner, the projection


76


on the first alternate embodiment of the universal edge strip


50


extends away from the longer thinner wall


68


at a right angle (not shown).




Preferably, the universal edge strip


50


and the retaining clip


60


are fabricated by extrusion from a transparent, rugged plastic material such as virgin polyvinyl chloride (PVC). Alternatively, any suitable metal may be used for either component. While either part may be fabricated of an opaque material, transparent materials are preferable since they have the distinct advantage of permitting visual checks of the proper mounting and registration of the retaining clip


60


on the first undercut lip


32


and thus proper mounting of the carrier sheet


36


and the printing plate


38


on the printing cylinder


24


. As extrusions, it will be appreciated that the universal edge strip


50


and the retaining clip


60


may be produced in continuous lengths which may be cut to any convenient length for shipment and further trimmed or cut to match the width of the carrier sheet


36


to which they are secured.




While described herein with general reference to carrier sheets for flexographic printing, it should be appreciated that the universal edge strip assembly


70


of the present invention will find broad application in those areas requiring a secure engageable lip disposed along an edge of sheet material to facilitate mounting or securement of such material to associated equipment or complementary structure.




The foregoing disclosure is the best mode devised by the inventor for practicing this invention. It is apparent, however, that apparatus incorporating modifications and variations will be obvious to one skilled in the art of printing. Inasmuch as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the instant invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.



Claims
  • 1. A universal edge strip assembly for disposition upon a sheet comprising, in combination;a universal edge strip having, a central web, a first pair of parallel sidewalls extending from said central web, said parallel walls defining a first slot for receiving the sheet, and a second pair of sidewalls extending from said central web in a direction generally opposite to said first pair of sidewalls and defining a second slot, one of said second pair of sidewalls having an overhanging lip defining a throat with another of said second pair of sidewalls; and a U-shaped retaining member having a center section and two sidewalls; wherein said retaining member is disposed within said second slot of said universal edge strip.
  • 2. The universal edge strip assembly of claim 1 wherein said center section of said retaining member is disposed at an oblique angle to said two sidewalls.
  • 3. The universal edge strip assembly of claim 2 wherein one of said two sidewalls is disposed at an acute angle to said center section.
  • 4. The universal edge strip assembly of claim 1 wherein said lip is disposed at an acute angle with respect to said one of said second pair of sidewalls.
  • 5. The universal edge strip assembly of claim 1 wherein said first slot defines a width at least equal to the sheet.
  • 6. The universal edge strip assembly of claim 1 wherein said another of said second pair of sidewalls is thicker than said one of said second pair of sidewalls.
  • 7. The universal edge strip assembly of claim 1 which is fabricated of transparent polyvinyl chloride.
  • 8. The universal edge strip assembly of claim 1 wherein said center section of said retaining member is disposed at a right angle to said two sidewalls.
  • 9. A universal edge strip assembly for disposition upon a sheet having a leading edge and a trailing edge, comprising, in combination;a central web, a first pair of parallel sidewalls extending from said central web, said parallel walls defining a first slot for receiving the sheet, and a second pair of sidewalls extending from said central web in a direction generally opposite to said first pair of sidewalls and defining a second slot, one of said second pair of sidewalls having an overhanging lip defining a throat with another of said second pair of sidewalls.
  • 10. The universal edge strip assembly of claim 9 further including a U-shaped retaining member disposed in said throat.
  • 11. The universal edge strip assembly of claim 10 wherein said retaining member includes two walls and an obliquely disposed center section.
  • 12. The universal edge strip assembly of claim 9 wherein said first slot defines a width at least equal to the sheet.
  • 13. The universal edge strip assembly of claim 9 wherein said another of said second pair of sidewalls is thicker than said one of said second pair of sidewalls.
  • 14. The universal edge strip assembly of claim 9 which is fabricated of transparent polyvinyl chloride.
  • 15. A carrier sheet assembly comprising, in combination;a carrier sheet for disposition on a printing cylinder, said carrier sheet having a leading edge and a trailing edge; an edge strip secured to each of said leading edge and said trailing edge having, a central web having a pair of opposed regions, a first pair of parallel walls extending from one of said pair of regions, said parallel walls defining a first channel for receiving said carrier sheet, and a second pair of walls extending from another of said pair of regions and defining a second channel, one of said second pair of walls having an overhanging projection defining a throat with said other of said second pair of walls; and a retaining clip having a center section and two end walls disposed in said throat of said second pair of walls of one of said edge strips.
  • 16. The carrier sheet assembly of claim 15 wherein said carrier sheet is secured to said first pair of parallel walls by staples.
  • 17. The carrier sheet assembly of claim 15 wherein said edge strips and said retaining clip are both transparent polyvinyl chloride.
US Referenced Citations (10)
Number Name Date Kind
1996582 Marchev Apr 1935
3295443 Devon Jan 1967
3387559 Horner Jun 1968
3675573 Hawks Jul 1972
3946670 Cerny et al. Mar 1976
4090444 Stearns May 1978
4932324 Pinkston et al. Jun 1990
5127327 Philpot Jul 1992
5410964 Koelsch May 1995
5562039 Fox et al. Oct 1996