Method of separating a sheet of print media from a stack of sheets

Information

  • Patent Grant
  • 6619654
  • Patent Number
    6,619,654
  • Date Filed
    Wednesday, January 23, 2002
    23 years ago
  • Date Issued
    Tuesday, September 16, 2003
    21 years ago
Abstract
A method of separating a sheet of print media from a stack of sheets, the sheets being porous, includes blowing fluid on to a top surface of a topmost sheet of the print media on the stack so that the fluid passes through at least the topmost sheet of the stack and capturing at least a part of the topmost sheet for conveyance to a printing station of a printer.
Description




FIELD OF THE INVENTION




This invention relates to a high speed, photographic quality printer. More particularly, the invention relates to a method of separating a sheet of print media from a stack of sheets, the sheets being porous.




BACKGROUND TO THE INVENTION




The applicant has developed various printheads which provide high speed, photographic quality printing. The printheads comprise ink jet nozzles arranged in an array. The ink jet nozzles are formed using microelectromechanical systems (MEMS) technology. The use of MEMS technology results in very high speed printing capabilities where pages can be printed at a rate of up to two pages per second (for double-sided printing).




To facilitate such high speed printing, it is important, firstly, that the paper fed to the printing station of the printer is accurately aligned and capable of the required feed rate with as little likelihood as possible of paper jams or the like, occurring. Secondly, the paper must be able to be fed to the printing station at a rate sufficient to use the high speed printing capabilities of the printing station to its fullest extent.




SUMMARY OF THE INVENTION




According to the invention, there is provided a method of separating a sheet of print media from a stack of sheets, the sheets being porous and the method including the steps of:




blowing fluid on to a top surface of a topmost sheet of the print media on the stack so that the fluid passes through at least the topmost sheet of the stack; and




capturing at least a part of the topmost sheet for conveyance to a printing station of a printer.




The method may include blowing the fluid on to the top surface of the topmost sheet through an aperture means of a pick up means of a print media feed arrangement. The pick up means may be in the form of a pick up bar. The aperture means of the pick up bar may be in any of a number of different forms. For example, the aperture means may be in the form of a channel extending longitudinally along the bar. Instead, the bar may support a plurality of longitudinally spaced, discrete orifices, the orifices defining the aperture means.




The method may include, initially, prior to capturing said at least part of the topmost sheet, lifting said at least part of the topmost sheet from the stack. The method may include causing said lifting of said at least a part of the topmost sheet by creating a low pressure region between a face of the pick up means and the top surface of the topmost sheet of print media.




Preferably, the method includes maintaining the pick up means in spaced relationship relative to the top surface of the topmost sheet of print media to cause said low pressure region.




The method may include capturing said at least part of the topmost sheet of print media by the pick up means, preferably by reversing a direction of fluid flow through the pick up means to cause a change from a blowing action to a suction action.




The method may include conveying said topmost sheet of print media in a direction substantially normal to a direction of flow of fluid blown on to the stack.











BRIEF DESCRIPTION OF THE DRAWINGS




The invention is now described by way of example with reference to the accompanying drawings in which:





FIG. 1

shows a part of a printer including a print media feed arrangement operated in accordance with the method of the invention;





FIG. 2

shows a three-dimensional view of an input region of the printer including part of the print media feed arrangement;





FIG. 3

shows a three dimensional view, on an enlarged scale, of the part of the print media feed arrangement of

FIG. 2

;





FIG. 4

shows a schematic, sectional side view of an initial stage of operation of the print media feed arrangement;





FIG. 5

shows a schematic, sectional side view of a second stage of operation of the print media feed arrangement;





FIG. 6

shows a schematic, sectional side view of a third stage of operation of the print media feed arrangement; and





FIG. 7

shows a schematic, sectional side view of a fourth stage of operation of the print media feed arrangement.











DETAILED DESCRIPTION OF THE DRAWINGS




Referring initially to

FIG. 1

of the drawings, a part of a printer is illustrated and is designated generally by the reference numeral


10


. The printer


10


is a high speed printer which prints both sides of print media at the rate of approximately one sheet per second or two pages per second (i.e. both sides of the sheet). The print media is, in this case, in the form of a stack of sheets. For ease of explanation, the invention will be described with reference to the print media being a stack of A


4


sheets of paper and, more particularly, sheets of paper having a predetermined degree of porosity.




The printer


10


uses a pair of opposed page width printheads


12


, arranged at a printing station


13


, to print on both sides of sheets of paper fed through the printing station


13


. Each printhead


12


is in the form of a microelectromechanical systems (MEMS) chip having an array of ink jet nozzles to achieve the high speed, photographic quality printing desired.




The printing station


13


includes a set of primary rollers


14


, comprising a drive roller


16


and a driven roller


18


, arranged upstream of the printheads


12


to convey a sheet of paper to the printheads


12


. A secondary set of rollers


20


, comprising a first roller


22


and a second roller


24


, is arranged intermediate the printheads


12


and the set of primary rollers


14


. A paper deflector


26


is arranged between the sets of rollers


14


and


20


.




As illustrated more clearly in

FIG. 2

of the drawings, the print media is, as described above, arranged in a stack


28


. The stack


28


is received in a bin (not shown) of the printer


10


and is retained against a metal bulkhead


30


of the printer


10


in a suitable cabinet (also not shown). A tapping mechanism


32


, which is solenoid driven, taps the paper stack


28


to ensure that the sheets of the paper stack


28


are maintained in accurate abutment with the metal bulkhead


30


so that, when a sheet is fed is to the printing station


13


, as will be described in greater detail below, the sheet lifted from the stack


28


is aligned to be in register with the printheads


12


. In other words, the tapping mechanism


32


inhibits skewing of a sheet picked from the stack


28


.




The printer


10


includes a paper feed arrangement


34


for feeding a sheet of paper from the stack


28


to the rollers


16


and


18


of the set of primary rollers


14


so that the sheet of paper can be transported to the printing station


13


for printing.




The feed arrangement


34


comprises a pivot rod or axle


36


which is rotatably driven by a drive means in the form of a stepper motor


38


. A swing arm


40


is arranged at each end of the axle


36


.




The paper feed arrangement


34


includes a pick up bar


42


which is connected to a fluid hose


44


. The pick up bar


42


is pivotally attached to the swing arms


40


. An arm


46


, having a bifurcated end (not shown) projects from one end of the bar


42


. The arm


46


is slidably received in a sleeve in the form of a pivot block


48


. The arm


46


and, more particularly, its bifurcated end, cooperates with an optical sensor


50


to determine when the pick up bar


42


is in its home position, the home position of the pick up bar


42


being shown, schematically, in

FIG. 4

of the drawings.




As described above, the printer


10


is a high-speed printer which has a capacity to print at the rate of one sheet per second. To make use of this capability, it is important that the sheets of paper are fed individually to the printing station


13


from the stack


28


in an accurate, controlled manner. Consequently, it is necessary for the pick up bar assembly


34


to separate a sheet to be transported to the printing station


13


from the stack


28


accurately. To separate a topmost sheet


28


.


1


from the stack


28


, the fluid hose


44


is connected to a fluid source (not shown). Air is blown down the hose


44


in the direction of arrow


52


as shown in

FIG. 4

of the drawings. The air exits through an outlet aperture


54


of the pick up bar


42


as shown by the arrows


56


. The air is forced between a foot portion


58


of the pick up bar


42


and the topmost sheet


28


.


1


of the paper stack


28


.




The invention is intended particularly for use with print media which is porous such as, for example, 80 gsm paper.




Due to the porosity of the paper, air is also driven through the topmost sheet


28


.


1


and impinges on a sheet of the stack


28


which is second from the top, as shown by arrow


60


in

FIG. 5

of the drawings. This results in an initial separation of the topmost sheet


28


.


1


from the remainder of the sheets of the stack


28


.




Also, as a result of localised low pressure occurring between a periphery of the foot portion


58


of the pick up bar


42


and the topmost sheet


28


.


1


of the stack


28


, the topmost sheet


28


.


1


is attracted to the pick up bar


42


as shown in

FIG. 6

of the drawings. Due to the passage of air through the topmost sheet


28


.


1


separation of the topmost sheet


28


.


1


from the remainder of the sheets of the paper stack


28


is aided.




Once the sheet


28


.


1


has been lifted off the stack


28


and transported a short distance from the stack


28


and when the pick up bar


42


reaches a predetermined altitude relative to the stack


28


, the direction of flow of the air is reversed so that a suction effect is imparted at the aperture


54


of the pick up bar


42


. This is shown in

FIG. 7

of the drawings by arrows


62


.




As the swing arms


40


of the paper feed arrangement


34


continue to rotate in the direction of arrow


64


(

FIG. 3

of the drawings), the pick up arm


42


moves in the direction of arrow


66


(

FIG. 7

) so that a leading edge of the topmost sheet


28


.


1


of the paper stack


28


is fed between the rollers


16


and


18


of the set of primary drive rollers


14


. The suction is then shut off in the hose


44


so that the sheet


28


.


1


is released from the pick up bar


42


for onward conveyance by the sets of rollers


14


and


20


to the printing station


13


for printing purposes.




It will be appreciated that the airflow parallel to a surface of the topmost sheet


28


.


1


of the stack


28


results in a low friction cushion which facilitates translational motion of the sheet


28


.


1


relative to the pick up bar


42


. This allows the sheet


28


.


1


to be moved by any suitable method in a direction normal to a face of the pick up bar


42


without hindering the picking action of the pick up bar


42


. It also facilitates maintaining a trailing portion of the sheet


28


.


1


in spaced relationship relative to the stack


28


while the sheet


28


.


1


is being fed to the set of rollers


14


.




The applicant has found that the velocity of air through the fluid hose in the initial, “blowing” direction is not critical, nor is the spacing between the pick up bar


42


and the topmost sheet


28


.


1


of the paper stack


28


. Further, the weight or grade of the paper of the stack is also not critical provided that the paper in the stack has a degree of porosity.




Typically, a pressure of approximately 5 kPa is present in the fluid hose


14


when the air is blown on to the paper stack


28


. The air is delivered at approximately 11/s and exits the gap between the foot portion


58


of the pick up arm


42


and the topmost sheet


28


.


1


at a pressure of approximately 1 kPa at a velocity of approximately 50 m/s. Experimentally, the pick up arm


42


has been held at a spacing of between 0.1 mm and 0.2 mm above the paper stack


28


to pick up the topmost sheet


28


.


1


and this has been found to be successful. In addition, the paper feed arrangement


34


has been found to operate with paper of a grade from 40 gsm to high resolution, photo-quality ink jet paper.




The aperture


54


of the pick up bar


42


can also be any suitable shape. For example, the aperture


54


could be in the form of a straight or wavy channel extending the length of the pick up bar


42


. Instead, the aperture could comprise a plurality of discrete nozzles arranged at spaced intervals along the length of the pick up bar


42


.




The applicant has found that, surprisingly, by blowing air on to the paper of the stack


28


separation of the sheets is facilitated. This is an entirely counter-intuitive approach as one would expect that a suction-type mechanism would operate better. However, provided the paper of the stack


28


is porous, very good separation of the topmost sheet of paper from the stack


28


can be effected.




It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.



Claims
  • 1. A method of separating a sheet of print media from a stack of sheets, the sheets being porous and the method including the steps of:blowing fluid on to a top surface of a topmost sheet of the print media on the stack so that the fluid passes through at least the topmost sheet of the stack; and capturing at least a part of the topmost sheet for conveyance to a printing station of a printer.
  • 2. The method of claim 1 which includes blowing the fluid on to the top surface of the topmost sheet through an aperture means of a pick up means of a print media feed arrangement.
  • 3. The method of claim 2 which includes, prior to capturing said at least part of the topmost sheet, lifting said at least part of the topmost sheet from the stack.
  • 4. The method of claim 3 which includes causing said lifting of said at least a part of the topmost sheet by creating a low pressure region between a face of the pick up means and the top surface of the topmost sheet of print media.
  • 5. The method of claim 4 which includes maintaining the pick up means in spaced relationship relative to the top surface of the topmost sheet of print media to cause said low pressure region.
  • 6. The method of claim 2 which includes capturing said at least part of the topmost sheet of print media by the pick up means.
  • 7. The method of claim 6 which includes capturing said at least part of the topmost sheet of print media by reversing a direction of fluid flow through the pick up means to cause a change from a blowing action to a suction action.
  • 8. The method of claim 1 which includes conveying said topmost sheet of print media in a direction substantially normal to a direction of flow of fluid blown on to the stack.
Priority Claims (1)
Number Date Country Kind
PR2925 Feb 2001 AU
US Referenced Citations (11)
Number Name Date Kind
3558126 Jiruse Jan 1971 A
4496143 Weyer Jan 1985 A
4579330 Lehmann Apr 1986 A
4887805 Herbert et al. Dec 1989 A
5058876 Grossmann Oct 1991 A
5098077 Russel Mar 1992 A
5110110 Wirz et al. May 1992 A
5836582 Ogawa et al. Nov 1998 A
6398206 Yang et al. Jun 2002 B1
6398207 Taylor et al. Jun 2002 B1
6398208 Yang et al. Jun 2002 B1
Foreign Referenced Citations (3)
Number Date Country
4227814 Feb 1993 DE
741098 Nov 1996 EP
1680606 Sep 1991 SU