Paper feeding apparatus of printing device

A paper feeding apparatus, of a printing machine which includes a cassette for receiving paper that is detachably coupled with a body of the printing device, guide members for supporting side portions of the received paper, slidingly installed in the cassette, and a pair of pick-up rollers for drawing the paper out from the cassette. The pick-up rollers are positioned for tight contact with the top of the received papers and are movably installed on a rotating shaft so as to be capable of moving along the shaft. The paper feeding apparatus also includes a moving mechanism, interlocking with the guide member, for moving the pick-up roller along the shaft.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a paper feeding apparatus of a printing 
device, and more particularly, to a paper feeding apparatus having an 
improved structure for supplying paper from a cassette to the inside of 
the printing device. 
2. Description of the Related Art 
In a typical printing device such as a printer or a copying machine, a 
paper feeding apparatus receives a multitude of paper sheets and supplies 
that paper into the body of the printing device in sequence. 
As shown in FIG. 1, a conventional paper feeding apparatus includes a 
cassette 20 capable of moving along guide rails 11 and 12 provided in the 
body 10 of the printing device and for receiving papers therein. The 
feeding apparatus also includes a pickup roller 13, rotatably installed in 
the body 10, for drawing out the paper received in the cassette 20. 
The cassette 20 includes side guide members 21 and 22 and a rear guide 
member 23 slidably installed, for supporting both sides and the rear end 
portion of the received paper, respectively. The cassette also includes 
finger members 25 and 26 for pressing and supporting corner portions of a 
fore end of the received paper, extended from the side guide members 21 
and 22, and a receiving plate 24 for receiving paper and lifting the fore 
end portion of the received paper toward the finger members 25 and 26. 
Reference numeral 13a denotes a rotation shaft of the pick-up roller 13, 
whereas arrow `A` indicates the direction in which the cassette 20 is 
connected to the body 10 of the printing device, and arrow `B` indicates 
the supply direction of the paper. 
As shown in FIG. 2, the paper received in the cassette 20 is supplied by 
rotating the shaft 13a. The pick-up roller 13 rotates, and thus an 
uppermost paper 100 tightly contacting the pick-up roller 13 is fed in the 
direction indicated by arrow `B`. At this time, the fore end corner 
portion of the paper 100 is caught by the finger members 25 and 26, so 
that the fore end portion of the paper is partially folded, which causes a 
curled portion `C` indicated by dotted lines. When the pick-up roller 13 
continues to rotate, the paper 100 is transferred in the direction 
indicated by arrow `B`, the fore end corner portion of the paper 100 slips 
out from the finger members 25 and 26 and is supplied to the inside of the 
body 10. 
The curled portion `C` facilitates drawing and supplying only the uppermost 
paper sheet from the cassette 20 to the inside of the body 10. That is, 
the curled portion suppresses the multitude of remaining supply sheets of 
paper at once. Thus, the curled portion must be appropriately formed in 
order to smoothly and repeatedly supply individual sheets of paper. A 
distance `D` between the pick-up roller 13 and the finger members 25 and 
26 is set considering the appropriate forming of the curled portion. That 
is, when the distance `D` is too long or short, the curled portion is 
inappropriately formed, thus crumpling or tearing the paper. 
However, by the above-described paper feeding apparatus, when the size of 
the received paper is changed, for example A4 to A3, the finger members 25 
and 26 together with the side guide members 22 and 21 move to correspond 
to the size of the changed paper. However, the pick-up roller 13 is fixed 
in a predetermined position. Thus, the distance `D` is changed, so that 
the curled portion may not be appropriately formed according to the change 
in the paper size. 
SUMMARY OF THE INVENTION 
To solve the above problem, it is an objective of the present invention to 
provide a paper feeding apparatus of a printing device capable of forming 
an appropriate curled portion by moving a pick-up roller according to the 
paper size. 
Accordingly, to achieve the above objective, there is provided a paper 
feeding apparatus of the present invention including a cassette for 
receiving paper, detachably coupled with a body of the printing device; 
guide members, slidingly installed in the cassette, for supporting side 
portions of the received paper; a pair of pick-up rollers for drawing the 
paper out from the cassette, wherein the pick-up rollers are positioned 
for tight contact with the top of the received papers, and are movably 
installed on a rotating shaft so as to be capable of moving along the 
shaft; and moving means, interlocking with one of the guide members, for 
moving the pair of pick-up rollers along the shaft. 
Also, the moving means includes a pinion rotatably installed in the body of 
the printing device; and a pair of rack members having geared portions 
which engage with the pinion such that the geared portions thereof face 
each other, and move in opposite directions to each other by interlocking 
with at least one of the guide members, thereby moving the pick-up rollers 
towards each other.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 3, a paper feeding apparatus according to the present 
invention includes a cassette 200 for receiving paper 100, detachably 
coupled with a body (not shown) of a printing device, and first and second 
pick-up rollers 131 and 132, for transferring the paper 100 received in 
the cassette 200 to the inside of the body of the printing device 
according to the rotation of a shaft 130a, tightly in contact with the 
upper surface of the paper 100. 
The cassette 200 includes first and second guide members 210 and 220 which 
support side portions of the received paper 100, and are slidingly 
installed therein. The cassette 200 also includes finger members 250 and 
260 for pressing and supporting the fore end corner portion of the paper 
100. The finger members 250 and 260 extend from the first and second guide 
members 210 and 220. Further, the cassette 200 includes a receiving plate 
240 for lifting the paper 100 toward the finger members 250 and 260. 
The first and second pick-up rollers 131 and 132 move along the shaft 130a 
by a moving means. The moving means includes a pinion 134 rotatably 
installed on the body of the printing device, first and second rack 
members 141 and 142 with the geared portions of each facing each other and 
engaging with the pinion 134. The first and second rack members also 
interlock with the first and second pick-up rollers 131 and 132, which 
have a spring 133 disposed therebetween to elastically-bias the pick-up 
rollers 131 and 132 away from each other. 
Also, an interlocking piece 132a is formed on the second rack member 142. 
The interlocking piece 132a interlocks with the first guide member 210 
when the cassette 200 is inserted into the body. Reference numeral 221 
denotes a groove formed on the second guide member 220 to prevent the 
interlocking piece 132a from being caught by the second guide member 220, 
when the cassette 200 is coupled with or separated from the body in the 
direction indicated by arrow `E`, as shown in FIGS. 3 and 4. 
FIG. 4 shows the configuration of the moving means. The first and second 
pick-up rollers 131 and 132 are coupled with a spline 130b formed on the 
shaft 130a, so as to be capable of moving along the shaft 130a. One end of 
each of the first and second rack members 141 and 142 is slidingly coupled 
with the shaft 130a, and includes contact pins 131b and 132b contacting 
the sides of the first and second pick-up rollers 131 and 132. Thus, when 
a pinion 134 rotates clockwise, thereby moving the first and second rack 
members 141 and 142 in the direction indicated by the arrow in FIG. 4, the 
contact pins 131b and 132b press the sides of the first and second pick-up 
rollers 131 and 132 and the first and second pick-up rollers 131 and 132 
move along the shaft 130a towards each other. When the pinion 134 rotates 
counterclockwise, thus moving the first and second rack members 141 and 
142 in an opposite direction, the first and second pick-up rollers 131 and 
132 come back to an initial position by an elastic force of the spring 
133. 
Referring to FIGS. 3 and 4, when the different-sized paper is to be 
received in the cassette 200, the cassette 200 is detached from the body, 
and then the guide members 210 and 220 are adjusted to the new paper size. 
In a state in which the cassette 200 is detached from the body, an 
external force is not applied to the first and second pick-up rollers 131 
and 132, which therefore separate to the maximum distance therebetween by 
action of the spring 133. 
When the cassette 200 having the different-sized paper is inserted into the 
body in the direction indicated by arrow `E` in FIG. 3, the first guide 
member 210 contacts the interlocking piece 132a and the second rack member 
142 moves in the direction indicated by arrow `F`. Thus, while the pinion 
134 rotates, the second rack member 142 interlocking with the pinion 134 
moves reversely to the first rack member 141. Also, the first and second 
pick-up rollers 131 and 132 interlocking with the first and second rack 
members 141 and 142 move towards each other. Thus, the distance `D1` 
between the first and the second guide members 210 and 220 and the first 
and the second pick-up rollers 131 and 132, respectively, can be 
maintained at a constant value. 
According to the present invention, a distance for forming the curled 
portion at an end portion of a paper is not changed even though the paper 
size is changed, so that paper supply can be smoothly performed regardless 
of the paper size. It is contemplated that numerous modifications may be 
made to the present invention without departing from the spirit and scope 
of the invention as defined in the following claims.