US20110241291A1

US20110241291A1 - Transportation device

Info

Publication number: US20110241291A1
Application number: US13/080,823
Authority: US
Inventors: Hideki NISHINAKAMA; Satoshi Nakano; Shoichi Fukuyama; Kiyoshi Chinzei
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2010-04-06
Filing date: 2011-04-06
Publication date: 2011-10-06
Also published as: CN102211469A; JP2011219202A; JP5526952B2

Abstract

A transportation device includes a pick-up unit having a first arm, a second arm that is rotatable about a second rotation section with respect to the first arm and is provided with a feeding roller fixed thereon, and a torsion coil spring that acts on the second rotation section so as to bias the feeding roller toward the paper sheets. The first arm has a first fixation section that fixes in place one end of the torsion coil spring, while the second arm has a second fixation section that fixes in place the other end of the torsion coil spring. A plurality of spring latches is disposed on at least one of the first fixation section and second fixation section so as to adjust a spring force of the torsion coil spring.

Description

BACKGROUND

1. Technical Field
The present invention relates to transportation devices for use in ink jet printers and the like.
2. Related Art
Printers are equipped with a transportation device to separate a paper sheet (transported medium) from a stack of paper sheets loaded on a loading tray of the printer and feed such separated paper sheets one by one. Such a transportation device, for example as disclosed in JP-A-2003-285936, includes a feeding roller that is biased toward the paper sheets so as to hold the feeding roller in pressing contact with the paper sheet, thereby ensuring the feeding of paper sheets by the feeding roller.
With reference to FIG. 10, the conventional configuration of a transportation device will be described. A transportation device 100 includes a loading tray 110 on which paper sheets Q are loaded and a feeding roller 120 that transports the paper sheets Q loaded on the loading tray 110 toward a recording unit of the printer. The feeding roller 120 is mounted on a drive shaft 140 which serves as a drive axis via an arm 130. The rotation of the drive shaft 140 is transmitted to the feeding roller 120 via a gear train, which is not shown, to rotate the feeding roller 120. Further, a torsion coil spring 150 is mounted on the transportation device 100 so as to bias the arm 130 toward the paper sheets Q, that is, in a counterclockwise direction as viewed in the figure. This makes the feeding roller 120 be in pressing contact with the paper sheets Q. When the feeding roller 120 rotates in a direction as indicated by the white arrow in the figure, the paper sheets Q are fed out in a paper sheet transport direction as indicated by the dashed and dotted line in the figure.
In this transportation device 100, as the number of the paper sheets Q decreases, a biasing force of the torsion coil spring 150 causes the arm 130 and feeding roller 120 to rotate about the drive shaft 140 toward the loading tray 110. Accordingly, the feeding roller 120 remains in pressing contact with the top paper sheet Q of the stack of paper sheets regardless of the number of the paper sheets Q.
The biasing force of the torsion coil spring 150, however, may deviate from a predetermined biasing force due to the piece to piece variation of the spring 150 or the mounting tolerance of the torsion coil spring 150 during mounting to the transportation device 100. This leads to variation in the pressing contact force of the feeding roller 120 applied to the paper sheets Q. Excessively increased pressing contact force leads to double feeding of the paper sheets Q.

SUMMARY

An advantage of some aspects of the invention is that a transportation device capable of preventing the double feeding of the transported media is provided. According to an aspect of the invention, there is provided a transportation device including a transportation device body in which a transported medium is transported by a feeding roller, a first arm that is mounted on the transportation device body so as to be rotatable about a first rotation section with respect to the transportation device body, a second arm that is mounted on the first arm so as to be rotatable about a second rotation section with respect to the first arm and is provided with the feeding roller fixed on the side opposite the first rotation section with respect to the second rotation section, a torsion coil spring that acts on the second rotation section so as to bias the feeding roller toward the transported medium, a first fixation section that is provided with the first arm and fixes in place one end of the torsion coil spring, a second fixation section that is provided with the second arm and fixes in place one end of the torsion coil spring, and a plurality of spring latches that is disposed on at least one of the first fixation section and the second fixation section so as to adjust a spring force of the torsion coil spring.
With this configuration, the plurality of spring latches enables the spring force of the torsion coil spring to be adjusted, thereby enabling variation in spring force of the torsion coil spring resulting from the piece to piece variation of the torsion coil spring or the mounting tolerance of the torsion coil spring to be reduced. Consequently, it is possible to prevent the pressing contact force of the feeding roller to the transported medium from being excessively increased, thereby preventing the double feeding of the transported media.
In the above aspect of the invention, the transportation device is configured such that the torsion coil spring biases the feeding roller toward the transported medium by means of resilient deformation of the torsion coil spring during the rotation of the second arm with respect to the first arm.
In the case when the second arm rotates relative to the first arm, the torsion coil spring biases the feeding roller toward the transported medium by means of resilient deformation of the torsion coil spring. This causes the biasing force to be increased compared with the case when the second arm does not rotate relative to the first arm and the first arm and the second arm rotate together about the first rotation section. In this configuration, when the transported media are inserted between the feeding roller and the loading surface, a force of the transported media to push the feeding roller causes the first arm and the second arm to rotate together about the first rotation section. This enables to prevent the biasing force from being increased, and thus the pressing contact force of the feeding roller to the transported media from being excessively increased. This allows the transported media to be loaded in the transportation device with ease.
In the above aspect of the invention, the transportation device further includes a loading surface arranged at a position opposite the feeding roller and on which the transported medium is loaded and a cover arranged at a position above the first rotation section opposite the transported medium so as to cover the first rotation section from the outside of rotation radius of the first rotation section, wherein a gap between the loading surface and the cover regulates the number of transported media to be loaded.
If a regulation mechanism that regulate the number of transported media to be loaded is provided at the second rotation section, the second rotation section rotates about the first rotation section depending on the rotation of the first arm and the second arm during the transportation of the transported media by the feeding roller, thereby leading to variation in position of the second rotation section with respect to the loading surface. As a result, the position to regulate the number of the transported media to be loaded also varies. This makes it impossible to clearly regulate the number of paper sheets P to be actually loaded in the transportation device.
In this invention, the cover is formed to cover the first rotation section from the outside of rotation radius of the first rotation section, allowing the position of the cover relative to the loading surface to remain unchanged when the first rotation section rotates. Consequently, the position of the cover relative to the loading surface remains unchanged during the transportation of the transported media by the feeding roller. Accordingly, a maximum number of the transported media to be loaded can be clearly regulated.
In the above aspect of the invention, the transportation device is configured such that the cover is disposed to cover the range over which the first arm rotates when the feeding roller transports the transported medium. With this configuration, the cover is disposed to cover the range over which the first arm rotates, thereby preventing the transported medium from being advanced out of the gap between the loading surface and the cover during the rotation of the first arm.
In the above aspect of the invention, the transportation device further includes a straight arm provided at at least one of the start and end of winding of the torsion coil spring, wherein the plurality of spring latches is formed of a plurality of ribs and the arm is engaged with a rib such that a spring force of the torsion coil spring is adjusted by changing the rib with which the arm is engaged.
With this configuration, an operator can adjust the spring force of the torsion coil spring simply by disengaging the arm from the rib and then engaging the arm with another rib. This allows the operator to adjust the spring force of the torsion coil spring with ease.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a schematic perspective view of a printer according to an embodiment.

FIG. 2 is a schematic perspective view of a transportation device according to an embodiment.

FIG. 3 is an exploded perspective view of a pick-up unit according to an embodiment.

FIG. 4 is a schematic view of a gear train of the pick-up unit according to an embodiment.

FIG. 5 is a perspective view of a front configuration of the pick-up unit according to an embodiment.

FIG. 6A is a side view of a transportation device in a stand-by state.

FIG. 6B is a schematic view of the transportation device of FIG. 6A.

FIG. 7A is a side view of the transportation device in a state immediately before the transportation.

FIG. 7B is a schematic view of the transportation device of FIG. 7A.

FIG. 8A is a side view of the transportation device in a paper sheet transportation state.

FIG. 8B is a schematic view of the transportation device of FIG. 8A.

FIG. 9A is a side view of the transportation device in a state immediately before transportation of thick paper sheet.

FIG. 9B is a schematic view of the transportation device of FIG. 9A.

FIG. 10 is a schematic view of a traditional transportation device.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A transportation device according to the present invention will be described below in an embodiment of a transportation device used in an ink jet printer (hereinafter, referred to as “printer”) with reference to FIGS. 1 to 9B. The terms “front-rear direction”, “up-down direction” and “left-right direction” as used herein mean the “front-rear direction”, “up-down direction” and “left-right direction” as indicated by the arrows in FIG. 1, respectively, unless otherwise described. In this embodiment, the up-down direction is defined as the direction that corresponds to the perpendicular direction.
As shown in FIG. 1, a printer 11 is a recording apparatus which performs recording of characters or images on the paper sheets as an example of transported media which are supplied from the rear side. The printer 11 includes a transportation device 12 which is an automatic sheet transportation device (ASF: Auto Sheet Feeder) that transports paper sheets, a recording device 13 that records images or the like on the paper sheet transported by the transportation device 12 and a discharge port 14 that discharges the paper sheet after the images or the like are recorded by the recording device 13.
As shown in FIG. 2, the transportation device 12 includes a loading tray 21 on which the paper sheets are loaded. The loading tray 21 has a loading surface 21 a which is inclined at an angle onto which the paper sheets are placed and a support surface 21 b which is a plane extending in the front-rear direction and the left-right direction. A guide wall 22 for positioning the paper sheets is arranged at the right end of the loading tray 21 and fixed to the loading tray 21. A support shaft 23 as a main body of the transportation device is disposed on the guide wall 22 and extends to the left from the guide wall 22. The support shaft 23 is connected to an electric motor, which is not shown, via a gear train. A pick-up unit 24 that transports the paper sheets toward the recording device 13 (see FIG. 1) is supported by the support shaft 23.
The loading surface 21 a is provided with a roller 25 (see FIG. 6) which abuts the paper sheets that are in contact with the loading surface 21 a. A separation pad 26 is disposed on the support surface 21 b as a separation mechanism to separate the paper sheets one by one. The separation pad 26 includes a case 26 a having a rectangular box shape which is mounted on the support surface 21 b and a separating member 26 b which extends in the front-rear direction of the case 26 a in the center of the case 26 a in the left-right direction. The separating member 26 b uses a material having a coefficient of friction higher than that of the case 26 a.
As shown in FIG. 3, the pick-up unit 24 includes a first arm 31 that is rotatably mounted on the support shaft 23, a second arm 32 that is rotatably mounted on the lower part of the first arm 31 and a feeding roller 33 that is mounted at the lower part of the second arm 32. A torsion coil spring 35 as a biasing member is mounted on the second arm 32 so as to bias the feeding roller 33 (second arm 32) toward the paper sheets P. Further, the rotation of the support shaft 23 is transmitted to the feeding roller 33 via a transmission mechanism 34 which is composed of driven gears 34 a to 34 c. The torsion coil spring 35 includes a coil 35 a, a first engaging portion 35 b as a straight shaped arm formed at one end of the coil 35 a at the start of winding and a second engaging portion 35 c as an L-shaped arm formed at the other end of the coil 35 a at the end of winding.
The first arm 31 includes a pair of first arm members 41 spaced apart in the left-right direction and an upper cover 42 which connects each of the first arm members 41 and covers the support shaft 23. A first bearing 43 which has a through hole that extends through the arm member 41 in the left-right direction is formed in the upper area of each of the first arm members 41. A first shaft 44 that extends in the right direction from the arm member 41 is formed in the lower area of the right one of the first arm members 41. A second bearing 45 which has a through hole that extends through the arm member 41 in the left-right direction is formed in the lower area of the left one of the first arm members 41. The support shaft 23 is slidably inserted into the first bearings 43. In this embodiment, the support shaft 23 and the first bearing 43 constitute a “first rotation section 61.”
The upper cover 42 has a curved portion 42 a that covers the first rotation section 61 from the outside and curves in an arc about the rotation center of the first rotation section 61. The curved portion 42 a extends over the range of rotation of the first arm 31. The transportation device 12 is configured such that a gap G (see FIG. 6) between the curved portion 42 a and the loading surface 21 a regulates the maximum loading of paper sheets (maximum number of paper sheets to be loaded). Since the curved portion 42 a does not cause the gap G to be changed by the rotation of the first arm 31, the maximum loading of paper sheets remains constant during the rotation of the first arm 31.
The upper cover 42 has a projection 42 b that extends in the right direction beyond the right one of the first arm members 41. The projection 42 b has a groove 42 c which is recessed backwardly in the rear inner surface thereof.
The second arm 32 includes a pair of second arm members 51 spaced apart in the left-right direction and a cover 52 which covers upper and front regions of the second arm member 51. A projection 53 that extends in the right direction from the right one of the arm members 51 and has a through hole which extends through the right one of the arm members 51 is formed in the upper area of the right one of the arm members 51. A cylindrical second shaft 54 that extends in the left direction from the left one of the second arm members 51 is formed in the upper area of the left one of the second arm members 51. A third bearing 55 which has a through hole that extends through the arm member 51 in the left-right direction is formed in the lower area of each of the second arm members 51. The second shaft 54 is slidably inserted into the second bearing 45 and the projection 53 is slidably inserted into the first shaft 44 so that the second arm 32 is attached to the first arm 31. In this embodiment, the second shaft 54 and the second bearing 45 constitute a “second rotation section 62,” while the projection 53 and the first shaft 44 constitute a left “second rotation section 62.”
A torsion coil spring 35 is fitted on the projection 53 so as to be coaxial with the second rotation section 62. A spring fixation section 70 composed of a plurality of ribs 76 is formed on the right one of the second arm members 51 in the front region with respect to the projection 53. The plurality of ribs 76 are arranged in an arc about the rotation center of the second rotation section 62 and each extend in the right direction from the arm member 51. In a plan view seen from the right position, each rib 76 is in a rectangular shape with its longitudinal axis extending radially from the rotation center of the second rotation section 62.
The first engaging portion 35 b of the torsion coil spring 35 is adapted to be inserted between the adjacent ribs 76. The second engaging portion 35 c of the torsion coil spring 35 is fitted in the groove 42 c of the upper cover 42 and inserted into a insertion hole (not shown) formed in the first arm member 41.
The feeding roller 33 has a roller body 33 a in a cylindrical shape which is fitted in the third bearing 55. A sliding contact member 33 b made of rubber in a cylindrical shape is attached to the outer circumference of the roller body 33 a so as to abut the paper sheet. A gear 33 c (see FIG. 4) is disposed at the left end of the roller body 33 a so as to mesh with the driven gear 34 c.
As shown in FIG. 4, the transmission mechanism 34 is composed of the driven gears 34 a to 34 c. The driven gear 34 a is arranged to rotate together with the support shaft 23.
The driven gear 34 b meshes with both the driven gears 34 a and 34 c. The driven gear 34 c meshes with the gear 33 c. As shown by the white arrows in the figure, when the support shaft 23 rotates counterclockwise, the driven gear 34 a is rotated counterclockwise. The counterclockwise rotation of the driven gear 34 a causes the driven gear 34 b to rotate clockwise and the driven gear 34 c to rotate counterclockwise. Then, the counterclockwise rotation of the driven gear 34 c causes the feeding roller 33 to rotate clockwise.
As shown in FIG. 5, the spring fixation section 70 has first to fifth adjusters 71 to 75 each formed between the adjacent ribs 76. The first engaging portion 35 b of the torsion coil spring 35 engages with one of the first to fifth adjusters 71 to 75 so that the biasing force of the torsion coil spring 35 is adjusted. The first to fifth adjusters 71 to 75 are arranged in ascending order from the bottom to the top. When the torsion coil spring 35 engages with the first adjuster 71, a minimum biasing force is applied, while when the torsion coil spring 35 engages with the fifth adjuster 75, a maximum biasing force is applied. The biasing force of the torsion coil spring 35 increases from the first adjuster 71 to the fifth adjuster 75.
In the case where the first engaging portion 35 b is moved from the position of the third adjuster 73 to the position of the fourth adjuster 74 in order to increase the biasing force of the torsion coil spring 35, an operator first resiliently deforms the first engaging portion 35 b in the right direction with respect to the third adjuster 73 as shown by the dashed line in the figure so as to disengage the first engaging portion 35 b from the third adjuster 73. Then the operator twists the torsion coil spring 35 in a clockwise direction about the second rotation section 62 and engages the first engaging portion 35 b with the fourth adjuster 74. Similarly, in the case where the first engaging portion 35 b is moved from the position of the third adjuster 73 to the position of the second adjuster 72 in order to decrease the biasing force of the torsion coil spring 35, an operator first resiliently deforms the first engaging portion 35 b in the right direction with respect to the third adjuster 73, then twists the torsion coil spring 35 in a counterclockwise direction about the second rotation section 62 and engages the first engaging portion 35 b with the second adjuster 72.
Reference is now made to FIGS. 6A to 9B for a description of the processes from the loading to the transportation of paper sheets P in the transportation device 12. FIGS. 6B, 7B, 8B and 9B are schematic views each showing the relationship between the forces exerted around the pick-up unit 24 and the angles formed by the pick-up unit 24. In FIGS. 6A to 8B, “plain paper sheets,” which are relatively thin and soft paper sheets, are used as paper sheets P.
Before the paper sheets P are loaded on the loading tray 21, the pick-up unit 24 is configured such that the feeding roller 33 abuts the loading surface 21 a. The pick-up unit 24 has a first distance between axes D1 which is defined by a straight line connecting between the rotation center of the first rotation section 61 and the rotation center of the second rotation section 62 and a second distance between axes D2 which is defined by a straight line connecting between the rotation center of the second rotation section 62 and the rotation axis J of the feeding roller 33 (see FIG. 6B), such that the first distance between axes D1 is smaller than the second distance between axes D2.
As shown in FIGS. 6A and 6B, in loading the paper sheets P onto the loading tray 21, the paper sheets P are loaded at a position upstream of the feeding roller 33 in the transport direction. When the paper sheets P move downstream, the paper sheets P come into contact with the feeding roller 33. As a consequence, the weight of the paper sheets P exerts a component force along the loading surface 21 a on the feeding roller 33. The component force acts to rotate the pick-up unit 24 clockwise about the first rotation section 61 as shown by the dashed line in the figure, which causes the first arm 31 and the second arm 32 to rotate together clockwise about the first rotation section 61 in the pick-up unit 24. Then, as the feeding roller 33 separates from the loading surface 21 a, the paper sheets P are passed through the gap between the feeding roller 33 and the loading surface 21 a. Accordingly, the paper sheets P come into contact with the separation pad 26 while the feeding roller 33 abuts the top paper sheet P.
As shown by the solid line in FIG. 6A, in a stand-by state in which the paper sheets P are loaded on the loading tray 21 and the feeding roller 33 is not rotating, the torsion coil spring 35 acts on the pick-up unit 24 so that the first arm 31 becomes inclined forward as it moves downward and the second arm 32 becomes inclined backward as it moves downward.
As the number of paper sheets P decreases, the weight of the pick-up unit 24 acts on the pick-up unit 24 so that the pick-up unit 24 moves from the state shown by the dashed line in FIG. 6A to the state shown by the solid line in FIG. 6A. That is, in the pick-up unit 24, the first arm 31 rotates about the first rotation section 61 so that the lower end of the first arm 31 moves toward the paper sheets P (in the counterclockwise direction as viewed in the figure). Accordingly, the second arm 32 rotates while maintaining the inclination angle with the first arm 31, that is, the first arm 31 and the second arm 32 rotate together toward the paper sheet P.
In the stand-by state, the torsion coil spring 35 has its natural length. Accordingly, the torsion coil spring 35 does not exert a force to bias the second arm 32 counterclockwise. That is, a biasing force of the torsion coil spring 35 (hereinafter, referred to as “biasing force S”) that biases the feeding roller 33 toward the top paper sheet P1 as a first transported medium of the stack of the paper sheets P is not exerted on the second arm 32. As a result, the feeding roller 33 simply abuts the paper sheet P1 in this state. Further, since the feeding roller 33 is not rotating, a roller frictional force f which is a frictional force exerted by the paper sheet P1 on the feeding roller 33 is 0.
An arm angle A between the first arm 31 and the second arm 32 in the stand-by state is defined as a reference angle A1. Further, an inclination angle B, which is an acute angle, between the straight line JL connecting the second rotation section 62 and the rotation axis J of the feeding roller 33 and the loading surface 21 a, that is, a surface of the paper sheet P1 where the feeding roller 33 is in contact with in the stand-by state is defined as a reference angle B1.
As shown in FIGS. 7A and 7B, in a state immediately before transporting the paper sheet P1 by the rotation of the feeding roller 33 (a state immediately before the transportation), a frictional force F between the paper sheets (hereinafter, referred to as “frictional force F1 between the paper sheets”) which is generated between the paper sheet P1 and a paper sheet P2 as a second transported medium that abuts the paper sheet P1 in a stack direction becomes a maximum. In addition, a separation load H (hereinafter, referred to as “separation load H1”) which is a load with which the separation pad 26 separates the paper sheet P1 from the paper sheet P2 becomes a maximum. Accordingly, since a force corresponding to the resultant force of the frictional force F1 between the paper sheets and the separation load H1 is necessary to transport the paper sheet P1, a force T (hereinafter, referred to as “transportation force T1”) that transports the paper sheet P1 due to the rotation of the feeding roller 33 becomes a maximum. Further, since the roller frictional force f corresponds to a reaction force of the transportation force T1, the roller frictional force f has the same magnitude as the transportation force T1 in the state immediately before the transportation.
In this state, a force is exerted on the pick-up unit 24 by the roller frictional force f so as to rotate the second arm 32 clockwise. This causes the lower end of the first arm 31 to rotate counterclockwise about the first rotation section 61 and the upper end of the second arm 32 to rotate clockwise about the rotation axis J of the feeding roller 33. As a result, the second rotation section 62 moves toward the paper sheets P. Due to the movement of the second rotation section 62, the arm angle A increases to an angle A2 which is greater than the reference angle A1 (A1<A2) while the inclination angle B increases to an angle B2 which is smaller than the reference angle B1 (B2<B1). In response to the change of the arm angle A and the inclination angle B, the feeding roller 33 moves downstream in the transportation direction of the paper sheets P compared with the stand-by state. Accordingly, a biasing force S1 is exerted toward a region downstream in the transportation direction compared with a virtual biasing force SK which is a virtual biasing force S1 assumed to be exerted in the stand-by state.
Meanwhile, as the second rotation section 62 rotates, the torsion coil spring 35 is bent in the direction opposite to the biasing direction. This results in a restoring force R1 of the torsion coil spring 35 being exerted on the second arm 32. That is, a biasing force S1 that corresponds to the restoring force R1 is exerted on the second arm 32. Consequently, as the arm angle A increases from the reference angle A1, the torsion coil spring 35 is bent in the direction opposite to the biasing direction, thereby increasing the restoring force R1 of the torsion coil spring 35.
In this state, a force exerted by the roller frictional force f when the inclination angle B is the angle B2 so as to cause the feeding roller 33 to be pressed against the paper sheet P1 (f·sinB2) is decreased compared with a force which is assumed to be exerted by the roller frictional force f in the stand-by state when the inclination angle B is the angle B1 so as to cause the feeding roller 33 to be pressed against the paper sheet P1 (f·sinB1) (f·sinB2<f·sinB1).
As shown in FIGS. 8A and 8B, when the paper sheet P1 is transported relative to the paper sheet P2 (paper sheet transportation state), a frictional force F2 between the paper sheet P1 and the paper sheet P2 is decreased from the frictional force Fl in the state immediately before the transportation as shown in FIG. 6B (F2<F1). In addition, since the paper sheet P1 and the paper sheet P2 are separated, the separation load H is 0. As a result, a force which corresponds to the frictional force F2 is necessary to maintain the transportation state of the paper sheet P1, therefore a transportation force T2 in the paper sheet transportation state is decreased from the transportation force T1 (T2<T1). Since the roller frictional force f corresponds to the transportation force T2, the roller frictional force f is decreased from the state immediately before the transportation.
In this state, as the roller frictional force f decreases, the lower end of the first arm 31 rotates clockwise and the upper end of the second arm 32 rotates counterclockwise in the pick-up unit 24. This causes the second rotation section 62 to move toward the paper sheets P. As a result, the arm angle A is changed to an angle A3 which is between the angle A1 and the angle A2 (A2<A3<A1). The inclination angle B is also changed to an angle B3 which is between the angle B1 and the angle B2 (B1<B3<B2). Due to the change of the arm angle A and the inclination angle B, the feeding roller 33 moves to a position which is upstream in the transportation direction compared with a state immediately before the transportation and downstream in the transportation direction compared with the stand-by state.
Moreover, as the second rotation section 62 rotates, the torsion coil spring 35 is bent in the same direction as the biasing direction. This causes the restoring force R2 to be decreased compared with the restoring force R1 (R2<R1). Accordingly, the biasing force S2 is decreased compared with the biasing force S1 (S2<S1).
As the pick-up unit 24 transitions from the stand-by state to the paper sheet transportation state, each of the roller frictional force f, the transportation force T, the biasing force S and the inclination angle B change accordingly. That is, as the transportation force T (roller frictional force f) increases, the biasing force S increases and the inclination angle B decreases.
In addition, each of the roller frictional force f, the biasing force S, the transportation force T and the inclination angle B also change depending on the different thicknesses of the paper sheets P. That is, when the thicknesses of the paper sheets P are different, the separation load H and thus the roller frictional force f change accordingly. Specifically, the separation load H in the case when a thick paper sheet P3 having a large thickness such as photo paper or a postcard is used as shown in FIGS. 9A and 9B is increased from the separation load H in the case when a thin paper sheet P1 having a small thickness such as plain paper is used as shown in FIGS. 7A and 7B. Accordingly, when the paper sheet P3 is transported in the state immediately before the transportation, the roller frictional force f is increased compared with that during the transportation of the paper sheet P1. As a result, the transportation force T3 for transporting the paper sheet P3 is increased compared with the transportation force T1 for transporting the paper sheet P1, therefore an angle B4 during the transportation of paper sheet P3 is decreased compared with the reference angle B1 during the transportation of paper sheet P1 (B4<B1).
According to the above embodiment, the following advantages can be achieved.
(1) The biasing force of the torsion coil spring 35 is adjustable by the first to fifth adjusters 71 to 75, thereby enabling variation in spring force of the torsion coil spring 35 resulting from the piece to piece variation of the torsion coil spring 35 or the mounting tolerance of the torsion coil spring 35 to be reduced. Consequently, it is possible to prevent the pressing contact force of the feeding roller 33 to the paper sheet P1 from being excessively increased, thereby preventing the double feeding of the paper sheets P.
(2) When the second arm 32 rotates relative to the first arm 31, the torsion coil spring 35 biases the feeding roller 33 toward the paper sheet P by means of resilient deformation of the torsion coil spring 35. This causes the biasing force S to be increased compared with the case when the second arm 32 does not rotate relative to the first arm 31 and the first arm 31 and the second arm 32 rotate together about the first rotation section 61. In this configuration, when the paper sheets P are inserted between the feeding roller 33 and the loading surface 21 a, a force of the paper sheet P to push the feeding roller 33 causes the first arm 31 and the second arm 32 to rotate together about the first rotation section 61. This enables to prevent the biasing force S from being increased, and thus the pressing contact force of the feeding roller 33 to the paper sheet P1 from being excessively increased. This allows the paper sheet P to be loaded in the transportation device 12 with ease.
(3) If a regulation mechanism that regulate the number of paper sheets P to be loaded is provided at the second rotation section 62, the second rotation section 62 moves toward and away from the paper sheets P depending on the rotation of the first arm 31 and the second arm 32 during the transportation of the paper sheets P by the feeding roller 33, thereby leading to variation in position of the second rotation section 62 with respect to the loading surface 21 a. As a result, the position to regulate the number of the paper sheets P to be loaded also varies. This makes it impossible to clearly regulate the number of paper sheets P to be actually loaded in the transportation device 12.
In this invention, the curved portion 42 a of the upper cover 42 is formed to cover the first rotation section 61 from the outside of rotation radius of the first rotation section 61. This allows the position of the curved portion 42 a relative to the loading surface 21 a to remain unchanged when the first rotation section 61 rotates. Consequently, the position of the curved portion 42 a relative to the loading surface 21 a remains unchanged during the transportation of the paper sheets P by the feeding roller 33. Accordingly, a maximum loading of paper sheets P (maximum number of paper sheets P to be loaded) can be clearly regulated.
(4) The curved portion 42 a of the upper cover 42 is formed to cover the range over which the first arm 31 rotates, thereby preventing the paper sheet P from being advanced out of the gap G between the loading surface 21 a and the curved portion 42 a during the rotation of the first arm 31.
(5) The first engaging portion 35 b can be hold with respect to the rib 76 simply by engaging the first engaging portion 35 b with the rib 76. An operator can adjust the spring force of the torsion coil spring 35 simply by disengaging the first engaging portion 35 b from the rib 76 and then engaging the first engaging portion 35 b with another rib 76. This allows the operator to adjust the spring force of the torsion coil spring 35 with ease.
(6) The pick-up unit 24 includes the first rotation section 61 and the second rotation section 62. In addition, the torsion coil spring 35 that exerts the biasing force on the second arm 32 is provided on the second rotation section 62. Accordingly, in the state immediately before the transportation and the paper sheet transportation state, a component force of the roller frictional force f exerts on the second arm 32 so as to rotate the second arm 32 clockwise. Due to this component force, as the first arm 31 rotates counterclockwise about the first rotation section 61 and the second arm 32 rotates clockwise about the rotation axis J of the feeding roller 33, the second rotation section 62 moves toward the paper sheets P. As a result, the inclination angle B is decreased according to the rotation of the second rotation section 62 compared with that in the stand-by state.
Moreover, as the second rotation section 62 rotates, a restoring force is exerted on the torsion coil spring 35. The restoring force of the torsion coil spring 35 exerted on the torsion coil spring 35 causes a biasing force to biases the second arm 32 toward the paper sheets P. This biasing force increases in proportion to the amount of the restoring force of the torsion coil spring 35.
As the biasing force exerted by the torsion coil spring 35 to the second arm 32 increases, the inclination angle B decreases. As a result, the increase of the roller frictional force f is smaller than the increase of the biasing force. This enables to prevent the roller frictional force f from being excessively increased relative to the frictional force F between the paper sheets, thereby preventing the double feeding of the paper sheets P.
Recent printers have been compact and the need for compact transportation devices has been increased. Such a compact transportation device can be achieved, for example, by reducing the size of the pick-up unit, that is, shortening the length of the arm 130 shown in FIG. 10. However, if the length of the arm 130 is shortened, the acute angle between the arm 130 and the loading surface 111 is increased to be larger than X shown in FIG. 10. This causes a problem in that the feeding roller 120 is pressed against the paper sheet Q with a greater force. Therefore, in order to reduce the force of the feeding roller 120 is pressed against the paper sheet Q, the acute angle between the arm 130 and the loading surface 111 needs to be reduced by increasing the length of the arm 130, that is, positioning the drive shaft 140 at an upper position. However, this configuration leads to a problem in that the size of the transportation device is increased.
In this embodiment in which the second arm 32 is inclined with respect to the first arm 31, when the second rotation section 62 rotates without displacing the position of the support shaft 23, the roller frictional force f increases and the inclination angle B which corresponds to the above-mentioned acute angle decreases, thereby reducing the force of the feeding roller 120 to be pressed against the paper sheet Q. Therefore, the transportation device 12 having a compact size and reduced pressing force can be achieved.
Specifically, in the transportation device 100 shown in FIG. 10, the acute angle (inclination angle B) is set regardless of the separation load of the paper sheet Q or the frictional force between the paper sheets and varies depending on the loaded amount of the paper sheet Q. This leads to a problem in that, when the number of the paper sheets Q is reduced, a frictional force (roller frictional force) exerted by the paper sheet Q to the feeding roller 120 unintentionally increases because the separation load and the frictional force between paper sheets can not be changed.
In this embodiment, the inclination angle B can be changed depending on the transportation force T which is composed of the separation load H and the frictional force F between the paper sheets, thereby enabling to prevent the force exerted by the roller frictional force f causing the feeding roller 33 to be pressed against the paper sheets P1 (f·sinB) from being excessively increased.
(7) Even though the same number of the paper sheet is used, the separation load H differs depending on the type of the paper sheet used. For example, in the case when a postcard is used, the separation load H is increased since a postcard has a thickness greater than that of a plain paper. Although the transportation device 100 shown in FIG. 10 can adjust the position of the feeding roller 120 depending on the number of the paper sheets, it does not have the ability to adjust the force of the feeding roller 120 to be pressed against the paper sheets depending on the type of the paper sheets. As a result, with the transportation device 100 in which the separation load H is set for a postcard for example, when a small number of paper sheets of a plain paper is loaded, the paper sheets may have a problem of double feeding. Alternatively, with the transportation device 100 in which the separation load H is set for a plain paper, when a small number of thick paper sheets is loaded, the transportation force T of the feeding roller 33 may not be enough to feed the thick paper sheets, leading to a problem of misfeeding of the paper sheets.
In this embodiment, the pick-up unit 24 allows the biasing force S to be increased when the separation load H increases, such that the transportation force T of the feeding roller 33 increases when a thick paper sheet such as a postcard is used as the paper sheet P. Further, the pick-up unit 24 allows the biasing force S to be decreased when the separation load H decreases, such that the transportation force T of the feeding roller 33 decreases when a thin paper sheet such as a plain paper is used as the paper sheet P. This enables to prevent the double feeding or misfeeding of the paper sheets P by the feeding roller 33, which is caused by different separation loads H for the paper sheets P of various thicknesses.
(8) In the pick-up unit 24 having the first distance between axes D1 which is smaller than the second distance between axes D2, the distance over which the second rotation section 62 rotates is greater than that in the pick-up unit 24 having the first distance between axes D1 which is greater than the second distance between axes D2. This allows a force exerted by the restoring force of the torsion coil spring 35 so as to bias the feeding roller 33 toward the paper sheet P1 to be adjusted to a greater extent.
(9) In the state immediately before the transportation, the frictional force F between the paper sheets and the separation load H each become a maximum, and thus the transportation force T becomes a maximum. This causes the second rotation section 62 to rotate so that the inclination angle B becomes minimum, thereby preventing the roller frictional force f from being increased. Accordingly, it is possible to prevent the feeding roller 33 from being pressed against the paper sheet P1.
(10) As the biasing force S increases, the feeding roller 33 moves downstream in the transportation direction of the paper sheet P and the distance between the feeding roller 33 and the separation pad 26 is decreased. This allows the resiliency of the paper sheet P is relatively increased when the leading end of the paper sheet P comes into contact with the separation pad 26. Accordingly, the paper sheet P can be advantageously separated.
Moreover, as the biasing force S increases, the biasing force S turns to downstream and the increase of the component force of the biasing force S in the upstream direction becomes gradual compared with the increase of the biasing force S. Accordingly, the increase of the roller frictional force f to the increase of the biasing force S is decreased. This makes it possible to prevent the feeding roller 33 from being pressed against the paper sheets P1.
(11) In a state immediately before the transportation as shown in FIGS. 7A and 7B or 9A and 9B, the second rotation section 62 is regulated to rotate at the position apart from the paper sheet P1, P3. Accordingly, even when the second rotation section 62 rotates toward the paper sheet P1, P3, it is possible to prevent the second rotation section 62 from coming into contact with the paper sheet P1, P3, thereby allowing the paper sheet P1, P3 to be advantageously transported by the transportation device 12.
The above embodiment may be modified as follows.
In the above embodiment, the first distance between axes D1 between the first rotation section 61 and the second rotation section 62 may be equal or greater than the second distance between axes D2 between the second rotation section 62 and the rotation axis J of the feeding roller 33.
In the above embodiment, the separation pad 26 may be omitted.
In the above embodiment, the transportation direction of the paper sheet P may be the direction extending in the front-rear direction. In this case, the feeding roller 33 abuts the top surface of the paper sheet P. Further, in the stand-by state, the second arm 32 is inclined upward toward the upstream in the transportation direction. The first arm 31 is inclined downward toward the upstream in the transportation direction. Further, in the state immediately before transporting the paper sheet, the arm angle A increases and the inclination angle B decreases. This causes the feeding roller 33 to move downstream in the transport direction. As the feeding roller 33 moves, the restoring force R of the torsion coil spring 35 increases, and the biasing force S of the feeding roller 33 increases. In the paper sheet transportation state, the arm angle A is decreased and the inclination angle B is increased compared with the state immediately before the paper sheet transportation. This causes the feeding roller 33 to move upstream in the transportation direction. Accordingly, the restoring force of the torsion coil spring 35 decreases, and the biasing force S of the feeding roller 33 also decreases.
In the above embodiment, the torsion coil spring 35 may be mounted on the first arm 31. In this case, the both ends of the torsion coil spring 35 may be each mounted on the first arm 31 and the second arm 32 so that the restoring force of the torsion coil spring 35 increases or decreases according to the rotation of the second rotation section 62.
In the above embodiment, the pick-up unit 24 may be mounted on a part of the loading tray 21 or any other part of the printer 11. In this case, these parts and the first bearing 43 form the first rotation section. Further, these parts may be formed into the shape corresponding to the first bearing 43 and the first arm 31 may be provided with a shaft that fits into these parts.
In the above embodiment, spring fixation section 70 may be formed on the first arm 31. In this case, the second engaging portion 35 c is formed into a straight shape and adapted to engage with the spring fixation section 70.
In the above embodiment, the curved portion 42 a of the upper cover 42 may be formed to cover the range which is smaller than the range of rotation of the first rotation section 61. Alternatively, the curved portion 42 a may be omitted.
In the above embodiment, although the biasing force of the torsion coil spring 35 is adjusted in five stages by the first to fifth adjusters 71 to 75, the adjustment stages are not limited to five stages, any number of stages may be used as long as a plurality of stages are provided.
In the above embodiment, the transported medium transported by the transportation device 12 is not limited to plain paper, photo paper, or postcard, but may include any media such as OHP.
In the above embodiment, the transportation device 12 is not limited to application in the ink jet printer 11, but may be applied to other printers such as dot impact printers, laser printers and thermal transfer printers. Further, it is not limited to printers, and may be applied to other devices that transport the transported medium.
The entire disclosure of Japanese Patent Application No. 2010-88037, filed Apr. 6, 2010 is expressly incorporated by reference herein.

Claims

1. A transportation device comprising:

a transportation device body in which a transported medium is transported by a feeding roller;

a first arm that is mounted on the transportation device body so as to be rotatable about a first rotation section with respect to the transportation device body;

a second arm that is mounted on the first arm so as to be rotatable about a second rotation section with respect to the first arm and is provided with the feeding roller fixed on the side opposite the first rotation section with respect to the second rotation section;

a torsion coil spring that acts on the second rotation section so as to bias the feeding roller toward the transported medium;

a first fixation section that is provided with the first arm and fixes in place one end of the torsion coil spring;

a second fixation section that is provided with the second arm and fixes in place one end of the torsion coil spring; and

a plurality of spring latches that is disposed on at least one of the first fixation section and the second fixation section so as to adjust a spring force of the torsion coil spring.

2. The transportation device according to claim 1, wherein the torsion coil spring biases the feeding roller toward the transported medium by means of resilient deformation of the torsion coil spring during the rotation of the second arm with respect to the first arm.

3. The transportation device according to claim 1, further comprising:

a loading surface arranged at a position opposite the feeding roller and on which the transported medium is loaded; and

a cover arranged at a position above the first rotation section opposite the transported medium so as to cover the first rotation section from the outside of rotation radius of the first rotation section, wherein a gap between the loading surface and the cover regulates the number of transported media to be loaded.

4. The transportation device according to claim 3, wherein the cover is disposed to cover the range over which the first arm rotates when the feeding roller transports the transported medium.

5. The transportation device according to claim 1, further comprising a straight arm provided at at least one of the start and end of winding of the torsion coil spring, wherein the plurality of spring latches is formed of a plurality of ribs and the arm is engaged with a rib such that a spring force of the torsion coil spring is adjusted by changing the rib with which the arm is engaged.