JPH1142766A - Ink fountain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink fountain which is easy of maintenance and capable of the miniatuarization of the whole device and reduction of production costs. SOLUTION: In the bottom part of an ink fountain 1, an ink feeding port 9 surrounded by an upper surface, a side plate 4, and a pot roller 7 is formed. A cam member 16 which is displaced in the rotary axis direction by a support axis 13 is installed on a fountain table 2. The displacement in the horizontal direction generated by the cam member 16 is transmitted as the displacement in the vertical direction to the first piece 26a of a L-shaped blade 26 through a push rod 19 and an L-shaped link. When the first piece 26a with a terminal part fixed is moved vertically, the second piece 26b of the blade 26 is moved vertically along the front end part 5. As a result, the terminal part of the second piece 26b narrows/widens the ink feeding port 9 to adjust the supply of ink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink fountain used in a printing press.

[0002]

2. Description of the Related Art In an offset printing machine, as shown in FIG. 8, an ink fountain 64 and a fountain roller 62 are arranged above and below a printing paper P, respectively. A plate cylinder 54 is connected to each of the pot rollers 62 via a plurality of kneading rollers 53.
The printing paper P is supplied between a pair of rubber cylinders 55 provided for the printing cylinder 4. The ink in the ink fountain 64 is supplied to the plate cylinder 54 via the outer peripheral surfaces of the rollers 62 and 53 with the rotation of the fountain roller 62, and is transferred from the plate cylinder 54 to the paper P via the rubber cylinder 55. It has become so.

By the way, in such a printing form,
Printing on the paper P is performed with a predetermined set width in the direction of the rotation axis of the fountain roller 62. In a normal case, the ink transfer area at each position within the set width differs depending on the design of printing. Therefore, if the ink supply amount at each position in the rotation axis direction of the fountain roller is the same, printing unevenness may occur on the printed paper P. Therefore, an ink fountain provided with a blade adjusting device as shown in FIG. 9 has been conventionally proposed.

In the conventional ink fountain blade adjusting device 61, a fountain base 63 provided adjacent to a fountain roller 62 is provided.
The bottom plate 64a of the ink fountain 64 is held on the upper surface of the ink fountain 64. The ink fountain 6 is held between the ink fountain 64 and the fountain roller 62.
5 are formed. A plurality of blades 67 are arranged on the upper surface of the front portion of the pot 63 so as to close the ink outlet 66 from below in the direction of the rotation axis of the pot roller 62. The tip of each blade 67 and the fountain roller 62
An ink discharge port 66 is formed between the ink supply port 66 and the outer peripheral surface of the ink supply port.

[0005] Each of the blades 67 has an elongated hole 68 extending in the front-rear direction.
A coil spring 69 that constantly urges 7 in a direction of retreating from the fountain roller 62 is disposed together with the receiving bracket 70 and the support shaft 71. A drive mechanism 75 including a push rod 72, a cam mechanism 73 having a cam 73a, and an actuator 74 is operatively connected to each blade 67. When the push rod 72 is advanced through the cam mechanism 73 by rotating the actuator 74 in the normal direction, the corresponding blade 67
The ink is advanced toward the fountain roller 62 against the urging force of No. 9 to narrow the ink discharge port 66 to reduce the amount of ink to be discharged. Conversely, when the actuator 74 is reversed, the blade 67 is retracted from the fountain roller 62 by the urging force of the coil spring 69, and the ink delivery port 66 is expanded to increase the amount of ink delivered.

[0006]

However, the ink fountain provided with the above-mentioned conventional blade adjusting device has the following problems.

[0007] There is a slight clearance between the adjacently arranged blades 67 to allow sliding. Therefore, the ink penetrates into the groove formed by the clearance, and the coil spring 69 in the long hole 68 is formed.
And receiving bracket 70, support shaft 71 and push rod 7
In some cases, the drive mechanism 75 composed of the second or the like may be soiled. Therefore, if the coil spring 69 or the like is contaminated, the entire apparatus must be disassembled and cleaned, and there is a problem that maintenance is troublesome.

Further, since each blade 67 has a block shape, a large space is required for disposing them. As a result, there is a problem that the entire apparatus becomes large.

Furthermore, an actuator with a high output was required to move the heavy block-shaped blade 67. In addition, the coil spring 69 and the receiving bracket 70
And a plurality of components such as the support shaft 71 are inserted into the small holes 68 of the small space.
The number of parts must be increased, and the number of parts increases, so that there is a problem that the number of working steps increases and the manufacturing cost increases.

Further, in order to finely adjust the interval between the ink discharge ports 66, the side surface of each blade 67 contacting the adjacent blade 67, the lower surface contacting the crucible base 63, and the upper surface of the crucible base 63 contacting each blade 67. Polishing with high precision was required. For this reason, the processing cost was increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an ink fountain equipped with a blade adjusting device so that maintenance of the device can be easily performed and the entire device can be maintained. An object is to reduce the size and simplify the configuration.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the invention according to claim 1 is characterized in that a blade made of a thin plate is provided on a front end surface of a bottom plate of a pot base so as to be able to move up and down. I do.

According to a second aspect of the present invention, the blade is substantially L-shaped by a first piece extending in the front-rear direction and a second piece extending in the vertical direction, and the end of the first piece is formed on the bottom plate. The gist is that the second piece is pressed against the front end face of the bottom plate.

According to a third aspect of the present invention, an adjustment member is provided at one end for engaging with the first piece, and the second piece is raised and lowered by moving and adjusting the adjustment member. .

The gist of the present invention is that the blade is pressed against the front end face of the bottom plate by a pressing member. The gist of the invention described in claim 5 is that the urging force is applied to the blade in one of upper and lower directions by an elastic member that generates an elastic force.

In the embodiments of the invention described below, the "adjusting member" described in claims or means for solving the problem corresponds to an L-shaped link or a push rod.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of the present embodiment taken along line AA of FIG. 2, and FIG. 2 is a schematic plan view of the present embodiment. As shown in FIG. 1, the ink fountain 1 in the present apparatus has an upper surface 3 of a fountain base 2 formed in an oblique shape, and side plates 4 disposed on both sides in the width direction. In front of an edge 6 where the upper surface 3 of the fountain table 2 and the front end surface 5 intersect, a fountain roller 7 is supported rotatably around an axis along the width direction of the ink fountain 1. An ink reservoir 8 is formed between the upper portion of the ink fountain 1 and the fountain roller 7.
An ink discharge port 9 is formed between the edge 6 of the fountain table 2 and the outer peripheral surface of the fountain roller 7.

A storage recess 10 is provided at the bottom of the pot base 2. A link fixing part 11 is provided below the front part of the pot base 2. A plurality of support holes 12 are formed through the rear wall forming the storage recess 10. A support shaft 13 is rotatably inserted and supported in each support hole 12 by a bearing bush 28. The support shaft 13 protrudes rearward of the pot base 2 through the support hole 12. And
A manual knob 15 is fixed to the protrusion. Further, a cam member 16 is fixed to an end of the large-diameter portion 13b in the accommodation recess 10. The small-diameter portion 13a has an annular origin adjusting screw 1 having a thread formed on the outer diameter.
4 is attached.

The cam member 16 has a disk shape, and a cam surface 17 is formed on the surface on the side of the pot roller 7. A plurality of through holes 18 are formed in the wall of the housing recess 10 facing the cam surface 17. Each of these through holes 18
A push rod 19 having a spherical tip is inserted therein so as to be able to move forward and backward. Push rod 19
Is biased in the backward direction by the biasing force of the leaf spring 20 engaging with the locking groove 21. Due to this biasing force, the distal end of the push rod 19 comes into contact with the cam surface 17 of the cam member 16.

A plurality of L-shaped links 22 are rotatably attached to the link fixing portion 11 via shafts 23, respectively. The L-shaped link 22 includes a first piece 22a and a second piece 22.
b. The first piece 22a is the push rod 1
9 is in contact with the tip. A pressing portion 24 protrudes upward from the tip of the second piece 22b. Above the second piece 22b, a blade fixing portion 25 is formed on the pot base 2, and a plurality of L-shaped blades 26 are arranged there.

A plurality of fixing recesses 25a are formed in the blade fixing portion 25, and each of the fixing recesses 25a is formed.
And an insertion hole 25e is formed to communicate with each other. A bolt 25c is inserted into the insertion hole 25e, and a fixing piece 25b located in the fixing recess 25a is screwed into a screw portion at the tip thereof. The fixing recess 25a and the fixing piece 25b have similar shapes, and wedge slopes 27a and 27b that engage with each other are formed on the upper portions thereof.

The end of the first piece 26a of the L-shaped blade 26 is held between the bottom of the fixing recess 25a and the lower surface of the fixing piece 25b. Therefore, by turning the bolt 25c to move the fixing piece 25b to the left in the drawing, the first piece 26a is fixed in a sandwiched state by the action of the wedge slopes 27a, 27b.

The L-shaped blade 26 has a first piece 26a and a second piece 26a.
And a piece 26b, and has a substantially L-shape as a whole. The two pieces 26a and 26b form an angle slightly narrower than 90 degrees. The pressing portion 24 of the L-shaped link 22 is engaged with the lower surface of the first piece 26a. The second piece 26 b is pressed against the front end face 5 of the fountain table 2, and the end of the second piece 26 b forms an ink discharge port 9 between the second piece 26 b and the fountain roller 7.

Next, the operation of supplying ink from the ink fountain during printing will be described. At the time of printing, the fountain roller 7 is rotated in the counterclockwise direction in the drawing, and the ink in the ink reservoir 8 adheres to the outer peripheral surface of the fountain roller 7 at the ink discharge port 9 in a film form. Supplied to copper. Then, printing is performed by transferring the ink from the plate copper to the paper via the rubber cylinder.

Next, adjustment of the ink supply amount during printing will be described. First, the origin adjustment screw 14
Is rotated to move the support shaft 13 back and forth to determine the reference position. When it is desired to reduce the ink supply amount, the required manual knob 15 is rotated. Then, the cam surface 17 of the cam member 16 presses the push rod 19 forward. Then, the push rod 19 moves forward in the through hole 18 against the urging force of the leaf spring 20, and the tip of the push rod 19 presses the first piece 22 a of the L-shaped link 22. By this pressing, the second piece 22b and the pressing portion 24
, The first piece 26a of the required L-shaped blade 26 is displaced upward, and the second piece 26b is displaced upward along the front end face 5. This displacement narrows the gap between the ink outlets 9 and reduces the amount of ink supply. The length from the first piece 22a with which the distal end of the push rod 19 is in contact to the shaft 23 is the second piece 22b with the pressing portion 24 protruding.
Therefore, the displacement generated in the first piece 22a can be transmitted to the pressing portion 24 as a smaller displacement. For this reason, the ink supply amount can be finely adjusted.

Conversely, when it is desired to increase the ink supply amount, the manual knob 15 is rotated in the direction opposite to the above. Then, the cam surface 17 in contact with the push rod 19 retreats. Accordingly, the push rod 19 is attached to the leaf spring 2.
By the urging force of 0, the inside of the through hole 18 moves backward. The second piece 22b is displaced downward by the downward elastic force of the first piece 26a of the L-shaped blade 26. Accordingly, the end of the second piece 26b is lowered, the gap between the ink discharge ports 9 is widened, and the ink supply amount is increased.

In the present embodiment, the following effects are obtained by configuring the ink fountain as described above. In the present embodiment, since the plate-shaped L-shaped blade 26 is used instead of the blade 67 having the block shape, the size of the ink fountain 1 can be reduced.

Further, since the L-shaped blade 26 is lighter than the block-shaped blade 67, even when the actuator is driven to adjust the interval between the ink discharge ports 9, the actuator can be operated with a low-output actuator.
Further, since the elastic force of the L-shaped blade 26 itself is used as a biasing force, there is no need to use a spring,
The number of parts can be reduced.

In addition, in the conventional embodiment, the gap between the ink discharge ports 9 is finely adjusted by moving the block-shaped blade 67. For this reason, the left and right surfaces of the blades 67 in which the adjacently arranged blades 67 contact each other and the bottom surface in contact with the crucible base 63 had to be polished with high precision. Therefore, processing costs can be reduced.

Further, since no groove is formed in the upper portion of the upper surface 3 by the clearance, it is possible to prevent the ink from entering the inside of the ink fountain 1. In the present embodiment, the bottom surface of the ink fountain 1 can be flattened.

Therefore, the ink can be easily replaced or cleaned. In the present embodiment, the L-shaped blade 26 is simply fixed between the fixing recess 25a and the fixing piece 25b, so that replacement is easy.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the same components as those in the first embodiment have the same reference numerals, and a detailed description thereof will be omitted.

In this embodiment, the first push rod 31
And a second push rod 32. A slope 31a is formed at the tip of the first push rod 31, and the end of the second push rod 32 is in contact with the slope 31a. The second push rod 32 is movably inserted into a through hole 33 formed below the first piece 26 a of the L-shaped blade 26 of the pot base 2.
The distal end of the second push rod 32 is in contact with the lower surface of the first piece 26a of the L-shaped blade 26. The first push rod 31 is urged by the leaf spring 34 in the direction of the cam surface 17. The second push rod 32 is L
The slope 31 is formed by the elastic force of the first piece 26a of the V-shaped blade 26.
It is urged in the direction of a.

When it is desired to reduce the ink supply amount, the manual knob 15 is rotated to rotate the cam surface 17.
Is advanced forward along the rotation axis direction. Then, the leaf spring 3
The first push rod 31 moves forward against the urging force of No. 4. Then, the distal end of the second push rod 32 slides in the direction in which the diameter of the slope 31 a increases, and the second push rod 32 moves forward in the through hole 33. Due to this moved displacement, the first piece 26a of the required L-shaped blade 26 is formed.
Is displaced upward, and the second piece 26b is displaced upward along the front end face 5. This displacement causes the ink delivery port 9
The gap of the ink becomes narrow, and the ink supply amount decreases.

Conversely, when it is desired to increase the ink supply amount, the manual knob 15 is rotated in the reverse direction,
The first push rod 31 is moved backward. Then, contrary to the above, the first piece 26a is lowered by its own elastic force, and the gap between the ink discharge ports 9 is widened.

As described above, according to the present embodiment, the following operation and effect can be obtained in addition to the same operation and effect as the first embodiment. -The displacement of the diameter of the contact position between the end portion of the second push rod 32 and the slope 31a, which is changed by the linear motion of the first push rod 31, is transmitted to the first piece 26a of the L-shaped blade 26, so that it can be saved. Can be composed of spaces.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. Support holes 12 and 41 are formed through the bottom of the pot base 2 in a straight line, and the support shaft 13 is rotatably supported. The distal end of the support shaft 13 projects forward of the pot base 2, and an outer peripheral cam 42 is fixed to the projected portion.

Above the outer peripheral cam 42, a push rod hole 44 is formed in a direction perpendicular to the axial direction of the support shaft 13. A push rod 45 is inserted into the push rod hole 44 so as to be able to move forward and backward. The tip of the push rod 45 is the first piece 26a of the L-shaped blade 26.
, And the lower end portion is in contact with the outer periphery of the outer peripheral cam 42.

When it is desired to reduce the ink supply amount, the outer peripheral cam 42 is rotated by rotating the manual knob 15, and the push rod 19 in contact with the outer peripheral cam 42 is moved upward by the action of the cam surface 43. Move to Then, the second piece 26b is displaced upward, and the gap between the ink discharge ports 9 is narrowed.

Conversely, when it is desired to increase the ink supply amount, if the outer peripheral cam 42 is rotated by rotating the manual knob 15, the push rod 19 becomes elastic with the first piece 26 a of the L-shaped blade 26. Pushed down by force. The downward displacement of the first piece 26a is caused by the second piece 2
6b is transmitted as a downward displacement. This displacement widens the gap between the ink discharge ports 9.

As described above, according to the present embodiment, the following operation and effect can be obtained in addition to the same operation and effect as the first embodiment. · Push rod 4 using elastic force of L-shaped blade 26
Since the urging force is applied to 5, the number of parts can be reduced, and the manufacturing cost can be reduced.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the manner of operation of the L-shaped link 22 by the manual knob 15 is the same as that of the first embodiment, and therefore, the constituent members are given the same reference numerals, and detailed description is omitted.

The bottom plate 3 of the pot base 2 above the L-shaped link 22
A bar spring fixing portion 81 is formed on the back surface of the device. The bar spring fixing portion 81 includes a first block 83 and a second block 84.
Are fixed with bolts (not shown) at intervals in the front-rear direction.

As shown in FIG. 6, the first block 83 has a block shape having a width equal to the width between both ends of the front end face 5, and a plurality of insertion holes 85 arranged at equal intervals in the front-rear direction. It is perforated. One end of a rod spring 82 is inserted into each insertion hole 85, and is arranged in parallel in a cantilevered support state.

The second block 84 also has a block shape having a width equal to the width between both ends of the front end face 5,
6 and a through-hole 87 for a bar spring are vertically arranged and penetrated.
Blades 88 are arranged on the front surfaces of the second blocks 84, respectively. Each blade 88 has a vertically long slot 8 in the center.
The second block 84 has a substantially rectangular plate-like shape having a portion 8a, and is arranged adjacent to each other along the front surface of the second block 84. A pressing plate 89 is disposed on the front surface of each blade 88. The pressing plate 89 has a width equal to the width between both ends of the front end face 5, and has a horizontally long substantially rectangular plate shape having a screw hole 89 a corresponding to the long hole 88 a of each blade 88 in the center. A female screw is cut in the inner periphery of each screw hole 89a, and a double screw 90 is provided in each screw hole 89a.
Is screwed. The double screw 90 has a cylindrical shape, an internal thread is cut on the inner circumference, and a male screw having a different pitch from the internal thread is cut on the outer circumference.

A bolt 91 is inserted into a bolt hole 86 of the second block 84, and the tip of the bolt 91 is connected to the inner periphery of a double screw 90 screwed into a holding plate 89 through a long hole 88 a of a blade 88. It is fitting. Therefore, by tightening the double screw 90, the blade 8
8 is pressed against the front end face 5 of the pot base 2 by a pressing plate 89. The open end of the bar spring 82 passes through the bar spring through hole 87 of the second block 84.

The open end of the rod spring 82 reaches the long hole 88a of the blade 88, and the lower surface of the peripheral surface of the open end abuts on the upper surface of the inner peripheral surface of the long hole 88a. The urging force is applied. The lower end of the blade 88 to which the downward urging force is applied is connected to the L-shaped link 2 as shown in FIG.
2 is supported by the second piece 22b.

Next, adjustment of the ink supply amount during printing will be described. First, as shown in FIG. 7A, the height of the tip of each blade 88 is set to the same height as the upper surface of the pot base 3, which is the position of the origin when controlling the ink supply amount. The adjusting screw 14 is rotated in a predetermined manner. By rotating the manual knob 15, the tip of the second piece 22b of the L-shaped link 22 is displaced upward.
Due to this displacement, the lower end of the blade 88 supported by the tip of the second piece 22 b is pushed upward against the elastic force of the bar spring 82, and becomes flush with the upper surface of the pot base 3. At this time, ink is not supplied from the ink delivery port 9 because the distance between the ink delivery port 9 formed between the pushed-up tip of the blade 88 and the fountain roller 7 is reduced.

When the ink is supplied, as shown in FIG.
As shown in (b), the manual knob 15 is rotated in the opposite direction to displace the second piece 22b of the L-shaped link 22 downward. Then, by the elastic force of the rod spring 82,
Along with the second piece 22b, the tip of the blade 88, which is at the same height as the upper surface of the pot base 3, is also lowered. The ink is supplied by widening the gap between the ink discharge ports 9. When supplying more ink, the ink supply amount can be increased by further operating the manual knob 15 to lower the blade 88 and further increasing the interval between the ink discharge ports 9.

As described above, in the present embodiment, the following effects can be obtained by configuring the ink fountain as described above. In the present embodiment, the blade 88 for adjusting the size of the gap between the ink discharge ports 9 and the bar spring 82 serving as a support portion are provided.
Since the blade 88 is a separate part, the blade 88 can be more closely contacted and pressed against the front end face 5 without being affected by a mounting error generated when the bar spring 82 is fixed to the pot base 2. In addition, since the blade 88 is a separate component, the blade 88 can be easily attached and detached, and the accuracy can be easily managed.

The above embodiments may be modified as described below, and the same operation and effect can be obtained in such a case. -The support shaft 13 may be rotated by a motor.

In this way, by controlling the motor, the supply of ink can be reliably adjusted. .Push rods 19 and 3 in contact with cam surfaces 17 and 43
Rolling members may be provided at the end portions of the 1,45.

In this way, the friction between the cam surfaces 17, 43 and the push rods 19, 31, 45 can be reduced, and a smoother operation becomes possible. Although the embodiments have been described above, technical ideas other than the claims that can be grasped from the embodiments will be described below along with their effects.

(1) An operating body, a cam which operates in accordance with the movement of the operating body, and a cam follower disposed between the cam and the blade, wherein the blade is moved by the movement of the cam follower in accordance with the operation of the cam. The ink fountain according to any one of claims 1 to 3, which is raised and lowered.

(2) An operation shaft, a cam fixed to the operation shaft, and a cam follower disposed between the cam and the blade, and the cam follower is operated by the operation of the cam as the operation shaft rotates. The blade is raised and lowered through
3. The ink fountain according to any one of items (1) to (3).

(3) The blades are leaf springs 1-3,
The ink fountain according to any one of (1) and (2).

[0057]

As described above in detail, according to the present invention, in an ink fountain provided with a blade adjusting device, the number of maintenances of the device involving cleaning work can be reduced, and the size of the entire device and the manufacturing cost can be reduced. Can be achieved.

According to the first aspect of the present invention, the space for installing the blade can be reduced. Also,
The weight of the blade can be reduced. According to the second aspect of the present invention, the L-shaped blade can be easily fixed to the pot base. In addition, since the second piece of the L-shaped blade is pressed against the front end surface of the pot base, it is possible to prevent the ink from penetrating into the inside of the printing press and fouling.

According to the third aspect of the present invention, the displacement generated in the first piece of the L-shaped blade can be transmitted to the second piece by the adjusting member, and the elastic force of the L-shaped blade is effectively utilized. Can be simplified.

According to the fourth aspect of the present invention, the blade can be brought into close contact with the front end face of the crucible base and pressed against it. According to the fifth aspect of the present invention, the blade is not affected by a mounting error on the pot base.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a first embodiment.

FIG. 2 is a schematic plan view of the first embodiment.

FIG. 3 is a schematic sectional view of a second embodiment.

FIG. 4 is a schematic sectional view of a third embodiment.

FIG. 5 is a schematic sectional view of a fourth embodiment.

FIG. 6 is an exploded perspective view of a fourth embodiment.

FIG. 7 is a schematic diagram illustrating an ink supply amount adjusting method according to a fourth embodiment.

FIG. 8 is a schematic view showing an ink supply process.

FIG. 9 is a schematic sectional view of a conventional embodiment.

[Explanation of symbols]

1 ... ink pot, 2 ... pot base, 3 ... bottom plate, 5 ... front end face,
22 L-link as an adjusting member, 26 L-shaped blade as a blade, 31 first push rod as an adjusting member, 32 second push rod as an adjusting member, 45 push rod as an adjusting member, 82: bar spring, 88: blade, 89: holding plate.

Claims (5)

[Claims] 1. An ink fountain having a blade made of a thin plate provided on a front end surface of a bottom plate of a fountain table so as to be able to move up and down. 2. The blade is substantially L-shaped by a first piece extending in the front-rear direction and a second piece extending in the vertical direction.
The ink fountain according to claim 1, wherein an end of the first piece is fixed to a lower portion of the bottom plate, and a second piece is pressed against a front end surface of the bottom plate. 3. An adjusting member is provided at one end for engaging with the first piece, and the adjusting member is moved and adjusted,
The ink fountain according to claim 2, wherein the second piece is raised and lowered. 4. The ink fountain according to claim 1, wherein the blade is pressed against a front end surface of the bottom plate by a pressing member. 5. The ink fountain according to claim 4, wherein an urging force is applied to the blade in one of upper and lower directions by an elastic member that generates an elastic force.