Patent Application
20110023679
This application claims the foreign priority benefit under Title 35, United States Code, §119 (a)-(d) of Japanese Patent Application No. 2009-181022, filed on Aug. 3, 2009 in the Japan Patent Office, the disclosure of which is herein incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a punching unit for punching holes through sheets of paper by engaging punches with dies and more specifically to a punching unit that is suitably mounted to and used in an image forming apparatus such as a copier, printer, facsimile or their combined machine to punch filing holes through sheets of paper.
2. Related Art
The present applicant et al. had developed a punching unit for punching holes through sheets of paper by vertically moving punches by reciprocally moving a cam plate that crosses at right angles with the punch moving direction (see Japanese Patent Application Laid-open No. 2001-9791 for example). As shown in
In operation, revolutions of an electric motor 13 is transmitted through a decelerator 15 to a pinion 16 that is engaged with a rack 17 to reciprocate the cam plate 3. As the cam plate 3 reciprocates, the cam 10 and the guide hole 12 guide the pin 11 and move the punches 6 in the vertical direction. Thus, the punch 6 punches holes through sheets of paper located in the space S with the die hole 9. As the cam plate 3 moves in one direction, the punch 6 upheld while being positioned at one-end linear portion 10a of the cam 10 is reciprocated in the vertical direction at a V-shaped portion 10b of the cam 10 and is then upheld again by moving to another-end linear portion 10c. At this time, the pin 11 is guided by the guide hole 12 formed of the linear long hole, so that the punch 6 moves in the vertical direction without turning around its axial line.
In a state in which a capacity of the driving motor 13 is limited to a predetermined capacity and a thrust force Q of the cam plate 3 is limited due to an installation space and others of the punching unit 1, it is effective to reduce an inclined angle (wedge angle) α of the V-shaped portion 10b of the cam 10 in order to obtain a large punching force F of the punch 6.
Because it is necessary to assure a punch moving distance PL to punch holes through sheets of paper, a moving distance (slide stroke) SL of the cam plate 3 must be increased if the inclined angle α of the cam 10 is to be reduced. If the moving distance SL of the cam plate 3 is thus increased, a time required for punching holes is prolonged and the size of the punching unit becomes large, so that it is unable to deal with the high speed operation of the late image forming apparatus such as a printer and to punch through heavy papers. Thus, it is desired to bring out a high-performance punching unit that takes an equivalent installation space with that of the prior art punching unit and does not involve a large modification.
Accordingly, the present invention aims at solving the abovementioned problems by providing a punching unit that is capable of punching holes through materials to be punched steadily and effectively with a relatively simple structure and without increasing a moving distance of a cam.
According to a first aspect of the invention, there is provided a punching unit for punching holes through materials to be punched by engaging punches with dies, including:
an actuation pin fixed so as to protrude from the side of each punch;
a cam member reciprocated in the direction, e.g., linear or turning horizontal direction, orthogonal to the moving direction, e.g., vertical direction, of the punch;
a cam formed of a grooved hole that is formed through the cam member, engages with the actuation pin and has a V-shaped portion, one linear portion that extends from one end of the V-shaped portion and another linear portion that extends from another end of the V-shaped portion; and
a guide hole formed through a fixing member and having a predetermined shape to guide the actuation pin;
wherein the guide hole has one end part having a width fitting with the actuation pin at positions corresponding to the linear portions of the cam and inclined surfaces extending to the both sides of the moving direction of the cam member from the one end part at positions corresponding to the V-shaped portion of the cam; and
as the cam member moves, the actuation pin engages with the inclined surface of the V-shaped portion of the cam and the punch moves in the axial direction and at the punching position for punching holes through the material to be punched, the actuation pin is guided by one inclined surface of the guide hole, turns the punch around its axial line and acts so as to reduce an inclined angle of the inclined surface of the cam that moves the punch in the axial direction.
According to a second aspect of the invention, preferably, the guide hole has another end part whose width is wider than the one end part at the position corresponding to the bottom part of the V-shaped portion of the cam and is formed into the shape of a bottle by the one end part, the both inclined surfaces and the other end part.
According to a third aspect of the invention, preferably, the punching unit further includes a body frame that movably supports the cam member and the punch and the guide hole is formed through the body frame.
According to the first aspect of the invention, the actuation pin is guided by the inclined surface of the guide hole at the punching position for punching holes through the material to be punched. Then, the actuation pin acts so as to reduce the inclined angle of the inclined surface of the cam that moves the punch in the punching direction, thus allowing a large punching force F to be obtained, and turns the punch itself around its axial line. Accordingly, cutting by the turn of the blade edge of the punch (so-called pulling-cut) is added to a shearing force effected by a punching force (so-called press-cutting), so that the material to be punched such as sheets of paper may be efficiently, steadily and readily punched.
Although the punch becomes slow by the inclined angle of the guide hole at the punching position where the large punching force is required, the delay of the punch described above is recovered in a return stroke for example of at least one stroke of the cam member, so that the reciprocating moving distance (SL) of the cam member is equal with the stroke (PL) of the punch. Thus, it is possible to deal with punching of heavy sheets of paper based on the highly efficient punching described above and also with a throughput of sheets of paper corresponding to high-speed image forming operations.
The present invention may be simply configured just by modifying the shape of the guide hole that guides the actuation pin, may be installed within the equal space with that of the prior art punching unit and the instant punching unit may be mounted on the conventional image forming apparatus while keeping its specification the same or may be replaced with the prior art unit.
According to the second aspect of the invention, the inclined surface of the guide hole corresponds to the punching stating position where the largest punching force is required and the punch is turned around the punching starting position, so that the material to be punched may be punched readily and steadily with the large punching force.
According to the third aspect of the invention, the guide hole is formed through the body frame that supports the cam member and the punch, so that the guide hole having the predetermined shape may be readily, steadily and compactly formed at the front wall of the body frame at low cost.
It is noted that the summary of the invention described above does not necessarily describe all necessary features of the invention. The invention may also be a sub-combination of the features described above.
Modes of a punching unit for carrying out the invention will be explained below with reference to the drawings. It is noted that the basic structure of the punching unit of the invention is the same with one shown in
As shown in
It is noted that while the direction in which the punch 6 moves is defined to be the vertical direction (Y direction), the direction in which the cam plate 3 moves to be the horizontal direction (X direction) and the direction of an axial line of the actuation pin 11 to be the front-back direction in the explanation described above, those directions are so defined because sheets of paper are conveyed in the horizontal direction and are punched perpendicularly to that direction in general. However, the directions are not limited to those directions described above and the respective directions mean three directions (X, Y and Z) orthogonal to from each other.
The punching unit 11 also includes a die plate 7 disposed so as to face to the lower wall 2b of the body frame 2. The die plate 7 is provided with a die (hole) 9 at the position facing to the punch 6. The die plate 7 and the lower wall 2b of the body frame 2 are positioned and fixed while keeping a paper passing space S between them. An end of the punch 6 is a V-shaped blade edge 6a and the die hole 9 has a diameter slightly larger than that of the blade edge 6a, so that sheets of paper are sheared and a round hole is opened when the blade edge 6a fits and engages with the die hole 9. It is noted that the shape of the blade edge of the punch is not limited to what is symmetrical about the center line as shown in
As shown in
As shown in
Then, the parts between the upper and lower parts 21a and 21b of the guide hole 21 are formed to continue smoothly with inclined surfaces 21c1 and 21c2 each having a predetermined angle β. The right and left inclined surfaces 21c are formed symmetrically at the same level and correspond to the inclined surfaces 10b1 and 10b2, having the angle α, of the cam 10 and to the neighborhood including at least a part where the largest punching force is required in punching a hole through the sheets of paper by the punch 6.
Next, operations of the present embodiment based on the structure described above will be explained with reference to
Beside the frictional force μ*F acting between the cam 10 formed of the grooved hole and the actuation pin 11, the equal frictional force μ*F also acts, as its reaction force, between the cam plate 3 and the body frame 2 in the vertical movement (A-B-C) of the punch 6 described above, so that the frictional force amounts [2*F*μ]. Because the inclined angle (wedge angle) of the inclined surfaces 10b1 and 10b2 of the cam 10 is α, the thrust force Q acting on the cam plate 3 and the punching force F acting on the punch 6 have the following relationship:
Q=F*(tan α+2*μ) (1)
Then, the effect of the inclined angle (wedge angle) α, i.e., the punching force F/cam plate thrust force, may be expressed as follows:
F/Q=1/(tan α+2*μ) (2)
At this time, the cam plate 3 moves by a moving distance SL in the horizontal direction and thereby the punch 6 moves by a moving distance PL in the vertical direction.
Still more, because the punch 6 is guided by the straight guide hole 12 during punching shown in
Next, a punching operation of the present invention will be explained with reference to
At the punching position B 1, the punch 6 acts in the minus direction, i.e., in the direction of reducing by inclined angle β of the guide hole 21, with respect to the inclined angle α of the cam 10. Thereby, the punch 6 turns centering on the axial line in the direction of slowing down with respect to the inclined surface of the cam 10 and acts so that the downward movement by the inclined surface of the cam 10 is slowed down by the inclined angle β of the guide hole. The punch 6 obtains a large punching force F by that. That is the relationship of the thrust force Q of the cam plate 3 and the punching force F of the punch 6 may be expressed as follows:
Q=F*{(tan(α−β)+2*μ)} (3)
And the effect of the inclined angle (punching force F/thrust force Q) may be expressed as follows:
F/Q=1/{(tan(α−β)+2*μ)} (4)
Accordingly, the inclined angle β of the guide hole 21 supplements the inclined angle (wedge angle) α of the cam 10 and increases the punching force F of the punch by that much (by the inclined angle β).
Still more, at the punching position B1 described above, the punch 6 turns along the inclined surface 21c1 of the guide hole 21 and may punch through sheets of paper efficiently by adding a method of cutting by turning the blade edge 6a of the punch 6, i.e., a so-called pulling-cut (a method of punching by turning a pipe-like blade edge while screwing and pressing it against sheets of paper) in addition to the press-cutting by way of shearing based on the punching force F described above.
When the cam plate 3 moves further in the right direction, the actuation pin 11 moves upward from the bottom part U of the cam by being guided by the right-downward inclined surface 10b2 and moves also along the right wall surface r of the wide lower part 21b (C1→B1). Then, the actuation pin 11 shifts to the upper part 21a along the inclined surface 21c1 of the guide hole 21 while turning the punch 6 in the reverse direction and shifts to the other-end linear portion 10c while moving the punch 6 to the stand-by position A. While the inclined angle β of the guide hole acts in the direction of advancing the inclined angle α of the cam, i.e., in the direction of increasing the cam inclined angle, at the position B1 in this stroke, this stroke is a return stroke, so that the punch 6 may be quickly returned to the stand-by position A without applying no large force to the punch 6.
When the cam plate 3 is moved in the left direction, the actuation pin 11 moves from the other-end linear portion 10c to the one-end linear portion 10a by going through the V-shaped portion 10b and also moves while abutting with the left wall surface 1 of the guide hole 21. That is, the actuation pin 11 shifts from A→B2→C2 and then C2→B2→A. The punch 6 increases its punching force F and turns in the same manner as described above, so that it may punch a hole efficiently at the punching position B2. When the cam plate 3 is moved in the right direction, the actuation pin 11 always abuts with the right wall surface r of the guide hole 21 by the frictional force with the cam 10 and when the cam plate 3 moves in the left direction, the actuation pin 11 abuts with the left wall surface 1 of the guide hole 21 in the same manner, so that the punch 6 may be guided accurately with the predetermined limited movement.
When the punching force is calculated based on the equation (4) described above by setting the frictional coefficient μ as 0.2, it turns out as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-181022 | Aug 2009 | JP | national |
