GB2306374A

GB2306374A - Hole punching device

Info

Publication number: GB2306374A
Application number: GB9622514A
Authority: GB
Inventors: Chuzo Mori
Original assignee: CARL Manufacturing Co Ltd
Current assignee: CARL Manufacturing Co Ltd
Priority date: 1995-10-30
Filing date: 1996-10-29
Publication date: 1997-05-07
Anticipated expiration: 2016-10-29
Also published as: JPH09123100A; CA2189178A1; TW305792B; KR100316748B1; GB9622514D0; GB2306374B; CN1156654A; MX9605201A; KR970020352A

Abstract

A hole punching device comprises a head member 1 attached to a base member 2 and has a movable punching blade 14. A hand operated lever arm 8 actuates a slider 10 which is vertically guided between guide projections 301 and a front face 101 of the head member 1. A head portion of the cylindrical blade 14 is detachably connected to the slider and the lower end of the blade cooperates with a fixed blade 27 on the base of a holder 28. The holder 28 is U-shaped, to accommodate paper to be punched, and comprises an upper horizontal portion 22 with a through hole 25, a lower horizontal portion 23 with a through hole 26 and a vertical interconnecting portion 24. The holder enables the lowering position of the tip of the blade to be more accurately determined. Also the device facilitates the interchanging of different sized blades.

Description

PUNCH BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a punch.

2. Description of the Related Art An example of a conventional punch will now be described with reference to Figs. 20 and 21. In Fig. 21, a head member 1 is fixed to a base 2. A guide member 3 is fitted in the head member 1 and fixed thereto by bolts 4. A proximal end of a support member 5 is rotatably mounted inside the guide member 3 by a pin 6. A proximal end of an arm 8 is rotatably mounted at the other end of the support member 5 by a pin 7.

A guide projection 301 is provided on the guide member 3. A guide gap 9 is formed between the guide projection 301 and a front face 101 of the head member 1. A guide groove 11 of a slider 10 is engaged with the guide projection 301. A guide flange 12 is engaged with the guide gap 9 so that the slider 10 may be movable in the vertical direction The slider 10 is connected to the arm 8 by a pin 13.

The arm 8 is rotated about a pin 7 in directions indicated by a double-headedarrow. As a result, the slider 10 is moved up and down in the vertical direction. A cylindrical blade 14 is detachably provided to a lower end of the slider 10. A pad 16 is provided on a paper laying surface 15 on which the tip end of the cylindrical blade 14 is to abut. As shown in Fig. 20, the mounting operation of the cylindrical blade 14 is attained by fixing the cylindrical blade 14 to the slider 10 by inserting a head portion of the cylindrical blade 14 into an insertion hole 19 without any displacement, screwing a stop screw 17 and pressfitting the tip end of the stop screw 17 to a concave groove 18. Also, the substantially same technology is also disclosed in Japanese Utility Model Publication No. Sho 59-39040.

The above-described conventional punch suffers from the following defects since the fixture of the cylindrical blade depends upon the holding manner of the fitting between the insertion hole and the head portion of the cylindrical blade and the guide portion of the slider by inserting the head portion of the cylindrical blade into the insertion hole without any displacement so that the cylindrical blade is not displaced when the paper is punched. When the cutting performance of the cylindrical blade is degraded or it is desired to change a size of the hole to be formed through the paper, it is necessary to exchange cylindrical blades.Upon the exchange of the blades, it is necessary to remove the stop screw away and subsequently draw the cylindrical blade from the insertion hole, then to newly insert a cylindrical blade into the insertion hole and thereafter to fix the cylindrical blade by the stop screw. The exchange of the cylindrical blades is troublesome.

Also, when a new cylindrical blade is inserted into the insertion hole, there is no displacement in the engagement between the cylindrical blade and the insertion hole, and it is impossible to carry out the insertion while observing the insertion hole.

Accordingly, it is difficult to insert the head portion of the cylindrical blade into the insertion hole. Also, in the case where the large number of the holes should be formed in the paper, the number of the cylindrical blades is increased. It is therefore troublesome to replace the cylindrical blades. This point should be improved for use in office instrument.

Also, since the cylindrical blade is substantially supported by the slider, this structure has the points to be improved as follows.

In the case where a large stack of paper should be punched, the arm should be pressed down by a considerably large force. This downward pressure is directly applied to the slider. Accordingly, if there is any displacement in the guide portion of the slider, on the way where the slider is pressed downwardly, the slider would be swung. The swing motion is transmitted to the cylindrical blade. At the worst, the cylindrical blade would be damaged. Accordingly, in order to eliminate the displacement of the slider, it is necessary to effect a high precision machining for the guide portion of the slider. The manufacture cost therefor would be increased disadvantageously.

Also, the displacement of the slider and the curvature of the cylindrical blade causes the positional displacement at the lowering position of the tip of the cylindrical blade. It is therefore difficult to insert the tip of the cylindrical blade into the lower blade to carry out the cutting operation between the lower blade and the tip. It is almost impossible to adopt a system in which the lower blade is provided. Accordingly, a pad is provided at the lowering position of the tip, and the tip of the cylindrical blade is pressed against the pad. Even if the position of the tip is somewhat displaced, the paper may be well punched. Until the pad is new, the cutting may be well performed. However, when the pad is subjected to flaws, even if the tip of the cylindrical blade is not worn but is sharp, the pads should be replaced.For this reason, the pads should be replaced frequently and this would be troublesome. This should be improved for the routine operation of the office instrument.

SUMMARY OF THE INVENTION An object of the present invention is to provide a punch in which replacement of cylindrical blades is simplified, even if there is a slight displacement in guide surfaces of a slider, the displacement does not adversely affect a displacement of a tip end of each cylindrical blade, and the punching is effected by a lower blade and the tip end to thereby dispense with a pad.

According to a first aspect of the invention, there is provided a punch in which a head portion of a blade is detachably held to a slider that moves up and down in a vertical direction, characterized in that a holder having a gap for insertion of paper, the gap is Ushaped in side elevation defined by an upper horizontal portion, a lower horizontal portion and a vertical portion, through holes are formed in the upper horizontal portion and the lower horizontal portion so that a cylindrical blade traverses the gap, the holder in which the cylindrical blade has been inserted into the through holes is inserted and drawn below the slider, and a head portion of the blade projecting in the upper horizontal portion is held by the slider.

According to a second aspect of the invention, a length of the through hole formed in the upper horizontal portion of the holder is elongated, namely larger than a length of the diameter of the through hole, so that the cylindrical blade is not swung, and a lower blade is formed in the through hole formed in the lower horizontal portion.

According to a third aspect of the invention, a recess groove is formed in a circumferential surface of the head portion of the cylindrical blade, and a convex surface engaged with the recess groove is formed in a holding portion of the slider for the cylindrical blade.

According to a fourth aspect of the invention, a flanged convex portion is formed in a circumferential surface of the head portion of the cylindrical blade, and a concave surface engaged with the flanged convex portion is formed in a holding portion of the slider for the cylindrical blade.

According to a fifth aspect of the invention, a recess groove is formed in a circumferential portion of the cylindrical blade, an insertion hole into which a head portion of the cylindrical blade is provided in a holding portion of the slider for the cylindrical blade, and a screw hole is provided so that a tip end of a screw is engaged with the recess groove of the head portion inserted into the insertion hole.

An explanation will be made as to how to solve the tasks by the above described structure. First of all, according to the first aspect of the invention, by the simple steps in which the gap defined by the upper horizontal portion, the lower horizontal portion and the vertical portion to form the U-shaped side elevation for insertion of the paper is traversed by the cylindrical blade, and the holder having the through holes formed in the upper horizontal portion and thelower horizontal portion through which the cylindrical blade traverses is inserted and drawn below the slider, it is possible to replace the cylindrical blades.Also, the head portion of the blade projecting into the upper horizontal portion of the holder is held to the slider and the up and down movement of the cylindrical blade is guided by the through hole formed in the upper horizontal portion of the holder irrespective of the guide portions of the slider. The swing of the cylindrical blade is obviated and the lowering position of the blade tip is exactly determined.

According to the second aspect of the invention, the length of the through hole formed in the upper horizontal portion of the holder is elongated, namely larger than a length of the diameter of the through hole, so that no swing motion of the cylindrical blade is generated, the guidance for the up and down movement of the cylindrical blade is more positive, the swing motion of the cylindrical blade is eliminated more effectively to keep constant the lowering position of the blade tip end, the lower blade is provided in the through hole formed in the lower horizontal portion, and the tip end of the cylindrical blade lowering to an accurate position is inserted into the lower blade with high precision for cutting and punching the paper between the lower blade and the tip end of the cylindrical blade.

According to the third aspect of the invention, since the prevention of the swing motion of the cylindrical blade does not depend upon the guide portions of the slider, simply by forming the recess groove on the circumferential surface of the head portion of the cylindrical blade, forming the convex surface, that is to be engaged with the recess groove, in the holding portion of the slider for the cylindrical blade, and inserting and drawing the holder below the slider in the engagement between the recess groove and the convex surface, it is possible to hold the head portion of the cylindrical blade to the slider.

According to the fourth aspect of the invention, since the prevention of the swing motion of the cylindrical blade does not depend upon the guide portions of the slider, simply by forming the flanged projection on the circumferential surface of the head portion of the cylindrical blade, forming the concave surface, that is to be engaged with the flanged projection, in the holding portion of the slider for the cylindrical blade, and inserting and drawing the holder below the slider in the engagement between the recess groove and the convex surface, it is possible to hold the head portion of the cylindrical blade to the slider.

According to the fifth aspect of the invention, the insertion hole into which the head portion of the cylindrical blade is provided in the holding portion of the slider for the cylindrical blade, a screw hole with which the tip end of the screw is engaged is provided in the recess groove formed in the head portion of the cylindrical blade which is inserted into the insertion hole, the holder having the through hole into which the cylindrical blade is inserted is located below the slider, the head portion of the cylindrical blade is inserted into the insertion hole by lowering the arm, the tip end of the screw is fitted in the recess groove of the head portion, and the head portion of the cylindrical blade is held to the slider.

The embodiment of the invention defined by the first aspect of the invention is as follows: According to the first aspect of the invention, in Fig. 1, there is provided a punch in which a head portion of a blade 14 is detachably held to a slider 10 that moves up and down in a vertical direction. A holder 28 having a gap for insertion of paper. The gap is U-shaped in side elevation defined by an upper horizontal portion 22, a lower horizontal portion 23 and a vertical portion 24. Through holes 25 and 26 are formed in the upper horizontal portion 22 and the lower horizontal portion 23 so that a cylindrical blade 14 traverses the gap.The holder 28 in which the cylindrical blade 14 has been inserted into the through holes 25 and 26 is inserted and drawn below the slider 10, and a head portion of the cylindrical blade 14 projecting in the upper horizontal portion 22 of the holder 28 is held by the slider 10.

The embodiment of the invention defined by the second aspect of the invention is as follows: In Fig. 4, a length H2 of the through hole 25 formed in the upper horizontal portion 22 of the holder 28 is elongated larger than a length of the diameter of the through hole, and a lower blade 27 is formed in the through hole 26 formed in the lower horizontal portion 23.

The embodiment of the invention defined by the third aspect of the invention is as follows: In Fig. 1, a recess groove 20 is formed in a circumferential surface of the head portion of the cylindrical blade 14, and a convex surface 21 engaged with the recess groove 20 is formed in a holding portion of the slider 10 for the cylindrical blade 14 as shown in Figs. 10 and 12.

The embodiment of the invention defined by the fourth aspect of the invention is as follows: A flanged convex portion is formed in a circumferential surface of the head portion of the cylindrical blade 14 instead of the recess groove 20, and a concave surface is formed in a holding portion of the slider 10 for the cylindrical blade 14 instead of the convex surface 21. In this case, also, it is possible to hold the cylindrical blade 14 at the lower end of the slider 10.

The embodiment of the invention defined by the fifth aspect of the invention is as follows: In Fig. 2, a recess groove 20 is formed in a circumferential portion of the cylindrical blade 14, an insertion hole 32 into which a head portion of the cylindrical blade 14 is provided in a holding portion of the slider 10 for the cylindrical blade 14 , and a screw hole 33 is provided so that a tip end of a screw 31 is engaged with the recess groove 20 of the head portion inserted into the insertion hole.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: Fig. 1 is a side elevational, longitudinal sectional view showing a primary part of a punch provided with a holder in accordance with one embodiment of the invention; Fig. 2 is a side elevational, longitudinal sectional view showing a primary part of a punch provided with a slider in accordance with another embodiment of the invention; Fig. 3 is a plan view showing the holder shown in Figs. 1 and 2; Fig. 4 is a longitudinal sectional view taken along the line X-X of Fig. 3; Fig. 5 is a frontal view as viewed from the right side of Fig. 4; Fig. 6 is a bottom view of Fig. 3; Figs. 7A, 7B and 7C are views showing the order of the steps for replacing the cylindrical blades of Fig. 1; Fig. 8 is a view showing an operational condition of the punch shown in Fig. 1; ; Fig. 9 is a plan view showing the slider shown in Figs. 1 and 2; Fig. 10 is a side elevational view showing the slider shown in Figs. 1 and 2; Fig. 11 is a longitudinal sectional view of the slider shown in Fig. 1, taken along the line Y-Y of Fig. 9; Fig. 12 is a back view showing the slider shown in Figs. 1 and 2; Fig. 13 is a frontal view of Fig. 11; Fig. 14 is a partially fragmentary, plan view of Figs. 1 and 2; Fig. 15 is a longitudinal sectional view of the slider shown in Fig. 2, taken along the line Y-Y of Fig. 9; Fig. 16 is a frontal view of Fig. 15; Fig. 17 is a plan view showing the guide member shown in Figs. 1 and 2; Fig. 18 is a side elevational view of Fig. 17; Fig. 19 is a perspective view showing the entire punch shown in Fig. 2; Fig. 20 is a longitudinal sectional view showing a primary part of a conventional punch; and Fig. 21 is a partially fragmentary, longitudinal sectional view showing the entire state of the conventional punch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described by way of example with reference to the accompanying drawings. An outline of a punch will now be described with reference to Fig. 19. Each head member 1 mounted on a base 2. An arm 8 is rotatably mounted on a support member 5 (Figs. 1 and 2) incorporated in the head member 1. A holder 28 is retractably/projectably provided in a U-shaped gap portion of the head member 1. The holder 28 is fixed under the condition that the lower horizontal portion 23 (Figs. 1 and 2) is inserted into a recess portion 151 formed in a paper loading surface 15. In this embodiment, for example, three punch holes are shown. The number of the punch holes may be two, four or any other number. Each component will now be described in order in detail.

The holder 28 will now be described. In Fig. 4, the holder 28 is U-shaped in side elevation. The holder 28 is composed of an upper horizontal portion 22, a lower horizontal portion 23 and a vertical portion 24. Through holes 25 and 26 are formed in the upper horizontal portion 22 and the lower horizontal portion 23, respectively, for insertion of cylindrical blades 14. A diameter of each through hole 25 is selected so that the static engagement is attained without any displacement between the through hole 25 and the blade 14 to be inserted into the through hole 25. The vertical movement of the cylindrical blade 14 may be well guided.

A boss 30 is provided for elongating a length H2 of the through hole 25. The length H2 is selected so that the vertical movement of the cylindrical blade 14 is positively carried out and the cylindrical blade 14 is not vibrated against the cutting resistance of the paper.

Thus, the position of the tip of the cylindrical blade 14 is not displaced. In this embodiment, the length H2 is about twice larger than the diameter of the through hole 25. It is preferable to select the length H2 at least longer than the diameter of the through hole 25.

A lower blade 27 is formed around an edge portion of the through hole 26. The lower blade 27 is fitted with the cylindrical blade 14 with high precision for cutting the paper.

Fig. 3 is a plan view showing the holder 28. Ribs 29 are provided in the holder 28. A dimension W1 between the outer walls of the ribs 29 is substantially equal to the inside dimension W2 of the head member 1, so that the ribs 29 function as a guide member when the ribs 29 engage with the head member 1. As shown in Figs. 3, 4 and 5, positioning surfaces 241 are provided on the vertical portion 24. The positioning surfaces 241 are brought into contact with the bottom portion 102 of the U-shaped cutaway portion of the head member 1, and an axis of the through hole 25 is coincided with an axis of the insertion hole 32 (Fig. 2) by the guiding action of the ribs 29. As shown in Figs. 3 and 5, a guide surface 221 is provided on the upper horizontal portion 22.When the guide surface 221 is in sliding contact with the upper horizontal portion 103 of the U-shaped cutaway portion of the head member 1 to thereby restrict the upward movement of the holder 28. Thus, the holder 28 is retractably and projectably positioned relative to the head member 1 by the ribs 29, the positioning surfaces 241 and the guide surface 221.

Also, as shown in Fig. 4, in the holder 28, the paper insertion portion having the U-shaped in side elevation and the height H1 is formed by the upper horizontal portion 22, the lower horizontal portion 23 and the vertical portion 24. The holder 28 is reinforced by the ribs 29 so that the upper horizontal portion 22 and the lower horizontal portion 23 are integral to have a rigidity. As shown in Figs. 4 and 6, the through hole 26 is formed in the lower horizontal portion 23. The lower blade 27 is formed in the edge of the through hole 26. The lower blade 27 and the tip of the cylindrical blade 14 are engaged with high precision and the paper is cut between the lower blade 27 and the tip to form a hole in the paper.

The slider 10 will now be described. Fig. 9 is a plan view of the slider 10. Guide grooves 11 and guide flanges 12 are provided in the slider 10. A slit 34 is formed in the central portion of the slider 10 for insertion of the arm 8. A width of the guide flange 12 is greater than a width W5 between the guide surfaces 36 and stepped portion of W6 are formed so that a guide member 3 (Figs. 1 and 2) to be described later may be engaged. A width W7 between the support member guide surfaces 37 is smaller than a width W5 of guide surfaces 36 so that the support member 3 do not interfere with the guide surfaces 36 by the stepped portions W8.

As shown in Fig. 10, a pin hole 35 through which the pin 13 shown in Figs. 1 and 2 are inserted is formed so as to pass between the guide surfaces 36. Also, cut chip guide portion 38 is provided in the slider 10. Namely, as shown in Figs. 11 and 12, the chips cut from the paper by the cylindrical blade 14 (Figs. 1 and 2) are caused to pass through the interior of the cylindrical blade 14 and discharged from the cut chip discharge hole 40 as indicated by the arrows to be discharged along the cut chip guide surface 39. When the chips are discharged, the chips are guided by the cut chip guide portion 38 so that the chips are dispersed to the outside.

Also, in the embodiment shown, as shown in Figs. 11 and 13, a convex surface 21 is provided in the holding portion of the cylindrical blade 14 to project toward the surface of the U-shaped portion opened at its front face, so that the recess groove 20 formed at the head portion of the cylindrical blade 14 shown in Fig. 1 is fitted with the convex surface 21. Also, the convex surface 21 may be concave, and the recess portion 20 formed at the head portion of the cylindrical blade 14 may be convex so that the concave portion and the convex portion may be engaged with each other. Figs. 15 and 16 show another embodiment of the invention. An insertion hole 32 is formed in the holding portion of the cylindrical blade 14. A diameter of the insertion hole 32 is greater than a diameter of the head portion of the cylindrical blade 14. In this case, a slight of displacement between the insertion hole 32 and the head portion to be inserted into the insertion hole 32 may be allowed. A screw hole 33 is provided to pass through the insertion hole 32. The other structure is the same as that shown in Figs. 9 to 12. The same reference numerals are used to indicate the same member. Accordingly, the duplication of explanation of the common parts will be omitted.

The guide member 3 will now be described. In Fig. 17, the plan view of the guide member 3 is U-shaped. Its open portion is provided with guide projections 301 for engagement with the guide grooves 11 (Fig. 9) of the slider 10. Also, an inside width W9 is set so that the guide member 3 may be engaged with the portion having the width W5 between the guide surfaces 36 shown in Fig. 9. An outside width W10 is set so that the guide member 3 may be engaged with the portion having the inside width W2 of the head member 1 shown in Fig. 3. As shown in Fig. 18, bolt holes 41 through which the bolts 4 shown in Figs. 1 and 2 pass and pin holes 43 through which the pin 6 passes for rotatably supporting the support member 5 are formed on side walls of the guide member 3. Also, oblong holes 42 are formed so that the pin 7 shown in Figs. 1 and 2 may be moved.

Fig. 14 shows an assembled state. The guide member 3 is fitted inside the head member 1. The guide flanges 12 of the slider 10 are fitted between the guide projections 301 and the front faces 101 of the head member 1. The guide projections 301 are fitted in the guide grooves 11. Furthermore, the guide surfaces 36 are in sliding contact with the inside walls of the guide member 3 so that the slider 10 may be moved up and down in the vertical direction. Also, the proximal end of the arm 8 is supported by the support member 5 by the pin 7. Both ends of the pin 7 are located within the oblong holes 42 formed in the guide member 3, so that the pin 7 may be moved in accordance with the rotation of the support member 5.

The operation of the above-described embodiments will now be described. The operation of the replacement of the cylindrical blades 14 will first be described. Under the condition that the cylindrical blade 14 is inserted into the through holes 25 and 26 of the holder 28 as shown in Fig. 7, the holder 28 is moved in the direction indicated by the arrow A and located below the slider 10 so that the head portion of the cylindrical blade 14 which is projected from the holder 28 may be held by the slider 10.

In holding the head portion of the cylindrical blade 14 to the above-described slider 10, the recess groove 20 is formed in the head portion of the cylindrical blade 14 is provided as shown in Fig. 1, and the convex surface 21 which engages with the recess groove 20 is formed in the holding portion of the slider 10 as shown in Figs. 11 and 13. As a result, the holder 28 is simply moved in the direction indicated by the arrow A as shown in Fig. 7A while lowering arm 8 to lower the slider 10 and engaging the convex surface 21 with the recess groove 20, so that the head portion of the cylindrical blade 14 may be held to the slider 10.

Also, the portion corresponding to the above-described recess groove 20 may be formed into a flanged portion having the convex surface, and the portion corresponding to the above-described concave portion 21 may be formed into a portion having the convex surface.

Only by moving the holder 28 in the direction indicated by the arrow A while engaging the convex and concave portion with each other as shown in Fig. 7A, it is possible to hold the head portion of the cylindrical blade 14 to the slider 10 in the same way.

Also, the insertion hole 32 is provided in the holding portion of the cylindrical blade 14 of the slider 10 as shown in Fig 15. The arm 8 is raised to raise the slider 10 so that the cylindrical blade 14 is inserted into the through holes 25 and 26 of the holder 28. Under this condition, the holder 28 is moved in the direction indicated by the arrow A in Fig. 7A so that the holder 28 is located below the slider 10. Thereafter, the arm 8 is lowered to lower the slider 10 so that the head portion of the cylindrical blade 14 which is projected from the holder 28 may be fitted in the insertion hole 32. Then, the screw 31 is threadedly engaged with the screw hole 33 so that the tip end of the screw 31 is engaged with the recess groove 20 formed in the head portion of the cylindrical blade 14.As a result, it is possible to hold the head portion of the cylindrical blade 14 to the slider 10.

In inserting the head portion into the insertion hole 32, by moving the holder 28 in the direction indicated by the arrow A in Fig.

7A while pressingly lowering the arm 8 with a small power and bringing the head portion of the cylindrical blade 14 projecting from the holder 28 in sliding engagement with the lower surface of the slider 10, it is possible to readily insert the head portion of the cylindrical blade 14 into the insertion hole 32 without observing the operation. Also, the ribs 29 are formed in the holder 28 and the positioning surfaces 241 are formed on the vertical portions 24. The holder 28 is inserted until the positioning surfaces 241 are brought into contact with the bottom portion 102 of the U-shaped cutaway portion of the head member 1 under the guidance of the ribs 29. As a result, it is possible to coincide the axis of the cylindrical blade 14, which is inserted into the through holes 25 and 26 of the holder 28, with the axis of the insertion hole 32.Under this condition without any additional operation, it is possible to readily insert the head portion of the cylindrical blade 14 into the insertion hole 32 without observing the insertion hole 32.

The order of replacement of the cylindrical blades 14 will now be described. First of all, the recess groove 20 formed in the head portion of the cylindrical blade 14 is fitted with the convex surface 21 formed in the slider 10. The case where the cylindrical blade 14 is held to the slider 10 will be explained. In Fig. 7A, the paper loading surface 15 is moved in the direction indicated by the arrow B. The fixing of the holder 28 by the recess portion 151 (see Fig. 19) is released. The holder 28 is drawn in the opposite direction to the direction A. Next a new cylindrical blade 14 is inserted into the through holes 25 and 26 of the holder 28. The arm 8 is lowered to the lowermost position. As a result, the heights of the recess groove 20 and the convex surface 21 are identified with each other. The holder 28 is moved in the direction A.As shown in Fig. 7B, the recess groove 20 and the convex surface 21 are fitted with each other. The holder 28 is located in the position below the slider, and the cylindrical blade 14 is held to the slider 10. Next, the paper loading surface 15 is moved in a direction indicted by the arrow C so that the holder 28 is fixed by the recess portion 151 as shown in Fig. 7C.

In the embodiment shown in Fig. 2, in the case where the head portion of the cylindrical blade 14 is inserted into the insertion hole 32 and the tip end of the screw 31 is fitted in the recess groove 20 so that the cylindrical blade 14 is held to the slider 10, the replacement order of the cylindrical blades 14 will now be described.

First of all, the screw 31 is loosened until the tip end of the screw 31 is disengaged from the recess groove 20. Next, the arm 8 is raised up to a position where the lower end of the slider 10 does not interfere with the head portion of the cylindrical blade 14. As a result, since the engagement between the insertion hole 32 and the head portion of the cylindrical blade 14 includes the displacement, the cylindrical blade 14 is not raised by the slider 10. Only the slider 10 is raised under the condition that the cylindrical blade 14 is left in the holder 28.

Subsequently, as shown in Fig. 7A, the paper loading surface 15 is moved in the direction B, and the fixing of the holder 28 by the recess portion 151 is released. The holder 28 is drawn in the direction opposite the direction A. When the holder 28 is drawn, since it is possible to increase a gap to any desired length between the lower end of the slider 10 and the head portion of the cylindrical blade 14, the cut chips do not clog the gap and the holder 28 may be smoothly drawn. Next a new cylindrical blade 14 is inserted into the through holes 25 and 26 of the holder 28. The holder 28 is inserted into the direction A in Fig. 7A. The head portion of the cylindrical blade 14 is inserted into the insertion hole 32. The tip end of the screw 31 is engaged with the recess groove 20. Next, the paper loading surface 15 is moved in the direction C as shown in Fig. 7B.The holder 28 is fixed by the recess portion 151 as shown in Fig. 7C.

The guidance of the cylindrical blade 14 by the holder 28 will now be described. In Fig. 8, the arm 8 is moved up and down among the positions 8A, 8B and 8C. The slider 10 is moved up and down in the vertical direction among the position 10A, 10B and 10C under the guidance by the guide flanges 12, the guide grooves 11 and the guide surfaces 36. By the up and down movement of the slider 10, the cylindrical blade 14 held at the lower end portion of the slider 10 is also moved up and down among the positions 14A, 14B and 14C. Then, the up-and-down movement of the cylindrical blade 14 is guided by the through hole 25 of the holder 28.Accordingly, even if there is a slight displacement in the guide portions of the guide flanges 12, the guide grooves 11 and the guide surfaces 36 between the recess groove 20 and the convex surface 21, the cylindrical blade 14 is guided by the through hole 25 and moved up and down in the vertical direction. Also, by increasing the height H2 of the through hole 25 (Fig. 4), it is possible to more positively restrict the escape of the tip end of the cylindrical blade 14 upon the punching operation. With respect to the guidance of the cylindrical blade 14 by the through hole 25, it is possible to enjoy the same effect in the case where the head portion of the cylindrical blade 14 is inserted into the insertion hole 32 as shown in Fig. 2.

Thus, even if there is a slight displacement in the engagement between the recess groove 20 and the convex surface 21 (engagement between the insertion hole 32 and the head portion of the cylindrical blade 14) and in the guide portions of the guide flanges 12, the guide grooves 11 and the guide surfaces 36, the cylindrical blade 14 is guided by the through holes 25. Since there is no up and down displacement of the tip end of the cylindrical blade 14, it is possible to form the lower blade 27 in the lower horizontal portion 23 of the holder 28 as shown in Fig. 4 and to carry out the high precision engagement of the tip end of the cylindrical blade 14 and the lower blade 27 for cutting and punching the paper.

As described above in detail, according to a first aspect of the invention that has been understood from the detailed description thereof, by the simple steps in which the gap defined by the upper horizontal portion, the lower horizontal portion and the vertical portion to form the U-shaped side elevation for insertion of the paper is traversed by the cylindrical blade, and the holder having the through holes formed in the upper horizontal portion and the lower horizontal portion through which the cylindrical blade traverses is inserted and drawn below the slider, it is possible to replace the cylindrical blades. Accordingly, the replacement of the cylindrical blades may be facilitated. It is therefore possible to enhance the handling property as the office instrument.

Also, the head portion of the blade projecting into the upper horizontal portion of the holder is held to the slider and the up-and- down movement of the cylindrical blade is guided by the through hole formed in the upper horizontal portion of the holder irrespective ofthe guide portions of the slider. Accordingly, the high precision machining work of the guide portions of the slider is dispensed with to reduce the manufacture cost. Then, the swing of the cylindrical blade is obviated and the lowering position of the blade tip is exactly determined. It is possible to cut the paper between the tip end of the cylindrical blade and the lower blade and to dispense with the pad. The handling property is enhanced as the office instrument by dispensing with the pad replacement. Also, it is possible to keep a long service life of the blades.It is possible to enhance the function as the office instrument.

According to a second aspect of the invention which is understood from the detailed description thereof, the length of the through hole formed in the upper horizontal portion of the holder is elongated larger than a length of the diameter of the through hole, the guidance for the up-and-down movement of the cylindrical blade is more positive, the swing motion of the cylindrical blade is eliminated more effectively to keep constant the lowering position of the blade tip end, the lower blade is provided in the through hole formed in the lower horizontal portion, and the tip end of the cylindrical blade lowering to an accurate position is inserted into the lower blade with high precision for cutting and punching the paper between the lower blade and the tip end of the cylindrical blade.Accordingly, it is possible to dispense with the pad, to enhance the handing property as the office instrument and to keep a long service life of the blades to enhance the function as the office instrument.

According to a third aspect of the invention which is understood from the detailed description thereof, since the prevention of the swing motion of the cylindrical blade does not depend upon the guide portions of the slider, simply by forming the recess groove on the circumferential surface of the head portion of the cylindrical blade, forming the convex surface, that is to be engaged with the recess groove, in the holding portion of the slider for the cylindrical blade, and inserting and drawing the holder below the slider in the engagement between the recess groove and the convex surface, it is possible to hold the head portion of the cylindrical blade to the slider. Accordingly, the replacement of the cylindrical blades is extremely simplified to enhance the handing property as the office instrument.

According to a fourth aspect of the invention which is understood from the detailed description thereof, since the prevention of the swing motion of the cylindrical blade does not depend upon the guide portions of the slider, simply by forming the flanged projection on the circumferential surface of the head portion of the cylindrical blade, forming the concave surface, that is to be engaged with the flanged projection, in the holding portion of the slider for the cylindrical blade, and inserting and drawing the holder below the slider in the engagement between the recess groove and the convex surface, it is possible to hold the head portion of the cylindrical blade to the slider. Accordingly, the replacement of the cylindrical blades is extremely simplified to enhance the handing property as the office instrument.

According to a fifth aspect of the invention which is understood from the detailed description thereof, the insertion hole into which the head portion of the cylindrical blade is provided in the holding portion of the slider for the cylindrical blade, a screw hole with which the tip end of the screw is engaged is provided in the recess groove formed in the head portion of the cylindrical blade which is inserted into the insertion hole, the holder having the through hole into which the cylindrical blade is inserted is located below the slider, the head portion of the cylindrical blade is inserted into the insertion hole by lowering the arm, the tip end of the screw is fitted in the recess groove of the head portion, and the head portion of the cylindrical blade is held to the slider. It is possible to insert the head portion of the cylindrical blade into the insertion hole without observing the insertion hole, to thereby extremely simplify the replacement of the cylindrical blades to enhance the function as the office instrument.

Claims

1. A punch in which a head portion of a blade is detachably held to a slider that moves up and down in a vertical direction, characterized in that a holder having a gap for insertion of paper, the gap is U-shaped in side elevation defined by an upper horizontal portion, a lower horizontal portion and a vertical portion, through holes are formed in the upper horizontal portion and the lower horizontal portion so that a cylindrical blade traverses the gap, the holder in which the cylindrical blade has been inserted into the through holes is inserted and drawn below the slider, and a head portion of the blade projecting in the upper horizontal portion is held by the slider.

2. The punch according to Claim 1, wherein a length of the through hole formed in the upper horizontal portion of the holder is larger than a length of the diameter of the through hole and a lower blade is formed in the through hole formed in the lower horizontal portion.

3. The punch according to Claim 1 or 2, wherein a recess groove is formed in a circumferential surface of the head portion of the cylindrical blade, and a convex surface engaged with the recess groove is formed in a holding portion of the slider for the cylindrical blade.

4. The punch according to Claim 1 or 2, wherein a flanged convex portion is formed in a circumferential surface of the head portion of the cylindrical blade, and a concave surface engaged with the flanged convex portion is formed in a holding portion of the slider for the cylindrical blade.

5. The punch according to Claim 1 or 2, wherein a recess groove is formed in a circumferential portion of the cylindrical blade, an insertion hole into which a head portion of the cylindrical blade is provided in a holding portion of the slider for the cylindrical blade, and a screw hole is provided so that a tip end of a screw is engaged with the recess groove of the head portion inserted into the insertion hole.

6. A punch substantially as hereinbefore described with reference to any one the accompanying drawings.