Cutter knife

[0002] The present invention relates to an automatic locking type cutter knife.

[0003] The present invention relates to an automatic locking type cutter knife. The automatic locking type cutter knife is known to have a variety of operations and structures. The automatic locking type cutter knife, as disclosed in Examined Published Japanese Utility Model Application No. 57-54771 or 61-35177, is equipped with a stopper mounted on the back face of the center protruding portion of a retaining leaf spring for preventing the leaf spring from turning. This structure can prevent the turning of the leaf spring when the stopper is moved in one direction. When the spring is released, it is troublesome to return the stopper. When a force acts to move a slider to be coupled to a cutter blade while the slider is being retained by the stopper, the center protruding portion of the leaf spring is pushed forward or backward onto the square hole of a blade holder. As a result, the center protruding portion of the leaf spring is pushed so much between the square hole and the corrugated ridge of the knife frame that it is unusably deformed.

[0004] On the other hand, an automatic locking type cutter knife, as disclosed in Unexamined Published Japanese Patent Application No. 6-327849, employs a leaf spring having a generally triangular projecting portion for a triangular engaging groove. This structure raises a problem in the reliability of the retaining force of the cutter blade. Another problem is that the leaf spring is liable to come out from the opening of a center recess, as formed in a body member of the slider, and to be deformed.

[0005] In an automatic locking type cutter knife, as disclosed in Examined Published Japanese Patent Application No. 7-85752, a leaf spring is provided with a flat spring portion extending in the forward direction of a cutter blade, and a protruding portion having an inverted U-shaped section and protruding at a right angle with respect to the spring portion. This structure has a problem that the force to be applied by the leaf spring to an engaging groove is weak in a neutral position.

[0006] The invention has been conceived with a view to the background thus far described and has an object to provide a cutter knife which can be stepwise automatically locked while preventing the leaf spring from being unusably deformed.

[0007] According to an embodiment of the invention there is provided a cutter knife comprising: a holder having a plurality of engaging recesses of an isosceles trapezoid shape formed intermittently in its upper face to have a larger width outward and a slide groove into which a cutter blade is to be inserted movably back and forth; a slider inserted in the slide groove of said holder and formed to mount said cutter blade thereon; and a leaf spring member supported by said slider to come into and out of engagement with said engaging recesses, characterized: in that said slider includes a body member, an operation member supported movably on said body member, and a leaf spring member; in that said leaf spring member includes leg portions expanded obliquely, a protruding portion of an isosceles trapezoid formed at the center portion of said leg portions and capable of engaging with said engaging recesses, and a wide portion formed in the vicinity of the root portion of said protruding portion and made wider than said obliquely expanded leg portions; in that said body member includes a center recess, an opening formed at the center in the upper face of said center recess for allowing the protruding portion of said leaf spring to go into and out of it, and a boss positioned in the vicinity of said opening for preventing the deformation of the protruding portion of said leaf spring; and in that said operation member includes a movable stopper for engaging with said wide portion at its neutral position to prevent the protruding portion of said leaf spring from moving backward, and an engaging groove for pushing downward said protruding portion against the elasticity of said leaf spring by the moving operation of said operation member so that the protruding portion of said leaf spring may be released from said engaging recesses.

[0008] 1. FIGS. 1(A)-(B) shows one embodiment of the cutter knife of the invention. FIG. 1(A) is a top plan view, and FIG. 1 (B) is a side elevation.

[0009] 2. FIG. 2 shows a section taken along line A—A of FIG. 1(B).

[0010] 3. FIG. 3 shows a section taken along line B—B of FIG. 1(A).

[0011] 4. FIG. 4 shows the leaf spring. FIG. 4(A) is a top plan view, and FIG. 4(B) is a side elevation.

[0012] 5. FIG. 5 shows a section taken along line A—A of FIG. 1 (B) and showing the state in which the operation member is moved forward.

[0013] FIGS. 1(A)-(B) show one embodiment of a cutter knife of the invention, and FIG. 1(A) is a top plan view whereas FIG. 1 (B) is a side elevation. In these Figures: reference numeral 1 designates a holder; numeral 1bengaging recesses; numeral 2 a body member; numeral 2aa base plate; numeral 3 an operation member; and numeral 5 a cutter blade.

[0014] The holder 1 is a molding of a synthetic resin, but may be made of a suitable material at its partial or entire portion, such as the portion in which the engaging recesses 1bare formed. However, the construction, in which the entirety of the holder 1 is made of the synthetic resin as in this embodiment, is advantageous in that it can reduce the number of parts and can be produced at a low cost. In the holder 1, there is formed a slide groove in which a number of engaging recesses 1bare formed at one edge portion of the opening in its upper face. These engaging recesses 1bare formed to have a shape of an isosceles trapezoid opened outward. The angle of inclination of the sides corresponding to the legs of the isosceles trapezoids is suitable within a range of 50 degrees to 85 degrees. In the slide groove of the holder 1 there is so inserted the slider as to move back and forth. This slider is assembled of three members of the body member 2, the operation member 3 and a leaf spring and can be moved to carry a cutter blade, mounted on the body member 2, back and forth. The movement of the slider can be effected by pushing the operation member 3 forward or backward, as will be described hereinafter.

[0015] The detail of the slider will be described with reference to FIGS. 2 to 4. FIG. 2 is a section taken along line A—A of FIG. 1(B); FIG. 3 is a section taken along line B—B of FIG. 1(A); FIG. 4(A) is a top plan view of the leaf spring; and FIG. 4(B) is a side elevation of the leaf spring. In these Figures, the description of the same portions as those of FIG. 1A will be omitted by designating them by the common reference numerals. Reference numeral 1adesignates a slide groove; numeral 2ba mounting pin; numeral 2can operation member supporting portion; numeral 2dan opening; numeral 2ea boss; numeral 2fa projecting portion; numeral 2ga center recess; numeral 3aa projecting portion; numeral 3ban engaging groove; numeral 3ca movable stopper; numeral 4 a leaf spring; numeral 4aa wide portion; numeral 4ba protruding portion; numeral 4cintermediate portions; numeral 4dleg portions; numeral 4ean engaging angular portion; and numeral 4fa back face.

[0016] The body member 2 includes: the mounting pin 2bfor mounting the cutter blade on the side of the leading end portion of the flat base plate 2a;the center recess 2gfor housing the leaf spring 4; and the operation member supporting portion 2c.The mounting 2bis fitted in the not-shown mounting hole of the cutter blade to joint the cutter blade to the slider body portion 2. The center recess 2gis formed into such a box shape as to rise from the slider body portion 2. In the vicinity of the center of one longitudinal side wall of the center recess 2g,there is formed the opening 2d,under which there is erected the boss 2e.This boss 2eplays a role as a stopper for regulating the moving range of the protruding portion 4bso as to prevent a deformation in which the protruding portion 4bof the leaf spring 4 could otherwise become unused. Moreover, the protruding portion 4bcan be prevented from coming out from the opening 2d,thereby to hold the spring member 4 reliably in position.

[0017] As shown in FIG. 4(A), the leaf spring 4 is a flat elastic member made of phosphor bronze, for example, and is made wider at its center portion than its righthand and lefthand sides to form the wide portion 4a.This leaf spring 4 is shaped, as shown in FIG. 4(B), to have the protruding portion 4bat the center, the intermediate portions 4cextended rightward and leftward generally at a right angle from the protruding portion 4b,and the leg portions 4dformed on the two sides of the intermediate portions 4cand extended obliquely rightward and leftward. These leg portions 4dmainly serve to generate the spring force. The protruding portion 4band the portions, as extended from the former, of the intermediate portions 4care formed into the wide portion 4a,as shown in FIG. 4(A). Here, the shape of the leaf spring 4 is one example, and the intermediate portions 4cmay be made so shorter than those shown in FIG. 4(B) that the wider portion 4amay contain the intermediate portions 4centirely. Moreover, the intermediate portions 4cmay be so eliminated that the leg portions 4dmay be extended directly from the protruding portion 4b.In this modification, the wider portion 4amay contain so much as to contain the leg portions 4dpartially. Since the protruding portion 4bis provided for engaging with the engaging recess, as will be described hereinafter, it could be said sufficient that the protruding portion 4bis provided with the leg portions having the spring force, and that the wide portion 4aforms the portion to engage with the movable stopper thereby to prevent the backward movement of the protruding portion 4b.

[0018] Reverting to FIGS. 2 and 3, the description will be made. In the opening 2din the side wall of the center recess 2gformed in the body member 2 of the slider, there is so arranged the leaf spring 4 toward the engaging groove 3bof the operation member 3 as can move to and away from the outside.

[0019] The operation member supporting portion 2csupports the operation member 3 such that the operation member 3 can moved back and forth (in the moving directions of the cutter blade), and mounts the operation member 3 on the body member 2 by holding the outward projecting portion 2fand the inward projecting portion 3aof the operation member 3 in engagement with each other.

[0020] The operation member 3 is slidably supported by its supporting portion 2cof the body member 2 and is so positioned in a neutral state that the center of the angular engaging groove 3brides on the protruding portion 4bof the leaf spring 4. The operation member 3 can moved back and forth across that position. The movement is limited within a predetermined range by the step portion which is formed by recessing the side faces of the operation member supporting portion 2c.The limiting mechanism should not be restricted thereto but could be modified to either a suitable retaining mechanism such as a stopper for limiting the forward and backward movements of the operation member 3 with respect to the body member 2 or a limiting mechanism for limiting the movements, although the modification is not shown.

[0021] The movable stopper 3c,as protruded from the inside of the operation member 3, can be moved by the operation member 3 with respect to the protruding portion 4b,and is positioned at the back of the leaf spring 4 in the center recess 2gof the body member 2. When the operation member 3 is in the neutral position, the crests, as protruded from the two sides of the movable stopper 3cof the operation member 3, are positioned at the back face 4f(as shown in FIG. 4) of the intermediate portions of the wide portions 4aof the protruding portion 4bof the leaf spring 4 so that they prevent the protruding portion 4bfrom moving backward and from coming out from the engaging recess 4bof the leaf spring 4 along the slopes of the engaging recess 1bof the holder 1. As a result, even if a force is applied to the edge of the cutter blade, the protruding portion 4bof the leaf spring 4 keeps biting the engaging recess 1bto prevent the cutter blade from moving back.

[0022] In order to move the cutter, the operation member 3 is manually moved in the moving direction. This state is shown in FIG. 5. In FIG. 5, the operation member 3 is moved forward (i.e., leftward, as shown, to extract the cutter blade). Then, the leaf spring 4 is moved downward, as shown, at its engaging angular portion 4e(as shown in FIG. 4) against the elastic force of the leaf spring 4 by the slope of the engaging groove 3bof the operation member 3. Since the crests of the movable stopper 3cof the operation member 3 have been moved forward till them, they are positioned not to retain the wide portion 4athereby to allow the backward movement of the protruding portion 4bso that the protruding portion 4bof the leaf spring 4 is pushed into the center recess 2gof the body member 2 to come out from the engaging recess 1bof the holder 1.

[0023] As the operation member 3 comes out from the engaging recess 1bof the protruding portion 4b,it can be further moved leftward so that the slider can be moved to a desired position. By releasing the operation member 3 after the movement to the desired position, the protruding portion 4bis returned to the position of FIG. 2 by the elasticity of the leg portions 4dso that the slider can be held in the locked state.

[0024] By the returns of the leg portions 4d,the engaging angular portion 4eabuts against the slop of the engaging groove 3bso that the operation member 3 can be returned to the initial neutral position. When the slider is to be moved backward (rightward, as shown, to return the cutter blade) of the direction of the foregoing description, the operation member 3 is moved rightward, as shown. As a result, the engaging angular portion 4eis pushed downward, as shown, against the elastic force of the leg portions 4dby the lefthand slope of the engaging groove 3b,and the protruding portion 4bcan also be brought from the engaging recess 1bso that the slider can be moved backward by further moving the operation member 3 rightward.

[0025] As apparent from the description thus far made, according to the invention, the automatic locking can be achieved by the movable stopper which can be moved together with the operation member. There is another effect that the deformation of the protruding portion of the leaf spring can be prevented by the boss which is mounted on the body member.