Patent Publication Number: US-6708410-B2

Title: Cutter knife for left handed and right handed persons

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a cutter knife in which the blade is slidably retracted into an elongated sleeve member. In particular, the present invention relates to a cutter knife wherein a space is kept between the blade edge and an inner wall of the sleeve member, in order to prevent the blade edge from being damaged by rubbing against the inner wall of the sleeve member, while sliding. 
     FIGS. 1 to  3 B show a cutter knife, which is disclosed in Japanese examined utility model publication No. 59-20872. A blade  1  and a slider  10  are connected in an elongated sleeve member  20 . A user can manipulate the slider  10  to cause the blade  1  to slide, so that the blade  1  is protruded from and retracted into the sleeve member  20 . The sleeve member  20  is provided with a pair of side walls  20   a  and  20   b , which extend in parallel to the sliding direction of the blade  1 . Being guided between the side walls  20   a  and  20   b , the blade  1  and the slider  10  slide in the longitudinal direction of the cutter knife. 
     As shown in FIG. 2, a spring member  11  is provided on one side of the slider  10 . Under the biasing force by the spring member  11 , the blade back  1   b  is pressed onto the inner surface of the side wall  20   a  (the side wall at the upper location in FIG.  1 ). As a result, a space is kept between the blade edge  1   a  and the inner surface of the side wall  20   b  (the side wall at the lower location in FIG.  1 ). Thanks to that space, the blade edge  1   a  can be prevented from rubbing against the inner surface of the side wall  20   b , and thus the blade edge  1   a  can be protected from damage. 
     The slider  10  is provided with two engagement protrusions  15 ,  16 , which are located at the forward end and at the rearward end of the slider  10  in the sliding direction. One of the engagement protrusions is inserted into a connection hole  2  of the blade  1 , so that the slider  10  and the blade  1  are connected. As shown inside the dash-lined frame in FIG. 1, when the inserting direction of the slider  10  into the sleeve member  20  is reversed, the engagement protrusion  16  is now engaged with the connection hole  2 , rather than the engagement protrusion  15 . As a result, the direction of the biasing force applied to the blade  1  by the spring member  11  is also reversed. In other words; when the inserting direction of the slider  10  is reversed, and further the blade  1  is turned so that the edge  1   a  faces upward as shown in FIG. 1, the blade back  1   b  is pressed onto the inner surface of the side wall  20   b  under the biasing force of the spring member  11 , As a result, a space is kept between the blade edge  1   a  and the inner surface of the side wall  20   a.    
     The reason why the biasing direction of the blade is reversed is for accommodating the cutter knife to both right handed users and left handed users. This is explained with reference to FIGS. 3A and 3B, which are partially broken end elevations seen from the user side who is grasping the cutter knife. 
     FIG. 3A shows a situation where a left handed user uses the cutter knife, which corresponds to the case where the slider  10  shown inside the dash-lined frame in FIG.  1  and the blade  1  connected thereto are inserted into the sleeve member  20 . In FIG. 3A, the blade edge  1   a  faces downwards. The user grasps the cutter knife in his left hand, and manipulates the slider knob  18  attached to the slider  10  with his left thumb for protruding and retracting the blade  1 . The blade  1  is connected with the slider  10  at the engagement protrusion  16 , and the engagement protrusion  15  in disengagement can be seen from the user side. The slider knob  18  is in threaded engagement with a threaded hole  17  provided on the slider. 
     FIG. 3B shows a situation where a right handed user uses the cutter knife, which corresponds to the case where the slider  10  and the blade  1  connected thereto are inserted into the sleeve member  20  as shown by the solid-lined arrow in FIG.  1 . Also in FIG. 3B, the blade edge  1   a  faces downwards. The user grasps the cutter knife in his right hand, and manipulates the slider knob  1   a  attached to the slider  10  with his right thumb for protruding and retracting the blade  1 . The blade  1  is connected with the slider  10  at the engagement protrusion  15 , and the engagement protrusion  16  in disengagement can be seen from the user side. 
     In the conventional cutter knife as explained above, with reversing the inserting direction of the slider, right handed users and left handed users can properly use it. However, the construction of the slider is inconveniently complicated. Specifically, in order to provide the spring member  11  constructed an shown in FIG. 2 on the slider  10 , it is necessary to attach a separate member of a leaf spring on the slider  10 , Alternatively, even if a spring portion is integrally formed into the slider  10 , a very complicated mold would be necessary, which would increase the cost. 
     SUMMARY OF THE INVENTION 
     In view of the above-mentioned circumstance, an object of the present invention is to provide a cutter knife, which has simpler construction and can be properly used by both right handed users and left handed users. 
     According to the present invention, there is provided a cutter knife, comprising: an elongated sleeve member, a blade slidably held in the sleeve member, and a slider which is connected with the blade and is slidable in the sleeve member in the longitudinal direction, via which the blade is manipulated to protrude from and retracted into the sleeve member. The slider is provided with a first engagement protrusion and a second engagement protrusion located on the forward end and the rearward end in the sliding direction of the slider, one of which is to be inserted into a connection hole of the blade for connecting the slider and the blade. The distance from each of the first engagement protrusion and the second engagement protrusion to an inner surface of one of the sidewalls of the sleeve member when the slider is inserted into the sleeve member is smaller than the distance between the connection hole and the back of the blade. The back of the blade is thereby biased against the inner surface of the sleeve member to keep a space between the edge of the blade and the inner surface of the other sidewall of the sleeve member while the blade is sliding. The first engagement protrusion and the second engagement protrusion are aligned parallel to the sliding direction of the slider. Thus, when the inserting direction of the slider into the sleeve member is reversed, the biasing direction of the blade is also reversed, 
     In the cutter knife constructed as above, when the facing direction of the blade and inserting direction of the slider are reversed, the biasing direction of the blade against the inner surface of the sleeve member is reversed. This advantage itself can be achieved also in the above-mentioned conventional cutter knife. However, in the present invention, the biasing force is attributed to the location (or arrangement) of the engagement protrusions provided on the slider. Thus, any separate members (such as a spring member  11 ) for providing the biasing force are not necessary, and thanks to this, the construction of the slider can be more simplified than in the conventional cutter knife. Accordingly, the cutter knife can be easily manufactured, leading to a lower manufacturing cost and a lower selling price. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Thin and other objects and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings. 
     FIG. 1 is an explanatory view showing a conventional cutter knife. 
     FIG. 2 is a perspective view of a slider which is employed in the cutter knife in FIG.  1 . 
     FIG. 3A is an explanatory view showing a condition that the cutter knife in FIG. 1 is used by a left handed user. 
     FIG. 3B is an explanatory view showing a condition that the cutter knife in FIG. 1 is used by a right handed user. 
     FIG. 4 is an exploded perspective view of a cutter knife according to an embodiment of the present invention. 
     FIG. 5 is a plan view of a slider which is employed in the cutter knife in FIG.  4 . 
     FIGS. 6A and 6B are respectively an explanatory view explaining the relationship between engagement protrusions and biasing direction, 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 4 to  6 B, a description is made below on a cutter knife according to an embodiment of the present invention. FIG. 4 shows an exploded perspective view of the cutter knife. 
     A slider  50  is slidably inserted into a sleeve member  20 , and is provided with a first engagement protrusion  54  and a second engagement protrusion  58 , which are located on the forward end and the rearward end of the slider in the sliding direction. In FIG. 4, the first engagement protrusion  54  is to be inserted into a connection hole  2  of the blade  1 . When the inserting direction of the slider  50  is reversed, the second engagement protrusion  58  is to be inserted into the connection hole  2  of the blade  1 . Note that, in such a case, the blade  50  is reversed so that the edge  1   a  of the blade  50  faces in the opposite direction. 
     A separate member  51 , which is to be attached to the slider, is employed as a grip face of the slider  50 . However, alternatively a slider integrally including a grip face would be molded. In practice, a user fits his finger on the grip face to manipulate the blade  50 . 
     Note that in the drawings a lock mechanism for the blade position is omitted, because the present invention is directed to a mechanism for biasing the blade. However, in an actual product, some lock mechanism may be provided for locking the blade in a position in practical use. A lock mechanism can be a screw-type knob  18  as shown in FIGS. 1 to  3 . Further, the lock mechanism can be what utilizes an elastic engagement between a spring member on the slider and recesses on the body of the cutter knife (not shown). Note that, the advantage of the simplicity of the slider construction brought by the present invention is directed only to a mechanism, by which the blade back is biased against the inner surface of the sleeve member. 
     FIG. 5 is a plan view of the slider  50 , which explains the construction of the slider  50 . In order to realize a smooth sliding of the slider  50  in the sleeve member  20 , the maximum width “W” of the slider  50  is sized nearly equal to the distance between the opposing side walls  20   a  and  20   b  of the sleeve member  20 . The first engagement protrusion  54  and the second engagement protrusion  58  are offset in the same direction (upper side in FIG. 5) with respect to the center-line “L” shown in FIG.  5 . The first engagement protrusion  54  and the second engagement protrusion  58  are aligned parallel with the center-line “L” (that is, parallel with the sliding direction of the slider). 
     The first engagement protrusion  54  is located on a first extending portion  52 , which projects from the grip face  51  in one direction. On the other hand, the second engagement protrusion  58  is located on a second extending portion  56 , which projects from the grip face  51 , oppositely to the first extending portion  52 . 
     A U-shaped opening  53  and a U-shaped opening  57  are formed on the first extending portion  52  and the second extending portion  56 , respectively, so that the configuration of the first extending portion  52  and the second extending portion  56  are frame-like. Thanks to that configuration, both of the extending portions  52  and  56  can be resiliently deformed, and this deformation allows the blade to be biased against the inner surface of the sleeve member, as explained below. Note that the configuration of the slider is not limited to any specific one in the present invention, as long as the distance from each of the first and second engagement protrusions  54 ,  58  to the inner surface of the side wall when the slider  50  is inserted into the sleeve member  20  is set smaller than the distance between the connection hole  2  and the blade back  1   a  whereby the blade can be resiliently biased against the inner surface of the sleeve member. 
     The advantage due to the above-mentioned arrangement of the first and the second engagement protrusions  54 ,  58  is explained below, with reference to FIGS. 6A and 6B. In FIGS. 6A and 6B, the dashed lines running on both sides of the blade  1  and the slider  50  almost correspond to the distance between the opposing side walls  20   a  and  20   b  of the sleeve member  20  (refer to FIG.  4 ). That is, the blade  1  and the slider  50  slide in the longitudinal direction, with making their center-line correspond to intermediary between the side walls  20   a  and  20   b.    
     As explained above, the first and the second engagement protrusions  54 ,  58  are offset from the center line “L”. Thus, in order to insert the blade  1  and the slider  50  after assembly into the sleeve member  20 , it is necessary to deform the first and the second extending portions  52 ,  56  on which the first and the second engagement protrusions  54 ,  58  are provided, so that the first and the second engagement protrusions  54 ,  58  are aligned to the center line “L”. Thanks to this, a biasing force is generated, which urges the blade back  1   b  onto the inner surface of the sleeve member. As a result, a space is kept between the blade edge  1   a  and the inner surface of the sleeve member, so that the blade edge  1   a  can be protected. 
     The first engagement protrusion  54  and the second engagement protrusion  58  are aligned parallel to the sliding direction of the slider  50 . Accordingly, when the inserting direction of the slider  50  into the sleeve member  20  is reversed, the direction of the biasing is also reversed. Since the blade  50  is turned around its longitudinal axis so that the blade edge  1   a  faces oppositely when the inserting direction of the slider  50  is reversed, the blade back is always pressed onto the inner surface of the sleeve member. 
     In the embodiment shown, since the blade is provided with the connection hole  2  at the center of its width, the two engagement protrusions  54 ,  58  are offset in the same direction from the center line “L”. That is, under this construction, the distance from each of the first engagement protrusion and the second engagement protrusion to the inner surface of the side wall when the slider is inserted into the sleeve member is made smaller than the distance between the connection hole and the back of the blade”. 
     Even in a cutter knife of which the connection hole is not located at the center of width, the same effect would be realized by satisfying the relationship of the above two distances. Thus, the present invention can be applied to any blades, which have the connection hole located at any position in its width direction. The degree of the biasing force can be adjusted by the difference between the above two directions. 
     Although the present invention has been fully described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.