Safety Utility Knife

Abstract

A safety utility knife includes a resin-made grip part, a blade projecting from the grip part, and a resin-made head part arranged at a tip of the projecting blade. The blade is formed with a through-hole so that a resin-made coupling part lying within the through-hole couples together the grip part and the head part that are made of resin. Since the safety utility knife of the present invention allows the three resin-made parts to be joined together, it can be manufactured easily and at low cost using a 1-gate type mold. Also, there is no unnecessary increase in the blade thickness, preventing an increased cutting resistance and a rough cut end from occurring.

Claims

1. A safety utility knife comprising: a grip part; a blade projecting from the grip part, the blade being formed with a through-hole; a head part arranged at a tip of the projecting blade; and a coupling part lying within the through-hole coupling the grip part and the head part together.

2. The safety utility knife according to claim 1, wherein the grip part, the head part, and the coupling part are made of resin.

3. The safety utility knife according to claim 1, wherein both ends of a single blade project from the grip part to both sides in opposite directions away from each other so as to be the blades respectively, and the head part is disposed at each of the both ends of the single blade, and the through-hole is formed in the single blade and extends from the head part on one hand to the head part on the other.

4. The safety utility knife according to claim 2, wherein both ends of a single blade project from the grip part to both sides in opposite directions away from each other so as to be the blades respectively, and the head part is disposed at each of the both ends of the single blade, and the through-hole is formed in the single blade and extends from the head part on one hand to the head part on the other.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0021] FIG. 1 is a view explaining an example of a conventional safety utility knife.

[0022] FIG. 2 is a view explaining another example of the conventional safety utility knife.

[0023] FIG. 3A is a schematic perspective view explaining a case of manufacturing the safety utility knife by use of a 3-gate type mold.

[0024] FIG. 3B is a schematic perspective view explaining a case of manufacturing the safety utility knife by use of a 1-gate type mold.

[0025] FIG. 4A is a view showing a tip-near region of a safety utility knife according to a first embodiment of the present invention.

[0026] FIG. 4B is an opened-up view showing a blade arranged within the safety utility knife of FIG. 4A.

[0027] FIG. 5 shows perspective views of back and front shapes of the safety utility knife of the present invention.

[0028] FIG. 6 shows six different views of the safety utility knife of FIG. 5.

EMBODIMENT(S) FOR CARRYING OUT THE INVENTION

First Embodiment

[0029] A first embodiment of the present invention will now be described with reference to the accompanying drawings. Although details of the first embodiment are described below, a grip part 31, head parts 33a and 33b, and a coupling part 35 are made of resin and manufactured using a mold.

[0030] FIG. 4A shows a safety utility knife 30 according to a first embodiment of the present invention. Although only near the tip of the safety utility knife 30 is shown in FIG. 4A, the whole is elongated similar to the conventional ones shown in FIGS. 1 and 2, and the user holds the grip part 31 and draws it toward the user to cut cardboard, etc. by a blade 50a or 50b on one hand.

[0031] FIGS. 5 and 6 show an example of the overall shape of the safety utility knife of the present invention.

[0032] The blades 50a and 50b protrude from (a tip region of) the grip part 31 toward both sides, with the head parts 33a and 33b being disposed on tips of the blades for the purpose of guide and guard. Such a feature itself is similar to a conventional safety utility knife shown in FIG. 1.

[0033] A principal feature of the present invention lies in that a blade 50 has an elongated hole (through-hole) 55. As a result, as described hereinbelow, effects can be obtained that a safety utility knife is manufacturable using a 1-gate type mold and, additionally, that there is no increase in the blade total thickness.

<Manufacturable Using 1-Gate Type Mold>

[0034] FIG. 4B is an opened-up view showing the blade 50 in the safety utility knife 30 of FIG. 4A. It can be seen that the elongated hole 55 formed in the blade 50 extends from the head part 33a on one hand to the head part 33b on the other.

[0035] Although the safety utility knife 30 is made by molding, the blade 50 is set in the mold at that time so that resin is poured thereinto.

[0036] For example, when allowed to flow from the gate into a cavity portion corresponding to the grip part 31 using the 1-gate type mold, resin flows through the interior of the cavity while advancing in the through-hole 55 of the blade, to finally form the head parts 33a and 33b. After completion of molding, cured resin remaining in the through-hole 55 is the coupling part 35 in FIG. 4A.

[0037] Although there exist three resin-made parts (the grip part 31 and the head parts 33a and 33b) in this manner, these three parts are integrated by the coupling part 35 similarly made of resin, and accordingly the safety utility knife 30 of the present invention can be manufactured using the 1-gate type mold.

[0038] FIG. 3B explains this schematically and shows, in a simplified manner, the safety utility knife immediately after molding using the 1-gate type mold. As is apparent from comparison with FIG. 3A referred to in the description of the prior art, the runner protrudes only from one point.

[0039] Generally speaking, as compared with use of the 3-gate type mold, use of the 1-gate type mold can suppress labor and cost for manufacture including deburring. The 1-gate type mold can simplify the mold configuration for suppression of cost.

<No Increase in Blade Total Thickness>

[0040] In addition, according to the configuration shown in FIGS. 4A and 4B, since the coupling part 35 joining the grip part 31 and the head parts 33a and 33b is enclosed in the elongated hole (through-hole) formed in the blade 50, there is no increase in thickness of the blade 50.

[0041] If the resin part 14 extends overlapping the blade as in the prior art shown in FIG. 2, the total thickness of the blade increases, which induces an increased cutting resistance or a deteriorated cut end. In the safety utility knife of the present invention, the coupling part 35 lies within the elongated hole 55 so that the blade thickness is unchanged from its original thickness (typically of the order of 0.5 to 0.6 mm), thereby preventing the increased cutting resistance or a rough cut end from occurring.

[0042] Moreover, since the coupling part 35 lies within the elongated hole 55 (in other words, since the entire circumference is surrounded by the blade 50), a higher durability is ensured as compared with the case of extending along the back of the blade 50. If the case is considered where the resin part extends outward along the back of the blade 50, repeated use of the safety utility knife allows upward forces in FIG. 4A to act on the coupling part 35 due to the friction with objects (cardboard, string material, etc.) to be cut, with the result that there is a high possibility that the coupling part 35 will break. In the present invention, since the coupling part 35 is surrounded over its entire circumference by the blade 50, such a break is hard to occur and hence it can effectively be prevented that the broken coupling part 35 mixes in somewhere as foreign fragments.

Second Embodiment

[0043] In the first embodiment, the “grip part 31”, “head parts 33a and 33b”, and “coupling part 35” making up the safety utility knife were made of resin and manufactured using the mold.

[0044] On the contrary, in a second embodiment, the safety utility knife is manufactured by diecast molding. That is, a molten metal (aluminum, zinc, magnesium, etc.) is injected at a high pressure into a die attached to a diecast machine and is solidified. Therefore, all of the “grip part 31”, “head parts 33a and 33b”, and “coupling part 35” are made of metal.

[0045] Also in the second embodiment, similarly to the case of the first embodiment, the 1-gate type mold can be used for manufacture with no increase in the blade total thickness. Accordingly, effects similar to the case of the first embodiment described above can be obtained.

[0046] For both of the first embodiment and the second embodiment described above, variants as will be described below can each be adopted.

Variants

[0047] (1)

[0048] In the embodiment shown in FIGS. 4A and 4B, the blades 50a and 50b project from the grip part 31 to both sides so that the safety utility knife 30 has a cutting part at two sites. The present invention is not limited to such a configuration, but, for example, the blade may project only to one side.

[0049] Also in such a case, the grip part and the head parts can be coupled together via the coupling part by providing a proper through-hole in the blade, thus enabling the 1-gate type mold to be used for manufacture.

(2)

[0050] In the embodiment shown in FIGS. 4A and 4B, a single blade 50 was embedded inside the grip 31 such that both ends 50a and 50b of the single blade each projected to the side of the grip part 31. However, the present invention is not limited to such a configuration, but two separate blades may be used to make up a safety utility knife.

[0051] Furthermore, three or more separate blades may be used to obtain a safety utility knife having three or more cutting parts. In any case, the blades are each formed with a through-hole so that the coupling part poured thereinto couples the grip part and the head parts together. Thereby, the safety utility knife can be manufactured using the 1-gate type mold.

EXPLANATIONS OF LETTERS OR NUMERALS

[0052] 11 grip part [0053] 12a, 12b blade [0054] 13a, 13b head part [0055] 14 resin part [0056] 15 edge [0057] 30 safety utility knife [0058] 31 grip part [0059] 33a, 33b head part [0060] 35 coupling part [0061] 50, 50a, 50b blade [0062] 55 elongated hole