Knife

Abstract: A knife (1) includes a blade (2) made of stainless steel and a hollow handle (4) made of stainless steel. The hollow handle (4) is comprised of right and left handle halves which are butt-joined to each other at their joining faces. The handle halves define therebetween a hollow portion which is filled with a filler, including river sand, for adjustment of overall weight balance of the knife. The blade and the handle are butt-joined into one piece at their confronting end edges.

Description: BACKGROUND OF THE INVENTION Technical Field The present invention relates to a knife, and more particularly, to a knife which is especially suitable for professional use and which has improved durability and ease-of-use features. Related Art A knife for domestic or professional use, such as utility knife or chef's knife, is typically comprised of a blade, a tang formed integrally with the blade and extending backward therefrom, and a wooden handle having handle halves riveted on opposite side faces of the tang. The wooden handle is poor in durability and permits the breeding of harmful bacterium to tend to impair the cleanliness of the knife. The overall weight balance of a knife, especially in the case of a knife for professional use which is ordinarily used for many hours, greatly affects the degree of fatigue of a user, and also affects the sharpness or ease-of-cutting ability of the knife. A conventional knife having the aforementioned construction is poor in the degree of freedom in adjusting the balance of weight, and makes it difficult to attain an optimum weight balance. US-A-4,147,918 discloses a knife comprising a metal blade having an end edge and a metal handle having an end edge confronting the blade, wherein the handle is formed with a hollow portion and is made of a metallic material of a kind which is the same or different from the metallic material of the blade, said blade and said handle being butt-joined at their end edges into one piece. US-A-4,470,327 discloses a knife comprising weight balancing means in the hollow portion of a handle, said weight balancing means including a filler filled within said hollow portion of said handle. SUMMARY OF THE INVENTION An object of the present invention is to provide a knife which is excellent in durability and ease of use. Another object of the present invention is to provide a knife which is excellent in overall weight balance. A knife according to the present invention comprises a metal blade having an end edge, and a metal handle having an end edge confronting the blade. The handle is formed with a hollow portion for adjustment of weight distribution mainly in a lengthwise direction of the handle. The handle is made of a metallic material of a kind which is the same or different from a metallic material for the blade. The blade and the handle are butt-joined at their end edges into one piece. Preferably, the blade and the handle are butt-welded at their end edges. According to the knife having the metal blade and the hollow metal handle which are formed into one piece, the handle is not decayed and does not permit the breeding of bacterium unlike the case of a conventional knife having a wooden handle. Thus, the knife according to the present invention has improved durability and cleanliness. The weight distribution mainly in the lengthwise direction of the handle is made proper by forming the hollow portion of the handle to have an appropriate volume, whereby a suitable overall weight balance of the knife can be attained. Further, this invention is advantageous in that the recycling of knives can be easily made. Preferably, the blade is made of stainless steel, e.g., hard stainless steel. More preferably, the blade is made of stainless steel to which molybdenum and vanadium are added. The handle is made of stainless steel of a kind which is the same as or different from the stainless steel of which the blade is made. According to this preferred construction, the blade is excellent in toughness and hardness and is permitted to be appropriately formed with a sharpened blade edge. Further, the handle and the blade are permitted to be properly welded together, and are prevented from being rusted. Preferably, the handle has side faces thereof each formed with a nonskid structure comprised of an array of dents. With this preferred construction, the knife is prevented from being slipped down from the user' hand, so that the knife is easy to use. Preferably, the handle is comprised of two handle halves which are butt-joined at their joining faces. These handle halves define therebetween the hollow portion of the handle. Preferably, the handle halves are but-welded at their joining faces. With this preferred construction, the weight distribution mainly in the lengthwise direction of the handle is optimized by using the handle halves obtained from a metal plate having an appropriate thickness, whereby the handle having an optimum weight distribution can be relatively easily obtained, and the overall weight balance of the knife can be optimized. Preferably, the knife further comprises weight balancing means provided in the hollow portion of the handle. More preferably, the weight balancing means includes a filler filled within the hollow portion of the handle. The filler is preferably filled tightly in the hollow portion. The filler is comprised of river sand or a mixture of river sand and cement or steel spheres. With this preferred arrangement, the overall weight balance of the knife can be optimized, so that the degree of fatigue of the user using the knife for many hours can be reduced, and the ease-of-cutting ability of the knife can be enhanced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view showing a knife according to an embodiment of the present invention; Fig. 2 is an exploded perspective view of the knife shown in Fig. 1; Fig. 3 is a transverse sectional view of the knife handle taken along III-III line of Fig. 1; Fig. 4 is a diagram showing manufacturing processes of the knife shown in Fig. 1; and Fig. 5 is a side view showing a knife according to a modification of the present invention. DETAILED DESCRIPTION As shown in Fig. 1, a knife 1 according to an embodiment of the present invention, which is especially suited for professional use, comprises a metal blade 2 and a metal handle 4 which is butt-joined to the blade 2. The handle 4 has a hollow portion in which a filler 6 for adjustment of the overall weight balance of the knife is tightly filled. The filler 6 is comprised of river sand or a mixture of river sand and cement or steel spheres. The volume of the hollow portion is determined such that a proper weight-balance adjustment is achieved in cooperation with the weight-balancing function of the filler. The knife blade 2 is made of a metallic material which has adequate toughness and hardness and which permits the blade to be formed with a blade edge. For example, the blade 2 is made of stainless steel, preferably, ultra-hard stainless steel containing molybdenum and vanadium. The ultra-hard stainless steel of this kind is used as a material, e.g., for surgical knife. In this embodiment, the handle 4 is made of a metallic material, such as ultra-hard stainless steel which is the same kind as that for the blade 2. Alternatively, the handle 4 may be made of a material of a kind different from that for the blade 2 so long as the handle 4 is permitted to be properly welded to the blade 2. The blade 2, which is solid, has an upper face, i.e., a back 2a, extending from a distal end (tip point) 2b of the knife to an upper end of a rear end edge 2c of the blade 2. The back 2a is slightly curved at its distal end portion and extends substantially straight in parallel to the longitudinal axis of the knife at the intermediate and rear end portions of the back 2a. The blade 2 has a blade edge 2d thereof extending, with a slight curvature, from the tip point 2b and terminating at a heel 2e. A remaining lower edge of the blade 2 extends from the heel 2c to a lower end of the rear end edge 2c with a steep curvature. The handle 4 is comprised of right and left handle halves 41 and 42 which are joined to each other. Preferably, these handle halves have their shapes which are symmetry with respect to their joining faces. Each handle half is obtained by forming a metal plate into a dish shape. The metal plate in this embodiment has a thickness which is about one-half of that of the blade 2. Each handle half 41 or 42 has a side wall 41a or 42a corresponding to the left wall or the right wall of the handle 4. Each of the side walls 41a and 42a is formed with a number of small semispherical dents (only those formed in the left handle half 41 are shown by reference numeral 43 in Fig. 2) at spatial intervals in an area extending from its intermediate portion to its rear end. The array of the dents 43 constitutes a nonskid structure for preventing the knife from being slip down from the user's hand. Each handle half has an upper wall 41b or 42b, a lower wall 41c or 42c, and a rear wall 41d or 42d which are formed integrally with the side wall concerned. The upper and lower walls are smoothly connected with the side wall, as best shown in Fig. 3. The widthwise dimension of each of upper and lower walls is equal to, e.g., zero at a front end edge 41e or 42e of the handle half, so that the below-mentioned hollow portion is not present at the front end edge of the handle. The right and left handle halves 41, 42 are butt-joined to each other at their joining faces 4a, and cooperate to each other to define a hollow portion 4b of the handle 4 therebetween. As explained above, the hollow portion 4b has an appropriate volume and is filled with a filler 6 for weight-balance adjustment. The handle 4 comprised of the handle halves 41, 42 is butt-joined at its front end edge 41f, 42f to the rear end edge 2c of the blade 2. The front end edge 41f, 42f has its length which is the same as that of the rear end edge 2c. The handle 4 has an upper edge 4b thereof extending substantially parallel to the longitudinal axis of the knife. At a distal end portion of the handle 4, i.e., at an intermediate portion of the knife, a lower edge 4c of the handle 4 extends, with a curvature, obliquely with respect to the longitudinal axis of the knife so that the height of the handle 4 becomes larger toward a rear end of the handle. On the other hand, in an area from an intermediate portion to a rear end portion of the handle 4, the lower edge 4c of the handle extends substantially straight and obliquely with respect to the longitudinal axis of the knife so that the height of the handle 4 becomes slightly smaller toward the rear end of the handle. The handle 4 has outer and transverse sectional shapes permitting the handle to be adequately fitted to the user's hand. This ease-of-grasp feature cooperates with the aforementioned array of the semi-spherical dents 43 to provide a nonskid feature. With reference to Fig. 4, processes of manufacturing the knife 1 having the aforementioned construction will be explained. First, hard stainless steel plates are subject to hot forging, for instance, to thereby obtain a blade 2 and right and left handle halves 41, 42 (processes 101, 102 and 103 shown in Fig. 4). Next, the handle halves 41 and 42 are subject to annealing, respectively (processes 104 and 105). Then, the handle halves 41 and 42 are clamped by a clamp mechanism (not shown) in a state where they are abutted against each other at their joining faces 4a, and are butt-joined into one piece by means of argon arc welding (process 106), to thereby obtain a hollow handle 4. Next, the handle 4 is subject to punching so that the handle is formed at its rear wall with a through hole, not shown (process 107). A filler 6, e.g., river sand, is tightly filled, through the through hole, in a hollow portion 4b of the handle (process 108), as exemplarily shown in Fig. 3. After the filler 6 is filled, the through hole of the rear wall of the handle 4 is sealed (process 109), whereby the handle filled with the filler 6 is obtained. On the other hand, the blade 2 obtained in process 101 is subject to annealing (process 110). By means of argon arc welding, for instance, the annealed blade is butt-joined to the handle filled with the filler (process 111), whereby a one-piece blade/handle assembly is obtained. The assembly is subject to grinding to remove excess materials and provide smooth finish around the welded portions (2c, 41f, 42f; 4a) at which the blade and the handle are welded and the handle halves are welded together (process 112). Further, the blade/handle assembly is subject, in its entirety or at its blade edge, to sub zero treatment (process 113). The sub zero treatment can be made in various manners. For instance, low temperature medium such as liquid nitrogen is directly sprayed to the blade edge to cool the same. Alternatively, the assembly is placed in a cooling pool after the ambient atmosphere in the cooling pool is cooled. Finally, the blade is sharpened to provide a blade edge 2d (process 114), to thereby obtain a knife 1. The knife according to the present invention is not limited to the foregoing embodiment but may be modified variously. For instance, a hollow handle may be obtained by bending a single metal sheet into a U-shape and by welding adjacent edges of the U-shaped sheet together, although the handle is obtained in the embodiment by butt-joining handle halves into one piece. One or more metal balancers serving as weight balancing means may be welded or mounted to an inner surface of the side wall of each handle half, although the weight balancing means in the embodiment is comprised of a filler filled in the hollow portion of the handle. The processes of manufacturing the knife of this invention are not limited to those shown in Fig. 4. For instance, it is not inevitably necessary to subject the knife to sub zero treatment. The outer and sectional shapes of the knife blade and the knife handle are not limited to those of the embodiment, but may be modified variously in accordance with, e.g., the purpose for which the knife is used. Fig. 5 shows a small knife 1' according to a modification of this invention. The knife 1' has a blade 2' and a handle 4' whose outer shapes and dimensions are different from those of the knife 1 of the embodiment. The handle 4' has its lower edge extending obliquely to form a considerable angle between itself and the longitudinal axis of the knife 1', so that the height of the handle 4' becomes considerably smaller toward the rear end of the handle. In the embodiment, an explanation has been given by taking, as an example, the knife 1 especially suitable for professional use. However, the present invention is also applicable to knives suited to household use, butcher-shop use or the like. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims: A knife comprising: a metal blade (2, 2') having an end edge (2c); and a metal handle (4, 4') having an end edge (41f, 42f) confronting the blade (2, 2'), said handle (4, 4') being formed with a hollow portion (4b) for adjustment of weight distribution mainly in a lengthwise direction of the handle (4, 4'), said handle (4, 4') being made of a metallic material of a kind which is the same or different from a metallic material for the blade (2, 2'), said blade (2, 2') and said handle (4, 4') being butt-joined at their end edges (2c, 41f, 42f) into one piece; said handle (4, 4') being comprised of two handle halves (41, 42) which are butt-joined at their joining faces (4a), said handle halves (41, 42) defining therebetween said hollow portion (4b) of said handle (4, 4') ; characterized in that weight balancing means (6) are provided in said hollow portion (4b) and in that said weight balancing means includes a filler (6) filled within the hollow portion (4b) of said handle (4, 4'). The knife according to claim 1, wherein said blade (2, 2') is made of stainless steel, and said handle (4, 4') is made of stainless steel of a kind which is the same or different from the stainless steel of which said blade (2, 2') is made. The knife according to claim 1, wherein said filler (6) includes river sand.

Inventors: WATANABE HIDEYO, WATANABE, HIDEYO, Watanabe, Hideyo c/o Yoshida Metal Industry Co.Ltd
Applicants: YOSHIDA METAL INDUSTRY CO LTD, YOSHIDA METAL INDUSTRY CO., LTD.
Application year: 1999
Main classification: B26B3
IPC codes: A47J43, B26B9, B26B3