Title: Electric hand nibbling machine

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Abstract: An electric hand nibbling machine having means for connecting a movable blade member with a rotary driving means transmitting a force from said rotary driving means in the axial direction of said movable blade member while allowing rotation of said movable blade member on its axis and having a sufficient clearance between the fixtures of the movable blade member and a confronting fixed blade member for free and exact operation for an angular material to be cut. This invention relates to an electric hand nibbling machine for shearing sheet iron, synthetic resin sheet or the like by nibbling operation, and more particularly to an electric hand nibbling machine appropriately adapted to cut a so-called keystone-plate or deck-plate used as a material for a ceiling or floor. As shown in FIGS. 5A and 5B, one type of nibbling machine effects shearing of a material in a pushing stroke of its movable blade member b which is adapted to move reciprocatively relative to its fixed blade member f (as shown in FIG. 5A), while another type of nibbling machine effects shearing of a material in a pulling stroke of its movable blade member b which is also adapted to move reciprocatively relative to its fixed blade member f (as shown in FIG. 5B). In either type of nibbling machine, shearing is effected the moment a cutting edge b1 of the movable blade member b come across an edge f1 of the fixed blade member f disposed in a position abuttable against said cutting edge b1 of the movable blade member b. A projecting pin g is provided on a lower end of the movable blade member (in case of FIG. 5A) or an upper end of the movable blade member (in case of FIG. 5B) to form a recessed portion in cooperation with the lower or upper end surface of the movable blade member b for receiving the material to be cut therein, determining a nibbling distance or pitch of one nibbling operation. Since the tip end of the material to be cut abuts against said pin g or the end wall of said recessed portion, the nibbling pitch per one nibbling operation is determined by the difference in diameters between said movable blade member b and said pin g. Such a pin g may be provided centrally on the upper or lower surface of the movable blade member b. This structure has an advantage that the shearing direction can be easily changed without changing the direction of the machine body since the shearing can be effected in any direction in relation with the movable blade member b, but it has the serious disadvantage that the pin g must be formed comparatively thin in relation with the diameter of the movable blade member b and subjected to a shock by nibbling operation in an unsupported position. In this connection, it is to be noted that the pin g bumps against the tip end of the material and is subjected to a shock in the lateral direction every nibbling operation. Further, a bending stress is applied to the pin g in case the nibbling machine is of a type as shown in FIG. 5B. Because of this serious disadvantage of the structure, it is recommended to dispose the pin g eccentrically on the lower or upper end of the movable blade member b though this eccentric pin disposition has a drawback that the shearing direction is restricted due to its eccentric arrangement. With this arrangement, the diameter of the pin g may be made larger as compared with that of the pin which is provided centrally and the pin g may be slidably supported at the back thereof by its support fixture so that it can well resist a bending stress. Due to this merit, this eccentric arrangement is widely employed in a nibbling machine. However, there still remains a drawback that the shearing direction can not be converted without changing the direction of the machine body, to wit, that the shearing can not be effected in a direction other than the forward direction of the machine body. Stated illustratively, the nibbling machine of this structure can not be operated when the shearing is required to be effected laterally or backwardly with reference to the front of the machine body, according to the size or situation of the material set and the machine body can not be freely turned to a desired direction in a corner etc. because the bulky head portion of the machine strikes against walls. Especially in the shearing of a keystone plate or deck plate, etc., which are in great demand as a material for a ceiling or floor, the shearing operation is required to be conducted substantially at a right angle to the direction of the machine body as shown in FIG. 4 and the nibbling machine as mentioned above can not meet this requirement. Further for shearing the keystone plate or the deck plate, there is preferably provided a sufficient clearance, in connection with the blade members, for conforming the machine with the angle of the keystone plate or deck plate without striking the corners thereof to snugly receive the angular material between the blade members for easy and right operation of the machine. It is therefore an object of the present invention to provide a nibbling machine having a sufficient strength against a shock given by the nibbling operation and capable of readily effecting shearing in a direction desired, in a corner or even in a circular contour, operating the machine in the most natural and convenient manner. It is another object of the present invention to provide a nibbling machine as mentioned above which is specifically adapted to shear a keystone plate, a deck plate or the like. According to the present invention, there is provided in a hand nibbling machine having a rotary driving means, a piston connected to said rotary driving means, a cylindrical movable blade member with a cutting edge and fixed to said piston, a fixed blade member having a cutting edge disposed in an abuttable relation to the cutting edge of the movable blade member and connected, through a support member, to a piston holding member fitted around said piston, the improvement comprising said cylindrical movable blade member is formed with a recessed portion for receiving a material to be cut therein and is provided with the cutting edge at one of the vertical ends of said recessed portion; means for connecting said piston with said rotary driving means transmitting a force from said rotary driving means in the axial direction while allowing rotation of said piston on its axis; and said piston holding member and said fixed blade member tapered at their respective end portions facing each other, forming a clearance for allowing free operation of the machine and defining a sectoral shape expanding towards the outside of the support member which is provided in the rear side of said movable blade member with reference to the cutting direction of the machine and in parallel with said movable blade member and has a thickness the same as or less than the diameter of said movable blade member.


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