JP3414914B2 - Gravure engraving machine engraving head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engraving head for a gravure engraving machine for engraving cells on the surface of a gravure cylinder. 2. Description of the Related Art A gravure engraving machine forms a microscopic recess called a cell on the surface of a gravure cylinder while rotating a cylindrical gravure cylinder having a copper plating on the surface. This is a device for producing intaglio used for printing. And cell depth and width (area)
Thus, the amount of ink to be filled in the cell is controlled, and the print density is expressed. An engraving head is used to form cells on the surface of a gravure cylinder. This engraving head is composed of a shaft having one end fixed to a fixed portion, a stylus supported by the other end of the shaft and having a diamond needle (bite) at its tip, and a stylus supported by an intermediate portion of the shaft and And a stator for applying a magnetic field to the rotor, and applying an engraving signal to the coil of the rotor to generate an alternating magnetic field, thereby rotating the rotor together with the stylus at several kHz. It is configured to vibrate at a frequency. FIG. 5C shows a waveform of an engraving signal applied to the engraving head, which corresponds to a stylus displacement waveform. This waveform signal is obtained by superimposing the density signal waveform shown in FIG. 5B on the high-frequency carry signal shown in FIG. By applying such an engraving signal to the coil of the engraving head, FIG.
As shown in (d), cells having a depth and a width corresponding to the density signal can be engraved on the surface of the gravure cylinder. The dashed line S in FIG. 5C corresponds to the surface of the gravure cylinder. FIG. 6 is a plan view showing the outline of a driving mechanism for vibrating the engraving head. As shown in this figure, a coil 6 indicated by a virtual line is wound near the left and right ends of the rotor 4 supported by the shaft body 2. Also, the rotor 4
A stator 7 is disposed around the periphery of the stator 7, and a permanent magnet 8 for applying a magnetic force to the stator 7 is disposed on a side portion of the stator 7. In this configuration, when a positive current is applied to the coil 6, a magnetic flux flows as shown by an arrow 9a in FIG. 6A, and the rotor 4 rotates clockwise by a slight angle. Also, the coil 6
When a negative current is applied to the rotor 4, a magnetic flux flows as shown by an arrow 9 b in FIG.
Rotates a slight angle counterclockwise. In such an engraving head, the stylus is reciprocally oscillated by rotating the shaft body 2 having one end fixed together with the rotor 4, so that the shaft body 2 may have a moderate torsional elasticity. Required. For this reason, as a material of the shaft body 2, conventionally, carbon steel (for example, S
UP7) is used. [0007] In such a conventional engraving head, when a continuously high engraving signal is applied to the coil 6 in order to continuously engrave cells having a large depth and a large width, these engraving signals may not be obtained. The present inventor has found that a phenomenon occurs in which the depth and width of a cell to be subsequently engraved after engraving of the cell become larger than a desired size. This phenomenon is assumed to be due to the following reasons. That is, in the conventional engraving head,
Since carbon steel having a large coercive force of about 200 to 350 A / m is used as the shaft body 2, when a large current is continuously applied to the coil 6 in the positive direction, FIG.
As shown virtually by the arrow 10a in FIG. 3A, the shaft body 2 made of carbon steel is magnetized by a large magnetic flux generated in the coil 6 due to this current. For this reason, even if a negative current is subsequently applied, the magnetic flux generated in the coil 6 by the negative current is opposite to the magnetic flux generated in the coil 6 as indicated by an arrow 10b in FIG. It is presumed that the above phenomenon occurs due to the residual hysteresis caused by this. When such a phenomenon occurs, the depth and width of the cell actually engraved on the gravure cylinder do not correspond to the engraving signal. However, there is a problem that printing unevenness occurs. The present invention has been made in order to solve the above-mentioned problems. Even when cells having a large depth and width are continuously engraved, the depth and width of the cells to be engraved subsequently can be accurately determined. It is an object to provide an engraving head that can be controlled. [0011] The present invention relates to an engraving head for engraving cells on the surface of a gravure cylinder, wherein at least one end of the engraving head has a torsionally elastic shaft. A rotor supported by the shaft, a stator disposed around the rotor and applying a magnetic field to the rotor, and applying an alternating magnetic field to the rotor, thereby applying the shaft to the rotor. A driving means for applying a reciprocating driving force in a rotation direction about the center, and a stylus connected to the shaft body and having a hard tool for cell engraving fixed at a tip thereof, and at least the rotor of the shaft body Is characterized in that the supporting portion is made of a non-magnetic metal. The "non-magnetic metal" described in this specification
The term includes not only a coercive force close to zero but also a small coercive force. The coercive force of the non-magnetic metal is preferably 70 A / m or less, particularly preferably 7 A / m or less. Embodiments of the present invention will be described below with reference to the drawings. First, a gravure engraving machine to which the engraving head according to the present invention is applied will be described. FIG. 1 is a front view of the gravure engraving machine, and FIG. 2 is a plan view thereof. The gravure engraving machine comprises a bed 30, a headstock 31 fixed on the upper surface of the bed 30, a headstock 31
Tailstock 32, which is disposed opposite to engraving head 40,
And a table 33 having The spindle 41 of the headstock 31 is provided with a synchronous belt 42.
Is connected to the drive motor 43 through the
3 rotates at high speed. On the other hand, the tailstock 32
Is connected to a ball screw 46 which receives a drive of a drive motor 45 via a synchronous belt 44, and moves along a pair of guide rails 47 provided on the upper surface of the bed 30 in the left-right direction in FIGS. It is configured to be movable.
The center 48 of the tailstock 32 is connected to an air cylinder 49 via a link mechanism.
, The headstock 31 can be moved toward and away from the main shaft 41. For this reason, the gravure cylinder G shown by the two-dot chain line in FIG. 1 is supported by the main shaft 41 and the center 48 and rotates at high speed. The table 33 is connected to a ball screw 52 which receives the drive of a drive motor 51, and moves in the left and right directions in FIGS. 1 and 2 along a pair of guide rails 53 provided on the upper surface of the bed 30. It is configured to be possible. In addition, the engraving head 40 is connected to a ball screw 55 that receives driving of a driving motor 54, and moves along a pair of guide rails 56 provided on the upper surface of the table 33 as shown in FIG.
Is configured to be movable in the vertical direction. For this reason, the engraving head 40 is configured to be able to move along the surface thereof in the state of being close to the gravure cylinder G. Next, the engraving head 40 according to the present invention will be described. FIG. 3 is a perspective view showing a main part of the engraving head 40 according to the present invention, and FIG. 4 is an enlarged perspective view showing the vicinity of the rotor 60. The engraving head 40 has a shaft 70 having one end fixed to a fixing portion 61 of the table 33, and a stylus 63 supported by the other end of the shaft 70 and having a diamond needle (bite) 62 at the tip. A rotor 60 supported by the support 70 b of the shaft 70, a stator 64 disposed around the rotor 60 and applying a magnetic field to the rotor 60, and a permanent magnet 65 for applying a magnetic force to the stator 64. And The stator 64 is required to efficiently apply the magnetic force from the permanent magnet 65 to the rotor 60. For this reason, the stator 64 employs a structure in which a material having a small coercive force and a high magnetic permeability is formed in a thin plate shape, and a plurality of such thin plates are stacked. As such a material having a small coercive force and a high magnetic permeability, for example, permendur which is an Fe—Co alloy can be used. The rotor 60 is, as shown in FIG.
It has a configuration in which a number of thin plates 69 supported by zero support portions 70b are stacked, and a coil 68 indicated by a virtual line in FIG. The rotor 60 also
Since it is required to efficiently generate a magnetic field by the current applied to the coil 68, it is necessary to employ a material having a small coercive force and a high magnetic permeability as the material. For this reason, as the material of the thin plate 69 constituting the rotor 60, permendur or the like is employed as in the case of the stator 64. The shaft 70 includes a supporting portion 70b of the rotor 60, a connecting portion 70a connected above the supporting portion 70b and connecting the rotor 60 and the stylus 63, and a supporting portion 7b.
0b, and a base 70c connecting the rotor 60 and the fixed portion 61. The engraving head 40 applies an engraving signal to the coil 68 of the rotor 60 to generate an alternating magnetic field, thereby causing the shaft 70 to twist and causing the rotor 6 to rotate.
0, the base 70 c of the shaft 70 that connects at least the rotor 60 and the fixed part 61.
Is required to have moderate torsional elasticity. The base 70c preferably has a spring property of at least soft iron, an elastic coefficient of 190000 MPa or more, a Poisson's ratio of 0.25 or more, and an elastic limit of 170 MPa.
It is preferably at least a. When the supporting portion 70b of the shaft 70 supporting the rotor 60 is magnetized by the magnetic flux generated by the coil 68, the hysteresis generated by this causes the cell 70 to be engraved as described above. The depth and width will not correspond to the engraving signal. For this reason, the support portion 70b is made of a non-magnetic metal having a small coercive force. As the nonmagnetic metal, not only a metal having a coercive force close to zero but also a metal having a relatively small coercive force can be adopted. According to the study of the present inventors, it has been found that the coercive force is preferably 70 A / m or less, particularly preferably 7 A / m or less. As described above, the shaft body 70 must be made of a non-magnetic metal having a moderate torsional elasticity.
As the metal having such properties, for example, "Elgiloy" (trade name) manufactured by Elgiloy Corporation in the United States can be mentioned. This metal is an alloy mainly composed of Cr, Ni, Co, and Fe, has a coercive force close to zero, and has spring elasticity higher than that of carbon steel. However, as the shaft body 70, not only "Elgiloy", but also a material having torsional elasticity and coercive force in the above-described range, such as austenitic steel, may be used. When engraving is performed on the gravure cylinder G by the engraving head 40, a reciprocating driving force in the direction of rotation about the shaft 70 is applied to the rotor 60 by the engraving signal applied to the coil 68, When the base 70c is twisted, the rotor 60 vibrates with the stylus 63 at a frequency of several KHz. At this time, since the supporting portion 70b supporting the rotor 60 is made of a non-magnetic metal, it is not magnetized as in the related art, and an accurate cell can be engraved. In the above embodiment, the shaft 7
Although the case where the entirety is made of a non-magnetic metal having a moderate torsional elasticity has been described, the connecting portion 70a of the shaft 70 has been described.
The support 70b and the base 70c may be made of different materials according to the required properties, and the shaft 70 may be formed by connecting and fixing them to each other. That is, the base 70c of the shaft 70 need not be a non-magnetic metal as long as it has an appropriate torsional elasticity. For this reason, carbon steel may be used as the base 70c as in the conventional case. Further, the support portion 70b may not have elasticity as long as it is a non-magnetic metal. For this reason, permendur having a coercive force of about 64 A / m, like the rotor 60 and the stator 64, may be used as the support 70b. Further, as the connecting portion 70a, any material can be adopted as long as it can connect the rotor 60 and the stylus 63 with appropriate rigidity. In the above embodiment, the shaft 7
Although only one end of the shaft 70 is fixed to the fixing portion 61, the other end of the shaft 70 extends through the stylus 63, and the other end is fixed to the fixing portion 61. The configuration may be such that both ends of 70 are fixed to the fixing portion 61. In this case, the connecting portion 70 of the shaft 70
It is preferable that the stylus 63 be displaced together with the rotor 60 by making the rigidity a larger than the rigidity of both ends of the shaft 70. According to the engraving head of the gravure engraving machine according to the present invention, since the supporting portion of the rotor in the shaft body is made of a non-magnetic metal, the supporting portion is formed by the magnetic field applied to the rotor. It is possible to effectively prevent the portion from being magnetized. Therefore, even when cells having large depths and widths are continuously engraved, the depth and width of the cells to be engraved subsequently can be accurately controlled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a gravure engraving machine to which the present invention is applied. FIG. 2 is a plan view of FIG. FIG. 3 is a perspective view showing a main part of the engraving head 40 according to the present invention. FIG. 4 is an enlarged perspective view showing the vicinity of a rotor 60; FIG. 5 is a diagram showing engraving signals and cell shapes. FIG. 6 is a plan view showing an outline of a driving mechanism of the engraving head. [Description of Signs] 40 Engraving head 60 Rotor 61 Fixed part 62 Byte 63 Stylus 64 Stator 65 Permanent magnet 68 Coil 70 Shaft 70a Connecting part 70b Supporting part 70c Base G Gravure cylinder

Claims (1)

(57) Claims: 1. An engraving head for engraving a cell on the surface of a gravure cylinder, wherein at least one end of the shaft body has torsion elasticity fixed to a fixing portion; A rotor supported by a shaft, a stator disposed around the rotor and applying a magnetic field to the rotor, and applying an alternating magnetic field to the rotor so that the rotor is centered on the shaft. A driving means for applying a reciprocating driving force in the rotating direction, and a stylus connected to the shaft body and having a hard tool for cell engraving fixed at a tip thereof, and supporting at least the rotor of the shaft body. An engraving head for a gravure engraving machine, wherein the portion is made of a nonmagnetic metal.