Printing die clamp

It is proposed to provide a printing die clamp which can clamp a printing die by rotating the take-up shaft without rotating the printing cylinder. A printing die clamp is proposed for clamping a printing die 1 wrapped around an outer periphery of a printing cylinder 2 of a printing press against the outer periphery of the printing cylinder 2 by engaging one end of the printing die 1 with the printing cylinder 2 through an engaging means 18 provided on the printing cylinder 2, engaging the other end of the printing die 1 with a take-up shaft 3 rotatably mounted in a receiving groove 19 formed in the outer periphery of the printing cylinder 2, and rotating the take-up shaft 3. The printing cylinder 2 has a tubular printing cylinder shaft 9 in which a control shaft 5 is inserted so as to be rotatable relative to the printing cylinder shaft 9. The printing die clamp further includes gears 21, 22 and 23 for transmitting the rotation of the control shaft 5 to the take-up shaft 3, a die clamp motor 4 for rotating the control shaft 5, and a first clutch 6 provided in a torque transmission path through which the rotation of the die clamp motor 4 is transmitted to the control shaft 5 for selectively transmitting the rotation of the die clamp motor 4 to the control shaft 5.

TECHNICAL FIELD

This invention relates to a printing die clamp for clamping a printing die wrapped around a printing cylinder of a printing press against the outer periphery of the printing cylinder.

BACKGROUND ART

Ordinarily, a printing die of a printing press is clamped against and fixed to the outer periphery of a printing cylinder by engaging one end thereof in an engaging groove formed in the outer periphery of the printing cylinder, then fixing the other end to a take-up shaft rotatably received in a groove formed in the outer periphery of the printing cylinder, and taking up the end of the printing die to the take-up shaft by rotating the take-up shaft. The take-up shaft is rotated manually while preventing reverse rotation of the take-up shaft with a ratchet mechanism. It is troublesome to rotate it manually.

In order to eliminate such manual labor, a printing die clamp is proposed which includes a pinion mounted to one end of the take-up shaft, a gear wheel rotatably mounted to a printing cylinder shaft and meshing with the pinion, and a brake mechanism for braking the rotation of the gear wheel (Patent document 1). With this device, by rotating the printing cylinder with the gear wheel braked, the pinion rotates about the axis of the gear wheel and its own axis, so that the take-up shaft rotates.

But with this printing die clamp, in order to rotate the take-up shaft, it is necessary to rotate the printing cylinder. Thus, there is the possibility that an operator may be caught by the printing cylinder, thus causing problems concerning safety.

Patent document 1: Registered JP utility model publication 2545184

DISCLOSURE OF THE INVENTION

Object of the Invention

An object of this invention is to provide a printing die clamp which can clamp a printing die by rotating the take-up shaft without rotating the printing cylinder.

Means to Achieve the Object

In order to achieve this object, the printing cylinder has a tubular printing cylinder shaft in which a control shaft is inserted so as to be rotatable relative to the printing cylinder shaft, and the printing die clamp further comprises a torque transmission mechanism for transmitting the rotation of the control shaft to the take-up shaft, a die clamp motor for rotating the control shaft, and a first clutch provided in a torque transmission path through which the rotation of the die clamp motor is transmitted to the control shaft for selectively transmitting the rotation of the die clamp motor to the control shaft. With this printing die clamp, by transmitting the rotation of the die clamp motor to the control shaft through the first clutch, the rotation of the control shaft is transmitted to the take-up shaft through the torque transmission mechanism. Thus, the take-up shaft rotates, taking up the end of the printing die. During printing, the first clutch is disengaged to prevent the transmission of rotation of the die clamp motor to the control shaft. This prevents rotation of the control shaft relative to the printing cylinder shaft.

Preferably, the printing die clamp further comprises a second clutch for selectively joining and separating the printing cylinder shaft and the control shaft to and from each other. With this arrangement, by joining the printing cylinder shaft to the control shaft through the second clutch during printing, the printing cylinder shaft and the control shaft rotate together with each other, so that it is possible to more reliably prevent the control shaft from rotating relative to the printing cylinder shaft. While the printing die is clamped, the second clutch is disengaged to keep the printing cylinder shaft separated from the control shaft.

Further preferably, the printing die clamp further comprises a ratchet mechanism provided at one end of the take-up shaft for preventing the take-up shaft from rotating in a direction in which the printing die loosens.

ADVANTAGES OF THE INVENTION

According to the present invention, because the printing die clamp motor is provided separately from the driving source for rotating the printing cylinder, it is possible to rotate the take-up shaft without rotating the printing cylinder. Thus, the printing die can be clamped safely. By disengaging the first clutch during printing to prevent the rotation of the die clamp motor from being transmitted to the control shaft, it is possible to prevent a change in clamping force of the printing die due to rotation of the control shaft relative to the printing cylinder, so that the printing accuracy is less likely to deteriorate due to changes in elongation of the printing die.

Further, in the arrangement in which the second clutch is provided for selectively joining and separating the printing cylinder shaft and the control shaft to and from each other, by coupling the printing cylinder shaft to the control shaft through the second clutch during printing, it is possible to more reliably prevent a change in the clamping force of the printing die due to rotation of the control shaft relative to the printing cylinder shaft. Thus, it is possible to further reduce deterioration in printing accuracy due to changes in elongation of the printing die.

By providing the ratchet mechanism at one end of the take-up shaft for preventing the take-up shaft from rotating in a direction in which the printing die loosens, the printing die is less likely to loosen during printing.

DESCRIPTION OF REFERENCE NUMERALS

BEST MODE FOR EMBODYING THE INVENTION

FIGS. 1 to 7show the die clamp embodying the present invention. The die clamp comprises a printing cylinder2on which a printing die1is mounted, a take-up shaft3for taking up an end of the printing die1, a die clamp motor4, a control shaft5rotated by the die clamp motor4, and first and second clutches6and7.

As shown inFIG. 1, the printing cylinder2has printing cylinder shafts8and9on both sides thereof which are rotatably supported by frames10and11of the printing press, respectively. The printing cylinder shaft9carries a printing cylinder gear14fixed thereto and meshing with an impression cylinder gear13fixed to a shaft (not shown) of an impression cylinder12, so that the printing cylinder2and the impression cylinder12rotate at the same speed in opposite directions.

As shown inFIG. 2, the printing cylinder shaft9is a tubular member in which the control shaft5is inserted. The control shaft5is rotatably supported by the printing cylinder shaft9through a bush15pressed into the printing cylinder shaft9. The die clamp motor4is coupled to the control shaft5through the first clutch6for selectively transmitting torque. Thus, by activating the die clamp motor4, the control shaft5can be rotated. The second clutch7is provided at the end of the printing cylinder shaft9to selectively couple and uncouple the printing cylinder shaft9to and from the control shaft5.

A speed reducer16is mounted to the die clamp motor4to reduce and transmit the rotation of the die clamp motor4. The speed reducer16includes a torque limiter17that serves to stop transmission of rotation if the resistance to rotation of the control shaft5increases excessively, thereby preventing damage to the control shaft5.

As shown inFIG. 5, an axial continuous engaging groove18is formed in the outer periphery of the printing cylinder2. The printing die1has an engaging piece1aat one end thereof which can engage in the engaging groove18. A receiving groove19is formed in the printing cylinder2at its position circumferentially spaced from the engaging groove18. The take-up shaft3is rotatably mounted in the receiving groove19. The take-up shaft3has a cutout20in the outer periphery thereof that continuously extends in the axial direction thereof. By engaging an engaging piece1bprovided at the other end of the printing die1in the cutout20, the other end of the printing die1is held in position.

As shown inFIG. 2, the control shaft5extends through the printing cylinder shaft9and carries at its portion protruding from the shaft9a gear21that meshes, as shown inFIG. 3, with a gear23fixed to the end of the take-up shaft3through gears22rotatably mounted to the printing cylinder2. Thus, when the control shaft5is rotated, its rotation is transmitted to the take-up shaft3through the gears21,22and23.

As shown inFIG. 4, a ratchet wheel24is mounted to the take-up shaft3at its end opposite to its end to which the gear23is mounted. A ratchet25that is pivotally mounted to the printing cylinder2is in engagement with the ratchet wheel24so that the take-up shaft3is rotatable only in one direction in which the printing die1is clamped against the printing cylinder. The ratchet25is kept in engagement with the ratchet wheel24by a spring26that biases the ratchet25toward the ratchet wheel24. The ratchet25is formed with a lever27for disengaging the ratchet25from the ratchet wheel24. By operating the lever27, the ratchet25can be pivoted in the direction in which the ratchet25disengages from the ratchet wheel24.

Using this die clamp, the printing die1can be clamped against the outer periphery of the printing cylinder2in e.g. the following manner.

First as shown inFIG. 5, the printing die1is wrapped around the printing cylinder2, the engaging piece1aat one end of the printing die1is engaged in the engaging groove18of the printing cylinder2, and the engaging piece1bat the other end of the printing die1is engaged in the cutout20of the take-up shaft3. Then, as shown inFIG. 7, the first clutch6is engaged so that the rotation of the die clamp motor4can be transmitted to the control shaft5. Simultaneously, the second clutch7is disengaged to separate the printing cylinder shaft9from the control shaft5. In this state, the die clamp motor4is activated to rotate the control shaft5. When the control shaft5rotates, the take-up shaft3rotates to take up the end of the printing die1as shown inFIG. 6, thereby clamping the printing die1against the outer periphery of the printing cylinder2.

Once the printing die1is clamped against the outer periphery of the printing cylinder2, as shown inFIG. 2, the first clutch6is disengaged to stop transmission of rotation from the die clamp motor4to the control shaft5, while the printing cylinder shaft9is coupled to the control shaft5through the second clutch7to perform printing. In this state, because the first clutch6prevents transmission of the rotation of the die clamp motor4to the control shaft5, the control shaft5is less likely to rotate relative to the printing cylinder shaft9. Thus, the force with which the printing die1is clamped against the printing cylinder is less variable, so that the printing accuracy is less likely to deteriorate due to changes in elongation of the printing die1. Also, because the printing cylinder shaft9is coupled to the control shaft5through the second clutch7, the second clutch7allows the printing cylinder shaft9and the control shaft5to rotate together, thus further reducing the possibility of rotation of the printing cylinder shaft9relative to the control shaft5. This further improves the printing accuracy. Further, by engaging the ratchet wheel24, the ratchet25prevents the take-up shaft3from rotating in the direction in which the printing die1loosens. This prevents loosening of the printing die1.

To dismount the printing die1from the printing cylinder2, after stopping the rotation of the printing cylinder2, as shown inFIG. 7, the first clutch6is engaged so that the rotation of the die clamp motor4can be transmitted to the control shaft5, and the second clutch7is disengaged to separate the printing cylinder shaft9from the control shaft5. Further, the ratchet25is disengaged from the ratchet wheel24. In this state, the die clamp motor4is reversed to rotate the take-up shaft3, thereby loosening the printing die1.

In this die clamp, since the take-up shaft3is rotated by the die clamp motor4, it is less troublesome to clamp the printing die. Since the take-up shaft3can be rotated without rotating the printing cylinder2, the printing die can be clamped safely.

The printing die1may be manually loosened and dismounted with the first clutch6disengaged, thereby preventing the rotation of the die clamp motor4from being transmitted to the control shaft5, with the printing cylinder shaft9separated from the control shaft5by means of the second clutch7, and with the ratchet25disengaged from the ratchet wheel24.