An apparatus for controlling paper transfer speed of printing section of a form printing machine

Abstract: A form printing machine having a printing section provided with a printing unit comprising a plate cylinder (6), a blanket cylinder (7) and an impression cylinder (8), a change speed means (23,50) for changing the rotation speed of the impression cylinder independently of the plate cylinder and the blanket cylinder being provided.

Description: The present invention relates to a form printing machine and is particularly concerned with cotrolling paper transfer speed of a printing section of a form printing machine which carries out successive steps from multicolor printing on a paper web to processing, such as punching and perforating. The whole structure of a typical multicolor form printing machine is shown in Fig.9 of the appended drawings. In this Figure, there is illustrated a paper feeding section 1 for transferring a paper web P from a roll, a printing section 2 for achieving multicolor offset printing on the fed paper web P, a processing section 3 for processing, for example, punching, perforating and the like the printed paper web P which is transferred from the printing section 2, and a paper discharge section for discharging the printed and processed paper web into a zigzag folded stack. In the printing section 2, printing units 5 are arranged on a printing line. The number of the printing units 5 coincides with the number of colors used in the multicolor printing, and in Fig.9, four printing units which coincide with the four color printing are arranged. The paper web P is successively passed through each of the printing units 5... and printed in multicolor. Each printing unit 5 comprises a plate cylinder 6, a blanket cylinder 7 formed of an elastic material such as rubber onto which images on the plate cylinder are transferred and a metal impression cylinder 8, these three cylinders being rotatably supported by a printing cylinder support in such a manner that their circumferential surfaces are substantially in contact with one another. The paper web P is passed between the blanket cylinder 7 and the impression cylinder 8, where the image transferred from the plate cylinder 6 onto the blanket cylinder 7 is printed on the paper web P. As shown in Fig. 6, the rotation of a drive motor(not shown) is transmitted through a drive shaft 11 to each of the printing units 5. The drive shaft 11 extends along the paper feed section 1 and all of the printing units 5...of the printing section 2. The rotation of the drive shaft 11 is transmitted through a transmission device 12 such as a worm gear mechanism to an infeed roll 10 and through a transmission gear 13 to the plate cylinders 6 of the printing units 5.... As shown in Fig. 7, spur gears 14, 15, 16 are mounted respectively on the rotatory shafts 6a, 7a, 8a respectively of the plate cylinder 6, the blanket cylinder 7 and the impression cylinder 8 of each printing unit 5. By the rotation of the spur gears 14, 15, 16 in engagement with one another, the rotation of the drive shaft 11 is transmitted to the plate cylinder 6, the blanket cylinder 7 and the impression cylinder 8. Thus, these cylinders 6, 7, 8 are rotated. In this case, the speed of transfer of the paper web P (hereinafter referred to as the paper transfer speed) of the printing unit 5 is controlled by the rotation speed of the blanket cylinder 7 and the impression cylinder 8, but it is also changed in accordance with the change of the thickness of the paper web P. Namely, in Fig. 12, if d is the diameter of the impression cylinder 8; N is the rotation frequency of the impression cylinder 8; t is the thickness of the paper web P; and V is the paper transfer speed, a formula V= N(d+t)π is obtained. And therefore, as the thickness t of the paper web P (hereinafter referred to as the paper thickness t) increases, the paper transfer speed V rises and the paper transfer amount per unit time increases. In the case of the blanket cylinder 7, the change of the paper thickness is compensated by diameter change due to the elasticity of the blanket cylinder 7, and therefore, the paper transfer speed is changed by the relation of the nonelastic impression cylinder 8 and the paper thickness. In other words, the paper transfer speed is determined by the rotation speed of the impression cylinder 8 and the paper thickness. Further, generally in a business form printing machine, the paper thickness changes within the range from 0.05mm to 0.2mm. Therefore, for the paper transfer speed V, the following formulas are obtained. Minimum value V min=N(d+0.05)π Minimum value V max=N(d+0.2) π In a conventional printing machine, however, since the impression cylinder 8 is always rotated together with the blanket cylinder 7 at a predetermined speed, independently of the paper thickness, the paper transfer speed changes with the change of the paper thickness. As a result, the following problems have been caused. 1. In the printing unit 5, monocolor or multicolor, the change of the paper transfer speed with respect to the blanket cylinder 7 rotating at a constant speed (i.e. the change of the printing pitch) causes the unevenness of printing precision. 2. Due to the change of the printing pitch, the tension of the paper web P of the printing section 2 become different from that of the preceding paper feed section 1 or of the following processing section 3. Consequently, a high tension is applied to the paper web P and a paper transfer mechanism, which causes the paper web P to be broken and the life span of the paper transfer mechanism to be shortened. 3. In multicolor printing, the difference of the diameters of the impression cylinders of the printing units 5 causes variation of the paper transfer speed between the printing units i.e. variation of the printing pitch therebetween, whereby the similar problems have arisen. Japanese Patent Application 60-94353 discloses a printing section having common speed changing means 13 operative to adjust the speed of all the impression cylinders together, to compensate for change of their diameter. No compensation for paper thickness is mentioned. An object of the present invention is to overcome the above-mentioned problems. The form printing machine of the present invention is set out in claim 1. With this arrangement of the invention, firstly the rotation speed of the impression cylinder of each printing unit, namely the paper transfer speed, can be controlled in correspondence with the change of the paper thickness. Secondly, the rotation speed of the impression cylinder of each printing unit can be controlled in accordance with the variation of the diameter of the impression cylinder between the printing units and the like, whereby the printing pitch can be suitably maintained. Fig. 1 is a schematic view illustrating an embodiment of the apparatus according to the present invention; Fig. 2 is a sectional view of a differential device suitable for use as a speed changing means in the present invention; Fig. 3 is a detailed side view of the apparatus of Fig. 1; Fig. 4 is a view illustrating the principle of the operation of a differential device used as a speed change means in the embodiment of Figs. 1 to 3; Fig. 5 is a view similar to Fig. 3 illustrating another example of the differential device; Fig. 6 is a view similar to Fig. 1 illustrating the prior art; Fig. 7 is a view similar to Fig. 3 illustrating the drive system of the printing unit in the prior art; Fig. 8 is a partly extended front view of the drive system; and Fig. 9 is a view illustrating the general structure of the form printing machine. An embodiment of the present invention is shown in Figs. 4 and 5. Here in the explanation of the embodiment, the same parts as the part shown in Figs. 6 to 9 are indicated with the same numerals and duplication of description will be avoided. Referring to Fig. 4; the rotary power of a drive shaft 11 is transmitted through a transmission device 12 to an infeed roll 10 and at the same time transmitted through a transmission device 13 to the plate cylinder 6 of each printing unit 5. Then in each printing unit 5 the rotary power of the plate cylinder 6 is transmitted directly to the blanket cylinder 7, and the rotary power of the blanket cylinder 7 is transmitted through a differential device 23 functioning as a speed change means to the impression cylinder 8. By the differential device 23, the rotation speed of the impression cylinder 8 can be controlled independently of the plate cylinder 6 and the blanket cylinder 7, whereby the paper transfer speed can be controlled. The particular structure of the power transmission system, including the differential device 23, of each printing unit 5 will be described with reference to Fig. 3. Spur gears 14, 15 are mounted respectively on the rotary shafts 6a, 7a of the plate cylinder 6 and the blanket cylinder 7 in such a manner that the spur gears 14, 15 are in engagement with each other. On the other hand, two spur gears 51, 52 are mounted on the rotary shaft 8a of the impression cylinder 8 and the spur gear 51 is in engagement with the spur gear 15 of the blanket cylinder 7. The spur gear 51 (hereinafter referred to as the transmission gear 51) is mounted through bearing 53 on the shaft 8a while the spur gear 52 (hereinafter referred to as the output gear 52) is mounted directly on the shaft 8a, and the differential device 23 is provided between the two gears 51, 52. The differential device 23 is illustrated in Fig. 2 and is referred as to a harmonic drive. It comprises an ellipsoidal wave generator 32, a flex spline 30 deformable into an ellipsoidal form by the rotation of a wave generator 32, and a pair of circular spines 34, 35, each provided with internal teeth which are engageable with the longitudinal portion, of the flex spline 30. The principle of the operation of the differential device 23 will be described with reference to Figs. 3 to 5 One circular spine 34 is engaged through a spur gear 36 with the transmission gear 51, while the other circular spline 35 is engaged through the spur gear 37 with the output gear 52. The wave generator 32 is mounted on the regulating spindle 38 so as to be integratedly rotatable with the regulating spindle 38. The regulating spindle 38 is rotatively driven through a belt transmission mechanism 39 by a regulating motor 40. The rotary power of the transmission gear 51 is transmitted to the output gear 52 via the spur gear 36 → the circular spine 34 → the flex spline 33 the circular spline 35 → the spur gear 37. On the other hand, the rotatory power of the regulating motor 40 is transmitted via the belt transmission mechanism 39 → the regulating spindle 38 → the wave generator 32, and by the rotation of the wave generation 32, the flex spline 33 is deformed into an ellipsoidal form and at the same time the longitudinal portion of the flex spline 33 comes into engagement successively with the internal teeth of the circular splines 34, 35. In this case, since the number of the teeth of the flex spine 33 is smaller by a few (e.g. by two) than that of the circular spines 34, 35, the flex spine 33 is moved in the corresponding distance in the direction opposite to the direction of the rotation of the wave generator 32. This movement is taken out as a differential output by the output gear 52, and thereby the impression cylinder 8 is rotated at the speed determined by the differential device 23. The output rotation speed of the differential device 23 can be freely changed by controlling the rotation speed of the regulating motor 40, and thereby the speed ratio of the impression cylinder 8 to the blanket cylinder 7 of each printing section 5 can be controlled. When the rotation of the regulating motor 40 is stopped, the ratio of the input speed to the output speed of the differential device 23 is R:(R+1). Here, R is the reduction gear ratio of the differential device 23. The rotation speed of the impression cylinder 8 of each printing unit 5, namely, the paper transfer speed of the printing section 2 can be freely controlled as abovementioned. Therefore, the printing pitch can be maintained uniform by reducing the rotation of the impression cylinder 8 thus to lower the paper transfer speed when the paper thickness is larger than the standard value, and by controlling reversely when the paper thickness is smaller. Consequently, it can be assuredly prevented that the obtained print is blurred due to the disharmony of the rotation speed of the blanket cylinder 7 with the paper transfer speed and that a high tension is applied on the paper web P and the paper transfer mechanism between the printing section 2 and the paper feed section 1 or the processing section 3 due to the change of the printing pitch. Further, when the difference of the paper transfer speed between the printing units 5... is caused by the difference of the diameter of the impression cylinders, by controlling the paper transfer speed of one or both of the units 5 as abovementioned a high tension can be prevented from being applied on the paper web P and the paper transfer mechanism between the printing unit 2 and the paper feed section 1 or the processing unit 3. Another example of the differential device 23 is shown in Fig. 5. In the embodiment of Figs. 2 and 3, the regulating spindle 38 is rotatively driven by another drive source i.e. the variable-speed regulating motor 40, but in the example shown in Fig. 5, the rotary power of the blanket cylinder 7 is introduced into a gear type or other speed change device 53 the reduction gear ratio of which can be controlled by manual operation, and the output thereof is transmitted through the belt transmission mechanism 54 to the regulating spindle 38 so as to function as a drive force. The speed change means for controlling the speeds of the impression cylinders 8... of the printing units 5... is not limited to the abovementioned differential device 23 but may comprise a gear type, belt type or other general speed change device. However, the use of the differential device 23 shown in the above embodiments is advantageous in that fine speed change control can be thereby achived with a high accuracy. With the use of the illustrated apparatus, as abovementioned, the rotation of the blanket cylinder of each printing unit of the printing section is transmitted through the speed change means such as the differential device to the impression cylinder, and the rotation speed of the impression cylinder, namely, the paper transfer speed can be control led by the speed change means. Consequently by controlling the paper transfer speed in correspondence with the paper thickness, the difference of the diameter of the impression cylinder between the printing units and the like, the printing pitch can be always suitably maintained thus to improve the printing precision and at the same time application of high tension to the paper web and the paper transfer mechanism between the printing section and the paper feed section or the processing section of a multicolor printing machine is prevented, whereby the life span of the paper transfer mechanism of each section can be increased.

Claims: A form printing machine having a plurality of printing units (5) each comprising a plate cylinder (6), a blanket cylinder (7) and an impression cylinder (8) and drive means (11,12,13,23) to drive said cylinders (6,7,8) including speed differential means (23) for causing said impression cylinders (8) to rotate at a predetermined speed difference relative to said plate cylinders (6) and blanket cylinders (7), characterised in that in each said printing unit, said drive means has speed differential means (23) for the impression cylinder (8) thereof to rotate at a said speed difference relative to the plate cylinder (6) and blanket cylinder (7) thereof, the speed differential means (23) of the respective printing units being independently adjustable. A form printing machine according to claim 1 wherein said speed differential means (23) of each printing unit is a harmonic drive. A form printing machine according to claim 1 wherein said drive means has a drive shaft (11) driving each said printing unit (5) and at each printing unit (5) a branch shaft driving said plate cylinder (6), said impression cylinder (8) in each unit (5) being driven from said branch shaft via said plate cylinder (6), and said speed differential means (23) for the impression cylinder in each printing unit (5) being interposed in the drive between said plate cylinder (6) and said impression cylinder (8). A form printing machine according to claim 3 wherein in each printing unit (5) said impression cylinder (8) is driven from said plate cylinder (6) via said blanket cylinder (7), and said speed differential means (23) is interposed in the drive between said blanket cylinder (7) and said impression cylinder (8).

Inventors: HANYU AKINOBU, KAWANA FUJIO, HANYU, AKINOBU, KAWANA, FUJIO
Applicants: FUJI KIKAI KOGYO KK, FUJI KIKAI KOGYO CO., LTD.
Application year: 1987
Main classification: B41F13
IPC codes: B41F13