JP3530790B2 - Sheet-fed printing press that can switch between double-sided printing and single-sided printing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-fed printing press capable of switching between single-sided printing and double-sided printing.

[0002]

2. Description of the Related Art A switchable sheet-fed printing press of this type includes a paper delivery unit between an upstream printing unit and a downstream printing unit. As shown in FIG. 10, the paper delivery unit includes a delivery cylinder 50, a storage cylinder 51, and a reversing cylinder 52 in order from the upstream side, and a sheet printed by the upstream printing unit is transferred to the downstream printing unit. The sheet delivered from the impression cylinder of the upstream printing unit to the storage cylinder 51 via the transfer cylinder 50 has its front edge gripped by the gripper 53 and its rear edge adsorbed by the paper. It is adsorbed and held by the device 54.

In single-sided printing, the reversing gripper 55 of the reversing cylinder 52 grips and receives the front edge of the sheet from the gripper 53 of the storage cylinder 51. On the other hand, in double-sided printing, the reverse gripper 55 grips and receives the trailing edge of the sheet from the paper suction device 54 of the storage cylinder 51, and the reverse gripper 55 causes the reverse cylinder 5
It turns with the rotation of 2 and flips the sheet upside down,
Deliver to the impression cylinder of the downstream printing unit.

As described above, in single-sided printing and double-sided printing,
It is necessary to change the phase between the reversing cylinder 52 and the storage cylinder 51 by an angle corresponding to the length of the sheet in the paper feeding direction.
As a mechanism therefor, for example, there is one as shown in FIG.

In this structure, the reversing cylinder 52 is provided with a fixed gear 56 and an adjusting gear 57 configured to change the phase with respect to the fixed gear 56, and the fixed gear 56 is a cylinder shaft 58 of the reversing cylinder 52. The adjustment gear 57 is formed in a donut shape and is externally mounted on the gear support shaft portion 60 provided on the fixed gear 56 so as to be rotatable relative to each other. , Meshes with the gear 61 of the storage cylinder 51. Further, at the time of printing, the adjustment gear 57 is clamped and fixed in the axial direction by the pressing lever 62 and the fixed gear 56 to rotate integrally with the fixed gear 56, and the rotation of the storage cylinder 51 causes the rotation of the storage cylinder 51. It is transmitted from the gear 61 to the adjusting gear 57, the fixed gear 56, and the gear 59 of the impression cylinder, and the storage cylinder 51, the reversing cylinder 52, and the impression cylinder rotate in synchronization.

On the other hand, when switching between single-sided printing and double-sided printing, the pressing force of the spring 63 is pressed by the pressing member 64 to release the clamping force of the pressing lever 62, thereby adjusting the gear support shaft portion 60. The fixed state of the gear 57 is released, and the adjustment gear 57 becomes rotatable relative to the fixed gear 56. By rotating the adjusting gear 57 relative to the fixed gear 56 by a predetermined angle in this state, the phase of the storage cylinder 51 and the reversing cylinder 52 is changed to a phase corresponding to single-sided printing or double-sided printing. Then, after this phase change, a clamping force is generated by the spring 63 so that the adjusting gear 57 and the fixed gear 56 rotate integrally.

In such a sheet-fed printing press, sheet registration accuracy is required to be high, and the accuracy is affected by the coaxiality of the adjusting gear 57 and the reversing cylinder 52. However, in the above-described configuration, there is a slight predetermined gap between the inner peripheral surface of the adjustment gear 57 and the outer peripheral surface of the gear support shaft portion 60.
Inevitably occurs due to its configuration. Therefore, even if each component such as the adjustment gear 57 is manufactured with high accuracy, the coaxiality is deteriorated due to the gap.

Moreover, since the sheet-fed printing press is switchable unlike a printing press that supports only one-sided printing, every time the fixing state of the adjusting gear 57 is released, that is, each time the switching is performed,
The state of the coaxiality of the adjusting gear 57 with respect to the reversing cylinder 52 (the state including not only the absolute value of the coaxiality but also the phase of the shift) changes. Therefore, it is necessary to perform the registration again each time the switching is performed.

Therefore, the present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to switch between double-sided printing and single-sided printing in which the register accuracy can be improved and the registering operation for each switching can be substantially unnecessary. An object is to provide a sheet-fed printing press.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a sheet-fed printing machine capable of double-sided printing according to the present invention includes a printing unit 2 on the upstream side and a printing unit on the downstream side. The storage cylinder 5 and the reversing cylinder 6 on the downstream side of the paper delivery unit for delivering the sheets to the unit 3 are
The gears 5a mounted on the reversing cylinder 6 and the adjusting gear 19 mounted on the reversing cylinder 6 rotate in synchronization with each other, and the reversing cylinder 6 includes a storage cylinder 5 and a reversing cylinder 6 when switching between double-sided printing and single-sided printing. A gear support shaft portion 17 that supports the adjustment gear 19 so as to be capable of relative rotation is provided so that the phase can be changed. The adjustment gear 19 is fixed to the gear support shaft portion 17 so as not to rotate relative to it during printing, and adjustment is performed during the switching. In the sheet-fed printing press capable of switching between double-sided printing and single-sided printing, in which the fixed state of the gear 19 to the gear support shaft portion 17 is released and the phase of the adjustment gear 19 with respect to the gear support shaft portion 17 is changed, Part 17 is
The adjusting gear 19 is provided with a plurality of supports that come into contact with the inner peripheral surface 19a of the adjusting gear 19, and the adjusting gear 19 is rotatably supported by the supports so that the coaxiality of the adjusting gear 19 with respect to the reversing cylinder 6 can be adjusted. The position of is adjustable in the radial direction of the reversing cylinder 6.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sheet-fed printing press according to the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic overall view of the sheet-fed printing machine according to the present embodiment. The sheet-fed printing machine is a four-color printing machine, and the sheet fed from the paper feed unit 1 is single-sided printed. In the printing unit 2 on the upstream side, two-color printing is performed, and by the paper delivery unit including the delivery cylinder 4, the storage cylinder 5, and the reversing cylinder 6 in order from the upstream side, the paper is transferred from the impression cylinder 7 of the upstream printing unit 2 to the downstream side. It is sent to the impression cylinder 8 of the printing unit 3, and further two-color printing is performed in the downstream printing unit 3 to complete a total of four-color printing, and the printing unit 3 is sent to the paper discharge unit 9.

On the other hand, in double-sided printing, two-color printing is performed on one side in the upstream printing unit 2, the paper is transferred to the impression cylinder 8 on the downstream side after being reversed upside down by the paper delivery unit, and then printed on the downstream printing unit 3. The other side is printed in two colors.

The impression cylinders 7 and 8, the transfer cylinder 4 and the reversing cylinder 6 have a perimeter approximately twice the length of the sheet in the paper feeding direction, that is, two sheets are rotated by one rotation. Is a so-called double diameter type (double cylinder), and the storage cylinder 5 is a so-called triple diameter type (triple cylinder) that can wind three sheets in one rotation. is there. Therefore, the transfer cylinder 4 is provided with grippers 10 for gripping the front edge of the sheet at two positions facing each other by approximately 180 degrees, and the storage cylinder 5 is provided with the gripper 11 and the paper suction device 12 respectively at approximately 120 degrees. There are a total of three places every time,
The reversing cylinder 6 is provided with reversing grippers 13 at two positions facing each other by approximately 180 degrees.

As described above, in the sheet-fed printing press, the delivery cylinder 4, the storage cylinder 5, and the reversing cylinder 6 of the paper delivery unit are
The body arrangement of double body, triple body and double body is adopted. Therefore,
Since the curvature of each cylinder is large, the curl amount of the sheet in the wound state is also small, which reduces the load on the sheet and is advantageous for maintaining the print quality and the stability of the sheet alignment at the sheet discharge section. . Also, the grippers 10 and 11 and the reversing gripper 1
Since a plurality of 3 are provided, the load on the individual grippers 10 and the like is reduced. Further, as compared with the case where a so-called single cylinder for winding one sheet of paper with one rotation is adopted as the paper delivery unit, the number of cylinders can be reduced, which is advantageous in terms of cost, and the printing unit 2 A sufficient space can be secured between the two.

On the other hand, each cylinder is provided with a gear on one end side on its axis (coaxial), and the rotation is transmitted by meshing these gears as shown in FIGS. 2 and 3. That is, the gears of each cylinder form a gear train. For example, when the rotational driving force of the motor is transmitted to the gear of the upstream impression cylinder 7, it is transmitted to the downstream impression cylinder 8 via the gear of each cylinder. , Thereby, the impression cylinders 7, 8, the transfer cylinder 4, the storage cylinder 5 and the reversing cylinder 6
All rotate in synchronization.

4 and 5 show the reversing cylinder 6 in FIGS. 2 and 3 in an enlarged manner. Body axis 14 of the reversing body 6
Is rotatably supported by a bearing portion 16 mounted on the frame 15. At one end of the body shaft 14, a gear support shaft portion 17 coaxially with the body shaft 14 is located outside the frame 15.
Is attached by screwing.

The gear support shaft portion 17 has a cylindrical shape with a bottom as a whole, a bottom portion 17a is screwed to one end surface of the body shaft 14, and an annular flange portion 17b is provided on the outer peripheral surface on the bottom portion side. ing. Then, two donut-shaped gears having a through hole in the center are externally attached to the gear support shaft portion 17 in order from the opening side, and the gear on the bottom portion 17a side is fixed to the flange portion 17b by screwing. Is a fixed gear 18, and the gear on the opening side is an adjustment gear 1 rotatably supported by the gear support shaft portion 17.
It is 9. The adjustment gear 19 has a gear support shaft portion so that a predetermined annular gap (for example, about 0.02 mm) is formed between the inner peripheral surface 19a and the outer peripheral surface 17d of the gear support shaft portion 17. 17 is loosely fitted. The fixed gear 18 meshes with the gear 8a of the impression cylinder 8 on the downstream side, and the adjustment gear 19 meshes with the gear 5a of the storage cylinder 5.

Further, a switching mode in which the adjustment gear 19 is supported by the gear support shaft portion 17 so as to be rotatable relative to it and a printing mode in which the adjustment gear 19 is fixed to the gear support shaft portion 17 so as not to be rotatable relative to each other are switchable. It is configured. That is, the gear support shaft portion 17
A donut disk-shaped support plate 20 is attached to the end surface on the opening side by fixing with screws. The supporting plate 20 is provided with a total of six projecting portions 20b radially from the supporting surface 20a on the gear support shaft 17 side to the gear support shaft 17 side at predetermined angles (every 60 degrees). ing. Therefore, each protrusion 20
Between b, gaps corresponding to the protruding height of the protrusion 20b from the support surface 20a are formed at a total of six positions at each predetermined angle. In this gap, the adjustment gear 19 is fixed gear 1
The pressing levers 21 for pressing to the 8 side are provided respectively.
As shown in FIG. 4, the pressing lever 21 has a substantially rectangular shape in a plan view, and is provided so that its longitudinal direction substantially corresponds to the radial direction of the reversing cylinder 6.

A hollow portion 17c of the gear support shaft portion 17 is also provided.
A support rod 22 is mounted coaxially with the body shaft 14 at the center of the support rod 22. The support rod 22 has a cylindrical slide body 23 having flanges at both ends in the axial direction. It is provided so that it can slide in any direction. Between the slide body 23 and the bottom portion 17a of the gear support portion 17, a pressing spring 24 formed by stacking disc springs one by one while inverting them is attached to the support rod 22. The slide body 23 is pressed and biased toward the tip end side of the support rod 22 by the spring 24.

While the base end of the pressing lever 21 is engaged between both flanges of the slide body 23, the clamp projection 21a abutting against the surface of the adjusting gear 19 is provided on the bottom surface of the tip end of the pressing lever 21. Is formed, and the pressing lever 21
A fulcrum projection 21b that abuts the support surface 20a of the support plate 20 is formed on the surface of the middle portion so as to serve as a pivot fulcrum of the pressing lever 21. That is, the fulcrum protrusion 21b
Is located between the clamp protrusion 21a and the base end portion, and the distance from the fulcrum protrusion 21b to the base end portion is several times larger than the distance from the fulcrum protrusion 21b to the clamp protrusion 21a. Is formed in position. Therefore, when the slide body 23 is pressed and biased toward the tip end side of the support rod 22 by the spring force of the pressing spring 24, the biasing force is applied to the pressing lever 21.
Acting on the base end of the lever, its force is amplified by the lever principle according to the ratio of the distance between the base end from the fulcrum protrusion 21b and the clamp protrusion 21a, and the clamp protrusion 21a of the pressing lever 21 is adjusted. 19 is pressed firmly against the fixed gear 18 and clamped. That is, the adjusting gear 19 is pressed and fixed to the fixed gear 18 by the pressing lever 21 at the time of printing, so that the adjustment gear 19 is in a fixed state in which it cannot rotate relative to the gear support shaft portion 17. Therefore, the adjusting gear 19 and the fixed gear 18 rotate integrally due to the frictional force between them, so that the fixed gear 18 is attached to the gear support shaft portion 17, and the gear support shaft portion 17 is attached to the body shaft 14, respectively. Since it is stopped, the rotation is transmitted from the gear 5a of the storage drum 5 to the gear 8a of the pressure drum 8 on the downstream side without loss, and the storage drum 5, the reversing drum 6, and the pressure drum 8 rotate synchronously. .

On the other hand, when switching between single-sided printing and double-sided printing, the surface of the slide body 23 is pressed by the fixing release member 25 and the slide body 23 is slightly slid to the base end side of the support rod 22. When the slide body 23 slides toward the base end side of the support rod 22, one flange portion of the slide body 23 pushes the pressing lever 21 in the opposite direction, whereby the clamping force of the pressing lever 21 on the adjusting gear 19 is released. The adjustment gear 19 is released from the fixed state on the gear support shaft portion 17 and can rotate relative to the gear support shaft portion 17. Therefore, by rotating the adjusting gear 19 relative to the gear support shaft portion 17 to change the phase with the gear support shaft portion 17 (the phase with the fixed gear 18) by a predetermined angle, the storage cylinder 5 and the reversing cylinder 6 are separated. The phase between can be changed.

Further, as shown in FIGS. 4 and 6, the outer peripheral surface 17d of the gear support shaft portion 17d is centered at a height at which the adjusting gear 19 is engaged, as shown in FIGS. A total of six cutouts 26 are formed in the shape of an arc toward the front. Each notch 26 is provided with a roller 27 as a rotation support. The roller 27
Is rotatably supported by the eccentric shaft portion 28 having an axis 28a parallel to the axis of the reversing cylinder 6 so as to contact the inner peripheral surface 19a of the adjusting gear 19 and rotate when switching. That is, as shown in an exaggerated manner in FIG. 7 and FIG.
A part of the reference numeral 7 projects radially outward from the outer peripheral surface 17d of the gear support shaft portion 17, so that the roller 27 causes the adjustment gear 1 to move.
The adjustment gear 19 is supported by these rollers 27 so as to be capable of relative rotation with respect to the gear support shaft portion 17 while being in contact with the inner peripheral surface 19 a of the gear 9.

Further, the position of the roller 27 can be adjusted individually in the radial direction of the reversing cylinder 6, whereby the adjusting gear 1
The configuration is such that the coaxiality with respect to the reversing cylinder 6 of 9 can be adjusted. The details will be described below.

First, the eccentric shaft portion 28 is provided on the adjusting shaft 29 having an axis 29a parallel to the body shaft 14, and the axis 28a of the eccentric shaft portion 28 is eccentric with respect to the axis 29a of the adjusting shaft 29 by a predetermined amount. There is. In this embodiment, the amount of eccentricity is about 0.5 mm. That is, as shown in FIG.
Is a small-diameter engagement portion 29b that is rotatably inserted into an engagement hole 30 of the gear support shaft portion 17 in order from the bottom 17a side of the gear support shaft portion 17, and an eccentric shaft portion 28 that is larger in diameter than the engagement portion 29b.
And a main portion 29c having a diameter larger than that of the eccentric shaft portion 28 and coaxial with the engaging portion 29b.
Also, the support plate 20 is penetrated, and the tip portion thereof is exposed from the support plate 20. A hexagonal hole 29d is provided at the tip portion, and the hexagonal bar wrench 31 is engaged with the hexagonal hole 29d to rotate the adjustment shaft 29. Also,
As shown in FIG. 7, a lateral hole 32 is formed in the support plate 20,
A fixing screw 33 is screwed to the tip of the adjusting shaft 29, and the adjusting screw 29 is screwed toward the adjusting shaft 29 side with a hexagonal wrench 34 or the like, whereby the adjusting shaft 29 can be stopped from rotating and fixed. When loosened, the adjustment shaft 29 can be rotated.

By rotating the adjusting shaft 29 in this manner, the axis 28a of the eccentric shaft 28 draws a circular locus around the axis 29a of the adjusting shaft 29, and the eccentric shaft 28 is rotated.
The roller 27, which is pivotally supported, also eccentrically moves. Therefore, the position of the roller 27 can be freely adjusted in the radial direction of the reversing cylinder 6 about the axis 29a of the adjustment shaft 29, and the protrusion of the roller 27 from the outer peripheral surface 17d of the gear support shaft portion 17 can be performed by the position adjustment. The amount can be varied. By performing this adjustment with each roller 27, the reversing cylinder 6 of the adjusting gear 19
The coaxiality with respect to can be adjusted to obtain a high coaxiality.

Therefore, the adjusting gear 19 and the gear support shaft portion 17
Even if the accuracy of each component is somewhat poor, it can be corrected by this coaxiality adjustment, and the unit price of the component can be reduced together with the yield improvement effect.

Moreover, once the coaxiality is adjusted, the fixing screw 33 is tightened in that state to fix the adjusting shaft 29 and maintain the position of the roller 27, so that the adjusting gear 19 is relatively rotated at the time of switching. The coaxiality does not change. Therefore, even if the switching is repeated, it is possible to always obtain a constant and high registration accuracy. Further, unlike the conventional case, it is substantially unnecessary to re-register each time switching is performed, the work load on the user can be significantly reduced, and the time required for switching can be shortened. Further, even if the registration is performed according to the switching, it can be performed in a shorter time and with less labor.

The above is the same even when the reversing cylinder 6 is a single cylinder, but as in the present embodiment, the reversing cylinder 6 and the reversing gripper 13 are provided.
When a plurality of are provided, the effect is particularly great.

That is, in the conventional configuration, if the reversing gripper is a single cylinder, it is possible to obtain the required accuracy by re-registering each time switching, but the reversing grippers are provided at a plurality of positions. However, if the registration is made based on the sheet gripped by one reversing gripper, the registration of the sheets gripped by the other reversing gripper will be adversely affected. It is not possible to accurately adjust the register of. The cause lies in the accuracy of the coaxiality of the adjusting gear with respect to the reversing cylinder.

On the other hand, if the above configuration is adopted, the coaxiality of the adjusting gear 19 with respect to the reversing cylinder 6 can be set with high accuracy by adjustment, so that the misregistration of each sheet gripped by each reversing gripper 13 can be adjusted. As a result, high register accuracy can be secured.

Further, in this embodiment, since the eccentric state of the roller 27 is changed by the rotation operation of the adjusting shaft 29, the protrusion amount of the roller 27 from the outer peripheral surface 17d of the gear support shaft portion 17 is adjusted. Since the coaxiality adjustment work is extremely simple and the position of the roller 27 can be easily finely adjusted, the coaxiality can be adjusted with high accuracy.

Further, by using the roller 27, the rotational load of the adjusting gear 19 at the time of switching is small and the position adjusting mechanism can be simplified. The rollers 27 are arranged at one of three positions.
The 20-degree uniform arrangement is preferable from the viewpoint of ease of adjustment and ensuring accuracy, and as in the present embodiment, by providing twice as many locations, more delicate adjustment becomes possible and higher precision adjustment is possible. However, the arrangement and the number of the rollers 27 are not limited, and the position adjusting mechanism of the roller 27 can be appropriately designed and changed. Also,
A configuration other than the roller 27 can be adopted as the rotation support, and the rotation load becomes larger than that of the rotation support, but the rotation support simply contacts the inner peripheral surface 19a and is switched to the inner peripheral surface 19a at the time of switching. It is also possible to use a sliding support.

The position adjusting mechanism of the roller 27 can also adopt various structures. For example, as shown in FIG. 9, a total of six support bases 41 including the rollers 27 supported by the support shaft 40 may be provided, and the entire support bases 41 may be moved in the radial direction. That is, at the time of adjustment, the screw 42 that fixes the support base 41 to the rotation support shaft portion 17 is loosened, and the pressing screw 43 that abuts the rear surface of the support base 41 is pushed or retracted by the hexagonal spanner 44 or the like. By doing so, the support base 41 can be moved back and forth in the radial direction, and when the adjustment is completed, the screw 42 can be tightened to firmly maintain the adjusted state.

Further, the shape and configuration of the gear support shaft portion 17 are not limited to the above configuration, and a plurality of supports whose positions can be adjusted in the radial direction are provided, and the adjustment gear 1 is provided through the supports.
Any configuration may be used as long as it rotatably supports 9. In the above description, the configuration of the entire sheet-fed printing press has been described, but the same effects can be obtained with a single paper delivery unit that employs the above configuration and a single reversing cylinder that employs the above configuration.

[0035]

As described above, since the adjustment gear is supported by the support so as to be relatively rotatable and the position of the support is adjusted to adjust the coaxiality of the adjustment gear with respect to the reversing cylinder, the register accuracy is improved. The accuracy can be improved as compared with the conventional one, and the registration work for each switching is substantially unnecessary.

[Brief description of drawings]

FIG. 1 is a front view schematically showing a sheet-fed printing press according to an embodiment of the present invention.

FIG. 2 is a schematic explanatory view showing a gear train of the same sheet-fed printing press when viewed from the back side.

FIG. 3 is a schematic explanatory view showing the gear train in plan view.

FIG. 4 is a schematic explanatory view of a reversing cylinder of the sheet-fed printing press as seen in an axial direction.

5 is a cross-sectional view taken along the line AA of FIG.

6 is a sectional view taken along line BB of FIG.

FIG. 7 is an enlarged view of a main part of FIG.

8 is a cross-sectional view taken along line CC of FIG.

FIG. 9 is an enlarged cross-sectional view of a main part of a sheet-fed printing press according to another embodiment.

FIG. 10 is a schematic explanatory diagram of a paper delivery unit of a conventional sheet-fed printing press.

FIG. 11 is a schematic sectional view of a reversing cylinder of a conventional sheet-fed printing press as seen from a plane.

[Explanation of symbols]

2, 3 ... Printing unit, 5 ... Storage cylinder, 5a ... Gear, 6 ...
Inversion cylinder, 17 ... Gear support shaft portion, 18 ... Fixed gear, 19 ... Adjustment gear, 19a ... Inner peripheral surface, 27 ... Roller, 28 ... Eccentric shaft portion, 28a, 29a ... Axis line, 29 ... Adjustment shaft

Claims (3)

(57) [Claims] 1. A storage cylinder (5) of a paper delivery unit for delivering sheets from an upstream printing unit (2) to a downstream printing unit (3) and a reversing cylinder (6) downstream thereof. Rotate synchronously when the gear (5a) mounted on the storage cylinder (5) meshes with the adjustment gear (19) mounted on the reversing cylinder (6), and double-sided printing is performed on the reversing cylinder (6). In order to change the phases of the storage cylinder (5) and the reversing cylinder (6) when switching between the single-sided printing and the single-sided printing, a gear support shaft portion (17) for rotatably supporting the adjustment gear (19) is provided. At times, the adjusting gear (19) is fixed to the gear support shaft portion (17) so as not to rotate relative to it, and at the time of the switching, the adjusting gear (19).
In a sheet-fed printing press capable of switching between double-sided printing and single-sided printing, in which the fixing state of the adjustment gear (19) with respect to the gear support shaft portion (17) is released The gear support shaft portion (17) includes a plurality of supports that come into contact with the inner peripheral surface (19a) of the adjustment gear (19), and the adjustment gear (19) is supported by the supports so as to be rotatable relative to each other. Double-sided printing and single-sided printing, characterized in that the position of the support is adjustable in the radial direction of the reversing cylinder (6) so that the coaxiality of the gear (19) with respect to the reversing cylinder (6) can be adjusted. Switchable sheet-fed printing press. 2. The sheet capable of switching between double-sided printing and single-sided printing according to claim 1, wherein the support is a rotatable support that is rotatable by contacting an inner peripheral surface (19a) of the adjusting gear (19). Printer. 3. The gear support shaft portion (17) comprises an adjusting shaft (29) having an axis (29a) parallel to the axis of the reversing cylinder (6), the adjusting shaft (29) being the adjusting shaft (29). Is rotatable about an axis (29a) of the adjustment shaft (29a), and the adjustment shaft (29) is provided with an eccentric shaft portion (28) having an axis (28a) eccentric from the axis (29a) of the adjustment shaft (29). The rotary support is a roller (27) axially supported by an eccentric shaft portion (28), and the position of the roller (27) can be adjusted by rotating an adjustment shaft (29). Sheet-fed printing machine that can switch between double-sided printing and single-sided printing.