JPH03128247A - Lithographic press - Google Patents

Abstract

PURPOSE: To suppress rubbing of an ink pattern to a minimum by disposing an outer surface of a blanket in a roll engaging state with a transfer surface of a plate cylinder at a nip, and performing rolling engagement of an outer circumferential surface of the blanket continuously without nip between an ink transfer surface and the blanket on the cylinder. CONSTITUTION: A blanket 18 has a continuous cylindrical outer surface 40 without gap. Accordingly, a rolling engagement of the blanket 18 with a cylindrical outer surface 42 of a printing plate on a plate cylinder 22. Further, the blanket 18 is manufactured compressibly by a nip 26 to prevent rubbing of an ink pattern.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an offset printing machine.

BACKGROUND OF THE INVENTION During operation of an offset printing press, an ink pattern is applied to sheet material by a blanket on a blanket cylinder. This pattern is applied to the blanket by a plate cylinder. During machine operation, the presence of vibrations in either the plate cylinder or the blanket cylinder invariably promotes rubbing of the ink pattern, which adversely affects print quality. Known blanket cylinders have an axially extending gap in which the ends of the blanket are supported. When the blanket cylinder gap is located at the nip between the plate cylinder and the blanket cylinder, vibrations tend to be induced into the cylinder flesh, and these vibrations adversely affect print quality and disrupt the ink pattern. This will encourage rubbing.

Ink pattern scuffing is also facilitated by slippage between surfaces at the nip where the ink pattern is transferred to the blanket. That is, if the velocity of the blanket surface is greater or less than the velocity of the surface transferring the ink pattern to the blanket, the surfaces will slip relative to each other, which can cause ink pattern rubbing. Become.

OBJECTS AND SUMMARY OF THE INVENTION The object of the invention is to improve the quality of the prints obtained with offset printing presses by eliminating or at least minimizing smearing of the ink pattern. Offset printing machines have a blanket cylinder with a blanket that applies an ink pattern to the sheet material. An ink transfer surface on the plate cylinder applies the ink pattern to the blanket.

The ink transfer surface on the plate cylinder and the blanket are arranged in rolling engagement at a nip formed between the plate cylinder and the blanket cylinder.

SUMMARY OF THE INVENTION According to the invention, the blanket has a tubular shape;
It has continuous outer and inner surfaces with no gaps. The blanket is movably mounted on the outer circumferential surface of the blanket cylinder. The outer surface of the blanket is disposed in rolling engagement with the transfer surface on the plate cylinder at a nip formed therebetween. The outer circumferential surface of the blanket is continuous and gap-free, with no gap between the ink transfer surface on the plate cylinder and the blanket.
A smooth, vibration-free rolling engagement is provided so that the transfer of the ink pattern to the blanket occurs without rubbing of the ink pattern.

The blanket is at least partially formed from a compressible material that is compressed by the plate cylinder at a nip between the plate cylinder and the blanket cylinder. Compressing the compressible material at the nip causes the outer surface of the blanket to have essentially identical surface velocities just before the nip, at the nip, and at the positions just after the nip. This prevents slippage between the surface of the printing plate and the blanket before the nip, at the nip, and after the nip, and prevents rubbing of the ink pattern.

The tubular blanket has an inner layer of rigid material, an outer cylindrical layer of incompressible material, and a cylindrical layer of compressible material. The outer layer of the blanket is deflectable such that the compressible layer of the blanket can be compressed. The compressible layer of the blanket has a number of voids that are relatively large before the compressible layer is compressed and are compressed by the deflection of the outer layer of the blanket at the nip. Within the portion of the compressible layer that is inside, it is relatively small.

The rigid inner layer material is tensioned by the blanket cylinder, creating a high pressure relationship between the blanket and the blanket cylinder. This pressure relationship secures the blanket onto the blanket cylinder so that there is no relative movement between them during operation of the printing press. The printing press has means for influencing the radial expansion of the tubular blanket, while above the blanket cylinder it has means for breaking the pressure relationship between the blanket and the blanket cylinder. There is. Once the pressure relationship is removed, the blanket can be manually moved so that it can be moved axially away from the blanket cylinder. In other words, the blanket is
In order for the blanket to be able to move axially on the blanket cylinder, it must be inflated and placed radially outward (radially tensioned). Printing machines are equipped with structures to perform this function.

In an advantageous embodiment, a passageway is provided at one end of the blanket cylinder to enable axial movement of the blanket over and away from the blanket cylinder. A portion of the frame adjacent one axial end is movable out of the way. The tubular blanket is axially movable through an opening in the frame, the opening being provided so that movement of the frame portions is unobstructed.

Air pressure must be available within the torso to inflate the blanket so that it can be positioned over the torso. A passageway to the outer circumferential surface of the blanket cylinder communicates with the interior of the blanket cylinder. That is, air pressure applied to the interior of the blanket cylinder is communicated to the interior of the blanket so that the blanket similarly expands as it is inserted onto the blanket cylinder.

After the blanket is positioned over the outer circumference of the blanket cylinder, air pressure is removed. Next, the blanket is
It contacts and firmly engages around the blanket cylinder, and firmly fixes the cylinder over an axial region of the blanket and a circumferential region of the inner surface of the blanket. This pressure relationship between the blanket and the blanket cylinder is broken by reapplying air pressure to the interior of the blanket cylinder, thereby allowing the blanket to be manually removed from the cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be embodied in many different configurations and applied to many different offset printing machines. By way of example, the drawings show the invention as applied to an improved printing press 10 for offset lithography.

Lithographic printing press 10 prints both sides of web 12 of sheet material. The lithographic printing press 1o has identical upper and lower blanket cylinders 14 and 16. blanket 1
8 and 2o are mounted on the blanket cylinders 14 and 16 and apply an ink pattern to both sides of the web 12. Upper and lower plate cylinders 22 and 24 support printing plates that are disposed in rolling engagement with blankets 18 and 20 at nips 26 and 28. The ink pattern is formed on plate cylinders 22 and 2 at nips 26 and 28.
It is applied to blankets 18 and 2o by a printing plate on 4. These ink patterns are printed on blanket 18
and 2o are sequentially applied to both sides of the web 12.

The printing press 10 has upper and lower dampening devices 30, 32 which supply dampening liquid to the plate cylinders 22 and 2.
It is coated on the printing plate above 4. Additionally, upper and lower inking units 34 and 36 apply ink to the printing plates on plate cylinders 22 and 24. The drive device is designated by reference numeral 3 in Figure 1.
As shown schematically at 8, blanket cylinders 14 and 16 and plate cylinders 22 and 24 are operable to rotate at the same surface speed. This drive 38 also provides power for driving the dampening devices 30 and 32 and the inking devices 34 and 36. This indicates that the printing press 10 may have a different structure than that shown. For example, the printing press 10 may be configured to print only one side of the web 12.

To prevent rubbing of the ink pattern, blanket 18 has a continuous cylindrical outer surface with no gaps. By forming the blanket 18 with a continuous outer surface without gaps, the rolling engagement between the blanket and the printing plate on the plate cylinder 22 is smooth and relatively vibration free. There is a tendency. Furthermore, by making the blanket 18 compressible at the nip portion 26, it is possible to prevent the ink pattern from being rubbed. Due to this, the blanket 18 is placed just before the nip portion.
It now has exactly the same surface velocity as the printing plate on plate cylinder 22 at the nip and immediately after the nip, reducing slip between the outer surface of blanket 18 and the outer surface of the printing plate on plate cylinder 22. be able to prevent it.

The cylindrical outer surface 40 of the blanket 18 is continuous and gap-free to promote smooth transfer alignment with the cylindrical outer surface 42 of the printing plate on the plate cylinder 22. The absence of gaps in the smooth cylindrical outer surface 40 of blanket 18 prevents collisions or vibrations compared to the presence of gaps. The gap shifts in and out of engagement with the surface 42 of the printing plate on the plate cylinder 22. By preventing this collision or vibration, ink pattern rubbing is minimized. Also, the ink pattern is formed on the blanket 1 by the printing plate on the plate cylinder 22.
When applied onto surface 40 of 8, scuffing is similarly minimized.

By attaching the blanket 18 to the continuous and gap-free cylindrical outer surface 40, the blanket 1
8 and the diameter of the blanket cylinder 14 can be minimized. The ink pattern is thus applied onto the blanket surface 40 over the entire area of the surface 40. This allows the ink pattern to extend beyond the areas where gaps were formed in the surface of previously known blanket cylinders.

Furthermore, a continuous and gap-free cylindrical outer surface 4
Providing blanket 18 at zero reduces the amount of web that is discarded during press operation. In one embodiment of the invention, for each revolution of the blanket cylinder, approximately 0
．． 25 inch web can be saved.

Blanket 18 is formed at least partially of a compressible material. When a force is applied to the compressible material of blanket 18, the volume of the compressible material decreases. The material of blanket 18 is compressed by rigid plate cylinder 22 at nip 26 . Blanket 18 is at least partially formed of a compressible material such that it deforms radially inwardly, thereby causing nip 26 to deform.
There is no radial outward deformation of the blanket at all.

Because the blanket 18 is formed at least in part from a compressible material, the surface velocity of the blanket is such that the surface velocity of the blanket is equal to or lower than the nip 26 between the blanket cylinder 18 and the plate cylinder 22, at the nip, and immediately after the nip. is exactly the same at all positions. Since the velocity of a point on the surface 40 of the blanket is the same on both sides of the nip 26 and in the center of the nip, the speed between the surface 40 of the blanket cylinder and the surface 42 of the printing plate on the plate cylinder 22 is the same. There is no slip in between.

This prevents the ink pattern from rubbing. Furthermore, when the ink pattern is applied to the blanket 18 by the printing plate on the plate cylinder 22, rubbing is similarly prevented.

If the blanket 18 is formed of an incompressible material, such as blanket 18a of FIG. 2, the incompressible blanket material deflects radially outwardly and The blanket is deformed laterally in the circumferential direction in the nip 26 by the pressure exerted against the blanket by the printing plate on the plate cylinder 22a in the manner shown schematically in the figure. 18
The incompressible material of a deflects due to deflection of the blanket at nip 26a, forming bulges 46a and 48a on opposite sides of nip 26a.

The bulges 46a and 48a (FIG. 2) are shaped as follows.
This is because even if the incompressible material flexes at the nip 26, the volume of the incompressible material forming the blanket 18a remains constant. The volume of material displaced by the printing plate on plate cylinder 22a is therefore equal to the volume of material in bulges 46a and 48a.

The volume of material deflected by the printing plate on plate cylinder 22a is equal to or smaller than the cylindrical outer side surface 4 of blanket 18a.
0a and the cylindrical outer side surface 42a of the printing plate on the plate cylinder 22a. This volume of material is defined by the arcuate plane illustrated by dashed line 50a in FIG.
a and the arched outer side surface 42a of the printing plate and extends over the entire axial area of the plate cylinder and the plant cylinder.

The velocity of a point on the surface of the incompressible material of blanket 18a (FIG. 2) changes as the point moves from one side of nip 26a to the opposite side of the nip. That is, as the material in the bulge 46a moves into the nip 6a, the material is accelerated and the surface velocity of the material increases. As the incompressible material moves out of nip 26a and into bulge 48a, the material is decelerated and the surface velocity decreases.

In the given example, point 52a on the surface of bulge 46a is moving at a slower speed than point 54a at the center of nip 26a. Similarly, point 5 on the surface of the bulge 48a
6a is moving at a slower speed than point 54a at the center of nip 26a. Blanket 18 at the bulges 46a and 48a and the center of the nip 26a
The magnitude of the difference in surface velocity of the incompressible material in a is the number of strokes of the amount of deflection of the incompressible material of the blanket cylinder at the nip.

As the surface velocity of the incompressible blanket cylinder moving through the nip 26a (FIG. 2) first increases and then decreases, the rubbing slip of the ink pattern is transferred to the outer side surface 40a of the blanket 18a. and the outer side surface 42a of the printing plate on plate cylinder 22a. In other words,
At a position away from the nip portion 26a, the blanket 18
The surface 40a of a and the surface 42a of the printing plate on the plate cylinder 22a have the same speed.

However, as a point on surface 40a moves onto bulge 46a during counterclockwise rotation (as seen in FIG. 2) of blanket 18a, the velocity of the point on the surface of the blanket increases. The surface speed is reduced to less than the surface speed of the printing plate on cylinder 22a.

A point on the surface 40a of the blanket 18a is the bulge 46
a (FIG. 2) toward the center of nip 26a, the dot velocity increases to a velocity greater than the surface velocity of the printing plate on plate cylinder 22a. blanket 18
While a continues to rotate, the velocity of the point decreases as the point moves from the center of nip 26a to a point on bulge 48a. The velocity of a point on the surface of the bulge 48a is smaller than the surface velocity of the printing plate on the plate cylinder 22a.

It should be understood that blanket 18 of FIG. 1 is not of the same construction as blanket 18a of FIG. 2. That is, plunget 1.8a in FIG. 2 is formed from an incompressible material. Blanket 18 in Figure 1
is at least partially formed from a compressible material. The blanket 18 of FIG. 1 is therefore not deformed in the manner as schematically illustrated in FIG.

Blanket 18 has a hollow tubular structure. The tubular blanket 18 is fixedly connected to the blanket cylinder 14 and rotates therewith under the action of a drive 38, however, the tubular blanket 18 is removed from the blanket cylinder 14 and will now be described. It can be rearranged as desired.

Although the tubular blanket 18 can have a variety of different structures, in the particular embodiment of the invention illustrated herein, the blanket 18 has a layered structure. Thus, the blanket 18 has a cylindrical outer layer 66 (FIG. 3) upon which the smooth cylindrical side surface 40 of the blanket is disposed. The cylindrical outer layer 66 is made of resiliently deflectable material, such as natural or synthetic rubber, for example.
and is made of an incompressible polymeric material.

The second or middle cylindrical layer 68 (FIG. 3) is the outer layer 66.
located radially inside. Intermediate layer 68 has a cylindrical outer side surface 70, which surface 70
It is fixedly supported on the cylindrical inner side surface 72 of G. According to one of the features of the invention, the cylindrical intermediate layer 68 consists of a resilient compressible polymeric material, such as natural or synthetic rubber.

The cylindrical third layer 74 is disposed radially inward of the second layer 68 . The third layer 74 has a cylindrical outer side surface 7
6, the surface 76 engages and is fixedly coupled to the cylindrical inner side surface 78 of the second layer 68. Although the third layer 74 may be formed from a variety of materials, in the illustrated embodiment of the invention, the third layer 74 is formed from the same incompressible material as the outer layer 66.

The third layer 74 is fixedly supported in a hollow, rigid metal inner layer that includes an assembly sleeve 80 that is fixedly connected to the blanket cylinder 14. Third layer 74
A cylindrical inner side surface 82 of the sleeve 80 is fixedly supported on a cylindrical outer side surface 84 of the sleeve 80 . The cylindrical inner side surface 86 of the sleeve 80 extends over the blanket body 1.
The cylindrical outer side surface 100 of 4 is engaged. Sleeve 80 is constructed of nickel in the illustrated embodiment of the invention and is releasably and permanently connected to blanket cylinder 14. All blankets 18 are
It is capable of sliding axially over and/or off the rigid metal blanket cylinder 14 (FIG. 1). This construction allows the blanket 18 to be repositioned after a period of use.

A tensile stress is applied to the sleeve 80 by the blanket cylinder 14, and the blanket 18 and the blanket cylinder 1
There is a strong pressure relationship between the two countries. This pressure relationship secures blanket 18 on blanket cylinder 14 and prevents relative movement between them during operation of the printing press. The printing press has means for causing a radial expansion of the tubular blanket while creating a pressure relationship on the blanket cylinder between the blanket 18 and the blanket cylinder 14 as described below. There are ways to release it. When the pressure relationship is released, blanket 18 becomes blanket I! 1l1
14 for manual movement in the axial direction.

That is, the sleeve 80 must be expandable radially, or radially under tension, outwardly to allow the blanket 18 to move over the blanket cylinder 14. The printing press is provided with means for performing this function, as described below.

Tubular blanket 18 includes a first layer 66 and a third layer 74 formed from an incompressible material, as previously described.
Although the second layer 68 is formed from a compressible material, the tubular blankerato 18 can have more or fewer layers if desired. For example, a further layer of compressible material may be provided. This additional layer of compressible material can be placed directly adjacent layer 68 and can be formed with a stiffness that is either greater or less than that of layer 68. It is possible.

If the plate cylinder 22 and the blanket cylinder 18 are located apart from each other before starting the printing operation, i.e. the printing press 1
0 is in the released condition, the tubular blanket 18 is in the unconstrained or original condition of FIG. The coaxial layers 66, 68 and 74 now have a cylindrical contour.

When the printing operation begins, the blanket 18 and plate cylinder 22
and the upper printing plate come into engagement with each other in the manner shown in FIG. As the blanket 18 and the printing plate on the plate cylinder 22 engage each other, the outer layer 66 of the blanket
is resiliently deflected inward in the radial direction at the nip portion 26. The distance that outer layer 66 deflects radially inwardly is such that the initial spatial extension of cylindrical outer side surface 40 of blanket 18 is on the outer side of the printing plate on plate cylinder 22. It is determined by its amount of overlap with the cylindrical spatial extension of the surface 42. That is, the outer side surface 40 of the outer layer 66 is oriented radially inwardly and is deflected from the position shown in dashed lines 88 in FIG. 4 to the position shown in solid lines.

The cylindrical outer layer 66 is formed from an incompressible material. When the outer layer 66 is deflected radially inwardly, the volume surrounded by the outer layer surface 40 is defined by the dashed line 88 and
The volume trapped in the space between the deflected outer layer 66 and the side surface 40 is reduced. Since the outer layer 66 is formed from an incompressible material, the volume of the outer layer body does not change and the outer layer is resiliently compressed by the plate cylinder 22 in the manner shown in FIG. It will be deflected by.

According to one feature of the invention, inner layer 68 of blanket 18 is formed from a compressible material. outer layer 66
is deflected by the printing plate of the plate cylinder 22, the inner layer 6
8 is elastically compressed. That is, the volume of the space occupied by the second layer 68 changes from an initial volume or uncompressed volume (FIG. 3) to a second volume or compressed volume (FIG. 4) that is smaller than the original volume. Decrease.

Since the second layer 68 is compressed by the printing plate on the plate cylinder 22, the outer layer 66 is radially oriented on both sides of the nip 26 without bulging, in a manner similar to that shown in FIG. and bend inward. That is, the outer layer 6 of the blanket 18
6 is deflected by the printing plate on the plate cylinder 22 (the fourth
), bulges corresponding to bulges 46a and 48a of FIG. 2 are not formed in outer layer 66.

This is because the inner layer 68 is compressed by an amount sufficient to accommodate the deflected material of the outer layer 66.

As the inner layer 68 is compressed and the bulge in the outer layer 66 is lost, the velocities at locations on the surface 40 of the outer layer are: just before the nip 26, at the center of the nip, and at the nip. is essentially the same as the surface velocity of the printing plate on plate cylinder 22 immediately after. That is, there is a smooth rolling engagement between the blanket 18 in the nip 26 and the printing plate on the plate cylinder 22, and no slippage occurs between the surfaces 40 and 42. This clearly facilitates the transfer of the ink pattern from the printing plate on the plate cylinder 22 to the blanket 18 without rubbing the pattern.

The compressible second or inner layer 68 is formed from a resilient foam containing voids. When outer layer 66 is deflected and inner layer 68 is compressed (FIG. 4), the voids are reduced in size or eliminated. As the void space within the polymeric foam forming the second layer 68 is compressed, the volume of the compressible material forming the second layer decreases.

Before outer layer 66 of blanket 18 flexes and inner layer 68
Before being compressed (FIG. 3), tubular blanket 18 and blanket body 14 occupy a relatively large first volume surrounded by continuous cylindrical outer surface 40 of outer layer 66. . The cylindrical intermediate layer 68 then contains a relatively large cavity and occupies a relatively large first or initial volume.

Upon engagement of blanket 18 and the printing plate on plate cylinder 22 (FIG. 4), outer layer 66 of blanket 18 deflects radially inwardly. The deflection of the tubular outer layer 66 causes the blanket 18 to occupy a smaller volume than its original volume or volume prior to deflection. However, the outer layer 66
remains constant and the outer layer does not bulge outwardly adjacent the sides of nip 26 in the form of blanket 18a shown in FIG.

As outer layer 66 flexes, inner layer 68 of blanket 18 is compressed to a smaller volume than the original volume of layer 68. The initial volume of the second layer 68 (FIG. 3) and the second layer 68
The difference between the compressed volume of (FIG. 4) is equal to the volume between dashed line 88 in FIG. 4 and the outer side surface 40 of outer layer 66. That is, a reduction in the spatial volume occupied by the blanket 18 is accommodated by the compression of the second layer 68, and the deflection of the outer layer 66 only takes place radially inward.

Blanket 18 may have a different construction than the specific construction shown in FIGS. 3 and 4. For example, each layer of flexible fibrous material or non-stretchable material
and 74 or within them.

The number of layers may be increased or decreased. Advantageously, the compressible second layer 68 is formed from a polymeric foam with a -like stiffness, but the second layer also comprises a void-filled foam with a different stiffness. Even if it is constructed with a cylindrical inner part and an outer part. Compressible inner layer 68 may also be formed from materials other than foam, such as resiliently flexible mesh or fibrous materials.

Blanket 18 is formed onto the cylindrical outer side surface 84 of metal sleeve 80 by spray adhesive. The preformed length of material is then wrapped in layers around the sleeve. The elongated material includes elongated lengths of outer layer 66 non-compressible material, second layer 68 compressible material, and third layer 74 non-compressible material. A length of rubber material is then flowed and formed into a solid body surrounding the metal sleeve 80. Alternatively, the blanket may be made of a smooth flat plate material which is subsequently wrapped around the sleeve 80 and adhered thereto. Both ends of the piece of material should abut each other.

Although only the structure of blanket 18 is shown in FIGS. 3 and 4, blanket 20 has exactly the same structure as blanket 18. That is, blanket 20 cooperates with the printing plate on plate cylinder 24 at nip 28 in the same manner that blanket 18 cooperates with the printing plate on plate cylinder 22 at nip 26.

As already pointed out, the tubular blanket 18 can be installed in a plug-in manner and removed from the blanket cylinder 14 while it remains in the printing press 1o. A passage is provided at one axial end of the blanket cylinder, advantageously a side frame 96 of the printing press 10 movable between an open and a closed position.
It has a portion 94. When the side frame portion 94 is in the closed condition, the portion 94 is connected to the blanket cylinder 14.
It engages a bearing device 98 that supports one end of the.

Remove the blanket 18 from the blanket body 14,
And when it is desired to replace it with another blanket, the frame section 94 transitions from the closed condition to the open condition shown in FIG. An opening 102 is provided in the frame 96 through which the blanket 18 can be moved. In the embodiment of the invention illustrated schematically in FIG. It is assembled so that it can pivot around an axis. However, if desired, the movable portion 94 may be assembled differently.

When movable portion 94 is rotated to the open position of FIG. 5, the end of blanket cylinder 14 opposite side frame 96 supports the entire weight of the blanket cylinder. In order to be able to support the blanket cylinder at only one end, a relatively strong bearing arrangement must be incorporated into the opposite side frame, or the end of the blanket cylinder 14 opposite the side frame 96 can be supported. A counterweight must be attached to the section.

When the movable portion 94 of the side frame 96 is moved to the fifth open condition, the blanket 18 may be manually removed axially from the blanket cylinder 14 through the opening 102.

The new blanket 18 is then replaced by blanket 1141
4 and slid over the blanket cylinder. When a new blanket 18 is placed on the blanket cylinder 14, the movable part 9 of the side frame
4 is returned to the closed state and engages the bearing arrangement 98 to support the blanket cylinder for rotation about its horizontal central axis.

Instead of having a movable part of the frame for removal of the blanket, it is also possible to remove the blanket cylinder completely from the printing press by means of a crane and replace the blanket at a location remote from the printing press. Alternatively, the blanket body may be hinged at one end so that the blanket body can be supported in a position such that the blanket can be removed from the blanket body.

Blanket 18 and blanket cylinder 14 have a metal-to-metal interference fit between an inner cylindrical metal sleeve 80 (FIG. 3) of blanket 18 and an outer peripheral surface of metal blanket cylinder 14. are doing. That is, the outer side surface 86 (FIG. 3) of the cylindrical sleeve 80 has a diameter slightly smaller than the diameter of the cylindrical surface 100 on the outer side of the metal blanket cylinder 14. . sleeve 80
The size of the interference between the blanket cylinder 14 and the blanket cylinder 14 is large enough to firmly grip the outer circumference of the blanket cylinder so that the blanket 18 does not slip against the blanket cylinder during operation of the printing press 10. Must.

To enable the blanket 18 to be manually slid over the blanket cylinder 14, the blanket 18 is filled with a fluid,
It expands elastically due to pressure. That is, the blanket cylinder 14 is provided with a radially extending passageway 106 (FIG. 3). The radially extending passageway 106 is
They are equally spaced apart in a number of radial planes extending through the blanket cylinder 14 over the length of the blanket cylinder.

Blanket cylinder 14 is hollow and connected under pressure to a source of fluid (air) by conduit 110 (FIG. 5).

Air pressure directed into the interior of blanket cylinder 14 through conduit 110 flows outwardly through passageway 106 (FIG. 3) and presses against interior side surface 86 of metal sleeve 80. The air pressure elastically expands the metal sleeve 80 in the circumferential direction, the expansion position being such that the blanket 18 can be manually slid onto the blanket cylinder 14 with little difficulty.

Once the blanket 18 is properly axially positioned on the blanket 14, the interior of the blanket cylinder 14 is open to the atmosphere. Sleeve 80 and blanket 18 then come into contact to ensure that the outer surface 100 of blanket cylinder 14 is captured. Sleeve 80 is then held under tension by blanket cylinder 14. In one particular embodiment of blanket 18, approximately 60 psi of air pressure is required to accomplish inflation of sleeve 80. Of course, the amount of air pressure required to achieve the desired elastic expansion of sleeve 80 will depend on the radial thickness of sleeve 80, the material of construction of the sleeve, and the interference between the sleeve and blanket body 14. It changes as the number of strokes.

It is an object of the present invention to improve the quality of prints obtained from offset printing presses by eliminating or minimizing smearing of the ink pattern applied by the printing press 10 to the sheet material 12. The printing machine has a blanket cylinder 14 supporting blankets 1-8, which apply an ink pattern to the sheet material. An ink transfer surface on plate cylinder 22 applies an ink pattern to blanket 18. The ink transfer surface and the blanket are the nip 2 formed between the two cylinders.
6 and are arranged in rolling engagement.

Blanket 18 has an axially extending, gapless outer circumferential surface 40. Blanket 18 is
The outer circumferential surface 10 of the blanket cylinder 14 is in the shape of a tube having a continuous outer surface 40 and an inner surface 86.
0. The outer surface 40 of the tube is positioned for transfer locking with the ink transfer surface on the plate cylinder 22 at the nip 26. The outer circumferential surface 40 of the blanket 18 is continuous and gap-free, thereby achieving a smooth, vibration-free rolling engagement between the ink transfer surface of the plate cylinder and the blanket. Therefore, the transfer of the ink pattern onto the blanket is facilitated without rubbing the ink pattern.

Blanket 18 is at least partially formed from a compressible material that is compressed by the printing plate at nip 26. Compressing the compressible material at the nip 26 causes the outer surface 40 of the blanket 18 to have essentially the same surface velocity immediately before the nip 26, at the nip and immediately after the nip. Become. This prevents slippage between the ink transfer surface of the plate cylinder and the blanket before the nip, at the nip, and after the nip, and prevents rubbing of the ink pattern.

Blanket 18 is a tube with an outer cylindrical layer 66 of non-compressible material and an inner cylindrical layer 68 of compressible material. The outer layer 66 of the blanket 18 is flexible to compress the inner layer 68 of the blanket. The inner layer 68 of the blanket has a number of voids which are relatively large before the inner layer of the blanket is compressed and which are compressed by the deflection of the outer layer of the blanket. It is relatively small within the square layer.

Blanket 18 is manually slid over blanket cylinder 14 from its axial end. Blanket body 1
4, advantageously the part of the frame adjacent to the axial end of the blanket cylinder must be able to be moved out of the way. Tubular blanket 18 is inserted axially through frame 96 over blanket cylinder 14 in alignment with the blanket.

Air pressure can be applied to the interior of the cylinder to facilitate insertion of the blanket 18 onto the blanket cylinder 14. A passage 106 to the outer circumferential surface 100 of the blanket cylinder 14 communicates with the interior of the blanket cylinder. That is, air pressure applied to the interior of blanket cylinder 14 communicates with the interior of blanket 18 to inflate the blanket so that it can be inserted onto blanket cylinder 14. After positioning blanket 18 over the outer circumferential surface of blanket cylinder 14, air pressure is removed.

The blanket 18 then contacts and firmly engages the circumference of the blanket cylinder 14, circumferentially over the entire axial area of the blanket and around the entire circumference of the inner surface 86 of the blanket 18. It firmly captures the blanket torso over the entire area.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. A printing machine comprising a rotating blanket cylinder, blanket means incorporated on the blanket cylinder for applying an ink pattern to a sheet material, and for transferring and transferring an image to be printed. a rotating plate cylinder for applying an ink pattern to the blanket means, the printing plate and the blanket means being arranged in rolling engagement in a nip formed therebetween; It also includes a drive means for rotating the plate cylinder and the blanket cylinder, and an inking device for applying ink to the plate cylinder, and the blanket means is in rolling engagement with the plate cylinder at the nip portion. and the blanket means is tubular in shape and has a continuous gapless outer circumferential surface and a gapless continuous inner circumferential surface; and the blanket means comprises, at least in part, a layer of compressible material compressed by the plate cylinder in the nip and an inner layer of rigid continuous material located on said inner circumferential surface. The inner layer of rigid, continuous material is tensilely stressed by a blanket cylinder, and between the inner surface and the blanket cylinder is a printing press. A lithographic printing machine characterized in that, during operation, a pressure relationship is created which allows the blanket means to be fixed on the blanket cylinder. 2. further comprising means for effecting radial expansion of said tubular blanket, on the one hand, establishing a pressure relationship between the inner circumferential surface of the blanket means and the blanket cylinder on the blanket cylinder; Release the blanket means,
2. A printing press as claimed in claim 1, characterized in that it can be manually moved axially from the blanket cylinder. 3. The blanket means has a cylindrical outer layer of incompressible material over a layer of compressible material, and the outer layer of the blanket means is bonded to the inner layer at the nip. is deflected by the plate cylinder to compress the blanket means, and the velocity of the outer surface of the blanket means has exactly the same surface velocity as the velocity at the position just before the nip, at the nip and just after the nip. 3. The printing press according to claim 2, wherein rubbing of the ink pattern in the nip is thereby prevented. 4. When the outer layer of the blanket means is in an undeflected state until it becomes deflected by the plate cylinder, the outer layer of the blanket means occupies a first volume and the outer layer of the blanket means When the layer is deflected by the plate cylinder, the compressible material of the inner layer of the blanket means occupies a second volume that is the same as the first volume, and the outer layer of the blanket means is in an unflexed state. when the outer layer of the blanket means is deflected by the plate cylinder, the inner layer of the blanket means occupies a third volume;
4. A printing press as claimed in claim 3, characterized in that it occupies a fourth volume smaller than the volume of . 5. The compressible material of the inner layer has a void, the void being of a first size while the outer layer of the blanket means is in an unflexed state; Some of them are
5. Printing machine according to claim 4, characterized in that the outer layer of the blanket means assumes a second size smaller than the first size when deflected by the printing plate on the plate cylinder. 6. The printing press further includes a frame for supporting the plate cylinder and the blanket cylinder, the frame having a support location in axial alignment with the blanket cylinder and an opening in the frame. having a movable portion between an open position remote from the blanket cylinder for providing
2. Printing machine according to claim 1, characterized in that the blanket means is movable through an opening in the frame which engages the blanket cylinder when said part of the frame is in the open position. 7. said blanket cylinder has a cylindrical rigid outer surface with a first diameter; said blanket means has a cylindrical rigid inner surface with a second diameter; has a diameter that is less than the first diameter, and an interference fit is provided between the blanket cylinder and the blanket means such that the blanket cylinder resists the flow of fluid against the inner surface of the blanket means. has passage means for guiding the
and inflating the blanket means to increase the second diameter, the blanket means being thereby movable axially over and away from the blanket cylinder. 1. The printing machine described in 1. 8. The blanket means has a cylindrical outer layer of incompressible material having a tubular profile, a cylindrical middle layer of compressible material and a hollow rigid inner sleeve. are coupled and disposed radially inwardly of the outer layer and the intermediate layer, the rigid inner sleeve being an interference fit to the blanket body;
A printing press according to claim 1. 9. The device is rotatable having a rotatable blanket cylinder, blanket means incorporated on the blanket cylinder for applying an ink pattern to the material, and an ink transfer surface for applying an ink pattern to the blanket means. a plate cylinder having an ink transfer surface and a blanket means disposed in rolling engagement in a nip formed therebetween, the blanket means comprising a non-compressible material. a cylindrical outer layer of a compressible material, an inner cylindrical layer of a rigid material, the outer layer of the blanket means having a cylindrical outer layer of a continuous outer surface without gaps disposed in rolling engagement with the ink transfer surface on the plate cylinder, and the outer layer of the blanket means has at least the inner layer of the blanket means. is deflectable so as to compress the portion from a first condition to a second condition, and the inner layer of the blanket means includes a number of voids;
The void is relatively large when the inner layer of the blanket means is in the first state, and the portion of the inner layer of the blanket means that is compressed into the second state by deflection of the outer layer of the blanket means. The device is characterized by being relatively small inside. 10. When the outer layer of the blanket means is in an undeflected state prior to deflection at the nip, the outer layer of the blanket means occupies a first volume and the outer layer of the blanket means is deflected at the nip. the compressible material of the intermediate layer of the blanket means occupies a third volume when the outer layer of the blanket means is in an unflexed state; 10. Apparatus according to claim 9, characterized in that the intermediate layer of the blanket means occupies a fourth volume smaller than the third volume when the outer layer of the blanket means is deflected in the nip. 11. The outer layer is formed of an elastically deflectable non-compressible polymeric material and a solid, and the inner layer is a elastically deflectable elastic material containing a void. 10. Device according to claim 9, characterized in that it is formed from a foam of polymeric material that is flexible. 12. The apparatus further includes a frame for supporting the plate cylinder and the blanket cylinder, the frame having a support location in axial alignment with the blanket cylinder and an opening in the frame. has a movable portion between the open position and the blanket body, and
The blanket means is movable through an opening in the frame engaging a blanket cylinder when the portion of the frame is in the open position, the blanket cylinder being in the first
and the blanket means has a cylindrical rigid inner wall with a second diameter, the second diameter being equal to or greater than the first diameter. and an interference fit between the blanket cylinder and the blanket means, the blanket cylinder having a diameter smaller than the diameter of the blanket cylinder.
passage means for directing the flow of fluid against the metal inner sidewall of the blanket means, and inflating the blanket means to increase a second diameter so that the portion of the frame is in an open condition; Once upon a time, blanket means
Claim 9, characterized in that it is movable in the axial direction on and away from the blanket cylinder.
The device described. 13. The apparatus has blanket means incorporated on the blanket cylinder and adapted to receive the ink pattern in a nip formed by the ink transfer surface and the blanket means; means for transferring a pattern to a material, the blanket means having an outer layer of incompressible material, an intermediate layer of compressible material, and an inner layer of rigid material; The outer layer of the blanket means has a continuous outer surface without gaps and is capable of being positioned in rolling engagement with the ink transfer surface at the nip; wherein at least a portion of the inner layer of the blanket means is deflectable such that it can be compressed from a first condition to a second condition at the nip, and wherein the inner layer of the blanket means has a plurality of It has a blank space of
When the inner layer of the blanket means is in the first state, it is relatively large and the blanket means is compressed into the second state by the deflection of the outer layer of the blanket means so that a portion of the inner layer of the blanket means is compressed into the second state. A device having blanket means, sometimes characterized by being relatively small. 14. The blanket cylinder has a cylindrical rigid outer surface with a first diameter, and the inner layer of rigid material comprises:
14. Printing machine according to claim 13, characterized in that it is a layer for contacting the rigid outer surface of the blanket cylinder. 15. The blanket means has a tubular profile, and the rigid inner layer includes a hollow sleeve, the diameter of which is smaller than the diameter of the blanket cylinder, and the blanket cylinder is in contact with the blanket cylinder. 15. The printing press according to claim 14, wherein the printing press is an interference fit.