Screen Printing Machine For Printing In Multicolor A Horizontally Advanced Web

Abstract

A screen printing machine for multi-color printing on a web which is advanced horizontally on a supporting blanket includes parallel frame halves across which are mounted bridges. Each bridge has stencil holders for journaling the ends of cylindrical thin-walled screen stencils with there being one bridge for each stencil and the bridges extending parallel to the respective stencils. At least one end of a stencil is provided with a gear which meshes with a driving gear mounted in the frame half and protruding upwardly therefrom. The bridge is mounted on a frame half by means of a structure which permits adjustment of the bridge vertically longitudinally and transversely thereof so as to position accurately the stencil with respect to the advancing web.

Description

The present invention relates to a screen printing machine for multi-color printing on a web which is horizontally advanced on a supporting blanket, more particularly, to the adjusting structure for mounting a cylindrical thin-walled screen stencil on the printing machine.

Screen printing machines to which the present invention is directed have been known wherein the stencils can be displaced transversely with respect to the web which is to be printed. Within limits, such a adjustment positions the stencil pattern correctly with respect to the edges of the web. However, a disadvantage of this and similar screen printing machines is that mutual adjustment of the stencils and the adjustment of the stencils with respect to the supporting and driving rollers for the supporting blanket are very critical.

These screen printing machines have the further disadvantage that the stencils cannot be adjusted with respect to height in order to take into account the thickness of the web being printed.

It sometimes occurs that the two end rollers of the supporting blanket are not exactly parallel with respect to each other and accordingly the speed of the supporting blanket is not uniform along its entire width. When the stencils themselves are not exactly parallel to each other the various colors comprising the printed pattern are displaced with respect to each other which is undesirable.

Another maladjustment occurs when a stencil is not exactly parallel with respect to the structure supporting the supporting blanket. This will result in a printed pattern which is not equally sharp and uniform along the width of the printed web.

It is, therefore, the principal object of the present invention to provide a screen printing machine having novel and improved adjusting structure therein.

It is another object of the present invention to provide a screen printing machine wherein the bridge upon which a stencil is mounted can be adjusted longitudinally, vertically or transversely so as to be inclined with respect to the web.

It is a further object of the present invention to provide a screen printing machine wherein the driving gear in the frame for driving the stencil is moveable together with the adjusting movement of the bridge, when the bridge is being moved transversely so as to be inclined to the web.

The screen printing machine according to the present invention incorporates adjusting structure which permits a universal adjustability of the stencils with respect to the supporting blanket and the web. This screen printing machine is also disclosed in the Netherlands patent applications BvE 69092, BvE 69452 and BvE 69415 applied for by the assignee of the present application.

The screen printing machine is of the type for multi-colored printing on a web which is advanced horizontally on a supporting blanket and includes a machine frame comprising a pair of spaced parallel frame halves. One or more bridges are mounted across the frame halves and each bridge has mounted thereon stencil holder means for supporting the ends of a thin-walled screen stencil so that each screen stencil is parallel to the bridge from which it is supported. A driving gear for each stencil is mounted in a frame half and protrudes above the upper surface of the frame half to engage a second gear on one end of the stencil. A single drive gear in one frame half or a pair of drive gears in both frame halves may be provided for each stencil. Hoods may be provided to cover the drive gears in the frame halves with the hoods being rotatably mounted on the bearing housings of the gears. The hoods are thus pivotable in a vertical plane parallel to the gear wheels and can be swung away to permit engagement of the drive gear with a stencil gear. The hoods may also be provided with a fork fitting around the gear with braking blocks being mounted on the fork to engage the faces of the gear. The hood is provided with a nose to facilitate opening of the hood and is so arranged that when the nose is not retained the hood will close over its gear.

Means are provided on one end of the bridge for moving the bridge perpendicularly with respect to the longitudinal direction of the bridge in a horizontal plane so that the bridge is inclined or obliquely positioned with respect to the web. This oblique positioning of the bridge and its accompanying stencil is important when the two end rollers of the supporting blanket are not exactly parallel and, as a result, the linear speed of the blanket is not uniform along its entire width. This oblique positioning of the stencil thus compensates for the difference of the linear speed of the blanket along its width since the end rollers of the supporting blanket and the stencil are now positioned so that their longitudinal axis all intersect at a common point which is obviously at a great lateral distance from the printing machine.

Means are also provided to connect the end of the bridge and its respective driving gear for moving the gear in a vertical plane parallel to the web only when the bridge is being obliquely positioned. The connection between the bridge and the drive gear may comprise a vertical rod whose upper end is provided with a fork fitting around a shaft mounted on the bridge and parallel thereto. Thus, the rod will move only on oblique positioning of the bridge. The lower end of the rod is fixed to a sliding shaft at right angles thereto with the sliding shaft being carried in two brackets which are fixedly mounted on a frame half so that the sliding shaft is moveable in a direction parallel to the web. Sliding shaft is provided with a flattened portion which is attached to the bearing housing of the drive gear.

Means are also provided for mounting the bridge on the frame halves for longitudinal movement so as to adjust the stencil transversely of the web.

Other objects and advantages of the present invention will be apparent upon reference to the accompanying description when taken in conjunction with the following drawings, which are exemplary, wherein;

FIG. 1 is a perspective view of a portion of the screen printing machine incorporating the present invention;

FIG. 2 is a perspective view of one end of the structure illustrated in FIG. 1 but viewed from the other side;

FIG. 3 is a longitudinal sectional view of the bridge and adjusting structure of FIGS. 1 and 2;

FIG. 4 is a sectional view taken along the line IV--IV of FIG. 3;

FIG. 5 is a sectional view taken along the line V--V of FIG. 3;

FIG. 6 is an elevational view of the structure connecting the bridge and the respective drive gear for moving the gear in response to oblique positioning of the bridge;

FIG. 7 is a sectional view taken along the line VII--VII of FIG. 6; and

FIG. 8 is a sectional view taken along the line VIII--VIII of FIG. 6.

Proceeding next to the drawings wherein like reference symbols indicate the same parts throughout the various views a specific embodiment of the present invention will be described in detail.

As may be seen in FIG. 1, each screen stencil 1 is hung on a bridge 2 positioned over a web 3 which is to be printed and is advanced horizontally in the direction of the arrow 4. The stencil 1 is supported by end rings 5 in stencil holders 6 mounted on the bridge 2. In the present embodiment of the invention the bridge comprises a hollow member having end covers 7 to which are secured projections 8 coupled to brackets 9 whose bottoms are fixedly secured onto frame halves 10 and 11 of the machine.

As may be seen in FIG. 1 an adjusting knob 12 is provided for moving the bridge 2 transversely with respect to the web 3. Adjusting levers 28 and 29 move the bridge vertically to adjust for height. An adjusting lever 14 mounted in one of the brackets 9 provides for oblique positioning of the bridge 2 with respect to the stencil. A projection 15 mounted on the bridge is connected to a vertical rod 16 which in turn is connected with a drive gear mounted in the frame half 11 in a manner to be later described.

The right hand end of the stencil 1 shown in FIG. 1 is illustrated in larger scale in FIG. 2 but is viewed from the opposite direction from that of FIG. 1. It is apparent from FIG. 2 that as the web 3 moves in the direction of the arrow 17, the stencil 1 will rotate in the direction of the arrow 18 and drive gear 19 will rotate in the direction of the arrow 20. The drive gear 19 meshes with a gear (not shown in the drawings) mounted on the end ring 5 of the stencil and supported in the stencil holder 6. Each drive gear 19 is covered by a protective hood 21 having a nose 22 which when moved in the direction of the arrow 23 will expose the drive gear so that the drive gear can drivingly engage the gear on the end ring 5 of the stencil. As may also be seen in FIG. 2 a nose 22' of a protective hood is retained in the open position by the stencil holder 6. The hood 21 is so mounted with respect to the drive gear 19 that when the nose 22 is not retained and is released the hood 21 will automatically close over its drive gear.

Proceeding next to the adjusting means shown in FIGS. 3, 4 and 5, the mechanism for adjusting the bridge in a direction transverse to the web is illustrated in the left hand portion of FIG. 3. The bracket 9 is provided with an end wall 23 in which the unthreaded portion 24 of a shaft is rotatably and non-slideably mounted. The adjusting knob 12 is on the outer end of the shaft 24. The inner end of the shaft is provided with external threads 25 which are engaged with an internally threaded sleeve 26. The sleeve 26 has collars on both ends thereof so as to be positioned on both sides of a vertical fork member 27 extending downwardly from the projection 8 of the end cover 7. The fork 27 is shown in FIG. 4 and is freely slideable in a vertical direction along the sleeve 26. Upon actuation of the adjusting knob 12, the sleeve 26 will shift since it is threaded upon the threaded end 25 of the shaft and the collars on the sleeve 26 will act upon the fork 27 so that the bridge 2 is moved in its longitudinal direction.

Illustrated in FIGS. 4 and 5 are the two adjusting levers 28 and 29 for the mechanism for adjusting the height of the bridge 2. The two levers 28 and 29 are fixedly mounted upon two eccentric shafts 30 and 31 respectively. On the central portions of the shafts 30 and 31 are eccentrics 32 and 33 respectively. The ends of the shafts 30 and 31 are positioned in horizontal slots 34 and 35 respectively in the vertical side walls 36 of the brackets 9 and are slideable therein in a horizontal direction. The vertical walls 36 extend in the longitudinal direction of the bridge 2. The eccentric portions 32 and 33 of the shafts are received in horizontally positioned U-shaped members 37 and 38 respectively from the projections 8 and are slideable therein in a horizontal direction. With this arrangement it is apparent that turning the adjusting levers 28 and 29 will move the bridge 2 in a vertical direction so that a bridge can be adjusted for height.

The lever 28 is shown in a position in which the bridge 2 is in the lower position and the lever 29 is shown in the position with the bridge 2 being in the higher position. Since the eccentric portions 32 and 33 are horizontally slideable in the U-shaped members 37 and 38 respectively, the shafts 30 and 31, which are for the height adjustment for the bridge 2, do not interfere with the longitudinal adjustment of the bridge resulting from actuation of the knob 12. Operating of the levers 28 and 29 transmits only vertical components of movement to the bridge.

The mechanism for inclining or obliquely positioning the bridge is shown in the right hand portion of FIG. 3. Analogous to the left hand portion of FIG. 3, the end cover 7 has a second vertical fork member 39 depending therefrom as shown In Fig. 5. The fork member 39 is vertically slideable about an eccentric portion 40 of a shaft 41. Since the lever 14 is fixedly mounted on the shaft 41 rotation of this lever will transmit horizontal components of motion of the eccentric 40 to the fork member 39 so that this end of the bridge 2 is moved in a longitudinal direction with respect to the web 3. Height adjustment of the bridge 2 is not affected by the eccentric portion of the shaft 41 since the fork member 39 can slide freely in a vertical direction on the eccentric. When the bridge 2 has been obliquely positioned or inclined, the shafts 30 and 31 will move to an inclined position in the slots 34 and 35. The horizontally disposed U-shaped members 37 and 38 are closed at their ends so that they carry along the shafts 30 and 31 respectively when the bridge is adjusted in its longitudinal direction.

In the right hand portion of FIG. 3 and in FIG. 5 there is shown a portion of the connection between the bridge 2 and the gear wheel 19 with this connection being shown in greater detail in FIG. 6. The connection is located in the vicinity of one end of the bridge 2 and comprises a vertical rod 16 having on its upper end a fork 42 which fits around a shaft 43 mounted on the bridge 2 and parallel thereto. The rod 16 thus moves only on an oblique positioning of the bridge 2 because the fork 42 can slide vertically along the shaft 43 and slides also along the shaft in a direction parallel to the bridge 2. The lower end of the rod 16 is fixedly attached at 44 to a shaft 45 to be at a right angle therewith with the shaft being slideably mounted in spaced brackets 46 and 47 which are fixedly mounted on the frame half. The shaft 45 has a circular cross-section throughout most of its length except for a flattened portion 48 which is connected by bolts 51 and 52 with a bearing housing 49 which is rotatably mounted on the end of driving shaft 50 of the gear 19 in frame half 11. It is apparent that upon movement of this end of the bridge 2 in a horizontal plane so as to obliquely position the bridge, the shaft 45 will slide in its brackets 46 and 47 to displace the gear 19. The drive gears 19 and gears on the end of the stencils are provided with gear teeth which are parallel to their axes of rotation so that meshing gears are slideable with respect to each other while remaining in driving engagement.

The drive shaft 50 might be constructed of several components or a bending load can be applied to it. Self adjusting bearings for this shaft may also be employed.

As may be seen in FIGS. 6, 7 and 8, the protective hood 21 for the drive gear 19 is rotatably mounted on the bearing housing 49 for the shaft of this drive gear. The hood 21 is provided with a fork 53 which fits around the drive gear 19. Braking blocks 54 are mounted on the fork and engage the faces of the drive gear. Upon any inclination or oblique positioning of the bridge 2 the hood 21 for the drive gear 19 will move in conjunction with this drive gear as a result of the structure wherein the hood 21 fits closely around the bearing housing 49. An important advantage of the protective hood feature of the present invention is that the hoods protect at all times operating personnel from the protruding drive gears in the frame halves.

In the frame half 10 in which the non-sliding drive gears are journaled, a hood 21 can be rotatably mounted around the bearing housing for the other end of the shaft 50 whose one end is shown in FIG. 7. The shaft 50 may on its other end be provided with a drive gear which engages a gear at the other end of the stencil.

The limits of adjustment of the bridge 2 depend on the space available for the projections 8 in the brackets 9. In practice, the adjustment of the bridge can be limited to less than 10 mm which is quite minute as compared to the length of the bridge which, in practice, may be more than 1 meter. The angular displacements of the bridge 2 and the drive shaft 50 are therefore very small so that the driving engagement of the gears is not affected and no torsion is produced in the stencils.

The adjustment of the stencils may be based upon reference to printers proofs made before commencing an actual run of the printing machine. Upon examination of these proofs, the stencil may be adjusted in any one of the several different ways described above. It is thus apparent that screen printing machine of the present invention is provided with a universal adjustability of the stencil.

It is understood that this invention is susceptible to modification in order to adapt it to different usages and conditions and, accordingly, it is desired to comprehend such modifications within the invention as may fall within the scope of the appended claims.

Claims

What is claimed is:

1. In a screen printing machine for multi-color printing on a web advanced horizontally on a support blanket, the combination of a machine frame having a pair of spaced parallel frame halves, a bridge mounted across said frame halves, stencil holder means on said bridge for supporting the ends of a thin-walled screen stencil so that the screen stencil is parallel to the bridge, a first gear in one of said frame halves drivingly engaging a second gear on one end of said stencil, means for mounting said bridge on said frame halves for longitudinal movement to adjust said stencil transversely of said web, means on one end of said bridge for moving said bridge perpendicularly with respect to the longitudinal direction of the bridge in a horizontal plane whereby the bridge is inclined with respect to the web, means connecting one end of said bridge and said first gear for moving said first gear in a vertical plane parallel to the direction of web advancement only in response to moving of said bridge one end in a horizontal plane and being non-responsive to movement of the bridge vertically and longitudinally, said gears having teeth thereon parallel to the rotary axes of the gears whereby said gear teeth are slidingly engageable with each other.

2. In a screen printing machine as claimed in claim 1 wherein said adjusting means comprises fork members on the ends of said bridge, and means on said machine frame comprising eccentric means engageable with said fork members for the vertical adjustment and a threaded spindle engageable with said fork members for the horizontal adjustment.

3. In a screen printing machine as claimed in claim 2 wherein said fork members comprise a first vertical fork member, said actuating means comprises an internally threaded sleeve horizontally positioned within said fork member, collar means on the end of said sleeve on both sides of said first fork member, a threaded spindle shaft rotatably and non-slideably mounted in a frame half engaging said sleeve, said spindle shaft extending longitudinally of said bridge whereby horizontal displacement of the sleeve resulting from rotation of the spindle shaft is transmitted to said first fork member.

4. In a screen printing machine as claimed in claim 2 wherein said fork members comprise a second vertical fork member at one end of said bridge, said actuating means comprising a shaft rotatably and non-slideably mounted in a frame half and having an eccentric thereon closely received within said second fork member, said shaft being longitudinally of said bridge whereby said eccentric is freely moveable vertically within said second fork member so that every horizontal component of movement of said eccentric is transmitted to said second fork member.

5. In a screen printing machine as claimed in claim 2 and comprising a horizontally positioned U-shaped member at each end of said bridge, a pair of shafts rotatably mounted in said frame halves transversely of said bridge and having eccentric portions thereon closely received within said U-shaped members respectively, said eccentric portions slideable freely in said U-shaped members longitudinally of said bridge whereby vertical components of the movement of the eccentric portions are transmitted to the respective U-shaped members.

6. In a screen printing machine as claimed in claim 5 wherein said U-shaped members are slideable along the respective eccentric portions in directions transverse to the web, said shafts being mounted in said frame halves for slideable movement in the longitudinal and transverse directions of the web.

7. In a screen printing machine as claimed in claim 5 and comprising a pair of brackets fixedly mounted on the bottoms thereof on the respective frame halves and supporting the ends of said bridge thereon, each bracket having a pair of vertical walls parallel to said bridge and an interconnecting end wall perpendicular to the bridge, there being horizontal slots in said vertical walls, said shafts being positioned in said slots respectively so as to be slideable in directions transverse to the bridge and web, and a threaded spindle shaft rotatably and non-slideably mounted in the end wall of one bracket and a shaft having an eccentric thereon rotatably and non-slideably mounted in the end wall of the other bracket.

8. In a screen printing machine as claimed in claim 1 wherein said gear moving means comprises a shaft mounted on said bridge parallel thereto, a rod having a fork on its upper end and receiving said shaft, a second shaft slideably mounted in one frame half for movement parallel to the direction of web advancement and perpendicular to said rod, the lower end of said rod fixedly secured to said second shaft, a bearing housing adjacent said first gear in a frame half and mounted on the driving shaft of the respective first gear, said slideable second shaft having a flattened portion connected to said bearing housing.

9. In a screen printing machine as claimed in claim 8 wherein each frame half has a first gear and said stencil has second gears on the ends thereof, the first gears in said frame halves protrude upwardly to engage the second gears on the stencil, a hood journaled on each bearing housing and pivotable in a vertical plane parallel to the first gear to expose the first gear to permit meshing thereof with a said second gear on a said stencil, a fork on each hood extending around the respective first gear, braking blocks on said fork engageable with the faces of the first gear, and a nose on said hood to define a handle for moving the hood, said hood closing over the first gear when the nose thereof is released and being moveable with the bearing housing.