RU2126743C1 - Doctor head for stencil process - Google Patents

Abstract

FIELD: application of pattern onto sealed up plane articles fed by a conveyer with a periodicity of 0.1 to 2 articles/s. SUBSTANCE: doctor head contains a printing doctor, doctor holder, mechanism for doctor damping in the plane of its movement attached to the base. The damping mechanism represents a parallelepiped with a rest in the form of a boss that is engageable with the base. The axis of the damping mechanism and the axis of the doctor holder are mutually perpendicular. The doctor damping mechanism is spring-loaded relative to the base. Both ends of the doctor holder are spring-loaded relative to the damping mechanism. EFFECT: enhanced accuracy of application of pattern. 2 cl, 3 dwg

Description

 The invention relates to equipment for applying a picture by silk-screen printing and can be used to apply a picture to sealed flat products supplied by the conveyor method with a frequency of from 0.1 to 2 products per second, in particular for drawing a picture on ceramic tile.

 To obtain an accurate, clear image of the pattern on the sealed product, it is necessary that the squeegee edge in the squeegee device follows the profile of the sealed product at a high speed of the squeegee during the entire printing cycle, ensuring uniform squeegee pressure over the entire area of the sealed pattern. In known designs of doctor blade devices, the doctor blade profile can fulfill the above conditions when the deformation of the flat surface of the printed product coincides with the direction of movement of the doctor blade.

 Known doctor device in a screen printing machine by and.with. USSR N 368077, M. cl. In 41 F 15/00, 1970, the squeegee device contains a base, movable guide rods with stops, fixedly connected to the squeegee holder, a spring with which the squeegee is pressed to the screen.

 This doctor blade device can take into account the deformation of the plane of the sealed product, which coincides with the direction of movement of the doctor blade.

 However, deformations of the plane of the sealed product across the movement of the squeegee and complex deformations of the plane of the torsion-type product are not sealed with this squeegee device, since uniform squeegee pressure is not provided over the entire area of the pattern, therefore, the specified squeegee device cannot provide high accuracy of the pattern .

 In addition, during the operation of the device, the guide carriages experience significant friction, which leads to an increase in the gaps between the holes in the base and the guides, which results in squeezing and vibration of the squeegee, i.e., the accuracy of drawing the drawing and the service life of the device itself are reduced.

The closest in technical essence and the achieved effect is a doctor blade for screen printing (see US patent N 4638733, M. class ⁵ B 41 F 15/44, 1987). The squeegee head contains a rubber squeegee, a squeegee holder that has clamps connected to the squeegee base at individual points, a squeegee damping mechanism in the plane of its movement, which consists of holding rods with springs for independent reciprocating movement in the plate holes when printing, and adjustable stops, which are installed at the ends of the rods, the base to which the squeegee damping mechanism is attached.

 The known design of the doctor blade allows you to take the contact edge of the doctor blade the shape of the working surface when printing, as the base of the doctor blade is connected at various points with independently moving clamps.

 However, the known design of the doctor blade has a large inertia and does not have time to react to a complex deformation of the plane of the sealed product of the “torsion” type and the deformation of the plane of the printed product across the movement of the doctor blade at a high speed of the squeegee, as a result, the squeegee pressure is not uniform over the entire area of the pattern, there is precision drawing.

 When the surface curvature between the edge of the clamp and the surface of the sealed product, an angle is formed, which is technologically impossible to eliminate when using this design of the doctor blade, therefore the pattern is printed unevenly on the product and can be striped. With complex deformation of the plane of the sealed product of the torsion type, the squeegee edge at a high speed of its movement cannot repeat the shape of the sealed product with uniform squeegee pressure over the entire area of the pattern.

 In addition, this design is difficult to manufacture due to complex technological equipment, unreliable in operation, as it includes a significant amount of rubbing, wearing parts.

 The objective of the invention is to increase the accuracy of applying the drawing by ensuring uniform squeegee pressure over the entire area of the picture, repeating the edge of the squeegee shape of the printed product with complex deformation of the plane and increasing the reliability of the device.

This object is achieved in that the application of the squeegee damping mechanism in the form of a parallelepiped with a stop in the form of a protrusion, the mutually perpendicular arrangement of the axes of the squeegee damping mechanism and the squeegee holder, the springing of both ends of the squeegee relative to the damping mechanism ensures uniform squeegee pressure over the entire area of the printed pattern and repeating the shape of the squeegee a sealed product with complex deformation of the plane during printing at an angle of 70 - 75 ^o between the planes and the squeegee and the stencil, eliminates the vibrations acting on the nodes and structural parts during operation, reduces the friction coefficient and reduces the wear of the damping mechanism parts, which increases the accuracy of drawing and the reliability of the doctor blade.

 In FIG. 1 shows a doctor blade for screen printing, side view; in FIG. 2 - the same front view.

 The squeegee head for screen printing contains a base 1 to which a squeegee damping mechanism is attached, which is a parallelepiped 2 with a stop in the form of a protrusion 3, which can interact with the base 1. The squeegee damping mechanism in the form of a parallelepiped 2 is mounted on the axis 4 using a rolling bearing 5 The rake holder 6 is installed in the damping mechanism 2 on the axis 7 using a rolling bearing 5. The axis 4 of the damping mechanism 2 and the axis 7 of the rake holder 6 are mutually perpendicular. The squeegee damping mechanism 2 is spring-loaded relative to the base 1 using a spring 8. Both ends of the squeegee holder b are spring-loaded relative to the damping mechanism 2 using a spring 9.

To reduce the size of unprintable fields on the surface of flat products, for example, ceramic tiles, the edge of the squeegee 10 can be made so that the shape of the working edge of the squeegee, acquired at an angle of 70 - 75 ^o between the planes of the squeegee 10 and the stencil 11 in a plane orthogonal to the stencil and the direction of movement of the squeegee, similar to the shape of the sealed product 12.

In FIG. 3 shows a profile view of the edge of the squeegee 10, interacting with the surface of the sealed product 12 at an angle of 70 - 75 ^o .

 The squeegee head for screen printing operates as follows.

The squeegee supply mechanism (not shown in the drawing) leads to the stencil 11 of the squeegee 10, which forms an angle of 70 - 75 ^o with the plane of the stencil 11 and is pressed against it with the necessary technological force by the spring 8. When the squeegee 10 is supplied to the stencil 11 between the protrusion 3 and the base 1, a gap is formed that prevents the protrusion 3 from contacting the base 1. The base 1, thus, does not interfere with the movement of the damping mechanism of the doctor blade 2, which, swinging on the axis 4, moves the doctor blade 10 in the direction longitudinal to the direction of movement of the doctor blade 10 and in the vertical the plane relative to the template 11. Rocket holder 6 by rotating the axis 7 provides the movement of the doctor blade 10 in the direction transverse to the direction of movement of the doctor blade 10. The action of the spring 9 on both ends of the holder 6 stabilizes the clamping forces along the entire length of the doctor blade 10. The presence of two degrees of freedom of the holder holder movement: movement on the axis damping mechanism and movement on the axis of the holder ensures uniform squeegee pressure over the entire area of the printed pattern throughout the printing cycle. After the printing cycle, the squeegee feed mechanism (not shown in the drawing) takes the squeegee 10 away from the stencil 11, the protrusion 3 of the squeegee damping mechanism 2 rests on the base 1 and raises the squeegee 6, which is held in the raised position by the protrusion 3 and the spring 8.

 The proposed doctor blade for screen printing can be used for sealing any flat products, for example, for drawing a pattern on ceramic tiles.

To reduce the size of unprintable fields on a ceramic tile, the edge of the holder was made with bends similar to the rounding around the perimeter of the tile face: with a radius of curvature of 5 mm, bends at the edge of the holder of the holder in places corresponding to the rounding of the tile were also made with a radius of 5 mm. The squeegee, fixed in such a curved squeegee holder at a working angle of 70 - 75 ^o , has bends, the radius of which corresponds to the radius of rounding around the perimeter of the front surface of the tile.

When applying a pattern to a ceramic tile using a squeegee having such a curved edge at an angle of 70 - 75 ^o , the size of the unprintable fields on the tile is reduced by 50%. With the speed of movement of the squeegee 1.2 - 2.0 m / s and the presence of complex deformation of the plane of the ceramic tile of the "torsion" type, the output of products that are suitable for the quality of the pattern is 98% versus 90% using the traditional design of the squeegee at Kharkov Tile Plant the service life of the stencil is increased by 40%, which corresponds to an output of 420 m ^{2 of} tile suitable for drawing quality against 300 m ^{2 of} tile produced at Kharkov Tile Plant CJSC using the traditional doctor blade design.

Offered screen doctor head for screen printing:
- easy to operate and manufacture, does not require complex technological equipment;
- reliable in operation, since the coefficient of friction between parts of the damping mechanism is reduced;
- has a high accuracy of drawing, as it provides uniform squeegee pressure over the entire area of the picture, and the squeegee edge repeats during printing the shape of the printed product with complex deformation of the product plane;
- increases the service life of the stencil due to the linearization of the specific pressure of the squeegee along the plane of the figure.

Claims (2)

 1. A squeegee head for screen printing containing a squeegee, a squeegee holder, a squeegee damping mechanism in the plane of its movement, having a stop and a spring, and a base to which a damping mechanism is attached, characterized in that the squeegee damping mechanism is a parallelepiped with a stop in the form of a protrusion having the ability to interact with the base, the axis of the damping mechanism and the axis of the holder are mutually perpendicular, while both ends of the holder are spring-loaded relative to the damper mechanism IAOD. 2. The head according to claim 1, characterized in that the squeegee is shaped so that the shape of the working edge of the squeegee, acquired at an angle of 70 - 75 ^o between the planes of the squeegee and the stencil in a plane orthogonal to the stencil and the direction of movement of the squeegee, is similar to the shape of the printed product.

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