GB2057357A

GB2057357A - Silk screen printing machine

Info

Publication number: GB2057357A
Application number: GB7925960A
Authority: GB
Original assignee: BRASA U
Current assignee: BRASA U
Priority date: 1979-07-25
Filing date: 1979-07-25
Publication date: 1981-04-01

Abstract

A silkscreen printing machine comprises an impression cylinder 20 and a doctor-blade 3B. The doctor- blade 3B should be parallel to the impression cylinder 20, but problems such as wear and incorrect fitting may result in a non-parallel arrangement. The doctor-blade 3B is therefor connected at opposite ends respectively to two pneumatically operable piston and cylinder devices. The supply of air to these devices is through independent manually controllable valves so that the blade 3B may be urged against the cylinder 20 with a force which varies along the axial length of the blade. The blade assembly may be lifted by further piston-and-cylinder devices 8 (only one shown). <IMAGE>

Description

SPECIFICATION Silk screen printing machine The present invention relates to a silk screen printing machine.

In a known machine, the doctor-blade is carried by a beam and is disposed parallel to the surface of the impression cylinder. Because of uneven wear along the doctor-blade or of incorrect fitting or some other reason, it is possible for the lower edge of the doctor-blade to be at an angle to the surface of the .impression cylinder. As a result, printing is uneven because of the uneven pressure exerted by the doctor-blade on the bottom of the printing frame.

According to the present invention, there is pro vided an impression cylinder and a doctor-blade arrangement parallel to the surface of the impress ion cylinder, the doctor-blade being connected to two pressure fluid operable piston and cylinder devices and mannually operable valve means dis posed in pressure fluid lines to the two devices enabling the supply of pressure fluid from a pressure fluid source to the devices to be independently controlled so as to control the forces urging the doctor-blade against the impression cylinder.

In order that the invention may be more clearly understood, one embodiment of the invention will now be described, by way of example, with refer ence to the accompany drawings in which: Figure 'shows diagrammatically a front eleva tional view of a silk screen printing machine; and Figure 2 shows a detail of the arrangement of Figure 1.

Referring to this drawing, the machine comprises an impression cylinder 20 above which is disposed a doctor-blade 3B. The doctor-blade is supported on a beam 21 which is connected at two spaced points via articulated joints to the pistons 22 and 23 of double acting piston and cylinder devices 1 and 2. The cylinders of these devices 1 and 2 are connected to a frame 24. Pressure fluid pipe lines 25,26, 27 and 28 (in this case pneumatic) connect an air compressor via an electrically operable valve 3A, to the cylinders of the devices 1 and 2. Lines 25 and 26 are connected to respective cylinders of the devices 1 and 2 above the corresponding pistons and lines 27 and 28 are connected below the corresponding pistons.

Two manually operable control valves 5 are disposed in respective lines 25 and 26. These valves 5 enable the pressure exerted on the pistons of the devices 1 and 2 to be varied as required. Two other control valves 6 are disposed in respective return lines 27 and 28 to control the rate of return of air to the air compressor 3 from the cylinder of the devices 1 and 2. This enables the downward speed ofthe pistons and consequently of the doctor-blade 3B to be controlled. The air compressor 3 may be an integral part of the machine or it may be a central ised compressor used also for other purposes.

Referring specifically to Figure 2, a cam 4 is shown which is arranged to be turned with the impression cylinder. The cam controls the lifting and lowering of the doctor-blade 3B.

In place of electric motors for lifting the doctorblade 3B, two pneumatically operable piston and cylinder devices are arranged on opposite sides respectively. Only the left hand side piston and cylinder device referenced 8 is shown. The piston of this piston and cylinder device has an extension 9 which is connected to a ring nut 10. The ring nut 10 is connected to the lower end of a hollow column 7 by means of screws 11. These hollow columns 7 support the beam 21 which carries the doctor-blade 3B. The piston and cylinder devices 8 are supplied from the air compressor through air pipe lines 30 and 31 in order to lift and lower the corresponding columns 7 and through them the doctor-blade 3B.

With the above described arrangement a more satisfactory control of the doctor-blade is achieved.

The downward speed of the doctor-blade may be more positively controlled and the pressure on the doctor-blade may be applied more selectively. If desired, the pressure at opposite ends respectively of the blade may be made equal or it may be made unequal.

1. A silk screen printing machine comprising an impression cylinder and a doctor-blade arrangement parallel to the surface of the impression cylinder, the doctor-blade being connected to two pressure fluid operable piston and cylinder devices and manually operable valve means disposed in pressure fluid lines to the two devices enabling the supply of pressure fluid from a pressure fluid source to the devices to be independently controlled so as to control the forces urging the doctor blade against the impression cylinder.

2. A silk screen printing machine as claimed in claim 1, wherein the doctor blade is connected to the two pressure fluid operable piston and cylinder devices through respective articulated joints.

3. A silk screen printing machine as claimed in claim 1 or 2, wherein the doctor-blade is connected to the piston and cylinder devices near its top edge.

4. A silk screen printing machine as claimed in any preceding claim, wherein the piston and cylinder devices are pneumatic.

5. A silk screen printing machine as claimed in any preceding claim, wherein pressure fluid to the piston and cylinder devices is also controlled by an electrically operated valve.

6. A silk screen printing machine as claimed in any preceding claim, wherein each pressure fluid operable piston and cylinder device is double acting and means are provided to control the return of pressure fluid from the devices.

7. A silk screen printing machine as claimed in any preceding claim, wherein a cam is rigidly coaxially connected to the impression cylinder in orderto control the timing of the lifting and lowering of the doctor-blade relative to the impression cylinder.

8. A silk screen printing machine substantially as hereinbefore described with reference to the accompanying drawing.

New claims or amendments to claims filed on 15th

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Silk screen printing machine The present invention relates to a silk screen printing machine. In a known machine, the doctor-blade is carried by a beam and is disposed parallel to the surface of the impression cylinder. Because of uneven wear along the doctor-blade or of incorrect fitting or some other reason, it is possible for the lower edge of the doctor-blade to be at an angle to the surface of the .impression cylinder. As a result, printing is uneven because of the uneven pressure exerted by the doctor-blade on the bottom of the printing frame. According to the present invention, there is pro vided an impression cylinder and a doctor-blade arrangement parallel to the surface of the impress ion cylinder, the doctor-blade being connected to two pressure fluid operable piston and cylinder devices and mannually operable valve means dis posed in pressure fluid lines to the two devices enabling the supply of pressure fluid from a pressure fluid source to the devices to be independently controlled so as to control the forces urging the doctor-blade against the impression cylinder. In order that the invention may be more clearly understood, one embodiment of the invention will now be described, by way of example, with refer ence to the accompany drawings in which: Figure 'shows diagrammatically a front eleva tional view of a silk screen printing machine; and Figure 2 shows a detail of the arrangement of Figure 1. Referring to this drawing, the machine comprises an impression cylinder 20 above which is disposed a doctor-blade 3B. The doctor-blade is supported on a beam 21 which is connected at two spaced points via articulated joints to the pistons 22 and 23 of double acting piston and cylinder devices 1 and 2. The cylinders of these devices 1 and 2 are connected to a frame 24. Pressure fluid pipe lines 25,26, 27 and 28 (in this case pneumatic) connect an air compressor via an electrically operable valve 3A, to the cylinders of the devices 1 and 2. Lines 25 and 26 are connected to respective cylinders of the devices 1 and 2 above the corresponding pistons and lines 27 and 28 are connected below the corresponding pistons. Two manually operable control valves 5 are disposed in respective lines 25 and 26. These valves 5 enable the pressure exerted on the pistons of the devices 1 and 2 to be varied as required. Two other control valves 6 are disposed in respective return lines 27 and 28 to control the rate of return of air to the air compressor 3 from the cylinder of the devices 1 and 2. This enables the downward speed ofthe pistons and consequently of the doctor-blade 3B to be controlled. The air compressor 3 may be an integral part of the machine or it may be a central ised compressor used also for other purposes. Referring specifically to Figure 2, a cam 4 is shown which is arranged to be turned with the impression cylinder. The cam controls the lifting and lowering of the doctor-blade 3B. In place of electric motors for lifting the doctorblade 3B, two pneumatically operable piston and cylinder devices are arranged on opposite sides respectively. Only the left hand side piston and cylinder device referenced 8 is shown. The piston of this piston and cylinder device has an extension 9 which is connected to a ring nut 10. The ring nut 10 is connected to the lower end of a hollow column 7 by means of screws 11. These hollow columns 7 support the beam 21 which carries the doctor-blade 3B. The piston and cylinder devices 8 are supplied from the air compressor through air pipe lines 30 and 31 in order to lift and lower the corresponding columns 7 and through them the doctor-blade 3B. With the above described arrangement a more satisfactory control of the doctor-blade is achieved. The downward speed of the doctor-blade may be more positively controlled and the pressure on the doctor-blade may be applied more selectively. If desired, the pressure at opposite ends respectively of the blade may be made equal or it may be made unequal. CLAIMS

7. A silk screen printing machine substantially as hereinbefore described with reference to the accompanying drawing.

New claims or amendments to claims filed on 15th October 1980.

Superseded claims 1,2,4, 5,6,7,8.

New or amended claims:1,2,4,5,6,7.

1. Asilkscreen printing machine comprising an impression cylinder and a doctor-blade arrangement parallel to the surface of the impression cylinder, the doctor-blade being connected to two pneumatic piston and cylinder devices and manually operable valve means disposed in air lines to the two devices enabling the supply of air from a source of compressed air to the devices to be independently controlled so as to control the forces urging the doctor blade against the impression cylinder.

2. Asilkscreen printing machine as claimed in Claim 1, wherein the doctor-blade is connected to the two piston and cylinder devices through respective articulated joints.

4. A silk screen printing machine as claimed in any preceding claim, wherein air supply to the piston and cylinder devices is also controlled by an electrically operated valve.

5. A silk screen printing machine as claimed in any preceding claim, wherein each pneumatically operable piston and cylinder device is double acting and means are provided to control the return of air from the devices.

6. A silk screen printing machine as claimed in any preceding claim, wherein a cam is rigidly coaxially connected to the impression cylinder in order to control the timing of the lifting and lowering of the doctor-blade relative to the impression cylinder.