A process for making a single layer flexographic printing plate which involves reinforcing and laser engraving a single layer flexographic printing element.

Laser engravable single-layer flexographic printing element

A process for making a multilayer flexographic printing plate which involves reinforcing and laser engraving a multilayer flexographic printing element.

Lasers engravable multilayer flexographic printing element

A continuous control system for a mining or tunnelling machine having a boom (12) with a motor driven cutting head (14) at one of its ends and a rotatable turret (20) at the other end, the control system comprising angular encoders (40, 44) for continuously measuring the angles of the boom (12) and of the turret (20) and a linear encoder (55) for continuously measuring the linear position of the cutting head (14), and further having pressure transducers (P1, P2, P3, P4) for continuously measuring the pressures of the various hydraulic cylinders or drives (41, 43) used to operate the boom (12) and the turret (20). It may also have a power transducer (57) for continuously measuring the power input to the motor (18) driving the cutting head (14) to control the RPM of the latter. The signals from the above various measurements are continuously processed by a computer (46) in accordance with a predetermined computer program and a controller (47) is provided which is responsive to the computer (46) and which continuously controls the various parameters so as to cut a preselected profile at a predetermined depth of cut and rate of advance.

Continuous control system for a mining or tunnelling machine

When laser engraving flexographic and rotary screen printing cylinders half-tones are generated by providing a series of regularly spaced cells (1) including dots or pits (3) which collectively are referred to as a screen. By varying the ratio between the areas of the dots or pits (3) and the cells (1) the intensity of the half-tone is varied. A laser engraving machine for engraving such printing cylinders includes variable timing means (37, 38) which are triggered by their engraving head (13) crossing into each cell (1) and which generate a variable time delay (D) to determine the start time of the laser engraving in each pass of each cell (1) and also to determine the duration (P) of the time for which the laser is turned ON to engrave material during each pass of each cell.

Printing cylinder engraving

A gravure printing cylinder is engraved with a pattern, such as a woodgrain pattern, by sensing and comparing the copy density at opposite ends of the pattern and then engraving the pattern with a correction for the unbalance in the copy density to produce a joint which is less visible to the human eye. A less visible joint is also formed by engraving the starting cells for the pattern at circumferentially spaced locations on the cylinder to produce either a non-linear interwoven joint and/or an irregular zig-zag joint.

Method of engraving an invisible joint within a gravure printing cylinder

Automatic electronic control means are for the movement of hydraulic boom(s) or e.g. in tunnel- boring and road-header machines. The automatic boom control is in accordance with stored information relating to a desired path of boom movement by means of hydraulic control valves connected in the hydraulic control circuit of the boom and uses feedback control. The boom includes a turret rotatable about a vertical axis, and a jib mounted on the turret for rotation about a horizontal axis. Two mechanically operated hydraulic control valves are connected in the hydraulic control circuit for the independent control of the movements of the turret and jib, and further mechanically operated control valve(s) control their speed of movement about their respective axis.

Control of hydraulic booms

The laser beam is passed through diffraction means (15), which may be of any suitable form such as a diffraction grating, zone plate or diffraction aperture or a beam shaping mirror, and is then focussed onto the surface of the workpiece in the form of a diffraction pattern. In addition, the workpiece may be moved relative to the laser beam during engraving while praferably also varying the intensity (pulse- shape) of the laser beam to produce the cells of different size and configuration. The disclosure also describes methods and apparatus for engraving an image or pattern on the surface of the workpiece by varying the output of the laser beam in accordance with stored image defining signals to produce cells of uniform or different size and shape while scanning the workpiece surface.

Improvement in or relating to methods and apparatus for laser engraving

A copying system has an artwork carrier cylinder and a printing cylinder, and electronic control means "stretches" the copy to exactly 360° on the printing cylinder, to produce matched endless joints. The circumferential length of the original is first determined and then the original is scanned by a "read" scanner, the output of which is digitized and temporarily stored in memory. The contents of the memory are used to modulate a power laser during scanning to "write" on the printing cylinder but readout from the memory is adjusted in accordance with the circumferential length determined to produce the required jointing. The system may be varied to produce flexographic rollers, gravure cylinders or general copying.

Apparatus for producing a seamless copy from an unjointed original

A copying process for producing a seamless copy from an unjointed original mounted on a carrier cylinder utilizes electronic control circuitry to "stretch" the copy of the artwork to exactly 360° on a printing cylinder, to produce matched endless joints. The circumferential length of the original is first determined and then the original is scanned by a "read" scanner, the output of which is digitized and temporarily stored in memory. The contents of the memory are used to modulate a power laser during scanning to "write" on the printing cylinder but readout from the memory is adjusted in accordance with the circumferential length determined to produce the required jointing. The system may be varied to produce flexographic rollers, gravure cylinders or general copying.

Peter Martin Zollman

Papers

Control of hydraulic booms

Improvement in or relating to methods and apparatus for laser engraving

Apparatus for producing a seamless copy from an unjointed original

Copying process for producing a seamless copy from an unjointed original