GB2315544A

GB2315544A - Improvements to thermography

Info

Publication number: GB2315544A
Application number: GB9615600A
Authority: GB
Inventors: Peter Colin Galilee
Original assignee: FAUST THERMOGRAPHIC SUPPLY Ltd
Current assignee: FAUST THERMOGRAPHIC SUPPLY Ltd
Priority date: 1996-07-25
Filing date: 1996-07-25
Publication date: 1998-02-04
Also published as: GB9615600D0

Abstract

A process of removing excess thermographic material from printed substrate, without physical contact between the suction uptake system used for the thermographic material and the printed substrate, comprises holding the substrate away from the suction uptake by suction applied to the non-printed side of the substrate. The substrate may be held by a perforated suction box, belt or cylinder.

Description

Description This invention relates to improvements in substrate control on thermographic machinery.

Thermography is a process by which a raised finish is produced on a printed substrate.

Printed substrate is taken from a printing machine and conveyed into the thermography machine.

Conventional or special inks or adhesives may be used in the printing process.

Finely chopped, ground or other materials, typically resins, are applied to the substrate by sprinkling, dipping or other means. Such materials may be applied singly or in combination.

These materials will hereinafter be referred to as thermographic materials. The substrate then passes into a suction section, which removes the thermographic material from the non-printed areas. This is accomplished by applying suction near to the surface of the substrate. The substrate is prevented from being sucked into the suction apparatus by wheels or rollers which bear on the surface of the substrate. Following this, the substrate may be further processed, for example by heating, which in the case of resin would cause the resin material to melt, flow and create a raised surface.

Thermography has typically been used to process sheets of substrate, i.e. a number of individual pieces. Such substrates have typically been lightweight, e.g. papers, and have been relatively flexible.

Attempts to produce thermography on heavy or inflexible substrates, or onto a web (continuous reel) have encountered a number of problems, one of which is the tendency for such substrates to scuff or mark where the wheels or rollers of the suction apparatus are in contact with the printed area. This can cause smearing or wiping of the printed image and can disturb the thermographic material such that blemishes are left in the finish. These problems are less obvious on lightweight sheet substrate since such substrates rise up against the wheels or rollers and conform to their movements. Problems described above when using heavy, inflexible, or web substrates, are due to differential movement between the suction apparatus wheels or rollers, and the substrate.

A typical system is shown in cross-section in diagram A in which suction (a) is applied to a semi-sealed suction box (b) to remove thermographic material (c) from the substrate (d) which is travelling in direction (e) beneath overlapping wheels (f) whose purpose is to prevent the substrate being sucked into the suction box.

According to the present invention there is provided a separate suction apparatus which is in contact with the non-printed surface of the substrate. The purpose of this is to hold the substrate (sheet or web) firmly, whilst the excess thermographic material is removed from the printed surface of the substrate. Removal of excess thermographic material from the printed surface of the substrate is achieved by applying suction at a small distance from the printed surface. No wheels or rollers are necessary since the substrate is firmly held by suction from below. Since there is no physical contact to the printed surface of the substrate, the previously described smearing and marking is eliminated.

A specific embodiment of the invention will now be described by way of reference to the accompanying drawings in which: Figure 1 shows in cross-section a stationary suction box (2) mounted beneath a continuous web or reel (3), with suction (1) applied to remove excess thermographic material.

Figure 2 shows the figure 1 in perspective.

Figure 3 shows in perspective, a suction box (2) with an open or perforated upper surface. Perforations may be any suitable shape. When processing webs or reels of different widths, suitable width suction boxes may be attached to the machine, or apertures may be sealed with tape, plugs or other means. Surfaces of the suction box may be flat or curved.

Figure 4 shows in cross section, an arrangement of the system for sheet-fed work. A perforated endless belt (5) conveys sheets of substrate (4) above the suction box (2), with suction (1) applied from above to remove excess thermographic material.

Surfaces of the suction box may be flat or curved.

Figure 5 shows the figure 4 in perspective.

Figure 6 shows in cross section an arrangement of the system for sheet fed or reel fed work. For sheet fed work a system of valves may be necessary (not shown). A perforated suction drum (2) conveys a web or sheet (3) with suction (1) applied to remove surplus thermographic material.

Referring to the drawings the system comprises a suction uptake (1) to remove surplus thermographic material from the printed web or reel (3) while the web or reel is held away from the suction uptake by the suction box (2). This is shown in figures 1-3 inclusive.

For individual sheet work as shown in figures 4 and 5 the system is arranged with a suction uptake (1) to remove surplus thermographic material from the printed sheets (4) while the sheets are held away from the suction uptake by suction from the suction box (2) below, applied through a perforated belt (5).

A variation of the system comprises a suction uptake (1) to remove surplus thermographic material from the printed sheet or web (3) while the sheet or web is held away from the suction uptake by the perforated suction cylinder (2). This is shown in figure 6.

Claims

1. A process of removing excess thermographic material from printed substrate, without physical contact between the suction uptake system used for removal of the thermographic material, and the printed substrate. The printed substrate is held away from the suction uptake by suction applied to the non-printed side of the substrate.

2. A system as claimed in claim 1 wherein the substrate, in reel or web form, is held away from the suction uptake by passing over a perforated suction box.

3. A system as claimed in claim 1 wherein the substrate is held away from the suction uptake by suction applied to the non-printed side of the substrate through a perforated endless conveyor belt.

4. A system as claimed in claim 1 wherein the substrate, in sheet or web form, is held away from the suction uptake by suction applied to the non-printed side of the substrate through a perforated drum.