GB2319990A

GB2319990A - Thermal transfer printer with pivoted end edge printhead for thickened substrates

Info

Publication number: GB2319990A
Application number: GB9625393A
Authority: GB
Inventors: Paul St John Ewer
Original assignee: Critchley Ltd
Current assignee: Critchley Group Ltd
Priority date: 1996-12-06
Filing date: 1996-12-06
Publication date: 1998-06-10
Anticipated expiration: 2016-12-06
Also published as: GB2319990B; GB9625393D0

Abstract

A printer unit 1 has a printhead 7 formed at the end edge of the unit, the other end of which is pivotally mounted. The unit is biased into contact with a platen roller 4 and prints onto thickened substrates 5 (e.g. plastic labels or a flattened tube) carried by a sheet 3 as the sheet and an ink ribbon are passed between the head and the platen, so that the enlarged ends of the tube do not disrupt printing. The contact between the ribbon and the tube can be increased by passing them to a downstream auxiliary roller (14,Fig.6) whereat the spent ribbon is led away. The ink ribbon may be a foil with a high tack, high viscosity ink, so that the ink adheres to the substrate after the foil is pulled away following thermal contact with the head.

Description

Improvements relating to Thermal Transfer Printinq In a method of printing information onto "paper" labels carried on a backing sheet, the backing sheet is fed past a thermal transfer print head set into a body of a printer unit. However problems arise where the substrate member mounted on the carrier sheet has a significant thickness.

Standard labels have a thickness comparable to the carrier sheet itself. The invention is concerned with a means whereby thermal transfer printing can be applied to relatively thick substrate members. These may be, for example, relatively rigid plates of a plastics material to be used as a tie-on label or a marker sleeve which will be mounted onto the carrier sheet in a flattened form. The conventional type of thermal transfer printing unit cannot adequately apply marks of an acceptable quality onto such substrate members, partly because the substrate members interfere with the body parts of the printer unit.

From one aspect this invention provides a printer unit for printing information onto individual substrate members of notable thickness carried on a continuous carrier sheet, wherein a thermal transfer print head is provided at the end edge of a printer body which is pivotally mounted at its other end and a pressure roller is positioned below the print head, with the printer body being biassed so that the print head presses down towards the roller, and means is provided for feeding the carrier sheet and a thermal transfer ink ribbon together between the print head and the pressure roller.

By utilising a thermal transfer print head at the end edge of the printer body problems of interference between parts of the printer body and the substrate member are substantially eliminated. Furthermore the positioning of the print head at the end edge (rather than using a conventional print head) can more readily apply the necessary pressure evenly over the substrate member during the printing procedure. Because the print head will be in contact with the ink ribbon and the substrate member for a relatively short period of time (as compared with a conventional type of thermal transfer print head), when using a conventional thermal transfer ink ribbon, there is the risk that inadequate transfer of ink onto the substrate member will be achieved. Ideally, therefore, the printer unit will be constructed such that a fixed auxiliary pressure roller or pressure pad is positioned beyond the print head to extend the in-line pathway of the carrier sheet together with the ink ribbon. During the movement of the carrier sheet and ink ribbon along the extended in-line pathway a greater opportunity for the heated ink to transfer to the substrate member will be created.

The invention also extends to a method of thermal transfer printing information onto individual substrate members of notable thickness carried on a continuous carrier sheet, wherein feed means causes the carrier sheet and a thermal transfer ink ribbon to be transported together between a thermal transfer print head and a pressure roller, the print head is provided at the end edge of a printer body which is pivotally mounted at its other end and so that the print head is positioned above the pressure roller, with the printer body being biassed so that the print head presses down towards the roller.

In order to ensure that a high quality print is achieved it may be preferred that the ink ribbon should be a foil with a special high tack, high viscosity ink, the ink and the surface characteristic of the substrate member being chosen so that the ink prefers to adhere to the substrate when the foil is pulled away after thermal transfer contact with the print head. Alternatively or additionally the method of printing can be carried out in such a manner that the carrier sheet together with the ink ribbon subsequently pass around a fixed auxiliary pressure roller or pressure pad which is positioned beyond the print head to extend the in-line pathway of the sheet and the ribbon.

This method is particularly suited for use with an rigid substrate member, or an uneven one such as a flattened tube (as the enlarged curved ends of the flattened tube will not interfere with the print head positioned at the end edge of the printer body during the thermal transfer part of the process). It is envisaged in any case that the substrate member employed will have a thickness of at least 500 microns. For example a flattened tube may have an overall thickness of about 1500 microns.

The invention may be performed in various ways and a preferred embodiment will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 is a representative view of a conventional type of thermal transfer printer; Figure 2 is an enlarged view of the print head of the printer of Figure 1; Figure 3 is a representative view of the printer unit of a printer of the invention; Figure 4 is a more detailed illustration of the general features of the printer unit of the invention; and Figures 5 and 6 show details of the unit shown in Figure 4, in enlarged view, in two different modes of operation of the printer unit of Figure 4.

Figures 1 and 2 illustrate a printer unit 1 having a print head 2 set into the printer body. A carrier sheet 3 is fed around a pressure roller 4. Mounted on the carrier sheet 3 are flattened sleeves 5. As can be seen clearly from Figure 2, the enlarged ends 6 of the flattened sleeves interfere with the body of the printer unit 1. The forward end of the sleeve 5 initially raises the print head out of contact with the surface of the sleeve, so that thermal transfer of the ink is not fully effective. The rearward end of the sleeve 5 can also interfere with parts of the printer body and raise the print head out of contact with the sleeve 5.

In order to overcome these difficulties the invention employs a modified printer unit 1 wherein a print head 7 is formed at the end edge of the body of the printer unit 1.

The enlarged ends of the flattened sleeves 5 will not then interfere with the printing operation over the area of the sleeve where printing is required.

The design of the preferred form of printer unit of the invention is shown in more detail in Figure 4. The backing sheet 3 is fed off a reel 8 and is then led to the front of the body of the printer unit 1. At the same time a thermal transfer ink ribbon is fed from a reel 9 to meet up with the substrate members (such as the flattened sleeves 5) at the end edge print head. The printer unit 1 is pivoted at 10 so that the print head is biassed into contact with the carrier sheet and the ink ribbon onto a pressure roller 11. The carrier sheet 3, with the printed substrate members thereon, is wound back onto a take up reel 12. The spent ribbon is rewound onto a reel 13.

The positioning of the end edge print head 7 can be seen in greater detail in Figures 5 and 6. If the ink ribbon used has a high tack, high viscosity so that it prefers to select the surface of the substrate member, after being subjected to heating at the print head 7, then the pressure applied solely onto the pressure roller 11 may suffice to achieve an adequate transfer onto the substrate member. The contact between the ink ribbon and the substrate can however be increased by passing them to an auxiliary roller 14 around which the spent ink ribbon is led away, as shown in Figure 6.

Claims

1. A printer unit for printing information onto individual substrate members of notable thickness carried on a continuous carrier sheet, wherein a thermal transfer print head is provided at the end edge of a printer body which is pivotally mounted at its other end and a pressure roller is positioned below the print head, with the printer body being biassed so that the print head presses down towards the roller, and means is provided for feeding the carrier sheet and a thermal transfer ink ribbon together between the print head and the pressure roller.

2. A printer unit according to Claim 1, wherein a fixed auxiliary pressure roller or pressure pad is positioned beyond the print head to extend the in-line pathway of the carrier sheet together with the ink ribbon.

3. A method of thermal transfer printing information onto individual substrate members of notable thickness carried on a continuous carrier sheet, wherein feed means causes the carrier sheet and a thermal transfer ink ribbon to be transported together between a thermal transfer print head and a pressure roller, the print head is provided at the end edge of a printer body which is pivotally mounted at its other end and so that the print head is positioned above the pressure roller, with the printer body being biassed so that the print head presses down towards the roller.

4. A method according to Claim 3, wherein the ink ribbon is a foil with a special high tack, high viscosity ink, the ink and the surface characteristic of the substrate member being chosen so that the ink prefers to adhere to the substrate when the foil is pulled away after thermal transfer contact with the print head.

5. A method according to Claim 3 or Claim 4, wherein the carrier sheet together with the ink ribbon subsequently pass around a fixed auxiliary pressure roller or pressure pad which is positioned beyond the print head to extend the in-line pathway of the sheet and the ribbon.

6. A method according to any one of Claims 3 to 5, wherein the substrate member is rigid or is uneven, such as in the form of a flattened tube.

7. A method according to any one of Claims 3 to 6, wherein the substrate member has a thickness in excess of 500 microns.

8. A printer unit or a thermal transfer method substantially as herein described with reference to the accompanying drawings.