GB2482657A

GB2482657A - Carrier for thermal transfer printing apparatus

Info

Publication number: GB2482657A
Application number: GB201010475A
Authority: GB
Inventors: Kylash Makenji; Kevin James Baumber
Original assignee: IDT SYSTEMS Ltd
Current assignee: IDT SYSTEMS Ltd
Priority date: 2010-06-22
Filing date: 2010-06-22
Publication date: 2012-02-15
Also published as: GB201010475D0

Abstract

A printing apparatus comprising a carrier 1 which supports a plurality of thermal transfer units 2; each thermal transfer unit comprises an enclosure including means for receiving an article 5 to be printed and means to secure in proximity to the article 5 a transfer medium bearing an image; wherein the carrier comprises a means 8 for reversibly connecting multiple thermal transfer units to a common means of forming a pressure differential. The pressure differential is preferably a vacuum and in use the carrier and thermal transfer units are preferably loaded into a heat chamber.

Description

Printing Method and Apparatus The present invention relates to printing an image onto the surface of an article. More specifically, the invention relates to a method and apparatus for image printing on an article, preferably a three-dimensional article, using thermal dye sublimation.

Traditionally, dye sublimation transfer processes are performed using an image printed on a transfer medium, which can be heated to make it flexible such that it may more easily thermoform around a three-dimensional article, subsequently placed onto an article contained within a suitable enclosure, pressed into place to allow thermoforming, placed inside a heating device and vigorously heated to induce transfer of the image to the article. During this process the dyes sublimate from the medium to the article. Once sublimation has occurred, the heat from this container is vented and cooled quickly to ambient temperature. This type of dye sublimation process has been disclosed in WO 02/072301, US4668239, US44587 155 and US4670084. A similar method and apparatus to the above is disclosed in WO 01/96123, however, in this method a protective coating is applied to the surface of a three-dimensional article prior to thermal transfer and involves heating the transfer element to at least partially transfer the image into the protective coating.

Transfer mediums such as the one described by EP1102682B1 allow an image to be transferred to their surface by using a digital printer in conjunction with sublimation dyes.

Transfer mediums of this kind are characterised as having a dye receptive layer and being able to thermo form around an article.

There are several disadvantages to the above described methods and apparatus. Current dye sublimation processes are inefficient and only a limited number of articles can be printed in each batch. Also, transfer mediums and articles are urged into contact and then placed into a heat chamber which must be vented and cooled before the removal of the articles. This is can lead to long time periods between batches due to the time required to heat the chamber to the desired temperature and then to cool it back to ambient temperature. Another disadvantage is that traditional methods of dye sublimation are prone to "thermal shock" when used with a three-dimensional article. Thermal shock occurs as different parts of a three-dimensional article's surface conduct heat at different rates and as this uneven thermal transfer increases the article begins to warp and deform. One of the key factors in thermal shock is that the transfer medium is heated to make it more flexible and then applied to the colder surface of the article to be printed. These factors demonstrate the inefficient nature of traditional dye sublimation processes which can be costly both in the time and energy.

It is an object of the present invention to address the issues of current thermal dye sublimation methods and apparatus.

According to one aspect of the present invention there is provided an apparatus for printing an image onto the surface of an article, the apparatus comprising a carrier adapted to support a plurality of thermal transfer units each said thermal transfer unit comprising an enclosure including means for receiving the article, means to secure in proximity to the article a transfer medium bearing an image and a means of forming a pressure differential to urge said transfer medium into contact with the article wherein the carrier comprises means of reversibly connecting multiple thermal transfer units to a common means of forming a pressure differential The carrier, which may also be described as a shuttle base, allows individual thermal transfer units to be prepared prior to placing them into a heat chamber. Tndividual thermal transfer units can be loaded with parts to be decorated, and transfer medium, in isolation from the heat chamber in order to facilitate minimum down time during production, and save heat energy escaping from the heat chamber once the door is opened.

The carrier may comprise two longitudinal sides, a plurality of apertures therein and two lips extending from the longitudinal sides, wherein one lip extends upwardly from the carrier and the other lip extends downwardly from the carrier. The upwardly extending lip may be used to support a thermal transfer unit placed upon it and the downwardly extending lip may be used to support a thermal transfer unit during transport to a heat chamber. Preferably, the carrier is able to hold a plurality of thermal transfer units such that they can be stacked horizontally or vertically.

Raised registration pins may extend upwards from the carrier. The raised registration pins can be used to ensure the correct loading of the carrier into the heat chamber and/or may be used to ensure the correct loading of the thermal transfer unit onto the carrier.

The apparatus of the present invention is particularly suited to use with multiple thermal transfer units and the multiple thermal transfer units are all connected to a single means of forming a pressure differential.

The means of forming a pressure differential may comprise a vacuum supply. Connection of a vacuum supply to at least one thermal transfer unit may be achieved using a quick release vacuum coupling. The vacuum can be used to urge at least one transfer medium and a three-dimensional article into contact. Vacuum hoses may be connected to the vacuum manifold on the at least one thermal transfer unit, these vacuum hoses may then connected to a common vacuum supply by quick release vacuum couplings. The quick connect system enables fast loading and unloading of the thermal transfer units thereby increasing the efficiency of the apparatus.

The apparatus of the present invention is particularly suited to use with three-dimensional articles, however, the apparatus could also be used for printing an image onto the surface of two-dimensional articles.

The apparatus of the present invention may further comprise at least one heat source. The at least one heat source can comprise a convection oven, an infrared lamp, a quartz lamp, a halogen lamp, or any combination thereof. More than one heat source may be used in the apparatus of the present invention, accordingly the apparatus may comprise a primary and a secondary heat source.

In a preferred embodiment the at least one thermal transfer unit is comprised of five wall portions arranged into an enclosure with a hollow interior for receiving an article to be printed, one of the said walls having a vacuum manifold. Tn this embodiment, the thermal transfer unit comprises an edge formed from the upper most region of four of the five wall portions and a means of applying a thermal transfer medium to said edge.

In an embodiment of the present invention, the means to secure a transfer medium is a frame.

The frame may be realisably affixed to the at least one thermal transfer unit by fastenings such that the transfer medium is secured between the frame and the edge of the thermal transfer unit and held in proximity to an article to be printed.

In another embodiment the apparatus comprises two means to secure a transfer medium bearing an image in proximity to an article, each transfer medium being loaded into said thermal transfer unit on opposite sides of the article such that two images may be simultaneously applied to the article. This allows for the printing of the entire surface of said three-dimensional article. Alternatively, multiple sections of a three-dimensional object could be printed with a single image, for example, a continuous label around the neck of a bottle.

Heat conductors may be positioned within the thermal transfer units and situated such that they contact areas of the an article where poor thermal transfer might result. The heat conductors may be similar in design to heat sinks traditionally used to remove heat from hot areas, although in the context of the present invention they may be used to focus heat on specific areas within the thermal transfer units. The heat conductors assist in the even distribution of heat over the surface of a three-dimensional article and prevents thermal shock.

According to a second aspect of the present invention there is provided a method for printing an image onto the surface of an article, the method comprising providing a transfer medium bearing an image positioning and securing an article within a thermal transfer unit positioning and securing said transfer medium bearing an image in proximity to said article within said thermal transfer unit loading a carrier and at least one thermal transfer unit comprising a transfer medium and an article into a heat chamber, applying a vacuum to urge said thermal transfer medium and said article into contact and heating the transfer apparatus to a uniform temperature for a sufficient length of time to enable transfer of the image from the transfer medium to the article.

In a preferred embodiment the at least one thermal transfer unit is removed from said heat chamber and allowed to cool slowly to ambient temperature. Suitable transfer mediums and sublimation dyes are known.

When applied to three-dimensional articles traditional dye sublimation methods can have detrimental effects. In these processes a transfer medium is pre-heated before it is applied to the colder surface of a three-dimensional article. This can cause thermal shock and deformation of the three-dimensional article. In the method of the present invention, printing an image onto the surface of an article can be achieved after only one intense heating cycle. A thermal transfer unit containing a transfer medium and a three-dimensional article may be loaded into a heat chamber which is maintained at the desired temperature. Typically, the thermal transfer unit is maintained at the desired temperature for a time of from 6 to 20 minutes. The temperatures of the heat chamber is commonly a temperature of from 160 to 220°C. The heat source for the dye sublimation process may comprise a convection oven, a source of infrared, quartz or halogen units or a combination of these heating apparatus such that one is the primary and another a secondary heat source.

A protective coating may be applied to an article before or after an image has been printed upon its surface by the described thermal transfer process. This protective coating is not an essential element of the process but may aid longevity of the image upon the article.

The present invention will now be described by way of example with reference to the following drawings, in which: Figure 1 is a view of an apparatus according to the invention; Figure 2 is an alternative view of the apparatus of Figure 2; and Figure 3 is a schematic drawing of a part of the apparatus according to the present invention.

Referring to the drawings there is illustrated the apparatus for printing an image on an article, the apparatus comprising a carrier 1 adapted to support a plurality of thermal transfer units 2 each said thermal transfer unit 2 comprising an enclosure including means for receiving the article 5, means to secure in proximity to the article 4 a transfer medium 3 bearing an image and a means of forming a pressure differential 7 to urge said transfer medium into contact with the article wherein the carrier comprises means of reversibly connecting multiple thermal transfer units to a common means of forming a pressure differential 8.

The carrier 1 is formed from four longitudinally spaced bars connected to two shorter bars connected at either end to form a support frame. The carrier also has a downwardly extending lip 12 and an upwardly extending lip 11. Each thermal transfer unit comprises a vacuum manifold 7 and each vacuum manifold 7 attaches to the vacuum hose 8, which in turn connects to a common means of forming a vacuum, e.g. a vacuum pump. Each thermal transfer unit 2 is in the form of a five sided enclosure and is made from sintered material (e.g. a sintered material comprising aluminium). The vacuum manifold 7 is built into one of the sides of the thermal transfer unit.

In use, an article to be printed is placed into the enclosure and a transfer medium bearing an image 3 is placed over the edges of the enclosure and secured using the frame 4. The frame 4 engages the transfer medium 3 onto the edge of the enclosure by means of fastenings 6.

Registration of the transfer medium and the article may be ensured using at least one registration pin. Vacuum hoses 8 are attached to the vacuum manifolds 7 and the carrier 1 (and the thermal transfer units 2 supported on the carrier 1) is placed into a heated chamber to be heated to a uniform temperature. The interior of the thermal transfer unit is then evacuated using a vacuum forming means through the vacuum manifold 7 and the vacuum hose 8.

Figure 3 represents an alternative embodiment of a thermal transfer unit 2a for use in an apparatus according to the present invention. The thermal transfer unit 2a comprising one or more thermal transfer units 2a adapted to secure a plurality of transfer media 3a and 3b bearing an image in proximity to the article, each transfer medium 3a and 3b being loaded into said thermal transfer unit 2a on opposite sides of the article such that two images may be simultaneously applied to the article. The thermal transfer unit 2a comprises an enclosure 5a in the form of a four sided structure with a hollow interior. Two frames 4a, 4b are located on either side of the enclosure 5a and are secured to the edge of the enclosure by means of a hinge 14a. The enclosure 5a comprises a vacuum manifold 7a and vacuum inlet ports 13a located within one of the four sides of the enclosure 5a. Fastenings 6a and rubber seals 1 5a allow the frames 4a, 4b to be closed around the enclosure 5a such that when a vacuum is applied using the vacuum manifold 7a gas may be drawn from within the enclosure 5a.

In use, an article is placed within said enclosure 5a and between two transfer mediums 3a and 3b each supported on a frame 4a, 4b. The frames 4a, 4b are closed around the enclosure 5a forcing the transfer mediums into contact with the rubber seals iSa. The fastenings 6a may the be used to secure the frames 4a, 4b and the enclosure 5a in position thereby creating an air-tight space housing the article and the two transfer mediums 3a, 3b. Vacuum may then be applied to the air-tight space.

Claims

Claims 1. An apparatus for printing an image on an article, the apparatus comprising a carrier adapted to support a plurality of thermal transfer units each said thermal transfer unit comprising an enclosure including means for receiving the article, means to secure in proximity to the article a transfer medium bearing an image and a means of forming a pressure differential to urge said transfer medium into contact with the article wherein the carrier comprises means for reversibly connecting multiple thermal transfer units to a common means of forming a pressure differential.
2. Apparatus according to claim 1, comprising one or more thermal transfer units adapted to secure a plurality of transfer media bearing an image in proximity to the article, each transfer medium being loaded into said thermal transfer unit on opposite sides of the article such that two images may be simultaneously applied to the article.
3. Apparatus according to claim 1 or 2, wherein a plurality of thermal transfer units are positioned upon the same carrier.
4. Apparatus according to any of the preceding claims, wherein the thermal transfer unit comprises at least one vacuum manifold, through which the said thermal transfer unit can be evacuated during operation by a vacuum forming means.
5. Apparatus according to any of the preceding claims, wherein, the thermal transfer unit is formed from a cast sintered material.
6. Apparatus according to any of the preceding claims, wherein the apparatus further comprises at least one heat source.
7. Apparatus according to claim 6, wherein the at least one heat source comprises a convection oven, an infrared lamp, a quartz lamp, halogen lamp, or any combination thereof.
8. Apparatus according to claim 6 or 7, wherein the apparatus comprises a primary and a secondary heat source.
9. Apparatus according to any of the preceding claims, ftirther comprising registration pins for positioning said carrier within said heating chamber.
10. Apparatus according to any of the preceding claims, further comprising heat conductors within said at least one thermal transfer unit positioned such that they contact areas of the said article where poor thermal transfer might result.
11. Apparatus according to any of the preceding claims, wherein at least one thermal transfer unit is connected to a common vacuum supply by a quick release vacuum coupling.
12. A method for printing an image onto the surface of an article, the method comprising providing a transfer medium bearing an image positioning and securing of an article within a thermal transfer unit positioning and securing of said transfer medium bearing an image in proximity to said article within said thermal transfer unit, loading of transfer apparatus comprising: a carrier and at least one thermal transfer unit, which itself comprises a transfer medium and an article, into a heat chamber, applying a vacuum to urge said thermal transfer medium and said article into contact and heating the transfer apparatus to a uniform temperature for a sufficient length of time to enable transfer of the image from the transfer medium to the article.
13. A method according to claim 12, wherein said thermal transfer unit is removed from said heat chamber and allowed to cool slowly to ambient temperature.
14. A method according to claim 12 or 13, wherein the apparatus comprises two means to secure a transfer medium bearing an image in proximity to the article, each transfer medium being loaded into said thermal transfer unit on opposite sides of the article such that two images may be simultaneously applied to the article.
15. A method according to claims 12 to 14, wherein the length of time sufficient to enable transfer of the image from the transfer medium to the article ranges from 6 to 20 minutes.
16. A method according to claims 9 to 15, wherein said heat chamber is heated to achieve a uniform temperature of from 160 to 220°C.
17. A method according to claim 9 to 16, wherein a protective coating is applied to said article after an image has been printed upon its surface by the described thermal transfer process.
18. A method according to claim 9 to 16, wherein a protective coating is applied to said article prior to an image being printed upon its surface by the described thermal transfer process.