WO1999048691A1

WO1999048691A1 - Ventilated printing substance carrier in printing machines for multi-colour printing

Info

Publication number: WO1999048691A1
Application number: PCT/SE1999/000512
Authority: WO
Inventors: Günter NIEMER
Original assignee: Niemer Guenter
Priority date: 1998-03-27
Filing date: 1999-03-29
Publication date: 1999-09-30
Also published as: SE509823C2; AU3543699A; SE9801093L; SE9801093D0

Abstract

A device at printing machines for printing of multi-colour prints on printing substrates (23), in particular textiles. The device is of a kind comprising a number of treatment stations (15), such as printing and drying stations (16, 17) and a number of carriers for printing substrates (22). These are arranged to successively bring the printing substrates from station to station or vice versa, that the stations are brought to cooperate with the carriers for the printing substrates. Each carrier for the printing substrates (22) consists of a channel plate provided with a number of ventilation channels (27). The carrier for the printing substrates (22) is essentially internally ventilated over its whole working area. The carrier for the printing substrates (22) is produced of a material having good heat conducting properties, and at least parts of the walls surrounding (24, 25, 26) the ventilation channels (27) are designed with a low weight and thereby a low heat accumulating capacity.

Description

VENTILATED PRINTING SUBSTANCE CARRIER IN PRINTING MACHINES FOR MULTI-COLOUR PRINTING

The present invention relates to a device at printing machines for the printing of multi-colour printing on printing substrates, in particular textiles and of a kind comprising a number of treatment stations, such as printing and drying stations and a number of carriers for printing substrates, which are arranged to successively bring the printing substrates from station to station or vice versa.

The background of the invention

Multi-colour printing, in particular on textile materials, e.g., on T-shirts, is performed by bringing them on a carrier for printing substrates, generally consisting of a massive plate of aluminium - a so called palette- which is brought to a number of stations, where printing and drying of the separate colours in the picture take place. Since the paint surface should be surface dry before the next layer of paint is applied, paint drying by means of infrared radiation is preferably used.

A conventional screen printing machine may e.g., have 8 stations, of which for instance two are required as drying stations, which means that no more than six colours can be printed using such machine. Printing tasks where 8 or even 10 colours are required, can, consequently, not be effectuated.

A printing frequency time of 5 - 10 seconds per station is normal today, which means that the heat supply must be relatively high during such short a dwell time, in order to achieve the desired surface drying on each layer of paint. However, the temperature has to be kept within very narrow limits. For certain paints the paint stiffens at 150 °C, while the curing takes place at 160 °C and the paint decomposes at 180 °C. A further important difficulty is present when working close to the stiffening temperature of the paint, the contact between the surface hot paint and the printing stencil plate - the screen- can result in an immediate stiffening of the paint in the stencil plate, whereby the paint can not be transferred to the garment and the stencil plate must

1 be cleaned before the printing can continue.

A number of solutions to the problem has been suggested, which all, however, also have negative effects.

From U.S. 5,136,938 A it is known to arrange a separate drying and a separate cooling station after each printing station. Of course, such a arrangement significantly reduces the number of printing stations and thereby also reduces a multi-colour printing machine to a few-colour printing machine, only.

WO 92/14610 A describes a multi-colour printing, where the applied layer of paint by a direct contact with a cold surface, is fixed/frozen as to prevent the paint from smearing. For this purpose, space is again required for the cooling stations and the mechanical cooling equipment.

DE 29 44 560 A shows a method where all separate layers of paint are applied on a cold, temporary support as to freeze every layer. When all layers have been transferred on a temporary support, the stacked layers of paint are thawed and are transferred as a unit to the final, permanent support.

The object of the invention and the solution of the problem

The object of the invention is to provide a device of the kind mentioned in the first paragraph, which:

• provides a qualitative high-quality multi-colour printing without a printing station being occupied for drying or cooling; has a production rate which widely exceeds conventional printing rates at continuous operation (e.g., 800 T-shirts/h to 200 T-shirts at conventional operation);

• keeps the temperature of the printing substrates within narrow limits in a very simple way; • can be installed on most of the printing machines on the market.

These objects has been solved by the fact that the carrier for the printing substrates consists of a channel plate provided with a number of ventilation channels, that the carrier for the printing substrates is ventilated at its interior essentially over its whole working area, that the carrier for the printing substrates is produced of a material having good heat conducting properties, and that at least parts of the walls surrounding the ventilation channels are designed having a low weight and thereby a low heat hosting capacity.

Description of the drawings

The invention will be described more in detail with reference to the enclosed drawings, where: Fig. 1 shows a schematic side view of a multi-colour printing machine of a conventional type provided with the device according to the invention and in a simplified form with only two oppositely situated treatment stations. Fig. 2 shows a view from above on the printing machine according to Fig. 1. Fig. 3 shows a cross-section of a carrier for printing substrates at unnatural scale. Fig. 4 shows a part of the carrier for printing substrates according to Fig. 3 in a view from above and partly broken.

Description of an embodiment

The printing machine showed in Fig. 1 and 2 includes a stand 11 , at which a vertical column 12 is attached, which at its upper part carries a fixed holder 13 , from which extends radially brackets 14, to which a treatment unit 15 is attached, e.g., a printing station 16 or a drying station 17.

Below the fixed bracket 13 a rotary upper ring 18 is arranged around the column 12 and on a somewhat lower level a likewise rotary lower ring 19. A number of actuators 20 are arranged between these rings, by which it is possible to raise and lower the radial arms 21 which are fixedly arranged at the upper ring 18, which in turn each carries a carrier for printing substrates 22, in direction towards e.g., a printing or drying station 16, 17.

At the carrier for printing substrates, in the following referred to as the palette, the printing substrate 23 is fixed and attached, which in the shown embodiment is a textile garment, for instance a T-shirt and which is moved stepwise from station to station, where the separate phases in the printing process is performed. The palette 22 is in contrast to conventional palettes not massive, but designed as a channel plate in accordance with Fig. 3. The channel plate consists of form stable upper and lower plates 24 and 25, respectively, spaced from each other by spacing means 26, which form longitudinal channels 27. These are open in both ends as to continuously become ventilated by flowing through of surrounding air.

In one end of each channel plate 22, a distribution tube 28 is arranged perpendicular to the longitudinal direction of the channels 27 which tube is provided with outlet openings 29 directed towards the channels 27 for adding of a pressurised, cold air flow. Each distribution tube 28 is connected to a male connector 30 being part of a connecting unit, which male connector is arranged in such a way that when the palette 22 is brought up against the treatment unit 15, this will cooperate with a second, female connector 31 being part of the connecting unit, whereby a one-way valve is opened and the distribution tube 28 will be connected to a pressure source (not shown). Each channel plate 22 is thus intermittently connectable to forced ventilation. A valve in the supply line to the connection unit 30, 31 can be controlled dependant of the temperature of the channel plate 22, so that forced cooling and ventilation can be applied when needed.

In order to be able to adjust the palette 22 in a more easy way relative the treatment station 15 and to be able to rapidly exchange this palette to others, it is provided with guiding rails 34 on its underside, in order to make it displacable along the arm 21 and being fixable by means of a clamping device 33 at different displacement positions.

The device works in the following way.

When the printing machine has been started, no harmful superfluous heat has not yet been accumulated in the palettes, whereby the cooling air to these is closed. In connection with the fact that the palettes have passed the drying station 17 a couple of times the palettes assume a higher and higher temperature, whereby, in the beginning, a self circulation through the channel plates is enough, until the current stiffening temperature for the paint, e.g., 120 - 150 °C has been reached. If this temperature is exceeded, the valve in the supply main is opened and chilled air having a temperature of about + 10 °C and a slight overpressure is intermittently introduced into the distribution tubes 28, whereby all palettes at all stations are cooled. It is of course possible to cool each palette individually, but the rotational speed of the printing machine, having a dwell time of about 3 - 4 seconds at each station, is so high that a collective cooling is enough.

By keeping the palette 22 and thereby also the printing substrate 23 at or close to the stiffening temperature of the paint neither freezing of the paint nor cooling stations between the printing stations are needed. All available stations can be used for the application of paint, except for a drying station, which means that even relatively small printing machines can be used for advanced multi-colour printing. Since a source for compressed air still is required for the operation and running of the printing machine, and the consumption of compressed air is very modest, and the cooling of the air takes place in connection with the reduction of the water content in the air by condensation, these conditions are already present and the otherwise necessary completion is economically very modest.

List of reference numerals

11 stand

12 column

13 holder

14 bracket

15 treatment unit

16 printing station

17 drying station

18 upper

19 lower

20 actuator

21 arm

22 carrier for printing substrates/ palette/ channel plate

23 printing substrate/ textile garment

24 upper plate

25 lower plate

26 spacing means

27 channel

28 distribution tube

29 outflow opening

30 male connection

31 female connection

33 clamping device

34 guiding rails

Claims

1. Device at printing machines for printing of multi-colour printing on printing substrates (23), in particular textiles and of a kind comprising a number of treatment stations (15), such as printing and drying stations (16, 17) and a number of carriers for printing substrates (22), which are arranged to successively bring the printing substrates from station to station or vice versa, that the stations are brought to cooperate with the carriers for the printing substrates, characterized in, that each carrier for the printing substrates (22) consists of a channel plate provided with a number of ventilation channels (27), that the carrier for the printing substrates (22) is essentially internally ventilated over its whole working area, that the carrier for the printing substrates (22) is produced of a material having good heat conducting properties, and that at least parts of the walls (24, 25, 26) surrounding the ventilation channels (27) are designed with a low weight and thereby a low heat accumulating capacity.

2. Device according to claim 1, characterized in, that the channel plate (22) at its one end is provided with or connected to a distribution pipe (28), for the distribution of cold compressed air to the separate channels (27) of the channel plate, and that the channel plate at both its opposite ends is open for the flow of atmospheric air.

3. Device according to claim 2, characterized in, that the distribution pipes (28) of the channel plates (22) are connectable to a common feed pipe provided with a thermostatic controlled shut down valve dependant of the temperature of the channel plate.

4. Device according to claim 3, characterized in, that the distribution pipes (28) of the channel plates (22) are arranged to be connected to a connecting means (30) being part of a connecting unit, which means is arranged to be brought in cooperation with a second connecting means (31) upon activation of a carrier for printing substrates for cooperation with a treatment unit (15).

5. Device according to claim 4, characterized in, that the carrier for printing substrates (22) on its under side is provided with guiding element (34) for the linear control along a carrying arm (21) of a carrier, and that the carrier for printing substrates (22) is fixed to the arm (21) by means of a clamping device (33) or the like.