EP0438410A1

EP0438410A1 - Drying element.

Info

Publication number: EP0438410A1
Application number: EP89906100A
Authority: EP
Inventors: Hans G Platsch
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-10-14
Filing date: 1989-05-24
Publication date: 1991-07-31
Anticipated expiration: 2009-05-24
Also published as: US5159763A; WO1990003888A1; JPH04502887A; DE3835000A1; DE58903419D1; EP0438410B1

Abstract

Dans un élément de séchage compact pour la section de séchage d'une imprimante, l'air soufflé chaud est produit lorsque l'on chauffe de l'extérieur un tube de chauffage (48) par un radiateur infrarouge (66) parallèle audit tube de chauffage. L'air soufflé chaud atteint un conduit de soufflage (50, 60) parallèle au tube de chauffage (48) en passant par un tuyau coudé à 180° (52). Un réflecteur (34, 36) entourant l'unité tube de chauffage/conduit de soufflage reflète le rayonnement infrarouge sur le tube de chauffage (48) et transmet l'énergie radiante qu'il a absorbée à un courant d'air secondaire (82, 84), qui se mélange au courant d'air chaud principal au niveau de la sortie du conduit de soufflage (50, 60).In a compact drying element for the drying section of a printer, hot blown air is produced when a heating tube (48) is heated from the outside by an infrared heater (66) parallel to said heating tube. heater. The hot blown air reaches a blast duct (50, 60) parallel to the heating tube (48) through a pipe bent at 180 ° (52). A reflector (34, 36) surrounding the heater tube / blower duct unit reflects infrared radiation onto the heater tube (48) and transmits the radiant energy it has absorbed to a secondary air stream (82 , 84), which mixes with the main hot air stream at the outlet of the blowing duct (50, 60).

Description

Dryer element

description

The invention relates to a dryer element for use in a printing press according to the preamble of claim 1, and a dryer unit constructed from such dryer elements.

Inks are used in the printing industry on a different basis, with different binders and different pigments. Infrared radiation dryer elements are preferred for drying conventional offset inks and for drying oil varnishes. When using water-based paints, such as those used in particular as a clear coat over the printing inks, in order to give the surface of the finished product gloss, warm air dryer elements are preferred. UV radiation dryer elements are used for special varnishes and printing inks that contain prepolymerized plastic materials.

UV drying requires special measures of a larger size not only because of the installation of very powerful UV rays but also because of the radiation protection and the extraction of the ozone generated by the UV rays, so that appropriately equipped printing machines are always fully utilized in connection with UV drying becomes.

For IR drying and blow air drying, on the other hand, a changeover would often make sense if other print jobs are to be processed on a given machine.

However, this conversion currently fails because IR dryers and blow air dryers have different space requirements: IR dryers can be used to dry the printed product in a very compact space; Conventional blow air dryers, on the other hand, require a lot of space. The present invention is therefore intended to create a dryer element which is very compact

Construction enables the local production of warm blown air in large quantities, so that a blown air dryer unit built with it is so compact that a conventional IR dryer can be easily replaced with it.

This object is achieved according to the invention by a dryer element according to claim 1.

In the dryer element according to the invention, a rod-shaped infrared radiator is used to provide a large heat output in a very compact volume. This heat output is first transferred to the blown air by absorption on a heating pipe running parallel to the infrared heater. The blown air to be heated is sent through this. The heating tube is in turn upstream of the blow molding, which emits the heated air.

On the one hand, you have an effective intensive heat transfer between the infrared heater and the heating pipe, which you could not achieve by blowing the air directly past the infrared heater. Since the entire heating up of the

Blown air is terminated before the same enters the blow bar, the same warm blow air also emerges at the different exit points of the blow bar. If one were to produce the hot air in a conventional manner by passing the blown air directly past Widei standing wires, one would have to provide a heating register which has to be set up separately outside the printing press. So you need additional

Installation space on machines already installed in generally not available, and you also have

additional heat losses on the way from the production site to the application site. Advantageous developments of the invention are specified in the claims.

A dryer element, as stated in claim 2, is particularly short overall, since the heating tube and blow bar are kept within the same transverse limits with respect to the direction of conveyance of the printed products.

The development of the invention according to claim 3 is advantageous in terms of avoiding eddies in the heating tube. In addition, the convexly curved outer surface of the heating tube ensures that the heat rays striking the heating tube are not reflected back into the infrared radiator, which is what

improves the effective heat flow from the infrared heater to the heating pipe.

You can then according to claim 4, the heat rays running away from the convex outer surface of the heating tube

catch again with mechanically simple means and

use for air heating.

With the development of the invention according to claim 5 it is achieved that those heat rays also reach the surface of the heating tube that, starting from the infrared radiator, first run past the heating tube.

According to claim 6, a light funnel leading these rays to the surface of the heating tube can be produced with elements having a circular cross-section that are particularly easy to manufacture. If one chooses the center point of the circular reflector and its radius according to claim 7 so that the ends of the two light funnels lying on both sides of the element center plane are opposite the infrared radiator and taper, an especially uniform heating of the heating tube is obtained in the circumferential direction.

The development of the invention according to claim B is in

With regard to the supply of those heat rays to the

Heating tube advantageous, which are emitted by the infrared radiator in the half-space away from the heating tube.

The development of the invention according to claim 9 is advantageous with regard to the supply of large amounts of heat to the heating tube with a compact construction of the dryer element.

The electrical installation and maintenance of the dryer element is simplified by the use of a twin infrared heater.

To cool the electrical connections and holding devices assigned to the infrared radiator, it is generally necessary to maintain a limited flow of cooling air on the infrared radiator. With the development of the invention according to claim 10, this cooling air flow is obtained very simply and without additional blowers in a mechanically very simple manner in that the reflector is part of a cooling air surrounding the infrared radiator, which is coupled in the manner of a water jet pump to the outlet of the blow bar.

As a rule, it is not possible for cost reasons to make the inner surface of the reflector genuinely reflective, for example to polish it and to provide it with a surface layer. A well reflective surface would be desirable in itself worth as much as possible of the heat radiation given by the infrared radiator to the outer surface of the

Bring heating tube, where it is then absorbed. However, if you let a secondary air stream pass the reflector and mix this secondary air stream, which is warmed up by the reflector, with the main blown air stream, the one taken up by the reflector also becomes

Heat quantity made usable. This side effect is obtained both in the case of a dryer element according to claim 10 and to an increased extent in the case of a dryer element according to claim 11. The secondary air flow is also generated in the dryer element according to claim 11 according to the principle of a water jet pump without an additional fan. The development of the invention according

Claim 11 also has the further advantage that the outer housing is already at a low temperature, which is advantageous in terms of accident protection.

The development of the invention according to claim 12 is advantageous with regard to a strong and effective secondary air entrainment effect, since the "water jet pump effect" is better for sharp, fast, small cross-section air jets than for large cross-section, slow air curtains.

A dryer unit as specified in claim 13 can simply be exchanged for an infrared dryer unit provided in the same standard slide-in frame. This makes it possible to work with infrared drying and blown air drying with short changeover times on the same printing press.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing. In this show: Figure 1: a transverse cross section through a

Blower air dryer unit dryer element for an offset printing machine;

Figure 2 is a schematic diagram on an enlarged scale, based on which the transfer of heat from

Infrared radiator for the heating tube of the dryer element of Figure 1 is explained;

FIG. 3: a basic illustration similar to FIG. 2,

which for a modified dryer element

applies; and FIG. 4: a view of a dryer learners according to FIG

Figure 1 constructed blown air dryer unit and an infrared dryer unit, which has the same outer geometry. FIG. 1 shows a dryer element, generally designated 10, which has an outer housing, generally designated 12. The outer housing 12 is delimited by side walls 14, 16, a bottom wall 18 and a grid 20 which is placed on folded support sections 22 of the side walls 14, 16. The walls 14-18 have a large dimension when viewed perpendicular to the plane of the drawing.

At the end of the outer housing 12 which is at the bottom left in FIG. 1, an elongated discharge duct 24 for warm air is provided, which is delimited by folded-over wall sections 26, 28 of the side wall 14 and the bottom wall IS.

The side walls 14, 16 carry, via arms 30, 32, reflector walls 34, 36, which together define an inner housing, designated overall by 38. This runs at a distance from Outer housing 12 so that secondary air channels are obtained between the two housings.

As can be seen from Figure 1, is on the reflector wall

36, a horizontal bottom section is formed, and the lower ends of the reflector walls 34, 36 essentially end in an extension of the delivery channel 24. Upper wall sections 40, 42 of the reflector walls 34, 36 are arc-shaped. Their free edges delimit a cooling air inlet opening

44 of the inner housing 38, the distance behind the

Grid 20 lies.

In the inner housing 38 there is provided a total of 46 heating / nozzle unit. This includes a heating pipe 48 running perpendicular to the drawing plane of Figure 1, a nozzle pipe 50 running parallel and at a distance below the heating pipe 48, and a 180 ° elbow 52 having the same cross section, which smoothly connects the ends of the heating pipe 48 and nozzle pipe 50 lying behind the drawing plane .

The front end of the heating tube 48 in FIG. 1 carries a connecting piece 54 which can be connected to the front of a blower, not shown, e.g. through a flexible hose. The front end of the nozzle tube 50 in FIG. 1 is closed by an end wall 56.

On a surface line, which is aligned with the axis of the delivery channel 24, openings 58 are provided in the peripheral wall of the nozzle tube 50 at intervals, into which nozzle bodies 60 are inserted. These each have a nozzle bore 62, which is aligned with the central plane of the delivery channel 24. As can be seen from Figure 1, the nozzle extends body 60 at a distance from the bounded by the free edges of the lower ends of the reflector walls 34, 36

Slot 64 through to the beginning of the discharge channel 24. The nozzle body 60 is thus also at a distance from the left end of the bottom wall 18 and from the lower end of the side wall 14.

In the space between the legs of the U-shaped heating / nozzle unit, a total of 66 twin infra-red radiator 66 is arranged. This has a transparent housing 68 made of quartz glass, in which two heating coils 70, 72 are accommodated.

The infrared radiator 76 extends over the entire length of the heating tube 48 and at a relatively short distance from the lowest point of the heating tube 48.

The half of the outer surface of the housing 68 which is remote from the heating tube 48 is provided with a reflective coating 74, which in practice can be an evaporated gold layer.

The ends of the infrared radiator 66 are held by angle brackets 76, which in turn are screwed to mounting brackets 78 welded to the top of the nozzle tube 50, as shown at 80.

The dryer element described above works as follows:

The air supplied to the nozzle 54 is pressed through the heating tube 48. Those emitted by the infrared radiator 66

Heat rays are absorbed by the outer surface of the heating tube 48, so that the heating tube 48 as a whole heats up to a high temperature. Heat is released from the heating tube 48 to the forced air, and the warm air enters the nozzle tube 50 through the 180 ° elbow 52. From there, the heated air passes through the nozzle body

60 delivered to the discharge channel 24. This release of the heated air takes the form of sharp jets. Because of the sudden increase in the cross section of the jet at the discharge end of the nozzle body 60, a vacuum is obtained there. As a result, air is drawn through the interior of the inner housing 38, as indicated by arrows 82. In addition, air is drawn in via the secondary air channels, as indicated by the arrows 84.

The reflector walls 34, 36, on which a portion of the radiation emitted by the infrared emitter 66 also falls, are thus surrounded by secondary air on both sides and are thereby cooled. The preheated secondary air, which over the

Grid 20 is sucked in, is mixed in the discharge channel 24 with the very hot air that has flowed through the heating tube 48. A large volume of warm blown air 86 is thus obtained, which emerges from the discharge channel 24 in the form of a curtain and meets, at an angle, a printed printed sheet 88 which moves in the direction of arrow 90. The hot blown air curtain dries dye and varnish layers on the printed sheet 88.

In practice, the infrared radiator 66 can have an output of 3.5 kW and heat an air quantity of 60 to 100 m ^{3 of} air per hour to about 140 ° C. By mixing with approximately half the amount of secondary air, blowing air of approximately 100 ° C. is then obtained, as is desired for drying water-based paints.

The ratio between the radiation power absorbed by the heating tube 48 and that by the reflector walls 34,

36 absorbed radiation power can be via the

Specify the surface quality of these elements:

If the inner surface of the reflector walls 35, 36 is well reflective, the surface of the heating tube 48, on the other hand, absorbs radiation well, so the heat emitted by the infrared radiator 66 largely goes to the air flowing through the heating tube 48. If the reflectivity of the reflector walls 34, 36 is deteriorated, an increasing proportion of the radiation power is emitted to the secondary air flow 82, 84 via the reflector walls 34, 36.

FIG. 2 shows, on an enlarged scale, the path of a few selected rays that originate from the heating coil 70. To simplify matters, it is assumed that only a single cylindrical reflector 92 is provided, which is the heating tube

48 coaxially surrounds. With this arrangement it can be seen that rays which emanate from the heating coil 70 at an angle of approximately 45 to the vertical are reflected by the surface of the heating tube 48 (assuming incomplete absorption of the rays). Such rays, which then reflect on the inner surface of the reflector 92 a second time on the outer surface of the

The heating tube 48, have the reference numbers 94,

96 and 98.

It can be seen that these rays no longer reach the infrared radiator 66 even after reflection on the surface of the heating tube 48.

Rays leaving the heating coil 70 inclined at an angle of more than 45 ° to the vertical, e.g. the beam 100 obviously does not reach the surface of the heating tube 48, but rather is often reflected on the inner surface of the cylindrical reflector 92.

In a cylindrical reflector arrangement surrounding the heating tube 48, part of the power of the infrared radiator 66 is thus already due to the geometry to the refector walls 34, 36 transmitted.

This effect is in the embodiment of the figure

1 weakened by the fact that the reflector is cylindrical only above the center line of the heating tube 48, but just below the center line. In this way it is achieved that the rays emitted by the heating coils, which are inclined at more than 45 to the vertical, reach the outer surface of the heating tube 48, as is also shown by the ray 100 shown there.

For the same purpose, if a cylindrical reflector is used, the reflector axis can be placed parallel to and at a distance from the heating tube axis, as shown in FIG. 3. There M ₁ denotes the heating tube axis, M ₂ the reflector axis.

On both sides of the vertical center line of the dryer element, two crescent-shaped light funnels are obtained, which guide the jet 100 and also a jet 102, which passes straight across the outer surface of the heating tube 48, to the outer surface of the heating tube 48. It can be seen that the rays in between, which represent approximately the same heat output as the rays lying between the vertical and the ray 102, just about reach the upper half of the heating tube 48. In the arrangement shown in FIG. 3, heating tube 48 is thus heated quite uniformly in the circumferential direction.

FIG. 4 shows a blown air dryer unit, designated as a whole by 104, with a frame 106 composed of angle profiles, which carries several dryer elements 10.

An infrared dryer unit, designated overall by 108, carries a plurality of infrared radiators 66 on an identical frame 106. It can be seen that the two types of dryer units on a printing press can thus be quickly exchanged for one another.

Claims

1.) Dryer element for use in a printing press, with an electrical flow of blown air

Heating device and with a blow bar, which emits the warm blowing air distributed transversely to the conveying direction of the printed products, characterized in that a

Rod-shaped infrared radiator (66) extends parallel to the outer surface of a heating tube (48) which is upstream of the blow bar (50, 60) and has an infrared radiation absorbing surface.

2.) Dryer element according to claim 1, characterized in that the blow bar (50, 60) extends parallel to the heating tube (48) and with this over a 180 ° elbow

(52) is connected.

3.) dryer element according to claim 1 or 2, characterized in that the heating tube (48) has a circular cross section.

4.) dryer element according to claim 3, characterized in that the heating tube (48) it at least partially

surrounding reflector (34, 36; 92) is assigned.

5.) dryer element according to claim 4, characterized in that the distance of the reflector (92) from the heating tube (48) decreases with increasing distance from the infrared radiator (66).

6.) dryer element according to claim 5 in conjunction with

Claim 3, characterized in that the reflector (92) has a circular cross section and the reflector axis (M ₂ )) runs parallel to the heating tube axis (M ₁ ) at a distance.

7.) dryer element according to claim 6, characterized in that the inner surface of the reflector (92) touches the heating tube (48) on the opposite surface of the infrared radiator (66).

8.) dryer element according to one of claims 1-7, characterized in that the infrared radiator in one

Has quartz glass housing (68) arranged heating coils (70, 72) and a mirror (74) is provided on the quartz glass housing in the part facing away from the heating tube (48).

9.) dryer element according to one of claims 1-8, characterized in that the infrared radiator (66)

Twin heater with two heating coils (70, 72) which are at a small distance from one another compared to the diameter of the heating tube (48).

10.) Dryer element according to one of claims 1-9, characterized in that the reflector (34, 36) is part of an inner housing (38) which has an outlet slot (64) on a section remote from the infrared radiator (66), which with a blown air discharge channel (24) is connected, and that the inner housing (38) in

has a suction opening (44) for cooling air in a section adjacent to the heating pipe (48).

11.) dryer element according to claim 9 or 10, characterized by an inner housing (38) at a distance surrounding outer housing (12), which has an inlet (20) for secondary air, which is adjacent to the reflector-side portion of the inner housing (38), and one the blow bar (50, 60) adjacent outlet for heated by the reflector (34, 36) secondary air.

12.) Dryer element according to claim 10 or 11, characterized in that the blow strip (50, 60) has discrete nozzles (60) which are successively spaced apart.

13.) dryer unit for use in a printing press, characterized by a plurality of dryer elements according to one of claims 1-12, which are carried in the same orientation parallel to one another and carried by a standard slide-in frame which can be inserted into a guide of a dryer frame.