Technical Field

The present invention relates to a method of impro- ving the function of a mobile infra-red paint curing de¬ vice, preferably for car repair shops, including a curing head with an array of IR panels for curing by means of IR beams. The invention also relates to such a curing device for carrying out this method. Technical Background

Mobile infra-red paint curing devices are used in car repair shops for curing paint applied after repair of cer¬ tain damaged parts of cars. By the construction of the de¬ vices, movable on wheels or on special rails or the like on the walls of the repair shop, the curing heads are movable so as to enable them to be brought into position for curing any part of a car.

Normally, the IR panels are working in the medium- wave range, because such panels have a comparatively long pre-heating time and provide for an even absorption of the heat in the paint, but also panels working in the short¬ wave range may be used. Such panels, however, have a very short pre-heating time and may accordingly be dangerous for operators . The problems with conventional curing devices of the kind referred to are that the heat on the object to be cured may be unevenly distributed, that the curing time may be longer than desired, especially if IR panels working in the medium-wave range are used, and also that the cooling after the curing may take a long time. Also, it may be difficult to have satisfactory control over the different parameters.

One way of diminishing the cited problems is disclosed in WO-A-9515471, where devices for blowing

laminar air parallel to the IR panels are attached to the panels or their frames. The Invention

Problems with conventional devices of the kind re- ferred to may according to the invention be obviated by a method which is characterized in that air is blown from an end portion of the curing head obliquely inwards towards the center of the head and the object to be cured and in that the supply of IR beams and air to the object to be cured is controlled by a common control system.

This control system, which is arranged on the device, can be programmed or adjusted according to different condi¬ tions and desires with respect to the sequence for the IR heating and the air blowing as well as the curing time and the time for the air blowing.

The air, which will be heated by the IR beams, has a positive effect on the heat distribution. The air will also carry the paint solvent away from the curing area. After the curing the air will cool the object to be cured. The effect of the air is best at paints with water as solvent, but the method can be used at all types of paints. It may be advantageous if the air is turbulent, which may be ob¬ tained by the shape of the holes or nozzles by which the air is supplied. As stated, the air is blown from an end portion of the curing head obliquely inwards towards the center of the head. If the air hereby is blown from the lowermost end of the curing head and obliquely upwards, the air will assist in carrying solvent away upwards. As already mentioned above, a problem with a conven¬ tional curing head is an uneven distribution of the heat on the object to be cured. A further improvement in this re¬ spect may according to the invention be obtained in that IR beams with different effects are directed towards different parts of the object to be cured.

A device for carrying out the method according to the invention is characterized in that a part of the head is provided with holes or nozzles for blowing air obliquely inwards towards the object to be cured and in that the device has a common control system for the IR panels and for the supply of air.

Preferably, the air is supplied through a hose to a tube of the curing head from a source of compressed air.

An even heat distribution may be obtained in that IR panels with different ratings are arranged in a certain array in the curing head.

For a good result it is important to keep the dis¬ tance between the curing head and the object at an optimal value. For assisting in obtaining this optimal value, the curing head may be provided with an appliance for optical indication of the distance.

Brief Description of the Drawings

The invention will be described in further detail be¬ low reference being made to the accompanying drawings, in which Fig 1 is a side view of a mobile infra-red paint curing device according to the invention. Fig 2 is a bottom view of a curing head for the device according to Fig 1, Figs 3 and 4 are schematic views of different arrays of IR panels for a curing head, Fig 5 is a schematic side view of an appliance for optical indication of the distance to an object to be cured, and Fig 6 is an illustration of the appearance of light beams from the appliance according to Fig 5.

Detailed Description of Preferred Embodiments A mobile infra-red paint curing device is shown in

Fig 1. It consists in essence of a base 1 with wheels 2, a lower arm 3 pivotally attached to the base 1, an upper arm 4 pivotally attached to the lower arm 3, and a curing head 5, which is attached to the upper arm 4 in such a way that it is movable in all directions, as appears by the three

arrows in Fig 1. A gas spring 6 may be arranged as shown between the two arms 3 and 4 so as to enable the upper arm

4 to be held in a set position. Also the articulation means between the upper arm 4 and the curing head 5 are such that any set position for the head 5 will be maintained.

The curing head 5 consists in essence of a frame 7 preferably composed of tubes, and a number of electrical, infra-red panels 8, which are pivotably attached for indi¬ vidual movements in the frame 7. When switched on, the panels 8 will supply IR beams.

The purpose of the device, so far described, is to cure wet paint on a newly painted car, which has been re¬ paired in a car repair shop. The device is moved to the vi¬ cinity of the car, and at least one of the wheels 2 are locked. By pivoting the arm 4 and adjusting the head 5 to a desired position, any point on the car can be exposed to the IR beams from the curing head 5.

The device as described so far is in principal con¬ ventional, although its construction has certain advantages over conventional mobile infra-red paint curing devices.

One of the inventive features is that the curing head

5 is provided with means for blowing air towards the object to be cured. In practice, a part of the head 5 is provided with holes 9 or nozzles for the air. Preferably, these holes 9 or nozzles are arranged in or on a longitudinal end tube of the frame 7. The air is supplied to this tube through a hose 10, which extends through the upper arm 4 and the lower arm 3, from a compressed air system in the repair shop through an inlet 11 at the lower part of the lower arm 3.

The holes 9 or nozzles are arranged in such positions that the air is blown obliquely inwards towards the center of the head 5, as shown in Fig 1. When the head 5 is held in a more vertical position for curing a substantially ver- tical surface on a car, the tube containing the holes 9 or

nozzles is to be in the lowermost part of the head 5, so that the air is directed upwards towards the surface of the car. The effect of this is that the air is lifted upwards by the heat from the IR panels 8 and brings paint solvent, preferrably water, with it. The air will also effect a more uniform distribution of the heat on the surface of the car. Further, when the IR panels 8 have been switched off, the air can effect a faster cooling down of the surface on the car. A problem with prior art devices of this kind is that the heat from the IR panels is not evenly distributed on the object to be cured. Some attempts have been made to ob¬ viate this problem by arranging the IR panels at different distances from each other or in different patterns. These attempts are, however, only partially successful.

According to the present invention the even heat dis¬ tribution on the object to be cured is obtained in that IR panels 8 with different ratings are arranged in a certain array in the curing head 5. Two examples of such arrange- ments are shown in Figs 3 och 4.

In Fig 3 there are in total nine IR panels 8. Only the four panels in the corner positions are panels with a higher rating or full rating, for example 1500 W or 500 W, whereas the five others, arranged in a cross, are at a lower rating of for example 1000 W or 375 W, respectively. In the second example according to Fig 4 there are altogether eight panels 8, where there are two rows with three full rating panels at each side and two low rating panels between them and with no panel at all in the center. Several other arrays are possible, and practical tests may show which array to use for a specific case.

An optimal curing result is obtained, when the curing head 5 is at a certain distance, for example 50 cm, from the object to be cured. The device may be equipped with an appliance for optical indication of the distance to the

object to be cured. Such an appliance is shown in Fig 5. Two light guides 12 are arranged in a block 13. The inner ends of these light guides 12 are placed in the vicinity of a bulb 14 and the opposite ends of the light guides 12 are directed towards a point at the desired distance, for exam¬ ple 50 cm, from the block 13, which is to be attached to the curing head 5. As illustrated in Fig 6, the light guides 12 will produce two dots or marks on an object, and if the two marks are too far apart, the distance has to be decreased, until the two dots coincide. Alternative designs of such an appliance are possible.