GB2151994A

GB2151994A - Heat-treating vehicle bodies

Info

Publication number: GB2151994A
Application number: GB08431654A
Authority: GB
Inventors: Anders Nordh; Ingemar Nilsson
Original assignee: INFRAPAINT AB
Current assignee: INFRAPAINT AB
Priority date: 1983-12-22
Filing date: 1984-12-12
Publication date: 1985-07-31
Also published as: SE455227B; SE8307100L; DE3446187C2; GB8431654D0; SE8307100D0; DE3446187A1; GB2151994B

Abstract

In order to obtain uniform intensity distribution in a movable tunnel-like structure (12) used for heat-treating newly enamelled surfaces of a vehicle body (10), the tunnel-like structure is provided with a secondary radiator (32) which embraces the vehicle-body profile at a given distance therefrom, and carries in mutually spaced relationship longitudinally of the movement direction of the tunnel-like structure a plurality of IR-radiators (36) operative in the medium-wave band. The shape of the secondary radiator (32) is substantially determined by circular-arcuate lines (44, 45), and the primary radiators (36) are so mounted that the radiation therefrom is directed onto focus axes through centres (42, 43) of the circular-arcuate lines. The extent to which the tunnel is moved with the heat-emitting sources activated is controlled with respect to vehicle-body designs and the nature of the treated surface, while the speed at which the tunnel-like structure is moved is determined with respect to the absorption and reflection capacity of the enamel or paint used. <IMAGE>

Description

SPECIFICATION A method and apparatus for heat-treating vehicle bodies When heat-treating vehicle bodies, and in particular when drying enamelled surfaces, there is often used a tunnel-shaped structure, which can be moved over the vehicle body being treated. With regard to the repair of damaged enamelled surfaces, the heat-sources provided in said tunnel-like structure need only be activated when they are located over the re-enamelled areas.

The aforesaid heat sources normally have the form of IR-radiators active within the mediumwave band. In radiators of this kind, the radiation source is not a thin filament, as in the case of short-wave radiators, but a spirally-wound resistance wire. The diameter of the spiral may be up to 10 mm, and the radiation is omnidirectional, from every point on the spiral. The spiral is placed in a quartz-glass tube, which absorbs the radiation emitted by the spiral and thus becomes heated, such as to emit IR-radiation itself.

The quartz-glass tube is placed in a reflector (primary reflector), which directs the radiation outwardly. The radiation pattern, namely the cumulative radiation from the spiral, the quartzglass tube and the reflected radiation, is restricted by the aperture angle of the primary reflector. This gives a diffuse radiation pattern with uniform intensity distribution.

IR-radiators have an elongate basic form. Within the short-wave band, the heating filaments are enclosed hermetically in the glass-tube, these tubes being of specific, given lengths. The power output of these radiators can be regulated if desired, by varying the voltage applied. Within the mediumwave band, the radiator comprises a resistance spiral housed in a quartz-tube which is open at both ends thereof, and hence the length of the tube can be readily adapted to provide the required effect. This latter expedient is important with regard to the positioning of the IR-radiators used in accordance with the present invention.

The object of the present invention is to provide a method and apparatus for heat-treating vehicle bodies, and in particular for drying re-enamelled surfaces, by means of which the heating process can be effected within a relatively short space of time and at a relatively low power consumption.

Compared with IR-radiation in the short-wave band, IR-radiation in the medium-wave band often results in less reflection and lower transmission, and hence greater absorption, in the case of the majority of paints and enamels. This means that a high percentage of the energy supplied from a medium-wave radiator is absorbed in the enamel layer. Nevertheless, it is worth collecting the radiation reflected by the car-body and the layer of enamel thereon, and the primary reflectors are mounted in a secondary reflector to this end. A maximum possible intensive distribution is also desired in this latter respect.

Different enamels and paints have different absorption and reflection properties. This can be corrected to different temperature levels, by varying the speed of tunnel movement, in accordance with a set programme. This programme must also take into account the fact that the mutually different car bodies being treated are of mutually differing lengths.

The invention relates to a method for heat-treating vehicle bodies with the aid of a tunnel-like structure, which incorporates heat-emitting sources and straddles said vehicle-bodies, and which is arranged for movement along a respective vehicle body being treated, said method being characterized by dividing the body lengthwise into four treatment zones and controlling the movement of the tunnel-like structure in a manner such that the heat-emitting sources remain inactive until entering a zone in which treatment is to take place, there being provided control means which include means for adjusting the extension of respective zones in relation to absolute car-length, and for adjusting the speed relative to the kind of surface being treated.

The tunnel-like structure is suitable provided with an arcuate secondary reflector, in which a primary reflector incorporating IR-radiators is mounted parallel with the transport direction of the tunnel-like structure.

The arcuate shape of the secondary reflector is preferably defined by radii extending from centres horizontally spaced from an imaginary centre-point of a plurality of vehicle-body cross-sectional profiles, the arcs determined by said radii extending up to vertical planes through centres, and said arcs being mutually linked by a straight line connecting the tangents of the arcuate lines.

The invention also relates to an arrangement for heat-treating vehicle bodies with the aid of the tunnel-like structure which carries heat-emitting sources, is markedly shorter than the vehicle-body, and is arranged for movement there-along, said arrangement being characterized in that the tunnellike structure carries a secondary reflector of substantially circular-arcuate shape, with the centre of the arc lying generally on a longitudinal mean plane passing through said vehicle body, and carrying mutually spaced primary reflectors incorporating IR-tubes arranged in the direction of movement of the tunnel-like structure.

The throw of the secondary reflector is suitably so wide that at least the lowermost primary radiators direct part of their radiation upwards. The geometric form of the secondary reflector is preferably determined by two circular arcuate lines, where the centres of respective radii are displaced outwardly relative to an imaginary centre-point of a plurality of cross-sections of conventional vehicle-bodies, the tops of said arcuate lines being joined by a substantially straight line having generally the same geometric extension as the distance between centres.

The primary radiators are suitably designed for diffuse radiation spread, emitting uniform intensity within the width of the beam, and are mounted at a mutual distance apart, such that the beams of mutually adjacent primary radiators intersect one another, externally of the embraced vehicle body profiles. Conveniently, the primary radiators include IR-tubes which emit radiation with an emission maximum within the medium-wave band.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a plant for treating damaged enamelled surfaces; Figure 2 is a front view of the heat-treatment tunnel-like structure; and Figure 3 is a schematic cross-sectional view of a primary radiator.

The damaged enamel on vehicle bodies is normally treated in a well ventilated, screened area equipped with blasting apparatus, enamel or paint spraying devices, etc. Such apparatus and devices are well known, and therefore need not be described here.

It is assumed that a vehicle whose bodywork 10 has suffered some enable damage, has been moved into a treatment booth and placed at one end thereof (the front) in a given position 11.

Treatment of the damage may include rubbing down the damaged surfaces, blasting said surfaces, and possibly also straightening and patching the sheet-metal body work, and also the application of a number of layers of primer and enamel.

In order to shorten the treatment time, it may be necessary to heat the treated surface after applying each layer. This is effected with the aid of a tunnellike structure or portal 12, which carries a plurality of heat-emitting sources and which is arranged for movement along the vehicle body being treated.

Figure 1 illustrates schematically means for moving the tunnel-like structure. The tunnel-like structure is supported on wheels 13, which move on rails 14, sunk into the floor of the treatment area.

The rails 14 are of sufficient length to enable the tunnel-like structure, when not in use, to be moved into a parking area which is protected against the ingress of dust and airborne enamel particles, and from which the tunnel-like structure can be moved along the whole length of the vehicle body.

The means driving the tunnel-like structure may have any known form, such as a rack and pinion.

Alternatively, said drive means may have the illustrated form of a chain 15 which extends over a driven wheei 16 on the tunnel-like structure 12.

The electrical power required to operate the heat-emitting sources, for driving the drive wheel 16, and for operating cooling fans in the tunnel-like structure, is applied through a flexible cable 17, which accompanies the movement of the tunnel like structure.

Although the illustrated arrangement can be used to enamel the whole of a vehicle body, the arrangement is normally only used to re-enamel a damaged part of said vehicle body, such as a front fender, the boot lid or tailgate, and the like.

In order to reduce the power consumption, it is desirable for the heat-emitting sources to be activated only when the tunnel-like structure moves across the area to be treated.

In principle, a vehicle body can be divided up into four zones, corresponding to the forward carriage 18, the front doors 19, the rear doors 20 (or the like) and the boot or baggage space 21. Different vehicle-bodies can have different lengths, and the sum of the zones 18-21 can, in total, correspond to the distance 22 and the distance 23 respectively, which is of importance with regard to guiding the tunnel.

In addition to being limited in the longitudinal direction of the vehicle body, a damaged surface may also be localized to one side or the other, such as the vehicle roof, the bonnet of the vehicle, or the boot-lid or tailgate thereof.

Consequently, with respect to energy consumption, it is desirable to energize only those heatemitting sources located on one or the other side of the vehicle body or along the roof thereof. This will become more apparent from the description given with reference to Figure 2.

The tunnel-like structure 12 is equipped with a control panel 24, which, among other things, carries a symbol 25, corresponding to the division of the vehicle body into four zones 18-21, and a symbol 26 showing an end view of the tunnel divided into right/left and roof sections.

Adjacent the symbol 25 is a first bank of buttons 27, by means of which it is possible to select one or more zones 18-21, and a second bank of buttons 28 for determining the length of tunnel movement relative to vehicle-body length, i.e. one button corresponding to the total length 22, a third button corresponding to the total length 23, and an intermediate button corresponding to an average length of movement.

Some enamels will absorb and reflect radiation more than others, and in order to obtain the desired heating effect, it is necessary to be able to control the speed of the tunnel-like structure over the area being treated. To this end, there is provided a third bank of buttons 29, by means of which it is possible to select different speeds of movement.

The damaged area can also be limited locally to one side or to the roof, a bonnet (hood) or boot cover. Accordingly, adjacent the symbol 26 is a further button bank 30, by means of which heat-emitting sources on either side of the tunnel-like structure or portal, or in the ceiling thereof, can be ignited.

The heat-treatment is suitably effected in the absence of any personnel in the immediate vicinity the enamelling process is often carried out in a closed, ventilated hall. Subsequent to applying a layer of enamel, the area to be treated with heat, and the speed at which the tunnel is to move, are selected by means of the button banks 27, 28, 29 and 30, whereafter the process can be started-up from a location outside the hall. The tunnel-like structure is programmed to return to its parking position, immediately it has passed the intended zone. It will be understood, however, that the tun nel-like structure may also be programmed to heat said area during its return movement.

One pre-requisite for achieving a satisfactory re sult is that a uniform heat intensity is obtained, irrespective of local differences indistance between primary radiators and the surface of the body work. Consequently, tunnel design is of decisive significance. The design of a suitable tunnel is illustrated in Figure 2.

The tunnel-like structure 12 comprises a supporting frame structure 31, and an arcuate secondary reflector 32 carried thereby. The secondary reflector is sufficiently large to encompass the vehicle body at a given distance therefrom, and reaches to beneath the lower edge of the bodywork, even in the case of a small car.

The cross-sectional profile of a "small car" is indicated by chain-lines 33 in Figure 2, while the profile of a standard model family car is shown by broken lines 34.

The tunnel-like structure is provided with at least one fan 35, which supplies cooling air to various sections within the tunnel.

A plurality of elongate primary radiators 36 are arranged in mutually spaced relationship in the secondary reflector, in the movement direction of said tunnel.

Figure 3 illustrates the design of one such primary radiator 36.

A primary radiator 36 is mounted on a beam 37, which may have any cross-sectional shape, provided with channels and flanges for mounting and cooling purposes. The channeled (primary) reflecting surface 38 is covered with gold foil or some other material having good reflecting properties and not being affected by the high prevailing operating temperatures.

The actual radiation source comprises a spirally wound resistance wire 39 placed in a quartz-glass tube 40. The quartz-glass tube is placed in a favourable position in relation to the reflecting surface 38, which is designed so as to provide a theoretically optimal optical system which delivers a diffuse radiation pattern and uniform intensity within the width of the beam. This is determined by the aperture angle a of the primary reflector.

The diffuse radiation pattern, which is composed of the direct radiation from the resistance wire 39 and the quartz-glass 40, together with the radiation reflected from the surface 38, implies the uniform intensity distribution and enables the primary ra diators to be mounted horizontally, i.e. parallel with the movement direction of the tunnel-like structure, while nevertheless providing a uniform temperature distribution over the vehicle body, without risk of leaving untreated strips in the surface. In order to avoid the occurrence of untreated strips, it is normal in known movable tunnel-constructions to arrange the primary radiators at right angles to the direction of tunnel movement.

The secondary reflector 32 is highly effective in contributing to the good distribution result obtained.

The secondary reflector 32 does not exactly conform with a circular-arcuate line. Normally, the width of a car body is greater than its height, and for space reasons it is desirable for the tunnel-like structure to be as low as possible.

A mean value for the centres of gravity of mutually different cross-sectional profiles is referenced 41 in Figure 2. The centres 42, 43 of the radii R determining the arcuate shape in the sides of the reflector and a substantial part of its ceiling, are displaced slightly outwardly relative to the mean point. The tops of the two circular-arcuate lines 44, 45 are connected by a planar line 46, which interconnects the tangents of the circular-arcuate lines.

The primary radiators 36 are placed at a mutual distance apart which, with respect to the aperture angle a of the primary reflectors and the clearance between the secondary reflector 32 and various vehicle-profiles, ensures that the beam of radiation from mutually adjacent primary radiators intersect one another externally of the vehicle-body surface.

In the illustrated embodiment, the mutual distance between the primary radiators 36 corresponds to the distance between centres 42, 43. Two radiators 36a are located in the transition region between the circular-arcuate structures 44, 45 and the straight line 45, and all primary radiators within each half of the tunnel will thus be directed towards a focus axis which extends through centre 42, 43 for each half of the tunnel concerned.

The circular-arcuate lines 44, 45 extend downwardly to an extent such that the lowermost primary ratiators 36b direct part of their radiation upwards, and thus also cover the bottom edge of the car body.

As mentioned in the introduction, there are used IR-radiators having an emission maximum within the medium wave-band. The secondary reflector is constructed on the basis of the desire to obtain a uniform temperature distribution over car bodies of large cross-section and of small cross-section.

The energy reflected from the car body and again reflected by the secondary reflector provides this desired uniform temperature distribution, irrespective of the size of the car body. The distance between the secondary-reflector surface and the surface of the car body may vary in dependence upon the size of said car body, although since the primary radiators are directed towards the focus axes, a surface which lies further away from the secondary reflector will receive radiation from several primary radiators and a greater part of the secondary-reflector surface. Even though the intensity decreases with distance, the energy flow to the enamel surface is automatically compensated for.

The energy flow has a fixed intensity. As before mentioned, the differing absorption and reflection abilities of mutually different enamels and paints are corrected to the desired temperature level, by varying the speed at which the tunnel-like structure moves, in accordance with the aforementioned programme.

Car-body surfaces which are located at right angles to the movement direction absorb a smaller part, but reflect a larger part of the radiation than those surfaces which are parallel, or approximately parallel with the movement direction. This results in a relatively lower temperature level for those surfaces located at right angles to the movement direction.

To compensate for this, a few radiators may be mounted vertically at the ends of the tunnel-like structure and provided with secondary reflectors directed inwardly toward the tunnel cavity, so as to obtain desired radiation against the "perpendicular" surfaces. These supplementary radiators may be controlled from the control panel 24, but are additional equipment which have no direct connection with the invention.

The afore-described embodiment illustrated in the drawings is simply an example of the invention, and can be modified in many ways within the scope of the appended claims.

With regard to the symbol 26 on the instrument panel 24, it can be mentioned that one side of the symbol does not fully correspond to circular-arcuate line 44 or 45, but that said symbol is operative in the control of so many primary radiators that the top of said symbol extends in, over the roof of the car body. Conversely, the roof portion of the symbol includes more than the primary radiators 36a located along the straight line 46. In this case, it is desirable that the outermost primary radiators reach down along the side of the car body.

As will be understood, a plurality of zones of "sides" can be treated simultaneously in one operation. In those plants in which it is desired to treat the whole of a car body, the instrument panel 24 can be provided with an additional button which controls the button banks 27 and 30.

Claims

1. A method for heat-treating vehicle bodies with the aid of a tunnel-like structure which carries heat emitting sources and straddles the vehicle body and which is arranged for movement therealong, characterised by dividing the vehicle body lengthwise into four treatment zones, and controlling movement of the tunnel-like structure so that only those heat-emitting sources located within a zone intended for treatment are activated, wherein control means include means for adjusting the extension of the zones in relation to absolute vehiclebody length, and for adjusting the speed of movement of the tunnel-like structure in relation to the type of surface being treated.

2. A method as claimed in claim 1, wherein the tunnel-like structure is provided with an arcuate secondary reflector, in which primary radiators containing IR-radiators are mounted parallel with the movement direction of the tunnel-like structure.

3. A method as claimed in claim 2, wherein the arcuate shape of the secondary reflector is determined so that the reflector embraces the vehiclebody profile to such an extent that lower primary radiators direct their radiation obliqueiy upwardly.

4. A method as claimed in either claim 2 or claim 3, wherein the arcuate shape of the secondary reflector is determined by radii extending from centres which are horizontally spaced from an imaginary center point of a plurality of vehicle-body cross-sectional profiles, the arcs determined by said radii extending up to vertical planes through said respective centres (42, 43), and the arcs being mutually connected by a straight line which connects the tangents of the arcuate lines.

5. A method as claimed in any one of claims 2 to 4, wherein the distance between primary radiators is selected so that the beams radiated from mutually adjacent reflectors intersect one another at a distance from the vehicle body.

6. An arrangement for heat-treating vehicle bodies with the aid of a tunnel-like structure which carries heat-emitting sources, which has a length markedly shorter than the length of the vehicle body, and which in use is arranged to be moved therealong, characterised in that the tunnel-like structure carries a secondary reflector of substantially circular-arcuate shape with its centre approximately located in a length-mean plane through the vehicle body, and carrying mutually spaced primary radiators incorporating IR-tubes arranged in the direction of movement of the tunnel-like structure.

7. An arrangement as claimed in claim 6, wherein the peripheral extension of the secondary reflector is such that at least the lowermost primary radiators direct part of their radiation upwards.

8. An arrangement as claimed in either claim 6 or claim 7, wherein the shape of the secondary reflector is determined by two circular-arcuate lines where the centres of radii for said lines are displaced outwardly in relation to an imaginary mean point of a plurality of cross-sections of conventional vehicle bodies, the upper parts of said arcuate lines being interconnected by a substantially straight line having a geometric extension which substantially corresponds to the distance between the centres.

9. An arrangement as claimed in any one of claims 6 to 8, wherein the primary radiators are designed for diffuse beam spread, permitting uniform intensity within the width of the radiated beam, and are mutually spaced apart in a manner such as to enable the beams radiated from mutually adjacent primary radiators to intersect one another externally of the embraced vehicle-body profile.

10. An arrangement as claimed in any one of claims 6 to 9, wherein the primary radiators incorporate IR-tubes emitting radiation with emission maximum within the medium-wave band.

11. A method for heat-treating vehicle bodies substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

12. An arrangement for heat-treating vehicle bodies substantially as hereinbefore described with reference to and as shown in the accompanying drawings.