GB2399093A - Heat treatment of vehicle body panels using cooling contact plate - Google Patents

Abstract

A device for stress relieving of body panels 7,8 after their assembly to a rail vehicle carriage 1 is disclosed. The device comprises a supporting structure 10 and a pair of contact plate 20,24 supported from the supporting structure on opposite sides of the carriage longitudinal axis, the contact plates being moveable to bring them into symmetrical engagement with body panels on opposing sides of the carriage, and being arranged to conform to the outer contour of the carriage. The symmetrical application ensures that asymmetric forces on the carriage during heat treatment are reduced. The contact plates 20,24 are provided with grooves (65; figures 4 and 5) which allow the plates to bend sufficiently to match the complex contours of modern rail carriages. Further contact plates 30,34,37,39 for the sloping roof panels 7 and undercut lower panels may also be provided.

Description

Device for Treating Body Panels The present invention relates to a device

for treating body panels and more particularly to a device for the sequential spot-wise heat treatment of body panels for the purpose of stress relief and the design of such a device for use in the construction of rail vehicle carriages. It also relates to a method of treating body panels in the construction of a rail vehicle carriage in particular the spot-wise heat treatment of body panels for stress relief.

During the construction of a rail vehicle carriage it is customary to initially assemble the vehicle framework, usually comprised of welded structural elements forming a rib like structure. After welding is complete, the framework may be brought into alignment, by hammering, hydraulic press or other means, to approach the desired configuration. The framework is then ready to receive the outer skin in the form of metal sheeting, which may be welded over the framework to form the outer contour of the carriage. The section of outer skin between adjacent ribs or framework elements will henceforth be referred to as a panel. Each panel may be formed of a separate sheet or plate of metal. Alternatively a single sheet may cover or span a number of body panels and may be bent or require bending to conform to the outer contour of the carriage. Once the outer skin is complete, a further stage of alignment and adjustment takes place.

The step of welding the outer skin to the framework can cause local stress concentrations within the metal sheet. These may manifest themselves as bulges and hollows over the surface of an individual panel and may comprise localised "boils", typically in the order of 10 cm in diameter, as well as general bulges spanning substantially the whole area from one framework element to the next. These imperfections must then be removed to provide an acceptable outer finish to the vehicle.

Existing methods of smoothing out the irregularities in the outer skin involve stress relieving by application of localized heat to a point or spot on the metal surface, followed by rapid cooling.

The metal sheet is heated to the strain relief temperature, which lies just below the softening Àseeace esee e eee e ee e eee e ee e eee e ee e eee e e ee e ee. . temperature. At this point, the metal sheet becomes ductile and can stretch or shrink to relieve internal forces present in the material. These forces may have been induced in the material as a result of the welding procedure or may be due to deformation of the sheet to meet the contour of the supporting framework. There may also be residual stresses arising from the manufacturing procedure for the metal sheet. As the metal sheet cools, it contracts and causes the sheet to be tensioned onto the supporting framework. The cooling induced stresses tend to be homogenous in all directions and since the whole panel is treated, uniformly distributed over the surface.

The precise way in which the heating and cooling take place is critical to the final result.

Generally, a skilled craftsman using a source of heat such as a gas torch will work over a body panel sequentially heating individual spots. The degree of heat will be determined by eye according to the colour change of the heated metal - for steel a temperature of approximately 900 C must be achieved, for stainless steel, the temperature should not exceed 850 C, while for aluminium temperatures in the region of 400 C are adequate. The cooling should be sufficient to return the surface temperature to below about 50 C as soon as the source of heat is removed.

Adequate cooling is essential to ensure that each spot has cooled sufficiently before the next spot reaches the strain relief temperature. The sequence of heating the different spots and the degree of heat may also be tailored by the craftsman to achieve the desired effect, depending on the shape, size and position of the irregularities to be corrected.

It has been found desirable to provide a generally flat contact surface against which the sheet may be flattened by e.g vacuum or magnetic force while the heat treatment takes place. In this way, the boils and bulges are substantially flattened out and the whole area of the sheet may be sequentially heat treated in a grid-wise pattern. Once the contact surface is removed after termination of the heat treatment, the panel retains its flattened configuration. Experience shows that the heating of 20 mm spots at a grid spacing of 64 mm over the surface of the panel provides the optimum result. This may be achieved by using a twin head torch with 64 mm spacing between the heads whereby the operator maintains the spacing by eye. Alternatively, a twin head torch with 128 mm spacing may be used whereby the operator need only estimate the mid-point À ace À. À ece À À À À À À À À C À À À . À À À between the previous spots for placement of the next spot. Clearly other variations of multi head torches could also be employed. The treatment of a panel of 1 m2 may be completed in as little as minutes, at which point the process continues with the following panel. Such procedures may also be automated using robot controlled heat sources or otherwise.

In order to achieve adequate cooling, it is known to provide such contact surfaces in the form of cooling plates, attached to one of the surfaces of the outer skin by suction or magnetic forces.

Such plates are supplied with cooling fluid such that the outer skin is cooled from one side as heat is applied from the other side. German Patent DE 1 217 910 B describes such a procedure and cooling plate. Such cooling plates were formed to be as rigid as possible within acceptable weight limits to ensure the flatness of the treated panel.

In order to improve the versatility of such cooling plates, whereby they can be easily manhandled and moved from one panel to the next, it has been suggested to provide the cooling plate on a moveable base, equipped with pneumatic actuators to press the plate against the panel. According to Gennan Patent DD 0151 558 C, a number of such plates may be provided whereby a number of panels may be treated together without the need to rearrange the cooling plates. The use of pneumatic force to press the plates against the vehicle was necessary to initially flatten the panel against the plate sufficiently for the vacuum to become effective. This force has been found to have a detrimental effect upon the careful set of the vehicle.

Current standards of surface finish, particularly for high-speed trains, require a much higher degree of precision. Whereas formerly, larger irregularities were acceptable, the present standards require a surface evenness tolerance of just 1 mm over a 1 m2 area. Such finishes are important both for aesthetic reasons and also for reducing wind noise.

To meet these increased tolerances requirements for surface finish, greater care during heat treatment must be observed. Attention must be paid to ensuring adequate cooling of the metal sheet fanning the outer skin to prevent further distortion. Attempts have been made to achieve e se. ece ece À À À À À e À À À c À À a À a e À e À À À e e e e the desired finish by the use of fillers prior to painting. Such practice is however generally unacceptable as the corrosion resistant properties of the vehicle are reduced. Alternatively, cold beating of the smallest irregularities may be performed, usually by a pair of skilled craftsmen located respectively inside and outside the carriage. This however causes damage to the surface finish, which must be removed by sandblasting prior to painting. Such a method is generally unacceptable for modern trains, which require a quality of surface finish similar to a family car.

Tighter tolerances are also required for the overall profile of the carriages. Profiles are generally determined by the rail network operator for a given rail network. All rail vehicles using that network must conform to the given profile. Where manufacturers seek to produce vehicles close to the profile limits in order to optimize the space available, any outward bulging of the body panels may cause the overall carriage profile to exceed the imposed limits.

A contact or cooling plate must therefore provide an accurate and stable surface corresponding to the desired profile. Presently used devices are however, under certain conditions, detrimental to the overall accuracy of the carriage profile. The strength of the vacuum needed to maintain adequate contact can result in the panel being distorted to match the shape of the contact plate and can actually cause the framework to distort. This is particularly true when working with contoured panels. Modern carriage designs tend to use increasingly complex outer contours to meet the profile restrictions and industrial design expectations of train operators. In order to take account of centre-line displacement on negotiating curved track sections, a carriage may be constructed to contoured in the longitudinal direction being narrower at its mid-point than at the two ends. Opposite sides of the carriage are thus no longer parallel and additionally, the adjacent ribs or framework elements supporting a given body panel, may not be parallel either. It is also frequent for modern carriage designs to include curved or contoured sidewalls in the vertical direction.

Rigid flat contact plates are clearly unsuitable for accurate surface finishing of such contours. In particular the use of force such as hydraulic presses to bring plate and panel together and also the À ee. À. À ee.

À À À À À À À À ::: À: ::: À À À À subsequent vacuum or magnetic force can all cause distortion of the vehicle frame. In areas where the plate and panel have failed to enter into contact, local boils may not be adequately flattened during heat treatment. Such gaps can also lead to inadequate and non-homogenous cooling heat transfer, resulting in the recurrence of surface deformities. Failure of the contact plate and the panel to meet can also reduce the effect of the attractive force between them. In the case of vacuum suction, reduced vacuum force is available due to leakage around the seal at points of reduced contact. A similar effect would occur in the case of magnetic force.

Flexible cooling plates have been employed in the past for the heat treatment of curved body panels, typically for roofs. These have been constructed to conform intimately to the panel surface, whereby optimal heat transfer can be achieved. They have the disadvantage however that by intimately following the surface, they fail to provide adequate support to remove all bulges and hollows from the panel surface since the flexible plate may itself take the shape of the bulge.

A flexible cooling device for vacuum attachment is known from German Patent DD 144 652 C, which discloses a plurality of longitudinal cooling elements attached to a flexible sheet, with vacuum being supplied to gaps between the elements. Trials with a device according to this patent have shown it to be uncontrollably flexible and incapable of providing the necessary support to straighten body panels The presently available cooling plates and devices for treatment of body panels are also provided individually, or in the case of DD 0151 558 C as a group, for working on a single area. The increased overall profile tolerance is however extremely sensitive to local heat treatment which can cause the whole vehicle to bend. Even were two teams to work on opposite sides of the vehicle in symmetrical fashion, differences in working speed and any variation in cooling capacity would still lead to asymmetric forces tending to distort the carriage.

There is therefore a need for an improved device to ensure that distortion of the outer profile of a rail vehicle carriage is minimized during treatment of the surface to remove irregularities. It is desirable that such a device should be quick and easy to operate and should be adaptable to the Àes e.e À eve À À À e À À À À À À À À À - . À À À many shapes and configurations of the panels used in the manufacture of such carriages. It is particularly desirable that the device should ensure symmetrical heating and cooling of opposing sides of the body under construction to avoid bending forces leading to distortion.

According to the present invention there is provided a device for treating body panels after their assembly to a vehicle or like structure, the device comprising a pair of contact plates supported on opposite sides of a vehicle longitudinal axis, the contact plates being moveable to bring them into symmetrical engagement with body panels on opposing sides of the vehicle, and being arranged to conform to the outer contour of the vehicle whereby asymmetric forces on the vehicle during heat treatment maybe reduced.

Preferably the contact plates are suspended from a supporting structure. By the use of such suspension without directly applied force being applied to press the plates against the body, they can move to conform to the vehicle contour rather than causing the vehicle itself to be misaligned. It is further preferable that the contact plates may be attached by vacuum suction or by magnetism.

It is furthermore desirable that the contact plates are flexible whereby they themselves can conform to the outer contour of the vehicle. To achieve this flexibility, the contact plates may be provided with grooves of a depth sufficient to increase flexibility. These grooves may also be used for the distribution of vacuum.

In order to ensure symmetrical cooling of both body panels, it is desirable that the device be provided with a cooling controller to control the cooling of the respective plates. This may take the form of a controlled fluid supply in which cooling fluids such as water, oil, gas or cooling emulsions may be circulated to the contact plates to achieve the desired effect. The controlled supply may provide fluid equally to both plates or may individually adjust the flow to each plate to take account of local heating conditions or differences in heat transfer between panel and plate.

mecat a sea À a À À a a a a À À À e À À À À À According to another aspect, the present invention provides a method of heat treating vehicle body panels comprising the steps of: providing a vehicle having a pair of symmetrically arranged body panels; engaging a pair of contact plates with the pair of symmetrically arranged body panels, the contact plates each being engaged with a first side of the respective body panel; and applying heat to the respective second sides of the body panels.

It is further advantageous that the contact plates can conform to the panels being treated to such an extent that the framework of the vehicle is not distorted on vacuum engagement of the plate to the panel. To achieve this, the plate should be able to flex sufficiently to adapt to the intended contour of the vehicle body without adapting to localised surface irregularities.

According to a further aspect, the present invention provides a contact plate comprising a generally planar plate, the plate being provided with channels for circulation of cooling fluid and having a front surface provided with a peripheral seal for engagement with the body panel and with grooves of sufficient depth to increase the flexibility of the contact plate, the contact plate being further provided with connectors for respectively coupling the channels to a source of cooling fluid and connecting the front surface of the plate to a source of vacuum, such that on engagement of the contact plate with a body panel and application of a vacuum, the contact plate may flex to adapt to the intended contour of the body panel.

According to an important feature of the invention, it is desirable that little force be used to bring the contact plates into contact with the body panel whereby distortion of the framework is avoided. The use of suspended contact plates is therefore advantageous, as in this configuration, it is the vacuum or other attractive force between the body panel and the contact plate which provides the contact force to flatten the panel rather than any externally applied force. In this context a method of attaching a contact plate to a contoured body panel is disclosed in which the contact plate is suspended for attachment to the body panel only by attractive force between the plate and the body, without the use of externally applied force. The attractive forces used may include vacuum force or magnetic force.

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Embodiments of the present invention will now be described, by way of example only, having reference to the accompanying figures, in which: Figure 1 is a cross sectional view of a rail carriage under construction showing the gantry and contact plates according to the present invention; Figure 2 is a partial side elevation of Figure 1 viewed from direction II - II in Figure 1; Figure 3 is a rear view of a contact plate according to the present invention; Figure 4 is a cross sectional view of Figure 3 along line IV - 1V; Figure 5 is a view of the front of the contact plate of Figure 3 from direction V - V showing the grooves; Figures 6a, 6b and 6c are examples of contact plates with alternative configurations of grooves; and Figure 7 is a schematic view of a flexed contact plate in position against a vehicle body.

While the present description refers to railway carriages, the method of heat treatment is equally applicable to other vehicles of similar construction. Thus railway locomotives, powered rail carriages, trams, metro trains, coaches, buses, boats, hovercraft, aircraft and even fixed constructions where a high quality of surface finish and profile accuracy are required may also be treated using the device and method according to the present invention. References to carriage or À bee.e eel À . e À . e À e À À . vehicle in the remainder of the description will thus be understood to apply equally to any of the above mentioned alternative constructions.

Referring to Figure 1 there is shown a railway carriage 1 under construction. The carriage 1 is formed of a rib like structure or framework 4 over which is formed a skin 6 of metal sheets. The sheets may be provided as individual panels 8, 9 welded to the framework between adjacent ribs and cross-members of the framework 4. The carriage 1 is supported during construction on fixed supports or jacks 5 adapted to ensure immobilization of the entire structure.

The carriage 1 is located beneath a gantry 10, which forms a portal over and around the area of the carriage 1 being treated. The gantry 10 is provided with runners 12, 14 which are arranged to follow respective guiding rails 13, 15 located on either side of the carriage 1 and running parallel therewith. Runner 12 is provided with a drive 16 having a motor and appropriate gearing, adapted to cause the gantry 10 to ride along the rails 13, 15 according to an operator's instructions. The construction of the gantry 10 is generally conventional in the art, as is its drive and method of control. The gantry 10 also supports a number of additional items including a hose or cable reel 17, refrigeration unit 18 and vacuum units 19 the function of which will become clear in the following.

Suspended from the gantry 10 is a pair of contact plates 20, 24. Contact plate 20 is suspended by cable 21 from a hoist 22. Hoist 22 is arranged for transverse movement along a girder 11 forming part of the gantry 10. A controller (not shown) allows an operator to remotely control movement of the contact plate 20 in 3-axes. By action of the drive 16, the contact plate 20 can be moved in the longitudinal direction. By actuation of the hoist 22 through cable 21, the contact plate 20 may be moved in the vertical direction. By movement of the hoist 22 along the girder 11, the contact plate 20 may be moved in the transverse direction. Contact plate 24 is similarly suspended from cable 25 and hoist 26.

r tee cue e eve À r e 8 À C e e. e e e À À e 7 e e À e À e A second pair of contact plates SO, 34 is arranged for treatment of undercut lower panels 9 of the carriage 1. order to engage the contact plates 30, 34 with the angled surfaces of the panels 9, the contact plates 30, 34 are provided with cantilevers 31, 35 to which anchors 32, 36 are attached. These anchors 32, 36 may in turn be suspended from further cables and hoists (not shown) for full directional control of contact plates 30, 34. The anchors 32, 36 or the cantilevers 31, 35 may be individually adjustable to vary the inclination of the contact plates 30, 34 to match the body panels 9 with which it is intended to engage.

Similarly, a further pair of contact plates 37, 39 is arranged for treatment of sloping roof panels 7.

Similar suspension means may be employed. While the illustrated contact plates span a single panel, it also within the scope of the present invention that a single contact plate may be used which can span a plurality of panels, whereby a number of panels may be treated without relocation of the contact plate.

While the present invention has been disclosed using cables and hoists to suspend the contact plates from an overhead gantry, alternative arrangements may also be used to achieve the same object. Hydraulic actuators carried by the gantry, or robotic arms mounted for movement along the carriage or having sufficient reach to cover the whole carriage length could be employed.

Instead of the moveable gantry 10, a longitudinally fixed construction could be used whereby the carriage itself is mounted e.g. on rails for movement with respect to the contact plates. According to an important feature of the invention, it is desirable that little force be used to bring the contact plates into contact with the body panel whereby distortion of the framework is avoided. The use of suspended contact plates is therefore advantageous, as in this configuration, it is the vacuum or other attractive force between the body panel and the contact plate which provides the contact force to flatten the panel rather than any externally applied force.

By arranging the contact plates in symmetrically arranged pairs, bending and distortional forces on the partly constructed carriage can be reduced to a minimum. Further individual contact plates may also be employed for individual treatment of specific panels e.g when working around doors Aee: À: Àe is: À À À À À À À À ÀÀÀ ÀÀ À ÀÀ À À À or other regions of the carriage 1 which have no symmetrical counterpart. In the above description, reference is made to the longitudinal symmetry of the carriage 1. Other axes of symmetry may also be relevant for reducing distortional forces, particularly when working on constructions other than rail vehicle carriages. The skilled man in the field of each type of construction will be aware of the details of the precise axis or axes which are of primary importance to reducing these forces.

Figure 2 shows a side view of the gantry 10 located over the carriage 1. In this view the runner 14 can be seen extending lengthways along rail 15. The carriage 1 is of a double-decker construction with two rows of windows 2, 3. The contact plate 24 is of a size sufficient to cover a panel 8 1 located between the two rows of windows 2, 3. For each specifically shaped panel a correspondingly sized contact plate or pair of contact plates is provided.

Figure 3 shows the contact plate 24 from the same direction as Figure 2 in greater detail. Contact plate 24 comprises a generally rectangular metal plate 40 provided with suspension points 42. A ' number of the suspension points 42 are provided with rings 44 for attachment of cables 21, 25 i and anchors 32, 36 for suspension of the contact plate from the gantry. The rear surface of the contact plate is provided with cooling channels 50. Cooling channels 50 provide a labyrinthine path from inlet 52 to outlet 54 through which cooling fluid may flow, openings 58 providing fluid connection between neighboring channels.

A vacuum distributor 60 is provided on the rear of the contact plate for connection to the vacuum I unit 19. Vacuum distributor 60 is provided with a number of spigots 62 to which further vacuum lines (not shown) may be connected. The vacuum lines may be connected to supply vacuum via bores 64, which pass through the contact plate to the front surface thereof.

Arcuate strips 46 are formed across the rear of the contact plate 24, spanning the cooling channels 50 and the inlet 52, outlet 54 and vacuum distributor 60 and serving to protect them from shock when the contact plate is maneuvered or dropped.

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À À À e À À À À À À c e À À À À e À À À À À 12 1 Figure 4 more clearly illustrates the construction of the contact plate 24, where it can be seen how arcuate strips 46 provide protection for the inlet 52 attached to inlet connector 53 and also for a vacuum connector 63 inserted in bore 64. Figure 4 also illustrates how the cooling channels 50 may be constructed as relatively thin sheets or webs 57 welded to the rear surface of plate 40 and/or to one another. Preferably, these cooling channels are formed in a way that they do not impede the necessary flexibility of the plate 40. It should be noted however, that the structure of the contact plate 24 in its entirety, including the cooling channels 50, is important in determining the extent of its flexibility. For this reason, the cooling channels may also be designed to facilitate bending of the contact plate 24 and could also include grooves, channels or cavities within the thickness of the plate 40.

In one embodiment of the invention, the front surface of the plate 40 is provided with grooves 65 which cross the plate in both directions and which also intersect with the bores 64. The depth and position of the grooves 65 is precisely calculated to provide the necessary degree of flexibility of the contact plate. This may depend on many factors including the height, width and thickness of! the plate 40, its material properties, the expected curvature of the panels to be treated and the properties of the material e.g. gauge of steel used for the panel.

Around its outer periphery, the plate 40 is provided with a seal 67. The seal may be formed of any suitable resilient material capable of withstanding the temperatures and pressures encountered during use of the contact plate. Typical materials may include natural rubber, silicon rubber, PTFE or other plastics materials. A fine resilient metal strip may also be used or alternatively for particular conditions of operation, the seal may be provided by an edge region of the plate 40 itself or by a bead formed thereon. The seal 67 is located in a trough 68 around the edge of the plate 40 and can be easily removed for replacement should it become worn in use.

Figure 5 is a view of the front face of the contact plate 24 of Figure 3 and Figure 4, illustrating a preferred distribution of grooves 65 over the surface thereof. It can also be observed how the e.e a e a e e e e e e e e a e e a e e e a e a À e a grooves 65 intersect with the bores 64 whereby the vacuum pressure may be distributed evenly over the whole front surface of the plate 40. For optimum flexibility, it is preferable that the grooves 65 are not aligned with the side walls of the channels where they attach to the rear surface. In the present embodiment, the grooves 65 are located on the front surface of the plate 40 such that they serve also as vacuum distribution channels. They may alternatively be provided on the rear surface of the plate 40, or on both surfaces thereof.

Various other groove patterns may be employed according to the mode of bending envisaged for the plate and as determined by the contour of the carriage under construction. Figure 6a indicates an alternative rectangular configuration for a contact plate 70 having only horizontal grooves 72 for encouraging flexure in a single mode. Figure 6b indicates a generally square contact plate 80 having diagonal grooves 82. Figure 6cindicates a generally square contact plate 90 having a complex groove structure 92. For the sake of clarity, other details of these contact plates such as the peripheral seal have not been shown in these views.

The depth and width of the different grooves may also vary with e.g. longitudinal grooves being deeper than transverse grooves. The groove cross-sections may also vary along the length of a given groove e.g. deeper at the edges of the plate than in the central region. While the illustrated grooves are rectangular in cross-section alternative shapes may also be used e.g. U-shaped to reduce stress concentrations. It has been found that for general use the groove may have an optimum dimension in the range from 3 mm to 7 mm in depth. More preferably the grooves will be between 4 mm and 6 mm in depth. Most preferably the grooves will be approximately 5 mm deep. Corresponding thickness dimensions for the plate 40 are preferably in the range of from 25 mm to 8 mm, more preferably from 18 mm to 12 mm and most preferably 15 mm. In general values at the highest end of the thickness range would correspond to a required groove depth at the maximum of the corresponding range and vice-versa.

These values have been given for plates of typical dimensions of from 0.5 m2 to 1.5 m2. For smaller plates, it is clear that lower thickness values may be appropriate, while for larger plates À 1 À À c À À e À . greater thickness may be required to achieve optimum flexibility. Clearly also, the relative I strength of the framework and the metal sheet forming the panel will influence the choice of dimensions. While the above description has been directed primarily to contact plates which are initially flat and can flex to adapt to the vehicle contour, it is also envisaged that initially curved or bent plates may be used which are already at least partially adapted to the intended contour of the body being treated.

The method of use of the device according to the present invention will now be described with! reference to Figures 1 to 5. In order to commence spot-wise heat treatment of a body panel 8 of a rail vehicle carriage 1, the gantry 10 is advanced by drive 16 along rails 13, 15 to a position level I with the body panel 8 to be treated. An operator then manipulates a contact plate 24 to a position closely adjacent to the panel 8 using the hoist as described above. Actuation of the vacuum unit 19, or if the vacuum is already engaged, approximation of the contact plate to the surface of the panel, will cause the contact plate 24 to be adhered to the panel 8 by virtue of the vacuum formed between the surfaces of the panel 8 and the contact plate 24 and the peripheral seal 67.

For panels that are not completely flat, a prior art rigidly formed contact plate would be unable to lie flat against the panel and must rely on the extensibility of its seal to maintain the vacuum along any of the edges which lie free of the panel. External e.g hydraulic forces used to attach the i plate as well as the vacuum force itself have in the past caused the panel and the vehicle frame to adapt to the rigid plate. The contact plate 24 according to the present invention is susceptible to a certain degree of bending as a consequence of the grooves 65 formed on its front face. By careful selection of plate thickness and groove depth, the contact plate 24 is tailored such that under the vacuum force (or other alternative force) applied, it is sufficiently flexible to conform to the local contours defined by the vehicle frame yet sufficiently rigid to not conform to distortions of the panel. In other words, the panel conforms to the contact plate 24 but the contact plate conforms to the framework. As a result of this conforming, it has been found that higher values of vacuum can be maintained.

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À À À À À À À À À À À.À À À Once the contact plate 24 is correctly engaged with the panel 8, flow of cooling emulsion may be commenced. The refrigeration unit 18 provides a controlled supply of cooling emulsion to the contact plate 24 through appropriate tubing or conduits (not shown) via inlet 52 and returned via outlet 54. The supply of cooling emulsion is precisely controlled to meet the cooling requirements of the particular material being treated. This requirement will in general vary dependent upon whether steel, stainless steel or aluminium is being used and will also depend upon the gauge of the material.

A person located within the railway carriage may then commence spot-wise heat treatment of the body panel 8. This involves applying heat to a spot on the inside of the panel by the use of a torch or other heat source. The spot is heated to just below the yield point. This is determined by observing the colour change as the metal is heated. As the temperature of the spot approaches the yield point, stresses within the material at that point are relieved by stretching or other deformation. The heat source is then removed and the spot allowed to cool. As the spot cools, the metal contracts causing a new stress distribution. The new stress distribution will generally be a uniform radial tension within the plane of the panel, centered on the spot. As the whole body panel 8 is treated, one spot at a time, it is subjected to the same level of uniform tension.

It is important that each spot can cool sufficiently before the next spot reaches the stress relieving temperature, to avoid the transfer of stresses from one spot to the next. This would lead to a non- uniform stress distribution, since stresses aligned between two adjacent spots would be relieved while those perpendicular to that direction would not be. To achieve rapid cooling of the heated area or the body panel 8, there must be not only sufficient cooling supply to the contact plate 24 but also adequate heat transfer between the outer surface of the body panel 8 and the front surface of the contact plate 24. Since air is a good thermal insulator, any gaps between the body panel 8 and the contact plate 24 will reduce the overall cooling capacity. The ability of the contact plate 24 to flex to adapt to the outer contour of the carriage 1 ensures that a closer contact is achieved with improved heat transfer capability. During heat treatment, as stresses are relieved, bulges and hollows present on the body panel 8 will be reduced as regions of the body panel 8 are pulled À À À À À e À À À À À À À À À À À into closer contact by the vacuum. In general, cooling should be sufficient to bring the temperature of the heated metal back from 900 C to under 50 C as soon as the heat source is removed.

At the same time as heat treatment proceeds with the contact plate 24, on the opposite side of the carriage 1 another person or team of people will be working with the contact plate 20 on a corresponding body panel 8. By working in a symmetrical fashion, both sides of the carriage 1 are subjected to similar levels of resulting tension and there is no resultant bending force on the carriage 1 and its framework 4 as a whole. While, to achieve optimal results according to the present invention, it is recommended to work on symmetrically located panels using pairs of contact plates 20, 24, it is noted that individual contact plates may also be used in isolation to treat individual body panels.

The refrigeration unit 18 supplies cooling emulsion to both contact plates 20, 24 and can ensure that both plates are equally cooled. This may involve supplying equal amounts of cooling emulsion to both contact plates 20, 24 or may involve controlling the respective flows to equalize heat transfer. Accuracy of control may be achieved by incorporating flow and temperature sensors (not shown) at various points in the system, including sensors on the supply lines and also temperature sensors on the contact plates themselves or on the body panels 8. The amount of vacuum supplied by vacuum units 19, may also be controlled to ensure equal vacuum pressure on both sides of the carriage.

Once the heat treatment of a first pair of body panels 8 is complete, the vacuum may be removed or reduced and the contact plates 20, 24 disengaged and prepared for the following pair of panels.

This may involve movement of the gantry 10 along the rails 13, 15 without further adjustment of the hoists 22, 26 or may involve realigning the contact plates 20, 24 with a similarly sized body panel at the same gantry position. Alternatively the carriage 1 may be moved with respect to the contact plates 20, 24.

À ÀÀ e À À À À e À À À e ÀeÀ Àe The pair of undercut body panels 9 in the floor region of the carriage 1 may also be treated in a similar way either concurrently with body panels 8, or thereafter. Depending upon the space available for work within the carriage, a number of pairs of body panels may be treated at the same time. It may be desirable to treat a symmetrical pair of panels in the roof region of the train at the same time as the pair of body panels 9 in the floor region. In this way, any upward bending of the carriage 1 about a transverse horizontal axis could also be reduced.

Figure 7 shows a schematic view of how the flexible contact plate 24 may adapt to a vehicle framework 4 formed of non-parallel ribs. For the sake of clarity, the panel 8 forming the vehicle skin 6 is not shown.

Alternatives to the method and devices described above may be employed according to the required effects. While the described embodiment contemplates the use of human operators to engage the contact plates and perform the heat treatment, automated systems and robotic devices may also be used or a combination of the above. The contact plates described have been attached to the body panels by vacuum actuated suction. Alternative systems using magnetic or electromagnetic forces may also be employed, or the contact plates may be held pressed into position by hydraulic or pneumatic force or any other means, which can ensure a distributed force over the area of the plate. It is however preferable that the contact plates are attached by mutual forces between the contact plate and the panel rather than by externally applied pressure which could serve to distort the framework. The contact plates may also engage the inside surface of the body panel with heat being applied from outside. In this case it would be possible for the contact plates to fit between adjacent framework elements and could locate and lock e.g. by expansion members between the framework elements in intimate contact with the inner surface of the panel.

The contact plates as described above are supplied with cooling emulsion from a refrigeration unit. Other means for cooling the plates may also be employed including open and closed systems involving emulsions, water, oil, gas or any other device or mechanism, which can effectively ensure removal of sufficient heat from the area of metal being heated.

. be: be: e. À e: À À À e À , e Although the above description contemplates the use of the device and method in the heat treatment of body panels welded to a framework, it may also be used for panels which have been attached by other means including but not limited to riveting and adhesive bonding and combinations of these methods. In particular such contact plates and structures may be used not only in the manufacture of vehicles but also during repair of such body panels to remove dents and other damage. In such circumstances, the requirement for working in symmetrical pairs While the above examples illustrate preferred examples of the present invention it is noted that various other arrangements may also be considered which fall within the spirit and scope of the appended claims.

Claims (36)

1. ÀÀ À- À À ÀÀ e À e À À e e - À e e Claims 1. A device for use in the heat

   treatment of body panels after their assembly to a vehicle, the device comprising a pair of contact plates supported on opposite sides of the vehicle longitudinal axis, the contact plates being moveable to bring them into symmetrical engagement with body panels on opposing sides of the vehicle, and being arranged to conform to the outer contour of the vehicle whereby asymmetric forces on the vehicle during heat treatment may be reduced.
2. 2. The device according to claim 1 whereby the contact plates are supported from a supporting structure, the vehicle and supporting structure being moveable with respect to one another in the axial direction.
3. 3. The device according to claim 2 whereby the contact plates are suspended from the supporting structure by a hoist arrangement.
4. 4. The device according to claim 2 or claim 3 whereby the relative axial movement of the vehicle and supporting structure is automated.
5. 5. The device according to any of claims 2 to 4 whereby the relative axial movement of the vehicle and supporting structure is remotely controlled
6. 6. The device according to any of claims 2 to 5 whereby the vehicle is generally immovable and the supporting structure is mounted for movement in the axial direction.
7. 7. The device according to claims 6 whereby the supporting structure comprises an overhead gantry mounted generally perpendicular to the longitudinal axis and arranged for axial movement.

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8. 8. The device according to claim 7 further comprising a cooling fluid supply mounted on the gantry for movement therewith.
9. 9. The device according to any preceding claim, further comprising a cooling controller to ensure equal cooling at both contact plates.
10. 10. The device according to any preceding claim whereby the contact plates are moveable perpendicular to the longitudinal axis for engagement with the body panels.
11. 11. The device according to any preceding claim whereby the contact plates can be inclined for engagement with the body panels.
12. 12. The device according to any preceding claim whereby the contact plates are provided with cantilevers for engagement with undercut body panels.
13. 13. The device according to any preceding claim further comprising additional contact plates.
14. 14. The device according to any preceding claim whereby the contact plates are supplied with cooling fluid.
15. 15. The device according to any preceding claim whereby the contact plates are supplied with vacuum for suctional engagement to the body panels.
16. 16. The device according to any preceding claim whereby the contact plates are provided with a seal for facilitating suctional engagement between the contact plate and the body panel.

    À À À ae À À À À C À ÀÀe À À À ÀÀ À À À
17. 17. The device according to claim 15 or claim 16 whereby the contact plates are provided with grooves on a forward contact surface for facilitating vacuum distribution over that surface.
18. 518. The device according to any preceding claim whereby the contact plates are provided with magnets for magnetic attachment to the body panels.
19. 19. The device according to any preceding claim whereby the contact plates are flexible.
20. 1020. The device according to claim 19 whereby the contact plates are provided with grooves for facilitating flexure.
21. 21. A method of spot-wise heat treating vehicle body panels comprising the steps of: providing a vehicle having a pair of symmetrically arranged body panels; 15engaging a pair of contact plates with the pair of symmetrically arranged body panels, the contact plates each being engaged with a first side of the respective body panel; applying spot-wise heat to the respective second sides of the body panels.
22. 2022. The method according to claim 21 whereby the contact plates are engaged to the body panels by suction.
23. 23. The method according to claim 21 whereby the contact plates are engaged to the body panels by magnetism.
24. 24. The method according to any of claims 21 to 23 whereby the step of engaging the contact plates with the body panels includes conforming the contact plate to the body panel.

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25. 25. The method according to any of claims 21 to 24 further comprising the step of providing cooling fluid to the contact plates.
26. 26. The method according to any of claims 21 to 25 whereby the step of applying heat to the respective second sides of the body panels includes heating individual points to the stress relieving temperature and subsequent cooling to below 50 C.
27. 27. A contact plate for use in a method of treating vehicle body panels attached to a framework according to claim 21, comprising a generally planar plate of a size substantially equal to or larger than that of the body panel to be treated, the contact plate being provided with channels for circulation of cooling fluid and grooves of sufficient depth to increase the flexibility of the contact plate, and having a front surface provided with a peripheral seal for engagement with the body panel, the contact plate being further provided with connectors for respectively coupling the channels to a source of cooling fluid and connecting the front surface of the plate to a source of vacuum such that on engagement of the contact plate with a body panel and application of a vacuum, the contact plate is caused to flex to adapt to the contour of the framework while being sufficiently rigid to resist conforming to the body panel.
28. 28. The contact plate according to claim 27 whereby the channels are formed between webs provided on the rear surface of the plate.
29. 29. The contact plate according to claim 28 whereby the grooves are formed on the front surface of the plate and are offset from the connections of the webs with the rear surface of the plate.
30. 30. The contact plate according to any of claims 26 to 29 in which the grooves have a depth and distribution such that on application of a vacuum, the plate can bend along the lines of reduced material thickness formed by the grooves.

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31. 31. The contact plate according to claim 30 in which the grooves are about 5 mm in depth and the plate is about 15 mm thick.
32. 32. The contact plate according to any of claims 26 to 31 in which the plate is of a size to cover a plurality of body panels.
33. 33. The contact plate according to any of claims 26 to 32 in which the plate is initially curved for treatment of contoured sections of the vehicle body.
34. 34. A device for treating body panels substantially as hereinbefore described with reference to I figures 1 to 7. t
35. 35. A contact plate substantially as hereinbefore described with reference to figures 3 to 7
36. 36. A method for treating body panels substantially as hereinbefore claimed.