The invention relates to a device and a method for masking fastening holes in rims using masking elements which can be for example balls or approximately conical plugs. The masking is usually carried out before the rims are lacquered or coated in another way. As a result, penetration of lacquer or other coating material into the fastening holes is prevented.
From the prior art, it is known to produce rims, as are provided for use on vehicles, from metal materials such as steel or aluminum. Such rims are provided with a coating which comprises one or more layers. The coating serves as corrosion protection for the metal material and often also for improving the aesthetic effect of the vehicle wheels. As coating methods for the vehicle wheels, wet lacquering methods and powder coating methods are customarily used, wherein these can also be combined with each other.
The rim has holes by means of which the rim can be fastened on an end-side flange of a vehicle axle. A first group of holes is formed by fastening holes, as such wheel bolt holes, which have contact surfaces for the heads of the wheel bolts. Furthermore, a rim as a rule has a central hole which serves for the centering of the rim with regard to the wheel axle and can accommodate a cover cap. The fastening holes—in contrast to the customary surface regions of the rim—are intended to be at least in the main free of coating after carrying out the coating of the rim. As a result, the effect of the pairing geometry between the wheel bolt and the rim in the region of the contact surface ensuring the necessary frictional engagement during operation is especially achieved. In the case of a coating remaining in the region of the contact surface the surface pressure between wheel bolt and rim can alter especially as a result of setting processes, which leads to the functional reliability being endangered.
From the prior art, it is known to mask the functional surfaces for the duration of the coating processes in order to prevent impingement and adherence of coating material there. To this end, before carrying out the coating by means of a handling device, which can be designed as a robot for example, masking elements such as balls or plugs are placed on the fastening holes and as a result these close these off. The robot is equipped with a multi-gripper as the tool, the gripping units of which are rigidly arranged corresponding to the fastening hole pattern of the rim. Such a multi-gripper can therefore only be used for one rim type. If rims of different types are to be masked in a coating plant then multi-grippers which are adapted to the rim types have to be made available to the robot, which is associated with high plant costs. Also, a change of rim types is only possible after a change of the multi-gripper in such coating plants. The tool change times which are required for this reduce the throughput of the coating plant.
A method for masking fastening holes of rims, in which a delta robot fits individual masking elements one after the other in the fastening holes, is known from the still unpublished German application DE 10 2015 013 117.6 of the applicant. As a result, the device, by reprogramming the movement paths, can be quickly adapted to different fastening hole patterns. However, this flexibility comes at the cost of speed since the holes are no long masked at the same time but in sequence.
It is the object of the invention to specify a device for masking fastening holes in rims which is constructed in a particularly simple manner and can be inexpensively produced. It is also the object of the invention to specify a method by means of which fastening holes can be masked using masking elements in a particularly efficient manner.
With regard to the device, the object is achieved by means of a device which has a storage container for the masking elements and a pressure generating unit. The device also has a connection unit, which is connected to the storage container, and an at least basically tubular discharge device which is fastened on one end of the connection unit and has a discharge opening on the opposite end for discharging the masking elements. According to the invention, the discharge device has a tubular wall in which is formed a channel, connected to the pressure generating unit, for conducting a fluid which can be air or another gas or even a liquid, e.g. water or hydraulic oil. The tube wall consists at least partially of an elastic material through which extends the channel or in which is formed a cavity which is connected to the channel so that if the pressure of the fluid is altered the tube wall deforms and as a result reduces a clamping force which is exerted by a part of the tube wall upon one of the masking elements. If a plurality of such discharge devices are fastened on the connection unit, a plurality of masking elements can be discharged at the same time by reducing the respectively acting clamping force.
The device according to the invention is based on the consideration of deforming an elastic part of the tube wall of the discharge device with the aid of a pressurized fluid. The deformation, which can be either the consequence of a pressure increase or a pressure decrease, leads to the clamping force which is exerted upon a masking element being reduced. A force which has at least one component acting in the radial direction between the tube wall and the masking element and which can also result from the gravity force of the masking element is understood by a clamping force in this context. The clamping force for most of the time during operation of the device is at such a level that the masking element in the discharge device is retained against the action of its gravity force and therefore cannot discharge from the discharge opening. If the clamping force is reduced by a sufficient amount, then the gravity force of the masking element can overcome the clamping force, as a result of which the masking element moves forward in the discharge device. This pressure-initiated release of the masking element can be used either for the purpose of separating out a masking element from a group of a plurality of masking elements, or for discharging a single masking element from the discharge opening in order to mask the fastening hole of the rim. The same naturally also applies if the clamping force is returned completely to zero as a result of the pressure change.
On account of this functioning principle, at least the tube wall and preferably the entire connection unit and the discharge device can be designed in one piece and produced in a 3D-printing process. In the 3D-printing process, three-dimensional workpieces are built up in layers and in a computer-controlled manner from one or more fluid or solid materials. During the buildup, physical or chemical hardening or melting processes take place. For the present application, plastics or synthetic resins are particularly suitable as material for the 3D-printing since these frequently have the best elastic properties. The buildup of the individual layers can be carried out for example by way of fused deposition modeling (FDM). If different materials are combined, other criteria, e.g. abrasion resistance, can also be taken into consideration in addition to elasticity. Therefore, for example those regions of the discharge device which exert clamping forces upon the masking elements can consist of a non-slip and particularly abrasion-resistant material. For the surrounding regions, which are to be particularly easily deformable, an elastic material is frequently more favorable, however.
The adaptability to manufacture of the tube wall, of the discharge device with the tube wall or even of the overall complex consisting of connecting unit and discharge device in a 3D-printing process has the advantage that the device can be produced very inexpensively in this way. This in turn makes it possible to undertake an adaptation to a quite different fastening hole pattern by a new connection unit, with a plurality of discharge devices fastening thereon, being designed in a simple manner and produced by way of the 3D-printing. A complete new construction and installation of a multi-gripper, as was previously necessary in the prior art, is therefore replaced by very simple adaptations in the 3D-design and by an inexpensive 3D-printing which is associated therewith.
Particularly large reductions of the clamping force can be created if a cavity, which is connected to the channel and designed in the style of a one-sided bellows, is formed in the elastic material. The shape of the bellows is preferably adapted to the cross section of the discharge device, which can be circular but can also for example have the shape of an oval or a polygon.
In a one-sided bellows, the cavity usually has a plurality of fluidically interconnected sections which are arranged in series along an axial direction of the tube wall and have a larger and a smaller width alternately, wherein one side of the bellows has no recesses. With of a pressure change in such a cavity, forces which lead to deformation of the tube wall and as a result alter the clamping force are created with each change of the width of the cavity. As a result of the series-connection of a plurality of such sections with alternating widths the forces and the deflections of the tube wall which are achieved as a result can be increased.
The sections of the bellows can be in the form of a ring or ring segment especially when the cross section of the discharge device is circular.
If the sections with the smaller width have a larger inner radius, this means that the “folded” side of the bellows points inward and the recess-free side points outward. With a pressure increase, such a bellows bends outward and therefore increases the clear cross section of the tube wall, as a result of which masking elements can be separated out or discharged. Such an embodiment has the advantage that in the event of an undesirable pressure drop (perhaps on account of a malfunction of the pressure generating unit) no masking elements can leave the discharge device.
If, on the other hand, the pressure generating unit generates no positive pressure but a negative pressure, then the conditions are exactly the other way round. In this case, a bellows in which the “folded” side points outward is more favorable. With a corresponding design, such a bellows bends inward in the unpressurized state and is straightened by applying a negative pressure.
In one exemplary embodiment, a first channel and a second channel are formed in the tube wall for conducting a fluid and connected to the pressure generating unit so that the pressure of the fluid in the first channel and in the second channel can be altered independently of each other. The tube wall has a first section and a second section which is arranged in an axially offset manner to it in the direction of the discharge opening. The shape of the tube wall can be altered in the first section by altering the fluid pressure in the first channel and in the second section by altering the fluid pressure in the second channel so that masking elements which have accumulated in the discharge device can be separated out by the first section and discharged by the second section. By forming a plurality of channels, the masking elements can therefore be separated out and discharged in different sections of the tubular discharge device. As a result, the masking elements can be continuously fed from the storage container and by discharge at the discharge opening be individually deposited in the fastening holes of the rim.
In a particularly advantageous development, two or more discharge devices are fastened on the connection unit, each having a first channel and a second channel. The connection unit also has a first fluid connection and a second fluid connection. Formed in the connection unit is a first channel system which connects the first fluid connection to the first channels, and a second channel system which connects the section fluid connection to the second channels. In this way, a plurality of masking elements can be discharged at the same time and placed in the fastening holes of the rim. After discharging a set of masking elements, the masking elements which have accumulated in front of the first section of the discharge devices can be separated out in order to then be deposited on the fastening holes of the next rim in a further working cycle.
It is favorable in this case if the first channel system is formed in a first plane and the second channel system is formed in a second plane which is parallel to the first plane. A connection unit with channel systems which are spatially separated in this way can be produced in a particularly simple manner in a 3D-printing process.
In another exemplary embodiment, the tube wall has two oppositely disposed cavities and designed so that first masking elements are separated out or released only in the case of a simultaneous pressure change in relation to the ambient pressure in both cavities. Second masking elements, which have a smaller diameter than the first masking elements, are already separated out or released, however, in the case of a pressure change in relation to the ambient pressure in only one of the two cavities. Consequently, masking elements with different diameters can be used. As a result, rims with fastening holes of different sizes can also be equipped with masking elements which are adapted thereto.
In another exemplary embodiment, two or more discharge devices are fastened on the connection unit. The device has a deflection device which is designed for the purpose of deflecting the discharge devices and elastically deforming them in the process so that the position of the discharge openings of the discharge devices can be altered. In this case, the fact that the tube wall of the discharge devices partially consists of an elastic material anyway is exploited so that these can be deflected in the manner of a solid-body joint. In this way, it is possible to adapt the position of the discharge openings to different fastening hole patterns.
The deflection device can in this case be formed by an additional channel or an additional cavity in the tube wall of the respective discharge device. With a pressure change in relation to the ambient pressure in the additional channel or in the additional cavity, the tube wall is deformed so that the respective discharge device is deflected and the position of the discharge opening is altered. The deflection device is therefore integrated into the tube wall and can also be fluidically operated. As a result, the construction of the device becomes simpler and more reliable.
With regard to the method, the object referred to in the introduction is achieved by means of a method for masking fastening holes in rims using masking elements. The method according to the invention features the following steps:
The advantageous embodiments which are explained above with reference to the device according to the invention correspondingly apply to the method.
Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. In these drawings:
Shown in
The rims 12 which are to be coated in a subsequent treatment step are fed to the masking device 10 by a transporting device 14, the transporting device extending perpendicularly to the paper plane of
The opposite end of the spindle 18 is connected to a chain drive which conveys the spindle 18 and the rim 12, which is retained by the mandrel 16, along a transporting direction. A plurality of such spindles 18 which carry the rims 12 are arranged in series along the transporting direction 14, as can be seen further down in the side view of
The masking device 10 comprises a storage container 22 which is located in a ceiling structure 23 and serves as a store for a multiplicity of balls 24 by means of which the fastening holes of the rim 12 can be masked. The storage container 22 is connected via a hose-like ball feed 28 to a distribution unit 30 in which the balls 24 are temporarily stored on a spiral track. The distribution unit 30 can be moved in the vertical direction with the aid of a lifting device 32, as is indicated in
Fastened on the bottom end of the distribution unit 30 is a connection unit 34 which is connected via hoses 36a, 36b to a pressure generating unit 38. The pressure generating unit 38 is able to adjust the air pressure in the hoses 36a, 36b independently of each other, specifically preferably between an outside operating normal pressure (approximately 1 bar) and an increased pressure, e.g. 2 bar. Alternatively to this, the pressure generating unit 38 can bring about a lowering of the pressure in the hoses 36a, 36b instead of an increase. Moreover, instead of air another gas or even a liquid cab can be fed to the hoses 36a, 36b as fluid.
Fastened on the bottom end of the connection unit 34 are four discharge devices 40, at the discharge openings 42 of which the balls 24 can be discharged in a compressed air-controlled manner. The discharge openings 42 are positioned in this case so that a discharge opening 42 is located over each fastening hole 21. Before discharge of the balls 24, the distribution unit 30 and the connection unit 34, with the discharge devices fastened thereto, are lowered with the aid of the lifting device to the extent that the discharge openings 42 are located directly over the fastening holes 21. By way of illustration, a ball 24 is shown in its final position in one of the fastening holes 21; in actual operation, all four fastening holes are always masked by balls 24 at the same time.
Fastened on the ceiling structure 23 is a camera 44 which monitors the discharge process so that a central control unit can engage in a correcting manner if necessary. It has to be ensured in particular that the rim 12 is located both in the correct rotational orientation and at the correct location along the transporting direction which is perpendicular to the paper plane. Only then can the balls 24 be reliably deposited in the fastening holes 21 of the rim 12.
The discharge devices 40 consist in the main of a tube wall 46, the external contour of which has the basic shape of a circular cylinder. Formed in each tube wall 46 is a first channel 48 and a second channel 50 which extend in the axial direction from the top downward through the tube wall 48. The channels 48, 50 terminate in each case in a first cavity 52 or in a second cavity 54 which are located in sections of the discharge devices 40 which are axially offset to each other. The cavities 52, 54 have in each case the form of a one-sided bellows 53 or 55 and are explained in detail further down with reference to
In a bottom section of the connection unit 34, designated 56, the first channels 48 and the second channels 50 of all four discharge devices 40 are connected to a common first fluid connection 58 or to a common second fluid connection 60.
The function of the channels 48, 50 and of the cavities 52, 54 which are fluidically connected thereto is explained below with reference to
If the pressure generating unit 38 is actuated so that via the hose 36a the air pressure at the first fluid connection 58 is increased, then the increased pressure is distributed via the first channel system 62 to the first channels 48 in all the discharge devices 40. The pressure increase in the second cavity 54 produces the effect of the first bellows 53 bending inward, as is shown in
In the unpressurized state shown in
In order to discharge the balls 24 with the aid of the discharge devices 40, the first bellows 53 therefore has to be pressurized with increased pressure in order to be able to initially retain the balls 24 in the discharge devices 40, as shown in
The second bellows 55 which are arranged above the first bellows 53 function in the same way. They have the object of separating out balls 24 which have accumulated in the discharge devices 40. In this way, it is ensured that during operation of the first bellows 53 not more than one ball 24 can ever escape from the discharge opening 42. In a corresponding manner, the second bellows 55 are pressurized in this case with compressed air from the pressure generating unit 38 via the second fluid connection 60. As a result of lowering the pressure, the clamping force is reduced so that a ball can pass through the second bellows 55. The process of the separating out is explained in more detail further down with reference to
In the exemplary embodiment shown in
It is therefore more favorable if the discharge of a ball 24 does not require a pressure drop but an increased air pressure.
If only the (comparatively low) ambient pressure is applied to the bellows 53, 55, then the clamping forces which are then in effect should be of such strength that the balls 24 are not able to leave the discharge devices 40.
Furthermore, an inwardly projecting protuberance 66 is located as the bottom end of the first bellows 53. In the unpressurized state shown in
If the air pressure in the first bellows 53 is increased, then this bends outward, as is shown in
Located in the second side 74a is a cavity 52a which is connected to the pressure generating unit 38 via a channel, which lies outside the sectional plane, and via the connection unit 34. A corresponding cavity 52b is located on the opposite side in the second side 74b. The two cavities 52a, 52b can be pressurized with compressed air independently of each other.
If both cavities 52a, 52b are filled with compressed air, then the cavities expand and deflect the yokes 70a, 70b so that the flange-like projections 76a, 76b move away and free the path for the ball 24, as is shown in
If only one of the cavities 52a or 52b is pressurized with compressed air, the respectively other yoke 70b or 70a remains in its original position, as is shown in
In the previously described exemplary embodiments, it was implied that the position of the discharge openings 42 cannot be altered. For different fastening hole patterns of the rims 12 at least the connection unit 34, with the discharge devices 40 fastened thereon, therefore has to be exchanged.
Fastened on the bottom end of the shaft 79 is a cam disk 80 which can be seen best in the bottom view of
The shaft 79 with the cam disk 80 can in principle also be produced by means of a 3D-printing process. It is also possible to produce the shaft 79 and the cam disk 80 from conventional metal materials.
It can be seen in
A first pair of channels 481a, 481b can be pressurized with compressed air only together and extend from the connection unit 34 downward as far as the discharge opening 42. As can be seen in
If the air pressure in the first channels 481a, 481b is reduced, then the tube wall 48 deforms in a way which leads to an increase of the inside diameter. The clamping forces acting upon the balls 24 disappear as a result, or become so small that the ball 24 can overcome these clamping forces on account of their own weight and fall out of the discharge opening 42, as in shown in
Instead of providing two oppositely disposed first channels 481a, 481b, the controlled discharge of the ball 24 can also be effected by means of only a single channel 481, as is the case in the variant shown in
With reference to
For this purpose, the air pressure is altered in the second channels 482a, 482b, which—unlike the first channels 481a, 481b—do not extend as far as the discharge opening but terminate approximately by a ball diameter above the discharge opening 42, as can be seen in the longitudinal section of
In order to separate out a ball from a plurality of accumulated balls 24, the air pressure in the second channels 482a, 482b is reduced, as is shown in
The deflection of the discharge devices 40 is explained below with reference to
If both channels 483, 484 are pressurized with compressed air, then the discharge device 40 remains oriented in a straight line as a consequence of the symmetrical tensile forces. If the air pressure in the third channel 483 is reduced, then the forces which are created by the channels 483, 484 no longer increase. The tensile forces in the fourth channel 484 lead to the sections beneath the third and fourth channels 483, 484 to be deflected sideways, as is illustrated in
If the discharge devices 40 are to be deflected in chosen directions, at least one additional fifth channel is to be provided in addition to the third channel 483 and the fourth channel 484. These three channels are then distributed over the periphery of the tube wall 46 preferably with a 120° angular spacing. As a result, the masking device can be adapted in a more flexible manner to different fastening hole patterns and to positional changes of the rim 12. If the rim 12 is for example not located in the desired angular orientation, then the discharge devices 40 can all be deflected tangentially in the same rotational direction. Alternatively or in addition to this, it is possible to rotate the spindle 18 by means of an operating device, which for example can be integrated into the lifting device 32 and is not shown in the figures, and/or to rotate the entire connection unit 34 with the discharge devices 40 fastened thereon.
Number | Date | Country | Kind |
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10 2016 112 797.3 | Jul 2016 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/066257 | 6/30/2017 | WO | 00 |