Abstract:
The subject-matter of the invention is deburring machine for deburring metal work pieces with a continuous circulating abrasive belt ( 7 ), with a contact roller ( 3 ) for pressing the abrasive belt ( 7 ) against the work piece ( 2 ) and with a tensioning roller ( 8 ) for tensioning the abrasive belt ( 7 ), wherein the contact roller ( 3 ) is surrounded by a resilient coating ( 4 ). Creating a deburring machine of the afore-mentioned type with a great resilience range, providing a counter-pressure on the burr sufficient for deburring and that is much simpler to operate is achieved by providing a pressure belt ( 5 ) between the contact roller ( 3 ) and the abrasive belt ( 7, 7 ′), which circulates continuously around the contact roller ( 3 ) and a second roller ( 9 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    a. Field of the Invention 
         [0002]    The present invention relates to a deburring machine for deburring metal work pieces according to the preamble of claim  1 . 
         [0003]    b. Background Art 
         [0004]    A deburring machine for deburring metal work pieces is known from DE 27 45 104 A1, which features a steel contact roller rotating around its longitudinal axis. A soft rubber coating with a thickness of up to 30 mm is vulcanized onto the outer side of the contact roller. A continuously circulating abrasive belt is provided around this contact roller, to the outer side of which the actual abrasive is fastened. This abrasive belt is not attached to the contact roller, but held in a rotating manner on the contact roller and on a second roller and tensioned in such a manner that the abrasive belt can be driven for example by way of the contact roller. In this regard, the continuously circulating abrasive belt is tensioned so tautly that it does not slip on the contact roller, at least not in any significant manner. 
         [0005]    The rubbery coating vulcanized onto the contact roller is designed in accordance with respective technical requirements, a coating with a thickness of up to 30 mm and a Shore hardness of 30° Shore to 70° Shore being customarily used. When deburring a work piece, the following must be taken into consideration: 
         [0006]    A relatively hard coating of 50° Shore to 70° Shore allows applying a comparatively great counter-pressure, because the hard coating has little resilience. In this regard, the height of the contact roller is adjusted, as a rule, in such a manner that the level of the abrasive belt is a little lower than the surface of the work piece, so that the abrasive belt is applied onto the edge of the work piece, with the consequence that the burr in the area next to the edge is also covered. Due to the little amount of resilience, a high contact pressure is achieved, which leads to high abrasion at the burr. 
         [0007]    At the same time, the contact pressure is correspondingly lower in other places, in particular on the surfaces of the work piece, and the abrasion at the surface is correspondingly lower. This is intended, since the work piece is to be deburred. 
         [0008]    In this regard, it must be taken into account that an additional advance of only 1/10 mm to 2/10 mm leads to a significant increase of the power requirement of the deburring machine, of the abrasion and of the amount of generated heat. Such hard contact rollers are advantageously used for work pieces that where produced by means of laser or waterjet cutters, because such work pieces have comparatively the same thickness along their entire surface. 
         [0009]    Work pieces that were manufactured by plasma cutting or gas cutting installations, in particular, can be warped due to the effects of heat. In that case, the abrasive belt must be designed so as to be resilient during deburring, so that the abrasive belt can at least partially follow the contour of the work piece and the machining process of the surface of the work piece can be reduced to a minimum, because unnecessary machining of the work piece, in particular of its surface, leads to increased power requirements of the deburring machine, to increased wear of the abrasive belt and causes an increased thermal load onto the work piece, which, in extreme cases, can lead to additional warping of the work piece. 
         [0010]    For this reason, softer coatings with a hardness value of 30° Shore to 40° Shore are used for deburring work pieces manufactured by plasma cutting or gas cutting, because contact rollers with such a soft coating can compensate for tolerances of up to 5/10 mm. Since the known vulcanization processes do not allow for softer hardness values, the coatings are provided with spiral-shaped or rhombic grooves, in order to provide a softer coating for the contact roller. 
         [0011]    However, when using a softer coating and consequently a lower counter-pressure, it might happen that high or pointed burrs pierce through the abrasive belt because of the lack in counter-pressure and thus damage it. The same applies to when the burr encounters a groove in the rubber coating. 
         [0012]    In order to solve this problem, DE 3238624 A1 proposes a grinding roll for a sheet-deburring machine, which features a highly elastic coating and which has a clamping device, in which a foil and an abrasive belt can be clamped. In this respect, the foil is disposed between the highly elastic coating and the abrasive belt. Depending on the requirements of the grinding operation, a foil with a suitable hardness value can be chosen, the foil being always designed so that it is harder than the coating. In conjunction with the highly elastic coating, such a comparatively hard foil provides a high resilience and a high counter-pressure at the burr. 
         [0013]    When changing the work piece, the foil must be changed together with the abrasive belt, in order to achieve the hardness value required for the respective work piece. This is very laborious. If the new work piece requires another degree of resilience, it is even necessary to use another contact roller with another coating, which is also very laborious. In addition, changing the abrasive belt is also very laborious. 
         [0014]    A contact disc for a belt grinder, which has a resilient work cushion, provided on its contact roller, is known from DE 10 42 416 A. This work cushion is enclosed in an abrasion-proof, closed, flexible but non-stretchable material. This mantle made of a cork, polyamide fiber or metallic fabric or the like can be in one piece or consist of several different layers. 
         [0015]    Such a contact disc is suitable for a certain field of application. If other work pieces having other deburring requirements are to be deburred in the deburring machine, it is necessary to provide another hardness. 
         [0016]    In order to achieve the hardness required by a respective work piece, it is also necessary to change the mantle, when changing the work piece, which is very laborious. If the new work piece requires another degree if resilience, it is even necessary to use another contact roller with another coating, which is also very laborious. 
         [0017]    Based on this, the problem underlying the invention is to create a deburring machine of the afore-mentioned type with a great resilience range, providing a counter-pressure on the burr sufficient for deburring and that is much simpler to operate. 
       BRIEF SUMMARY OF THE INVENTION 
       [0018]    As a technical solution to this problem, the invention proposes a deburring machine for deburring metal work pieces with the features of claim  1 . Advantageous embodiments of this deburring machine can be gathered from the dependent claims. 
         [0019]    A deburring machine designed according to this technical teaching has the advantage that a comparatively high counter-pressure is built up on the burr by the circulating pressure belt provided in addition to the circulating abrasive belt, in particular when the pressure belt has a higher hardness than the resilient coating, in order to effectively abrade the burr. This allows using a softer coating, so that the resilience is increased, for example in order to smooth out irregularities in the work piece more effectively. 
         [0020]    Another advantage is that with the comparatively hard pressure belt and the associated counter-pressure on the burr, damage to the abrasive belt by pointed or particularly protruding burrs is prevented. 
         [0021]    One particular advantage is that exchanging the pressure belt only requires loosening the tensioning roller of the abrasive belt, and if necessary the tensioning device of the pressure belt, before removing the pressure belt and replacing it with another one. Thus it is not necessary to remove the heavy contact roller as required in DE 32 38 624 A1. Thus the pressure belt can be exchanged in a simple manner and replaced by a pressure belt with a different hardness. 
         [0022]    In a preferred embodiment, the pressure belt is tensioned by means of a proprietary tensioning devices. This has the advantage that the pressure belt can be tensioned independently from the abrasive belt with the consequence that both the pressure belt and the abrasive belt can be tensioned in the best possible manner in order to prevent them from slipping on the contact roller. 
         [0023]    In another preferred embodiment, the pressure belt is tensioned in such a manner that the pressure belt exerts a contact pressure onto the coating located on the contact roller during the abrasion process. This has the advantage that the hardness of the coating can thus be adjusted in a simple manner, without requiring a laborious exchange of the contact roller and/or of the pressure belt. Thus different work pieces can be machined, without having to exchange the pressure belt. 
         [0024]    This effect is amplified by the fact that the abrasive belt can be correspondingly tensioned more strongly, so that the pressure on the coating is further increased. 
         [0025]    In an advantageous embodiment, the pressure belt is designed so that it is has at least exactly the same width as the abrasive belt. This has the advantage that the required counter-pressure is provided over the entire width of the abrasive belt. 
         [0026]    Using a pressure belt also means that a softer coating can be used, which as a high resilience, while the counter-pressure built up by the pressure belt together with the abrasive belt allows for a sufficient abrasion of the splinter or burr without damaging the abrasive belt. Consequently, it is even possible to use a coating of a foam material, in particular a technical cellular foam material, preferably made of ethylene propylene diene monomer rubber (EPDM), natural rubber, foamed rubber or sponge rubber with a hardness of 5° Shore to 25° Shore, without the abrasive belt taking damage, so that a resilience of up to 15 mm, in extreme cases even 20 mm, can be achieved during grinding. 
         [0027]    In another particularly preferred embodiment, the contact roller has a diameter of 250 mm to 600 mm, preferably of 400 mm. Currently commonly used contact rollers have a diameter of 180 mm. Such an enlarged contact roller has the advantage that the abrasive surface acting onto the burr is increased, with the consequence that the burr is machined for a correspondingly longer period of time and that the burr is removed and the edge is even rounded off in a reliable manner. 
         [0028]    In yet another preferred embodiment the pressure belt has a structured surface on its side oriented toward the coating of the contact roller. The advantage thereof, particularly when this structured surface has a structure depth of 0.1 mm to 2 mm, is that protruding parts of the structured surface press into the comparatively soft coating and that a form fit is formed between the pressure belt and the contact roll, resulting in a good force transmission from the contact roller to the pressure belt, which minimizes slippage. 
         [0029]    In a particularly preferred embodiment, a resilient coating with a medium hardness of 60° Shore to 70° Shore, preferably 65° Shore, is provided on the contact roller, while the pressure belt  5 ″ is composed of three layers, with an inner layer (oriented toward the contact roller) made of a fabric belt absorbing the tensile forces, with a middle layer made of a resilient coating having a hardness of 5° Shore to 25° Shore and with an outer layer (oriented toward the abrasive belt) made of a harder layer with a hardness of 80° Shore to 100° Shore, preferably of 90° Shore. This has the advantage that the deburring of the work piece can be very good due to the soft coating of the pressure belt. 
         [0030]    Another advantage is that after removal of the pressure belt, a contact roller with a medium hardness of circa 65° Shore is provided, with which a micrograph can be obtained that would not be possible to achieve with a soft system. Thus different work steps can be completed in one and the same deburring machine, which considerably increases the range of application of the deburring machine. 
         [0031]    Other advantages of the deburring machine according to the invention can be gathered from the attached drawing and the embodiments described in the following. In addition, according to the invention, the features mentioned above and described in the following can be used respectively individually or in any combination of each other. The mentioned embodiments must not be understood as an exhaustive list but as examples. In the drawings: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  shows a schematic sketch of a first embodiment of a deburring machine according to the invention; 
           [0033]      FIG. 2  shows a cross-sectional representation of an enlarged detail of a pressure belt of the deburring machine of  FIG. 1 , according to line II in  FIG. 1 ; 
           [0034]      FIG. 3  shows a schematic sketch of a second embodiment of a deburring machine according to the invention; 
           [0035]      FIG. 4  shows a schematic sketch of a third embodiment of a deburring machine according to the invention; 
           [0036]      FIG. 5  shows a cross-sectional representation of an enlarged detail of a pressure belt of the deburring machine of  FIG. 4 , according to line V in  FIG. 4 ; 
           [0037]      FIG. 6  shows a schematic sketch of a fourth embodiment of a deburring machine according to the invention; 
           [0038]      FIG. 7  shows a cross-sectional representation of an enlarged detail of a pressure belt of the deburring machine of  FIG. 6 , according to line VII in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    A first preferred embodiment of a deburring machine according to the invention is represented in  FIGS. 1 and 2 . This deburring machine comprises a circulating conveyor belt  1  for transporting a work piece  2 , and a contact roller  3 , preferably electrically driven so that it rotates in a clockwise direction, on the surface of which a soft and thus resilient coating  4  made of an EPDM is applied, wherein this resilient coating  4  has a thickness of circa 20 mm. A continuously circulating pressure belt  5 , which is tensioned by way of a tensioning device  6 , is provided around the contact roller  3 . A continuously circulating abrasive belt  7 , which is tensioned by way of a tensioning roller  8  is provided around the contact roller  3  and the pressure belt  5 . 
         [0040]    The tensioning device  6  comprises a roller  9 , which is oriented coaxially with the contact roller  3  and tensioned by means of known spring mechanisms  10 . The tensioning roller  8  is constructed in a similar manner. The pressure belt  5  runs on the one hand around the contact roller  3  and on the other hand around the roller  9 , wherein the tensioning roller  6  moves the roller  9  in order to tension the pressure belt  5 . 
         [0041]    In the present embodiment, the EPDM coating  4  applied onto the contact roller  3  has a thickness of circa 20 mm and has a hardness of 15° Shore. It is also conceivable to provide the coating with a hardness of only 5° Shore or of up to 25° Shore. The thickness of the coating can vary between 5 mm and 50 mm. 
         [0042]    The pressure belt  5  is composed of two layers and features a comparatively hard layer  11  of PVC on its outer side oriented toward the abrasive belt  7 , whereas the inner side of the pressure belt  5  oriented toward the contact roller  3  is formed by a stretch-resistant fabric  12  with a structured surface. The hardness of the PVC layer  11  is higher by a factor of 5.33 than the hardness of the coating  4  and amounts to 80° Shore. In other embodiments, in particular when the coating has a hardness of 5° Shore, the PVC layer can also be harder by a factor of 16. 
         [0043]    It is possible to tension the pressure belt  5  across the tensioning device  9  so strongly that the coating  4  is compressed a little during the actual grinding operation, so that the coating  4  has a higher hardness during the grinding operation. Thus it is possible to set different hardness values with the same deburring machine, without having to change the contact roller or the coating. 
         [0044]    During the grinding process, the structured surface of the fabric belt  12  of the pressure belt  5  is at least partially pressed into the coating  4 , so that this form fit results in a good transmission of force from the electrically driven contact roller  3  to the pressure belt  5 . In the process, the abrasive belt  7  running around the pressure belt  5  is tensioned by means of the tensioning roller  8  in such a manner that slippage between the pressure belt  5  and the abrasive belt  7  is reduced to a minimum, so that the electrically driven contact roller  3  drives the abrasive belt  7  reliably and quasi without slippage. 
         [0045]    In order to machine the work piece  2 , the contact roller  3  is adjusted in such a manner that the lowest point of the abrasive belt  7  lies under the upper edge of the work piece  2 . When the work piece  2  arrives under the contact roller  3 , the abrasive belt  7 , with the assistance of the pressure belt  5  and the coating  4 , exerts a force onto the burr (not shown here) protruding from the work piece  2  and grinds it down. Since the contact roller  3  has a diameter of 400 mm, a comparatively long machining time is provided, so that the bur is removed in a reliable manner. If the work piece has asperities or is warped, the belt grinding machine is able to yield by a few millimeters, in particular up to 10 mm, because of the soft, 20 mm thick coating  4 , in order to follow the contour of the work piece. A sufficiently high counter-pressure is built up on the work piece  2  by way of the comparatively hard PVC layer  11  of the pressure belt  5 , so that the burr does not damage the abrasive belt  7 . 
         [0046]    If another work piece is to be machined, in particular a work piece with less asperities or less warping, it is possible to increase the operative hardness during the grinding process, by increasing the tension force onto the pressure belt  5  by way of the tensioning device  9 . The coating  4  is hereby compressed in the area of contact with the work piece, with the consequence that a greater hardness is thus achieved. The tensioning roller  8  must be correspondingly readjusted, so that as to prevent slippage between the pressure belt  5  and the abrasive belt  7 . With this belt grinding machine adjusted to a greater hardness, it is now possible to machine greater burrs or to do so more quickly. 
         [0047]    If a work piece with a lot a warpage and high burrs is to be machined, it is possible to increase the grinding pressure exerted onto the burr while maintaining the resilience for compensating for work piece tolerances, by using a thicker and harder pressure belt and exerting a lesser tensioning force on the pressure belt. 
         [0048]    In an embodiment not shown here, a resilient coating  4  with a higher hardness of 60° Shore to 70° Shore, preferably 65° Shore is used, which makes it possible to achieve a different micrograph than with the soft coating of 15° Shore. 
         [0049]    In a totally different embodiment not shown here, a pressure belt is provided between the contact roller and the tensioning roller on the one hand and the abrasive belt on the other hand, wherein both the pressure belt and the abrasive belt are tensioned by the same tensioning roller. Here too, the pressure belt leads to an increased counter-pressure on the burr and allows using a softer coating, which has the advantage of a higher resilience and of a simpler handling when changing the pressure belt and/or the abrasive belt. 
         [0050]      FIG. 3  shows a second embodiment of a deburring machine according to the invention, which differs from the first embodiment shown in  FIGS. 1 and 2  in that the pressure belt  5 ′ is guided both around the contact roller  3 ′ and around the tensioning roller  8 ′ and that the tensioning device  6 ′ acts onto the pressure belt  5 ′ from the outside. The advantages described above with respect to the afore-mentioned embodiments apply in a similar manner to the embodiment described in  FIG. 3 . 
         [0051]    Thus the grinding belt machine described here combines the advantage of a high resilience and a high counter-pressure with the advantage that the hardness at the contact roller can be adjusted in a simple and quick manner, at any rate without having to change the contact roller. 
         [0052]    In  FIGS. 4 and 5 , a third embodiment of a deburring machine according to the invention is shown, which differs from the first embodiment shown in  FIGS. 1 and 2  only in that in the third embodiment the resilient coating is placed on the pressure belt  5 ″ instead of the contact roller  3 . Here too, the resilient coating can be very soft with a Shore hardness of 5° to 25° Shore or with a medium hardness of 60° to 70° Shore. 
         [0053]    As can be seen in particular in  FIG. 5 , the pressure belt  5 ″ is composed of three layers, wherein an outer layer  11 ″ of the pressure belt  5 ″ oriented toward the abrasive belt  7  is very hard, with a Shore hardness of 80° Shore to 100° Shore, preferably of 90° Shore, while an inner layer  12 ″ of the pressure belt  5 ″ oriented toward the contact roller  3  is made of a stretch-resistant fabric belt with a structured surface, which is very flexible and while a middle layer  4 ″ is provided in between them, which has either a soft resilient coating with a Shore hardness of 5° Shore to 25° Shore or a medium hard resilient coating with a Shore hardness of 60° Shore to 70° Shore, preferably 65° Shore. 
         [0054]    In this embodiment the resilient coating of the middle layer  4 ″ can be made of EPDM, PVC, PU, rubber or cellular rubber. 
         [0055]      FIGS. 6 and 7  show a fourth preferred embodiment, which differs from the previous embodiments in that a resilient coating  4   a ′″ is provided on the contact roller  3 , whereas the pressure belt  5 ′″ is composed, similarly to the pressure belt  5 ″ of the third embodiment, of three layers with a soft middle layer  4   b ′″. In this respect, the resilient coating  4   a ′″ attached to the contact roller  3  has a medium hardness of 60° to 70° Shore, preferably of 65° Shore, whereas the approximately 20 mm thick middle layer  4   b ′″ of the pressure belt  5 ′″ is kept soft with a hardness of 5° to 25° Shore, preferably of 25° Shore. The inner layer  12 ′″ is made of a stretch-resistant fabric belt with a structured surface and the outer layer  11 ′″ is made of a PVC with a Shore hardness of approximately 90° Shore. 
         [0056]    In this embodiment, almost any degree of hardness can be provided in a quick and cost-effective manner since removing the pressure belt and installing a pressure belt with another hardness is comparatively simple, so that the deburring machine can be used for deburring many different work pieces.