Conveyor belt for a sheet metal processing machine

Abstract

Conveyor belt (14) for a sheet metal working machine (10) with continuous operation, with: a plurality of perforations (26) for transmitting a negative pressure from openings (44) in a negative pressure support box (22) carrying the conveyor belt to workpieces (12) resting on the perforations of the conveyor belt in order to hold the workpieces by suction, wherein in a first area (32) on the conveyor belt and in a second area (34) of the same size on the conveyor belt i) a plurality of perforations are arranged in each case and an average distance between perforations in the first region is smaller than an average distance between perforations in the second region; and / or ii) at least one perforation is arranged in each case and a total cross-sectional area of ​​the at least one perforation in the first region is larger than a total cross-sectional area of ​​the at least one perforation in the second region, so that a higher suction force per area is achieved in the first area than in the second area.

Description

[0001] The present invention relates to a conveyor belt for a sheet metal working machine with continuous operation and to a sheet metal working machine.

[0002] When cutting and punching parts made of sheet steel, annoying burrs form on the cut edges and the edges of holes and recesses, protruding from the top or bottom of the sheet steel. Especially for parts made of sheet steel several centimeters thick, deburring—i.e., rounding the edges and grinding the surface—requires considerable technical effort.

[0003] EP 4 015 147 A1 discloses a machine for processing sheet metal parts. The machine comprises a machine frame, a conveyor belt for transporting the sheet metal part to be processed in a horizontal direction, and a plurality of processing units arranged one behind the other along the conveyor belt. The processing units comprise a brush unit with grinding brushes, a first grinding belt unit, and a second grinding belt unit. The grinding belt units are mounted in auxiliary frames that can be moved vertically relative to the machine frame. Adjustment devices are arranged between the machine frame and the auxiliary frame. The brush unit is also mounted so that it can be moved vertically, so that the various processing units can be adjusted separately from one another to enable graduated processing of workpieces in a single pass.

[0004] Such sheet metal processing machines are typically designed for continuous operation. Workpieces are fed into the machine on one side, processed in a continuous flow at one or more stations, and discharged on the other side. A conveyor belt is typically used to transport the workpieces through the sheet metal processing machine, onto which the workpieces are placed. For double-sided processing from above and below, several separate conveyor belts can also be used.

[0005] A conveyor belt with perforations is often used which is designed to hold the workpieces on it by suction. The conveyor belt runs over a support box in which a negative pressure is built up. This negative pressure is passed on to the workpieces resting on the conveyor belt via openings on a side of the support box facing the conveyor belt and perforations in the conveyor belt. The workpieces are then held in position on the conveyor belt by suction. This holding is particularly necessary when processing smaller and lighter workpieces. If the workpieces slip on the conveyor belt, processing can be disrupted or impaired. It can also cause damage to the machine. The number and size of the perforations in the conveyor belt result in varying power densities in the suction power.A higher power density leads to a stronger fastening force, but also requires a higher power of a vacuum pump to generate the negative pressure and may reduce the stability of the conveyor belt itself.

[0006] Against this backdrop, conveyor belts in state-of-the-art sheet metal processing machines are often optimized for a specific application. Based on the application, a balance is struck between the design of the conveyor belt and the machine, as well as the exertable clamping force, and the conveyor belt is designed accordingly with regard to the density and number of perforations. However, this approach can lead to oversizing the suction power and thus significantly and ultimately unnecessarily increasing the operating and manufacturing costs of the sheet metal processing machine. Furthermore, it can result in limited flexibility with regard to the parts that can be processed.

[0007] Against this background, the present invention addresses the problem of enabling efficient machining of workpieces in a sheet metal processing machine. In particular, the flexible machining of workpieces of different sizes and shapes should be enabled. Adequate clamping should be ensured. Furthermore, the operating and manufacturing costs of the sheet metal processing machine should be low.

[0008] To achieve this object, the present invention relates in a first aspect to a conveyor belt for a sheet metal working machine with continuous operation, comprising: - a plurality of perforations for transmitting a vacuum from openings in a vacuum support box carrying the conveyor belt to workpieces resting on the perforations of the conveyor belt in order to hold the workpieces by suction, wherein - in a first area on the conveyor belt and in a second area of ​​the same size on the conveyor belt i) a plurality of perforations are arranged in each case and an average distance between perforations in the first region is smaller than an average distance between perforations in the second region; and / or ii) at least one perforation is arranged in each case and a total cross-sectional area of ​​the at least one perforation in the first region is larger than a total cross-sectional area of ​​the at least one perforation in the second region, - so that a higher suction force per area is achieved in the first area than in the second area.

[0009] In a second aspect, the present invention relates to a sheet metal working machine with continuous operation, comprising: - a conveyor belt as previously described; - a vacuum support box with a vacuum area within the vacuum support box, recesses on a support surface of the vacuum support box facing the conveyor belt for transmitting a vacuum from the vacuum area via perforations in the conveyor belt to workpieces resting on the perforations of the conveyor belt; - a vacuum unit for providing a negative pressure, which is connected to the negative pressure area, in particular a vacuum pump; and - at least one sheet metal processing station for processing workpieces on the conveyor belt in a processing area, wherein the at least one sheet metal processing station preferably comprises a grinding belt unit and / or a brush unit, wherein - the openings of the vacuum support box are arranged in at least one area of ​​the at least one sheet metal processing station, so that the workpieces are held in this at least one area by suction during processing.

[0010] Preferred embodiments of the invention are described in the dependent claims. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or individually, without departing from the scope of the present invention. In particular, the sheet metal processing machine can be designed according to the embodiments described for the conveyor belt in the dependent claims.

[0011] The conveyor belt according to the invention comprises several perforations. Through these perforations, a vacuum is transferred from a vacuum support box in a sheet metal processing machine to workpieces resting on the conveyor belt. These workpieces are suctioned in order to secure or temporarily secure them at processing stations in the sheet metal processing machine during processing. Suctioning the workpieces (especially sheet metal parts) prevents them from slipping during processing, which could lead to errors such as excessive material abrasion, uneven processing, or even damage to the machine.

[0012] The vacuum from the vacuum support box is transmitted via openings on the side of the vacuum support box facing the conveyor belt. These openings are advantageously not evenly distributed across the entire top of the vacuum support box, but are located only in the processing areas of the sheet metal working machine. This ensures that the workpieces are only secured in these processing areas. No vacuum is built up outside of the processing areas. This reduces the required vacuum.

[0013] In the conveyor belt according to the invention, the perforations are arranged unevenly. In particular, a plurality of perforations are arranged in a first region on the conveyor belt and in a second region of the same size on the conveyor belt. An average distance between perforations in the first region is smaller than an average distance between perforations in the second region. A distance is understood in particular to be a distance between the center of gravity of the cross-sectional areas of the perforations. Additionally or alternatively, it can be provided according to the invention that at least one perforation is arranged in each of the two regions and that a total cross-sectional area of ​​the at least one perforation in the first region is larger than a total cross-sectional area of ​​the at least one perforation in the second region.On the one hand, a different number of perforations can be provided in the two areas, thus transmitting a different intake pressure. On the other hand, the effective cross-section of all perforations within the two areas can be different, regardless of whether the number of perforations differs or not.

[0014] With the second alternative, the shapes or diameters (in the case of round perforations) of the perforations can be different in the two areas. Both options result in the suction force per area differing in the two areas. This in turn requires that there are areas on the conveyor belt where different suction forces per area are realized. This allows both smaller and larger workpieces to be fastened sufficiently securely. A machine operator who places workpieces on the conveyor belt, or even an automated system, can be given the opportunity to secure workpieces of different sizes sufficiently securely through targeted placement. It also makes it possible to reduce the total number of perforations, which in turn means that even a lower vacuum is sufficient to secure and hold workpieces on the conveyor belt with sufficient suction force.

[0015] Compared to previous approaches, in which the perforations are arranged in a regular pattern on the conveyor belt, the inventive approach enables a reduction in the required vacuum. This results in cost savings. Furthermore, the inventive approach allows different workpiece sizes to be processed with the same conveyor belt. Even smaller workpieces can be positioned so that they cover multiple perforations and are thus suctioned with sufficient or greater suction force. Flexibility in workpiece processing is increased. Costs can be saved.

[0016] In one embodiment, groups of perforations are arranged in lines running parallel to a longitudinal direction of the conveyor belt, in particular a total of between 20 and 50 groups of perforations. Preferably, all perforations have an identical and / or circular cross-section. The fact that the perforations are arranged in lines makes it possible for the outlets in the vacuum support box to also be arranged in lines or to be at least partially linear. This in turn enables an efficient design of both the conveyor belt and the vacuum support box. The regularity also enables automatic or manual feeding of the sheet metal processing machine. Placing workpieces on the conveyor belt is simplified. Furthermore, there are advantages in the production of both the conveyor belt and the vacuum support box.An identical and / or circular cross-section of all perforations can also enable more efficient production of the conveyor belt.

[0017] In one embodiment, at least two different distances are provided between adjacent perforations, so that areas with different levels of suction force per area are formed within the group. Preferably, either a smaller first distance or a larger second distance is provided between adjacent perforations. Because at least two different distances are provided within each group, or at least within a group, a regular sequence of areas with high and lower suction force can be achieved within the group. This enables workpieces to be supported in a regular manner. Support is simplified in both automated and manual systems. This results in advantages in handling. In particular, it is possible to provide two different distances, i.e. a smaller first distance and a larger second distance.This results in a further simplified support option.

[0018] In a preferred embodiment, perforations with a smaller first spacing are repeatedly arranged in a group in the longitudinal direction of the conveyor belt, followed by perforations with a larger second spacing. Along the conveyor belt, there are repeatedly areas within the group with a smaller average spacing between perforations and areas with a larger average spacing between perforations. Preferably, at least two smaller first spacings are followed by at least two larger second spacings. In particular, exactly two smaller first spacings can be followed by exactly three larger second spacings. Within each group, there are alternating areas with higher and lower suction force per area. This means, for example, that smaller workpieces can be placed on the conveyor belt at regular intervals and can be held sufficiently in place to enable processing.With a comparatively small overall dimensioning of the negative pressure, i.e. the vacuum pump required for this, for example, even small workpieces can be processed.

[0019] In a preferred embodiment, areas with a smaller average distance between perforations and areas with a larger average distance between perforations alternate several times along the length of the conveyor belt, in particular at least four times. This enables a regular alternation of areas with higher suction force per area and areas with lower suction force per area. This further simplifies the placement of workpieces on the conveyor belt.

[0020] In one embodiment, areas with a smaller average distance between perforations of several groups are offset from one another in the longitudinal direction of the conveyor belt. Preferably, the offset can increase proportionally to the distance between the groups, so that an increasing offset results at least in sections across the width of the conveyor belt. This makes it possible for workpieces that are machined consecutively to be placed on the conveyor belt at different transverse positions, and for areas with a higher suction force to be used to hold the workpieces. An efficient support option is achieved. By providing an increasing offset, the conveyor belt moves further and transports a first workpiece into the sheet metal processing machine.The second workpiece can then be placed next to and behind the first workpiece and yet also rest on the conveyor belt at a point where a high suction force is exerted to hold the workpiece.

[0021] In one embodiment, several groups arranged side by side in the transverse direction of the conveyor belt have an identical sequence of spacing between the perforations of the respective group. In other words, the perforations in the different groups are arranged in the same regular manner. This regular arrangement simplifies the placement of the workpieces for an operator or an automated system (robot). Throughput can be optimized.

[0022] In one embodiment, at least two different distances are provided between adjacent perforations of a first group, which belongs to a first part of all groups. In addition, identical distances are provided between adjacent perforations of a second group, which belongs to a second part of all groups. Finally, the second part of all groups is preferably arranged on both sides in edge regions of the conveyor belt and in particular comprises three groups per edge region. In other words, there are two different sequences in the lines of perforations on the conveyor belt. In particular, for example, in a central region of the conveyor belt, different distances between perforations can be provided and the perforations can be arranged irregularly so that regions with different suction forces per area are created there.In contrast, regularly arranged perforations, each of which has regular spacing within the group, can be provided in an edge area of ​​the conveyor belt in order to enable workpieces to be placed or held securely at all points in the edge areas and thus to avoid damage to the workpieces as well as to the machine.

[0023] In one embodiment, the conveyor belt is designed as a circulating endless conveyor belt.

[0024] In one embodiment, the conveyor belt has a two-layer construction, with a first layer for low-friction sliding over the vacuum support box and a second layer for high-friction holding of the workpieces resting thereon. A two-layer construction enables the use of two different materials. The upper layer of the conveyor belt, which faces the workpieces, can have higher friction to hold the workpieces securely. The lower layer of the conveyor belt, or the layer facing the vacuum support box, in contrast, should glide as smoothly as possible over the vacuum support box to minimize power loss and enable efficient operation of the sheet metal processing machine. Suitable materials can be combined to make this possible. This results in further improved operation of the conveyor belt.

[0025] In one embodiment, the first layer is wider than the second layer in the transverse direction of the conveyor belt. In addition, the first layer is designed to engage in a guide of the vacuum support box, in particular a guide rail, in both edge areas. The guide is designed to guide the conveyor belt in processing areas of the sheet metal processing machine. In particular, the first layer, which slides over the vacuum support box, can be wider than the second layer. This embodiment allows the use of a guide rail or guide whose height above the vacuum support box does not exceed, or only slightly exceeds, the height of the two layers of the conveyor belt. This means that material abrasion on the guide by processing machines of the sheet metal processing machine, in particular by grinding brushes, is reduced. In a sense, the guide is protected, thus saving the costs of frequent replacement.In addition, damage to the conveyor belt's edges and / or damage to / high stress on the tools can be avoided. The tools in sheet metal processing machines often reach the edges of the conveyor belt. For example, using grinding brushes or sanding belts can lead to material abrasion or damage to a conveyor belt guide or the conveyor belt itself.

[0026] In one embodiment, the guide comprises a sheet metal bent around a bending axis running in the longitudinal direction of the conveyor belt, which has a blunt edge in the longitudinal direction of the conveyor belt on its side facing away from the conveyor belt. A bent sheet metal can be manufactured relatively inexpensively. Because a bent sheet metal has a blunt edge in the longitudinal direction of the conveyor belt, the load on the guide or the material abrasion caused by a tool in the sheet metal processing machine is reduced. Sharp edges in particular can even lead to damage to tools. The approach of using a bent sheet metal enables a cost-effective and more material-friendly approach to the guide.

[0027] In a preferred embodiment of the sheet metal processing machine, the openings of the vacuum support box are designed as elongated holes. Additionally or alternatively, the openings of the vacuum support box are at least partially connected to one another by longitudinal grooves in the support surface of the vacuum support box. Sucked-in air can be exchanged between adjacent perforations through the longitudinal grooves. While maintaining the stability of the vacuum support box without further openings, the suction force is further increased in the relevant areas. By connecting the openings via longitudinal grooves, a permanent suction can be enabled in the relevant areas. The perforation is located over a longer area above a opening or over a longitudinal groove that connects two openings, so that a suction force is exerted over a longer area. The activation time of the perforation can be extended.This further improves the holding of the workpieces, especially in relevant areas.

[0028] In this context, a conveyor belt is understood to be an endless belt that, in the sense of a circulating conveyor system, serves as a support surface for the workpieces or sheets to be processed. It moves the workpieces at a defined speed through the various processing stations of the sheet metal processing machine. A sheet metal processing machine can, in particular, be a deburring machine. The workpieces are usually processed in a continuous operation, so that a continuous production process is achieved. A perforation is an opening or hole in the conveyor belt. Air can be drawn in through the perforation to suck in and hold workpieces on the perforation. The perforation is only active as long as a vacuum is introduced or applied from below. This is usually only the case in processing areas in which the vacuum support box has corresponding openings.The suction force is, in particular, the physical force created by the negative pressure. This force acts perpendicular to the surface of the workpiece on the conveyor belt. The suction force per unit area can also be referred to as suction pressure and indicates, in particular, the density of the force acting on a specific surface section of the workpiece. It can be measured, for example, in Pascal (Pa) or Newton per square meter (N / m). 2). An area on the conveyor belt refers to a defined zone or section of the belt surface. Suction is the process in which air flows through the perforations by creating a negative pressure below the perforated conveyor belt, thereby pressing the sheets lying on it against the belt. The longitudinal direction of the conveyor belt corresponds to the main direction of movement in which the workpieces are transported through the machine. The transverse direction of the conveyor belt runs perpendicular (90 degrees) to this longitudinal direction, i.e. across the width of the belt. The distance between perforations describes in particular the distance from the center of one perforation to the center of the adjacent perforation on the conveyor belt. The total cross-sectional area of ​​several perforations corresponds to the sum of all (effective) cross-sections of the perforations through which air is sucked in.

[0029] The invention is described and explained in more detail below using selected embodiments in conjunction with the accompanying drawings. They show: Fig. 1 is a schematic representation of a sheet metal working machine with continuous operation according to the present invention; Fig. 2 a schematic representation of a conveyor belt of the prior art; Fig. 3 is a schematic representation of an embodiment of a conveyor belt according to the present invention; Fig. 4 is a schematic representation of another embodiment of a conveyor belt according to the present invention; Fig. 5 a schematic representation of the structure of a vacuum support box in an embodiment of the sheet metal processing machine according to the invention; and Fig. 6 a schematic representation of a guide and a two-layer conveyor belt in a sheet metal processing machine according to the invention.

[0030] In Fig. Figure 1 schematically shows a sheet metal processing machine 10 according to the invention. The machine shown as an example enables the processing of sheet metal parts made of steel or stainless steel. For example, the sheet metal processing machine 10 can be a deburring machine. The illustration is a schematic side sectional view.

[0031] Workpieces 12 are conveyed by means of a conveyor belt 14 along a throughput direction (in the illustration from left to right, x-direction) from a feed area 16 to an output area 18. For example, one machine operator can deposit the workpieces 12 in the feed area 16 and another machine operator can pick them up again in the output area 18. It is understood that automated handling of the workpieces 12 is also possible. The workpieces 12 pass through the sheet metal processing machine 10 in a throughput plane, which in the illustrated embodiment runs parallel to the floor or parallel to a setup surface of the machine (in the illustrated example, this plane runs perpendicular to the z-direction).

[0032] As they pass through, the workpieces 12 pass through several sheet metal processing stations 20a, 20b, 20c, each with corresponding processing areas. In the illustrated embodiment, these sheet metal processing stations comprise a first grinding station 20a with a wide belt grinding unit, a brushing station 20b with several rotating grinding brushes, and a second grinding station 20c with a second wide belt grinding unit. First, deburring takes place at the first grinding station 20a. Subsequently, the edges are rounded at the brushing station 20b to achieve clean surfaces. Finally, fine grinding takes place at the second grinding station 20c. In the illustrated embodiment, processing takes place exclusively from above.

[0033] For better orientation, Fig. 1 and in the following figures, directions are indicated. The x-direction corresponds to a direction of passage through the sheet metal processing machine or a longitudinal direction of the conveyor belt 14. The y-direction corresponds to a transverse direction of the sheet metal processing machine 10 or a transverse direction of the conveyor belt 14. The z-direction corresponds to a vertical direction.

[0034] The conveyor belt 14 serves to convey the workpieces 12 through the sheet metal processing machine 10 past the processing stations 20a, 20b, 20c and, in the illustrated embodiment, is designed as a circulating endless belt. To hold the workpieces 14 during processing, they are sucked in by negative pressure and thus fixed or suctioned onto the conveyor belt 14. This prevents damage to the tools, the machine, and the workpieces. For this purpose, the conveyor belt 14 has perforations through which a negative pressure can be transferred from a negative pressure support box 22 to the workpiece 12 resting on the perforations. The negative pressure in the negative pressure support box 22 is generated by means of a negative pressure unit 24, which can be designed, in particular, as a vacuum pump.A vacuum is generated within the vacuum support box, which acts on the workpieces lying on the belt via openings in the vacuum support box 22 and perforations in the belt, holding them by suction. The openings in the vacuum support box 22 are preferably not arranged across its entire upper surface, but rather are located only in the processing areas assigned to the sheet metal processing stations 20a, 20b, 20c, in which processing takes place and the workpieces must be held.

[0035] In Fig. 2 shows a conveyor belt 14 of the prior art. The illustration is to be understood as a plan view perpendicular to the z-axis. The perforations 26 on the conveyor belt 14 are arranged in a regular pattern and are designed, for example, as holes with a round cross-section. The illustration in Fig. Figure 2 shows a top view of the conveyor belt 14 and, for better visualization, an enlarged (circular) section of the lower section. The suction pressure per unit area is constant across the belt (at least in the relevant central area, which corresponds, so to speak, to the used area of ​​the conveyor belt).

[0036] The disadvantage of such a regular arrangement of perforations is that the available suction power is often not used optimally. When larger workpieces are processed, they rest on a large number of perforations 26. The strong hold thus achieved may not be necessary in certain circumstances. When smaller workpieces are processed, however, the distance between the perforations 26 is often too large for the workpiece to rest on a sufficient number of perforations 26. The workpiece may not be held sufficiently. In any case, a larger number of perforations 26 requires more power from the vacuum unit, which can lead to excessive energy consumption or loud noise during operation. Likewise, excessive suction can lead to faster contamination, as dust or ground-off material can get into the perforations 26.

[0037] In Fig. 3 schematically shows a conveyor belt 14 according to the invention. Also in Fig. For better visualization, an enlarged section is shown in the lower section of Figure 3. The perforations 26 are arranged irregularly, so that there are regions with higher suction force per area and regions with lower suction force per area on the conveyor belt 14. According to the invention, a plurality of perforations 26 are arranged in a first region 32 and in a second region 34 of the same size on the conveyor belt, and an average distance between the perforations 26 in the first region 32 is smaller than an average distance between the perforations 26 in the second region 34.

[0038] Additionally or alternatively (not in the example shown), at least one perforation 26 can be arranged in each of two regions, wherein a total cross-sectional area of ​​the at least one perforation in the first region is larger than a total cross-sectional area of ​​the at least one perforation in the second region.

[0039] In the example shown in Fig. 3, all perforations 26 are the same size and formed as round holes. The perforations 26 are arranged in lines along the longitudinal direction of the conveyor belt 14, wherein the lines form groups 28, 30 of perforations. In a first group 28, which belongs to a first part of the groups (in the illustrated embodiment in the upper section of the conveyor belt 14 in the illustration), there is within this first group 28 a first region 32 with higher suction force per area and a second region 34 with lower suction force per area. In a second group 30, which belongs to a second part of the groups, there are constant distances between the perforations 26 of the group in the illustrated embodiment. The second part of the groups in this example comprises the lower half of the groups / lines or the lower section in the illustration.

[0040] In the illustrated embodiment, the first group 28 contains three consecutive perforations 26 arranged at a short distance from one another. A larger distance follows after such a group of three. The regions 32, 34 with different suction forces per area are formed, so to speak, within the first group 28. The regions 32, 34 alternate. In the illustrated example, there are exactly two different distances between adjacent perforations 26 within the same group in the longitudinal direction of the conveyor belt.

[0041] Additionally, in the illustrated embodiment, in the upper area of ​​the conveyor belt 14 (in the first part of the groups), areas with higher suction force per area (groups of three perforations) of adjacent groups are offset from one another in the longitudinal direction of the conveyor belt 14 (x-direction). In plan view, patterns run diagonally across the conveyor belt 14. In the illustrated example, there is an increasing offset in the upper section of the conveyor belt 14. This arrangement can enable the efficient placement of smaller workpieces on a continuously moving conveyor belt 14.

[0042] In Fig. 4 shows a further embodiment of a conveyor belt 14 according to the invention. Fig. For better visualization, an enlarged section is shown in the lower section of Figure 4. In the middle section of the conveyor belt 14 (in the transverse or y-direction), within a first group 28, three longer distances between adjacent perforations follow two shorter distances. In the first area 32, the average distance between perforations is smaller than in the second area 34, whereby a higher suction force per unit area is achieved in the first area 32.

[0043] In Fig. 4, three second groups 30 with perforations 26 are arranged at a constant distance from each other on both sides in edge sections (edge ​​areas) of the conveyor belt 14. As in the embodiment in Fig. 3 is in Fig. 4 the variation that groups with constantly rejected perforations are also provided, optional and usable independently of the inventive approach.

[0044] Also in Fig. 4 results in a regular pattern with an offset increasing across the width of the conveyor belt between the areas of different suction force in neighboring groups.

[0045] In Fig. Figure 5 shows a design of a vacuum support box 22. The upper illustration (a) shows a side view, the middle illustration (b) shows a corresponding top view of a support surface 38, and the lower illustration shows an enlarged section. Also shown are deflection rollers 40 for the conveyor belt on both sides of the vacuum support box 22, as well as a corresponding drive unit 42 for the conveyor belt.

[0046] The openings 44 of the vacuum support box are located in only three processing areas of the sheet metal processing machine, as can be seen in the middle illustration (b). Only in these processing areas is a vacuum transmitted to workpieces resting on the conveyor belt via the perforations in the conveyor belt. In other areas, the perforations are inactive, since no openings 44 transmit the vacuum from the vacuum support box 22 to the perforations.

[0047] In the illustrated embodiment, longitudinal grooves 45 are provided between adjacent recesses 44 in the longitudinal direction, each connecting two recesses 44. A perforation is active as long as it is located over a recess 44 or over a longitudinal groove 45. The suction force can thus be exerted continuously (in the processing areas), which further improves the securing of the workpieces on the conveyor belt. The longitudinal grooves 45 can, for example, have a wedge-shaped or triangular cross-section (perpendicular to the x-direction) and / or a width and depth of one or two millimeters.

[0048] In Fig. Figure 6 schematically shows an embodiment of a conveyor belt 14 with a two-layer structure. The illustration corresponds to a sectional view perpendicular to the longitudinal direction (x-direction) of the conveyor belt 14. A first layer 46 with lower friction slides over the vacuum support box 22. A second layer 48 with higher friction serves to support the workpieces. The layers are connected to one another, for example, by adhesive bonding.

[0049] In the illustrated embodiment in Fig.6 shows that the two layers 46, 48 can have different widths (in the y-direction). The first layer 46 engages beneath a guide 50 (on both sides in the example shown) and is guided by this guide 50. This results in improved securing of the conveyor belt 14 with respect to the negative pressure load 22, which can be particularly advantageous in the processing areas. During processing, comparatively high forces can act on the conveyor belt there and, under certain circumstances, pull it off track. The approach shown with a guide 50 prevents or impedes this. In the example, the guide 50 is designed as a guide rail in the form of a bent sheet metal. The bending axis runs along the longitudinal direction of the conveyor belt (parallel to the x-direction). The bending creates a blunt edge 52 in the outer area.This blunt edge 52 makes it possible to avoid damage to the tools, the guide 50 and the conveyor belt 14 during material processing when the tools come into contact with the guide 50.

[0050] The invention has been comprehensively described and explained with reference to the drawings and the description. The description and explanation are to be understood as exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other embodiments or variations will become apparent to those skilled in the art upon use of the present invention and upon careful analysis of the drawings, the disclosure, and the following claims.

[0051] In the claims, the words "comprising" and "having" do not exclude the presence of further elements or steps. The indefinite article "a" or "an" does not exclude the presence of a plurality. A single element or unit can perform the functions of several of the units recited in the claims. The mere reciting of some measures in several different dependent claims should not be understood to mean that a combination of these measures cannot also be used advantageously. Reference signs in the claims are not to be understood as limiting. Reference symbol 10 sheet metal working machine 12 Workpiece 14 Conveyor belt 16 Task area 18 Output area 20a, 20b, 20c processing stations 22 Vacuum support box 24 vacuum unit 26 Perforation 28 first group 30 second group 32 first area 34 second area 38 contact surface 40 pulleys 42 drive unit 44 Omission 45 Longitudinal groove 46 first layer 48 second layer 50 leadership 52 blunt edge QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 4 015 147 A1

[0003]

Claims

[1] Conveyor belt (14) for a sheet metal working machine (10) with continuous operation, comprising: a plurality of perforations (26) for transmitting a negative pressure from openings (44) in a negative pressure support box (22) carrying the conveyor belt to workpieces (12) resting on the perforations of the conveyor belt in order to hold the workpieces by suction, wherein in a first area (32) on the conveyor belt and in a second area (34) of the same size on the conveyor belt i) a plurality of perforations are arranged in each case and an average distance between perforations in the first region is smaller than an average distance between perforations in the second region; and / or ii) at least one perforation is arranged in each case and a total cross-sectional area of ​​the at least one perforation in the first region is larger than a total cross-sectional area of ​​the at least one perforation in the second region, so that a higher suction force per area is achieved in the first area than in the second area. [2] Conveyor belt (14) according to one of the preceding claims, wherein groups (28, 30) of perforations (26) are arranged in lines running parallel to a longitudinal direction of the conveyor belt, in particular a total of between 20 and 50 groups of perforations; and preferably all perforations have an identical and / or circular cross-section. [3] Conveyor belt (14) according to claim 2, wherein in a group (28) at least two different distances are provided between adjacent perforations (26), so that areas (32, 34) with different suction forces per area are formed within the group; and preferably either a smaller first distance or a larger second distance is provided between adjacent perforations. [4] Conveyor belt (14) according to claim 3, wherein in a group (28) in the longitudinal direction of the conveyor belt, perforations (26) are arranged repeatedly at a smaller first distance followed by perforations at a larger second distance, so that along the conveyor belt within the group there are repeatedly regions with a smaller average distance between perforations and regions with a larger average distance between perforations; and preferably at least two smaller first distances are followed by at least two larger second distances, in particular exactly two smaller first distances are followed by exactly three larger second distances. [5] Conveyor belt (14) according to one of claims 3 and 4, wherein in a group, regions with a smaller average distance between perforations (26) and regions with a larger average distance between perforations alternate several times over the length of the conveyor belt, in particular at least four times. [6] Conveyor belt (14) according to one of claims 3 to 5, wherein a region with a smaller average distance between perforations (26) of a first group is offset from a region with a larger average distance between perforations of an adjacent second group in the longitudinal direction of the conveyor belt, preferably by an offset in the order of magnitude of a distance of the adjacent groups (28, 30) from one another in the transverse direction of the conveyor belt. [7] Conveyor belt (14) according to claim 6, wherein regions with a smaller average distance between perforations (26) of a plurality of groups (28) are offset from one another in the longitudinal direction of the conveyor belt, preferably by an offset increasing proportionally to the distance between the groups, so that an increasing offset results at least in sections across a width of the conveyor belt. [8] Conveyor belt (14) according to one of claims 2 to 7, wherein a plurality of groups (28) lying next to one another in the transverse direction of the conveyor belt have an identical sequence of distances between the perforations (26) of the respective group. [9] Conveyor belt (14) according to one of claims 2 to 8, wherein at least two different distances are provided between adjacent perforations (26) of a first group (28) belonging to a first part of all groups (28, 30); identical distances are provided between adjacent perforations of a second group (30) belonging to a second part of all groups; and the second part of all groups is preferably arranged on both sides in edge regions of the conveyor belt and in particular comprises three groups per edge region. [10] Conveyor belt (14) according to one of the preceding claims, wherein the conveyor belt is designed as a circulating endless conveyor belt. [11] Conveyor belt (14) according to one of the preceding claims, wherein the conveyor belt is constructed in two layers with a first layer (46) for low-friction sliding over the vacuum support box (22) and a second layer (48) for high-friction holding of the workpieces (12) lying thereon. [12] Conveyor belt (14) according to claim 11, wherein the first layer (46) is wider than the second layer (48) in the transverse direction of the conveyor belt; and is designed to engage in both edge regions in a guide (50) of the vacuum support box (22), in particular a guide rail, wherein the guide is designed to guide the conveyor belt in processing regions of the sheet metal processing machine (10). [13] Conveyor belt (14) according to claim 12, wherein the guide (50) comprises a sheet metal bent about a bending axis running in the longitudinal direction of the conveyor belt, which sheet metal has a blunt edge (52) in the longitudinal direction of the conveyor belt on its side facing away from the conveyor belt. [14] Sheet metal working machine (10) with continuous operation, with a conveyor belt (14) according to one of the preceding claims; a vacuum support box (22) with a vacuum region within the vacuum support box, openings (44) on a support surface (38) of the vacuum support box facing the conveyor belt for transmitting a vacuum from the vacuum region via perforations (26) in the conveyor belt to workpieces resting on the perforations of the conveyor belt; a vacuum unit (24) for providing a negative pressure, which is connected to the negative pressure area, in particular a vacuum pump; and at least one sheet metal processing station (20a, 20b, 20c) for processing workpieces (12) on the conveyor belt in a processing area, wherein the at least one sheet metal processing station preferably comprises a grinding belt unit and / or a brush unit, wherein the outlets of the vacuum support box are arranged in at least one area of ​​the at least one sheet metal processing station, so that the workpieces are held in this at least one area by suction during processing. [15] Sheet metal working machine (10) according to claim 14, wherein the recesses (44) of the vacuum support box (22) are designed in the form of elongated holes and / or are at least partially connected to one another by longitudinal grooves (45) in the support surface (38) of the vacuum support box.

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