Positioning device and positioning assembly for holding flat flexible elements and sheet material processing machine - Patents.com

Abstract

A positioning device (38) for holding a flat flexible element, particularly a sheet material, on a positioning surface is disclosed. The positioning device (38) has a body (44) having a fluid inlet port (52) for supplying a drive fluid to the body (44). The positioning device (38) further has a fluid outlet port (58) for exhausting the drive fluid from the body (44) and a suction opening (59) for drawing suction through the flat flexible element. A circulation channel (60) connects the fluid inlet port (52) and the fluid outlet port (59), and a suction channel (70) connects the suction opening to the circulation channel (60). The suction channel (70) is connected to the circulation channel (60) adjacent the cross-sectional area reduction section (64) so ​​as to form a jet pump (71). The cross-sectional area (S) of the circulation channel (60) along its entire length is determined by the cross-sectional area (S) of the circulation channel (60). c ) and / or any cross section (S s ) has a smooth rim. Additionally, a positioning assembly is provided that includes at least one such positioning device (38). Further, a sheet material processing machine is provided that has at least one positioning assembly.

Description

[Technical field]

[0001] The present invention relates to a positioning device for holding a flat flexible element, in particular a sheet material, on a positioning surface. The positioning device has a body, which has a fluid inlet port for supplying a drive fluid to the body, a fluid outlet port for discharging the drive fluid from the body, and a suction opening for sucking the flat flexible element. The suction opening is provided in the positioning surface, which is the outer surface of the body. Furthermore, a circulation channel connects the fluid inlet port and the fluid outlet port to one another, the circulation channel having a section with a reduced cross-sectional area. A suction channel connects the suction opening to the circulation channel, the suction channel being connected to the circulation channel adjacent to the reduced cross-sectional area section so that a jet pump is formed. In this context, the term "holding" should also be understood to mean the deceleration and subsequent holding of the sheet material.

[0002] The invention also relates to a positioning assembly for holding a flat flexible element, in particular a sheet material, on a holding surface, comprising a base with a central air supply duct and at least one positioning device of the type described above, the positioning device being mounted on the base such that an air inlet port of the positioning device is fluidly connected to the central air supply duct and the positioning surface forms the holding surface.

[0003] Furthermore, the invention relates to a sheet material processing machine having at least one such positioning assembly. [Background technology]

[0004] Sheet material processing machines, positioning assemblies and positioning devices of the type described above are known in the art. In some cases, the positioning devices are also referred to as tablets.

[0005] Sheet material converting machines, such as paper or cardboard converting machines, often have a number of converting units or stations, in each of which a particular type of processing is performed on the sheet material, for example the sheet material is cut, stripped or blanked. Typically, a conveyor system is provided within such machines, the purpose of which is to transport the sheet material from one converting unit to the next.

[0006] In order to perform the corresponding processing in an accurate and reliable manner, each of the processing units may have a positioning assembly of the type described above. The positioning assembly may include at least one positioning device of the type described above. The positioning of the sheet material performed by the positioning assembly and the positioning device may be static or dynamic, i.e. the sheet material may be stationary or move while being held against the positioning device. In the first case, the positioning device may also be called a holding device. In the second case, the positioning device may be used to slow down the sheet material as a so-called suction brake.

[0007] When the positioning device is used as a suction brake, it is customary for this device to slow down the sheet material from its maximum feed speed on reaching the work station, thereby braking its rear part to maintain a certain flatness of the sheet material during the sheet material introduction stage by using a suction bed, which may also be called a suction brake or suction brake. When such a brake is installed transversely close to the entrance to the work station, it performs its function by using suction to restrain the rear part of the sheet material, while at the same time allowing the sheet material to gradually slip as its front part is being pulled forward. In particular, when the sheet material reaches the work station for processing, the gripper bar pulling the leading edge of the sheet material stops to allow the sheet material to be processed. Suction brakes are used to create a frictional force between the sheet material and a stationary surface, thereby providing a braking action on the trailing part of the sheet material, so that the inertia of the sheet material does not cause the sheet material to buckle, crumple or develop creases.

[0008] In operation, a suction brake first sucks out any air between the sheet material and the working surface of the braking device, and then applies a restraining force to the sheet material that acts as a braking force by drawing the sheet material against the working surface of the device. Ideally, the initial operation of sucking out the air between the sheet material and the working surface of the braking device is accomplished as quickly as possible to avoid deformation of the sheet material as a result of its inertia. This requires maximum suction force.

[0009] In the second operating phase, the sheet material is sucked against the working surface of the braking device, blocking the suction holes and the air flow through the suction holes drops to zero. The sheet material is still decelerating in this phase and the applied braking force must be high enough to effectively brake the sheet material, thereby avoiding the formation of ripples in the sheet material and keeping it flat. For optimal performance and especially to avoid deformation of the sheet material, it is necessary in this second phase to adjust the amount of suction based on the type of sheet material (e.g. the type of material of the sheet material and its weight) and the cut shape of the sheet material. This means that the pressure and / or the volume of the gas creating the suction must be adjusted based on the requirements of this second operating phase, even if this is contrary to the requirements of the first phase. Applying too much braking force in this operating phase can result in machine stalls, damage to the packaging blanks, etc.

[0010] In all cases, the sheet material to be processed is straddled between a positioning assembly including at least one positioning device and a gripper unit of the conveyor system. The sheet material is held on a positioning surface so that it is accurately positioned in the machine. The sheet material is held on the corresponding positioning device by suction force generated by a jet pump formed by the interconnected circulation channel and suction channel. With respect to the suction opening, the jet pump acts as an aspirator.

[0011] As is generally known, the suction force is determined by the acceleration of the fluid present in the suction channel. This fluid is accelerated by the driving fluid flowing through the circulation channel. To increase the suction force, the acceleration of the fluid in the suction channel needs to be high. This can be achieved by providing the driving fluid under high pressure. In summary, a high suction force requires a high level of power or energy in providing the driving fluid.

[0012] WO 2011 / 064226 A1 shows an apparatus for processing sheet-like printing substrates, the apparatus having a fluid flow generator for inducing a fluid flow into a sheet support surface and a Venturi-type low pressure source. The Venturi-type low pressure source has a first passageway extending from an inlet to an outlet and a second passageway connecting the first passageway to a suction endpoint. The junction of the first passageway and the second passageway is located adjacent to a diametric flow restriction in the first passageway.

[0013] Furthermore, US 2013 / 269817 A1 discloses a pump suction pipe for a pumping station having a suction pipe outlet section, a suction pipe inlet section, and a suction pipe bend section connecting the suction pipe outlet section and the suction pipe inlet section to each other and changing the flow from lateral to vertical, whereby the vertical cross section of the suction pipe bend section increases uniformly from upstream to downstream.

[0014] Furthermore, US 2018 / 274831 A1 discloses a refrigerant compressor with a suction line having a geometry with a cross-sectional area that decreases steadily in a direction toward the compressor, the geometry of the suction line being configured to reduce the amount of swirl, the amount of pressure loss, and provide a relatively uniform flow of refrigerant through the compressor.

[0015] WO 2017 / 137170 A1 shows a device for loading insert sheets, in which a longitudinal bar is fixed to a transverse member, so that the longitudinal bar forms a positioning surface. The longitudinal bar has a suction duct with at least one suction orifice provided in the positioning surface. The suction duct is configured to be coupled to a vacuum source. Another transverse duct is formed in the transverse member, which opens at a transverse end of the transverse member to which a vacuum source can be coupled.

[0016] Furthermore, WO 2014 / 067611 A1 shows another device for holding sheet-like flat elements comprising two series of suction members, each of which is made up of a number of suction members, both of which are arranged in a specific manner between and with respect to each other. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] International Publication No. 2011 / 064226(A1) Brochure [Patent Document 2] US Patent Application Publication No. 2013 / 269817(A1) [Patent Document 3] US Patent Application Publication No. 2018 / 274831(A1) [Patent Document 4] International Publication No. 2017 / 137170(A1) Brochure [Patent Document 5] International Publication No. 2014 / 067611(A1) Brochure Summary of the Invention [Problem to be solved by the invention]

[0018] It is an object of the present invention to improve known sheet material processing machines, positioning assemblies and positioning devices with respect to their energy efficiency, meaning that a given suction force level should be achieved with a relatively small amount of power or energy in providing the drive fluid. [Means for solving the problem]

[0019] This problem is solved by a positioning device of the above-mentioned type, characterized in that every cross section of the circulation channel along its entire length and / or every cross section of the suction channel along its entire length has a smooth rim. In this connection, the cross section is substantially perpendicular to the axis of the circulation channel or the axis of the suction channel, which axis is a local axis, since the circulation channel and / or the suction channel can have bends or curves. The rim is to be understood as the outer contour of the cross section. The rim is always a closed geometric shape. Since the rim is smooth, it does not comprise corners or kinks and may have substantially straight segments. Mathematically explained, this means that the first derivative of the rim is continuous. Furthermore, the rim may be convex or have concave and convex segments. Thus, in a first variant, the radius of curvature of the rim does not change its direction or sign. In a second variant, the radius of curvature changes its direction or sign at least twice. In particular, the rim is circular, elliptical or egg-shaped. As a result, the unwanted pressure losses along the path or paths of the circulation and / or suction channels are significantly reduced. As a result, less power or energy is required to maintain a given level of suction provided at the suction openings compared to known positioning devices. Alternatively, with a given level of power or energy, an increased level of suction can be provided. This is due to the smooth cross-section reducing the frictional forces of the fluid flow in these channels. As can be noted, within the section with reduced cross-sectional area, or more precisely downstream of the section with reduced cross-sectional area, a pressure drop is desirable and necessary for the functioning of the jet pump. In conclusion, the energy efficiency of the positioning device is increased.

[0020] The positioning surface may be a top surface in its operative state. The inlet port may be provided on a lower surface of the positioning device and the outlet port may be provided on a side surface thereof.

[0021] According to one embodiment, the profile of the cross section of the circulation channel along its length has only one discontinuity. This means that along the circulation channel, its cross section changes only once in an abrupt, stepwise manner. Moreover, the cross section may of course change continuously. Preferably, the single discontinuity is provided at the downstream end of the cross-sectional area reduction section. In particular, the circulation channel merges into the suction channel adjacent to this discontinuity. Thus, upstream and downstream of the single discontinuity, the circulation channel is designed such that a relatively low pressure loss occurs when the fluid flows through the circulation channel. This further increases the energy efficiency of the positioning device.

[0022] In one configuration, the cross-section of the suction channel varies continuously along the entire length of the suction channel, such that the suction channel does not include any discontinuities, and as a result, the suction channel is also designed to experience a relatively low pressure drop as fluid flows through it.

[0023] Specifically, the extension direction of the circulation channel changes continuously along the entire length of the circulation channel. Additionally or alternatively, the extension direction of the suction channel changes continuously along the length of the suction channel. This means that the circulation channel and / or the suction channel exhibit smooth changes without abrupt changes in direction. This design also results in relatively low pressure losses for the fluid flowing through the respective channels.

[0024] The circulation channel may have a bend, in particular a bend of approximately 180°. Such a circulation channel may be described as being hairpin shaped. As a result, the circulation channel may be positioned in a narrow space. A corresponding positioning device is compact.

[0025] The circulation channel may further include a substantially 90 degree bend, preferably located adjacent the inlet port, which facilitates positioning of the inlet port so that it can be readily coupled to a fluid supply.

[0026] According to one variant, the fluid inlet port and the fluid outlet port are provided at the same end of the body. They may be provided on the same surface of the body, but this is not necessarily the case. According to one embodiment, the inlet port may be provided on the lower surface of the body and the outlet port may be provided on the side of the body. Especially in combination with the hairpin-shaped circulation channel, a compact design of the positioning device is obtained.

[0027] Preferably, the radius of curvature of the walls laterally defining the circulation channel is in the range from 0.2 mm to 30 mm, in particular from 0.5 mm to 20 mm. Such a channel is particularly smooth, so that the friction forces of the fluid flowing through it are reduced, so that only relatively small pressure losses occur.

[0028] At least 60%, preferably at least 75%, more preferably at least 90% of the length of the circulation channel may have a cross-sectional area that is at least twice that of the remaining portion of the length of the circulation channel. Preferably, the remaining portion has a reduced cross-sectional area section. As mentioned above, the reduced cross-sectional area section is necessary to form a jet pump. Thus, in other words, the cross-sectional area is kept as large as possible for as long as possible. This reduces friction losses occurring in the circulation channel. In a preferred embodiment, approximately 87% of the length of the circulation channel has a cross-sectional area that is at least twice that of the remaining portion of the length. In this embodiment, this larger cross-sectional area is approximately 30 mm 2 It is.

[0029] A cleaning fluid inlet port may be provided in the body through which a cleaning fluid, e.g., pressurized air, may be provided to the body for cleaning at least some portions of the circulation channel and / or the suction channel. By keeping the circulation channel and / or the suction channel clean, the positioning device may operate reliably over long periods of time.

[0030] A washing fluid channel may fluidly connect the washing fluid inlet port to the circulation or suction channel, and the cross section of the washing fluid channel has a smooth rim along its entire length. As a result, the washing fluid channel is also designed such that relatively small losses occur when the washing fluid flows through it. Thus, high energy efficiency is achieved for the washing process.

[0031] According to one embodiment, the body is an additively manufactured part. In other words, the body is manufactured by additive manufacturing techniques, e.g. 3D printing techniques. Such manufacturing techniques mean that there are very few design constraints on the manufactured parts, e.g. the body. As a result, in particular the suction and circulation channels can be designed without having to take into account the constraints of conventional manufacturing techniques. Thus, in particular the suction and circulation channels having the above mentioned characteristics can be manufactured with relatively low effort.

[0032] It may be said that the body is in particular designed to be manufactured by additive manufacturing techniques. The body preferably has wall segments, in particular forming its outer surface. In the wall segments, channel segments forming suction channels and / or circulation channels may be formed. In addition, the body may have support segments. The wall segments, the channel segments and the support segments may all have substantially equal wall thicknesses. As a variant, it may be said that the thickness differences only vary within a range of ±20% relative to each other.

[0033] The section of the circulation channel with reduced cross-sectional area may have a nozzle with a substantially circular cross section. The nozzle is part of a jet pump, the nozzle being used to accelerate the fluid in the suction channel. In an idealized positioning device, the pressure drop occurs only in the nozzle. The rest of the circulation channel is loss-free.

[0034] Additionally, the problem is solved by a positioning assembly of the type described above, which includes at least one positioning device according to the invention, which can be operated in an energy-efficient manner, for the reasons already explained in connection with the positioning device.

[0035] Furthermore, the number and / or dimensions of the positioning devices may be selected such that, as a result of a combination of different numbers of positioning devices or positioning devices of different dimensions, a desired width of the positioning assembly is obtained. This width may be selected such that it corresponds to a common width of the sheet material processing machines. In other words, the positioning assembly is modular as far as the positioning devices are concerned. As a result, the positioning assembly is easily adaptable to different types of sheet material processing machines.

[0036] Moreover, all of the effects and advantages discussed in connection with the positioning device also apply to the positioning assembly, and vice versa.

[0037] Furthermore, the problem is solved by a sheet material processing machine of the above-mentioned type, which comprises at least one positioning assembly according to the invention. Since the positioning assembly can be operated in a very energy-efficient manner, the same applies to a sheet material processing machine equipped with it.

[0038] Moreover, all of the effects and advantages described in connection with the positioning device and positioning assembly also apply to sheet material processing machines, and vice versa.

[0039] The present invention will now be described with reference to the embodiments illustrated in the accompanying drawings. [Brief description of the drawings]

[0040] [Figure 1] FIG. 2 shows a sheet material processing machine according to the invention having several positioning assemblies according to the invention, each positioning assembly having at least one positioning device according to the invention. [Diagram 2] FIG. 2 shows a partially assembled view of a portion of the positioning assembly of FIG. 1 including two positioning devices. [Diagram 3] 3 is a cross-sectional view of the positioning assembly of FIG. 2 taken along line III. [Figure 4] FIG. 3 is a perspective view of the positioning device of FIGS. 1 and 2; [Diagram 5] FIG. 3 shows a detail V of one of the positioning devices of FIG. 2. [Figure 6] 6 is a cross-sectional view of the positioning device of FIG. 5 taken along line VI. [Figure 7] 7 is a perspective view of a portion of the positioning device of FIG. 5 including the cross section of FIG. 6. [Figure 8] 8 is a cross-sectional view of the positioning device of FIG. 5 taken along line VIII. [Figure 9] 9 is a cross-sectional view of the positioning device of FIG. 8 taken along line IX. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] FIG. 1 illustrates a sheet material converting machine 10 (hereinafter machine 10).

[0042] In the embodiment of FIG. 1, the machine 10 is configured for cutting sheet material and comprises five units, each of which performs a particular operation on the sheet material.

[0043] The first unit is a feeder unit 10a which provides or supplies sheets 12 to be processed. For purposes of illustration, only one sheet 12 is shown in feeder unit 10a.

[0044] The second unit has a platen press 14 configured to cut the sheet 12. The second unit is thus a platen press unit 10b.

[0045] The third unit is a stripping unit 10c that is configured to strip the cut sheet 12 of certain debris elements.

[0046] The fourth unit is a blanking unit 10d, in which the actual desired portion of the cut sheet 12 is removed therefrom and placed on a pile 16.

[0047] The fifth unit is a waste discharge unit 10e, which serves to remove further waste elements of the cut sheet 12.

[0048] The sheet 12 is transported through the machine 10 by a conveyor system 18 that essentially includes a conveyor belt 20 having a plurality of gripper units 22 attached thereto, the plurality of gripper units being configured to selectively grip the sheet 12.

[0049] The platen press unit 10 b , the stripping unit 10 c and the blanking unit 10 d further include a positioning assembly 24 that holds the sheet 12 on a holding surface 26 .

[0050] In the embodiment shown in FIG. 1, the support surface 26 is the top surface of the positioning assembly 24 .

[0051] During processing of the sheet 12 in any one of the platen press unit 10b, the stripping unit 10c and the blanking unit 10d, the leading edge of the sheet 12 is gripped by a corresponding gripping unit 22 and the trailing edge of the sheet 12 is held by a corresponding positioning assembly 24 (see running direction T).

[0052] FIG. 2 shows the positioning assembly 24 in greater detail.

[0053] The positioning assembly includes a base 28 with a central air supply duct 30 .

[0054] Thus, pressurized air can be supplied to the base 28 through a central air supply duct 30 .

[0055] The base 28 further has a plurality of fluid outlet ports 32 in fluid communication with a central air supply duct 30 .

[0056] Additionally, the base 28 has a cleaning fluid inlet port 34. Thus, cleaning fluid can be supplied to the positioning assembly 24 through the cleaning fluid inlet port 34.

[0057] The base 28 further includes a cleaning fluid outlet port 36 in fluid communication with the cleaning fluid inlet port 34 .

[0058] In the embodiment shown in FIG. 2, two positioning devices 38 are attached to the base 28 by fastening means 40, such as bolts or rivets.

[0059] A gasket 42 is interposed between the base 28 and each of the positioning devices 38 .

[0060] One of the positioning devices 38 will now be described in detail with reference to Figures 3 to 9. The two positioning devices 38 shown in Figure 2 are substantially identical, so the following description applies to both of these positioning devices.

[0061] The positioning device 38 has a body 44 that is an additively manufactured part.

[0062] One exterior surface of the body 44 is a positioning surface 46 .

[0063] The positioning surface 46 forms part of the holding surface 26 .

[0064] In the depiction of FIG. 2, positioning surface 46 is the top surface of body 44 .

[0065] The body 44 has an outer bonding surface 48 .

[0066] The bonding surface 48 is provided opposite the positioning surface 46 and thus is the underside of the body 44 in the representation of FIG.

[0067] Positioning surface 46 is provided with suction openings 50 configured to draw sheet 12 therethrough so that sheet 12 is retained on positioning surface 46.

[0068] The mating surface 48 is provided with a fluid inlet port 52 for supplying a drive fluid to the body 44 (see Figures 3 and 4).

[0069] Additionally, a wash fluid inlet port 54 is provided in the bonding surface 48 (see FIG. 4).

[0070] The body 44 further includes a side surface 56 that joins the positioning surface 46 and the bonding surface 48 to one another.

[0071] Side 56 defines a fluid outlet port 58 for discharging drive fluid from body 44 (see Figures 4 and 5).

[0072] Fluid inlet port 52 and fluid outlet port 58 are located at the same end of body 44. In the depiction of Figure 4, the ports are located at the top end of body 44.

[0073] Each of the fluid inlet ports 52 is coupled to a corresponding fluid outlet port 58 by a circulation channel 60. In other words, the circulation channel 60 extends from the respective fluid inlet port 52 to the respective fluid outlet port 58 (see FIG. 8).

[0074] The circulation channel 60 has a general hairpin shape, ie, the circulation channel has a bend 62 of approximately 180°.

[0075] Downstream of the bend 62, the circulation channel has a section 64 of reduced cross-sectional area.

[0076] Section 64 has a nozzle 66 for accelerating the flow of motive fluid through circulation channel 60 .

[0077] The nozzle 66 has a substantially circular cross-section (see FIG. 9).

[0078] The cross section S of the circulation channel 60 along its length c , this cross section has a single discontinuity 68 at the downstream end of the nozzle 66.

[0079] In the remaining section of the circulation channel 60, the cross section S c is continuously changing.

[0080] For ease of illustration, the cross section S of the circulation channel 60 is c Only a few of these are shown with reference numbers in FIG.

[0081] In this regard, approximately 87% of the length of the circulation channel 60 has a cross-sectional area that is at least twice the cross-sectional area of ​​the remainder of the length of the circulation channel 60 .

[0082] This means that the circulation channel 60 has a relatively large and relatively uniform cross-sectional area for all sections outside the reduced cross-sectional area section 64 .

[0083] In addition, the extension direction E of the circulation channel 60 c varies continuously along the entire length of the circulation channel 60, ie, the circulation channel 60 is free of corners or kinks.

[0084] Furthermore, any cross-section S of the circulation channel 60 along its entire lengthc has a smooth rim, i.e., cross section S c The contour defining the axial length φ also does not include corners or kinks.

[0085] In particular, the radius of curvature r of the walls laterally defining the circulation channel 60 lies in the range from 0.5 mm to 20 mm.

[0086] For ease of illustration, only some of the radii of curvature r of the circulation channels 60 are labeled in FIG.

[0087] Also provided within body 44 is a suction channel 70 which connects suction opening 50 to circulation channel 60 .

[0088] A suction channel 70 surrounds the circulation channel 60 within the cross-sectional area reduction section 64 and is joined to the circulation channel 60 adjacent the cross-sectional area reduction section 64, thereby forming a jet pump 71.

[0089] More specifically, the suction channel 70 merges directly into the circulation channel 60 at the location of the discontinuity 68 .

[0090] Thus, the flow of driving fluid flowing through the circulation channel 60 is accelerated by the nozzles 66 and accelerates the fluid present in the suction channels 70, so that the sheet 12 is sucked by the suction openings 50.

[0091] Cross section S of the suction channel 70 s varies continuously along the entire length of the suction channel 70. s The path does not include discontinuities.

[0092] Again, two representative cross sections S s Only those components are shown and referenced in FIGS.

[0093] Also, the extension direction E of the channel 70 s varies continuously along the entire length of the suction channel 70.

[0094] Further, like the circulation channel 60, any cross-section S of the suction channel 70 along its entire length s also has a smooth rim.

[0095] As can be noted, although the suction opening 50 is generally D-shaped, the cross-sectional rim of the suction opening 50, and thus the cross-sectional rim of the suction channel 70, does not include kinks or corners, meaning that all corners of the D-shape are rounded.

[0096] Additionally, an irrigation fluid channel 72 is provided that fluidly couples the irrigation fluid port 54 to the suction channel 70 (see Figures 7 and 9).

[0097] In the illustrated embodiment, the washing fluid channel 72 is bifurcated at its downstream end such that a first washing fluid channel portion 72a and a second washing fluid channel portion 72b merge into the suction channel 70.

[0098] The wash fluid channel 72 has a cross-section with a smooth rim along its entire length.

[0099] As will be appreciated, in the embodiment described in connection with the figures, sheet 12 is used as a representative example of a flat flexible element, which means that machine 10, positioning assembly 24 and positioning device 38 are also intended for use in connection with any other flat flexible element.

Claims

1. A positioning device (38) for holding a flat flexible element, in particular a sheet material (12), on a positioning surface (46), said positioning device (38) comprising: a body (44) having a fluid inlet port (52) for supplying a drive fluid to the body (44), a fluid outlet port (58) for discharging the drive fluid from the body (44), and a suction opening (50) for drawing in the flat flexible element, the suction opening (50) being provided in the positioning surface (46), which is an exterior surface of the body (44); a circulation channel (60) connecting said fluid inlet port (52) and said fluid outlet port (58), said circulation channel (60) having a section (64) of reduced cross-sectional area; A positioning device (38) having a suction channel (70) connecting the suction opening (50) to the circulation channel (60), the suction channel (70) being connected to the circulation channel (60) adjacent the cross-sectional area reduction section (64) to form a jet pump (71), Any cross section (S c ) and / or any cross section (S s ) is the cross-sectional area (S c ) and / or any cross section (S s ) has a smooth rim, meaning that the contour defining the rim is free of corners or kinks; The circulation channel (60) has a bend (62), in particular a bend (62) of approximately 180°, the circulation channel (60) has a section (64) of reduced cross-sectional area downstream of the bend (62), and the suction channel (70) is coupled to the circulation channel (60) adjacent the section (64) of reduced cross-sectional area; A positioning device (38), wherein the path of the cross section (Sc) of the circulation channel (60) along its length has only one discontinuity (68) at the downstream end of a nozzle (66).

2. The cross section (S s The positioning device (38) of claim 1, wherein the angle (A) varies continuously along the entire length of the suction channel (70).

3. The extension direction (E c ) may vary continuously along the entire length of the circulation channel (60) and / or may vary in the extension direction (E s 3. The positioning device (38) of claim 1 or 2, wherein the angle (A) varies continuously along the length of the suction channel (70).

4. The positioning device (38) of any one of claims 1 to 3, wherein the fluid inlet port (52) and the fluid outlet port (58) are provided at the same end of the body (44).

5. The positioning device (38) according to any one of the preceding claims, wherein the radius of curvature (r) of the walls laterally defining the circulation channel (60) is in the range from 0.2 mm to 30 mm, in particular from 0.5 mm to 20 mm.

6. A positioning device (38) according to any one of claims 1 to 5, wherein at least 60%, preferably at least 75%, more preferably at least 90% of the length of the circulation channel (60) is at least twice the cross-sectional area of ​​the remainder of the length of the circulation channel (60).

7. The positioning device (38) of any one of claims 1 to 6, wherein a cleaning fluid inlet port (54) is provided in the body (44).

8. 8. The positioning device (38) of claim 7, wherein a cleaning fluid channel (72) fluidly couples the cleaning fluid inlet port (54) to the circulation channel (60) or the suction channel (70), and a cross-section of the cleaning fluid channel (72) has a smooth rim along its entire length.

9. The positioning device (38) of any one of claims 1 to 8, wherein the body (44) is an additively manufactured part.

10. The positioning device (38) according to any one of the preceding claims, wherein the section (64) of reduced cross-sectional area of ​​the circulation channel (60) comprises a nozzle (66) having a substantially circular cross-section.

11. A positioning assembly (24) for holding a flat flexible element, in particular a sheet material (12), on a holding surface (26), comprising a base (28) with a central air supply duct (30) and at least one positioning device (38) according to any one of claims 1 to 10, The positioning device (38) is attached to the base (28) such that the fluid inlet port (52) of the positioning device (38) is fluidly connected to the central air supply duct (30) and the positioning surface (46) forms the support surface (26).

12. A sheet material processing machine (10) having at least one positioning assembly (24).

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