Workpiece clamping element and workpiece table with workpiece clamping elements

Abstract

A workpiece clamping element (70; 71) comprising a cylinder (81) and a lifting plunger assembly (100) guided in the cylinder (81), with an annular piston (102) and an inner tube (105), wherein the lifting plunger assembly (100) carries a suction plate (111) with a workpiece support surface (113), wherein a cylinder base (83) of the cylinder (81) penetrated by the lifting plunger assembly (100), the lifting plunger assembly (100), and a cylinder jacket tube (85) of the cylinder (81) define a pressure chamber (142), and wherein the lifting plunger assembly (100) is mounted so as to be at least axially displaceable in both the cylinder base (83) and the cylinder head (84), characterized in that the suction plate (111) has suction channels (112) penetrating it in its longitudinal direction, and that a spring energy storage device is located in the suction plate (111). (137) loaded excavation plunger (131) is stored,wherein, with the spring energy storage unit (137) unloaded, the lifting plunger (131) protrudes beyond the workpiece support surface (113) and, with the lifting plunger (131) extended, the suction channels (112) are closed off by means of a support disc (132) of the lifting plunger (131).

Description

The invention relates to a workpiece clamping element comprising a cylinder and a piston assembly guided in the cylinder with a ring piston and an inner tube, wherein the piston assembly carries a suction plate with a workpiece support surface, wherein a cylinder base of the cylinder penetrated by the piston assembly, the piston assembly and a cylinder jacket tube of the cylinder define a pressure chamber, and wherein the piston assembly is mounted in a manner that is at least axially displaceable in both the cylinder base and the cylinder head, as well as a workpiece table with a plurality of such workpiece clamping elements. A workpiece clamping element is known from DE 103 50 572 A1. The height adjustment of this workpiece clamping element is effected by means of an electric motor and a spindle. From DE 38 10 711 A1 a pneumatically actuated workpiece clamping element with suction cups adjustable in inclination is known. US Patent 5,346,193 A discloses a workpiece clamping element that is raised by means of a spring and lowered manually or by means of a robot. DE 42 15 140 A1 shows a workpiece clamping element which is inserted against the force of an extension spring for workpiece machining. US 2017 / 0 219 504 A1 proposes using a double-acting cylinder to drive a slide that raises and lowers lifting pins. The present invention is based on the problem of enabling a short setup time and a reduced throughput time for workpieces. This problem is solved by the features of the main claim. For this purpose, the suction plate has suction channels penetrating it in its longitudinal direction. A lifting plunger, loaded by at least one spring energy storage device, is mounted in the suction plate. When the spring energy storage device is unloaded, the lifting plunger projects beyond the workpiece support surface, and when the lifting plunger is extended, the suction channels are closed off by means of a support disc of the lifting plunger. In the workpiece clamping element, the lifting plunger assembly is supported at two points within the cylinder, with a large bearing distance. One bearing point is located in the cylinder base, the other in the cylinder head. The pressure chamber lies between the two bearing points, resulting in a bearing distance greater than the total stroke of the workpiece clamping element. This ensures stable support during the extension and retraction of the lifting plunger assembly, enabling high extension and retraction speeds. Furthermore, the large bearing distance allows for the absorption of high forces and moments during workpiece machining. This enables machining with high material removal rates. Further details of the invention will become apparent from the dependent claims and the following description of schematically illustrated embodiments. Fig. 1: Workpiece clamping element; Fig. 2: Workpiece clamping element in the retracted end position; Fig. 3: Sectional view of the lifting plunger; Fig. 4: Suction cup; Fig. 5: Lifting plunger; Fig. 6: Detail of the lifting connection; Fig. 7: Detail of the return stroke connection; Fig. 8: Detail of the suction connection; Fig. 9: Workpiece clamping element in the extended end position; Fig. 10: Workpiece clamping element in the operating position; Fig. 11: Workpiece mounting plate with raised workpiece; Fig. 12: Workpiece table; Fig. 13: Frame; Fig. 14: Workpiece plate carrier with workpiece mounting plates; Fig. 15: Sectional view of the workpiece mounting plates; Fig. 16: Machining cell. Figures 1-11 show a workpiece clamping element (70; 71) and some of its individual parts. Workpiece clamping elements (70; 71) are used in workpiece tables (30), see Figure 12, to fix workpieces (2; 3) for machining. The workpiece table (30) has at least one workpiece clamping device (33; 34) with a plurality of workpiece clamping elements (70; 71). The workpiece clamping elements (70; 71) of a workpiece clamping device (33; 34) are mounted in a support plate (55) of the workpiece table (30). Each workpiece clamping element (70; 71) is adjustable relative to the support plate (55) between a retracted end position (72) and an extended end position (73). The individual workpiece clamping elements (70; 71) are, for example, identical in construction. In the workpiece clamping device (33, 34), each of these workpiece clamping elements (70; 71) can be individually controlled pneumatically, hydraulically, and / or electrically. The signals from a measuring and / or testing system of each individual workpiece clamping element (70; 71) can be individually acquired. Figure 1 shows a workpiece clamping element (70; 71) in its extended end position (73) without a workpiece (2; 3) resting on it. The workpiece clamping element (70; 71) has a cylinder-piston unit (82), the cylinder (81) of which is designed as a tie-rod cylinder in this embodiment. The cylinder (81) has a cylinder base (83) with a plate-shaped cylinder base ring (87) and a cylinder head (84) with a plate-shaped cylinder head cover (88). The cylinder base ring (87) and the cylinder head cover (88) are, for example, parallel to each other. Together they support a cylinder shell tube (85). The cylinder shell tube (85) has a constant inner diameter and a constant wall thickness along its length. Several external tie rods (86) penetrate the cylinder base ring (87) and the cylinder head cover (88).Furthermore, these tie rods (86) penetrate a distribution cover (91) of the cylinder head (84) which lies on the cylinder head cover (88). In the illustration of Fig. 1, a piston assembly (100) with the suction plate (111) arranged on it protrudes from this distribution cover (91). A base distribution plate (94) of the cylinder base (83) is, for example, screwed onto the cylinder base ring (87). A protective tube (96) with a protective cap (97) at the bottom protrudes from the base distribution plate (94). In the exemplary embodiment, the individual workpiece clamping element (70; 71) has three pneumatic connections (141, 151, 161). These pneumatic connections (141, 151, 161) are a stroke connection (141), a return stroke connection (151), and a suction connection (161). The return stroke connection (151) is located on the underside of the cylinder head cover (88) in the illustration of Fig. 1. The stroke connection (141) and the suction connection (161) are located opposite each other on the underside of the base distribution plate (94) in this illustration. Furthermore, a switching valve (144) for enabling and disabling the stroke connection (141) is arranged in the base distribution plate (94). The switching valve (144), e.g., a 3 / 2-way valve, is electromagnetically actuated in the exemplary embodiment. The use of a throttle valve is also conceivable. The lifting connection (141) and the return lifting connection (151) can also be designed as hydraulic connections. Fig. 2 shows a sectional view of a workpiece clamping element (71; 70) in its retracted end position (72). The lifting plunger assembly (100) is retracted, so that the suction cup (111) protrudes only a small amount, e.g., 9% of the total height of the retracted workpiece clamping element (71; 70), beyond the cylinder head cover (88). The lifting plunger assembly (100) is guided in a sealed manner in the distribution cover (91) and in the cylinder jacket tube (85). The lifting plunger assembly (100) is mounted in the cylinder head (84) so ​​that it is movable, at least in the axial direction. The bearing point (172) in the cylinder head (84) is, for example, designed as a sliding bearing (172). The piston assembly (100) has a piston (101) in which an inner tube (105) is attached. The inner tube (105) is oriented in the stroke direction of the piston assembly (100). The lower end of the piston (101) shown in Figs. 1-2 is designed as an annular piston (102). In the illustrated embodiment, this annular piston (102) separates a displacement chamber (152) from a pressure chamber (142) within the cylinder (81). The displacement chamber (152) is located between the annular piston (102) and the distribution cover (91) of the cylinder head (84). In the radial direction, the displacement chamber (152) is bounded by the cylinder jacket tube (85) of the cylinder (81). The pressure chamber (142) is bounded by the cylinder base (83), the piston assembly (100), and the cylinder jacket tube (85) of the cylinder (81). In the illustrated embodiment, the pressure chamber (142) lies between a base ring (99) of the cylinder base (83) located in the cylinder base ring (87) and the annular piston (102). The annular piston (102) has a frustoconical shape on its side facing the distribution cover (91). The imaginary apex of the cone lies on a center line of the workpiece clamping element (70; 71) in the direction of the suction plate (111), offset from the reciprocating piston (102). A frustoconical recess (92) complementary to the reciprocating piston (102) is formed in the distribution cover (91). This ensures that the reciprocating piston assembly (100) is centered in the cylinder head (84) when the reciprocating piston assembly (100) is extended, i.e., at the maximum volume of the pressure chamber (142). In the exemplary embodiment, the inner diameter of the displacement chamber (152) is 80% of its outer diameter. The inner diameter of the pressure chamber (142) is 35% of its outer diameter. Both the outer diameter of the displacement chamber (152) and the outer diameter of the pressure chamber (142) are determined, for example, by the cylinder (81). Thus, the piston pressure area of ​​the annular piston (102) on the pressure chamber side is more than twice as large as the piston pressure area on the displacement chamber side. The stroke of the lifting plunger (101) relative to the cylinder (81) during extension is limited, for example, by the annular piston (102) striking the distribution cover (91). The retraction of the lifting plunger (101) is limited, for example, by the annular piston (102) striking the base ring (99). In the exemplary embodiment, the stroke of the lifting plunger (101) is 35% of the total length of the workpiece clamping element (70; 71) oriented in the stroke direction. The stroke of the lifting plunger (102) is therefore greater than 30% of the total length of the workpiece clamping element (70; 71). Figure 3 shows a sectional view of the piston (101). The annular piston (102) has a pressure plate (108) facing the pressure chamber (142). This plate is, for example, screwed onto the piston body (109). The pressure plate (108) secures a piston sealing element (121). When the workpiece clamping element (70; 71) is mounted, this piston sealing element (121) rests against the inner wall of the cylinder (81). It hermetically seals the pressure chamber (142) against, for example, the displacement chamber (152). At its upper end, the lifting plunger (101) has an internal thread (122). When the workpiece clamping element (70; 71) is mounted, the suction cup (111) is screwed into this internal thread (122). Furthermore, the lifting plunger (101) has, for example, four spring receptacles (104). These are, for example, cylindrical in shape. In the illustration of Fig. 3, they are arranged below the internal thread (122) and are open at the top. Fig. 4 shows the suction cup (111) in an isometric bottom view. The suction cup has a central threaded bore (116). Below the workpiece support surface (113), the suction cup (111) has a cylindrical section (117). The thread of the threaded bore (116), for example, is formed within the cylindrical section (117). The cylindrical section (117) has an annular groove (118) on the underside for receiving a sealing ring (114). Six expanding jaws (119), arranged on a common pitch circle, adjoin the cylindrical section (117). Each expanding jaw (119) is connected to the cylindrical section (117) by means of a film hinge (124). In a view of the suction plate (111) from below, each expanding jaw (119) covers an angle of, for example, 60 degrees. The apex of this angle lies on a circle around the center line of the suction plate (111), the diameter of which is, for example, one-sixteenth of the diameter of the workpiece support surface (113). Each expanding jaw (119) has an internal pressure surface (125). The pressure surface (125) can be wedge-shaped. On its outer surface, each expanding jaw (119) can have a threaded section (126). In three of the illustrated spreading jaws (119) the suction channels (112) are formed in the illustration of Fig. 4. With the workpiece clamping element (70; 71) mounted, the suction cup (111) is screwed into the free end of the stroke plunger (101). The sealing ring (114) seals the underside of the suction cup (111) against the stroke plunger (101). The suction cup (111) has, for example, three suction channels (112) extending longitudinally through the suction cup (111). The diameter of the workpiece support surface (113) of the suction cup (111) is, for example, 95% of the diameter of the cylinder (81). A clamping and guide sleeve (115) is screwed into the suction cup (111). The clamping and guide sleeve (115) secures the position of the suction cup (111) relative to the telescopic tube (101). For example, to adjust the individual suction cups (111) to a common working plane, the clamping and guide sleeve (115) is loosened and then tightened again after adjustment. A lifting plunger (131) is located in the clamping and guide sleeve (115), see Fig. 5. The lifting plunger (131) has a support disc (132) and a shock tube (133) integrally formed on the support disc (132). The support disc (132), which is parallel to the plane, has three openings (134) oriented in the longitudinal direction of the lifting plunger (131). A central channel (135) penetrates the support disc (132) and the shock tube (133). The shock tube (133) has a constant circular internal cross-sectional area along its length. The outer surface (136) of the shock tube (133) is coaxial with the internal cross-sectional area. The spring receptacles (104) of the telescopic tube (101) face the lifting plunger (131). Each of these spring receptacles (104) contains a spring energy storage device (137). In this embodiment, the individual spring energy storage device (137) is a compression spring (137). These compression springs (137) compress the lifting plunger (131), which is displaceable relative to the telescopic tube (101), in the direction of the suction plate (111). When the spring energy storage devices (137) are unloaded (see Fig. 2 and Fig. 9), the support disc (132) rests against the suction plate (111). The free end of the plunger tube (133) protrudes, for example, 1.5 millimeters beyond the workpiece support surface (113) of the suction plate (111). With loaded spring energy storage units (137), see Fig. 10, the support disc (132) has only a small distance to the telescopic tube (101) or is in contact with it. In the illustration of Fig. 10, the shock tube (133) is, for example, located slightly below the workpiece support surface (113) of the suction plate (111).The spring energy storage device (137) is loaded by means of a vacuum that acts through the inner tube (105) on the support disc (132) and attracts it. Fig. 6 shows a detail of the stroke connection (141) and its connection to the pressure chamber (142). The pressure chamber (142) is shown in this illustration with its maximum volume. The T-shaped stroke connection (141) is screwed into the base distribution plate (94). A first feed channel (143) runs in the base distribution plate (94) to a valve spool (145) of the switching valve (144). From the valve spool (145), a second feed channel (146) runs through the base ring (99) to the pressure chamber (142). A throttle channel (147) connects a second valve position to the environment (1). Figure 7 shows the connection of the return stroke port (151) to the displacement chamber (152). In this illustration, the workpiece clamping element (70; 71) is also in the extended end position (73). The return stroke port (151) is screwed into the cylinder head cover (88). A return stroke channel (153) leads into the distribution cover (91). There, the return stroke channel (153) opens into the displacement chamber (152) below the cylinder seal (103) at the through-hole (93) of the distribution cover (91). The tubular lifting plunger (101) and the inner tube (105) are rigidly connected to each other, for example, by means of a wedge press fit (106). During a lifting movement of the lifting plunger assembly (100), both the lifting plunger (101) and the inner tube (105) are thus carried along. The inner tube (105) has a cylindrical inner wall and is open at both ends. The inner diameter of the inner tube (105) is, for example, one-quarter of the outer diameter of the cylindrical shell tube (85). In the exemplary embodiment, the length of the inner tube (105) is 2.3 times the stroke of the workpiece clamping element (70; 71). The lifting plunger assembly (100) is mounted in the cylinder base (83) so that it can move at least in the lifting direction. In the exemplary embodiment, the inner tube (105) and the base part (94) form a bearing point (172) designed as a sliding bearing (171). Other mounting configurations are also conceivable. In the retracted end position (72) shown in Fig. 2, the inner tube (105) projects into the protective tube (96). An annular gap (107) exists between the protective tube (96) and the inner tube (105) along the entire length of the protective tube (96). The protective cap (97) carries a shaft seal (98) into which the inner tube (105) dips when lowered. Fig. 8 shows the suction port (161) and the first section of the suction channel (162). In this illustration, the lifting plunger assembly (100) is also extended to its maximum stroke. The suction port (161) is screwed into the base distribution plate (94). The suction channel (162) runs at an angle to the inner wall (95) of the base distribution plate (94). Here, it opens into the central interior space (164) of the workpiece clamping element (70; 71). In this illustration, the opening cross-section (163) of the suction channel (162) lies between the inner tube (105) and the protective tube (96). The inner tube (105) is sealed against the base ring (99) and the base distribution plate (94). In the illustration of Fig. 2, the inner tube (105) obscures the opening cross-section (163). When the lifting plunger assembly (100) is retracted, the extraction via the lifting plunger assembly (100) is blocked. Fig. 9 shows the workpiece clamping element (70; 71) with the lifting plunger assembly (100) extended. The workpiece clamping element (70; 71) is shown in its extended end position (73). The pressure chamber (142) has its maximum volume. The lifting plunger (101) rests with its annular piston (102) in the conical recess (92) of the distribution cover (91). The inner tube (105) is in the position described in connection with the illustration of Fig. 8, so that the suction port (161) is pneumatically connected to the interior (164), the inner tube (105), and the channel (135) of the thrust tube (133). The lifting plunger (131) is extended, as described in connection with Fig. 2. For example, the support disc (132) of the excavation plunger (131) blocks the suction channels (112) of the suction plate (111). Figure 10 shows an operating position (74) of the workpiece clamping element (70; 71). The lifting plunger assembly (100) is extended, as described in connection with Figure 9. The lifting plunger (131) is retracted relative to the suction plate (111). The compression springs (137) are compressed. Fig. 11 shows two workpiece clamping elements (70; 71) after machining a workpiece (2, 3). The workpiece (2, 3) rests on both workpiece clamping elements (70; 71). The vacuum for suctioning the workpiece (2, 3) is switched off. For example, ambient pressure prevails in the interior (164) of the inner tube (105). The compression springs (137) are released. In this illustration, they have moved the respective lifting plunger (131) upwards relative to the suction plate (111), so that the support disc (132) rests against the suction plate (111). The push tube (133) extends beyond the workpiece support surface (113). The workpiece (2, 3) rests on the push tubes (133) and can be removed from them. Figures 12-15 show a workpiece table (30). The workpiece table (30) has a frame (31) in which a workpiece plate carrier (32) with workpiece clamping devices (33, 34) is pivotably mounted. In the illustration of Figure 12, the workpiece table (30) has two workpiece clamping devices (33, 34). The workpiece clamping sides (36, 37) of these workpiece clamping devices (33, 34) point in opposite directions in this embodiment. The pivot axis (35), about which the workpiece plate carrier (32) can pivot relative to the frame (31), is horizontally oriented in this embodiment. A pivot drive (51) is arranged on the frame (31) for driving the workpiece plate carrier (32). In this embodiment, the workpiece plate carrier (32) with the workpiece clamping devices (33, 34) can be pivoted from the position shown in Fig. 12 by a pivot angle of 180 degrees about the pivot axis (35) and back again. However, it is also conceivable to arrange the workpiece plate carrier (32) so that it can rotate relative to the frame (31). In this case, the workpiece plate carrier (32) can be rotated 360 degrees or more about the axis of rotation. The pivot axis (35) or the axis of rotation of the workpiece table (30) can also be vertically oriented. The workpiece plate carrier (32) can support more than two workpiece clamping devices (33, 34). In this case, the swivel or rotation angle between the individual positions is 360 degrees divided by the number of workpiece clamping devices (33, 34). Again, each of the workpiece clamping devices (33, 34) is oriented in a different direction. The frame (31) of the workpiece table (30), see Fig. 13, has two spaced-apart vertical supports (41) which are connected to each other by means of a lower longitudinal support (43) and an upper longitudinal support (44). The lower feet (46) are, for example, arranged asymmetrically to the vertical supports (41). In use, see Fig. 16, the feet (46) project further outwards than inwards. The vertical supports (41) each have bearing points (47) for the pivoting support of the workpiece plate carrier (32). For example, a rolling bearing (48) in the form of a slewing ring is used in each bearing point. This slewing ring (48), for example, a multi-row bearing, has radially oriented cylindrical rollers and an axially oriented spherical rolling element. One of the bearing points can be designed as a fixed bearing point, the other as a floating bearing. The bearing points (47) can also be designed with spherical roller bearings, angular contact ball bearings, etc. In Figures 12 and 16, sealing plates (57) projecting outwards are arranged on the vertical beams (41) and the longitudinal beams (43, 44). When the workpiece table (30) is used, see Figure 16, these sealing plates (57) abut, for example, the housing (11) of the machining cell (10). Additionally, one or more inflatable tubes can be used for sealing between the workpiece table (30) and the housing (11). These are arranged, for example, on the inner sides (42) of the vertical beams (41) as well as on the inner sides (45) of the longitudinal beams (43, 44). When a workpiece clamping device (33; 34) is in a working position, these inflatable air tubes surround it. Before swiveling the workpiece plate carrier (32), the air hoses can be relieved by releasing or relocating the filling air.Other designs for sealing the work area against the environment (1) are also conceivable. The rotary actuator (51) is arranged on the vertical support (41) on the left in Fig. 12. This actuator has an electric drive motor (52). In the exemplary embodiment, the drive motor (52) is an electric motor in the form of a geared motor. For example, it can be designed as an actuator motor. The swivel drive (51) further includes a locking mechanism. By means of this locking mechanism, the workpiece plate carrier (32) can be locked relative to the frame (31) in at least one angular position in which one of the workpiece clamping devices (33, 34) is in, for example, a vertical working position. In the exemplary embodiment, when one of the workpiece clamping devices (33; 34) is in the working position, exactly one other workpiece clamping device (34; 33) is in a loading and unloading position (38) outside the housing (11). Fig. 14 shows the workpiece plate carrier (32). It comprises a support section (54) on each of its two end faces (39), which are connected by means of two support plates (55). Each of the two support sections (54) carries a pivot pin (56) by which the workpiece plate carrier (32) is mounted in the frame (31) in the illustrations of Figs. 12 and 16. The workpiece plate carrier (32) is supplied with media, for example, through this pivot pin (56). This media supply includes electrical power, control, and data lines, as well as pneumatic and / or hydraulic control, pressure, and suction lines. In the exemplary embodiment, the two support plates (55) are arranged parallel to each other. Each support plate (55) defines a workpiece clamping side (36, 37). The area of ​​each workpiece clamping side (36, 37) corresponds, for example, to the maximum workpiece contact area. In the exemplary embodiment, workpieces with a length of up to 3600 millimeters and a width of up to 2100 millimeters can be clamped onto each of the workpiece clamping devices (33; 34). The thickness of each support plate (55) is, for example, 4% of its length. In an embodiment of the workpiece table (30) with three workpiece clamping devices (33, 34), it has three support plates (55). These support plates (55) are arranged in an equilateral triangle in an end view of the workpiece table (30). In a longitudinal view (5) along the pivot axis (35) or the axis of rotation, the individual workpiece clamping device (33; 34) is in the loading and unloading position (38) in the exemplary embodiment. However, the workpiece clamping device (33; 34) can also form an angle of up to and including 30 degrees with a vertical plane containing the pivot axis (35) or the axis of rotation, with the line of intersection lying above the pivot axis (35) or the axis of rotation. For example, in this case, each support plate (55) has the same maximum workpiece support area. An embodiment of the workpiece table (30) with more than three workpiece clamping devices (33, 34) is also conceivable. Each support plate (55) carries a workpiece clamping device (33; 34). In the exemplary embodiment, the two workpiece clamping devices (33; 34) are identical to each other. However, it is also conceivable to use differently designed workpiece clamping devices (33; 34) on the individual support plates (55). The individual workpiece clamping device (33; 34) has a plurality of workpiece clamping elements (70; 71). In the exemplary embodiment, these are arranged in rows and columns on the support plate (55). In an area shown in the lower left of Fig. 14, the arrangement of the tool clamping elements (70; 71) is denser. In this matrix-like arrangement, within the respective densification area, the spacing of the workpiece clamping elements (70; 71) arranged side by side in a row corresponds, for example, to the spacing of the workpiece clamping elements (70; 71) arranged one above the other in a column. These spacings can also be configured differently. The arrangement of the workpiece clamping elements (70; 71) can also be formed on, for example, concentric circles, spirals, along a diagonal pattern, etc. The formation of several areas with different densities is also conceivable. Fig. 15 shows a sectional view of the workpiece plate carrier (32) with the workpiece clamping devices (33, 34). In this view, for example, the left side is a momentary loading side (61) and the right side is a momentary working area side (62). The individual workpiece clamping elements (70; 71) each penetrate a support plate (55) and are attached to it. Each workpiece clamping element (70; 71) has a cylinder (81) and a lifting plunger (101) that is hydraulically or pneumatically adjustable relative to the cylinder (81). The suction cup (111) is arranged at the free end of the lifting plunger (101). The lifting plunger (101) is oriented perpendicular to the support plate (55). The stroke of the workpiece clamping element (70; 71) is, for example, 100 millimeters. The diameter of the cylinder (81) is, for example, 70% of the stroke. In the illustration of Fig. 15, the loading side (61) and the working area side (62) each carry a workpiece (2; 3). Each workpiece rests on two workpiece clamping elements (70). These two workpiece clamping elements (70) are in an operating position (74) in which the telescopic tube (101) is fully extended. The lifting plunger (131) is retracted. The remaining workpiece clamping elements (71) are shown in a retracted end position (72). The adjustment of the workpiece clamping elements (70; 71) between the retracted end position (72) and an extended end position (73) can also be performed in steps. It is also conceivable, for example, to continuously adjust any intermediate position between the retracted end position (72) and the extended end position (73). In the illustrated embodiment, the adjustment of the workpiece clamping elements (70; 71) is pneumatic. The workpiece table (30) shown in Figures 12-15 has a frame (31) that supports and / or holds two or more workpiece clamping devices (33; 34). The workpiece clamping devices (33, 34) can also be located in a common plane or in several planes offset from one another. The planes can be arranged, for example, horizontally or inclined. For instance, the workpiece clamping devices (33, 34) are then movable relative to one another. The direction of travel can be linear or along a curved path. The workpiece clamping devices (33, 34) can be adjustable individually, in groups, or together relative to the frame (31). In these cases, each of the workpiece clamping devices (33; 34) has at least one loading and unloading position (38) and at least one working area position. In the respective working area position, each workpiece (2, 3) clamped onto the workpiece clamping device (33; 34) is, for example,Can be processed using the processing unit of the industrial robot. Instead of a workpiece table (30) with several workpiece clamping devices (33, 34), a workpiece table (30) with a single workpiece clamping device (33; 34) can also be used. This workpiece clamping device (33; 34) has a plurality of workpiece clamping elements (70; 71). These can be arranged as described above. Fig. 16 shows a machining cell (10). The machining cell (10) has an internal work area surrounded by an enclosure (11). This enclosure (11) has an air supply device (21) located at the top. A chip conveyor (22) is arranged in the longitudinal direction (5) of the machining cell (10), which conveys chips accumulating in the work area out of the enclosure (11). In this illustration, control cabinets (23) are located next to the enclosure (11). These control cabinets (23) contain the control system for workpiece machining. In this embodiment, machining is performed with the workpiece (2; 3) stationary, using a machining robot. The workpiece table (30) is arranged on one loading side (12) of the machining cell (10) within the enclosure (11). The workpiece table (30) is integrated into the enclosure (11). The workpiece table (30) defines the working area of ​​the machining cell (10). The workpiece clamping device (33), oriented towards the surroundings (1) in this illustration, is in the loading and unloading position (38). In the material flow of the machining cell (10), a workpiece (2; 3) to be machined is placed onto the workpiece clamping device (33; 34), for example, by means of a handling device or manually, and held there by means of a vacuum. To machine the workpiece (2, 3), it is pivoted into the work area about the pivot axis (35) by means of the workpiece plate carrier (32). Simultaneously, the other workpiece clamping device (34; 33), with a workpiece (3; 2) that has been machined, moves from the work area into the loading and unloading position (38). In both positions, the workpiece table (30) seals the machining cell (10) against the environment (1). The machined workpiece (3; 2) can now be removed by means of a handling tool or manually and fed into further processing. In the rest state of the machining cell (10) and / or the workpiece table (30), all workpiece clamping elements (70; 71) are in their respective retracted end positions (72). The stroke connections (141), the return stroke connections (151), and the suction connections (161) are, for example, depressurized. If necessary, the stroke connections (141) and / or the return stroke connections (151) can be in a locked position, so that the respective pressure chamber (142) and / or the displacement chamber (152) are completely isolated from the environment (1) and from the compressed air supply. For clamping a workpiece (2; 3) onto the workpiece clamping device (33; 34), the stroke connections (141) of individual workpiece clamping elements (70; 71) are connected, for example, to the compressed air supply. The return stroke connections (151) of all workpiece clamping elements (70; 71) are pressurized with, for example, a constant pressure of 3 bar. The stroke connections (141) can be connected, for example, separately from the return stroke connections (151) to one or more pressure sources. In the case of hydraulically controlled workpiece clamping elements (70; 71), these can be integrated into a closed hydraulic circuit, so that the annular piston (102) is pressurized on both sides. It is also conceivable to connect the stroke ports (141) and the return stroke ports (151) to the same pressure source. By means of the switching valve (144) upstream of the pressure chamber (142), the pressure chamber (142) can be pressurized simultaneously with the displacement chamber (152). In this case, the pressure chamber (142) and the displacement chamber (152) are pressurized to the same pressure, for example, the specified pressure value. The area of ​​the annular piston (102) facing the pressure chamber (142) is larger than the area of ​​the annular piston (102) facing the displacement chamber (152). When the switching valve (144) is switched to the flow position, the stroke plunger (101) is extended. When the switching valve (144) is switched to the relief position, the air from the pressure chamber (142) is displaced through the throttle channel (147) into the environment (1). The pressure present in the displacement chamber moves the lifting plunger group (100) into its retracted starting position. When setting up such an arrangement, the stroke port (141) and the return stroke port (151) can be directly connected to each other. This connecting line can be connected to the pressure source. The switching valve (144) is located downstream of the stroke port (141). The displacement chamber (152) can also be connected to a compressed air reservoir separate from the compressed air network or form a compressed air reservoir itself. The use of a spring energy storage device, e.g., in the form of a gas spring, a helical spring designed as a compression spring, etc., is also conceivable. The selection of the workpiece clamping elements (70; 71), released, for example, by a control system, depends on the geometry of the workpiece (2; 3) to be machined and on the machining steps planned in the machining cell (10). For example, if the creation of a through-hole in the workpiece (2; 3) is planned, the workpiece clamping elements (70; 71) located in this area after the workpiece (2; 3) has been clamped are not released. The unreleased workpiece clamping elements (70; 71) remain in their retracted end position (72) as shown in Fig. 2. If the machining of one or more edges (4) is planned, only workpiece clamping elements (70; 71) are released where a minimum distance to the machined edge (4) of the workpiece (2; 3) is guaranteed. This minimum distance is, for example, five millimeters. In the released workpiece clamping elements (70; 71), the pressure chamber (142) is pressurized with a pressure medium, e.g., compressed air. This is done, for example, by switching the, e.g., electromagnetically actuated, bistable switching valve (144) of this workpiece clamping element (70; 71). The lifting plunger assembly (100) moves against the pressure of the displacement chamber (152) relative to the cylinder (81) into the extended end position (73), cf. Fig. 9. In this process, the lifting plunger (101), the inner tube (105), and the suction plate (111) are moved. By centering the lifting plunger assembly (100) in the cylinder head (84), the transverse stiffness of the workpiece clamping element (70; 71) is increased, for example. In the extended end position (73), the workpiece clamping elements (70; 71) are held, for example, by maintaining pressure or by locking the respective switching valve (144). For example, the ring piston (102) is thus firmly clamped. In the non-released workpiece clamping elements (71; 70), for example,The pressurization of the displacement chamber (152) consists of the following: The lifting plunger assembly (100) is supported in the retracted state, in the extended state and during the entire lifting movement by means of the first bearing point (171) in the cylinder base (83) and by means of the second bearing point (172) in the cylinder head (84). As the lifting plunger assembly (100) extends relative to the cylinder (81), the inner tube (105) is moved upwards as shown in Fig. 2. The lifting plunger assembly (100) only releases the opening cross-section (162) when the workpiece clamping element (70; 71) reaches its extended end position (73). This establishes a pneumatic connection between the suction port (161) and the suction plate (111). The individual extended workpiece clamping element (70; 71) is pressurized with a vacuum via the suction port (161). Air is drawn from the respective suction port (161). In these workpiece clamping elements (70; 71), the air is drawn from the lifting plunger (131) through the inner tube (105). For example, the lifting plungers (131) are drawn towards the telescopic tubes (101) under load of the spring energy storage devices (137). If a retracted workpiece clamping element (71; 70) is pressurized with a vacuum, the inner tube (105), together with the shaft seal (98), blocks the extraction of air from this workpiece clamping element (71; 70). The workpiece (2; 3) is first placed manually or by means of a handling device in the specified position onto the workpiece support surfaces (113) of the suction plates (111). Here, the workpiece is positioned against, for example, extendable guide pins for centering. The workpiece (2; 3) is pulled against the suction cups (111) and fixed to the workpiece table (30) by means of the workpiece clamping device (33; 34). The air is extracted through the suction channels (112) of the suction cups (111), the respective lifting plunger (131), and the respective inner tube (105). The suction pressure can be adjustable if necessary. For example, it can be reduced during workpiece alignment. This facilitates, for example, correction of the workpiece position during the positioning of the workpiece (2; 3). During the swiveling of the workpiece table (30) and during the machining of the workpiece (2; 3) or workpieces (2, 3), the media control of the workpiece clamping elements (70; 71) remains unchanged. The workpiece (2; 3) is thus held securely in its position during machining. During the main operation of the machining cell (10), in which the last clamped workpiece (2; 3) or the last clamped group of workpieces (2; 3) is being machined, for example, the next workpiece (3; 2) or the next group of workpieces (3; 2) is prepared on the loading side (12) of the enclosure. Clamping onto the workpiece clamping device (34; 33), which is in the loading and unloading position (38), is carried out as described above. Machining of the workpiece (2; 3) is carried out, for example, by means of the industrial robot arranged inside the enclosure (11), which carries a machining unit with a plurality of driven tools. After machining is complete, the workpiece table (30) is swiveled so that the machined workpiece (2; 3) is in the loading and unloading position (38). Simultaneously, the previously temporary loading side (61) is swiveled into the work area. No setup of the workpiece (2; 3) or workpieces (2; 3) is required in the work area. For example, the non-productive time for machining a batch of workpieces (2; 3) is limited to swiveling the workpiece table (30). The workpiece (2; 3) is gripped using the handling device or manually. The differential pressure between the suction pressure and the ambient pressure is reduced, or the suction is switched off. The spring energy storage units (137) release and push the support disc (132) towards the suction plate (111). The workpiece (2; 3) is lifted from the suction plates (111) by means of the lifting plungers (131), see Fig. 11. The machined workpiece (2; 3) can now be removed from the workpiece clamping elements (70; 71) with almost no resistance. Subsequently, a new workpiece (3; 2) can be clamped onto the workpiece table (30) for machining. If the newly clamped workpiece has different geometric dimensions, other or additional workpiece clamping elements (70; 71) can be used to fix the workpiece (2; 3). Releasing additional workpiece clamping elements (70; 71) is carried out as described above. If individual workpiece clamping elements (70; 71) are no longer required for machining further workpieces (3; 2), they are moved into the retracted end position (72). For this purpose, the switching valve (144) is switched, for example, so that the pressure chamber (142) is connected to the environment (1) via the throttle channel (147). The pressure present in the displacement chamber (152) moves the telescopic tube (101) into the retracted position. When the lifting plunger assembly (100) retracts, it closes the pneumatic connection between the suction port (161) and the suction plate (111). Combinations of the individual implementation examples are also conceivable. Reference symbol list: 1 Environment 2 Workpiece 3 Workpiece 4 Edges of (2; 3) 5 Longitudinal direction 10 Machining cell 11 Enclosure 12 Loading side 21 Air supply device 22 Chip conveyor 23 Control cabinets 30 Workpiece table 31 Frame 32 Workpiece plate carrier 33 Workpiece clamping device 34 Workpiece clamping device 35 Swivel axis 36 Workpiece clamping side 37 Workpiece clamping side 38 Loading and unloading position 39 End faces of (32) 41 Vertical beam 42 Inner sides of (41) 43 Lower longitudinal beam 44 Upper longitudinal beam 45 Inner sides of (43, 44) 46 Feet 47 Bearing points 48 Rolling bearingsSlewing ring 51 Swivel drive 52 Drive motor of (51) 54 Support part 55 Support plates 56 Swivel pin 57 Sealing plates 61 Instantaneous loading side 62 Instantaneous working area side 70 Workpiece clamping elements 71 Workpiece clamping elements 72 Retracted end position 73 Extended end position 74 Operating position 81 Cylinder 82 Cylinder-piston unit 83 Cylinder base 84 Cylinder head 85 Cylinder jacket tube 86 Tie rods 87 Cylinder base ring 88 Cylinder head cover 91 Distributor cover 92 Fractional conical recess in (91) 93 Through-hole of (91) 94 Base distribution plate 95 Inner wall of (94) 96 Protective tube 97 Protective cap 98 Shaft seal in (97) 99 Base ring 100 Stroke plunger assembly 101 Telescopic tube, stroke plunger 102 Stroke piston103 Ring piston 104 Cylinder seal 104 Spring receptacles in (101) 105 Inner tube 106 Wedge press connection 107 Annular gap 108 Pressure plate 109 Piston body 111 Suction plate 112 Suction channels in (111) 113 Workpiece support surface of (111) 114 Sealing ring 115 Clamping and guide sleeve 116 Threaded bore 117 Cylindrical area 118 Annular groove 119 Expanding jaws 121 Piston sealing element 122 Internal thread 124 Film joint 125 Pressure surface 126 Threaded section 131 Lifting plunger 132 Support washer 133 Shock tube 134 Openings 135 Channel 136 Circumferential surface 137 Spring energy storage, compression spring 141 Pneumatic connection, stroke connection 142 Pressure chamber 143 First feed channel 144 Switching valve 145 Valve slide 146 Second feed channel 147 Throttle channel 151 Pneumatic connection, return stroke connection 152 Displacement chamber 153 Return stroke channel 161 Pneumatic connection, suction connection 162 Suction channel 163 Outlet cross-section of (162) 164 Interior of (70, 71) 171 Bearing point, plain bearing 172 Bearing point, plain bearing

Claims

Workpiece clamping element (70; 71) comprising a cylinder (81) and a lifting plunger assembly (100) guided in the cylinder (81) with an annular piston (102) and with an inner tube (105), wherein the lifting plunger assembly (100) carries a suction plate (111) with a workpiece support surface (113), wherein a cylinder base (83) of the cylinder (81) penetrated by the lifting plunger assembly (100), the lifting plunger assembly (100) and a cylinder jacket tube (85) of the cylinder (81) define a pressure chamber (142) and wherein the lifting plunger assembly (100) is mounted so as to be at least axially displaceable in both the cylinder base (83) and the cylinder head (84), characterized in that the suction plate (111) has suction channels (112) penetrating it in its longitudinal direction, and that a spring energy storage device is located in the suction plate (111). (137) loaded excavation plunger (131) is stored,wherein, with the spring energy storage unit (137) unloaded, the lifting plunger (131) protrudes beyond the workpiece support surface (113) and, with the lifting plunger (131) extended, the suction channels (112) are closed off by means of a support disc (132) of the lifting plunger (131). Workpiece clamping element (70; 71) according to claim 1, characterized in that the cylinder head (84), the lifting plunger group (100) and the cylinder shell (85) define a displacement space (152). Workpiece clamping element (70; 71) according to claim 1, characterized in that the stroke plunger group (100) is centered in the cylinder head (84) when the pressure space (142) is at maximum. Workpiece clamping element (70; 71) according to claim 1, characterized in that the distance of the workpiece support surface (113) relative to the ring piston (102) is adjustable. Workpiece clamping element (70; 71) according to claim 1, characterized in that a switching valve (144) arranged in a bottom distribution plate (94) of the cylinder bottom (83) is connected upstream of the pressure chamber (142). Workpiece clamping element (70; 71) according to claim 1, characterized in that the lifting plunger assembly (100) is mounted in the cylinder (81) by means of sliding bearings (171, 172). Workpiece clamping element (70; 71) according to claim 1, characterized in that, when the lifting plunger group (100) is in an extended end position (73) of the workpiece clamping element (70; 71), a pneumatic connection between the suction plate (111) and a suction port (161) is released, and that this pneumatic connection is blocked by means of the lifting plunger group (100) when the lifting plunger group (100) is in a retracted end position (72) of the workpiece clamping element (70; 71). Workpiece table (30) with a plurality of workpiece clamping elements (70; 71) according to claim 1 . Workpiece table (30) according to claim 8, characterized in that it has at least one support plate (55) with workpiece clamping elements (70; 71) attached therein. Workpiece table (30) according to claim 8, characterized in that each workpiece clamping element (70; 71) can be controlled individually.

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