FLUID FORMING APPARATUS

Abstract

A fluid forming apparatus includes a main frame having at least two tensile frame struts extending along a clamping axis and adapted to carry a tensile force along the clamping axis. An upper pressure plate and a lower pressure plate are arranged inside a frame space, and a tool space is disposed between the upper and the lower pressure plate, the tool space being adapted to take up a fluid forming tool mold. A first closure pressing unit is arranged inside the frame space such that by a pressure force exerted by the closure pressing unit, a pressure closing force along the clamping axis is exerted onto the upper and lower pressure plates, wherein the upper pressure plate, the lower pressure plate, the tool space and the first closure pressing unit are arranged in a functional serial arrangement along the clamping axis.

Claims

1-22. (canceled)

23. A fluid forming apparatus, comprising: a main frame further comprising at least two tensile frame struts extending along a clamping axis and adapted to carry a tensile force along the clamping axis, wherein the main frame circumscribes an inner frame space which extends along the clamping axis and is delimited by an upper and a lower frame plate at two sides opposed to each other along the clamping axis, and wherein the upper and the lower frame plate are connected with each other by the at least two tensile frame struts; an upper pressure plate arranged inside the frame space; a lower pressure plate arranged inside the frame space; a tool space disposed between the upper and the lower pressure plates, the tool space being adapted to take up a fluid forming tool mold; a first closure pressing unit arranged inside the frame space in a functional serial arrangement to the upper and lower pressure plates such that by a pressure force exerted by the first closure pressing unit, a pressure closing force along the clamping axis is exerted onto the upper and lower pressure plates; wherein the upper pressure plate, the lower pressure plate, the tool space and the first closure pressing unit are arranged in a serial arrangement along the clamping axis and the first closure pressing unit comprises a first fluid cavity, the first fluid cavity being delimited by a first flexible membrane and being connected to a pressurized closure pressing fluid source.

24. The fluid forming apparatus according to claim 23, wherein the upper and the lower pressure plates comprise a tool surface area lying in a plane perpendicular to the clamping axis and facing towards the tool space and wherein the first membrane comprises either or both a pressurized membrane face having a size of at least 75% of the tool surface area or a rectangular geometry in a plane perpendicular to the clamping axis.

25. Fluid forming apparatus according to claim 23, wherein the first membrane is composed of a plurality of membranes arranged adjacent to each other and lying in a plane perpendicular to the clamping axis.

26. The fluid forming apparatus according to claim 23, further comprising a first stamp plate, the first stamp plate extending perpendicular to the clamping axis and being displaceable along the clamping axis, wherein the first membrane has a first membrane surface facing towards the fluid cavity and a second membrane surface abutting the first stamp plate.

27. The fluid forming apparatus according to claim 23, further comprising a second closure pressing unit arranged inside the frame space in a functional serial arrangement to the upper and lower pressure plate such that by a pressure force exerted by the second closure pressing unit, a pressure closing force along the clamping axis is exerted onto the upper and lower pressure plates; wherein the first and the second closure pressing unit, the upper pressure plate, the lower pressure plate, and the tool space are arranged in a serial arrangement along the clamping axis; and wherein the second closure pressing unit comprises a single or a plurality of second fluid cavities and a corresponding single or a plurality of second flexible membranes, each of the second fluid cavities being delimited by a second flexible membrane and connected to a source of a pressurized fluid.

28. The fluid forming apparatus according to claim 23, further comprising a second closure pressing unit arranged inside the frame space in a functional serial arrangement to the upper and lower pressure plate such that by a pressure force exerted by the second closure pressing unit, a pressure closing force along the clamping axis is exerted onto the upper and lower pressure plates; wherein the first and the second closure pressing unit, the upper pressure plate, the lower pressure plate, and the tool space are arranged in a serial arrangement along the clamping axis; and wherein the second closure pressing unit comprises a plurality of second fluid cavities, the second fluid cavities being arranged in an adjacent arrangement in a direction perpendicular to the clamping axis, and wherein a piston is disposed in each of the fluid cavities, the piston sealing the fluid cavity, respectively, and being moveable in a direction along the clamping axis in relation to the fluid cavity.

29. The fluid forming apparatus according to claim 23, further comprising a first shifting unit, the first shifting unit being adapted to be shifted from a shifting minimum height to a shifting maximum height and vice versa, wherein the shifting maximum height minus the shifting minimum height define a shifting amplitude of the first shifting unit; wherein the first closure pressing unit is adapted to have a closure pressing maximum height defined by a maximum deflection of the first membrane and a closure pressing minimum height defined by the thickness of the membrane, wherein the closure pressing maximum height minus the closure pressing minimum height define a closure pressing amplitude of the first closure pressing unit; wherein the closure pressing minimum height, the closure pressing maximum height, the shifting minimum height, and the shifting maximum height are oriented in the direction of the clamping axis; wherein the first shifting unit, the upper pressure plate, the lower pressure plate, the tool space, the first closure pressing unit, and the first shifting unit are arranged in a serial arrangement along the clamping axis; and wherein the shifting amplitude is at least two times the closure pressing amplitude.

30. The fluid forming apparatus according to claim 23, further comprising a first shifting unit, the first shifting unit comprising a first recess unit having a first side comprising a at least one recess and a first protrusion unit having a first side comprising at least one protrusion, wherein the first side of the first recess unit and the first side of the first protrusion unit face each other; wherein the first recess unit, the first protrusion unit, the upper pressure plate, the lower pressure plate, the tool space, the first closure pressing unit, and the first shifting unit are arranged in a serial arrangement along the clamping axis; and wherein the first recess unit and the first protrusion unit extend along a direction perpendicular to the clamping axis and are displaceable in relation to each other in the direction perpendicular to the clamping axis and in a direction along the clamping axis, such that in a first, open position the at least one protrusion of the first protrusion unit is positioned inside the recess to establish a short height of the first shifting unit in a direction of the clamping axis, and in a second, closed position the at least one protrusion of the first protrusion unit is supported on the first side of the first recess unit sideways from the recess to establish a large height of the first shifting unit in the direction along the clamping axis, the large height being larger than the short height.

31. The fluid forming apparatus according to claim 30, further comprising a second shifting unit, the second shifting unit comprising a second recess unit having a first side comprising a at least one recess and a second protrusion unit having a first side comprising at least one protrusion, wherein the first side of the second recess unit and the first side of the second protrusion unit face each other; wherein the first recess unit, the first protrusion unit, the second recess unit, the second protrusion unit, the upper pressure plate, the lower pressure plate, the tool space and the first closure pressing unit are arranged in a serial arrangement along the clamping axis; and wherein the second recess unit and the second protrusion unit extend along a direction perpendicular to the clamping axis and are displaceable in relation to each other in the direction perpendicular to the clamping axis and in a direction along the clamping axis, such that in an open position the at least one protrusion of the second protrusion unit is positioned inside the recess to establish a short height of the second shifting unit in a direction of the clamping axis, and in a closed position the at least one protrusion of the second protrusion unit is supported on the first side of the second recess plate sideways from the recess to establish a large height of the second shifting unit in the direction along the clamping axis, the large height being larger than the short height.

32. The fluid forming apparatus according to claim 31, wherein each of the first and the second recess unit comprises at least two recesses and the first and the second protrusion unit comprises at least two protrusions, and wherein each of the protrusions is positioned inside one of the recesses in the open position and each of the protrusions is supported on the first side of the first and second recess unit, respectively, sideways from one of the recesses in the closed position.

33. The fluid forming apparatus according to claim 31, wherein each of the first and the second recess units comprises at least one recess and at least one protrusion and the first and the second protrusion unit comprises at least one protrusion and at least one recess, and wherein each of the protrusions is positioned inside one of the recesses in the open position and each of the protrusions is supported on the first side, respectively, sideways from the at least one recess in the closed position.

34. The fluid forming apparatus according to claim 31, wherein the first recess unit or the first protrusion unit is defined by the upper frame plate or the second recess unit or the second protrusion unit is formed by the lower frame plate, and wherein the upper or lower frame plate comprises a plurality of struts being arranged in a distance to each other such that a space is provided between two adjacent struts, wherein the space forms a recess.

35. The fluid forming apparatus according claim 23, further comprising a fluid forming tool mold, wherein the fluid forming tool mold comprises an upper mold part and a lower mold part, the upper and lower mold part being positioned one on the other in relation to the clamping axis such that an abutting face of the upper mold part faces an abutting face of the lower mold part, the abutting face of the upper mold part establishes an upper sealing surface, and the abutting face of the lower mold part establishes a lower sealing surface; wherein the sealing surfaces surround a fluid forming cavity provided in an abutting face of one of the upper and lower mold part; wherein the corresponding other part of the upper and lower mold part comprises a fluid channel connected to a pressurized molding fluid source, the fluid channel having an opening in the abutting face opposed to the fluid forming cavity; and wherein the upper or lower mold part comprising the fluid forming cavity further comprises a protruding section which protrudes above the sealing surface of the upper or lower mold part comprising the fluid forming cavity in the direction towards the respective other lower or upper mold part.

36. The fluid forming apparatus according to claim 35, further comprising a pressure control unit adapted to control the fluid forming pressure to correlate to the fluid closing pressure or to control the fluid forming pressure to be at least 125%, of the fluid closing pressure; wherein the pressurized molding fluid source has a pressure higher than the pressurized closure pressing fluid source or the fluid forming tool mold defines a work piece space such that a work piece is in direct contact to the upper sealing surface and the lower sealing surface; and wherein a pressurized molding fluid is applied via the fluid channel and the pressurized molding fluid is in direct contact to the work piece when positioned in the work piece space.

37. The fluid forming apparatus according to claim 35, further comprising a pressure control unit adapted to control the fluid forming pressure to correlate to the fluid closing pressure or to control the fluid forming pressure to be at least 125%, of the fluid closing pressure; wherein the pressurized molding fluid source has a pressure higher than the pressurized closure pressing fluid source or the fluid forming tool mold defines a work piece space such that a work piece is in direct contact to the upper sealing surface and the lower sealing surface; and wherein the sealing surface comprises a first surface section and a second surface section, the first and second surface section being arranged in a distance to each other with respect to a direction along the clamping axis.

38. The fluid forming apparatus according to claim 35, wherein the upper or lower fluid forming tool mold part is guided for a horizontal movement between a forming position, wherein the fluid forming tool form part is positioned between the upper and the lower frame plate, and a work piece removal position, which is horizontally distanced from the forming position.

39. The fluid forming apparatus according to claim 35, wherein the fluid forming tool mold defines a work piece space such that the work piece is in direct contact to one of the upper sealing surface and the lower sealing surface, wherein an elastic molding membrane is disposed between the work piece and the corresponding other of the lower and upper sealing surface, and wherein a pressurized molding fluid is applied via the fluid channel and the pressurized molding fluid transfers a molding pressure via the molding membrane to the work piece such that the pressurized molding fluid is not in direct contact to the work piece when positioned in the work piece space.

40. The fluid forming apparatus according to claim 23, wherein the first closure pressing unit is disposed between the upper frame plate and the upper pressing plate or between the lower frame plate and the lower pressure plate; wherein the first closure pressing unit is disposed between the upper frame plate and the upper pressing plate and wherein the second closure pressing unit is disposed between the lower frame plate and the lower pressure plate, the first closure pressing unit and the first shifting unit are disposed between the upper frame plate and the upper pressing plate, wherein the second closure pressing unit is disposed between the lower frame plate and the lower pressure plate, or the first closure pressing unit and the first shifting unit are disposed between the upper frame plate and the upper pressing plate, wherein the second closure pressing unit and the second shifting unit are disposed between the lower frame plate and the lower pressure plate.

41. The fluid forming apparatus according to claim 23, wherein the tool space is adapted for taking up a sheet material for an external fluid forming process.

42. The fluid forming apparatus according to claim 23, wherein a fluid forming tool is arranged inside the tool space, the fluid forming tool comprising a first section having a molding cavity and a second section having a pressurized fluid line, wherein the first and second section are adapted to sealingly engage a sheet material such that the sheet material is sealingly clamped along a peripheral clamping line between the first and the second section, and wherein the clamping line circumscribes the molding cavity.

43. The fluid forming apparatus according to claim 42, further comprising a pressure control unit adapted to control the pressure of the pressurized closure pressing fluid source applied to the membrane to such a level as to apply a clamping force to the sheet material allowing a small fluid leakage of pressurized forming fluid and a small relative movement of the sheet material through the clamping line.

44. A method of fluid forming a metal sheet, the method comprising the steps of: inserting the metal sheet into an open space between an upper mold part and a lower mold part of a fluid forming tool mold; fixing and sealing the metal sheet between the upper and the lower mold part by applying a sealing pressure along a clamping axis; applying the sealing pressure by applying a fluid pressure into a fluid cavity delimited by a pressure plate and a membrane, the membrane extending in a direction perpendicular to the clamping axis; applying a fluid forming pressure via fluid line formed in one of the upper and lower mold part; and molding the metal sheet into a mold cavity by the fluid forming pressure, wherein the mold cavity is formed in the other part of the upper and lower mold part.

45. The method of claim 44, further comprising the step, after the inserting step, of: shifting the upper and lower mold part in relation to each other to reduce the distance between the upper and lower mold part by a shifting action, wherein the shifting step is accomplished by: a first relative movement of a recess plate in relation to a protrusion plate in a direction perpendicular to the clamping axis, the recess plate having a first side and a second side and the protrusion plate having a first side and a second side, the first relative movement moving the recess plate in relation to the protrusion plate in a position, wherein a recess in the second side of the recess plate is in line with a protrusion of the second side of the protrusion plate with respect to the clamping axis, and a second relative movement of the recess plate in relation to the protrusion plate in a direction along the clamping axis, the second relative movement moving the recess plate in relation to the protrusion plate in a position, wherein the protrusion is positioned inside the recess.

46. The method of claim 44, further comprising the step of: controlling the sealing pressure to be maintained at such a level to allow a movement of the metal sheet through a clamping line established between the metal sheet and the upper mold part or the metal sheet and the lower mold part, wherein the movement is induced by a deformation of the metal sheet caused by the fluid forming pressure.

47. The method of claim 44, wherein the metal sheet conducts a small movement through a clamping line established between the metal sheet and the upper mold part or the metal sheet and the lower mold part.

48. The method of claim 47, further comprising the step of: controlling the sealing pressure to be maintained at such a level to allow a leakage of fluid under the fluid forming pressure to pass through a clamping line established between the metal sheet and the upper mold part or the metal sheet and the lower mold part.

49. The method of claim 44, wherein the fluid forming pressure fluid passes through a clamping line established between the metal sheet and the upper mold part or the metal sheet and the lower mold part with a small leakage to lubricate the movement of the metal sheet through the clamping line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Preferred embodiments of the invention are described with reference to the appending figures. In the figures:

[0065] FIG. 1 is a sectional front view of a first preferred embodiment of the invention;

[0066] FIG. 2 is a sectional front view of a second preferred embodiment of the;

[0067] FIG. 3a is a sectional front view of a third preferred embodiment of the invention in an open condition;

[0068] FIG. 3b is a sectional front view of the embodiment of FIG. 3a in an intermediate position;

[0069] FIG. 3c is a sectional front view of the embodiment of FIG. 3a in a closed position;

[0070] FIG. 4 is a partial-cut side view of the embodiment of FIG. 1;

[0071] FIG. 5 is a top view of a pressure plate having a rectangular membrane; and

[0072] FIG. 6 is a sectional side view of a pressure plate having multiple membranes.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0073] Making reference first to FIG. 1, a frame is shown comprising an upper frame plate 11, a lower frame plate 12, and tensional struts 13, 14. The upper and lower frame plate 11, 12 and the tensional struts 13, 14 circumscribe a tool space 15. The tensional struts 13, 14 are integrally formed as a cutout frame plate. Multiple identical cutout frame plates are arranged side-by-side and parallel to each other to form the frame. The multiple cutout frame plates are mounted to each other and held in a distanced arrangement to each other by bolts with sleeves 16a, 16b, 16c, 16d arranged in the corner sections of the cutout frame plates. The cutout in the frame plates provides the tool space 15.

[0074] In the tool space 15, a fluid forming tool mold comprising an upper molding plate 21 and a lower molding plate 22 is positioned. The upper molding plate 21 and the lower molding plate 22 abut each other along a sealing face 23. It is understood that a sheet metal to be formed in a fluid forming process is inserted between the upper and lower fluid forming tool mold plates 21, 22 and thus seals versus the upper and the lower mold plates 21, 22 along said line 23.

[0075] In the upper mold plate 21, a pressure channel 23a is present, which serves to direct a pressurized fluid into the middle of the plate and which opens into a cavity 24 provided in the lower mold plate. Thus, a sheet metal placed between the upper and lower mold plates 21, 22 can be deformed into the recess 24 by applying a pressure via the pressure channel 23a.

[0076] Above the upper mold plate 21, an upper pressure plate 31 is positioned in abutting contact to the upper mold plate 21. The upper pressure plate 31 sealingly engages a membrane 32 along the circular periphery 32a of the membrane. The membrane is embedded in a cavity having a circular cross section along a clamping axis 1 oriented vertically. The membrane seals a fluid space 33, which is present between the membrane and the upper surface of the upper pressure plate 31. A fluid channel 34 is provided, which opens into said fluid space below the membrane. Via said fluid channel 34, a pressurized fluid can be directed into the fluid space 33 and thus, a pressure exerted onto the membrane.

[0077] The membrane 32 is disposed between the fluid space 33 and a stamp plate 35. The stamp plate 35 has a circular cross section with reference to the clamping axis 1 with a diameter corresponding to the diameter of the membrane of being slightly smaller than the membrane. The stamp plate 35 is guided by lateral guiding elements 36a, 36b to allow for a vertical movement along the clamping axis of the stamp plate 35. The stamp plate 35 abuts an upper holding plate 41, which is supported within the upper frame plate 11 via a further distance plate 42. Two lateral clamps 43a, 43b secure the upper pressure plate 31 and the lateral guiding members 36a, 36b to the upper holding plate 41 in such a way as to allow a vertical movement of the upper pressure plate 31 in relation to the upper holding plate 41.

[0078] The apparatus shown in FIG. 1 has a mirror-symmetrical arrangement of the components with reference to a horizontal plane coinciding with the sealing plane 23. Thus, a lower pressure plate 51, a fluid space 53, a membrane 52, a lower stamp plate 55, a lower holding plate 61, a lower distance plate 62, lateral guiding elements 56a, 56b, and lateral clamps 63a, 63b are present on the lower part adjacent to the lower mold part in a serial arrangement. By this, a certain amplitude of opening and closing is possible by applying a pressurized fluid into the fluid spaces 33, 53, thus effecting a longitudinal movement of the stamp plates with 35, 55 a downward movement of the lower stamp plate 55 and an upwards movement of the upper stamp plate 35. By this, a closing force can be applied onto the sealing face 23 to seal against a sheet metal inserted along this face. Reducing the pressure will allow opening of the mold to take out a molded part.

[0079] FIG. 2 shows a second embodiment of the invention. The second embodiment is configured identical to the first embodiment in the lower part with reference to a lower mold part 122, a lower pressure plate 151, a fluid space 153, a membrane 152, a stamp plate 155, a holding plate 161, and a distance plate 162.

[0080] Further, a similar upper molding part 121 defining a sealing face for inserting a sheet metal between the upper and lower mold parts 121, 122 is configured identical to the first embodiment of FIG. 1.

[0081] In contrast to the first embodiment, on the upper side of the fluid forming tool mold 121, 122, a closure pressing unit is positioned, which is composed of a first cylinder block plate 171, wherein a multiple cylindrical recesses 172a, 172b, 172c, 172d, 172e are provided, which are open to the upper face of said cylindrical plate 171. Each of the cylindrical recesses 172a-172e is connected to a fluid channel 171a in the cylinder plate 171. By this a pressure can be exerted into each of the recesses 172a-172e via the fluid channel 171a.

[0082] Pistons 182a-182e are positioned in each of the recesses 172a-172e. The pistons 182a-182e are sealingly guided for a vertical movement in the recesses 172a-172e along a clamping axis 101.

[0083] The pistons 182a-182e are loosely supported by an upper supporting plate 191. By applying a pressure via the channel 171a, the pistons 182a-182e thus can move vertically inside the recesses 172a-172e to thus allow opening and closing of the fluid forming tool mold and to apply a closing pressure to effect a sealing against a sheet metal inserted along face 123. The upper supporting plate 191 is supported via a distance plate 192 at the upper frame plate.

[0084] Making reference to FIG. 3a, a third embodiment is shown in an open position. In such open position, a sheet metal can be inserted between the two mold parts 221, 222. The embodiment shown in FIG. 3a is similar with regard to an upper pressure plate 231 and a lower pressure plate 251, an upper fluid space 233 and a lower fluid space 253, an upper membrane 232 and lower membrane 252, an upper stamp plate 235 and a lower stamp plate 255, and an upper holding plate 241 and a lower holding plate 261.

[0085] The third embodiment is different from the embodiment shown in FIG. 1 in that a shifting unit is provided between the upper holding plate 241 and the upper frame plate 211 and a further shifting unit is provided between the lower holding plate 261 and the lower frame plate 212.

[0086] The upper shifting unit comprises a protrusion plate 291 having a total of four protrusions 292a-292d rising from the upper face of the protrusion plate in a vertical direction. Further, the shifting unit comprises a recess plate 293, comprising a plurality of recesses 294a-294d. The recess plate 293 abuts the upper frame plate 211 and is thus supported for vertical forces thereon.

[0087] In FIG. 3a, an open position of the apparatus is shown, wherein the protrusions 292a-292d are fully taken up by the recesses 294a-294d. As can be seen, the protrusion plate 291 is thus fully supported by the recess plate 293 and the height of the protrusion plate and the recess plate is a minimum height in this position.

[0088] FIG. 3b shows the embodiment of FIG. 3a in a second position. In this second position, the protrusion plate 291 and the recess plate 293 are displaced in relation to each other in a vertical direction. By this, the protrusions 292a-292d are driven out of the recesses and the fluid forming tool mold is closed by this vertical movement of both the upper mold part and the lower mold part implied by the vertical movement of the protrusion plate 291 of the upper shifting device and the corresponding protrusion plate of the lower shifting device.

[0089] FIG. 3c shows a third position, which is a closed and locked position of the apparatus. In this third position, the protrusion plate 291 is moved laterally in relation to the recess plate 293 when compared to FIG. 3b. By this, the protrusions 292a-292d come into abutting contact with the lower side surface of the recess plate sideways from the recesses 294a-294d. By this, a vertical force can be transferred from the protrusion plate to the recess plate and thus a fluid forming process can be conducted in the apparatus. It is understood that for a proper sealing effect, starting from this position, a pressurized fluid can be applied to the fluid space of the pressure closing unit and thus a small shifting induced by this pressurized fluid via the membranes will exert the high closing and sealing force required for the fluid forming process.

[0090] In the lateral view according to FIG. 4 a total of four cutout frame plates 313 can be seen which are held in parallel distanced position by bolts and sleeves 316 in the upper and lower corner sections of the cutout frame plates. The distance between two adjacent cutout frame plates is dimensioned such that protrusions of a recess plate 493 may be inserted between the cutout frame plates in the area of the upper or lower frame plate in a shifted arrangement of the recess plate, as shown for the bottom recess plate 493 in FIG. 4. In an extended position, the protrusions of a recess plate 393 may abut the struts of the cutout frame plates forming the upper or lower frame plate, as shown for the upper recess plate 393 in FIG. 4. By this, an upper molding plate and an upper pressing plate, schematically shown and referenced 330, and a lower molding plate and a lower pressing plate, schematically shown and referenced 350 can be axially driven apart along the longitudinal axis of the fluid forming apparatus.

[0091] In FIG. 5 a top view of a pressing plate 431 according to a further preferred embodiment is shown. The pressing plate comprises a membrane 432. As can be seen, the membrane 432 has a rectangular shape and thus, the pressing plate comprises a cavity having a rectangular cross section corresponding to the shape of the membrane. As can be further seen, said rectangular shape and cross section comprise rounded corners to facilitate sealing of the membrane versus said cavity. The pressure plate according to this embodiment may be installed as upper or lower pressing plate.

[0092] In FIG. 6 a sectional side view of a pressing plate 531 according to a further preferred embodiment is shown. The pressing plate 531 comprises a total of 36 membranes 532. The membranes 532 are arranged in a matrix-like arrangement in rows and line. However, it is understood that the membranes 532 may be arranged in different preferred arrangements like, e.g., an arrangement where the membranes in adjacent rows and line are shifted versus each other. The membranes 532 may have a circular or a rectangular shape or another preferred shape. The pressing plate comprises a plurality of thirty-six cavities 533 having a cross section corresponding to the shape of the membranes 532. The pressure plate according to this embodiment may be installed as upper or lower pressing plate.