Rounded Sonotrode

Abstract

The invention provides a sonotrode (100) for welding a material, the sonotrode (100) comprising a welding section (110) configured for contacting the material, wherein the welding section (110) defines a rounded shape (111) in a cross-section parallel to a longitudinal axis (A) of the sonotrode (100), wherein the rounded shape (111) approximates a circular sector (20), wherein the circular sector (20) has a central angle α.sub.c selected from the range of 25°-300°, and wherein the circular sector (20) has a central radius r.sub.c selected from the range of 5-30 mm, and wherein the sonotrode (100) has a width W perpendicular to the longitudinal axis (A) [and to the cross-section], wherein W is selected from the range of 10-100 mm.

Claims

1. A sonotrode (100) for welding a material (10), the sonotrode (100) comprising a welding section (110) configured for contacting the material (10), wherein the welding section (110) defines a rounded shape (111) in a cross-section parallel to a longitudinal axis (A) of the sonotrode (100), wherein the rounded shape (111) approximates a circular sector (20), wherein the circular sector (20) has a central angle α.sub.c selected from the range of 25°-300°, and wherein the circular sector (20) has a central radius r.sub.c selected from the range of 5-30 mm, and wherein the sonotrode (100) has a width W perpendicular to the longitudinal axis (A), wherein W is selected from the range of 10-100 mm.

2. The sonotrode (100) according to claim 1, wherein in a cross-section the welding section (110) defines an outline (112), wherein at least part of the outline (112) has a radius of curvature selected from the range of 5-30 mm.

3. The sonotrode (100) according to claim 1, wherein the welding section (110) has a welding shape approximating a semi-cylindrical shape, wherein the semi-cylindrical shape has a cylinder height h.sub.c perpendicular to a longitudinal dimension of the sonotrode (100), wherein the cylinder height h.sub.c is selected from the range of 10-100 mm, and wherein the semi-cylindrical shape has a cylinder radius r.sub.c selected from the range of 5-30 mm, wherein h.sub.c>r.

4. The sonotrode (100) according to claim 1, wherein the welding section (110) defines the circular sector (20).

5. The sonotrode (100) according to claim 1, wherein the width W is selected from the range of 20-60 mm.

6. The sonotrode (100) according to claim 1, wherein the central radius r.sub.c is selected from the range of 7-15 mm.

7. The sonotrode (100) according to claim 1, wherein the sonotrode (100) comprises a sonotrode material (105) selected from the group comprising stainless steel, titanium, and aluminum.

8. The sonotrode (100) according to claim 1, having a length (L), wherein the sonotrode (100) comprises a first part (121), a second part (122), and the welding section (110), wherein the length (L) is defined by the first part (121), the second part (122), and the welding section (110), wherein the second part (122) is configured between the first part (121) and the welding section (110), wherein the second part (122) has a thickness (T) and a second part width (WL), wherein the welding section (110) tapers from the second part (122) to a welding section top (115), wherein the thickness (T) and the second part width (WL) are constant over at least 40% of the length (L) of the sonotrode (100), wherein WL=W, and wherein r.sub.c<W≤4*r.sub.c.

9. The sonotrode (100) according to claim 1, wherein the sonotrode (100) is an unslotted sonotrode (101).

10. The sonotrode (100) according to claim 1, wherein the central angle α.sub.c is selected from the range of 40°-300°.

11. The sonotrode (100) according to claim 1, wherein the central angle α.sub.c is selected from the range of 100°-300°.

12. A method for welding a material using a sonotrode (100) according to claim 1, wherein the method comprises: (i) arranging the sonotrode (100) on the material (10); and (ii) providing ultrasonic vibrations with the sonotrode (100).

13. The method according to claim 12, wherein the sonotrode (100) is functionally coupled to a consolidator (200), wherein the consolidator (200) is arranged downstream from the sonotrode (100) at a distance d.sub.1 from the sonotrode (100), wherein d.sub.1≤8 cm.

14. The method according to claim 12, wherein the material (10) comprises a curved panel, and wherein the material comprises a polymer composite material.

15. Use of the sonotrode (100) according to claim 1 to weld a material (10).

16. Use according to claim 15, wherein the material (10) comprises a curved panel.

17. Use according to claim 15, wherein the material (10) comprises a thermoplastic composite laminate.

18. Use according to claim 17, wherein the material (10) comprises an aerospace material.

19. A sonotrode welding device comprising the sonotrode (100) according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which: FIG. 1A-D schematically depict embodiments of the sonotrode. FIG. 2A-B schematically depict experimental data obtained with a comparative example of the method. FIG. 3A-C schematically depict experimental data obtained with embodiments of the sonotrode and the method. The schematic drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0077] FIG. 1A-D schematically depict embodiments of the sonotrode 100 for welding a material 10. The sonotrode 100 comprises a welding section 110 configured for contacting the material 10. In particular, the welding section 110 defines a rounded shape 111 in a cross-section parallel to a longitudinal axis A of the sonotrode 100. The rounded shape 111 may approximate a circular sector 20. In embodiments, the circular sector 20 may have a central angle α.sub.c selected from the range of 135°-210°. In the depicted embodiment, the central angle α.sub.c may be about 180°. In further embodiments, the circular sector 20 may have a central radius r.sub.c selected from the range of 5-30 mm, especially from the range of 7-15 mm. In embodiments, The sonotrode 100 may have a width W perpendicular to the longitudinal axis A (and to the cross-section), especially wherein W is selected from the range of 10-100 mm, especially from the range of 20-60 mm.

[0078] In the depicted embodiment, the welding section 110 (further) has a welding shape approximating a semi-cylindrical shape. In particular, the semi-cylindrical shape has a cylinder height perpendicular to a longitudinal dimension of the sonotrode, especially wherein the cylinder height is selected from the range of 10-100 mm. In particular, the cylinder height h.sub.c may be identical to the width W of the sonotrode. Further, the semi-cylindrical shape may have a cylinder radius selected from the range of 5-30 mm. In particular, the cylinder radius may be identical to the central radius r.sub.c.

[0079] FIG. 1A further schematically depicts an embodiment wherein the sonotrode is an unslotted sonotrode 101.

[0080] In embodiments, the sonotrode 100 may comprise a sonotrode material 105 selected from the group comprising stainless steel, titanium, and aluminum.

[0081] In particular, in the depicted embodiment, the sonotrode 100, especially the welding section 110, may define the circular sector 20.

[0082] In the depicted embodiments, the welding section 110 defines an outline 112, especially wherein at least part of the outline 112 has a radius of curvature selected from the range of 5-30 mm. The outline 112 may especially coincide with a circular arc defined by the circular sector 20.

[0083] In the depicted embodiment, the sonotrode has a thickness T perpendicular to the longitudinal axis A and the width W, wherein the thickness may vary along the longitudinal axis and/or the width W, especially along the longitudinal axis. In particular, the thickness T may, in the depicted embodiment, have a constant value along approximately 40% of the sonotrode along the longitudinal axis. In particular, the constant value for this thickness T is equal to twice the radius r.sub.c of the circular sector.

[0084] In further embodiments, the thickness T may have a constant value along at least 10% of the sonotrode along the longitudinal axis, such as along at least 20%, especially along at least 30%, such as along at least 40%, especially along at least 50%.

[0085] In particular, in embodiments the sonotrode 100 may comprise a first part 121, a second part 122, and the welding section 110. The length L may be defined by the first part 121, the second part 122, and the welding section 110. Yet further, the second part 122 may be configured between the first part 121 and the welding section 110. As indicated above, the first part 121, the second part 122, and the welding section 110 may be a single body, especially of metal or metal alloy. The second part 122 may have a second part thickness T and a second part width WL. Further, the welding section 110 tapers from the second part 122 to a welding section top 115. Hence, there may be an essentially stepless change from second part to welding section to the welding section top 115. Hence, the largest width of the welding section and the largest thickness of the welding section are in embodiments identical to the thickness and the width of the second part. Especially, the second part thickness T and the second part width WL may be constant over at least 40% of the length L of the sonotrode 100, such as at least 50%. Further, in specific embodiments WL=W. Further, especially good results may be obtained when r.sub.c<W≤4*r.sub.c, such as 1.5*r.sub.c<W≤4*r.sub.c.

[0086] The first part may have a width larger than the second part width. Further, the first part may have a thickness larger than the second part. Especially, this width and thickness are gradually achieved. In other words, the first part tapers to its maximum width and thickness. In this way, there may be an essentially stepless change from the second part to the maximum width and thickness parts of the first part.

[0087] FIG. 1B schematically depicts an embodiment wherein the central angle α.sub.c may be about 135°. Similarly, FIG. 1C may schematically depict an embodiment wherein the central angle α.sub.c may be about 290°.

[0088] FIG. 1D schematically depicts an embodiment of the sonotrode 100 during operation. In the depicted embodiment, the sonotrode 100 is depicted on a material 10. Further, the sonotrode 100 is functionally coupled to a consolidator 200, wherein the consolidator. Hence, in embodiments, the sonotrode may be (configured for) functionally coupled (coupling) to a consolidator 200.

[0089] The material 10 may comprise a first adherend 11 (or “top adherend”), a second adherend 12 (or: “bottom adherend”), and an energy director 16. In particular, the material may further comprise a welding line 15, wherein, during operation, the sonotrode may be moved over the welding line 15 to weld the first adherend and the second adherend to one another.

[0090] FIG. 1D further schematically depicts the method for welding a material using a sonotrode 100 according to the invention. The method comprises: arranging the sonotrode 100 on (an upper surface of) the material 10, especially on the welding line 15; and providing ultrasonic vibrations with the sonotrode 100. In particular, the method may comprise exerting mechanical vibrations onto the upper surface of the first adherend 11 and thus indirectly applying mechanical energy to the energy director 16 located at the welding line 15. The method may further comprise moving the sonotrode 100 along the material 10, especially along the welding line 15.

[0091] In further embodiments, the sonotrode 100 may be functionally coupled to a consolidator 200, especially wherein the consolidator 200 is arranged downstream from the sonotrode 100 at a distance d.sub.1 from the sonotrode 100, especially wherein d.sub.1≤8 cm.

[0092] In further embodiments, the material 10 may comprise a curved panel.

[0093] FIG. 1D further schematically depicts an embodiment of the use of the sonotrode 100 according to the invention to weld a material 10. In embodiments, the material 10 may especially be a curved panel. In further embodiments, the material 10 may comprise a thermoplastic composite laminate. In yet further embodiments, the material 10 may comprise an aerospace material.

[0094] In particular, in the depicted embodiment, the sonotrode 100 may, during operation, move towards the right, followed by the consolidator 200 at the distance d.sub.1. Hence, the part left of the hyphened line has been exposed to the sonotrode, whereas the part right of the hyphened line has not yet. Hence, the welding line may have a first thickness t.sub.1 right of the hyphened line, and a second thickness t.sub.2 left of the hyphened line, wherein t.sub.2<t.sub.1. For visualizational purposes, the welding line left of the hyphened line has been depicted thinner; it will be clear to the person skilled in the art, however, that the thickness of the first adherent 11 and of the second adherent 12 essentially does not change due to the sonotrode (application).

[0095] Experiments

[0096] FIG. 2A-3C relate to experimental observations obtained using a comparative example and the sonotrode of the invention.

[0097] Materials

[0098] The experiments were performed with thermoplastic composite laminates made out of carbon fiber fabric (five harness satin weave) impregnated with polyphenylene sulfide powder (CF/PPS semipreg), CF 0286 127 Tef4 43% from Toray Advanced Composites, the Netherlands. The laminates were stacked according to a [0/90].sub.3, sequence and consolidated in a hot adherend press for 20 min at 320° C. and 1 MPa pressure. The consolidated laminates had a size of 580 mm by 580 mm, and a thickness of approximately 1.85 mm. Adherends measuring 220 mm by 101.6 mm were cut from the consolidated laminates for the continuous welding experiments. For the adherends the main apparent fiber direction was in the 101.6 mm-direction. A 0.20 mm-thick woven polymer mesh energy director was used for all experiments to focus heat generation at the welding interface. The PPS woven mesh (product name PPS100) was supplied by PVF GmbH, Germany.

[0099] Procedure

[0100] The experiments were performed with a welding machine that consists of a stiff frame with a X-Y table on a guiding system allowing automatic translation in its x direction and an off-the-shelf ultrasonic welder from Herrmann Ultrasonics of the type VE20 SLIMLINE DIALOG 6200. The ultrasonic welder records feedback data (such as time, power consumption, energy, vertical sonotrode displacement, and amplitude) at a 1 kHz frequency. The operating frequency of the welder is 20 kHz. The welding train consisted of the converter, booster and sonotrode.

[0101] Two sonotrode types were compared. A comparative ‘common’ flat surface sonotrode with a contact surface of 15 mm in width, and the sonotrode of the invention. Specifically, the sonotrode of the invention had a rounded contact surface with a radius of 7.5 mm. For both sonotrodes the same peak-to-peak vibrational amplitude of 80 μm was used. For the welds made with the comparative sonotrode a welding force of 500 N was used and for the rounded sonotrode a welding force of 1000 N was used. A copper consolidator block of 40 mm (width) by 30 mm was used, which applied a consolidation force of 800 N, corresponding to a pressure of 1.6 MPa. For the comparative sonotrode three consolidation distances (d.sub.1) were used in different experiments: 18.4 mm, 63 mm, and 86.4 mm. For the rounded sonotrode the consolidation distance was 9.5 mm from the middle of the sonotrode, corresponding to 2.5 mm directly from the edge of the sonotrode.

[0102] The 220-mm wide adherends were welded together over an overlap width of 12.7 mm. The CF/PPS top and bottom adherends were kept in place by two aluminum bar clamps. A mesh energy director was placed in between the two adherends. In order to consistently ensure a fixed overlap width of 12.7 mm between the two adherends, alignment pins were used. During the welding process the X-Y table moved underneath the sonotrode in X-direction over a welding distance of 205 mm as shown in FIG. 1, while the sonotrode applied the static welding force and the high-frequency vibrations.

[0103] To visualize void formation, void closure and squeeze flow for the comparative sonotrode during the continuous welding process the welding process was stopped prematurely (before welding the entire overlap), and cross-sectional micrographs were cut from different locations of the overlap and analyzed using a microscope. In other words, the movement of the table was stopped, the sonotrode was retracked and the comparative consolidator remained stationary applying a consolidation pressure. This made it possible to cut cross-sectional micrographs from different phases of the welding process: the presence of voids and the squeeze flow in between the sonotrode and the consolidator (no consolidation yet), directly under the consolidator (consolidating), and behind the consolidator (underwent consolidation). For the sonotrode of the invention the void formation and squeeze was visualized by welding with and without a consolidator since the consolidator had to be placed close to the sonotrode.

[0104] Five evenly spaced thermocouples were placed along the overlap. Specifically, the thermocouples were spaced with 40 mm between adjacent thermocouples, and the outer two thermocouples were spaced 30 mm from the edge of the adherend. The same welded adherends were used for a single lap shear test. The thermocouples were placed in between the bottom adherend and energy director. The temperature at the weld interface was measured using K-type thermocouples supplied by Tempco (product number 2-2200-0004 and description GG220-2K-0). An analog output K-type thermocouple amplifier was used from Adafruit with product number AD8495 sampling the temperature at 1 kHz. The thermocouples had a wire diameter of 0.10 mm. A 25 moving average filter was applied to the measured temperature data in order to filter out small high frequency fluctuations.

[0105] FIG. 2A-B schematically depict the experimental observations obtained using the comparative example.

[0106] The experiments have been performed with a comparative sonotrode 100b either without a functionally coupled consolidator 200, or with functionally coupled consolidators 200 arranged at distances of 18.4 mm, 63 mm, or 86.4 mm from the comparative sonotrode 100b. The experiments performed with a consolidator 200 outperformed those without a consolidator 200, and the larger the distance between the consolidator 200 and the comparative sonotrode 100b the better the observed results were, i.e., the experiments with the consolidator 200 arranged at a distance of 86.4 mm from the comparative sonotrode 100b outperformed those wherein the distance was 63 mm, which outperformed those where the distance was 18.4 mm.

[0107] FIG. 2A schematically depicts the experimental setup, wherein the comparative sonotrode 10b is functionally coupled to a consolidator 200 at a distance d.sub.1, wherein d.sub.1 is 86.4 mm. Hence, the comparative sonotrode 100b and the consolidator 200 move along the material 10 together, wherein the comparative sonotrode 100b moves over (any section of) the material first, and wherein the consolidator 200 follows. In particular, the comparative sonotrode 100b (and the consolidator) was moved at a welding speed of 35 mm/s, with a vibrational peak-to-peak amplitude of 80 μm, and at a welding force of 500 N (Pressure=2.6 MPa), and a consolidation pressure of 1.6 MPa.

[0108] FIG. 2A further depicts three cross-sections of the material 10 as the material was being welded. In particular, the welding was stopped and cross-sections of the material 10 were made based on predefined positions. The first cross-section C.sub.1 is arranged between the comparative sonotrode 100b and the consolidator 200, i.e., the consolidator 200 has not yet passed over the first cross-section C.sub.1. The second cross-section C.sub.2 is arranged such that half of the consolidator has passed over the second cross-section C.sub.2 and kept on the cross-section until the weld interface cooled down below Tg. The third cross-section is arranged such that the consolidator 200 has fully passed over the third cross-section C.sub.3. Further, each of the cross-sections depicts substantial material distortion 17. In particular, fiber may be squeezed out of the material 10, especially at the edges, which may be detrimental to the material properties.

[0109] FIG. 2A further schematically depicts the material 10 at the three cross-sections. As may be appreciated by the person skilled in the art, at cross-section C.sub.1 there is a large degree of voids. In particular, in cross-section C1 a large degree of deconsolidation voids can be seen within both adherends. These voids are detrimental for the quality of the material as they significantly lower the strength of the joint. Additionally, a significant fiber and resin squeeze out can be observed from the two edges. This effect damages the adherends and the squeeze flow might introduce extra voids within the adherends. At cross-section C.sub.2, there is a low degree of voids. At cross section C.sub.3 deconsolidation voids can still be observed and a significant fiber squeeze out is present. Hence, although the consolidator improves the weld (compare C.sub.3 to C.sub.1), a substantial amount of voids remain, and substantial fiber/resin squeeze out is observed at each cross-section.

[0110] FIG. 2B further schematically depicts the temperature T (in ° C.) of a specific spot of the material 10 over time t (in ms), wherein t=0 corresponds to the moment where the specific spot is no longer in direct contact with the sonotrode. Each line corresponds to a different thermocouple, wherein along the welding path TC2 is downstream of TC1, TC3 is downstream of TC2, TC4 is downstream of TC3, and TC5 is downstream of TC4. The column indicates when the consolidator 200 (with d.sub.1=86.4 mm) is present on the specific spot of the material.

[0111] Ideally, the consolidator may be applied to the material 10 as it cools down from below the glass transition temperature T.sub.g. However, this would require an impractically large consolidator 200 with the comparative sonotrode 100b.

[0112] Further, it has been observed that the welded material obtained with the comparative sonotrode may fail in a single lap shear test at an off-set from the welding line. This may be indicative of damage to the adherends close to the welding line, due to, for example, excessive heat exposure, material distortion and/or voids within the adherends.

[0113] FIG. 3A-C schematically depict experimental observations obtained with embodiments of the method and the sonotrode 100.

[0114] In particular, FIG. 3A schematically depicts experimental observations obtained after welding the material 10 with an embodiment of the sonotrode 100 without a consolidator 200. In particular, the sonotrode 100 was moved over the material 10 at a welding speed of 12 mm/s, with a vibrational peak-to-peak amplitude of 80 μm, and at a welding force of 1000 N (Pressure=52 MPa; based on an 1.5 mm by 12.7 mm area of the imprint of the sonotrode with the top adherend). After welding, the material 10 shows a low number of voids and relatively little material distortion 17, especially no fiber squeeze out.

[0115] Hence, the sonotrode according to the invention may facilitate acquiring improved welds. In particular, even without using a consolidator, the welded material obtained with the sonotrode of the invention shows less material distortion than the welded material obtained with the comparative sonotrode 100 functionally coupled to the consolidator (see C.sub.3 in FIG. 2A).

[0116] FIG. 3B schematically depicts experimental observations obtained after welding the material 10 with the sonotrode 100 functionally coupled to a consolidator 200, wherein the consolidator 200 is arranged at a distance d.sub.1 of 2.5 mm from the sonotrode. In particular, the sonotrode 100 was moved over the material 10 at a welding speed of 12 mm/s, with a vibrational peak-to-peak amplitude of 80 μm, and at a welding force of 1000 N (Pressure=52 MPa). After welding, the material 10 shows a minute number of voids and no adherend material distortion 17.

[0117] Hence, the sonotrode of the invention coupled to a consolidator, specially wherein the consolidator is arranged in close proximity to the sonotrode, may provide higher quality welds than the comparative sonotrode functionally coupled to a consolidator.

[0118] FIG. 3C further schematically depicts the temperature T (in ° C.) of a specific spot of the material 10 over time t (in ms), wherein t=0 corresponds to the moment where the specific spot is in direct contact with the center of the welding section 110. Each line corresponds to a different thermocouple. The column indicates when the consolidator 200 is present on the specific spot of the material. Note that, in comparison to FIG. 2B the consolidator appears broader, which is due to the lower welding speed Hence, as the use of the sonotrode 100 of the invention may result in less heat being provided to the material 10 close to the welding line, the material 10 may cool down faster, and the consolidator may be applied as the material 10 cools down (slightly) above the glass transition temperature T.sub.g.

[0119] Experiments performed with a sonotrode of the invention having a central angle α.sub.c, of 44° and a radius of 17.5 mm gave comparable results. Specifically, the welding was performed with a welding force of 1000 N, a peak-to-peak amplitude of 80 and 15 mm/s with 1.6 MPa of consolidation. Almost no voids could be distinguished from cross-sections and fracture surfaces. A lap shear strength of 34.3±2.6 MPa (n=5) was obtained.

[0120] The term “plurality” refers to two or more. Furthermore, the terms “a plurality of” and “a number of” may be used interchangeably.

[0121] The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. Moreover, the terms “about” and “approximately” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. For numerical values it is to be understood that the terms “substantially”, “essentially”, “about”, and “approximately” may also relate to the range of 90%-110%, such as 95%-105%, especially 99%-101% of the values(s) it refers to.

[0122] The term “comprise” includes also embodiments wherein the term “comprises” means “consists of”.

[0123] The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term “comprising” may in an embodiment refer to “consisting of” but may in another embodiment also refer to “containing at least the defined species and optionally one or more other species”.

[0124] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0125] The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.

[0126] The term “further embodiment” and similar terms may refer to an embodiment comprising the features of the previously discussed embodiment, but may also refer to an alternative embodiment.

[0127] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0128] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0129] Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, “include”, “including”, “contain”, “containing” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

[0130] The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

[0131] The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0132] The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

[0133] The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. Moreover, if a method or an embodiment of the method is described being executed in a device, apparatus, or system, it will be understood that the device, apparatus, or system is suitable for or configured for (executing) the method or the embodiment of the method respectively.

[0134] The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.