Abstract:
The present utility model relates to the field of X-ray diffraction technology. With different combinations, the X-ray diffractometer in the utility model is enabled to have functions of powder diffraction measurement, double crystal diffraction measurement, mirror reflection measurement and diffuse scattering measurement, thus becoming a multi-functional X-ray diffractometer. Further, the X-ray diffractometer is fully automatic in operation, with data collection being under the control of a microcomputer; and is suitable for microstructure analysis of materials, especially for microstructure analysis of solid film materials. The X-ray diffractometer has convenient operation and stable performance, and the technical parameters thereof may meet a general demand in the research of epitaxial film. Also, the X-ray diffractometer is low in cost, and may provide experience for the reconstruction of a diffractometer of the same kind.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to X-ray diffraction measurement, especially a short-wavelength X-ray diffraction scan measuring device and the method thereof for test samples or work pieces made of lower-atomic-number crystalline. 
       BACKGROUND OF THE INVENTION 
       [0002]    Presently, X-ray diffraction analysis for substances is widely used in many fields. For example, it can be used to measure structure of crystalline substances (e.g., phase analysis), structural changes of crystalline substances (e.g., residual stress measurement), etc. During X-ray diffraction analysis in the prior art, an X-ray tube with a material Cu, Cr, Fe, or Mo as the anode target are often used. However, the characteristic X-ray emitted from such an X-ray tube is of long wavelength and therefore can only achieve a depth of penetration not greater than 10 −4  m in some materials such as Mg, Al, or Si. As a result, X-ray diffraction analysis is only applicable to the surface of a test sample or work piece made of such a material, up to the present. 
         [0003]    In view of the drawback that the penetration capability of X-ray is not so strong due to a long X-ray wavelength, patent CN1049496C discloses an “X-Ray Residual Stress Measuring Device and Method”; wherein, the device in that patent employs a X-ray tube emitting a short-wavelength characteristic X-ray and high tube voltage modified based on that of an existing X-ray residual stress measuring device, and the receiving slit is a position-restricting receiving slit. In the X-ray diffraction measuring method disclosed in the patent, short-wavelength characteristic X-rays are employed based on a measuring method for the existing device; the measured part is placed at the center of a goniometer circle, and only the diffracted rays from the measured part is permitted to enter into the radiation detector due to the position-restricting receiving slit, while the diffracted rays and scattered rays from any other part of the work piece are shielded, so that the residual stress at any part in the measured work piece can be measured within the range of penetration depth of the X-rays. By displacing the work piece, the X-ray stress analyzer can measure the residual stress at another part in the work piece; in that way, determination of three-dimensional distribution of residual stress in a work piece made of a material such as beryllium alloy is achieved. In addition, due to the fact that the shorter the X-ray wavelength is and the lower atomic number of the irradiated work piece materials is, the greater the penetration depth of the incident X-ray will be, diffracted rays from different depths and different positions in an even thicker work piece can be detected with such a method. 
         [0004]    However, since the X-ray stress analyzer employs an X-ray diffraction back reflection method to collect a diffraction pattern, the X-ray propagates over a longer path in the work piece. Furthermore, the intensity of the emergent ray from the work piece becomes more attenuated as the propagation path length increases, the principle being shown in  FIG. 1 , in which the intensity of an emergent ray corresponding to an incident X-ray with an intensity I 0  after passing through a work piece with a linear absorption coefficient α and a thickness t is I=I 0 ×e −αt . It can be seen from the above formula, the intensity of an emergent X-ray not only depends on the properties of the work piece and the intensity of the incident ray, but also varies with the propagation distance in the work piece; the longer the propagation distance is (i.e., the longer the sum of the propagation path lengths of the incident ray and diffracted ray in the work piece), the more the intensity loss will be, and thereby the lower the intensity of the emergent ray (the intensity of the diffracted ray) will be. A decreased intensity of the diffracted ray will cause a reduced SNR of measurement and thereby an adverse effect on the measurement of X-ray diffraction. As a result, the technique in the above patent cannot take full advantage of the strong penetration capability of a short-wavelength X-ray, resulting in a lower measurable depth inside of a measured work piece. 
       SUMMARY OF THE INVENTION 
       [0005]    An object of the invention is to provide a tomoscan device for short-wavelength X-ray diffraction analysis mainly for lower-atomic-number crystalline test samples or work pieces made of Al, Mg, Si, etc., which can increase the measurable depth or thickness in work piece by about 10 times. 
         [0006]    Another object of the invention is to provide an easy-to-operate and quick short-wavelength X-ray diffraction measuring method in which the above device is used. 
         [0007]    It is common knowledge that the shorter X-ray wavelength is and the lower the atomic number of a radiated work piece substance is, the thicker the penetration of an incident X-ray in the work piece will be. Based on that principle, the invention employs an X-ray diffraction transmission method instead of an X-ray diffraction back reflection method, so as to reduce greatly the path length of an incident ray and diffracted ray in the work piece, and thereby reduces the intensity loss of the diffracted ray in the measured work piece, increases the intensity of the emergent ray, improves the SNR of the signals received by the detector, and improves the sensitivity of the entire diffraction measuring device. Therefore, diffracted X-rays from different depths and different positions in an even thicker work piece can be collected, so as to implement non-destructive X-ray diffraction analysis for the interior of the entire work piece, and obtain three-dimensional distributions of phase, stress, etc. 
         [0008]    An embodiment of the invention provides a short-wavelength X-ray diffraction measuring device, consisting of an X-ray tube, an entrance diaphragm, a table, a receiving slit, a goniometer, a detector, and an energy analyzer; wherein, the X-ray tube and the detector are located at the two sides of the table. 
         [0009]    The receiving slit and detector are fixed to the goniometer and synchronously rotatable around a measured part of a work piece on the table. The measured part is located on a rotating axis of the goniometer. The goniometer is fixed on a platform. The table is fixed to the goniometer or the platform. The X-ray tube is fixed to the goniometer or the platform. The entrance diaphragm is fixed to the goniometer, the platform, or a clamp for the X-ray tube. An exit of the entrance diaphragm is located on or within the circumference of the goniometer. The work piece on the table can be displaced in X, Y, Z three dimensions along with the table, rotated to an angle Ψ around the rotating axis of the goniometer, or moved in X, Y, Z three dimensions and to an angle Ψ in a cooperative manner. In addition, the receiving slit in an embodiment of the invention also serves to permit only diffracted rays from the measured part of the work piece entering into the detector and shield scattered rays and diffracted rays from other parts of the work piece. 
         [0010]    An anode target of the X-ray tube is made of a heavy metal material such as W, Au, or Ag, etc. so that it can emit a short-wavelength characteristic X-ray at 0.01 nm-0.07 nm wavelength with a strong penetration capability, which can penetrate to a depth at cm or dm level in a metal, non-metal, or ceramic material (e.g., Al, Mg, Si, etc.) with a low atomic number (Z&lt;20). The tube voltage is 120-350 KV and the tube current is 2-10 mA, adjustable steplessly. The detector is a radiation detector, a position-sensitive detector, or a one-dimensional semiconductor detector array. The entrance diaphragm is a collimator entrance diaphragm. The receiving slit is a parallel position-restricting receiving slit or a tapered position-restricting receiving slit to shield scattered X-rays incident to the detector or diffracted rays from other parts of the work piece. The energy analyzer is a single-channel energy analyzer or a multi-channel energy analyzer, with the output signals input to a computer. The table is controlled by a computer to be displaced in X, Y, Z three dimensions or rotated around the rotating axis of the goniometer. 
         [0011]    The distance from the X-ray tube to the center of the goniometer circle is equal or not equal to the distance from the detector to the center of the goniometer circle, and is adjustable. The distance from the center of the goniometer circle to the radiation detector or position-sensitive detector is 200-800 mm. The center of the goniometer circle in an embodiment of the invention is an intersection point between the rotating axis of the goniometer and the rotation plane of the radiation detector or position-sensitive detector. An incident X-ray is in the rotation plane of the radiation detector or position-sensitive detector and passes through the center of the goniometer circle. A part of the work piece at the center of the goniometer circle is right a measured part. 
         [0012]    The collimator entrance diaphragm is a round-aperture collimator entrance diaphragm or a rectangular-aperture collimator entrance diaphragm. A barrier material for the collimator entrance diaphragm is Pb or a heavy metal that has a stronger X-ray absorption capability than Pb, such as Au. If a single-point radiation detector, such as a scintillation counter, is used to scan and collect a diffraction pattern, the round-aperture collimator entrance diaphragm or rectangular-aperture collimator entrance diaphragm is used as a parallel position-restricting receiving slit, and the parallel position-restricting receiving slit and the radiation detector can be moved in a cooperative manner. 
         [0013]    The round-aperture collimator entrance diaphragm is in an inner diameter of 0.1-2 mm and a length of 50-200 mm. The rectangular-aperture collimator entrance diaphragm is composed of two or more diaphragms, which are parallel to each other in the same direction and the center lines of which coincide with each other. The barrier material for each diaphragm is in a thickness of ≧4 mm. The spacing between the diaphragms is 20-200 mm. The inner aperture of each diaphragm is of (1-4)×(0.1-0.8) mm. The total thickness of the barrier materials for the entire rectangular-aperture collimator entrance diaphragm is not less than 15 mm. 
         [0014]    The detector is packaged by a lead sheet in a thickness greater than 2 mm or another heavy metal sheet with a stronger X-ray absorption capability to shield X-rays, leaving only a window over against the receiving slit and a pinhole for leading out electric wires. 
         [0015]    The taper of the tapered position-restricting receiving slit depends on a limited angle detectable by the position-sensitive detector. A casing of the tapered position-restricting receiving slit is covered with a lead sheet in a thickness greater than 2 mm, and inlaid with 3-10 tungsten or molybdenum plates that divide the taper of the tapered position-restricting receiving slit evenly. The dimension of the larger opening of the slit matches the effective dimension of the position-sensitive detector, and the slit may be fixed to the position-sensitive detector. The tapered surface of the tapered position-restricting receiving slit intersects with the extension of the inlaid tungsten or molybdenum plates at the rotating axis of the goniometer. The tapered position-restricting receiving slit and the position-sensitive detector can be moved in a cooperative manner. If a position-sensitive detector is used to collect a diffraction pattern, a tapered position-restricting receiving slit is used as the receiving slit. The position-sensitive detector in an embodiment of the invention can also be a one-dimensional detector array. 
         [0016]    Another embodiment of the invention provides a short-wavelength X-ray diffraction measuring method for the above device, in which a short-wavelength X-ray diffraction transmission method is employed, including: (1) selecting radiation and diffraction test parameters, including tube voltage, tube current, diaphragm and slit system, and the distance from the center of the goniometer circle to the radiation detector or position-sensitive detector, etc; (2) placing the measured part of the work piece at the center of the goniometer circle under the control of the computer; (3) measuring the diffraction pattern under the control of the computer; (4) moving the table in X, Y, Z three dimensions or rotating around the rotating axis of the goniometer as required under the control of the computer, so as to measure the diffraction pattern at any part in or any rotated angle of the work piece; (5) processing the data by the computer and obtaining the phase, residual stress parameters, and their distribution at the measured parts. 
         [0017]    Selection of radiation and diffraction test parameters may be as follows: WKα, AuKα, or AgKα short-wavelength X radiation is selected; an X-ray diffraction and transmission method is chosen; a parallel position-restricting receiving slit or tapered position-restricting receiving slit is used to permit only diffracted rays from the measured part entering into the detector and shield the remaining rays. 
         [0018]    The measured part of the work piece is placed at the center of the goniometer circle under the control of the computer; the measured part is any part on the surface of the work piece or inside of the work piece within a measurable thickness range. 
         [0019]    During measurement of the diffraction pattern, the table on which the measured work piece is located can be moved in X, Y, Z three dimensions at a step length of 0.1-2 mm or rotated around the rotating axis of the goniometer as required under the control of the computer, so as to measure the diffraction pattern at any part in the work piece or the diffraction pattern at any rotated angle to that part around the rotating axis of the goniometer. 
         [0020]    The device provided in the invention can measure an X-ray diffraction pattern at different depths and different positions in an even thicker work piece of crystalline material composed of one or more element with lower atomic number, such as Al, Mg, Si, C, N, or O, etc., without destructing the work piece of crystalline material. The invention breaks through the traditional concept that a short-wavelength X-ray is not applicable to the X-ray diffraction analysis field; it employs a method of short-wavelength X-ray radiation+X-ray diffraction transmission to improve the measurable thickness of a work piece by about 10 times compared with that by the device and method described in CN1049496C; especially for a work piece of a material such as Si, Al, Mg, etc., the measurable thickness can be up to cm to dm level. Therefore, the invention can be used to obtain an X-ray diffraction pattern at different depths and different positions in an even thicker work piece, and thereby obtain phase, residual stress, etc., and their distribution. Furthermore, the invention also breaks through the limit that the X-ray diffraction analysis is only applicable to a depth range of several tens of microns under the surface of a test sample with an existing X-ray diffractometer and method without destructing the test sample. In addition, the invention is advantageous for easy operation and short test time, and can obtain a true and reliable X-ray diffraction pattern. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0021]      FIG. 1  is a schematic diagram of X-ray penetration through a substance; 
           [0022]      FIG. 2  is a block diagram of a device according to an embodiment of the invention; 
           [0023]      FIG. 3  is a sectional view of the structure of a round-aperture collimator entrance diaphragm according to an embodiment of the invention; 
           [0024]      FIG. 4  is a view in direction A of  FIG. 3 ; 
           [0025]      FIG. 5  is a sectional view of the structure of a rectangular-aperture collimator entrance diaphragm according to an embodiment of the invention; 
           [0026]      FIG. 6  is a view in direction A of  FIG. 5 ; 
           [0027]      FIG. 7  is a sectional view of the structure of a tapered position-restricting receiving slit according to an embodiment of the invention, with a larger opening at the upper end  14  and a smaller opening at the lower end  15 ; 
           [0028]      FIG. 8  is a top view of  FIG. 7 ; 
           [0029]      FIG. 9  is a schematic diagram of measurement with the work piece being moved according to an embodiment of the invention; 
           [0030]      FIG. 10  is a block diagram of the measurement and calculation according to an embodiment of the invention; 
           [0031]      FIG. 11  is a diffraction pattern for the central part in a magnesium alloy work piece in a thickness of 25 mm. 
       
    
    
       [0032]    In the figures,  1  represents a X-ray tube;  2  a collimator entrance diaphragm;  3  a work piece;  4  a table;  5  a receiving slit;  6  a detector;  7  a goniometer;  8  a power source for an X-ray generator;  9  a energy analyzer;  10  a computer;  11  a data output unit;  12  a voltage stabilizer;  13  a platform for fixing the measuring device;  14  a larger opening at the upper end of a tapered position-restricting receiving slit;  15  a smaller opening at the lower end of the tapered position-restricting receiving slit. 
       DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0033]    Hereunder the invention is described in detail in preferred embodiments, with reference to the attached drawings. First, it should be noted that the terms, words, and the meanings of the claims in this invention shall not be understood with their literal and ordinary meanings; instead, they also contain implications and concepts associated with the techniques provided in the invention, because, as the inventors, we have to provide appropriate definitions for the terms, so as to describe the invention in the most appropriate way. Therefore, the configurations described in embodiments of the invention and shown in the attached drawings are only preferred solutions instead of covering all technical features of the invention. It should be appreciated that there may be various equivalent or modified solutions to substitute those provided here. 
         [0034]    In a first embodiment, as shown in the figures, a short-wavelength X-ray diffraction measuring device includes an X-ray tube  1 , an entrance diaphragm  2 , a table  4 , a receiving slit  5 , a goniometer  7 , a detector  6 , and an energy analyzer  9 ; wherein, the X-ray tube  1  and the detector  6  are located at the two sides of the table, i.e., at the two sides of a measured work piece. 
         [0035]    The receiving slit  5  and the detector  6  are fixed to the goniometer  7  and can be rotated synchronously around a measured part of a work piece  3  on the table  4 . The measured part is located on a rotating axis of the goniometer  7 . The goniometer  7  is fixed to a platform  13 . The table  4  is fixed to the goniometer  7  or the platform  13 . The X-ray tube  1  is fixed to the goniometer  7  or the platform  13 . The entrance diaphragm  2  is fixed to the goniometer  7 , the platform  13 , or a clamp for the X-ray tube  1 ; an exit of the diaphragm  2  is on or within the circumference of the goniometer  7 . The measured work piece on the table  4  can be translated along with the table  4  in X, Y, Z three dimensions, rotated around the rotating axis of the goniometer  7  to an angle Ψ, or moved in X, Y, Z three dimensions and to an angle Ψ in a cooperative manner. 
         [0036]    In an embodiment of the invention, an anode target of the X-ray tube  1  is made of a heavy metal material such as W, Au, or Ag. The tube voltage is 320 KV and the tube current is 5 mA, adjustable steplessly, so that the X-ray tube  1  can emit a short-wavelength characteristic X-ray at a wave length of 0.01 nm-0.07 nm with a strong penetration capability, which can penetrate to a depth of dm level in metal, non-metal, or ceramic material with a low atomic number (Z&lt;20), such as Al, Mg, Si, etc. The detector  6  is a position-sensitive detector. The entrance diaphragm  2  is a collimator entrance diaphragm. The receiving slit  5  is a tapered position-restricting receiving slit for shielding scattered X-rays incident to the detector  6  and diffracted rays from any other part of the work piece, i.e., it only permits the diffracted rays from the measured part entering into the detector and shields the remaining rays. The energy analyzer  9  is a multi-channel energy analyzer. The table  4  can be translated in X, Y, Z three dimensions and rotated around the rotating axis of the goniometer  7  under the control of the computer  10 . Signals from the multi-channel energy analyzer  9  are inputted to the computer  10 . 
         [0037]    The distance from the X-ray tube  1  to the center of the circle of the goniometer  7  is equal or not equal to the distance from the detector  6  to the center of the circle of the goniometer  7 , and is adjustable. The distance from the center of the circle of the goniometer  7  to the radiation detector or position-sensitive detector is 600 mm. 
         [0038]    The collimator entrance diaphragm is a round-aperture collimator entrance diaphragm or rectangular-aperture collimator entrance diaphragm. The barrier material for the collimator entrance diaphragm is Pb or a heavy metal with stronger X-ray absorption capability than Pb. If a single-point radiation detector, such as a scintillation counter, is used to scan and collect a diffraction pattern, a round-aperture collimator entrance diaphragm or rectangular-aperture collimator entrance diaphragm is used for the parallel position-restricting receiving slit. 
         [0039]    The round-aperture collimator entrance diaphragm is in an inner diameter of 0.1-2 mm and a length of 50-200 mm. The rectangular-aperture collimator entrance diaphragm is composed of two or more diaphragms, which are parallel to each other in the same direction and the center lines of which coincide with each other. The barrier material for each diaphragm is in a thickness of 5 mm. The spacing between the diaphragms is 180 mm. The inner aperture of each diaphragm is of (1-4)×(0.1-0.8) mm. The total thickness of the barrier materials for the entire rectangular-aperture collimator entrance diaphragm is not less than 15 mm. 
         [0040]    A lead sheet or a heavy metal sheet with a stronger X-ray absorption capability in a thickness greater than 2 mm is used for the radiation detector or position-sensitive detector to shield X-rays, leaving only a window over against the receiving slit  5  and a pinhole for leading out electric wires. 
         [0041]    The taper of the tapered position-restricting receiving slit depends on a limited angle detectable by the position-sensitive detector. A casing of the tapered position-restricting receiving slit is covered with a lead sheet in a thickness greater than 2 mm, and lined with 3-10 tungsten or molybdenum plates that divide the taper of the tapered position-restricting receiving slit evenly. The dimension of a larger opening  14  of the slit matches the effective dimension of the position-sensitive detector, and the slit is fixed to the position-sensitive detector. The tapered surface of the tapered position-restricting receiving slit intersects with the extension of the lined tungsten or molybdenum plate at the rotating axis of the goniometer, wherein the center line of the tapered position-restricting receiving slit intersects with the center line of the lined tungsten or molybdenum plate at the center of the goniometer circle. The tapered position-restricting receiving slit and the position-sensitive detector can be moved in a cooperative way. If a position-sensitive detector is used to collect a diffraction pattern, a tapered position-restricting receiving slit is used as the receiving slit. 
         [0042]    A short-wavelength X-ray diffraction measuring method for the above device, in which a short-wavelength X-ray diffraction and transmission method is employed, includes: (1) selecting radiation and diffraction test parameters, including tube voltage, tube current, diaphragm and slit system, and the distance from the center of the goniometer circle to the radiation detector or position-sensitive detector; (2) placing the measured part on the work piece at the center of the goniometer circle under the control of the computer; (3) measuring the diffraction pattern under the control of the computer; (4) moving the table in X, Y, Z three dimensions or rotating around the rotating axis of the goniometer as required under the control of the computer, so as to measure the diffraction pattern at any part in or at any rotated angle Ψ of the work piece; (5) processing the data under the control of the computer and obtaining the phase, residual stress parameters, and their distribution at the measured parts. 
         [0043]    Selection of radiation and diffraction test parameters may be as follows: WKα, AuKα, or AgKα short-wavelength X radiation is selected; an X-ray diffraction and transmission method is chosen; a parallel position-restricting receiving slit or tapered position-restricting receiving slit is used to permit only the diffracted rays from the measured part entering into the detector and shield the remaining rays. 
         [0044]    The measured part of the work piece is placed at the center of the goniometer circle under the control of the computer; the measured part is any part inside of the work piece within a measurable thickness range. In order to implement part-by-part tomoscan, the measured work piece  3  on the table  4  shown in  FIG. 9  is controlled by the computer to move in three dimensions at a step length of 0.1-2 mm. In order to measure a diffraction pattern for a measured part in any direction, the work piece  3  on the table  4  shown in  FIG. 9  can be controlled by the computer to rotate to a certain angle around the rotating axis of the goniometer. The computer processes the obtained data and the output unit outputs the phase, residual stress parameters, and their distribution at individual parts in the measured work piece. 
         [0045]    In a second embodiment, as shown in  FIG. 9 , the device and method used in this embodiment are identical to those used in the first embodiment, with the difference in parameter selection: in this embodiment, WKα radiation is used, the tube voltage is 280 KV, the tube current is 3 mA, the distance from the center of the goniometer circle to the radiation detector is 220 mm±1.0, a NaI scintillation counter  6  is connected to the multi-channel energy analyzer  9 , the collimator entrance diaphragm is a round-aperture collimator entrance diaphragm in an inner diameter of 2 mm±0.1 and a length of 120 mm±0.5 length, a round-aperture collimator entrance diaphragm in an inner diameter of 0.5 mm±0.1 and a length of 120 mm±0.5 is used for the position-restricting receiving slit, and the NaI scintillation counter  6  is shielded with an 8 mm±0.1 thick lead sheet. After the optical path is conditioned, a magnesium alloy casting  3  in a thickness of 25 mm±0.5 is placed on the table  4 . The table  4  is adjusted so that the center of the magnesium alloy casting  3  is located in the center of the circle of the goniometer. The position indicated by the dotted line shown in  FIG. 9  is an actual position of the magnesium alloy casting  3 ; in that case, the center of the circle of the goniometer is located inside of the magnesium alloy casting  3  with a distance of 12.5 mm±0.1 to the surface of the casting. The scan range 2θ is 2-10°, the step length of scan is 0.05°, and the measurement is performed for 10 s at each step. An obtained X-ray diffraction pattern is shown in  FIG. 11 . 
         [0046]    In a third embodiment, the device and method used in this embodiment are identical to those used in the first embodiment, with the difference in parameter selection: in this embodiment, WKα radiation is used, the tube voltage is 320 KV, the tube current is 6 mA, the distance from the center of the goniometer circle to the radiation detector is 500 mm±1.0, a NaI scintillation counter  6  is connected to the multi-channel energy analyzer  9 , the collimator entrance diaphragm is a round-aperture collimator entrance diaphragm in an inner diameter of 1 mm±0.1 and a length of 150 mm±0.5, a round-aperture collimator entrance diaphragm in an inner diameter of 0.8 mm±0.1 and a length of 120 mm±0.5 is used for the position-restricting receiving slit, and the NaI scintillation counter  6  is shielded with a 10 mm±0.1 thick lead sheet. After the optical path is conditioned, the work piece  3  is placed on the table  4 . The table  4  is adjusted so that the center of the work piece  3  is located at the center of the circle of the goniometer; in that case, the center of the circle of the goniometer is located inside of the work piece  3 . The scan range 2θ is 2-10°, the step length of scan is 0.05°, and the measurement is performed for 10 s at each step. 
         [0047]    Though the invention is disclosed in the embodiments as above, it should be noted that those embodiments do not constitute any limitation to the invention. Any variations conceivable by those skilled in the art shall fall into the scope of the invention.