Abstract:
Disclosed is a sample handling assembly facilitating a sample holding cell used for XRD analysis. The assembly holds the sample cell upright during sample loading and analysis phases. The sample handling assembly is vibrated, partly by a tuning fork, to allow the powder to flow into the sample cell. After the XRD analysis, a rotating arm holding the sample cell is rotated 180° to orient the sample cell completely upside down so that the sample can be emptied. Also disclosed are jets of air that are pulsed onto the sample cell, and/or into the sample cell funnel-tube assembly, to shake and clean the components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit and priority of U.S. Provisional patent application Ser. No. 62/073,250 filed Oct. 31, 2014 entitled AN IMPROVED XRD SAMPLE HANDLING APPARATUS, the entire disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to X-ray Diffraction (XRD) instruments, more particularly to an improved sample handling assembly for the loading, analysis, emptying, and cleaning of powder samples in sample cells. 
     BACKGROUND OF THE INVENTION 
     X-ray Diffraction (XRD) is a method of analyzing the crystal structure and elemental composition of samples. XRD is used in a wide variety of applications, including the manufacture of pharmaceutical compounds, and industrial characterization of cement and mining materials. 
     Powder samples of minerals are a practical necessity for XRD, because a very large number of different crystal orientations need to be presented to the incoming X-rays in order to produce a predictable XRD pattern. A further advantage of using powder samples of minerals is that the powder can be moved during analysis when using coarse grained materials, so that all crystalline orientations are evaluated over time. One method for obtaining such powder motion is to use convective sample cells placed under intense vibration in order to generate granular convection movement in the powder during XRD analysis. 
     In practice, XRD instruments require insertion of powdered samples into a sample cell. The sample cell is then placed on a sample holder, which is introduced into the instrument. After analysis, the sample cell must be replaced or fully emptied of the sample in a manner that prevents cross-contamination. U.S. Pat. No. 7,113,265 B1 discloses the automated use of vibrations to fluidize powder for loading a sample cell, and emptying it. However this patent does not propose a full automation solution for the sample loading and removal. 
     Previous effort of the present Applicant includes U.S. Pat. No. 8,302,477, herein incorporated by reference in its entirety for all purposes, which teaches creating the vibrational movement by means of a tuning fork, including an actuator, a resonator, a holder arm, and a balancing arm to induce granular convection in a sample during XRD analysis; however, it does not include an assembly for loading and emptying the sample conveniently. 
     U.S. Pat. No. 7,134,459 B2 discloses a method for preparing a mixed powder sample, including motorized vibration for fluidization, a suction port, a pneumatic blower, and a gas flow control system. However this solution is primarily for mixing powders instead of analyzing them, and uses an array of source and destination wells in place of a single sample holder. 
     US Pat. No. 2007/0021929 A1 discloses a computerized high-throughput method for sample delivery to instruments, including XRD. This solution is heavily dependent on technology, involving data sets, optimal formulations, robotics, and multiple sample sites, and is not practical for loading and emptying a single sample holder containing mineral powder. 
     Applicant&#39;s co-pending U.S. application Ser. No. 14/313,411, filed on 24 Jun. 2014 and herein incorporated by reference under 37 C.F.R. §1.57(d) in its entirety for all purposes, discloses a sample cell assembly for containing and holding samples for X-ray analysis, which is configured to be attached to a tuning fork assembly for vibrating the samples, and means of locking and unlocking said sample cell assembly. However this solution too does not include a means allowing automatic or semi-automatic loading and emptying the sample conveniently. 
     Considering the background information above, a simple, robust solution which accepts loose materials loaded into an inlet by the user, and automates a series of operations to transfer the sample, perform the analysis, remove the sample and clean all components that come into contact with the powder samples, would be of great economic value. XRD sample analysis would take place in less time and with more effectiveness. 
     SUMMARY OF THE INVENTION 
     It is a general object of the present disclosure to provide a sample handling assembly facilitating a sample holding cell for XRD analysis, with the sample particle size ranging from loose powder to grain. The assembly holds the sample cell upright during the phases of sample loading and analysis. The sample handling assembly is vibrated, partly by a tuning fork to allow the powder to flow into the sample cell. After the XRD analysis, a rotating arm holding the sample cell is rotated 180° so that the sample can be emptied with the sample cell completely upside down. 
     A funnel or a series of two funnels connecting to a vertical tube is devised to guide the powder to the inlet of a vibrated sample cell. The funnel-tube assembly is optionally vibrated, by a non-concentric motor, and the vertical tube has mechanical impulses applied, preferably by a thwacker sub-assembly, to allow the powder to flow into the sample cell. XRD analysis is performed once the sample cell is properly located in the optical path of the measurement instrument and a predetermined amount of powder is loaded into the cell. After analysis, an arm holding the sample cell is rotated to place the sample cell in an upside down position. The sample is emptied with the assistance of gravity and the vibration of the tuning fork. Furthermore, jets of air are pulsed on the sample cell window, and/or into the funnel-tube assembly, to clean the components. Vacuum suction is provided in places where the sample flows down to ensure the evacuation of all of the powder. After cleaning, the arm is rotated back to its initial position to allow the next sample to be loaded. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevation view of the present disclosure, showing the present disclosure both in the loading and unloading positions. 
         FIG. 2  is an elevation view of the present disclosure, showing the swing arm assembly. 
         FIG. 3  is an elevation view of the present disclosure, showing the sample handling assembly at the loading position. 
         FIG. 4 a    is a cross section view of the present disclosure, showing the sample handling assembly at the loading position. 
         FIG. 4 b    is another cross section view of the present disclosure, showing and the sample handling assembly at the loading position, and the swing arm assembly. 
         FIGS. 5 a  and 5 b    show the cleaning operation of the present disclosure with the sample handling assembly at the unloading position. 
         FIG. 6  is an elevation view of the loading funnel shaking means. 
         FIG. 7  is a flow chart of the procedural steps involved with the loading, analyzing, unloading, and cleaning of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , an XRD sample handling assembly is shown to be configured for serving sequential functions of sample filling, holding and removing or emptying in order for an XRD analysis to be conducted on the sample. In  FIG. 1 , with reference to the direction of gravity, the portion depicted in solid lines shows the assembly in an upright sample loading and XRD analyzing phase. The portion depicted in dashed lines shows the assembly in a sample removing phase. 
     As shown in  FIG. 1 , the sample handling assembly comprises a sample feeding tube  16 , a rotating arm  20 , a rotation shaft  22 , a sample transfer funnel  18  and a sample cell  12 , which further comprises a cell window  11  and a sample cell opening  26  (later shown in  FIG. 4 a   ). The sample handling assembly further comprises a tuning fork sub-assembly, which further comprises a tuning fork base  10 , a tuning fork sample arm  6   a , a tuning fork balancing arm  6   b , and a piezoelectric actuator  8 , wherein sample cell  12  is attached to and held by one end of sample arm  6   a.    
     Sample arm  6   a  functions as one prong of a tuning fork which vibrates during the powder loading, analyzing, and unloading processes. As can be seen, the tuning fork sub-assembly, attached to a piezoelectric actuator  8  by fasteners  7   a  and  7   b , holds sample cell  12  in place for the duration of the sample loading, XRD analysis and sample unloading cycle. While vibrating, the sample handling assembly loads sample powder from sample feeding tube  16 . Sample transfer funnel  18  envelopes the bottom of sample feeding tube  16  and receives the sample from it to guide the sample into sample cell  12 . 
     At the starting position, piezoelectric actuator  8  is turned on to vibrate the sample handling assembly. In the preferred embodiment of the disclosure, sample material in the form of powder or loose grain is dropped from sample feeding tube  16  to flow down into sample cell  12  for analysis. 
     Still referring to  FIG. 1 , the sample loading into sample feeding tube  16  is optionally and preferably assisted by an auxiliary shaking or vibrating means, such as a thwacker device  60   b  later shown in  FIG. 6 . Details on an exemplary embodiment of the shaking means are later described in association with  FIG. 6 . 
     It should be noted that sample feeding tube  16  and sample transfer funnel  18  are intentionally detached so that sample transfer funnel  18  rotates together with sample cell  12  to the removing phase. This is also the reason an auxiliary shaking means is provided to sample feeding tube  16 , since the vibration from tuning fork sample arm  6   a  and tuning fork balancing arm  6   b  does not transfer to sample feeding tube  16 . 
     In  FIG. 2 , the side view of  FIG. 1 , rotation shaft  22  is clearly shown. It should be appreciated that the mechanism which rotates the sample cell upside down for sample dropping and removing can be achieved by many mechanical implementations. One of the novel aspects of the present disclosure is that rotation of sample cell  12  is achieved by rotation of the whole tuning fork assembly. And yet the rotation of sample cell  12  is only one of the exemplary embodiments herein shown, and should not be viewed as restrictive to the scope of the present disclosure. 
     For example, although not shown, sample cell  12  can also be configured in such a way that, instead of being flipped upside down, there is a second opening opposite to the opening for receiving the loaded sample, so that during the sample removing phase, the second opening can be opened for the sample to flow out. Such alternation should also be considered to be within the scope of the present disclosure. 
     An important aspect of the present disclosure is use of the tuning fork assembly during the sample filling and removing phase of the XRD analysis to assist the fluidity of the samples; in contrast, the tuning fork used in prior art U.S. Pat. No. 8,302,477 as discussed in the “Background” section is mainly for the purpose of causing sample convection in order to provide a full spectrum of diffracted angles from an incident beam of X-rays for XRD analysis. 
     Reference is now made to  FIG. 3 , together with  FIGS. 4 a  and 4 b   , wherein the sampling handling assembly at the loading position is shown with cross-sectional views.  FIG. 4 a    shows a cross-sectional view of tuning fork base  10 , sample transfer funnel  18 , and rotating arm  20 . Fasteners  7   a  and  7   b  (shown in  FIG. 3 ) pass through a hole  7 .  FIG. 4 b    shows a second cross-sectional view of sample transfer funnel  18 , rotating arm  20 , and rotation shaft  22 . 
     Also shown in  FIG. 4 a    is that, in one embodiment, the sample handling assembly is configured to locate sample cell  12  in the optical path between an X-ray source  96   s  and an X-ray detector  96   d . It should be noted that the optical path shown in  FIG. 4 a    between X-ray source  96   s  and X-ray detector  96   d  is a through-transmission configuration in which source and detector face each other with sample cell  12  in the middle. Alternatively, the optical path between X-ray source  96   s  and X-ray detector  96   d  can also be a reflection configuration (not shown) in which source and detector both face sample cell  12  from the same side, and the optical path angle of each with respect to a location on the surface of cell window  11  may be different. Both the through-transmission and reflection configurations are within the scope of the present disclosure. 
     As further shown in  FIG. 4 a   , X-ray detector  96   d  is also configured to be coupled with a signal and data processor  96   p  for analyzing the X-ray response from the sample received via detector  96   d.    
     Referring to  FIG. 5 a   , the sample handling assembly is shown at the sample removing phase, with optional auxiliary means for efficient sample removal. After analysis of the sample, a vacuum means (device not shown, air-stream exhibited by arrowed lines) is turned on, and the sample handling assembly is flipped upside down on rotation shaft  22 , with the sample handling assembly at the sample removal position. The rotation of the assembly is powered by an electric motor. The electric motor is controlled by a computer combined with an encoder and/or position switches, or is limited mechanically by bump stops at either end. It should be appreciated that the use of motors, position switches and bump stops are well known in the practice of mechanical design. All variations of designs enabling the flipping of the sample handling assembly are within the scope of the present disclosure. 
     The continued vibration of the tuning fork assembly fluidizes the sample so that it falls down by gravity through sample transfer funnel  18 . An auxiliary air flow is then applied to the opening of sample transfer funnel  18  and sample cell  12  to ensure evacuation of the sample. A nozzle (not shown) is placed under the area of powder removal to collect the sample falling down onto a purging tray  24 . The sample is then permanently removed by the vacuum stream through a purging tube  25 . 
     Reference is now made to  FIG. 5 b   . Once most of the sample material has been removed, the sample handling assembly is cleaned by applying air jet pulses onto cell window  11  and/or into sample transfer funnel  18 . The air jet pulses are repeated a predefined number of times (exemplary instance 5 times, exemplary duration 1 second), the repetition and duration of the pulses being controlled by electromechanical valves controlled by a computer. The pulsed air jets are powered by an air compressor, or another source of pressurized air that is within the scope of the present disclosure. 
     Blowing pulsed air on cell window  11  while the cell is being vibrated improves the efficiency of powder removal. The pulsed air does not go inside the cell, but instead applies pressure on the window surface which breaks agglomerated powder that might have formed inside sample cell  12 . Referring to Applicant&#39;s co-pending U.S. application Ser. No. 14/313,411, herein incorporated by reference, window  11  is of a thin film structure, which vibrates upon receiving air bursts. 
     Residual powder in the tube and from sample transfer funnel  18  is removed using air jet pulses directed into sample transfer funnel  18 , combined with suction from the vacuum applied at purging tray  24 . The air jet pulses at sample transfer funnel  18  are also fixed in duration and number, and can be timed parallel to the air jet pulses that are cleaning cell window  11 . 
     Still referring to  FIG. 5 b   , the air-jet pulses that blow toward sample transfer funnel  18  force air inside sample cell  12  via the channel between the inside of the cell and the sample transfer funnel, causing the windows to bulge out due to increased internal air pressure, and to loosen agglomerates of powder that might be stuck between the windows. The pulsed air jets going in and coming out of sample cell  12  further flush out small particles. 
     Referring back to  FIG. 1 , with the sample cell and sample transfer funnel-tube assembly clean, both the vacuum means, and piezoelectric actuator  8  for the tuning fork assembly, are turned off. The sample handling assembly is rotated back to the starting position, and the apparatus is ready to receive the next batch of sample. 
     Referring now to  FIG. 6 , the sample handling assembly further comprises a sample loading funnel  98  which loads samples into sample feeding tube  16  shown in  FIG. 1 . The sample handling assembly optionally, yet preferably, comprises a shaking means for sample loading funnel  98  and sample feeding tube  16 . Shaking can be in the form of a non-concentric shaker  60   a  and/or thwacker  60   b . Non-concentric shaker  60   a  comprises a stator  97  and a rotor  97   a . Thwacker  60   b  comprises a rotor  99  and a thwacker arm  99   a.    
     At the starting of sample loading, non-concentric shaker  60   a , thwacker  60   b  and piezoelectric actuator  8  (shown in  FIG. 1 ) are turned on to vibrate the sample handling assembly to facilitate the flow of the sample powder. In the preferred embodiment of the present disclosure, sample material in the form of powder or loose grain is provided to sample loading funnel  98  to be dispensed into sample feeding tube  16  to flow down towards sample cell  12  for analysis. More specifically, stator  97  achieves its wobbling function by means of rotor  97   a , which is mounted off center with respect to its rotational axis and rotated by a motor (not shown). Stator  97  then subsequently applies a wobbling force to sample feeding tube  16  to facilitate the flow of the sample powder from sample loading funnel  98  into sample feeding tube  16 . 
     Alternatively, thwacker  60   b  imparts a mechanical impact by means of thwacker arm  99   a  to assist the flow of powder as well. Thwacker arm  99   a  is preferably spring loaded to allow it to be in position to thwack sample feeding tube  16 , and then move out of the way of sample feeding tube  16  to rotate 360°, in order to apply the next thwack with thwacker arm  99   a  returned to its thwacking position. 
     Referring back to  FIG. 1 , the sample handing assembly optionally includes a computerized controller module  80 , which can be configured to control piezoelectric actuator  8 , and actuate rotating arm  20  and other auxiliary devices as introduced above, such as non-concentric shaker  60   a , thwacker  60   b , and the vacuum means. 
     Reference is now made to  FIG. 7 , which is a flowchart of the operational steps of the sample handling assembly at starting, loading, analysis, flipping, cleaning, and returning back to the starting position. In step  601 , initialization occurs, and the sample handling assembly is brought to the loading position for analysis. In step  602 , piezoelectric actuator  8  for the tuning fork assembly, the non-concentric shaker  60   a , and the thwacker sub-assembly  60   b  for sample feeding tube  16 , are turned on. In step  603 , the sample is poured into sample cell  12  via sample feeding tube  16 . In step  604 , the rotary thwacker and the non-concentric shaker devices for sample feeding tube  16  are turned off. In step  605 , XRD analysis of the sample occurs. In step  606 , the vacuum for purging tray  24  and purging tube  25  is turned on, and in step  607  the sample holder assembly is turned upside down by the apparatus. In step  608 , with continued vibration of the tuning fork assembly, the sample pours out of sample cell  12  through sample transfer funnel  18  onto purging tray  24 . In step  609 , air jet pulses are applied onto cell window  11  and into sample transfer funnel  18 . In step  610 , piezoelectric actuator  8  for the tuning fork assembly, and the vacuum, are turned off. In step  611 , the apparatus rotates sample cell  12  back to the starting position, ready to receive the next sample. 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. For example, the methods to facilitate the motion of the sample powder into sample cell  12 , including flipping sample cell  12 , applying vibration to feeding tube  16  and loading funnel  98 , and applying vibration and air bursts to sample cell  12  and transfer funnel  18 , can be conducted in a continuous or non-continuous manner, simultaneously or sequentially, automatically or semi-automatically, or in any combination thereof. It is preferred, therefore, that the present invention not be limited by the specific disclosure herein, but only by the appended claims.