Abstract:
A dry particle-size distribution measuring apparatus and method is provided for suspending a plurality of bristle members across a support surface of a dispensing trough with bristles being arranged to contact and disperse any clusters of particles to a primary state prior to releasing the particles to a sample flow cell. A source of light can irradiate the sample flow cell and a detector unit can measure any scattered and/or diffracted light to provide corresponding signals. A control unit can determine the size and distribution of particles from the corresponding signals. The bristle members can be mounted on a brush unit that is directly mounted on the trough and both the trough and the brush unit can be driven by the same vibrator unit.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a sample supplying device for a dry particle-size distribution measuring apparatus, and more particularly, to an improved sample supplying device and method of providing a preliminary dispersion of particles into a primary state during the initial introduction of the sample into the measuring apparatus. 
   2. Description of Related Art 
   In a dry particle-size distribution measuring apparatus, usually, a powdery and particulate sample is accommodated in a trough of a sample supplying device which is disposed above a measurement flow cell, and, when the particle-size distribution of the sample is to be measured, the trough may be vibrated by a linear feeder to drop the sample through a drop hole formed in the trough, thereby causing the sample to be supplied into a conduit connected to the flow cell. 
   However, relatively small particles in a sample, such as powdery and particulate members are sometimes aggregated by an electrostatic force, a Van der Waals force, a magnetic force, or the like which acts among the powdery and particulate members even in a dry state, so that the powdery and particulate members are not formed as so-called primary particles in which powdery and particulate members are completely separated from each other, but rather may be formed as secondary particles (in each of which several primary particles are aggregated) or tertiary particles (in each of which several secondary particles are aggregated). When such powdery and particulate members including not only primary particles but also secondary and tertiary particles are supplied to a flow cell as a sample and measurement is then conducted while irradiating the sample with light, it is difficult to obtain a true particle-size distribution of the powdery and particulate members. 
   In conventional sample supplying devices, therefore, there has been attempts to employ the following techniques: (1) a sieve member is disposed under the drop hole with a size to prevent such secondary and tertiary particles from being dropped and thereby allow only powdery and particulate members of a predetermined size or smaller relative to the sieve size to be passed; and (2) a plurality of bearing balls are placed in the sieve member, and secondary and tertiary particles are dispersed by rotation and sliding contact with the bearing balls to change them into primary particles. 
   In both of the above techniques, however, it is difficult to attain a complete state in which a powdery and particulate sample is configured only by primary particles and does not contain secondary and tertiary particles, and additionally the sieve can sometimes be clogged by secondary and tertiary particles, so that powdery and particulate members cannot be smoothly dropped in a predetermined quantity. Particularly, in the case where a sample of a high density is supplied by vibration of a linear feeder, and so-called submicron powdery and particulate members in which the particle size is smaller than 1 μm are charged as a sample, there arises a disadvantage that only dispersion up to 1 μm which corresponds to the secondary particle state may be performed. 
   Thus, there remains a need in this field of particle measurement to provide a compact and economical solution to these problems. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide a sample supplying device in which, even when a powdery and particulate sample contains secondary and tertiary particles, these particles can be preliminarily dispersed to be changed into a primary particle state before the particles are dropped by vibration of a trough, thereby enabling the powdery and particulate sample to be stably supplied in the desired primary particle state and in a predetermined and controlled drop quantity. 
   In order to attain this objective, in a sample supplying device for a dry particle-size distribution measuring apparatus which is configured by a trough that accommodates a sample, and uses a linear feeder that vibrates the trough, and in which the sample in the trough is dropped from a sample drop hole formed in the trough, by vibrating the trough, a brush which is positioned within the trough to be vertically vibrated due to vibration of the trough and the sample is dispersed by vibration of the brush. 
   In the sample supplying device, a brush unit is disposed in the trough which forward feeds powdery and particulate members by vibration in upward and forward directions to drop the members therefrom, and the brush unit is vertically vibrated by the vibration of the trough. When a powdery and particulate sample accommodated in the trough contains secondary and tertiary particles, the secondary particles and the like are dispersed (pulverized) by the brush bristles which are vertically vibrated, to be changed to primary particles, and then dropped from the sample drop hole while maintaining the primary particle state. Consequently, the powdery and particulate members are dropped and supplied into a flow cell in the desired primary particle state. 
   A method of separating particles into a primary state for a particle-size distribution measuring apparatus includes supplying a sample of particles to a support surface, vibrating the support surface to move the particles to a dispensing portion, and contacting the sample with a plurality of bristles that vibrates to the support surface prior to the dispensing portion, the arrangement of bristles being spaced to assure contact with any cluster of particles to dispense them into a primary particle state. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects and features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings. 
       FIG. 1  is a view schematically showing a schematic diagram of a dry particle-size distribution measuring apparatus into which the sample device of the invention is incorporated; 
       FIG. 2  is a schematic side cross sectional view showing an example of a sample supplying device of the invention; 
       FIG. 3A  is a perspective view showing an example of a trough and a brush unit; 
       FIG. 3B  is a partial enlarged cross sectional view illustrating the arrangement of the brush unit in the trough; 
       FIG. 4A  is a schematic of a first arrangement of brush bristles; 
       FIG. 4B  is a schematic of a second arrangement of brush bristles; 
       FIG. 4C  is a schematic of a third arrangement of brush bristles; 
       FIG. 4D  is a schematic of a fourth arrangement of brush bristles; and 
       FIG. 4E  is a schematic of a fifth arrangement of brush bristles. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the general principles of the present invention have been defined herein specifically to provide a sample supplying device and method for a dry particle-size distribution measuring apparatus of measuring particles in a primary state. 
   Hereinafter, the invention will be described in detail with references to the Figures.  FIGS. 1 to 3  show one embodiment of the invention.  FIG. 1  schematically shows a configuration of a dry particle-size distribution measuring apparatus into which the sample supplying device of the invention is incorporated. In the Figure,  1  denotes a measuring section, and  2  denotes a sample supplying device disposed above the measuring section  1 . 
   The measuring section  1  is configured for example in the following manner. The reference numeral  3  denotes a tubular flow cell or measurement cell which is vertically disposed to receive the sample. Optical windows  3   a  and  3   b  are formed in opposed side faces of the flow cell  3 , respectively. A laser light source  6  can irradiate a sample  4  that is dropped in the flow cell  3  with a laser beam  5 . Laser source  6  is placed outside one of the optical windows such as optical window  3   a . An optical detecting section  7  which receives scattered light and/or diffracted light that is produced by irradiating the sample  4  with the laser beam  5  is placed outside the other optical window  3   b . Measurement of the light contacting the particles by the detecting section  7  permits a determination of particle size. 
   The reference numeral  8  denotes an ejector device which serves as a sample introducing section disposed immediately above the flow cell  3 , and which includes a funnel-shaped section  8   a . A sample guiding section  9  which communicates with the flow cell  3  is positioned under the funnel-shaped section  8   a . A gas supply path  11  for compressed air  10  is connected to the ejector device  8 . An air flow path  8   b  which guides the compressed air  10  supplied through the compressed air supply path  11 , into the sample guiding section  9  is formed on the side of the lower face of the funnel-shaped section  8   a , so that compressed air  10   a  flowing in the air flow path  8   b  is blown as a dispersion flow to the sample  4  being dropped from a trough  18  (described later) of the sample supplying device  2 . The lower end of the sample guiding section  9  is insertedly connected to the flow cell  3 . In a lower end portion of the guiding section, there is a partitioning section  9   a  which extends to the vicinities of the upper ends of the optical windows  3   a  and  3   b . The reference numeral  12  denotes straightening guide vanes which are disposed around the portion of the sample guiding section  9  and are insertedly connected to the flow cell  3 , so as to be in parallel with the partitioning section  9   a , and through which outside air  13  is sucked or aspirated into the flow cell so that a sheath flow  14  is formed in the flow cell  3  by the sucked outside air  13  about the sample. 
   The reference numeral  15  denotes a sample recovery flow path which is formed on the lower end side of the flow cell  3 , and which comprises a suction or vacuum apparatus  16 . The reference numeral  17  denotes a hopper which is disposed above the ejector  8 , and which is used for guiding the sample  4  that is dropped from the trough  18  of the sample supplying device  2 , into the ejector device  8 . 
   The configuration of the sample supplying device  2  will be described with reference also to  FIGS. 2 ,  3 A, and  3 B. The sample supplying device  2  is configured mainly by the trough  18  which accommodates the powdery and particulate sample  4 , and a linear feeder  19  which can vibrate the trough  18 . The vibration of the linear feeder  19  is controlled by a controller  20 . 
   The configuration of the trough  18  will be described with reference to  FIGS. 2 and 3A . The trough  18  is configured with a bottom support surface portion  21  which has a thin isosceles trapezoidal shape in a plan view; a front plate portion  22  which extends upward from the short edge side (hereinafter, referred to as the front end side) of the bottom portion so as to be perpendicular to the bottom portion  21 ; a rear plate portion  23  which has an isosceles trapezoidal shape, and which extends from an end on the long edge side (hereinafter, referred to as the rear end side) of the bottom portion in an upward inclined direction with respect to the rear end portion of the bottom portion  21 ; and side plate portions  24  which extend upward from lateral sides of the bottom portion  21  so as to couple the front plate portion  22  with the rear plate portion  23 . The trough is formed into a box-like shape which has a thin isosceles trapezoidal shape in a plane view, and in which the upper side is opened for receiving samples. As shown in  FIG. 3A , the trough  18  has a tapered shape in a plan view, and is configured so that, as seen from  FIG. 2 , the height of the front plate portion  22  is lower than the level of the rear top  23   a  of the rear plate portion  23  so that a larger quantity of the sample  4  can be placed and accommodated on the rear end side. The reference numeral  25  denotes a sample drop hole or a dispensing portion which is opened in the bottom portion  21  and in close proximity to the front plate portion  22 , and which is formed into a rectangular shape in a plan view so as to extend over the whole lateral length of the bottom portion  21 . The trough  18  is preferably made of a material which has an adequate mechanical strength and a property of not adsorbing the sample  4 , and which is nonmagnetizable in consideration of the linear feeder  19  that will be described later. Examples of such a material are stainless steel and an appropriate synthetic resin. 
   The configuration of the linear feeder  19  will be described with reference to  FIG. 2 . The reference numeral  26  denotes a pedestal on which a base  28  is horizontally held via vibration proof pieces  27  made of rubber or the like. The reference numeral  29  denotes an electromagnet fixing unit which is disposed on the upper face of the base  28 , and to which an electromagnet  30  is fixed. The reference numerals  31   a  and  31   b  denote a pair of plate springs which are separated from each other by an adequate distance. The lower ends of the plate springs are fixed to the side faces of the electromagnet fixing unit  29  in such a manner that the plate springs are parallel to each other and inclined in a rearward direction (in a leftward direction in  FIG. 2 ). An attractive driving piece  32  having a plate-like shape in which the upper and lower faces are parallel to each other is held in a horizontal state on the upper ends of the plate springs. The attractive driving piece  32  is made of a material which is attracted by a magnetic attractive force, such as iron. The attractive driving piece  32  is disposed in a state where its upper face is fixed to the bottom portion  21  of the trough  18  and a small gap is formed between the lower face and an attractive face of an upper portion of the core of the electromagnet  30 . The pair of plate springs  31   a  and  31   b  are used for converting the vertical vibration into longitudinal vibration, and are configured so that the pressing force of one (the rear end side) of the plate springs or the plate spring  31   b  is stronger than that of the other (the front end side) plate spring  31   a . In a normal state where the electromagnet  30  is not energized, the bottom portion  21  assumes a resting horizontal posture. 
   In the sample supplying device  2 , when a rectangular pulse voltage in which the lowest level is 0 V and the highest level is several volts is applied to the coil of the electromagnet  30 , the attractive driving piece  32  is intermittently attracted to the electromagnet at a constant period, whereby vibration is applied to the trough  18  in the upward and forward directions while using the masses of the electromagnet  30  and the base  28  as a reaction force. This vibration causes the sample  4  which is placed and accommodated in the trough  18 , to be moved toward the front end side of the trough  18 , so that the sample can be dropped from the sample drop hole  25 . 
   As can be appreciated, vibration can be provided by other devices such as shaker units and other mechanical units and the electromagnetic drive force is only a preferred embodiment. 
   Referring again to  FIG. 1 ,  33  denotes a control unit with a calculation and control section which is configured by, for example, a personal computer, and which controls the whole apparatus. Furthermore, the calculation and control section has functions of calculating the particle-size distribution of the sample  4  on the basis of an output signal from the measuring section  1  and by using an arithmetic expression according to Fraunhofer analytic theory or Mie scattering theory, displaying a result of the calculation on a displaying device  33   a , and storing the calculation result into a memory section which is disposed in the apparatus, or a memory card or a memory disc which can be detachably attached to the apparatus. 
   As described above, in this configured sample supplying device  2 , vibration caused by the linear feeder  19  is applied to the trough  18 , and the sample  4  placed on the trough  18  is moved forward in the trough  18  by the force vector of vibration along the horizontal axis of the trough  18 , so that the sample can be dropped from the sample drop hole  25  which is opened in the front end side of the trough  18 . In the sample supplying device  2  of this embodiment, a brush unit  34  which is vertically vibrated due to the vibration of the trough  18  is disposed in the trough  18  and on the upstream side of the drop hole  25  in the direction of moving the sample, so that the sample  4  is dispersed by contact with the vibration of the brush unit  34  before the sample is dropped. 
   The brush unit  34  is configured by a holder  35  and bristles  36  implanted into the holder, and as shown in  FIG. 3A  is laterally placed in the trough  18  so that the longitudinal direction of the brush is perpendicular to the advancing direction  37  of the sample  4 . The holder  35  can have, for example, an elongated rectangular parallelepiped shape, and as shown in  FIG. 4A  the plurality of the bristles  36  are evenly implanted in the bottom face  35   a  of the brush  34  and spaced to insure operative contact with any cluster of particles. More specifically, the width W in the longitudinal direction of the holder  35  is slightly larger than the width w of the front plate portion  22 , and the width of the trough  18  in a plan view is gradually more reduced in a direction moving toward the front plate portion  22 . Therefore, the holder  35  is blocked by the lateral side plate portions  24  of the trough  18  at a position which is in the upstream side in the direction of moving the sample  4  and separated from the sample drop hole  25  by an adequate distance a. At the blocked position, the holder is vibrated in vertical directions indicated by the bidirectional arrow  38  in  FIG. 3B , and slightly moved in forward and rearward directions indicated by the bidirectional arrow  39 . The holder  35  can be made of an adequate supporting material such as a synthetic resin, and the bristles  36  can be made of a synthetic resin such as nylon or metal wires. 
   When appropriate powdery and particulate members are placed as the sample  4  in the rear end side of the trough  18  and a predetermined pulse voltage is applied to the electromagnet, the trough  18  is vibrated, and the vibration of the trough  18  causes the sample  4  to forward move in the direction indicated by the arrow  37  in  FIG. 3A . In this case, the brush unit  34 , for example, of a rectangular parallelepiped shape is laterally disposed in the trough  18 , and the bristles  36  are vertically and horizontally vibrated due to the vibration of the trough  18 , at the position which is separated and upstream from the sample drop hole  25  by the distance a. 
   The powdery and particulate sample  4  which is advanced from the rear end side of the trough  18  to the front end side is initially blocked by the bristles  36  of the brush  34  and then enters below the bristles  36  which are vertically vibrated. In this case, primary particles contained in the powdery and particulate sample  4  will generally pass between the bristles  36  because the primary particles are smaller in size than the gaps between the bristles  36 , but clusters of secondary and tertiary particles cannot pass between the bristles  36  because the secondary and tertiary particles are larger in size than the gaps. The secondary and tertiary particles are pulverized and dispersed by the bristles  36  which are vertically vibrated, to be changed to primary particles. The powdery and particulate sample  4  which has passed through the brush  34  is advanced toward the sample drop hole  25  by the vibration of the trough  18 , and then dropped from the sample drop hole  25  to be supplied into the flow cell  3  via the hopper  17 , the ejector  8 , and the sample guiding section  9 . 
   As described above, the brush unit  34  is disposed so as to be perpendicular to the direction  37  of feeding the sample  4  and to move relative to the sample in the vibrating trough  18  which is used for forward feed of the sample  4  by vibration in the upward and forward directions, and the brush unit  34  is vertically vibrated by the vibration of the trough  18 . If the sample  4  accommodated in the trough  18  contains secondary and tertiary particles, the secondary particles and the like are dispersed (pulverized) by the brush unit  34  which is vertically vibrated, to be changed to primary particles, and then dropped from the sample drop hole  25  while maintaining the primary particle state. Therefore, the sample  4  is dropped and supplied into the flow cell  3  in the desired primary particle state for measurement purposes. 
   In this case, the driving force of vertically vibrating the brush unit  34  for pulverizing secondary particles and the like is realized only by the vibration of the trough  18 , and the brush unit  34  is vertically vibrated in the tapered trough  18  while being separated by the constant distance a from the sample drop hole  25 . Therefore, a special driving apparatus for the brush unit  34 , parts for fixing the vibration position, and the like are not required as long as the brush is secured in position but permits relative movement to the trough  18 . 
   When the intensity of the vibration of the trough  18  is adequately adjusted, the quantity of the powdery and particulate sample  4  to be dropped can be controlled with excellent quantitativeness. For example, the vibration frequency and intensity are changed about 65±10 Hz, duty ratio 20% (it can be changed 0 to 100% in response to particular sizes of samples) of which a pulse intensity is about 0–5 V (rectangular waves). 
   The shape of the brush unit  34  is not restricted to that of the above embodiment, and may be variously modified. For example, the manner of implanting the bristles  36  may be modified in the following manner. As shown in  FIG. 4B , small groups  36 A each configured by several to several tens of bristles  36  may be formed, and the small groups  36 A may be continuously formed in the periphery of the bottom face (hereinafter, referred to as the implanted face)  35   a  of the holder  35  in which the depth D is slightly larger. The bristles  36  may not be disposed in a center area  35   a  of the implanted face  35   a.    
   The holder  35  in  FIGS. 4A and 4B  has a rectangular parallelepiped shape, and the implanted face  35   a  is rectangular (the face may be square). Alternatively, as shown in  FIG. 4C , the implanted face  35   a  may be trapezoidal. In the alternative, when the length of the long edge is not shorter than W, the implanted face is not always required to have an isosceles trapezoidal shape. 
   As shown in  FIG. 4D , the depth D of the implanted face  35   a  may be set to be large, and the small groups  36 A may be disposed in a large number over the whole area of the implanted face  35   a.    
   As shown in  FIG. 4E , a cylindrical member (or a columnar member)  35 A having a length W may be used as the holder  35 , and the bristles  36  may be densely implanted to the peripheral face of the member. The cylindrical member  35 A can be mounted to rotate while being vibrated. 
   The trough  18  should have a tapered shape in a plan view in which the portion on the side of the sample drop hole  25  is narrowed, but it is not always required to have an isosceles trapezoidal shape. The sample drop hole  25  which is formed in the front end side of the bottom portion  21  of the trough  18  is not required to have a rectangular shape in a plan view, and may have any shape such as a square, a circle, or an oval. 
   In the preferred embodiment, the trough  18  is held in such a manner that the bottom portion  21  is horizontal when stationary. Alternatively, the bottom portion  21  may be inclinedly disposed so that the portion on the side of the sample drop hole  25  is provided at a lowered position. 
   Thus, a sample supplying device for a dry particle-size distribution measuring apparatus is configured by a trough that accommodates a sample, and a linear feeder that vibrates the trough. The sample in the trough is dropped from a sample drop hole formed in the trough, by vibrating the trough. A brush which is vertically vibrated due to vibration of the trough is disposed in the trough, and the sample is dispersed by vibration of the brush. Even a small size powdery and particulate sample accommodated in the trough containing secondary and tertiary particles are dispersed (pulverized) by bristles which are vertically vibrated, to be changed to primary particles, and then dropped from the sample drop hole while maintaining the primary particle state. Consequently, the powdery and particulate sample can be supplied in a desired primary particle state and in a predetermined and controlled drop quantity. 
   Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.