Patent Publication Number: US-2011074451-A1

Title: Particle measuring apparatus

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2009-220880 filed on Sep. 25, 2009, the entire content of which is hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a particle measuring apparatus for measuring the size of a particle from a signal obtained when a particle within a particle suspension liquid passes through a aperture provided in a detection device. 
     BACKGROUND 
     There are various conventional particle diameter measuring apparatuses for detecting particles such as fine ceramic particles, pigments, cosmetic powders and the like contained in particle suspension liquids (for example, refer to Japanese Registered Utility Model No. 6-22203). Japanese Registered Utility Model No. 6-22203 discloses a particle diameter measuring apparatus including a detection device configured by a tubular detection body with a mounted pellet having a pore, external electrode disposed outside the detection body, and an internal electrode disposed inside the detection body. 
     The particle detection device is immersed in a liquid preparation accommodated within a container. When the liquid preparation is aspirated through the particle detection device via a syringe provided in the apparatus, the particles in the liquid preparation pass through the aperture of the pellet and move into the particle detection device. The electrical resistance changes at the aperture when an electrical current flows from the internal electrode toward the external electrode and a particle passes through the pore, thus generating a pulse signal corresponding to the size of the particle passing between the two electrodes. The particle is detected and the size of the particle measured based on the pulse signal. 
     In the apparatus disclosed in Japanese Registered Utility Model No. 6-22203, it becomes difficult to distinguish the noise from the signal obtained from the particle when the size of the detection target particle diverges from the diameter of the pore. Generally, when the size of the particle is smaller than approximately 2% of the pore, it becomes difficult to distinguish the noise from the signal from the particle. 
     Therefore, the size of the aperture must variable according to the size of the detection target particle. Since it is essential to distinguish noise from a weak signal generated from a very fine particle particularly when specifically detecting such fine particles, the diameter of the aperture must become smaller to conform to the fine particles. 
     However, when the aperture diameter is reduced to approximately 25 micrometers or less in order to measure particles of, for example, 1 micrometer in diameter, vibration from a drive source within the apparatus, such as a fan, syringe pump and the like, propagates to the particle detection device and becomes noise that is difficult to distinguish from the weak signal from the particle. 
     SUMMARY OF THE INVENTION 
     The scope of the invention is defined solely by the appended claims, and is not affected to any degree by the statements within this summary. 
     A first aspect of present invention is a particle measuring apparatus comprising: a detection device with an aperture through which pass particles contained in a particle suspension liquid, for detecting a signal generated when a particle passes through the aperture; and a detection device supporting part comprising an elastic body, for supporting the detection device through the elastic body. 
     A second aspect of present invention is a particle measuring apparatus, comprising: a detection device with an aperture through which passes particles contained in a particle suspension liquid; a detection device supporting part comprising an elastic body, for supporting the detection device through the elastic body; electrodes for applying a voltage to the particle suspension liquid; and a signal obtainer for obtaining signals based on the change in electrical resistance when a particle contained in the particle suspension liquid passes through the aperture. 
     A third aspect of the present invention is a particle measuring apparatus comprising: a detection device through which particles can internally pass through; a detection device supporting part comprising an elastic body, for supporting the detection device through the elastic body; and a signal obtainer for obtaining signals from particles passing through the interior of the detection device. 
     A fourth aspect of the present invention is a particle measuring apparatus comprising: a detection device with an aperture through which passes particles contained in a particle suspension liquid; and a detection device supporting part comprising a vibration absorbing member, for supporting the detection device through the vibration absorbing member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of the particle diameter measuring apparatus of the present invention; 
         FIG. 2  is a fluid circuit diagram and block diagram of the particle diameter measuring apparatus of  FIG. 1 ; 
         FIG. 3  is a perspective view of a detection device; 
         FIG. 4  is a perspective view of the detection device including a partial cross section; 
         FIG. 5  is a front view of the detection device including a partial cross section; 
         FIG. 6  is a bottom view of the detection device; 
         FIG. 7  is a top view of a mounting fixture; 
         FIG. 8  is a front view of the mounting fixture; 
         FIG. 9  is a side view of the mounting fixture; 
         FIG. 10  is a cross sectional view on the A-A line of  FIG. 9 ; 
         FIG. 11  is a cross sectional view on the B-B line of  FIG. 9 ; 
         FIG. 12  is a top view of a tube adapter; 
         FIG. 13  is a side view of the tube adapter; 
         FIG. 14  is a cross sectional view on the C-C line of  FIG. 13 ; 
         FIG. 15  is a perspective view of a buffer; 
         FIG. 16  is a top view of a top plate; 
         FIG. 17  is a perspective view of a connector piece; 
         FIG. 18  is a top view of a bottom plate; 
         FIG. 19  is a top view of a foam elastic body; 
         FIG. 20  shows a grip piece; (a) is a top view, (b) is a side view, (c) is a cross sectional view on the D-D line; 
         FIG. 21  is a perspective view of the detection device including a partial cross section; 
         FIG. 22  is a front view of the detection device including a partial cross section; 
         FIG. 23  is a bottom view of the detection device; 
         FIG. 24  shows a baseline waveform when a 250 Hz sound is generated; 
         FIG. 25  shows a baseline waveform when a 4000 Hz sound is generated; 
         FIG. 26  shows a baseline waveform when a 1,000 Hz sound is generated; and 
         FIG. 27  illustrates another example of a lockmechanism. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the particle diameter measuring apparatus of the present invention will be described in detail with reference to the accompanying drawings. 
     [Particle Diameter Measuring Apparatus] 
     The general structure of the particle diameter measuring apparatus is first described below. 
       FIG. 1  is a perspective view of the particle diameter measuring apparatus  1  of the first embodiment. 
     The particle diameter measuring apparatus  1  is a particle analyzer of the electrical resistance type for measuring the size and number of particles based on the change in electrical resistance when a particle suspension liquid containing particles such as cells, toner or the like flows through a aperture and a particle in the suspension passes through the aperture.  FIG. 1  shows a door  3  on the front side of a container platform  2  in an open state to allow the placement of a beaker  52 , which is a container accommodating a particle suspension liquid. The container platform  2  is vertically movable so that when the beaker  52  containing the particle suspension liquid is placed on the platform  2 , the container platform  2  moves to a bottom position and a detection device  10  is arranged within the beaker  52 , and thereafter the container platform  2  is moved to a top position. 
     As shown in  FIGS. 2 and 3 , the particle diameter measuring apparatus  1  is mainly configured by a detection device  10  provided with an aperture  9  for the passage of a particle suspension liquid, detection device supporting part  40  for supporting the detection device  10 , syringe pump  54  for aspirating the particle suspension liquid through the aperture  9  of the detection device  10 , waveform signal processor  58  for processing the waveform of the signal obtained when a particles passes through the aperture  9 , controller  59  configured by a CPU and memory and the like, display unit  6 , and touch panel  60  provided on the front surface of the display unit  6 . These components may be installed or accommodated within a box-like casing  7 . 
     The structure of the various components is described below according to the flow of the measurement series. 
     As shown in  FIG. 1 , the measurement starts when the detection device  10  is arranged within the beaker  52  and the operator inputs a measurement start instruction on the touch panel  60 . When the measurement starts, the controller  59  sends an instruction signal for the aspiration of the preparation to a drive circuit  61 . The drive circuit  61  drive a stepping motor  62  based on the received instruction signal. The syringe pump  54  is driven by the stepping motor  62  and aspirates the particle suspension liquid within the beaker  52  through the detection device  10  and a particle suspension aspirating tube  53 . 
     The particle diameter measuring apparatus  1  is provided with a first electrode (negative electrode)  55  disposed within the beaker  52  and outside of the detection device  10 , second electrode (positive electrode)  56  disposed within the detection device  10 , and a constant current circuit  57  for providing a constant current between the first electrode  55  and second electrode  56 . The constant current circuit  57  applies a voltage between the electrodes so that a constant current flows to the first and second electrodes at the same time the syringe pump  54  aspirates the particle suspension liquid. When a particle passes through the aperture  9  of the detection device  10 , there is a change in the electrical resistance between the first electrode  55  and second electrode  56 , and the current representing this change of electrical resistance is input to the waveform signal processor  58 . 
     The waveform signal processor  58  is provided with an amp  581 , analog signal processing unit  582 , AD converter  583 , and digital signal processing unit  584 . When a current representing a change in the electrical resistance is input, the amp  581  converts the input current to a voltage, and generates an analog signal, which is output to the analog signal processing unit  582 . The analog signal processing unit  582  amplifies and filters the analog signal received from the amp  581  to obtain a signal suited for output to the AD converter  583 , which is described later. The AD converter  583  samples the received analog signal for a waveform corresponding to 1 particle, and converts the signal to a digital signal, which is output to the digital signal processing unit  584 . The digital signal processing unit  584  extracts characteristic data from the pulse signal corresponding to one particle contained in the received digital signal. The characteristic data, for example, includes pulse height and pulse width. The digital signal processing unit  584  generates histogram data based on the characteristic data of a plurality if particles and stores the data in memory, and also sends the histogram data to the controller  59 . The digital signal processing unit  584  counts the number of particles based on the number of received digital signals, and sends the particle count to the controller  59 . The controller  59  analyzes the particle diameter, volume, and concentration in the particle suspension liquid from the characteristic data received from the digital signal processing unit  584 . The controller  59  performs statistical analysis based on average particle diameter, standard deviation and the like, and displays the analysis results and particle count on the display unit  6 . 
     [Detection Device] 
     The detection device  10  is described in detail below.  FIG. 3  is a perspective view of the detection device  10  of the particle diameter measuring apparatus  1  showing the detection device  10  being supported by a detection device supporting part  40 , which is described later.  FIG. 4  is a perspective view of the detection device  10  including a partial cross section.  FIG. 5  is a front view of the detection device  10  including a partial cross section.  FIG. 6  is a bottom view of the detection device  10 . Note that, in  FIGS. 3 through 6 , and  FIGS. 21 through 23  which are described later, the detection device supporting part  40  for supporting the detection device  10  and a casing  8  within which the detection device supporting part  40  is arranged are both described in terms of the detection device  10  installed in the apparatus. The casing  8  is arranged within the casing  7  on the outer side of the mentioned particle diameter measuring apparatus  7 . 
     The detection device  10  is mainly configured by a mounting fixture  20 , and a detection body  30  removably mounted to the bottom end of the mounting fixture  20 . The detection device  10  is supported by the detection device supporting part  40  via the mounting fixture  20 . 
     As shown in  FIGS. 3 through 5 , the detection body  30  is configured by a tubular member that is closed at one end (the bottom end while in use as shown in the drawing), and a ruby pellet  32  is disposed in a concavity  31  in the vicinity of the bottom end. An aperture  9  for the passage of the particle suspension liquid containing particles is disposed in the center of the pellet  32 . The interior of the detection device  10  forms a first flow path  34 ; the first flow path  34  connects to a second flow path  23  (refer to  FIG. 4 ) of the mounting fixture  20  which is described later. 
     A collar  35  is formed at the top end of the detection body  30 . As will be described below, the detection body  30  is connected to the mounting fixture  20  by fitting the installation ring  90  (refer to  FIGS. 4  and  5 ) in the detection body  30  so that the collar  35  is supported from below, such that the installation ring  90  is mounted on the mounting fixture  20 . The detection body  30 , for example, can be made of glass, ABS resin or the like. 
     The detection body  30  must be exchanged in accordance with the detection target particle since the diameter of the aperture  9  must change according to the size of the detection target particle. In the electrical resistance type particle diameter measuring apparatus  1  of the present embodiment, it is possible to detect particles of approximately 2 to 60% of particle diameters via the diameter of the aperture  9 . Therefore, in the particle diameter measuring apparatus  1 , the detection body which has an aperture diameter of 25 micrometers is used when the detection target particle diameter is 0.5 to 15 micrometers. The detection body which has an aperture diameter of 50 micrometers is used when the detection target particle diameter is 1 to 30 micrometers. The detection body which has an aperture diameter of 100 micrometers is used when the detection target particle diameter is 2 to 60 micrometers. The detection body which has an aperture diameter of 200 micrometers is used when the detection target particle diameter is 4 to 120 micrometers. 
     The mounting fixture  20  is described below.  FIG. 7  is a top plan view of the mounting fixture  20 ,  FIG. 8  is a front view of mounting fixture  20  (viewed from the arrow A direction of  FIG. 7 ),  FIG. 9  is a side view of the mounting fixture  20  (viewed from the arrow B direction of  FIG. 7 ),  FIG. 10  is a cross sectional view on the A-A line of  FIG. 9 , and  FIG. 11  is a cross sectional view on the B-B line of  FIG. 9 . 
     The mounting fixture  20  is mainly a component for mounting the replaceable component of the detection body  30  to the detection device supporting part  40  of the particle diameter measuring apparatus  1 . As shown in  FIGS. 8 through 10 , the mounting fixture  20  is a short tube. A protrusion (flange)  21  is provided on the top end of the mounting fixture  20  in the longitudinal direction. The flange  21  has a collar shape that protrudes laterally, and has an external diameter that is large compared to the barrel  19  in the center of the longitudinal direction of the mounting fixture  20 . The detection device  10  is supported by the detection device supporting part  40  through the flange  21 . As will be described later, the detection device supporting part  40  incorporates a buffer  41  (refer to  FIG. 15 ) including a foam elastic body  46 , and the buffer  41  also includes a top plate  44  that sits on top of the foam elastic body  46 . The flange  21  is mounted on the top plate  44 , and the barrel  19  of the mounting fixture  20  is inserted into an opening  44   a  provided in the top plate  44 , as shown in  FIG. 2 . 
     The function of the mounting fixture  20  is described below with reference to  FIG. 16 . In  FIG. 16 , the single dash line represents the planar shape of the flange  21  of the mounting fixture  20 , and the double dash line represents the horizontal cross sectional shape of the barrel  19  of the mounting fixture  20 . As shown in  FIG. 16 , the flange  21  is sized to protrude from the opening  44   a  of the buffer  41  when the flange  21  is seated on the top plate  44  of the buffer  41  with the barrel  19  inserted in the opening  44   a . More specifically, the four corners protrude from the opening  44   a  when the barrel  19  of the mounting fixture  20  has been inserted in the opening  44   a . Thus, the flange  21  can be latched to the top plate  44 , and the detection device  10  is supported so as to hang perpendicularly from the top plate  44  via its own weight. Referring again to FIGS.  7  through  117 ˜ 11 , the structure of each part of the mounting fixture  20  is described below. 
     The mounting fixture  20  includes the flange  21  disposed at the top thereof, the mounting part  22  disposed at the bottom, and a second flow path  23  disposed within. As shown in  FIG. 7 , the flange  21  is flat and approximately square. Screw holes  24   a  are provided at two opposed corners so that the second flow path  23  is situated therebetween in the center of the flange  21 , the screw hole  24   a  being configured by a through hole for the insertion of a screw  61  (refer to  FIG. 3 ) for connecting the tube adapter  60  (refer to  FIGS. 3 through 5 ). 
     As indicated by the dashed lines in  FIG. 7 , screw holes  24   b  (refer to  FIG. 8 ) are formed on the side surface of the flange  21  in the vicinity of the remaining two opposed corners with the center second flow path  23  interposed therebetween, the screw holes  24   b  being provided for the insertion of screws  71  for anchoring, to the flange  21 , the connecting piece  70  (refer to  FIGS. 3 ,  4 , and  17 ) used to anchor the flange  21  to the detection device supporting part  40  (refer to  FIGS. 3 and 4 ). The screw hole  24   a  is formed in a vertical direction (longitudinal direction of the mounting fixture  20 ), whereas the screw hole  24   b  is formed in a horizontal direction (direction perpendicular to the longitudinal direction of the mounting fixture  20 ). A step  26  is also formed on the side surface on which the screw hole  24   b  is provided. The connecting piece  70  (to be described later) is positioned so as to communicate with the screw hole  24   b  and through hole  73  (refer to  FIG. 17 ) of the connecting piece  70  via a vertical piece  70   a  (refer to  FIG. 17 ) abutting the step  26 . 
     As shown in  FIG. 9 , the flange  21  is provided with a washing liquid supply port  25  that connects to a washing liquid tube  62  for supplying washing liquid into the detection device  10  to wash the flow path of the detection device  10 . The washing liquid supply port  25  communicates with the second flow path  23 , as shown in  FIG. 11 . 
     As shown in  FIG. 10 , a channel  28   a  for the disposition of an O-ring  27  is formed on the top surface  21   a  of the flange  21 . 
     A male threaded part  22   b  for engaging a female threaded part  91  (refer to  FIG. 5 ) of the installation ring  90  (described layer) is provided on the outer surface of the mounting part  22  disposed on the bottom of the mounting fixture  20 . A channel  28   b  for the disposition of an O-ring  27  is formed on the bottom surface  22   a  of the mounting part  22 . 
     A channel  29  which has an approximate V-shaped cross section, as shown in  FIGS. 8 and 9 , is formed at locations from the mounting part  22  on the outer surface of the barrel  19  between the flange  21  and mounting part  22 . The channel  29  is formed at two symmetrical locations on the side surface centered on the second flow path  23 . As shown in  FIG. 8 , the channel  29  is provided in the horizontal direction (a direction perpendicular to the longitudinal direction of the mounting fixture  20 ). The two channels  29  are mutually parallel in disposition. Using the channels  29 , the mounting fixture  20  can be anchored (prevented from moving, including rotation) when the detection body  3  is installed on the mounting fixture  20  and removed from the mounting fixture  20 . 
     [Installation Ring] 
     In the present embodiment, the detection body  30  and the mounting fixture  20  are connected via the installation ring  90 . 
     As shown in  FIGS. 4 and 5 , the installation ring  90  is a short tubular member, the top interior surface of which is provided with a female threaded part  91  capable of engaging the previously mentioned male threaded part  22   b  disposed on the outer surface of the mounting part  22  of the mounting fixture  20 . The interior of the installation ring  90  is provided with a latch  92  configured by a step formed to engage the diameter intermediate to the top opening and bottom opening. The latch  92  latches to the bottom surface of the previously mentioned collar  35  of the detection body  30 . 
     The bottom outer side of the installation ring  90  is tapered with a decreasing diameter toward the tip (bottom end). The outer surface of the installation ring  90  is preferably grooved to be grasped easily when screwing or unscrewing the male threaded part  91  and female threaded part  22   b  of the mounting part  22 . 
     The top opening of the installation ring  90  is large enough to allow passage of the collar  35  of the detection body  30 , whereas the bottom opening of the installation ring  90  is not large enough to allow passage of the collar  35  but is large enough for the passage of the tubular part  30   a  of the detection body  30 . 
     The mounting of the detection body  30  on the mounting fixture  20  is performed as follows. 
     First, the closed end (end on the side on which the pellet  32  with the aperture is disposed) of the detection body  30  provided with an aperture  9  of a desired diameter is inserted toward the bottom opening from the top opening of the installation ring  90 . 
     The detection body  30  is fitted to the mounting fixture  20  so that there is contact between the top end surface (top surface of the collar  35 ) of the detection body  30  and the bottom end surface of the mounting fixture  20 , and the female threaded part  91  of the installation ring  90  is screwed onto the male threaded part  22   b  of the mounting fixture  20 . The collar  35  of the detection body  30  is anchored by the latch  92  of the installation ring  90  and the mounting part  22  of the mounting fixture  20 . Thus, the detection body  30  is mounted on the mounting fixture  20 . The detection body  30  can be readily installed on the mounting fixture  20  and easily removed from the mounting fixture  20  because the mounting part  22  of the mounting fixture  20  protrudes downward from the opening of the base as will be described later. 
     Thus, the detection body  30  can be simply connected to the mounting fixture  20 . Note that, in the present embodiment, although a locking mechanism is provided to prevent operation of the mounting fixture  20  when engaged, details of the locking mechanism are described later. 
     When removing the detection body  30  from the mounting fixture  20 , the installation ring  90  is rotated in the reverse direction to disengage the engagement of the female threaded part  91  of the installation ring  90  and the male threaded part  22   b  of the mounting part  22 . Thus, the detection body  30  can be removed from the mounting fixture  20  with the collar  35  latched to the latch  42  of the installation ring  90  so as to avoid the danger of the detection body  30  falling. 
     [Tube Adapter] 
     The tube adapter  60  is described in detail below.  FIG. 12  is a top view of the tube adapter  60 ,  FIG. 13  is a side view of the tube adapter  60 , and  FIG. 14  is a cross sectional view on the C-C line of  FIG. 13 . 
     The tube adapter  60  is an approximately cube shape member. The bottom surface  60   a  is open. As shown in  FIG. 12 , the opposed corners are provided with through holes  67  for the insertion of a screw  61  for anchoring the tube adapter  60  to the flange  21  of the mounting fixture  20 . The tube adapter  60  is anchored to the flange  21  by screwing the screw  61  inserted in the through hole  67  into the screw hole  24  formed in the top surface of the flange  21 . The top surface  60   a  of the tube adapter  60  is provided with a hole  69  for the disposition of a connector  68  (refer to  FIG. 3 ) used to connect the wire  65  and a lead (not shown in the drawings) from the first electrode  55  within the detection device  10 . 
     The side surface (side surface of the inner side of the mechanism when the tube adapter  60  is locked to the flange  21 )  60   c  of the tube adapter  60  is provided with a washing liquid aspirating port  81  connected to the tube  63  for aspirating the washing liquid and a particle suspension liquid aspirating port  80  connected to a suspension liquid aspirating tube  53  for aspirating the particle suspension liquid. 
     The suspension liquid aspirating port  80  and washing liquid aspirating port  81  communicate with the internal space  82  of the tube adapter  60  (refer to  FIG. 14 ), and the internal space  82  communicates with the internal space of the detection device  10 , that is, the flow path configured by the first flow path  34  and second flow path  23 , as shown in  FIGS. 4 and 5 . 
     The tube adapter  60  and mounting fixture  20 , and the detection body  30  and mounting part  22  of the mounting fixture  20  are respectively connected via the respective O-ring  27  so as to be liquid-tight. 
     [Detection Device Supporting Part] 
     The detection device supporting part  40  is described in detail below. 
     The detection device supporting part  40  supports the detection device  10  at a predetermined position within the apparatus, that is, supports the detection device  10  at a measurement position for aspirating the particle suspension liquid within the detection device  10  and detecting particles. As shown in  FIG. 3 , the detection device supporting part  40  is provided with a buffer  41  (refer to  FIG. 16 ) that includes a foam elastic body  46 , and a base  42 . The base  42  has an opening  42   c  (refer to  FIG. 5 ) large enough for the passage of the mounting part  22  of the mounting fixture  20  and the surface  43  on which the buffer  41  is seated, and is anchored to the casing  8  of the particle detection unit. 
       FIG. 15  is a perspective view of the buffer  41 . The buffer  41  is configured by a top plate  44 , bottom plate  45 , and the foam elastic body  46  disposed medially to the top plate  44  and bottom plate  45 . The foam elastic body  46  is adhered to the top plate  44  and bottom plate  45  with adhesive. 
     The top plate  44  is an annular flat member having an opening  44   a  in the center of sufficient size for the passage of the mounting part  22  of the mounting fixture  20 , and has a thickness of approximately 1.5 mm, as shown in  FIG. 16 . The plate material is not specifically limited, but is preferably aluminum from the perspective of being light weight. When the top plate  44  is made of lightweight aluminum, the foam material of the foam elastic body  46  is not crushed and there is no reduction of the damping effect of the foam elastic body  46 . The protrusions  44   b  extending from the outer diameter direction are provided at opposed positions with the opening  44   a  between on the top plate  44   a , and a threaded hole  44   c  is formed on the protrusion  44   b . The threaded hole  44   c  is used to anchor the mounting fixture  20  to the top plate  44  using the connection piece  70 . The connection piece  70  is configured by two pieces joined to form an L-shaped cross section, with the vertical piece  70   a  abutting the flange  21  of the mounting fixture  20 , and the horizontal piece  70   b  abutting the top plate  44 , as shown in  FIG. 17 . The vertical piece  70   a  is provided with a through hole  73  for the insertion of a screw, and the horizontal piece  70   b  is provided with a through hole  74  for the insertion of a screw. The flange  21  of the mounting fixture  20  is anchored to the top plate  44  by inserting a screw  71  through the through hole  73  of the vertical piece  70   a  and screwing into the side surface of the flange  21 , and inserting a screw  72  through the through hole  74  of the horizontal piece  70   b  and screwing into the screw hole  44   c  of the top plate  44 . 
     Similar to the top plate  44 , the bottom plate  45  is an annular flat member having an opening  45   a  in the center of sufficient size for the passage of the mounting part  22  of the mounting fixture  20 , and has a thickness of approximately 1.5 mm, as shown in  FIG. 18 . The plate material is not specifically limited, but is preferably aluminum from the perspective of being light weight. The protrusions  45   b  extending from the outer diameter direction are provided at opposed positions with the opening  45   a  between, and a threaded hole  45   c  is formed on the protrusion  44   b . The threaded hole  45   c  is sued to anchor the bottom plate  45  to the base  42 . As shown in  FIG. 5 , the base  42  is provided with a hole  42   a  corresponding to the threaded hole  45   c  of the bottom plate  45  seated on the base  42 , such that the bottom plate  45  is anchored to the base  42  by inserting a screw  47  into the hole  42   a  via the bottom surface of the base  42  and screwing into the threaded hole  45   c  of the bottom plate  45 . 
     The foam elastic body  46  is an annular member with a central opening  46   a , and has a thickness of approximately 1 to 10 mm, and preferably 3 to 7 mm, as shown in  FIG. 19 . In the present embodiment, the thickness of the foam elastic body  46  is 5 mm. The foam elastic body  46  is a member preventing the transmission of vibration from the drive sources of the fan, syringe pump and the like within the apparatus, and vibration from outside the apparatus (including vibration generated by the propagation of sound waves to the apparatus casing from conversation among technicians around the apparatus) to the detection device  10 . 
     The material of the foam elastic body  46  may be a porous material with elasticity (foam), such as, for example, semi-independent semi-continuous foam of ethylene propylene diene monomer (EPDM) and polyurethane foam. An example of semi-independent semi-continuous foam EPDM is EPT-SEALER series (commercial name; Nitto Denko Corporation), and an example of polyurethane foam is Calmflex series (commercial name; INOAC Foam Company). Note that a spring may used used rather than a foam elastic body insofar as the spring blocks the transmission of vibration to the detection device. The spring used may be a coil spring, plate spring or the like. As a result of investigations by the present inventors, it has been confirmed that using polyurethane foam and semi-independent and semi-continuous foam effectively eliminates generation of noise caused by vibration, and allows signals from particles to be distinguished from noise. 
     [Lock Mechanism] 
     In the present embodiment, the detection device  10  is supported by the buffer  41  of the detection device supporting part  40 . More specifically, the flange  21  of the mounting fixture  20  of the detection device  10  is anchored to the top plate  44  configuring the buffer  41  via the connecting piece  70 , and the bottom plate  45  configuring the buffer  41  is anchored to the base  42  of the detection device supporting part  40 . The foam elastic body  46  is disposed between the top plate  44  and the bottom plate  45 . The detection device supporting part  40  therefore supports the flange  21  of the detection device  10  through the foam elastic body  46 . More specifically, the detection device supporting part  40  supportively floats the detection device  10  from the base  42  via the foam elastic body  46 . Viewed from the detection device  10 , the detection device  10  is supported by the detection device supporting part  40  that includes the foam elastic body  46  through the flange  21 . 
     Supporting the detection device  10  on the detection device supporting part  40  through the flange  21  alone means the detection device  10  does not contact the detection device supporting part  40  unless through the flange  21 . Insofar as the detection device  10  is not anchored by the lock mechanism  100  (to be described later), the detection device  10  does not contact the base  42  except through the flange  21  since the detection device  10  is supportively floated from the base  42  by the flange  21  seated on the buffer  41  of the detection device supporting part  40 . Therefore, vibration propagated to the base  42  from the drive sources such as the syringe pump  54  and stepping motor  64  (refer to  FIG. 2 ) of the particle diameter measuring apparatus  1  is invariably transmitted to the detection device  10  intermediated by the foam elastic body  46  of the buffer  41 . The vibration transmitted to the detection device  10  is thus blocked by the foam elastic body  46 , and virtually none of the vibration from the drive sources is propagated to the detection device  10 . 
     As previously described, the foam elastic body  46  effectively prevents transmission to the detection device  10  of the vibration generated within the apparatus and the vibration transmitted to the apparatus from outside the apparatus due to the high capacity for damping vibration transmission. As a result, it is possible to prevent noise caused by such vibration, signals generated by the passage of microparticles can be readily distinguished from noise, and particle measurement accuracy is thereby improved. 
     On the other hand, although the installation ring  90  must be rotated when installing the detection body  30  on the mounting fixture  20  or the removing from the mounting fixture  20 , the mounting fixture  20  is moved relatively simply with little force since the flange  21  of the mounting fixture  20  is supported only by the soft part of the foam elastic body  46 . Therefore, some effort must be expended in the operation to rotate the installation ring  90  while the fingers press the mounting fixture  20  so that the mounting fixture  20  will not move. When the installation ring  90  is rotated without anchoring the mounting fixture  20 , a shearing force acts on the foam elastic body  46  and may cause the foam elastic body  46  to separate from the plates  44  and  45  and lead to ultimate damage. 
     In the present embodiment, therefore, the lock mechanism  100  is used to anchor the mounting fixture  20  of the detection device  10  when installing or removing the detection body  30 . 
     The lock mechanism  100  is provided on the back surface  42   b  of the surface  43  of the base  42  of the detection device supporting part  40 . As shown in  FIGS. 3 through 6 , the lock mechanism  100  mainly provides a pair of clamps  101  capable of gripping the mounting fixture  20 , and a ring body  102  which is a locking tool for locking the two clamps  101  while the clamps  101  are gripping the mounting fixture  20 . The lock mechanism  100  further provides a spring  103  for pressing both clamps  101  in mutually opposite directions, positioning block  104  (refer to  FIG. 3 ) for positioning when the grips are proximate to one another, and stopper  105  for regulating the separation position of the clamps  101 . 
       FIG. 20  shows the clamps  101 , (a) in top view, (b) in side view (from the arrow C direction of  FIG. 20(   a )), and (c) in cross sectional view on the D-D line. In the following description, only one of the pair of clamps  101  is mentioned. In the present embodiment, the two identically configured clamps  101  are disposed so as to be opposed as shown in  FIG. 6 . 
     In the following description, the end on the side provided with the through hole  107  (side indicated by the arrow D in  FIG. 20 ) is referred to as the base end, and the end on the side provided with the latch channel  110  for fitting the lock ring  102  (side indicated by the arrow E in  FIG. 20 ) is referred to as the tip end. The side surface on the side opposite the two clamps  101  engaging the lock  20  (side in the arrow D direction in  FIG. 20 ) is referred to as the inside surface, and the side surface on the back side of the inside surface (side in the arrow E direction in  FIG. 20 ) is referred to as the outside surface. 
     The clamp  101  is an elongated member having a certain thickness, the base end of which is provided with a through hole  107  for the insertion of a pin  106  (refer to  FIG. 6 ). The clamp  101  is mounted on the back surface  42   b  of the base  42  so as to be rotatable. A hole  108  is formed from the through hole  107  in the inside surface of the tip end side, and an end of a spring  103  is disposed inside this hole  108 . Both clamps  101  are pressed in a direction to cause mutual separation of the tips  101   b  on the tip ends thereof by the elastic force in the expansion direction of the spring  103 , and the movement of the clamps  101  is regulated by the stopper  105  disposed on the base end from the pin  106  so that the movement does not exceed a predetermined range. 
     A notch-like pinch-grip  120  is formed approximately intermediate to the inside surfaces  101   c  of the clamps  101 . The pinch-grip  120  includes two inclinations  121  that incline from the inside surface toward the outside surface, and a convexity  122  formed along the longitudinal direction between the two inclinations  121 . As shown in  FIG. 20(   c ), the convexity  122  has a height contracting toward the inside surface. The outside surface of the end  101   b  of the clamp  101  is provided with a lock channel  110  for locking the ring body  102 . 
     As shown in  FIG. 1 , the positioning block  104  is anchored to the back surface  42   b  of the base  42  approximately intermediate to the tip ends  101   b  of the two clamps  101 . The positioning block  104  is a member for positioning each clamp  101  essentially equidistant from and in proximity to the mounting fixture  20  with the mount position of the gripped mounting fixture  20  centered between the clamps  101  when the ends  101   b  of the clamps  101  are gripping and the clamps  101  are in mutual proximity, as shall be described later. 
     The positioning block  104  supports the lock tool of the ring body  102  so as to be freely oscillatable on the positioning block  104 . The ring body  102  is a frame of bent wire, as shown in  FIG. 3 . The ends of the ring body  102  are an axis supported on the side surface of the positioning block  104 , so as to be vertically rotatable as a pendulum. 
     [Locking Operation and Unlocking Operation] 
     The mounting fixture  20  locking and unlocking operations using the lock mechanism  100  are described below. 
       FIGS. 3 through 6  show the mounting fixture  20  in the locked state via the lock mechanism  100 . In this state, the detection body  30  is mounting on the mounting fixture  20  and removed from the mounting fixture  20 . In this locked state, the pair of clamps  101  are positioned in mutual proximity and the end  101   b  abut the positioning block  104 . The ring body  102  is fitted to the ends  101   b  of the clamps  101  so as to be mutually separated by the elastic force in the expansion direction of the spring  103 . 
     In the locked state, the barrel  19  of the mounting fixture  20  is positioned between the opposed pinch-grips  120  of the clamps  101 . Thus, the convexity  122  of the pinch-grip  120  is fitted in the channel  29  formed in the barrel  19 , and the vertical (perpendicular direction) movement of the mounting fixture  20  is regulated. The inclination  121  formed on the tip end of the convexity  122  and the inclination  121  formed on the base end thereof abut the outer surface of the barrel  19 , and the movement of the mounting fixture  20  in the forward and back directions (direction from the tip end toward the base end) is regulated. The mounting fixture  20  is therefore solidly anchored. 
       FIGS. 21 through 23  show the unlocked state of the mounting fixture  20  via the lock mechanism  100 ;  FIG. 21  is a perspective view of the detection device with a partial cross section and corresponds to  FIG. 4 ,  FIG. 22  is a front view of the detection device with a partial cross section and corresponds to  FIG. 5 , and  FIG. 23  is a bottom view of the detection device and corresponds to  FIG. 6 . 
     The lock release is accomplished simply by removing the ring body  102  from the channel  110  formed in the end  101   b . That is, when the ring body  102  is removed from the channel  110 , the clamps  101  move in the separation direction via the elastic force in the expansion direction of the spring  103 . Then, since the convexity  120  of the clamps  101  also separate from the barrel  19 , the contact between the outer surface of the barrel  19  and the inclination  121  of the clamp  101  is released as is the engagement between the convexity  122  and the channel  29 . 
     In the present embodiment described above, vibration transmission to the detection device  10  is blocked by the mediation of the foam elastic body  46  in the path in which the vibration from the drive sources is propagated to the detection device  10 . When the mounting device  20  is anchored to the detection device supporting part  40  by the lock mechanism  100 , the vibration from the drive sources propagates to the detection device  10  through the lock mechanism  100 , not just the foam elastic body  46 . The vibration propagated through the lock mechanism  100  makes it difficult to distinguish the noise from the particle when measuring particle diameter in this state since the vibration propagates to the detection device  10  and is not blocked by the foam elastic body  46 . 
     The particle diameter measuring apparatus of the present embodiment effectively eliminates noise caused by vibration by releasing the locked state of the lock mechanism  100  when measuring particle diameter (when particles are aspirated from the suspension liquid and pass through the aperture, and avoids the risk of damage to the foam elastic body  46  when replacing the detection device  10  by locking the mounting fixture  20  via the lock mechanism  100  when replacing the detection device  10 . 
     [Vibration Damping Effect] 
     In the present embodiment described above, blank measurements were performed when the detection device was supported by the foam elastic body alone (unlocked state in the examples), and when the detection device was anchored via the lock mechanism (locked state in a comparative examples), and the influence of noise generated during these measurements was investigated. The blank measurement was a measurement of a liquid preparation (blank preparation) that did not contain a suspension of particles, and was performed identically to the measurement of the particle suspension liquid. In the blank measurement, the particle count is ideally zero since only the baseline waveform signal is obtained, that is, only a waveform signal that does not contain a signal of a particle passing through the aperture is obtained. The particle count obtained by the blank measurement was made the index for evaluating the disruption of the base line, that is, the magnitude of the noise. 
     The signal waveforms obtained from the blank preparation was investigated using an oscilloscope with a detection device having an aperture diameter of 25 micrometers. Noise was generated during measurements as follows. 
     A speaker was placed at a position 150 mm from the door on the front surface of the apparatus, and sine waves were generated from the speakers at frequencies of 250, 400, and 1,000 Hz during measurements using sound generating software. Note that the volume of the sound was suitable for comparative investigation, and the evaluations of the examples and comparative examples were made using the same volume of sound at each frequency. 
     The results are shown in  FIGS. 24 through 26 .  FIG. 24  shows the baseline waveform at a frequency of 250 Hz,  FIG. 25  shows the baseline waveform at 400 Hz, and  FIG. 26  shows the baseline waveform at 1,000 Hz. In the drawings, (a) shows the comparative example with the detection device locked, and (b) shows the example with the detection device unlocked. 
     As can be clearly understood from  FIGS. 24(   b ),  25 ( b ), and  26 ( b ), when the detection device is locked, the baseline waveform is disrupted by the influence of the vibration caused by the generated sound, and the count increases in the blank measurement as shown in Table 1. Conversely, as can be understood from  FIGS. 24(   a ),  25 ( a ), and  26 ( a ), when the detection device is unlocked, the baseline is stable and there is no observed increase of the count during the blank measurement as shown in Table 1. 
     Thus, reduction of the influence of noise on the measurement at an aperture diameter of 25 micrometers via the vibration damping by the foam elastic body was confirmed. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Blank Measurement Counts 
               
            
           
           
               
               
            
               
                   
                 Frequency 
               
            
           
           
               
               
               
               
            
               
                   
                 250 Hz 
                 400 Hz 
                 1,000 Hz 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Comparative Example 
                 20.494 
                 29.007 
                 19.061 
               
               
                   
                 (detection device 
               
               
                   
                 locked) 
               
               
                   
                 Example (detection 
                 275 
                 207 
                 451 
               
               
                   
                 device unlocked) 
               
               
                   
                   
               
            
           
         
       
     
     [Modifications] 
     The present invention is not limited to the embodiment described above, and may be variously modified. For example, although a member provided with the lock piece and ring body is used as the lock mechanism in the embodiment described above, a parallel bar guide  130  and parallel bar unit  131  may also be used as shown in  FIG. 27 . 
     The parallel bar guide  130  is a substantially square plate with a circular opening  132  disposed in the center, and is anchored to the back surface of the base  42  so that the opening  132  is concentric to the opening  42   c  of the base  42 . 
     The parallel bar unit  131  is configured by two mutually parallel bars  133 , base  134  to which the parallel bars  133  are attached, and a knob  135  disposed in the center of the base  134 . A shaft  136  extends from one end of the knob  135 , and a male threaded part  137  is formed on the tip end of the shaft  136 . The shaft  136  is inserted in a through hole  138  formed in the base  134  so as to be rotatively movable. 
     The parallel bar plate  130  is provided with a hole  139  into which the bar  133  can be inserted, and the front surface  130   a  of the parallel bar guide  130  is provided with a threaded hole  140  into which can be screwed the make threaded part  137  on the tip end of the shaft  136 . 
     When locking the detection device, the bars  133  of the parallel bar unit  131  are inserted into the holes  139  of the parallel bar plate  130 . Then, after the male threaded part  137  on the tip end of the shaft  136  contacts the threaded hole  140 , the knob  135  is rotated to screw the male threaded part  137  into the threaded hole  140 . The parallel bar unit  131  is thus attached to the parallel bar guide  130 . 
     The bars  133  of the parallel bar guide  131  are set at the positions of the holes  139  so as to cross the opening  132  of the parallel bar guide  130 . Part of the bars  133  that cross the opening  132  is inserted in a channel formed on the outer surface of the small diameter part of the mounting fixture disposed within the opening  132 . Thus, the vertical and lateral movement of the detection device is regulated, and the detection device anchoring is complete. 
     When releasing the lock of the detection device, the knob  135  is rotated in the opposite direction, the male threaded part  137  is extracted from the threaded hole  140 , and the parallel bar unit  131  is drawn forward to remove the bars  133  from the holes  139 . The detection device is thus unlocked. 
     Although the present embodiment has been described by way of example in which the mounting fixture  20  and detection body  30  are separate, the present invention is not limited to this example inasmuch as the mounting fixture  20  and detection body  30  also may be integratedly formed as a single unit. 
     Although the present embodiment has been described by way of example in which the detection device is supported by the foam elastic body  46  of a piece formed in an annular configuration, the present invention is not limited to this example inasmuch as the foam elastic body also may be divided among a plurality of pieces so that the detection device is supported by a plurality of foam elastic bodies  46 . 
     Although the present embodiment has been described by way of example in which the particle diameter is obtained by the controller  59  provided within the particle diameter measuring apparatus  1 , the present invention is not limited to this example inasmuch as the particle diameter also may be obtained by, for example, sending the characteristic data obtained by the digital signal processor  584  to an external computer, and analyzing the characteristic data in the external computer. 
     Although the present invention describes a particle diameter measuring apparatus of the electrical resistance type, the present invention is not limited to this example. For example, the present invention also may be applied to a particle diameter measuring apparatus of the optical type. In this case, the configuration may provide a detection device that allows passage of particles through the interior thereof, a detection device supporting part that includes an elastic body to support the detection device through the elastic body, and a signal obtainer for obtaining signals from particles that pass through the interior of the detection device. 
     The present embodiment has been described by way of example that uses an elastic body configured by a foam elastic body and spring to block vibration from propagating to the detection device. However, the present invention is not limited to this example inasmuch as a gel material also may be used as the material for supporting the detection device insofar as the gel material has properties that absorb or block vibration. 
     Although the present embodiment describes a particle diameter measuring apparatus, the present invention is also applicable to apparatuses for measuring particles in a particle suspension liquid.