Abstract:
A disposable sampling device for an apparatus for counting particles contained in a liquid, including a solid block-shaped housing connectable in a defined position to the apparatus. The housing has a member for introducing a sample therein, a device for metering a defined volume of the sample, and a chamber for containing a defined volume (V) of a diluting liquid. A diluting chamber is provided together with a device for simultaneously directing the defined volume of a sample and the defined volume of diluting liquid to the diluting chamber for obtaining therein a diluted sample. A device is provided for directing at least a portion of the diluted sample past a particle detecting member, and a signal transmitting member connects the particle detecting member and terminal member located at an outer boundary of the housing in a position corresponding to a location of a terminal member of the apparatus when the housing is connected thereto in the defined position.

Description:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/SE98/01033 which has an International filing date of May 29, 1998, which designated the United States of America. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns a disposable sampling device for an apparatus for counting particles contained in a liquid, such as blood cells in a blood sample and yeast fungus in wort, according to the preamble of claim 1. 
     2. Description of Background Art 
     It is known in the state of art to count blood cells by causing a volume of diluted blood sample to pass a so-called capillary, i.e., an extremely small hole, generally in a ruby, the hole having a diameter considerably larger than the size of a blood cell, typically 80 μm. A voltage is applied over the capillary, and, when a blood cell passes through the hole, the electrical resistance changes. This is because the cells can be regarded as insulators. Each change in resistance can be detected by suitable electronic equipment, and the sum of all changes detected corresponds to the number of blood cells having passed through the capillary. In order to obtain the concentration of cells in the original sample, the concentration of cells in the diluted sample is multiplied by the dilution factor, typically 1:40000 when counting of red blood cells (RBC) is concerned. It is obvious, that measuring of sample volumes and dilution liquid volumes must be performed in an accurate and repeatable way such that not only a correct degree of dilution can always be guaranteed but also a thorough and uniform mixing of the two volumes is ensured. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     In a typical state of art apparatus, used for counting blood cells, a syringe is employed for providing a defined volume (typically 5 ml) of diluting liquid, and this volume is displaced through a conduit to a measuring chamber. On its way to the measuring chamber, the diluting liquid brings with it a defined volume (typically 25 μl) of blood sample previously introduced into the conduit. The blood sample mixes with and is diluted by the diluting liquid in the measuring chamber, which is, thus, also a dilution or mixing chamber, and a defined fraction of the diluted sample is further displaced through a capillary located in a wall of the measuring chamber, or, in a transducer located within the measuring chamber. In this state of art device, all components, except a vessel containing a blood sample, are permanently included in an apparatus containing also electronic equipment needed for counting particles and performing calculations necessary for obtaining resulting concentration values. Consequently, all components contacted by blood must be thoroughly cleaned after each counting procedure, such as by flushing with a suitable rinsing liquid. Also, this device is expensive and rather cumbersome, and, therefore, does not lend itself to use outside more well-equipped and established medical institutions, such as hospitals, public health centres and larger private surgeries. 
     There is a need, thus, to provide a relatively cheap and simple device for sampling, e.g. a blood sample or a wort sample, for use with a more stationary particle counting apparatus. The sampling device shall be useful outside medical institutions of the general kind mentioned—as regards blood sampling—as well as in breweries—as regards wort sampling. It shall also be easy to handle even by relatively unskilled personnel, and all its components contacted by a sample shall be contained within a disposable housing. The housing shall not contain expensive components, such as electronic equipment for the actual particle counting and evaluating purposes. 
     The present invention has as its object to provide a sampling device that fulfills the above need. 
     To achieve this, the present invention suggests a disposable sampling device for an apparatus for counting particles contained in a liquid, comprising a solid block-shaped housing connectable in a defined position to said apparatus, said housing having therein means for introducing a sample into said housing; means for metering a defined volume of said sample; means containing a defined volume of a diluting liquid; means defining a diluting chamber; means for simultaneously directing said defined volume of said sample and said defined volume of said diluting liquid to said diluting chamber for obtaining therein a diluted sample; means for directing at least a portion of said diluted sample past particle detecting means; signal transmitting means connecting said particle detecting means and terminal means located at an outer boundary of said housing in a position corresponding to a location of terminal means of said apparatus when said housing is connected thereto in said defined position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will be described hereinafter, reference being made to the annexed drawings, wherein: 
     FIG. 1 is a schematic view showing a state of the art apparatus; 
     FIGS. 2-9 show schematic sections through a first embodiment of a device according to the present invention in various steps of its measuring cycle; 
     FIGS. 10 and 11 show corresponding sections through a second embodiment of the present invention; 
     FIG. 12 shows a schematic perspective view of an embodiment of a particle counting apparatus and a disposable sampling device according to the present invention; 
     FIG. 13 shows the enlarged portion XIII of FIG. 12; and 
     FIG. 14 shows a third embodiment of a disposable sampling device according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the state of art arrangement according to FIG. 1,  11  is a syringe including a cylinder  12  and a piston  13  axially movable within the cylinder by means of a piston rod  14  extending through one end of the cylinder, that may be an open end. The opposite end of the cylinder is closed and connected to a conduit  15 . This conduit  15  in turn communicates with a supply conduit  16  for diluting liquid having a valve  17  therein, and a discharge conduit  18  having a valve  19  therein. In the conduit  18  there is also a turning valve  20 , the non-shown rotatable valve body of which has a through channel  21  and is positionable in two different positions. In a first position (shown in FIG.  1 ), the through channel communicates with a conduit  22  leading to a non-shown pump, and a conduit  23  communicating with a vessel  24  containing a blood sample to be diluted. The blood sample in the vessel  24  may be diluted already to a certain extent. The discharge conduit  18  ends in a mixing and measuring chamber  25 . In a wall of the chamber  25  there is a capillary  26  and a discharge conduit  27  including a metallic portion  28  constituting an electrode connected to an electric wire  29 . A further electrode  30  is located within the chamber  25  and is connected to an electric wire  31 . A voltage may be applied across the capillary by connecting wire  29  to one pole and wire  31  to the other pole of a suitable electronic counting equipment. 
     Upon operation of the pump, blood sample is transported from the vessel  24  through the valve  20  so as to fill the through channel  21 . In a second position of the valve body, the through channel communicates with the conduit  18 . Since the through channel  21  contains an accurately defined volume, turning of the valve body to the second position will put this defined volume in communication with the conduit  18 . 
     The function of the known device is as follows: The valve  17  is opened and the piston lowered to suck a defined volume of diluting liquid into the syringe. Thereafter, the valve  17  is closed and the valve  19  opened, and the piston  13  is raised thereby displacing diluting liquid through the conduit  18  through the valve  20 , the valve body of which being positioned in its second position so that the defined volume of blood sample is brought by the diluting liquid to the mixing and measuring chamber  25  where the very small volume of blood sample is mixed with and diluted by the relatively large volume of diluting liquid. A defined portion of the mixed and diluted sample is brought through the capillary  26 , and the blood cells are counted by the electronic counting equipment. 
     The embodiments of the disposable particle counting device of present invention to be described hereinafter with reference to FIGS. 2-9 (first embodiment) and FIGS. 10 and 11 (second embodiment) utilize some of the features of the prior art device described above, while others have been replaced by such more suitable for a disposable, self-contained product. 
     The device comprises a substantially block-shaped body  40  (see FIG.  12 ), preferably made of a transparent material, such as a moldable synthetic resin and having an upper wall  41 , a bottom wall  42  and a front wall  43 . In the body  40 , there is provided a cylinder  44  having an upper end  45  and a lower end  46 . A piston  47  is axially movable within the cylinder by means of a piston rod  48  accessible from outside the housing at the lower end  46  of the cylinder, the upper end  45  of which being connected to a channel  49  provided in the housing. 
     In the housing there is also provided a turning valve  50  having a valve body  51  rotatable within a cylindrical valve chamber  52 . An actuating means, such as a diametrically extending slot or two diametrically opposed holes  51 ′, is provided to rotate the valve body from outside the housing. A through channel  53  extends across the valve body which is positionable in two different positions. 
     In a first position (shown in FIGS. 2,  3 ,  4 ,  9 ,  10  and  11 ), the through channel communicates with an intake channel  54  in the housing opening in a sample receiving aperture  55  in the front wall  43  and a sucking channel  56  leading to a sucking means in the shape of a diaphragm pump  57  having a resilient diaphragm  58  covering a conical recess  59  in the upper wall  41 . 
     In a second position (shown in FIGS.  5 - 8 ), the through channel  53  communicates with the channel  49  from the cylinder  44  and with a channel  60  leading to the bottom of a relatively large volume space  61  provided within the housing  40 . 
     In the second position of the valve body, a bleeding recess  62  provided at the circumference of the valve body  51  communicates with a channel  63  opening in the cylinder  44 . 
     In the channel  63  there is a capillary  64  and on either sides thereof an electrode  65 ,  66  connected to a respective conductor  67 ,  68  terminating in a respective terminal  69 ,  70 . In the channel  63  there are also two detectors  71  and  72  having signal transmitting conductors  73 ,  74 , respectively, terminating in respective terminals  75 ,  76  in the bottom wall  42 . The detectors may, e.g., be optical detectors, and in such case the conductors  73 ,  74  are optical fibres. Also possible is that the detectors are capacity sensitive detectors, and in such case the conductors  73 ,  74  are electric coductors. In any case, the detectors are adapted to start and stop, respectively, particle counting. 
     When manufacturing a device according to the present invention, a volume V of the cylinder  44  is filled with a liquid L, such as a diluting liquid. The volume V is defined by the piston  47  in an axial position thereof where it covers the mouth of the channel  63 . 
     Operation of the device will now be described with reference to blood sampling. Initially, the valve body and the piston occupy the positions shown in FIG.  2 . 
     In FIG. 3 is shown that the diaphragm has been depressed, e.g. by a fingertip of an operator, so as to expel a volume of air contained under the diaphragm within the conical recess  59  through the sucking channel  56 , the through channel  53  and the channel  54  to the open air. It is also shown how a punctured fingertip F having a drop D of blood on it is approached to the front wall  43  of the device where the wall exhibits a stepped recess  43 ′ so as to locate the drop in a proper position in relation to the mouth of the channel  54 . Next, the diaphragm is released and allowed to regain its original position as shown in FIG.  4 . 
     In FIG. 4 is shown how a sample S of blood has been sucked from the drop D to fill the channels  54 ,  53  and  56  as well as a portion of the conical recess  59 . As initially stated, it is important to make sure that the through channel is properly filled, since it contains an accurately defined volume. When the housing  40  and the valve body  51  are made of a transparent material, it is easy to determine whether the through channel  53  is filled or not. When it is established that the sample taken is satisfactory, the aperture  55  is closed, for instance by an adhesive tape or the like. This is the last step that is ordinary performed by a sampling person in the field. The following steps are ordinarily performed by a-centrally located particle counting apparatus. 
     In the first following step, the valve body  51  is rotated to its second position as shown in FIG. 5 so as to separate the volume of sample contained within the through channel from the remainder thereof contained within the channels  54  and  56  and within the conical recess  59  and so as to connect the through channel to the channels  49  and  60 . 
     In the next step, shown in FIG. 6, the piston rod  48  is operated to displace the piston  47  towards the upper end  45  of the cylinder  44 . Such displacement causes the liquid L to flow through the channel  49  into the through channel and displace the sample contained therein through the channel  60  into the space  61 , where the major part of liquid L mixes with the sample brought along therewith. Only a minor part of the liquid L still remains within the channel  60  in an unmixed state. Air within the space  61 , being originally under atmospheric pressure, is now compressed by the mixture of liquid L and sample S introduced therein. 
     Now, the piston rod is operated to displace the piston towards the lower end  46  of the cylinder as shown in FIG.  7 . Such displacement causes the mixture of liquid L and sample S to be withdrawn from the space  61  through the channel  60 , the through channel  53  and the channel  49  into the cylinder above the piston  47 . Withdrawal is supported by the compressed air within the space  61  above the liquid level. When the piston passes its original position, the pressure within the cylinder  44  is restored to its original value. Further displacement of the piston towards the lower end  46  of the cylinder causes a negative pressure within the cylinder, and when the piston passes the mouth of the channel  63 , communication is established between the cylinder and the bleed recess  62  through the capillary  64 . Atmospheric air is now drawn into the cylinder  44 , and the bubbles thereby created cause a further mixing of the liquid L and the sample S within the cylinder  44 . The piston is kept in position until the pressure within the cylinder has been equalized. 
     The piston rod  48  is then operated according to FIG. 8 to displace the piston  47  a relatively short distance towards the upper end  45  of the cylinder to create an overpressure within the cylinder  44  above the piston and within the space  61  thereby to displace at least a portion of the mixed and diluted sample L+S through the capillary  64  located in the channel  63 . When the sample reaches the detector  71 , counting is started, and when it reaches the detector  72 , counting is stopped. In this position, or shortly thereafter, the valve body  51  is returned to its first position, shown in FIG. 9, such that the bleed recess  62  is closed. In this final position, the entire system is closed, and no waste liquid has to be disposed of since it is all contained within the housing  40 . 
     second embodiment of the present invention shown in FIGS. 10 and 11 corresponds to the first embodiment in all respects except that there is no sucking means. Thus, all unchanged items bear the same reference numerals as in the first embodiment. Instead of sucking means there is provided in the front wall  43  a recessed aperture  77  having, e.g., a conical shape, and communicating through a channel  54 ′ and the through channel  53  in the first position of the valve body  51  with a channel  56 ′ leading to a closed space  78  containing atmospheric air. 
     The aperture  77  and the channel  54 ′ are shaped so as to receive in a liquid tight manner a cannula  79  (FIG. 10) in cases where a blood sample is to be taken by way of venipuncture. In such case, the blood pressure within a vein is sufficient to press blood through at least the through channel  53  against the increasing air pressure within the space  78 . 
     Alternatively, the second embodiment may be used for the finger-tip puncture (capillary) type of blood sampling. In that case, a drop of blood D is received within the aperture  77  (FIG.  11 ). In order to displace the sample through at least the through channel  53 , there is provided a circular closure  80 , also acting as a piston means, having an annular flange  81  mating with a corresponding annular recess  82  in the front wall  43 . Placing the closure with its flange  81  in the recess  82 , and further pressing the flange into the recess, will cause the drop of blood D to be displaced at least through the through channel  53 . Thereafter, the closure may be sealed by an adhesive tape or the like. Alternatively, the flange  81  and the recess  82  may be made with co-operating interlocking snap-lock means permanently locking the closure and the housing once the closure is pressed into its bottom position. 
     Not mentioned before is a translucent light path  83  in the housing enabling photometric determination of certain parameters of the liquid contained in the cylinder  44 , such as, initially, a reference value of the liquid L and the side walls of the body  40 , and, finally, the haemoglobin value, e.g. in the position according to FIG.  8 . 
     As initially stated, a device according to the present invention contains no electronic equipment necessary to perform the various measurements and calculations necessary. 
     Instead, there is provided a counting apparatus  84  as exemplified in FIG. 12 for use as a base instrument for serving a plurality of disposable sampling devices according to the present invention. Such a base instrument can be placed, e.g., centrally Within a health care region to be used by several nurses acting in the field, or, centrally in a brewery. The counting apparatus  84  has means for receiving the housing  40  such as a slot  85 . As best appears from the enlarged view of FIG. 13, there are operating means  86 ,  87  in the slot for cooperation with the piston rod  48  and the actuating means  51 ′ for the valve body  51 , respectively, terminal means  88 ,  89 , and  90 ,  91  for cooperation with the terminals  69 ,  70 , and  75 ,  76 , respectively, as well as a light source  92  for sending a ray of light through the light path  83 , and a light sensor  93  for photometric measurement through the cylinder  44 . 
     When a disposable sampling device has been properly placed in the slot  85 , the steps described with reference to FIGS. 5-9 can be automatically or manually initiated, and the result be displayed on a display  94 . 
     A preferred embodiment of a disposable sampling device according to the present invention, that is advantageous from a manufactural point of view, is shown in FIG.  14 . Items corresponding to those of the first embodiment have the same reference numeral increased by 100. As appears, the cylinder  144  and the diluting chamber  161  are coaxially aligned and the valve chamber  150  is placed immediately therebetween such that its valve body  151  closes the opposed ends of the cylinder and the diluting chamber. In the first position of the valve body  151 , corresponding to the position of the valve body  51  shown in FIGS. 2-4 and  9 - 11 , its through channel  153  and bleed recess  162  are drawn in full lines, whereas the second position, corresponding to the position of the valve body  51  shown in FIGS. 5-8, is drawn in dotted lines. It appears that the angular distance between the two positions is considerably less than in the previous embodiment.