Patent GB-1352256-A (GB)
Title: Apparatus for determining the pack volume of particulates in liquid mixtures
Inventor: CALOGERO W J
IPC: G01N33/48
Filed: 1971-09-14
Abstract: 1352256 Centrifugal separators TECHNICON INSTRUMENTS CORP 14 Sept 1971 [14 Sept 1970] 42850/71 Heading B2P [Also in Division G1] An apparatus for determining the quantity of particulates in a liquid mixture comprises a rotatable centrifuge head 47, a loading well 41 and a chamber 43 defined within the centrifuge head, the chamber having a fluid inlet in flow communication with the loading well to receive liquid mixture therefrom and being shaped to define a fluid trap along a portion thereof for centrifugally retaining liquid mixture received from the loading well when the centrifuge head is rotated, and means being provided for measuring the volume of particulates packed as a result of centrifugation in the trap portion of the chamber 43. The apparatus is particularly suitable for determining the packed cell volume of whole blood samples. The blood samples are contained in receptacles 7 carried by a turntable 5 which is indexable to position each receptacle in turn below an off-take tube 9. The tube 9 is controlled by a mechanism 11 to move into and out of a receptacle 7 located beneath it during each dwell period of the turn table 5 and into and out of a wash-liquid container 13, preferably during indexing of the turntable, the tube 9 being connected to a peristaltic rollertube type pump 17. As a result, offtake tube 9 successively aspirates a segment (S) of blood sample from each receptacle and segments of air (A), wash liquid (W) and air (A) in turn between successively aspirated blood sample segments and directs them along a conduit 3 connected to a storage tank 27 having a T-section outlet 31a, 31b. The leg 31a of the T-section is connected to a flexible conduit 35 which is controlled by the pump 17 and opens to waste. The leg 31b is connected to a flexible conduit 39 which opens into the well 41. The flexible conduits 35, 39 are positioned between pinch clamps C 1  and C 2 , respectively, which are controlled by a programmer 46 to pinch or release the conduits in such a manner that sequentially: (a) a blood sample segment is introduced and accumulated in the storage chamber 27 and then transferred into the loading well 41; (b) liquid remaining in the chamber 27 and conduit 39 is aspirated and cleared to waste via conduit 35; (c) a wash liquid segment is introduced in chamber 27 and passed along conduit 35 to waste; (d) an air segment is introduced in chamber 27 which is thereby drained of wash liquid along conduit 35 by the action of pump 17. The cycle is then repeated. The programmer 46 also controls the turntable 5 and the mechanism 11 to maintain a proper phase relationship between the operation of clamps C 1  and C 2  and the introduction of the continuous stream into storage chamber 27. The centrifuge head 47 is positioned at its periphery within an annular container 49 and is mounted on a spindle 51 driven by an electric motor 53. The chamber 43 is of the capillary type and of serpentine configuration to provide a fluid trap T to effectively retain a given volume of blood sample during centrifugation. It may consist of a capillary glass tube. The chamber 43 and the well 41 may be formed as an integral structure and contained in a transparent plastics insert 55 fitted within a recess 57 in the head 47. A viewing window 59 machined through the base of recess 57 is aligned, for example, with leg 43a of chamber 43. A mirror 63 and a lightdetector 65 are mounted in alignment on opposite sides of the head 47 so as to be exposed through window 59 and capillary chamber 43 during each revolution of the head. The output of detector 65 is fed via an amplifier 67 the output of which is coupled via a fast-response integrator circuit 66 to a first input of a differential amplifier 70 to a second input of which an offset voltage across a potentiometer 72 is applied. The output of amplifier 70 is coupled to a motor 71 onto the armature 75 of which is mounted a mirror 73 for reflecting a light beam 77 onto the mirror 63. The offset voltage across potentiometer 72 is sufficient to energize motor 71 to maintain light beam 77 at the inner radial end of window 59. When blood sample segment S has been introduced in capillary chamber 43, the mirror 73 has been reset and the light beam 77 is located at the inner-radial end of window 59. As the blood sample segment is being packed in chamber 43, and since plasma 91 is transparent, a pulse of light passes through the chamber and onto detector 65 during each revolution of the centrifuge head 47 and operates amplifier 67 to charge integrator circuit 66 whereby the voltage applied to the first input of the differential amplifier 70 rapidly and continuously increases in opposition to the offset voltage coupled to the second input. Accordingly, motor 71 is energized to cause mirror 73 to rotate in a counter-clockwise direction whereby light beam 77 is advanced outwardly as indicated by arrow 85 tracking continuously the interface 89 between plasma 91 and packed cells 61 in leg 43a of chamber 43. When the cells 61 have been packed and interface 81 is fixed, the light beam 77 will remain substantially fixed at the interface, the position of mirror 73 being indicative of the packed cell volume in chamber 43. When the packed cell volume has been measured, programmer 46 opens clamp C 2  to introduce a next successive blood sample segment S into chamber 43 purging the packed cells which have been previously measured. Since this next sample is opaque at first it shields detector 65 from light beam 77. Accordingly, integrator circuit 66 rapidly discharges and the offset voltage applied to the second input of amplifier 70 causes motor 75 to rotate mirror 73 clockwise and reset light beam 77 at the inner-radial end of window 59, the cycle being then repeated. A second capillary chamber 43' can be arranged diametrically to chamber 43 to enable blood sample segments to be centrifuged concurrently in the centrifuge head. In a modification. Fig. 3 (not shown), instead of the annular container 49, a waste well (101) may be provided in the centrifuge head 47 concentric with the feed well 41. One end of the capillary chamber opens into the waste well into which also open the end of a waste probe (123) and the end of a waste liquid probe (127).