US3768727A

US3768727A - Centrifuge with sample holding means for sedimentation study

Info

Publication number: US3768727A
Application number: US00191768A
Authority: US
Inventors: O Proni
Original assignee: Coulter Electronics Inc
Current assignee: Coulter Electronics Inc
Priority date: 1971-10-22
Filing date: 1971-10-22
Publication date: 1973-10-30
Anticipated expiration: 1990-10-30
Also published as: DE2246675A1; DE2246675B2; CA961019A; NL7212820A; DE2246675C3; GB1399486A; JPS4851364A

Abstract

An improved centrifuge apparatus for blood sedimentation study is described for applying a G force in the range of 6.25 to 8 G laterally to the long axis of plural test sample columns arranged substantially vertically in holders provided on the centrifuge head. Each of the sample columns are rotated about their own vertical axes between each periodic spin cycle of said centrifuge head and only between applications of said G force by means of inertia. A test operation using four 45 second duration applications of said G force is described with rotation of the columns being effected by reversal of the centrifuge head at the end of each 45 second force application.

Description

ted States Patent Proni Oct. 30, 1973 CENTRIFUGE WITH SAMPLE HOLDING MEANS FOR SEDIMENTATION STUDY Primary Examiner-George H. Krizmanich [75] Inventor: Oscar Proni, Hollywood, Fla. Attorney-I Irving Sllverman et [7 3] Assignee: Coulter Electronics Inc., Hialeah, [57] ABSTRACT An improved centrifuge apparatus for blood sedimen- [22] Filed: O t, 22, N71 tation study is described for applying a G force in the range of 6.25 to 8 G laterally to the long axis of plural [21] Appl' 19l768 test sample columns arranged substantially vertically in holders provided on the centrifuge head. Each of 52 US. Cl. 233/26, 23/259 the Sample columns are rotated about their own verti- [51] cal axes between each periodic spin cycle of said cen- [58] Field of Search 23/259; 233/24, 23 R, trifugo head and y between applications of Said 6 233/23 A 25 2 17; 2 0 335 force by means of inertia. A test operation using four 45 second duration applications of said G force is de- [56] References Cited scribed with rotation of the columns being effected by UNITED STATES PATENTS reversal of the centrifuge head at the end of each 45 3,199,775 8/1965 Drucker 233 25 Second force apphcanon' 749,104 1/1904 Schoenefeldt 233/17 13 Claims, 5 Drawing Figures 11 27 "Elm" PATENIEnucI 30 1975 3,768,727

sum 1 UF 2 CENTRIFUGE WITH SAMPLE HOLDING MEANS FOR SEDIMENTATION STUDY CROSS-REFERENCE TO RELATED APPLICATION This application is an improvement of the centrifuge disclosed and claimed in co-pending application of Brian S. Bull, Ser. No. 191,886, filed Oct. 22,1971 entitled METHOD AND MEANS FOR SEDIMENTA- TION STUDY and assigned to a common assignee.

FIELD OF THE INVENTION This invention relates generally to diagnostic examination of whole blood and more particularly concerns the provision of a centrifuge for whole blood sedimentation study.

BACKGROUND OF THE INVENTION It is well known that the suspension stability of whole human blood is altered in the presence of many functional disorders. The determination of this characteristic generally has been effected by performance of wellknown standardized sedimentation tests in the course of clinical analysis. Using the sedimentation test results, the presence of more or less occult disease can be brought to medical attention. Such results particularly are of importance in the differential diagnosis as between functional disorders having closely similar symptomatic manifestations, as well as in supplying a guide to the progress of certain diseases. Accordingly, it is believed that substantial benefit could be obtained in the diagnosis and treatment of medical disorders by the establishment of sedimentation study procedures which would produce comparative information quickly and economically so that a sedimentation study could become a routine procedure in clinical examination. However, as practiced presently, the sedimentation test is too time consuming, too affected by laboratory introduced artifacts and subject to misinterpretation in anemic individuals, so that the test is not a test offered to every patient as a routine clinical test procedure such as a blood count, for example.

Present methodology involves essentially the mixing of a whole blood sample with a selected anticoagulant, introducing this well mixed sample in a vertically arranged glass tube and permitting the red cells of the sample to sediment under the influence of gravity. This process is slow, usually taking sixty or more minutes. The only accepted variations in this method takes the form, singly or in combination, merely of changing the length of the glass tubes employed, varying the bore of such tubes, careful selection of the anticoagulant employed and/or modification of the degree of dilution utilized. None of these variations have alleviated the principal drawback to adoption of the sedimentation test as a routine procedure, this drawback being that present sedimentation rate tests methods are too time consuming for routine employment or mass studies.

Another important deterrent to adoption of sedimentation testing as a routine procedure has been the extreme sensitivity of this test to the arrangement of the test sample in an absolutely vertical orientation for the duration of the test. It has been found that a sample column which is oriented at only a three degree offset from vertical will result in inconsistent acceleration of the sedimentation rate and reduces the relative differences between the comparative normal and abnormal blood sedimentation characteristics, thereby reducing the value of the test in diagnosis.

The co-pending application provides an improved sedimentation study method for whole blood which meets the requirements for rapidity, economy, accuracy and reliability essential for adoption as a mass applied clinical laboratory test procedure, and, concomitant therewith, provided a sedimentation rate centrifuge particularly adapted for implementing and carrying out the steps of the improved study method.

The principal object of this invention is to provide an improved centrifuge for blood sedimentation study particularly adapted for use with the method of the aforementioned application.

SUMMARY OF THE INVENTION A centrifuge apparatus is provided for implementing the subject method, including a centrifuge head and a reversible direction motor, the centrifuge head carrying at least a pair of sample tube holders arranged to orient sample columns carried in elongate tubes held in substantially vertical columnar array, drive means connected between the motor and the centrifuge head for rotating same, means associated with the head and tube holders, rotating the tube holders about their own vertical axes and timing means operable on said drive means for operating the centrifuge head in timed cycles with the centrifuge head being brought substantially to a rest condition between cycles and means to restrict the rotation of the tube holders about their own vertical axes to periods during which the centrifuge head is at substantial rest condition, said drive means including a first gear means coupled to said motor, second gear means coupled to said tube holders and the said centrifuge head, said centrifuge head being mounted for free rotation about the drive shaft axis, said means to restrict comprising pin and slot means on the first gear means and centrifuge head, said first gear means transmitting its motion to said second gear means for first rotating said tube holders about their own axes, said means to restrict serving to couple said centrifuge head and first gear means for simultaneous rotation subsequent to said rotation of said tube holders.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of the improved centrifuge apparatus in accordance with the invention;

FIG. 2 is a perspective of the centrifuge head and drive means of the centrifuge arrangement of FIG. I with portions broken away to show interior detail;

FIG. 3 is a diagrammatic representation of the embodiment illustrated in FIG. 1;

FIG. 4 is a bottom view of the timing means utilized in the embodiment of FIG. 1;

FIG. 5 is a schematic view of the centrifuge head of the embodiment illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of studying the sedimentation characteristics of whole blood described in the co-pending application capitalizes in part upon the fact that the blood from a normal, healthy individual has greater suspension stability than does blood from a sick individual. Three phases are known to occur during the sedimentation of whole blood. The first packing characterized as the phase of rouleaux formation. During this phase, the

red cells of the whole blood stack together in what is defined in the art as rouleaux. This phase occupies the first few minutes subsequent to filling of the sedimentation tube with sample. Next begins the phase of maximum sedimentation wherein about 3 to 5 minutes, the red cell rouleaux reach their maximum velocity of fall. This velocity is dictated by the average density of the rouleaux and the viscosity of the plasma through which they are falling. The last phase concerned is characterized as the package phase. As the rouleaux reach the bottom of the sedimentation tube, they pack and, as a consequence, the average rate of fall decreases and eventually, when packing is complete, no further change occurs.

The sample from both normal and sick individuals, given enough time, will pack to approximately the same extent; but the blood samples from the ill patient goes through the rouleaux formation phase and into the phase of maximum velocity of fall more rapidly than does the blood from a healthy individual. An isolated red cell is so small a particle that even through its density is considerably greater than that of the plasma, the large relative surface area becomes the overriding factor and an isolated red cell in plasma falls very slowly under the influence of gravity. The rate of fall of red cells is thus governed almost entirely by the size of the rouleaux which they form. The blood from a. healthy individual forms such rouleaux much more slowly than does blood from a sick person. If both samples are set up simultaneously, there is a period of time when application of force greater than gravity to the blood will affect the blood from a healthy individual minimally and that from a diseased patient maximally. This crucial or critical time is obvious when the healthy blood has just only begun to form rouleaux and the sick blood has formed large rouleaux which have already begun to sediment.

lt had been critical to the study of sedimentation rate that the conventional test must be performed under conditions where the sample column is disposed in absolutely vertical orientation. A tilt as little as three degrees from vertical under gravity will accelerate the sedimentation rate considerably, and decrease the relative differences between normal and abnormal blood. It is believed that this effect is due to the fact that red cells falling through the plasma hit the walls of the container and roll down the walls permitting the plasma free egress from the depth of the sample. Whenever the plasma is forced to traverse the descending column of red cells, the sedimentation rate is slowed. Normal red cell rouleaux fall much more slowly than do abnormal red cell rouleaux, probably because the forces holding them together are weaker and the upsweeping plasma either breaks them up or prevents them from forming large enough clumps to sediment rapidly. Accordingly, by applying a greater than gravity force to the sedimenting blood, according to the method, the ascending plasma is forced to traverse the descending red cells. As will be explained, a slight inclination of the column up to about 6 from vertical is permissible with the method of the invention, particularly to avoid spilling of the sample during the run.

According to the method, greater than gravitational force is applied laterally to a long thin column of whole blood sample by rotation thereof in a centrifuge capable of delivering a force in the range of 2 to 12 G with the test taking fron Ar hour at a minimum (3 to about 1 minute at the high end of the aforesaid range. The higher the G Force, the shorter the elapsed time of the test. The net effect is to force the red cells to traverse the plasma component of the blood over a very short distance since the effective cross-sectional area of the tube is now vast relative to the wall surface area and the red cells cannot collect in one portion of the tube against the wall so as to permit the plasma to escape freely elsewhere. insofar as the sedimentation process is concerned, the long thin column has been transformed to a shallow wide diameter pool and since the force is directed substantially perpendicular to the long axis of the column, the problems of channeling heretofore experienced in sedimentation testing are obviated.

The laterally applied force acts to pack the red cells rapidly, permitting the plasma physically to change location therewith and approach the final packing state over a much shorter time period, than normally would be expected under gravitational force.

The selection of the duration of the centrifugation cycles as well as their number are dependent also upon the speed of the drive or synchronous spinner motor utilized, the diameter of the column and of the sedimentation tube utilized, and the degree of cant or tilt permitted.

A preferred program involves a program selected to use four cycles of applied force laterally to the column and of 45 second duration each. Between the first and second, the second and third and the third and fourth cycle of centrifugation, the columns are rotated about their own vertical axes. Care is taken to assure that the axial rotation of the columns take place only when the force applied laterally to the long axes of the columns is less than one G. This condition occurs when the column is at rest. substantially at rest or, to put it another way, beings its translation in its circumferential rotation with and on the centrifuge head. Abrupt stoppage of the columns must be avoided, and likewise, jarring or other sharp disturbance of the columns are avoided so that the cells which have separated from the plasma and gathered at the inner wall of the tube containing the test sample column will not be broken away from each other or from the tube wall. The cells in the column must rotate with the tube, and the column as the same is rotated about its own axis. Between each application of greater than gravity force, the test sample column is rotated about its own long axis, preferably This seems to provide benefical results in obtaining reproducible packing by alternatively permitting resuspension of the cells by rotating the tube and its column contents and again effectively forcing those cells back through the plasma. Thus, cohesive forces are utilized during the centrifugation under the relatively low G force to force the cells against the wall and dispersion forces are utilized when the cells are forced back through the plasma by again centrifuging but after 180 rotation of the tube and column of test sample.

The performance of the method described and claimed in the co-pending application required a centrifuge capable of applying the preferable G force in the range of 6.25 to 8 G in separate cycles of predetermined duration. The centrifuge is required to rotate the tube containing the sample in a circumferential path about the axis of rotation with the tube being in substantially vertically oriented disposition parallel to the axis of rotation of the centrifuge head although a cant from vertical of up to 6 is permitted, contrary to standard sedimentation rate methods. Additionally, the centrifuge is required not only to permit rotation of the tube along said circumferential path for a predetermined length of time and then the tube periodically must be brought at least to a momentary substantially rest or stationary condition, then rotated about its own axis a predetermined number of degrees, and the rotation of the tube along said circumferential path resumed for the next cycle of greater than G force application. At least, the rotation of the tube about its axis must not occur during the application of greater than G force.

The centrifuge also should have timing means T for selectively controlling and/or varying the duration of the cycles. The column contents of the sample tube must rotate axially with the tube wall and care must be taken to assure only such rotation.

The centrifuge apparatus according to the instant invention is illustrated in FIG. 1 and designated by reference character 101). Apparatus 100 as described herein particularly is adapted to practice the subject method where the cycle utilized comprises four cycles of 45 second duration applications of greater than gravity force laterally to substantially vertically arranged columns of whole blood with means provided to effect limited rotation of each column about its own axis between each force application by reversal of the direction of rotation of the centrifuge head after each cycle.

The centrifuge apparatus 100 includes a housing 102, including a troughlike portion 104 and a cover 106. Wall 108 of housing 162 carries exterior accessible switch levers 110 and 112 for activating the power and buzzer means respectively which will be described hereinafter.

Indicator lights

114 and 116 likewise are provided. Start switch 11% for initiating each test operation is provided.

The electrical control components of apparatus 100 are mounted within the troughlike portion while the head, centrifuge 120, drive means 122, and the timing means 124 are mounted on the cover portion, the centrifuge head being removably mounted to the protruding portion of the motor drive shaft 154 of means 122. The drive means 122 and timer means 124 are mounted to be enclosed within the housing 102 when the cover 1116 is engaged onto the portion 104.

The centrifuge head 120 comprises a spool formed by mounting a spinner plate 126 fixedly secured to the shaft 128 and a disc 130 is mounted to the upper end of said shaft 128 with the disc 130 arranged coaxial with said spinner plate 126 and being rotatable therewith to complete the spool. The shaft 128 is mounted removably on the motor drive shaft 154 for free rotation about the axis thereof.

Support means 132 is arranged secured to drive shaft of motor 156 for rotation therewith by set screw 127 and includes a collar portion 192 mounting a spur gear 134. Gear 134 has a circumferential ring portion 134 carrying circumferential teeth 134" and a central disc portion 135 to which it is fixedly mounted and by which the spur gear is mounted for driven rotation with the shaft 154. The shaft 128 has a depending extension 123' and carries a bottom opening axial bore 128" by which spool 121) is mounted on shaft 154 for free rotation thereabout. (see FIG. 5)

Tube holders 136, are mounted on spinner plate 126 for movement therewith about the axis of shaft 128.

The holders are spaced circumferentially substantially equidistant one relative to the other closely adjacent the peripheral edge of the spinner plate 126. Each tube holder 136 has a top opening cavity 137 defined therein to receive the lower end of sample tube 150 and has resilient means for gripping said tube seated therein, such as O-ring 139. Each holder is mounted on the upper end of a shaft 138 which extends through suitable openings formed in said plate 126. Pinion gears 141) fixedly are secured to the opposite ends of each shaft 138 thereby mounting the holders 136 on plate 126. The holders 136 are rotatable with rotation of gears 140.

The teeth 134" of spur gear 134 are arranged meshed with the plural pinion gears 140. Thus, rotation of the gear 134 will effect rotation of gears 140 while the plate 126 remains stationary, rotating holders 136 about their own vertical axes. Limit means in the form of the upstanding pin 142 secured to the disc and movable within the substantially circular slot 144 formed in the spinner plate 126 are provided to limit the independence of movement of the spinner plate 126 and gear 134, thereby limiting the degree of rotation of the gears about their own axes. With the pin 142 at one end of the slot 144, the rotation of gear 134 in the direction of arrow A will cause simultaneous rotation of the plate 126 and hence the tube holders will be translated circumferentially about the axis of shaft 154. On completion of the first cycle, gear 134 stops. The plate 126 stops with gear 134 or coasts until pin 142 is at the opposite side of slot 144. In changing direction of rotation of the plate 126, gear 134 rotates gears 141) until the pin 142, moving in slot 144, engages the opposite end of the slot 144. Then the motion of the gear 134 in the opposite rotational direction is transmitted to the plate 126 and the gear 134 and head 120 rotate together. The tubes within holders 136 are always rotated about their own axes before the head reaches sufficient rotational speed to apply greater than 1 G force laterally to the tubes.

The disc 130 has a plurality of bottom opening recesses 146 formed equispaced about the peripheral edge thereof and arranged in alignment with the axes of the holders 136 but slightly offset inwardly therefrom so that one end of the sample tube 150 can be seated within cavity 137 of holder 136 and the upper end retained within the respectively matching recess 146 to position the tube substantially vertically arranged but canted inwardly at its upper end toward the shaft 128. Thus, when properly seated, tubes 150 are disposed, canted inwardly from true vertical between 3 and 6, preferably by 3 and generally not more than about 6. In this disposition, the tendency for the contents of the tube to be flung outward during the application of higher than gravity force on rotation or spinning of the centrifuge head 120 materially is reduced.

Motor mount 152 is secured to the undersurface of cover 106 with the drive shaft 154 thereof protruding through a suitable opening formed in said cover 106. The drive means 122 for the apparatus 100 is supplied by a 400 RPM, 60 HZ, l 15 volt AC reversible direction motor 156. Here, motor 156 causes centrifugal force between 6 and 8 G to be applied laterally to the tubes 1511 during the spin of header 120. The particular size and RPM drive motor selected determines the centrifugal force exerted on the tubes 150, and thereby is an important factor in selection of the duration of greater than gravity application cycle and program.

The method of study concerned requires application of the greater than gravity force laterally and periodically to the sample in the tube i.e., the sample tube 150 and the column of blood therein. The duration of each cycle generally can be selected to provide results correlative with specifically known blood sedimentation methods.

With apparatus 100, timer means 124 are provided to effect rotation of the spinner plate automatically through a sequence of four cycles of 45 seconds duration with the reversal of direction and rotation of the columns 180 about their own axes between each application of centrifugal force.

in the apparatus 100 illustrated, the timer motor 156 is an AC 60 cycle, 1 10 volt motor delivering RPI-l.

The timing means 124 operates switch means 184, 186 which operates relays 184" and 186 automati cally taking the sample columns through the selected test program.

A timing means 124 comprises a timer motor 158 mounted on platform 159, which in turn is secured suspended below the cover 106 by means of bolts 160 and spacers 162. The resultant drive shaft 164 of motor 158 is passed through a suitable opening in the platform 159 and wheel gear 166 is mounted at the free end thereof for rotation therewith. A second wheel gear 168 is coupled to gear 166 and is driven thereby. Gear 168 is fixedly secured to shaft 170 for rotation therewith. One end of shaft 170 is seated in journal 172 and the other end 174 carries timer disc 176. Timer disc 176 is secured to shaft 170 and continuously rotates therewith so long as timer motor 158 operates through the complete test program. The timer disc 176 has three

paddle assemblies

178, 178 and 178" mounted thereto about the periphery thereof with the

paddles

180, and 180 and 180" extending outwardly from the circumferential edge thereof in vertical planes normal to the axis of shaft 170. As illustrated, disc 176 is rotatable in the direction of arrow 177 with the

paddle assemblies

178, 178' and 178" fixed in an equispaced series along said path. An upstanding pin 182 is secured normal to the disc 176 and rotates therewith. The

paddle assemblies

178, 178 and 178", when considering the direction of rotation of the disc, can be said to be substantially equispaced one relative to the others with

paddle assemblies

180 and 180" being disposed 180 apart. A pair of push-button activated

switches

184 and 186 are arranged with their actuators 184' and 186 mounted to suitable bracket means (not shown) secured to the platform 159 so that the actuator 184 of switch 184 is arranged in the path of travel of the

paddles

180, 180 and 180" of

paddle assemblies

178, 178' and 178" whereby each respective paddle can engage and depress said actuator 184' by engaging same during passage therepast during rotation of the disc 176.

The actuator 186' of switch 186 is positioned to intercept the pin 182 whereby the continuing rotation of disc 176 causes pin 182 first to bear against actuator 186 to depress same. On passing of said pin 180 past actuator 186, said actuator returns to its normal condition. The switch 184 is connected to relay assembly 184' which is electrically coupled to the reversible sychronous drive motor 156 to cause reversing of the direction of said motor each time the actuator 184 is depressed. The switch 186 is connected to relay assembly 186" operatively coupled electrically to both the drive motor 156 and to the buzzer means 190. Depression of the actuator 186' energizes the buzzer 190 and release of the actuator 186' from engagement with the pin 182, causes de-energization of the drive or spinner motor 156.

A friction or other drag represented by pad 194 may be applied to the centrifuge head 120 so that application of braking force to the motor 156 on deenergization of the same, causes a braking force to be applied directly to the head.

An example of a testing operation utilizing apparatus now will be described. Samples of whole blood are taken and placed respectively in closed end, elongate tubes known as sedimentation tubes. The tubes are filled with sample to a predetermined level mark. The tubes containing the test samples are placed between the disc 130 and the spinner plate 126, the lower ends of the tubes seated within the tube holders 136 and held firmly by the resilient means 139 while the upper ends are seated in the recessed holes 146. The switch levers and 112 are actuated respectively activating the apparatus 100. The start toggle switch 118 is actuated initiating the test procedure and causing the spinner motor 156 to operate in one direction, say clockwise. Greater than gravity force in the range of 6.25 to 8 G is applied to the column of sample in each tube as the centrifuge head 120 is spun.

When motor 156 is energized to spin gear 134, motor 158 is energized simultaneously to rotate disc 176. Timer disc 176 rotates to bring paddle 180 in contact with the actuator 184. Disc 176 continues to rotate so as to carry paddle 180 past said actuator 184. In passing, the paddle 180 depresses the actuator 184', causing the spinner motor 156 to reverse direction. This occurs 45 seconds after initiation of the spinner operation.

In reversing direction, the gear 134 and hence the centrifuge head 120 comes to a momentary halt with the pin 142 at one end of the slot 144. The gear 134 then begins to rotate in the clockwise direction. The plate 126 will remain stationary. The pinion gears being coupled to the gear 134, will move along the circumference of now moving gear 134 and will rotate about their respective axes until engagement of the pin 142 at the opposite end of the somewhat circular hole 144 will drive the plate 126 to rotate same, iimiting the rotation of the pinion gears 140 to 180. The rotation of the pinion gears 140 rotates the tube holders 136 and with same, the tubes and the column of blood sample will be rotated.

The spinner motor 156 operates to drive the gear 134 and head 120 in a clockwise direction for the next cycle of 45 seconds. At the elapse of 45 seconds, the next paddle will have brought around to depress the actuator 184 and cause a second reversal of the drive motor 156. The gear 134 again is brought to a momentary halt. The plate 126 stops with the gear 134 or coasts until the pin 142 now is at the other end of the slot 144. The reversal of motor 156 rotates the pinion gears 140 180 about their own axes until the pin 142 is at the opposite end of the slot 144 and hence before any appreciable centrifugal force has been generated.

On completion of the movement of the pin 142 in the slot 144, and engagement of said pin 142 with the spinner plate 126, the spinner plate and the gear 134 are locked for rotation together, now in the counterclockwise direction for another 45 seconds until the spinner motor direction is reversed by engagement of the paddle 180" against the actuator 184' of switch 184 depressing same. The pinion gears 140 and hence, the holders 136, tubes 150 and test sample columns therein, again are rotated about their own axes between applications of centrifugal force by the inertia of the plate 126.

Coupled rotation of the spinner plate 126 and gear 134 is resumed for another and final 45 second interval. The timer plate 176 is continuously rotating during these last described operations, and, accordingly, continues to rotate. Approximately 45 seconds after the last-mentioned motor reversal, the pin 182 is brought into contact with the actuator 186' by the continued rotation of the timer disc 176, the actuator 186 is released from its depressed condition. Now the motor 156 is de-energized and the gear 134 and the centrifuge head is brought to a halt, the program completed.

It should be explained that the centrifuge apparatus of the copending application has means whereby a friction drag was applied to the spool or head driven by the motor 156 with thegear 134 thereof mounted for free rotation about the drive axis. Friction under some circumstances can become unreliable, may change with time and/or may be different from one unit to another. It is for this reason the inertial operation of the instant apparatus is so advantageous.

In FIG. 2, a resilient or elastic belt coupling 141 is utilized between the motor drive shaft and the main drive shaft (dotted line) which aids taking the inertia load off the synchronous motor 156 while it is reversing direction, or at least most of it, making starting of the motor more reliable.

What it is desired to be secured by Letters Patent of the United States is:

l. A centrifuge apparatus for studying the sedimentation characteristics of whole blood by application of greater than gravity force laterally to a generally vertically oriented column of test sample of whole blood; comprising, a centrifuge head having a peripheral edge and a central shaft, a driven shaft and a drive motor coupled to said driven shaft for imparting rotative motion thereto, in intermittent periods of predetermined duration, said central shaft being mounted to said driven shaft for free rotation thereabout, independently rotatable sample tube holder means carried by said head near the peripheral edge thereof, said sample tube holder means having sample tubes each adapted to contain a thin column of blood, said sample tubes being vertically arranged and oriented substantially parallel to the axis of rotation of the centrifuge head and means for causing periodic rotation of said head at high speed about its axis and periodic rotation of each sample tube holder means and the sample tubes therein about its own long axis intermediate the periodic high speed rotation of said head, said last means comprising gear means mounted to said driven shaft for rotation therewith, said gear means being coupled to said holder means for driving said heat to rotate the head in said periodic cycles and pin and aperture means operable to limit the extent of rotation of the holder means about their own axes.

2. The centrifuge as claimed in claim 1 in which the rotation of said holders about their own axes for each rotation in one direction is limited to approximately 3. The centrifuge as claimed in claim 1 and timing means for periodically controlling the duration of centrifugation.

4. The centrifuge as claimed in claim 3 wherein said drive motor is reversible and means for exerting gradual braking force at each reversal of motor direction.

5. The centrifuge as claimed in claim 3 in which said drive motor is reversible and said timing means comprise a timing motor, a timing disc, first switch means coupled to said drive motor for deenergizing same, second switch means for reversing said motor, means for coupling said timing motor to said timing disc, means on said timing disc constructed and arranged to engage said first switch means after an elapse of time equal to the total cycle duration and second means on said timing disc constructed and arranged to engage said second switch means periodically to reverse the direction of said drive motor, said second means on said timing disc being adjustably positioned thereon whereby to determine the interval between drive motor reversals.

6. The centrifuge as claimed in claim 1 and timing means for controlling the total duration of centrifugation and the respective cycle durations.

7. The centrifuge as claimed in claim 1 wherein the head is mounted removably to the driven shaft for rotation thereabout and the gear means is arranged coaxially relative to said head but for driven rotation with said driven shaft.

8. The centrifuge as claimed in claim 1 and timing means for periodically causing reversal of the direction of rotation of said head.

9. The centrifuge as claimed in claim 1 in which said head is mounted for removal and replacement as a unit.

10. The centrifuge as claimed in claim 1 in which said gear means includes one gear means coupled to the driven shaft and another gear means coupled to the sample holder and engaged with said one gear means, and said pin and aperture means comprise a pin mounted on one of said gear means and head and a substantially circular slot formed in the other of said gear means and head, said pin being disposed within said slot to limit independent relative rotation of said gear means and head.

11. The centrifuge as claimed in claim 1 in which said gear means comprise a spur gear secured to the driven shaft and pinion gears secured to each respective sample holder and operably engaged with said spur gear..

12. The centrifuge as claimed in claim 11 in which said pin and aperture comprise a pin on one of said spur gear and head and an arcuate slot on the other of said spur gear and head, the pin being received and movable within the slot and the length of the slot determining the maximum rotational movement of said pinion gears about their own axes.

13. The centrifuge as claimed in claim 12 in which said motor is of the reversible type, timer means for periodically changing the direction of rotation of the gear means for each period, said gear means being arranged to rotate said pinion gears and said head each time the gear means is rotated in a new direction.

Claims

1. A centrifuge apparatus for studying the sedimentation characteristics of whole blood by application of greater than gravity force laterally to a generally vertically oriented column of test sample of whole blood; comprising, a centrifuge head having a peripheral edge and a central shaft, a driven shaft and a drive motor coupled to said driven shaft for imparting rotative motion thereto, in intermittent periods of predetermined duration, said central shaft being mounted to said driven shaft for free rotation thereabout, independently rotatable sample tube holder means carried by said head near the peripheral edge thereof, said sample tube holder means having sample tubes each adapted to contain a thin column of blood, said sample tubes being vertically arranged and oriented substantially parallel to the axis of rotation of the centrifuge head and means for causing periodic rotation of said head at high speed about its axis and periodic rotation of each sample tube holder means and the sample tubes therein about its own long axis intermediate the periodic high speed rotation of said head, said last means cOmprising gear means mounted to said driven shaft for rotation therewith, said gear means being coupled to said holder means for driving said heat to rotate the head in said periodic cycles and pin and aperture means operable to limit the extent of rotation of the holder means about their own axes.

2. The centrifuge as claimed in claim 1 in which the rotation of said holders about their own axes for each rotation in one direction is limited to approximately 180*.

3. The centrifuge as claimed in claim 1 and timing means for periodically controlling the duration of centrifugation.

11. The centrifuge as claimed in claim 1 in which said gear means comprise a spur gear secured to the driven shaft and pinion gears secured to each respective sample holder and operably engaged with said spur gear.