Apparatus for centrifugal separation of test samples

A rotor, adapted for rotation at high speeds, has symmetrically arranged radial channels for receiving tubular containers of material to be evaluated, such for example as samples of blood. The outer end of each radially extending container is placed against a resilient abutment at the rim of the rotor, and its inner end is placed against a clamping collar arranged centrally of the rotor and having limited movement in the direction of the axis of rotation. In the initial loading position, the tubular containers are inclined upwardly from the rim toward the center of the rotor. They are clamped firmly into position on the rotor by axial movement of the clamping member which carries the inner ends of the containers downwardly, to force the containers slightly radially outwardly, compressing the resilient abutments at their outer ends. The invention relates to details of construction of the axially movable clamping member, which has a spring tending to move it to unclamping or loading position, and a latch to hold it in clamped position, against the force of the spring.

BACKGROUND OF THE INVENTION 
This invention relates to the evaluation or testing of various substances 
placed in small cylindrical containers, sometimes called cuvets. Such 
containers are well known in the medical and biological field, and are 
frequently made of glass tubes of such small diameter that a liquid to be 
tested is drawn into the tube by capillary action. A typical material 
frequently tested is blood. The evaluation tests to be made on blood or 
other substances frequently include the separation of the ingredients or 
components of the liquid being tested, by subjecting the liquid to 
centrifugal force, and a subsequent measurement of the separated 
components. 
A basic structure for performing such tests or centrifugal separation 
procedures comprises a rotor having radial grooves or recesses for 
receiving the sample containers, with resilient abutments at the outer 
ends of the containers, and with axially movable clamping means located 
centrally of the rotor, for receiving the inner ends of the containers. 
When the clamping means is moved axially to its loading position and the 
sample containers are placed in the apparatus, the containers are 
initially inclined upwardly from their outer ends toward their inner ends. 
Then the clamping member on which the inner ends of the containers rest is 
moved axially downwardly, to carry the inner ends of the containers 
downwardly to a straight line position and a little beyond the straight 
line position; in other words, to carry the inner ends down to the 
transverse plane (perpendicular to the axis of rotation of the rotor) 
which contains the outer ends of the containers, and a little beyond such 
plane, until the containers have a slight downward slope or inclination 
from their outer ends to their inner ends. Similarly to the action of 
straightening a toggle, this motion pushes the sample containers slightly 
radially outwardly into the resilient abutments at their outer ends, thus 
firmly sealing the outer ends of the respective containers, and at the 
same time holding them firmly in place for the subsequent high speed 
rotation of the rotor, to apply the desired centrifugal force to the 
contents of the containers. 
The basic structure for accomplishing this is disclosed in the copending 
U.S. patent application of Wolfgang Konig, entitled "Apparatus for 
centrifugal separation and measurement of samples," Ser. No. 732,218 filed 
Oct. 14, 1976. The present invention is an improvement on the basic 
apparatus invented by Konig, the improvement relating to various details 
of the construction of the clamping means, including the provision of a 
spring tending to move a clamping member axially from clamped position to 
unclamped or loading position, and a latch for holding the clamping member 
in its clamping position until the latch is released. 
An object of the present invention is to improve the basic Konig structure 
by providing a better and more easily operated clamping means, more easily 
and quickly operable by the user, and having greater certainty of 
remaining in clamped position during high speed rotation of the parts, 
eliminating any possibility of accidental movement from clamped position 
to unclamped or loading position. 
This object is well fulfilled by apparatus according to the construction 
herein disclosed as an example of a preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As above stated, the present invention is in the nature of an improvement 
on the basic structure disclosed in the above mentioned application of 
Wolfgang Konig, and relates particularly to the clamping means disclosed 
broadly in that application. The entire disclosure of the Konig 
application in incorporated herein by reference. 
The apparatus includes a rotor 110 in the form of a circular plate of 
slightly dished shape as seen in diametrical axial section in FIGS. 1 and 
3. The hub portion 110a of the rotor is firmly mounted on a shaft 112 
having a suitable drive of known form for rotating the shaft at high 
speed. It may be, for example, the shaft of a conventional centrifuge. 
On the upper surface of the rotor plate are any desired number of 
symmetrically arranged radially extending grooves 110r for receiving 
tubular containers or cuvets 18 containing the blood or other material to 
be evaluated or tested. Four such grooves or radial recesses are here 
illustrated, but more or less may be used. The outer rim of the rotor has 
an upstanding marginal flange with appropriate openings for insertion, 
opposite the other end of each recess or groove, of a resilient buffer or 
abutment 114 of resilient compressible material with good sealing 
properties, such as natural or artificial rubber. 
The hub portion 110a extending upwardly from the main body of the rotor is 
surrounded by clamping means in the form of a clamping collar or sleeve 
116 fitting snugly but axially slidably on the hub. A coiled compression 
spring 120 seated in an axial bore in the hub member 110a presses 
downwardly on a shoulder in this axial bore and presses upwardly on a 
central pin portion of the clamping collar or sleeve 116, constantly 
tending to move this collar upwardly on the rotor hub. 
A latch member 122, pivotally mounted on the clamping collar 116 by means 
of a pivot 124, has a lower end which projects down through an opening 
110f in the rotor when the clamping collar is in its lowermost position, 
as seen in FIG. 4, and this lower end has a lateral projection or 
hook-like portion 122s which, in the latched position, engages a bottom 
abutment surface 110e of the rotor and holds the clamping collar 116 in 
its lower position, against the upward force of the spring 120, until the 
latch is released. The clamping member 116 is flattened at 116a and is 
partially slotted radially and axially at 116b, the flat arm 122b of the 
latch member 122 being accommodated in this slot. The upper end of the 
latch lever, above the pivot 124 thereof, is provided with a wide head 
122k which is opposite the flattened portion 116a, and which provides a 
convenient operating portion for contact with a thumb or finger of the 
user, to be swung radially inwardly toward the axis of rotation in order 
to swing the lower end 122s outwardly to release the latch and permit the 
clamping member to move upwardly under the influence of its spring 120. 
The latch lever 122 has a further arm 122a which slips into a vertical 
guide slot 110s in the hub 110 (FIGS. 5 and 6) during the axial movement 
of the clamping member 116. This, together with the position of the arm 
122b in the opening 110f of the hub, serves to couple the clamping member 
116 to the hub 110 in a rotational sense, to insure that the clamping 
member rotates bodily with the rotor. 
The hub 110a is flattened below the guide slot 110s so that there are two 
projections or noses 110m on either side of the vertical slot 110s, as 
illustrated in FIGS. 5 and 6. These noses cooperate with lateral lugs 122f 
on the latching lever 122, and serve to limit the upward extent of axial 
movement of the clamping member under the influence of its spring 120. The 
engagement of the parts 122f and 110m thus define the upper limit position 
or unclamped loading position of the clamping means. 
The sample containers or cuvets are intially loaded in the apparatus in the 
position illustrated in FIG. 3, with the outer end of each container 18 
resting against the resilient abutment 114, and the inner end resting on a 
ledge at the bottom of a vertical groove in the clamping collar 116, as 
illustrated in FIG. 2 and 3. Thereupon, the clamping collar 116 is moved 
downwardly by hand, against the force of the spring 120, until the nose 
122s on the latching lever 122 latches against the abutment surface 110e 
on the rotor, this position being illustrated in FIG. 1. During the 
downward movement, the sample container 18 is moved slightly radially 
outwardly because of the toggle effect, compressing the abutment 114, to 
what may be called a straight line or dead center position, and then 
slightly downwardly a little further beyond the dead center position, 
until each cuvet 18 is seated in its individual radial recess or groove 
110r, with the outer end of the container still tightly engaged with and 
somewhat compressing the resilient abutment 114, to seal the outer end 
tightly. In this final clamping position, the container 18 is inclined 
relative to the transverse plane containing the outer end of the cuvet, in 
a downward direction from the outer end to the inner end, but at somewhat 
less inclination or angle to the transverse plane than the angle of 
previous upward inclination in the loading position (FIG. 3). 
Any possible danger of premature upward movement of the clamping member is 
prevented by the positive latch provided by the cooperating parts 122s and 
110e. The tight clamping of the sample containers 18 cannot be released 
until the operating surface 122k is moved radially inwardly toward the 
axis of rotation, in order to release the latch. 
Advantageously the arm 122a on the latch is slightly resilient, and its 
engagement with the hub 110a causes a force tending to turn the latch 122 
in a clockwise direction (viewed as in FIGS. 1 and 3) on the pivot 124, 
thus resiliently keeping the latch in its latching position when the 
clamping collar 116 is in its lower or clamping position. In the upper or 
unclamping position shown in FIG. 3, the arm 122a is no longer in contact 
with a portion of the hub 110a but is above the top end of this hub, as 
illustrated, thereby releasing the resilient clockwise force on the 
latching lever in this upper position, but providing such resilient 
clockwise force in the lower position of the parts (FIG. 1) as the arm 
122a of the latching lever comes down to a position opposite and is 
engaged by the upper portion of the hub 110a. 
The parts 110, 116, and 122 are advantageously made as injection moldings, 
which enables favorable and economic mass production of the clamping 
assembly. With the arrangement according to the present invention, the 
cuvets or sample containers can always be inserted and gripped in a 
definite predetermined position of the parts, with the clamping member 116 
in a definite loading position under the influence of the spring 120, and 
then can be fully and tightly clamped when the clamping member is moved 
downwardly to its clamping position, without danger of accidental release 
during the high speed rotation of the parts. 
The radial recesses 110r for receiving the tubular containers are 
preferably individually numbered, as by the numerals "1", "2", "3", and 
"4" shown in FIG. 2. Graduated scales are preferably marked alongside each 
recess, as also seen in FIG. 2, to enable a numerical reading of the 
proportion of heavy components to light components in each tubular vessel 
at the conclusion of the centrifuging operation.