Centrifuge timer clamp

A timing and control mechanism for a centrifuge comprising a piston to which is attached a cam having cam surfaces which interact with flexible tubing to control the rate of flow through the tubing. The velocity of the piston in the centrifugal force field is determined by the resistance to flow of fluid which the piston displaces. The movement of the cam is therefore a measure of the speed and duration of the centrifugal force.

DESCRIPTION 
TECHNICAL FIELD 
The technical field is blood processing centrifuges. 
BACKGROUND ART 
In the treatment or processing of biological liquid such as blood; 
equipment has been provided whereby red blood cells, white cells, plasma, 
and platelet components are separated from whole blood in a centrifuge. In 
the course of processing blood within the centrifuge, portions of the 
separated blood components are either retained for storage or transferred 
to another patient or are returned to the donor. The blood processing may 
take place intervivos as is shown in U.S. Pat. No. 4,146,172 dated Mar. 
27, 1979 entitled Centrifugal Liquid Processing System to Cullis et al. 
In other centrifuge blood processing systems the process is not completely 
intervivos and the centrifuge may be stopped as the blood is processed 
into its constituent component elements and then some or all of the 
separated elements are stored or returned to the donor as the case may be. 
Such a system is described in U.S. patent application Ser. No. 005,126 
filed Jan. 22, 1979, now U.S. Pat. No. 4,303,193, entitled Apparatus for 
Separating Blood into Components Thereof to Allen Latham, Jr. 
U.S. Pat. No. 3,679,128 entitled Centrifuge issued July 25, 1972 to Unger 
et al also shows a centrifuge for processing blood in which an 
electromagnetic valve operates to control the flow of processed blood from 
one container to another container during the centrifuge process--that is 
to say, while the centrifuge rotor is spinning. 
In each of the above-described processes it is desirable to provide a 
simple and reliable mechanism to control the timing of the separation 
procedures. Preferably such a timing mechanism should operate in a manner 
directly proportional to the magnitude of the centrifugal force field 
since it is this quantity that directly influences the blood separation 
process. 
Present controlling means usually operate on the basis of an electronic or 
electromagnetic switch which is coupled into the centrifuge through slip 
rings or other means and is remotely operated based on some predetermined 
time or sensor setting. For example, see the valve 22 in U.S. Pat. No. 
3,679,128 or the hydraulically actuated clamp 142 in patent application 
Ser. No. 005,126 previously referenced. 
Such prior art systems suffer from the same drawback; variations in the 
rotational speed of the rotor are not automatically compensated for and 
must be compensated for by some other means. In addition, prior art 
systems require means to transmit a control signal to the rotor through 
some form of slip seal. These seals are expensive and tend to have short 
life expectancies in application. 
INVENTION DISCLOSURE 
In the apparatus of the present invention a hydraulically actuated timer 
clamp is mounted directly on the rotor of a centrifuge and is thereby 
subjected to the same centrifugal motion as the processed blood. The 
hydraulic timer clamp consists of two assemblies, a timer mechanism and a 
clamp actuator. The timer mechanism consists of a cylinder having first 
and second volumes separated by a movable piston. The piston contains two 
fluid passageways for fluid flow between first and second volumes. The 
first passageway has a needle valve control which is adjusted to control 
the fluid velocity through this passageway. In practice, this needle valve 
is adjusted to provide a relatively small cross-sectional area to the 
passageway; thus producing a relatively high resistance to flow. 
Alternatively, the variable needle valve passageway may be replaced by a 
fixed capillary of small internal diameter. 
The second passageway in the piston is of relatively large cross-sectional 
area and thus is relatively low in flow resistance. This passageway is 
provided with a check valve which will close the passageway when the 
centrifuge is spinning and thereby prevent flow through the second 
passageway when the rotor of the centrifuge is spinning. 
The piston is arranged so it is able to move radially outward with respect 
to the axis of rotation of the centrifugal force, or inward by manually 
re-setting the plunger. The diameter of the capillary or needle valve 
opening, the viscosity and density of the oil or other fluid in th two 
volumes, and the mass of the piston determines the distance the piston 
moves during a given period of time under the influence of the centrifugal 
force for a given radius of center of gravity of the piston with respect 
to the center of rotation of the centrifuge rotor. Thus, the movement of 
the piston directly represents the duration and speed of rotation of the 
centrifuge. 
The second assembly of the hydrauic timer clamp is the clamp actuator 
consisting of a cam, a cam follower and one or more actuator pins. The cam 
is coupled to the piston. The cam moves in response to the motion of the 
piston. A cam follower moves in response to the surface of the cam. The 
cam follower in turn moves one or more actuator pins which clamp flexible 
wall tubing through which specific blood components flow. In this manner, 
motion of the piston in turn results in planned opening or clamping of 
flexible tube walls which in turn results in planned control of flow 
through the tubing. 
Thus, the hydraulic timer clamp times and controls the blood processing 
system while the centrifuge is in operation under the direct influence of 
the centrifugal force and without the necessity for elaborate slip rings 
or other means for connecting the timing mechanism from the rotor to the 
external system and without additional compensation for variations in 
rotor speed. 
In other words, the response of the piston is directly proportional to the 
speed and duration of the centrifugal force and is therefore an accurate 
measure of the timing of the blood separation process which relies 
basically on the speed and duration of the centrifugal force for 
separation.

BEST MODE CONTEMPLATED 
Referring to the Figures and particularly to FIG. 1, a hydraulic timer 
clamp is shon generally at 8 mounted on the side of a rotor cylinder 34 of 
a centrifuge 2. The centrifuge is capable of rotating at relatively high 
speeds sufficient to effect the desired processing of blood from or within 
blood processing chambers such as, for example, the bags 38. The blood 
processing chamber 38 has connected to it one or more flexible tubes 36 
through which blood passes in the centrifuge process. The details of a 
particular centrifuge process, for which this timer clamp is suitable are 
shown in patent application U.S. Ser. No. 005,126 previously referenced. 
Referring now to FIGS. 2-4, there is shown the exterior of the hydraulic 
timer clamp 8 of this invention consisting of a timer mechanism 80 
(described in connection with FIGS. 5 and 6) and a clamp actuator 
described in detail in connection with FIGS. 2-4. The clamp actuator 
consists of one or more tube clamping mechanisms which are actuated by the 
piston of the hydraulic timer 80. The control cycle for each such clamping 
mechanism is established by the rise and fall contour of a cam such as 39 
or 51 shown in FIG. 2. Each such cam is secured to the pisto 10 of timer 
mechanism 80 so that its motion is timed by the motion of piston 10. 
The rise and fall of the cam is transmitted to tube clamp pin 325 and 326 
by respective follower arms 350 and 365. The follower arms are attached to 
respective pivot shafts 30 and 37 which pivot in bearings. Pivot shaft 30 
attached to follower arm 350 pivots on bearings 360 and 362 and couples 
the follower arm motion through arm 351 to tube clamp pin 325. A spring 
262 serves to hold follower arm 350 against the profile of cam 39. 
Correspondingly, follower arm 365 is attached to pivot shaft 37 which 
pivots on bearings 361 and 330. The pivot shaft is also attached to arm 90 
on the end of which is a tube clamp pin 326. 
Pins 325 and 326 ride within slots 324 and 391 in respective tube guides 32 
and 31 in response to the rise and fall of the cam contour as just 
described. Arcuate slots 323 and 393 are provided in each tube guide 32 
and 31 and the flexible tubes such as 36 through which blood components 
pass in the centrifuge process are retained in these arcuate slots. 
Slot 324 extends into or intersects with arcuate slot 323 thus pin 325 may 
be moved up or down to open or pinch clamp flexible tube 36. 
To recapitulate, as cam 39, which is secured to piston 10, moves away from 
the center of rotation (CR) under the influence of the centrifugal force 
created by rotation of rotor 34; follower arm 350 under the influence of 
spring 262 will follow the contours of surface "S" of cam 39. The 
rotational motion of arm 350, as it follows the contours of surface "S", 
is converted to a corresponding motion of pin 326 within slot 324 by the 
rotation of shaft 30 intermediate arms 350 and 351. Thus, pin 326 moves in 
or out of slot 324, compressing or opening tubing 36 in response to the 
motion of cam 39 which is controlled by the movement of plunger 10. The 
relative motion can be seen by comparing FIGS. 3 and 4. In FIG. 3, 
follower cam 350 is riding on level "a" of surface "S" and pin 326 
compresses tube 36 and so prevents flow. In FIG. 4 follower arm 350 is at 
level "b" and pin 326 has moved away from tube 36 permitting flow. 
The operation of follower arm 365 with respect to cam 51 and pin 326 is 
identical to that of follower arm 350, accordingly the above description 
will suffice for both. 
Referring now to FIGS. 5 and 6, the timer mechanism shown generally at 80 
may be described. This mechanism comprises a cylinder 12 containing a 
piston 10 and first and second fluid volumes 16 and 18, respectively. 
Preferably the fluid is an oil such as silicone oil having relative 
constant viscosity over a wide temperature range. A second volume of 
identical fluid 18 is also contained in the cylinder. The cylinder with 
fluid is disposed about piston 10 in a fluid-tight relationship. Piston 10 
is allowed to move in either direction longitudinally within the cylinder 
12. Piston 10 extends beyond the cylinder housing at both ends and it is 
important that the cross-sectional area of the piston is equal on both 
sides. 
A narrow fluid path 20 is provided between the first volume of fluid and 
the second volume of fluid. The opening in this path and thus the velocity 
of flow throughout is controlled by the setting of needle valve 13. 
Alternatively, a fixed capillary may be provided at this point. 
By use of ball 14 as a check valve; flow can occur in channel 26 only in 
the direction indicated by the arrow in channel 26 thus allowing 
re-setting of the piston to its starting position more easily than by 
forcing the oil through the small pathway controlled by the needle valve. 
In the active stroke of the piston, the piston moves longitudinally (from 
right to left as indicated by the arrow in FIG. 5) along the axis of 
cylinder 12 as will occur when the centrifuge rotates about the center of 
rotation (CR) (shown in FIG. 1). The piston generates considerable force 
trying to fly out from the center of rotation; but it is constrained by 
the oil in the two volumes, and in particular the oil in volume 18 of the 
cylinder. During this active stroke the check valve 14 is closed thus 
preventing flow of oil through path 26. The check valve is held closed 
both by the pressure differential across it and the weight of the metal 
rod 15 that is resting on it, as well as on its own weight. It should be 
noted that weight 15 may, or may not, be required to maintain ball valve 
closed in the active stroke. Thus, the only way the oil can move out of 
volume 18 is through path 20. 
As the piston 10 moves farther and farther away from the center of rotation 
there is a higher centrifugal force acting on it. Thus, the rate of 
movement of the piston away from the center of rotation is not at a fixed 
rate. However, by appropriate shaping of the cam surfaces of the cams 39 
and 51, the non-linear movement of the plunger can be compensated for. 
After the centrifuge has come to rest, the reset stroke of the piston can 
be accomplished by manually pulling the piston towards the center of 
rotation. That is in the left to right direction as shown by the arrow in 
FIG. 6. When the rotor 34 is stopped, ball valve 14 may be unseated, since 
centrifugal force is no longer holding the ball against its seat. Thus, 
the flow of oil may be reversed as shown in FIG. 6 and oil may flow from 
the inner or second volume of oil 16 through conduit 24 and into conduit 
26, through conduit 28 and into the outer volume of oil 18. 
Referring back to FIG. 2, some further details of the invention may now be 
described. Cams 39 and 51 may be removably mounted on one end of the 
plunger 10 by means of set screws 380 and 381 respectively. The cam 
surfaces of the control keys are provided with notches and slots which 
will either open or clamp off the flexible tubing 36, thus controlling the 
flow of blood components. Cam 51 of FIG. 2 is provided, for illustrative 
purposes, with six regions on the cam surface. When region 432 is adjacent 
to the follower arm 500 the flow through flexible tubing (not shown) is 
blocked by pin 326 for a period of time proportional to the length of 
region 432 on cam 51. This would correspond to the time when the 
centrifuge is initially spinning at, for example, 2,000 RPM for initial 
separation of blood. Next, region 434 would allow a low rate of flow 
through the tubing, then region 436 would gradually increase the flow to a 
maximum. Region 438 would then clamp off the tube completely for a period 
of time proportional to the length of region 438. This could be for a 
period when a higher speed spin was to take place, say at 3,000 RPM. Next, 
as the cam follower was engaged with region 440, pin 326 would move away 
from the flexible tube (not shown) to allow flow again and finally region 
442 would clamp off the tube for deceleration. 
Other embodiments may occur to those skilled in the art. For example, a cam 
having two opposite cam surfaces could be used to control two follower 
arms, one positioned on either side of the cam. This would be useful in 
controlling a two bag plasmapheresis procedure. 
FIGS. 7 and 8 show an embodiment of the cam and follower arm structure of 
the invention wherein the cams are rotatably mounted so that the slotted 
surfaces of the cam can be readily disengaged from the cam follower level 
arms permitting the plunger to be moved in or out more readily. It is 
advantageous to have a cam which may be rotated rather than unfastened. 
Such a feature would greatly facilitate and speed up resetting of the 
plunger and placement and removal of the tubing in or from the arcuate 
slots in the tubes guides 31 and 32. In FIGS. 7 and 8 parts similar to 
those previously described are correspondingly numbered and primed. 
Thus, a pair of lever arms 350' and 365' are held by spring 262' in 
resilient contact against cams 39' and 51'. Cam surface S' contacts the 
edge of the cam follower lever arm when handles 700 and 702 are in the 
positions shown in FIG. 7. 
The cams 39' and 51' in FIGS. 7 and 8 are generally rod-shaped and are 
rotatably mounted on end piece 704. Cross-sectional views of a typical cam 
39' at various locations along cam 39' are shown in FIGS. 9 and 10. 
Handles 700 and 702 are attached to one end of each rod-shaped cam. Thus, 
when it is desired to release the cam follower arms 350' or 365' from 
engagement in a slot in the cam surface S' it is only required to rotate 
the handles into the positions shown in FIG. 8. 
While a particular embodiment of the invention has been shown and described 
above, it will be obvious to those skilled in the art that changes and 
modifications may be made without departing from the invention in its 
broader aspects and therefore the aim in the appended claims is to cover 
all such changes and modifications as fall within the true spirit and 
scope of the invention.