Device for separating the components of a liquid, especially whole blood

A device for obtaining from at least two spatially separated areas the heterogeneous components of a liquid, especially stabilized whole blood in a flexible and transparent bag with at least one line leading out of it. The device consists of a front plate that is part of a housing, of a pressure-application plate that pivots toward the front plate, of a drive mechanism, and of a sensor. The point that the pressure-application plate pivots around is below the bag and at the point of intersection between the surfaces of the plates, specifically at least 30% of the length of the pressure-application plate away, and the drive mechanism engages a lever that is rigidly secured to the pressure-application plate. A bag employed in conjunction with the device has an intake line at the top and an outlet line and a filling and blood-collecting tube at the bottom, only one bag-to-bag transport system at the top, and no outlet connections.

BACKGROUND OF THE INVENTION 
The invention concerns a device for obtaining one after another and from at 
least two spatially separated areas the components of a liquid, especially 
stabilized whole blood contained in a flexible bag with at least one line 
leading out of it. 
In the devices that have been available up to now for separately obtaining 
the components of a liquid, especially whole blood in centrifuged bags, 
the bag containing the liquid or whole blood is squeezed between a 
perpendicular and stationary plate and another plate that is hinged to the 
bottom of the first and can be pivoted toward it. 
The requisite force is obtained with springs. These devices, conventional 
plasma squeezers, have considerable drawbacks, however. First, the 
squeezing procedure must be constantly monitored and decelerated or 
terminated once a particular layer of components has been attained at the 
upper edge. Second, since the force of the springs decreases while the bag 
is being squeezed, greater force than can be obtained from the springs 
alone must be exerted to squeeze a more viscous layer, the Buffy-coat 
layer for instance, out of the blood. Layers of that type can usually be 
obtained only by adding manual force. Finally, only bags with an outlet at 
the top can be employed in these devices. 
The conventional plasma squeezers have been improved by the addition of a 
cell sensor, making it unnecessary to monitor the squeezing procedure. The 
inhomogeneities in pressure due to the use of springs, however, are still 
present along with the associated drawbacks. 
A considerable improvement in the aforesaid devices has been attained with 
automatic drive mechanisms. 
German OS 3 012 228 describes a device wherein the pressure is applied 
hydraulically, pneumatically, or hydropneumatically. Sensors for 
determining the various component layers allow automatic squeezing. 
German OS 3 417 892 also describes an automatic device wherein the 
squeezing structure is accommodate between an upper and a lower 
pressure-application plate, requiring three separately operated 
pressure-application structures. 
The stationary plate and the moving plate are parallel in both devices, and 
the bag must accordingly be manually secured between the plates until the 
squeezing procedure is initiated and it can be secured by the commencing 
pressure. Since the bag is teardrop-shaped, however, it will rapidly 
deform and create turbulence in the interface between its contents, making 
it more complicated to squeeze out a pure layer of component. Since the 
force exerted on the stationary plate is relatively high (approximately 50 
kp), the plates must be relatively strong. 
OBJECT OF THE INVENTION 
The object of the invention is accordingly to improve a device of the 
aforesaid type for separately obtaining the components of a liquid to the 
extent that the bag does not need to be manually secured and will not 
rapidly deform initially, preventing the centrifuged layers from mixing 
together again. The pressure will also be applied automatically and 
continuously. Use of appropriate sensors and of a bag with at least one 
and preferably two outlet lines will on the whole result in a rapidly and 
efficiently operating and simple device for obtaining pure blood 
preparations in particular. 
This object is obtained in accordance with the invention in a device for 
obtaining from at least two spatially separated areas the heterogeneous 
components of a liquid, especially stabilized whole blood in a flexible 
and transparent bag with at least one line leading out of it and 
consisting of a front plate 1 that is part of a housing 11, of a 
pressure-application plate 2 that pivots toward the front plate, of a 
drive mechanism, and of a sensor, by the improvement wherein the point 3 
that the pressure-application plate pivots around is below the bag and at 
the point of intersection between the surfaces of the plates, specifically 
at least 30% of the length of the pressure application plate away, and the 
drive mechanism engages a lever 12 that is rigidly secured to the 
pressure-application plate. 
The essential feature is that the stationary plate and the 
pressure-application plate are not parallel but initially at an angle to 
each other and that the pivoting point is in the aforesaid specific 
location. The bag can accordingly be adequately secured before any 
pressure is applied just be placing it in the device and will not rapidly 
deform as the squeezing procedure commences. The more extensive 
cross-section at the top of the bag will also considerably eliminate 
interface turbulence toward the end of the procedure as compared to what 
occurs with parallel plates. The multiple bag-to-bag communication system, 
the break-off section for example, at the top will also be much easier to 
remove than it is when the plates are parallel because of the wider 
opening. Since the pressure-application plate is approximately 30% shorter 
than the stationary plate, it is possible to use bags with another outlet 
line at the bottom. The automatic operation provided by the drive 
mechanism that is rigidly secured to the pressure-application plate by way 
of a lever and by the associated sensors in the device in accordance with 
the invention make it possible to obtain pure blood preparations for 
example efficiently, simply, and rapidly. 
The scanner can be an optical detector 4 or 10 that activates a mechanism 9 
that blocks off at least one of the outlets when a specific component 
layer attains a prescribed level in the bag. 
The optical detector 4 can be positioned on the front plate in the vicinity 
of the bag. 
The optical detector 10 can be positioned in the vicinity of the tubing. 
The device can also have a limit switch. 
The drive mechanism can be hydraulic or electric. 
The drive mechanism can be positioned on the front plate. 
A pressure sensor 5 can be positioned in the center of the front plate. 
The bag employed in conjunction with the device in accordance with the 
invention can have an intake line 13 at the top and an outlet line 14 and 
a filling and blood-collecting tube 15 at the bottom, only one bag-to-bag 
transport system at the top, and no outlet connections.

DETAILED DESCRIPTION OF THE INVENTION 
The device in accordance with the invention consists of a housing 11 that 
accommodates the drive mechanism and has a stationary front plate 1 and a 
pressure-application plate 2 that is initially at an angle to the front 
plate. The pressure-application plate can be made of plastic and is 
secured in a metal frame. The line of intersection between the surfaces of 
the two plates is approximately 30% of the length of pressure-application 
plate 2 below the bag. Positioned on the line of intersection and about 
30% below the length of pressure-application plate 2 or of the bag is the 
point 3 that the pressure-application plate pivots around. This 
arrangement allows the additional tubing connections characteristic of 
such bags as the one described in European Patent 8 611 079.9, with more 
than one outlet, one at the top and one at the bottom for example, to be 
secured in the space between the pivoting point 3 and the bag preventing 
them from impeding complete compression of the bag. 
Lowering the point 3 that pressure-application plate 2 pivots around 
farther below the bag in accordance with the invention than it is in known 
devices reduces the powerful deformation of the bag at the beginning of 
the squeezing procedure and considerably decreases turbulence at the 
interface. 
The angle between the two plates keeps the bag in a constant position. The 
upward flow of the lighter-weight components will be reduced due to the 
wider cross-section at that point of the bag, and much less of the heavier 
components will be entrained. 
The drive mechanism is rigidly connected to pressure-application plate 2 by 
way of a lever 12. Pressure-application plate 2 is set in motion by 
electric or hydraulic force for example. The drive mechanism, which 
consists of a motor 6, a transmission 7, and a spindle 8, is preferably 
positioned on front plate 1, ensuring that approximately the same force 
will be exerted on front plate 1 from outside and from inside, and it is 
accordingly exposed only to torques that are less than those to which the 
device on the whole is subjected. The weakness of these forces makes it 
possible to keep front plate 1 thin because it does not need to be 
especially strong. 
The sensors can be tubing detectors 10 of the type described in GB Patent 1 
537 096 or a detector 4 positioned in the center of the front plate. An 
interface can accordingly be detected as it rises during the squeezing 
procedure and associated tubing clamps 9 tightened as soon as one 
component has been squeezed out. 
The device in accordance with the invention can also be equipped with a 
pressure sensor 5 positioned below bag detector 4 on front plate 1 and 
controlling the drive mechanism. This system will ensure constant 
compression, which will be automatically decreased if an outlet line 
becomes obstructed to prevent undesirable excess pressure. 
The device being claimed can also be equipped with a limit switch that will 
activate the device's clamp or clamps once the plates are separated by a 
prescribed distance or once the bag has been emptied to a prescribed 
level. 
The embodiment just described is especially appropriate for bags with an 
upper and a lower exit. An interface detector controls the upper clamp. It 
can be positioned on front plate 1 in the vicinity of the bag or in the 
vicinity of the tubing. If a bag detector 4 is employed, the upper clamp 
is closed as soon as it detects the rise of the interface from the more 
rapid outflow of the lighter-weight component. The heavier component will 
then flow down and the interface will descend again. As soon as the 
detector determines that the interface is at a particular level, the upper 
clamp will be opened again. This process will maintain the interface at a 
level defined by bag detector 4 throughout the squeezing procedure. Once 
the plates are at a certain distance from each other or once the bag has 
been emptied to a certain extent, the clamp or clamps are closed and the 
procedure is over. 
When a tube detector 10 positioned at the top of the tube is employed, the 
upper clamp is closed once all the lighter-weight component has been 
squeezed out. The heavier component is squeezed out until the plates are 
at a prescribed distance apart or the bag has been emptied to a prescribed 
extent. 
FIG. 2 is a side view of the device in accordance with the invention. 
The drive mechanism is accommodated in a housing 11 with a front plate 1. 
Motor 6 and transmission 7 are fastened to front plate 1 by spindle 8 and 
rigidly secured to pressure-application plate 2 by lever 12. Accommodated 
in the center of front plate 1 is a bag detector 4 with a pressure sensor 
5 below it. At the top of front plate 1 are tube clamps 9 and a tube 
detector 10. 
Pressure-application plate 2 is more than 30% shorter than front plate 1. 
The line of intersection between the surfaces of the plates and the point 
3 that pressure-application plate 2 pivots around are accordingly below 
the bag. 
The bag that contains the fluid, preferably a bag with two outlet lines, is 
positioned in accordance with the invention between the two plates such 
that the space below it remains free and can be used for the second outlet 
line without impeding the squeezing procedure. 
The bag illustrated in FIG. 3 has an upper intake line 13 and a lower 
outlet line 14. It contains no connections and only one bag-to-bag 
transport system, breakoff section 16 for example, which is at the top. 
Outlet line 14 is at the same end of the bag as a filling and 
blood-collecting tube 15. 
This bag design ensures that break-off section 16 will always be at the top 
during the centrifuging process and cannot break of prematurely. The 
layers separated by the centrifuging will not become turbulent when the 
section is broken off, as might easily happen if it were at the bottom. 
Furthermore, no undesired blood cells will be retained at the top of the 
bottle as might happen if there were a connection at that point. 
Furthermore, contamination at the top of the bottle is prevented for the 
same reason, because filling and blood-collecting tube 15 is at the 
opposite end along with outlet line 14. 
This type of bag can as previously described herein simply be placed in the 
device in accordance with the invention and completely squeezed out. 
One essential advantage of the device being claimed herein is that, since 
pressure-application plate 2 is shorter than front plate 1, a DIN-standard 
bag that is filled to a specific level can always be inserted in the same 
position. It will be unnecessary to hold it in place manually until the 
squeezing procedure begins as it is when the two plates are parallel. 
Furthermore, the initial rapid deformation of the bag and the concomitant 
undesired interface turbulence are considerably decreased. Making 
pressure-application plate 2 shorter than front plate 1 in accordance with 
the invention ensures that the bag will be squeezed completely empty 
unimpeded by extra outlet lines as would happen with bags with outlets at 
the top and bottom. 
The more extensive cross-section at the top of the bag in accordance with 
the invention also reduces the risk of interface turbulence toward the end 
of the squeezing procedure. 
The force exerted on front plate 1 as the bag is squeezed out is, in 
contrast to systems employing parallel plates, compensated in that the 
position of the drive mechanism ensures that the force exerted on the 
plate from outside will equal the force exerted on it from inside. Thinner 
plates can accordingly be employed. 
The device in accordance with the invention can for example be employed for 
separately obtaining whole-blood components in leukophoresis, 
plasmaphoresis, thrombophoresis, etc., which preferably employ bags with 
more than one outlet line. 
It is understood that the specification and examples are illustrative but 
not limitative of the present invention and that other embodiments within 
the spirit and scope of the invention will suggest themselves to those 
skilled in the art.