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Field of the Invention
The invention relates to blood processing systems and apparatus. More specifically, the invention relates to blood processing apparatus such as centrifuges which are provided with an improved heater assembly for maintaining the temperature of the blood during processing.
Background of the Invention
Whole blood is separated by centrifugation into its various constituents, such as red blood cells, platelets, and plasma. Conventional blood processing methods use centrifuge equipment in association heaters that maintain the temperature of the processing system during the centrifuging process. A need has existed for improved heating assemblies capable of efficiently maintaining the temperature of blood within the centrifuge during processing.
Summary of the Invention
The invention provides improved blood processing systems with a closed circuit heater system. Briefly, in accordance with the invention, a blood processing assembly includes a centrifuge contained within a heated housing or chamber. A heater assembly is provided that is connected to the chamber for maintaining the temperature of liquids within the interior of the chamber during process- ing, the assembly including a closed loop air flow conduit having an inflow opening discharging into the chamber and an outflow opening for receiving air into the loop. An air flow impeller is in the loop for causing a flow of air t srethrough, a heating element in the loop for heating air flowing therethrough, and a temperature sensor in the loop for sensing the temperature of air flowing into the loop from the chamber, the sensor being operatively connected to the heater to control the operation thereof to maintain the temperature of the air in the chamber within a selected range.
Further features and advantages of the invention will become apparent from the following description, the drawings, and the claims.
Brief Description of the Drawings
FIGURE 1 is a perspective view of a centrifugal assembly that embodies the features of the invention;
FIGURE 2 is a perspective view of the assembly 'of FIGURE 1 showing the centrifuge chamber in the open position;
FIGURE 3 is a sectional view of a centrifuge shown in FIGURE 1 taken along Line 3-3 with parts broken away to show the compartment that houses the associated centrifuge;
FIGURE 4 is a perspective view of a centrifuge shown in FIGURE 1 with parts the centrifuge removed to show the interior of the compartment that houses the associated centrifuge with parts of the heating assembly shown by phantom lines;
FIGURE 5 is a top sectional view of the compartment shown in FIGURE 4 ;
FIGURE 6 is a sectional side view taken along Line 6-6 of FIGURE 5;
FIGURE 7 is a fragmentary side view taken along Line 7-7 of FIGURE 5; and,
FIGURE 8 is a fragmentary sectional view taken along Line 8-8 of FIGURE 6.
Description of the Preferred Embodiments
FIGURES 1 through 3 show a centrifugal processing system 10 that embodies the features of the invention. The system 10 can be used for processing various fluids. The system 10 is particularly well suited for processing whole blood and other suspensions of biological cellular materials. Accordingly, the illustrated embodiment shows the system 10 used for this purpose.
The system 10 includes a centrifuge assembly 12 (see FIGURE 1) and a fluid processing assem-bly (not shown) used in association with the centrifuge assembly.
The centrifuge assembly 12 is intended to be a durable equipment item capable of long term, maintenance free use. The fluid processing assembly is a single use, disposable set loaded on the centrifuge assembly 12 at time of use in accordance with known practices. The operator removes the fluid processing assembly from the centrifuge assembly 12 upon the completing the procedure and discards it.
FIGURE 2 shows a centrifuge or processing chamber 14 and containment housing 16 usable in association with the assembly 12. In use, the centrifuge assembly 12 rotates the processing chamber 14 to centrifugally separate blood compo- nents. The construction of the processing chamber

14 can vary, with numerous constructions being known in the art.
The processing assembly 12 includes an array of flexible tubing that forms a fluid circuit 18. The fluid circuit 18 conveys liquids to and from the processing chamber 14.
The fluid circuit 18 includes a number of containers 20. In use, the containers 20 fit on hangers within the centrifuge assembly 12 see FIGURE 3) to dispense and receive liquids during processing. Centrifuge 14 is rotationally driven by a motor 22.
The fluid circuit 18 includes one or more in line fluid processing containers and devices, as is known in the art, in association with pump and valve stations on the centrifuge assembly 12 to direct liquid flow among the multiple liquid sources and destinations during a blood processing procedure. A portion of the fluid circuit 18 leading from the containers 20 is bundled together to form an umbilicus 24. The umbilicus 24 links the rotating parts of the processing assembly 12 with the nonrotating, stationary part of the processing assembly 12. The umbilicus 24 links the rotating and stationary parts of the processing assembly 12 without using rotating seals.
In the illustrated and preferred embodiment, the fluid circuit 18 preconnects the processing chamber 14, the containers 20, and other fluid processing parts of the system. The assembly 12 thereby forms an integral, sterile unit.
The umbilicus 24 consolidates the multiple fluid paths leading to and from the blood separation chamber. It provides a continuous, sterile environ- ent for fluids to pass. In construction, the umbilicus 24 is flexible enough to function in the relatively small, compact operating space the centrifuge assembly 12 provides. Still, the umbilicus 24 is durable enough to withstand the signifi- cant flexing and torsional stresses imposed by the small, compact spinning environment, where rotation rates up to about 4000 revolutions per minute (RPM) can be encountered.
The processing chamber 14 can be variously constructed. For example, it can be constructed like the double bag processing chambers shown in

Cullis et al. U.S. Patent 4,146,172. Specific details of the construction of the processing chamber 14 and other components of the system are not essential to an understanding of the invention and can be also be found in copending U.S. Patent

Application Serial No. 07/965,074, filed October 22,

1992, and entitled "Enhanced Yield Blood Processing

Systems and Methods Establishing Vortex Flow Condi-tions," which is incorporated herein by reference.
The centrifuge assembly 12 includes a processing controller 246. The controller 246 governs the operation of the centrifuge assembly 12. The processing controller 246 preferably includes an integrated input/output terminal 248 as seen in FIGURE 1) , which receives and display information relating to the processing procedure.
The centrifuge 14 rotates about an axis within the compartment 16. As FIGURE 2 shows, unlike conventional centrifuges, the rotational axis of the centrifuge 14 is not oriented perpendicular to the horizontal support surface. Instead, the rotational axis slopes in a plane outside a vertical plane. The centrifuge 14 is supported within the compartment 16 outside the vertical plane such that its rotating components lie near the access door 17 (see FIGURE

2) . In this way, opening the door 17 provides direct access to the rotating components of the centrifuge 14. The sloped orientation of rotational axis allows the centrifuge 14 to be mounted in a way that conserves vertical height.
The angled relationships established between the rotational axis of the centrifuge 14 and the plane of top panel 19 make it possible to place the rotating centrifuge components for access in a zone that lies between the knees and chest of the average person using the machine. These relationships also make it possible to place the stationary functional components such as pumps, sen-sors, detectors, and the like for access on the panel 19 by the user within the same zone. Most preferably, the zone lies around the waist of the average person.
Statistics providing quantitative informa-tion about the location of this preferred access zone for a range of people (e.g., Large Man, Average Man/Large Woman, Average Adult, Small Man/Average Woman, etc.) are found in the Humanscale™ Series Manuals (Authors: Niels Diffrient et al., a Project of Henry Oreyfuss Associates) , published by the MIT Press, Massachusetts Institute of Technology, Cambridge, Massachusetts.
These angled relationships established among the rotating and stationary components of the centrifuge assembly 12 provide significant ergonomic benefits that facilitate access to and operation of the assembly 12.
Further details of the chamber assembly are found in copending U.S. Patent Application Serial No. 07/814,403, filed December 23, 1991, and entitled "Centrifuge with Separable Bowl and Spool Elements Providing Access to the Separation Chamber," which is incorporated herein by reference. The centrifuge 14 made and operated according to the invention provides a small, compact operating environment. The compact operating environment leads to rates of rotation greater than those typically encountered in conventional blood centrifuges. As best seen in FIGURES 3 and 4, a splatter detector assembly 30 is provided on an interior wall of housing 16.
Referring to FIGURES 3-8, a heater assembly is indicated generally by numeral 40. The heater assembly is in the form of a closed loop which includes an airflow conduit 42 extending externally of centrifuge housing chamber 16 which is heated by the assembly. At one end of conduit 42 there is a housing 43 which connects conduit 42 for an opening 44 for inflow of air into chamber 16. Another opening 46 for outflow of air is provided at the opposite end of loop 42 as best seen in FIGURE 4. A housing 47 is provided to connect the opposite end of conduit 42 to the outflow opening 46. Contained within housing 47 is an impeller 50, for example, an electrically operated fan, which continuously causes air to be moved through conduit 42 and back into housing 16 during operation of the centrifuge.
Also, as seen in FIGURE 4, the discharge openings 44 and 46 are located in an offset fashion not diametrically opposed on opposite sides of the housing 16. Thus discharge of air as shown by arrows 51 forms a vortex within chamber 16 for uniformly heating centrifuge 14 contained therein.
As seen in FIGURE 5, a temperature sensor 52 is provided within conduit 42 to measure the temperature of air flowing out of chamber 16 into conduit 42. Temperature sensor 52 is connected to a controller 54 which governs the operation of an electrical heater 56 contained within housing 43. If sensor 52 detects a drop in the temperature of the air within chamber 16 below a predetermined, selected range, the heater 56 is activated so that the temperature is raised to a level within the selected range.
Filters 48 are provided over the inflow opening 44 and outflow opening 46. The filters are preferably formed of a wire mesh material. Such filters have been found to permit the passage of air therethrough while preventing the passage of liquid droplets. Thus, contamination of the interior of conduit 42 is prevented or minimized. Conduit 42 and housings 43 and 47 can be formed of a rigid material such as metal or a plastic resin.
In the event that blood is leaking, for example from containers 20 or from conduits 18 or connections thereof, it is important that the centrifuge be stopped and the problem remedied before excessive amounts of blood are lost within the interior of assembly 12 and leak into the surrounding area.
In the preferred embodiment shown in the drawings, the splatter detector assembly 30 consists of two splatter detectors 32 and 34. Each of these detectors consists of a pair of parallel electrodes which may take the form of metallic strips on a non- conductive, for example plastic base. These strips may be in the form commonly used in printed circuits. When droplets of a liquid such as blood are deposited, on the splatter detector a short circuit can be formed between the electrodes which enables a greater flow of current to pass through the circuit, thus triggering a message on the screen of processor 248, as well as cutting off the power on driving the rotation of centrifuge 14. This enables the operator to open and clean the interior of - 9 - assembly 12 and to remedy the problem.
The invention may be embodied in several forms without departing from its spirit or essential characteristics. The scope of the invention is defined in the appended claims, rather than in the specific description preceding them. All embodiments that fall within the meaning and range of equivalency of the claims are therefore intended to be embraced by the claims.