Patent Publication Number: US-6334841-B1

Title: Centrifuge with Ranque vortex tube cooling

Description:
FIELD OF THE INVENTION 
     The present invention relates to a centrifuge comprising a chamber, a rotor arranged therein, means for driving the rotation of the rotor, and means for cooling the atmosphere of the chamber. 
     The invention applies in particular to the centrifuging of biological products. 
     BACKGROUND OF THE INVENTION 
     The cooling of the atmosphere of the chamber of a centrifuge of this type is generally achieved by cooling a wall of the chamber, for example by causing a cooling fluid to circulate on the outside of the chamber, or by using a Peltier-effect system. 
     However, it is found that these methods of cooling are not very effective and/or generate a significant amount of heat outside the chamber. 
     The latter aspect is particularly troublesome in the case of the centrifuging of products likely to release pathogenic or toxic substances, it being necessary for such centrifuging to be performed in specially appointed rooms. The volume of these rooms, which meet, for example, the type P3 or P4 confinement standards, is limited and numerous items of apparatus giving off large amounts of heat are generally gathered in these rooms. Now, such release of large amounts of heat is detrimental to the correct operation of these items of apparatus, to their life, and to the results of the manipulations. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the invention is to solve these problems by providing a centrifuge in which the cooling means are effective and lead to a limited production of heat outside the chamber. 
     To this end, the subject of the invention is a centrifuge comprising a chamber, a rotor arranged therein, means for driving the rotation of the rotor, and means for cooling the atmosphere of the chamber, characterized in that the means for cooling the atmosphere of the chamber comprise a Ranque vortex tube, a cold outlet of which is connected to one inlet of the chamber, and in that the centrifuge comprises a pressurized-gas supply circuit which is connected to an inlet of the Ranque vortex tube and which is intended to be connected to a source of pressurized gas. 
     According to particular embodiments, the centrifuge may comprise one or more of the following features, taken in isolation or in any technically feasible combination: 
     the centrifuge comprises a gas-purification unit, one inlet of this unit being connected to an outlet for drawing gas from the chamber, 
     the purification unit comprises at least one filter, 
     the purification unit comprises at least one device for the chemical treatment of the drawn-off gas, 
     one outlet of the said gas-purification unit is connected to a suction device, 
     the means for driving the rotation of the rotor are pneumatic rotational-drive means connected to the pressurized-gas supply circuit, 
     the pneumatic rotational-drive means comprise a turbine, 
     the suction device is controlled by the pressurized gas supplied to the pneumatic means for driving the rotation of the rotor, 
     the suction device comprises a venturi injection system including an inlet for entraining fluid intended to be connected to the said source of pressurized gas, an inlet for entrained fluid connected to the said outlet of the purification unit, and an outlet for entraining fluid and entrained fluid which is connected to the pneumatic means for driving the rotation of the rotor, 
     the centrifuge comprises a source of decontamination gas connected to one inlet of the chamber, 
     the chamber is leak-tight, 
     the centrifuge comprises a pneumatic device for braking the rotor, 
     the supply circuit comprises a timer-controlled valve, 
     the centrifuge comprises a door which can move between a position for access to the inside of the chamber and a closed position, the centrifuge further comprises a pneumatic device for locking the door in its closed position, which locking device is connected to the pressurized-gas supply circuit, 
     the locking device comprises a first lock which can move between a position for locking and a position for unlocking the door, the first lock being secured to a rod of a first pneumatic ram connected via at least one individual pipe to the said pressurized-gas supply circuit, the locking device comprises a valve for selectively switching the individual pipe or pipes to the pressurized-gas supply circuit, 
     the supply circuit comprises an automatic-locking valve which itself includes a shut-off member which can move between a position for opening and a position for closing the automatic-locking valve, one outlet of this automatic-locking valve is connected to the said switching valve, the said shut-off member is kept in the open position when the door of the centrifuge is in the closed position, and the said switching valve, when at rest, places the said outlet of the automatic-locking valve and the first ram in communication so that the first lock is driven towards its locking position, 
     the automatic-locking valve is intended to be permanently connected to the said source of pressurized gas, 
     the locking device comprises a second lock which can move between a position of immobilizing the first lock in its locking position and a position of releasing the first lock, and the second lock is secured to the rod of a second pneumatic ram permanently connected to one outlet of the said timer-controlled valve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood from reading the description which will follow which is given merely by way of example and made with reference to the appended drawings, in which: 
     FIG. 1 is a diagrammatic side view, partially in section, of a centrifuge according to a preferred embodiment of the invention; 
     FIG. 2 is an enlarged diagrammatic view from above of the pneumatic brake of the centrifuge of FIG. 1; 
     FIGS.  3 . to  5  are enlarged diagrammatic views, in section, illustrating the structure and operation of the device for locking the door of the centrifuge of FIG. 1; and 
     FIG. 6 is a view similar to FIG. 1 illustrating another embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 diagrammatically depicts a centrifuge  1  which essentially comprises: 
     a lagged tank  3  borne by a stand (not depicted) and fitted with a door  4 , the tank  3  and the door  4  forming a chamber  5 , 
     a rotor  6  arranged in the chamber  5  and equipped with housings  7  for holding containers for products to be centrifuged, 
     pneumatic means  8  for driving the rotation of the rotor  6 , 
     a unit  10  for purifying gas drawn from the chamber  5 , and 
     means  11  for cooling the atmosphere of the chamber  5 . 
     The door  4  is hinged at  13  to the tank  3  so that it can move between a closed position, as depicted in FIG. 1, and an open position, not depicted, for access to the inside of the chamber  5 . 
     When the door  4  is in the closed position, the chamber  5  is rendered leak-tight with respect to the outside, particularly by virtue of a seal  14  which is compressed between the door  4  and the tank  3 . 
     In the open position, the door  4  is raised with respect to its closed position. 
     The centrifuge  1  further comprises a pneumatic device  16  (in dotted line) for locking the door  4  in the closed position. This device will be described later on with reference to FIG.  3 . 
     The drive means  8  comprise a shaft  18  secured to the rotor  6  and a turbine  19 , the blades  20  of which are depicted diagrammatically in FIG.  1 . This turbine  19  is secured to the shaft  18 . 
     The drive means  8  also comprise a venturi injection system  21  which itself includes: 
     an injector  22  of entraining fluid, 
     a divergent nozzle  23 , the inlet of which is spaced slightly away from the outlet of the injector  22  and which opens near to the blades  20 , and 
     an inlet  24  for entrained fluid, communicating with the space  240  separating the inlet of the nozzle  23  from the outlet of the injector  22 . 
     The centrifuge  1  also comprises a pneumatic brake which comprises (FIG. 2) two jaws  26  articulated to a shaft  27  and arranged one on each side of the shaft  18  that drives the rotor  6 . 
     These jaws  26  can move transversely to the shaft  18  between a close-together braking position (not depicted), in which they clamp the shaft  18 , and a spaced-apart position, in which the shaft  18  turns freely between the jaws  26  as depicted in FIG.  2 . 
     The brake  25  further comprises a spring  28  for returning the jaws  26  to their close-together position and a single-acting pneumatic ram  29  arranged between the jaws  26 . When the pneumatic ram  29  is supplied with pressurized gas, as depicted diagrammatically in grey in FIG. 2, the jaws  26  are in the spaced-apart position. When the ram  29  is not supplied with pressurized gas, the jaws  26  are in the close-together position. 
     The gas-purification unit  10  comprises, for example, a filter of the HEPA type. 
     The means  11  for cooling the atmosphere of the chamber  5  comprise a Ranque vortex tube  30 . This conventional device comprises a vortex-flow generator  31  to which are connected one inlet  32  for supplying pressurized gas, a cold outlet  33  and a hot outlet  34  for gas. 
     As illustrated in FIG. 3, the locking device  16  comprises a keeper  36  secured to the door  4 , a first lock  37  and a second lock  38 . 
     The first lock  37  can slide between a position for locking the door  4  (FIG.  3 ), in which the first lock is engaged in the keeper  36 , and a position for unlocking the door (FIG.  5 ), in which the lock  37  is withdrawn from the keeper  36 . 
     The second lock  38  can slide at right angles to the first lock between a position of immobilizing the first lock  37  in its locking position (FIG.  3 ), and a position of releasing the first lock  37  (FIG.  5 ). 
     In its immobilizing position, the second lock  38  is engaged in a recess  39  made in the first lock  37 . 
     The first lock consists of the rod of a first double-acting pneumatic ram  40 , and the second lock  38  consists of the rod of a second single-acting pneumatic am  41 . 
     The pneumatic locking device  16  also comprises: 
     a three-way two-position automatic-locking valve  44 , the shut-off member  45  of which is held in the open position, against the effect of a spring  450 , by the keeper  36  of the door  4  when the latter is in the closed position, and 
     a five-way, two-position switching valve  46 , the shut-off member  47  of which can be operated manually. 
     The shut-off member  47  can slide between a position for unlocking the door  4 , in which it compresses a spring  470 , and a position for locking the door  4 , or position of rest, in which the spring  470  is not compressed. 
     The centrifuge further comprises a silencer  48 , a source  49  of pressurized air and a source  50  of decontamination gas, for example formol. The air of the source  49  is, for example, at a pressure of between 3 and 6 bar. 
     The structure of the fluid circuit connecting the various elements of the centrifuge  1  will become clearly apparent during the description of the operation of this centrifuge  1 , which will be given, to start with, on the basis of FIGS. 1 and 3. 
     In FIG. 3, as in FIGS. 4 and 5, the inside of the pipes containing pressurized air is depicted in grey. 
     With the door  4  in the closed position, pressurized air from the source  49  passes through the automatic-locking valve  44 , which is in the open position, and is then split into two streams. 
     The first of these streams is conveyed by a pipe  51  to the switching valve  46 . As the shut-off member  47  is at rest, that is to say in the position for locking the door  4 , this first stream is then conveyed by an individual pipe  52  to a first part  53  of the chamber  54  of the first ram  40 . 
     This first stream pushes back the piston  55  of the first ram  40  to the left in FIG. 3, so that the first lock  37  is pushed into its position for locking the door  4 . 
     It will be noted that when the shut-off member  47  is at rest, the first part  53  of the chamber  54  of the first ram  40  is automatically placed in communication with an outlet of the valve  44  and therefore with the source  49 , so that locking of the door  4  is automatic. 
     The second stream from the automatic-locking valve  44  passes through a valve  57  which is timer-controlled by a control unit  58  which keeps it open during centrifuging. The control unit  58  is, for example, a pneumatic or mechanical unit. 
     This second stream is itself split into two streams as it leaves the valve  57 . 
     The first of these streams is sent, via a pipe  59 , to the chamber  60  of the second ram  41  so as to push the piston  61  of this ram upwards in FIG. 3, so that the second lock  38  is pushed into its position for immobilizing the first lock  37 . 
     Thus, throughout centrifuging, that is to say as long as the valve  57  is open, the second lock  38  is in a position of immobilizing the first lock  37 , and it is therefore impossible to unlock the door  4 . 
     The second stream of pressurized air from the valve  57  is conveyed by a pipe  62  and is then supplied to (FIG.  1 ): 
     the inlet  32  of the Ranque vortex tube  30 , via a manual valve  63 , 
     the ram  29  of the pneumatic brake  25 , constantly, and 
     the injector  22  of the venturi injection system  21 , constantly. 
     Thus, throughout centrifuging, the pneumatic ram  29  of the brake  25  is supplied with pressurized air so that the jaws  26  are in the spaced-apart position and allow the shaft  18  to turn freely. 
     The injection of pressurized air by the injector  22  creates a depression at the periphery of the space  240  and therefore at the inlet  24  of the venturi injection system. Gas is thus drawn via an outlet  64  of the chamber  5 , then filtered in the filter  10 . This drawn-off and filtered gas is then sucked into the venturi injection system  21  through the inlet  24 , then ejected from the nozzle  23  with the pressurized air from the injector  22 , driving the turbine  19 , the shaft  18  and the rotor  6 . 
     Having driven the turbine  19 , this flow of fluid is then removed to outside the centrifuge  1  via the silencer  48 . 
     The pressure-reduced air from the hot outlet  34  of the Ranque vortex tube is also removed to outside the centrifuge  1  via the silencer  48 . 
     The low-temperature, for example −10° C., pressure-reduced air from the cold outlet  33  of the Ranque vortex tube is conveyed by a pipe  65  to an inlet  66  of the chamber  5 . The cold air is ejected from this inlet  66  under and towards the rotor  6 , therefore cooling the atmosphere of the chamber  5 . 
     It is possible, by opening a manual valve  67 , to cause the decontamination gas to flow from the source  50  into the pipe  65  then into the chamber  5  and thus sweep the atmosphere of the chamber  5 , of the filter  10 , of the turbine  19  and of the silencer  48  with this decontamination gas. 
     At the end of the centrifuging cycle, the valve  57  is automatically closed by the control unit  58 . As the pneumatic ram  29  of the brake  25  is no longer supplied with pressurized air, the jaws  26  will automatically position themselves in the close-together position for braking the rotor  6 . 
     As illustrated by FIG. 4, the pressurized air contained in the chamber  60  of the second ram  41  is removed by the pipe  59  then by the pipe  62  to the silencer  48 , and the piston  61  of the second ram  41  is pushed back by a spring  68 . Thus, the second lock  38  is returned to its position of releasing the first lock  37 . 
     By manually bringing the shut-off member  47  of the switching valve  46  into its unlocking position, the pipe  51  is therefore placed in communication, via an individual pipe  69 , with a second part  70  of the chamber  54  of the first double-acting ram  40 . Thus, this second part  70  of the chamber  54  is supplied with pressurized air because the automatic-locking valve  44  is in the open position. 
     At the same time, the first part  53  of the chamber  54  is vented, via a pipe  71  (FIGS. 1 and 4) then via the silencer  48 . 
     Thus, the piston  55  of the first ram is pushed back to the right in FIG.  1  and the first lock  37  is returned to its unlocking position. 
     When the first lock  37  is in the unlocking position, it is possible to open the door  4 . 
     When the door  4  leaves its closed position (FIG.  5 ), the shut-off member  45  of the valve  44  is returned by the spring  450  to its position of closing the valve  44 . 
     Now that the shut-off member  47  of the switching valve  46  has been returned to its position of rest by the spring  470 , the pressurized air present in the second part  70  of the chamber  54  of the first ram  40  has been removed by, in succession, a pipe  72 , the pipe  71  and the silencer  48 . 
     The number of electrical and mechanical devices in the centrifuge  1 , particularly for heating and for driving the rotation of the rotor  6 , is limited. 
     This characteristic is particularly advantageous when centrifuging products liable to release explosive substances. 
     Moreover, the combination of the pneumatic means  8  for driving the rotor  6  and the unit  10  for purifying the gas drawn from the chamber  5 , in which the circulation of drawn-off gas is brought about by the pressurized air driving the turbine  19 , makes it possible simultaneously to drive the rotor  6  and to filter the atmosphere of the chamber  5 . Thus, the centrifuge  1  is suited to the centrifuging of dangerous products by limiting the risks of these substances being emitted to outside the centrifuge  1 . 
     It is to be noted that the use of the venturi injection system  21  delivering, at output, a flow rate of gas which is greater than that with which the injector  22  is supplied, allows the turbine  19  and therefore the rotor  6  to be driven at relatively high speeds. 
     Furthermore, the possibility of decontaminating the atmosphere of the chamber further limits the risks associated with the centrifuging of such products. 
     The use of an injection of cold gas, particularly one obtained using a Ranque vortex tube, allows satisfactory cooling of the atmosphere of the chamber  5 , with good efficiency and limiting the emissions of heat to outside the chamber  5 . What is more, the use of the Ranque vortex tube makes it possible to limit the size of the means  11  for cooling the atmosphere of the chamber  5 . 
     It will also be noted that the use of a turbine  19  for driving the rotor  6  makes it possible to limit the emissions of heat to outside the chamber  5 . 
     According to an alternative form which has not been depicted, the gas-purification unit  10  comprises a device for the chemical treatment of gases drawn from the chamber  5 , which allows the dangerous substances likely to be released by the products being centrifuged to be neutralized. 
     FIG. 6 illustrates a simplified embodiment of a centrifuge  1 . 
     In this embodiment, in which the locking device  16  has not been depicted for reasons of greater clarity, the means  8  for driving the rotation of the rotor  6  comprise, for example, an electric motor. 
     The outlet  73  from the unit  10  for purifying the drawn-off gas is then connected directly to the silencer  48 . 
     The stream of cold gas from the cold outlet  33  of the Ranque vortex tube  30 , possibly mixed with the decontamination gas from the source  50 , is injected into the chamber  5  under the rotor  6 , cooling the atmosphere of the chamber  5 . This gas stream also creates an overpressure in the chamber  5 , which means that, since the chamber  5  is leak-tight, this overpressure causes gas to be drawn off via the outlet  64  of the chamber  5 . 
     The drawn-off gas is then purified by the purification unit  10 , then removed via the silencer  48 . 
     This centrifuge  1  can be used for centrifuging toxic non-explosive substances. 
     In another embodiment, not depicted, the outlet  64  from the tank  3  is vented directly, the centrifuge comprising no purification unit  10 . 
     The latter embodiment is particularly well suited to the centrifuging of products which do not release dangerous substances.