Centrifugal separator having a structure for facilitating opening and closing a door

An air flow valve capable of being opened and closed is provided between the interior of the rotor chamber sealed with the door and the exterior thereof, and formed so that, when the door is closed, or when the door is opened, the air flow valve is temporarily opened.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a centrifugal separator, and more particularly to structure for facilitating the opening and closing of a door for sealing a rotor-housed rotor chamber.

2. Description of the Related Art

In a centrifugal separator, a rotor on which a sample to be separated is supported via a tube and a bottle is held in a rotor chamber (rotary chamber), and the rotor is rotated at a high speed by a driving unit, such as a motor with an opening of the rotor chamber closed tightly with a door, the separation and the refining of the sample supported on the rotor being thereby done. The rotational speed of the rotor differs depending upon the use of a separated or refined product. Products having a wide range of rotational frequencies from a comparatively low maximum level of around several thousands (rpm) to a high maximum level of around one hundred and fifty thousands (rpm) are generally provided.

When the rotor of the centrifugal separator is rotated at a high speed in the rotor chamber closed tightly with the door, frictional heat occurs between the rotor and the air existing in the rotor chamber, to cause a windage loss to be brought about, so that the temperature of the rotor increases to an abnormal level. Therefore, many centrifugal separators rotated at a high speed of, for example, not smaller than twenty thousands rpm are mounted with cooling units. On a high-speed or super high-speed centrifugal separator, a vacuum unit for reducing the pressure of the interior of the rotor chamber to a high vacuum or a low vacuum is mounted in addition to the above-mentioned cooling unit. The mounting of the vacuum unit serves as techniques for practicing the more complete prevention of a temperature rise ascribed to the windage loss.

A cooling unit-carrying centrifugal separator is provided with a cooler made of refrigerating pipes extending along an inner circumferential surface of a rotor-holding chamber as shown, for example, in JP-A-2002-336738. This cooler makes the rotor chamber cool, suppresses the generation of heat occurring due to the rotation of the rotor, and thereby controls the rotor temperature to be at not higher than a predetermined level. Therefore, it is demanded in the related art centrifugal separator that the interior of the rotor chamber closed tightly with the door and the outside thereof be thermally shut off from each other, and that the degree of closure of the space (closed chamber) defined by and sealed with wall members of the rotor chamber and door against the outside air is improved.

The rotor chamber is made as a space closed against the outside except the opening portion thereof which is provided with the door used when the rotor and sample are inserted and withdrawn thereinto and therefrom. Furthermore, a packing made of an elastic member is provided between the rotor chamber and door. When the door is closed, the packing is pressed so that the outside air does not enter the rotor chamber, and thus a space closed with the rotor chamber and door is formed. The “closed space” or “sealed space” used in the specification of the present invention means usually a space defined by wall members which permit such a little leakage of a small quantity of the air that does not have influence upon the cooling capacity of the space. Such a space may, of course, be a space thermally shut off from or defined with respect to the outside air more completely by using a vacuum seal.

An example of a centrifugal separator mounted with a vacuum pump for making the interior of a rotor chamber vacuous in order to reduce a windage loss to as great an extent as possible of a high-speed rotated rotor is disclosed in JP-A-9-75782. In the techniques disclosed in JP-A-9-75782, a door is closed so as to seal an opening of the rotor chamber off the outside air, and an air leakage valve for communicating the interior of the rotor chamber and the outside air with each other is then closed to make the rotor chamber highly vacuous. The rotor is rotated in this condition at a high speed. After the operation finishes being carried out, the rotor is taken out from the rotor chamber by opening the air leakage valve by using a special switch to open the rotor chamber into the atmospheric air, and thereafter opening the door. Especially, the characteristics of this centrifugal separator reside in that the switch controlled by both a valve-opening signal and a rotational frequency detecting signal is provided so as to prevent the air leakage valve from being opened inadvertently by an erroneous operation during the rotation of the rotor.

SUMMARY OF THE INVENTION

In the centrifugal separator in which the sealed chamber is formed by the rotor chamber and door, a large force is needed to open and close the door. Especially, the manual door is opened and closed frequently by an operator handling the centrifugal separator, and this causes a decrease in the operation efficiency or work efficiency and the inconvenience of using the centrifugal separator to occur. Although a centrifugal separator having an automatic door opening and closing mechanism utilizing an external power source, such as a motor having a large driving power instead of a manual door opening and closing mechanism has been known, the automatic mechanism for opening and closing the door becomes complicated, and this centrifugal separator became expensive as compared with the centrifugal separator having such a manual door opening and closing mechanism.

The schematic diagram ofFIG. 6shows a calculation expression of a reaction force occurring when the opening and closing of the door are done. When the door supported on one end of the opening of the rotor chamber via a hinge is closed, a pressing margin of the packing is compressed, so that a reaction force F similar to an air spring action shown inFIG. 6is received with the reaction force from the packing. However, the influence of the reaction force F of this air spring action is gradually lost owing to the leakage of a very small quantity of air occurring after the door is closed.

The door is formed so that the door can usually be opened and closed via hinge. When a scatter of the hinge fixing position, a scatter of the packing manufacturing operation and the like are taken into consideration, it is necessary that a pressing margin of the packing be designed with a certain degree of allowance left so as to heighten the degree of closure and sealing of the rotor chamber. However, forming the pressing margin with allowance left necessarily causes the pressure P1in the rotor chamber to further increase. As a result, the reaction force F due to the air spring action is further increased. This causes the operator to require a larger force when the door is closed, so that a decrease in the operation efficiency and work efficiency occurred in the manual door.

When the door is opened, the pressure in the rotor chamber decreases contrariwise to the case where the door is closed, and a large force was required in the same manner as in the case where the door is closed. This makes it difficult as well to open the door. However, in this case, the reaction force generated by the packing works in the door-opening direction, so that a decrease in the operation efficiency is lessened as compared with that in the case where the door is closed.

JP-A-9-75782 shows that, before a door is opened after a centrifugal separation operation finishes, in, especially, a centrifugal separator having a highly vacuum rotor chamber, an air leakage valve is opened so as to open the highly vacuum rotor chamber into the outside air. In order to open and close the air leakage valve, a special switch is needed. The switch for opening and closing the air leakage valve is formed so that the switch is operated irrespective of the opening and closing of the door. Therefore, the door operating efficiency and the convenience of using the door are low. In a centrifugal separator having a cooling unit in a rotor chamber, an air leakage valve is left as it is after the door is opened, so that dew drops readily occur in an air flow passage communicating with the air leakage valve.

Therefore, a primary object of the present invention is to provide a centrifugal separator having improved operation efficiency or work efficiency by forming a door for sealing an opening of a rotor chamber so that the door can be opened and closed by a small force.

Another object of the present invention is to provide a door opening and closing mechanism suitable for a centrifugal separator provided with a cooling unit for making a rotor chamber cool, and adapted to open and close the door manually.

These and other objects of the present invention as well as the novel features thereof will become more apparent from the following description in the specification and the accompanying drawings.

In order to solve the above problems, the inventor of the present invention paid his attention to the elimination of the influence of an air spring effect, which is ascribed to the above-mentioned pressure variation, upon the opening and closing of the door with respect to the opening of the rotor chamber. The present invention has the features of providing an air flow passage, which permits the air to freely flow between the interior and exterior of the rotor chamber closed with the door, in such a manner that the pressure in the sealed chamber defined by the rotor chamber and door does not fluctuate with respect to the atmospheric pressure outside the sealed chamber when the door is in a transient state in which the door is opened and closed. This air flow passage is kept closed so as not to lower the cooling capacity of the interior of the rotor chamber during a steady condition in which the rotor is rotated.

Out of the inventions according to the present invention, the outlines of typical inventions will now be described as follows.

(1) The centrifugal separator according to the present invention includes a driving unit, a rotor rotated by the driving unit and holding a sample to be separated, a rotor chamber holding the rotor therein and having an opening on an upper side thereof, and a door adapted to seal the opening of the rotor chamber off the outside air and provided so that the door can be opened and closed freely, wherein an air flow valve provided between the interior and exterior of the rotor chamber sealed with the door, and formed so that the air flow valve can be opened and closed, the air flow valve being opened when closing or opening the door.

(2) A centrifugal separator according to (1) above, wherein the air flow valve becomes opened when the door is closed and when the door is opened, and becomes closed in other state, i.e., in a steady state.

(3) A centrifugal separator according to (2) above, wherein the door has a door lever for opening and closing the door, and is formed so that the air flow valve becomes opened when the door is closed and opened in accordance with an operation of the door lever and so that the air flow valve becomes closed in other state, i.e., in a steady state.

(4) A centrifugal separator according to (1) above, wherein the air flow valve is a check valve adapted to make the air to flow from the interior of the rotor chamber to the exterior thereof when the door is closed.

(5) A centrifugal separator according to (1) to (4) above, wherein the air flow valve is provided in the door.

(6) A centrifugal separator according to (1) to (5) above, wherein the air flow valve is provided in the portion of the door which an extension of the axis of rotation of the rotor crosses or partition member of the rotor chamber.

(7) A centrifugal separator according to (1) to (6) above, wherein the centrifugal separator is further provided with a cooling unit used to cool the rotor.

In the centrifugal separator according to the present invention, the air flow valve communicates the rotor chamber sealed with the door and the exterior (outside air) of the rotor chamber with each other, so that the pressure in the rotor chamber can be set equal to the atmospheric air pressure. As a result, the door can be opened and closed by a small force without receiving the influence of a reaction force occurring due to the sealed rotor chamber.

In the centrifugal separator according to the present invention, the air flow valve communicates the rotor chamber, which is sealed in accordance with the opening and closing of the door, and the outside air of the rotor chamber with each other, so that the pressure in the rotor chamber can be set equal to the atmospheric air. As a result, the operation efficiency or work efficiency of the centrifugal separator can be improved.

In the centrifugal separator according to the present invention, the pressing force necessary for the door opening and closing mechanism can be saved, so that a manual door opening and closing structure of a high operation efficiency can be provided. An inexpensive centrifugal separator as compared with a centrifugal separator having an automatic complicated door opening and closing mechanism can also be provided.

DETAILED DESCRIPTION OF THE PREFFERED EMBODIMENTS

The modes of embodiments of the present invention will now be described in detail on the basis of the drawings. In all the drawings for describing the modes of embodiments, the same reference numerals are added to the members having the same functions, and repeated descriptions of the members will be omitted.

FIGS. 1 to 3are sectional views (side views) of a principal portion of the centrifugal separator in a first mode of embodiment of the present invention, whereinFIG. 1is a sectional view in a steady state after the closure of the rotor chamber opening and closing door;FIG. 2a sectional view of the same in a transient state in which the door is being closed; andFIG. 3a sectional view of the same in a steady state after the opening of the door.

Referring toFIG. 1, a centrifugal separator20is provided with a case (frame)21having a square horizontal sectional view. The case21is provided therein with a sample container2assembled therein and containing a sample, such as blood to be centrifugally separated, a rotor holding the sample container2therein and giving a high-speed rotation thereto, a driving unit4having a motor and the like therein for giving a driving force to the rotor1via a rotary shaft4b, and a rotor chamber (rotary chamber)3housing the rotor1. The centrifugal separator is further provided with a door5for sealing an upper opening of the rotor chamber3formed in the interior of the case21.

The rotor chamber3is formed by a bowl-shaped partition member including a side wall portion3aand a bottom portion3b. On an outer circumference of the side wall3a, a helical refrigerating pipe (9) is provided, which is formed so that the interior of the rotor chamber3is cooled. This structure cools the rotor1in a rotational movement, and prevents a temperature rise thereof. In order to prevent a decrease in the efficiency of cooling the rotor chamber3from occurring in the rotor chamber3, the refrigerating pipe9is provided on the outer circumference thereof with a heat insulating layer9amade of a heat insulating material.

In order to further improve the efficiency of cooling the rotor chamber3, a bottom opening of the rotor chamber3, from which the housing4aof the driving unit4projects inward, is sealed with seal rubber8made of an elastic material, such as rubber fixed on a base member8amade a heat insulating material. In the meantime, the upper opening of the rotor chamber3out of and from which the rotor1and sample container2and the like are taken and inserted is provided with a door packing6made of an elastic material, such as rubber, the upper opening being sealed by crushing the packing6by the door5.

The upper opening of the rotor chamber3is thus sealed with the door5, while the bottom opening of the rotor chamber3is sealed with the seal rubber8. Therefore, in the related techniques for the centrifugal separator, the operator necessarily receives when he closes the door5and crushes the door packing6by the door5a reaction force of the door packing6and a reaction force due to the air spring effect ascribed to an increase in the pressure in the rotor chamber3as shown inFIG. 6. In order to open the door5, the pressure in the rotor chamber3decreases conversely, so that the door is set difficult to be opened.

According to the present invention, an air flow valve (which will hereinafter be referred simply as “air flow valve”) having the following switch valve is provided between the interior and exterior of the rotor chamber3closed with the door5is provided so as to prevent the influence of the reaction force at the time of opening and closing of the door. The air flow valve is formed so that this valve is opened when the door5is closed or opened.

As shown inFIG. 1, the door5is provided in a front side wall (right side in the drawing) thereof with a door lever10which can be turned around a pin10aas a shaft. The door5is provided at a central portion of a lower wall thereof, i.e. at the portion of the same lower wall which is on an extension of the axis of rotation of the rotor1, or in the position in the vicinity thereof with a first opening14, and at a rear side wall portion of the door5with a second opening5. As a result, an air flow passage extending from the rotor chamber3to the exterior (outside air) of the rotor chamber3via the first opening14and second opening15is formed. This air flow passage is provided therein with a switch valve11(which will hereinafter be referred to as an air flow valve). One end11aof the air flow valve11is supported pivotably on the door5, and the other end11bthereof presses the opening14constantly by the spring12, i.e., the opening14being urged so that the opening14is sealed. The air flow valve11connected by the door lever10and a link rod13, and formed so that the same valve11is operatively connected to the door lever10.

FIG. 2shows the operational condition of the air flow valve11with the door lever10gripped by the hand (not shown) to close the door5. When the door lever10is pressed up (in the direction of an arrow10c) by the hand, the link rod13is drawn during a transient condition in which the door lever10is pressed, to cause the air flow valve11to be put in an opened condition. In this condition, a claw portion10bof the door lever10is engaged with a hook portion21aprovided on the case21to close the door5. In a steady state after the closure of the door, the valve11seals the opening14by the urging pressure of the spring12as shown inFIG. 1. In this steady state, the claw portion10bof the door lever10is engaged with the hook portion21a, and the sealed condition of the rotor chamber3is thereby maintained.

In the transient state in which the door5is being closed, the valve11provided in the opening14is opened, and the rotor chamber3communicates with the outside air through the opening14and opening15. As a result, the pressure in the rotor chamber3becomes equal to the external pressure (atmospheric pressure) of the centrifugal separator even when the door5crushes the door packing6. Therefore, the reaction force due to the air spring action does not occur, and the door5can be closed easily with a small force.

The door5is not opened unless the door lever10is operated upward by the hand in the same manner as shown inFIG. 2, so that the air flow valve10operatively connected to the door lever10is in an opened state. As a result, the pressure in the rotor chamber3does not differ from the outside pressure (atmospheric pressure) in the same manner as in the case where the door5is closed, so that the inner pressure does not receive a reaction force ascribed to the air spring action. Namely, it is also easy to open the door5. In the steady state after the opening of the door5, the valve11is not opened unless the door lever10is not operated.

Since the door5directly contacts the rotor chamber3, the door5is exposed to the cool air in some cases while the rotor1is rotated. Therefore, especially, the rear surface side, which is positioned on the side of the rotor chamber3, of the door5is cooled in the same manner as the rotor1. The dew drops easily occur on the cooled portion since the temperature of the cooled portion is lower than that of the surrounding portion when the door5is opened as shown inFIG. 3. When the opening14and opening15are opened in such condition, dew drops occur even in the interior of the door5. As a result, inconveniences occur, i.e., the metal in the interior of the door5is corroded, or the water collected in the interior of the door5is discharged from the rear opening15of the door when the door5is opened. In order to prevent the occurrence of such inconveniences, the air flow valve11is preferably formed so that the same valve be opened only when the pressure in the interior of the rotor chamber3is set equal to the external pressure in a transient state in which the door5is opened and closed.

A second mode of embodiment of the present invention will now be described with reference toFIG. 4. In the second mode of embodiment shown inFIG. 4, an electromagnetic valve16is used as an air flow valve. The electromagnetic valve16detects during an operation for opening or closing a door5a movement of a door lever10by a detecting element19, such as a microswitch in a transient condition in which a door5contacts a door packing6, and sends a signal detected to a control circuit17. The controlling of the electromagnetic valve16is done so that the electromagnetic valve16is opened in the transient condition only. This system using the electromagnetic valve carries out an action identical with that of the above-described first mode of embodiment, so that the same effect as described above can be obtained. The signal detecting the opening and closing of the door5may also be obtained by detecting the inclination of the door by an inclination sensor fixed to the door5.

Furthermore, a third mode of embodiment of the present invention uses a check valve18as an air flow valve as shown inFIG. 5. The check valve18is provided so that the air flows in the direction of an arrow18a. As a result, when the door5is closed in the system using the check valve18with the inner pressure in the rotor chamber3becoming high, the air is exhausted to the outside, so that the force imparted to the door5ecan be lessened. However, when the door5is opened in this mode of embodiment, the check valve18is not opened, so that the pressure in the rotor chamber3cannot be reduced. Therefore, after the operation of the centrifugal separator20finishes, the door5has to be opened by a force the level of which is equal to that of the force by which the door in a regular centrifugal separator is opened. Therefore, the convenience of using the centrifugal separator20is improved.

In the above-described modes of embodiments, the various types of air flow valves are provided at the central portion of the door5but, basically, the air flow valves may be provided in any portion of the partition members3a,3bof the door5and rotor chamber3. However, when the rotor1is rotated, the wind pressure due to the rotation of the rotor becomes high in the portion of the door5which is far from the center of rotation of the rotor1. Therefore, it is preferable that the air flow valve be in the position on the axis of rotation of the rotor1in which the influence of the wind pressure is rarely received.

As is clear from the above description, the centrifugal separator according to the present invention is capable of setting the pressure in the rotor chamber equal to the atmospheric air in the transient condition in which the door is opened and closed, since the rotor chamber sealed with the door through the air flow valve and the outside (outside air) are communicated with each other. This enables the door to be opened and closed by a small force without receiving the influence of the sealed chamber. Therefore, since the pressing force needed for the door opening and closing mechanism can be saved, so that a manual opening and closing mechanism having a high operation efficiency can be provided.

The invention made by the inventor of the present invention has been described on the basis of the modes of embodiments thereof. The present invention is not limited to the above-described mode of embodiments, and various modifications within the scope not departing from the gist of the invention can be made.