Rotor mounting structure for centrifugal separator

A rotor mounting structure arranged in a centrifugal separator. A cylindrical shaft having elastic tongue pieces provided substantially equidistantly on the peripheral edge of the upper surface of the cylindrical shaft is provided at the distal end of a drive shaft; the tongue pieces have hooks; a shaft accommodation orifice accommodates the cylindrical shaft is formed in the center of the rotor; elastic tongue piece insertion grooves mate with the elastic tongue pieces of the cylindrical shaft; the rotor is joined to the cylindrical shaft, while bending the elastic tongue pieces; and in a state in which the rotor is completely joined to the cylindrical shaft by engaging the hooks of the elastic tongue pieces with the upper edges of the grooves of the rotor by the elastic force of the elastic tongue pieces.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotor mounting structure for a centrifugal separator, and more particularly to a rotor mounting structure for a centrifugal separator in which the rotor is one-touch mounted on a drive shaft.

2. Description of the Related Art

For example, in small centrifugal separators such as used, e.g., for DNA and RNA purification operations in the field of generating engineering, a rotor is formed from a lightweight material such as a synthetic resin and this rotor is joined to a drive shaft of the motor by tightening with a screw (for example, Japanese Patent Application Laid-open No. H10-328582).

SUMMARY OF THE INVENTION

In a small centrifugal separator such as described in Japanese Patent Application Laid-open No. H10-328582, a boss extending downwardly is formed in the central portion of the rotor, a drive shaft accommodation orifice that is open downwardly is formed in the boss, a threaded hole is provided from the peripheral surface of the orifice toward the shaft center, the drive shaft accommodation orifice of the rotor is fitted onto the drive shaft of the motor, and then the rotor is joined to the drive shaft with a screw that is screwed in the threaded hole from the side of the rotor.

Thus, in the centrifugal separator such as described in Japanese Patent Application Laid-open No. H10-328582, when the rotor is mounted on the drive shaft, a tool such as a screwdriver is required, the screwing operation has to be conducted from the side, and operability is poor.

Furthermore, with certain rotors, a screwdriver insertion hole has to be formed in the side edge section of the rotor and the screw has to be rotated by inserting the shaft of the screwdriver into this hole. As a result, special screwdrivers with a long shaft have to be used.

With the foregoing in view, it is an object of the present invention to provide a rotor mounting structure for a centrifugal separator that enables easy one-touch mounting of the rotor on the drive shaft, without using a tool such as a screwdriver.

In order to resolve the above-described problems, the rotor mounting structure for a centrifugal separator according to a first embodiment, comprises, at the distal end of a drive shaft, a cylindrical shaft, in which a plurality of elastic tongue pieces provided substantially equidistantly on the peripheral edge of the upper surface of the cylindrical shaft extend upward from the upper surface and have hooks formed so as to protrude radially outwardly at the upper ends thereof; a shaft accommodation orifice which is open downward and accommodates the cylindrical shaft is formed in the center of the rotor: elastic tongue piece insertion grooves for inserting the elastic tongue pieces therethrough are provided through the upper wall of the shaft accommodation orifice: the elastic tongue piece insertion grooves of the rotor are mated with the elastic tongue pieces of the cylindrical shaft; the rotor is joined to the cylindrical shaft, while bending the elastic tongue pieces; and in a state in which the rotor is completely joined to the cylindrical shaft, the rotor is locked to the cylindrical shaft by engaging the hooks of the elastic tongue pieces with the upper edges of the grooves of the rotor by the elastic force of the elastic tongue pieces.

In the rotor mounting structure of a centrifugal separator of a second embodiment, in the first embodiment, the cylindrical shaft is formed separately from the drive shaft, a drive shaft accommodation orifice which is open downwardly is formed in the center of the cylindrical shaft: and the cylindrical shaft is integrally coupled with the drive shaft after the drive shaft accommodation orifice has been joined to the drive shaft.

In the rotor mounting structure of a centrifugal separator of a third embodiment, in the first embodiment, a taper surface expanding downwardly is formed at the inner peripheral surface of the shaft accommodation orifice of the rotor, and a taper surface corresponding to the inner peripheral surface of the shaft accommodation orifice of the rotor is formed at the outer peripheral surface of the cylindrical shaft.

In the rotor mounting structure of a centrifugal separator of a fourth embodiment, in the first embodiment, a cap is provided that covers portions of tongue pieces of the cylindrical shaft which protrude from the upper surface of the rotor.

In the rotor mounting structure of a centrifugal separator of a fifth embodiment, a cylindrical shaft, in which a plurality of protrusions or protrusion accommodation grooves extending in the up-down direction are formed substantially equidistantly on the peripheral surface, is provided at the distal end of a drive shaft; a shaft accommodation orifice which is open downward and accommodates the cylindrical shaft is formed in the center of the rotor; protrusion accommodation grooves or protrusions corresponding to the protrusions or protrusion accommodation grooves of the cylindrical shaft are formed in the inner peripheral surface of the shaft accommodation orifice; a ball, which is impelled in the direction of protruding and can be protruded and withdrawn back, is provided in one of the mutually corresponding portions of the peripheral surface of the cylindrical shaft and the shaft accommodation orifice of the rotor, a ball accommodation recess for accommodating the ball is formed in the other corresponding portion; and after the protrusions and the protrusion accommodation grooves have been mated, the shaft accommodation orifice of the rotor has been joined to the cylindrical shaft, and the rotor has been completely joined to the cylindrical shaft, the rotor is locked to the cylindrical shaft by engaging the ball with the ball accommodation recess.

With the above-described the first embodiment, the rotor can be one-touch locked to the drive shaft by dropping the rotor from above onto the cylindrical shaft. Furthermore, the rotor can be removed from the drive shaft by bending the respective hooks inwardly and, therefore” the rotor can be easily mounted and dismounted.

Furthermore, with the above-described the second embodiment, in addition to the above-described effect, the manufacturing process is facilitated because the cylindrical shaft of complex shape can be formed separately from the drive shaft of the motor.

Furthermore, with the above-described third embodiment, in addition to the above-described effects, centering of the rotor with respect to the cylindrical shaft can be conducted reliably and the rotor can be reliably attached to the cylindrical shaft.

Furthermore, with the above-described the fourth embodiment, in addition to the above-described effects, after the rotor has been mounted on the cylindrical shaft, no external force can act on the hooks and, therefore, the rotor cannot be inadvertently removed from the cylindrical shaft.

Furthermore, with the above-described the fifth embodiment, the rotor and the cylindrical shaft of the drive shaft are prevented from rotating with respect to each other by the protrusions and protrusion accommodation grooves formed therein, and the rotor is prevented from falling off from the cylindrical shaft by engaging the ball with the ball accommodation recess.

Therefore, the rotor can be easily mounted on the drive shaft and can be easily dismounted from the drive shaft with a simple structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The above-described rotor mounting structure of a centrifugal separator in accordance with the present invention will be described below in greater detail with reference to the appended drawings.

Here,FIG. 1is a perspective view illustrating schematically a centrifugal separator comprising the rotor mounting structure in accordance with the present invention.FIG. 2is a cross-sectional view of the section along the2-2line of the rotor shown inFIG. 1.FIG. 3is a cross-sectional view of the section along the3-3line of a cylindrical shaft shown inFIG. 1.FIG. 4is a cross-sectional view of the section along the4-4line of a cylindrical shaft shown inFIG. 1.FIG. 5is a cross-sectional view illustrating an intermediate state of mounting a rotor on a drive shaft.FIG. 6is a cross-sectional view illustrating a state after the rotor has been mounted on the drive shaft.

The above-described centrifugal separator is a small centrifugal separator1such as used, e.g., for DNA and RNA purification operations in the field of genetic engineering and comprises a cylindrical apparatus body2and a semispherical lid3covering the upper surface of the apparatus body2. Part of the lid3is pivotally mounted on the apparatus body2so that it can be opened and closed. A latch (not shown in the figure) formed in another part of the lid3can be engaged with a catch2aformed in the upper peripheral surface of the apparatus body2to lock the lid3to the apparatus body2.

A rotor10is formed from a synthetic resin and can be rectangular or round, as shown inFIG. 1. Those rotors10comprise tube accommodation orifices11in the side edge or peripheral edge thereof. Furthermore, a shaft section12protruding in the up-down direction is formed in the center of the rotor10.

This shaft section12, as shown inFIG. 2, has a shaft accommodation orifice13open downward in the central portion thereof, and the inner peripheral surface13aof the shaft accommodation orifice13is formed by a taper surface that expands downwardly. Furthermore, two or four elastic tongue piece insertion grooves14corresponding to the below-described hooks of the cylindrical shaft are provided so as to pass through the upper wall of the shaft accommodation orifice13, and the lower ends of the those grooves14are connected by the inner peripheral surface13aof the shaft accommodation orifice13and an inclined surface15.

As shown inFIG. 1, a drive shaft4of a motor installed inside the apparatus body2protrudes upward from the central portion of the apparatus body2.

The cylindrical shaft20is formed from a synthetic resin. As shown inFIG. 3, the peripheral surface20aof the cylindrical shaft20expands downwardly and is formed by a taper surface corresponding to the inner peripheral surface13aof the shaft accommodation orifice13of the rotor10. Furthermore, elastic tongue pieces21protruding upward from the upper surface20bof the cylindrical shaft20are provided in corresponding zones of the peripheral surface. Hooks22protruding radially outwardly are formed at the upper ends of those elastic tongue pieces21.

A drive shaft accommodation orifice23open at the lower surface is formed in the central portion of the cylindrical shaft20. As shown inFIG. 4, a threaded hole24is formed toward the drive shaft accommodation orifice23in the peripheral surface20aof the cylindrical shaft20, and a balancer25is embedded in the zone of the cylindrical shaft which is opposite the threaded hole24via the drive shaft accommodation orifice23.

The cylindrical shaft20is fixed to the drive shaft4by fitting the drive shaft accommodation orifice23thereof on the drive shaft4of the motor, screwing a screw26into the threaded hole24, as shown inFIG. 1, and pressing the distal end thereof against the peripheral surface of the drive shaft4.

Further, the rotor10is attached to the cylindrical shaft20by mating the elastic tongue piece insertion grooves14thereof with the elastic tongue pieces21of the cylindrical shaft20, as shown inFIG. 5, and joining the rotor10to the cylindrical shaft20, while bending the elastic tongue pieces21.

As shown inFIG. 6, in a state in which the rotor10is completely joined to the cylindrical shaft20, the rotor10is engaged with the cylindrical shaft20by engaging the hooks22of the elastic tongue pieces21with the upper surface14aof the elastic tongue piece insertion grooves14of the rotor10by the elastic force of the elastic tongue pieces21. Furthermore, in this state, the inner peripheral surface13aof the rotor10is brought into intimate contact with the peripheral surface20aof the cylindrical shaft20and centered with respect to the cylindrical shaft20of the rotor10.

The rotor10in this state can be removed from the cylindrical shaft20, by bending the respective tongue pieces21inwardly, removing the respective hooks22from the upper edges of the elastic tongue piece insertion grooves14of the rotor10, and pulling the rotor10upward in this state.

Furthermore, with the rotor mounting structure of the present embodiment, there is a risk of the rotor10falling off the cylindrical shaft20when elastic tongue pieces21are bent inward and the rotor10is raised upward by any external force. In order to prevent such an event reliably, it is preferred that a cap30, such as shown by a two-dot-dash line inFIG. 6, be provided.

This cap30, for example, comprises a protruding section31that will be inserted between the elastic tongue pieces21and is locked with the rotor10so as to cover the elastic tongue pieces21. An appropriate structure such as screwing or press joining can be employed for locking the cap30to the rotor10.

In the above-described embodiment, the cylindrical shaft20was formed separately from the drive shaft4of the motor and the cylindrical shaft20was locked to the drive shaft4, but the cylindrical shaft20may be formed integrally with the drive shaft4.

FIG. 7andFIG. 8illustrate another embodiment of the rotor mounting structure of the present invention.

In the present embodiment, a plurality of protrusions20cextending in the up-down direction are formed almost equidistantly on the peripheral surface20aof the cylindrical shaft20, and protrusion accommodation grooves16corresponding to the protrusions20cof the cylindrical shaft20are formed in the inner peripheral surface13aof the shaft accommodation orifice of the rotor10. Furthermore, ball accommodation orifices20dopen at the peripheral surface of the protrusions are formed in the protrusions20cof the cylindrical shaft20. A spring27and a ball28are accommodated in the ball accommodation orifice, and the ball28is retained inside the ball accommodation orifice20dby a ring29locked to the open edge of the ball accommodation orifice20dand impelled outwardly by the spring27. On the other hand, a ball accommodation recesses17for accommodating the balls28are formed in the bottom surface of the protrusion accommodation groove16.

In the present embodiment, when the protrusions20care mated with the protrusion accommodation grooves16of the rotor10, the shaft accommodation orifice13of the rotor10is joined to the cylindrical shaft20, and the rotor10is completely joined to the cylindrical shaft20, the rotor10is locked to the cylindrical shaft20by engaging the balls28with the ball accommodation recesses17.

Furthermore, in the present embodiment, relative rotation of the rotor10and the cylindrical shaft20of the drive shaft4is prevented by the protrusions20cand protrusion accommodation grooves16formed therein, and the rotor10is prevented form falling off the cylindrical shaft20by engaging the balls28in the ball accommodation recesses17.

Moreover, in the present embodiment, the balls28were installed in the protrusions20c, and the ball accommodation recesses17were formed in the protrusion accommodation grooves16, but the balls28may be formed in the peripheral surface20aof the cylindrical shaft20and the ball accommodation recesses17may be formed in the inner peripheral surface13aof the shaft12of the rotor10. Furthermore, the balls28may be installed in the rotor10and the ball accommodation recesses17may be formed in the cylindrical shaft20.

Furthermore, in the present embodiment, the protrusions20cwere formed in the cylindrical shaft20and the protrusion accommodation grooves16for mating with the protrusions20cwere formed in the rotor10, but the protrusions20cmay be conversely formed in the rotor10and the protrusion accommodation grooves16may be formed in the cylindrical shaft20.