Swinging Bucket Rotor Assembly

Abstract

A swinging bucket centrifuge rotor having a plurality of machined bucket receiving cavities with a hanger disposed in each cavity. The cavity includes surfaces which guide a bucket cap hook to facilitate engagement of the hanger by the hook to support the bucket in the cavity and further guide the bucket as it swings.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to high speed swinging bucket centrifuge rotor assemblies and more particularly to a centrifuge rotor assembly including a hanger disposed in a rotor head cavity which is formed to receive and guide a bucket cap hook onto the hanger for securely supporting and guiding the associated bucket.

Swinging bucket centrifuge rotor assemblies have included rotor heads with cavities each provided with cross pins which are inserted in the head to engage a bucket support and removed to disengage the bucket from the head. The bucket includes ears with holes through which the cross pin passes to swingingly support the bucket. A difficulty with such prior art rotors is that because of the rotor head geometry required to accommodate a cross pin, the number of cavities is limited. To overcome the latter restriction, hangers have been constructed to dispose a cross pin or cross pin support in the cavity. The bucket or its cap is provided with hooks which are spaced apart a distance greater than the tube carried by the bucket. This design is subject to either improper hooking or to dislodging during movement of the rotor. Another type of rotor employs a cross pin at the end of an elongated hanger. However, this rotor requires complex machining to assure proper functioning of the hanger and hook.

OBJECTS AND SUMMARY OF THE INVENTION

It is a general object of the present invention to provide an improved swinging bucket centrifuge rotor assembly.

It is another object of the invention to provide a swinging bucket centrifuge rotor assembly including a rotor having a plurality of cavities each provided with a hanger adapted to receive an improved bucket cap.

It is a further object of the present invention to provide a centrifuge rotor assembly in which a hanger supports the bucket and serves as a spring as the bucket swings from the vertical to the horizontal position during centrifuge operation and guides the bucket cap as the bucket swings to the horizontal position.

It is another object of the present invention to provide an improved bucket cap which can be manually threaded onto the bucket without the use of a tool.

It is a further object of the present invention to provide a rotor assembly in which the part of the cavity for receiving the hanger with cross pin and a bucket cap is formed in three simple machining operations. One part serves to guide the bucket cap towards a slot which guides the cap onto the cross pin where it is securely held on the cross pin. The slot also provides a guide for the bucket as it swings about the cross pin during a centrifuge operation.

The foregoing and other objects are achieved by a centrifuge rotor including a plurality of bucket receiving cavities with means in said cavities for supporting the bucket in a vertical position and allowing the bucket to swing into a horizontal position during centrifugation. Each of said cavities includes a pocket provided with a cross pin and having a slotted wall with the slot adapted to receive a relatively flat budket cap to guide the same onto the pin and guide the bucket cap during swinging movement of the bucket from the vertical to the horizontal position.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an elevational view of a rotor in accordance with the present invention.

FIG. 2 is a sectional view taken along the line 2--2 of FIG. 1.

FIG. 3 is an enlarged view taken along the lines 3--3 of FIG. 1.

FIG. 4 is an enlarged view showing the deflection of the cross pin holder during centrifuge operation.

FIG. 5 is a view taken along the line 5--5 of FIG. 3.

FIG. 6 is a sectional view of the centrifuge rotor assembly showing the cavity and supported swinging bucket.

DESCRIPTION OF PREFERRED EMBODIMENT

The rotor comprises a body 11 which is provided with a plurality of cavities 12 which accommodate swinging buckets 13. FIG. 1 shows the rotor in its stationary condition with the buckets 13 depending vertically downward. FIG. 6 shows the rotor assembly under centrifugation with the swinging bucket 13 in the horizontal position. The bucket shoulder 14 is seated against the rotor seat 16 to limit outward movement of the bucket during centrifugation.

In accordance with the present invention, there is provided an improved hanger assembly for the swinging buckets. The assembly includes a hanger 17, FIGS. 2, 3, 4 and 5, having an elongated body 18 with a cross pin 19 secured at the lower end. The hanger body 18 is disposed in hole 20 extending through the rotor parallel to and spaced from the axis of the rotor. As will be presently described, the cross pin is engaged by the bucket cap hooks to support the bucket. The body 18 also serves as a spring which deflects, as indicated in FIG. 4, when centrifugal forces act on the bucket whereby the bucket seats against the rotor seat. The cross pin 19 has its ends 21, FIG. 2, machined with a radius R corresponding to the radius R of surface 22 of the wall of pocket 23 whereby during centrifugation and deflection of the body 18, the ends of the cross pin are seated on the surfaces 22. When a bucket is being carried, the cross pin is not seated until after the bucket shoulder 14 contacts the rotor seat 16. Under extremely high forces, the boss 24 formed on the body 18 will seat against the wall of hole 20. This limits deflection of the body 18. The hanger is positioned axially in the hole 20 by means of a screw 26 which screws into the threaded hole 27 at the top of the hanger body 18. The hanger body is split at 28 whereby when the screw is threaded into the hole, it expands the upper end of the body and locks the hanger in the rotor.

In accordance with another feature of the invention, there is provided an improved bucket cap 30 which has a flat stem portion with the upper hooked end slotted 31 to form a pair of spaced hooks or tangs 32 which serve to straddle the body 18. It is impossible to attach the bucket assembly to the cross pin with only one of two hooks engaged. The cooperation between the slot 31 and body 18 serves to guide the bucket as it swings from the horizontal to the vertical position.

As described, cavities 12 each include a pocket 23 formed by a simple machine operation and which is concentric to the hanger stem and hole 20. Cavity 12 also includes an adjacent cut or well 37 which serves as a guide to guide hooks or tangs 32 of the bucket cap as the bucket is inserted in the rotor cavity. The wall separating the pocket 23 and well 37 is slotted to form slot 38. The slot width is slightly wider than the width across the outside tangs 32 whereby it guides the hook inwardly to assure that the spaced tangs straddle the hanger body 18. The slot cooperates with the hanger body 18 to guide the bucket as it swings. Preferably, the depth of the pocket 23 is controlled to provide a minimum clearance above the cross pin to minimize the possibility of unhooking when the rotor is moved about.

Thus, there has been provided an improved swinging bucket centrifuge assembly in which the rotor cavities and bucket caps cooperate to guide the bucket cap to easily engage the hanger pin and which guide the rotor cap as the bucket swings. The bucket cap is shaped to provide a firm grip to unscrew the cap from the associated bucket without the need for a tool. The entire rotor assembly occupies a minimum space making available more load carrying capacity.

Claims

I claim:

1. A centrifuge rotor of the type including a rotor head having a plurality of cavities configured for receiving buckets having enlarged shoulders and means in each of said cavities for supporting a bucket by a bucket cap having hook means, the bucket being supported in a vertical position and being allowed to swing into a horizontal position where the shoulder seats on a portion of said cavity during centrifugation the improvement comprising for each cavity a pocket formed within said cavity for receiving at least a portion of said hook means, a hole for retaining the bucket supporting means, said hole extending through the rotor spaced from and parallel to the axis of the rotor communicating with said pocket, a well formed within said cavity and spaced radially outwardly from the pocket forming a portion of said rotor therebetween, and a slot in that portion of the rotor, said slot having a width sufficient for passage therethrough of the hook means of the bucket cap.

2. A centrifuge rotor assembly of the type including a rotor body having a plurality of bucket receiving cavities and pin means in said cavities adapted to support an associated bucket in a vertical position and allowing it to swing into a horizontal position where it moves outwardly to seat on a portion of said cavity during a centrifugation operation the improvement comprising for each cavity a pocket formed within said cavity, a hole extending through the rotor spaced from and parallel to the axis of the rotor communicating with said pocket, a well formed within said cavity and spaced radially outwardly of the rotor axis, said rotor being slotted for forming a guide slot extending between said pocket and well, said pin means including an elongated hanger extending through said hole with one end disposed in said pocket and a cross pin secured to said one end of the hanger, said cross pin including end portions shaped for seating on the adjacent wall portions of said pocket under the action of centrifugal force.

3. A rotor assembly as in claim 2 wherein the upper portion of said hanger includes a split threaded hole, a screw in said threaded hole for securing the hanger to the rotor body.

4. A rotor assembly as in claim 3 wherein said hanger includes a boss engaging the wall of said hole when the hanger is deflected a predetermined amount.

5. A centrifuge rotor assembly of the type including a rotor body having a plurality of cavities configured for receiving buckets having enlarged shouders and pin means in said cavities adapted to support an associated bucket in a vertical position and allowing it to swing into a horizontal position where the shoulder seats on a portion of said cavity during centrifugation the improvement comprising for each cavity a generally cylindrical pocket formed within said cavity, a hole extending through the rotor spaced from and parallel to the axis of the rotor communicating generally centrally with said pocket, a well formed within said cavity and spaced radially outwardly from said pocket forming a portion of said rotor therebetween, a guide slot cut into said portion, said pin means being secured within said hole and extending into said pocket, and a bucket cap including at least one hook engaging said pin means to support the bucket, said hook including a flat stem portion adapted to cooperate with said guide slot to guide the stem portion.

6. A rotor assembly as in claim 5 wherein said pin means include a cross-pin at the end of a hanger disposed in said hole and said hook is slotted to form spaced portions straddling said hanger.

7. A rotor assembly as in claim 5 wherein said hanger includes a boss engaging the wall of said hole when the hanger is deflected a predetermined amount.

8. A rotor assembly as in claim 4 wherein said hole has a substantially uniform cross section and said hanger is tapered downwardly with the upper portion thereof having approximately the same cross-section as said hole, said boss being disposed adjacent the lower edge of said hole.

9. A rotor assembly as in claim 7 wherein said pin is a cross pin secured to the free end of said hanger, said cross pin including end portions shaped for seating on the adjacent wall portions of said pocket, the parts of said rotor assembly being so configured that under the action of the centrifugal force after the shoulder of the bucket is seated on a portion of said cavity said cross pin travels an additional distance to seat on said wall portion to relieve the strain of the hook on said cross pin.