Background of the Invention

Field of the Invention The present invention relates to a bottle for use in a centrifuge rotor, and in particular, to a centrifuge bottle having a canted neck.

Description of the Prior Art Centrifuge bottles with multi-piece sealing arrangements are known. Exemplary of such a bottle and sealing arrangement is the 250 mL "Oak Ridge-type" bottle sold by the Biotechnology Systems Division of E. I. du Pont de Nemours and Company. Reference is invited to Figures 1 and 2 which respectively are an exploded side- elevational view in section of such a bottle and multi-piece capping arrangement and an enlarged fragmentary side elevational view in section of the bottle of Figure 1 while in use in a centrifuge rotor. The bottle generally indicated by the reference character B includes a molded body portion M having a neck N with exterior threads T thereon. The neck N has an annular seat S formed about its rim. An O-ring seal G is receivable on the seat S and is there held in place by *a cap insert I. The insert I is itself receivable within a threaded cap C. The cap C is threadedly engageable with the threads T on the neck N thereby to secure the cap C to the body M.

Figure 2 illustrates the bottle B when the same is received in a cavity H of a centrifuge rotor R having an axis of rotation AR extending therethrough. The rotor cavity H is circular in shape and has a predetermined diameter D. The axis AH of the cavity defines a predetermined angle of inclination β with respect to the axis of rotation AR. AS seen in Figure 2 when the bottle B is charged with a liquid sample F and the same is spun about the axis AR the meniscus F of the

liquid F becomes parallel to the axis of rotation AR. When so disposed the seal G is challenged by the high pressure liquid (pressurized due to centrifugal force). The region of primary challenge is shown by the reference arrow X.

Moreover, owing to the orientation of the cap C with respect to the axis of rotation AR, a large component of the centrifugal force of the cap is exerted on the rotor body near the mouth of the cavity H. Therefore this component of centrifugal force of the cap does not contribute to the sealing force exerted by the cap on the seal G. In addition centrifugal force acting on the O-ring causes the same to become unevenly distributed around the mouth of the bottle, thus diminishing the sealing effectiveness of the O-ring at the radially inward region of the bottle. Depending upon the volume of liquid in the bottle diminution of seal effectiveness may lead to potential leakage at the radially inward region of the bottle.

Either the presence of a defect in any of the structures of the bottle B or the seal or the omission of the seal G will likely lead to leakage of liquid sample. Depending upon the nature of the liquid being centrifuged such a leak could cause a health and/or rotor safety problem.

The risk associated with leakage is so great that it has become a practice either to underfill significantly a bottle of a given volumetric capacity or to utilize larger volume bottles and larger sized rotors. In either case the volume efficiency of the bottle, that is, the percentage of the available volume of the bottle that is occupied by sample, is significantly reduced. This would result in an increase in the time needed to process a given amount of sample, assuming a larger sized rotor is not used. Moreover the use of a larger rotor carries with it an increase in necessary run time.

Accordingly it is believed to be advantageous to provide a bottle for use in a centrifuge which maximizes the volume efficiency of the bottle while the liquid contained in the bottle presents little or no challenge to the seal.

Summary of the Invention

The present invention is directed toward a bottle for holding a liquid sample during centrifugation in a centrifuge rotor, the rotor being of the type having a circular rotor cavity therein and an axis of rotation extending centrally therethrough. The rotor cavity has a diameter D. The axis of the rotor cavity defines a predetermined angle of inclination β with respect to the axis of rotation. The axis of the cavity is spaced a predetermined distance R from the axis of rotation in a plane perpendicular to the axis of rotor. The bottle comprises a circular body portion and a neck portion formed integrally therewith. The body portion has a diameter substantially equal to the diameter D of the cavity, while the neck portion has a predetermined dimension L associated therewith. The body portion and the neck portion each have an axis therethrough with the axis of the neck defining a predetermined angle α with respect to the axis of the body. In accordance with the present invention the angle α lies in the range from ten (10) degrees to (100-β) degrees.

The bottle further comprises a cap engageable with the neck portion, the cap having a predetermined diametrical dimension associated therewith. The diametrical dimension of the cap is less than the dimension of a chord spaced r distance from the axis of rotation and subtended by an angle of (360/N) degrees in the plane perpendicular to the axis of rotor. The distance r is the distance that the diametrical dimension of the cap lies from the axis of rotation when the bottle is received in

the rotor. In practice the distance r is defined in accordance with the relationship:

r = R - L sin (α + β).

The cap has a base and a sidewall thereon, with the sidewall of the cap defining a predetermined angle with respect to the base, the angle being substantially equal to (90 + 180/N) degrees.

Brief Description of the Drawings

The invention may be more fully understood from the following detailed description thereof, taken in connection with the accompanying drawings, which form a part of this application and in which:

Figure 1 is an exploded side-elevational view, in section, of a prior art bottle and multi-piece sealing arrangement;

Figure 2 is an enlarged, fragmentary side elevational view, in section, of the bottle of Figure 1 while in use within a centrifuge rotor;

Figure 3 is a side elevational view, in section, illustrating a bottle in accordance with the present invention;

Figure 4 is a side elevational view, in section, of the bottle of Figure 3 while disposed within a cavity of a centrifuge rotor, illustrating the location of a liquid meniscus within a bottle of Figure 3 while under centrifugation;

Figure 5 is a full plan view of Figure 4; and

Figure 6 is a view generally similar to Figure 5 illustrating a modification of the bottle cap in accordance with the present invention.

Detailed Description of the Invention

Throughout the following detailed description, similar reference numerals refer to similar elements in all Figures of the drawings.

With reference to Figure 3 shown is a side elevational view, in section, of a bottle generally indicated by the reference 10 in accordance with the present invention. The bottle 10 is useful for holding a liquid sample F (Figure 4) during centnfugation in a centrifuge rotor R of the type discussed in connection with Figure 2.

The bottle 10 comprises a circular body portion 12 having an outside diameter 14 substantially equal to the diameter D of the rotor cavity H. The body portion 12 has an axis 16 extending therethrough. A neck portion 18 is formed integrally with the body portion 12. The neck portion 18 has an axis 20 extending therethrough.

The axis 20 of the neck 18 intersects with the axis 16 of the body 12 at a point of intersection 22. In accordance with this invention the axis 20 of the neck 18 defines a predetermined angle α, indicated by the reference character 24, with respect to the axis 16 of the body 12. For other reasons that are developed more fully herein the angle α 24 lies in the range from ten (10) degrees to (100-β) degrees. For reasons also becoming clearer herein the optimum value of the angle α 24 is (90- β) degrees.

The neck 18 has a predetermined length dimension 26 as indicated by the character L. The dimension L 26 is measured along the axis 20 of the neck from the rim 28 of the bottle to the point of intersection 22. The exterior surface of the neck 18 adjacent to the rim 28 is provided with threads 30.

A cap generally indicated by the reference character 34 is provided for engagement with the bottle 10. The cap 34 comprises a planar base portion 36 having in interior surface 361 and an exterior surface 36B thereon. A skirt 38 extends from the base 36. The skirt 38 also has an interior surface 361 and an exterior surface 36E. The interior surface 381 of the skirt 38 is threaded, as at 40, whereby the cap 34 is engageable with the threads 30 on the neck portion 18.

The base portion 36 of the cap 34 is generally circular in perimetrical configuration and has a predetermined diametrical dimension 36D associated therewith. A limit on the magnitude of the diametrical dimension 36D is discussed hereinafter.

Although the base 36 is preferably generally circular it should be understood that the base portion 36 may assume any convenient polygonal configuration. In such a case the diametrical dimension 36D corresponds to the diameter of the corresponding circumscribed circle.

The exterior surface 38E of the skirt 38 has in the preferred instance a generally cylindrical configuration. However the exterior surface 36E of the skirt 38 may be frustoconical in shape, as is illustrated in Figure 6. The angle 42 defined between the exterior surface 38E of the skirt 38 and the exterior surface 36E of the base 36 is substantially equal to an angle of (90 + 180 N) degrees, where N is the number of cavities H disposed in the rotor R.

In practice the inner surface of the of the cap 34 of the bottle 10 provides a static seal to prevent leakage of a sample from the bottle during normal handling prior to and subsequent to centnfugation. The cap may be fabricated from any material structurally rigid yet sufficiently compliant to provide a static seal against the mouth 28 of the bottle 10. A suitable material is polypropylene. Preferably the bottle 10 is also fabricated from polypropylene.

As is shown in Figures 5 and 6 the bottle 10 is used within a cavity H in the rotor R. To facilitate such usage the diametrical dimension 36D of the cap 34 is selected such that when the bottle 10 is disposed within a cavity H the cap 34 lies fully within a sector bounded by radially extending sector boundary lines SBi, SB2. The sector is defined in a plane perpendicular to the axis of rotation AR and subtends an angle of (360/N) degrees. The lines SBi, SB ₂ bisect webs W that lie between adjacent cavities H.

More precisely the magnitude of the diametrical dimension 36D may be expressed in terms of the dimension of a chord CH defined in the plane perpendicular to the axis of rotor and subtended by an angle of (360/N) degrees and spaced a distance r from the axis of rotation. The distance r is defined in accordance with the relationship:

r = R - L sin (α + β).

To insure that the cap lies within the sector bounded by the lines SBi, SB2 the diametrical dimension 36D must be less than or at most equal to the dimension of the chord CH.

In use, as shown in Figures 4 and 5, a sample of liquid is introduced into the bottle 10 and the cap 34 threadedly secured thereto. The bottle is introduced into the cavity H of

the rotor R and the cover of the rotor (if one is used) is attached. The angle α of the bottle exhibits the optimal value, i. e., the angle α == (90- β) degrees. When the angle α is thus optimally matched to the rotor a normal 36N of the exterior surface 36E of the cap 36 is perpendicular to the axis of rotation AR. Care should be exercised to insure that the exterior surface 36E of the cap 34 is presented toward the axis of rotation AR. In some instances unless this orientation is achieved difficulty will be encountered in securing the cover to the rotor.

At speed the meniscus FM of the liquid F in the bottle 10 (Figure 4) becomes oriented parallel to the axis of rotation AR. Owing to the inclination of the neck 18 with respect to the body 12 of the bottle 10, none of the liquid in the bottle challenges the interface 42 between the cap 34 and the neck 18. Since the possibility of leakage along this interface 42 is precluded, in practice, when the angle (X 24 is its optimum value no high pressure seal is needed.

It should be appreciated that when the angle of the neck is optimally matched to any rotor the volume efficiency of the bottle is one hundred percent (100%). That is the entire available volume of the bottle 10 is occupied by a liquid sample. In contrast, for example, if a 250 mL "Oak Ridge-type" bottle mentioned earlier is used in a rotor such as a GSA rotor sold by the Biotechnology Systems Division of E. I. du Pont de Nemours and Company, (angle β equal to twenty-eight (28) degrees) then only sixty percent (60%) of the available volume of the bottle may be used if no challenge is to be presented to the seal by the liquid.

It should be appreciated that even if a bottle having an angle β different from the optimum angle is used (i. e. either less than or more than the optimal angle) advantages are still

obtained. Assuming no high pressure seal is provided, the volume efficiency of the bottle is less than one hundred percent (100%) but is still greater than the comparable volume efficiency for a standard bottle used in the same rotor with the requirement that liquid not challenge the cap-bottle interface.

With a high pressure seal included in the bottle, if a value of the angle β different from the optimum value is used, then both the bottle in accordance with the invention and the prior art bottle are equal in terms volume efficiency one hundred percent (100%). However, even in such a case, seal reliability is improved in a bottle in accordance with the present invention. Owing to the inclination of the neck the component of centrifugal force of the cap that contributes to sealing the bottle is increased. The tendency of the O-ring to become unevenly distributed around the mouth of the bottle in response to centrifugal force is also reduced.

As noted the angle oc 24 lies in the range from ten (10) degrees to (100-β) degrees with the optimum value of the angle α 24 being (90- β) degrees. Since most rotors have an angle of inclination β in the range from twenty (20) to forty (40) degrees, the value of the angle oc 24 is in the range ten (10) to eighty (80) degrees. The lower limit of the angle α 24 is the value at which the component of centrifugal force that contributes to sealing the bottle first becomes significantly greater than the component contributing to sealing a straight neck bottle. The upper limit of the angle α 24 is the value at which the volume efficiency advantages of the bottle 10 begin to diminish.

In some instances to guarantee that adjacent bottles are prevented from rotation within a given cavity H about their own axis 16 the cap 34 having the frustoconical skirt 38 may be used. A rotor loaded with a full complement of bottles

having such caps is shown in Figure 6. The exterior surface 38E of adjacent bottles 10 are disposed in close proximity such that rotation of a bottle about the axis 16 of its body is prevented.

Those skilled in the art, having the benefit of the teachings of the present invention may impart numerous modifications thereto. It should be understood, however, that such modifications are to be construed as lying within the contemplation of the present invention, as defined by the appended claims.