Centrifuge bowl having a line of weakness therein

A bowl for use in a centrifuge instrument wherein the bowl has a predetermined line of weakness formed therein. The line of weakness, which may be disposed on either the inside or the outside surface of the bowl, subdivides the bowl into an upper and a lower region.

BACKGROUND OF INVENTION 
1. Field of Invention 
The present invention relates to a bowl for use in a centrifuge instrument. 
2. Description of Prior Art 
The containment system for a centrifuge instrument includes a vessel 
commonly called a bowl or a chamber. The bowl is usually surrounded by a 
guard ring that may itself be rotationally mounted with respect to the 
framework of the instrument. The bowl is formed of a substantially 
cylindrical sidewall having a planar floor portion. An outer flange is 
provided about the upper edge of the bowl whereby the bowl may be rigidly 
attached to the flamework. 
The floor of the bowl has a central axial opening therein. The shaft upon 
which a centrifuge rotor is received projects through the opening in the 
floor of the bowl. The shaft is connected to and driven by any suitable 
source of motive energy. 
A centrifuge rotor is mechanically secured to the top of the shaft for 
rotation within the confines of the bowl about a rotational axis extending 
through the shaft. A rotor fabricated from a suitable material such as 
aluminum will operate at a particular performance level for a specific 
number of cycles. This predetermined number of cycles is usually referred 
to as the cycle life of the rotor. After this predetermined number of 
cycles is reached the likelihood of a rotor disruption occurring due to 
material fatigue is greatly increased. When the rotor fails the rotor 
fragments will impact the sidewall of the bowl with a large amount of 
energy. 
User error may cause another form of rotor disruption. If the rotor is not 
securely affixed to the shaft by the user it may become disengaged from 
the shaft during operation and impact against the sidewall of the bowl. 
The containment system of the instrument is always designed to contain the 
energy of impact of the rotor or its fragments (if any) and to prevent the 
fragments from escaping the interior of the instrument. 
The energy imparted to the sidewall of the centrifuge bowl can have 
devastating effects. In an improperly designed centrifuge a rotor failure 
can cause gross instrument movement, possibly injuring personnel who 
happen to be located nearby. In large floor model instruments the 
deformation and rotation of the guard ring allows the energy imparted by 
the rotor into the containment system to dissipate. By allowing the guard 
ring to rotate the amount of energy that is transferred to the instrument 
framework is greatly reduced. 
In some models of tabletop centrifuge instruments insufficient available 
space precludes the provision of a rotatable guard ring surrounding the 
bowl. The bowl must, therefore, function as the guard ring. A tabletop 
instrument has the additional problem in that it is usually light in 
weight, which allows greater movement in the event of a rotor failure. Due 
to the potential for injury resulting from a rotor failure, the 
performance of rotors for use in a tabletop centrifuge instrument is 
usually degraded both to reduce its potential energy and to extend the 
life of the rotor. 
Accordingly, it is believed advantageous to provide a centrifuge bowl that 
is adapted to separate itself from the framework of the centrifuge 
instrument in the event of a rotor failure, reducing the amount of energy 
that is transferred from the rotor to the centrifuge framework, thus 
preventing gross instrument movement. 
SUMMARY OF INVENTION 
The present invention is directed to a bowl for use in a centrifuge 
instrument wherein the bowl has a predetermined line of weakness formed 
therein. The line of weakness, which may be disposed on either the inside 
or the outside surface of the bowl, subdivides the bowl into an upper and 
a lower region. The line of weakness is preferably implemented in the form 
of a V-shaped groove. In the event of a rotor disruption the bowl responds 
to a force imposed on the inside surface of the lower region (due, for 
example, to the impact of a rotor fragment) by separating from the upper 
region along the line of weakness. As a result the lower region is free to 
deform and to rotate to dissipate the energy of the rotor fragment. In the 
preferred instance the line of weakness should be formed in the bowl at a 
height dimension at least equal to the height occupied by the top surface 
of a rotor when the same is mounted on the rotor shaft.

DETAILED DESCRIPTION OF INVENTION 
Throughout the following detailed description similar reference characters 
refer to similar elements in all Figures of the drawings. 
FIG. 1 shows a centrifuge instrument generally indicated by the reference 
character 10 having a bowl 12 in accordance with the present invention. 
The bowl 12 is defined by a cylindrical sidewall 12W and a bottom 12B. The 
bowl has an inner surface 1 21 and an outer surface 12E. A central opening 
12A is provided on the bottom 12B. A rotor mounting shaft S extends 
through the opening 12A. The shaft S has an axis of rotation VCL extending 
therethrough. The bowl 12 is fabricated from any suitable material, such 
as aluminum. 
Contained within the bowl 12 is a rotor indicated by the reference 
character R. The rotor R is shown as mounted to the upper end of the drive 
shaft S. The rotor 10 rotates on the shaft S about the axis of rotation 
VCL. The rotor R has a top surface F thereon. 
The bowl 12 includes a groove 12G that extends circumferentially around 
outside surface 12E of the sidewall 12W of the bowl 12. For purposes that 
will become more clear herein the groove 12G defines a line of weakness in 
the bowl 12. The line of weakness is generally indicated by the reference 
character 12L. The area of the bowl 12 adjacent to the line 12L of 
weakness is a relatively high stressed region of likely failure in the 
event of a rotor disruption. 
The groove 12G separates the bowl 12 into an upper portion 12C and a lower 
portion 12D. The radially outer portion of the upper portion 12C is 
out-turned to form a flange 12F. Although it can be disposed at any 
predetermined position on the sidewall the groove 12G is, in the preferred 
instance, located at a vertical position along the axis VCL equal to or 
greater than the top surface of the rotor R. 
The bowl 12 is mounted to the instrument framework 14 through the flange 
12F. This attachment can be accomplished using a number of different 
methods. As shown in FIG. 1 the flange 12F is clamped in a gasket 15 
between the instrument framework 14 and the instrument bowl door 16. The 
door 16 may be formed from metal or from a transparent material (e.g., 
acrylic) as illustrated. 
As is best viewed in FIG. 2 the groove 12G is defined by a radially upper 
surface 12R-1 and a radially lower surface 12R-2. The two surfaces 
intersect to form an edge 12T. The distance between the edge 12T and the 
opposite surface (in the case shown, the inner surface 121) of the bowl 12 
represents the smallest cross section of material in the bowl 12. Although 
shown as V-shaped in the Figures it should be understood that the groove 
12G may take any convenient cross sectional shape. 
In the event that a rotor R disruption occurs during operation, since the 
rotor R has both a rotational velocity and a linear velocity, it will 
translate from the shaft S and impact on the lower portion 12D of the 
inner surface 121 of the bowl 12. At the point of impact the rotor R will 
transmit a substantial amount of energy to the bowl. This energy will have 
both linear (i.e., radial) and rotational components. The radial component 
may impact the sidewall 12W causing the bowl to deform and fail along the 
line of weakness 12L. The rotational component will impart a torque to the 
bowl wall 12W causing the bowl 12 to fail circumferentially at its 
narrowest cross section, that location being the line of weakness 12L 
defined by the groove 12G. The lower portion 12D of the bowl will separate 
from the upper portion 12C and will rotate within the framework 14. 
The energy of the rotor is dissipated by a combination of bowl deformation 
and heat generated through frictional contact between the rotating lower 
portion 12D of the bowl and the instrument framework. 
It should be appreciated that the groove 12G could be disposed on the inner 
surface 121, as illustrated in FIG. 2B. In either case (FIG. 2A or FIG. 
2B) the groove 12G could be circumferentially continuous, or 
circumferentially interrupted. It should be appreciated that 1 he line of 
weakness 12L could be alternatively defined, as, for example, by a 
circumferential series of closely spaced perforations 12P as illustrated 
in FIG. 2C. The perforations 12P extend completely through the wall 12W of 
the bowl, as illustrated, or may extend only partially thorough the wall 
12W. The perforations may originate on either the inside surface 121 or 
the outer surface 12E. 
Those skilled in the art, having the benefit of the teachings of the 
present invention as hereinbefore set forth, may effect numerous 
modification thereto. Such modifications are to be construed as lying 
within the contemplation of the present invention, as defined by the 
appended claims.