GB2033257A

GB2033257A - Container Assembly for Centrifuge

Info

Publication number: GB2033257A
Application number: GB7934777A
Authority: GB
Original assignee: Fisons Ltd
Current assignee: Fisons Ltd
Priority date: 1978-10-28
Filing date: 1979-10-08
Publication date: 1980-05-21
Also published as: GB2033257B

Abstract

A container assembly for use in a centrifuge comprises an elongated rigid container (1) adapted to receive a sample to be centrifuged, the container having one end open and provided with an external generally circumferential shoulder (2). An external sleeve member (3) is adapted to receive the container (1) and has an internal shoulder (4) adapted to engage with the shoulder (2) on the container (1). A cap member (6) is adapted to be mounted on the sleeve member (3) and has sealing means (7) adapted to engage with the open end of the container (1) so as to provide a closure to the container (1). <IMAGE>

Description

SPECIFICATION Sealing Attachment for Standard Tubes The present invention relates to a sealing assembly for use with a centrifuge sample tube.

By virtue of their mode of operation, centrifuges have a tendancy to form an aerosol of a small part of the contents of sample tubes which are not closed during operation of the centrifuge. Where the contents are potentially hazardous, e.g. are bacterial or viral cultures, it is desirable to use sealed tubes. It has therefore been proposed to provide screw or other caps for the sample tubes. However, this has required that two types of tube be available; ones for normal use without sealing and ones which are capable of being sealed.

We have now devised a sealing assembly which can be used with conventional open ended tubes.

Accordingly, the present invention provides a container assembly for use in a centrifuge which assembly comprises an elongated rigid container adapted to receive a sample to be centrifuged, the container having one end open and provided with an external generally circumferential shoulder; there also being provided an external sleeve member adapted to receive the container, the sleeve member having an internal shoulder adapted to engage with the shoulder on the container, and a cap member adapted to be mounted on the sleeve member, the cap member having sealing means adapted to engage with the open end of the container so as to provide a closure to the container.

For convenience, the present invention will be described by way of reference to a preferred form thereof shown in the accompanying drawing, which is a vertical section thereof.

The container 1 is provided by a rigid hollow body usually having one end closed. Typically, container 1 is a stainless steel, titanium, aluminium or other metal tube 1. The tube 1 can be used to contain the sample to be centrifuged directly or, more preferably, acts as a carrier for two or more glass, plastic or metal sample tubes.

Where tube 1 is to act as a carrier, it can be provided with appropriate inserts to receive the individual sample tubes. These inserts are of conventional design and construction. By providing a sealing cap on the carrier tube, the risk of escape of the contents should the internal sample tube break is reduced.

Tube 1 is provided with an external shoulder 2, which is usually around the periphery of the open end of the tube. However, shoulder 2 could be located intermediate the ends of the tube as shown dotted in the drawing. Shoulder 2 can take the form of a series of individual projections around the circumference of the tube. However, it is preferred that shoulder 2 extends substantially continuously around tube 1. Thus, shoulder 2 is conveniently provided by the bead around the open end of a conventional tubular sample tube carrier or bucket as shown in the drawing.

Shoulder 2 preferably has a rounded or squared cross section, but could be of other shaped cross section.

Tube 1 is journalled in a sleeve member 3 which is preferably of substantially the same cross-sectional shape as tube 1. Sleeve 3 is provided with a shoulder which engages with the shoulder 2 on the tube 1 so that the open end of tube 1 will not pass through sleeve 3. The shoulder on sleeve 3 can be provided by forming sleeve 3 as a sliding fit upon tube 1 so that the 'end face of sleeve 3 engages shoulder 2.

However, it is preferred that part of sleeve 3 passes beyond shoulder 2 as shown in the drawing. Thus, sleeve 3 is a clearance or loose fit over shoulder 2 and is provided with an internal shoulder 4 which engages shoulder 2. Shoulder 4 can take the form of a series of individual internal projections which engage or interlock with shoulder 2. For example, shoulder 4 could take the form of an annular shoulder with sockets into which individual projections on shoulder 2 locate, or vice versa. However, it is preferred that shoulder 4 take the form of an internal rim extending substantially continuously around one end of sleeve 3 as shown in the drawing. If desired, shoulder 4 can be contoured to match the cross section of shoulder 2.

The sleeve 3 is provided with a cap member which acts to close the open end of tube 1. Where sleeve 3 extends beyond the end of tube 1 , the cap can be provided by a screw-in or other type of plug which engages with sleeve 3. Alternatively, the cap is provided by a domed member 6 which engages with sleeve 3 as shown in the drawing. It is preferred that member 6 is a screw fit into or over sleeve 3. The screw threads can be of triangular, squared, rounded, trapezoidal, buttressed or other suitable cross-section and more than one start thread may be used to improve the speed of tightening up of the cap.

However, other means, e.g. bayonet fixing, can be used to mount member 6 on sleeve 3. Member 6 can be made from any suitable material and can be of any appropriate shape.

Member 6 also engages with the open end of tube 1 to provide a sealed closure to the tube.

Member 6 can merely bear against the rim of tube 1 and draw sleeve 3 into sealing engagement with shoulder 2 or cause an external sealing sleeve located between sleeve 3 and tube 1 to deform (eg under compression) to provide the necessary seal. However, it is preferred that member 6 incorporate a resilient sealing means whereby a seal is formed between member 6 and the open end of tube 1 by urging member 6 and tube 1 together by means of the mounting of member 6 upon sleeve 3. This sealing means can take the form of an internal tapered plug carried by member 6, which plug is driven into the open end of tube 1 as member 6 is tightened down into sleeve 3. A preferred form of seal comprises an O ring or washer 7 carried by member 6 and which is squeezed between member 6 and the rim, for example the upper surface of shoulder 2, of tube 1 as member 6 is tightened down in sleeve 3.It is also preferred that the means by which member 6 engages with sleeve 3 (e.g. the screw fit or the bayonet mounting) be a loose fit so as to provide at least 0.1 mm clearance between the engaging parts. In this way, when member 6 is urged home upon the resilient sealing means, member 6 and sleeve 3 are held by the resilience of the sealing means at one extremity of the clearance of their engaging parts (e.g. of the screw threads). When the assembly is subjected to centrifugal forces member 6 can move against the resilience of the sealing member to take up the clearance in the engaging part and this will reduce the risk of extrusion of the sealing member through gaps left between the member 6, the tube 1 and the sleeve 3. Thus, where the member 6 is a screw fit on sleeve 3, we prefer that the screw threads be a 'free fit' as defined by BSS 3643.The term clearance is used herein to denote the fit between the members when not under load, specifically when not under load from the compressed sealing member.

In use, a sample is placed in tube 1 (using separate sample tubes and inserts if desired).

Sleeve 3 is passed over the closed end of tube 1 until shoulders 2 and 4 engage. Cap member 6 with its seal 7 is then screwed onto or into sleeve 3 until seal 7 is trapped between member 6 and shoulder 2. The tube 1 is now sealed for use and is mounted in the trunnion ring 10 of a swing out rotor of a centrifuge. If desired the sealed tube can be used in a fixed angle or vertical tube rotor.

The above assembly can be used with conventional sample tubes or carriers without the need to modify the tube or carrier or the centrifuge rotor. Also, we have found that when used in a swing out rotor the centrifugal forces cause sleeve 3 and cap member 6 to move radially outward along tube 1, thus further compressing seal 7 and improving the seal of the closure of tube 1. This is not possible with conventional screw-in sealing caps where the screw thread prevents radial movement of the cap. Also, as indicated above, clearance between the engaging surfaces of member 6 and sleeve 3 permits member 6 to move and reduce the size of any gaps between member 6, sleeve 3 and tube 1, thus reducing the risk of the sealing member extruding itself through those gaps during use.

The invention has been described above in respect of a sleeve 3 which is performed and has a solid wall. Where a seal 7 is used between tube 1 and cap 6, the wall of the sleeve can be partially cut away to reduce the weight of the assembly. It is also within the scope of the invention to form sleeve 3 as a member which snap fits onto shoulder 2, e.g. by forming shoulder 4 as a sprung member or by forming sleeve 3 as a longitudinally split member which can be splayed to permit shoulder 4 to pass shoulder 2 and is then relaxed so that shoulder 4 is held by shoulder 2.

Claims

1. A container assembly for use in a centrifuge which assembly is characterised in that it comprises an elongated rigid container (1 ) adapted to receive a sample to be centrifuged, the container having one end open and provided with an external generally circumferential shoulder (2); there also being provided an external sleeve member (3) adapted to receive the container (1), the sleeve member (3) having an internal shoulder (4) adapted to engage with the shoulder (2) on the container (1), and a cap member (6) adapted to be mounted on the sleeve member (3), the cap member (6) having sealing means (7) adapted to engage with the open end of the container (1) so as to provide a closure to the container (1).

2. An assembly as claimed in claim 1 wherein there is a clearance of at least 0.1 mms between engaging parts of the sleeve (3) and the cap member (6).

3. An assembly as claimed in claim 2 wherein the cap member (6) is a screw fit in or on the sleeve (3) and the screw fit is a free fit as defined in BSS 3643.

4. An assembly as claimed in any one of the preceding claims wherein the sealing means (7) comprises a resilient seal adapted to be held between the cap member (6) and the container (1).

5. An assembly as claimed in claim 1 substantially as hereinbefore described.

6. An assembly substantially as hereinbefore described with respect to and as shown in the accompanying drawing.

7. A centrifuge provided with an assembly as claimed in any one of the preceding claims.