Background to the invention Historically, tubes, vials and micro titre plates have been used to contain samples in a centrifugal evaporator. By contrast in rotary evaporators samples have tended to be contained in round-bottomed flasks.

There are various reasons why round bottomed flasks have not been used in centrifugal evaporators, such as: i) Flasks are delicate and the high G-forces acting on the flasks (typically over 200G) when a centrifugal evaporator is operating, can cause the flask walls to fracture and break. ii) A flask breaking within a centrifugal evaporator is likely to cause severe damage to the inside of the evaporator as a result of the glass being ground up. iii) Flasks often contain relatively large volumes of solvent and the mass of such flasks requires a far stronger rotor than those which have been employed in traditional centrifugal evaporators. iv) In traditional centrifugal evaporators, high temperatures and large quantities of heat have been required to sufficiently heat the solvents to achieve evaporation times that were comparable to those achievable when using rotary evaporators. Using a flask with its even larger volume of solvents requiring heat merely aggravates the temperature gradient/heat energy problem.

A centrifugal evaporator is now available which is more robust and has sufficient heating power and control over the heat input, to allow flasks to be mounted and rotated therein, for drying liquid samples in an acceptable time, and without overheating. However the mounting of the flasks in the vacuum chamber has presented problems.

Object of the invention The invention seeks to provide a flask holder, into which a glass flask can be placed for sample evaporation within a centrifugal evaporator, which does not impart undue stress and strain on the flask during centrifuging which could result in fracture of the flask wall.

Summary of the invention According to one aspect of the present invention, there is provided a flask holder adapted to receive and support at least one spherical flask in a centrifugal evaporator the interior of which is heated by an infra red radiation source, which holder comprises a body of thermally conductive material having formed therein a generally cylindrical sleeve terminating in a closed hemispherical cavity, the wall of the sleeve and of the cavity being solid and serving to protect the contents of a flask therein from UV light and also to prevent localised overheating of the flask wall and its contents by incident infra-red radiation, an annular flask support surface formed in the hemispherical cavity, and a disc or ring of compliant and thermally conductive material located in the cavity between the support surface and the flask to provide a cushion between the flask and the cavity wall, to reduce stress on the wall of the flask.

Preferably the cavity has a radius of curvature at least equal to and preferably slightly greater than that of a flask which is to be located therein.

Preferably the annular support surface formed in the hemispherical cavity restricts contact between the rounded base of the flask and the cavity to a ring of contact having a diameter in the range 15% to 80% of the diameter of the flask.

Preferably the diameter of the annular support surface is 40 % of the flask diameter.

The annular support surface removes the stress concentration that can otherwise arise as a result of any point contact between the wall of the flask and the cavity wall.

Most flask manufacturing processes tend to produce a bulge in the otherwise spherical wall of the flask. The annular support surface also provides a region into which any such bulge can be accommodated. If any bulge in the base of the flask is not accommodated and if the disc or ring of compliant material where for example omitted so that the bulge in tht flask base could make contact with the surface of the holder, the flask will almost certainly break.

Preferably the body is formed from metal, preferably aluminium.

According to a preferred feature of the invention a support member is provided having an opening through which the neck of the flask can extend to prevent tilting of the flask in use. This ensures that the flask sits square in the cavity and further ensures that the bulge in the base of the flask is always located within the ring created by the annular support surface, and clear of the cavity wall. According therefore to another aspect of the present invention there is provided a flask holder adapted to receive and support at least one spherical flask in a centrifugal evaporator the interior of which is heated by an infra red radiation source, which holder comprises a body of thermally conductive material having formed therein a generally cylindrical sleeve terminating in a closed hemispherical cavity, the wall of the sleeve and of the cavity being solid and serving to protect the contents of a flask therein from UV light and also to prevent localised overheating of the flask wall and its contents by incident infra-red radiation, and wherein an annular support surface is formed in the hemispherical cavity, which further comprises a support member having an opening through which the neck of a flask fitted in the holder will extend, to prevent tilting of the flask in use.

The support member requires to be removable or at least movable to facilitate loading and removal of flasks.

In one embodiment the neck supporting member is hinged to the remainder of the body, to allow it to be swung up and clear of the top of the flask, to allow the latter to be removed and replaced by another.

In another embodiment, the neck supporting member is slidably supported on rods to enable it to be slid clear of the neck of the flask, for flask removal and insertion.

In a preferred arrangement the neck supporting member comprises a ring attached to a pair of cylindrical rods which extend perpendicularly relative to the plane of the ring on one side thereof from two circularly spaced apart regions around the ring and the body of the holder includes a pair of cylindrical bores positioned so as to slidingly receive the two rods and long enough to accommodate the length of the rods, to allow the ring to be pushed down to engage the top of a flask.

The circularly spaced apart regions may be diametrically opposite regions or may be staggered relative to the diameter of the ring.

Preferably the rods are held captive in the bores so that they cannot be pulled completely out of the bores.

Preferably the extent to which the ring can be pulled up relative to the body provides sufficient clearance between the ring and the body to allow a flask to be inserted below the ring into the body or removed therefrom after use.

Preferably the fit of the rods in the bores is such that the rods can be slid up and down relative to the body but there is a brake or catch to lock the ring in an elevated position for flask insertion or removal or there is sufficient friction between the rods and the bores as to cause the ring to remain in place to wherever it is lifted.

Each rod conveniently has an enlarged diameter lower end which is a sliding fit in a bore and its enlarged lower end is prevented from leaving the bore by an annular collar fitted at the top of the bore around the rod, in which the rod is a sliding fit.

Preferably the collar is formed externally with a screw thread profile and the upper end of the bore is formed with a complementary screw thread profile into which the collar can be screwed and tightened.

The collar may be formed from a plastics material such as Nylon and if the body and rods are formed from aluminium, the friction required to hold the ring in lace when lifted, can be readily obtained by selecting the inside diameter of the collar so that the latter is a relatively tight fit around the rod, which can still be pushed and pulled through the coollar but will remain in place when lifted up.

If the collar tapers slightly so that the outside diameter of the screw thread increases towards the top end of the collar, the action of screwing the collar into the bore will increase the grip on the rod, and this allows for adjustment of the friction force acting on the rod. The exterior of the collar may be formed with two or more flats for engagement by a spanner to allow for it to be screwed into the bore.

The cavity and the cylindrical sleeve form a container so that should a flask fracture in use, the solvent and glassware will be contained there-within and will not damage or contaminate the inside of the evaporator chamber, and according to a further aspect of the present invention there is provided a flask holder adapted to receive and support at least one spherical flask in a centrifugal evaporator the interior of which is heated by an infra red radiation source, which holder comprises a body of thermally conductive material having formed therein a generally cylindrical sleeve terminating in a closed hemispherical cavity containing an annular flask support surface, the wall of the sleeve and the cavity being solid and serving to protect the contents of a flask therein from UV light and also to prevent localised overheating of the flask wall and its contents by incident infra-red radiation, wherein the cavity and the cylindrical sleeve form a container so that should a flask fracture in use, the solvent and glassware will be contained therewithin to reduce the risk of damage or contamination to the interior of a centrifugal evaporator chamber in which the holder is rotatable.

Preferably the disc or ring of compliant and thermally conductive material is formed from reinforced alumina-filled silicon gel, and typically is between lmm and 2mm thick.

Typically the disc or ring has a diameter of between 0.25 and 0.75 times the diameter of the flask.

Preferably the diameter of the disc or ring is selected so that it extends radially beyond the annular support surface in the wall of the hemispherical cavity.

The presence of the disc or ring of compliant material serves to reduce stress on the wall of the flask. This is particularly useful in centrifugal evaporators that are to be operated at high rotational speeds and so generate significant G-force loads on the flask, and/or where thin glass walled flasks are being used.

The disc or ring can also improve the conduction of heat between the wall of the holder and the flask and so reduce the time required to evaporate any particular sample.

Insofar as the neck supporting member at least partially closes off the flask containing region of the holder, it constitutes a lid for the holder and is referred to as such elsewhere herein. When closed, the lid further assists in retaining fractured glass and/or solvent within the holder.

In the drawings: Figure 1 illustrates an assembled holder and flask; Figure 2 is a section through the assembly of Figure 1; Figure 3 is a section through an assembly of flask and holder with a disc cushion in place; Figure 4 is a section through the base of the holder, and illustrates a preferred profile for the annular support surface; Figure 5 is a perspective view of another holder adapted to receive 6 flasks in which the lid is slidable up and down relative to the base, and is shown in its lower position; Figure 6 is a similar view to that of Figure 5, but with the lid shown raised relative to the base to allow flasks to be inserted or removed; Figure 7 is a perspective view of a holder adapted to receive a single flask (similar to Figures 1 to 3) but in which the lid is slidable up and down relative to the base; Figure 8 is a similar view to that of Figure 7, but with the lid shown raised relative to the base, to allow a flask to be inserted or removed; Figure 9 is a perspective view of a holder adapted to receive three flasks in which the lid is slidable up and down relative to the base; Figure 10 is a similar view to that of Figure 9, but with the lid shown raised to allow a flask to be inserted or removed; Figure 11 is a perspective view of a holder adapted to receive four flasks in which the lid is slidable up and down relative to the base; Figure 12 is a similar view that of Figure 11, but with the lid shown raised to allow a flask to be inserted or removed; Figure 13 is a perspective view of a holder adapted to receive three flasks, each having a parallel wall, and a hemispherical base, in which the holder does not include a lid of any type (hinged or sliding); Figure 14 is a plan view from above of the holder of Figure 13 and shows the annular seatings at the lower ends of the flask receiving sections; Figure 15 is a plan view from above of the holder of Figure 5 and shows the annular seatings at the lower ends of the flask receiving seatings which are visible through the circular openings in the lid; Figure 16 is a plan view from above of the holder of Figure 11, and shows the annular seatings at the lower ends of the flask receiving seatings which are visible through the circular openings in the lid, and Figure 17 is a cross sectional elevation of the holder of Figures 7 and 8.

In the drawings, where shown, a flask is designated by reference 10 and the base of the holder by 12. The hinged lid of Figures 1 to 3 is denoted by reference 14 with a circular opening 16 through which the flask neck 18 protrudes. The hinge is shown at 20 and a V- shaped slot is provided on opposite sides of the base 10, for mounting the base to a rotor (not shown) of a centrifugal evaporator (not shown).

The slot in the nearside of the base and visible in Figure 1 is denoted by 22. The similar slot 24 at the other end is visible in Figures 2 and 3.

The annular ring of contact is visible in the scrap section of Figure 4 and is denoted by reference 26.

An optional thermal cushion between the flask and the ring 26 is shown at 28 in Figure 3.

Figures 5 and 6 show an alternative type of lid for the flask holder and illustrates this alternative lid in relation to a holder adapted to take six small 25ml flasks.

The lid 30 includes six circular openings such as 32 to accommodate the necks of six flasks when located in the holder, and is carried by two rods 34,36 best seen in Figure 6. The rods are of circular cross-section and attached to the lid at their upper ends and are slidable in two openings 38,40 in the base 42. The rods are a sliding fit in the openings which may be the upper ends of cylindrical cavities in the base. Typically the sliding fit is not friction free, and if sufficient friction exists the lid will remain at whatever level to which it is lifted or pushed down, so that when the holder is to be unloaded the lid will remain in an elevated position without having to be held in place, while flasks are removed and/or replaced.

Figures 7 and 8 show a holder with a sliding lid for use with larger 250ml flasks. The lid 44 is carried by rods 46,48 and their sliding engagement with the base 50 may be as previously described in relation to Figure 5 and 6. The upper ends 46'and 48'of the rods are of increased diameter with a step 45,45'between the sections 46'48'and the remainder of the rods 46,48. See also Figure 17 and the description thereof. Figures 9 and 10 show a 3-flask holder having a base 52 and lid 54 slidably supported on two rods 56,58. Again the sliding fit may be as described in relation to Figures 5 and 6.

Figure 11 shows a four flask holder having a base 60 and lid 62 slidably supported on three rods, 64,66, 68. As before, the sliding engagement may be as described in relation to Figures 5 and 6.

Although not shown an enlargement or other device is preferably provided at the lower end of at least one of the rods (such as 34,36) to prevent the lid from being raised to such an extent that the rods leave their openings in the base. The lid is thereby retained captive to the base of the holder.

Figures 13 and 14 show an open topped base 70 having three flask receiving cavities 72, 74,76. Figure 14 shows the contact rings 78,80 and 82 in the bases of the cavities.

The plan views of Figures 15 and 16 also show the respective contact rings in the bases of the cavities in the six and four flask holders, this time visible through the circular openings in the lids of the holders which are shown closed.

Figure 17 shows how the rods 46,48 are mounted in the base 50, and held captive therein and how sliding friction can be created so as to permit the lid 44 to remain at whatever height it has been pulled up to, to facilitate insertion and removal of a flask 10.

To this end two parallel cylindrical bores 41,43 are provided in the base 50 each greater in diameter than the diameter of the two rods 46,48, and dimensioned to form a sliding fit with two cylindrical ends 51,53 screwed into the lower ends of the rods 46,48. The ends 51,53 may be of plastics or metal and are of greater diameter than the rods themselves, so that the lower end of each rod now has a region of increased diameter in a similar way to the regions 46'48'at their upper ends (see Figure 7).

The rods are held captive in the bores 41,43 by means of two sleeves 47,49 which are threaded onto the rods 46,48 before the ends 51,53 are screwed in place, and are a sliding fit around the rods. After pushing the rods 46,48 into the bores 41,43 the sleeves are secured in the upper ends of the bores as by complementary screw thread profiles around the sleeves and in the upper ends of the bores as denoted by 47'49'.

The sleeves 47,49 may be of plastics or metal, and if made of resiliently deformable material such as a plastics, the action of screwing them into the upper ends of the bores can be arranged to lightly compress the sleeves around the rods 46,48 so as to create a sliding friction fit between the rods and the sleeves, sufficient to hold the lid 44 at any selected elevation within the limits defined by the engagement of the enlarged ends 46'48' with the upper ends of the sleeves 47,49 at one extreme and the engagement of the enlarged ends 51,53 at the lower ends of the rods, with the underside of the sleeves 47, 49, at the other extreme.