WO2001036104A1

WO2001036104A1 - Improvements relating to evaporating apparatus

Info

Publication number: WO2001036104A1
Application number: PCT/GB2000/004369
Authority: WO
Inventors: Michael Cole
Original assignee: Genevac Limited
Priority date: 1999-11-18
Filing date: 2000-11-16
Publication date: 2001-05-25
Also published as: GB0028004D0; GB2357715A

Abstract

A centrifugal evaporator has a lid (14) closing an access or opening (12) and a port connected to a filter unit (28) by a duct (26). When the evaporation process is completed, air is drawn through the duct to entrain dangerous fumes and prevent them exiting through the opening (12). In a modification (Figure 2) there are three sample supports, each being accessible by an internal flap (42 to 46), the entire opening being closeable and sealable by a main door (38).

Description

Title: Improvements relating to evaporating apparatus

Field of the Invention

This invention concerns apparatus by which liquid samples contained in open-ended sample holders can be evaporated by reducing the ambient pressure to a vacuum and facilitating the retention of the liquid material in the sample holders by rotating the latter at high speed so as to exert centrifugal forces on the liquid in the sample holders. Such apparatus is referred to as a centrifugal evaporator.

Background to the Invention

When samples containing toxic or odoriferous liquids are loaded into or unloaded from centrifugal evaporators, fumes in the form of gases or vapours can escape and can constitute a hazard to operators performing the tasks.

When samples of this type are being handled, it is normal practice to place the evaporator in a fume cupboard or fume hood. This is not always possible because there is often significant pressure on space in fume hoods. In addition such devices are .cot fully effective in preventing a hazard to an operator because a fume hood still has to be opened to allow access to the evaporator for the operator to open the lid or door of the chamber containing the samples. Air flow past the evaporator, with the fume hood open, is usually too low to prevent hazardous gases or vapours from reaching the operator. Object of the Invention

It is an object of the invention to provide a method and apparatus for restricting the exit of gases and vapours from a centrifugal evaporator, especially while unloading sample holders after evaporating. It is also an object of the invention to draw fumes away from an operator while the evaporator is being loaded.

Summary of the Invention

According to a first aspect of the invention, where a centrifugal evaporator comprises a chamber having a loading/unloading entrance which is sealable during evaporation by closure means, and in which drive means is provided for moving the closure means to open or close the entrance, a remote control for controlling the operation of the drive means is provided, to allow an operator to at least open the chamber remotely.

Preferably the chamber is opened while still in a closed fume hood.

In this way, any vapours or gases within the chamber can be allowed to exit therefrom into a fume hood before an operator has any need to approach the chamber closely.

Additionally, or alternatively, means may be provided for drawing air out of the chamber at a position remote from the open entrance. This enables a large volume of air to be drawn into the chamber with a low pressure drop.

The closure means may for example comprise a hinged door or lid, a sliding door or panel or a pivoting flap.

The drive means may for example be an electric motor, a pneumatic or hydraulic drive or a stored energy device such as a spring or a gravitational device incorporating a weight, which when released moves the closure means so as to expose the opening. The lifting devices could be triggered by means of a solenoid. The remote control unit actuated by an operator may, for example, comprise a hand-held unit which is attached to the housing by an electric cable, a pipe, or a mechanical linkage such as a so-called Bowden cable.

Alternatively, the remote control may include a radio, infra-red, or acoustic transmitter/receiver arrangement.

According to another aspect of the invention, where a centrifugal evaporator comprises a chamber having a loading/unloading entrance which is sealable during evaporation by closure means, a remote control is provided for moving the closure means into a position in which the chamber is sealed or into a position in which the entrance is open. This alternative arrangement does not require a drive means as such but requires the remote control device to effect the movement of the closure means, and to enable this to be performed from a safe distance by an operator.

Where the apparatus is to be used with samples which tend not to emit vapours or gases before evaporation, it is possible for the operator to manually close the entrance after the evaporator has been loaded with samples and to fix the closure means in place to seal the chamber. In this event, provided there is a stored energy mechanism or a gravitational drive (such as merely for example the weight of the closure means itself), which normally acts to open the entrance by moving the closure means clear thereof, it is possible to merely provide a latch for maintaining the closure means in position, and the remote control arrangement is merely required to release the latch to cause the closure means to move so as to open the entrance.

By performing this operation inside a closed fume hood, an operator is largely protected from exiting fumes, vapours or gases. According to a further aspect of the invention, where a centrifugal evaporator comprises a chamber having loading/unloading entrance which is sealable during evaporation by a closure means, a remote control is provided, adapted to move the closure means directly in one direction to close the entrance and in the other direction to open the entrance to allow an operator to both close and open the closure member remote from the evaporator chamber.

One example of a remote control device of this type is a Bowden cable based device, with a lever or rotatable member attached to a housing at the remote end of the Bowden cable, movement of which is transmitted via the inner core of the cable to the closure means so as to effect movement of the closure so as to close or open the entrance.

Where the closure means is operated by a solenoid, an electric motor, pneumatic drive or hydraulic drive, the remote control device comprises a means for controlling the supply of electric current, pneumatic fluid such as air, or hydraulic fluid such as oil, to the drive unit associated with the closure means, for causing the drive to move the closure means in one direction or the other as required.

According to a further aspect of the invention a method of sealing and unsealing a chamber forming the housing of a centrifugal evaporator comprises the steps of closing the opening by a closure member, latching or otherwise securing the closure member in place, and from a remote location, releasing the latch or other closure securing device after the evaporator process has been completed.

According to a still further aspect of the invention there is provided a method of opening and closing a sealed chamber forming the housing of a centrifugal evaporator wherein a closure member is provided for covering or otherwise closing an opening to effect the said sealing of the chamber, and drive means is provided for moving the closure member into and out of the sealing position, wherein the method comprises the step of actuating the drive means after the chamber has been loaded with samples, to move the closure member into the sealing position, leaving the closure member in the sealed condition while the centrifugal evaporation process is performed, and after the process has been completed, and from a remote location, transmitting a signal to the drive means to move the closure member so as to leave the opening unobstructed and allow samples to be removed.

The signal which is transmitted to the drive means may be a mechanical signal, a pneumatic or hydraulic signal, an electric current, or may be a signal transmitted by a radio, acoustic or infra-red link.

According to a still further aspect of the invention, in apparatus or method as aforesaid, an interlock or disabling device is provided to prevent the closure member from being opened until an evaporation process has been completed, and/or the rotating assembly within the chamber has come to rest.

According to a particularly preferred aspect of the invention, an alternative approach is employed in which means is provided for withdrawing air from the interior of the chamber shortly before, or at the same time as, the closure member is moved, so as to unseal the chamber, the air being withdrawn from the chamber serving to set up an air flow such that vapours or gases resident within the chamber are caught up into the air stream and drawn out of the chamber into a filter or other collection means, and to this end the air flow from the chamber is arranged to leave the interior of the chamber from a point or points therein such as to convey any vapours or gases away from the entrance to the chamber.

Once the opening is unsealed, the chamber will of course be open to the atmosphere via the entrance but with the air flow having been established from the chamber in a direction away from the entrance, there will be a tendency for air from outside the chamber to pass into the chamber through the opening in the opposite direction to that which any gases or vapours would have to travel in order to leave the chamber through the opening, and the inflow of air will tend to facilitate the purge of the interior of the chamber of any vapours or gases resident therein and given off by the samples during or after the evaporation process. In this way any such gases or vapours will be gathered up by the incoming air flow and swept into the exiting air flow from the chamber for transfer to the filter or other collecting device for separation and collection and disposal. Filtered air can be returned to ambient from the filter if required.

Preferably the opening is only partially exposed when access is required so as to reduce the open area through which air is drawn into the chamber, thereby increasing the air velocity so as to improve the efficiency with which undesirable gases or vapours in the chamber are prevented from emerging through the opening.

The partial exposure may be achieved by means of an intermediate cover which will normally be located below the closure member if the closure member is at the top of the chamber, or behind it if the closure member is a front opening door. The closure member serves to completely close the opening, but the intermediate cover includes an aperture (which may be an opening therein or a cut away region thereof) just large enough to allow samples to be loaded or unloaded.

According therefore to a further aspect of the invention a method of limiting the discharge of vapours or gases through the opening in the wall of the chamber forming the housing of a centrifugal evaporator, comprises the steps of establishing an air flow from the interior of the chamber at the end of the evaporation and centrifuging process, so as to gather gases or vapours from within the chamber into the exiting air stream, conveying the exiting air and gases and/or vapours via duct means to a filter or other separating device so as to purge the air stream of unwanted gases or vapours, collecting means for retaining separated components from the air stream and means for returning the air stream to atmosphere, closure means for closing the entrance in the wall of the chamber at least for the duration of the centrifugal evaporation process, means to effect movement of the closure means to open the entrance to allow samples to be inserted into, or withdrawn from, the chamber, and control means operable to effect the establishment of the air flow away from the interior of the chamber after the centrifugal evaporation process has ceased and prior to if not at the same time as the closure member is removed from the opening in the wall of the chamber. The means for establishing the outflow of air from the chamber may comprise fan means or a suction pump.

According to a still further aspect of the invention, in a centrifugal evaporator comprising a chamber within a housing within which two or more rotatable suppoπs are mounted one above the other and all of which are rotatable about a common axis, and drive means for rotating the supports as a single unit, and wherein an opening in the wall of the chamber is closeable and sealable by means of a closure member such as a hinged door, there are provided a corresponding number of intermediate independently hingeable internal doors each of which can be employed so as to close off a respective part of the overall opening and each of the internal doors is aligned relative to the stack of samples supports within the chamber such that one of the support members is accessed through the aperture which is created by opening one of the internal doors.

This aspect of the invention is of particular value where in combination with a fan or pump means, a net outflow of air and gases or vapours is established from the chamber before or when the main closure is opened, and by restricting the opening of the inner doors to only one at a time, so the opening giving access to samples, to allow the latter to be removed or replaced, is restricted to a percentage only of the overall area of the opening, thereby increasing the velocity of the inflow of air into the chamber by an amount which is commensurate with the area of the overall opening relative to the area of the aperture left by the opening of one of the inner doors. Thus where there are three equal sized inner doors, the area exposed by opening just one of the doors is one third of the area which would be unrestricted if all three inner doors were opened simultaneously, and the inflow of air through the area exposed by the opening of one inner door, will be approximately three times the rate of inflow were all three inner doors to be opened simultaneously.

In general it is only necessary to permit access to one of the layers of samples at a time, and therefore a significant increase in the velocity of the inflow of air into the chamber can be achieved by merely opening the inner door appropriate to the layer of samples to be handled at any time. The invention also lies in a remotely controllable door or other closure device for closing and opening in the walls of the housing the interior of which form the chamber of a centrifugal evaporator, to allow the chamber to be closed and opened inside a closed fume hood from a remote position to limit the exposure of the operator to any fumes gases or vapours which may otherwise escape when the chamber is initially unsealed and thereafter.

The invention will now be described by way of example with reference to Figures 1 and 2 of the accompanying drawings which illustrate diagrammatically two arrangements embodying the invention.

Detailed description of the drawings

In Figure 1 a housing or chamber 10 houses a rotatable assembly (not shown) of sample holders for containing liquid samples which are to be evaporated whilst subjected to centrifugal forces due to the rotation of the sample holders.

The housing 10 is generally cylindrical and has a large circular opening 12 at its upper end to allow access to the interior of the housing. A lid 14 hinged at 16 can be lowered to close off and seal the opening 12 when the evaporation and centrifuging process is to occur.

The large circular opening 12 is in fact restricted by a removable inner cover 18 which is generally circular but has an arcuate peripheral cut-away region 20 which actually restricts access to the interior of the housing 10 to the minimum required to load and unload samples.

In a modification (not shown) the inner cover 18 may be fixed, the rotor of the evaporator being rotatable by hand to present each sample in turn to the cut-away region 20. Seals 22 are provided around the periphery of the opening 12 which cooperate with the underside of the lid 14 to allow a vacuum to be established within the chamber as and when required.

The vacuum pump and associated control apparatus drive for the rotatable assembly within the chamber are not shown, but a port 24 is provided in a side wall of the housing 10 for communicating with a duct 26 which conveys air and any gases or vapours entrained therein from the inside of the housing 10 to a filter and separating unit 28. Intermediate the port 24 and the filter unit 28 is a valve 30 and a suction device 32.

In accordance with the invention, remote control means is provided (preferably of a mechanical nature, e.g. via an electric, pneumatic or hydraulic actuator, or via a Bowden cable, not shown) for fully opening and closing of the lid 14. This prevents an operator from being exposed to toxic fumes, especially when the lid is closed and fumes are expelled outwards to where the operator would otherwise be standing.

Further in accordance with the various aspects of the invention, the cover plate 18 restricts the area through which air can flow into the interior of the housing 10 when the lid 14 is open and the duct 26 conveys air and unwanted gases and vapours from within the chamber to the filter by means of the operation of the suction device 32. By restricting the area through which air can enter the interior of the housing as by the solid arrow shown at 34, so the speed of the air entering the housing through the opening 20 is increased relative to what it would have been if the inner cover 18 were not in place, and purging of the unwanted gases and vapours from within the housing is made more efficient and more effective than might otherwise have been the case.

Figure 2 shows a modification of the invention as applied to a housing 36 of a multi-layer centrifugal evaporator. Here the housing can accommodate three parallel and vertically spaced apart rotatable sample supports (not shown) and access to the latter is obtained by opening a door 38 hinged at 40 to the main housing 36 so as to occupy the fully open position as shown in Figure 2. The door is shown partly cut away to allow the ducting and other members of the purging line to be seen.

The opening exposed by hinging the door 38 into the position shown would normally allow access to, and visibility of, all three sample supports.

However, in accordance with one of the features of the invention, the larger opening is in fact substantially closed off by three internal hinged flaps 42, 44 and 46. When the three flaps are shut, as shown, the opening is largely (if not fully) closed and the action of the suction device 32 (described in relation to Figure 1) is to withdraw air, gases and vapours from within the housing 36 and convey them to the filter unit 28 via valve 30 and duct 26. By largely obscuring the opening exposed by the opening of the door 38, the speed of any air entering the housing 36 around the edges of the flaps 42, 44 and 46 will be very high, so that fumes from inside the housing are prevented from passing through the opening and a scavenging effect will be produced, causing any such air entering the housing to purge the interior of any gases or vapours therein and to be conveyed into the duct 26 towards the filter unit 28.

In order to give access to one or the other of the three parallel sample supports within the housing 36, any one of the flaps 42, 44, 46 can be opened by hinging it about its right hand edge, and this gives access whilst still restricting the area of the opening to one third of what would otherwise be exposed without the presence of the other two flaps. A high rate of ingress of air into the container is thus maintained which tends to prevent toxic gases or vapours from exiting and coming into contact with an operator who is checking, removing or replacing samples.

As with Figure 1 , there is provided a remote control means of a mechanical or equivalent type (not shown) for opening and closing of the door 38. However, since here the main risk to an operator is in opening of the chamber after evaporation has taken place, it may only be necessary for the control means to effect initial opening and final closing of the door, as the remainder of the opening and closing can usually safely be done manually by the operator.

Claims

1. A method of limiting the discharge of fumes through an entrance of a chamber forming part of a centrifugal evaporator, comprising the steps of withdrawing air from the interior of the chamber and simultaneously or shortly thereafter moving a closure member away from the entrance, the air being withdrawn through a port in the chamber which is displaced from the entrance so as to set up an air stream whereby the fumes resident within the chamber are caught up into the air stream and drawn out of the chamber away from said entrance.

2. A method according to claim 1, in which the closure member is moved to only partially expose the entrance, so as to reduce the open area through which air is drawn into the chamber, thereby increasing the air speed and improving the efficiency with which undesirable fumes in the chamber are prevented from emerging through the entrance.

3. A method according to claim 1 or claim 2 further comprising the steps of passing the air stream through a filtering unit, collecting and retaining the separated fume components from the air stream, and returning the purified air stream to atmosphere.

4. A centrifugal evaporator comprising a chamber having an entrance, a closure member for closing the entrance, a port in the chamber displaced from the entrance, and extraction means for drawing an air stream through the port, whereby fumes resident in the chamber are entrained in the air stream and drawn away from the entrance.

5. An evaporator according to claim 4. in which the extraction means comprises a fan or a suction pump connected to the port by a duct.

6. An evaporator according to claim 4 or claim 5 further comprising a filtering unit for separating fume components from the air stream.

7. An evaporator according to any one of claims 4 to 6 further comprising a plurality of rotatable sample supports mounted one above the other, motor means for rotating the sample supports about a common axis as a single unit, an entrance in the wall of the chamber which is closeable and sealable by means of a closure member, such as a hinged door, an internal door for each sample support, each internal door being arranged to close off a respective part of the overall opening, such that each support member is accessed through an aperture which is created by opening the respective internal door.

8. A centrifugal evaporator comprising a chamber within which a plurality of rotatable sample supports are mounted one above the other, motor means for rotating the sample supports about a common axis a single unit, an entrance in the wall of the chamber which is closeable and sealable by means of a closure member, such as a hinged door, an internal door for each sample support, each internal door being arranged to close off a respective part of the overall opening, such that each support member is accessed through an aperture which is created by opening the respective internal door.

9. An evaporator according to claim 7 or claim 8 and further comprising a remote control means for at least opening the closure means.

10. An evaporator according to any one of claims 4 to 9,further comprising a fume hood surrounding at least the chamber, so that it can be opened whilst still in the closed fume hood enclosing the evaporator.

11. A centrifugal evaporator comprising a chamber having a loading/unloading entrance which is sealable during evaporation by a closure member, drive means for moving the closure means to open or close the entrance, and a remote control device for controlling the operation of the drive means to allow an operator to at least open the chamber remotely.

12. An evaporator according to claim 11 , further comprising a fume hood surrounding at least the chamber, so that it can be opened whilst still in the closed fume hood.

13. An evaporator according to claim 11 or claim 12 further comprising means for drawing air out of the chamber at the position remote from the entrance when open, enabling a large volume of air to be drawn into the chamber with a low pressure drop.

14. An evaporator according to any one of claims 11 to 13, in which the closure member comprises a hinged door or lid, a sliding door or panel or a pivoting flap.

15. An evaporator according to any one of claims 11 to 14, in which the drive means comprises an electric motor, a pneumatic or hydraulic drive, or a stored energy device such as a spring or gravitational device incorporating a weight, which when released moves the closure member so as to expose the opening.

16. An evaporator according to any one of claims 11 to 15, in which the remote control device is actuated by an operator and comprises a hand-held unit which is attached to the chamber by an electric cable, a pipe, or a mechanical linkage such as a Bowden cable.

17. An evaporator according to any one of claims 11 to 15, in which the remote control device comprises a radio, infrared, or acoustic transmitter/receiver arrangement.

18. A centrifugal evaporator comprising a chamber having a loading/unloading entrance which is sealable during evaporation by a closure member, and a remote control device for moving the closure member between a position in which the chamber is sealed and a position in which the entrance is open.

19. A centrifugal evaporator comprising a chamber having a loading/unloading entrance which is sealable during evaporation by a closure member, a remote control device adapted to move the closure member directly in one direction to close the entrance and in the other direction to open the entrance to allow an operator to both close and open the closure member remote from the evaporator chamber.

20. An evaporator according to claim 19, in which the remote control device is a Bowden cable, with a lever or rotatable member attached to a housing at the remote end of the cable, movement of which is transmitted via the inner core of the cable to the closure means so as to effect movement of closure to close or open the entrance.

21. An evaporator according to claim 19, in which the closure member is operated by a solenoid, an electric motor, pneumatic drive or hydraulic drive, the remote control device comprising means for controlling the supply of electric current, pneumatic fluid such as air, or hydraulic fluid such as oil, to the drive means associated with the closure means, for causing the drive means to move the closure means in one direction or the other as required.

22. A method of sealing and unsealing a chamber forming a housing of a centrifugal evaporator comprising the steps of closing an entrance by a closure member, latching or otherwise securing the closure member in place, and from a remote location releasing the latch or other closure securing device after the evaporation process has been completed.

23. A method of opening and closing a sealed chamber forming a housing of a centrifugal evaporator, wherein a closure member is provided for covering or otherwise entrance an opening to effect sealing of the chamber, and drive means for moving the closure member into and out of the sealing position, comprises the steps of actuating the drive means after the chamber has been loaded with samples, to move the closure member into the sealed position, leaving the closure member in the sealed position while the centrifugal evaporation process is being performed, and after the process has been completed transmitting a signal from a remote location to the drive means to move the closure member so as to leave the entrance unobstructed and allow samples to be removed.

24. A method according to claim 23, in which the signal is transmitted to the drive means as a mechanical signal, a pneumatic or hydraulic signal, an electric current, or a signal transmitted by a radio, acoustic or infrared link.

25. An apparatus or a method as claimed in any one of claims 18 to 24, in which an interlock or disabling device is provided to prevent the closure member from being opened until an evaporation process has been completed, and/or the rotating assembly within the chamber has come to rest.

26. A method of limiting the discharge of fumes through an entrance in a chamber forming part of a centrifugal evaporator, substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

27. A centrifugal evaporator substantially as herein described with reference to, and as illustrated in, the accompanying drawings.