GLOVE BOXESThis invention relates to glove boxes. Glove boxes are containers within which scientific experiments are carried out in which manipulation is necessary, but the materials used are dangerous or must be isolated from a normal atmosphere for other reasons.
Conventional anaerobic glove boxes are based on a design originating in the nuclear industry and are, therefore, heavily made with heavy metal walls and relatively small, thick windows. The equipment for conditioning the atmosphere within the glove box is located outside the housing and, therefore, numerous connections for pipes and cables lead from the outside into the glove box and this leads to difficulties in maintaining a leak-free housing.
It is an object of the present invention to provide a simpler and more efficient glove box for general scientific purposes.
According to one aspect of the present invention there is provided a glove box for carrying out experiments in a controlled atmosphere which comprises a housing which is at least partially transparent and a conditioning unit wholly contained within the housing, said conditioning unit including at least one cartridge for removing water and/or oxygen from the atmosphere and a fan for circulating gas within the housing through the cartridge.
The conditioning unit is preferably free-standing within the housing and the cartridges are demountable and can be removed through the transfer port for recharging outside the housing. A regenerating or recharging unit for use with the cartridges fitted to the conditioning unit may comprise a heating jacket which clamps around the cartridge case and heats the contents by conduction to the required temperature. An electrical heating jacket is generally satisfactory. While the cartridge is being heated to the desired temperature, valves are connected to each end of the cartridge so as to pass the required regenerating gas through the cartridge. Such a gas is typically a mixture of nitrogen and hydrogen.
In general, the conditioning units will consist of two or more cartridges, one of which is a catalyst and the other a molecular sieve. Activated charcoal cartridges may also be employed. Preferably, four cartridges are employed of two different types. By using such an arrangement, the atmosphere in the glove box can be easily maintained at levels of approximately 0.5 ppm and less than 5 ppm of water or less. Because it is necessary only to provide an entry to the glove box housing for a power supply to the conditioning unit, and a safety tube connected to a lute, (such as of paraffin oil), the remainder of the glove box housing can be sealed. It is, therefore, possible to manufacture the housing cheaply from a transparent plastics material which can be moulded, heat-formed and/or glued.An essentially wholly transparent glove box makes it much easier to manipulate materials within the housing, since they can be viewed from all sides while avoiding the need for internal illumination.
Cartridges can be introduced through a transfer port attached to the side of the glove box. Also, materials to be investigated may also be introduced through the transfer port. The transfer port consists of a tube which may also be formed from a transparent plastics material, secured to a plate which is clamped to seal off an opening on one side of the glove box. A particular design of seal has been found very satisfactory which will be described in detail later in this specification.
The internal end of the tube has a door which can be opened internally by inserting the hand into one of the gloves in the glove port and opening the door inwardly.
The external end of the tube is sealed by a second door which opens outwardly. A control unit sits on top of the tube and houses the components for controlling power to the conditioning unit and to the glove box and for nitrogen purging the transfer port.
Further features of the present invention will become clear from the attached drawings, in which:Figure 1 is a perspective view of the glove box in accordance with the invention without the conditioning unit in place,Figure 2 is a perspective view of the conditioning unit whose overall dimensions are such that it can be free-standing within one corner of the glove box,Figure 3 is a plan view of the control unit,Figure 4 is a section through one of the cartridges.
Figure 5 is a plan view of the glove box flange plate,Figure 6 is a section through a flange plate sealing gasket, andFigure 7 is a second perspective view of the glove box in accordance with the invention showing a conditioning unit within the housing.
Referring to the drawings and in particular toFigures 1 and 2, the glove box comprises a rectangular plastics box formed from sheets of acrylic plastics material glued together in sealed manner, the dimensions being approximately 1080 mms long by 650 mms wide, and 775 mms high for a two-port glove box.
Sealed into the front face of the box 1 are a pair of glove ports 2, into which neoprene gloves 3 are sealed at their cuffs. At the rear of the housing 1 is a safety outlet which is connected to a lute (or gas bubbler) 4 filled with paraffin oil. To one side of the glove box is fitted a transfer port 5 consisting of a transparent plastics tube 6 having an internal diameter of about 200 mms, and being sealed to a flange 7 which is itself sealed to a plate 8. Plate 8 is clamped into an aperture 9 in the side of the housing by a large number of thumbscrew clamps.
A control box 11 is mounted on the top of the tube 6.
The length of the tube 6 is selected so that the cartridges of the conditioning unit can be contained within its length. Entry from the transfer tube 6 to the housing 1 is controlled by an interior door 12 which is pivotably mounted on the flange 7, so as to be openable inwardly. An 0-ring seals the door into the internal end of the tube 6. Externally, the tube is fitted with a second door 13 which opens outwardly and closes onto a similar O-ring. At least the external door 13 is provided with an annular chamber in the door seat having generally inwardly radially directed nozzles. The chamber is connected to a nitrogen gas feed so as to flush air from the region of the external door.
The construction of the conditioning unit is shown inFigure 2, from which it will be seen that it comprises four cartridges, usually of two different types 21 and 22, mounted vertically on a platform 23, above a header chamber 24. Mounted below the header chamber 24 is a centrifugal fan 25 which is arranged to blow into the header chamber 24. Fan 25 is mounted on feet 26 to provide a gap so as to allow gas within the glove box to circulate through the fan into the header chamber and thence through the cartridges 21 and 22 to exit at the upper ends of the cartridges, e.g. at 27 and 28. In this way, the atmosphere within the housing 1 is continuously circulated through the cartridges 21 and 22.AlthoughFigure 2 shows the cartridges clamped on the top of the unit with a plate 101 and a bolt 102, this is not essential and the cartridges can be free-standing on the top of the conditioning unit.
The construction of the cartridges is shown in Figure 4. As can be seen, each cartridge comprises an outer tube B, e.g. made from aluminium having a central tie rodC extending axially through the main part of the tube and tapped at each end to receive end cap screws. At each end of the tube a molecular sieve steel mesh I is supported on the tie rod by a circlip J and support washerK. The support mesh is impregnated with or supports catalyst distributed over its surface. Disposable filters A & E are located at the inlet and outlet from the cartridge. Filter A is a particulate filter, e.g. of the type used in respirators and arranged to filter particles down to about 5 to 10 microns. Filter E is an activated charcoal filter and is intended to remove materials such as solvents which might be present in the glove box.
After regeneration of the cartridge as described above, the cartridges are sealed by attaching an end cap 5 to both ends and are then introduced into the glove box through the transfer port. Once in the port the end caps can be removed using the glove ports and assembled into the conditioning unit.
Referring now to Figures 5 and 6, the seal between the side of the glove box and the large flange plate 9 is achieved using a plurality of thumb clamps 10 and a sealing gasket 30. Sealing gasket 30 is formed by taking a neoprene tube 32, inserting a wire 34 into the tube having a diameter to substantially fill the tube, forming the wire into the desired shape and then completing the gasket by gluing the ends of the neoprene tube together.
Such a gasket is thought to be new per se, and provide a gasket which is self-supporting and enables satisfactory seals of large openings to be securely made.
The clamps have a screw stud which is glued at one end into the material of the housing. The end of the stud passes through holes in the flange and a seal is achieved by applying the thumb screw to the end of the studs with the seal 30 between the side of the housing and the flange.
The control unit is shown in Figure 3 and as can be seen the solenoid valves 16 control the flow of gas from a source of nitrogen (not shown) out through the tube 41 to the transfer port.