GB2112129A - Fume cupboard - Google Patents

Abstract

A transparent workfront screen of a fume cupboard comprises three horizontally slidable vertical panels 10, 11, 12 which are separable from each other to provide access to the cupboard interior. The panels 10, 11, 12 may be locked in position relative to each other, e.g. by means of rigid connection member 21, to provide apertures 17 for the arms of an operator carrying out an experiment in the cupboard. The side panels 10 and 12 may be made of flexible material and mounted so that rollers 24, 25 at each side of the workfront take up the flexible material of the respective side panels, so that all panels move in unison when an operator with his arms in apertures 17 moves them from side to side. <IMAGE>

Description

SPECIFICATION Fume cupboard This invention relates to a fume cupboard, in particular a protective workfront screen in a fume cupboard.

Fume cupboards are of course well known in chemical and other scientific laboratories. They are conventionally provided with an adjustable air exhaust system and with a workfront screen in the form of a glass sash window which may be raised or lowered as occasion and safety precautions demand to permit access to the interior of the cupboard. When such a fume cupboard is in use, it is customary practice to leave an aperture, e.g. of about 45 cm., between the bottom of the window and the lower edge of the front of the fume cupboard in order that an operator working at the cupboard may have work access while hazardous or toxic substances are being boiled or otherwise treated within. Moreover, it is mandatory that whatever size the aforesaid aperture is there must be an inflow of air of at least 1 00ft/min.

(30.5m/min, 0.51 m/sec). In fact, 1 20ft/min.

(31 .0m/min, 0.52m/sec) is usual.

There are two unsatisfactory aspects of such an arrangement of fume cupboard workfront. Firstly, an operator's body is only partially protected if explosion or implosion should occur and disseminate hazardous substances. Secondly, the amount of warm laboratory air which is being continually exhausted to the outside atmosphere while the fume cupboard is in use involves a considerable heat loss. For example, a 1 85 m wide fume cupboard with a 45 cm aperture can exhaust about 500 GJ of energy per year.

An object of the present invention is to provide a fume cupboard with a protective workfront screen which enhances safety for operators and also decreases the amount and cost of heat lost through the cupboard.

With this object in view, the invention provides a fume cupboard including an exhaust sytem and a transparent, movable workfront screen characterised in that the workfront screen comprises a plurality of horizontally slidable, vertical panels which are separable from each other to provide one or more vertical apertures which permit access to the interior of the fume cupboard.

Preferably, the panels are shatter-proof and three in number. Also these panels are preferably all in the same plane, with the central panel formed of rigid material and the two side panels formed substantially of flexible material.

It is an advantage if the vertical edges of the panels are either rounded and/or curved inwardly to the cupboard interior.

The panels are conveniently suspended by runners from a track above the workfront of the fume cupboard and their lower ends are conveniently guided in a slot along the bottom of said workfront.

Preferably, the panels are capable of being locked in position relative to one another and thereby of being moved sideways in unison with each other. In a practical embodiment, this is achieved in that the flexible panels are connected by a rigid member from which the central panel may be suspended.

It is also convenient if vertical rollers and/or pulley assemblies are provided at each side of the workfront to take up the flexible material of the respective side panels when they are pushed and slide towards the respective sides of the workfront.

The workfront screen proposed by the present invention may be provided either in place of or as well as conventional, vertically-moving sash window. When the conventional window is retained it may be positioned either inside or outside the proposed workfront screen, as considered necessary, depending on the type of work being carried out in the fume cupboard.

A further preferred feature of the workfront screen according to the present invention is that, in order to promote safe working practice, gas and power should only become available in the fume cupboard when the panels are appropriately positioned.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a front view of a preferred embodiment of the fume cupboard of the present invention; Fig. 2 is a cross section on the line 2-2 of Fig.

1;and Fig. 3 is an enlarged fragmentary front view of the same embodiment of the fume cupboard of the invention illustrating means by which the panels are fixed in position relative to one another.

As shown in Figs. 1 and 2 of the drawings, a preferred embodiment of the fume cupboard of the present invention includes an exhaust duct 30 and a workfront screen comprising three vertical panels 10, 11, 12 all aligned in the same plane and extending the entire height of the cupboard workfront. These panels 10, 11, 12 are suspended from a track 14 mounted above the workfront behind an upper pelmet 20 (Fig. 1). The lower ends of all the panels 10, 11, 12 are loosely guided in a slot 1 5 along the bottom of said workfront, above a conventional lower air entry 16.

The central panel 11 is formed of rigid, transparent shatter-proof material and its vertical edges are curved inwardly towards the interior of the cupboard. At each side of the central panel 11, which is of the order of 30 cm wide and the full height of the cupboard workfront. Beyond each arm aperture 1 7 lies a side panel, 10, 12 respectively, each comprising an inwardly curving rigid edge strip 1 8 attached along its outer edge to a sheet 1 9 of flexible, transparent plastics material which also extends in a vertical plane from top to bottom of the cupboard workfront. As indicated in Fig. 3, the upper edge of the flexible sheets 19 are suspended by runners 1 3 from the track 14 located behind the pelmet 20.The panels 10 and 12 may be locked in position relative to one another by means of a rigid member in the form of a narrow rod 21 having a hook at each end. These hooks are slotted into respective holes 22 in the tops of the respective edge strips 1 8 of said panels 10 and 12. As shown, the central panel 11 has an overturned upper edge 23 which is hooked over the rod 21 so as firmly to secure the panel 11 in a desired position along the rod 21 between panels 1 0, 1 2. As previously mentioned, arm entry apertures 1 7 remain between the central panel 11 - and the respective side panels 1 0, 12.

At each side of the fume cupboard workfront, the sheet 1 9 of respective side panels 10, 12 passes around a respective roller 24, 25, recessed in a respective double-side space 26,27 of the fume cupboard. Each flexible sheet 19 terminates in a rigid connection piece (not shown) which in turn is connected by respective plastics cords 28, 29 (Fig. 2) which pass over respective pairs of pulleys 31,32 at the top and bottom of the respective spaces 26, 27 to respective balance weights 33, 34. The balance weights 33, 34 move vertically up and down whever the side panels 10, 1 2 are moved horizontally and, at the same time, maintain a suitable tension on the flexible sheets 19 so that they remain substantially flat at the front of the fume cupboard.

A cleaning roller 35 is positioned adjacent each roller 24, 25 and is rotated in the opposite direction to the movement of the respective flexible plastics sheet 1 9 in order to clean said sheet 1 9. The surface of each cleaning roller 35 is formed of soft fabric and is easily replaceable, being removably secured in position by contact adhesive or the like.

Control knobs 36 are located adjacent the sides of the fume cupboard, as shown in Fig. 1. They permit control of the supply of gases, power, water etc., to the interior of the cupboard via inlets 37 indicated in Fig. 2 and other inlets which are not shown.

Use of the fume cupboard of the present invention, in particular the protective workfront screen, formed by the three panels 1 0, 11, 12 will readily be appreciated from the foregoing description.

Firstly, when an operator wishes to conduct an experiment in the interior of the fume cupboard, all apparatus necessary for the experiment is assembled within the cupboard. In order to allow the passage of equipment into or out of the cupboard, one of the side panels 10, 12 may be released from the rod 21 and slid along the track 14 completely to the left or right side respectively of the cupboard workfront. The central panel 11 in register with the other panel 10 or 1 2 may also be slid to the left or right as appropriate. When necessary to permit large items of equipment to ,be installed in or removed from the cupboard, both side panels 1 0, 1 2 may be released from the rod 21 and the central panel 11 lifted out completely.

Before the experiment begins the side panels 10, 12 should be locked in position by the rod 21 and the central panel 11 should be hooked back in position, such that an arm entry aperture 17, approximately 1 5 cm wide, remains between each respective side panel 10, 1 2 and the central panel 11. The operator is then able to insert his arms through the apertures 17, actuate the exhaust system and manipulate the equipment to commence and carry out the experiment involving hazardous substances while himself remaining in comparative safety, protected by the rigid, shatter proof panel 11. The flexible side panels 10, 12 supplement the protection e.g. in the event of an explosion of other accident, afforded by the central panel while also contributing significantly to preventing escape of noxious gases etc., from the cupboard.Moreover the inwardly curving edge strips 18 and the inwardly curving edges of the central panel 11 facilitate the inflow of air rather than the outflow of dangerous gases and are also more comfortable for the operator against whose arms they abut.

As the operator manipulates the equipment during the course of the experiment, he may move his arms to left and right and the panels 10, 11, 12 will also move in unison along the track 14 and his arms push against them.

Consider, for example, with reference to Fig. 2, the situation when the operator moves his arms to the right. The operator's right arm pushes the rigid edge strip 18 of the side panel 12 to the right, thus slackening the attached flexible plastics sheet 19. The balance weight 34 immediately falls lower to maintain the tension of the said sheet 19 and of the associated cords 29 and thus pulls the sheet 19 around the roller 25. The cleaning roller 35 adjacent roller 25 moves in the opposite direction to the sheet 1 9 to clean and minimise scratching of said sheet 1 9 and prevent excessive soiling of the roller 25. As the three panels 10, 11, 12 are all locked in respective positions relative to each other, movement of panel 1 2 necessarily causes corresponding movement of panels 11 and 10.

When the fume cupboard is not in use, or when it is in use but operator access to the interior is not required, the arm apertures 1 7 may be closed up by removing the central panel 11 and the rod 21 and bringing the inwardly curved edges of the panels 1 0, 1 2 into contact with each other. The panels 10, 1 2 can then be locked together by means of a small rod which is just long enough to hook into the holes 22 when the rigid edge strips 1 8 of the panels 1 0, 1 2 adjoin. Alternatively, the arm apertures may be closed up with the central panel 11 left in place. This is achieved by using, in place of the rod 21, another rod of length such that its hooks just protrude from the inwardly curved edges of the central panel 11. Panels 10, 12 are pulled towards the centre of the workfront until their respective edge strips 1 8 abut the central panel 11, whereupon they are locked in place by the hooks of the aforesaid rod.

While fully retaining the necessary feature of access to the interior of a fume cupboard during an experiment by means of vertical apertures between slidable panels 10, 11, 12, provision of a central, rigid, shatter-proof panel 11 in the present invention ensures greater safety of the operator than in any fume cupboard arrangement hitherto proposed. Furthermore, the surface area of the arm apertures 17 is less than the areas of apertures in previous fume cupboard protective screens so that the cost of the heat loss through the air exhausted from the cupboard is considerably reduced compared to known fume cupboards.

The scope of the invention is not limited to the foregoing details and variations may be made thereto. For example, details of the upper suspension means, the means by which the panels are locked in position relative to one another, and the lower guide means may vary, the dimensions of the fume cupboard, panels and apertures may vary and the vertical rigid edges of panels may simply be rounded instead of curving inwardly. In particular, in certain circumstances, the lower edge of the workfront need not be siotted or alternatively a narrower slot than that desired above may be provided to accommodate the straight portions of the panels in a case when the curved edges of the panels terminate above such a slot.Any suitable rigid or flexible transparent material may be used for the panels and the tensioning means for the flexible sheets of the side panels may be different from that described.

As mentioned above, the workfront screen formed by the panels may be used instead of or as well as a conventional sash window. Alternatively, only an upper rigid section of a conventional sash window may be present while the usual lower movable portion is not provided. Also, it may be arranged such that gas and power only become available in the fume cupboard when the panels are located in predetermined positions. For example, correct location of the central rigid panel with respect to the side panels or the correction rod might complete a low voltage circuit which, via soienoid valves and relay switches actuated the supply of gas and power to their respective fume cupboard inlets.

Claims (14)

1. A fume cupboard including an exhaust system and a transparent, movable workfront screen characterised in that the workfront screen comprises a plurality of horizontally slidable, vertical panels which are separable from each other to provide one or more vertical apertures which permit access to the interior of the fume cupboard.

2. A fume cupboard as claimed in claim 1 wherein the panels are all in the same plane.

3. A fume cupboard as claimed in claim 1 or 2 wherein the panels are shatterproof and three in number.

4. A fume cupboard as claimed in claim 3 wherein the central panel is formed of a rigid material and the two side panels are formed substantially of flexible material.

5. A fume cupboard as claimed in any preceding claim wherein the vertical edges of the panel are rounded.

6. A fume cupboard as claimed in any preceding claim wherein the vertical edges of the panels curve inwardly to the fume cupboard interior.

7. A fume cupboard as claimed in any preceding claim wherein the flexible side panels are suspended from runners mounted on a track above the workfront and their lower ends are guided in a slot along the bottom of said workfront.

8. A fume cupboard as claimed in any preceding claim wherein the panels are capable of being locked together in position relative to one another and thereby of being moved sideways kn unison with each other.

9. A fume cupboard as claimed in any preceding claim wherein the flexible panels are connected by a rigid member from which the central panel may be suspended.

10. A fume cupboard as claimed in any preceding claim wherein vertical rollers are provided at each side of the workfront to take up flexible material of the respective side panels when they are pushed and slide towards the respective sides of the workfront.

11. A fume cupboard as claimed in any preceding claims wherein pulley assemblies are provided to aid the movement of the respective side panels when they are pushed and slide towards the respective sides of the workfront.

12. A fume cupboard as claimed in any preceding claim wherein the workfront screen also includes a conventional vertically-moving sash window.

13. A fume cupboard as claimed in any preceding claim wherein gas and power are only available when the panels are appropriately positioned.

14. A fume cupboard substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.