Title:
MOVABLE-APRON HOOD, NOTABLY FOR LABORATORIES
United States Patent 3593646
Abstract:
A hood, notably of the type adapted to be associated with the working surface of a laboratory table for protecting the operators against the deleterious fumes developed, and the gaseous noxious products handled, during manipulations carried out on said surface, which comprises a movable apron suspended at its upper and rear portion from two points located each on a separate endless transmission and support line passing over rotary driving and guide members, each transmission and support line being provided with a balance counterweight, said line and members being part of the apron hoisting system.
Application Number:
04/830372
Publication Date:
07/20/1971
Assignee:
Teclab (Rueil-Malmaison, FR)
International Classes:
B08B15/02; B08B15/00; (IPC1-7): F23J11/00
Field of Search:
160/37,222 98
Primary Examiner:
Perlin, Meyer
Claims:
I claim
1. A hood particularly of the type associated with the working surface of a laboratory table for protecting the operators against the deleterious fumes developed, and the gaseous noxious products handled, during manipulations carried out on said surface, comprising rotary driving and support means, separate and endless transmission and support lines passing over said driving and support members, a movable apron suspended at its upper end rear portion from two points located each on a separate endless transmission and support line passing over said rotary driving and guide members, a balance counterweight on each transmission and support line, a horizontal shaft, said rotary driving and guide members being interconnected in pairs by said horizontal shaft, said lines and members comprising the apron hoisting system.
2. A hood as set forth in claim 1, wherein said apron is secured to its hoisting system by means permitting the tilting of said apron about its mounting points in case of deflagration occurring in the hood space.
3. A hood as set forth in claim 2, wherein said means permitting the tilting of said apron about each mounting point consists of a tubular member rigidly secured to the rear vertical plate of the apron and receiving therein a stub shaft trunnioned in a strap rigid with the corresponding endless transmission and support line of the hoisting system.
4. A hood as set forth in claim 1 wherein a plurality of movable aprons are provided each suspended at its upper and rear portion from two points located each on a separate endless transmission and support line passing over said rotary driving and guide members.
5. A hood as set forth in claim 4, wherein said aprons are secured to their hoisting systems by means permitting the tilting of said aprons about their mounting points in case of deflagration occuring in the hood space.
6. A hood as set forth in claim 5, wherein said means permitting the tilting of said aprons about each mounting point consist essentially of a tubular member rigidly secured to the rear vertical plate of the apron concerned and receiving therein a stub shaft trunnioned in a strap rigid with the corresponding endless transmission and support line of the hoisting system.
7. A hood as set forth in claim 4, wherein said endless transmission and support lines of the hoisting system are equipped with means such as springs for taking up any play developing during the hood operation.
8. A hood as set forth in claim 4, wherein each apron set of endless transmission and support lines is enclosed in a casing disposed at the rear portion of the hood, outside the enclosure proper thereof, in order to protect the component element of the apron hoisting system from the internal hood atmosphere.
9. A hood as set forth in claim 8, wherein the aprons are held in a proper position by rollers bearing against the casings enclosing the apron hoisting system.
10. A hood as set forth in claim 4, wherein said rollers are disposed some at the lower portion of each apron and bear against the outer face of the relevant casing, and others on the strap solid with the endless transmission line on which each apron is pivotally mounted, said last-named rollers engaging the inner surface of said casing.
11. A hood as set forth in claim 1, wherein said endless transmission and support line of the hoisting system is equipped with means such as springs for taking up any play developing during the hood operation.
12. A hood as set forth in claim 1 wherein said transmission and support lines consist of endless chains each attached to a separate apron and said means consist of sprockets wedged to a common shaft, pitch circles of said sprockets differing from one sprocket to another in order to ensure a differential hoisting of the relevant aprons when one or the other of said sprockets is driven, the ratio of the pitch circles of said sprockets being selected as a function of the desired proportion of the relative movements to be performed by the aprons associated therewith.
13. A hood as set forth in claim 1, wherein each of said endless transmission and support lines comprise a chain and said driving and guide members comprise chain sprockets.
14. A hood as set forth in claim 1, wherein each of said endless transmission and support lines comprises an endless belt and said driving and guide members therefore comprise pulleys.
15. A hood as set forth in claim 1, wherein said endless transmission and support lines of each apron is enclosed in a casing disposed at the rear portion of the hood, outside the enclosure proper thereof, in order to protect the component elements of said apron hoisting system from the internal hood atmosphere.
16. A hood as set forth in claim 15, wherein the apron is held in a proper position by rollers bearing against the casing enclosing the apron hoisting system.
17. A hood as set forth in claim 16, wherein said rollers are disposed some at the lower portion of the apron and bear against the outer face of the relevant casing, and others on the strap solid with the endless transmission line on which said apron is pivotally mounted, said last-named rollers engaging the inner surface of said casing.
Description:
The present invention relates to improvements in or relating to hoods, and more particularly to laboratory hoods of the fume-cupboard or fume-chamber type equipping laboratory tables.
These hoods comprise as a rule a movable apron adapted to be set at different heights in relation to the working surface of the laboratory table, or even lowered to the table level when an operation or manipulation in a closed chamber is to be performed. These movable aprons are secured in general to the hood by various hoisting systems comprising ropes provided with balance-weights and passing over one or several grooved pulleys disposed at any suitable location on the hood structure. These systems, whatever their design, are attended in all cases by one or more inconveniences.
In fact, some of these known systems are so located and/or disposed that some of their component elements, for example the ropes connecting the apron to the balance-weights, are exposed to the atmosphere, mostly of noxious nature, developing inside the hood. Other systems although free of this inconvenience are nevertheless objectionable in that they reduce to far from negligible proportions the vertical dimension of the useful volume available for handling purposes in the hood. In any case, all these systems are attended by frequently delicate mounting problems concerning the necessary balance.
It is the essential object of this invention to provide an improved hood construction whereby the various inconveniences characterizing hitherto known systems are completely eliminated.
According to a specific feature characterizing this invention the or each movable apron equipping the hood is suspended at its upper and rear portion from two points each located on endless chain, belt or the like passing over sprockets pinions, pulleys, rollers or equivalent means, at least one of said chains or belts being provided with a balance counterweight.
According to another feature characterizing this invention, each chain, belt or like means aforesaid is mounted within a suitable shaped casing disposed at the rear of the hood, outside the enclosure proper thereof, so as to protect the various component elements of the apron hoisting apparatus against any deleterious atmosphere likely to prevail in the hood.
According to a further feature characterizing this invention, the apron is secured to its hoisting system by means permitting the tilting of said apron about said two fastening or mounting points thereof in case of deflagration explosion or like accident taking place within the hood.
According to still another feature of this invention, in the case of a plurality of movable aprons the means provided for driving each apron are so coupled or operatively interconnected and so arranged that the relative movements of the aprons can be obtained according to any desired proportion by effecting a single control movement.
These various features and advantages of the invention will appear as the following description proceeds with reference to the attached drawing illustrating diagrammatically by way of example a few typical forms of embodiment of the invention, it being understood that these are given by way of illustration only and that various modifications may be brought to the shapes, proportions and relative arrangement of its component elements without departing from the spirit and scope of the invention as set forth in the appended claims. In the drawing:
FIG. 1 is a side-elevational and vertical section showing a hood construction according to a first form of embodiment;
FIG. 2 is a side elevational view taken from the side opposite to that of FIG. 1;
FIG. 3 is a side-elevational and vertical section showing the same form of embodiment of the hood construction of this invention;
FIGS. 4 and 5 are front elevational views thereof, and
FIG. 6 is a plane view from above showing a modified form of embodiment of the invention in the case of a fume-cupboard comprising a single movable apron;
FIG. 7 is a sectional view showing the mounting of the movable apron on its driving means, in this case chain means;
FIG. 8 is a side-elevational and vertical section showing a fume-cupboard comprising two movable aprons, and
FIG. 9 is a plane view from above showing the "differential" type single-control system for driving both movable aprons.
The movable apron 10 of the hood is carried by a lever system consisting, according to this invention and in the example illustrated, of two parallel endless chains such as 11; each chain is disposed symmetrically in relation to the vertical median plane of the hood and pass over sprockets 12, 12a, one at least of said chains comprising a balance counterweight 13. Each one of the assemblies thus obtained is housed in a casing 14 (see notably FIGS. 6 and 9) consisting for example of a section element of adequate contour, open towards the front of the hood.
One or both chains advantageously comprise a spring 15 adapted to take up any play developing therein after a certain service period. The registering pairs of sprockets 12, 12a lying in a common horizontal plane are interconnected by a cross bar 16 (FIG. 4) in order to impart a perfect symmetry to the operation of the system.
The movable apron (or aprons) is secured to the chains of the hoisting system by its rear upper portion as follows (see FIGS. 7 and 9): Secured to the apron is a member comprising a tube 17 projecting from the apron and receiving therein a shaft 18 screwed or otherwise secured to the bore of said tube, said shaft 18 being pivoted by means of a pin 19 to a strap 20 secured to the chain 11.
The arrangements contemplated according to this invention are characterized by several advantages.
Thus, they are such that all the component elements of the hoisting system provided for driving the movable apron are practically protected from the noxious atmosphere developing or prevailing within the hood. Moreover, the internal space of this hood is completely free in the vertical plane, thus affording a complete visibility and permitting the use of instruments and equipments of relatively large vertical dimensions. Moreover, no difficulty is experienced when balancing the movable apron during the assembling of the hood, the operation of the hoisting system being, by its very conception, particularly regular and flexible. Finally, the mounting of the movable apron on its hoisting system permits a free movement of the apron with respect to the fixed portion of the hood by tilting said apron about its pivot points so that in case of accidental combustion, deflagration or explosion produced within the hood the apron can take a position (as shown in FIG. 2) permitting the escape of the gaseous products suddenly emitted under conditions and in a direction ensuring a maximum reduction of the dangerous consequence of this combustion, deflagration or explosion.
To maintain the apron in its proper position in relation to its hoisting system, there is provided according to this invention, at the lower portion of the apron, at least one roller 21 carried by an angle member 22 rigid with the apron, said roller 21 engaging the wings of casing 14. Moreover, the strap 20 carries externally another roller 23 engaging the inner edge of the wings of casing 14. Thus, any tendency of the movable apron, due to its mounting on the hoisting system, to steeve up- and downwards in two opposite direction, is safely prevented.
FIGS. 8 and 9 relate more particularly to a specific form of embodiment of the invention which is applicable to a fume-cupboard comprising two superposed movable aprons 24 and 25.
The apron hoisting system and the means contemplated for securing the aprons thereto is the same as the one described hereinabove but according to this invention there is provided a modified sprocket arrangement for the chains of each system, in order to provide a "differential" system permitting, by acting only upon the lower apron, of producing the relative movement of the two aprons to a predetermined extent.
FIG. 9 illustrates by way of example a typical arrangement of this character. On a common shaft 26 trunnioned in bearings 26a carried by the casing 14 are wedged sprockets such as 27 over which the chains are passed, for example chain 28 for hoisting the upper apron, and sprockets such as 29 over which other chains, such as 30, for hoisting the lower apron 24, are passed. These sprockets 27 and 29 have different pitch circles such that the relative movements of the two aprons will take place according to a predetermined proportion.
The fume-cupboard may be equipped with a ventilation device according to this invention, of which a typical form of embodiment is illustrated in FIG. 3 by way of example.
This device comprises a fan 31 mounted beneath the table 32 comprising a working surface 33. This fan is adapted, through a ventilation chamber 34 communicating through ports 35 with the manipulation chamber or enclosure of the fume-cupboard or hood, to suck the air introduced into said chamber or enclosure through the upper part thereof, namely through the space left free between the movable apron 10 and the stationary apron, and through orifices such as 36 provided in the top plate 37. Thus, a rational supply of air to the working surface is obtained without the detrimental "scavenging" effect to which this working surface is currently submitted by the lateral introduction of local or room air at the level of the working surface. The used air loaded with residues from the handling operations performed on said working surface is forced by the fan 31 into an exhaust chamber 38 from which it is expelled to the outside through adequate means (not shown).
The partition separating said ventilation chamber from the manipulation chamber may be provided with inertia means for separating the particles carried by the air stream, as described in my U.S. Pat. No. 3,358,579 granted Dec. 19, 1967.
Of course, many modifications and variations may be brought to the various forms of embodiment shown, described and suggested herein, without inasmuch departing from the basic principles thereof. Thus, the chains of the hoisting system may be replaced by belts, tapes, etc. passing over suitably shaped grooved pulleys, or even on shafts having a common axis but different diameters, in order to produce a differential hoisting of the aprons, in case the hood comprised a plurality of movable aprons.
Finally, it will be readily understood by anybody conversant with the art that this invention is applicable not only to laboratory fume-cupboards and chambers, but also to any types of hoods comprising a movable apron or several movable aprons.