Ventilation – Workstation ventilator – Covered workbench chamber
Patent
1992-03-30
1994-05-17
Joyce, Harold
Ventilation
Workstation ventilator
Covered workbench chamber
454190, 454191, F24F 900
Patent
active
053122941
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method and device for maintaining a clean atmosphere at controlled temperature at a workstation, accessible from a contaminated room.
The problem of maintaining a clean atmosphere at a workstation arises for example, in the agri-foodstuffs industry.
For packaging products (for example: bottling, packing of cooked dishes in vinyl, . . . ), it is necessary to work in a very clean atmosphere: the maximum acceptable concentrations of particulate and microbiological contaminants, fixed by regulations, must not be exceeded.
Moreover, to avoid the proliferation of microorganisms, the work is normally conducted in a cold atmosphere.
Therefore, the workstations should be isolated from:
particulate, microbiological and gas pollution,
heat transfers, while leaving a free access thereof to the operators.
Heretofore, operators have been working in so-called "white rooms". All the air in these rooms is treated so as to bring the concentrations in contaminants to below acceptable thresholds. Also, the temperature of the air in such rooms is controlled. The required ventilation system is important and especially costly. The working conditions are also unpleasant for the staff, and in particular the temperature conditions.
To prevent such disadvantages, the Applicant has sought to isolate workstations from the air in the room where the operators are; the air in that room no longer requiring the "white room" treatment.
Already, in the nuclear field, it is known to confine the pollution of a room by using a curtain of air (French Patent Application 82/12382 published under No. 2 530 163).
According to this technique, a contaminated zone is isolated from the outside (clean zone) by placing on the opening of the room two air-injecting nozzles creating two air jets:
a first jet situated on the contaminated zone side; this jet comprises a potential flowing zone (inner cone) whose range is at least equal to one of the dimensions of the opening; the jet spreading also over the entire other dimension in order to cover the opening; which implies an injection nozzle of great width; (this first jet constitutes the confinement barrier);
a second jet situated on the clean zone side (outside), which is parallel and has the same direction as the first jet, and such that the air flowrate induced by its inner face in contact with the first jet is equal to the flowrate of said first jet (this second jet stabilizes the first).
In the present description:
slow jet will designate the first jet;
fast jet, the second jet;
inner cone, the potential flowing zone;
width, the dimension (of the opening or of the jets) parallel to the flowing direction of the curtain;
length the dimension (of the opening or of the jets) perpendicular to the flowing direction of the curtain.
This technique makes it possible to isolate a room from pollution and to prevent heat transfers, but it must be adapted so as to give the operator access to a workstation situated inside such room.
Thus, the present invention provides a method and device which improve the object of French Patent Application No. 82/12382 (published under No. 2 530 163) for maintaining a clean atmosphere at a workstation (internal), although the curtain of air is traversed by an obstacle (such as for example, the operator situated outside thereof).
The invention is not limited to air atmospheres in which men work; it can be applied to any gaseous atmosphere, since the work can be done by robot, remote handling, etc.
More specifically, the invention resides in a method for maintaining a clean atmosphere at controlled temperature at a workstation, said workstation being accessible from a contaminated zone through at least one opening, method in which a curtain of gas is generated at the level of said opening in the form of a slow jet and a fast jet, the slow jet having an inner cone of range at least equal to the width of the opening, the fast jet having a flowrate induced by its internal face in contact with the slow jet equal to the injection flowrate of the slow jet, and th
REFERENCES:
patent: 3771323 (1973-11-01), Simons et al.
patent: 4576613 (1986-03-01), Miline
patent: 5145459 (1992-09-01), Meline et al.
Joyce Harold
Societe Generale Pour les Techniques Nouvelles -SGN-
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