Gas separation – Combined or convertible – In environmental air enclosure
Reexamination Certificate
2001-06-22
2003-09-30
Smith, Duane (Department: 1724)
Gas separation
Combined or convertible
In environmental air enclosure
C055SDIG001, C055SDIG007, C454S056000, C454S057000, C454S061000, C454S187000
Reexamination Certificate
active
06626971
ABSTRACT:
The invention relates to a method for separating at least two spatial areas and for reducing the transmission of airborne particles between the spatial areas in order to protect persons and/or products from the airborne particles, the person being located at least in part in the first spatial area and the products in the second spatial area, and at least one planar air jet of purified air being used for the separation.
The invention further relates to devices for carrying out the method.
Products within the meaning of this application are all articles, starting products, intermediate products and end products which are in any way handled, filled, tested or modified.
In many industries, for example in the manufacture of pharmaceuticals and electronics components, either the product has to be protected from airborne foreign particles or the persons involved in the operating process have to be protected from airborne product particles. It is also common for both protective functions, for product and persons, to have to be provided.
Such devices (also called safety workbenches depending on their size and design) operating according to the laminar flow principle are known from the prior art, which devices, in order to protect personnel or products, permit only limited access to the product space. This principle is employed, for example, in the HERAsafe® cytostatic safety workbenches according to DIN 12980 and in the LaminAir® workbenches from the company Heraeus Instruments GmbH, Hanau. Filtered air is delivered in the form of a vertical, low-turbulence displacement stream onto the top surface of the workbench and is suctioned off at the base in front of the rear wall of the workbench and at the front behind the front boundary of the workbench. The front has a vertically displaceable protective screen. When the protective screen is fully or partly raised, outside air flows into the workbench through the access port of the workbench, and this air is likewise suctioned off via the suction arrangements on the base. A disadvantage of these devices is that the narrow access into the product space greatly restricts the operator's freedom of movement. Maneuvers requiring greater freedom of movement than these devices permit in the operating state cannot be performed in such devices unless the protective screen is raised above the correct operating position or is completely removed, as a consequence of which the protection of persons and products is no longer ensured to the full extent.
Devices operating according to the laminar flow principle are also known, which devices do not spatially separate the product from the personnel. This principle is employed, for example, in the Dispensing Booths from the company Extract Technology Limited, Huddersfield, England. Purified air is delivered, for example in the form of a vertical, low-turbulence displacement stream, to the top of the booth and is suctioned off at the base area. A disadvantage of these devices is that the product can only be handled well below the head level of the personnel if protection of the personnel from the product is to be guaranteed. A further disadvantage is that the product in these devices is not adequately protected from foreign particles caused by the personnel.
Moreover, devices operating according to the laminar flow principle are known in which only the product is protected, not the operating personnel. This principle is employed, for example, in the horizontal laminar flow workbenches from the company Babcock-BSH, Bad Hersfeld, Germany. Purified air is delivered horizontally behind the product space in the direction of the personnel. A disadvantage of these devices is the total lack of protection of the personnel.
Devices operating according to the support jet principle are also known which protect only the personnel. This principle is employed, for example, in the WIBOjekt® work tables from the company GWE, Hude. The operating personnel pass their hands through a support jet which is delivered via an ejector rail in the front area of the work table and generates a curtain of air between the head level of the operator and the product space. Further support jets can also be directed from the ceiling to the rear area of the work table. In this principle, the suctioning arrangements are located in the rear area of the work table. The air capacity of the support jet is typically 1 to 10 liters per second per meter of booth width. A disadvantage of these devices is the lack of product protection.
Against the background of this prior art, the object of the invention was to develop alternative methods and devices for protecting persons and products from airborne particles, and which methods and devices will not have the disadvantage of significantly restricting the freedom of movement of the operating personnel.
According to the invention, this object is achieved by a method of the type specified in the introduction, in which at least one low-turbulence displacement stream is generated with purified air near the at least one air jet in at least the second spatial area, said at least one displacement stream being directed in essentially the same direction as the at least one air jet.
The subject of the invention is therefore a method for separating at least two spatial areas and for reducing the transmission of airborne particles between the spatial areas in order to protect persons and/or products from the airborne particles, the person being located at least in part in the first spatial area and the products in the second spatial area, and at least one planar air jet of purified air being used for the separation, wherein at least one low-turbulence displacement stream is generated with purified air near the at least one air jet in at least the second spatial area, said at least one displacement stream being directed in essentially the same direction as the at least one air jet.
A “low-turbulence displacement stream” within the meaning of the invention is a stream in which a unidirectional air stream flows over the whole cross section of a defined area with as far as possible a uniform velocity and almost parallel flow lines (laminar flow). This definition is taken from the guidelines of the Verein deutscher Ingeniouje (VDI) No. 2083 of December 1976, which are thus by reference a constituent part of the description.
A further subject of the invention is a device for carrying out this method, having one or more first means for generating one or more planar air jets, with which, in its intended use, at least one space is divided into at least a first spatial area and a second spatial area by means of the planar air jet or by means of each planar air jet, and products being able to be arranged in the second spatial area, the device in the second spatial area having second means for generating a low-turbulence displacement stream.
Particular embodiments or designs are disclosed in the respective subclaims. It is also possible for one or more of the features disclosed in the subclaims, in combination with the features of the main claims, to represent inventive solutions to the object on which the invention is based, and the features can also be combined in any desired way.
In a first preferred embodiment of the method according to the invention, the displacement stream is guided at least partially at a distance of at most 0 to 50 cm from the at least one air jet. A displacement stream with an air velocity of 0.1 to 1.5 m/s, preferably 0.2 to 0.6 m/s, especially preferably 0.3 to 0.45 m/s, is advantageously generated, likewise at least one air jet with an air outlet velocity of 2 to 30 m/s, preferably 3 to 10 m/s, especially preferably 5 to 8 m/s. In a further preferred embodiment, an air jet or a displacement stream is generated with an air outlet capacity of at least 10 li.N. (liters in norm) per second per meter breadth of the air jet transverse to the direction of flow, preferably 10 to 300 li.N., especially preferably 20 to 100 li.N., very especially preferably 40 to 80 li.N. At least the second spatial area can
Eigenherr Ekkehard
Forbert Rainald
Gail Lothar
Connolly Bove & Lodge & Hutz LLP
Pham Minh-Chau T.
Siemens Axiva GmbH & Co. KG
Smith Duane
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