Classifications

• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D7/00—Control of flow
  • G05D7/01—Control of flow without auxiliary power
  • G05D7/0186—Control of flow without auxiliary power without moving parts
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D7/00—Control of flow

Definitions

• the method according to the invention serves to set a specific flow for a specific fluid flowing through a pipe, and the method is characterised by causing the fluid to flow through a porous body having predetermined flow resistance characteristics, and being selected to permit a through-flow in the desired flow interval, and also by setting the specific desired flow by adjusting the fluid pressure drop across the body.
• One embodiment of the method comprises prefabricating various series of porous bodies having fluid through-flow characteristics, carefully predetermined within each series, designed to produce a predetermined flow for a specific fluid and a predetermined fluid pressure differ ⁇ ence above the body.
• the method according to the invention also entails the advantage that many impurities in the fluid can be filtered out by the body. If the body becomes clogged by such impurities, this will result in the flow being re ⁇ stricted which in most applications is an advantage, if any deviation from rated flow appears.
• the method according to the invention also permits the use of one body for each occasion, i.e. the bodies are of disposable nature.
• the various series of bodies can thus be provided with markings corresponding to a certain flow interval.
• the container in which the body is to be placed may be transparent to enable the marking on the body to be inspected after insertion in the container.
• the container is naturally inserted in the pipe through which the fluid is flowing, its two ends suitably being joined to respective parts of the pipe, and a casing tightly sealed to the casing of the body, thus causing the fluid to flow through the body in predetermined manner.
• the method as claimed is also based on the realization that porous bodies having all the properties mentioned above can be produced by sintering a compacted body made from a suitable powder.
• a sintered body of stainless metallic powder is thus suitable and conventional methods of manufacturing such bodies give very slight variations in the flow characteristics for each type of body. It has been found, for instance, that sintered compacted bodies made of powder from stainless billets (e.g. steel or titanium) have predictable properties at compacting- and sintering, which are suitable and conventional for the materials in question. It has thus been found that a standard deviation curve with substantially vertical flanks can be obtained in the bodies, indicating that the charact- eristics in the bodies are extremely similar.
• the bodies do not release any free particles which can be flushed away by the fluid flowing through them.
• the porous bodies may advantageously be shaped as straight cylinders. It is of course desirable for the flow distri ⁇ bution to be constant across the fluid through-flow cross ⁇ ection of the body and it is relatively simple to achieve this by suitably chosen geometry for the body and suitable compacting conditions.
• An apparatus for setting a desired flow for a specific fluid flowing through a pipe is characterised by a container with fluid flowing through it connected into the pipe, and a porous body inserted in the container, said body having predetermined fluid through-flow characteristics, and means for regulating the pressure difference across the body.
• the porous body is a sintered compacted body of powder, particularly stainless metallic powder.
• the body is suitabl of disposable nature and it is therefore advantageous to be able with simple means to produce a series of bodies with predetermined flow-resistance characterised, all the bodies in practice having almost identical through- flow characteristics, so that the pressure can be used as control magnitude to set a predetermined flow, particularly without any calibration of the bodies.
• the apparatus may thus include at least two series of bodies, the bodies in each group having substantially constant flow characteristics and the bodies in the various groups having different and predetermined flow characteristics.
• the bodies are suitably provided with markings corresponding to their flow characteristics.
• the invention also encompasses the use of porous bodies with well defined flow-resistance characteristics, offering simple control of fluid flowing through them, by means of pressure-control equipment.
• the invention can be described by stating that, thanks to its properties, the porous body determines the size of the flow due to the pressure drop over the body.
• the flow can thus be controlled, using relatively simple means to control the pressure, provided the porous bodies are manufactured having identical fluid through-flow characteristics, particularly bodies having flow characteristics which can be predetermined.
• the bodies are normally a few mm long and have a diameter of 3 - 8 mm.
• Titanium is the alternative and this may be preferred if sterile porous bodies are required.
• the bodies When being used for gas, the bodies may be provided with a sealing casing, ensuring that the flow will pass axially through the whole body.
• the seal between the casing of the body and the surroundings (chamber wall or the like) is more efficient and the sintered bodies can therefore be used as they are.
• predetermined porosity can be produced with great certaint if a specific fraction or distribution of grain size is used. Compacting the powder bodies will then result in a specified porosity within wide compacting pressure limits (e.g. up to about 4000 bar) and under normal sintering conditions for the material selected.
• Bodies according to the invention may be cylindrical in shape with a length of about 3 - 6 mm and a diameter of about 3 - 6 mm.
• a cylindrical body with diameter 6 mm, length 4 mm and porosity about 2 micron, using a glucose solution (Ringer-solution) will give a through-flow of 1.4-28 cc/min at a pressure drop of. 100 cm water column. A flow of up to 60 cc/min was obtained in some tests.
• bodies according to the invention having diameter 3 - 6 mm and length 3 - 6 mm produce a
• the bodies can be used to advantage as main components in simple, robust new designs for dosing equipment.
• the complicated dosing pumps currently used for dosing insulin, cytotoxins, etc. can therefore perhaps be entirely avoided.
• the bodies can also be used, for instance, for supplying gas to liquid, e.g. for oxygenating liquid (0 2 to water in fish farms) .

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Automation & Control Theory (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Powder Metallurgy (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20373349

Family Applications (1)

Country Status (3)

Family Cites Families (9)

• 1988
  • 1988-09-16 SE SE8803272A patent/SE464599B/sv not_active IP Right Cessation
• 1989
  • 1989-09-15 EP EP19890910216 patent/EP0434723A1/en not_active Ceased
  • 1989-09-15 WO PCT/SE1989/000498 patent/WO1990002988A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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