Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/62—Regenerating the filter material in the filter
  • B01D29/66—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
  • B01D29/668—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps with valves, e.g. rotating valves for coaxially placed filtering elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/11—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
  • B01D29/13—Supported filter elements
  • B01D29/15—Supported filter elements arranged for inward flow filtration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/44—Edge filtering elements, i.e. using contiguous impervious surfaces
  • B01D29/46—Edge filtering elements, i.e. using contiguous impervious surfaces of flat, stacked bodies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
  • B01D29/62—Regenerating the filter material in the filter
  • B01D29/66—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
  • B01D29/665—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps by using pistons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/50—Details of extruders
  • B29C48/69—Filters or screens for the moulding material
  • B29C48/694—Cylindrical or conical filters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/04—Particle-shaped
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
  • B29C48/08—Flat, e.g. panels flexible, e.g. films

Definitions

• the invention relates to a screen unit for removing solid particles from a viscous mass, in particular molten plastic, comprising a housing provided with a supply channel and a discharge channel for the viscous mass, a screen element which is suitably fitted in the housing between the supply channel and discharge channel and can be flowed through by the viscous mass, and means for cleaning the screen element by means of backflushing at least during operation, which means comprise backflush channels which are intended to discharge during the backflushing solid particles screened off by the screen element, which backflush channels can be placed in communication with an outflow channel by way of a shut -off element which can be opened.
• a screen unit is known from, for example,
• the disadvantage of the known screen unit is that in each case only a small part of the screen element is cleaned by backflushing. If the viscous mass is greatly polluted, the apertures of the screen element will become blocked more quickly than the cleaning of the screen element occurs. The pressure in the supply channel of the screen unit will therefore become increasingly high and the capacity of the screen unit will decrease.
• the object of the invention is to provide a screen unit of the type mentioned in the preamble which does not have this disadvantage.
• a screen unit according to the in the introductory part mentioned type, which is characterized in that the screen element is provided in a predetermined fixed position in the housing and that the means for cleaning the screen element further comprise a pressure element which can be operated to flush the viscous mass back through the screen element at a pressure which is higher than the pressure in the supply channel, and which interacts with the shut-off element in order to discharge the solid particles screened off by the screen element .
• a pressure element which can be operated to flush the viscous mass back through the screen element at a pressure which is higher than the pressure in the supply channel, and which interacts with the shut-off element in order to discharge the solid particles screened off by the screen element .
• Fig. 1 is a diagrammatic illustration in section of a screen unit according to the invention
• Fig. 2 is a view on an enlarged scale of an axial side of one of the rings from which the screen casing of the device of Fig. 1 is composed;
• Fig. 3 is a perspective view of a part of the ring of Fig. 2;
• Fig. 4 is a view in the radial direction of a part of the screen casing composed of rings according to Fig. 2;
• Fig. 5 is a diagrammatic illustration in section of another embodiment of the screen unit according to the invention;
• Fig. 6 is a perspective view of a component for forming a flat screen element
• Fig. 7 is a perspective view of further embodiment of a component for forming a flat screen element
• Fig. 8 is a diagrammatic illustration of a stack of conical rings.
• Fig. 1 shows diagrammatically a screen unit for removing solid particles from a viscous mass, for example a molten plastic.
• the screen unit comprises a housing 1.
• a supply channel 2 for viscous mass polluted with solid particles is provided in the housing 1, which supply channel 2 opens out into a central space 3 situated in the housing by way of the radial peripheral wall of the space 3.
• a connecting channel 4 is provided in the housing 1 in such a way that it is coaxial with the space 3.
• a discharge channel 5 for cleaned viscous mass is provided in the housing 1, the inflow aperture of which discharge channel is provided in the radial peripheral wall of the connecting channel 4.
• the supply channel 2 is in communication with the discharge channel 5 by way of the space 3 and the connecting channel 4.
• a device (not shown) for producing viscous mass can be connected to the supply channel 2, such as, for example the extruder for producing molten plastic.
• the discharge channel 5 can be connected to a device (not shown) for manufacturing plastic products, such as, for example, recycled granulated material and/or films.
• a screen element is placed in the space 3 of the housing 1.
• the screen element is composed of a positioning aid 7 and a screen casing 8.
• the positioning aid 7 is formed by a hollow cylinder which is shut off at one axial end and at the other axial end is provided with a radially outward projecting flange 6.
• the external diameter of the flange 6 corresponds to the diameter of a circular opening - A -
• Slits 9 are cut out at a distance from -each other in the positioning aid 7, which slits extend in the axial direction from the flange 6 to the shut-off axial end of the positioning aid 7.
• the slits 9 have dimensions which ensure that an optimum relationship is obtained between the strength and the throughput capacity of the positioning aid 7.
• the slits 9 extending in the axial direction can also be replaced for example by radial drill holes in the wall of the positioning aid 7, which drill holes are distributed in a regular pattern over the wall .
• a screen casing 8 is fitted on the radial outer periphery of the positioning aid7.
• the screen casing 8 has an internal diameter which corresponds to the external diameter of the positioning aid 7.
• the external diameter of the screen casing 8 corresponds to the diameter of the opening 20.
• the external periphery of the screen casing 8 is situated at a distance from the peripheral wall of the space 3, so that the screen casing 8 can be circumfused fully by viscous mass coming from the supply channel 2.
• the positioning aid 7 and the screen casing 8 are fixed in such a way that they are immovable in the axial and radial direction in the space 3 by a shut-off means 10.
• the positioning aid interacts with the shut-off means 10 to attend to the positioning of the screen casing 8 in the space 3.
• the screen casing 8 is formed by a substantially hollow cylinder with radial screen channels which extend from an inflow face of the screen casing 8 to an outflow face of the screen casing.
• the screen channels diverge from the inflow face towards the outflow face.
• the screen casing 8 is constructed of coaxially stacked rings 22, ribs 23, 24 being provided on each ring 22 for forming the radial screen channels (see Fig. 2) .
• Backflush channels 11 are provided in the shut-off means 10, which backflush channels open out into the space 3 at one side. At the other side the backflush channels 11 open out into a central opening 12 in the shut -off means 10.
• the central opening 12 is in communication with an outflow channel 16 situated in a shut-off element 13 and can be shut off by the shut-off element 13, in which a shut-off ball 14 is situated.
• the shut-off ball 14 can be moved in the direction of the central opening 12 by a control element 15.
• the outflow channel 16 is in communication with the environment.
• a plunger which shuts off the outflow channel 16 and the backflush channels 11 can also be used or another suitable shut-off element.
• a connecting channel 4 is provided in the housing 1, the diameter of which connecting channel corresponds to the internal diameter of the positioning aid 7.
• the connecting channel 4 extends from the space 3 to the other axial end of the housing 1.
• the discharge channel 5 extends from the connecting channel 4 to the outer periphery of the housing 1.
• a drive cylinder 18 is fixed coaxially with the connecting channel 4 on the housing 1.
• a backflush plunger 17 fitted in the drive cylinder 18 projects into the connecting channel 4 and can be moved by the drive cylinder 18 until it is inside the screen element.
• the drive cylinder 18 is provided with a stop 21. Interacting with a stop 19 fitted on the backflush plunger 17, the stop 21 determines the maximum distance over which the plunger 17 can move through the connecting channel 4 and into the screen element .
• Fig. 2 shows an axial view of a ring 22 from which the screen casing 7 is constructed.
• radial ribs 23 are provided at regular distances from each other.
• the other axial side of the ring 22 is flat.
• the ribs 23 are of a substantially triangular shape in cross-section. The height and the width of the ribs 23 decrease from the outer periphery of the ring 22 towards the inside.
• Fig. 3 shows a perspective view of a part of the ring 22.
• the cross-section of the ribs 23, 24 is substantially triangular in shape and that the distance rib 24 has the same height over the entire length.
• Fig. 4 shows in radial view a part of the screen casing 8 which is composed of several rings 22.
• the screen apertures of the screen casing 8 are determined by apertures 25 between the ribs 23, 24 on the outer periphery of the ring 22 and the outer periphery of the flat axial side of the adjacent ring 22, inscribed circles with a diameter of 50 ⁇ m, for example, being possible in the apertures 25.
• the orientation of the rings 22 is the same for all rings 22.
• the screen casing 8 is resistant to high pressures both from the inside and from the outside.
• the positioning aid 7 ensures that the rings 22 remain coaxial. For a screen casing constructed in this way it is not necessary to place a supporting element on the outer periphery, in order to support the screen casing when a pressure is being exerted from the inside for cleaning the screen casing by means of backflushing.
• the rings 22 coaxial by providing at least two drill holes at a distance from each other in each ring.
• the rings can subsequently be pushed over positioning pins which are provided in a fixed position in the axial end of the space 3 of the screen unit and correspond to the number of drill holes.
• the shut -off element 10 can subsequently be placed over the free ends of the positioning pins, in order to hold the positioning pins in place.
• the screen unit works as follows: A viscous mass, for example molten plastic, containing impurities is conveyed by way of the supply channel 2 to the space 3. The viscous mass is forced through the screen casing 8, impurities remaining behind on the outside of the screen casing. The impurities remaining behind are greater in size than the apertures 25 on the outer periphery of the screen casing 8.
• the screen apertures of the second screen unit can then be smaller, so that impurities with a smaller diameter than the impurities screened off in the first screen unit are screened off by the second screen unit. In this way it is possible to place several screen units according to the invention in series, in order to obtain a viscous mass of a desired purity.
• the capacity of the screen unit can be adapted as desired by altering the dimensions of the screen element .
• the capacity of the screen unit is increased by placing several screen elements in parallel, each screen element being situated in a corresponding space in the housing. For discharging the cleaned viscous mass each space is in communication with a common channel, into which the backflush plunger is inserted. When the backflush plunger is operated to clean the screen elements, all screen elements are cleaned simultaneously by means of backflushing.
• the backflush plunger does not move into a screen element.
• the backflush plunger does shut off a common discharge channel, after which the pressure in the common channel, and consequently in all channels in communication therewith, rises. All corresponding screen elements are therefore cleaned simultaneously.
• each screen element of the embodiment described above cleaned by a corresponding backflush plunger.
• the backflush plungers can be operated simultaneously or in succession for cleaning the screen element belonging to the backflush plunger concerned.
• Fig. 5 shows a variant of a screen unit according to the invention.
• the unit comprises a housing 101, which is provided with a space 103.
• a supply channel 102 opens into the space 103.
• a communication channel 104 also opens into the space 103, the communication channel 104 being in line with the supply channel 102.
• the communication channel 104 extends from the space 103 to an outside of the housing 101.
• a drive cylinder 118 with a backflush plunger 117 is provided coaxially with the communication channel 104 on the housing 101.
• the backflush plunger 117 projects into the communication channel 104.
• a discharge channel 105 which extends from the communication channel 104 to an outside of the housing 101 and can be shut off by the backflush plunger 117, is also provided in the housing 101.
• a substantially flat screen element 108 assembled by means of components consisting of flat plates 122 on which ribs 123 and 124 are provided, is provided in the space 103.
• the screen element 108 divides the space 103 into two parts.
• the screen element 108 is held in place by a shut -off means 110.
• a backflush channel 111 which can be shut off by means of a shut-off element 113, is provided in - the shut-off means 110.
• the shut-off element 113 comprises a plunger 115 which can move a shut- off ball valve 114 in the direction of the backflush channel 111.
• the backflush channel 111 is in communication with an outflow channel 116.
• the screen element 108 comprises an inflow face on the side facing the supply channel 102 and an outflow face on the side facing the communication channel 104.
• the throughput channels extend from the inflow face in the direction of the outflow face, the flow cross-section of the throughput channels increasing constantly in the direction of the outflow face.
• the throughflow channels preferably meet each other at a distance from the outflow face and therefore merge into each other.
• Fig. 7 shows a component for forming a screen element, in which two adjacent ribs determine a substantially semi -circular interspace. When assembled, the screen element concerned has a relatively large throughflow surface on the inflow side.
• peripheral edges of the conical rings resting against each other are forced apart, so that impurities lodged there are easily dislodged and can be removed.
• the rings When the initial tension is applied, the rings are pressed into a substantially flat state, so that two adjacent rings are at equal axial distances from each other both on the inner periphery and on the outer periphery.
• the ribs are provided on the rings in such a way that in the state under initial tension all rings have the same orientation.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=19764827

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (10)

Family Cites Families (7)

• 1997
  • 1997-04-22 NL NL1005864A patent/NL1005864C2/nl not_active IP Right Cessation
• 1998
  • 1998-04-22 JP JP54551898A patent/JP2001521458A/ja active Pending
  • 1998-04-22 AU AU70850/98A patent/AU7085098A/en not_active Abandoned
  • 1998-04-22 EP EP98917792A patent/EP0977659A1/en not_active Ceased
  • 1998-04-22 WO PCT/NL1998/000224 patent/WO1998047688A1/nl not_active Application Discontinuation

Non-Patent Citations (1)

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