WO1997021479A1 - A plastic liquid strainer and method and apparatus for fabricating same - Google Patents

A plastic liquid strainer and method and apparatus for fabricating same Download PDF

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Publication number
WO1997021479A1
WO1997021479A1 PCT/CA1995/000687 CA9500687W WO9721479A1 WO 1997021479 A1 WO1997021479 A1 WO 1997021479A1 CA 9500687 W CA9500687 W CA 9500687W WO 9721479 A1 WO9721479 A1 WO 9721479A1
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WO
WIPO (PCT)
Prior art keywords
cone
mandrel
strainer
plastic
film sheet
Prior art date
Application number
PCT/CA1995/000687
Other languages
French (fr)
Inventor
Savars Gurarslan
Original Assignee
Canimport Ltee
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Canimport Ltee filed Critical Canimport Ltee
Priority to PCT/CA1995/000687 priority Critical patent/WO1997021479A1/en
Priority to AU41132/96A priority patent/AU4113296A/en
Publication of WO1997021479A1 publication Critical patent/WO1997021479A1/en

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Classifications

    • 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
    • B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
    • B29C51/26—Component parts, details or accessories; Auxiliary operations
    • B29C51/44—Removing or ejecting moulded articles
    • B29C51/445—Removing or ejecting moulded articles from a support after moulding, e.g. by cutting
    • 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
    • B01D29/111—Making 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
    • B01D29/23—Supported filter elements arranged for outward flow filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • B23K26/382—Removing material by boring or cutting by boring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2201/00—Details relating to filtering apparatus
    • B01D2201/02—Filtering elements having a conical form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/30—Organic material
    • B23K2103/42—Plastics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
    • 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
    • B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
    • B29C51/08—Deep drawing or matched-mould forming, i.e. using mechanical means only

Definitions

  • the present invention relates to a plastic strainer for filtering liquids, preferably but not exclusively for filtering paints and to a method and an apparatus for the manufacture thereof.
  • Paint filters are usually constructed of paper and cotton material and an example of such prior art filters is described and illustrated in my previous U.S. Patent No. 4,559,140 issued on December 17, 1985.
  • paper filters for filtering paint There are many undesirable problems associated with paper filters for filtering paint. For example, when the paper becomes saturated with paint it deforms and often breaks down. Also, dust or fibers are released in the paint by the paper which is made of pulp. Because the filtering material is a cotton meshing, often lint is also released within the paint as well as flakes which peel off from the cotton.
  • the glue seam along an edge which forms the filter cone and the glue often dissolves by the solvent in the paint and can contaminate the solvent and the paint, particularly when the paint is a water-base paint.
  • filters will also find many special applications such as medical use, for example.
  • Plastic filters which have more rigidity are known but they have been found insufficient for fine filtering due to the difficulty in creating a fine mesh in the plastic suitable for use in filtering paints.
  • plastic filters have been used for other applications and these have been produced by injection molding techniques wherein holes are made by pins extending into the mold cavities. However, such holes are much too big to provide proper filtration of fine particles and the filters are too expensive for one-time use.
  • Another feature of the present invention is to provide a method of fabricating a plastic film strainer from a heated plastic film sheet to form a cone which is then perforated in a filtration zone thereof by a plurality of laser beams capable of forming holes of circular cross section and of a fine mesh and within a short time duration for mass production.
  • Another feature of the present invention is to provide an apparatus for making a conical plastic film strainer for filtering liquids and wherein plastic cones are formed from a plastic film sheet and supported and retained on a mandrel in such a manner as to permit laser beams to pierce a plurality of holes, of predetermined size, within a filtration portion of the cone.
  • the present invention provides a strainer for filtering liquids.
  • the strainer comprises a cone of plastic film material and defines a conical tapered side wall, an apex end and an open top end.
  • a perforated filtration section is provided in at least a filtration zone of the cone and extends from the apex end thereof.
  • the filtration zone has a plurality of substantially circular holes fabricated from laser beams. The holes have a diameter falling within the range of from about 30 to 300 microns.
  • a method of fabricating a strainer having a conical side wall, an apex end and an open top end comprises feeding a solid heated plastic film sheet to a cone forming machine. Cones are then formed from the heated solid plastic sheet. Each of the cones are placed on a support means to support the cone with a space present in at least a portion of the cone adjacent an inner surface thereof. One or more laser beams pierce a plurality of holes in a filtration section of the cone. According to a still further broad aspect of the present invention there is provided an apparatus for making a strainer for filtering liquids.
  • the strainer has a conical tapered side wall having an inner and an outer surface, an apex end and an open top end.
  • the apparatus has one or more mandrels. Each mandrel is adapted to support and retain the conical strainer in a predetermined manner with the inner surface of at least a portion of the cone spaced from an outer surface portion of the mandrel to create a space behind the inner surface.
  • a laser beam generating means is used to pierce a plurality of holes in the portion of the cone which is spaced from the outer surface of the mandrel .
  • Figure 1 is a simplified schematic diagram illustrating the method and apparatus for fabricating the conical plastic strainer of the present invention and used for filtering liquids ;
  • Figure 2 is an enlarged cross-section view showing the construction of a mandrel having a conical plastic strainer retained thereon;
  • Figure 3 is a side view showing a plastic conical strainer for filtering liquids and formed in accordance with the method and apparatus of the present invention as illustrated in Figures 1 and 2.
  • the strainer for filtering liquids.
  • the strainer comprises a cone which is formed from plastic sheet material and defines a conically tapered side wall 11, an apex end 12 and an open top end 13.
  • a perforated filtration section 14 is provided in at least a filtration section of the cone which extends from the apex end 12 and terminates at a predetermined zone along the side wall 11 depending on the application of use of the filter.
  • the perforated filtration section 14 has a plurality of substantially circular holes 15 which are fabricated from laser beams, as will be described later. Each of the holes has a diameter which falls within the range of from about 30 to about 300 microns.
  • the apex end 12 has an inner conical cavity 16 which defines a small cone 17 having a solid circumferential side wall which projects inwardly of the cone and which is not perforated. Accordingly, liquids contained within the cone will flow to the bottommost holes 15' disposed about the base of the cone 17 in the tapered side wall 11.
  • the purpose of this small cone 17 projecting inwardly of the filter will be described later with reference to the apparatus and method of manufacture.
  • the plastic strainer as hereinshown is preferably, but not exclusively, used for filtering paints. There are several other applications for this filter such as for filtering gallbladder stones from urine, etc.
  • the filter is also fabricated from a plastic sheet material that does not contaminate paint when in contact therewith and which is capable of maintaining its shape when heat-formed, such as with the fabrication of plastic drinking glasses.
  • the filter is fabricated in such a manner that it is relatively inexpensive and can be discarded after use. It is preferable to discard the filter due to the small diameter of the circular holes as this would be time-consuming and difficult to clean with a solvent after its use in filtering paint.
  • the use of circular holes gives the filter a better hydraulic characteristic and the fact that the holes are very small provides for finer filtering and a stronger filter in the filtration section. The distance between the holes is approximately half the hole diameter.
  • a roll 20 of a plastic film sheet material 21 is unwound by a winder roll 22 and passes under a heating device 23 which heats the plastic film sheet to within a predetermined temperature range.
  • the sheet is then conveyed through a former device 24 which is provided with forming cones (not shown) whereby to stamp a plurality of cones 25 in close proximity to one another in the plastic sheet 21.
  • the sheet with a plurality of cones formed therein may be conveyed through a cooling zone 26 before being fed to a die-cutting device 27 where the cones 25 are cut out from the plastic film sheet.
  • the cone thus formed may also be provided with a small circumferential lip li as shown in Figure 3, and the remainder of the plastic film sheet 21' is rolled on the winder roll 22. After the plastic sheet 21 is unwound from the supply roll 20, the scrap material on the winder roll 22, as shown at 28, is recycled into new plastic film sheets.
  • the cones 25 cut out of a plastic film sheet 21 are engaged by a transfer mechanism 26 which transfers the cone onto a mandrel 27 secured to an indexing mechanism 28 designed to displace the mandrel from a strainer loading station 29 to a laser beam piercing station 30 and then to a strainer discharge station 31.
  • a plurality of laser beams are generated by a laser 32 which is disposed at the laser piercing station 30 and the beam may be split and oriented to pierce a plurality of holes through the solid plastic cone simultaneously as the cone rotates.
  • the mandrel is rotated at high speed and a single laser can perforate a complete cone within one second.
  • the laser beam can be split, in say four beams, and perforate four cones at the same time.
  • the laser beam can make at least 20,000 holes per second.
  • the mandrel 27 is provided with a base 33 and a conical outer surface 34.
  • a main vacuum port or channel 35 extends into the base 33 and communicates with a plurality of equidistantly spaced distribution channels 36 whereby vacuum suction is distributed circumferentially about the outer surface 34 of the mandrel whereby to retain a plastic film cone 25 in a spaced manner from a portion of the outer surface 34 thereof.
  • the cone inner surface 25' is disposed equidistantly spaced about the outer surface 34 of the mandrel 27 by spacer means which is comprised by a plurality of spacer pins 37 projecting from the outer surface 34 of the mandrel.
  • the spacer means is further comprised of a spacer ridge 38 which projects about an outer circumferential area of the mandrel conical outer surface 34.
  • the spacer means is still further provided by an apex conical end portion 39 on which sits the apex of the small inner cone 17 formed at the apex end 12 of the strainer. This assures for uniform spacing of the inner surface 25' of the cone 25 about the conical outer surface 34 of the mandrel. Accordingly, the cone is positioned in substantially perfect alignment with the mandrel.
  • a control circuit 40 assures the proper operation of the apparatus and controls the vacuum pump 41, or a switch therein and not shown, to apply and remove the suction from each of the three mandrels secured to each of the arms 28' of the indexing machine 28.
  • the control circuit also synchronizes the lasers and all other devices in the process, as illustrated in Figure 1.
  • the method of fabricating the conical plastic film strainer of the present invention in one of its aspect, consists in feeding a solid heated plastic film sheet to a cone forming machine where cones are formed in the film sheet.
  • Laser beams pierce a plurality of holes in at least a portion of the cone to form a filtration section 14.
  • the holes are pierced with minimal cycle time.
  • a strainer which is formed from a plastic film cone having no seams and incorporating a filtration section having a plurality of substantially uniform circular holes having a diameter falling within the range of from about 30 to 300 microns. It is within the ambit of the present invention to cover any obvious modifications thereof, provided such modifications fall within the scope of the appended claims.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Plasma & Fusion (AREA)

Abstract

A plastic liquid strainer (10) and a method and apparatus for the fabrication of same is described. The plastic strainer is a cone-shape strainer having a conical side wall (11), an apex end (12) and an open top end (13). The strainer is formed from a plastic film sheet (21) which forms a cone which is then perforated by using laser beams (32) so that a filtration section is made in the plastic and extends from the apex end of the cone. The filtration section (14) is comprised of a plurality of substantially circular holes (15) of predetermined size. The cone thus formed is particularly useful for filtering paints and is disposable after use. Because it uses plastic film material, the paint is substantially free from dust generated by paper filters or lint which were normally released by the cotton sieve sections. The filter does not stretch nor does it become soiled during use as with paper cone filters.

Description

A PLASTIC LIQUID STRAINER AND METHOD AND APPARATUS FOR FABRICATING SAME
TECHNICAL FIELD The present invention relates to a plastic strainer for filtering liquids, preferably but not exclusively for filtering paints and to a method and an apparatus for the manufacture thereof.
BACKGROUND ART
Paint filters are usually constructed of paper and cotton material and an example of such prior art filters is described and illustrated in my previous U.S. Patent No. 4,559,140 issued on December 17, 1985. There are many undesirable problems associated with paper filters for filtering paint. For example, when the paper becomes saturated with paint it deforms and often breaks down. Also, dust or fibers are released in the paint by the paper which is made of pulp. Because the filtering material is a cotton meshing, often lint is also released within the paint as well as flakes which peel off from the cotton. In fabricating these filters there is also a glue seam along an edge which forms the filter cone and the glue often dissolves by the solvent in the paint and can contaminate the solvent and the paint, particularly when the paint is a water-base paint. Such contaminants are undesirable when filtering special paints such as those used for painting automotive vehicles. As mentioned hereinabove, because the filters are made with a glue seam, they are not rigid and do not maintain a uniform shape as they stretch and deform and this leads to breakdown. Paint filters are also economical as they have a one-time use and are discarded as it would be too time consuming to try to clean and dry them.
A need has therefore existed for providing a stronger filter which is capable of filtering paints or other liquids and wherein the filter would retain its original shape, not contaminate the liquid and be made inexpensive enough to be discarded after use. Such filters will also find many special applications such as medical use, for example. Plastic filters which have more rigidity are known but they have been found insufficient for fine filtering due to the difficulty in creating a fine mesh in the plastic suitable for use in filtering paints. Heretofore, plastic filters have been used for other applications and these have been produced by injection molding techniques wherein holes are made by pins extending into the mold cavities. However, such holes are much too big to provide proper filtration of fine particles and the filters are too expensive for one-time use.
SUMMARY OF INVENTION
It is therefore a feature of the present invention to provide a plastic strainer for filtering liquids, such as paints, and wherein the strainer is formed as a cone having a perforated filtration section which is constituted by a plurality of substantially circular holes fabricated by laser beams. Another feature of the present invention is to provide a method of fabricating a plastic film strainer from a heated plastic film sheet to form a cone which is then perforated in a filtration zone thereof by a plurality of laser beams capable of forming holes of circular cross section and of a fine mesh and within a short time duration for mass production.
Another feature of the present invention is to provide an apparatus for making a conical plastic film strainer for filtering liquids and wherein plastic cones are formed from a plastic film sheet and supported and retained on a mandrel in such a manner as to permit laser beams to pierce a plurality of holes, of predetermined size, within a filtration portion of the cone.
According to the above features, from a broad aspect, the present invention provides a strainer for filtering liquids. The strainer comprises a cone of plastic film material and defines a conical tapered side wall, an apex end and an open top end. A perforated filtration section is provided in at least a filtration zone of the cone and extends from the apex end thereof. The filtration zone has a plurality of substantially circular holes fabricated from laser beams. The holes have a diameter falling within the range of from about 30 to 300 microns.
According to a further broad aspect of the present invention there is provided a method of fabricating a strainer having a conical side wall, an apex end and an open top end. The method comprises feeding a solid heated plastic film sheet to a cone forming machine. Cones are then formed from the heated solid plastic sheet. Each of the cones are placed on a support means to support the cone with a space present in at least a portion of the cone adjacent an inner surface thereof. One or more laser beams pierce a plurality of holes in a filtration section of the cone. According to a still further broad aspect of the present invention there is provided an apparatus for making a strainer for filtering liquids. The strainer has a conical tapered side wall having an inner and an outer surface, an apex end and an open top end. The apparatus has one or more mandrels. Each mandrel is adapted to support and retain the conical strainer in a predetermined manner with the inner surface of at least a portion of the cone spaced from an outer surface portion of the mandrel to create a space behind the inner surface. A laser beam generating means is used to pierce a plurality of holes in the portion of the cone which is spaced from the outer surface of the mandrel .
BRIEF DESCRIPTION OF DRAWINGS
A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:
Figure 1 is a simplified schematic diagram illustrating the method and apparatus for fabricating the conical plastic strainer of the present invention and used for filtering liquids ; Figure 2 is an enlarged cross-section view showing the construction of a mandrel having a conical plastic strainer retained thereon; and
Figure 3 is a side view showing a plastic conical strainer for filtering liquids and formed in accordance with the method and apparatus of the present invention as illustrated in Figures 1 and 2.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings and more particularly to Figure 3, there is shown generally at 10 the strainer of the present invention for filtering liquids. As hereinshown the strainer comprises a cone which is formed from plastic sheet material and defines a conically tapered side wall 11, an apex end 12 and an open top end 13. A perforated filtration section 14 is provided in at least a filtration section of the cone which extends from the apex end 12 and terminates at a predetermined zone along the side wall 11 depending on the application of use of the filter.
The perforated filtration section 14 has a plurality of substantially circular holes 15 which are fabricated from laser beams, as will be described later. Each of the holes has a diameter which falls within the range of from about 30 to about 300 microns.
As hereinshown the apex end 12 has an inner conical cavity 16 which defines a small cone 17 having a solid circumferential side wall which projects inwardly of the cone and which is not perforated. Accordingly, liquids contained within the cone will flow to the bottommost holes 15' disposed about the base of the cone 17 in the tapered side wall 11. The purpose of this small cone 17 projecting inwardly of the filter will be described later with reference to the apparatus and method of manufacture. The plastic strainer as hereinshown is preferably, but not exclusively, used for filtering paints. There are several other applications for this filter such as for filtering gallbladder stones from urine, etc. The filter is also fabricated from a plastic sheet material that does not contaminate paint when in contact therewith and which is capable of maintaining its shape when heat-formed, such as with the fabrication of plastic drinking glasses. The filter is fabricated in such a manner that it is relatively inexpensive and can be discarded after use. It is preferable to discard the filter due to the small diameter of the circular holes as this would be time-consuming and difficult to clean with a solvent after its use in filtering paint. The use of circular holes gives the filter a better hydraulic characteristic and the fact that the holes are very small provides for finer filtering and a stronger filter in the filtration section. The distance between the holes is approximately half the hole diameter.
Referring now to Figure 1 there will be described the method of fabricating the conical plastic strainer 10 of the present invention. As shown in Figure 1, a roll 20 of a plastic film sheet material 21 is unwound by a winder roll 22 and passes under a heating device 23 which heats the plastic film sheet to within a predetermined temperature range. The sheet is then conveyed through a former device 24 which is provided with forming cones (not shown) whereby to stamp a plurality of cones 25 in close proximity to one another in the plastic sheet 21. At the output of the former device 24 there is thus exposed the sheet with a plurality of cones formed therein and it may be conveyed through a cooling zone 26 before being fed to a die-cutting device 27 where the cones 25 are cut out from the plastic film sheet. The cone thus formed may also be provided with a small circumferential lip li as shown in Figure 3, and the remainder of the plastic film sheet 21' is rolled on the winder roll 22. After the plastic sheet 21 is unwound from the supply roll 20, the scrap material on the winder roll 22, as shown at 28, is recycled into new plastic film sheets.
With further reference to Figure 2, it can be seen that the cones 25 cut out of a plastic film sheet 21 are engaged by a transfer mechanism 26 which transfers the cone onto a mandrel 27 secured to an indexing mechanism 28 designed to displace the mandrel from a strainer loading station 29 to a laser beam piercing station 30 and then to a strainer discharge station 31.
A plurality of laser beams are generated by a laser 32 which is disposed at the laser piercing station 30 and the beam may be split and oriented to pierce a plurality of holes through the solid plastic cone simultaneously as the cone rotates. The mandrel is rotated at high speed and a single laser can perforate a complete cone within one second. The laser beam can be split, in say four beams, and perforate four cones at the same time. The laser beam can make at least 20,000 holes per second.
Referring now more specifically to Figure 2 there is shown one example for the construction of the mandrel 27. As hereinshown the mandrel 27 is provided with a base 33 and a conical outer surface 34. A main vacuum port or channel 35 extends into the base 33 and communicates with a plurality of equidistantly spaced distribution channels 36 whereby vacuum suction is distributed circumferentially about the outer surface 34 of the mandrel whereby to retain a plastic film cone 25 in a spaced manner from a portion of the outer surface 34 thereof. The cone inner surface 25' is disposed equidistantly spaced about the outer surface 34 of the mandrel 27 by spacer means which is comprised by a plurality of spacer pins 37 projecting from the outer surface 34 of the mandrel. The spacer means is further comprised of a spacer ridge 38 which projects about an outer circumferential area of the mandrel conical outer surface 34. The spacer means is still further provided by an apex conical end portion 39 on which sits the apex of the small inner cone 17 formed at the apex end 12 of the strainer. This assures for uniform spacing of the inner surface 25' of the cone 25 about the conical outer surface 34 of the mandrel. Accordingly, the cone is positioned in substantially perfect alignment with the mandrel.
As shown in Figure 1, a control circuit 40 assures the proper operation of the apparatus and controls the vacuum pump 41, or a switch therein and not shown, to apply and remove the suction from each of the three mandrels secured to each of the arms 28' of the indexing machine 28. The control circuit also synchronizes the lasers and all other devices in the process, as illustrated in Figure 1.
In summary, the method of fabricating the conical plastic film strainer of the present invention, in one of its aspect, consists in feeding a solid heated plastic film sheet to a cone forming machine where cones are formed in the film sheet. Laser beams pierce a plurality of holes in at least a portion of the cone to form a filtration section 14. The holes are pierced with minimal cycle time. There is thus formed a strainer which is formed from a plastic film cone having no seams and incorporating a filtration section having a plurality of substantially uniform circular holes having a diameter falling within the range of from about 30 to 300 microns. It is within the ambit of the present invention to cover any obvious modifications thereof, provided such modifications fall within the scope of the appended claims.

Claims

1. A method of fabricating a plastic strainer having a conical side wall, an apex end and an open top end, said method comprising the steps of: i) feeding a solid heated plastic film sheet to a cone forming machine, ii) forming cones from said heated plastic film sheet, iii) placing each said cone on a support means to support said cone with a space present in at least a portion of said cone adjacent an inner surface thereof, and iv) laser piercing a plurality of holes in said portion of said cone to form a filtration section.
2. A method as claimed in claim 1 wherein said step (iv) comprises piercing a plurality of round holes having a diameter within the range of from about 30 to 300 microns whereby to form a fine mesh filtration section.
3. A method as claimed in claim 2 wherein said step (iii) comprises placing said cones on a displaceable mandrel constituting said support means, and displacing said mandrel to a plurality of positions with said laser piercing step being effectuated at at least one of said positions.
4. A method as claimed in claim 3 wherein said cone is supported on said mandrel and retained thereon by applying a vacuum to said mandrel.
5. A method as claimed in claim 3 wherein said step (i) comprises unwinding a plastic film sheet from a roll of plastic film sheet material and heating said sheet as it is fed to said forming machine.
6. A method as claimed in claim 3 wherein said step (ii) comprises forming a plurality of cones in said heated plastic film sheet to form a plurality of cone shape forms in said sheet, die- cutting said sheet to detach said cone shape forms to obtain said cones, transferring each one of said cones sequentially to a mandrel, there being at least three of said mandrels supported for displacement by an indexing machine.
7. A method as claimed in claim 6 wherein mandrels are displaced in sequence by said indexing machine from a cone receiving position at which a cone is positioned on said mandrel and a vacuum is applied to said mandrel to retain said cone, a cone piercing position where said laser piercing step (iv) is performed, and a cone discharge position where said perforated cone is discharged.
8. A method as claimed in claim 6 wherein said sheet after being die-cut is wound about a support roll whereby said die-cut sheet is recycled.
9. An apparatus for making a conical plastic strainer for filtering liquids, said strainer having a conically tapered side wall having an inner and an outer surface, an apex end and an open top end; said apparatus having one or more mandrels, each mandrel being adapted to support and retain said conical plastic strainer in a predetermined manner with said inner surface of at least a portion of said cone spaced form an outer surface portion of said mandrel to create a space behind said inner surface, and laser beam generating means for piercing a plurality of holes in said portion of said cone which is spaced from said outer surface of said mandrel.
10. An apparatus as claimed in claim 9 wherein said mandrel outer surface is provided with spacer means to support said inner surface of said cone spaced from said outer surface portion of said mandrel.
11. An apparatus as claimed in claim 10 wherein said mandrel is provided with actuable retention means to firmly engage and release said mandrel against said spacer means.
12. An apparatus as claimed in claim 11 wherein said actuable retention means is comprised by a plurality of vacuum ports distributed in said mandrel and in communication with said outer surface portion, a vacuum pump connected to said ports, and control means to apply and remove vacuum pressure to said ports to retain and release said conical plastic strainer.
13. An apparatus as claimed in claim 12 wherein said spacer means is comprised by a plurality of spacer pins projecting from said outer surface of said mandrel, said outer surface being a conical outer surface.
14. An apparatus as claimed in claim 13 wherein said spacer means further comprises a spacer ridge projecting from about an outer circumferential area of said mandrel conical outer surface, and an apex conical end portion, said conical plastic strainer having an inner conical cavity at said apex end, said conical cavity forming an abutment support to abut said apex conical end portion of said mandrel whereby said inner surface of at least a portion of said cone is substantially equidistantly spaced from said mandrel outer surface.
15. An apparatus as claimed in claim 12 wherein there are three or more mandrels secured to an indexing mechanism to displace said mandrel from a strainer loading station to a laser piercing station and to a strainer discharge station.
16. An apparatus as claimed in claim 15 wherein there is further provided a cone forming machine to form a plurality of plastic cones from a heated plastic film sheet, and transfer means to transfer said cones to said mandrels of said indexing mechanism at said strainer loading station.
17. An apparatus as claimed in claim 16 wherein there is further provided supply means for feeding a plastic film sheet relative to a heating means to heat said plastic film sheet to within a predetermined temperature range to form said heated plastic film sheet, means to feed said heated plastic film sheet to said forming machine to form a plurality of cone shape forms in said heated film sheet, means to cool said film sheet with said cone shape forms, die-cutting means to cut said cone shape forms from said film sheet, said transfer means engaging one of said cones cut from said film sheet and transferring same onto said mandrel at said loading station.
18. An apparatus as claimed in claim 13 wherein there are a plurality of laser beams oriented to pierce a plurality of said holes through said cone simultaneously, as said mandrel is axially rotated at high speed whereby holes are pierced entirely about the circumference of said cone.
19. A plastic strainer for filtering liquids, said strainer comprising a cone of plastic sheet material and defining a conically tapered side wall, an apex end and an open top end; a perforated filtration section in at least a filtration section of said cone extending from said apex end, said filtration section having a plurality of substantially circular holes fabricated by laser beams, said holes having a diameter falling within the range of from about 30 to 300 microns.
20. A plastic strainer as claimed in claim 19 wherein said perforated filtration section is a conical end portion of said cone.
21. A plastic strainer as claimed in claim 20 wherein said apex end has an inner conical cavity which defines a small cone having a solid circumferential side wall projecting inwardly in said cone.
22. A plastic strainer as claimed in claim 19 wherein said liquids are paints.
23. A plastic strainer as claimed in claim 22 wherein said strainer is constructed of a plastic film material that does not contaminate paint when in contact therewith and maintains its original shape, said strainer being a disposable strainer.
PCT/CA1995/000687 1995-12-08 1995-12-08 A plastic liquid strainer and method and apparatus for fabricating same WO1997021479A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/CA1995/000687 WO1997021479A1 (en) 1995-12-08 1995-12-08 A plastic liquid strainer and method and apparatus for fabricating same
AU41132/96A AU4113296A (en) 1995-12-08 1995-12-08 A plastic liquid strainer and method and apparatus for fabricating same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CA1995/000687 WO1997021479A1 (en) 1995-12-08 1995-12-08 A plastic liquid strainer and method and apparatus for fabricating same

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WO1997021479A1 true WO1997021479A1 (en) 1997-06-19

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3115677A (en) * 1957-11-08 1963-12-31 Thiel Alfons Wilhelm Apparatus for the production of shaped plastic workpieces
DE1604554A1 (en) * 1966-02-10 1970-11-05 Eberhard Kutschera Machine for deep drawing of plastics, especially for cups, and operating procedures for this
FR2153534A7 (en) * 1971-09-14 1973-05-04 Broussaud Et Ses Fils
US4559140A (en) * 1984-03-30 1985-12-17 Centre De Recherche Industrielle Du Quebec Paint filter
DE4016253A1 (en) * 1990-05-19 1991-11-21 Brieden Filtration Gmbh Und Co Domed sieve element mfr. for heat exchanger - esp. useful in cooling water filter unit by deforming flat metal plate into conical cap shape and forming sieve holes
US5105833A (en) * 1989-06-13 1992-04-21 G. D. Societa' Per Azioni Device for perforating ventilation holes in cigarettes or similar

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3115677A (en) * 1957-11-08 1963-12-31 Thiel Alfons Wilhelm Apparatus for the production of shaped plastic workpieces
DE1604554A1 (en) * 1966-02-10 1970-11-05 Eberhard Kutschera Machine for deep drawing of plastics, especially for cups, and operating procedures for this
FR2153534A7 (en) * 1971-09-14 1973-05-04 Broussaud Et Ses Fils
US4559140A (en) * 1984-03-30 1985-12-17 Centre De Recherche Industrielle Du Quebec Paint filter
US5105833A (en) * 1989-06-13 1992-04-21 G. D. Societa' Per Azioni Device for perforating ventilation holes in cigarettes or similar
DE4016253A1 (en) * 1990-05-19 1991-11-21 Brieden Filtration Gmbh Und Co Domed sieve element mfr. for heat exchanger - esp. useful in cooling water filter unit by deforming flat metal plate into conical cap shape and forming sieve holes

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