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
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/68—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks
  • B29C70/72—Encapsulating inserts having non-encapsulated projections, e.g. extremities or terminal portions of electrical components
• • 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
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/0033—Moulds or cores; Details thereof or accessories therefor constructed for making articles provided with holes
• • 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
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
  • B29C33/48—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling
  • B29C33/50—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling elastic or flexible
  • B29C33/505—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling elastic or flexible cores or mandrels, e.g. inflatable
• • 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
  • B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
  • B29C39/003—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor characterised by the choice of material
  • B29C39/006—Monomers or prepolymers
• • 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
  • B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
  • B29C39/02—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles
  • B29C39/10—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles incorporating preformed parts or layers, e.g. casting around inserts or for coating articles
• • 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
  • B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
  • B29C39/22—Component parts, details or accessories; Auxiliary operations
  • B29C39/40—Compensating volume change, e.g. retraction
• • 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
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/68—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks
  • B29C70/74—Moulding material on a relatively small portion of the preformed part, e.g. outsert moulding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/0058—Liquid or visquous
  • B29K2105/0067—Melt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2031/00—Other particular articles
  • B29L2031/32—Wheels, pinions, pulleys, castors or rollers, Rims
  • B29L2031/324—Rollers or cylinders having an axial length of several times the diameter, e.g. embossing, pressing or printing
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49826—Assembling or joining
  • Y10T29/49863—Assembling or joining with prestressing of part
  • Y10T29/49874—Prestressing rod, filament or strand

Definitions

• the invention relates to a new process for the production of polyamide castings containing cavities or fitted with a metal shaft which comprises an activated anionic polymerization of a lactam or a mixture of lactams in a mould.
• the core or the metal shaft Prior to the actual polymerization, the core or the metal shaft is provided with an outer inflatable jacket prepared by winding an elastic tube around the inner core or metal shaft with neighboring turns in engagement.
• the composite core is removed after polymerization and cooling of the casting.
• the metal shaft remains together with the outer inflatable jacket tightly gripped by the casting. In both cases the high shrinkage stress ordinarily resulting in cracks of the castings is eliminated.
• 1,214,865 describes the production of calender bowls coated with a layer of alkali polym erized lactams by rotational casting, which process removes the shrinkage of the casting in the direction towards-the metal shaft. But since the process requires a centrifugal acceleration of at least 500 g. and the axial shrinkage of the surface is eliminatedby the position of the rotation axis, the requirements for machinery equipment are very high. According to US. Pat. No.
• the present invention relates to a process for the production of polyamide castings containing cavities or fitted with a metal shaft by the process of using an activated anionic polymerization of lactams in a mould containing a composite core or a metal shaft.
• the core or metal shaft is provided with an outer inflatable jacket prepared by winding an elastic tube around the inner core or metal shaft with neighboring turns in engagement.
• the tube is inflated with compressed gas, and said' composite core or metal shaft is inserted into a preheated stationary mould, the mould is then filled with melted lactam or a mixture of lactams containing an alkali catalyst, promoter, and optionally pigments and/or fillers and/or other additives.
• This reaction mixture is polymerized at a temperature lower than the melting point of the polylactam formed thereby.
• the composite core including the outer inflatable jacket is removed from the casting to give a casting with a cavity or the tightly gripped metal shaft together with the outer in- 1 During the production of castings containing a metal shaft,
• the pressure formed in the elastic tube is progressively lowered during the polymerization and the cooling is carried out simultaneously with and according to the shrink-' age of the casting.
• the pressure in the elastic tube is" exerted by air compressed to l'20 atm.
• the stationary mould used in the process of the invention is made of metal and preheated to a temperature of 120-200 C., preferably 130-160 C.
• the melt of lactam or-mixture of lactams is heated to a temperature of 80- 180? C., preferably 120-150 C.
• 6-caprolactam or its mixture with w-laurolactam are the lactams most frequently and preferably used for the purpose of the present invention.
• the polymerization isv effected in the presence of 0.1-2 mole percent, preferably 0.250.4 mole percent, of an alkaline catalyst, which is preferably an alkaline salt of a lactam, such as the sodium salt of 6-caprolactam.
• the polymerization is accelerated by the addition of 0.05- 5 mole percent, preferably 0.25-0.5' mole percent, of a promoter, preferably an acyl compound, such as N-acetyl- 6-caprolactam, or an isocyanate, such as hexamethylene- 1,6-diisocyanate or triphenylmethane4,4,4"-triisocyanate.
• a promoter preferably an acyl compound, such as N-acetyl- 6-caprolactam, or an isocyanate, such as hexamethylene- 1,6-diisocyanate or triphenylmethane4,4,4"-triisocyanate.
• the present process for the production of castings from alkaline activated polyamide as disclosed and claimed herein ofiers a number of advantages in comparison with processes known before.
• Castings containing transverse or blind holes can be produced by direct casting into moulds containing cores. There is no danger of high internal stresses being formed andremoval of the cores from the castings is much easier.
• the influence of shrinkage can be eliminated in any required direction, particularly by the use ofthe inflatable hollow jackets, held under excess pressure as described herein.
• the castings fitted with a metal shaft are produced according to the present invention by a single operation in contrast to the three operations necessary for the known and previously used procedures, i.e. production of the casting, mechanical working by boring a hole therein, followed by fitting the worked casting onto a metal shaft.
• the production by the present invention does not require any complicated equipment such as is necessary for rotation casting.
• the process according to the invention facilitates the production of polyamide castings fitted with a metal shaft with a reproducible tension, by which the casting grips the metal shaft, depending on the tangential forces, which the metal shaft has to transmit onto the casting.
• 6capro1actam is the most frequently used and most desirable lactam for the process according to the inven.
• alkaline activated polymerization of these lactams is most often activated by alkaline reacting substances (alkali metals, alkaline earth metals or the hydrides, oxides, hydroxides, alcohols, amides, salts, and other derivatives thereof), Grignard reagents, and organometallic compounds.
• alkaline reacting substances alkali metals, alkaline earth metals or the hydrides, oxides, hydroxides, alcohols, amides, salts, and other derivatives thereof
• Grignard reagents and organometallic compounds.
• organometallic compounds organometallic compounds.
• the most important catalyst isnan alkaline salt of a lactam, such as the sodium salt of 6-caprolactam,
• the amount of initiators can. vary lactam or mixture of lactams being polymerized.
• acyl compounds N-acyllactams, N,N-diacyl-bis-lactams, cyclic imides of dicarboxylic acids, and the like
• isocyanates butylisocyanate, hexamethylene-1,6-diiocyanate, toluylendiisocyanates, 4,4-diphenylmethanediisocyanate, triphenylmethan-4,4,4T '-triisocyanate, and the like).
• Suitable and useful activators are carbodiimides, anhydrides, chlorides, hydrazides, amides, and esters of acids, lactones, imines, substituted ureas, nitrogenous, hetero? cyclic and other compounds, and various ethers and ke- 4. tones.
• the amount thereof required for promoter usage varies from about 0.05 to about 5 mole percent, preferably from 0.25 to 0.4 mole percent, based on the lactam or mixture of lactams being polymerized.
• the useful promoters can be used either separately or as a mixture or can be formed in situ in the course of the polymerization. Most frequently used promotersare the N-acyllactams, particularly N-acetyl-6- caprolactam.
• a third component into the catalyst and promoter system for example an alcohol, phenol or amine, which prolongs the catalytic effect of the system and controls the value and distribution of the medium molecular weight of the polylactams.
• optionally reinforcing and nonreinforcing fillers and pigments glass, asbestos, metal, cellulose and synthetic fiber materials, metal salts and oxides, metallic powders, carbon black, graphite, cement, silica, cadmium, zinc sulphide, molybdenum sulphide, various macromolecular substances, such as polyolefins, polytetrafluoroethylene, and the like.
• optionally reinforcing and nonreinforcing fillers and pigments glass, asbestos, metal, cellulose and synthetic fiber materials, metal salts and oxides, metallic powders, carbon black, graphite, cement, silica, cadmium, zinc sulphide, molybdenum sulphide, various macromolecular substances, such as polyolefins, polytetrafluoroethylene, and the like.
• additives such known additives as stabilizers, lubricants, plasticizers, blowing agents, solvents, surface active agents, and the like.
• Substantially sealed moulds made of material thermally stable up to 250 C., are suitable for the production of the castings according to the present invention. Particularly convenient are aluminum and aluminum alloys, nickel and chromium. It is also possible to use ceramic or laminated moulds and the like. Into the mould there are inserted suitable cores, preferably made of metal, or a metal shaft, usually made of steel.
• the composite cores or metal shafts used in accordance with the present invention are provided with an outer jacket made of an elastic inflatable tube prepared from an elastic material, which is capable of withstanding temperatures'upto about 200 C., which does not affect the polymerization of the lactam unfavorably and which does not have an affinity for the reaction mixture. It is possible to use thermostable macromolecular materials, such as silicone rubber, fluoroplastics, polyimides, polysulphones, thermostable, synthetic rubbers, and the like. A pressure of 1-20 atm., preferably 1- 5 atm., is produced in t e clascastings.
• polyamide castings according to the present invention are usually carried out in the following manner:
• the elastic tube is inflated by gas to a suitable pressure.
• the mould containing the composite core or metal shaft isplaced into appropriate heating equipment and is warmed to-the desiredtemperature.
• the filling tube is removed and the temperature in the heating equipment is raised to the selected and appropriate polymerization temperature.
• the pressure in the elastic tube is gradually lowered during the polymerization and the cooling is effected according to the shrinking characteristics of the casting.
• the Casting grips the metal shaft firmly together with the outer inflatable jacket.
• the present invention facilitates the production of castings made of polyamides produced by anionic activated polymerization, containing one or more cavities or metal shafts.
• the invention process can be used for the production of bearings, linings, propellers, carrying rollers, cams, flanges, packings and the like.
• the process according to the invention is well adapted for the production of rolls covered by a polyamide layer for textile, paper, tanning and printing machines.
• the outstanding properties of polyamides such as retention of shape at high temperatures, high abrasion resistance, non-sensitivity to passage of flashes, and the like, find extensive utilization.
• Other applications are in the production of large gears, trolley wheels for cranes, cableways and similar, i.e. in any instance or circumstance where it is necessary to transmit forces from the shaft to the polyamide casting and at the same time utilize the outstanding properties of polyamides.
• EXAMPLE I Two cores around which elastic tubes made of a silicone rubber of 1 mm. thickness were previously wound with neighoring turns in engagement are fitted by means of screws to the mould. These tubes had been previously blinded on one end by cold curable silicone rubber and the first turn (containing the blinded end) was glued by the same material at the face of the cores. A similar method was used at the last turn (at the walls of the mould) and the inlets of compressed air were introduced into both tubes through the openings in the wall of the mould and sealed in these openings by cold curable silicone rubber. The mould is loosely closed by a cover through the openings of which the filling tube is inserted into the mould.
• the mould assembled in this way is put into the heating equipment and heated to a temperature of 135 :5. Both tubes are inflated through the inlets by compressed air in such a way, that the outer dimensions of the jacket formed by these are at least 68% greater than the corresponding dimensions of the core increased by a quadruple of the thickness of the walls of the tube.
• the mould is then filled with anhydrous 6-caprolactam, 125 :5 warm, containing 0,50% of the potassium salt of 6-caprolactam and 0.18 of hexamethylene-1,6-diisocyanate. After the mould is filled, the filling tube is removed and the temperature in the heating equipment is raised to 190:5 during 15 minutes. Afterwards the mould is let to cool during 36 hours to about 20".
• the excess pressure from the tubes is released.
• the mould containing the casting is taken out of the heating equipment and after unscrewing the screws and releasing the inlets of compressed air, the casting is taken out of the mould together with both cores and the tubes.
• the last step is the removing of both cores and tubes from the casting.
• EXAMPLE II Into a steel mould for casting a gearwheel there is inserted the metal shaft of this wheel.
• the metal shaft had been previously wound by a tube made of silicone rubber, so that the neighboring turns are in engagement.
• the lower part of the tube was blinded in advance by cold curable silicone rubber, its upper part being fixed on the metal shaft by a suitable clamp.
• the metal shaft, provided with the tube is fixed in the steel mould by means of a packing made of silicone rubber.
• the steel mould is closed by a loosely placed cover, through which passes the upper part of the wound elastic tube and the filling tube.
• the mould assembled in this way is warmed in suitable heating equipment to the temperature of 135 :5 C., the wound elastic tube is filled with compressed air to a pressure of 1.5 atm.
• anhydrous 6-caprolactam heated to :5 and containing 0.40% of the potassium salt of 6-caprolactam and 0.18% of hexamethylene-1,6-diisocyanate, is fed into the assembled steel mould.
• the filling tube is removed and the temperature of the heating equipment is raised to 190:5 C. during 15 minutes.
• the casting is then allowed to cool to a temperature of about 20 C. during 24 hours.
• the steel mould containing the casting is removed from the heating equipment and its cover is taken off together with the packing.
• the gear-wheel, joined firmly with the metal shaft and the wound tube, is taken out of the steel mould. All air has been expelled from the tube by shrinkage during polymerization and cooling, so that a firm joint between the metal shaft and the casting is obtained without causing such stress in the casting that it might be spontaneously damaged.
• the metal shaft of a calender bowl is connected by means of a sealing and a nut to a steel mould, open on top.
• the mould containing the shaft is heated in a suitable heating equipment to the temperature of :5 C.
• a filling tube reaching up into the bottom is inserted and the mould is filled with the reaction mixture.
• This mixture contains 65% of anhydrous caprolactam and 35% of anhydrous laurolactam, heated to 130:5 C.
• EXAMPLE IV The metal shaft of a calender bowl, provided with a closely fitting hollow jacket made of silicone rubber, the walls of which are 1 mm. thick and provided with an inlet tube for compressed air, is fixed in the mould by means of a gasket ring, made of silicone rubber, and a nut.
• the hollow jacket is joined with the gasket ring by a cold vulcanizable silicone rubber adhesive.
• a filling tube is introduced into the mold, the top of which is closed by a loosely placed cover. After the mould has been warmed in suitable heating equipment to the temperature of 145 :5 C., the hollow jacket is filled with air, compressed to 1.2 atm. Then the mould is filled through the filling tube with anhydrous 6-caprolactam, heated to 135:5 C.
• the filling tube is removed and the temperature of the heating equipment is raised to :5 C. during 20 minutes.
• the mould containing the casting is allowed to cool to a temperature of 20 C. for 36 hours.
• the mould containing the casting is taken from the heating equipment, the cover is removed and, after unscrewing the nut, the calender bowl is removed from the mould.
• the hollow jacket is compressed by the shrinkage during polymerization and cooling so that all air has been expelled from the hollow jacket and there is only a layer of compressed silicone rubber between the metal shaft and the casting.
• EXAMPLE V Into a steel mould for casting a gear-wheel there is inserted the metal shaft of this wheel.
• the metal shaft had been previously wound by a tube made of silicone'rubber.
• the lower part of the tube was blinded in advance by cold curable silicone rubber, its upper part being fixed on the metal shaft by a suitable clamp.
• the metal shaft, provided with the tube is fixed in the steel mould by means of a packing made of silicone rubber.
• the steel mould is closed by a loosely placed cover, through which passes the upper part of the tube and the fillin-g tube.
• the mould assembled in this way is warmed in suitable heating equipment to the temperature of 1351- C., the tube is filled with compressed air to a pressure of 1.5 atm.
• anhydrous 6-caprolactam heated to 125i5 C. and containing 0.40% of the potassium salt of 6-caprolactam and 0.18% of hexamethylene-1,6- diisocyanate, is fed into the assembled steel mould.
• the filling tube is removed and the temperature of the heating equipment is raised to 190:5 C. during minutes.
• the casting is then allowed to cool to a temperature of about C. during 24 hours.
• the steel mould containing the casting is removed from the heating equipment and its cover is taken off together with the packing.
• the gearwheel, joined firmly with the metal shaft, is taken out of the steel mould. All air has been expelled from the tube by shrinkage during polymerization and cooling, so that a firm joint between the metal shaft and the casting is obtained without causing such stress in the casting that it would be spontaneously damaged.
• a process according to claim 1, comprising after cooling, removing the composite core including said outer inflatable jacket from said casting to give a casting with a cavity.
• a process according to claim 1, comprising after cooling, allowing the tightly-tripped metal shaft together with the outer inflatable jacket to remain in said casting.
• said elastic tube is made of a thermostable macromolecular material.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Polyamides (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=27179500

Family Applications (1)

Country Status (8)

Cited By (3)

Families Citing this family (2)

• 1969
  • 1969-09-02 CH CH1328569A patent/CH520739A/de not_active IP Right Cessation
  • 1969-09-03 DE DE19691944570 patent/DE1944570A1/de active Pending
  • 1969-09-09 GB GB44456/69A patent/GB1284923A/en not_active Expired
  • 1969-09-10 FR FR6930788A patent/FR2017794A1/fr not_active Withdrawn
  • 1969-09-10 NL NL6913800A patent/NL6913800A/xx unknown
  • 1969-09-11 US US857204A patent/US3658975A/en not_active Expired - Lifetime
  • 1969-09-11 SE SE12553/69A patent/SE358108B/xx unknown
  • 1969-09-11 BE BE738738D patent/BE738738A/xx unknown

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