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
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/34—Auxiliary operations
  • B29C44/58—Moulds
  • B29C44/588—Moulds with means for venting, e.g. releasing foaming gas
• • 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
  • B29C33/34—Moulds or cores; Details thereof or accessories therefor movable, e.g. to or from the moulding station
• • 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
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/34—Auxiliary operations
  • B29C44/36—Feeding the material to be shaped
  • B29C44/46—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length
  • B29C44/461—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length dispensing apparatus, e.g. dispensing foaming resin over the whole width of the moving surface
  • B29C44/462—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length dispensing apparatus, e.g. dispensing foaming resin over the whole width of the moving surface provided with pre-foaming devices
• • 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
  • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
• • 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
  • B29K2075/00—Use of PU, i.e. polyureas or polyurethanes or derivatives thereof, as moulding material

Definitions

• This invention relates to a method of and apparatus for the manufacture of slab-stock polymeric foam, such as polyurethane foam of the type used in seats, cushions and the like.
• polyurethane foam reactants in particular surfactants, catalysts, blowing agents and modifiers, are thoroughly mixed and deposited into a mould.
• the reactants are polyol, isocyanate, for example toluene di-isocyanate (TDI), and water.
• TDI toluene di-isocyanate
• Polyol reacts with the TDI to form urethane linkages that build the polymer.
• TDI reacts with water to produce carbon dioxide which blows the foam. Additional water lowers the density of the foam and also increases exothermic heat output. This heat limits water blown foams to a density of 19.2 Kg/ m ⁇ at an atmospheric pressure of 1 bar.
• Inert blowing agents such as CFC-11 (also known as chlorofluorocarbon-11 or fluorotrichloromethane) or methylene chloride are used to produce lower density and softer foams. These materials soften the foam by reducing the number of hard segments of the polymer caused by water for any given density.
• the other active ingredients are a silicone surfactant which stabilizes the gas bubbles and permits efficient use of the foam blowing gases, a polymer building catalyst such as stannous octoate, a gas producing catalyst that catalyzes the isocyanate- water reaction such as an amine compound, and various modifiers such as colours, anti-static agents and combustion modifiers.
• the mould into which the expanding foam is introduced takes the form of a channel with stationary or moving sidewalls 122 cm. to 152 cm. high and a bottom conveyor usually about 244 cm. wide.
• One or both the sidewalls may be adjustable so that variable width foam buns can be made.
• Foam is deposited onto the bottom of the channel by means of a lay-down assembly including a trough having a volume of approximately 100 litres. As the foam expands, it spills out of the trough into the channel.
• Foam expansion takes approximately 75 to 180 seconds depending on the foam formulation.
• the foam rises freely in the production channel until it reaches maximum height.
• These gases are.mainly carbon dioxide and the inert blowing agents CFC-11 and methylene chloride.
• These hot gases pull small amounts of TDI vapours and possibly some of the other components with them.
• TDI is a dangerous respiratory irritant and regulations in the USA at least require a maximum exposure of .02 parts per million in the workplace.
• foam plants typically have extensive high capacity ventilation systems that expel large volumes of air from the foam production areas. It is difficult to get all of these chemical vapours out of the plant so that workers are exposed to acceptable levels of these chemical vapours. Even so, exhausting these chemicals into the atmosphere is now suspected of causing injury to the environment, for example by damaging the ozone layer of the atmosphere, and by causing smog.
• the aim of the present invention is to increase the production rates which can be achieved in polymeric foam manufacturing plants in which the foam reactants are deposited into stationary moulds which are substantially closed for the collection of gases.
• a method of moulding polymeric foam comprising the steps of transporting a mobile trough and fall plate along an elongate mould while delivering foam reactants to the trough, thereby to lay down partially expanded foam over the bottom of the mould, and as the mould is charged with foam, and during curing of said foam, exhausting gases from the mould through venting means provided thereon, said exhausted gases being conducted from the mould for processing and/or disposal, characterised by the steps positioning the mould at a filling station before laying down the foam therein, after charging the mould with foam closing said venting means to seal substantially closed the mould and moving the mould to a curing position remote from the filling station, and extracting gases from the foam at the curing position by connecting the venting means to gas extraction equipment.
• a plant for the production of polymeric foam comprising a mould having top and bottom walls, opposed side walls and end walls, gas venting means for venting gases from the interior of the mould, gas exhausting means connected to the venting means for conducting gas exhausted from the mould as the mould is charged with foam, a mobile trough and fall plate transportable along the mould, and means to deliver foam reactants to the trough as the trough and fall plate are transported along the mould, characterised in that mould conveying means is provided for conveying the mould from a filling station at which the mould is located during charging with foam to a curing position remote from the filling station, gas extraction means is provided for connection to the venting means of the mould at the curing position, and the mould includes means for closing the venting means during transfer of the mould from the filling station to the curing position.
• Some gases of generation can be removed from the mould at the filling station to control pressure within the mould until the mould is removed to the curing position, at which time the gases of generation are removed from the mould for disposal or recycling.
• Conditioned gas can be introduced into the mould at the curing position while the bun is curing to assist the extraction of the gases of generation.
• the conditioned gas is introduced at the top of the mould and the gases of generation are exhausted from the bottom of the mould.
• the gases of generation can be removed from the mould during charging of the mould at a rate different than the rate of gas generation within the mould to thereby control the pressure within the mould and thereby the properties of the cured foam.
• an overhead conveyor is preferably used for moving the moulds from the filling station to the curing position.
• the moulds are arranged in a plurality of vertically- stacked ranks and files.
• the mould comprises a longitudinally-extending, channel- shaped enclosed casing through which the mobile vessel and fall plate are progressively transportable from one end to the other of the mould to lay down partially-expanded foam over the bottom of the mould while the mould is at the moulding station.
• Gas venting means are attached to the casing to vent gases from the interior of the mould.
• the gas venting means may be pipes which also serve to reinforce the casing which in turn can be of relatively lightweight construction to facilitate movement between the filling station and the curing position.
• the gas venting means includes valves adapted to close the mould against the escape of gases therefrom when the mould is moved from the filling station to the curing position, and to open the venting means when the mould is in the curing position to permit gases of generation to be extracted from the mould and conditioned gas to be supplied to the mould.
• the mould can be at least 10 metres long, and preferably is at least 30 metres long.
• the bottom and at least the lower portions of the sides of the mould are preferably covered with a liner, e.g. a polyethylene foil, to assist removal of the cured foam.
• a liner e.g. a polyethylene foil
• means may be provided on the mould for perforating the bottom liner for allowing gases of generation to be removed therefrom.
• the mould has inner side walls which are movable to vary the width of the foam moulding channel defined between them, and means operable to move the inner side walls inwardly during movement of the mould from the filling station to the curing station.
• the inner side walls have vent openings near their lower edges and means, such as an apertured sliding plate is provided for opening and closing these openings.
• the mould preferably comprises door means in one side for removing the cured bun from the mould.
• the bottom of the casing may be hinged at - 7 -
• the mobile vessel comprises a trough of novel construction enabling the trough to be progressively collapsed from the bottom to expel the foam mixture in the trough.
• the trough comprises a rigid back plate and a front plate which is movable against the back plate to collapse the trough.
• the front plate may be flexible, e.g. a wire mesh, with means such as a roller for gradually pressing it against the rigid back plate.
• the front wall is a mesh a liner of flexible sheet material can be provided in the trough to retain the liquid foam mixture.
• the foam mixture is preferably delivered to the trough from a mixing chamber mounted directly on the trough and arranged to mix the liquid components by their impingement upon delivery into the mixing chamber, with means being provided for emptying the contents of the mixing chamber into the trough at the end of a mould filling run.
• FIGS 1-5 inclusive are fragmentary sequential views of the moulding process in connection with which the invention is practiced;
• Figure 6 is a plan view of a plant for moulding foam according to the invention.
• Figure 7 is a plan view of a mould according to the invention.
• Figure 8 is a side elevation of the mould illustrated in Figure 7;
• Figure 9 is an end elevation of the mould illustrated in Figures 7 and 8;
• Figure 10 is a vertical cross-section of a gas valve in the mould
• Figure 11 is a vertical cross-section of another gas valve in the mould
• Figure 12 is a fragmentary vertical view of a plunger which punctures a plastic liner in the mould to permit removal of gas from the mould;
• Figure 13 is a side elevation of the crane by which the mould is removed to the curing position after moulding has occurred;
• Figure 14 is a side elevation of the curing station showing the stacking arrangement of the moulds in which the foam is curing;
• Figure 15 is a fragmentary end view of the crane and the mould release apparatus
• Figure 16 is a side elevation of a curing station as in Figure 14 but with longer moulds;
• Figure 17 is a partly cut away schematic perspective view of a modified mould
• Figure 18 is a partial transverse cross- section through the mould of Figure 17;
• Figure 19 is a partial side view of the mould of Figure 17;
• Figure 20 is a schematic cross-section illustrating a preferred mixing head and foam trough.
• Figures 21 and 22 are views similar to Figure 20 showing the trough at successive stages during emptying.
• the production channel comprises a mould 10 which may be a variety of sizes but in the preferred embodiment disclosed in this application comprises a casing or box fabricated of mutually opposed top, bottom and side sheet metal segments which collectively define a mould 10 which is 30 metres long, 127 cm. high and 244 cm. wide. Mould 10 is stationary during the mould filling process.
• Two mobile units 11, 12 are provided., The first mobile unit 11 comprises a fall plate mobile and the second mobile unit 12 comprises a chemical holding vessels for the reactants and pumping means for delivery the reactants to a mixing trough 14.
• the two mobile units are referred to hereinafter as the fall plate mobile and the chemical pumping mobile. They are driven remotely along the mould and no human operators are exposed to any chemical fumes.
• the mobile 12 also carries a roll 90 (Fig. 1 ) of polyethylene liner film "P" which is arranged to be supplied over the fall plate mobile.
• the liner film is when stored on the roll folded laterally in three equal layers, the width of the folded film being 91.5 cms. As the film is unwound from the roll it is spread out the full width of 274.5 cms. by a pair of nip rollers 91 so that the liner will cover the full width of the mould bottom and form a turn up of about 10 cms. at each side.
• FIG. 1 A vertically slidable front end wall or door 13 is raised and rests with its lower edge on the inclined bed of the fall plate mobile 11 near its higher end and near the chemical mixing trough 14 carried on the adjacent end of chemical pumping mobile 12.
• the door 13 has associated with it a roll 93 (Fig. 1 ) of polyethylene liner film which is pulled from the roll as the door is lowered to provide a liner on the inside of the door, the free edge of the film being held by a clamp 94 on the top of the mould.
• Fall plate mobile 11 is covered with the polyethylene liner film "P".
• the polyethylene film "P” keeps the foaming material off the fall plate mobile 11 and the 10 cm. of turn-up prevents foam from leaking down the gap between the fall plate mobile 11 and the mould 10.
• the free edge of the film at the lower edge of the inclined bed of the fall plate is fixed to the floor by a clamp bar (not shown).
• Mould 10 is positioned at a filling or pouring station 16 to receive the chemical pumping mobile 12 and the fall plate mobile 11.
• a separate room 17 contains all of the process controls necessary to carry out the moulding and curing operations.
• An overhead crane 20 lifts moulds 10 from the pouring station 16 and moves them to a curing station 18 where in the particular embodiment shown in Figure 6 twenty-five moulds 10 (five ranks stacked five high) can be placed for curing. After curing, and removal of the bun from the mould 10 at a conveyor 19, conveyor 19 moves the bun downstream for shipment or further processing.
• Figure 6 is essentially schematic and it does not show the additional space which is needed at the upper end (as shown) of the mould at the filling station to accommodate the fall plate mobile at the start of the filling operation.
• the mould has a casing or box formed by sheet metal panels defining top, bottom - 12 -
• the casing is reinforced by frameworks 20 extending around the casing at locations spaced apart along its length e.g. at about 3 metre intervals,.
• the frameworks are defined by tubes of rectangular section and also constitute the gas venting means of the mould.
• Each framework includes an upper transverse tube 21 which extends across the top wall of the casing and communicates directly with the interior of the mould through holes in the tube and top wall, a right side vertical tube 22 which is in constant communication with tube 21 , a lower transverse tube 23, and a left side vertical tube 24 in constant communication with tube 23.
• the bottom wall of the casing is hinged to the left side wall to define a door which can be opened to remove the cured foam bun, as explained in more detail below with reference to Figure 15, and the tube 23 includes a flexible section to allow the hinged movement of the bottom wall of the mould.
• the tube 23 has holes which register with corresponding holes in the bottom wall of the casing for communicating tube 23 with the mould interior and at the locations of these holes the tube is fitted with spring loaded plungers 55 for rupturing the film P lining the bottom of the mould " , as described below with particular reference to Fig. 12.
• Each of the vertical tubes 22, has a valve 25 at its upper end and a further valve 26 at its lower end, and the vertical tubes 24 are each similarly fitted with a valve 27 at the upper end and a valve 28 at the lower end.
• the valves 25-28 are preferably arranged to be normally close and to be opened automatically when required, as will become clear from the description which follows.
• the valves 25 and 27 at the tops of the tubes 22, 24 may be as shown in Figure 11 and designated by the numeral 30 therein.
• the valve is illustrated in an open position.
• a spring 31 biases a sealing plate 32 against an apertured seat which may comprise O-ring seals 33 or flat washers surrounding the apertures and made of rubber or Viton which is a synthetic rubber ⁇ like product which resists solvents and TDI better than rubber.
• valve is equipped with a guide cone fitted with a seal 39 to facilitate correct connection with the valve 26 or 28 at the bottom of a second mould placed on top of the first mould, the moulds being stacked one on top of the other at the curing position as shown in Figure 14.
• the valves 26, 28 at the lower ends of the tubes 22, 24 may be of generally similar construction, but inverted relative to the valve shown in Figure 11. Thus , the valves 26, 28 may be as depicted in Figure 10.
• Mould 10 is designed so that the foam never touches the top of the mould. Gases are pulled from within the mould during pouring and foaming to control the atmospheric pressure within mould 10.
• Valves 26 are arranged to be open, but the valves 25, 27 and 28 closed when the mould 10 is in its pouring position.
• valves 26 of tubes 22 on the mould 10 are arranged to be cooperated with an elongate emission extraction pipe 37 on or in the floor at the filling station and through which the gases withdrawn from the top of the mould during foam lay-down and expansion are conducted to a remote location for reprocessing or disposal.
• the extraction pipe 37 has branches which are equipped with automatically openable valves, e.g. as shown in Figure 11 , and which cooperate with the valves 26 of the respective frameworks 20.
• a bed is provided to give flat firm support for the mould bottom allowing it to withstand the substantial weight of the mobiles as they are transported through the mould, yet still allowing the mould to be of relatively lightweight construction so that it can be lifted and moved to the curing position when filled.
• the support bed includes grooves or channels which receive the frameworks 20 so the bottom wall of the mould will lie flat against the supporting surface of the bed.
• mould 10 just filled with foam is lifted by an overhead crane 50, as is shown in Figure 13.
• the structure of mould 10 is such that it will not support its own weight when filled with foam. Therefore, crane 50 uses a pair of long lifting bars 51 each formed of 8 cm. diameter pipe which can lift mould 10 at multiple spaced-apart points. This configuration is best shown in Figure 15, where it can be seen that mould 10 includes downwardly facing curved lifting hooks 52 which cooperate with lifting bars 51 to support mould 10 along its length.
• the bottom of the mould 10 is enclosed with a polyethylene film "P". Since gases of generation are much heavier than air it is desirable to remove the gases from the bottom of mould 10.
• holes are punched in the film at intervals along its length. This is accomplished by means of the punches 55 with claw-like teeth 56 thereon, illustrated in Figure 12.
• the punches 55 are positioned in alignment with apertures 57 in the bottom of mould 10. The number of punches can vary based on size, spacing, etc.
• punches 55 are pushed upwardly against their spring bias and pass through apertures 57 so that the teeth 56 tear into and puncture the polyethylene film "P" as well as about 2.5 cm. of the foam bun itself. When the film has been ruptured gas can escape through the mould bottom into the tubes 23 and hence to the tubes 24.
• crane 50 includes three double hoists 59 which control the lifting bars 51.
• Each lifting bar 51 is pressurized to 70,310 Kg./m2 by a rotary air compressor 60 and therefore each lifting bar 51 functions as a supply reservoir for compressor 60.
• Pressurized air from the lifting bars 51 operates respective pairs of pneumatic cylinders 62 which function to latch and unlatch the lifting bars 51 from the lifting hooks 52 as is best shown in Figure 15.
• the hoists 59 are aligned with proximity switches located at each pick-up or drop point. Hoists 59 each have a directional encoder for up and down positioning and are operated by synchronous motors. These elements are not shown in the drawings.
• the vertical tubes 24- at the left side of the mould interconnect with an extraction pipe 80 through which gases flow away from the moulds for disposal or recovery, the valves 28 at the lower ends of these tubes being opened automatically.
• the tubes 22 at the right side of the mould are connected with a gas pipe 88 through which conditioned gas, e.g. dry air may be introduced into the tops of the moulds for controlling pressure within the mould and/or to be drawn down through the foam to improve the removal of generation gases, the valves 26 of the tubes being opened automatically.
• conditioned gas e.g. dry air
• a longer mould 96 having the same characteristics as the mould 10 de ⁇ scribed above except for length is moved by a crane 100 have 6 spaced-apart hoists 101 carrying a pair of lifting bars 102.
• a modified mould is illustrated in Figures 17 to 19.
• inner side walls 120 coupled to the respective outer side walls 122 by pairs of parallel link arms 124 having their inner ends pivoted to the inner side walls 120, and their outer ends pivoted to a slide block incorporating a nut 126 threaded on a rotatable lead screw 128 journalled on the outer side wall.
• the slide block is guided for vertical movement in response to rotation of the lead screw.
• an additional pivotal link arm 130 extends between the outer side wall and the mid-point of the lower arm 124, and the link arms 124, 130 combine to ensure that the inner side wall remains - 1 7 -
• the upper end of the lead screw is equipped with a drive connector 129 for coupling with a driving unit which may be computer controlled and carried by the overhead crane.
• a driving unit which may be computer controlled and carried by the overhead crane.
• the inner side walls 120 can be moved inwardly a small amount, e.g. by 2-3% of the moulded block width, upon the block reaching its full height, which can help in ensuring a skin of minimum thickness on the foam block after it has completely cured. This inward displacement of the inner side walls is performed during carriage of the mould from the filling to the curing station.
• the inner side walls 120 have their inside surfaces lined with a non-stick layer 132 provided by a self-adhesive glass-reinforced Teflon (p.t.f.e.) tape which facilitates removal of the moulded block and contributes to attainment of good skin properties.
• a self-adhesive glass-reinforced Teflon (p.t.f.e.) tape which facilitates removal of the moulded block and contributes to attainment of good skin properties.
• the inner side walls are provided with vent openings conveniently formed by a longitudinal row of spaced parallel slots 134 extending along the entire length of the mould.
• a similarly slotted shutter plate 136 is slidably mounted on the exterior of the inner side wall for movement between a closed position in which the plate covers the slots 134 and an open position in which the slots 138 in the plate register with the slots 134 in the side wall.
• the surface of the shutter plate confronting the inner side wall 120 is also covered with glass reinforced Teflon tape 132 to deter the foam sticking to the plate and impeding its opening.
• the slots 134 are positioned to be above the top edges of the tur «n ups 140 formed at the sides of the mould when the polyethylene film liner P is layed along the bottom of the mould.
• the slots 34 and shutter plate 136 obviate the need to puncture the liner film P for extraction of the gases of generation during curing of the foam, and thus they are an alternative to the punches 55 described above and shown in Figure 12.
• the shutter plates 136 are adjusted to their closed positions when the mould is disposed at the filing station and during the filling process. They remain closed while the filled mould is conveyed to the curing station and upon being set down at the curing station the shutter plates are slid to their open positions by an appropriate actuating mechanism.
• the gases exhausted through the slots 134, 138 are conducted to the vent tubes (not shown) of the mould, possibly passing to these tubes via the spaces 144 between the inner and outer side walls, and the gas extraction proceeds essentially as described above. Alternatively and/or additionally these spaces 144 may serve to collect gases from the top of the mould during the lay-down of the foam and its expansion in the mould.
• FIGS 20- 22 illustrate a trough assembly equipped with means for emptying the trough.
• the trough comprises a rigid back plate 150, and a movable front wall capable of being displaced from a normal, in use, position defining an open-topped trough chamber with the back plate and an emptying position lying substantially flat against the back plate to collapse and empty the trough of its contents.
• the front wall is a flexible sheet constituted by a steel wire mesh 152 having a lower edge attached to the lower edge of the back plate and an upper edge held fixed at a position spaced forwardly from the back plate and near the top of the fall plate.
• a device for collapsing the trough comprises a roller 156 mounted on the mobile 12 for vertical movement parallel to the front face of the back plate 150. In a normal position the roller is located at its lowermost position adjacent the bottom edge of the back plate 150 and the trough can fill with foam, as illustrated in Figure 20.
• the roller When the trough is to be emptied the roller is driven upwardly and causes the wire mesh 152 to be progressively displaced against the back plate 150 and hence the liner 154 to be gradually collapsed from its bottom to expel the contents of the trough. In the uppermost position of the roller, shown in Figure 22, the trough is essentially emptied of foam.
• the trough assembly also incorporates a novel form of mixer unit for mixing the foam constituents prior to delivery to the trough. It comprises a cylinder 160 mounted directly on the back plate 150 of the trough and having an axial outlet for discharging the foam mixture through a hole in the back plate, and a corresponding hole in the liner 154, into the trough.
• a piston 162 Accommodated in the cylinder 160 is a piston 162 which can be advanced from the retracted position shown in Figure 20 to empty the contents of the cylinder into the trough 14.
• the cylinder is provided with ports for delivery of the liquid constituents into the mixing chamber defined by the cylinder from suitable metering devices.
• the mixing chamber is devoid of any mechanical mixing element and is arranged to mix the liquids under the effect of high pressure (50-80 bar) metering of polyol premix, TDI, water, etc. and impingement of the liquid streams on entry into the mixing chamber.
• the mixing chamber can have a very small volume, e.g. 1 d ⁇ .3.
• the supply of chemicals to the mixing chamber is interrupted and the piston 162 is driven forwardly to discharge the contents of the chamber into the trough.
• the roller 156 is then activated to empty the trough.
• the described mixing head and its mounting directly on the trough has the advantage of minimising the "dead” volume which must be flushed and cleaned after mould filling, whereby usage of foam chemicals is optimised and the consumption of solvents for cleaning is substantially reduced and could even be eliminated.
• valves are of the spring loaded type and they could alternatively take the form of flapper valves which could be arranged to be opened automatically by cable and lever mechanisms.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=25675793

Family Applications (1)

Country Status (3)

Cited By (1)

Family Cites Families (4)

• 1991
  • 1991-05-04 EP EP91909285A patent/EP0537169A1/de not_active Ceased
  • 1991-05-04 CA CA002086622A patent/CA2086622A1/en not_active Abandoned
  • 1991-05-04 WO PCT/EP1991/000858 patent/WO1992019441A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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