Abstract: An apparatus for injection molding two compatible polymeric materials, in which two or more plasticizing zones on a screw are used to simultaneously or sequentially plasticize the two materials into a common accumulation space through separate pathways. The charge comprising multiple layers of material is then injected into a closed mold by means of forward axial motion of the screw with respect to its enclosing barrel. Once inside the mold, the first material forms a skin layer, totally or partially surrounding the other material. In this way a part having a plurality of material properties may be produced in a single operation.

Abstract: An injection molding machine is equipped with a drive mechanism which reciprocates a movable member, such as a screw or a mold clamping mechanism, by use of a servomotor and a ball screw mechanism. In the injection molding machine, an end portion of a rotor shaft of the servomotor is connected directly to an end portion of a ball screw (or a nut) of the ball screw mechanism for reciprocating the movable member. This structure enables rotation of the servomotor to be transmitted directly to the ball screw (or the nut) of the ball screw mechanism without intervention of a rotation transmission mechanism.

Abstract: An injection-molding machine is disclosed. The machine has an injection unit and nozzle and the injection unit includes a tubular cylinder and a screw that is capable of back and forth movements along the tubular cylinder. Means are provided to stop the movement of the screw at its end/stop position at a distance from the nozzle so as to form a gap between the screw head and nozzle. The gap has a volume of more than &pgr;/4 ·D3 and up to the volume of a shot wherein D is the dimension of a single screw stroke. The use of the machine yields molded articles that are virtually streak free.

Abstract: An injection molding apparatus for injecting resin into a mold comprises an injection cylinder (9, 109, 209, 309) in fluid communication with the mold (5, 105, 205, 305), wherein movement of a piston (11, 111, 211, 311) relative to the cylinder injects a selected quantity of resin into the mold. A plasticizing unit (1, 101, 201, 301) includes a flighted screw (3, 103, 203, 303) rotating in a heated containment barrel for plasticizing resin. The plasticizing unit is in fluid communication with the injection cylinder for supplying the injection cylinder with plasticized resin. A valving means is provided for selectively placing the injection cylinder in fluid communication with the mold and placing the plasticizing unit in fluid communication with the injection cylinder, wherein the valving means is actuated by relative movement between the mold and one of the injection cylinder and the plasticizing unit.

Abstract: The invention relates to an electric injecting molder and an injection velocity and injection pressure controlling method for an electric injecting molder, and it is an object of the present invention to make it possible, in injection molding by an electric injection molder, to mold stable resin products having a minimized dispersion in the quality even if the operation environment varies. When an injection screw (23) disposed in an injection cylinder (22) is driven to move in forward and backward directions by an electric motor (29A) to inject resin material (3) in the injection cylinder (22) into a metal mold (1, 2) to fill the metal mold (1, 2), the electric motor (29A) is first velocity-controlled to fill the resin material (3) into the metal mold (1, 2), and, after the filling, the electric motor (29A) is pressure-controlled to replenish the resin material for shrinkage of the resin.

Abstract: Device for injection moulding of plastics, with a plasticizing and injection unit (3), that is provided with at least one electrical drive system (6) for turning a plasticizing screw and for injecting the plasticized plastics material between the mould halves (16), wherein the injection moulding device is provided with at least one additional drive unit that firstly moves a machine part in a linear manner, and subsequently presses it against a fixed stop, and the additional drive unit is configured as a pneumatically actuated piston-cylinder unit (8, 18, 28, 38) and the force exerted by the piston assumes different values at a given gas pressure according to the setting of the piston.

Abstract: An object is to increase the mechanical efficiency of an injection molding machine, decrease the inertia, and decrease the axial length. The injection molding machine comprises a cylinder member; an injection member disposed within the cylinder member such that the injection member can advance and retract; an injection motor (82); and a transmission shaft which is connected to the injection member such that the transmission shaft can rotate relative to the injection member. The transmission shaft has a rotation transmission portion, to which rotation of the injection motor (82) is transmitted, as well as a motion conversion portion for converting rotational motion to linear motion. The injection motor (82) and the transmission shaft are disposed on the same axis, and the transmission shaft is advanced and retracted inside the rotor (92) of the injection motor (82).

Abstract: A two-stage, electrically-powered injection unit for an injection molding machine includes an extruder for plasticating material, and a separate melt accumulator to receive the plasticated material. The accumulator includes an injection plunger that is slidably positioned to inject the plasticated material from the accumulator into a mold. The plunger is rotated and translated by an electrically-driven linear actuator, such as a roller screw mechanism. The plunger extends outwardly of the accumulator barrel at the commencement of an injection stroke and is peripherally supported by a bushing at the outer end of the accumulator barrel. The outwardly-extending portion of the plunger can also be supported by a movable intermediate support member to minimize lateral deflection of the plunger and enable a longer injection stroke to be employed.

Abstract: An electric injection assembly for injection presses for plastic materials, comprising a plasticating screw (5) that performs a translational feed movement during injection of the plastic material into a mould cavity and a rotary movement around its own axis and a rotary translational movement of rotation around its own axis and retraction during the plasticating stage of the plastic material, the plasticating screw being connected to a drive screw (30) comprising two sections (30A, 30B) with threads having the helix in opposite directions, each of the sections (30A, 30B) engaging in respective screw nuts (31A, 31B) driven in rotation by respective electric motors (32A, 32B) through respective reduction units (33A, 33B).

Abstract: Molding material consisting of resin coated reinforcing fiber strands in a molten mass of resin is prepared at a molding site for controlled supply to a molding machine. Continuous strands of fiber from supply spools are entrained with pressurized, molten resin flowing through a coating device and coated with the resin. The movement of the fiber and resin through the coating die may be controlled so as to accurately and predictably produce any desired quantity the molding material, i.e. the coating apparatus may be operated in a discontinuous manner to provide any predetermined quantity of molding material to a receiving device. The receiving device may be the feed screw for an injection molding machine or simply a plate movable to and from a compression molding machine. The fiber strands may be cut into predetermined lengths by a cutting device positioned downstream of the aforesaid coating device.

Abstract: An injection molding machine is equipped with an injection apparatus support mechanism comprising paired main tie-bars disposed to extend between a mold attachment plate and a back plate disposed to face each other; front and rear support plates connected to each other via paired auxiliary tie-bars and slidably supported by the main tie-bars; and an intermediate support block slidably supported by the main and auxiliary tie-bars. Since the mold attachment plate and the back plate are supported by the paired main tie-bars disposed symmetrically with respect to the screw, a sufficient level of mechanical strength (fixation strength) is secured for the mold attachment plate and the back plate. In addition, since the front support plate and the rear support plate are connected to each other by the paired auxiliary tie-bars disposed symmetrically with respect to the screw at positions different from those of the main tie-bars, the mechanical strength of these plates is secured.

Abstract: A motor-driven injection molding machine comprises an injection device which includes a heating cylinder for heating resin powder therein to melt the resin powder into molten resin and a screw disposed in the heading cylinder for feeding the molten resin in the heating cylinder forward to meter the molten resin. A controller positions, in response to a position detected signal detected by a position detector, the screw at a metering position using an injection servomotor on and immediately after completion of the plasticization and metering process. In addition, the controller rotates, in response to a pressure detected signal detected by a load cell, the screw in the opposite direction using a screw-rotation servomotor on and immediately after the completion of said plasticization and metering process to carry out depressurization of the molten resin in the heating cylinder that is metered ahead of the screw.

Abstract: A process for forming detergent bars by injection moulding in which a pressure is applied to a partially structured detergent composition to deliver it to a mould. The detergent composition can be delivered to the mould in a substantially semi-solid state, at a temperature below 70° C. and at a pressure at the point of injection of greater than 20 psi. Apparatus for forming detergent bars according the invention are also described.

Abstract: A system and method are disclosed for molding a part, such as a point-of-purchase display, is shown. The system comprises a plasticator and press. The molded part comprises an in-molded graphics sheet which becomes molded integral with the part.

Abstract: A screw adapted for plasticizing a fiber-reinforced thermoplastic resin wherein screw lead (distance of the resin advancement in the direction of the axis per 1 revolution of the screw when it is postulated that the screw channel is 100% filled with the resin) of the screw in its compression section decreases in the direction toward the forward end of the screw. A plasticizing apparatus wherein such screw is mounted. A method for molding a fiber-reinforced thermoplastic resin by using such an apparatus. A molded article produced by such molding method. In the present invention, shear force of sufficient level can be obtained to avoid the formation of clumps while breakage of the reinforcing fibers is avoided to leave long fibers in the molded article. The resulting molded article has excellent mechanical properties, and such article is quite useful as a material for use in automobile parts and other parts.

Abstract: An injection molding machine includes an injection molding cylinder with a material supply at one end and an injection nozzle at the other end and a material conveyance unit attached to a drive and movable in the injection molding cylinder. The injection molding machine also includes a vibration element for inducing a flow of melt within the injection molding cylinder for homogenizing the melt.

Abstract: A method for controlling a screw injecting apparatus having a heating cylinder and a screw slidably and rotatably received in the heating cylinder and designed to carry out a plasticizing-metering phase in which a predetermined amount of a molten material is accumulated forwardly of the screw by plasticizing and kneading a raw molding material via the screw and the heating cylinder, a waiting phase in which the screw is held inactive for a period between completion of the metering and subsequent injection of the molten material, and an injecting phase in which the molten material is injected. The method comprises the step of causing the apparatus to vibrate the molten material at a predetermined low frequency axially of the screw during the plasticizing-metering phase. By vibrating the molten material at a low frequency during the relatively long plasticizing-metering phase, the viscosity of the molten material can be reduced.

Abstract: Molding material consisting of resin coated reinforcing fibers in a molten mass of resin and fibers is prepared at a molding site for controlled supply to a molding machine. A conveying device, such as a pair of pinch rollers, serves to pull fibers from supply spools through guide orifices of a coating die having a chamber within which the fiber is coated with molten resin. Further impregnation of the fibers with resin takes place in the conveying device, which also develops pressure on its output side serving to push the mass of hot resin and fiber into a receiving device for movement to a molding machine. The receiving device may be the feed screw for an injection molding machine or simply a plate movable to and from a compression molding machine. The fibers may be cut into predetermined lengths by a cutting device positioned downstream of the aforesaid conveying device.

Abstract: An injection molding process wherein the times of heating to melt a resin are reduced to minimize the thermal hysteresis and to decrease the deterioration of physical properties caused by the thermal hysteresis, so that high quality information recording disks may be produced. A molding process wherein the plasticating and the injection and filling of a material resin are carried out in separate cylinders, allows constant molding for a long period of time. A material resin such as polycarbonate is supplied without predrying to an injection apparatus for a first time molding. Resin is kneaded by the apparatus while volatile components are heated to be vaporized and exhausted through a vent port. An inert gas atmosphere is provided within the cylinder to prevent the material resin from being oxidized. Since predrying can be dispensed with, the thermal hysteresis will be extremely small and the deterioration of the resin caused by such heating may be suppressed.

Abstract: Gas (air) is supplied into an oil transfer line extending between a front oil chamber of an injection cylinder and an oil tank during a molding cycle, excluding an injection step, thereby preventing impact which would otherwise occur due to oil pressure generated upon start of injection in the injection step. Thus, immediately before the start of the injection step, the oil transfer line becomes empty of or almost empty of oil. Accordingly, even when high-pressure oil is supplied into the injection cylinder in an impactive manner upon start of injection, pressure oil ejected from the injection cylinder flows swiftly through the oil transfer line.

Abstract: An injection molding unit is provided with a carrier block and an injection bridge, movable towards and away from the carrier block for a relative movement of a feeding means relative to a receiving body. An injection motor drives a plurality of spindle drives for generation of this injection movement. The injection bridge has a sparing or recess, in which the injection motor is placed.

Abstract: A plasticizing unit having a plasticizing screw, an injection piston connected to the screw, a quill connected to the piston, and hydraulic cavity formed by the piston and a quill end face. Hydraulic fluid is transferred to the hydraulic cavity to move the piston and screw away from the quill. The screw and piston are subsequently moved towards the quill to displace hydraulic fluid out of the hydraulic cavity and cause back pressure. The back pressure is counteracted by acting on the back of the quill.

Abstract: An injection unit for injection moulding machines comprising a plasticizing cylinder and a plasticizing screw which is arranged rotatably therein and axially displaceably by a crank drive, wherein there is provided a drive motor (1) which selectively either rotates the plasticizing screw (2) or advances same by means of a crank (5) which is pivotably connected to a thrust rod (4), and wherein there is provided a further drive motor (8) which by way of a crank (10) drives a thrust rod (9) arranged in mirror image relationship in plan view in relation to the first thrust rod (4).

Abstract: An injection molding process and apparatus to manufacture asphalt-based products which utilizes a heated mixing chamber to continuously blend molten thermoplastic polymer and asphalt to form an injection moldable composition.

Abstract: A charging barrel and screw as well as their associated components for carrying out the processes of plasticization, injection and pressure maintaining of the polymer are all disposed in the inner cavity of a metal moving body driven to rotate pulsatorily by an electromagnetic winding. At the time when the screw and the metal moving body are simultaneously rotating pulsatorily, the screw is at the same time making axial pulsative displaments, so that the processes of plasticization, injection and pressure maintaining are all carried out in a periodic oscillating state. This type of injection moulding method and apparatus have the advantages of small volume, light weight, low manufacturing cost, low energy consumption, low noises, wide adaptability to materials and excellent quality of the moulded products.

Abstract: An injection-molding machine for plastic, including an injection cylinder, a screw arranged in the injection cylinder and having a drive shaft, an electric motor, a mechanical rotary drive for connecting the electric motor to the drive shaft so that rotary motion is imparted to the drive shaft, and a linear drive for connecting the electric motor to the drive shaft so that linear motion is imparted to the drive shaft. The linear drive includes a pressure medium pump connected to the electric motor, and at least one synchronous piston-cylinder unit connected to the drive shaft and in fluid communication with the pump. A control unit is connected to the pump for controlling one of pump and motor absorption level. Hydraulic lines are configured and arranged to directly connect an input of the synchronous cylinder with an output of the pump and an output of the synchronous cylinder with an input of the pump in a closed hydraulic circuit.

Abstract: A pre-plasticizing type injection molding machine includes a plasticizing device for plasticizing a molding material supplied from a hopper by a first screw disposed within a first barrel, an injection device 8 for measuring a molten resin supplied from the plasticizing device 5 and for injecting the measured molten resin by a second screw disposed within a second barrel. A switching valve is provided in a resin passage between a resin outlet of the plasticizing device and a resin inlet of the injection device, and an accumulation device is provided for housing a pushing plunger having a stock chamber communicated with the resin passage at a position between the switching valve 10 and the resin outlet of the plasticizing device.

Abstract: There is provided a preplasticizing injection machine including a resin vent formed in the injection cylinder behind the plunger stroke wherein said resin vent is connected to a pressure reducing device and/or an inert gas feeding machine. The resin entrapped in the clearance prevents gases generated within the cylinder from being exhausted and it may be blackened due to the oxidation thereof. According to the present invention, these problems can be solved by the above construction. Furthermore, a band heater is provided on the outer surface of the cylinder behind the injection plunger stroke over the resin vent to prevent the entrapped resin from being solidified.

Abstract: A method for injecting a molten resin by an injection machine comprises the steps of opening a ring valve mounted on an injection screw by the normal revolution of a injection screw thereof; metering the molten resin; stopping the revolution of said injection screw; moving said injection screw backward, performing the reverse revolution of the injection screw at the moved-back position for the required amount to generate a differential pressure; making the ring valve come in proximity to or into contact with a valve seat at the tip of a screw body of the injection screw by said differential pressure; and injecting the metered resin by the forward movement of the injection screw so as to complete the closure of the ring valve. According to the longer stroke of the injection screw, the ring valve is certainly closed by the backward, rotative and forward movements of the injection screw and thereby an injection operation is maintained more precisely in the dispersion of the injecting quantities than before.

Abstract: An arrangement of oil cylinders of a plastic injecting machine is provided which positions a large oil cylinder and a small oil cylinder respectively on both the left and right sides of an oil cylinder base and a bearing base. The large and small oil cylinders are located at such a distance away from a material injecting cylinder that the oil seals of the four oil cylinders are not heated by the electric heaters that heat the material injecting cylinder. By this arrangement, the oil seals have a normal service life. In addition, an oil route plate is located on the bearing base to secure oil pipes formed of hard steel connected between the four oil cylinders and an oil pump, to keep oil flowing smoothly.

Abstract: The problem of insufficient friction along the wall of a rotating funnel feeding viscous material to an extruder or injection molding machine so that the material sweeps past the conveying screw and prevents the conveying screw from continuously feeding that mass to the outlet of the funnel, is solved by providing pins which project inwardly from the rotating funnel wall and engage in interruptions in the flight of the conveying screw. The funnel wall can also be provided with pockets or grooves.

Abstract: A method of injection molding polyethylene terephthalate without being predried or with having an irregular-shape wherein a vent type injection machine is employed and the vent is forcedly performed by vacuum suction within a range of a specified degree of vacuum, i.e. 50 to 150 torr (equal to 6666.1.about.19998.3 Pa.) and/or at the same time the material is forcedly fed by a feed screw having a specifically set revolution speed. According to the present invention, it is possible to provide an injection molding method in which an PET without being predried or with having an irregular-shape can be molded.

Abstract: An injection molding method characterized in that after resin charging is completed, with the screw allowed to rotate, process is shifted to the metering process, and using the back pressure in the metering process as a dwelling pressure, dwelling is performed simultaneously with the resin metering. In addition, with the back pressure required for metering set to a higher value as a primary back pressure, and using the back pressure as a dwelling pressure, dwelling is performed simultaneously with the resin metering, and after the dwelling time has elapsed, with the pressure allowed to lower so as to use as a secondary back pressure, the metering is continued to a set time. According to the above-mentioned method, as a whole, the required cycle time becomes shorter than in a conventional case where metering is started after dwelling.

Abstract: A screw driving mechanism E which uses a hydraulic cylinder (main cylinder) 2 arranged on the same axis with respect to a screw 3 so as to allow the screw 3 to perform frontward and rearward driving. A pair of auxiliary cylinders 4 and 5 are arranged in parallel at both sides of the main cylinder 2, and the forward ends of piston portions 4p and 5p of the auxiliary cylinders 4 and 5 are joined to the forward end of a piston portion 2p of the main cylinder 2 via a joint mechanism 6. This makes it possible to select a plurality of different injection pressures.

Abstract: A screw of a screw-in-line type plasticizing device of an injection molding machine has a cylindrical main part and a spiral screw flight on the main part. A portion of the screw flight of the screw facing a resin supply port has a parallelogrammic axial sectional shape which is inclined towards the discharge end of the screw.

Abstract: A first direction shifting valve adapted to supply pressurized hydraulic oil to a hydraulic chamber on the rearward displacement side and discharge hydraulic oil from the hydraulic chamber on the rearward displacement side, and moreover, discharge hydraulic oil from a hydraulic chamber on the forward displacement side is disposed in a hydraulic path extending between a hydraulic pump and an injection cylinder. In addition, a second direction shifting valve adapted to supply pressurized hydraulic oil to a chamber on the forward displacement side is disposed in the foregoing hydraulic path. Additionally, a third direction shifting valve is disposed to build a bleeding-off circuit in cooperation with the second direction shifting valve. While a hydraulic path on the rearward displacement side is blocked by the third direction shifting valve, a hydraulic path on the forward displacement side is hydraulically connected to the tank side.

Abstract: A pre-plasticization type injection molding machine is equipped with a plasticizing part for plasticizing synthetic resin material by turning a screw in a heating cylinder and an injection part for injecting the plasticized material through a nozzle by advancing and retreating an injection plunger into and from an injection cylinder. A conduit connects the tip of a plasticizing chamber, consisting of the heating cylinder, with the tip of an injection chamber consisting of the injection cylinder. The screw advances at the time of injection, closes the conduit with its tip. The opening of the conduit in the injection chamber is arranged on the periphery of a nozzle side-wall. An injection passage extends from the injection chamber toward the nozzle, the passage being open to the center of the nozzle side-wall.

Abstract: Flanges are provided on a screw casing and a cylinder member of a screw driving unit in opposition to each other, and coupled with each other with fastening bolts. An adjusting ring is screwed onto the outer circumference of one of the flanges. The screw member is moved together with the ring in a backward direction until the end of the screw hits. The ring is rotated thereafter to bring it into contact with a side of the other flange, where a datum position is established. The cylinder member is then retreated an adequate amount in this state, and the ring is moved by a specified quantity. The specified quantity, represents the stroke quantity and bolts are fastened so that the ring comes into contact with the side of the other flange. The screw is thereby adjusted in its stroke.

Abstract: An apparatus for injecting molding material into a self-clamping mole. The apparatus includes a support frame with spaced plates and support bars interconnecting the plates, and a C-shaped opening formed in the plates. An injector is included for injecting molding material into the self-clamping mold under pressure, and an extruder for providing molding material to the injector. Temperature controllers are also provided for controlling the temperature of the molding material within the injector and extruder. A lift mechanism supported on the frame provides clamped engagement between the self-clamping mold and the frame. During the injection operation wherein the injector is engaged with the mold, the lift mechanism clamps the mold to resist internal mold forces resulting from the injection of molding material.

Abstract: A highly viscous or dough-like material, especially glass fiber-filled polyester, polyamide or polypropylene is fed from a rotating funnel via a feed worm lying along a generatrix of the funnel directly into an extruder or an injection molding cylinder and without passing through an elbow or other jacket. The system is thereby able to operate at reduced pressure with least damage to the fibers and reduced drive energy for the feed worm or screw.

Abstract: A synthetic-resin article is molded by plastifying a virgin granulate into a fluent stream and plastifying a recycle granulate into another fluent stream. The recycle stream is then filtered while still plastified to removing particulate impurities from it. Then the filtered recycle stream while still plastified is combined with the virgin stream to form a combined stream and the combined stream is fed into a mold. The stream is mechanically filtered.

Abstract: In a process for the manufacture of thick, preferably sheet-shaped, thermoplastic molded parts or molded parts having areas of variable cross sections, at least one part of the plastic material is conveyed as a melt into a heatable and optionally coolable compression mold and is subsequently compressed. Plastic granules are mixed in with the melt before the melt is conveyed into a compression mold. A device to prepare such mixture of melt and plastic granules includes a first section designed as a melt extruder and a subsequent section designed as a mixing extruder. The granules can be fed into the melt between both extruder sections or into the second section.

Abstract: A lightweight, compact, and low-cost two-plate type injection apparatus attached to an injection molding machine which includes an injection screw (50) spline-connected to a screw sleeve which is rotatably supported by a pusher plate (20) movable toward and away from a front plate (10). The screw is coupled through a transmission mechanism (62, 63) to a metering motor (160) which is fixed to the top face of the pusher plate so that the motor body is located above and between the two plates. First and second ball screws (91, 92), which are individually rotatably supported by the front plate, are threadedly engaged with first and second ball nuts, respectively, which are fixed to the pusher plate, and are coupled through a transmission mechanism (111 to 113) to an injection motor (140) which is fixed to the front plate so that the injection motor body is located above and between the front plate and the pusher plate and does not interfere with the metering motor body.

Abstract: A non-return valve for an injection molding machine is provided which includes a conventional tip member threaded into the end of a plasticating screw and carrying therewith an annular valve seat member. An annular check ring receives the tip member. Tang protuberances axially extend from the check ring to rotably engage the retainer end of the tip member. This causes the check ring to couple with the tip member during screw rotation to minimize valve wear while permitting the check ring to axially move relative to the tip member for effecting valve closure by pressure differentials in the normal manner. A ramp surface is provided on the tang protuberances which engages a drive surface on the retainer end of the tip/stud member upon reverse rotation of the screw through a predetermined rotational angle or for a set time to positively close the valve prior to injection.

Abstract: A single-state apparatus for injection molding structural foam articles has a resin plasticating barrel in which a cylindrical plunger reciprocates and rotates. The plunger has a screw section for plasticating resin and advancing the plasticate into a metering section with grooves in which plasticate flows. The grooves are contiguous to a fluid foaming agent inlet in the side of the barrel so that they alternately open and close the inlet to introduce fluid foaming agent periodically into the plasticate. Downstream, the plunger has channels for mixing and advancing plasticate to the forward end of the plunger where it accumulates and is periodically rammed by the plunger into the mold.

Abstract: A resin composition of a thermoplastic resin and long fiber is injected into a molded article having good physical properties by molding the composition in the form of a pellet having a length of 3 mm or more and containing 10 to 80% by weight, based on the composition, of a fiber having a length substantially equal to that of the pellet and arranged in the lengthwise direction of the pellet, characterized by using an injection molding machine having a nozzle diameter of 6 mm or more.

Abstract: An apparatus for supplying a resin material to molds of a resin press molding machine includes a supply cylinder for supplying the resin material to the molds, resin material charge hopper mounted to the supply cylinder, a plunger for extruding the resin material within the supply cylinder, a drive device for moving forward and backward the plunger in an axial direction, an opening and closing device for opening and closing an opening of a fore end of the supply cylinder, and a die positioned between the opening and closing device and the molds to form the resin material into a predetermined shape.

Abstract: In an injection unit of an in-line screw type injection molding machine, a screw is provided rotatably in both normal and reverse directions within a heating cylinder. The screw is periodically reversed in a charging stroke with the period of normal rotation being longer than that of reverse rotation, whereby a resin material is kneaded and plasticized. As a result, the resin in a melting and pooling zone (flow zone) between the inner wall of the heating cylinder and the outer peripheral wall of the screw is effectively moved back and forth and hence plasticized and molten into a uniform molten resin.

Abstract: A method controlling the injection of a molten resin through an in-line screw type injection molding machine. The molding machine is equipped with a check ring for permitting the injection of the molten resin by an advancement of the screw and also for preventing the molten resin from flowing backward. According to the method, the screw is rotated in the normal direction to knead and plasticize a resin material and further to feed the resultant molten resin to the free end portion of the screw. The screw then retracts to meter and store a predetermined quantity of the molten resin adjacent to the free end portion of the screw. The screw is next rotated in the reverse direction to pressure of the molten resin on the rear side of the check ring lower than that of the molten resin thus metered and stored on the front side of the check ring. The screw retracts to reduce the pressure of the resin on the front side of the check ring, thereby performing a decompression stroke.

Abstract: An extruder screw of a plastic injection molding machine has a tip seal device at its forward end. The tip seal device has a body portion and a tapering tip portion, a circumferential sealing skirt is provided between the tip portion and the body portion. During extrusion, the pressure of molding material behind the skirt compresses it radially to allow for passage of the material through an extruder nozzle. When the screw is moved forwardly after extrusion, pressure of material forwardly of the skirt increases and expands the skirt radially into contact with the extruder barrel to form a seal.