Technical Field The present invention relates to an injection molding machine.

More particularly, the present invention relates to an injection molding machine of a balance product having a plastic powder and an iron powder mixed therein, wherein a load can be reduced in transferring an injection material being a compound matter of a plastic powder and a scrap iron powder.

Background Art An injection molding machine is an apparatus for producing a raw material such as plastic (thermosetting resin, thermoplastic resin) into a molding product of a desired shape. This injection molding machine includes a hopper into which a raw material is inputted, a feed unit that melts the raw material supplied from the hopper and then transferring it, an injection molding plunger for injecting the raw material received from the feed unit, and a mould for molding the raw material injected from the injection molding plunger into a predetermined shape. In the above, the feed unit includes screws that are rotated at a given rotary speed in order to transfer the raw

material, and heaters for fusing the raw material. Through the above structure, the raw material introduced from the hopper is transferred to the injection molding plunger while being melted in the feed unit.

The injection molding plunger injects the fused raw material of a predetermined amount as a mould, so that a molding product of a predetermined shape is produced.

However, in case of a conventional commercial apparatus, for example, a washing machine, when the center of a rotary drum is light, other pressure is weak and a washing effect of the laundry is thus low.

For this reason, in order to increase the centrifugal force and other pressure, a balance made of a weight material is attached the main surface of the rotary drum. It is preferred that such a balance is injected using a plastic powder that contains lots of iron powder of a high specific gravity. When the iron powder is contained a lot, abrasion of the injection machine screws is severe and lots of mechanical load is applied. Thus, a balance in which a cement mortar is filled is attached to the inside of a case formed using synthetic resin. In this case, there is difficulty in manufacturing and the case is easily broken when hitting other object. Accordingly, there is a problem that the life span is short.

Furthermore, in the above the injection molding machine, the balance component that is injected from the combined plastic powder and metallic powder is better than the balance component made of the

cast-iron. This is because the cast-iron manufacturing process must be produced every component, but the injection molding process can mass-produce an exact mould consecutively. Furthermore, the injection molding process has good efficiency in comparison with the price and can mass-produce products utilizing a cheap raw material.

However, the metallic power injection molding has abnormally used a cheap cement raw material as a fused raw material of an injection product of a metallic powder since an expensive raw material is used. However, there is a danger that a cement raw material of a thin thickness may be broken. Due to this, there are problems that a cement raw material of a thick thickness can be used, a high quality balance product cannot be produced and reliability of a product is low.

Furthermore, in order to produce a high quality balance product, the compound matter in which the iron powder and the plastic powder are combined is used as the injection material. This injection material exists as the solid state until it is melted after being transferred from the feed unit. In this state, the screws that transfer the raw material is applied with lots of load. More particularly, if the material contains a large amount of iron powder as a molding raw material, the screws are applied with more load.

Therefore, there is a problem that the entire screw or feed unit may be damaged.

Disclosure of Invention Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an injection molding machine in which a combined feed cylinder connected to a low-speed motor is disposed at the top of a common injection plunger body, and a transfer tube disposed in an exhaust port of an oil pressure (or air pneumatic pressure) cylinder connected to a plastic powder hopper or an extrusion cylinder rotated by a sub- motor for injection and a transfer tube disposed in an iron powder material hopper are connected, whereby processes from the input of a plastic powder and iron powder to the extrusion and injection of a feed fused powder can be performed consistently.

Another object of the present invention is to provide an injection molding machine in which a transfer tube having a check valve for preventing counter-pressure inserted therein is disposed in an injection fusion material input port formed at the front end of an injection plunger body, a front end extrusion portion of an extrusion cylinder is connected to the top of the transfer tube and an iron powder-dedicated high temperature dry hopper having a feed control port is disposed at the rear end of the extrusion cylinder whereby the supply amount of an iron powder inputted to the extrusion cylinder does not exceed 50% to minimize a load applied to extrusion screws, and a plastic powder hopper having a feed control port is disposed at

a location 1/3 from the exit at the front end of the extrusion cylinder whereby mixture and melting of the iron powder and plastic powder can be performed rapidly.

Still another object of the present invention is to provide an injection molding machine in which damage to the entire screw or feed unit is minimized in such a way that a load applied to the screws becomes less when a compound matter of a plastic powder and an iron powder (or scrap iron powder) are applied to the screw.

Still another object of the present invention is to provide an injection molding machine capable of further reducing the entire screw or feed unit by adopting an inverter that can control the speed of the screws depending on the amount of a raw material of a plastic powder and iron powder (or scrap iron powder) that is transferred to an injection molding plunger.

Still another object of the present invention is to provide an injection molding machine in which a scrap iron powder can be suitably utilized and a high quality balance product can be thus produced at low cost in such a manner that a scrap iron powder or other scrap iron powder (or iron powder) generated when an iron powder metallurgical component is fabricated is compounded with a plastic powder in an appropriate ratio and is then used as an injection fused raw material.

To achieve the above objects, according to the present invention, there is provided an injection molding machine including a hopper 10

into which a raw material is inputted, a feed unit 20 that heats, melts and transfers the raw material introduced from the hopper 10, an injection molding plunger 30 for injecting the raw material transferred from the feed unit 20, and a mould 40 that molds the raw material injected from the injection molding plunger 30 into a predetermined shape, wherein the feed unit 20 comprises screws 23 disposed within a body 21 having heaters 22 disposed therein, for transferring the raw material, and a motor 29 for rotating the screw 23, the screws 23 are rotated by the motor 29 and include a shaft unit 24 having an inclined shaft 24a of a constant tilt angle and a diameter shaft 24b of the same diameter as the inclined shaft 24a, the height of spiral wings 25a formed in the inclined shaft 24a is lower than that of spiral wings 25b formed in the diameter shaft 24b.

In the present invention, the injection molding machine further comprises an inverter 50 for reducing the rotary speed of the screws 23 by reducing the rotary speed of the motor 29 when the supply of the raw material from the feed unit 20 to the injection molding plunger 30 is stopped or the supply amount of the raw material varies.

In the present invention, the hopper 10 comprises screws 11 that evenly mix other kinds of a raw material.

In the present invention, the raw material is a compound matter of a plastic powder and a scrap iron powder.

Furthermore, according to the present invention, there is

provided an injection molding machine of a balance product in which an iron powder is mixed with a plastic powder, the injection molding machine including an input port for inputting a fused injection material to an injection plunger, a piston rod that moves forward and backward in order to extrude the injection material, heaters for heating the injection material, and an oil pressure cylinder that moves the piston rod forward and backward, comprising: a combined feed cylinder being a combined feed cylinder disposed in an input port 301d vertically, the combined feed cylinder having screws disposed within the combined feed cylinder in equal distances, an exhaust port formed at its bottom, a plurality of band type heaters formed on its main wall at a predetermined distance, and a pulley disposed at the top of a rod of the screws; a pulley disposed at the shaft of a low-speed motor connected to a pulley by means of a belt ; a transfer tube disposed at the top of the combined feed cylinder, wherein a plurality of band type heaters are disposed on a main wall of the transfer tube at regular intervals ; an extrusion cylinder connected to the transfer tube and disposed against the combined feed cylinder in a horizontal direction, wherein equidistant feed screws are mounted within the extrusion cylinder, a plurality of band type heaters are disposed around the extrusion cylinder at regular intervals, a plastic powder input port is disposed at one top of the extrusion cylinder, and a motor is disposed at the rear side of the road of the equidistant feed

screws ; a plastic powder hopper disposed in the plastic powder the input port of the extrusion cylinder with a plastic powder supply control port inserted into the plastic powder hopper ; a transfer tube disposed at the top of the combined feed cylinder, wherein a plurality of band type heaters are disposed on a main wall of the transfer tube at regular intervals; and an iron powder hopper in which an iron powder feed control port is inserted into a transfer tube.

According to the present invention, there is provided an injection molding machine of a balance product in which an iron powder is mixed with a plastic powder, the injection molding machine including an input port for inputting a fused injection material to an injection plunger, a piston rod that moves forward and backward in order to extrude the injection material, heaters for heating the injection material, and an oil pressure cylinder that moves the piston rod forward and backward, comprising: a transfer tube disposed at the input port and having a plurality of band type heaters disposed on its main wall at regular intervals ; an extrusion cylinder connected to the transfer tube, the extrusion cylinder has equidistant feed screws mounted therein, a plurality of band type heaters disposed on its main wall at regular intervals, a mixed raw material input port disposed at its one upper side, and a motor disposed at the front end of the road of the equidistant feed screws in a horizontal direction; and a plastic powder hopper disposed in the mixed raw material input port of

the extrusion cylinder with a mixed raw material supply control port inserted into the plastic powder hopper.

According to the present invention, there is provided an injection'molding machine of a balance product in which an iron powder is mixed with a plastic powder, the injection molding machine including an input port for inputting a fused injection material to an injection plunger, a piston rod that moves forward and backward in order to extrude the injection material, heaters for heating the injection material, and an oil pressure cylinder that moves the piston rod forward and backward, comprising : a combined feed cylinder being a combined feed cylinder disposed in an input port in a vertical direction, the combined feed cylinder having screws disposed therein in equal distances, an exhaust port formed at its bottom, a plurality of band type heaters formed on its main wall in a predetermined distance, and a pulley disposed at the top of the road of the screws ; a pulley disposed at the shaft of a low-speed motor connected to the pulley by means of a belt ; a transfer tube disposed at the top of the combined feed cylinder and having a plurality of band type heaters disposed on its main wall at regular intervals; and a mixed material extrusion barrel disposed with heaters inserted into the transfer tube.

According to the present invention, there is provided an injection molding machine of a balance product in which an iron powder is mixed with a plastic powder, the injection molding machine

including an input port for inputting a fused injection material to an injection plunger, a piston rod that moves forward and backward in order to extrude the injection material, heaters for heating the injection material, and an oil pressure cylinder that moves the piston rod forward and backward, comprising: a transfer tube disposed at the input port, the transfer tube having a check valve disposed on the part of the input port and a plurality of heaters disposed on its main wall at regular intervals ; an extrusion cylinder connected to the transfer tube, the extrusion cylinder having equidistant feed screws mounted therein, a plurality of heaters disposed on its main wall at regular intervals, a high temperature dry hopper disposed at its upper one end with a feed control port inserted therein, a plastic powder hopper disposed with a feed control port inserted into its front end portion, and a pulley disposed the rear end of the road of the equidistant feed screw horizontally; and a pulley disposed on a deceleration motor connected to the pulley by means of a belt, wherein the amount of the iron powder within the extrusion cylinder does not exceed 50%.

Brief Description of Drawings Further objects and advantages of the invention barrel be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a front view illustrating the structure of an injection molding machine according to a first embodiment of the present invention ; Fig. 2 is an extracted view of a screw used in the injection molding machine shown in Fig. 1 ; Fig. 3 is a perspective view illustrating the structure of an injection molding machine according to a second embodiment of the present invention; Fig. 4 is a perspective view illustrating the structure of an injection molding machine according to a third embodiment of the present invention; Fig. 5 is a perspective view illustrating the structure of an injection molding machine according to a fourth embodiment of the present invention ; and Fig. 6 is a perspective view illustrating the structure of an injection molding machine according to a fifth embodiment of the present invention.

Best Mode for Carrying Out the Invention The present invention will now be described in detail in connection with preferred embodiments with reference to the accompanying drawings.

FIG. 1 is a front view illustrating the structure of an

injection molding machine according to a first embodiment of the present invention. Fig. 2 is an extracted view of a screw used in the injection molding machine shown in Fig. 1.

Referring to Figs. 1 and 2, the injection molding machine according to the present invention includes a hopper 10 into which a raw material is inputted, a feed unit 20 that heats, melts and transfers the raw material introduced from the hopper 10, an injection molding plunger 30 for injecting the raw material transferred from the feed unit 20, a mould 40 that making the raw material injected from the injection molding plunger a specific shape, and an inverter 50 that controls the transfer amount of the raw material in the feed unit 20, as main components. The raw material introduced into the hopper is a compound matter in which scrap iron powder or other scrap iron powder (or iron powder) generated when iron powder metallurgical components are fabricated are compounded with plastic powder in a predetermined ratio.

A given amount of plastic powder and iron powder (or scrap iron powder) that are well compounded is inputted to the hopper 10. A rotary screw 11 for smoothly supplying the compound matter in the same volume and specific gravity according to the mixture ratio so that the plastic powder and the iron powder (or scrap iron powder) can be mixed regularly is disposed within the hopper 10. A motor 12 for rotating the screws 11 is disposed at the top of the hopper 10.

The feed unit 20 is disposed below the hopper 10. After the plastic powder and the iron powder (or scrap iron powder) are inputted to the hopper 10, the raw material of the plastic powder and the iron powder that are agitated evenly by means of the screw from the hopper 10. The feed unit 20 includes a screw 23 disposed within a body 21 having heaters 22 disposed therein, for transferring the raw material, and a motor 29 for rotating the screw 23. In the above, the heaters 22 melt the raw material that passes through the body 21.

At this time, the screw 23 is rotated by the motor 29 and includes a shaft unit 24, and spiral wings 25a and 25b that are formed in the shaft unit 24 and have the same diameter, as shown in Fig. 2.

In the above, the shaft unit 24 includes an inclined shaft 24a formed in an"a"region and having a predetermined tilt angle, and a shaft 24b formed in a"b"region and having the same diameter as the shaft 24a. That is, the inclined shaft 24a is disposed on the part of the hopper 10 and is tapered toward the same diameter shaft 24b. In this embodiment, the inclined shaft 24a is 1/3 of the whole length of the shaft unit 24 and the remaining 2/3 of the total length corresponds to the same diameter shaft 24b.

In the above, the whole diameter of the spiral wings formed on the outer circumference of the shaft unit 24 is the same. As a result, the height of spiral wings 25a formed in the inclined shaft 24a is lower than that of spiral wings 25b formed in the same diameter shaft

24b. In this embodiment, the heights of the spiral wings 25a formed in the inclined shaft 24a are 9mm, 10mm, 11mm, 12mm, 13mm and 14mm sequentially and the heights of the spiral wings 25b formed in the same diameter shaft 24b is 15mm. Furthermore, a distance between a spiral wing and a next spiral wing is 75mm and the width of the spiral wing is about 8 to 10mm. It has been described that the above numerical values of the spiral wing is only for illustrative and the present invention is not limited thereto. It will be evident to those skilled in the art that various modifications and/or changes can be made.

The injection molding plunger 30 includes a piston 31 and a cylinder 32 for injecting the raw material transferred from the feed unit 20 to the mould 40. A heater 33 for heating the transferred raw material is disposed in the injection molding plunger 30. A barrier valve 35 of a piston type for preventing the raw material from counter-flowing toward the feed unit 20 when the piston 31 is pushed by the injection molding plunger 30 between the injection molding plunger 30 and the feed unit 20. The barrier valve 35 can selectively shut the supply of the raw material between the feed unit 20 and the injection molding plunger or vary the supply amount of the raw material. This construction is the same as an injection molding machine of a balance product in which a plastic powder and an iron powder are mixed (Korean Utility Model Registration No. 20-2003-

0023569) or an injection molding machine of a balance product in which a plastic powder and an iron powder are mixed (Korean Utility Model Registration No. 20-2003-0021434), both of which were filed by the present applicant. Thus, further description on it will be omitted.

The inverter 50 is a current control device for outputting a constant current although an input or an output voltage is changed.

When the supply of the raw material from the feed unit 20 to the injection molding plunger is stopped or the supply amount of the raw material varies, the rotary speed of the screw 23 is reduced by reducing the rotary speed of the motor 29. For example, in order to repeatedly inject a molding product of a predetermined shape, it is required that the supply of the raw material into the injection molding plunger be selectively stopped. If the screw 23 continues to rotate when the supply of the raw material is stopped or varied, however, the raw material does not exit toward the injection molding plunger 30. Accordingly, since lots of load is applied to the screw 23, the screw and the feed unit can be broken. In this case, the inverter 50 controls the motor 29 to reduce the rotary speed of the screw 23 so that the load applied to the screw 23 becomes small.

The operation of the injection molding machine of the plastic powder and the iron powder the raw constructed above will now be described.

The plastic powder and the iron powder of the solid state are

well combined and then inputted to the hopper 10. They are then transferred downwardly from the feed unit 20 by means of the screws 11.

The well-mixed plastic powder and iron powder are introduced into the feed unit 20 and are heated by the heaters 22. The fused raw material is transferred to the injection molding plunger 30 by means of the screw 23.

At this time, in the screw 23, the diameter of the inclined shaft 24a is higher than that of the same diameter shaft 24b.

Therefore, the height of the spiral wings 25a formed in the inclined shaft 24a becomes lower than that of the spiral wings 25b formed in the same diameter shaft 25a. Accordingly, the density of the raw material is lowered as the raw material introduced from the hopper 10 is transferred to the same diameter shaft 24b through the inclined shaft 24a. In this case, although the supply of the raw material to the injection molding plunger 30 is stopped or varied by the barrier valve 35, the raw material transferred by the screw 23 can be collected around the same diameter shaft. Resultantly, a load is not applied to the screw 23 and damage of the screw 23 and the feed unit 20 is thus prevented.

Furthermore, the inverter 50 serves to reduce the rotary speed of the screw 23 when the supply of the raw material to the injection molding plunger 30 is stopped or the supply amount of the raw material varies. Thus, a load applied to the screw 23 becomes small although

the raw material does not exit to the injection molding plunger 30.

Fig. 3, Fig. 4 and Fig. 5 are each perspective views illustrating injection molding machines of second, third and fourth embodiments of the present invention.

The injection molding machine will be described in more detail.

An oil pressure (or air pneumatic pressure) cylinder (or a servo motor for injection) is disposed at the rear end of a piston rod 301a disposed within an injection molding plunger body 301. A product mould 303 is disposed at the front end of a nozzle 301b formed at the front end of the body 301. A plurality of band type heaters 301c are formed on the outer circumference of the body 301 at regular intervals.

An exhaust port 304c formed at the bottom of a combined feed cylinder 304 that is disposed in the vertical direction is connected to an input port 301d. A plurality of band type high-temperature heaters 304d are disposed on the main wall of the combined feed cylinder 304 at regular intervals. Equidistant feed screws 304a are disposed within the combined feed cylinder 304. A pulley 305a and a belt 305b disposed at the shaft of a low-speed motor 305 are connected to a pulley 304e disposed at the top of the rod of the screws 304a.

Further, the front end portion of a transfer tube 306e disposed in an exhaust port 306d of an extrusion cylinder 306 that is disposed horizontally is connected to the input port 304b formed at the top of the combined feed cylinder 304. A plurality of band type heaters 306f

are disposed on the main wall of a transfer tube 306e at regular intervals. A motor (or a sub-motor for injection) 307 is disposed at the rear end of the rod of equidistant feed screws 306a disposed within the extrusion cylinder 306. A feed control port 308a connected to the bottom of a plastic powder hopper 308 is connected to an input port 306c formed at one side of the extrusion cylinder 306. A transfer tube 309b into which a feed control port 309a is inserted is connected to the bottom of a high-temperature dried iron powder hopper 309 on the other side of a top input port 304b of the combined cylinder 304. A plurality of band type heaters 309c are disposed on the main wall of the transfer tube 309b at regular intervals.

If a plastic powder and an iron powder are inputted to the hopper 308 and 309 and power is then applied, the extrusion cylinder 306, the combined feed cylinder 304, and the plunger piston rod 301a of the injection molding plunger 301 are driven. At this time, if the supply amount of the powder to the feed control ports 308a and 309a each disposed at the bottoms of the plastic powder hopper 308 and the iron powder hopper 309, the plastic powder dropped from the hopper 308 is melted within the extrusion cylinder 306 and is then inputted to the combined feed cylinder 304 through the transfer tube 306e. If the iron powder is inputted to the combined feed cylinder 304 through the transfer tube 309b of the iron powder hopper 309, the plastic powder and the iron powder are mixed by the equidistant feed screws 304a. In

a state where the plastic powder and the iron powder are heated to a temperature that is suitable for injection, they are inputted to the injection plunger body 301 and then injected into the product mould 303 by means of the piston, thereby molding a balance product.

Accordingly, according to the present invention, if the plastic powder and the iron powder are inputted to the hoppers 308 and 309 and the supply amount of the powder is (plastic powder of 5 to 25weight% and the iron powder of 75 to 95weight% in 200 mesh range), the balance product is produced consistently and consecutively through extrusion, mixing, fusion and injection processes.

Fourth and fifth embodiments of the present invention are similar to a case where the combined feed cylinder 304 and the extrusion cylinder 306 in the second embodiment are each separated are then coupled to the injection plunger body 301. Thus, description on them will be omitted in order to avoid redundancy.

An injection molding machine according to the third embodiment of the present invention is shown in Fig. 4.

Referring to Fig. 4, the injection molding machine of a balance product in which a plastic powder and an iron powder are mixed includes an input port for inputting a fused injection material to an injection plunger, a piston rod 401a that moves forward and backward in order to extrude the injection material, heaters 401c for heating the injection material, and an oil pressure cylinder 402 for moving

the piston rod 401a forward and backward, as basic components. A transfer tube 404c is disposed at the input port of the fused injection material. A plurality of band type heaters 404d are disposed around the transfer tube 404c at regular intervals.

An extrusion cylinder 404 is connected to the transfer tube 404c.

Equidistant feed screws 404a are mounted in the extrusion cylinder 404.

A plurality of band type heaters 404b are disposed on a main wall of the extrusion cylinder 404 at regular intervals. A mixed raw material input port is disposed at one upper side of the extrusion cylinder 404.

A motor 405 is disposed at the rear end of the road of the equidistant feed screws 404a in the horizontal direction.

A plastic powder hopper 406 is disposed with a mixed raw material supply control port connected to the mixed raw material input port of the extrusion cylinder 404.

An injection molding machine according to a fourth embodiment of the present invention is shown in Fig. 5.

Referring to Fig. 5, the injection molding machine of a balance product having a plastic powder and an iron powder mixed therein includes an input port for inputting a fused injection material to an injection plunger, a piston rod 501a that moves forward and backward in order to extrude the injection material, heaters 501c for heating the injection material, and an oil pressure cylinder 502 for moving the piston rod 501a forward and backward, as basic components. A

combined feed cylinder 504 is disposed in an input port 501d in the vertical direction. The combined feed cylinder 504 has screws 504a disposed therein in equal distances, an input port 501d formed at its bottom, a plurality of band type heaters 504d disposed on its main wall in given distances, and a pulley 504c disposed at the top of the rod of the screws 504a.

A motor 505 has a pulley 505a and the pulley 505a is connected to a belt 505B so that it is cooperatively operated with the pulley 504c.

A transfer tube 506c is disposed at the top of the combined feed cylinder 504 and has a plurality of band type heaters 506d formed on its main wall at regular intervals.

A plastic powder of 10weight% and an iron powder of 90weight% of 200mesh are inputted to a material supply barrel 507. The mixed material inputted to a material supply barrel 707 is inputted to a mixed material extrusion barrel 506 through a mixed material supply tube 507a. The mixed material of the mixed material extrusion barrel 506 is heated by heaters 506b and is then compressed by an oil pressure cylinder 506a. Next, the hated mixed material is extruded through a 1-shaped extrusion hole of a slot shape that is pressurized by a 1-shaped extrusion pin of a press plate and is then supplied to the combined feed cylinder 504 through the transfer tube 506c.

Fig. 6 is a perspective view illustrating the structure of an

injection molding machine according to a fifth embodiment of the present invention.

The injection molding machine according to the fifth embodiment of the present invention will described with reference to Fig. 6.

Heaters 601c are disposed on the outer circumference of an injection molding plunger body 601. A piston rod 601a is disposed within the body 601 and is moved forward and backward by means of an oil pressure (or air pneumatic pressure) cylinder 602 disposed at the rear end of the body 601. A product mould 603 is disposed in a nozzle 601b formed in the front end of the injection molding plunger the body 601. A transfer tube 604 into which a check valve 604b for preventing counterpressure is disposed in an input port 601d formed in the front end portion of the injection molding plunger the body 601. Heaters 604a are formed on the outer circumference of the transfer tube 604.

A distal end extrusion portion of an extrusion cylinder 605 is connected at the top of the extrusion cylinder 605. A plurality of heaters 605b are formed on the outer circumference of the extrusion cylinder 605 at regular intervals and equidistant feed screws 605a are disposed within the extrusion cylinder 605. The pulley 605c disposed at the rear end of the road of the screws are cooperatively operated with an isometric pulley 606a and a belt 606b of a deceleration motor 606. A high temperature dry hopper 607 is disposed at the rear end of the extrusion cylinder 605 with a feed control port 607a inserted into

the high temperature dry hopper 607. A plastic powder hopper 608 into which a feed control port 608a is inserted is disposed at about 1/3 inwardly from the extrusion port of the extrusion cylinder 605.

The insertion molding machine constructed above is an injection molding machine of a balance product in which a plastic powder and an iron powder. The operation of the insertion molding machine will be described below.

A high-temperature dried iron powder is inputted to the high temperature dry hopper 607 and a plastic powder is inputted to the plastic powder hopper 608. In this state, if power is applied to the deceleration motor 606, the equidistant feed screws 605a within the extrusion cylinder 605 is driven. At this time, when the iron powder inputted to the high temperature dry hopper 607 to the extrusion cylinder 605 by controlling the feed control port 607a, a load applied to the extrusion screws can be minimized by controlling the amount of the iron powder within the extrusion cylinder 605 not more than 50%.

If the high-temperature dried iron powder is transferred forward by the equidistant feed screws 605a, the plastic powder that is controlled and inputted by the feed control port 608a of the plastic powder hopper 608 is fused rapidly and is then transferred to the transfer tube 604. In this transfer process, if the plastic powder is inputted to the injection plunger body 601 with it kept warm by the heaters 604a formed on the main wall of the transfer tube 604, the

piston rod 601a injects an iron powder mixed melt solution to a product mould through the nozzle 601b while being moved forward and backward by the oil pressure (or air pneumatic pressure) cylinder 602.

Thereby, a product is molded.

At this time, a counter-pressure phenomenon applied to the transfer tube 604 within the cylinder while the piston rod 601a moves forward is prevented by the check valve 604b. Thus, the material transferred to the transfer tube 604 can be smoothly inputted.

Furthermore, heaters for drying the iron powder at high temperature can be disposed within the high temperature dry hopper 607.

Industrial Applicability As described above, according to an injection molding machine of the present invention, a screw in which the diameter of an inclined shaft is greater than that of a same diameter shaft and the height of spiral wings formed in the inclined shaft is higher than that of spiral wings formed in a diameter shaft are used. Also an inverter that can reduce the rotary speed of the screw is adopted. Therefore, although the supply of a raw material to an injection molding plunger is stopped or varied, lots of loads are prevented from being applied to the screw. It is thus possible to prevent damage of the screw and the feed unit.

Moreover, according to an injection molding machine of the

present invention, a scrap iron powder or other scrap iron powder (or iron powder) generated when an iron powder metallurgical component is fabricated are mixed with a plastic powder and is then used as an injection fused raw material. As such, the scrap iron powder is utilized appropriately. Therefore, the present invention has an effect that an injection product of a high quality can be produced at low cost.

Furthermore, according to an injection molding machine of the present invention, in molding a balance product by mixing a large amount of 75 to 95weight% iron powder with a plastic powder of 5 to 25weight%, input, extrusion, mixing, feed and injection processes of the raw material can be performed consistently and consecutively.

Therefore, there are effects in that the quality of a product can be increased and a manufacturing cost can be significantly reduced.

In addition, according to an injection molding machine of the present invention, in injecting a balance product in which a large amount of iron powder is contained in a plastic powder, a high temperature dry hopper into which a high temperature dry iron powder is inputted with a feed control port inserted into the hopper is disposed in a rear end of an extrusion cylinder. When the iron powder raw material that is dried at high temperature is inputted to the extrusion cylinder, the amount of the iron powder within the extrusion cylinder is controlled not more than 50%. It is thus possible to

minimize a load applied to the extrusion screw. At the same time, the plastic powder inputted to the plastic powder hopper is mixed with the high-temperature dried iron powder at the front end of the extrusion cylinder. Thus, mixing and melting states are rapidly performed. In addition, a counter-pressure phenomenon applied to the transfer tube while injecting the material within the injection plunger is stopped by a check valve. Therefore, it is possible to obtain a mold product of a high quality since a mixed melt material can be inputted smoothly.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.