JPH0535054B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an injection molding machine, and in particular to a BMC (Bulk
This invention relates to an injection molding machine that is suitably used for bulk molding materials containing glass fibers, such as molding compounds.

[Prior Art] Molding materials made of synthetic resins such as unsaturated polyester mixed with glass fibers have various compositions and properties depending on the molding method.

The mechanical properties of a molded article are highly correlated with the condition of the glass fibers in the molded article; the longer the fiber length and the less bent, the better the mechanical strength.

The length of the glass fiber in a molded product is not only related to the length of the raw glass fiber, but also to the molding method, and it is important to use a molding method that minimizes breakage as much as possible. It is necessary to improve one's physical characteristics.

Conventionally, injection molding of BMC and the like has used a barrel in which a screw is movable back and forth, but the problem has been that the rotation of the screw causes considerable damage to the glass fibers in the material. Therefore, the present applicant proposed Japanese Patent Application Nos. 60-79197, 1982-168898, and 61-77309 as plunger type injection molding machines suitable for injection molding of materials such as BMC.

In the plunger type injection molding machines according to these earlier applications, material is introduced into the barrel from a supply device such as a staff member, and after a predetermined amount of material is measured, it is injected by advancing the plunger within the barrel. Ru. In these metering and injection steps, the material is heated and softened by a heater provided in the staff or barrel.

[Problems to be Solved by the Invention] In conventional plunger-type injection molding machines, the amount of heat transferred from the heater provided in the staff or barrel to the material tends to be insufficient, and the temperature of the material tends to rise slowly. Therefore, the time required for metering and injection becomes longer, resulting in a longer molding cycle.

[Means for Solving the Problems] The present invention provides a method for rotating a plunger with a material passage provided between the inner circumferential surface of the barrel and the outer circumferential surface of the plunger in a barrel having a material inlet on the rear end side. A pressing device is provided to advance the material entered into the barrel from the material inlet into the material passage within the material passage, and a heater for heating the material in the material passage is provided on the outer peripheral surface of the plunger. It is characterized by this.

[Function] In the injection molding machine of the present invention, the material in the barrel is also heated by the heater provided in the plunger, so the temperature rises quickly and the time required for the metering and injection processes is shortened. Ru.

In the present invention, a material inlet is provided on the rear side of the barrel, and a plunger having a diameter that forms a material passage between the outer circumferential surface and the inner circumferential surface of the barrel is employed, and the plunger is rotationally driven. As a result, the contact area between the material and the plunger is large, and the heat conduction coefficient between the plunger peripheral surface and the material is increased, making it possible to heat the material extremely efficiently. In addition, the material does not flow in the barrel in a short circuit or stay in the barrel.
Smooth transfer throughout the barrel. Furthermore, the material is uniformly kneaded and homogenized.

[Example] Examples will be described below with reference to the drawings.

FIG. 1 is a schematic vertical sectional view showing an embodiment of an injection molding machine according to the present invention. In the figure, a cylindrical barrel 22 has a nozzle 21 at its tip and a relatively low-temperature heater at its outer periphery. It is arranged in such a way that it can be easily accessed. 6
2 is a column, 63 is a column nut, 64 is a machine base on the mold clamping device side, 65 is a machine base on the injection device side, 66 is a block provided slidably in the axial direction on the machine base 65;
A barrel 22 is fixed in front on top of the
A motor holding member 67 is slidably attached to the rear. 68 is a cylinder for moving the block 66 fixed to the fixed plate 60, 69 is a piston rod, and the tip of the piston rod 69 is connected to the block 6.
It is fixed to the center of the outer surface of cylinder 6.
8, the nozzle 21 can be brought into contact with the fixed mold 61 or moved back to the illustrated state.

Inside the barrel 22, a plunger 24, which has an outer diameter smaller than the inner diameter of the barrel 22 and has a backflow prevention mechanism consisting of a check ring 23, a ball, etc. near the tip, is provided so as to be movable forward and backward as well as rotatable. . Then, the inner peripheral surface of the barrel 22 and the plunger 2
A material passage 70 was provided between the outer peripheral surface of the material and the outer peripheral surface of the material. A shaft of a rotary drive device such as a hydraulic motor 35 fixed to the motor holding member 67 is connected to the rear of the plunger 24 via a bearing portion 71 within the motor holding member 67 . Further, an injection cylinder 72 and a piston rod 73 are attached between the barrel 22 and the lower side of the motor holding member 67.

A convex portion 25 in contact with the inner circumferential surface of the barrel 22 is provided at the center of the plunger 24. Further, a screw 29 for discharging leaked material is provided on the rear side of the convex portion 25 of the plunger 24. This Skrill 29 is
The leak material leaking backward from the clearance between the outer peripheral surface of the convex portion 25 and the inner peripheral surface of the barrel 22 is
This is for smooth discharge to the rear of the barrel 22, and is provided in a threaded direction opposite to the direction of rotation of the plunger 24.

Reference numeral 27 denotes a staff provided perpendicularly to the material inlet 28 on the rear side of the barrel 22, and a staff plunger 30 for pushing down the material is provided inside the staff. Furthermore, on the outer periphery of this stud 27,
A relatively low temperature heater is provided. Reference numeral 31 designates an inlet provided on the side surface of the staff 27 for supplying materials. 74 is a cylinder for the staff plunger 30, which is vertically attached to a portion of the barrel 22 so as to face upward. 75 is piston rod, 7
6 is a connecting member.

As shown in FIG. 2, which is a cross-sectional view taken in a direction perpendicular to the axial direction of the plunger 24, a plurality of elongated holes 80 are bored along the outer circumferential surface of the plunger 24. A heater 81 such as a sheathed heater is inserted into the plunger, and the heater 81 is configured to increase the temperature of the peripheral surface of the plunger.

In the device shown in FIG.
is positioned at the forward limit and rotated at, for example, 25 to 150 rpm, a material such as BMC is charged into the stuffer 27, and the material is pushed down by the stuffer plunger 30. The material is then sent forward through the outer periphery of the plunger 24, passes through the check ring 23, and is sequentially collected in the barrel 22 in front of the plunger 24. Of course, during this metering process, the plunger 24 gradually retreats.

At this time, back pressure can be applied to the material by controlling the oil pressure in the rod end side chamber of the injection cylinder 72 connected to the rear of the plunger 24. Note that the convex portion 2 of the retreating plunger 24
Back pressure can also be applied to the material by friction between the outer circumferential surface of the barrel 22 and the inner circumferential surface of the barrel 22. Further, the backward resistance of the plunger 24 may be reduced by applying hydraulic pressure in the opposite direction to the back pressure.
(In this way, damage to the glass fibers in the material will be extremely reduced.) As the plunger 24 rotates, the plunger 24
The resin material around the material is homogenized, and the material flow path is prevented from shorting. Further, due to the pressing action of the staff plunger 30 and the rotation action of the plunger 24, the material does not pass only through the material passage 70 above the plunger 24, but also wraps around towards the material passage 70 below the plunger 24. Also, since the material is sent around the plunger 24 from the lower side to the upper side or from the upper side to the lower side, even in areas where it is difficult for the material to flow or material that is difficult to flow, it does not stay in the barrel 22. , are smoothly transferred throughout the barrel 22.

When a desired amount of material is collected at the tip of the barrel 22, the rotation of the plunger 24 is stopped and the injection cylinder 72 is activated to move the plunger 24 forward and inject the material into the mold.

In the above-mentioned metering and injection process, the material is heated not only by the heaters (not shown) provided in the barrel 22 and the staff 27 but also by the heater 81 provided in the plunger 24. The heat from the heater 81 is transferred extremely efficiently into the passage 70 because the circumferential surface area of the plunger 24 is large and the heat transfer area is large, and the heat transfer coefficient is increased by rotating the plunger 24. is transmitted to the material, causing it to heat up quickly. Additionally, shearing forces and friction are applied to the material as it passes through the passageway 70, which also generates heat in the material. Therefore, in the injection molding machine of this embodiment, the viscosity of the material is quickly reduced, and the time required for the metering and injection processes is significantly shortened.

Note that in the present invention, other types of heaters may be provided on the plunger 24. For example, in FIG. 3, a plurality of shallow and wide grooves 82 are provided along the circumferential surface of the plunger 24, extending in the longitudinal direction of the plunger.
A heater 83 made of a planar heating element is inserted into the groove 82, and a lid 84 is placed over the heater 83 and fixed with bolts 85. The heater-equipped plunger 24 shown in FIG. 3 can also efficiently heat the material within the passage 70.

In addition, in such a rotary plunger type injection molding machine, damage to the glass fibers in the material can be minimized by appropriately selecting the rotational speed of the plunger.

In the above embodiment, a pressure supply device using a staff plunger is shown, but other supply devices may be used.

[Effects] As described above, according to the present invention, the material in the barrel can be efficiently heated by the heater provided in the plunger, shortening the molding cycle and significantly reducing molding costs. It is considered possible.
Furthermore, since the injection molding machine of the present invention is of the plastic type, there is less damage to the glass fibers in the material. Furthermore, the loss of homogenized material ensures that a high quality product is formed.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing an embodiment of the present invention, Fig. 2
3 and 3 are cross-sectional views of the plunger. 22... Barrel, 23... Check ring, 24...
plunger, 27... staff, 30... staff plunger, 70... material passage, 81, 83... heater.

Claims (1)

[Claims] 1 In a barrel having a material inlet on the rear end side, a material passage is provided between the inner circumferential surface of the barrel and the outer circumferential surface of the plunger, and the plunger is provided so as to be rotatable and movable back and forth, and the material is inserted from the material inlet into the barrel. An injection molding machine comprising: a pressing device for advancing the material entered into the material passage within the material passage; and a heater for heating the material within the material passage provided on the outer circumferential surface of the plunger.