JPS5812145B2 - Method for manufacturing wheels made of high-polymer material with medium to high ground contact surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a wheel made of a high polymeric material with a medium-height contact surface.

Synthetic resin (or hard rubber, hereinafter the same) wheels used for various types of casters and the like are manufactured by forming a mold using upper and lower molds, and injection molding a synthetic resin material using this mold.

Among the above-mentioned wheels, wheels with a medium-height contact surface are widely used because they have low running resistance and roll smoothly.However, when molding these wheels, in the conventional manufacturing method, there are no The cutting surface of the mold had to be placed at the middle part of the outer peripheral surface of the wheel, that is, at the middle and high part.

In this case, the parting line (molding burr), which is the mark of the split surface of the mold during molding, is located in the center of the contact surface of the outer peripheral surface of the wheel.
Since this parting line remains, it takes time and effort to remove and finish the parting line, which deteriorates the appearance of the product and lowers its value.When used, it damages the floor and easily gets dirty, spoiling the aesthetics.Also, in the case of a brake-type model, it is difficult to brake. Performance also deteriorates.

Moreover, since the cutting surface of the mold is located in the middle of the product, the shape of the mold becomes complicated.

In order to solve the above problems, the method of the present invention focuses on the solidification shrinkage and thermal shrinkage of polymer synthetic resin materials during processes such as injection molding, and utilizes the various conditions for these shrinkages. By also utilizing shrinkage deformation, the molded surface of the molded surface is placed at the end of the molded surface of the molding surface rather than the middle, and the mold opening is smaller in diameter than the center and height of the molded wheel. This makes it possible to manufacture wheels without parting lines in the middle and high parts of the ground contact surface.

Next, an example of a wheel manufacturing apparatus for carrying out the present invention will be explained based on the drawings.

In the figure, 1 is a movable side mold, 2 is a fixed side mold, 3 is a wheel molding chamber, 4 is an injection part mouthpiece, 5 is a spool bush, 6 is a split surface of the mold, 7 is a main guide pin, 8 is an auxiliary guide pin.

The movable mold 1 is a molding surface 3a of the wheel contact surface in the wheel molding chamber 3.
The core plate 1b that forms the core bushing 1a and the core plate 1 that forms the mold inside the lower half of the wheel molding chamber 3
These are mounted on a movable plate 9, and this movable plate 9 is supported by a base 12 via a middle plate 10 and a lower plate 11, and fixed to the base with bolts 13. .

The above-mentioned wheel contact surface forming peripheral surface 3a has a shape that swells from both ends toward the center in a continuous, gently curved shape.

The stationary mold 2 includes a core plate 1b, a cavity plate 2c that is in close contact with the upper surface of the mold mounting plate 1c, and a wheel molding chamber 3.
It consists of a cavity bush 2b that forms a mold for the inside of the upper half of the wheel, and an axle mold 2a that is coaxially inserted into the center of the cavity bush 2b to form a mold for the axle hole of the wheel molding chamber 3.

The upper end of the cavity bush 2b is fitted into the mold plate 14 that is in close contact with the upper surface of the cavity plate 2c.
On the top surface of 4 is a cooling water plate 1 with a cooling water channel 16 provided inside.
5 are brought into close contact with each other, and an upper board 17 is brought into close contact with the upper surface of this cooling water board 15.

The upper plate 17, the cooling water plate 15, and the mold plate 14 are fixedly formed.

On the other hand, a ram of a hydraulic cylinder (shown in the figure) is connected to the base 12 to form the cavity plate 2c, the movable mold 1, the movable plate 9, the middle plate 10, the lower plate 11, and the base 12 so as to be vertically slidable.

In this case, in order to guide the molds 1 and 2 so that their relative positions do not shift, an auxiliary guide pin 8 is provided that penetrates from the upper plate 17 to the middle plate 10, and a main guide fixed to the mold mounting plate 1c is provided. A main guide bush 18 is fitted onto the pin 7, and the upper end of the main guide bush 18 is fixed to the cavity plate 2c.

The ejector pin 19 installed through the core bush 1a movable platen 9 forms the shape of the lower end surface of the boss of the wheel forming chamber 3 with its upper end surface, and its lower end is fixed to the ejector pin mounting tool 20.

This protruding pin mounting tool 20 is formed so that it can move forward and backward by the height of the wheel within the middle platform 10, and its lower part (the path shown) is connected to the base 12.
penetrates and protrudes downward.

In order to cool the mating mold 2a, a thermopipe 21 is inserted into its central shaft portion, a cooling water hole 22 is formed around the upper part of the thermopipe 21, and cooling water from the cooling waterway 16 is introduced for cooling.

Incidentally, the dividing surface 6, which is the interface between the stationary mold 2 and the movable mold 1, that is, the surface that is divided when taking out the product, is the boundary surface between the cavity plate 2c and the core plate b, and this dividing surface 6 is It is located near the upper end of the wheel contact surface molding peripheral surface 3a of the molding chamber 3.

In addition, the cooling water channel 23 for cooling the movable mold 1 is connected to the mold mounting board 1.
c and inside the movable platen 9 to introduce cooling water.

The injection port and injection channel for injection molding are constructed by inserting a spool bush 5 onto the cooling water plate 15 in the upper plate 17 in the middle of the two molds, as shown in Figures 2 and 3. At the same time, a spool channel 24 is formed downward from the injection port 5a at the center of the spool bushing 5 into the cooling water plate 15 and the mold plate 14, and a spool flow path 24 is formed in the cooling water plate 15 and mold plate 14. Mold board 14
A runner flow path 2 is provided at the boundary between the cavity plate 2c and the cavity plate 2c.
5 is formed to communicate with the spool flow path 24, and an inverted conical flow path 26 is formed to communicate from both ends of the runner flow path 25 to the rim upper end molding surfaces of the left and right wheel molding chambers 3.

Next, an example of a procedure of a wheel manufacturing method using the above-mentioned wheel manufacturing apparatus will be explained.

After setting the fixed side mold 2 and the movable side mold 1 to the state shown in FIG. 1, a synthetic resin material such as nylon in a molten state is injected into the injection part mouthpiece 4 at a predetermined pressure, thereby forming the flow path 24. 2
5 and 26 into the wheel molding chamber 3 without any gaps.

At this time, the air in the wheel molding chamber 3 is pushed out through the gas vent in the gap between the molds, and the wheel molding chamber 3 is filled with molten polymer material, which is then cooled by cooling water and molds 1 and 2. to solidify.

After sufficiently solidifying, operate the hydraulic cylinder to lower the movable mold 1 and below together with the cavity plate 2c, and after lowering to a predetermined height, only the cavity plate 2c can be locked to the stopper (path shown). It is stopped and separated from the movable mold 1 at the split surface 6.

Here, the spool and runner solidified in the injection channel are removed from between the mold plate 14 and the cavity plate 2c to empty the injection channel.

The portion of the movable mold 1 and below is successively lowered, and after lowering to a predetermined height, the lower end of the ejecting pin mounting tool 20 is attached to a stopper (
When stopped at the path shown in the figure, the ejector pin mounting tool 20 moves through the space inside the middle plate 10, and the ejector pin 19 pushes the product wheel upward, separating it from the movable mold 1 and moving the wheel molding chamber 3 into the wheel molding chamber 3. Push out the wheel from the opening 27 of the cut surface 6.

Thereafter, the lowering is stopped and the movable mold 1 is returned to its original position.

In the method of manufacturing a wheel made of a high-divided material with a medium-height contact surface according to the present invention, the split surface 6 of the mold is not provided in the middle of the wheel contact surface forming peripheral surface 3a, but near the end of the wheel contact surface forming peripheral surface 3. The reason why the product can be taken out from the opening 27 having a smaller diameter than the middle and high part of the wheel by injection molding can be explained as follows.

In the case of polymeric materials such as nylon and urethane, the high-temperature molten polymeric material filled in the wheel molding chamber 3 undergoes solidification shrinkage when solidified by cooling, and heat shrinkage occurs after solidification, so it is difficult to remove the product from the mold. This is because the wheels of the product have slightly shrunk and become smaller in size at the time of removal.

In addition, since the slope from the edge of the outer circumferential surface of the wheel to the mid-height part is extremely small, even if the extrusion force applied to the wheel by the ejecting pin 19 is not that large, the force of the wheel pushing the mold apart is extremely large (Boku effect). In other words, the force with which the wheel is pushed out of the mold becomes extremely large.

Therefore, the wheel elastically contracts and deforms during this extrusion.

After all, as mentioned above, the principles of solidification contraction, thermal contraction, and elastic contraction are effectively utilized.

In addition, in order to promote the solidification shrinkage and heat shrinkage described above, it is necessary to consider the following conditions.

(1) A synthetic resin material with a high molding shrinkage rate is used as the polymer material for the wheels.

(2) Increase the melting temperature during injection molding.

(3) Lower the injection pressure appropriately.

(4) Effectively cool the mold with cooling water to lower the mold temperature.

Next, examples of dimensions of wheels and molds manufactured by the manufacturing method of the present invention using the apparatus shown in FIGS. 1 to 3 are shown in the table.

FIG. 4 shows another example of a wheel manufacturing apparatus for implementing the present invention.

Examples of dimensions of wheels and molds manufactured using this equipment are shown in the following table.

Since the present invention has the above configuration, it has the following effects.

In the wheels formed by the manufacturing method of the present invention, the parting line does not appear in the middle part of the contact surface of the wheel, so removal and finishing of the parting line can be omitted, and the product has a beautiful appearance and a high commercial value. In addition, when in use, it does not damage the floor surface, does not easily become dirty, maintains its aesthetic appearance, and improves flake braking performance.

Moreover, since the cut surface of the mold of the manufacturing device is also flat, the mold is also simplified.

[Brief explanation of the drawing]

The figures show an embodiment of a wheel manufacturing apparatus for carrying out the present invention, in which Fig. 1 is a longitudinal sectional front view of the main part, Fig. 2 is a sectional plan view taken along the line ■-■ of Fig. 1, and Fig. 3 is a partial longitudinal sectional side view. FIG. 4 is a diagram corresponding to FIG. 1 of another embodiment. 1... Movable side mold (1a... core bush, 1b...
...Core plate, 1c...mold mounting board), 2...
Fixed side mold, 3...Wheel molding chamber, 3a...Wheel contact surface forming peripheral surface, 6...Cut surface, 27...Opening.

Claims (1)

[Scope of Claims] 1. A wheel molding chamber for molding a wheel in which the middle part in the width direction of the ground contact surface is higher than both ends is formed between the abutting surfaces of a stationary mold and a movable mold. By locating the split surfaces of both molds near the ends of the wheel contact surface molding surface in the wheel molding chamber, the wheel contact surface molding peripheral surface is formed in one of the molds, and the wheel molding chamber is filled with polymeric material. The material for the wheel is put in and molded according to the shape of the wheel molding chamber, the movable side mold is separated from the fixed side mold, and the molded wheel on the mold side that has the wheel contact surface forming peripheral surface is placed in the mold. A method for manufacturing a wheel made of a polymeric material with a medium-high contact surface, characterized in that the wheel is taken out from an opening in a split surface. 2. In the method for manufacturing a wheel described in claim 1, the split surface is located near the end of the molded peripheral surface of the wheel contact surface formed in the movable mold on the fixed mold side, and after molding. An ejection pin for the wheel is provided on the movable side mold, so that when the movable side mold is opened after molding, the molded wheel follows the movable side mold and protrudes out of the movable side mold with the ejection pin. What I did.