JPS6249164B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a synthetic resin wheel having an oil reservoir in the middle of an axle insertion hole.

Wheels made of polymer materials such as hard rubber and synthetic resin used for various types of casters are manufactured by forming upper and lower molds into molds, and then injection molding the polymer material using these molds. These wheels are generally used by being mounted on an axle so that they can roll freely, but in this case, in order to lower the coefficient of friction between the axle and the inner circumferential surface of the axle insertion hole cut through the wheel. Grease is interposed between the axle and the inner peripheral surface of the axle insertion hole.

However, in wheels made using conventional molding methods, the axle insertion hole is formed as a stepped hole, and a bush is inserted from the large diameter side to form a grease reservoir, or a straight through hole is formed with bushes at both ends. was inserted to form a grease reservoir in the center. This not only complicates the structure of the wheel, but also increases the number of parts and manufacturing man-hours, leading to higher costs.

The present invention has been proposed in view of these points, and is such that a grease reservoir is formed on the inner peripheral surface of the axle insertion hole at the same time as the wheel is formed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a wheel manufacturing apparatus for carrying out the present invention will be described below with reference to the drawings.

In the figure, 1 is a movable mold, 2 is a fixed mold, and 3 is a movable mold.
is a shaft mold for forming a wheel insertion hole formed integrally with the stationary side mold 2, 4 is a wheel molding chamber, 5 is an injection part mouthpiece,
6 is a spool bush, 7 is a split surface of the movable mold 1 and the fixed mold 2, 8 is a main guide pin, and 9 is an upper plate for fixing the fixed mold 2.

The movable side mold 1 consists of a core plate 16 that forms the wheel contact surface molding peripheral surface 4a, a core bush 1a that forms the lower surface of the wheel, and a mold mounting plate 1c into which the core plate 16 is inserted, and these are movable. The movable board 10 is mounted on a board 10, supported by a base 12 via a middle board 11, and fixed with bolts 13.
The above-mentioned wheel contact surface molding peripheral surface 3a has a shape that bulges out from both ends toward the center in a continuous gently curved shape.

A ram of a hydraulic cylinder (not shown) is connected to the base 12, and the movable mold 1, movable platen 10, middle plate 11,
The base 12 is formed to be vertically slidable. In this case, in order to guide the molds 1 and 2 without shifting their relative positions, an auxiliary guide pin (not shown) passing through from the upper plate 9 to the middle plate 10 is provided, and the mold mounting plate 1c is provided with an auxiliary guide pin (not shown). The main guide bush 14 is externally fitted onto the fixed main guide pin 8, and the main guide bush 14
The upper end of is fixed to the upper plate 9.

The ejector pin 15 that is installed so as to penetrate the core bush 1a and the movable platen 10 has its upper end surface forming a mold for the lower end surface of the boss forming portion of the wheel molding chamber 4, and its lower end is attached to the ejector pin mounting tool 16. Fixed. This ejection pin attachment tool 16 is attached to the middle part 11
It is formed so that it can move forward and backward within the width of the wheel, and its lower part (not shown) penetrates the base 12 and projects downward.

As shown in FIG. 2, a drum-shaped bulge 17 is formed in the center of the axle mold 3 for forming an axle insertion hole, which is installed upright in the center of the wheel molding chamber 4. A concave portion that will serve as a grease reservoir can be formed at the same time in the insertion hole.

The injection port and injection flow path for injection molding are constructed by inserting the spool bush 6 into the upper plate 9, providing the injection part mouthpiece 5 above it, and extending downward from the injection port 6a in the center of the spool bush 6. A spool flow path 18 that widens toward the end is bored, and communicates between the spool flow path 18 and the wheel molding chamber 4 via a runner flow path 19 and a communication passage 20.

Note that cooling water channels are bored in the movable mold 1, the fixed mold 2, and the shaft mold 3.

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

After setting the stationary side mold 2 and the movable side mold 1 to the state shown in FIG. 1, a flow path 18 is formed by injecting a polymeric material such as molten nylon into the injection part mouthpiece 5 at a predetermined pressure. , 19 and 20, and is injected into the wheel molding chamber 4 without any gaps.

At this time, the air inside the wheel molding chamber 4 is pushed out of the wheel molding chamber 4 through the gap between the molds, and the inside of the wheel molding chamber 4 is filled with molten polymer material. 3 to cool and solidify. After sufficiently solidifying, a hydraulic cylinder is operated to lower the movable mold 1 and below to a predetermined height, thereby separating the movable mold and the fixed mold 2.
At this time, since the shaft mold 3 is formed integrally with the stationary mold 2, as the movable mold 1 descends, the shaft mold 3 also allows the product wheel to be inserted into the shaft even if there is a bulge 17. Get out of the hole. When the lower end of the ejector pin attachment tool 16 is stopped by the stopper during the lowering operation of the movable mold 1, the ejection pin attachment tool 1 is stopped.
6 moves through the space in the middle plate 11, and the ejector pin 15 pushes the product wheel upward, separates it from the movable mold 1, and releases the wheel from the opening formed in the split surface 7 of the wheel molding chamber 4 part. Take out. Thereafter, the movable mold 1 is raised and returned to its original position.

In addition, the protrusion amount of the bulge 17 formed in the shaft mold 3 for forming the wheel insertion hole from the outer peripheral surface of the shaft mold 3 is set to 0.5 mm so that it can be extracted within the range of elastic deformation of the wheel.
It is desirable to form it to a certain degree.

As a modification of the apparatus for implementing the present invention, the shape of the bulge formed in the shaft mold may be made into a Soroban bead shape, and depending on the position of the mold split surface, the movable side mold and the shaft mold may be separated. It is conceivable to form them integrally and provide ejector pins on the stationary side mold.

As described in detail above, in the present invention, a recess for an oil reservoir can be formed in the axle insertion hole of the wheel at the same time as the wheel is formed. Since the above-mentioned operations can be omitted and the manufacturing process can be simplified, a wheel having an oil sump can be manufactured at low cost.

In addition, since both sides of the oil reservoir formed in the axle insertion hole of the product wheel are integrated with the wheel boss, it is possible to reduce oil leakage as much as possible, ensuring smooth operation over a long period of time. It can be rotated.

[Brief explanation of the drawing]

The drawings show an example of an apparatus used to carry out the method of the present invention, with FIG. 1 being a longitudinal sectional front view and FIG. 2 being an enlarged view of the main parts.

Claims (1)

[Claims] 1. Form a wheel molding chamber in the space surrounded by the fixed side mold, the movable side mold, and the axle mold for forming the axle insertion hole,
A bulge for forming an oil reservoir is formed on the outer peripheral surface of the axially intermediate part of the shaft mold, and after filling the wheel molding chamber with wheel material and molding the wheel according to the wheel molding chamber, the movable side mold is A polymeric material having an oil reservoir in the middle of a wheel insertion hole, characterized in that the mold is separated from the stationary mold, and the molded wheel is separated from both molds and simultaneously extracted from the shaft mold. A method for manufacturing wheels.