JPH0347175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a resin duct used as a grass discharge duct for a lawn mower, for example.

(Prior art) In the case of riding lawn mowers, etc., in order to discharge the cut grass into the grass bag, a duct is connected between the cutter deck and the grass bag, and the airflow generated by the rotation of the cutter blade is guided to the duct. This airflow carries the cut grass through the duct and stores it in the grass bag.

Here, since the duct is required to be lightweight and resistant to corrosion, a duct made of resin has conventionally been used.

Such resin ducts are generally produced by rotational molding or by bending a sheet-like resin plate.

(Problems to be Solved by the Invention) In the above-mentioned rotational molding, after blastisol is charged into the mold, the mold is heated and rotated in a furnace, which requires large equipment and is disadvantageous in terms of manufacturing efficiency. In addition, bending requires post-processing and wastes material.

On the other hand, if a transparent resin is used as the material for the duct, clogging in the duct can be easily detected, but transparent resin, especially polyvinyl chloride, cannot be used with organic solvents such as thinner or gasoline. However, it has the disadvantage of being weak and prone to cracking.

(Means for Solving the Problems) In order to solve the above problems, the present invention extrudes and molds a parison using polypropylene or polyethylene as a material, and blow molds this parison in a mold to form the inner wall shape of the mold. This hollow body was taken out from the mold, both ends were cut, an opening was formed in the side wall, and a transparent plate was attached to this opening.

(Example) Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a side view of a riding lawn mower using a resin duct manufactured by the method of the present invention. A seat 5 is disposed at the upper center of the frame 2, a handle 6 is arranged in front of the seat 5, and a cutter deck 7 containing a cutter blade is supported at the lower center of the frame 2. and a glass bag 8 attached to the rear of the vehicle body are connected by a duct 9.

Here, the duct 9 is divided into three divided ducts 10, 1
1 and 12, a method for manufacturing the middle divided duct 11 will be explained in the order of steps with reference to FIGS. 2 to 7.

First, as shown in FIG. 2, the left and right molding molds 13,
With 14 open, an extrusion molding machine 15 is placed above between the molds 13 and 14, and a parison 17 is placed between the molds 13 and 14 from the nozzle 16 of this molding machine 15.
(Hollow molten tube) is extruded. Here, as the material for the parison 17, polypropylene or polyethylene is used. In addition, the shape of the inner wall surface of the molds 13 and 14 is a shape that matches the outer shape of the divided duct 11 when the molds are matched, that is, a part of the molds 13 and 14 has a large diameter into which another divided duct 10 is inserted. Large-diameter recesses 13a and 14a are provided for molding the window portion, and a recess 14b is provided in a portion of the mold 14 for molding the window portion.

Furthermore, when pushing out the parison 17, air is blown into the parison 17 from an air outlet 18 provided at the lower end of the nozzle 16 to expand the parison 17 to some extent. Furthermore, while the parison 17 is being extruded, a compressed air blowing nozzle 19 is kept on standby below the molds 13 and 14.

Next, as shown in FIG. 3, the left and right molds 13,
14 and compressed air blowing nozzle 19 from below.
is inserted into the molds 13 and 14 through the parison 17, and compressed air is supplied from the nozzle 19 to the parison 17.
supply within. Then, since the parison 117 is in a softened state, it expands and is molded to follow the shape of the inner wall surfaces of the molds 13 and 14.

After this, once the resin has cooled and solidified, the mold 13,
14 is opened, a hollow body 20 which is a hollow product is taken out, and both ends of this hollow body 20 are cut as shown in FIG. At this point, the hollow body 20 has a cylindrical body 20a, a large diameter portion 20b, and a bulging portion 20c formed therein.

Next, as shown in FIG. 5, a backing plate 21 is inserted into the hollow body 20, and an opening 23 is punched out using a jig 22. Thereafter, as shown in FIG. 6, a rivet insertion hole 24 is drilled around the opening 23 using a drill or the like.
Furthermore, as shown in FIG. 7, a transparent plate (including a semi-transparent plate) 25 such as a polyvinyl chloride plate is inserted into the opening 23 from the inside.
The transparent plate 25 is held between the inner periphery of the opening 23 and the annular metal plate 26, and these are integrated with the rivets 27 to complete the divided duct 11. In this embodiment, the metal plate 26 and the cylindrical body 2 are connected with the metal plate 26 attached.
The depth of the bulging portion 20c is set so that it is flush with the inner circumferential surface of the duct 0a to prevent turbulence from occurring within the duct.

In addition, in the example, an example was shown in which a duct manufactured by the method of the present invention was used as a grass conveying duct for a riding lawn mower, but a duct manufactured by the method of the present invention could also be used as a duct through which various fluids pass. can do.

(Effects of the Invention) As explained above, according to the present invention, when manufacturing a resin duct, first a parison is molded and then this parison is blow molded, so that the duct can be manufactured efficiently. . In addition, by selecting polypropylene or polyethylene as the duct material, it has increased durability against thinner or gasoline compared to polyvinyl chloride, and also has less sagging during blow molding than other resins. , it has many effects such as being able to obtain a duct with uniform thickness.

[Brief explanation of drawings]

FIG. 1 is a side view of a riding lawn mower to which a duct manufactured by the method of the present invention is applied, and FIGS. 2 to 7 are diagrams showing the steps from the parison forming process to the completion of the duct in order of process. In addition, 1 in the drawing is a riding lawn mower, 11 is a duct, 1
3 and 14 are molding molds, 15 is an extrusion molding machine, and 17
is a parison, 19 is a compressed air blowing nozzle, 20
is a hollow body, 20a is a cylindrical body, 20b is a large diameter part,
20c is a bulging portion, 23 is an opening, 25 is a transparent plate, 2
6 is a metal plate.

Claims (1)

[Claims] 1 A parison is formed by extrusion molding polypropylene or polyethylene, this parison is held in a molding mold, and while the parison is in a softened state, compressed air is blown into the parison to swell the parison and mold it. A hollow body that follows the shape of the inner wall is molded, and then, after the hollow body is solidified, it is taken out of the mold, both ends of the hollow body are cut, and an opening is formed in the side wall, and this opening is closed with a transparent plate. A method for manufacturing a resin duct characterized by: