JP2676546B2 - Hollow paddy wheel manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a hollow paddy wheel.

(Prior Art) Conventionally, in the manufacture of paddy wheels, a terminal vulcanized rubber is press-fitted from a pot type in contact with the mold into a cavity where a tire inside a mold in which the wheel is arranged is to be formed, and the vulcanized rubber is filled into the cavity. A common method is to perform heat vulcanization after heating (press-fit molding method), but this method reliably molds relatively deep lugs, etc., and it is extremely difficult to form cavities inside the tire. Is.

On the other hand, in manufacturing a hollow paddy wheel, a rod-shaped body of unvulcanized rubber having holes inside is extruded by an extruder, the molded product is placed in the mold along with the periphery of the wheel rim, and it is emptied from outside the mold. There is a method of vulcanizing by pressurizing and heating the mold while sending pressurized air into the holes and applying internal pressure to the holes. With this method, it is easy to form cavities inside the tire. There is a drawback that the holes inside the lug protruding to the outer circumference of the tire are not uniform and irregular recesses are formed.

(Problems to be Solved by the Invention) In view of the present circumstances, the present invention is a novel manufacturing method in which it is easy to form lugs, ribs, and the like, and in which recesses of holes and the like are not generated. Is to be proposed.

(Means for Solving the Problem) A powdered vulcanized rubber sheet is formed by a pressure roll into a belt-shaped body having a lateral width cross-section that is entirely thick in the central portion, and left and right fin portions extending on both sides thereof. Protrusions (lugs) protruding outward on the upper surface of the central strip and a gentle arcuate concave portion on the lower surface are provided, and the arc length of the concave portion is not approximately equal to the cavity circumference of the tire, and the left and right fins are In addition to making the upper and lower wall thickness gradually smaller toward the end, the lower surface has a gentle arc shape, and the arc length of the recess is configured to be approximately equal to 1/2 of the outer diameter of the wheel. The unvulcanized rubber sheet was rolled inward to form a relatively large hole in the center, and below that, an adhesive treatment was applied to the open part formed by the arcuate recesses of the left and right fins facing each other. Insert the wheel rim and use it to form the outer shape of the hollow tire. It is a method for manufacturing a hollow paddy wheel, which is characterized in that the hollow paddy wheel is manufactured by placing it in a mold and heating and pressing.

(Example) FIG. 1 is a cross-sectional perspective view of the unvulcanized rubber sheet 1 used in the present invention, in which a pressure roll (not shown) is used to make the center of the width as a whole thick. It is made up of the central strip 1a and left and right fin portions 1b, 1b extending on both sides thereof.

The molding is performed using a pressure roll (not shown), and a protrusion (lug) 1c protruding outward is formed on the upper surface e of the central strip 1a, and the lower surface f is a gentle circle. It becomes an arcuate recess, and the arc length of the recess is approximately equal to the cavity circumference of the tire. On the other hand, the fin portions 1b, 1b extending on both sides of the belt-like body gradually reduce the vertical wall thickness toward the end, and the lower surfaces of both fins are also made into a gentle arc-shaped recess g, and the arc length of the recess is 1/2 the outer diameter of the wheel rim
Is almost equal to.

FIG. 2 shows the vulcanized rubber sheet having the above-mentioned structure in the central strip 1a.
The fins 1b, 1b are rounded inward so that the arcuate concave portion f is centered, and the tops k of the central strip 1a and the left and right fins 1b, 1b are joined to form a relatively large hole in the center. 2 was formed, and surface treatment (shock blasting, degreasing, adhesive coating, drying) was performed on the open portion 3 formed by the arcuate concave portions g of the left and right fin portions 1b, 1b facing each other below. The wheel rim 4 is inserted so that the wheel rim 4 can be attached directly to the recesses g, g or via a thin powdered rubber sheet. (Since it is a sticking of unvulcanized vulcanizates, it is easy to mold.) Then, place this in a mold (not shown) that has the cavity that forms the outer shape of the hollow tire and pressurize and heat. At the same time as the vulcanization of the unvulcanized rubber, the adhesion between the rubber and the metal is performed.

At that time, pressurized hot air or pressurized steam is blown into the holes 2, or a foaming agent is put in the holes 2 in advance, and internal pressure is applied to the holes to simultaneously heat the tire from the outside. It is better to heat and mold from the inside.

 FIG. 3 shows the product 5 thus manufactured.

(Advantages of the Invention) The present invention is configured as described above, and since the pressure vulcanized rubber sheet is used in advance to form a protrusion having a shape to be a lug, a rib or the like by using a pressure roll, Even if the pressure applied during sulphation is comparatively small, the formation of lugs and ribs can be reliably and easily performed, and the internal cavities can be formed in a desired size by bending the strip inward. It is possible to obtain a product excellent in quality and standard, which is formed properly and does not cause irregular recesses inside the conventional voids.

It should be noted that the type of protrusions such as lugs of the unvulcanized rubber sheet and the arc-shaped recesses can be easily obtained by engraving on the rolling roll machine, and therefore the overall production should be highly efficient and low cost. It can be done.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view of an unvulcanized rubber sheet used in the present invention, FIG. 2 is a manufacturing state diagram in which the unvulcanized rubber sheet is rolled inward, and FIG. 3 is a product diagram. 1 ... Unvulcanized rubber sheet, 1a ... Central strip 1b, 1b ... Fins, 2 ... Hole 4 ... Wheel rim

Claims (1)

(57) [Claims] 1. An unvulcanized rubber sheet is formed by a pressure roll into a central belt-shaped body having a generally thick cross-section, and left and right fin portions extending on both sides thereof are integrally formed. A protrusion (lug) protruding outward is provided on the upper surface of the central strip, and a gentle arcuate concave portion is provided on the lower surface. The left and right fins gradually reduce the vertical wall thickness toward the terminal. Is a gentle arcuate recess, and the unvulcanized rubber sheet is rolled inward to form a relatively large hole due to the recess of the central strip at the center, and below it. A hollow paddy field characterized by inserting a wheel rim treated with an adhesive into the open part formed by the arcuate recesses of the left and right fins, arranging this in the mold and heating and pressing to manufacture Wheel manufacturing method.