JPS6353026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing lug pneumatic tires.

Conventionally, in the production of pneumatic tires, tire components such as rubberized cord cloth layers and beads are sequentially pasted onto a metal cylindrical former, and then an extruded tread rubber layer is further wrapped around the outermost layer to create a so-called green tire. After molding the tire,
After removing the green tire from the former, the green tire was placed in a vulcanizing mold, shaped into a toroidal shape using, for example, a bladder, and vulcanized under heat and pressure to form a completed tire.

By the way, the tread surface of a completed tire has a tread pattern (an uneven pattern) that has been devised in various ways in order to obtain a predetermined tire performance.

For this reason, the thickness of the tread varies depending on its pattern.

On the other hand, the extruded tread rubber layer used in green tire molding must have a uniform thickness in its longitudinal direction.

For this reason, in the case of the tread rubber layer 3 having the lugs 2 on the tread surface 1 after vulcanization as shown in FIG. 2
The inner surface of may form a concave surface 5.

Furthermore, if the difference in height between the lug 2 and the tread surface 1 becomes extreme as shown in FIG. 2, a concave surface 5 will be formed at the base of the lug 2 such that the cord cloth layer 4 is exposed.

Furthermore, while the lugs 2 require a large amount of rubber, not so much rubber is required between the lugs 2. However, as described above, in the conventional method, the tread rubber layer 3 must have a uniform thickness in the longitudinal direction, so the thickness is determined according to the lug portion.

For this reason, the areas between the lugs, which do not require much rubber, become extremely thick as shown in FIG. 3, and as a result, the inner surface of the tread portion has a wavy shape in the circumferential direction corresponding to the number of lugs.

For these reasons, according to the conventional general tire manufacturing method, the weight of the tire increases due to excessive materials, resulting in increased costs, as well as deterioration in straight running performance and field performance.

In particular, pneumatic tires for rice transplanters are formed with webbed wings (a type of lug) to increase traction, and agricultural tires for binders, combines, etc. are so-called high-lug tires. The aforementioned drawbacks are notable.

From this point of view, for example, there is a method for manufacturing pneumatic tires disclosed in Japanese Patent Publication No. 50-36672,
Some advantages can be recognized.

However, in this conventional example, the tread rubber layer is molded in advance in the form of a crown connected in the circumferential direction of the tire, and on the inner periphery of the crown-shaped tread rubber layer, a pair of mainly rubberized cord cloth layers formed separately on a former are formed. Since the raw case body consisting of beads is transformed into a toroidal shape and bonded together, the tread rubber layer must necessarily be unvulcanized or semi-vulcanized. When opening the mold and removing the core,
The rubber layer will adhere to the core mold, and the tread rubber layer may not remain in the mold or may remain deformed.

Therefore, in this conventional example, it is necessary to apply chrome plating to at least all parts of the surface of the core mold that come into contact with the molded rubber, while the corresponding surface of the mold has to be specially treated by making it rough. Even with this special work, the tored rubber layer is unvulcanized or semi-vulcanized, so it is first set in a mold and shaped, then the mold is opened and the raw case body is removed. As long as the material is charged, the tread rubber layer may remain in a deformed state within the mold.
This sometimes resulted in tires with irregular shapes. Furthermore, it was necessary to inflate the raw case body, which was extremely difficult to control.

It is an object of the present invention to provide a new method for manufacturing a pneumatic tire with lugs that eliminates all the disadvantages of the general tire manufacturing method using an extruded tread rubber layer as described above and the conventional tire manufacturing method using a molded tread rubber layer. purpose.

According to the present invention, the cavity having the shape of a pneumatic tire with lugs to be produced is a mold which is composed of at least three matching mold parts: an upper mold element, a lower mold element and a core mold element. In a method of manufacturing a pneumatic tire with lugs using a tightenable tire manufacturing machine, a green tire having a semi-vulcanized rubberized cord fabric layer covering a pair of left and right bead portions is separately molded, and the green tire is divided. It is set in a flexible metal core mold element, and when this metal core mold element is inserted into the cavity of the mold part, a lug wider than the tire width is formed to protrude outward in the tire axial direction from the tire sidewall. After that, the cavity is filled with rubber in an amount corresponding to the volumes of the tread surface layer including the lugs, the sidewall surface layer, and the bead surface layer, and the rubber is filled into the green tire body. The present invention provides a method for manufacturing a pneumatic tire with lugs, which is characterized in that the entire outer peripheral surface is bonded in a mold-clamped state and then vulcanized.

Note that the lugs herein are defined as including the blades of pneumatic tires for rice transplanters.

Embodiments of the present invention will be described in detail with reference to FIG. 4 and subsequent figures.

FIG. 4 shows the process or procedure for forming the green tire 10. FIG. 4 shows the process of wrapping a pair of left and right bead portions 12 on a general cylindrical former 11, and semi-vulcanized rubber covering the bead portions 12. A green tire 10 wrapped with a cord cloth layer 13 is separately molded.

In the example shown in FIG. 5, a pair of left and right beads 12, unvulcanized or semi-cured, are placed on the core-shaped element 14, which can be raised and lowered by a cylinder device (not shown), using a known tire cord mounting machine or manually. A green tire 10 is formed by wrapping and mounting a vulcanized rubberized cord cloth layer 13.

Here, the core mold element 14 is a first mold 14
It is a split type consisting of a second mold 14C that is slidably and fixedly attached to this via a bolt 14B, and is attached to an annular ring 14D via a bolt 14E so that it can be assembled and disassembled, and each mold 14A, 14
When C is matched, the shape of the outer peripheral surface follows the shape of the inner surface of the tire body 15 of the green tire 10.

In addition, the cord of the cord cloth layer 13 may be made of nylon, polyester, rayon, or other synthetic or artificial fibers or natural fibers with low elongation, metal materials such as steel or aluminum, or composite materials thereof. It may also be a monofilament, a tape, a sag, or a thick weave, and a semi-vulcanized topping rubber is provided on this cord.

The main body 15 of the green tire 10 has so-called raw rubber bonded to the bead portion, sidewall portion, and tread portion, and the gauge thickness thereof is made thinner than the gauge thickness of the finished tire.

The green tire 10 separately formed or molded as described above is mounted on a tire manufacturing machine shown in FIGS. 6 and 7.

The tire making machine consists of at least three matching mold parts: an upper mold element 16, a lower mold element 17 and a core mold element 18, in this example the lower mold element 17 is fixed and the mold parts relative to it are fixed. Specifically, the lower mold element 17 and the core mold element 18 are movable up and down, and the upper and lower mold elements 16 and 17 can be clamped and opened.

When the molds are matched, a cavity 19 having the outer shape of the pneumatic tire with lugs to be manufactured can be constructed, and in this embodiment, the lug molding portion is shown as a large blade extending from the sidewall portion to the tread portion. 20 are formed on the upper and lower mold elements 16 and 17 at predetermined intervals in the circumferential direction, and furthermore, a plurality of trapezoidal lug molding parts 21 are formed at predetermined intervals in the circumferential direction between the lug molding parts 20. Bead portion molding portions 20A are formed around the entire periphery of the elements 16 and 17.

A cylinder (not shown) is attached to an annular rim 22 of the core element 18 so that it can be moved up and down.A first die 24 is attached to the rim 22 via bolts 23, and a second die is attached to the first die 24. 25 is a split mold made of metal (steel, aluminum, etc.) that can be freely divided and is slidably fixed via the handle 18B;
When the first mold 24 and the second mold 25 are molded together, the inner surface of the toroidal tire body is formed. Note that the core mold element 15 for green tire molding can also be used as it is as the core mold element 18.

In this embodiment, the core element 18 has a shape minus the tread gauge, side gauge and bead gauge, and the minus gauge is replenished by rubber, which will be described later.

That is, the bead portion surface layer, sidewall surface layer, and tread surface layer are made to have a predetermined gauge thickness by adhering and integrating separate rubber.

Then, a separately molded green tire 10 is mounted on the core mold element 18 via a tire mounting machine such as an unloader, and this core mold element 18 is loaded into the lower mold element 17 as shown in FIG. Ru.

When the green tire 10 is inserted into the cavity 19 of the mold part through this metal core mold element 18, a lug wider than the tire width is formed to protrude outward in the tire axial direction from the tire sidewall. form the remainder of the cavity.

Further, on the mating surface 26 of the lower die element 17, an annular slug, that is, an unvulcanized rubber 27 constituting a tread surface layer including lugs, a sidewall surface layer, and a bead surface layer is attached.

Therefore, this rubber 27 has a capacity corresponding to the volume of the tread surface layer including the lugs, the sidewall surface layer and the bead surface layer,
As shown in FIG. 7, when the upper mold element 16 is clamped, the cavity 19 is filled with fluid radially inward, and the entire outer peripheral surface of the main body 15 of the green tire 10 is bonded. A predetermined tire is completed by integrating and heating and vulcanizing.

In particular, when molding a tire whose lugs are wider than the tire width and protrude outward from the sidewall, the rubber flows not only in the radial direction but also in the width direction (tire axial direction), so the inner surface of the tire in the area corresponding to the lugs is In addition, there is a risk that dents are likely to be formed and the flow of rubber strongly hits the shoulder of the tire, causing not only the cord to become disordered in this area, but also the cord to bulge outward in the radial direction. A green tire with a vulcanized rubber-attached cord layer is separately molded, set in a metal core mold element, and rubber is filled in the remaining part of the cavity while the mold is still in the closed state, adhered, and then vulcanized. Therefore, it is possible to manufacture a pneumatic tire with lug blades without dents on the inner surface or disturbance of the cord layer.

Note that the shape of the rubber 27 is circular in cross section,
They may be of any shape such as rectangular or square, and may be arranged at predetermined intervals in the circumferential direction depending on the case.

Further, the rubber 27 may be of a type in which a rubber injection port 28 shown in FIG. 7 is formed, and rubber sufficient to fill the cavity 19 is injected from this port 28 by injection or the like. In this case,
A plurality of rubber injection ports 28 are radially connected to the cavity 19, and an air vent is formed.

Therefore, in this embodiment, the tire body 29
A pneumatic tire 32 having vane lugs 30 and trapezoidal lugs 31 is vulcanized and molded, and after going through processes such as opening the mold and disassembling the core mold elements, it is transported to the next inspection process etc. by a tire unloading machine (unloader, etc.). will be moved to.

8 to 12 show pneumatic tires 32 of various shapes that can be manufactured by the method of the present invention, and FIGS. 8 to 12 mainly show pneumatic tires 32 for rice transplanters. The arrangement of the fabric layers 13 may be the example shown in FIG. 8, the example shown in FIG.
As shown in the figure, it may be a double-winged type that protrudes.

As mentioned above, it is desirable that the rubber that makes up the tire body and the rubber that makes up the tire tread have different rubber properties due to their functions.For example, the hardness of the rubber in green tires, especially the side The hardness of the wall portion is approximately JIS 40 to 70, and the hardness of the tread portion including the lugs is approximately JIS 60 to 80. No matter which range is chosen, the difference in hardness between the two should be 10 or more. Here, the hardness is after vulcanization.

Therefore, in the case of the rice transplanter shown in FIGS. 8 to 12, the blade lugs 30 need to have considerable rigidity in order to obtain traction force, while the sidewall parts need to be flexible from the viewpoint of vibration absorption. (elasticity), but the desired tire can be obtained by changing the rubber properties that make up the tire body and the surface layer that is thinly adhered to the entire outer peripheral surface of the tire body.

Furthermore, even in the case of the high lug type shown in FIG. 13, the lug portion can be made rigid or wear resistant.

In summary, in the present invention, a green tire having a semi-vulcanized rubberized cord cloth layer covering the pair of bead portions is set in a splittable core-shaped element, which is then inserted into a cavity and separately separated. Since the tire is vulcanized and molded by filling a cavity with rubber in a volume equivalent to the volume of the tread surface layer including the lugs, the sidewall surface layer, and the bead surface layer, the inner surface of the tire is shaped like a core during vulcanization molding. It is physically ensured by the element, so there is no need for bladder inflation or the like.

In particular, when molding a tire whose lugs are wider than the tire width and protrude outward from the sidewall, the rubber flows not only in the radial direction but also in the width direction (tire axial direction), so the inner surface of the tire in the area corresponding to the lugs is In addition, the flow of rubber strongly hits the shoulder part of the tire, and there is a risk that the cord will not only become disordered in this area but also bulge outward in the radial direction. A green tire with a vulcanized rubber-attached cord layer is separately molded, set in a metal core mold element, and rubber is filled into the remaining part of the cavity while the mold is still in the closed state, adhered, and then vulcanized. Therefore, it is possible to manufacture a pneumatic tire with lug blades without dents on the inner surface or disturbance of the cord layer.

Further, since the rubberized cord cloth layer is semi-vulcanized, the cord will not be disturbed even when the so-called rubber compound described above is flowed.

Furthermore, the rubber constituting the tread surface layer including the lugs, the sidewall surface layer, and the bead surface layer does not need to be opened until the end of vulcanization after the rubber is injected into the mold to fill the cavity. Therefore, there is no deformation of the green tire in the mold, and a pneumatic tire with lugs of a predetermined shape that is structurally uniform can be manufactured using the minimum necessary amount of rubber.

In addition, the bead surface layer and sidewall surface layer of the tire body are covered with the same rubber as the tread surface layer with lugs, so while reducing scratches and tears on the outer circumferential surface of the tire, A pneumatic tire with appropriate elasticity can be obtained.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams of a tread part showing a conventional example, FIG. 4 is an explanatory diagram of a first example of green tire molding according to the present invention, and FIG. 6 is a cross-sectional view of the essential parts of the tire manufacturing machine of the present invention, FIG. 7 is a cross-sectional view of the same mold clamped state, FIG. 8 is a cross-sectional view of the first example of the tire obtained by the present invention, and FIG. 9 is a cross-sectional view of the tire manufacturing machine of the present invention. Front view with the same parts omitted, Figures 10 and 1
1 is a partially omitted side view with a different lug shape from FIG. 9, and FIG. 12 is a sectional view of a main part of an example with a different cord shape. 10... Green tire, 12... Bead part,
13... Cord cloth layer with rubber, 16... Upper mold element, 17... Lower mold element, 18... Core mold element, 1
9... Cavity, 20... Lug molding part, 20A
...Bead molding part.

Claims (1)

[Claims] 1 Using a clampable tire making machine, the cavity having the shape of the lug pneumatic tire to be produced is composed of at least three matching mold parts: an upper mold element, a lower mold element and a core mold element. In a method for manufacturing a pneumatic tire with lugs, a green tire having a semi-vulcanized rubberized cord fabric layer covering a pair of left and right bead portions is separately formed, and the green tire is formed into a divisible metal core-type element. and when this metal core mold element is inserted into the cavity of the mold part, a cavity remainder is formed for forming a lug wider than the tire width so as to protrude outward in the tire axial direction from the tire sidewall; Thereafter, the cavity is filled with rubber in an amount corresponding to the volumes of the tread surface layer including the lugs, the sidewall surface layer, and the bead surface layer, and the rubber is molded over the entire outer peripheral surface of the tire body of the green tire. A method for manufacturing a pneumatic tire with lugs, characterized by adhering in a tightened state and then vulcanizing.