JP5665341B2 - Vulcanization mold for agricultural tires with lugs - Google Patents

Description

  The present invention relates to a vulcanized mold for agricultural tires with lugs, and more particularly to reduce rubber squeezing of the peripheral surface of the unvulcanized tire due to the mold ridges when the mold of the vulcanized mold is closed. The present invention proposes a technique for preventing the molded lug from being damaged by the mold ridges when the vulcanization mold is opened after the vulcanization of the tire is completed.

  In agricultural tires, there are many cases where a U-shaped lug and lug groove are formed on the tread surface, and vulcanization molds of this type of tire are mostly tires as described in Patent Documents 1 and 2. The equatorial plane is divided into two parts in the vertical direction, and is configured to be opened and closed in the tire width direction.

  However, since such a vulcanization mold has a sharp corner or a sharp corner bent at about 90 ° on the mold dividing surface, for example, when the vulcanization mold is closed, the corner, particularly the mold, When the projecting corners contact (rub) with the tread outer peripheral surface of the unvulcanized tire, the rubber is grinded particularly at the dividing position of the mold, resulting in the rubber sticking out or the rubber gathering (rubber Chris). As a result, there was a risk of appearance failure and cracking due to running.

  On the other hand, when vulcanization of the molded tire is completed and the vulcanization mold is opened vertically with respect to the portion corresponding to the equator surface of the tire, the state of mold opening after vulcanization is schematically shown in FIG. As shown in Fig. 4, the corners on the dividing surface side, in particular, the lugs of the vulcanized tires (especially in the vicinity of ¼ point of the extended length of the lugs from the dividing position of the mold) By hooking, the edge of the lug may be damaged at the corner or rubber chips may be generated, which may cause poor appearance of the tire and consequently defective products.

Japanese Utility Model Publication No. 62-154812 Japanese Patent Laid-Open No. 9-94831

  Therefore, the present invention is a vulcanized mold for agricultural tires with lugs, and there is no risk of the occurrence of rubber sticking or the occurrence of crisps on the tread outer peripheral surface of the molded tire tread outer peripheral surface. An object of the present invention is to provide a vulcanized mold for agricultural tires with lugs that can effectively prevent damage to lugs of product tires at the time of mold opening.

The vulcanized mold for agricultural tires with lugs according to the present invention has recesses and ridges for forming lugs and grooves in the tread surface area of the unvulcanized tire, and two upper and lower portions corresponding to the equatorial plane of the tire. This is a mold for vulcanizing at least the tread surface of agricultural tires with lugs with a rim diameter of 24 inches , and the height to the top of the ridge as measured from the bottom of the ridge at each mold division surface. Chamfering curvature radius R1 toward the facing divided surface at the position of 20% to 65% of LH is set to a range of 0.06LH to 0.09LH, and a corner cutting curvature toward the facing divided surface at the top of the ridge. The radius R2 is in the range of 0.10 LH to 0.15 LH.

  Here, the “part corresponding to the equator plane of the tire” refers to a position corresponding to the center of the equator plane of the tire ± 30 mm.

Therefore, in the vulcanized mold for agricultural tires with lugs according to the present invention, at each mold dividing surface, measured from the bottom surface of the concave stripe, at the position of 20 to 65% of the height LH to the top of the convex stripe, The chamfering curvature radius R1 facing the dividing surface is set in a range of 0.06 LH to 0.09 LH, and the chamfering curvature radius R2 facing the facing dividing surface at the top of the ridge is 0.10 LH to 0.15 LH. By setting it as a range, the shape of the divided part of the mold that faces the dividing surface becomes a curved shape without corners, and it comes in contact with the tread surface area of the unvulcanized tire and reduces the amount of rubber gathering. Occasionally, hooking of vulcanized tire lugs at corners on the split surface side is reduced, so that manufacturing defects can be reduced without deteriorating the appearance of the product tire.

  That is, when the radius of curvature R1 is less than 0.06LH, the radius of curvature R1 at the position of 20 to 65% of the height LH to the top of the ridge is small, and the lag of the rug is caused by hooking the vulcanized tire lug when the mold is opened. There is a risk that the edges may be easily damaged. On the other hand, if it exceeds 0.09 LH, the radius of curvature R1 at a position of 20 to 65% of the height LH to the top of the ridge will increase, and the protrusion of rubber from the divided surface will increase, which may be unfavorable in terms of appearance. is there.

Also, if the radius of curvature R2 is less than 0.10 LH, the radius of curvature R2 at the top of the ridge will be small, and the rubber will increase at the top of the ridge on the outer surface of the tread of the unvulcanized tire when the mold is closed. There is a risk that the rubber crisp will be generated, or the lug hooking at the top of the ridge will become large when the mold is opened, and the lug chipping will occur, impairing the appearance. On the other hand, if it exceeds 0.15 LH, R2 at the top of the ridge will increase, and the protrusion of rubber from the dividing surface will increase, which may be undesirable in appearance.

(A) is a perspective view of the lower mold | type which shows one Embodiment of the vulcanization mold of the agricultural tire with a lug of this invention, (b) is the elements on larger scale of the B area | region of (a). 2 is an enlarged plan view schematically showing a part of FIG. (A) (b) is a figure which respectively shows an example of the chamfering shape which faces the opposing division surface side in a mold division surface in the vulcanization mold of the agricultural tire with a lug of this invention. It is a figure which shows an example of the chamfering shape which faces the opposing division surface side in the mold division surface of the vulcanization mold of the agricultural tire with a conventional lug. It is a figure which shows the relationship between a chamfering curvature radius and lug height of an Example mold and a comparative example mold. It is a figure which shows typically the mode of the mold opening after vulcanization.

Below, the vulcanization mold of the agricultural tire with a lug of this invention is demonstrated in detail, referring drawings.
In the figure, reference numeral 1 denotes a lower mold of a vulcanization mold that is divided into two in the upper and lower directions. In this lower mold vulcanization mold 1, a groove 2 and a groove for molding lugs are formed on a tread surface area of an unvulcanized tire. The ridges 3 are alternately provided continuously at a predetermined pitch on the inner periphery.

And in this vulcanized mold for agricultural tires with lugs, at each mold dividing surface, measured from the bottom surface of the concave strip 2, at a position C of 20 to 65% of the height LH to the vertex D of the convex strip 3 The corner radius of curvature R1 facing the facing split surface is in the range of 0.06LH to 0.09LH, preferably 3.0mm, and the corner radius of curvature R2 facing the facing split surface at the vertex D of the ridge 3 is as follows. Is in the range of 0.10 LH to 0.15 LH, preferably 4.5 to 6.0 mm, and more preferably a chamfered shape over the opposing divided surface side on the mold dividing surface.

Such a vulcanized mold 1 has an unvulcanized tire on the mold dividing surface when the mold is closed after the unvulcanized tire is placed in a cavity formed between the inner surface of the lower mold and the bladder, and then the upper mold is lowered. Rubber tucking (rubber chris) caused by scratching the tread surface of the tread can be reduced.
In addition, a vulcanization medium at a predetermined pressure and temperature is supplied into a vulcanization bladder housed in an unvulcanized tire to expand the vulcanization bladder, and the unvulcanized tire is pressed against the inner surface of the vulcanization mold for vulcanization. After vulcanization, the vulcanization bladder is shrunk to raise the upper mold, resulting from the hooking on the mold dividing surface when the mold is opened, particularly the 1/4 point of the extended length of the lug from the mold dividing position Neighboring lug chipping can be reduced.

  Also, in the vulcanization mold (upper mold off-center mold) that divides above the position corresponding to the tire equatorial plane, the thickness of the lower mold is larger than that of the upper mold, and the upper mold and the tire rub on the divided surface when the mold is closed. In order to increase the area, it is preferable to provide a chamfered shape on the upper mold dividing surface facing the opposed dividing surface.

Next, a tire vulcanization mold having a structure as shown in FIGS. 1 and 2 and having a size of AGR 13.6R24 was prototyped, and various specifications were changed as shown in Table 1 and FIG. For each of the example molds 1 and 2 and the comparative example molds 1 and 2, the lag chipping rate of the vulcanized tire and the rubber-criss rate of division at the product tire were measured.
In addition, since the comparative example mold does not require modification for a structure other than the square cut shape facing the facing division surface side, it was assumed to conform to the example mold. In addition, in each of the example molds 1 and 2 and the comparative example molds 1 and 2, the height LH to the top of the ridge as measured from the bottom surface of the ridge is 45 mm.

[Rag chipping rate of vulcanized tires]
For each of the example molds 1 and 2 and the comparative example molds 1 and 2, the lugs on the entire circumference of the tire were carefully observed visually for chipping at the edge of the lug, and the occurrence rates of chipping with respect to the total number of lugs were compared. The results are shown in Table 2.
In addition, the value in a table | surface shows that performance is so favorable that there are few appearance defect generation | occurrence | production as a numerical value is small.

[Rate of occurrence of rubber chris at product divisions]
For each of the example molds 1 and 2 and the comparative example molds 1 and 2, a rubber mesh is attached to the molded raw tire, the disappearance of the rubber mesh in the product tire is confirmed, and the crack of the rubber covering part due to rubbing by the driver is confirmed. The results are shown in Table 2.
The values in the table indicate that the smaller the numerical value, the lower the appearance defect occurrence rate and the better the performance.

  From the results of Table 2, the example molds 1 and 2 were able to reduce the occurrence rate of rag chipping of the vulcanized tire and the generation rate of rubber chris at the division position in the product tire, compared to the comparative example molds 1 and 2. .

1 Vulcanization mold 2 Concave strip 3 Convex strip

Claims (1)

Agricultural tire with lugs having a rim diameter of 24 inches , which has ridges and ridges that form lugs and grooves in the tread tread area of unvulcanized tires, and is divided into two parts at the top and bottom at the part corresponding to the equator of the tire In at least the mold for tread vulcanization,
In each mold dividing surface, the chamfered curvature radius R1 facing the opposing dividing surface at a position of 20 to 65% of the height LH to the top of the protruding strip measured from the bottom surface of the protruding strip is 0.06 LH to 0. A vulcanization mold for agricultural tires with lugs, characterized in that the range is 0.09 LH, and the corner radius of curvature R2 at the apex of the ridges is the range of 0.10 LH to 0.15 LH. .

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