JPH03284912A - Manufacture of rubber crawler - Google Patents

Abstract

PURPOSE:To significantly reduce the distortion produced on the outer peripheral surface, and thus prevent cracks from occurring by fixing in a curved state a rubber crawler of being vulcanized and molded into a flat plate, and effecting a heat process repeatedly therefor. CONSTITUTION:By the use of an upper and lower molds, a rubber crawler main body 1 being vulcanized and molded into a flat plate is fixed such that the inner peripheral side thereof is formed into a recession, and heat process is performed repeatedly therefor at the heat temperature of the order of 120 deg.C for 15min. For example, after the rubber crawler 1 is made into an approximately uniform circle at an upper view and then put into a vulcanizing can, further, the lid is closed thereover, steam is sealed directly therein and heating is effected for a predetermined time. Besides, the curvature degree alpha of fixing into a curved shape is 5 deg. or above.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a rubber crawler that is attached to the suspension of civil engineering machinery, etc., and the present invention relates to a rubber crawler that is attached to the suspension of a civil engineering machine, etc. This article relates to an RF Mukubi-solar construction method for improving the durability of.

(Prior art) Figures 1A, B, and C are plan views showing a conventional rubber crawler;
FIG. 2 is a cross-sectional view and a vertical cross-sectional view, in which a large number of core metals 2 are lined up and buried at regular intervals in the circumferential direction of the crawler inside the crawler body 1, and a large number of metal cores 2 are arranged close to the outer circumferential side of the wing portion 2a of the core metal 2. The steel cords 3 are laid out in a layer in the circumferential direction of the crawler, and grounding lugs P made of rubber are provided on the outer circumferential surface of the crawler at regular intervals. In this case, 4 is a retaining hole that engages with the tooth of the drive wheel.

Therefore, the production of the rubber crawler that we own is as shown in Fig. 2, that is, as shown in Fig. A, a core metal 2 is placed in a long mold 5 consisting of an upper mold 5a and a lower mold 5b that are installed in advance on a plenue machine. , place the steel cord 3, unvulcanized rubber 6, etc., and then
As shown in the figure, the upper mold 5a and the lower mold 5b are combined, and the rubber material is vulcanized by applying pressure and heating for a predetermined period of time to form a belt-shaped crawler body 1 inside the elongated mold 5.

After this, although not shown in the drawings, both ends of the pea-shaped crawler body 1 are also pressurized and heated in the same manner as described above to form an endless band rubber crawler.

(Problem to be Solved by the Invention) When a rubber crawler is wound around a driving wheel or an idler wheel, the outer circumferential side of the curved portion is stretched in the circumferential direction and the inner circumferential side is compressed. The crawler is divided into an extension side and a compression side with the steel cord layer buried inside the crawler as a boundary, that is, distortion occurs due to compression force on the inner circumference side and extension force on the outer circumference side. however,
Vulcanized rubber has good durability against compressive strain, so no problems occur on the inner circumferential side, but if strain due to stretching force occurs repeatedly, the rubber gets fatigued and cracks occur, impairing durability. Therefore, the outer circumferential side becomes a problem.

By the way, in the thickness direction of the rubber crawler, the rubber is thick at the ground lug part and the core metal is buried inside, but the rubber is thin between the lugs, so the ground lug part is thicker. There is almost no elongation, and the elongation force concentrates between the lugs, causing the rubber to fatigue and cracking.As these cracks grow, crushed stones, etc. enter, pushing the cracks wider and causing the steel to deteriorate. If it reaches the cord layer, moisture will enter from the road surface and corrode the steel cord, causing it to rapidly deteriorate and break.

Figure 3 explains the position where cracks occur between the lugs.If the curvature of the root r is relatively small, strain will be concentrated in this area and a crack will occur; When the curvature of is increased, the location where cracks occur gradually becomes closer to the center, but in any case, strain concentrates somewhere between the lugs and cracks occur.

Ratio between lug width 11 and lug spacing in the diffused layer
The larger the lL, the greater the strain concentrated between the lugs, but in recent years, in rubber crawlers for large civil engineering machinery, the lug width has been increased, so the lug spacing has become smaller, and the crawler body has become smaller. The thickness and lug height are large, and the core metal is also large and wide, so large distortions concentrate between the lugs at the curved part, which causes cracks and damages the internal steel cord as described above. The problem is deterioration and decreased durability.

Regarding the above points, there is also a problem in the production of conventional rubber crawlers.In other words, since conventional rubber crawlers are vulcanized and molded in the shape of a flat plate, when this is made into a ring shape as an endless band, there is a problem of curvature. Distortion has already occurred in this part, so if it is attached to a crawler device and wound around the drive wheel and idler wheel to create tension, the distortion will become even greater.

(Means for Solving the Problems) The present invention aims to solve the above-mentioned problems, and involves reheating a rubber crawler that has been vulcanized into a flat plate and molded into an endless band. It is characterized in that it is fixed in a curved state concave toward the inner circumferential side and then heat-treated.

(Example) As shown in Fig. 4, the rubber crawler 1 is placed in a vulcanizing can (not shown) in a uniform circular shape when viewed from above, the mold is clamped, and then steam is directly filled to form a predetermined shape. Heat for a while. In this case, the steam temperature in the vulcanizer was about 150° C., and the treatment time was about 100 minutes.

FIGS. 5A and 5B relate to a bending test showing the effects of the invention, and S is a test piece having a shape and size used in a normal bending test of vulcanized rubber. (U is the depression in the center). In this test, test pieces were prepared based on the type of membrane material, vulcanization time, and presence or absence of heat treatment, and the test pieces were tested using an ordinary bending tester (Demarsha type).Table 1 shows the results.

Table 1 (1) Types of rubber: 8 used for rubber crawlers
Test pieces were prepared using different types of compounded rubber.

(2) Vulcanization time: The vulcanization temperature of the test piece is 150°C. (8) Reheating treatment: As shown in Figure 6, the test piece is wrapped around a pipe with a diameter of approximately 80fi and steamed directly in the vulcanizer. It was heated well. In this curved state, a strain of 1/2 of the maximum strain in the bending test is applied to the surface of the depression U.

The heating temperature and time were 150° C. and 15 minutes.

(4) Bending test: maximum grip distance 119m, minimum 5gI
nI Fig. 7 relates to a rotation test for confirming the effects of the present invention, and 7 is a rotation test machine in which a driving wheel 8, an idler wheel 9, a rolling wheel 1o, 1°, etc. are actually tested. The crawler device is combined in the same manner as y and rotated at high speed by motor M.

In this test, a rubber crawler that had been placed in a partially curved position in a vulcanizing can and directly subjected to steam heat treatment was attached to the rotation tester 7 as shown in the figure, and a rotation test was conducted.

The results were as shown in Table 2.

Table 2 Rotation test (1) Dimensions of test rubber crawler: width 600 mm, total length 64 mm
00 ff, base thickness 52wIK (thickness of the crawler body ``excluding lugs'') (2) Heat treatment conditions: 150°C x 100 minutes (3) Number of rotations: 1.24 million times (one rotation of the rubber crawler is defined as one rotation) ) (4) Rotation speed: 48.6 times/min (5) Curved layer α: As shown in Figure 8, it indicates the angle at which the widthwise tangents of the wings of adjacent core metals of the curved part intersect ( The degree of curvature α is preferably 5° or more, particularly 8° or more.) (Effects of the Invention) The present invention provides a rubber crawler that has been vulcanized and molded into a flat plate shape as described above, is fixed in a curved state, and then reheated. In order to perform this treatment, the crosslinked structure of the rubber molecules is rearranged so that no distortion occurs on the outer circumferential surface even in a curved state. However, since the distortion occurring on the outer circumferential surface is greatly reduced, no cracks will occur, which will greatly contribute to improved durability.

[Brief explanation of the drawing]

Figures 1A, B, and C are plan views, cross-sectional views, and longitudinal sectional views showing conventional rubber crawlers, Figures 2A and B are manufacturing state diagrams, and Figure 3 shows cracks occurring between the lugs. Figure 4 explains the reheating treatment of the present invention.
Figures 5A and B illustrate the bending test, Figure 6 illustrates the reheating treatment of the test piece, Figure 7 illustrates the rotation test, and Figure 8 shows the curvature during the reheating treatment. This explains the angle. 1... Crawler body 2... Core metal

Claims (2)

[Claims] (1) The rubber crawler body is vulcanized and molded into a flat plate using upper and lower molds, fixed in a curved shape with a concave inner circumference, and reheated at a heating temperature of approximately 120°C or higher for approximately 15 minutes or more. A method for manufacturing a rubber crawler, which comprises: (2) The method for manufacturing a rubber crawler according to claim (1), characterized in that the degree of curvature α when fixing in a curved shape is 5° or more.