1. Field of the Invention
The present invention relates to a leaf chain, particularly to a leaf chain for machinery with a high loading transmission.
2. Description of the Related Art
Generally, chains are applied to transmit dynamics. With practical applied occasions, various chains with divergent types and structures are designed. For example, the leaf chain is usually applied to the occasion that requires a high driving force, such as the machinery for transmission or for hanging weighty objects.
Referring to FIG. 1, a conventional leaf chain 1 substantially comprises a plurality of links 11 strung together. Each of the links 11 includes two aligned rollers 12, at least one first inner plate 13 pivotally disposed on the rollers 12 (four first inner plates set of lines are adopted in the illustration), a second inner plate 14 provided between any two of the first inner plates 13, and two outer plates 15 respectively fixed to the rollers 12 and positioned at external sides of the first inner plate 14. Wherein, a plurality of first and second apertures 131, 141 respectively defined on the first and the second inner plates 13, 14 would be penetrated by the rollers 12. Concurrently, a lubricant 2 is added within an interstice formed by each roller 12 and apertures 131, 141 to attain the lubricating efficiency, thereby preventing the rollers 12 and the apertures 131, 141 from abrasion and rustiness in time of operation.
However, some drawbacks exist in the conventional leaf chain 1 as follows:                1. The lubricant 2 spreads within the interstice between the first and the second apertures 131, 141 and the roller 12; namely, the lubricant 2 utilizes an inherent adhesion force thereof to fill with the interstice. However, when the leaf chain 1 is applied, components contained therein are subjected to a reciprocal abrasion, thereby resulting in a soaring temperature of the lubricant 2 to decline the adhesion force thereof. Concurrently, since the first inner plate 13, the second inner plate 14, and the outer plate 15 adopt a loose engagement, the lubricant 2 might be undesirably released out of the interstice. As a result, the lubricating efficiency adapted to the leaf chain 1 is poor, which however influences the integral transmission stability of the leaf chain 1 and increases the abrasion rate between the rollers 12, the first and the second inner plates 13, 14 to accordingly reduce the service life of the same.        2. Since the first inner plate 13 would be commonly built to a tolerance to the dimension of the aperture 131 in time of manufacturing, the contacting surface between the first inner plate 13 and the roller 12 would be somewhat uneven that unfavorably incurs a slackened engagement. Thus, when the leaf chain is operated, such slackened engagement thereof is easily subjected to collision and abrasion. A worse situation would be even brought out after the leakage of the lubricant 2.        3. A fixed engagement is merely applied between the rollers 12 and the outer plate 15. That is, the first and the second apertures 131, 141 of the first and the second inner plates 13, 14 and the rollers 12 are in a pivotal engagement. Herein, if the leaf chain 1 is applied to a high-loading operation, the rollers 12 would become rotated since a twisting force applied on the roller 12 is larger than the engaging force formed on the outer plate 15 and the rollers 12. As a result, an undesirable abrasion would be caused between the roller 12 and the outer plate 15, thence affecting the service life of the same.        