Teoria i praktyka eksploatacji przekładni ślimakowych
Sabiniak, Henryk Grzegorz
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Worm gears are used for drive transrnission as reducers. They are practically not applicable as intensifiers. Worm gears are characterised by great compactness of structure, which is a consequence of the capability of achieving very large ratios, up to 70, at one degree. Still cases of greater speed reductions at one degree are also known. The gears can transrnit quite heavy loads, which results from the number of pairs of teeth in a worm and a worm wheel working subsequently. The minimum number of pairs of teeth in continuous cooperation in cylindrical worm gears usually does not fall below 2 (Fig. 2), whereas in globoidal worm gears the number of pairs of teeth being at the same time in the mesh can reach 5 (Fig. 2) or more. Moreover they are silent-running. Among the problems most frequently occurring in the process of the gear exploitation there is a proper selection of lubricator, its amount, and the way of complementing it as well as the frequency of its replacement. This problem results from a serious fault characteristic for worm gears. Due to a specificity of their teeth geometry a great amount of heat is ernitted during the work. Thus the exploitation of the gears consists mainly in quick reception of the losses of thermal energy in the mesh and in dissipating it as quickly as possible. In order to offer a solution to the above problems mathematical relations, graphs, tables and appendant drawings supported by specific examples have been included in the paper. . This short description already gives a clue of the difficulty of decisionmaking on the selection of proper worm gear for drive transrnission in a given machine or a mechanical device. A description of the course of action when selecting a worm gear also offered in the paper can be helpful in such cases. The paper provides a complete idea of the elastothermohydrodynarnic lubricating theory in worm teeth as well as a complete description of mathematical and physical relations. The whole theory has been illustrated with an example. The considerations have also been supported by a description of numerous experiments made on models as well as on real gears and devoted to the type of friction taking place in the worm teeth in various exploitation conditions. The contents of the paper also include a complete selection of lubricating agents, with oils and greases. The influence of the assembling and of the gear running-in on the further exploitation parameters has been described, with a stress placed on an important feature of self-locking. The current state and the perspectives of worm gears development have been presented and further tendencies and directions in the research have been introduced.