| 摘要 |
A climbing rung is provied for anchoring to the wall of a manhole shaft. The climbing rung has a generally U-shaped core of two parallel legs spaced apart by a central tread. Each leg is sheathed in a pre-formed protective sleeve, closed at one end, by inserting the leg into the mounth of the sleeve. An injection moulded protective coating is bonded to the core of the tread and the core of each leg, extending to proximate the mouth of each pre-formed sleeve when a leg is sheathed therein, forming a sealing interface proximate the annular lip circumferentially defining the mouth of each sleeve. A method is provided including the steps of gripping the climbing rung only proximate the pre-formed protective sleeves when both legs are sheathed therein, so as to permit positioning the core of the tread and legs, extending only to proximate the mouth of each pre-formed protective sleeve, in an injection moulded cavity radially spaced equidistant the surface of the mould cavity. Advantageously, positioning pins inside the injection mould cavity for radially spacing the core of the climbing rung from the surface of the mould cavity are thereby not required. In another aspect of the invention it is not necessary to grip the step using pre-formed protective sleeves-all that is necessary is to alternately grip at last two oppositely spaced portions of the core of the climbing rung; alternately coating the portion of the climbing rung opposite the end which is being gripped.
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