| 摘要 |
<p>A gearbox 12 comprises a gear 46 encased in a close fitting cavity 34 defined by part of the gearbox. Lubricant may be arranged in the cavity to cover the teeth of the gear. In a preferred embodiment the gearbox has at least two planes or levels of casings for gears 14a-c, wherein the casing is a single piece of material having a plurality of cavities 32-44 machined therein. The casings 14a-c are preferably formed from plastic or aluminium. The gearbox is preferably used on with a drill head. The casings 14a-c are preferably held together with through dowels, pins, rods or the like.</p> |
