The invention is about an innovative mechanism for opening and closing of entry/exit hatch of an Armoured Fighting Vehicle (AFV), which facilitate the crew to access the vehicle. Contemporary AFV has hatches which need to be lifted, traversed and finally lowered to resting position during opening cycle. The closing cycle would be the reverse.
This hatch mechanism is designed in such a way that opening and closing cycles can be performed manually using a single handle. Here, during opening cycle, the hatch will first be lifted by 50mm, then traversed by 120 degree to clear the entry/exit opening and finally lowered by 15mm to rest on the stopper surface. The complete opening cycle can be achieved with same direction of rotation (anti-clockwise) of the handle. This is same for closing cycle also, but the direction of rotation of handle needs to be clockwise.
The above motions are achieved by having three assemblies inside the mechanism, viz, a left hand screw thread assembly (for lifting/lowering by 50mm), a clutch assembly (for traversing by 120 degree) and a right hand screw thread assembly (for lifting/lowering by 15mm). Here all the motions are guided by two set of keys and keyways, one between tube lift outer and top cover and the other between tube lift inner and middle cover. The smooth linear motion, rotational motion and alignment of components are ensured by the presence of a linear bearing (SKF LBBR 40), steel balls (IS:2898-2007) and a thrust bearing (SKF 51105). Thrust bearing also supports the axial thrust due the weight of the hatch.
During opening cycle, when the handle is rotated in anti-clockwise direction, the left handed screw thread assembly at the bottom becomes active, while the right handed screw thread assembly at the top remain inactive. This is because during the 50mm travel both the keys are restricted to move along vertical portion (50mm) of the keyways. Thus, tube lift outer and tube lift inner move as a single body, as a result, the hatch will be lifted by 50mm.
After the hatch gets lifted by 50 mm, the female clutch in the tube inner will engage with male clutch (rotating member along with spindle) attached on the spindle and the hatch will be traversed by 120 degree. While traversing, the vertical portion (50 mm) of both keyways will end and horizontal portion (120 degree) will be open, which arrests the lifting action of thread, guiding the hatch to traverse.
After the hatch traverses by 120 degree, the horizontal slot of keyway top ends, opening the vertical slot (15mm), while the key bottom will continue to be in horizontal portion. Thus, the right handed screw thread assembly becomes active which results in the lowering of hatch by 15mm, while the clutch will still be active.
The operation during closing cycle is exactly the reverse of opening cycle.
This mechanism can be automated by attaching a motor in place of the handle or can be made semi-automatic by using both motor and handle.