Wood planing machine with a carriage height adjusting unit

A wood planing machine comprising:

• a base having left and right sides;
• left and right pairs of parallel posts extending upright from said left and right sides of said base, respectively;
• left and right screw rods extending upright from said left and right sides of said base between said left and right pairs of said posts, respectively, and parallel to said posts;
• a cutter carriage extending among said posts and having left and right mounting seats that are slidably sleeved on said posts and that have left and right outer walls, respectively, said left outer wall being formed with an opening;
• a motor mounted on said cutter carriage and having an output shaft that extends outwardly through said opening in said left outer wall;
• a bracket secured to said left outer wall;
• and
• a carriage height adjusting unit including
• a driving shaft mounted rotatably on said bracket,
• a sliding member having opposite front and rear ends that are slidably sleeved on said driving shaft so as to permit sliding movement of said silding member along said driving shaft,
• opposing first and second shaft-driving gears slidably sleeved on and engaging said driving shaft so as to co-rotate with said driving shaft, and mounted on said front and rear ends of said sliding member, respectively, so as to slide with said sliding member along said driving shaft,
• a driving gear coaxially and securely connected to said output shaft and disposed between said first and second shaft-driving gears,
• a first gear mechanism operably coupled to said sliding member in such a manner that operation of said first gear mechanism via an external force applied thereto results in sliding movement of said sliding member together with said first and second shaft-driving gears along said driving shaft from a middle position, in which, said driving gear disengages from said first and second shaft-driving gears, to an upward position, in which, said first shaft-driving gear engages said driving gear so as to permit rotation of said driving shaft in a first direction upon actuation of said motor, and from the middle position to a downward position, in which, said second shaft-driving gear engages said driving gear so as to permit rotation of said driving shaft in a second direction that is opposite to said first direction upon actuation of said motor, and
• a second gear mechanism coupled to said driving shaft and said left and right screw rods so as to permit upward and downward movements of said cutter carriage along said posts upon rotation of said driving shaft in said first and second directions, respectively.