Transmission with a threaded rod which is engaged threadably within an output gear and which is movable axially on a thrust bearing

A transmission comprising:

• a first housing half having a hollow first cylindrical portion, which has a first end wall;
• a second housing half connected removably to said first housing half and having a second hollow cylindrical portion, which has a second end wall, each of said first and second cylindrical portions defining a cylindrical chamber;
• an output gear;
• a shaft formed integrally with said output gear and having a threaded axial hole that is formed therethrough, said shaft being divided by said gear into a long shaft section and a short shaft section, which are located on two sides of said gear and which are disposed rotatably within said first and second cylindrical portions, respectively, said long shaft section being longer than said short shaft section;
• a thrust bearing disposed in said second cylindrical portion of said second housing half and clamped between said short shaft section of said shaft and said second end wall, total axial length of said thrust bearing and said short shaft section of said shaft being longer than axial length of either of said cylindrical chambers and being approximate to axial length of said long shaft section of said shaft;
• and
• a threaded rod extending threadably through said threaded hole in said shaft to convert rotation of said gear into axial movement of said threaded rod;
• whereby, positions of said long and short shaft sections of said shaft can be exchanged between said first and second housing halves to locate said long and short shaft sections in said second and first cylindrical portions, respectively.