Pedal adjustable device for exercisers

A pedal adjustable device comprising:

• a case fixed to an end of a link and including a first member and a second member connected between two sidewalls of the case respectively, the first part including a polygonal hole defined therethrough and the second part including a circular hole defined therethrough, the polygonal hole being larger than the circular hole;
• a support plate having a first end pivotably connected to the case and an extension extending from an underside of a second end of the support plate, the extension including an elongate hole defined axially therethrough and a plurality pairs of protrusions extending from two insides of the elongate hole so as to define a space between each pair of the protrusion, the extension is located between the first and second members, a pedal is fixed on the support plate, and
• an operation member having a handle and a shank connected to the handle, the shank including a polygonal section which has one end connected to the handle and a circular rod connected to the other end of the polygonal section, the circular rod extending through the polygonal hole, the elongate slot and the circular hole, the polygonal section engaged with the polygonal hole, the space between each pair of the protrusion being larger than the circular rod and smaller than the polygonal section.