Center-pull hydraulic brake caliper structure for a bicycle

A center-pull hydraulic brake caliper structure for a bicycle, at least comprising:

• a body, having a first cylinder and a second cylinder fluidly connected with each other, a first female thread portion and a second female thread portion are respectively arranged at two ends of the first cylinder, a third female thread portion is arranged at one end of the second cylinder adjacent to the first female thread portion, the third female thread portion is screwed with a third male thread portion of an end cap, the first cylinder has a first flange and a second flange, the first flange is arranged adjacent to the first female thread portion, the second flange is arranged adjacent to the second female portion;
• a movable tube, passing through the first cylinder of the body, an outer convex ring is protruded radially and outwardly from one end of the movable tube, the outer convex ring is exposed outside the first cylinder, a first male thread portion is arranged at an outer surface adjacent to the outer convex ring, a fourth female thread portion is arranged at an inner surface adjacent to the outer convex ring, the first male thread portion is rotatably and adjustably screwed with the first female thread portion, the female fourth thread portion is screwed with a fourth male thread portion of a first end plug, and the movable tube has two flowing opening spaced apart from each other and arranged between two ends of the movable tube;
• a first piston, having a large diameter section and a small diameter section connected with each other, the large diameter section is passed through the movable tube, the small diameter section is exposed outside the movable tube, the connection of the large diameter section and the small diameter is against the first end plug, a fifth male thread portion is arranged at one end of the small diameter portion distant from the large diameter portion, the inner surface of the small diameter portion which has the fifth male thread portion is an inner outward tapered portion, a fifth female thread portion of an outer sleeve is screwed with the fifth male thread portion, a third flange is arranged inside one end of the outer sleeve distant from the fifth female thread portion, a fourth flange is arranged outside one end of the outer sleeve adjacent to the fifth female thread portion, two elastic sheets of an inner connection member are plugged in the inner outward tapered portion, an outer protruding ring between two ends of the inner connection member is against a location of the third flange adjacent to the fifth female thread portion, and the two elastic sheets are pressed to fasten one end of a brake cable;
• a second piston, one end thereof is plugged in one end of the large diameter section of the first piston distant from the small diameter section, and the other end thereof is plugged in the first cylinder, against the second flange, and adjacent to the second female thread portion, a second male thread portion of a second end plug is rotatably and adjustably screwed with the second female thread portion of the first cylinder and against one end of the second piston adjacent to the second female thread portion;
• and
• a brake caliper, fluidly connected with the body;
• wherein the brake cable is passed through the first end plug, the second piston, the first piston, and then fastened by the two elastic sheets;
• and
• wherein the second piston, the small diameter section of the first piston, or both are passed through an elastic member.