Rolling diaphragm pump

A rolling diaphragm pump comprising:

• a housing;
• a rolling diaphragm defining a pump chamber in the housing;
• a piston in the housing that is reciprocatable in an axial direction along an axis of the housing;
• a motor serving as a drive source;
• a motion conversion mechanism that converts rotational motion of the motor into linear motion to cause the piston to reciprocate;
• and
• a mounting frame fixed to the housing and to which the motion conversion mechanism is attached, wherein
• a transport fluid is sucked and discharged by changing a volume of the pump chamber by deformation of the rolling diaphragm due to reciprocation of the piston,
• the mounting frame comprises a first partition plate and a second partition plate spaced apart from each other in the axial direction,
• the motion conversion mechanism comprises:
• a screw shaft disposed coaxially with the axis between the first partition plate and the second partition plate and rotationally driven about the axis relative to the housing by the motor;
• and
• a nut portion screwed to the screw shaft, reciprocatable in the axial direction and, having an insertion portion formed over an entirety of the nut portion in the axial direction at a position eccentric to the axis,
• the rolling diaphragm pump further comprises a guide shaft inserted through the insertion portion of the nut portion, fixed to the housing, and that guides the reciprocation of the piston in the axial direction,
• the nut portion further comprises:
• a nut body screwed to the screw shaft and that is reciprocatable in the axial direction;
• a first tubular portion fitted to an outer periphery of the nut body and fixed to the nut body;
• and
• a second tubular portion having a smaller outer diameter than the first tubular portion and into which a portion of the screw shaft that protrudes from the nut body toward the first partition plate is inserted,
• the insertion portion is disposed at a portion of the first tubular portion that is radially outward of the second tubular portion, and
• the first partition plate has an insertion hole into which the second tubular portion is inserted.