Diaphragm pump with a rail to restrict rotation and a piston cavity to engage with a guiding member at the end of the suction stroke

A diaphragm pump including:

• a housing;
• a piston which is placed in the housing to be coaxial with the housing, and which is disposed to be reciprocally movable in an axial direction of the housing;
• a shaft which is configured to be moved in conjunction with the piston in a state where one axial end side of the shaft is in contact with the piston;
• a rolling diaphragm having:
• a lid portion which is placed on one axial end side of the piston;
• an open-end portion which is attached to the housing;
• and a folded portion which is placed between the lid portion and the open-end portion, the lid portion being reciprocally movable integrally with the piston with respect to the open-end portion which is positionally fixed by the housing;
• a pump chamber which is defined by the rolling diaphragm on one axial side in the housing, a volume of an interior of the chamber being variable;
• a driving device having:
• a motor section;
• and an output axle which is placed coaxially with the shaft, and which is coupled to another axial end side of the shaft, the driving device being attached to an other side in the axial direction of the housing, the driving device being able to, in order to cause the piston to reciprocally move in the axial direction of the housing through the shaft, convert rotational movement of the motor section to linear movement, and output the linear movement from the output axle to the shaft;
• a guiding member which is placed on the other side in the axial direction of the housing with respect to the piston in the housing, and which is attached to the housing in a manner to extend in a direction perpendicular to the axial direction of the housing, and which is able to guide the shaft in a manner to be movable in the axial direction in a state where the shaft is passed through the guiding member in the axial direction of the housing;
• and
• a restricting mechanism which is disposed in the housing and between the output axle of the driving device and the shaft, and which is able to restrict rotation of the shaft about an axis of the housing while allowing reciprocal movement in the axial direction of the housing, wherein:
• the output axle of the driving device has a rod-like portion at one axial end side and a screw shaft portion at another axial end side, and the screw shaft portion is integrally connected to the rod-like portion;
• the restricting mechanism includes a coupling member that couples the shaft to the rod-like portion of the output axle of the driving device by clamping the other axial end side of the shaft and the rod-like portion of the output axle such that the other axial end side of the shaft faces the rod-like portion of the output axle;
• the piston includes a concave portion that opens toward the other axial end side of the housing;
• the guiding member includes a boss portion that is projected toward the one axial end side of the housing to support the shaft and guide the shaft toward the axial direction of the housing;
• and,
• the boss portion enters the concave portion of the piston when the piston moves toward the most retracted position, and the boss portion gets out of the concave portion when the piston moves toward the most advanced position.