A pump or compressor includes a rotating shaft, and at least a first piston rod substantially perpendicular to the rotating shaft and connecting a first pair of pistons at opposite ends of the piston rod. The piston rod moves back and forth relative to the rotating shaft. The compressor additionally includes a circular eccentric, and a circular ring connected to the circular eccentric via a bearing. A drive pin engages the circular ring at a fixed position on the circular ring and engages the at least a first piston rod. When rotational motion of the shaft rotates either the first piston rod and first pair of pistons or the circular eccentric, the drive pin and the first piston rod move back and forth relative to the rotating shaft.

A pump or compressor includes a rotating shaft, and at least a first piston rod substantially perpendicular to the rotating shaft and connecting a first pair of pistons at opposite ends of the piston rod. The piston rod moves back and forth relative to the rotating shaft. The compressor additionally includes a circular eccentric, and a circular ring connected to the circular eccentric via a bearing. A drive pin engages the circular ring at a fixed position on the circular ring and engages the at least a first piston rod. When rotational motion of the shaft rotates either the first piston rod and first pair of pistons or the circular eccentric, the drive pin and the first piston rod move back and forth relative to the rotating shaft.

A pump or compressor includes a rotating shaft, and at least a first piston rod substantially perpendicular to the rotating shaft and connecting a first pair of pistons at opposite ends of the piston rod. The piston rod moves back and forth relative to the rotating shaft. The compressor additionally includes a circular eccentric, and a circular ring connected to the circular eccentric via a bearing. A drive pin engages the circular ring at a fixed position on the circular ring and engages the at least a first piston rod. When rotational motion of the shaft rotates either the first piston rod and first pair of pistons or the circular eccentric, the drive pin and the first piston rod move back and forth relative to the rotating shaft.

A pump or compressor includes a rotating shaft, and at least a first piston rod substantially perpendicular to the rotating shaft and connecting a first pair of pistons at opposite ends of the piston rod. The piston rod moves back and forth relative to the rotating shaft. The compressor additionally includes a circular eccentric, and a circular ring connected to the circular eccentric via a bearing. A drive pin engages the circular ring at a fixed position on the circular ring and engages the at least a first piston rod. When rotational motion of the shaft rotates either the first piston rod and first pair of pistons or the circular eccentric, the drive pin and the first piston rod move back and forth relative to the rotating shaft.