A rack assembly for a rack and pinion gear system may comprise: a rack housing; and a rack disposed within the rack housing, the rack and the rack housing at least partially defining a first hydraulic chamber disposed between a first side of the rack and the rack housing, a second hydraulic chamber disposed between a second side of the rack and the rack housing, a third hydraulic chamber disposed within the rack proximal the first hydraulic chamber, and a fourth hydraulic chamber disposed within the rack proximal the second hydraulic chamber.

A solenoid valve includes a housing including a channel, a single-acting through hole, a double-acting through hole, a spring biased spool in the channel, a lateral outlet communicating with the double-acting through hole, and a hole element passing through an edge of the channel to communicate with both the double-acting through hole and the channel; a switch on the housing and including an axial tunnel, a shaft in the tunnel, a lateral single-acting hole communicating with the tunnel, a double-acting hole communicating with the tunnel, and a linking hole perpendicular to the tunnel but not communicating therewith; a pilot valve on the switch; a base at a bottom of the housing, and a spring biased check valve at a lower opening of the housing and the base, the check valve communicating with the single-acting through hole.

A drive system includes: a remote drive configured for being driven by an electrical motor; and an actuator spaced apart from and fluidically coupled with the remote drive and configured for being fluidically powered by the remote drive.

A drive system includes: a remote drive configured for being driven by an electrical motor; and an actuator spaced apart from and fluidically coupled with the remote drive and configured for being fluidically powered by the remote drive, the remote drive including a rack and pinion system and a plurality of piston assemblies coupled therewith, the rack and pinion system including a first rack, a second rack, and a pinion engaging the first rack and the second rack, the plurality of piston assemblies each including an inner piston and an outer piston which are configured for sliding relative to one another and thereby for selectively opening and closing a working medium passage therebetween.

A pivot actuator comprising: a housing; a piston supported in the housing; a drive shalt protruding from the housing wherein the piston engages the drive shaft to rotate the drive shaft about a drive axis by a pivot angle between two end positions; and a switching cam coupled to the drive shaft and configured to contact a stop element in the two end positions, wherein the switching cam includes two discs arranged adjacent to one another along the drive axis.

A pneumatic stepper motor includes a housing, said housing accommodating at least part of: a rack or geared axle comprising a plurality of gear elements; and two pistons, each comprising at least two teeth, said pistons being arranged to cooperate with said rack or geared axle. The racks may either be straight or curved. The pistons are preferably double-acting pistons. A device includes at least one, and preferably a plurality of, such pneumatic stepper motor(s). The device may in particular be an MRI-compatible robotic system, more in particular for example an MRI-guided breast biopsy device.