A device includes an outer cylinder having a cylinder inner wall and a cylinder outer wall and at least one magnet disposed on or between the cylinder inner wall and the cylinder outer wall and a piston having a piston inner wall and a piston outer wall and at least one magnet disposed on or between the piston outer wall and the piston inner wall. In one embodiment, the piston is rotatable within the cylinder and slidably movable along an axis respective to the cylinder. The piston is also disposed within the cylinder such that the at least one magnet disposed on or between the cylinder inner wall and the cylinder outer wall is aligned with the at least one magnet disposed on or between the piston outer wall and the piston inner wall, substantially preventing the piston from rotating relative to the cylinder.

A transmission includes a case, a clutch pack, a piston. The case defines a bore that transitions along a step from a first to a second diameter. The piston is disposed within the bore. The piston has first and second seals that engage the case along the first and second diameters, respectively. The piston defines a chamber that is encompassed by the piston, the case, the first seal, and the second seal. The piston is configured to engage a clutch pack when hydraulic fluid is channeled into the chamber.

A pneumatic device includes a cylinder, a buffer member and a piston unit. The cylinder includes a cylinder wall defining an air chamber. The buffer member has a tubular wall that defines a communicating hole. The tubular wall has a length greater than the wall thickness thereof. The piston unit includes a sealing member, and a rod member movably extending through the communicating hole. The rod member has a driven section received within the air chamber and mounted with the sealing member. The piston unit is movable between a restoring position where the driven section is spaced apart from the buffer member, and an impact position where at least one of the driven section and the sealing member is in contact with the buffer member.

A control device for a hydraulic brake for a bicycle includes a reservoir for hydraulic fluid. The reservoir has a variable volume. The control device also includes a reservoir cover at least partially defining the reservoir, and a support that is attachable to a handlebar of the bicycle via an inner annular surface of the support. A handlebar proximity zone is radially outer relative to the inner annular surface of the support and is within two centimeters of the inner annular surface of the support. At least part of the reservoir cover is within the handlebar proximity zone.

A bottom cylinder for a high-temperature and high-pressure environment simulator of a high-fidelity corer is provided. The bottom cylinder includes a cylinder barrel. The bottom of the cylinder barrel is provided with a cylinder base. The piston is provided inside the cylinder barrel and divides an inner cavity of the cylinder barrel into a rodless cavity and a rod cavity. The piston is provided with a piston rod. The outer wall of the cylinder barrel is provided with an oil inlet hole communicated with the rodless cavity, an oil outlet hole communicated with the rod cavity, and a reserved hole. The lower end surface of the piston is provided with a first buffer ring, and the upper surface of the cylinder base is provided with a second buffer ring mated with the first buffer ring. The bottom cylinder is applied to the simulator for oil and gas resource exploitation.

A fluid pressure cylinder is equipped with a piston rod connected coaxially with a piston and which slides linearly in the interior of a body. A cutout recess having a predetermined length along an axial direction of the piston rod is formed on a side surface of the piston rod. A planar bearing is provided, which projects toward the cutout recess from an inner surface of the body, and includes a distal end surface that abuts on the same plane with a bottom surface of the cutout recess.

In a piston unit of a fluid pressure cylinder a plurality of magnets are disposed through holes provided in a ring body. The magnets are disposed in facing relation to detection sensors that are mounted on connecting rods, and are provided in the same quantity as the connecting rods. Further, a guide rod extending from a head cover to a rod cover is inserted through the interior of the ring body. When the piston unit is displaced along the cylinder tube, rotational displacement is restricted by the piston unit being displaced along the guide rod, whereby the magnets are retained to face toward the connecting rods at all times. Therefore, the position of the piston unit is detected by the detection sensors through the magnets.

A hydraulic lift apparatus for operating a downhole pump features a hydraulic linear actuator with a piston longitudinally slidable on a central axis of a rotatable portion of a housing. An anti-rotation rod runs longitudinally through the piston at a position radially offset outwardly from the central axis to prevent rotation between the piston and housing. A stationary motor powers a drive train whose output is connected to the rotatable portion of the housing and centered on the central axis. The actuator is one-way actuator with a hydraulically driven upstroke. A leak detection passage extends through the piston to collect fluid that has leaked across the piston seals and convey it to a leak detection port and associated containment tank. A position sensor for monitoring the piston movement features a sensing rod depending downwardly into a hollow piston shaft carried by the piston and connected to the pump rod.

A control device for a hydraulic brake for a bicycle includes a reservoir for hydraulic fluid. The reservoir has a variable volume. The control device also includes a reservoir cover at least partially defining the reservoir, and a support that is attachable to a handlebar of the bicycle via an inner annular surface of the support. A handlebar proximity zone is radially outer relative to the inner annular surface of the support and is within two centimeters of the inner annular surface of the support. At least part of the reservoir cover is within the handlebar proximity zone.

A guide unit for an actuator includes a slide part and a guide part. The actuator includes a drive rod extending from a cylinder main body. The slide part includes: a slider detachably connected to the drive rod; and a guide rod fixed to the slider. The guide part includes: a guide plate fixed to the cylinder main body; and a guide tube fixed to the guide plate. The guide rod is slidably inserted into the guide tube.