The present disclosure relates to a pumping assembly, a piston pump and an oral irrigator. The pumping assembly includes: a cylinder, cavities providing therein with at least two cavities with different inner diameters; a piston mechanism successively extending through the at least two cavities, the piston mechanism being in slidable cooperation with walls of the cavities, and a gap being formed between a sidewall of part of the piston mechanism and the walls of the cavities; and a drive mechanism connected to the piston mechanism, the drive mechanism being configured to drive the piston mechanism to move.

The invention relates to a sealing piston, which is designed for use in a hydraulic expansion chucking device. The sealing piston comprises a pin that extends in an axial direction (A), and a seal that adjoins the pin and likewise extends in said axial direction (A). The seal comprises a sealing shaft that adjoins the pin and has a shaft radius (Rs). The seal further comprises a sealing head that adjoins the sealing shaft, wherein the sealing head comprises a circumferential sealing lip, which has a sealing radius (Rd) that is greater than the shaft radius (Rs). The sealing lip forms a contact surface in radial direction (R) for abutment and sealing against an inner wall of a bore in the expansion chucking device, and, measured in axial direction (A), has a sealing length (Ld) that is greater than the difference between the sealing radius (Rd) and the shaft radius (Rs). The invention further relates to a corresponding expansion chucking device.

A piston for a fluid-actuated working cylinder, with a piston base unit which is coaxial to a piston longitudinal axis, consisting of a rigid core body which has radial outer peripheral surface and of an annular filling body which is seated in an annular receiving groove. The receiving groove is coaxial to the piston longitudinal axis and in the region of the radial outer peripheral surface is designed with a radially outwardly facing groove opening in the core body. The piston further includes a ring element which consists of plastic. The ring element radially outwardly coaxially encompasses the piston base unit at least in the region of the filling body, being radially supported with a radial inner peripheral surface on the piston base unit, projecting radially beyond the radial outer peripheral surface of the core body and comprising an axially orientated axial support surface radially outside the piston base unit on its two axial face sides. The piston further includes an annular enveloping body which has rubber elastic characteristics.

A piston accumulator having an accumulator housing (4) and a separating piston (10), which is guided longitudinally displaceable therein, which separates two media chambers (12, 14) from each other and which has a dual sealing system (16), wherein one of the sealing systems (18) faces one media chamber (12) and the other sealing system (20) faces the other media chamber (14), wherein at the location (58) a compensation device is at least partially accommodated in the separating piston (10) between the two sealing systems (18, 20), which compensation device enables hydrostatic pressure compensation between the two sealing systems (18, 20) to prevent an undesirable pressure buildup during operation.

A piston assembly is provided for a human-powered vehicle. The piston assembly includes a main body, a primary seal and a secondary seal. The main body is configured to be movable from a rest position to an actuated position along an actuation direction in a cylinder bore. The primary seal includes a primary seal body arranged on the main body, the primary seal body being made of the first seal material. The secondary seal includes a secondary seal body arranged on the main body at upstream of the primary seal with respect to the actuation direction. The secondary seal body is made of a second seal material that is more elastic than the first seal material.

The hydraulic piston with a depressurized groove is capable of translating in a cylinder and includes a fixed skirt, an axial compression face which forms with the cylinder a fluid chamber, and an axial working face which cooperates with a transmission; the piston also includes a seal, a depressurized radial groove emerging onto the surface of the fixed skirt, an axial decompression duct fitted inside the skirt which emerges in the vicinity of the axial working face, and a radial decompression duct which depressurizes the radial groove in communication with the axial decompression conduit.

A piston and cylinder assembly structured to reduce breakaway friction (stiction) upon movement of the piston within the cylinder. The assembly includes a cylinder housing, a piston having a piston crown with a top face and one or more peripheral grooves, and a sealing ring positioned on the piston in each of the one or more peripheral grooves. The piston crown incorporates one or more passageways extending from a space above the piston to a location within the peripheral groove inside of (behind) the sealing ring. An increase in a volume of fluid in the chamber above the piston directs fluid through the passageways into the peripheral groove, thereby pressing the sealing ring against the cylinder wall. A double acting piston embodiment uses at least two sealing rings positioned within at least two grooves, each with associated fluid flow passageways into the grooves behind the sealing rings.

A fluid actuator includes housing defining a cylinder bore and first and second fluid passages. A circumferential detent groove extends into the housing from the cylinder bore. The cylinder bore receives a piston having a top face and a skirt in sliding engagement. A circumferential detent ring groove extends radially inwardly into the skirt. The detent ring groove has a first portion of a first depth and a second portion of a second, greater depth. An o-ring is at least partially received in the second portion. A wear ring is at least partially received in the first portion and overlies the o-ring. The o-ring biases the wear ring outwardly of the detent ring so that the wear ring may be selectively engaged with the detent groove.

An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted therein. The piston may be configured to move in a first stroke that includes an expansion stroke portion and a non-expansion stroke portion. The engine may further include first and second piston rod portions extending from opposite faces of the piston. A recess in the piston rod portions may be configured to communicate gases between a combustion chamber and locations outside the cylinder. There may also be a chamber surrounding the first or second piston rod portion, the chamber configured to be supplied with gas and the chamber being isolated from the first combustion chamber and the second combustion chamber.

A vacuum valve placed between a vacuum vessel and a vacuum pump to adjust a valve opening degree using an operating fluid includes a packing mounted in a recessed groove of a piston. The packing is provided with a contact portion on a radially inner side and a contact portion on a radially outer side, and a slide-contact portion contacting with an inner peripheral surface of a cylinder. A portion between the contact portion and the slide-contact portion has a thin thickness.