Abstract: A rodless power cylinder includes a tube having an oblong circular cross section bore and a slit extending along the longitudinal axis of the bore and penetrating the wall of the tube. The bore includes a slit-side inner surface on which the slit opens and a counter-slit-side inner surface which opposes the slit-side inner surface. The slit-side inner surface of the bore is formed as a flat plane or a curved plane having substantially no curvature. Further, recesses are formed on the slit side inner surface at both sides of the slit. The surfaces of the recesses are formed as curved planes having a curvature larger than the curvature of the slit-side inner surface. An inner seal band made of a flat, thin metal band is provided to seal the opening of the slit. The seal band contacts the surface of the recess at its transverse edges. Therefore, a good sealing capability is achieved by the contacts between the surfaces of the recesses and the edges of the seal band.

Abstract: A slide drive device has a principal housing, in which at least one actuating element able to be driven linearly is arranged. Externally on the principal housing there is a slide kinetically coupled with the actuating element. Two stroke limiting means render possible a variable preset of the two end positions of the slide and each comprise an adjustable arranged on the one part and a counter-abutment arranged opposite to same on the other part. The one adjustable abutment is arranged on the slide and the other adjustable abutment is located on the principal housing. Both abutments are provided in end regions facing in the same axial direction, on the slide and, respectively, on the principal housing.

Abstract: A stop cylinder and piston assembly has both a firing piston and a piston ed for both firing and return located on the same piston rod. The stop cylinder and piston assembly is designed with gas passages so that gas injected for firing purposes through a single aperture in the sidewall of a cylinder is applied to the rear surface of both the firing piston and the piston used for both firing and return. The system is reset by injecting return gas through a second sidewall aperture that is applied to the forward surface of the return piston. A vessel bumper is installed in the forward end of a chamber containing the firing piston to provide cushioning for the firing piston upon being fired.

Abstract: A fluid pressure cylinder includes a cylinder body, a piston accommodated in the cylinder body to define first and second pressure chambers therein, means for supplying fluid to each chamber to reciprocate the piston between a first stroke end and a second stroke end, first and second bumper surfaces, an annular cushion retainer connected to the first bumper surface, and an elastomeric cushion for deforming and cushioning an impact produced when the piston reaches the first stroke end. The bumper surfaces approach each other when the piston reaches the first stroke end and separate from one another when the piston moves toward the second stroke end. The cushion has a shape corresponding generally to a hollow conical section. The cushion includes a base section retained by the cushion retainer and a buffer section joined to the base section. The buffer section has an outer surface for contacting the second bumper surface and an inner surface that faces the first bumper surface.

Abstract: A cylinder apparatus includes a base plate, a piston fixed to the base plate and having a piston head and a piston rod connected thereto, a cylinder body having a cylinder chamber defined on one side of the piston head and a cylinder chamber defined on another side of the piston head around the piston rod, the cylinder body being supported for reciprocating movement with respect to the base plate in axial directions of the piston, an upper plate fixed to the cylinder body, and a bushing held in slidable contact with an outer circumferential wall surface of the cylinder body for guiding the reciprocating movement of the cylinder body.

Abstract: In a power tilt cylinder device 100, a hydraulic fluid is supplied to the opposite piston side space 22B of a free piston 25, in the upper limit position of upward tilting, which is performed for discharging the hydraulic fluid from the first chamber 21, an operation valve 62 is pushed open by a rod guide 18A, and a flow passage 64 directed from the opposite piston side space 22B of the free piston 25 toward the first chamber 21 is caused to be conductive via a check valve 61 and the operation valve 62.

Abstract: A percussion tool comprises a cylinder 3 communicated to a pressure accumulating chamber 16 storing pressurized air therein, and a piston 4 slidable in the cylinder 3 when pressurized air is introduced into the cylinder 3 from the pressure accumulating chamber 16 and pressure of the introduced air is applied on the piston 4. A circular groove 6 is recessed on a peripheral surface of the piston 4, the peripheral surface adjacently facing to an inside wall of the cylinder 3. A piston ring 10 is accommodated in the circular groove 6, so as to provide a hermetical sealing between the piston 4 and the cylinder 3. And, a ring bumper 11 made of resilient member is provided in the circular groove 6 adjacent to the piston ring 10 in a sliding direction of the piston 4.

Abstract: A heavy-load hydraulic or air cylinder comprises a main body provided therein with an action rod having an driven end. The driven end is exerted on by the liquid or air pressure to actuate the action rod. The driven end is provided respectively on both sides thereof with a pressure bearing piece. The driven end and the pressure bearing piece are provided therebetween with a leakproof ring. The main body is further provided at the exit end thereof with at least one pressure bearing piece. The pressure bearing piece and an exit cap are provided therebetween with a leakproof ring. When the action rod is at work to bring about the pressure, the pressure bearing piece is acted on by the pressure, which is the transferred to act on the leakproof ring, which in turn generates the reaction force to act against the inner wall surface of the main body so as to enable the cylinder to withstand a heavy burden or weight.

Abstract: A cylinder apparatus includes a base plate, a piston fixed to the base plate and having a piston head and a piston rod connected thereto, a cylinder body having a cylinder chamber defined on one side of the piston head and a cylinder chamber defined on another side of the piston head around the piston rod, the cylinder body being supported for reciprocating movement with respect to the base plate in axial directions of the piston, an upper plate fixed to the cylinder body, and a bushing held in slidable contact with an outer circumferential wall surface of the cylinder body for guiding the reciprocating movement of the cylinder body.

Abstract: A reciprocal type of pump structure wherein a piston has a linear function actuated by a pair of coils energized alternately and includes a plurality of tapered flutes. A check valve in an outlet of the structure which stretches to open said outlet under the impact of expelled fluids and of its own volition retracts to the closed position immediately upon the cessation of fluids being expelled.

Abstract: In a pyrotechnic linear piston and cylinder drive in a belt pretensioner, the cylinder (10) has a frustoconical free end (12) and the piston (14) is attached to the end of a cable (16). The piston (14) is tapered frustoconically at its end adjacent to the free end (12) of the cylinder (10). An annular piston member (22) is slipped over and frictionally engaged with the tapered end portion (20) of the piston (14). When the annular piston member (22) reaches the frustoconical free end (12) of the cylinder (10), the piston (14) is forced further into the annular piston member, deforming both parts and dissipating energy.

Abstract: A weight piston according to the present invention, which is slidable along the axis of drive of a drive piston, is moved in the direction opposite to the direction of movement of the drive piston, to cancel the reaction force which is produced by the movement of the latter, thereby to prevent application of the upward reaction force to the housing of the tool. More specifically, the diameter of the weight piston is made larger than that of the drive piston, so that a part of the reaction force produced by the weight piston acts on the housing in the direction of movement of the drive piston.

Abstract: An improved water pressurizer comprises a pair of piston and plunger type intensifiers each driven by pressurized oil on one side of the piston and returned to the starting position by air pressure on the opposite side of the piston. Magnetic sensing switches detect proximity of the piston as it nears the end of a power or return stroke and send enabling signals to electropneumatic relays controlling air actuated ball valves on input and output oil lines. Because of the displacement volume and piston to plunger ratio, the intensifiers reciprocate at unusually low frequencies, reducing down time for maintenance or repair and thereby increasing reliability and capacity factor. Installed on a trailer for transportation, the apparatus can be attached to any available water supply for providing pressurized working fluid to a remote site.

Abstract: A short travel pneumatic cylinder device for transmitting a high force, comprising a cylinder housing having a cylindrical bore for guiding of the piston and of the piston rod, two pistons which upon generation of an overatmospheric pressure between the pistons will move in opposite direction, and further comprising a mechanical lever system with a housing cover. The first of the pistons is connected with the piston rod, and the second of the two pistons is arranged coaxially relative to the first piston, is hollow, and is movable coaxially relative to the piston rod. The first of the two pistons is connected to the lever system at the side of the interior of the cylinder opposite to the second of the two pistons. The pressure force exerted by the second piston is transmitted to the piston rod via the lever system in a direction opposite to the direction of movement of the second piston.

Abstract: An impact damping element is provided including an annular bumper portion and a seal portion surrounding the bumper portion for engaging an inner wall of a cylinder in sealing contact. The impact damping element is adapted to absorb the impact between a piston and the end of a cylinder wall. In one embodiment of the invention, a primary and a secondary bumper are provided wherein the primary bumper has a greater height than the secondary bumper such that the primary bumper absorbs an initial impact between the piston and the cylinder wall and the secondary bumper absorbs the remaining force to prevent direct contact between the piston and the cylinder wall.

Abstract: The invention relates to an arrangement for an axial bearing in a drilling machine. The drilling machine includes a frame (6), a percussion device (1) fitted in the frame, and a shank (2) positioned on an axial extension of the percussion device. The frame (6) further includes an axial bearing formed by a number of pistons (4a, 4b) to receive axial forces acting on the frame (6) through the shank (2). The length of travel of some pistons (4b) towards the forward portion of the drilling machine is limited so that when they are in their forward position and the shank (2) is supported by the pistons (4a, 4b), the shank (2) is substantially at its optimal percussion point.

Abstract: A linear movable apparatus for imparting rotational movement to a turntable is provided. The turntable is secured to a rotatably mounted shaft having a ring gear thereon for meshed engagement with gear teeth provided on a piston rod which extends between a pair of pistons. Each piston is reciprocally carried in aligned cylinder housings mounted in a support structure. An adjustable mechanism is provided for retaining the piston rod in snug-fitting relation with the ring gear, and a bracket assembly is secured around the ring gear to support the adjustable mechanism against the ring gear.

Abstract: A pneumatic rotary drive includes a housing which is connectable to a pressure medium source and is closed in a pressure medium-tight manner by plane covers. A rotatable shaft extends out of the housing through at least one of the covers. A belt which is in engagement with the shaft is arranged within the housing so as to form moveable pressure chambers. At least one guide body arranged within the housing is surrounded by the belt. At least one of the guide bodies is provided with a spring element for resiliently adjusting the effective circumference of the at least one guide body.

Abstract: An engine (40) comprising a piston (2); a top ring (3) and a second ring (4) attached to the piston (2); partitioning members (9)(10) attached to the piston (2) and connecting the top ring (3) and the second ring (4) so as to form a gas chamber (8) at the side surface of the piston (2); a gas passage (15) for communicating the gas chamber (8) to an upper surface (7) of the piston.

Abstract: An impact dampening ring is disclosed having a primary bumper and a secondary bumper for dampening the engagement of a piston against an end of a power cylinder. The primary bumper has a curved or arcuate surface for initial engagement with the end of the cylinder and the secondary bumper has a flat surface for secondary engagement with the end of the cylinder. The engagement of the primary and secondary bumpers dampens the impact and prevents the piston from directly engaging the end of the power cylinder. A mounting flange on the impact dampening rings provides a means for mounting the impact dampening ring onto a mounting surface of the piston. A seal along the outer perimeter of the impact dampening ring provides a fluid tight seal for the piston inside of the power cylinder.

Abstract: A damping mechanism for decelerating the movement of a piston of a cylinder/piston mechanism includes at least one elastically deformable damping element, which in the installed state is disposed undetachably between two holding regions which are spaced apart in the direction of the piston movement and wherein one holding region communicates with the cylinder and the other holding region communicates with the piston during deceleration.

Abstract: A cylinder without a piston rod comprising a cylinder, a piston for moving along the axial direction within the cylinder, and tension belt means for directing the piston witnin the cylinder. The piston comprises two piston halves which are interconnected by bayonet connection elements. A holding element is held within the piston halves for holding the ends of the tension belt means in place.

Abstract: The invention relates to an arrangement for the axial bearing of the drilling machine. The drilling machine thereby comprises a body (6), a percussion device (1) fitted in the body, and a rotation bushing (3) functioning as a rotating means of a shank (2) positioned on an axial extension of the percussion device. Furthermore, an axial bearing is fitted within the body (6) for receiving the axial forces exerted on the body (6) through the shank (2). In order to provide resilience, the axial bearing is arranged to be displaceable in the axial direction under the influence of a pressure medium acting thereon. To resiliently receive a percussion impulse reflected from the rock during the drilling process, the pressure and volume flow of the pressure medium of the axial bearing is adjustable so that the position (Y) of the axial bearing is between the extreme positions (0,.DELTA.X) of the axial bearing under the normal operating conditions of the drilling machine.

Abstract: A rodless cylinder assembly comprises a cylinder barrel provided with an axial bore in which a piston is slidably fitted and a slit formed in the outer surface thereof so as to be directed upwardly. A slide mount is operatively connected to the piston through connecting member integrally formed with the piston and projecting outwardly through the slit to be slidable along the upper surface of the cylinder barrel in an axial direction in accordance with the movement of the piston. The slide mount is slid along first guide rails disposed on the upper surface of the cylinder barrel at both sides of the slit and along second guide rail formed in opposite side walls of the cylinder barrel. Guide members are disposed between the second guide rails and side depending walls portions of the slide mount and the clearance between the second guide rails and the guide members can be adjusted by screw means.

Abstract: An electromagnetically reciprocating apparatus includes a piston assembly which is driven by an electromagnet repeating magnetization and demagnetization and a compression coil spring so as to reciprocate a front and rear pistons of the assembly in a front and rear cylinders. An air hole is formed in the rear cylinder to communicate a sealed inner space partitioned in the cylinder by the rear piston with an atmosphere. A valve is mounted on the air hole to adjust a resonance frequency of the vibration system of the apparatus.

Abstract: A pressure fluid actuator having an elongated tubular chamber, a slot extending longitudinally along the wall of the chamber, a flexible hose member within the chamber and an improved reciprocally movable bracket having an upper portion extended through said slot and connected to a workpiece, which is slidable along the exterior of said chamber, and a lower portion having a rotatably mounted shaft with a pair of rollers for engagement with said flexible hose member to create a reciprocal movement of the bracket.

Abstract: A low pressure metering pump having a hollow piston reciprocated in a cylindrical guide by a solenoid coil. A pair of check valves provide for unidirectional fluid flow through the cylindrical guide in response to the reciprocation of the piston. A seal attached to the piston prohibits a fluid backflow between the external surface of the piston and the internal surface of the cylindrical guide. A bumper seal at the output end of the piston prevents fluid flow through the cylindrical guide when the solenoid coil is de-energized. A control circuit periodically energizes the solenoid coil at a frequency determined by a variable resistance responsive to predetermined operational parameters. In a preferred embodiment, the metering pump is a fuel control element for a heater and the variable resistance is a thermistor or similar type of temperature sensitive resistance, which controls the rate at which fuel is delivered to the heater.

Abstract: A differential hydraulic jack with a damping system for the control of electric circuit-breakers is provided with a floating ring which produces a damping action at the end of travel and is also provided with a damping extension stud which forms part of the jack piston and penetrates into the damping ring. No provision is made on the jack piston for any packing ring forming a seal with the jack cylinder. The damping ring carries two projecting lips constituting a double valve which forms a leak-tight seal with the bottom face of the jack piston and the internal face of the cylinder end. At the end of the travel of the piston, the damping ring forms a double sealing valve for shutting-off the supply/drain orifice of the jack.

Abstract: A fluid power apparatus particularly useful for an industrial robot which includes a pair of expansible chamber devices each having a pair of control chambers in fluid communication with each other to intensify the working fluid output pressure and a working chamber that expands to receive a charge of working fluid and contracts to expel working fluid therefrom. A working fluid circuit includes a first line connected with one of the working chambers and a second line connected with the other of the working chambers. A fluid actuator is connected with the circuit and has a moveable element that moves in response to flow of working fluid in the circuit to the actuator. The apparatus has a static condition in which the one working chamber is contracted with the moveable element of the actuator stationary in a first position.

Abstract: A diaphragm type pump device has an elastic material imparting elasticity by the change of its volume which is placed in an operation chamber to decrease residual volume in the operation chamber when a diaphragm reaches the upper dead point.

Abstract: A refrigerating machine having a displacer reciprocable in a hollow space having a substantially-closed end for the refrigerating operation has a spring between the displacer and the substantially-closed end of the hollow space for damping vibration and noise of the displacer reciprocation.

Abstract: A sensing cell for sensing pressures which includes a housing and a diaphragm that deflects relative to a housing surface under pressure differentials, the movement of the diaphragm is sensed to provide indications of pressure changes. The diaphragm has a center disc like deflecting portion, an outer peripheral support ring that is clamped for supporting the diaphragm in a housing, and an integral, reduced section web joining the center portion and the support ring. The reduced cross section web causes the diaphragm to act as a free edge diaphragm during deflection. The housing and/or the diaphragm are configured so that at near a rated overpressure stop means support the central disc portion at its annular edge where the web joins the central disc portion to reduce the maximum stress on the web and thus prevent over stressing of the web portion of the diaphragm under maximum overpressures, to reduce hysteresis and innaccuracies.

Abstract: The present invention relates to a sound-dampened driving apparatus for fasteners wherein a main valve means is arranged above a working cylinder of the apparatus and movable within a cylindrical bore. When the main valve means is in its lower at rest position, the main valve means separates the working cylinder from a source of compressed air and connects the cylinder to the atmosphere. When the main valve means is in its upper actuating position, the working cylinder is connected to the source of compressed air and the valve means blocks the cylinder connection to the atmosphere. The space above the main valve member within the cylindrical bore is capable of being alternately connected to either the atmosphere or compressed air, and includes a sound dampening means arranged in the space above the main valve member.

Abstract: A gear positioning cylinder having forward, reverse, and neutral gear selection provided by a positioning rod attached to a main piston in which an auxiliary piston is telescopically arranged for compactness.

Abstract: A driving device having a piston pyrotechnically driven in a cylinder, the piston being connected by pulling means to an element to be driven, the cylinder having a stroke limit stop at a rear end thereof, as viewed in driving direction of the piston in the cylinder, includes damping means disposed between the piston and the stroke limit stop of the cylinder, the damping means braking the piston in a predetermined manner upon failure of the pulling means.

Abstract: A combination cable crimper and cutter. A frame mounts a piston for reciprocating axial movement. A reciprocating drive is connected to the piston. A pair of cable-crimping jaws is pivotally mounted on the frame and connected by links to the piston. A cutter anvil is mounted on the frame adjacent one of the jaws. A cutter is mounted on the jaw in cable-cutting relation to the cutter anvil.

Abstract: A hydraulic piston cylinder device comprising a cylinder, a piston dividing the cylinder into two cylinder spaces (A and B), and valve members between the cylinder spaces and respective pressure medium pipes. The problem is to achieve a hydraulic piston cylinder device in which the pressure or tractive force of the cylinder is maintained even if the external pressure led into the cylinder would stop. To solve this problem, an elastic material is interposed between two piston parts, and is elastically compressible by the external pressure applied to the cylinder; and the valve members are coupled to each other so that when one of the valve members is closed the other cannot be closed.

Abstract: This relates to a pneumatic feed system for moving a labeler head of a labeling apparatus for depositing labels in mold halves of a blow molding apparatus. The relatively heavy labeler head must be rapidly accelerated and then rapidly decelerated and at the same time moved sufficiently so as to provide for a large number of back and forth cycles per minute. There is provided in association with compressible shock absorbers a pneumatic system including a high pressure supply and a low pressure supply together with throttle valves such that the gas in the unpressurized end of the cylinder is rapidly compressed near the end of the stroke to function as a shock absorber and further, the cylinder is of a much larger diameter than that required for moving the labeler head so as to permit for the rapid acceleration as well as the rapid deceleration.

Abstract: A pneumatic hydraulic hand-held riveting tool having a pneumatic operative means arranged to generate pressure upon a hydraulic fluid whereby a rivet set plunger is brought into contact with a rivet to be set without deformation of the rivet, and being further arranged to generate hydraulic pressure on the rivet set plunger effective to set the rivet, as well as to provide rapid hydraulic pressure relief.

Abstract: A rodless cylinder having a piston and an operation member slidable along the outer circumferential surface of a cylinder tube, each mounted with permanent magnets, and adapted to move the operation member along the cylinder tube by utilizing the attraction force between these permanent magnets, in which a plurality of individual magnets disposed axially to the cylinder in each of driving and driven magnet rows are arranged such that identical poles of the individual magnets are in adjacent to each other, and both of the driving and driven magnet rows are arranged such that the different poles of the individual magnets in each of the magnet rows are opposed to each other can provide a greater attraction force between the magnet rows with no changes in the size of the magnet and thereby reduce the size of the entire apparatus.

Abstract: A door closer includes a spring-loaded piston forming part of a conventional pneumatic dashpot, which retards the speed of a door during closing, and an elastomeric sleeve which is longitudinally compressed during opening of the door to retard the speed of the door during opening and to apply substantial resistance to further opening movement as the door approaches its fully open position. Closing speed of the door is also initially retarded by the compressed sleeve.

Abstract: Door speed is controlled by a pneumatic dashpot including a spring-loaded piston having a piston rod which extends through an elastomeric silicone rubber braking sleeve which is longitudinally compressed as the door opens to increase the friction between the piston rod and the sleeve. One or more enlargements on the piston rod provide increased friction as the rod moves through the braking sleeve to control closing speed and to provide greater wind resistance.

Abstract: A manually operable quick-release mechanism for use with a spring-loaded brake cylinder including an energy-storing piston operable by fluid pressure to a brake release position with a ball type clutch for locking said piston and a piston rod in said brake release position, and a manually rotatable member effective, when angularly displaced, for releasing the ball clutch and the piston and allowing the piston and piston rod to move to a brake-applying position.

Abstract: An impact damping or cushioning means is provided to overcome the noise occasioned when a reciprocating slide block member, to which steering rods are secured, is limited in motion by engaging the ends of a housing slot in which the member slides. Such slide block is secured to a drive rod in the housing, which may be a pinion driven rack or operated by a pressure piston, and protrudes through the slot for connection to steering rods. The construction effects a damped or cushioned initial impact engagement of increasing resilient resistance up to the point of metallic non-yielding engagement of either end of the slide block with the respective end of the slot. Thus, the cushioning means at each end of the travel is of deforming, compressible rubber-like plastic material compressed in comfinement during initial impact in a recess which may be in the slide block or in the housing slot edge.

Abstract: The present buffer system for a fastener driving device includes two cooperating buffer elements (16, 22) located at the bottom (17) of the driving cylinder (2). A first buffer element (16) of hard elastic material rests on the inwardly facing surface of the cylinder bottom (17) in such a manner that at least a portion of the surface (18) of the first buffer element (16) contacting the bottom (17) is movable relative to the bottom (17) of the driving cylinder (2). A second buffer element (22) made of an elastic material softer than the hard elastic material of the first buffer element, rests on the first buffer element.

Abstract: The drive cylinder comprises: an elongated rigid element having an internal chamber in which is located a rod guide dividing the chamber into two compartments; the rod, adapted to move longitudinally within the chamber, carries at one end a piston accommodated in one compartment and, at the other end, a head accommodated in the other compartment; a longitudinal aperture is arranged in the body of the cylinder, allowing a drive finger, secured to the head of the rod, to extend to the outside of the rigid element and to impart, to a slide carried by the cylinder, a longitudinal movement parallel with the axis of the cylinder.

Abstract: A pneumatic servo booster includes a shell housing consisting of front and rear shells, a valve body slidably extending through the rear shell, a flexible diaphragm cooperating with the valve body for partitioning the interior of the shell housing into front and rear chambers, a plunger connected to an input rod and being slidably fitted in the valve body, a valve mechanism including a poppet valve and two valve seats which are formed respectively on the valve body and the plunger, and at least one rigid rod secured respectively to the front and rear shells and extending through the front and rear chambers. The valve mechanism communicates the two chambers when the poppet valve is spaced from the valve seat of the valve body and is seated on the valve seat of the plunger. A return movement restricting member is slidably mounted on the rigid rod and engages with the plunger, and resiliently restricts the return movement of the plunger at the end of the return stroke of the input rod.

Abstract: An internal combustion engine or pumping device is disclosed including a block forming a plurality of cylinders, each divided into a combustion chamber and a pumping chamber by a reciprocable piston, energy developed by internal combustion within the combustion chamber being transferred directly through the piston for pressurizing transmission drive fluid in the pumping chamber which is then communicated through a high pressure conduit for performing useful work and returned to the engine through a low pressure conduit. The engine or pump preferably includes pairs of such pistons which are mechanically interconnected for operation in opposition to each other. Couplings and controls synchronize operation of the pistons and regulate fuel and air supply to the combustion chambers. The engine is also equipped with a number of systems for preventing piston overtravel, particularly a self-actuating brake which is also novel apart from the present engine or pumping device.

Abstract: This invention relates to a rolling diaphragm apparatus in which an annular diaphragm is secured by its outer and inner peripheries respectively to a housing and a piston between which the diaphragm seals against fluid leakage. One of said peripheries is formed as a bead which locates in an annular seat on the part to which said one periphery is attached, the bead being retained on its seat by a resilient retaining ring that snaps into position on the seat part. The bead has a substantially radially directed face and a substantially axially directed face, both of said faces engaging with corresponding faces on the retaining ring which snaps into positive engagement with the seat part.Such a construction is particularly useful in vacuum boosters for motor vehicle braking systems.

Abstract: In a cylinder with a two-stage movement, a first piston moves in a housing, and in the first piston a second piston moves, which has a piston rod sliding in an end of the housing. On its side facing away from the piston rod, the second piston is provided with a guide member which is guided in the first piston. The first piston can be held in a position in which the piston rod is extended far out of the housing. With the aid of the second piston, the piston rod can perform a certain axial movement relative to the first piston, at the same time as guiding is effected with the aid of the guide member and the first piston.