Abstract: Disclosed is an electronic parking brake system, which is configured to push first and second brake shoes respectively disposed on inner opposite sides of a drum to an inner surface of the drum for braking, including an actuator including a motor configured to rotate forward and reverse to generate a driving force for braking, and a reduction gear unit configured to amplify the driving force transmitted from the motor, and a power converter configured to convert a rotational motion from the actuator into a linear motion to press or release the first and second brake shoes.

Abstract: Reciprocally moving an output rod mounted to a force transfer member includes applying hydraulic pressure to a first piston and cylinder device to operate the first piston and cylinder device in compression to move the force transfer member in a first direction; applying hydraulic pressure to a second piston and cylinder device to operate the second piston and cylinder device in compression to move the force transfer member in an opposite second direction; refraining from applying tension to the second piston and cylinder device while applying hydraulic pressure to the first piston and cylinder device; and refraining from applying tension to the first piston and cylinder device while applying hydraulic pressure to the second piston and cylinder device.

Abstract: The invention is an accumulator system in which multiple elastomeric accumulators are attached in series or parallel in order to generate total differential pressure in excess of that generated in a non-series system. Also disclosed is a “stacked” accumulator system. The system stores energy when the accumulators deform from their original shape in response to the flow of a pressurized fluid. The stored energy is available for use when the fluid is released from the accumulators and the accumulators return to their original shape.

Abstract: A pressure wave generator (40) for driving one or more cryogenic refrigerator systems. The pressure wave generator (40) comprises a housing with one or more inlet/outlet ports (57,58) through which generated pressure waves of gas may pass through to drive a cryogenic refrigerator system or systems connected to the inlet/outlet ports (57,58). The pressure waves are generated by at least one pair of opposed diaphragms (41,42) located in the housing that are moveable in a reciprocating motion within the housing to create pressure waves in gas spaces (55,56) associated with each diaphragm (41,42). The gas spaces (55,56) each having associated inlet/outlet ports (57,58) through which the pressure waves may pass. An operable drive system is also provided to move the pair of diaphragms (41,42) in a reciprocating motion.

Abstract: A co-axial crankless engine (1) having at least one cylinder (3) defining a longitudinally extending axis (XX). A pair of pistons (5, 6) are positioned to reciprocate in opposite directions along the longitudinal axis of the cylinder. A space (7) between the pistons defines a common combustion chamber (70). A first shaft (10) is positioned substantially parallel to and spaced laterally from the longitudinal axis of the cylinder. A second shaft (12) is positioned substantially parallel to and spaced laterally from the longitudinal axis of the cylinder. The second shaft (12) has a longitudinally extending bore (14) through which the first shaft can extend and rotate. Each piston is connected to an axially spaced cam (16, 17). A first cam being supported by the first shaft, a second cam being supported by the second shaft. In use, reciprocation of the pistons imparts on respective shafts rotating motion in opposite directions to drive the engine.

Abstract: A pump cartridge which has a polymer shell with moveable cores inserted from each end. The polymer shell contains perpendicular passages along the top for connection of fluid supply and prime chambers. Statically mounted elastomers adjacent to perpendicular passages provide sealing around movable cores. Fluid moves by translation within the pump cartridge by filling the cavity volume between the oblate ends of the moveable cores with a liquid and matching the rotation angle and translation position of advancing left moveable core with retreating right moveable core, maintaining equivalent volume. Both moveable cores can be directed toward one another or one moveable core can remain stationary while the other advances to extrude fluid. Pump cartridge rotation changes the angle of the fluid exit passage.

Abstract: A system for moving fluids includes a pump device having a housing and at least one piston movable in the housing to displace fluids thereby causing flow. An actuator device is connected to the at least one piston for moving the piston within the housing to displace fluids as the actuator device is moved. The actuator device includes a plurality of side portions connected to one another to form a vacuum therein and movable relative to one another as the actuator device moves reciprocally between first and second positions with one of the side portions being connected to at least one piston thereby moving the at least one piston within the housing.

Abstract: A hydraulic piston machine includes a plurality of pistons (12, 14) which are driven by a drive/output shaft (40), guided in an axially displaceable manner in a piston barrel (4) of a housing (2), and, in each case, bound one working chamber (44) into which the pressure medium may be fed via a suction valve (46), and from which the pressure medium may be discharged via a pressure valve (48). The housing (2) includes at least one further housing part (6) which is connected to the piston barrel (4) on the front side. The suction valves (46) and pressure valves (48) are situated in the region of a parting plane (50) between the housing parts (4, 6), in housing receptacles (52, 54), approximately axially parallel to the longitudinal axis of the piston machine.

Abstract: A pressure wave generator (40) for driving one or more cryogenic refrigerator systems. The pressure wave generator (40) comprises a housing with one or more inlet/outlet ports (57,58) through which generated pressure waves of gas may pass through to drive a cryogenic refrigerator system or systems connected to the inlet/outlet ports (57,58). The pressure waves are generated by at least on pair of opposed diaphragms (41,42) located in the housing that are moveable in a reciprocating motion within the housing to create pressure waves in gas spaces (55,56) associated with each diaphragm (41,42). The gas spaces (55,56) each having associated inlet/outlet ports (57,58) through which the pressure waves may pass. An operable drive system is also provided to move the pair of diaphragms (41,42) in a reciprocating motion.

Abstract: A system for measuring one or more physical properties of cementitious material is operable to cure a slurry of cementitious material under desired conditions of temperature and pressure. Particularly, the system may be operable to cure the slurry under a temperature and pressure expected to be experienced downhole. The system may also be used to determine properties of the cured cementitious material, such as maximum yield strength and shear bond strength at the desired temperature and pressure. The desired conditions of temperature and pressure may be applied both during curing and testing of the cementitious material.

Abstract: A double-acting deformable fluid actuator with three chambers consists of three axisymmetrical coaxial membranes (10, 11 and 12), constrained by two end pieces (13 and 14) so as to identify three chambers, namely, an inner chamber (15), an intermediate chamber (16), and an outer chamber (17); each chamber is supplied with fluid under pressure through respective connectors (18, 19 and 20) set on one of the end pieces.

Abstract: A variable camshaft timing phaser for an internal combustion engine having at least one camshaft comprising a plurality of vanes in chambers defined by a housing and a spool valve. The vanes define an advance and retard chamber. At least one of the vanes is cam torque actuated (CTA) and at least one of the other vanes is oil pressure actuated (OPA). The spool valve is coupled to the advance and retard chamber defined by the CTA vane and the advance chamber defined by the OPA vane. When the phaser is in the advance position, fluid is routed from the retard chamber defined by the OPA vane to the retard chamber defined the CTA vane. When the phaser is in the retard position fluid is routed from the retard chamber defined by the CTA vane to the advance chamber defined by the CTA vane.

Abstract: A wheel cylinder for engaging a brake shoe according to which at least one piston is disposed in the bore of a body member and is adapted to move outwardly in response to a predetermined fluid pressure in the bore into engagement with a brake shoe.

Abstract: A hydraulically actuated artificial muscle for use with orthetic devices, prosthetic devices or as an actuator for other applications in medical or robotic devices. Working fluid is pumped between two expandable fluid-containing cells, which are complimentary active elements of the artificial muscle. This eliminates the need for a storage reservoir, thereby providing a self-contained, force efficient device. Each of the preferred embodiments described has one or more expandable fluid-containing cell defined by at least one flexible wall. The flexible walls are configured so as to have elastic properties that are limited to predefined directions of expansion and contraction.

Abstract: A mechanical pneumatic piston is comprised of an upper cylindrical section and a lower cylindrical section, wherein each section has four linearly elongated, miter-cut staves, an end sleeve, and a slide-guide ring. The mechanical pneumatic piston is further defined as having an internal upper, central, and lower cavity adjacently aligned and extending axially within the piston.

Abstract: A three-position stop type swing actuator has a main piston freely moving in forward and backward directions in an axial direction within a casing, an output shaft placed at a coaxial position with the main piston in such a manner as to be fixed in an axial direction and freely rotate around an axis, a conversion and transmission mechanism converting a forward and backward motion of the main piston into a rotating and swinging motion of the output shaft, and a sub piston having a stroke smaller than that of the main piston a fluid pressure operating force larger than that of the main piston and arranged within the casing in such a manner as to freely move in the forward and backward directions and be capable of being brought into contact with the main piston so as to restrict a middle stop position of the main piston.

Abstract: An intelligent multi-functional hydraulic expanding apparatus includes a hydraulic expanding head, an automatic control hydraulic center, and a depth measuring system. The expanding head includes a hydraulic positioning device, an automatic hydraulic revolving device, a bi-directional cylinder uni-directional pulling type cylinder, and expanding arms that are rigidly connected. As the expanding apparatus adopts steel rope connection, the automatic reviving device performs transfer of torque, multi-arm expanding arms are installed in the same circular cross-section with displacement sensors, computer, and depth measuring system, the present invention provides a solution to the drag problem, increasing efficiency of construction of concrete piles for various foundations of buildings, bridges and obtain pressure angles and depth values so as to improve quality of the construction project.

Abstract: A hydraulically-operated micromanipulator apparatus is disclosed.

Abstract: A side strut (5) for a lower steering arm (1) of a tractor has a single action hydraulic cylinder (9) whose piston (12) includes first attaching means (6) to be connected to the rear of the tractor. The strut (5) also has a telescopic unit (10) and a setting unit (11). The hydraulic cylinder (9), the telescopic unit (10) and the setting unit (11) are arranged, one behind the other on a longitudinal axis (20). The setting unit serves to achieve a categorical setting and the telescopic unit (10) serves to offset the change in the length of the side strut (5) when the lower steering arm is deflected sideways.

Abstract: A device for opening and closing a trunk lid comprises: a trunk lid opening/closing switch operated between an opening mode and a closing mode; a cylinder having one end rotatably fixed to a body panel; a piston dividing a space within the cylinder into a first chamber and a second chamber; a piston rod having one end rotatably fixed to the trunk lid; and a pneumatic section for selectively supplying compressed air into one of the first and second chambers and discharging air in the other one of the first and second chambers, out of the cylinder, according to an operation of the trunk lid opening/closing switch.

Abstract: A hydraulically-operated micromanipulator apparatus is disclosed.

Abstract: This electrohydraulic actuator comprises a pair of hydraulic rams (12, 13) and a rocker (14) integral in terms of rotation with an input shaft (7) of the barrel, the rams are arranged parallel with one another in such a way as to be able to control the rotation of the rocker to make it adopt predetermined angular positions corresponding to the gears (R, N, 1, 2, . . . ) selected and this actuator also comprises solenoid valves for controlling the rams. The rocker (14) extends transversely to the shaft (7) and its ends are designed to be able to interact with respective pistons (17, 18) of the rams (12, 13), each ram comprises three pistons (24, 25, 17; 26, 27, 18) which are coaxial and have different cross sections, arranged in chambers (28, 29) of corresponding cross sections formed in the body (11). This electrohydraulic actuator permits extremely quick and easy control of gear selection for a structure which is relatively simple and has a modest cost of manufacture.

Abstract: A hydraulic actuator including a single cylinder body which defined therein a pressure chamber in which a first piston with a piston rod and a second piston with a piston rod are independently movably inserted, a first working member secured to the first piston rod, a second working member secured to the second piston rod, and pressurized fluid inlet and outlet ports provided in the cylinder body to be connected to the pressure chamber.

Abstract: A power cylinder (10) has two pistons (12, 20) slidably mounted within separate cylinders (14, 22) to define inner and outer chambers (16, 18; 24, 26) within each cylinder. One or more rods (28) are coupled between the pistons. The outer chambers (18, 26) are coupled together to allow pressurized hydraulic or pneumatic fluid to flow therebetween. The inner chambers (16, 24) are coupled together to allow pressurized hydraulic or pneumatic fluid to flow therebetween. The fluid flow aforesaid may be achieved by using two hollow rods (128, 130) and allowing the fluid to flow through the rods between the respective chambers. A guard (44) may surround first and second cylinders (14, 22). Bearings (46, 48) may be fixed around the opposed inner ends of cylinders (14, 22) to allow slidable displacement of the cylinders relative to guard (44).

Abstract: A lock cylinder for a backhoe slide frame which provides for a positive lock of the slide frame in selected positions is described. The slide frame is supported on two generally horizontal rails that are vertically spaced, and the lock cylinders mount between the vertically spaced rails. The lock cylinders each have a piston that acts to hold the slide frame seated against the upper one of the rails. The piston also provides a wedging action on at least one rail to hold the slide frame from fore and aft movement relative to the rail.

Abstract: The hydraulic cylinder comprises a cylinder jacket (1), a piston-rod guide flange (2), and a cylinder bottom (3). Disposed within the cylinder are a primary piston (4) provided with a piston rod (6) and a secondary piston (11) connected to two plungers (7, 8). The plungers enter two bores (5, 6) in the primary piston. Two spring-biased (19, 20), openable check valves (17, 18) are disposed in the cylinder bottom. In each valve there is a bore (41, 42) connecting the front and rear sides of the valve. The rear portions (24, 25) of the valve chambers (26, 27) each contain a spherical unstopping piston (21, 22). Two supply ducts (23, 30) for the hydraulic fluid are connected to the valve chambers, these chambers in turn having supply ducts at various locations (36, 40, 45) of the interior of the cylinder. A very compact construction is possible for the hydraulic cylinder with pressure transmission.

Abstract: A piston assembly comprising a primary piston and a co-centric secondary piston. The pistons are received within a housing for reciprocating movement therein and relative to each other. The housing and the pistons are arranged for operating pressure to be applied to the secondary piston so as to drive both pistons within the housing. The secondary piston is provided with means enabling the operating pressure to be equalized across the secondary piston and at least one bypass passage extends through the secondary piston. The arrangement is such that upon completion of the stroke of the pistons pressure equalization occurs across the secondary piston which causes the pistons to separate. The bypass passage becomes fully operable subsequent to pressure equalization, whereby a fast return stroke is achieved.

Abstract: A three position actuator which is used to position the gear range control lever on a two speed transfer case. Three positions are required to achieve HIGH, LOW and NEUTRAL. Two individual air chambers may be selectively charged with compressed air to move two pistons along a common actuator rod to achieve linear translation of the control lever to selectively position the transfer case in HIGH, NEUTRAL or LOW range. The transfer case is shifted from LOW to NEUTRAL or HIGH to NEUTRAL by releasing the respective charge of compressed air thereby permitting a spring to shift the control lever to neutral. Thus, in the event of a failure of the system supplying the compressed air, the actuator will return the transfer case to NEUTRAL as required for towing.

Abstract: A direct drive type rotation dividing table includes a dividing table mounted on an output shaft of a rotor which is accommodated in a housing together with a stator. A clamp mechanism for maintaining the dividing table at a stopped position includes a cylinder slidably disposed in the housing in an axial direction and having a radially extending plane portion and a friction surface adapted to contact the output shaft, an elastic member having one end connected to the housing and urging the friction surface of the cylinder to move away from the output shaft, and a piston having an elastically deformable thin plane portion opposing the plane portion of the cylinder and having one side fixed to the housing and the other free end slidable on the inner surface of the slider. The piston has a friction surface which is adapted to contact a backside of the dividing table.

Abstract: Actuator (14) drives inlet vanes (22) selectively to three positions, using high (58) and low (56) pressure fuel as the driving medium. Each of the three position is externally adjustable (94, 92, 68). An overboard leak path (86) is provided at the most often sliding seal.

Abstract: A fluid actuator including a pair of hingedly interconnected members between which is located a fluid expansible element such as a bellows which may be expanded upon application of fluid pressure to cause pivotal movement of the hingedly interconnected members. The actuator may also include a further pair of hingedly interconnected members which are themselves hinged to the first pair of members and which define with the first pair of members a space for receipt of the fluid expansible element.

Abstract: The present invention is directed to a self-adjusting servo mechanism (10). That is, the servo pin (30) presented from the servo mechanism (10) will protract sufficiently to effect operative engagement of a friction band assembly (13) with a rotating member (18) in a planetary gear set--even though the required axial displacement of the servo pin (30) during such protraction may exceed the axial displacement available to the actuating piston (33). The servo mechanism (10) is incorporated in a housing (20). The housing (20) presents a socket cavity (24) within which an actuating piston (33) is received for axial displacement through a predetermined distance. The servo pin (30) is supported by the housing (20) for axial reciprocation, and a coupling means (35) is interposed between the servo pin (30) and the actuating piston (33) operatively to protract the servo pin (30) in response to displacement of the actuating piston (33).

Abstract: A pneumatic piston/cylinder unit comprises primary and secondary pistons operable in first and second cylinder zones respectively. Each of the primary and secondary pistons divide its respective cylinder zone into two chambers, one of the chambers of the first cylinder zone being connected to one of the chambers of the second cylinder zone via a passageway which includes at least one control for the flow of hydraulic fluid therethrough. A tertiary piston is provided in the one chamber of the first cylinder zone and divides that chamber into two parts, one of which is between the primary and tertiary pistons. In use the passageway, the one chamber of the second cylinder zone and the other part of the one chamber of the first cylinder zone are filled with hydraulic fluid. Application of pneumatic pressure to the other chamber of the first cylinder zone causes the primary piston to be displaced until it abuts the tertiary piston whereupon movement of the primary piston may be arrested or controlled.

Abstract: The invention concerns a cylinder-piston combination actuated by a pressure medium, comprising an outstretched cylinder space (1) and a two-part piston assembly (3, 8) movable in opposite directions in the longitudinal direction of the cylinder space (1). The piston rod (6) of the first part (3) of the piston assembly is of a tubular construction. The first part (3) is provided with a sealing between the piston (4) and the inner surface (2) of the cylinder space (1). The cylinder space (1) is provided with a connection (27) through which the pressure medium can be passed into the space (31) limited by the cylinder space (1) and the outer surface of the first part (3). The second part (8) is constructed to dimensions allowing it to fit inside the first part (3) and arranged to be movable relative to the latter. The combination includes an auxiliary piston (14) fitted around the piston rod (13) of the second part and sealed relative to the inner surface (2) of the cylinder space (1).

Abstract: An automatic indexing chuck comprises a dividing pivot separately and in succession, operated by a dividing shaft and a locking sleeve. The dividing shaft is slideably and sealingly accommodated in a cavity of the locking sleeve which has retention planes for the dividing pivot and is in turn sealingly accommodated in a mandrel body cavity defining two adjacent chambers; the dividing shaft and the locking sleeve defining independent pistons operated by a single hydraulic circuit with reversible inlet and outlet ports, the pistons moving in opposite directions to perform consecutively unlocking, rotation and locking of the dividing pivot.

Abstract: This invention relates to an internal combustion engine comprising a combustion chamber having at least two rigidly fixed inner wall surfaces and at least three movable inner wall surfaces reciprocally mounted and adapted to reciprocate from a first position lessening the internal volume of the combustion chamber to a second position expanding the internal volume of the combustion chamber. The reciprocal linear movements of the movable, inner wall surfaces are operatively coupled to a crankshaft means. A spark plug is secured in the combustion chamber and has the spark gap terminals thereof extending into the combustion chamber. A pair of inlet and exhaust valves disposed in the combustion chamber and opening inwardly thereinto complete the mamor components of the novel engine.

Abstract: A rotary/linear convertor which comprises a first member may be in the form of a piston (14, 15, 16, 17, 114, 115, 116, 117) and a guide which is preferably in the form of a cylinder (12, 112) the first member being arranged for linear movement within or along the guide and a second member (23, 24, 137) which is adapted for rotational movement. The convertor further includes connecting means operatively connecting the first and second members so that the respective linear or rotational movement of one member causes the respective linear or rotational movement of the other member.

Abstract: According to the invention, the device comprises a housing (1), two chambers (2, 3) interconnected through a pipeline (4) and disposed in the housing opposite to each other. Each chamber (2 or 3) has a piston made in the form of an elastic sleeve (10 and 11), whose one end is turned inside out and secured to the inner surface of the pipeline (4) at the point of its connection to the chamber (2 to 3). Each piston is kinematically connected to the working member (7) via a shaft (5 or 6) mounted in the chamber (2 to 3), one end of which is kinematically connected to the working member (7), and a drum (8 or 9) connected to the other end of the shaft (5 or 6) and provided with a reverser. Secured on the drums (8 and 9) are the other ends of the sleeves (10 and 11). The pressure space formed by the spaces of the chambers (2, 3) and the space of the pipeline (4) is communicated with a fluid medium supply system (14).

Abstract: A reaction mechanism (462) that is carried on a disc (80) of a wall (70) to provide a control mechanism (81) with an indication of the output force being supplied to a push rod (132) through the combined outputs of wall (70) and wall (18) which move in opposite directions.

Abstract: A free piston machine comprising a mounting, an inner movable mechanism comprising a central cross-member and guided in translation so as to be able to move with an alternating motion along the axis of the mounting and an outer movable mechanism comprising two outer cross-members connected by at least one tie-rod. The mounting includes a base (10) and a header (11) connected by at least one central one-piece structure. The inner movable mechanism comprises four inner drive pistons movable along drive cylinders (15a-15b) arranged at the corners of a rectangle and two compressor pistons sliding in compressor cylinders (17a-17b) whose axles pass outside of said rectangle.

Abstract: A reaction mechanism for use in a vacuum brake booster (10). A lever (86) transfers a reaction force from a first plunger (64) into a second plunger (110) to provide an operator with an indication of the output force being produced in response to an input force. A resilient member (118) urges a first connecting member (116) into engagement with the lever (86). When a predetermined input force is applied, the reaction force overcomes the resilient member (118) and thereafter allows the input force to be directly transmitted through a second connecting member (122) and added to the output force.

Abstract: This invention relates to an internal combustion engine comprising: a combustion chamber having at least one rigidly fixed inner wall surface and at least two movable inner wall surfaces reciprocally mounted and adapted to reciprocate from a first position lessening the internal volume of the combustion chamber to a second position expanding the internal volume of the combustion chamber; the two movable, inner wall surfaces are adapted to remain in the first position lessening the internal volume of the combustion chamber of a crankshaft means operatively attached to each of the movable, inner wall surfaces; a spark plug secured in the combustion chamber and having the spark gap terminals thereof extending into the combustion chamber; and a pair of inlet and exhaust valves disposed in the combustion chamber and opening inwardly thereinto complete the major components of the novel engine.

Abstract: A fluid-pressure operated actuator comprises a housing, at least one piston reciprocable in the housing, a rotatable output shaft having a portion thereof within the housing, means operatively connecting the piston and the output shaft, and stop means mounted on the housing and engageable with the shaft portion for limiting rotary movement of the shaft.

Abstract: The thread winding machine comprises a rotatable chuck having a thread catching device adjacent to a location for a bobbin tube upon the chuck. A thread guide engages the thread and moves it axially of the chuck into the catching device at a first speed and then onto the bobbin tube location at a second, higher speed. An overwound thread reserve or transfer tail is formed by moving the thread guide against a resilient damper, causing it to stop and rebound.

Abstract: A brake effective between a rotating part and a non-rotating part has a substantially nondeformable brake disk secured to one of the parts, centered on an axis, and having a pair of axially oppositely directed brake-disk faces. A housing is secured to the other of the parts, at least partially surrounds the brake disk, and has a pair of end walls having wall faces axially confronting the respective disk faces. Respective brake elements are limitedly axially displaceable between the wall faces and the respective disk faces and engageable with the respective disk faces. Formations on the elements and housing prevent the elements from rotating relative to the housing. Spring packs between the brake elements and the respective wall face urge the elements with a substantially constant force axially together into braking engagement with the disk. Seals between the brake elements and housing define a pressurizable chamber between the brake elements.

Abstract: A brake system includes a brake booster coupled to a front wheel brake cylinder. The brake booster substantially defines a pair of rear wheel brake cylinders separate from the front wheel brake cylinder so that a pair of diaphragms are separated during braking to generate a power assist for the front and rear brake cylinders. A control valve cooperates with the brake booster to alter the power assist for the rear brake cylinders in response to a signal from an electronic control unit.

Abstract: A wheel cylinder assembly has telescoping brake actuating pistons with a brake pressure proportioner in the larger actuating piston to proportion brake actuating pressure.

Abstract: An oscillator is proposed which comprises a pair of cylinders having a common, circular-cylindrical outer wall (100) and two sealingly guided pistons (120, 122) each having one piston rod (121, 123), which are likewise guided in a sealing manner to the outside through the closure walls of the cylinder. The cylinder is divided by the pistons (120, 122) into outer chambers (124, 125) and inner chambers combined into one common chamber (126). The chamber (126) is filled with fluid. The outer chambers (124, 125) have two openings (102, 103) offset from one another by 180.degree.. A control cylinder (101) having axially offset, oppositely disposed holes (104, 105, 106, 107) connects the outer chambers in alternation with an annular high-pressure chamber (113, 115) and an equalization chamber (114) whenever the control cylinder (101) is rotated. The two pistons (120, 122) thereby execute movements in common toward the left or right, respectively.

Abstract: In a cylinder with two-step movement there is in a housing (7) a first piston (6) which slides in contact with the inside of the housing. A second piston (10), which supports a piston rod (11), which moves sealingly through a first end-piece (8) also slides against the inside of the housing. In the second end-piece (9) of the housing, there is a pressure medium tube (12) passing through the first piston (6) and which extends with its end distant from the second end-piece (9) into, and is guided against the inside of the tubular piston rod (11).

Abstract: A drum brake hydraulic wheel cylinder assembly comprises a pair of piston assemblies and an abutment member. The piston assemblies are of the kind comprising an adjustable variable length tappet assembly having interengaged screw-threaded components. To enable thrust to be transmitted from one adjacent brake shoe to the other, i.e. for parking purposes, the abutment member is slidable in the cylinder bore against a spring centering device.