Abstract: A detachable connecting rod includes a first member (410)a large end portion (411) having a trough hole (H1), and a first connection rod portion (412) extending from the large end portion (411), the first connection rod portion (412) having a pair of spaced apart arms defining a coupling groove (413) extending in the same direction as an axial direction of the through hole (H1); a second member (420) including a small end portion having a through hole (H2), and second connection rod portion (422) extending from the small end portion, the second connection rod (422) portion being inserted into the coupling groove (413) and a coupling unit for coupling the first connection rod portion (412) to the second connection rod portion inserted (412) into the coupling groove (413) of the first member (410). The detachable connecting rod is useable in a compressor.

Abstract: A method of installing annular seals on a plunger. A first step involves positioning an annular seal on a seal installation tool adapted to hold the annular seal in an expanded state. A second step involves positioning the annular seal so that the annular seal overlies a body of a plunger. A third step involves transferring the annular seal from the seal installation tool to a seal groove in the body of the plunger.

Abstract: A variable displacement fluid working machine includes an inward ring and an outward ring, one of the inward ring and the outward ring including a rotatable ring cam coupled to a drive shaft, the other including a plurality of radially extending piston cylinders circumferentially spaced around the respective ring. The outward ring has first and second axially spaced structural members and a plurality of demountable blocks demountably retainable therebetween, the demountable blocks having either piston cylinders or ring cam segments. The demountable blocks are removable radially to facilitate maintenance and repair and to facilitate radial access to the inward ring.

Abstract: The invention relates to a master brake cylinder arrangement of a motor vehicle brake system with a master brake cylinder housing, a transmission piston disposed in a displaceable manner in the master brake cylinder housing, and a force input member which can be workingly coupled to the transmission piston in order to introduce a braking force. According to the invention, in order to simplify assembly and to reduce the required construction space, an adapter is coupled to the master brake cylinder housing, to which adapter a contact sleeve is fitted, the force input member being supported at the contact sleeve in a non-actuated starting position.

Abstract: A fluid pressure apparatus for a bicycle comprises a piston, a housing with a chamber dimensioned to receive the piston therein so that the piston can move axially, and first and second fluid ports in fluid communication with the chamber. The first and second fluid ports are located so that the piston is disposed between the first and second fluid ports when the piston is disposed in a piston home position. A first positioning element moves from a first home position towards a first direction, and a first biasing element biases the first positioning element towards the first home position. A first coupling element couples the first positioning element to move with the piston in the first direction, but the first positioning element and the piston move relative to each other when the piston moves in an opposite second direction.

Abstract: The present invention relates to a linear actuator. A slide table of the linear actuator includes a table main body and an end plate connected to another end of the table main body. On a base portion of the table main body, four workpiece retaining holes are formed, and fitting seats are disposed respectively about the workpiece retaining holes on radial outer sides thereof. The fitting seats are formed at the same time that the table main body is formed by press molding.

Abstract: A plunger assembly including a pony rod adapter, a plunger releasably attached to the pony rod adapter, and a pony rod being releasably attached to the pony rod adapter. The pony rod adapter has a first cylindrical body and a number of apertures penetrating the first cylindrical body for receiving a lever. A first helically threaded pin is affixed to the first cylindrical body and projects from one of its ends. A second helically threaded pin is affixed to the first cylindrical body and projects from the other of its ends. The plunger has a second cylindrical body for reciprocating within a pumping chamber. The second cylindrical body has a first outer end with a first helically threaded bore for threadably receiving the first helically threaded pin. The second cylindrical body also has a first inner end with a polygonal socket for receiving a plunger key. The pony rod has a third cylindrical body for reciprocating into, and out of, the power end of a pump.

Abstract: There is disclosed a valve cap for sealing an aperture in a pump; a plugging assembly for use in a valve cap to provide a seal at an aperture in a pump; a docking unit for use with a plugging assembly for sealing an aperture in a pump; and a method of sealing an aperture in a pump.

Abstract: A cylinder tube includes a cylinder hole therein through which a piston is displaceably inserted. A head cover and a rod cover are installed respectively into ends of the cylinder hole. Locking rings, each having a bent section, a pair of arm sections that extend from both ends of the bent section, and claw sections disposed on ends of the arm sections, are disposed in the cylinder hole. In addition, the locking rings are installed respectively in the cylinder hole through ring grooves, wherein the head cover and the rod cover are fixed by means of the locking rings.

Abstract: A brake actuating device of a motor vehicle brake system includes a master cylinder and a brake booster with a booster housing, with an attaching element for attaching the brake actuating device to a wall on the vehicle projecting through an opening from the booster housing. To improve the assembly, a means for the provisional attachment of the brake actuating device to the wall on the vehicle is provided, which cooperates in operative and/or positive engagement with the vehicle wall or a component that is arranged at the vehicle wall in an attached fashion.

Abstract: There is disclosed a valve cap for sealing an aperture in a pump; a plugging assembly for use in a valve cap to provide a seal at an aperture in a pump; a docking unit for use with a plugging assembly for sealing an aperture in a pump; and a method of sealing an aperture in a pump.

Abstract: Apparatus and method for securing a cylinder liner to a pumping module. A first part of an assembly housing pistons is fastened to a pumping module and a second part of the assembly is brought against the first so that the pistons act on tensioning plates which each have a stud rod extending therefrom through the assembly at an end distal to the pumping module. Each rod has a first portion substantially surrounded in an elastomeric member and a second portion threaded to receive a nut. The rods are passed through a clamping ring on the cylinder liner and the nut is attached to the rod. Actuating the pistons causes initial compression of the elastomeric member by the tension plate and allows tightening of the nut toward the pumping module. Release of the pistons then causes expansion of the elastomeric member to forcibly compel the cylinder liner towards the pumping module.

Abstract: To provide an attachment structure of a swash plate support, that is, an attachment structure which suppresses an unstably fixed state of the swash plate support and realizes easy attachment and detachment of the swash plate support to and from a casing. A casing of a piston pump and a swash plate support which is attachable to the casing include a displacement preventing device and a rotation preventing device. In the swash plate support and the casing, since an engaging pawl portion of the displacement preventing device engages with an engaging portion, relative displacements in a first direction and a second direction along the rotational axis are prevented, and since a pin member of the rotation preventing device fits in the pin fit hole, relative rotations around the rotational axis are prevented.

Abstract: A clamp band for spring brakes which comprises an annular clamp band pre-formed with a side wall and a rim extended perpendicularly from a first end thereof, wherein during assembling of a spring brake when an edge of a first chamber, a diaphragm and an edge of a second chamber are positioned in sequential order on the rim a second end of the side wall is deformed to bend inwards to encompass the edge of the second chamber to secure the edges of the two chambers and the diaphragm in place. The annular clamp band comprises a first clamp band and a second clamp band having identical semi-annular shape.

Abstract: A hydraulic pump apparatus having an internal sump formed by a housing having an internal portion and an end cap secured to the housing. A rotatable cylinder block is located in the sump and driven by an input shaft extending into the housing. The pump apparatus also has a system of hydraulic porting in fluid communication with the cylinder block. The porting includes a pair of system ports located on a first side of the hydraulic pump apparatus, a fluid inlet on a second side of the hydraulic pump apparatus, opposite the first side, and a bypass valve positioned on the second side adjacent to the fluid inlet.

Abstract: The hydraulic cylinder assembly of the present invention provides an enlarged barrel and a compressible locking ring that secure a rod gland in the rod end of the cylinder. The tapered barrel prevents the rod gland from sliding into the cylinder and the locking ring seated in an annular groove prevents the rod gland from sliding out of the cylinder. A small hole in the cylinder barrel is provided through which the round ring may be punched out of the annular groove and easily removed with a screwdriver or pick. These features allow the hydraulic cylinder to be easily assembled and disassembled without compression tools and eliminate the need for threaded components, welds or bolts. The enlarged rod end of the cylinder barrel also provides a smooth cylinder barrel that is elegant in appearance and more easily manufactured, repaired and maintained.

Abstract: Each of two members to be fastened has a connecting surface, a communication groove opening on the connecting surface, and an engagement groove communicating with the communication groove and having an engagement surface parallel to the connecting surface. A fastening assembly has a connecting portion and two engaging pieces, each engaging piece having a fastening surface. The two members are placed with the connecting surfaces opposed, so that the engagement grooves are in communication each with the other through the communication grooves. The fastening assembly is inserted into the engagement grooves and the communication grooves, and the connecting portion is operated to draw together the two engaging pieces, causing the fastening surfaces of the engaging pieces to press upon the engagement surfaces of the engagement grooves, thereby clamping the two members together through their opposed connecting surfaces.

Abstract: A connecting rod for a hermetic compressor is provided. The connecting rod includes a piston connecting portion, a body having an end connected to the piston connecting portion, a crankshaft connecting portion connected to a different end of the body and extending a predetermined length so that a curved surface is formed, an inner peripheral surface of the crankshaft connecting portion making surface contact with an outer peripheral surface of a sleeve fitted to an off-center pin of a crankshaft, and a clamp fastened to both ends of the crankshaft connecting portion and exerting elastic force to retain the sleeve on the inner peripheral surface of the crankshaft connecting portion. The sleeve does not deform, even when retained on the crankshaft connecting portion, and makes uniform surface contact with the off-center pin, which is inserted into the sleeve. This substantially reduces the abrasion of the sleeve and the off-center pin and improves the compressor's efficiency.

Abstract: A fluid activated cylinder assembly including an end cap having an annular protrusion and a hollow cylinder having an end zone. The cylinder applies compressive force to the annular protrusion in the end zone. The end zone having no accommodating cavity and no accommodating protrusion for the annular protrusion.

Abstract: A method of installing annular seals on a plunger. A first step involves positioning an annular seal on a seal installation tool adapted to hold the annular seal in an expanded state. A second step involves positioning the annular seal so that the annular seal overlies a body of a plunger. A third step involves transferring the annular seal from the seal installation tool to a seal groove in the body of the plunger.

Abstract: A hermetic compressor with a connecting rod that can be assembled with a crankshaft and a piston while the piston is in a cylinder integrally formed with a frame. The hermetic compressor includes the frame formed with a hollow portion, a drive unit disposed on the frame, a cylinder integrally formed with the frame, the piston disposed within the cylinder, a crankshaft, and a connecting rod. The piston linearly reciprocates within the cylinder. The crankshaft has a main shaft portion adapted to rotate by a drive force of the drive unit, an eccentric shaft portion provided at one end of the main shaft portion, and a weight balance portion provided between the main shaft portion and the eccentric shaft portion. The main shaft portion is rotatably supported in the hollow portion. The eccentric shaft portion is positioned eccentrically relative to the main shaft portion. The weight portion is adapted to compensate for a rotating imbalance caused by the eccentric shaft portion.

Abstract: A hydraulic cylinder having a gland that is rotatable relative to the cylinder tube, the pivotal connection provided by a pair of aligned annular grooves on the gland and the cylinder tube, a key slot located through the cylinder tube, and a key positionable through the key slot to be located within the annular grooves to rotatably attach the gland to the cylinder tube. The key includes one end configured to engage the gland for facilitating installation and another end configured in a wedge shape to facilitate removal of the key.

Abstract: The invention is directed to improvements to the assembly of a unitized spring device. The spring device comprises a pair of retainer members which are tubular in shape and hollow inside. The retainer members have different outer circumference diameters which allow the second retainer member to fit onto the outer circumference of the first retainer member. The first retainer member has a first outward claw portion at one end and the second retainer member has a second inward claw portion at one end, such that the second claw portion can move beyond the first claw portion to couple the first and second retainer members in the axial direction. These first and second claw portions prevent one another from being pulled out in the coupled state. The first retainer member also comprises a slit which extends in the axial direction and divides at least the side having the first claw portion.

Abstract: A blowout preventer which, in certain aspects, has a main body with a main top, a main bottom, and a main bore therethrough from the main top to the main bottom, at least one breech assembly secured to the main body, ram apparatus movable within the breech assembly and the main body, the breech assembly having a chamber for enclosing part of the ram apparatus, the chamber having a side opening, a sleeve around the breech, and the sleeve movable with respect to the breech assembly to uncover the side opening to permit access to ram apparatus within the chamber of the breech.

Abstract: The present device relates to a housing module 1 for a brake booster. The housing module has a housing shell 3 that accommodates a movable wall 4. The movable wall subdivides an interior space of the brake booster into a low-pressure chamber 5 and a working chamber 6. Also, a control housing 11, in which a control valve 10 is arranged, controls a pressure difference acting on the movable wall 4 and is operable of an actuating rod 9. The control valve includes two sealing seats 12, 13 which are arranged concentrically to one another and of an elastically deformable valve body 14.

Abstract: A composite material and framework structure adapted to be utilized as a piston and cylinder apparatus. A cylindrical tube composed of a composite material is compressed between two end caps at the axial ends of the cylindrical composite tube. Beam elements extend between the end caps and maintain the compression force on the cylindrical composite tube. The cylindrical composite tube comprises a continuous glass fiber reinforced structure embedded in a resin matrix. The resin matrix provides a self contained lubricant system in a resin rich layer, the lubricant system migrating to the inner surface of the cylindrical composite tube.

Abstract: A linear drive has a drive housing and a carriage guide for relative motion in the direction of a principal axis. The carriage possesses a row of openings on it with several first carriage openings, whereas the drive housing has a row of openings on the housing side with mutually spaced first housing openings. Given suitable positioning of the carriage it is possible for attachment screws to be inserted right through the first carriage openings and inserted into the first housing openings. Second carriage openings belonging in addition to the row of openings on the carriage side are designed in the form of threaded openings, which render possible screwing in of attachment screws, that are inserted in the first housing openings of a further similar linear drive directly fitted to the carriage in a piggy-back fashion, through the first carriage openings thereof.

Abstract: A fluid actuator and retainer assembly, such as a master cylinder assembly for a vehicular braking system, includes a housing having a groove, a cylinder provided within the housing, and a piston assembly. The piston assembly includes a piston disposed within the cylinder for sliding movement relative thereto and a rod connected to the piston and extending from the cylinder and the housing. A retaining structure includes a rod engagement surface in contact with the rod, a plurality of engagement fingers extending from the rod engagement surface, and a detent extending from each of the plurality of engagement fingers into cooperation with the groove to retain the piston assembly in position relative to the cylinder housing.

Abstract: A method for assembling a piston on a rod, and resultant piston and rod assembly, uses one or more lock rings that are mechanically deformed radially inwardly into respective locking grooves in the rod, thereby axially locking the lock ring to the rod. The lock ring can function as an axial stop for the piston or can be formed integrally with the piston. The method of assembly minimize unwanted strains and stresses in the piston and rod, while providing a secure and durable joint between the piston and rod.

Abstract: A pressure assembly including a cylinder, an end plug and a split ring band. The cylinder has an end, an inner surface and an outer surface. The end plug is inserted into the end of the cylinder, the end plug having an outer surface that is in partial contact with the inner surface of the cylinder. The split ring band is in contact with the outer surface of the cylinder, the split ring band being secured to the cylinder and to the end plug.

Abstract: A face wall for a motor vehicle comprises a first wall and a second wall that is disposed at a distance from the first wall. The first wall is provided with a recess for accommodating a brake booster that is fastened exclusively to the first wall. This assembly permits effective soundproofing in the area of the face wall, thereby increasing comfort during driving.

Abstract: A piston arrangement for master and/or slave cylinders of a hydraulic actuating device for clutch and/or brake systems on motor vehicles is disclosed. An insert is inserted into a recess of the piston up to a first stop, the insert having a ball seat and an expandable insertion sleeve which is undercut with respect to the ball seat and protrudes with its expandable region. A ram is pushed into the sleeve with its ball end until it snaps into the ball seat. As the ram is further pressed axially, the insert slides over the first stop, is firmly pressed into a narrow hole section of the recess and strikes a second stop at the inner end of the recess. The insertion sleeve is then tightly enclosed by the piston wall and can no longer expand even in the event of very high pull-out forces, i.e. cannot release the ball end of the ram.

Abstract: A hydraulic pump apparatus having an internal sump formed by a housing having an internal portion and an end cap secured to the housing. A rotatable cylinder block is located in the sump and driven by an input shaft extending into the housing. The pump apparatus also has a system of hydraulic porting in fluid communication with the cylinder block. The porting includes a pair of system ports located on a first side of the hydraulic pump apparatus, a fluid inlet on a second side of the hydraulic pump apparatus, opposite the first side, and a bypass valve positioned on the second side adjacent to the fluid inlet. A case drain may also be formed on a third side of the pump apparatus.

Abstract: A camshaft is formed at a generally middle portion with an enlarged cylindrical portion. An annular vane member is mounted on the enlarged cylindrical portion and secured thereto by means of a nut. An annular housing or sprocket is arranged to receive therein the annular vane member in a manner to permit a rotation of the vane member relative to the annular housing. Each of a circular opening of the vane member and a circular opening of the annular housing is so sized as to permit cam lobes of the camshaft to pass therethrough.

Abstract: A master cylinder for a vehicle hydraulic brake system has a housing with a bore formed therein, which is open at one end and in which a first pressure piston and a second pressure piston are guided sealingly and displaceably along an axis. Acting counter to an actuating direction upon the first pressure piston is a restrained first restoring spring and upon the second pressure piston a second restoring spring. In order, in a transportation or disassembly state of the master cylinder, to prevent the first pressure piston from being pressed excessively out of the bore, the second pressure piston is supported by means of a stop component counter to the actuating direction positively in the housing of the master cylinder.

Abstract: A fluid activated cylinder assembly including an end cap having an annular protrusion and a hollow cylinder having an end zone. The cylinder applies compressive force to the annular protrusion in the end zone. The end zone having no accommodating cavity and no accommodating protrusion for the annular protrusion.

Abstract: A pump having a symmetric end cap is disclosed. The end cap is attachable in a first position or a second position wherein the second position is rotated relative to the housing. A trunnion arm extends in a first direction and a system port opens in a first orientation when the housing is connected to the end cap in a first position. The end cap includes structure such that the housing may be connected in a second position so that the trunnion arm extends in a second direction while maintaining the system port opening in the first orientation. The end cap may be provided with a symmetric porting system. A control device for affecting movement of the swashplate is disclosed. Methods of locking the swash plate into a predetermined position are also taught.

Abstract: An arrangement (10) for the fixing of an axially oriented (A) brake booster (12) on a dashboard (14) of an automobile wherein a rear face (16) of the booster (12) is fixed on a front face (18) of the dashboard (14) through a first bayonet fitting (26) interposed between the rear face (16) of the booster (12) and the front face (18) of the dashboard (14) to prevent the brake booster (12) from rotating.

Abstract: Apparatus and methods for assembling a piston assembly that comprises a piston comprising a head end flange and a crank end flange and a rod having a head end shoulder and a crank end shoulder. The head end shoulder of the rod contacts the head end flange of the piston and the crank end shoulder of the rod contacts the crank end flange of the piston. A nut engages the rod such that the head end flange of the piston is disposed between the nut and the head end shoulder of said rod. A collar engages the piston such that the crank end shoulder of the rod is disposed between the collar and the crank end flange of the piston.

Abstract: A fluid power linear drive has a drive housing (1) in which a housing chamber (4) is located containing at least one piston (5). The drive housing possesses two housing parts (2 and 3) placed alongside each other, which at mutually facing joint faces (16 and 17) are provided with half chambers (18a and 18b) constituted by elongated, groove-like recesses, which half chambers are united in a complementary fashion to form at least one housing chamber (4).

Abstract: A power steering assembly is provided that enables a secure, simultaneous connection of supply and return hose assemblies to a steering gear. The assembly includes a mounting bracket having an aperture through which one of the hose assemblies extends and a notch configured to receive the other hose assembly. The bracket is deformable such that the other hose assembly can be secured within the notch after insertion. The pressure and return hose assemblies include either a connector having opposed shoulders on either side of the bracket or are deformed to create beads on either side of the bracket to restrict movement thereby eliminating welds or brazes. Each of the hose assemblies further includes a groove formed to receive a seal. These grooves on the external portion of the hose assemblies reduce costly machining on the steering gear head.

Abstract: A connecting rod apparatus for converting a rotational motion to a reciprocal linear motion by connecting an eccentric portion of a crank shaft to a piston. The connecting rod apparatus has a bushing, a connecting rod and a connecting member. The bushing is rotatably connected with the eccentric portion, and has a sloping side on its outer surface with a predetermined slope in regard to an axis of the eccentric portion. The connecting rod has a piston attachment formed at one end for being connected with a piston pin which is connected with the piston. A connecting portion is formed at another end of the connecting rod and is connected with the bushing in a direction of the axis along the sloping side of the bushing. The connecting member connects the connecting portion and the bushing so that the connecting portion and the bushing can move relative to one another.

Abstract: A method and structure for connecting a pneumatic booster (S) to a brake pedal (F) by nesting a second element (3) inside a second element (2) of a control rod (1). The second element (3) is held one inside the first element (2) by a spring clip (25) that is housed in a circular groove (26) of an adapter (5) to define an elastic attachment and allow for play to be taken up to stabilize the connection.

Abstract: Single-acting cylinder-piston unit of plunger type, having a cylinder (1) closed at one end and containing a slidable cylindrical rod (5), the inner end of which presents two adjacent circumferential grooves (18, 28), the first (18) of which acts as a final seat for a split ring (8) defining the limit of the outward stroke of the rod and the second (28) of which acts as a temporary seat for the split ring, enabling the rod with the split ring mounted thereon to be inserted into the cylinder, the second groove (28) being at the inner end of the rod and the first groove (18) being more towards the opposite end of the rod, in proximity to the base, a counteracting member being arranged to interfere with the split ring to cause it to transfer from the second groove to the first groove during the final stage of insertion.

Abstract: A slide-type cylinder coupling which is suitable for the quick connect/disconnect attachment of a lift piston on a pedestal lift cylinder to a lift pedestal on a load cup or HCLU station of a chemical mechanical polishing apparatus. The cylinder coupling includes a coupling bolt which is provided on the lift piston and a coupling bracket which is provided on the bottom surface of the lift pedestal. The coupling bolt is slidably inserted in the coupling bracket to removably connect the lift cylinder to the lift pedestal. The coupling bolt is slidably removed from the coupling bracket to disconnect the lift cylinder from the lift pedestal for replacement or maintenance of the lift cylinder.

Abstract: A hydraulic actuator for use in a work vehicle includes a tube including a first end, a second end and an inner surface; a plug with a portion of the plug disposed inside the tube and a portion of the plug extending outside the tube; a weld extending around the perimeter of the plug and coupling the first end of the tube to the plug, the weld forming a fluid-tight seal between the plug and the tube; a seal abutting against the plug and the inner surface of the tube and being spaced from the weld; an end plug affixed to the second end of the tube to enclose and seal the second end of the tube, the end plug defining a rod opening; a piston configured to be slidingly supported within the tube, the piston including a retract face, an extend face oppositely disposed from the retract face and a lip protruding from the extend face; and a piston rod affixed to the piston, the piston rod extending out of the tube through the rod opening.

Abstract: A ball-joint connection for a braking system comprising a male element (2) and a female element (4). A first end (14) of the male element (2) includes pegs (30,30?) that are automatically radially extracted when the first end (14) is mounted in a female element (4) defined by a housing (16). The pegs (30,30?) collaborate with the interior surface (18) of the housing (16,66) to define a ball-joint connection between the male element (2) and the female element (4). The female element (4) being formed on one end of a piston (66) of for a master cylinder and the male element (2) forms the actuating rod of the master cylinder.

Abstract: A device that eliminates the need for torque, usually applied by large tools, in the assembly or maintenance of pumps. This device connects the cylinder (7) and upper housing (5) of a pump using a simple locking pin (9) that inserts through the upper housing (5) of the pump and along the flat (7a) on the pump cylinder (7). The cylinder (7) inserts into the upper housing (5) until the holes (11) for the pin are (9) aligned. Upon alignment, the locking pin (9) is inserted through both components and locked, thus connecting them.

Abstract: A hollow cylinder has an opening at one end, and a push rod passes through the opening so that a coupling at one end of the push rod is in the cylinder. A piston is reciprocally movably in the cylinder, and a spring urges the piston into contact with the coupling. The opening includes a through groove configured to pass the coupling when the longitudinal axes of the cylinder and the push rod are normal and to prevent the coupling from coming out when the longitudinal axes of the cylinder and the push rod align. An insertion groove in the side surface of the cylinder is continuous with the through groove and is adapted for passing a rod portion in the inserting state.

Abstract: A spacer for positioned a boost unit in an engine compartment of a vehicle. The spacer is defined by a wall located between a front face and a rear face, bearing surfaces, an axial opening with a flange thereon, ribs that extend from the flange to define a plurality of radial slots, an axial slot that extends from the front face toward the rear face and a peripheral slot that connects the axial slot with the engine compartment. A base of a boot that surrounds a hub on the boost unit engages the front face to define a flow path from the engine compartment to the hub. Tabs on the spacer assure that the front face is aligned with the base while the radial ribs prevent the base from engaging the wall to assure that the size of flow path remains constant during the communication of air to the hub.