Abstract: A connecting rod has a central body made of composite material and suitable for taking up traction and compression forces. A composite material little end is fixed to a first end of the central body and connected thereto by a first strap bearing against the little end and against the first end of the central body. A composite material big end comprising an inner half is fixed to the second end of the central body. The big end has an outer half pressed against the inner half by a second strap bearing against the other half and against the second end of the central body and means for pre-stressing the second strap.

Abstract: A precision cast connecting rod which has an elongate tubular shank member defining a hollow section for producing desired stiffness to weight characteristics. Piston and crankpin connecting members are attached to opposite ends of the shank member. The connecting members are provided with passages which extend axially therewithin from the hollow section. Defined within the elongate tubular shank member is a radially extending central aperture.

Abstract: A method of making a connecting rod for attachment to a bearing journal by separation of parts of the connecting rod, comprising: (a) forging a powder metal sintered preform to provide a one-piece connecting rod having an annular wall defining a crank opening with a center axis and with stress risers for establishing a cracking plane that extends across said crank opening; (b) providing access for a compression coupling across the cracking plane; (c) while at ambient conditions, applying tension substantially uniformly across the cracking plane to propagate fracture from the stress risers along said cracking plane and thereby separate the connecting rod into a cap and body with cracked surfaces; and (d) remating the cap and body by applying a compression coupling through the access to draw said cap and body together under guidance and with metal yielding pressure to effect substantially an exact rematch of said cracked surfaces.

Abstract: An internal combustion engine is provided by reciprocating force is translated to rotational motion without the use of a conventional crankshaft. A series of crank bearings are aligned linearly whereby piston rods disposed therebetween provide rotational motion for a power take-off or the like.

Abstract: A piston assembly is disclosed having a wrist pin for pivotably attaching a connecting rod to a piston for use in an internal combustion engine. The wrist pin is formed from an elongated circular cylindrical body having a pair of deformable sections formed adjacent each end and a relatively hard middle section therebetween. The wrist pin is sized for insertion along a longitudinal axis defined by a pair of coaxially aligned, spaced apart bores formed in diametrically opposed portions of the piston. The deformable end sections are adapted to be deformed sufficiently to engage the bores of the piston to limit the axial movement therebetween. The relatively hard middle section spans between the bores in the piston for pivotably engaging one end of the connection rod.

Abstract: A novel prefinished piston pin insert bearing is described wherein the tight radial clearances required for acceptable bearing function are maintained in spite of the tolerances required for assembly through a unique inner bearing surface geometry and through a unique methodology of bearing retention against axial and rotational movement. The interior bearing geometry is formed of radii equal to that of the piston pin which are offset vertically into the upper and lower bearings and of radii of nonspecific size which are offset horizontally. The bearings are retained against movement through connections with the piston head, the piston skirt, and between the various bearing pieces. Means are also provided for feeding oil under pressure to the piston pin and bearing interface for lubrication and to the piston assembly for cooling.

Abstract: A large drive shaft is formed of an extruded metal, thin wall tube, having integral, annular, inwardly thickened, ring-like areas at its opposite ends. A number of radially inwardly directed ribs are integrally formed upon the inner wall surface of the tube wall and extend the full length of the tube between the ring-like areas. The ribs are spaced apart from each other and, preferably, area of a height which is less than the thickness of the thin wall. The opposite ends of the shaft are provided with conventional connecting means for connecting the shaft to a drive device and a driven device transmitting power therebetween.

Abstract: A precision cast connecting rod which has an elongate tubular shank member defining a hollow section for producing desired stiffness to weight characteristics. Piston and crankpin connecting members are attached to opposite ends of the shank member. The connecting members are provided with passages which extend axially therewithin from the hollow section. Defined within the elongate tubular shank member is a radially extending central aperture. A precision casting method for preparing the hollow connecting rod includes forming an elongate core with a locating member positioned at each end thereof and a disk-shaped protuberance extending radially therefrom. The core is secured in a die and defines a cavity therebetween for preparing a pattern of the connecting rod using a molding material which substantially encapsulates the core within the cavity. After removing the pattern from the die, coatings of refractory material are applied to form a shell mold which encrusts the pattern.

Abstract: An internal combustion engine is provided by reciprocating force is translated to rotational motion without the use of a conventional crankshaft. A series of crank bearings are aligned linearly whereby piston rods disposed therebetween provide rotational motion for a power take-off or the like.

Abstract: A connecting rod assembly comprising a connecting rod having a rod lug, a connecting rod cap having a cap lug with the rod lug having a straight bore therein which coaxially aligns with a straight bore in said cap lug when the cap lug engages the rod lug. The connecting rod assembly further includes a bolt comprising a shank having an enlarged portion and a pilot portion. The enlarged portion has a cross section larger than each of the bores prior to insertion therein. The enlarged portion also has a tapered part, and is constructed of a sufficiently deformable material to enable insertion of said enlarged portion into each of the bores and fricitional retainment of the enlarged portion therein. The enlarged portion has a length sized so that it extends through a sufficient axial portion of each of the bores to hold the rod and cap lugs in abutting relation wherein the tapered part constitutes the entire part of the enlarged portion extending into one of the bores.

Abstract: In a method for producing workpieces of metal having profiled outer and/or inner contours which have any desired shape contours and are or can be profiled in thickness, the workpiece (R) is to be divided in terms of construction into simple part-profiles (4, 7, 13, 14), which are then produced by precision blanking and then fitted together and joined to one another by lamination to form the finished part.

Abstract: Wrist pins for use in pistons are described. The wrist pin comprises an elongate, substantially hollow member having two spaced-apart convex surface portions of substantially cylindrical or oval curvature, the two convex portions being connected by two walls of different curvature. Because the connecting walls are more nearly in compression and bending loads are minimised a lighter wrist pin for a given application may be produced.

Abstract: A method of cracking bearing assembles including the steps of (a) forming a ductile metal (steel, aluminum or titanium) connecting rod in one piece (e.g., by hot forging) having an annular wall defining a crankshaft opening with preformed surface crevices for guiding the initiation of a cracking plane that extends across the crank opening; (b) charging (i.e., for about 40 seconds) the region of such wall along at least one portion of the cracking plane with hydrogen by means of an electrolytic cell or by means of reacting the metal rod with a strong acid (e.g., concentrated sulfuric) to cause hydrogen to dissolve in the metal to facilitate hydrogen stress cracking thereat, with or without the imposition of static mechanical tensile loading at such crevices (i.e., for about 40 seconds) of a magnitude insufficient to cause yielding of the metal; and (c) prolonging, increasing, or imposing the static mechanical loading (i.e.

Abstract: A connecting rod for an internal-combustion, steam or the like, engine, having hydraulic means for converting the reciprocating motion of engine piston to the rotating motion of crankshaft. While producing the same torque on crankshaft, the hydraulic connecting rod enables the crankshaft throw to be shorter and, therefore, enables a decrease of the centrifugal force and inertia load produced by crankshaft rotating motion. Futhermore, the present invention enables a significant decrease of piston-ring friction and significantly reduces total engine friction. The present invention also yields significant decreases of centrifugal, inertia and friction loads resulting in a significant increase of total engine efficiency and power output.

Abstract: There is provided a connecting rod for connecting a crank pin of an electric motor to a reciprocated piston. The connecting rod includes a sheet metal shaped member that at each end has a deep drawn cylinder mounting which in turn mounts a bushing that is of a greater axial length than the cylinder mounting. The shaped member has a longitudinal bead providing a depression extending adjacent to one of the mountings and terminate in spaced relationship to the other mounting whereby there is a planar surface extending transversely across the member longitudinally between the bead and the other mounting and adjacent to the widest part of the member to provide a bending line.

Abstract: A method of making a connecting rod for attachment to a bearing journal by separation of parts of the connecting rod, comprising: (a) forging a powder metal sintered preform to provide a one-piece connecting rod having an annular wall defining a crank opening with a center axis and with stress risers for establishing a cracking plane that extends across said crank opening; (b) providing access for a compression coupling across the cracking plane; (c) while at ambient conditions, applying tension substantially uniformly across the cracking plane to propogate fracture from the stress risers along said cracking plane and thereby separate the connecting rod into a cap and body with cracked surrfaces; and (d) remating the cap and body by applying a compression coupling through the access to draw said cap and body together under guidance and with metal yielding pressure to effect substantially an exact rematch of said cracked surfaces.

Abstract: In a compressor which has a connecting rod comprising: a second eye (31) connected to the crank pin (12) and a crankshaft (7) and including a radial projection (32) with a longitudinal slot (33), said longitudinal slot (33) having at least two end faces (35) and two opposite lateral faces (34);a first eye (21) connected to the piston and including a rod (22) with an end portion, said end portion having at least two end faces (25) and two opposite lateral faces (24), said end portion being fitted in said longitudinal slot (33) so as to bring the end faces of the slot (33) and the rod (22) into contact therefore defining the axial distance between the centers of the eyes.According to the invention a clamp (40) preferably of spring steel, is fitted in the housing (28, 29, 38, 39) of the radial projection (32) of the second eye (31) and the end portion of the rod (22).

Abstract: Pistons are described comprising a crown portion and a skirt portion, the crown portion having depending from the underside thereof a boss, the boss having secured thereto at least two bearing members in fixed relationship to the piston body and which bearing members co-operate with an associated connecting rod. The bearing members may be located in rebates in the boss such that piston firing loads are born substantially in compression. The bearing members are in one embodiment secured to the boss by a bolt and nut. The bearing members may comprise ferrous, copper-based or aluminium based alloys depending upon the application environment.

Abstract: A piston assembly for compressors wherein a piston is connected to a crankshaft by a connecting rod having a ball at its one end, the ball being, with the rear portion thereof, joined to the piston by clamping a clamp portion provided on the piston, while the front portion of the ball is in contact with a ball seat formed in the inner portion of the piston, the crankshaft being formed at its upper end with an oil outlet for scattering an oil upon ejection therefrom, the piston assembly being characterized in that a plurality of holes are formed in the clamp portion, the piston having a skirt portion formed with a plurality of holes opposed to the respective holes.

Abstract: A connecting rod has a rod member formed from fiber reinforced plastic material secured to a cap member to define the big end of the connecting rod. Securement is by a metal member rigidly attached to the rod member, to which the cap member is secured. Attachment of the rod member and the metal member is via a locally transversely expanded end portion of the rod member enclosed within a similarly shaped (e.g. wedge shaped) cavity in the metal member such that the expanded end portion cannot be withdrawn axially of the rod member from the cavity.

Abstract: Piston rod assembly includes a composite piston rod having an entrapment ridge along the length thereof, and a non-integral metallic piston head having two separate piston head sections which are welded together in preloaded engagement against opposite sides of the entrapment ridge. The entrapment ridge has oppositely facing external tapered ramp surfaces which are engaged by correspondingly tapered internal ramp surfaces on the respective piston head sections. When the piston head sections are initially brought into engagement with opposite sides of the entrapment ridge, there is a slight gap between the inner faces on the piston head sections which determines the amount of preload force that must be applied to the piston head sections to eliminate the gap and bring the inner faces into substantial mating engagement with each other for welding.

Abstract: A refrigeration gas compressor comprises a piston reciprocably movable to effect gas compression, a motor-driven rotatable crankshaft, and a connecting rod between a crank pin on the crankshaft, and a wrist pin on the piston. A crank pin receiving hole and a wrist pin receiving hole in opposite ends of the connecting rod are connected by an oil passage. The oil passage is connected to a groove in the upper side wall in the crank pin receiving hole. The crank pin has two lubricating oil supply ports at opposite sides of its outer surface through which lubricating oil is pumped. A bearing assembly comprising semi-circular upper and lower bearing sections is disposed around the crank pin. Each bearing section has a smooth inner surface. The upper bearing section has oil well recesses near, but spaced from, opposite ends of its inner surface which receive oil from the oil supply ports each time a port moves therepast.

Abstract: A multi-piece connecting rod has the large eye end formed with a yoke receiving a bearing bracket supported on an angled wedge surface by an angled counter surface of a wedge. The wedge is carried by a pin-like bolt between legs of the yoke and includes a threaded portion engaged by the bolt for tightening the angled wedge surfaces to clamp the bearing bracket in position.

Abstract: A bolt retainer (10,110) for holding bolts (22,23,122,123) against rotation consists of a flat plate (12,112) having two or more bolt holes (18,20,118,120) therethrough and an upstanding portion (14,114). Specifically configured bolts (22,32,122,132) have surfaces (28,128) that abut the upstanding portion (4,114) thereby preventing rotation of the bolts (22,32,122,132) upon applying a nut (46) thereto.

Abstract: A multi-piece connecting rod is provided in which the piston pin bearing boss is divided along a transverse plane perpendicular to its bearing axis and is formed by extensions of two rod components provided with bearing holes while the crankpin bearing boss is divided along an axial plane through its bearing axis. For installation, the rod components are pivotable about the piston pin axis to open or unfold the crankpin end to receive the crankpin prior to closing and securing the rod components in their closed positions.

Abstract: In order to achieve a positioning close to a combustion chamber of a swivelling axis between a connecting rod and a piston, a curved surface region facing a piston head of a tensioned band which is subjected only to tractive stress and is looped around a connecting rod shank, forms also the pressure transmitting component of a pivot bearing in that it rests directly on a bearing surface on the piston head.

Abstract: A connecting rod having a pair of spaced apart flanges parallel to a plane defined by a crankshaft axis and a piston pin axis. A web connects the flanges to form a rod portion having an I-shaped cross section. The inner surfaces of the flanges include a lateral rounded projection adjacent to the flange edges to improve bending and stress characteristics.

Abstract: A peristrophic internal combustion engine with increased power output has greater torque and reduced friction. The distance of rotation between the inertia weights and the crankpins is increased to increase torque. These transposed inertia weights are embodied in top and bottom journals of the connecting rods and in the pistons assemblies. Each piston assembly includes a top piston-ring-holder piston and a lower, bearing piston joined to reciprocate in the cylinder. The lower bearing piston may have a circumferential ring, cylindrical barrel rollers, or spherical ball bearing arrangement contacting the cylinder wall while the upper piston carries the piston rings. The spherical ball bearing arrangement allows lower piston rotation about the piston axis. Inner and outer cylinder liners increase the cylinder operating life and reduce combustion heat loss through the cylinder wall.

Abstract: A connecting rod shank of a connecting rod is composed of a plurality of laminated plates having a thickness so that they can be introduced through a gap provided in a partially cylindrical base body of a loop tensioner for a tightening band which encloses the connecting rod shank.

Abstract: A connecting rod for reciprocally driving a piston within a cylinder wherein the piston rod includes upper and lower portions which are connected by an area of thinner dimension which is also yieldable so as to permit the lower end of the connecting rod to assume varying angular orientations with respect to the upper end thereof and wherein the lower end of the rod includes a bearing surface which is cooperatively received so as to be driven by the end of an operating lever by way of which motion is imparted to the connecting rod.

Abstract: A three-point torque strut connected between an engine and support resists rolling of the engine by reactive torque thereon while inducing with a portion of the reactive torque force from the engine a bending moment in the support that counteracts against the remainder of the reactive torque force transmitted by the strut from the engine tending to twist such support.

Abstract: A compression linkage is disclosed for use between a first swivel pin having a first thermal expansion characteristic and a second swivel pin of a second and differing thermal expansion characteristic, comprising: (a) a first shaft comprised of substantially the same material as the first pin and having a mateable end and another end adapted for swivel connection to said first pin; (b) a second shaft comprised of substantially the same material as the second pin and having a mateable end and another end adapted for swivel connection to said second pin; and (c) means providing a rigid compression joint between the mateable ends of said first and second shafts. Preferably, the first pin is adapted to operate in a high temperature environment, such as 400.degree.-500.degree. F., and is comprised of a ceramic effective to have a flexural strength of at least 100,000 psi (500 MPa) in such temperature range.

Abstract: A crankshaft and connecting rod assembly comprises a driver having a crank lobe with a shank received in a radial slot through a shaft so as to be driven thereby. The crank lobe has an inner side that operably contacts the shaft and an outer side that operably contacts a bore in a connecting rod and the shank has an end that also operably contacts the bore. The outer side of the crank lobe and the end of the shank each have a semi-circular cylindrical surface and these surfaces are located diametrically opposite each other and have a common axis eccentric and parallel to that of the shaft and a radius substantially equal to that of the bore whereby upon shaft rotation the crank lobe through sliding contact with the bore drives the connecting rod while the end of the shank slidingly follows the bore and cooperates with the crank lobe to prevent radial movement of the driver on the shaft to thereby maintain such drive.

Abstract: Small compressors for refrigeration usually have a motor-compressor unit suspended within a sealed housing by springs. An electric motor produces the rotation of a crankshaft having on its end portion a crank pin, which by means of a connecting rod produces the reciprocating motion of a piston in the cylinder. Two-piece connecting rods are applied to this type of machine, allowing for a new mounting procedure of the crank pin, connecting rod and wrist pin assembly. The connection of the parts is carried out in the rod of the connecting rod, and it has such a geometrical form that eliminates undesirable transverse deviations in this kind of part, ensuring full integrity of the device, without increasing mass or additional parts that impair functioning of the connecting rod. Furthermore, the fastening process is accomplished through brazing, braze-welding or glueing and can be done in reduced space conditions.

Abstract: A two part tool fits into the crankshaft bore of a partially manufactured connecting rod for an internal combustion engine and expands the bore to break the bore housing into two pieces, one of which comprises a bearing cap to permit installation of the rod onto a crankshaft journal. The tool is retracted to fit within the bore for the bearing and a high pressure acts on a piston to provide a high enough force to move two parts of the tool away from each other in direction perpendicular to a bisecting plane that lies along the central axis of the bore and to split the one piece bearing housing into two parts along a place defined by notches which weaken the bearing housing in selected areas. The piston is centered on the bisecting plane of the connecting rod so that the forces are balanced to ensure uniform, repeatable operation.

Abstract: A piston/crank connection mechanism for an internal combustion engine, including first and second pin members mounted on a piston and a crank of the engine, respectively, a connecting rod member having formed at opposite ends thereof first and second fitting holes in which the first and second pin members are fitted, respectively, and a self-lubricating, heat-resisting, wear-resisting and relatively hard film layer having a slippery surface thereon and interposed between an outer peripheral portion of the first pin member and an inner peripheral portion of the first fitting hole in the connecting rod. The structure eliminates any need for further consideration with respect to lubrication between the pin members and the connecting rod member, provides for reduction in size and weight of an engine, and is advantageous in controlling vibrations and noises.

Abstract: A link joint containing, between two component parts to be connected pivotably, a tension ring placed in corresponding cavities in the component parts extending from a pin, which tension ring, in addition to the pin on which the component parts bear with opposing bearing surfaces, encloses a tension pin which extends fully within one of the component parts and parallel to the pin axis.

Abstract: An improved piston-connecting rod unit is described comprising a piston provided with a seat housing a gudgeon pin, and a connecting rod having a small end into which a first bush is driven. The main characteristic of the present invention is that a second bush is driven over said gudgeon pin and is fitted idly into the first bush to form a floating connection between the gudgeon pin and connecting rod.

Abstract: A tubular piston pin for an internal combustion engine being of lightweight and high strength design with a cylindrical exterior surface and a double hourglass shaped aperture defined by thin-walled end portions; a thin-walled intermediate portion and two thicker-walled portions therebetween. A method for easy and inexpensive piston pin manufacture includes: the formation of half pins by molding a metal slug between two dies each having tapered end portions, punching out a midportion or intermediate web or wall to form an aperture therethrough with a generally hourglass shape, and aligning and joining two half pins axially together to form a piston pin with the double hourglass shaped interior aperture.

Abstract: In a connecting rod of reciprocating motion system in which a larger diameter end portion is divided into a body side bearing half and a bearing cap, and in which after a bearing metal is incorporated in a bearing hole defined by the bearing half and the bearing cap, the bearing half and bearing cap are integrally connected together by bolts, chamfers are made in the peripheral portions of the bearing half and the bearing cap facing their broken and divided surfaces. Such chamfers are made before the dividing of the larger diameter end portion and thus cause the breaking and dividing operation to be facilitated.

Abstract: A connecting rod for reciprocating piston machines having piston pin and crankshaft ring portions with bores therein connected together by a load bearing member. The load bearing member has voids within it adjoining the outer perimeters of the piston pin and crankshaft ring portions. When press-fitting a liner or cup bearing within the ring portion bores, the voids allow the piston pin and crankshaft ring portions to expand radially uniformly at the connection between the ring portions and the load bearing member such that the liner and bearing retain a substantially circular shape.

Abstract: A connecting rod or similar machine component comprising an assembly of two seperable parts having a spherical or cylindrical bearing surface provided therebetween. The parts comprising the assembly are manufactured from a ductile material, i.e., brass, aluminum or any alloy thereof. The two seperable parts are aligned by providing the confronting surfaces of the respective parts' first and second sides with intermeshing serrations extending in generally linearly, angularly disposed paths. When the parts are assembled, the intermeshing serrations on the parts' first side coact with the serrations on the parts' other side to create a wedging relationship therebetween whereby preventing lateral and lengthwise displacement of the bearing parts relative to each other.

Abstract: Split bearing assemblies are disclosed having separable bearing caps for both single applications, such as connecting rods, and multiple applications, such as engine crankshaft supports, together with methods and apparatus for making such assemblies by integrally forming the caps with the main body and separating them by fracture separation. A two step separation method is disclosed with bore starter notches and semicircular die expanders that minimize split plane and bore distortion.

Abstract: A connecting-rod system particularly for mowers, wherein a crank, supporting a couple of rods, is linked to the driving shaft by means of a clamp fastened to said shaft by means of a threaded ring, and wherein the mutual positioning of crank and clamp is achieved by means of a key.

Abstract: The invention relates to a small, efficient hermetic compressor for refrigeration wherein reduction in size and minimization of parts is emphasized. The motor compressor unit is mounted within a sealed outer housing and comprises a cast crankcase, which is connected to the stator of the electrical motor by means of only three connecting screws that extend through the stator and are threadedly received in sockets in the downwardly depending legs of the crankcase. The crankshaft is pressed into the motor rotor and is journaled within the crankcase for rotation about a vertical axis. The crankcase includes a slot extending into the cylinder so that the connecting rod can be inserted laterally into the cylinder at the same time that it is slipped over the end of the crankshaft, and the wrist pin is then inserted through the same slot, through the piston and connecting rod, and is held in place by a spring clip.

Abstract: A connecting rod has a closed bearing at one end for connecting, for exam, a piston bolt to the rod. At the other end the rod has a divided bearing for connecting, for example, a crankpin to the rod. The rod is made of fiber reinforced synthetic materials. The divided bearing is enclosed by an inner and an outer bearing bail and by a compression member. The free ends of a fiber reinforced loop which surrounds the closed bearing and the ends of the inner and outer bearing bails are formed into flanges which are interlocked by bolts. In another embodiment an endless loop is folded to form an open loop and the free ends of the open loop legs are interconnected by a bolt extending through the loop ends and through an outer bail made of fiber compound material or metal.

Abstract: A piston and connecting rod assembly comprises a one-piece yoke thrust bearing disposed between the piston and connecting rod to provide bearing surfaces therebetween. The piston includes a pair of wrist pin bosses disposed therein and in spaced-apart facing relationship. The bosses have oppositely disposed faces with axially aligned bores therein, and the faces have disposed therein respective shoulder-like depressions. The yoke thrust bearing comprises a pair of washer portions in abutment against respective boss faces and interconnected by a yoke element, and the washer portions have respective projections conformably received in respective depressions, thereby aligning the holes in the washers with the bores and preventing rotation of the yoke thrust bearing in the piston. On end of the connecting rod is received between the washer portions, and a wrist pin is passed through the boss bores, washer portions, and the connecting rod opening to thereby pivotally connect the piston and connecting rod together.

Abstract: A connecting-rod system for mowers in particular, wherein, for actuating elements driven by alternate motion, there are used rods mounted on a crank which can be linked to the drive shaft by fitting a crank pin into a seat in the shaft itself. On the crank pin there is at least one flat wall intended for properly positioning the crank pin itself by interacting with a corresponding flat wall provided in said seat.

Abstract: A connecting rod has a closed bearing at one end for connecting, for exam, a piston bolt to the rod. At the other end the rod has a divided bearing for connecting, for example, a crankpin to the rod. The rod is made of fiber reinforced synthetic materials. The divided bearing is enclosed by an inner and an outer bearing bail and by the free ends of a fiber reinforced loop which surrounds the closed bearing. At the divided bearing end the rod components are interlocked in a dovetail manner. The loop is an open loop and the free ends of the loop legs extend substantially in parallel to the longitudinal axis of the rod.

Abstract: In the embodiments of the invention described in the specification, a piston and a connecting rod of an internal combustion engine have opposed approximately semi-cylindrical bearing regions partially enclosing a pin, leaving free gaps between the bearing regions to permit swivel motions of the piston and connecting rod about the axis of the pin. Two symmetrical rings which surround the pin axis retain the bearing regions against the pin. The provision of such opposed bearing regions reduces the oscillating mass of the link joint.