VOLUMETRIC MACHINE WITH CURVED LINERS

Abstract: The piston is provided with the possibility of sliding on a plane (C) parallel to the plane of rotation (B) of the pistons by means of a spacer (10) coupled also in oscillation on the semi-cylindrical surface (9) of the extremity of the drive shaft; the plate spring (6), interposed between the lower part (7, 8) of the piston and the said extremity, with the semi-cylindrical spacer (3) inside the double diameter hole (4, 5), ensures contact, also in the presence of variations in motion and/or pressure. The articulation with prevalent unloading of the thrust from the pistons is such that the load transmission component (63, 79) is exposed to the pressure of the fluid over an area which is much greater than that of the piston (65, 77). The seal system with compensated ring comprises rings (85) having at least two internal symmetrical protuberances (86), of which one is provided with an outward incision (87); a pair of rings is assembled in a single seat with the rings arranged in mirrored positions with respect to the axis of symmetry (SM), in such a way as to cover the protuberance/s with incision with that/those without; the rings may be cut (89) to facilitate assembly in seats that may not be dismantled, but in a position away from the zone of the protuberances and the axis of symmetry.

Description: DESCRIPTION OF THE INVENTION VOLUMETRIC MACHINE WITH CURVED LINERS. The invention concerns : articulation of the pistons with correction of the trajectories, prevalent unloading of the thrust from the pistons and seal system with com- 10 pensated ring, that is connection devices of the pistons of volumetric machines with curved cylinder liners to their relative rotating supports, to compensate for the deviations in trajectory, due to their rigid assembly, that arise at the intermediate angles of rotation of 45° , 15 135° , 225° , and 315° during the rotation through one com¬ plete revolution, within and in combination with the in¬ clined block of liners to a significant degree with re¬ spect to the average at the maximum displacement; articu¬ lation of the pistons of volumetric machines with crank 20 mechanism or with curved liners that reduces the thrust of the fluid acting on the piston to a minimum, and, further¬ more, an improved sealing systemwith compensated ring with recovery of wearing and of the manufacturing imper¬ fections of the liner, in volumetric machines in general. 25 Prior art comprises the pistons of volumetric machines with curved liners as described in patent application PCT/IT92/00134, where three types of piston are described: piston for endothermic engines or for gaseous fluids with 30 a high angle of inclination, coupled to the extremities of the engine shaft by means of gudgeons arranged radially at the centre of curvature of the trajectories; piston ri¬ gidly connected to the relative support plate; pistons with rigid stem and a spherical coupling with oscillating 35 clearance on the screwwith semi-spherical head, positio¬ ned in axis with the stem of the piston. Prior art also comprises articulations of the pistons of volumetric machines, with crankmechanism, of the known type with gudgeons or spherical couplings between the pi ¬ ston and the connecting rod. Prior art solutions, however, do not permit a satisfac¬ tory transmission of the thrust generated by the fluid on the connecting rod or support element and, in the case of machines with curved liners, a satisfactory simultaneous compensation of the errors in the paths of the trajecto¬ ries at the intermediate angles of rotation, 45° , 135° , 225,° and 315° : the correction has to occur in a direction which is tangential to the trajectory of the piston, that is, perpendicular to the radial direction. At the same time as the said correction it is also neces¬ sary to compensate the centrifugal load acting on the pi¬ ston that is free to oscillate, in order to prevent it from sliding against the internal surface of the curved liner: this causes both a rapid deterioration of the seal rings and an ovalisation of the liner. The combined effect of the error in the trajectory and of the centrifugal load is not compensated by any of the prior art pistons; at least one oscillating element is present in all of these: the piston on the gudgeon, the seal ring on the piston or the head of the piston on the stem that does not comple¬ tely counteract the said combined effect. Volumetric ma¬ chines with curved liners obtained with the said solutions have a high degree of wearing of the curved liner, short lifetime of the fluid seal and excessive noise levels due to the clearance required for the oscillation. Prior art also comprises various types of seals in all kinds of materials, split rings, with clearance recovery with separate internal elastic elements or due to their elastic properties, though always requiring the arrange¬ ment of a plurality of rings, each in its own seat, in the sealing surface and/or with a limited capacity for recove¬ ring wearing and/or manufacturing clearances in the liner- piston coupling. Prior art, therefore, has considerable limitations as re¬ gards improving the sealing and the articulations in volu¬ metric machines with crank mechanism; there are also con- siderable limitations as regards the exploitation of the potential capabilities of volumetric machines with curved liners, due to their intrinsic better balancing with re¬ spect to preceding machines, and due to the exploitation of the evolution of the piston within the liner without contact between the side of the piston and the said liner. Such prior are may be subject to considerable improve¬ ment with a view to eliminating the said drawbacks . From the foregoing emerges the need to resolve the technical problem of inventing: a way of articulating the piston on the respective stem enabling it, in volumetric machines with curved liners, to carry out displacements that are tangential to the trajectory and oscillations on the radial axis, but with the possibility of preventing displacements that are radial with respect to the axis of rotation; a way of articulating the piston on the respec¬ tive stem, or, for in crank mechanisms, on the connecting rod, achieving a more direct transfer of the thrust of the fluid; a seal system that enables contact to be maintained with the surface of the liner even with high levels of wearing and/or large manufacturing clearances . The invention resolves the said technical problem by adopting: articulation of the pistons with correction of the trajectories, for volumetric machines with curved li¬ ners, comprising the seal ring of the piston positioned outside the plane of rotation of the pistons, but in a plane oriented at the centre of intersection of the axes of rotation of the pistons and of the liner block, charac¬ terised in that it has sliding and/or oscillating elements in a direction which is tangential to the instantaneous trajectory of the piston and has elements in radial con- tact between the piston and the relative support, to com¬ pensate the centrifugal forces acting on the mass of the piston. Also adopting: constituting the said sliding elements a plane which is parallel, at the dead-centre positions, with the said plane of rotation of the pistons, fashioned inside the piston and on which slides a means made to oscillate on an axis which radial with respect to the axis of rotation of the pistons. Also adopting: constituting the said oscillating ele¬ ments, a spherical surface coupled with the piston posi- tioned at the intersection between the plane of rotation of the pistons and the axis of the piston itself, coinci¬ ding with the tangent to the axis of the curved liner. Also adopting: a piston coupled, internally, so that it slides with spacer parallelepiped, in turn coupled so that it oscillates on the extremity of the engine shaft: an elastic element is placed inside a radial hole of the said extremity which act on the lower part of the said pi¬ ston, by means of a semi-cylinder with the convex part fa- cing towards the piston, so as to keep the sliding surface in contact with the surface of oscillation between the pi¬ ston and the extremity of the shaft. Also adopting: the said elastic element consisting of a plate spring with flexibility limited by the conformation of the said radial hole, conveniently shaped or with two diameters; the spring is kept in place by an internal axial safety ring assembled in the lower part of the said piston. Also adopting: a piston coupled to the prismatic stem by means of a semi-cylinder whose plane slides on the said internal plane of the piston and the curved surface, with a radial axis of curvature, with concave side facing to- wards the piston; the said piston has an internal lower protruding bulge, with centre of curvature coinciding with the semi-cylinder, kept in position by a retaining ring under the action of the axial clearance recovery spring: the internal sides of the piston are inclined in a direc¬ tion which is tangential to the trajectory to permit the piston to be inclined with respect to the prismatic stem. Also adopting: a hollow sphere piston coupled to a sphe¬ rical support and kept in position there so that it may slide by means of a cap of the fixing screw; an annular zone with eccentric sphere with respect to the centre of curvature; the screw has an intermediate shank for the ad- mission of the edges of the central hole; a lower stretch of the piston with rake angle greater than the semi-incli¬ nation of the block of curved liners; the piston is advan¬ tageously made of a plastic or other similar material, suitable for the type of fluid used. Also adopting: a piston with spherical support surface oscillating on the spherical head of the prismatic stem, kept in position by two ledges positioned in the lower part of the said piston, which in turn are in contact with the protrusions of an annular spring positioned between the ledges and the head; two flexing chambers in the said head corresponding with the protrusions and the ledges; the sides of the ledges are inclined to facilitate as¬ sembly. Also adopting: the curvature of the sides of the piston in a tangential direction having a radius which is less than the radius of the liners; in a radial direction with the major and minor radius of curvature equal to that of the curved liner. Also adopting, in combination, or not, with the said articulations, in volumetric machines with curved liners : an articulation for volumetric machines with prevalent un- loading of the thrust from the pistons, comprising the pi¬ ston with spherical coupling to the load transmission ele¬ ment, characterised in that the said load transmission element is directly exposed to the pressure of the fluid over an area which is much greater than that to which the piston is exposed; an elastic element is positioned bet¬ ween, even using a ring with a semi-spherical cap, between the said piston and the said load transmission element, to close any clearance. Also adopting: for volumetric machines for gases, the po¬ sition of the seal ring between the piston and the liner in a position behind the spherical coupling with the load transmission element. Also adopting: for volumetric machines for liquids, the position of the seal ring between the piston and the liner in a position behind the spherical coupling with the load transmission element. Also adopting: the said elastic element advantageously consisting of a Belleville washer. Also adopting: in machines with curved liners: the piston coupled to the piston support plate with spherical cou¬ pling and with radial support on a bevel on the stem to compensate the radial thrust. Also adopting, in volumetric machines in combination, or not, with the said articulations of the pistons: a seal system with compensated ring, comprising rings with an elastic return, characterised in that the said rings have at least two internal symmetrical protuberances, of which half of them having an incision towards the outside; a pair of rings is assembled in a single seat with the rings arranged specularly with respect to the axis of symmetry so as to cover the protuberance/s with incision with that/those without incision; the rings may be broken in order to facilitate assembly in seats that may not be dis¬ mantled, but in a position that is removed from the zone of the protuberances and from the axis of symmetry. Also adopting: the arrangement of the protuberances con¬ centrated prevalently on a stretch of ring; the eccentri¬ city arising being on the said axis of symmetry. Also adopting: the depth of the protuberances and of the incisions being proportional to the said eccentricity. Also adopting: a lining of low friction material securely anchored to the external diameter. The advantages obtained with this invention for volume¬ tric machines with curved liners are: the recovery of clearances enables the noise generated in passing the dead centre positions to be eliminated, in as much as the clea- ranees are recovered automatically by the articulation; the reaction of the piston support against centrifugal forces enables the elimination of the wearing of the li¬ ners and of the seal rings; it is possible to use larger angles of inclination of the piston with respect to the liner block, so enabling volumetric machines with larger displacements to be obtained; it is possible to achieve improved balancing in the presence of a variable and rota¬ ting distribution; the radial forces of inertia acting on the piston are compensated entirely; the variety of solu- tions proposed enables all design requirements to be sati¬ sfied in relation to the required displacements and fluids employed. The distribution of the pressure of the fluid, furthermo¬ re, in function of the surface exposed to it, enables the thrust on the piston to be reduced, thereby reducing the load on the oscillating surfaces; in this way, the seals, the oscillating surfaces and the piston, being subjected to lower loads, have a longer lifetime. Also, the lower loads on the components that have reci- procal motion with respect to each other, reduce wearing and enable, without the use of special low friction mate¬ rials, a significant reduction in the internal friction of the mechanism and a longer lifetime of the volumetric ma- chine. The advantages, finally, are: in the compensated sealing system the ring, with its elastic recovery, enables the variations in the diameter of the liner to be absorbed and to compensate for manufacturing tolerances between the pi¬ ston and the liner that are not necessarily very small,- wearing is prevalent in the seal rings, however, with the ring with a low friction coating, it is only the liner that is subject to wear and the ring is able to compensate for up to a 1% increase in the diameter before the assem¬ bling cut opens; the pair of seal rings, finally, superim¬ posed so that the internal protuberances with the inci¬ sions cover those without incisions, guarantees the neces¬ sary fluid seal for the operation of volumetric machines; the isolation of the fluid chamber is considerably greater in that this sealing system does not function as with the labyrinth systems, the isolation being total due to the positioning of the two rings. Moreover, the rings carry out an accurate scraping action removing impurities from the surface of the liner. Some embodiments of the invention are illustrated, pu¬ rely by way of example, in the seven tables of drawings attached in which Figure 1 is section I-I of Figure 2, showing just the piston; Figure 2 is the section of a cur¬ ved liner with piston for an endothermic engine or com¬ pressor, with articulation as described; Figure 3 is a diametric section of a piston-curved liner block group for an hydraulic machine, with articulation as described in a second form of embodiment; Figure 4 is section IV-IV of Figure 3 limited to just the piston and the relative por¬ tion of plate with stem; Figure 5 is section V-V of Figure 3 limited to just the zone of contact between the protube¬ rance of the piston and the retaining ring; Figure 6 is the diametric section of a piston-curved liner block group in a third form of embodiment of the invention, suitable for an hydraulic machine, for medium or low pressures, or a pneumatic machine; Figure 7 is the section of the just the piston with hollow sphere and eccentric contact, sho¬ wing the radiuses and the eccentricity; Figure 8 is the detail Z, enlarged, of the previous Figure 7; Figure 9 is the diametric section of a piston, in a fourth form of em- bodiment, inside the curved liner in a median point of the stroke; Figure 10 is section X-X of Figure 9, tangential to the trajectory and at the top and bottom dead centre points of the stroke; Figure 11 is a section analogous to the previous one, but in an intermediate point of the stroke; Figure 12 is a section of the piston with spheri¬ cal support; Figure 13 is a diametric section of a piston- curved liner block group for hydraulic machine, with arti¬ culation, with prevalent unloading of the thrust, accor¬ ding to the invention; Figure 14 is section X V-XIV of Fi- gure 13, limited to just the piston and the relative stem; Figure 15 is the longitudinal section of a volumetric ma¬ chine with crank mechanism, with articulation and preva¬ lent unloading of the thrust, according to the invention; Figure 16 is a view of a piston seal ring according to the invention; Figure 17 is the partial section XVII-XVII of Figure 16. The figures show: 1, Figure 1, the piston for endother- mic engines or pneumatic machines, in the first form of embodiment, that has the central axis Al coinciding, every half of a revolution, with the axis of the drive shaft A2 in Figure 2, in the figure at the top dead centre posi¬ tion; 2, the extremity of the drive shaft on which the pi¬ ston oscillates, on axis Bl at the crossing between the plane B with the said axis Al, by means of semi-cylindri¬ cal spacer 3 inserted by rotation in the upper minor dia¬ meter 4 of the two-diameter hole 5 : the hole with the greater diameter is eccentric with respect to the axis of oscillation Bl; 6, a plate spring, centrally in contact with flat surface of the said spacer 3, and externally re¬ sting on both sides on a safety ring 7 for holes, assem¬ bled in the lower part 8 of the said piston; 9, the upper semi-cylindrical surface of the extremity 2 of the drive - 10 - shaft on which there is a parallelepiped spacer 10 with oscillating coupling on the same axis Bl, in sliding con¬ tact with plane C, parallel to plane B, and internal to the said piston; 11, an internal cavity; 12, the seal ring; 13, Figure 2, the clearance arising due to the cen¬ trifugal force between the external surface of the extre¬ mity 2, normal to axis Bl, and the internal wall of the piston, whereas there is contact between the opposite sur¬ face 14 and the piston; 15 the block of curved liners ro- tating on axis D; 16 the combustion chamber; 17, the outer casing; 18 the drive shaft. The figures also show for the second form of embodiment for hydraulic fluids: 19, Figure 3, the drive shaft, onto which is splined the piston support plate 20, by means of splined coupling 21; 22, the piston with prismatic stem, with oscillating coupling on radial axis El contained in plane E normal to axis F2 of the said drive shaft; Fl the central axis of the piston, intersecting with plane E in a position corresponding to that of El; 23, the block with the curved liners, rotating on axis G; 24, the prismatic stem of the pistons, with semi-cylindrical spacer 25, in sliding contact with the top internal face of the said pi¬ ston 22, plane E, and oscillating on the said prismatic stem 24 by means of the semi-cylindrical surface 26 with axis El as centre of curvature; 27, the bearing and 28, the feed channel, in stem 24, in the spacer 25 and in the piston 22, for the compensation of the hydraulic thrust; 29, an internal lower protrusion in the piston, with oscillating coupling with a retaining ring 30, in turn splined on the said piston support plate 20; 31, the Bel¬ leville washer for recovering the clearance between liner block 23 and said plate 20; 32, the seal ring of the said piston 22; 33 the clearance arising as a result of centri- fugal forces between the external surface of the stem 24, normal to axis El, and the internal wall of the piston, whereas there is contact between the opposite surface 34 and the piston; 35, Figure 4, the inclined sides to enable the oscillation of the piston on said axis El; L, Figure 5 the radius of curvature between the said ring and the pro¬ tuberance 29 of the piston 22. The figures also show: 36, Figure 6, the piston-support plate in the third form of embodiment, coupled to the dri¬ ve shaft with axis M2 , with splined coupling 37; N, the axis of rotation of the liner block 38; 39, the spherical support for the hollow sphere piston 40 with eccentric contact, the support being splined to the said plate 36 and fixed with bolts 41 with spherical cap head: the bolts and the plate a drilled for the compensation of the hydraulic thrust; Ml, the axis of symmetry of the piston, at whose crossing with plane O the sphere of oscillation of the piston 40 is positioned; 42, the annular, eccentric spherical zone of the said piston, moved by an amount P from the plane O; 43, a central upper hole of the piston 40, with rake angle which is greater than the semi-angle of inclination of the liner block 38; 44 an intermediate shank of bolt 41 for the admission of the edges of the said central hole 43; RI, Figure 7, the radius of the in¬ ternal sphere of oscillation of the piston 40; RE, the ra¬ dius of the external sphere, coinciding with the internal radius of the spherical cap head of the bolt 41; R, the displacement from the plane O of the centre of curvature of the annular zone 42; Q, the radius of the said eccen¬ tric spherical annular zone 42; 45, the lower part of the piston 40 with rake angle greater than the semi-inclina¬ tion of the said block 38; RS, the fillet between the ex- ternal spherical surface of the piston 40 and the eccen¬ tric annular zone 42 for the admission of the said sphe¬ rical cap of the bolt 41. The figures show, finally, in the fourth form of embodi- ment, the common references to the pervious form remaining valid: 46, Figure 6, the curved liner fashioned in the block 47 rotating on axis N; 48, the piston with spherical support, oscillating on the spherical head of 49 of the - 12 - prismatic stem 50; 51, the axial hole for the compensation of the hydraulic thrust; 52, the seal ring, positioned in a plane advanced by an amount P and inclined by an amount U with respect to the plane of oscillation O; 53, two lo- wer shelves of the piston with spherical plane of contact, for retaining, by means of annular spring 54, between the said shelves and the said head 49, maintaining contact on the spherical surface; T, the positioning angle of the pi¬ ston, corresponding to half the angle U; V, the complemen- tary angle of U between the internal surface of the shelf and the base plane for machining the piston 48: the said surface rests on the internal side of the prismatic stem 50 of the piston with a view to compensating the centrifu¬ gal forces, in association with the contact on the spheri- cal surface; 55, the protrusions of the annular spring re¬ sting on the said shelves with localised contact; 56, the flexing chamber of the stretches of annular spring, in correspondence with the said protuberances 55 and shelves 53; 57, Figure 12, the seat of the seal ring on the said piston with spherical support; 58, the sides of the said shelves, inclined to facilitate assembly; , the radius of curvature of the sides of the piston with spherical sup¬ port surface in a direction which is tangential to the trajectory: the radiuses in a radial direction are shown in Figure 9 and are equal to the major and minor radiuses of curvature of the liner. The figures also show, in the case of articulation with prevalent unloading of the thrust in volumetric machines with curved liners: 61, Figure 13, the piston-support pla¬ te with splined coupling 62 with the drive shaft, not shown; 63. the bevelled head of the stem 64, coupled to the piston 65 with oscillation on radial axis Hi contained in plane H normal to axis J2 of the said drive shaft; Jl, the central axis of the piston, intersecting the plane H correspondingly with axis HI; 66, the block with the cur¬ ved liners, rotating on axis K; 67, the bevel on the stem 64 on whose head the piston 65 is coupled, in spherical contact on plane H and oscillating on the said stem 64 on axis HI; 68, the bearing compensating the axial thrust and the feed channel 69, in the piston-support plate 61, and in the drilled bolt 70 for the said bearing; 71, an exter- nal spherical surface of the piston 65, with oscillating coupling with an analogous surface of the piston-support plate 61; 72, the Belleville washer for taking up the clearance between the head 63 and the piston 65, by means of spherical support ring SA; 73, the pair of seal rings of the said piston 65; 74, the clearance arising from the centrifugal forces between the external surface of the stem 64, normal to axis HI, and the internal wall of the piston, whereas there is contact between the opposite sur¬ face 67 and the piston 65; 75, Figure 14, the clearance between the internal sides to allow the oscillation of the piston on the said axis HI. The figures also show, in the case of the volumetric ma¬ chine with crank mechanism: 76, Figure 15, the straight liner within which the annular piston 77 slides, with spherical seat, with external seal ring 78; 79, the assem¬ bled spherical foot of the connecting rod 80, connected to the rotating crank on axis MA and with trajectory TM of the eccentric: the crank is not shown in the figure as it may be of any type; 81, the spherical annular cap, with a sliding coupling on axis SP with the stem and with the spherical surface of a lower ring 82 fixed to the said pi¬ ston 77, by means of connection 83; 84, a Belleville was¬ her to take up the clearance between the said foot 79 and the said annular cap 81. The figures also show, in the sealing system with compen¬ sated ring: 85, Figure 16, the seal ring according to the invention, having internal protuberances 86, with or wi- thout incision 87; AN, the angle between two successive protuberances 86; SM, the axis of symmetry of the said protuberances: the incisions 87, of a width IB, are made in stretches of ring with protuberances that are not symmetrical with one another; RT, the radius at the base of the incisions, measured from the eccentric circumferen¬ ce RG, with an eccentricity Y on the said axis of symmetry SM; RB, the radius of the said protuberances ; DE, the in- ternal eccentric diameter, again by an amount Y, tangen¬ tial to the internal diameter DI of the ring 85 and the innermost part of the protuberances 86; DC, the nominal diameter of the ring, equal to the nominal diameter of the liner for which it is intended; 89, the break in the seal ring made in order to permit its assembly in seats which may not be dismantled: it is positioned away from the zone of the protuberances 86 and not in line with the said axis of symmetry SM; 90, Figure 17, a covering in low-friction material applied to the external side of the ring at the nominal diameter, in a peripheral hollow 91 with serrated surface for anchoring the covering. Operation of the articulations described is as follows: the zone of contact and, therefore, that creating the seal between the piston and the liner, is displaced from the plane of rotation of the pistons (planes B, E and O) ; the seal ring (12, 32 and 52) or the annular zone 42 are posi¬ tioned in a plane oriented towards the common centre of rotation of the liner block and of the pistons projected over the said plane of rotation of the pistons; the pre¬ sence of planes of linear correction in a direction which is tangential to the trajectory of the pistons, plane C in the first form of embodiment, plane E in the second, and the slight variation in the inclination of the piston in the third and fourth forms, enables the actual position of the piston to be adapted to the combination of the respec¬ tive positions between the curved liner and the piston. The correction angles of oscillation are small whereas the angles of oscillation to compensate for the inclination of the liner as it passes through the mid-stroke point need to be much higher, of the order of the maximum inclination that may be reached by the liner block: the said rotation occurs on surface 9 of the extremity 2 in the case of the first form of embodiment, on the surface of semi-cylindri¬ cal spacer 25 in the second form, and with an oscillation of the hollow sphere piston 40, or of the piston with spherical support 48 on the respective sphere 39 or 49. The radial loads on the piston, due to centrifugal for¬ ces, are compensated with the contact of a surface of the said piston against the stem on the internal side 14, 34, leaving, on the opposite, external side a clearance 13, 33 both between the stem of the piston and between the piston and the said liner; the loads acting on the hollow sphere piston, being made of a plastic, or similar, material very low due to the reduced mass, and, moreover the, extensive surface of contact with the spherical support 39 does not permit an effective action of the said centrifugal force. As mentioned earlier, in the fourth form of embodiment the piston 48 is supported with a double contact, both on the spherical head 49, and with the contact between the shelf 53 and the internal part of the prismatic stem 50. The elastic elements: the plate spring 6, the Belleville washer 31 and the ring spring 54 keep the relative piston in its position in contact with each surface of oscilla¬ tion, preventing the separation of the piston, avoiding generating noise on inversion of the sense of rotation and/or of the thrust. Operation of the articulation describedwith prevalent unloading of the thrust from the pistons, in the case of volumetric machine with curved liners, Figures 13 and 14, is as follows: the zone of contact and, therefore, that creating the seal between the piston and the liner, is displaced from the plane of rotation of the pistons, plane H; the seal rings 73 are positioned in a plane oriented towards the common centre of rotation of the liner block and of the pistons, in a rearward position with respect to said plane H of rotation of the pistons; the linear cor¬ rection in a direction which is tangential to the trajec¬ tory of the pistons at the said angles of rotation 45° , 135,° 225° and 315°, in plane H, occurs because of the - 16 - considerable tolerance left between the piston and the li¬ ner, whereas sealing occurs between the head 63 of the stem 64 and the internal spherical surface of the piston 65. The corrections are small, but in the lower part of the piston 65, where the pair of seal rings 73 are posi¬ tioned, cause a significant amount of oscillation, compen¬ sated by clearance 75 between the piston and the stem 64 in a direction which is tangential to the trajectory of rotation. The radial loads on the piston of machines with curved liners, due to centrifugal forces, are compensated by the contact of the internal surface of the said piston against the bevel 67 of the stem 64, leaving, on the opposite, outward side, clearance both between the stem of the pi- ston and between the said piston and the said liner. The Belleville washer 72 keeps the respective piston 65 con¬ stantly in contact with the corresponding spherical seat of the piston-support plate 61, preventing the separation of the piston, avoiding generating noise on inversion of the sense of rotation and/or of the thrust. In this way the thrust of the fluid acts mostly on the head 63 of the stem 64 and only in small part on the piston 65, limited only to the surface of the annular crown exposed to the pressure: the lower positioning of the seal rings 73 fa- vour, by means of the pressure of the fluid, the internal seal of the piston 65 with the spherical surface of the head 63. As a result the thrust generated by the fluid is transmitted directly to the component that makes use of its effect: the piston-support plate 61, by means of the said heads 63 rigidly fixed to it with respective stems 64. The thrust that the said piston 65 is subjected to, to favour the oscillations on the spherical surface 71, are minimal and enable the piston to operate with absolute fluid seal and compensation of trajectory even with the highest operating pressures without, moreover, increasing wearing of the piston, the liners and of the seal rings. Operation of the articulation for volumetric machines with crank mechanism is analogous: the annular piston 77 oscillates on the assembled spherical foot 79 of the con¬ necting rod 80 and, in its lower part, the annular spheri¬ cal cap 81, acted on by spring 84, takes up the clearance against the lower ring 82 connected rigidly to the annular piston 77; the surface of connecting rod exposed to the pressure is much greater than the free annular surface of the piston 77, with, therefore, a considerable difference in relative loads to be supported; the seal between the assembled spherical foot 79 of the connecting rod and the piston 77 occurs at the said spherical surface; the oscil¬ lation between the foot 79 and the piston 77, which is equal to the angles of oscillation of the connecting rod 80, in function of its length and the trajectory TM of the eccentric, does not compromise operation because of the action of increased sealing effected, on the annular pi¬ ston 77 and the spherical surface, by the pressure of the fluid: during operation without pressure, or with negative pressure, the spring 84 and the spherical annular cap 81, taking up any design clearance and possible wearing, pre- vents knocking andvibrations . The assembly of the compensated seal ring according to the present invention is as follows: the ring 85 with pro¬ tuberances 86, eccentric by an amount Y, is introduced in- to the seat with an analogous ring arranged in a mirrored position with respect to axis SM, so that the incisions 87 on one ring correspond with protuberances 86 on the other ring without incisions; introduction into seats that may not be dismantled is made possible by the cut 89 provided in the part of the ring opposite the protuberances; the angular positioning of the pair of seal rings 85 is ensu¬ red by the eccentricity Y and the corresponding eccentri¬ city in the seat in the piston. Subsequently, the intro¬ duction of the piston with the pair of rings 85 occurs by overcoming the slight interference between the diameter DC of the ring and the effective diameter of the liner: the contraction required, to slightly reduce the diameter, oc¬ curs in the protuberances 86 provided with incisions 87 that operate as elastic elements; both the rings of the pair contract, but the reciprocal covering of the respec ¬ tive protuberances 86, with or without incision 87, arran¬ ged in mirrored positions, is not affected. Assembly of seal rings with protuberances arranged, not eccentrically, but along the entire internal diameter, is carried out in an analogous manner, but a means for preventing the rota¬ tion of the pair of seal rings has to be provided, as they always have to remain superimposed in a mirrored position, that is with the protrusions 86 provided with incision 87 coupled with protuberances 86 without incision. The recovery of clearance and wearing on the external diameter DC of the seal ring 85 occurs with the reduction of the contraction due to assembly with the said interfe- rence: the covering 90 with low friction material reduces wearing of the liner and of the seal rings to very low va¬ lues, permitting a very long lifetime even with tolerances that are not very limited. if in practice the materials, dimensions and operative details should be different from those indicated, but technically equivalent, the patent will still apply. So as the displacement P, for example, of the seal ring (12, 32, 52) can be negative, that is in an opposite posi- tion with respect to the plane of rotation of the pistons (B, E, or O) , for a more precise balancing in hydraulic transmissions with variable and rotating distribution. Also, the spherical foot 79 of the connecting rod 80 and the connecting rod itself may be lightened in the known manner, so reducing reciprocating masses .

Claims: CLAIMS 1. Articulation of the pistons with correction of the tra¬ jectories, for volumetric machines with curved liners, comprising the seal ring (12, 32, 52) of the piston posi¬ tioned outside the plane of rotation of the pistons (B, E, O) , but in a plane oriented at the centre of intersec¬ tion of the axes of rotation of the pistons and of the liner block, characterised in that it has sliding (10,C, 25, E) and/or oscillating elements (42, 48) in a direction which is tangential to the instantaneous trajectory of the piston and has elements in radial contact (14, 34, 53) between the piston and the relative support, to com¬ pensate the centrifugal forces acting on the mass of the piston. 2. Articulation of the pistons with correction of the tra¬ jectories according to claim 1, characterised in that to constituting the said sliding elements is a plane (C, E) which is parallel, at the dead-centre positions, with the said plane of rotation of the pistons (B, E) , fashioned inside the piston (1, 22) and on which slides a means (10, 25) made to oscillate on an axis which radial (Bl, El) with respect to the axis of rotation of the pistons. 3. Articulation of the pistons with correction of the tra¬ jectories according to claim 1, characterised in that, to constituting the said oscillating elements is a spherical surface (39,RI, 49,RI) coupledwith the piston positioned at the intersection between the plane of rotation of the pistons (O) and the axis (Ml) of the piston itself, coin¬ ciding with the tangent to the axis of the curved liner. 4. Articulation of the pistons with correction of the tra- jectories according to one of the claims 1, 2, characte¬ rised in that of a piston coupled, internally, so that it slides with spacer parallelepiped (10) , in turn coupled so that it oscillates on the extremity of the engine shaft (2) : an elastic element (6) is placed inside a ra¬ dial hole (4) of the said extremity which act on the lo¬ wer part (8) of the said piston, by means of a semi- cylinder (3) with the convex part facing towards the pi- ston, so as to keep the sliding surface (C) in contact with the surface of oscillation (9) between the piston (1) and the extremity of the shaft (2) . 5. Articulation of the pistons with correction of the tra- jectories according to previous claim 4, characterised in that of the elastic element consisting of a plate spring (6) with flexibility limited by the conformation of the said radial hole (4) , conveniently shaped or with two diameters (4,5) ; the spring is kept in place by an inter- nal axial safety ring (7) assembled in the lower part (8) of the said piston. 6. Articulation of the pistons with correction of the tra¬ jectories according to one of the previous claims 1, 2, characterised in that of the piston (22) is coupled to the prismatic stem by means of a semi-cylinder (25) whose plane slides on the said internal plane of the piston (E) and the curved surface (26) , with a radial axis of curva¬ ture (El) , with concave side facing towards the piston; the said piston has an internal lower protruding bulge (29) , with centre of curvature coinciding with the semi- cylinder, kept in position by a retaining ring (30) under the action of the axial clearance recovery spring (31) : the internal sides (35) of the piston are inclined in a direction which is tangential to the trajectory to permit the piston to be inclined with respect to the prismatic stem (24) . 7. Articulation of the pistons with correction of the tra- jectories according to one of the previous claims 1, 3, characterised in that of a hollow sphere piston (40) is coupled to a spherical support (39) and kept in position there so that it may slide by means of a cap (41) of the fixing screw; an annular zone (42) with eccentric sphere (R) with respect to the centre of curvature; the screw has an intermediate shank (44) for the admission of the edges of the central hole (43) ; a lower stretch of the piston (45) with rake angle greater than the semi-incli¬ nation of the block of curved liners; the piston is ad¬ vantageously made of a plastic or other similar material, suitable for the type of fluid used. 8. Articulation of the pistons with correction of the tra¬ jectories according to one of the previous claims 1, 3, to the previous claim, characterised in that of the pi¬ ston with spherical support (48) surface oscillating on the spherical head (49) of the prismatic stem (50) , kept in position by two ledges (53) positioned in the lower part of the said piston, which in turn are in contact with the protrusions (55) of an annular spring (54) posi¬ tioned between the ledges and the head; two flexing cham¬ bers (56) in the said head corresponding with the protru- sions and the ledges; the sides of the ledges are incli¬ ned (58) to facilitate assembly. 9. Articulation of the pistons with correction of the tra¬ jectories according to one of the previous claims 1, 3, 8, characterised in that of the curvature of the sides of the piston in a tangential direction having a radius ( ) which is less than the radius of the liners; in a radial direction with the major and minor radius of curvature equal to that of the curved liner (46) . 10. Articulation for volumetric machines with prevalent unloading of the thrust from the pistons, in combination, or not, with the said articulations of the pistons with correction of the trajectories, in volumetric machines with curved liners, comprising the piston with spherical coupling to the load transmission element (64, 80) , cha¬ racterised in that of the load transmission element is directly exposed (63, 79) to the pressure of the fluid over an area which is much greater than that to which the piston is exposed (65, 77) ; an elastic element (72, 84) is positioned between, even using a ring with a semi- spherical cap (SA, 81) , between the said piston and the 5 said load transmission element, to close any clearance. 11. Articulation for volumetric machines with prevalent unloading of the thrust from the pistons, according to the previous claim, characterised in that for volumetric 10 machines for gases the position of the seal ring (73, 78) between the piston and the liner is in a position behind the spherical coupling (63, 79) with the load transmis¬ sion element . 15 12. Articulation for volumetric machines with prevalent unloading of the thrust from the pistons, according to the previous claim 10, characterised in that of for volu¬ metric machines for liquids, the position of the seal ring (73, 78) between the piston and the liner in a posi- 20 tion behind the spherical coupling (63, 79) with the load transmission element. 13. Articulation for volumetric machines with prevalent unloading of the thrust from the pistons, according to 25 the previous claim 10, characterised in that of the ela¬ stic element advantageously consisting of a Belleville washer. 14. Articulation for volumetric machines with prevalent 30 unloading of the thrust from the pistons, according to one of the previous claims 10, 11, 12 or 13, characteri¬ sed in that in machines with curved liners: the piston (65) is coupled to the piston support plate (61) with spherical coupling (71) and with radial support on a be- 35 vel (67) on the stem to compensate the radial thrust. 15. Seal system with compensated ring, for volumetric ma¬ chines in combination, or not, with the said articula- - 23 - tions of the pistons of previous claims, comprising rings with an elastic return, characterised in that the said rings (85) have at least two internal symmetrical protu ¬ berances (86) , of which half of them having an incision 5 (87) towards the outside; a pair of rings is assembled in a single seat with the rings arranged specularly with re¬ spect to the axis of symmetry (SM) so as to cover the protuberance/s with incision with that/those without in¬ cision; the rings may be broken (5) in order to facili- 10 tate assembly in seats that may not be dismantled, but in a position that is removed from the zone of the protube¬ rances and from the axis of symmetry. 16. Seal system with compensated ring, according to pre- 15 vious claim , characterised in that of the arrangement of the protuberances concentrated prevalently on a stretch of ring; the eccentricity (Y) arising being on the said axis (SM) of symmetry. 20 17. Seal system with compensated ring, according to pre¬ vious claim 16, characterised in that of the depth (RB) of the protuberances and of the incisions (IB, RI) being proportional to the said eccentricity (Y) . 25 18. Seal system with compensated ring, according to one of previous claim 16, 17, characterised in that of a li¬ ning (90) of low friction material securely anchored (91) to the external diameter (DC) . 30 35

Inventors: PECORARI FELICE, PECORARI, FELICE
Applicants: I SOCIETA APPARECCHIATURE IDRA, PECORARI FELICE, PECORARI, FELICE, S.A.I. SOCIETA' APPARECCHIATURE IDRAULICHE S.P.A.
Application year: 1996
Main classification: F04B1
IPC codes: F04B1, F04B39, F04B53