Abstract:
A hydraulic machine includes radial cylinders including, oscillating radial cylinders arranged in a crown or star of cylinder-piston units, the pistons of the groups are made slidable on a crankshaft or with a cam, or on interposed members concentric to it, and realizing the reciprocating motion in the oscillating cylinders. The oscillating cylinders are placed in contact with a surface of distribution concentric or corresponding to the surface of oscillation of the respective cylinder on which a distributor body is placed separate from the machine body and housed in a seat in the body, or part fixed to the body, of the hydraulic machine, and each distributor body is mobile in its seat under the action of the pressure of liquid in connection on the back surface of the distributor body against the surface of distribution of the oscillating radial cylinder subject to the distribution.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a hydraulic machine with oscillating radial cylinders and single distribution members for each cylinder, that is to say, a hydraulic machine of the type known in the art, with radial cylinders, where cylinders arranged in a star pattern and acting on the same throw or crank of the motor shaft are placed in oscillation with respect to the body of the machine. Moreover, the distribution of the pressurized or discharge liquid is carried out in each cylinder individually and has improved characteristics with respect to the known art of radial hydraulic machines in order to achieve relevant technical-economic results with respect to it. 
       PRIOR ART 
       [0002]    The prior art includes various types of radial hydraulic machines with cylinders arranged in a star pattern and in particular it includes solutions proposed to realize the distribution with the application of one single distributor for each cylinder in such a way as to have a better operation of the hydraulic machine and reduce its axial encumbrances. 
         [0003]    In the art, as said above, these hydraulic machines are made in various ways in which a first way is to use the oscillation of the cylinder body to open and close ports on the surface of oscillation in their turn connected to channels of feeding and discharge, respectively, of the hydraulic liquid. A realization with these characteristics is described in the patent DE 359543 in which each cylinder has a cylindrical external surface with an axis parallel to the motor shaft in such a way as to make the cylinder and the piston oscillating, with reciprocating motion, with the coupling sliding on the throw of said motor shaft. At a diameter external to the cylinders there are annular channels with the delivery and discharge liquid and, between them and the surface of oscillation, two radial ports connecting each channel to a slit in the cylinder head in communication with its inside. The oscillation of the cylinder around its own axis determines the connection to one or the other channel and the passage in the intermediate position at the upper and lower dead centres of the piston with the closure of each passage of liquid from the cylinder to the channels. 
         [0004]    Moreover, a similar solution makes it necessary to make the surface of oscillation of the cylinder tight, inasmuch as the ports, if they are not in connection with the port of the cylinder, must seal the pressurized liquid inside them with respect to the internal space of the hydraulic machine where the drawn liquid, that is to say, come out due to the inaccuracy of the seals and of the sliding surfaces in the oscillating or sliding motion of the parts, is collected, making the known solution unsuitable in the construction of current hydraulic machines with radial cylinders with high performances. They are known for their high rotation speeds and, in particular for the hydraulic motors, also for their minimum working displacements, being commonly built with variable displacement, and for the very high pressures reached in these conditions. 
         [0005]    Therefore, in the art is known a second way of realizing the single distribution for each cylinder with a slide valve, controlled by the oscillating motion of the cylinder by means of cams or by means of the same oscillating motion of the cylinder and/or of the piston. In this second way of distribution of the feeding to the cylinder among the various solutions, also the document GB 2167138 is known, in which a radial hydraulic motor has a slide valve, single for each radial cylinder, which is controlled in an electronic way by a microprocessor on the basis of the values of the motor operation parameters connecting the respective channel with the liquid from or to the cylinder, to realize its operation. 
         [0006]    A similar realization, even if adjustable in the best of the ways with the modulation and control of the opening and closing of the valve, makes the radial hydraulic motor very expensive and always needing electronic devices such as the sensors, the slide valves controlled by a solenoid and the microprocessor, so as to exclude its application in mobile machines or that, for safety reasons, cannot be equipped with electric installations. Moreover, the realizations of hydraulic motors with a slide valve, as one single distributor per cylinder, are expensive, due to the mechanical parts of connection between the valve and the oscillating cylinder-piston complex, and furthermore are highly sensitive to the impurities in the hydraulic fluid in such a way as to make the greater construction cost in the presence of more marked maintenance costs not convenient. 
         [0007]    In the art hydraulic machines with radial cylinders with no liquid or fluid leaks are also known. An embodiment of these machines is described in the patent U.S. Pat. No. 6,511,306 in which the cylinders, four and opposite two by two and with the pairs of opposite cylinders at a right angle, are slidable from and towards a distributor sliding transversely to the axis of the cylinder and provided with a port of connection of the cylinder to respective delivery and discharge ports on the sliding surface. The avoidance of the leaks is obtained by making the sliding surfaces flat and providing the piston with a protuberance at the upper dead centre engages the connection port and translates the distributor on the sliding surface in an alternate way, like the motion of the piston within the cylinder, but cylinders associated at a right angle and connected to each other on a rigid cross. The delivery and discharge ports are made on a body inserted in the housing of the hydraulic machine, at the head to each cylinder, and housed with elastic elements, to press on the sliding distributor and prevent fluid leaks. Finally, the connection of the fluid delivery and discharge channels from the housing to an inserted body occurs on a surface parallel to the direction of axial sliding of the pistons, to eliminate the influence of the pressure forces, due to the pressure of the fluid, between the inserted body and the translating distributor. 
         [0008]    Thus, if the realization described allows to achieve the aim of having no leaks, it is not applicable to usual hydraulic motors or hydraulic machines with many oscillating radial cylinders both due to the limitation in the direction of the movements, forcedly right-angled, and in the realization of a similar distributor for each of the radial cylinders to reach greater displacement in a very reduced encumbrance, after the complexity of construction described in the mentioned document. 
         [0009]    The prior art are also comprises hydraulic machines with radial cylinders, as in document FR 2296778A1, in which a disc distributor is arranged coaxial to the motor shaft and rotating synchronously with it. The rotating disc distributor opens and closes with its motion the connection channel with a respective cylinder of one of the two crowns of radial cylinders of the specific realization described. The single cylinder is provided with a spherical surface of oscillation and put in contact with a spherical surface made mobile to maintain a constant contact pressure on the spherical surface of oscillation of the cylinder as pressure changes. The distribution is carried out by the rotating disc distributor maintaining long channels under pressure or discharge on the basis of the momentary connection ensured by the angular position of the distributor disc. This embodiment does not suggest any solution for the limits of the prior art seen in the previous prior documents, because it maintains the limits of most of the hydraulic machines with radial cylinders: a harmful volume of hydraulic liquid between the distributor and the cylinders and the pouring of hydraulic liquid between the body of the machine and the oscillating cylinder affects the distribution of the forces between the cylinder and the seat, in such a way as to have a different behaviour on the basis of the connection of the feeding channel when connected to the pressurized branch or to the discharging branch. 
         [0010]    A hydraulic motor with radial cylinders, in which the cylinders have a spherical surface of oscillation with a centre of oscillation next to the centreline of the piston stroke in the cylinder, is also known from document FR 1530605. The distribution occurs by means of radial channels from the exterior of the spherical surface, from opposite areas of the surface and towards the centre with separate channels: on the one side an branch of the hydraulic circuit; on the other side the other branch of the hydraulic circuit to which the motor is connected. Therefore the distribution occurs by oscillation of the cylinder, which with the motion opens and closes the ports between feeder channels and the cylinder itself in such a way as to introduce or discharge the hydraulic liquid from the cylinder on the basis of the pressure of the branch that is connected to the cylinder and of the rotation of the motor shaft. Even if this embodiment shows how it is possible to realize the distribution without the aid of rotating (disc) or translating (slide valve) external means, the technical problem of balancing the pressure of the hydraulic liquid on the external surface of oscillation on the basis of which branch is under pressure. That is to say, only one of the branches being under pressure, the other is obviously connected to the exhaust, to carry out the passage of hydraulic liquid that generates rotational mechanical energy of the motor shaft. Therefore the surface of oscillation of the cylinder remains subject to a non-small pressure, but from time to time towards one side or the opposite side, on the basis of which branch is under pressure, creating overload and sliding wear inasmuch as, on the spherical surface, there is also the reaction of the thrust of the pressure internal to the cylinder always and anyway released on the spherical surface between the two side zones that perform the distribution. The deriving wear limits the use of such embodiment to hydraulic motors operating at relatively low pressures of liquid and low rotation speeds. 
         [0011]    Such background art is susceptible of significant improvements as regards the possibility to make an improved radial hydraulic machine, of the type with oscillating cylinders, which overcomes the aforementioned drawbacks realizing a single distribution for each cylinder, in such a way as to reduce the encumbrances and the harmful spaces to distribute hydraulic fluid to the cylinders avoiding the drawbacks generated in the embodiments known in the art. 
         [0012]    The technical problem, therefore, that is at the basis of the present invention is to make an improved radial hydraulic machine of the type with oscillating cylinders in which an effective and simple distributor operates in connection with each oscillating radial cylinder, avoiding leaks in all conditions of use, as well as it allows sealing also at high pressures, high rotation speeds of the machine as well as at the known operations with minimum oscillation angles. 
         [0013]    An additional and further aim of the present invention is to realize the distribution in a radial hydraulic machine of the type with oscillating cylinders in which the passage of the fluid occurs in the best sealing and dynamic conditions also upon changing of the displacement in hydraulic motors that, notoriously, occurs by decreasing the angle of oscillation, maintaining acceptable the thrusts that are generated between the surface of the distributor and the sliding surface of oscillation of the radial hydraulic cylinder. 
         [0014]    Finally, a further part of the technical problem mentioned above concerns the realization of an improved radial hydraulic machine of the type with oscillating cylinders in which the section of the feeding/discharge ducts from each cylinder realizes a constancy of the speed of passage of the fluid also in the presence of angles of oscillation of different size. 
       SUMMARY OF THE INVENTION 
       [0015]    This problem is solved, according to the present invention, by a hydraulic machine, comprising oscillating radial cylinders arranged in a crown or star pattern of cylinder-piston units; the pistons of said units are made sliding on a crankshaft or with a cam, or on interposed devices concentric to it, and realize the reciprocating motion in the oscillating cylinders; characterised in that said oscillating cylinders are put in contact with a concentric surface of distribution or corresponding to the surface of oscillation of the respective cylinder on which a distributor body is placed separate from the machine body and housed in a seat in the body, or part fixed to the body, of the hydraulic machine; moreover, each distributor body is mobile in its seat under the action of the pressure of the liquid in connection on the back surface of said distributor body against the surface of distribution of the oscillating radial cylinder subject to the distribution. 
         [0016]    Moreover, in an improved embodiment: each back surface, with respect to said surface of distribution, of said distributor body is divided into liquid tight zones with an equivalent area, in order not to influence sealing according to the direction of the motion of the hydraulic liquid. 
         [0017]    Furthermore, in a preferred embodiment: said liquid tight zones, of the back surface of the distributor body, are made concentric and subdivided into a central zone and peripheral zone. 
         [0018]    Moreover, in a further embodiment: each cylinder has a pair of slits for the connection of an branch of the hydraulic circuit to one or the other corresponding pair of distribution ports for the connection of an branch of the hydraulic circuit: the two pairs of slits being made interposed and with an angular position relative to the axis of the cylinder corresponding to the maximum oscillation in the operation of the oscillating hydraulic cylinder allowed to the machine. 
         [0019]    Furthermore, in an advantageous embodiment: the connection between the respective liquid tight zone, be it central, peripheral or generic, and the corresponding opening or pair of ports is made with holes having a predetermined section. 
         [0020]    Moreover, in an improved embodiment: each cylinder is hydraulically connected by means of the respective distributor body to annular channels of feeding and discharge of the hydraulic liquid. 
         [0021]    Furthermore, in a preferred embodiment: in which each cylinder is hydraulically connected by means of the respective distributor body to internal channels of feeding and discharge of the hydraulic liquid from a static central body. 
         [0022]    Moreover, in a specific embodiment: the feeding or discharge ports in the distributor body have a protuberance for anticipating or delaying the opening or closing of the passage of the hydraulic liquid of the distribution. 
         [0023]    Furthermore, in a preferred embodiment: the ports are shaped with the edge facing the slit in the cylinder that has a swell to realize sections of passage of the hydraulic liquid variable with the variation of the angle of oscillation in the hydraulic motors working with reduced displacement. 
         [0024]    Finally, in a specific embodiment: the hydraulic machine has a connection channel in each oscillation guiding trunnion and a respective distribution slit facing a corresponding single port on a single distributor body on each trunnion, having a surface of distribution corresponding to the surface of oscillation of the trunnions and of the cylinder as a whole. 
         [0025]    The characteristics and the advantages of the present invention, in the embodiment of a hydraulic machine with oscillating radial cylinders and single distribution members for each cylinder, are mentioned in the description made in the following, of some schematic examples of execution given for indicative and non-exhaustive purposes, with reference to the nine tables of drawings enclosed. 
     
    
     
       SHORT DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  shows a schematic section on a plane transverse to the axis of the motor shaft of a hydraulic machine with radial cylinders, here a hydraulic motor, in correspondence of the plane containing the cylinders of the star, according to the invention, provided with single distributors of the hydraulic fluid one for each cylinder at their external end of oscillation; 
           [0027]      FIG. 2  shows a schematic section II-II of the hydraulic motor with radial cylinders of  FIG. 1  made on a cylinder at the upper dead centre; 
           [0028]      FIG. 3  shows a schematic section of a single distributor body present in the oscillation head of each cylinder of the hydraulic motor of  FIGS. 1 and 2 ; 
           [0029]      FIG. 4  shows a schematic view axial to the axis of the cylinder and from the side of the feeding and discharge channels of the hydraulic fluid, of the single hydraulic distributor of  FIG. 3 ; 
           [0030]      FIG. 5  shows a partially sectioned schematic view, in the surface of oscillation, of an oscillating cylinder of the hydraulic motor with radial cylinders of  FIGS. 1 and 2 ; 
           [0031]      FIG. 6  shows a schematic view of a hydraulic machine with radial cylinders, here a hydraulic motor with a double crown of radial cylinders, wherein the cam is external and the central pin acts as a support and body with the channels of feeding/discharge of the hydraulic fluid: it is used in the power-operated wheel centres because it has the external skirt rotating with the cams to constitute a hollow motor shaft; 
           [0032]      FIG. 7  shows a schematic section on a plane transverse to the axis of the motor shaft of a hydraulic machine with radial cylinders, here the hydraulic motor of  FIG. 6 , in correspondence of the plane containing the cylinders of a star, according to the invention, equipped with single distributors of the hydraulic fluid, one for each cylinder at their oscillating internal ends; 
           [0033]      FIG. 8  shows a schematic section on a diametral plane containing the axis of the motor shaft of a hydraulic machine with oscillating radial cylinders on trunnions, here a hydraulic motor, in correspondence of the plane containing a cylinder and its axis of oscillation, according to the invention, and equipped with single distributors of the hydraulic fluid, one for each cylinder, on one of the two trunnions; 
           [0034]      FIG. 9  shows a schematic perspective view of an oscillating hydraulic cylinder, similar to that of  FIG. 1 ,  2  or  5  in which the connection slit of the hydraulic cylinder with the ports has a spilt arrangement to increase the section of passage; 
           [0035]      FIG. 10  shows a schematic perspective view of a distributor for oscillating hydraulic cylinder, similar to that of  FIG. 1 ,  3  or  4  in which the delivery/discharge ports of the distributor have a split arrangement to increase the section of passage towards the connection slits of the hydraulic cylinder of  FIG. 9 ; 
           [0036]      FIG. 11  shows a schematic perspective view of an oscillating hydraulic cylinder, similar to that of  FIG. 1 ,  2  or  5 , and wherein the connection slit of the hydraulic cylinder with the ports has a split arrangement to increase the section of passage, as well as the oscillation of this cylinder is provided on the sealing surface of the hydraulic distributor; 
           [0037]      FIG. 12  shows a schematic view of a distributor like that of  FIG. 10  from the side of the surface of oscillation of the cylinder; 
           [0038]      FIG. 13  shows a schematic diametral section XIII-XIII of the distributor of  FIG. 12 ; 
           [0039]      FIG. 14  shows a schematic diametral section XIV-XIV of the distributor of  FIG. 12 ; 
           [0040]      FIG. 15  shows a schematic view from the side of the channels of feeding/discharge of the distributor of  FIG. 11 ; 
           [0041]      FIGS. 16   a  to  16   h  schematically show the movement of oscillation of the pair of slits on the cylinder with respect to the pair of ports of the distributor of  FIGS. 12 to 15 , during the cycle of a complete oscillation of the cylinder in sequence from  16   a  to  16   h;    
           [0042]      FIGS. 17 ,  17   rn  and  17   rp  show a schematic representation of the shapes of the ports with respect to a generic central slit of an oscillating cylinder, with no overlap,  FIG. 17 , negative overlap,  FIG. 17   rn , or positive overlap,  FIG. 17   rp , respectively; 
           [0043]      FIGS. 18   a  to  18   d  schematically show a shape of the ports with respect to the generic central slit of an oscillating cylinder, according to the invention, with no overlap, in the position at the dead centres, and in three different phases of opening with a low angle of inclination of the respective cylinder in the oscillation, evidencing the progressiveness of the port of the section of passage between the involved port and the slit. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0044]    In  FIGS. 1 and 2 , in a first embodiment of a single distributor for oscillating cylinder, according to the invention, one can see a hydraulic machine  1 , here is represented a hydraulic motor with radial cylinders  2  arranged in a star pattern, placed to slide on a motor shaft  3 , with a cam to constitute the crank  4 , by means of known shoes  5  of the single piston. On the head of each cylinder there is a slit  6  of communication with annular channels  7  and  8 , to the star of cylinders, to carry out the delivery and the return of the hydraulic fluid for operation. Each annular channel is provided, towards each cylinder, with a fluid feed radial duct  9 . The two radial ducts  9  connected to a respective cylinder  2  feed the fluid in a seat  10  for housing a distributor body  11 , housed with play, but sealed in said seat: each radial duct  9  is connected to a different zone of the surface of the distributor body, but on the same side, the zones are provided with a separation seal between them and towards the inside of the hydraulic machine. The distributor body  11  has on its inside shaped ducts  12  and  13 , respectively, to put in hydraulic connection the different zones  14  and  15 , respectively, of said distributor body with the oscillating cylinder  2  on the cylindrical surface of distribution  16 , where there is the passage of the hydraulic fluid from the distributor body, through ports of distribution  17  and  18  corresponding to said shaped ducts  12  and  13 , to realize the alternate passage in delivery and in discharge of the hydraulic fluid through said slit  6  at each of the two annular channels and the respective cylinder  2  as required by the instantaneous phase of the cycle. 
         [0045]    Furthermore, the cylinder  2  has trunnions  19  for defining an axis of oscillation with respect to which the cylindrical surface of distribution  16  is centred, that is to say, the oscillation occurs by means of the guide of the rotation surfaces  20  of the trunnions, which are connected in a rotating manner to the walls  21  and  22  of the hydraulic machine  1 ; each of the annular channels  7  and  8  is connected with a respective attachment  23  and  24  of the duct of the hydraulic circuit, on said walls of the hydraulic machine, by means of holes  25  in said walls. Therefore, the piston  26  is provided with a crown  27  which at the upper dead centre occupies the high part  28  of the cylinder  2  considerably reducing the harmful volume that remains occupied by the fluid. Moreover, in  FIG. 3  one can see the seat  29  of the front seal, for the zone  14  of the shaped channel  12 , as well as the seat  30 , for the circumferential seal of the zone  15  of the shaped channel  13 . 
         [0046]    The sizing of the zones  14 , of the shaped channel  12 , and zone  15 , of the shaped channel  13 , are calculated in such a way as to have the same surface and, therefore, the thrusts generated through them by the pressure of the hydraulic fluid are almost identical in proportion to the pressure. The pressure, which is present in the cylindrical surface of distribution  16 , is balanced by the constancy of the pressure due to the equality of the surfaces of the zones  14  and  15 , in such a way as to ensure a balance of the thrusts on the body distributor  11  and limit the thrusts between the trunnions  19  and the rotation surfaces  20  of the latter. The constancy of the thrust between the distributor  11  and cylinder  2  ensures the sealing on the surface of distribution also in the absence of specific holding means, because the mobility of the distributor body does not transfer all the thrust of the hydraulic liquid on the cylinder in the surface of oscillation of the trunnions, but only the residual thrust not compensated for between the thrust of the hydraulic liquid in the cylinder and the thrust on the surface of distribution. 
         [0047]    In  FIGS. 6 and 7  one can see a further embodiment of hydraulic machine  31  with radial cylinders  32  arranged in a star pattern and having each piston  33  sliding on the internal cam  34 ; the cylinders are subdivided, in the representation of the hydraulic machine, here a hydraulic motor, on a double crown of cylinders and in which the internal cams  34  are connected and rotating with a hollow motor shaft  35 , which is usually known to constitute a wheel centre with hydraulic motor, housed directly inside the driving wheels of a vehicle. The hydraulic machine  31  has a side wall  36 , of connection to the supporting structure, not shown here, and a side wall  37  of attachment of an off-axis duct  38  and an axial duct  39 , for the feeding and discharge hydraulic fluid to it; said ducts are extended in a static central body  40  of the hydraulic machine  31 . 
         [0048]    As it can be seen in the Figures, each cylinder  32  is supported in its oscillation by means of trunnions  41  on the rotation surface  42 , in a way similar to the cylinders  2 ; there being two crowns of cylinders arranged in a star pattern, between them is provided an intermediate support ring  43  of the rotation surfaces  42  of the trunnions  41  between the two crowns  44  and  45  of oscillating cylinders. Each cylinder  32  is constituted in a way similar to the cylinder  2  with a slit  6  in contact with a surface of distribution  16  of a distributor body  11 . Each piston  33  has a shoe  5  sliding on said cam  24  of the crown  44 ,  45  of the cylinders arranged in a star pattern. Moreover, the piston  33  has a crown  27  which at the upper dead centre occupies a high part  28  of the cylinder  32 , to reduce the harmful volume of hydraulic fluid that at every cycle remains inside the cylinder. Thus, as visible, each duct  38  or  39  in the static central body  40  is connected to a seat  46  of the distributor body  11  by means of connection channels, respectively,  47 , from the axial duct  39 , and  48  from the off-axis duct  38 ; the latter in correspondence of each crown of cylinders has an annular duct  49  to allow for the connection of the corresponding channels  48  of each cylinder, avoiding the central part of the static central body  40 , that is to say, where there is the axial duct  39 . 
         [0049]    In  FIG. 8  one can see a further embodiment in which a usual hydraulic machine  50  with radial cylinders, here advantageously in the form of a motor, with the cylinders  51  oscillating on axes of oscillation defined by trunnions lateral to the oscillating cylinder, a supporting trunnion  52  and a trunnion of feeding  53  and discharge of the hydraulic fluid, which occurs by means of a channel  54  in the trunnion. In the rotation surface  55  of the trunnion of feeding  53  there is a distributor body  56 , similar to the body  11  described at the head of the cylinders  2  or  32 , here to connect for the distribution adjacent annular channels  57  and  58 , internal to said rotation surface  55 , for the delivery and discharge, which acts simultaneously as a surface of distribution of the hydraulic fluid. The annular channels  57  and  58  are connected by ducts in the axial direction  59  and  60 , respectively, to the attachments  61  and  62  of feeding and discharge from the hydraulic circuit in which the hydraulic machine  50  is connected. In this way the side cover  63  of the motor case  64  allows for the passage of a second end  65  of the motor shaft  66  wherein, in the known embodiments, a rotating disc distributor is generally housed for the delivery/discharge of the hydraulic fluid from the cylinders. Finally, a usual piston  67  is placed in sliding contact on the crank  68  of the motor shaft in a known way. For similarity of construction the distributor body  56  is constituted and operates in a way similar to the already described distributor body  11 . The distribution therefore occurs by the oscillation of a slit  69  present in the rotation surface of the trunnion of feeding  53  in correspondence of ports, in the distributor body towards the annular channels through the surface of distribution, ports connected to said annular channels  57  and  58 , as described for the previous embodiments. 
         [0050]    In  FIGS. 9 and 11  one can see embodiments of an oscillating cylinder  70  with rotation trunnions  71  and an oscillating cylinder  72  where the rotation surface  73  coincides with the surface of distribution and the function of positioning to rotation is performed by parts  74  of the surface of oscillation undercut with respect to the radial direction of positioning of the cylinder in the star of cylinders of the hydraulic machine in which they are inserted. In  FIG. 10  one can see a distributor body  75 , similar to the distributor bodies  2  and  32 , with a different arrangement of the ports and of the shaped channels of distribution from and towards the oscillating cylinder. That is to say, the oscillating cylinders  70  and  72  have a double connection slit  76  through the surfaces of distribution with an increased section of passage with respect to the previous ports  6  or  69  because it is determined not by the width of the slits, but by the holes  77  present in them, which connect the surface of distribution  73  to the inside of the oscillating cylinder  70  or  72 . 
         [0051]    Each of the two slits  76  is positioned at a radial angle, with respect to the axial direction D of the centreline of the relative oscillating cylinder  70  or  72  at an angle greater than the corresponding maximum angle of oscillation of said cylinder. In this way each single slit  76  behaves like a slit  6  or  69  of a distributor body  11  or  56  with the relative oscillation of the surface of distribution  73  of the cylinder on the surface of distribution  78  of the distributor body  75  with split ports  79 , for a connection of the hydraulic fluid from a central zone  80 , of connection of the shaped channels, and  81 , for the connection of the hydraulic fluid from a peripheral zone  82 , on the corresponding and opposite branch of the hydraulic circuit in the operation of the hydraulic fluid in delivery or discharge. The connection between the peripheral zone  82  and the ports  81  occurs by means of peripheral holes  83  between said zone and the ports; thus, the connection between the central zone  80  and the ports  79  occurs by means of central holes  84 ; thus the peripheral zone is delimited on the external diameter of the distributor body  75  by means of a seal housed in a circumferential hollow  85 . 
         [0052]    In  FIGS. 12 to 15  the shape is clearly shown with the already indicated numerical references; moreover,  86  indicates an annular channel in the peripheral zone  82  for distributing hydraulic fluid to the peripheral holes  83  in a uniform way;  87  indicates a front annular seat for a seal of delimitation between said peripheral zone  82  and said central zone  80 . 
         [0053]      FIGS. 16   a  to  16   h  show the reciprocal oscillating movement between a distributor body  75 , housed in its seat  88 , of a generic motor case of a hydraulic machine with radial cylinders, on which a central duct  89 , of feeding of the central zone  80 , and peripheral ducts  90 , of feeding of the peripheral zone  82  converge. In the sequence of the phases one can clearly see the following positioning of the slits  76  on the surface of distribution of the oscillating cylinder, in contact with the corresponding surface of distribution  78  in the distributor body  75 . In  FIG. 16   a , with the cylinder and the piston at the upper dead centre, the slits  76  are in the closing position with respect both to the ports  81  of the peripheral zone and to the ports  79  of the central zone of the distributor body; then, in the following,  FIG. 16   b , the oscillation in the direction A of the cylinder begins the opening of the passage of hydraulic fluid from the ports  81  of the peripheral zone in the slits  76 ; in  FIG. 16   c  the amplitude of the oscillation towards A is maximum, so  FIG. 16   d  shows the return oscillation motion in the direction B of the cylinder, until reaching, at the lower dead centre,  FIG. 16   e , the closing position of the ports, both of the peripheral zone  81  and of the central zone  79 , with respect to the slits  76 . So again in the oscillation in the opposite direction, in  FIG. 16   f  one sees that the slits  76 , in the oscillation of the cylinder in the direction B, are put in communication with the ports of the central zone  79 , until reaching the complete opening, in  FIG. 16   g ; and, moreover, the completion of the cyclical oscillation motion can be seen in  FIG. 16   h  in which, with a following oscillation in the direction A from the position of complete opening, of the ports of the central zone  79  towards the slits  76 , the oscillation motion of the cylinder causes the closure of the passage of hydraulic fluid from the ports  79  of the central zone of the distributor body  75  towards the cylinder through the slits  76 . At the end of the cycle of oscillation the position of the slits and of the ports in the distributor body  75  returns that of  FIG. 16   a , that is to say, again with the cylinder and the stroke of the piston in it at the upper dead centre. 
         [0054]      FIGS. 17 ,  17   rn  and  17   rp  show the embodiments of a single slit like  6  or  69  of the arrangements with a distributor body  11  for single slit in the corresponding oscillating cylinder  2  or  32  or even in the trunnion of feeding  53 . In fact, the ports  17  and  18  are made with no detachment or overlap with respect to the width of the slit  6 , as shown in  FIG. 16 , in such a way as to realize no overlap, that is to say, a clear opening/closing of the passage of hydraulic fluid and with no possibility also of partial mixing of the flows of hydraulic fluid. In the case, on the other hand, of realizing a gentler or softer way of opening and closing of the hydraulic flow of fluid through the ports of delivery and discharge, there is provided a small protuberance of advance  91  towards the slit  6  of a port  92 , for example the left one in  FIG. 17   rn , so that, in the opening of the passage of fluid at the dead centres of the piston of the cycle of oscillation of the cylinder, the fluid begins to flow also a moment before the effective opening of the port; in a similar way the port  93  of the branch of the opposite hydraulic circuit has a small protuberance of delay  94  towards the slit  6 , which maintains slightly in communication the port  93  with the slit  6  also in the position of centred overlap shown in  FIG. 17   rn . This arrangement of the protuberances that anticipate and delay the passage of hydraulic fluid between the ports  92  and  93  and the slit  6  makes a negative overlap, that is to say, allows for a short mixture of the flows of hydraulic fluid inflowing/outflowing from the oscillating cylinder decreasing their noise and vibrations and realizing a gentle and soft operation of the hydraulic machine on which they are made. In particular embodiments, then, if precision and safety of the operation of distribution are required, the overlap can be made greater than the simple port of the slit  6 , as shown in  FIG. 17   rp , in it in the position of passage at the so-called dead centres of the oscillation of the cylinder between the slit  6  and the ports  17  and  18  of delivery/discharge of the distributor body there remains, due to construction, a thin overlap strip  95  in which the oscillation between the ports and the slit occurs, but not the passage of the hydraulic fluid between them, to make a positive overlap of distribution. 
         [0055]    As visible, finally, in  FIGS. 18   a  to  18   d  that show successive moments of port of the passage from a shaped port  96  of the hydraulic fluid, the constitution of the ports of delivery/discharge of the hydraulic fluid from the oscillating cylinder can occur also with a variable section of passage of the port with the increase/decrease of the amplitude of oscillation of the cylinder. This particular construction is useful in hydraulic motors with oscillating radial pistons and variable displacement, that is to say, which from a maximum value can be reduced to a minimum value, without for this reason cancelling the displacement, that is to say, the amplitude of oscillation; the motor, not having displacement would behave like a closed—that is to say—locking valve, failing its function of transforming the motion of the hydraulic fluid into rotational motion of the motor shaft. Said specific Figures show a variable port  97  to the left of the slit  6  and in a position of no overlap, as said for  FIG. 17 ; here, however, the variable port  97  has a swell  98  facing the slit  6  to open a minimum passage  99  of hydraulic fluid with a small angle of oscillation,  FIG. 18   b . As oscillation increases, the swell  98  opens the passage of hydraulic fluid in a more consistent way, as can be seen in  FIG. 18   c , of an increased passage  100 , and  18   d , of a complete passage  101 , in which the hydraulic fluid finds the port  97  almost completely open on the edge of the slit  6  facing it. 
         [0056]    The operation of the radial hydraulic machine described above, provided with oscillating cylinders  2 ,  32 ,  70  or  72  with one single distributor for each cylinder, occurs by the oscillation of the cylinder that, as known in the art, opens and closes the respective ports of feeding or discharge of the hydraulic liquid. Moreover, the present invention introduces a new solution in the way of realizing and operating the position of the ports of feeding and discharge and such as to significantly modify the way of construction of the hydraulic machines with oscillating radial cylinders in which it is applied. 
         [0057]    In fact, as it has been seen in the prior art, the main disadvantage was the sealing security of the ports on the surface of oscillation, which is also the surface of distribution of the hydraulic liquid from the body of the machine to the oscillating cylinder, for the correct operation. Mainly the pressure of the hydraulic liquid in one of said ports is generally different from the pressure in the other. In the solution proposed by the present invention this pressure, besides being present in the port, is also present in a back surface of the distributor body  11 ,  56  or  75 , that is to say, in the sealing zones  14  or  15  or in the central zone  80  and peripheral zone  82 , with respect to the cylinder head, in such a way as to push said body against the surface of oscillation of the cylinder. Moreover, the ports are always at least two, so considering the port with greater pressure, the other is obviously connected to the branch of the hydraulic circuit in discharge, it is the same pressure that acts inside the cylinder  2 ,  32  or  75 . In order to realize the most convenient operation of the distributor body  11 ,  56  or  75  described above, the force exerted by said pressure acts on the back face of the distributor body itself and ensures its contact, on the surface of distribution  16 ,  55  or  78 , in all operating conditions of the hydraulic machine and, moreover, the residual thrust from the compensation of the axial force developed in the oscillating cylinder by the pressure of the liquid that opposes it is the only one that is released through the surfaces of oscillation  20 ,  42  or  55  of the trunnions  19 ,  41  or  53  of the cylinder; that is to say, the thrust on the trunnions is reduced to values limited to the guide of the cylinder in the oscillation, but is not subject to the strong thrusts that are generated in the hydraulic machine with the oscillating cylinders provided with trunnions known in the art. Thus, considering that the high pressure can indifferently be present in one or the other of the ports of feeding or discharge, the back surface of the described distributor body is divided into two areas having an equivalent surface. In this way it is indifferent which of the two branches is under pressure and which in discharge: in any case the pressure that acts on the distributor body  11 ,  56  or  75  realizes the greatest thrust towards the surface of distribution in order to ensure tightness in the passage of the hydraulic liquid from the ports to the slit in the oscillating cylinder. 
         [0058]    Said operation does not comprise completely the embodiment of  FIG. 8  because the trunnions in it make up the support to the oscillation in the known way and also the surface of distribution, but said realization allows to free the encumbrance caused by the known disc distributor, arranged axially to the motor shaft, therefore to be able to realize hydraulic machines with a double connection of the motor shaft on both sides as visible in the Figure. Moreover, said construction shown is specifically a hydraulic motor with oscillating radial cylinders and, with the present invention, the change in the position of the distributor, from the usual of the disc type in a position axial to the shaft in the new represented shape, can also be made on hydraulic machines, or better hydraulic motors, already built, that is to say, it can be applied in a second moment with respect to the construction, or, can be made making only partial changes without designing a new hydraulic motor with oscillating radial cylinders with trunnions. 
         [0059]    The operation, instead, of the embodiment of the distributor body of  FIG. 9  and  FIGS. 12 to 15  is explained by the sequence of the phases of operation, that is to say, of oscillation of the cylinder of  FIGS. 16   a - 16   h , in which one sees that fundamentally the behaviour of the distributor body  75  operates in the way described above for the previous embodiment. The difference consists of the shape of the two slits  76  shown in the surface of distribution  73  of the cylinder; each slit is connected inside the cylinder through holes  77 , which determine the section of passage of the hydraulic liquid, in such a way as to obtain a wide section of passage of hydraulic liquid, wider than that obtainable from the single slit  6  of the cylinders  2  or  32 . Correspondingly the surface of oscillation  78  of the distributor body  75  has pairs of ports  79  and  81  angularly placed to simultaneously perform the closing of the ports at the dead centres of the stroke of the piston in the cylinder and the port of one or the other pair of ports, when opposite said pair of slits, during oscillation. Each port is connected to the back surface of the distributor body  75  with central holes  84 , to connect the ports  79  to the central zone  80 , and with peripheral holes  83 , to connect the peripheral zone  82 . The development of the two surfaces of the central and peripheral zone are similar and slightly greater than the area developed by the bore of the cylinder involved at the distributor body. The sections of passage from said zones on the back surface of the distributor body and the pairs of ports  81  and  79  are defined by said peripheral  83  or central holes  84 . 
         [0060]    Finally, the distribution ports  17 ,  18  or  79 ,  81  can, in order to realize gentler and less loud operations in the opening and closing of the passage of hydraulic liquid between them and the corresponding slit in the cylinder, be provided with contact edges with negative overlap, even if it is made only at one point of the side of the port, as visible in  FIG. 17   rn  in which the ports  92  and  93  are provided with protuberances  91 , of advance, and  94  of delay, respectively, in such a way as to realize even a very short passage of liquid from one port to the other, thus limiting the drops of pressure of the liquid in the cylinder. In a similar way, if a secure closure of the ports is required, it is possible to realize a positive overlap with an overlap strip  95  between the ports and the edges of the slit  6 . 
         [0061]    With the specific shape of the edge of the ports, as shown in  FIGS. 18   a  to  18   d , the edge itself can be made not linear in such a way as to make progressive, with the respective angular position reached, the section of port of the passage of a port with respect to the slit in the cylinder, where a so shaped distributor body act. In fact, in  FIG. 18   a  the two shaped ports  96 , drawn close to the slit  6 , realize a variable port  97  because they are of a shape with a swell  98  of the edge of the port drawn close to the slit  6 . In this way the passage of the relative position of the slit  6  towards a shaped port  96  generates an increasingly wide section of passage as, in the motion of oscillation of the cylinder, the slit  6  moves towards the shaped port  96  enlarging on the section of passage, but not in a sudden way: from the minimum passage  99  to the increased passage  100  to the complete passage  101  in which the front of the opening is almost completely open because of the variability of the side of the port due to the swell  98 . In this way in the operation of hydraulic machines with reduced displacement, typical of the hydraulic motors operated with minimum displacement, the section of passage of the hydraulic fluid allows to keep the speed of the hydraulic liquid in the passage of the port constant. 
         [0062]    The advantages in the realization and use of a hydraulic machine, with oscillating radial cylinders provided with a distributor for each single cylinder as described above, are expressed by a simple construction, for the realization of the distributor that, being made very close to the cylinder, does not need long connection channels of the single cylinder with the distributor, reducing the volume of hydraulic liquid between the cylinder and the surface of distribution, with respect to the distribution realized with the rotating discs known in the art. 
         [0063]    Moreover, the distribution of the hydraulic liquid by the described distributor body  11 ,  56  or  75  allows to balance in a correct way the sealing of the liquid in the surface of distribution  16 ,  55  or  78  both for the thrusts transmitted on it and for the reduction of the thrusts on the trunnions  19 ,  41  or supporting surface  20 ,  42  or  73  and  74 , and guide in the rotation of oscillation of the cylinder involved. That is to say, the possibility of movement allowed to the distributor body  11 ,  56  or  75  allows to realize the distribution of the hydraulic liquid as precisely as possible with respect to the known art. 
         [0064]    The realization of the single distributor for each cylinder, as visible in the Figures, allows to make hydraulic machines, in particular hydraulic motors, that, besides reducing axial sizes and encumbrances, allow for the construction of motor shafts  3  or  35  with two free ends  65  and  66  and this is also possible on already built hydraulic machines or hydraulic motors. 
         [0065]    Moreover, the realization of double slits  79  and  81  rather than one single slit in the cylinder  70  or  72  allows to increase the section of passage of the hydraulic liquid in the surface of distribution  73 , so the distributor body  75  is more balanced as the zones of pressure on its back surface are concentric to a central zone  80  for two ports  79  and a peripheral zone  82  for the other two ports  81 . 
         [0066]    Furthermore, the described shape of the distribution ports allows to adapt the mode of operation of the hydraulic machine to the specific needs also of hydraulic motors with variable displacement in such a way as to considerably improve operation with minimum displacement. 
         [0067]    In conclusion, the most evident advantages are achieved with one single distributor body for each cylinder that is made mobile and balanced in the thrusts to which it is subject, but further and more significant advantages are obtained with the shape of the edge of the ports, as described above. 
         [0068]    Obviously, an expert of the sector, in order to meet specific needs, may bring several changes to the above-described hydraulic machine with oscillating radial cylinders and single distribution members for each cylinder, all included within the scope of protection of the present invention as defined by the following claims. Thus, even if less conveniently, thanks to the subdivision of the back surface of a distributor body into central zone and peripheral zone each zone can be connected to a respective single port in correspondence of and operating with on single slit in the head of the cylinder involved. 
         [0069]    Moreover, even if less conveniently for production costs, the surface of distribution in addition to the cylindrical shape shown can also be of a convex, barrel-like or even spherical shape, so in combination with the sizing of the zones of pressure of the back surface of the distributor body the contact and the liquid tightness of the distributor is improved. 
         [0070]    Furthermore, the distributor body can be made with one single port and associated with a surface of distribution of a trunnion provided with a connection channel with the cylinder, similarly to what is shown in  FIG. 8 , but with both trunnions provided with a channel, with a respective slit centred in the position corresponding to the dead centres of the oscillating piston-cylinder complex, which connect the cylinder with annular ducts one on each side of the crown of cylinders. The distributor body for a similar realization has only one port angularly placed on the surface of rotation and distribution in such a way as to realize one of the overlap positions described in  FIG. 17  or  18  and on the other distributor body with single port the corresponding port to realize the described positioning between the ports and the slit. 
         [0071]    Moreover, an internal cam, like the cam  34  of the hydraulic machine of  FIG. 6  or  7 , can be made with several protuberances to realize several cycles of a single cylinder in the single rotation of the hollow motor shaft  35 . Finally, said internal cams in the case of a multiple crown of cylinders can be angularly offset in such a way as to increase the number of the thrust pulses and generate in a hydraulic motor a uniform torque.