Abstract:
The subject of the invention is an engine that is actuated by a fluid under pressure, preferably water, and comprises one or more oscillating, connecting-rod assemblies ( 13 ), including a cylinder ( 14 ) and a piston ( 15 ), and at least one or more cranks ( 16 ) driven by the connecting-rod assemblies ( 13 ). For each connecting-rod assembly ( 13 ), a preferably stationary valve ( 20 ) controls the feed and the discharge of the pressure fluid to and from it, synchronically with the angular position of the corresponding crank ( 10 ), and acts as the pivot about which connecting-rod assembly ( 13 ) oscillates. The engine can be applied for producing mechanical work in any apparatus, for example in sprinklers, concrete mixers, apparatus for winding cables or garden hose reels, and so on, or for the production of electrical energy. The actuating fluid can be used, after its discharge from the engine, for purposes for which high pressure is not required.

Description:
RELATED APPLICATIONS 
   This application is a National Phase Application of PCT/IL03/00231 having International Filing Date of Mar. 17, 2003, which claims priority from Israel Patent Application No. 148748, filed Mar. 18, 2002. 
   FIELD OF THE INVENTION 
   This invention relates to the production of mechanical power from hydraulic energy; in particular, it relates to an engine that is actuated by a fluid, preferably water, or gas, preferably air, under pressure. It further relates to a mechanism for actuating a shaft by means of a pressure fluid which comprises an oscillating, connecting-rod assembly and at least a crank driven by said connecting-rod assembly, as hereinafter defined. The invention further relates to the use of such a mechanism for actuating various mechanical apparatus. The invention further relates to a valve for controlling the feed and the discharge of pressure fluid to and from a connecting-rod assembly, synchronically with the angular position of the crank driven by said assembly. 
   BACKGROUND OF THE INVENTION 
   Fluid-actuated mechanisms for carrying out mechanical work are known in the art and have been described in a number of patents. U.S. Pat. No. 2,518,990 describes a fluid-actuated hose reel in a lawn sprinkler. U.S. Pat. No. 2,989,605 describes a water-powered retractable shower head. More recently, U.S. Pat. No. 5,741,188 discloses a ride-on toy or a garden tool which includes a stationary element, a movable element connected thereto, water pressure operating means for moving the movable element with respect to the stationary element, a water inlet and a water outlet, and a valve for controlling the flow of the water through the device. 
   European Application 136414 A2 discloses a water flow operated device for winding and/or unwinding a layer of flexible material which comprises a stationary element, a spool having a central axis, said spool being rotatable about a central axis when engaged with the stationary element; and a water flow-operated mechanism engaged by said stationary element for controllably rotating said spool. 
   Of particular interest to the present invention is Eliot U.S. Pat. No. 1,954,408 which discloses a fluid-driven engine, comprising: a drive unit connectable to a source of pressurized fluid and including a piston movable within a cylinder; a valve assembly controlling the introduction of pressurized fluid into the cylinder, and the discharge of spent fluid therefrom for driving the piston with respect to the cylinder; and a rotatable drive shaft including a crank arm coupled to the drive unit for rotating the drive shaft about a rotary axis; the piston projecting through one end of the cylinder and being pivotally coupled to the crank arm for rotating the drive shaft during forward and return strokes of the piston with respect to the cylinder; the opposite end of the cylinder being pivotally mounted to the valve assembly so as to oscillate with the piston between opposite sides of the drive shaft rotary axis during the forward and return strokes of the piston; the opposite end of the cylinder being formed with a port through which pressurized fluid is introduced and spent fluid is discharged as controlled by the valve assembly during the oscillations of the cylinder and piston. 
   OBJECTS AND BRIEF SUMMARY OF THE PRESENT INVENTION 
   An object of the present invention is to provide a fluid-driven engine of the type described in the above-cited U.S. Pat. No. 1,954,408, but having a number of advantages as will be described more particularly below. According to the present invention, therefore, there is provided a fluid-driven engine of the type described in U.S. Pat. No. 1,954,408, as set forth above, and as more particularly defined in the first part of accompanying claim  1 , characterized in that the valve assembly includes a valve body of cylindrical configuration pivotally mounting the opposite end of the cylinder for pivotal movement about the longitudinal axis of the valve body; the valve body including a cylindrical surface serving as the pivotal mounting seat for the opposite end of the cylinder and formed with a pair of valve openings circumferentially spaced from each other so as to be selectively alignable with the port formed in the opposite end of the cylinder during pivotal movements of the cylinder for controlling the introduction of pressurized fluid into the cylinder and the discharge of spent fluid from the cylinder. 
   Thus, whereas the valve body in the Eliot Patent U.S. Pat. No. 1,954,408 is particularly described (and chimed) as being of spherical configuration, in the engine of the present application the valve body is of cylindrical configuration. Such a configuration provides a number of important advantages. 
   One important advantage is that the cylindrical valve seat defined by the valve body constrains all the movements of the cylinder and piston to axial force-transmitting movements, i.e., to movements parallel to the longitudinal axis of the cylinder which are effective to rotate the drive shaft, and prevents lateral movements of the cylinder and piston which not only decrease the efficiency of the engine, but also contribute to rapid wear of its parts. In addition, by providing the engine with a valve body having a cylindrical seat, rather than a spherical seat, the valve openings may be elongated in the axial direction of the valve body, and in addition sealing rings may be provided, to produce a more efficient transfer of the pressurized fluid from the valve body to the cylinder, and of the spent fluid from the cylinder back to the valve body for discharge therefrom. Further, making the valve body of a cylindrical configuration better enables a plurality of such drive units to be assembled in a modular fashion, according to the requirements of any particular application, for driving a common drive shaft. 
   According to further features in the preferred embodiments of the invention described below, the valve openings are of relatively long length in the axial direction of the cylindrical surface of the valve body ( FIGS. 4 ,  5 ,  13 ) and of relatively narrow width in the circumferential direction of the cylindrical surface of the valve body. As indicated above, this feature provides a more efficient transfer of the fluid between the valve body and the cylinder. 
   According to still further features in some described preferred embodiments, the valve body includes a cap for at least one of said valve openings, and an elastomeric sleeve between the valve body and the cap for urging the cap against the surface of said cylinder pivotally mounting the cylinder and piston to the valve body. 
   This feature provides an effective seal between the valve body and the cylinder during the pivotal movements of the cylinder. 
   According to still further features in some described preferred embodiments the engine comprises a plurality of at least three drive units each including a piston movable within a cylinder; and a valve assembly for each of the drive units for controlling the introduction of pressurized fluid into the cylinder of the respective drive unit and the discharge of spent fluid therefrom for driving the piston of the respective drive unit; each of the pistons being coupled to the drive shaft such that the pistons initiate their respective forward strokes at different angular positions of the drive shaft. 
   Such a construction eliminates the need of a fly wheel, as would be required in Eliot. Preferably, the pistons are coupled to the drive shaft such as to initiate their respective forward strokes at equally-spaced angular, positions of the drive shaft. 
   According to one preferred embodiment described below, the drive units and valve assemblies are each arranged in a linear array with the valve assembly at one end of the respective drive unit and in abutting relation to the valve assembly of the adjacent drive unit, and with the drive shaft coupled to the pistons at the opposite ends of the drive units. In the described embodiment, the pistons of the drive units are coupled to the drive shaft via a crank shaft which includes a crank arm for each piston. Such a construction thus permits any desired number of drive units to be coupled to the drive shaft in a modular manner according to the force requirements for any particular application. 
   Other embodiments are described below wherein the drive units and valve assemblies are arranged in a radiating array with the valve assembly at the outer end of the respective drive unit and pivotally coupled to the cylinder of the respective drive unit, and with the drive shaft at the inner ends of all the drive units and coupled to the pistons of all the drive units. Preferably, the drive shaft includes a single crank arm to which the pistons of all the drive units are pivotally coupled. Such a construction is particularly advantageous in that it permits the drive units to be coupled, in a convenient and compact manner, to a common drive shaft of a rotary device, such as a cement mixer, a rotary fan, or a rotary reeling device. 
   Traditional connecting-rod-crank mechanisms must be provided with control means for admitting pressure fluid, in many cases compressed air or steam, to the cylinder and discharging said pressure fluid from it. If more than one connecting-rod were provided, a plurality of control means would have to be provided and synchronized, as required, to impart a rotational impulse to the crank at appropriate stages of its swinging motion. In the mechanism of the invention, the admission and discharge of the pressure fluid are controlled in each connecting-rod assembly by a valve, preferably a stationary valve which also operates as a pivot, and therefore are automatically synchronized with the stages of the crank rotation. 
   In more detail, the preferred: form of the mechanism of the invention comprises a crank rotatably connected to a shaft either because it is solid with it, or is keyed to it, or is a part of a crankshaft. The connecting-rod assembly comprises a cylinder, which has a pivotal connection to the crank, preferably wherein the cylinder is provided with a pivot seat, such as an annular one, while the crank is provided with a pivot pin or is part of a crankshaft which engages the pivot seat, the opposite being equally possible. The cylinder is provided with a pivot seat or surface, preferably being cylindrical or a segment of a cylinder, which has an aperture providing a communication with the inside of the cylinder. The aperture may be a single, preferably an elongated, one, or may be constituted by a plurality of openings, e.g., circular openings arranged one after the other along a line, in which cases it will be called herein “composite aperture”. In a preferred embodiment of the invention the aperture, whether single or composite, is arranged on a transverse axial line or is symmetric with respect of said line. “Transverse axial line” means herein the intersection of the pivot seat of the connecting-rod assembly cylinder with the plane of symmetry of the cylinder that passes through the axis of symmetry of the pivot pin of the crank and the pivot seat of the connecting-rod: assembly. It is preferred that said aperture of said pivot seat, whether single or composite, be symmetric to said transverse axial line, but it is possible that it be not so symmetric but arranged on a line that is symmetric with respect to said transverse axial line, as will be better explained later on. 
   The mechanism, in its preferred form, further comprises a stationary valve, the body of which is partly hollow, and which comprises an outer pivot surface slidingly engaged by the pivot seat of the connecting-rod assembly cylinder. Said pivot surface is a part of a cylinder or consists of parts of a cylinder, while the remaining part of the outer surface of the valve body may have a different shape. The valve body has a first and a second aperture communicating with its inner hollow, and which are preferably longitudinal, viz. symmetric with respect to an axial plane of the valve body, but in general are so shaped that they may be juxtaposed to said aperture of the pivot seat of the connecting-rod assembly cylinder. Each of the valve body apertures communicates, through inner channels of the valve body, with a respective port. One of the two ports is in communication with a source of pressure fluid and the other one with or a fluid discharge respectively, and thus communication is established between the respective apertures of the valve body and said pressure fluid source or fluid discharge, respectively. In some applications, as will be explained hereinafter, the functions of the two ports are periodically switched, viz. each communicates alternatively with said source of pressure fluid and with said fluid discharge. In other applications, one of the ports communicates always with said source of pressure fluid and the other communicates always with said fluid discharge. 
   As the connecting-rod assembly oscillates, its angular position shifts from one extreme end to another extreme end. The first and second apertures of the valve body are angularly spaced by the same angle as the two extreme positions of the connecting-rod assembly. At a given angular position of said assembly, generally at the center or near the center of its oscillation, the aperture (whether single or composite, viz consisting of several openings close to one another) of said pivot seat or surface of the cylinder of the connecting-rod assembly is juxtaposed to an unapertured portion of the valve body. As said assembly oscillates, said aperture of said pivot seat or surface becomes gradually juxtaposed to one (first juxtapositions or to the other (second juxtaposition) of the apertures of the valve body. In the first juxtaposition, the inside of the cylinder is placed in gradually increasing communication with a source of pressure fluid which is fed to the inside of the cylinder, and therefore the piston is subjected to an axial force which it transmits to the crank or crankshaft as a rotational impulse. In the second juxtaposition, the inside of the cylinder is placed in gradually increasing communication with the discharge, there is gradually decreasing resistance to the motion of the piston, and the fluid is gradually discharged from the cylinder. At one of the extremes of the oscillation of the connecting-rod assembly, said first juxtaposition is complete or at least at a maximum, and said piston is subjected to a maximum axial force; at the opposite extreme, and the discharge of the fluid from said cylinder is complete or at least as complete as it will be. Said operative phases will be further described hereinafter, with reference to  FIG. 18 . 
   For the sake of clarity, the outwardly or projecting motion of the piston, with respect to the cylinder, from its innermost or most retreated position to its outermost or most extended position, during which it transmits to the crank a rotational impulse, will be called the positive or active stroke, and the inwardly or retreating motion of the piston from said outermost to said innermost position, during which it discharges the fluid from the cylinder, will be called the negative or passive stroke. As will be explained in detail hereafter, the choice of which port communicates with a source of pressure fluid and which communicates with a discharge depends on the phases of the swinging motion of the crank, and is established so as to impart to the crank a rotational impulse when this is desired and allow it to continue freely in its swinging motion when-no further impulse is to be transmitted from the respective connecting-rod. It will be understood that, if the shaft connected to the crank always rotates in the same direction, one port will always be in communication with the source of pressure fluid and the other port will always be in communication with the discharge. However, if the shaft is to rotate alternatively in opposite directions, the ports will periodically switch their aforesaid communications. 
   In one of the preferred embodiments of the invention, the crank is associated with a plurality of connecting-rod assemblies, which are angularly spaced, preferably by the same angle. Each connecting-rod assembly has an angular position that can be called the “null” or “zero angle position”, which is the position at which the axis of the piston of the connecting-rod assembly and the radius of the crank are aligned. Actually, there are two such positions, in one of which the piston is at its greatest retraction, while in the other it is in its greatest extension. When it is said herein that various connecting-rod assemblies are angularly spaced from one another, what is meant is that the null angle positions thereof are angularly spaced from one another. Preferably, the angular spacing is uniform, but this is not necessary and dynamic considerations may suggest a different angular spacing. Since in a preferred embodiment of the invention three connecting-rod assemblies are provided, any two of them are adjacent to one another and are spaced from one another by 120° or by any other chosen angle. The connecting-rod assemblies, however, when a plurality of them is present, need not be at an angle to one another but may be linearly spaced, viz. placed one next to the other in such a way that the axes of their null angle positions are all coplanar, parallel to one another in the common plane, and displaced from one another perpendicularly to their common direction. In this case, each connecting-rod assembly operates on a different crank and all the cranks are part of a crankshaft. An apparatus in which the connecting-rod assemblies are linearly spaced is also a preferred embodiment. 
   Another aspect of the invention is the provision of an apparatus for the production of mechanical work from hydraulic energy, which comprises a source of pressure fluid and a mechanism for actuating at least one rotatable shaft from the said pressure fluid, as hereinbefore described. 
   Preferably, the invention also comprises the use of the mechanism hereinbefore described for producing mechanical work the mechanism can be applied for producing mechanical work in any apparatus. Among such applications are, for example, sprinklers, mixers, in particular concrete mixers, apparatus for winding cables or garden hose reels, for spreading pool covers, for actuating shading canvases, valve control motors, robots for cleaning swimming pools, ride-on garden toys, cooling fans, rotary watering filters, and the like. The mechanism can also be used for the production of electrical energy, viz. can be coaxial with or otherwise drive an electricity generator it should be noted that, in some cases of engines according to the invention, the actuating fluid can be used, after its discharge from the engine, for other purposes for which only a low pressure or no pressure at all is required. For instance, if the fluid is water, the discharged water may be used in water sprinklers, drip systems, humidification of cooling fans, supplying water to cement mixers, and the like. Such a further use and the resulting apparatus are also aspects of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIGS. 1A ,  1 B and  1 C illustrate the motion of the connecting-rod assembly during the phase of the rotation of the crank in which a rotational impulse is to be transmitted to said crank, according to an embodiment of the invention; 
       FIGS. 2A ,  2 B and  2 C illustrate the motion of the connecting-rod assembly during the phase of the rotation of the crank in which no impulse is to be transmitted to said crank, according to the embodiment of  FIG. 1 ; 
       FIG. 3  is a schematic cross-section of the connecting-rod assembly and the valve, axial with respect to the assembly and transverse with respect to the valve, according to an embodiment of the invention; 
       FIG. 4  illustrates in exploded perspective the relationship between the connecting-rod assembly and the valve, according to an embodiment of the invention; 
       FIG. 5  illustrates in perspective view the valve of  FIG. 4 , which relates to a motor that rotates in one direction; 
       FIGS. 6 and 7  illustrate an embodiment of the invention in which the connecting-rod assemblies and the valves are spaced linearly; 
       FIGS. 8 and 9  illustrate an embodiment of the invention which comprises three angularly spaced connecting-rod assemblies; 
       FIG. 10  illustrates in perspective view the use of the apparatus of  FIGS. 8 and 9  in a mixer; 
       FIGS. 11 and 12  are schematic cross-sections of pistons of the connecting-rod assembly, according to two embodiments of the invention; 
       FIG. 13  illustrates in perspective view a variant of the valve of  FIG. 5 , which relates to a motor that rotates in two directions; 
       FIG. 14  is a schematic cross-section analogous to  FIG. 3 , but embodying the valve of  FIG. 13 ; 
       FIG. 15  is an enlarged cross-section of the valve of  FIG. 14 ; 
       FIG. 16  illustrates in schematic perspective view a use of the embodiment of  FIGS. 6 and 7  in a hose reel; 
       FIG. 17  illustrates in schematic perspective view a use of the embodiment of  FIGS. 8 and 9  in a fan; 
       FIG. 18  is an enlarged cross-section of the valve body, illustrating the phases of its operation; and 
       FIG. 19  is a cross-sectional detail of the valve body, illustrating a device for preventing leakage of fluid under pressure. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The operation of a connecting-rod assembly according to an embodiment of the invention will be understood with reference to  FIGS. 1A , B, C and  FIG. 2A , B, C.  FIGS. 1  illustrate the motion of the connecting-rod assembly during the phase of the rotation of the crank in which a rotational impulse is to be transmitted to said crank. During said phase, the piston of said assembly moves in its positive or active stroke.  FIGS. 2  illustrate the motion of the connecting-rod assembly during the phase of the rotation of the crank in which no impulse is to be transmitted to said crank. During said phase, the piston of said assembly moves in its negative or inactive stroke. 
   As seen in  FIG. 1 ; numeral  10  indicates a shaft, which rotates, together with a crank  16 , solid with it or keyed to it, about an axis  11  in the direction indicated by the arrow  12 .  13  generally indicates the connecting-rod assembly.  14  is the cylinder of said assembly and  15  is the piston. Piston  15  is connected to crank  16  by a pivotal connection generally indicated at  17 . 
   The connecting-rod assembly  13  is pivoted to a stationary valve  20 , only one end of which is visible in  FIG. 1 , showing port  21  which communicates either with the source of pressure fluid or with the discharge. Another port communicates with the discharge or with a source of pressure fluid, respectively, and can be provided on the opposite end (not visible in the drawing) of the valve. 
   In  FIG. 1A  the connecting-rod assembly  13  is in its first null angle position, which will be called herein the “retracted” null angle position, or briefly, “the retracted position”. Line  22 , which is the trace on the drawing of the plane of symmetry of cylinder  14  and piston  15 , passes through the axis of the shaft  10 . The valve axis, the crank axis and the shaft axis are on one plane. Piston  15  is retracted inside cylinder  14  as far as it will go. As crank  16  rotates as shown by arrow  12 , connecting-rod assembly  13  rotates in an opposite direction, as shown by arrow  24 , about valve  20 , which acts as a stationary pivot. 
   In the position of  FIG. 1B , the connecting-rod assembly has rotated by an angle α, which is the maximum one. Piston  15  has accomplished part of its active stroke. 
   As the motion of the mechanism continues, as shown in  FIG. 1C , it reaches its second null angle position, which will be called herein the “extended” null angle position, or briefly, “the extended position”. The center of valve  20 , the axis of cylinder  14 , the axes of piston  15 , of shaft  10  and of pivot connection  17  are all on the same plane, the trace of which on the drawing is indicated at  25 . The active or active stroke of piston  15  has come to an end. 
     FIG. 2  shows the second phase of the operation of the connecting-rod assembly. At the starting point, in  FIG. 2A , it is in its extended null angle position, as in  FIG. 1C . In  FIG. 2B , it is in a position symmetric to that of  FIG. 1B . The piston  15  has reentered partly into cylinder  14 , and they both have reached the outermost angular deviation of the connecting-rod assembly from its null angle positions, indicated by an angle α symmetric to that of  FIG. 1B . 
   As the motion of the mechanism continues, piston  15  accomplishes its negative or passive stroke and retracts into cylinder  14  as far as it can go. At  FIG. 2C , the apparatus has reached the same position as in  FIG. 1A , viz. its retracted null angle position. 
   It is apparent therefore that pressure fluid, particularly water, must be introduced into cylinder  14  while it swings from the position of  FIG. 1A  to that of  FIG. 1C , and must be discharged while it swings from the position of  FIG. 2A  (the same as that of  FIG. 1C ) to that of  FIG. 2C  (the same as that of  FIG. 1A ). 
     FIG. 3  generally illustrates, in a cross-section that is axial with respect to connecting-rod assembly  13  and the valve  20 . The assembly  13  comprises a cylinder  14  and a piston  15 , provided with a sealing ring  11 . (see also  FIG. 11 ). Numeral  30  indicates a cylindrical surface, spanning an arc of about 240°, which serves as a pivot seat for a pivot pin driven by the crank  16 . This embodiment is desirable when the piston is made of plastic matter, because then the pivotal connection between the piston  15  and the crank  16  may be obtained by snapping surface  30  over the pivot pin driven by the crank  16 . In other embodiments, such as that of  FIG. 4 , the pivot seat is a fill ring and must be slid over the pivot pin. The cylinder  14  of the connecting-rod assembly terminates with a transverse cylindrical portion  31 . By ‘transverse cylindrical portion” is mean therein a portion of a cylinder the axis of which is parallel to the axis about which the connecting-rod assembly oscillates. Within said cylindrical portion  31  is inserted a valve body  32  and said portion  31  is open, at least at one end, to permit the introduction of said valve body. Said cylindrical portion  31  has an aperture  36 , through which fluid may be fed into the cylinder  14  or discharged therefrom. Said aperture may be single and preferably symmetric about a central transverse line which is the intersection of said cylindrical portion with a plane of symmetry of the connecting-rod assembly passing through the axis about which the connecting-rod assembly oscillates and the axis of the crank pin. Said aperture may be composite, viz. consisting of a plurality of openings close to one another and centered on said central transverse line. Optionally, however, though less preferably, it could be arranged about a line slanted with respect to said central transverse line, or about a curved line, said slanted or curved line being symmetric with respect to said central transverse line. 
   In  FIG. 3 , the cylinder  14  of the connecting-rod assembly, is shown in a position in which aperture  36  of cylindrical sleeve  31  overlaps partially aperture  38  of the valve body and partially a rib  35  of the valve body  32 . In either of the null angle positions (only one of them being marked in the drawing) the aperture  36  would be placed on a line  37  which coincides with line  22  of  FIG. 1A , and would be stoppered (closed) by said rib  35 . As the connecting rod assembly swings one way or the other from a null angle position, the aperture  36  comes into gradually increasing juxtaposition to one or the other of two apertures  38  and  39  of the valve body. The phases of said juxtaposition are illustrated in the enlarged cross-section of the valve body  32  in  FIG. 18 , wherein the cylindrical portion  31  is in its central position and the aperture  36  is closed by rib  35  of valve body  32  (see  FIG. 3 ). As said cylindrical portion  32  swings clockwise (as seen in  FIG. 18 ) in the oscillation of the connecting-rod assembly, aperture  36  gradually overlaps aperture  38  of the valve body, until, after clockwise rotation by an angle α, point A coincides with point C, or is as close as possible to it, and the overlapping of aperture  36  with aperture  38  reaches a maximum. If said cylindrical portion  32  swings counterclockwise. (as seen in  FIG. 18 ), said overlapping decreases until it is annulled in the central position shown in the figure, and as the counterclockwise rotation continues, aperture  36  gradually overlaps aperture  39  of the valve body, until, after counterclockwise rotation by an angle α, point D coincides with point F, or is as close as possible to it, and the overlapping of aperture  36  with aperture  39  reaches a maximum. 
   Apertures  38  and  39  are in communication with inner channels  33  and  34  which lead to opening  21 , or to an equivalent opening, not shown in the drawing, and located on the opposite side of the valve. One of these ports is in communication with a source of pressure fluid, while the other port is in communication with the discharge; but, as has been said hereinbefore, in some embodiments said communications may be periodically switched. Switching of communications causes the inversion of the motor direction of rotation. Aperture  36  of the connecting-rod cylinder becomes gradually juxtaposed to one of openings  38  and  39 , as has been explained, during the swinging of the connecting-rod assembly between the two maximum angular deviations shown in  FIG. 1B  and  FIG. 2B , and becomes juxtaposed completely or to the maximum degree at either of the said two extreme angular positions which the cylinder  14  may assume. It is seen therefore that when the mechanism swings towards the position of  FIG. 1B , pressure fluid will be gradually admitted through one of the apertures  38  or  39 , while, when the mechanism swings towards the position of  FIG. 2B , pressure fluid will be gradually discharged through the other of said apertures. 
     FIG. 4  is a further illustration in exploded perspective of the relationship between the connecting-rod assembly and the valve. Piston  15  is seen as outside of cylinder  14 . In this and in other figures, the piston is seen as not as solid as in  FIG. 3 , but as formed by a number of longitudinal ribs  40 , which is desirable for the purpose of lightening the apparatus, particularly in plastic pieces in which thin flat portions are preferred.  42  is the pivot seat, shown herein as ring-shaped. Elastomeric seals, such as seal ring  44 , are provided to assure that the fluid should not pass around or through the piston from the bottom of cylinder  14  through which it is admitted or discharged.  FIGS. 11 and 12  schematically show in cross-section two ways for producing a seal in plastic pistons. The piston body is shown as full in these figures, but this representation is only schematic and the piston will have any desired cross-section. In  FIG. 11 , the piston generally indicated at  100 , is provided with an annular rubber seal  101 . In  FIG. 12 , the piston  102  has a flexible edge  103 , which serves as a seal, and is an integral part of the piston. The valve body, generally indicated in  FIG. 4  at  45 , is illustrated as being outside the cylindrical seat  31 , in which it is received during the operation of the device. 
   The valve body  45  is better illustrated in  FIG. 5 . It is shown herein as partly cylindrical in order to provide smooth motion of the sleeve  31  about the body  45  of the valve.  109  and  109 ′ are two seal rings. If the valve body is precise in its shape and dimensions, as it may be if it is made of metal it will closely fit sleeve  31  and there will be no fluid leakages. However, if it is not precise in its shape, particularly when made of plastic, additional means must be provided to prevent leakage at least about the aperture  38  (or  39 ) through which passes actuating fluid under pressure, although leakage may not be a serious danger when the fluid flows to the discharge. A means for this purpose is illustrated in  FIGS. 5 and 19 .  FIG. 19  is an enlarged cross-section of a single aperture  38 ′ of the valve body, the rest of said valve body being omitted. The cylindrical portion  31  of the connecting-rod assembly cylinder and the valve body  45  do not match precisely and a gap  40  exists between them. The aperture  38 ′ through which passes actuating fluid under pressure, indicated at  104 , has an edge  105  spaced from the edge  106  of a broader opening of the valve body (see  FIG. 5 ). An elastomeric sleeve  107 : fits tightly over edge  105 . A rigid cap  108 , e.g. of plastic, having a very thin radial wall  108 ′, fits tightly over elastomeric sleeve  107 , but can slide over edge  106 . It is provided with an aperture, indicated at  38 ′ because it has the function of the previously described aperture  38  (or  39 ). The elastomeric sleeve  107  pushes the rigid cap  108  outwardly until the radial wall  108 ′ of the cap is flush with the valve body surface. Sleeve  107 , therefore, functions as a spring forcing cap  108  outwardly and as a seal between the cap and the valve body, while the radial wall  108 ′ of the cap functions as a diaphragm urged by the fluid pressure against the inner surface of the cylindrical part  31 , whereby to improve sealing. 
   If the shaft driven by the mechanism always rotates the same direction, fluid and only one seal is required. If the shaft driven by the mechanism alternatively rotates in opposite directions, both valve body ports alternatively communicate with the source of pressure fluid and both must be provided with a seal-cap unit as hereinbefore described. This is illustrated in the exploded perspective of  FIG. 13 , in the cross-section of  FIG. 14 , and in the enlarged partial cross-section of  FIG. 15 . In  FIG. 13 , the valve body  45  is provided with two ports  21  and  21 ′ for communication with a fluid source and with a discharge respectively. Two elastomeric seal rings  109  and  109 ′ are mounted on said body. Two openings  110  and  110 ′ of the valve body accommodate two apertures  38  and  39 . For aperture  38 , are provided elastomeric sleeve  107  and rigid cap  108 , having the functions described in connection with  FIG. 5 . Similar elastomeric sleeve  111  and rigid cap  112  are provided to carry out the same functions for aperture  39 . Opening  110  of the valve body can be broad enough to accommodate two apertures  38  and  39 . In such configuration, elastomeric sleeves  107  and  111 , and rigid caps  108  and  112 , could be connected to form a single elastomeric sleeve and/or a single rigid cap.  FIG. 14  is an axial cross-section of the connecting rod assembly and a transverse cross-section of the valve. The connecting-rod assembly  13  is the same as in,  FIG. 11  but the piston  100  is provided with an elastomeric seal  101 , as in  FIG. 11 . The valve body,  45  is better seen in  FIG. 15 , which is an enlarged cross-section thereof, taken across apertures  38  and  39 .  113  and  114  are two channels through which said apertures communicate with port  21  and, a corresponding port on the other side of the valve body. The two elastomeric sleeves are seen at  107  and  111  and the two rigid caps at  108  and  112 . 
     FIGS. 6 and 7  illustrate an embodiment of the invention in which the cranks are part of a crankshaft and the connecting-rod assemblies and the valves are spaced linearly, perpendicularly to their axes in the null angle positions. In  FIG. 6 , numeral  50  indicates a crankshaft which comprises three cranks  51 ,  52  and  52 ′. Corresponding to each of said cranks, the apparatus comprises three connecting-rod assemblies, which comprise pistons  53 ,  54  and  55 , and cylinders  56 ,  57  and  58 . Said assemblies are similar to those of the embodiment previously described. Valve  60 ,  61  and  62 , similar to those hereinbefore described, serve as pivots of the connecting-rod assemblies, being inserted respectively into sleeves  63 ,  64  and  65 . Valves  60 ,  61  and  62  can be designed as one unit. Numeral  66  indicates a cover element overlapping the apparatus and  67  is a plate attached to one end of over  66 , provided with a projection that serves as a support to engage a stationary frame.  68  is a shaped projection for engaging the crankshaft  50  to any chosen driven apparatus. 
     FIG. 7  shows in perspective view the assembly of the crankshaft, the connecting-rod assemblies with their terminal sleeves and the valves, not visible because enclosed in the terminal sleeves. This figure also shows at  70 ,  71  and  72  the pivotal connections between the pistons and the crankshaft. In  FIG. 7 , the device is shown in different angular positions of the three connecting-rod assemblies. Piston  53  is approximately at the end of its positive stroke and piston  72  is at or near the end of its negative stroke. 
     FIGS. 8 and 9  illustrate in perspective view an embodiment of the device which comprises the three connecting-rod assemblies  80 ,  81  and  82 . They comprise three cylinders  83 ,  84  and  85  respectively and pistons  86 ,  87  and  88  respectively. The crank which they drive is identified by numeral  89  and is solid with or keyed to shaft  92 .  91  indicates a supporting plate. In  FIG. 9  the device is shown in exploded perspective view, in which the crankshaft  90  is clearly visible. The three cylinders  83 ,  84  and  85  of the connecting-rod assemblies are provided with transverse sleeves  93 ,  94  and  95 , respectively for housing valves  96 ,  97  and  98  respectively. The valves are supported on a trilateral support  99  attached to a support plate  91 . 
     FIG. 10  illustrates in perspective view an embodiment in which the apparatus of  FIGS. 8 and 9  is used to drive a cement mixer  100 . The cement mixer is supported on a base  101  by means of legs  102 , to which the axis of the cement mixer is pivoted. The device according to the invention, such as illustrated in  FIGS. 8 and 9 , is generally indicated at  103  and is supported on a transverse bar  104 . The three connecting-rod assemblies are visible and indicated by the said numerals  80 ,  81  and  82 , as in  FIG. 9 . A handle  105  permits to rotate the mixer manually, as may be required to place it in an angular position, for loading or unloading. 
     FIG. 16  shows in perspective view a mechanism such as that of  FIGS. 6 and 7 , mounted on a garden hose reel with a stationary stand  120 . The mechanism is provided with a cover.  121 , partly broken off to show part of the connecting-rod assemblies.  122  generally indicates the driven reel of the hose reel. In this configuration, the mechanism/motor according to the invention is located inside the reel. 
     FIG. 17  illustrates in exploded perspective view the use of a mechanism such as that of  FIGS. 8 and 9  for driving a fan schematically indicated at  126 . Mechanism  125  is supported on a stand  127 . 
   While specific embodiments have been shown by way of illustration, it should be understood that the invention can be carried out with many modifications, variation and adaptations, without departing from its spirit or exceeding the scope of the claims.