Patent Publication Number: US-9850981-B2

Title: Mechanical reducer device with high reduction ratio

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention is inserted the technical field relative to mechanical reducers, i.e. to the devices intended to transmit mechanical momentum, by varying the modulus and angular speed thereof. 
     In particular, the invention regards a mechanical reducer device with gears with high reduction ratio. 
     Description of the Related Art 
     Different types of mechanical speed reducers are known, which differ for the configuration and complexity of the couplings between the various members composing them. In general, though, they possess an input and an output, from which a rotation speed lower than that at the input can be drawn as well as a greater mechanical modulus of momentum. 
     The reducer of simplest type is that composed by a ring gear that engages in a corresponding pinion, with smaller diameter than the ring. Both are fit on corresponding drive shafts; the shaft of the pinion, or input shaft, provides the mechanical momentum to be reduced in speed and increased in modulus, whereas the ring gear shaft, or output shaft, provides the mechanical momentum with increased modulus and reduced rotation speed. The speed reduction ratio is given by the ratio between the number of gears of the pinion and that of the ring gear, and hence substantially by the ratio between the respective circumferences. 
     A reducer of this type is per se very simple, but in practice it does not supply a high reduction ratio, since the dimensions of the ring gear increase considerably, as does therefore the overall bulk of the reducer. 
     Another known type of reducer is the so-called worm reducer, in which a toothed wheel is coupled to a shaft whose surface has a high-angle helical thread, whose teeth are called worm teeth. The coupling between the worm and the helical cylindrical ring gear has the object of transferring motion and mechanical momentum between two axes that are orthogonal to each other and do not intersect. The worm or “conductor” is usually the member that transmits the motion to the helical ring gear. The reduction ratio depends on the ratio between the diameters and on the pitch of the worm, i.e. the thread angle. 
     The disadvantage of such reducer, in addition to that of only operating with axes orthogonal to each other, is that of having low efficiency, and in any case becoming increasingly bulky as the transmission ratio increases. 
     A further type of simple reducer is that of the epicycloidal reducers in which, for example, a system of one or more gears called “satellite gears”, mounted on a member defined “planet gear”, rotates around a central pinion defined “sun gear”. All of this is placed inside an internally toothed wheel called “ring gear”. The rotation axis of the planet and sun gears coincide. During use, one of the three elements is maintained fixed, while the other two constitute the input and output of the mechanical momentum to be transmitted. 
     The transmission ratio is given by the number of teeth, but also by which elements constitute the input and output. In general, epicycloidal reducers are not adapted to supply a high transmission ratio, but are considered optimal for transmitting a high mechanical momentum. 
     Other types of reducers allow obtaining more advantageous reduction ratios, but always at the cost of considerable bulk and/or considerable structural complexity. 
     BRIEF SUMMARY OF THE INVENTION 
     One object of the invention is to propose a mechanical reducer of rotation speed capable of obtaining high reduction ratios, maintaining a limited bulk. 
     A further object of the invention is to propose a mechanical reducer with high reduction ratio with a simple and reliable structure, and with limited production costs. 
     Another object of the invention is to propose a mechanical reducer with high reduction ratio in which such ratio is easily modifiable, without however compromising the structure, the simplicity and reliability of the reducer itself. 
     The abovementioned objects are all achieved by the mechanical reducer device with high reduction ratio, object of the present finding, which is characterized as provided for in the below-reported claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other characteristics will be clearer from the following description of several embodiments that are illustrated, as a mere non-limiting example, in the enclosed set of drawing tables where  FIGS. 1-9  illustrate nine embodiment variants of the present reducer, in accordance with corresponding side section views of the device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The mechanical reducer device with high reduction ratio described here is of the type comprising a box-like case C, provided on an input wall C 1  thereof with an input opening  2  and on an output wall C 2  thereof with an output opening  3 , an input shaft I, entering said case C through said input opening  2 , rotatably supported by the same and adapted to be brought into rotation at an input angular speed VI, and an output shaft U, exiting outward from said case C through said output opening  3 , rotatably supported by the same and mechanically connected to the abovementioned input shaft I by means of reduction members  301 , 401 , 501 , 601 , 701  and adapted to provide an output angular speed VU that is reduced with respect to said input speed VI. 
     With particular reference to  FIG. 1 , a mechanical reducer device obtained according to a first non-limiting embodiment of the invention is indicated in its entirety with the reference number  100 . In particular, the reducer  100  comprises a box-like case C, provided on an input side wall C 1  thereof with an input opening  2 , and on an output side wall C 2 , opposite the wall C 1 , with an output opening  3 . 
     An input shaft I enters into the case C from the input opening  2 ; one distal end of such input shaft I is connected to rotary motion generator members, not illustrated since they are not relevant with regard to the invention, adapted to bring the same input shaft I to a specific rotation speed VI. The input shaft I is rotatably supported in the aforesaid input opening  2  by means of suitable bearings or groups of bearings  2   a , in order to allow the rotation thereof with minimum friction. 
     An output shaft U exits outward from the case C from the output opening  3 ; such output shaft U is rotatably supported by means of further bearings or groups of bearings  3   a , adapted to rotate with rotation speed VU substantially less than the speed VI. 
     For such purpose, between the input shaft I and the output shaft U, speed reduction members  1  are interposed, inside the case C, adapted to transmit the rotation motion between the two shafts and to reduce the rotation speed thereof. 
     More specifically, the speed reduction members  1  comprise an input movable drive group  10 , mechanically connected to the input shaft I and conducted in rotation by the same, a reference fixed drive group  20 , mechanically connected to the movable drive group  10 , and an output movable drive group  30 , also mechanically connected to the input drive group  10  and to the output shaft U, according to that which will be illustrated in more detail below. 
     The input drive group  10  comprises a rotor R, with cylindrical shape, fit at the end to the input shaft I and on the axis with the same. 
     A pair of secondary shafts S is fixed at opposite ends of the lateral face R 1  of the rotor R, such shafts identical to each other and extended from the rotor R perpendicular to the axis thereof and to the axis of the input shaft I. 
     Each of the secondary shafts S supports, by means of suitable groups of bearings, one first secondary toothed wheel Z 2  and one second secondary toothed wheel Z 3 , idle on their axes and integral with each other. The latter is mounted in the part of the secondary shaft S that is more internal with respect to the rotor R, whereas the first secondary wheel Z 2  is mounted more external with respect to the same. 
     The two secondary wheels Z 2 ,Z 3  have conical toothing, and respectively possess Z 2   n  and Z 3   n  teeth which can be present with the same or different number as a function of the reduction ratio that one intends to obtain, as will be described hereinbelow. 
     In particular, in the illustrated embodiment, the secondary wheels Z 2 ,Z 3  are obtained in a single body, only for reasons of structural simplicity. 
     The reference drive group  20  comprises a reference toothed wheel Z 1 , mounted fixed on the internal face of the output wall C 2 , coaxial with respect to the output shaft U. Also the reference wheel Z 1  has conical toothing, with teeth Z 1   n  that engage on both the abovementioned first secondary toothed wheels Z 2 . 
     The output movable drive group  30  comprises an output toothed wheel Z 4 , fit at the end of the output shaft U, coaxial with the latter and internally with respect to the reference toothed wheel Z 1 , such that its teeth Z 4   n  engage in both of the abovementioned second secondary toothed wheels Z 3 . 
     In this manner, the rotation motion of the input shaft I is transmitted to the output shaft U, through the first Z 2  and second Z 3  secondary toothed wheels, and the output toothed wheel Z 4 , with a reduction ratio that in substance depends on the ratios between the number of teeth of the different toothed wheels. In particular, the reduction ratio RR for a mechanism such as that described is given by the following formula: 
     
       
         
           
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     The functioning of the reducer device  100  according to the first embodiment of the invention will be described below with reference to several numeric examples, in the first of which Z 1   n= 40, Z 2   n= 20, Z 3   n= 20 e Z 4   n= 39. 
     By applying a rotation on the input shaft I, the rotor R rotates with the same angular speed, as do therefore the two secondary shafts S and the two pairs of secondary toothed wheels Z 2 ,Z 3 . The first secondary toothed wheel Z 2 , by rolling on the reference toothed wheel Z 1 , completes two revolutions on itself for every rotation of the rotor R, as does therefore the second secondary toothed wheel Z 3 , integral with the first, which in turn rolls on the output toothed wheel Z 4 . 
     Two complete revolutions of the second secondary wheel Z 3  correspond to 40 teeth, since Z 3   n= 20 teeth. Since the output toothed wheel Z 4  possesses only 39 teeth, for each rotation of the input shaft I itself, and hence also the output shaft U, such teeth are obliged to rotate an angle corresponding to a single tooth. In this case, therefore, the output shaft U completes a complete revolution every 39 revolutions of the input shaft I, and the reduction ratio RR is therefore equal to 39. 
     In a second embodiment, in which Z 1   n= 39, Z 2   n= 20, Z 3   n= 20, Z 4   n= 38, from the application of the abovementioned considerations, one obtains that the reduction ratio RR is equal to 19. It was therefore sufficient to decrease the value of Z 4   n  by 1 in order to halve the reduction ratio. 
     It is in any case obtained that, if the secondary wheels Z 2 ,Z 3  possess the same number of teeth, the maximum reduction ratio is obtained when the number of teeth of the output toothed wheel Z 4   n  and of the reference toothed wheel Z 1   n  differ by one tooth. 
     A more substantial variation of the reduction ratio RR can be obtained by varying the number of teeth of the first Z 2  and second Z 3  secondary wheels. 
     A further embodiment, in which Z 1   n= 40, Z 2   n= 30, Z 3   n= 29 and Z 4   n= 39, by applying the abovementioned calculation formula, provides a reduction ratio RR=117. 
     By suitably varying the number of teeth of the various toothed wheels, it is possible to obtain a high number of values of the reduction ratio RR, without however modifying the structure or the size of the reducer device  100 . In order to better exploit the characteristics of the latter, it is also advisable that the number of teeth Z 1   n  of the reference wheel Z 1  and Z 4   n  of the output wheel Z 4  differs by at least one tooth. For the same reason, it is preferable that the number of teeth of the secondary wheels Z 2   n  and Z 3   n  differs by one tooth. 
     According to a further embodiment, aimed to emphasize the versatility of the reducer device  100  in obtaining exceptionally high reduction ratios RR with small modifications of the characteristics of the device  100  itself, one assumes having toothed wheels Z 1 ,Z 2 ,Z 3 ,Z 4  that respectively possess the following number of teeth: Z 1   n= 40; Z 2   n= 39; Z 3   n= 38; Z 4   n= 39. 
     In this case, the application of the simple formula illustrated above provides a reduction ratio RR=1521, much higher than those of the preceding embodiments, without having to significantly modify the size of the toothed wheels or of the entire reducer device  100 . 
     In a second embodiment of the invention, illustrated in  FIG. 2 , a reducer device  200  provides for speed reduction members  201  comprising an input movable drive group  210 , mechanically connected to the input shaft I and conducted in rotation by the same, a reference fixed drive group  220 , mechanically connected to the movable drive group  210 , and an output movable drive group  230 , also mechanically connected to the input drive group  210  and also connected to the output shaft U. 
     The input drive group  210  comprises a rotor R shaped as a disc, with an enlargement at the center to which the head of the input shaft I is fixed. The axis of the rotor R coincides with the axis of the input shaft I. 
     From the face of the rotor R directed towards the interior of the case C, in proximity to the lateral edge of the rotor R itself, a pair of secondary shafts S exits outward, which are extended parallel with respect to the axis thereof and to that of the input shaft I. 
     Each of the secondary shafts S idly supports, on the axis thereof, one first secondary wheel Z 2  and one second secondary wheel Z 3 , respectively in a more internal position and a more external position with respect to the rotor R. The latter are cylindrical toothed wheels, integral with each other and, in the illustrated embodiment, are by way of example obtained in a single body. 
     The reference drive group  220  provides that the reference toothed wheel Z 1  is also a cylindrical wheel, is fixed to the internal face of the output wall C 2  of the case C coaxial with the axis of the output opening  3 , and engages with the first secondary toothed wheel Z 2 . 
     The reference wheel Z 1  possesses an axial hole  204 , through which the output shaft U passes and inside of which a group of bearings is provided adapted to rotatably support the same shaft. 
     The output drive group  230  provides that the output toothed wheel Z 4  is also a cylindrical toothed wheel, mounted in the terminal portion of the output shaft U, internally with respect to the reference wheel Z 1  and engaged with the second secondary wheel Z 3 . 
     The output shaft is in turn rotatably supported, not only by the aforesaid reference wheel Z 1  but also at an axial cavity  205  obtained in the internal part of the rotor R. 
     In a third embodiment of the invention, illustrated in  FIG. 3 , a reducer device  300  provides for speed reduction members  301  comprising an input movable drive group  310 , mechanically connected to the input shaft I and conducted in rotation by the same, a reference fixed drive group  320 , mechanically connected the movable drive group  310 , and an output movable drive group  330 , also mechanically connected to the input drive group  310  and also connected to the output shaft U. 
     In particular, the input movable drive group  310  comprises a rotor R having tubular conformation, mounted at the end of the input shaft I with axis slightly tilted with respect to the perpendicular to the axis of the same shaft. A secondary shaft S is mounted coaxial and without engagement inside the rotor R, and is extended for the entire length thereof, slightly exiting outward from the ends thereof. 
     One first secondary toothed wheel Z 2  and one second secondary toothed wheel Z 3 , of the type with conical toothing, are mounted opposite each other at the opposite ends of the rotor S, idly supported by the same by means of suitable groups of bearings. 
     The first Z 2  and second Z 3  secondary wheels are also fixed to the opposite ends of the secondary shaft S, so as to be integral with each other. 
     The reference group  320  provides a reference toothed wheel Z 1 , also with conical toothing, fixed to the internal face of the input wall C 1  of the case C, coaxial with respect to the input shaft I, and it rotatably supports such shaft at an axial hole  304  thereof by means of suitable bearings. 
     Due to the abovementioned tilted positioning of the rotor R, the reference toothed wheel Z 1  only engages with the first secondary wheel Z 2  and not with the second Z 3 . 
     The output drive group  330  provides for an output toothed wheel Z 4 , with conical toothing, mounted at the end of the output shaft U, in a position coaxial with the input shaft I and facing the reference toothed wheel Z 1 . Due to the tilted positioning of the rotor R, the output toothed wheel Z 4  engages with the second secondary wheel Z 3  and not with the first Z 2 . 
     A fourth embodiment of a speed reducer device  400  according to the invention is illustrated in  FIG. 4 . 
     According to such embodiment, in the movable drive group  410  the rotor R is obtained in fork form, and is idly mounted on a sleeve  404  that is extended from the internal face of the output wall C 2  of the case C. 
     A pair of arms R 1 ,R 2  of the rotor R is extended parallel to the input shaft I, towards the interior of the case C. The secondary shaft S is mounted, freely rotatable, between the opposite ends of the arms R 1 ,R 2 , with axis slightly tilted with respect to the perpendicular of the input shaft I. 
     The latter is mechanically coupled to the secondary shaft S by means of a spur gear  405 , adapted to transmit the rotation motion to the latter, with a first speed reduction depending on the ratio between the pinion and ring gear teeth in the aforesaid spur gear  405 . 
     As described above, also in this case a reference toothed wheel Z 1  is provided fixed to the input wall C 1  of the case C, and an output toothed wheel  404  is provided mounted at the end of the output shaft U and facing the aforesaid reference wheel Z 1 . 
     Since the coupling between the reference Z 1 , secondary Z 2 ,Z 3  and output Z 4  toothed wheels is always identical, the functioning of the reducer device  400  remains substantially unchanged with respect to that described in the first embodiment of the invention. The overall reduction ratio, obtainable as a function of the different combinations of the number of teeth of the same toothed wheels, must however also take under consideration the reduction ratio given by the spur gear  405 . In practice, the overall reduction ratio is in this case obtained by multiplying that given by the above formula times the reduction ratio of the spur gear  405 . 
     A fifth embodiment of the reducer  500  according to the invention is illustrated in  FIG. 5 . 
     According to such fifth embodiment, speed reduction members  501  are provided that comprise: an input movable drive group  510 , mechanically connected to the input shaft I and conducted in rotation by the same; a reference fixed drive group  520 , mechanically connected to the movable drive group  510 ; an output movable drive group  530 , also mechanically connected to the input drive group  510  and also connected to the output shaft U. 
     In particular, the input movable drive group  510  comprises a rotor R constituted by a block with cylindrical symmetry mounted at the end of the input shaft I. At the end opposite the rotor R, the head of the output shaft U is idly mounted, which is on the axis with the input shaft I. 
     In the rotor R, a through hole  502  is obtained whose axis is arranged transverse and slightly tilted with respect to the perpendicular to the axis of the same input shaft I. A secondary shaft S is idly mounted inside the through hole  502 , by means of bearings  503   a , 503   b  provided at the opposite ends of the same, and the shaft is extended for the entire length of the through hole, exiting outward from the ends thereof. 
     One first secondary toothed wheel Z 2  and one second secondary toothed wheel Z 3 , of the type with conical toothing, are mounted opposite each other at the opposite ends of the secondary shaft S, integral therewith. 
     The reference group  520  provides a reference toothed wheel Z 1 , also with conical toothing, fixed to the internal face of the input wall C 1  of the case C, coaxial with respect to the input shaft I, and it rotatably supports such shaft at an axial hole  504  thereof by means of suitable bearings. 
     Due to the abovementioned tilted positioning of the rotor R, the reference toothed wheel Z 1  only engages with the first secondary wheel Z 2  and not with the second Z 3 . 
     The output drive group  530  provides for an output toothed wheel Z 4 , with conical toothing, mounted at the end of the output shaft U, in a position coaxial with the input shaft I and facing the reference toothed wheel Z 1 . Due to the tilted positioning of the rotor R, the output toothed wheel Z 4  engages with the second secondary wheel Z 3  and not with the first Z 2 . 
     A sixth embodiment of the reducer  600  according to the invention is illustrated in  FIG. 6 . 
     According to such sixth embodiment, in a manner entirely similar to that described for the preceding embodiment, speed reduction members  601  are provided that comprise: an input movable drive group  610 , mechanically connected to the input shaft I and conducted in rotation by the same; a reference fixed drive group  620 , mechanically connected to the and it rotatably supports such shaft group  610 ; an output movable drive group  630 , also mechanically connected to the input drive group  610  and also connected to the output shaft U. 
     In particular, the input movable drive group  610  comprises a rotor R constituted by a frame  611 , having substantially elongated plate form, arranged inside the case C transversely with respect to the axis of the input shaft I. From the greater sides of the frame  611 , two input  612  and output  613  supports are perpendicularly extended, provided with holes on which the ends of the input shaft I and the output shaft U are respectively fixed in a manner so to be aligned with the common rotation axis. 
     From the shorter sides of the frame  611 , two further first  614  and second  615  supports are extended, perpendicular and in the same direction as the two abovementioned supports; first  614  and second  615  supports are provided with through holes  616 , 617 , aligned with each other in transverse direction with respect to the axis of the input I and output U shafts, with a slight tilt with respect to the perpendicular to the aforesaid input I and output U shaft axes. A secondary shaft S is extended between the two further supports  614 , 615 , with the ends thereof idly mounted in the aforesaid through holes  616 , 617 , by means of a pair of bearings. 
     One first secondary toothed wheel Z 2  and one second secondary toothed wheel Z 3 , of the type with conical toothing, are mounted opposite each other at the opposite ends of the secondary shaft S, immediately inside the aforesaid further supports  614 , 615  and integral therewith. 
     The reference group  620  provides a reference toothed wheel Z 1 , also with conical toothing, fixed to the internal face of the input wall C 1  of the case C, coaxial with respect to the input shaft I, and it rotatably supports such shaft at an axial hole  604  thereof by means of suitable bearings. 
     Due to the abovementioned tilted positioning of the rotor R, the reference toothed wheel Z 1  only engages with the first secondary wheel Z 2  and not with the second Z 3 . 
     The output drive group  630  provides for an output toothed wheel Z 4 , with conical toothing, mounted at the end of the output shaft U, in a position coaxial with the input shaft I and facing the reference toothed wheel Z 1 . Due to the tilted positioning of the rotor R, the output toothed wheel Z 4  engages with the second secondary wheel Z 3  and not with the first Z 2 . 
     Since the coupling between the different toothed wheels is always identical, the functioning of the reducer device  500 , 600  according to the above-described fifth and sixth embodiments remains unchanged with respect to that described in the first embodiment of the invention, just as the reduction ratio remains the same, obtainable as a function of the different combinations of the number of teeth of the same toothed wheels. 
     A seventh embodiment of the present reducer, with reference number  700 , is illustrated in  FIG. 7 . 
     The structure and the mechanical couplings of the reducer  700  according to the aforesaid seventh embodiment assume the characteristics of the reducer  500  of the above-described fifth embodiment of the invention. 
     Therefore, with reference to the abovementioned  FIG. 5 , speed reduction members  701  are provided that comprise: an input movable drive group  710 , mechanically connected to the input shaft I and conducted in rotation by the same; a reference fixed drive group  720 , mechanically connected to the movable drive group  710 ; an output movable drive group  730 , also mechanically connected to the input drive group  710  and also connected to the output shaft U. 
     In particular, the input movable drive group  710  comprises a rotor R constituted by a block with cylindrical symmetry mounted at the end of the input shaft I. At the opposite end of the rotor R, the head of the output shaft U is idly mounted, which is on the axis with the input shaft I. 
     A through hole  702  is obtained in the rotor R; the axis of such hole is arranged transverse and slightly tilted with respect to the perpendicular to the axis of the same input shaft I. A secondary shaft S is idly mounted inside the through hole  702 , by means of bearings provided at the opposite ends of the same, and such shaft is extended for the entire length of the hole, exiting outward from the ends. 
     One first secondary toothed wheel Z 2  and one second secondary toothed wheel Z 3 , of the type with conical toothing, are mounted opposite each other at the opposite ends of the secondary shaft S, integral therewith. 
     The output drive group  730  provides for an output toothed wheel Z 4 , with conical toothing, mounted at the end of the output shaft U, in a position coaxial with the input shaft I and facing the reference toothed wheel Z 1 . Due to the tilted positioning of the rotor R, the output toothed wheel Z 4  engages with the second secondary wheel Z 3  and not with the first Z 2 . 
     The reducer  700  differs in particular from the above-described reducer  500  according to the fifth embodiment due to the fact that the reference group  720  provides for a reference toothed wheel Z 1 , also with conical toothing, idly mounted on the axis thereof in a protrusion  721  of the internal face of the input wall C 1  of the case C, by means of suitable bearings. The protrusion  721  has an input axial hole  704 , and rotatably supports the input shaft I, also by means of suitable bearings. 
     Due to the abovementioned tilted positioning of the rotor R, the reference toothed wheel Z 1  only engages with the first secondary wheel Z 2  and not with the second Z 3 . 
     The reducer  700  also provides for a control group  750 , which comprises a cylindrical toothed control wheel Z 5 , provided with a given number of teeth NC 1  and fixed to the rear part of the reference toothed wheel Z 1 . The toothed control wheel Z 5  hence comes to be situated between the reference wheel Z 1  and the input wall C 1  of the case C. In particular, in the illustrated embodiment, the toothed control wheel Z 5  is made in a single body with the reference toothed wheel Z 1 . 
     In the lower part of the case C, a control hole  705  is obtained through which a control shaft AC passes, idly supported by means of bearings and parallel to the input shaft I. At the end of the control shaft AC, a control pinion Z 6  is mounted, provided with a number of teeth NC 2 , which engages in the abovementioned toothed control wheel Z 5 . The control shaft AC is actuatable in rotation in an independent manner with respect to the input shaft I, by suitable non-illustrated control members. 
     The functioning of the reducer  700 , as with the law that regulates the reduction ratio between the output shaft U and the input shaft I, are identical to that of the reducer according to the other embodiments described above if the control shaft AC is maintained still/stopped. In this manner, indeed, the reference toothed wheel Z 1  is maintained fixed. 
     If a rotation is set to the control shaft AC, the reduction ratio obtained by the reducer  700  depends on the rotation speed of the aforesaid control shaft AC, on the ratio NC 1 /NC 2  between the number of teeth of the toothed control wheel Z 5  and those of the control pinion Z 6 , as well as on the rotation direction of the control shaft AC itself. 
     As a function of the rotation of the latter, the reduction ratio can be progressively decreased or increased, until the reducer is substantially deactivated, annulling the rotation speed of the output shaft. 
     It should be underlined that the above-described control group  750  for the aforesaid seventh embodiment of the reducer according to the invention can be advantageously applied also to the reducer obtained according to all the other embodiments described here, without having to make non-readily deducible structural modifications to the same. 
     The reduction members  301 , 401 , 501 , 601 , 701  comprise, arranged inside said case C:
         an input movable drive group  310 , 410 , 510 , 610 , 710 , mechanically connected to said input shaft I, conducted in rotation by the same,   a rotor R mounted at the end of said input shaft I, at least one secondary shaft S conducted in rotation by said input shaft I and arranged with orientation slightly tilted with respect to the perpendicular to the latter,   at least one first secondary toothed wheel Z 2  and one second secondary toothed wheel Z 3 , constrained to said secondary shaft S; a constrained reference drive group  320 , 420 , 520 , 620 , 720 , comprising a reference toothed wheel Z 1  which engages said first secondary toothed wheel Z 2 ; an output movable drive group  330 , 430 , 530 , 630 , 730 , mechanically connected to said output shaft U and comprising an output toothed wheel Z 4  which engages the abovementioned second secondary wheel Z 3 .       

     In  FIG. 8 , an eighth embodiment of the invention is illustrated, in which a reducer device  800  is described which has different structure from that of the reducer devices already described in the preceding embodiments of the invention, even if the main structural characteristics and the general functioning remain unchanged. 
     In the reducer device  800 , the reduction members  801  which interconnect the input shaft I with the output shaft U provide for an input movable drive group  810  which comprises a rotor R with cylindrical conformation, fit at the end to the input shaft I. The rotor R provides for, at the opposite end, a cavity RC adapted to rotatably support the proximal end of the output shaft U, in cooperation with the output wall C 2  of the case C. 
     A pair of first S 1  and second S 2  secondary shafts is fixed to the lateral surface RL of the rotor R; such shafts are parallel to each other, and are extended from the same rotor R perpendicular to the axis of the input shaft I. 
     The secondary shafts S 1 ,S 2  respectively support, idly on the axes thereof, a pair of first Z 2  and second Z 3  secondary toothed wheels. The latter comprise a more external portion with cylindrical toothing Z 2 S,Z 3 S and a more internal portion with conical toothing Z 2 C,Z 3 C, with respect to the aforesaid rotor R. 
     The external portions with cylindrical toothing Z 2 S,Z 3 S of the secondary toothed wheels Z 2 ,Z 3  engage with each other, and preferably possess the same number of teeth. 
     The fixed reference group  820  provides for a reference toothed wheel Z 1  also with conical toothing, fixed to the internal face of the input wall C 1  of the case C coaxial with respect to the input I and output U shafts, or also, as illustrated, in a single body therewith. The reference toothed wheel Z 1 , in particular, engages with the internal portion with conical toothing Z 2 C of the first secondary toothed wheel Z 2 . 
     The output movable drive group  830  provides for an output toothed wheel Z 4  with conical toothing, mounted at the end of the output shaft U between the aforesaid output wall C 2  of the case C and the rotor R, and engaging with the internal portion with conical toothing Z 3 C of the second secondary toothed wheel Z 3 . 
     For the purpose of increasing the torque transferred by the reducer device  800 , multiple pairs of secondary shafts S 1 ,S 2  and of corresponding secondary toothed wheels Z 2 ,Z 3  can be provided. In  FIG. 6 , a possible arrangement of the second pair of the aforesaid secondary shafts S 1 ,S 2  is outlined, opposite with respect to the first pair. 
     The functioning principle of the reducer device  800  is very similar to that already described for the preceding embodiments of the same. In this case, the first Z 2  and second Z 3  secondary toothed wheels are not integral with each other, but constrained by a toothed coupling, with the same number of teeth. A complete rotation of the first secondary wheel Z 2  is followed by a complete rotation of the second toothed wheel Z 3 , with opposite rotation direction. 
     The particular conformation of the reducer device described above has the characteristic of non-reversibility, i.e. that it is not possible to transfer a rotation of the output shaft U to the input shaft I. Indeed, from the standpoint of the output shaft U, the meshing chain Z 4 -Z 3 S-Z 2 S-Z 1  concludes in the aforesaid fixed reference toothed wheel Z 1 . The output shaft thus results blocked with respect to both rotation directions. 
     It should be observed that, pursuant to the aforesaid combination of couplings between the toothed wheels Z 1 ,Z 2 ,Z 3 ,Z 4 , it is possible to obtain a high number of configuration variants of a reducer device according to the invention, along with a high number of possible values for the reduction ratio. 
     With particular reference to  FIG. 9 , the ninth embodiment is observed; in particular, this is a variant of the reducer of  FIG. 1 . The ninth variant is indicated with reference number  900  in its entirety. 
     Z 0  indicates the input toothed wheel, Z 1  the reference toothed wheel; Z 2  and Z 3  indicate the secondary toothed wheels, while Z 4  indicates the output toothed wheel. 
     The reducer of  FIG. 9  differs from the base reducer ( FIG. 1 ) due to the fact that the rotor R 9  is not placed in rotation directly by the input shaft I (as instead occurs in the reducer of  FIG. 1 ) but rather by the toothed wheel Z 0  integral with the input shaft; said toothed wheel Z 0  is engaged with the toothed wheel Z 2  which in turn rotates the rotor R 9  on which it is installed. 
     The main advantage offered by the mechanical speed reducer device according to the invention is constituted by the possibility to obtain high reduction ratios, maintaining a bulk, and consequently a weight, of the reducer that is particularly limited. 
     A further advantage is given by the fact that a mechanical reducer with high reduction ratio is obtained with a simple and reliable structure, and with reduced production costs. 
     Another advantage of the invention is to obtain a mechanical reducer with high reduction ratio in which such ratio is easily modifiable, without however compromising the structure, the simplicity and the reliability of the reducer itself.