FR2471878A1 - Drive take=off for vehicle gear box - has attached case with gear train to give rear wheel drive and supplementary low power take off speeds - Google Patents

Abstract

The gearbox has a train (11) with a case (13) fixed to the main gear case (2). In this is a transmission (14) between a primary shaft (3) and a secondary (4) and engagement couplings (29,31). There is a second group (12) with another case (15) to fix on the differential housing (7). In the differential a take off (17) can rotate around an axis perpendicular to that of the differential. The take off is gear (18) driven. Another shaft (20) pivots in the case (15) and is joined to the rear wheels and can be coupled to the take off.

Description

METHOD AND ASSEMBLY FOR CONVERTING A BOX OF SPEED

  SES OF A MOTOR VEHICLE AND GEARBOX OBTAINED BY

SUCH CONVERSION.

  The present invention relates to a gearbox of a motor vehicle of the type comprising a primary shaft and a secondary shaft carrying con stammemt in engagement and comprising a differential for the transmission of the propulsion movement to a pair of haliaries which are substantially arranged parallel to the shafts of the gearbox and which are intended to be connected to the front wheels of a motor vehicle

  In the description below, the expression "box

  [0002] The present invention relates to an assembly for the conversion or conversion of a gearbox from a vehicle to a motor vehicle of the type specified above. engine of the type specified above in one

  same type of gearbox equipped in addition to a

  lower speed and a PTO for the trans-

  mission of the propulsion movement to the rear wheels of the vehicle

engine.

  The main feature of the assembly which is the subject of the present invention comprises: a) a first conversion unit comprising: a first auxiliary casing intended to be fixed on the casing of the casing on a continuation of the casing on the opposite side; to that of the motor, a gear transmission mechanism is provided in the aforementioned first auxiliary casing and can be acdionn to establish the transmission between the primary aro and the secondary shaft of the gearbox with a corresponding ransmision report at the first lower speed, and means for establishing and suppressing the aforesaid transmission, b3 a second conversion unit comprising: a second auger casing intended to be fixed to the load cell by means of a PPP by

247 1878

  second auxiliary casing so as to allow its rotation about an axis perpendicular to the axis of the differential; - a bevel gears transmission

  allowing the transmission of the propulsion movement to be

  shot of the differential to the PTO shaft; a transmission shaft mounted pivotably in the second auxiliary casing, this shaft being intended to be connected to the rear wheels of the motor vehicle and being able to be coupled to the aforesaid power take-off shaft, and means for producing the coupling and uncoupling between the aforementioned drive shaft and

  the aforementioned PTO shaft.

  The present invention also relates to a method for converting or transforming a gearbox of a motor vehicle of the type specified above, into a

  boot of the same type equipped in addition to a first

  lower speed and a PTO for the

  transmission to the rear wheels of the motor vehicle, this

  assigned being characterized by the fact that it comprises the opera-

  following conditions: - the attachment of a first auxiliary housing to the

  crankcase of the gearbox, on an extension of that

  on the opposite side to that of the engine;

  - the forecast in the first auxiliary crankcase pre-

  cited a gear transmission mechanism that can be operated to establish transmission between

  the primary shaft and the secondary shaft of the speed boot

  with a transmission ratio corresponding to the first

lower speed;

  - the forecast of means to produce the coupling

  or the uncoupling of the abovementioned transmission; - Attaching a second auxiliary housing on the differential housing; - Mounting in the second auxiliary casing of a PTO shaft pivotally mounted about an axis perpendicular to the axis of the differential; - the forecast of a transmission mechanism - by

  conical gears to transmit the propulsion movement

  differential output to the power take-off shaft assembly so as to allow rotation in the second auxiliary casing of a transmission shaft intended to be connected to the rear wheels of the motor vehicle and which can be coupled with the shaft above-mentioned power take-off, and the provision of means for coupling and uncoupling between the aforesaid drive shaft and

the PTO shaft.

  The present invention also relates to a vehicle gearbox L engine equipped with a first

  speed and a PTO for the transmission of

  propulsion movement to the rear wheels of the vehicle.

  the engine, obtained by conversion of a gearbox of the type specified above, characterized in that it comprises: - a first auxiliary casing fie on the housing of

  the original speed booster, on an extension of this

  on the opposite side to that of the engine,

  a gear transmission mechanism supporting

  in the first auxiliary housing and operable to establish the transmission between the primary shaft and the secondary shaft of the original gearbox with

  a transmission ratio corresponding to the first

is lower,

  means to establish and suppress the transmission

  a second auxiliary casing for attachment to the differential gearbox which is incorporated in the original gearbox; a power take-off shaft supported by the second casing at the plane so as to allow its rotation about an axis perpendicular to the axis of the differential; a bevel gear transmission mechanism for transmitting the propulsion movement of the differential to the aforesaid PTO shaft; a transmission shaft pivotally mounted in the aforesaid second auxiliary casing which is intended to be connected to the rear wheels of the motor vehicle and which can be coupled to the aforesaid power take-off shaft, and

  -means for producing mating and

  mating between the aforesaid transmission shaft and the

  above mentioned power take-off. To better understand the object of the invention,

  will be described below, by way of purely illustrative example.

  process and not limiting, an embodiment shown

in the attached drawing.

  In this drawing - Figure 1 is a perspective view, in section, which schematically shows a gearbox of a motor vehicle according to the present invention;

  FIG. 2 is a section along II-II of FIG.

  re 3; - Figure 3 is a view along the arrow III of Figure 1; - Figure 4 is a section of a detail of Figure 1; FIG. 5 is a section along line V-V of FIG.

figure 4.

  In the drawing, 1 has been designated as a whole, a gearbox of a motor vehicle, provided with a first lower speed and a PTO for the transmission of the propulsion movement to the rear wheels of the vehicle. a motor vehicle, obtained by converting a boot

  speeds of the type specified above.

  The original boot has a housing 2 in which a primary shaft 3 is pivotally mounted and

  a secondary shaft 4. The primary shaft 3 has one end

  mity 3a protruding out of the casing 2 of the boot of vi-

  and is intended to be connected to the motor drive shaft of a motor vehicle. Four helical gears are attached to the primary shaft and mesh with four equally helical d6 gears that are pivotally mounted

  on the secondary shaft 4. In the drawing, there is no representation

  the usual sleeves and synchronizers used to make the pinions 6 of the shaft selectively

secondary 4.

e

247 1878

  The original gearbox includes a

  7 which the sun gear carrier is integral with a toothed wheel 8 which is engaged with a toothed wheel 9 fixed to the secondary shaft 4, the differential 7 serves to transmit the propulsion movement of the secondary tree 4 to a pair of demiarzbres 10 intended to be connected to the wheels

before a motor vehicle.

  As shown in FIG. 1, the ends are arranged in a direction substantially parallel to the shafts 3 and 4 of the gearbox. This gearbox is in fact intended to be mounted on a motor vehicle in a transverse arrangement with respect to the longitudinal dirzection of the vehicle itself, the original gearbox is converted into the gearbox shown in FIG. 1. by means of a conversion set that includes a first uniDt

  of conversion Il and a second conversion unit 12.

  The first conversion unit 11 comprises a first auxiliary casing 13 which is fixed on the casing 2 of the gearbox of origin, on an extension of the casing 2 on the side opposite to that of the vehicle engine. In the first auxiliary casing 13 find a transmission gear 14 to connect the primairza tree 3 and lazabre secondary 4 of the original gearbox with a contribution of transmission corresponding lna first

lower speed.

  The second conversion unit 12 comprises a second housing 15, which is attached to the housing of the differential (which is indicated by the reference numeral 16), a force-gripping shaft 17 having at one end a bevel gear 18 meshing with a conical toothed wheel 19 fixed to the toothed wheel 8, and a deostined transmission shaft 20 to be connected to the rear wheels of the motor vehicle

  and may be driven to the PTO shaft 17.

  3S It is seen in Figures 1 to 3 that the transmission A eng-enages 14 comprises a first gearwheel 21 attached to a trmitd 3b of the primary tree 3 which protrudes into the Ceter 30 o The wheel deante 21 engrme with a cecoa

  gear 22 pivotally mounted on an intermediate shaft

  Fig. 23 is fixed in the housing 13. The gear 22 is part of a one-piece tubular element 24 which includes a third gear 25 meshing with a toothed wheel 26 which is pivotally mounted on an axle 27

fixed in the housing 13.

  The toothed wheel 26 meshes with a toothed wheel 28 which is mounted to pivot freely on one end 4a of the secondary shaft 4 which projects into the casing 13.

  toothed wheel 29 is also attached to the end 4a together.

  with a gear wheel 28. A sleeve 31, provided with a crown

  toothed 32 on its outer surface is slidably mounted

  on the toothed wheel 29 by means of a splined coupling

  30. Means (not shown) of known type are

  seen to produce an axial displacement of the sleeve 31 on the gear wheel 29 which is fixed on the end 4a of the shaft

  4. The sleeve 31 is movable between a first

  the end position in which the grooved inner surface engages a ring gear 33 of the toothed wheel 28, and a second end position in which the ring gear 32 engages a toothed wheel 34 forming part of the tubular element; 24 (it should be noted that although in FIG. 2, the toothed wheel 34 seems to be spaced apart from the toothed wheel 32, that

  reality the primitive circles of these gears are tan-

  relative to each other, the apparent distance shown in Figure 2 being the result of the

  particular of which this section has been made).

  When the sleeve 31 is in its first po-

  extreme position (toothed wheels 28 and 29 secured), the primary shaft 3 and the secondary shaft 4 of the speed boot

  are linked together with a transmission ratio corresponding to

  laying at the first lower speed.

  When the sleeve 31 is in its second extreme position (rings 32 and 34 meshing with each other), the primary shaft 3 and the secondary shaft 4 are

  interconnected with a corresponding transmission ratio

to the inverter mechanism.

  Naturally, the example shown concerns the case where the gears provided in the original gearbox to obtain the inverter mechanism have been removed. As a result, the use of the first conversion unit 11 allows the addition to the original gearbox, not only of a first lower gear, but also

  of a new report of the inverter mecaxism.

  It is obvious that if it were necessary to add

  a first speed lower than the boot of speed of

  Without modifying the ratio of the inverter, it would not be necessary to provide the ring gear 32 and the

toothed 34.

  Referring now to FIGS. 4 and 5, it will be seen that the toothed wheel 8 is fixed to the sun gear carrier 35 of the differential 7 by means of bolts 36. The same bolts are used to secure the bevel gear

19 on the toothed wheel 8.

  As can be seen in Figure 4, the Tree 17 of

  it is provided at one end of the bevel gear 18 in engagement with the bevel gear 19 is rotatably mounted in the housing 16 at

means of bearings 37.

  The drive shaft 20 has an end a which is pivotally mounted to the inside of an orifice 38

  made in the end of the shaft 17 on the opposite side from the

  At this end is also fixed a toothed wheel 40 by means of an annular nut 39. The extrusion

  of the transmission shaft 20 which is of the opposite side to the ex-

  20a comprises a flange 20b for coupling the transmission shaft 20 to a shaft capable of transmitting the propulsion movement to the rear wheels of the motor vehicle. The transmission shaft 20 has, on the inside housing 15, a splined portion 20c on which is slidably mounted a sleeve 41. The sleeve 41 has a grooved inner surface for coupling with the portion 20c of the transmission shaft 20 and is provided with an inner ring gear 42 able to mesh with the

  toothed wheel 40 rigidly fixed to the shaft 17.

  The sleeve 41 is movable between a first end position (shown in FIG. 4) in which the internal gear ring 42 is spaced apart from the gear wheel 40 so that the shaft 17 and the shaft 20 are uncoupled, and a second extreme position in which the inner ring gear 42 is engaged with the toothed wheel 40 so that the shaft 17 is secured in

rotation of the shaft 20.

  The control of the axial displacement of the sleeve 41 is obtained by means of a fork member 43 fixed on a shaft 44 which is arranged perpendicular to the axis of the shaft 20

  on one of the sides of the latter The shaft 44 is mounted

  in the housing 15 and has an end 44a protruding from the housing 15 and on which is fixed a lever 45 to control the movement of the element

fork 43.

  Each of the two arms of the forked element is

  nor a sliding block 46 which is engaged in a groove

circular 47 of the sleeve 41.

  In order to retain the fork member 43 in each of these two extreme positions corresponding to the extreme positions described above of the sleeve 41, there is provided a protrusion 48 similar to a finger, mounted coullisante in a

part 15a of the casing 15.

  The free end of the projection 48 is maintained in

  contact with the free end of one of the two arms of the

  fork 43 by means of a helical spring 49. The arm of the fork member 43 which cooperates with the projection

  48 is provided with two notches 43a (see FIG. 4) in each

  one of which, the free end of the projection 48 is

  to engage in one or other of the two positions

  extremes of the forked element 43.

  The profile of the notches 43a has the shape of a cam such that when the fork member 43 is rotated, the projection 48 is returned to its retracted position until it engages with the cam. another notch 43a when the fork member reaches the opposite extreme position. Naturally, the described embodiments can be varied within wide limits, without leaving the

framework of the invention.

  It is obvious, for example, that although the example of @onversion shown in the appended drawing is relative to the case in which the gearbox of origin is of the type having four speeds, it is possible to obtain such a verge of an atheism % reb ts at Cq% and PO2o

Claims (16)

  1 - Assembly for the conversion of a gearbox of a motor vehicle of the type comprising a shaft   primary and secondary shaft bearing   in particular engaged and having a differential for transmitting the propulsion movement to a pair of half-shafts which are substantially arranged parallel to the gearbox shafts and which are intended to be connected to the front wheels of a vehicle to engine, in a gearbox of the same type provided in addition to a first inferior speed and a PTO for the transmission of the   propulsion movement to the rear wheels of the vehicle,   characterized in that it comprises: a) a first conversion unit (11) comprising: - a first auxiliary casing (13) intended to be fixed on the casing (2) of the boot of speeds, on an extension thereof. on the opposite side to that of the engine; - a gear transmission (14) mounted   in this first auxiliary casing (13) and which can be ac-   designed to allow transmission between the tree   (3) and the secondary shaft (4) of the speed box.   with a transmission ratio corresponding to the first   lower speed, and means (29, 31) for establishing and suppressing this transmission; b) a second conversion unit (12) comprising: - a second auxiliary casing (15) intended to be fixed on the housing (16) of the differential (7); a PTO (17) supported in the   differential casing (16) so as to enable rotation thereof   about an axis perpendicular to the axis of the differential (7); - a bevel gear transmission (17, 18) for transmitting the propulsion movement of the differential (7) to the aforesaid PTO shaft (17);   a transmission shaft (20) pivotally mounted   in the second auxiliary casing (15), this shaft being intended to be connected to the rear wheels of the motor vehicle and which can be coupled with the shaft of the force prlse (17) above, and means (40 to 45). for coupling and uncoupling the above-mentioned transmission shaft (20) and the shaft PTO (17).   Assembly according to Claim 1, characterized in that the gear transmission (14) forming part of the first conversion unit (11) comprises: a first gear (21) fixed on one end (3b) of U ' Primary shaft (3) protruding into the first auxiliary housing (13)   a second toothed wheel (22) pivotally mounted   on an intermediate shaft (23) fixed in the first 1.5 auxiliary housing (13) and in abutment with the aforementioned first gear (21) a third gear (25) secured to the second gear (22); a fourth gear wheel (26) mounted in   pivoting on an axis (27) fixed in the first housing   liaire (13), the toothed wheel (26) meshing with the aforementioned third gear (25)   a fifth gear wheel (28) mounted   one end (4a) of the secondary shaft (4) which protrudes into the first auxiliary housing (13) and meshes with the aforesaid fourth toothed wheel (26) 1 - a sixth toothed wheel (29) fixed on the lextr The aforesaid means (4a) of the secondary shaft of the aforesaid means for passing the first aforesaid speed and for performing the corresponding disengagement being constituted by a sleeve (31) slidably mounted by means of a splined coupling (30) on the siXIème gear wheel (29) and which is capable of meshing with its suro inner fluted with a ring gear (33) rigidly fixed on the aforementioned fifth gear (28) the aforementioned sleeve being axially movable relative to the sime wheel toothed tooth (29) so as to allow the removal of the anamiesio and the ouppressioon of a   transmission between the sixth gearwheel (29) and the fifth gear me gear (28).   3 - An assembly according to claim 2, characterized in that the aforesaid gear transmission (14) comprises a seventh gear (34) for the inverter mechanism, integral with the second and the third gear (22 and 25) and that the aforesaid sleeve (31) is provided   a ring gear (32) which can mesh with the seventh said gear wheel (34).   4 - Assembly according to claim 1, characterized   in that the bevel gear transmission has   part of the second conversion unit (12) comprises   a conical gear (19) fixed to the planar support   the differential (7) and a conical gear (18) meshing with the aforementioned conical gear (19) and rigidly fixed on the PTO shaft (17).   - Assembly according to claim 1, characterized in that the means for coupling and uncoupling the shaft of the PTO 17 and the transmission shaft (20) comprise a sleeve (41) slidably mounted by means of a coupling with splines on the above-mentioned transmission shaft (20) and provided with a ring gear (42)   capable of meshing with a toothed wheel (40) fixed on the armature   PTO member (17), said sleeve (41) being axially displaceable so as to cause coupling and the aforementioned uncoupling.   6 - Assembly according to claim 5, characterized   by the fact that the aforementioned means for carrying out the   and disconnection between the power take-off shaft and   it (17) and the transmission shaft (20) further comprise a fork member (43) whose arms bear at their free ends two sliding blocks (46) which engage in the interior of a groove circumferential member (47) of said sleeve (41; said forged member (43) being supported by a lateral shaft (44) so as to be pivotable in the second auxiliary housing (15) about an axis perpendicular to the the axis of the aforesaid sleeve (41), the aforesaid lateral shaft (44) having an end (44a) projecting from the housing (15) and comprising a como mance lever (45) 0 7 - An assembly according to claim 6, characterized in that it comprises retaining means (48) for holding the fork member (45) in each of its extraneous positions corresponding to the coupling and uncoupling of the PTO shaft (17). and transmission shaft (20).   An assembly according to claim 7, characterized in that the aforesaid retaining means comprises a finger-like projection (48) elastically pressed against the free end of one of the two pile arms (43) and able to engage selectively dano dzux notches (43a) forwmes sr the exflexite libre EXITGE corresponding LS respectiaement auu deu positions eatrâmes de V ament with fork (43).   9 assembly according to claim 8, characterized in that the profile of the two notches (43a) pr ~ cited formed at the free end of one of the two arms of the 1 = 2 msent fork in the form of a cam so that the displacement of the forklift (43) causes the return to   arrirse of the finger-shaped protrusion (48).   - a conversion of a gearbox of a motor vehicle comprising a primary shaft and a secondary shaft bearing gears constantly in grip and having a differential for the transmission of the propulsion movement to a pair of half-shafts which are substantially arranged in parallel with the shafts of the gearbox and which are intended to be linked to the front wheels of the motor vehicle, in a gearbox of the same type provided in addition to a first gear.   is a PTO for the transmission of the   yament propulsion yus the rear wheels of the vehicule au - teuri aractériS 'by it that this process includes the following opreo tions: A fi rst case aUdliairt (13) is fi xed on the Cazteg (2) of the box of speeds, sM an olongent of ceinoel dcgti oppese I cetui of, engine 247-1878   In the first auxiliary housing (13) there is provided a gear transmission (14) capable of establishing the transmission between the primary shaft and the secondary shaft of the gearbox with a transmission ratio corresponding to the first gear. lower; Means are provided for establishing and suppressing this transmission; A second auxiliary casing (15) is attached to the differential casing (7); In the differential housing (16) there is provided a PTO shaft (17) rotatable about an axis perpendicular to the axis of the differential (7); A bevel gear transmission is provided   (18, 19) to transmit the propulsion movement of the dif-   feral (7) to the PTO shaft (17);   It is pivoted in the second housing auxiliai-   a transmission shaft (20) intended to be connected to the   rear wheels of a motor vehicle which can be accom-   connected to the above-mentioned PTO shaft (17), and   Means are provided for mating and   coupling between the aforesaid transmission shaft (20) and the PTO shaft (17).   11 - Process according to claim 10, characterized in that the aforesaid gear transmission (14) disposed inside the first auxiliary casing (13) comprises:   a first toothed wheel (21) fixed on one end   mite (3b) of the primary shaft (3) which protrudes into the first auxiliary housing (13); a second toothed wheel (22) mounted pivotably on an intermediate shaft (23) fixed in the first casing   (13), the toothed wheel (22) meshing with the first   first gear wheel (21); - a third gear (25) rigidly attached to the second gear wheel (22); a fourth gear wheel (26) pivotally mounted   on an axis (27) fixed in the first auxiliary casing   cited (13), the toothed wheel (26) meshing with the dense trdikerumes (25)   a fifth gear wheel (28) mounted to pivot   one end (4a) of the secondary shaft (4) which   protrudes into the first auxiliary housing (13) and   gripping with the fourth gear wheel (26); - a sixth gear (29) fixed on the aforementioned end (4a) of the secondary shaft (4); - the aforementioned means to pass the first speed   mentioned above and to carry out the corresponding gearing   comprising a sleeve (31) slidably mounted by means of a splined coupling (30) on the sixth gear (29) and capable of meshing with its internally splined surface with a toothed ring gear (33) rigidly fixed   on the fifth gear wheel (28); the sleeve   cited (31) being axially displaceable so as to cause coupling and uncoupling between the fifth and the first sixth gear wheels.   12 - Process according to claim 11, characterized in that the aforesaid gear transmission (14) comprises a seventh gear (34) for the reversing mechanism, rigidly fixed to the aforementioned second and third gear wheels (22, 25) and that the aforementioned sleeve (31) is provided with a ring gear (32) capable of meshing   with the aforementioned seventh gear (34).   13 - Process according to claim 10, characterized   in that the bevel gears transmission pre-   citẻ comprises a bevel gear (19) attached to the differential sun gear carrier (7) and a bevel gear (18)   meshing with the aforementioned conical gear (19) rigidly   attached to the PTO shaft (17).   A method according to claim 10, characterized in that the means for coupling and uncoupling between the PTO shaft (17) and the transmission shaft (20) comprise a sliding sleeve (41). by means of a splined assembly on said transmission shaft (20) provided with an internally-toothed ring gear (42) capable of meshing with a gear wheel (40) attached to a PTO shaft ( 17)   the aforesaid sleeve (41) being axially displaceable so as to   re to perform the aforementioned coupling and uncoupling.   - Process according to claim 14, characterized   by the fact that the aforementioned means for carrying out the   and the disengagement between the PTO shaft (17) and the transmission shaft (20) further comprises a fork member (43) whose arms carry at their free ends two sliding blocks (46). who   engage in a circumferential groove (47) of the man-   chon (41) supra, the aforesaid fork member (43) being carried by a lateral shaft (44) rotatably mounted in the second auxiliary housing (15) about an axis perpendicular to the axis of the sleeve aforesaid (43); the tree   lateral section (44) having an end (44a)   connected to the housing and having a control lever.   16 - A method according to claim 15, characterized in that qLton proit desmonys deretenue (48) to retain the élmnent   four (43) in each of its two extreme positions corresponding to   when coupling and uncoupling the tree of   PTO and the drive shaft (20).   17- Method according to claim 16, characterized in that the aforesaid retaining means comprise a finger-shaped protrusion (48) pressed elastically against   the free end of one of the two arms of the furnace element   (43) and able to engage selectively in two   sizes (43a) formed on the aforementioned free end, corresponding to   respectively at the two extreme positions of the fork (43).   18 - Process according to claim 17, characterized in that the two aforementioned cuts (43a) which are   formed on the free end of one of the two arms of the   fork (43) have a cam-shaped profile so that the movement of the fork member (43a) causes the   back to the projection (48) above.   19 - Motor vehicle gearbox having a first lower gear and a PTO for transmitting the propulsion movement to the rear wheels of the motor vehicle, obtained by converting a gearbox comprising a primary shaft and a solid shaft carrying a constant force and having a differential for transmitting the propulsion movement to a pair of axles which are substantially parallel to the shafts of the gearbox and which are to be connected to the wheels. rear of a vehicle & engine, characterized in that it comprises a first auxiliary casing (13) fixed on the car = ter (2) of the kofte of vitessedorigine an extension thereof of the ce6t opposite that of the engine a transmission & gears (14) mounted in the first auxiliary casing (13) and capable of establishing   transmission between the primary shaft (3) and the secondary shaft   (4) of the itesses box with a transmission ratio   mission corresponding to the first lowest truth prg = quoted;   means to establish and delete this trams   mission; u a second auxiliary casing (15) fixed on the gearbox of the differential (16)} - a PTO shaft (17) pivotally mounted on the housing of the differential (16) about an axis epepndal cular axis differential (7) D = bevel gears transmission (18, 19) p2oe transmit the propulsion movement diffrentil (7) to 1'trebre aforesaid PTO (17); a transmission shaft (20) pivotally mounted to the auxiliary casing (15) which is intended to be connected to the rear wheels of the motor vehicle and which can be coupled to the PTO shaft (11), and means for effecting the coupling and coupling between the aforementioned transmission shaft (20) and the PTO shaft (17).   The gearshift has the same effect as the gear transmission (1) of the first auxiliary housing (13). comprend.-   u first toothed wheel (21) fixed on a e: atfré mité (3b) of 1'arbre primary (3) which protrudes into the 2 471878   first auxiliary housing (13); a second toothed wheel (22) mounted pivotably on an intermediate shaft (23) fixed in the first casing   (13), the toothed wheel (22) meshing with the first   first gear wheel (21); - a third gear (25) rigidly fixed to the second gear wheel (22); a fourth gear wheel (26) pivotally mounted   on an axis (27) fixed in the first auxiliary casing (13).   the toothed wheel (26) meshing with the aforementioned third gear (25); a fifth gear (28) pivotally mounted on one end (4a) of the secondary shaft (4) projecting into the first auxiliary casing (13) and meshing with the aforesaid fourth gear (26); sixth gear wheel (29) fixed on said end (4a) of the secondary shaft; - the aforementioned means to pass the first speed   mentioned above and to perform the correct decoupling   respodant comprises a mancxhon (31) slidably mounted at the expense of a   spline-like projection (30) on the sixth gear (29) and capable of meshing with its fluted interior surface   with a ring gear (33) fixed rigidly to -----   the fifth gear wheel (28) mentioned above; the aforementioned sleeve (31) being axially displaceable so as to effect coupling and uncoupling between the fifth and the sixth gear wheels (28,29).   21 - Boot according to larevendication 20, characterized in that the aforesaid gear transmission (14) comprises a seventh gear (34) for the   reversing mechanism, rigidly attached to the second and third   second gears (22, 25) and that said sleeve (31) is provided with a ring gear (32) capable of meshing with   the aforementioned seventh gear (34).   Gearbox according to Claim 19, characterized in that the aforesaid bevel gear transmission comprises a conical gear (19) fixed to the sun gear carrier of the differential (7) and -247.1878   a conical pinion (18) meshing with the aforesaid conical toothed wheel (19) and rigidly fixed to the engagement shaft; strength (17).   Gearbox according to claim 19, characterized in that the means for effecting the coupling and uncoupling between the PTO shaft (17) and the transmission shaft (20) comprise a   sleeve (41) slidably mounted by means of an assembly   cracks on said transmission shaft (20) and provided with a ring gear (42) capable of meshing with a gear wheel (40) fixed to the PTO shaft (17); the aforementioned sleeve (43) being axially displaceable from   to obtain the precise coupling and uncoupling tees.   13 24 - Gearbox according to claim 23,   characterized in that the aforesaid means for obtaining said coupling and uncoupling between the PTO shaft (17) and the transmission shaft (20) comprise a fork member (43) whose arms their free ends are two sliding blocks (46) which are engaged in a circumferential groove (47) of the aforementioned sleeve (41), the aforementioned fork member (43) being carried by a pivotally mounted lateral shaft (44).   in the second auxiliary casing (15) around an axis   to the axis of the aforesaid sleeve (41), the aforementioned lateral shaft (44; having an end (44a) projecting out   housing (15) and having a control lever (45).   Gearbox according to Claim 24,   characterized by the fact that it includes means of   holding (48) for retaining the fork member (43) in each of its two extreme positions corresponding to the coupling and uncoupling between the setting shaft   of force (17) and the transmission shaft (20).   Gearbox according to claim 25, 33 characterized in that the aforesaid restraint means   comprise a finger-shaped protrusion (48) pressed   against the free end of one of the two arms of the fork (43) and capable of engaging olectively in two notches (43a) formed on the ends   aforementioned free words respectively corresponding to the two posi-   extremes of the forked element (43).   27 - gearbox according to claim 26, characterized in that the aforementioned notches, which are formed on the free end of one of the two arms of the fork member (43), have a profile in the form of cam so that the displacement of the element fork (43)   causes the back projection (48) above.