Power transmission with 5-stage planetary gear unit

A power transmission has a 5-stage planetary transmission unit having first, second, third, fourth and fifth transmission shafts, a reverse mechanism and a coupling through which the first transmission shaft is connectable with a drive, a hydrostatic adjusting mechanism through which the second transmission shaft is connectable to the drive, and stage gears and associated stage couplings arranged so that the third, the fourth, and the fifth transmission shafts are each connected with a power take off through a respective one of the stage gears and the stage couplings. The hydrostatic adjusting mechanism is connectable through the reverse transmission and the coupling to the drive.

BACKGROUND OF THE INVENTION 
The present invention relates to a power transmission with a 5-stage 
planetary gear unit. 
More particularly, it relates to a power transmission with a planetary gear 
unit with a first transmission shaft connectable with a drive through a 
reverse mechanism and a coupling, a second transmission shaft connected 
through hydrostatic adjusting mechanism with the drive, and third, fourth 
and fifth transmission shafts connected with at least one power take-off 
through a corresponding toothed gear transmission stage and an associated 
gear shift coupling. 
Such a power transmission is disclosed for example in the German document 
DE-C1-43 23 358. In this transmission the hydrostatic adjusting mechanism 
is always coupled at the input side with the drive unit, and from it the 
planetary gear unit is controlled on the one hand which on the other hand 
is coupled through the reverse coupling with the drive unit. Thereby the 
adjusting mechanism runs idly, or in other words when no gear stage is 
introduced and the coupling is not actuated, always with the swinging-in 
adjusting unit. During starting first the reverse coupling is turned on 
and simultaneously the hydrostatic adjusting unit fully swings out, so 
that at the planetary gear unit a balance of both drive units is provided, 
or in other words a so-called regulated zero point is obtained, and a 
vehicle connected at the output side is stopped. During turning back of 
the adjusting unit the vehicle starts the drive in correspondence with the 
rotary speed difference of the planetary gear unit. This obtaining of the 
parallelity of the coupling-in step and swinging-out of the adjusting 
unit, or in other words holding of the regulated zero point, poses high 
requirements to the electronic control of the associated adjusting means. 
The angle acceleration steps which for the different adjusting means 
actuate with respect to the power pickup must be brought completely 
parallel since in the event of a timely different engagement of the 
reverse coupling when compared with the swinging step, a power pickup can 
be performed in a not desired direction which endangers the safety and is 
completely unacceptable, in particular for vehicles. The further 
disadvantage is that during reversing the adjusting unit in standstill 
must be adjusted to the opposite extreme position so that for reversing 
takes unacceptably long time. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a power 
transmission which avoids the disadvantages of the prior art. 
More particularly, it is an object of the present invention to provide a 
power transmission in which a reliable starting a fast reversing can be 
provided with reduced control expenses. 
In keeping with these objects and with others which will become apparent 
hereinafter, one feature of the present invention resides, briefly stated, 
in a power transmission in which the hydrostatic adjusting mechanism to 
the inlet side is connected with the drive unit through the reversing 
mechanism and the coupling. 
The crux of the invention is that the hydrostatic adjusting mechanism is 
not permanently connected with the drive unit but instead is connected 
behind the reversing mechanism and the start reversing coupling as the 
direct input of the planetary transmission unit or in other words always 
has a synchronous and phase identical drive. A synchronous regulation of 
the adjusting unit during start coupling and its change from one extreme 
position to the other during reversing are dispensed with. 
Preferably the start and reverse coupling is a so-called wet multi-plate 
coupling. Therefore during starting and reversing higher drive regions can 
be obtained which serves for substantial safety and easy operation. 
Depending on the application the transmission can be formed with 
insignificant changes as four stage transmission or five stage 
transmission. 
In order to simplify the construction all stage couplings are arranged, 
therefore the accompanying inertia moment of the coupling shaft is 
extraordinarily small. For a four stage transmission the couplings can 
include only two coupling pairs each with a three position control, while 
for the five stage transmission it suffices to provide only one further 
individual coupling. 
The whole transmission unit is arranged very compact in a block housing. 
The hydrostatic adjusting mechanism with parallel axles is located 
centrally and the planetary transmission unit is arranged coaxially with a 
constant unit. The input shaft and the coupling shaft are arranged at both 
sides of the adjusting mechanism substantially in its plane of symmetry 
and serve conventionally as main power take off shaft. 
In accordance with a further embodiment of the invention a proportional 
power take off shaft is arranged in the above mentioned plane of symmetry 
and connected with the coupling shaft, preferably through a power take off 
coupling. 
The main output shaft serves for example for the rear wheel drive of a 
vehicle and the connectable proportional take off shaft serves for the 
front wheel drive and the front wheels and rear wheels usually have 
different diameters. The input shaft preferably extends from the block 
housing at both sides. Therefore it is connectable on one side with a 
crankshaft of a drive motor, and on the other side operates as a power 
take off shaft. 
The small compact construction of the inventive power transmission is 
especially suitable for so-called frame assembly tractors and block 
assembly tractors. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a 5-stage transmission which is formed by a planetary 
transmission unit UG which at a drive side is connected with a web gear 
shaft 1 and at the other side is connected with a hydrostatic adjusting 
mechanism HG through a sun gear shaft. At the take off side three hollow 
shafts A, C, E are provided on the planetary transmission unit UG. Two of 
these hollow shafts are connected with further sun gears, and one hollow 
shaft is connected with a hollow gear HR of another planetary stage P1. 
The planetary transmission unit UG contains total three planetary stages 
P1, P2, P3. A reverse coupling R, V is located before the web gear shaft. 
It is connected through a reverse mechanism WG with an input shaft EW 
which is controlled by a drive AT, for example an internal combustion 
engine. The reverse mechanism WG includes reverse gears UR for the reverse 
driving. A hydraulic supply source HY is coupled outside of the housing G 
with one of the reverse gears UR. 
A web wheel toothed rim SK is mounted on the web gear and engages with a 
toothed gear ZG which controls the adjusting unit of the hydrostatic 
mechanism HG. The constant component KE of the hydrostatic adjusting 
mechanism HG controls the inner sun gear shaft B of the first planetary 
stage P1. 
A coupling KW is further supported in the housing G, and couplings K1-K5 of 
five stages are arranged on the coupling shaft. The gears Z1-Z5 for the 
five stages are each connected on the one hand with one of the hollow 
shafts A, C, E of the planetary transmission unit UG and on the other hand 
supported with the associated coupling part on the coupling shaft KW. 
Advantageously, one individual coupling is provided for the first stage, 
whose hollow shaft C stands still in the start condition during starting. 
Furthermore, two coupling pairs K3, K5; K2, K4 are provided for the 
corresponding stages Z3, Z5; Z2, Z4. Both coupling pairs have each 
three-position adjusting devices KS1, KS2 whose neutral position is 
located centrally between both coupling positions. The first stage has 
only a simple coupling actuator KS. The arrangement of all stage couplings 
K1-K5 in series on one shaft, provide for a construction which is simple 
and ease to monitor. 
The power take off AUS is carried out for example by the coupling shaft KW. 
It leads to the rear wheels as a main power take off HA when it is used in 
the power take off of a tractor or a similar vehicle. 
Optionally, a further power take off with proportional rotary speed can be 
provided, in particular on the front wheels of a vehicle. For this purpose 
a take off coupling AK is provided on the coupling shaft KW, and the 
proportional take off shaft PAW is controlled from it through a toothed 
gear. The proportional take off shaft leads in particular to the front 
wheel drive unit VA of the vehicle. 
In a known manner, the input shaft EW can be arranged on a power take off 
shaft ZW at the other side of the housing G relative to the drive side 
EIN. 
Both inputs of the planetary transmission unit UG are connected behind the 
reverse coupling R, V. Therefore, after the coupling, the transmission 
shaft C of the first stage is brought by adjusting of the adjustment 
element to standstill and then the synchronous coupling is introduced. 
Also, the further couplings K2-K5 of other stages are synchronous 
couplings, for example claw couplings, which have a very simple 
construction and they are always actuated during rotary speed equilibrium 
on the parts to be coupled. Therefore practically there is wear. 
The whole transmission has the minimal losses when the individual stages 
are brought to the central position, the hydrostatic adjusting mechanism 
HG runs idle and its power take off shaft stands still. 
FIG. 2 shows a 4-stage transmission which is substantially similar to the 
above described 5-stage transmission. Therefore, only the differences of 
these transmissions are described hereinbelow. 
Two coupling pairs K1, K3; K2, K4 are arranged on the coupling shaft KW and 
belong correspondingly to the gears Z1-Z4 of the four stages. The gear Z1 
of the first stage is arranged on the hollow shaft C of the planetary 
transmission unit UG and is driven so that with the introduced start 
coupling R, W the control of the planetary transmission unit via the web 
gear shaft 1 and via the sun gear shaft B through the hydrostatic 
adjusting mechanism HG is located in standstill. The further hollow shaft 
E of the planetary transmission unit UG leads to the gear Z3 of the third 
stage, and the further hollow shaft A carries the gears of the second and 
fourth stages. 
The first coupling pair K1, K3 is activated from a 3-position adjusting 
device with a neutral central position. The second coupling pair K2, K4 is 
controlled by a second 3-position adjusting device with a neutral central 
position. 
FIG. 3 shows a diagram for a transmission which is used in a vehicle and is 
to be driven forward and rearward with the speed v in the stages 1-5. The 
vertical axis represents the power which is transmitted on the shaft B 
from the hydrostatic adjusting mechanism HG to the planetary transmission 
unit. It can be seen that in the neutral position N in which no stages are 
introduced and also the reverse coupling R, V is not actuated, no power is 
used. 
FIG. 4 shows an advantageous arrangement of the whole transmission unit in 
a housing G on an end view. In the drawing the hydrostatic adjusting 
mechanism HG with its adjusting unit VE and its constant unit KE is 
arranged centrally transversely. Coaxial to the constant unit, there are 
arranged the reversing coupling R, V and the planetary transmission unit 
UG with its drive axes 1, B. The input shaft EW on the one hand, and the 
coupling shaft KW on the other hand are arranged substantially in the 
symmetry plane between the adjusting unit VE and the constant unit KE at 
both sides of these units. The input shaft EW extends on the one side to 
the drive AT and on the other side to the take off shaft ZW and carries 
the reverse mechanism WG. The coupling shaft KW extends from the housing 
to the main or rear gear drive HA. 
In accordance with a first simple embodiment, the housing G ends at the 
dash-dot line in the drawing and therefore has an extremely compact block 
form. As for the proportional drive shaft PAW, it is provided that it 
leads to a front wheel drive VA formed another wheel diameter, so that the 
housing is extended outwardly by a housing portion G* beyond the dash-dot 
line. The proportional drive shaft PAW is supported there preferably in 
the above mentioned plane of symmetry and carries the associated gear 
which is connected with the coupling shaft KW through the power take off 
coupling. 
FIG. 5 shows a switching diagram for the individual couplings K1-K5; R, V 
with the associated forward stages V1-V5 and the rearward stages R1-R5, as 
well as the neutral position N. As can be seen from the drawing, from the 
neutral position N the reverse mechanism R, V is turned either with the 
rearward coupling or with the forward coupling to the neutral position N, 
and then one of the stage switching couplings K1-K5 is introduced. A 
control is therefore introduced which takes care of the situation that the 
couplings are turned on or turned off only in the synchronous position. 
The transmission is designed so that the hydraulic adjusting mechanism is 
brought in each stage from one extreme position to another extreme 
position. Correspondingly limiting passing synchronization for the 
coupling of the neighboring stage is produced. In particular, in the 
neutral position N no changeover of the adjusting unit is needed for going 
from a forward drive to a rearward drive. With the uncoupled reverse gear 
R, V, no power flows in the transmission UG, HG, since both the planetary 
transmission unit UG and the hydrostatic element HG are separated from the 
drive AT. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
power transmission with 5-stage planetary gear unit, it is not intended to 
be limited to the details shown, since various modifications and 
structural changes may be made without departing in any way from the 
spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.