Centralized wet-brake and other improvements for running gears with adjustable wheel track

A differential mechanism for heavy-duty power machines with adjustable wheel tracks, such as farm machinery. The mechanism is provided with a specially constructed differential gear arrangement, including first and second differential gear housing parts. The first part supports an annular crown gear. The second part defines an open ended chamber. The housing is supported at each end in roller bearings. A centralized disc brake may be mounted externally on the second housing part. An anti-slip mechanism may be mounted on the inside of the second housing part. The anti-slip mechanism is controllably engagable.

BACKGROUND OF THE INVENTION 
The invention relates to a differential mechanism with double gear ratio 
transmission for vehicles, in particular for heavy-duty power machines 
with adjustable wheel tracks, such as farm machinery, in which a combined 
main drive is used, which is provided with a central wet disc brake 
construction and a connectable gear mechanism with restricted slip. 
Epicyclic gear mechanisms are arranged in the main gear housing to have an 
improved self-aligning ability, while the driving axles are arranged with 
improved bearing locations. 
Running gears used in power machines with adjustable wheel tracks (also 
known as rod-type running gears) have to meet the most complicated--and 
frequently contradictory--requirements. For example, wide wheel tracks 
require solid half-shafts carried by perfectly adjusted bearing supports 
with high loadability; narrow wheel tracks require a middle-part with the 
minimum space requirement, which influences negatively realization of 
proper conditions related to the wide wheel tracks. 
In vehicles lacking wheel hub drives, brake constructions can be arranged 
in main gear housings only. These are the so-called internal or 
wet-brakes. However, these solutions influence negatively the realization 
of the narrow and wide wheel track as well, as in this case the width of 
the middle-part is increased and, simultaneously, the space serving for 
the bearing supports of the drive shafts will be reduced. 
Running gears of heavy-duty power machines with adjustable wheel tracks are 
designed generally with double gear transmissions based largely on 
conceptions that enable the width of the middle-part of the running gear 
to be reduced. This involves, however, the application of epicyclic gears 
with a high reduction ratio (generally over 5) and a bevel 
gear-crown-wheel pair also with a high gear ratio. The wide bearing basis 
required for a stiff bearing to support a crown wheel of a large diameter 
also exerts a negative influence on the possible realization of narrow and 
wide wheel tracks respectively. 
When using wide wheel tracks, wheel forces are transmitted through large 
arms via the half-shafts to the gear housings and the middle-part of the 
running gear. When these half-shafts are stiffly assembled and not 
arranged as so-called "floating" half-shafts, they require most careful 
assembly. Otherwise, their useful life will be very short due to the 
considerable deformation of elements of the drive-chain. 
Modern types of running gears used in agricultural power machines require 
differential mechanisms with restricted slip, with the possibility of 
coupling and decoupling the limited slip mechanism. Taking into 
consideration that, with the rod-type gears, "everything" is arranged in 
the middle-part and "everything" performs a rotary motion, a coupling fork 
cannot be built in. This is particularly true if the running gear is to be 
provided with an internal brake construction. For this reason, 
mechanically actuated differential gears with restricted slip--considered 
as the most reliable construction--have never been used. 
The requirements mentioned above are met by the known construction only 
functionally. That means that they are reliable and able to function. 
However, contradictory characteristics are not eliminated. In other words, 
new constructional solutions are not paired with these running gears in 
order to fulfill tasks different from the traditional ones. By choosing 
obvious and offered solutions, the users accept the fact that parameters 
of the running gears are such as can be obtained with the traditional 
solutions. From this it results that generally known running gears for 
adjustable wheel track equipment (John-Deere, Massey-Ferguson, Steyr, 
etc.) are based on nearly identical principles of design, and they differ 
only in respect to partial solutions of the construction. These basic 
principles can be summarized as follows: 
The differential gear driven with a bevel gear/crown wheel pair is 
generally supported by bearings in an "X"-arrangement. After the 
differential gear, the sun wheels --forming a monolithic unit with inner 
half-shafts--drive epicyclic gears, which are arranged adjacent the sides 
of the middle-part of the main housing. The carriers of the epicyclic 
gears are provided with an internal rib to drive directly the external 
axles. 
One unit each of the generally hydraulically actuated inner disc 
brakes--one for each side--is arranged between the middle-part of the main 
housing and the epicyclic gears so that the active rotating discs engage 
with the teeth of the sun wheel. 
A solution is also known, with which the rotating braking discs engage the 
carrier of the epicyclic gear, that being the drive element with the 
largest moment. 
In the housing of the differential gear, formed with one or more dividing 
planes, differential gears with main drive pinion are used. Restricted 
slip is achieved in such manner that the traditional differential gear 
includes a hydraulically actuated or spring-pre-stressed bundle of 
lamellae, or the increased internal friction is established proportionally 
with the moment of the differential gear, e.g., by inserting a disc with 
spur-gearing with a large contact angle. 
Now let us survey the negative features resulting from the described and 
presently used basic principles of projecting: 
(1) Uniform support of the crown-wheel differential gear housing by 
bearings in an "X"-arrangement enables simple adjustment of the backlash 
and the bearings of the equalizing gear by means of the generally known 
bearing nuts. At the same time, in practice, a cross-spread arrangement 
(in other words, an "O"-arrangement) would result in a far more effective 
bearing basis. 
(2) The disc brake, arranged on one side of the bridge housing has a 
considerable space requirement. If the users demand an external 
transmission brake instead of the internal wet-brake, the remaining 
unutilized empty space influences negatively the parameters of the running 
gear. This results from the fact that it is not at all economical to 
design separate constructions for both external and internal braking 
systems, as the number of produced running gears of either type is 
relatively low. 
(3) In known constructions, active discs of the disc brake usually engaged 
with teeth of the sun-gear (side gear) or with the ribs on internal 
self-adjusting (so-called "floating") half-shafts. This is a rather 
contradictory solution, desirably affecting both the brake and the 
epicyclic gear, because the rotating brake discs, loaded with moment and 
requiring a good driving connection, are engaged with the side gears 
requiring, which must have the ability of self-adjustment, or with the 
inner half-shafts. 
(4) Supporting bearings of the crown-wheel in an "X"-arrangement, as well 
as arranging the brake units along side of the middle-part of the main 
housing, practically excludes the possibility that a mechanically actuated 
differential gear with a selectively engageable restricted slip could be 
used. Hydraulically actuated lamella-bundles are more expensive and less 
reliable. At the same time, lamella-bundles which are are constantly 
pre-stressed with spring force, and which cannot be uncoupled, exert a 
negative influence on the driving system and abrade the tires, if the 
power machine travels on good surfaces, e.g., on a concrete road. 
Differential gears mechanisms where the coefficient of friction is 
increased proportionally with the moment (e.g., differential gears, 
incorporating discs with spur-gears with a large connection angle and 
combined with a bundle of lamellae) are efficient generally only if the 
desired high moment is available. 
(5) With crown-wheel-differential gear supported in bearings with an 
"X"-arrangement, the differential gear housing is laterally closed. 
Accordingly, to obtain lamella-bundles with proper energy absorption, 
i.e., of sufficient volume--more than one dividing plane must be provided 
in the differential gear housing, involving compellingly increased costs. 
(6) Bar-axles of running gears with adjustable wheel tracks are rigidly 
assembled. Bearing support is provided by bearings with high loadability 
adjusted to be tight fitting. Driving bar-axles are driven directly from 
the carriers of the epicyclic gears, through a ribbed drive. In practice, 
this drive is realized so that the ribbed hub of the carrier of the 
epicyclic gears is clamped rigidly between an inner taper-roller bearing 
of the bar-axle and a so-called supporting plate, as the hub of the 
carrier of the epicyclic gear also partakes in the support. Due to the 
rigid clamping of said carrier, self-adjusting ability of the gears is 
restricted. As a consequence, the gears receive accessory loads, as 
deformations of the loaded bar-axles are transferred to the epicyclic 
gears, thus shortening their useful life. That means that there is a 
disturbing interaction between the epicyclic gears and the bearings of the 
bar-axles. 
The invention is based on the development of a heavy-duty running gear with 
internal disc brakes and a differential gear with restricted slip which 
can be mechanically coupled and uncoupled with restricted dimensions of 
the middle-part in consideration of the requirements of equipment with 
adjustable wheel tracks. 
Power machines are known to which running gears with constant wheel tracks 
are used and with which epicyclic gear and brakes are arranged at the hub. 
Power machines are also known which contain a central brake construction, 
which is mounted either on an auxiliary gear box or on the drive of the 
main drive of the--generally frontal--running gear. In both cases, it is 
important that the vehicle should meet all the requirements in respect to 
safe braking. It is quite obvious that the conventional solution for 
running gears with adjustable wheel tracks, wherein separate wet-brake 
constructions are arranged on each side, in other words for each wheel, 
results from the practice followed with traditional running gears, where 
wheel brakes used to be applied. The present invention is based on the 
recognition that one central so-called wet-brake suffices for running 
gears with adjustable wheel tracks, if this wet-brake is incorporated as 
part of the running gear. 
In the middle-part of the running gears with adjustable wheel tracks, next 
to the driving bevel gear--on the side lying opposite to the 
crown-wheel--there is an expedient space for installing a centralized 
brake construction. If the centralized brake is arranged here, widening of 
the middle-part of the running gear becomes superfluous, as space 
requirements of the side facing the crown-wheel will be determinant in 
this case. In running gears designed in compliance with generally known 
practice, due to the symmetry related to the longitudinal axis of the 
vehicle (e.g., generally the two sides of the main housing are completely 
identical), the side facing the crown-wheel is not at all utilized. By the 
central arrangement according to the invention the housing of the 
equalizing gear is part of the brake construction; active brake discs are 
connected with the housing of the equalizing gear. 
In order to be able to realize controllable, mechanical coupling of the 
differential gear with restricted slip, the housing of the equalizing gear 
must be accessible from the end. This could be achieved by placing the 
brake construction around the equalizing gear. A further prerequisite of 
accessibility is that the housing of the equalizing gear should be open on 
the end. This requirement can be met if the unit consisting of the 
equalizing gear and the crown-wheel is supported in bearings in a 
"cross-spread" arrangement, and in this way, further accessory advantages 
can be obtained. First of all, compared to the "X"-arrangement, the 
"cross-spread" arrangement of the bearings guarantees--with the same space 
requirement--a far better bearing basis. On the other hand, it enables the 
bundles of lamellae to be of sufficient volume, i.e., having the required 
ability of energy absorption to be installed from the outside. Further 
advantages are that the housing of the equalizing gear does not require 
more than one dividing plane. Moreover, the bundle of lamellae providing 
restricted slip, which completes the traditional differential gear with 
bevel gears, can be simply omitted, where desired, without disassembling 
the differential gear. 
Adjacent the end of the middle-part of the running gear lying opposite to 
the crown-wheel--we established the conditions for installing a coupling 
fork. Thus, we produced a combined main drive unit provided with a 
centralized brake construction and with a differential gear with 
restricted slip with the possibility of controlled coupling. 
The centralized braking system according to the invention--in contrast to 
general practice--does not brake the sun wheel (which requires the ability 
of self-adjustment) or the inner half-shafts, but it is connected to the 
housing of the equalizing gear. The latter is supported in bearings and 
provides an excellent guide to the rotating brake discs. In such a manner, 
the self-adjusting ability of the epicyclic gears can be improved. 
The other part of the task to be solved is to make the epicyclic gears 
independent of the effect of the loaded half-shafts. As already mentioned 
before, according to presently known general practice, the hub-part of the 
carrier of the epicyclic gear, being clamped rigidly between the inner 
taper-roller bearing of a bar-axle and the supporting plate, transfers the 
driving moment to said bar-axles with the aid of ribs. Deformations of the 
loaded bar-axles are transferred to the carriers of the epicyclic gears 
and produce external loads in the epicyclic gear elements, which are 
restricted in respect to self-adjusting ability. This results in a 
shortened useful life. 
In accordance with the invention independence of the epicyclic gears is 
realized so that a bushing--provided with ribs on both the outside and 
inside--is inserted between the bar-axle and the hub-parts of the 
epicyclic gear carriers. This bushing is clamped rigidly between an inner 
taper-roller bearing of the bar-axle and a supporting disc fitted tightly 
on the bar-rod by means of the ribs, while the hub-part of the carrier of 
the epicyclic gear is fitted loosely to the outer ribs. However, this 
hub-part does not partake in supporting the bearing of the bar-axle. In 
such a manner, the carrier of the epicyclic gear becomes completely 
self-aligning and independent: by the aid of the ribbed bushing it 
continues to transfer the driving moment to the bar-axle, but it is 
relieved from the deformations. 
It is considered as essential that the loose rib bond be arranged outside 
the plane of the epicyclic gear. In such a manner, not only angle-setting 
but also compensation of errors resulting from eccentricity become 
possible. Application of the ribbed bushing yields the possibility that 
adjustment of the bearings of the bar-axles can be performed without 
affecting the carriers of the epicyclic gear, as only the bushing is 
involved in sustaining the bearings. 
Application of the bushing according to the invention facilitates servicing 
of the running gears, as in the course of repairing or exchanging the 
epicyclic gears, bearings of the bar-axles need not be disassembled, which 
would be unavoidable with the presently known constructions. 
Accordingly, we succeeded to realize another most important aim: epicyclic 
gears can be rendered completely independent and self-aligning. They are 
not influenced either by the brake constructions or the bar-axles, 
resulting obviously in the considerable prolongation of the useful life of 
the force transmitting elements without the necessity of increasing the 
dimensions or using special material quality or technologies.

Referring to FIG. 1 it seems to be sufficient to discuss only the part of 
the construction which is provided with the centralized brake and the 
differential gear with restricted slip, as with the exception of these 
main components the other side of the mechanism is quite identical. 
The bevel gear 1 drives a crown-wheel 2, which is screwed to the housing of 
an equalizing gear consisting of the halves 3a, 3b. The sun wheel 5, 
connected to an inner half-shaft 4 with ribs, transfers the drive from the 
differential gear with the traditional bevel gear to the planet pinions 9, 
which are supported in the carrier 6a, 6b by means of needle-roller 
bearings 8 and pins 7. The gear rim 12 is clamped rigidly between the main 
gear box 10 and the end cover 11 and serves as a torque support. The 
carrier of the epicyclic gears is composed of carrier halves 6a and 6b, 
out of which the half-part 6b transfers the torque to the bushing 13 by 
means of a loose splined connection, which provides both radial and and 
axial clearance. The bushing 13 transfers the torque through its inner 
ribs or splines to the bar-axle 14, connected to the wheels of the 
vehicle. Bar-axle 14 is supported in bevel roller bearings 15 and 16. 
These can be adjusted by means of a bolt 17, the support disc 18 and the 
joining plates 19 and so that the bushing 13, provided with ribs on the 
inside and outside as well, is clamped between the supporting disc 18 and 
the inner bevel-roller bearing 15. 
The structural unit consisting of the box of the equalizing gear and the 
crown-wheel is supported in bearings, in a "cross-spread" arrangement, 
namely in the bevel roller bearing 21 seated on the carrier 20 and in the 
bevel roller bearing 23 seated on the carrier 22. 
The half-part 3b of the equalizing gear box is provided with splines or 
ribs on both the inside and outside. The outer ribs are in a driving 
connection with a set of rotating brake discs 24, which are braked by an 
interleaved set of stationary brake discs 25 provided with ribs on their 
external surfaces, a brake housing 26 is provided with inner ribs which 
engage the stationary brake discs loosely, but non-rotatively. When the 
brake housing becomes pressurized an annular brake-piston 27 is displaced 
to compress the stack of brake discs 24, 25. The brake housing 26 is fixed 
with screws 28 to the machined inner surface of the lateral face of the 
main gear box 10. 
The bracket-supported carrier of the cylindrical roller bearing 29 for the 
bevel gear 1 is desirably cast as a monolithic unit with the brake housing 
26. 
The liquid space of the brake is separated by means of sealing rings 30 and 
31 from the oil space of the running gear. A hollow tube 32, sealed by 
means of a sealing element 34, is secured with a fixing-screw 33. Said 
hollow extension can be mounted on the rear side of the running gear from 
outside. Brake fluid is introduced through the pipe 36 attached with a 
hollow screw 35. By means of components identical with those indicated 
with the reference numbers 32, 33, 34, 35, located on the bottom of the 
running gear, brake fluid can be suitably discharged, while on the upper 
part the working space of the brake can be deaerated without dissembling 
the oil space of the running gear. 
In the half-part 3b of the box of the equalizing gear, we arranged the 
bundles of lamellae for restricting revolving of the equalizing gear box 
relative to the half-shaft 4. Compression springs 39 provide for constant 
pre-stress of the bundle of anti-slip lamellae arranged between a pressure 
disc 37 and a supporting disc 38. The axial force of the springs is 
regulated by a locking ring 40. The bevel roller bearing 23 bears against 
the other side of the locking ring 40 by the intervention of a spacer 41. 
Lamellae 42 formed with outer ribs engage with the inner ribs of the 
half-part 3b of the equalizing gear housing. These structural elements are 
dimensioned so that, after having removed the bevel roller bearing 23, 
lamellae 42 with the external ribs can be installed from outside. Lamella 
43 with the internal ribs are engaging with the outer ribs of the toothed 
hub 44, while the inner end of said toothed hub is guided by a large bevel 
gear 45, and the other end thereof is guided by the centralizing ring 46. 
The task of the centralizing ring 46 is to guide concentrically the 
toothed hub 44 and frontal teeth of a sliding coupling sleeve 47. The 
sliding coupling sleeve 47 is able to slide on the ribs of the inner 
half-shaft 4 by mean of the coupling fork 50, which is supported in 
bearings by a pin 49, which again is clamped in the carrier 48. The 
coupling fork 50 can be led between the lateral wall of the gear box 10 
and the epicyclic gear outside the gear box 10, and can be actuated with 
any optional fork-actuating device. The coupling fork 50 engages with the 
slotted part of the sliding coupling sleeve 47, which extends through an 
end opening in the bearing bracket 22. The installation of the coupling 
fork 50 and leading the same outside the gear box 10 are illustrated in 
FIG. 4. 
If the frontal teeth 44a, 47a of the sliding coupling sleeve 47 and the 
splined hub 44 become engaged by means of the coupling fork 50, the torque 
of friction of the pre-stressed bundle of lamellae restricts the gyration 
of the equalizing gear. By proper pre-stressing of the compression springs 
39, the so-called closing torque of the bundle of lamellae can be easily 
set to a desired value in accordance with the character of utilization. 
The extent of pre-stress can be varied by modifying the number of 
lamella-pairs or by choosing the thickness of the aforementioned 
supporting disc 38. It goes without saying that, if the sliding coupling 
sleeve 47 and the frontal toothing of the hub 44 are disengaged, the 
so-called closing torque of the bundle of lamellae does not influence the 
function of the equalizing gear with the traditional bevel gear. Thus, a 
power machine is operated under good soil conditions, e.g., it travels on 
a road coated with concrete or any other hard surface, the anti-slip 
lamellae can be uncoupled to avoid superfluous overload of the force 
transmitting elements and in accelerated wear of the tires. 
FIG. 2 shows a version of the construction according to the invention, in 
which the internal wet-brake is replaced by external brake means (not 
shown). A carrier 51 supported in brackets, is fixed to the machined inner 
plane of the lateral face of the gear-box 10 by means of screws 28, 
instead of attaching a brake-housing. This carrier serves for clamping the 
cylinder roller bearing 29 of the driving bevel gear 1. 
As the centralized brake construction is omitted, it suffices to construct 
the half-part 3c of the equalizing gearbox with ribs in the inside only. 
FIG. 3 illustrates the most simple embodiment of the construction according 
to the invention. With this solution, the running gear does not contain 
either an internal brake construction or an equalizing gear with 
restricted slip. In this case, the bracket-supported carrier of the roller 
bearing 29 of the bevel gear 1 can be formed as a cast monolithic unit 
with the gearbox 10. It also seems to be expedient to apply the half-part 
3d of the equalizing gearbox, as it is to be seen in FIG. 3, i.e., of the 
generally same open-ended configuration as in FIGS. 1 and 2. 
From the figures, it becomes obvious that a running gear can also be 
assembled which contains a centralized internal brake, but at the same 
time it is provided with a traditional equalizing gear without the bundle 
of lamellae for assuring restricted slip. 
From FIGS. 1, 2 and 3 it becomes quite obvious that by the application of 
the centralized wet-brake according to the invention, and by using the 
connectable equalizing gear with restricted slip, a combined main drive 
unit may be obtained, which yields the possibility of producing heavy-duty 
running gears with adjustable wheel track, constructed in different forms. 
The mechanism can be assembled with or without an internal brake unit, 
provided with a traditional equalizing gear, or with a controllably 
connectable equalizing gear with restricted slip. It can be observed that 
application or omission of main units fulfilling different functions do 
not influence negatively either technical parameters of the running gears 
or economical production. 
It should be separately emphasized that in known practice--due to the brake 
units arranged on both sides--a double quantity of the components was 
required. At the same time, with the central arrangement according to the 
invention, only one single brake unit is to be installed. Technical 
parameters are thus considerably improved, as installation of the central 
brake does not demand increased dimensions of the middle-part of the 
running gear. 
Bearing support of the centralized brake construction, and the unit 
consisting of the crown-wheel and the equalizing gear, in a "cross-spread" 
"O" arrangement (i.e., the housing for equalizing gears is supported by 
internal bearings) enables the bevel-geared equalizing gear to be 
completed with a mechanically connectable/disconnectable bundle of 
anti-slip lamellae. In addition, this bundle of anti-slip lamellae can be 
installed into the equalizing gear box from outside. Accordingly, the gear 
box requires but one dividing plane. 
In the construction according to the invention, disturbing interaction 
between brake constructions and epicyclic gears can be eliminated. And by 
using a simple sleeve with inner and outer ribs, epicyclic gears are 
completely separated from the bar-axles. Adjustment of bearings of the 
bar-axles, and servicing of the running gears, is thus facilitated. By 
these measures, the useful life of the gears of the driving system can be 
considerably prolongated. 
It should be understood that the forms of the invention illustrated and 
described are representative only, reference should be made to the 
appended claims in determining the full scope of the inventions.