Sluing drive for excavator

A sluing mechanism driven by one or more electric or hydraulic motors, for excavating or bulk handling machines comprises a pivotable discharger boom mounted on a rotary support or turntable, and a coaxially pivotable superstructure carrying further equipment. The sluing drives of the two coaxially pivotable parts of the machine are connected to each other in such a way that upon pivoting the superstructure, the discharger boom does not follow this pivotal motion. The sluing drive of the discharge boom is designed as a superposed gear and connected to a drive motor for separately sluing the discharger boom. The turntable is provided with a second discharger sluing gear which is driven by a motor having a weaker characteristic than the drive motor or motors for sluing the superstructure. The characteristic of the motor driving the second discharger sluing gear may be adjustable.

FIELD AND BACKGROUND OF THE INVENTION 
The present invention relates in general to sluing gear arrangements and in 
particular to a new and useful sluing drive for excavators having a 
pivotable superstructure and a pivotable discharge boom. 
Excavating or bulk handling machines are known which utilize sluing 
mechanisms that are driven by one or more drive motors. Such machines 
include discharge boom assemblies which are mounted on rotary supports 
that are coaxial with rotatable superstructures. The superstructures carry 
the rotary support as well as other equipment. Sluing drives of the rotary 
support and the superstructure are connected to each other so that the 
superstructure and discharge boom can be pivoted separately. 
Such machines have the advantage that upon sluing the superstructure and 
the equipment, for example digging means supported in the superstructure, 
the discharger boom does not change its position. This facilitates the 
operation of the machine. On the other hand, the discharger boom can be 
slued independently of the superstructure. In prior art excavating or bulk 
handling machines, the respective sluing gears are positively engaged. 
This positive engagement can be provided only at a single location between 
the gear rim of the sluing gear of the discharger boom and the main sluing 
gear of the superstructure, which is disadvantageous. Upon a failure in 
this positive engagement due to a shaft fracture, tooth breakage, and the 
like, the discharger boom is no longer retained by the discharger sluing 
gear and may accidentally change its position due to wind pressure or tilt 
of the machine. When this happens the boom may hit other parts of the 
superstructure and destroy the machine. 
SUMMARY OF THE INVENTION 
An objective of the present invention is to eliminate said disadvantages of 
the prior art, and to provide a sluing mechanism of the above-mentioned 
kind by which the discharger boom is firmly and safely retained in its 
position even upon a destruction of the positive engagement or failure in 
the connection between the sluing gear of the superstructure and the 
sluing gear of the discharger boom. Free uncontrollable motion for example 
under wind pressure or a tilted position, which might result in major 
damage, is thus prevented. 
In accordance with the invention, a turntable of the device is provided 
with a second sluing gear for the discharger boom, having a drive motor 
with a weaker characteristic than the drive motor or motors for sluing the 
superstructure. A sluing gear for the discharger boom is obtained which is 
hydraulically or electrically connected to, and driven by, the main sluing 
gear. In addition, a mechanism is obtained which becomes effective as soon 
as the sluing gear for the discharger boom, coupled to the main sluing 
gear, fails and no longer transmits any torque to the discharger boom. In 
such a case, the second sluing gear takes up the load and prevents a 
possible destruction of the machine. 
According to a development of the invention, the characteristic of the 
drive motor for the second sluing gear of the discharger boom may be 
adjustable. Due to such a provision, the idle run otherwise present in 
normal operation of the second discharger boom sluing gear which is not 
positively engaged, is eliminated. A drive motor with an adjustable 
characteristic rather operates to the effect that any load compensation 
can be adjusted, so that the discharger boom sluing drive serving so to 
speak as a safety device, can also participate in the drive of the 
discharger sluing gear. The characteristics of the drive motors of the 
main sluing gear and the discharger boom sluing gear may be brought into 
such relation that an adjustable load is produced for the drive of the 
main sluing gear at the discharger boom sluing gear. 
The drive motors may be electric motors or hydraulic motors. 
With a hydraulically driven inventive sluing gear, the following further 
advantages may be obtained: 
Since in normal operation, the hydraulic drive of the discharger boom runs, 
through the positively connected discharge sluing gear, in synchronism 
with the drives of the main sluing gear, the adjustment of a definite 
motor characteristic prevents uncontrollable reactive forces. Upon a 
failure of the positively engaged discharger boom sluing gear, the 
mechanism prevents the discharger boom from an uncontrollable behavior. 
Accordingly an object of the present invention is to provide a sluing 
device for a machine having a carriage, a turntable rotatable about an 
axis to the carriage, a superstructure connected to the turntable and a 
discharge boom assembly rotatably mounted to the carriage about the axis, 
comprising, first drive means having at least one drive motor connected 
between the carriage and turntable to rotate the turntable, second drive 
means having at least one drive motor connected between the turntable and 
discharge boom assembly for rotating the discharge boom assembly, said 
first and second drive means connected to each other so that rotation of 
the turntable with respect to the carriage in one direction causes 
rotation of the discharge boom assembly in an opposite direction, so that 
the superstructure moves alone with respect to the carriage, and further 
drive means having at least one motor connected between the turntable and 
discharge boom assembly, said further drive means motor having a weaker 
drive characteristic than that of said first drive means motor. 
A further object of the invention is to provide adjustment means for said 
further discharge means motor to adjust the drive characteristic thereof. 
A still further object of the invention is to provide each of the drive 
means with hydraulic drive motors. 
A still further object of the invention is to provide a sluing device for 
such machines which is simple in design, rugged in construction and 
economical to manufacture. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
is made to the accompanying drawings and descriptive matter in which 
preferred embodiments of the invention are illustrated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings in particular, the invention embodied therein 
comprises a sluing device for a machine having a carriage 2 which 
rotatably carries a turntable 4 which itself rotatably carries a discharge 
boom assembly having discharge turntable 10. Turntable 4 and discharger 
turntable 10 are coaxially rotatable about substantially vertical axis 6. 
The excavator comprises a crawler gear 1 and undercarriage 3 supporting, 
through a ball bearing sluing gear 2, turntable 4 of the superstructure 5 
which is pivotable about vertical axis 6. A take-up boom 8 of a head part 
(not shown) of the excavator is hinged to superstructure 5 for pivoting 
about a horizontal axis 7 and carries, on its free other end, digging 
equipment, for example (not shown). On top of turntable 4, a discharger 
boom 11 is mounted through another ball bearing sluing gear 9 and 
discharger turntable 10, also for pivoting about vertical axis 6. For 
lifting and lowering its free other end by means of a hoisting device (not 
shown), boom 11 is hinged to turntable 10, by a pivot pin 12 extending 
horizontally through vertical axis 6. Superstructure 5 is pivotable about 
its vertical axis 6 by means of three main sluing gears 13, 14, 15 which 
are driven by motors 24, 25, 26 and include pinions which engage a gear 
rim 17 secured to undercarriage 2. 
In FIGS. 1 and 2, only one of the pinions, namely pinion 16 of main sluing 
gear 13, is shown. Turntable 4 carries a discharger boom sluing gear 18 
which is coupled, through a differential gear 20 and universal shafts 20a, 
20b and 20c, to main sluing gears 13 and 14. A pinion 21 of discharger 
boom sluing gear 18 meshes with a gear rim 22 secured to discharger 
turntable 10. 
In the course of excavation, superstructure 5 carrying takeup boom 8 is 
moved in pivotal motion about vertical axis 6 by means of the three main 
sluing gears 13, 14, 15. During this pivoting motion, discharger boom 11 
and discharger turntable 10 remain fixed relative to undercarriage 2 and 
crawler gear 1. This is obtained by means of discharger sluing gear 18 by 
which discharger turntable 10 is turned relative to turntable 4 in the 
opposite direction through exactly the same angle through which turntable 
4 is turned relative to undercarriage 2, so that the resulting 
differential angle of rotation between turntable 10 and undercarriage 2 is 
zero. 
To operate the discharging belt carried by discharger boom 11 it is 
necessary to pivot boom 11 in certain time intervals about its vertical 
axis 6. A possibility must be given to do this independently of the 
rotation of turntable 4. To this end, a drive motor 28 is provided which 
operates on discharger boom sluing gear 18 designed as a superposed gear, 
and with which discharger boom 11 can be pivoted relative to undercarriage 
2. This customary combination of discharger boom sluing gear 18 with main 
sluing gears 13, 14 is a positive connection between discharger turntable 
10 and undercarriage 2. The operation of the excavator requires a positive 
connection between undercarriage 2 and discharge turntable 10. Upon a 
failure, such a breakage in discharger sluing gear 18, differential gear 
20, pinion 21 or another part producing the positive connection between 
main sluing gears 13, 14 and discharger turntable 10, a holding force can 
no longer be exerted on discharger turntable 10. If the excavator occupies 
a tilted position and a force resulting therefrom acts on discharger boom 
11, or if boom 11 is under a wind pressure, boom 11 and discharger 
turntable 10 are set in an uncontrollable motion until the boom collides 
with superstructure 5. This may destroy discharger boom 11 and, in 
particularly unfavorable circumstances, even the entire excavator. 
To avoid such hazards and other disadvantages, a second discharger sluing 
gear 19 is provided on turntable 4 in addition, which may be of identical 
design with discharger sluing gear 18. This second gear is driven by a 
motor 27 whose speed is equal to the speed of the universal shaft 20a at 
discharger sluing gear 18. To avoid static indeterminacy, load balancing 
is provided which may be effected in various ways. 
For example, drive motor 27 may have a weaker characteristic (e.g. torque) 
than drive motors 24, 25. This produces the effect that under regular 
conditions, the motor transmits only a small torque. However, in case of a 
failure of discharger sluing gear 18, discharger sluing gear 19 takes up 
the force transmission to discharger turntable 10, and thus forestalls the 
risk of destroying the machine. 
Another way is to design drive motor 27 with an adjustable characteristic. 
Then the load balance can be adjusted so that during the sluing operation 
the two discharger sluing gears 18, 19 transmit mutually equal torques. 
An additional motor 28 may be connected to discharger sluing gear 18, and 
an additional motor 29 to discharger sluing gear 19. Under normal 
operating conditions, additional motor 28 may effect the sluing of 
discharger boom 11, along with additional motor 29. With a failure of 
force transmission through discharger sluing gear 18, discharger sluing 
gear 19 and motor 29 can not only safely hold discharger turntable 10 in 
position but also change the position of the discharger boom 11 through 
motor 29, and control this position for a certain time so accurately that 
the machine can continue to operate correctly. 
As already mentioned, both electric or hydraulic drive motors 24, 25, 26, 
27 may be employed. What is important is to employ a motor 27 having a 
weaker characteristic than motors 24, 25, 26 which otherwise are of 
identical design, or a motor 27 whose characteristic is adjustable for 
proper operation. 
In the following, some hydraulic drives are explained with reference to 
FIGS. 4 to 6, where similar parts are designated with similar numerals. 
The hydraulic system comprises one or more hydraulic pumps 30 which are 
driven by an electric motor or internal combustion engine (diesel) in each 
case. 
In the embodiment of FIGS. 4 and 5, a flow divider 31 is connected in the 
line leading to drive motors 24 to 27, by which the rates of flow of the 
oil are adjusted to synchronize the drive motors. Flow divider 31 ensures 
that upon a line breakage at one of the drive motors, the pressure and 
speed are reduced also for the other drive motors. 
The pressure lines are connected to each other through mutualy 
communicating throttles 32 in FIGS. 4 and 6. 
One throttle 33 is connected parallel to drive motor 27 of discharger 
sluing gear 19. This throttle may have a variable cross-section which is 
so dimensioned that drive motor 27 idles along without load. Throttle 33 
may be adjustable, however, so that drive motor 27 has a variable 
characteristic and operates with a variable proportional load. This is the 
same for the devices of FIGS. 4, 5 and 6. 
The system operates in a closed cycle in both directions, wherefore the 
needed throttles 32 and flow dividers 31 are provided at both sides of 
hydraulic pumps 30. Further features, like a cooler, feed pump, etc., 
corresponding to standard equipment have been omitted for clarity and are 
considered known per se. 
Since in normal operation, hydraulic drive motor 27 of discharger sluing 
gear 19, due to the positively connected drive of discharger sluing gear 
18, runs in synchronism with drive motors 24, 25, 26 of the main sluing 
gear, the occurrence of reactive forces is prevented by the adjustment of 
a definite characteristic of the motor. Upon a failure of positively 
connected discharger sluing gear 18, the system prevents an uncontrolled 
behavior of the discharger sluing gear and produces the effect that the 
discharger sluing gear, now driven through discharger sluing gear 19, 
continues to run at a speed corresponding to the basis of the preceding 
speed minus the speed variation caused by slippage. Thus, aside from 
negligible deviations which may be controlled by additional motor 29, the 
discharger boom will keep its initial position and a risk of destruction 
will be avoided. 
In the shown embodiment, additional motors 28, 29 for the discharger sluing 
gears are supplied by separate hydraulic pumps 34 which also are connected 
to electric motor 35. 
FIG. 5 shows an embodiment in which pressure safety switches 36 are 
provided in the pressure lines instead of throttles 32, to stop the 
pivotal motion upon an undue pressure drop caused by failure in the 
hydraulic system. 
FIG. 6 shows a circuit for providing a plurality of hydraulic pumps 30a, 
30b, 30c, 30d driven at equal speeds. Each of the pumps is connected to 
one of drive motors 24 to 27. 
Again, mutually communicating throttles 32 are connected in the pressure 
lines by hydraulic pumps 30a to 30b. The design of the throttles is 
identical to that of the embodiment of FIG. 4. 
In another embodiment, the individual motors or their volumetric efficiency 
may be used for performing the function of the throttles. 
It is also possible to allow the oil to flow out of the closed circuit, 
thus to omit a closed circuit. 
An electrical system of driving the inventive sluing mechanism is designed 
basically in a similar way. Drive motors 24 to 27 are synchronized in 
accordance with the shown hydraulic system. Main sluing gears 13, 14, 15 
are equipped with drive motors 24, 25, 26 having a normal characteristic, 
while discharger sluing gear 19 is driven by a motor 27 having a fixed, 
weaker characteristic than motors 24, 25, 26. Instead of a drive motor 
with a fixed weaker characteristic, a drive motor with an adjustable weak 
characteristic may be employed. The operation of an electrically driven 
mechanism is the same as described in connection with a hydraulic drive. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.