The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2008 059 467.9 filed on Nov. 28, 2008. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d).
The present invention relates to an agricultural tractor, and focuses on, although is not limited to, a tractor comprising at least one crawler track assembly.
Agricultural tractors which include a crawler track assembly are known in many forms, e.g., from EP 0 000 211 B1. In comparison to a ground drive comprising individual wheels, a crawler track assembly makes it possible to distribute the weight of the tractor over a large surface area of the ground, thereby allowing a heavy tractor to also be used on ground surfaces that are sensitive to high loads. Since the production of a crawler track assembly is much more complex than that of a ground drive comprising individual wheels, tractors which include a crawler track assembly are therefore more expensive than are machines which include a conventional ground drive. They therefore comprise only a small portion of all of the agricultural tractors in use. As a result, they are manufactured in small production series, which greatly increases the costs of these machines.
The object of the present invention, therefore, is to create a concept for agricultural tractors that results in the largely uniform production of machines having a crawler track assembly and a conventional ground drive, thereby enabling the parts common to both machines to be manufactured in a uniform manner and, therefore in a larger production series, which has cost advantages.
The object is attained via an agricultural tractor system in which an engine-cab unit and a front ground-drive part are combined to form one front assembly, and the front assembly may be joined, in a modular fashion, to a first rear ground-drive part or to the second rear ground-drive part which is structurally different from the first rear ground-drive part, in order to form a driveable tractor. The front assembly may therefore be manufactured identically and economically in large production runs for a large number of tractor types; the cost disadvantages associated with a smaller production series usually involve the rear ground-drive parts, and not the entire machine.
The design differences between the at least two different rear ground-drive parts may be, in particular, that the first rear ground-drive part includes at least one wheel pair, and the second rear ground-drive part includes two track roller units.
According to a first embodiment, the wheels or track roller units may comprise substantially all of the rear ground-drive parts, and they may be mountable on the same axle of the tractor.
According to a second embodiment, the rear ground-drive parts may each include a carrier in addition to the wheels or track roller units; the wheels are rotatably mounted on the carrier of the first rear ground-drive part, and the two track roller units are mounted on the carrier of the second rear ground-drive part.
It is also feasible to combine the two designs by making it possible to swap the wheels and track roller units on at least one of the carriers. It may also be possible for a swap of this type to be carried out by an operator, although joining the front assembly and the rear ground-drive part may be a substantially more complex procedure, which may possibly be so complex that it is carried out only when the tractor is manufactured or undergoes repair work.
Preferably, each of the track roller units includes a central driven roller situated between non-driven front and rear deflection rollers. A track roller unit of this type is easily converted from crawler track operation to wheel operation by removing the crawler track, possibly removing the deflection rollers, and replacing the driven roller.
There are various possibilities for steering a tractor of the system according to the present invention, one or two of which is/are preferably realized simultaneously in the same tractor:
There are two variants, in particular, for the latter case: The rear ground-drive part may be connected to the front assembly such that it is pivotable about a vertical axis, i.e., the rear ground-drive part may be inherently rigid, or the rear ground-drive part includes, in addition to the carrier, a bridge part which is fixedly connected to the front assembly; the carrier is located underneath the bridge part, and it is pivotable about a vertical axis, toward the bridge part.
Since the front ground-drive part of an agricultural tractor usually carries a lighter weight than does the rear ground-drive part, it is generally sufficient for the front ground-drive part to have a single axis. The front assembly is therefore not stable on its own, nor is it driveable. Only when it is combined with the rear ground-drive part is a driveable machine attained.
Preferably, more than one axle may be provided on the rear ground-drive part, since it is usually loaded to a greater extent than is the front ground-drive part.
An adapter for a device to be pulled is preferably provided on the rear ground-drive parts. Potential adapters include a trailer hitch, a hydraulic lift, and a saddle.
When the rear ground-drive part includes a bridge part and a rotatable carrier installed underneath it, then the adapter is preferably located on the bridge part.
The novel features which are considered as characteristic for the present 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.
Rear module 4 includes a carrier block 7 having a rear axle on which wheels 6 comprising air-filled tires are mounted. The rear axle may be a rigid axle, or it may be steerable, like the front axle, in order to improve the maneuverability of the tractor, in particular to reduce its turning clearance circle and to enable travel in a “dog walking” manner.
At an interface 8 between the modules, a drive shaft, e.g., extends from the engine in front module 5 to wheels 6 of rear module 4.
Rear module 4 is shown separately from front module 5 using solid lines, and it is shown connected to front module 5 using dashed lines, in order to indicate that modules 4, 5 are preassembled separately and are joined together in a subsequent phase of the tractor assembly. This makes it possible to use front module 5 in conjunction with rear modules having a design that differs from that shown in
An example of the combination of front module 5 with another type of rear module is shown in
Axles 9, 10 may be rigid axles. To improve the ability of tractor to travel around curves, preferably at least one rear axle 10 is steerable. Both axles 9, 10 must be steerable for dog-walking travel to be possible. Each axle 9, 10 may be controlled individually using steering knuckles, or a common carrier block of both axles 9, 10 may form a fifth wheel which is rotatable about a vertical axle and toward a bridge part—which is fixedly connected to front module 5—of rear module 4′.
In the case of front ground-drive part 3 and rear modules 4 and 4′, the extension of the ground-contact surface is determined mainly by the diameter and number of wheels 6; however, in the case of a crawler track assembly, such as that belonging to rear module 4″, the distance between deflection rollers 14 is the main determining factor of the extension of the ground-contact surface. As shown in
The rotational axis of flange joint 17 coincides with the center point of saddle 12, and therefore braking forces applied by a trailer lying on the saddle do not affect the rotation of carrier 7. A coupling 18 for a trailer drawbar 19 or a ground-working tool drawn behind is located on carrier 7, since the rear end of bridge part 11 swivels outward when passing around a curve, and there is a risk that a trailer drawbar coupled thereto could tilt.
An alternative design of the steering of the tractor is shown in
In the embodiment shown in
Of course, rear module 4″ which includes a crawler track assembly and which is shown as an example may be replaced in the machines shown in
In addition to the relative great pivot movement freedom, a further advantage of the stacked roller track is convertibility.
To improve the driving behavior when the wheels are used, drive rollers 22 may be provided with an elastic enclosure 24.
The operator may convert rear module 4′″ from roller track operation to wheel-driven operation and back as necessary.
A further embodiment of a convertible rear module 4″″ is shown in
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 an agricultural tractor, 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.
Number | Date | Country | Kind |
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10 2008 059 467.9 | Nov 2008 | DE | national |