Motor vehicles – Special driving device – Portable track
Reexamination Certificate
1997-07-30
2001-03-13
Hurley, Kevin (Department: 3619)
Motor vehicles
Special driving device
Portable track
C180S009500
Reexamination Certificate
active
06199646
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a working vehicle having a body frame, front wheels, propelling drive shafts mounted in a rear portion of the body frame, and semicrawler units driven by the propelling drive shafts.
2. Description of the Related Art
Such a working vehicle has high utility; it has a wide range of use including operations in paddy fields and other farming fields and on dairy farms. Working vehicles, particularly agricultural working vehicles, may be classified by the running device broadly into the wheel type and crawler type. The wheel type having two axles and four wheels may be subdivided into the four wheel drive type, rear wheel drive type and front wheel drive type. The crawler type may be subdivided into the full crawler type and semicrawler type. (See Agricultural Machine Handbook, New Edition, pages 257-259).
The wheel type working vehicle equipped with a three-point linkage, a PTO shaft and hydraulic control devices may be used in a wide range of operations including plowing, sowing, tilling, weeding, harvesting and transport. This type of working vehicle is used as a power vehicle in all seasons and is a mainstream of agricultural automation.
The full crawler type working vehicle has a large ground-engaging area, and therefore has a smaller ground contact pressure than the wheel type working vehicle. Thus, the full crawler vehicle can run on soft or unleveled grounds. This type of vehicle, with a heavy weight and a large adhesion coefficient, is suited for a heavy operation requiring a strong tractive force. This type of vehicle is a seasonal dedicated vehicle used exclusively in land development or land improvement. Such an operation is impossible with a wheel type working vehicle, and requires a sub-soiler to secure drainage in wet fields, for example.
The semicrawler type working vehicle has belt units in place of rear wheels to act as an apparatus supplemental to the wheel type working vehicle. On soft grounds, the semicrawler working vehicle exhibits a performance intermediate between the wheel type and the full crawler type.
The wheel type working vehicle is highly mobile to be suitable for a wide range of operations. Its disadvantage is that the running performance is low unless the fields become dry in plowing times, e.g. under changeable weather of autumn and the influence of snow in early spring (the latter being called spring plowing practiced substantially during a fixed period in spring in view of the growth and harvest of crops).
In such a situation, i.e. under unfavorable conditions or in very wet fields, the full crawler working vehicle demonstrates an excellent performance. However, this vehicle, which lacks in mobility and is a specialized machine applicable only to a limited operation. When used in a harvesting operation in a dry field, the vehicle would damage the field. After all, both the wheeled working vehicle and the full crawler working vehicle must be made available. This requires a huge investment in agricultural management.
Under such circumstances, semicrawler working vehicles have been proposed as disclosed in Japanese Patent Laying-Open Publication H4-257778 (hereinafter called conventional example 1), and in Japanese Utility Model Publication H6-5974 and Utility Model Laying-Open Publication S63-70488 (hereinafter called conventional example 2).
Conventional example 1 includes rollers disposed rearwardly of the rear wheels, and crawler belts (endless tracks) wound around the rear wheels and rollers. The running devices (rollers) project to a large extent rearwardly of the vehicle body to be obstructive to a working implement using a three-point linkage. Further, the vehicle has an excessively large wheelbase to impair turning performance. A high operating quality cannot be expected when running on unleveled grounds or the like.
Conventional example 2 includes oscillatable semicrawler units to have some adaptability to operations in rugged fields, for example. However, this example is applied to a specialized machine such as a combine harvester. This working vehicle cannot be used in varied operations without changing its construction for attaching the semicrawler units to the vehicle body.
SUMMARY OF THE INVENTION
The object of this invention is to provide a working vehicle which is essentially a front wheel type vehicle to which semicrawler units may be attached without changing its basic body structure.
The above object is fulfilled, according to this invention, by a working vehicle comprising semicrawler units each including a drive rolling element attached to one of the propelling drive shafts, an endless crawler track driven by the drive rolling element and contacting the ground, driven rolling elements engaged by the endless crawler track, and a track frame for supporting the driven rolling elements, the track frame being supported by the body frame to be vertically oscillatable through a pivot shaft.
With this construction, the track frame supporting the driven rolling elements is supported by the body frame to be vertically oscillatable through a pivot shaft. Thus, the vehicle can run steadily even on rugged grounds.
In a preferred embodiment of this invention, each semicrawler unit further includes a stopper for limiting vertical oscillation of the track frame to a predetermined oscillating angle. This provision prevents a deterioration in running performance due to an excessive oscillation of the track frame. Preferably, the stopper may be set to equalize an upward permissible oscillating angle and a downward permissible oscillating angle from a horizontal reference position of the track frame, or to provide an upward permissible oscillating angle larger than a downward permissible oscillating angle from the horizontal reference position of the track frame. Where the vehicle body is not suited for directly attaching the smeicrawler units, the track frames may be oscillatably supported by the body frame through a rectangular mounting frame fixed to the body frame and including the pivot shafts. This feature allows the semicrawler units to be attached to varied front wheel type working vehicles without changing the basic vehicle structures.
Preferably, the pivot shafts are disposed at a lower level above the ground than the propelling drive shafts. Then, the semicrawler units have a reduced amplitude of oscillation to allow the working vehicle to run steadily while suppressing pitching thereof.
It will also be advantageous if the endless crawler track has a ground contacting length divided by a vertical line passing through an axis of the drive rolling element, into a longer forward portion and a shorter rearward portion. This secures a sufficient ground engaging length without increasing an overall length of the working vehicle. In addition, a space may be secured with ease for connecting a working implement to an attaching device such as a three-point linkage disposed rearwardly of the vehicle body.
The driven rolling elements may be distributed to a forward end and a rearward end of the track frame to produce a linear ground-engaging portion of the endless crawler track. Then, the endless crawler track includes a forwardly and downwardly inclined portion extending from the drive rolling element to one of the driven rolling elements disposed at the forward end. Boarding steps may provided above the inclined portion of the endless crawler track. The inclined portion may serve as a boarding step for the driver.
In the working vehicle according to this invention, rear wheels may be interchangeable with the semicrawler units for attachment to the propelling drive shafts. This feature provides the following advantages.
When a wheel type vehicle has difficulties in plowing fields under changeable weather of autumn or the influence of snow in early spring, the right and left rear wheels may be replaced with the right and left semicrawler units. Then the vehicle can engage in a plowing operation with sufficient running performance. The semicrawler type vehicle has a low
Fukawatase Katsushi
Kuriki Ryoji
Sato Masayuki
Takahashi Seiichi
Tani Yoshifumi
Fischer Andrew J.
Hurley Kevin
Kubota Corporation
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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