Hydraulic travelling agricultural machine

Motor vehicles – Steering by driving – Independently operable drive motors

Reexamination Certificate

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Details

C180S006700, C180S006320, C074S473110, C074S473300

Reexamination Certificate

active

06325166

ABSTRACT:

BACKGROUND TECHNOLOGY
The present invention relates to a hydraulic travelling agricultural machine with traveling sections of a crawler type.
BACKGROUND TECHNOLOGY
Hitherto, as a hydraulically travelling agricultural machine with traveling sections of a crawler type disposed on left-hand and right-hand sides so as to travel discretely, there is known a tractor, for example, which is disclosed in U.S. Pat. No. 2,015,886. The tractor is configured such that a pair of the traveling sections of the crawler type on the left-hand and right-hand sides are provided with hydraulic motors for traveling the left-hand and right-hand traveling sections, respectively, and a variable flow rate control pump is connected to each of the hydraulic motors via a closed circuit oil path to drive the respective hydraulic motors. A trunnion lever of each of the left-hand and right-hand variable flow rate control pumps is coupled with left-hand and right-hand bar-shaped operating levers disposed discretely, respectively, to implement the steering operation by moving each of the operating levers pivotally in a forward or backward direction.
Further, each of the two operating levers is elongated vertically in an axial direction so as to reduce an operating load.
Moreover, the tractor is configured such that a power pickup shaft is coupled with an output shaft of the engine via a decelerating shaft on which in turn are mounted a hydraulic clutch unit and a hydraulic brake device. To each of the hydraulic clutch unit and the hydraulic brake device is connected a pilot oil path for feeding pilot oil, and an oil path change-over valve is mounted on the pilot oil path at its intermediate portion. By shifting the oil path change-over valve, the hydraulic clutch unit implements the clutching action, while braking the hydraulic brake device, forcibly terminating the rotation of the power pickup shaft.
The tractor as disclosed in the prior art patent, however, poses the following disadvantages.
1. As the operating levers are disposed each in a long extended form, the inherent vibration of the variable flow rate control pump and the vibration of the machine upon traveling may be caused to propagate to the operating levers, thereby vibrating a gripping section disposed at an upper end portion of each operating lever in a large amplitude. As a result, there is the risk that the operator holding the gripping section may make a mistake in operating the machine. In this respect, the machine leads to a poor operability.
2. As each of the operating levers is in a long elongated form, the scope of the pivotal movement of each operating lever may become large so that a smooth turning operation becomes difficult.
3. When a pair of the variable flow rate control pumps are to be operated with the two discrete operating levers, the speed changing operation for shifting the traveling speed of the machine and the turning operation for steering the machine have to be effected with the identical operating lever so that the such operation may suffer from the difficulty in carrying out a smooth operation of the operating levers. Further, in the work requiring a repetition of forward and backward movements of the machine, there may be caused to occur the risk that the operator cannot recognize the neutral position during the speed changing operation, thereby causing a failure of appropriate operation and leading to an accident.
Moreover, the tractor may suffer from the difficulty that the operator may be unable to quickly deal with the demand, for instance, to narrow the scope of the speed changing operation even if the such demand would be made.
4. The prior art tractor is so configured that the clutching action of the hydraulic clutch unit and the braking action of the hydraulic brake device are to be done by a rapid flow of pilot oil into or out from the hydraulic clutch unit and the hydraulic brake device by the operation of shifting the oil path change-over valve. Thus, a large shock is caused to occur, thereby hindering a smooth operation of shifting the clutch of the hydraulic clutch unit and braking the hydraulic brake device.
Therefore, the present invention has the object to provide a hydraulically traveling agricultural machine that can solve the disadvantages and difficulties prevailing in the conventional machines.
SUMMARY OF THE INVENTION
The present invention provides a hydraulically traveling agricultural machine in which a hydraulic motor is mounted on each of a pair of left-hand and right-hand traveling sections each of a crawler type, a pair of variable flow rate control pumps are connected to the hydraulic motors via a closed circuit oil path, an operating section is coupled with and associated with both the variable flow rate control pumps to implement a steering operation and a change in respective speeds of the traveling sections, characterized in that a pump operating unit is provided in the operating section; and the pair of the variable flow rate control pumps are coupled with and associated with the pump operating unit via a spool link mechanism; wherein the operating section is disposed so as to be operated with a steering mechanism and a speed changing mechanism.
The hydraulically traveling agricultural machine according to the present invention is further provided with the features as will be described hereinafter:
1. The steering mechanism is configured so as to be operated with a circle-shaped steering wheel disposed above the operating section.
2. The pair of the variable flow rate control pumps are provided each with a cam plate angle control unit for controlling a cam plate of each of the variable flow rate control pumps, in which the cam plate angle control unit comprises a cam plate operating shaft for operating the cam plate, a servo cylinder connected to the cam plate operating shaft, a spool inserted in the servo cylinder over the entire length thereof, a spool control lever with its base end portion side connected to the spool and with its top end portion side connected to the spool link mechanism, a support shaft for supporting an intermediate portion of the spool control lever on a machine frame of the variable flow rate control pump, and a connecting rod disposed at an end of the spool link mechanism for connection to the spool, wherein the spool is disposed generally in parallel to the connecting rod disposed at the end of the spool link mechanism; and a support section for connecting the spool to the spool control lever is disposed on a plane substantially on a level with a support section for connecting the connecting rod to the spool control lever.
3. The pair of the spool link mechanisms are provided each with a connecting rod, and the connecting rods have each a substantially equal length.
4. The steering mechanism is provided with a circle-shaped steering wheel and the speed changing mechanism is provided with a lever for shifting forward and backward movements and for adjusting the speed of the travelling sections. Further, the lever is connected to a lever regulating member which can adjust the scope of the transmission shift of the lever and holding the lever in the neutral position. Moreover, the lever regulating member is disposed in parallel to a coupling passage for operating the speed changing mechanism.
5. An output shaft of the engine is coupled with and associated with a power pickup shaft via a transmission section which in turn is provided with a hydraulic clutch unit and a hydraulic brake device for forcibly stopping the rotation by inertia force of the hydraulic clutch unit, in which a pilot oil path for feeding pilot oil to the hydraulic clutch unit and the hydraulic brake device is connected thereto in series, an oil path change-over valve is mounted on the oil path at an intermediate portion thereof, a spool is inserted in a main valve body of the oil path change-over valve so as to be slidable, and a communicating passage communicating with the pilot oil path is provided by cutting away a communicating groove from a portion of a land section of the spool in an ax

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