Planting – Drilling – Having depositor feature
Reexamination Certificate
1999-04-29
2001-02-06
Batson, Victor (Department: 3671)
Planting
Drilling
Having depositor feature
C111S200000, C111S921000, C060S486000, C060S456000, C180S053610
Reexamination Certificate
active
06182588
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improvements in hydraulic systems for agricultural implements and to control and drive systems for same.
Air seeders typically comprise a seeding implement and a product carrying aircart. Sometimes additional implements such as a packer are operated in combination with air seeders. Hydraulic systems for aircarts with hydraulic fan drives have large power demands which can be in excess of what a tractor hydraulic system can properly provide. This can be more of a problem when the air seeder is used in combination with other implements having hydraulic systems.
A boost system which provides additional fluid power for aircarts is shown in the related patent specification “Hydraulic System Having Boost Pump in Parallel with a Primary Pump And Boost Pump Drive Therefor” of Russell J. Memory et al. In the Memory et al system the tractor primary pump and a boost pump are arranged in parallel in a hydraulic circuit to supply an aircart fan motor. Flow controls for the system enable one pump to maintain at least a minimum flow to the load when the flow provided by the other pump diminishes. The boost system increases total fluid capacity so that reserve capacity for serving other loads is maintained. In the Memory et al specification prior art related to such hydraulic systems is presented and the benefits of the Boost Pump parallel system are described. The parallel system, however, has some shortcomings which the present invention overcomes.
As noted above, the Memory et al parallel boost system provides additional fluid volume to maintain the aircart fan operation when the tractor primary hydraulic system is insufficient. However, the speed at which the aircart fan operates is also limited by the pressure provided to it. Demand for increased sizes of air seeders requires aircart fans to provide more airflow to deliver the seeding products farther distances across the larger implements.
One prior art system is disclosed in the article titled White Hydraulics PTO Pump System” appearing in Design News, Jul. 20, 1992. The system shown in that article is one in which a tractor system operates as a charge pump for a PTO driven hydraulic pump. The circuit shown is not a series boost system but, rather, the tractor system provides only a charge pressure as is required by gerotor pumps. The circuit shows that the pressure across the motor is the difference between the charge pressure and the PTO pump pressure and the circuit is not a series boost pressure circuit.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a hydraulic drive having a boost series system which boosts the pressure provided by the tractor system and delivers this boosted pressure to a hydraulic motor, e.g. an aircart fan motor. This can provide pressure much higher than can be delivered by the tractor hydraulic system alone and allows the tractor pump to operate at a lower pressure, at which pressure it is capable of delivering more flow.
Accordingly, the invention in one aspect provides a hydraulic drive system adapted to be connected to a primary or main source of hydraulic power including a main pump and a reservoir; said hydraulic drive system comprising: a hydraulic motor for driving a load, a high pressure supply line connected to an inlet of said hydraulic motor and a low pressure return line connected to an outlet of said hydraulic motor, said supply and return lines adapted to be connected to output and return ports respectively of said main source, and a boost pump having an outlet and an inlet in communication with downstream and upstream portions of said supply line respectively, such that when said drive system is connected to said main source, said boost pump is in series with said main pump whereby the boost pump serves to boost the pressure of the flow delivered thereto, a drive for said boost pump, and a fluid control means disposed between the outlet of said boost pump and the inlet of said hydraulic motor to assist in controlling the speed of said hydraulic motor.
The present invention in one preferred form provides a hydraulic system for boosting pressure to a hydraulic motor, e.g. an aircart fan motor and for controlling flow pressure or volume delivered to the motor as a means of motor fan speed control. Specifically, a boost pump is connected in series with an aircart fan motor and tractor primary hydraulic system. The tractor primary system supplies flow to the boost pump and the boost pump increases the pressure. A flow control downstream of the boost pump is controlled to deliver a portion of the boosted pressure flow to the aircart fan motor sufficient to maintain a particular fan speed and any remaining portion is directed back to the inlet side of the boost pump. The flow passing through the fan motor is returned to the tractor hydraulic system where it is filtered and cooled.
Alternatively the invention can also include boost pumps driven by other means, such as a PTO drive pump which is hydraulically connected in place of the ground drive boost pump in the aircart circuit described above.
The control for the flow delivered from the boost pump is preferably a pressure compensated adjustable flow control, or the control might alternatively be a form of pressure control to control the fan motor speed by maintaining or varying the pressure delivered to the aircart fan. The control preferably relieves the excess flow to the inlet side of the boost pump to minimize power loss. However the excess flow may otherwise be relieved to the tractor return depending on the nature of the control valve that is used. Either type of control may be adjusted from a remote location to set the fan speed as desired.
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Bardi Danick J.
Bodie Cameron D.
Neudorf Blake R.
Batson Victor
Flexi-Coil Ltd.
Miller Larry W.
Stader J. William
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