Fluid handling – Systems – With pump
Patent
1980-05-05
1982-05-18
Michalsky, Gerald A.
Fluid handling
Systems
With pump
60434, 60484, 60DIG2, 91530, F15B 1308
Patent
active
043300073
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to control of hydraulic circuits of the type including a plurality of hydraulic motors operable by separate control valves, with fluid under pressure for the various valves and hydraulic motors being supplied by a single pump.
2. Background Art
Hydraulic circuits of the type contemplated by the present invention are commonly employed, for example, in material handling vehicles such as lift trucks where the vehicles include a number of hydraulic motors or jacks which must be separately operable to regulate material handling implements associated with the vehicles. For example, one of the motors might be used to control tilting of a mast assembly of a lift truck, another might be used to control side shifting of a lift truck carriage, still another of the motors might be utilized to rotate the carriage and yet another of the motors might be utilized to control lifting of the carriage relative to the lift truck mast assembly.
There are a number of other machines which include a plurality of hydraulic motors which may be operated by a single hydraulic pump. The present invention provides a control apparatus which may be adapted to use with such machines.
Apparatus is available, for example, as shown in U.S. Pat. No. 4,102,132 of Norman H. G. Palmer issued July 25, 1978, wherein individual switches are tripped by the control spools of the control valves for each of the functions of a lift truck. This is relatively complicated, however, in that the circuitry must be such as to accommodate the several switches. Also, each switch must be properly aligned and positioned. Further, the switches must be located beneath the control valves in a position difficult to service and subject to oil and dirt contamination.
It is known to have separate control valves for separate hydraulic motors and to supply fluid under pressure to all the control valves from a single hydraulic pump. U.S. Pat. No. 3,962,871 of James G. Blaha and Richard C. Maher, issued June 15, 1976, illustrates one useful control or synchronizing unit which serves to initiate or terminate operation of the hydraulic pump, responsive to positioning of the spools of any one of a number of control valves. The control unit of this patent does not directly actuate the pump on response to linear travel of control rods which position the spools of the control valves. Instead, levers are rotated as the spools are moved linearly, with the free ends of the levers bearing against cam shoes which are attached to a gang plate. Rotation of the gang plate actuates a switch which controls the pump motor. Such units are relatively difficult to adjust, since each of the cam shoes must be separately adjusted. Also, control is not as precise as would be desired. Further, the various cam shoes are relatively expensive to manufacture, thus, adding to the overall cost of the unit.
Still further, the control unit of the aforementioned patent is not useful in all environments because of its bulk. In particular, such a unit is relatively bulky for use in lift trucks where the unit is to be mounted adjacent the operator's seat. Thus, when such units have been utilized in lift trucks, they have generally been mounted forward in the operator compartment and relatively far away from the operator seat. This has required the operator to lean forward to move the control knobs of the unit, thus lessening, somewhat, operator control of the various hydraulic motors.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF INVENTION
According to the present invention, an improvement is provided in a hydraulic system having an electric motor driven pump which supplies pressurized fluid to a control valve arrangement having a plurality of spool controlled valves which move from neutral in response to generally longitudinal movement of one of a plurality of rod members from a neutral position. A single electric switch is provided in a circuit supplying power to the motor. The switch, when
REFERENCES:
patent: 3962871 (1976-06-01), Blaha et al.
patent: 4102132 (1978-07-01), Palmer
Michalsky Gerald A.
Towmotor Corporation
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