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US 4,065,922 AGranted
Load lifting and lowering control system
AssigneeHyster Company
InventorsJames I. Ott, Delmar G. Schwab
Life of this patent
Estimating the term…
Abstract
A hydraulic control arrangement for the lifting and lowering of loads is disclosed. The system is illustrated in an industrial truck and includes a multiple element control valve with timing circuitry to eliminate unwanted transient pressure surges during valve actuation. Series-parallel oil flow paths are provided for directing and controlling oil from the load lifting cylinder to the oil reservoir when the load is being lowered.
Claims21
A hydraulic control system for controlling the lifting and lowering of a load comprising:
- a source of hydraulic pressure fluid;
- a hydraulic lifting and lowering motor;
- a main control valve having a first, selectively positionable, control spool, the valve operatively connected to the fluid source and to the motor;
- and a variable pressure compensated lowering speed control, the control including a second control spool sensitive to system flow associated with the main control valve, the second spool operable to vary fluid flow within the system in response to selective positioning of the first spool.
1 more element
A hydraulic fluid control system for controlling the lifting and lowering of loads comprising:
- a pump;
- a reservoir of hydraulic fluid operatively connected to the pump;
- a control valve for directing pressure fluid from the pump to and from a load lifting and lowering motor;
- passage means connecting the valve to the pump and to the motor;
- a first manually controlled spool within the valve;
- a second pressure-compensated spool associated with an end chamber within the valve body, the second spool respnsive to flow rates across the first spool;
- first pilot passage means connecting the first spool to the second spool through the end chamber;
- second pilot passage means connecting the first spool to the second spool opposite the end chamber;
- third pilot passage means adapted for communication of the end chamber with the pump;
- by-pass passage means within the valve for routing fluid around the second spool during lowering of the load lifting motor;
- and return passage means for routing fluid from the valve to the fluid reservoir.
8 more elements
A hydraulic directional control system comprising:
- a pump having means for controlling the output volume of the pump;
- a reservoir of hydraulic fluid operatively connected to the pump;
- a hydraulic valve for directing pressure fluid from the pump to the load moving motor;
- a first manually controlled spool within the valve;
- a second spool within the valve responsive to positioning of the first spool within the valve;
- means associated with the second spool for delaying response of the pump output control after positioning of the first spool;
- plural passage means within the valve including by-pass means around the second spool;
- a hydraulic line connecting the load motor with the valve;
- and a fluid return line from the valve to the reservoir.
6 more elements
A hydraulic fluid directional control system for controlling the movement of loads comprising:
- a pump including means for controlling the output of the pump;
- a reservoir of hydraulic fluid operatively connected to the pump;
- a load moving motor;
- a directional control valve having a plurality of chambers, the valve connected to the pump through a supply line and to the load moving motor, the valve including a manually operated first spool, the spool including a plurality of separate spool segments connected by at least one spool neck segment of a diameter smaller than the spool segments, the first spool adapted for selectively controlling operation of the motor;
- a timing circuit associated with the directional control valve, the circuit including a second spool within the valve the spool operatively connected to the motor, the valve defining an end chamber associated with the second spool, the second spool adapted to act as a compensator spool during return movement of the motor and as a load check valve when the first manual spool is in a neutral position or in a position which directs fluid to the load moving motor;
- the timing circuit further including a load-sensing pilot line operatively connected to the pump control means and to the end chamber, and a fluid supply passage with an orifice therein from the first spool to the pilot line, the timing circuit operable to delay build-up of pressure in the pilot line.
3 more elements
Dependencies are inferred from the claim text.