Power plants – Pressure fluid source and motor – Condition responsive control of motive fluid flow
Patent
1994-02-08
1995-05-30
Look, Edward K.
Power plants
Pressure fluid source and motor
Condition responsive control of motive fluid flow
60493, 60494, F16D 3102, F16D 3900
Patent
active
054191327
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an inertial body drive mechanism for use on construction machines such as hydraulic power shovels or the like, and more particularly to a hydraulic inertial body drive mechanism which is arranged to prevent rotational reversing motions of an inertial body which normally take place upon stopping the inertial body.
BACKGROUND OF THE INVENTION
It is the general practice in construction machines like hydraulic power shovels to have an upper rotary body, which is rotatably mounted on a lower mobile vehicular body, rotationally driven from a hydraulic drive circuit which constitutes an inertial body drive mechanism for the upper rotary body.
In this regard, FIGS. 11 and 12 show an example of prior art hydraulic rotational drive circuit of the sort mentioned above, namely, an inertial body drive for rotationally driving a hydraulic power shovel.
In these figures, indicated at 1 is a hydraulic motor for rotational drive, which is connectible to a hydraulic pump 2, which serves as a hydraulic pressure source, and to a tank 3, through conduits 4 and 5 from the pump 2 and the tank 3 and through first and second main conduits 6A and 6B. The hydraulic motor 1 is rotationally driven by charging and discharging the oil pressure which is supplied from the hydraulic pump 2, and as a result the inertial body or the upper rotary body is put in rotation on the lower mobile vehicular body (both upper and lower bodies not shown).
Indicated at 7 is a directional switch valve which is interposed to connect the main conduits 6A and 6B selectively with the conduit 4 from the pump 2 or the conduit 5 to the tank 3. The directional switch valve 7 has its ports on the side of the hydraulic pressure source connected to the hydraulic pump 2 and tank 3 through the pump and tank conduits 4 and 5, and its ports on the side of the motor connected to the hydraulic motor 1 through the first and second main conduits 6A and 6B, respectively. The directional switch valve 7 is provided with a manual lever 7A to be operated by the operator to shift the valve from a neutral position A to either one of left and right drive positions B and C, which control the direction of the oil pressure to be supplied to the motor 1 and from the hydraulic motor 1, namely, the directions of oil pressure flows to and from the hydraulic motor 1. When returned to the neutral position A, the directional switch valve 7 blocks communication of the pump and tank conduits 4 and 5 with the main conduits 6A and 6B to stop oil pressure flows to and from the hydraulic motor 1.
Indicated at 8A and 8B are a pair of charging check valves which are connected to the main conduits 6A and 6B at halfway points between the hydraulic motor 1 and the directional switch valve 7. These check valves 8A and 8B are connected to the tank 3 through an auxiliary conduit 9 and a tank conduit 10 to supply the operating oil in the tank 3 to the main conduits 6A and 6B when a negative pressure is developed in these conduits 6A and 6B, for example, at the time of inertial rotation of the hydraulic motor 1.
Denoted at 11A and 11B are a pair of overload relief valves which are connected to the main conduits 6A and 6B at halfway points between the hydraulic motor 1 and the directional control valve 7. These overload relief valves 11A and 11B are connected to the tank 3 through the auxiliary conduit 9, and at the same time to the oil inlets of the check valves 8A and 8B, respectively. The overload relief valves 11A and 11B are calibrated to open at a predetermined control pressure level PC (see FIG. 12) which is determined by a valve spring 12A or 12B. When an excessive pressure, that is, a pressure in excess of the predetermined control pressure level PC develops in the main conduit 6A (or 6B), for example, at the time of inertial rotation of the hydraulic motor 1, the overload relief valve 11A (11B) is opened to relieve the excessive pressure into the opposite main conduit 6B (6A) through the check valve 8B (8A), thereby limiting the maximum pressure
REFERENCES:
patent: 4420935 (1983-12-01), Kobald
patent: 4628690 (1986-12-01), Arai et al.
patent: 4694647 (1987-09-01), Yoshida
patent: 4850192 (1989-07-01), Mitsumasa et al.
Patent Abstracts of Japan, vol. 7, No. 189 (M-237) [1334] Aug. 18, 1983 of 58-91902.
Ino Kazuyuki
Kimura Ken-ichi
Sato Hitoshi
Hitachi Construction Machinery Co. Ltd.
Look Edward K.
Nguyen Hoang
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