Power plants – Pressure fluid source and motor – Ram driven by fluid pumped from reservoir
Reexamination Certificate
1999-09-13
2001-06-19
Ryznic, John E. (Department: 3745)
Power plants
Pressure fluid source and motor
Ram driven by fluid pumped from reservoir
Reexamination Certificate
active
06247307
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
A hydraulic raising apparatus with automatic regulated speeds comprises additional hydraulic circuits, check valves and adjustable relief valves arranged between the piston rod side chamber and the rodless side chamber of hydraulic cylinders and pumps. The arrangement enables hydraulic cylinders and pumps to change their role in circuit, depending on loaded conditions, from a piston to a spool and vice versa. Hence the hydraulic apparatus can adjust its raising speeds in agreement with loads. When a load is light the apparatus can quickly carry it to position. On the other hand, when the load is heavy the apparatus will gradually move it with reduced input energy.
(b) Description of the Prior Art
A conventional hydraulic raising apparatus, the so-called jack, primarily comprises a working cylinder, a piston rod, a hydraulic pump, a reservoir, a return valve (or release valve), a safety valve and connection circuits. The piston rod is provided on the outer end with a raising arm. In operation a rocker or handle is usually pulled and pushed to pump hydraulic fluid into the working cylinder and drive the piston rod to raise a load.
In such a conventional structure, it does not have variable speeds for different loading conditions. The same speed occurs either at no load or in a light or a heavy load condition. Consequently users must operate the handle repeatedly to activate the working cylinder until the load is moved by the raising arm to a desired position. The raising speed does not vary in agreement with the apparatus's load condition. It not only wastes time and but also leads to a low working efficiency. Users must spend more energy to operate. Evidently an invariable speed can not satisfy users' need. It is desirable to have improvements made on conventional structures.
SUMMARY OF THE INVENTION
The primary object of the invention is to provide a hydraulic raising apparatus that can automatically adjust it own raising speeds and that comprises an additional hydraulic circuit and a check valve arranged between the piston rod side chamber and the rodless chamber of the working cylinder, and hydraulic circuits and check valves or relief valves disposed between the rodless side chamber of the working cylinder and an oil reservoir, and corresponding adjustable relief valves and check valves located between the piston rod side chamber and the rodless side chamber of the hydraulic pump. The hydraulic raising apparatus further comprises an inlet circuit, a return circuit, and a safety circuit between the working cylinder and the hydraulic pump. With this arrangement, the working cylinder and the hydraulic pump can change the driving mode they act on hydraulic fluid from a spool to a piston rod or vice versa depending on load conditions. The apparatus automatically adjusts its own raising speeds for varying load conditions to quickly raise a light load but to provide a slow speed for raising a heavy load and minimizing the required energy that users have to exert on the handle. The apparatus according to the invention can enhance the working efficiency to the greatest extent and reach a significant effect of saving time and labor.
Another object of the invention is to provide a raising apparatus with automatic adjustable raising speeds in which the working cylinder and/or the hydraulic pump has also a multiple stage design. The interiors of cylinders and pumps are divided into many working chambers. Each chamber communicates with another through hydraulic circuits, checking valves and relief valves. Thus the raising apparatus can provide more various speeds for different lifting requirements.
REFERENCES:
patent: 5755099 (1998-05-01), Hung
patent: 5937647 (1999-08-01), Hung
patent: 5992149 (1999-11-01), Hu
patent: 1352133 (1974-05-01), None
Bacon & Thomas PLLC
MVP (H. K.) Industries Limited
Ryznic John E.
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