Multilevel speed regulation jack and method of operation

Power plants – Pressure fluid source and motor – Ram driven by fluid pumped from reservoir

Reexamination Certificate

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

Reexamination Certificate

active

06748740

ABSTRACT:

BACKGROUND OF THE INVENTION
A jack is one of the commonly used tools in our daily life. It is typically used to lift a load a preset lift distance with smaller forces than that required to lift it directly. Its input piston, which has a small surface area to move with a small force, pushes the hydraulic oil into the output cylinder, thus driving the output piston, which has a larger surface area to lift the load. In accordance with the Law of Conservation of Energy, the input piston travels a much larger distance than the output piston does. As a result, it is typically necessary to pump the input piston repeatedly. In this process, each pump cycle of the input piston results in the same lift distance of the load, being independent of the magnitude of the load. As a result, in the case of an idle, or no, load, light load, or heavy load, it is necessary to pump the input piston repeatedly. The load goes up very slowly even if the load is small. This wastes both time and effort.
To solve the above-identified problem, a hydraulic jack described in Chinese Pat. No. 99209440.2 adopts a double-jacket piston structure—a smaller piston is located within a larger one of the input cylinder. There are two pressurized surfaces in the input cylinder. In the case of an idle load, the jack uses its larger piston to pump oil to increase the quantity of hydraulic oil pumped into the output cylinder, thus making the lift distance for each pumping cycle larger and thus increasing the overall lifting speed. In the case of a heavy load, the jack then uses its smaller piston, which is equivalent to a piston of a conventional jack. This configuration can therefore yield a saving of effort relative to a conventional jack.
Although the double-jacket piston structure solves the problem of wasted time and effort in the case of an idle load, a problem can arise during the process of changing from a small to a large load, when it is used to lift a light load. Besides, if this kind of jack is used to lift a small weight, it still needs the same number of pumping cycles as when it is used to lift a heavy weight, and the problem of wasted time still remains. Moreover, since it adopts a structure with a smaller piston in a larger one, the manufacture process and structural strength are limited, thus the area ratio of the pressurized surface in the case of an idle load and a heavy load is relatively small. As a result, there is little improvement in lifting speed in the case of an idle load. Practical application indicates that this jack still needs many pumping cycles to reach the necessary height; its efficiency is thus not high.
There is another type of hydraulic jack, which opens a blind hole in the middle of the piston of its output cylinder. An oil pipe is inserted into the blind hole. In the case of an idle load, when the piston of the input cylinder is pressed, the hydraulic oil flows into the blind hole via this oil pipe to push the piston for a rapid lift against the end face of the blind hole. In the case of a heavy load, part of the hydraulic oil opens a sequential valve and flows into the output cylinder. The force applied against the ring type surface of the piston of the output cylinder by the oil which flows into the output cylinder together with that applied against the end face of the blind hole by the oil which flows into the blind hole, jointly lift the load at a slow speed. Since the blind hole has a small area to receive force, the lift speed of the jack is very fast in the case of an idle load. Generally, the piston of the output cylinder can reach the height with only one or two pump cycles or strokes. On the other hand, in the case of a heavy load, since the whole end face of the piston of the output cylinder is taken as the area to receive force, the purpose of saving effort is also achieved.
However, it is found from practical application of this type of hydraulic jack that it cannot meet the requirements as expected above. The reason is that when the hydraulic oil is pressed into the output cylinder via the oil pipe, the piston of the output cylinder goes up rapidly; the pressure in the ring type cavity of the output cylinder goes down swiftly to suck hydraulic oil from the oil tank. However, since the piston moves relatively fast and the area of the ring type cavity changes very much, the sucked hydraulic oil cannot fully fill up the ring type cavity, resulting in a phenomenon of inefficient oil suction. Since there exists some air in the ring type cavity of the output cylinder, when the output cylinder starts to lift load, the load applies forces to the piston and makes the piston fall back a certain distance, thus reducing the speed of lift of the load. Moreover, after repeated pump cycles, the air held in the ring type cavity of the output cylinder flows into the input cylinder via the oil path, bringing about the same phenomenon of inefficient oil suction for the input cylinder; this reduces the lift distance for each pump cycle, and moreover the lifting efficiency. Additionally, this type of jack has also another disadvantage. Since the lifting force comes from the joint effort of the hydraulic oil flowing into the blind hole via the oil pipe and that flowing into the ring type cavity of the output cylinder via the one-way valve, the area of the blind hole and that of the ring type cavity changes at each pump press, it is necessary to ensure a balance between the pressures from the hydraulic oil flowing into the ring type cavity and that flowing into the blind hole to achieve a steady movement of the output piston. Unfortunately, it is very difficult to accomplish such a result in practical batch production process. As a result, when the controlled hydraulic oil enters the ring type cavity and is locked there, cracks of the thin-wall oil pipe can occur often owing to a large pressure in the blind hole. This results in low rate of finished products for this type of jack and thus increases its production cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a multilevel speed regulation method for a jack, which enables the jack to transfer between different lift speed levels in the case of different loads and avoid the phenomenon of time waste in the case of an idle load and a light load, so that the objectives of saving both time and effort and increasing lifting efficiency are achieved.
It is also an object of the present invention to provide a multilevel speed regulation jack, which can transfer between different lift speeds in the case of different loads, so that the lifting efficiency of the jack is enhanced.
The purposes of the present invention are achieved by using the following technical arrangement. In the multilevel speed regulation method and system for a jack, a hydraulic speed regulation line is arranged between the input and output cylinders, which includes at least two parallel hydraulic sub-lines to form a hydraulic speed regulation line with at least three speed levels. It takes the pressure applied by the output cylinder against the load as its control signal to control the opening and closure of the hydraulic sub-lines and their combination at different speed levels in the hydraulic speed regulation line.
The hydraulic speed regulation line comprises, in one implementation, three or more than three parallel hydraulic sub-lines, and, with one hydraulic sub-line added, two speed levels are added accordingly. A control valve is set in the hydraulic sub-lines to control the opening and closure through the control signal taken from the load pressure. The opening pressure of the hydraulic sub-lines is set in sequence and opens with the increase of the load.
In general, according to another aspect, the invention features a multilevel speed regulation jack, which includes at least one input cylinder and one output cylinder, and one oil path interconnecting the input cylinder and output cylinder, wherein there is a hydraulic speed regulation line connected in series between the input and output cylinders that provides at least three speed

LandOfFree

Say what you really think

Search LandOfFree.com for the USA inventors and patents. Rate them and share your experience with other people.

Rating

Multilevel speed regulation jack and method of operation does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Multilevel speed regulation jack and method of operation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multilevel speed regulation jack and method of operation will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFUS-PAI-O-3322285

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.