Abstract:
A hydraulic raising apparatus with automatic regulated speeds can automatically adapt its raising speeds for various load conditions. It mainly 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 working modes in a hydraulic circuit, depending on loaded conditions, from a piston type to a spool type and vice versa. Hence the hydraulic apparatus can adjust its raising speeds in agreement with loads. When the apparatus bears a light load, it will quickly carry the load to position. On the other hand, when the load is heavy the apparatus will move it at a slower speed and thus need just reduced input energy. Therefore, the apparatus according to the invention can enhance efficiency to the greatest extent.

Description:
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&#39;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&#39; 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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a circuit drawing schematically indicating the constituents of a raising apparatus according to the invention. 
     FIG. 2 is a cross sectional view showing the internal structure of the raising apparatus of FIG. 1 in an assembled state. 
     FIG. 3 is another cross sectional view partially showing the interior of the raising apparatus of FIG.  1 . 
     FIG. 4 illustrates an example of a working cylinder used in a three-stage raising apparatus. 
     FIG. 5 illustrates an example of a hydraulic pump used in a three-stage raising apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, the hydraulic raising apparatus with automatically adjustable speeds according to the invention comprises a hydraulic cylinder  1 , a piston rod  2 , a hydraulic pump  3 , a reservoir  4 , a return valve  5  and a safety valve. 
     The hydraulic cylinder  1  is provided with a piston rod  2  and its interior is divided into two parts, a rodless side chamber  11  and a piston rod side chamber  12 . A hydraulic circuit  14  connects the rodless side chamber  11  with the piston rod side chamber  12 . The hydraulic circuit  14  consists of a check valve  141  that restricts hydraulic liquid flow in a single direction from the piston rod side chamber  12  to the rodless side chamber  11 . Further, the piston rod side chamber  12  communicates with the reservoir  4  via another hydraulic circuit  15  and a relief valve  7 . Besides, the piston rod side chamber  12  is also provided with a supply circuit  16  and a check valve  161  through which the hydraulic liquid in the reservoir  4  can flow into the piston rod side chamber  12  in a single direction for replenishment. The rodless chamber  11  is connected to the reservoir  4  via a return circuit  17  and a return valve  5 . 
     The interior of the hydraulic pump  3  is provided with a piston rod  30  and divided into a rodless chamber  31  and a piston rod side chamber  32 . Two oil channels  33  and  34  connect the piston rod side chamber  32  with the rodless side chamber  31  through an adjustable relief valve  331  and a check valve  341  respectively. The adjustable relief valve  331  and the oil channel  33  restrict hydraulic liquid flow in a single direction from the rodless side chamber  31  to the piston rod side chamber  32 . When hydraulic liquid flows from the piston rod side chamber  32  to the rodless side chamber  31 , it must pass through the oil channel  34  and the check valve  341  in a unidirectional return flow. The pump  3  is connected to the reservoir  4  via a supply circuit  35  and a check valve  351 , which restrict hydraulic liquid flows in a single direction from the reservoir  4  to the piston rod side chamber  32  of the pump  3 . When the piston rod  30  of the pump  3  is raised, hydraulic fluid passes through the oil channel  34  and the check valve  341  and gets into the rodless side chamber  31 . 
     The aforesaid working cylinder  1  is connected to the pump  3  through an inlet circuit  8  and a check valve  81 . The inlet circuit  8  is also equipped with a safety valve  6 . 
     With the above arrangement, the adjustable relief valve  331  connected to the pump  3  is closed when the raising apparatus is at no load. At this moment the hydraulic pump  3  drives hydraulic liquid to flow by the piston rod. When the pump is activated, the piston rod  30  moves down and hydraulic liquid flows from the rodless side chamber  31  of the pump  3  into the rodless side chamber  11  of the working cylinder  1  through the inlet circuit  8  and the check valve  81 . On the other hand hydraulic liquid flows into the piston rod side chamber  32  from the reservoir  4  through the supply circuit  35  and the check valve  351  to replenish the pump  3  due to the motion of the piston rod  30 . Thus it functions as a piston pump. In other words, the hydraulic liquid flowing out of the rodless side chamber  31  of the pump  3  will directly enter the rodless side chamber  11  of the working hydraulic cylinder  1  via the inlet circuit  8  to move the piston rod  2  upwards when the pump  3  is operated at no load conditions. At the same time the excessive hydraulic liquid in the piston rod side chamber  12  of the cylinder  1  flows into the rodless side chamber  11  through the check valve  141 . Thus one downward movement of the piston rod  30  of the pump  3  will synchronously urge the hydraulic liquid in both the rodless side chamber  31  and the piston rod side chamber  12  to flow into the rodless side chamber  11 . The invention makes use of such differential motion to hasten raising the piston rod  2  of the working cylinder  1 . At this moment the piston rod  2  of the working cylinder  1  is driven as a spool and hydraulic liquid can open only the check valve  141  not the relief valve  7 . 
     When the raising apparatus is under a light load, the pump  3  operates in the same way as the described above. However, the relief valve  7  of the hydraulic circuit  15  connected to the hydraulic cylinder  1  is open and the check valve  141  is closed due to the hydraulic pressure of the piston rod side chamber  12  being overwhelmed by the boosted pressure inside the rodless side chamber  11 . As a result the hydraulic liquid in the working cylinder  1  is driven by the piston rod  2  of the cylinder  1 . Only the hydraulic liquid coming from the rodless side chamber  31  of the pump  3  can enter the rodless side chamber  11  of the working cylinder  1  when the pump  3  is operated. The hydraulic liquid leaving the piston rod side chamber  12  directly flows into the reservoir  4  via the circuit  15 . Hence the raising apparatus will not be accelerated by any differential motion. The piston rod  2  of the cylinder  1  will move at a speed slower than the one it moves at when no load. 
     When a load taken by the cylinder  1  reaches a limit, the apparatus will operate in a heavy load condition. In this case the working cylinder  1  still functions as if it is a piston in the circuit. The adjustable relief valve  331  of the oil channel  33  of the pump  3  is opened and thus the pump  3  functions like a spool. When the pump  3  is operated, the hydraulic liquid in the rodless side chamber  31  passes through the adjustable relief valve and then enters the piston rod side chamber  32 . Thus a part of hydraulic fluid leaving the rodless side chamber  31  of the pump  3  returns to the piston rod side chamber  12 . Only reduced quantity of hydraulic fluid enters the rodless side chamber  11  of the working cylinder  1 . As a consequence, the cylinder raises a load at a speed slower than the previous two speeds. Returned hydraulic liquid also provides an effect of saving energy that users have to exert on the pump. 
     When a job has been done and users want to release the piston rod of the working cylinder from an elevated position, the return valve  5  is opened to discharge the hydraulic liquid of the rodless side chamber  11  of the cylinder  1  into the reservoir  4 . In the meantime hydraulic liquid flows into the piston rod side chamber  12  through the supply circuit  16  and the check valve  161  for replenishment. In this way the piston rod  2  returns to its original position and the cylinder  1  gets sufficient hydraulic fluid for the next differential movement operation. 
     The foregoing adjustable relief valve  331  of the oil channel  33  of the pump  3  has a rated hydraulic pressure. If the pressure of hydraulic fluid is lower than that rated pressure, the relief valve  331  will be closed. On the other hand, the valve  33  will be opened when the pressure of hydraulic fluid is higher than the rated value. As to the relief valve  7  and the safety valve  6  of the hydraulic circuit  15  connected to the piston rod side chamber  12  of the cylinder  1 , they work like average relief valves. 
     FIGS. 2 and 3 illustrate the embodied structure of the raising apparatus according to the invention. To make the construction simpler and feasible for the aforementioned supply circuit  35  of the pump  3 , provided on the inner wall of the piston rod side chamber  32  are an annular groove  352  and a side channel  353  communicated with same. The annular groove  352  and the side channel  353  constitute a part of the supply circuit  35 . The hydraulic fluid of the reservoir  4  can pass through the check valve  351 , the supply circuit  35 , the annular groove  352  and the side channel  353  and finally flow into the piston rod side chamber  31  of the pump  3  in a single direction. 
     Also can be seen from FIGS. 2 and 3, the aforesaid hydraulic circuit  14  between the rodless side chamber  11  of the cylinder  1  and the piston rod side chamber  12  is formed on the rear end of the piston rod  2  to allow communication between the rodless side chamber  11  and the piston rod side chamber  12 . However, a check valve  141  is added to restrict hydraulic fluid flow in a single direction from the piston rod side chamber  12  to the rodless side chamber  11  only. 
     Further, both the hydraulic circuit  15  and the supply circuit  16  connected to the piston rod side chamber  12  of the cylinder  1  are located in the front block  101  of the cylinder  1 . These two circuits  15  and  16  are provided with a relief valve  7  and a check valve  161  respectively. 
     The above embodiments are illustrative examples of two-staged cylinders or pumps. They can produce three different raising speeds for different load conditions. With the same principles, the raising apparatus can be of multiple stages by dividing the internal chambers of pumps and cylinders into more cells as long as these cells are respectively provided with adjustable relief valves and check valves. The combination of multiple-staged pumps and cylinders can produce various raising speeds for different load conditions and more effectively reach the effects of raising a light load promptly and providing slow speeds for raising a heavy load with reduced input energy. It is to be realized that various modifications and substitutions can be made without deviation from the principles and spirit of the invention and they are intended to be encompassed by the present invention. 
     FIG. 4 indicates an embodiment of the raising apparatus with three-staged hydraulic cylinders  1 A and piston rods  2 A according to the invention. The rodless side chamber  11 A, the first piston rod side chamber  12 A and the second piston rod side chamber  12 B are connected by hydraulic circuits  14 A and  14 B. The hydraulic circuits  14 A and  14 B are respectively provided with a check valve  141 A and  141 B, which restrict hydraulic fluid flows in a single direction from the first piston rod side chamber  12 A to the rodless side chamber  11 A or from the second piston rod side chamber  12 B to the first piston rod side chamber  12 A only. The first piston rod side chamber  12 A and the second rod side chamber  12 B are connected to a reservoir  4 A via another hydraulic circuit  15 A and  15 B and a relief valve  7 A and  7 B respectively. Similarly the first piston rod side chamber  12 A and the second piston rod side chamber  12 B are provided with a supply circuit and a check valve (not shown in the drawings) that allow hydraulic fluid to flow from the reservoir  4 A into the first piston rod side chamber  12 A or into the second piston rod side chamber  12 B in a single direction for oil replenishment. Also the rodless side chamber  11 A is connected with the reservoir  4 A via a return circuit and a return valve. Evidently more divided chambers of a hydraulic cylinder can produce more raising speed variations. 
     FIG. 5 shows an embodiment of a raising apparatus using three-staged hydraulic pumps  3 A and corresponding three-staged piston rods  30 A according to the present invention. The interior of the pump is divided into a rodless side chamber  31 A, a first piston rod side chamber  32 A and a second piston rod side chamber  32 B. Between the first piston rod side chamber  32 A and the rodless side chamber  31 A, and between the first piston rod side chamber  32 A and the second piston rod side chamber  32 B are respectively provided with two oil channels  33 A and  34 A, and  33 B and  34 B. The two oil channels  33 A and  34 A,  33 B and  34 B are individually furnished with an adjustable relief valve  331 A,  331 B and a check valve  341 A,  341 B. The adjustable relief valves  331 A and  331 B and the oil channels  33 A and  34 A restrict hydraulic fluid flow in a single direction from the rodless side chamber  31 A to the first piston rod side chamber  32 A or from the second piston rod side chamber  32 B to the first piston rod side chamber  32 A. Similarly the hydraulic fluid flows from the first piston rod side chamber  32 A to the rodless side chamber  31 A must pass through the oil channel  34 A and the check valve  341 A in a single direction and the flows from the second piston rod side chamber  32 B to the first piston rod side chamber  32 A must go through the oil channel  34 B and the check valve  341 B in a single direction. With the same reason, a hydraulic pump with four stages or five stages or more stages can be obtained by dividing the interior of the pump into chambers of corresponding number. Such apparatuses can produce more speed variations. 
     Not to mention, the structures of a raising apparatus with automatic regulated speeds described above are also applicable to hydraulic jacks of various forms, such as upright types, horizontal types, hand jacks or motor-driven types. 
     From the above description, evidently the raising apparatus according to the invention can automatically adapt its raising speeds for various loads to achieve the objects set forth in the beginning of the text. It has significant advantages over prior art and its structural arrangement has never been found in conventional hydraulic jacks. Thus the present invention meets the requirements of granting a patent.