WO1993022233A1

WO1993022233A1 - A method and apparatus for conveying pressure medium to actuators

Info

Publication number: WO1993022233A1
Application number: PCT/FI1992/000131
Authority: WO
Inventors: Seppo Ensio Nisula; Ali Markku Juhani Nisula
Original assignee: Seppo Ensio Nisula; Ali Markku Juhani Nisula
Priority date: 1991-04-10
Filing date: 1992-04-30
Publication date: 1993-11-11
Also published as: FI911706A; FI90584B; FI911706A0; FI90584C

Abstract

A method to convey medium, especially in cranes, loaders and excavators, which have at least two medium driven actuators (5, 6). When the pressure of medium pressure, allowed to exit from one or several actuators, exceeds the pressure required by one or several other actuators, the discharging pressure medium is conveyed to actuators functioning with lower working pressure.

Description

A METHOD AND APPARATUS FOR CONVAYING PRESSURE MEDIUM TO ACTUATORS

The invention relates to motion-producing machines and de¬ vices fitted with several medium driven actuators, such as hydraulic cylinders. According to the invention, discharge of highly pressurized medium, with no operative function, to lower pressure or free space is prevented or diminshed.

Previously known as medium driven devices are among others timber cranes, in which two or several tandem coupled arms are moved by means of hydraulic cylinders. Often two or several cylinders are operated simultaneously during the lifting and loading motions. Actually, this means that the pump pressure and the pump deplacement must be sufficient for the simultan¬ eous function of two cylinders, at least. Therefore, the crane is furnished with a pump with great capacity and, accordingly, a motor with great output is needed to operate the pump. Further, the cranes have also a number of other devices, which are operated by much smaller deplacements and often used in¬ dividually. Such devices are, among others, the slewing gear ring of the swivelling and timber loading grapple.

In cranes the medium pipes are taken from the valves direct to the cylinders, whereby all cylinders are independent and the returnig mediums discharged from the cylinders over the return line to the pressure fluid tank even though the medium would have much pressure and a great volume of flow. So more or less, pressure energy of the medium is wasted even though it could be utilized at that very moment. As a result of the present arrangement, the devices must be furnished with a pump with great deplacement and, accordingly, a pump actuator with a great output.

By means of the solution according to this invention these disadvantages are avoided and the invention is characterized in what is presented in the patent claims. It can be considered the most important advantage of this in¬ vention that the rotation pump, which produces pressure to the medium, and its driving motor can be dimensioned much smaller than before, because the motions of actuators, which require a great flow of medium, can be combined so that the highly pressurized return flow generated in one actuator can be con- vayed to the benefit of another actuator. Further, in combin¬ ing two actuators in this manner and carrying out a simultan¬ eous motive function with the same, their movements become interdependent with each other, an thus a remarkable operat¬ ional advantage is achieved, because it is possible to control repeated series of motive functions during operation.

In the following the invention is described in detail with reference to the enclosed drawing, where

Fig. 1 is a crane with a 2-armed boom

Fig. 2 is a delivery pipeline assembly for the cylinders of a crane as per fig. 1.

Figure 1 shows a timber crane 1 with a boom with two arms 3 and 4 swivelling on pillar 2. Arm 3 is operated by cylinder 5 and arm 4 by cylinder 6. Cylinder 5 is single-acting and cylinder 6 two-acting, pipes 7, 8 and 9 are delivery pipes. In fact, the most general utilization of this construction is the simultaneous function of cylinders 5 and 6. When one of the cylinders 5 is extending, the other cylinder 6 is also extending and when the one is shortened, the other one becomes shorter, too. This occures in reaching out with the boom and in moving the grapple 17 farther out to grip a load and bring it closer and, vice versa, in moving the load to a farther spot. In the construction as per fig. 1 there is always some pressure in the delivery hoses 7 and 9 during operation, even though there is no load in the crane. In trying to move the grapple 17 almost horizontally, cylinders 5 and 6 function simultaneously and, in folding the boom, it is possible to convay pressure fluid from delivery hose 9 to cylinder 5, because there is less pressure in hose 7. Rather high pressure is generated in the fluid discharching from hose 9, because the pressure rises by the weight of grapple and arm 4 as well as the pressure which is conveyed along hose 8 to the other side of piston in cylinder 6. The figure also shows extension cylinder 18 of the boom.

While reaching out with the boom, whereat the grapple is moved to farther out, pressurized fluid is vacant from cylinder 5. This fluid can be convayed by hose 9 in order to shorten cylinder 6 , however dependant of the cross sectional area of the cylinders. Usable pressurized fluids can be convayed direct to other cylinders or, when possible, to the pressure side of hydraulic pump 11, whereby they go to the advantage of any actuator.

Figure 2 shows a delivery pipeline assembly for the utilizat¬ ion of medium from a pressurized cylinder. The graph shows a valve board 10 with delivery pipes to cylinders 5 and 6. Pressure to valves (not shown) in the valve board comes from pump 11. The pressure fluid flows back to the pump along re¬ turn line 12 over the fluid tank. In the example case shown in the figure, pressure generated in hose 9 is convayed for the cylinder extension. In the pipeline a pressure driven valve 14 and a directional valve 15 are used in the line that leads to cylinder 5. Unintentional extension of cylinder 6 is prevented by pressurized valve 14. Extension and conveyance of return fluid to cylinder 5 is not possible until pressure is conveyed to cylinder 6 along hose 8. Directional valve 13 prevents pressurized fluid from not usable discharging over valve board 12 to return line 12. The dotted line 16 shows an alternative method of utilizing pressurized fluid in conveying it to the pressure side of pump 11 in order to increase the pump de¬ placement. In this alternative, cylinder 5 receives the utilized extra volume flow from the total fluid flow over valve board 10. Figure 2 shows a graph of the utilization of return fluid from one cylinder only but the return fluid also of other cylinders and actuators can be conveyed as feed fluid for other actuators by a similar pipeline assembly if only the produced pressure is sufficient. Naturally, cylinder 5 is then such a cylinder as well as cylinder 18 in figure 1, by means of which, for instance at lowering the load in grapple 17 with boom 4 in downward slanting position, it is possible to get from the return side of a double-acting cylinder a highly pressurized fluid flow, which can be utilized in another de¬ vice which is in function at the same time.

In utilizing the method the valves (as per fig. 2) can be electrically controlled, whereby they are easy to switch on and off. In such a construction the inventional energy-saving operation is easy to switch on, when the facilities are there and, vice versa, one can quickly shift over to conventional control of valves if so wanted.

By means of the invention it is possible, for instance, to reduce the capacity of the hydraulic pump as well as power demand. In applying the invention the increase of pressure luid temperature does not become such a problem as in present systems, which work with great volume flow and in which the fluid circulates over the pump.

The invention is not restricted to the presented crane only but it can be modified within the limits of the inventional concept prescribed in the patent claims. The invention can be applied to a number of devices utilizing compressed air or pressure fluid, whereby the actuator can be a cylinder, a turbine, a pump or a motor. It is essential that in the actuator such a pressure is generated in the medium that it can be additionally utilized for another function. Pressure can be generated by gravity, braking motion, mass inerta a.s.o.

Claims

PATENT CLAIMS

1. A method to convey medium, discharging from an actuator, for utilization in devices, especially in cranes (1), loaders and excavators, which have one or several medium driven actu¬ ators (5) (6) to perform different jobs, characterized in that the pressure of medium, generated in one or several of said actuators by external force, gravity or combination of the same, is conveyed as pressurized volume flow to one or several medium driven actuators that perform some other job, when the said volume flow is piloted out from the first mentioned actuator(s) .

2. A method according to patent claim 1 characterized in that pressure medium is conveyed to a pressure line (7) leading to another actuator (5) .

3. A method according to patent claim 1 characterized in that pressure medium is conveyed to the pressure side of a pressure generator (11) to increase the volume flow of pressure medium that is to be fed.

4. A method according to patent claims 1 - 3 characterized in that the utilization of said discharging pressure medium is restricted and/or piloted by valves.

5. A method according to patent claims 1 - 4 characterized in that the pressure medium total volume flow conveyed to the actuators momentarily or throughout a motive function exceeds the deplacement of flow volume of the pressure generator.

6. A method according to patent claims 1 - 5 characterized in that medium driven cylinders, motors, pumps, turbines or similar are used as actuators.

7. An apparatus in medium driven cranes, excavators and other similar devices, which perform different motive functions, for implementation of the method according to patent claim 1 characterized in that the apparatus comprises pessure medium pipelines for conveying pressurized medium from one or several actuators (6) to one or several actuators (5) performing some other job, the feed pressure of which actuator(s) is lower or in the feed pipelines of which the pressure is lower.

8. An apparatus according to patent claim 7 characterized in that the apparatus comprises pressure medium pipelines with pressure or flow regulating means (13,14,15) between the actu¬ ators (5,6).

9. An apparatus according to patent claim 7 or 8 characterized in that the apparatus comprises electrically controlled valves in the pressure medium pipelines.

10. An apparatus according to patent claim 7 or 8 characteriz¬ ed in that the apparatus comprises a pressure medium pipeline (16) from at least one actuator to the pressure side of the pressure generator (11).