GB2111594A

GB2111594A - Hydraulic cylinder, in particular prop, with a combined function

Info

Publication number: GB2111594A
Application number: GB08235619A
Authority: GB
Inventors: Tamas Kovacs; Otto Lukonits; Miklos Petrassy; Csaba Pinter
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-12-15
Filing date: 1982-12-14
Publication date: 1983-07-06
Also published as: GB2111594B; DE3246481A1; ZA829170B; CS914282A2; HU183739B; DE8235289U1; JPS58131401A; PL239587A1; CS241518B2; FR2518163A1; AU9152682A

Abstract

A hydraulic cylinder consists of the outer cylinder (11), at least one inner cylinder (12) arranged therein, as well as the valve system, in case of necessity the rapid yield valve(s) and other safety valve(s). The hydraulic cylinder according to the invention can be characterized in that between the outer cylinder (11) and the inner cylinder (12) there is a hydraulic pressure space (13) which is connected to a pneumatic gas pressure space (14) for cushioning shock loadings and in the hydraulic pressure space (13) there is a hollow extension (17) which fits into the inner cylinder (12) to effect end of stroke damping. In a preferred embodiment the gas space (14) is formed in the inner cylinder (12) and/or in the hollow extension (17) and the gas space (14) and the hydraulic pressure space (13) are separated by a piston (15). <IMAGE>

Description

SPECIFICATION Hydraulic cylinder, in particular prop, with a combined function The invention relates to a hydraulic cylinder with a combined function-carrying the load also pneumatically-, in particular to a prop, for the elastic absorption of static and/or dynamic loading forces, expediently sudden shocking loads, which are representing in a given case, due to rock burst power effects of quick course and with an impact character, the magnitude of which is mostly exceeding normal stresses.

The main task of the hydraulic props lies in to absorb the static and/or dynamic loads resulting from the rock, in the last case by the elastic accumulation of the energy. It is a well known fact that the larger is the energy storing capacity of the prop up to reaching the pressure which results in crash, the larger dynamic loads may occur.

For solving the task-with a special view to the danger of rock burst-several method have been proposed. With one of the groups of said solutions with an exclusively hydraulic system the required convergence of the prop, the absorption of the occurring abrupt loading forces, which-in general- exceed statical pressure, are absorbed by using mechanical and hydraulical means, and exclusively hydraulic auxiliary equipments, respectively. These auxiliary equipments are the so-called rapid yield valves.

The patent specifications SU-PS 571 610 and DE-AS 21 30 472 describe a prop having been provided with a rapid yield valve with a mechanical-hydraulical layout. The prop according to the patent DE-AS 26 36 791 is provided with a valve with an exclusively hydraulic function.

In general, the disadvantage of these solutions lies in that the connection between the rapid yield valve and the hydraulic pressure space is of an insufficient cross-section, as a consequence due to the inertia of the pressure space and the valve, the rapid yield valve is unable to prevent the detrimental overpressure and overload resulting therefrom. In addition to this, the rapid yield valve enables but an unelastic convergence or a convergence with restricted elasticity.

A solution is also known, by which the elastic convergence of the prop is increased by using an inner cylinder being open in the direction of the outer cylinder and having been filled up with liquid (E.g. DE-AS 26 36 791). In this case the elastic compressibility of the liquid excess ensures-due to the open inner cylinder-the energy storing capacity and increases simultaneously the period of the increase in pressure.

The elastic convergence, energy storing capacity and the prolonged period of pressure increase are not to be considered as advantageous. However, a disadvantage lies in that the elasticity of the prop depends on the position of the inner cylinder. In a more closed position the prop is more rigid, at the same time elastic convergence is also less. In case of a quick pulse-like load, in general, the period of pressure increase is not sufficient for the safe operation of the rapid yield valve.

In the French patent FR-PS 75 04902 a solution has been specified, with which in the piston head of the inner cylinder a gasaccumulator with a diaphragm is applied. The inner wall of the diaphragm confines a gas chamber, while the outer wall communicates with the hydaulic pressure space of the prop via the bore having been formed at the end of the inner cylinder.

The aim of this solution is to attenuate the pressure wave occurring in course of an abrupt pulse-like load, i.e. to yield the proper time for opening the traditional safety valve.

However, the resistance of the smalldimensioned bore restricts disadvantageously and considerably the pressure-equalizing and energyabsorbing effect of the gas accumulator. However, if the dimension of the communicating bore is increased, at a pre-stressing pressure of the gas-which can even reach 500 bars-the diaphragm would be damaged in case of the atmospheric pressure of the hydraulic circle.

Neither the increase of the volume of the gas accumulator seems to be expedient, since the resistance of the bore defines the circumstances of load absorption by all means. As a consequence, the prop is able to absorb only relatively small dynamic energy of a restricted extent in an elastic manner, supposed, that the pressure prevailing in the hydraulic space does not exceed the permissible value.

At the same time, the prop is showing a smoother characteristic, accordingly, there is an increased danger that the inner cylinder performs a metallic impact on the outer cylinder, in particular, if the impact happens in a closed position of the prop.

The aim of the invention is to eliminate the disadvantageous features of the known traditional solutions, i.e. to develop a hydraulic cylinder with a combined function, which is able to accumulate a higher impact energy than the known ones without increasing the dimensions, its operation and the convergence of proper extent are elastic, the period of the load increment is of the proper magnitude even under critical circumstances, at the same time considerable metallic impacts can be avoided or at least considerably reduced and the process of impact decelerated, respectively.

Essentially, the invention relates to a hydraulic cylinder consisting of the outer cylinder, of at least one inner cylinder having been arranged therein, of the valve system and in case of necessity of the and/or other safety valve/s/; the hydraulic cylinder can be characterized in that between the outer cylinder and the inner cylinder there is a hydraulic pressure space, the hydraulic pressure space is connected to the gas space and in the hydraulic pressure space there is a hollow extension arranged which is fitting into the inner cylinder.

At a preferred embodiment of the hydraulic cylinder according to the invention the gas space is formed in the inner cylinder and/or in the hollow extension, while the hydraulic pressure space and the gas space are separated by the piston.

With a further preferred embodiment the gas space is arranged outside the outer cylinder.

With a further preferred embodiment on the mantle of the hollow extension and/or in the matching hollow of the inner cylinder one or more diameter-stages are formed with a certain clearance. It is to be considered as advantageous, if the clearance between the matching parts decreases in the direction of displacement.

With a further preferred embodiment of the hydraulic cylinder the gas space consists of the diaphragm and of the liquid-cushion having been arranged in case of necessity between the diaphragm, the piston and the inner cylinder, i.e.

the inner wall of the hollow extension. With a futher preferred embodiment of the invention in the inner cylinder, in a given case between the membrane and the inner cylinder, i.e in the hollow extension a mantel is arranged.

With a preferred embodiment the diaphragm can be formed as a tubular diaphragm.

It is to be considered as advantageous, if the piston is provided with a sealing on the mantle and/or on the frontal surface.

In a given case of loading and application it is mostly advantageous, if the gas space is filled with a noble gas with an adiabatic exponent larger than 1.4.

The invention will be described by means of some preferred embodiments serving as an example, by the aid of the drawings enclosed, which are showing the longitudinal section.

Figure 1 is showing a prop, in which the gas space is formed in the inner cylinder, Figure 2 the gas space of the prop is formed by an elastic diaphragm within the inner cylinder, Figure 3 is showing an embodiment with the gas space having been arranged in the hollow extension of the outer cylinder, Figure 4 is showing an arrangement, where the gas space is formed by the diaphragm having been arranged in the hollow extension outer cylinder.

With all the embodiments the components of the hydraulic cylinder are indicated as follows: the outer cylinder 1 the inner cylinder 12, the hydraulic pressure space 13, the gas space 14, the piston 15, the bottom 16, the hollow extension 17, the diaphragm 18, the liquid-cushion 19, the filling valve 20, the bore 21, the mantle 22, the filling armature 23, the filling system 24 and the deaerator 25 (Fig. 3).

At the arrangement to be seen in fig. 1 and fig.

2 the piston 1 5 having been arranged in the inner cylinder 12 separates the hydraulic pressure space 1 3 and the gas space 14 lying between the outer cylinder 11 and the inner cylinder 12. The piston is be able to move within the inside of the inner cylinder 12 and it is provided with a seal 1 2a along its mantle and in a standstill, when it is impacting in the inner cylinder 12, the frontal surface is also sealed. The gas space 14 is arranged on the part of the inner cylinder 12 lying behind the piston 15; the gas space may be filled to the necessary pre-stress pressure by means of the filling armature 23 /in case of the arrangement according to figure 2 by means of the filling system 24/.It seems to be expedient to choose the value for the pre-stress pressure so as to exceed the blow-off pressure of the traditional safety valve /not illustrated here/, since in this case, when the convergence is slow, the prop behaves as a traditional prop, whereas sealing of the gas space 14 is ensured by the sealing on the frontal surface of the piston 15, being now in a stationary state.

With the embodiment to be seen in figure 2 the gas space 14 is formed by the elastic diaphragm 1 8 having been arranged in the inside of the inner cylinder 1 2. The diaphragm is arranged in the mantle 22, which is ensuring the proper countersupport for the diaphragm 1 8 made of an elastomer; the membrane 1 8 and the gas space 14 formed thereby are namely smaller that the inner space of the inner cylinder 12.

Within the mantle 22, the space between the piston 1 5 and the diaphragm 18 is filled by the liquid-cushion 19, which becomes pre-stressed under the influence of the pressure of the gas space 14 and prevents clamping of the diaphragm 1 8 is course of the displacement of the piston 1 5.

The liquid-cushion 1 9 is filled by means of the filling valve 20 having been arranged in the piston 1 5 and by the deaerating-discharging bore 21.

The diaphragm 18 can be filled through the filling system 24, in the same way pressure values may be adjusted.

With the arrangements to be seen in fig. 1 and 2. on the bottom 16 of the outer cylinder 11 a hollow extension 17 is to be found, the outer diameter of which is smaller than the diameter of the hollow of the inner cylinder 12 lying below the piston 15. Advantageously, on both interconnecting elements several diameter-stages may be formed, while the clearance inbetween-i.e. the difference between the single diameters-should be continuously decreased.

With the arrangement illustrated in fig. 3 and fig. 4 the gas space 14 is formed in the inside of the hollow extension 1 7 on the bottom 1 6 of the outer cylinder 11. Charging of the gas space 14 and adjustment of the required gas pressure is taking place via the filling armature 23. In this case it is also valid for the adjustment of the pre stress pressure, that it should be higher than the blow-off pressure of the traditional safety-valve.

With both solutions the gas space.1 4 is confined by the piston 15 having been arranged at the open end of the hollow extension 17, the sealings of which are in compliance with those according to figure 1 and 2, respectively. The piston 1 5 separates the gas space 14 from the hydraulic pressure space 1 3.

At the arrangement according to figure 3, as a matter of fact, the gas space is forming the part of the hollow extension 1 7 having been closed by the piston 15.

In accordance with figure 4 the gas space 14 is formed by elastic diaphragm 1 8 having been arranged inside of the hollow extension 17. In this case between the diaphragm 1 8 and the piston 1 5 the liquid-cushion 1 9 is to be found, the task is the same as with the solution according to figure 2.

The liquid-cushion 1 9 is filled up by means of the filling-valve 20, while deaeration of the hollow is performed via the deaerating-discharging bore 21.

The solutions according to figures 3 and 4 can also be characterised in that the hollow extension 1 7 is fitting into the cavity of the inner cylinder 12.

Also in this case it seems to be expedient to form diameter-stages with continuously reduced gap sizes. Filling up of the inner cylinder 12 is promoted by the deaerator 25.

The hydraulic cylinders according to the invention with a layout having been previously detailed, operate as follows: If the inner cylinder 12 of the hydraulic cylinder is subjected to a shock-like dynamic load of high energy and taking place very rapidly, the pressure in the hydraulic pressure space 13 increases and reaches the value needed for the displacement of the piston 15, which is practically equal to the prestress pressure of the gas space 14 and the liquidcushion 19, respectively.

By increasing the hydraulic pressure the piston 1 5 is displaced in the direction of the gas space 14, as a consequence, due to the compression, the pressure of the gas also increases, so the prop will be able to accumulate the impact energy. In such a manner, the highest hydraulic pressure prevailing in the prop depends on the initial pressure of the gas space 14, the quantity and type of the gas and comparing identical circumstances, it will be considerably lower than with the traditional props. The period of pressure increases is also prolonged accordingly the time staying at disposal suffices for opening the safety valve or the optionally existing tremor valve.

If the hydraulic cylinder in its nearly closed state is subjected to a dynamic force effect of such an extent that a larger convergence would be produced than the distance between the bottom 1 6 and the inner cylinder 12, the inner cylinder 12 is advancing due to the force effect and separates the inner space of the inner cylinder shaft 12 from the hydraulic pressure space 1 3 enclosing also the hollow extension 17; the inner cylinder 1 2 is sliding namely onto the hollow extension 17, accordingly, pressure equalization may take place only through the gap inbetween. In such a manner, by hydrodynamic braking considerable and damaging metallic impact can be avoided, or significantly reduced at least.

The solution specified and serving as an example only does not fully cover the disclosure; within the disclosed solution several modifications are possible, so e.g. the gas space 14 can be formed with a tubular diaphragm, however, in a given case, it may be arranged outside the hydraulic cylinder.

The main advantages of the hydraulic cylinder according to the invention may be summarized as follows: 1./ In case of an impact energy which would lead to the opening of the rapid yield valve of the traditional prop and to the discharge of the liquid, the pressure does not reach the value adjusted for the opening of the rapid yield valve, accordingly, the prop and the safety equipment remain active.

2./ Further impact energies, being even larger, which would lead to the crash of any traditional prop, induce a pressure below the critical value at the hydraulic cylinder according to the invention, i.e. a sufficient time will be ensured for the opening of the rapid yield valve and other existing safety valves. As a consequence, peak loads are considerably reduced, enabling a significant reduction in dimension and weight of the hydraulic cylinders and the equipments incorporating them.

3./In case of a dynamic load of high energy and with a quick course accompanied by a rock burst, metallic impact, otherwise resulting in the damage or even crash of the hydraulic cylinders, can be avoided.

4./When the dynamic overload ceases, in the pressure space of the hydraulic cylinder pressure conditions are elastically restored by the expansion of the gas space.

5./The elastic convergence of the hydraulic cylinder does not depend on the closed or open state of the prop.

6./The cross-section of the gas space approximates that of the inner cylinder, accordingly, the pressure equalizing and energy absorbing properties may prevail undisturbed and without any restriction even in case of abrupt, quick and impact loads.

7./ By the proper selection of the filling material of the gas space conditions of energy absorption and increase of load can be well controlled.

8./The hydraulic cylinder has a simple design, due to the advantages regarding to operation and work-safety, its use is most advantageous.

Claims

1. Hydraulic cylinder, consisting of the outer cylinder, at least one inner cylinder having been arranged therein, as well as of the valve system, in case of necessity of the rapid yield valves and other safety valve/s/, characterized in that between the outer cylinder 1/and the inner cylinder /12/ there is a hydraulic pressure space /13/ arranged, the hydraulic pressure space /1 is connected to the gas space /14/and in the hydraulic pressure space there is a hollow extenstion /1 which fits into the inner cylinder /12/.

2. Hydraulic cylinder as claimed in claim 1, characterized in that the gas space /14/ is formed in the inner cylinder /12/ and/or in the hollow extension and the gas space /14/ and the hydraulic pressure space /13/ are separated by the piston /15/.

3. Hydraulic cylinder as claimed in claim 1, characterized in that the gas space /14/ is arranged outside the outer cylinder/11/.

4. Hydraulic cylinder as claimed in claim 1, characterized in that on the mantle of the hollow extension /17/ or/and in the matching cavity of the inner cylinder /12/ diameter-stage/s/ is /are/ formed.

5. Hydraulic cylinder as claimed in claim 4, characterized in that the clearance of matching is formed with a reduced dimension in the direction of the displacement.

6. Hydraulic cylinder as claimed in claim 2, characterized in that the gas space /14/ consists of the diaphragm /18/ and a liquid-cushion /1 9/ arranged in case of necessity between the diaphragm /18/, the inner cylinder and the inner wall of the hollow extension /17/, respectively.

7. Hydraulic cylinder as claimed in claim 2 or 6, characterized in that in the inner cylinder /12/, in a given case between the diaphragm /18/ and the inner cylinder /12/, i.e. in the hollow extension /17/ a mantle /22/is arranged.

8. Hydraulic cylinder as claimed in claim 6 or 7, characterized in that the diaphragm /18/ is formed as a tubular diaphragm.

9. Hydraulic cylinder as claimed in claim 2, characterized in that on the mantle of a piston 5/ and/or on the frontal surface thereof a seal is arranged.

10. Hydraulic cylinder as claimed in any of the claim 1 to 3, characterized in that the gas space /14/ is filled with a noble gas with an adiabatic exponent larger than 1.4.

11. A hydro-pneumatic safety device, comprising an outer cylinder accommodating at least one inner cylinder therein, valve means for the control of the supply and discharge of hydraulic pressure fluid into the cylinders, a hydraulic pressure fluid into the cylinders, a hydraulic pressure chamber between the outer cylinder and the inner cylinder (or one of them), a pneumatic pressure chamber connected for receiving the pressure of said fluid in the hydraulic pressure chamber, and a radially inward extension on the outer cylinder so formed and dimensioned as to enable the (or the adjacent) inner cylinder to be received in and entrained bv the space between said extension and the surrounding wall of the outer cylinder.

12. A hydraulic cylinder according to claim 1, or the device according to claim 11, substantially as herein described with reference to and as shown in Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.