ZA201008640B

ZA201008640B - Ore pass door control system

Info

Publication number: ZA201008640B
Application number: ZA2010/08640A
Authority: ZA
Inventors: Rudolph Buhrmann; Peter Duncan Fraser
Original assignee: Hydro Power Equipment (Pty) Ltd
Priority date: 2009-09-03
Filing date: 2010-12-01
Publication date: 2011-11-30

Description

ORE PASS DOOR CONTROL SYSTEM

FIELD OF THE INVENTION

This invention relates to control systems. In particular, the invention relates to an hydraulic control system. More particularly, the invention relates to an hydraulic control system for use in an ore pass door assembly of a mine, also known as a box hole door assembly.

BACKGROUND TO THE INVENTION

It is sound engineering practice to provide hydraulic mechanisms that cause a prescribed action to take place under command of a control device and that revert an initial position when the command is removed or cancelled. This is particularly important where the command causes a condition that is potentially dangerous, such as opening a door or valve at the bottom of a reservoir to permit the reservoir contents flow out, but where such door or valve must be closed, even if the supply of drive fluid is lost or if connecting hoses to, or in, the operating device fail. Such situations can occur when hoses burst or the drive power is interrupted.

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Fail safe devices as described above may be applied to hydraulically released brakes and load holding devices.

Furthermore, it is common practice to use a gas-charged accumulator, also called an alleviator, which is in essence a volume of compressed gas contained in a chamber an in fluid communication with the hydraulic fluid used to drive the an operating cylinder that operates the door or valve, in such control devices.

The energy stored in the gas is used to provide the drive power to cause the mechanism to revert to the desired safe condition in the event of loss of control drive pressure. In a typical application, the gas energy stored in an hydraulic accumulator is used to normally bias the door of a mine ore pass outlet control to close, in the event of interruption of the hydraulic supply to the controls, as may result from one or more hydraulic hoses of the control system failing. These systems usually depend for their proper functioning on the integrity of the accumulator, since if the gas has leaked from the accumulator, the system may be inoperable or may generate pressures in the operating cylinder and accumulator that exceed the rated working pressure of the components of the control system, resulting in component failures that may render the whole control system inoperable and set in an unsafe condition.

OBJECT OF THE INVENTION

It is an object of this invention to provide an ore pass door control system to improve the safety of an ore pass door assembly that employs an accumulator to provide power to an hydraulic operating device to ensure that the door reverts to a safe condition in the event of failure of the hydraulic fluid supply or in the event of loss of accumulator function. .

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an ore pass door control system, the system including an hydraulic piston and cylinder assembly operably connectable to an ore pass door, the cylinder comprising a working chamber and a return chamber separated by the piston; a first operating fluid supply line in fluid communication with the operating chamber through an actuating valve; a second operating fluid supply line in fluid communication with the return chamber and with a fluid pressure chamber of a fluid accumulator through a non- return valve, the actuating valve being operable in a first, operating position to permit a flow of fluid under pressure to the operating chamber and a second, non- operating position in which the said flow of fluid is prevented; return means for permitting the escape of fluid from the operating chamber when the actuating valve is in its second position; wherein the control system further includes a relief valve intermediate the accumulator and the return chamber of the hydraulic piston and cylinder assembly.

According to a second aspect of the invention there is provided an ore pass door control system, the system including an hydraulic piston and cylinder assembly operably connectable to an ore pass door, the cylinder comprising a working chamber and a return chamber separated by the piston; a first operating fluid supply line in fluid communication with the operating chamber through an actuating valve; a second operating fluid supply line in fluid communication with the return chamber and with a fluid pressure chamber of a fluid accumulator through a non- return valve,

the actuating valve being operable in a first, operating position to permit a flow of fluid under pressure to the operating chamber and a second, non- operating position is which the said flow of fluid is prevented, return means for permitting the escape of fluid from the operating chamber when the actuating valve is in its second position; wherein the control system further includes means for permitting the escape of fluid from the return chamber at a preselected rate of flow.

The ore pass door control system of the second aspect of this invention may include a relief valve intermediate the accumulator and the return chamber of the hydraulic piston and cylinder assembly. Further, the means for permitting the escape of fluid from the return chamber at a preselected rate of flow may comprise a fluid bypass of pre-selected cross-sectional area to permit a reverse flow of fluid around or through the non-return valve.

The fluid accumulator may be intermediate the non-return valve and the return chamber and in direct fluid communication with the return chamber.

The first and second operating fluid supply lines may be connected to a single supply inlet.

In one embodiment of the invention, the actuating valve is a manually operated valve of the “dead man’s handle” type and the return means comprises a return flow path incorporated in the actuating valve, which allows a return flow from the operating chamber to exhaust to a region at ambient atmospheric pressure via the actuating valve.

The invention extends to a combination ore pass door and ore pass door control system, wherein the ore pass door control system is as described above and the

6 i i hydraulic piston and cylinder assembly is operably connected to the ore pass door.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example with reference to the following diagrammatic drawing, in which

Figure 1 shows the hydraulic system diagram of the apparatus/invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawing, reference numeral 1 generally refers to an ore pass control system in accordance with the invention. The system 1 controls operation of an ore pass door 9, shown diagrammatically only, by means of an hydraulic cylinder 2, the construction of which is well known. An end of an operating connecting rod 3 of the cylinder 2 is attached to the door 9 and slides sealingly in seals 4 of an end plate 5 of the cylinder 2. An opposed inner end of the connecting rod 3 is attached to a piston 6 that slides in a bore 7 of the cylinder 2.

An end of the cylinder 2 opposed to the end plate 5 is closed by means of an end cap 9 that may be attached to an anchor 10 for the cylinder 2 to react thereupon.

It will be appreciated that the piston 6 has an annular exposed surface on the face of the piston 6 to which the connecting rod 3 is attached, and a circular surface, or crown, on its opposed side, the crown having a greater surface area than the annular surface. Thus, the cylinder 2 has an annulus chamber 20 (or return chamber) and a crown chamber 32 (or operating chamber), which are separated by the piston 6.

The annulus chamber 20 is connected via a duct 21 to the fluid storage chamber 22 of a gas-charged accumulator 23, which is also connected to a duct 24 that feeds fluid through a non-return valve 25 via the duct 24 from a common fluid inlet 26. A relief valve 36 is in fluid communication with the duct 21 and is located intermediate the storage chamber 22 and the annulus chamber 20. The common fluid inlet 26 also connects to a manually operated actuating valve 29 of the well known dead man’s hand type, via a duct 28. A further duct 31 leads from an operating port 30 of the actuating valve to the crown chamber 32 of the cylinder 2.

In normal operation, the system is charged by allowing fluid under pressure from the inlet 26 to flow through the non-return valve 25 to the storage chamber 22 of the accumulator 23 and compress a gas in an upper chamber 37 of the accumulator 23 to provide a store of energy. Fluid also flows to the annulus chamber 20 of the cylinder 2 and exerts a force on the annular surface of the piston 6, thereby causing the connecting rod 3 to retract into the cylinder 2 and to close the door 9. A remaining fraction of the fluid will flow to the actuating valve 29.

When it is required to open the door 9, the actuating valve 29 is operated manually and fluid will flow from the inlet 26 via the ducts 28 and 31 to pressurize the crown chamber 32 of the cylinder 2. If sufficient fluid is provided through the actuating valve 29, the piston 6 will be urged against the pressure exerted on the smaller annular face of piston 6 causing the connecting rod 3 to extend from the cylinder 2 and thereby to exert a force on the door 9 to open the door 9. In so doing, the fluid in the annulus chamber 20 will be displaced to the fluid storage chamber 22 of the accumulator 23.

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A bypass 35 is positioned on the duct 24 to bypass the non-return valve 25. This bypass permits fluid to flow upstream of the normal direction of flow through the non-return valve 25 at a predetermined rate of flow allows a controlled amount of fluid to flow through the bypass 35 to the inlet 26.

When the actuating valve 29 is released, fluid flows from the crown chamber 32 and tanks (ie exhausts to a region at ambient atmospheric pressure) via the actuating valve 29 at 33. The pressure on the annular face of the piston 6 will then be sufficient to urge the connecting rod 3 to retract, closing the door 9, much of the fluid pressure in the annulus chamber 20 being provided by fluid stored in the storage chamber 22 of the accumulator 23.

In the event of the accumulator 23 malfunctioning such that it cannot accept the displaced fluid from the annulus chamber 20, pressure in the annulus chamber 20 may rise. The rise in pressure will be in relation to the ratio of the area of the annulus with respect to the area of the crown of the piston. Thus, should the fluid not be allowed to drain through the bypass 35 and/or the relief valve 36, the excess pressure so generated may prevent the piston 6 from moving, with the result that the door 9 cannot open. In addition, damage due to the excess the pressure generated may occur in the hydraulic components downstream of the non-return valve 25. In the event of such a component failing, the door 9 can fail to the open or may be locked in a partly open position, leading to a loss of control of the door function and a potentially dangerous situation.

The bypass 35 may be provided with a restrictor (not shown) or may simply be of a preselected cross-sectional area to restrict the fluid flow rate through the bypass. The employment of the restricted bypass 35 allows the cylinder to release pressure from the annulus chamber 20 gradually and thereby to open the door 9 slowly in the event of the accumulator 23 being inoperative. The relief valve 36 is employed to prevent excess pressure in the annulus chamber 20.

When the accumulator 23 is in good working order, but the fluid supply to the system is interrupted or fails, the restricted outflow through bypass 35 is small enough to allow the cylinder 2 to operate and to close the door 9 before there is a total loss of fluid from the storage chamber 22. In such conditions, and the relief valve 36 remains inoperative as the pressure in the duct 21 does not increase sufficiently to trigger the relief valve 36 because the pressure in the crown chamber 32 drains to the inlet 26 via duct 28 or, if the actuating valve 29 is set to close the door 9, the closing action will continue until the door 9 is closed or until the stored fluid in the storage chamber 22 is exhausted. The fluid volume in the storage chamber 22 of the accumulator 23 should be designed to be sufficient to feed the outflow through duct 35 and to close the door 9 under the most demanding conditions.

The control system of the invention is described with reference to an ore pass door. It will, however, be appreciated that the system has application in other fields and may be uses to control operation of a valve, a lifting device, a latch, a clamp or the like.

Persons skilled in the art will appreciate that the safety and operating improvement resulting from the use of a restricted bypass and to some extent a relief valve provides structural protection and ensures the safe and reliable operation of the system.

Claims

qi , CLAIMS

1. An ore pass door control system, the system including an hydraulic piston and cylinder assembly operably connectable to an ore pass door, the cylinder comprising a working chamber and a return chamber separated by the piston; a first operating fluid supply line in fluid communication with the operating chamber through an actuating valve; a second operating fluid supply line in fluid communication with the return chamber and with a fluid pressure chamber of a fluid accumulator through a non-return valve; the actuating valve being operable in a first, operating position to permit a flow of fluid under pressure to the operating chamber and a second, non-operating position in which the said flow of fluid is prevented; return means for permitting the escape of fluid from the operating chamber when the actuating valve is in its second position; wherein the control system further includes a relief valve intermediate the accumulator and the return chamber of the hydraulic piston and cylinder assembly.

2. An ore pass door control system, the system including an hydraulic piston and cylinder assembly operably connectable to an ore pass door, the cylinder comprising a working chamber and a return chamber separated by the piston; a first operating fluid supply line in fluid communication with the operating chamber through an actuating valve; a second operating fluid supply line in fluid communication with the return chamber and with a fluid pressure chamber of a fluid accumulator through a non-return valve;

the actuating valve being operable in a first, operating position to permit a flow of fluid under pressure to the operating chamber and a second, non-operating position is which the said flow of fluid is prevented; return means for permitting the escape of fluid from the operating chamber when the actuating valve is in its second position; wherein the control system further includes means for permitting the escape of fluid from the return chamber at a preselected rate of flow. +

3. The ore pass door control system as claimed in claim 2, which includes a relief valve intermediate the accumulator and the return chamber of the hydraulic piston and cylinder assembly.

4. The ore pass door control system as claimed in claim 2 or claim 3, wherein the means for permitting the escape of fluid from the return chamber at a preselected rate of flow comprises a fluid bypass of pre- selected cross-sectional area to permit a reverse flow of fluid around or through the non-return valve.

5. The ore pass door control system as claimed in any one of the preceding claims, wherein the fluid accumulator is intermediate the non-return valve and the return chamber and in direct fluid communication with the return chamber.

6. The ore pass door control system as claimed in any one of the preceding claims, wherein the first and second operating fluid supply lines are connected to a single supply inlet.

7. The ore pass door control system as claimed in any one of the preceding claims, wherein the actuating valve is a manually operated valve of the “dead man’s handle” type and the return means comprises a return flow

12 oo path incorporated in the actuating valve, which allows a return flow from the operating chamber to exhaust to a region at ambient atmospheric pressure via the actuating valve.

8. A combination ore pass door and ore pass door control system, wherein the ore pass door control system is as claimed in any one of the preceding claims and the hydraulic piston and cylinder assembly is operably connected to an the pass door.

9. An ore pass door control system substantially as herein described with reference to the accompanying diagrammatic drawing. DATED THIS 1°" DAY OF DECEMBER 2010.

F. B. JOFFE BOWMAN GILFILLAN INC. FOR THE APPLICANT