GB2086989A - Hydraulic charging systems - Google Patents

Abstract

A hydraulic charging system for charging a hydraulic circuit (5, 6) comprises an input connector (1) for connecting the system to an external pressurised fluid source (2, 3) a hydraulic motor (8) arranged to be driven by the external source, a pump (11, 12) drivably connected to the motor and arranged to draw fluid from, and to deliver pressurised fluid to, the circuit to be charged. <IMAGE>

Description

SPECIFICATION Hydraulic charging systems This invention relates to hydraulic charging systems.

In particular, although not exclusively, the present invention relates to hydraulic charging systems for use in the starting operation of hydraulically controlled, self propelled vehicles.

One such known self propelled vehicle comprises a diesel engine for propelling the vehicle and a hydraulic circuit including an accumulator and a starting control arrangement for controlling and energising the starting operation of the diesel engine. During normal running conditions the accumulator remains sufficiently charged to enable the starting control arrangement to restart the diesel engine.

However, should the vehicle engine be shut off for a relatively long period of time or should a leak develop in the hydraulic circuit then the accumulator frequently does not retain sufficient charge for the engine to be restarted.

Consequently, the vehicle is stranded requiring a manually activated pump to recharge the accumulator. It will be appreciated that manual pumping involves a relatively long and tedious operation particularly if the diesel engine does not start at the first attempt.

An object of the present invention is to provide a hydraulic charging system which tends to overcome or reduce the above mentioned restarting problem.

According to the present invention a hydraulic charging system comprises hydraulic input connector means for hydraulically connecting the system to an external pressurised hydraulic circuit, hydraulic output connector means for hydraulically connecting the system to the hydraulic circuit to be charged, a hydraulic motor adapted to be driven by pressurised fluid which, in use, is fed from the external pressurised hydraulic circuit, and a hydraulic pump drivably connected to the motor and arranged, in use, to draw hydraulic fluid from, and to return pressurised fluid to, the hydraulic circuit to be charged, in use, the flow of fluid between the external pressurised circuit and the motor being via the input connector means and the flow of fluid between the circuit to be charged and the pump being via output connector means, the two flows of fluid being isolated from one another.

Preferably, the pump is a multi-stage pump.

Advantageously, pilot operated relief valves are provided in the circuit associated with each stage of the pump.

By way of example, one embodiment of the present invention will be described with reference to the accompanying drawing which shows a hydraulic circuit diagram for a hydraulic charging system constructed in accordance with the present invention.

The Figure shows the hydraulic charging system to comprise hydraulic input connector means 1 including two quick release, self sealing, connection joints for hydraulically connecting the charging system to feed and return lines 2 and 3, respectively, provided by an external pressurised hydraulic circuit which may be, for example the pressurised hydraulic circuit of a running self propelled vehicle.

The charging circuit also comprises hydraulic output connector means 4 including two quick release, self sealing, connection joints for hydraulically connecting the charging system to feed and return lines 5 and 6, respectively, provided by a further external hydraulic circuit, which may be, for example, the initially nonpressurised hydraulic circuit of a shut-off self propelled vehicle, the hydraulic circuit including at least one accumulator (not shown).

Pressurised fluid is fed from the aforesaid feed line 2 of the pressurised external hydraulic circuit via input connector means 1 and line 7 to a hydraulic motor 8, spent fluid being returned to the return line 3 of the external circuit via line 9 and the second quick release joint of the input connector means. A bleed line 10 is provided to exhaust fluid leaking from the motor.

The drive motor 8 is driveably connected to first and second stages 11 and 12 of a two stage pump by drive means 13 and 14, the stages of the pump being driven simultaneously.

Fluid is fed to the first stage of the pump from the return line 6 of the hydraulic circuit to be charged via output connector means 4 and line 1 6. The pressurised fluid delivered by the first stage of the pump is fed into a line 17 which includes a pilot operated relief valve 18 which in its normal operational mode closes line 1 7 and which is arranged to sense the pressure of fluid in the section of line 1 7 adjacent to the first stage of the pump. Thus, in operation the first stage of the pump is set to deliver fluid into line 17 at a preselected pressure, typically, one thousand, three hundred pounds per square inch.As soon as the pressure in line 17 tends to increase above the preselected pressure the relief valve 1 8 opens to dump excess pressure fluid in line 19 which contains pressure fluid at the same pressure as lines 16 feeding the first stage of the pump.

Pressure fluid at the preselected pressure is fed from the first stage of the pump via line 1 7 and line 20 to the second stage 12 of the pump which delivers the fluid into line 21 at a second preselected pressure higher than the first mentioned preselected pressure. Typically, the second preselected pressure is two thousand, seven hundred pounds per square inch.

Pressure fluid at the second preselected pressure is fed along line 21 to a spring return valve 25 which under its spring bias feeds fluid via line 40 to line 1 6 (as shown in the drawing). When the valve 25 is operated manually against its spring bias, pressure fluid is fed to line 41 and hence to line 5 on the receiving vehicle. An additional check valve 42 allows the receiving vehicle when started to be quickly released. A pressure gauge 26 is provided to sense the fluid pressure in line 21. A branch line 27 including a pilot operated relief valve 28 is arranged to dump excess fluid pressure into line 1 6 feeding the first stage of the pump.The valve 28 senses the fluid pressure in line 21 via pilot line 30 and is arranged to connect line 27 to line 1 6 when the said second preselected pressure tends to be exceeded.

In use, with the hydraulic circuit including lines 5 and 6 at a relatively low pressure insufficient to activate the starting mechanism of the diesel engine of the associated standing vehicle, a second running vehicle including a pressurised hydraulic circuit with lines 2 and 3 is hydraulically connected to input connector means 1 of the charging system. The hydraulic circuit to be charged and including lines 5 and 6 is hydraulically connected to the output connector means 4.

Pressure fluid is fed along lines 7 and 9 to energise the motor 8 thereby driving both stages of the pump 11 and 12. Fluid is drawn from low pressure line 6 and delivered through both stages of the pump until it is fed along line 21 to the pressure feed line 5 for the circuit to be charged.

At this stage of the charging operation the valve 25 is in its open flow mode allowing flow along line 21. The pressure fluid fed to the circuit to be charged increases the pressure in the circuit including the accumulators until a desired pressure is reached. The desired pressure is indicated on the gauge 26. As soon as the desired pressure is reached, typically two thousand pounds per square inch, the operator actuates the valve 25 to close the feed line 21.

The circuit of the standing vehicle then is fully charged with fluid pressure and the starting mechanism can be actuated to start the diesel engine. Once the engine is started the charging system is disconnected from the input and output connector means 1 and- 4 and both vehicles are able to commence their normal operations.

It will be noted that the fluid flows from the two vehicles are kept isolated from one another.

Consequently, the vehicle circuits cannot be starved of fluid.

From the above description it will be appreciated that the present invention provides a simple method for charging a hydraulic starting circuit of a shut-off diesel engine.

Claims (5)

1. A hydraulic charging system comprising hydraulic input connector means for hydraulically connecting the system to an external pressurised hydraulic circuit, hydraulic output connector means for hydraulically connecting the system to the hydraulic circuit to be charged, a hydraulic motor adapted to be driven by pressurised fluid which, in use, is fed from the external pressurised hydraulic circuit, and a hydraulic pump drivably connected to the motor and arranged, in use, to draw hydraulic fluid from, and to return pressurised fluid to, the hydraulic circuit to be charged, in use, the flow of fluid between the external pressurised circuit and the motor being via the input connector means and the flow of fluid between the circuit to be charged and the pump being via output connector means, the two flows of fluid being isolated from one another.

2. A hydraulic charging system as claimed in claim 1, in which the pump is a multi-stage pump.

3. A hydraulic charging system as claimed in claim 2, in which pilot operated relief valves are provided in the circuit associated with each stage of the pump.

4. A hydraulic charging system as claimed in claim 3, in which the relief valves are arranged to relieve excess fluid into the feed line to the pump.

5. A hydraulic charging system substantially as described herein and substantially as shown in the accompanying drawing.