Longwall mining machine with haulage motor sensed pressure controlled rail brake

The control of a mineral mining machine having a hydraulic haulage motor senses the pressure of pressure fluid fed to the drive motor to apply brake mechanism when the sensed pressure is below a preselected value.

This invention relates to mineral mining machines and in particular to 
mineral mining machines which in use traverse to and fro along an 
anchorable elongated member. 
In particular, although not exclusively this invention relates to such 
mining machines which in use have rotary cutter heads mounted on ranging 
arms and rotatable about axes transverse to the direction of travel of the 
machine. With such a mining machine it is possible for the machine 
operator to place the machine haulage in neutral whilst he ranges the arm 
to change the cutting horizon of the cutter head within the mineral seam. 
Unfortunately, with the machine haulage control in neutral it is possible 
for the rotating cutter head to react with a hard boundary of the mineral 
seam to act as a drive mechanism for the machine which, thereby may be 
propelled along at a dangerously high speed. 
An object of the present invention is to provide an improved mineral mining 
machine. 
According to the present invention a mineral mining machine comprises a 
driven hydraulic pump for feeding pressure fluid to a hydraulic drive 
motor arrangeable to drive the machine's haulage mechanism, and means 
sensitive to the pressure of the pressure fluid feed to the hydraulic 
motor to control actuation of a brake on the machine such that in use when 
the sensed pressure is below a preselected value the brake is applied. 
Preferably, the brake is biased towards the applied position and the 
machine comprises a further driven hydraulic pump for supplying pressure 
fluid to release the brake and in which case the said means may include a 
hydraulic control valve sensitive to the pressure fluid fed to the drive 
motor and arranged to block the feed of pressure fluid to the brake when 
the sensed pressure is below the preselected value.

The machine is arranged to traverse to and fro along a track assembly 
including a longwall face armoured conveyor and a rail anchored to the 
conveyor pans. The machine has a cutting arrangement (not shown) including 
a rotary cutter head mounted on a ranging arm projecting from the machine 
body, the axis of rotation of the cutter head being transverse to the 
machine's cutting direction. 
Referring to the drawing, the machine has an electrically driven hydraulic 
pump arrangement 2 including a fixed delivery pump 3 and a variable 
delivery pump 4. The single pump 4 normally is used during cutting when 
the machine traverses along the face at relative low speeds while both 
pumps 3 and 4 are used when the machine flits along the face at relatively 
high speeds. The pump arrangement 2 feeds pressure fluid along feed pipe 5 
to a hydraulic drive motor 6 arranged to drive the machine's haulage 
mechanism a portion of which is indicated by a shaft 8 and which for 
example may comprise a sprocket (not shown) drivably engageable with a 
fixed haulage chain arranged along the longwall face. 
The machine comprises a further electrically driven pump 7 which is 
independent of the pump arrangement 2 and which feeds pressure fluid along 
feed pipes 9 and 10 via a hydraulic valve block 11 to a brake mechanism 12 
diagrammatically indicated as a plurality of piston and cylinder 
arrangements 13 acting on a brake pad 15 against the action of a spring 16 
urging the brake pad 15 to its applied position engaging the previously 
mentioned rail extending along the longwall face. The pressure fluid 
supply to the brake mechanism can be interrupted by valves 20 and 21 
included in the valve block 11 to allow the brake mechanism to be applied 
under the action of its spring loading. 
The spring loaded valve 20 is sensitive to the feed of pressure fluid in 
the feed pipe 5 to open the valve against the action of its spring loading 
and allow pressure fluid along a branched line 25 to a spring loaded 
solenoid valve 27 and the previously mentioned spring loaded valve 21. 
The valve 27 controls the actuation of the valve 21 and is itself 
controlled by an electric signal feed from an electrical control panel 
position adjacent the end of the longwall face and sensitive to the 
tension in the previously mentioned fixed haulage chain. The control panel 
ensures that the brake mechanism 12 is applied if the haulage chain should 
break. Such a safety arrangement would only be provided on machines 
required to operate on steeply inclined faces. 
When the valve 27 is actuated by the control panel it moves against its 
spring loading to feed pressure fluid along pilot line 30 to actuate valve 
21 against its spring loading to feed pressure fluid to the brake 
mechanism to release the brake. If in operation the haulage chain should 
break, the signal from the control panel is cut off allowing the valve 27 
to move under its spring loading to remove the pilot pressure on valve 21 
which thereby moves under its spring loading to exhaust pressure fluid 
from the brake mechanism 12 to rapidly apply the brake. 
Thus, in use when the machine operator starts the pump arrangement 2, the 
machine's haulage control would normally be in neutral so that pressure 
fluid from the pump arrangement is fed back to tank and the valve 20 
remains in the closed position under the action of its spring loading and 
the brake mechanism remains applied under the action of its spring 
loading. Upon the operator moving the haulage control to drive the haulage 
drive motor, the build up of pressure in feed pipe 5 is sensed by the 
valve 20 which moves against its spring loading to permit pressure fluid 
to flow into branched line 25. Upon the haulage chain becoming tensioned 
the control panel actuates the valve 27 which in turn (as previously 
described) actuates the valve 21 to feed pressure fluid to the brake 
mechanism to release the brake against its spring loading. 
If, in operation the operator moves the machine's haulage control into 
neutral the pressure fluid in feed pipe 5 is exhausted causing the valve 
20 to close under its spring loading exhausting pressure fluid from the 
brake mechanism which, thereby is applied rapidly. Thus, when the sensed 
pressure is below a preselected value the brake is automatically applied. 
Consequently when the haulage control is in neutral and no pressure fluid 
is fed to the device motor the brake is applied to prevent uncontrolled 
movement of the machine. 
From the above description it will be seen that the present invention 
provides a mining machine in which the brake is applied every time the 
machine is parked, i.e. the machine's haulage control is placed in its 
neutral position. 
In other embodiments of the invention for use on faces which are not 
steeply inclined the valves 21 and 27 may be dispensed with. 
In further embodiments the means for sensing pressure fluid in feed pipe 5 
may be other than a hydraulic valve, for example, an electrical device. 
In still other embodiments of mining machine the haulage mechanism may 
comprise a drive component or arrangement arranged to engage abutments 
arranged along the longwall face.