GB2140171A

GB2140171A - Ball mill control device

Info

Publication number: GB2140171A
Application number: GB08312129A
Authority: GB
Inventors: Eric Birks
Original assignee: William Boulton Ltd
Current assignee: William Boulton Ltd
Priority date: 1983-05-04
Filing date: 1983-05-04
Publication date: 1984-11-21
Also published as: EP0125117A3; EP0125117A2; GB8312129D0

Abstract

A control device for a ball mill includes sensing means 14, 16 to determine and signal the number of revolutions of the mill, the signals from the sensing means being passed to a preset counter and control assembly 18 which when a predetermined number of driven revolutions has been counted deactuat es the drive 20 and counts the decelerating free-wheeling revolutions so that just before the mill stops rotating a brake 22 can be applied to stop it and hold it with its discharge port in a predetermined position. <IMAGE>

Description

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GB 2 140 171 A 1

SPECIFICATION Ball mill control device

5 The present invention concerns improvements in or relating to control devices forballmillsorsimilar apparatus, that is apparatus including a rotatable cylinder containing product to be processed by a tumbling action. In this specification, for convenience, 10 such apparatus will be referred to as ball mills.

In ball millsan entry port is provided in the drum side and the mill is intended to be loaded and unloaded when the port occupies a particular position, for exam pie, at top dead centre. In most operating 15 arrangements an operator switches off the motor driving the cylinder of the mill when a predetermined time has elapsed or a predetermined number of rotationshas been achieved.The cylfnderthen freewheelsto rest and there is no guarantee that the 20 port occupies the desired unloading position. The operator mustthen operate the start control forthe motor in an attemptto bring the port to top dead centre. This is difficult and damaging to the motor and its control gear.

25 A further disadvantage with the existing arrangement is thatthe drum, during loading and unloading may free-wheeland as a result may move away from the top dead centre position. This could be dangerous and is certainly inconvenient.

30 It is an object of the present inventionto obviate or mitigate these disadvantages.

According to the present invention there is provided a ball mill control device comprising brake means for arresting rotation of the cylinder of the mill, sensing 35 means arranged alongside said cylinder, means on the cylinderto actuate said sensing means and counting means actuable by said sensing means, said counting means being adapted to deactuate drive means for said cylinder and apply said brake at a 40 predetermined time.

Preferably said sensing means is magnetic, alternatively it may be light sensitive.

Preferably said counting means counts the number of revolutions of the cylinder. It may have two 45 counters,oneto countthe number of revolutions of the cylinder when it is driven, one to countfree-wheeling revolutions.

Preferably the means on thecylinderfor actuating the sensing means are adjustable relative to the 50 cylinder whereby the position of a port in the cylinder mayoccupya predetermined position when the brake is applied.

Preferably thecounting means is adjustable whereby varying driven and free-wheeling revolutions can 55 be pre-set therein.

Preferably the brake is a frictiondisc brake. Alternatively it may be a drum brake, or a positive mechanical locking means,for example a latch.

Further according to the present invention there is 60 provided a method of controlling a ball mill whereby after operation the cylinder of the mill comes to rest in a predetermined position including counting the number of revolutions of the cylinder, de-actuating thedrivetothecylinderwhena predetermined number of revolutions has been counted, counting a further predetermined number of revolutions of the cylinder as it decelerates, and applying a brake to stop the cylinder in said predetermined position.

An ambodiment of the present invention will now be described by way of exa m pie only with reference to the accompanying drawing which shows diagramma-tically a ball mill control device.

A ball mill comprises a cylinder 10for productto be treated rotatably mounted at each end on trunnions 12. A loading and unloading port is provided in the cylinder wall and the mill is designed for loading and unloading operations with the port atthe top dead centre position.

A sensing device 14 is adjustably mounted on framework (not shown) supporting cylinder 10 and detects a sensor actuator, in the form of a ferrous block 16, mounted on aflanged end ofthe cylinder. The mounting means forthe block 16 are so designedthat the block may be mounted at a desired angular position on the flange. Each time theblock 16 passes the sensing means 14 on rotation ofthe cylinder a signal is generated by the means 14 and transmitted to a counting means 18 which incorporates controls for the electric motor 20 which drives the cylinder by way of a suitable transmission (notshown)andforabrake assembly 22 actuable on the cylinder orthe transmission.

The counting means is provided with two presetting arrangements, a first 24 on which a predetermined number of revolutions ofthe cylinder when it is being driven by the motor can be set, and a second 26 on which a predetermined number of revolutions ofthe cylinder when it is decelerating to rest can be set.

Thefirst number of revolutions is determined by the productto be treated in the cylinder and the degree of treatment to which it is to be subjected and the second is determined on setting up and commissioning the mill.

In operation, after loading the mill and closing the loading port, a predetermined number of revolutions is set on the first preset arrangement 24. This number is thetotal number of revolutions required for complete processing ofthe product less the number of revolutions which has been predetermined by experimentation which are required forthe cylinderto decelerate almostto a stop when drive to the cylinder is discontinued. This second number is present on the second means 26.

The motor20 is then started and each revolution of the cylinder is detected by the sensing means 14 and signalled to thecounting means 18wherebythe revolutions are counted off thefirst preset means 24. When this reaches zero the supply to the motor is discontinued, the cylinder begins to free-wheel to rest and the second preset means aresubjectedta the

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The drawing(s) originally filed was (were) informal and the print here reproduced is taken from a later filed formal copy.

The claims were filed fater than the filing date within the period prescribed by Rule 25(1) of the Patents Rules 1982.

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GB 2 140 171 A

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signal from the sensing means and commence to count down. When zero is reached the second means cause the brake to be actuated to stop the cylinder and by pre-adjustment ofthe block 16 and/orthe sensing 5 means 14the cylinder stops and is held with the port in the correct top dead centre position. The brake is only released just priorto the start ofthe next operating cycle ofthe mill.

Various modifications can be made without depart-10 ingfromthe scope ofthe invention. The revolution sensing means need not be magnetic but could be mechanical or light sensitive. The brake 22 may be a drum or disc brake actuable on the cylinder or the motor orthe transmission therebetween or may be a 15 positive mechanical locking device such as a latch.

Whilst endeavouring in the foregoing specification to draw attentionto those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in 20 respect of any patentable feature orcombination of features hereinbefore referred to whether or not particular emphasis has been placed thereon.

Claims

1. Aball mill control device comprising brake

25 meansfor arresting rotation ofthe cylinder of the mill, sensing means arranged alongside saidcylinder, means on the cylinderto actuate said sensing means and counting means actuable by said sensing means, said counting means being adapted to deactuate drive 30 meansfor said cylinder and apply said brake ata predetermined time.

2. Acontrol device as claimed in claim 1, in which said sensing means is magnetic.

3. A control device as claimed in claim 1, in which 35 said sensing means is light sensitive.

4. A control device as claimed in any one of claims 1 to 3, in which said counting means counts the number of revolutions of the cylinder.

5. Acontrol device as claimed in anyone of claims 40 1 to 4, in which thecounting means has two counters,

oneto countthenumberof revolutions ofthe cylinder when it is driven, one to countfree-wheeling revolutions,

6. Acontrol device as claimed in anyone ofthe 45 preceding claims, in which the means on the cylinder foractuating thesensing means are adjustable relative to the cylinder whereby the position of a port in the cylinder may occupy a predetermined position when the brake is applied.

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7. Acontrol device as claimed in any one ofthe preceding claims, in which the counting means is adjustable whereby varying driven andfree-wheeling revolutions can be pre-settherein.

8. A control device as claimed in any one ofthe 55 preceding claims, in which the brake is a friction disc brake.

9. Acontrol device as claimed in any one of claims 1 to 7, in which the brake is a drum brake.

10. Acontrol devrce as claimed in any oneof 60 claims 1 to 7, in which the brake is a positive mechanical locking means.

11. Amethod of controlling a ball mill whereby after operation the cylinder ofthe mill comes to rest m a predeterminedposition including countingthe

65 number of revolutfonsof the cylinder,deactuatingthe drive to the cylinderwhen a predetermined number of revolutions has been counted, counting a further predetermined numberof revolutions ofthe cylinder as it decelerates, and applying a brake to stop the 70 cylinder in said predetermined position.

12. A ball mill control device substantially as hereinbefore described with reference to the accompanying drawings.

13. A method of controlling a ball millsubstantial-75 ly as hereinbefore described with reference to the accompanying drawings.

14. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relatingtothe

80 same inventionas any ofthe preceding claims.

Printed In the United Kingdom for Her Majesty's Stationery Office, 88TSS35, 11/84, 18996. Published at the Patent Office, 25 Southampton Buildings;. London WC2A 1AY, from which copies may be obtained.