GB2123142A - Transducer for measuring speed of rotation - Google Patents

Abstract

A transducer arrangement has an annular disc 32 which is, for example, mountable on a bearing housing 12 secured within a hollow cylindrical roller 10 which is engageable with the underside of a return run of a continuous conveyor belt such as a coal conveying belt in a mine. The disc 32 has an inner periphery from which extend angularly- spaced projections which, upon rotation of the disc 32, move relative to a sensor device 20 so as to successively interact with it. The device 20 can be an electrooptic device having two elements, one being a source of electromagnetic radiation and the other being a sensor responsive to the radiation. The projections are successively movable between the elements. The device 20 operates, in response to the successive interactions, to produce electric pulses at a frequency corresponding to the speed of rotation of the disc 32 and thus to the speed of the belt. <IMAGE>

Description

SPECIFICATION Transducer arrangement The invention relates to transducer arrangements.

A well-known type of roliertransducer arrange- ment has been widely used in coal mines and elsewhere for monitoring the movement of conveyor belts in orderto detect slippage ofthe belt on its drive drum and for other purposes. The transducer comprises a roller or pulley engageable with the underside or some other part of the belt and fixedly mounted on a shaft connected to a rotatable assembly including centrifugally responsive weights. Movement of the weights caused by a predetermined fall in the speed of the belt during running or by failure of the belt to attain a predetermined proportion of its full speed causes a microswitch to operate to stop the belt drive motor.

The object of the invention is to provide an improved transducer arrangement responsive to belt motion which can be used for purposes similar to thoseforwhichthe known transducers are used.

Atransducer arrangement according to the invention comprises an annular rotatable disc and a fixed sensor device, the disc having an inner periphery from which extend angularly-spaced projections which, upon rotation ofthe disc, move relative to the device so as to successively interact with the device, the device being operable, in response to said successive interactions,to produce electric pulses at a frequency corresponding to the speed of rotation ofthe disc.

Preferably, the sensor device comprises an electrooptic device having two elements, one being a source of electromagnetic radiation and the other being a sensor responsive to said radiation, the projections of the disc being successively movable between said elements.

Preferably, the disc is coaxially mounted on and within a hollow cylindrical member for rotation therewith. The member preferably is a component engageablewithaconveyorbelt,forexamplea roller, pulley or drum, whether a driving member or an idling member.

Preferably, a bearing housing is secured to one end ofthe hollow member, the disc being secured to the housing.

Preferably, a bearing mounted in the housing is supported by a shaft, a projection of which extends coaxiallythrough the housing into the hollow member and carries the device.

Preferably, the projections are co-planar.

One form oftransducer arrangement will now be described byway of example to illustrate the invention with reference to the accompanying drawings, in which: Figure lisa vertical section on the line 1-1 in Figure 2; Figure 2 is partly a side elevation of and partly a diametral section through the transducer arrangementshown in Figure land Figure 3 is a schematic diagram showing part of an electric circuit included in the arrangement shown in Figures 1 and 2.

Figures 1 and 2 show an end partofa hollow cylindrical roller 1 Oen-gageable with the underside of a return run of a continous conveyor belt (not shown), such as a coal conveying belt in a coal mine. An annular bearing housing 12 is secured within the end ofthe roller 10 and a roller bearing 14 mounted in the housing 12 is supported by a fixed hollow stub-shaft 16. The bearing 14 is retained by an end-cap 17 carrying an annular seal 19.

The stub-shaft 16 carries a hollow cylindrical projection 18 which extends into the roller 10 away from the stub-shaft 16 through a central aperature in the housing 12 andwhich carries an electro-optic device 20 designated Type 306-061 and available from R.S. Components Limited. The device 20 is carried within the roller 10 on a circuit board 22 carried on a column 24, which has an aperturethrough which the projection 18 extends. The column 24 is carried by the projection 18 and secured to it by an allen screw 26.

The electro-optic device 20 includes two elements, one being a source of infra-red light in the form of a light-emitting diode 28 (Figure 3) and the other a detector in the form of a phototransistor 30 arranged to receive light from the source 28. The electro-optic device 20 straddles the inner periphery of a flat annular brass disc 32 which is secured to the housing 12 coaxiallytherewith and with the roller 10.

The disc 32 is mounted on four rods 34 screwed into the housing 12 and is spaced from the housing 12 by hollow cylindrical pillars 36 through which respective rods 34 extend. The disc32 is secured by nuts 38 on the rods 34.

The disc 32 has twenty co-planar projections 40 extending inwardly from the inner periphery of the disc 32 so thatthe projections 40, on rotation of the roller 10, are sucessively interposed between the diode 28andthetransistor30.

The diode 28 and the transistor30 are connected into a circuit (Figure 3) including two resistors 42,44 which are mounted on the circuit board 22, which also carries a terminal block 46. Leads 48from the block46 extend through the projection 18 and thence through the stub-shaft 1 6to other equipment (not shown) operable to monitor or control the conveyor belt.

Typically, each projection 40 is 6.35 millimetres (0.25 inch) long and the sides of the projection converge slightly towards the centre of the disc 32, the included angle being 9 . Typically, the disc has an outer diameter of 82.6mm (3.25 inches) and an inner diameter of 55.6 mm (2.19) to the tips ofthe projections 40.

On rotation of the roller 10 the repeated interruption ofthebeamofinfra-red lightfallingonthephoto- transistor 30 (which is energised by circuit arrangements which are not shown) produces an output signal attheterminal 50(Figure3) in the form of pulses at a frequency corresponding to the speed of rotation ofthe roller 10 and thus to the speed of the belt.

The output signal is fed to circuit arrangements (not shown) by which the conveyor belt drive motor (not shown) can be stopped shouid the belt speed fall below 90% of required speed, for example, owing to belt slippage. Other uses can also be made ofthe output signal.

In modifications (notshownOthetransducer arrangement may be driven by other forms of conveyor roller, pulley, or drum, whether driving members or idling members. The sensor may be a proximity-type sensor device, the projections produc ingfluctuations in an electromagnetic field.

Claims (8)

1. Atransducerarrangementcomprising anannu- lar rotatable disc and a fixed sensor device, the disc having an inner periphery from which extend angularly-spaced projections which, upon rotation of the disc, move relative to the device so as to successively interact with the device, the device being operable, in response to said successive interactions, to produce electric pulses at a frequency corresponding to the speed of rotation of the disc.

2. Atransducerarrangementaccording to claim 1, in which the sensor device comprises an electro-optic device having two elements, one being a source of electromagnetic radiation and the other being a sensor responsive to said radiation, the projections of the disc being successively movable between said elements.

3. Atransducer arrangement according to claim 1 or claim 2, in which the disc is coaxially mounted on and within a hollow cylindrical memberforrotation therewith.

4. Atransducer arrangement according to claim 3, in which a bearing housing is secured to one end ofthe hollow member, the disc being secured to the housing.

5. Atransducer arrangement according to claim 4, in which a bearing mounted in the housing is supported buy a shaft, a projection of which extends coaxiallythrough the housing into the hollow member and carries the device.

6. Atransducerarrangementaccording to anyone of claims 3 to 5, in which the hollow member is a component engageable with a conveyor belt.

7. Atransducer arrangement according to any preceding claim, in which the projections are coplanar.

8. Atransducer arrangement according to claim 1 substantially as hereinbefore described with reference to the accompanying drawings.