GB2242529A

GB2242529A - Transducers/encoders

Info

Publication number: GB2242529A
Application number: GB9101696A
Authority: GB
Inventors: Peter John Loughran
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-03-27
Filing date: 1991-01-25
Publication date: 1991-10-02
Anticipated expiration: 2011-01-25
Also published as: GB9101696D0; GB9006774D0; GB2242529B

Abstract

A transducer/encoder for use with a part rotatable about a fixed axis comprises a hollow body (10) containing a shaft element (15) rotatably supported in the body (10) by bearings (18) and couplable to said rotatable part for rotary movement together. A disc (16) is fixed on the shaft element and a sensor (28) senses movement of the disc past the sensor by detecting regular variation of the disc. The disc may thus have a toothed or slotted periphery and cooperate with a sensor of inductive, capacitive or photoelectric type. The shaft element (15) has a stepped bore (25) to receive the head end of a bolt screwed into the rotatable part. A strap (34) prevents rotation of the body (10). <IMAGE>

Description

Title: Transducers/Encoders DESCRIPTION This invention concerns transducers/encoders for use with apparatus, equipment or machinery that rotates or has a part or parts which rotate about a fixed axis.

In process machinery it is often desirable to monitor speeds of rotation, position, directions and other parameters of rotating parts such as, for example, speed of rotation of conveyor belt rollers.

An object of this invention is to provide a transducer/encoder for monitoring rotation of a part rotatable about a fixed axis.

According to the invention there is provided a transducer/encoder for use with a part rotatable about a fixed axis comprising a hollow body containing a shaft couplable to said rotatable part for rotary movement together,a disc on the shaft and a sensor for sensing movement of the disc past the sensor by detecting regular variation of the disc.

The shaft is preferably directly couplable to said rotatable part being fixed tight against the rotatable part, such as by a through-bolt threadedly engaged in the rotatable part. The rotatable part may have to be tapped prior to fitting of the transducer/encoder.

The sensor preferably produces an electrical or electronic signal which can be evaluated by a microprocessor or computer to indicate a desired parameter of the rotating part such as speed, position and revolution counting. By including a second disc on the shaft offset relative to the first disc and a sensor therefor whereby direction of rotation may be detected.

One preferred form of disc has a castellated edge and may be used in combination with an inductive, capacitive or magnetic type sensor. The disc and sensor are arranged so that as the castellations pass close to the sensor there are changes in inductance or capacitance of the sensor which changes produce the signals.

An alternative form of disc has an annular arrangement of apertures regularly spaced at or near its periphery and is used with a photo-electric sensor that transmits a light beam from an emitter to a receiver on opposite sides of the disc, in the region of the apertures. Then the beam is interrupted by the disc material between the apertures to produce signals.

The body of the transducer/encoder preferably has a strap or the like fixed thereto and for fixing at its other end to a fixed machine part or any other suitable point to prevent rotational movement of the body itself. The body may be rendered more suitable for use in locations where water ingress may present operational problems by having sealed covers one over the free end of the shaft and the other around the coupled end of the shaft.

Electric cable from the sensor to the evaluation apparatus is preferably enclosed in liquid tight conduit.

In use the shaft of a transducer/encoder of the invention maybe attached directly to a rotatable part firstly by providing a suitably tapped bore in that part to receive a threaded bolt or the like through the shaft either with the bolt head abutting against the shaft end or against a ledge formed in the hollow shaft. A spring washer or the like may be advisable between the bolt head and the shaft abutment to prevent loosening of the bolt as the shaft rotates. If present the securing strap is fixed in place. The transducer/encoder is then connected to appropriate monitoring/evaluation apparatus for recording and evaluating signals received from the sensor as the disc rotates with its shaft and the rotatable part.

This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a section through a first shaft transducer/encoder; Figure 2 is a section transverse to that of Figure 1; Figure 3 is a side view of the transducer/encoder of Figures 1 and 2 fitted to a shaft; Figure 4 is a front view of the transducer/encoder of Figures 1 and 2; Figure 5 is a section through a second shaft transducer/encoder; Figure 6 is a section transverse to that of Figure 5; Figure 7 shows a third shaft transducer/encoder fitter to a shaft; Figure 8 is a front view of the transducer/encoder of Figure 7.

Referring to Figures 1 to 4 of the accompanying drawings, a shaft transducer/encoder comprises a body 10 having an open ended cylindrical part 12 and a hollow radial extension part 14 communicating therewith. The cylindrical part 12 has within it a hollow rotatable shaft 15 which carries a castellated disc 16, The shaft 15 is rotatable in a pair of bearings 18 which are a tight fit in the cylindrical part 12. The shaft 15 is hollow to receive a threaded bolt 20 (see Figure 3) and spring washer 22 thereon to secure the transducer/encoder to a rotating shaft 24 of a piece of machinery, such as of a conveyor belt roller. The head of the bolt abuts against ledge 25 in the hollow shaft 15.

The hollow extension 14 is internally screwthreaded over part of its length i.e. at 26 to receive a corresponding externally threaded inductive or capacitance probe 28 so that the probe is in line with the disc 16. Electric cable 30 from the probe is enclosed in liquid tight conduit 32.

A strap 34 is bolted to the body 10 and will normally be bolted at its other end to a fixed machinery part to prevent relative rotation of the body 10.

The transducer/encoder operates by inductive or capacitive detection of rotation of the castellated disc 16. Each time a castellation passes over the probe the inductance or capacitance thereof will change and send a signal to measuring apparatus. The rate at which the signals are received can via suitable calibration give the speed of rotation of the shaft to which the transducer/encoder is coupled. The transducer/encoder may have other applications such as positional detection, counting completed revolutions. Furthermore, by incorporating a second disc offset relative to the first and a probe therefor, by comparison of the signals from both probes direction of rotation of a shaft can be monitored.

Turning to Figures 4 and 5 of the accompanying drawings, a second transducer/encoder is shown that is identical to that of Figures 1 to 4 except that photoelectric sensing is used. Like parts in the respective drawings have been given the same reference numerals for ease of reference and only the respective differences will be described in detail. In this embodiment the rotatable disc 16' is a circular disc with a series of spaced apertures 40 close to its periphery. The probe 28' is a photoelectric probe having a light emitter 44 and a light receiver 46 on opposite sides of the disc in line with its apertures 40, whereby interruption of the light beam between the emitter and receiver produces a signal from which speed of rotation of a shaft, to which the transducer/encoder is fitted, can be measured, as well as other possible measurements or information obtained.

Finally, in Figures 7 and 8 a transducer/encoder is shown, which is substantially the same as that of Figures 1 to 4 in terms of operation, but which has been adapted for heavy duty uses and, in particular, for use in areas where water ingress might cause operational difficulties. In this embodiment, the transducer/encoder has protective covers 50, 52 bolted front and back respectively to the body 10 with '0' ring seals 54 therebetween. The cover 52 is, of course, apertured for the shaft 14 to extend therethrough but includes an oil seal 56 for sealing around the shaft.

Whilst the invention has been described specifically with reference to shaft transducer/encoders, it will be appreciated the transducers/encoders of the invention may be used in combination with any other piece of apparatus, equipment or machinery that rotates about a fixed axis.

Claims

1. A transducer/encoder for use with a part rotatable about a fixed axis comprising a hollow body containing a shaft couplable to said rotatable part for rotary movement together, a disc on the shaft and a sensor for sensing movement of the disc past the sensor by detecting regular variation of the disc.

2. A transducer/encoder as claimed in claim 1, wherein said shaft is directly couplable to said rotatable part being fixed tight against the rotatable part.

3. A transducer/encoder as claimed in claim 2, wherein said direct coupling is a by a through-bolt threadedly engaged in the rotatable part.

4. A transducer/encoder as claimed in claim 1, 2 or 3, wherein the sensor produces an electrical signal.

5. A transducer/encoder as claimed in any one of claims 1 to 4 comprising a second disc on the shaft offset relative to the first disc and a sensor therefor whereby direction of rotation may be detected.

6. A transducer/encoder as claimed in any one of claims 1 to 5, wherein the or each disc has a castellated edge and the sensor is an inductive, capacitive or magnetic sensor.

7. A transducer/encoder as claimed in any one of claims 1 to 5, wherein the or each disc has an annular arrangement of apertures regularly spaced at or near its periphery and the sensor is a photo-electric sensor.

8. A transducer/encoder as claimed in any one claims 1 to 7 having a strap or the liked fixed thereto and for fixing at its other end to a fixed point to prevent rotational movement of the body itself.

9. A transducer/encoder as claimed in any one of claims 1 to 9, wherein electric cable therefor is enclosed in liquid tight conduit.

11. A transducer/encoder substantially as hereinbefore described with reference * to and a illustrated in the accompanying drawings.

12. Apparatus having a part rotatable about a fixed axis and a transducer/encoder as claimed in any one of claims 1 to 11 coupled to said rotatable part.