GB2528951A

GB2528951A - Speed monitor using hall effect devices

Info

Publication number: GB2528951A
Application number: GB1413980.2A
Authority: GB
Inventors: James Weygang
Original assignee: Schenck Process Ltd
Current assignee: Schenck Process UK Ltd
Priority date: 2014-08-07
Filing date: 2014-08-07
Publication date: 2016-02-10
Anticipated expiration: 2034-08-07
Also published as: GB2528951B; GB201413980D0

Abstract

A conveyor system features a driven drive shaft, or other shaft, to which is mounted a speed sensor 20, made up of a plurality of Hall Effect sensors 24. A magnet 22 may feature at the centre of the shaft. The system finds application in the measuring of low speed conditions, around the 3-5 rpm mark, which may indicated a problem in the mechanical operation of the conveyor, upon which a control signal from a controller, may shut down operation of the conveyor.

Description

I

SPEED MONITOR USING HALL EFFECT DEVICES

FIELD OF THE INVENTION

The present invention relates to a speed monitor using Hall Effect devices. More particularly, the present invention relates to a speed monitor using Hall Effect devices to be used in the under-speed detection of a shaft such as in a materials handling conveyor/elevator or other machine, as well as also relaying speed information to a PLC system.

BACKGROUND OF THE INVENTION

Although there are products on the market for measuring the under-speed of devices for materials handling apparatus all of these use a single sensor and therefore have associated disadvantages.

The present applicant currently markets a product called the "RoCon for measuring the under-speed of devices used for materials handling. The RoCon is therefore an under-speed IS monitoring device or a rotational speed change sensor. The speed of a shaft on a conveyor is set on the RoCon and when the speed drops by a set percentage threshold the RoCon switches off the machine, It ads as a machine/plant safety device.

Problems have been encountered with using devices with a single sensor and a solution therefore sought. In the event damage occurs to the materials handling device this can be expensive to repair and further preventative measures to prevent this damage from occurring have been sought.

It is an objed of at least one aspect of the present invention to obviate or mitigate at least one or more of the aforementioned problems.

It is a further object of at least one aspect of the present invention to provide an improved speed monitor for materials handling apparatus.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an apparatus comprising: a conveyor system capable of conveying and/or mixing material; a motor used for driving a shaft on the apparatus; and a speed monitor system for monitoring the speed of the conveyor system wherein the speed monitor system comprises multiple Hall Effect sensors which are capable of detecting under-speed rotation of the shaft used to propel or driven by the conveyor system.

The present invention therefore resides in the provision of a speed monitor using multiple Hall Effect devices to be used in the under-speed detection of a shaft such as in a materials handling conveyor/elevator or other related type of machine, as well as also relaying speed information to a PLC system.

The apparatus may be a materials handling conveyor apparatus. Alternatively, the apparatus may be used for pumps, mixers and in the process industry or any slow rotating shaft IS driven device subject to loads high enough to cause damage.

The shaft driven device may be used to convey oi mix fluids and solids.

The apparatus may comprise a variable speed drive.

The conveyor system may be any suitable system used to transport and convey materials, goods and products throughout the processes of cleaning, preparation, manufacturing, distribution, consumption and disposal of all related materials, goods and their packaging.

Materials handling systems may range from simple pallet rack systems to complex belt systems and automated storage and ielrieval systems. The systems may also be used in mining and drilling equipment to custom built barley malt drying rooms in breweries.

The speed monitor system may comprise at least two Hall Effect sensors which has cost advantages. The cost effectiveness of the Hall Effect sensors has been found to be of a particular advantage in the present invention.

The speed monitor system may comprise multiple sensors located around and attached to a drive shaft used to diive the conveyor system. The sensois may optionally be separated by an angle of about 100 -1800, about 100 -60° and about 30°. By using multiple low cost Hall Effect sensors provides more pulses per rotation and this helps overcome the issue of slow RPMs (i.e. revolutions per minute). By slow RPMs is meant less than 5 RPM or less than 2 RPM. The speed sensor can be used in multi-voltage applications and across a broad range of RPMs. As slow RPMs are used in the materials handling industry the use of multiple Hall Effect sensors as used in the present has been found to be highly advantageous.

The under-speed rotation may be caused by a number of situations such as a chain break, a stall in the motor, belt slippage, foreign bodies entering the apparatus and a shaft break.

All of these situations would result in an under-speed rotation which would be detected by the Hall Effect sensors and thereby cause the apparatus to come to a halt and stop. This would prevent any damage being caused to the apparatus.

The speed sensor may also use a magnet attached to the centre of a shaft. The magnet rotates triggering the Hall Effect by disturbing the magnetic field.

By having multiple Hall Effect sensors the time taken for under-speed conditions to be IS noticed by the circuitry will be decreased and thereby providing material handling apparatus with increased safety. As mentioned any incurred damage is expensive to repair.

The speed monitor system may therefore prevent a conveyor system from operating in an under-speed condition fora prolonged period of long time.

A microcontroller may process the outputs from the Hall Effect sensors which will generate a time between pulses in a numerical figure or a pulses/seconds numerical figure. The microcontroller may convert this figure to an RPM. There will be inputs available to the user for them to be able to set the switching threshold (for example 10%), when the shaft speed drops below the set threshold an alarm/output is given which will shut the machine down.

The speed of the shaft that has been calculated by the microcontroller can be shown on a display and the switching threshold also shown on the same or a different display.

Because of the arrangement of the multiple Hall Effect sensors the invention can also be used to monitor correct direction of rotation. The magnet(s) will trigger the devices in a specific sequence. If the machine shaft is rotating the wrong way the Hall Effect devices will be triggered in the wrong sequence and trigger an alarm. This is a further advantage of presently described sensor.

The speed sensor may also be protected within a protective housing which not only provides protection but also keeps ambient conditions away from the circuitry that could cause problems.

The speed sensor may also be used to provide an output to a PLC system. The microcontroller has potential for change and functionality may be added or removed. Notable functions that may be included are user defined switching thresholds and totalisation of the machine running hours.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is representation of a prior art speed monitor device called a RoCon used in IS materials handling and which uses a single sensor; Figures 2 to 4 are representations of the speed monitor device according to embodiments of the present invention.

BRIEF DESCRIPTION

Generally speaking, the present invention resides in the provision of a speed monitor using Hall Effect devices to be used in the under-speed detection of a shaft such as in a materials handling conveyor/elevator or other related type of machine, as well as also relaying speed information to a PLC system.

Figure 1 is a representation of a prior art speed monitor called the RoCon which is generally designated 10. In the speed monitor 10 the speed is obtained by circuitry within a sensor calculating the time taken between two outputs given by metal vanes passing over a sensor face. On a slow speed shaft the time between outputs can be large relative to a faster RPM machine. A machine eeriencing under-speed conditions will rotate even slower and during that time can suffer damage which can be expensive to repair. More vanes are not possible as limitations are in place because of the size of the sensor and vane faces as well as the size of the housing.

Figures 2 and 3 are representations of a speed monitor 20 according to the present invention. The speed monitor 20 overcomes the problems found in the prior art device by using multiple Hall Effect sensors. This has been found to provide a number of advantages such as reducing cost. Cost is therefore reduced by using Hall Effect sensors. The sensors used in the prior art devices are relatively expensive such as being in the order of 50 times more expensive than Hall Effect sensors.

As shown in Figure 2 the speed sensor 20 used in the present invention uses a magnet ID 22 attached to the centre of a shaft. The magnet 22 rotates triggering the Hall Effect by disturbing the magnetic field. This in contrast to prior art devices where a rotor with multiple vanes is used to generate multiple outputs per rotation.

The apparatus may also include a delay mechanism where the under-speed rotation has to occur for a set period such as a full 1 -5 seconds. This prevents any anomaly from inadvertently triggering a switch off of the machine.

As shown in Figure 2 there are twelve Hall Effect sensors 24 located around the magnet 22 and a shaft. The sensors are separated by an angle of about 300. By using multiple low cost Hall effect sensors 24 provides more pulses per rotation and this helps overcome the issue of slow RPMs. The speed sensor can be used in multi-voltage applications and across a broad range of RPMs. As slow RPMs are used in the materials handling industry the use of multiple Hall Effect sensors as used in the present has been found to be highly advantageous.

By having multiple Hall Effect sensors the time taken for under-speed conditions to be noticed by the circuitry will be decreased and thereby providing material handling apparatus with increased safety. A rough approximation of the technical improvement is that RPM operation such as 0.4 RPM is a decrease from say 6 seconds to a decrease to as little as 0.5 seconds.

These figures depend upon the design and the quantities of both the magnets and Hall Effect devices but provides an indication of the improvement possible. It is important these times are short because expensive damage can occur if a machine is working in under-speed conditions for a long time.

In the invention a microcontroller will process the outputs from the Hall Effect sensors which will generate a time between pulses in a numerical figure or a pulses/seconds numerical figure. The microcontroller may convert this figure to an RPM. There will be inputs available to the user for them to be able to set the switching threshold (for example 10%), when the shaft speed drops below the set threshold an alarm/output is given which will shut the machine down.

Because of the arrangement of the multiple Hall Effect sensors the invention can also be used to monitor correct direction of rotation. The magnet(s) should trigger the devices in a specific sequence. If the machine shaft is rotating the wrong way the Hall Effect devices will be triggered in the wrong sequence and trigger an alarm.

The speed sensor 20 is also protected within a protective housing which not only provides protection but also keeps ambient conditions away from the circuitry that could cause I 5 problems.

The speed sensor 20 may also be used to provide an output to an external controlling system such as a PLC system. The microcontroller has potential for change and functionality may be added or removed.

Figure 3 shows a further speed sensor 30 where there are multiple magnets 34 located in the device.

The invention may therefore include devices with multiple magnets and multiple sensors to increase the number of outputs/pulses per rotation.

EXAMPLE

In the present invention the configuration of sensors in relation to the objects that trigger them is such as to minimise the interval between each pulse generated from the sensor. This is achieved by ensuring a difference in quantity of the sensors and the triggers. This gives a minimal angular offset. In order to calculate the rotational speed the angle of rotation from one sensor to the next must always be consistent or substantially consistent. This means that at a constant speed the value for time taken between pulses will also be the same or substantially the same.

This configuration also reduces inefficiency. It is only necessary for one sensor to trigger at any given time. By having multiple sensors triggering simultaneously this is considered inefficient.

In the case of the embodiment shown in Figure 4, the sensors 50 are fixed in position and the magnets 60 will rotate as they will be attached to a shaft. The sensor 50 positioned at the top and the magnet 50 positioned at the top of the diagram are both "perfectly" aligned. The next sensor 50 to trigger requires an angle of rotation of 4 in either direction. There will always be an angular distance of 4° before the sensor 50 can be triggered. This diagram works by assuming ideal conditions. The sensors 50 will trigger early and turn off late through rotation and this may be accounted for in the programming of the invention.

The following are calculations for the switching time of the currently used RoCon' and I 5 similar products that have five triggers and one sensor. In the case of the RoCon it has 5 blades that rotate and pass over the sensing face. (See figure 2 for RoCon).

Table 1

No. of I Switching Threshold: 20% Sensors: No. of -Degrees Between Each 72 Triggers: Pulse:

Table 2

0.5 3 24 28.8 1 6 12 14.4 30 2.4 288 60 1.2 1.44 50 300 0.24 0.288 600 0.12 0.144 The following are calculations for the embodiment shown in Figure 4. As shown it drastically improves on the switching times. Notably at RPMs lower than one using the five bladed RoCon a machine could expect to experience under speed conditions for up to 72 seconds before a machine shut down.

Using this multiple sensor and multiple trigger invention the maximum switching time is reduced as can be shown below.

Table 3

No. of 9 Switching Threshold: 20% Sensors: No. of Degrees Between Each 4 Triggers: Pulse:

Table 4 -ag-

0 2 1.2 3.333333333 4 *05 a 1.333333333 1 6 0.666666667 Ô.8 30 0.133333333 0.16 60 0.066666667 0.08 600 0.006666667 0.008 Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention. For example, any suitable arrangement of multiple magnets and multiple sensors may be used.

ID

IS

Claims

CLAIMS1. An apparatus comprising: a conveyor system capable of conveying and/or mixing material; a motor used for driving a shaft on the apparatus; and a speed monitor system for monitoring the speed of the conveyor system wherein the speed monitor system comprises multiple Hall Effect sensors which are capable of detecting under-speed rotation of the shaft used to propel or driven by the conveyor system.
2. An apparatus according to claim 1, wherein the apparatus is a materials handling conveyor apparatus.
3. Apparatus according to any preceding claim, wherein the apparatus is used for pumps, mixers and in the process industry.
4. Apparatus according to any preceding claim, wherein the driven shaft is used to convey or mix fluids and solids.
5. An apparatus according to any preceding claim, wherein the speed monitor system is used to detect the under-speed rotation of a shaft driven by a conveyor in a materials handling conveyor as well as also relaying speed information to a PLC system.
6. An apparatus according to any of claims 1 or 2, wherein the conveyor system is used to transport and convey materials, goods and products throughout the processes of cleaning, preparation, manufacturing, distribution, consumption and disposal of all related materials, goods and their packaging including in mining and drilling equipment to custom built barley malt drying rooms in breweries.
7. An apparatus according to any preceding claim, wherein the speed monitor system comprises at least two Hall Effect sensors.
8. An apparatus according to any preceding claim, wherein the speed monitor system comprises multiple sensors located around and attached to a shaft driven by the conveyor system.
9. A materials handling conveyor apparatus according to claim 5, wherein the sensors are separated by an angle of about 10°-180°, about 10° -60° and about 30°.
10. An apparatus according to any preceding claim, wherein at least one or more magnets ID are attached to the centre of a shaft wherein the magnet rotates triggering the Hall Effect bydisturbing the magnetic field.
11. An apparatus according to any preceding claim, wherein by having multiple Hall Effect sensors the time taken for under-speed conditions to be noticed by the circuitry will be decreased and thereby providing material handling apparatus with increased safety.
12. An apparatus according to any preceding claim, wherein the speed monitor system prevents a conveyor system from operating in an under-speed condition for a prolonged period of long time.
13. An apparatus according to any preceding claim, wherein a microcontroller processes the outputs from the Hall Effect sensors which generates a time between pulses in a numerical figure or a pulses/seconds numerical figure.
14. An apparatus according to any preceding claim, wherein the microcontroller converts the numerical figure to an RPM.
15. An apparatus according to any preceding claim, wherein a threshold is set (e.g. 10%), when the shaft speed drops below the set threshold an alarm/output is given which will shut the apparatus down.
16. An apparatus according to any preceding claim, wherein the speed of the shaft that has been calculated by the microcontroller is capable of being shown on a display and the switching threshold also shown on the same or a different display.
17. An apparatus according to any preceding claim, wherein the multiple Hall Effect sensors ID are also capable of monitoring the direction of rotation, and if the machine shaft is rotating the wrong way the Hall Effect devices will be triggered in the wrong sequence and trigger an alarm.
18. An apparatus according to any preceding claim, wherein the speed sensor is protected within a protective housing which not only provides protection but also keeps ambient conditions IS away from the circuitry that could cause problems.Amendments to the claims have been made as follows:CLAI MS1. An apparatus comprising: a conveyor system capable of conveying and/or mixing material; a motor used for driving a shaft on the apparatus; and a speed monitor system for monitoring the speed of the conveyor system wherein the speed monitor system comprises multiple Hall Effect sensors located around at least one or more magnets, wherein the Hall Effect sensors are capable of detecting under-speed rotation of a shaft used to propel or driven by the conveyor system; wherein the at least one or more magnets are attached to the centre of a shaft on the apparatus or a shaft used to propel or driven by the conveyor system wherein the magnet rotates triggering the Hall Effect by disturbing the magnetic field.2. An apparatus according to claim 1, wherein the conveyor system is a materials handling conveyor system.3. Apparatus according to any preceding claim, wherein the apparatus comprises pumps and mixers.4. Apparatus according to any preceding claim, wherein the driven shaft is capable of conveying or mixing fluids and solids.5. An apparatus according to any preceding claim, wherein the speed monitor system is capable of detecting the under-speed rotation of a shaft on the apparatus or the shaft used to propel or driven by the conveyor system in the conveyor system as well as also relaying speed information to an electronic control system.6. An apparatus according to any of claims I or 2, wherein the conveyor system is capable of transporting and conveying materials, goods and products.7. An apparatus according to any preceding claim, wherein the speed monitor system comprises two Hall Effect sensors.8. An apparatus according to any preceding claim, wherein the speed monitor system complises multiple sensors located around and attached to a shaft on the apparatus of the shaft used to propel or driven by the conveyor system.9. A materials handling conveyor apparatus according to claim 5, wherein the sensors are separated by an angle of about 10°-1800, about 10°-60° and about 30°.10. An apparatus according to any preceding claim, wherein a microcontroller processes the LU outputs from the Hall Effect sensors which generates a time between pulses into a numerical figure or a pulses/seconds numerical figure. r11. An apparatus according to claim 10, wherein the microcontroller converts the numerical C'J figure to an RPM.12. An apparatus according to any preceding claim, wherein a threshold is set (e.g. 10%), when the shaft on the apparatus or the shaft used to propel or driven by the conveyor system speed drops below the set threshold an alarm/output is given which will shut the apparatus down.13. An apparatus according to claim 10, wherein the speed of the shaft on the apparatus or the shaft used to propel or driven by the conveyor system that has been calculated by the microcontroller is capable of being shown on a display and the switching threshold also shown on the same or a different display.14. An apparatus according to any preceding claim, wherein the multiple Hall Effect sensors are also capable of monitoring the direction of rotation, and if the shaft on the apparatus or the shaft used to propel or driven by the conveyor system is rotating the wrong way the Hall Effect devices will be triggered in the wrong sequence and trigger an alarm.15. An apparatus according to any preceding claim, wherein the speed sensor is located within a protective housing. IC) r (4