Field of Invention

The present invention relates to a roller for an undercarriage track system suitable for a mining or construction machine. More particular it relates to a roller comprising a wear measuring system for measuring wear in the roller bearing.

Background

Mining and construction machines, such as hydraulic mining shovels, excavators, rope shovels, electric powered excavators and bucket wheels commonly employ undercarriage track systems. Typically, such an undercarriage track system has a track chain assembly formed by interconnected track links. The track chain is supported and guided by rollers. The rollers may experience stress during use which may result in wear and tear of the roller bearings.

It is preferred to monitor the internal wear in the rollers to determine when to service the bearings and provide a timely replacement. If the servicing of the rollers is conducted too early, the mining machine may be taken out of operation and the bearing changed unnecessarily. If the servicing is carried out too late, the bearing may be completely worn-out and steel-to-steel contact between a shaft and roller may provide damage and require additional reparation.

Mining and construction machines operate in harsh environments, and the rollers of such machines may become very hot during use. It is therefore essential that the monitoring system is reliable and is suitable for such an environment.

The prior art comprises rollers having different types of monitoring systems e.g. for measuring temperature, vibrations, revolutions, or rotational speed, which may be compared to historical data or other measured data from rollers. Such rollers may require detectable inserts, e.g. magnets, located in the bearing or rollers which can be sensed by a sensor in the shaft. Other solutions may comprise sensors located in the roller housing.

Summary

With this background, it is therefore an object of the present invention to provide an alternative roller for an undercarriage track system that comprises a measuring system which is reliable and by which it is possible to mitigate some of the drawbacks of the prior art.

In a first aspect of the invention, these and further objects are obtained by a roller comprising: a roller body for rotating about a roller axis, the roller body having a bore surface defining a bore extending through the roller body, the bore surface being a radially inner surface of the body, and a roller surface located outward from the bore surface; a shaft located centrally in the bore along the roller axis, said shaft having a shaft body and a shaft surface; a bearing arranged in the bore, the bearing having an inner surface surrounding the shaft and an outer surface facing the roller body; and wherein: the roller further comprises a bearing sensor device arranged in the shaft body and measuring in a radially outward direction from the shaft onto the bearing inner surface for measuring the distance from the shaft surface to the inner surface of the bearing and wherein the bearing sensor device is arranged in the shaft such that it measures in a direction different from vertically downwards, and/or; the bearing comprises a gap and the roller additionally comprising a gap sensor device arranged in the shaft body for measuring in a radially outward direction from the shaft and wherein the sensor device is arranged to measure in a substantially vertically downward direction through the bearing gap onto the bore surface of the roller body.

In one or more embodiments, the shaft body is cylindrical. Preferably, the shaft surface is uniform when seen from one end of the shaft to the other end of the shaft, i.e. the shaft surface does not comprise any protrusions.

By bearing sensor is meant a sensor measuring onto a surface of the bearing. Optionally, the bearing sensor device may be substantially flush with the shaft surface.

By gap sensor device is meant a sensor measuring through the bearing gap into a bore surface of the roller body. Optionally, the gap sensor device may be substantially flush with the shaft surface.

The bearing sensor device is suitable for measuring the distance from the shaft surface to the bearing inner surface. This means that the sensor device is suitable for measuring a parameter indicative of a distance and which may be processed into a distance. If the sensor device is not arranged flush with the shaft surface, the distance may be corrected based on the distance from a measuring point of the sensor device to the shaft surface.

For an unworn bearing, the bearing sensor device will measure a very short or even zero distance between the shaft surface and the bearing inner surface. The shaft is located substantially centered in the roller body due to the bearing.

As the bearing is worn the thickness of the bearing decreases. Because of the weight of the machine resting on the shaft, the shaft will be decentered towards the lower part of the roller body. Hence the lower most part of the shaft is always in contact with the bearing when the weight of the machine is provided onto the shaft. The wear of the bearing can therefore be measured as the half of the upward vertical distance from the upper most portion of the shaft to the bearing.

Hence, the wear pattern provided by the bearing sensor device will start with zero (or a very low distance) and increase towards a distance having twice the thickness of the bearing which is when the bearing is completely worn.

Depending on the type of sensor device and bearing thickness, it may not be possible for the sensor device to measure the full distance from the shaft to the inner surface of the bearing when the bearing is worn beyond a certain point. This may be compensated for by orienting the bearing sensor device such that it has an angle of between 1° and 179° with respect to a vertical direction, preferably between 90° and 179° with respect to vertical. Because the lower part of the shaft is always in contact with the lower portion of the bearing surface, the distance between the shaft surface and the bearing inner surface is the largest when measuring in a vertically upward direction and zero when measuring in a vertically downward direction. Using the angular orientation of the sensor with respect to vertical, the known bearing thickness together with the measured distance of the bearing sensor device, it is possible using trigonometry to calculate the vertical distance between the shaft surface and the bearing inner surface, i.e. to calculate the wear.

All directions mentioned are indicated with respect to intended use of the roller. A vertical direction means the direction of gravity or the direction opposite of the direction of gravity. All angles referred to in this application is with respect to upwards, i.e. 0° is the direction opposite of the direction of gravity, 90° is a horizontal direction and 180° corresponds to the direction of gravity.

The direction of the sensor device may be a direction having an angle with respect to the vertical of around 20° to 180°. Preferably the direction may be an angle of more than 45°, more preferably more than 90°, most preferably more than 135°. The sensor device may be arranged such that is has an acute angle or obtuse angle with respect to vertical. The sensor device may be arranged to have an angle with respect to the vertical of 30°, 40°, 45°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120, 125°, 130°, 135°, 140°, 145°, 150°, 155° 160°, 165°, 170°, 175°, 179°, 180° or any interval in between.

The gap in the bearing may be an empty space or opening in the bearing or between two parts of the bearing. The bearing may be a two-part bearing, inserted from opposite sides of the roller body and providing a gap between the two parts of the bearing.

When the bearing is unworn, the gap sensor device will measure a maximum distance of approximately the thickness of the bearing. As the bearing is worn and the thickness of the bearing decreases, the weight of the machine resting on the shaft forces the shaft towards a lower portion of the roller body.

Because the gap sensor device is oriented to measure in a downward direction onto the inner surface of the roller body, the measured distance will decrease over time towards zero. Zero corresponds to a completely worn bearing.

In one or more embodiments, the roller comprises one or more additional sensor devices arranged in the shaft body and measuring in a radially outward direction from the shaft onto the bearing inner surface for measuring the distance from the shaft surface to the inner surface of the bearing and wherein the one or more additional sensor devices are arranged in the shaft such that it measures in a direction different from vertically downward.

By having additional sensor devices, it possible to have a more detailed measurement of the wear.

In one or more embodiments, the bearing is a bushing. Typically, the bushing has a thickness of 10 mm to 30 mm, but it may have any thickness making it suitable for its application.

In one or more embodiments, the bushing is made of a bronze alloy such as Manganese Bronze.

In one or more embodiments, two sensor devices each having a sensing range lower than the thickness of the bearing may be arranged to measure the complete wear of the bearing.

In one or more embodiments, the bushing thickness is at least 1.5 times larger than the sensing range of at least one of bearing sensor device or the gap sensor device, preferably at least 2 times larger, more preferably 3 times larger, more preferably 4 times larger, more preferably 5 times larger than the sensing range. By orienting the sensor device at a desired angle with respect to vertical, is it possible to measure the wear of a bearing thicker the sensing range.

Especially when the roller body comprises two sensor devices which are oriented to measure in a vertically downward direction and a direction different from vertically downwards, it is possible to utilize sensor devices which have sensing ranges less than the thickness of the bearing. This allows for the use of cheaper sensors and thereby provide a more economical roller. This is due to the wear pattern of each of the two sensor devices, which measures an increasing and decreasing distance, respectively. Also the material of the bearing affects the effect of the sensor devices. As an example, a bearing made of Manganese Bronze.

In the case where the bearing thickness is larger than the sensing range of both the bearing sensor device and the gap sensor device, the bearing sensor device will initially measure zero or a very low distance. The gap sensor device will not measure anything since the sensing range is lower than the thickness of the bearing. As the bearing is worn, the bearing sensor device will measure a greater distance towards the bearing. When the thickness of the bearing has decreased to be equal to the sensing range, the gap sensor device will start to measure the distance from the shaft surface to the roller body inner surface. Similarly, the bearing sensor device will stop to measure the distance between the upper portion of the shaft and the inner surface of the bearing when this distance is greater than the sensing range.

Sensor devices with different or similar sensing ranges may be used. When the bearing sensor device and gap sensor device have sensing ranges larger than the bearing thickness, this provides a more reliable measurement since both sensor devices are able to provide a valid measurement during the entire wear period.

In one or more embodiments, at least one of the bearing sensor device or the gap sensor device have a sensing range equal to or larger than the thickness of the bearing. This may provide dual measurements in a chosen wear range to provide more reliable data.

In one or more embodiments, the bearing sensor device and gap sensor device may be a capacitive or inductive type proximity sensor.

The chosen sensor type should have a distance measuring output (versus object detection). This is typically done by adding electronics to convert the signal to an industrial standard, of which 0-10V and 4- 20mA is the most common, and an amplitude measurement of a square PNP or NPN signal also is possible.

In one or more embodiments, the shaft may comprise a data access unit coupled to the bearing sensor device and/or gap sensor device. The data access unit may be a transmitter for wirelessly transmitting data from the transmitter to a computing unit. The transmitter may be located in or near one end of the shaft.

In a preferred embodiment, the data access unit is a socket suitable for being connected to external electronics by plugging in a cable to e.g. a computer. During normal operation, the temperature of the roller and surroundings may be well above a temperature environment suitable for electronics. By having external electronics removably attached to the roller, expensive electronic shielding can be avoided which otherwise should protect the electronics from dirt and high temperatures.

According to another aspect, the invention relates to a method for monitoring bearing wear in a roller for an undercarriage track system. The method comprising the steps of: measuring in a downward direction through a gap in the bearing, a first parameter relating to the radial distance between the shaft surface and a corresponding bearing surface; receiving by one or more processors the first parameter; determining by the one or more processors the wear of the bearing based on the value of the first parameter.

Based on the determined wear, it may be decided if maintenance should be conducted or the determined wear may be used to predict an optimal maintenance day.

If the data access point is configured for wirelessly transmitting data, the monitoring of wear may be conducted while the roller is in operation. If the data access point requires electronics to be connected by wire, the machine comprising the roller will typically be out of operation. Once the electronics in the form of a processer, such as a computer, is coupled to the one or more sensor devices, a measurement point may be obtained. Optionally, the roller may perform a full rotation.

In one or more preferred embodiments, the method further comprises the steps of: measuring in an upward direction, a second parameter relating to the radial distance between a shaft surface and an inner surface of an adjacent bearing; receiving by one or more processors the second parameter; determining by the one or more processors the wear of the bearing based on the value of the second parameter.

During measurement of the second parameter, it may be beneficial to perform a full rotation of the roller. In this way, the second parameter may comprise data relating to the radial distance between the shaft and the entire inside circumference of the bearing. Once the first and/or second parameter has been obtained, the machine comprising the roller may resume operation.

Further presently preferred embodiments and further advantages will be apparent from the following detailed description and the appended dependent claims.

Brief description of the drawings

The invention will be described in more detail below by means of non-limiting examples of presently preferred embodiments and with reference to the schematic drawings, in which:

Fig. 1 shows a schematic cross-sectional view of a roller according to an embodiment of the invention;

Fig. 2 shows a wear monitoring system;

Fig. 3 shows a schematical cross-sectional view of a roller with substantially no bushing wear;

Fig. 4 shows a schematic cross-sectional view of a roller with some bushing wear;

Fig. 5 shows a schematic cross-sectional view of a roller with extensive bushing wear. Detailed description of embodiments of the invention

Fig. 1 shows a schematic view of a roller 1 for an undercarriage track system. The roller 1 comprising a roller body 10 for rotating about a roller axis 2. The roller body 10 having a bore surface 11 defining a bore extending through the roller body 10. The bore surface 11 is a radially inner surface of the roller body 10. The roller has a roller surface 12 located outward from the bore surface. A shaft 20 is located centrally in the bore along the roller axis 2. The shaft 20 having a shaft body 21 and a shaft surface 22. A bearing in the form of a bushing 30 is arranged in the bore. The bearing has an inner surface 31 surrounding the shaft 20 and an outer surface 32 facing the roller body 10 and in contact with the bore surface 11. A first shaft bore 23 is located in the shaft body 21. A bearing sensor device 40 is arranged in the first shaft bore 23 and fastened in place. The bearing sensor device 40 is arranged for measuring in a radially outward direction from the shaft 20 onto the bearing inner surface 31, to measure the distance from the shaft surface 22 to the inner surface of the bearing 31. In the shown embodiment, the bearing sensor device 40 is arranged substantially flush with the shaft surface 22, such that the measurement of the bearing sensor device 40 is indicative for the distance between the shaft surface 22 and the bearing inner surface 31. Alternatively, the bearing sensor device 40, may be arranged in the first shaft bore 23 below the shaft surface 22. The measured distance by the bearing sensor device 40 will in this case have to be corrected, based on the distance from sensor measuring point to the shaft surface 22. The bearing sensor device is arranged in the shaft 20 such that it measures in an upward direction. The bearing sensor device 40 is coupled to a data access unit in the form of a socket 60 by means of a cable 62. The cable 62 runs from the bearing sensor device 40 through the shaft 20 to the socket 60. The socket 60 is located behind a protective cover 61 which is removable. In the embodiment shown, the protective cover 61 is removable by losing a screw, but other removable fastening means may be provided. During a measurement, the protective cover 61 is removed and a data cable (not shown) is plugged into the socket. Alternatively, the data access unit may be a wireless transmitter. The data access unit and how data is transferred from the bearing sensor device and optionally the gap sensor device is described further below with reference to Fig. 2.

The roller 1 comprising only the bearing sensor device 40 is fully operational for measuring wear in the roller. As described previously, additional advantages are obtained by providing a gap sensor device 50. The gap sensor device 50 is located in a second shaft bore 24 in the shaft body 10. The gap sensor device 50 is arranged to measure in a radially outward direction from the shaft 20. Additionally, the gap sensor device 50 is arranged to measure in a downward direction and located at a gap 33 in the bearing 30. The gap sensor device 50 therefore measures the distance though the gap 33 onto the bore surface 11 of the roller 1. The gap sensor device 50 may be substantially flush with the shaft surface 22. Alternatively, the gap sensor device 50 may be arranged in the second shaft bore 24 below the shaft surface 22. The measured distance by the gap sensor device 50, will in this case have to be corrected, based on the distance from the sensor measuring point to the shaft surface 22. The gap sensor device 50 is coupled to the data access unit in the form of a socket 60 by means of a cable 63. The cable 63 runs from the gap sensor device 50 through the shaft 20 to the socket 60. In the embodiment shown in Fig. 1, the bearing 30 is a two-part bearing having a first bearing part 34 and a second bearing part 35. The gap 33 separated the first bearing part 34 and the second bearing part 35. Each of the first bearing part 34 and second bearing part 35 has a bearing flange 36 located on opposite sides of the roller and ensuring correct positioning of the bearing parts.

During intended use of the roller 1, the shaft 20 is connected to the undercarriage track system of a machine (not shown). As the roller body 10 rotates around the shaft 20, the bearing 30 experiences wear. This results in a decreasing thickness of the bearing 30 over time. The bearing may have a thickness suitable for a specific application. As an example, the bearing may have a thickness of around 10 mm to 30 mm.

Weight of the machine rests of the shaft in the direction indicated by the arrows 80. As the bearing 30 is worn down, space will occur between the shaft 20 and the bearing 30. The bearing 30 will experience wear all around the inner surface 31, but due to the weight of the machine forcing the shaft 20 downwards, the space arising from a worn bearing 30, will be biggest towards the topmost part of the shaft 20. This means that the bearing sensor device 40 will measure an increasing distance as the bearing 30 decreases in thickness. The gap sensor device 50 will measure a decreasing distance as the bearing 30 decreases in thickness, since the shaft 20 will be decentered towards the bottom part of the roller bore.

Turning now to Fig. 2 showing a wear monitoring system. Data from the bearing sensor device 40 and gap sensor device 50 are utilized to determine wear. During testing, a connection from a reading apparatus 110 to the bearing sensor device and/or gap sensor device is established via the plug 65 / socket 60 configuration. The reading apparatus 110 is handheld and is provided with batteries 112 for powering itself and the sensor devices 40 and 50. The reading apparatus 110 is configured to read the data from the bearing sensor device 40, the gap sensor device 50 and optionally an ID tag 101 and configured to pass on the data. To pass on the data, the reading apparatus 110 may comprise a screen 111 for viewing the data or a transmitting means (not shown) for transmitting the data to a separate device. Additionally, the reading apparatus 110 may comprise a processing unit (not shown) to process and convert the data into a readable wear data in the form of a distance, percentage or other preferred unit. Optionally, the reading apparatus 110 may also comprise a data storing unit (not shown).

Once the bearing sensor device 40 and gap sensor device 50 are connected and powered by the reading apparatus 110, the measurement is initiated. Data indicative of the bearing wear from both sensors are obtained. The reading from the gap sensor device is a direct measurement of the bushing remaining. The reading from the bearing sensor device 40 is a measurement of bushing wear. Specifically, the distance measured by the bearing sensor device is the wear corresponding to two times the bushing thickness. The data and roller ID data are transferred to the reading apparatus 110. The wear data may be manually read from the screen 11 or transmitted to another unit 130 where the data can be viewed and stored. The unit 130 may be a mobile phone, tablet, laptop or the like. The data is preferably transmitted wirelessly via e.g. Bluetooth or Wi-Fi, but may also be transmitted by a cable connection. The data may be viewed and approved on the unit 130 and uploaded to a server 140 and/or to an auditing system 150.

Alternatively, if the data access unit is a wireless transmitter, it may comprise an internal battery for powering the sensors. Preferably, the sensors are powered by pressing a start button hidden behind the protective cover 61. The data may then be wirelessly transferred to the reading apparatus 110.

As each roller is identified by the ID tag 101, each dataset may automatically be linked to the wear data, and it is easy to identify the specific rollers which require maintenance.

If the wear data indicates that one or more rollers 1 require maintenance, the unit 130 may create an alert.

Turning now to Fig. 3, Fig. 4, and Fig 5 a cross section of a roller 300, 400, 400 with different bushing wear states.

Fig. 3 shows an illustration of a roller 300 with substantially no wear. The bushing 330 has it original thickness and is in contact with an inner surface of the roller body 310 and an outer surface of the shaft 320. A number of sensor orientations 340 are indicated by radial lines from the center of the shaft. In the following description 0° refers to vertically upwards and 180° refers to vertically downwards. The remaining radial lines are intermediate orientations at 45°, 90°, and 135°.

As can be seen only the sensor orientation at 180° will measure a distance equal to the bushing thickness, because it measures through the gap 333. A sensor at the remaining sensor positions will measure 0 distance.

Turning to the roller 400 illustrated in Fig. 4 showing a bushing 430 with some degree of wear. A sensor at the 180° orientation would measure a distance lower than measured in Fig. 3. A sensor with a 0° orientation would measure the largest value corresponding to 2 times the radial bushing wear. At intermediate orientations, a sensor would measure a lower distance as the orientation approaches 180°.

Turning to the roller 500 illustrated in Fig. 5 showing a bushing 530 with a large degree of wear. At a sensor orientation of 0°, the distance from the shaft 520 to the bushing 530 is quite large and would therefore require a proximity sensor with a long range. If one of the intermediate sensor orientations are used, e.g., 90°, a proximity sensor with a lower range could be utilized to measure wear in the entire wear range.

Examples

The proximity probes from Bently Nevada were tested against steel and manganese bronze in a setup similar to that in an undercarriage roller. This was conducted to evaluate the performance and reliability when used on different materials. The following probes where tested:

Probe 1 was a 3300 XL 16mm Proximity Probe.

Prope 2 was a 3300 XL 25mm Proximity Probe

Prope 3 was a 3300 XL 50 mm Proximity Probe.

The table below shows the maximum sensing range in mm against the specified materials in the experimental setup.

Example 1

A roller, having a 100mm axel with a 12.5mm Manganese Bronze sleeve bearing pressed onto it, was tested at different states of wear between 0 mm of wear to 10 mm of wear.

The table below was created to identify how many probes, which type of probes and at which position the probes should be arranged to measure wear in the whole wear interval. The column having the 180° position (downwards) is to measure through the gap in the bearing. Therefore, at this position a probe will see a decrease in distance as the bearing is worn, whereas probes in other positions will see an increase in distance.

The table shows that a downward oriented probe measuring through the gap in the bearing will show a reading from 12.5 mm to 2.5mm. This measurement will be made onto a steel surface, since it will measure through the gap in the Manganese Bronze bearing onto the inner surface of the roller.

A single probe of the type "probe 2" could therefore be used to measure the whole wear interval.

A sensor arranged to measure in a direct upward direction will show a reading from 0 mm to 20 mm. This would not be possible with the available probe types since none of them are able to measure at distances of 20 mm at manganese bronze surfaces.

As an alternative, a single probe of the type "probe 1 arranged at 135° could also measure the entire wear interval.

The test was conducted with a single probe of the type "probe 2" in the 180° position. It was validated that the specific sensor could in fact be used for this setup.

Example 2

A roller, having a 125mm axel with a 25mm Manganese Bronze sleeve bearing pressed onto it, was tested at different states of wear between 0 mm of wear to 20 mm of wear, i.e. the bearing was worn down to 5 mm of thickness.

The table below was created to identify how many probes, which type of probes and at which position the probes should be arranged to measure wear in the whole wear interval. The column having the 180° position (downwards) is to measure through the gap in the bearing. Therefore, at this position a probe will see a decrease in distance as the bearing is worn, whereas probes in other positions will see an increase in distance. The table shows that a downward oriented probe measuring through the gap in the bearing will show a reading from 25 mm to 5 mm.

A probe oriented up (0°) would see from 0 to 40 mm.

A probe arranged to measure in a horizontal direction (90°) should be able to measure from 0 mm to 17 mm.

A probe arranged at 135° would reduce the required sensing range to from 0 mm to 4.5 mm.

A single probe of the type "probe 3" arranged at 180° will not be able to measure the state of wear until the bearing is worn below 3 mm. This sensor will therefore initially be in a blind zone.

To see the state of wear during the complete interval, a gap sensor is therefore necessary. A probe of the type "probe 2" could be arranged in the 135° position. This sensor would be able to see the whole wear interval. Alternatively ,a probe of the type "probe 1 could be arranged at the 135° position or the 90° position to see the initial wear.

The test was conducted with a "probe 3" in the 180° position and a "probe 1" in the 135° position. As expected initially, only the second probe at the 135° position showed measurements and the distance between probe and bearing exceeded the sensing range as wear increased above around 16 mm. The first probe of the type "probe 3" showed measurements in the wear interval between 3 mm and 20 mm, i.e. a distance between probe and roller of 22 mm to 5 mm.

Example 3

A roller, having a 225mm axel with a 20mm Manganese Bronze sleeve bearing pressed onto it, was tested at different states of wear between 0 mm of wear to 20 mm of wear, i.e. the bearing was worn down to 5 mm of thickness.

The table below was created to identify how many probes, which type of probes, and at which position the probes should be arranged to measure wear in the whole wear interval. The column having the 180° position (downwards) is to measure through the gap in the bearing. Therefore, at this position the probe will see a decrease in distance as the bearing is worn, whereas probes in other positions will see an increase in distance.

The table shows that a downward oriented probe measuring through the gap in the bearing, should show a reading from 20 mm to 5 mm to measure the full wear interval. At the 0° position, the full sensing interval would be from 0 to 30 mm.

In a horizontal direction (90°), the full sensing interval would be from 0 mm to 13.8 mm.

In the 135° position, the full sensing interval would reduce to from 0 mm to 3.9 mm.

A single probe of the type "probe 3" arranged at 180° would in this case be able to measure the complete state of wear. Initially, the probe will measure near close to its maximum sensing range and therefore it could be beneficial to supplement with a second probe of the type "probe 2" arranged at the 135° position.

The test was conducted as suggested above and validated that the specific sensors could in fact be used for this setup.

It should be clear from the description and the examples that the probes may be positioned at other positions than 0°, 35°, 90° or 135° which has been shown in the three examples. In fact, the angular orientation of the probes may be optimized and determined based on the sensing range of the probes, the thickness of the bearing and diameter of the axel to provide measurements in the desired wear intervals.