WO2020070686A1

WO2020070686A1 - Measuring device

Info

Publication number: WO2020070686A1
Application number: PCT/IB2019/058421
Authority: WO
Inventors: Philip Stephen PIPER; Diederik Arnoldus KAPP
Original assignee: PIPER, Trudi
Priority date: 2018-10-03
Filing date: 2019-10-03
Publication date: 2020-04-09
Also published as: WO2020070695A1

Abstract

This invention relates to a measuring device (11) and more particularly, to a measuring device (11) for measuring the change of the length of a cable (100) wound from a spool (24). In accordance with this invention there is provided a measuring device (11) comprising a housing (18) having a cable (100), at least part of the length of the cable (100) woundable onto or from a biased spool (24) to rotate the spool (24) and a magnet (35) in close proximity to a sensor (36), the sensor (36) sensing rotation of the magnet (35) as a result of linear movement of the cable (100).

Description

MEASURING DEVICE

FIELD OF THE INVENTION

This invention relates to a measuring device and more particularly, to a measuring device for measuring the change of the length of a cable wound from a spool.

BACKGROUND TO THE INVENTION

Various apparatus and methods exist for measuring the relative movement between hanging walls and foot walls in mines or the relative movement of strata in mine walls.

A prior art measuring device makes use of a cable wound on a spool or drum to rotate a potentiometer as the cable unwinds from (or winds onto) the drum. A coil spring provides a rotational bias for the drum to maintain tension on the cable. The drum together with other equipment that forms part of the measuring device, are typically attached to a hanging wall or a foot wall with an outer, free end of the cable attached to an opposite foot wall or hanging wall in the mine. Relative closure of the walls causes the cable to wind onto the drum under the bias of the coil spring, thus turning the potentiometer. A transducer calculates the relative movement as a function of the change in resistance of the potentiometer.

OBJECT OF THE INVENTION

It is an object of this invention to provide a measuring device of the type described above.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a measuring device comprising a housing having a cable, at least part of the length of the cable woundable onto or from a biased spool to rotate the spool and a magnet in close proximity to a sensor, the sensor sensing rotation of the magnet as a result of linear movement of the cable. There is provided for the sensor to be, or to be included in, an integrated circuit.

A further feature of the invention provides for computing means to calculate a distance of movement of the cable or a result representative of a distance of movement of the cable as a function of the rotation of the magnet.

The sensor unit includes a wireless transmission means or wireless transceiver to enable wireless communication with a remote unit.

The measuring device includes a memory means for storing the distance of movement or result as a function of time.

An accelerometer is also included.

A temperature measurement means is also included.

This invention extends to a measuring method for measuring the movements of two objects or parts of a structure relative to each other, comprising the steps of: - winding a cable on a drum of a measuring device;

- securing the measuring device in a first location;

- attaching a free end of the cable at a second remote from the measuring device;

- applying a bias to the drum to maintain tension in the cable;

- attaching a magnet to the drum so that the magnet moves over a sensor as the remote point moves relative to the measuring device.

There is provided for the magnet to be attached to an axis of the drum. A further step includes recording rotation of the magnet as a function of time.

These and other features of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention is described below, by way of example only, and with reference to the drawings in which:

Figure 1 shows a perspective transparent view of a measuring means;

Figure 2 shows a side transparent view of the measuring device of figure 1 ;

Figure 3 shows a top transparent view of the measuring device of figures 1 and

2;

Figure 4 shows a perspective underside view of a drum, brace and plate or pc board of the measuring device of figures 1 to 3;

Figure 5 shows a perspective view of a magnet rotating over an integrated circuit of the measuring device of figures 1 to 3;

Figure 6 shows an exploded perspective view of a measuring device of figures 1 to 3;

Figure 7 shows a perspective view of the measuring device of figures 1 to 3 and

5 inserted in a telescoping housing (the telescoping housing shown in transparent view); Figure 8 shows the same view as figure 7 with the housing installed between a hanging wall and a foot wall in a mine and compressed so that the housing is bent;

Figure 9 shows the same view as figure 8 but with the housing straight and installed in an initial extended installation condition; and

Figure 10 shows the same view as figure 9, with the housing straight but in a compressed condition, compressed along its length between hanging and a foot walls.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to the drawings, a measuring device is generally indicated by reference numeral 11.

The measuring device (also referred to as a sensor) 11 includes a rectangular support plate on which most of its components are mounted. This support plate 19 can be a printed circuit board or part thereof. The printed circuit board (PCB) can include multiple identical sections divided by lines of weakness. The measurement functionality is repeated in this manner. This enables the measuring device to conduct a plurality of different measurements at the same time, as described below, in effect, it contains a plurality of sections for conducting the measurement functionality. Any unused sections of the PCB can be removed by breaking them off at the lines of weakness thus, in effect, reducing the amount of measuring devices it contains.

A U-shaped inverted brace 21 having a central and operatively downwardly extending hollow pin 21a (extending from its base), supports a cable spool or drum 24 and associated components. The pin, extending downwardly and centrally from the bridge or base section of the brace, extends through a spring stop plate 22 in the form of a disc having a centrally located hole for receiving the pin therethrough. The plate is thus in the form of a washer. The pin then extends through a coil spring 23. The coils spring 23 engages inside the spool to rotationally bias the spool.

A bearing pin 26 extends centrally upwards from a spool receptacle 27. The spool receptacle is cup-shaped, thus has an open top so that it locates underneath the spool to house the spool therein. The receptacle fits snugly within the arms of the inverted U-shaped brace with the open end of the receptacle facing the bridge or base of the brace.

The bearing pin extends into a bearing bus 25 and terminates inside the hollow pin. An inner ring of the bearing bus thus locates around the pin 26 and an outer ring thereof locates inside the spool. The spool is thus free to rotate about the pin.

Free ends of the arms of the inverted U-shaped brace are secured to the PCB to hold the abovementioned components in place.

A cable 100 is wound on the spool.

A magnet 35 is rotatable over an integrated circuit (IC) 36 as is shown in figure 5. The magnet is attached to an underside of the spool so that movement of the cable causes rotation of the magnet. A sensor in the IC senses the rotation of the magnet and calculates the distance of movement of the cable as a function of the rotation of the magnet.

The magnet is attached, through a stub axle, through a central hole (not shown) in the receptacle 27 inside the hollow bearing pin 26, thus indirectly to the spool or cable drum 24. The magnet is slightly spaced from the IC to allow an airgap therebetween. All the above components are housed in a tubular housing 18. The housing includes a front closure cap 17 and a rear closure cap 30. An end ring 29 has an internal screw thread for receiving a screw thread on a side circumferential surface of a raised surface extending operatively inwardly from the disc-shaped rear closure cap. The ring has slits 29a therein for receiving and supporting an operatively rear end of the PCB therein.

A front end of the cable 100 protrudes out of the closure cap 17 so that this front end may be pulled away from the housing to unwind part of the cable from the drum and to attach the front end of the cable remotely from the housing.

Some of the electronic components are housed in the tubular housing 20.

In use, the front end of the cable is pulled away from the housing to unwind part of the cable from the drum. The front end of the cable is attached remotely from the housing. The bias on the drum maintains pressure on the cable at ensures that there is no slacking of the cable. When the remote location, where the drum is attached, moves relative to where the housing is attached, part of the cable winds further from the drum or back onto the drum. When the cable is thus further unwound or wound up, the movement is registered by the 1C through the resultant rotation of the magnet. The distance of movement can now be calculated.

In one example, the housing may be attached to a floor or foot wall in a mine working with the front end of the cable attached to the hanging wall. Closure (or opening) of the mine working can now be measured and recorded in a memory means of the device.

The distance of movement or the representative result can now be communicated via a wireless transceiver or wireless transmitter included in the sensor device, to a remote unit. The sensor may also transmit identification means so that information received from different sensors can be identified and sorted according to their location in a mine working.

The apparatus also includes an accelerometer in communication with computing means. Mine walls normally only close on each other. It is only in very exceptional circumstances that walls will open. It is for this reason that in most cases, any movement that appears to record the opening of mine walls, is an indication that the apparatus was tampered with. The accelerometer will aid to confirm such a suspicion. Sudden movement is indicative of tampering with the apparatus. The apparatus may have been removed and re-inserted. One could then discard such movement. Data from the accelerometer can also assist with quantifying any ride (shear movement) between the mine walls. Furthermore, should rapid closure take place between the mine walls due to a seismic event, data from the accelerometer could assist in determining the rate of movement. An example is the inclusion of a low power consumption accelerometer for activating the device from a‘sleep mode’ when not in use. Inclusion of an accelerometer leads to many benefits - it can be used to activate (wake-up) the device from a sleep (low power consumption) mode, indicate that there has been no tampering, it assists in the quantification of rapid closure, assists in the determination of ride/shear movement between the two points being measured for relative movement.

Should temperature changes occur these can result in very small amounts of expansion and contraction of both the measuring cable and the telescopic housing. In order to quantify true rock movement between mine walls it is necessary to eliminate temperature effects. This is done by measuring temperature changes and adjusting the movement using known coefficient of expansion relationships.

In another example, and to protect the exposed cable, the device can be attached in a telescoping housing as is shown in figures 7 to 10. Three (or more) telescoping members (1 ,2 and 3) can telescopingly move into and out of each other. A screw threaded stub (not shown) inside of the first telescoping member can receive the screw threaded bore 30a of the housing to secure the housing inside an outer end of the member 1. Additional spacer elements may be provided in the space around the housing and the inside of the member to support and protect the device. The cable end may now be attached to the second or third members (2 and 3). In other word, the cable extends inside the tubular members and is protected from the environment. The members are of a diameter sufficient to allow a certain amount of bending before they interfere with the cable, as is shown in figure 8. With reference to figures 9 and 10, the telescoping housing can be installed between the walls of a mine working to measure closure of the mine working from a distance A to a distance B as shown in figures 9 and 10.

The apparatus described herein will be convenient to use in that the cable is secured and protected inside the telescoping members. Furthermore, should a telescoping member buckle, bend or otherwise be forced out of alignment, under compressive forces, some amount of such buckling, bending or misalignment will not interfere with the cable and hence the accuracy of the recording actual movement between the mine walls, depending on the inside diameter of the members. This is shown in figure 12. The cable remains in straight line even when the lower tubular member is bent.

The sensor unit can be easily removed from the tubular member in which it is located to be replaced or to be used in another tubular member or members having different lengths.

With a current prior art measuring device, a potentiometer is rotated by a friction wheel. The analog voltage output of the potentiometer is sampled by an analog to digital converter with a 10-bit resolution. Over the 300mm measurement range, the resolution is 0.25mm.

The unit described herein measures the direction of the magnetic flux lines of the rotating magnet. The sensor has a resolution of 14 bits or 16384 steps per revolution. The cable drum rotates once per 62mm of cable movement giving a maximum theoretical resolution of 0.0038mm.

Furthermore, using the above design, a movement range of at least 700mm can be obtained whilst maintaining the maximum theoretical resolution of 0.0038mm throughout out this range.

A measuring means without communication means but having some visual indication means can also be implemented and used as a“robot” (warning or monitoring device device). The visual indication means may be in the form of LED lights inside.

The device described herein is a fully integrated measuring device. The sensor, the power supply, the data logger and the wireless communication means are all integrated into one housing. It is designed to fit into a 26mm ID capsule which is small enough to fit into a borehole and also ensure the diameter of the telescopic housing is as small and unobtrusive as possible.

The theoretical resolution and range is better than 3.8 microns over a full 700mm range.

The cable take-up system is designed to fit inside a 26mm tube without cable overlay errors and to provide a range of 700mm without loss of resolution over the entire range.

Cable inside telescoping housing which allows for a certain amount of buckling without affecting the accuracy of the measurement.

Battery power eliminates all the electrical noise, voltage fluctuations and supply continuity issues associated with mains power. Extending the operating life to a minimum of 12 months, and still being able to house the battery in a very small capsule whilst not compromising features, has been a major challenge and required very clever design and embedded programming. An example is the inclusion of a low power consumption accelerometer for activating the Logger from a‘sleep mode’ when not in use.

Obtaining maximum power from one small battery so that the capsule can be fully sealed for environmental protection and that the risk of problems arising from customers changing batteries is eliminated.

Experience has shown that high resolution is possible with many sensors but not when used with other components required for the system. A telescoping housing is critical for ease of installation and protection of the cable and sensor but prior art telescoping housings have been considerably limited in respect of accuracy of measurement so that resolution better than 0.5mm has not been possible in practice until this design. Exposed cables are vulnerable to damage and, at 3.8 micron theoretical resolution, to air velocity and temperature changes in the mine. The apparatus described herein overcomes this difficulty.

Telescopic housing coupling design provides for preferential slip when more than 2 tubes are used.

Advantage of more than 2 tubes is that only one size of telescoping housing is required to cover almost all stoping width ranges in practice (1 .0 - 2.5m).

Telescoping housing has couplings with no stick-slip behavior.

The apparatus has a range of applications with the sensor being useable independent of the telescopic housing. Inclusion of an accelerometer leads to many benefits - it can be used to activate (wake-up) the logger from a sleep (low power consumption) mode, indicate that there has been no tampering, it assists in the quantification of rapid closure, in assists in the determination of ride/shear movement between the two points at which the telescoping housing connects with the rock surfaces.

Data values continue to be provided and verifiable with the inclusion of a ruler as part of the smallest tube.

The apparatus includes the capability to provide early warning based on rate of movement between the rock surfaces through logging of data, embedded software and different colour LEDs.

It will be appreciated by those skilled in the art that the invention is not limited to the precise details as described herein. For example, instead of using the measuring device (also“capsule”) in the measuring apparatus, the measuring device can be used on its own. In this case the cable will not necessarily be protected in a telescoping sleeve but can protected with other sleeves if desired or necessary. The cable may be attached to rock formation or strata remote, concrete soils, any two objects or substrates that can move relative to each other and the like from where the sensor’s housing is installed. Closure or movement in a borehole may for example be measured in this manner. It will be appreciated that many other applications are possible for the measurement of relative movement between two points by using the measuring device on its own.

Claims

1. A measuring device comprising a housing having a cable, at least part of the length of the cable woundable onto or from a biased spool to rotate the spool and a magnet in close proximity to a sensor, the sensor sensing rotation of the magnet as a result of linear movement of the cable.

2. A measuring device as claimed in claim 1 in which the sensor is or is included in, an integrated circuit.

3. A measuring device as claimed in any one of the preceding claims in which computing means calculates a distance of movement of the cable or a result representative of a distance of movement of the cable as a function of the rotation of the magnet.

4. A measuring device as claimed in any one of the preceding claims including a wireless transmission means or wireless transceiver to enable wireless communication with a remote unit.

5. A measuring device as claimed in any one of claims 3 or 4 in which a memory means stores the distance of movement or result as a function of time.

6. A measuring device as claimed in any one of the preceding claims including a an accelerometer.

7. A measuring device as claimed in any one the preceding claims including a temperature measurement means.

8. A measuring method for measuring the movements of two objects or parts of a structure relative to each other, comprising the steps of: winding a cable on a drum of a measuring device; securing the measuring device in a first location; attaching a free end of the cable at a second remote from the measuring device; applying a bias to the drum to maintain tension in the cable; attaching a magnet to the drum so that the magnet moves over a sensor as the remote point moves relative to the measuring device.

9. A method as claimed in claim 8 in which the magnet is attached to an axis of the drum.

10. A method as claimed in any one of claims 8 or 9 including recording rotation of the magnet as a function of time.