WO2005073666A1

WO2005073666A1 - A diameter measurement instrument

Info

Publication number: WO2005073666A1
Application number: PCT/AU2005/000124
Authority: WO
Inventors: Alan John Vincent
Original assignee: Alan John Vincent
Priority date: 2004-02-02
Filing date: 2005-02-01
Publication date: 2005-08-11
Also published as: WO2005073666B1

Abstract

A device (1) for measuring the curvature of an arc to determine the diameter or radius of an object with the curvature. The device (1) has a support structure (3, 3A) for supporting the device (1) on the arc or for enabling the device (1) to be positioned relative to the arc. A first sensor (4) produces an output dependent upon the curvature of the arc. A controller controls the device (1) and processes the output of the sensor to provide an output indicative of the radius or diameter of the object.

Description

A DIAMETER MEASUREMENT INSTRUMENT

FIELD OF THE INVENTION

The present invention relates generally to devices for measuring the curvature of an arc and, in particular, to devices that measure the radius or diameter of curvature of an arc.

The invention has been developed primarily for measuring the radius or diameter of train wheels and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular use.

DESCRIPTION OF THE PRIOR ART

Most people are familiar with the basic configuration of a modern railway system. The tracks of such a system usually comprise a pair of parallel metal tracks that are spaced apart from each other by a constant width. The trains that run upon these tracks usually have metal wheels that roll along the rails. It can be appreciated that over time, portions of the train wheels in contact with the rails will gradually wear down due to friction. This wear presents itself as a reduction in the diameter of the wheel.

Once a train wheel has been sufficiently worn down, it becomes necessary to replace the wheel with a new one. In order to ascertain whether a wheel needs to be replaced, the radius or diameter of the wheel is usually measured in order to determine the amount of wear experienced by the wheel. If the diameter or radius of the wheel is less than a predetermined radius or diameter, this indicates that the wheel must be replaced. If the wheel is not replaced at this time, the performance and safety of the train can be adversely effected.

In theory, measuring the diameter or radius of a wheel that is mounted on a train may be accomplished by using a tape measure, ruler or even a calliper measuring device. However, because the train wheels usually form part of a bogie, gaining access to the radius and hence, the diameter of a train wheel in order to make an accurate measurement can prove difficult. Thus, in order to accurately measure the diameter or radius of a train wheel, it is usually necessary to remove the bogie from the train and then remove the wheel from the bogie in order to gain access to the diameter of the wheel. This process is time consuming and costly.

It is therefore an object of the present invention to provide a device that enables the diameter or radius of a train wheel to be accurately measured without removing the wheel from the train. SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a device for measuring the curvature of an arc to determine the diameter or radius of an object with the curvature, the device comprising: a support structure for supporting the device on the arc or for enabling the device to be positioned relative to the arc; a first sensor that produces an output that is dependent upon the curvature of the arc; a controller for controlling the device and processing the output of the sensor to provide an output indicative of the radius or diameter of the object.

Preferably, the support structure comprises two sets of protrusions spaced apart from each other. The support structure need not contact the arc and instead of protrusions, two additional sensors may be employed. These additional sensors produce outputs representative of the distance to which the device is held spaced from the arc. This output together with the curvature dependent output of the first sensor allow an indication of diameter to be determined.

Preferably, the sensor is centrally located between the two sets of protrusions. Preferably, the sensor is either a light or a sound sensor but more preferably an infra red sensor is employed.

The protrusions can have spherical points that contact the arc, wherein the points are parallel to each other.

Preferably, the infra red sensor comprises: an infra red transmitter/receiver which provides an output indicative of the distance which separates the sensor from the curved surface for which the radius/diameter is being determined. Whilst the particular infra red transmitter/receiver used in the device of the invention is not critical, it is preferred that the transmitter/receiver be device GP2D120 manufactured and sold by the Sharp company. This device is able to detect distances from 4 to 30cm.

The controller can comprise: a microprocessor; an analogue to digital converter connected to the microprocessor and the infra red sensor; an input power detection circuit for determining the input power supplied to the device, wherein the input power detection circuit is connected to the microprocessor; a display connected to the microprocessor; a keypad connected to the microprocessor; and a data port connected to the microprocessor.

The device can calculate the dimensions of a circle whose perimeter includes the arc and then store or transmit data as required.

A bluetooth wireless transmitter capability may be provided to allow outputs to be transmitted to remote locations.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described with reference to the drawings in which: Figure 1 is a perspective view of a diameter measurement instrument according to an embodiment of the present invention; Figure 2 is a simplified schematic diagram of the circuit used in the diameter measurement instrument of Figure 1; Figure 3 is a detailed schematic diagram of the circuit illustrated in Figure 2; and Figure 4 is a diagram useful in understanding the triangulation technique employed by the sensor to determine distance.

DETAILED DESCRIPTION

The general structure of the preferred embodiment of the diameter measurement instrument 1 is illustrated in Figure 1. The diameter measurement instrument 1 has a body 2 that is substantially enclosed- and substantially rectangular in shape. The body 2 includes an elongate side 2B and a front face 2A.

Integrally formed on the side 2B are protrusions 3 and 3 A. The points 3 and 3 A are positioned transverse relative to the longer side of side 2B.

Located centrally between the protrusions 3, is a sensor 4 with an emitter 4 A and receiver 4B. The sensor is an infra red sensor.

Located in the front face 2A of body 2 is an LCD 5 and an alphanumeric keypad 6 A.

Figure 2 illustrates a simplified schematic diagram of a circuit 19 contained within body 2 of the diameter measurement instrument 1 illustrated in Figure 1. The circuit 19 comprises an infra red sensor 4. The operation of the sensor 4 is described below. An electrical output of the sensor 4 is input into a first channel ChO of a 12 bit analogue to digital converter (ADC) 13. The digital output of ADC 13 corresponding to input channel ChO is input to a microprocessor 11. The microprocessor 11 is also connected to an LCD 5 and keypad 6 A. The circuit 19 is powered by a power supply circuit 18 whose input power level is monitored by an input power detection circuit 14. The input power detection circuit 14 is also connected to microprocessor 11.

A detailed schematic diagram of the preferred embodiment of the circuit 19 shown in Figure 2 is illustrated in Figure 3. From this diagram, it can be seen that ADC 13 is preferably an LCT1298 IC, microprocessor 11 is preferably a BS2 microprocessor, input power detection circuit 14 preferably utilises a LM358 IC and power supply circuit 18 uses a 7805 voltage regulator IC. The connections between each component in the circuit 19 are clearly shown in Figure 3. A keyboard encoder 7 is connected between the microprocessor 11 and the keyboard 6A.

The basic operation of the diameter measuring apparatus 1 will now be explained. Firstly, the device 1 is placed on the perimeter of the train wheel (not shown) so that the points 3 and 3 A contact the surface of the wheel perimeter. In order to achieve an accurate measurement, it is necessary for the points 3 and 3 A to be substantially parallel with the axis of rotation of the wheel. A bluetooth expansion port 20 is shown coupled to microprocessor 11.

The sensor 4 operates as shown in Figure 4. Infra red radiation transmitted or emitted by emitter 4A is directed towards the wheel whose diameter is being measured and radiation is reflected to the receiver 4B and the sensor provides an electrical output indicative of the distance between the emitter and the wheel whose diameter is being determined.

The ADC 13 continuously samples the output voltage of the sensor 4 and converts each sample into a 12 bit digital word which is output to the microprocessor 11. Each time the microprocessor 11 receives a digital word from the ADC 13, the microprocessor 11 calculates the diameter of the wheel using the following formula: D = 2R = H + C 4H

Where: D = the diameter of the wheel; R = the radius of the wheel; C = the length of the chord defined by an imaginary line connecting edges 3A; and H = the distance between the emitter and the surface of the wheel. After calculating the value of the diameter of the wheel, the microcontroller 11 then outputs the calculated value to the LCD 5 for display to the user. Thus, by simply placing the device 1 across a portion of the perimeter of the wheel and looking at the LCD 5, the user is able to quickly and accurately measure the diameter of the wheel without having to remove the wheel from the train.

From the above description, it can be appreciated that once the device is removed, the measured value will no longer be displayed on the LCD 5 as the sensor 4 will no longer be able to direct radiation from the emitter to the receiver. A hold button 6 on a keypad 6A on the front face 2A of the device 1 enables the user to maintain the display of the measured wheel diameter or radius on the LCD 5 when the device 1 is removed from the perimeter of the wheel. This is achieved if the user presses the hold button 6 of the keypad 6 A when the points 3 and 3 A of the device 1 are still in contact with the surface of the wheel. In order to revert to the normal mode of operation, the hold button 6 is pressed again.

A metric/imperial button 7 of the keypad 6A is also connected to an input of the microcontroller 11. Pressing this button enables the user to convert the value displayed on the LCD 5 between metric and imperial units.

A calibrate button 8 of the keypad 6A is connected to an input of the microprocessor 11. This enables the user to calibrate the device 1.

A diameter/radius button 9 of the keypad enables the user to convert the displayed diameter value to a corresponding radius value and vice versa. .

A sweep button 10 of the keypad is also provided. When this button is pressed once, the device 1 enters a sweep mode, the sweep mode enables the user to accurately measure the diameter (or radius) of the wheel without the need to precisely position the device on the perimeter of the wheel.

In the sweep mode the user merely places the device 1 on the perimeter of the wheel in the usual manner. However, the points 3 and 3A can be at an angle relative to the axis of rotation of the wheel. The user then rotates the device 1 about an axis extending through the emitter and receiver.

As the device 1 is rotated, it measures variations in the distance detected between the emitter and the wheel. It can be appreciated that if the device 1 is initially positioned such that points 3 and 3 A are angled relative to the axis of rotation of the wheel, and the device 1 is rotated so that the angle decreases below zero, the distance detected by the sensor will increase from a minimum to a maximum then return to a minimum. It follows that the measured diameter corresponding to the minimum distance will be an accurate measurement of the wheel diameter.

In the sweep mode, the device maintains the display of the calculated diameter (or radius) that corresponds to the minimum distance determined by the sensor.

The sensor 4 is a infra red sensor, the sensor has an emitter which generates a infra red output that is directed onto the surface of the object whose diameter is being measured. A portion of the infra red that is incident on the surface is reflected off the surface towards a receiver the sensor 4. The sensor 4 detects the reflected infra red and is able to determine the distance from the sensor 4 to the reflecting surface by comparing certain characteristics of the transmitted infra red with corresponding characteristics of the received infra red.

The foregoing describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

The device may determine internal and external diameters.

For example, the protrusions 3 may terminate into an edge or any number of spherical points instead of a pair of points 3 and 3 A. Also, the sensor does not necessarily have to be central to the protrusions 3. The device may include more than one sensor between the protrusions.

It is to be understood that the term "comprising" as used herein is to be understood in the inclusive sense "having" or "including" and not in the exclusive sense of "consisting essentially of 7

Claims

CLAIMS:

1. A device for measuring the curvature of an arc to determine the diameter or radius of an object with the curvature, the device comprising: a support structure for supporting the device on the arc or for enabling the device to be positioned relative to the arc; a first sensor that produces an output that is dependent upon the curvature of the arc; a controller for controlling the device and processing the output of the sensor to provide an output indicative of the radius or diameter of the object.

2. The device of claim 1 having two additional sensors each spaced from the first sensor, with the additional sensors producing outputs representative of the distance to which the device is held spaced from the object having the curvature from which said outputs the controller provides the radius or diameter indicative output.

3. The device of claim 2 wherein the additional sensors are located on opposite sides of the first sensor.

4. The device of claim 3 wherein the sensors are either sound or electromagnetic radiation sensors which direct sound or radiation towards the object and receive reflections of sound or radiation to provide the respective outputs.

5. The device of claim 1 wherein the support structure includes two protrusions spaced on opposite sides of the first sensor.

6. The device of claim 5 wherein the protrusions have spherical points that contact the object at spaced locations along the curvature of an arc along the object.

7. The device of claim 6 wherein the spherical points of the protrusions are parallel to one another.

8. The device of any one of claims 5 to 7 wherein the first sensor comprises an infrared transmitter/receiver which provides an output indicative of the distance which separates the sensor from the object.

9. The device of any one of claims 5 to 8 wherein the controller comprises a microprocessor, an analogue to digital converter (A to D converter) connected to the microprocessor, an input power detection circuit and a display connected to the microprocessor.

10. The device of claim 9 including a keypad with input buttons connected to the microprocessor for controlling the microprocessor.

11. The device of claim 9 wherein the microprocessor calculates the diameter of the object using a formula D = H + C² 4H where: D = the diameter of the object; C = the distance between the points of contact between the protrusions; and H = the distance between the sensor and the object.

12. The device of claim 11 including a control button for causing the microprocessor to selectively provide either a radius or diameter indicative output for the display.

13. The device of any one of claims 9 to 12 including a sweep control button operative to allow the microprocessor to enter a sweep mode where a user may move the device relative to an axis through the object to cause the microprocessor to provide an output which varies between a minimum and a maximum and back to the minimum whereby the diameter or radius of the object corresponds to a displayed minimum.