GB2253700A - Apparatus to measure the profile of a surface - Google Patents

Abstract

An apparatus 2 to measure the profile of a surface, for example the re-surfaced area of a hole in a road comprises parallel rails 4, 6 each of circular cross-section and mounted on a tripod arrangement 8, 10. A manually propelled carriage 12 has rollers running along the tops and undersides of the rails. The carriage carries a vertically movable surface follower comprising a rod 58 having a wheel 60 to run on the surface being measured. Variation in the surface profile causes the wheel and rod 58 to move up and down. This is observed by electro-optical sensor means. Further electro-optical means on the carriage produce a trigger signal each time it passes a marking 72 on the rail 6. The occurence of each trigger signal causes a record to be made of the height of the surface follower. <IMAGE>

Description

APPARATUS TO MEASURE THE PROFILE OF A SURFACE This invention relates to apparatus to measure the profile of a surface.

When a hole is dug in the ground, for example a hole in the road for access to gas or water mains or to sewers or to electricity cables or to the telephone system, it is often necessary, particularly if the hole is in the road, to fill it and resurface it (i.e.

to reinstate the ground) so that the new surface is substantially level with the original surrounding surface. If the reinstated surface is at a significantly different level, the reinstatment may not comply with legal requirements, also it can be a danger to traffic or at least cause shock and discomfort to those travelling over the reinstatement in vehicles.

One object of the invention is to provide apparatus which can be constructed to observe and record profile measurements of a surface of the ground, for example a road surface.

According to the invention there is provided an apparatus to measure a profile of a surface, said apparatus comprising rail means mountable over said surface, carriage means to run on said rail means, a surface follower to contact said surface, said follower being movable to and fro relative to said carriage means by interaction between the surface and the follower, and electronic measuring means to observe said to and fro movement of the follower to provide height measurements relative to a datum point of portions of said surface contacted in succession by said follower as the carriage means travels along said rail means.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a perspective view of an apparatus formed according to the invention to measure the profile of a road surface, for example a reinstated road surface after a hole therein has been refilled and resurfaced; Fig. 2 shows a fragment of the apparatus in Fig. 1 to illustrate the surface follower and the carriage means; Fig. 3 is a fragmentary end view of the carriage means in Fig. 1; Fig. 4 is an end elevation of the surface traveller in Fig. 1; Fig. 5 is an elevation of a side plate of the carriage means in Fig. 3; Fig. 6 is a plan view of the carriage means in Fig. 3 with parts omitted; Fig. 7 is a fragmentary elevation of the carriage means in Fig. 1;; Fig. 8 is an end view of the carriage means in Fig. 7, and Figs. 9 to 13 show electrical circuits which may be used.

With reference to Fig. 1 of the accompanying drawings an apparatus 2 to measure the profile of reinstated road surface comprises two substantially parallel stiff rails 4 and 6 of circular cross-section mounted at one set of ends or two legs 8 and at the other set of ends on one leg 10 so that if the tripod 8,10 is on level ground, the rails 4,6 are horizontal.

The rails may be of steel or aluminium.

A carriage 12 runs on the rails.

Now continuing with reference to Figs. 1 to 8, the carriage 12 comprises a pair of spaced, vertical side plates 14 and 16 spaced by and secured to a bottom strut 18 and top strut plate 20 bearing a top surface plate 22.

Within the carriages are eight grooved rollers each having a groove profile corresponding with the curvature of the rails 4,6. Four of these rollers are shown in Fig. 3 at 24,26,28 and 30. The rollers 24 and 26 are freely rotatable on the same top shaft 32 bearing spacer sleeves 34, ends of the shaft being disposed in holes in the side plate 14,16, for example hole 36 in plate 14. Both the rollers 24,26 run on top of the rails. Directly below each roller 24 or 26 is the respective roller 28 or 30 freely mounted on bottom shaft 38 carrying spacers 34 and having its ends in oval or vertically elongated holes in the side plate 14,16 for example the elongated hole 40 in plate 14. The shafts 32 and 38 carry bushes or collars 42 and 44 pulled towards one another resiliently by an helical spring 46 so that the rollers 28 and 30 clamp against the underside of the rails 4,6.The other four rollers are similarly arranged at the other end of the carriage on respective top and bottom shafts having ends which in the plate 14 are disposed in round hole 48 and elongated hole or slot 50. Thus the carriage can under manual propulsion run along the rails 4,6, being maintained thereon by the roller grooves and the clamping action between upper and lower rollers.

A carrying plate 52 is mounted by an arrangement of spacer bolts 54 over the plate 14.

Plate 52 mounts two vertically spaced brackets 56 guiding a vertically movable composite rod 58 mounting a wheel 60 at its lower end. The wheel and rod 60,58 constitute a surface follower and spring or other resilient means may be employed to act to urge the rod 58 downwards to keep the wheel in contact with the ground. Alternatively, the weight of the surface follower may keep it in contact with the ground. The rod 58 has rack teeth between a pair of side cheeks.

A pinion 62 meshing with the rack teeth has side faces between the cheeks to act as a guide to ensure the plane of the wheel remains substantially parallel with the rails 4,6.

A combined bracket and housing 66 masks the pinion and provides support for one end of a shaft 64 (Fig. 3) to which the pinion 62 is keyed to rotate with the shaft 64.

The shaft 64 drives a rotary part 68 of a rotary encoder means also comprising counting or observing means 70 from which a signal, for example an electrical signal, is output representing how high the wheel 60, in contact with the ground, is above or below a reference datum or zero position. In other words the encoder 68,70 is part of measuring means observing and measuring the height of the wheel with reference to the datum. The rotary encoder 68,70 or an electronic measuring and recording system on the carriage may be triggered to make a height measurement or record it each time a trigger signal occurs. A trigger signal may be generated in accordance with the position of the carriage along the rails. In this case dark markings 72 are provided on the rail 6 each marking a predetermined distance, for example one centimetre, from the next.The carriage 12 carries a horizontal position sensor for example an optical sensor 74 on support bracket 76 on the strut 18. The sensor 74 observes a marking 72 each time it passes one and thus initiates a trigger signal so that a measurement is made or recorded of the position of the vertical position sensor, namely the height of the surface follower 58,60 above the datum.

The measurements are recorded and stored and may be identified as relating to a particular hole reinstatement by allocating an identifying name or number to the hole concerned.

A desirable feature of the apparatus is that it be made as light as possible so it can be easily carried and be compact enough to fit in the boot of a normal car.

Factors which influenced the design of the apparatus, further indication of the construction and further description of its use are set out hereinbelow.

Electronics Element Horizontal Position Sensor (72,74) By choosing various solutions to the electronics problems we were in a way setting an outline of what to work towards. Manual measurement of the Horizontal position was to inaccurate and the physical means would cause too much friction between track and carriage. Magnetic and Optical methods were both deemed possible but optical was chosen as it was cheaper than purchasing many magnets. We did opt for operator intervention in the process of resetting the device. This was asthe gains derived from an automatic system were lengthening manufacturing time.

The vertical position sensor was also based indirectly on an optical method so this should allow for some simplication of circuitry due to duplication of a simple base circuit, i.e. the optical sensor decoder.

Storing the measurements may be done with a simple non-intelligent digital system.

Vertical Position Senor (58,60,62,64,68,70) (height of road above or below datum) Somehow the rotary pulse generator idea had to be developed into a form suitable for use in a measuring rig. The mounting problem has already been solved as part of the mechanical section. The task is to interface it with the follower so that the vertical movement can be converted into a pulsed signal for input into the data-logging system.

The way in which the encoder works is to count pulses as a strobed wheel rotates. The vertical motion of the follower is turned into rotary motion via the mechanical process described above. At an early stage we saw that this problem was very similar to that of sensing the horizontal position of the carriage along the rails so the possibility of adapting the same circuit used in this earlier application was very good.

We connected the optical encoder to the circuit that we had built on the protoboard earlier for testing the horizontal position sensor to see whether it would be possible to use it for this similar part of the project. This worked successfully so we decided to extend the tests to cope with the full operation of the optical shaft encoder. As the encoder can rotate in both directions two sensors are provided so that as well as finding out how far the shaft 64 had turned the direction of rotation could also be ascertained.

This would be imporant so that we could tell whether the follower 58,60 was moving up or down. To simplify the circuitry and to save on time and expense as well as ease of manufacture we chose to use a single integrated circuit, the (LM324N) instead of three separate operation amplifiers.

The Interpretation Circuit The two outputs from the optical rotary encoder circuit 68,70 have to be manipulated so as to turn them into a form manageable by the our chosen storage medium. To do this a simple two-stage circuit has been devised. These stages are as follows:1. Decode pulses from optical encoder 68,70 into two signals, a clean pulse to be counted and a direction flag.

2. A counter to count the decoded pulses from the above system with regard to their direction.

To generate a clean pulse from the two produced by the rotary shaft encoder 68,70 is quite easy. If a pulse arrives from either input it is to be redirected to a pulse counter. Direction on the other hand is more difficult. Fortunately for us the rotary encoder has a special property that allows its direction of rotation to be determined. The two signals that it generates are slightly out of phase with each other. A simple circuit to recognise this and give a pulse accordingly can be formed out of a couple of "flip-flops". It is called a "Rat-Race Arbiter".

The Storage Circuit The storage system may be based around a Z8671 microprocessor. This device has input/output ports, a built-in ROM with a BASIC interpreter, debugger and monitor, and a standard RS-232 serial interface port.

Like any microprocessor the Z8671 needs to be provided with external memory, a clock pulse and some way of connecting its input/output facilities to the outside world. This has to be supplied by its support circuitry or "glue-chips" - a name derived from the way in which a collection of small integrated circuits seems to "glue" the whole microprocessor system together.

Sources of input signals Vertical Movement Detector (58,60,62,62,68,70) Detection of vertical movement is performed by a rotary encoder 68,70. This device gives out electronic pulses on being rotated, the number of pulses being proportional to the distance through which it moves. It is also possible to determine the direction.

Horizontal Movement Detector (72,74) This is used to give signals to instruct the recording circuitry when to record the data. It gives a signal for every centimetre of horizontal travel.

The decoding and recording curcuits Step counter This is used to keep track of the operation in progress and, when that process is complete, prompt the user to perform the next task to be done. For example, when the recording system is turned on the step counter registers one. This prompts the user to perform task one; to enter the number of the hole to be measured. The step counter simultaneously connects the memory inputs to the encoded keypad output, therefore allowing the storage of the hole number.

When the entry of the hole number is complete the user signals this by pressing the ENTER key. The step counter, now on step two, then prompts the user to move the scanner to the start of its travel and to set the zero level, by pressing the ZERO key. The step counter at this stage also stores a code in the memory to indicate the end of hole number data and the beginning of reinstatement dimensions.

When the entry of the hole number is complete the user signals this by pressing the ENTER key. The step counter, now on step two, then prompts the user to move the scanner to the start of its travel and to set the zero level, by pressing the ZERO key. The step counter at this stage also stores a code in the memory to indicate the end of hole number data and the beginning of reinstatement dimensions.

Pressing the ZERO buttom increments the step counter, to step 3, and prompts the user to begin scanning the reinstatement. It also connects the memory input to the counting/decoding circuits, to allow the storage of reinstatement dimensions. When 100 data entries have been made, or the user signals the end of reinstatement measurement, by pressing the NEXT HOLE key, the step counter is again incremented.

On reaching four the step counter stores a code in memory to signal the end of data for that hole. It then resets the system including the step counter, to allow the storage of the dimensions for the next hole.

The key pad and decoder unit The key pad is used to input numerical data to allow the identificiation of a reinstatement by a hole number. The decoder simply converts the keypress into a number, for storage in the memory.

Electronics The selected electronic circuitry allows the following:i) recording of the height of a reinstatement, above or below a definable zero, every lcm across it.

ii) the display, via an LCD display, of the distance, in millimetres, which the vertical sensor is above or below the defined zero during measurement.

iii) the entry of a hole number or address.

iv) the facility at any time to abandon or restart measurement.

v) the downloading of this information to a microprocessor, for example a BBC micro.

vi) the storage data for many holes before downloading is necessary.

The Fig. 9 block diagram shows the general outline of the electronics.

The counting/decoding circuits This unit performs several functions: i) determining the direction in which the vertical direction sensor 68,70 is moving.

ii) decoding the pulses received into millimetres iii) keeping track of the distance which the vertical sensor is above or below the defined zero iv) decoding this information and displaying it via an LCD display v) giving a suitable output to allow the storage in memory of the distance above or below the defined zero.

The meory unit The memory is used to store both the hole number and data for that reinstatement. To give the address at which to store the next byte of data a simple counter is used. This is incremented with each byte of data entered and therefore data is stored in consecutive addresses.

To allow the computer, to which the data is downloaded, to distinguish between the key pad and reinstatement dimension data and also consecutive sets of data, certain codes are stored after each set of data is input.

The unit also multiplexes the data inputs, i.e. it connects them to the data outputs of the unit which at that time needs to store information.

In a modification the carriage 12 may be driven along the rails by motor means, for example a stepper motor.

The individual circuit loads may be stored in a specially designed rack, similar to those used on some computers, so if a fault develops it is simple to rectify and the whole circuitry will not need changing.

The optical sensor 74 may have a small brush-type collar attached to it for two reasons. Firstly, it would protect the sensor from dust and so prolong its life and make it more reliable and secondly, help to clean the graduated markings that the sensor needs so improving the reliability of the device.

An automatic reset system may be incorporated into the system so that when the carriage is returned to the starting position for a pass over a reinstatement the device will start taking measurements as soon as the carriage is moved.

The storage circuity may be upgraded to enable it to do more things, for example, automatic dating of information, an indication of memory left or battery level display, or any other functions deemed necessary or desirable.

Claims (17)

1. An apparatus to measure a profile of a surface, said apparatus comprising rail means mountable over said surface, carriage means to run on said rail means, a surface follower to contact said surface, said follower being movable to and fro relative to said carriage means by interaction between the surface and the follower, and electronic measuring means to observe said to and fro movement of the follower to provide height measurements relative to a datum point of portions of said surface contacted in succession by said follower as the carriage means travels along said rail means.

2. An apparatus as claimed in Claim 1, in which said follower moves to and from substantially rectalinearly along an axis.

3. An apparatus as claimed in Claim 1 or Claim 2, in which resilient means acts to keep the surface follower in contact with said surface.

4. An apparatus as claimed in any preceding claim in which the surface follow comprises rolling means to contact the ground.

5. An apparatus as claimed in Claim 4 in which the rolling means is a wheel.

6. An apparatus as claimed in any one preceding claim, in which said electronic measuring means comprises a rotary encoder, and means is provided to convert linear motion of the follower into rotary motion for driving said encoder.

7. An apparatus as claimed in Claim 6, in which the encoder is an electro-optical arrangement.

8. An apparatus as claimed in any one preceding claim, in which an arrangmeent is provided whereby a trigger signal occurs at intervals as the carriage means moves along the rails, and the electronic measuring means is responsive to said trigger signals to provide a said height measurement and/or record a said height measurement in response to the occurence of each trigger signal.

9. An apparatus as claimed in Claim 8, in which means to produce said trigger signals comprises spaced markings on a said rail and electro-optical means on the carriage means to observe passing said markings in turn as the carriage means travels along the rail and initiates a said trigger signal each time the passing of a marking is observed.

10. An apparatus as claimed in any one preceding claim including storage means wherein a record of the height measurments is automatically stored.

11. An apparatus as claimed in Claim 10, in which said record includes an identification to identify to which particular surface a set of height measurements relates.

12. An apparatus as claimed in any one preceding claim, in which the carriage means is driven along the rail means by motor means.

13. An apparatus as claimed in any one preceding claim, in which said rail means comprises at least one rail having a curved cross-sectional shape transversely to the longitude axis of the rail.

14. An apparatus as claimed in Claim 13, in which the carriage means is mounted on rollers running on said rail means and at least one roller has a grooved circumference which fits against said curved cross-section shape of said rail.

15. An apparatus as claimed in any one preceding claim, in which the carriage means is mounted on rollers running on a top side of said rail means, and below said rollers is at least one further roller acted on by urging means to clamp said further roller against an underside of said rail means.

16. An apparatus as claimed in any one preceding claim, in which said rail means is mounted on a tripod.

17. An apparatus to measure the profile of a surface, said apparatus being substantially as hereinbefore described with reference to the accompanying drawings.