GB2108672A

GB2108672A - Vehicle body repair detector

Info

Publication number: GB2108672A
Application number: GB08131365A
Authority: GB
Inventors: Michael John Taylor
Original assignee: Armstrong Patents Co Ltd
Current assignee: Armstrong Patents Co Ltd
Priority date: 1981-10-17
Filing date: 1981-10-17
Publication date: 1983-05-18

Abstract

A vehicle body repair detector comprises a Hall effect sensor (18) and a magnet (25) mounted behind the sensor so that when the sensor (18) is applied to a vehicle body the magnetic flux of magnet (25) passes through said sensor into the ferrous material of the vehicle body. In order to give a useful visual display, the sensor is arranged to provide three output levels corresponding respectively to the sensor being applied to a region of a vehicle body where (i) the ferrous material of the body is separated from the sensor only by the thickness of the normal paint layers (i.e. an undamaged region), (ii) the ferrous material of the body is separated from the sensor by a relatively thin layer of non-ferrous filler and paint layers (i.e. a shallow dent has been repaired), and (iii) ferrous material is completely absent (i.e. a hole has been repaired) or is widely separated from the body surface (i.e. a deep dent has been repaired). The three signal levels are used to control a pair of red and green lamps e.g. LED's (24), (26) such that in condition (i) the green lamp is fully ON and the red lamp is OFF, in condition (ii) both the red and green lamps are ON and in condition (iii) the red lamp is fully ON and the green lamp is OFF. <IMAGE>

Description

SPECIFICATION Vehicle body repair detector The present invention is concerned with a device for detecting the presence of repairs in vehicle bodies made of pressed steel plate.

Most vehicles are manufactured using pressed steel panels which are covered by a number of protective coatings, e.g. paint or under seal. These layers, which are of course non-ferrous, vary in thickness, but this thickness is usually less than 1 millimeter. When such a panel is damaged by corrosion or by an accident, one of two conditions usually results. Either the panel has a hole right through it or it has a dent wherein the original panel material remains but is deformed inwardly to form a recess in the original panel configuration. Obviously, in any particular case, a combination of dents and/or holes might be incurred.

The conventional way of mending a hole in a metal panel is to fill the hole with a mass of resin filler and glass-fibre mat or with a suitable solder.

In either event the hole is filled with an essentially non-ferrous substance. Similarly, in the case of dents, the recess if filled with a non-ferrous substance -- again usually resin filler or a solder.

The non-ferrous filler is rubbed down so as to be flush with the original panel configuration and covered with paint layers until the presence of the damaged area is completely hidden.

Clearly, there are many circumstances when it is desirable to be able to establish the fact that such repairs have been made to an apparently "perfect" vehicle body, for example when purchasing a second-hand vehicle whose history is unknown.

The traditional method for detecting such repairs is to run a magnet over the vehicle body by hand and to "feel" for areas where the magnetic attraction of the magnet to the vehicle body is reduced or absent. The problems with such a test are that (1) running the magnet over the vehicle body could itself cause scratching of the paintwork; and (2) it is a subjective test relying on the "feel" of the tester to properly identify the regions where the magnetic attraction has altered.

Thus, although it may be easy enough to identify regions where a hole has been filled (due to the complete absence of any magnetic attraction), it is difficult to correctly identify a filled dent and almost impossible if the dent is very shallow.

It is an object of the present invention to provide a device for detecting repaired regions in vehicle bodies in which the problems of the known technique are mitigated.

In accordance with the present invention there is provided a vehicle body repair detector comprising a Hall effect sensor and a magnet mounted behind the sensor so that when the sensor is applied to a vehicle body the magnetic flux of the magnet passes through said sensor into the ferrous material of the vehicle body, the sensor being arranged to provide at least three output levels corresponding respectively to the sensor being applied to a region of a vehicle body where (i) the ferrous material of the body is separated from the sensor only by the thickness of the normal paint layers (i.e. an undamaged region), (ii) the ferrous material of the body is separated from the sensor by a relatively thin layer of non-ferrous filler and paint layers (i.e. a shallow dent has been repaired), and (iii) ferrous material is completely absent (i.e. a hole has been repaired) or is widely separated from the body surface (i.e. a deep dent has been repaired).

Preferably, the three signal levels are used to control a pair of lamps (e.g. red and green) such that in condition (i) one lamp (green) is fully ON and the other lamp (red) is fully OFF, in condition (ii) both lamps (red and green) are ON, and in condition (iii) the other lamp (red) is fully ON and the one lamp (green) is fully OFF. This thus provides an objective visual indication of the nature of the surface region to which the sensor has been applied.

The lamps could be provided at a location remote from the sensor but, preferably, are mounted in a common holder with the sensor and a power supply therefor. Conveniently, the holder should be small enough to be hand-held and arranged to be operable in several planes. Such a configuration could be that of a writing pen housing, the sensor being located at one end of the housing so that in use the housing is applied to the vehicle body panel under test so as to extend perpendicularly thereto. The housing can have a conventional clip, as in a fountain pen, for clipping the housing to, for example, the lip of a jacket or trouser pocket.

The sensor output can also be used to control the tone of an audio signal so that, in addition to the visual signal supplied by the coloured lamps, the user is given an audio indication of the conditions (i), (ii) and (iii). Alternatively, any form of visual display could be used, i.e. an analogue meter or barograph display, The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic illustration of a car body in various states of repair; and Fig. 2 is a simplified circuit diagram of one embodiment of a repair detector in accordance with this invention.

Fig. 1 is a section through a steel panelled vehicle body, the steel part being indicated by the reference numeral 10 and the covering paint layers by the numeral 12. In the region X, the body panel is in its original, unrepaired state and the steel plate is covered by a thin paint layer 1 2. In the region Y, the body panel has a hole whereby steel is completely absent and the paint layer 1 2 covers only a layer 14 of non-ferrous filler (i.e. a resin filler or a solder). In the region Z, the body panel has a dent of varying depth, i.e. the ferrous material 10 is still present but is covered by a layer 1 6 of non-ferrous filler of non-constant thickness beneath the paint layer 1 2.

In Fig. 1 , the arrowhead A indicates the detector positioned over the undamaged region X, the arrowhead B indicates the detector positioned over a repaired hole Y, the arrowhead C indicates the detector positioned over a shallow filled region of the dent Z and the arrowhead D indicates the detector positioned over a deep filled region of the dent Z.

The detector of Fig. 2 comprises a Hall effect sensor 1 8 connected between a stabilized d.c.

power supply (in this case +3 volts). Mounted closely adjacent to the sensor is a small permanent magnet 25. The output of the sensor on line 20 is connected to the base of an NPN transistor Tr1 by way of a resistor R1. The emitter of the transistor is connected to the Ov line and its collector is connected to the +3v line 22 by way of a red LED 24. The output line 20 is also coupled to the +3v line 22 by way of a green LED 26.

The detector operates as follows.

When the detector is brought into the position of arrowhead A (Fig. 1), the output of the Hall sensor 18 is arranged to be at or near Ov so that the green LED 26 is effectively placed across a supply of 3v and it is turned fully ON. The transistor Tr, is OFF so that the red LED 24 is also OFF. the presence of the green lamp alone indicates that the detector is over a sound region which has not been filled.

When the detector is brought into the position of arrowhead B, the output of the Hall sensor 18 is arranged to be at or near +3 volts so that the green LED 26 is fully OFF. The transistor is, however, turned ON via the resistor R1 and the red LED 24 is therefore also fully ON. This same situation is also arranged to prevail when the detector is brought into the position of arrowhead D when the metal 10 is so far from the detector as to be undetectable by the sensor. Thus, the presence of the red lamp alone indicates that the detector is over a filled hole or over a relatively deep filled dent.

When the detector is brought into the position of the arrowhead C, the output of the Hall sensor 18 is arranged to lie at a level intermediate the supply voltage (e.g. 1.5 volts) in which condition the green LED is still ON and the transistorTr1 is receiving the sufficient base current to still be ON whereby the red LED is also still ON. Thus, the presence of the red and green lamps together indicates that the detector is over a filled dent but in a region where the dent is only relatively shallow, with sound metal beneath it.

The aforegoing device has the advantage that it provides an objective visual indication of the composition of the material to which it is applied.

Since the magnetic attraction between the permanent magnet of the detector and the steel of the vehicle body is at all times of very low magnitude and the detector is itself very light, the detector can be run over the vehicle body without fear of damage to the paint surface.

The Hall effect sensor 1 8 used in the aforngoinc device can be of the linear output type i.e. which provides an output signal which varies linearly with the magnetic flux density through it. It has been found, however, that cheaper Hall sensors not normally regarded as providing a "linear" output can be operated so as to provide an output which is sufficiently linear for the present purposes.

Claims

1. A vehicle body repair detector comprising a Hall effect sensor and a magnet mounted behind the sensor so that when the sensor is applied to a vehicle body the magnetic flux of the magnet passes through said sensor into the ferrous material of the vehicle body, the sensor being arranged to provide at least three output levels corresponding respectively to the sensor being applied to a region of a vehicle body where (i) the ferrous material of the body is separated from the sensor only by the thickness of the normal paint layers (i.e. an undamaged region), (ii) the ferrous material of the body is separated from the sensor by a relatively thin layer of non-ferrous filler and paint layers (i.e. a shallow dent has been repaired), and (iii) ferrous material is completely absent (i.e.

a hole has been repaired) or is widely separated from the body surface (i.e. a deep dent has been repaired).

2. A detector as claimed in claim 1 wherein the three signal levels are used to control a pair of lamps (e.g. red and green) such that in condition (i) one lamp (green) is fully ON and the other lamp (red) is fully OFF, in condition (ii) both lamps (red and green) are ON, and in condition (iii) the other lamp (red) is fully ON and the one lamp (green) is fully OFF.

3. A detector as claimed in claim 1 or 2, wherein the lamps are mounted in a common holder with the sensor and a power supply therefor.

4. A detector as claimed in claim 3, wherein the holder is adapted to be hand-held.

5. A detector as claimed in claim 4 wherein the holder has the configuration of a writing pen housing, the sensor being located at one end of the housing so that in use the housing is applied to the vehicle body panel under test so as to extend perpendicularly thereto.

6. A detector as claimed in claim 5, wherein the housing has a clip, as in a fountain pen, for clipping the housing to, for example, the lip of a jacket or trouser pocket.

7. A detector as claimed in claim 2 wherein the lamps are positioned at a location remote from the sensor.

8. A detector as claimed in any of claim 1 to 7 wherein the sensor provides an electrical output which is used to control the tone of an audio signal so that, in addition to the visual display, the user is given an audio indication of the conditions (i), (ii) and (iii).

9. A detector as claimed in any previous claim adapted to provide a visual display in an analogue or barographic form.

10. A vehicle body repair detector constructed substantially as hereinbefore described with reference to and as illustrated in Fig. 2 of the accompanying drawings.