Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
INCLINATION AND INERTIA INDICATING APPARATUS
Document Type and Number:
WIPO Patent Application WO/1989/010623
Kind Code:
A1
Abstract:
An apparatus for detecting inclination and/or inertial/centrifugal forces and for generating a signal when such criteria exceed a pre-determined level. The apparatus comprises a box in which is housed a pivotal conductive element which triggers an alarm when the box is tilted. The apparatus has particular application for use on motor vehicles.

Inventors:
Wersin
Heinz
Erich
Application Number:
PCT/AU1989/000169
Publication Date:
November 02, 1989
Filing Date:
April 19, 1989
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
Wersin
Heinz
Erich
International Classes:
G01C9/06; G01C9/12; H01H35/14; (IPC1-7): H01H35/02; H01H35/14; G01C9/06; G01C9/12; G01P15/135; H01H35/10
Foreign References:
FR808724A1937-02-13
DE3618808A11987-12-10
GB2032182A1980-04-30
US3835273A1974-09-10
DE3022452A11981-01-15
DE1287675B
DE3638360A11988-05-19
US3161739A1964-12-15
US4320384A1982-03-16
US3144528A1964-08-11
Download PDF:
Claims:
THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:
1. An apparatus for detecting inclination and/or inertial/centrifugal forces and for generating a signal when such criteria exceed a predetermined level, said apparatus comprising a housing in which a conductive element is pivoted for relative displacement with respect thereto, and detection means consisting of electrical contact means with associated circuitry for cooperating with said conductive element when said predetermined level is reached, wherein the axis of displacement of the conductive element is located sufficiently distant from the centre of inertia of the conductive element such that the conductive element is displaced relative to the housing in response to both inclination of the housing and the conductive element and to inertial/centrifugal forces on the conductive element.
2. An apparatus as claimed in Claim 1, wherein the housing is a closed vessel.
3. 2 An apparatus as claimed in Claim 2, wherein the vessel includes an external expansion chamber in fluid communication therewith.
4. An apparatus as claimed in Claim 3, wherein the expansion chamber is in direct fluid communication with the atmosphere.
5. An apparatus as claimed in any one of Claims 2 4, wherein the vessel is filled with a damping fluid.
6. An apparatus as claimed in Claim 5, .wherein the damping fluid is a dielectric transformer oil.
7. An apparatus as claimed in any one of the preceding claims, wherein the conductive element is a rectangular plate which is folded into a substantially flattened Vshaped configuration.
8. An apparatus as claimed in Claim 7, wherein the plate comprises a metal substrate coated with silver.
9. An apparatus as claimed in Claim 7 or Claim 8, wherein the conductive element is supported by a conductive wire which passes under the apex of the "V" section so that said conductive element may swing freely with respect thereto.
10. An apparatus as claimed in any one of the preceding claims, wherein the electrical contact means comprises an elongate member which extends preferably through a top wall of the housing and has a finely honed point for making electrical contact with the conductive element.
11. An apparatus as claimed in Claim 10, wherein the elongate electrical contact means is cast in situ into the top wall of the housing with an epoxy resin, or is retained in position by an Oring and an Oring adjustment nut to permit continuous adjustment thereof.
12. An apparatus as claimed in any one of the preceding claims wherein the associated circuitry acts to power an audible or visible alarm when the conductive element makes contact with the electrical contact means.
13. An apparatus for detecting inclination and/or inertial/centrifugal forces and for generating a signal when such inclination and/or inertial forces exceed a pre determined level, substantially as herein described with reference to the drawings.
Description:
INCLINATION AND INERTIA INDICATING APPARATUS THIS INVENTION relates to apparatus for detecting inclination and/or inertial/centrifugal changes in regions of variance from travel in a straight line, which apparatus is adapted to generate a signal when pre-determined levels of such criteria are reached. The invention is particularly concerned with apparatus for use in vehicles for indicating safe cornering speeds and safe side slopes, and will therefore be primarily described in this context. It will nevertheless be readily appreciated by the skilled addressee that the invention has much broader application than this and that the following is merely for the purpose of ease of description and ready understanding of the invention.

Land vehicles have limits on their safe operation with respect to the slope of the terrain which they are to traverse, as is the case for tractors, military vehicles, off-road recreational four-wheel drive vehicles and the like; and also on their cornering speed limits, as is particularly the case for road vehicles such as trucks, semi-trailers and buses.

Seagoing vessels of all types have similar limits of safe operation with respect, for instance, to acceptable roll angle, and aircraft have limits to safe turn rates, related to the acceptable maximum structural load rating of the airfra e.

Inclinometers have been used in the past to

indicate visually to the operator of such vehicles the angle

.made with, the horizon of the chosen plane through the vehicle. Such inclinometers have generally conformed to one of three types. These types are mechanical inclinometers,

5 bubble inclinometers and gyroscopic inclinometers.

Mechanical inclinometers generally comprise a beam balanced on a pivot, the pivot being fixed to the frame of the vehicle to be referenced. The beam, when the vehicle is level, is in equilibrium and indicates horizontal, usually on

I ' LJ. a« fixed visual scale via a pointer or other indicating means.

As the vehicle inclines, the beam tends to maintain its orientation relative to the force of gravity, resulting in the angle of inclination being indicated by the pointer on the scale. Such apparatus does not, however, indicate

15 inertial/centrifugal changes in the vehicle such as those imported by high cornering or turning forces. Generally speaking such inclinometers have in the past been limited to indicating inclination in two dimensions and cannot be used for a remote sensing operation.

ZG- Bubble type inclinometers generally consist of a curved, closed ended, fluid filled, tube containing a bubble of gas. The concave side of the tube is oriented towards the earth with the radius of curvature of the tube at its highest point being parallel to the earth's gravitational force

25 vector. The plane within which the tube is orientated in the vehicle is transverse the expected axis of rotation of the

vehicle in inclination. The bubble type inclinometer works on the principle that the bubble of gas will always travel to the highest point in the tube. As the vehicle and hence tube inclines, the high point of the tube changes, causing the bubble to travel along the tube to the new high point. The tube is generally transparent such that the position of the bubble can be referenced to a scale behind the tube. Again, this type of inclinometer generally is constrained to measure inclination in two dimensions and cannot measure inertial/centrif gal changes in the vehicle and cannot be used for a remote sensing operation.

Gyroscopes consist of a rapidly rotating motor gimballed to isolate the rotor from movements of the vehicle to be referenced. The high inertia of the spinning rotor enables use of the physical laws relating to changes in inertia to maintain its orientation relative to an external reference frame. Although usually used as a compass referenced against a magnetic or true compass point, the principle of the gyroscope has been used to indicate, for example, an artificial horizon and the orientation of a vehicle relative to that horizon. The gyroscope substantially maintains its orientation in response to both inclination and normally encountered external inertial/centrifugal changes and is thus not particularly suited to indicate cornering and turning forces as much as it is for indicating changes of direction. Gyroscopes are also

complex apparatus requiring recalibration with each use.

Instrumentation for assessing the forces acting on a> vehicle includes load sensing devices, acσelerometers and the like. Examples of present accelerometers are aircraft rate of turn indicators and pressure transducers provided between reactive components of land vehicles. Generally such instrumentation cannot be used to indicate inclination to a horizon.

There are basically six separate factors which - influence the lateral-stability of a land vehicle of constant track width, whether at rest, in rectilinear or curvilinear motion. These factors are:

1. The relative inclination between the vehicle body and the ground surface, 5 2. The relative inclination between the ground surface and the horizontal plane,

3. The magnitude of the sprung mass concentrated at the centre of inertia of the vehicle,

4. The height of the vehicle's centre of inertia G from the ground surface,

5. The horizontal radius of curvature of the track along which the vehicle is proceeding, and

6. The velocity of the vehicle during cornering. All these factors change constantly and in order to safely operate the vehicle, they have to be correctly estimated by the operator.

For a vehicle with constant mass and a fixed location of its centre of inertia, whether at rest or in linear-motion, where variables 1 or 2 above are changed, a simple inclinometer would detect the change in inclination. 5 For the same vehicle in curvilinear-motion, where variables 5 or 6 above are changed, an accelerometer would detect the inertial/centrifugal forces acting on its centre of inertia.

It is therefore an object of the present invention to provide an apparatus which senses both inclination and 10' inertial/centrifugal limits and is of simple construction.

That is, the aim is to provide an appartus which will add the Gravitational-Force effect to the Centrifugal- Force effect, and detect when the "combined maximum level" to which it has been previously calibrated, has been reached. 15 Accordingly, there is provided an apparatus for detecting inclination and/or inertial/centrifugal forces and for generating a signal when such criteria exceed a pre¬ determined level, said apparatus comprising a housing in which a conductive element is pivoted for relative 20 displacement with respect thereto, and detection means consisting of electrical contact means, with associated circuitry for co-operating with said conductive element when said pre-determined level is reached, wherein the axis of displacement of the conductive element is located 2.5 sufficiently distant from the centre of inertia of the conductive element such that the conductive element is

displaced relative to the housing in response to both inclination of the housing and the conductive element and to inertial/centrifugal forces on the conductive element.

The housing of the detection apparatus of the present invention can be any suitable container, frame or the like which is capable of retaining the conductive element and associated electrical detection means in the required configuration. The housing is generally stationary in the reference frame of the vehicle in which the inclination and/or inertial/centrifugal force are to be detected.

Preferably, the housing is a closed, vessel which is designed to isolate the conductive element from extraneous and undesirable influences such as wind, dust and other foreign bodies. In a particularly preferred form, the housing is filled with a damping fluid to eliminate gross transitory displacements of the body due to vibration which would cause false indications, and to act as a lubricant. Additionally, the damping fluid should preferably act as a micro-spark arrestor and should therefore have dielectric properties. A preferred damping fluid is a dielectric transformer oil.

The housing may form a rigid, sealed chamber for the damping fluid. However, in circumstances where expansion of the damping fluid is a problem, advantage may be had in providing an external expansion chamber or the like. The expansion chamber may take the form of a chamber in fluid

communication with the housing such that the expansion of damping fluid in the housing causes fluid to enter the expansion chamber. The expansion chamber may be provided with a gas space sealed from the atmosphere, which is compressed in response to the expansion of the damping fluid. Alternatively, the sealed expansion chamber may contain no gas space but may be isobaric with the atmosphere by means of, for example a flexible diaphragm or the like which can distend in response to expansion of the damping fluid. A third possibility may be an expansion chamber in direct fluid communication with the atmosphere via, for example a breather hole. Such an expansion chamber is provided with sufficient space above the normal damping fluid level to permit expansion of the fluid without loss of fluid through the breather hole. However, in certain situations where the damping fluid exhibits significant cohesion- with the walls of the expansion chamber, a capillary tube may need to be connected to the breather hole to ensure that no seepage occurs . The provision of an expansion chamber as described above may avoid potential accuracy problems caused by distortion of the housing. An expansion chamber also avoids internal pressure build-up leading to fluid leakage. In certain embodiments the expansion chamber may also provide a "bubble trap" to collect any bubbles which may form in the fluid or are trapped in the housing when it is being charged

with the fluid.

The conductive element can take any form consistent with the requirements dictated by its function. For example, the conductive element can be any shape or density which permits it to be displaced within the housing in response to either or both of inclination of the housing and subjection the body to inertial/centrifugal forces. Thus, the conductive element may be in the form of a plate, disc, rod or like member having greater length and/or breadth than thickness, the greater length providing a more positive response to changes in inclination on the principle of a simple lever. Preferably, the conductive element is a rectangular plate which is folded about a mid-point short axis to form a substantially flattened "V-shape" configuration-. The actual angle between the "V" is an important consideration and it is related to the tilt of the vehicle to which the apparatus is fixed; as will become apparent in the following description. Generally, the angle will be arranged to allow a relative pivoting between a normal horizontal level position and an inclination in the order of 10 to 30°. Thus, for most road tankers, the calibrated worst condition may be about 20° while for a fully loaded cane truck it may be about 13°. The plate may be fabricated entirely from a conductive metal or it may be a laminate structure with a metal coating. Most preferably it comprises a base metal such as Cu which is coated with a

highly conductive metal such as silver.

In an alternative preferred construction, the conductive element is a plane rectangular plate, pivotally supported at one end and weighted at the other end. The plate is fabricated from the same range of materials as the

"V-shaped" plate described above.

The conductive element is supported within the housing by any means ensuring that the centre of inertia of the conductive element is located sufficiently distant from the axis of displacement of the conductive element to achieve the desired result. The type of support used may include a spring strip or pivotal inter-connection between the housing and the conductive element, both providing the necessary separation between the centre of inertia and the axis of displacement. In one embodiment of the present invention, a pivoted link is provided between the conductive element and housing. Alternatively, the pivotal inter-connection between the housing and the conductive element may comprise a shaft from which the conductive element is suspended, or needles or pivotal edge upon which the conductive element may pivotally rest. When the conductive element is a rectangular plate folded into a substantially flattened V-shaped configuration, it is preferably supported adjacent a top wall of the housing by a conductive wire which passes under the apex of the "V" section so that the conductive element may swing freely. The conductive wire is preferably bent into a base-flattened "U"

configuration such that the ends of the wire extend out through the top wall of the housing on each side of the conductive element.

More than .one conductive element may be provided, 5- for example, to indicate different limiting values for the inclination and/or inertial centrifugal force. Each of the conductive elements may be provided with its own means for support within the housing, or, in the case of shaft-mounted bodies for example, may be supported on common means for QJ support.

Additional conductive elements may serve to indicate appropriate limits for different load conditions. For example, one conductive element may be calibrated to indicate safe limits in a loaded-vehicle situation, whilst 5 another may be calibrated to indicate the safe limits on the vehicle when unloaded. Although there is metal to metal contact between shaft and conductive element, wear of the pivot will generally be reduced by selecting a damping fluid with lubricant properties. U The detection means of the present invention may be αf any type consistent with the aim of detecting relative movement between the housing and the conductive element. Preferably the detection means comprises means for measuring the relative movement without significantly influencing the 5 relative movement which is to be measured. Accordingly the detection means is an electrical or magnetelectrical sensing

arrangement which actuates external indication means such as an audible alarm and/or warning light. The detection means may continuously monitor changes in the orientation of the conductive element relative to the housing or may only indicate preset limits to the displacement of the conductive element within the housing.

It is particularly preferred to use a simple stop or stops as the electrical contact means, contact between the conductive element and the stop either making or breaking an electrical circuit. Where this type of detection means is used, it is advantageous to select a damping fluid of high dielectric strength. Preferably, the material used for the stops is chosen to minimize both contact resistance and wear. The stops may ideally be fabricated from stainless steel. The contact point of each of the stops will preferably be honed to a fine point to ensure good contact with the conductive body. For highly accurate detection, such honing may be essential.

The stops are preferably adjustable such that the inclination and/or inertial/centrifugal limits of the apparatus may be set. The stops may be adjustable by altering the positions of the contact point thereof relative to the housing. Preferably, each stop comprises a member which extends through the upper wall of the housing and is adjustable by movement of the member into and out of the housing. The stop members may be moved into and out of the

housing in adjustment by means of being screw threaded thereto or otherwise. The stop members may be sealed at their point of entry to the housing by any suitable means including O-rings or the like. Alternatively, the point of entry may be sealed by a resinous material different to that of the housing such as cured liquid epoxy resin ferrule cast at the entry point.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 is a plan view of a detection apparatus in accordance with the present invention;

Figure 2 is a vertical cross-section of the apparatus depicted in Figure 1 through the line A-A; Figure 3 is a vertical cross-section of the apparatus depicted in Figure 1, through the line B-B;

Figure 4A is a detail through an alternative terminal post according to the present invention;

Figure 4B is a detail through a terminal post of the apparatus of Figure 1;

Figure 5 is a circuit diagram for a condition- responsive circuit suitable for use with the apparatus illustrated at Figure 1;

Figure 6 is a schematic drawing illustrating the mode of action of apparatus in accordance with the present invention under the influence of inclination of the

apparatus;

Figure 7 is a schematic representation illustrating the mode of action of the apparatus in accordance with the present invention under the influence of inertial/centrifugal changes;

Figure 8 is a plan view of a further detection apparatus in accordance with the present invention;

Figure 9 is a vertical cross-section of the apparatus depicted in Figure 8 through the line C-C; and Figure 10 is a side-on view of the apparatus depicted in Figure 8 with part of the side wall removed.

Referring firstly to Figures 1 - 4B, the apparatus comprises a housing 10 consisting of a receptacle 11 with a lid closure 12. A high dielectric damping fluid 13 such as a transformer oil is contained within the housing and extends into a fluid expansion chamber 14 which is in fluid communication with the interior of the housing. The fluid expansion chamber includes a vent hole 17, and is tapered at its lower end 18 so that any gaseous bubbles in the housing may be collected and directed to the vent hole. The housing is fabricated from an insulating thermoplastic material and the lid and receptacle components are sealed together by ultrasonic welding.

Two conductive elements 15aι, 15b are supported for free pivotal movement within the housing. The conductive elements comprise rectangular silver-coated copper strips

which have been bent about their mid-axial regions into substantially flattened V-shaped configuration. The conductive elements 15a_, 15b are supported on a conductive wire 16 which extends under the apex of the conductive 5" elements in a substantially "square-wave" pattern as can be readily seen in Figure 3. The wire may be a silver-plated copper thread to ensure good electrical contact with the conductive elements.

It will be observed in Figures 2 and 3 that the

10 conductive elements are supported a very short distance from the lid closure 12 so as to ensure that the conductive elements- are freely pivotal in the directions indicated by the said arrows in Figure 2.

Insulated housing extensions 19 are provided on lid

15 closure 12. These have threadedly mounted therein stainless ε eei terminal posts 20 penetrating the upper housing 1. Stainless: steel is the material of choice for its resistance to mechanical and arc erosion. In order to prevent loss of the high dielectric fluid 13 past the terminal posts 11, cast

20' in situ sealing rings 21 may be formed by pouring a liquid epαx-y resin into a depression 22 formed in the top of the housing- extension 10, (see Figure 4B) . Alternatively, in order to provide for continuous adjustment for the terminal posts 20, the posts may be retained in position and sealed by

25. an O-ring 20a_ and an O-ring adjustment nut 20b_ which is screw threaded to the housing extension (see Figure 4A) ,

The terminal posts 20 are maintained at a common electrical potential by the action of conducting springs 23. Each of the terminal posts has at its inner extremity a contact point 24 positioned in use to provide electrical contact with the electrical conductive elements 15a_, 15b, when the elements move by a preselected distance in response to inertial/centrifugal changes or inclination. The position of the contact points 24 relative to the lid closure 12 is adjustable by way of adjusting slots 25 to enable adjustment and/or calibration of the apparatus.

The receptacle 11 is mounted to a mounting plate or vehicle by way of holes 27 through which fixing screws (not illustrated) pass. Isolation mounts may be interposed to isolate the apparatus from vibration. In use, the apparatus functions in the following manner.

At rest, the electrical conductive elements 15a_, 15b are in an equilibrium position relative to the gravitational force vector 42a (see Figure 6) . If the housing assembly is level, then the electrical conductive elements 15a, 15b and the contact points 24 will be separated. As the apparatus is inclined, the electrical conductive elements 15a, 15b maintain their equilibrium position relative to gravity and rotate about the electrical conductive pivot wire 16. At a point predetermined by the adjustment of the contact points 24, the contact points 24

will make electrical contact with the electrical conductive elements 15 _, 15b, thus closing any circuit made between the terminal posts 26 and the electrical conductive pivot wire 16. 5 A suitable circuit for use with the apparatus according to the preferred embodiment is illustrated in Figure 5. The closed circuit condition caused by contact between the contact points 24 and the conductive elements 15a, 15b is used as the input signal for an operational

Id amplifier 30 which in turn fires a power transistor 31. With suitable time constants induced by arrangements of resistors and capacitors, dampening of erratic signalling may be improved. The operating current through the apparatus can be minimized by incorporating a series resistor to prevent

15 pitting of the conductive elements 15a., 15b and arc erosion of the contact points 24.

The output of the power transistor 31 can be used to drive, for example, a warning light 32 or audible alarm 33 or may be used to trigger an automatic brake or ignition σut-

20 out.

In response to the inertial/centrifugal changes caused by the action of, for example, the centrifugal force experienced by vehicles in turns or bends, the centrifugal force vector 45 (see Figure 7) is countered by the frictional

25 force of the tyres 46 against the road surface 47, until the resolved component of the centrifugal force vector 45 acting

on the centre of gravity of the vehicle and about the roll axis 48 is sufficient to overcome the gravitational force vector 42 acting on the centre of gravity of the vehicle and about the roll axis 48. At this point, the vehicle will roll over.

To provide warning of this impending event, the electrical conductive elements 15a, 15b are isolated from the frictional force of the tyres and are subject only to the centrifugal force vector 45a. However, the conductive wire pivot 16 is constrained by the frictional force of the tyres via the vehicle and therefore the action of the centrifugal force vector 45 causes the electrical conductive elements 15a, 15b to rotate about the conductive wire pivot to make contact at a predetermined displacement with the contact points as before.

Referring now to the alternative embodiment depicted in Figures 8 - 10, the apparatus comprises a sealed thermoplastic housing 50 containing a high dielectric transformer oil. A fluid expansion chamber 51 is in fluid communication with the housing by means of passageway 52 and includes a vent hole 53 to the atmosphere.

Two conductive elements 54, 55 are supported at their upper ends for pivotal or flexural movement within the housing in the directions indicated by the solid arrows in Figure 9. The conductive elements comprise rectangular thin spring steel strips which are weighted at their free ends 56,

56a with layers of similar or different conductive material which is coated with silver. The elements are connected into an electrical circuit of the type previously described.

Insulated housing extensions 57, 58, 59, 60 provide support for stainless steel terminal posts 61, 62, 63, 64 which are cast in situ with epoxy resin 65 and are connected to a common electrical potential in the aforementioned circuit.

The apparatus is mounted and operated in a similar manner to the previously described embodiment. The main difference here, however, is that the weighted ends of the conductive elements trip the alarm system when they pivot by a pre-set amount and contact the pointed ends of the stainless steel terminal posts. In conclusion, the apparatus of the present invention is such as to add the Gravitational-Force effect to the Inertial-Force effect, and detect when the COMBINED MAXIMUM LIMIT to which it has been previously calibrated has been reached. At any given instant, the resultant-force angle from the vector-forces acting on the apparatus is absolutely identical (parallel) to the resultant-force angle from the vector-forces acting on the vehicle to which it has been installed, whether the vehicle is at rest, in motion, or tilted at any angle.

The above mentioned lateral resultant-forces sensed

by the apparatus, are not influenced by longitudinal Accelerating or De-accelerating forces which may be developed by vehicle acceleration, braking or pitching.

The apparatus of the invention is a highly sensitive device, to the order of 0.5 deg. of arc on a static tilt test of a vehicle. For example, if installed in a vehicle, the 0.5 degree angular accuracy will be equivalent to a change in curvilinear velocity from 40 km/h to 41 km/h in a 60m curve radius, which represents approximately a change of 0.01 lateral g-force.

Therefore the apparatus, when located preferably at any vertical location from the C.G. of a vehicle, will be affected (in the same proportion) by ALL lateral vector forces acting on the C.G. ignoring longitudinal vectors and will detect accurately when previously calibrated limits are reached.

The apparatus is particularly suitable for use in high speed - high centre of gravity vehicles such as high C.G. bulk transport semi-trailers, single or two storey buses and road tankers. The advantages in such vehicles include:

1. Once installed in a vehicle and having undergone Static Calibration on a tilting platform for maximum load mass and highest C.G. including adequate Safety Factor, the apparatus will quickly and accurately detect the stability limits of that vehicle on ANY road curve, whether horizontal or inclined, regardless of its radius or velocity of the

vehicle whilst cornering.

2. By paying attention to the WARNING signals (lights and/or sound) emitted, "guess work" by the driver is eliminated during cornering. 3. By thus eliminating driver "guess-work", fatigue on high speed curved roads can be reduced.

4. By assisting any driver (specially the inexperienced) to develop a "feeling for his vehicle", without having to undergo dangerous "on road testing" for lateral- stability limits.

5-. Following the installation of the apparatus in a double storey coach, an increased sense of security may be felt by the passengers, with the knowledge that "guess-work" by the driver is reduced. 6. The WARNING sounds can be of assistance for drivers, who suffering under the influence of driving fatigue, tend to loose concentration and could over-estimate the side-stability limits of their vehicle.

7. By recording in a Data Logger, fleet computer or digital counter the number of extremely dangerous situations in a given time, the apparatus can be used to monitor drivers who transport people or hazardous products.

8. The apparatus could correct the tendency for drivers of articulated vehicles, to over-estimate their stability limits at low-speed turns as in roundabouts .

The apparatus of the invention may also be

adaptable for use in off-road vehicles such as road building machinery, agricultural tractors and similar equipment and 4 x 4 vehicles (both private and military). In such adaptables, the apparatus is useful for warning against roll- over or dangerous slopes at rest or in motion.

Whilst the above has been given by way of illustrative example, many modifications and variations may be made thereto without departing from the broad scope and ambit of the invention as herein set forth in the following claims.