GB2324871A

GB2324871A - Lateral stability indicator

Info

Publication number: GB2324871A
Application number: GB9802699A
Authority: GB
Inventors: Nicholas James Handy; Kevin Anthony Doyle
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-04-30
Filing date: 1998-02-10
Publication date: 1998-11-04
Anticipated expiration: 2018-02-10
Also published as: GB9708803D0; GB2324871B; GB9802699D0

Abstract

A system that continually indicates the lateral (side to side), not longitudinal (for and aft) stability of a rough terrain materials hander or similar agricultural/industrial vehicle. The system can recognise the change in the position of the centre of gravity as the boom geometry and boom loadings alter. The degree of lateral stability of the materials handler is continually displayed on an audio visual display unit which is mounted in the vehicle's cab. This display unit has LED's which progresses from green, through amber to red. When the vehicle reaches it lateral safe working limit (a sensible percentage of the total maximum) the red LED's illuminate and the alarm sounds. The materials handler can always be used to its maximum lateral angle as the system can detect the shift in the position of the centre of gravity of the materials handler.

Description

LATERAL STABILITY INDICATOR This invention relates to a lateral stability indicator.

Rough terrain materials handlers (as in drawing number one) are well known vehicles, common place for moving loads, for instance, in the agricultural and construction industries.

Referring to drawing number one, as the load (A) on the forks, the extension (x) and the working angle (e) all increase, there is a danger that the materials handler will overturn forwards, i.e., the rear axle leaves the ground, the load (A) moves closer to the ground and the front axle is the centre of rotation. In this instance the materials handler has become unstable in the longitudinal plane, i.e., not longitudinally stable. The majority of materials handlers manufacturers fit devices to warn the operator in due time before a longitudinal overturn takes place.

Referring to drawing number two, it is also possible for the materials handler to overturn laterally when it is operated on a lateral incline. At the point when a materials handler overturns laterally, the line of action of the centre of gravity (COG) passes through the centre line of the wheel about which the overturn is rotating. Figures available from safety statistics suggest that between 15 - 20% of machinery related deaths are caused by machinery overturning.

The centre of gravity of a materials handler can change. It can become higher or lower in relation to the (referring to drawing number one) magnitude of the load (A) being carried, the extension (x) of the telescopic boom or the working angle () of the boom or a combination of any of the three. The higher the centre of gravity (referring to drawing number two) the smaller the lateral working angle (0), i.e., the materials handler becomes more unstable. Similarly, the lower the centre of gravity, the greater the lateral working angle (0), i.e., the materials handler is more stable. Research has shown that typical minimum and maximum values for the lateral angle are 10 and 36 respectively, i.e., a difference of around 72% between the two states.

Therefore a lateral stability indicator can warn the operator before a lateral overturn occurs.

However, if the system warned the driver that a lateral overturn was going to occur at 100 and the centre of gravity was at its lowest state the machine could not be operated to it fuil 36 potential - wasting 260 of range. Similarly, if the system alerted the driver that a lateral overturn was going to occur at 360 and the centre of gravity was at its highest state the machine would capsize at 10 - with potentially lethal consequences.

Therefore the lateral stability indicator as described in this specification has suitable intelligence to take into account the respective position (referring to drawing number two) of the centre of gravity in relation to the respective lateral angle (0), before it warns the driver of a potential lateral overturn. Allowing the machine to be operated with its full safe potential.

The system consists of (referring to drawing number three) a display unit which is mounted in the cab of the materials handler. This display unit has a range of light emitting diodes going from green, through amber to red. The display unit also has a buzzer. The display unit is of a plastic box type construction and also houses the main components of the electronic circuitry.

The materials handler would have two strain gauge assemblies fitted along the axis of the front axle (as in drawing number three). These strain gauge assemblies would be incorporated inside, along the centre axis in the bolts which attach the front axle to the chassis of the materials handler. The rest of the circuitry is housed within the display unit.

When a materials handler is operated on no lateral incline (referring to drawing number two) the reaction forces on each of the front wheels, i.e., R1 and R2 are equal. However, as the materials handler is operated along a progressively greater lateral incline (as on drawing number two) the magnitude of force R1 will become proportionally greater than that of R2 as the lateral angle (8) increases. This is because of the shift in weight distribution as the centre of gravity revolves around the centre of rotation. At the point of overturning, i.e., when the higher wheel looses contact with the ground R2 will equate to zero.

The strain gauges incorporated within the front axle assembly are connected to the control box with suitable wiring. The system (referring to drawing number four) is powered by the materials handlers own electrical system, i.e., its battery - commonly 12 volt lead/acid. The main components in the circuit are as follows: (Numbering coincides with the labels on drawing number four).

1. Chokes to stabilise the voltage coming from the battery to smooth power surges from the materials handlers altemator.

2. Voltage regulators to keep voltage at the operating range. In this case 5 volts. These then pass the flow of current to the operational amplifiers and whetstone bridges.

3. Strain gauges mounted in whetstone bridge configuration including balance resistors to act as comparitors, i.e., detect change in resistance due to temperature as oppose to the change in resistance due to mechanical distortion of the gauges due to the weight of the materials handler transferring from Rl to R2 or vice versa. These are mounted with the front axle assembly as previously mentioned.

4. Operational amplifiers connected to the whetstone bridges. These operation amplifiers convert the change of resistance due to the mechanical distortion from the strain bridges into a voltage.

5. Operational amplifier which acts as a comparitor. It compares the voltage differential from the two previous operational amplifiers. The output voltage from this operational amplifier (5) is proportional to the stability of the materials handler.

The output goes to the bar graph driver chip (6).

6. Bar driver chip which illuminates the light emitting diodes incrementally according to the safeness of the current lateral angle, (i.e., the magnitude of the voltage from operational amplifier (5)). The LED's range from green (safe) through amber (warning) to red (danger). When the red section of the LED's are lit the buzzer (7) will sound to alert the operator of the danger.

7. Buzzer, operation as above.

Therefore the lateral stability indicator as described in this specification measures the weight distribution as the lateral angle increases. This weight distribution is not affected by the change in the position of the centre of gravity which occurs as the boom geometry and load changes as previously mentioned - only the lateral angle at which the distribution change takes place will change.

The circuitry would be calibrated so that when R1 is 1.75 times (or a similar safety margin) greater than R2 or vice versa the last red light emitting diode will illuminate and the buzzer would sound to indicate that the maximum safe working angle has been reached.

The system will continually monitor and display the materials handlers stability on the display unit.

Claims

CLAIMS.

1. A device that monitors the lateral stability of a materials handler which can detect the change of maximum allowable safe lateral working angle (and alert the operator) as the centre of gravity of the materials handler changes.

2. A device as in claim 1 that uses strain gauges to compare weight distribution at two positions along an axle or chassis member to assess lateral stability.

3. A device as in claim 2 that uses a comparitor circuit connected to strain gauges to asses the lateral stability of the materials handler via the weight distribution

4. A device as in claim 3 that continually displays the safeness of the lateral angle by converting the voltage from the comparitor circuit to a audio visual display on the progressive audio visual light emitting diode unit.

5. A device as in claim 4 that is an integral part of the vehicle.