WO1991000983A1

WO1991000983A1 - Safety tilt alarm

Info

Publication number: WO1991000983A1
Application number: PCT/AU1990/000301
Authority: WO
Inventors: Christopher Mark Baker
Original assignee: Christopher Mark Baker
Priority date: 1989-07-13
Filing date: 1990-07-12
Publication date: 1991-01-24
Also published as: NZ234491A

Abstract

A tilt sensing device (10) comprises an enclosure and an imbalanced disc (11) freely rotatable about a horizontal axis (13) within the enclosure. The disc has a circumference (18) with first and second pairs of maskings (30, 31, 40, 41). Each masking provides an irregularity in optical reflectivity. The first and second pair of masking are associated with first and second reflectivity sensors (14, 15) mounted adjacent the circumference of the disc. The sensors sense reflectivity of the circumference and transmit signals when an irregularity is sensed, to indicate a first or second degree of tilt. Magnets (20, 21) provide damping for vibration of the disc. The device is suited to rugged applications and off-road or field vehicles such as bulldozers, tractors or semi-trailers.

Description

SAFETY TILT ALARM TECHNICAL FIELD

The present invention relates to a vehicle safety tilt alarm which acts as an operator awareness indicator, that is, a warning device for vehicle operators using field vehicles such as bulldozers, farm tractors, four wheel drive, semi-trailers and other off-road recreational type vehicles, in rough, undulating or hilly terrain.

BACKGROUND ART

Previous means for warn-i-ng & vehicle operator of dangerous tilt angles of a vehicle have suffered from accuracy and durability problems. For example heavy earth moving vehicles such as bulldozers tend to vibrate severely. Accordingly, components of such vehicles are necessarily heavy duty and should not be affected by continuous vibration. Further, previous devices have been inaccurate when they are used in dynamic working conditions in that sudden although small changes in the tilt angle of the vehicle would cause the alarm to go off, even though the safe operating tilt angle of the vehicle had not been reached or exceeded. In such applications, the tilt alarm would preferably be activated to warn the operator that the vehicle is approaching its safe predetermined working angle, and later to warn that the critical working angle has been reached.

A reliable tilt alarm which is set to activate within an accuracy of approximately 0.5 to 1 degree of the predetermined safe working angle 1n the vehicles sideways tilting planes, would be desirable. Preferably such a device would not be effected by the continuous and often severe vibrations encountered in off-road vehicle operation. Preferably the alarm would continue only while the angle of tilt of the vehicle exceeded the predetermined value.

It is the object of the present invention to provide such a device.

DISCLOSURE OF INVENTION

In one broad form the present invention provides a tilt alarm device comprising: an enclosure; an imbalanced disc freely rotatably supported about a central axis within the enclosure; at least one sensor proximate to the disc, and adapted to sense an irregularity on the disc. Preferably, the disc is round whereby the circumferential edge surface is masked along predetermined portions. It is also preferred that the device have two optical sensors, the first adapted to sense a first masked portion corresponding to the limit of safe predetermined working angles of the vehicle from the horizontal, and the second adapted to sense a second masked portion of the disc corresponding to a critical working angle for the vehicle where toppling 1s imminent.

A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a schematic rear view of a vehicle to which the present device may be mounted.

Figure 2 is a schematic front elevation of the present device.

Figure 3 is a schematic perspective view of the device of Figure 2. BEST MODE AND OTHER MODES OF CARRYING OUT THE INVENTION

There is depicted in Figs. 2 and 3 tilt alarm device 10 comprising an aluminium disc 11 having an eccentric opening or recess 12 which provides an out of balance for a controlled pendulum motion around the central axis 13 relative to the circuit board 16. When the disc is upright, the recess 12 has the effect of maintaining less mass vertically above the axis 13 than below the axis 13, thus ensuring an equilibrium orientation of the disc 11 relative to the horizontal. For reference purposes, the device 10 will be discussed with respect to a reference horizontal position in which the disc 11 assumes a vertical orientation, that is, an axis passing through the center of mass of the disc and the central axis 13 of the disc is considered vertical.

The aluminium disc 11 1s attached to the circuit board 16 by means of a non-lubricated high precision stainless-steel or teflon coated ball bearing assembly 17.

The bearing/disc assembly is ridgedly mounted on a brass bushing 19, ensuring correct spacing of the disc 11 from the circuit board 16. The mounting also ensures that the disc 11 is precisely centred in relation to the sensors, preferably optical sensors 14, 15 situated on opposite sides of the disc 11. The bearing assembly 17 is preferably of high quality to ensure that the tilt angles of the board 16 from the horizontal can be measured 1n a wide range of temperatures (ie. from sub-zero to high temperatures) which may be encountered in all-weather vehicle operation.

The relatively small mass of the aluminum disc 11 ensures that the effects of vibration and movement of the vehicle which may tend to cause a spurious pendulum motion are negated. This ensures that false or premature activation of the warning device does not occur, and thereby overcomes the inherent difficulties of such other known inclinatlng measuring devices such as mercury solenoids, micro switches and spirit level-bubble type devices.

To further resist such unwanted pendulum motion of the aluminium disc, two rare earth magnets 20 and 21 may be securely mounted in a bracket assembly 22.

The bracket assembly is aligned in such a way as to fully utilise the rare earth magnet's inherent molecular sintered properties. These properties are evidenced by the reaction of this process, known as the "eddy wave" to the atomic structure of the aluminium comprising the disc itself.

These properties have been utilised to further provide a dampening effect to counteract possible excessive pendulum motion of the disc. The strength of dampening relates to the velocity of the disc motion caused by the side-to-side motion of the vehicle concerned. The clearance of the mounted magnets 20 and 21 from the surface of the disc 11 also determine the degree of resistance. The closer they are the greater the dampening effect. The position of the bracket, located above the disc, is noted on Fig. 3.

The application of the above rare earth magnets and their arrangement above the disc, further negate the prior art approach of using friction bearings and or greases etc (which have inherent problems in providing dampening) while maintaining sensitivity to angle changes of the vehicle. Such advantages are further evidenced when the problems of dust and temperature are considered in relation to alternative dampening methods. The disc 11, for example, has a diameter of approximately 80 mm and thickness of approximately 5 mm. The circumferential edge surface 18 bears one or more surface irregularities which allow the two optical sensors 14 and 15 to sense the reflective properties thereof.

In a preferred embodiment, an irregularity on the the disc's edge 18 is a non-reflective matt black surface or mask 30 which is applied to or chemically etched onto the surface at predetermined portions. This masking of the disc's 11 reflective edge surface 18 is predetermined to define tilt angle safety range of the vehicle. For example, and as illustrated 1n Fig. 1, a bulldozer 25 may have a safe operating range of ± 26° from the horizontal and may have a critical tilt angle of ± 30° from the horizontal (ie. an angle at which toppling of the vehicle is imminent). As shown in Fig. 2, the maskings 30, 31 on the edge surface 18 is positioned so that the first sensor 14 senses a tilt angle of the vehicle of ± 26° whereby the sensor is adapted to send a signal to an amber warning light 20 and persist until a safe angle is restored. Thus, the masking continues around the edge 18 so that if the vehicle exceeds ± 26° from the horizontal the light 20 remains lit. The second sensor 15 detects maskings 40, 41 on the opposite side of the disc 11 which are positioned to align with the sensor 15 when the vehicle reaches or exceeds ± 30° from the horizontal. That is, if the vehicle tilts 30° in either direction from the horizontal, the sensor 15 will sense a masking and send a signal to trigger a two-tone audible alarm 21. It has been found this arrangement has an accuracy of 1/2 to 1 degree when the vehicle 1s operational, that is with continuous vibration. It should be understood that once the principal of the imbalanced disc is employed to provide an equilibrium orientation or reference horizon, any number of sensing devices may be employed to sense an optical, mechanical, electrical or magnetic irregularity in, or on the surface of, the disc.

The discs are easily calibrated and marked at the point of manufacture, and therefore any angle can be selected depending on what type of vehicle the tilt alarm is to be fitted. The safe working title angle and critical tilt angle can be predetermined by calculating the centre of gravity, track etc of the vehicle 1. The alarm should remain on until the operator brings the vehicle 1 within the predetermined safe working angles. The marking on the disc 11, and the sensors are disposed about the horizontal axis so that regardless of which side the vehicle tilts, the amber warning light will be activated first, followed by the audible alarm. This is owing to the masking being provided in pairs e.g. 30, 31 and 40, 41 with each pair bisected by a sensor when the alarm 10 is in the reference horizontal position.

The invention further comprises the following optional features:

The alarm system may be momentarily activated, with both the warning light and buzzer operating when the ignition is switched on. This ensures that the operator is made aware that the tilt alarm is operational.

The device is housed in a sealed die-cast box 33 which contains the electronic circuit 24, the rotatable disc 11, and the audible alarm 21, thus protecting these components from sunlight, rain, heat or dust.

The box 23 is made electrically neutral so that reversing the polarity on connecting wires will not cause damage to the circuitry 24.

The electronics drive capability is rated at a factor of four, with further protection of an internal fuse 25.

Built in colour filters (not shown) in the optical sensors 14, 15 protect against accidental operation as a result of foreign light entering the die-cast box 23.

Disk is lightweight to avoid pendulum effect and 1s corrosion resistant.

The device 20 may be connected to a suitable power supply or alternatively have its own built-in power source.

The device 10 may be adapted to send a radio wave to an operator console to trigger an alarm situated on the consol .

The two-tone buzzer 21 can be heard by operator over engine noise and the wearing of earmuffs. The sound level omitted by the buzzer 21 from within the box 23 is approximately at 85-97db in accordance with some statutory requirements for equipment noise ratings.

The tilt alarm may be attached to a vehicle as described above, or alternatively it can be utilised wherever there is a need to reduce potential danger from a given situation where the tilt from the horizontal is important. For example, the device could be adapted to detect the inclination of a pile of coal or sugar, or the inclination of a sailing boat. INDUSTRIAL APPLICABILITY The device of the present invention is applicable to a wide variety of off-road or field vehicles. The invention provides a rugged, simple indicator which would be useful in any setting in which a tilt angle limit was sought, particularly with regard to human safety.

Claims

1. A tilt sensing device comprising: an enclosure; an imbalanced disc freely rotatable about a horizontal axis within the enclosure, the disc having an equilibrium orientation and at least one detectible irregularity in a first location; and a sensor mounted in the enclosure which can detect a first irregularity.

2. The device of claim 1, wherein: the disc is characterized by a circumference; the irregularity is an irregularity in the optical reflectivity of the circumference; the sensor is an optical reflectivity sensor mounted adjacent to the circumference.

3. The device of claim 2, wherein: two irregularities in the optical reflectivity of the disc's ci cumference are provided; and a second optical sensor is located adjacent to the circumference and diametrically opposite the first sensor with respect to the disc.

4. The device of either of claims 1, 2 or 3 wherein: at least one further irregularity is provided in the disc, each further Irregularity forming a pair with each said detectible Irregularity; each further irregularity being similar 1n kind to each aforementioned detectible irregularity; wherein each pair is angularly bisected by a sensor when the device is in a reference horizontal position.

5. The device of any of claims 1-3 wherein: the disc is metallic; and a dampening mechanism is provided, the dampening mechanism further comprising a bracket mounted adjacent to the disc, the bracket having one or more magnets mounted on it, the magnet or magnets adjacent to a face of the disc.

6. The device of claim 3, wherein: the first irregularity is angularly displaced with reference to the first sensor; and the second irregularity is angularly displaced with reference to the second sensor; whereby the angular displacements of the first and second irregularities are not equal, one of the irregularities indicating a first degree of tilt and the other irregularity indicating a second degree of tilt.

7. A tilt sensing device comprising: an enclosure; an imbalanced disc freely rotatable about a horizontal axis within the enclosure; the disc having a circumference on which is formed a first and second pair of maskings; each masking providing an irregularity in the optical reflectivity of the circumference; the first and second pairs being associated with first and second reflectivity sensors mounted with the enclosure and adjacent to the circumference; the sensors each angularly bisecting a pair of maskings when the device is in a reference horizontal position; the angles bisected by each sensor being unequal; whereby the first pair of maskings are indicative of a first degree of tilt and the second pair of maskings are indicative of a second degree of tilt; the first and second sensors adapted to sense the reflectivity of the circumference and transmit first and second signals when an irregularity is sensed.

8. The device of claim 7, wherein: the irregularities continue about the circumference so that the first and second signals persist, when either of said respective degrees of tilt are exceeded.

9. The tilt sensing device of claim 7 wherein the disc is metallic; and a dampening magnet is supported by a bracket adjacent a face of the disc.

10. The tilt sensing device of claim 7 wherein: the disc is aluminium.

11. The tilt sensing device of claim 7, wherein: the disc is aluminium and has formed therein a transverse opening which creates an imbalance of the disc.

12. The tile sensing device of claim 7, wherein: the enclosure is sealed with respect to light.

13. The tilt sensing device of claim 7, further comprising: a first alarm responsive to said first signal; and a second alarm responsive to said second signal.

14. The tilt sensing device of claim 13, wherein: the first alarm is visual; and the second alarm is audible.