GB2271189A - Axle load sensing arrangement - Google Patents

Abstract

An axle load sensing arrangement comprises an elongate member adapted to be mounted on the chassis of a road haulage vehicle or on an axle of the vehicle, a limit indicator provided on the elongate member, a sensor 13 mounted on the other of the chassis or the axle and signal means (not shown) to signal when the limit indicator on the elongate member is detected by the sensor means. The elongate member may be a guide rod 3 slidable in a sheath 7, the limit indicator the free end of the guide rod and the sensor means a proximity switch 13. Alternatively the elongate member may be a plastics channel piece (16, Fig 3) slidable in a sensor box (18, Fig 3) and the limit indicator a magnet (17, Fig 3). To aid calibration the guide rod may be adjustable on threads 5 and locked by nut 6, and the magnet may be adjustable in channel 16 and locked by a screw 19. The signal means may comprise an array of light emitting diodes or an audible signal device. An axle load sensing air bag (not shown) is also disclosed comprising an air pressure source eg an air suspension system, a pressure sensor and signal means. <IMAGE>

Description

AXLE LOAD SENSOR This invention relates to an axle load sensor, and more particularly to an axle load sensor for use in road haulage vehicles.

As a vehicle is loaded the height of the back of the vehicle over the wheels decreases. There are legallyapplied load limits placed on individual axles of road haulage vehicles which a driver may be fined for exceeding.

Although the overall load limit of the vehicle may not be exceeded, the load over a specific axle may be over the legal limit.

The present invention aims to provide means for checking the load over an axle and means for indicating to the driver of such a vehicle whether such a limit has been exceeded.

According to one aspect of the present invention there is provided an axle load sensor comprising an elongate member adapted to be mounted on the chassis of a road haulage vehicle or on an axle of the vehicle, a limit indicator provided on the elongate member, a sensor mounted on the vehicle and responsive to movement of the elongate member relative to the sensor and signal means connected to the sensor means, the arrangement being such that a signal is passed from the sensor to the signal means when the limit indicator on the elongate member is detected by the sensor means.

Preferably, the elongate member is a guide rod and the limit indicator comprises the free end of the guide rod.

Advantageously, the sensor means comprises a proximity switch which senses the presence of the free end of the guide rod within a detection zone and passes a signal to the signal means.

Alternatively, an axle load sensor according to claim 1 wherein, the elongate member is a C-shaped channel and the limit indicator comprises a magnet mounted vertically repositionable within the channel member, the sensor means comprises a proximity switch which senses the presence of the magnet within a detection zone and passes a signal to the signal means.

In a further alternative, an axle load sensor comprising an inflatable air bag adapted to be mounted on the chassis of a road haulage vehicle or on an axle of the vehicle, an air pressure source for increasing or decreasing the pressure in the air bag, a sensor mounted on the vehicle and responsive to a change in pressure within the air bag and signal means connected to the sensor means, the arrangement being such that a signal is passed from the sensor to the signal means when the sensor means detects a change in air pressure within the air bag.

Conveniently, the signal means comprises an array of light emitting diodes each of which indicate whether the permitted load over a specific axle has been exceeded.

Alternatively, the signal means may comprise an audible signal device which acts as a warning to a driver that the load over an axle has exceeded the permitted limit.

Embodiments of the present invention will now be described with reference to the accompanying Figures in which: FIGURE 1 shows a perspective view of an axle load sensor according to one aspect of the present invention; FIGURE 2 shows a part-sectional view of the axle load sensor of Figure 1, and FIGURE 3 shows a schematic view of an axle load sensor according to a further aspect of the present invention.

A mounting plate 1 is adapted to be mounted onto the underside of a road haulage vehicle. The plate 1 as shown is substantially square but may be of any suitable configuration. An aperture 2 is provided in the plate 1 at each corner to receive fixing means such as screws (not shown) for fixing the plate 1 to the underside of the vehicle.

A metal guide rod 3 in the form of an elongate member depends from the centre of the underside of the plate 1.

The guide rod 3 is attached to the plate by a rod holder 4 which has an internal screw thread. The guide rod 3 has an externally screw threaded portion 5 which co-operates with the screw thread of the guide rod holder 4. A locknut 6 is provided on the threaded portion of the guide rod 3 to lock the guide rod in a required position.

The guide rod 3 passes through the sheath 7 which is provided in a through bore of a support block 8. The support block is formed of a non-conductor for example plastics or nylon. The support block 8 is mounted on a steel pivot rod 9. One end of the pivot rod 9 is mounted to an axle clamping bracket 10 which is adapted to clamp the wheel axle of the vehicle (not shown). The clamp 10 is in the form of two formed members 11 having corresponding apertures 12 for receiving fixing means (not shown) which draw the clamping members 11 together around the wheel axle of the vehicle.

A proximity switch 13 is mounted in a bore 14 in the support block 8. The bore 14 extends through the support block 8 and communicates with the sheath 7. The proximity switch 13 is connected to an array of light emitting diodes (not shown) which are located in the cabin of the haulage vehicle and provide a visual display of the legality of the load on the vehicle.

In order to calibrate the load sensor it is attached to a vehicle axle and a known load, which should be just over the legal limit for the load on the axle is placed over the axle. The position of the guide rod 3 in the support block 8 is noted. The metal guide rod 3 is then marked by inserting a drill through a pre-drilled hole in the support block. The guide rod 3 is then cut to the desired length and the end of the rod is sealed to prevent tampering. The guide rod may be sealed using wax or any other suitable means.

Fine adjustment of the guide rod 3 is completed by turning the threaded portion of the guide rod in the rod holder 4. A drill is then placed into a pre-drilled hole in the rod holder 4 and the rod holder is drilled through. A wire 15 is placed through the hole and the ends of the wire are sealed for example by the application of a wax seal.

The proximity switch 13 is then mounted in the bore 14 through the support block 8.

The operation of the axle load sensor will now be described. The mounting plate 1 is fixed to the underside of a vehicle by appropriate means and the axle clamping bracket 10 is mounted onto a wheel axle of the vehicle. The free end of the guide rod 3 is then passed through the sheath 7 in the guide block 8.

The materials are then loaded onto the back of the vehicle and the weight is distributed over the axles. As an increasing weight is loaded over the axles, the back of the vehicle sinks and the guide rod 3 moves downward through the sheath of the support block 8. When the load over any of the axles of the vehicle passes the permitted limit, the presence of the metal guide rod is sensed by the proximity switch 13 and a signal is passed to the corresponding light emitting diode of the display means. The driver of the vehicle will be given an indication of which axle is overloaded.

The display means in the cabin of the vehicle will give an indication of the legality of the load over the wheel axles of the vehicle. The display means will continue to indicate that the legal limit has been exceeded until the load is re-distributed over the axles. As the load over the axle is decreased, the back of the vehicle rises, the guide rod 3 rises in the sheath of the support block 8 and passes out of the detection zone of the proximity switch 13 and the signal to the display means is cut thereby turning off the light emitting diode.

As an alternative to the elongate member (AEM) described above, a reinforced plastic member 16 in the form of a C-shaped channel is used incorporating a magnet 17 whose vertical position relative to the vehicle chassis can be adjusted. The sensor 18 to suit the alternative AEM comprises an enclosed box encapsulating two proximity switches (not shown) mounted against an internal duct (not shown) running through the centre of the sensor box. The two proximity switches may, for example, represent 90t and 105W of the legal limit. The AEM passes through the centre of the sensor box and is free running having gravitational connection with the vehicle axle. The serial box 18 is mounted on the axle by an appropriate mounting means such as brackets 20.In addition to the vertical calibrations the length of the magnet 17 can be altered thereby controlling the extent of the influence of the magnet over the proximity switches (not shown) located on the axle mounted sensor 18.

Figure 3 shows the revised elongate member showing the locations of the controlling magnet and the method of adjusting.

A known test load is applied to the vehicle chassis; the resultant movement of the chassis relative to the axle is calibrated by adjusting the vertical position of the magnet to energise the cabin mounted light emitting diodes (LEDS). The position of the magnet is adjusted by an adjusting and locking screw 19. The initial load applied to the chassis represents 90t of full legal axle limit and energises the appropriate LED. The test load is increased to represent 105t of legal axle limit, the magnet in the AEM is further calibrated to energise the LED warning the driver that the vehicle has a specific axle over the legal limit.

In a further embodiment of the present invention for use on vehicles with air suspension a flexible member such as an air bag is mounted between fixed member and the underside of the vehicle above an axle of the vehicle. The fixed member may be in the form of a plate-like flange mounted on a axle of the vehicle. A pressure sensor is linked to the air bag and monitors the pressure within the bag thereby giving an indication of the load placed over the axle. The sensor is connected to the array of light emitting diodes located in the cabin as described above, to give a visual indication of the legality of the load.

This embodiment may be calibrated, for example, by placing known loads on the vehicle, over the axles and monitoring the pressure in the bag at those loads.

In operation of the device, as a load is placed on the vehicle, the back of the vehicle sinks and the bag is compressed between the fixed member and the underside of the vehicle. The air suspension system increases the pressure in the air bag so maintaining the level of the chassis. The pressure sensor monitors the pressure in the air bag and if the load over the axle of the vehicle exceeds the calibrated permitted limit, the pressure sensor passes a signal to the corresponding light emitting diode of the display and the driver is given a visual indication of the overloaded axle.

Redistribution of the load causes the back of the vehicle to rise thus reducing the pressure in the bag and as the pressure in the bag falls below the permitted limit, the pressure sensor passes a signal to the light emitting diode in the display as before and the light emitting diode is switched off.

It can be appreciated that the present invention will be most useful for spot checks on haulage vehicles. At the present time, the police will escort a vehicle to a weigh bridge in order to check the load of the vehicle. With the axle load sensor a police officer will have an immediate indication of the load distribution over the axles and whether any particular axle load exceeds the permitted limit.

It can further be appreciated that a device may be fitted to the display to record the output of the display in a similar manner to a tachograph and thereby retain a record of the load over each axle during a journey.

It is to be understood that the visual display may be replaced by an audible signal which alerts the driver to the overloading of an axle of the vehicle. Furthermore, the guide rod may be provided with a fluorescent mark which will be detected by suitable means.

It is to be understood that a load sensor may be mounted to each axle of the vehicle. It may be advantageous to provide a sensor adjacent each wheel of the vehicle in order to eliminate over-loading across the vehicle.

Alternatively, a single sensor may be provided in the centre of each wheel axle of the vehicle.

Claims (10)

1. An axle load sensor comprising an elongate member adapted to be mounted on the chassis of a road haulage vehicle or on an axle of the-vehicle, a limit indicator provided on the elongate member, a sensor mounted on the vehicle and responsive to movement of the elongate member relative to the sensor and signal means connected to the sensor means, the arrangement being such that a signal is passed from the sensor to the signal means when the limit indicator on the elongate member is detected by the sensor means.

2. An axle load sensor according to claim 1 wherein, the elongate member is a guide rod and the limit indicator comprises the free end of the guide rod.

3. An axle load sensor according to claim 2 wherein, the sensor means comprises a proximity switch which senses the presence of the free end of the guide rod within a detection zone and passes a signal to the signal means.

4. An axle load sensor according to claim 1 wherein, the elongate member is a C-shaped channel and the limit indicator comprises a magnet mounted vertically repositionable within the channel member.

5. An axle load sensor according to claim 4 wherein, the sensor means comprises a proximity switch which senses the presence of the magnet within a detection zone and passes a signal to the signal means.

6. An axle load sensor comprising an inflatable air bag adapted to be mounted on the chassis of a road haulage vehicle or on an axle of the vehicle, an air pressure source for increasing or decreasing the pressure in the air bag, a sensor mounted on the vehicle and responsive to a change in pressure within the air bag and signal means connected to the sensor means, the arrangement being such that a signal is passed from the sensor to the signal means when the sensor means detects a change in air pressure within the air bag.

7. An axle load sensor according to any one of the preceding claims wherein, the signal means comprises an array of light emitting diodes each of which indicate whether the permitted load over a specific axle has been executed.

8. An axle load sensor according to any of claims 1 to 6 wherein, the signal means comprises an audible signal device which acts as a warning to a driver that the load over an axle has exceeded the permitted limit.

9. An axle load sensor substantially as hereinbefore described with reference to and as shown in Figures 1 or 2.

10. An axle load sensor substantially as hereinbefore described with reference to and as shown in Figure 3.