GB2136141A

GB2136141A - Vehicle Axle Load Indicator

Info

Publication number: GB2136141A
Application number: GB08306521A
Authority: GB
Inventors: Marvin D Strange
Original assignee: Leyland Vehicles Ltd
Current assignee: Leyland Vehicles Ltd
Priority date: 1983-03-09
Filing date: 1983-03-09
Publication date: 1984-09-12
Also published as: GB8306521D0

Abstract

The load carried by an axle of a vehicle with air suspension is derived from the pressure in the air spring A between the axle and chassis. The air pressure is sensed during vehicle loading by a transducer E which controls a visual display G calibrated in units of equivalent axle weight, or by a pressure switch E which triggers an alarm when the weight exceeds a threshold. An electro-pneumatic valve D and/or restrictor X protect the transducer or switch E during normal suspension movements. The suspension is self-levelling under the control of a height sensor C. <IMAGE>

Description

SPECIFICATION Vehicle Axle Load Indicator This invention relates to systems for providing an indication of the load borne by the axle or axles of a vehicle, and in particular to vehicles with air suspension such as trucks and public service vehicles.

Air suspension has the particular advantage of constant height of the vehicle floor above the axle under varying loads, but this makes it difficult to measure the axle weight. With trucks for tipping or bulk delivery operations, for example, it is notoriously difficult to judge axle weight without the use of a weighbridge.

It is an object of the invention therefore to provide a simple system for indicating axle weight in air suspension vehicles.

An air suspension system according to the invention comprises: an air spring adapted to space a chassis from an axle; a duct for supplying gas under pressure to the air spring by way of a levelling valve regulated in response to the spacing of the chassis from the axle; and means responsive to the gas pressure in the air spring to provide an indication of the load supported by the axle.

The pressure of gas in the air spring is directly related to the load it transmits to the axle, and the indicating means in one example is a pressure transducer which converts the gas pressure into an electric signal fed to means providing a visual indication of the equivalent axle load. In another example, for use particularly in public service vehicles, an overload condition is indicated by the indicating means which is a pressure switch connected to provide an electric signal when the pressure is equivalent to an axle load above a predetermined threshold.

In order to protect the indicating means from pressure surges during normal suspension, movements, a switchable electro-pneumatic valve and/or a restrictor may be connected in series to isolate the indicating means from the air spring.

The suspension system may be independent for each wheel of the vehicle, i.e. with a separate indicating means for each end of the or each axle having air suspension, or a single indicating means may be arranged to provide an overall indication of the vehicle load. The invention is applicable to any vehicle with air suspension.

The invention will be better understood from the following description of a preferred embodiment, with reference to the accompanying drawing which is a schematic representation of the air suspension system at one end of an axle.

The drawing shows one road wheel and a portion of the associated axle which supports the vehicle floor (shown parallel to the axle) by way of an air spring A. The air spring works in a conventional manner, whereby long-term changes in load are sensed by a control arm linking the levelling valve C to the axle and result in air either being exhausted from the air spring or being admitted to the air spring from the reservoir B.

A pressure-sensitive transducer E is connected via an air pipe to the air pipe between the levelling valve C and the air spring A, but is protected from possible damage during normal suspension movements by means of a restrictor X and an electro-pneumatic valve D in series. The valve D is connected via a switch F to receive power from a vehicle auxiliary circuit H, ensuring that the valve is only powered and open when the vehicle is stationary. The transducer E may be a meter providing an analogue electric signal to a visual display G calibrated in units of axle weight equivalent to the air pressure; the load-pressure relationship may be predetermined empirically.

Alternatively, the transducer E may be a pressure switch responding to pressure above a predetermined preset threshold to cause a light or horn, for example, G, to indicate an overload condition. In this example the indicating means and the electro-pneumatic valve are powered from the same auxiliary circuit H.

There is normally only one such load indicator per axle; the vehicle is then loaded until the maximum has been reached at one of two or more axles. In some applications, it may be desirable to connect such a load indicator to the air springs at both ends of the or each axle.

1. An air suspension system comprising: an air spring adapted to space a chassis from an axle; a duct for supplying gas under pressure to the air spring by way of a levelling valve regulated in response to the spacing of the chassis from the axle; and means responsive to the gas pressure in the air spring to provide an indication of the load supported by the axle.

2. A vehicle with air suspension between a chassis and at least one axle, comprising: an air spring supporting the chassis on the axle; a duct for supplying gas under pressure to the air spring by way of a levelling valve regulated in response to the spacing of the chassis from the axle; and means responsive to the gas pressure in the air spring to provide an indication of the load supported by the axle.

3. A system according to Claim 1 or a vehicle according to Claim 2, wherein the indicating means comprises a transducer which converts the gas pressure into an electrical signal fed to means providing a visual indication of the equivalent axle load.

4. A system according to Claim 1 or a vehicle according to Claim 2, wherein the indicating means comprises a pressure switch providing an indication that the gas pressure is equivalent to an axle load above a predetermined threshold.

5. A system or a vehicle according to any of claims 1 to 4, further comprising a switchable electropneumatic valve connected in series for isolating the indicating means from the air spring.

6. A system or a vehicle according to any of claims 1 to 5, wherein the indicating means

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Vehicle Axle Load Indicator This invention relates to systems for providing an indication of the load borne by the axle or axles of a vehicle, and in particular to vehicles with air suspension such as trucks and public service vehicles. Air suspension has the particular advantage of constant height of the vehicle floor above the axle under varying loads, but this makes it difficult to measure the axle weight. With trucks for tipping or bulk delivery operations, for example, it is notoriously difficult to judge axle weight without the use of a weighbridge. It is an object of the invention therefore to provide a simple system for indicating axle weight in air suspension vehicles. An air suspension system according to the invention comprises: an air spring adapted to space a chassis from an axle; a duct for supplying gas under pressure to the air spring by way of a levelling valve regulated in response to the spacing of the chassis from the axle; and means responsive to the gas pressure in the air spring to provide an indication of the load supported by the axle. The pressure of gas in the air spring is directly related to the load it transmits to the axle, and the indicating means in one example is a pressure transducer which converts the gas pressure into an electric signal fed to means providing a visual indication of the equivalent axle load. In another example, for use particularly in public service vehicles, an overload condition is indicated by the indicating means which is a pressure switch connected to provide an electric signal when the pressure is equivalent to an axle load above a predetermined threshold. In order to protect the indicating means from pressure surges during normal suspension, movements, a switchable electro-pneumatic valve and/or a restrictor may be connected in series to isolate the indicating means from the air spring. The suspension system may be independent for each wheel of the vehicle, i.e. with a separate indicating means for each end of the or each axle having air suspension, or a single indicating means may be arranged to provide an overall indication of the vehicle load. The invention is applicable to any vehicle with air suspension. The invention will be better understood from the following description of a preferred embodiment, with reference to the accompanying drawing which is a schematic representation of the air suspension system at one end of an axle. The drawing shows one road wheel and a portion of the associated axle which supports the vehicle floor (shown parallel to the axle) by way of an air spring A. The air spring works in a conventional manner, whereby long-term changes in load are sensed by a control arm linking the levelling valve C to the axle and result in air either being exhausted from the air spring or being admitted to the air spring from the reservoir B. A pressure-sensitive transducer E is connected via an air pipe to the air pipe between the levelling valve C and the air spring A, but is protected from possible damage during normal suspension movements by means of a restrictor X and an electro-pneumatic valve D in series. The valve D is connected via a switch F to receive power from a vehicle auxiliary circuit H, ensuring that the valve is only powered and open when the vehicle is stationary. The transducer E may be a meter providing an analogue electric signal to a visual display G calibrated in units of axle weight equivalent to the air pressure; the load-pressure relationship may be predetermined empirically. Alternatively, the transducer E may be a pressure switch responding to pressure above a predetermined preset threshold to cause a light or horn, for example, G, to indicate an overload condition. In this example the indicating means and the electro-pneumatic valve are powered from the same auxiliary circuit H. There is normally only one such load indicator per axle; the vehicle is then loaded until the maximum has been reached at one of two or more axles. In some applications, it may be desirable to connect such a load indicator to the air springs at both ends of the or each axle. CLAIMS

6. A system or a vehicle according to any of claims 1 to 5, wherein the indicating means communicates with the air spring by way of a gas duct, the duct having a restrictor for resisting rapid pressure surges.

7. An air suspension system substantially as herein described with reference to the accompanying drawings.