Overload detector of vehicle for high lift work

1. An overload detection device for a high-lift work vehicle having a work platform mounted at a front end of a telescopic boom via a bracket, characterized in that:

a base of said work platform is supported with said bracket, at, at least, three supporting portions,

load sensors each constituted of a plate member and distortion gauges pasted onto said plate member to detect an extent of flexure thereof are provided at, at least, two of said supporting portions; and

each of said load sensors is mounted with two ends of said plate member connected with said bracket and said base by using bolts and an elastic member which allows a displacement of said load sensor relative to said bracket or said base along an upward direction and a downward direction is provided at the area where said load sensor is connected with either said bracket or said base.

2. An overload detection device for a high-lift work vehicle according to claim 1 , characterized in that:

said load sensors are each constituted by pasting distortion gauges capable of detecting positive and negative loads onto a front surface and a rear surface of said plate member.

3. An overload detection device for a high-lift work vehicle according to claim 2 , characterized in that:

said load sensors are each constituted by pasting distortion gauges two each onto the front surface and the rear surface of said plate member so that distortion gauges on one surface face opposite distortion gauges on the other surface; and

said distortion gauges are built into a wheatstone bridge to achieve a circuit structure through which a load detection signal is obtained as a sum of a distortion detection quantity from one pair of distortion gauges facing opposite each other at the front and the rear surface of said plate member and a distortion detection quantity from the other pair of distortion gauges facing opposite each other at the front surface and the rear surface of said plate member.

4. An overload detection device for a high-lift work vehicle according to claim 3 , characterized in that:

output lines of individual wheatstone bridges are connected in parallel to one another and are input to an amplifier circuit to obtain an average of distortion detection quantities from said wheatstone bridges by averaging the distortion detection quantities.

5. An overload detection device for a high-lift work vehicle according to claim 1 , characterized in that:

said base is supported by said bracket at four supporting portions equivalent to corners of a square or a rectangle having two sides thereof extending along a front/rear direction and said load sensor are provided at, at least, two of said supporting portions.

6. An overload detection device for a high-lift work vehicle according to claim 1 , further provided with:

a means for comparison that compares a load detection value obtained based upon detection signals from said load sensors with a predetermined overload value; and

a means for warning generation that issues a warning if an overload state is detected by said means for comparison.

7. An overload detection device for a high-lift work vehicle according to claim 1 , further provided with:

a means for comparison that compares a load detection value obtained based upon detection signals from said load sensors with a predetermined overload value; and

a means for control that disallows an operation that would increase the work radius if an overload state is detected by means said means for comparison.

8. An overload detection device for a high-lift work vehicle according to claim 1 , further provided with:

a means for comparison that compares a load detection value obtained based upon detection signals from said load sensors with a predetermined overload value;

a means for warning generation that issues a warning if an overload state is detected by said means for comparison; and

a means for control that disallows an operation that would increase the work radius if an overload state is detected by said means for comparison.

9. An overload detection device for a high-lift work vehicle according to claim 1 , characterized in that:

said base is supported by said bracket at four supporting portions equivalent to corners of a square or a rectangle having two sides thereof extending along a front/rear direction and said load sensor are provided at, at least, two of said supporting portions; and further provided with

a means for comparison that compares a load detection value obtained based upon detection signals from said load sensors with a predetermined overload value; and

a means for warning generation that issues a warning if an overload state is detected by said means for comparison.

10. An overload detection device for a high-lift work vehicle according to claim 1 , characterized in that:

said base is supported by said bracket at four supporting portions equivalent to corners of a square or a rectangle having two sides thereof extending along a front/rear direction and said load sensor are provided at, at least, two of said supporting portions; and further provided with

a means for comparison that compares a load detection value obtained based upon detection signals from said load sensors with a predetermined overload value; and

a means for control that disallows an operation that would increase the work radius if an overload state is detected by said means for comparison.

11. An overload detection device for a high-lift work vehicle according to claim 1 , characterized in that:

said base is supported by said bracket at four supporting portions equivalent to corners of a square or a rectangle having two sides thereof extending along a front/rear direction and said load sensor are provided at, at least, two of said supporting portions; and further provided with:

a means for comparison that compares a load detection value obtained based upon detection signals from said load sensors with a predetermined overload value;

a means for warning generation that issues a warning if an overload state is detected by said means for comparison; and

a means for control that disallows an operation that would increase the work radius if an overload state is detected by said means for comparison.