Method and apparatus for providing operating information to an operator of a fork lift truck

• US 5,995,001 A
• Filed: 07/01/1998
• Issued: 11/30/1999
• Est. Priority Date: 07/09/1997
• Status: Expired due to Term

• Current Assignee: Crown Equipment Corporation
• Original Assignee: Crown Equipment Corporation
• Inventors: Wellman, Timothy A., Magoto, Daniel C.
• Primary Examiner(s): Wu, Daniel J.
• Assistant Examiner(s): Huang, Sihong
• Application Number:
  US09/108,735
• Time in Patent Office: 517 Days
• Field of Search: 340/438, 340/440, 340/689, 340/686, 340/691, 340/685, 414/634, 414/273, 414/635
• US Class Current: 340/438
• CPC Class Codes: B66F 17/003 for fork-lift trucks

Abstract

A fork lift truck capacity monitor or alerting device informs operators of the weight on the forks and fork height and alerts operators whenever truck speed is above creep with the forks raised above a collapsed height or whenever the forks are raised above a recommended height for a given load. The alerting device includes a control circuit that receives inputs from a speed sensor, a fork height sensor and a weight sensor and reads a memory storing data correlating load weights with maximum recommended fork heights. A truck icon is displayed on a display panel. A plurality of height zone lamps representing the weight of the load on the forks are arranged in a vertical column over the truck icon and selectively illuminated according to the load on the forks. A plurality of lamps represent the height of the forks with the fork height lamps, which include one lamp positioned to represent a lowered position of the forks and a plurality of lamps equal in number to the height zone lamps and placed horizontally opposite therefrom, being selectively illuminated according to the height of the forks. An alarm signal alerts operators whenever the forks are raised above the recommended height for a given load weight, or whenever truck speed exceeds a predetermined maximum speed and the forks are above the collapsed height. The alarm signal may include a combination of an audible signal, a text message, and a flashing lamp.

Claims

1. A fork lift truck comprising:

a truck speed sensor;

a mast carrying forks which can be moved in height between a lowered position and desired raised positions;

a fork height sensor; and

an alerting system indicating status of said fork height and truck speed to an operator of said truck, said alerting system comprising;

a control circuit responsive to signals generated by said truck speed sensor and said fork height sensor; and

an indicator connected to an output of said control circuit, said indicator being illuminated by said control circuit when said forks are raised above a predetermined height and flashed by said control circuit when said forks are raised above said predetermined height and truck speed is above a predetermined speed.

2. A fork lift truck as claimed in claim 1 wherein said alerting system further comprises an audible alarm connected to an output of said control circuit, said audible alarm being sounded by said control circuit whenever said forks are raised above said predetermined height and truck speed is above said predetermined speed.

3. A fork lift truck as claimed in claim 1 wherein said alerting system further comprises a representation of a fork lift truck and wherein said indicator is in the form of a fork positioned above said truck representation.

4. A fork lift truck as claimed in claim 1 wherein said fork height sensor senses whether said forks are at or above a collapsed height or below a collapsed height.

5. A fork lift truck as claimed in claim 1 wherein said indicator comprises a lamp.

6. A fork lift truck comprising:

a mast carrying forks which can be moved in height between a lowered position and desired raised positions;

a fork height sensor;

a fork load weight sensor; and

an alerting system indicating sensed fork height and sensed fork load weight to an operator of said truck, said alerting system comprising;

a storage device storing data correlating recommended fork heights and fork load weights;

a control circuit responsive to said data from said storage device and signals generated by said fork height sensor and said fork load weight sensor;

a plurality of height zone indicators coupled to said control circuit, said height zone indicators being selectively illuminated by said control circuit according to sensed weight of a load on said forks;

a plurality of fork height indicators coupled to said control circuit, said fork height indicators being selectively illuminated according to the height of said forks; and

an operator correctable error indicator coupled to said control circuit for alerting an operator of said truck whenever said forks are raised above a recommended maximum height for a given load weight.

7. A fork lift truck as claimed in claim 6 wherein at least one of said indicators comprise a lamp.

8. A fork lift truck as claimed in claim 6 wherein said operator correctable error indicator is activated when a given load weight exceeds a maximum load weight for said fork lift truck.

9. A fork lift truck comprising:

a mast carrying forks which can be moved in height between a lowered position and desired raised positions;

a hydraulic tilt cylinder for tilting said forks through a fork tilt range;

a fork height sensor;

a fork load weight sensor, said weight sensor being coupled to said tilt cylinder for monitoring the pressure of hydraulic fluid in said tilt cylinder which pressure is a function of the weight being carried by said forks; and

an alerting system indicating sensed fork height and sensed fork load weight to an operator of said truck, said alerting system comprising;

a storage device storing data correlating recommended fork heights and fork load weights;

a control circuit responsive to said data from said storage device and signals generated by said fork height sensor and said fork load weight sensor;

a plurality of height zone indicators coupled to said control circuit, said height zone indicators being selectively illuminated by said control circuit according to sensed weight of a load on said forks;

a plurality of fork height indicators coupled to said control circuit, said fork height indicators being selectively illuminated according to the height of said forks; and

an operator correctable error indicator coupled to said control circuit for alerting an operator of said truck whenever said forks are raised above a recommended maximum height for a given load weight.

10. A fork lift truck as claimed in claim 9 further comprising a fork tilt monitoring device, said fork tilt monitoring device being actuated when said forks are tilted to extremes of said fork tilt range and being coupled to said control circuit to disable said alerting system when actuated.

11. A fork lift truck as claimed in claim 10 wherein said fork tilt monitoring device comprises a switch.

12. A fork lift truck as claimed in claim 9 wherein said alerting system further comprises a text display screen coupled to said control circuit for visually instructing said operator concerning sensed fork height, sensed fork load weight and sensed truck speed.

13. A fork lift truck as claimed in claim 12 further comprising a fork tilt monitoring device, said fork tilt monitoring device being actuated when said forks are tilted to extremes of said fork tilt range and being coupled to said control circuit to disable said alerting system when actuated, said control circuit displaying a monitor disabled message on said text display screen when said fork tilt monitoring device is actuated.

14. A fork lift truck comprising:

a mast carrying forks which can be moved in height between a lowered position and desired raised positions;

a truck speed sensor;

a fork height sensor;

a fork load weight sensor; and

an alerting system indicating sensed fork height and sensed fork load weight to an operator of said truck, said alerting system comprising;

a storage device storing data correlating recommended fork heights and fork load weights;

a control circuit responsive to said data from said storage device and signals generated by said fork height sensor and said fork load weight sensor;

a plurality of height zone indicators coupled to said control circuit, said height zone indicators being selectively illuminated by said control circuit according to sensed weight of a load on said forks;

a plurality of fork height indicators coupled to said control circuit, said fork height indicators being selectively illuminated according to the height of said forks; and

an operator correctable error indicator coupled to said control circuit for alerting an operator of said truck whenever said forks are raised above a recommended maximum height for a given load weight, said truck speed sensor being coupled to said control circuit which causes said selectively illuminated fork height indicators to flash when truck speed exceeds a predetermined value and sensed fork height is above a collapsed height for said fork lift truck.

15. A fork lift truck as claimed in claim 14 wherein said alerting system further comprises an audible alarm coupled to said control circuit, said control circuit sounding said audible alarm when truck speed exceeds said predetermined value and sensed fork height is above a collapsed height for said fork lift truck.

16. A fork lift truck as claimed in claim 15 wherein said alerting system further comprises a text display screen to visually instruct said operator concerning sensed fork height, sensed fork load weight and sensed truck speed.

17. A fork lift truck comprising:

a mast carrying forks which can be moved in height between a lowered position and desired raised positions;

a truck speed sensor;

a fork height sensor;

a fork load weight sensor; and

an alerting system indicating sensed fork height, sensed fork load weight and sensed truck speed to an operator of said truck, said alerting comprising;

a control circuit receiving input signals from said truck speed sensor, said fork height sensor and said load weight sensor;

a storage device storing data correlating fork load weights and recommended fork heights;

a representation of a fork lift truck on a display;

a plurality of height zone indicators on said display and responsive to said control circuit for representing load weight on said forks, said plurality of height zone indicators being placed above said representation of a fork lift truck in a vertical column and being selectively illuminated according to sensed load weight on said forks;

a plurality of fork height indicators on said display and responsive to said control circuit for representing sensed height of said forks, said plurality of fork height indicators including one fork height indicator placed relative to said representation of a lift truck in a position representing a lowered position of said forks, and a remainder of said plurality of fork height indicators equal in number to said plurality of height zone indicators and placed horizontally opposite therefrom, said plurality of fork height indicators being selectively illuminated by said control circuit according to sensed fork height and said remainder of said plurality of fork height indicators being selectively flashed by said control circuit whenever said forks are raised above a predetermined height and the speed of said truck is above a predetermined speed; and

an operator error indicator activated by said control circuit to provide an output signal to alert said operator whenever said forks are raised above a recommended height for a given load weight.

18. A fork lift truck as claimed in claim 17 wherein at least one of said indicators comprise a lamp.

19. A fork lift truck as claimed in claim 17 wherein said operator error indicator is a symbol which is illuminated to indicate when said forks are raised above a recommended height for a given load weight.

20. A fork lift truck as claimed in claim 17 wherein said alerting system further comprises a text display screen to visually instruct said operator concerning sensed fork height, sensed fork load weight and sensed truck speed.

21. A fork lift truck as claimed in claim 17 further including an audible alarm which is sounded by said control circuit whenever said forks are above a predetermined height and sensed speed of said fork lift truck exceeds a predetermined value.

22. A fork lift truck as claimed in claim 17 wherein only one of said plurality of fork height indicators is energized at any time during operation of said truck.

23. A method of displaying a recommended maximum height to which forks of a fork lift truck should be raised under a given load condition comprising the steps of:

measuring weight of a load carried by said forks;

measuring height of said forks;

comparing said height of said forks to said weight of said load;

providing a visible indication whenever the height of the forks exceeds a recommended height limit dictated by a measured load weight;

monitoring speed of said truck; and

providing a visible and audible indication whenever said speed of said truck exceeds a predetermine speed and said forks are raised above a predetermined height.