BOOM LOAD INDICATING SYSTEM

• US 3,586,841 A
• Filed: 02/14/1969
• Issued: 06/22/1971
• Est. Priority Date: 02/14/1969
• Status: Expired due to Term

• Current Assignee: Robert F. Griffin
• Original Assignee: Robert F. Griffin
• Inventors: Griffin, Robert F.
• Application Number:
  US04/799,379
• Time in Patent Office: 858 Days
• US Class Current: 702/43
• CPC Class Codes: B66C 23/905 electrical

Abstract

A boom load indicating system for a self-supporting boom which determines the maximum bending stress on the boom and, in the case of a telescoping boom, determines the bending stress on each section of the boom. A strain transducer is mounted on the boom as close as possible to the pivot where the boom lift force is applied. Electrical analog circuitry indicates when bending stress is approaching or at a maximum permissible value. When the boom is operated at a substantial slewing angle, the predetermined maximum permissible tipping moment provides the standard against which the actual bending stress on the boom is compared.

Claims

1. In combination with a boom which is subject to a substantial bending moment, a strain transducer, and means operatively connecting said transducer to the boom at a location effective to produce on the transducer a strain which is substantially a predetermined function of the bending moment on the boom, said predetermined function is a substantial linear function of the strain on the transducer with respect to the total bending moment on the boom due to its own weight and the weight of any load suspended from its outer end.

2. In combination with a self-supporting boom for supporting a load from its outer end, boom lift means operatively engaging the underside of the boom near its lower end for lifting and lowering the boom, a strain transducer, and means rigidly attaching said transducer to the underside of the boom in close proximity to the location thereon where said boom lift means engages the boom so that the strain measured by the transducer is substantially linearly proportional to the total bending moment on the boom due to the load and due to the weight of the boom itself.

3. The combination of claim 2, wherein said boom has a plurality of extensible sections which interfit in succession along its length.

4. The combination of claim 3, wherein said boom has telescoping sections.

5. The combination of claim 3, and further comprising circuit means operative in response to the output signal of said transducer and in response to the individual lengths and weights of the boom sections to determine the actual bending momenT on each boom section.

6. The combination of claim 5, wherein said circuit means comprises electrical analog circuitry.

7. The combination of claim 5, wherein said circuit means comprises means for producing reference signals proportional respectively to predetermined maximum safe bending moments for each of the boom sections, and means for comparing each of said reference signals against a signal proportional to the actual bending moment on the corresponding boom section.

8. The combination of claim 7, and further comprising indicator means for each boom section operable by the comparison between each reference signal and the corresponding actual bending moment signal to provide an indication when the actual bending moment signal is at least a predetermined percentage of the respective reference signal.

9. An indicator system for use with a self-supporting boom having a plurality of boom sections in succession outwardly from its base and certain of which sections, at least, are extensible, said system comprising means for sensing the bending moment on the boom at a location thereon where the response of said sensing means is substantially linearly proportional to the actual bending moment at said location on the boom, an analog circuit including circuit elements operatively connected to provide signals which are substantially proportional to the lengths of the respective boom elements, the circuit elements which correspond to the extensible boom sections being variable in accordance with the individual extended lengths of the latter, said analog circuit also including circuit elements operatively connected to provide signals which are substantially proportional to the weights of the respective boom elements, and said analog circuit including means for combining the output signal of said sensing means and said boom section length signals and said boom section weight signals to provide for each boom section a signal substantially proportional to the actual bending moment thereon.

10. A system according to claim 11, and further comprising means for producing reference signals proportional respectively to predetermined maximum safe bending moments for the individual boom elements, and means for comparing each of said reference signals against the signal representing the actual bending moment on the corresponding boom section.

11. In combination with a self-supporting boom having a base section and a plurality of additional sections in succession outwardly from the base section, at least certain of said sections of the boom being extensible, strain transducer means operatively coupled to the boom to determine the bending moment on the boom at a particular location thereon, and circuit means operable in accordance with the respective weights and extended lengths of the several boom sections and the output of said strain transducer means to produce a plurality of signals which individually are representative of the bending moments on respective sections of the boom.

12. The combination of claim 11, and further comprising boom lift means operatively engaging the base section of the boom from below for lifting and lowering the boom, and means rigidly coupling said strain transducer means to the underside of said base in close proximity to its operative engagement by said boom lift means so that the strain measured by said strain transducer means is substantially linearly proportional to the total bending moment on the boom due to its own weight and the weight of any load suspended from its outer end.

13. The combination of claim 11, wherein said circuit means is an analog circuit including circuit elements operatively connected to provide signals which are substantially proportional to the lengths of the respective boom elements, the circuit elements which correspond to the extensible boom sections being variable in accordance with the individual variable lengths of the latter, said analog circuit also including circuit elements operatively connected To provide signals which are substantially proportional to the weights of the respective boom elements, and said analog circuit including means for combining the output signal of said strain transducer means and said boom section length signals and said boom section weight signals to provide for each boom section a signal which is substantially proportional to the actual bending moment thereon.

14. The combination of claim 13, and further comprising boom lift means operatively engaging the base section of the boom at a predetermined location for lifting and lowering the boom, and means operatively connecting said strain transducer means to the base section of the boom to measure the strain at the underside of the boom in close proximity to the location where said boom lift means is operatively connected to the base section of the boom.

15. The combination of claim 13, and further comprising means for producing reference signals proportional respectively to predetermined maximum safe bending moments for the respective boom sections, and means for comparing each of said reference signals against a signal proportional to the actual bending moment on the corresponding boom section.

16. The combination of claim 15, and further comprising means for producing a maximum safe tipping moment signal, and means for comparing said tipping moment signal against the signal proportional to the actual bending moment on the base section of the boom when the slewing angle of the boom exceeds a predetermined value while at the same time disabling the comparison between said actual bending moment signal for the base section and the corresponding reference signal which is proportional to the maximum safe bending load for the base section.

17. A method comprising the steps of changing the length of a boom for supporting an external load and having telescoping sections by varying the telescopic relationship between sections of the boom, sensing the length of the boom, changing the angular position of the boom relative to a support surface by moving the boom transversely to the support surface, sensing the angular position of the boom relative to the support surface, sensing bending moment induced in the boom under the combined effects of the external load and weight of the boom, and generating a load signal which is a function of the sensed bending moment in the boom, the sensed length of the boom and the sensed angle of the boom relative to the support surface.

18. A method comprising the steps of changing the length of a boom having telescoping sections by varying the telescopic relationship between sections of the boom with a resulting change in the bending moment in the sections of the boom, changing the angular position of the sections of the boom relative to a support surface by moving the sections of the boom transversely to the support surface with a resulting change in the bending moment in the sections of the boom, generating a plurality of load signals each of which is associated with a different one of the sections of the boom, and varying said load signals in response to and as a function of changes in the bending moment in the associated one of the boom sections resulting from changes in the length of the boom and changes in the angular position of the boom relative to the support surface.

19. A method as set forth in claim 18 further including the method steps of generating a reference signal corresponding to a predetermined maximum safe load, comparing said load and reference signals, and generating an output signal when said load signal exceeds a predetermined function of said reference signal.

20. A method as set forth in claim 18 further including the steps of changing the magnitude of an external load supported by the boom with a resulting change in the bending moment in each of the sections of the boom, and varying each of said load signals in response to changes in the bending moment in the associated one of the boom sections resulting from cHanges in the magnitude of the external load supported by the boom.

21. A method comprising the steps of changing the length of a boom for supporting an external load and having telescoping sections by varying the telescopic relationship between sections of the boom, changing the angular position of the sections of the boom relative to a support surface by moving the sections of the boom transversely to the support surface, sensing bending moment induced in a section of the boom under the combined influence of the external load and weight of the boom, generating as a function of the sensed bending moment a plurality of load signals each of which is associated with a different one of the sections of the boom and is representative of the bending moment induced in the associated section of the boom by the external load, generating a plurality of boom signals each of which is associated with a different one of the sections of the boom and is representative of the bending moment induced in the associated section of the boom by the weight of the boom, and producing a plurality of combined signals each of which is associated with a different one of the boom sections, each of said combined signals being a function of the load and boom signal associated with the same boom section as the combined signal and being representative of the bending moment induced in the associated boom section under the combined influence of the external load and weight of the boom.

22. An assembly comprising a boom having a plurality of telescoping sections, means for moving said telescoping sections of said boom relative to each other to thereby vary the telescopic relationship between said sections and the length of said boom, means for varying the angular relationship of said boom to the support surface by moving said boom toward and away from the support surface, and circuit means for producing a signal representative of the bending moment in said boom, said circuit means including means for varying said signal in response to changes in length of said boom and means for varying said signal in response to changes in the angular relationship of said boom to the support surface.

23. An assembly as set forth in claim 22 further including means operatively connected to said boom of engaging external loads of different magnitudes, said circuit means including means for varying said signal in response to changes in the magnitude of the load engaged by said means for engaging external loads.

24. An assembly comprising a boom having a plurality of telescoping sections, means for moving said telescoping sections of said boom relative to each other to thereby vary the telescopic relationship between said sections and the length of said boom, means for varying the angular relationship of said sections of said boom relative to a support surface by moving said boom toward and away from the support surface, and circuit means for generating a plurality of signals each of which is associated with a different one of said sections of said boom and is representative of at least a portion of the bending moment in the associated one of said boom sections, said circuit means including means for varying at least some of said signals in response to changes in the length of said boom and means for varying at least some of said signals in response to variations in the angular relationship of said sections of said boom relative to the support surface.

25. An assembly as set forth in claim 24 further including means operatively connected to said boom for engaging external loads of different magnitudes, said circuit means including means for varying at least some of said signals in response to changes in the magnitude of the load engaged by said means for engaging external loads.

26. An assembly as set forth in claim 25 wherein said circuit means includes means for generating a plurality of reference signals each of which is associated with one of said boom sections and is representative of the magnitude of the maXimum permissible bending moment in the associated one of said boom sections, and means for comparing each of said signals which is representative of the bending moment in an associated one of said boom sections with the reference signal which is associated with the same boom section and for providing an output signal when a predetermined relationship exists between the signal representative of the bending moment in one of said boom sections and the reference signal associated with the same boom section.

27. An assembly comprising a boom having a plurality of telescoping sections for supporting an external load, means for moving said telescoping sections of said boom relative to each other to thereby vary the telescopic relationship between said sections and the length of said boom, means for varying the angular relationship of said boom to a support surface by moving said boom toward and away from the support surface, a sensor means operatively connected with said boom for sensing bending moment induced in a section of said boom under the combined influence of the external load and weight of said boom, first circuit means operatively connected to said sensor means for generating a plurality of load signals each of which is associated with a different one of said sections of said boom and is representative of the bending moment induced in the associated section of said boom by an external load, second circuit means for generating a plurality of boom signals each of which is associated with a different one of said sections of said boom and is representative of the bending moment induced in the associated section of said boom by the weight of said boom, and third circuit means connected with said first and second circuit means for generating a plurality of combined signals each of which is associated with a different one of said boom sections and each of which is representative of the bending moment induced in the associated boom section under the influence of the external load and the weight of the boom.