US 8,818,548 B2Granted

Work apparatus with safety equipment

AssigneeYamabiko Corporation

InventorsTatsuya Aoki, Tadashi Ishimura

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Abstract

In a brush cutter (100), when it is determined based on acceleration information including frequency components, supplied from an acceleration sensor (24) included in the brush cutter (100) that the acceleration shows a peak in a range of frequencies lower than 100 Hz, the flow moves to step S5 to amplify the acceleration peak. In next step S6, the acceleration peak is compared with a threshold. When the result of comparison shows that the acceleration peak is higher than the threshold, the flow moves to step S7 to produce a safety signal. The safety signal is output from the controller (26) to a high voltage generation circuit (30) to stop generation of a high voltage in the high voltage generating circuit (30). In this manner, the acceleration sensor (24) is used to detect any unexpected, sudden danger, while diminishing influence of the acceleration caused by vibration inherent to the own nature of the work apparatus, its intended regular operation and its posture change in regular operation.

Claims10

Dependent claims

A work apparatus including a cutting tool and equipped with a safety device for stopping motion of the cutting tool upon detection of a particular phenomenon possibly inviting an unexpected, unsafe situation from acceleration information received from an acceleration sensor, comprising:

a single-cylinder internal combustion engine mounted in a drive unit in which a drive source for driving said cutting tool is provided;
a uniaxial, biaxial, or triaxial type acceleration sensor having one, two, or three detection axes and attached to said drive unit in such an orientation that said detection axes of said acceleration sensor extend aslant from an axial line of a cylinder bore of said internal combustion engine;
an arithmetic operation means supplied with acceleration information from said acceleration sensor and executing arithmetic operation of the acceleration information to find out an acceleration peak;
a frequency range judgment means for judging whether or not the acceleration peak found out by said arithmetic operation means is within a first frequency range in which acceleration peaks indicative of phenomena possibly inviting any unexpected, unsafe situations normally appear;
an amplification means for amplifying the acceleration peak in the first frequency range when the frequency range judgment means determines that the frequency of the acceleration peak is in the first frequency range;
a first comparison means for comparing the acceleration peak amplified by the amplification means with a first threshold;
a second comparison means for comparing the acceleration peak with a second threshold when the frequency range judgment means determines that the frequency of the acceleration peak is in a frequency out of the first frequency range;
and
an output means for issuing a safety signal to a disabling means when comparison of said first comparison means results in determining that the acceleration peak in the first frequency range is equal to or higher than the first threshold or when comparison of said second comparison means results in determining that the acceleration peak in the acceleration peak in the frequency range out of the first frequency range is equal to or higher than the second threshold, said disabling means responsively disabling said cutting tool of said work apparatus directly or indirectly to stop the cutting tool from moving.

6 more elements

a single-cylinder internal combustion engine mounted in a drive unit in which a drive source for driving said cutting tool is provided;
a uniaxial, biaxial, or triaxial type acceleration sensor having one, two, or three detection axes and attached to said drive unit in such an orientation that said detection axes of said acceleration sensor extend aslant from an axial line of a cylinder bore of said internal combustion engine;
a frequency range judgment means supplied with acceleration information from said acceleration sensor and judging whether an acceleration indicated by the acceleration information has a frequency in a first frequency range in which acceleration peaks indicative of phenomena possibly inviting any unexpected, unsafe situations normally appear or in a frequency range other than the first frequency range;
a first arithmetic operation means for executing arithmetic operation of the acceleration having the frequency in the first frequency range to find out an acceleration peak;
an amplification means for amplifying the acceleration peak found out from the acceleration having the frequency in the first frequency range;
a second arithmetic operation means for executing arithmetic operation of the acceleration having a frequency in the frequency range other than the first frequency range to find out an acceleration peak;
a first comparison means for comparing the acceleration peak in the first frequency range amplified by the amplification means with a first threshold;
a second comparison means for comparing the acceleration peak in the frequency range other than the first frequency range, which has been found out by the second arithmetic operation means, with a second threshold;
an output means for issuing a safety signal to a disabling means when comparison of said first comparison means results in determining that the acceleration peak in the first frequency range is equal to or higher than the first threshold or when comparison of said second comparison means results in determining that the acceleration peak in the acceleration peak in the frequency range out of the first frequency range is equal to or higher than the second threshold, said disabling means responsively disabling said cutting tool of said work apparatus directly or indirectly to stop the cutting tool from moving.

6 more elements

Dependencies are inferred from the claim text.