JP7820283B2 - Brush cutter with safety device - Google Patents

Description

The present invention relates to a brush cutter with a safety device.

Brush cutters equipped with safety devices are known. In this prior art, an acceleration sensor is installed on the brush cutter, and the safety device is activated when the detected value of the acceleration sensor is greater than a threshold value. The acceleration sensor is attached to the brush cutter with its detection axis tilted relative to the left-right direction of the brush cutter (see Patent Document 1 below).

JP 2010-268732 A

The above-mentioned conventional technology uses an acceleration sensor to detect forces acting on the brush cutter in various directions, making it possible to detect situations that the operator does not anticipate, such as the brush cutter falling or the blade colliding with an obstacle (kickback), and stop the brush cutter from operating. This ensures the safety of the operator working with the brush cutter.

In contrast, brush cutters are structurally characterized by a cutting blade attached to the tip of a long operating rod, making it necessary to ensure safety not only for the operator using the brush cutter, but also for people and objects around the brush cutter while it is in use.

When cutting brush, workers have difficulty identifying surrounding sounds due to noises such as the sound of the engine operating and the sound of the blades hitting each other. Additionally, they wear protective equipment such as earmuffs to block out these noises, making it difficult to hear surrounding sounds. Furthermore, concentrating on the position of the blades while working can narrow the worker's field of vision. This can lead to situations where a worker does not notice a person or object approaching, and as they turn around, they point the tip of the long operating rod at the approaching person or object. To avoid such situations, there is a need for a brush cutter safety device that can detect people or objects approaching the brush cutter while in use.

The present invention was proposed to address these circumstances. In other words, the objective of the present invention is to ensure the safety of people and objects around a brush cutter while it is in operation by effectively detecting people and objects approaching the brush cutter while it is in operation.

In order to solve such problems, the present invention has the following configuration.
A brush cutter with a safety device, comprising a main body, an operating rod connected at one end to the main body, and a brush cutting working part attached to the tip of the operating rod, and further comprising a safety device having a Doppler sensor for detecting an object approaching the brush cutter and a processing device for processing the output of the Doppler sensor, the Doppler sensor being disposed on the side of the main body opposite to the side to which the operating rod is connected , a motion detection sensor being installed in the brush cutter for detecting the movement of the brush cutter, and the processing device performing processing to remove noise associated with the movement of the brush cutter from the output of the Doppler sensor based on the output of the motion detection sensor.

By installing a Doppler sensor on a brush cutter, the present invention, which has these characteristics, can provide a brush cutter equipped with a safety device that effectively detects people or objects approaching the brush cutter while it is in use.

1 is an explanatory diagram showing a brush cutter with a safety device according to an embodiment of the present invention; FIG. 1 is an explanatory diagram showing the working state of a brush cutter equipped with a safety device. FIG. 4 is an explanatory diagram showing the function of a processing device in the safety device. FIG. 4 is an explanatory diagram showing an example of processing by a noise removal unit.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts with the same function, and duplicate descriptions in each drawing will be omitted as appropriate.

In FIG. 1, the brush cutter 10 comprises a main body 11, an operating rod 12 connected at one end to the main body 11, and a cutting unit 13 mounted on the tip of the operating rod 12. The cutting unit 13 can be driven in a variety of ways, including transmitting the rotation of a prime mover (engine or electric motor) mounted on the main body 11 to the cutting unit 13 via a transmission shaft within the operating rod 12, or mounting a prime mover (electric motor) on the cutting unit 13 and connecting the prime mover to a battery mounted on the main body 11 via wiring within the operating rod 12. The cutting unit 13 itself can also be in any form, such as a rotary blade, a reciprocating blade, or a resin cord.

The safety device 1 provided on the brush cutter 10 includes a Doppler sensor 1A mounted on the brush cutter 10 and a processing device 1B that processes the output of the Doppler sensor 1A. The Doppler sensor 1A emits transmitted waves within a specified detection range, receives reflected waves returning from the detection range, and outputs a signal including a Doppler signal. The Doppler signal becomes a signal with a different frequency depending on the change in distance to a moving object within the detection range, based on the phase difference between the transmitted wave and the reflected wave. The processing device 1B removes noise and determines the presence or absence of an approaching object based on the output of the Doppler sensor 1A.

In the illustrated example, the Doppler sensor 1A is installed on the side of the brush cutter 10 body 11 opposite the side to which the operating rod 12 is connected. This causes the transmission waves emitted by the Doppler sensor 1A to be emitted in the direction opposite the extension direction of the operating rod 12. Since the operator M of the brush cutter 10 works while looking at the brush cutting unit 13 attached to the tip of the operating rod 12 in the extension direction, the installation of the Doppler sensor 1A described above allows the transmission waves to be effectively emitted behind the operator M.

Furthermore, it is preferable to position the Doppler sensor 1A on the main body 11 below the center line O that passes through the center of the operating stick 12. By positioning the Doppler sensor 1A below the center line O in this way, it is possible to prevent parts of the main body 11 from interfering with the transmission waves when in the working position shown in Figure 1.

In this case, it is preferable to place the Doppler sensor 1A above the bottom 11A of the main body 11. By placing the Doppler sensor 1A above the bottom 11A of the main body 11, the Doppler sensor 1A can be prevented from receiving direct impact from the ground when the brush cutter 10 is placed on the ground or when the main body 11 of the brush cutter 10 is dropped to the ground, and the Doppler sensor 1A can be expected to be waterproof in cases where there are shallow puddles on the ground or water droplets on the grass.

Furthermore, if there is a heat source in the main body 11, it is preferable to place the Doppler sensor 1A away from that heat source. More specifically, in the case of an engine-powered brush cutter 10, it is preferable to place the Doppler sensor 1A near the bottom of the recoil starter on the main body 11 equipped with the engine. By placing the Doppler sensor 1A away from the heat source in this way, it is possible to avoid the adverse effects of exposing it to high temperatures.

As shown in Figure 1, the Doppler sensor 1A is preferably positioned so that the transmission wave is directed approximately parallel to the ground when the operator M is holding the handle 12A of the control stick 12 and performing brush cutting work. To achieve this, the Doppler sensor 1A is preferably positioned on the main body 11 so that the transmission wave is emitted along the central axis O of the control stick 12, in a direction perpendicular to the rotation axis 13A of the brush cutting working part 13. Furthermore, since reflected waves that occur when the transmitted wave hits the ground and returns become noise when detecting approaching objects, to prevent this, it is more preferable to orient the Doppler sensor 1A horizontally or slightly upward relative to a plane parallel to the ground during brush cutting work.

More specifically, in brush cutters 10 where the angle θa between the operating rod 12 and the rotation axis 13A of the brush cutting unit 13 is adjustable, it is preferable that the orientation of the Doppler sensor 1A mounted on the main body 11 be changeable in accordance with the adjustment of the angle θa.

In contrast, the brush cutter 10 is equipped with a motion detection sensor 1A1 that detects the movement of the brush cutter 10. The motion detection sensor 1A1 can be any sensor capable of detecting the movement of the brush cutter 10's main body 11 and operating stick 12 during brush cutting, and can be a gyro sensor or acceleration sensor. The number of motion detection sensors 1A1 is not limited to one, and multiple sensors may be provided. In the illustrated example, the motion detection sensor 1A1 is installed on the operating stick 12, but it can be installed anywhere on the brush cutter 10 as long as it moves simultaneously with the Doppler sensor 1A installed on the brush cutter 10.

By placing the Doppler sensor 1A on the side of the brush cutter 10 body 11 opposite the side to which the operating rod 12 is connected, the detection range of the Doppler sensor 1A can be aimed behind the operator M while he or she is cutting brush, allowing the transmission wave to be effectively transmitted to the blind spot behind the operator M.

As shown in Figure 2, when cutting brush, the cutting unit 13 attached to the tip of the control stick 12 is swung left and right while the work is being performed. As a result, the transmission direction of the Doppler sensor 1A, which is opposite to the extension direction of the control stick 12, moves left and right in response to the left and right swing of the control stick 12. This makes it possible to detect the presence or absence of approaching objects behind the worker M over a wide detection range. In other words, by utilizing the swinging motion of normal work, the detection range can be expanded without the worker having to perform any additional operations.

However, when the operating rod 12 swings back and forth during brush cutting, the Doppler signal output by the Doppler sensor 1A mounted on the main body 11 contains noise caused by the movement of the Doppler sensor 1A in conjunction with the movement of the brush cutter 10. This noise occurs in synchronization with the movement of the brush cutter 10 during brush cutting, so the movement of the brush cutter 10 during brush cutting is detected by the motion detection sensor 1A1, and the noise in the Doppler sensor 1A associated with the movement of the brush cutter 10 is removed based on the output of the motion detection sensor 1A1.

The processing device 1B of the safety device 1 may be installed on the brush cutter 10, like the Doppler sensor 1A, or, as shown in Figure 1, it may be installed in a location separate from the brush cutter 10, for example, on the worker M's clothing (such as work clothes or a harness). The output signal from the Doppler sensor 1A to the processing device 1B can be transmitted by wire or wirelessly.

The functions of the processing device 1B are explained using Figure 3. The output of the Doppler sensor 1A is amplified by the signal amplifier 20, and if necessary, undergoes fast Fourier transformation by the FFT calculation unit 21, before being input to the noise reduction unit 22. In contrast, the output of the motion detection sensor 1A1, which detects the movement of the brush cutter 10, is subjected to signal processing by the motion detection unit 21A, and the output is input to the noise reduction unit 22.

The motion detection unit 21A uses the output of the motion detection sensor 1A1 to analyze the period of the movement (swinging motion) of the brush cutter 10 when the operating stick 12 is swung left and right to perform work. The swinging motion of the brush cutter 10 is not constant, but the swinging motion that goes back and forth left and right has times when the motion stops as it reverses direction, and also has times when the motion accelerates midway through the swinging motion. By analyzing these changes in motion from the output of the motion detection sensor 1A1, the period of the swinging motion of the brush cutter 10 can be determined.

The noise removal unit 22 removes noise associated with the movement of the brush cutter 10 based on the output from the Doppler sensor 1A and the output from the movement detection unit 21A.

To explain an example of processing by the noise removal unit 22, the change over time in the sensor output of the Doppler sensor 1A is represented by a waveform like the one shown in Figure 4(a). This waveform combines frequencies derived from the speed of an approaching object and frequencies derived from the speed of the swing motion detected when the Doppler sensor 1A moves due to the swing motion of the brush cutter 10.

By dividing the waveform of the sensor output from this Doppler sensor 1A into arbitrary time intervals and performing frequency analysis for each interval using the FFT calculation unit 21, it is possible to separate the output level for each frequency as shown in Figure 4(b). By continuously performing this analysis while shifting the interval, it is possible to confirm the change in output level for each frequency band over time.

On the other hand, analysis of the output from the motion detection unit 21A makes it possible to determine the specific frequency bands associated with the non-constant period of the swing motion of the brush cutter 10. As shown in Figure 4(c), by removing the time change in the specific frequency bands caused by the swing motion from the time change in the output level for each frequency in the sensor output of the Doppler sensor 1A, it is possible to remove noise associated with the movement of the brush cutter 10 from the sensor output of the Doppler sensor 1A.

The output signal from which noise has been removed by the noise removal unit 22 is subjected to a determination process by the approach determination unit 23 to determine whether or not an object approaching the brush cutter 10 is present within the detection range of the Doppler sensor 1A. If it is determined that an approaching object is present within the detection range, a determination output is sent to the alarm device 1C, etc.

The alarm device 1C alerts the worker M performing brush cutting work of the presence of an approaching object, for example by sounding an alarm, vibrating, or displaying an illuminated light. Instead of the alarm device 1C, a control device may be provided that includes a drive control unit to which a judgment output is input, and that controls the driving of the brush cutting unit 13 to stop in response to the judgment output.

As explained above, the brush cutter safety device 1 according to an embodiment of the present invention has a Doppler sensor 1A located on the side of the brush cutter body 11 opposite the side to which the operating rod 12 is connected. This allows the detection range of the Doppler sensor 1A to be aimed behind the operator M, which would be in the operator M's blind spot, and effectively detects people or objects approaching the brush cutter 10 while in use. This ensures the safety of people and objects around the brush cutter 10 while in use.

Then, by removing noise from the Doppler sensor 1A that is associated with the movement of the brush cutter 10 based on the output of the motion detection sensor 1A1, it is possible to accurately detect an object approaching the brush cutter 10.

Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes design changes that do not deviate from the gist of the present invention. Furthermore, the above-mentioned embodiments can be combined by utilizing each other's technology, as long as there are no particular contradictions or problems with their purpose, configuration, etc.

1: Safety device, 1A: Doppler sensor, 1A1: Motion detection sensor,
1B: Processing device, 1C: Notification device,
10: brush cutter, 11: main body, 11A: bottom,
12: Operating rod, 12A: Handle,
13: brush cutting working part, 13A: rotating shaft,
20: signal amplifier, 21: FFT calculation unit, 21A: motion detection unit,
22: noise removal unit, 23: approach determination unit,
M: Worker

Claims (2)

A brush cutter comprising a main body, an operating rod connected at one end to the main body, and a brush cutting unit provided at the tip of the operating rod,
a safety device including a Doppler sensor for detecting an object approaching the brush cutter and a processing device for processing the output of the Doppler sensor;
The Doppler sensor is disposed on the side of the main body opposite to the side to which the operation stick is connected,
The brush cutter is provided with a motion detection sensor that detects the motion of the brush cutter,
The processing device performs processing to remove noise associated with the movement of the brush cutter from the output of the Doppler sensor based on the output of the motion detection sensor. A brush cutter with a safety device as described in claim 1, characterized in that the motion detection sensor is an acceleration sensor or a gyro sensor.