Patent Application
20240375197
The present application claims priority from Japanese Patent Application No. 2023-076623 filed on May 8, 2023, and the entire contents of which are hereby incorporated by reference.
The present invention relates to a power cutting machine.
A power cutting machine is a working machine configured to cut objects with a cutting blade by transmitting power of a motor such as an engine and an electric motor to the cutting blade to drive the cutting blade. Examples of the power cutting machine include a concrete cutter to cut concrete and asphalt, and a chain saw to cut wood and trees.
A conventional power cutting machine includes a main body including a motor such as an engine, an arm including a belt transmission mechanism configured to transmit power of the motor to the head end of the arm, and a working device including a cutting blade configured to be driven by the transmitted power on the head end of the arm. A handheld power cutting machine generally includes a rear handle provided on the rear side of the main body, and a front handle provided on the head side of the main body.
Depending on a type of power cutting machine, such as a concrete cutter, uses a cutting blade having a large inertial force for a hard object to cut. This sort of power cutting machine is known to include a brake controller provided in the main body to stop the rotation of the cutting blade immediately after the motor stops. See Japanese Patent Application Laid-Open No. 2011-251348. The entire contents of this disclosure are hereby incorporated by reference.
The present invention provides a power cutting machine including a main body including a motor, an arm connected to the main body at its base end and including a belt transmission mechanism configured to transmit drive power of the motor, and a working device connected to the head end of the arm and including a cutting blade configured to be rotated by power transmitted via the belt transmission mechanism. The working device includes a brake mechanism configured to be actuated when the cutting blade is subject to overload and apply a brake to the cutting blade.
When the cutting blade of the above-described power cutting machine is subject to a large load, for example, the cutting blade is caught in a cut during cutting work, the reaction force of the load acts on the cutting blade. Then, the cutting blade provided on the head end of the power cutting machine may be recoiled from the object, which is a phenomenon called as “kickback.” Especially in the case of a handheld power cutting machine, the kickback causes the cutting blade to approach the worker holding the handle. Therefore, it is necessary to take measures to prevent the kickback for safety work.
However, the brake mechanism in the above-described prior art is provided in a clutch drum of a centrifugal clutch which is directly connected to the driving shaft of the engine; therefore, the brake mechanism cannot be applied to electric products not requiring clutch drums and products even with clutch drums depending on their positions. In addition, the brake mechanism is actuated to stop the rotation of the cutting blade by detecting a throttle lever not operating after the engine stops; therefore, the brake mechanism is ineffective against the kickback which suddenly occurs during the cutting work, that is, during the operation of the motor.
The present invention is proposed to address these problems. Therefore, the objects of the invention are to make it possible to apply a brake mechanism regardless of a type of motor used in a power cutting machine and to take an effective measure against a kickback.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The same reference numbers in the different drawings indicate the same functional parts, and therefore repeated description for each of the drawings is omitted.
A power cutting machine 1 includes a main body 2, an arm 3, and a working device 4. The main body 2 includes a motor 10 such as an engine and an electric motor. The base end of the arm 3 is connected to the main body 2 and the head end of the arm 3 is connected to the working device 4. The arm 3 includes a belt transmission mechanism 20 configured to transmit drive power of the motor 10. The working device 4 includes a cutting blade 5 connected to the head end of the arm 3 and configured to be rotated by power transmitted via the belt transmission mechanism 20.
The output shaft of the motor 10 provided in the main body 2 is connected to a drive pulley 21 of the belt transmission mechanism 20 via a well-known clutch mechanism. The belt transmission mechanism 20 includes the drive pulley 21, a driven pulley 22 provided in the head end of the arm 3, and an endless belt 23 wound around these pulleys. A rotating shaft 5A of the cutting blade 5 is connected to the driven pulley 22 to transmit power of the motor 10 to the cutting blade 5 via the belt transmission mechanism 20.
The main body 2 includes a rear handle 11 and a front handle 12 as handle parts. The rear handle 11 is provided on the rear side of the main body 2, which is close to the operator's body when the operator uses the power cutting machine 1; an actuating lever 13 of the motor 10 is provided inside the rear handle 11. When the motor 10 is an engine, the actuating lever 13 is a throttle lever. The front handle 12 is provided on the head side of the main body 2 and extends along the direction orthogonal to the longitudinal direction of the arm 3. The working device 4 includes a protecting frame 14. The protecting frame 14 is fixed to the head end of the arm 3 and configured to cover the half circle of the cutting blade 5. This power cutting machine 1 includes a brake mechanism 30 provided in the working device 4 at the head end of the machine.
As illustrated in
The detection mechanism 31 includes a swing lever 31C configured to pivotally support a mass part 31A around a rotating shaft 31B.
Meanwhile, the tightening mechanism 32 includes a bending members 32B configured to bend along with the swing of the swing lever 31A and pull one end of the tightening belt 32A. In the initial state of the swing lever 31C illustrated in
One end of the tightening belt 32A of the tightening mechanism 32 is connected to the bending members 32B, and the other end is fixed to a fixed shaft 32E in the housing of the working device 4. By this means, the tightening belt 32A naturally tightens the outer circumference of the driven pulley 22 to apply a brake to the driven pulley 22 when the bending members 32B are bent to tighten the tightening belt 32A.
According to the power cutting machine 1 as described above, the brake mechanism 30 is actuated upon detection of a bounce when the working device 4 bounces up due to a kickback during cutting work and applies a brake to the driven pulley 22. Therefore, the power cutting machine 1 can stop the rotation or reduce the speed of the cutting blade 5 connected to the driven pulley 22 without stopping the motor 10. In addition, the brake mechanism 30 is provided in the working device 4 provided at the head end of the power cutting machine 1; therefore, it is possible to directly detect the working device 4 bouncing up due to the kickback and actuate the brake mechanism 30. Thus, the power cutting machine 1 can implement an effective measure against the kickback.
The power cutting machine 1 according to the invention has a structure in which the brake mechanism 30 is provided directly on the head end of the machine. This structure is applicable to an electrically-driven machine without a clutch drum in the main body 2 and an engine-driven machine not allowing a brake mechanism to be provided around a clutch drum depending on its position. Furthermore, the brake mechanism 30 is directly provided in the working device 4 in the present invention. There are no drive power transmission mechanisms such as an endless belt between the brake mechanism 30 and the cutting blade 5. Therefore, a delay in stopping the cutting blade 5 due to an intervening component is avoidable. In contrast, the brake mechanism 30 is provided on the base end of the arm 3 in the prior art. The brake mechanism 30 stops the rotation or reduces the speed of the cutting blade 5 by applying a brake to the driven pulley 22 provided in the head end of the arm 3. Therefore, a delay in stopping the cutting blade 5 due to the slip of the endless belt 23 wound around the arm 3 is unavoidable.
The brake mechanism 30 of the power cutting machine 1 is not limited to the above-described mechanism including the detection mechanism 31 and the tightening mechanism 32. As another example illustrated in
In this case, when the cutting blade 5 is subject to overload, for example, the cutting blade 5 is caught in a cut, the torque limiter 33 works to shut off power transmitted to the cutting blade 5. By this means, the torque limiter 33 works to shut off power transmitted to the cutting blade 5 depending on an increase in overload which applies to the cutting blade 5 before a kickback occurs. Consequently, it is possible to prevent the kickback from occurring.
According to the invention having the above-described features, a power cutting machine can apply a brake to a cutting blade even though a motor is being driven; therefore, it is possible to effectively prevent a kickback during cutting work. In addition, a brake mechanism is provided in a working device bouncing up due to the kickback. Therefore, it is possible to actuate the brake mechanism upon detecting the working device bouncing up and to take an effective measure against the kickback. Also, it is applicable regardless of a type of motor in a main body.
As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and the design can be changed without departing from the scope of the present invention. In addition, the above-described embodiments can be combined by utilizing each other's technology as long as there is no particular contradiction or problem in the purpose and configuration.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-076623 | May 2023 | JP | national |
