Disc grinder

Abstract

Reduces the risk of the rotating tip tool coming into contact with an unintended object. [Solution] The disc grinder 1 comprises a grinding disc 2 for processing a workpiece, a motor 9 for rotating the grinding disc 2, a controller 10 for controlling the motor 9, and a sensor 7 for detecting an object within a predetermined range from the grinding disc 2. The controller 10 controls the motor 9 based on the detection result of the sensor 7.

Description

Technical Field

[0001] The present invention relates to a disk grinder which is a portable tool.

Background Art

[0002] FIG. 8 is a perspective view showing the configuration of a conventional disk grinder 101 disclosed in Non-Patent Document 1. The disk grinder 101 includes a polishing disk 102, a grip 103, and a switch 104. When the switch 104 is turned on, a motor (not shown) rotates the polishing disk 102. By pressing the rotating polishing disk 102 against the workpiece, the workpiece can be grinded or polished.

[0003] When using the disk grinder 101, in order to confirm that the polishing disk 102 is properly attached, it is necessary to perform a test run before the grinding operation. In the test run, the operator drives the motor to rotate the polishing disk 102 while confirming that there are no people or objects in front of the polishing disk 102.

[0004] When performing a grinding operation, the operator checks the positional relationship between the workpiece and the polishing disk 102 and presses the rotating polishing disk 102 against the workpiece with an arbitrarily appropriate pressing pressure.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

[0006] In conventional disc grinders 101, if a person unexpectedly steps in front of the rotating grinding disc 102 during a trial run, the operator must quickly change the orientation of the grinding disc 102 or switch off the disc grinder 101. Similarly, if the grinding disc 102 detaches from the workpiece due to the operator's posture changing or a kickback, the operator must quickly change the orientation of the grinding disc 102 or switch off the disc grinder 101. Thus, conventional disc grinders 101 have the disadvantage of not adequately ensuring safety, as the only way to deal with situations where a person unexpectedly comes into contact with the rotating grinding disc 102 is through the operator's quick reaction.

[0007] The present invention has been made in view of the above problems, and aims to reduce the risk of a rotating tip tool coming into contact with an unintended object. [Means for solving the problem]

[0008] To solve the above problems, the disc grinder according to the present invention comprises an end tool for processing a workpiece, a motor for rotating the end tool, a controller for controlling the motor, and a sensor for detecting an object within a predetermined range from the end tool, wherein the controller controls the motor based on the detection result of the sensor.

[0009] In the disc grinder according to the present invention, when the operating mode of the disc grinder is the trial run mode, it is preferable that the controller drives the motor when the sensor does not detect an object within the predetermined range.

[0010] In the disc grinder according to the present invention, when the operating mode of the disc grinder is the work mode, it is preferable that the controller drives the motor when the sensor detects an object within the predetermined range. [Effects of the Invention]

[0011] According to the present invention, the risk of a rotating tip tool coming into contact with an unintended object can be reduced. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view showing the configuration of a disc grinder according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing an example of a circuit configuration for driving a motor. [Figure 3] This is a schematic diagram showing another example of a circuit configuration for driving a motor. [Figure 4] This is a flowchart showing the motor control procedure. [Figure 5] This is an explanatory diagram illustrating an example of an accident involving a disc grinder. [Figure 6] This is an explanatory diagram showing other examples of accidents involving disc grinders. [Figure 7] This is a side view showing an example of the sensor's detection range. [Figure 8] This is a perspective view showing the configuration of a conventional disc grinder. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below, and various modifications are possible without departing from its spirit.

[0014] (Overall structure) Figs. 1(a) and (b) are perspective views showing the configuration of a disk grinder 1 according to an embodiment of the present invention. The disk grinder 1 is a hand-held power tool and includes a polishing disk 2, a motor, a main grip 3, a sub-grip 4, a paddle switch 5, an operation mode changeover switch 6, and a sensor 7.

[0015] The polishing disk 2 is a tip tool for processing a workpiece and is provided at the tip of the disk grinder 1. The motor for rotating the polishing disk 2 is a rotational power source such as an electric or pneumatic fluid machine and is built into the main body of the disk grinder 1. An operator performs a work of grinding or polishing the workpiece by pressing the rotating polishing disk 2 against the workpiece.

[0016] The main grip 3 is a grip held by the right hand of the operator and extends in front of the polishing disk 2 as viewed from the operator. The sub-grip 4 is a grip held by the left hand of the operator and extends to the left of the polishing disk 2 as viewed from the operator. That is, the operator uses the disk grinder 1 while holding the main grip 3 and the sub-grip 4 with the right hand and the left hand, respectively.

[0017] When the polishing disk 2 is small (generally less than 100 mm in diameter), the sub-grip 4 may be omitted.

[0018] The paddle switch 5 is provided on the main grip 3 and is pressed when the right hand holds the main grip 3. In the present embodiment, the paddle switch 5 is provided at the lower part of the main grip 3 and is pressed by the index finger of the right hand when the right hand holds the main grip 3.

[0019] The operation mode changeover switch 6 is a switch for switching the operation mode of the disk grinder 1. The operation modes include a test run mode and a work mode, and the operator can select the test run mode or the work mode by operating the operation mode changeover switch 6.

[0020] The sensor 7 is provided above the polishing disk 2 and detects an object within a predetermined range from the polishing disk 2. The sensor 7 is not particularly limited as long as it can detect an object, and for example, it can be composed of a photoelectric sensor or an ultrasonic sensor. The predetermined range is set to a range where there is a risk of contact with the object when there is an object other than the work such as a human body, or a range where the work usually exists in the cutting operation.

[0021] Inside the housing above the polishing disk 2, a motor for rotating the polishing disk 2 and a controller for controlling the motor are built in. Only the controller may be built in another housing and connected to this housing by wiring. The motor is a rotational power source by an electric motor or a pneumatic fluid machine. The controller controls the motor based on the detection result of the sensor 7. The controller may be realized hardware-wise by a logic circuit or the like, or may be realized software-wise using a CPU (Central Processing Unit).

[0022] Figure 2 is a schematic diagram showing an example of a circuit configuration for driving a motor. In Figure 2, the motor 9 is a universal motor and is supplied with power from the power source 8. The sensor 7 detects an object within a predetermined range from the polishing disk 2 and outputs a detection signal indicating the detection result to the controller 10. The controller 10 controls the motor 9 based on the detection result of the sensor 7.

[0023] Figure 3 is a schematic diagram showing another example of a circuit configuration for driving a motor. In Figure 3, the motor 9 is a synchronous motor or an induction motor under inverter control, and the power supply is controlled by an inverter circuit 11 provided between the power source 8 and the motor 9. The sensor 7 detects an object within a predetermined range from the polishing disk 2 and outputs a detection signal indicating the detection result to the controller 10. The controller 10 indirectly controls the motor 9 by controlling the inverter circuit 11 based on the detection result of the sensor 7.

[0024] (Control of the motor) The motor control is described below. The controller 10 performs two types of control on the motor depending on the operating mode of the disc grinder 1. Specifically, when the operating mode of the disc grinder 1 is the trial run mode, the controller 10 drives the motor if the sensor 7 does not detect an object within a predetermined range. Also, when the operating mode of the disc grinder 1 is the work mode, the controller 10 drives the motor if the sensor 7 detects an object within a predetermined range.

[0025] Figure 4 is a flowchart showing the motor control procedure.

[0026] In step S1, the operator attaches the polishing disc 2, which is the tip tool, to the disc grinder 1. If the polishing disc 2 is already attached, step S1 is omitted.

[0027] In step S2, the operator connects the disc grinder 1 to the power supply.

[0028] In step S3, the operator operates the operation mode selector switch 6 to select the operation mode of the disc grinder 1.

[0029] If the trial run mode is selected ("1" in step S3), the process proceeds to step S4 and sensor 7 is activated.

[0030] Subsequently, in step S5, when the operator grasps the main grip 3 and the paddle switch 5 is turned ON, the controller 10 drives the motor (step S7) if the sensor 7 does not detect an object within a predetermined range (NO in step S6). In other words, the controller 10 does not drive the motor if the sensor 7 detects an object within a predetermined range (YES in step S6). Also, after the motor has been driven, if the sensor 7 detects an object within a predetermined range (YES in step S8), the controller 10 stops the motor (step S9).

[0031] If the motor is running idle for a predetermined time (3 minutes if a new polishing disc 2 is installed at the start of use, or 1 minute if a polishing disc 2 is already installed at the start of use) (if "YES" is selected in step S10), the operator turns off the paddle switch 5 (step S11) and ends the test run.

[0032] Thus, when the disc grinder 1 is in trial operation mode, the controller 10 drives the motor if the sensor 7 does not detect an object within a predetermined range. This prevents accidents such as a person unexpectedly standing in front of the grinding disc 2 and the rotating grinding disc 2 coming into contact with the person, as shown in Figure 5.

[0033] Returning to Figure 4, if the work mode is selected as the operating mode of the disc grinder 1 (2 in step S3), the process proceeds to step S12 and the sensor 7 is activated.

[0034] Subsequently, in step S13, when the operator grasps the main grip 3 and the paddle switch 5 is turned ON, the controller 10 drives the motor (step S15) if the sensor 7 detects an object within a predetermined range (YES in step S14). In other words, the controller 10 does not drive the motor if the sensor 7 does not detect an object within a predetermined range (NO in step S14). Also, after the motor has been driven, if the sensor 7 no longer detects an object within a predetermined range (NO in step S16), the controller 10 stops the motor (step S17).

[0035] Thus, when the disc grinder 1 is in work mode, the controller 10 drives the motor when the sensor 7 detects an object within a predetermined range. This prevents accidents such as the rotating grinding disc 2 coming into contact with a person or other object if the disc grinder 1 unexpectedly separates from the workpiece due to the operator's posture changing or rebound due to a kickback phenomenon, as shown in Figures 6(a) and (b).

[0036] (Detection range) Figure 7 is a side view showing an example of the detection range of sensor 7. In Figure 7, sensor 7 is a photoelectric sensor that can measure the distance to an object using an infrared laser. If d is the diameter of the polishing disc 2, D1 is the height difference between the lower limit of the detection range and the bottom surface of the polishing disc 2, D2 is the height difference between the upper limit of the detection range and the surface of the polishing disc 2, and θ is the angle between the bottom surface of the polishing disc 2 and the infrared laser from sensor 7, 8d / 9≦D1 <d 3d / 50≦D2 <d / 10 110°<θ<115° It is preferable that this be the case.

[0037] Furthermore, the detection range of the sensor 7 may be set differently depending on the operating mode of the disc grinder 1. For example, if the operating mode of the disc grinder 1 is the trial run mode, the detection range of the sensor 7 may be set to the range where there is a risk of contact with an object other than the workpiece, such as a person's body. Alternatively, if the operating mode of the disc grinder 1 is the work mode, the detection range of the sensor 7 may be set to the range where the workpiece is normally located during cutting.

[0038] (Summary) As described above, the disc grinder 1 according to this embodiment is equipped with a sensor 7 that detects objects within a predetermined range from the polishing disc 2, and the controller 10 that controls the motor controls the motor based on the detection result of the sensor 7. This prevents accidents in the trial run mode, such as when a person or other object unexpectedly steps in front of the polishing disc 2 and the rotating polishing disc 2 comes into contact with the person or object. Furthermore, in the work mode, it prevents accidents in which the rotating polishing disc 2 comes into contact with a person or object if the disc grinder 1 unexpectedly moves away from the workpiece due to a change in the operator's posture or a rebound due to a kickback phenomenon. Thus, the risk of the rotating polishing disc 2 coming into contact with an unintended object can be reduced.

[0039] (Additional notes) The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Forms obtained by appropriately combining the technical means disclosed in the embodiments are also included in the technical scope of the present invention.

[0040] The disc grinder 1 according to the above embodiment is equipped with a grinding disc 2 as an end tool for cutting or polishing a workpiece, but the end tool is not limited to this. For example, the disc grinder 1 may be equipped with an industrial grinding wheel for cutting a workpiece as an end tool.

[0041] Furthermore, in the above embodiment, one sensor 7 was provided to detect objects near the front of the polishing disc 2, but the present invention is not limited to this. Multiple sensors 7 may be provided to detect objects near the front and left and right of the polishing disc 2. [Explanation of Symbols]

[0042] 1. Angle grinder 2. Polishing disc (tip tool) 3 Main Grip 4 Sub-grips 5 Paddle Switches 6. Operation mode selector switch 7 Sensors 8 Power 9 Motors 10 Controllers 11. Inverter Circuit

Claims

1. Advanced tools for machining workpieces, A motor for rotating the aforementioned tip tool, A controller for controlling the motor, A sensor that detects objects within a predetermined range from the aforementioned tip tool, Equipped with, The disc grinder is characterized in that the controller controls the motor based on the detection result of the sensor.

2. If the operating mode of the disc grinder is in trial mode, The disc grinder according to claim 1, characterized in that the controller drives the motor when the sensor does not detect an object within the predetermined range.

3. When the operating mode of the disc grinder is set to work mode, The disc grinder according to claim 1 or 2, characterized in that the controller drives the motor when the sensor detects an object within the predetermined range.

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