Core drill device

Abstract

To provide a large-diameter core bit that cuts at an accurate position.SOLUTION: A core drill device includes: an output shaft to which a core bit is attached; a feed mechanism for relatively displacing the output shaft to an object to be cut by the core bit; a drill motor for driving the output shaft; and a drill motor control part for controlling the voltage value and / or the current value of the drill motor. The drill motor control part can select between a normal rotation mode in which a drill normal rotation button 41 is pressed and the voltage and / or the current values are controlled to drive the output shaft at a predetermined normal rotation speed, and a low-speed rotation mode in which a cutting assist button 45 is pressed and the voltage and / or the current values are controlled to drive the output shaft at a predetermined low-speed rotation speed that is lower than the normal rotation speed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a core drill device for cutting a concrete structure with a core bit. [Background technology]

[0002] A core drill device that rotates a cylindrical core bit at high speed while pressing it against a concrete structure to cut and core the concrete structure is known, for example, from Japanese Patent Laid-Open Publication No. 2009-61749 (Patent Document 1). The core drill device of Patent Document 1 comprises a base, a support erected on the base, a core drill head attached to the support, a drill motor supported by the core drill head, a core bit attached to the core drill head and driven to rotate by the drill motor, and a feed mechanism that changes the relative position of the core drill head with respect to the base and the support. Drill motors are generally AC motors, and only the rated voltage is applied to drive the drill motor. For this reason, the rotational speed of the drill motor is determined as a rated rotational speed (unit: [min -1 ] (also called [rpm]) or angular velocity [° / sec]), and there is no electrical control of the rotational speed. The core drill head has a main switch that turns the power to the drill motor on and off, but does not have any switches or controls that electrically adjust the rotational speed of the drill motor by increasing or decreasing it. When coring, the core bit is rotated at the rated rotational speed while separated from the concrete surface, and the feed mechanism is used to press the rotating core bit closer to the concrete surface, forming a kerf of the same shape and size as the core bit, a process known as cutting. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-61749 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have discovered that the above-described conventional core drilling device requires further improvement. Specifically, while a core drilling device is typically fixed to a concrete surface with only one anchor bolt, when a larger-diameter core bit is attached to the core drilling device and used to drill a core, the circumferential speed (e.g., m / min) of the large-diameter core bit is too high at the normal rated rotational speed. This can cause the cutting edge of the rotating large-diameter core bit to be repelled by the concrete surface during cutting, or undesirable vibrations to occur in the core drill head, including the core bit and drill motor. This can lead to concerns about unstable fixation of the core drilling device, resulting in wider kerfs, deviations from the desired position, or deviations in the direction of the coring hole, which can interfere with cutting and ultimately result in inaccurate core drilling. These concerns are exacerbated by factors such as roughened concrete surfaces, uneven concrete surfaces with protruding coarse aggregate, and inclined concrete surfaces that cause the cutting edge to contact one side of the concrete. Increasing the number of anchor bolts is not desirable in terms of labor costs and damage to the concrete surface.

[0005] In view of the above-mentioned circumstances, the present invention aims to provide a core drill device that can perform accurate cutting more easily than conventional methods, even with a large-diameter core bit. [Means for solving the problem]

[0006] For this purpose, the core drill device according to the present invention comprises an output shaft to which a core bit is attached, a feed mechanism for displacing the output shaft relative to the object to be cut by the core bit, a drill motor for driving the output shaft, and a drill motor control unit for controlling the voltage and / or current of the drill motor, and the drill motor control unit is capable of selecting between a normal rotation mode in which the voltage and / or current are controlled to drive the output shaft at a predetermined normal rotation speed, and a low-speed rotation mode in which the voltage and / or current are controlled to drive the output shaft at a predetermined low-speed rotation speed that is lower than the normal rotation speed.

[0007] According to the present invention, when cutting with a large-diameter core bit, it is advisable to select the low-speed rotation mode. This makes the peripheral speed [m / min] of the core bit slower than conventional methods, allowing the core bit to cut smoothly into the concrete surface without being repelled or vibrating. When cutting with a small-diameter core bit, it is advisable to select the normal rotation mode. The predetermined normal rotation speed in the normal rotation mode may be the rated rotation speed of the drill motor. The predetermined low rotation speed in the low-speed rotation mode may be in the range of 55% to 90% of the rated rotation speed, and preferably in the range of 55% to 75% of the rated rotation speed.

[0008] The drill motor of the present invention is not particularly limited in structure or characteristics. The drill motor of the present invention is preferably an AC motor, and more preferably an AC motor supplied with power from a commercial power source. The characteristics of the drill motor of the present invention, such as the voltage-torque relationship and the rotation speed-torque relationship, are not particularly limited, and may be a positive correlation such as a direct proportionality, a negative correlation such as an inverse proportionality, or other characteristic curves. In one aspect of the present invention, the drill motor outputs a torque in low-speed rotation mode that is smaller than the torque of the drill motor driven in normal rotation mode. According to this aspect, when the core bit is driven into the concrete surface in low-speed rotation mode, the core bit is less likely to be repelled by the concrete surface, resulting in smoother cutting.

[0009] In one aspect of the present invention, the drill motor control unit has an interface unit for selecting a low-speed rotation mode, and when the low-speed rotation mode is selected via the interface unit while the output shaft is stopped, the low-speed rotation mode is executed. According to this aspect, the low-speed rotation mode can be selected during cutting. An example of the interface unit is an operation unit including a control operated by a core drilling operator or a touch panel. Another example of the interface unit may be an input port for inputting a signal from an external device.

[0010] In one aspect of the present invention, when the rotation speed of the output shaft falls below a predetermined minimum rotation speed that is even lower than the predetermined low-speed rotation speed while the drill motor control unit is operating in the low-speed rotation mode, the drill motor control unit stops the low-speed rotation mode and controls the voltage and / or current of the drill motor to zero. According to this aspect, it is possible to prevent the rotation of the drill motor from locking and an overcurrent from flowing.

[0011] The feed mechanism of the present invention may be manual, such as by a handle, or may be an automatic feed mechanism for efficient core drilling in normal rotation mode. The automatic feed mechanism includes a feed motor as a power source and a feed control unit that controls the feed amount. In one aspect of the present invention, the feed mechanism includes a feed motor and a feed control unit that controls the feed motor to adjust the feed amount corresponding to the movement of the output shaft toward the workpiece. The feed control unit monitors the current value flowing through the drill motor and adjusts the feed amount so that the current value flowing through the drill motor is within a predetermined range during normal rotation mode. If the current value flowing through the drill motor exceeds the predetermined range, the feed control unit sets the feed amount to zero or reverses the feed amount to move the output shaft away from the core bit. This aspect prevents the drill motor from locking and excessive current from flowing through the drill motor when the automatic feed mechanism controls the feed amount of the core bit to core a concrete structure. While the feed mechanism is preferably operated manually during low-speed rotation mode, this is not limited to manual operation. [Effects of the Invention]

[0012] As described above, the present invention allows for smoother cutting than conventional methods, improving the efficiency of large-diameter core drilling (those with an outer diameter of 200 mm or more and 500 mm or less or 600 mm or less) and shortening the work time. Furthermore, it is no longer necessary to assign skilled personnel who are skilled in operating the core bit device when drilling large-diameter cores, which contributes to labor savings. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a side view showing an embodiment of the present invention. [Figure 2] FIG. 10 is a front view showing another embodiment of the present invention. [Figure 3] FIG. 10 is a diagram showing an interface unit provided in another embodiment. [Figure 4] 1 is a graph showing the normal rotation mode and the low-speed rotation mode of Examples 1 to 5 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a side view showing a core drill device according to one embodiment of the present invention. The core drill device 10 includes a base 11, a support 12 erected on the base 11, a core drill head 13 slidably supported on the support 12, a core bit 14 detachably attached to the core drill head 13, and a drill motor 15 supported on the core drill head 13 and driving the core bit 14.

[0015] The base 11 is placed on the concrete surface S (the object to be cut) that will be the object of core drilling. The base 11 is fixed to the concrete surface S with anchor bolts 16, and the horizontality or parallelism to the concrete surface S is appropriately adjusted with level adjustment bolts 26. This allows the support 12 to be held in a position perpendicular to the concrete surface S.

[0016] A rack 12b is provided on the support 12, a pinion (not shown) that meshes with the rack is provided inside the core drill head 13, and a handle 17 for driving the pinion is provided on the side of the core drill head 13. When the core drilling operator rotates the handle 17 forward or backward, the core drill head 13 slides along the support 12, moving closer to or away from the concrete surface S (feed amount), and pressing the cutting tool 18 at the tip of the core bit 14 against or away from the concrete surface S. In other words, the handle 17 and other components constitute the feed mechanism of the core drill head 13. The feed amount of the core drill head 13 is proportional to the number of rotations of the handle central axis input to the handle 17 (handle operation amount).

[0017] The core drill head 13 has an output shaft 19 that protrudes downward. A drill motor 15 is attached to the upper side of the core drill head 13, opposite the output shaft 19. Output rotation output from a motor shaft (not shown) of the drill motor 15 is transmitted to the output shaft 19 via a gear mechanism (not shown) provided inside the core drill head 13. The upper end of a cylindrical core bit 14 is detachably connected to the output shaft 19. A water supply port 27 is provided on the side of the core drill head 13 to allow for wet coring work.

[0018] The core bit 14 can be selected from a variety of outer diameters. The cutting tool 18 is a diamond tip arranged circumferentially around the lower end circle of the core bit 14. To prevent mud from scattering from the cutting tool 18, which rotates at high speed, an annular cover 22 is installed at the bottom of the core bit 14. The cover 22 is supported on the base 11 by a support 11c attached to the base 11.

[0019] The core drill head 13 incorporates an electric circuit 21 that applies a voltage to the drill motor 15 to supply power, and a drill motor control unit 23 that controls this voltage. The electric circuit 21 is connected to an external power source (not shown) by a power cord 25. The electric circuit 21 also has a breaker that cuts off the power supply to the drill motor 15 when the current flowing through the drill motor 15 exceeds a predetermined value.

[0020] The core drill head 13 further includes an interface unit 24. The interface unit 24 is installed, for example, on the side of the drill motor 15, and includes a main switch for turning on and off the power supply to the drill motor 15, a normal rotation button and a cutting assist button for adjusting the rotation speed of the motor shaft of the drill motor 15, and other controls.

[0021] The drill motor 15 is an AC motor. Regarding the characteristics of the powering operation of the drill motor 15, there is a positive correlation between the motor torque and the motor rotation speed. When the drill motor 15 is an AC commutator motor, the drill motor control unit 23 adjusts the rotation speed of the motor shaft of the drill motor 15 by phase control, which changes the waveform of the AC voltage flowing through the drill motor 15 using a switching element, or by PMW control (inverter), which changes the overall wave height of the waveform. An example of such phase control is a triac, which cuts off (sets to zero) part of the waveform. In this way, the drill motor control unit 23 controls the rotation speed of the drill motor 15 by changing the effective value of the voltage applied to the drill motor 15.

[0022] For Examples 1 to 5 of this embodiment, the relationship between the voltage applied to drill motor 15 and the no-load rotation speed of output shaft 19 was examined. In Example 1, the model SPX-400A3 Pro manufactured by Consec Corporation was used, and the speed change position was LOW, and the no-load rated speed at the no-load rated voltage was 300 [min -1 ]. In Example 2, the model SPE-400A3 Pro manufactured by Consec Corporation was used, and the speed change position was LOW, and the no-load rated speed at the no-load rated voltage was 300 [min -1 ]. In Example 3, the model SPO-400A3 manufactured by Consec Corporation was used, and the speed change position was LOW, and the no-load rated speed at the no-load rated voltage was 300 [min -1 ]. In Example 4, the motor is a model SPM-404A3 manufactured by Consec Corporation, and the speed change position is LOW, and the no-load rated speed at the no-load rated voltage is 260 [min-1 ]. In Example 5, the model SPM-404A3 manufactured by Consec Corporation was used, the speed change position was MID, and the no-load rated speed at the no-load rated voltage was 700 [min -1 ]. Regarding the no-load power running of Examples 1 to 5, the rated voltage [V] of the drill motor 15 is set to 100% and the rated rotation speed [min -1 ] is 100% (normal rotation mode) and when these applied voltages and rotation speeds are reduced below the rated values ​​(low-speed rotation mode), as shown in Table 1 and Figure 4. In Table 1, the horizontal axis represents the reduction value (%) relative to the rated voltage [V], and the vertical axis represents the rated rotation speed [min -1 ] is the reduction value in %. [Table 1]

[0023] 4, it can be seen that in Examples 1 to 5, when a voltage of 60% or less and 40% or more of the rated voltage is applied to drill motor 15, output shaft 19 rotates at a low speed in the range of approximately 90% or less and 55% or more of the rated voltage. Specifically, as shown by the shaded boxes in Table 1, when the rated voltage is 60%, output shaft 19 rotates at a low speed of 88.5% to 91.3% (approximately 90%), when the rated voltage is 50%, output shaft 19 rotates at a low speed of 75.1% to 78.1% (approximately 75%), and when the rated voltage is 40%, output shaft 19 rotates at a low speed of 52.4% to 58.8% (approximately 55%).

[0024] A typical small-diameter core drilling operation will now be described. As a preliminary step, the core drilling operator fixes the base 11 to the concrete surface S, connects the power cord 25 to an external power source such as a commercial power supply, attaches a core bit 14 of the desired diameter to the output shaft 19, and rotates the handle 17 to position the core drill head 13 in the appropriate feed position so that the cutting tool 18 at the tip of the core bit 14 is close to but away from the concrete surface S. The operator then turns on the main switch of the interface unit 24. This puts the core drill device 10 into a state where it is ready to perform the coring operation.

[0025] Next, the operator presses the normal rotation button on the interface unit 24. When the normal rotation button is pressed, the rated voltage is applied to the drill motor 15 (normal rotation mode), and the output shaft 19 and core bit 14, which had been stopped, begin to rotate and reach the rated rotation speed. Once the rotation of the core bit 14 has stabilized so that it is rotating at a constant speed, the operator can turn the handle 17 forward at an appropriate speed. This causes the cutting tool 18 to come into contact with the concrete surface S, and the core bit 14 begins cutting into the concrete surface S.

[0026] The rated rotation speed of the output shaft 19 is predetermined, for example, about 250 to 700 [min -1 ] range. The outer diameter φ of a typical wet diamond core bit used in coring work is in the range of φ14.5 to φ120 [mm]. Therefore, the peripheral speed of a φ120 core bit is in the range of approximately 200 to 250 [m / min], even when a speed change mechanism (not shown) attached to the core drill head 13 is operated. The peripheral speed is the speed at which the outer diameter of the core bit 14 moves in the circumferential direction, and the larger the outer diameter of the core bit 14, that is, by connecting and fixing a large-diameter core bit with a diameter more than twice that of φ120 to the output shaft 19, the faster the peripheral speed becomes.

[0027] The speed change mechanism provided in the core drill head 13 of this embodiment allows the operator to select the rotational speed of the output shaft 19 from a plurality of speed stages, such as first speed, second speed, third speed, etc., or low speed (LOW), medium speed (MID), and high speed (HI). If the outer diameter of the core bit 14 is large, φ160 [mm] or more, the operator should select the low speed (LOW) stage. If the outer diameter of the core bit 14 is small, φ77 [mm] or less, the operator should select the high speed (HI) stage. If the outer diameter of the core bit 14 is between these two, the operator should select the medium speed (MID).

[0028] For example, when a large diameter core bit having an outer diameter φ in the range of φ200 to φ600 [mm] is rotated at the above-mentioned rated rotational speed, the peripheral speed reaches a range of approximately 157 to 1319 [m / min]. (Formula 1) 250×0.2×π=157 (Formula 2) 700×0.6×π=1319 Within this range of 157 to 1319 m / min, in the region exceeding 250 m / min, the peripheral speed is too fast, causing the fast-moving blade 18 to be repelled by the concrete surface S, making it difficult to make smooth and proper cuts.

[0029] Therefore, when performing a core drilling operation with a larger diameter than usual, the operator presses the cutting assist button on the interface unit 24 instead of the normal rotation button. When the cutting assist button is pressed, a low voltage within the range of 60% to 40% of the rated voltage is applied to the drill motor 15 in the above-mentioned preparation state (low-speed rotation mode), and the output shaft 19 and core bit 14, which had been stopped, start rotating at a rotation speed (hereinafter referred to as the cutting rotation speed) lower than the above-mentioned rated rotation speed. The cutting rotation speed, although it depends on the outer diameter of the core bit 14, is in the range of 55% to 90% of the rated rotation speed (138 to 630 [min -1 ]) is included. (Formula 3) 250×0.55=138 (Formula 4) 700×0.9=630

[0030] At a rotational speed exceeding 90% of the rated speed, the peripheral speed [m / min] of the large-diameter core bit 14 does not slow down significantly, and the cutting problem described above is not resolved. At a rotational speed below 55% of the rated speed, the torque of the core bit 14 becomes small, resulting in insufficient torque and making it unsuitable for cutting.

[0031] In the low-speed rotation mode of this embodiment, the peripheral speed of the large-diameter core bit 14 is slower than in the past, so the core bit 14 experiences less recoil from the concrete surface S when cutting begins, making it less likely to shift position and allowing cutting at an accurate position to prevent the circumferential groove from widening. Furthermore, cutting with the large-diameter core bit can be performed smoothly, eliminating the need for skilled personnel for large-diameter core extraction work, contributing to labor savings and improved work efficiency.

[0032] The low-speed rotation mode of this embodiment is selected by the turning assist button when the output shaft 19 is stopped from rotating, and is used for turning, and the rotation speed of the output shaft 19 increases from 0 to the turning rotation speed. Therefore, the low-speed rotation mode of this embodiment can also be called a low-speed rotation mode for turning.

[0033] According to the cutting assist button of this embodiment, when cutting begins, the peripheral speed of the large-diameter core bit 14 can be reduced (in the range of 55% to 90%) compared to the normal rotation mode. For example, in a large-diameter core bit 14 where the cutting assist button is set to 75% of the rated rotation speed and the normal rotation button reaches a peripheral speed of 360 m / min, pressing the cutting assist button reduces the peripheral speed to 225 m / min, or 75%. Furthermore, when the rotating blade 18 is brought close to and pressed against the concrete surface S, the blade 18 is not repelled by the concrete surface S.

[0034] Furthermore, the cutting assist button (low-speed rotation mode) of this embodiment not only allows the peripheral speed of the core bit 14 to be slower than in normal rotation mode, but also allows the torque of the core bit 14 to be slower than in normal rotation mode. Therefore, when the rotating blade 18 is brought close to and pressed against the concrete surface S, the blade 18 is not repelled by the concrete surface. Furthermore, because the torque is small, the drill motor 15 is not overloaded during cutting, preventing motor burnout.

[0035] The cutting assist button of this embodiment can prevent vibration and misalignment of the core bit 14, even if the rotating blade 18 makes a one-sided contact when pressed against the concrete surface S due to an uneven or inclined surface of the concrete. During operation of the low-speed rotation mode (for cutting) by operating the cutting assist button, a speed change mechanism (not shown) attached to the core drill head 13 may be operated to adjust the peripheral speed to within a range of 200 to 250 m / min. When operating in the low-speed rotation mode by pressing the cutting assist button, it is recommended to set a slow speed, such as low speed (LOW), to a low-speed gear position of the speed change mechanism (not shown) installed inside the drill head 13.

[0036] Next, another embodiment of the present invention will be described. Fig. 2 is a front view showing another embodiment of the present invention. Fig. 3 is a diagram showing an interface section of the other embodiment. In this embodiment, an automatic feeder 30 is additionally attached to the embodiment shown in Fig. 1 described above. The automatic feeder 30 has a feed motor 31, a feed shaft 32, a feed control section 33, an interface section 34, a core drill device cord 35, and a power cord 36.

[0037] The automatic feed device 30 automatically controls the feed mechanism of the core drill head 13 described above, instead of the operator operating the handle 17. The automatic feed device 30 houses a feed motor 31, a feed shaft 32, and a feed control unit 33 in a substantially rectangular parallelepiped housing 37. The housing 37 is detachably attached to the side of the core drill head 13 by means of a stay or metal fittings, a screw fastening method, a one-touch method, or the like. At this time, an end portion (not shown) of the feed shaft 32 is connected to the feed mechanism inside the core drill head 13 and drives a pinion (not shown) of the feed mechanism. The feed motor 31 receives power from a power cord 36 and drives the feed shaft 32.

[0038] The feed control unit 33 executes automatic feeding of the core drill head 13 based on the operation of the interface unit 34 by the operator, and specifically controls the voltage, current, torque, rotation speed, or roughly speaking, output of the feed motor 31. Details will be described later.

[0039] The core drill device cord 35 is connected to the power cord 25 of the core drill head 13. This allows the interface unit 34 to be electrically connected to and communicate with the core drill head 13, and to operate and control the core drill head 13. The interface unit 34 has several controls, such as a drill normal rotation button 41, an automatic feed button 42, a drill torque + setting button 43, a drill torque - setting button 44, a cutting assist button 45, and a button for emergency stopping the rotation drive of the rotary shaft 19 and the automatic feed. The interface unit 34 is used to operate both the automatic feed device 30 and the core drill device 10.

[0040] The operation of the core drill device 10 shown in Figure 2 from the interface unit 34 shown in Figure 3 is basically the same as the operation of the core drill device 10 from the interface unit 24 shown in Figure 1 described above, but here we will provide a supplementary explanation of the on / off operation related to the automatic feed button 42.

[0041] First, we will explain the operation of drilling a normal small-diameter core. The core drilling worker performs the above-mentioned preliminary preparations. Next, the worker presses the normal drill rotation button 41 on the interface unit 34. When the normal drill rotation button 41 is pressed, the rated voltage is applied to the drill motor of the core drill head 13 (normal rotation mode), and the output shaft 19 and core bit 14, which had been stopped, begin to rotate and reach the rated rotation speed. Once the rotation of the core bit 14 stabilizes and rotates at a constant speed, the worker manually rotates the handle 17 to manually lower the core bit 14, bringing the rotating cutting tool 18 into contact with the concrete surface S. This causes the core bit 14 to begin cutting into the concrete surface S.

[0042] With the cutting tool 18 still in contact with the concrete surface S, the core bit 14 is manually lowered another 5 to 10 mm to complete the cut. Next, the operator can press the automatic feed button 42 to start automatic feed. Note that while the drill motor is rotating by pressing the normal drill rotation button 41 and / or automatic feed is operating by pressing the automatic feed button 42, indicators near each button will light up to indicate that the respective operation is in progress. To cancel each operation, press the respective button. In other words, the normal drill rotation button 41 is the main switch that turns the power to the drill motor on and off. The automatic feed button 42 is an on / off control.

[0043] If the torque of the drill motor (core bit 14) is to be increased, the drill torque + setting button 43 can be pressed. Alternatively, if the torque of the drill motor (core bit 14) is to be decreased, the drill torque - setting button 44 can be pressed.

[0044] The feed control unit 33 connected to the interface unit 34 monitors the current value flowing through the drill motor 15 of the core drill head 13, and executes automatic feed within a range where the current value is neither overloaded nor underloaded. If the drill motor is locked by forcibly pressing the core bit 14 against the concrete surface S, the feed control unit 33 cuts the current value of the drill motor to prevent the breaker from tripping.

[0045] When the normal rotation mode is executed by pressing the normal drill rotation button 41, the feed control unit 33 adjusts the feed rate of the output shaft 19 toward the concrete surface S so that the value of the current flowing through the drill motor 15 falls within an appropriate predetermined range, and if the value of the current flowing through the drill motor 15 rises above this predetermined range, the feed rate is set to 0 or the feed rate is reversed to move the output shaft 19 away from the concrete surface S. This makes it possible to prevent the drill motor from locking and excessive current from flowing through the drill motor.

[0046] Second, we will explain the operation of drilling a large diameter core. The core drilling worker performs the above-mentioned preliminary preparation. Next, the worker presses the cutting assist button 45 on the interface unit 34. In the above-mentioned preparation state, the output shaft 19 and core bit 14, which had been stopped, begin to rotate. Once the rotation of the core bit 14 stabilizes, rotating at a constant speed slower than the rated rotation speed, the worker operates the handle 17 to bring the cutting tool 18, which is rotating at a peripheral speed slower than normal, into contact with the concrete surface S. This causes the large diameter core bit 14 to begin cutting into the concrete surface S.

[0047] When the drill motor is rotating in low-speed rotation mode by pressing the cutting assist button 45 and / or when automatic feed is operating by pressing the automatic feed button 42, the indicators near each button will light up to indicate that the corresponding operation is in progress. To cancel each operation, simply press the corresponding button.

[0048] Even when the low-speed rotation mode is activated by pressing the cutting assist button 45, if you want to increase or decrease the torque of the drill motor (core bit 14), you can press the drill torque + setting button 43 to increase the drill torque or the drill torque - setting button 44 to decrease the drill torque. The torque in the low-speed rotation mode is smaller than the torque in the normal rotation mode described above. This embodiment allows for fine adjustment of the torque during cutting.

[0049] Once the operator confirms by sight or sound that the cutting is complete, he or she can press the cutting assist button 45 to cancel the low-speed rotation mode and automatically return to normal rotation mode, starting normal rotation mode. Then, the automatic feed button 42 can be pressed to start automatic feeding. This allows for a smooth transition from cutting to coring. The cutting is complete when the cutting tool 18 carves a circular groove in the concrete surface S with the same diameter as the core bit 14.

[0050] Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the illustrated embodiments within the same scope as the present invention or within an equivalent scope. For example, some components can be extracted from one embodiment described above, and other components can be extracted from another embodiment described above, and these extracted components can be combined. The core bit can be wet or dry. [Industrial Applicability]

[0051] The present invention is advantageously used on construction sites. [Explanation of symbols]

[0052] 10 core drill device; 12b rack of feed mechanism; 13 Core drill head (variable speed mechanism), 14 Core bit, 17 feed mechanism handle, 19 output shaft, 23 drill motor control unit, 30 automatic feed device, 24 interface unit, 33 feed control unit, 34 interface unit, 41 Drill normal rotation button (normal rotation mode selection / cancellation), 42 Automatic feed button (select / cancel automatic feed), 45 Turning assist button (select / cancel low speed rotation mode).

Claims

1. an output shaft to which a core bit is attached; a feed mechanism that displaces the output shaft relative to the cutting object of the core bit; a drill motor that drives the output shaft; a drill motor control unit that controls a voltage value and / or a current value of the drill motor, The drill motor control unit is capable of selecting between a normal rotation mode in which the voltage value and / or the current value are controlled so as to drive the output shaft at a predetermined normal rotation speed, and a low-speed rotation mode in which the voltage value and / or the current value are controlled so as to drive the output shaft at a predetermined low-speed rotation speed that is lower than the normal rotation speed.

2. The core drill device according to claim 1 , wherein the drill motor outputs a torque in the low-speed rotation mode that is smaller than a torque of the drill motor driven in the normal rotation mode.

3. 2. The core drill device according to claim 1, wherein the drill motor control unit has an interface unit for selecting the low-speed rotation mode, and when the low-speed rotation mode is selected via the interface unit while the rotation of the output shaft is stopped, the low-speed rotation mode is executed.

4. 2. The core drill device according to claim 1, wherein the drill motor control unit, when executing the low-speed rotation mode, if the rotation speed of the output shaft falls below a predetermined minimum rotation speed that is even lower than the predetermined low-speed rotation speed, stops the low-speed rotation mode and controls the voltage value and / or current value of the drill motor to zero.

5. the feed mechanism includes a feed motor and a feed control unit that controls the feed motor to adjust a feed amount corresponding to the approach movement of the relative displacement, The feed control unit monitoring a current value flowing through the drill motor; adjusting the feed amount of the output shaft toward the workpiece so that the value of the current flowing through the drill motor is within a predetermined range while the normal rotation mode is being executed; The core drill device according to claim 1, wherein when the current value flowing through the drill motor fluctuates above the predetermined range, the feed amount is set to 0 or the feed amount is reversed to move the output shaft away from the object to be cut by the core bit.

Images