A control method for preventing accidental firing of a nail gun

Abstract

The present application relates to a kind of control methods for preventing accidental trigger of nail gun, belong to the technical field of electric tool.The nail gun is provided with power-on key, mode selection key, trigger switch, first magnetic component is installed on the driving wheel and opposite first Hall sensor on the lifting mechanism fixed part, second magnetic component is installed on the touch arm and opposite second Hall sensor on the touch mechanism fixed part;Control circuit contains the controller chip of corresponding signal input end respectively connects power-on key, mode selection key, trigger switch signal output and first Hall sensor, second Hall sensor signal output, the control output end of controller chip is connected with the motor of driving lifting mechanism by drive circuit;Controller chip judges whether the trigger switch pressing time and Hall signal holding time is greater than predetermined length of time, identifies whether the touch signal is caused by abnormal factors such as vibration displacement, shields the accidental nail shooting caused thereby, and the result ensures the safety of nail shooting operation.

Description

Technical Field

[0001] This invention relates to the control of a nail gun, and more particularly to a control method for preventing accidental firing of a nail gun, belonging to the field of power tool technology. Background Technology

[0002] Electric pneumatic nail guns and similar fastener-driving tools use compressed air to power a piston in a cylinder, which in turn drives a firing pin to drive nails into the workpiece. These are commonly used tools in the construction and decoration industries. A typical structure is disclosed in Chinese patent document application number 202180025167.1, entitled "Powered Fastener Driver." During operation, pressing down the nose of the gun moves the striking arm, which in turn moves a magnet on the striking arm. This causes a Hall sensor on the gun body to send a strike signal to the control circuit board. Pressing the trigger then activates the control motor, which drives the lifting mechanism to move the firing pin from a temporarily locked, ready position, driving the piston to compress air until the firing pin disengages from the lifting mechanism and is suddenly released, striking the nails pushed from the nail magazine into the nail holder by the nail pusher, thus completing the nail-driving operation from the nose of the gun. When continuous firing is selected, holding down the trigger while pressing down the nose allows for continuous nail driving.

[0003] However, due to the non-linear characteristics of the sensing distance of magnets and Hall sensors, magnets can cause changes in the Hall sensor's readings over a wide range. Therefore, in practice, during high-speed nailing with a nail gun, vibrations can easily cause the Hall sensor to become oversensitive, switching back and forth between a signal within the sensor's sensing range (usually low level) and a signal outside the sensor's sensing range (usually high level). This generates a "false impact" signal, leading to accidental firing and posing a safety hazard, especially during continuous firing. For example, when nailing hard wood at high speed, the impact arm may vibrate and rebound, causing the Hall sensor to send a false impact signal to the control circuit board, resulting in a false nail firing due to unintended contact, causing harm. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a control method to prevent accidental firing of nail guns by effectively preventing interference factors such as rebound vibration from generating false triggering signals, thereby ensuring the safety of nailing operations.

[0005] To achieve the above objectives, the applicant, through repeated experiments and research, realized that the operation of a nail gun in single-shot mode involves first pressing down on the gun body, causing the nose and striking arm to retract, resulting in a low-to-high level strike signal from the Hall sensor, followed by pressing the trigger to fire the nail. After firing, the gun body is lifted to allow the striking arm to return to its forward position, and the trigger is released to fire again. In continuous-fire mode, the operation involves pressing the trigger, then pressing down on the gun body to retract the nose and striking arm, generating a strike signal to fire the nail. After firing, the gun body is lifted to allow the striking arm to return to its forward position; firing again is possible without releasing the trigger, simply by pressing down on the gun body. In continuous-fire mode, pressing the trigger causes the firing pin assembly to rise when the nose is pressed down, compressing the piston until it reaches the release position. The stored energy of the compressed gas is then converted into the kinetic energy of the firing pin, thus striking and firing the nail. Let the mass of the firing pin assembly be m1. During the release acceleration stroke L1, it reaches its maximum speed v1 after an acceleration time t1, then its kinetic energy is m1v1. According to the law of conservation of momentum, the nail gun with mass m2 will acquire a reverse momentum m1v1 and generate a reverse velocity v2 = m1v1 / m2, resulting in a vibration displacement distance L2 = v2 * t1. Since the Hall sensor is relatively fixed to the nail gun body, it will also cause displacement. Furthermore, the impact spring between the impact arm and the body will cause this displacement distance to be greater than L2 by L3. Once L3 exceeds the critical distance Lmax of the Hall sensor, because the magnet has exceeded the Hall sensor's sensing range, even if the impact arm is released from its depressed state, the Hall sensor will still output a high-level impact signal. As a result, the nail gun in continuous firing mode will continue firing due to misjudgment. However, research shows that... Figure 1 Compared to the regular touch signals shown under normal circumstances, Figure 2 The high-level "false touch" signals t1 and t2 caused by the vibration displacement shown not only have short durations themselves, but also short intervals with the normal touch signals, thus making them identifiable.

[0006] Based on this understanding, the basic technical solution of the control method for preventing accidental firing of a nail gun proposed in this invention is as follows: the nail gun contains a control circuit, and its body is equipped with an energy storage mechanism consisting of a cylinder and a piston, an impact mechanism consisting of a retractable impact arm in the nail holder, a nail-driving mechanism consisting of a firing pin connected to the piston and extending to the nail holder, a lifting mechanism consisting of a motor-driven wheel meshing with the firing pin, and a nail feeding mechanism consisting of a nail magazine installed on the side of the nail holder. The control panel of the machine body is equipped with a power button and a mode selection button, and a trigger switch is installed on the grip. The drive wheel is equipped with a first magnetic element that is opposite to the first Hall sensor on the lifting mechanism fixing component, and the striking arm is equipped with a second magnetic element that is opposite to the second Hall sensor on the striking mechanism fixing component. The control circuit includes a controller chip with corresponding signal input terminals that receive signal outputs from the power button, mode selection button, trigger switch, and the first and second Hall sensor signals, respectively. The control output terminal of the controller chip is connected to the motor that drives the lifting mechanism through the drive circuit. The controller chip performs drive control according to the following steps: Step 1: Proceed to the next step while the device is powered on; The second step is to determine whether it is in burst fire mode based on the mode selection key signal. If so, proceed to the next step; otherwise, proceed to the fifth step. Step 3: Determine whether the trigger switch pressing time is greater than the first predetermined time. If so, proceed to the next step; otherwise, return to step 1. Step 4: Determine whether the holding time of the superdomain signal before the second Hall signal switching is greater than the second predetermined duration and whether the holding time of the domain signal after the switching is greater than the third predetermined duration. If so, proceed to step 7; otherwise, return to step 1. Step 5: Determine whether the holding time of the superdomain signal before the second Hall signal switching is greater than the second predetermined duration, and whether the holding time of the domain signal after the switching is greater than the third predetermined duration. If so, proceed to the next step; otherwise, return to step 1. Step 6: Determine if the trigger switch pressing time is greater than the first predetermined time. If so, proceed to the next step; otherwise, return to step 1. Step 7: Output the motor drive signal for the lifting mechanism to drive the motor to rotate and proceed to the next step; Step 8: Determine whether the drive wheel rotation angle is greater than the predetermined angle based on the first Hall signal. If yes, proceed to the next step; otherwise, return to the previous step. Step 9: Stop the motor.

[0007] It is understandable that by adopting this invention, it is possible to reasonably determine whether the impact signal is a "false impact" signal caused by abnormal factors such as vibration and displacement, eliminate the motor operation caused by it, and thus avoid accidental nail shooting, thereby ensuring operational safety.

[0008] A further improvement of the present invention is that the second predetermined duration is longer than the first predetermined duration and the third predetermined duration.

[0009] A further improvement of the present invention is that the first predetermined duration is equal to the third predetermined duration.

[0010] A further improvement to the present invention is that, in the striking mechanism, the nail-driving seat and the striking arm bracket located at the front of the machine body constitute a moving pair in the nail-driving direction.

[0011] A further improvement to the present invention is that: a front striking arm and a rear striking arm are respectively installed at the front and rear ends of the striking arm bracket; a second magnetic element is installed at the rear end of the rear striking arm, which is opposite to the second Hall sensor on the striking mechanism fixing component; and the rear part of the rear striking arm abuts against the striking reset spring.

[0012] The invention is further improved by having a power button and a mode selection button on the control panel of the device body, and a trigger switch on the grip.

[0013] A further improvement to the present invention is that the striking arm bracket is equipped with an axially limiting depth adjustment knob and a depth adjustment rod that forms a helical pair with it. Attached Figure Description

[0014] Figure 1 This is a waveform diagram of a normal touch signal from a Hall sensor.

[0015] Figure 2 This is a waveform diagram of a Hall sensor containing a vibration displacement "touch" signal.

[0016] Figure 3 This is a three-dimensional structural diagram of a nail gun according to an embodiment of the present invention.

[0017] Figure 4 for Figure 3 An exploded three-dimensional structural diagram of the striking mechanism in the embodiment.

[0018] Figure 5 for Figure 3 Block diagram of the control circuit in the embodiment.

[0019] Figure 6 for Figure 3 The control circuit logic block diagram of the embodiment.

[0020] Figure 7 for Figure 3 Schematic diagram of the control circuit in the embodiment. Detailed Implementation Example

[0021] The nail gun in this embodiment is as follows: Figure 3As shown, the fuselage houses an energy storage mechanism consisting of a cylinder 1 and a piston, an impact mechanism consisting of a retractable striking arm 2 (2' being the nose of the gun) in the nail-driving seat, a nail-driving mechanism consisting of a firing pin 3 connected to the piston and extending to the nail-driving seat, a lifting mechanism consisting of a motor 4 driving a drive wheel 5 that meshes with the firing pin, and a nail-feeding mechanism consisting of a nail magazine 6 mounted on the side of the nail-driving seat. The control panel 8 at the lower part of the fuselage has a power button and a mode selection button. The grip 9 of the fuselage is equipped with a trigger switch. The drive wheel 5 is equipped with a first magnetic element C1 opposite to the first Hall sensor HALL1 (drive wheel rotation detection) on the lifting mechanism fixing component. These basic components are similar to those in the prior art and will not be described in detail.

[0022] The specific structure of the striking mechanism is as follows: Figure 4 As shown, the nail-driving seat 2-1, located at the front of the fuselage, and the impact arm bracket 2-3 form a nail-driving direction moving pair. The impact arm bracket 2-3 contains an axially limiting depth adjustment knob 2-5 and a depth adjustment rod 2-4 forming a helical pair with it. Turning the depth adjustment knob 2-5 adjusts the extension length of the depth adjustment rod 2-4, thereby adjusting the nail-driving depth limit. The front impact arm 2-2 and the rear impact arm 2-6 are respectively installed at the front and rear ends of the impact arm bracket 2-3, thus forming a complete impact arm 2. The rear end of the rear impact arm 2-6 is equipped with a second magnetic element C2, which corresponds to the second Hall sensor HALL2 (impact state) on the mounting base 2-7, the fixing component of the impact mechanism. The rear part of the rear striking arm 2-6 abuts against the striking reset spring 2-8, so the striking arm 2 tends to extend forward. Only when it is subjected to downward pressure will it retract relative to the body, causing the relative position of the second magnetic component C2 and the second Hall sensor HALL2 to change. Usually, when C2 exceeds the critical distance Lmax, the Hall sensor HALL2 outputs a high-level striking signal.

[0023] The control circuit of the nail gun is as follows: Figure 5 and Figure 7 As shown, the signal input terminals of the FU6861L controller chip U3 are respectively connected to the corresponding output terminals of the power button, mode selection buttons S1 and S2, as well as the corresponding signal outputs of the trigger switch TRIFER signal, the first Hall sensor for detecting the drive wheel rotation angle, and the second Hall sensor for the touch state. The control output terminal of the controller chip U3 is mainly a drive circuit composed of a bridge circuit of six field-effect transistors Q4-Q9, which is connected to the brushless motor M that drives the lifting mechanism. The basic structure of this circuit is similar to that of existing technology and will not be described in detail.

[0024] To prevent accidental firing, such as Figure 6 As shown, the controller chip performs drive control according to the following innovative control steps: Step 1: Proceed to the next step with the power button on. The second step is to determine whether it is in continuous firing mode based on the mode selection key signal. If so, proceed to the next step and enter the continuous firing operation process; otherwise, proceed to the fifth step and enter the single firing operation process. The third step is to determine whether the trigger switch pressing time is greater than the first predetermined time of 10ms. If so, it indicates that the operator is preparing to carry out continuous firing and proceeds to the next step to determine whether the trigger operation has been actually carried out; otherwise, it indicates that the operator is not preparing to carry out continuous firing and returns to the first step. Step 4: Determine whether the holding time of the over-domain signal before the second Hall signal switching is greater than the second predetermined duration of 90ms, and whether the holding time of the in-domain signal after the switching is greater than the third predetermined duration of 10ms. If so, it indicates that the operator has indeed performed the continuous striking operation and proceeds to step 7, charging nail firing. Otherwise, it indicates that the "striking" signal of the second Hall is caused by abnormal factors such as vibration displacement, and charging nail firing is not performed. Instead, return to step 1. Step 5: Determine whether the over-domain signal holding time before the second Hall signal switching is greater than the second predetermined duration of 90ms, and whether the intra-domain signal holding time after the switching is greater than the third predetermined duration of 10ms. If so, it indicates that the operator is ready to perform a single-touch operation and proceeds to the next step: determine whether the trigger switch is pressed. Otherwise, it indicates that the "touch" signal of the second Hall is caused by abnormal factors such as vibration and displacement. Ignore the trigger switch status judgment and return directly to step 1. Step 6: Determine if the trigger switch pressing time is greater than the first predetermined time of 10ms. If so, it indicates that the operator has pressed the trigger switch and proceeds to the next step of charging nail firing; otherwise, it cannot be guaranteed that the trigger switch has been pressed. Return to step 1. Step 7: Output the motor drive signal for the lifting mechanism to drive the motor to rotate and proceed to the next step; Step 8: Determine whether the rotation angle of the drive wheel is greater than the predetermined angle of 270° based on the first Hall signal. If so, it indicates that the rotation of the drive wheel is sufficient to enable the piston to complete the required energy storage movement until the firing pin is released and strikes the nail, and proceed to the next step; otherwise, return to the previous step and the motor continues to rotate. Step 9: The motor stops, and then the next nail-shooting control cycle begins.

[0025] Tests have shown that this embodiment has the following advantages compared with the prior art: Tests have shown that by judging the second and third predetermined time intervals, this embodiment can ensure that the user can identify the effective nail-shooting time interval at the maximum nail-shooting speed, shielding against misjudgments caused by abnormal factors, thereby effectively ensuring the safety and reliability of high-speed nail-shooting operations. Furthermore, compared with existing technologies that passively avoid misjudgments by adopting mechanical vibration reduction measures, the shielding method of identifying abnormal impacts by judging detection signals is clearly more scientific, more reliable, and more beneficial for extending service life.

[0026] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A control method for preventing accidental firing of a nail gun, the nail gun comprising a control circuit, wherein the body houses an energy storage mechanism consisting of a cylinder and a piston, an impact mechanism consisting of a retractable impact arm in the nail holder, a nail-driving mechanism consisting of a firing pin extending from the piston to the nail holder, a lifting mechanism consisting of a motor-driven drive wheel meshing with the firing pin, and a nail-feeding mechanism consisting of a nail magazine mounted on the side of the nail holder; the control panel of the body is provided with a power button and a mode selection button, and a trigger switch is provided on the handle; the drive wheel is equipped with a first magnetic element opposite to a first Hall sensor on the fixing part of the lifting mechanism, and the impact arm is equipped with a second magnetic element opposite to a second Hall sensor on the fixing part of the impact mechanism; the control circuit comprises a controller chip with corresponding signal input terminals receiving signal outputs from the power button, mode selection button, trigger switch, and first Hall sensor and second Hall sensor, respectively; the control output terminal of the controller chip is connected to a motor driving the lifting mechanism via a drive circuit; characterized in that: The controller chip performs drive control according to the following steps: Step 1: Proceed to the next step while powered on; Step 2: Determine whether it is in continuous firing mode based on the mode selection key signal. If yes, proceed to the next step; otherwise, proceed to Step 5; Step 3: Determine whether the trigger switch pressing time is greater than the first predetermined duration. If yes, proceed to the next step; otherwise, return to Step 1; Step 4: Determine whether the over-domain signal holding time before the second Hall signal switching is greater than the second predetermined duration, and whether the intra-domain signal holding time after the switching is greater than the third predetermined duration. If yes, proceed to Step 7; otherwise, return to Step 1; Step 5: Determine whether the over-domain signal holding time before the second Hall signal switching is greater than the second predetermined duration, and whether the intra-domain signal holding time after the switching is greater than the third predetermined duration. If yes, proceed to the next step; otherwise, return to Step 1; Step 6: Determine whether the trigger switch pressing time is greater than the first predetermined duration. If yes, proceed to the next step; otherwise, return to Step 1. Step 7: Output the motor drive signal for the lifting mechanism to drive the motor to rotate and proceed to the next step; Step 8: Determine whether the drive wheel rotation angle is greater than the predetermined angle based on the first Hall signal. If so, proceed to the next step; otherwise, return to the previous step. Step 9: Stop the motor.

2. The control method for preventing accidental firing of a nail gun according to claim 1, characterized in that: The second predetermined duration is longer than the first predetermined duration and the third predetermined duration.

3. The control method for preventing accidental firing of a nail gun according to claim 2, characterized in that: The first predetermined duration is equal to the third predetermined duration.

4. The control method for preventing accidental firing of a nail gun according to claim 1, 2, or 3, characterized in that: In the striking mechanism, the nail-driving seat and the striking arm bracket located at the front of the fuselage form a moving pair in the nail-driving direction.

5. The control method for preventing accidental firing of a nail gun according to claim 4, characterized in that: The front and rear ends of the striking arm bracket are respectively equipped with a front striking arm and a rear striking arm. The rear end of the rear striking arm is equipped with a second magnetic element that is opposite to the second Hall sensor on the striking mechanism fixing component. The rear part of the rear striking arm abuts against the striking reset spring.

6. The control method for preventing accidental firing of a nail gun according to claim 5, characterized in that: The control panel of the device is equipped with a power button and a mode selection button, and the handle is equipped with a trigger switch.

7. The control method for preventing accidental firing of a nail gun according to claim 6, characterized in that: The striking arm bracket is equipped with an axially limiting depth adjustment knob and a depth adjustment rod that forms a helical pair with it.

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