Digital wrench for precise control of preload

Abstract

This invention relates to the field of wrench technology, specifically to a digital display wrench for precise control of preload. It includes a wrench body with a ratchet head and a directional lock at the head. The middle surface of the wrench body has a display screen, a buzzer, and mechanical buttons, and an internal controller. A power supply is located at the tail of the wrench body. A magic socket is detachably connected to the ratchet head. The magic socket includes a socket body with a connecting cavity between the socket opening and the socket handle. A slip ring is located within the connecting cavity, and a connecting plate is fixed to the rotating part of the slip ring. A piezoelectric crystal is fixed to the connecting plate. The piezoelectric crystal is electrically connected to the slip ring, and the slip ring allows it to remain relatively stationary with respect to the bottom of the bolt during tightening. The slip ring is electrically connected to the controller. The preload is measured by emitting ultrasonic pulse signals from the piezoelectric crystal, solving the problem of high preload dispersion that easily occurs when tightening bolts using the torque method. This method offers high integration and adaptability to bolts of different sizes.

Description

Technical Field

[0001] This invention relates to the field of wrench technology, and in particular to a digital display wrench for precise control of preload. Background Technology

[0002] Bolted connections are the most widely used connection method in engineering. They are usually installed and disassembled using wrenches. Currently, the wrenches in published patents are mainly based on digital torque display (such as the existing patent CN215318353U - bolt preload setting wrench for contact wire), which applies a fixed torque to the bolt connection. However, tightening bolts according to the torque method can easily lead to high preload dispersion. Excessive or insufficient preload can easily damage the bolt connection structure. Therefore, it is urgent to solve the problem of precise control of preload during bolt assembly in engineering, which is also the key to improving the reliability of bolted connections. Summary of the Invention

[0003] To address the aforementioned problems, embodiments of the present invention provide a digital display wrench for precisely controlling preload.

[0004] One aspect of this invention provides a digital display wrench for precise control of preload, comprising a wrench body, a ratchet wrench head and a directional lock at the head of the wrench body, a display screen, a buzzer and mechanical buttons on the surface of the middle part of the wrench body, a controller inside the wrench body, a power supply inside the tail of the wrench body, and a magic sleeve detachably connected to the ratchet wrench head; the magic sleeve includes a sleeve body, a connecting cavity provided between the sleeve opening and the sleeve handle inside the sleeve body, a slip ring provided in the connecting cavity, a connecting plate fixed on the rotating part of the slip ring, a piezoelectric crystal fixed on the connecting plate, the piezoelectric crystal being electrically connected to the slip ring and achieving relative stillness between the slip ring and the bottom of the bolt during the tightening process, and the slip ring being electrically connected to the controller;

[0005] During the tightening process, the piezoelectric crystal sends ultrasonic pulse signals into the bolt from the contact surface between the bolt and the bottom of the bolt, and receives the pulse echo signals after the ultrasonic pulse signals are reflected and propagated inside the bolt. The piezoelectric crystal sends the pulse echo signals to the controller through a slip ring. The controller calculates the preload based on the echo flight time of the received pulse echo signals and displays the calculated preload on the display screen.

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: It utilizes a piezoelectric crystal to send ultrasonic pulse signals into the bolt. After receiving the pulse echo signal after the ultrasonic pulse signal propagates and reflects inside the bolt, the controller uses the echo flight time of the pulse echo signal to calculate the preload, thus providing a novel method for measuring and calculating preload. This solves the problem that tightening bolts using the torque method easily leads to high preload dispersion, achieving precise control of the preload. The overall integration is high, avoiding redundancy in traditional measurement methods, and the magic sleeve can be directly adapted to bolts of different sizes through adjustment.

[0007] Optionally, a release mechanism is provided inside the wrench body on one side of the ratchet head. The release mechanism includes a pawl for engaging with the ratchet head. The pawl is hinged to the wrench body. A mounting plate is provided on the side of the pawl away from the ratchet head. A push rod is provided on the mounting plate. A multi-stage lever transmission structure is provided between the push rod and the pawl. An electromagnet is driven by the push rod and electrically connected to the controller.

[0008] Optionally, the sleeve body surface is provided with mounting grooves at intervals relative to the sleeve opening. The mounting grooves are provided along the axis of the sleeve body, and sleeve clamps are hinged in the mounting grooves. The sleeve clamps are L-shaped, with the long arm of the sleeve clamp placed in the mounting groove and its end hinged to the mounting groove. The long arm has a gradually thickening structure towards the sleeve opening, and the short arm of the sleeve clamp is fastened to the end of the sleeve opening. An adjusting cylinder is screwed to the surface of the sleeve body. One end of the adjusting cylinder is sleeved on the outside of each sleeve clamp. Rotating the adjusting cylinder can change the distance between the sleeve clamps, making the magic sleeve suitable for clamping bolts of different sizes.

[0009] Optionally, a torque sensor is installed in the wrench body near the head, and the torque sensor is electrically connected to the controller.

[0010] Optionally, the controller includes a PCB board and an analog-to-digital converter circuit and a microcontroller integrated on the PCB board and electrically connected to each other; the analog-to-digital converter circuit is used to convert pulse echo signals into digital signals, which facilitates subsequent signal processing and calculation; the microcontroller is the hardware foundation for the implementation of the controller's functions, and controls the various actuators in the digital display wrench by receiving, processing and outputting signals through the microcontroller.

[0011] Optionally, during the tightening process, the microcontroller receives the pre-tightening force mode and preset pre-tightening force value input by the operator via mechanical buttons;

[0012] The piezoelectric crystal sends ultrasonic pulse signals into the bolt from the contact surface between the crystal and the bottom of the bolt, and receives the pulse echo signals after the ultrasonic pulse signals are reflected and propagated inside the bolt. The pulse echo signals are then sent to the analog-to-digital conversion circuit.

[0013] The analog-to-digital converter circuit converts the pulse echo signal into a digital signal and sends the digital signal to the microcontroller;

[0014] After receiving the pulse echo signal converted into a digital signal, the microcontroller determines the echo flight time of the pulse echo signal and calculates the preload using the following expression:

[0015]

[0016] Where V0 represents the propagation speed of the ultrasonic pulse signal within the bolt under stress-free conditions, and A 11 S represents the acoustic elastic constant, E represents the Young's modulus of the bolt material, and S represents the elastic constant. e L represents the effective cross-sectional area of ​​the bolt. e ε1 represents the uniaxial stress length in the bolt, ΔT represents the change in echo flight time, ε1 represents the first-order unfolding error, and ε2 represents the measurement error.

[0017] The microcontroller displays the calculated preload force synchronously on the display screen.

[0018] Optionally, the microcontroller synchronously displays the calculated preload force on the display screen, including:

[0019] The calculated preload is temporarily stored, and it is determined whether the calculated preload is within a reasonable range.

[0020] If the force is within a reasonable range, it is determined that the tightening is in the normal tightening stage. The preload of this buffer is stored and displayed synchronously on the display screen.

[0021] If the force is not within a reasonable range, it is determined to be in an abnormal tightening stage. The current preload is cleared and the previously stored preload is displayed on the screen.

[0022] Optionally, after the microcontroller synchronously displays the calculated preload force on the display screen, it also includes:

[0023] The microcontroller determines whether the calculated preload has reached the preset preload value. If the preset preload value has been reached, it controls the tripping mechanism to trip and simultaneously sounds an alarm via a buzzer. Attached Figure Description

[0024] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute a limitation of the present invention. In the drawings:

[0025] Figure 1 A three-dimensional structural schematic diagram of a digital display wrench for precisely controlling preload force, provided in an embodiment of the present invention;

[0026] Figure 2This is a schematic diagram of the front sectional view of a digital display wrench for precisely controlling preload, provided in an embodiment of the present invention.

[0027] Figure 3 A three-dimensional structural diagram of a magic sleeve provided in an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the front sectional view of a magic sleeve provided in an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of a multi-stage lever transmission structure provided in an embodiment of the present invention;

[0030] Figure 6 A flowchart of an analog-to-digital converter circuit provided in an embodiment of the present invention;

[0031] Figure 7 The following diagrams illustrate the bolt states and corresponding pulse echo signal waveforms provided in the embodiments of the present invention, wherein diagram a shows the state of stress-free bolts and corresponding pulse echo signal waveforms, and diagram b shows the state of stress-bearing bolts and corresponding pulse echo signal waveforms.

[0032] Figure 8 This is a flowchart illustrating a microcontroller control logic provided in an embodiment of the present invention.

[0033] The components include: wrench body 1, ratchet wrench head 2, directional lock 3, display screen 4, buzzer 5, mechanical button 6, controller 7, power supply 8, magic socket 9, socket body 10, socket mouth 11, socket handle 12, connecting cavity 13, slip ring 14, connecting plate 15, piezoelectric crystal 16, release mechanism 17, pawl 18, mounting plate 19, push rod 20, multi-stage lever transmission structure 21, socket clamp 22, adjusting cylinder 23, and torque sensor 24. Detailed Implementation

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0035] See Figures 1-4This invention provides a digital display wrench for precise control of preload, comprising a wrench body 1, a ratchet wrench head 2 and a directional lock 3 at the head of the wrench body 1, a display screen 4, a buzzer 5 and mechanical buttons 6 on the middle surface of the wrench body 1, a controller 7 inside the wrench body 1, a power supply 8 inside the tail of the wrench body 1, and a magic sleeve 9 detachably connected to the ratchet wrench head 2; the magic sleeve 9 comprises a sleeve body 10, a connecting cavity 13 located between the sleeve opening 11 and the sleeve handle 12 inside the sleeve body 10, a slip ring 14 inside the connecting cavity 13, a connecting plate 15 fixed on the rotating part of the slip ring 14, a piezoelectric crystal 16 fixed on the connecting plate 15, the piezoelectric crystal 16 being electrically connected to the slip ring 14 and achieving relative stillness between the slip ring 14 and the bottom of the bolt during the tightening process, and the slip ring 14 being electrically connected to the controller 7;

[0036] During the tightening process, the piezoelectric crystal 16 sends an ultrasonic pulse signal into the bolt from the contact surface between the bolt and the bottom of the bolt, and receives the pulse echo signal after the ultrasonic pulse signal is reflected and propagated inside the bolt. The piezoelectric crystal 16 sends the pulse echo signal to the controller 7 through the slip ring 14. The controller 7 calculates the preload based on the echo flight time of the received pulse echo signal and displays the calculated preload on the display screen 4.

[0037] In practice, a release mechanism 17 is provided inside the wrench body 1 on one side of the ratchet wrench head 2. The release mechanism 17 includes a pawl 18 for engaging with the ratchet wrench head 2. The pawl 18 is hinged to the wrench body 1. A mounting plate 19 is provided on the side of the pawl 18 away from the ratchet wrench head 2. A push rod 20 is provided on the mounting plate 19. A multi-stage lever transmission structure 21 is provided between the push rod 20 and the pawl 18. The push rod 20 is driven by an electromagnet, which is electrically connected to the controller 7.

[0038] See Figure 5 In a specific implementation, the multi-stage lever transmission structure 21 consists of 5 L-shaped levers. The use of L-shaped levers can change the setting direction of the levers while realizing force transmission, thereby saving installation space. When setting up, the long arm of each L-shaped lever is used as the power arm and the short arm is used as the resistance arm, forming a multi-stage amplification structure. After the electromagnet is activated, it drives the push rod 20 to push out and push each L-shaped lever in turn to realize the progressive amplification of the thrust. Finally, it actuates the pawl 18 to achieve the purpose of disengaging from the ratchet in the ratchet wrench head 2.

[0039] In practice, the sleeve body 10 has mounting grooves spaced apart on its surface relative to the sleeve opening 11. The mounting grooves are arranged along the axis of the sleeve body 10, and sleeve clamps 22 are hinged in the mounting grooves. The sleeve clamps 22 are L-shaped, with the long arm of the sleeve clamp 22 placed in the mounting groove and its end hinged to the mounting groove. The long arm has a gradually thickening structure towards the sleeve opening 11, and the short arm of the sleeve clamp 22 is fastened to the end of the sleeve opening 11. An adjusting cylinder 23 is screwed onto the surface of the sleeve body 10. One end of the adjusting cylinder 23 is sleeved on the outside of each sleeve clamp 22. Rotating the adjusting cylinder 23 can change the distance between the sleeve clamps 22, so that the magic sleeve 9 can be used to clamp bolts of different sizes.

[0040] In practice, a torque sensor 24 is installed in the main body 1 of the wrench near the head, and the torque sensor 24 is electrically connected to the controller 7; so that the current torque value can be displayed synchronously.

[0041] In implementation, the controller 7 includes a PCB board and an analog-to-digital converter circuit and a microcontroller integrated on the PCB board and electrically connected to each other; the analog-to-digital converter circuit is used to convert pulse echo signals into digital signals, which facilitates subsequent signal processing and calculation; the microcontroller is the hardware foundation for the implementation of the controller's functions, and the microcontroller receives, processes and outputs signals to control the various actuators in the digital display wrench.

[0042] See Figure 6 In a specific implementation, the analog-to-digital conversion circuit includes a preamplifier circuit, a sample-and-hold circuit, an analog-to-digital conversion circuit, and a digital filter circuit connected in sequence.

[0043] The preamplifier circuit is used to amplify the input signal (the weak pulse echo signal from the piezoelectric crystal) to an appropriate range so that it can be effectively sampled and converted to analog-to-digital format.

[0044] Sample-and-hold circuits are used to capture transient values ​​of the input signal and hold them in a stable voltage or current state for subsequent analog-to-digital conversion.

[0045] Analog-to-digital conversion circuits are used to convert continuous analog signals into discrete digital codes;

[0046] Digital filters are used to smooth and filter out noise in digital coding and perform additional digital signal processing operations such as decimation or compensation as needed to reduce errors.

[0047] During implementation, in the tightening process, the microcontroller receives the pre-tightening force mode and pre-tightening force preset value input by the operator through mechanical button 6; the pre-tightening force mode is divided into ultrasonic pulse measurement mode and conventional torque measurement mode;

[0048] The piezoelectric crystal 16 sends ultrasonic pulse signals into the bolt from the contact surface between the bolt and the bottom of the bolt, and receives the pulse echo signals after the ultrasonic pulse signals are reflected and propagated inside the bolt. Then, it sends the pulse echo signals to the analog-to-digital conversion circuit.

[0049] The analog-to-digital converter circuit converts the pulse echo signal into a digital signal and sends the digital signal to the microcontroller;

[0050] After receiving the pulse echo signal converted into a digital signal, the microcontroller determines the echo flight time of the pulse echo signal and calculates the preload using the following expression:

[0051]

[0052] Where V0 represents the propagation speed of the ultrasonic pulse signal within the bolt under stress-free conditions, and A 11 S represents the acoustic elastic constant, E represents the Young's modulus of the bolt material, and S represents the elastic constant. e L represents the effective cross-sectional area of ​​the bolt. e ε1 represents the uniaxial stress length in the bolt, ΔT represents the change in echo flight time, ε1 represents the first-order unfolding error, and ε2 represents the measurement error.

[0053] The microcontroller synchronously displays the calculated preload force on display screen 4.

[0054] See Figure 7 Under stress-free conditions, the propagation distance of an ultrasonic pulse signal within a bolt can be expressed as:

[0055] L1 = L0 + L e +L h +L f 2)

[0056] Among them, L σ L is the non-stress length. e L is the uniaxial stress length. h L is the length of the bolt head. f Let be the thickness of the coupling agent. After applying stress, the propagation distance of the ultrasonic pulse signal within the bolt can be expressed as:

[0057] L2 = L0 + L σ +L h +L f 3)

[0058] Wherein, stress length L σ =Le(1+E) -1 σ).

[0059] Under stress, the pulse echo flight time can be expressed as:

[0060]

[0061] The first-order expansion of Equation 4) yields the expression for calculating the preload, i.e., Equation 1).

[0062] During implementation, the microcontroller synchronously displays the calculated preload force on the display screen, including:

[0063] The calculated preload is temporarily stored, and it is determined whether the calculated preload is within a reasonable range.

[0064] If the force is within a reasonable range, it is determined that the tightening is in the normal tightening stage. The preload of this buffer is stored and displayed synchronously on the display screen.

[0065] If the force is not within a reasonable range, it is determined to be in an abnormal tightening stage. The current preload is cleared and the previously stored preload is displayed on the screen.

[0066] During the bolt tightening process, the wrench sleeve may detach from the bolt surface due to human operation. At this time, the ultrasonic measurement signal is invalid and does not need to be output or stored. When the sleeve returns to the bolt surface and tightening continues, the measurement results are output and stored to ensure the accuracy and stability of the test results throughout the tightening process.

[0067] In implementation, after the microcontroller synchronously displays the calculated preload force on the display screen, the process also includes:

[0068] The microcontroller determines whether the calculated preload has reached the preset preload value. If the preset preload value has been reached, it controls the tripping mechanism to trip and simultaneously sounds an alarm via a buzzer.

[0069] To ensure a stable and reliable tightening result, the wrench must automatically disengage when the preload reaches the target value to prevent over-tightening.

[0070] See Figure 8 The control logic shown is as follows: when preparing for tightening, the wrench is powered on and the system is initialized. After that, the operator can select the mode and input the preset value of the preload. After preparation, tightening begins. During the tightening process, the piezoelectric crystal emits an ultrasonic pulse signal. The ultrasonic pulse signal is reflected after propagating inside the bolt to form a pulse echo signal. The pulse echo signal is processed by the analog-to-digital converter circuit and then sent to the microcontroller for temporary storage. After temporary storage, a reasonableness judgment is performed. If the signal is within a reasonable range, it is considered that the normal tightening stage is in progress, and the normal storage and output signal values ​​are displayed synchronously. If it is not within a reasonable range, it is considered that the wrench has disengaged from the bolt surface, and the output result is the previously stored valid value, that is, the torque and preload information at the moment before disconnection, until the tool returns to the bolt surface and the next valid value is detected.

[0071] After making a reasonable judgment, in order to ensure that the tightening result is stable and reliable, it is necessary to determine whether the detected preload has reached the preset preload value. Once the preset preload value is reached, the microcontroller controls the electromagnet to complete the automatic release function and issue an audible and visual alarm. The operator can then choose whether to store and transmit the tightening information and whether to start the next tightening process according to their own needs. If transmission is required, the current preload information can be transmitted to an external device such as a laptop computer for information collection and storage via wired or wireless means.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A digital display wrench for precise control of preload, comprising a wrench body, a ratchet wrench head and a directional lock at the head of the wrench body, a display screen, a buzzer and mechanical buttons on the middle surface of the wrench body, a controller inside the wrench body, a power supply inside the tail of the wrench body, and a magic sleeve detachably connected to the ratchet wrench head; characterized in that... The magic sleeve includes a sleeve body, a connecting cavity located between the sleeve opening and the sleeve handle inside the sleeve body, a slip ring inside the connecting cavity, a connecting plate fixed on the rotating part of the slip ring, a piezoelectric crystal fixed on the connecting plate, the piezoelectric crystal being electrically connected to the slip ring and achieving relative stillness between it and the bottom of the bolt during the tightening process through the slip ring, and the slip ring being electrically connected to the controller. During the tightening process, the piezoelectric crystal sends ultrasonic pulse signals into the bolt from the contact surface between the bolt and the bottom of the bolt, and receives the pulse echo signals after the ultrasonic pulse signals are reflected and propagated inside the bolt. The piezoelectric crystal sends the pulse echo signals to the controller through a slip ring. The controller calculates the preload based on the echo flight time of the received pulse echo signals and displays the calculated preload on the display screen simultaneously. The wrench body has a release mechanism located on one side of the ratchet wrench head. The release mechanism includes a pawl for engaging with the ratchet wrench head. The pawl is hinged to the wrench body. A mounting plate is located on the side of the pawl away from the ratchet wrench head. A push rod is passed through the mounting plate. A multi-stage lever transmission structure is provided between the push rod and the pawl. The push rod is driven by an electromagnet, which is electrically connected to the controller. The sleeve body has mounting grooves spaced apart from the sleeve opening on its surface. The mounting grooves are arranged along the axis of the sleeve body, and sleeve jaws are hinged in the mounting grooves. The sleeve jaws are L-shaped, with the long arm of the sleeve jaw placed in the mounting groove and its end hinged to the mounting groove. The long arm has a gradually thickening structure towards the sleeve opening, and the short arm of the sleeve jaw is fastened to the end of the sleeve opening. An adjusting cylinder is screwed onto the surface of the sleeve body. One end of the adjusting cylinder is sleeved on the outside of each sleeve jaw. Rotating the adjusting cylinder can change the distance between the sleeve jaws, making the magic sleeve suitable for clamping bolts of different sizes. The controller includes a PCB board, an analog-to-digital converter circuit integrated on the PCB board and interconnected with each other, and a microcontroller; Analog-to-digital converters are used to convert pulse echo signals into digital signals, facilitating subsequent signal processing and calculations. The microcontroller is the hardware foundation for the implementation of the controller's functions. It receives, processes, and outputs signals to control the various actuators in the digital display wrench. During the tightening process, the microcontroller receives the pre-tightening force mode and pre-tightening force preset value input by the operator through mechanical buttons; The piezoelectric crystal sends ultrasonic pulse signals into the bolt from the contact surface between the crystal and the bottom of the bolt, and receives the pulse echo signals after the ultrasonic pulse signals are reflected and propagated inside the bolt. The pulse echo signals are then sent to the analog-to-digital conversion circuit. The analog-to-digital converter circuit converts the pulse echo signal into a digital signal and sends the digital signal to the microcontroller; After receiving the pulse echo signal converted into a digital signal, the microcontroller determines the echo flight time of the pulse echo signal and calculates the preload using the following expression: ； in, This indicates the propagation speed of an ultrasonic pulse signal within a bolt under stress-free conditions. Represents the acoustic elastic constant. This indicates the Young's modulus of the bolt material. Indicates the effective cross-sectional area of ​​the bolt. Indicates the uniaxial stress length in the bolt. Indicates the change in echo flight time. This represents the first-order expansion error. Indicates measurement error; The microcontroller synchronously displays the calculated preload force on the display screen. The process of the microcontroller synchronously displaying the calculated preload force on the display screen includes: The calculated preload is temporarily stored, and it is determined whether the calculated preload is within a reasonable range. If the force is within a reasonable range, it is determined that the tightening is in the normal tightening stage. The preload of this buffer is stored and displayed synchronously on the display screen. If the force is not within a reasonable range, it is determined to be in an abnormal tightening stage. The current preload is cleared and the previously stored preload is displayed on the screen. After the microcontroller synchronously displays the calculated preload force on the screen, the process also includes: The microcontroller determines whether the calculated preload has reached the preset preload value. If the preset preload value has been reached, it controls the tripping mechanism to trip and simultaneously sounds an alarm via a buzzer.

2. The digital display wrench for precise control of preload as described in claim 1, characterized in that, A torque sensor is located near the head of the wrench body, and the torque sensor is electrically connected to the controller.

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