Power tool and clutch for a power tool

Abstract

The present specification relates to a power tool comprising an electric motor (10), a clutch (20) comprising a shaft (23) and a preloaded spring element (40) arranged around the shaft (23) configured to control a clutch release torque of the clutch, and a torque setting mechanism (30) for adjusting the clutch release torque of the clutch comprising an adjustment arrangement (50) acting on the spring element and having a first thread (70a) for cooperating with a second thread (70b) provided on the shaft to adjust a deflection of the spring element upon relative rotation between the shaft and the adjustment arrangement, wherein the adjustment arrangement is arranged to be selectively locked against rotation such that rotation of the output shaft and / or the electric motor results in a change in spring deflection. The present specification also relates to a method for determining a clutch release torque and a control device configured to control such a power tool.

Description

Power tools and clutches for power tools Technical Field

[0001] This invention relates generally to power tools, and more specifically, to power tools including clutches. Background Technology

[0002] Different types of power tools are known to be used in various industries, one common type being tightening tools for tightening screws or bolts.

[0003] For example, it is known to use a so-called clutch tool, in which a clutch is arranged between the motor and the output so as to stop tightening when a predetermined torque value is reached, which is called the clutch release torque value.

[0004] The clutch release torque value can be set in various ways. One known solution involves an elastic element, such as a spring element, arranged to control the clutch release value. To set the clutch release value in these tools, the user can adjust the stiffness of the spring element.

[0005] Known solutions involve users manually adjusting the spring length using, for example, a screwdriver. Typically, no feedback is provided to the user regarding the set torque value, making it difficult for the user to know which release torque level the tool has been set to and / or to feel how much torque has been adjusted.

[0006] Therefore, this setting of the clutch release torque value is usually only done as part of a complex calibration process before starting work, and the tool must be calibrated regularly to ensure that the torque applied by the tool (i.e., the clutch torque release value) is correct.

[0007] As an alternative, another common solution for applications requiring different torque levels, due to the complexity and time-consuming nature of torque value setting, is to simply use several clutch tools calibrated to different torque levels. This, of course, increases the cost and complexity of the workspace.

[0008] Therefore, there is a need for improvement in the field of clutch tools, especially regarding the setting of clutch torque release values. Summary of the Invention

[0009] Therefore, it is desirable to provide a clutch tool with improved functionality regarding the setting and adjustment of clutch release torque. In particular, it is desirable to provide a clutch tool with improved capabilities, allowing the user to more precisely control the clutch release torque value. To better address one or more of these problems, a power tool as defined in this application, a method for determining the clutch release torque in such a power tool, and a control device configured to control such a power tool are provided. Preferred embodiments are provided in this application.

[0010] According to a first aspect of the invention, a power tool for tightening threaded fasteners is provided. The power tool includes a motor, a clutch, and a torque setting mechanism. The clutch includes a pressure plate, a cam follower plate, a shaft, and a preloaded spring element. The pressure plate is configured to be rotatably driven by the motor. The shaft is rotatably fixed relative to the cam follower plate. The preloaded spring element is arranged about the shaft and configured to press the cam follower plate against the pressure plate to control the clutch release torque. The torque setting mechanism for adjusting the clutch release torque includes an adjustment arrangement acting on the spring element and having a first thread for engaging with a second thread disposed on the shaft to adjust the deflection of the spring element when the shaft and the adjustment arrangement rotate relative to each other. The adjustment arrangement is arranged to selectively lock in a position where rotation of the motor (and / or the shaft) causes a change in the spring deflection.

[0011] According to the first aspect, the clutch tool provides an ingenious solution to the aforementioned problem by incorporating an adjustment arrangement designed to mate with the shaft, thereby allowing the user to adjust the spring deflection by rotating the motor (and / or the shaft) relative to the arrangement. Those skilled in the art will recognize that rotation of the shaft typically results in rotation of the motor, and vice versa.

[0012] Since the adjustment arrangement can lock the rotation, it provides the possibility of convenient and accurate control of the clutch release torque by using a motor to rotate the shaft instead of using manual tools.

[0013] Therefore, this design cleverly provides a clutch tool that allows users to more easily adjust the release torque, thereby improving control over the torque setting.

[0014] Regarding power tools, according to one embodiment, the motor is an electric motor. The tool may be, for example, an electric handheld power tool. In some embodiments, the power tool may be a battery-powered tool.

[0015] The spring element can be a helical spring, such as a compression helical spring, and the deflection of the spring can also be called the spring travel.

[0016] According to one embodiment, the power tool further includes a sensor arranged to sense parameters from which the deflection of the spring can be determined.

[0017] According to one implementation, the parameters are those from which the rotation angle of the motor and / or output shaft can be derived.

[0018] In one implementation, the parameter is a parameter that indicates the rotational behavior of the motor and / or output shaft. This behavior may include, for example, angle, speed, or rotational resistance.

[0019] In one implementation, the sensor is an angle sensor, and the parameter is the rotation angle of the motor. This can be particularly advantageous because relatively small changes in spring deflection (and therefore the clutch release torque value) typically require a large amount of motor rotation, as the provided resolution can be very high.

[0020] According to one embodiment, the power tool further includes processing circuitry configured to determine a clutch release torque value based on parameters.

[0021] For example, a parameter or parameter value can first be converted to spring deflection, and then the spring deflection can be converted to determine the clutch release torque. Alternatively, the parameter can be directly converted to the clutch release torque.

[0022] A lookup table can be used to convert between parameters and clutch release torque, or between parameters and spring deflection. In the latter case, another lookup table can be used to determine the torque between spring deflection and clutch release torque.

[0023] The lookup table is predetermined and can be created during the design phase of the power tool.

[0024] Alternatively, at least one equation can be used for the transformation. The at least one equation may include an equation describing the relationship between spring deflection (displacement) or spring force and clutch release torque, or a parameter value and clutch release torque. Alternatively, two equations may be used: one between the parameter value and spring deflection or spring force, and another between the spring deflection or force and clutch release torque.

[0025] The processing circuitry 90 may use, for example, one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), etc., in any combination.

[0026] According to one embodiment, the processing circuit is further configured to determine the change in spring deflection caused by the operation of the adjusting mechanism based on parameters and preset values ​​indicating the pitch of the first and second threads, and to determine the clutch release torque value based on the determined change in spring deflection.

[0027] In some implementations, the circuit is configured to determine the change in clutch release value based on the above description. For example, in one implementation, if the number of revolutions performed by the motor is known, the corresponding spring element deflection can be found based on the number of revolutions and the pitch, for example, by estimation or calculation or by using known table values ​​or the like. The corresponding change in spring force, and therefore the clutch release torque, can then be determined based on the known force deflection ratio of the spring element, which may also be referred to as the spring deflection ratio.

[0028] In one embodiment, the tool further includes a gear assembly, and the processing circuitry is configured to determine the spring deflection based on parameters, preset values ​​indicating the pitch of the first and second threads, and a known gear ratio of the gear assembly.

[0029] According to one embodiment, the processing circuitry is further configured to receive an input indicating a desired clutch release torque value and / or a desired change in the clutch release value, and to control the motor to rotate when the adjusting mechanism is locked and cannot rotate, until the spring element deflects to the amount that achieves the desired clutch release torque value. In some embodiments, the required deflection amount can be determined based on or at least considering a stored value of the currently set torque value.

[0030] According to one implementation, the circuit is further configured to control the motor to rotate to a predetermined starting point before controlling the motor to rotate to achieve a desired deflection value. Therefore, in some implementations, the desired clutch release torque value can be set as an absolute value based on the known starting point and the variation in clutch release torque achieved by the deflection.

[0031] In one implementation, the tool further includes a trigger for controlling the motor to rotate in response to a triggering action, i.e., in response to an operator pressing the trigger.

[0032] In one embodiment, the trigger can be operated to achieve rotation of the motor in the first and second directions, and the circuit is configured to: increase a set clutch release torque value by a predetermined amount in response to the start of the motor in the first (forward) direction, and decrease the clutch release value by a predetermined amount in response to the start of the tool in the second (reverse) direction.

[0033] In some implementations, the circuit may be further configured, for example, in response to a triggering action, to step between fixed torque values, which may correspond to different bolt sizes, be mapped to different stations and / or positions, etc.

[0034] In some implementations, the circuit is further configured to selectively operate the motor in a set mode, in which, for example, in response to a user pressing a trigger, the motor is controlled to rotate much slower than in normal operating mode.

[0035] In some embodiments, the power tool may further include an HMI that allows the user to configure the tool. For example, this may include inputting a desired clutch torque release value or setting the tool to the aforementioned setting mode. In one embodiment, the power tool is further configured to provide the user with feedback, for example, regarding the current clutch torque release value. In one embodiment, the power tool further includes a display, with circuitry further configured to display information on the screen to provide feedback. The information may include the set clutch torque value, changes in the clutch torque value, etc.

[0036] According to one implementation, the sensor is arranged to sense the motor current of the motor. The resistance of the spring element to deflection, and therefore the motor current required to rotate the motor, is proportional to the length of the spring. Therefore, the absolute value of the spring deflection can be estimated based on the motor current data, and thus the absolute value of the clutch torque release value can be estimated.

[0037] In one embodiment, the clutch tool includes a first sensor arranged to sense the rotational angle of the motor and a second sensor arranged to sense the motor current. In this embodiment, data from the current sensor can, for example, be used to provide additional verification of the actual torque release clutch value. In one embodiment, changes in the motor current can be used to verify whether the adjustment arrangement has locked rotation.

[0038] According to one implementation, the adjustment arrangement includes an adjusting nut acting on the spring element to adjust the deflection of the spring element when it rotates relative to the output shaft and the adjusting nut.

[0039] According to one embodiment, the adjustment arrangement further includes a support plate unit arranged adjacent to the adjusting nut, wherein a spring element abuts against a plate-like portion of the support plate unit. For example, one end of the spring element may abut against the plate and the other end against a cam follower plate of the clutch.

[0040] According to one embodiment, the support plate unit further includes an axially extending cylindrical portion on which a first thread is disposed. The first thread may be an internal thread disposed on the inner side of the cylindrical portion, which is arranged to engage with a second thread disposed on the outer side of the shaft.

[0041] According to one embodiment, the adjusting nut and support plate unit include respective mating locking devices arranged to prevent relative rotation between them. In one embodiment, the locking devices can allow relative axial movement while preventing relative rotation. This is advantageous because the support plate unit can travel with the spring as the deflection changes. In one embodiment, the locking devices are formed by mating splines respectively disposed on the nut and adjusting plate unit. The splines may be disposed on the outer side of the cylindrical portion of the support plate unit.

[0042] According to one embodiment, the adjusting nut further includes a first engaging device arranged to lock rotation of the adjusting nut. In one embodiment, the engaging device may be formed by a hole provided in the adjusting nut that allows a locking pin to be inserted. In some embodiments, the locking pin may be manually inserted by a user. In other embodiments, the tool may include an automatic locking pin assembly.

[0043] In some implementations, the clutch tool may include a mechanical or electrical switch for automatically locking the adjusting nut.

[0044] According to one embodiment, the adjusting nut further includes a second engagement device for allowing manual rotation of the adjusting nut to change the clutch release torque. This provides an additional possibility for manual adjustment. In one embodiment, these engagement devices may include teeth or similar structures to which a screwdriver can engage, such that rotation of the screwdriver results in manual rotation of the nut. In this case, as the nut rotates relative to a stationary shaft, the deflection of the spring will change.

[0045] According to a second aspect of the invention, a method is provided for determining the clutch release torque in a power tool according to any of the foregoing embodiments, the method comprising the steps of: receiving data from which spring deflection can be derived, and determining a clutch release torque value based on the received data. Optionally, the method may further include storing and / or communicating the determined clutch release torque.

[0046] For example, spring deflection can be derived and converted to determine the clutch release torque. Alternatively, the data can be directly converted to clutch release torque. This conversion can be performed using lookup tables between the data and clutch release torque, or between the data and spring deflection. In the latter case, another lookup table between spring deflection and clutch release torque can be used to determine the torque. These lookup tables are predetermined and can be created during the power tool design phase.

[0047] Alternatively, at least one equation can be used for determination. The at least one equation may include an equation describing the relationship between spring deflection (displacement) or spring force and clutch release torque, or a relationship between data and clutch release torque. Alternatively, two equations may be used: one between data and spring deflection or spring force, and another between spring deflection or force and clutch release torque.

[0048] According to a third aspect of the invention, a control device is provided, configured to control a power tool according to any of the foregoing embodiments. The control device may include circuitry configured to perform the steps of the method according to the second aspect described above. The control device may be disposed within the tool or may be an external control device. The control device may be further separated from the tool (and optionally remotely) or may be included within the tool. The control device may include a memory and a processing device. The control device may, for example, be a computer. The control device may be included in a single unit or may be distributed across multiple units (e.g., cloud-based).

[0049] By referring to the above discussion of the first aspect of the invention, the purpose, advantages and features of the methods conceivable within the scope of the second and third aspects of the invention can be readily understood.

[0050] Further objects, features, and advantages of the invention will become apparent upon studying the following detailed disclosure, drawings, and appended claims. Those skilled in the art will recognize that different features of the invention can be combined to create embodiments other than those described below. Attached Figure Description

[0051] The present invention will be described in the following illustrative and non-limiting detailed description of exemplary embodiments with reference to the accompanying drawings, in which:

[0052] Figure 1 is a side view showing some components of an exemplary power tool according to one embodiment.

[0053] Figure 2 is a perspective view of some components of an exemplary power tool according to one embodiment.

[0054] Figure 3 is a side view of the tool housing of an exemplary power tool according to one embodiment.

[0055] Figure 4 illustrates a method according to one implementation scheme.

[0056] All accompanying drawings are schematic and not necessarily drawn to scale, and generally only show the parts necessary to illustrate the invention, wherein other parts may be omitted or only implied. Detailed Implementation

[0057] Figure 1 is a side view of a portion of an exemplary power tool according to one embodiment, showing some of the tool's internal components, more specifically, which may be referred to as the power transmission system.

[0058] The motor 10 is connected to the clutch 20 via a gear assembly. The clutch 20 includes a pressure plate 21 driven by the motor, a cam follower plate 22 attached to a shaft 23, and a spring 40 arranged around the shaft 23. The spring 40 is arranged to press the cam follower plate against the pressure plate to control the value of the clutch release torque.

[0059] More specifically, spring 40 pushes cam follower plate 22 against pressure plate 21, thereby engaging pressure plate 21 and transmitting its rotation to shaft 23. The clutch release torque, i.e., the torque required to release the clutch, is controlled by setting spring 40 in a compressed state. Further compression will release the clutch from the compressed state (i.e., at the clutch release torque) – controlled by adjusting the spring deflection, which will be explained further later / below.

[0060] In the exemplary embodiment shown, a ball joint 24 is arranged between plates 21 and 22, preventing relative rotation between the two plates 21 and 22 as long as the torque is less than the clutch release torque value. The cam follower plate 22 has a cam surface 22a configured to mate with the ball joint 24. As the nut, bolt, or screw is tightened by rotation of the output shaft 23, the torque eventually increases to the clutch release torque level. When the cam follower plate 22 disengages from the pressure plate 21, the clutch is released, allowing the pressure plate 21 to rotate freely. Therefore, when the clutch is released, the cam follower plate 22 is not driven by the pressure plate 21. As will be apparent to those skilled in the art, other types of cam follower mechanisms without the use of a ball joint are also conceivable.

[0061] The power tool further includes a torque setting mechanism 30 for adjusting the clutch release torque. Mechanism 30 includes an adjustment arrangement 50 acting on a spring 40 to adjust the deflection or compression state of the spring element when rotated relative to the shaft and the adjustment arrangement.

[0062] In the illustrated embodiment, the deflection can be adjusted by an adjusting nut 51 and a support plate unit 52 arranged adjacent to the adjusting nut, the support plate unit acting on a spring element abutting against the plate-shaped portion 52a of the support plate unit. Therefore, axial movement of the plate unit 52 changes the deflection of the spring 40.

[0063] To allow for adjustment of the axial position of the adjustment arrangement 50 during relative rotation with respect to shaft 23, shaft 23 and adjustment arrangement 50 are provided with mating threads 70a and 70b. For this purpose, the support plate unit includes an axially extending cylindrical portion 52b, wherein the first thread 70a is disposed on the inner side of the cylindrical portion. The second thread 70b, which mates with the first thread 70a, is disposed on the outer side of shaft 23.

[0064] Shaft 23 can be easily rotated by a motor or by the output shaft of a manual rotary tool (which is connected to shaft 23). Those skilled in the art will recognize that rotation of the shaft generally results in rotation of the motor, and vice versa.

[0065] In the illustrated embodiment, rotation of the adjusting arrangement 50 can be selectively locked to allow relative rotation, which in turn causes the deflection of the spring 40 to vary with the rotation of the shaft and / or motor. For this purpose, four holes 53 are provided in the adjusting nut 51 at circumferential intervals to allow a locking pin or the like to be inserted into one of the holes, thereby preventing any rotation of the nut 51, and to provide rotational locking between the adjusting nut and the support plate unit, both components include splines 80a, 80b arranged to prevent relative rotation (but allowing axial movement of the support plate unit 52 relative to the nut 51 as the spring deflection changes).

[0066] However, to also allow for manual adjustment, the adjusting nut 51 of the illustrated embodiment further includes a second engagement device in the form of teeth 54, with which, for example, a screwdriver can engage for manual rotation of the adjusting nut. In this operation, the shaft 23 remains stationary, such that the relative rotation between the adjusting arrangement 50 and the shaft 23, and consequently the spring deflection, is achieved in a manner that can be described as the opposite of the operation described above.

[0067] As can be seen from Figure 3, the housing of the tool in the illustrated embodiment includes an opening 2 located at the front end of the portion of the housing adjacent to the adjustment arrangement 50, and arranged to allow insertion of a locking pin (or the like) into a hole 53 or to allow insertion of a screwdriver or the like for manual adjustment to engage the teeth 54. To assist the user in utilizing the manual mode, the housing in the embodiment shown in Figure 3 includes markings (+ / -) indicating the direction of increasing and decreasing the clutch release torque.

[0068] To determine the torque clutch release value, the power tool may further include a sensor arranged to sense parameters from which the deflection of spring 40 can be derived.

[0069] As described above, when the adjustment mechanism is locked and cannot rotate, since the deflection can be controlled by the rotation of the motor, one example of such a parameter is a parameter from which the rotation angle of the motor and / or the output shaft can be derived. In the illustrated embodiment, an angle sensor 80, such as an encoder, is arranged to sense the rotation angle of the motor.

[0070] The embodiment of Figure 1 further includes a processing circuit 90 configured to determine a clutch release torque value based on the parameter. For example, the change in spring deflection caused by the operation of the adjusting mechanism is determined based on the parameter and a preset value indicating the pitch of the first and second threads, and the resulting clutch release torque value or change in torque value is determined based on the determined change in spring deflection.

[0071] Based on the known rotational speed of the motor sensed by the angle sensor, this speed can be converted into the known rotational speed of shaft 23. Knowing the gear ratio of gear assembly 60, the deflection of spring 40 can be obtained using the known pitch of the thread on the shaft. Using the known spring deflection ratio, the generated spring force can be obtained, and thus the clutch release torque value can be derived.

[0072] The processing circuitry can be further optionally configured to control the motor to achieve a desired change in clutch release torque or a desired clutch release torque value. When the adjustment mechanism is locked, the motor can be rotated to achieve a desired change in spring deflection, possibly starting from a predetermined starting point.

[0073] Method 100 according to the embodiment will now be described with reference to FIG4. Method 100 may be executed, for example, by the processing circuit 90 described above and / or by a control device (possibly an external control device).

[0074] Method 100 may include step 101 of receiving data from which the deflection of the spring can be determined.

[0075] Method 100 further includes a step 102 of determining a clutch release torque value based on received data. This step 102 may include a first step 102a and a second step 102b, in which the change in spring deflection is determined based on the data and a preset value indicating the pitch of the first and second threads; and in the second step 102b, the clutch release value is determined based on the determined spring deflection and a known spring deflection ratio.

[0076] Although the invention has been shown and described in detail in the accompanying drawings and the foregoing description, such showing and description should be considered illustrative or exemplary, not restrictive; the invention is not limited to the disclosed embodiments. Those skilled in the art will understand that many modifications, variations, and alterations will occur within the scope defined by the appended claims. Furthermore, in practicing the claimed invention, variations of the disclosed embodiments can be understood and implemented by those skilled in the art upon studying the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. The fact that certain measures are recited in mutually different dependent claims does not mean that a combination of these measures cannot be advantageous. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A power tool (1) for tightening threaded fasteners, the tool comprising: - Motor (10), - Clutch (20), comprising: a pressure plate (21) configured to be rotatably driven by the motor, a cam follower plate (22), a shaft (23) attached to the cam follower plate, and a preloaded spring element (40) arranged around the shaft (23) and configured to press the cam follower plate against the pressure plate to control the clutch release torque; and - Torque setting mechanism (30) for adjusting the clutch release torque of the clutch, the torque setting mechanism comprising: an adjustment arrangement (50) acting on the spring element and having a first thread (70a) for engaging with a second thread (70b) disposed on the shaft to adjust the deflection of the spring element when rotated relative to the shaft and the adjustment arrangement, wherein the adjustment arrangement is arranged to selectively lock in a position to prevent rotation such that rotation of the shaft and / or the motor causes a change in the spring deflection, wherein the power tool further comprises a sensor arranged to sense a parameter from which the deflection of the spring can be determined, and wherein the parameter is a parameter from which the rotation angle of the motor and / or the shaft can be determined.

2. The power tool according to claim 1, wherein, The sensor is an angle sensor and the parameter is the rotation angle of the motor.

3. The power tool according to claim 1, wherein, The sensor is arranged to sense the motor current of the motor.

4. The power tool according to any one of claims 1 to 3 further includes a processing circuit configured to determine a clutch release torque value based on the parameters.

5. The power tool according to claim 4, wherein the processing circuit is further configured to: - determine the change in spring deflection caused by the operation of the adjustment arrangement based on the parameters and a preset value indicating the pitch of the first and second threads, and - determine the clutch release torque value based on the determined change in spring deflection.

6. The power tool according to claim 4, wherein, The processing circuit is further configured to: - receive an input indicating a desired clutch release torque value, - control the motor to rotate when the adjustment arrangement is locked and cannot rotate, until the spring element deflects to the amount that reaches the desired clutch release torque value.

7. The power tool according to claim 6, wherein, The processing circuit is further configured to: control the motor to rotate to reach a predetermined starting point before controlling the motor to rotate to reach the desired deflection value.

8. The power tool according to claim 1, wherein, The adjustment arrangement includes an adjusting nut (51) acting on the spring element to adjust the deflection of the spring element when it rotates relative to the shaft and the adjusting nut.

9. The power tool according to claim 8, wherein, The adjustment arrangement further includes a support plate unit (52) arranged adjacent to the adjustment nut, wherein one end of the spring element abuts against the plate-shaped portion (52a) of the support plate unit.

10. The power tool according to claim 9, wherein, The support plate unit further includes an axially extending cylindrical portion (52b), on which the first thread (70a) is arranged.

11. The power tool according to any one of claims 9 or 10, wherein, The adjusting nut and the support plate unit include mutually engaging locking devices (80a, 80b) arranged to prevent relative rotation between them.

12. The power tool according to claim 8, wherein, The adjusting nut further includes a first engagement device (53) arranged to lock the rotation of the adjusting nut.

13. A method for determining the clutch release torque in a power tool according to any one of the preceding claims, the method comprising the steps of: - Receive data including parameters from which the deflection of the spring can be determined, - Determine the clutch release torque value based on the received data.

14. A control device configured to control a power tool according to any one of claims 1 to 12, the control device comprising circuitry configured to perform the steps of the method according to claim 13.

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