Fastening tool with crank drive

Abstract

A fastening tool includes a motor assembly (20), a drive mechanism coupled to the motor assembly and adapted to drive a piston, and an energy storage mechanism coupled to a striking element (38) adapted to strike a workpiece. The energy storage mechanism includes a driven member (36). The drive mechanism further includes a crank assembly (28) coupled between the motor assembly (20) and the driven member, such that rotational force from the motor assembly (20) is converted to linear movement of the driven member (36). With the crank assembly, the fastening tool eliminates gear meshing components in its movement conversion mechanism, which not only simplifies the structure, saves cost, but also prolongs the product life of the fastening tool.

Description

Technical Field

[0001] This invention relates to power tools, and more particularly to fastening tools suitable for driving fasteners into workpieces. Background Technology

[0002] Fastening tools, such as nail guns (also known as nail hammers), typically use high-pressure gas as a power source to drive workpieces such as nails out of the tool at high speed. Generally, during each cycle of workpiece firing, the high-pressure gas in the cylinder must first be compressed to a certain level to position the piston. The piston is then released upon firing, which generates powerful kinetic energy to complete the impact operation. This cylinder-piston configuration is often called a "gas spring".

[0003] Traditional pneumatic tools typically use single-cylinder or dual-cylinder configurations for their gas springs. In a dual-cylinder configuration, an electric motor typically drives the accumulator piston via a pinion gear connected to the motor shaft and engaged with a toothed rack, thus converting the rotational drive force from the motor into linear movement of the rack, and consequently, linear movement of the accumulator piston. However, to move the impact piston in the other cylinder to drive the impactor and fastener, a latching device (e.g., electronic or magnetic) is needed to control the timing of the impactor's strikes. Therefore, the entire dual-cylinder configuration is complex and expensive due to the need for additional components such as latching devices to control the timing of the two cylinders' operation. Furthermore, the pinion and rack drive includes teeth that mesh between the pinion and rack and are susceptible to mechanical wear.

[0004] On the other hand, some single-cylinder configurations in fastening tools use gears with asymmetrically arranged teeth in the circumferential direction to engage with an elongated rod having multiple stop elements for movement conversion, wherein a large circumferential clearance exists between two of the multiple teeth. This structure is called an asymmetric gear-rod structure. When each tooth engages with its corresponding stop element, the piston in the single cylinder moves in the direction of compressed gas. Then, after all the teeth have engaged with all the stop elements in turn, the piston rapidly reverses direction to apply an impact force to the impactor while the gear is operating in the area of ​​large clearance. However, in this configuration, there is also the problem of mechanical wear, because the teeth on the gear engage and disengage from the stop elements on the rod during each impact cycle, and the fastening tool's lifespan is shortened due to mechanical wear. Summary of the Invention

[0005] In view of the above background, one object of the present invention is to provide an alternative pneumatic power tool that eliminates or at least mitigates the above-mentioned technical problems.

[0006] The above objectives are achieved by combining the features of the independent claims; the dependent claims disclose other advantageous embodiments of the invention.

[0007] Other objects of the invention will become apparent to those skilled in the art from the following description. Therefore, the foregoing statements of objects are not exhaustive and are merely illustrative of some of the many objects of the invention.

[0008] Therefore, one aspect of the present invention is a fastening tool comprising a motor assembly, a drive mechanism connected to and adapted to drive a piston, and an energy storage mechanism connected to an impact element suitable for impacting a workpiece. The energy storage mechanism includes a driven member. The drive mechanism further includes a crank assembly connected between the motor assembly and the driven member to convert rotational force from the motor assembly into linear movement of the driven member.

[0009] Preferably, the energy storage mechanism further includes a cylinder, and the driven member is a piston housed in the cylinder and adapted to reciprocate within the cylinder.

[0010] More preferably, the crank assembly further includes a crank that is connected at one end to the output shaft of the motor assembly and at the other end to a connecting rod. The connecting rod connects the crank to the piston, wherein the connecting rod is pivotally connected to the piston.

[0011] More preferably, the piston is adapted to move linearly within the cylinder between top dead center (TDC) and bottom dead center (BDC). The crank is located at two angular positions corresponding to the piston in the TDC and BDC, respectively, wherein these two angular positions differ from each other by 180 degrees.

[0012] According to a variant of a preferred embodiment, the crank assembly further includes a one-way clutch connected between the output shaft and the crank.

[0013] In one implementation, the one-way clutch is a one-way roller bearing or a one-way overrunning bearing.

[0014] In another embodiment, the one-way clutch includes an inner wheel connected to one of the output shaft and the crank, and an outer wheel connected to the other of the output shaft and the crank. The inner and outer wheels are connected to each other by a ratchet mechanism.

[0015] According to another variation of the preferred embodiment, in order to store energy, the cylinder is filled with high-pressure gas or the cylinder contains a mechanical spring.

[0016] According to another variation of the preferred embodiment, the motor assembly includes a motor and a gearbox connected to the motor.

[0017] Therefore, embodiments of the present invention provide a fastening tool that is simple in structure, safe, and reliable. Since only a single drive mechanism (a crank assembly) is needed to enable the piston to move in two different directions, the fastening tool of the present invention requires only one cylinder instead of two. By configuring the lengths of the connecting rod and crank in the crank assembly, the energy storage (compression) period and the subsequent impact (release) period in each impact cycle can be precisely controlled. Furthermore, due to the continuous operation of the crank assembly, the impact cycles can be continuously and automatically repeated, meaning that the operation of the motor in the fastening tool does not need to be interfered with, but it can always rotate at a constant speed in a single direction, and the rotation of the aforementioned gear will automatically complete each impact cycle and then begin the next impact cycle.

[0018] Furthermore, by utilizing a crank assembly, the fastening tool eliminates the gear meshing portion in its movement conversion mechanism, which not only simplifies the structure and saves costs but also extends the product life of the fastening tool. This contrasts with conventional pinion-rack structures or asymmetrical gear-link structures, which suffer from tooth meshing and the resulting mechanical wear. In some embodiments of the invention, a one-way clutch is used to address the problem of the motor being reverse-driven by the piston through the crank assembly during the impact phase of the impact cycle. Attached Figure Description

[0019] The foregoing and further features of the present invention will become apparent from the following description of preferred embodiments, which are provided by way of example only in conjunction with the accompanying drawings, wherein:

[0020] Figure 1 The appearance of a nail gun according to an embodiment of the present invention is shown.

[0021] Figure 2 yes Figure 1 A 3D view of the motor assembly and drive mechanism in the nail gun.

[0022] Figure 3 Shown in different orientations Figure 1 The impact element and crank assembly of the nail gun.

[0023] Figure 4 yes Figure 1 Exploded view of the crank and one-way clutch in the nail gun.

[0024] Figures 5a to 5d They are shown respectively Figure 1 The state of the crank, piston, and connecting rod in the nail gun at four different angular positions of the crank.

[0025] Figure 6A crank assembly of a nail gun according to another embodiment of the present invention is shown.

[0026] Figure 7 yes Figure 6 An exploded view of part of the crank assembly.

[0027] Figure 8 yes Figure 6 A plan view of the one-way clutch in the crank assembly.

[0028] In the accompanying drawings, in the several embodiments described herein, the same reference numerals denote the same parts. Detailed Implementation

[0029] In the following claims and in the foregoing description of the invention, unless the context otherwise requires it due to the language of expression or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” are used in the sense of inclusion, that is, to indicate the presence of the stated feature, but not to exclude the presence or addition of other features in various embodiments of the invention.

[0030] As used in the specification and claims, unless otherwise stated, “connection” or “link” means an electrical connection or link, directly or indirectly, via one or more electrical means.

[0031] Terms such as “horizontal,” “vertical,” “upward,” “downward,” “above,” and “below” used in the specification are for the purpose of describing the invention in its normal use orientation and are not intended to limit the invention to any particular orientation.

[0032] See Figures 1 to 3In a first embodiment of the invention, a fastening tool, particularly a nail gun (or nailing machine), is disclosed. The nail gun includes a housing 48, a grip 50, a battery housing 52, a trigger switch 54, etc., components well known to those skilled in the art, but not described in detail here for simplicity. The battery housing 52 is adapted for detachable connection to a battery pack (not shown) of the nail gun. The nail gun is a pneumatic tool and includes an energy storage mechanism comprising a cylinder 34, an end cap (not shown) located at the end of the cylinder 34, and a valve (not shown) constructed on the end cap. The cylinder 34 is the only cylinder in the nail gun. Both ends of the cylinder 34 are open, and one end needs to be closed by the end cap. The valve is used to connect to a high-pressure gas source (e.g., an air compressor, not shown) outside the pneumatic tool and to control the amount of high-pressure gas entering the cylinder 34. The energy storage mechanism also includes a piston 36, which is housed within the cylinder 34 and adapted to reciprocate within the cylinder. In this embodiment, the piston is also referred to as a driven member. Piston 36 and cylinder 34 together form the gas spring of the nail gun. Piston 36 is connected to one end of impact element 38. Impact element 38 has an elongated shape adapted to achieve the working effect of the nail gun by impacting a workpiece (e.g., a nail) with an impactor (not shown) at the other end of the impact element. The end of impact element 38 is close to the impactor, which is movably housed in drive guide 26. To ensure the airtightness of cylinder 34, a gasket and a liner (both not shown) are arranged at the other end of cylinder 34 (away from the end cap) to prevent accidental leakage of high-pressure gas from cylinder 34 and to prevent the impact of piston 36 from affecting other parts of the nail gun. A cartridge 24 is detachably attached to the front end of the nail gun to provide nails for impact.

[0033] In addition, at the front end of the nail gun, besides the cartridge 24, a motor assembly including a motor 20 and a gearbox 22 is provided. The motor 20 is adapted to rotate and output rotational driving force when energized, and the output end (not shown) of the motor 20 is connected to the input end (not shown) of the gearbox 22. The gearbox reduces the rotational speed at its output end compared to the rotational speed of the motor 20, but increases the torque at its output end. The gearbox 22 contains a multi-stage planetary gear set (not shown). Both the motor 20 and the gearbox 22 are well known to those skilled in the art, and for the sake of brevity, the details of the motor 20 and the gearbox 22 will not be described in further detail here. In this embodiment, the motor 22 and the gearbox 22 form the motor assembly of the nail gun.

[0034] Figure 1 and Figure 2The nail gun also includes a drive mechanism comprising a crank assembly connected to the output of gearbox 22. This drive mechanism is connected to a motor assembly and adapted to drive piston 36. To drive piston 36 in reciprocating motion, the drive mechanism is adapted to convert the rotational force from the motor assembly into linear movement of piston 36, which is achieved via the crank assembly. Figures 2 to 3 As shown, the crank assembly includes a crank 28, a one-way clutch 30 connecting the crank 28 and the output end of the gearbox 22, and a connecting rod 32 connecting the crank 28 to the piston 36. One end 28c of the crank 28 is pivotally connected to the gearbox 22 via the one-way clutch 30. The other end 28b of the crank 28 is pivotally connected to one end 32a of the connecting rod 32. The other end 32b of the connecting rod 32 is pivotally connected to the piston 36. The connecting rod 32 has an elongated shape similar to that of the impact element 38, but is shorter than the impact element 38. In the operating mechanism of the nail gun, the position and orientation of the connecting rod 32 and the crank 28 will change continuously, which will be described in more detail below.

[0035] Go to Figure 4 , Figure 4 The connection between crank 28 and one-way clutch 30 is shown in detail. One end 28c of crank 28 has an enlarged annular shape, the diameter of which is substantially equal to the length of the remaining portion of crank 28, including the other end 28b (which has an elongated shape). The annular shape of end 28c defines a hollow space 28d for accommodating one-way clutch 30. End 28c is rigidly connected to the outer portion 30a of one-way clutch 30 because a first limiter 56 is partially accommodated in a first recess 28e on the inner circumference of end 28c of crank 28 and partially accommodated in a second recess 30d on the outer circumference of the outer portion 30a of one-way clutch 30. Thus, end 28c always rotates together with the outer portion 30a. At end 28b of crank 28, a hole 28a is defined for connecting crank 28 to end 32a of connecting rod 32 via a hinge (not shown).

[0036] The one-way clutch 30 is, for example, a one-way roller bearing or a one-way sprag bearing, both of which are well known to those skilled in the art and will not be described in detail here. The one-way clutch 30 includes an outer portion 30a and an inner portion 30b rotatable relative to the outer portion 30a. The one-way clutch 30 is designed such that when the rotational speed of the inner portion 30b is greater than the rotational speed of the outer portion 30a, the outer portion 30a and the inner portion 30b engage to transmit torque between them. However, when the rotational speed of the inner portion 30b is less than the rotational speed of the outer portion 30a, they disengage, and no torque transmission occurs between them. The inner portion 30b of the one-way clutch 30 receives rotational driving force from the intermediate shaft 60 and is rigidly connected to the intermediate shaft 60 due to a second limiter 58, which is partially received in a third recess 30c on the inner circumference of the inner portion 30b and partially received in a fourth recess 60a on the outer circumference of the intermediate shaft 60 near one end of the intermediate shaft. A non-circular shank 60b is formed at the other end of the intermediate shaft 60 opposite to the fourth recess 60a. This shank 60b is connected to an output member (not shown) of the gearbox 22, which has a complementary non-circular shape. The intermediate shaft 60 is rotatably supported on a fixed part (e.g., housing) in the nail gun by means of a roller bearing 62.

[0037] Now let's examine the working principle of the nail gun in the above embodiments. When the user actuates the nail gun (e.g., by pressing the trigger), Figures 1 to 2 The motor 20 in the motor starts to rotate, and the original high-speed rotational movement output by the motor 20 is converted into low-speed, high-torque rotation at the output end of the gearbox 22. Then, the rotational force at the output end of the gearbox 22 begins to drive the crank assembly. Now refer to... Figures 5a to 5d These diagrams illustrate four different states of crank 28, connecting rod 32, and piston 36 during a complete impact cycle. In this embodiment, each impact cycle of the nail gun is defined as beginning when the impact element 38 moves away from its BDC and ending when the impact element 38 returns to the BDC after completing its entire stroke. The entire stroke (e.g., one cycle) is further broken down into an energy storage phase and an impact phase, which will be explained below.

[0038] Figure 5a The initial positions of crank 28, connecting rod 32, and piston 36 are shown before the nail gun is activated and before the impact cycle begins. Those skilled in the art will understand how a stopping mechanism can be designed to move crank 28, connecting rod 32, and piston 36 to a position where the user has completed the nail firing operation or when the nail gun is de-energized. Figure 5a The positions shown are, for example, based on the use of position sensors to control motor operation. For ease of discussion, let's assume that... Figure 5aThe crank 28 is in the 0° angle position, and the piston 36 is now in its BDC. The connecting rod 32 and the impact element 38 are parallel to each other and both are along the longitudinal axis of the cylinder block 34. However, in this state, the connecting rod 32 overlaps with an elongated portion of the crank 28, which includes an end 28b extending in a direction defined by the central axis of the end 28c of the crank 28.

[0039] Next, if the user presses trigger 54, motor 20 is actuated. In this example, it is assumed that the output shaft of motor 20 always rotates counterclockwise as indicated by arrow 64. The output rotational force from motor 20 is input to gearbox 22, which further converts this rotational force into a gearbox output force with lower speed and higher torque, which is then transmitted to one-way clutch 30. At this point, before motor 20 is actuated, the inner portion 30b of one-way clutch 30, which is directly connected to the output end of gearbox 22, has a faster rotational speed than the outer portion 30a of one-way clutch 30. Then, when one-way clutch 30 is now in its power transmission mode, the inner portion 30b engages with the outer portion 30a, and the outer portion 30a begins to rotate because it is driven by the inner portion 30b. The rotation of the outer portion 30a, in turn, drives crank 28 to rotate counterclockwise along the central axis defined by end 28c.

[0040] As crank 28 rotates, it eventually moves to the position where Figure 5b The position shown is defined as the 90° position of crank 28. Simultaneously, the rotation of crank 28 causes connecting rod 32 to move in a plane substantially parallel to crank 28 and impact element 38. The movement of connecting rod 32 then causes piston 36 to move linearly within cylinder block 34. Two pivot points at both ends of connecting rod 32 enable the movement of the aforementioned components. When crank 28 is moved to the 90° position, a portion of crank 28, connecting rod 32, and impact element 38 forms as shown... Figure 5b The right-angled triangle is shown. At this moment, piston 36 is moving a short distance away from its BDC towards its TDC.

[0041] As crank 28 continues to rotate, it eventually moves to the position where... Figure 5c The position shown is defined as the 180° position of crank 28. This movement of crank 28 then drives connecting rod 32 from... Figure 5b The position of the link 32 is moved back to an orientation parallel to the impact element 38, but the position of the link 32 is different from that of the impact element 38. Figure 5aThe position is offset compared to the previous position. Specifically, connecting rod 32 is now parallel to impact element 38 again, and both are along the longitudinal axis of cylinder block 34. However, in this state, connecting rod 32 no longer overlaps with crank 28 along the direction defined by the central axis defined by end 28c of crank 28. Instead, in this state, connecting rod 32 appears to extend further from end 28b of crank 28, causing piston 36 to be driven to move across the maximum distance to TDC. Now, the nail gun is ready to fire the nail at the workpiece. It should be noted that, in such cases... Figures 5a to 5c The energy storage phase of the gas spring shown means that the one-way clutch 30 is always in its power transmission mode, so that the rotational force from the motor 20 can be transmitted to the crank 28 and other parts.

[0042] from Figure 5c Initially, as piston 36 moves rapidly from its TDC in the opposite direction to BDC due to the stored energy stored in the gas spring, the nail gun automatically fires the nail. The stored energy is converted into the large kinetic energy of piston 36, which in turn drives the impact element 38 and the impactor to strike the nail and fire it. Figure 5d The diagram shows a state of the components during the impact phase, with crank 28 in its 270° position. However, in this impact phase, motor 20 and gearbox 22 will be unaffected because the outer part 30a has a much higher rotational speed than the inner part 30b, which is always driven by motor 20 during the cycle, as the outer part is connected to crank 28 and rotates due to piston 36 moving back to the BDC. Then, when the inner part 30b disengages from the outer part 30a, the one-way clutch 30 is in freewheel mode. In this way, motor 20 and gearbox 22 are protected from rapid reverse rotational forces, which would damage motor 20 and gearbox 22 without this one-way clutch 30. When the impact pin is completed, the entire cycle is finished, and the states of the various components in the crank assembly return to their original positions. Figure 5a The state is shown in the diagram. As motor 20 continues to rotate counterclockwise, the next cycle can begin again.

[0043] Go to Figures 6 to 8 According to another embodiment of the present invention, a method is provided that has the same characteristics as... Figures 2 to 5d This refers to a replacement crank assembly for a different one-way clutch. This replacement crank assembly can be used to replace... Figures 1 to 5d The crank assembly of the nail gun is retained while other parts of the nail gun are preserved. Figures 6 to 8 The crank assembly includes a crank 128 connected to one end of a connecting rod 132, the other end of which is connected to a piston 136. The piston 136 is connected to the impactor (not shown) of a nail gun via an impact element 138. The crank 128 is connected via a crank having a... Figures 7 to 8The one-way clutch of the structure shown in the diagram is connected to the output flange 170, which serves as the output end of the nail gun gearbox (not shown).

[0044] Specifically, one end 128c of crank 128 is pivotally connected to the gearbox via a one-way clutch, specifically via a pawl carrier 168 and an intermediate shaft 160. The other end 128b of crank 128 is pivotally connected to one end 132a of connecting rod 132 via hinge 166. The other end (not shown) of connecting rod 132 is pivotally connected to piston 136. Connecting rod 132 has a similar elongated shape to impact element 138, but is shorter than impact element 138. During the operation of the nail gun, the position and orientation of connecting rod 132 and crank 128 will continuously change, similar to... Figures 2 to 5d The positions and orientations mentioned in the embodiments. A non-circular shank 160b is formed at the other end of the intermediate shaft 160 opposite to the toothed portion 142, which is connected to the output flange 170 having a complementary non-circular shape.

[0045] Go to Figures 7 to 8 , Figures 7 to 8 The connection between crank 128 and one-way clutch is shown in detail. The end portion 128c of crank 128 has a generally triangular shape. A hole 128d is defined at the center of end portion 128c for receiving one end of intermediate shaft 160, and a plurality of teeth 142 fixedly connected to intermediate shaft 160 are present at the same end of intermediate shaft 160. Each tooth 142 has a shark fin shape extending radially from the periphery of intermediate shaft 160. This shark fin shape is formed by a generally radially extending edge 142a and another edge 142b extending generally tangentially from the periphery of intermediate shaft 160. Cooperating with the teeth 142 are three pawls 144, which are pivotally connected to a pawl carrier 168 defining a pivot axis 172, and each pawl 144 is biased away from the sidewall of crank 128 by a spring 140. It should be noted that during rotation of intermediate shaft 160, each pawl 144 contacts more than one tooth 142. The pawl carrier 168 has a triangular shape similar to the end 128c of the crank 128, and they are adapted to rotate together.

[0046] During operation, the crank 128, under different conditions, can rotate together with or relative to the intermediate shaft 160. Specifically, as those skilled in the art will understand, the one-way clutch is designed such that when the rotational speed of the intermediate shaft 160 is greater than the rotational speed of the crank 128, the crank 128 and the intermediate shaft 160 engage to transmit torque between them. In this power transmission mode of the one-way clutch, when the intermediate shaft 160 rotates faster than the crank 128, for example in the counter-clockwise direction indicated by arrow 164, each pawl 144 is pushed by the edge 142a of the teeth 142. Because the direction of the pushing force is substantially through the pivot axis 172 of the pawl 144, the pushing force subsequently causes the crank 128 to rotate in the same direction as the intermediate shaft 160. During the energy storage phase of the gas spring, the one-way clutch is in power transmission mode.

[0047] However, when the rotational speed of the internal portion of the intermediate shaft 160 is less than the rotational speed of the crank 128, they disengage, and no torque transmission occurs between them. In this freewheel mode of the one-way clutch, when the intermediate shaft 160 rotates slower than the crank 128, for example, in the counterclockwise direction indicated by arrow 164, each pawl 144 actually moves counterclockwise relative to the teeth 142, and thus each pawl 144 slides over the edge 142b of the teeth 142 as it also pivots counterclockwise against the spring force of the spring 140. In this way, the motor and gearbox are protected from rapid reverse rotational forces, which would damage the motor and gearbox without this one-way clutch. During the impact phase of the gas spring, the one-way clutch is in freewheel mode.

[0048] Thus, exemplary embodiments of the present invention have been fully described. Although this description relates to specific embodiments, it will be apparent to those skilled in the art that the invention can be practiced with variations of these specific details. Therefore, the invention should not be construed as limited to the embodiments set forth herein.

[0049] While the invention has been shown and described in detail in the accompanying drawings and the foregoing description, it should be considered illustrative rather than restrictive. It should be understood that exemplary embodiments are shown and described only, and that the exemplary embodiments do not limit the scope of the invention in any way. It is understood that any features described herein may be used in conjunction with any embodiment. The illustrative embodiments do not exclude each other or other embodiments not listed herein. Therefore, the invention also provides embodiments that include combinations of one or more of the illustrative embodiments described above. Modifications and variations of the invention described herein may be made without departing from the spirit and scope of the invention; therefore, only the limitations indicated by the appended claims should be applied.

[0050] It should be understood that if any prior art publications are cited in this article, such citation does not constitute an acknowledgment that such publications constitute common general knowledge in the field in Australia or any other country.

[0051] exist Figures 5a to 5d The different states of the crank assembly shown represent the movement of multiple components within the crank assembly in a complete cycle. Those skilled in the art will recognize that fastening tools can be designed to perform either a single-shot mode or a multi-shot mode. In the latter mode, as long as the motor remains rotating in the same direction, it can be repeatedly and automatically applied to… Figures 5a to 5d Similar operating steps are shown in the diagram.

[0052] Furthermore, although the above embodiments are pneumatic tools, those skilled in the art will recognize that the present invention can be used in other fastening tools that have different types of energy storage units instead of gas springs. For example, the present invention can also be applied to fastening tools with metal springs.

[0053] exist Figures 6 to 8 The ratchet mechanism in the one-way clutch shown can be modified to have, for example, different numbers of teeth, different numbers of pawls, and different shapes / or orientations of the teeth and pawls. However, such substitutions still fall within the scope of the present invention.

[0054] In the above embodiments, the fastening tool is in the form of a pneumatic fastening tool using a gas spring with a single cylinder. However, those skilled in the art will recognize that the implementation of the fastening tool is not necessarily limited to this configuration. For example, instead of a single cylinder for the gas spring, mechanical springs or other types of energy storage will also work under the spirit of this invention.

[0055] Similarly, the fastening tools described in the above embodiments use different forms of one-way clutches to disengage the crank assembly from the gearbox and motor during the impact phase, thereby preventing the latter from interrupting the rapid impact of the fastener. However, those skilled in the art will recognize that other types of mechanisms can be used during the impact phase to disengage the gearbox from the motor and piston, for example, by using a double-cylinder structure with a latch, such that the impact action of the piston in one cylinder does not adversely affect the crank assembly, gearbox, and motor connected to the other cylinder.

Claims

1. A fastening tool, comprising: Motor assembly; A drive mechanism, which is connected to the motor assembly and adapted to drive the piston; as well as An energy storage mechanism is connected to an impact element suitable for impacting a workpiece; the energy storage mechanism includes a driven member. The drive mechanism further includes a crank assembly connected between the motor assembly and the driven member to convert rotational force from the motor assembly into linear movement of the driven member. The energy storage mechanism further includes a cylinder; the driven member is a piston housed in the cylinder and adapted to reciprocate within the cylinder. The crank assembly further includes a crank and a one-way clutch. The crank is pivotally connected at one end to the output end of the motor assembly via the one-way clutch, and at the other end to a connecting rod. The connecting rod connects the crank to the piston, wherein the connecting rod is pivotally connected to the piston and the piston is connected to the impact element. The one-way clutch includes multiple teeth, three pawls cooperating with the teeth, and a pawl carrier pivotally connected to the pawls. The pawl carrier is adapted to rotate together with the crank. An intermediate shaft connects the multiple teeth to the output end. Each tooth has a shark fin shape extending radially from the periphery of the intermediate shaft. The shark fin shape is formed by a first edge extending substantially radially and a second edge extending substantially tangentially from the periphery of the intermediate shaft. Each pawl is spring-biased away from the sidewall of the crank. The fastening tool's stroke includes an energy storage phase and an impact phase. During the energy storage phase, the motor assembly drives the crank to rotate via the one-way clutch, causing the piston to move. When the rotational speed of the intermediate shaft exceeds the rotational speed of the crank, each pawl is pushed by the first edge of the teeth. The crank and the intermediate shaft engage to transmit torque between them. During the impact phase, the piston causes the crank to rotate at a speed greater than that of the intermediate shaft via the connecting rod. The pawls overcome the spring force of the spring, and each pawl slides over the second edge of the tooth, causing the crank and the intermediate shaft to disengage.

2. The fastening tool according to claim 1, wherein, The piston is adapted to move linearly between top dead center (TDC) and bottom dead center (BDC) within the cylinder. The crank is located at two angular positions corresponding to the pistons located in the TDC and the BDC, respectively, wherein the two angular positions are 180 degrees apart from each other.

3. The fastening tool according to claim 1, wherein, To store energy, the cylinder is filled with high-pressure gas, or the cylinder contains a mechanical spring.

4. The fastening tool according to any one of the preceding claims, wherein, The motor assembly includes a motor and a gearbox connected to the motor.

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