WO2022011631A1

WO2022011631A1 - Fastening tool with a crank transmission

Info

Publication number: WO2022011631A1
Application number: PCT/CN2020/102290
Authority: WO
Inventors: Ying Xiang TAN; Hai Ling LIN; Jin Lin Zhou
Original assignee: Techtronic Cordless Gp
Priority date: 2020-07-16
Filing date: 2020-07-16
Publication date: 2022-01-20
Also published as: CN115803150A; EP4182122A1; EP4182122A4

Abstract

A fastening tool includes a motor assembly (20), a drive mechanism connected to the motor assembly and adapted to drive a piston; and an energy accumulating mechanism that is connected to a striking element (38) suitable for striking a workpiece. The energy accumulating mechanism contains a driven member (36). The drive mechanism further contains a crank assembly (28) connected between the motor assembly (20) and the driven member to transform a rotational force from the motor assembly (20) to a linear motion of the driven member(36). With the crank assembly the fastening tool eliminates gear meshing parts in its motion conversion mechanism, which does not only simplify the structure, saves cost, but also prolongs the product life of the fastening tool.

Description

FASTENING TOOL WITH A CRANK TRANSMISSION

FIELD OF INVENTION

This invention relates to power tools, and more particularly to fastening tools that are adapted to drive fasteners into workpieces.

BACKGROUND OF INVENTION

Fastening tools such as nail guns (a.k.a. nailers) often use high-pressure gas as a power source to drive a workpiece such as nails or the like to eject from the tool at a high speed. Generally speaking, during each cycle of a workpiece being fired, it is necessary to firstly compress the high-pressure gas in a cylinder to a certain extent so that the piston is in position. Then the piston is released at the moment it is fired, which produces a powerful kinetic energy to complete the striking operation. This cylinder-piston configuration is commonly referred to as "gas spring" .

Conventional pneumatic tools typically use either a one-cylinder configuration or a two-cylinder configuration for the gas spring. In the two-cylinder configuration, for the high-pressure gas in a first, energy-accumulating cylinder to be compressed, an electric motor is generally used to drive an accumulator piston through a pinion which is connected to the motor shaft and coupled with a rack having teeth, so that the rotational driving force from the motor can be converted to a linear movement of the rack and in turn the accumulator piston. However, for a striking piston in another cylinder to move a striker to drive a fastener, a latch device (e.g. electronic or magnetic) is needed to control the timing for the striker to strike. The entire structure for the two-cylinder configuration is therefore complicated and costly because of additional components such as the latch device needed to control the timing of operation of the two cylinders. Also, the pinion and rack transmission includes teeth meshing between the pinion and rack, and is vulnerable to mechanical wearing.

On the other hand, some of the one-cylinder configurations in fastening tools use a gear with asymmetrically arranged teeth on the circumferential direction to engage with an elongated rod with multiple stopping elements for the motion conversion, where there is a large circumferential gap between two of the multiple teeth. Such a structure is known as an asymmetrical gear-rod structure. When the teeth each engage with a corresponding stopping element, the piston in the single cylinder is moved in a direction to compress the gas. Then, when all teeth have engaged with all stopping elements in turns, then as the gear runs in the region of the large gap, the piston quickly moves reversely to exert an impact force on the striker. However, in such a configuration there is also the problem of mechanical wearing as teeth on the gear engaging and disengaging with stopping elements on the rod in each striking cycle, and the fastening tools have reduced product life time because of the mechanical wearing.

SUMMARY OF INVENTION

In the light of the foregoing background, it is an object of the present invention to provide an alternate pneumatic power tool which eliminates or at least alleviates the above technical problems.

The above object is met by the combination of features of the main claim; the sub-claims disclose further advantageous embodiments of the invention.

One skilled in the art will derive from the following description other objects of the invention. Therefore, the foregoing statements of object are not exhaustive and serve merely to illustrate some of the many objects of the present invention.

Accordingly, the present invention, in one aspect, is a fastening tool includes a motor assembly, a drive mechanism connected to the motor assembly and adapted to drive a piston; and an energy accumulating mechanism that is connected to a striking element suitable for striking a workpiece. The energy accumulating mechanism contains a driven member. The drive mechanism further contains a crank assembly connected between the motor assembly and the driven member to transform a rotational force from the motor assembly to a linear motion of the driven member.

Preferably, the energy accumulating mechanism further contains a cylinder, and the driven member is a piston that is accommodated in the cylinder and suitable for a reciprocating motion within the cylinder.

More preferably, the crank assembly further contains a crank coupled to an output shaft of the motor assembly on one end, and pivotally coupled to a connecting rod on another end. The connecting rod connects the crank to the piston wherein the connecting rod is pivotally connected to the piston.

More preferably, the piston is adapted to move linearly within the cylinder between a top dead center (TDC) and a bottom dead center (BDC) . The crank is located at two of its angular positions corresponding to the piston located in the TDC and the BDC respectively, where the two angular positions are different from each other by 180 degrees.

According to a variation of the preferred embodiments, the crank assembly further contains a one-way clutch connected between the output shaft and the crank.

In one implementation, the one-way clutch is a one-way roller bearing or a one-way sprag bearing.

In another implementation, the one-way clutch contains an inner wheel connected to one of the output shaft and the crank, and an outer wheel connected to the other one of the output shaft and the crank. The inner wheel and the outer wheel are coupled to each other through a ratchet mechanism.

According to another variation of the preferred embodiments, for accumulating energy, the cylinder is filled with high pressure gas or the cylinder contains a mechanical spring.

According to another variation of the preferred embodiments, the motor assembly contains a motor and a gearbox connected to the motor.

Embodiments of the present invention thus provide a fastener tool that is simple in construction, safe and reliable. Since only a single drive mechanism (which is the crank assembly) needs to be used to enable the piston to move in two different directions, the fastener tool of the present invention requires only one cylinder instead of two. By configuring the lengths of the connecting rod and the crank in the crank assembly, the energy accumulation (compression) period and the subsequent striking (release) period in each striking cycle can be precisely controlled. Also, the striking cycle can be automatically repeated continuously because of the continuous operation of the crank assembly, which means that operation of the motor in the fastener tool does not need to be interfered, but it can always rotate in a single direction at a constant speed, and the rotation of the above-mentioned gear will automatically complete each striking cycle and then start the next one.

In addition, with the crank assembly, the fastening tool eliminates gear meshing parts in its motion conversion mechanism, which does not only simplify the structure, saves cost, but also prolongs the product life of the fastening tool. This is in contrast to a conventional pinion-rack structure or an asymmetrical gear-rod structure which suffers from teeth meshing and the resultant mechanical wearing. In some embodiments of the invention, the use of the one-way clutch solves the problem of the motor being reversely driven by the piston via the crank assembly during the striking phase of the striking cycle.

BRIEF DESCRIPTION OF FIGURES

The foregoing and further features of the present invention will be apparent from the following description of preferred embodiments which are provided by way of example only in connection with the accompanying figures, of which:

Fig. 1 shows the appearance of a nail gun according to one embodiment of the invention.

Fig. 2 is a perspective view of the motor assembly as well as the drive mechanism in the nail gun of Fig. 1.

Fig. 3 shows the drive blade and the crank assembly of the nail gun of Fig. 1 in a different orientation.

Fig. 4 is an exploded view of the crank as well as the one-way clutch in the nail gun of Fig. 1.

Figs. 5a-5d show respectively the status of the crank, piston, and connecting rod at four different angular positions of the crank in the nail gun of Fig. 1.

Fig. 6 shows the crank assembly of a nail gun according to another embodiment of the invention.

Fig. 7 is a partially exploded view of the crank assembly in Fig. 6.

Fig. 8 is a planar illustration of the one-way clutch in the crank assembly in Fig. 6.

In the drawings, like numerals indicate like parts throughout the several embodiments described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

As used herein and in the claims, “couple” or “connect” refers to electrical coupling or connection either directly or indirectly via one or more electrical means unless otherwise stated.

Terms such as “horizontal” , “vertical” , “upwards” , “downwards” , “above” , “below” and similar terms as used herein are for the purpose of describing the invention in its normal in-use orientation and are not intended to limit the invention to any particular orientation.

Referring to Figs. 1-3, in a first embodiment of the present invention, a fastening tool, in particular a nail gun (or called a nailer) , is disclosed. The nail gun includes housing 48, a handle 50, a battery receptacle 52, a trigger switch 54, etc. which are well known to those skilled in the art but which are not described here in details for the sake of simplicity. The battery receptacle 52 is adapted to removably connect to a battery pack (not shown) of the nail gun. The nail gun is a pneumatic tool, and includes an energy accumulating mechanism that includes a cylinder 34, an end cap (not shown) at the end of the cylinder 34, and a valve (not shown) configured 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 mentioned above is used to connect to a source of high-pressure gas external to the pneumatic tool (e.g., an air compressor, not shown) and controls the amount of high-pressure gas entering the cylinder 34. The energy accumulating mechanism further includes a piston 36 that is received within the cylinder 34 and is adapted to reciprocate therein. The piston is also called a driven member in this embodiment. The piston 36 and the cylinder 34 together form the gas spring of the nail gun. The piston 36 is connected to one end of a drive blade 38. The blade 38 has an elongated shape adapted to strike a workpiece (e.g., a nail) through a striker (not shown) at the other end of the blade 42 to achieve the working effect of the nail gun. The blade 38 has its end that is close to the striker movably received in a driver guide 26. In order to ensure the airtightness of the cylinder 34, at the other end of the cylinder 34 (which is the end far away from the end cap) , a gasket and a cushion (both not shown) are arranged to prevent any accidental leakage of high-pressure gas from the cylinder 34, and to prevent an impact by the piston 36 from affecting other parts of the nail gun. A magazine 24 is removably attached to a front end of the nail gun to supply nails for striking.

In addition, at the front end of the nail gun besides the magazine 24, a motor assembly is disposed which includes a motor 20 and a gearbox 22. The motor 20 is adapted to rotate and outputs a rotational driving force upon energization, and an output (not shown) of the motor 20 is connected to an input (not shown) of the gearbox 22 where the gearbox reduces the rotational speed of its output, but increases the torque of its output, as compared to the rotational speed of the motor 20. The gearbox 22 contains multiple stages of planetary gears (not shown) . Both the motor 20 and the gearbox 22 are well-known to skilled persons in the art, and for the sake of brevity the details of the motor 20 and the gearbox 22 will not be further elaborated herein. The motor 22 and the gearbox 22 form a motor assembly of the nail gun in this embodiment.

The nail gun in Figs. 1 and 2 further contains a drive mechanism which includes a crank assembly connected to an output of the gearbox 22. The drive mechanism is connected to the motor assembly and adapted to drive the piston 36. In order to drive the piston 36 for reciprocating motion, the drive mechanism is adapted to transform a rotational force from the motor assembly to a linear movement of the piston 36, which is achieved by the crank assembly. As shown in Figs. 2-3, the crank assembly contains a crank 28, a one-way clutch 30 connected between the crank 28 and the output of the gearbox 22, and a connecting rod 32 connecting the crank 28 to the piston 36. The crank 28 has one end 28c pivotally coupled to the gearbox 22 via the one-way clutch 30. Another end 28b of the crank 28 is pivotally connected to one end 32a of the connecting rod 32. Another end 32b of the connecting rod 32 is pivotally connected to the piston 36. The connecting rod 32 has a similar elongated shape as the drive blade 38, but is shorter than the drive blade 38. During operation of the nail gun, the positions and orientations of the connecting rod 32 and the crank 28 will continuously vary, as will be described in more details below.

Turning to Fig. 4, which shows the connection between the crank 28 and the one-way clutch 30 in details. One end 28c of the crank 28 has an enlarged ring shape which has a diameter substantially equal to the length of the remaining part (which has an elongated shape) of the crank 28 that includes the other end 28b. The ring shape of the end 28c defines a hollow space 28d which receives the one-way clutch 30. The end 28c is rigidly coupled to an outer part 30a of the one-way clutch 30 due to a first limiter 56 received partially in a first notch 28e on the inner circumference of the end 28c of the crank 28, and partially in a second notch 30d on the outer circumference of the outer part 30a of the one-way clutch 30. In this way the end 28c always rotate with the outer part 30a. At the end 28b of the crank 28, there is defined a hole 28a for coupling the crank 28 to the end 32a of the connecting rod 32 via a hinge (not shown) .

The one-way clutch 30 for example is 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 any details here. The one-way clutch 30 contains the outer part 30a as well as an inner part 30b rotatable relative to the outer part 30a. The design of the one-way clutch 30 is that the outer part 30a and the inner part 30b are engaged for transmission of torque between the two when the rotation speed of the inner part 30b is larger than that of the outer part 30a. However, when the rotation speed of the inner part 30b is smaller than that of the outer part 30a, they become disengaged, and no transmission of torque happens between the two. The inner part 30b of the one-way clutch 30 receives a rotational driving force from an intermediate shaft 60, and is rigidly coupled to the intermediate shaft 60 due to a second limiter 58 received partially in a third notch 30c on the inner circumference of the inner part 30b, and partially in a fourth notch 60a on the outer circumference of the intermediate shaft 60 near one end thereof. Another end of the intermediate shaft 60 opposite to the fourth notch 60a is formed with a non-circular shank 60b that is coupled to an output member (not shown) of the gearbox 22 that has complemental non-circular shape. The intermediate shaft 60 is rotatably supported on fixed part in the nail gun (e.g. housing) via a roller bearing 62.

Now look at the working principle of the nail gun in the above embodiment. When the user activates the nail gun (e.g., by pressing a trigger) , the motor 20 in Figs. 1-2 begins to rotate, and the raw high-speed rotary motion outputted by the motor 20 transforms through the gearbox 22 to a low-speed, high-torque rotation at the output of the gearbox 22. The rotational force at the output of the gearbox 22 then starts to drive the crank assembly. Reference will now be made to Figs 5a-5d which show four different states of the crank 28, the connecting rod 32, and the piston 36 during a complete striking cycle. Each striking cycle of the nail gun is defined in this embodiment as starting from the drive blade 38 moving away from its BDC and ending as the drive blade 38 returns to its BDC after the drive blade 38 has completed the entire stroke. The entire stroke (e.g. one cycle) is further split into an energy accumulating phase and a striking phase as will be explained below.

Fig. 5a shows the initial positions of the crank 28, the connecting rod 32, and the piston 36 before the nail gun is activated and before a striking cycle begins. Skilled persons in the art would understand how to design a parking mechanism for moving the crank 28, the connecting rod 32, and the piston 36 to the positions shown in Fig. 5a when the user finishes nail shooting operations or when the nail gun is powered off, for example by using position sensors as a basis for controlling the motor operation. For the sake of easy discussion, assume that in Fig. 5a the crank 28 is at the 0° angular position, and the piston 36 is now at its BDC. The connecting rod 32 and the drive blade 38 are parallel to each other, and are both along the longitudinal axis of the cylinder 34. However, the connecting rod 32 at this status overlaps with the elongated portion of the crank 28 that includes the end 28b along a direction defined by the central axis of the end 28c of the crank 28.

Next, if the user presses the trigger 54, then the motor 20 is activated. In this example it is assumed that the output shaft of the motor 20 rotates always along the counterclockwise direction as indicated by arrow 64. The output rotational force from the motor 20 is inputted to the gearbox 22, which transfers further the rotational force to a gearbox output force with lower speed and higher torque, which is then transmitted to the one-way clutch 30. At this moment, the inner part 30b of the one-way clutch 30 which is directly connected with the output of the gearbox 22 has a rotational speed faster than the outer part 30a of the one-way clutch 30 which is still before the motor 20 is activated. The inner part 30b is then engaged with the outer part 30a as the one-way clutch 30 is now in its power transmitting mode, and the outer part 30a starts to rotate as it is driven by the inner part 30b. Rotation of the outer part 30a in turn drives the crank 28 to rotate also along the counterclockwise direction along the central axis defined by the end 28c.

As the crank 28 rotates, it eventually moves to the position shown in Fig. 5b, which is defined as the 90° position of the crank 28. At the same time, rotation of the crank 28 makes the connecting rod 32 to move in a plane substantially parallel to the crank 28 and the drive blade 38. The movement of the connecting rod 32 then leads to movement of the piston 36 linearly in the cylinder 34. The two pivot points at the two ends of the connecting rod 32 enable the movements of the various components as mentioned above. When the crank 28 moves to the 90° position, the crank 28, the connecting rod 32, and a portion of the drive blade 38 form a right-angled triangle as shown in Fig. 5b. At this moment, the piston 36 has left its BDC for a small amount toward its TDC.

As the crank 28 continues to rotate, it eventually moves to the position shown in Fig. 5c, which is defined as the 180° position of the crank 28. This movement of the crank 28 then drives the connecting rod 32 to move from the position in Fig. 5b back to an orientation that is parallel to the drive blade 38, but the position of the connecting rod 32 has offset as compared to that in Fig. 5a. In particular, the connecting rod 32 is now again parallel to the drive blade 38, and they are both along the longitudinal axis of the cylinder 34. However, the connecting rod 32 at this status does not overlap with crank 28 any more along the direction defined by the central axis defined by the end 28c of the crank 28. Rather, the connecting rod 32 at this status appears to extend further from the end 28b of the crank 28, which results in the piston 36 being driven to move across a maximum distance to the TDC. The nail gun is now ready for shooting the nail to a workpiece. It should be noted in the energy accumulating phase of the gas spring as shown from Figs. 5a to 5c the one-way clutch 30 is always in its power transmitting mode so that the rotational force from the motor 20 can be transmitted to the crank 28, etc.

Starting from Fig. 5c, the nail gun shoots the nail automatically as the piston 36 from its TDC quickly moves in a reverse direction to the BDC due to the accumulated energy stored by the gas spring. The accumulated energy transforms to a large kinetic energy of the piston 36, which in turn drives the drive blade 38 and the striker to strike the nail and shoot the nail out. Fig. 5d shows one status of the components in the striking phase where the crank 28 is at its 270° position. However, in this striking phase the motor 20 and the gearbox 22 will not be affected, because the outer part 30a as it is connected to the crank 28 and rotates as a results of the piston 36 moving back to BDC has a much larger rotational speed than the inner part 30b which has always been driven by the motor 20 during the cycle. The one-way clutch 30 is then in a freewheel mode as the inner part 30b is disengaged from the outer part 30a. In this way, the motor 20 and the gearbox 22 can be protected from suffering from a quick reverse rotational force and be damaged if there is no such one-way clutch 30. When the nail striking is completed, the entire cycle is completed and the status of the various components in the crank assembly goes back to that shown in Fig. 5a. The next cycle could start again as the motor 20 continues to rotate in the counterclockwise direction.

Turning to Figs. 6-8, according to another embodiment of the invention there is provided an alternative crank assembly with a different one-way clutch as compared to that in Figs. 2-5d. Such an alternative crank assembly could be used to replace the crank assembly in the nail gun in Figs. 1-5d while keeping other components of the nail gun. The crank assembly in Figs. 6-8 contains a crank 128 connected to one end of a connecting rod 132, where the connecting rod 132 on its other end connects to a piston 136. The piston 136 connects to a striker (not shown) of the nail gun through a drive blade 138. The crank 128 is coupled to an output flange 170 as an output of a gearbox (not shown) of the nail gun through the one-way clutch with a structure best illustrated in Figs. 7-8.

In particular, the crank 128 has one end 128c pivotally coupled to the gearbox via the one-way clutch, and in particular via a pawl carrier 168 and an intermediate shaft 160. Another end 128b of the crank 128 is pivotally connected to one end 132a of the connecting rod 132 via a hinge 166. Another end (not shown) of the connecting rod 132 is pivotally connected to the piston 136. The connecting rod 132 has a similar elongated shape as the drive blade 138, but is shorter than the drive blade 138. During operation of the nail gun, the positions and orientations of the connecting rod 132 and the crank 128 will continuously vary, similar to those mentioned in the embodiment of Figs. 2-5d. Another end of the intermediate shaft 160 opposite to the teeth 142 is formed with a non-circular shank 160b that is coupled to the output flange 170 that has complemental non-circular shape.

Turning to Figs. 7-8, which show the connection between the crank 128 and the one-way clutch in details. The end 128c of the crank 128 has a substantially triangular shape. At the center of the end 128c there is defined a bore 128d which receives one end of the intermediate shaft 160, and at the same end of the intermediate shaft 160 there are multiple teeth 142 fixedly connected to the intermediate shaft 160. Each tooth 142 has a shark fin shape extending radially from the perimeter of the intermediate shaft 160. Such a shark fin shape is formed by one edge 142a that extends substantially radially, and another edge 142b that extends substantially tangentially from the perimeter of the intermediate shaft 160. Cooperating with the teeth 142 are three pawls 144 pivotally connected to the pawl carrier 168 defining a pivot axis 172, and each pawl 144 is biased by a spring 140 away from a side wall of the crank 128. It should be noted that during rotation of the intermediate shaft 160 each pawl 144 contacts with more than one of the teeth 142. The pawl carrier 168 has a similar triangular shape as the end 128c of the crank 128, and they are adapted to rotate together.

During operation, the crank 128 at different conditions may rotate together with the intermediate shaft 160, or rotate relative to the intermediate shaft 160. In particular, as skilled person will appreciate, the design of the one-way clutch is that the crank 128 and the intermediate shaft 160 are engaged for transmission of torque between the two when the rotation speed of the intermediate shaft 160 is larger than that of the crank 128. In this power transmission mode of the one-way clutch, when the intermediate shaft 160 rotates faster than the crank 128, say along the counterclockwise direction as indicated by arrow 164, then each pawl 144 is urged by the edge 142a of a tooth 142. Because the direction of the urging force substantially penetrates the pivot axis 172 of the pawl 144, the urging forces then pushes the crank 128 to rotate along the same direction as the intermediate shaft 160. The one-way clutch is in the power transmission mode during the energy accumulating phase of the gas spring.

However, when the rotation speed of the inner part intermediate shaft 160 is smaller than that of the crank 128, they become disengaged, and no transmission of torque happens between the two. In this freewheel mode of the one-way clutch, when the intermediate shaft 160 rotates slower than the crank 128, say along the counterclockwise direction as indicated by arrow 164, then each pawl 144 actually moves relative the teeth 142 along the counterclockwise direction, and as a result each pawl 144 slips over the edge 142b of a tooth 142 as the pawl 144 pivots also in the counterclockwise direction by overcoming the spring force of the spring 140. In this way, the motor and the gearbox can be protected from suffering from a quick reverse rotational force and be damaged if there is no such one-way clutch. The one-way clutch is in the freewheel mode during the striking phase of the gas spring.

The exemplary embodiments of the present invention are thus fully described. Although the description referred to particular embodiments, it will be clear to one skilled in the art that the present invention may be practiced with variation of these specific details. Hence this invention should not be construed as limited to the embodiments set forth herein.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only exemplary embodiments have been shown and described and do not limit the scope of the invention in any manner. It can be appreciated that any of the features described herein may be used with any embodiment. The illustrative embodiments are not exclusive of each other or of other embodiments not recited herein. Accordingly, the invention also provides embodiments that comprise combinations of one or more of the illustrative embodiments described above. Modifications and variations of the invention as herein set forth can be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as are indicated by the appended claims.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

The different status of the crank assembly shown in Figs. 5a-5d represents the movements of various components in the crank assembly in one complete cycle. One skilled in the art should realize that the fastening tool can be design to be carrying out a single-shot mode or a multiple-shot mode. In the latter mode, similar operation steps to those shown in Figs. 5a-5d can be applied repetitively and automatically as long as the motor keeps rotating in the same direction.

In addition, although the embodiments described above are pneumatic tools, one skilled in the art should realize that the invention can be used on other fastener tools with different types of energy storage unit instead of a gas spring. For example, the invention can also be applied to fastener tools with metal springs.

The ratchet mechanism in the one-way clutch shown in Figs. 6-8 can be altered to have for example different number of teeth, different number of pawls, and the shape /orientations of the teeth and pawls. Such alternations however still fall within the scope of the invention.

In the embodiments above, the fastening tools are in the form of pneumatic fastening tools that use the gas-spring with a single cylinder. However, those skilled in the art should realize that the implementation of the fastening tool is not necessarily limited to such configurations. For example, instead of a single cylinder for gas spring, a mechanical spring or other kind of energy storage would also work under the spirit of the invention.

Similarly, the fastening tools described in the embodiments above use one-way clutches in different forms to disengage the crank assembly from the gearbox and the motor in the striking phase to avoid the latter interrupting the rapid striking of the fastener. However, those skilled in the art should realize that other types of the mechanism can be used to disengage the gearbox and the motor from the piston in the striking phase, for example by using a two-cylinder structure with latches so that the striking action of the piston in one cylinder will not reversely affect the crank assembly, the gear box and the motor connected to another cylinder.

Claims

A fastening tool comprising:

a motor assembly;

a drive mechanism connected to the motor assembly and adapted to drive a piston; and

an energy accumulating mechanism that is connected to a striking element suitable for striking a workpiece; the energy accumulating mechanism comprising a driven member;

wherein the drive mechanism further comprising a crank assembly connected between the motor assembly and the driven member to transform a rotational force from the motor assembly to a linear movement of the driven member.
The fastening tool of claim 1, wherein the energy accumulating mechanism further comprises a cylinder; the driven member being a piston that is accommodated in the cylinder and suitable for a reciprocating motion within the cylinder.
The fastening tool of claim 2, wherein the crank assembly further comprises a crank coupled to an output of the motor assembly on one end, and pivotally coupled to a connecting rod on another end; the connecting rod connecting the crank to the piston wherein the connecting rod is pivotally connected to the piston.
The fastening tool of claim 3, wherein the piston is adapted to move linearly within the cylinder between a top dead center (TDC) and a bottom dead center (BDC) ; the crank located at two of its angular positions corresponding to the piston located in the TDC and the BDC respectively, where the two angular positions are different from each other by 180 degrees.
The fastening tool of claim 3, wherein the crank assembly further comprises a one-way clutch connected between the output shaft and the crank.
The fastening tool of claim 5, wherein the one-way clutch is a one-way roller bearing or a one-way sprag bearing.
The fastening tool of claim 5, wherein the one-way clutch comprises an inner part connected to one of the output shaft and the crank, and an outer part connected to the other one of the output shaft and the crank; the inner part and the outer part coupled to each other through a ratchet mechanism.
The fastening tool of claim 2, wherein for accumulating energy, the cylinder is filled with high pressure gas or the cylinder contains a mechanical spring.
The fastening tool of any one of the preceding claims, wherein the motor assembly comprises a motor and a gearbox connected to the motor.