GB2577109A

GB2577109A - Impact wrench

Info

Publication number: GB2577109A
Application number: GB1814996.3A
Authority: GB
Inventors: John Kaye Michael
Original assignee: Design Prototype Manufacture and Supply Ltd
Current assignee: Design Prototype Manufacture and Supply Ltd
Priority date: 2018-09-14
Filing date: 2018-09-14
Publication date: 2020-03-18
Also published as: GB201814996D0

Abstract

The impact wrench (10, Figure 1) includes a bi directional clutch 16 comprising a clutch cup 18 fixed to a power transfer shaft 12. The clutch cup has an inner surface (20, Figure 11) which bounds a clutch assembly 22 fixed to an output drive shaft 30. The clutch assembly comprises a clutch plate 24 having an engagement surface (26, Figure 9). The clutch plate is moveable between a first position relative to the inner surface of the clutch cup such that a clearance (28, Figure 11) is maintained between the clutch plate and the inner surface of the clutch cup and a second position relative to the inner surface of the clutch cup such that at least part of the engagement surface of the clutch plate is in driveable contact with the inner surface of the clutch cup. In the first position, the output drive shaft and power transfer shaft are rotatable relative to one another. In the second position, the output drive shaft and power transfer shaft are drivingly coupled to one another. The output drive shaft extends from an electric motor 14. The drive and power transfer shafts are rotatable about a first axis 40.

Description

(54) Title of the Invention: Impact wrench

Abstract Title: Impact wrench with bi-directional clutch (57) The impact wrench (10, Figure 1) includes a bi directional clutch 16 comprising a clutch cup 18 fixed to a power transfer shaft 12. The clutch cup has an inner surface (20, Figure 11) which bounds a clutch assembly 22 fixed to an output drive shaft 30. The clutch assembly comprises a clutch plate 24 having an engagement surface (26, Figure 9). The clutch plate is moveable between a first position relative to the inner surface of the clutch cup such that a clearance (28, Figure 11) is maintained between the clutch plate and the inner surface of the clutch cup and a second position relative to the inner surface of the clutch cup such that at least part of the engagement surface of the clutch plate is in driveable contact with the inner surface of the clutch cup. In the first position, the output drive shaft and power transfer shaft are rotatable relative to one another. In the second position, the output drive shaft and power transfer shaft are drivingly coupled to one another. The output drive shaft extends from an electric motor 14. The drive and power transfer shafts are rotatable about a first axis 40.

Figure 5

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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Figure 10

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Figure 12

IMPACT WRENCH

The present disclosure relates to an impact wrench.

In particular, the disclosure is concerned with an impact wrench with a bi-directional clutch.

Background

Impact wrenches for tightening and loosening fixtures (for example, screws, nuts and bolts) are well-known in the art. In light duty applications, for example home improvement and general building applications, they are often provided as hand-held devices, with one handle, so a user may operate the device with one hand. It is common for such impact wrenches to be electrically powered with a replaceable battery. Additionally, impact wrenches are known for industrial applications. These are powered by a petrol engine-driven motor in order to achieve the desired high torque output required. Although the devices produce analogous technical effects, the different power output (i.e. torque) requirements necessitate entirely different technical solutions.

In both cases, in order to be able to both tighten and loosen fixtures, the impact wrench must be able to deliver a torque output in both a clockwise and anti-clockwise rotational direction. Petrol-powered engines can only achieve this by use of a reverse gear mechanism. Such reverse gear mechanisms increase weight and complexity of industrial impact wrench designs.

Commonly a planetary gear mechanism is provided to reduce rotational speed output of the motor and increase output torque. Impact wrenches must include a clutch between the motor and the output in order to protect the motor and gearbox when the fixture is sufficiently tightened, or if it becomes locked. Such clutches are only operational in one direction (i.e. clockwise or anti clockwise, but not both). Hence a reverse gear mechanism is required in order to convert output from the clutch to both clockwise and anti-clockwise output rotational directions.

Planetary gears include many moving parts which are difficult to assemble and maintain, for example multiple intermeshed gearwheels.

The use of a petrol engine is problematic also because while they are adequate for use in the open air, they cannot be used in an enclosed environment (for example, inside a building, tunnel, or other structure) without the provision of some form of ventilation to stop the user from being affected by exhaust fumes. Additionally, such petrol-powered motors, being small, tend also to be noisy, which provides a further health and safety risk for the user. That is to say, use of the device requires ear defenders, which generate a further risk as hazards which would be apparent to the hazard without ear defenders (for example an approaching vehicle) cannot be heard when the user is wearing ear protection. Additionally, the operation of petrol-powered motors may cause physical harm, e.g. hand-arm vibration syndrome as a result of the vibrations of such motors.

Hence, an impact wrench for an industrial heavy duty application which overcomes the above problems of the related art is highly desirable.

Summary

According to the present disclosure there is provided an apparatus as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

Accordingly there may be provided an impact wrench (10) comprising an output drive shaft (30) extending from an electric motor (14) and rotatable about a first rotational axis (40). The output drive shaft (30) may be engageable with a power transfer shaft (12) via a bi directional clutch (16). The power transfer shaft (12) may be rotatable about the first rotational axis (40). The bi directional clutch (16) may comprise : a clutch cup (18) fixed to the power transfer shaft (12), the clutch cup (18) having an inner surface (20) which bounds a clutch assembly (22) fixed to the output drive shaft (30), the clutch assembly (22) comprising: a clutch plate (24) having an engagement surface (26), the clutch plate (24) moveable between: a first position relative to the inner surface (20) the clutch cup (18) such that a clearance (28) is maintained between the clutch plate (24) and the inner surface (20) of the clutch cup (18); and a second position relative to the inner surface (20) of the clutch cup (18) such that at least part of the engagement surface (26) of the clutch plate is in driveable contact with the inner surface (20) of the clutch cup (18); such that in the first position the output drive shaft (30) and power transfer shaft (12) are rotatable relative to one another; and in the second position the output drive shaft (30) and power transfer shaft (12) are drivingly coupled to one another.

The clutch plate (24) may be operable to be moved from the first position to the second position by centrifugal force generated by the rotation of the clutch assembly (22) around the first rotational axis (40).

The clutch plate (24) may be operable to move from the first position to the second position when the rotational speed of the clutch assembly (22) around the first rotational axis (40) rises to and/or above a first predetermined rotational speed.

The clutch plate (24) may be operable to move from the second position towards the first position when the rotational speed of the clutch assembly (22) around the first rotational axis (40) decelerates from the first predetermined rotational speed to a second predetermined rotational speed.

The clutch plate (24) may be operable to be moved from the first position to the second position when the clutch assembly (22) is rotated in a first direction around the first rotational axis (40) and when the clutch assembly (22) is rotated in a second direction around the first rotational axis (40).

The impact wrench (10) may further comprise a control unit (50) operable to determine power output of the electric motor (14) and to limit power output of the electric motor (14) to a first predetermined power output value.

The clutch plate (24) and inner surface of the clutch cup (18) may be configured to allow relative rotational movement when power output of the electric motor (14) exceeds a second predetermined power output value.

The first predetermined power output value may be the same as, more than or less than the second predetermined power output value.

The impact wrench (10) may be configured such that after the rotational speed of the clutch assembly (22) around the first rotational axis (40) rises to and/or above the first predetermined rotational speed, the clutch plate (24) is operable to remain drivingly coupled to the inner surface (20) of the clutch cup (18) until the power output of the electric motor (14) exceeds the second predetermined power output value.

A support member (36) may be fixed to the output drive shaft (30). The clutch plate (24) may be carried on a shoe (34). The shoe (34) may be carried on the support member (36), and the shoe (34) may be moveable relative to the support member (36) in a radial direction between the first position and the second position.

The shoe (34) may be resiliently biased towards the first rotational axis (40).

The clutch assembly (22) may comprise at least two clutch plates (24A, 24B) carried on respective shoes (34A, 34B) spaced equidistantly around the output drive shaft (30) and a resilient member (42) extends from each shoe (34A, 34B) to one other shoe (34A, 34B).

The clutch assembly (22) may comprise three shoes (34A, 34B, 34C) and three resilient members (42), two resilient members (42) extending from each of the shoes (34A, 34B, 34C), each of the two resilient members (42) extending to a different one of the other shoes (34A, 34B, 34C).

The control unit (50) may be programmable to define the maximum electric motor power output value.

The impact wrench (10) may further comprise a trigger switch (52) configured to generate a control signal; the control unit (50) being operable to receive the control signal and control the power output of the electric motor (14) in dependence of the control signal, and configured to provide infinitely variable speed/power output between predetermined limits.

The power transfer shaft (12) may be coupled to a tool carrier (60) via an impact mechanism (62); the impact mechanism (62) operable to receive a rotational input from the power transfer shaft (12) and output a combination of rotational output and rotational impulse force via the tool carrier (60).

The impact mechanism (62) may be operable to receive a rotational input from the power transfer shaft (12) via a gearbox (64).

The tool carrier (60) may be rotatable around a second rotational axis (68), the second rotational axis (68) being offset from the first rotational axis (40).

The impact wrench (10) may further comprise a housing (70), the electric motor (14) located within the housing (70), with terminals extending to the exterior of the housing (70) for engagement with a replaceable battery pack (74) to transmit electrical energy from the battery pack (74) to the motor (14).

The impact wrench (10) may further comprise a first handle (76), the trigger switch (52) provided on the first handle (76).

The impact wrench (10) may be further provided with a second handle (78) and a third handle (80); the first, second and third handles (76, 78, 80) comprising a first, second and third elongate grip member (86, 88, 90) respectively; the first, second and third handles (76, 78, 80) centred on a first, second and third grip axes (96, 98, 100) respectively, the first, second and third grip axes (96, 98, 100) being parallel, spaced apart from one another, and at right angles to the first and second rotational axes (40, 68).

The handles (76, 78, 80) are provided on arms (102) which extend from the housing (70); such that the first handle (76) and second handle (78) are located to one side of the first rotational axis (40) and the third handle (80) is located on an opposite side of the first rotational axis (40).

The first handle (76) may be provided beyond an end of the housing (70) which houses the electric motor (14). The second handle (78) may be provided to one side of the gearbox (64). The third handle (80) may be provided between the first handle (76) and third handle (78).

Hence, there is provided an industrial rated electrically-powered impact wrench which is operable to tighten and loosen fixtures without provision of a planetary gearbox or reverse gear box.

The clutch assembly of the device of the present disclosure is provided separate to the gearbox, hence isolating the motor and gearbox from operation of the clutch. This is functionally advantageous as each of the motor, clutch and gearbox may be optimally and individually configured. Hence they may each perform optimally and, with such a modular design, may be easier to build and maintain.

Also, since the impact wrench of the present disclosure is electrically-operated, with a replaceable battery, it overcomes the issues of exhaust fumes, vibration and noise of a similar industrially-rated impact wrench which uses a petrol engine or such like.

Brief Description of the Drawings

Examples of the present disclosure will now be described with reference to the accompanying drawings, in which:

Figures 1 to 4 show different external views of the impact wrench of the present disclosure;

Figure 5 shows a cross-sectional view of the impact wrench as shown in Figures 1 to 4;

Figure 6 shows a perspective-exploded view of the internal components of the impact wrench of the present disclosure;

Figures 7, 8 show further exploded views of the arrangement shown in Figure 6;

Figures 9, 10 show views of a bi-directional clutch which forms a part of the mechanism of the impact wrench of the present disclosure;

Figures 11, 12 show the interaction of a clutch assembly and clutch cap of the impact wrench of the present disclosure, as shown in figures 9, 10.

Detailed Description

Figures 1 to 4 show external views of an impact wrench 10 according to the present disclosure. Figure 5 shows a sectional view of an assembly 71 of the assembled core impact wrench 10 components. A casing (or housing) 70, shown in Figures 1 to 4, extends around the assembly 71 shown in Figure 5. Exploded views of the assembly 71, shown in Figure 5, are presented in Figures 6, 7 and 8.

As shown in Figures 5 to 8, the impact wrench 10 comprises an electric motor 14 which, indirectly, drives a tool carrier 60. The tool carrier 60 comprises a head end 61 to which a tool (for example a socket, not shown) may be attached. The socket may be configured for attaching to a nut, bolt, screw or other fixture-engagement means, and hence the impact wrench of the present disclosure may be utilised for tightening/loosening of such fixtures.

An output drive shaft 30 of the electric motor 14 is rotatable about a first rotational axis 40. The output drive shaft 30 is engageable with a power-transfer shaft 12 via a bi-directional clutch 16. The power-transfer shaft 12 is rotatable about the first rotational axis 40. The power-transfer shaft 12 is coupled to the tool carrier 60 via an impact mechanism 62.

The impact mechanism 62 is operable to receive a rotational input from the powertransfer shaft 12 and output a combination of rotational output and rotational impulse force.

The impact mechanism 62 is operable to receive a rotational input from the powertransfer shaft 12 via a gearbox 64. The gearbox 64 may be a reduction gearbox. That is to say, the input to the gearbox 64 is the power-transfer shaft 12, and the output from the gearbox 64 is delivered to the impact mechanism 62 via a gearbox output shaft 65.

Hence the output drive shaft 30 is coupled to the electric motor 14 and rotatable about the first rotational axis 40. Alternatively, or additionally, the output drive shaft 30 may extend from the electric motor 14. The bi-directional clutch 16 sits between the motor 14 and the gearbox 64, and is engaged with the gearbox 64 via the power transfer shaft 12 which is also rotatable about the first rotational axis 40. The gearbox output shaft 65 is co-axial with the impact mechanism 62 and the tool carrier 60. The gearbox output shaft 65, impact mechanism 62 and tool carrier 60 are rotatable around the second rotational axis 68. The impact mechanism 62 is provided between gear box 64 and the tool carrier 60. The gearbox 64 is provided between the impact mechanism 62 and the bi directional clutch 16. Hence the motor 14, bi directional clutch 16, gearbox 64, impact mechanism 62 and tool carrier 60 are provided in series along the rotational axis 40, 68 (i.e. along the length of the impact tool 10).

The electric motor 14 may be located within the housing 70, with a terminal extending to the exterior of the housing 70 for engagement with a replaceable battery pack 74 to transmit electrical energy from the battery to the motor 14.

As can be shown in Figures 1 to 4, the impact wrench further comprises a first handle 76 mounted to the housing 70. That is to say, the first handle 76 may be connected to and/or fixed relative to the housing 70. A trigger switch 52 is provided on the handle 76. The handle 76 may incorporate vibration damping means.

There may be further provided a second handle 78 and a third handle 80 mounted, connected and/or fixed relative to the housing 70. The first, second and third handles 76, 78, 80 may comprise a first, second and third elongate grip members 86, 88, 90, respectively. The first, second and third handles 76, 78, 80 may be centred on a first, second and third grip axes 96, 98, 100, respectively. The first, second and third grip axes 96, 98, 100 may be parallel, spaced apart from one another, and at right angles to the first and/or second rotational axes 40, 68.

According to the present example, the handles 76, 78, 80 are configured for horizontal and vertical operation of the impact wrench 10.

The handles 76, 78, 80 may be provided on arms 102 which extend from the housing 70. That is to say each of the handles 76, 78, 80 may be provided on respective arms 102 which carry the housing 70. The end of each arm 102 is linked to only one of the handles 76, 78, 80. As shown in Figures 1 to 4, a different pair of arms 102 may extend from the housing 70 to each handle 76, 78, 80. That is to say, a pair of arms 102 may extend from the housing 70 to each handle 76, 78, 80.

The first handle 76 and second handle 78 may be located to one side of the first rotational axis 40 and/or the second rotational axis 68, and the third handle 80 may be located on an opposite side of the first rotational axis 40 and/or the second rotational axis 68.

That is to say, as shown in Figure 3, the first handle 76 and second handle 78 may be located to one side of the housing 70, and the third handle 80 may be located on an opposite side of the housing 70.

The first handle 76 may be provided beyond an end of the housing 70 which houses the electric motor 14, the position of which is indicated in Figure 3. The second handle 78 may be provided to one side of the gearbox 64, the position of which is indicated in Figure 3. The third handle 80 may be provided between the first handle 76 and second handle 78. That is to say, the third handle 80 may be provided between the first handle 76 and second handle 78 in the direction along the first rotational axis 40, as well as being spaced apart from the first handle 76 and second handle 78 by the first rotational axis 40.

As described above, the thumb-trigger switch 52 may be provided on the first handle 76. The trigger-switch 52 is configured to generate a control signal.

Hence the handles 76, 78, 80 are arranged to allow the tool 10 to be held firmly by one user in two locations (i.e. by two of the three handles, a hand on each of the two handles) in a number of orientations, including substantially horizontally and substantially vertically. The user must hold the first handle 76 during operation in order to operate the trigger switch 52.

The spacing between the first handle 76 and the second handle 78 may be greater than the spacing between the first handle 76 and the third handle 80. That is to say, the distance between the first grip axis 96 and second grip axis 98 may greater than the distance between the first grip axis 96 and third grip axis 100. The separation of the first handle 76 (i.e. first grip axis) and the second handle 78 (i.e. second grip axis) along the rotational axis 68 may be between 350 centimetres and 430 centimetres, preferably 390 centimetres. According to the present example, the second handle 78 (i.e. second grip axis 98) is provided closer to the rotational axis 68 than the first handle 76 (i.e. first grip axis 96). The separation of the first handle 76 (i.e. first grip axis) and the third handle 80 (i.e. third grip axis 100) may be between 240 centimetres and 300 centimetres, preferably 275 centimetres. According to the present example, the third handle 80 (i.e. third grip axis 100) is provided closer to the rotational axis 68 than the first handle 76 (i.e. first grip axis).

As shown best in Figures 11, 12, the bi-directional clutch 16 comprises a clutch cup 18 fixed to, and rotatable with, the power shaft 12. The clutch cup 18 has an inner surface 20 which bounds, that is to say surrounds, a clutch assembly 22 fixed to the output drive shaft 30. The clutch assembly 22 comprises a clutch plate 24 having an engagement surface 26.

As shown in Figures 9 to 11, a support member 36 is fixed to the output drive shaft 30. The support member 36 may be fixed directly or indirectly to the output drive shaft 30. For example, the support member 36 may be formed integrally with, or adhered to, or otherwise mechanically fixed to the output drive shaft 30. For example, the support member 36 may extend from a body, sleeve or ring member 37 configured to fit around, and be engageable with, the output drive shaft 30.

The clutch plate 24 is carried on a shoe 34. This shoe 34 may be slideably engaged with, or otherwise carried on, the support member 36. Hence the support member 36 defines the path the shoe 34 may travel, effectively acting as a guide member. The support member 36 may define a path which extends in a radial direction along which the shoe 34 is operable to travel. The shoe 34 may be carried on and/or engaged with the support member 36 such that the shoe 34 is constrained to travel only in a radial direction relative to the support member 36. That is to say, the shoe 34 may be carried on and/or engaged with the support member 36 such that it is constrained to travel only in a radial direction away from and towards the first rotational axis 40. Hence the clutch plate 24 may also only move in a radial direction with the shoe 34. That is to say, the clutch plate 24 may not be pivotable relative to the support member 36 and/or rotational axis 40. The shoe 34 is thus moveable relative to the support member 36 in a radial direction between the first position and the second position. Put another way, the shoe 34 is thus moveable relative to the support member 36 in a radial direction between the first position and the second position, along the points in between, as the support member 36, shoe 34 and clutch plate 24 rotate with the output drive shaft 30 around the first rotational axis 40.

The shoe 34 may be resiliently biased towards the first rotational axis 40. That is to say, a spring (i.e. resilient member 42) may be provided between the shoe 34 and another point in the clutch assembly to pull (or at least urge) the shoe 34, and hence the clutch plate 24, towards the first rotational axis 40.

The clutch assembly 22 may comprise at least two clutch plates 24 carried on respective shoes 34. The clutch plate 24 may be spaced equidistantly around the output drive shaft 30, and a resilient member 42 may extend from each shoe 34 to the other shoe(s) 34. In another example, the clutch assembly may comprise only one clutch plate 24 carries on a sole shoe 34.

As shown in Figures 11, 12, the clutch assembly 22 may comprise three shoes 34 and three resilient members 42. Two resilient members 42 may extend from each of the shoes 34. Each of the two resilient members 42 may extend to a different one of the other shoes 34. That is to say, there may be provided three resilient members 42, and a first shoe 34A, second shoes 34B, and a third shoes 34C which carry respective clutch plates 24A, 24B, 24C.

As described above, the clutch plate 24 is moveable between the first position (as shown in Figure 11) and the second position spaced apart from the first position (as shown in Figure 12). In the first position (Figure 11), the clutch plate 24 is spaced apart relative to the inner surface 20 of the clutch cup 18 such that a clearance 28 is maintained between the clutch plate 24 and the inner surface 20 of the clutch cup 18. In the second position (Figure 12), the clutch plate 24 is maintained radially outward of its first position, such that the clutch plate 24 is positioned relative to the inner surface 20 of the clutch cup 18 such that at least part of the engagement surface 26 of the clutch plate 24 is in driveable contact with the inner surface 20 of the clutch cup 18. Put another way, in the second position (Figure 12), the clutch plate 24 has moved radially outward of its first position, away from the first rotational axis 40, to reduce the clearance 28 to zero in at least one region of the engagement surface 26 of the clutch plate 24. In one example substantially all of the engagement surface 26 of the clutch plate 24 is in contact with the inner surface 20 of the clutch cup 18.

In the first position (Figure 11), the output drive shaft 30 and power-transfer shaft 12 are rotatable relative to one another. That is to say, when the clutch plate 24 is in the first position, the output drive shaft 30 and the power-transfer shaft 12 are not engaged and may rotate freely relative to one another. In the second position (Figure 12), the output drive shaft 30 and power-transfer shaft are drivingly coupled to one another. That is to say in the second position (Figure 12), the output drive shaft 30 and the power-transfer shaft 12 are drivingly engaged with one another such that rotation of the output drive shaft 30 will cause rotation of the power-transfer shaft 12 by virtue of being coupled via the clutch assembly 22 and clutch cup 18.

The clutch plate 24 is operable to be moved from the first position (Figure 11, disengaged) to the second position (Figure 12, engaged) by centrifugal force generated by the rotation of the clutch assembly 22 around the first rotational axis 40. That is to say, when the output drive shaft 30 is rotated (for example by the motor 14), the clutch assembly 22 rotates with the output drive shaft 30 and the clutch plate 24 thus moves (i.e. is “thrown”) under centrifugal force from the first position (Figure 11, disengaged) to the second position (Figure 12, engaged). The clutch plate 24 is operable to move from the first position (disengaged) to the second position (engaged) when the rotational speed of the clutch assembly 22, as driven by the output drive shaft 30 for example, around the first rotational axis 40 rises to/or above a first predetermined value. That is to say, when the output drive shaft 30 reaches the first predetermined rotational speed, then the clutch plate 24 will move from the first position (disengaged), away from the first rotational axis 40, to the second position (engaged) under the influence of centrifugal force generated by rotation of the output drive shaft 30. In other words, the clutch shoes 34 throw to engage the inner surface of the clutch cup 20 as rotational speed ramps up (i.e. increases).

The rotational speed of the clutch assembly 22 may continue to increase (i.e. exceed the first predetermined rotational speed), thereby increasing rotational speed and/or output torque of the shafts 12, 65 and tool carrier 60.

Conversely, the clutch plate 24 is operable to move from the second position (engaged) towards, but not necessarily all of the way to, the first position (disengaged) when the rotational speed of the clutch assembly 22 around the first rotational axis 40 reaches and/or falls below a second predetermined value. That is to say, when the output drive shaft 30 decelerates from the first predetermined rotational speed to the second predetermined rotational speed, then the clutch plate 24 will move from the second position (engaged) to the first position (disengaged), towards the first rotational axis 40, under the influence of the resilient members 42, which act to draw the or each shoe 34 (and hence the clutch plate 24) away from the inner surface 20 of the clutch cup 20.

The first predetermined rotational speed is higher in value (i.e. faster) than the second predetermined rotational speed.

The second predetermined rotational speed may be greater than 0 (zero) revolutions per second.

The second predetermined rotational speed may be no more than about 90% of the first predetermined rotational speed.

The second predetermined rotational speed may be no more than about 90% of the first predetermined rotational speed, but no less than about 25% of the first predetermined rotational speed.

The second predetermined rotational speed may be no more than about 90% of the first predetermined rotational speed, but no less than 10% of the first predetermined rotational speed.

The output speed of the motor 14 may be about 4800 rpm. The gearbox 64 may be configured to have a reduction ratio of around 6.7. Hence the gearbox output shaft 65 and tool carrier may have an impact rotational speed of about 685 rpm.

The clutch plate 24 is operable to be moved from the first position to the second position when the clutch assembly 22 is rotated in a first direction (for example, but not limited to, clockwise) around the first rotational axis 40. The clutch plate 24 is also operable to be moved from the first position to the second position when the clutch assembly 22 is rotated in a second direction (for example, but not limited to, anticlockwise, opposite to the first direction) around the first rotational axis 40.

That is to say, the clutch plate 24 is operable to move from the first position (disengaged configuration) to the second position (engaged configuration) regardless of whether the clutch assembly 22, and hence the output drive shaft 30, is rotating in an anti-clockwise or clockwise direction. Put another way, regardless of which rotational direction the output drive shaft 30 and clutch assembly 22 rotate, the or each clutch plate 24 will be operable to be moved from the first position (disengaged configuration) to the second position (engaged configuration) by virtue of the centrifugal force generated by said rotation. Not only will the clutch plate 24 be operable to be moveable from the first position to the second position, regardless of the direction of rotation (i.e. either clockwise or anti-clockwise around the first rotational axis 40) but will also engage with the clutch cup 18 when in the second position regardless of the direction of rotation (i.e. either clockwise or anti-clockwise around the first rotational axis 40).

Hence all of the shoes 34A, 34B, 34C, and hence clutch plates 24A, 24B, 24C, are operable to move from the first position to the second position, and from the second position to the first position. The clutch plates 24A, 24B, 24C and shoes 34A, 34B, 34C are operable to move from the first position to the second position, and from the second position to the first position at substantially the same time as each other, under the influence of centrifugal force, or lack of centrifugal force.

The impact wrench may further comprise a control unit 50 operable to determine power output (that is to say, output torque) of the electric motor 14. The power output of the electric motor may be determined based on voltage and current drawn by the motor.

The control unit 50 may also be operable to limit power output of the electric motor 14 to a predetermined power output value, for example a first predetermined power output value.

After the rotational speed of the clutch assembly 22 around the first rotational axis 40 rises to and/or above the first predetermined rotational speed, the clutch plate 34 is operable to remain drivingly coupled to (i.e. engaged with) the inner surface 20 of the clutch cup 18 until the power output of the electric motor 14 exceeds, or is equal to, a second predetermined power output value.

The clutch plate 24 and inner surface of the clutch cup 18 are configured to allow relative rotational movement when power output of the electric motor 14 exceeds, or is equal to, the second predetermined power output value. That is to say, the clutch plate 24 and inner surface of the clutch cup 18 are configured to allow slip between the clutch plate 24 and clutch cup 18 when the output torque of the electric motor 14 exceeds the second predetermined power output value. The slip ensures that the motor 14 cannot apply more than a defined/desired torque to the tool carrier 60. This slip functionality thus protects the gearbox 64, shafts 30, 12, 65, impact mechanism 62 and tool carrier 60 from being over torqued, and hence becoming damaged.

The control unit 50 may also be operable to limit power output of the electric motor 14 to a predetermined power output value, for example the first predetermined power output value or the second predetermined power output value.

The first predetermined power output value output may be the same as, more than, or less that the second predetermined power output value.

Friction between the cup 18 and clutch plate 24 may hold the clutch plate 24 in the second position (i.e. engaging with the clutch cup) until power output from the electric motor is cut off or reduced. Hence, for example, when a nut or screw is tightened up, then the clutch plate 22 will remain in contact with the clutch cup 18 and continue to apply torque to thereby ensure the desired amount of force torque is delivered until the clutch slips. Additionally or alternatively, when a nut or screw is tightened up, then the clutch plate 22 will remain in contact with the clutch cup 18 and continue to apply torque to thereby ensure the desired amount of force torque is delivered until the motor 14 stalls.

The control unit 50 is operable to receive the control signal from the thumb trigger switch 52 and control the power (i.e. speed and/or torque) output of the electric motor 14 in dependence of the control signal from the thumb trigger switch 52. The control unit 50 may also be operable/configured to provide infinitely variable speed/power output within the limits of output capability of the motor 14 in dependence of control signal generated by the thumb trigger switch 52.

The control unit 50 may be programmable to define the maximum power (i.e. torque) output value. Hence the motor may be tuned to a specific performance criteria as required by the expected application of the impact wrench. For example, the control unit may be configured to control amperage and/or voltage to balance power output of the electric motor 14.

There is thus provided an industrially rated (i.e. heavy duty) impact wrench with an individually-programmable motor controller such that each unit may be configured for maximum power output. This is advantageous as it means the motor can be tuned to a specific performance criteria for the application the tool is to be used in.

The design of the clutch plate 24, and how the clutch plate 24 is mounted, is such that the clutch may be operable in either rotational direction, hence whether the tool carrier 60 is being rotated in a first direction or a second direction opposite to the first direction around the first rotational axis 40, the clutch plate assembly 22 and clutch cup 18 will still interact to engage, disengage and slip as previously described. Hence, forwards/reverse-operation is available without the need for a reverse gear mechanism between the clutch 16 and the tool carrier 20.

The use of a battery 74 means that incorporation of a petrol-powered engine, or the like, can be avoided, which also obviates the need for carrying around a flammable fuel in potentially hazardous situations, and thus also avoids health and safety issues for users. Using a battery unit 74 as a power source also means that no exhaust is produced during operation of the device, as well as the impact wrench of the present disclosure overall being quieter than a petrol engine equivalent.

Lower noise levels provide an obvious health and safety benefit to a user, avoiding the need for ear defenders as well as allowing the user to be overall more aware of their environment when operating the device. The thumb trigger switch of the present disclosure provides more control over output speed/power output in a more convenient fashion than examples of the related art.

The impact wrench of the present disclosure is inherently a low vibration device, by the fact than an electric motor is used rather than an internal combustion engine. Hence the device is overall more comfortable to operate.

The power output torque of the impact wrench of the present disclosure may also be higher than that of an equivalent petrol engine.

Additionally, the configuration of the impact wrench is such that a minimum number of parts are required for the clutch assembly 22, relative to examples of the related art to, provide the clutch operation in a forward and reverse direction.

The housing 70 provides a total enclosure for the main body of the apparatus, which may be configured for maximum Ingress Protection (“IP”) rating.

Additionally, the battery allows for rapid change of power source, without the need for refuelling which would be needed with a petrol-powered device.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1 An impact wrench (10) comprising an output drive shaft (30) extending from an electric motor (14) and rotatable about a first rotational axis (40);

the output drive shaft (30) being engageable with a power transfer shaft (12) via a bi directional clutch (16);

wherein the power transfer shaft (12) is rotatable about the first rotational axis (40);

the bi directional clutch (16) comprising :

a clutch cup (18) fixed to the power transfer shaft (12), the clutch cup (18) having an inner surface (20) which bounds a clutch assembly (22) fixed to the output drive shaft (30), the clutch assembly (22) comprising:

a clutch plate (24) having an engagement surface (26), the clutch plate (24) moveable between:

a first position relative to the inner surface (20) the clutch cup (18) such that a clearance (28) is maintained between the clutch plate (24) and the inner surface (20) of the clutch cup (18); and a second position relative to the inner surface (20) of the clutch cup (18) such that at least part of the engagement surface (26) of the clutch plate is in driveable contact with the inner surface (20) of the clutch cup (18);

such that in the first position the output drive shaft (30) and power transfer shaft (12) are rotatable relative to one another; and in the second position the output drive shaft (30) and power transfer shaft (12) are drivingly coupled to one another.

2 An impact wrench (10) as claimed in claim 1 wherein the clutch plate (24) is operable to be moved from the first position to the second position by centrifugal force generated by the rotation of the clutch assembly (22) around the first rotational axis (40).

3 An impact wrench (10) as claimed in claim 2 wherein the clutch plate (24) is operable to move from the first position to the second position when the rotational speed of the clutch assembly (22) around the first rotational axis (40) rises to and/or above a first predetermined rotational speed.

4 An impact wrench (10) as claimed in claim 3 wherein the clutch plate (24) is operable to move from the second position towards the first position when the rotational speed of the clutch assembly (22) around the first rotational axis (40) decelerates from the first predetermined rotational speed to a second predetermined rotational speed.

5 An impact wrench (10) as claimed in any one of claims 2 to 4 wherein the clutch plate (24) is operable to be moved from the first position to the second position when the clutch assembly (22) is rotated in a first direction around the first rotational axis (40) and when the clutch assembly (22) is rotated in a second direction around the first rotational axis (40).

6 An impact wrench (10) as claimed in any one of claims 1 to 5 further comprising a control unit (50) operable to determine power output of the electric motor (14) and to limit power output of the electric motor (14) to a first predetermined power output value.

7 An impact wrench (10) as claimed in anyone of claims 1 to 6 further wherein the clutch plate (24) and inner surface of the clutch cup (18) are configured to allow relative rotational movement when power output of the electric motor (14) exceeds a second predetermined power output value.

8 An impact wrench (10) as claimed in claim 7 wherein the first predetermined power output value is the same as, more than or less than the second predetermined power output value.

9 An impact wrench (10) as claimed in any one of claims 6 to 8 wherein after the rotational speed of the clutch assembly (22) around the first rotational axis (40) rises to and/or above the first predetermined rotational speed, the clutch plate (24) is operable to remain drivingly coupled to the inner surface (20) of the clutch cup (18) until the power output of the electric motor (14) exceeds the second predetermined power output value.

10 An impact wrench (10) as claimed in any one of claims 1 to 9 wherein a support member (36) is fixed to the output drive shaft (30), the clutch plate (24) is carried on a shoe (34);

the shoe (34) is carried on the support member (36), and the shoe (34) moveable relative to the support member (36) in a radial direction between the first position and the second position.

11 An impact wrench (10) as claimed in claim 10 wherein the shoe (34) is resiliently biased towards the first rotational axis (40).

12 An impact wrench (10) as claimed in claim 10 or claim 11 wherein the clutch assembly (22) comprises at least two clutch plates (24A, 24B) carried on respective shoes (34A, 34B) spaced equidistantly around the output drive shaft (30) and a resilient member (42) extends from each shoe (34A, 34B) to one other shoe (34A, 34B).

13 An impact wrench (10) as claimed in claim 12 wherein the clutch assembly (22) comprises three shoes (34A, 34B, 34C) and three resilient members (42), two resilient members (42) extending from each of the shoes (34A, 34B, 34C), each of the two resilient members (42) extending to a different one of the other shoes (34A, 34B, 34C).

14 An impact wrench (10) as claimed in claim 6 wherein the control unit (50) is programmable to define the maximum electric motor power output value.

15 An impact wrench (10) as claimed in claim 14 further comprising a trigger switch (52) configured to generate a control signal;

the control unit (50) being operable to receive the control signal and control the power output of the electric motor (14) in dependence of the control signal, and configured to provide infinitely variable speed/power output between predetermined limits.

16 An impact wrench (10) as claimed in any one of the preceding claims wherein the power transfer shaft (12) is coupled to a tool carrier (60) via an impact mechanism (62);

the impact mechanism (62) operable to receive a rotational input from the power transfer shaft (12) and output a combination of rotational output and rotational impulse force via the tool carrier (60).

17 An impact wrench (10) as claimed in claim 16 wherein :

the impact mechanism (62) is operable to receive a rotational input from the power transfer shaft (12) via a gearbox (64).

18 An impact wrench (10) as claimed in claim 17 wherein the tool carrier (60) is rotatable around a second rotational axis (68), the second rotational axis (68) being offset from the first rotational axis (40).

19 An impact wrench (10) as claimed in any one of the preceding claims further comprising a housing (70), the electric motor (14) located within the housing (70), with terminals extending to the exterior of the housing (70) for engagement with a replaceable battery pack (74) to transmit electrical energy from the battery pack (74) to the motor (14).

20 An impact wrench (10) as claimed in claim 19 further comprising a first handle (76), the trigger switch (52) provided on the first handle (76).

21 An impact wrench (10) as claimed in claim 20 wherein there are further provided a second handle (78) and a third handle (80);

the first, second and third handles (76, 78, 80) comprising a first, second and third elongate grip member (86, 88, 90) respectively;

the first, second and third handles (76, 78, 80) centred on a first, second and third grip axes (96, 98, 100) respectively, the first, second and third grip axes (96, 98, 100) being parallel, spaced apart from one another, and at right angles to the first and second rotational axes (40, 68).

22 An impact wrench (10) as claimed in claim 21 wherein the handles (76, 78, 80) are provided on arms (102) which extend from the housing (70);

such that the first handle (76) and second handle (78) are located to one side of the first rotational axis (40) and the third handle (80) is located on an opposite side of the first rotational axis (40).

23 An impact wrench (10) as claimed in any one of claims 21,22 wherein :

the first handle (76) is provided beyond an end of the housing (70) which houses the electric motor (14);

the second handle (78) is provided to one side of the gearbox (64); and the third handle (80) is provided between the first handle (76) and third handle (78).

Intellectual

Property

Office

Application No:

GB1814996.3