POWER TOOL HAVING FASTENER GRIPPING PORTION POSITION TRACKING FUNCTIONALITY

A power tool comprising: a motor; a fastener gripping portion operatively coupled to the motor for causing movement of the fastener gripping portion between a home position and a retracted position to set a fastener; a home position sensor for generating output indicative that the fastener gripping portion has reached the home position during a reset stage of operation in which the fastener gripping portion is moved towards the home position; and a controller for receiving motor turn information indicative of the number of turns of the motor and for monitoring the position of the fastener gripping portion based on the motor turn information and the output generated by the home position sensor.

FIELD OF THE INVENTION

The present disclosure relates to a power tool having fastener gripping portion position tracking functionality.

BACKGROUND OF THE INVENTION

Some existing blind rivet setting tools comprise a plurality of sensors for determining the position of the jaw assembly such as in U.S. Pat. No. 8,109,123, however, depending on multiple sensors to monitor jaw assembly position increases likelihood of tool failure.

BRIEF SUMMARY OF THE INVENTION

According to the present invention there is provided a power tool comprising: a motor;

a fastener gripping portion operatively coupled to the motor for causing movement of the fastener gripping portion between a home position and a retracted position to set a fastener; a home position sensor for generating output indicative that the fastener gripping portion has reached the home position during a reset stage of operation in which the fastener gripping portion is moved towards the home position; and a controller for receiving motor turn information indicative of the number of turns of the motor and for monitoring the position of the fastener gripping portion based on the motor turn information and the output generated by the home position sensor.

The controller may determine the fastener gripping portion has reached the home position during the reset stage of operation upon occurrence of the first to occur of the controller receiving the home position sensor output indicative that the fastener gripping portion has reached the home position or the number of motor turns determined during the reset stage of operation equaling the number of motor turns determined during movement of the fastener gripping portion to the retracted position.

During the reset stage of operation if the controller determines the fastener gripping portion has reached the home position based on output from the home position sensor the motor turn information stored in memory is reset.

The controller may determine that the fastener gripping portion has reached the retracted position when the number of motor turns determined during a fastener setting stage of operation reaches a predetermined maximum number of motor turns stored in memory, whereby in response the controller stops the fastener setting stage of operation.

The home position sensor may be a Hall sensor mounted in a fixed position within the tool which is configured to detect a magnet which is axially fixed relative to the fastener gripping portion. Optionally the Hall sensor generates a signal when exposed to magnetic flux from the magnet of one polarity but not when exposed to magnetic flux of the other polarity and the magnet is arranged so that as the magnet moves past the Hall sensor in use the Hall sensor generates a signal indicative that the fastener gripping portion has reached the home position during the reset stage of operation.

The controller may be configured to control the motor to move the fastener gripping portion to the home position if in response to receiving a tool actuation signal the controller determines that the fastener gripping portion is not at the home position.

The motor may be a brushless motor and control circuitry thereof may generate the motor turn information.

The power tool may further comprise at least one sensor for monitoring turns of the motor and for generating the motor turn information.

The fastener gripping portion may be a jaw assembly.

The power tool may be a blind rivet setting tool.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG.1shows a side cross-sectional view of a blind rivet setting tool100. The tool100has a housing102of a clam shell type construction having two halves which are fastened together. A battery104is releasably connected to the base122of the handle106via a battery attachment feature. To use the tool100a user inserts the mandrel of a blind rivet into a nose108of the tool100and pulls a trigger110. In response to a controller112of the tool determining that the trigger110has been pulled the controller112generates a signal to activate a motor114, which is a brushless motor. The motor114is located in the handle106and has a motor output shaft116. Torque from the motor output shaft116is transferred via a transmission118to a first bevel gear120. The transmission118comprises a series of planetary gear arrangements for reducing output speed while increasing torque. The first bevel gear120rotates at a lower speed than the motor output shaft116however with an increased torque relative to the motor output shaft116. The motor output shaft116, transmission118and first bevel gear120are aligned along a first axis A-A which extends along a longitudinal length of the handle106. By also locating the battery104on the first longitudinal axis A-A weight distribution of the tool100is improved.

A second bevel gear124is provided on the end face of a driving sleeve126. The driving sleeve126is rotationally fixed relative to an input sleeve128of a ball screw arrangement130. The driving sleeve126and input sleeve128are fixed relative to each other due to a friction fit arrangement. An internal surface of the input sleeve128comprises a threaded surface. The outer surface of the driving sleeve126is supported by bearings132which enable rotation of the driving sleeve126with respect to the housing102. A threaded rod134is mounted within the input sleeve128, which extends through the input sleeve128. A plurality of balls, such as metal ball bearings, ride in the opposing threaded surfaces of the input sleeve128and threaded rod134, thereby defining a ball screw arrangement130.

When the input sleeve128is rotatably driven by the driving sleeve126this causes axial movement of the threaded rod134. In other words, torque from the motor114is transferred through the transmission118, first and second bevel gears120,124and driving sleeve126to the input sleeve128, whereby rotation thereof causes axial movement of the threaded rod134. The threaded rod134is configured to move along a second longitudinal axis B-B of the tool100. The threaded rod134can move forwards or backwards along the axis B-B depending on the motor driving direction.

Referring toFIG.2a connecting sleeve300is attached to a first end302of the threaded rod134, which is mounted to the threaded rod134via a screw thread. A pull-back hull304is threadably attached to the connecting sleeve300. Axial movement of the threaded rod134along the second longitudinal axis B-B therefore also causes axial movement of the pull-back hull304.

A jaw assembly500is located within the pull-back hull304. The jaw assembly (shown inFIG.3a) has a plurality of circumferentially arranged jaws306each of which has a ramped outer surface308for cooperating with a conical inner surface310of the pull-back hull304. A separator sleeve312is forced by a spring314against the jaws306; more specifically a ramped front surface316of the separator sleeve312is forced against ramped rear surfaces318of the jaws306. A nosepiece320is releasably attached at the opening to the nose108of the tool100which has an annular ramped surface402. Each of the jaws306have a front ramped surface400for cooperating with the annular ramped surface402of the nose piece320. Cooperation between the ramped outer surfaces308of the jaws306and the conical inner surface310of the pull-back hull304, between the ramped rear surfaces318of the jaws306and the ramped front surface316of the separator sleeve312and between the front ramped surfaces400of the jaws and the annular ramped surface402of the nose piece320enables the tool100to set blind rivets in use.

To set a blind rivet a mandrel thereof is inserted through the nose piece320such that the mandrel extends between the jaws306, thereby urging the jaws306radially apart (seeFIG.3b). Upon pulling the trigger110of the tool100the controller112causes the threaded rod134, and thus the pull-back hull304, to move along the second longitudinal axis B-B to the right inFIGS.1and2. As the pull-back hull304is retracted its conical inner surface310is forced against the outer surfaces308of the jaws306, whereby a component of force draws the jaws306backwards with the pull-back hull304whereas another component of force urges the jaws306radially inwards thereby clamping the mandrel of the blind rivet being set between the jaws306.

In other words, pulling the pull-back hull304to the right inFIGS.1and2causes the jaws306to grip and pull the mandrel of a rivet being set. The blind rivet thus is pulled against the nose piece320for deforming the blind rivet and when the mandrel of the blind rivet is pulled far enough for setting the blind rivet the mandrel snaps.

Subsequently the tool100is required to perform a reset operation to dispose of the broken mandrel and to accept a fresh blind rivet for setting. During a reset operation of the tool100the controller112causes the motor114to reverse its direction for moving the threaded rod134, and thus the pull-back hull304, in the other direction along the second longitudinal axis B-B to the left inFIGS.1and2. When the pull-back hull304has been moved sufficiently far to the left the spring314via the separator sleeve312will urge the front ramped surfaces400of the jaws306against the annular ramped surface402of the nose piece320. Further movement of the threaded rod134to the left inFIGS.1and2will increase the pressure of the spring314against the separator sleeve312and thus cause the front ramped surfaces400of the jaws306to ride along the annular ramped surface402of the nose piece320while the ramped rear surfaces318of the jaws306ride along the ramped front surface316of the separator sleeve312. This causes the jaws306to move radially outwards and release the grip on the snapped mandrel, whereby with reference toFIG.1the released snapped mandrel can be caused to fall under gravity along an internal path204in the direction of a collection chamber200. For example, after a rivet setting operation, the user tilts the tool100such that the snapped mandrel moves into the collection chamber200. The internal path204is defined by aligned openings extending through components between the jaws306and the collection chamber200, including a first channel202extending through the threaded rod134along the second longitudinal axis B-B and a second channel204through a guidance sleeve206.

Turning toFIGS.3aand3bthe jaw assembly500will now be discussed in more detail.FIG.3ashows a perspective view of the jaw assembly500in a first configuration in which the jaws306are located radially as close to each other as possible.FIG.3bshows a perspective view of the jaw assembly500in a second configuration in which the jaws306are urged radially apart from each other such as by a mandrel of a blind rivet being inserted through the space between the jaws306or the jaws306being forced against the annular ramped surface402of the nose piece320. The jaw assembly500comprises three identical jaws306circumferentially arranged about a jaw assembly axis G-G. When the jaw assembly500is mounted in the tool100, the jaw assembly axis G-G is coaxial with the second longitudinal axis B-B of the tool100. The three jaws306can move radially with respect to the jaw assembly axis G-G.

There are situations during which the jaw assembly500is removed from the tool, in particular during routine maintenance of the tool100during which it is disassembled and then reassembled after being cleaned. Alternatively, the jaw assembly500may be swapped with a new jaw assembly because the jaws306of the original jaw assembly have worn. Further alternatively the jaw assembly500may be swapped with a new jaw assembly because the different jaw assemblies are configured for use with different sized mandrels. Referring again toFIGS.3aand3bthe jaw assembly has a flexible o-ring502for holding the jaws306of the jaw assembly500together when it is not located within the tool100. Each of the jaws306defines part of an annual groove504when the jaws306are in the configuration shown inFIG.3awherein the o-ring502is located in the annular groove504and biases the jaws306together. The o-ring502can be made from an elastic material such as rubber.

The controller112will be discussed in more detail with reference toFIG.6which shows a schematic diagram of the tool100. The controller112is connected to the motor114and the battery104. The controller112is configured to selectively control the motor114based on an actuation signal received from a trigger sensor111which is configured to generate a signal indicative that the trigger110has been pulled or released and a jaw assembly home position sensor800.

A problem with some blind rivet setting tools which calculate the position of the jaw assembly500is that the calculated position of the jaw assembly500can drift over time due to cumulative inaccuracies. Some tools address this by including a clutch mechanism for protecting components of the tool if the jaw assembly500overshoots its intended range of movement during tool use.

The tool100advantageously does not need a clutch mechanism because the controller112can determine the absolute position of the jaw assembly500with respect to the housing102every fastening operation. This means that after each fastening operation inaccuracies in the jaw assembly500position calculation performed by the controller112are reset to zero.

The jaw assembly home position sensor800is configured to generate a signal indicative that the jaw assembly500is at the home position, which is the position in which the tool100is ready to receive a new blind rivet for setting. Based on information received from the jaw assembly home position sensor800the controller112determines that the jaw assembly500is at the home position irrespective of other position data the controller112receives or calculates regarding the jaw assembly500.

With reference toFIGS.5aand5ban anti-rotation bar700is engaged with the threaded rod134in a manner whereby the anti-rotation bar700is axially and rotationally fixed to the threaded rod134. As the input sleeve128is rotated the anti-rotation bar700cooperates with the threaded rod134and slots600,602in the housing102for causing the threaded rod134to move axially along the axis B-B. Since the anti-rotation bar700is rotationally fixed with respect to the housing102it slides relative to the housing102through the slots600,602during axial movement of the threaded rod134.

The anti-rotation bar700comprises a central hole702with a threaded inner surface704which is tightly threadably engaged with a reciprocal threaded surface208at an end of the threaded rod134.

The anti-rotation bar700comprises a first arm706and a second arm708. The first and second arms706,708are mounted in first and second slots600,602in the housing102. When the threaded rod134moves along the second longitudinal axis B-B, the first and second arms706,708slide along the first and second slots600,602. The first and second slots600,602extend along longitudinal axes which are parallel to the second longitudinal axis B-B.

The anti-rotation bar700has a mounting plate710projecting from a central portion712of the anti-rotation bar700. A magnet714is mounted to the mounting plate710. A sleeve housing716is mounted over the anti-rotation bar700as shown inFIG.5b.

The sleeve housing716comprises a magnet pocket718for receiving the magnet714and the sleeve housing716ensures that the magnet714does not move with respect to the anti-rotation bar700when mounted to the anti-rotation bar700as shown inFIG.5b. The magnet pocket718comprises a window720exposing a portion of the magnet714. This means that the sleeve housing716is not positioned between the magnet714and a Hall sensor comprising the home position sensor800(hereafter referred to as Hall sensor800). Accordingly, the sleeve housing716itself does not attenuate the magnetic field generated from the magnet714in the direction of the Hall sensor800when the jaw assembly500is in the home position.

The sleeve housing716comprises an arm window722configured to receive the first arm706. When the sleeve housing716is mounted on the anti-rotation bar700, the first arm706projects through the arm window722. The sleeve housing716comprises a snap-fit mechanism724for engaging a locking ramp726and snapping against a locking shoulder portion728of the anti-rotation bar700. This securely engages the sleeve housing716against the anti-rotation bar700. The sleeving housing716comprises a similar lower snap-fit mechanism730configured to engage a lower locking ramp732and snapping against a lower locking shoulder portion734of the anti-rotation bar700.

Looking atFIG.4the tool100comprises a printed circuit board (PCB)606comprising the Hall sensor800. The Hall sensor800is configured to detect the magnet714when the jaw assembly500is in the home position. The Hall sensor800and the magnet714are arranged to be close to each other when the jaw assembly500is in the home position. In some examples, the minimum distance X1between the Hall sensor800and the magnet714is 1.1 mm. It has been noted that this minimum distance allows for sufficient sensitivity in the Hall sensor800detecting relative movement of the magnet714with respect to the Hall sensor800. At the same time this allows sufficient clearance between the first and second arms706,708and the first and second slots600,602to allow slidable movement of the first and second arms706,708in the first and second slots600,602.

As mentioned above, the anti-rotation bar700is axially and rotationally fixed relative to the threaded rod134and is rotationally fixed with respect to the housing102. Given that the jaw assembly500is caused to move axially upon axial movement of the threaded rod134this means that the anti-rotation bar700, the magnet714, the threaded rod134and the jaw assembly500move together along the second longitudinal axis B-B in use. Detecting movement of the magnet714thus allows movement of the jaw assembly500to be detected.

The Hall sensor800is configured to detect a specific magnetic pole. In other words, the Hall sensor800is configured to detect magnetic flux of one polarity while being blind to magnetic flux of the other polarity, meaning the Hall sensor800generates a signal in response to detection of a specific pole of the magnet714. For example the Hall sensor800is configured to detect magnetic flux emanating from the north pole of the magnet714while being blind to magnetic flux emanating from the south pole of the magnet714, meaning the Hall sensor800generates a signal in response to detection of the North pole of the magnet714. The tool100is configured such that the middle portion of the magnet714—the transition between north and south magnetic poles—is aligned with the Hall sensor800when the jaw assembly500is in the home position. That is, upon occurrence of a change in polarity of the magnetic flux to which the Hall sensor800is exposed then the Hall sensor800generates a signal which is indicative of the jaw assembly500being in the home position.

This can be used to detect when the jaw assembly500has reached its home position during a reset operation of the tool100. Continuing with the example in which the Hall sensor800is configured to detect magnetic flux emanating from the north pole of the magnet714only while being blind to magnetic flux emanating from the south pole of the magnet714: the magnet714may be aligned such that during a rivet setting operation when the jaw assembly500is retracted and the magnet714moves away from the Hall sensor800the Hall sensor800is only exposed to magnetic flux emanating from the south pole of the magnet714meaning no signal is generated by the Hall sensor800. During a reset operation of the tool as the jaw assembly500is moved towards the home position, and the magnet714is moved towards the Hall sensor800, the Hall sensor800is exposed to magnetic flux emanating from the south pole of the magnet714meaning no signal is generated by the Hall sensor800. However, after the jaws500have reached the home position and continue to move beyond the home position, the magnet moves past the Hall sensor800such that the Hall sensor800is only exposed to magnetic flux emanating from the north pole of the magnet714meaning a signal is suddenly generated by the Hall sensor800. The controller112can use this signal to determine that the reset operation is complete.

As shown inFIG.5a, the magnet714comprises a magnetic axis H-H which extends in a direction between opposite poles of the magnet714and the magnetic axis H-H is parallel with the second longitudinal axis B-B of the tool100along which the jaw assembly500moves from the home position to a retracted position during a rivet setting operation. In some examples the heretofore described arrangement is configured to detect variations in position of the magnet714as low as 0.6 mm, which means the jaw assembly500can be determined to have reached the home position to an accuracy of 0.6 mm.

Operation of the tool100will now be discussed in more detail with respect toFIGS.7,8and9.FIG.7shows a simplified mode of operation of the tool100. The functionality illustrated inFIG.7is implemented by the controller112on the basis of software stored in memory804, whereby upon the controller112running such software it implements the functionality illustrated inFIG.7. The controller112is configured to control the tool100based on a signal received from the Hall sensor800and motor status information.

Based on input from the trigger sensor111the controller112initiates a pull action operation (otherwise referred to as a rivet setting operation) as shown in step900ofFIG.7. The jaw assembly500is in the home position when the controller112starts the pull action operation. The controller112starts the pull action operation900by issuing a control instruction to the motor114at time T=T1whereby the motor114is caused to ramp up in speed to a predetermined target speed which is attained at time T2shown inFIG.9. In some examples the predetermined target speed is the maximum driving speed of the motor. In some examples the predetermined target speed may fall in the range between 24,000 RPM to 30,000 RPM. By configuring the tool100so that the predetermined target speed of the motor114between T1and T2is the maximum driving speed of the motor this provides that the jaw assembly500moves from the home position to the retracted position as quickly as possible. It will however be appreciated that in practice the maximum driving speed of the motor114is dependent on various factors such as the level of charge of the battery104, the temperature of the battery104, the magnitude of force required to deform the rivet being set and the magnitude of friction experienced by internal features of the tool100in use.

The controller112issues another control instruction to stop the motor114when the threaded rod134and the jaw assembly500are in the retracted position as shown in step902, wherein how this is determined is explained below. In response the motor114brakes at t=T3and stops at t=T4; preferably between t=T3and t=T4the motor114is braked at the maximum achievable deceleration rate. The retracted position corresponds with the maximum distance which the tool100is configured to enable the jaw assembly500to be retracted.

The controller112is configured to determine the position of the threaded rod134and thereby the jaw assembly500based on motor status information such as the number of turns (or partial turns) the motor114has made since initiation of the pull action operation in step900when the jaw assembly500was in the home position. Deriving the position of a jaw assembly in a blind rivet setting tool based on motor turns is a known technique, described for example in EP3530372A1 and EP3530370A1 the contents of which are incorporated herein by reference.

The controller112is configured to receive information indicative of the motor status information from the motor114e.g. information indicative of the number of motor turns performed. Alternatively, the controller112can optionally determine the number of motor turns based on information received from the motor114upon implementing software functionality stored in memory804.

The controller112determines that the jaw assembly500is in the retracted position when the number of motor turns since initiation of the pull action operation in step900reaches a predetermined maximum value stored in the memory804. This means that the controller112is configured to determine the position of the threaded rod134and thus the jaw assembly500when moving towards the retracted position away from the home position based on motor status information alone.

The tool100then needs to perform a drive back home operation1104(as shown inFIG.9), alternatively referred to as a reset operation, in order to move the jaw assembly500back to the home position in order to release the snapped mandrel of the blind rivet being set and to be ready to receive a mandrel of a subsequent blind rivet to be set. To enact the reset operation the controller112issues a control instruction to the motor114to drive in a reverse direction and thereby move the jaw assembly500towards the home position as shown in step904. In response to the controller112issuing this instruction at T=T5the motor114is caused to ramp up in speed (in a reverse direction) to the predetermined target speed which is attained at t=T6. As a reminder, in some examples the predetermined target speed is the maximum driving speed of the motor114so that the jaw assembly500moves from the retracted position towards the home position as quickly as possible; again though as mentioned previously the maximum driving speed of the motor114which is achievable in practice is dependent on various factors such as the level of charge of the battery104, the temperature of the battery104and the magnitude of friction experienced by internal features of the tool100in use.

In order to protect the tool100the controller112does not drive the motor114at the predetermined target speed through the entire distance that the jaw assembly500moves from the retracted position to the home position. Instead, the controller112is configured to cause the motor114to drive in reverse direction at a reduced speed when the jaw assembly500is determined by the controller112to be within a threshold distance of the home position, which will be described in more detail later.

During reverse driving of the motor114in step906ofFIG.7the controller112compares the number of motor turns occurring during reverse movement with the number of motor turns which occurred during the pull action operation. When the number of motor turns determined to have occurred during reverse movement is within a threshold amount of the number of motor turns which occurred during the pull action operation the controller112in step908causes the motor driving speed in the reverse direction to be reduced so that the jaw assembly500can be more precisely positioned in the home position to reduce the extent to which the jaw assembly500overshoots the home position. The threshold amount is realised in step906when the number of motor turns determined to have occurred during reverse movement is within 25% of the number of motor turns which occurred during the pull action operation. In other words, the threshold condition of step906is realised when the jaw assembly500has been driven 75% of the way back towards its home position. If during reverse driving of the motor114in step906the controller112determines that the threshold condition has not been satisfied the motor114is caused to continue driving in reverse at the predetermined target speed wherein step906is repeated.

In some embodiments the distance of travel of the jaw assembly500from the home position to the maximum stroke pull back position is 25 mm. Thus, during a return operation, the threshold condition of step906is determined to have been satisfied when the jaw assembly has been returned 75% of the way back towards its home position, namely when the jaw assembly is within 6.25 mm of the home position.

In some embodiments the distance of travel of the jaw assembly500from the home position to the maximum stroke pull back position is 30 mm. Thus, during a return operation, the threshold condition of step906is determined to have been satisfied when the jaw assembly has been returned 75% of the way back towards its home position, namely when the jaw assembly is within 7.5 mm of the home position.

Returning toFIG.9, in response to the controller112in step908issuing a control instruction to slow the motor114down at time T7the motor114decelerates to a predetermined early braking speed which is lower than the predetermined target speed of the motor114between times T2to T3and T6to T7. In this way, the controller112provides early braking to the motor114before the jaw assembly500reaches the home position.

In embodiments in which the predetermined motor target speed between times T2to T3and T6to T7ranges between24,000RPM to30,000RPM the predetermined early braking speed ranges between 15,000 RM to 20,000 RPM. More specifically in an embodiment in which the target motor driving speed between T2to T3and T6to T7is 24,000 RPM the early braking speed is 15,000 RPM. In another embodiment in which the target motor driving speed between T2to T3and T6to T7is 30,000 RPM the early braking speed is 20,000 RPM.

The rate of deceleration between times T7and T8when the motor114reaches the predetermined early braking speed is such that the early braking speed is achieved before the jaw assembly500reaches the home position, wherein the rate of deceleration between T7and T8can be the maximum achievable deceleration rate although there is freedom to use a less steep rate of deceleration provided that the early braking speed is achieved before the jaw assembly500reaches the home position. When the early braking speed has been achieved at time t=T8the controller112controls the motor114to keep driving at that speed until the controller112detects input from the Hall sensor800in step910which is indicative that the jaw assembly500has reached the home position as heretofore described. In response the controller112issues in step912at t=T9a stop instruction to stop the motor114completely whereby the motor114decelerates (preferably at the maximum achievable deceleration rate) until the motor114stops turning.

When the controller112receives the signal from the Hall sensor800in step910the controller112is configured to reset the motor status information to correspond with the jaw assembly500being in the home position. For example, the controller112resets the active number of motor turns to zero. This means that any drift between the active number of motor turns determined by the controller112and the actual number of motor turns is reset to zero each time the tool100is operated.

This means that the controller112is configured to determine the position of the jaw assembly500, and thereby control the operating speed of the motor114, when the jaw assembly500is moving towards the home position away from the retracted position based on the motor status information and a signal received from the Hall sensor800.

The jaw assembly500has now returned to the home position and the tool100is ready to accept a new blind rivet.

As already mentioned, the maximum driving speed of the motor114which is achievable in practice is dependent on multiple factors such as the level of charge of the battery104, the temperature of the battery104, the magnitude of force required to deform the particular rivet being set and the magnitude of friction experienced by internal features of the tool100in use. In tools in which a jaw assembly is driven backwards during a reset operation at maximum speed all the way until the home position is detected and a complete stop of the motor is initiated the level of overshoot passed the home position is variable based on the multiple factors effecting the maximum driving speed of the motor. Thus, when such tools are designed, they need to have high tolerances built into the design to accommodate the variable extents which the jaw assembly may overshoot the home position. The heretofore described early braking functionality addresses this issue. The early braking speed is chosen to be lower than the maximum driving speed of the motor and so is less effected by the factors mentioned above such as battery charge level, meaning that the tool100can more reliably control the motor114to operate at a specific predetermined early braking speed. By causing the motor114to have slowed down to the early braking speed by the time when the jaw assembly500reaches the home position means that when the home position is finally reached, and the jaw assembly500is braked hard, the jaw assembly500is always braking from the same speed regardless of tool operating conditions (e.g. ambient temperature/battery charge level) and so the level of overshoot past the home position is more predictable meaning the tool100can be controlled within tighter operational tolerances, whereby the tolerances required to be built into the tool design are less.

In view of the foregoing paragraph, it will be appreciated that there is some freedom for a designer to select a suitable percentage change reduction in motor speed during a reset stage of operation between the predetermined target speed and the early braking speed. If the early braking speed is very low this will of course reduce the potential level of overshoot of the jaw assembly500past the home position, however, the overall duration of the reset operation will be increased. On the other hand, if the early braking speed is much closer to the predetermined target speed this will reduce the overall duration of the reset operation but will increase the potential level of overshoot of the jaw assembly500past the home position. Some balance must therefore be struck in selecting a suitable percentage change reduction in motor speed during a reset stage of operation between the predetermined target speed and the early braking speed, which maintains the potential level of overshoot of the jaw assembly500past the home position within acceptable levels while maintaining a reasonable overall duration of the reset operation. With this in mind, it is envisaged that in some embodiments during a reset stage of operation the early braking speed can range between 50% to 80% of the predetermined target speed. In some embodiments during a reset stage of operation the early braking speed can range between 60% to 70% of the predetermined target speed. In some embodiments during a reset stage of operation the early braking speed can be range between 62% to 67% of the predetermined target speed.

Another example will now be discussed with reference toFIG.8which is identical toFIG.7except that the operation of the tool100comprises additional functionality which will now be described. The functionality illustrated inFIG.8is implemented by the controller112on the basis of software stored in memory804, whereby upon the controller112running such software it implements the functionality illustrated inFIG.8

The controller112is configured to actuate the tool100in response to receiving an actuation signal from the trigger sensor111in step1000. The controller112then determines that the user wishes to use the tool100and in response determines whether the jaw assembly500is in the home position in step1002. The controller112can determine whether the jaw assembly500is in the home position similarly to before, namely based on whether a signal is generated by the Hall sensor800. If in step1002the controller112determines that a signal is generated by the Hall sensor800then the jaw assembly500is determined to be in the home position and in response the controller112proceeds to step900and initiates the pull action of step900as before.

Conversely if in step1002the controller112determines that a signal is not generated by the Hall sensor800then the jaw assembly500is determined not to be in the home position. This may be the case if power was removed before the tool100could finish performing a reset operation1104. In response to the controller112making a negative determination in step1002it issues a control instruction to drive the motor114in reverse at a low speed in step908until in step910the controller112detects a signal generated by the Hall sensor800indicative that the jaw assembly500is in the home position; the low reverse driving speed of the motor114is lower than the aforementioned target driving speed between T2to T3and T6to T7discussed in connection withFIG.9.

In some embodiments in which the target motor driving speed between T2to T3and T6to T7ranges between 24,000 to 30,000 RPM the low reverse driving speed ranges between 15,000 to 20,000 RPM. More specifically in an embodiment in which the target motor driving speed between T2to T3and T6to T7is 24,000 RPM the low reverse driving speed is 15,000 RPM. In another embodiment in which the target motor driving speed between T2to T3and T6to T7is 30,000 RPM the low reverse driving speed is 20,000 RPM.

In response to the controller112receiving a positive determination in step910subsequently the controller112in step912stops reverse driving of the motor114(preferably at the maximum achievable deceleration rate), whereby the jaw assembly500is now in the home position. The user then depresses the trigger110again and the tool repeats steps1000,1002and then proceeds to step900to initiate the pull action.

Once the pull action has been initiated in step900, the controller112determines the displacement of the jaw assembly500from the home position in the manner already described based on counting motor turns. If the controller112determines in step1004that the number of motor turns during the rivet setting stage of operation has reached a predetermined maximum number of motor turns stored in memory804(whereby the jaw assembly500is in the maximum pull back stroke position) the controller112stops the motor114in step902as before.

If the controller112makes a negative determination in step1004the controller112continues the pull action and then determines in step1006whether the number of motor turns during the rivet setting stage of operation has reached a predetermined minimum number of motor turns stored in memory804.

If in step1006the controller112makes a negative determination the controller112continues the pull action.

If in step1006the controller112makes a positive determination the controller112then determines in step1008whether the trigger110is deactivated based on input from the trigger sensor111.

If in step1008the controller112makes a negative determination, then the controller112continues the pull action in step900. However, if in step1008the controller112makes a positive determination the controller112stops the motor114in step902as before.

Subsequently steps902to912inFIG.8are implemented in a similar manner to the correspondingly numbered steps inFIG.7which have already been discussed.

It will be appreciated that whilst various aspects and embodiments have heretofore been described the scope of the present invention is not limited thereto and instead extends to encompass all arrangements, and modifications and alterations thereto, which fall within the spirit and scope of the appended claims.

For instance, whilst illustrative embodiments have been described as employing software it will be appreciated by persons skilled in the art that the functionality provided by such software may instead be provided by hardware (for example by one or more application specific integrated circuits), or indeed by a mix of hardware and software.

In some examples the battery104is removable from the tool100or alternatively the battery104is integral to the tool100. Alternatively, or additionally the tool100may comprise other power sources e.g. it may be configured to receive power from a mains power supply.

As shown inFIG.1, the driving sleeve126and input sleeve128are fixed to each other due to a friction fit arrangement. Alternatively, the driving sleeve126and input sleeve128can be fixed via an interlocking arrangement such as a spline fit arrangement or other male and female interlocking-type arrangement.

As shown inFIG.3a, the o-ring502is seated in a groove504. In some alternative examples the o-ring502may be replaced with any suitable means to keep the jaws306together such as a c-clip, a circlip, an e clip, a snap ring, or another spring fastener.

The o-ring502is made from an elastic material such as rubber. In other examples, the o-ring502is optionally made from polyurethane, PTFE, ethylene propylene rubber, neoprene, nitrile, or silicone.

As shown inFIG.3athe jaw assembly500comprises three jaws306. However, in alternative examples, the jaw assembly500can comprise any number of jaws306more than two.

In some examples the jaws306do not interlock with each other for maintaining jaw alignment.

As shown inFIGS.3aand3bthe jaws306are identical. This makes manufacture simpler because a single tooling can be used to create multiple jaws306.

In general, the functionality described in connection withFIGS.7and8may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. For example some aspects may be implemented in hardware while other aspects may be implemented in firmware or software which may be executed by the controller112, microprocessor or other computing device although the disclosure is not limited thereto. While various aspects of the disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or by the controller112or other computing devices or some combination thereof.

The examples of this disclosure may be implemented by computer software executable by a data processor or by hardware or by a combination of software and hardware. The data processing may be provided by means of one or more data processors. Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions.

The memory804may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. Also, the controller112may be of any type suitable to the local technical environment, and may include one or more of general purpose microprocessors, digital signal processors (DSPs) or processors based on multi core processor architecture as non-limiting examples.

Some examples of the disclosure may be implemented as a chipset, in other words a series of integrated circuits communicating among each other. The chipset may comprise microprocessors arranged to run code, application specific integrated circuits (ASICs), or programmable digital signal processors for performing the operations described above.

As already described in connection with step906the threshold amount is realised when the number of motor turns determined to have occurred during reverse movement is within 25% of the number of motor turns which occurred during the pull action operation. However there is flexibility in the specific distance implemented in practice provided the same overall functionality is achieved, for instance in some embodiments the threshold amount is realised in step906when the number of motor turns determined to have occurred during reverse movement is reaches a specific percentage of the number of motor turns which occurred during the pull action operation ranging between 5% to 25% (optionally between 10% to 15%) of the number of motor turns which occurred during the pull action operation.

As shown inFIG.5a, the anti-rotation bar700optionally comprises the mounting plate710projecting from the central portion712of the anti-rotation bar700for receiving the magnet714. In some other examples, the magnet714is mounted to the central portion712(or any other part of the anti-rotation bar700) in a recess in the central portion712. The magnet714is optionally mounted to the anti-rotation bar700(whether in a recess or on the mounting plate710) using glue or the attractive magnetic force of the magnet714against the ferrous anti-rotation bar700.

As shown inFIG.5a, the anti-rotation bar700optionally comprises the sleeve housing716configured to secure the magnet714against the anti-rotation bar700. In some other examples, the sleeve housing716is not provided.

It will be appreciated that the specific shape of the anti-rotation bar700and position of the slots600,602can be adapted, provided that the anti-rotation bar700achieves the purpose of guiding axial movement of the threaded rod134. Moreover, the specific location of the magnet714on the anti-rotation bar700and the way in which the magnet714is attached to the anti-rotation bar700may be adapted provided that the controller112is still able to determine when jaw assembly500is in the home position based on interaction between the magnet714and Hall sensor800.

WhilstFIGS.4,5a,5bdisclose an example for mounting the magnet714on the anti-rotational bar700, in alternative embodiments the magnet714can be mounted to another component which moves together with the threaded rod134during operation of the tool100, wherein the position of the Hall sensor800is correspondingly adapted.

FIG.4shows a Hall sensor800which is mounted on a PCB606and configured to detect the relative movement of the magnet714with respect to the Hall sensor800. In alternative embodiments the Hall sensor800can be replaced with an alternative sensor configured to detect when the jaw assembly500is in the home position. For example, instead of a Hall sensor800the home position sensor can be a switch e.g. a microswitch which is actuated by interacting with the anti-rotation bar700(or a feature attached thereto) when the jaw assembly500is in the home position. In other words, in such embodiments when the jaw assembly500is in the home position the switch is actuated by the anti-rotation bar700and generates output indicative that the jaw assembly500is in the home position whereby in response the controller112implements step912. In other embodiments instead of a Hall sensor800the home position sensor can be replaced by an optical sensor configured to detect the presence or absence of a reference indicator on the threaded rod134or the anti-rotation bar700when the jaw assembly500is in the home position for indicating that the jaw assembly500is in the home position. In other words, in such embodiments when the jaw assembly500is in the home position the optical sensor generates output indicative that the jaw assembly500is in the home position whereby in response the controller112implements step912.

In some embodiments the tool100can be configured to detect the occurrence of a mandrel snapping such as by monitoring current usage by the motor114. During a pull back stage of operation as the jaw assembly500pulls the mandrel of a rivet more tightly the current draw of the motor will increase and then suddenly decrease when the mandrel snaps. The controller112can monitor for such a sudden drop in current and in response to detecting such occurrence determine that the mandrel of the rivet being set has snapped and thus initiate step902to stop the jaw assembly500. Subsequently the controller112initiates the reset stage of operation either automatically or in response to release of the trigger110.

In other embodiments the tool100can be configured to detect the occurrence of a mandrel snapping by monitoring motor speed. During a pull back stage of operation as the jaw assembly500pulls the mandrel of a rivet more tightly the speed of the motor114will decrease and then suddenly increase when the mandrel snaps. The controller112can monitor for such a sudden increase in motor speed and in response to detecting such occurrence determine that the mandrel of the rivet being set has snapped and thus initiate step902to stop the jaw assembly500. Subsequently the controller112initiates the reset stage of operation either automatically or in response to release of the trigger110.

Regardless of how the controller determines when it is time to implement step902and thus stop retraction of the jaw assembly500in use the controller112keeps track of the position of the jaw assembly500based on motor turns and output from a single sensor namely the home position sensor800as heretofore described.

The motor114has been described as being a brushless motor and the controller112cooperates with the brushless motor (in particular with its control electronics) in order to control the brushless motor and determine motor status information e.g. number of motor turns. In other embodiments however the motor114may be a brushed motor having a motor output shaft driven by a stator and having at least one magnet on the motor output shaft. For the controller112to determine motor turn information of such a brushed motor the tool100additionally has a motor sensor (not shown) for generating output indicative of motor turn information; such as a Hall sensor which cooperates with the at least one magnet on the motor output shaft and which generates output indicative of variations in magnetic flux density as the motor shaft rotates which can be used by the controller112to determine motor turn information e.g. number of motor turns. Since the concept of determining motor turn information in the context of brushed and brushless motors is already known, meaning that the aforementioned ways of determining motor turn information are not the only ways of doing so, there is freedom for a designer to select a way of determining motor turn information when designing a tool100which implements the invention described herein. Whether or not a brushless motor is used the controller112can determine the direction of rotation of the motor114based on whether the controller112is implementing a pull action900(in which case the motor114will be rotating in a first direction) or whether the controller is implementing a reset operation (in which case the motor114will be rotating in a second direction). It is here mentioned that in battery operated embodiments the motor114is configured to operate using DC current, whereas in mains operated embodiments the motor is configured to operate using AC current. Finally the heretofore described functionality need not necessarily be used exclusively in blind rivet setting tools but may be used in other power tools having a fastener gripping portion which moves backwards from a home position in order to set a fastener and which is then returned to the home position. For example the heretofore described functionality can be implemented in other tools such as rivet setting tools (not necessarily blind rivet fastening tools), swage fastener tools and lockbolt fastener tools wherein the fastener gripping portion of such tools is configured to grip the type of fastener which the tool is used to set e.g. the fastener gripping portion of a swage fastener tool is configured to grip a swage fastener.