Patent Description:
Some existing blind rivet setting tools have a ball screw mechanism driven by an electric motor for causing movement of a set of jaws in order to pull the mandrel of a rivet. Such a tool is described in <CIT> for example, wherein the motor is located above the handle. In order for the tool to feel balanced in a user's hand the manufacturer needs to carefully consider the arrangement of features within the housing relative to the handle. Having the motor and all transmission features above the handle makes the tool top heavy. Also due to space limitations within the housing there is some play off between arranging internal features of the tool such that the tool works vs. arranging such features so that weight distribution of the tool is optimised.

Document <CIT> discloses a power tool for setting fasteners and forms the basis for the preamble of claim <NUM>.

According to an aspect of the present invention there is provided a power tool comprising: a motor at least partially located within the handle of the tool and having a motor output shaft extending along a first axis extending along the length of the handle; and a fastener gripping portion operatively coupled to the motor via a transmission which in use causes movement of the fastener gripping portion along a second axis, perpendicular to the first axis, between a home position and a retracted position to set a fastener engaged by the fastener gripping portion; the transmission comprising a bevel gear arrangement for redirecting torque flowing along the first axis in use which is input to the bevel gear arrangement so that torque output from the bevel gear arrangement flows along the second axis and wherein the transmission further comprises a mechanism for converting torque output from the bevel gear arrangement in use into a linear force for causing linear movement of the fastener gripping portion.

The mechanism may be a ball screw mechanism extending along the second axis between the bevel gear arrangement and the fastener gripping portion. Alternatively the mechanism may be a roller screw mechanism extending along the second axis between the bevel gear arrangement and the fastener gripping portion.

The motor may be located entirely within the handle.

The transmission may comprise at least one planetary gear stage for transferring torque from the motor along the first axis in use.

The at least one planetary gear stage may be at least partially located within the handle, optionally entirely located within the handle.

The power tool may comprise a battery attachment portion on the handle such that a notional line extending between the battery attachment portion and the motor output shaft extends along the first axis.

The fastener gripping portion may be a jaw assembly.

The power tool may be a blind rivet setting tool.

Various aspects and embodiments of the invention will now be described by way of nonlimiting example with reference to the accompanying drawings, in which:.

<FIG> shows a side cross-sectional view of a blind rivet setting tool <NUM>. The tool <NUM> has a housing <NUM> of a clam shell type construction having two halves which are fastened together. A battery <NUM> is releasably connected to the base <NUM> of the handle <NUM> via a battery attachment feature. To use the tool <NUM> a user inserts the mandrel of a blind rivet into a nose <NUM> of the tool <NUM> and pulls a trigger <NUM>. In response to a controller <NUM> of the tool determining that the trigger <NUM> has been pulled the controller <NUM> generates a signal to activate a motor <NUM>, which is a DC brushless motor. The motor <NUM> is located in the handle <NUM> and has a motor output shaft <NUM>. Torque from the motor output shaft <NUM> is transferred via a transmission <NUM> to a first bevel gear <NUM>. The transmission <NUM> comprises at least one planetary gear arrangement for reducing output speed while increasing torque. The first bevel gear <NUM> rotates at a lower speed than the motor output shaft <NUM> however with an increased torque relative to the motor output shaft <NUM>. The motor output shaft <NUM>, transmission <NUM> and first bevel gear <NUM> are aligned along a first axis A-A which extends along a longitudinal length of the handle <NUM>. By also locating the battery <NUM> on the first longitudinal axis A-A weight distribution of the tool <NUM> is improved.

It will be appreciated that there is some design freedom in the transmission <NUM> between the motor output shaft <NUM> and the first bevel gear <NUM>. In particular the number of planetary gear stages, and its (or their) configuration, forming the tranmission <NUM> depends on the required gear ratio to be achieved between the motor output shaft <NUM> and the first bevel gear <NUM>. Given that it is well known that planetary gear stages step down rotation speed while stepping up torque persons skilled in the art, based on the disclosure given herein, will be able to decide upon a suitable transmission arrangement which achives the required gear ratio for thier tool to function; wherein the appropriate gear ratio depends on multiple factors including maximum achieveble motor output torque, pitch of the ball screw arrangement <NUM> described below, friction between moveable featiures within the tool <NUM> and the maximum pull force required to set a fastener. It will be appreciated that for some tools <NUM> a suitable transmisison <NUM> may only have a single planetary gear stage, whereas for other tools a suitable transmisison <NUM> may have a plurality of planetary gear stages arranged in series.

Continuing with reference to <FIG> a second bevel gear <NUM> is provided on the end face of a driving sleeve <NUM>. The driving sleeve <NUM> is rotationally fixed relative to an input sleeve <NUM> of a ball screw arrangement <NUM>. The driving sleeve <NUM> and input sleeve <NUM> are fixed relative to each other due to a friction fit arrangement. An internal surface of the input sleeve <NUM> comprises a threaded surface. The outer surface of the driving sleeve <NUM> is supported by bearings <NUM> which enable rotation of the driving sleeve <NUM> with respect to the housing <NUM>. A threaded rod <NUM> is mounted within the input sleeve <NUM>, which extends through the input sleeve <NUM>. A plurality of balls, such as metal ball bearings, ride in the opposing threaded surfaces of the input sleeve <NUM> and threaded rod <NUM>, thereby defining a ball screw arrangement <NUM>.

When the input sleeve <NUM> is rotatably driven by the driving sleeve <NUM> this causes axial movement of the threaded rod <NUM>. In other words, torque from the motor <NUM> is transferred through the transmission <NUM>, first and second bevel gears <NUM>, <NUM> and driving sleeve <NUM> to the input sleeve <NUM>, whereby rotation thereof causes axial movement of the threaded rod <NUM>. The threaded rod <NUM> is configured to move along a second longitudinal axis B-B of the tool <NUM>. The threaded rod <NUM> can move forwards or backwards along the axis B-B depending on the motor driving direction.

Referring to <FIG> a connecting sleeve <NUM> is attached to a first end <NUM> of the threaded rod <NUM>, which is mounted to the threaded rod <NUM> via a screw thread. A pull-back hull <NUM> is threadably attached to the connecting sleeve <NUM>. Axial movement of the threaded rod <NUM> along the second longitudinal axis B-B therefore also causes axial movement of the pull-back hull <NUM>.

A jaw assembly <NUM> is located within the pull-back hull <NUM>. The jaw assembly (shown in <FIG>) has a plurality of circumferentially arranged jaws <NUM> each of which has a ramped outer surface <NUM> for cooperating with a conical inner surface <NUM> of the pull-back hull <NUM>. A separator sleeve <NUM> is forced by a spring <NUM> against the jaws <NUM>; more specifically a ramped front surface <NUM> of the separator sleeve <NUM> is forced against ramped rear surfaces <NUM> of the jaws <NUM>. A nosepiece <NUM> is releasably attached at the opening to the nose <NUM> of the tool <NUM> which has an annular ramped surface <NUM>. Each of the jaws <NUM> have a front ramped surface <NUM> for cooperating with the annular ramped surface <NUM> of the nose piece <NUM>. Cooperation between the ramped outer surfaces <NUM> of the jaws <NUM> and the conical inner surface <NUM> of the pull-back hull <NUM>, between the ramped rear surfaces <NUM> of the jaws <NUM> and the ramped front surface <NUM> of the separator sleeve <NUM> and between the front ramped surfaces <NUM> of the jaws and the annular ramped surface <NUM> of the nose piece <NUM> enables the tool <NUM> to set blind rivets in use.

To set a blind rivet, while the jaw assembly <NUM> is in a home position a mandrel of the blind rivet is inserted through the nose piece <NUM> such that the mandrel extends between the jaws <NUM>, thereby urging the jaws <NUM> radially apart (see <FIG>). Upon pulling the trigger <NUM> of the tool <NUM> the controller <NUM> receives output from a trigger sensor and in response activates the motor <NUM> for causing the threaded rod <NUM>, and thus the pull-back hull <NUM>, to move along the second longitudinal axis B-B to the right in <FIG> and <FIG>. As the pull-back hull <NUM> is retracted its conical inner surface <NUM> is forced against the outer surfaces <NUM> of the jaws <NUM>, whereby a component of force draws the jaws <NUM> backwards with the pull-back hull <NUM> away from the home position whereas another component of force urges the jaws <NUM> radially inwards thereby clamping the mandrel of the blind rivet being set between the jaws <NUM>.

In other words pulling the pull-back hull <NUM> to the right in <FIG> and <FIG> causes the jaws <NUM> to grip and pull the mandrel of a rivet being set. The blind rivet thus is pulled against the nose piece <NUM> for deforming the blind rivet and when the mandrel of the blind rivet is pulled far enough for setting the blind rivet the mandrel snaps.

Designers are free to select a suitable way for the controller <NUM> to control operation of the motor <NUM> in use to implement a fastening operation. In other words designers are free to select a suitable way for the controller <NUM> to determine when the jaw assembly <NUM> has been retracted far enough during a fastener setting stage of operation at which point in time retraction of the jaw assembly <NUM> is ceased. For example a mechanical switch may be provided within the tool <NUM> and in response to the controller <NUM> determining that the trigger <NUM> has been pulled by a user the controller <NUM> causes the pull-back hull <NUM> (and thus the jaw assembly <NUM>) to be retracted until a feature of the pull-back hull <NUM> actuates the mechanical swich thereby generating output indicative that the jaw assembly <NUM> has been pulled back sufficiently far to set a blind rivet. Alternatively an optical sensor may be provided within the tool <NUM> which generates output based on the presence or absence of a feature on the pull-back hull <NUM> wherein based on output from the optical sensor the controller <NUM> can determine that the pull-back hull <NUM> (and thus the jaw assembly <NUM>) has reached a predetermined retracted position for setting a blind rivet. Alternatively the controller <NUM> may be configured to monitor the magnitude of current drawn from the battery <NUM> during a fastening operation and when the current draw drops by at least a predetermined extent during a fastening stage of operation the controller <NUM> can determine that the mandrel of the blind rivet being fastened has snapped and thus that the jaw assembly <NUM> has been pulled back sufficiently far.

Subsequently to the fastening stage of operation the tool <NUM> is 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 tool <NUM> the controller <NUM> causes the motor <NUM> to reverse its direction for moving the threaded rod <NUM>, and thus the pull-back hull <NUM>, in the other direction along the second longitudinal axis B-B to the left in <FIG> and <FIG>. When the pull-back hull <NUM> has been moved sufficiently far to the left the spring <NUM> via the separator sleeve <NUM> will urge the front ramped surfaces <NUM> of the jaws <NUM> against the annular ramped surface <NUM> of the nose piece <NUM>. Further movement of the threaded rod <NUM> to the left in <FIG> and <FIG> will increase the pressure of the spring <NUM> against the separator sleeve <NUM> and thus cause the front ramped surfaces <NUM> of the jaws <NUM> to ride along the annular ramped surface <NUM> of the nose piece <NUM> while the ramped rear surfaces <NUM> of the jaws <NUM> ride along the ramped front surface <NUM> of the separator sleeve <NUM>. This causes the jaws <NUM> to move radially outwards and release the grip on the snapped mandrel, whereby with reference to <FIG> the released snapped mandrel can be caused to fall under gravity along an internal path <NUM> in the direction of a collection chamber <NUM>. For example, after a rivet setting operation, when the jaw assembly <NUM> has been returned to the home position, the user tilts the tool <NUM> such that the snapped mandrel moves into the collection chamber <NUM>. The internal path <NUM> is defined by aligned openings extending through components between the jaws <NUM> and the collection chamber <NUM>, including a first channel <NUM> extending through the threaded rod <NUM> along the second longitudinal axis B-B and a second channel <NUM> through a guidance sleeve <NUM>.

Designers are free to select a suitable way for the controller <NUM> to control operation of the motor <NUM> in use to implement a reset operation. In other words designers are free to select a suitable way for the controller <NUM> to determine when the jaw assembly <NUM> has returned to the home position at which point in time reverse movement of the jaw assembly <NUM> is ceased. For example a mechanical switch may be provided within the tool <NUM> and in response to the controller <NUM> determining that the trigger <NUM> has been released by a user the controller <NUM> causes the pull-back hull <NUM> (and thus the jaw assembly <NUM>) to be moved in the reverse direction until a feature of the pull-back hull <NUM> actuates the mechanical swich thereby generating output indicative that the jaw assembly <NUM> has returned to the home position. Alternatively an optical sensor may be provided within the tool <NUM> which generates output based on the presence or absence of a feature on the pull-back hull <NUM> wherein based on output from the optical sensor the controller <NUM> can determine that the pull-back hull <NUM> (and thus the jaw assembly <NUM>) has reached the home position. Alternatively a magnet is provided on the pull-back hull <NUM> and a Hall sensor is provided in a fixed location within the tool, wherein such features can be arranged such that upon the Hall sensor generating a suitable output based on interacting with the magnet on the pull-back hull <NUM> the controller <NUM> can determine that the pull-back hull <NUM> (and thus the jaw assembly <NUM>) has reached the home position.

Turning to <FIG> the jaw assembly <NUM> will now be discussed in more detail. <FIG> shows a perspective view of the jaw assembly <NUM> in a first configuration in which the jaws <NUM> are located radially as close to each other as possible. <FIG> shows a perspective view of the jaw assembly <NUM> in a second configuration in which the jaws <NUM> are urged radially apart from each other such as by a mandrel of a blind rivet being inserted through the space between the jaws <NUM> or the jaws <NUM> being forced against the annular ramped surface <NUM> of the nose piece <NUM>. The jaw assembly <NUM> comprises three identical jaws <NUM> circumferentially arranged about a jaw assembly axis G-G. When the jaw assembly <NUM> is mounted in the tool <NUM>, the jaw assembly axis G-G is coaxial with the second longitudinal axis B-B of the tool <NUM>. The three jaws <NUM> can move radially with respect to the jaw assembly axis G-G.

There are situations during which the jaw assembly <NUM> is removed from the tool, in particular during routine maintenance of the tool <NUM> during which it is disassembled and then reassembled after being cleaned. Alternatively the jaw assembly <NUM> may be swapped with a new jaw assembly because the jaws <NUM> of the original jaw assembly have worn. Further alternatively the jaw assembly <NUM> may be swapped with a new jaw assembly because the different jaw assemblies are configured for use with different sized mandrels. Referring again to <FIG> the jaw assembly has a flexible o-ring <NUM> for holding the jaws <NUM> of the jaw assembly <NUM> together when it is not located within the tool <NUM>. Each of the jaws <NUM> defines part of an annual groove <NUM> when the jaws <NUM> are in the configuration shown in <FIG> wherein the o-ring <NUM> is located in the annular groove <NUM> and biases the jaws <NUM> together. The o-ring <NUM> can be made from an elastic material such as rubber.

In view of the foregoing it will be appreciated that by locating the motor <NUM>, the transmission <NUM> and the battery <NUM> on the same axis A-A extending along the length of the handle <NUM> improves weight distribution of internal features of the tool <NUM>. Also by providing the motor <NUM> within the handle <NUM> leaves more space available within the tool housing above the handle, whereby there is more freedom to position features of the tool in positions which improve weight distribution of internal features of the tool.

By providing the motor <NUM> only partially within the handle <NUM> achieves the abovementioned advantages to a lesser extent. By providing the motor <NUM> and also at least part of the transmission <NUM> within the handle <NUM> achieves the abovementioned advantages to a greater extent.

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 scope of the appended claims.

In some embodiments the motor <NUM> is only partially received within the handle <NUM>.

In some embodiments at least one planetary gear stage of the transmission <NUM> is received in the handle <NUM>.

In some embodiments the motor <NUM> and the transmission <NUM> are received in the handle <NUM>.

In some examples the battery <NUM> is removable from the tool <NUM> or alternatively the battery <NUM> is integral to the tool <NUM>. Alternatively or additionally the tool <NUM> may comprise other power sources e.g. it may be configured to receive power from a mains power supply.

As shown in <FIG>, the driving sleeve <NUM> and input sleeve <NUM> are fixed to each other due to a friction fit arrangement. Alternatively the driving sleeve <NUM> and input sleeve <NUM> can be fixed via an interlocking arrangement such as a spline fit arrangement or other male and female interlocking-type arrangement.

As shown in <FIG>, the o-ring <NUM> is seated in a groove <NUM>. In some alternative examples the o-ring <NUM> may be replaced with any suitable means to keep the jaws <NUM> together such as a c-clip, a circlip, an e clip, a snap ring, or another spring fastener.

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

As shown in <FIG> the jaw assembly <NUM> comprises three jaws <NUM>. However, in alternative examples, the jaw assembly <NUM> can comprise any number of jaws <NUM> more than two.

In some examples the jaws <NUM> do not interlock with each other for maintaining jaw alignment.

In some embodiments the tool <NUM> can be configured to detect the occurrence of a mandrel snapping by monitoring motor speed. During a pull back stage of operation as the jaw assembly <NUM> pulls the mandrel of a rivet more tightly the speed of the motor <NUM> will decrease and then suddenly increase when the mandrel snaps. The controller <NUM> can 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 in response cease retracting the jaw assembly <NUM>. Subsequently the controller <NUM> initiates the reset stage of operation either automatically or in response to release of the trigger <NUM>.

The motor <NUM> has been described as being a brushless motor and the controller <NUM> cooperates with the brushless motor (in particular with its control electronics) in order to control the brushless motor. In other embodiments however the motor <NUM> may be a brushed motor having a motor output shaft driven by a stator and having at least one magnet on the motor output shaft. It is here mentioned that in battery operated embodiments the motor <NUM> is configured to operate using DC current, whereas in mains operated embodiments the motor is configured to operate using AC current.

In some embodiments the tool <NUM> may have a roller screw mechanism instead of a ball screw arrangement <NUM> for transferring rotational motion into linear motion. A person skilled in the art will appreciate that this can be achieved by rotationally fixing the driving sleeve <NUM> to an input sleeve of the roller screw mechanism; wherein a set of rollers are provided between the internal surface of the input sleeve and an external surface of the threaded rod <NUM>. When the driving sleeve <NUM> is caused to rotate it drives rotation of the input sleeve of the roller screw mechanism and thus via the rollers causes linear movement of the threaded rod <NUM> and thus the jaw assembly.

Claim 1:
A power tool comprising:
a motor at least partially located within the handle of the tool and having a motor output shaft extending along a first axis extending along the length of the handle; and
a fastener gripping portion operatively coupled to the motor via a transmission which in use causes movement of the fastener gripping portion along a second axis, perpendicular to the first axis, between a home position and a retracted position to set a fastener engaged by the fastener gripping portion;
characterized in that
the transmission comprises a bevel gear arrangement for redirecting torque flowing along the first axis in use which is input to the bevel gear arrangement so that torque output from the bevel gear arrangement flows along the second axis and wherein the transmission further comprises a mechanism for converting torque output from the bevel gear arrangement in use into a linear force for causing linear movement of the fastener gripping portion.