Patent Description:
Hair cutting appliances which have heads which can pivot about an axis relative to handles to follow contours of an object, such as a user's face are known. Some hair cutting appliances have heads which can pivot about two axes relative to a handle, but this presents difficulties in electric hair cutting appliances in transferring the motion from a motor in a handle to a blade in a head which is pivotable about two different axes.

<CIT> discloses to an electric shaver with a first cutter element and a second cutter element which are movable relative to each other in an oscillating manner along a first horizontal cutter oscillation axis. Each cutter unit is mounted in the cartridge pivotably about a second horizontal tilting axis and axially displaceable parallel to a vertical axis. The first horizontal cutter oscillation axis is perpendicular to the vertical axis and perpendicular to the second horizontal tilting axis. It comprises a drive shaft which drives oscillating motion of one of the cutter elements. <CIT> discloses a processing head comprising: a powered blade set; a linkage unit; and a razor blade wherein the razor blade is removably attached to the powered blade set.

According to a first specific aspect, there is provided a mounting assembly for a hair cutting appliance, the mounting assembly comprising: a base and a head, the head comprising a body and a driving bridge and being configured to receive a cutting unit, wherein the driving bridge is configured to couple to the cutting unit and to reciprocally move relative to the body; a pivoting mechanism disposed between the head and the base and configured to permit pivoting movement of the head relative to the base about a primary axis and a secondary axis; and a driving unit comprising a frame and a driving axle, wherein the frame is rotatable relative to the driving axle about an elongate axis of the driving axle, and provides a bearing surface for the driving axle; wherein the frame comprises a body coupling which is configured to couple to the body of the head to permit pivoting movement of the head relative to the frame about a body pivot axis which is parallel to the primary axis, and wherein the driving unit comprises a base coupling which is configured to couple to the base to permit pivoting movement of the frame relative to the base about a base axis which is parallel to the secondary axis; wherein the driving axle comprises: an eccentric driving pin at a distal end of the driving axle, the eccentric driving pin configured to interact with the driving bridge to induce reciprocating movement to the driving bridge relative to the body of the head; and a socket on a proximal end of the axle for engaging with a driving head on a motor axle for rotary transmission.

The primary axis and the secondary axis may be perpendicular.

The frame may comprise the base coupling which is configured to couple to the base to permit pivoting movement of the frame relative to the base about the base axis.

The base axis may be a secondary base axis; and wherein the base coupling may be further configured to couple to the base to permit pivoting movement of the frame relative to the base about a primary base axis which is parallel to the primary axis.

The base coupling may be further configured to translate in a direction away from, or towards, the head.

The frame may comprise a protrusion which acts as the base coupling, and which is configured to cooperate with a channel in the base extending away from the head, to permit pivoting movement of the frame relative to the base about the primary base axis, and to permit translating movement of the protrusion along the slot or channel.

There may be two opposing protrusions which each cooperate with respective opposing channels in the base. The protrusion may be a pin configured to cooperate with a slot in the base.

The base coupling may be configured such that the pin of the base coupling is disposed within the slot, and such that the pin can be translated along the slot to accommodate pivoting movement of the head about the primary axis, and into and out of the slot to permit pivoting movement about the secondary base axis.

The two opposing protrusions may define a surface curved in a plane perpendicular to the primary axis which interfaces with, and bears against, the channel to permit pivoting movement of the base coupling about the primary base axis.

The base coupling may comprise a void between the frame and the base so as not to obstruct pivoting movement about the secondary base axis, thereby permitting pivoting movement about the secondary base axis.

The pivoting mechanism may comprise a four-bar linkage comprising two arms pivotably disposed between the head and the base such that each of the head, the base and each arm is one arm of the four-bar linkage, such that the primary axis is a virtual axis.

The frame may comprise a pair of opposing body couplings which are configured to permit pivoting movement of the frame relative to the head about the body pivot axis which passes through both body couplings.

The body couplings of the frame may each comprise an arm, each arm having a distal pin or a hole, the pin or hole cooperating with a corresponding hole or pin in the body of the head to permit pivoting movement about the body pivot axis through the pins and holes, and wherein the arms are configured such that they are held under pretension to push the respective pins and holes together.

The frame may be suspended from the body of the head at the body couplings.

According to a second aspect, there is provided a hair cutting appliance comprising a mounting assembly according to the first aspect, and a handle fixed to the base of the mounting assembly, the handle comprising a motor to rotate an elongate motor axle, the elongate motor axle comprising a driving head at a distal end which is coupled to the socket of the driving axle of the mounting assembly to form an articulated joint configured to transfer rotary motion from the motor axle to the driving axle, and configured to permit pivoting movement between the motor axle and the driving axle.

<FIG> shows a hair cutting appliance <NUM> comprising a handle <NUM>, a mounting assembly <NUM> fixed to the handle <NUM> and a cutting unit <NUM> received on the mounting assembly <NUM>. The mounting assembly <NUM> is configured to enable pivoting movement about a primary axis <NUM> of the cutting unit <NUM> relative to the handle <NUM>. The mounting assembly <NUM> further enables pivoting movement of the cutting unit <NUM> about a secondary axis <NUM> relative to the handle <NUM>, the secondary axis <NUM> being perpendicular to the primary axis <NUM>, such that the cutting unit <NUM> is pivotable about two perpendicular axes with respect to the handle <NUM>.

In this example, the primary axis <NUM> and the secondary axis <NUM> are skew lines (i.e. they do not intersect one another and are not parallel). In some examples, the primary axis and the secondary axis may be orthogonal (i.e. they may be perpendicular and intersect one another). In other examples, the primary axis and the secondary axis may not be perpendicular, but they are not parallel.

In this example, the handle <NUM> comprises a motor <NUM> to rotate an elongate motor axle <NUM> about an elongate axis of the motor axle <NUM>. The motor axle <NUM> comprises a driving head <NUM> at a distal end thereof which is configured to couple with the mounting assembly <NUM>, to transfer rotary motion from the motor axle <NUM> to a part of the mounting assembly <NUM>.

<FIG> shows a side view of a first example mounting assembly <NUM> in a neutral position and <FIG> shows a cross-sectional view of the first example mounting assembly in the neutral position. <FIG> show the same views as <FIG> respectively, with the mounting assembly <NUM> in a first contour following position, in which the cutting unit <NUM> is pivoted, from the neutral position, relative to the handle <NUM> about the primary axis <NUM>. <FIG> also shows the same views as <FIG> respectively, with the mounting assembly <NUM> in a second contour following position, in which the cutting unit <NUM> is pivoted, from the neutral position, relative to the handle <NUM> about the secondary axis <NUM>.

The mounting assembly <NUM> comprises a base <NUM> which is configured to attach to the handle <NUM>, and a head <NUM> which is configured to receive the cutting unit <NUM> (not shown in <FIG>), such as a blade. The head <NUM> comprises a body <NUM> and a driving bridge <NUM> (shown in <FIG>, <FIG> and <FIG>). The driving bridge <NUM> is configured to move reciprocally, by translation, relative to the body <NUM>, and is configured to couple to the cutting unit <NUM>. When coupled to the driving bridge <NUM>, the cutting unit <NUM> can therefore also move reciprocally relative to the body <NUM> within a plane of the cutting unit <NUM>. The body <NUM> may comprise a counteracting blade such that the cutting unit <NUM> together with the counteracting blade on the body <NUM> can cut hairs.

A pivoting mechanism <NUM> is disposed between the base <NUM> and the head <NUM> and is configured to permit pivoting movement of the head <NUM> relative to the base <NUM> about the primary axis <NUM> and the secondary axis <NUM>.

In this example, the pivoting mechanism comprises a pair of arms <NUM> pivotably disposed between the base <NUM> and the head <NUM>. In other words, each arm <NUM> is pivotably coupled to the base <NUM> at one end and is pivotably coupled to the head <NUM> at another end to form a four-bar linkage in which the head <NUM> forms one bar, the base <NUM> forms one bar and each arm <NUM> forms one bar of the four-bar linkage. The four-bar linkage permits pivoting movement of the head <NUM> about the primary axis <NUM>, which is a virtual axis on an opposing side of the head <NUM> to the arms <NUM>.

In this example, each arm <NUM> comprises two diverging strands 30a, 30b to form a U-shape such that the two ends of each U-shape are connected to the head <NUM>. The head <NUM> is therefore supported by the arms <NUM> at four points in total. The apex of each U-shaped arm is connected to the base <NUM> with a ball and socket joint (not shown) to further permit pivoting movement of the arms <NUM> and the head <NUM> in unison relative to the base about the secondary axis <NUM>. The primary axis <NUM> therefore also moves about the secondary axis <NUM> when the four-bar linkage is pivoted about the secondary axis <NUM>.

In other examples, each arm may comprise a single strand to form an I-shape such that the head is supported by the arms at only two points in total, or the arms may comprise more than two diverging strands so that the head is supported by the arms at more than two points per arm. Each arm may have a different number of diverging strands to support the head at, for example <NUM> or <NUM> points. In yet further examples, the arms may comprise two diverging strands in the form of a T, V or Y shape such that each arm supports the head at two points. The arms may alternatively be inverted so that the ball and socket joint is between the arms and the head.

It will be appreciated that the pivoting mechanism may include any suitable mechanism for permitting pivoting of the head relative to the handle about two different axes. In some examples, instead of a four-bar linkage, the pivoting mechanism may comprise a simple pivot between the head and the base to permit pivoting movement of the head about the primary axis with respect to the base, and a further simple pivot between the head and the base to permit pivoting movement of the head about the secondary axis with resepct to the base. In other examples, the pivoting mechanism may comprise ball and socket joints to simultaneously permit pivoting movement of the head about both the primary axis and the secondary axis.

The mounting assembly <NUM> further comprises a driving unit <NUM> which is configured to drive the reciprocating movement of the driving bridge <NUM>. The driving unit <NUM> comprises a frame <NUM> and a driving axle <NUM>.

The driving axle <NUM> extends along an elongate axis <NUM> and comprises an eccentric driving pin <NUM> at a distal end of the driving axle <NUM>, which is offset from the elongate axis <NUM>. The eccentric driving pin <NUM> is configured to interact with the driving bridge <NUM> to induce reciprocating movement of the driving bridge <NUM> relative to the body <NUM>. In other words, the driving bridge <NUM> comprises a channel in which the eccentric driving pin <NUM> is loosely received so that the driving pin <NUM> can move up and down the channel freely. Rotation of the driving axle <NUM> therefore induces movement of the driving pin <NUM> in circles, which transfers linear motion to the driving bridge <NUM> since the driving pin <NUM> is freely moveable along the channel but pushes the channel back and forth in a direction perpendicular to the extent of the channel.

The driving axle <NUM> also comprises a socket <NUM> at a proximal end for engaging with the driving head <NUM> on the motor axle <NUM> in the handle <NUM> for rotary transmission. Rotary motion of the driving axle <NUM> (about the elongate axis <NUM>), which is transferred from the motor axle <NUM> to the driving axle <NUM>, via the socket <NUM>, is therefore converted into reciprocating linear motion of the driving bridge <NUM> due to the interaction of the eccentric pin <NUM> with the driving bridge <NUM>.

The socket <NUM> is configured to engage with the driving head <NUM> of the motor axle <NUM> such that the motor axle <NUM> and the driving axle <NUM> can pivot up to <NUM> degrees relative to one another whilst still transferring rotary motion from the motor axle to the driving axle <NUM>. Such a coupling is described in patent application publication number <CIT>.

The body <NUM> of the head <NUM> comprises a stroke limiter <NUM> projecting towards the base <NUM> and configured to abut an arm <NUM> of the four-bar linkage when the head <NUM> is pivoted approximately <NUM> degrees about the primary axis <NUM> from the neutral position in either direction, such as shown in <FIG>. This prevents pivoting of the driving axle <NUM> relative to the motor axle <NUM> by more than <NUM> degrees to ensure that they do not decouple. It will be appreciated that in some examples, the stroke limiter may be configured to abut an arm at any suitable angle. In other examples, there may be no stroke limiter or the stroke limiter may be disposed on the base and configured to abut the arms, or may be disposed on the arms and configured to abut the head or the base.

The base <NUM> comprises a pair of stops <NUM>, each projecting towards the head <NUM>. Each stop <NUM> is configured to abut the body <NUM> when the head <NUM> is pivoted approximately <NUM> degrees about the secondary axis <NUM> from the neutral position in both directions, as shown in <FIG>. This also prevents pivoting of the driving axle <NUM> relative to the motor axle <NUM> by more than <NUM> degrees to ensure that they do not decouple. It will be appreciated that, in some examples, each stop may be configured to abut the body at any suitable angle. In other examples, there may be no stops, or the stops may be configured to abut the arms of the four-bar linkage, or may be disposed on the arms or head and configured to abut the base.

A combination of movements about both the primary axis <NUM> and the secondary axis <NUM> can therefore be made without decoupling of the driving axle <NUM> and the motor axle <NUM>, since the movements about both axes are constrained.

The frame <NUM> surrounds at least part of the driving axle <NUM> and is rotatable relative to the driving axle <NUM> about the elongate axis <NUM>. The frame <NUM> provides a bearing surface <NUM> for the driving axle <NUM> to rotate relative to the frame <NUM>.

The frame <NUM> comprises a pair of body couplings <NUM> on opposing sides at a distal end of the frame <NUM>, the body couplings <NUM> being configured to couple with the body <NUM> of the head <NUM> to permit pivoting movement of the head <NUM> relative to the frame <NUM> about a body pivot axis <NUM>, which is parallel to the primary axis <NUM>.

In this example, the body couplings <NUM> each comprise an arm <NUM> extending towards the body <NUM> and comprising a hole, which hole cooperates with a pin in the body <NUM>. In other examples, each arm may comprise a pin which cooperates with a corresponding hole in the body.

The body pivot axis <NUM> passes through both body couplings <NUM> in this example (i.e., through both holes and pins). In other examples, there may be only a single body coupling which pivotably couples the frame to the body of the head. In this example, the arms <NUM> of the frame <NUM> are held under pretension in order to push the pin of the body <NUM> into the hole of the body coupling <NUM>. Such pretension therefore removes the need for other forms of reliably securing the frame and body together, such as screws for example, and removes any play between the body <NUM> and the frame <NUM> which would otherwise lead to a loss of effective stroke of the cutting unit <NUM>. The pretensioned arms therefore improve the ease of assembly.

In this example, the frame <NUM> also comprises a pair of opposing base couplings <NUM> which are configured to couple to the base <NUM> to permit pivoting movement of the frame <NUM> relative to the base about a primary base axis <NUM> which is parallel to the primary axis <NUM>, and a secondary base axis <NUM> which is parallel to the secondary axis <NUM>. In this example, the secondary base axis <NUM> is the same as the secondary axis <NUM>. In other examples, the secondary base axis may not be the same as the secondary axis.

The frame <NUM> comprises a pair of protrusions in the form of pins which act as the base couplings <NUM>. The pins are received within corresponding opposing slots <NUM> in the base <NUM>, which slots <NUM> extend in a direction away from the head <NUM>. The pins are configured to cooperate with the slots <NUM> to permit translation of the pins away from, and towards, the head <NUM>, along the respective slots <NUM>. The pins cooperate with the slots <NUM> further to permit pivoting movement of the frame <NUM> relative to the base <NUM> about the primary base axis <NUM>, which passes through both of the pins. The pins also permit movement about the secondary base axis <NUM> by moving into and out of the slots <NUM> and translating along the slots <NUM>, as shown in <FIG>.

In some examples, there may be only a single base coupling, and the base coupling may permit pivoting movement of the frame relative to the base about only the secondary base axis. For example, in examples whether the movement of the head about the primary axis is facilitated by a simple pivot, there may be no need for the base coupling to permit pivoting movement about a primary base axis, since movement of the head about the primary axis is already accommodated by the body couplings. In some examples, the base coupling(s) may be disposed on another part of the driving unit, such as the driving axle, as shown in <FIG>.

Since the frame <NUM> of the driving unit <NUM> is coupled to the head <NUM> at the body pivot axis <NUM>, which is not collinear with the primary axis <NUM> about which the head <NUM> pivots relative to the body <NUM>, when the head <NUM> pivots about the primary axis <NUM>, the base couplings <NUM> will also move in translation relative to the base <NUM>. The slots <NUM>, which permit translating movement of the pins, therefore accommodate this pivoting movement of the head <NUM> about the primary axis <NUM> relative to the base <NUM> by permitting translating movement of the pins. The frame <NUM> is suspended from the body <NUM> of the head <NUM> at the body couplings <NUM> (i.e., not directly fixed or attached to the base <NUM>) in order to accommodate such movement. In other words, the base couplings <NUM> are not directly fixed to the base <NUM>, rather merely constrained to move along the slots <NUM>, such that the frame <NUM> is only attached to the body <NUM> of the head <NUM>.

Further, the socket <NUM> of the driving axle <NUM> will also translate due to the difference in the body pivot axis <NUM> and the primary axis <NUM> and due to the connection to the frame <NUM>. The socket <NUM> is therefore also configured to accommodate such translating movement relative to the motor axle <NUM> whilst remaining coupled to the motor axle <NUM>, since the motor axle <NUM> would not move relative to the handle <NUM> and would therefore remain stationary relative to the base <NUM>. In other examples, the frame and the driving axle may be configured to translate relative to one another, such that translating movement of the frame relative to the base due to pivoting movement of the head about the primary axis does not mean that the driving axle also moves relative to the base.

Further, the base <NUM> and the slots <NUM> have a depth sufficient to permit the pins to move into and out of the slots <NUM> to permit pivoting movement of the frame about the secondary base axis <NUM>, and thereby to permit pivoting movement of the head <NUM> about the secondary axis <NUM>.

Therefore, in <FIG>, with the mounting assembly <NUM> in the neutral position, the pins of the base couplings <NUM> are disposed centrally in the slots <NUM> such that there is space for each pin to translate towards the head <NUM> and away from the head <NUM> along the slot <NUM>, and there is space for each pin to move into and out of the slot <NUM>.

In <FIG>, the mounting assembly <NUM> is in the first contour following position in which the head <NUM> is pivoted about the primary axis <NUM> from the neutral position, such that the pin is marginally translated along the slot <NUM> to accommodate the pivoting movement of the head about the primary axis <NUM>.

In <FIG>, the mounting assembly <NUM> is in the second contour following position in which the head <NUM> is pivoted about the secondary axis <NUM> from the neutral position. The movement of the head <NUM> about the secondary axis <NUM> causes movement of the frame <NUM> about the secondary base axis <NUM>, such that one pin has moved outward from the respective slot <NUM>, and the other opposing pin has moved further into the respective slot <NUM>. In this example, it can be seen that the elongate extent of the slot <NUM> further enables the pivoting movement of the frame <NUM> about the secondary base axis <NUM>.

Although it has been described that there are slots in the base which receive, and cooperate with, protrusions on the frame, in other examples, the slots may alternatively be channels which do not extend through the thickness of the base.

<FIG> shows a second example mounting assembly <NUM> which is similar to the first example mounting assembly <NUM> in that it comprises a head <NUM>, a base <NUM> and a pivoting mechanism <NUM> in the form of a four-bar linkage having arms <NUM> which are configured to permit pivoting movement of the head <NUM> relative to the base <NUM> about the primary axis <NUM> and the secondary axis <NUM>. This base <NUM> in this example differs from the first example base <NUM> in that it does not comprise slots.

The second example mounting assembly <NUM> comprises a driving unit <NUM> which is similar to the driving unit <NUM> of the first example mounting assembly <NUM>. Specifically, the driving unit <NUM> of this example comprises a frame <NUM> and a driving axle <NUM>, where the frame <NUM> is rotatable relative to the driving axle <NUM>, and which provides a bearing surface <NUM> for the driving axle <NUM>. The frame <NUM> comprises body couplings <NUM> which are similar to the body couplings <NUM> in the first example mounting assembly <NUM>, and which pivotably couple the frame <NUM> to the body <NUM> of the head <NUM>. The frame <NUM> in this example differs from the first example frame <NUM> in that it does not comprise the base couplings.

The driving unit <NUM> of this example differs from the driving unit <NUM> of the first example mounting assembly <NUM> in that the driving axle <NUM> comprises a bearing having a curved outer surface and which has been hollowed out at one end to form the socket <NUM>, similar to the socket <NUM> of the first example mounting assembly <NUM>. The curved outer surface acts as the base coupling <NUM> which is configured to permit pivoting movement of the frame <NUM> relative to the base <NUM> about a primary base axis <NUM> and a secondary base axis <NUM> which, as in the first example mounting assembly <NUM>, are parallel to the primary axis <NUM> and the secondary axis respectively. The base coupling <NUM> in this example therefore essentially forms a ball of a ball and socket joint, where the base <NUM> comprises a hole to receive the base coupling <NUM> and to permit pivoting movement of the driving axle <NUM> about the primary base axis <NUM> and the secondary base axis <NUM>, and therefore of the head <NUM> relative to the base <NUM> about the primary axis <NUM> and the secondary axis <NUM>.

Since there are no protrusions on the curved outer surface of the base coupling <NUM>, the base <NUM> does not have need a channel or slot to receive such a protrusion.

<FIG> shows a third example mounting assembly <NUM> which is similar to the first example mounting assembly <NUM> and the second example mounting assembly <NUM> in that it comprises a head <NUM>, a base <NUM> and a pivoting mechanism <NUM> in the form of a four-bar linkage having arms <NUM> which are configured to permit pivoting movement of the head <NUM> relative to the base <NUM> about the primary axis <NUM> and the secondary axis <NUM>. The base <NUM> in this example differs from the first example base <NUM> in that it comprises channels which extend away from the head <NUM>, rather than through slots <NUM>.

The third example mounting assembly <NUM> comprises a driving unit <NUM>, also shown in <FIG>, which is similar to the driving unit <NUM> of the first example mounting assembly <NUM>. Specifically, the driving unit <NUM> of this example comprises a frame <NUM> and a driving axle <NUM>, where the frame <NUM> is rotatable relative to the driving axle <NUM>, and which provides a bearing surface <NUM> for the driving axle <NUM>. The driving axle <NUM> is similar to the driving axle <NUM> in the first example mounting assembly <NUM>.

The frame <NUM> comprises two arms <NUM> with body couplings <NUM> which are similar to the body couplings <NUM> in the first example mounting assembly <NUM>, and which pivotably couple the frame <NUM> to the body <NUM> of the head <NUM>. The frame <NUM> in this example differs from the frame <NUM> in the first example in that it comprises a base coupling <NUM> having different protrusions to the pins.

The driving unit <NUM> of this example differs from the driving unit <NUM> of the first example mounting assembly <NUM> in that the two opposing protrusions on the frame <NUM> which act as the base couplings <NUM> each define a surface curved in a plane perpendicular to the primary axis <NUM> (e.g., the cross-sectional plane shown in <FIG>). The protrusions interface with, and bear against, the channels in the base <NUM>, thus permitting pivoting movement of the base coupling <NUM> about the primary base axis <NUM>, which is parallel to the primary axis <NUM>, and permitting translating movement of the base coupling <NUM> along the channels.

The base coupling <NUM> comprises a void <NUM> (best shown in <FIG>) between the frame <NUM> and the base <NUM> so as not to obstruct pivoting movement of the frame <NUM> relative to the base <NUM> about the secondary base axis <NUM>, thereby permitting pivoting movement of the frame <NUM> relative to the base <NUM> about the secondary base axis <NUM>.

Each of the examples therefore permits pivoting movement of the head about the primary axis <NUM> and the secondary axis <NUM>, and connects the driving unit <NUM>, <NUM>, <NUM> to the head <NUM> and the base <NUM>, <NUM>, <NUM> to permit pivoting movement about the body pivot axis <NUM>, the primary base axis <NUM>, and the secondary base.

Claim 1:
A mounting assembly (<NUM>) for a hair cutting appliance (<NUM>), the mounting assembly (<NUM>) comprising:
a base (<NUM>, <NUM>, <NUM>) and a head (<NUM>), the head (<NUM>) comprising a body (<NUM>) and a driving bridge (<NUM>) and being configured to receive a cutting unit (<NUM>), wherein the driving bridge (<NUM>) is configured to couple to the cutting unit (<NUM>) and to reciprocally move relative to the body (<NUM>); a pivoting mechanism (<NUM>) disposed between the head (<NUM>) and the base (<NUM>, <NUM>, <NUM>) and configured to permit pivoting movement of the head (<NUM>) relative to the base (<NUM>, <NUM>, <NUM>) about a primary axis (<NUM>) and a secondary axis (<NUM>); and
a driving unit (<NUM>, <NUM>, <NUM>) comprising a frame (<NUM>, <NUM>, <NUM>) and a driving axle (<NUM>, <NUM>), wherein the frame (<NUM>, <NUM>, <NUM>) is rotatable relative to the driving axle (<NUM>, <NUM>) about an elongate axis (<NUM>) of the driving axle (<NUM>, <NUM>), and provides a bearing surface (<NUM>, <NUM>, <NUM>) for the driving axle (<NUM>, <NUM>);
wherein the frame (<NUM>, <NUM>, <NUM>) comprises a body coupling (<NUM>) which is configured to couple to the body (<NUM>) of the head (<NUM>) to permit pivoting movement of the head (<NUM>) relative to the frame (<NUM>, <NUM>, <NUM>) about a body pivot axis (<NUM>) which is parallel to the primary axis (<NUM>), and wherein the driving unit (<NUM>, <NUM>, <NUM>) comprises a base coupling (<NUM>, <NUM>, <NUM>) which is configured to couple to the base (<NUM>, <NUM>, <NUM>) to permit pivoting movement of the frame (<NUM>, <NUM>, <NUM>) relative to the base (<NUM>, <NUM>, <NUM>) about a base axis (<NUM>) which is parallel to the secondary axis (<NUM>);
wherein the driving axle (<NUM>, <NUM>) comprises:
an eccentric driving pin (<NUM>) at a distal end of the driving axle (<NUM>, <NUM>), the eccentric driving pin (<NUM>) configured to interact with the driving bridge (<NUM>) to induce reciprocating movement to the driving bridge (<NUM>) relative to the body (<NUM>) of the head (<NUM>); and
a socket (<NUM>) on a proximal end of the axle for engaging with a driving head (<NUM>) on a motor axle (<NUM>) for rotary transmission.