Patent Description:
Hair cutting appliances such as beard trimmers and shavers typically have a contour following function which enables the blade to follow the contours of an object such as a face. However, these hair cutting appliances often also require a function which allows a particularly close shave, which appears to be best achieved when the blade it at an angle of approximately <NUM>-<NUM> degrees to the surface of the skin, particularly when hairs grow in random direction, which has been experimentally derived. Therefore, having the contour following for some applications can reduce the efficacy of the trimmer for close shaving.

<CIT> discloses an electric shaver including a gripper portion to be held by the user's hand and a head portion configured to hold a shaving-blade unit and supported to be swingable in predetermined directions with respect to the gripper portion. The head portion is provided with an edge-trimmer-blade unit configured to be switched between a ready-for-use state and a stored state by an operation element and an engaging portion for fixing the head portion, the engaging portion configured to be engaged with the operation element when the edge-trimmer-blade unit is switched to the ready.

According to a first specific aspect, there is provided a mounting assembly for a hair cutting appliance, the mounting assembly comprising: a head configured to receive a cutting unit; a base coupled to the head; a pivoting mechanism coupling the base to the head, wherein the pivoting mechanism is configured to permit pivoting movement of the head relative to the base about a head pivot axis; and a rotatable locking element configured to be rotated between: (i) an engaged position, in which the locking element obstructs pivoting movement of the head to thereby lock the head in a locked position about the head pivot axis, and (ii) a disengaged position in which the locking element does not obstruct pivoting movement of the head such that the head is freely pivotable relative to the base about the head pivot axis; wherein the locking element is configured such that rotating the locking element to the engaged position drives the head into the locked position.

The locking element may be configured to rotate about a locking axis, the locking axis being perpendicular to the head pivot axis.

The mounting assembly may comprise a paddle fixed to the head and extending from the head towards the base. The locking element may be configured to interact with the paddle to lock the head in the locked position, when in the engaged position. The paddle may be configured to extend between arms of the pivoting mechanism disposed between the bar and the head, and to engage with each arm at a respective limit to obstruct pivoting movement of the head beyond the limit.

The locking element may comprise a locking tab, wherein the locking tab is configured to obstruct pivoting movement of the head when the locking element is in the engaged position. The locking element may comprise two locking tabs which are configured to obstruct pivoting movement of the head in opposing directions when the locking element is in the engaged position, to thereby lock the head in the locked position.

The locking tabs may be disposed on opposing sides of a locking element and may obstruct pivoting movement for example by engaging the head, a paddle fixed to the head, or the pivoting mechanism. The two locking tabs may each engage different parts of the mounting assembly to provide opposing moments to the head or the pivoting mechanism to thereby lock the head in the locked position. The tabs may be disposed <NUM> degrees apart on a base of the locking element. During rotation of the locking element, the tabs may therefore approach and engage with different parts of the mounting assembly to provide opposing moments.

The mounting assembly may comprise two paddles spaced apart in a direction parallel to the head pivot axis. Each locking element may be configured to interact with a respective paddle to provide opposing pivoting moments to the head about the head pivot axis.

The locking element comprises a third locking tab and optionally a fourth locking tab such that rotating the locking element in opposite directions can lock the head in two different locked positions.

The locking tabs may have a stiffness defined by an increase in moment on the pivoting mechanism for every degree of rotation when in the locked position. The stiffness may be more than approximately <NUM>. 5Nmm/degree. The stiffness may be between approximately <NUM>. 5Nmm/degree and <NUM>. 5Nmm/degree.

The pivoting mechanism may comprise a four-bar linkage including a pair of arms extending between the head and the base and coupled to the head and the base at respective head joints and base joints, which each permit pivoting movement about respective parallel pivot axes, wherein the head is one bar, the base is one bar and each arm is one bar of the four-bar linkage. The locking element may be configured to interact with the pivoting mechanism in the engaged position to lock the head in the locked position.

The pivoting mechanism may comprise two four-bar linkages which are spaced apart in a direction parallel to the head pivot axis, wherein the head is one bar, and the base is one bar, of both four-bar linkages. There may be two arms extending between the head and the base for each four-bar linkage such that there are a total of four arms, or there may be two arms where each arm may comprise two diverging strands, with each diverging strand forming one bar of a different four-bar linkage.

Each paddle may be configured to extend from the head to the base between the arms at different four-bar linkages.

According to a second aspect, there is provided a hair cutting appliance comprising a mounting assembly according to any preceding claim.

<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 head pivot axis <NUM> of the cutting unit <NUM> relative to the handle <NUM>. In some examples, the mounting assembly may further enable pivoting movement about a secondary axis, perpendicular to the head pivot axis, such that the cutting unit is pivotable about two perpendicular axes with respect to the handle.

<FIG> shows the mounting assembly <NUM> in more detail, <FIG> shows an exploded view of the mounting assembly <NUM> and <FIG> shows a cross sectional view through line A-A of the mounting assembly <NUM>. Each of these figures omits driving parts for driving a cutting unit which may be attached to the mounting assembly, however, it will be appreciated that the mounting assembly may further comprise such driving parts to reciprocally drive a cutting unit.

The mounting assembly <NUM> comprises a base <NUM> and a head <NUM> (only the head <NUM> is shown in <FIG>). The base <NUM> is configured to be fixed to the handle <NUM>. The head <NUM> is configured to receive the cutting unit <NUM>. The base <NUM> is coupled to the head <NUM> such that the head <NUM> is pivotably moveable relative to the base <NUM>. In some examples, the base may be integral with a handle.

The mounting assembly <NUM> comprises a pivoting mechanism <NUM> coupling the base <NUM> to the head <NUM> and configured to permit pivoting movement of the head <NUM> relative to the base <NUM> about the head pivot axis <NUM>. In this example, the pivoting mechanism <NUM> comprises two four-bar linkages, the four-bar linkages spaced apart in a direction parallel to the head pivot axis <NUM>, and each four-bar linkage including a pair of arms <NUM> extending between the head <NUM> and the base <NUM>. Each arm <NUM> is coupled to the head <NUM> at respective a head joint <NUM>, and coupled to the base at a respective base joint <NUM>, such that the head <NUM> is one bar and the base <NUM> is one bar of both four-bar linkages, and each arm <NUM> is one-bar of a respective one of the four-bar linkages. Therefore, there are a total of four arms <NUM> in this example.

The head joints <NUM>, four in total in this example, permit pivoting movement between the respective arm <NUM> and the head <NUM> which they couple together about respective pivot axes which are parallel to the head pivot axis <NUM>. The base joints <NUM> permit pivoting movement between the respective arm <NUM> and the base <NUM> which they couple together about respective pivot axes which are also parallel to the head pivot axis <NUM>. The pivot axes of the head joints <NUM> are therefore parallel to the pivot axes of the base joints <NUM> to enable both four-bar linkages to move in unison with one another. The two four-bar linkages have the same dimensions, the head joints <NUM> of one four-bar linkage share the same pivot axes as the head joints <NUM> of the other four-bar linkage, and the base joints <NUM> of one four-bar linkage share the same pivot axes as the base joints <NUM> for the other four-bar linkage.

The pivoting mechanism <NUM> comprising a four-bar linkage ensures that the head pivot axis <NUM>, about which the head <NUM> is pivotably moveable, is a virtual pivot axis which is located just above the head <NUM> on an opposing side of the head to the base <NUM>. Having the head pivot axis <NUM> as a virtual pivot axis just above the head <NUM> enables better conformance of the head to the object to the which the hair cutting appliance <NUM> having this mounting assembly <NUM> is applied.

In other examples, the pivoting mechanism may comprise only a single four-bar linkage or the two four-bar linkages may have arms which comprise two diverging strands, with each diverging strand of a single arm forming one bar of different four-bar linkages. In yet further examples, the pivoting mechanism may comprise any suitable mechanism which permits pivoting movement of the head relative to the base about a head pivot axis, such as the head being coupling to the base by a simple pivot.

In this example, the mounting assembly <NUM> comprises a pair of paddles <NUM> fixed to the head <NUM> and extending from the head <NUM> towards the base <NUM>. The paddles <NUM> are spaced apart along a direction parallel to the head pivot axis <NUM>, and each paddle <NUM> extends between the arms <NUM> at different four-bar linkages. Therefore, each paddle <NUM> acts as a stroke limiter for each four-bar linkage, obstructing pivoting movement of the four-bar linkage beyond a limit on both pivoting directions. In other examples, the paddles may not extend between the four-bar linkages, or there may be only a single paddle, or no paddles.

The mounting assembly <NUM> further comprises a rotatable locking element <NUM> which is configured to selectively lock the head <NUM> in a locked position by selectively preventing pivoting movement of the head <NUM> relative to the base <NUM>. The locking element <NUM> is fixed to the base <NUM>, and in this example is rotatable about a rotation axis <NUM> which is perpendicular to the head pivot axis <NUM>. In other examples the rotation axis may be any suitable axis, such as parallel to the head pivot axis.

In this example, the locking element <NUM> comprises a pair of locking tabs <NUM> protruding from a support <NUM> having a hollow, shallow, cylindrical profile, and disposed on opposing sides of the support <NUM>, about the rotation axis <NUM>. The locking tabs protrude from the support <NUM> in a direction towards the head <NUM>. In this example, the locking tabs <NUM> are disposed <NUM> degrees apart around the rotation axis <NUM> on the support <NUM> of the locking element <NUM>. In other examples, the locking tabs may protrude in any suitable direction and may be disposed in any suitable locations around the support.

The locking element <NUM> is configured to sit around a central column <NUM> projecting from the base <NUM> towards the head <NUM>, and to rotate relative to the central column <NUM>. The locking element <NUM> is configured to rotate between an engaged position (shown in <FIG>) and a disengaged position (not shown). The central column may include a central aperture for receiving parts of a driving unit for reciprocally driving a cutting unit on the mounting assembly. In other examples, a driving unit may be placed in any suitable location.

In this example, in the engaged position, the locking tabs <NUM> of the locking element <NUM> are configured to interact with the paddles <NUM> fixed to the head <NUM> to obstruct pivoting movement of the head <NUM> to lock the head <NUM> into the locked position. Being able to lock the head <NUM> in a locked position may be advantageous, if for example, a user would like to be able to use the hair trimmer at a predefined angle without movement of the trimmer, or for travel.

When the locking element <NUM> is rotated between the engaged and the disengaged position, the locking tabs <NUM> on opposing sides of the locking element each approach, and engage with, different paddles <NUM> such that each locking tab <NUM> is configured to provide opposing pivoting moments to the head <NUM> via the paddles <NUM> about the head pivot axis <NUM>, thereby locking the head <NUM> in the locked position.

When the locking element <NUM> is rotated to the disengaged position, the locking tabs <NUM> do not obstruct pivoting movement of the head <NUM> relative to the base <NUM> about the head pivot axis <NUM>, such that the head <NUM> is freely pivotable relative to the base <NUM> about the head pivot axis <NUM>.

The locking element <NUM> is configured to engage with the head <NUM> or the pivoting mechanism during its rotation towards the engaged position, which drives the head <NUM> into the locked position such that the head does not have to be manually positioned in the locked position to be locked there.

The locking element <NUM> is held in the engaged position by interaction of the support <NUM> of the locking element <NUM> with the central column <NUM> (best seen in <FIG>). The support <NUM> comprises a pair of snap tabs <NUM> projecting from an inner surface of the hollow cylindrical shape, which are configured to cooperate with a corresponding respective pair of snap channels <NUM> projecting from an outer surface of the central column <NUM> in a snap fit arrangement. In other examples, there may be a frictional fit which holds the locking element in the engaged position, or any other means of holding the locking element relative to the central column or other part of the base with which the locking element may interact.

The support <NUM> also comprises a block <NUM> projecting from the inner surface of the support <NUM>. The block <NUM> is configured to cooperate with a stop <NUM> on an outer surface of the central column <NUM> to prevent rotation of the locking element <NUM> relative to the central column <NUM> beyond the disengaged position. The outer radius of the central column <NUM> also increases up to the stop <NUM> so that the block <NUM> frictionally cooperates with the central column <NUM> to hold the locking element <NUM> in the disengaged position when the block <NUM> abuts the stop <NUM>.

The locking tabs <NUM> have a stiffness defined by an increase in moment on the head <NUM> for every degree of rotation of the head <NUM> about the head pivot axis <NUM> when the locking tabs <NUM> are in engagement with the paddles <NUM>. The stiffness in this example is approximately <NUM> Nmm/degree to ensure that the locking tabs <NUM> remain securely lock the head <NUM> in the locked position. In other examples, the locking tabs may be more flexible such that they have a stiffness of approximately <NUM> Nmm/degree. This enables the head to move slightly in the locked position, effectively increasing the stiffness of the pivoting mechanism. Having more flexible locking tabs which allow some movement of the head can be beneficial to users with non-sensitive skin as they can apply higher loads to the mounting assembly to achieve an even closer shave.

Although it has been described that the locking element <NUM> comprises two locking tabs <NUM> which interact with respective paddles <NUM> to lock the head <NUM> in the locked position, in some examples, the locking element may comprise only a single locking tab, which may obstruct pivoting movement of the head by engaging with the paddle, the head or the pivoting mechanism, and pushing the head, paddle or pivoting mechanism up to a locked position being the limit where the paddle engages one of the arms of the four-bar linkage. In other examples, the locking element may comprise three or four locking tabs such that the locking element can be rotated in two different directions to two different engaged positions, to provide two different locked positions for the head.

In further examples, if there are no paddles, the locking tabs may be configured to engage with the arms of the four-bar linkage to obstruct pivoting movement of the head to thereby lock the head in the locked position when the locking element is in the engaged position.

In yet further examples, in which there are no locking tabs on the locking element, other parts of the locking element may be configured to obstruct pivoting movement of the head with respect to the base to lock the head in the locked position about the head pivot axis, for example, the locking element may be disposed between two arms of the same four-bar linkage with a rotationally irregular shape about the rotation axis, such as an oval cross sectional shape. When the long dimension of the oval is parallel to the head pivot axis, the locking element may be in a disengaged position so as not to interfere with the pivoting movement of the head, and when the long dimension is rotated towards being perpendicular to the head pivot axis, the locking element may be engaged with the arms of the pivoting mechanism to prevent pivoting movement of the arms relative to the base, and thus prevent pivoting movement of the head about the head pivot axis.

Although it has been described that the locking element has an engaged position and a disengaged position, the locking element may have further intermediate positions between the engaged position and the disengaged position to which the locking element can be rotated and held, for example by a frictional interaction between the central column and the support. In the intermediate positions, the locking tabs may permit the head to move freely about the head pivot axis, but may limit pivoting movement of the head to a new limit before the paddles engage with the arms. This may enable a user to select a more limited range of pivoting movement of the head.

Claim 1:
A mounting assembly (<NUM>) for a hair cutting appliance (<NUM>), the mounting assembly (<NUM>) comprising:
a head (<NUM>) configured to receive a cutting unit (<NUM>);
a base (<NUM>) coupled to the head (<NUM>);
a pivoting mechanism (<NUM>) coupling the base (<NUM>) to the head (<NUM>), wherein the pivoting mechanism (<NUM>) is configured to permit pivoting movement of the head (<NUM>) relative to the base (<NUM>) about a head pivot axis (<NUM>); characterised by:
a rotatable locking element (<NUM>) configured to be rotated between:
(i) an engaged position, in which the locking element (<NUM>) obstructs pivoting movement of the head (<NUM>) to thereby lock the head (<NUM>) in a locked position about the head pivot axis (<NUM>), and
(ii) a disengaged position in which the locking element (<NUM>) does not obstruct pivoting movement of the head (<NUM>) such that the head (<NUM>) is freely pivotable relative to the base (<NUM>) about the head pivot axis (<NUM>);
wherein the locking element (<NUM>) is configured such that rotating the locking element (<NUM>) to the engaged position drives the head (<NUM>) into the locked position.