Patent Description:
Hair cutting appliances, such a manual or electric razors typically have a blade head mounted to a handle, and the blade head may be pivotably attached to the handle to rotate relative to the body about an axis, such as <CIT>. However, such pivoting movement may have a hard stop providing a sudden limit to the pivoting movement of the head, which is unpleasant for the user and can result in poor cutting performance on complex geometries such as faces.

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, wherein the head is mounted to the base via a pair of arms to form a linkage, each arm being coupled at a joint to a head coupling on the head, and coupled at a joint to a respective base coupling on the base, the base couplings spaced apart along a movement line, and each joint configured to permit pivoting movement about parallel pivot axes; a stroke limiter configured to obstruct pivoting movement of the head relative to the base beyond a limit; wherein at least one of the base couplings is a flexible base coupling which is elastically mounted to a body of the base such that the respective flexible base coupling is moveable relative to the body in a direction having a component which is parallel to the movement line and away from the other base coupling, to permit pivoting movement of the head relative to the base beyond the limit imposed by the stroke limiter.

The pivoting movement of the head relative to the base may include the head pivoting about a virtual axis, which is parallel to the pivot axes.

Each arm may be coupled to a different respective head coupling to permit pivoting movement about different parallel pivot axes thereby forming a four-bar linkage, such that the head is pivotably moveable relative to the base. The stroke limiter may be configured to obstruct pivoting movement of the four-bar linkage to thereby inhibit pivoting movement of the head relative to the base beyond the limit.

The stroke limiter may comprise a tab protruding from the head, the tab being arranged to engage with at least one of the arms to obstruct movement of the four-bar linkage within the movement plane.

The mounting assembly may comprise a primary spring which is configured to engage with the arms to bias the four-bar linkage to the limit.

Both base couplings on the handle may be flexible base couplings.

Each flexible base coupling may be mounted to the body of the base on a cantilevered elastic beam which permits movement of the base coupling relative to the body in the direction having a component which is parallel to the movement line and away from the other base coupling.

The body may comprise a stop for each flexible base coupling, wherein the stop may be configured to abut the elastic beam to limit movement of the elastic beam in a direction towards the other base coupling.

The base may further comprise a pretension spring which is configured to bias the elastic beam for each flexible base coupling towards the stop.

The pretension spring may be configured to bias the flexible base coupling to abut the stop.

The stiffness of the pretension spring may be higher than the stiffness of the elastic beam in the movement plane.

Each base coupling may be a ball bearing configured to cooperate with a corresponding ball socket on the respective arm.

The base couplings may be spaced apart and aligned within the movement plane.

Each flexible base coupling may be moveable relative to the body such that the base couplings move only within a single plane. In other words, the elastic beam on which the flexible base coupling is mounted may not permit movement in a direction parallel to the pivot axes.

According to a second aspect, there is provided a hair cutting appliance comprising a mounting assembly according to the first aspect.

<FIG> shows a cross-sectional view of an example mounting assembly <NUM> for a hair cutting appliance, in a first position. <FIG> shows an exploded isometric view of the same mounting assembly <NUM>.

The mounting assembly <NUM> comprises a head <NUM> which is configured to receive a cutting unit, such as a blade or electric trimming attachment, and a base <NUM> for connection to a handle configured to be held by a user. In some examples, the base may be integral with a handle.

The head <NUM> is mounted to the base <NUM> via a pair of arms <NUM>. Each arm <NUM> is connected at a joint <NUM> to respective head couplings <NUM> and connected at a joint <NUM> to respective base couplings <NUM>.

In this example, the arms <NUM> each comprise two diverging strands in a U-shape such that each arm <NUM> is connected to the base <NUM> at a single base coupling <NUM> at the apex of the U-shape, and such that each arm <NUM> is connected at the two ends of the U-shape to a respective head coupling <NUM>. Therefore, there are two base couplings <NUM> on the base <NUM>, and there are four head couplings <NUM> on the head <NUM>. The head <NUM> is supported relative to the base <NUM> by the four head couplings <NUM> which connect to the arms <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 head couplings in total, or the arms may comprise more than two diverging strands so that the coupler link is supported by the arms at more than two coupler joins per arm. Each arm may have a different number of diverging strands to support the coupler link at, for example <NUM> or <NUM> coupler joins. 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 coupler link at two coupler joins.

Each joint <NUM> is configured to permit pivoting movement between the respective arms <NUM>, head <NUM> and base <NUM>, about parallel primary pivot axes <NUM> (shown as going into the page on <FIG>) to form a four-bar linkage in which each arm <NUM> is one bar, the head <NUM> is one bar and the base <NUM> is one bar of the four-bar linkage. The four-bar linkage is therefore permitted to move within a movement plane which is perpendicular to the primary pivot axes <NUM>.

In this example, the two head couplings <NUM> connecting the same arm <NUM> to the head <NUM> are spaced apart only in a direction parallel to the primary pivot axes <NUM> such that they share a primary pivot axis <NUM> (i.e. their pivot axes are collinear). The head couplings <NUM> connecting different arms <NUM> to the head <NUM> are spaced apart within the movement plane (i.e. perpendicular to the primary pivot axes <NUM>), such that the joint <NUM> at head couplings <NUM> for different arms <NUM> each permit pivoting movement about different parallel primary pivot axes <NUM>. The base couplings <NUM> are also spaced apart within the movement plane along a movement line, which in this example is the secondary pivot axis <NUM>. The four-bar linkage therefore permits pivoting movement of the head <NUM> relative to the base <NUM> about a virtual pivot axis, where the virtual pivot axis is parallel to the primary pivot axes <NUM> of the joints <NUM>.

In other examples, the pivot axes of all of the joints at the head couplings are collinear, so that the head no longer forms a bar of the linkage, and such that the arms, head and base form a three-bar linkage. In such examples, the head is pivotable about the primary pivot axis which passes through the head couplings.

Each of the head couplings <NUM> in this example are linear bearings, and so only permit pivoting movement about the parallel primary pivot axes <NUM> within the movement plane. Each of the base couplings <NUM> in this example are ball bearings which are configured to cooperate with a corresponding ball socket <NUM> on the respective arms <NUM> to form a ball joint (best shown in <FIG>). The ball joints permit pivoting movement about three perpendicular pivot axes. However, due to the four-bar linkage, the ball joints (i.e. the joints <NUM> at the base couplings <NUM> in this example), are constrained to permit pivoting movement about only their respective primary pivot axes <NUM>, and a secondary pivot axis <NUM> within the movement plane, which passes through both base couplings <NUM>. The secondary pivot axis <NUM> permits movement of the whole four-bar linkage in unison such that the primary pivot axes <NUM> also pivot about the secondary pivot axis <NUM>, thereby also pivoting the movement plane about the secondary pivot axis <NUM>.

In some examples, the ball bearings may be linear bearings such that there is no pivoting movement about a secondary pivot axis. It will be appreciated that in other examples, the ball bearing may be disposed on the head and the linear bearings may be disposed on the base.

The mounting assembly <NUM> comprises a stroke limiter <NUM> which is configured to obstruct pivoting movement of the head relative to the base beyond a limit. In this example, the stroke limiter <NUM> is configured to obstruct pivoting movement of the four-bar linkage to inhibit pivoting movement of the head <NUM>. In other examples, when the linkage is a three-bar linkage, the stroke limiter may merely limit pivoting movement of the head about the primary pivot axis passing through the head coupling.

The stroke limiter <NUM> in this example comprises a tab protruding from the head <NUM> in a direction towards the base <NUM>, such that the tab is disposed between the pair of arms <NUM>. The tab is arranged to engage with each of the arms <NUM> at a respective limit to obstruct movement of the four-bar linkage within the movement plane. <FIG> shows the tab engaged with one of the arms <NUM> at a limit. The four-bar linkage is therefore constrained to move within the movement plane between limits imposed by the stroke limiter <NUM> engaging with each arm <NUM>.

It will be appreciated that the tab may be disposed on the head outside the arms and may be configured to engage the outside of one of the arms to obstruct movement of the four-bar linkage beyond a limit. In other examples, the tab may be disposed on one of the arms or on the base and may be configured to engage with the head or the base to obstruct pivoting movement of the four-bar linkage or pivoting movement of the head. The stroke limiter may only obstruct pivoting movement of the head in one direction, or may obstruct pivoting movement of the head in both pivoting directions.

The mounting assembly <NUM> further comprises a pair of primary springs <NUM> in this example which are attached to the base <NUM> and are each configured to engage with one of the arms <NUM> to bias the four-bar linkage to one of the limits (i.e. to the first position shown in <FIG>). In this example, each primary spring <NUM> comprises a leaf spring which abuts an inner protrusion <NUM> on one of the arms <NUM> to push the protrusion <NUM> upwards. Both protrusions <NUM> are on the same arm <NUM> and therefore the primary springs <NUM> both act in unison to pivot the arm <NUM> until the stroke limiter <NUM> obstructs further pivoting movement at a limit in the first position, in this example, by engaging the same arm <NUM>.

The primary springs <NUM> are spaced apart along a direction parallel to the primary pivoting axis <NUM> (i.e. they are disposed on either side of the movement plane). It will be appreciated that only one primary spring is necessary to provide the biasing force to bias the head to the first position shown in <FIG>, and that there may be no primary springs to bias the head to the first position. It will also be appreciated that the primary springs may be disposed elsewhere, such as on the arms or the head, to bias the four-bar linkage to the limit.

In this example, the base couplings <NUM> are flexible base couplings <NUM> which are mounted to the body <NUM> of the base <NUM> on a cantilevered elastic beam <NUM> and moveable to a second position.

<FIG> shows the mounting assembly <NUM> of <FIG> in the second position. The elastic beam <NUM> is attached at one end to the body <NUM>, and the base coupling <NUM> (i.e. the ball bearing) is mounted to the other end of the elastic beam <NUM> to form the flexible base coupling <NUM>. The elastic beam <NUM> therefore permits movement of the flexible base coupling <NUM> relative to the base body <NUM> in a direction having a component which is parallel to the movement line (i.e. the secondary pivot axis <NUM> in this example), to the second position, on application of an external force. In the second position, the primary pivot axis <NUM> of the joint <NUM> has moved with the flexible base coupling <NUM>. It will be appreciated that in some examples, there may be only one flexible base coupling.

In this example, the elastic beam <NUM> permits movement only in a single plane. In other words, the stiffness of the elastic beam <NUM> prevents movement of the flexible base coupling <NUM> in a direction out of the single plane. In some examples, the elastic mounting of the base coupling to the base may permit movement of the flexible base only within the movement plane, such as movement along the secondary pivot axis, for example, if the elastic mounting is in the form of a simple linear spring, such as a coil spring.

When the head <NUM> is biased to a limit by the primary spring <NUM> or moved to a limit by an external force, the stroke limiter <NUM> obstructs movement of the head <NUM> relative to the base <NUM> beyond the limit (as shown in <FIG>). If further external force is applied, one of the flexible base couplings <NUM> is forced to move within the single plane from the first position, towards the second position in a direction having a component which is parallel to the movement line, which is away from the other base coupling <NUM>. This makes the bar of the four-bar linkage defined by the base <NUM> longer, thereby changing the layout of the four-bar linkage and permitting pivoting movement of the head <NUM> relative to the base <NUM> beyond the limit imposed by the stroke limiter <NUM>. Having this arrangement provides a soft stop to the pivoting movement of the head <NUM> relative to the base <NUM> when an external force is applied to the head <NUM>, such as when the head <NUM> is applied to skin for shaving. Further, having an arrangement in which both base couplings <NUM> are flexible base couplings <NUM> can act as a suspension unit, when excessive force is applied to the head <NUM> in the direction of the base <NUM>, the flexible base couplings <NUM> can both move to provide some suspension. This can improve user comfort.

Referring back to <FIG>, in this example, the body <NUM> of the base <NUM> comprises a stop <NUM> for each flexible base coupling <NUM>. Therefore, the base <NUM> comprises two stops <NUM>, which are on opposing sides of the body <NUM>. Each stop <NUM> is configured to abut the elastic beam <NUM> on which the respective base coupling <NUM> is mounted (or obstruct any other flexible mounting) to limit movement of the elastic beam <NUM> in a direction towards the other base coupling <NUM>.

In this example, the base <NUM> further comprises a pretension spring <NUM> which is configured to bias the elastic beam <NUM>, and thereby the flexible base coupling <NUM>, towards the stop <NUM>, to abut the stop <NUM>. In this example, the pretension spring is in the form of a clip which is disposed around the stops <NUM>, and acts on both stops <NUM> from opposing sides. In other examples, each stop may have its own pretension spring which limits movement of the flexible mounting.

In this example, the pretension spring <NUM> has a higher stiffness than the elastic beam <NUM> in the single plane in which the flexible base couplings <NUM> are configured to move, such that it provides a smooth transition of movement for the head <NUM> beyond the limit imposed by the stroke limiter <NUM>.

It will be appreciated that in some examples, the base coupling may be mounted on a beam which is pivotably mounted to the body of the base, and the pretension spring may provide the elastic movement of the base coupling.

Claim 1:
A mounting assembly (<NUM>) for a hair cutting appliance, the mounting assembly (<NUM>) comprising:
a head (<NUM>) configured to receive a cutting unit;
a base (<NUM>), wherein the head (<NUM>) is mounted to the base (<NUM>) via a pair of arms (<NUM>) to form a linkage, each arm (<NUM>) being coupled at a joint (<NUM>) to a head (<NUM>) coupling on the head (<NUM>), and coupled at a joint (<NUM>) to a respective base coupling (<NUM>) on the base (<NUM>), the base couplings (<NUM>) spaced apart along a movement line, and each joint (<NUM>) configured to permit pivoting movement about parallel pivot axes;
a stroke limiter (<NUM>) configured to obstruct pivoting movement of the head (<NUM>) relative to the base (<NUM>) beyond a limit;
characterised in that
at least one of the base couplings (<NUM>) is a flexible base coupling (<NUM>) which is elastically mounted to a body (<NUM>) of the base (<NUM>) such that the respective flexible base coupling (<NUM>) is moveable relative to the body (<NUM>) in a direction having a component which is parallel to the movement line and away from the other base coupling (<NUM>), to permit pivoting movement of the head (<NUM>) relative to the base (<NUM>) beyond the limit imposed by the stroke limiter (<NUM>).