Patent Description:
It is known for a shroud to cover a cutting disc of a power tool to restrict the path of debris generated in use. Additionally, it is known to remove debris using a vacuum device in communication with a volume within the shroud. The health benefits of efficiently managing removal of debris (particularly dust) will be appreciated by persons skilled in the art, wherein one way of increasing the efficiency of debris removal is to increase vacuum power. Even slight improvements in the efficiency of dust removal are of interest in the field of tools because of the benefits to user health.

<CIT> relates to a portable electric circular saw with chip-breaker ribs arranged in the saw housing, a chip-discharge opening, which is made in the saw housing and into which the chips pass due to the air flow produced by the fan of the drive motor.

<CIT> relates to a severing device such as a hand-held circular saw, abrasive cutting device or the like. Its disc-shaped tool, for example a circular saw blade, can be driven by a drive motor in rotary motion. The part, which in operation is at the time out of engagement with the workpiece to be machined, of the tool is covered at least partially by a protective hood. The device has a fan driven by the drive motor and a facility for removing dust from the interior of the protective hood. The latter contains an inlet orifice introduced into the protective hood and connected to the delivery side of the fan, and a dust outlet orifice. The two orifices are arranged at a mutual distance as viewed in the direction of rotation of the tool. The air jet blown through the inlet orifice into the protective hood covers, until it leaves from the outlet orifice a length of travel essentially in the circumferential direction of the tool, proceeding in an at least approximately tangential direction relative to the outer circumference of the tool.

According to the invention there is provided a power tool according to claim <NUM> wherein optional features thereof are defined in dependent claims <NUM> to <NUM>.

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

<FIG> illustrate a power tool, which in the embodiment described hereafter is a wall chaser <NUM>. <FIG> illustrates the wall chaser <NUM> in a ready-to-use configuration and <FIG> illustrates the wall chaser <NUM> in a cutting-disc-changing configuration.

The wall chaser <NUM> has a rotatable support arrangement <NUM> for supporting a pair of cutting discs <NUM>. The cutting discs <NUM> can be mounted to a shaft <NUM> of the support arrangement <NUM> in a manner familiar to persons skilled in the art. For example, the cutting discs <NUM> can be placed around the shaft <NUM> with a spacer element between them, wherein a nut <NUM> is then threaded onto the shaft <NUM>. The action of threading the nut <NUM> onto the shaft <NUM> causes the first cutting disc to be mounted on the shaft <NUM> to be essentially sandwiched between a supporting flange of the wall chaser <NUM> and a first side of the spacer element, whereas the second cutting disc to be mounted on the shaft <NUM> will be essentially sandwiched between a second side of the spacer element and the nut <NUM>. The cutting discs <NUM> are thus rotationally locked relative to the shaft <NUM> such that upon an electric motor of the wall chaser <NUM> causing the shaft <NUM> to rotate the cutting discs <NUM> will be rotationally driven as well. It will be appreciated that various configurations and combinations of spacer elements can be used depending on the required distance between the cutting discs <NUM>. For example in another usage implementation the spacer element used could be shorter in length thereby providing a smaller distance between the cutting discs <NUM>. Alternatively the spacer element used could be longer in length (or more than one spacer element could be used) thereby providing a greater distance between the cutting discs <NUM>.

An upper shroud member <NUM> and a lower shroud member <NUM> cooperate to define a volume in which the cutting discs <NUM> can be supported. The shaft <NUM> extends from an internal surface of the upper shroud member <NUM> such that movement of the upper shroud member <NUM> towards the lower shroud member <NUM> causes the cutting discs <NUM> to protrude through an opening <NUM> in the lower shroud member <NUM>; this opening <NUM> extending through the base of the wall chaser <NUM> which is engaged with a work surface in use as shown in <FIG>. In this manner the cutting discs <NUM> can be brought into engagement with a work surface e.g. a masonry surface in use.

The upper shroud member <NUM> is pivotally coupled to the lower shroud member <NUM>. Biasing means urges the upper shroud member <NUM> and the lower shroud member <NUM> away from each other. In this embodiment the biasing means is a torsion spring <NUM>. With reference to <FIG> the lower shroud member <NUM> has a pair of flanges <NUM>, <NUM> each having an opening extending therethrough. A bolt member <NUM> extends through these openings, wherein the torsion spring <NUM> wraps around the bolt member <NUM> in the space between the flanges <NUM>, <NUM>. A first arm 26a of the torsion spring <NUM> is for urging against the lower shroud member <NUM> and a second arm 26b of the torsion spring <NUM> is for urging against the upper shroud member <NUM>. The upper shroud member <NUM> is pivotally coupled to the lower shroud member <NUM> so when a user pivots such members towards each other the torsion spring <NUM> is compressed, wherein upon releasing such members the torsion spring <NUM> urges them apart. Looking at <FIG> the feature of the upper shroud member <NUM> which the second arm 26b of the torsion spring <NUM> urges against is the connecting element <NUM>.

Referring back to <FIG>, one hand of a user grips the primary handle <NUM> in use, whereas the other hand grasps secondary handle <NUM>. Pushing downwards on the secondary handle <NUM> in use causes the upper shroud member <NUM> to pivot towards the lower shroud member <NUM> and the cutting discs <NUM> to plunge into the masonry surface to be cut. Various internal features required for the wall chaser <NUM> to function as heretofore described will be apparent to persons skilled in the art, including a battery for powering an electric motor and a power train for transferring torque from the electric motor to the shaft <NUM> for rotating the cutting discs <NUM>. Moreover, a trigger <NUM> is provided on the primary handle <NUM> for enabling a user to selectively cause actuation of the electric motor and thereby rotation of the cutting discs <NUM>.

The upper shroud member <NUM> is formed of two parts, a first shroud part 20a and a second shroud part 20b which are coupled together via a hinge coupling <NUM>. The upper shroud member <NUM> can thus be reconfigured between a closed configuration as in <FIG> and an open configuration as in <FIG>. The first shroud part 20a and the second shroud part 20b are maintained in a closed configuration by a securing mechanism that can be selectively released by a user. In this embodiment the securing mechanism comprises a first latch part 27a on the first shroud part 20a that can be releasably coupled to a second latch part 27b on the second shroud part 20b but other suitable mechanisms will be apparent to persons skilled in the art.

A limiting mechanism is provided for limiting the range of pivotal movement of the upper shroud member <NUM> relative to the lower shroud member <NUM> under action of the torsion spring <NUM> when the upper shroud part <NUM> is in the closed configuration. A first part 34a of the limiting mechanism is carried by the upper shroud member <NUM> and a second part 34b of the limiting mechanism is carried by the lower shroud member <NUM>.

With reference to <FIG> and <FIG> the first part 34a of the limiting mechanism is provided on an internal surface of the upper shroud member <NUM>, in the embodiment shown on the internal surface of the second shroud part 20b. The view in <FIG> includes a cross sectional view of the second shroud part 20b, otherwise the outer surface thereof would obscure the features extending from its internal surface. Protrusions <NUM> extending from the internal surface of the second shroud part 20b cooperate to define a substantially L-shaped channel <NUM>, wherein an opening <NUM> is left in communication with the channel <NUM>. A metallic spring feature <NUM> is received in the channel <NUM> and maintained therein by interference fit with the internal surfaces of the protrusions <NUM>. The metallic spring feature <NUM> extends from the channel <NUM> via the opening <NUM>.

The metallic spring feature <NUM> has a first section <NUM> that extends from the opening <NUM> of the channel <NUM> into contact with a blocking surface <NUM>. In this embodiment the blocking surface <NUM> is defined by a feature <NUM> coupled to the internal surface of the upper shroud member <NUM>, in the embodiment shown on the internal surface of the second shroud part 20b. The metallic spring feature <NUM> also has a second section <NUM> that extends away from the blocking surface <NUM>. The first and second sections <NUM>, <NUM> of the metallic spring feature <NUM> define an acute angle A between them. The purpose of these specific features will become apparent upon reading further.

With continued reference to <FIG> and <FIG> the second part 34b of the limiting mechanism is carried by the lower shroud member <NUM> and comprises a rigid feature integrally formed with the lower shroud member <NUM>. The rigid feature 34b has a first surface <NUM> and a second surface <NUM>, wherein the second surface <NUM> has a larger surface area than the first surface <NUM>. A ramped portion <NUM> is provided between such first and second surfaces <NUM>, <NUM>.

Looking at <FIG>, consider the scenario in which a user closes the upper shroud member <NUM> and then urges the upper shroud member <NUM> towards the lower shroud member <NUM>. This involves the user closing the first and second parts 20a, 20b of the upper shroud member <NUM> and securing the first latch part 27a to the second latch part 27b. Upon subsequently pivoting the upper shroud member <NUM> towards the lower shroud member <NUM>, against bias of the torsion spring <NUM>, the first section <NUM> of the metallic spring feature <NUM> carried by the upper shroud member <NUM> will be brought into engagement with the first surface <NUM> of the rigid feature 34b carried by the lower shroud member <NUM>. Upon further pivoting the upper shroud member <NUM> more towards the lower shroud member <NUM> the rigid feature 34b cooperates with the metallic spring feature <NUM> to cause deflection of the metallic spring feature <NUM>. In other words, the metallic spring feature <NUM> is caused to recoverably flex by the rigid feature 34b thus enabling such features to move passed each other. The upper shroud member <NUM> can thus be pivoted further towards the lower shroud member <NUM> by a user against bias of the torsion spring <NUM>.

Looking at <FIG> the first section <NUM> of the metallic spring feature <NUM> is configured to be ramped relative to the first surface <NUM> of the rigid feature 34b when they initially engage. This reduces the extent of deflection required by the metallic spring feature <NUM> to move passed the rigid feature 34b compared to if the first section <NUM> of the metallic spring feature <NUM> simply extended directly from the opening <NUM> along the axis of the channel <NUM>.

With continued reference to <FIG> upon a user subsequently refraining from urging the upper shroud member <NUM> towards the lower shroud member <NUM> against bias of the torsion spring <NUM> the torsion spring <NUM> will urge such members apart. As the upper shroud member <NUM> pivots away from the lower shroud member <NUM> under bias of the torsion spring <NUM> the second section <NUM> of the metallic spring feature <NUM> carried by the upper shroud member <NUM> is brought into engagement with the second surface <NUM> of the rigid feature 34b carried by the lower shroud member <NUM>. The second surface <NUM> of the rigid feature 34b thus cooperates with the metallic spring feature <NUM> to cause deflection of the metallic spring feature <NUM> in the opposite direction to that heretofore described, however, the extent of such deflection is limited by the blocking surface <NUM>. In other words, the blocking surface <NUM> prevents the spring element <NUM> from deflecting sufficiently to enable it to move passed the rigid feature 34b as the upper shroud member <NUM> is pivoted away from the lower shroud member <NUM> under bias of the torsion spring <NUM>. The extent of pivotal movement of the upper shroud member <NUM> relative to the lower shroud member <NUM> is thereby restricted. Moreover the blocking surface acts as heretofore described to restrict the lower shroud member <NUM> from falling away from the upper shroud member <NUM> under gravity when a user lifts the tool up.

It is here mentioned that when the upper shroud member <NUM> is at its upper limit of pivotal movement away from the lower shroud member <NUM> (defined by engagement between the second section <NUM> of the metallic spring feature <NUM> and the second surface <NUM> of the rigid feature 34b as heretofore described) the cutting discs <NUM> carried by the wall chaser <NUM> do not protrude through the opening <NUM> in the base thereof. The cutting discs <NUM> only protrude through the opening <NUM> in the base of the wall chaser <NUM> when a user urges the upper shroud member <NUM> towards the lower shroud member <NUM> against bias of the torsion spring <NUM> in use.

To enable replacement of the cutting discs <NUM> a user must release the first and second latch parts 27a, 27b to open the upper shroud member <NUM>. On doing so the second shroud part 20b can be pivoted away from the first shroud part 20a about the hinge coupling <NUM>, thereby the metallic spring feature <NUM> carried by the upper shroud member <NUM> is moved out of engagement with rigid feature 34b carried by the lower shroud member <NUM>. The heretofore described limiting mechanism is thus disengaged and the extent of pivotal movement between the upper shroud member <NUM> and lower shroud member <NUM> is increased. In the open configuration of the upper shroud member <NUM>, when a user holds the wall chaser <NUM> from only the secondary handle <NUM> the lower shroud part <NUM> pivots away from the upper shroud part <NUM> under the influence of gravity and bias of the torsion spring <NUM>.

With further reference to <FIG> when the upper shroud part <NUM> is in the open configuration, parts of the wall chaser <NUM> can pivot about two axes of freedom. The first such axis <NUM> is defined by the hinge coupling <NUM> and the second such axis <NUM> is defined by the pivotal connection between the upper and lower shroud members, wherein such axes are orthogonal relative to each other. Users of the wall chaser <NUM> are thus provided with quick and easy access to the cutting discs <NUM> mounted to the shaft <NUM> for facilitating their replacement or otherwise e.g. changing the distance between the cutting discs <NUM> by modifying the arrangement of spacer elements heretofore described which will be familiar to persons skilled in the art. Also since features of the wall chaser <NUM> merely hinge apart to enable blade replacement the risk of a user losing a feature or not reassembling it correctly is reduced.

Lastly it is pointed out that after a cutting disc replacement operation the wall chaser <NUM> can be reconfigured into its ready-to-use configuration illustrated in <FIG> in multiple ways. For example, starting from the configuration illustrated in <FIG> a user may secure the first and second shroud parts 20a, 20b of the upper shroud member <NUM> and then urge the upper shroud member <NUM> towards the lower shroud member <NUM> to engage the limiting mechanism as heretofore described.

Alternatively, starting from the configuration illustrated in <FIG> a user may urge the first shroud member <NUM> towards the lower shroud member <NUM> against the torsion spring <NUM> by pushing down on the secondary handle <NUM>. Subsequently the user may then secure the first and second shroud parts 20a, 20b of the upper shroud member <NUM> together before releasing the pressure exerted against the torsion spring <NUM>. On releasing such pressure the upper shroud member <NUM> will be pivoted away from the lower shroud member <NUM> by the torsion spring <NUM>, thereby engaging the second section <NUM> of the metallic spring feature <NUM> with the second surface <NUM> of the rigid member 34b for restricting further pivotal movement of the shroud members away from each other under bias of the torsion spring (and gravity when the tool is lifted).

In some embodiments the blocking surface <NUM> is not defined by a feature <NUM> coupled to the internal surface of the upper shroud member <NUM>, whereas instead it is merely an internal surface of the shroud part which carries the metallic spring feature <NUM> e.g. the inner surface of the shroud part or a flange integrally formed with the shroud part. In some embodiments the blocking surface <NUM> is a rib integrally formed with the upper shroud member <NUM> and extending from an inner surface thereof.

Although the first and second heretofore mentioned axes <NUM>, <NUM> defining the degrees of freedom of movement of respective features of the wall chaser <NUM> have been described as being orthogonal relative to each other, in some embodiments this need not necessarily be the case provided the wall chaser <NUM> can be opened and closed in substantially the same manner for cutting disc replacement i.e. opening the upper shroud member <NUM> disengages the limiting mechanism.

Looking at <FIG> the connecting element <NUM> couples directly to the first shroud part 20a of the upper shroud member <NUM>, thus providing that only the second shroud part 20b moves about the hinge connection <NUM>. In some embodiments the connecting element <NUM> may be shaped such that both the first shroud part 20a and the second shroud part 20b are separately coupled thereto about respective hinge couplings. In other words, the first shroud part 20a may be coupled to the connecting element <NUM> via a first hinge coupling and the second shroud part 20b may be coupled to the connecting element <NUM> via a second hinge coupling; thereby providing that in such embodiments both the first and second shroud parts 20a, 20b can be hingedly moved relative to each other in order to open the upper shroud member <NUM>.

Although the protrusions <NUM>, metallic spring feature <NUM> and blocking surface <NUM> have been described as carried by the upper shroud member <NUM>; and the rigid feature 34b has been described as carried by the lower shroud member <NUM>; it will be appreciated that such an arrangement could be reversed. For example, the protrusions <NUM>, the metallic spring feature <NUM> and the blocking surface <NUM> could alternatively be carried by the lower shroud member <NUM>; and the rigid feature 34b could alternatively be carried by the upper shroud member <NUM> provided that the rigid feature 34b is capable of being disengaged from the metallic spring feature <NUM> when the shroud parts of the upper shroud member <NUM> are opened relative to each other.

In some embodiments the spring feature <NUM> need not necessarily be metallic and could be plastic or rubber for example, provided it is able to perform the same function as the metallic spring feature <NUM> heretofore described.

Although the foregoing embodiments are described as including a torsion spring <NUM> for urging the upper shroud member <NUM> away from the lower shroud member <NUM> in some embodiments an alternative biasing means could be used such as a cap spring, coil spring, clock spring or pressure spring.

It will be appreciated that in other embodiments, respective features need not necessarily have the same shape and configuration of the parts heretofore described provided they achieve the same function. For example, with reference to <FIG> (wherein like features are denoted with similar reference numerals to those used up to now but increased by <NUM>) in one embodiment the second part 134b of the limiting mechanism carried by the lower shroud member <NUM> may be a rod or pin feature extending from the lower shroud <NUM>. As for the first part 134a of the limiting mechanism carried by the upper shroud member the metallic spring feature <NUM> cooperates with a blocking surface <NUM> formed by a rib extending from an internal surface of the second shroud part 120b. Upon closing the first and second shroud parts 120a, 120b and pushing the upper shroud member <NUM> towards the lower shroud member <NUM> against spring bias as heretofore described, the rod or pin feature will cooperate with the metallic spring portion <NUM> causing it to deflect and move past the rod or pin feature and spring back to its original configuration. Upon a user refraining from pushing the upper shroud member <NUM> towards the lower shroud member <NUM> the spring bias will cause the section <NUM> of the metallic spring feature <NUM> to engage the rod or pin feature which will urge it into contact with the blocking surface <NUM>, thereby restricting the spring bias from being able to urge the upper and lower shroud members <NUM>, <NUM> apart. Moreover, the blocking surface <NUM> acts as to restrict the lower shroud member <NUM> from falling away from the upper shroud member <NUM> under gravity when a user lifts the tool up. The mechanism can be released by opening the upper shroud member <NUM> via the hinge opening <NUM>.

Although the foregoing is described in the specific context of a wall chaser <NUM> it will be appreciated that the teachings herein could be applied in the context of other power tools having rotatable cutting discs that are shielded from user access in use but that a user must have access to in order to replace them, e.g. circular saw power tools. It will thus further be appreciated that in some embodiments the power tool in which the foregoing teachings are applied could have only a single cutting disc.

Referring back to <FIG> how debris is removed in use will be discussed in detail. The wall chaser <NUM> has a vacuum device attachment <NUM>, which defines a channel in fluid communication with the volume defined by the upper and lower shroud members <NUM>, <NUM>. When the wall chaser <NUM> is grinding a concrete surface and thereby generating debris in the form of dust a vacuum device coupled to the vacuum device attachment <NUM> will be able to suck dust from within said volume, thereby drawing it away from the cutting discs <NUM> and into a storage of the vacuum device. The efficient removal of dust is very important due to the adverse health effects which can occur in the event of users being exposed to dust. Therefore even slight improvements in the efficiency of dust removal are of interest in the field of tools.

With additional reference to <FIG>, in which the vacuum device attachment <NUM> is not shown, the heretofore described wall chaser <NUM> is shown in an open configuration. The first shroud part 20a has a hole <NUM> in its side, which is referred to hereafter as the shroud outlet opening <NUM>. In use dust is sucked though the shroud outlet opening <NUM> on route to a vacuum device. When the first and second shroud parts 20a, 20b are in a closed configuration relative to each other the shroud outlet opening <NUM> is in a side wall of the upper shroud member <NUM>.

A first guide part <NUM> provided on the internal wall of the first shroud part 20a
defines a substantially arc-like shape. A top end <NUM> is located proximal the shroud outlet opening <NUM> and a bottom end <NUM> is is located distal to the shroud outlet opening <NUM>. A second guide part <NUM> is provided on the internal wall of the second shroud part 20b and is configured to cooperate with the first guide part <NUM>. More specifically when the first and second shroud parts 20a, 20b of the upper shroud member <NUM> are in a closed position an edge <NUM> defined by the first guide part <NUM> engages an edge <NUM> defined by the second guide part <NUM>. The first guide part <NUM>, the second guide part <NUM> and the internal wall of the upper shroud member <NUM> then cooperate to define a conduit which is the boundary of a sub-volume within the overall volume encompassed by the shroud (the shroud being the combination of the upper and lower shroud members <NUM>, <NUM>). From <FIG> it will be apparent that when the first and second shroud parts 20a, 20b are in a closed position an outlet from the sub-volume is in fluid communication with the shroud outlet opening <NUM> and an inlet to the sub-volume is distal to the shroud outlet opening <NUM> in fluid communication with remaining volume encompassed by the shroud.

Surface features of the conduit are configured to facilitate the removal of dust from within the shroud as will be discussed below.

With continued reference to <FIG> the inlet to the sub-volume extends along a first axis <NUM> (in the plane of the page) but the shroud outlet opening <NUM> in the side of the shroud extends along a second axis <NUM> (extending out of the page), meaning that the first axis <NUM> and the second axis <NUM> are in different planes relative to each other.

When negative air pressure is applied to the shroud outlet opening <NUM> for drawing dust away from the vicinity of the cutting discs <NUM> in use, dust rides along walls of the conduit defining the sub-volume on route to the shroud outlet opening <NUM>. Dust is required to change its direction of travel by substantially <NUM> degrees on route from within the shroud <NUM>, firstly upon entering the sub-volume by travelling substantially along the first axis <NUM> and then by exiting the sub-volume through the shroud outlet opening <NUM> by travelling substantially along the second axis <NUM>. Walls of the conduit guide dust as it travels along the sub-volume and cause it to change direction.

In particular the second guide part <NUM> has two components of curvature, namely a vertical component of curvature since the outlet from the sub-volume is higher than the inlet thereto and also a horizontal component of curvature for twisting towards the side wall of the upper shroud member <NUM> defining the shroud outlet opening <NUM>. Overall the second guide part <NUM> twists upwards and sidewards from the inlet to the sub-volume to the shroud outlet opening <NUM>, essentially defining part of a helix. The second guide part <NUM> is thus configured so that dust contacting the second guide part <NUM> upon being sucked along the sub-volume has its direction of travel changed so that it exits the shroud outlet opening <NUM> travelling substantially horizontally.

<FIG> shows the second guide part <NUM> in isolation, wherein a primary guide section <NUM> defines a substantially arc-like shape. The edge of the primary guide section <NUM> is the edge <NUM> already described in connection with <FIG>. The primary guide section <NUM> is curved in a vertical plane <NUM>, wherein a top end <NUM> thereof is located closer to the shroud outlet opening <NUM> in use than a bottom end <NUM> thereof. A secondary guide section <NUM> is curved in a horizontal plane <NUM>, providing that the width of the upper surface of the primary guide section <NUM> gradually narrows from the bottom end <NUM> of the primary guide section <NUM> to the top end <NUM> thereof. A bottom end <NUM> of the secondary guide section <NUM> extends parallel to the first axis <NUM>, whereas a top end <NUM> of the secondary guide section <NUM> extends parallel to the second axis <NUM>. The purpose of this configuration is to urge dust in a direction towards the shroud outlet opening <NUM>. In other words it is here stated that due to the curvature of the secondary guide section <NUM>, the secondary guide section <NUM> sweeps across the primary guide section <NUM> between the bottom ends and top ends thereof.

It is realised that in use not all dust sucked through the sub-volume on route to the shroud outlet opening <NUM> will ride along the secondary guide section <NUM> of the second guide part <NUM>. However to the extent that dust does impact the secondary guide section <NUM>, such dust will ride along the secondary guide section <NUM> and undergo a change in direction such that it rides off the top end <NUM> of the secondary guide section <NUM> travelling in a direction substantially parallel to the second axis <NUM>.

Since removal of dust from the shroud is facilitated by features of the wall chaser <NUM> itself, efficiency of dust removal for a given degree of suction power is improved.

It will be appreciated that the first and second guide parts <NUM>, <NUM> do not need to have the specific shape illustrated in <FIG> and <FIG> and that there is some flexibility regarding different configurations provided that the same function is achieved. For example in some embodiments the primary guide section <NUM> and the secondary guide section <NUM> may continuously merge into each other in a gradual manner, instead of defining a step-like interface therebetween as illustrated in <FIG>.

In some embodiments the first guide part <NUM> may comprise an integral part of the first shroud member 20a but in other embodiments it may be coupled thereto and be formed of plastic for example. Furthermore, in some embodiments second guide part <NUM> may comprise an integral part of the second shroud member 20b but in other embodiments it may be coupled thereto and be formed of plastic for example.

In some embodiments instead of first and second guide parts <NUM>, <NUM> a single guide part is provided. This single guide part is provided on either the first or second shroud part 20a, 20b of the upper shroud member <NUM> so that when the upper shroud member <NUM> is closed the single guide part engages the inner wall of the other shroud part 20a, 20b to define the heretofore described conduit and thereby the sub-volume. Such a single guide part may comprise an integral part of the first or second shroud member 20a, 20b but in other embodiments it may be coupled thereto and be formed of plastic for example.

Although the conduit has been described as being formed by cooperating features of a guide and internal surfaces of the shroud, in some embodiments the conduit may comprise a feature which itself defines the sub-volume and which is coupled to the first or second shroud part 20a, 20b of the upper shroud member <NUM>. For example such a feature may comprise a tubular member or otherwise, one end of which communicates with the shroud outlet opening <NUM> and the other end of which communicates with remaining volume within the shroud.

It is again mentioned that although the foregoing is described in the specific context of a wall chaser <NUM> it will be appreciated that the teachings herein could be applied in the context of other power tools having rotatable cutting discs that are shielded from user access in use but that a user must have access to in order to replace them, e.g. circular saw power tools. Such power tools may not have a shroud comprising of upper and lower shroud members as heretofore described but may instead have a single shroud which can be hinged open similar to the upper shroud member <NUM>. Debris being sucked from within such a shroud may be wood chips instead of dust, although the specific type of debris generated depends on the use context of the tool.

Claim 1:
A power tool (<NUM>) comprising:
a rotatable support arrangement (<NUM>) for supporting at least one cutting disc (<NUM>) and being configured to be rotatably driven by an electric motor;
a shroud for restricting the path of debris generated in use and defining a shroud outlet opening (<NUM>) through which debris can be sucked by a vacuum device;
a sub-volume defined within the shroud by a conduit having an inlet to the sub-volume and an outlet from the sub-volume, the outlet from the sub-volume in fluid communication with the shroud outlet opening and the inlet to the sub-volume distal to the shroud outlet opening in fluid communication with remaining volume in the shroud;
wherein the inlet to the sub-volume and the outlet from the sub-volume extend along first and second axes (<NUM>, <NUM>) in different planes and the conduit defining the sub-volume is configured so debris sucked through the sub-volume between the inlet to the sub-volume and the outlet from the sub-volume undergoes a change in direction by riding along a curved wall (<NUM>) of the conduit providing that debris exits the sub-volume travelling along a direction substantially parallel with the second axis.