The present invention relates to drawing boards and multipurpose desks which can be used for (though not exclusively) drawing, drafting writing and reading. More particularly, the present invention relates to a drawing board having a mechanism for maintaining the alignment of drawing instruments.

Common equipment and mechanisms for maintaining the alignment of drawing instruments on drawing boards are disadvantageous for a variety of reasons; mechanisms such as drafting machines and straightedge parallel bars intrude on the drawing environment of the user, are relatively difficult to use and configure and require specialised components that are costly to purchase and maintain. Furthermore, the attachment and/or detachment of such mechanisms to/from drawing boards is often laborious and time-consuming. Additionally, there is a desire for such mechanisms to be as visually unobtrusive as possible.

According to a first aspect of the invention, there is provided a drawing board comprising :

a wall defining a working surface; and

a mechanism for maintaining alignment of a drawing instrument relative to the working surface, the mechanism comprising a magnetic mount which is moveable, relative to the working surface, in a locus, and magnetically engageable with the drawing instrument when positioned over the working surface such that movement of the instrument parallel to the surface is confined to the locus.

Preferably, the drawing board is configured such that the guided movement of the component(s) is effectible by movement of the drawing instrument over the working surface when the or each component is magnetically engaged with the drawing instrument. Alternatively, the drawing board may include an actuator operable to effect the guided movement of the component(s) such that the mechanism draws the drawing instrument over the working surface when the or each component is magnetically engaged with the instrument.

Preferably, the or each component is arranged behind the wall. Preferably, the wall is formed from material which is such that the wall does not magnetically engage the component(s) and does not magnetically engage the drawing instrument when it is positioned over the working surface. Preferably, the mechanism comprises a closed drive-transmitting loop to which the or each component is attached. In embodiments of the invention, the continuous drive- transmitting loop comprises at least one, belt, chain or cable (cord). The the cord(s) is/are may be trained over wheels. Preferably, the wheels and cord(s) are configured to intermesh such that slippage between the wheels and cord(s) can be substantially precluded. In at least one embodiment, the wheels are sprockets.

In embodiments in which the continuous drive-transmitting loop is one or more cables or belts, the/each cable or belt is toothed and the wheels are likewise toothed.

Preferably, the locus comprises a straight line.

In embodiments of the invention, the or each component is attached to the cord(s) at positions which are spaced along an axis which is transverse to said locus. The or each component may an elongate member extending between said positions.

In certain embodiments of the invention, the mechanism comprises a first pair of said wheels, which are spaced apart along a first axis, and a second pair of said wheels, which are spaced apart along a second axis that is spaced from the first axis, said belt, chain or cable is continuous and trained over said wheels to assume a crossed- over configuration, and the component(s) is/are attached to a section of the belt, chain or cable which extends, in alignment with said locus, from one wheel of said first pair to the other wheel of said first pair, and attached to a section of the belt, chain or cable which extends, in alignment with said locus, from one wheel of said second pair to the other wheel of said second pair.

Preferably, the crossed-over configuration is defined by a figure-eight configuration of the cord(s). In embodiments of the invention, the mechanism of the drawing board comprises wheels laterally outward of wheels of said first and second pairs lying adjacent a common end of the working surface, and wherein the cord(s) is/are trained over the laterally outward wheels, whereby sections of the cord extend from those wheels of said first and second pairs to said laterally outward wheels to define said crossed-over configuration. In a preferred embodiment, the crossed-over configuration is defined adjacent said common end.

The drawing board may comprise at least one track with which the component(s) is/are engaged such that movement of the component(s) is guided along said at least one track. Preferably, the mechanism comprises two said tracks which are spaced apart and extend in alignment with said locus. In embodiments of the invention, the or each track comprises a rail and the component(s) is/are configured to engage the rail(s) to be moveable therealong.

In embodiments of the invention, the or each component of the drawing board includes at least one wheel receivable against the wall such that that component rolls along the wall during movement of the component(s) in said locus. Preferably, the wheel(s) of the component(s) are arranged to engage the rail(s) such that the rolling movement of the or each component is guided by said rail(s).

In certain embodiments of the invention, the mechanism of the drawing board comprises a tension adjustor operable to adjust tension in the belt(s), chain(s) or cable(s).

In preferred embodiments of the invention, the mechanism is configured such that at least one of the wheels thereof is placeable into an unlocked condition such that it can be moved translationally with respect to the wall, whereby tension in the belt(s), chain(s) or cable(s) is adjusted, and placeable into a locked condition, in which it is fixed translationally with respect to the wall. Preferably, the/each translationally moveable wheel is received against a respective said rail and placeable into a locked condition, in which it is fixed with respect to the rail, and into an unlocked condition, in which it can roll along the rail. Preferably, the mechanism of the drawing board is provided with a resistance adjustor operable to adjust resistance, offered by the mechanism, to the guided movement of the component(s). Even more preferably, the resistance adjustor is operable to vary a resistance to rotation of at least one of the wheels.

It is envisaged that the drawing instrument, when positioned over said working surface so as to be magnetically engaged by the component(s), aligns to a datum on or associated with the drawing board. Preferably, the mechanism of the drawing board is able to be calibrated to adjust a position of the component(s) relative to the datum.

In embodiments of the invention, the or each component comprises magnetic or magnetically susceptible material and the instrument comprises magnetic or magnetically susceptible material whereby to engage magnetically the component(s) when positioned over the working surface.

According to a second aspect of the invention, there is provided a drawing apparatus comprising a drawing board according to the first aspect and said instrument.

In preferred embodiments of the drawing apparatus, the mount and instrument include magnets of opposite polarity, whereby they magnetically interengage, and wherein at least one magnet of one of the mount and the instrument is moveable so as to align with a magnet of the other of the mount and instrument which has the same polarity such that the mount repels the instrument when mounted to the board in one orientation. Preferably, it is the instrument which includes the at least one moveable magnet. The drawing apparatus may include an actuator operable to effect the movement of the moveable magnet(s). It is envisaged that the actuator can be a switch, knob, button, lever and any other actuating device.

The apparatus may comprise a pair of said moveable magnets, wherein the moveable magnets are of the same polarity and moveable from a first configuration, in which they are contacting or adjacent each other, so as to align with at least one magnet of said other of the mount and instrument ("the first magnet(s)"), and a second configuration, in which they are remote from each other, so as to align with at least one other magnet of said other of the mount and instrument ("the second magnet(s)"), the first magnet(s) being of opposite polarity to the second magnet(s), such that the mount repels the instrument when the moveable magnets assume one of the first and second configurations and attracts the instrument when the moveable magnets assume the other of those configurations.

Preferably, the moveable magnets of the apparatus are opposite in polarity to the first magnet(s), whereby said other configuration is the first configuration. In preferred embodiments of the invention, said one of the mount and instrument comprises a cam mechanism operable via said actuator to move the moveable magnets from their first configuration to their second configuration. The moveable magnets may be resiliently biased, preferably spring-biased, towards their first configuration so as to reassume that configuration when operation of the actuator is discontinued.

Preferably, said magnets of opposite polarity extend parallel to a longitudinal axis of the instrument and/or In embodiments of the invention, the movement of said moveable magnets of the apparatus is perpendicular to a longitudinal axis of the instrument. The apparatus may be configured such that said magnets of opposite polarity extend perpendicular to a longitudinal axis of the instrument. Preferably, the movement of the moveable magnets of the apparatus is in a direction parallel to a longitudinal axis of the instrument.

Said magnets of opposite polarity may comprise magnets of the instrument arranged at spaced positions along a longitudinal axis of the instrument, having one polarity, and magnets of the mount arranged at corresponding positions, having the other polarity.

Said at least one magnet may comprise magnets arranged to lie at spaced positions along a longitudinal axis of the instrument such that each aligns with a respective said magnet of the other of the mount and instrument which has the same polarity. In embodiments of the invention, said at least one magnet is arranged to lie adjacent a longitudinal edge of the instrument, whereby the repulsion of the instrument by the mount is exerted on said edge.

In an apparatus embodying the invention, said one of the mount and instrument includes at least one further magnet arranged to lie adjacent an other longitudinal edge of the instrument and moveable so as to align with a magnet of said other of the mount and instrument when the instrument is mounted to the board in another orientation, the other orientation being a half-rotation from said one orientation about an axis perpendicular to the working surface.

According to a third aspect of the invention, there is provided a drawing instrument for an apparatus of the second aspect.

The drawing instrument may include rollers and/or fabric arranged so as to be received against a sheet on the working surface, on which sheet a drawing is to be produced, to facilitate the movement of the instrument across the sheet. Preferably, the drawing instrument comprises one or more projections arranged to be received against the sheet to resist movement of the instrument across the sheet. The or each projection may be configured to be movable between a retracted condition, in which it is housed within a body of the drawing instrument, and an extended condition, in which it projects from the body so as to be receivable against the sheet.

In embodiments of the invention, the drawing instrument includes an actuator operable to move the projection(s) between the extended and retracted conditions. The or each projection may be resiliently biased, preferably spring biased, towards the retracted condition, and the actuator may be operable to overcome the bias to move the or each projection into the extended condition. The actuator may comprise a button depressible to effect movement of the projection(s) into the extended condition. The button may be resiliently biased, preferably spring biased, towards an undepressed position. In embodiments of the invention, the actuator of the drawing instrument comprises a cam and the instrument includes one or more cam followers housed within the body such that depression of the button moves the cam follower(s) toward a respective lateral end of the drawing instrument, thereby moving the projection(s) into the extended condition.

Preferably, the or each cam follower is configured with a bevel and the button comprises at least one bevel engageable with the cam follower bevel(s) upon depression of the button such that the or each projection(s) is moved into the extended condition. In certain embodiments, the bevel with which the or each cam follower is configured is arranged at a proximal end of that cam follower.

The actuator of the drawing instrument may comprise at least one arm connected at one end to the button, so as to be pivotable thereabout, and engaged at the other end with a said cam follower, such that depression of the button causes the arm(s) to pivot about the button and urge outwardly the cam follower(s) engaged thereby, whereby the movement of the or each cam follower towards a respective lateral end of the drawing instrument is caused by both the button bevel(s) and the arm(s). In embodiments of the invention, The actuator of the drawing instrument comprises one or more leaf springs arranged to engage said cam follower(s) and so as to be deflected upon operation of the actuator so as to urge laterally outwardly the cam followers, whereby the movement the cam follower(s) towards the lateral end(s) of the drawing instrument is caused by both the button bevel(s) and the leaf spring(s).

In preferred embodiments of the invention, the number of button bevels is two, and the button bevels are laterally opposed;

each bevel abuts bevels of a respective pair of said cam followers; and the cam followers in each pair are arranged to engage a respective said projection, whereby depression of the button causes each projection to move into the extended condition.

In embodiments of the invention, the or each cam follower is resiliently, preferably spring biased, biased away from the respective lateral end. Preferably, the or each projection is a pin.

In embodiments of the invention, a proximal end of the or each projection is connected to the actuator and a distal end of the or each projection is arranged to bend such that it is displaced through an opening in the body upon the operation of the actuator, whereby it assumes its extended condition.

In preferred embodiments of the invention, the or each projection comprises a proximal end configured with a bevel arranged to be abutted by a bevel at a distal end of a respective said cam follower, such that movement of the cam follower(s) towards said lateral end(s) urges the or each projection into the extended condition.

According to a fourth aspect of the invention, there is provided a drawing apparatus comprising :

a drawing board according to the first aspect; and

said drawing instrument.

In embodiments of the invention, the drawing instrument is configured to be releasably engageable with at least one other drawing instrument such that the releasably engaged instruments define a composite instrument magnetically engageable with the component(s) when positioned over the working surface whereby movement of the composite instrument parallel to the surface is confined to said locus. Preferably, the drawing instrument of the drawing apparatus is magnetically and releasably engageable with one or more secondary drawing instrument(s).

According to a fifth aspect of the invention, there is provided a drawing system comprising :

a drawing apparatus according to the fourth aspect; and

said other drawing instrument(s).

The present invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which : Figure 1 is a plan view of a drawing board in accordance with an embodiment of the present invention, together with a drawing instrument in accordance with an embodiment of the present invention; Figure 2 is a plan view of a mechanism of the drawing board for maintaining the alignment of the drawing instrument relative to a working surface of the drawing board;

Figure 3 is a plan view showing the outlines of the drawing board and drawing instrument, the drawing instrument in magnetic engagement with a magnet of the mechanism;

Figure 4 is a plan view of the drawing board, showing additional drawing instruments engaged with the drawing instrument of Figure 1;

Figure 5 is a plan view of an alternative mechanism for maintaining the alignment of the drawing instrument relative to the working surface of the drawing board;

Figure 6 is a plan view of a magnetic mount for engaging and repelling the drawing instrument;

Figure 7 is a rear plan view of a drawing instrument configured to be magnetically engageable with the magnetic mount of Figure 11; Figure 8 is a rear plan view of the drawing instrument of Figure 7 configured to be magnetically repelled by the magnetic mount of Figure 6;

Figure 9 is a plan view of a drawing board, together with a drawing instrument with an actuator operable to affect the magnetic interaction between the drawing instrument and a magnetic mount of the drawing board;

Figure 10 is a side cross-sectional view of the drawing board of Figure 9 having the magnetic mount of Figure 6 repelling the drawing instrument of Figure 9; Figure 11 is a side cross-sectional view of the drawing board of Figure 9 having the magnetic mount of Figure 6 magnetically engaging the drawing instrument of Figure 9;

Figure 12 is a rear plan view of a magnetic mount having magnets of one polarity for magnetically repelling the drawing instrument and magnets of the opposite polarity for magnetically engaging the drawing instrument;

Figure 13 is a rear plan view of an embodiment of the drawing instrument having movable magnets of one polarity for magnetically engaging with corresponding magnets of the mount of Figure 12, and movable magnets of the opposite polarity for magnetic repulsion from corresponding magnets of the mount of Figure 12, the instrument being shown in a configuration in which the movable magnets are aligned with corresponding magnets of Figure 12 for magnetic engagement; Figure 14 is a rear plan view of the drawing instrument of Figure 13, the instrument being shown in a configuration in which the movable magnets are aligned with corresponding magnets of Figure 12 for magnetic repulsion;

Figure 15 is a plan view of an embodiment of a magnetic mount configured for magnetically engaging and repelling the drawing instrument;

Figure 16 is a rear cross-sectional plan view of a drawing instrument having movable magnets of one polarity configured to magnetically engage with corresponding magnets of the magnetic mount of Figure 15, and movable magnets of the opposite polarity configured to be magnetically repelled by corresponding magnets of the magnetic mount of Figure 15, the movable magnets being shown in a configuration in which they are aligned with corresponding magnets of the magnetic mount of Figure 15 so as to effect magnetic repulsion; Figure 17 is a rear cross-sectional plan view of the drawing instrument of Figure 16, the movable magnets being shown in a configuration in which they are aligned with corresponding magnets of the magnetic mount of Figure 15 so as to effect magnetic repulsion along an edge of the drawing instrument; Figure 18 is a side view of a drawing board having the magnetic mount of Figure 15, the magnets of the mount shown to be magnetically repelling an edge of the drawing instrument of Figure 16;

Figure 19 is a cross-sectional plan view of a drawing instrument comprising projections for resisting movement of the instrument across a surface to be drawn on;

Figure 20 is a cross-sectional front view of the drawing instrument of Figure 19 with the projections in a extended condition; Figure 21 is a cross-sectional front view of the drawing instrument of Figure 19 with the projections in a retracted condition;

Figure 22 is a cross-sectional front view of the drawing instrument of Figure 19 having an alternative arrangement for biasing the projections, the projections being shown in the extended condition;

Figure 23 is a cross-sectional front view of the drawing instrument of Figure 22 with the projections shown in the retracted condition; Figure 24 is a rear plan view of a drawing instrument mechanism for controlling the magnetic engagement of the instrument with the magnetic mount of Figure 11, the mechanism shown in its open configuration;

Figure 25 is the mechanism of Figure 24 shown in its closed configuration;

Figure 26 is an exploded assembly view of a drawing instrument having the mechanism of Figure 24;

Figure 27 is an exploded assembly view of the drawing instrument of Figure 26 as viewed from an underside;

Figures 28(a) is a rear plan view of a magnetic mount and a front plan view of associated magnetic strips of a drawing instrument in a closed configuration; Figures 28(b) is a rear plan view of the magnetic mount of Figure 28(a) and a front plan view of the magnetic strips of Figure 28(a), the strips shown in an open configuration;

Figure 29 is an exploded assembly view of an embodiment of a drawing instrument having recesses for magnets of one polarity for magnetically engaging with corresponding magnets of the mount of Figure 12, and recesses for magnets of the opposite polarity for magnetic repulsion from corresponding magnets of the mount of Figure 12; Figure 30 is an exploded assembly view of an embodiment of a drawing instrument having recesses for magnets of one polarity configured to magnetically engage with corresponding magnets of the magnetic mount of Figure 15, and recesses for magnets of the opposite polarity configured to be magnetically repelled by corresponding magnets of the magnetic mount of Figure 15;

Figure 31 is an exploded assembly view of one end of an embodiment of a drawing instrument having retractable projections for gripping onto a working surface;

Figure 32 is an exploded assembly view of a drawing instrument having retractable projections for gripping onto a working surface;

Figure 33 is a cross-sectional front view of the drawing instrument of Figure 32 with the projections in a retracted state; and Figure 34 is a cross-sectional front view of the drawing instrument of Figure 32 with the projections in a deployed state.

Referring to Figure 1, a drawing board 1 comprises a top/front wall defining a working surface 2 and is provided with a drawing instrument 3, which in the present embodiment comprises a ruler that includes at least one magnet.

Referring to Figure 4, in an embodiment of the invention, at least one additional drawing instrument, such as a T-Square 21 may engage with the drawing instrument 3. The T-Square 21, consistent with conventional T-Squares is adjustable in its position along the ruler. In certain embodiments, the drawing instrument 3 comprises wheels 30 which allow the instrument 3 to roll along the working surface 2. It is envisaged that the ease with which the wheels 30 rotate can be adjusted to affect the ease with which the instrument 3 can be moved across the working surface 2. Referring to Figure 2, the drawing board further comprises a rear wall 4 behind the working surface 2, and a mechanism 5, arranged over the rear wall 4, for maintaining the alignment of the drawing instrument 3. The mechanism 5 comprises a pair of laterally spaced apart first sprocket wheels 6 and 9 disposed adjacent an upper edge 10A of the wall 4, a pair of laterally spaced apart second sprocket wheels 7 and 8 disposed adjacent a lower edge 10B of the wall 4, a continuous toothed belt 11 trained over and meshed with the wheels 6, 7, 8, 9 in a figure-eight configuration, and a magnetic mount 12 secured to the belt 11; Figure 2 depicts the magnetic mount 12 as a bar magnet, though it is envisaged that the magnetic mount 12 can comprise any arrangement of one or more magnets. The magnetic mount 12 is secured to sections of the belt that extend, between sprocket wheels 7 and 6 and sprocket wheels 8 and 9, respectively along axes substantially perpendicular to a longitudinal axis of the magnetic mount 12, and parallel to the plane of the surface 2.

Still with reference to Figure 2, the mechanism 5 may include two laterally spaced guides 14, each with a longitudinal axis that is substantially perpendicular to the longitudinal axis of the magnetic mount 12 and parallel to the working surface 2. One guide 14 extends between upper wheel 9 and lower wheel 8 and the other guide extends between upper wheel 6 and lower wheel 7. It is envisaged that the guides 14 can be received in slots in the magnetic mount 12 so as to assist in maintaining the alignment of the magnetic mount 12 relative to the working surface 2. It is envisaged that the guides may comprise elongate slots (not shown) and the magnetic mount 12 may comprise pins (not shown) which fit into the slots and allow the magnetic mount 12 to slidingly engage with the guides 14. Other known means for engaging the magnetic mount 12 with the guides 14 in an adjustable manner are possible without departure from the invention. For example, each guide 14 may comprise a toothed rack and the magnetic mount 12 may be pinions which mesh with the teeth of the rack. Alternatively, the magnetic mount 12 may comprise at least two wheels (not shown) and each guide 14 may comprise ribs (not shown) arranged to receive the wheels such that as the magnetic mount 12 translates in a direction that is parallel to the longitudinal axes of the guides 14, any rotational displacement of the ruler is substantially limited.

Adjustability of the mechanism 5 may vary from one embodiment of the present invention to another. For example, the position of at least one of wheels 6, 7, 8 and 9 may be adjustable in order to vary the tension of the belt 11. By varying the tension of the belt 11, the force required to move the drawing instrument 3 across the working surface 2 may be varied. In an embodiment which utilises guides 14, each guide 14 may engage at least one of the wheels of a respective one of pairs of wheels 6, 7 and 8, 9 via known means. For example, at least one of wheels 6, 7, 8, and 9 can be provided with a pin which has a threaded end and is received in a said slot, to form a substantially size-for-size sliding fit therewith, and further provided with a nut, secured to the threaded end, which is tightenable to fix the wheel translationally relative to the respective slot and loosenable to allow sliding axial movement of the pin in the slot and thus guided movement of the wheel relative to the slot, such that the position of the wheel along the slot can be adjusted. Alternatively or additionally, the rotational resistance of at least one of the wheels 6, 7, 8, 9 may be adjustable whereby the force required to move the drawing instrument 3 across the working surface 4 of the drawing board 1 when it is engaged with the magnetic mount 12 can be controllably varied. Other means for adjusting the resistance of the magnetic mount 12 to movement are possible without departure from the invention.

Another mechanism 80 for maintaining the alignment of the drawing instrument 3 is shown in Figure 5. The mechanism 80 comprises four outer sprocket wheels 81, 82, 83, 84, each being disposed adjacent a corner of the rear wall 4, and four inner sprocket wheels 85, 86, 87, 88, each disposed laterally inwardly from a respective outer sprocket wheel 81, 82, 83, 84. In this configuration, the belt 11 is trained over the outer wheels 81, 82, 83, 84, and inner wheels 85, 86, 87, 88, such that the section of the belt 11 that crosses over itself in a typical figure-eight configuration is disposed substantially towards the upper edge 10A of the wall 4. The magnetic mount 12 is secured to sections of the belt 11 that extend between inner sprocket wheels 85 and 86, and inner sprocket wheels 87 and 88. In the depicted embodiment, the magnetic mount 12 comprises roller wheels 89 to facilitate its movement across the rear wall 4. The movement of the roller wheels 89 can be guided by guide rails or tracks 24. It is envisaged that the resistance of the wheels 89 to rotation can be calibrated to affect how smoothly the magnetic mount 12 travels across the rear wall 4.

In a preferred embodiment of the invention, the alignment of the magnetic mount 12 relative to the working surface 2 may be calibrated. For example, a calibration screw (not shown) at points where the magnetic mount 12 is secured to the belt 11 may allow the user to adjust the orientation and/or position of the magnetic mount 12.

Referring to Figure 3, the drawing board 1 and the drawing instrument 3 are depicted as transparent such that only an outline of the drawing board 1 and an outline of the drawing instrument 3 are shown in order to depict how the drawing instrument 3 engages with the magnetic mount 12. When the drawing instrument 3 is manually moved (pushed or pulled) over the working surface 2 of the drawing board 1, the/each magnet of the drawing instrument 3 engages with the magnetic mount 12, through the front wall of the drawing board 1, such that the magnetic mount 12 influences the orientation and/or position of the drawing instrument 3 relative to the working surface 2. Preferably, the drawing instrument 3 comprises at least one straight edge 18 such that, when the/each magnet of the drawing instrument 3 engages with the magnetic mount 12, the/each straight edge 18 of the drawing instrument 3 is aligned to be substantially parallel to an edge of the drawing board 1, such as the upper edge 10A. Furthermore, when the/each magnet of the drawing instrument 3 is engaged with the magnetic mount 12, movement of the drawing instrument 3 over the working surface 2 along an axis parallel to the surface effects movement of the belt 11 and thus turning of the wheels 6, 7, 8, 9 such that the magnetic mount 12 is displaced in a guided manner so as to maintain, owing to its being engaged with the magnet(s) of the drawing instrument 3, alignment of the drawing instrument 3 relative to the working surface 2. Referring back to Figure 2, the arrows depict the directions in which the belt 11 and magnetic mount 12 move when the drawing instrument 3 is moved across the working surface 2.

It is envisaged that the drawing instrument 3 may comprise structures to facilitate its movement over the working surface. For example, the drawing instrument 3 may comprise spaced apart rollers/wheels (not shown) rotatably supported at an underside thereof so as to be received against the working surface 2 whereby to roll therealong when the drawing instrument 3 is moved over the working surface 2. Alternatively or additionally, the drawing instrument 3 may comprise one or more sections of fabric (not shown) arranged at said underside thereof so as to be slidably received against the working surface 2. Referring to Figures 6 to 18, the drawing instrument 3 can be selectively engaged with and disengaged from the working surface 2 by virtue of its attraction and repulsion, respectively, with the magnetic mount 12. Referring specifically to Figure 6, the magnetic mount 12 comprises a central magnetic strip 41 for magnetically engaging two corresponding and movable magnetic strips 44 arranged on the drawing instrument 3. The magnetic mount 12 also comprises a pair of repulsive magnetic strips 40 disposed on either side of the central magnetic strip 41 and arranged for magnetically repelling the two movable magnetic strips 44 of the drawing instrument 3. Referring to Figures 7 to 11, the magnetic strips 44 of the drawing instrument 3 can be moved from an engagement position (Figure 7), in which they are attracted to the central magnet 41 of the magnetic mount 12 (Figure 11) such that alignment of the instrument 3 on the working surface 2 can be guided by the magnetic mount 12, to a disengaged position (Figure 8), in which the magnetic strips 44 of the instrument 3 are repelled by the repulsive magnetic strips 40 (Figure 10) of the magnetic mount 12 so as to facilitate the removal of the instrument 3 from the working surface 2. A mechanism for moving the magnetic strips 44 of the drawing instrument 3 is described below.

Referring to Figures 6 to 9, a sliding switch 25 on an upper surface of the drawing instrument 3 controls movement of a series of triangular components 46 disposed on a bar 45 arranged at an underside of the drawing instrument 3. The movable magnetic strips 44 comprise recesses 43 for housing the triangular components 46 when the magnetic strips 44 are adjacent one another. The recesses 43 are shaped such that upon sliding the switch 25 and thus moving the triangular components 46, said components 46 function as linear cams which urge against surfaces of the recesses 43 to displace each magnetic strip 44 of the drawing instrument 3 outwardly and away from one another. In preferred embodiments of the drawing instrument 3, it is envisaged that the magnetic strips 44 thereof are biased into a position in which they are adjacent to each other. For example, in the depicted embodiment, each end of one magnetic strip 44 is connected to a respective end of the other magnetic strip 44 by a tension spring 47 such that as the switch 25 is moved so as to align the triangular components 46 with their respective recesses 43, the magnetic strips 44 are urged towards one another by the springs 47. To facilitate the movement of the magnetic strips 44 toward and away from one another, the drawing instrument 3 is provided with guide rails 48 and the magnetic strips 44 are provided with corresponding brackets 49 into which the guide rails 48 are received.

Of course, other methods for displacing the magnetic strips 44 of the drawing instrument 3 outwardly are envisaged. Figures 24 and 25 illustrate one such example, wherein in place of the triangular components 46 are components 119 having arms 120 which are biased, preferably spring-biased, into a closed configuration shown in Figure 25, in which the arms are folded inwardly toward one another whereby they are housed in the recesses 43 of the magnetic strips 44. Movement of the sliding switch 25 urges the arms into an open configuration, as shown in Figure 24, such that they urge against the surfaces of the recesses 43 so as to displace each magnetic strip 44 outwardly and away from one another.

Figures 26 and 27 illustrate a drawing instrument 3 having the magnetic strips 44 shown in Figures 24 and 25. In this drawing instrument 3, the armed components 119 are provided along an elongate bar 45. The bar 45 includes apertures 66 which receive corresponding protrusions 64 on an underside of the sliding switch 25 such that sliding of the switch 25 effects horizontal movement of the bar 45 within the drawing instrument 3. A base 3b of the drawing instrument 3 has a recess 3a for receiving the magnetic strips 44. In the depicted embodiment, the recess 3a includes a series of spaced apart grooves 62 configured to receive ball bearings (not shown) which facilitate a gliding movement of the magnetic strips 44 towards and away from one another. The base 3b of the drawing instrument 3 also has two central guide rails 61 arranged for insertion into corresponding grooves 60 in the magnetic strips 44 so as to limit horizontal movement of those strips 44 within the drawing instrument 3. As can be seen in Figure 27, the magnetic strips 44 have recesses 69 for receiving magnets. The magnetic strips 44 also have at their opposed ends axially extending projections 47a onto which a spring 47 can hook so as to bias the magnetic strips 44 toward one another.

Figure 28(a) shows the magnetic strips 44 of Figures 24 and 25 in a closed configuration such that the row of magnets 65a on each magnetic strip 44 is aligned with respective attraction magnets 65c of the corresponding magnetic mount 12. By sliding the switch 25, the magnetic strips 44 are urged against the bias applied by the springs 47 into an open configuration, whereby the magnets 65a align with respective repulsive magnets 65b of the magnetic mount 12.

Referring to Figures 12 to 14, another mechanism for selectively engaging the drawing instrument 3 with the magnetic mount 12 is shown. In this embodiment, the magnetic mount 12 comprises a series of thinner attraction magnets 15 for attracting corresponding thinner attraction magnets 16 of the drawing instrument 3, and a series of thicker repulsion magnets 17 for repelling corresponding thicker repulsion magnets 18 of the drawing instrument 3. The thinner attraction magnets 16 and thicker repulsion magnets 18 of the drawing instrument 3 are mounted on the bar 45, the movement of which can be controlled by the sliding switch 25 on an upper surface of the drawing instrument 3. Referring to Figure 13, when the switch 25 is slid into a first position, the thicker repulsion magnets 18 of the drawing instrument 3 are moved to a position in which they are not aligned with the thicker repulsion magnets 17 of the magnetic mount 12, while the thinner attraction magnets 16 of the drawing instrument 3 are moved to a position in which they are aligned with the thinner attraction magnets 15 of the magnetic mount 12. In this position, the drawing instrument 3 is magnetically attracted to the magnetic mount 12 and can thus be moved across the working surface 2 in a guided manner. Referring to Figure 14, when the switch 25 is slid into a second position, the thicker repulsion magnets 18 of the drawing instrument 3 are moved to a position in which they are aligned with the thicker repulsion magnets 17 of the magnetic mount 12, while the thinner attraction magnets 16 of the drawing instrument 3 are moved to a position in which they are not aligned with the thinner attraction magnets 15 of the magnetic mount 12. In this position, the drawing instrument 3 is magnetically repelled by the magnetic mount 12 and can thus be lifted off the working surface 2 with the aid of the magnetic repulsion. Figure 29 shows a drawing instrument 3 arranged to carry magnets for engagement with the magnetic mount of Figure 12. A magnet holder 67 is slidably mounted within the drawing instrument 3 and has recesses 16a, 18a for receiving the thinner attraction magnets 16 and thicker repulsion magnets 18 respectively. The magnet holder 67 also includes apertures 66 which receive corresponding protrusions 64 on an underside of the sliding switch 25 such that sliding of the switch 25 effects horizontal movement of the magnet holder 67 within the drawing instrument 3.

Referring to Figures 16 to 18, certain embodiments of the drawing instrument 3 allow for only a single edge 56 thereof to be repelled from the magnetic mount 12. To this end, the magnetic mount 12 comprises a series of generally vertically oriented attraction magnets 51. The magnetic mount 12 also comprises two series of generally horizontally oriented repulsive magnets 52 and 55; one series 52 is disposed towards an upper edge of the magnetic mount 12 and the other series 55 is disposed towards a lower edge of the magnetic mount 12. Furthermore, each upper edge repulsive magnet 52 is disposed on one side of a respective attraction magnet 51 whereas each lower edge repulsive magnet 55 is disposed on the other side of that respective attraction magnet 51. Meanwhile, the drawing instrument 3 comprises a sliding switch 25 arranged on an upper surface thereof, which is connected to a bar 45 at an underside of the instrument 3 which is mounted with a series of magnets 53 and 54. More specifically, the drawing instrument 3 comprises a series of generally vertically oriented magnets 54 arranged to be attracted to and engage with the attraction magnets 51 of the magnetic mount 12. The drawing instrument also comprises generally horizontally oriented magnets 53 disposed towards one of the longitudinal edges of the drawing instrument 3 and spaced apart such that when the attraction magnets 54 of the instrument 3 and the attraction magnets 51 of the magnetic mount 12 are engaged, the repulsive magnets 53 of the instrument 3 and the repulsive magnets 52 or 55 of the magnetic mount 12 are not aligned and thus do not repel one another, and vice versa . With this arrangement of magnets, once the switch 25 is slid into a position such that the attraction magnets 51 and 54 are not aligned with one another, lifting of the drawing instrument from the working surface is further facilitated by the repulsive forces between the repulsion magnets 52 or 55 of the magnetic mount 12 repelling the repulsion magnets 53 of the drawing instrument 3. The longitudinal edge of the drawing instrument 3 along which the repulsive force is desired can be chosen simply by rotating the instrument 3 about its central point in the plane of the working surface 2 such that either an upper edge of the instrument 3 or a lower edge of the instrument 3 is repelled by the repulsion magnets 52 or 55 of the magnetic mount 12.

Figure 30 shows a drawing instrument 3 configured to carry magnets for engagement with the magnetic mount of Figure 15. A magnet holder 67 is slidably mounted within the drawing instrument 3 and has recesses generally horizontally oriented recesses 53a and generally vertically oriented recesses 54a for receiving the aforementioned magnets 53, 54 respectively. The magnet holder 67 also includes apertures 66 which receive corresponding protrusions 64 of the sliding switch 25 such that sliding of the switch 25 effects horizontal movement of the magnet holder 67 within the drawing instrument 3.

It is envisaged that the polarities of the aforementioned magnetic arrangements can be reversed such that an engagement position/magnet is a repulsion position/magnet.

Referring to Figures 19 to 23, the drawing instrument 3 comprises retractable projections, such as pins 115, for gripping onto the working surface 2 so as to resist movement of the drawing instrument across the working surface and/or a surface to be drawn on. The pins 115 are housed within a body of the drawing instrument 3 and do not protrude therefrom in the retracted condition. In their extended condition, each pin 115 protrudes from a respective laterally spaced apart hole 100 in an underside of the body of the drawing instrument 3 such that the pins 115 can engage with and grip onto the working surface 2 or a surface to be drawn on. One mechanism for retracting and deploying the pins is described below.

Referring to Figures 19 to 21, the drawing instrument 3 comprises a compression spring-biased button 20 which can be pressed to deploy the pins 115. The button 20 is partially housed within the drawing instrument 3 and projects from an upper surface thereof as a result of the spring bias. Housed within the drawing instrument 3 are four rods 114 extending in a direction that is substantially parallel to the longitudinal axis of the drawing instrument 3. An inner edge 112 of each rod 114 is arranged to be in mechanical engagement with the button 20 such that pressing the button 20 causes the rods 114 to slide away from the button 20 and towards a respective lateral end of the drawing instrument 3. In the depicted embodiment, the button 20 comprises two bevels 111 and the inner edge 112 of each rod 114 comprises corresponding bevels 112 arranged to engage with the bevels 111 of the button 20. By pressing the button 20 downwardly so as to overcome the spring bias, the button 20 functions as a linear cam wherein its bevels 111 press downwardly on the bevels 112 of the rods 114, thereby urging them outwardly towards the lateral ends of the drawing instrument 3. The button 20 also comprises four pivotable arms 113 for extending and retracting the respective rods 114 when the button 20 is pressed and released, respectively. To this end, an end of each arm 113 is disposed at least partially within a hole or against a groove of a respective rod 114 such that movement of the arm 113 results in corresponding movement of the rods 114. By pressing the button 20, each arm 113 is caused to pivot upwardly and urge a respective rod 114 outwardly. Releasing the button 20 causes the arms 113 to pull back against the each respective rod 114, thereby facilitating retraction of the rods 114. Each pin 115 extends from a respective rod 114 in a direction substantially parallel to the longitudinal axis of the drawing instrument 3, and terminates in a curved end arranged to project from the drawing instrument 3. Therefore, pressing the button 20 moves the rods 114 outwardly towards respective lateral ends of the drawing instrument 3, thereby causing the pins 115 to extend from the drawing instrument 3 such that the pins 115 can engage with and grip the working surface 2. Releasing the button 20 retracts the rods 114 and thus the pins 115 back into the drawing instrument 3 such that the drawing instrument 3 can be moved across the working surface 2 more smoothly. Means such as tension springs 117 can also be used to facilitate the urging of the rods 114 into the retracted condition when the button 20 is released. It is envisaged that instead of each pin 115 terminating with a curved end, each rod

114 can extend from the button 20 to substantially a respective hole 100. In this embodiment, each rod 114 terminates in a bevel (not shown) which functions as a cam and interacts with a corresponding bevel (not shown) of a respective pin, which bevel functions as a cam follower, such that linear movement of each rod towards the lateral ends of the drawing instrument 3 results in the urging of each pin downwardly and thus into the extended condition.

Figure 31 shows an end of another embodiment of a drawing instrument 3 having retractable pins 115 which can similarly be deployed by pressing the button 20 so as to move respective rods 114 outwardly. In this embodiment, each pin 115 is provided on an element 156 which sits in a respective recess 100a at an end of the drawing instrument 3. Each recess 100a also has an opening 100 for locating a respective pin

115 and through which the pin 115 can protrude and contact the working surface. A cone spring 162 sits between each element 156 and corresponding recess 100a so as to bias the element 156 and thus the pin 115 into the retracted condition. To deploy the pins 115, each element 156 can be depressed downwardly against the bias applied by the respective cone spring 162 and towards the working surface. To this end, the outer end of each rod 114 terminates in or is in mechanical engagement with a movable component 160 having a ramped surface 160a which is configured to ride against a complementarily ramped surface 156a of a respective element 156. When the button 20 is pressed, the rods 114 and thus the ramped components 160 are moved outwardly such that the ramped surface 160a of each movable component 160 rides against the ramped surface 156a of a respective element 156, thereby depressing each element 156 so as to deploy the pins 115.

Referring to Figures 22 and 23, instead of the four arms 113, the drawing instrument 3 can comprise a leaf spring 116 for retracting the rods 114 and thus the pins 115. In this embodiment, the button 20 is biased upwardly by two compression springs 118 and a central portion of leaf spring 116 is disposed between the button 20 and a respective compression 118. Both ends of each leaf spring 116 are disposed at least partially within a hole or against a groove of a respective rod 114 such that movement of the leaf spring 116 results in corresponding movement of the rods 114. In this arrangement, the compression springs 118 urge the central portion of the respective bar 116 upwardly such that each leaf spring 116 is arched. By pressing the button 20, the spring bias of the compression springs 118 is overcome and the tension of each leaf spring 116 decreases as the rods 114 extend outwardly towards a respective lateral end of the drawing instrument 3. When the button 20 is released, the bias of the compression springs 118 increase the tension of the respective leaf springs 116, which thus draw in their respective rods 114 so as to retract the pins 115.

Figures 32 to 34 show another embodiment of a drawing instrument 3 having a retractable pin mechanism. In this embodiment, each pin 115 is provided on a pivotal component 155 which is received in a recess located towards opposed ends of the instrument 3. The recess includes opposed grooves 157 for receiving a pin 154, the pin extending through the pivotal component 155 so as to locate it in the recess and to define the axis about which the pivotal component 155 pivots. The pivotal components 155 can thus pivot between a first position whereby the pins are retracted and thus do not protrude from the drawing instrument so as to contact the working surface, and a second position whereby the pins are deployed so as to contact the working surface. As will now be described, a series of mechanically linked components of the drawing instrument 3 interact with one another to effect pivoting of the pivotal components 155. As can be seen in Figures 33 and 34, a lower end of the button 20 has two spaced apart chamfered surfaces 150 for abutting against respective inner sides of two wheels 151 which are laterally movable within the drawing instrument 3. An outer side of each wheel 151 is arranged to engage with a respective movable member 152 which houses one end of a rod 153, the other end of the rod 153 being received in a groove 99 formed in an upper portion of the pivotal component 155. By depression of the button 20, the chamfered surfaces 150 abut against and move the wheels 151 laterally away from one another such that the wheels 151 push outwardly against respective movable members 152 so that they too are moved laterally outwardly, thereby driving the respective rods 153 into their respective pivotal components 155 so as to pivot those components 155 into the second position. The drawing instrument 3 includes springs 158 for biasing the button 20 to an undepressed position such that the pins 115 are normally in a retracted condition.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.