Background of the Invention It is common practice for many stock materials such as M. D. F. (medium-density- fibreboard), Chipboard and Plywood to be supplied to the trade and public in large, dif- ficult to handle sheets.

A number of tools are available to cut this stock material i. e. Hand Saws, Hand- held power tools and Circular Table Saws. As it stands all of these tools have their own inherent problems. Hand Saws are labour intensive and require a high level of skill in their use; also further work may be required to finish the cut edge.

Hand-held power tools immediately present a danger to the operator and re- quire a reasonable level of skill in order to achieve the desired result. These tools re- quire a manual feed; and when the material is fed by hand the working will not be con- stant. One possible result could be an uneven cut, raising the need for further work to finish the cut edge.

Circular Table Saws are probably the best method available to the trade and the public but due to costs involved, portable circular table saws are the more affordable option. With portable table saws the stock material is normally fed through by hand which produces extreme danger for the operator. Another disadvantage is that when handling large sheets of stock material it is normally a two-man job to feed the sheets through the saw. Once again due to uneven feed rates further work may be necessary to finish the cut edge. A further disadvantage with table saws is the workspace required to cut a given sheet, generally at least twice the area of the sheet.

Summary of the Invention In response to the above problems, one aspect of the invention provides a power tool and guide assembly comprising: a track securable to the work-piece; a car- riage slideably mounted to the tracks; mounting means on the carriage mounting a

power tool for working the work-piece as the carriage slides along the track; and drive means for propelling the carriage along the track.

Preferably, the mounting means removably mounts the power tool on the car- riage, and even more preferably is adapted to removably mount a power hand-tool or a variety of power hand-tools. Preferably, the mounting means is adapted to mount at least one power hand-tool from a list comprising: circular saws; jig saws; sanders; plan- ers; routers; and angle grinders.

It will be understood from the invention that the term work-piece refers to an object, which is the subject of tooling by a power tool, examples of which being stock material such as MDF, plywood and even sheet metal or structural objects such as walls and floors.

The track may be made from a light alloy so as to allow the assembly to be transported more easily.

Preferably, the tool is a power hand-tool.

In a preferred embodiment the track may have adjustable clamps, such as G- clamps, which can be adjusted to accommodate work pieces of different thickness. It may be of further benefit for the track to have a range of gradation points along its length, onto which the clamps can be arranged so that work-pieces of different lengths can be accommodated by the clamps.

Preferably the track will have an end limiting means to physically limit the movement of the carriage along the track beyond a certain point. It may be of further advantage-for safety amongst other things-if the end limiting means were to have a system cut off switch, so that when the carriage reaches the end of its journey along the track the system switches off causing both the tool and the driving means to stop.

It may be advantageous if the track were to have a start marker means, which provides a start point from which the carriage can only travel forwards down the track.

However, it is appreciated that the gearing of the driving means may act to limit the movement of the carriage. Further benefit may be gained if the start marker means has a locking means, which can be engaged to hold the carriage at the start point; this may be of use when the invention is not in use or even during transport of the assembly.

Alternatively, it may be possible for the track to have release means, which al- low the carriage to be completely removed for ease of transport.

It may also be of advantage for the driving means to be capable of returning the carriage back to the start of its run, with the start point possibly providing the means of stopping the returning carriage.

In order to reduce the friction between the track and the carriage as it travels along the track it may be preferable for the carriage to have inserts made from self- lubricating materials such as brass. The inserts could be arranged so as to provide the best lubrication to the movement of the carriage along the track.

Alternatively, the self-lubricating inserts could be arranged in the track itself thereby providing the necessary lubrication for the carriage movement along the track.

In the preferred embodiment the track comprises guiding rails, which are ar- ranged to receive the carriage so that the movement of the carriage is restricted to a single plane as it travels along the track.

The drive means may be provided by a rack and pinion arrangement, wherein the rack runs along the length of the track and the pinion is mounted on the carriage.

Whereby the rotating of the pinion along the rack causes the carriage to travel along the track.

Alternatively the drive means may be provided by wheels, which run along a runway. It will be appreciated by the man skilled in the art that other arrangements of drive means may be used to transport the carriage along the track.

The drive means may be powered by its own motor, which may have a power pick-up from the power hand-tool. It is also appreciated that the motor may have its own power source. The motor may preferably have a reduction gearbox so that the pinion is caused to rotate at a speed, which is slow enough to give a suitable standard of tooling by the associated power tool.

It may be of further advantage if the drive means has a variable speed motor, to allow for tooling of different materials more conveniently.

It is also understood that the drive means may be powered directly by the power hand-tool itself. This could be achieved by a power hand-tool with an integrated

gearbox that has a two output shafts. The first shaft, which would run at the tool mo- tor's normal speed, would power the hand tool. The second shaft, which could be geared to run at a slower rate than the first shaft, would power the drive means.

Another aspect of the invention provides a power hand-tool guide comprising: a track securable to a work-piece; a carriage slideably mounted to the tracks; mounting means on the carriage to receive a power hand-tool for working the work piece as the carriage slides along the track; and drive means for propelling the carriage along the track.

With this aspect, the mounting means on the carriage is preferably arranged to receive a variety of different power hand-tool types. This embodiment therefore pro- vides a more versatile system where tools can be interchanged as desired.

It will be appreciated by the man skilled in the art that most of the features al- ready discussed with relation to the first aspect will be equally beneficial to the second aspect. One exception may be the use of the power tool to power the drive means, but as discussed above the drive means may be powered by its own motor.

It will be understood from the invention that in practice the work-piece would preferably be secured to a workable and then the assembly would be clamped onto the work-piece in order to achieve the best results. Although this is a preferred method of using the disclosed invention, it is appreciated that work-pieces may not require secur- ing to a workable in order to use the invention.

Preferably the assembly also comprises a controller, remote from the carriage, for controlling the drive means, for example for controlling the drive motor speed. The controller may be a hand held controller, which may simply be connected to the drive means by means of a suitable cable, or alternatively may be wirelessly coupled. Advan- tageously, the controller may provide control of drive speed for the carriage along the track. The remote controller provides for much safer operation of the power tool as the user need not be standing directly next to it as it works on the work piece. This also provides the advantage that the operator may be able to stand well away from the power tool and guide assembly when cutting materials such as MDF, the dust from which is a health hazard.

Preferably the drive means comprises a DC motor.

Preferably, the drive means comprises a motor mounted in-board on the car- riage. This provides the advantage that the overall length/footprint of the assembly can be reduced.

Preferably the track is formed from a plurality of longitudinal sections which are rigidly jointed together. Using the appropriate number of track sections, an appropri- ate overall length of track can be assembled to suit the particular work piece.

The rigid jointing of the track sections may conveniently be achieved by using dowels and linking plates.

Preferably, the track may be formed by extruding aluminium.

Brief Description of the Drawings The invention will now be described with reference to the accompanying draw- ings in which: Figure 1 is a side view of a preferred embodiment of the invention; Figure 2 is a plan view of the preferred embodiment illustrated in Fig. 1; Figure 3 is an enlarged side view of the power tool section of the preferred em- bodiment illustrated in Figs. 1 and 2; Figure 4 is an enlarged end view of the power tool section of the preferred em- bodiment illustrated in Figs. 1 and 2; Figure 5 is a plan view of part of a power tool and guide assembly embodying the invention; Figure 6 is an end view of the track from the assembly shown in Figure 5; Figure 7 is an end view of a further embodiment; Figure 8 is a plan view of part of a track suitable for use in embodiments of the invention; Figure 9 is a sectional view of the track shown in Figure 8; and Figure 10 is a diagram of the link plates used in joining the tracks sections as shown in Figure 8.

Detailed Description of the Illustrated Embodiments Figure 1 shows the side view of a preferred embodiment of the Guided power tool assembly 1. A power tool 2 is mounted on a carriage 4, by fixings such as bolts, rivets or even by welding. The carriage 4 is in turn mounted on the track 3. Although the power tool shown is circular saw it will be understood from the invention that other tools such as jig saws, power planers, routers and the like may be used.

The object, which is to be worked on by the power tool, shall be referred to as the work-piece for the sake of clarity. The work-piece (not shown) is held in position by the adjustable clamps 6 which are attached to the track 3 at receiving points 9.

Also attached to the carriage, by bolts, rivets or the like, are a pinion 5 and a motor 7 to drive it. As the power tool tools the work-piece, the pinion 5 is rotated by the associated motor 7. The rotating pinion 5 interacts with the rack 10, which is at- tached under tension along the length of the track 3, causing the carriage 4 and thus the tool to travel along the track at a uniform speed giving an even tooling to the work- piece.

Figure 2 shows a plan view of the preferred embodiment, with the rack 10 and pinion 5 arrangement illustrated more clearly. It is appreciated that other methods of driving the carriage along the track as possible including amongst other things, the use of rubber wheels and a runway.

In order for different sized work-pieces to be tooled the adjustable clamps 6 can be attached to the track 3 at any of a range of receiving points 9 along the length of the track 3, as dictated by the length of the work-piece being tooled. The adjustable clamps 6 comprise fixing means, which can be engaged with any particular receiving point 9 to hold the clamp to the track at a set position, and clamping means, which can be adjusted to clamp the work piece in position. Preferably the clamping means could be screw-adjustable, but it is appreciated that other methods of adjusting the clamp are possible.

The movement of the carriage 4 along the track 3 is directed and restricted by the guide rails 8. The guide rails are securely mounted, in parallel to one another, along the track by an appropriate fixing means, such as bolts, rivets or welding. It is appreci-

ated that other types of fixing means may be suitable. The arrangement of the track 3 with the guide rails 8 creates two channels along which the carriage 4 moves. The resis- tance to the movement of the carriage 4 along the track 3 may be reduced by the use of inserts (not shown) made of self-lubricating materials such as brass or the like.

In the preferred embodiment shown the tool possesses a cut off switch (not shown), which will be activated by a limit switch when the tool reaches the end of its run. For convenience the limit switch may preferably be mounted in association with one of the adjustable clamps 6.

Figures 3 and 4 show enlarged views of the power tool mounted on the track, from which the interactions of the carriage and guide rails can be more clearly seen.

For example, from Figure 3 it can be seen that in this embodiment the rack and pinion drive takes the form of a toothed sprocket 5 which engages with a roller link chain 10.

The power tool in this embodiment is a circular saw.

Referring now to Figure 5, in this embodiment the carriage 4 carries a power tool 2 in the form of a circular saw having a saw blade 21 and a blade guard 22. The drive means for driving the carriage along the track 3 comprises a DC motor 7 which is mounted in-board on the carriage 4, i. e. it does not extend past the edges of the car- riage 4 in a direction along the track 3. The DC motor 7 is controlled by means of a hand held controller 71, which is attached to the motor by a cable 72. The controller 71 includes a start/stop button 74 and a direction control button 75. In addition, it in- cludes a speed control knob 73 for controlling the speed at which the motor 7 propels the carriage along the track. The cable 72 is a sufficient length so that the user can stand a safe distance away from the power tool as it is working on the work piece. The positioning of the motor 7 on the carriage 4 reduces the overall length of the saw un- dercarriage. The drive means comprises a toothed sprocket 5 fixed to the output shaft of the motor 7. The teeth of the sprocket 5 engage with a rack 10 in the form of a chain (in this case a roller link chain). The chain 10 is held in tension by means of ten- sioning bolts 101 located in adjustment slots 102 on the track. The track in this exam- ple is fabricated from mild steel flats. The track comprises a back plate 82 to which spacer plates 81 and captivating guide plates 8 are secured by means of bolts 83. The

carriage 4 comprises a sliding foot which is captivated by the guide plates 8 so that the carriage can slide along the track but is restricted to movement in a plane.

Referring now to Figure 7, this shows an end view of an alternative embodiment in which the carriage 4 is adapted to permit adjustment of the angle at which the power tool 2 is held. In the shown configuration the power tool is again a circular saw, with the saw blade 21 being held at 45'to the vertical. Again, the drive means comprises an electric motor 7 driving a gear box 71 the output shaft 72 of which is connected to a pinion 5 having an array of teeth 51. The teeth 51 engage with a chain 10 to provide drive of the carriage along the track 3. From Figure 7 one can clearly see the foot por- tion of the carriage 4 captivated by the track top plates 8.

Referring now to Figure 8, this shows part of a jointed track assembly. Adjacent longitudinal sections of track 3a and 3b are rigidly held together by means of linking plates 31 and quick release fixing studs 32. The link plates are keyed into the receiving points 9 to maintain the pitching of the drive across the joint between the adjacent track sections. Correct alignment of the adjacent track sections across the joint is further as- sisted by the presence of location dowels 85.

Figure 9 shows the track section along A-A from Figure 8. The track 3 is a one piece aluminium extrusion, such that the captivating rails 8 and the base plate 82 are integral. The track includes longitudinal holes 84 to receive the location dowels 85.

Further details of the link plates can be seen in Figure 10.

A further embodiment of the invention comprises a portable circular saw with an integral gear box. The gear box has two output shafts. One shaft runs at motor speed to drive the saw blade and the other shaft runs at a substantially lower speed and is fitted with a drive pinion. Attached to the portable saw is an under plate designed to be captivated by and slide along a linear slide track. Along the linear slide there is fitted a rack to mesh with the slow speed drive pinion to move the saw at a constant speed along the length of cut. The saw is operated with a simple no volt release switch and a limit switch is provided to bring the saw to rest at the end of its cut. In this embodiment the linear slide is manufactured from a light alloy to facilitate portability. This embodi- ment can provide an extremely accurate straight line cut with a good finish after a sim-

ple setting up procedure. Furthermore, the operation of the power tool throughout the cutting process is achieved safely.

It will be appreciated that in embodiments of the invention the track may be fab- ricated from suitable flats and plates, or alternatively may be formed by an extrusion process. The drive means may conveniently comprise a reduction worm gear unit to drive the power tool along the linear slide.

Certain embodiments of the present invention are particularly suited to the DIY market, and the carriage mounting means may be adapted to accept more than one type of power hand tool.

Another embodiment provides a relatively portable assembly for cutting sheets of heavy material, such as marble. Marble is a material used for work tops and also ex- tensively by monumental masons. To cut large pieces of stone such as marble and granite it has traditionally been necessary to transport the extremely heavy sheets of material to suitable robust fixed cutting equipment. This transportation is clearly diffi- cult, and has associated with it the risk of breaking the work piece. Embodiments of the invention can provide a solution to these problems as the power tool and guide assem- bly can instead be transported to the work piece. Further embodiments of the inven- tion are directed to use for finishing the edges of large steel sheets for example. As with the marble and granite sheets mentioned above, transportation of large metal sheets to appropriate tooling is difficult, and the power tool and guide assemblies of cer- tain embodiments of the invention provide the advantage that they may be conveniently transported to the work piece at a convenient location.

Embodiments of the present invention may also be used to work on vertical sur- faces such as walls, and timbers in situ. For example, with a power tool in the form of a router the guide rail assembly can be attached to a wall so that the router can chase out a channel for housing wiring, pipes or the like. This produces a much neater and more satisfactory end result that the traditional methods of hand chiseling or guiding the router or drill by hand.

It will be appreciated that with the use of a tightly tolerance linear slide and slide adjustment on the underplate, embodiments of the invention can be adapted to

use routers, planers and sanders and the like. Embodiments can be adapted for use in the engineering industry for steel plate edge preparation with the use of a grinding head or milling cutter. The powered guide utilised in embodiments of the present invention can operate in the horizontal direction, on an incline, or even up and down on a vertical plane, such as on a wall to chase out for hiding cables or pipes. Variable speed motors can be used to achieve different speeds and feeds to suit various materials.

It is thus apparent that embodiments of the present invention provide safe, portable, precise labour saving powered guides adaptable to a wide variety of power tools which are normally hand held or bench mounted.

Embodiments of the invention are able to satisfy the requirements of factory based and on-site trades as well as the domestic DIY trade.

A further preferred embodiment of the invention comprises a guided power saw assembly. The main in-coming power supply of the assembly is interrupted to feed a hand held remote control which houses an on/off switch for the saw motor and a forward/reverse switch for the control of the feed motor. A reverse switch is also provided for returning the saw to the start position in anticipation of the next cut.

In certain embodiments of the invention the mounting means for the power tool on the carriage enables the angle of cut to be varied, and also the depth of cut.

During the testing of embodiments of the invention it has become apparent that very light clamping pressure is required to maintain the stability of the assembly on the work piece. The track has been found to be self-cleaning by the motion of the carriage ploughing any material cuttings away from the captivated track. No form of lubrication to the carriage and captivation rails was necessary.

In a further embodiment the drive means further comprises a feed motor brake which facilitates operation when vertical cuts are to be catered for.

Embodiments of the invention are adapted to portable powered wood routing machines, which are extensively used but inherit the same disadvantages as the portable circular saws. Further embodiments are tooled for mild steel plate edge grinding and plate edge preparation (weld preps) which up to now have only been accurately under- taken with the use of expensive fixed bed machines by specialist engineering companies.

The use of jointed tracks in certain embodiments of the invention places no limitation on the length of plate to be worked. This is in contrast to the problems associated with existing fixed bed machines.

Preferably the drive motor is a commutator type DC motor. The out put speed can be varied by the use of a thyristor, which is less expensive than a frequency inverter for varying the speed of a single phase induction motor. To reduce the overall length of the saw/feed motor undercarriage, the feed motor is preferably positioned in-board, which results in less overhang of the track assembly. The jointed track used in certain preferred embodiments results in no limitation on overall track length, and improves portability. Preferably, the drive means comprises a roller link chain with a toothed sprocket locating in the links of the chain. This type of drive is less sensitive to pitch variations, which may occur on track joints, and the cost to manufacture is less than on alternative rack and pinion type drives. There is also the possibility of cut fines becom- ing lodged between rack and pinion type drives creating high separating forces resulting in premature failure of the gearbox. Trials using a roller link chain have shown the method to be self-cleaning.

Portable systems embodying the present invention are particularly useful for stone masons, as by transporting the cutting apparatus to the work piece, the problems associated with the task of transferring stock marble, granite, etc from the stocking area onto the traditional machine beds are avoided.