GB2182280A - Improvements in or relating to guide apparatus for cutting tools - Google Patents

Abstract

In guide apparatus for a cutting tool comprising an elongate track (17) to which a work piece (18) to be cut is held eg by clamps (19), the track has parallel rails (24, 25) and the tool has spaced followers to guide the tool along the track. As shown an electric motor driven circular saw (13) has a base plate on which pairs of guide rollers (32, 33) are mounted in spaced locations to support the saw for movement along the track to effect a cutting operation on the workpiece. One of the rails of the track has an upstanding flange along the length thereof and the rollers (32) of the cutting tool engaging the rail have peripheral grooves to receive and locate on the rail to align the cutting tool with respect to the track and the other rail has a plain surface on which the rollers (33) of the base engage. The track may be formed in lengths with interlocking means so that one or more lengths of track may be utilised to extend beyond each end of the workpiece. The saw body may be adjustable relative to the guide rollers (32, 33). <IMAGE>

Description

SPECIFICATION Improvements in or relating to guide apparatus for cutting tools The invention relates to guide apparatus for cutting tools and is particularly although not exclusively applicable to guide apparatus for portable electric motor-driven circular saws.

When cutting large sheets of material with a cutting tool such as a Portable Circular Saw, a guide consisting of a strasight edge is often used. Two difficulties encountered with usingastraightedge are: 1. Due to friction between the Circular Saw and the material to be cut, it is difficu It to keep the Saw against the straight edge causing irregularity in the cut edge.

2. Due to the Saw being un-suspended during entry and exit from a sheet being cut, it is difficultto geta straight cut both laterally and vertically atthese two points.

The invention provides a guide apparatus for a cutting tool comprising an elongate track, means for mounting the track on a component to be operated on bythecuttingtool,thetrackhaving a pairof parallel rails to support and guide the cutting tool for movement along the track and the cutting tool having spaced apart follower means to support and align the cutting tool with the track and to guide the cutting tool for movement along the track.

The follower means may include first follower means for engaging one of the tracks to support and align the cutting tool in respect of the trackfor movement along the track and second follower means for engaging the othertrackforsupporting the cutting tool.

More specifically the first follower means may comprise two spaced apart follower devices each engageable with one track to run along the track and constrained against lateral movement in either direction with respect to the track whereby the cutting tool is held in alignmentwith respect to the track and the other follower means comprise a further pair of follower devices spaced apartto engage the track at spaced locations and supportthe cutting tool.

For examplethe first follower devices may each comprise a roller having a peripheral groove in which the first track engages whereby the roller is constrained against lateral movement with respect to the track by the sides of the peripheral groove engaging the sides of the track and the second pair of follower devices comprise plain rollers to bear on the surface ofthe second track.

Preferably means are provided for adjusting the position ofthe cutting tool laterally ofthe direction of movement of the cutting tool along the track with respect to the follower devices whereby the line of cut of the cutting tool can be adjusted with respect to the track.

In one construction the cutting tool may have a separate base plate and mounting means are provided for mounting pairs of first and second follower devices at spaced locations along the base plate, the mounting means incorporating means for adjusting the positions of the pairoffollowerdevices with respect to the base plate laterally of the direction of movement of the cutting tool along the trackto adjustthe location of the lineofcutwith respectto the track.

Each pair of first and second follower devices may be mounted on a bracket and means may be provided for clamping the bracket to the base plate of the cutting tool and adjustment means are provided on the bracketforengaging the base plate to adjust the position ofthe pairoffollowerdevices laterally of the base plate with respect to the direction of movement of the cutting tool.

In an alternative construction the follower devices may be mounted directly on the cutting tool.

In any of the above arrangements the track may comprise one or more sections each comprising a pair of rails mounted on an elongate member and means being provided at each end of the section for interlocking the section with the ends offurther sections to provide a track of the required length.

More specifically each section may have a socket at one end and a projecting tongue at the other end to receive and engage respectively a tongue and a socket of adjacent sections to interlocktherewith and hold the rails of the respective sections in alignment with one another.

Byway of example the cutting tool may be a portable power driven circular saw.

The foilowing is a description of specific embodiments ofthe invention, reference being made to the accompanying drawings in which: Figure 1 is a plan view of a cutting tool and trackfor supporting and guiding the cutting tool in the required direction of cut; Figure2 is a front view of the cutting tool and track with the track mounted on a workpiece to be cut; Figure 3 is a plan view of a section of thetrack; Figure 4 is a section along the line 4-4 on Figure 3; Figure5is a section along the line 5-5 on Figure3; Figure 6 is a detailed view of the guide rol lers and mounting means for attachment to the cutting tool for supporting the tool on the track; and Figure 7 is a detailed view of one of the guide rollers engaging a rail of the track.

Referring firstly to Figures 1 and 2 of the drawings, there is shown a cutting tool in the form of a portable electric motor-driven circular sawindicated generally at 10 and comprising a base plate 11 on which a housing 12 containing an electric motor drive is mounted. The motor has an output shaft to which a circular saw blade 13 is attached which is partially enclosed in a retractable housing 14 of conventional construction. A motor housing 12 is pivotally mounted on the base plate 11 to vary the angle ofthe cut with respectto the base plate and an arcuate slotted plate 15 is mounted on the base plate and is engaged bya clamp locked and released bya knob 16 connected to the motor housing.Normally the motor housing is locked to the base plate with the plane of the cutting blade 13 extending transversely to the plane of the base plate.

The base plate of the motor is supported on attack indicated generally at 17 which is clamped to the workpiece 18to be cut by means of conventional G-clamps one of which is indicated at 19. One section or length of the track is shown in greater detail in Figures 3 to 5 to which reference will now be made.

The section of the track illustrated comprises an elongate support member 20 having laterally extending plate 21 and 22 at opposed ends thereof and 23 disposed partway along the member. Parallel rails 24,25 are secured to the laterally extending plates 21 to 23. Rail 24 is mounted atthe ends ofthe plates 21 to 23 and is of "L-section". Rail 25 is disclosed partway along the plates 21 to 23 and it is of rectangular cross-section. Atone end of the section, the plate 21 is partly cut-away between the rails to provide a recess 26 and atthe other end ofthe section, plate 22 is formed with a projecting tongue extending from between the rails. Thus one section may be interlocked with another section by engagement of the tongue at one end of the section in the recess at the end of the adjacent section.

To mount the base plate ofthe cutting tool on the track, the base plate 10 has "L-section" bracket members 28,29 extending across and mounted at the ends of the base plate. Each bracket 28 carries a pairofclamping members 29 spaced apart along the bracket having screws 30 for clamping the bracket to the base plate. Further the brackets support between them a spindle 31 one end of which carries a guide roller 32 engaging track 24 and the other end of which carries a guide roller 33 for engaging the track 25.The guide roller 32 is formed with a peripheral groove 32a in which the upper edge portion ofthe track 24 engages so thatthe side cheeks of the guide roller on either side of the groove engage either side of the track 24. The groove 32a is dimensioned so that the track 24 is a close sliding fit in the groove and the guide rollers 32 are thereby positively constrained against lateral movementwith respect to the track whilst being permitted to run along the track. By reason ofthe guide rollers 32a at each end ofthe base 11,the cutting tool is held in alignment with respect to the track and thereby the workpiece on which the track is mounted.The rollers 33 have a plain cylindrical outersurfaceto bear on the rail 25 and thereby assist in supporting the cutting tool for movement along the track. At the side of the base plate 11 remote from the cutting blade of the saw, the brackets 28,29 are provided with lateral adjustment devices for adjusting the position ofthe base plate and thereby the saw with respectto the guide rollers.

The adjustment devices comprise mounting blocks 34 secured to the ends of the brackets through which screws 35 extend to bear against the side of the base plate 11. To adjust the position ofthe sawwith respect to the guide rollers, the clamping screws 30 are slackened slightly and then the screws 35 can be adjusted in either direction as required to move the line of cut of the saw blade with respect to the guide rollers and in particular with respect to the laterally constrained guide rollers 32. When the adjustment has been effected, the screws 30 are tightened to lock the saw with respect to the base plate.

As indicated above, the track may be formed in sections of a conveniently portable length. For example the track may be formed in 4ft. 6ins. lengths so that when connected together, two such lengths adequately span a standard 8ft length plank of plywood, chipwood, blockboard or plasterboard to perform a cutting operation along the length thereof.

The appropriate number of sections are planked to thesheetorplankto becutorto a work surface on which the sheet or plank is resting using "G-clamps".

The cutting tool is located on the track at one end thereof beyond the end of the workpiece to be cut ready for the cutting operation. If necessary, the position of the cutting tool is adjusted utilising the screws 35 to set the cutting blade in the required line of cut. The motor is then switched on and the tool is advanced along thetrackto engage the workpiece.

The track provides an accurate linear guideforthe cutting tool so that once the cutting blade has been located in linewith a required line of cut, the cutting operation can readily be performed without risk of the cutting blade deviating from the required line of cut. Since the saw is constrained laterally bythe engagement of the rollers 32 with the rail 24 ofthe track. Since the rail 24 projects upwardlyfrom the track, any chippings, dust or other swarfformed by the cutting operation does not accumulate on the rail and does not therefore build up under the rollers32a and cause the rollers to deviate from the track.The rail 24 is disposed nearest the cutting blade and it is therefore particularly important that chippings, dust orotherswarfshould notaffectthe proper engagement of the rollers 32 with that rail. the other rail 25 is disposed furtherfromthe line of cut and is therefore less prone to accumulation ofswarffrom the cutting operation and the rollers 33 engaging the track 25 are simple plane rollers merely assisting in supporting the cutting tool on the track and not providing any guidance for the cutting tool so as not to "fight" the guidance and alignment provided by the engagement of the rollers 32 with the rail 24.

At the end of the cutting operation, the cutting tool is guided cleanly away from the workpiece so that there is no deviation from the required line of cut at the point of completion ofthe cutting operation.

Once the cutting operation has been completed, the track is then removed from the workpiece and re-positioned as and where required forthe next cutting operation.

Thus instead of a traditional straight edge being clamped to the sheet of material to be cut, a component consisting oftwo rails is clamped on the material with over-hang at each end. The Saw is supportedonthetwo rails by carriage rollers running on the rails. One of each pair of rollers preferably those nearestthe Circular Saw, are goovedtoform a pulley to give guidance on the rail itis placed on,the other wheel of the pair being plain to reduce, friction and competition with the guide rollerthrough lack of tolerance. Thus one ofthe rails namely the one nearest the saw blade acts as a guide rail. The other rail acts as a levelling device. Both rails are raised rails in order to avoid sawdust or swarf interferring with the quidance mechanism. With the rails over-hanging the job to be cut guidance is provided at the lead in and lead out of the job.

By providing adjustment screws, the Saw can be adjusted from the guide rail to the line of cut, the rail to cut distance can be fixed to a precise value i.e.

10mum or 1/2" making the position ofthe rail structure easy to determine.

The rail structure has atthe rear of the levelling rail a flat protrusion to enable clamping to the structure on the job, so thatthe ciamps arefree ofthe Circular Saw as it travels along the rail.

The rails are made in sections so that they butt into oneanothertoform anylengthoftrackrequiredfora particular job, to allow easy storage and transportation.

The above device makes it easy to cut very large sheets of material, fibreous or metal, easily single handed. It gives very precise control of the cut, the friction having been reduced meansthatlittle effort is required during the cutting process.

Additional means can be provided to enablethe saw blade to tilt so that a non-right angle cut can be made, this is achieved by having the base plate made in two parts hinged atthefront,with a clamping arrangement at the rearto enable the angle required to be placed on the saw blade.

It will be appreciated that many modifications may be made without departing from the scope of the invention. For example the base plate may be omitted and the brackets carrying the rollers for engaging the track rails may be mounted directly on the body of the saw.

Claims (12)

1. A guide apparatus for a cutting tool comprising an elongate track, means for mounting thetrackon a component to be operated on by the cuttingtool,thetrackhavingapairofparallel raisto support and guide the cutting tool for movement along the track and the cutting tool having spaced apartfollower means to support and align the cutting tool with the track and to guide the cutting tool for movement along the track.

2. A guide apparatus as claimed in claim 1 wherein the follower means include firstfollower means for engaging oneofthetrackstosupportand align the cutting tool in respect of the track for movement along the track and second follower means for engaging the othertrackfor supporting the cutting tool.

3. A guide apparatus as claimed in claim 2 wherein the firstfollower means comprise two spaced apartfollower devices each engageable with one trackto run along the track and constrained against lateral movement in either direction with respect to the track whereby the cutting tool is held in alignment with respect to the track and the other follower means comprise a further pair offollower devices spaced apart to engage the track at spaced locations and support the cutting tool.

4. A guide apparatus as claimed in claim 3 wherein the firstfollower devices each comprise a roller having a peripheral groove in which the first track engages whereby the roller is constrained against lateral movement with respect to the track by the sides of the peripheral groove engaging the sides of the track and the second pair of follower devices comprise plain rollersto bearonthesurfaceofthe second track.

5. A guide apparatus as claimed in any of the preceding claims wherein means are provided for adjusting the position of the cutting tool laterally of the direction of movement of the cutting tool along the track with respect to the follower devices whereby the line of cut of the cutting tool can be adjusted with respect to the track.

6. A guide apparatus as claimed in claim 5 wherein the cutting tool has a separate base plate and mounting means are provided for mounting pairs offirst and second follower devices at spaced locations along the base plate, the mounting means incorporating means for adjusting the positions of the pair offollower devices with respect to the base plate laterally of the direction of movement of the cutting tool along the track to adjust the location of the line of cut with respect to the track.

7. A guide apparatus as claimed in claim 6 wherein each pair of first and second follower devices is mounted on a bracket and means are provided for clamping the bracket to the base plate of the cutting tool and adjustment means are provided on the bracket for engaging the base plate to adjust the position of the pair of follower devices laterally of the base platewith respect to the direction of movementofthe cutting tool.

8. A guide apparatus as described with reference to and as illustrated in the accompanying drawings.

9. A guide apparatus as claimed in any of the preceding claims wherein the track comprises one or more sections each comprising a pair of rails mounted on an elongate member and means being provided at each end of the section for interlocking the section with the ends of further sections to provide a track of the required length.

10. A guide apparatus as claimed in claim 9 wherein each section has a socket at one end and a projecting tongue atthe other end to receive and engage respectively a tongue and a socket of adjacent sections to interlock therewith and hold the rails of the respective sections in alignment with one another.

11. A guide apparatus as claimed in any of the preceding claims wherein the cutting tool is a power driven circularsaw.

12. A cutting apparatus substantially as described with reference to and as illustrated in the accompanying drawings.