GB2096942A

GB2096942A - Saw

Info

Publication number: GB2096942A
Application number: GB8207686A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-04-21
Filing date: 1982-03-16
Publication date: 1982-10-27
Also published as: GB2096942B

Abstract

Motor 17 is mounted for swinging about an axis provided by spindle 19 for saw blade 14 to be withdrawn into guard 13 or to protrude through base plate 10 which is connected to bedplate 26, having guide flange 31, by pivot bolt 27. Spring 37 loads the bedplate towards an inoperative position in which guide flange 31 is parallel to the plane of the blade 14. When swingable arm 33 is brought to its illustrated position it turns eccentric body 32 to cause the blade 14 to be angled relative to the guide flange 31 and it brings stop 34 into an operative position limiting the downward protrusion of the blade by providing an abutment for the motor 17. This arrangement enables a shallow slot of width greater than the blade thickness to be made during a first traverse across a workpiece (with the saw teeth attacking the workpiece on entry and thereby avoiding chipping of any surface facing) and the workpiece to be cut right through in a subsequent traverse. <IMAGE>

Description

SPECIFICATION Saw This invention concerns portable power saws of the kind comprising a planar base plate whereon is mounted a motor which serves to drive a circular saw blade accommodated within a guard and adapted to protrude below the under-surface of the base plate for effecting a sawing operation on a workpiece.

I have already proposed, in my prior patent application No. 8030021, a construction of saw wherein a latch arrangement permits a first traverse of the saw to be made over a workpiece with the blade protruding by only a small amount so as firstly to cut only a groove or slot in the workpiece, followed by a second traverse with the blade protruding fully to cut right through the workpiece. This cutting sequence is of particular advantage in the sawing of melamine-faced and like faced or laminated sheet materials in that it will avoid chipping of the surface material along the edges of the cut.

I have also proposed, in my aforesaid prior patent application, for the possibility of angling the saw so that the plane of the blade is at a very slight angle relative to a straight edge, along the side of the base plate, used for guiding the saw when cutting a workpiece. This arrangement permits the use of the saw in such a way that the cut produced by the blade is wider than the kerf width of the blade. In the cutting of faced sheet materials or boards using two traverses as above discussed, the saw is preferably angled during the first traverse so that the groove or slot then produced is wider than the saw blade thickness.

This ensures that there is a clearance between the blade and the walls of the groove or slot during the second traverse when the blade is in its parallel position.

My prior patent application No. 8107725 (which is divided from the said application No.

8030021) is specifically directed towards this feature of providing for the angle of the blade to be varied for producing a cut wider than the blade thickness.

The arrangements described in the specification of my prior applications aforesaid are particularly designed substantially for automatic operation and if it is desired to adapt an existing saw thereto, a significant amount of work and modification is involved. An object of the present invention is to provide a very much simplified arrangement which enables the blade angle to be varied as aforesaid and can, also, be adapted to serve to define depths of projection of the blade for cutting a slot or groove only, if desired, the arrangement being such that existing saws can be adapted thereto very simply.

With this object in view, the present invention provides, as a first feature, a device for use in conjunction with a portable power saw, of the kind above referred to, to enable its blade to be angled relative to its direction of cut, whereby to permit production of a slot wider than the thickness of the blade, in the form of a bedplate adapted for the saw's base plate to be secured thereon for limited pivotal movement relative thereto, the bedplate including a cam, eccentric or like adjuster disposed so as to face a lateral guiding edge of the base plate, whereby actuation of said cam, eccentric or like adjuster will vary the angular disposition of the base plate on the bedplate and thus correspondingly vary the angular disposition of the saw blade relative to a respective lateral guide edge on the bedplate.

A manually-shiftable arm is preferably provided for varying the position of the cam, eccentric or the like.

For use in the case where the motor and blade are mounted on the base plate for up and down swinging movement, the adjusting arm is preferably so disposed that its free end can serve as a stop which defines the possible depth of descent of the blade. For this purpose, the free end of the adjusting arm preferably carries a stop member of adjustable height, against which a part of a body of the saw, or its drive motor, will abut when the motor and saw blade are swung down for the blade to protrude through the base plate.

The invention further provides, as a further feature thereof, a portable power saw of the kind referred to characterised in that its base plate is secured to a bedplate for limited pivotal movement relative thereto, there being a cam, eccentric or like adjuster carried by the bedplate and disposed so as to face a lateral guiding edge of the base plate, whereby actuation of the cam, eccentric or like adjuster serves to vary the angular disposition of the base plate on the bedplate and thus correspondingly vary the angular disposition of the saw blade relative to a respective lateral guide edge on the bedplate.

Preferably the guide edge of the base plate is flanged to provide a relatively broad guide surface which latter faces the cam, eccentric or like adjuster, and this guide edge or flange may provide or mount abutment means which serves to permit determination of a predetermined relative disposition (e.g. a parallel relationship) of the guide edges of the base plate and the bedplate. This abutment means may comprise a screw or the like lockable in a flange of the base plate and facing an adjacent flange along the guide edge of bedplate; preferably, however, it comprises a screw or the like lockable in the flange of the bedplate and facing an abutment lug or a flange on the base plate.

A spring or like resilient means is preferably provided, for example between the two flanges, for urging the base plate towards its position abutting the cam, eccentric or like adjuster or to its parallel position. This spring may be a flat spring or leaf spring between the two flanges, or it may be a coiled or helical spring.

The arrangement is preferably such that the saw blade, and the motor driving it, are mounted on the base plate for up and down swinging movement. Then, the cam, eccentric or like adjuster is preferably provided with an actuating arm which serves, in an operative position corresponding to the blade being angled relative to the guide edge of the bedplate, as a stop defining the possible depth of descent of the blade. This stop may be adjustable.

In order that the invention may be fully understood, it will be described further, by way of example, with reference to the accompanying drawing, in which:~ Fig. 1 is a perspective view illustrating diagrammatically a practical embodiment of the saw of the invention; Fig. 2 is a fragmentary detail illustrating a first modification; and Fig. 3 is a view similar to Fig. 2 but illustrating a second modification.

In the various figures of the drawing, similar reference numerals have been allocated to similar parts.

The embodiment of the portable power saw conforming to the invention as illustrated in Fig. 1 comprises a planar base plate 10 having a lateral guiding edge 11 along which is a flange 12.

Formed integrally with the base plate 10, at its side remote from the flange 12, is an upstanding blade guard 13 the purpose of which is to protect a user against accidental contact with a circular saw blade 14 only part of which is visible in the drawing through an aperture 15 in the guard 13. A suction connection 16 enables suction to be applied to the guard 13, if desired, for conducting away saw-dust.

The saw blade 14 is mounted upon a shaft (not visible) of an electric motor 17 which is mounted by way of a yoke 18 so as to be swingable up and down about a pivot axis, substantially parallel to the plane of the base plate 10, provided by a pivot spindle 19 extending through the arms of a Ushaped bracket 20 fixed to the base plate 10. A helical compression spring 21 abutting by one end against a tongue 22 secured to the yoke 18 and the other end against a cup 23 fixed to the base plate 10 urges the motor 17 upwards to a rest position in which the blade 14 is disposed wholly within the guard 13 and none of the periphery of the blade 14 protrudes downwards below the plane of the base plate 10. A manually releasable latch (not shown) is provided for retaining the arrangement in the rest position.

The motor 17 is fitted with a handle 24 by which it may be traversed back and forth across a workpiece (not shown) and this handle 24 incorporates a trigger switch 25 by which the motor 17 may be controlled.

The saw can be used in the form so far described, with the base plate 10 resting directly upon and sliding across a workpiece (not shown) being cut and the flange 12 along the guiding edge 11 being guided along a guide fence or other suitable saw guide arrangement (not shown). The spring 21 is operative to ensure that the saw blade 14 protrudes below the base plate 10 only when the user, after having released the latch, applies an appropriate downward pressure by way of the handle 24, so that cutting is effected only when specifically required by the user and ceases as a result of rising of the motor 7 and blade 14 upon relaxation of the downward pressure.

In accordance with the present invention, however, the saw is fitted with a planar bedplate 26 on which the base plate 10 rests. This bedpiate 26 has the base plate 10 secured thereto by a pivot bolt 27 providing a pivot axis which is substantially perpendicular to the planes of the plates 10 and 26 and which extends through or close to the axis of rotation of the shaft of the motor 17, as close as is practicable to the saw blade 14. This arrangement permits the base plate 10 to pivot relative to the bedplate 26 whilst being loosely held thereto by one or more studs 28 secured to the bedplate 26 and projecting through a slot or respective slots 29 in the base plate 10.

At the guiding edge of the base plate 1 0, the bedplate 26 projects therepast and terminates at a respective lateral guide edge 30 provided with a respective flange 31 which is approximately parallel with the flange 12. Pivotally mounted on the bedplate 26 in the projecting part thereof, by means of a pivot 40, so as to be disposed between the two flanges 12 and 31 is an eccentric adjusting member in the form of a circular body 32 having a lobe on which is a chordally-disposed flat. To enable it to be actuated manually, the body 32 has an arm 33 fixed by one end thereto so as to extend across the flange 12 and terminate above the base plate 10. At its free end, the arm 33 is fitted with a stop member indicated generally by the reference numeral 34.This comprises a lower rest part 35 of height sufficient to maintain the arm 33 in a disposition substantially parallel to the plane of the base plate 10, and an upper adjustable part 36 the height of which can be adjusted (e.g. by twisting) and locked as required.

The axis of rotation of the eccentric body 32 is offset relative to an imaginary plane perpendicular to the flange 31 and extending through the pivotal axis of the pivot bolt 27. This ensures that, upon rotation of the body 32 by means of the arm 33, reaction of the lobe of the body 32 against the flange 12 causes the base plate 10 to pivot about the bolt 27 thereby swinging the saw so that the plane of the saw blade 14 is not parallel with the guide edge 30 but is at a very slight angle relative thereto. In the fully rotated position of the body 32, corresponding to the maximum angle of the blade 14 relative to the guide edge 30, the flat on the lobe of the body 32 faces and abuts the flange 12. With the saw so set up, the saw blade 14 will, as has already been described, produce a cut which is slightly wider than the thickness of the blade 14.

The pivot 40 securing the eccentric body 32, to the bedplate 26 is adjustable (e.g. by being adjustably secured in a slot in the bedplate 26) to permit variation of the degree of angling of the saw blade 14 achieved by rotation of the body 32.

The pivotal movement of the base plate 10, as just described, occurs against the action of a return spring, which in the illustrated case is a helical spring 37, disposed between the confronting flanges 12, 31 at a location so as to tend to resist the action of the eccentric body 32.

Thus, the spring 37 serves, by loading the flat on the body 32 against the flange 12, to ensure that the body 32 and arm 33 remain in the illustrated position during the initial traverse.

When the body 32 is moved to an inoperative position, corresponding to the lobe on the body 32 facing away from the flange 12, the spring 37 urges the base plate 10 back to a rest position in which the plane of the blade 14 is parallel to the guide edge 30, a lockable abutment screw 38 through the flange 12 enabling this parallel position to be finely adjusted.

The manner of cutting a workpiece with the saw, using two traverses, as described in the introduction hereto, will readily be understood from the foregoing description. For the initial traverse, in which the saw blade 14 is required to protrude only by a restricted amount below the bedplate 26, the arm 33 is moved into the illustrated position in which it is retained by reason of the flat on the eccentric body 32 abutting the flange 12 and in which (a) the blade 14 is angled relative to the guide edge 30 to ensure that the cut produced by the blade is wider than the blade thickness, and (b) the body of the motor 17 abuts against the stop member 34 with the result that the blade 14 is prevented from protruding fully below the plate 26 and only a relatively shallow slot is cut in the workpiece.At the end of this initial traverse, the user's pressure on the handle 24 is relaxed to permit the motor 1 7 and blade 14 to rise under the action of the spring 21. Then, the arm 33 is swung to its inoperative position with the lobe on the body 32 no longer abutting the flange 12, which permits the base plate 10 to shift back to its parallel disposition under the action of the spring 37. The second traverse is now effected, and since the stop member 34 is out of the path of the up and down movement of the motor 17, the blade 14 can now protrude to its full extent below the bedplate 26 to cut right through the workpiece.

The invention is not confined to the precise details of the foregoing example which have been given for the purpose of illustrating the invention, and variations may be made thereto. Thus, for example, as shown in Fig. 2, in the place of abutment screw 38 through the flange 12, an adjusting screw 50, provided with a locking nut 51, may be threadedly located in a boss 52 fixed to the flange 31. With this construction, the saw can be used in conventional manner straightaway upon removal of the bedplate 26, since it involves no obstruction on the flange 12, whereas in the Fig. 1 construction, the abutment screw 38 has to be removed to leave the flange 12 unobstructed when the saw is to be used without the bedplate 26.

The same advantage is obtained with the construction of Fig. 3 in which no flange is provided along the lateral guiding edge 11. In this case, the adjusting screw 50 faces an integral lug 53 upstanding from the base plate 10.

Other modifications are possible. For instance, the motor 17 and the blade 14 of the saw can be mounted upon the base plate 10 in any suitable manner, and any appropriate form of spring and/or other return means may be provided for returning the saw to its rest position with the blade 14 wholly within the guard 13. Any suitable arrangement may be provided for mounting the base plate 10 upon the bedplate 26 (which may be of any suitable planar material) so as to be pivotable relative thereto, and means other than the eccentric body 32 may be provided for effecting the pivoting. Use could be made, for instance of a cam, a two-link or three-link toggle, or any other suitable arrangement. As has already been described use can be made of a leaf spring or other suitable resilient means for loading the two plates 10, 26 towards their parallel disposition against the action of the eccentric body 32 or the like. Other modifications are, of course, possible.

It is possible, for ease of use to make the bedplate immediately detachable by providing a simple pivot pin in the place of the bolt 27, in which case, two or more bolt-end slot arrangements 28, 29 may be employed to hold the bedplate pivotally to the base plate.

Claims

1. A device for use in conjunction with a portable power saw, of the kind above referred to, to enable its blade to be angled relative to its direction of cut, thereby to permit production of a slot wider than the thickness of the blade, in the form of a bedplate adapted for the saw's base plate to be secured thereon for limited pivotal movement relative thereto, the bedplate including a cam, eccentric or like adjuster disposed so as to face a lateral guiding edge of the base plate, whereby actuation of said cam, eccentric or like adjuster will vary the angular disposition of the base plate on the bedplate and thus correspondingly vary the angular disposition of the saw blade relative to a respective lateral guide edge on the bedplate.

2. A device as claimed in claim 1 wherein a manually-shiftable arm is provided for varying the position of the cam, eccentric or the like.

3. A device as claimed in claim 2, for use in conjunction with a power saw in which the motor and blade are mounted on the base plate for up and down swinging movement, the adjusting arm being so disposed that its free end can serve as a stop which defines the possible depth of descent of the blade.

4. A device as claimed in claim 3 wherein the free end of the adjusting arm carries a stop member of adjustable height, against which a part of a body of the saw, or its drive motor, abuts when the motor and saw blade are swung down for the blade to protrude through the base plate.

5. A portable power saw of the kind referred to characterised in that its base plate is secured to a bedplate for limited pivotal movement relative thereto, there being a cam, eccentric or like adjuster carried by the bedplate and disposed so as to face a lateral guiding edge of the base plate, whereby actuation of the cam, eccentric or like adjuster serves to vary the angular disposition of the base plate on the bedplate and thus correspondingly vary the angular disposition of the saw blade relative to a respective lateral guide edge on the bedplate.

6. A saw as claimed in claim 5 in which the guide edge of the base plate is flanged to provide a relatively broad guide surface which latter faces the cam, eccentric or like adjuster.

7. A saw as claimed in claim 6 wherein the guide edge or flange provides an abutment means which serves to permit determination of a predetermined relative disposition of the guide edges of the base plate and the bedplate.

8. A saw as claimed in claim 7 wherein the abutment means serves to determine a parallel relationship of the guide edges of the base plate and the bedplate.

9. A saw as claimed in claim 7 or 8 wherein the abutment means comprise a screw lockable in a flange of the base plate and facing an adjacent flange along the guide edge of the bedplate.

10. A saw as claimed in claim 7 or 8 wherein the abutment means comprises a screw or the like lockable in the flange of the bedplate and facing an abutment lug or flange on the base plate.

11. A saw as claimed in any of claims 5 to 10 further including a spring or like resilient means for urging the base plate to its parallel position.

12. A saw as claimed in any of claims 5 to 11 in which the saw blade and the motor for driving it are mounted on the base plate for up and down swinging movement, the cam, eccentric or like adjuster being provided with an actuating arm which serves, in an operative position corresponding to the blade being angled relative to the guide edge of the bedplate, as a stop defining the possible depth of descent of the blade.

13. A saw as claimed in claim 12 wherein the stop is adjustable.

14. A portable power saw substantially as hereinbefore described with reference to and as illustrated in Fig. 1, in Fig. 2, or in Fig. 3 of the accompanying drawing.