GB2345461A

GB2345461A - Reciprocating saw blade provided with abrasive for scribing a workpiece

Info

Publication number: GB2345461A
Application number: GB9925862A
Authority: GB
Inventors: Uwe Engelfried; Arnold Hug; Urs Karlen
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-11-09
Filing date: 1999-11-01
Publication date: 2000-07-12
Anticipated expiration: 2019-11-01
Also published as: DE29819959U1; GB9925862D0; FR2785563A1; GB2345461B

Abstract

A reciprocating saw blade (12, fig 1) for coupling with a hand-held reciprocating power saw (9, fig 1), is supported so as to be displaceable to and fro in a guide rail 44 connectable to the hand-held reciprocating power saw. The saw blade comprises a saw blade tip 123, a clamping end 124, and also a saw blade back 121 and a row of teeth 122. A region of the row of teeth and/or of the saw blade back has a saw tooth-free region, which is provided with abrasive 60, and used for scribing a workpiece. The saw blade may be disposed offset parallel to the centre plane of the guide rail 44 in such a way that the saw blade extends flush with an outer side of the guide rail, or projects beyond it. Preferably the saw blade has a front region 120, and the saw blade tip projects in a forward direction beyond the guide rail.

Description

2345461 Reciprocating saw blade

Background art

The invention proceeds from a reciprocating saw blade according to the preamble of claim I and according to claim 5.

From EP patent application 979 228 47.5 a hand-held reciprocating power saw is known, which takes the form of a motor-operated precision cutting saw for flush sawing workpieces. It comprises a saw blade, which is made of particularly flat sheet steel and which in the region of its back is held in a U-shaped guide, which partially overlaps both flat sides and stiffens the saw blade. Said saw blade is disposed with one flat side laterally cranked to such an extent that said flat side extends flush with the outer side of one of the limbs of the U-shaped stiffening. As a result, flush sawing of e.g. the bottom edges of a door frame opposite a newly laid wooden floor or the like is possible, wherein the cranked flat side duning sawing rests on the floor and is brought into tool action at a minimal distance from the floor and wherein only the guide piece limits the depth of cut.

Saw blades of said type are known also from precision cutting hand saws which, on the stiffening guide, carry a handle for moving the saw back and forth.

For the hand-held reciprocating power saw, saw blades are also provided which are not cranked to one side of the U-shaped guide or stiffening piece but are guided centrally between the limbs of the latter, wherein a substantial region of the saw blade projects in forward direction beyond the stiffening piece. Witb said saw 2 blades it is possible to saw through workpieces without the stiffening piece limiting the depth of cut.

As a result, the scope for using precision cutting saws or hand-held reciprocating power saws with a flush saw blade has up till now been limited to a depth of cut which corresponds to the saw blade width up to the bottom edge of the stiffening piece.

Advantages of the invention The reciprocating saw blade according to the invention for a precision cutting saw or hand-held reciprocating power saw for flush sawing has the advantage that, even when flush sawing with the precision cutting saw, the depth of cut is now no longer limited and so the scope for using precision cutting saws is considerably widened. Furthermore, by virtue of the characterizing features of claim 5 a reliable positioning of the saw blade on an intended line of action of the tool is possible in that said region is previously notchable by means of an abrasive-coated region of the saw blade in the manner of centring with a centre punch to prevent run-out of the bit during drilling.

The abrasive, because it is fastenable detachably to the saw blade, is easily renewable.

By virtue of using hard metal flakes as an abrasive, a particularly effective cut is ensured during scribing.

3 By virtue of the fact that a saw-tooth-free, straight region of the saw blade is coated with hard metal flakes, particularly sensitive, lowvibration scribing or marking of the line of action of the tool is possible.

By virtue of the fact that the region of the saw blade provided with abrasive is disposed immediately adjacent to and in alignment with the row of saw teeth, there may be a seamless transition from scribing to sawing through.

By virtue of the fact that the saw-tooth-free region of the of the row of teeth is provided with abrasive, the scribing channel is particularly narrow because its width is determined not by - relatively wide - crossed saw teeth but only by the low - sheet thickness of the saw blade.

By virtue of the fact that the saw blade takes the form of a flush saw blade having a region which projects in forward direction beyond the guide rail, it is usable to particular advantage for flush sawing with an unrestricted depth of cut.

The combination of the flush saw-through blade in the region of its toothed side with abrasive for scribing purposes is advantageous because by said means a drifting/shifting of the saw blade at the start of the sawing-through action is preventable.

Drawings The invention is described below with reference to embodiments and the accompanying drawings. The drawings show:

4 Figure I a longitudinal section of a hand-held reciprocating power saw with a flush saw-through blade according to the invention, Figure 2 a cross section of the hand-held reciprocating saw according to Figure 1, Figure 3 the plan view of a flush saw-through blade, Figure 4 a further embodiment of the flush saw-through blade and Figure 5 a plan view of a guide piece of the flush saw-through blade.

Descnption of the embodiments The hand-held reciprocating power saw 9 illustrated in Figure I in longitudinal section and in Figure 2 in cross section comprises a machine housing 10, an electric motor I I accommodated in the latter and an exchangeable saw blade 12, which takes the form of a flush saw-through blade and is described in detail with reference to Figures 3 to 5. Said saw blade may be set by the electric motor I I into an oscillating, reciprocating sawing motion with a preset saw stroke. The electric motor I I comprises a motor shaft 14, which terminates in a pinion 15 forming part of a night-angle gear 16, the output shaft 17 of which is aligned at right angles to the motor shaft 14. The pinion 15 meshes with a contrate gear, which is non-rotatably connected to the output shaft 17.

Seated axially in succession and non-rotatably on the output shaft 17 are an eccentric plate 20, a disk-shaped crank 21 and a connecting rod 22. The connecting rod 22 coupled to the crank 21 carries in its front end region a driving finger 23 for the saw blade 12, which driving finger is axially displaceable.

For coupling the connecting rod 22, a bearing pin 24 extending parallel to the output shaft 17 is fastened in the crank 21. Said bearing pin projects at right angles from the crank 2 1.

The connecting rod 22 is mounted by means of a bearing bush 25 onto the bearing pin 24 and locked against axial detachment by means of a clamping ring 26 inserted into a shaft recess. A needle bearing 27 is disposed between bearing pin 24 and bearing bush 25.

The connecting rod 22 in its front region accommodating the driving finger 23 is guided on both sides in two guide plates, which are fastened to the machine housing 10 and not described in detail, with the result that the drive finger 23 is movable along an exactly Imear path and the connecting rod 22 is unable to yield in an upward direction.

The eccentric plate 20 at its outer periphery accommodates a con-rod 29 for the oscillating drive of a counterbalance weight 30. The con-rod 29 operates against an upper annular shoulder of the eccentric plate 20 and against a disk 31 disposed between eccentric plate 20 and the counterbalance weight 30.

In its front region the con-rod 29, in an eye 291, accommodates in a sliding manner a pin 302 which projects from the counterbalance weight 30. The support of the counterbalance weight 30 is effected by means of four positioning springs (not described in detail), which are pressed and held in the housing 10.

ID 6 For exchangeable clamping of the saw blade 12, a clamping device 33 is provided on the machine housing 10. The clamping device 33 comprises a fastening plate 34 fixed to the machine housing 10. Two locking elements are arranged spaced apart from one another in the direction of the saw stroke on the underside of said fastening plate remote from the machine housing 10, of which locking elements one is designed as a clevis hook 35 and the other as a sphingback retaining plate 36 with a non-illustrated insertion opening. The retaining plate 36 is suspended movably in an opening (not described in detail) formed in the fastening plate 34 and is loaded in the direction of the clevis hook 35 by a spring (not descnibed in detail), which is supported against the retaining plate 36 and against the fastening plate 34. Projecting from the underside of the fastening plate 34 is a journal 39, which is inserted in a captive manner into a bore in the fastening plate 34. The function of the journal 39, which has a high surface hardness, is described with reference to Figures 3 to 5.

Figure 2 reveals that the driving finger 23 driving the saw blade 12 is guided in a bore 221 of the connecting rod 22 and in an oblong hole (not described in detail) of the fastening plate 34. Said oblong hole has a length exceeding the saw stroke so that the oscillating reciprocating motion of the driving finger 23 is not impeded by the fastening plate 34. The oblong hole is provided with a silicone-impregnated felt seal 41 and closed off by a round cover plate 42, which encloses the driving finger 23 and is simultaneously movable linearly with the latter. In so doing, the cover plate 42 slides on the felt seal 41 and hence closes off the machine in an outward direction.

For operation of the hand-held reciprocating power saw 9 a saw blade 12 is provided, which takes the form of a flush saw-through blade and is cranked in 7 such a way that its blade back 121 and its row of teeth 122 lie, as a result of the cranked portion 222, 'in two planes parallel to one another, i.e. the flat side of the saw blade 12 extends flush with the outer flat side of a U-shaped guide rail 44, which embraces the blade back 121. The saw blade is accommodated in a longitudinally displaceable, captive manner in the guide rail 44 and forms with the latter a separate, preferably inseparable unit, which forins a saw ca rtridge 43 clampable into the clamping device 3 3 on the machine housing 10.

Figure 3 shows a saw cartridge 43 for flush left sawing-through and Figure 4 shows a different saw cartridge 431 for right flush sawing- through of workpieces, wherein in the embodiment of Figure 4 the guide rail 44 is so dimensioned that it overlaps approximately half of the length of the blade back 121 of the flush sawthough blade 12, wherein the guide limbs 441 and 442 are supported against each flat side of the flush saw-through blade 12. The saw-through blade 12 therefore projects beyond the guide rail 44, with the result that the region 120 which is not restricted in terms of the possible depth of cut is relatively long and so may be used to saw through relatively large diameters.

The guide rail 44 comprises a sheet-metal piece which, as a result of being folded at a bending edge 443, forms the two guide limbs 441, 442. By means of a tongue-and-slot connection the flush saw-through blade 12 is held captive and guided so as to be longitudinally displaceable to a limited extent in the guide rail 44. The tongue-and-slot connection comprises a slot 58 (indicated by dashes) extending parallel to the blade back 121 in the flush saw-through blade 12 and a tongue-like guide lug 45, which is bent out from the guide limb 441 and into the slot 58. The tongue-and-slot connections delimit the stroke of the flush saw blade 8 12 inside the guide rail 44 and limit the vertical clearance of the saw blade 12 inside the guide rail 44.

The slot length of the slot 58 in the flush saw blade 12 is in said case slightly greater than the saw stroke.

The outer flat side of the guide limb 442 of the guide rail 44 together with the row of teeth 122 defines a plane E (indicated by dashes), in which flush sawingthrough of a workpiece may be effected by the saw blade 12.

Figure 5 shows the inside of the guide limb 441 of the guide rail 44. Here it may be seen that there are provided on the inner surface of the guide limb 441 cams 46 and ribs 47, in which the flat sides of the saw blade 12 are supported. The same applies to the inner surface of the opposing guide limb 442. The height of the cams 46 and ribs 47 is deterinmiable during manufacture of the guide rail 44 so that flush saw blades 12 of differing thickness may be accommodated by the, in principle, identical guide rail 44 simply by varying the dimensions of ribs 47 and cams 46.

The cams 46 and ribs 47 reduce the friction of the saw blade 12 in the guide rail 44 and ensure a defined, low-clearance guidance over the guided length of the saw blade 12. To prevent rubbing of the saw blade back 121 against the bending edge 443, the comers of the bent-round portions of the bending edge 443 are relieved so that the edges of the blade back 121 run free of guidance in the region of the bending radius of the bending edge 443.

9 In the two guide limbs 441, 442 two mutually aligned oblong holes 48, 49 of a length greater than the saw stroke are formed parallel to the blade back 121. Formed collinearly with each oblong hole pair 48, 49 in the saw blade 12 is an external guide 50 for the positive engagement of the driving finger 23. An opening 51 is used to receive the journal 39 projecting from the fastening plate 34 during insertion of the saw cartridge 43 into the clamping device 33. To ensure problem-free engagement of the journal 39, the inside width of the opening 51 is slightly greater than the diameter of the journal. In the region of the opening 5 1, an oblong hole (not described in detail) is disposed in the saw blade 12 itself so that the journal 39 may fully penetrate the saw cartridge 43 transversely without impeding the saw stroke.

Figures 4 and 5 show two lugs 54, 55 which are directed away from one another in longitudinal direction of the saw blade 12, serve as clamping elements and are disposed on the guide limb 44 1. Each lug 54 is bent at the end of the guide limb 441 and each lug 55 is cut and bent out in the opposite direction from the guide limb 441. The clamping device 33 operates on the principle of an alpine ski binding in that the saw cartridge is first fitted by the one lug 55 into the clevis hook 35 and then, using the latter as a fulcrum, by depressing the saw cartridge 43 the associated lug 54 is swivelled, with simultaneous deflection of the retaining plate 36, into the latter's insertion opening 361 and latched therein. After the retaining plate 36 has sprung back, the saw cartridge 43 is fixed by means of clevis hook 35 and retaining plate 36 tightly against the underside of the fastening plate 34. The journal 39 disposed at the underside of the fastening plate 34 and engaging into the opening 51 prevents, on the one hand, rotation of the guide rail 44 itself and also rotation of the saw blade 12 inside the guide rail 44 so that, during sawing, a force acting upon the retaining plate 36 and pressing the latter away in the direction of release of the clamping device 33 is compensated.

In the case of the saw cartridge 43 shown in Figure 3 and having the flush sawthrough blade 12, the latter is cranked to the left and is situated with a part of its blade back 121 in the guide rail 44, wherein a large region 120 of the saw blade 12 projects in forward direction. The oblong holes 48, 49 and the opening 51 in the guide limbs 441, 442 as well as the recess 50 are clearly visible in the saw blade 12.

Claims

1. Reciprocating saw blade for coupling with a hand-held reciprocating power saw (9), which blade is supported so as to be displaceable to and fro in a guide rail (44) connectable to the hand-held reciprocating power saw (9), having a saw blade tip (123), a clamping end (124) as well as having a saw blade back (121) and a row of saw teeth (122), characterized in that a region of the row of saw teeth (122) and/or of the saw blade back (121) has an, in particular saw-tooth-free region, which is provided with abrasive (60) and used for scribing of a workpiece.

2. Reciprocating saw blade according to claim 1, characterized in that the abrasive (60) is fastenable detachably to the saw blade (12).

3. Reciprocating saw according to claim I or 2, characterized in that abrasive grain, in particular hard metal flakes, connected nondetachably to the saw blade (12) are used as abrasive.

4. Reciprocating saw blade according to one of the preceding claims, characterized in that a saw-tooth-free region, in particular the row of teeth (122), is coated with hard metal flakes.

5. Reciprocating saw blade for coupling with a hand-held reciprocating power saw (9), which blade is supported so as to be displaceable to and fro in a guide rail (44) connectable to the hand-held reciprocating power saw (9), having a clamping end (124), having 12 a saw blade back (12 1) as well as a row of saw teeth (122), wherein the saw blade (12) for flush sawing is disposed offset parallel to the centre plane of the guide rail (44) in such a way that the saw blade (12) extends flush with an outer side of the guide rail (44) or so as to project beyond the latter, characterized Mi that the saw blade (12) with a front region (120), in particular with a saw blade tip (123), projects in forward direction beyond the guide rail (44).

6. Reciprocating saw blade according to claim 5, characteni zed in that in the region of the saw teeth (125) which are most remote from the saw blade tip (123), the row of teeth (122) and/or a region without saw teeth (125) aligned therewith is provided for receiving abrasive (60).

7. A reciprocating saw blade substantially as herein described with reference to the accompanying drawings.