GB2336128A

GB2336128A - Manually operated electric sawing machine with a variably fixable saw blade guide

Info

Publication number: GB2336128A
Application number: GB9917548A
Authority: GB
Inventors: Wolfgang Fuchs; Eduard Gansel; Uwe Engelfried
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-12-19
Filing date: 1998-10-22
Publication date: 1999-10-13
Anticipated expiration: 2018-10-22
Also published as: JP2001512377A; CN1248192A; DE19756765A1; TW434070B; WO1999032250A1; GB9917548D0; GB2336128B; CN1100637C

Abstract

The invention relates to a manually operated sawing machine, especially a precision saw, comprising a machine housing (10), a replaceable saw blade (12) and an electric drive mechanism (11) for driving the saw blade (12) in an oscillating sawing movement, back and forth. The aim of the invention is to considerably simplify the construction of the saw blade drive mechanism (11). To this end, the saw blade (12) is accommodated in a guide (44) which is variably fixed to the machine housing (10). The saw blade is able to move lengthways, and is directly driven by a drive mechanism (11) in an oscillating movement in said guide (44).

Description

1 (711 1 HAND-HELD ELECTRIC MACHINE SAW WITH A SAW BLADE GUIDE WHICH CAN

BE FIXED IN POSITION IN A CHANGEABLE MANNER

Prior art

The starting point of the invention is a hand-held electric machine saw, in particular a precision-cutting saw, of the kind defined in the pre-characterising clause of claim 1.

In a hand-held machine saw of the type initially mentioned (DE 196 25 081 A1), it has already been proposed, for the purpose of rapidly changing the saw blade without an auxiliary tool on an oscillating plate which is guided in the machine housing and can be driven so as to travel to and fro in an oscillating manner, to dispose on the said oscillating plate two clamping jaws which are located at a distance from one another in the direction of oscillation of the oscillating plate and can be displaced relative to one another for the purpose of altering the said distance. The two clamping jaws are connected to one another by a coupling unit which can be manually actuated for the purpose of displacing at least one of the clamping jaws.

The oscillating plate is formed by the yoke of a U-shaped metal toolcarrier sheet, the legs of which protrude inwards between the legs of a Ushaped metal ball-carrier sheet which is fixed in position on the machine housing. Travelling balls are disposed between mutually facing legs of the metal tool-carrier sheet and the metal ball-carrier sheet.

Advantages of the invention The hand-held electric machine saw according to the invention having the features in claim 1 has the advantage that, as a result of the guidance of the saw blade 1 CI 2 independently of the machine and as a result of the direct actuation of the saw blade by the electric drive, a substantial simplification of the saw blade drive in terms of design is achieved, which ultimately results in a lowering of the manufacturing costs, and a compact structural shape of the machine is made possible, which shape is of reduced height. Expensive carriage-type guidance of the oscillating plate with the aid of rolling bearings is eliminated and is replaced by a sawing cassette of very shallow build which consists of the guide and the saw blade and may form a self-contained structural unit. The sawing cassette is simply placed on a clamping-in device present on the machine, and pressed in, resilient locking members provided in the said clamping-in device holding the sawing cassette fast automatically. Under these circumstances, the coupling of the saw blade to the electric drive takes place automatically after the insertion of the sawing cassette in the clamping-in device and the switching-on of the machine or the manual displacement of the saw blade in the guide. The operation of changing the sawing cassette can be performed extremely quickly and with any auxiliary tool, so that setting-up times are low.

Advantageous further developments of, and improvements to the hand-held electric machine saw indicated in claim 1 are possible by means of the measures set out in the other claims.

According to one preferred form of embodiment of the invention, the guide has a guide rail which engages, at least partially, over the saw blade back facing away from the saw teeth, and has two guide legs lying on each side. The guide rail possesses clamping-in elements for insertion in the clamping-in device and, in at least one guide leg, an elongated hole extending parallel to the blade back and having a length that exceeds the sawing stroke.

1 (71 3 r_ Constructed in the saw blade is a clearance, collinear with the elongated hole of which there is at least one, for a drive finger which belongs to the electric drive and penetrates in a shape-mating manner. Under these circumstances, the guide rail with the two guide legs can be constructed in one piece as a result of a 1800 bendingover operation. In this case, the inner bent edge does not possess a bending cur-vature but recessed corners, so that the blade back facing away from the saw teeth does not run against the bending radius, so wear and major friction, with the heating- up associated therewith, is avoided. In an alternative form of embodiment, the guide rail may also be of bipartite design. Under these circumstances, each guide leg is manufactured separately, and the two guide legs are riveted to one another along one rim of the leg. The bimartite solution for the guide rail has the advantage of higher processing safety, since the bending-over operation is eliminated and each guide leg can be corrected individually. A collinear elongated hole in one guide leg is sufficient for the free stroke of the drive finger, which penetrates into the clearance in the saw blade in a shape-mating manner. However, for reasons connected with manufacturing tolerances and the possibility of putting the sawing cassette on the clamping-in device when turned by 1801, at least one elongated hole is provided in each guide leg, the two elongated holes being disposed so as to be orientated coaxially, that is to say congruently with one another.

According to one advantageous form of embodiment of the invention. the saw blade is held and guided in the guide rail by means of at least one pin-and-slot connection, each pin-and-slot connection having a slot which runs parallel to the blade back and has a length exceeding the sawing stroke, and a pin which is held on at least one leg, or a tab which is bent out of one leg, which pin or tab Drotrudes'into the said slot. In the event of guide tabs 1 1 (7 is PCT/DE98/03103 4 being bent out, the accuracy of the upper edge of the tab in relation to the bent-over edge must be very precisely correct and harmonise with the saw blade, in order to minimise the vertical play of the latter in the guide rail. The guide tabs are stamped out of only one guide leg so that the vertical tolerance can be better controlled, the saw blade does not run on a boundary point between two guide tabs, and offsetting of the two guide legs does not have any effect. The pin-and-slot connection limits the travel which the saw blade is able to perform inside the guide rail in its condition when demounted from the machine. This is important in order to ensure automatic penetration of the drive finger into the clearance in the saw blade. At the same time, the pin-and-slot connection also limits the vertical play of the saw blade in the guide rail.

According to one advantageous form of embodiment of the invention, cams and/or ribs, on which the saw blade rests, project on that inner face of each guide leg of the guide rail which faces towards the saw blade. These cams and ribs minimise the friction of the saw blade and guarantee defined, lowplay guidance of the said saw blade over its entire length in the guide rail. The height of the cams and ribs can be set during manufacture, so that saw blades of different thickness can be inserted in guide rails of identical construction.

According to one advantageous form of embodiment of the invention, the guide legs of the guide rail are connected running parallel to the saw blade back. In the region of those free longitudinal edges of the guide legs which 'Lace away from the bent-over edge, there is stamped out of one guide leg at least one guide segment, and preferably two guide segments disposed at a distance one behind the other in the direction of sawing, which guide segment(s) abut/s against to one another in one piece via a bent-over edge 1 1 PCT/DE98/03103 the other guide leg and is/are fixedly connected to the latter, preferably by weld points. Under these circumstances, the saw blade itself has a clearance which runs parallel to its blade back and runs out freely at the rear saw blade edge extending transversely to the blade back, and which has a breadth which is little larger than the breadth of the guide segments. This guide, which is provided in addition to the pin-and-slot connection and consists of the guide segments on the guide leg and of the guide clearance in the saw blade, substantially improves the guidance of the saw blade, particularly in the case of socalled ',saw-through blades", since in the case of the latter, the saw blade has the guide rail engaging over it only in a short region of its blade back. The free run- out of the elongated clearance at the rear transverse edge of the saw blade allows the insertion of the saw blade into the guide rail from the front, after which it is then fixed in position in the guide rail, with limited possibility of displacement, by the bending-out of the guide tab into the slot in the saw blade. The welding of the guide rail to four points on the guide segments prevents gaping-open of the guide rail, particularly at the front transverse edge of the said guide rail, beyond which the saw blade projects. Under these circumstances, the distance between the upper edge of the guide segment, of which there is at least one, and the bottom of the bent-over edge of the guide rail is subject to very close tolerances, as is the size of the distance between the upper edge of the guide clearance in the saw blade and the back of the said saw blade, in order to minimise the vertical play of the saw blade. The stamping-in of the two guide segments from only one guide leg has the advantage that the saw blade does not run on a boundary point between the guide segments, offsetting of the two bent legs does not have any effect, and the vertical tolerance can be better controlled. Instead of the stamping-out of guide segments from the one guide leg, it is possible to fasten an intermediate metal sheet of the same width to the inner face of the guide leg by spot- welding.

According to one alternative form of embodiment of the invention, the guide rail is made up of two individually manufactured guide legs, under which circumstances either one guide leg is kept at a distance by being offset and is connected to the other guide leg by welding in the offset region, or else a metal sheet is inserted, for the purpose of achieving the distance between the guide legs, between the guide legs which are of planar and symmetrical design, and is welded to the said two guide legs.

According to one advantageous form of embodiment of the invention, a grease-filled pocket is machined into the bottom of the bentover edge in the region of that front transverse edge of the guide rail which extends transversely to the bent-over edge and beyond which the saw blade projects. The stamped-in grease pocket forms a grease reservoir from which the front transverse edge of the guide rail, which forms a butting edge for the saw blade, is supplied with grease during the sawing operation, and minimises the friction between the saw blade and the guide rail. In order not to impair this effect, the butting edge is designed so as to be completely burr-free, at least on those two inner edges of the two guide legs which 'Lace towards the saw blade.

According to one advantageous form of embodiment of the invention, the clamping-in device has a fastening plate which is fixed in position on the machine housing and has two locking members which are disposed at a distance from one another in the direction of the sawing stroke and of which one is constructed as a hooking-in hook and the other as a back-springing metal holding sheet with a plug-in anerture.

PCT/DE98/03103 7 The clamping-in elements on the guide rail have at least one pair of tabs which project on at least one outer side of the guide rail and correspond with the locking members, and which are preferably bent away from the guide rail. This results in a clamping-in device which is very simple in design and easy to operate and which functions on the principle of a ski- binding, that is to say, hooking-in at the front and latching-in at the rear. If, according to another form of embodiment of the invention, one pair of tabs in each case is disposed symmetrically in relation to the centre line, the blade can be inserted in the clampingin device in a manner rotated by 1800 in the plane of the saw blade. As a result of this, cuts which are flush on the left and on the right are possible, for which purpose the saw blade is completely enclosed in the guide rail with its back and offset in such a way that the blade back and the strip of saw teeth lie in two mutually parallel planes.

If, according to one advantageous form of embodiment of the invention, the saw blade is inserted, with its back, only partially in a short guide rail, an unlimited cutting depth is possible in the front region of the blade. On each guide leg, the guide rail possesses a pair of tabs which correspond with the locking members in the clamping-in device and are disposed symmetrically in relation to the plane of the saw blade. As a result of this, the saw blade can be turned by inserting the guide rail in the clampingin device, on the one hand, with the tabs on the one guide leg and, on the other hand, with the tabs on the other guide leg. The hand-held machine saw can thereby be handled equally well by left and right-handed people when working in corners which are difficult of access. If one pair of tabs on one guide leg is dispensed with, sawing which is flush on the right or left is possible with the saw- through blade.

According to one advantageous form of embodiment of the invention, there projects on the lower side of the fastening plate of the clamping-in device a peg which, after the clamping-in of the sawing cassette in the clamping-in device, penetrates into mutually aligned apertures in the guide legs of the guide rail and into an elongated hole in the saw blade, which hole is coaxial with the said apertures and has a length which exceeds the sawing stroke. The peg prevents twisting of the rail in the clamping-in device and of the saw blade in the guide rail, particularly in the case of a saw-through blade which is only partially received in the guide rail. The peg also nrevents the action of force on the metal holding sheet of the clamping-in device during sawing, and thereby unintentional release of the sawing cassette in the clamping-in device. For the purpose of safe introduction of the peg when the sawing cassette is inserted in the clamping-in device, the apertures in the guide legs are constructed after the fashion of an elongated hole, their clear width which points in the direction of sawing being dimensioned so as to be larger, for example slightly larger, than the diameter of the peg.

According to one advantageous form of embodiment of the invention, the peg is connected to the fastening plate by resistance welding or hot riveting. Both methods have the advantage that the high surface hardness of the peg in the outer region is not impaired.

According to one advantageous form of embodiment of the invention, the drive finger extends essentially at right angles to the plane of the sawing cassette clamped into the clamping-in device, and is guided in an axially displaceable manner and loaded by a spring in the direction of the sawing cassette. Axial guidance of the drive finger, which is preferably of cylindrical construction, is effected in the fastening plate of the clamping-in device 1 n, 9 and in a connecting rod belonging to the drive, the said drive finger carrying a flange which engages over the guide in the connecting rod on the side facing away from the said clamping-in device. The spring, which is constructed as a leaf spring, for axially loading the drive finger is secured on the connecting rod by means of a clamping ring against axial displacement.

According to one advantageous form of embodiment of the invention, the drive finger is guided in the connecting rod in a shape- mating manner and in the fastening plate parallel to the direction of sawing, for which purpose there is provided, in the said fastening plate, an elongated hole which is enclosed by a collar and has a length exceeding the sawing stroke and which is masked by a metal masking sheet enclosing the drive finger. Under these circumstances, the metal masking sheet rests on a felt seal which surrounds the collar of the elongated hole and preferably contains a silicone impregnation. The silicone impregnation has the advantage that the felt does not swell up, and the pre-tensioning between the metal masking sheet and the fastening plate thereby remains within calculable limits, so that the friction produced can be kept within limits. The metal masking sheet prevents the egress of oil towards the outside through the elongated hole in the fastening plate. Because of the axial mobility of the drive finger and of its resilient attachment by means of the leaf spring, it is immaterial, during the changing or putting-in of the sawing cassette, what position the drive finger is in in relation to the saw blade. If the drive finger does not find the shape-mating clearance in the saw blade, it is displaced against the force of the leaf spring. When the electric drive is switched on, the drive finger then travels along the saw blade and automatically latches into the clearance in the saw blade under the action of the leaf spring.

1 n PCT/DE98/03103 According to one advantageous form of embodiment of the invention, the connecting rod, which is articulated on a disc-shaped crank seated in a torsion-proof manner on an output shaft of the drive, is guided on both sides, in its front region which guides the drive finger, in two mountings, for example metal guide sheets, fixed in position on the machine housing. The connecting rod is thereby unable to deviate in the front region, so that the saw blade is driven in an exactly linear manner. The connecting red is articulated on the crank via a rolling bearing, preferably a needle bearing, and a clamping ring enclosed in a recess in the shaft prevents the connecting rod from slipping off the output shaft of the gear unit.

According to one advantageous form of embodiment of the invention, the oscillations originating from the saw blade are reduced by means of a compensating weight which is specially coordinated with the moving masses, namely the saw blade connecting rod, drive finger, etc. The compensating weight is mounted in a longitudinally disulaceable manner in the machine housing and driven to nerform an oscillating displacing movement by a linking rod which is rotatably seated on an eccentric disc connected to L-he output shaft of the gear unit in a torsion-proof manner.

For temnerature-reduction purposes, grease pockets are, according to one advantageous form of embodiment of the nvention, machined-in on the periphery and on the base of the eccentric disc. This improves the lubricating film. iDroduced and feeds grease out of the said pockets a-Eterwards.

According to one advantageous form of embodiment of the invention, the linking rod is fixed in position axially by an annular shoulder on the eccentric and by a disc which, n11 PCT/DE98/03103 for its part, rests against the disc-shaped crank. This prevents tilting of the linking rod when driven.

According to one advantageous form of embodiment of the invention, the compensating weight carries a projecting bolt which is received in a sliding manner in an eye constructed in the linking rod, the said eye having an indentation projecting towards the compensating weight. Because of the indentation, the length of guidance or of engagement between the eye of the linking rod and the bolt on the compensating weight becomes greater, the point of application of force comes closer to the compensating weight, and the moments that occur are reduced.

According to one advantageous form of embodiment of the invention, the compensating weight is guided by means of fixing springs which are disposed in the machine housing and engage over the said compensating weight on its upper and lower sides with the aid of two spring legs in each case. At the same time, the fixing springs also guide the compensating weight at its side rim. This fixing of the compensating weight transversely to the direction of sawing ensures linear movement of the said compensating weight. The fixing springs are preferably inserted in housing shells belonging to the machine housing and are held in the said housing via hooks. The fixing springs guarantee compensation for tolerances between the components, and thereby a play-free course for the compensating weight.

In one alternative form of embodiment of the invention, the compensating weight is guided via four U-bolts which are inserted in the housing instead of the fixing springs. Instead of the four U-bolts, four needle rollers may be used for axial guidance purposes, vertical guidance taking place via ribs on the housing.

1 1 n, Drawings C is PCT/DE98/03103 12 The invention is explained in greater detail in the description below with the aid of an exemplified embodiment represented in the drawings, in which:

figure 1 shows a longitudinal section through a handheld electric machine saw, figure 2 shows a section along the line II-II in figure 1, figure 3 shows a perspective representation of a detail of the machine housing of the machine according to figure 1, with a compensating weight, figure 4 shows a view from below of an eccentric disc in the machine according to figure 1, in the direction of the arrow IV in figure 5, figure 5 shows a section along the 'Line V-V in figure 4, figure 6 shows a plan view of a linking rod belonging to the machine in figure 1, in the direction of the arrow VI in figure 7, figure 7 shows a section along the line VII-VII in figure 6, figure 8 shows a perspective view from below of a sawing cassette for the machine in figure 1, figure 9 shows a perspective plan view of the sawing cassette in figure 8, is PCT/DE98/03103 13 figure 10 shows a section along the line X-X through the sawing cassette in figure 8, figure 11 shows a detail XI of the sawing cassette in figure 9, in longitudinal section, figure 12 shows a detail of the sawing cassette in figure 9, in longitudinal section, figure 13 shows a section along the line XIII-XIII through the sawing cassette in figure 9, figure 14 shows a perspective view of a sawing cassette with a saw- through blade according to another exemplified embodiment, figure 15 shows an enlarged representation of an individual item belonging to the machine in figure 1, with the sawing cassette according to figure 14 attached, figure 16 shows an enlarged perspective representation of a metal holding sheet in figures 1 and 15, figure 17 shows an identical representation to that in figure 14, of a modified sawing cassette with a saw-through blade, figure 18 shows a plan view of the guide rail belonging to the sawing cassette in figure 17, figure 19 shows a section along the line XIX-XIX in figure 18, 1 is PCT/DE98/03103 14 figure 20 shows an enlarged representation of the detail XX in figure 19, figure 21 shows a section along the line XXI-XXI in figure 19, figure 22 shows an enlarged representation of the detail XXII in figure 21, and figure 23 shows a plan view of the saw blade belonging to the sawing cassette in figure 17.

Description of the exemplified embodiment

The hand-held electric machine saw represented in longitudinal section in figure 1 and in cross-section in figure 2 has a machine housing 10, an electromotive drive 11 received in the said housing, and a changeable saw blade 12 which can be driven by the electromotive drive 11 to perform an oscillating sawing movement that travels to and fro, the said saw blade 12 performing a predetermined sawing stroke. The electromotive drive 11 has an electric motor 13 constructed as a commutator motor and having a motor shaft 14 on which a fan wheel 15 is seated in a torsion-proof manner, and an angular gear unit 16, the output shaft 17 of which is orientated at right angles to the motor shaft 14. At its end, the motor shaft 14 carries a spur wheel toothing system 18 which meshes with a crown wheel 19 connected to the output shaft 17 in a torsionproof manner. In this way, large tolerances in the axial displaceability of the motor shaft 14 are admissible, a fact which reduces the manufacturing cost of the gear unit. An eccentric disc 20 and a disc-shaped crank 21 are seated on the output shaft 17 in a torsion-proof manner. Articulated on the crank 21 is a connecting rod 22, in the front end region of which a drive finger 23 for the saw PCT/DE98/03103 is blade 12 is received in an axially displaceable manner. A bearing bolt 24 which extends parallel to the output shaft 17 and projects from the crank 21 at right angles is fastened in the crank 21 for articulating the connecting rod 22. The connecting rod 22 is slipped onto the bearing bolt 24 with the aid of a bearing bush 25 and secured against falling off axially by means of a clamping ring 26 inserted in a recess in the shaft, although the clamping ring 26 may alternatively be dispensed with. Rolling bodies 27 (needle bearings) are inserted between the bearing bolt 24 and the bearing bush 25. Instead of a rolling bearing, it is also possible to use a plain bearing. In its front region which receives the drive finger 23, the connecting rod 22 is guided, on both sides, in two.metal guide sheets 28 (figure 2) fixed in position on the machine housing 10, so that the said drive finger 23 performs an exactly linear movement and the connecting rod 22 cannot deviate upwards.

On its outer periphery, the eccentric disc 20, which is represented in enlarged form in figures 4 and 5, receives a linking rod 29 for driving a compensating weight 30 in an oscillating manner. The linking rod 29 runs on an upper annular shoulder 201 on the eccentric disc 20 and on a disc 31 disposed between the eccentric disc 20 and the compensating weight 30. As can be seen in figure 4, grease Dockets 202 are machined into that lower side of the eccentric disc 20 which faces towards the disc 31, as a result of which the lubricating film produced is improved and grease is fed out of the said grease pockets 202 afterwards. The annular shoulder 201 and disc 31 prevent the linking rod 29 from tilting when driven. A blind bore 203 in the lower side of the eccentric disc 20 and a peg 301 on the crank 21 which penetrates into the said bore 203 guarantee the incorporation of the eccentric disc 20 in the correct location, so that the compensating weight 30 operates exactly in phase opposition to the saw blade 12.

t PCT/DE98/03103 16 In its front region, the linking rod 29, which is represented in enlarged form in figures 6 and 7, receives, in a sliding manner in an eye 291, a bolt 302 (figures 1 and 3) projecting from the compensating weight 30. The bolt 302 may be designed in one piece with the compensating weight 30 or be pressed into the latter. As can be seen in figure 7, the eye 291 has an indentation 292 projecting in the direction of the compensating weight 30, which results in a greater length of guidance or of engagement between 10 the eye 291 of the linking rod and the bolt 302 on the compensating weight 30. As a result of this, the point of application of force is, at the same time, also located closer to the compensating weight 30, so that moments that occur are reduced.

is The compensating weight 30 is mounted in the machine housing 10 so as to be axially displaceable in the direction of sawing. As is apparent from the perspective representation in figure 3, the compensating weight 30 is mounted both in the z-coordinate and also in the ycoordinate, if the xcoordinate coincides with the direction of sawing. Under these circumstances, mounting is effected by means of four fixing springs 32 which are pressed into housing shells 101 and held in the housing 10 via hooks 321. The location of the fixing springs 32 in the v direction is exactly limited by abutment faces constructed in the housing 10. The fixing springs 32 engage, with two spring legs 322 in each case, over the compensating weight 30 on its upper and lower sides, and rest against the said sides with pre-tensioning. The said fixing springs 32 guarantee bor-h compensation for tolerances between the components and also play-free running of the compensating weight 30. The said compensating weight 30 encloses the disc-shaped crank 21 with the aid of an oval clearance 57.

PCT/DE98/03103 17 A clamping-in device 33 is constructed on the machine housing 10 for the purpose of clampingin the saw blade 12 in a changeablemanner. The clamping-in device 33 has a fastening plate 34 which is fixed in position on the machine housing 10 and is represented in enlarged form in figure 15. Disposed at a distance from one another on the fastening plate 34, on the lower side that faces away from the machine housing 10, are two locking members, of which one is constructed as a hooking-in hook 35 and the other as a back-springing metal holding sheet 36 with a plug-in aperture 361 (figure 16). The metal holding sheet 36 is hooked movably into an aperture 341 constructed on the fastening plate 34 and is loaded in the direction of the hooking-in hook 35 by a spring 37 supported on the said metal holding sheet 36 and on the said fastening plate 34. The metal holding sheet 36 has a freely projecting leg 362 by means of which the metal holding sheet 36 can be pivoted, in the direction of the arrow 38 in figure 15, against the force of the spring 37. Projecting on the lower side of the fastening plate 34 is a peg 39 which is inserted in a bore in the fastening plate 34 and is connected to the latter by resistance welding or hot riveting. The function of the peg 39, which. has a high surface hardness, will be further explained below.

As is apparent from figure 2, the drive finger 23 driving the saw blade 12 is guided in a bore 221 in the connecting rod 22 and in an elongated hole 40 in the fastening plate 34. Under these circumstances, the elongated hole 40 (figure 15) has a length which exceeds the sawing stroke, so that L-he oscillating to-and-fro movement of the drive finger 23 is not hindered by the fastening plate 34. Under these circumstances, the elongated hole 40 is surrounded by a collar 342 (figure 15) which is bent out of the fastening nlate 34 and onto which a felt seal 41 with silicone impregnation is slipped (figures 1 and 2). The elongated hole 40 is sealed off by a round metal masking sheet 42 1 PCT/DE98/03103 18 which encloses the drive finger 23 and is moved with the latter in a linear manner. Under these circumstances, the metal masking sheet 42 slides on the felt seal 41 and thus seals off the machine towards the outside. Because of the silicone impregnation, a dimensionally accurate thickness of the felt seal 41 and, as a result of this, tension-free disposition of the connecting rod 22 is achieved.

Two saw blades are intended for operation on the hand-held machine saw: a flush-sawing blade (figures 8 and 9) which is offset in such a way that its blade back 121 and its strip of teeth 122 lie in two mutually parallel planes, and a so-called ',saw-through blade,, (figures 14 and 15 or 17) which is of flat construction. The saw blade 12 is received in a longitudinally displaceable manner in a guide and forms, with the latter, a separate, preferably inseparable, structural unit, which will be referred to below as a ',saw blade cassette" or "sawing cassette" 43 and which is constructed so as to be capable of being clamped into the clamping-in device 33 on the machine housing 10. A sawing cassette 43 for right-hand and left-hand flushsawing is represented in figures 8 and 9, and a sawing cassette 43 for sawing-through is represented in figures 14 and 15 and in figure 17 in each case.

In the exemplified embodiment in figures 8 and 9, the guide is formed by a guide rail 4,- which engages over the back 121 of the saw blade 12 over its entire length and has two guide legs 441 and 442 lying on each side of the blade. In the exemplified embodiment represented, the guide rail 44 is in one piece and the two guide legs 441, 442 are connected to one another in one piece by a bent-over edge 443. Alternatively, the two guide legs 441, 442 may also be manufactured as separate components and then connected to one another, for example riveted, welded or the like, along one longitudinal edge. The saw blade 12 is held in the guide rail 44, and guided for longitudinal displacement 1 1 1 PCT/DE98/03103 19 in a limited manner, by means of two pin-and-slot connections which are disposed symmetrically in relation to the centre line 60 of the sawing cassette 43. Each pinand-slot connection consists of a slot 58 in the saw blade 12 (cf. also figure 23), which slot is indicated in broken lines here and runs parallel to the blade back 121, and of a guide tab 45 which is bent out of the spring leg 441 and into the slot 58. The said pin-and-slot connections limit the travel which the saw blade 12 is able to perform inside the guide rail 44 in its condition when demounted from the machine, and also limit the vertical play of the saw blade 12 in the guide rail 44. Under these circumstances, the length of the two slots 58 in the saw blade 12 is selected so as to be somewhat greater than the sawing stroke of the said saw blade 12. As is apparent from the sectional representation in figure 10, cams 46 and ribs 47, on which the saw blade 12 rests, project on the inner face of the guide leg 441. The same applies to the inner face of the guide leg 442. The height of the cams 46 and ribs 47 can be set during manufacture, so that saw blades 12 of different thickness can be received with the aid of the same guide rail 44. The cams 46 and ribs 47 minimise the friction of the saw blade 12 in the guide rail 44 and guarantee defined, low-play guidance over the entire length of the said saw blade 12. In order to avoid friction of the saw blade 12 against the bent-over edge 443, the corners of the bending curvature in the bent-over edge 443 are recessed, so that the edges of the blade back 121 run freely in the region of the bending radius of the bent-over edge 443. The recess is designated by 59 in figure 13..Pigure 13 also shows that intermediate metal sheets 56, which take over the sliding functions for the saw blade 12, may be fastened on the inner faces of the guide legs 441 and 442 in each case, instead of the cams 46 and ribs 47.

The friction of the saw blade can be minimised, and wear reduced, by suitable selection of the material of the intermediate metal sheets 56.

PCT/DE98/03103 Constructed in the two guide legs 441, 442, parallel to the blade back 121, are two pairs of mutually aligned elongated holes 48, 49 with a length which exceeds the sawing stroke. Under these circumstances, the elongated holes, 48 and 49 respectively, in each guide leg 441, 442 are, once again, disposed symmetrically in relation to the centre line 44. Constructed in the saw blade 12 in a manner collinear with each pair of elongated holes 48, 49 is a clearance 50 (cf. also figure 2) for the shape-mating penetration of the drive finger 23. The two clearances 50 in the saw blade 12 are, once again, disposed symmetrically in relation to the centre line 60. Moreover, two apertures 51 disposed symmetrically in relation to the centre line 60 are disposed in the guide leg 441, and two apertures 52, which are coaxial with the said apertures 512 in each case, are disposed in the guide leg 442. The apertures 51 and 52 serve to receive the peg 39 projecting on the fastening plate 34 (figure 15), when the sawing cassette 43 is inserted in the clamping-in device 33. In order to guarantee trouble-free penetration of the peg 39, the clear width of the apertures 51, 52 in the direction of sawing is dimensioned so as to be slightly larger than the diameter of the peg 34, so that the apertures 51, 52 are slightly oval. An elongated hole 53 (figure 12 and also figure 23) with a hole length which exceeds the sawing stroke is constructed in the saw blade in the region of the apertures SIL, 52 in each case, so that the sawing stroke is not hindered by the peg 39 which penetrates into the apertures 51, 52.

Clamr-ping-in elements are constructed on the guide rail 44 for- clamping the sawing cassette 43 into the clamping-in device 33 of the hand-held machine saw. In the exemplified embodiment in figures 8 to 10, the clamping-in elements have two pairs of tabs 54, 55 which are disposed on one guide leg 441 symmetrically in relation to the centre line 60. Under these circumstances, each tab 54 is bent away at PCT/DE98/03103 21 the end of the guide leg 441 and each tab 55 is cut out and bent out of the guide leg 441 close to the centre line. The clamping-in device 33 functions on the principle of a ski-binding, through the fact that - as is indicated in broken lines in figure 15 - the sawing cassette 43 is hooked, with the aid of one tab 55, into the hooking-in hook 35 and, by pressing down the said sawing cassette 43, the appertaining tab 54 is latched into the plug- in aperture 361 in the metal holding sheet 36, with springing- out of the latter. After the springing-back of the metal holding sheet 36, the sawing cassette 43 is fixed in position in a defined manner on the lower side of the fastening plate 34 by the hooking-in hook 35 and the said metal holding sheet 36. The peg 39 on the underside of the fastening plate 34, which peg penetrates into the apertures 51 and 52, on the one hand prevents twisting of the guide rail 44 and twisting of the saw blade 12 within the guide rail 44, particularly in the case of the saw-through blade, and on the other hand prevents a force from acting upon the metal holding sheet 36 during sawing, and forcing the said metal holding sheet away in the direction of release of the clamping-in device 33. Sawing which is flush on the right and on the left with the aid of the sawing cassette according to figures 8 and 9 is possible by rotating the sawing cassette 43 in the plane of the saw blade 12, for which purpose, now one pair of tabs 54, 55, and now the other pair of tabs 54, 55,- on the guide leg 441 of the guide rail 44 is hooked into the clamping-in device 33. Since all the necessary apertures 51, 52, elongated holes 48, 49, clearances 50 and elongated holes 53 are present twice in the sawing cassette 43, that is to say are disposed symmetrically in relation to the centre line 60, the said sawing cassette 43 interacts with the hand-held machine saw in the same way in both pivoting positions.

In the case of the sawing cassette 43 represented in figures 14 and 15 with the saw-through blade 12, the latter PCT/DE98/03103 22 is not offset but is of flat construction and is enclosed in the guide rail 44 only with part of its back 121. The elongated holes 48, 49 and the apertures 51, 52 in the guide legs 441, 442, and also the clearance 50 and the elongated hole 53 in the saw blade 12 are only present once. One pair of tabs 54, 55, in each case, is constructed on each guide leg 441 and 442, so that the sawing cassette 43 can be inserted in the clamping-in device 33, now by the guide leg 441 and now, after being turned over, by the guide leg 442. By this means, lefthanded and right- handed persons are able to work with the hand-held machine saw in an equally optimum manner in corners which are difficult of access. otherwise, the sawing cassette 43 is constructed as previously described.

Figures 17 to 23 illustrate a sawing cassette 43 which has a saw-through blade 12 and is modified compared with the sawing cassette 43 in figures 14 and 15. The saw blade 12 is once again guided in the guide rail 44 for limited axial displacement between the guide legs 441, 442 which are connected to one another in one piece via the bent-over edge 443. Since the guide rail 44 engages only partially over the back 121 of the saw blade 12, for improved guidance of the said saw blade 12 in the guide rail 44 there are stamped out in the guide leg 441, in addition to the slot-and-pin connection consisting of the slot 58 in the saw blade 12 and the guide tab 45 bent out of the guide leg 441, two further guide segments 64 which are disposed in alignment and at a distance one behind the other in the direction of sawing. Under these circumstances, the stamping-out operation takes place in such a way that the guide segments 64 rest against the inner face of the other guide leg 442. Each guide segment 64 is welded to the guide leg 442 with the aid of two weld points. This welding of the guide rail 44 ensures that the said guide rail 44 does not gape open at its two edges that face away from the bent-over edge 443, above all in the front region PCT/DE98/03103 23 at the exit of the saw blade. The stamping of the guide segments 64 out of the spring leg 441 can be seen, in particular, in figure 19 and in the enlarged representation in figure 20. The two guide segments 64 are stamped, together with the guide tab 45, out of the same guide leg 441, so that the saw blade 12 does not run on a boundary point between the guide segments 64 and the guide tab 45, any offsetting of the two guide legs does not have any effect, and the vertical tolerance of the saw blade 12 in the guide rail 44 can be better controlled. Interacting with the two guide segments 64 is a clearance 65 (figure 23) in the saw blade 12, which clearance runs parallel to the blade back 121 and, for the insertion of the saw blade 12 in the guide rail 44, runs out freely at the rear edge 123 of the blade, which rear edge runs transversely to the back blade 121. The breadth of the clearance 65 is dimensioned so as to be slightly larger than the breadth of the guide segments 64, so that the saw blade 12 is guided on the guide segments 64 on both sides with play. The accuracy of the distance from the upper edge of the clearance 65 to the back 121 of the saw blade, and also of the distance between the upper edge of the guide segments 64 and the bottom of the bent-over edge 443 of the guide rail 44 must be very precisely correct in order to minimise the vertical play of the saw blade 12 in the said guide rail 44. Because of the free rear run-out of the clearance, the saw blade 12 can be inserted in the finished guide rail 44 from the front. The saw blade 12 is fixed in position in the guide rail 44 in a longitudinally displaceable manner by then bending the guide tab 45 on the guide leg 441 into the slot 58 in the said saw blade 12.

In a variant of embodiment, of which nothing further is represented, of the sawing cassette 43, the guide segments 64 are replaced by at least one intermediate metal sheet which rests against the inner faces of the two guide legs 441, 442 and is fastened by weld points to the latter and PCT/DE98/03103 24 which forms the abutment or guide for the saw blade 12. By means of this intermediate metal sheet, the vertical play in relation to each saw blade can be set during assembly and it is)ossible, as a result of free selection of its material, to set a higher hardness for the guide, compared with the saw blade 12.

As in the case of the sawing cassettes according to figures 8 and 9 and also figure 14, the saw blade 12 rests, inside io the guide rail 44, with its blade faces on ribs 47 (figure 21) which are stamped out of the guide legs 441, 442 and project on the inner faces of the latter. The height of the ribs 47 can be set during manufacture, so that saw blades 12 of different thickness can be received with the aid of the same guide rail 44. In this case too, the ribs 47 minimise the friction of the saw blade 12 in the guide rail 44, the corners of the bending curvature in the bentover edge 443 being recessed, in this case too, for the purpose of avoiding greater friction of the saw blade 12 against the said bent-over edge 443, so that the edges of the blade back 121 run freely in the region of the bending radius of the bent-over edge 443. Recessing is carried out in the same way as is represented in figure 13. For the purpose of further reducing the friction, a grease-filled pocket 66 (figure 22) is machined into the bottom of the bent-over edge 443 of the guide rail 44 in the region of that front transverse edge 444 of the guide rail 44 which extends transversely to the said bent-over edge 443 and forms the so-called "butting edge" for the saw blade 12 and above which the saw blade 12 projects. The grease reservoir in the grease pocket 66 supplies the front transverse edge 444 of the guide rail 44 with grease during the sawing operation and ensures good lubrication between the saw blade 12 and the guide legs 441, 442. In this connection, it is necessary for the front transverse edge 444 to be designed to be completely burr-free, at least on those inner edges of the guide legs 441, 4442 which. face 1 1 PCT/DE98/03103 towards the saw blade 12. For clamping the sawing cassette 43 into the clamping-in device 33 provided on the machine, the clamping-in tabs 54 and 55 are, once again, constructed on the two guide legs 441, 442 in the same way, so that the said sawing cassette 43 can be inserted in the clamping-in device 33, now by the guide leg 441 and now, after being turned by 1800, by the guide leg 442. For flush-sawing purposes, the sawing cassette 43 is designed with only one pair of clamping-in tabs 54 and 55. Sawing-through which is flush on the right or left is possible, according to which guide leg 441 or 442 of the guide rail 44 the pair of tabs is omitted on.

As has been observed in connection with the sawing cassette 43 described in figures 8 and 9, it is also possible, in the case of the sawing cassette 43 according to figure 14 or 17, for the guide rail 44 to be made up of two separately manufactured guide legs 441 and 442, for which purpose, for example, one guide leg is offset in a shallow manner close to the back of the rail, for the purpose of producing a gap receiving the saw blade 12 between the guide legs 441 and 442, rests, with the offset portion, against the other guide leg, and is connected inseparably to the latter by weld points. The advantage of this bipartite construction of the guide rail 44 lies in higher processing safety since, on the one hand, the bending operation to be carried out in the case of the one-piece guide rail 44 is eliminated and, on the other hand, each guide leg can be corrected individually. The one-piece guide rail 44 with the bent-over edge 443, on the other hand, has the advantage of lower outlay on assembly and of integrating all the functions in one part, and represents the best solution, both ergonomically and optically.

In the bipartite guide rail 44 described above, the two guide legs 441 and 442 can also be designed as flat, symmetrical sheet-metal halves.In this case, at least one PCT/DE98/03103 26 narrow metal sheet can be inserted at the top between the guide legs 441 and 442, and welded to them, for the purpose of producing the distance between the said guide legs 441 and 442 in the region of the back of the rail. The inwardly pointing longitudinal edge of the metal sheet then forms the upper abutment point or guide for the saw blade, which upper abutment point or guide can be optimised by free selection of the material of the metal sheet welded in. At least one lower metal sheet is inserted between the two guide legs 441 and 442, and welded to them, at a suitable distance from the upper metal sheet, for the lower guidance of the saw blade 12 via its clearance 65. In this case too, the guidance of the saw blade 12 can be optimised by free selection of the sheetmetal material.

PCT/DE98/03103 27

Claims

Claims

1. Hand-held electric machine saw, in particular a precision-cutting saw, with a machine housing (10), with a changeable saw blade (12) and with a drive (11) which is received in the machine housing (10) and drives the saw blade in an oscillating sawing movement (sawing stroke) that travels to and fro, characterised in that the saw blade (12) is received in a longitudinally displaceable manner in a guide that can be fixed in position in a changeable manner on the machine housing (10), and that the drive (11) acts directly upon the saw blade (12).

2.

Machine according to claim 1, characterised in that the saw blade (12) and guide form a separate, preferably inseparable, structural unit (sawing cassette 43) which is constructed so as to be capable of being clamped into a clamping-in device (33) fixed in position on the machine housing (10).

Machine according to claim 2, characterised in that the guide has a guide rail (44) which engages, at least partially, over the back (121) of the saw blade (12), the said back facing away from the strip (122) of saw teeth, and has two guide legs (441, 442) which lie on either side of the blade, that the guide rail (44) carries clamping-in elements for insertion in the clamping-in device (33) and has at least one elongated hole (48, 49) extending parallel to the blade back (121) in at least one guide leg (441, 442) and having a length that exceeds the sawing stroke, and that at least one clearance (50), collinear with the elongated hole (48, 49) of which there is at least one, is constructed in the saw blade (12) for a drive finger (23) which belongs to the drive (11) and penetrates in a shape-mating manner.

1. 1 is PCT/DE98/03103 28 Machine according to claim 3, characterised in that the saw blade (12) is held in the guide rail (44), and guided in a longitudinally displaceable manner, by means of at least one pin-andslot connection which has a slot (58) running parallel to the blade back (121) and having a length exceeding the sawing stroke, and a pin held on at least one guide leg (441, 442) or a tab (45) bent out of one guide leg (441), which pin or tab projects into the said slot (58).

5.

Machine according to claim 3 or 4, characterised in that cams (46) and/or ribs (47), on which the saw blade (12) rests, project on that inner face of each guide leg (441, 442) which faces towards the saw blade (12).

6. Machine according to claim 4 or 5, characterised in that the guide legs (441, 442) of the guide rail (44) are kept at a distance via an offset on at least one guide leg, which offset runs parallel to the back (121) of the blade, or an insert between the guide legs, or a bent-over edge (443), and are connected to one another in the region of their abutment by welding or in a one-piece manner, that in the region of the free longitudinal edges of the guide legs (441, 442) there is stamped out of one guide leg (441) at least one guide segment (64), or else there is fastened at least one intermediate metal guide sheet, which rests against the other guide leg (442) and is fixedly connected to the latter, preferably by weld points, and that the saw blade (12) has an elongated clearance (65) running parallel to its blade back (121), which clearance runs out freely at the rear saw blade edge (123) extending transversely to the saw blade back (121) and has a breadth which is little larger than the breadth of the guide segment (64) or intermediate metal guide sheet, of which there is at least one.

is PCT/DE98/03103 29 Machine according to one of claims 2 to 6, characterised in that the clamping-in device (33) has a fastening plate (34) which is fixed in position on the machine housing (10) and has two locking members which are disposed at a distance from one another in the direction of sawing and of which one is constructed as a hooking-in hook (35) and the other as a back-springing metal holding sheet (36) with a plugin aperture (361), and that the clamping-in elements on the guide rail (44) have at least one pair of tabs (54, 55) which project on the outer side of at least one guide leg (441, 442) of the guide rail (44) and correspond with the said locking members and which are preferably bent away, in one piece, from the guide leg (441, 442), of which there is at least one.

Machine according to claim 7, characterised in that the metal holding sheet (36) is hooked movably into an aperture (341) constructed in the fastening plate (34) and is loaded in the direction of the hooking-in hook (35) by a spring (37) supported on the said metal holding sheet (35) and on the said fastening plate (34).

Machine according to claim 7 or 8, characterised in that the dispositions of the locking members on the fastening plate (34) and of the pair, of which there Js at least one, of tabs (54, 55) on the guide leg (441, 442), of which there is at least one, are coordinated with one another in such a way that, after the hooking of one tab (55) into the hooking-in hook (35), the other tab (54) can be latched into the plugin aperture (361) in the metal holding sheet (36), with the latter yielding in a resilient manner.

10. Machine according to one of claims 7 to 9, characterised in that there projects, on the lower 1 - PCT/DE98/03103 side of the fastening plate (34), a peg (39) which penetrates, after the clamping of the sawing cassette (43) into the clamping-in device (33), into mutually aligning apertures (51, 52) in the guide legs (441, 442) and an elongated hole (53), which is coaxial therewith, in the saw blade (12), and preferably that the clear width of the apertures (51, 52), which points in the direction of sawing, is dimensioned so as to be little larger than the diameter of the peg (39).