GB2271735A

GB2271735A - Reciprocating drive in hand held machine tools

Info

Publication number: GB2271735A
Application number: GB9321551A
Authority: GB
Inventors: Anne Miller; William Trennemann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1992-10-20
Filing date: 1993-10-19
Publication date: 1994-04-27
Anticipated expiration: 2013-10-19
Also published as: DE4235278A1; ITMI932160A1; GB9321551D0; ITMI932160A0; CH687962A5; GB2271735B; IT1271492B

Abstract

A hand-hold machine tool for the machining of workpieces, in particular a motor-driven file, has a reciprocating plate (25) with a holder (42) for the releasable fastening e.g. a file blade (12), and a driving unit (11) which imparts a continuous longitudinal reciprocation to the plate (25) and hence the blade (12). In order to prevent the blade (12) from becoming increasingly clogged with filings or metal dust during the work process with the consequent drop in efficiency, means (45, 51) are integrated into the driving unit (11) which impose an additional transverse stroke, at least during its return movement. The transverse movement of the metal-removing tool or file blade (12) has the effect of pushing the filings out sideways so that the teeth of the metal-removing tool or file blade (12) are at all times exposed and cut in an optimum manner. A counterweight (26) reciprocates oppositely to the plate (25) and a roller (43) holds plate (25) against a sliding surface of a plate (23). <IMAGE>

Description

2271 735 Hand-held machine tool, in Darticular motor-drive file

Prior art

The invention starts from a hand-held machine tool for machining workpieces, in particular a motordriven file, of the generic type defined in the precharacterizing clause of Claim 1.

In a known motor-driven file of this kind (US Patent 3.535.983), the reciprocating or driving plate is driven by a pair of-pneumatic pistons which are connected in tandem and are controlled via pneumatic valves. A continuous longitudinal reciprocating motion is thereby imparted to the file blade held in the tool holder. Material is here removed from the workpiece during the forward stroke of the file blade.

Advantages of the Invention The hand-held machine tool according to the invention for machining workpieces, in particular a motor-driven file, with the characterizing features of Claim 1 has the advantage that the filings detached from the workpiece are pushed out sideways from the metal-removing tool, i.e. the file blade, by the transverse stroke of the reciprocating plate and the metal-removing tool. Gradual choking and clogging of the metal-removing tool with filings or metal dust is thereby prevented and hence the efficiency of the metal-removing tool increased.

In addition, the transverse stroke facilitates the uniform machining of large surfaces because, by virtue of the lateral movement of the metalremoving tool, its teeth do not move continuously in the same path and, as a result, the tendency of the metalremoving tool to dig a bed or unwanted furrows into the surface of the workpiece is greatly reduced. The finish of the machined workpiece surface is simultaneously improved.

Claims

Advantageous further developments and improvements of the hand-held

machine tool specified in Claim 1 are possible by means of the measures presented in the further claims.

According to a preferred embodiment of the invention, the transverse stroke of the reciprocating plate is achieved by means of a driver which is arranged swivellably on the side of the reciprocating plate remote from the tool holder, at a distance from the pin/slot guide, and is coupled to the stroke motion of the reciprocating plate in such a wd. y that it swivels inwards during the return stroke of the reciprocating plate and, in the process, swivels the reciprocating plate about the guide pin of the pin/slot guide. The driver is preferably secured rotatably on a swivelling plate which is arranged parallel to the reciprocating plate and can be swivelled about a swivelling peg, the driver projecting at right angles from the said plate and engaging laterally on the reciprocating plate.

According to a preferred embodiment of the invention, adjusting means are provided and with these it is possible to determine the size of the transverse stroke and limit it right down to a zero stroke. These adjusting means have an eccentric boss which is attached to the swivelling peg, designed to be rotatable about its axis, of the swivelling plate, a slot which is formed in the reciprocating plate, extends along the stroke axis of the forward and return stroke and fits over the eccentric boss with transverse clearance, and a contact-pressure roller which is loaded by a contact-pressure spring, is arranged against the side of the reciprocating plate, opposite the swivelling peg, and presses the reciprocating plate by one slot edge of the slot against the eccentric boss. Depending on the rotational position of the swivelling peg, the eccentric boss frees the reciprocating plate to an extent such that the contactpressure roller displaces the reciprocating plate sideways in the direction of the driver pin and, in the position of maximum rotation of the swivelling peg, lays the reciprocating plate against the driver pin.

In a preferred embodiment of the invention, a counterweight plate is guided parallel to the reciprocating plate in a manner which allows it to be displaced axially along the stroke axis of the forward and return stroke of the reciprocating plate, the counterweight plate being coupled in such a way to the stroke motion of the reciprocating plate that it is displaced longitudinally in the opposite direction to the reciprocating plate. This reduces vibrations of the hand-held machine tool to a large extent. The stroke of the counterweight plate is here preferably made greater than the stroke of the reciprocating plate in order to keep the mass of the counterweight plate as small as possible.

Drawing The invention is explained in greater detail in the description which follows with reference to an illustrative embodiment depicted in the drawing, in which:

Fig. 1 shows a side view of an electric motordriven file, Fig.
2 shows a longitudinal section of the machine head of the motor- driven file in Fig. 1, Fig.
3 s hows a section along the line III-III in Fig. 2, Fig. 4 shows a plan view of a counterweight plate in the machine head of the motor-driven file in Figs. 2 and 3, on an enlarged scale, Fig. 5 shows a plan view of a swivelling plate in the machine head of the motor-driven file in Figs. 2 and 3, on an enlarged scale, Fig. 6 shows an elevation of the swivelling plate in the direction of arrow VI in Fig. 5.

Description of the Illustrative Embodiment The electric motor-driven file shown in side view in Fig. 1 and partially in section in Figs. 2 and 3, as an example of a hand-held machine tool for the machining of workpieces has a two-shell plastic casing 10 which, in its rear section, is configured as a handle 101 and in its front section, which adjoins the rear section seamlessly, is configured as a casing head 102. Integrated into the casing head 102 there is essentially the driving unit 11 for a f ile blade 12 which projects from the casing head 102 and to which a continuous reciprocating stroke motion in the direction of its longitudinal axis is imparted by the driving unit 11. The electric motor forming part of the driving unit 11 is accommodated in the front part of the handle 101, the part directly adjoining the casing head 102, and is switched on and off by means of a switch strip 14 projecting from the underside of the handle 101. The electric motor is supplied with electric current via a cable 15 which is introduced into the plastic casing 10 on the rear side of the plastic casing 10, the side facing away from the casing head 102. To cool the electric motor, cooling air is drawn over the electric motor by means of a fan impeller 17 seated firmly on the output shaft 16 of the electric motor in terms of rotation, the cooling air entering the plastic casing 10 via air slots 18. The air slots 18 are made in the plastic casing 10 at that end of the handle 101 which is remote from the casing head 102.

The sectional representations of Figs. 2 and 3 show details of the driving unit 11. The only parts of the electric motor which are shown are the output shaft 16 and the fan impeller 17 seated firmly on the latter in terms of rotation. The output shaft 16 is connected via a bevel-wheel mechanism 19 with a reduction ratio of 3:1 to a driving shaft 20 which is arranged at right angles to the output shaft 16 and is rotatably mounted in the casing head 102 by means of an upper ball bearing 21 and a lower needle bearing 22. The needle bearing 22 is accommodated in a supporting plate 23 which covers the casing head 102 at its underside.

Seated firmly on the driving shaft 20 in terms of rotation is an eccentric 24 with an upper eccentric portion 241 for driving a reciprocating or driving plate 25 and with a lower eccentric portion 242 for driving a counterweight plate 26. The two eccentric portions 241, 242 are designed with a 180 rotational offset relative to one another, with th e result that the stroke movements of the reciprocating plate 25 and the counterweight plate 26 are opposed. At the same time, the eccentric portions 241 and 242 are designed in such a way that the reciprocating plate 25 executes a smaller displacement, here 6 nun, than the counterweight plate 26, here 7.6 mm. The counterweight plate 26 rests on the supporting plate 23 via a thin thrust plate 27, while the reciprocating plate 25 rests on the counterweight plate 26 via spacer washers 28, 29. Both plates 25, 26 are guided in axially displaceable fashion in the longitudinal direction by means of pin/slot guides. The front guide for the reciprocating plate 25 comprises a guide pin 30, held in the supporting plate 23, projecting at right angles therefrom and having a bush 31 seated on it, and a closed slot 33 formed in the reciprocating plate 25 (Fig. 3). The front guide for the counterweight plate 26 is formed by the same guide pin 30 with a bush 32 seated thereon and a slot 34 in the counterweight plate 26 (Fig. 4). In both cases, the bushes 31, 32 rest against the slot edges of the slots 33, 34. The rear guide for the counterweight plate 26 is formed by a peg 35, held in the supporting plate 23, projecting at right angles from the latter and rotatable about its axis and with a bush 36 seated on it, and a slot 37 formed in the counterweight plate 26. The peg 35 is also used to guide the reciprocating plate 25 at the rear, the reciprocating plate fitting over, by means of a slot 38, an eccentric boss 39 formed on the peg 35. The width of the slot 38 is chosen to be greater than the maximum diameter of the eccentric boss 39, allowing the reciprocating plate 25 to execute a transverse movement in the slot 38, around the eccentric boss 39. As can be seen from Figs. 3 and 4, both the reciprocating plate 25 and the counterweight plate 26 have an approximately elliptical aperture 40 and 41 respectively, the minor ellipse axis of which extends in the stroke direction. As can be seen from Fig. 2f eccentric portion 241 of the eccentric 24 lies in aperture 40 and eccentric portion 242 Lies in aperture 41, those edges of the apertures 40, 41 which run transversely to the stroke direction in each case resting against eccentric portions 241, 242. Upon rotation of the driving shaft 20, the eccentric portions 241 and 242 impart to the reciprocating plate 25 and the counterweight plate 26 continuous stroke movements in the longitudinal direction, the stroke movements being in the opposition direction to one another, i.e. during a forward stroke of the reciprocating plate 25, the counterweight plate 26 is executing a return stroke and vice versa. The reciprocating plate 25 is offset in the forward region, with the result that its forward portion lies approximately in the plane of the counterweight plate 26. At the front end, the reciprocating plate 25 carries a tool holder 42 into which the file blade 12 is inserted and firmly connected therein to the reciprocating plate 25. A detailed description of the tool holder 42 is not given here. The forward and return stroke movements of the reciprocating plate 25 are in this way transmitted to the file blade 12, which thus likewise executes a reciprocating motion in its longitudinal direction. Vertical forces acting on the file blade 12 during the machining process are absorbed by a roller 43 which is arranged rotatably and firmly on the casing transversely to the stroke direction of the reciprocating plate 25, in front of the guide pin 30. During its stroke movement, the reciprocating plate 25 is supported on the roller 43 with its upper side, the side facing away from the counterweight plate 26. Inserted in the casing 10 in front of the roller 43 in an offset position towards the tool holder 42 is a seal 44 which surrounds the reciprocating plate 25 in a sealing manner and thus protects the driving unit 11 from the penetration of dust from the tool holder 42.

In order to prevent gradual clogging of the file blade 12 with filings or metal dust and hence to improve the efficiency of the motor-driven file. means are provided in the driving unit 11 whkeh impart to the reciprocating plate 25 and h6nce to the file blade 12 an additional transverse stroke within the plane of the stroke during the return stroke of the said blade. By means of this transverse stroke, the filings are pushed sideways out of the file blade 12 and the interspace between the file teeth is kept free, allowing the file teeth to develop their full effect during the metalremoving stroke. The means for producing the transverse stroke comprise a wobble or swivelling plate 45, as depicted in plan view and side view in Figs. 5 and 6 respectively and as indicated in chain lines in Fig. 3. The swivelling plate 45 is mounted rotatably on the peg 35 by means of a hole 46 and rests via plain washers 47, 48 on the reciprocating plate 25. The swivelling plate 45 engages, by means of two mutually opposite limbs 49, 50, around the upper eccentric portion 241 for driving the reciprocating plate 25. The swivelling plate 45 carries a driver 51 extending parallel to its swivelling axis - defined by the peg 35 - and at a distance from the said swivelling axis, the driver here being formed by a needle bearing comprising a bearing pin 52 and a bearing ring 53. The bearing pin 52 is held in mutually opposite holes 54, one of which is made in the swivelling plate 45 and the other is made in a lug 55 bent out at right angles from the swivelling plate 49 and bent at the end. As can be seen from Fig. 3,, the driver 51 is arranged in such a way relative to the hole 46 in the swivelling plate 45 and to the peg 35 that. when the swivelling plate 45 is rotated in the clockwise direction in Fig. 3, it strikes against the side of the reciprocating plate 25 and, during its further movement, displaces the reciprocating plate 25 sideways, the latter executing a swivelling motion about the guide pin 30 in the direction of arrow 56 in Fig. 3. A sideways displacement motion is thereby imposed on the front part of the reciprocating plate 25 and the file blade 12 held there, this motion being superimposed on the return stroke of.the file blade 12 A contact-pressure r61ler 57 is held on a swivelling clip 58 on the side of the reciprocating plate 25 remote from the driver 51. The contactpressure roller 57 lies directly opposite the peg 35 with the eccentric boss 39. The swivelling clip 58 is fixed at one end in the casing 10 and, at its other end, is acted upon by a compression spring 59 which, via the swivelling clip 58, presses the contactpressure roller 57 laterally against the reciprocating plate 25 and thereby presses the reciprocating plate 25 by its slot edge in the slot 38 against the eccentric boss 39 on the peg 35. As can be seen from Fig. 2, an actuating button 60 is attached to the lower end of the peg 35 held rotatably in the supporting plate 23 and the peg 35 can be turned manually by means of this actuating button. When the peg 35 occupies the position illustrated in Figs. 2 and 3, in which the largest dimension of the eccentric boss 39 faces towards the contact-pressure roller 57, the contact-pressure roller 57 is pushed back to the maximum extent by the reciprocating plate 25, the compression spring 59 being compressed. The driver 51 on the swivelling plate 45 assumes its maximum distance from the reciprocating plate 25. If the electric motor is now switched on and the driving shaft 20 rotates, the swivelling plate 45 is swivelled in the clockwise direction via the limb 50 (Fig. 3) with every return stroke of the reciprocating plate 25. As a result. the driver 51 turns towards the reciprocating plate 25. The swivelling distance of the swivelling plate 45 is, however, not sufficient to bring the driver 51 into engagement with the reciprocating plate 25. The reciprocating plate 25 executes a purely axial backwards and forwards movement.

If the peg 35 is turned through 18C, the minimum dimension of the eccentric boss 39 faces in the direction of the contactpressure roller 57. The compression spring 49 lays the reciprocating plate 25 against the driver 51 by means of the dontact-pressure roller 47. During the return stroke of the reciprocating plate 25, the swivelling plate 45 is, in the same manner, swivelled in the clockwise direction by the eccentric portion 241, via the limb 50. As a result, the driver displaces the swivelling plate 45 sideways by 0.8 mm, as a result of which the reciprocating plate 25 swivels through an angle of 0.85 about the guide pin 30. If the peg 35 is turned through less than 180, the lateral deflection of the reciprocating plate 25 by the driver 51 and, accordingly, also the transverse stroke of the file blade 12 are smaller.

Claims 1. Hand-held machine tool for the machining of workpieces, in particular a motor-driven file, with a reciprocating plate which carries a tool holder for the releasable fastening of a metal-removing tool, in particular a file blade, and with a driving unit which continuously imparts to the reciprocating plate a forward and return stroke in the longitudinal direction of the metal-removing tool, characterized in that means (45, 51) are integrated into the driving unit (11) which impose on the reciprocating plate (25) an additional transverse stroke within the plane of the stroke, at least during its return stroke. 2. Machine according to Claim 1, characterized in that the reciprocating plate (25) has a pin/slot guide (30, 33) arranged near to the tool holder (42) and in that the means for producing the transverse stroke have a driver (51) which is arranged swivellably on the side of the reciprocating plate (25) remote from the tool holder (42), at a distance from the pin/slot guide (30, 33), and is coupled to the stroke motion of the reciprocating plate (25) in such a way that it swivels inwards during the return stroke of the reciprocating plate (25) and, in the process, swivels the reciprocating plate (25) about the guide pin (30) of the pin/slot guide (30. 33). 3. Machine according to Claim 2, characterized in that a swivelling plate (45), mounted to swivel about a peg (35), is arranged parallel to the reciprocating plate (25) and in that the driver (51) is held, preferably rotatably, on the swivelling plate (45), projecting at right angles from the latter, and is capable of coming to rest laterally against the reciprocating plate (25).
4. Machine according to Claim 3, characterized in Z T that the driving unit (11) has an eccentric (24) driven by an electric motor, in that the eccentric (24) rotates in an elliptical aperture (40) which is formed in the reciprocating plate (25) and the minor ellipse axis of which lies in the stroke axis of the forward and return stroke of the reciprocating plate (25), and in that the swivelling plate (45) rests against the eccentric (24) by means of at least one swivelling arm (49, 50).
5. Machine according to one of Claims 1 - 4, characterized in that adjusting means (35, 39, 57, 58, 59, 60) for reducing the transverse stroke of the reciprocating plate (25) down as far as zero are provided.
6. Machine according to Claim 5, characterized in that the adjusting means has an eccentric boss (39) attached to the swivelling peg (35), designed to be rotatable about its axis, for the swivelling plate (45), a slot (38) which is formed in the reciprocating plate (25), extends along or parallel to the stroke axis of the forward and return stroke and fits over the eccentric boss (39) with transverse clearance, and a contact-pressure roller (57) which is loaded by a contact-pressure spring (59), is arranged to the side of the reciprocating plate (25), opposite the swivelling peg (35), and presses the reciprocating plate (25) by one slot edge of the slot (38) against the eccentric boss (39).
7. Machine according to Claim 6, characterized in that the driver (51) is arranged on the swivelling plate (45) in such a way relative to the swivelling peg (35) of the latter, and the eccentric boss (39) on the swivelling peg (35) is shaped in such a way that, in a first position of the eccentric boss (39), the said boss presses the reciprocating plate (35) against the contact-pressure roller (57) via the slot edge of the slot (38)f compressing the contact-pressure spring (59), and, in the process, moves the reciprocating plate (25) so far away from the driver (51) on the swivelling plate (45) that the said driver does not come into engagement with the reciprocating plate (25) during the swivelling motion of the swivelling plate (45), and that, in a second position of the eccentric boss (39), turned through 180 relative to the first position, the said boss frees the reciprocating plate (25) to the maximum extent so that the contact-pressure roller (57) lays the reciprocating plate (25) against the driver (51).
8. Machine according to Claim 7, characterized in that the eccentric boss (39) on the swivelling peg (35) is shaped in such a way that, between its first and second rotational position. it frees th e reciprocating plate (25) to an extent such that the driver (51) strikes against the reciprocating plate (25) after a greater or lesser swivelling distance and takes the latter along over the remainder of its swivelling distance.
9. Machine according to one of Claims 6 - 8, characterized in that an actuating button (60) is arranged on the swivelling peg (35) for the manual turning of the latter.
10. Machine according to one of Claims 4 9, characterized in that the eccentric (24) is seated firmly in terms of rotation on a driving shaft (20) which is supported in the machine casing (10) and is coupled to the output shaft (16) of the electric motor via a bevel-wheel mechanism (19).
11. Machine according to one of Claims 2 - 10, characterized in that a counterweight plate (26) is guided parallel to the reciprocating plate (25) in a manner which allows it to be displaced axially along the stroke axis of the forward and return stroke of the reciprocating plate (25), the counterweight plate being coupled in such a way to the stroke motion of the reciprocating plate (25) that it is displaced longitudinally in the opposite direction to the reciprocating plate (25).
12. Machine according to Claim 11, characterized in E that the eccentric (24) has a first eccentric portion (241), which interacts with the aperture (40) in the reciprocating plate (25), and a second eccentric portion (242), which is arranged with a 180 rotational offset relative to the first eccentric portion and interacts with an identical elliptical aperture (41) in the counterweight plate (26).
13. Machine according to Claim 11 or 12, characterized in that the stroke of the counterweight plate (26) is made larger than that of the reciprocating plate (25).
14. Machine according to one of Claims 11 - 13, characterized in that the counterweight plate (26) is guided by means of two slots (34, 37), on the one hand on the guide pin (31) of the pin/slot guide of the reciprocating plate (25) and, on the other hand, on the swivelling peg (35) for the swivelling plate (45).
15. Machine according to one of Claims 2 - 14, characterized in that the reciprocating plate (25) rests in 'Sliding fashion on a supporting plate (23) and, on its opposite side, is supported against a roller (43) rotatably mounted transversely to the stroke direction.
16. A machine tool substantially as herein described with reference to the accompanying drawings