GB2314288A

GB2314288A - Electric combination hammer

Info

Publication number: GB2314288A
Application number: GB9712401A
Authority: GB
Inventors: Karl Frauhammer; Frank Mueller; Heinz Schnerring; Karsten Blaier
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1996-06-15
Filing date: 1997-06-13
Publication date: 1997-12-24
Anticipated expiration: 2017-06-13
Also published as: IT1292120B1; ITMI971363A0; GB9712401D0; ITMI971363A1; CH692658A5; GB2314288B

Description

2314288 Electric Combination Hamme The invention proceeds from an electric

combination hammer for selective use as a drilling or chisel hammer of the type defined in the preamble of claim 1.

In such combination hammers, the bow-like handle is formed as an integral part of the hous mig and the operating pawl is positioned -at the inside of the handle directed towards the housing. Thus, when the handle is gripped, the index fmger of the operating handautomatically comes to rest on the operating pawl. By pressing in the.operating pawl, the electrical onloff switch is closed and so the combination hammer is set in operation and, when the operating pawl is released, the on/off switch opens automatically and the combination' hammer is stopped.

For selecting the drilling mode, in which a percussion drill inserted into the tool holder of the combination hammer is driven in a percussive and rotary manner, or the chiselling mode, 'm which a chisel inserted into the tool holder is driven exclusively in a percussive manner, the knob, which is disposed on the housing and via a suitable operating mechanism engages and disengages the rotary drive acting upon the tool holder, has to be manually operated.

In electric hand tools, such as electric circular saws, jig saws, chain saws and electric drilling or impact drilling machines, when the on/off switch is switched on it is known to lock the operating pawl in the closing position of the on/off switch by means of an arresting button. The arresting button protrudes laterally from the handle and once the operating pawl has been pressed in, may be pushed in lateraRy by the thumb of the operating hand. The arresting button enables continuous operation of the electric hand tool without the need to keep the operating pawl depressed. When the operating pawl is pressed again, the arresting 2 button is lifted back out of its interlock and, when the operating pawl is released, the on/off switch opens.

Advantages of the mivention The electric combination hammer according to the invention having the characterizmg features of claim 1 has the advantage that the combmiation hammer during impact drilling (drilling mode) may be operated merely with an accidentproof, non-latching closing/opening operation and, upon a switchover to exclusive hammering with a chisel (chiselIffig mode), there is an automatic switchover to a latching closing/opening operation. Thus, both from a safety and a work point of view, optimum operation of the combination hammer is possible in both modes. In chiselling mode, life is made easier for the operator because his operating hand, which is very often required to effect gripping, is no longer additionally required to hold the operating pawl, which generally leads to premature fatigue. During impact drilling, on the other hand, when there is no need for constant gripping with the operating hand, the safety aspect which allows operation only with the operating pawl held depressed is to the fore so that, at any time, release of the operating pawl will bring rotation of the percussion drill abruptly to a halt. Said automaticity, particularly in the case of heavy and medium-weight combination hammers, leads to a considerable improvement in operating comfort because such combination hammers are used much more for chiselling than for drilling. Studies have revealed that 70% of the operating time is spent in chiselling mode.

By virtue of the measures outlined in the further claims, advantageous developments and improvements of the electric combination hammer indicated in claim 1 are possible.

3 According to a preferred embodiment of the invention, the detent comprises at least two corresponding detent elements, of which one is disposed on the operating pawl and the other is disposed on a carrier, which is displaceable 'm the housing by means of the operating knob and as a result of the displacement of which the associated detent element may be swivelled into and out of the operating path of the detent element associated with the operating pawl. The carrier advantageously takes the form of a pivoted lever, which is pivotally supported in the housing and has an extension arm, on the free end of which the detent element is disposed. The pivoted lever is acted upon by the operating knob in such a way that, in the one position of the operating knob, it assumes its one pivoted end position and, mi the other position of the operating knob, it assumes its other pivoted end position. By suitably arranging the swivelling axis of the pivoted lever and suitably selecting the dimensions of the extension arm, the spatial distance between operating knob and operating pawl in the machine housing may be bridged without difficulty and adapted easily to the individual spatial conditions which exist in the machine housing.

When switching over from drilling to chisellmig mode and vice versa, the pivoted lever may be used simultaneously to activate special flirictions which are required in one or the other mode when, according to an advantageous embodiment of the invention, the pivoted lever takes the form of a two-anned lever, on one lever ann of which an extension arm and a sensing lug for sensing the rotary position of the operating knob are disposed and on the other lever arm of which the auxiliary means of activating the special flinction are provided. The auxiliary means preferably comprise a permanent magnet disposed on the lever arm and a Halleffect sensor disposed on the housing and connected to control electronics. The swivelling motion of the pivoted lever when the operating knob is switched over from drilling to chiselling mode and vice versa is detected by the Hall-effect 4 sensor and signalled to the control electronics, which accordingly activate or deactivate the special flinction.

According to a flirther embodiment of the invention, the operating knob is situated m a trough mi the housing without projecting beyond the housmig contour. The danger of accidental operation of the operating knob, which would lead to malfunctionffig of the combination hammer, is therefore effectively avoided.

Drawmgs There follows a detailed description of an embodiment of the invention which is illustrated in the drawmigs. The drawings, each in a diagrammatic manner, show:

Fig. 1 a side view of an electric combination hanimer, Fig. 2 'm a cutout manner, a plan view of the electric combmiation hammer according to arrow II in Fig. 1, Fig. 3 an miverted plan view of a mode selection knob which is set to "drilling" mode, Figs. 4 and 5 in each case in side view, the spatial association of operating knob and operating pawl mi the electric combmiation hammer according to Fig. 1 'm "drilling" mode, namely with an unoperated operating pawl (Fig. 4) and a pressed operating pawl (Fig. 5), Fig. 6 an inverted plan view of the mode selection knob which is set to "chiselling" mode, Figs. 7 and 8 m each case m side view, the spatial association of operating knob and operating pawl in the electric. combination hammer according to Fig. 1 in "chiselling" mode, namely with an unoperated operating pawl (Fig. 7) and a pressed operating pawl (Fig. 8).

Description of the embodiment

The electric combination hammer, which is diagrammatically illustrated in side view mi Fig. 1, may be operated selectively as a drilling hammer or as a chisel hammer. It comprises a housing 10, firom. which a hollow workspindle 11 with a tool holder 12 projects. The tool holder 12 is used to receive a percussion drill or a chisel. An electric motor with a gear unit, which is not shown here, is used for driving purposes. In drilling mode, the tool holder 12 with percussion drill is set in rotation and at the same time the percussion drill is driven percussively in an axial direction by means of a header. In chiselling mode, the rotary drive of the tool holder 12 is decoupled and the chisel held in the tool holder 12 is driven exclusively percussively in an axial direction. For mode changing, an operating knob 13 is used, which is disposed on top of the housing 10, close to its end remote from the tool holder 12, Mi a trough 101 in the housing 10 without projecting beyond the housing contour (Figs. 1 and 2). The operating knob 13 is seated non-rotatably on an axis of rotation 14 supported in the housing 10 (Figs. 4 + 5). At the end of the housing 10 remote from the tool holder 12, a bow-like handle 15 is formed as an integral part of the housing 10. Disposed at the inside 6 of the handle 15 directed towards the housmig 10 is an operating pawl 16 for operating an electrical on/off switch 17 for the electric motor. As Figs. 4, 5 and 7, 8 reveal, the operating pawl 16 takes the form of a rocker 18 fastened to the handle 15 so as to be capable of swivelIffig about a swivelling axis 29 and having two rocker arms 181, 182, a contact pm' 19 of the on/off switch 17 resting under the action of an operating spring 20 against the bottom rocker arm 182. The operating spring 20 via the contact pin 19 holds the rocker 18 in the basic position shown in Figs. 4 and 7, mi which the on/off switch 17 is open. By pressing the rocker 18, e.g. with the index finger of the operating hand placed around the handle 15, m the direction of arrow 21 mi Fig. 5, the rocker 18 is swivelled 'm a clockwise direction, with the result that the bottom rocker arm 182 pushes the contact pin 19 with simultaneous compression of the operating spring 20 into the electrical contact 'm the on/off switch 17 and hence closes the on/off switch 17. The electric drive of the electric combmation hammer is therefore switched on, and is namely switched on until, as a result of release of the rocker 18, the operating spring 20 pushes the contact pin 19 back out of the on/off switch 17 and in so doing swivels the rocker 18 in an anti-clockwise direction in Fig. 5. Associated with the operating pawl 16 or the rocker 18 is a detent 22 comprising two corresponding detent elements 221, 222 which, under specific conditions, lock the operating pawl 16 at the end of its switch- on travel which closes the on/off switch 17 so that the operating pawl 16 may be let go but the on/off switch 17 remains closed and, by operating the operating pawl 16 again, the operating pawl 16 is unlocked once more. The one detent element 221 is disposed on the operating pawl 16 and the other detent element 222 is disposed on a earner 23 fastened displaceably in the housing 10. The carrier 23 is coupled in such a way to the operating knob 13 that its detent element 222, in the position M of the operating knob 13 which adjusts the chiselling mode, lies in the operating path of the detent element 221 disposed on the operating pawl 16 (Figs. 6 - 8) and, in the 7 position B of the operating knob 13 which adjusts the drilling mode, is removed firom said operating path (Figs. 3 - 5).

In particular, for said purpose the carrier 23 takes the form of a pivoted lever 24 with a swivelling axis 25 held in the housing 10 and carries at the free end of an extension arm 241 the detent element 222, which here takes the form of a detent trough 26. Formed on the operating knob 13, which is rotatable about the axis of rotation 14, is an eccentric cam 27 which lies inside the housing 10. The pivoted lever 24 lies under the action of a contact pressure spring 28 with a sensing lug 242 applied against the periphery of the eccentric cam 27. The detent element 221 carried by the operating pawl 16 takes the form of a detent spring 30, which is disposed on the rocker arm 181 of the rocker 18 and at its free end carries a bump 301, which may engage substantially positively into the detent trough 26 of the pivoted lever 24 in the manner shown Mi Fig. 8. The eccentric cam 27 of the operating knob 13 is so designed that the pivoted lever 24, which has its sensmig lug 242 constantly applied against the eccentric cam 27, in mode B position of the operating knob 13 (Fig. 3) assumes the pivoted end position shown 'm Figs. 4 and 5, in which the extension arm 241 with detent trough 26 is swivelled away from the rocker 18, and so the detent trough 26 is swivelled out of the swivelling path of the detent spring 30 upon operation of the rocker 18. Upon shifting of the operating knob 13 into the mode M position (Fig. 6), the pivoted lever 24 is moved by the eccentric cam 27 into its other pivoted end position shown in Figs. 7 and 8, m which the extension arm 241 is swivelled forward towards the rocker 18. When the rocker 18 is not operated (Fig. 7), the extension arm 241 therefore lies slightly above the detent spring 30 of the rocker 18. When the rocker 18, in the manner shown in Fig. 8, is swivelled in a clockwise direction as a result of pressure in arrow direction 2 1 upon its rocker arm 18 1, the detent spring 3 0 moves towards the extension arm 241 and the bump 301 of the detent spring 30 engages 8 positively into the detent trough 26. When the rocker 18 is released, because of the latching between detent trough 26 and bump 301 the operating spring 20 is unable to tilt the rocker 18 back. The on/off switch 17 remains closed, and in chiselling mode the operating hand may be re-positioned many times without there beffig any need to hold the rocker 18 in the operated position. For disconnection of the drive, a force has to be exerted by a finger of the operating hand in arrow direction 31 upon the bottom rocker arm 182. The bump 301 of the detent spring 30 is therefore pressed out of the detent trough 26 and the rocker 18 is swivelled back by the operating spring 20 - with simultaneous opening of the on/off switch 17 - before finally reassuming the basic position shown in Fig. 7. Unlocking may be made smoother when the detent spring 30, instead of the bump 3 0 1, carries a roller which engages into the detent trough 26. As a result of the rollmg friction which is then provided, the required force in the direction of arrow 31 for cancelling the interlock is lower.

M is additionally indicated 'M Figs. 7 and 8, switching of the operating knob 13 from its mode B position to its mode M position and vice versa may be used simultaneously to activate and deactivate special functions Mi the drillmig hammer. To said end, the pivoted lever 24 takes the form of a two-armed lever, on the upper lever arm of which, as described, the extension arm 241 and the sensmg lug 242 are disposed and the contact pressure spring 28 acts and on the lower lever arm of which a permanent magnet 32 is fastened, which cooperates with a Halleffect sensor 33 disposed in the housing 10. In a manner not shown in detail, the Halledect sensor 33 is connected to control electronics. Upon switching of the operating knob 13, the pivoted lever 24 is moved Mi the described manner out of its pivoted end position shown in Figs. 4 and 5 into the pivoted end position shown M Figs. 7 and 8 and vice versa. In the process, the permanent magnet 32 approaches the Hall-effect sensor 33 or conversely swivels away from it again.

9 The swivelling motion of the permanent magnet 32 leads in the Hall-effect sensor 33 to a change in its output voltage, which is converted by the control electronics into the desired activation or deactivation of a special function.

The invention is not restricted to the illustrated embodiment. For mstance, it is alternatively possible for the bump 301 to be formed on the extension arm 241 of the pivoted lever 24 and for the detent trough 26 to be suitably formed on the detent spring 30. In said case also, a roller may be provided on the extension arm 241 in the region of the detent point, which forms the bump 301.

The handle 15 may, e.g. for the purpose of vibration damping, be capable of swivelling or displacement relative to the housing 10. In said case, care should be taken to ensure that the detent point 22 is housed in the movable handle 15 so that, m the latched position, there is no relative displacement between the detent elements 221, 222. The relative movement of the handle 15 may then be compensated, for example, by a multi-section pivoted lever 24.

Claims

1. Electric combination hammer for selective use as a drilling or chisel hammer, having a housmig (10) with a handle (15), having an operating pawl (16) fastened to the handle (15) for operating an electrical on/off switch (17) and havmg an operating knob (13) for switching manually from drilling to chiselling mode and vice versa, characterized in that associated with the operating pawl (16) is a detent (22) which, in a position (M) of the operating knob (13) which adjusts the chiselling mode, allows a latching of the on/off switch (17) Mi a closing position and, in a position (B) of the operating knob (13) which adjusts the drillmig mode, does not allow a latching of the on/off switch (17).

2. Combfflation hammer according to claim 1, characterized in that the detent (22) comprises at least two corresponding detent elements (221, 222), of which the one detent element (22 1) is disposed on the operating pawl (16) and the other detent element (222) is disposed on a carrier (23) fastened displaceably in the housing, and that the carrier (23) is coupled in such a way to the operating knob (13) that the detent element (222) associated with the carrier, in the position (M) of the operating knob (13) which adjusts the chiselling mode, lies in the operating path of the detent element (22 1) disposed on the operating pawl (16) and, in the position (B) of the operating knob (13) which adjusts the drilling mode, is removed from said operating path.

3. Combination hammer according to claim 2, characterized in that the carrier (23) takes the form of a pivoted lever (24), which is pivotally supported in the housing (10) and at the free end of an extension arm (241) carries the 11 one detent element (222), and that the pivoted lever (24) in the one position (B, M) of the operating knob (13) assumes its one pivoted end position and in the other position (M, B) of the operating knob (13) assumes its other pivoted end position.

4. Combination hammer according to claim 3, characterized in that the operating knob (13) is seated non-rotatably on an axis of rotation (14) supported in the housing (10), that an eccentric cam (27) is formed on the operating knob (13), that the pivoted lever (24) is frictionally applied by a sensing lug (242) against the periphery of the eccentric cam (27) and that the eccentric cam (27) is so designed that, upon rotation of the operating knob (13) through approximately 180', the pivoted lever (24) is movable from its one pivoted end position into the other.

5. Combination hammer according to one of claims 2 - 4, characterized 'M that the one detent element (222) is a detent trough (26) and the other detent element (22 1) is a detent spring (3 0) havm'g formed on its free end a bump (301) which engages substantially positively into the detent trough (26).

6. Combination hammer according to claim 5, characterized Mi that the detent trough (26) is disposed in the extension arm (24 1) of the pivoted lever (24) and the detent spring (3 0) with bump (3 0 1) is disposed on the operating pawl (16).

7. Combination hammer according to claim 6, characterized in that the operating pawl ( 16) takes the form of a rocker ( 18) fastened pivotally to the handle (15) and having two rocker arms (181, 182) extending on either side of the swivelling axis (29) and that a contact pin (19) of the onloff switch 12 17) is applied by means of an operating spring (20) against the one rocker arm (182) and the detent spring (30) is supported on the other rocker arm (181).

8. Combination hammer according to one of claims 3 - 7, characterized in that the pivoted lever (24) is a two-armed lever, on one lever arm of which extension arm (241) and sensmig lug (242) are disposed and to the other lever aim of which are fastened auxiliary means of activating at least one special flinction upon switching of the operating knob (13) from its position (B) adjusting the drilling mode to its position (M) adjusting the chiselling mode or vice versa.

9. Combination hammer accordmig to claim 8, characterized in that the auxiliary means comprise a permanent magnet (32) disposed on the lever arm and a Hall-effect sensor (33), which is disposed on the housing (10) and is connected to control electronics.

10. Combination hammer according to one of claims 1 - 9, characterized 'M that the operating knob (13) is disposed M a trough (10 1) in the housing (10) in such a way that it does not project beyond the housing contour.

11. Combffiation hammer according to one of claims 1 to 10, characterized in that the handle (15) is arranged so as to be movable to a limited extent relative to the housing (10) and the detent (22) is housed in the movable handle (15).

12. Combination hammer according to claim 5, characterized in that the bump (3 0 1) is formed by a roller.

13. An electric combination hammer substantially as herein described with referente to the accompanying drawmigs.

13 13. An electric combination hammer substantially as herein described with reference to the accompanying drawings.

14, Amendments to the claims have been filed as follows An electric combination hammer for selective use as a drilling or chisel hammer, comprising a housing with a handle, an operating pawl fastened to the handle for operating an electrical on/off switch, and an operating knob for switching manually betwen a drilling mode and a chiselling mode, the operating pawl having associated with it a detent which, with the operating knob in a position corresponding to the chiselling mode, allows the on/off switch to be latched in a closed position, and, with the operating knob in a position corresponding to the drilling mode, does not allow such latching of the on/off switch.

2. A combination hammer as claimed 'm claim 1, wherein the detent comprises at least two complementing detent elements, one detent element being disposed on the operating pawl and the other detent element being disposed on a carrier fastened displaceably in the housing, the carrier being coupled to the operating knob such that with the operating knob mi the position corresponding to the chiselling mode, the detent element associated with the carrier lies in the operating path of the detent element disposed on the operating pawl, and, with the operating knob mi the position corresponding to the drilling mode, that detent element is removed firom said operating path.

3. A combmation hammer as clauined in claim 2, wherein the carrier takes the form of a pivoted lever, which is pivotally supported in the housing and which has an extension arm, at the free end of which is carried the said other detent element, and the pivoted lever in one position of the operating knob assumes its one pivoted end position and in the other position of the operating knob assumes its other pivoted end position.

Is 4. A combination hammer as clairnedmi claim 3, wherein the operating knob is seated rotatably about an axis of rotation supported in the housing, and an eccentric cam is formed on the operating knob, the pivoted lever having a sensing lug which is in contact with the periphery of the eccentric cam and the eccentric cam being so designed that, upon rotation of the operating knob through approximately 180', the'pivoted lever is movable from its one pivoted end position into the other.

5. A combination hammer as claimed in claim 4, wherein the pivoted lever is a two-armed lever, on one lever arTn of which the extension arm and sensing lug are disposed and to the other lever aim of which are fastened auxiliary means of activating. at least one special function upon switching of the operating knob from its position corresponding to the drilling mode to its position ID corresponding to the chiselling mode or vice versa.

6. A combination hammer as claimed in claim 5, wherein the auxiliary means comprise a permanent magnet disposed on the lever arm and a Hall- effect sensor, which is disposed on the housing and is connected to control electronics.

7. A combination hammer as claimed in any of claims 2 to 6, wherein one detent element is a detent trough and the other detent element is a detent spring having formed on its free end a bump which engages substantially positively into the detent trough.

8. A combffiation hammer as claimed in any of claims 2 to 6, wherein one detent element is a detent trough which is disposed 'm the extension arm of the pivoted lever and the other detent element is a detent spring with a bump which is disposed on the operating pawl.

J (p 9. A combination hammer as claimed in claim 8, wherein the operating pawl takes the form of a rocker fastened to the handle pivotally about a swivelling axis and having two rocker arms extending on either side of the swivelling axis, and a contact pin of the on/off switch is applied by means of an operating spring against the one rocker arm and the detent spring is supported on the other rocker arm.

10. A combmadon hammer as claimed in any of claims 7 to 9, wherein the bump is formed by a roller.

11. A combination hammer as claimed in any of the preceding clahins, wherein the operating knob is disposed in a trough 'm the housmig in such a way c c that it does not project beyond the housing contour.

12. A combmation hammer as claimed in any of the preceding claims, wherein the handle is arranged so as to be movable to a limited extent relative to the housing and the detent is housed in the movable handle..