GB2191971A - Powered hand tool, in particular a hammer drill and/or percussion hammer - Google Patents

Abstract

A hammer drill has an air-cushion percussion mechanism 13 which includes a piston 17, that is oscillated by motor (11) via an eccentric gear mechanism 12. The mechanism 12 has a radially projecting dog (32) (e.g. a ball) on the end of a pin (34) received in the piston 17 and a drive member (e.g. gear 26) which is rotationally driven about axis (30) running perpendicular to the longitudinal centre axis (21) of the piston (17). At a radial distance from the axis (30), drive member 26 bears a driving device (31) (e.g. a bore 38) engaging on the dog (32). The ball (36) is located in freely pivotable mariner in the bore 38. For length compensation, the ball (36) is axially displaceable in the bore (38), or the dog (32) is displaceable relative to the piston (17) in the radial direction. The drill is compact, inexpensive and has only a few, and in addition simple, components (Figure 1). The drive member may be a radial lever or a disc mounted on a rotatable spindle 29. The dog 32 may be designed as a spherical pivot bearing instead of as a ball. <IMAGE>

Description

SPECIFICATION Powered hand tool, in particular a hammer drill andl or percussion hammer The invention is based on a powered hand tool, in particular a hammer drill and/or percussion hammer, according to the generic part ofthe main claim. Thus both eiectro-pneumatic hammer drills as well as chipping hammers with an air-cushion percussion mechanism are outlined.In a known powered hand tool of this type, an eccentric gear mechanism (German Auslegeschrift 1,206,817) is provided for converting the rotatory drive motion of the drive motor and its gear mechanism into the translatory drive motion for the drive piston, which eccentric gear mechanism, as in an internal combustion engine, contains a connecting rod which engages on the drive piston via a gudgeon pin, extends as a prolongation of the longitudinal centre axis of the drive piston and, at the far end, engages via a connecting rod bearing on an eccentric pin on a drive member which is driven via a gear mechanism by the drive motor arranged transversely to the longitudinal centre axis of the drive piston. This powered hand tool is of extremely long construction, especially in the direction of the longitudinal centre axis of the drive piston.This impairs the handling and the handiness ofthe tool. A considerable number of individual components is required. In addition, these components are relatively complicated and expensive.

Advantages ofthe invention In contrast, the powered hand tool according to the invention with the characterizing features ofthe main claim has the following advantages. The eccentric drive is exceptionally simple. It can be realized by simple components which are inexpensive to manufactu re. The number of components is reduced to a minimum. Atthe sametime, a compact type of construction is achieved for the powered hand tool, namely both in the longitudinal direction of the drive piston and transversely thereto.

Claims 2 to 25 contain advantageous further developments hereto. By the features in claims 2 to 4, the type of construction can be made even more compact. Even when the dog can be a direct component of the drive piston,thefeatures in claims Sand 6can prove to be especially advantageous with regard to manufacture and assembly. Further simplification is achieved bythefeatures in claim 8, because the gear which is present anyway ifthe powered hand tool is atthesametimedesignedasa hammer drill and which is used for the rotational drive is at the same time used as an element of the eccentric drive. This can, furthermore, lead to an even more compact type of construction to which the features in claim 9 also contribute.

An especially simple design of the dog is achieved by the features in claim 10. By the features of claims 11 to 13,the driving device allocated to the ball is realized in an especially simple, inexpensive manner requiring no additional components.

Constructions which are ofdifferenttypecompa- red with a ball, are just as advantageous and need only simple, inexpensive components for example production components, are realized by the features of claims 14to 19.

Also of advantage are the further developments according to claims 20 to 33.

The design according to the invention is equally suitablefora hammerdrill or chipping hammer as well asfora hammer drill and percussion hammer.

Further details and advantages of the invention follow from the description below.

The full wording of the claims, merely to avoid unnecessary repetition, is not reproduced above, but instead reference is made thereto simply by giving the claim number, whereby, however, all of these claim features have to be regarded here as expressly disclosed and disclosed as essential to the invention.

Drawing The invention is described in greater detail below with reference to exemplary embodiments shown in the drawings, in which: Figure 1 shows a schematic, partial axial long itudinalsectionofa hammer drill according to a first exemplary embodiment, Figure2 shows a schematic section along line Il-Il in Figure 1 to an enlarged scale, Figures3and4on each caseshowaschematic section approximately corresponding to that in Figure 2 of a part of a hammer drill according to a second any third embodiment, Figure 5shows a schematic axial longitudinal section approximately corresponding to that in Figure 1 of a part of a hammer drill according to a fourth exemplary embodiment, Figure 6shows a schematic section along line VI-VI in Figure 5 of the fourth exemplary embodiment, approximately corresponding to that in Figures 2 - 4, Figure 7shows a schematic axial longitudinal section approximately corresponding to that in Figure 1 of a part of a hammer drill according to a fifth exemplary embodiment, Figure 8 shows a schematic section approximately corresponding to that in Figure 2 of the part of the hammer drill in Figure7.

Description ofthe invention Figure 1 schematically shows a powered hand tool in the form of a hammerdrill which has a housing 10 in which an electric drive motor 11 is arranged which is designed as a universal motor. Moreover, the housing 10 contains a drill gear mechanism 12 and a percussion mechanism 13 which are designed, for example, according to German Offenlegungsschrift 2,449,191 and German Offenlegungsschrift 2,820,128 which are specifically referred to here so that particular details of the drill gear mechanism 12 and also the percussion mechanism 13 need not be described here in greater detail. At the rear end,the housing 10 merges into an indicated handle 14 into which a switch is fitted, which is provided with a trigger 15 and via which the drive motor 11 can be started.Atthefront end remote from the handle 14, a tool holder 16 for locating a tool (not shown), for ex- ample a drill our chisel bit, is arranged in the housing 10.

A component part ofthe percussion mechanism 13 is an inner hollow drive piston 17 which is tightly guided in a cylinder sleeve 18 and contains on the inside a striker 19 which is tightly guided in the cylindex sleeve 18 and is acted upon by the drive piston 17 with axial percussion energyforthetoolvia an air cushion 20 in between. The drive piston 17 is driven in reciprocating translatorymannerinthe direction of its longitudinal centre axis 21 via the percussion mechanism 13. In the position according to Figure 1, the drive piston 17 is located precisely in its furthest advanced forward position,tothe left in Figure 1. In contrast, Figure 2 shows the drive piston 17 in a centre position between the fully advanced to the left and the fully retracted position to the right.

The drive motor 11 is essentially aligned with its longitudinal centre axis 22 at right angles to the longitudinal centre axis 21 of the drive piston 17. Its drive shaft 23 is provided at the end with a tooth system 24 or a motor pinion, which tooth system 24 is directly meshed with part of a circumferential tooth system 25 on a gear 26, which part is the lower part in Figure 1 and is located atthe level ofthetooth system 24.

The gear 26 is held on a spindle 29, rotatably mounted by means of bearings 27 and 28, and is therefore rotatable about its rotational axis 30 which runs at least essentially parallel to the longitudinal centre axis 22 and at right angles to the longitudinal centre axis 21. The gear 26 is part of an eccentric gear mechanism and forms a drive member of the latter which, art a radial distance from its rotational axis 30, bears a driving device which is designated generally as 31 and is therefore arranged eccentrically to the rotational axis 30.The eccentric gear mechanism is used for converting the rotatory drive motion of the drive motor 11 into a translatory drive motion of the drive piston 17, which rotatory drive motion is passed directly by means ofthe tooth system 24 and the circumferential tooth system 25 to the gear 26 forming a drive member.

Moreover, on the drive piston 17, a component part of the eccentric gear mechanism is a dog 32 which projects transversely, in particular app rnximately radially, and on which a driving device 31 directly engages. As shown in particular by Figure 2, the gear 26 runs directly next to the drive piston 17 having a dog 32. The dog 32 is located on that end of the drive piston 17 which is remote from the striker 19, that is, the rsar end. Figures 1 and 2 showthatthe rotational axis 30 runs within a longitudinal plane of symmetry which contains the longitudinal centre axis 21 of the drive piston 17.In the front position of the gear 26, which position is shown in Figure 1,the dog 32 is at the sametime located, with its centre, within this longitudinal plane of symmetry just as in the rear end position, which in contrast is turned through 1800. Moreover, the rotational axis 30 is located in the axial area of the end of the drive piston 17; in other words it is moved to the left in Figure 1 to the extentthat it is located in the axial area ofthe drive piston 17 through which the latter passes during its translatory stroke. This leads to an axially compact type of construction.

The drive member in the form ofthe gear 26, with its end face 33 which faces towards the drive piston 17, is essentially aligned tangentially to the working piston 17 and at the same time is arranged practically directly adjacent to its outer side without there being large intermediate spaces in the direction ofthe rotational axis 30. This leads to a compact type of construction in this axial direction.

Whereas inthefirstexemplaryembodiment shown the drive member of the eccentric gear mech anism is formed by the gear 26, the drive member in anotherexemplary embodiment (not shown) con sists of a radial lever, sitting on the spindle 29, or of a corresponding disk, with both the lever and the disk bearing the driving device 31 in the same manner eccentrically to the rotational axis 30.

The dog 32 is arranged on the end of a, for example round, pin 34 which runs radially to the drive piston 17 and is held on the latter. The pin 34 sits in a dia metral bore 35 at the free end of the drive piston 17, which end is remote from the striker 19. In the first exemplary embodiment shown, the pin 34 is non displaceably arranged in the diametral bore 35, for example non-displaceably anchored therein or firmly pressed therein or held in some otherway such that it cannot be displaced axially. Here, the dog 32 consists of a ball 36. In corresponding allocation, the driving device 31 of the gear 26 is formed from a ball seat surface 37 which in simple manner consists of a bore 38. Here, the bore 38 is made as a blind bore which starts from the end face 33.It is located ata radial distance from the rotational axis 30 and runs essentially parallel to the latter. The diameter ofthe bore 38 corresponds at least essentially to that ofthe ball 36. The ball 36 can therefore move insidethe bore 38 about all three spatial axes and is otherwise displaceable relative to the bore 38 in the longitudinal direction ofthe latter, that is, in the depth direction ofthe bore 38. The ball 36 is at least partly located and held in the bore 38. The depth of the bore 38 is in any case of such a size that the ball 36 has adequate clearance of movement in the depth direction relative to the bore 38.

During the rotational motion of the gear 26 in one direction of rotation, its eccentric bore 38 also revolves about the axis 30 of rotation. The ball 36 engaging therein is driven along in each case during this motion. The pin 34therefore produces a reciprocating drive motion of the drive piston 17. In the front end position according to Figure 1 and the rear end position, in contrast turned 180% of the gear 26 and the ball 36 having the pin 34, the pin 34 is in each case disposed as shown in Figure 1, that is, with its longitudinal centre axis essentially parallel to the rotational axis 30 and essentially at right angles to the longitudinal centre axis 21. In the position shown in Figure 2 of the gear 26, which position is in con trast swivelled through a 900 circumferential angle, the pin 34 runs with its longitudinal centre axis in a correspondingly sloping position. During the rotation ofthe gear 26, the drive piston 17 rotates about its longitudinal centre axis 21 via the ball 36 and the driving device 31, namely within the limits as set by the pin 34 in one sloping position according to Figure 2 and in the other sloping position turned in contrast through a 180" circumferential angle. This rotation of the drive piston 17 therefore acts as compensation.

In the positions between those in Figure 2 and Figure 1, a length compensation is effected by the ball 36 being displaced to the necessary extent in the axial direction of the bore 38.

The hammer drill described is exceptionally com- pact. It is extremely compact in the direction of the longitudinal centre axis 21 and the longitudinal centre axis 22 essentially at right angles thereto. A short and lowtype of construction therefore results.

It is also of advantage that the hammer drill consists only of a few components, with the percussion mechanism l3inparticular,astheresultoftheel- ements described, being substantially simplified with regard to the components and being reduced to only a few components. At the same time, these are otherwise simple and inexpensive components, which enables the costs to be further reduced.

In the second exemplary embodiment shown in Figure 3, reference numerals increased by 100 are used for the parts which correspond to the first exemplary embodiment so that reference is thereby madetothe description of the first exemplary embodimentto avoid repetition.

In the second exemplary embodiment, the end of the pin 134 is provided with a cylinder section 140 which here has the same diameter and represents an extension of the pin 134. In another exemplary emb- odiment (not shown), the cylinder section 140 is larger in diameter. Here, the dog is designed as a spher ical pivot bearing 139. At the end ofthe pin 134, the pivot bearing 139 has a sleeve 141 which is held on the pin 134 and is provided with an outersurface 143 approximately curved in the shape of a spherical cap.

Located between the sleeve 141 and the cylinder section 140 is a bearing 145 in the form of a needle bearing which is directly mounted on the cylinder section 140. The sleeve 141 is firmly attached on the outer ring 146 of the bearing 145. The bearing 145 ensures that the pin 134 and the sleeve 141 can rotate relative to one another about the pin longitudinal axis and in particularthatatthesametimethetwo parts can be displaced axially relative to one another for length compensation, so that the pin 134, as in the first exemplary embodiment, can be held in axially nondisplaceable manner within the diametral bore 135 ofthedrivepiston 117.

Thedriving device 131 ofthegear126designedas a drive member has a bore 138 essentially parallel to the rotational axis 130 and an outer ring 142 which is held in the bore 138 and, with an inner bearing surface 144 in the shape of spherical segment, acts as a bearing socket for the sleeve 141 with the outer such face 143 curved in the shape of a spherical segment.

The outer ring 142 is held non-rotationally and also axially non-displaceably inside the bore 138, which is achieved by means of an axial shoulder on the one hand and a snap ring 147 on the other hand. The pin 134 can be axially displaced relative to the sleeve 141 by means of the bearing 145. Moreover, by means of the spherical pivot bearing 139, the pin 134 is pivotable in all directions inside the outer ring 142.

In the first exemplary embodiment according to Figures 1 and 2, and also in the second exemplary embodiment according to Figure 3, the length compensation can also be achieved by the pin 34 and 134 respectively being displaceable inside a diametral bore 35 and 135 respectively relative to the drive piston 17 and 117 respectively, for example by means of a bearing bush or a needle sleeve which is inserted into the drive piston.

In a different arrangement from Figure 3, the sleeve 141 in another exemplary embodiment (not shown), with the bearing 145 omitted, is held directly on the cylinder section 140, for example pressed-on on the latter. The design ofthe spherical pivot bearing is otherwise the same. The requisite length compensation between the drive piston and the pin 134 is then achieved in the manner described above by means of a bearing bush, needle sleeve or the like in the drive piston,within which bearing bush or needle sleeve the pin 134 is held in axiallydis- placeable manner. In a further modification,the pin in the drive piston can of course be rotatably mounted about its longitudinal axis, for example by means of a bearing bush, needle bearing orthe like, but can be held in axially non-displaceable manner relative to the drive piston.In this case, the sleeve 141 sits on the cylinder section 140 either via the bearing 145 or atleast in displaceable sliding manneronthecylin- der section 140 so that the requisite length compensation is thereby ensured, because the pin 134, with its cylinder section 140 is then axially displaceable with respectto the sleeve 141.

In a further exemplary embodiment (not shown) the bearing 145 is again omitted. The sleeve 141 is held directly on the cylinder section 140, for example pressed-on on the latter. Instead of containing the outer ring 142, the allocated driving device then contains, in the bore 138, a cylinder sleeve which is rotatably mounted in the bore about the bore axis and the inside diameter of which corresponds to the outside diameter of the spherical outer surface 143, so that the sleeve 141,with its outer surface 143, sits in the cylindersleeveand on the one hand is heldtherein such that it can be pivoted spherically and on the other hand can also be axially displaced therein for length compensation.In an especially simple manner, the bearing consists of a needle bearing our a needle sleeve, the inner ring of which atthesame time forms the cylinder sleeve.

lnthethirdexemplaryembodimentshownin Figure4, reference numerals increased by200are used, for the reason stated, for the parts which correspond to the first and/or second exemplary emboddment in Figures 1-3.

The third exemplary embodiment according to Figure 4 differs from the first exemplary embodi- ment in Figures 1 and 2 in that the dog 232 in Figure 4, in particularthe ball 236 on the end ofthe pin 234, is mounted in relatively displaceable manner with respectto the drive piston 217 in the radial direction of the latter. For this purpose, the drive piston 217 contains a bearing bush 251 in a diametral bore 234, inside of which bearing bush 251 the pin 234 is mounted in displaceable sliding manner in its longitudinal direction. The bearing bush 251 is pressed,for example, into the drive piston 217. During each revolution ofthe gear 226, length compensation is effected in that here the pin 234 having the ball 236 can be freely displaced axially relative to the drive piston 217.Here, the bore 238 in the gear 226 can be made shorter, which bore 238 locates the ball 236.

Although the ball 236 is connected to the gear 226 such that it can be pivoted about all three spatial axes, it is not displaceably connected because a retaining plate 252 grips over it which prevents the ball 236from lifting out ofthe bore 238. The retaining plate 252 is fixed, for example screwed on, to the end face 233 of the gear 226.

In the fourth exemplary embodiment shown in Fig ures 5 and 6, the dog 332 is designed as a bearing boss 361 on the free end ofthe pin 334. The centre axis 362 ofthe bearing boss 36, is aligned essentially parallel to the longitudinal centre axis 321 ofthe drive piston 317 and atthe sametime at rightangles to the rotational axis 330 of the drive member ofthe spindle 329, which drive member is designed as a gear 236. Via the bearing boss 361, the pin 334 is held on the driving device 331 ofthe gear 326 such that it can pivot aboutthis centre axis 362.

The driving device 331 has a bearing pin 363 on a retaining fork364through which the bearing boss 361 passes. The retaining fork 364 sits on a pivot pin 365 which is mounted in freely rotatable manner on the gear 326. In the exemplary embodiment shown, the pivot pin 365 is freely rotatable about an axis 366 which runs essentially parallel to the rotational axis 330 and at a radial distance from the latter. At a radial distance from the rotational axis 330, the gear 326 contains a bearing bore 338, inside of which the pivot pin 365 is mounted, for example by means of a needle bearing 367.The length compensation between the drive piston 317 and the pin 334, as in the third exemplary embodiment according to Figure 4, is effected via a bearing bush 351 in the drive piston 317, along which bearing bush 351 the pin 334 is guided in relatively displaceable manner in its longitudinal direction.

In another exemplary embodiment (not shown), the pivot pin 365 does not run parallel to the rotational axis 330, but extends approximately horizontally. Itis held in freely rotatable manner above the end face of the gear 326 about an axis which runs essentially parallel to the longitudinal centre axis 321 ofthe drive piston 317 and essentially at right angles to the rotational axis 330 ofthe gear 326. For this purpose, a cylindrical bearing bush, for example, is located on the end face of the gear 326, which bearing bush is radially aligned and in which the pivot pin 365 is secured in axially non-dis-placeable manner, with it being pivotable relative thereto about its longitudinal centre axis.

In the fifth exemplary embodiment shown in Figures 7 and 8 the relationships are reversed in comparison with thefeurth exemplary embodiment. The pin 434 bears a bearing fork 464 on the end, whereas sitting on the pivot pin 465 is a retaining boss 461 which engages into the bearing fork 464 and is pivotably coupled to the latter via the bearing pin 463. In addition to the needle bearing 467, another axially adjacent second bearing 470, which here consists of a ball bearing, is provided for mounting the pivot pin 465inthegear426.

In the fourth exemplary embodiment in Figures 5 and 6, it has to be ensured that the centre axis 362 of the fork joint is always aligned parallel to the long itudinal centre axis 321 ofthe drive piston 317 as shown in Figures 5 and 6. In figures 5 and 6, this can be achieved for example by securing the pin 334 against rotating about its longitudinal axis relative to the drive piston 317. For example, the pin 334 in Fig ures 5 and 6 can be positively located non rotationally inside the bearing bush 351 byan app ropriate cross-sectional contour.

In the fifth exemplary embodiment in Figures 7 and 8, the bearing fork 464, in a different arrange mentfrom the fourth exemplary embodiment, is coupled, together with the pin 434, in such a wayto the guide 471, which locates and guides the drive piston 417 and is mounted in freely rotatable manner about a longitudinal centre axis, that the bearing fork 464, together with the pin 434, cannot rotate about the pin longitudinal axis relative to the drive piston 417 and the guide tube 471. Thus the longitudinal axis of the bearing pin 463 likewise always remains in a position approximately parallel to the long itudinal centre axis of the drive piston 417. The pin 434 can be displaced relative to the guide tube 471 in the axial direction of the latter.For this purpose, the bearing fork 464 engages into an axial longitudinal slot 472 ofthe guide tube 471, as a result of which the pin 434 cannot rotate about the longitudinal axis. The opposite free end of the pin 434 engages in the same manner into an axial longitudinal slot 473 ofthe guide tube 471. Otherwise, the relationships are as in the fourth exemplary embodiment. Here, too, the length compensation between the drive piston 417 on the one hand and the pin 434 on the other hand is achieved in that the pin 434 is longitudinally dis placeable relative to the drive piston 417 by means of a bearing bush 451 in the drive piston 417. Here, too, the bearing bush 451 can be replaced by anothersliding bearing arrangement or rolling bearing arrangement, for example by a needle bearing, in particular a needle sleeve.

In a different arrangementfrom thefourth ex emplaryembodimentin Figures5and6and/orthe fifth exemplary embodiment in Figures 7 and 8, the pin 343 and 434 respectively can instead also be connected non-displaceably in fixed mannertothedrive piston 317 and 417 respectively. The requisite length compensation is instead achieved in that the pivot pin 365 and 465 respectively is longitudinally displaceable inside the bore 338.

Claims (34)

1. Powered hand tool, in particular a hammer drill and/or percussion hammer, having a housing (10) in which a drill gear mechanism (12)and/orpercussion mechanism (13) is arranged for the rotatory ortranslatory drive of a tool, which drill gear mechanism (12) and/or percussion mechanism (13) is driven by a drive motor (11) and has a reciprocally driven drive piston (17) and a coaxial striker(19), which can be acted upon preferably via an air cushion (20), for producing the percussion energy forthe tool, with the percussion mechanism (13) having an eccentric gear mechanism by means of which the rotatory drive motion ofthe drive motor (11) can be converted into the translational motion of the drive piston (17), characterized in thattheeccentric gear mechanism has a transversely, in particular approximately radially, projecting dog (32; 32; 232; 332) on the drive piston (17; 117; 217; 317) and, next to the drive piston (17; 117; 217; 317) having the dog (32; 132; 232; 332), a drive member (26; 126; 226; 326) which is rotationally driven about a rotational axis (30) runningapproximatelyatrightanglestothe longitudinal centre axis (21; 121; 221; 321) ofthe drive piston (17; 117; 217; 317) and which, at a radial distance from its rotational axis, (30; 130; 230; 330), bears a driving device (31; 131; 231 ;331) engaging on the dog (32; 132; 232; 332).

2. Powered hand tool according to claim 1, characterized inthatthe dog (32; 132; 232; 332) isarranged on the end ofthe drive end ofthe drive piston (17; 117; 217; 317),which end is remote from the striker (19).

3. Powered hand tool according to claim 1 or2, characterized in that the rotational axis (30; 130; 230; 330) ofthe driving device (31; 131; 231; 331) runs within a longitudinal plane of symmetry, containing a longitudinal centre axis (21; 121; 221; 321) ofthe drive piston (17; 117; 217; 317), and in the axial area of the drive piston (17; 117; 217; 317).

4. Powered hand tool according to claim 3, characterized in that the rotational axis (30; 130; 230; 330) essentially runs in the axial area of the free end ofthe drive piston (17; 117; 217;317)through which the drive piston (17; 117; 217; 317) runs during in its translational stroke.

5. Powered hand tool according to one of claims 1 to 4, characterized inthatthedog (32; 132; 232; 332) is arranged on the end of a pin (34; 134; 234; 334) which runs radiallytothedrive piston (17; 117; 217; 317) and is held thereon.

6. Powered hand tool according to claim 5, characterized in that the pin (34; 134; 234; 334) is held on the free end ofthe drive piston (17; 117; 217; 317) in a diametral bore (35; 135; 235), which free end is re motefromthe striker(19).

7. Powered hand tool according to one of claims 1 to 6, characterized in that the drive member is designed as a radial lever or as a disk, in particularas a gear (26; 126; 226; 326), and is held on a rotatably mounted spindle (29; 129; 229; 329).

8. Powered hand tool according to claim 7, characterized in that the gear (26) is provided with circumferential teeth (25) and directly meshes with a tooth system (24) of the drive shaft (23) ofthe drive motor (11), with the drive motor (11), with its long- itudinal centre axis (22), preferably being aligned es sentially at right angles to the longitudinal centre axis (21) ofthe drive piston (17) and with the rotational axis (30) of the gear (26) running nextto it and approximately parallel to it.

9. Powered hand tool according to claim 7 or8, characterized in thatthe radial ieverorthe diskorthe gear (26; 126; 226; 326), with the end face (33; 233) which faces towards the drive piston (17; 117; 217; 317), is arranged essentially approximatelytangenti- allyto the drive piston (17; 117; 217; 317) and directly adjacent to its outer side.

10. Powered hand tool according to one of claims 1 to 9, characterized in that the dog (32; 232) is directly designed as a ball (36; 236) or a spherical pivot bearing (139).

11. Powered hand tool according to one of claims 1 to 10, characterized in that the driving device (31, 231) ofthe drive member (26; 226) is formed from a ball seat surface (37) which is arranged on orinthe drive member (26; 226).

12. Powered hand tool according to claim 11, characterized in that the ball seat surface (37) is formed from a bore (38; 238) which, at a radial distance from the rotational axis (30; 230) of the drive member (26; 226), essentially runs parallel to this rotational axis (30; 230), its diameter at least essentially corresponds to the diameterofthe ball (36; 236) and in which the ball (36; 236) is at least partlylocated and held.

13. Powered hand tool according to claim 12, characterized in thatthe depth of the bore (38) is of such a size that the ball (36) has clearance of movement relative to the bore (38) in the depth direction of the latter (Figures 1,2).

14. Powered hand tool according to one of claims 1 to 10, characterized in that the dog (132) orthe spherical pivot bearing (139) has a sleeve (141 )which is held on the end ofthe pin (134) and has an outer surface (143) curved in the approximate shape of a spherical cap (Figure 3).

15. Powered hand tool according to claim 14, characterized in that the sleeve (141) is arranged in fixed manner on the pin (134),forexamplepressed- on on the latter.

16. Powered hand tool according to claim 14, characterized in that the sleeve and the pin are axially displaceable relative to one another and/or are rotatably held aboutthe pin axis.

17. Powered hand tool according claim 16, char acterized in that a bearing (145), in particular a needle bearing, is arranged between the sleeve (141) and the pin (134), by means of which bearing (145) the sleeve (141) is rotatably mounted with respect to the pin (134).

18. Powered handtool according to claim 17, characterized in thatthe pin (134) is axially dis- placeable relative to the bearing (145), in particular a needle bearing.

19. Powered hand tool according to one of claims 14to 18, characterized in that the driving device (131) ofthe drive member (126) has a bore (138), essentially parallel to the rotational axis (130), and an outer ring (142)which is held in the bore (138) and has an inner bearing surface (144) in the shape of a spherical segment as a bearing socketforthe sleeve (141) hav- ingtheoutersurface (143) curved in the shape ofa spherical cap.

20. Powered hand tool according to claim 19, characterized in thatthe outer ring (142) is held nonrotationally and axially non-displaceably in the bore (138).

21. Powered hand tool according to claim 15, characterized in thatthe driving device of the drive member has a bore, essentially parallel to the rotational axis, and a cylindrical sleeve, in particular a needle sleeve, rotatably mounted in the bore, inside of which the sleeve, with its outersurface which is curved in the shape of a spherical cap, is held axially displaceable and rotatably and also pivotably.

22. Powered hand tool according to one of claims 1 to 9, characterized in thatthe dog (332) is designed as a bearing boss (361) or bearing fork, the centre axis (362) of which is aligned essentially parallel to the longitudinal centre axis (321) of the drive piston (317) and at right angles to the rotational axis (330) of the drive member (326) and with which the pin (334) is held pivotably aboutthis centre axis (362) on the driving device (331) ofthe drive member (326) (Figures 5,6).

23. Powered hand tool according to claim 22, characterized in thatthe driving device (331) has a bearing pin (363) which penetrates through the bearing boss (361) or the bearing fork and is on a retaining fork (364) or a retaining boss, which retaining fork (364) or retaining boss is pivotably mounted on the drive member (326).

24. Powered hand tool according to claim 23, characterized in that the retaining fork (364) orthe retaining boss sits on a pivot pin (365) mounted in freely rotatable manner.

25. Powered hand tool according to claim 24, characterized in thatthe pivot pin (365) is held on the drive member (326) in freely rotatable manner about an axis (366) running essentially parallel to the rotational axis (330) of the drive member (326) and ata radial distance therefrom.

26. Powered hand tool according one of claims 22 to 25, characterized in that the dog designed as a bearing fork (464),togetherwith the pin (434), is coupled non-rotatably about the pin axis to a guide tube (471) accommodating the drive piston (417) but is displaceable relative to the guide tube (471) in the axial direction ofthe latter.

27. Powered hand tool according to claim 26, characterized in thatthe bearing fork (464) engages in a longitudinal slot (472) ofthe guide tube (471).

28. Powered hand tool according to claim 24, characterized in thatthe pivot pin, about an axis which runs essentially parallel to the longitudinal centre axis ofthe drive piston and essentially at right angles to the rotational axis ofthe drive member, is held on the drive member in freely rotatable manner and at the sametime is axially non-displaceable.

29. Powered hand tool according to one of claims 1 to 28, characterized in that the dog (32; 132), in part icularthe pin (34; 134) bearing it, is arranged on the drive piston (17; 117) in non-displaceable manner with respectto the drive piston (17; 117) in the radial direction of the latter.

30. Powered handtool according to 29, characterized in thatthe pin (34; 134) is anchored non displaceablyon the drive piston (17; 117).

31. Powered hand tool according to claim 29 or 30, characterized in that the pin (34; 134) is firmly pressed into the drive piston (17; 117).

32. Powered hand tool according to one of claims 1 to 28, characterized in that the dog (232; 332), in particularthe pin (234; 334) bearing it, is mounted on or in the drive pisiton (217; 317) in relatively dis placeable manner with respect to the drive piston (217; 317) in the radial direction of the latter.

33. Powered hand tool according to claim 32, sharacterized in that the drive piston (217; 317) contains a radial bearing bush (251; 351), for example a needle sleeve, in which the pin (234; 334) is mounted in displaceable sliding manner.

34. Any of the embodiments of powered hand tool substantially as herein described with reference to the accompanying drawings.