GB1587545A

GB1587545A - Vibration-damped rotary-percussive hand tool machine

Info

Publication number: GB1587545A
Application number: GB4968877A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1976-12-09
Filing date: 1977-11-29
Publication date: 1981-04-08
Also published as: NL7713509A; CH626824A5; ES464860A1; DE2655899A1

Abstract

The powered hand tool, also called a hammer drill, has a percussion mechanism (45) which delivers axial blows to a drilling spindle (51), which transmits these axial blows, if need be together with a rotary movement, to a tool fastened to the drilling spindle. The drilling spindle (51) is guided in an axially movable manner in two rolling bearings (56, 57). Between the rolling bearings it has a collar (58) which reaches into a space defined by two stop shoulders (59, 60). The stop shoulders (59, 60) are formed on bodies (61, 62) which are supported via damping means (63, 64) on the housing of the machine. This dampens in particular the blows arising when the tool or the drilling spindle rebounds onto the powered hand tool. <IMAGE>

Description

(54) A VIBRATION-DAMPED ROTARY-PERCUSSIVE HAND TOOL MACHINE (71) We, ROBERT BOSCH GmbH, a German company of Postfach 50, 7000 Stuttgart 1, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a hand tool machine arranged to impart a rotary movement and axial impacts to a tool, such as a drill. Such a hand tool machine is also called a drill hammer and comprises a percussion mechanism which delivers the axial impacts to a drill spindle which then transmits the impacts to the tool guided in the hand tool machine, if necessary together with a rotary motion.

Up to now, the axial forces in such hand tool machines have remained undamped, resulting in an increased load on the wrist and arm of the operators using the hand tool machines.

In accordance with the invention, a hand tool machine is provided comprising a housing, an electric motor and a percussion mechanism arranged to be driven by the electric motor, the percussion mechanism including a striker through which a driving member, performing an axial reciprocating movement, can impart energy to a tool rotatably arranged and guided in the hand tool machine, in which a drill spindle for transmitting to the tool, a rotary movement derived from the motor and the axial movement of the driving member, is arranged between the percussion mechanism and a tool holder and is axially and rotatably guided in two bearings and in which, between the two bearings, the drill spindle is provided with a flange arranged to move axially in a chamber between two abutment shoulders which are supported by the housing through damping means.

Preferably, the abutment shoulders are arranged on at least partially annular members, each forming part of the chamber.

Moreover, the abutment shoulders may be formed of damping material, especially of a polyamide, and damping may be further improved by an O-ring arranged behind each abutment shoulder.

With a hand tool machine in accordance with the invention, a minimum of noise is developed during percussion drilling, especially noise due to so-called B-impacts.

(By B-impacts is meant the rebound of the tool or the drill shank into the hand tool machine.) Moreover, a hand tool machine in accordance with the invention, can be of a simple and cheap construction less prone to breakdown. Assembly and dismantling of the hand tool machine is especially suited to workshops, especially due to the drill spindle construction in accordance with the invention. Finally, sealing of the interior of the hand tool machine is made more secure and permanent.

In order that the invention may be clearly understood and more readily carried into effect, a hand tool machine in accordance therewith will now be described with reference to the accompanying drawings in which: Figure la is a general view of a hand tool machine in accordance with the invention designed as a drill hammer.

Figure lb is a longitudinal section through the drill hammer of Figure la, Figure 2 is a cross-section along the line II-II in Figure ib, Figure 3 is a cross-section along the line III-III in Figure lb, and Figure 4 is a partial cross-section along the line IV-IV in Figure ib.

A hand tool machine in accordance with the invention, more accurately described as a drill hammer, is represented in the drawing. The drill hammer 1 has a housing consisting substantially of three parts: a central housing part 2, which is closed at the front end by a housing cover 3 and at the rear end by a rear housing portion 5 provided with a shaped spade handgrip 4.

All the housing parts 2, 3, 5 are made from impact resistant plastics. A switch provided with a pushbutton 6 through which the hand tool machine can be set in operation, is incorporated in the spade handgrip 4. A current conductor cable 7 is introduced through a resilient nozzle at the lower end of the spade handgrip 4. A tool holder 8, which serves for the reception of tools not illustrated in detail-such as drills or chisels-is arranged on the drill hammer 1 at the forward end remote from the spade handgrip 4.

An electric motor 9-in this instance a universal motor-is arranged in the lower region of the central housing part 2, the motor having a rotor 10 which is arranged in known manner on a driving shaft 13 of the electric motor mounted at both ends in roller bearings 11, 12. The forward roller bearing 11-in this instance a grooved ballbearing-is mounted by means of its inner ring as a press fit on the driving shaft 13 and is mounted by means of its outer ring in a rubber bush 14 which, once again, is retained in a bearing extension 15 of the forward housing cover 3. The bearing bush 14 is so distorted that the driving shaft 13 experiences a force in a direction towards the rear roller bearing 12 which is likewise formed as a grooved ballbearing.The force is greater than all the forces occurring in the driving shaft 13 opposing the said force in any operating condition of the drill hammer. Due to its softness, the rubber bush 14-it is made of a material of high heat resistance and good compression-set-response is in the position to so withstand relatively large tolerances which possibly occur with plastics parts, that only a small variation in the axial deforming force is applied to the rotor 10. Also axial misalignment occasioned by manufacturing tolerances or variations in dimensions as a result of heating or creeping possibly of the plastics parts, can easily be compensated hereby. A fan wheel 16 accommodated in the housing cover 3 is mounted on the driving shaft 13 on the end facing the rotor 10.A commutator 17 is connected to the fan wheel 16 on the driving shaft 13 on the end remote from the roller bearing 11.

A brush holder plate 19 the side of which remote from the rotor is formed as an air conducting disc 20 for the fan, is arranged between the central housing portion 2 representing the motor housing and the housing cover 3 which is adjustable in central housing portion 2 where it fits at 18.

The brush holder plate 19 has two bag-like brush guides 21 (Figure 2) lying diagonally opposite one another, in which carbon brushes 24 are guided. Moreover, screwthreads 22 are arranged in the brush holder plate 19 into which are screwed bolts 25.

The bolts 25 secure closure covers 26 made of plastics by means of which the rear, outwardly open ends of the brush guides 21 are closed. Furthermore, threaded extensions 23 for the cable connections associated with the carbon brushes 24 are arranged in the brush holder plate 19 adjacent the brush guides 21. The portions of the brush holder plate 19 carrying the screwthread 22 are made as supporting extensions 27 for the laminated stator 28 of the electric motor (Figure 4).

The stator 28 is, of course, pushed into abutment on four correspondingly fashioned guide rails 29 of the central housing portion 2 serving as the motor housing-as can be seen especially well in Figure 3.

Thus, the stator 28 is securely prevented from slipping out of its innermost position illustrated in Figure 1 by the supporting extensions 27 which, at their ends facing the stator 28, can also be provided with rubber pads 30.

On the side of the roller bearing 12, where it projects out of the stator 28, the driving shaft 13 passes through the wall 32 of the central housing portion which bounds the interior of the motor, sealed by a lip sealing ring 31. The driving shaft 13 at this point it has a hardened, ground steel surface its mounted by way of a sliding seating in the hardened and ground bore of the inner ring of the roller bearing 12.

In this way, on the one hand, the abovedescribed axial alignment of the two roller bearings 11, 12 with respect to each other is made possible and on the other hand, a convenient removal and insertion of the rotor 10 in the drill hammer. The roller bearing 12 is not only highly stressed mechanically but also thermally, is mounted by way of its outer ring with a press fit in a bearing block 33 made of cast aluminium and is lubricated and cooled by lubricant provided in the gearbox 34 of the hammer. In this manner, bleeding of the roller bearing 12 and also a rolling out of the bearing seating is securely prevented.

The aluminium bearing block made up of a plurality of parts screwed together is especially well-suited to the dissipation of the existing heat.

The end of the driving shaft 13 mounted in the roller bearing 12 carries a motor pinion 35. The inner ring of the roller bearing 12 is supported axially on an abutment ring 36 fixed with a press fit on the driving shaft 13. The motor pinion 35 drives an intermediate shaft 38 through gear teeth 37. The intermediate shaft is guided in two roller bearings 39, 40 formed as grooved ball bearings, the outer rings of which are both pressed into receiving bores in the bearing block 33. Moreover, the intermediate shaft 38 is pressed into the large roller bearing 40 at the handgrip end and is mounted in the inner ring of the other roller bearing 39 with a push fit.

A swashplate member 41 consisting of two parts 41', 41" axially fitting together, is pressed onto the intermediate shaft 38.

An annular groove 42 is arranged at the periphery of the swashplate member 41, the axis of which groove is inclined with respect to the axis of the swashplate member. A ring 43, on which is arranged a radially extending cam follower 44, is rotatably guided in the annular groove 42 and is supported by the sides of the annular groove through axial needle bearings. The cam follower 44 drives the percussion mechanism 45 of the drill hammer.

Elastically deformed means are arranged axially between the roller bearing 39 and the swashplate member 41. The elastic means are formed by a spring washer 46 the smaller diameter of which engages the inner ring of the bearing member 39 and the larger diameter of which engages the swashplate member 41. In an appropriate manner, the spring washer not only compensates for variations in spacing between the axial bearing surfaces on the intermediate shaft 38 and in the bearings 39, 40 resulting from manufacturing tolerances but also for those resulting from heat expansion or wear in the bearings. Moreover it leads to a slight axial deformation of the two roller bearings 39, 40 which is important for the life of the bearings and to a rigid transfer to the massively dimensioned roller bearing 40 of the considerable forces existing in the percussion mechanism.The comparatively small inertia forces acting on the roller bearing 39, can be transmitted without difficulty through the slightly pretensioned spring washer 46.

The percussion mechanism 45 of the drill hammer is arranged inside a fixed guide tube 47. It consists of a striker 48 sealingly and slidingly guided in the guide tube 47 and a drive member formed as a piston 49 likewise sealingly and slidingly guided in the guide tube 47. A number of passages are arranged in the wall of the guide tube 47, which can be opened and closed by the striker 48.

The rear end of the piston 49 remote from the striker 48 is made forked and carries a rotary pin 50. A transverse bore in which the cam follower 44 engages with a small amount of clearance is arranged in the centre of the rotary pin 50.

Thereby, the cam follower 44 can easily move axially in the transverse bore.

The inner end of a drill spindle 51 extends into the forward end region of the interior of the guide tube 47 remote from the piston 49. Furthermore, the forward end of the intermediate shaft 38 remote from the motor 9, is formed as a pinion 52 which meshes with an externallytoothed flange 53 which is arranged on a rotary sleeve 54. The rotary sleeve is rotatably mounted on the forward portion of the fixed guide tube 47; at its forward end, the rotary sleeve 54 has internal teeth 55 which engage in a corresponding external spline on the rear end of the drill spindle 51 projecting into the guide tube 47, for rotation with the spline. The rotary sleeve 54 is supported, on the one hand on the guide tube 47 radially inwards of the externally-toothed flange and on the other hand, on the drill spindle 51 by the inner teeth 55.This arrangement caters in a special manner for the axial misalignment always present in practice between the drill spindle and the bearing surface on the bearing block or on the guide tube 47 fixedly arranged in the bearing block.

Since the bearing surface of the rotary sleeve 54 lying radially inwardly of the flange 53, is made slightly cambered, a small angular displacement can be taken into account without disadvantageous results.

The drill spindle 51 is arranged with a push fit in two roller bearings 56, 57 designed as grooved ballbearings, between the percussion mechanism 45 and the tool holder 8 arranged on the drill spindle at the free end. Between the roller bearings 56, 57, the drill spindle 51 has a flange 58 which is arranged to move axially in a chamber between two abutment shoulders 59, 60 which are supported by the housing of the drill hammer through damping means. Each abutment shoulder 59, 60 is formed on an annular member 61, 62 of a damping material in this instance a poly amide surrounding the cylindrical outer surface of the drill spindle 51.The two annular members 61, 62 arranged as mirror images of one another, are each supported in the housing of the drill hammer rearwardly on the side remote from the abutment shoulders 59, 60, through a respective O-ring 63, 64 and the roller bearings 56, 57. So as to improve centering of the annular members 61, 62 when the flange 58 strikes each of the abutment shoulders 59, 60, the abutment shoulders 59, 60 are in the shape of a convergent inner cone in the direction of striking, the flange 58 is in the form of an associated external cone converging in the same direction.

In the region of the drill spindle, the construction of the drill hammer is characterised by a robust and simple rotary drive, by the most effective damping of axial forces in both directions and by a collectively very robust, cheap, compact, light construction very suitable for workshops.

A sealing ring 65 sealing the interior of the hammer towards the tool end, is arranged on the side of the roller bearing 56 facing the tool holder 8.

As already referred to above, the gearbox 34 is at least partially filled with oil for lubricating and for cooling all the bearings as well as the impact mechanism. In this way, the best lubricating conditions may be achieved up to the point at which the oil has been completely used up, as well as good heat conducting properties. A requirement for that is certainly that the gearbox is so sealed that the oil cannot arrive outside it. It can of course be shown that, in the case where the gearbox is not provided with outward ventilation, higher pressures and subsequently during cooling of the drill hammer low pressures can prevail. In order to prevent this, the gearbox is provided with an oil sealing ventilation.

This consists of a ventilation duct 66, which proceeds from the interior of the motor connected to atmosphere whilst passing through the wall 32. The ventilation duct 66 is arranged in a plug-shaped housing extension 67, the preferably sharp edged end of which terminates inside a coaxial bore 68 in the intermediate shaft 38. At the inner end, the coaxial bore 68 has a radial opening 69 which issues into the base of the annular groove 42 of the swashplate member 41. A narrow sealing gap 70 exists between the end of the pinion like end of the intermediate shaft 38 and the housing wall 32 forming the base region of the housing extension 67. An effective ventilation of the gearbox 34 is guaranteed by the described ventilation duct 66, whereby the above-described high and low pressures are more definitely avoided.The pointed projection of the housing extension 67 and the centrifugal effect on the oil forced into the bore 68, prevent oil which arrives therein even with sudden splashing, entering into the motor chamber due to the ventilation. Moreover, a sufficient lubrication of the needle bearings supporting the ring 53 is guaranteed through the radial opening 69.

In a modification of the invention-with- out having to take account of the narrow sealing gap 70-the forward opening of the coaxial bore 68 leaving the intermediate shaft 38 can be closed by a sealing disc not shown in detail in the drawing, which, on the one hand, contacts the wall of the coaxial bore in the intermediate shaft 38 and on the other hand, contacts the pluglike housing extension 67. Then, the ventilation no longer takes place through the narrow sealing gap 70 but directly through the radial opening 69 in the base of the annular groove 42 and the bore 68 to the ventilating duct 66.

As can easily be seen, rotation of the swashplate member 41 produces a reciprocating motion of the piston 49. When the tool clamped in the tool holder 8 is applied to a workpiece-thus, for example, to masonry to be operated on-whereupon the drill spindle 51 arrives in the position illustrated in Figure 1, in which the inner end of the latter carrying an external spline projects into the percussion mechanism 45, the percussion mechanism is located in its percussive position. The striker 48 is likewise displaced in an axially reciprocating manner through the air cushion, which acts as an energy store, formed between the piston 49 and the striker 48.

On striking the inner end of the drill spindle 51, the striker gives up its energy which finally becomes effective on the tool held in the tool holder 8 as an axial impact.

In so doing, the drill spindle executes a certain forward axial movement out of the position illustrated in Figure 1, which, however, is not so extensive that the flange 58 comes to rest against the forward shoulder 59. Since, as regards the tool and usually also as regards the workpiece to be operated on, it is a question of highly elastic materials, the tool, after the abovedescribed so-called A-impact, experiences a rebound into the hand tool machine, the so-called B-impact. In so doing, the drill spindle 51 arrives once again in the position illustrated in Figure 1 wherein the flange 58 strikes the shoulder 60. Hereby, the annular member 62 of plastics or polyamide which transmits the force damped by the O-ring 64, is urged against the rear roller bearing 57 which conducts the impact into the housing. Due to this arrangement, a minimum development of noise results from the described B-impacts during percussion drilling. Moreover, the load on the wrist and elbow of the operator working with the hand tool machine is, of course, also reduced.

Now if the operator removes the hand tool machine from the workpiece then the drill spindle 51 can move forwards until finally the flange 58 strikes the forward shoulder 59. If the removal of the hammer from the workpiece takes place during operation of the hammer, then the striker 58 will still exert at least one axial impact on the spindle 51. The spindle 51 is then forced against the front shoulder 59 whereupon the impact is then damped in a similar manner as described above in connection with the B-impact. The percussion mechanism 45 is then located in its idling position in which, since the drill spindle 51 is located in its most forward possible position, the striker 48 can move up to the forward end of the guide tube 47.So that, during the above-described transition into the idling condition, the striker 48 does not rebound once again into the percussion mechanism, the striker is provided with a striker trapping device. This striker trapping device consists of an elastic expansible O-ring 71 retained at the forward workpiece end of the guide tube 47. At its forward free end, the striker 48 has around its periphery a damping flange 73 the diameter of which is greater than the inner diameter of the undeformed O-ring 71. During transition of the percussion mechanism into the idling condition, the damping flange 73 on the striker penetrates into the O-ring whereupon the latter is deformed and a portion of the striker's kinetic energy is absorbed, whilst the superfluous portion of the striker's kinetic energy is once again delivered to the drill spindle 51.The O-ring 71 fully absorbs the slight rebound energy still remaining after the rebound of the striker from the drill spindle 51 and retains the striker 48 securely in the idling position. If the percussion mechanism is to be brought once again into its percussion condition, then the hammer must be applied once again to the workpiece whereupon the drill spindle 51 is pushed to the rear and the striker 48 is again forced out of the O-ring 71.

A hand tool machine in accordance with the invention can be provided with damping means for a crank-driven percussion mechanism rather than one driven by a cam and follower arrangement as specifically described.

WHAT WE CLAIM IS:- 1. A hand tool machine comprising a housing, an electric motor and a percussion mechanism arranged to be driven by the electric motor, the percussion mechanism including a striker through which a driving member, performing an axial reciprocating movement, can impart energy to a tool rotatably arranged and guided in the hand tool machine, in which a drill spindle for transmitting to the tool, a rotary movement derived from the motor and the axial movement of the driving member, is arranged between the percussion mechanism and a tool holder and is axially and rotatably guided in two bearings and in which, between the two bearings, the drill spindle is provided with a flange arranged to move axially in a chamber between two abutment shoulders which are supported by the housing through damping means.

2. A hand tool machine according to claim 1, in which the abutment shoulders are arranged on at least partially annular members, each forming part of the chamber.

3. A hand tool machine according to claim 1 or claim 2, in which the abutment shoulders are formed of damping material.

4. A hand tool machine according to claim 3, in which the abutment shoulders are formed of polyamide.

5. A hand tool machine according to any preceding claim, in which the damping means for each abutment shoulder is an O-ring arranged behind the respective abutment shoulder.

6. A hand tool machine according to any preceding claim, in which the drill spindle is guided in two roller bearings, pressed into the housing, and the support for each abutment shoulder takes place through one of the roller bearings.

7. A hand tool machine according to claim 6, in which the roller bearings are grooved ball bearings.

8. A hand tool machine according to any preceding claim, in which each abutment shoulder is in the form of an inner cone converging away from the flange, and the flange is in the form of an associated outer cone converging in the same direction.

9. A hand tool machine according to any preceding claim, in which the armature of the electric motor is arranged in two bearings, elastic means being provided which force the armature bearings axially towards one another.

10. A hand tool machine according to claim 9, in which one end of the armature shaft is provided with a pinion and is guided in a manner transmitting axial force to the inner ring of a first roller bearing pressed into a metal bearing block, and in which the other end of the driving shaft carries a fan wheel and is likewise guided in a manner transmitting an axial force to the inner ring of a second roller bearing which is held in a rubber bush which is so deformable that the armature shaft is subject to a force towards its pinion end, which is greater than all opposing forces acting under any operating condition.

11. A hand tool machine according to claim 10, in which the bearing at the fan wheel end is a grooved ballbearing retained on the armature shaft by a force fit and the bearing at the pinion end is a grooved ballbearing retained with a push fit engaging a pressed-on abutment ring.

12. A hand tool machine according to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. on the spindle 51. The spindle 51 is then forced against the front shoulder 59 whereupon the impact is then damped in a similar manner as described above in connection with the B-impact. The percussion mechanism 45 is then located in its idling position in which, since the drill spindle 51 is located in its most forward possible position, the striker 48 can move up to the forward end of the guide tube 47. So that, during the above-described transition into the idling condition, the striker 48 does not rebound once again into the percussion mechanism, the striker is provided with a striker trapping device. This striker trapping device consists of an elastic expansible O-ring 71 retained at the forward workpiece end of the guide tube 47.At its forward free end, the striker 48 has around its periphery a damping flange 73 the diameter of which is greater than the inner diameter of the undeformed O-ring 71. During transition of the percussion mechanism into the idling condition, the damping flange 73 on the striker penetrates into the O-ring whereupon the latter is deformed and a portion of the striker's kinetic energy is absorbed, whilst the superfluous portion of the striker's kinetic energy is once again delivered to the drill spindle 51. The O-ring 71 fully absorbs the slight rebound energy still remaining after the rebound of the striker from the drill spindle 51 and retains the striker 48 securely in the idling position.If the percussion mechanism is to be brought once again into its percussion condition, then the hammer must be applied once again to the workpiece whereupon the drill spindle 51 is pushed to the rear and the striker 48 is again forced out of the O-ring 71. A hand tool machine in accordance with the invention can be provided with damping means for a crank-driven percussion mechanism rather than one driven by a cam and follower arrangement as specifically described. WHAT WE CLAIM IS:-

1. A hand tool machine comprising a housing, an electric motor and a percussion mechanism arranged to be driven by the electric motor, the percussion mechanism including a striker through which a driving member, performing an axial reciprocating movement, can impart energy to a tool rotatably arranged and guided in the hand tool machine, in which a drill spindle for transmitting to the tool, a rotary movement derived from the motor and the axial movement of the driving member, is arranged between the percussion mechanism and a tool holder and is axially and rotatably guided in two bearings and in which, between the two bearings, the drill spindle is provided with a flange arranged to move axially in a chamber between two abutment shoulders which are supported by the housing through damping means.

12. A hand tool machine according to

any preceding claim, in which the percussion mechanism is operated by a swashplate drive which has a shaft guided in two bearings and provided with a swashplate member, and in which the outer rings of the bearings are formed as roller bearings pressed into a bearing block, the swashplate shaft is guided in the inner ring of the first bearing with a push fit and in the inner ring of the second bearing with a forced fit and means which are elastically deformable axially, are arranged between the first bearing and the swashplate member.

13. A hand tool machine according to claim 12, in which the roller bearings are grooved ball bearings.

14. A hand tool machine according to claim 12 or claim 13, in which the bearing block is made of aluminium.

15. A hand tool machine according to any one of claims 12 to 14, in which the elastically deformable means are formed by a spring washer the smaller diameter of which engages the inner ring of the first roller bearing and the larger diameter of which engages the swashplate member.

16. A hand tool machine according to any one of claims 1-15 in which the electric motor is provided with a commutator, the motor bearing at the commutator end being arranged in a bearing-protecting housing cover fixed to the motor housing, and in which a bag-like brush holder plate provided with brush guides and screwthreads for cable connectors, is arranged between the motor housing and the housing cover, the side of the brush holder plate remote from the electric motor being designed as an air guiding disc for a motor fan and extensions for supporting the laminated stator of the electric motor being arranged on the side of the brush holder plate carrying the brush guides.

17. A hand tool machine according to claim 16, in which the housing cover is fixed to the motor housing with a close fit.

18. A hand tool machine according to claim 16 or claim 17, in which the brush guides extend radially with respect to the axis of the commutator and their outer ends are closed by a closure cover secured by means of screws.

19. A hand tool machine according to any preceding claim, comprising a sealed, at least partially oil-filled housing inner chamber with a lubricated percussion mechanism and/or drive and oil-tight ventilation arranged therein, in which a ventilation duct proceeds from a space connected to atmosphere, into a plugshaped housing extension, the end of which terminates inside a coaxial bore in a rotary shaft in the gearbox.

20. A hand tool machine according to claim 19, in which the end of the housing extension terminating inside the coaxial bore is sharp edged.

21. A hand tool machine according to claim 19 or claim 20, in which the said rotary shaft is a swashplate shaft.

22. A hand tool machine according to any one of claims 19 to 21, in which a narrow sealing gap exists between the end of the rotary or swashplate shaft and the base region of the housing extension of the housing wall.

23. A hand tool machine according to any one of claims 19 to 22, in which the said coaxial bore has a radial opening at its inner end.

24. A hand tool machine according to any one of claims 19 to 23, in which the forward end of the coaxial bore leading from the shaft is closed by a sealing disc which forms a seal between the shaft and the plug-like housing extension.

25. A hand tool machine according to claim 24, in which the sealing disc con slsts of an elastic, light, flexible material, such as polyurethane foam.

26. A hand tool machine according to any preceding claim, comprising a fixed guide tube accommodating the percussion mechanism and a rotary sleeve transmitting rotary movement to the tool guided on the guide tube, the driving end of the rotary sleeve being provided with an externallytoothed flange and the driven end of the rotary sleeve being provided with internal teeth in engagement with the drill spindle, in which the rotary sleeve is supported radially inwards of the externally-toothed flange and is supported on the drill spindle by means of the internal teeth.

27. A hand tool machine according to claim 26, in which the bearing surface of the rotary sleeve lying within the flange, is formed as an annular rib with a cambered inner surface.

28. A hand tool machine according to any one of claims 1 to 25, the percussion mechanism also comprising a guide tube within which the striker is freely movable and is guided axially, in which an elastically extensible O-ring is retained at the forward workpiece end of the guide tube, a damping flange, the diameter of which is greater than the inner diameter of the un-deformed O-ring, being arranged on an extension at the forward end of the striker and arranged to enter the O-ring at the transition of the percussion mechanism into the idling condition.

29. A hand tool machine according to claim 28, in which the damping flange is provided with conical transition surfaces and the extension has a diameter corresponding substantially to the inner diameter of the un-deformed O-ring.

30. A hand tool machine according to any preceding claim, in which the driving member imparts energy to the striker through an air cushion.

31. A hand tool machine according to any preceding claim, in which the electric motor is a universal motor.

32. A hand tool machine substantially as herein described with reference to the accompanying drawings.