GB2160810A

GB2160810A - Hammer drill

Info

Publication number: GB2160810A
Application number: GB08510813A
Authority: GB
Inventors: Manfred Bleicher; Ulrich Bohne; Karl Wanner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1984-06-29
Filing date: 1985-04-29
Publication date: 1986-01-02
Also published as: DE3423919A1; GB2160810B; GB8510813D0; CH666439A5

Abstract

In a hammer drill having an air-cushion percussive mechanism 6 driven by a motor 4 the drive member of the percussive mechanism is moved by a wobble plate 16, the drive shaft 9 of the drive motor 4 is arranged at an angle to the percussive mechanism axis, an intermediate shaft 15 which carries the wobble plate 16 is arranged parallel to the percussive mechanism axis and a bevel gear 14 which effects the drive of the intermediate shaft 15 and/or the plate 16 is arranged on that side of the intermediate shaft 15 which runs from the plate 16 in the direction pointing towards the tool head 38. The toothing of the bevel gear 14 is turned away from the plate 16 and meshes with a bevel pinion 13 which is arranged on the drive shaft 9 of the drive motor 4. This arrangement also ensures simple assembly and also makes it possible for worn parts to be exchanged in an especially simple manner <IMAGE>

Description

SPECIFICATION Hammer drill The invention is based on a hammer drill according to the generic part of the main claim. Such a hammer drill is already known, for example from US Patent Specification 4,280,359. In this known hammer drill, however, the drive shaft of the electric motor runs parallel to the percussive mechanism axis, which, especially in the case of high-powered heavy hammer drills, results in large-sized housings as far as the area of the toolholder and consequently makes it mdre difficult to handle the hammer drill. Therefore the drive motor in heavy hammer drills has been arranged in such a way that its drive shaft runs at an angle to the percussive mechanism axis, preferably at right angles thereto.A crank drive is used in th4e known hammer drills to transmit movement from the drive shaft of the electric motor to the reciprocatingly moved drive member of the percussive mechanism, which crank drive, however, together with the rotary drive for the tool holder which is usually also present, occupies a relatively large space. Such a hammer drill has been disclosed, for example, in US Patent Specification 4,066,136.

Advantages of the invention In contrast, the hammer drill according to the invention having the characterising features of the main claim has the advantage of an extremely compact construction which aids handling of the hammer drill. Moreover, a hammer drill of such configuration is especially simple to assemble, which has a favourable effect on the manufacturing costs. If a repair should prove to be necessary in the high stressed percussive mechanism area, then this type of construction only requires a minimum of parts to be disassembled in order to dismantle the percussive-mechanism, which offers the advantage of simple, quick and cost-effective repair possibilities.

Advantageous further developments and improvements of the hammer drill stated in the main claim are possible by means of the measures listed in the sub-claims. It is particularly advantageous, in the interest of simple assembly, to mount the intermediate shaft in the housing of the hammer drill or the components arranged on the intermediate shaft in an axially displaceable manner and to subject said components to the effect of a spring which holds the intermediate shaft and/or the components arranged on the latter in a non-positive manner against a stop which if necessary can be adjusted.

A favourable effect is also obtained, in the interest of compact construction, if the intermediate shaft is in rotary drive connection with the toolholder via an intermediate gear stage and the axis of the intermediate stage runs parallel to the intermediate shaft.

Moreover, the space-saving arrangement of a safety clutch designed as an overrun clutch can be effected on the spindle for the intermediate gear shaft.

Drawing An illustrative embodiment of the invention is shown in the drawing and described in greater detail in the following description. Figure 1 shows a side view of a hammer drill according-to the invention, partly in section; Figure 2 shows a cutout of the hammer drill shown in Figure 1, partly in section; Figure 3 shows a section A-A according to Figure 1; and Figure 4 shows a side view of a detail according to Figure 3. Description of the illustrative embodiment The hammer drill shown in the drawing has a housing which consists of several main parts. The first housing part 1 is made from plastic and accommodates inside it a housing part 2 whichis made of metal and designed as a percussive mechanism housing. A motor housing 3 for an electric drive motor 4 is connected to the housing part 2.The motor housing 3 is preferably made of plastic and is injection-moulded onto the housing part 2. The housing part 2 essentially accommodates a tool holder 5 and a percussive mechanism 6.

On the side facing away from the tool holder 5, the housing of the hammer drill supports in known manner a hand grip 7. Arranged in the latter is a trigger switch 8 which controls the electric drive motor 4.

The electric drive motor 4 arranged in the motor housing 3 has a drive shaft 9 which is located in two ball bearings 10 and 11. The ball bearing 10 is mounted in the base part 12 of the motor housing 3, and the ball bearing 11 is mounted in the housing part 2. On the free end projecting out of the ball bearing 11, the drive shaft 9 supports a bevel pinion 13 or forms this itself. The bevel pinion 13 meshes with a bevel gear 14 which is arranged on an intermediate shaft 15. The intermediate shaft 15 also supports the drum 16 which is part of a wobble-plate drive which is known per se and is used for driving the percussive mechanism 6 in a manner still to be described. The bevel gear 14 and the drum 16 are pressed onto the intermediate shaft 15.The latter is located on one side in a needle bearing 17 arranged in the housing part 2 and on the other side in a ball bearing 18 which is arranged in a housing cover 21 which is placed onto the housing part 2 and fixed to the iatter by screws 19 and 20. The intermediate shaft 15 penetrates a compression spring 22 which is supported on one side against the bevel gear 14 and on the other side against an extension 24 of the housing part 2 via an axial bearing 23. In this'way, the constructional unit consisting of the intermediate shaft15,the bevel gear 14andthedrum 16is clamped to the housing cover 21 free from play. The desired tooth play between the bevel pinion 13 and the bevel gear 14 is set by a spacer 25 inserted between the drum 16 and the ball bearing 18.On assembly of the hammer drill, possible production tolerances will be compensated by seleting and using a spacer 25 of appropriate size.

On its outside, the drum 16 of the wobble-plate drive for the percussive mechanism 6 has an integrally closed, annular track 26 for balls 27, which track 26 is located in a plane at an oblique angle to the axis of the drum 16. An outer track 29 cut on in the inside of a ring 28 is allocated to the track 26, so that the balls 27 are guided between the tracks 26 and 29. To keep the balls at a defined spacing, they are guided in a cage 30 which is known from ball bearings. A wobble finger 31 is integrally formed on the ring 28, which wobble finger 31 drives the percussive mechanism 6 of the hammer drill in a reciprocating manner The percussive mechanism 6 is arranged in the inside of a percussive mechanism tube 32 which is rotatably mounted in the housing part 2 and in the housing cover, 46 connected to the latter by screws 45.It consists of a skirt-type piston 33 which is guided in a sliding manner in the percussive mechanism tube 32, and in the cylindrical bore 34 of which is guided, also in a tight and sliding manner, a striker 35 which is designed as a freely floating piston. This striker 35, on its end face facing away from the base 36 of the skirt-type piston 33, has a prolongation 37 which faces towards the toolholder Sand acts on a tool head 38 which is arranged in an axially displaceable and rotatable manner in the toolholder 5 and is similar two an intermediate riveting die. This tool head 38 has a blind locating hole 39 on the wall of which are arranged means 40 which transmit torque and are designed here as a splined shaft. The correspondingly designed shank of a tool (not shown in the drawing) is pushed into the locating hole 39.On the side facing away from the locating hole 39, the tool head 38, on a cylindrical prolongation, carries spline teeth 41 which engage in allocated internal spline teeth 42 of the percussive mechanism tube 32. This connection of the tool head 38 to the percussive mechanism tube 32, which can be set in rotation in a manner still to be described, forms the rotary drive for the tool inserted into the hammer drill.

The rear skirt-type piston end facing away from the toolholder 5 has a forklike design and carries a pivot pin 43. A transverse hole 44 is made in the pivot pin 43, into which transverse hole 44 the wobble finger 31 engages with slight clearance of motion. In this way, the wobble finger 31 can easily move in the axial direction in the transverse hole 44.

Of course, it would also be quite possible to form the connection of the wobble finger 31 and the skirt-type piston 33 in other ways than in the case of the preferred way shown in the illustrative embodiment.

The end of the intermediate shaft 15 facing the toolholder 5 and projecting beyond the needle bearing 17 is provided with toothing 47. The latter engages in a gear wheel 48 which is arranged in a rotatable and displaceable manner on a spindle 49. A rolling bearing which is located between the gear wheel 48 and the spindle 49 is designated by 50. One end of the spindle 49 is mounted in a rolling bearing 51 located in housing part 2 and the other end is mounted in a rolling bearing 52 located in the housing cover 46. A collar 53 of the spindle 49, on its periphery, carries toothing 54 which engages in a gearwheel 55 which is mounted in a rotatable and displaceable manner on the percussive mechanism tube 32. On the spindle 49 is arranged a locking plate 56 between the collar 53 and the gearwheel 48.A collarlike edge 57 of the locking plate 56 has internal toothing 58 which in shape and tooth division corresponds to the toothing 54 of the collar 53, so that the collarlike edge 57 can be pushed positively onto the toothed collar 53. On the side of the locking plate 56 opposite the coliarlike edge 57, the locking plate 56 supports one or more detents 59 which are intended for interacting with detents 60 on the end face of the gearwheel 48. A compression spring 61, which is penetrated by the spindle 49, is fixed between a support plate 62 and the gear wheel 48. It is thus constantly endeavouring to hold the gear wheel 48 against the locking plate 56 and the latter against the collar 53 of the spindle 49, that is, to hold the detents 59 and 60 in the engaged position.Under the pressure of the spring 61, the support plate 62 sits against a retaining ring 63 which is arranged at such a location on the spindle 49 that the support plate 62 sitting against it does not come into contact with the housing cover 46 in order to minimize the occurrence of friction. The detents 59 arranged on the locking plate 56 could of course also be directly arranged on the end face of the collar 53 facing towards the gearwheel 48. The locking plate 56 could then be dispensed with. However, the type of construction shown in the illustrative embodiment has the advantage that, by using a special locking plate, the possibility is provided for compensating the diameters of the gear wheels 48 and 53, which diameters differ beacuse of the transmission stage, and for reaching the largest possible locking diameter.In this way, a low-wear but optimally effective overrun clutch is obtained.

The percussive mechanism tube 32, at its end facing away from the tool holder 5, is rotatably mounted in the housing part 2, and at its end facing towards the tool holder 5, is rotatably mounted in the housing cover46. Rolling bearings64and 65 are arranged atthe mounting locations to reduce friction in those areas. A gear wheel 55 sits in a rotatable and displaceable manner on the percussive mechanism tube 32, which gear wheel 55 meshes with the toothing 54 of the ollar 53 of the spindle 49. Internal toothing 67 is formed in a recess 66 in the gearwheel 55, which toothing 67 is intended for interaction with a gear rim 68 formed on the periphery of the percussive mechanism tube 32.A compression spring 71, which is pushed over a cyclindrical extension 69 of the gearwheel 55, is supported on one side against the gearwheel 55 and on the other side against an axial bearing 70 resting againstthe housing part 2. The compression spring 71 is thus endeavouring to continually hold gearwheel 55 in the position shown in Figure 1 in which the toothing of the gear rim 68 engages in the internal toothing 67 in the gear wheel 55, and the gear wheel 55 is supported against the shoulder of the gear rim 68 by the root of the recess 66.

For disengaging the rotary drive for the tool, a switch-over manipulator 72 (see Figure 3) is arranged on the outside of the housing part 1. The cylindrical prolongation 73 of the switch-overman- ipulator 72 extends into the inside of the housing and is rotatably mounted in the housing part 2. A leg spring 74 secures the switchover manipulator 72/73 in the axial direction in interaction with a clearance cut 75 located in the prolongation 73, but permits the manipulator to rotate about its axis. An O-ring 76 is used as a seal to the outside. The prolongation 73 of the switch-over manipulator 72 has an eccentrically arranged finger 77.The latter penetrates through a slotlike opening 79 of a slide 78 which is guided in a displaceable manner, and parallel to the axis of the percussive mechanism tube 32, on a pin 80 which is arranged in the housing part 2. The slide 78 carries a bolt 81 on which a ball bearing 82 is arranged. The bolt 81 is arranged in such a way that the rotary axis of the ball bearing 82 intersects the axis of the percussive mechanism tube 32 at right angles, and the outer race of the ball bearing 82, when the rotary drive is disengaged, comes into contact with the end face 83 of the gearwheel 55. When the slide 78 is in its inoperative position, that is, when the rotary drive is engaged, the outer race of the ball bearing 82 is no longer in contact with the end face 83 of the gear wheel 55 so that the gear wheel 55 can rotate free from contact.This is achieved by the gear wheel 55, which is acted upon by the compression spring 71, being supported against the shoulder of the gear rim 68 by the root of the recess 66, and by the ball bearing 82, when switching over to rotary drive, being removed an appropriately large distance from the end face 83 of the gear wheel 55 by the switch-over device 72 to 81.

The drive motor 4 is engaged by actuating the trigger switch 8. The rotation of the drive shaft 9 is transmitted to the intermediate shaft 15 via the bevel pinion 13 and the bevel gear 14. The drum 16 of the wobbleplate drive sitting on the intermediate shaft 15 participates in this rotary movement, by which means the wobble finger 31 is set in a reciprocating movement in a known manner. By the engagement of the wobble finger 31 into the transverse hole 44 of the rotary pin 43, the skirt-type piston 33 participates in this reciprocating movement, with a striker 35 being driven by an air cushion 84 in a manner which is known and therefore not described in greater detail.At the same time, the prolongation 37 of the striker 35 intermittently strikes the rear end of the tool head 38, by which means the blows are transmitted to the tool (not shown in the drawing) inserted into the latter.

The toothing 47 on the intermediate shaft 15 transmits the rotary movement of the latter to the gearwheel 48 which is mounted in a freely rotatable manner on the spindle 49. The collar 53 and thus the spindle 49 are driven via the detents 59 and 60 and the locking plate 56. At the same time, the coupling 59,60, 56 and 53 is maintained by the action of the compression spring 61. By the engagement of the toothing 54 of the collar 53 into the gear wheel 55, the latter also participates in the rotary movement and transmits it via the coupling consisting of the internal toothing 67 and the gear rim 68 to the percussive mechanism tube 32 and thus via the interlocking spline teeth 41 and 42 to the tool head 38 and the tool (not shown in the drawing) inserted into the latter.This functionai mode of the hammer drill requires the switch-over manipulator 72 to be set to the "percussive drilling" method of operation shown in the drawing.

In case the tool should jam during the percussive drilling operation in the material to be worked, it is necessary to protect the operator by a safety clutch so that the hammer drill, which is acted on further by the drive motor 4, is not torn out of his hand.

Because of the jammed and thus locked tool the tool head 38 and the parts 32, 55, 53 and 56 in drive connection with the tool head 38 are prevented abruptly from further rotary movement. The drive originating from the drive motor 4 and also acting further on the gear wheel 48 via the gear connections 9, 13, 14, 15 and 47 causes its detents 59 which have a certain angle of inclination, to be pressed out of the corresponding detents 60 in the axial direction when a predetermined, maximum transmission torque is exceeded, with the gear wheel 48 being axially displaced against the force of the spring 61. This overrun procedure continues until eitherthe drill starts to rotate again or the drive is stopped. Efforts to freethe drill from its jammed position are aided by the described safety clutch being arranged at such a location of the drive train that the percussive operation is maintained even when the drill is jammed.

When the manipulator 72 is switched over to "percussive operation", the ball bearing 82 is brought into contact with the end face 83 of the gear wheel 55 and displaces the latter on the percussive mechanism tube 32 against the force of the compression spring 71 until the internal toothing 67 of the gear wheel 55 has left the area of the gear rim 68.

The consequence of this is that the drive connection between the gear wheel 55 and the percussive mechanism tube 32 is interrupted and the gear wheel 55 only rotates loosely on the percussive mechanism tube 32. The rotary drive to the tool is thus interrupted.

Claims

1. Hammer drill having a percussive mechanism which is driven by a motor, in which percussive mechanism a reciprocating drive member acts via an air ushion on an axially movable striker which releases its energy to a tool guided in the hammer drill, with the drive member of the percussive mechanism being moved by an electric motor via a gear transmission which contains a wobble plate as a movement convertor, the drum of which wobble plate is arranged on an intermediate shaft which is at least approximately parallel to the percussive mechanism axis, characterised in that the drive shaft (9) of the drive motor (4) runs at an angle to the percusive mechanism axis and/or the axis of the intermediate shaft (15), and that a bevel gear (14) which effects the drive of the intermediate shaft (15) and/or the drum (16) is arranged on that side ofthe intermediate shaft (15) which runs from the drum (16) of the wobble plate in the direction pointing towards the toolholder, the toothing of which bevel gear (14) is turned away from the drum (16) and meshes with a bevel pinion (13) arranged on the drive shaft (9) of the drive motor (4).

2. Hammer drill according to claim 1, characterised in that the intermediate shaft (15) or the components arranged on the intermediate shaft (15) is or are mounted in an axially displaceable manner in the housing (2,21) of the hammer drill and is or are acted upon by a spring (22) which holds in a non-positive manner the intermediate shaft 5) andlor the components arranged on the latter against a stop (85) fixed to the housing.

3. Hammer drill according to claim 2, characterised in that the spring (22), in the direction opposite to a working stroke of the percussive mechanism (6), acts on the intermediate shaft (15) and/or the components arranged on the latter.

4. Hammer drill according to one of claims 2 or 3, characterised in that the intermediate shaft (155, between the stop (85) fixed to the housing and a component arranged on the intermediate shaft (15) and/or between the components arranged on the latter, carries at least one spacer (25) in orderto exactly fix the nominal position of one or more of these components in the axial direction.

5. - Hammer drill according to one of claims 1 to 4, characterised in that the bevel gear (14) and the drum (16) of the wobble plate are connected in a non-twistable manner to the intermediate shaft (15) and form, together with the platter, a constructional unit.

6. Hammer drill according to one of claims 1 to 5, characterised in thatthe intermediate shaft (15) is in rotating drive connection with the tool head (38) via an intermediate gear stage, and that the spindle (49) of the intermediate stage runs parallel to the intermediate shaft (15).

7. Hammer drill accordingto claim 6, characterised in that a safety clutch is arranged on the spindle (49) for the intermediate stage.

8. Hammer drill according to claim 7, characterised in that the safety clutch is designed as an overrun clutch (59,60).

9. Hammer drill according to claims 7 and 8, characterised in that a locking plate (56) is connected in a positive manner oras one piece to a gearwheel (53,54) of the intermediate gear stage and interacts - with a second locking plate which is formed by an end face of a gear wheel (48) which is displaceably mounted on the spindle (49) and is acted upon by a spring (61).

10. Hammer drill according to claim 9, characterised in that the spring (61) acting on the gear wheel (48) is clamped between the gearwheel (48) and a support plate (62) which is pushed onto the spindle (49) and held there by a retaining means (retaining ring 63) at a predetermined axial position.

11. Hammer drill according to one of claims 6 to 10, characterised in that the driven gearwheel (53/54) of the intermediate gear stage is constantly in engagement with a gearwheel (55) which is arranged in a rotatable and displaceable manner on the percussive mechanism tube (32), and that a clutch which can be engaged and disengaged is arranged between this gear wheel (55) and the percussive mechanism tube (32) effecting the rotary drive of the tool.

12. Hammer drill according to claim 11, characterised in that the gearwheel (55) is continually acted upon by a compression spring (7which endeavours to keep the gearwheel (55) in a constantly engaged position with the percussive mechanism tube (32), and on the other hand is selectively acted upon by a switching device, be means ofwhich the gearwheel (55) can be displaced against the force of the spring (71) into a position in which the clutch is released.

13. Hammer drill according to claim 12, characte rised in that the switching device has a slide (78) which can be moved parallel to the percussive mechanism tube (32), which slide (78) can be moved by an outwardly projecting adjusting manipulator (72-77) from an inoperative position to a position which acts on the gear wheel (55) with the object of releasing the cluth, and vice versa.

14. Hammer drill according to claim 13, characte - rised in that the slide (78), on its end facing towards the gearwheel (55), carries a ball bearing (8?) and acts via the latter on the spring-loaded gear wheel (55) when the clutch is to be released and/or held in the released position.

15. Hammer drill according to claim 14, characte rised in that the ball bearing (82) is arranged in such a position on the slide (78) that its extended rotary axis runs at least approximately radially to the axis of the percussive mechanism tube (32) and in tersects the latter at approximately right angles.

16. Hammer drill according to one of claims 11 to 15, characterised in that the percussive mechanism tube (32) and the gear wheel (55) have stop means which interact with one another and which limit an axial displacement of the gearwheel (55) under the action of the spring (71), in such a way that there is a space between the gearwheel (55) and the slide (78) or the ball bearing (82), which sits on the latter, when the slide (78) is in its inoperative position.

17. Hammer drill according to claim 16, characte rised in that the stop means are formed by the cluth elements (67,68) arranged on the gearwheel (55) and the percussive mechanism tube (32).