GB2418635A

GB2418635A - Drilling and percussion hammer with dome shaped bearing

Info

Publication number: GB2418635A
Application number: GB0519216A
Authority: GB
Inventors: Willy Braun
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-09-25
Filing date: 2005-09-20
Publication date: 2006-04-05
Anticipated expiration: 2025-09-20
Also published as: DE102004046627A1; GB2418635B; GB0519216D0

Abstract

The hand held percussive tool includes a plain bearing 32 between a pot 31 connected to an eccentric 25 and a dome 30 connected to the eccentric's support 26. An eccentric gear 24, comprising the eccentric 25, converts the rotational movement of a driving pinion 14 into a translational movement of a piston (22, figure 1). The piston (22, figure 1) is axially displaceable within a hammer tube (17, figure 1). Preferably the pinion is rotated by an electric motor (12, figure 1). The bearing dome 30 preferably includes an axially protruding holding stud 34. Preferably the eccentric gear 24 includes a spur gear 37 that meshes with the pinion 14.

Description

24 1 8635 Hand tool machine, in particular a drilling and/or percussion

hammer

Background art

The invention proceeds from a hand tool machine, in particular a drilling and/or percussion hammer, according to the preamble of claim 1.

In a known hand tool machine, in particular a drilling and/or percussion hammer (DE 36 21 183 Al), the eccentric is designed as a spur gear, which meshes with the driving pinion formed on the output shaft of the electric motor.

The eccentric is seated in a rotationally fixed manner on an eccentric bolt, which in turn is accommodated by means of a needle bearing and a ball bearing in the impact mechanism housing. For this purpose, the impact mechanism housing has a pot-shaped indentation, into which is inserted a bearing pot having a stepped inside diameter.

The needle bearing is disposed in the smaller-diameter pot portion and the deep groove ball bearing is disposed in the larger-diameter pot portion, in each case between pot wall and eccentric bolt.

Advantages of the invention The hand tool machine according to the invention having the features of claim 1 has the advantage that, by designing the eccentric bearing seat on the operating mechanism housing as a bearing dome, a large bearing diameter for the eccentric is achieved, which allows the use of a plain bearing that is more economical and stable than needle bearings and deep groove ball bearings. The large bearing diameter has a positive influence on the operational performance and load capacity of the plain bearing so that, compared with needle and deep groove ball bearings, no loss of comfort has to be accepted. The eccentric bolt that is provided in the known hand tool machine and is relatively costly to produce no longer applies, and in conjunction with the bearing dome being easy to form on the impact mechanism housing, it is possible to reduce the manufacturing costs.

Advantageous developments and improvements of the hand tool machine indicated in claim 1 are possible by virtue of the measures outlined in the further claims.

According to an advantageous form of construction of the invention, the plain bearing is of a two-part design and comprises a plain bearing sleeve, which is mounted, preferably pressed, so as to be locked against rotation on the bearing dome, and a plain bearing shell, which slides on the plain bearing sleeve and is preferably an integral component of the bearing pot. The merely two-part design of the plain bearing contributes towards a further cost reduction.

In order, for the drilling mode, to provide a disconnect facility for the operating mechanism, according to an advantageous form of construction of the invention a spur gear, which meshes with the driving pinion on the output shaft of the electric motor, is mounted in a freely rotating and axially displaceable manner on the outside of the pot lateral surface of the bearing pot. A concentric recess is introduced into the end face of the spur gear and provided with internal gearing. The bearing pot carries preferably integrally on its pot lateral surface a toothed ring having external gearing, which meshes with the internal gearing in the spur gear. An operating or adjusting lever acts on the spur gear for axial displacement thereof, wherein axial displacement of the spur gear leads to the disengagement of internal and external gearing.

In an alternative form of construction of the invention, the spur gear is seated in an axially non-displaceable manner on the plain bearing sleeve, and the bearing pot of the eccentric in turn carries on its pot lateral surface a toothed ring, which is preferably integral with the bearing pot and has external gearing. An operating ring forming a coupling element between bearing pot and spur gear has, introduced into its end face facing the bearing pot, a concentric recess having internal gearing that is in mesh with the external gearing of the toothed ring on the bearing pot. The operating ring, on its end face remote from the recess, is provided with axially protruding coupling elements, e.g. webs or pins, which are positively insertable into indentations, e.g. radial grooves or axial bores, that are introduced axially into the spur gear. An operating or adjusting lever acts in turn on the operating ring for axial displacement thereof, so that the coupling elements are withdrawable from the spur gear.

For hand tool machines that provide no disconnection of the impact mechanism, according to an advantageous form of construction of the invention the spur gear, which meshes with the pinion of the output shaft of the electric motor, is formed integrally with the eccentric and preferably disposed like a flange on the pot opening of the bearing pot.

Drawings There now follows a detailed description of the invention by way of embodiments that are illustrated in the drawings.

The drawings show: Fig. 1 a side view of a hand tool machine, partially cut open, Fig. 2 an enlarged view of the detail II in Fig. 1, Figs. 3 and 4 in each case a view identical to Fig. 2 according to two further embodiments.

Description of the embodiments

The hand tool machine illustrated in Fig. 1 in side view and, to the extent relevant here, partially in longitudinal section takes the form of a drilling and/or percussion hammer, which may be switched between the "drilling" and "percussion drilling" modes of operation. The hand tool machine has a housing 11 containing an, in particular, electric drive motor 12, which acts via a gear unit upon a downstream drilling and/or percussion mechanism. For this purpose, a driving pinion 14 is formed on the output shaft 13 of the drive motor 12 and meshes with an intermediate gear wheel 49, which in turn via a bevel gear 15 sets a driving gear wheel 16 in rotation. The driving gear wheel 16 is seated rotatably on a hammer tube 17 and connected thereto in a rotationally fixed manner by an overload clutch 18. The hammer tube 17 in a known manner carries on its front end a tool holder 19, in which a tool 20 is clampable in an axially displaceable manner.

During the rotation of the tool 20, an impact mechanism 21 acts axially upon the tool 20. The, as such, known impact mechanism 21 has - arranged successively and with axial guidance in the hammer tube 17 - a piston 22 that may be set in reciprocating motion, a striker or striking bolt 23, a snap die that transfers the impact energy from the striking bolt 23 to the tool shank of the tool 20, and an eccentric gear 24 that converts the rotary driving movement of the drive motor 12 to a translatory movement of the piston 22. The eccentric gear 24, which is shown to an enlarged scale in Fig. 2, comprises an eccentric 25, which is supported rotatably on an impact mechanism housing 26, and a spur gear 37, which meshes with the driving pinion 14 on the output shaft 13 of the drive motor 12 and is connectable in a rotationally fixed manner to the eccentric 25. The eccentric 25 carries an eccentric bolt 27, which is accommodated in a sliding manner in an eye 28 of a piston rod 29 connected to the piston 22.

For the rotational support of the eccentric 25, a bearing dome 30 is constructed on the impact mechanism housing 26 and a bearing pot 31, which overlaps the bearing dome 30, is integrally moulded on the eccentric 25. Between the bearing dome 30 and the pot lateral surface 311 of the bearing pot 31 a two-part plain bearing 32 is disposed.

The plain bearing 32 comprises a plain bearing sleeve 33, which is pressed so as to be locked against rotation onto the externally machined bearing dome 30, and an outer plain bearing shell that is formed by the bearing pot 31 of the eccentric 25 itself. The bearing dome 30 has a holding stud 34, which protrudes axially from the dome cap and is incorporated into a stepped bore 35 in the eccentric 25, namely into the region thereof that forms the pot base of the bearing pot 31. Situated in the larger-diameter bore portion of the stepped bore 35 remote from the bearing dome 30 is a clamping washer 36, which is clamped firmly on the holding stud 34. By means of this clamping washer 36 the eccentric 25 is held down axially on the bearing dome 30.

The spur gear 37 is mounted in a freely rotatable and axially displaceable manner on the outside of the bearing pot 31. In its one end face, it has a recess 39 that is provided with internal gearing. The bearing pot 31 on the outside of its pot lateral surface 311 carries a toothed ring 38, which is integral with the bearing pot 31 and has external gearing, which by virtue of axial displacement of the spur gear 37 on the bearing pot 31 may be brought into mesh with the internal gearing of the spur gear 37. For this purpose, an adjusting lever 40 engages with a lug 41 in an annular groove 42 formed in the spur gear 37.

In the position of the spur gear 37 illustrated in Fig. 2, spur gear 37 and eccentric 25 are in mesh with one another via the gearing in the recess 39 and the gearing on the toothed ring 38. When the drive motor 12 is switched on by means of an on/off switch 48 (Fig. 1), via the driving pinion 14 the spur gear 37 is set in rotation and the spur gear 37 in turn rotates the eccentric 25. The rotating eccentric bolt 27 via the piston rod 29 sets the piston 22 into a translatory reciprocating motion. If the impact mechanism is to be disconnected, the spur gear 37 is displaced by means of the adjusting lever 40 in Fig. 2 in a downward direction so that the gearings between spur gear 37 and eccentric 25 disengage. The spur gear 37, which is still in mesh with the driving pinion 14, rotates freely on the bearing pot 31, and the eccentric 25 is stationary.

The embodiment illustrated in Fig. 3 differs from the embodiment described with reference to Fig. 2 in that the spur gear 37 is seated in an axially non-displaceable manner on the plain bearing 32, namely on the plain bearing sleeve 33 pressed on the bearing dome 30. As before, the eccentric 25 carries on its pot lateral surface 311 the toothed ring 38 with external gearing. The coupling between spur gear 37 and eccentric 25 is produced by means of an operating ring 43, which is seated in an axially displaceable manner on the pot lateral surface 311 of the bearing pot 31 of the eccentric 25. The operating ring 43 on its front end facing the spur gear 37 carries axially protruding coupling elements 44, which engage positively into axial indentations 45 provided in the end face of the operating ring 43. In the embodiment of Fig. 3, the coupling elements are designed as webs and the indentations as radial grooves 45. In the sectional view of Fig. 3 two webs and two radial grooves may be seen, which are arranged diametrically. Alternatively, the coupling elements 44 may be designed as pins and the axial indentations 45 may be designed as bores in the spur gear 37.

The operating ring 43 on its other front end remote from the coupling elements 44 carries a recess 36 with internal gearing, which may be brought into and out of mesh with the external gearing of the toothed ring 38 on the bearing pot 31. For this purpose, the operating ring 43 carries a flange 431, behind which the lug 41 of the adjusting lever 40 engages. On the side of the operating ring 43 remote from the lug 41, on the one hand, and against a holding ring 50 disposed on the eccentric 25, on the other hand, a compression spring 47 slipped onto the pot lateral surface 311 of the bearing pot 31 is supported, so that the operating ring 43 is applied by its flange 431 non- positively against the lug 41 of the adjusting lever 40.

When the adjusting lever 40 is displaced in Fig. 3 in an upward direction counter to the action of the compression spring 47, the coupling elements 44 are lifted out of the indentations 45 in the spur gear 37, and the spur gear 37 may rotate freely on the plain bearing 32, while the eccentric 25 is stationary.

The embodiment for supporting the eccentric 25 on the impact mechanism housing 26 that is sketched in Fig. 4 is designed for hand tool machines that do not provide a disconnect facility for the impact mechanism 21. This embodiment differs from the previously described embodiments only in that the spur gear 37 is formed integrally with the eccentric 25, wherein the spur gear 37 is disposed on the pot opening of the bearing pot 31. The adjusting lever naturally no longer applies.

Claims

Claims 1. Hand tool machine, in particular a drilling and/or percussion

hammer, having an impact mechanism (21), which comprises a piston (22) guided in an axially displaceable manner in a hammer tube (17), having a driving pinion ( 14), which may be set in rotation by an in particular electric drive motor (12), and having an eccentric gear ( 24), which converts the rotational movement of the driving pinion (14) to a translational movement of the piston (22) and comprises an eccentric (25) supported rotatably on an impact mechanism housing (26), characterized in that for rotatable support of the eccentric (25) the impact mechanism housing (26) has a bearing dome (30) and the eccentric (25) has a bearing pot (31) overlapping the bearing dome (30) and that between the pot lateral surface (311) of the bearing pot ( 31) and the bearing dome ( 30) a plain bearing (32) is disposed.
2. Hand tool machine according to claim 1, characterized in that the bearing pot (31) is formed integrally with the eccentric (25) .
3. Hand tool machine according to claim 1 or 2, characterized in that the plain bearing (32) is of a two-part design and comprises a plain bearing sleeve (33), which is mounted, preferably pressed, so as to be locked against rotation on the bearing dome (30), and a plain bearing shell, which slides on the plain bearing sleeve (33) and is connected in a rotationally fixed manner to the bearing pot (31), preferably being formed on the bearing pot (31) itself.
4. Hand tool machine according to one of claims 1 - 3, characterized in that the bearing dome (30) has a holding stud (34), which protrudes axially from the dome cap and projects with clearance into a stepped bore (35) disposed in the pot base of the bearing pot (31), and that a clamping washer (36) firmly clamped on the holding stud (34) lies in the larger-diameter bore portion of the stepped bore (35) remote from the bearing dome (30).
5. Hand tool machine according to one of claims 1 - 4, characterized in that the eccentric gear (24) comprises a spur gear (37) that meshes with the driving pinion (14).
6. Hand tool machine according to claim 5, characterized in that the spur gear (37) is mounted in a freely rotating and axially displaceable manner on the outside of the pot lateral surface (311) of the bearing pot (31) and has, introduced into its end face, a concentric recess (39), which is provided with internal gearing, and that the bearing pot (31) on its pot lateral surface (311) carries a toothed ring (38), which is preferably integral with the bearing pot (31) and has external gearing, which meshes with the internal gearing in the spur gear (37).
7. Hand tool machine according to claim 6, characterized in that acting on the spur gear (37) is an adjusting lever (40), which is capable of displacing the spur gear (37) axially in such a way that internal and external gearing disengage.
8. Hand tool machine according to claim 5, characterized in that the spur gear (37) is seated in an axially non displaceable manner on the plain bearing sleeve (33), that the bearing pot (31) of the eccentric (25) on its pot lateral surface (311) carries a toothed ring (38), which is preferably integral with the bearing pot (31) and has external gearing, that on the pot lateral surface (311) of the bearing pot (31) an operating ring (43) is disposed in an axially displaceable manner and has, introduced into its one end face, a recess (46) having internal gearing that meshes with the external gearing of the toothed ring (38) and, on its other end face, axially protruding coupling elements (44), and that the spur gear (37) in its end face facing the operating ring (43) has axial indentations (45), preferably radial grooves, into which the coupling elements (44) are positively axially insertable.
9. Hand tool machine according to claim 8, characterized in that an adjusting lever (40) acts on the operating ring (43) for axial displacement thereof.
10. Hand tool machines according to claim 5, characterized in that the spur gear (37) is formed integrally with the eccentric (25) and is disposed preferably on the pot opening of the bearing pot (31) of the eccentric (25).

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