GB2439186A

GB2439186A - Hammer drill with bevel gear transmission

Info

Publication number: GB2439186A
Application number: GB0711121A
Authority: GB
Inventors: Dietmar Saur
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2006-06-12
Filing date: 2007-06-08
Publication date: 2007-12-19
Anticipated expiration: 2027-06-08
Also published as: GB0711121D0; DE102006027110A1; GB2439186B

Abstract

An electric hand-held power tool 1, such as a hammer drill and/or percussion hammer, comprises a drive spindle, a striking mechanism 47 and an electric drive motor 12. The motor can be connected, via a transmission and clutch mechanism 21, to an intermediate shaft 34 which drives the drive spindle, and/or to a striking-mechanism drive element 40. The transmission and clutch mechanism has only a bevel gear transmission 54 as a transmission. Preferably the bevel gear transmission has a bevel gear 18 which can be selectively coupled to a sliding sleeve 25. The intermediate shaft may acted on by an actuating piece (61, fig 4), driven by an operating mode selector switch (6, fig 1), to choose between hammer only, hammer and drilling, or drill only modes.

Description

Description Title

Rammer drill and/or percussion hammer

Prior art

The invention relates to an electric hand-held power tool realized as a hammer drill and/or percussion hammer, having a drive spindle, an electric drive motor which can be connected, via a transmission and clutch mechanism, to an intermediate shaft which drives the drive spindle and/or to a striking-mechanism drive element, the transmission and clutch mechanism having a transmission which has a bevel gear transmission.

Hammer drills and/or percussion hammers in the weight class up to approximately 3 kg are usually realized in a pistol-type configuration. This is characterized by axes disposed in parallel to each other, such that the motor axis of an electric drive motor extends parallel to the drive spindle, to which a tool, for example a drill bit, can be coupled.

The pistol design is characterized by a relatively large overall length.

Compared with those of a pistol-type design, hammer drills and/or percussion hammers of an L-shaped configuration have a shorter overall length. The L-shaped configuration is distinguished by the fact that the motor axis of the electric drive motor extends at an angle relative to the drive spindle.

A known design of an electric hand-held power tool realized as a hammer drill and/or percussion hammer is realized in an L-shaped configuration, an electric drive motor being able to be connected to an intermediate shaft via a transmission. The transmission consists of a bevel gear transmission and a spur gear transmission adjoining the bevel gear transmission. A clutch mechanism provides for driving of a striking-mechanism drive element, in order to actuate the striking mechanism. If the clutch mechanism also drives the drive spindle via the intermediate shaft, a combined drilling and percussive operating mode is obtained. If the clutch mechanism decouples the intermediate shaft, only the striking-mechanism drive element remains coupled to the electric drive motor, such that an exclusively chipping operating mode is obtained.

If the striking-mechanism drive element is decoupled from the drive motor by means of the clutch mechanism, but with the intermediate shaft being driven, an exclusively drilling operating mode is obtained.

The design of the known electric hand-held power tool is relatively complex, and therefore expensive. Furthermore, the design requires a substantial amount of space, resulting in a corresponding size of the electric hand-held power tool.

Disclosure of the invention

In the case of the electric hand-held power tool, realized as a hammer drill and/or percussion hammer, of the type stated at the outset, being designed according to the invention, provision is made whereby the transmission and clutch mechanism has only the bevel gear transmission as a transmission. There is thereby realized the objective of a simple, inexpensive design, while maintaining a high quality of the electric hand-held power tool. The omission of the spur gear transmission connected immediately after the bevel gear transmission means that fewer components are required, and the absence of the spur gear transmission saves structural space. Consequently, a very compact design can be realized.

According to a development of the invention, provision is made whereby the bevel gear transmission is of a single-stage design. It preferably consists only of a driving bevel gear, which is connected to the motor shaft in a rotationally fixed manner, and in particular of a driven bevel gear, which engages with the driving bevel gear and is coupled to a sliding sleeve for the purpose of rotary driving. The driving bevel gear, driven bevel gear and sliding sleeve are constituent parts of the said transmission and clutch mechanism.

In particular1 the electric hand-held power tool according to the invention is realized in an L-shaped design, in which a motor shaft of the drive motor extends at an angle relative to the drive spindle.

In a first slide position, the sliding sleeve is coupled to the striking-mechanism drive element for the purpose of rotary driving, and in a second slide position it is decoupled from the striking-mechanism drive. Consequently, the striking mechanism is driven in the first slide position and deactivated in the second slide position. In addition, provision is preferably made whereby the intermediate shaft is mounted so as to be axially displaceable, and in a first slide position is coupled to the sliding sleeve for the purpose of rotary driving, and in a second slide position is decoupled from the sliding sleeve. If there is no driving of the intermediate shaft, it in turn cannot drive the drive spindle. The different operating modes are preferably assumed through axial displacement of the intermediate shaft. The latter in this case also controls the slide position of the sliding sleeve. In total, three operating modes are possible: a) combined drilling and percussive operating mode, b) exclusively chipping operating mode and c) exclusively drilling operating mode.

According to a development of the invention, provision is made whereby the rotational axis of the driven bevel gear is in alignment with the rotational axis of the intermediate shaft and/or the rotational axis of the sliding sleeve. Consequently, these two or three components are in series relative to one another, with rotational axes in alignment.

The axially displaceable intermediate shaft is also a constituent part of the said transmission and clutch mechanism.

Brief description of the drawings

The drawings illustrate the invention with reference to exemplary embodiments, in which drawings: Figure 1 shows an electric hand-held power tool, of an L-shaped design, realized as a hammer drill and/or percussion hammer, Figure 2 shows a longitudinal sectional view through an inner region of the electric hand-held power tool of Figure 1, Figure 3 shows a longitudinal sectional view through an inner region of an electric hand-held power tool according to a further exemplary embodiment, and Figure 4 shows a longitudinal section view of a region of an intermediate shaft of the electric hand-held power tool.

Embodiment(s) of the invention Figure 1 shows an electric hand-held power tool 1, which is realized as a hammer drill and/or percussion hammer 2. A housing 3 of the electric hand-held power tool 1 is provided with a handle 4, which has an on-off switch 5. An operating-mode selector switch 6 is also disposed on the housing 3. A tool holder 7 connected to a drive spindle of the electric hand-held power tool 1 can accommodate a tool 8, for example a drill bit. Electrical power is supplied to an electric drive motor of the electric hand-held power tool 1 via a mains power supply lead 9. A dot-dash line 10 indicates the longitudinal extent of a motor shaft of the drive motor. This motor shaft extends at an angle, in particular at a 90 angle, relative to the rotational axis of the drive spindle, said rotational axis being indicated by a dot-dash line 11.

According to Fig. 2, the electric drive motor 12 is accommodated inside the housing 3 of the electric hand-held power tool 1, the motor shaft 13 of said drive motor having a rotational axis 14. The motor shaft 13 is rotatably mounted by means of a ball bearing 15 and has, at its end 16, a driving bevel gear 17 which engages with a driven bevel gear 18 whose rotational axis 19 encloses an angle of 900 relative to the rotational axis 14. The driving bevel gear 17 and driven bevel gear 18 constitute a transmission of a transmission and clutch mechanism 21.

The driven bevel gear 18 is rotatably mounted by means of a ball bearing 22 and a sliding bearing 23 which axially adjoins the latter. In addition, the driven bevel gear 18 has a profiled, axial rotary driving projection 24, which extends in the direction of the rotational axis 19 and is connected to the driven bevel gear 18 in a rotationally fixed manner. A sliding sleeve 25 is displaceably mounted on the rotary driving projection 24 in such a way that said sliding sleeve can be displaced along the rotational axis 19, in the direction of the double arrow 26 shown by Figure 2, while yet being continuously rotationally driven by the rotary driving projection 24. Supported on a collar 27 of the rotary driving projection 24 is a helical compression spring 28, which acts upon an inner annular flange 29 of the sliding sleeve 25 and forces the latter in the direction of the arrow 30. At the one end 31 of the sliding sleeve 25, the driving projection 24 engages in the interior of said sliding sleeve, and a mating profiling, which corresponds to the profiling of the rotary driving projection 24, is realized in said sliding-sleeve interior such that it is possible for torque to be transmitted between the driven bevel gear 18, or its rotary driving projection, and the sliding sleeve 25. This transmission of torque is effected irrespective of the current slide position of the sliding sleeve 25. An end portion 33 of an intermediate shaft 34 engages in the other end 32 of the sliding sleeve 25 -according to the position shown by -Figure 2 -in such a way that a toothing 35 on the end portion 33 of the intermediate shaft 34 is in engagement with an internal toothing 36 of the sliding sleeve 25. In addition, the end face 37 of the intermediate shaft 34 bears against the inner annular flange 29.

A holding cup 38 of the housing 3 carries a ball bearing 39 which carries a striking-mechanism drive element 40 which, in addition, is mounted on the intermediate shaft 34 by means of a bearing sleeve 41. The bearing sleeve 41 is located in the region of the end portion 33. The intermediate shaft 34 has a toothing 42, adjoining which is an end portion 43 of the intermediate shaft 34, said end portion being mounted so as to be rotatable and axially displaceable in the housing 3. The intermediate shaft 34 can be displaced axially, according to the direction of a double arrow 26, by means of the operating-mode selector switch 6. According to Figure 4, in addition to the toothing 42 there is a ball bearing 60 on the intermediate shaft 34. This ball bearing is disposed between the rotary body 52 and the toothing 42, and cooperates with an actuating piece 61. Through an eccentric linkage to the actuating piece 61, a manual rotation of the operating-mode selector switch 6 is converted into a linear motion, such that the intermediate shaft 34 can be displaced axially according to the direction of the double arrow 26.

A pivoted lever 44 is mounted on the striking-mechanism drive element 40 by means of a ball bearing 45 and at an acute angle a relative to the rotational axis 19, which also constitutes the rotational axis for the intermediate shaft 34, the pivoted lever 44 being connected in a rotatably movable manner to a piston 46 of a striking mechanism 47. The piston 46 is mounted, along the directions of the double arrow 26, in a hammer tube 48 of the striking mechanism 47 (axis 49) . The axis 49 runs parallel to the rotational axis 19. The toothing 42 of the intermediate shaft 34 engages with a spur gear 50 disposed on the hammer tube 48, the hammer tube 48 being able to rotate about the axis 49. The spur gear 50 is connected to a locking disc 62 in a positive and non positive manner.

The locking disc 62 is connected to the hammer tube 48 in a positive manner. If the insert tool, i.e. for example a drill bit, becomes jammed, the spur gear 50 is moved in the direction of the arrow 30, against the force of a spring 63, and the connection (claws, cams and/or balls or the like) to the locking disc 62, and thus to the electric drive motor 12, is disengaged.

The following function is obtained: If the operating-mode selector switch 6 is in a position which results in the intermediate shaft 34 being in the slide position shown in Figure 2, a rotation of the motor shaft 13 is transmitted to the driven bevel gear 18 through the driving bevel gear 17, the driving projection 34 accordingly putting the sliding sleeve 39 into rotation. By means of the internal toothing 36, the sliding sleeve 25 drives the intermediate shaft 34 by engaging in its toothing 35, such that said intermediate shaft also rotates accordingly, the rotation of the intermediate shaft 34 being transmitted, through the toothing 42 and the spur gear 50, to the hammer tube 48, and from there to the drive spindle of the electric hand-held power tool 1, said drive spindle not being shown in Figure 2. Driving projections 51 in the region of the end 32 of the sliding sleeve 25 transmit the rotary motion of the sliding sleeve 25 to a rotary body 52 of the striking-mechanism drive element 40 on which is mounted -in an oblique position -the ball bearing 45 and, accordingly, the pivoted lever 44. Rotation of the rotary body 52 causes the pivoted lever 44 to be pivoted back and forth according to the double arrow 53, such that the piston 46 in moved back and forth in the hammer tube 48.

Consequently, an air cushion resulting from the piston motion acts upon a striker which drives a striking pin such that the tool B executes percussive movements. Since there is rotation of the drive spindle, in addition to striking movements, a combined drilling and percussive operating mode is obtained.

If the operating-mode selector switch 6 is adjusted such that the intermediate shaft 34 is displaced in the direction of the arrow 30, i.e. assumes a new slide position, the toothing 35 will come out of the internal toothing 36, i.e. the sliding sleeve 25 no longer imparts rotary drive to the intermediate shaft 34. The result is that the drive spindle is no longer driven, but there is nevertheless operation of the striking mechanism 47, such that an exclusively chipping operating mode is obtained.

The operating-mode selector switch 6 can also be adjusted in such a way that the intermediate shaft 34 is displaced axially contrary to the direction of the arrow 30 to such an extent that, through driving of the inner annular flange 29 by means of the end face 37, the sliding sleeve 25 is axially displaced to such an extent that the driving projections 51 come out of a corresponding mating toothing of the rotary body 52, and there is consequently no rotary drive of the rotary body 52, as a result of which the striking mechanism 47 is put out of operation. The sliding sleeve 25 nevertheless continues to impart rotary drive to the intermediate shaft 34, as a result of which an exclusively drilling operating mode is obtained.

According to the invention, a simple changeover of operating mode is thus effected by means of the axially movable intermediate shaft 34. A very simple structural design is provided in this case. The design is also characterized by non-dependence on tolerances, owing to a functional separation between the striking mechanism 47 and the transmission 20. All parts are well mounted, and a compact arrangement is created. The mounting is characterized by the fact that the bevel gear transmission 54, which is constituted by the driving bevel gear 17 and the driven bevel gear 18, is mounted separately from the striking mechanism 47. Owing to the optimal mounting of the bevel gear transmission 54, the torque of the drive motor is transmitted, whereas bearing forces are not transmitted through the striking mechanism. There is a short tolerance chain, and consequently the play of the toothing of the bevel gear transmission 54 is small. The transmission 20 is realized directly on the axis (rotational axis 19) of the intermediate shaft 34.

The exemplary embodiment of Figure 3 differs from the exemplary embodiment of Figure 2 only in that the driven bevel gear 18 is mounted by means of a radial/axial bearing 55. This results in a precise arrangement having little play, with forces arising from the transmission of the torque being routed directly into the housing 3 (transmission flange) . The sliding sleeve 25 is not mounted on a rotary driving projection 24 of the driven bevel gear 18, but engages in an axially displaceable manner in a rotary driving recess 56 of the driven bevel gear 18. In other respects the design corresponds to the embodiment according to Figure 2, and reference is

therefore made to the statements relating thereto.

Because of the sliding sleeve 25, an axial displacement and/or tolerance equalization is realized between the bevel gear transmission 54 and the intermediate shaft 34, or the drive mounting. The bevel gears (driving bevel gear 17 and/or driven bevel gear 18) may be of a single-part or multi-part design. A sintered component or a forming production process is conceivable in each case. In the case of a multi-part design, a mandrel of the corresponding bevel gear may be inserted by means of pressing. The sliding sleeve 25 may be realized as a formed part or sintered part.

Claims

Claims 1. Electric hand-held power tool realized as a hammer drill

and/or percussion hammer, having a drive spindle, a striking mechanism and an electric drive motor, which drive motor can be connected, via a transmission and clutch mechanism, to an intermediate shaft which drives the drive spindle and/or to a striking-mechanism drive element, the transmission and clutch mechanism having a transmission which has a bevel gear transmission, characterized in that the transmission and clutch mechanism (21) has only the bevel gear transmission (54) as a transmission (20).

2. Electric hand-held power tool according to claim 1, characterized in that the bevel gear transmission (54) is of a single-stage design.

3. Electric hand-held.power tool according to either of the preceding claims, characterized by an L-shaped design, in which a motor shaft (13) of the drive motor (12) extends at an angle relative to the drive spindle.

4. Electric hand-held power tool according to any one of the preceding claims, characterized in that the bevel gear transmission (54) has a driving bevel gear (17) which is connected to the motor shaft (13) in a rotationally fixed manner.

5. Electric hand-held power tool according to any one of the preceding claims, characterized in that the bevel gear transmission (54) has a driven bevel gear (18) which engages with the driving bevel gear (17) and is coupled to a sliding sleeve (25) for the purpose of rotary driving.

6. Electric hand-held power tool according to any one of the preceding claims, characterized in that, in a first slide position, the sliding sleeve (25) is coupled to the striking-mechanism drive element (40) for the purpose of rotary driving, and in a second slide position it is decoupled from the striking-mechanism drive element (40) 7. Electric hand-held power tool according to any one of the preceding claims, characterized in that the intermediate shaft (34) is mounted so as to be axially displaceable, and in a first slide position is coupled to the sliding sleeve (25) for the purpose of rotary driving, and in a second slide position is decoupled from the sliding sleeve (25) 8. Electric hand-held power tool according to any one of the preceding claims, characterized in that the rotational axis (19) of the driven bevel gear (18) is in alignment with the rotational axis (19) of the intermediate shaft (34) and/or the rotational axis (19) of the sliding sleeve (25) 9. An electric hand-hel.d power tool substantially as herein described with reference to the accompanying drawings.