HANDHELD MACHINE TOOL COMPRISING A MECHANICAL STRIKING MECHANISM

A handheld machine tool including a mechanical striking mechanism, which has a striking member equipped with at least one drive cam and an output shaft equipped with at least one output cam, which is connected to a tool holder for holding a tool, the drive cam being designed to drive the output cam in a striking manner during the striking operation of the mechanical striking mechanism, the output shaft being drivable by a barrel shaped drive member, which at least partially encloses the output shaft and the striking body and is connected via a threaded connection to a drive member that is drivable by an associated gearbox.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1shows a handheld machine tool100equipped with a tool holder450and a mechanical striking mechanism200, having a housing110with a hand grip126. According to one specific embodiment, the handheld machine tool100may be mechanically and electrically connected to a battery pack130for cordless power supply.

Handheld machine tool100is developed exemplarily as a battery-operated impact screwdriver. It should be noted however that the present invention is not limited to battery-operated impact screwdrivers, but rather may be applied in a variety of power tools, in which a tool is rotated, e.g., in a hammer drill etc., regardless of whether or not the power tool may be operated cordlessly using a battery pack. Furthermore, it should be noted that the present invention is not limited to motor-operated handheld machine tools, but may generally be used in tools in which the striking mechanisms200and600, respectively, described inFIGS. 2 to 7, may be utilized.

Housing110contains an electric drive motor114supplied with current from battery pack130, a gear box118and striking mechanism200. Drive motor114may be operated, e.g., by a manual switch128, i.e., may be switched on and off, and may be any type of motor, e.g., an electronically commutated motor or a direct current motor. Drive motor114is preferably electronically controllable so that reverse operation as well as setting a desired rotating speed is possible. Operation and design of a suitable drive motor are not described in detail here for the sake of brevity.

Drive motor114is connected to gearbox118via an associated motor shaft116, which converts a rotation of motor shaft116into a rotation of drive member125. This conversion preferably occurs in such a manner that drive element125rotates in relation to motor shaft116at an increased torque, but reduced speed of rotation. Drive motor114is illustrated as situated in motor housing115and gearbox118in gearbox housing119, gearbox housing119and motor housing115being exemplarily situated in housing110.

The mechanical striking mechanism200connected to drive member125is for example a rotary striking mechanism located in an illustrative striking mechanism housing220, having a striking body500, which through associated drive cams512,514produces striking angular momenta of high intensity, transferring them onto an output shaft400, e.g., an output spindle. It should be noted, however, that striking mechanism housing220is used only by way of example and does not limit the present invention. Rather, the present invention may also be applied to striking mechanisms without separate striking mechanism housings, which are, e.g., located directly in housing110of handheld machine tool100. An exemplary construction of striking mechanism200is described in conjunction with section150of handheld machine tool100shown inFIGS. 2 and 6.

Tool holder450is provided by way of illustration on output shaft400, the tool holder being preferably designed to hold insertion tools and being connectible with an insertion tool140having an outer polygonal coupling142. Furthermore, according to one specific embodiment, tool holder450may also or alternatively be connected to an insertion tool having an inside polygonal coupling, e.g., a socket wrench. Insertion tool140is designed for example as a screwdriver bit having the outside polygonal coupling142, illustrated as an octagonal coupling, which is situated in a suitable inner receptacle (455inFIGS. 2 and 6) of tool holder450. A detailed description of this type of screwdriver bit as well as a suitable socket wrench, for the sake of brevity, is not provided herein.

FIG. 2shows section150ofFIG. 1including gearbox118located in gearbox housing119, and mechanical striking mechanism200ofFIG. 1in operative connection with output shaft400and equipped with striking mechanism housing220, according to a first specific embodiment. Mechanical striking mechanism200, as described inFIG. 1, has drive body300, which is connected with drive element125of gearbox118, which together with striking body500is located in striking mechanism housing220. The latter is illustrated as mounted on gearbox housing119.

According to one specific embodiment, gearbox118is a reduction gear that is, e.g., designed in the manner of a planetary gear and is characterized by one or several planetary stages. For illustrative purposes, planetary gear118has a single planetary stage201including a sun wheel203, planetary wheels204,205, a rotor gear208and a planet carrier207. Sun wheel203is drivable by a drive element202, which is connected with engine shaft116in a torque proof manner or which may be molded to it or developed in one piece with it. Sun wheel203and drive element202are advantageously also developed in one piece. The construction and function of a planetary gear118is not described further herein for the sake of brevity.

Planet carrier207is illustrated as being connected to drive member125and preferably molded to it or developed as a single piece with it. According to one specific embodiment, planet carrier207forms anterior area270of drive member125. This anterior area270, by way of example, is developed in a plate-shaped and flange-like manner and is equipped with a mounting device240for torque proof mounting of planetary carrier207and drive member125, respectively, to drive body300. On one—in FIG.2—axial side of anterior area270, a bearing pin470is constructed and on the opposite axial side, the anterior, flange-like area270merges into central, cylindrical area271. In this central area271, radial recesses (452,454inFIGS. 4 and 5) are provided, by way of example, for accommodating planetary wheels204and205, respectively, which are supported on associated bearing bolts278and279, respectively, in these recesses (452,454inFIGS. 4 and 5). For example, bearing bolts278,279are pivoted in cylindrically shaped openings (462,646inFIGS. 4 and 5). According to one specific embodiment, central area271merges into a posterior ring-shaped area272of drive member125, which is illustrated as being pivoted in an antifriction bearing214, e.g., in a ball bearing, and forms a cavity289for accommodating sun wheel203and drive element202. An exemplary development of drive member125is illustrated inFIGS. 4 and 5.

Drive member125and its planet carrier207, respectively, is connected to drive body300in a torque proof connection for rotationally driving drive body300. To this end, drive body300has counter mounting device340acting together with mounting device240, for example. Mounting device240and counter mounting device340form a threaded connection199, as shown by way of illustration, mounting device240being developed, e.g., by an external thread and the counter mounting device340, e.g., by an associated internal thread. According to one specific embodiment, external thread240and internal thread340are designed as having spiral threads, so that drive member125may be screwed into drive body300. However, the description of spiral threads is provided as only an example and does not limit the present invention. Rather, the present invention may be applied in a variety of thread types, such as, e.g., threads having concentric rings, as, e.g., described below inFIGS. 4 to 7.

To prevent drive member125from being unscrewed from drive body300, e.g., in reverse operation of handheld machine tool100inFIG. 1, drive member125is illustrated as being supported by an annular disk247, which is situated in drive body300in an axially fixed manner. Annular disk247is mounted downstream from drive member125and planet carrier207and affixed, e.g., in an annular groove245provided on an interior wall320of drive body300.

According to one specific embodiment, output shaft400is pivoted in striking mechanism housing220via a slide bearing280and, as shown by way of example, has a shaft body250equipped with an annular shoulder255. At least one output cam, as illustrated, two output cams412,414, are developed on shaft body250, as well as tool holder450fromFIG. 1, which is provided with, e.g., an octagonal interior receptacle455. One axial end of shaft body250, which is provided with output cams412,414is illustrated as pivotable on bearing pin470of drive element125, preferably gliding.

According to one specific embodiment, output shaft400is at least partially enclosed by drive body300. The latter is barrel-shaped, for example, and on a first axial end351has a barrel-bottom type wall350having an opening360. As shown, this opening360forms an annular collar254. On its opposite axial end352, barrel-shaped drive body300has an opening305, on which counter mounting device340is developed. As illustrated, barrel-shaped drive body300is provided with interior wall320and forms a cavity310, in which shaft body250with the two output cams412,414of output shaft400are located up to the annular shoulder255provided on it, such that output shaft400is situated rotatably, but axially immovably in drive body300. In this context, annular shoulder255, by way of example, abuts on annular collar254formed on drive body300. Furthermore inside cavity310, striking body500is mounted, in exemplary fashion, on output shaft400so as to be rotatable and axially displaceable.

Striking body500is barrel-shaped for example, having an exterior wall510and a bottom wall550, which form an interior space560. Bottom wall550has an opening599, penetrated by shaft body250of output shaft400. Striking body500is impacted by a spring element242also located in cavity310in the direction of output cams412,414. This direction of output cams412,414corresponds to an axial direction of output shaft400pointing away from tool holder450, which in the example provided is identified as244. For this purpose, spring element242, which is developed, e.g., as a pressure spring, is preferably located between annular collar254or barrel type bottom wall350of drive body300and bottom wall550of striking body500, spring element242penetrating interior space560of striking body500. According to an example embodiment of the present invention, striking body500is impacted by spring element242in direction244, i.e., in a direction axially opposite to a corresponding direction of advance of handheld machine tool100fromFIG. 1during operation. This direction of advance is identified inFIG. 2as299by way of example.

According to one specific embodiment, striking body500is supported on drive body300by at least one carrier ball. Striking body500is illustrated as being supported on drive body300by two steel balls290,295. For this purpose, interior wall320of drive body300is provided with at least one groove-like notch to guide the at least one carrier ball. A preferably V-shaped groove-like notch330is provided as illustrated to guide steel ball290and a preferably V-shaped groove-like notch335to guide steel ball295, which in the following are also denoted as “V grooves.” On exterior wall510of striking body500there is at least one recess or notch for supporting the at least one carrier ball. By way of illustration, a recess or notch530is developed for supporting steel ball290and a recess or notch535is developed for supporting steel ball295. In the striking operation of mechanical striking mechanism200, steel balls290,295are able to move in V grooves330,335and in recesses or notches530,535to enable rotation of striking body500in relation to output shaft400and in relation to drive body300. The mode of operation of a V groove rotating striking mechanism is, however, generally conventional such that a detailed description of the mode of operation of striking mechanism200is omitted here.

FIG. 3shows the barrel-shaped drive body300ofFIG. 2with opening305provided on axial end352and barrel bottom type wall350developed on the opposite axial end351, which has opening360.FIG. 3illustrates V groove330formed on interior wall320as well as the counter mounting device340provided in the area of opening305. According to one specific embodiment, this counter mounting device340has concentric rings345, which are designed for torque proof mounting on corresponding concentric rings (445inFIGS. 4 and 5) of drive member125.

FIG. 4shows drive member125fromFIGS. 1 and 2with anterior, central and posterior area270,271and272respectively, and planet carrier207provided in anterior area270, on which exemplarily bearing pin470and mounting device240are developed. According to one specific embodiment, mounting device240has concentric rings445for torque proof fastening to the concentric rings (345inFIG. 3) of drive body300ofFIG. 3, and in the central area271of drive member125radial recesses452,454are provided for accommodating respectively planetary wheels204and205fromFIG. 2. Radial recesses452,454have cylindrical openings462,464for supporting bearing bolts278and279respectively associated with planetary wheels204,205ofFIG. 2.

FIG. 6shows section150ofFIG. 1with gearbox118located in gearbox housing119, and a mechanical striking mechanism600in operative connection with output shaft400, according to a second specific embodiment. Striking mechanism600may be used to realize striking mechanism200ofFIGS. 1 and 2, but contrary to the latter it has a drive member625, which generally corresponds to drive member125ofFIG. 2, except that it has a planet carrier607, which compared to planet carrier207ofFIG. 2has a reduced diameter. Furthermore, to provide threaded connection199, planet carrier607has the concentric rings445shown inFIGS. 4 and 5and drive body300has the concentric rings345shown inFIG. 3.

According to one specific embodiment, an anti-rotation lock640is allocated to the threaded connection199for torque proof mounting of drive member625in drive body300, which is designed to prevent drive member625from twisting in relation to the drive body300. Anti-rotation lock640is illustrated as having at least two fixing bolts643,645, through which the concentric rings345of the drive body300engage in a torque proof manner with the concentric rings445of drive member625. Fixing bolts643,645are developed exemplarily to prevent an unscrewing of drive element625from drive body300. To this end, fixing bolts643,645are able to lock drive member625or its planet carrier607e.g. in drive body300in the radial and axial direction.

FIG. 7shows striking mechanism600and gearbox118ofFIG. 6without striking mechanism housing220ofFIG. 6, but including the barrel shaped drive body300ofFIG. 6, which is shown in a partly sectional view. Furthermore, drive body300is shown in a transparent manner in the region of drive member625or planetary carrier607so as to illustrate an exemplary embodiment of fixing bolt645. Furthermore,FIG. 7illustrates planetary wheels204,205mounted on drive member625ofFIG. 6.