This application is a 35 U.S.C. 371 application of PCT/EP2009/053441 filed on Mar. 24, 2009.
1. Field of the Invention
The invention relates to a machine tool, in particular a handheld power tool, which has a housing for receiving and mounting both a drive unit and a tool, in which the housing has two separate housing parts which are connected to one another via a connecting device.
2. Description of the Prior Art
Handheld power-tools driven by electric motor are known, such as drills, angle grinders, saws, or the like, which have as their drive an electric motor that is disposed in a motor housing and whose driving motion is transmitted to a drive shaft with a tool disposed on it. Grip elements are connected to the motor housing and are embodied as separate components, and the user holds the handheld power tool by these grip elements. The grip for instance comprises two grip half-shells, on each of which, to make the connection with the motor housing, an annular, radially inward-oriented connection projection is disposed, which protrudes into an associated annular gap on the motor housing.
In general, in making a connection between the various housing parts of a machine tool, care must be taken that forces and moments that occur in typical operation will also be absorbed over a long period of operation by the housing without interference. Thus in handheld power tools, for instance, not only forces in the longitudinal direction but bending moments between the various housing parts as well have to be transmitted. The connection between the housing parts must be capable of absorbing these forces and moments.
European Patent Disclosure EP 0 493 033 A1 shows a handheld power tool whose housing in two parts with a front housing part for receiving and mounting a drive unit 2 and with a rear housing part that forms the grip part. The two housing parts are connected to one another via a connecting device, which has two connection projections on the rear housing part and complementary connection recesses on the front housing part. There are two connection projections and two connection recesses each, which are located one after the other in the connection and release direction, which at the same time is the longitudinal axis of the handheld power tool. The connection projections have a rectangular cross section, as do the connection recesses, and extend perpendicular to the connection and release direction.
The object of the invention is to embody a machine tool, in particular a handheld power tool, with simple structural provisions in such a way that various housing parts can be connected to one another in a simple way, and at the same time a connection with which strong forces and moments can be transmitted is ensured.
The machine tool of the invention has a housing in at least two parts for receiving and mounting both the drive unit and the tool. The connecting device that holds the two housing parts together has at least two connection projections, which are located one after the other in the connection and release direction of the housing parts and which in form-locking fashion engage associated connection recesses in the other housing part. Because of the positioning in line with one another of the connection projections on one housing part, the forces to be transmitted via the connection, in comparison to conventional connecting devices, are distributed to the at least two projections and the associated recesses, so that the forces are cut at least in half. The reduction in the forces to be transmitted protects the housing material in the vicinity of the connection, so that it is fundamentally possible to use thinner housing walls. However, it is also possible for overall greater forces and moments to be transmitted between the housing parts without impermissible deformation. Overall, the forces and moments are distributed over a larger contact area between the housing parts. In general, the connection by means of the connecting device is made via a form lock, which is attained by the undercutting, operative in the connection and release direction of the housing parts, of the connection projections and connection recesses.
A further advantage of the multi-row connection projections is the increased safety in the event of an overload. If one connection projection fails, the connection function can be maintained by the second connection projection; this prevents the housing from breaking apart, or at least postpones it.
In a preferred embodiment, the connecting device is designed in such a way that a rotational capability between the connecting housing parts exists. The rotation takes place about the longitudinal axis of the machine tool, or in other words about the release and connection direction between the housing parts. Thus the connecting device is capable both of transmitting mounting forces in the connection direction and moreover of absorbing bending moments between the housing parts; at the same time, rotation between the housing parts is allowed, which enables and simplifies use by both right-handed and left-handed users. To achieve the rotation capability, the connection projections and the associated connection recesses are embodied identically in the circumferential direction. It may optionally be expedient to limit the rotation capability to a defined angular range, for instance by means of stops or the like.
It is also expedient to construct the at least two connection projections as intrinsically identical, that is, to provide them with the same cross section. On the one hand, this facilitates production; on the other, at least approximately equally strong forces are transmitted via the identical connection projections.
It is furthermore possible for the connection projections to extend over the entire length of the parting line between the housing parts to be connected. However, it is also possible for the parting line to be covered only partially in the circumferential direction. Moreover, the at least two connection projections can be embodied with either the same length or different lengths in the circumferential direction.
If no capability of relative rotation between the housing parts is wanted, then advantageously stops are provided between the housing parts; they may also optionally be disposed directly on the connecting device, for instance by means of radial engagement of a peg or the like with an associated recess. The stops prevent a relative rotation between the housing parts.
The connection projections are advantageously embodied in one piece with the housing parts. The connection recesses on the other housing part can also be embodied in one part with it, so that the form lock between the housing parts is attained by simply slipping them on axially.
Furthermore, however, an embodiment of the connection projections as a separate component is also possible, in particular by disposing the connection projections on a separate housing portion, which is to be connected to one of the housing parts via further, connection elements.
In a further advantageous embodiment, the connection projections have a tooth shape and expediently have an inclination that is opposite that of the release direction between the housing parts to be connected. In this way, greater connection forces can be transmitted between the housing parts. The tooth shape of the connection projections makes it possible on the one hand for the bending stress to be distributed uniformly over the entire connecting device, and on the other, slipping one housing part onto the other housing part is made easier, and the release of the housing parts is made more difficult, by the tapering to a point of the connecting teeth and by the inclination of the connecting teeth. The embodiment in tooth shape furthermore has the advantage of better compensation for play and tolerances.
In a further expedient embodiment, the base between the adjacent connection projections, that is, the transition from one connection projection to the next connection projection, is rounded, to avoid peak stresses that can cause component damage.
In a further advantageous embodiment, a damping element is integrated with the housing portion having the connection projections and the connection recesses, for instance by means of an undulating or bellowslike embodiment of the housing wall, which permits a longitudinal expansion and contraction in the connection and release direction and contributes, by way of the intrinsic damping of the material, to vibration damping. However, the embodiment of the damping element as a separate component, which is integrated with or secured to the wall of the housing portion of the connecting device, is also possible.
Further advantages and expedient embodiments can be learned from the further claims, the description of the drawings, and the drawings. In the drawings:
In the drawings, identical components are provided with the same reference numerals.
The handheld power tool 1 shown in
As can be from
As can be seen from
Because of the tooth shape, the cross section of the connection projections 10 and 11 tapers radially from the outside inward; the connection recesses 12 and 13 are correspondingly embodied in complementary fashion. The base (not enumerated) at the transition between the connection projections 10 and 11 that are adjacent and are located in line with one another in the axial or release direction, is provided with a rounded cross section, to avoid notch effects.
It may optionally be expedient to provide more than two connection projections located in line with one another in the connection and release direction, and to associate a number of connection recesses corresponding to the connection projections on the other housing part.
The foregoing related to the preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.
Number | Date | Country | Kind |
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10-2008-001-252 | Apr 2008 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2009/053441 | 3/24/2009 | WO | 00 | 10/14/2010 |
Publishing Document | Publishing Date | Country | Kind |
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WO2009/127501 | 10/22/2009 | WO | A |
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