US 20070137875 A1
An electric hand-held power tool (2) has a main housing (4) of a shell-type construction a tool spindle (14) projecting from the main housing (4) at a working tool-side end (18) of the housing and which can be rotated around a operational axis (A) by a motor (12) and a gear unit (16) which are accommodated in the main housing (4), with an axial percussion movements being applied to the tool spindle (14) by a ratchet percussion mechanism (38) having a toothed rim (43), which is fixed with respect to the housing and which is connected to a supporting body (44) that is supported in the main housing (4), the toothed rim (43) cooperating with a toothed rim (41) which is movable so as to be coupled with the tool spindle (14) for joint rotation therewith, and the supporting body (44) being supported by a supporting element (58) in a direction remote from the working tool-side end (18) of the housing, with the supporting element (58) being formed in a circumferentially extending manner at an inner surface (56) of an outer shell (34) of the main housing (4), and the supporting body (44) directly contacting the supporting element (58).
1. Electric hand-held power tool (2), comprising a main housing (4) having a shell-type construction; a tool spindle (14) projecting form the main housing (4) at a working tool-side end (18) of the main housing (4) and rotatable around a operational axis (A) by a motor (12); a gear unit (16) which is accommodated in the main housing (4) and transmits a driving torque form the motor (12) to the spindle (4); a ratchet percussion mechanism (38) for applying a percussion movement to the spindle (4) and having a toothed rim (43) which is fixed with respect to the housing and which is connected to a supporting body (44) supported at the main housing (4), the toothed rim (43) cooperating with a toothed rim (41) which is connected with the tool spindle (14) for joint rotation therewith; supporting means (58) for supporting the supporting body (44) in a direction remote from the working tool-side end (18), the supporting means (58) being formed in a circumferentially extending manner at an inner surface (56) of an outer shell (34) of the main housing (4), and the supporting body (44) directly contacting the supporting means (58).
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1. Field of the Invention
The invention relates to an electric hand-held power tool including a main housing, formed particularly of a plastic material and having a shell-type construction, and a tool spindle which can be connected to a tool holder for joint rotation therewith and which projects from the main housing at its working tool-side end. The tool spindle can be rotated around a operational axis by a motor and a gear unit which are accommodated in the main housing. In addition, axial percussion movements can be applied to the tool spindle along the operational axis by a ratchet percussion mechanism. For this purpose, the ratchet percussion mechanism has a toothed rim which is fixed with respect to the housing and which is connected to a supporting body that is supported in the main housing. The toothed rim cooperates with a toothed rim which is movable so as to be coupled with the tool spindle for joint rotation therewith, and the supporting body is supported by supporting means in a direction remote from the working tool-side end of the housing.
2. Description of the Prior Art
In hand-held power tools of the kind mentioned above, a rotating movement of the tool spindle which is used for a drilling process or a screw-driving process can be combined, in addition, with an axial reciprocating movement in order to increase the forward feed of the drill or the screwing speed, e.g., of self-cutting screws. The above-mentioned ratchet percussion mechanism is used particularly in smaller power tools such as screw-driving tools having an added percussion function, or hammer drills. Power tools of this kind often have a main housing of shell-type construction made of a plastic material and which is essentially formed of two shells which extend along the operational axis and, when the tool device is oriented in typical fashion with the handle directed downward, contact one another along a abutment which extends substantially along a vertical plane parallel to the operational axis.
Accordingly, all of the essential functional components of the hand-held power tool can be assembled beforehand in a half-shell and subsequently secured in a finalized manner by attaching the second half-shell, which appreciably facilitates assembly as a whole compared to tools with a cup-type construction, for example, and lowers production costs.
DE 42 36 819 A1 discloses a rotary tool that is operated by a motor and has a spindle which is movable in an axially reciprocating motion by a percussion device. The percussion device has a movable cam member which is arranged at the spindle. This movable cam member cooperates with a fixed cam member which is formed on a cam disk. The cam disk is supported away from a chuck in the axial direction in an inner housing, which encloses a gear unit, with the intermediary of a steel plate.
When this known rotary tool is pressed against a surface to be treated, the flow of force is directed from the hand of the operator, via a grip area at the main housing, to the inner housing and then, via the steel plate, to the fixed cam member. The movable cam member repeatedly moves away from the fixed cam member during the rotational movement of the spindle so as to generate the axially impacting reciprocating movement of the spindle.
Due to relative movements of the two housing parts caused by deformations, impact energy losses occur particularly between the main housing and the portion of the inner housing that is supported at a relatively large distance from the latter. This can impair operational efficiency particularly in comparison with tools of cup-type construction which also have main housing portions that extend transverse to the operational axis and support the supporting body axially form behind. A tool of this kind having a cup-type construction, is known, for example, from German Patent DE 1 204 126 C2.
Also, a tool of the kind mentioned above which has a shell-type construction, usually a plastic housing, in order to reduce weight, is relatively susceptible to forces acting on the housing from the outside transverse to the operational axis. For example, attaching a side handle with a clamping band that is securely clamped around the housing, can lead to a deformation of the housing. These deformations can lead, in turn, to malfunction or complete blocking of components of the tool such as the gear unit, a torque clutch, or an on/off circuit of the percussion device, for example.
It is an object of the present invention to eliminate the disadvantages mentioned above in a hand-held power tool of a shell-type construction and to increase operational efficiency and stability.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a power tool in which the supporting means are formed so as to extend circumferentially at an inner surface of an outer shell of the main housing, and the supporting body directly contacts the supporting means. In this way, a direct flow of force is achieved from the main housing to the supporting body with the toothed rim held thereon and which is fixed with respect to the housing. Thereby, the impact energy loss can be appreciably reduced, and the operational efficiency of the hand-held power tool can be increased. The circumferentially arranged supporting means provides for a particularly stable support in the operational direction. The circumferential arrangement can be circumferentially continuous or circumferentially discontinuous.
The supporting body advantageously forms a radial contact surface which contacts the outer shell circumferentially in radial direction. In this way, the supporting body supports the main housing on the inner side and accordingly imparts a greater stability, particularly with respect to external loads on the main housing acting transverse to the operational axis.
In a particularly preferred embodiment of the invention, the radial contact surface contacts the inner surface of the outer shell at the axial height of a cylindrical outer surface of the outer shell. In this way, the supporting body can stabilize the main housing precisely at that location where a side handle can be attached with a clamping band. This prevents a deformation which can cause malfunctions or even damage the main housing.
The supporting body is preferably formed as a sleeve-shaped base body from which a plurality of support arms project radially, the free ends of these support arms forming a radial contact surface. This results in a stable radial supporting action of the support arms while, at the same time, a large portion of the supporting body can be positioned in axial direction of the toothed rim. This increases the mass of the area of the supporting body that is primarily responsible for the supporting action and, in turn, increases the operational efficiency of the power tool.
The supporting body is advantageously made of metal so that, on the one hand, a stable radial support is achieved and, on the other hand, the toothed rim which is fixed with respect to the housing is supported axially by a particularly large mass, which further increases the operational efficiency of the power tool.
Further, the supporting body is advantageously held at a gear unit housing. In this way, the gear unit housing can also be stabilized by the supporting body, and assembly is also facilitated.
In this connection, it is especially advantageous when the supporting body is cast integrally with the gear unit housing. The space requirement can be reduced in this way. Further, the two elements are handled jointly in this way, which further facilitates assembly. Also, the gear unit housing is considerably stabilized in this way.
It is advantageous when a spindle bearing is pressed into the supporting body. In this way, the two toothed rims of the ratchet percussion mechanism can be positioned especially accurately relative to one another, resulting in reduced wear.
Bearing recesses for guiding slip clutch means are advantageously incorporated in the supporting body so that the supporting body takes on an additional function and the quantity of individual components of the tool device is further reduced which again facilitates assembly.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings.
The drawings show:
The tool spindle 14 projects in operational direction R from a working tool-end side 18 of the main housing 14 and is connected at its free end to a tool holder 20 in the form of a chuck for a joint rotation therewith. The tool spindle 14 projects through an adjusting sleeve 21 which is supported for rotation between the main housing 4 and the tool holder 20 for adjusting a maximum torque.
Further, a side handle 22, which is fixedly clamped to the main housing 4 by a clamping band 24, is provided at the hand-held power tool 2.
In the state of final assembly, the left-hand housing shell half 26 contacts ajoint face 30 of the right-hand housing shell half 28 extending parallel to the handle 10, and the two housing shell halves 26, 28 are screwed together with a screw mandrel 32, forming together an outwardly closed outer shell 34. The closed outer shell 34 defines a cylindrical outer surface 36 and the clamping band 24 of the side handle 22 can be secured thereon.
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When fixing the side handle 22, the clamping band 24 is placed on the cylindrical outer surface 36 and is tightened. The outer shell 34 is supported in the area of the cylindrical outer surface 36 on the inner side by the supporting body 44. This prevents deformations at the main housing 4 when fixing the side handle 22, which deformations could impair the operation of the slip clutch 64 or gear unit 16, for example.
When operating the hand-held power tool 2, a contact pressure P, which is applied by an operator to the handle 10 or to the contact pressure surface 8, is delivered directly to the supporting body 44 in the operational direction R via the supporting means 58 facing the rear end 6. Since this supporting body 44 contacts the inner surface 56, no offset torque, which could result in a noticeable deformation of the supporting means 58, occurs between the support arms 50 and the outer shell 34.
Alternative supporting means in the form of an abrupt narrowing of the inner surface 56 in direction of the rear end are also conceivable.
Because of the especially rigid support in the operational direction R which is brought about in both of these cases, the contact pressure P is transmitted with particularly low loss from the main housing 4 to the supporting body 44 and, therefore, to the toothed rim 43 which is fixed with respect to the housing. Because of this and because of the large mass of the metal supporting body which provides an additional supporting action, the impact energy transmitted to the tool holder 20 by the ratchet percussion mechanism 38 and, accordingly, the operational efficiency of the device 2 can be increased.
Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments with the spirit and scope of the present invention as defined by the appended claims.