Abstract:
A drilling tool has a shifting unit including a rotatable shifting lever (6) with a shifting cam (9) for switching between different operating positions corresponding to different operating speeds. For holding the shifting lever (6) in the operating positions, a spring clip (14) is mounted on the lever and is rotatable relative to the tool housing. The spring clip has detents (14a, 14b) arranged to snap into recesses (1d, 1e) in a bolt-like part of the housing which rotationally supports the shifting lever (6).

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to a drilling tool with a shifting unit for selection of the tool operating speed The shifting unit includes a shifting lever rotatable into different operational positions relative to the tool housing and equipped with shifting cams for the shifting unit and a spring clip with detents capable of snapping into detent recesses in the different operational positions. 
     A drilling device with a rotatable switching knob for selecting different operating speeds is known from DE-OS 32 40 466 with the switching knob being retained in the operational positions by a spring clip fixed in the housing of the device, so that the spring clip can snap into detent recesses in the rotatable knob. 
     The force to be applied to the switching knob is determined by the force of the spring. In the known device it is noted that the spring force depends largely on the manner in which the spring clip is secured to the device housing. Depending on the manner in which the spring clip is secured, different switching forces develop. The manner in which the spring clip is clamped is a source of problems with regard to the way in which the spring force is influenced. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a drilling tool with a lever of simple construction which is easy to manipulate for switching between different tool operational conditions, wherein the shifting force for the lever, independent of the retention of the spring clip, is assured. 
     In accordance with the present invention, the spring clip is rotatable by the lever relative to the tool housing and is secured in operating positions by detent recesses in the housing. 
     The present invention permits the elimination of means for the fixed clamping of the spring clip. The spring clip, rotatable relative to the tool housing, is not affected by external influences, such as the type of installation, the type of fabrication, or the like as far as its spring forces are concerned, so that a shifting force, independent of the retention of the spring clip, is achieved. 
     Preferably, the detent recesses are located in a bolt-like part of the housing. Advantageously, the spring clip is rotatable around the bolt-like part. As a result, the bolt-like part serving as a rotational bearing for the spring clip, can be partially embraced with prestress by the spring clip. This arrangement affords a simple retention of the spring clip. 
     In a preferred arrangement, the spring clip snaps into the bolt-like part at two locations, by providing pairs of diametrically opposite detent recesses for detents adjacent the ends of the spring clip for locating the operational positions. The individual pairs of the detent recesses are arranged angularly offset relative to one another to afford the required shifting or switching travel. 
     To achieve rotationally locked engagement with the lever, driving shoulders cooperating with the lever are preferably made part of the spring clip. Driving or engagement cams are provided on the lever for engaging the driving shoulders. The driving shoulders are formed by wall portions of a shaped section of the spring clip with the driving cams engageable with the shoulders. With this arrangement, rotary motion in both directions of rotation of the spring clip can be effected. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
    
    
     DESCRIPTlON OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a side view of a drilling tool embodying the present invention; 
     FIG. 2 is an enlarged sectional view of the drilling tool taken along the line II--II in FIG. 1; and 
     FIG. 3 is a sectional view taken along the line III--III in FIG. 2. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, a drilling tool is shown comprising a tool housing 1 with a handle 2 at the right hand end. A trigger or switch 3 for operating an electric motor within the tool housing 1, is located in the handle 2. In addition, a mechanical shifting unit is located in the tool housing 1 so that different operational speeds can be imparted to a tool bit receptacle 4 at the left hand end of the housing. The tool housing 1 has a leading end on the left hand side and a trailing end at the right hand or handle end of the housing. A side grip 5 extends downwardly from the tool housing 1 at its leading end adjacent to the tool bit receptacle 4. The shifting unit include a lever 6 accessible on the outside of the tool housing 1 for movement into two operating positions &#34;1&#34;, &#34;2&#34; for driving the tool bit receptacle 4 at different speeds. Between the operating positions, there is a middle position &#34;0&#34; and when the lever is in this position the rotation of the tool bit receptacle 4 is interrupted. The middle position &#34;0&#34; represents the transitional position between the two operating positions &#34;1&#34; &#34;2&#34; which represent the two different speeds. 
     As illustrated in FIGS. 2 and 3, the lever 6 has a gripping member 7 located outside the tool housing 1 and an arm 8 rigidly connected with the gripping member and extending through the housing into its interior. Arm 8 is rotationally supported on a bolt-like part 1a formed integrally with and located inside the housing 1. The axis of the bolt-like part 1a forms the axis of rotation for the arm 8. Spaced radially outwardly from the axis of rotation of the arm 8 are a pair of driving cams 8a, 8b, each arranged symmetrically relative to one another about a plane extending parallel to the axis of rotation and through the center line of the arm 8. These cams 8a, 8b extend parallel to the axis of rotation in the leading end-trailing end direction of the housing 1. In addition, a support tap 8c is provided on the arm 8 located between the driving cams 8a, 8b. Spaced below the support tap 8c as viewed in FIGS. 2 and 3, a bolt or pin shaped shifting cam 9 extends parallel to the axis of rotation and is spaced radially from the support 8c tap. The cam 9 extends completely through the arm and protrudes from both sides of the arm. 
     Shifting cam 9 displaces a slide 11 transversely of the axis of rotation. Slide 11 is a shaped sheet-metal plate part guided between the side walls 1b, 1c of the tool housing 1, and also by the bolt-like part la which extends through an elongated hole 11a in the slide, note FIG. 3. Slide 3 is held on the bolt-like part 1a by a circlip 12, note FIG. 2. Two elongated openings 11b, 11c are formed in the slide for entrainment or driving engagement with the shifting cam 9. Note in FIG. 2 that the cam 9, extending from the opposite sides of the arm 8 projects through the two openings 11b, 11c. The displacement of the slide is transmitted to a shifting rod 13 positioned in the slide 11 and coupled to it in a known manner, note FIG. 3. 
     The shifting lever 6 can be secured in the operating positions &#34;1&#34; and &#34;2&#34;. A spring clip 14 holds the shifting lever 6 in the desired position. Spring clip 14 is symmetrically shaped relative to the center line of the arm 8 passing through the axis of rotation of the bolt-like part 1a. The spring clip, adjacent its opposite ends, has detents 14a, 14b which engage the outer peripheral surface of the bolt-like part 1a with a prestress. Pairs of snap-in recesses 1d, 1e are provided in the outer peripheral surface of the bolt-like part 1a, so that the detents 14a, 14b snap into the recesses 1d, 1e for securing the lever in the desired operating position. Accordingly, spring clip 14 is rotated on the bolt-like part 1a by the shifting lever 6 and the driving cams 8a, 8b rotational displace the spring clip into the desired operating position. One of the driving cams 8a, 8b, during rotational movement, engages one of the entrainment shoulders 14c, 14d, so that the spring clip is rotated about the axis of rotation of the bolt-like part 1a with its detents 14a, 14d snapping into the desired pair of recesses 1d, 1e. The support tap 8c fits into a recess (14e formed by a V-shaped part of the spring clip and prevents radial displacement of the spring clip from the bolt-like part 1a. In FIG. 3 the two operating positions &#34;1&#34; and &#34;2&#34; of the shifting lever are displayed in dot dash lines. Further, in FIG. 3 the lever 6, shown in full line, is located between the two operating positions.