Convertible Rotary/Percussion Drill

The present invention relates to convertible rotary/percussion drills.

Convertible rotary/percussion drills are described, for example, in U.S. Pat. No. 3,785,443, Armbruster, assigned to the assignee of this application.

Convertible drills as known may be relatively complicated, subject to material fatigue and relatively difficult to assemble.

It is an object of the present invention to furnish a selection member for selectively operating a drill as a percussion drill or a rotary drill which is simple, reliable, and has a minimum number of parts thereby simplifying the alignment during assembly.

Briefly, a plastic slider is formed with at least one latching element for arresting the slider in a first and second end position in which the drill is operative, respectively, as a rotary and a percussion drill. The latching elements are elongated and have cam-like projections at their free ends which engage corresponding recesses in the housing. The plastic slider has end portions by means of which the slider is pushed from the first to the second position and vice versa. Separate elements for engaging the slider to be pushed are therefore eliminated.

For providing a thrust bearing for the spindle when the drill is operating as a rotary drill, the slider has an opening which receives a ball. In a preferred embodiment of the present invention, the slider has an additional recess in the region of this opening for receiving a bearing plate which, together with the ball, constitutes the thrust bearing for the spindle when the drill is operating as rotary drill. The use of a small hardened bearing plate made of steel assures a long life and a relatively foolproof conversion for the drill. Alternatively, a stationary steel plate may be mounted in the part of the housing opposite the slider and extending in the direction of travel of the slider. This stationary steel plate can serve as a sliding surface for the above mentioned moveable plate or, alternatively, the moveable plate can be eliminated and the thrust bearing would then comprise the ball and the stationary steel plate. The selection member then comprises only the single plastic member which includes the latching elements and the inserted supporting member for the spindle.

In a further preferred embodiment, the ball and the moveable supporting plate, if present, are maintained in position by the housing itself when the drill is operating as a percussion drill. Further building elements for guiding and mounting the selection member are therefore also eliminated. The construction in accordance with the present invention can be utilized in a number of differently shaped housings

FIG. 1 is a cross section through the drill housing in the region of the selection member;

FIG. 2 is a longitudinal cross section of the front part of the drill when operative as rotary drill; and

FIG. 3 is a longitudinal cross section of the same part of the drill when operative as a percussion drill.

In FIG. 1, reference numeral 10 denotes the housing in which a selection slider 11 is slidably mounted. Slider 11 has projections 12 which abut inner guide surfaces of housing 10. Slider 11 has end sections 13 which may be pushed to move the slider transversely across the housing (compare FIGS. 2 and 3) from its first position wherein the drill is operating as a rotary drill to its second position wherein the drill is operating as a percussion drill. End sections 13 project through recesses in housing 10. The portions of housing 10 which form these recesses cooperate with projections 12 to form stops which limit the movement of the slider in its lengthwise direction. An elongated latching element 14 extends from each projection 12, so that slider 11, porjections 12 and latching elements 14 form a single plastic structure. The latching elements are diagonally opposite each other and extend in opposite directions. Each latching element 14 has a free end with a cam-like projection 15. Each projection 15 engages a corresponding one of two latching detents 16 in the housing when the drill is operating as rotary and percussion drill respectively. Depending upon the material used for latching elements 14, it may be desirable to provide further detents 17 in the housing to receive projections 15 when the latter are not engaged in the detents 16. The further detents would prevent fatiguing of the material and a resulting decrease of the retaining power of the detent mechanism.

A circular opening 18 is provided in the central region of slider 11 to receive a ball 19. A further square recess 20 is also provided to receive a bearing plate 21. The spindle is denoted by reference numeral 22.

Elements shown in FIGS. 2 and 3 which were shown in FIG. 1 have the same reference numerals. Further shown in FIGS. 2 and 3 is a stationary steel plate 24 mounted on a part 23 of the housing opposite slider 11. Bearing plate 21 slides on stationary steel plate 24. If bearing plate 21 is eliminated to simplify the construction, then ball 19 rolls directly on steel plate 24.

To switch the drill from rotary to percussion type operation, a sidewise push applied to end portions 13 of slider 11 cause it to move in the lengthwise direction within housing 10 in such a manner that the latching elements shown in FIG. 1 engage the upper or the lower recess 16 with one of their projections 15 thereby arresting the slider in the first or the second position. Movement of slider 11 causes a corresponding movement of ball 19 which is in opening 18 and of bearing plate 21 which is in recess 20. In the arrangement shown in the figures, bearing plate 21 ends flush with the top surface of slider 11 which faces steel plate 24. Use of the small and relatively inexpensive bearing plate 21 prevents deformations in ball 19 which would interfere with the slidability of slider 11. In FIG. 2, spindle 22 thrusts against ball 19 and is axially maintained in this position in such a manner that a ratchet supplied for percussion drill operation is disengaged. In the position shown in FIG. 3, the ratchet is engaged and spindle 22 together with the drill chuck execute a translatory movement corresponding to the rotational movement of the ratchet, since the end of spindle 22 away from the chuck is free to move within the required limits.

Various changes and modifications may be made within the scope of the inventive concept.