The present invention relates to an adapter of the kind which is intended for connecting a tool bit to a drive device which is provided with a chuck and which is in¬ tended for rotating the tool bit, and particularly, although not exclusively, to an adapter for connecting a chisel-headed bit or a bit having a head of cruciform section, such as a Phillips bit, to an electric drive device, said adapter forming a unit which is separate in relation to the drive device and which is adapted to be firmly clamped in the chuck and include:? a tool-bit accommodating sleeve.

in one known screw-driving device (DE-C-3205118) a tool tip, a so-called tool bit, is axially moveable between a forward and a rearward position in a sleeve arrangement. The tool bit is spring biassed in a direction towards its forward position in the sleeve arrangement, and can be urged into its rearward position therein against the action of the spring. The bit is connected automatically to the motor of the screw driving device, as the tool bit is pressed into its rearward position. On the other hand, when the tool bit occupies its forward position in the sleeve arrangement, the bit and part of the sleeve arrangement are out of driving engagement with said motor and can thus rotate freely in relation to the remainder of said device. When using the known screw driving device, a screw is fitted onto the tool bit, the motor is started, and the tool bit is pressed against the location at which the screw is to be applied. In conjunction herewith, the tool bit is first pressed to its rearward position in the sleeve arrangement, therewith engaging the tool bit with the drive motor of the screw driving device and driving-in the screw. When the forward or leading end of the sleeve arrangement comes into contact with the

surface into which the screw is driven, only the tool bit will be able to move further forwards, under the action of the aforesaid spring, since the remainder of the screw driving device is held against further movement through engagement of the device with said surface, this further forward movement of the bit continuing until the bit has moved away from its rear-a¬ ward position through a distance sufficient for the bit and said part of the sleeve arrangement to be disengaged from the motor of the screw driving device. This known screw driving device is a complidated and expensive special-purpose device and consequently has not met with commercic.1 success outside the professional field, despite the fact that there is a great need for screw driving devices even in minor construction work carried out by non-professional people, particularly when fitting plasterboard in conjunction with, for instance, insulating building structures and other building work, such as rearrangement of interior walls etc.

The object of the present invention is to provide a simple and inexpensive arrangement which is, nevertheless, reliable and effective and which will enable so-called tool bits or tool tips to be used without requiring expensive special-purpose devices herefor.

To this end there is proposed in accordance with the present invention an adapter of the aforementioned kind which is further characterized in that the sleeve is adapted to be accommodated in the chuck with substantially only a widened or flared forward end-part of said sleeve located outside the chuck, said end-part having a coherent annular end-surface, wherein the sleeve is slotted axially along a part of its length located rearwardly of said end-part, and wherein the tool bit can be firmly held in any selected axial position in the sleeve by

means of the chuck when firmly clamping the sleeve in the chuck. This arrangement obviates the need of an expensive special-purpose device and will enable a conventional electrical chuck-drill or so-called hobby machine to be used, such drill or machine being normally found in the tool kit of, for example, every householder.

So that the invention will be more readily understood and further features thereof and advantages afforded thereby made more apparent, the invention will now be described in more detail with reference to an exemplifying embodiment thereof illustrated in the accompanying drawing.

Figure 1 illustrates a sleeve which forms part of the adapter according to the invention, the sleeve being shown partly in an axial sectional view taken on the line I - I in Figure 2 and partly in side view.

Figure 2 is a front view of the sleeve illustrated in Figure 1.

Figure 3 is an axial sectional view of the adapter and shows a tool bit inserted in the adapter.

Figure 4 is a side view showing the adapter fitted to a chuck of a partially shown drive device, and illustra¬ ting the manner in which the adapter functions.

The adapter illustrated in the drawing comprises a sleeve 1 that has a widened or flared forward end-part 2 and a partially closed rearward end-part 3. The rearward end-part 3 has provided therein an aperture 4 which receives a setting screw 5, as shown in Figures 3 and 4. The sleeve 1 incorporates axially extending slots 6, and the part of the sleeve located between the end-parts 2 and 3 has a polygonal cross-sectional shape. The slots 6

extend along the major part of the axial extension of the sleeve 1 and divide the end-part 3 into segments.

The end-part 2 has the form of a circular collar which presents an opening 8 which diverges conically towards the front end-surface 7 of the sleeve 1. The reference number 9 designates generally a tool bit which has a head or front end 10 of cruciform section and a rear¬ wardly located part 11 of polygonal cross-sectional shape.

The polygonal cross-sectional shape of the part 11 con¬ forms essentially with the polygonal cross-sectional shape of the inside of the sleeve 1 , such that while the tool bit 9 can be moved axially in the sleeve 1 , subsequent to being inserted thereinto, it is unable to rotate relative to said sleeve. The cross-slotted end of the screw 5 is located within the sleeve 1 and faces towards the flared sleeve-end 2, arid the screw forms a stop abutment for engagement with the inwardly located end of the tool bit 9, thereby enabling the axial position of the tool bit 9 in the sleeve 1 to be set by turning the screw 5 in one direction or the other.

The sleeve 1 is constructed in a manner which will enable it to be clamped in the chuck 12 of a drive device 13,

Figure A , which, in the illustrated embodiment is assumed to be a conventional chuck-drill or hobby machine. The outer surface of the sleeve 1 , in the region thereof located behind the end-part 2 , has a polygonal cross- sectional shape, as seen in cross-section through the sleeve, which facilitates clamping of the sleeve in the chuck and also prevents undesirable rotation of the sleeve when claped in the chuck. The tool bit is fixed firmly in the sleeve by means of the chuck 12, the.jaws of which press the sleeve segments defined by the slots 6 radially towards one another, therewith to clamp the tool bit firmly in the sleeve.

When fitting the adapter to the drive device 13, the end-part 3 of the sleeve 1 is first inserted into the chuck 12, preferably until either the end-part 3 or the screw 5 comes into abutment with the bottom of the chuck bore or the rearwardly located side of the collar- shaped end-part comes into contact with the forwardly located end-surfaces of respective chuck jaws. Subsequent or prior hereto, the tool bit 9 is inserted into the sleeve until its rear end-surface abuts the head of the setting screw 5, whereafter the chuck 12 is tightened so as to grip the sleeve 1 firmly in the chuck and to clamp the tool bit 9 firmly in the sleeve by contracting the slotted part thereof.

The use of the adapter is illustrated in Figure 4, in which the reference number 14 designates part of a wall panel, e.g. a plasterboard, the reference 15 designates a lightmetal profiled stud or battern, and the reference 16 designates a so-called plastboard screw having a cross- grooved or Phillips screw-head. The screw 16 is placed on the forward end 10 of the tool bit, which end has a cruciform section or Phillips configuration, and is pressed against the location at which the screw is to be driven with the aid of the drive device 13 during activation of said device. The screw 16 is shown in full lines in Figure 4 partially inserted into the plaster¬ board 14, and in ghost lines fully inserted therein. When the screw 16 has been driven fully home in the plasterboard 14, the head of the screw will lie somewhat inwardly of the surface 17 of the plasterboard 14, as shown in Figure 4, so that the screw head can be readily covered with a suitable filling compound, so as to leave no traces of the screw head that might impair the appearance of a wallpaper covering or paint covering subsequently applied to the plasterboard surface 17. Upon correct adjustment of the setting screw 5, the correct pentrating depth of the screw is automatically

obtained through contact between the surface 7 of the end-part 2 and the plasterboard surface 17 preventing further forward movement of the adapter to the left in Figure 4. As the drive device 13 continues to operate, with the end-surface 7 in contact with the plasterboard surface 17, the tool bit will continue to drive in the screw 16, until the tool bit of cruciform section cams out of driving engagement with the cross-slotted screw head of the screw 16. The setting screw 5 is adjusted to a setting at which this will occur immediately the screw 16 has been driven to the depth required.

The invention is not restricted to the aforedescribed and illustrated embodiment, but can be realised in any appropriate manner within the concept of the invention as defined in the following Claims. For example, the sleeve 1 may have a round external surface, and the forward end-part 2 of the sleeve 1 may have a permanent magnet fitted thereto, for detachably holding a screw placed on the screw driving end 10 of the tool bit 9.