Hammer drill spindle and chuck assembly

The drill chuck comprises a chuck body connected to a drive shaft of a drilling drive device so as to deliver hammer blows to the working tool (e.g. the drill) of a hammer drill and the like, a plurality of clamp jaws which axially guide and hold the drill bit centered on the chuck axis, and a catch device which optionally acts to restrain the drill bit from rotary slipping with respect to the chuck body. The chuck jaws are positioned to axially overlap any axially extending working grooves provided in the drill bit shaft. At least one catch device is provided circumferentially between the clamp jaws, is radially movable in the chuck body and is constructed to engage in grooves running axially in the drill bit shaft or not according to the desire of the operator without loosening during drilling.

CROSS REFERENCE TO RELATED APPLICATIONS 
This application is related to the commonly assigned copending 
applications: Ser. No. 658,133 filed Oct. 5, 1984, Ser. No. 686,243 filed 
Dec. 26, 1984, Ser. No. 702,049 filed Feb. 15, 1985, Ser. No. 692,902 
filed Jan. 18, 1985, Ser. No. 692,907 filed Jan. 18, 1985, Ser. No. 
702,053 filed Feb. 15, 1985 and Ser. No. 703,888 of Feb. 21, 1985. 
Specifically reference should be had to the concurrently filed copending 
applications Ser. No. 719,760 and Ser. No. 726,596 corresponding to German 
applications P 34 16 946.6 and P 34 16 954.4. 
FIELD OF THE INVENTION 
My present invention relates to a drill chuck for a working tool (bit) for 
percussion or rotary impact (hammer) drilling having a chuck body 
connected to a hammer-drill drive shaft or spindle equipped for delivery 
of hammer blows to the bit. 
BACKGROUND OF THE INVENTION 
A hammer drill chuck can have a plurality of clamp jaws centered about and 
axially advanced against the bit, the clamp jaws defining a drill-bit 
cavity coaxial with the chuck axis for receiving the shank of the bit and 
are simultaneously moved centrally toward the chuck axis, and further 
having means for rotational locking of the bit against rotary slipping in 
the chuck. 
A working tool with a smooth cylindrical shaft held slidably axially 
between clamp jaws in a chuck of the foregoing type is taught in German 
Patent document DE-OS 31 33 085. The catch device here is an adjustable 
V-block or dog braceable from the exterior against the shaft of the 
working tool. The chuck dog secures the bit against relative rotation and 
is axially slidable at least to the extent of the hammer stroke as well as 
radially according to the diameter of the working tool shaft. 
The braced chuck dog takes part in the hammer motion of the drilling tool 
and hence its mass may damp the hammer motion or the hammer blows on the 
working tool. Above all, the bracing of the chuck dog on the cylindrical 
working shaft, which also serves to restrain the drill bit rotationally, 
should be sufficient to permit a series of hammer strokes to be applied. 
The chuck dog more or less digs into the drill bit shaft, but the grip of 
the chuck dog can be loosened. The chuck dog can then slip axially as well 
as in the circumferential direction which of course defeats the desired 
locking of the drill bit. 
A percussion drill bit with at least one axially closed axially extending 
groove on its shank is described in German utility model DE-GM 81 32 988, 
in which the lengthwise groove is divided by at least one cross-piece in 
conformity to the contour of the shank into a plurality of sections. This 
structure of the shank makes possible the use and interchangeability of 
drill bits both in the common drilling machine and also in the hammer 
drill. The cross pieces offer the possibility, being positioned laterally 
across the axially extending groove, for the clamp jaws of the chuck to 
grasp the drill bit in the case of the hammer drill. On the other hand the 
groove structure makes possible holding the drill bit in specially 
constructed percussion drilling device. A number of these grooves exist in 
the drill bit shaft of this prior art design and they are engaged by 
locking elements of the drill bit holder so as to be secured rotationally, 
but with some freedom of limited axial play. However, there is no 
possibility in this prior art drill chuck, having the locking elements for 
the grooves of the drill bit, to clamp a drill bit which has a smooth, 
cylindrical surface without such grooves. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide an improved drill chuck for a 
percussion drill device, hammer drill and the like having an improved 
efficiency of operation with a high work capacity due to a reliable 
locking of the drill bit against rotational as well as axial slipping. 
A more specific object of my invention is to provide an improved drill 
chuck of the foregoing kind so that rotational locking of the drill bit in 
the common percussion drilling device or the hammer drill is provided in 
an equally good, reliable way while granting an improved working capacity 
to the drilling machine with a high efficiency, and, of course, so that 
clamping of the drill bit with its companion moving parts is insured 
without impairment of the rotational locking of the drill bit in the chuck 
and without impairment of the axial guiding and coaxial alignment of the 
drill bit held in the chuck by engagement of locking elements in the 
lengthwise extending grooves of the drill bit. 
It is a further object of this invention to provide an improved drill chuck 
for a hammer drill and the like which can hold a drill bit with a grooved 
or without a grooved drill bit shaft so as to provide an improved drill 
chuck versatility as well as an improved operating efficiency. 
SUMMARY OF THE INVENTION 
These objects and others which will become apparent hereinafter are 
attained in accordance with the invention in a drill chuck comprising a 
chuck body connected to a drilling machine drive shaft or spindle equipped 
for delivery of hammer blows to a drill bit, a plurality of clamp jaws 
centered about an axially fed drill bit, the clamp jaws defining a drill 
bit cavity coaxial to the chuck axis for the drill bit and are adjustable 
toward the chuck axis, and further at least one catch device for 
rotational locking of the drill bit against rotational slipping. 
According to the invention the clamp jaws axially overlap drill bit grooves 
provided in the drill bit shaft (i.e. are angularly offset from these 
grooves), and at least one catch device or element is provided 
circumferentially between the chuck jaws, wherein the catch element is 
shiftable radially in the chuck body and is constructed for engagement in 
the lengthwise running grooves in the drill bit shaft without loosening 
during drilling so as to restrain the drill bit from rotational slipping. 
Consequently a conventional drill bit with a smooth shaft can be grasped 
and held in the drill chuck in a conventional manner, when the catch 
device is drawn back from the drill bit cavity in the chuck body and the 
drill bit cavity is freed to accept the drill bit shaft only. 
Alternatively in the drill chuck of the invention a drill bit with radially 
extending grooves on its drill bit shaft can also be used, wherein the 
catch device engages in these grooves and rotationally restrains the drill 
bit securely, without which the clamp jaws alone must clamp against the 
drill bit shaft radially tightly. 
The drill bit is hence held by engagement with the groove axially loosely 
and is guided and is movable against the fixed clamp jaws axially. 
Therefore the hammer stroke motion occurs without corresponding axial 
locking of the drill bit by the chuck jaws and therefore without damping 
by the mass of those jaws or the chuck. 
In this type of operation it is only important that the drill bit shaft in 
the drill bit cavity be guided above and below the grooves of the drill 
bit, in order that the engagement of the catch device in one of the 
grooves can not lead to jamming of the bit shaft. It is enough that the 
chuck jaws guide the drill bit shaft axially only at the drill bit side 
offset from the grooves, if precautions for guiding of the shaft ends are 
properly taken in other ways. 
The drill chuck can have an axial opening in the chuck body, through which 
the blows of the hammer are transmitted directly down by the drive shaft 
(for example, by means of an axially shiftable ram) against the end of the 
drill-bit shaft found in the drill-bit cavity. Thus it is a feature of 
this invention to provide the drill-bit cavity end portion of the chuck 
with an axial opening acting as an axial guide for the shaft of the drill 
bit extending into the opening. 
The catch device can comprise a catch bolt, which is urged radially 
outwardly by a spring to contact an outer adjustable ring guided rotatably 
about the chuck body, whereby the adjustable ring holds the catch bolt so 
that it protrudes into the drill bit cavity when its inner surface is 
flush with the chuck body, and has indentations on other portions of its 
inner surface into which the catch bolt can enter, when the adjustable 
ring is rotated into a position where the bolts and the indentations 
coincide. Thus the drill bit will be freed from engagement with the catch 
bolt. It requires therefore only a rotation of the adjustable ring for the 
catch bolt, under the force of the spring, to be drawn out of the drill 
bit thus unlocking it. 
Another preferred embodiment of the catch device, which makes possible an 
especially reliable operation, comprises a headpiece and a rotatable piece 
adjustable to and fro on the headpiece in the drill-bit cavity, wherein 
the headpiece is radially shiftable, but unrotatable, about the 
radially-directed shift axis. 
The rotatable piece however is radially unshiftable, but is rotatable about 
the shift axis in the chuck body, and between the headpiece and the 
rotatable piece isi a threaded coupling, which converts the rotational 
motion of the rotatable piece into a radial displacement of the headpiece 
(to or from the chuck axis). 
Advantageously the headpiece is constructed like a U-shaped shackle or 
stirrup, which is positioned with its shackle back oriented for engagement 
with the drill bit grooves of the drill bit shaft, and further is guided 
in an oblong slot of the chuck body, whose longitudinal axis runs in the 
direction of the chuck axis. The U-shaped headpiece has at the ends of the 
shackle legs pins directed toward one another which engage in a thread 
gear or coupling groove in the outer surface of the rotatable piece to 
form the threaded coupling. 
The cylindrical rotatable piece is positioned in the central enlargement of 
the elongated hole which comprises a blind hole, and the rotatable piece 
is secured in the blind hole partially covered by an overlapping apron, 
which makes accessible the key hole provided in the front side of the 
rotatable piece, which is so arranged for the rotation of the rotatable 
piece by the key. The apron can be constructed from a circular ring 
encircling the chuck body.

SPECIFIC DESCRIPTION 
The drill chuck 2 serves as a tool holder for the drill bit 1 which is 
shown in the drill chuck 2 in FIGS. 1 and 2. 
The drill chuck 2 has a chuck body 3 which is connected to a drive shaft 4 
of an unshown drilling machine equipped to deliver hammer blows onto the 
drill bit 1, wherein the drive shaft 4 transmits the hammer impact as well 
as the rotation in the embodiment according to FIG. 1. 
In the embodiment according to FIG. 4 the drive shaft 4 is constructed in 
two parts, namely, a drill spindle 41 which transmits the rotary motion to 
the drill chuck 2 and a ram 42 fed through the hollow drill spindle 41, 
which transmits the hammer impact. The drill chuck 2 has the drill bit 1 
centered in and axially guided by the chuck jaws 5, which form a drill bit 
holding cavity 6 for the drill bit shaft 61 coaxial to the chuck axis. The 
clamp jaws 5 are adjustable centrally toward the chuck axis. Therefore the 
teeth 51 of the chuck jaws 5 mesh with the inner gearing 71 of a toothed 
ring 7, which is axially unshiftable but is rotatable and with the 
assistance of an insertable geared key 9 can be rotated for tightening or 
loosening of the drill chuck 2. 
In order to prevent undesired clamp jaw movements, the position of the 
toothed ring 7 can be held fixed. Therefore in the embodiment according to 
FIG. 1, a restraining jacket 11 is axially slidable between two positions 
rotatably against the pressure of a spring 10. The restraining jacket 11 
carries on its forward edge directed toward the toothed ring 7 restraining 
gear teeth 12, which can mesh in an opposing gear on the ring and restrain 
thereby the ring, when the restraining jacket 11 occupies its forward 
position shown in FIG. 1. In the axial position drawn back from the 
toothed ring 7 the restraining jacket 11 does not prevent free rotation of 
the toothed ring 7. Both positions of the restraining jacket 11 are 
flexible in both rotary and axial position by a locking device as seen in 
FIG. 3. Therefore the restraining jacket 11 is provided with ribs 13, 
preferably axially oriented, protruding from its inner surface which 
engage in lock cavities 81 and 82 having different depths in the chuck 
body 3. The lock cavities 81 are shaped so as to be uniformly closer to 
toothed ring 7 than lock cavities 82 and preferably the ribs 13 are all 
the same distance from the front edge of the restraining jacket 11 so that 
the restraining jcket 11 can either sit with ribs 13 engaging lock 
cavities 81 as seen in FIG. 3 and thus be in engagement with the toothed 
ring 7 or it can sit with the ribs 13 in the lock cavities 82 and thereby 
be held out of engagement with the toothed ring 7. 
In the embodiment according to FIG. 4 a lock bolt 15 fed axially on the 
chuck body 3 serves to restrain the toothed ring 7. Under the force of the 
spring 16 the lock bolt or pin 15 engages with its forward, drill bit 
directed, end in a corresponding bolt cavity 37 of the toothed ring 7, 
wherein the sides of the bolt cavity 37 and the bolt end engaging therein 
are so inclined that in the engaged position the toothed ring 7 is secured 
from undesired rotation with respect to the chuck body 3, but nevertheless 
by rotation of the toothed ring 7 by hand or by means of key 9 the lock 
bolt 15 is lifted or pressed out of the bolt cavity 37 so that the toothed 
ring 7 is again freely rotatable. 
Alternatively free rotation of the toothed ring 7 can be achieved by prior 
disengagement of the bolt 15 from the bolt cavity 37. 
The chuck body 3 has axial opening 19 through which the downwardly directed 
hammer blows of the drive shaft 4 or the ram 42 are directly transmitted 
onto the end of the drill bit shaft 61 seated in the drill bit cavity 6. 
In both embodiments, the chuck jaws 5 have are adjacent drill bit groove 62 
formed in the drill-bit shaft 61 by which it is gripped. In the 
circumferential direction between the clamp jaws 5 one finds a catch 
device 18, which is displaceable radially in the chuck body 3 and is 
constructed for engagement in the groove 62 running lengthwise on the 
drill bit shaft 61. 
It is sufficient that the clamp jaws 5 should guide drill bit shaft 61 
axially only by engaging the surface thereof; if, as in FIG. 4, the 
possibility exists, that the shaft end of the drill-bit cavity 1 can 
extend into the drill bit end of the opening 19, then the opening 19 is 
constructed, and acts as an axial guide for the shaft 61. 
In FIGS. 1 and 2, the catch 18 is formed by a catch bolt 91 which is pushed 
outwardly radially by a spring 92 and against the inner surface of a 
rotatable adjustable ring 93 affixed on the chuck body 3. The adjustable 
ring 93 is securable against axial movement by an elastic washer 95. With 
its inner circumferential surface, the adjustable ring 93 holds the catch 
bolt 91 in the forward position extending into the drill-bit cavity 6 
according to FIGS. 1 and 2. The adjustable ring 93 has on its inner 
circumferential surface a bolt cavity 94 in which the head of the catch 
bolt 91 can enter due to the force exerted by spring 92, when a rotation 
of the adjustable ring 93 positions cavity 94 and adjacent catch bolt 91. 
When this occurs the drill bit 1 is released, if a drill bit 1 with a 
grooved shaft 61 is gripped between the clamp jaws 5. 
In the embodiment according to FIGS. 4 to 10 the catch 18 is formed by a 
headpiece 96 and a rotatable element 97, which moves the headpiece 96 back 
and forth in the drill-bit cavity 6. The headpiece 96 is radially 
shiftable relative to the chuck axis and is unrotatable around the element 
axis, so that the rotatable element 97 is radially and axially unshiftable 
and is rotatable about its own axis. 
Between the headpiece 96 and the rotatable element 97 a threaded coupling 
exists, which converts the rotary motion of the rotatable element 97 into 
a radial shift of the headpiece 96 to or from the chuck axis. 
In particular, the headpiece 96 is structured essentially as a U-shaped 
shackle which is installed in the drill-bit cavity 6 with the shackle back 
98 protruding for engagement in the drill bit groove 62, the shackle back 
98 being particularly constructed corresponding to the shape of the 
groove. 
The headpiece 96 is guided in an oblong opening 20 in the chuck body 3, 
whose long axis runs in the direction of the chuck axis. Therefore 
rotation of the headpiece 96 is impossible. At the ends of the shackle 
legs 99 pins 100 are directed toward one another. The pins 100 engage in 
the thread 101 on the outer surface of the rotatable piece 97. The 
cylindrical rotatable element 97 is positioned in a central cylindrical 
widening of the oblong hole 20 constructed as a blind bore 21 and is 
secured to the chuck body against the back 65 of the blind bore 21 and 
with rotatable element 97 partially covered by an overlapping apron 22, 
which is constructed as a circular ring surrounding the chuck body 3. The 
apron 22 allows a key cavity 23 provided in the front of rotatable element 
97 to be accessible, in which an unshown key for rotation of the rotatable 
piece can be inserted and with it the headpiece 96 can be shifted 
radially. 
Moreover, the drill chuck 2 is of course rotatably driven, but axially 
shiftable with free play on the drive shaft 4 or 41. In the embodiment 
according to FIG. 1 axial coupling bolts 24 serve to rotatably bind the 
collar 23 of the drive shaft 4 to the chuck body 3. The coupling bolts 24 
are held in cavities extending in both the collar 23 and the chuck body 3 
and conformed so that axial relative motion of the chuck body 3 and the 
drive shaft 4 is allowed. The axial motion play of the shaft 4 is directly 
limited by a circular shoulder 25 provided in the chuck body 3. The drill 
chuck 2 is secured on the drill shaft 4 by a spring ring 26, which is 
overlapped by, and engaged in a circular groove in chuck body 3 and which 
overlaps the collar 23 lying against the circular shoulder 25. 
In the embodiment of FIGS. 4 and 5 a restraining jacket 27 sits fixed on 
the drill spindle 41, and carries two radial extending pegs 28, which are 
held in cavities 29 of chuck body 3. The pegs 28 allow a rotational 
locking of the drill chuck 2 to the drill spindle 41. In order to make 
possible optionally an axial free play of the drill chuck 2 on the drill 
spindle 41, the peg cavities 29 which are open axially in the spindle side 
direction are axially overlapped by an internal collar 30 of a coupling 
ring 31. This internal collar 30 has axially extending indentations 32 
which can be positioned opposite pegs 28 by a corresponding rotation of 
the coupling ring 31. When coupling ring 31 with the circular surface of 
its internal collar 30 lies directly on the pegs 28, as shown in FIG. 11, 
every axial motion of the drill chuck 2 with respect to the drill spindle 
41 is restrained thus preventing axial motion free play. However when the 
coupling ring 31 is rotated so that the indentations 32 are in 
registration with the pegs 28, the drill chuck 2 is free to slide axially 
to the extent of the axial height of the indentations 32.