Contra-angle head for dentistry

A rigid tubular housing provides separate enclosures for a drive shaft and a dental tool that are rotatable on axes that are angularly related. A wall separating the two enclosures provides bearing support for tool-driving gears in one of the enclosures and connection to a driving shaft in the other. A latching mechanism envelops the housing and covers it smoothly. The latching mechanism is movable on the longitudinal axis of the tubular housing for controlling access to the enclosure for a dental tool.

BACKGROUND OF THE INVENTION 
Contra-angle heads for use in dentistry, as presently known in the art, 
have become highly developed for both general and specific purposes. 
Examples, taken at random, are described in U.S. Pat. Nos. 3,369,298; 
3,578,745; and 4,053,983; which are directed respectively to a clutch 
mechanism, an oscillating broach for endodontic work, and a prophylactic 
head for a dental handpiece. These examples illustrate, in a limited way, 
the variety of applications existing for contra-angle heads, and the 
variety of structures which have evolved in response to them. 
Those contra-angle heads intended for use by a dentist to drive 
interchangeably one or more of drills, burs, broaches, files and other 
tools used in dentistry incorporate rugged and usually precise mechanisms 
for accepting and locking the tools in place, driving them at desired 
speeds, and releasing them for removal, quickly and reliably, but for the 
most part such contra-angle heads are bulky and large, have awkward 
shapes, and are heavy. The positions into which a dentist can put a tool 
in the mouth of a patient are restricted, and often a tool can be used to 
treat a patient only at the expense of great discomfort to the patient, 
and risk of harming surrounding tissue that is not directly involved in 
the procedure being undertaken. 
Projecting parts, such as extending gear boxes and external latching 
levers, which are commonly found on contra-angle heads currently in use 
tend to aggravate such discomfort and risks. For example, in U.S. Pat. No. 
3,369,298 a clutch is permanently rotatably fixed in a stub-housing 
oriented transverse to the principal housing, and gears to rotate the 
clutch on an axis transverse to the main drive shaft axis are housed in 
the stub housing, which is enlarged for that purpose. A tool can be 
removably inserted into the clutch from one end of the stub housing, and a 
lock lever is provided, externally, at the other end. 
Attempts to provide smaller and smoother contra-angle heads with 
interchangeable tools have lead, in one instance, to a construction in 
which the tool is inserted through the stub housing from the locking end, 
and a threaded cap is provided at the same end to perform the locking 
function. As it is attempted to make a contra-angle head smaller, these 
parts, especially removable caps, become so small that they are easily 
lost, wasting the time of the dentist, and so expensive that their prices 
are difficult to justify in times of rising prices of other more important 
medical procedures. 
GENERAL NATURE OF THE INVENTION 
With this invention I provide a new contra-angle head that is rugged, safe 
and convenient to use, has a convenient latch mechanism which is devoid 
entirely of projections and extensions and which has a smooth outer 
surface surrounding the entire end of the head that is put into the mouth 
of a patient, can be made without angular contours, and while providing 
ready interchangeability of tools can be made smaller in size than prior 
contra-angle heads having similar operating features. My new contra-angle 
head can be used with a limitless variety of tools, as well as for 
prophylactic devices. 
In my new contra-angle head, a rigid tubular housing, which can be made in 
one piece of any suitable material, such as metal or plastic, provides in 
one body elongated on the tubular axis two separate enclosures, one being 
an alley for a drive shaft and the other being a chamber for a dental 
tool, respectively, which rotate on axes that are angularly related, A 
comparatively massive wall separates the shaft alley from the tool 
chamber, and has an aperture communicating with both enclosures. This wall 
supplies bearing support for a drive shaft extending into the tool chamber 
from the shaft alley, or for a stub shaft communicating with both 
enclosures. Either shaft supports tool-driving gears in the tool chamber, 
which has an opening through a side wall of the housing for passage of a 
tool being installed or removed. A tubular latch member closely envelopes 
substantially the entire housing, including the end enclosing the tool 
chamber, with a thin-walled cover having a smooth outer surface that is 
entirely devoid of projections, extensions, and angular surfaces. This 
latch mechanism is movable on the tubular axis relative to the housing, 
either circumferentially, or longitudinally (ie: "telescopically") to 
latch or unlatch a tool in the tool chamber. Some embodiments of the 
invention will now be described with reference to the accompanying 
drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
In FIGS. 1-6, inclusive, a principal tubular housing 10 provides a shaft 
alley 11 for enclosing a drive shaft 12 which is rotatable around the 
longitudinal axis A--A of the housing. The housing 10 has one end 14 
rounded on the outside transversely to the axis A--A, and fitted with a 
tool chamber 16 having an opening 18 into the housing at one side and 
extending from that opening transversely to the axis A--A toward the 
opposite side of the housing where it terminates in a dome-like interior 
wall 20, with an aperture 21 through it (FIGS. 3,5). A transverse wall 22 
between the tool chamber 16 and the shaft alley 11 has an aperture 24 on 
the axis to provide bearing support for the shaft 12 (FIG. 3). A coupling 
member 26 is fitted over the end 28 of the shaft and into the aperture 24. 
The coupling member has driving gear teeth 30 projecting into the tool 
chamber beyond the shaft end 28, for engaging the mating gear teeth 32 of 
a tool member 34 when the latter is present in the tool chamber, as shown 
in the drawings. In practice the contra-angle head will be fitted at the 
left-hand end of the housing 10 (as seen in the drawings) with means to 
couple it to a hand piece, of which several varieties are now in 
professional use. Such coupling means are not part of the invention, and 
are not illustrated. It will be understood that the shaft 12 is intended 
to be driven from the handpiece to which the contra-angle head is coupled. 
The tool member 34 is similar to the dental tool (30) which is described 
and claimed in the co-pending U.S. Application Ser. No. 970,468 filed Dec. 
18, 1978 by the present inventor and another. Like the tool (30) described 
in the referenced copending application, the gear teeth 32 of the present 
tool member 34 are particularly adapted to engage with the driving gear 
teeth 30 when the tool member is pushed into the tool chamber 16 and to 
disengage from the driving gear teeth 30 when the tool member is withdrawn 
from the tool chamber, as is illustrated in and will be described with 
reference to FIG. 5A. The tool shaft 31 has a rounded end 33 extending 
into the aperture 21 in the interior wall 20, when the tool is fully 
seated in the tool chamber. 
An outer locking member 40 is coaxially fitted over the principal housing 
10, covering the major portion of the principal housing axially and 
smoothly embracing the rounded end 14 of it. This essentially smooth 
covering for the entire "nose" end 66 of the contra-angle head is sanitary 
and safe to use; it has no projecting parts which could damage tissue in 
the mouth of a patient. The locking member has a round hole 42 through it 
from which a slot 44 extends a fixed distance circumferentially around the 
longitudinal axis A--A. This locking member 40 is rotatable 
circumferentially around the axis A--A, between limits set by a stop tab 
46 bent radially inward from the locking member and engaged in a 
circumferential slot 48 in the principal housing 10, extending essentially 
one-quarter turn (90 degrees) around the axis A--A, as is best seen in 
FIG. 4. When the locking member is in the locked position shown in FIGS. 
1-4, inclusive, the slot 44 overlies the opening 18 into the tool chamber, 
and if a tool member 34 is present, it is retained in place, as is best 
shown in FIGS. 3 and 5. The slot 44 has a width sufficient to let the 
shaft 31 of the tool member rotate in it. The tool member is fitted with a 
gear hub 35 (which may be made of a molded plastic or a sintered metal 
material, for example) having rounded end surfaces 36, 37 generally 
conforming, respectively, to the surface of the dome-like interior wall 20 
of the tool chamber and the inner surface of the locking member. The 
rounded end 33 of the tool shaft extends through the aperture 21, to 
provide bearing support for the inner end of the tool shaft 31. 
When the locking member 40 is moved to the unlocked position, which is done 
by rotating the locking member one-quarter turn clockwise around the axis 
A--A, as viewed in FIG. 4, the round hole 42 comes into register with the 
entrance 18 to the tool chamber, and a tool member 34 can be withdrawn or 
installed by moving it transversely to the longitudinal axis A--A, as FIG. 
5A shows. 
FIGS. 7 to 11, inclusive, show a second version of the invention, in which 
an axially-movable locking member 50 is substituted on the principal 
housing 10 for the circumferentially-movable locking member 40 of the 
version shown in FIGS. 1-6, inclusive. The operating principles are the 
same in both versions, and only the structural differences will be 
described. 
The locking member 50 has a pair of diametrically opposed limit tabs 52 
extending radially inward, toward each other, in respective longitudinal 
slots 54 that are provided for them in the walls of the principal housing 
10. These slots establish the limits of axial motion of the locking 
member. A round hole 62 from which a slot 64 extends in the axial 
direction toward the free end 66 is provided in the locking member, near 
the free end. A coaxial coil spring 56 is retained between a flanged 
washer 58 abutting the tabs 52 at one end, and the transverse wall 22 at 
the other. The coil spring urges the locking member to the locked 
position, shown in FIGS. 7 and 8, for example, in which the outer end 66 
embraces the curved end 14 of the principal housing, and the slot 64 
overlies the opening 18 into the tool chamber. When the locking member is 
moved axially against the force of the coil spring 56 (to the right, in 
the views shown in FIGS. 7, 8 and 9) so that the tabs 52 approach the 
right-hand ends of the slots 54, the round hole will overlie the opening 
into the tool chamber, and a tool member 34 can then be exchanged by 
moving it transversely to the longitudinal axis A--A, as is shown in FIG. 
8A. 
The housing 10 can be made as rigid as desired, and provides the basic 
foundation, or principal housing, for the contra-angle head. As has been 
noted, this housing can be made to fit any style or design of hand-piece 
that is or may be in use. Some handpieces are designed to retain the drive 
shaft 12 permanently fixed to the handpiece, in which case the housing 10 
is capable of being separated from the drive shaft 12 when the 
contra-angle head is removed from a handpiece, as FIG. 12 illustrates. The 
transverse wall 22 defining the bearing aperture 24 is thick relative to 
other walls of the housing 10, and provides full support for the free end 
28 of the shaft 12 and the coupling member 26 when the contra-angle head 
is installed on such a handpiece. For that reason, the shaft 12 can be 
made thinner than would be required if no bearing support were provided at 
its free end, and the designer is more free to choose a composite shaft in 
which torsional rigidity is the major concern. For example, a cable-like 
shaft, made of thin wires or fibers twisted around the axis A--A, can be 
used notwithstanding that it might be more flexible than a solid shaft in 
directions transverse to the longitudinal axis A--A. 
The bearing space 24 can be fitted with an antifriction bearing 74, as is 
shown in FIG. 13, in which case the shaft 12 can be formed with drive 
gears 72 directly on its free end 28. The shaft 12 with gears 72 can be 
fixed in the housing 10, or removable according to FIG. 12. 
In FIG. 14, the shaft 82 is fixed to the handpiece (not shown) and fitted 
at its free end 88 with a clutch member 86. THe driving gear teeth 30 are 
on a short coupling member 26' (similar to the coupling member 26 in FIG. 
3, for example) fixed on a stub shaft 90 that is supported in the 
anti-friction bearing 70, through the transverse wall 22. On the side of 
the wall 22 opposite the driving gear teeth, the stub shaft 90 has a head 
92 fitted with a slot 96 for engagement by the clutch member 86 when the 
contra-angle head is fully installed on an appropriate handpiece. The 
clutch member 86 and slot 96 are representative of any suitable mechanism 
for engaging the drive shaft 82 with the stub shaft 90 when the 
contra-angle head is installed, and for disengaging those shafts when the 
head is removed from a handpiece. FIG. 14 illustrates that group of 
embodiments of the invention in which the driving gears 30 or the like for 
a tool member are permanently installed in the principal housing 10 as an 
entity apart from the main drive shaft. 
The tool chamber 16 may also be fitted with anti-friction bearing means for 
tool members, if desired. Embodiments of the invention which include such 
obvious structural details are intended to be included within the scope of 
the claims which follow.