Note: Descriptions are shown in the official language in which they were submitted.
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HS 0063
SURGICAL ~u~ G DEVICE WITH SAFETY INTERLOC~
BACRGROUND OF THE lNV~..ION
FIELD OF THE lNV~ lON
This invention relates generally to powered surgical
cutting devices. More particularly, this invention relates to
powered surgical blades and means for joining these blades to a
surgical handpiece. Still more particularly, this invention
relates to a powered sternum saw provided with a guard and a
safety interlock to prevent operation of the saw unless all parts
are properly assembled.
DESCRIPTION OF THE PRIOR ART
Surgical saws are well known for cutting various types
of tissue during surgical procedures. The saws are often
provided with shields or guards to prevent inadvertent damage to
tissue adjacent the surgical work site. Such guards are
particularly important when using powered surgical saws.
One type of known surgical cutting device is a sternum
saw which is, as the name implies, used for cutting through the
sternum during a surgical procedure. A collet mechanism is
provided to secure the reciprocating saw blade to the handpiece
and the collet nut is tightened with a wrench or other tool in
order to hold the flat "saber saw" in a longitudinally
reciprocating drive shaft. The collet not only grips the saw
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blade but also acts to squeeze a locking alignment ball into a
hole formed in the proximal end of the blade in order to prevent
the blade from falling out of the handpiece should the collet
become loose. Because of the sensitive location of the sternum
such surgical saws are generally provided with a saw blade guard
in order to partially enclose the reciprocating saw blade to
preclude it from accidentally cutting unintended tissue.
However, the presence of the guard limits access to the collet
nut and makes it more difficult to tighten the blade. Addition-
ally, the need to keep track of a separate tool or wrench to
tighten the collet adds to the difficulty. Improvements in
design are desirable to facilitate the assembly of the blade onto
the handpiece. In addition to facilitating attachment of the saw
blade to the handpiece, it is always desirable to incorporate
additional safety features in powered surgical saws.
Consequently, it is an object of this invention to provide a
safety interlock which requires all components of the powered
surgical saw to be properly assembled before the saw can
effectively cut tissue.
It is another object of this invention to provide a
sternum saw with a sternum safety guard which necessarily has to
be in proper position in order to enable operation of the saw.
It is also an object of this invention to produce a
powered surgical saw with a means for attaching the saw blade to
the handpiece without using an extra tool. Such a handpiece
will be sometimes referred to as a "wrench-less" handpiece.
It is yet another object of this invention to produce,
in a powered surgical saw, a safety interlock which simultane-
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ously locks and properly positions a blade and a blade guard.
8UMMARY OF THE l~.v~ ION
These and other objects of this invention are achievedby the preferred embodiment disclosed herein which is a surgical
saw for use with an elongated surgical blade having a proximal
end, a distal end and at least one notch detent at the proximal
end. The saw comprises a housing or handpiece having an opening
at its distal end and a drive shaft having an end adjacent the
opening for receiving the surgical blade. The handpiece includes
a means for driving the drive shaft. A blade receiving means at
the end of the drive shaft comprises a first locking-ball holding
means situated on the drive shaft for holding the proximal end
of the surgical blade. The balls of the first locking-ball
holding means are held in the notch of the surgical blade by a
cylindrical cam ring attached to the base of the blade guard.
An outer surface of the cam ring is provided with an annular
groove which operates with the balls of a second locking-ball
holding means situated on the handpiece. A cylindrical collar
means on the handpiece holds the balls of the second locking-ball
holding means in the annular groove and thereby locks the blade
and the guard in proper position.
The invention is also embodied in the method of
connecting a surgical cutting blade to a power source for driving
the device. The method comprises the steps of providing a
surgical cutting device having a notch detent at its proximal
end, providing a first locking-ball holding means to hold the
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device to the power source and holding the cutting device and the
first locking-ball holding means in locked position with a cam
ring which is itself locked in place by a second locking-ball
holding means.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross-sectional view of a sternum saw
constructed in accordance with the principles of this invention.
Figure 2 is an exploded diagrammatic view of the distal
end of Figure 1.
Figure 3 is a cross-sectional view of Figure 2 taken
along the line 3-3.
Figure 4 is a cut-away cross-sectional side elevation
view of a portion of the distal end of a prior art surgical saw
showing a known collet mechanism for holding a saw blade.
Figure 5 is a cross-sectional view of Figure 4 taken
along the line 5-5.
Figure 6 is a view of Figure 2 showing the components
partially assembled.
Figure 7 is a cross-sectional view of Figure 6 taken
along the line 7-7.
Figure 8 is a side elevation view of the saw guard of
Figure 1.
Figure 9 is a top plan view of Figure 8.
Figure 10 is a view of Figure 8 taken along the line
10--10 .
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DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figures 1 and 2, powered surgical saw
1 is shown comprising a "wrench-less" handpiece 2 having a
battery receptacle 3 (to receive a battery, not shown), motor 4,
trigger 5, motor output shaft 6, drive shaft 7 and a distal
working end 8 to which a sternum saw blade 9 and guard 10 are
attached. Most of the foregoing components are conventional and
form no part of this invention. The invention relates to the
distal end 8 and the manner in which blade 9 and guard 10 are
attached to handpiece 2.
For comparison and explanatory purposes, the distal end
20 of a prior art handpiece is shown in Figure 4. It will be
understood that the distal end 8 of handpiece 2 in Figure 1 is
comparable in function to prior art distal end 20 and, therefore,
the proximal end of handpiece 2 (to the right of distal end 8 in
Figure 1) may be used in a prior art handpiece to drive distal
end 20. The prior art distal end 20 comprises a collet/output
shaft assembly 22 having a blade receiving collet 24 threaded on
the distal end of drive shaft 26, an annular, guard receiving
chamber 28 surrounding collet 24 and a guard locking mechanism
30. Blade receiving collet 24 comprises a threaded collet tip
25 provided with a nut 25A, a flat, blade receiving opening 32
(in the plane of the paper) and a ball 34 intended to be received
within a corresponding alignment aperture 35 of a surgical saw
blade. As will be understood below, one advantage of the
invention is that saw blades made for use with the new "wrench-
less" handpiece may continue to include alignment aperture 35 for
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use with a prior art handpiece (depending on user preference).
Collet 24 is operated in a conventional manner by being tightened
by the turning of the nut to clamp and frictionally engage the
saw blade. Annular guard receiving chamber 28 is provided to
receive the base of a sternum guard similar to that shown in
Figures 1 and 2 and in greater detail in Figures 8-10. The guard
is retained in chamber 28 by locking mechanism 30 which relies
on the interaction of three annularly spaced locking balls 32
with a cam ring in the form of retractable, spring-loaded,
cylindrical locking collar 34 in a conventional manner. Spring
37 urges collar 34 distally to lock balls 32 within an associated
annular groove of the base of the guard. As best seen in Figures
4 and 5, annular chamber 28 is provided with three locking balls
32 and a pair of diametrically opposed keys 36 in order to
properly orient the guard relative to the blade as will be
understood below. It should be noted that the prior art
collet/output shaft assembly 22 operates independently of locking
mechanism 30. As will be understood, the invention described
below makes proper functioning of a new collet/output shaft
assembly dependent upon the guard locking mechanism.
The invention will now be described with reference to
a new collet/output shaft assembly SO best seen in Figures 1, 2,
6 and 7. The invention produces a "wrench-less" design by
enabling a slightly modified guard and saw blade to be attached
to a handpiece without the use of any auxiliary tools to tighten
a collet as in the prior art device. In Figure 2, the distal end
52 of collet/output shaft assembly 50 is shown in exploded
association with saw blade 9 and guard 10. In Figure 6, the
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components are shown partially assembled to show the operation
of the safety locking mechanism. The proximal portion of
collet/output shaft assembly 50 (not shown) is similar to that
of prior art collet/output shaft assembly 22 and does not need
to be described to understand the present invention.
Collet/output shaft assembly 50 comprises a
reciprocating cylindrical drive shaft 60 provided with an inner
locking ball retaining mechanism 62 near its distal end 64.
Locking ball retaining mechanism 62 comprises a pair of
diametrically opposed retaining balls 66 situated in restricted
apertures in drive shaft 60 in a conventional manner. A ball
retaining insert 68 is provided to prevent the balls from falling
into the interior of drive shaft 60 when blade 9 is not in
position. The distal end of insert 68 is provided with a
diametrical slit 70 designed to receive the proximal end of flat
blade 9 in aligned orientation relative to balls 66.
Saw blade g and guard 10 are slightly modified versions
of the prior art components in order to enable them to work in
the invention hereof. Blade 9 is a conventional saber saw type
reciprocating surgical blade modified by having notches 80 formed
on opposite sides of the blade shaft. Aperture 35, best seen in
Figure 2, is used in blade 9 even though it has no function in
the invention and is only provided to make blade 9 usable in
prior art handpieces. Notches 80 are spaced a predetermined
distance distally from the proximal end 82 of blade 9 and, as
will be understood below, are intended to receive balls 66 when
blade 9 is properly seated within collet/output shaft assembly
50.
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Guard 10, best seen in Figures 8-10, comprises a ball
locking cam in the form of cylindrical cam ring base portion 90,
a connecting arm 92 and a slotted, distal guard head 94. Cylin-
drical base 90 has an outer diameter adapted to fit annular
chamber 28a surrounding the distal end of drive shaft 60 and
includes in its outer surface an annular groove 96 which is
adapted to receive locking balls 32a of locking mechanism 30a.
A pair of diametrically opposed keyways 99 (only one of which is
seen in Figure 8) is provided to engage keys 36 (best seen in
Figure 5). A cylindrical insert 98 is utilized to modify the
prior art guard design to assure the inside diameter of base 90
is approximately equal to the outside diameter of shaft 60. The
inner surface of insert 98 serves as a bearing surface for balls
66 during operation of the saw. Alternatively, the guard base
could be made as an integral piece having the appropriate inner
diameter. The locking ball retaining mechanism 30a of
collet/output shaft assembly 52 is essentially identical to the
locking ball retaining mechanism 30 of the prior art device shown
in Figure 4.
It will be understood that as the components shown in
Figure 2 are assembled together, with blade 9 first being
inserted into slot 70 at the end of drive shaft 60, balls 66 are
pushed radially outwardly as best seen in Figures 6 and 7 into
guard receiving chamber 28a by the opposed lateral edges of the
proximal end of blade 9. When the blade is fully pushed into
proper position as best seen in Figure 1, balls 66 will fall into
notches 80. Once the blade is thus properly positioned, the base
90 of guard 10 will be able to be inserted into guard receiving
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chamber 28a. If blade 9 is not properly positioned, balls 66
will interfere with the guard and prevent base 90 from fully
entering annular chamber 28a. When guard 10 is fully seated,
outer balls 32a will fall into annular groove 96 in order to lock
guard 10 within distal end 8 while enabling the collet/output
shaft assembly 50 to reciprocate. It will be understood that the
action of locking guard 10 within chamber 28a also locks blade
g by virtue of trapping balls 66 in notches 80. The base of
guard 10, therefore, is essentially an intermediate cam surface
acting upon both the blade and the guard locking mechanism.
While the invention is disclosed with respect to a
surgical cutting device in the form of a flat and reciprocating
saber type saw blade, other modifications of the invention may
be made to make it suitable for other types of cutting blades
with or without associated guard devices. For example, the
invention may be adaptable to rotating arthroscopic shavers
having elongated, relatively rotating surgical shaver blades.
As an additional safety feature (best seen in Figure
6) the cylindrical locking ring 34a may be provided with a notch
100 in its proximal annular edge 102 and the body of distal end
8 of the handpiece could be provided with a radially outwardly
extending pin 104. The longitudinal placement of pin 104 is such
that ring 34a must be rotated to align notch 100 with pin 104 in
order to enable ring 34a to be retracted.
It will be understood that numerous other improvements
and modifications may be made to the preferred embodiment
disclosed herein without departing from the spirit and scope of
the invention.
