Specification
[0001] This application claims benefit to U.S. Provisional Patent Application Serial
Number 61/670,914 filed on July 12, 2012 and U.S. Provisional Patent Application Serial
Number 61/692,869 filed on August 24, 2012, the entire disclosures of each application is herein
incorporated by reference for all purposes.
TECHNICAL FIELD
[0002] The present disclosure relates to saw blades, a connection mechanism for
connecting a saw blade to a saw, a saw, a method of cutting and a method of removing saw
blades from a saw.
BACKGROUND
[0003] Powered saws are often used in surgical procedures, particularly osteotomies. It
is desirable to apply a high torque to the bone by the blades of a saw during the cutting procedure
to improve the precision of the cutting and reduce the time it takes to perform the procedure. In
addition, cutting efficiency can be affected by the frequency of oscillation of the saw blades, if
the frequency of the saw is similar to that of the bone, cutting performance would be zero. U.S.
Patent No. 5,846,244 discloses a counter-balanced oscillating saw in which the momentum
produced by one blade is offset by momentum produced by its counterpart cutting blade to
reduce mechanical vibration, rotational and linear movement of the saw.
[0004] The blades of surgical saws are often used in sterile environments. It is useful to
be able to provide disposable blades or blades that can be processed for reuse independently of
the saw so that a saw can be reused while avoiding the expense or time of sterilizing the whole
saw. However, it is important that any blade is securely connected to the handpiece during use to
avoid the highly unsatisfactory consequences of the blades becoming loose during a cutting
procedure. Therefore, it is desirable to provide an independent blade which is easily removable
from the saw for processing but which can be securely connected to the saw during use.
[0005] There is thus a need to provide an improved saw which can cut using high
torque and prevents the object to be cut oscillating in harmony with the saw, and blades which
are independent of the saw but can be securely connected to the saw.
SUMMARY
[0006] In a first aspect of the present disclosure there is provided a saw blade that
includes a cutting edge at a distal end thereof. The saw blade can have an attachment portion at a
proximal end of the blade that is configured to connect the blade to a saw, and a projection that
extends from the blade and is resiliently biased into a position in which it extends away from a
surface of the blade. The saw blade can be configured to cut bone. The attachment portion and
the projection act can act in tandem to allow the blade to be removably connected to the saw.
The projection may be positioned towards the proximal end of the blade. The projection may be
integral to the blade. Alternatively, the projection may be a separate component fixed to the
blade. In an embodiment, the attachment portion comprises a spanner shaped head. The
attachment portion can also comprise a pair of arms that are substantially parallel with respect to
each other. The spanner shape head and the pair of arms can define an inner surface that extends
along an angle of between about 45° and about 75° relative to a plane of the blade. In the
exemplary embodiment, the angle can be about 60°. When the attachment portion is configured
in this way, the attachment portion of the blade can be connected to a complementarily angled
surface to provide an interlock thereto.
[0007] In a second aspect of the present disclosure there is provided a connection
mechanism for connecting a saw blade to a saw. The connection mechanism can include a
mounting member, for instance a mounting portion, that defines a receiving surface and a raised
portion. The blade can define an opening that extends through the blade. The blade can define a
surface that can be slid into engagement with the receiving surface. The raised portion is can be
received by the opening of the blade. Engagement between the opening and the raised portion
can prevent undesirable relative axial, i.e., longitudinal movement of the blade with respect to
the saw. Thus, the blade is configured to securely connect to the raised portion of the mounting
portion without the need for additional components. In an embodiment, the blade can define an
inner surface that defines the opening. Further, the raised portion can define an outer surface.
The opening inner surface and the outer surface of the raised portion can be complementarily
angled so as to provide an interlock between the blade and the raised portion of the mounting
portion. The interlock can prevent relative axial or longitudinal movement of the blade, which,
although it may cause vibrations between the surfaces of the blades (for instance when two
blades are used) allows the blade to be slid into connection with the saw. In an embodiment, the
opening inner surface may extend at an angle of between 45° and 75° relative to the plane of the
blade. The angle of the opening inner surface relative the plane of the blade is about 60°. As
noted above, the blade may comprise two substantially parallel arms that at least partially define
the opening. The configuration of the arms can permit the blade to be slid easily into connection
with the saw. The blade may also comprise a latching projection that extends into a latching
surface in the mounting portion to prevent removal of the blade from the mounting portion or
saw. The latching projection can be resiliently biased into a position extending away from the
plane of the blade. As a result, the latching projection can be biased into the position in which it
extends into the latching surface. Thus, the blade can be securely connected to the mounting
portion once it has been slid into engagement with the receiving surface thereof. The blade
according the second aspect of the present disclosure may be the saw blade according to the first
aspect of the present disclosure. The saw may be a motor driven saw, a pneumatically driven saw
or a manually driven saw.
[0008] In a third aspect of the present disclosure, there is provided a saw that includes a
drive, a first blade configured to oscillate about an axis that is perpendicular to the plane defined
by a surface of the blade. The saw can include a second blade configured to oscillate about an
axis that is perpendicular to the plane in a direction opposite to that of the first blade. The axes
can be the same or each axis can be different. The gearing is disposed between the drive and the
first and second blades and is configured to reduce the speed of oscillation of the blades about
the respective axes. The axes can be similar. The saw is thus configured to gear up the torque
transferred to the blade from the drive. The increased torque output at the blades acts to perform
the cut, while the blades oscillating in opposite direction reduces countertorque, which can
prevent the object to be cut oscillating in harmony with the saw. The saw may further comprise
an eccentric drive shaft rotatably connected to the drive, wherein the eccentric drive shaft acts to
cause the first and second blades to oscillate. The eccentric drive shaft may be disposed
perpendicular to the plane of each blade. The configuration of the eccentric drive shaft allows
symmetrical design of the saw. The gearing may comprise at least one gear, for instance a 90°
gear transmission or a planetary gear. The 90° gear allows the drive to be disposed parallel with
the plane of the blade. The 90° gear transmission can provide a gear ratio of 1:1.5. Regardless
of the specific type of gear or number thereof, the speed of oscillation of the blades may be
between 7000 to 10000 rpm, or 8000 to 10000 rpm. In an exemplary embodiment, the speed of
oscillation of the blades is about 7000 rpm. Although the saw may function at lower speeds, for
example 2000 to 3000 rpms, there is a tendency among surgeons to apply considerable pressure
to the bone using the saw. At lower saw speeds, this tendency limits the ability of the saw.
Operating the saw at oscillation speeds of 7000 rpm compensates for this tendency. In an
alternative embodiment, the gearing may comprise a planetary or a bevel gear. A planetary or
bevel gear acts effectively to provide high torque at low speeds to the blades from the drive. In
this embodiment, the 90° gear transmission may provide a gear ratio of 1:1.3846. The gearing
can provide a gear ratio of 1:3.9474 and the speed of oscillation of the blades may be between
2000 to 3000 rpm. The gearing allows the blades to operate at lower speeds, thereby generating
less heat. The drive can be a motor drive. Further, the saw can includes drive location
configured to support, for instance, at least partially support the drive.
[0009] As noted above, according to the third aspect of the disclosure, the blades
oscillate about the same axis. Further, the blades can be removably attached to the saw. The saw
is designed to cut bone. In addition, the blades can include first and second blades that comprise
the blades of the first aspect of the present disclosure. The saw may further comprise a
connection mechanism according to a second aspect of the present disclosure.
[0010] In a fourth aspect of the present disclosure there is provided a method of cutting
comprising the step of transferring torque from a drive to first and second blades to oscillate the
first and second blades in opposite directions relative to one another. The method includes the
step of transferring the motion of the drive, via a gearing, so as reduce the speed of oscillation of
the first and second blades. The gearing increases the torque output to the blades from the drive,
improving the blades cutting ability. Oscillating the first and second blades in opposite
directions can prevent the object to be cut oscillating in harmony with the blades. The method
may comprise the step of transferring torque from a drive to an eccentric drive shaft which
causes the first and second blades to oscillate. The method may further comprise the step of
transferring motion through a 90° gear transmission between the drive and the first and second
blades. The method may also comprise the step of transferring motion via a planetary gear that
is disposed between the drive and the blades. The drive may be a motor drive, a pneumatic drive
or a manual drive. The method can include cutting bone. The method according the fourth
aspect of the disclosure can include the blade according to the first aspect of the disclosure, the
connection mechanism according to the third aspect of the disclosure, and the saw according the
third aspect of the disclosure.
[0011] In a fifth aspect of the present disclosure a method of removing saw blades from
a saw is provided. The method comprises the step of moving a resiliently biased latch member
of a blade from a first position in which it engages a mounting member of the saw to a second
position in which it no longer engages the mounting member and removing the blade axially
from the mounting member. The blade can be easily removed from the saw by sliding it out of
engagement with a mounting member once a latch member has been moved from a latching
position. The method according the fifth aspect of the disclosure can include the blade according
to the first aspect of the disclosure, the connection mechanism according to the third aspect of
the disclosure, and/or the saw according the third aspect of the disclosure.
[0012] A sixth aspect of the present disclosure provides for use of a saw as described
above in a procedure for cutting bone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The foregoing summary, as well as the following detailed description of
illustrative embodiments of the devices and methods of the present application, will be better
understood when read in conjunction with the appended drawings. For the purposes of
illustrating the device and methods of the present application, there is shown in the drawings
illustrative embodiments. It should be understood, however, that the application is not limited to
the precise arrangements and instrumentalities shown. In the drawings:
[0014] Figure 1A is a cut-away perspective view of a powered saw according to an
embodiment of the present disclosure;
[0015] Figure IB is a sectional side elevation view of a powered saw similar to the
powered saw illustrated in Figure 1A, but constructed in accordance with an alternative
embodiment;
[0016] Figure 1C is a side elevation view of an eccentric shaft of the powered saw
illustrated in Figures 1A-B;
[0017] Figure 2 is a perspective view of a proximal end of a saw blade according to an
embodiment of the present disclosure;
[0018] Figure 3 is a perspective view of a mounting member according to an
embodiment of the present disclosure;
[0019] Figure 4A is a cut away perspective view of the connection mechanism
according to an embodiment of the present disclosure, illustrating the blade shown in figure 2
engaged with connection mechanism shown in figure 3;
[0020] Figure 4B is a bottom plan view of the connection mechanism illustrated in
Figure 4A;
[0021] Figure 5 is a sectional perspective view of a portion of connection mechanism
according to an embodiment of the present disclosure;
[0022] Figure 6 is a bottom plan view of the proximal end of a saw blade shown in Fig.
2; and
[0023] Figure 7 is a cross-section of the proximal end of the saw blade along the line BB
in Fig. 6.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0024] Referring to Fig. 1A, a powered saw 100 having a drive location that is
configured to support a motor drive 110 that is operably connected to eccentric shaft 140 via
gearing. The powered saw 100 can include the motor drive 110, for instance at the drive location
as illustrated in Fig. 1A, or the drive location can define a receptacle 11 1 (see Fig. IB) that is
configured to receive, for instance removably receive, a drive, such as a motor drive. The saw
100 can include a handle portion or handpiece 102 and a cutting portion 104 spaced from the
handle portion 102 along the longitudinal direction L. The saw 100 can include a housing 107
for carrying at least a portion of the drive 110 and gearing. The housing 107 can at least partially
define the receptacle 111.
[0025] The saw 100, or cutting portion 104, can include a first blade 220 and a second
blade 240. The first and second blade 220 and 240 includes a proximal end 252 and 352,
respectively, each of which is configured to attach to the saw (detailed below), and a distal end
254 and 354, respectively, spaced from the proximal end 252 and 352 along the longitudinal
direction L when the blades are attached to the saw 100. The proximal ends of the blades can
define respective blade attachment portions. The first blade 220 includes a first or upper surface
256 and a second or lower surface 258 spaced from the first surface 256 along the transverse
direction T. The transverse direction T can be substantially perpendicular to the longtidunal
direction L of the saw 100. The blades 220,240 can extend along the longtidunal direction L and
have a transverse directional component. Further, the second blade 240 includes a first or upper
surface 356 and a second or lower surface 358 spaced from the first surface 356 along the
transverse direction T. Each respective blade surfaces extend between the proximal end 252,352
and the distal end 254,354 of the blades 220, 240, and can define the respective planes that
extend along the longitudinal direction L. The blades 220, 240 each comprise a cutting portion
221, 241 disposed at the distal end 254, 354 thereof, which is positioned distal to the blade
attachments 320, 340 along the longitudinal direction L when the blade is connected to the saw
100. In order the cut an object, the first and second blades 220, 240 are configured attach to the
saw 100 so as to oscillate about a similar axis, or alternatively, about a different axes. For
instance, the first and second blades 220 and 240 can oscillate about an axis that is perpendicular
to a plane defined by any of the respective surfaces of each respective blade, such that the blades
oscillate in an oscillation direction O. As further detailed below, the first and second blades
220,240 oscillate in opposite directions.
[0026] Blades 220, 240 can be removably connected to the saw 100 by blade
attachments 320, 340 which are configured to hold the blades 220, 240 in parallel planes that
extend along the longitudinal direction L. The blade attachments 320, 340 each have a first pair
of arms 320a and 320b and a second pair of arms 340b, 340b (Figs. 1C and 4B) which surround
the eccentric shaft 140 (see also Figure 1C). The eccentric shaft 140 is disposed along a
transverse direction T, which is perpendicular to the blades 220, 240 and the blade attachments
320, 340. The gearing is provided between the drive location and the first and second blades
220,240 to reduce the speed of oscillation of the blades 220,240. The gearing can include one or
both of a planetary gear 120 and a 90° gear transmission 130.
[0027] In use, torque is transferred from the drive 110 via the planetary gear 120 and
the 90° gear transmission 130 to rotate the eccentric shaft 140 about a central shaft axis 140a. As
the shaft 140 rotates it converts rotational movement from the drive 110 to oscillation of the
blades 220, 240 via the blade attachments 320 and 340. The blade attachments 320 and 340
define respective central axes 329 and 339 that are spaced from the central shaft axis 140a, and
can be disposed opposite each other such that the central shaft axis 140a is disposed between the
central axes 329 and 339. The eccentric shaft 140 is configured such that, as it rotates, it moves
the first pairs of arms 320a and 320b, and a second pair of arms 340a and 340b of the attachment
mechanism in opposite directions, thus oscillating the blades in opposite directions O relative to
one another. The eccentric shaft 140 has a central portion 150, a first offset portion 152, and a
second offset portion 154. The central portion 150 extends along the central shaft axis 140a.
The first offset portion 152 second offset portions 154 extend along respective central offset axes
(not shown) that lie in a similar plane with respective the central axes 339 and 329. The first
pairs of arms 320a and 320b attach to the offset portion 154 and the second pair of arms 340a
and 340b attach to offset portion 152. The blades 220, 240 are attached to the saw such that
blades oscillate about the same axis, for instance the central shaft axis 140a, that extends along
the transverse direction T. For instance, the central shaft axis 140a can extend along the
transverse direction T and is substantially perpendicular to the first blade surfaces 256 and 258,
and/or the second blade surfaces 356 and 358. The blades 220, 240 are securely connected to the
blade attachments 320, 340, as described below, such that torque is transferred from the drive to
the blades 220 and 240.
[0028] The planetary gear 120 achieves a reduction of the speed of the drive
transmitted to the blades, and conversely an increase in torque. The ratio of reduction of speed
along a direction from the drive 110 to the blades 220, 240 caused by the planetary gear is
1:3.9474, though it should be appreciated that the reduction of speed caused by the planetary
gear can be configured as desired, for example between 1:1.1 and 1:10. The 90° gear
transmission 130 can include a first or input gear 131, which can be a bevel gear, and a second or
output gear 133, which can be a bevel gear, that is intermeshed with the first gear 131. The
planetary gear 120 can be disposed between the drive location (and thus the motor drive 110) and
the 90° gear transmission 130. The 90° gear transmission can be disposed between the planetary
gear 120 and the eccentric shaft 140.
[0029] During operation, the first gear 131 rotates about a first axis of rotation 331 (Fig.
1A), and the second gear 133 rotates about a second axis of rotation 333 that is angularly offset,
for instance oriented substantially 90°, with respect to the first axis of rotation 331. The first gear
13 1 is coupled to the drive 110. The first gear 13 1 is configured to be driven to rotate by the
drive 110 along the first axis of rotation, and the second gear 133 is coupled to the shaft 140, so
as to drive the shaft to rotate about a corresponding axis of rotation that can be parallel or
coincident with the second axis of rotation. Thus, the first gear 13 1 is disposed between the
second gear 133 and the drive 110, and the second gear 133 is disposed between the shaft 140
and the first gear 131. The second gear 133 is configured to drive the eccentric shaft 140 to
rotate, thereby causing the blades 220, 240 to reciprocally oscillate. The first gear 131 can be
sized smaller than the second gear 133, and thus can have fewer teeth than the second gear 133.
Accordingly, the second gear 133 rotates at a speed that is less than that of the first gear 131, and
at a torque that is proportionally greater than that of the first gear 131. In accordance with one
embodiment, the gear ratio can be as desired, for instance between 1:1.1 and 1:2. In accordance
with the illustrated embodiment, the gear ratio can be 1:1.3846. The gear reduction of the 90°
gear transmission produces a corresponding reduction of speed that is equal to the gear ratio, and
a corresponding increase in torque output that is equal to the gear ratio. When the ratio of
reduction of speed of the planetary gear is 1:3.9474 and the ratio of reduction of speed of the 90°
gear transmission is 1:1.3846, the powered saw 100 produces a ratio of reduction in speed from
the drive 110 to the eccentric shaft 140 of approximately ratio 1:5.4656. Although a planetary
gear is illustrated, it would also be possible to use a bevel gear in its place.
[0030] The planetary gear 120 acts to provide high torque to the blades 220, 240 at low
speed. In this way, the blades can be operated at low speed but with high torque. The blades cut
with torque, not speed, and less heat is transmitted to bone. In addition, because cutting is
performed by two blades that are oscillating in opposite directions about the same axis, for
instance the central shaft axis 140a, there is limited, if any, resulting vibration of the bone or
countertorque transmitted to the handpiece 102. Since limited, if any, counter-torque is
transmitted to the handpiece, handling of the tool is made easier, resulting in a more precise cut.
The entry speed of the saw blades is between 2000 to 3000 rpm.
[0031] In an alternative embodiment of the saw, the planetary or bevel gear may be
omitted so that there is a direct drive between the 90° gear transmission 130 and the blades 220,
240. For instance, referring to Figure IB, the powered saw 100 defines a receptacle 1 1 1 that can
provide the drive location. The receptacle 111 is configured to receive a drive, such as a motor
drive, at the drive location, the drive operable to rotate at a desired speed and produce a
corresponding torque output. The powered saw 100 can be devoid of the planetary gear
illustrated in Fig. 1A, such that the speed and torque output from the motor drive is
communicated to the first gear 13 1 of the 90° gear transmission 130. Thus, the first gear 131 can
be driven to rotate at substantially the same speed as the motor drive at substantially the same
torque as is output from the motor drive. As described above, the first gear 131 can be sized
smaller than the second gear 133, and thus can have fewer teeth than the second gear 133.
Accordingly, the second gear 133 rotates at a speed that is less than that of the first gear 131, and
at a torque that is proportionally greater than that of the first gear 131. In accordance with one
embodiment, the gear ratio can be as desired, for instance between and including approximately
1:1.1 and approximately 1:5, including approximately 1:1.3846, approximately 1:1.5, or any
suitable alternative gear ratio as desired. The gear reduction of the 90° gear transmission 130
produces a corresponding reduction of speed that is equal to the gear ratio, and a corresponding
increase in torque output that is equal to the gear ratio. Furthermore, in accordance with the
embodiment illustrated in Figure IB, the gear ratio of the 90° gear transmission 130 can define
the gear ratio, and thus the speed reduction and torque increase, between the motor drive and the
blades.
[0032] The output speed of the oscillation of the blades 220, 240 can be between 7000
to 10000 rpm, including 8000 rpm to 10000 rpm. In accordance with one embodiment of the
powered saw 100, the speed of oscillation of the blades can be 7000 rpm.
[0033] The blades 220, 240 and the corresponding blade attachments 320, 340 may be
symmetrical. Therefore, a saw 100 is provided that can have two identically configured blades.
It should be appreciated that the blades can have different configurations as needed. For purpose
of illustrating the configuration of first and second blades 220 and 240, only blade 220 will be
further detailed below. It should be appreciated that the features described herein with respect to
the first blade 220 are applicable to the second blade 240. Further, the features described herein
regarding the blade attachment 320 are applicable to the blade attachment 340.
[0034] Referring to Figs. 2, 3 and 6, the proximal end 252 of the blade 220 a spanner
shaped head 222. The spanner shaped head 222 defines an opening 223 that extends along a
longitudinal direction L. For instance, the head 222 has two arms 223a and 223b that are spaced
apart and extend substantially parallel with respect one another. The arms 223a and 223b at least
partially define and surround the opening 223. The proximal end 252 of the blade 220 also
comprises a projection 227 that extends from the surface 258 (or 256) of blade 220 along a
transverse direction T. The projection 227 can be a latch which is milled out from the blade 220
and is bent downwards along the transverse direction T so that it is resiliently biased into a
position in which it extends from the surface 258 of the blade 220.
[0035] Referring to Fig. 3, the blade attachment 320 includes a mounting member 321,
for instance a mounting portion 321. The mounting portion 321 has a receiving surface 322, and
a raised portion 323, for instance a portion that raised relative to the receiving surface 322 along
the transverse direction T. The raised portion 323 is configured to correspond to the shape of the
opening 223 of blade 220 shown in Fig. 2. The blade 220 can thus be slid into engagement with
the receiving surface 322 such that the arms 223a and 223b surround the raised portion 323 of
the mounting portion 321 (Fig. 4A) as shown in figure 4.
[0036] Referring to Figs. 2, 6 and 7, the blade 240 can define an inner surface 225, the
at least partially defines the opening 223. The inner surface 225 can extend from the upper blade
surface 256 to the lower blade surface 258, and along the spaced apart arms 223a and 223b to
define a U-shape. The inner surface 225 of arms 223a, 223b of the blade 220 are angled relative
to the lower surface 258, or plane of the blade 220. In an embodiment, the angle of the inner
surface 225 relative to the plane of the blade is about 60°. As can be seen in Fig. 3, the mounting
portion 321 can also define an outer surface 325 that extends from the raised portion 323 to the
receiving surface 322. The outer surface 325 of the raised portion 323 is angled relative the
raised portion 323 to define a complementarily angle with respect to the inner surface 225 of
blade 220. Thus, the outer surface 325 of the raised portion 323 and the inner surface 225 of the
arms 223a and 223b interlock when the blade opening 223 is slid into close engagement with the
raised portion 323 as shown in figures 4A-B. As a result, movement relative to the surface of the
blade is effectively prevented so that vibration between the two blade surfaces is minimized.
[0037] Referring to Figs. 2 and 3, the receiving surface 322 has an aperture 327 that is
positioned distal to the raised portion 323 along the longitudinal direction L. The aperture 327 is
configured to receive at least a portion of the projection 227. The aperture 327 can act as a
latching surface, against which the projection 227 of the blade 220 latches once the blade 220
has been slid into the position shown in figures 4A-B. From this position, the blade 220 cannot
be moved axially, for instance, along the longitudinal direction L out of engagement with the
mounting portion 321. The latching projection 227 is resiliently biased towards the latching
surface. However, the latching projection 227 is accessible through the aperture 327 by means
of an opening in the opposing side of the mounting portion 321 to the receiving surface 322 (see
for example opening 349 in Fig. 5). As a result, it is possible to release the latching projection
227 from its first position in the aperture 327 into which it is resiliently biased as shown in figure
4A and 4B, into a second position in which the projection 227 no longer latches against the
latching surface. When projection is in the second position, the blade 220 is no longer
prevented from moving axially relative to the mounting portion 321 and can be moved out of
engagement therewith. Thus, the blade 220 is readily removable from engagement with the
mounting member 321, and thus, the powered saw 100. As shown in Fig. 5, the second blade 240
can have a latching projection 247 which can engage the aperture 347 of the blade attachment
340.
[0038] It will of course be understood that the present disclosure has been described above
purely by way of example, and that modifications of detail can be made within the scope of the
present disclosure.
WE CLAIMS:-
1. A saw, comprising:
a drive;
a first blade configured to oscillate about an axis perpendicular to a plane defined by a
surface of the blade;
a second blade configured to oscillate about an axis perpendicular to the plane in a
direction opposite to that of the first blade, and
a gearing disposed between the drive and the first and second blades, the gearing
configured to reduce the speed transmitted from the drive to the blades.
2. A saw according to claim 1, further comprising an eccentric drive shaft rotatably
connected to the drive, wherein the eccentric drive shaft acts to cause the first and second blades
to oscillate.
3. A saw according to claim 2, wherein the eccentric drive shaft is perpendicular to the
plane of each blade.
4. A saw according to any one of the preceding claims, wherein the gearing comprises a
planetary or a 90° gear transmission.
5. A saw according to claim 4, wherein the gearing comprises a 90° gear transmission such
that the drive is substantially parallel with the plane.
6. A saw according to claim 4 to 5, wherein the gearing provides a gear ratio of
approximately 1:1.5.
7. A saw according to claim 5, wherein the gearing comprises the 90° gear transmission that
includes a first bevel gear configured to be coupled to a drive, a second bevel gear that is coupled
to the eccentric drive shaft, the first gear having fewer teeth than the second gear.
8. A saw according to claim 6, wherein the 90° gear transmission provides a gear ratio of
1:1.3846.
9. A saw according to any one of claims 5 to 8, wherein the gearing further comprises the
planetary gear transmission disposed between the drive and the 90° gear transmission.
10. A saw according to claim 9, wherein the planetary gear defines a gear ratio of 1:3.9474
that defines a reduction of speed along a direction from the drive to the first and second blades.
11. A saw according to any one of the preceding claims, wherein the blades oscillate about
the same axis.
12. A saw according to any one of the preceding, wherein the blades are removably attached
to the saw.
13. A saw blade comprising:
a cutting edge at a distal end;
an attachment portion at a proximal end of the blade, the attachment portion configured
to connect the blade to a saw; and
a projection extending from the blade and resiliently biased into a position in which it
extends away from a surface of the blade.
14. A connection mechanism for connecting a saw blade to a saw comprising:
a mounting portion defining a receiving surface and a raised portion;
a blade defining an opening;
wherein a surface of the blade can be slid into engagement with the receiving surface and
the raised portion is received in the opening of the blade in the plane of the blade.
15. A saw according to any of claims 1 to 12, wherein the first and second blades comprise a
blade according to 13.
16. A saw according to any of claims 1 to 12, further comprising a connection mechanism
according to claim 14.
