Note: Descriptions are shown in the official language in which they were submitted.
CA 02359556 2009-09-23
FLEXIBLE SWITCH MEMBERS FOR HAND ACTIVATION
HANDPIECE SWITCHES
10
BACKGROUND OF THE INVENTION
This application relates to ultrasonic surgical systems and, more
particularly, to switch
members having membrane seals which prevent gas and water vapor from
contacting switch
assemblies which are disposed within an internal switch chamber formed in a
surgical
handpiece.
It is known that electric scalpels and lasers can be used as surgical
instruments to
perform the dual function of simultaneously effecting the incision and
hemostatis of soft
tissue by cauterizing tissues and blood vessels. However, such instruments'
employ very high
temperatures to achieve coagulation, causing vaporization and fumes as well as
splattering.
CA 02359556 2001-10-17
2
Additionally, the use of such instruments often results in relatively wide
zones of thermal
tissue damage.
Cutting and cauterizing of tissue by means of surgical instruments, e.g.,
blades,
vibrated at high speeds by ultrasonic drive mechanisms is also known. In such
systems, an
ultrasonic generator is provided which produces an electrical signal of a
particular voltage,
current and frequency, e.g., 55,500 cycles per second. The generator is
connected by a cable
to a handpiece, which contains piezoceramic elements forming an ultrasonic
transducer. In
response to a switch on the handpiece or a foot switch connected to the
generator by another
cable, the generator signal is applied to the transducer, which causes a
longitudinal vibration
of its elements. A structure connects the transducer to a surgical blade,
which is thus vibrated
at ultrasonic frequencies when the generator signal is applied to the
transducer. The structure
is designed to resonate at the selected frequency, thus amplifying the motion
initiated by the
transducer.
In order to activate the handpiece so that the blade is vibrated or otherwise
operated, a
switch mechanism is manipulated by the user. The switch mechanism typically
includes one
or more switch button members which the user depresses to cause activation of
the blade.
Because it is necessary for the handpiece to be cleaned and/or serviced after
use, the internal
electronic components of the switch mechanism must be sealed from the
environment outside
of the handpiece to prevent damage to the electronic components during the
cleaning, use,
handling, or servicing thereof. This is particularly true for handpieces which
are autoclavable
and/or immersible. Consequently, a membrane (e.g., a flexible seal) may be
included as part
of the switch member for sealing the electronic components of the switch
mechanism so that
CA 02359556 2001-10-17
3
the handpiece may be cleaned and/or serviced without having the electronic
components
damaged.
Typically, the switch member (having button portions) is formed of a resilient
material, such as an elastomeric material, to provide a sealing action between
the switch
member and the handpiece. Elastomeric switch buttons are generally not good
barriers to
moisture ingress (water vapor), especially moisture ingress due to an
autoclave operation.
Elastomeric materials are vulnerable to piercing by sharp instruments. Also,
if moisture does
pass through these elastomeric barriers during the autoclave operation, the
moisture does not
have a rapid means for escaping the handpiece following completion of the
autoclave
operation. The presence of moisture in an inner cavity of the handpiece, where
the electronic
components are stored, can cause damage and/or malfunction of the handpiece or
lead to
premature wear.
When the switch member is in the form of an elastomeric switch member, an
integral
flexible membrane may be provided around the periphery thereof. This flexible
membrane is
often referred to as a "web" or skirt which permits the switch member body to
be readily
depressed when pressed upon and return to its original position when released.
There are at
least two associated disadvantages of using a thin elastomeric web as part of
the rocker switch
member body. First, the puncture/tear resistance of the web area is limited
because the web
area has a relatively thin cross section and has limited durability to resist
puncture from sharp
instruments contacting the flexing portion (the web). Second, the thinness of
the web
membrane does not provide a very robust seal since air and humidity can pass
through. In
other words, the web membrane has a sufficiently high permeability that
permits air and
hnmidity to nass through-
CA 02359556 2001-10-17
4
One example of the difficulty that is encountered with a switch member having
a high
permeability occurs when the switch member is subjected to an autoclaving
process. When
the rocker switch member is used to seal off an inner cavity of the handpiece,
an autoclave
vacuum can cause the air pressure inside the inner cavity to be higher than
outside of the inner
cavity. The switch member has limited travel in an outward direction and thus
can not
accommodate the higher pressure. Consequently, the pressurized air escapes
through the web
membrane due to its relatively poor permeability. It is also possibly that the
pressurized air
can escape through other portions of the switch member body. However, during
autoclave
repressurization to normal atmosphere, the reduced pressure inside the inner
cavity causes the
switch member to deflect downward. This results in the switch member being
pulled
downward, similar to someone pressing on the switch member. Thus, the switch
member
equalizes the pressure and there is inadequate pressure differential to draw
air back through
the web membrane. This results in the switch member being held down without
user
intervention. This is not desirable because it leads to unwanted activation of
the switch
mechanism due to the switch member being in a depressed position.
While existing membranes have been suitable for some applications, there is a
need
for providing improved membranes which are good barriers to moisture ingress
along with
providing a good barrier to gas vapor and other gas (air) transmission along
with improved
resistance to puncture.
SUMMARY OF THE INVENTION
The present application is directed toward methods and switch members which
control
fluid flow (e.g.. flow of water vapor and gases, such as air) through the
switch members which
CA 02359556 2008-09-09
are used to seal an interior cavity of a surgical handpiece and each provides
a
depressable member for actuating the handpiece. The switch members provide
improved sealing properties which prevent transmission of fluids across the
entire
switch member or at least a treated portion thereof (e.g., a skirt) and into
and out of
the sealed internal switch chamber. The switch members are also resistant to
puncture due to striking by tools or cleaning instruments, and the like.
In some aspects, there is provided a depressable switch member for use in a
surgical handpiece to seal an interior of the handpiece, the switch member
comprising:
a body and a skirt peripherally extending around the body; and
a metallic layer disposed in at least one location of at least one of the
body and the skirt.
In some aspects, there is provided a depressable switch member for use in a
surgical handpiece to seal an interior of the handpiece, the switch member
comprising:
a body and a skirt extending peripherally around the body; and
a substrate disposed between at least one of the body and the skirt and
the handpiece interior, wherein at least a portion of the substrate is covered
with a permeability barrier.
In some aspects, there is provided a depressable switch member for use in a
surgical handpiece to seal an interior of the handpiece, the switch member
comprising:
a body and a skirt peripherally extending around the body; and
a permeability barrier disposed within at least one of the body and the
skirt for reducing a fluid transmission rate therethrough.
In some aspects, there is provided a switch member for use in a surgical
handpiece to seal an interior of the handpiece, the switch member comprising:
a body and a skirt peripherally extending around the body, wherein at
least the skirt is formed of a material that is impermeable to fluids.
CA 02359556 2008-09-09
5a
The switch members find particularly utility in handpieces which are
autoclavable. Autoclave pressures and vacuums can induce gas flow and water
vapor flow across the membranes of conventional switch members and
particularly,
across the thin skirt portion thereof. The present application discloses
various
methods of controlling the gas and water vapor flow across the depressable
switch
member (particularly the skirt portion) such that the handpiece may be used in
an
autoclave environment and other adverse settings without experiencing the
disadvantages associated with conventional members.
Other features and advantages will be apparent from the following detailed
description when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other features will be more readily apparent from the
following detailed description and drawings of illustrative embodiments in
which:
FIG. 1 is an illustration of a console for an ultrasonic surgical cutting and
hemostatis system, as well as a handpiece and foot switch in accordance with
an
exemplary embodiment;
FIG 2 is a cross-sectional view showing one exemplary switch end cap;
CA 02359556 2001-10-17
6
FIG. 3 is a top perspective view of one exemplary switch member for use in the
switch
end cap of FIG. 2;
FIG. 4 is a bottom perspective view of the switch member of FIG. 3;
FIG. 5 is a bottom perspective view of a switch member according to one
exemplary
embodiment;
FIG. 5A is a fragmentary cross-sectional view taken along the line A-A of FIG.
5;
FIG. 6 is a fragmentary cross-sectional view of a switch member according to
another
exemplary embodiment where a substrate is provided between the switch member
and a
permeability barrier;
FIG. 7 is a top perspective view of a switch member according to another
exemplary
embodiment;
FIG. 8 is a bottom perspective view of a switch member according to another
exemplary embodiment;
FIG. 8A is a side view of a switch member according to another embodiment;
FIG. 9 is a bottom perspective view of a switch member according to another
exemplary embodiment;
FIG. 9A is a fragmentary cross-sectional view taken along the line A-A of FIG.
9;
= FIG. 10 is a partially fragmented cross-sectional view of a switch end cap
having a
vent formed therein;
FIG. 11 is a cross-sectional view of a durable switch assembly according to
another
embodiment;
FIG. 12 is an exploded view of a switch end cap according to another exemplary
embodini t;
CA 02359556 2001-10-17
7
FIG. 13 is a cross-sectional view of switch end cap of FIG. 12 in an assembled
state;
FIG. 14 is a side elevational view of a bellow switch used in the switch end
cap of
FIG. 12;
FIG. 15 is a cross-sectional view taken along the line 15-15 of FIG. 14;
FIG. 16 is an exploded view of a switch end cap according to another exemplary
embodiment.
DESCRIPTION OF ILLUSTRATIVE EXEMPLARY EMBODIMENTS
Referring first to FIG. I in which one exemplary surgical cutting and
hemostatis
system according to one embodiment is illustrated and generally indicated at
10. In the
exemplary embodiment, the system 10 is an ultrasonic surgical system. The
system 10
includes a console or housing 20 for containing an ultrasonic generator (not
shown) and a
control system located within the console 20 which forms a part of the system
10. A first
cable 22 connects the console 20 to a handpiece 30 and serves to provide an
electrical
connection therebetween. The first cable 22 includes a first set of wires (not
shown) which
permit electrical energy, i.e., drive current, to be sent from the console 20
to the handpiece 30
where it imparts ultrasonic longitudinal movement to a surgical instrument 11.
The surgical
instrument 11 is preferably a scalpel blade or shear. This instrument 11 can
be used for
simultaneous dissection and cauterization of tissue.
The supply of ultrasonic current to the handpiece 30 is controlled by a switch
mechanism 40 disposed within the handpiece 30. As will be described in greater
detail
hereinafter, the switch mechanism 40 is electrically connected to the console
20, more
cr+PC ifically the venerator thereof by one or more wires (not shown) of the
first cable 22. The
CA 02359556 2001-10-17
8
generator may also be optionally and further controlled by a foot switch 50
which is connected
to the console 20 by a second cable 60. Thus, in use, a surgeon may apply an
ultrasonic
electrical signal to the handpiece 30, causing the instrument 11 to vibrate
longitudinally at an
ultrasonic frequency, by operating the switch mechanism 40 on the handpiece 30
or the foot
switch 50. The switch mechanism 40 is activated by the hand of the surgeon and
the foot
switch 50 is activated by the surgeon's foot.
The console 20 also includes a liquid crystal display device 24, which can be
used for
indicating the selected cutting power level in various means, such as
percentage of maximum
cutting power or numerical power levels associated with the cutting power. The
liquid crystal
display device 24 can also be utilized to display other parameters of the
system. A power
switch 26 and power "on" indicator 28 are also provided on the console 20 to
permit the user
to further control the operation of system 10. Additional buttons and control
switches,
generally indicated at 70, control various other functions of the system 10
and may be located
on the front panel of the console 20. When the power is applied to the
ultrasonic handpiece
30 by operation of either switch mechanism 40 or switch 50, the surgical
scalpel or instrument
11 is caused to vibrate with the amount of longitudinal movement varying
proportionately
with the amount of driving power (current) applied, as adjustably selected by
the user.
Now referring to FIGS. 1 through 4, one exemplary switch mechanism 40 is shown
in
greater detail in FIG. 2. The handpiece 10 is formed of a switch end cap 90
which is attached
to a handpiece body 92. The switch mechanism 40 includes multiple electrical
components,
e.g., one or more circuit boards 80, and also includes one or more depressable
switch
members 82, which are manipulated by the user for activation or deactivation
of the switch
mechanism 40. For purpose of illustration only, each switch member 82 is shown
in the form
CA 02359556 2009-09-23
9
of a rocker type switch; however, it will be understood that the switch member
82 may
comprise any number of types of depressable switch members 82 and is not
limited to a
rocker-type switch. The exemplary switch member 82 includes a body 83 (in this
case a
rocker type body) and a skirt 85 which peripherally extends around the body
83. The switch
member 81 serves to seal an interior of the handpiece 10 and therefore acts as
a water vapor
and gas barrier (i.e., a permeability barrier to liquids and gases).
Preferably, both the body 83
and the skirt 85 act as permeability barriers. The switch member 82 also
includes a pair of
spaced posts 87 extending outwardly from the body 83 for engaging a contact
(not shown) to
cause activation of the switch mechanism 40 (FIG. 1). The posts 87, in a non-
compressed
state, preferably do not extend below a plane containing the lower surface of
the skirt 85.
Because the posts 87 are preferably formed of an elastomeric material, as is
the body 83 and
skirt 85, a force exerted on the upper surface of the body 83 above the posts
87 causes the
respective post 87 to be driven downward so that it extends beyond the plane
containing the
lower surface of the skirt 85. This is the compressed position of the switch
member 82.
In the illustrated embodiment, the switch end cap'90 includes two opposing
switch
members 82 which are coupled to the switch end cap 90. The switch end cap 90
has an outer
shell 94 which houses electrical switch components, such as the circuit boards
80. Because
each switch member 82 is in communication with the switch mechanism 40,
openings are
formed in the outer shell 94 to permit the switch member 82 to engage the
switch mechanism
40 so that signals are generated by the switch mechanism 40 and delivered to
the console 20
to permit operation of the handpiece 10.
CA 02359556 2009-09-23
The handpiece 10 is preferably intended for use in a surgical system, such as
that
disclosed in commonly assigned U.S. Patent No. 7,476,233, filed October 20,
2000 and the
handpiece 10 is described in greater detail in U.S. Patent No. 6,623,500,
filed October 20,
2000.
In one aspect, an improved switch member 82, in the form of an elastomeric
rocker
type switch button, is disclosed. It will be understood that while the term
"elastomeric" is
used herein, the switch member 82 may be formed of other suitable plastics,
e.g., a
thermoplastic, or other materials (such as a metal with a compressible
structure so that the
switch member deforms under application of a force). In addition, while the
discussion will
focus on switch members used in switch mechanisms, one will appreciate that
other types of
plastic components, such as seals, walls, or other components may be
substituted for the
switch membranes. Furthermore, while exemplary switch members are discussed
herein as
being of a rocker type, it is understood that the scope of the present
application covers other
types of switch members. Accordingly, the description and illustration of
rocker type switch
members is merely exemplary and not limiting.
Referring to FIGS. 3-5A, in one exemplary embodiment, a metallic layer 110 is
applied to the elastomeric rocker type switch member 82, as shown in FIG. 5.
Preferably,
the skirt 85 is integrally formed with the body 83. More specifically, the
metallic layer 110
is applied to an underside 112 of the elastomeric rocker switch member 82. The
layer 110
may be formed from any number of suitable metal materials, e.g., aluminum,
gold, titanium,
platinum. The layer 110 is in the form of a thin layer of metal which is
applied to
predetermined sections of the underside 112 of the body 83 and the skirt 85.
For example,
the complete underside 112 (including the body 83 and skirt 85) may be coated
with the
metallic
CA 02359556 2001-10-17
11
layer 110 which is a thin coating (for example, the thickness may be from
about 5 kt inch to
about 0.0005 inch. Alternatively, only the skirt 85 of the switch member 82
has the metallic
layer 110 disposed thereon. The metallic layer 110 dramatically reduces the
water vapor and
gas transmission rates of the treated part, e.g., the underside 112.. Since
the layer 110 is very
thin, the layer 110 is flexible and does not hinder the flexibility of the
elastomeric part (the
switch member 82). The presence of the metallic layer 110 thus improves the
seal properties
of the switch member 82. The metallic layer 110 is not limited to being
applied to only the
underside 112 but rather the metallic layer 110 may be formed in an
intermediate layer of the
switch member 82 between the upper surface and the underside 112. The metallic
layer 110
may be formed only in an intermediate layer of the skirt 85. The metallic
layer 110 may also
be applied to the upper surface of the member 82 by itself or in combination
with being
disposed on the underside 112 or at an intermediate layer. The metallic layer
110 can be
applied using conventional techniques, including using a spray apparatus or
other type of
equipment that serves to apply a thin metallic layer, preferably of uniform
thickness, to a
body. Other techniques that may be used to apply the metallic layer 110
include but are not
limited to ion beam deposition, metal vapor deposition, and chemical vapor
deposition.
In another embodiment, shown in FIG. 6, a thin flexible substrate 120 is
provided and
is coated with a metallic layer 122. The substrate 120 is preferably formed of
a flexible
material, such as polyurethane, vinyl, silicone, a thermoplastic elastomer,
polyvinylidenefluoride, poly-paraphenylene terephthalamide, polyimide, and a
combination of
any of the foregoing. For example, a polyimide film may be coated with an FEP
fluoropolymer resin to provide a moisture barrier and a slippery surface that
reduces the
tendency for a tool to vuncture the member. In one exemplary embodiment, the
substrate 120
CA 02359556 2001-10-17
12
has a thickness from about 0.0005 inch to about 0.003 inch. The metallic layer
122 may be
formed of any number of suitable metals, including but not limited to
aluminum, gold,
titanium, and platinum. Preferably, the metallic layer 122 is formed of a
metal which permits
the metallic layer 122 to be thin, while at the same time. the metallic layer
122 has low water
vapor and gas transmission rates. The thickness of the metallic layer 122, in
one embodiment,
is between about 5,u inch and about 0.0005 inch. The metallic layer 122 is
formed on a first
surface 124 of the thin flexible film substrate 120. An opposing second
surface 126 of the
thin flexible film substrate 120 is attached to or faces the underside 112 of
the elastomeric
rocker switch member 82 when the handpiece 30 is assembled. In one embodiment,
the
substrate 120 is adhered to the underside 112 of the switch member 82 using an
adhesive.
The thin flexible film substrate 120 may be placed on or just underneath the
underside 112.
For example, the thin flexible film substrate 120 may be in laminated contact
with the
elastomeric rocker switch member 82 such that the metallic layer 122 faces
away from the
elastomeric rocker switch member 82 as shown in FIG. 6. The thin flexible film
substrate 120
may also be positioned in close proximity yet separated from the elastomeric
rocker switch
member 82. It will be understood that the substrate 120 may be applied to
select portions of
the underside 112. For example, the substrate 120 may be applied only to the
underside of
skirt 85 or may be applied to the complete underside 112.
Referring to FIGS. 1-4, in another embodiment, the water vapor and gas
transmission
rates are reduced by structurally altering a surface, e.g., underside 112, of
the elastomeric
switch member 82 via an ion implantation process. In an ion implantation
process, the surface
properties of the switch member 82 are modified while leaving the bulk
properties intact. .
Treatment san he to the underside 112 and/or an upper surface of the member 82
or a laminate
CA 02359556 2001-10-17
13
affixed to the member 82 resulting in cross-linking of the polymer chains in
three dimensions.
Once again, the surface treatment may be to an entire surface or it may only
be to selected
surfaces, such as the underside of the skirt 85. By using a suitable ion
implantation process,
the pore size/porosity of the member 82 is reduced resulting in the water
vapor and gas
transmission rates being likewise reduced because the water vapor and gas are
unable to be
transmitted through the elastomeric switch member 82 due to this permeability
barrier being
formed. Another benefit of ion implantation is the improved strength and
surface hardness
which improves the switch member's puncture resistance, thereby reducing the
likelihood that
a puncture may occur. For example, during a normal sterilization cleaning
process (e.g., an
autoclave operation), instruments, such as wire brushes, are used that may
puncture weak
conventional switch membranes.
Another method of altering a surface of the member 82, such as the underside
112, is
to shallow melt or heat fuse the surface to more tightly bond the surface
molecules together.
One such process for accomplishing this is a laser sintering process which
modifies the
underside surface 112 and/or top surface so that the molecules thereat are
more tightly
bonded. This makes it more difficult for the water vapor and gas (e.g., air)
to be transmitted
through the underside 112 and thus a reduction in the water vapor and gas
transmission rates
is realized. Ion beam assisted deposition or low temperature arc vapor
deposition can be used
to deposit materials with low gas permeability on the underside 112, such as
ceramics, metals
and polymers, thereby providing a water vapor and gas diffusion barrier.
Ceramics which
may be used include, but are not limited to, alumina, silicon dioxide, and
metals include, but
are not limited to, aluminum, gold, titanium, platinum, alloys, or
combinations thereof can be
used in sequential layers. The entire underside 112 of the body 83 and skirt
85 may be surface
CA 02359556 2001-10-17
14
treated or select portions of the underside 112 may be treated. For example,
only the
underside of the skirt 85 may be surface treated.
Any pressure differential problems experienced across the member 82 (such as
during
an autoclave cleaning process) can be reduced to insignificant levels by
reducing the volume
of air in the sealed switch chamber underneath the member 82. Filling the void
area under the
member 82 reduces the amount of air under the member 82 that is influenced by
heat and
pressure, thereby reducing the differential pressure across the member 82 and
subsequently
reducing the adverse effects to the switch member 82. This is especially
noticed in
applications, e.g., autoclave process, where a force acts on the member 82. It
will be
appreciated that a small area under the member 82 is needed so as to allow the
posts 87 or the
like to move as the member 82 is depressed or when it returns to a non-
compressed position.
Yet another method for reducing the water vapor and gas transmission rates is
to apply
a petroleum product, e.g., an oil or grease film 130, to the elastomeric
switch member 82,
particularly to the underside 112 where it will not be disturbed from user
handling, as shown
in FIG. 7. For example, a petroleum jelly 130 may be applied to the entire
underside 112 or
select portions thereof. This oil or grease film 130 could be further
prevented from migration
by placing a laminate 140 over the oil or grease film 130. The laminate 140
acts as a cover to
retain and contain the oil or grease film 130. A similar method is to mix
silicone oil or
another type of compatible oil or grease into the elastomeric rocker switch
member 82. This
reduces the water vapor transmission rate. Once again, a barrier film, such as
the laminate
140, could be used to prohibit migration of residual oils to parts that do not
tolerate the oils.
The water vapor and gas transmission rates of the elastomeric switch member 82
may
also be reduced by subiecting the elastomeric switch member 82 to a cryogenic
temperature
CA 02359556 2001-10-17
environment to reorganize and/or more tightly organize and/or refine the
molecular
microcrystallinic structure of the elastomeric switch member 82. This results
in a decrease in
the porosity, water vapor and gas transmission rates, and improves gas sealing
capability of
the elastomeric switch member 82. One suitable technique is to introduce the
elastomeric
5 switch member 82 into a progressive thermally controlled liquid nitrogen
treatment. Another
benefit of this treatment is improved strength (ruggedness) and resistance to
puncture of the
elastomeric switch member 82. This is particularly beneficial for durability
of thin members
being heavily flexed or challenged by pointed instruments.
One of skill in the art will further understand that combinations of the above
method
10 may be used according to the present invention. For example, a relatively
thick elastomeric
switch member 82 may be used with a grease coating being applied in the area
of the thin
flexible joint area. Another example would be a switch button that has a thin
flexible
perimeter with a solid low-porosity, non-elastomer switch button being fused
to a relatively
porous flexible member, resulting in a narrow flexible skirt around the body.
The resulting
15 assembly has only a small surface area with relatively higher vapor
transmission rate, thus the
amount of vapor passing into the handpiece 10 is negligible.
Referring to FIG. 8 and accordance with the present invention, a web membrane
area
(e.g., the skirt surrounding the rocker body) of a rocker switch member 200 is
replaced with a
puncture resistant flexible material 210 made from materials, such as
polyimide, a polyester,
poly-paraphenylene terephthalamide, and thermoplastic elastomers (referred to
hereinafter as a
"puncture resistant skirt"). In an exemplary embodiment, the puncture
resistant skirt 210 has
a thickness between about 0.0005 inch and about 0.003 inch. One method of
creating such
device 200 is to attach (e.g., adhere) a rocker shaped element 83 on top of
the puncture
CA 02359556 2001-10-17
. ~ z
16
resistant skirt 210, thereby providing a profile of a rocker with the benefits
of a flexible web
zone with puncture/slit resistance that is superior to thin wall elastomers.
Another method is
to insert mold the puncture resistant skirt 210 into the rocker body, creating
an integral two-
material item that combines the benefits of a profiled rocker and a durable
web (skirt). The
puncture resistant skirt 210 acts as the skirt 85 of FIG. 3.
The flexibility and displacement ability can be further enhanced by
fabricating folds or
rolls 220 into the puncture resistant skirt 210 as shown in FIG. 8A. Due to
the superior
puncture resistance of the puncture resistant skirt 210, the flex area is
substantially more
resistant to puncture than an elastomeric web (skirt). These folds/rolls 220
provide a spring-
like return action that returns the rocker 200 to its upward position when the
rocker 200 is no
longer depressed. These folds/rolls 220 may also provide detent snap action
behavior that
provides tactile feedback to the user. Springs or domes (not shown) may be
used under the
rocker 200 if needed to supplement or completely provide the means for rocker
return upward
when the rocker 200 is released. Plastic springs/domes may be especially
useful due to their
non-corrosive nature in the presence of steam and heat. Also, the puncture
resistant skirt 210
has improved resistance to air flow through it, thus reducing the permeability
of the rocker
200. This reduced permeability facilitates proper behavior of the rocker
during and after
autoclaving.
Furthermore, selection of the film to form the puncture resistant skirt 210 or
a
supplemental coating that has a relatively low friction slick surface
(compared to an elastomer
which has a higher friction) discourages puncture/slitting during
cleaning/handling. Suitable
low friction materials include but are not limited to polyimides, polyseters,
polytetrafluoroethylene materials, and titanium nitride. For example,
instruments, such as
CA 02359556 2001-10-17
17
brushes, striking a slippery member are more apt to slide across the member
than pierce it, as
compared to a normal elastomeric member. Thus, forming the puncture resistant
skirt 210 so
that at least a surface thereof has a low friction surface enhances the
puncture resistance of the
puncture resistant skirt 210. A supplemental surface treatment, such as ion-
implantation, may
also be used.
Another method of improving the switch member 200 for better durability and
improved resistance to passage of air/humidity is to keep the web membrane
intact but surface
treat predetermined surfaces of the switch member 200 using a suitable surface
treatment
process. More specifically, at least the web membrane area (skirt) is surface
treated and
preferably, the surface treatment is done to the interior (underside) and/or
exterior of the
rocker switch member 200. For example, the entire underside may be surface
treated.
Surface treatments that can be used include, but are not limited to, applying
parylene,
ceramics (such as silicone dioxide, titanium nitride, etc.), metal coatings
(such as aluminum,
gold, titanium, platinum, etc.) or other suitable coating materials having the
desired properties.
As shown in FIGS. 9 and 9A, another method of improving an elastomer switch
member 300 for better durability and improved resistance is to impregnate the
elastomeric
resin that is used to make the elastomeric switch member 300 with microspheres
310. The
microspheres 310 may be formed of any number of materials and in an exemplary
embodiment, the microspheres 310 are made of glass, carbon, silicon,
aluminumoxide,
alumina etc. The microspheres 310 may be solid or hollow. These microspheres
310 provide
a pierce-resistant substrate and reduce the permeability of a skirt 312 and/or
a body portion
314 of the member 300 since they impede gas flow. Because the microspheres 310
have a
very small diameter; e.g.. from about 15 microns to about 100 microns, and
have a generally
CA 02359556 2001-10-17
J
18
annular shape, the microspheres 310 do not significantly interfere with web
flexibility.
However, the microspheres 310 may have any number of other shapes.
Alternatively, the
elastomer may be impregnated with superfine fibers such as quartz fibers,
ceramic fibers,
synthetic fibers, such as polyvinylidenefluoride fibers, having an exemplary
diameter from
about 1 to about 15 microns. Another method of reducing the water vapor and
gas
transmission rates is to increase the thickness of the elastomeric switch
member over most of
the part, leaving the part thin only where it functionally needs to be of
reduced thickness.
Increased thickness of the elastomeric switch member dramatically reduces the
vapor
transmission rate. The microspheres 310 may be located only in the skirt 312
or may be
dispersed throughout the entire switch member, including the body 314 and the
skirt 312
areas.
As previously-mentioned, the thinness of the skirt (i.e., a flexible seal) may
not
provide a very robust seal, since air and humidity can pass through. In other
words, the
permeability of the skirt is high in conventional configurations. While it is
desired that the
skirt have a low permeability, some amount of permeability is typically
present. The amount
of gas/humidity passage across the skirt and other portions of the member is
dependent upon
on the pressure difference on each side of the member.
The switch member 82 (FIG. 3) is designed to provide substantial displacement
in an
outward/upward direction and an inward/downward direction. This symmetrical
displacement
capability reduces the differential pressure across the member, thereby
reducing the
gas/humidity flow across the member. By reducing the flow across the member,
the rocker is
able to return to it normal position after autoclaving unlike conventional
rockers which tended
to he held down without user intervention. as previously-described. Another
benefit of
CA 02359556 2001-10-17
19
reduced flow is higher reliability since humidity is not as readily traveling
inside the sealed
chamber to potentially influence components.
According to the present invention, the symmetrical displacement can be
accomplished by several means. One example is the use of folds or rolls 220 as
shown in the
switch member 200 of FIG. 8A. The use of folds/rolls 220 in the skirt region
210 permits
upward motion as well as downward motion. Another method is to provide
adequate slack in
the member which permits member expansion outward as well as inward.
Furthermore, a
elastic material, e.g., polyurethane, that readily elongates may be used to
form the rocker,
thereby permitting the rocker to expand outward. In all of these embodiments,
the differential
pressure across the member is controlled through adequate rocker motion in
both directions.
Referring now to FIG. 10 in which another embodiment to avoid the difficulties
associated with differential pressure across the member is to use a vent that
does not allow
fluid into the sealed interior cavity 100 but allows for pressure
equalization. The main
purpose for sealing the interior cavity 100 is to prevent fluids (e.g., water,
saline, cleaners,
blood, etc.) from entering the sealed interior cavity 100 which houses the
switch mechanism
40 (FIG. 2). Ingress of such materials could corrode or otherwise jeopardize
the functionality
of the switch mechanism 40 and could provide debris to the interior cavity 100
that would be
unacceptable from a sterility standpoint, especially if it were to leak out
subsequently. The
vent according to the present invention does not permit fluid to enter the
interior cavity 100
and if for some reason, fluid did enter the interior cavity 100, the vent
would resist fluid flow
outward toward the patient.
Referring still to FIG. 10 in which one exemplary method of venting gas yet
blocking
fi raids from entering the interior cavity 100 is shown. In situations where
it is difficult to seal
CA 02359556 2001-10-17
off the handpiece interior cavity 100 due to material porosity, the water
vapor may
aggressively enter the interior cavity 100 (due to autoclave pressures) but
only slowly exit
back through the elastomeric rocker switch member 82 since the pressure and
heat are not
advantageous following autoclave. A vent 150 is formed in the outer shell 91
of the switch
5 end cap 90 and is covered with a microporous hydrophobic membrane 160. The
microporous
hydrophobic membrane 160 is formed from any number of suitable hydrophobic
materials,
including but not limited to polytetrafluoroethylene (PTFE) and polypropylene.
The
hydrophobic membrane 160 permits air to freely enter and exit the handpiece 30
but blocks
the entrance of liquids. Thus, while air can rapidly enter the interior cavity
100 of the
10 handpiece 30, it will also exit the handpiece 30 in a reasonably short
period of time. The
hydrophobic membrane 160 permits air pressure equalization between the
interior cavity 100
and the exterior of the handpiece 30 (FIG. 1) while at the same time, liquids
are blocked. The
microporous hydrophobic membrane barrier 160 also acts as a viral and
bacterial barrier that
filters the air entering and leaving through it.
15 In another embodiment, one or more vent holes are formed in the switch end
cap 90
and are of a size which permits gasses to travel therethrough; however,
liquids, such as water,
are not inclined to traveling through the vent 150 due to the small size of
the vent 150. In'
other words, because of the surface tension, liquids do not readily pass
through the one or
more vent openings. The resistance to liquid passage of the one or more vent
holes may be
20 enhanced by disposing a hydrophobic material within the hole wall or by
using a hydrophobic
mesh (i.e. hydrophobic membrane 160 of FIG. 10) across the hole opening.
Another method
involves providing torturous path vent holes. By using a relatively long
passage way vent
hole (e_g._ about 0.1 to about 1.0 inch long with a diameter of about 0.01
inches according to
CA 02359556 2001-10-17
21
one embodiment), liquid ingress into the sealed interior cavity 100 is further
discouraged. The
use of a single vent hole can discourage liquid flow since the single
torturous path passage
into the sealed interior cavity 100 does not really allow simultaneous passage
of liquid in one
direction into the interior cavity 100 and displacement of gas, e.gõ air, in
the other direction.
Alternatively, vent 150 may be located such that when the switch end cap 90 is
fully
assembled, the vent 150 is not fully accessible. Thereby, any remote chance of
residual fluid
flow out the vent 150 will not present itself to the user/patient. Instead, it
is harmlessly
emitted into another fairly contained space within the assembled handpiece.
Referring now to FIG. 11 in which a durable switch assembly is shown and
generally
indicated at 400. The switch assembly 400 is easily depressed with light
pressure yet has a
relatively thick outer shell 402 that is resistant to piercing damage and gas
flow. For example
and according to one exemplary embodiment, the thickness of the outer shell
402 is from
about 0.04 inches to about 0.06 inches. Outer shell 402 is in the form of a
bubble dome
shaped finger depressing shell and may be formed of various materials,
including but not
limited to, polyimides, polyesters, and other suitable materials. The outer
shell 402 has two
active regions, namely a first region 404 and a second region 406. Due to the
dome shape, the
outer shell 402 is readily deformable by forger pressure to cause activation
of the switch
mechanism 410. The first region 404 has a first post 408 extending from the
outer shell 402
towards the switch mechanism 410. One end 407 of the first post 408 is
connected, preferably
integrally, to the outer shell 402 and an opposite end 409 is disposed
proximate to but not in
contact with the switch mechanism 410 in the rest position shown in FIG. 11.
The second end
409 has a first contact pad 412 which engages a first switch pad 414 formed on
a PCB 420,
which forms a part of the switch mechanism 410. The first switch pad 414 is
preferably
CA 02359556 2001-10-17
22
axially aligned with the first contact pad 412 so that depressing the first
region 404 causes the
first contact pad 412 to contact the first switch pad 414 resulting in
activation of the switch
mechanism 410.
Similarly, the second region 406 has a second post 416 extending from the
outer shell
402 towards the switch mechanism 410. One end 417 of the second post 416 is
connected,
preferably integrally, to the outer shell 402 and an opposite end 419 is
disposed proximate to
but not in contact with the switch mechanism 410 in the rest position shown in
FIG. 9. The
second end 419 has a second contact pad 422 which engages a second switch pad
424 formed
on the PCB 420, which forms a part of the switch mechanism 410. The second
switch pad
414 is preferably axially aligned with the second contact pad 422 so that
depressing the
second region 406 causes the second contact pad 422 to contact the second
switch pad 424
resulting in activation of the switch mechanism 410.
Optionally, a center support post 430 may be provided to reduce inadvertent
activation
when holding or pressing the center of the outer shell 402. The center support
post 430
extends from the outer shell 402 to the switch mechanism 410. In the rest
position of FIG. 11,
the center support post 430 rests against or is in close proximity to an
inactive portion of the
switch mechanism 410. Furthermore, each of the first and second regions 404,
406 may have
its own flexible membrane (not shown) to further reduce depression activation
pressure. The
exemplary outer shell 402 illustrates a stepped zone 440 provided at each of
the first and
second regions 404, 406. The stepped zones 440 provide a finger contact point
for the user to
depress so that the respective first and second posts 408, 416 is directed
downward toward the
switch mechanism 410. Preferably, the centermost portion of the zone 440 is
positioned
directly above one of the first and second posts 408, 416.
CA 02359556 2001-10-17
23
Referring now to FIGS. 12-15, a second exemplary switch end cap is shown and
generally indicated at 500. The switch end cap 500 is of a different
configuration than the
rocker type switch shown in FIG. 2. The switch end cap 500 has a pair of
bellow type switch
assemblies 510 which are coupled to an outer shell 520 of the switch end cap
500. The outer
shell 520 houses electrical switch components 530, such as circuit boards 532,
which
generally act to provide switch signals when actuated by the user. Each of the
circuit boards
532 has two depressable contact pads 534 which provide the signals typically
as a result of a
circuit being closed due to the depression of one of the contact pads 534.
Each switch assembly 510 includes a switch retainer 512, a pair of bellows
514, and an
upper gasket 516. Unlike the unibody rocker type switch member 81 of FIG. 2,
the switch
assembly 510 utilizes two separate bellows 514 which act as depressable switch
buttons for
causing a signal to be generated. By physically separating the bellows 514,
the risk that the
user will depress both switch buttons is greatly reduced. To accommodate the
switch
assemblies 510, the outer shell 520 has a pair of spaced openings 522 formed
therein. The
openings 522 should have complimentary shapes relative to the bellows 514. In
the
exemplary embodiment, the bellows 514 have annular shapes and therefore, the
openings 522
are generally annular in shape. The openings 522 should also be sized to
receive the bellows
514 so that at least a portion of the bellows 514 extend therethrough.
Each switch retainer 512 is disposed over one respective circuit board 532.
Accordingly, the dimensions and shape of the switch retainer 512 are
preferably
complimentary to the circuit board 532. In the exemplary embodiment, each of
the switch
retainer 512 and the circuit board 532 has a generally rectangular shape. The
switch retainer
512 has a first surface 540 and an opposing second surface 542 which faces the
circuit board
CA 02359556 2001-10-17
24
532. The first surface 540 has a first platform 544 formed thereon. The first
platform 544 has
a planar portion and also has a pair of raised stepped sections 546 formed
thereon. Each
stepped section 546 is formed of a pair of stacked concentric rings of varying
diameters, as
best shown in FIGS. 12 and 13. The ring with the greater diameter is the
lowermost ring with
the other ring, having the lesser diameter, being formed on the lowermost ring
so as to form a
projecting structure formed on the first platform 544.
Each stepped section 546 has an opening 550 formed therethrough. The
opening 550 extends completely through the switch retainer 512. The stepped
sections 546
are spaced from another so that a gap is formed therebetween. The stepped
sections 546 are
spaced so that they are generally axially aligned and disposed over the
contact pads 534 of the
circuit board 532. Consequently, the openings 550 are axially aligned with the
contact pads
534 when the retainer 512 is disposed over the circuit board 532 in the
assembled state. As
best shown in FIGS. 12 and 13, the first surface 540 of the retainer 512 seats
against upper
gasket 516 with the pair of stepped sections 546 being axially aligned with
and disposed
underneath the openings 522 formed in the outer shell 520. A portion of the
outer ring of the
stepped section 546 may protrude slightly from the outer shell 520.
FIGS. 14 and 15 best illustrate the configuration of the exemplary bellows
514. FIG. .
14 is a side elevational view of the bellow 514 and FIG. 15 is a cross-
sectional view of the
bellow 514. The bellow 514 has a body 515 with an upper section 560 which
serves as a
contact surface between the user's finger or thumb and the bellow 514 as it is
depressed or
released. The body 515 also has a lower section 562 which seats against and
mates with one
respective stepped section 546. Between the upper section 560 and the lower
section 562, the
6-11 nw hotly 515 has a number of integral folds 566. In the exemplary
embodiment, the folds
CA 02359556 2001-10-17
566 are annular in shape and are spaced from another. The diameter of the
folds 566 is
preferably approximately equal to the diameter of the upper and lower sections
560, 562;
however, the body 515 has a lesser diameter between the folds 566. The folds
566 thus form a
generally accordion-like structure.
5 The folds 566 give the bellow 514 spring-like characteristics as the
accordion-like
structure folds when pressure is applied to the upper section 560. As soon as
the pressure is
removed from the upper section 560, the compressed folds 566 expand, thereby
returning the
bellow 514 to its original state. In one exemplary embodiment, the bellow 514
is made of a
folded metal material; however, other materials may be used so long as the
materials provide
10 the bellow 514 with the above-described spring-like characteristics. For
example, the bellow
514 may be formed of nickel with a gold coating or it may be formed of
beryllium copper. In
an exemplary embodiment, the thickness of the metal bellow 514 is from about
0.0005 inch to
about 0.002 inch.
As best shown in FIG. 15, the bellow 514 has a post 570 attached to the upper
section
15 560. Preferably, post 570 is integrally formed with the upper section 560.
The body 515 of
the bellow 514 has a central compartment formed therein with the folds 566
surrounding the
central compartment and radially extending therefrom. The central compartment
is open only
at the second section 562 and is configured so that the post 570 extends
through the central
compartment and through the opening formed in the lower section 562. In a
first non-
20 compressed position, as shown in FIGS. 14 and 15, a lowermost tip 572 of
the post 570
extends below the lower section 562. The post 570 has a generally annular
cross-section of
varying diameter in different sections along the length of the post 570. More
specifically, the
post 570 has an annular flange 578 which has a greater diameter than the
surrounding sections
CA 02359556 2001-10-17
26
of the post 570. The annular flange 578 thus defines a first shoulder 579 and
a second
shoulder 580, closer to the lowermost tip 572. The post 570 has a slight taper
from the second
shoulder 580 to the lowermost tip 572.
Because the post 570 is connected to the upper section 560 and is movable
within the
central compartment, a force applied to the upper section 560 and the
resulting compression of
the folds 566 causes the post 570 to be directed downward through the central
compartment.
This results in even a greater length of the post 570 protruding below the
lower section 562
when the bellow 514 is in this compressed position. As best shown in FIGS. 13
and 15, the
post 570 is received within the opening 550 formed through the switch retainer
512. The
opening 550 has a diameter that is slightly larger than the diameter of the
annular flange 578.
In the non-compressed position and when the switch end cap 500 is assembled,
the lowermost
tip 572 does not extend below or only slightly extends below the second
surface 542 of the
retainer 512. Because the openings 550 of the switch retainer 512 are axially
aligned with the
contact pads 534, the posts 570 are likewise axially aligned with the contact
pads 534. The
contact pads 534 of the circuit boards 532 are preferably collapsible domes,
whereby the
circuit is completed when one of the domes is collapsed. The collapsible dome
is a self-
returning structure in that once a force that causes the collapsing of the
dome is removed, the
dome returns to its initial non-collapsed position.
The bellows 514 are disposed over the stepped sections 546 of the retainer 512
using
conventional techniques so that the bellows 514 are coupled to the stepped
sections 546. The
central compartment of the body 515 thus receives a portion of the stepped
section 546 of the
retainer 512 permitting the bellow 514 to be easily located and coupled to the
retainer 512.
The upper gasket 516 is disposed over the bellows 514 and further secures the
bellows 514
CA 02359556 2001-10-17
27
within the overall structure. The upper gasket 516 has a pair of spaced
openings 517 which
receive the bellows 514 with a significant amount of the bellows 514 extending
above the
upper gasket 516 in the assembled, non-compressed position. The upper gasket
516 is
disposed within the outer shell 520 so that it seats against and inner surface
of the outer shell
520. The folds 566 of the bellows 514 preferably extend above the outer
surface of the outer
shell 520; however, the openings 522 of the outer shell 520 have a diameter
which
accommodates the bellow 514 and therefore the bellow 514 can be compressed and
driven
further into the opening 550 toward the circuit board 532.
The compression of the bellow 514 is caused by the bellow 514 compressing
against
the stepped section 546 of the retainer 512. This compression permits the
lowermost tip 572
of the post 570 to be driven toward the circuit board 532 and more
specifically, the bellow
514 compresses to a degree such that the lowermost tip 572 is driven into
contact with the
contact pad 534. This causes the contact pad 534 (dome) to collapse and the
switch signal to
be generated. Thus, in this embodiment, the switch assembly 510 is formed of a
folded metal
member which has spring-like characteristics permitting the bellow 514 to be
compressed
under force and then return to its initial, non-compressed position once the
force is removed.
The upper gasket 516 preferably provides a barrier preventing undesired
material from
entering the interior of the outer shell 520.
Because the bellow 514 is formed of a metal, the bellow 514 is puncture
resistant to
objects that are used in normal usage of the surgical handpiece and
instruments (e.g., wire
brushes) used in a normal cleaning operation (e.g., a sterilization process).
The bellow 514
also provides a permeability barrier which prevents water vapor and gas
transmission through
the hellnw 514. Therefore, the bellow 514 offers all of the advantages that
were described
CA 02359556 2001-10-17
28
hereinbefore with reference to earlier embodiments of switch members having
permeability
barriers formed therein.
It will be understood that while the previous embodiment has been described as
including bellow elements 514, other types of depressable switch-members may
be used so
long as the switch members freely move from a non-compressed position to a
compressed
position under an applied force and then self return to the non-compressed
position once the
applied force has been removed. For example, instead of having folds 556, the
depressable
and collapsible switch member may have a collapsible wall structure (e.g., see
FIG. 11) which
collapses under the applied force but returns to the non-compressed position
once this applied
force is removed. This may be metal switch member having a dome structure
similar to that
of FIG. 11 or it may include a different collapsible configuration.
FIG. 16 illustrates yet another embodiment which is similar to the embodiment
shown
in FIGS. 12-15. In this embodiment, the bellow 514 does not include a post 570
(FIG. 15).
Instead, the bellow 514 has a hollow interior compartment and the portion of
the bellow 514
which impinges the contact 534 of the circuit board 532 is actually an inner
surface of the
upper section 560 of the bellow 514.
The contact 534 is still preferably a collapsible contact (e.g., dome type
configuration);
however, a post 535 extends outwardly from the contact 534. The post 535 is
similar to the
post 570 (FIG. 15) in its dimensions and size as it is designed to be received
in the opening
550 formed in the stepped section 546 of the retainer 512 when the retainer
512 is properly
positioned over the circuit board 532. The post 535 thus extends through the
opening 550 and
extends at least partially into the interior compartment of the bellow 514. In
the non-
compressed position, the upper section 560 of the bellow 514 is spaced
slightly above the top
CA 02359556 2001-10-17
29
of the post 535. When a force is applied to the upper section 560, the body
515 of the bellow
514 compresses and the upper section 560 makes contact with the post 535.
Because the post
535 is attached to a collapsible structure itself (the dome contact 534), the
further application
of force against the upper section 560 causes the post 535 to be driven
downward. This
results in the dome structure (contact 534) collapsing and the circuit being
closed. A switch
signal is then sent. Once the force is removed or the force becomes less, the
upper section 560
moves outward as well as the post 535 as the dome structure 534 expands.
While the invention has been particularly shown and described with reference
to the
preferred embodiments thereof, it will be understood by those skilled in the
art that various
changes in form and detail may be made therein without departing from the
spirit and scope of
the invention.
