U.S. patent application number 11/809305 was filed with the patent office on 2007-12-06 for multi-joint fixture system.
Invention is credited to Jason Robert Cahayla, Anthony J. La Rosa, Edward J. Laganis, Christopher P. Scott.
Application Number | 20070282311 11/809305 |
Document ID | / |
Family ID | 38791247 |
Filed Date | 2007-12-06 |
United States Patent
Application |
20070282311 |
Kind Code |
A1 |
Scott; Christopher P. ; et
al. |
December 6, 2007 |
Multi-joint fixture system
Abstract
A multi-joint fixture including a proximal base unit, one or
more arms serially connected by electromagnetically lockable ball
joints, and a distal hub. The ball joints unlock when not powered.
A centering mechanism biases the ball joints toward a neutral
position. A control system activates the electromagnetic brake with
a high-then-low voltage profile. A headpiece attaches to the hub
and holds a drape that covers the fixture. A connector connects a
surgical device to the headpiece. A switch on the hub can be
actuated via actuators on the headpiece or connector.
Inventors: |
Scott; Christopher P.;
(Hackensack, NJ) ; Laganis; Edward J.; (Hoboken,
NJ) ; La Rosa; Anthony J.; (Rockaway, NJ) ;
Cahayla; Jason Robert; (Saddle Brook, NJ) |
Correspondence
Address: |
THE LAW OFFICE OF JOHN A. GRIECCI
703 PIER AVE., SUITE B #657
HERMOSA BEACH
CA
90254
US
|
Family ID: |
38791247 |
Appl. No.: |
11/809305 |
Filed: |
May 31, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60810265 |
Jun 1, 2006 |
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Current U.S.
Class: |
606/1 |
Current CPC
Class: |
F16C 11/10 20130101;
A61B 2050/105 20160201; A61B 50/13 20160201; A61B 34/70 20160201;
F16D 63/002 20130101; A61B 50/20 20160201; F16M 13/022 20130101;
A61B 50/10 20160201; A61B 2017/00398 20130101; Y10T 403/32311
20150115; A61B 46/10 20160201; F16C 11/06 20130101; A61B 2017/00876
20130101; A61B 90/50 20160201; A61B 17/02 20130101; A61B 46/23
20160201; A61B 2090/508 20160201 |
Class at
Publication: |
606/1 |
International
Class: |
A61B 17/00 20060101
A61B017/00 |
Claims
1. A ball joint, comprising: a ball; and a body containing a
portion of the ball; a brake element; and an electromagnetic brake
mechanism configured to actuate the brake element between a locked
state wherein the brake element presses against the ball with a
force adequate to fix the orientation of the ball, and an unlocked
state wherein the brake element does not press against the ball
with a force as high as that of the locked state.
2. The ball joint of claim 1, wherein: the electromagnetic brake
mechanism is configured to actuate the brake element to the locked
state when the electromagnet is energized; and the electromagnetic
brake mechanism is configured to actuate the brake element to the
unlocked state when the electromagnet is not energized.
3. The ball joint of claim 1, wherein: the electromagnetic brake
mechanism is configured to actuate the brake element to the
unlocked state when the electromagnet is energized; and the
electromagnetic brake mechanism is configured to actuate the brake
element to the locked state when the electromagnet is not
energized.
4. The ball joint of claim 1, wherein the electromagnetic brake
mechanism includes a paired electromagnet and draw-plate,
electromagnet and draw-plate each being positioned along an
electromagnet axis and establishing a closable gap between them
that is normal to the electromagnet axis.
5. The ball joint of claim 4, wherein a spherical portion of the
ball and the brake element are each concentric with the
electromagnet axis.
6. The ball joint of claim 4, wherein: the ball joint defines a
ball axis passing through a spherical portion of the ball; the
brake element is concentric with the ball axis; and the ball axis
and the electromagnet axis are parallel to, and offset from, one
another.
7. The ball joint of claim 4, and further comprising a lever arm
connecting the brake element to the paired electromagnet and
draw-plate, and being configured to use leverage to react against
the brake element with a greater force than against the paired
electromagnet and draw-plate.
8. The ball joint of claim 4, wherein the brake element and paired
electromagnet and draw-plate act upon one another with equal
force.
9. The ball joint of claim 1, and further comprising a centering
mechanism configured to bias ball toward a neutral position.
10. The ball joint of claim 9, wherein: the ball includes a
spherical portion and a shaft extending from the spherical portion;
and the centering mechanism includes a spring spiraling in three
dimensions to connect the shaft to the body.
11. A ball joint locking system, comprising: the ball joint of
claim 1; and a control system configured to actuate the
electromagnetic brake mechanism with a voltage profile
characterized by a first, transient portion and a second,
steady-state portion, the transient portion voltage being
significantly greater than the steady-state portion voltage.
12. A system for holding an instrument, comprising: a base unit; a
hub configured to detachably hold the instrument; and a group of
one or more arms serially connected by a plurality of joints
between the base unit and the hub, one or more of the plurality of
joints being the ball joint of claim 1; a control system configured
to actuate the electromagnetic brake mechanism with a voltage
profile characterized by a first, transient portion and a second,
steady-state portion, the transient portion voltage being
significantly greater than the steady-state portion voltage; and a
system cart, wherein, the system cart houses the control system and
one or more storage compartments configured to house the group of
one or more arms serially connected by the plurality of joints when
not in use.
13. A multi-joint fixture for holding an instrument, comprising: a
base unit; a first arm; a first joint adjustably connecting a
proximal end of the first arm to the base unit; a second arm; a
second joint adjustably connecting a proximal end of the second arm
to a distal end of the first arm; a hub configured to detachably
hold the instrument; and a third joint adjustably connecting the
hub to a distal end of the second arm; wherein at least one of the
group comprising the first ball joint, the second ball joint and
the third ball joint is a ball joint as defined in claim 1.
14. The multi-joint fixture of claim 13, and further comprising a
switch carried proximate the hub, the switch being configured to
control actuation of the electromagnetic brake mechanism.
15. A jointed arm; comprising: an arm generally extending along a
longitudinal arm axis from a proximal end to a distal end; and the
ball joint of claim 1; wherein the body extends distally along the
longitudinal axis from the distal end of the arm; wherein the ball
has a spherical portion lying along the longitudinal axis and a
shaft extending out of the body in a direction perpendicular to the
longitudinal axis; and wherein the electromagnetic brake mechanism
includes a paired electromagnet and draw-plate lying along the
longitudinal axis;
16. A multi-joint fixture for holding an instrument, comprising: a
base unit; a hub configured to detachably hold the instrument; and
a group of one or more arms serially connected by a plurality of
non-separable joints between the base unit and the hub, one or more
of the joints having a brake mechanism configured to lock the
orientation of the joint when the brake mechanism is actuated;
wherein the electromagnetic brake mechanism is only configured to
actuate the brake mechanism when the system is powered.
17. A multi-joint fixture for holding an instrument, comprising: a
base unit; a hub configured to detachably hold the instrument; and
a group of one or more arms serially connected by a plurality of
joints between the base unit and the hub, one or more of the joints
having a brake mechanism configured to unlock the orientation of
the joint when the brake mechanism is actuated; wherein the
electromagnetic brake mechanism is only configured to actuate the
brake mechanism when the system is powered.
18. A multi-joint fixture for holding an instrument, comprising: a
base unit; a hub configured to detachably hold the instrument; and
a group of one or more arms serially connected by a plurality of
joints between the base unit and the hub, one or more of the joints
having a brake mechanism configured to lock the orientation of the
joint when the brake mechanism is actuated; wherein the brake
mechanism includes a brake element, a driver configured to actuate
the brake element, and a lever arm connecting the driver to the
brake element, and being configured to use leverage to react
against the brake element with a greater force than against the
driver.
19. A multi-joint fixture for holding an instrument, comprising: a
base unit; a hub configured to detachably hold the instrument; and
a group of one or more arms serially connected by a plurality of
joints between the base unit and the hub, the joints having a brake
mechanism configured to lock the orientation of the joint when the
brake mechanism is actuated; wherein one or more of the joints
include a centering mechanism configured to bias the joint toward a
neutral position.
20. A control system configured to actuate an electromagnetic brake
mechanism via an electronic brake circuit, comprising: a control
circuit configured to create a voltage profile across the brake
circuit in response to an activation signal; wherein the voltage
profile is characterized by a first, transient portion and a
second, steady-state portion, the transient portion having a
voltage significantly greater than the steady-state portion
voltage.
21. A multi-joint fixture for holding an instrument, comprising: a
base unit; a hub configured to detachably hold the instrument; and
a group of one or more arms serially connected by a plurality of
joints between the base unit and the hub, one or more of the joints
having a brake mechanism configured to lock the orientation of the
joint when the brake mechanism is actuated; and a switch carried
proximate the hub, the switch being configured to control actuation
of brake mechanism.
22. The multi-joint fixture of claim 21, wherein every joint has a
brake mechanism configured to lock the orientation of the joint
when the brake mechanism is actuated, and wherein the switch
controls actuation of the brake mechanism of each joint.
23. A surgical-instrument adaptor for use with a surgical
instrument and an apparatus having a hub and a switch to be
actuated, comprising: a first connector configured for connection
to the surgical instrument; a second connector configured for a
quickly detachable connection to the hub; and a switch actuator in
actuation communication with the switch.
24. The surgical-instrument adaptor of claim 23, wherein the switch
actuator includes a body configured to physically actuate against
an actuator on the hub.
25. A surgical instrument for use with a hub, comprising: a
surgical-instrument portion configured for use in surgery; a
connector configured for a quickly detachable connection to the
hub; and a switch actuator in actuation communication with the
switch.
26. A multi-joint fixture for holding a sterile instrument having a
connector, comprising: a proximal base unit; a distal first hub; a
group of one or more arms serially connected by a plurality of
joints extending distally from the base unit to the hub, one or
more of the joints having a brake mechanism configured to lock the
orientation of the one or more joints when the brake mechanism is
actuated; and a surgical drape including a sterile curtain sealed
to a headpiece, the headpiece being detachably connected to the
first hub, and the sterile curtain being extended over the first
hub, the group of one or more arms, and the base unit, isolating
them from instruments external to the sterile curtain; wherein the
headpiece forms a second hub configured to receive the instrument
connector.
27. The multi-joint fixture of claim 26, wherein the first hub
includes a switch configured to control the actuation of the brake
mechanism of the one or more joints, and wherein the headpiece has
an actuator configured to control the actuation of the brake
mechanism of the one or more joints.
28. The multi-joint fixture of claim 27, and further comprising a
connector connected to the instrument, wherein the connector
includes an actuator configured to control the actuation of the
brake mechanism of the one or more joints.
29. The multi-joint fixture of claim 28, wherein the headpiece
actuator is configured to actuate the switch, and the connector
actuator is configured to actuate the headpiece actuator.
30. The multi-joint fixture of claim 27, wherein the sterile
instrument includes an actuator configured to control the actuation
of the brake mechanism of the one or more joints.
31. The multi-joint fixture of claim 30, wherein the headpiece
actuator is configured to actuate the switch, and the sterile
instrument actuator is configured to actuate the headpiece
actuator.
32. The multi-joint fixture of claim 26, wherein the brake
mechanism of each of the one or more joints is an electromagnetic
brake mechanism.
Description
[0001] This application claims the benefit of U.S. provisional
Application No. 60/810,265, filed Jun. 1, 2006, which is
incorporated herein by reference for all purposes.
[0002] The present invention relates generally to an arm-like
fixture for positioning objects such as surgical instruments, and
more particularly, to a multi-joint fixture for holding such
objects, the fixture having arm segments connected with lockable
ball joints.
BACKGROUND OF THE INVENTION
[0003] There is a need during various surgical procedures for
instruments such as retractors to be held for extended periods of
time in stationary positions. Typically, such holding is done by a
medical practitioner, such as a surgical assistant, under the
direction of a doctor. In some cases, the instruments must be held
with some degree of strength, and/or with a great deal of
precision. Frequently, the instruments must be held for extended
periods of time, causing fatigue in the practitioner holding the
instrument, and increasing their risk of the instrument being held
with less strength and/or precision than is desirable.
[0004] Such instruments are often repositioned several times
throughout a surgical procedure. Moreover, such instruments must be
placed and held in positions that do not interfere with a doctor's
access to various portions of the patient's body. Furthermore, all
devices used in a surgical field must either be sterile, or
shielded from a patient by a sterile barrier.
[0005] Several fixtures for holding retractors and other
instruments have been introduced to the industry. Such fixtures
tend to be manually intensive and cumbersome, requiring significant
labor to position and lock in place. Additionally, many of these
fixtures have limited range of motion, often with discrete position
settings that can limit their usefulness. Some forms of
multi-joint, arm-like support structures are cumbersome and require
two-handed operation and/or foot pedal operation, adding complexity
to the procedure. While such fixtures might provide consistent
holding power, their limited configurations and complex methods of
reconfiguring might make their use frequently impractical in the
surgical field.
[0006] Accordingly, there has existed a need for a medical
instrument fixture that is easily and quickly configurable, and
provides consistent holding power for instruments. Moreover, the
fixture needs to meet the requirements of being usable in a
surgical field. Typical embodiments of the present invention
satisfy these and other needs, and provide further related
advantages.
SUMMARY OF THE INVENTION
[0007] In various embodiments, the present invention solves some or
all of the needs mentioned above, providing a jointed fixture for
holding an object such as a surgical instrument. The fixture
includes a base unit, a hub configured to detachably hold the
instrument, and a group of one or more arms serially connected by a
plurality of joints between the base unit and the hub. The joints
are typically ball joints that have a ball, a body containing a
portion of the ball, a brake element, and an electromagnetic brake
mechanism configured to actuate the brake element between a locked
state wherein the brake element, presses against the ball with a
force adequate to fix the orientation of the ball, and an unlocked
state, wherein the brake element does not press against the ball
with a force as high as that of the locked state.
[0008] Advantageously, such embodiments provide for a fixture
having a high degree of positional flexibility and ease-of-use.
More particularly, the plurality of arms and the plurality of ball
joints provides for a fixture that can place a surgical instrument
in a given position with a variety of different configurations,
thereby avoiding configurations that would obstruct a medical
practitioner's work. Moreover, the electromagnetic brakes provide
for a fixture configuration that is strong, and yet can be locked
and unlocked rapidly with the press of a single button.
[0009] The invention may further provide for lever arms that
leverage the force of the electromagnetic actuators to increased
levels of force. Such lever arms advantageously allow the use of
electromagnets that consume less power and are smaller, lighter in
weight and less expensive.
[0010] The invention may further provide the fixture with ball
joint centering mechanisms that bias ball joint positions toward a
single, neutral (center) position. Such centering mechanisms
typically provide the fixture with a single, predictable
configuration (or limited number of configurations) having a
minimum potential energy for most any position of the surgical
instrument. Moreover, the invention may further provide for a level
of joint rigidity while the joints are unlocked.
[0011] Thus, for any surgical-instrument position, the fixture will
have a natural and predictable, low-energy configuration toward
which it tends to move, and a medical practitioner can adjust to
other configurations as desired prior to locking the ball joints.
Moreover, the joint rigidity of the fixture will tend to resist
movement even when unlocked, thereby providing the fixture a supple
yet damped movement that is not limp or susceptible to significant
oscillation.
[0012] A surgical drape may be used to cover the fixture to
maintain the sterility of a surgical field, the drape having a
headpiece that is intermediate the distal end of the fixture and
the surgical instrument. A switch to control the electromagnetic
locks may be provided at the distal end of the fixture and within
the drape. An actuator may be placed on or adjoining the surgical
instrument and external to the drape, the actuator being configured
to actuate the switch through a hermetically sealed portion of the
headpiece. A medical practitioner may therefore control the
position of the surgical instrument and control the electromagnetic
brakes with a single hand external to the drape, leaving the other
hand free, and not exposing the surgical field to possible
contaminants on the fixture.
[0013] A control system of the invention is configured to actuate
the electromagnetic brake mechanisms with a voltage profile
characterized by a first, transient portion and a second,
steady-state portion that is less than the transient portion in
voltage level. Advantageously, the voltage profile provides for the
electromagnets to initially assure that they fully actuate to apply
maximum locking forces on the ball joints, and do so without
needing to use electromagnets large enough to maintain such power
levels for extended periods, and without using the power required
to maintain such high power levels throughout a surgical
procedure.
[0014] Other features and advantages of the invention will become
apparent from the following detailed description of the described
embodiments, taken with the accompanying drawings, which
illustrate, by way of example, the principles of the invention. The
detailed description of particular described embodiments, as set
out below to enable one to build and use an embodiment of the
invention, are not intended to limit the enumerated claims, but
rather, they are intended to serve as particular examples of the
claimed invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a perspective view of a surgical retractor
attached to a multi-joint fixture that includes a headpiece of a
surgical drape, with a sterile curtain of the surgical drape and
three tethers not being depicted.
[0016] FIG. 2 is a perspective view of the surgical drape of FIG.
1, including a shortened view of the sterile curtain that was not
depicted in FIG. 1.
[0017] FIG. 3 is a front cross-section view of a ball joint as used
in the multi-joint fixture depicted in FIG. 1.
[0018] FIG. 4A is an exploded rear perspective view of a third ball
joint, a fixture hub, and the headpiece of the multi-joint fixture,
as depicted in FIG. 1.
[0019] FIG. 4B is a rear view of the third ball joint, the fixture
hub, and the headpiece depicted in FIG. 4A.
[0020] FIG. 5A is a perspective view of the fixture hub depicted in
FIG. 4A.
[0021] FIG. 5B is a second perspective view of the fixture hub
depicted in FIG.4A.
[0022] FIG. 6 is a perspective view of the headpiece depicted in
FIG. 4A.
[0023] FIG. 7A is a perspective view of a surgical-instrument
adapter as used in the multi-joint fixture depicted in FIG. 1.
[0024] FIG. 7B is a left side view of the surgical-instrument
adapter depicted in FIG. 7A.
[0025] FIG. 8 is a rear cross-sectional view of the third ball
joint, the fixture hub, and the headpiece depicted in FIG. 4A, with
the surgical-instrument adapter of FIG. 7 connected to the
headpiece.
[0026] FIG. 9 is a system diagram of a multi-joint fixture system,
including the retractor and multi-joint fixture depicted in FIG.
1.
[0027] FIG. 10. is a front cross-section view of a second
embodiment of a ball joint that could be used in the multi-joint
fixture depicted in FIG. 1.
[0028] FIG. 11. is a system diagram of a third embodiment of a ball
joint that could be used in the multi-joint fixture depicted in
FIG. 1.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0029] The invention summarized above and defined by the enumerated
claims may be better understood by referring to the following
detailed description, which should be read with the accompanying
drawings. This detailed description of particular described
embodiments of the invention, set out below to enable one to build
and use particular implementations of the invention, is not
intended to limit the enumerated claims, but rather, it is intended
to provide particular examples of them.
[0030] Typical embodiments of the present invention reside in a
jointed fixture system for use in surgical procedures with an
operating table, the various components of the system, and methods
of using the same.
[0031] With reference to FIG. 1, a first embodiment of the
invention forms a multi-joint fixture for holding a surgical
instrument 101 such as a surgical retractor (shown), an endoscope,
a limb positioner, or the like. In this context, the term
instrument should be understood to include any useful object that a
medical practitioner might wish to be held stationary during
surgery.
[0032] The fixture includes a base unit 103, a first joint 105, a
first arm 107, a second joint 109, a second arm 111, a third joint
113 and a fixture hub 115. The first joint adjustably connects a
proximal end of the first arm to the base unit, the second joint
adjustably connects a proximal end of the second arm to a distal
end of the first arm, and the third joint adjustably connects the
fixture hub to a distal end of the second arm. The fixture thus
includes a plurality of three joints interconnecting a plurality of
four members (including the two arms), each joint having an
attached member to which it is rigidly attached and a connected
member that it can allow to rotate with respect to the attached
member.
[0033] Typically, the first joint is rigidly attached to the base
unit and is connected to the first arm, the second joint is rigidly
attached to the first arm and is connected to the second arm, and
the third joint is rigidly attached to the second arm and is
connected to the fixture hub. This series of connections prevents
each joint from having to carry its own weight, potentially making
the multi-joint fixture a more reliable and stable device.
[0034] Each ball joint defines a longitudinal axis, along which its
elements are positioned. The longitudinal axis also forms a neutral
position for the ball joint, which will be referred to as a center
position. The first ball joint 105 is configured with its
longitudinal axis aligned with (and passing through the center of)
its attached member (the base 103) and aligned with the general
direction of its connecting member (the first arm 107). The second
ball joint 109 is configured with its longitudinal axis
perpendicular to the general directions of both its attached member
(first arm 107) and its connected member (second arm 111). The
third ball joint 113 is configured with its longitudinal axis
perpendicular to the general direction of its attached member
(second arm 111), but aligned with its connecting member (the
fixture hub 115).
[0035] With reference to FIGS. 1 & 2, the fixture hub 115 is
configured to detachably receive and connect to a headpiece 117 of
a sterile surgical drape. The headpiece is configured with a drape
hub to detachably receive and connect to (and thereby hold) a
surgical-instrument adaptor 119 that is attached to the surgical
instrument 101.
[0036] The surgical drape includes a sterile curtain 121 (not
depicted in FIG. 1) that is generally tubular in shape (tapering
slightly from a smaller diameter at a distal end near the headpiece
to a larger diameter at a proximal end) and at least as long as the
entire multi-joint fixture. The headpiece 117 is internally
configured to form a sterile barrier. At the distal end, the
sterile curtain is hermetically sealed around a periphery of the
headpiece. Thus, with the headpiece connected to the fixture hub
115, the surgical drape can be extended over the multi-joint
fixture before a surgical procedure, thereby maintaining a sterile
environment in the surgical field without having to sterilize the
multi-joint fixture itself. The sterile drape will typically be a
single-use, disposable device that is provided in a sterile state
within hermetically sealed packaging.
[0037] The base unit 103 is typically mounted to a rail clamp 123,
which is configured with a mechanism to clamp onto a rail of an
operating table. The clamping mechanism can be a screw clamp as is
commonly used, or a quick connect mechanism, as is depicted.
Alternatively, the base unit may be otherwise positioned with
respect to the operating table, for example, being attached to a
floor stand or permanently affixed (i.e., not readily removable
from) the operating table or some nearby device.
[0038] The plurality of ball joints (i.e., the fist, second, and
third ball joints) are each configured with an electromagnetic
brake that can be actuated between a locked and an unlocked state.
In the locked state each ball joint is locked from any rotational
movement, thereby firmly holding the members that the joint
connects in a substantially rigid relationship. Thus, in their
locked states, the first ball joint 105 holds the base unit 103 and
the first arm 107 in a substantially rigid relationship, the second
ball joint 109 holds the first arm 107 and the second arm 111 in a
substantially rigid relationship, and the third ball joint 113
holds the second arm 111 and the fixture hub 115 in a substantially
rigid relationship. In this context, the term substantially rigid
should be understood to indicate that it is rigid enough to hold
surgical instruments, such as retractors, with adequate force for
use in surgery.
[0039] In the unlocked state, each ball joint is free to allow
movement between the members that the joint connects without the
application of undue force. Thus, in their unlocked states, the
plurality of ball joints provide for the surgical instrument 101 to
be positioned in a wide variety of positions (i.e., locations and
orientations). Additionally, for most surgical-instrument
positions, the arms and ball joints can be placed in a variety of
configurations so as to avoid obstructing the work of medical
practitioners. Moreover, while this system has an arm-like
configuration wherein the first, second and third joints
effectively operate as shoulder, elbow and wrist joints,
respectively, it has even greater flexibility of configuration than
a human arm, in that it uses three ball joints.
[0040] The surgical-instrument adaptor 119 includes a
surgical-instrument switch actuator 125 that can be actuated by a
medical practitioner between a free position and an actuated
position. This surgical-instrument switch actuator is biased by a
spring toward the free position. The surgical-instrument switch
actuator is part of a switch system configured such that, when the
surgical-instrument switch actuator is in the free position, the
electromagnetic brake of each ball joint is actuated to the locked
state, and when the surgical-instrument switch actuator is in the
actuated position the electromagnetic, brake of each ball joint is
actuated to the unlocked state. Optionally, the switch system may
be adapted as a multiple position switch system, or as a system
including a plurality of switches, to separately control the
actuation of the electromagnetic brakes of the ball joints so that
various combinations of the electromagnetic brakes can be actuated
without actuating the remaining brake(s).
[0041] While it is advantageous for medical practitioners to have
flexibility of fixture configuration for desired
surgical-instrument positions, it is also advantageous for
movements of the fixture to be predictable and supple, but not
limp. To this end, each ball joint is configured with a centering
mechanism 129 that provides a spring-based or spring-like restoring
force that biases (i.e., actuating or driving) the ball of the ball
joint to a neutral (center) position (i.e., location and/or
orientation). As a result, for every surgical-instrument position
there will typically be a fixture configuration having the lowest
combined potential energies of the three centering mechanisms, and
the fixture will tend toward moving to that fixture configuration
unless stopped by some other force (such as optional manipulation
by a medical practitioner). Center, in this context, should be
understood as referring to the central position of the spring
bias.
[0042] While in the unlocked state, each ball joint may maintain
some joint rigidity (i.e., resistance to movement) between the
members that the joint connects. The typical level of resistance is
set at a level high enough to damp the motion of the fixture and
avoid sloppiness and oscillation, and low enough to provide for a
medical practitioner to easily manipulate the location of the
surgical instrument and the configuration of the fixture. It is
noteworthy that the joint rigidity will frequently work against the
restoring force of the centering mechanism 129. The combination of
the joint rigidity with the restoring force provides for a fixture
that can be positioned and used with a minimum of attention and
effort.
[0043] With reference to FIGS. 1 & 3, each of the ball joints
includes an outer housing 151, a ball, the ball-centering
mechanism, and the electromagnetic brake mechanism. The outer
housing is affixed to or unitary with the rigidly attached member.
The ball includes a spherical portion 153 and a shaft 155. The
shaft extends from a proximal end affixed to the spherical portion
to a distal end, the distal end serving as an attachment point for
the connected member.
[0044] The joint of this embodiment is modular, having an inner
housing that is removably received within the outer housing 151
along the longitudinal axis. The inner housing includes a first
housing portion 161, a second housing portion 163 and a third
housing portion 165 serially connected with threaded connections.
The electromagnetic brake is comprised of the inner housing, an
electromagnet 167, a draw-plate 169, a plurality of three lever
arms 171, a keel 173, a spring element in the form of a Belleville
washer 175, a thrust-cup 177, and a first hardened ring 179 (the
brake ring). The second housing portion 163 is provided with a
hardened reaction ring 181, and the third housing portion 165 is
provided with a second hardened ring 183 (the retaining ring). Each
hardened ring is characterized by a central axis that is concentric
with and parallel to the longitudinal axis of the ball joint.
[0045] A screw 185 is inserted along the longitudinal axis, through
the outer housing 151 and the inner housing first housing portion
161, to be threadedly received in the electromagnet 167, thereby
holding the electromagnet and the first housing portion rigidly
with respect to the outer housing portion. The second housing
portion 163 is threadedly received along the longitudinal axis on
the first housing portion, and contains the draw-plate 169, which
is held apart from the electromagnet (as described below) along the
longitudinal axis at a distance creating a small air gap (between
the electromagnet and the draw-plate) normal to the longitudinal
axis (i.e., the gap generally establishes a plane to which the
longitudinal axis is perpendicular).
[0046] The draw-plate 169 includes three posts 187 defining holes
for three pins 189 that connect the draw-plate to the three lever
arms 171, but allow each lever arm to rotate around its respective
pin. The lever arms extend radially outward from the draw-plate
posts, circumferentially spaced at 1200 angles, over the reaction
ring 181, such that an outer end of each lever arm contacts the
keel 173 at locations radially outside of the reaction ring.
[0047] The third housing portion 165 is threadedly received along
the longitudinal axis on the second housing portion 163. Using a
shim 191, the longitudinal spacing of the second and third housing
portions is set such that the keel 173 presses down against the
outer ends of the lever arms 171, making the lever arms act as
levers, with the reaction ring 181 acting as their fulcrums, to
pull the draw-plate 169 away from the electromagnet 167 and
establish the gap (i.e., the air gap between the draw-plate and the
electromagnet, through which the draw-plate can be actuated by the
electromagnet).
[0048] The third housing portion 165 contains a substantial part of
the ball, and the shaft 155 extends out from an orifice 193 of the
third housing portion. The first and second hardened rings 179
& 183 have diameters smaller than the diameter of the spherical
portion 153 of the ball. They are concentrically located along the
ball joint longitudinal axis on longitudinally opposite sides of
the center of the spherical portion, and are in contact with the
spherical portion. The second hardened ring 183 is a retaining ring
in that it retains the spherical portion of the ball within the
housing, thus making the joint a non-separable joint (i.e., the
ball cannot separate from the assembled joint). The thrust cup 177
is configured to drive the first hardened ring along the
longitudinal axis toward the second hardened ring such that these
two rings hold the spherical portion in place and frictionally
resist its rotational movement.
[0049] When the second and third housing portions 163 & 165 are
threadedly attached and properly shimmed, the Belleville washer 175
is compressed between the thrust cup 177 and the keel 173, defining
relaxed-state reaction forces between the thrust cup and the keel.
The relaxed-state reaction force on the thrust cup drives the first
hardened ring towards the second hardened ring and against the
spherical portion of the ball. The longitudinal length of the shim
191 and a spring constant of the Belleville washer 175 are
configured such that the relaxed state reaction force on the thrust
cup drives the first hardened ring towards the second hardened ring
with the proper amount of force to establish the joint rigidity of
the ball joint, and thus the presence of the relaxed-state reaction
force establishes the unlocked state of the ball joint.
[0050] The relaxed-state reaction force on the lever arm by the
keel is reacted over the reaction ring 181, pulling the draw-plate
169 away from the electromagnet 167, to maintain the gap. The
configuration of the reaction ring and the lever arms provides a
four to one leverage ratio for each lever arm. Thus, the
longitudinal force between the keel and each lever arm is four
times the longitudinal force between each lever arm and the
draw-plate. When the electromagnet is not energized, there are no
system forces drawing the draw-plate toward the electromagnet
against the pull of the lever arms.
[0051] The electromagnet 167 is not energized when the
surgical-instrument switch actuator 125 is actuated to the actuated
position. When the surgical-instrument switch actuator is released,
a spring bias actuates the surgical-instrument switch actuator to
the free position, which causes the electromagnet to be energized.
The energized electromagnet draws the draw-plate 169 down toward
the electromagnet to close the gap. The draw-plate in turn pulls an
inner end of each lever arm 171 down over its portion of the
reaction ring 181 which acts as a fulcrum for the lever arm to push
up on the keel 173. Because of the four to one leverage of each
lever arm, the keel is pushed with four times as much force as the
draw-plate is pulled down by the electromagnet.
[0052] The upward movement of the keel 173 further compresses the
Belleville washer 175, defining energized-state reaction forces
between the thrust cup and the keel. The energized-state reaction
force on the thrust cup presses the first hardened ring 179 against
the spherical portion of the ball and towards the second hardened
ring 183 to statically hold the spherical portion of the ball and
lock the ball joint from any rotational movement, thereby firmly
holding the members that the joint connects in a substantially
rigid relationship. The presence of the energized-state reaction
force establishes the locked state of the ball joint.
[0053] Thus, each ball joint has an electromagnetic brake mechanism
configured to switch between locked and unlocked states, wherein
the orientation of the ball within the body is statically held when
the brake mechanism is in the locked state, and wherein the
application or removal of electrical energy switches the brake
mechanism between the locked and unlocked states. Relative to the
unlocked state, in the locked state the keel is actuated toward the
ball and the thrust cup and first hardened ring press against the
ball with greater force.
[0054] Each ball joint 105, 109 & 113 is further configured
with a neutral-bias centering mechanism 129 in the form of a
retaining cap 195 and a spring 197 spiraling in three dimensions
(such as in the shape of a conical spring). The spring is
concentric with the longitudinal axis, and extends longitudinally
from a wide-radius end to a small-radius end. The wide-radius end
is received in helical grooves around an exterior of the third
housing portion 165, longitudinally closer to the center of the
spherical portion 153 of the ball. The small-radius end is wound
around, and thereby connected to, a bushing 157 located distantly
along the shaft 155. The retaining cap surrounds the wide-radius
end of the spring and retains it in place.
[0055] This spring 197 is configured to laterally react against the
shaft 155 so as to drive it laterally back toward the neutral
position on the longitudinal axis when it is not already there.
Optionally, this spring may also be configured to react against the
shaft in axial rotation so as to rotate it back to a neutral
position orientation. Additionally, the spring may be preloaded
such that it axially pulls the shaft away from the third housing
portion, thus preloading the spherical portion of the ball against
the second hardened ring, and thereby contributing to the joint
rigidity of the ball joint.
[0056] The ball joint of this first embodiment is of a linear
configuration in that its actuation and braking elements (e.g., an
electromagnet, a draw-plate that establishes a closable gap with
the electromagnet, and a plurality of brake elements) extend along
a single longitudinal axis, along which its electromagnet gap is
closed and its primary brake elements (the first and second
hardened rings) and secondary brake elements (the third housing
portion and the thrust cup) react. It is also of a levered
configuration that leverages the electromagnet force, in that the
three lever arms provide a four to one mechanical advantage,
allowing for a smaller electromagnet to be used to produce a given
level of force.
[0057] With reference to FIGS. 1, 2, 4A, 4B, 5A & 5B, the
fixture hub 115 is longitudinally received on the shaft 155 of the
third joint ball (i.e., longitudinally along the ball joint axis).
The fixture hub includes a body 201 that is pinned or otherwise
affixed to the shaft. A cover plate 203 (not shown in FIG. 4A) is
attached to the body on a distal side of the body, and defines four
slots 205 for receiving four pins 211 of the headpiece 117. A lock
ring 207 is held intermediate the cover plate and the body. The
lock ring can rotate between an open position and a locked
position, and is spring biased toward the locked position. The lock
ring has four tabs 209 that extend partially a cross the four slots
of the cover plate when the lock ring is in the locked position,
but not when it is in the open position, thus configuring the
fixture hub to removably receive the headpiece.
[0058] The fixture hub 115 includes an electrical switch 212 facing
distally on its distal side. This electrical switch, which is a
part of the switch system, forms an electrically closed circuit
when in a not-pressed state, and an electrically open circuit when
in a pressed state. The electrical switch is directly wired to a
tether connector 127 (not shown in FIGS. 4A, 4B, 5A & 5B) of
the fixture hub, and is in control of the electromagnetic brakes of
each joint (as is described later). When the fixture hub does not
have a headpiece 117 attached thereon, the electrical switch may be
manually actuated by a medical practitioner to unlock the
electromagnetic brakes of the three joints when pressed (to form an
open circuit), and to lock the electromagnetic brakes of the three
joints when released (to form a closed circuit).
[0059] The headpiece 117 includes a body 213, a headpiece switch
actuator 215, a base plate 217, a flexible button pad 219, and the
four pins 211 that are received by the fixture hub. The pins extend
proximally from a proximal face of the headpiece. The pins include
grooves 221 in which the tabs 209 of the lock ring 207 can be
received to lock the headpiece onto the fixture hub 115 when the
proximal face of the headpiece is received against the cover plate
203 on the distal side of the fixture hub.
[0060] The headpiece body 213, which may be formed in two halves
and assembled, contains the headpiece switch actuator 215, which is
a part of the switch system. The headpiece switch actuator extends
longitudinally through the headpiece body, from a distal knob 223
to a proximal tip 225. The distal knob extends distally beyond a
distal end of the headpiece body. The proximal tip extends through
an orifice in the center of the base plate 217 and presses against
the button pad 219, which extends across a proximal face of the
base plate (which in turn forms the proximal face of the
headpiece). The headpiece switch actuator is longitudinally
slidable from a distal position to a proximal position, and may be
spring loaded toward the distal position.
[0061] With the headpiece 117 attached to the fixture hub 115, the
proximal tip 225 of the headpiece switch actuator 215 is in close
proximity to the electrical switch 212 of the fixture hub 115, with
the button pad 219 extending therebetween. With the headpiece
switch actuator 215 in its distal position, the electrical switch
is in its not-pressed state. When the headpiece switch actuator is
slid from its distal position to its proximal position, the
proximal tip of the headpiece switch actuator flexibly extends the
button pad and presses the electrical switch, causing the
electrical switch to form an open circuit.
[0062] Because the distal knob 223 extends distally from the distal
end of the headpiece body, a medical practitioner may manually
actuate the electrical switch by pressing on the distal knob. Thus,
the medical practitioner can still actuate and release the
electrical switch when the surgical drape is received on the
multi-joint fixture over the electrical switch (i.e., when the
headpiece 117 is connected to the fixture hub 115 and the sterile
curtain 121 is extended over the multi-joint fixture).
[0063] The button pad 219 is hermetically sealed to the base plate
217, and the sterile curtain 121 is hermetically sealed around the
periphery of the base plate. Thus, the surgical drape effectively
forms a complete sterile barrier between a patient in the surgical
field and the multi-joint fixture.
[0064] With reference to FIGS. 2, 4A, 4B & 6, the headpiece
body 213 defines a headpiece hub in the form of a protrusion having
a generally square cross-section, a distal end of which forms the
distal face of the headpiece body from which the distal knob 223
protrudes. The hub protrusion forms a groove 227 around its
perimeter, and four access holes 229, one access hole being on each
side of the square perimeter. The four access holes provide
external access from all four sides of the protrusion to an
intermediate knob 231 on the headpiece switch actuator 215
intermediate its distal knob 223 and its proximal tip 225.
[0065] Both the distal knob 223 and the intermediate knob 231 form
conical surfaces concentric with the longitudinally extending
headpiece switch actuator 215. The conical surfaces extend from a
wide radius at a proximal end of each knob to a narrow radius at a
distal end of the knob. As a result, a lateral force against the
conical face of either knob will tend to drive the headpiece switch
actuator toward its proximal position.
[0066] With reference to FIGS. 1, 7A, 7B & 8, the
surgical-instrument adapter 119 includes a connector 233, a
lockdown 235, and the surgical-instrument switch actuator 125. The
lockdown 235 is configured to rigidly clamp the surgical instrument
101 onto, and affix (connect) it to, the connector 233. In use, it
is anticipated that a different surgical-instrument adapter will be
permanently affixed to each surgical instrument to be used with the
multi-joint fixture. Thus, each surgical-instrument adapter is
constructed to withstand repeated sterilization and use with its
surgical instrument. Optionally, the surgical-instrument adapter
and the surgical instrument may be integral, offering cost, weight
and size advantages in the construction and use of the resulting
surgical instruments with integral adapters.
[0067] The surgical-instrument adapter connector 233 is configured
with flanges 234 sized and spaced to be conformingly received over
the groove 227 of the headpiece hub. The connector 233 and
headpiece hub are mutually configured such that the connector can
be placed onto any of the four sides of the hub, and oriented in
either of the two lateral directions for that hub-side, thereby
forming a total of eight different connection configurations. The
connector 233 is further configured with a spring-loaded connector
lock mechanism 236 having a tab 237 positioned for gripping the
headpiece hub when the connector is received on the hub, thus
making the connector quickly detachable from the hub.
[0068] The surgical-instrument switch actuator 125 is hingedly
attached along a hinge axis to the connector 233 and lockdown 235.
The surgical-instrument switch actuator includes two pins 239, each
extending down through a separate orifice that extends through the
connector 233 and lockdown 235. The pins are offset from the hinge
axis such that each pin is driven down through its respective
orifice when the surgical-instrument switch actuator is actuated
from its free position to the actuated position, such as by a
finger of a medical practitioner. The surgical-instrument switch
actuator further includes two springs configured to drive the
surgical-instrument switch actuator and each pin back up when the
medical practitioner's finger releases the surgical-instrument
switch actuator, allowing it to return to its free position.
[0069] The pins 239 are positioned and oriented on the connector
233 such that, with the connector received on the headpiece hub,
each pin aligns with and extends to the conical surface of one knob
of the headpiece switch actuator 215. The four access holes 229 are
configured to provide the pins access to the intermediate knob 231
from any of the four sides of the hub. No access holes are required
to reach the distal knob 223, as it extends distally outward from
the distal end of the headpiece body.
[0070] Accordingly, for a given configuration of the
surgical-instrument adapter 119 mounted on the headpiece hub, a
first pin will press against the distal knob 223, and a second pin
will press against the intermediate knob 231. Thus, when the
surgical-instrument switch actuator is pressed, the pins drive the
conical surfaces of both knobs of the headpiece switch actuator to
press the electronic switch. It may be noted that when the
surgical-instrument adapter 119 is repositioned on the headpiece
hub such that it is on the same side of the hub, but extending in
the opposite lateral direction, the pin positions will be reversed
and the first pin will press against the intermediate knob 231,
while the second pin presses against the distal knob 223.
[0071] The surgical-instrument adapter 119 is adapted to be
connected to the surgical instrument 101 in a position where the
surgical-instrument switch actuator 125 can be conveniently
actuated by a medical practitioner's hand that is holding the
surgical instrument. Using just one hand a medical practitioner may
both hold the surgical instrument and manually actuate the
electrical switch 212 by pressing on the surgical-instrument switch
actuator 125. Thus, with one hand the medical practitioner can hold
the surgical instrument and actuate or release the electromagnetic
brakes while the surgical drape is received on the multi-joint
fixture and the surgical instrument is attached to the headpiece of
the surgical drape.
[0072] As described above, this switch system, which controls the
electromagnetic brake of each joint, includes the electrical switch
212 on the fixture hub 115, the headpiece switch actuator 215 on
the headpiece of the surgical drape, and the surgical-instrument
switch actuator 125 on the surgical-instrument adapter 119, which
is connected to the surgical instrument 101. The electrical switch
212 may be directly accessed when the surgical drape is not
connected to the fixture hub. The electrical switch may be
indirectly accessed by pressing on the headpiece switch actuator
when the surgical drape is connected to the fixture hub, but no
surgical instrument is connected to the headpiece of the surgical
drape. And finally, the electrical switch may be indirectly
accessed by pressing on the surgical-instrument switch actuator 125
when the surgical drape is connected to the fixture hub and a
surgical instrument is connected to the headpiece of the surgical
drape.
[0073] In an alternative variation, the headpiece body may be
unitary, and may extend longitudinally past the distal knob. In
this variation, the body will define an additional four access
holes for the surgical-instrument adapter pin that is to contact
the distal knob. Also, the switch actuator has a distal extension
extending past the distal knob, providing manual access to the
headpiece switch actuator when the surgical drape is connected to
the fixture hub, but no surgical instrument is connected to the
headpiece of the surgical drape.
[0074] With reference to FIGS. 1 & 9, to facilitate
communication between the switch system and each electromagnetic
brake, each arm forms a hollow tube in which electrical wiring
extends. At either end of each arm wiring exits the hollow tube via
a tether connector 127. Tether connectors are also located on the
base unit 103 and the fixture hub 115 (as noted above). External,
hollow tethers 241 extend between tether connectors on either side
of each joint. Each tether provides a passageway for the wiring to
extend between externally around a given joint, between the tether
connectors on immediately on either side of the joint. The wiring
also extends directly into each joint, to its electromagnetic
brake, from the member to which the joint is rigidly attached. The
tethers are configured long enough and flexibly enough (possibly in
a wound cord configuration) to allow for significant free movement
of the joints.
[0075] The electrical wiring of the system connects via the tether
connector 127 on the base unit 103 to an electrical connector 243
on the base unit. The electrical connector 243 connects to an
electronic control system 245 integrated into a system cart 247.
The system cart is further provided with drawers 249 that are
configured with one or more compartments with holding devices to
conformingly receive and store the multi-joint fixture, and a
supply of packaged, unused surgical drapes, and the like, when the
device is not in use. Alternatively, the cart could have open
compartments behind a cabinet-type door, or even in an open
cabinet.
[0076] The electronic control system is configured to power and
control the electromagnetic brakes. Furthermore, it is configured
to do so in response to signals from the electrical switch. More
particularly, it is configured to energize the electromagnetic
brakes to be locked when the switch forms an electrically closed
circuit (i.e., when the switch is released to be in a not-pressed
state), and to leave the electromagnetic brakes unlocked when the
switch forms an electrically open circuit (i.e., when the switch is
in a pressed state). Additionally, the electronic control system is
configured to transition the electromagnets from being unlocked to
being locked with the application of a non-typical voltage profile
to the electromagnetic brakes.
[0077] More particularly, the applied voltage profile in the
transition includes a first-in-time, transient portion and a
second, steady-state portion. The transient portion reaches a
transient voltage significantly greater than the steady-state
portion voltage, wherein a voltage difference between the transient
and steady-state levels is considered significant when it
appreciably changes the electromagnet's ability to fully close the
gap (between the electromagnet and the draw-plate) and thereby lock
the joint (i.e., it appreciably changes the likelihood of the gap
closing). Typical anticipated values include that the transient
level is approximately twice the steady-state level, and that the
transient level is significantly greater than the steady-state
level.
[0078] While assembled with a surgical drape, the actuation of the
electrical switch of this embodiment occurs indirectly and
physically through the use of manual actuators, namely the
surgical-instrument switch actuator and/or the headpiece switch
actuator. Alternative variations of this embodiment can be
configured with electrical actuators, i.e. electrical switches on
the surgical drape headpiece and the surgical-instrument adapter.
In such variations, the surgical drape headpiece would require
electrical contacts that extend on both sides of the base plate to
provide electrical communication through the sterile barrier
provided by the surgical drape. The headpiece and/or fixture
connector may also include shielding to prevent interaction with
other operating room systems.
[0079] Additionally, alternative variations of this embodiment can
be configured with electromagnetic actuators, i.e. the
communication of switch signals through the surgical drape sterile
barrier via electromagnetic fields. In such variations, a field
could be intermittently generated on one side of the sterile
barrier and its presence (or lack thereof) could be sensed on the
other side of the sterile barrier to communicate a switch signal.
Likewise, a field generated on one side of the sterile barrier
could be manipulated by moving conductors on the other side of the
sterile barrier to communicate a switch signal. The headpiece
and/or fixture connector may also include shielding to prevent
interaction with other operating room systems.
[0080] Furthermore, alternative variations of this embodiment can
be configured with a headpiece having an actuator that extends in
reach of the surgical instrument even while the surgical instrument
is attached to the headpiece. In this variation a
surgical-instrument switch actuator is not necessary (though it
still might be desirable). Moreover, the surgical-instrument
connector could be integral with the headpiece.
[0081] A second embodiment of the invention is configured similar
to the first embodiment, except for the second and third ball
joints, which have an offset (and levered) configuration. More
particularly, with reference to FIG. 10, each of the offset ball
joints includes a primary housing 251, a ball, a ball-centering
mechanism of the type described for the first embodiment, and an
electromagnetic brake mechanism. The outer housing is affixed to or
unitary with the rigidly attached member for that ball joint. More
particularly, the outer housing of the second ball joint is affixed
to or unitary with the first arm, and the outer housing of the
third ball joint is affixed to or unitary with the second arm.
[0082] Similar to the first embodiment, the ball includes a
spherical portion 253 and a shaft 255. The shaft extends from a
proximal end at the spherical portion to a distal end, the distal
end serving as an attachment point for the connected member. The
ball joint defines a ball longitudinal axis that forms a neutral
position for the ball and the centering mechanism. As in the first
embodiment, the second ball joint is configured with its ball
longitudinal axis perpendicular to the general directions of both
its attached member and its connected member, and the third ball
joint is configured with its ball longitudinal axis perpendicular
to the general direction of its attached member, but aligned with
and passing through the center of its connecting member (the
fixture hub).
[0083] Unlike the first embodiment, this particular embodiment is
not equipped with a removable inner housing. Instead, the primary
housing 251 reacts all housing loads. The primary housing forms a
tub-like structure defining a ball cavity 261 in the bottom of the
tub and concentric with the ball longitudinal axis, a magnet cavity
263 in the bottom of the tub and concentric with an electromagnet
longitudinal axis, and an open top that is covered by a housing
cover 265. The electromagnet longitudinal axis is parallel to and
offset from the ball longitudinal axis.
[0084] The electromagnetic brake is comprised of an electromagnet
267, a draw-plate 269, a lever arm 271, a thrust-cup 277, and a
first hardened ring 279. The primary housing 251 is provided with a
reaction joint 281 and a second hardened ring 283. Each hardened
ring is characterized by a central axis that is concentric with and
parallel to the ball longitudinal axis.
[0085] A screw 285 is inserted through the primary housing 251 to
be threadedly received in the electromagnet 267 along the
electromagnet longitudinal axis, thereby holding the electromagnet
rigidly with respect to the primary housing. The lever arm 271
holds the draw-plate 269 spaced from the electromagnet along the
electromagnet longitudinal axis at a distance creating a small gap
normal to the longitudinal axis. The draw-plate includes a post 287
defining a hole for a pin 289 that connects the draw-plate to the
lever arm, but allows the lever arm to rotate with respect to the
draw-plate. The lever arm extends laterally between the ball
longitudinal axis and the electromagnet longitudinal axis,
connecting the draw-plate to the thrust-cup 277.
[0086] The primary housing reaction joint is located such that the
lever arm acts as a lever, with the thrust-cup acting as its
fulcrum, to pull the draw-plate 269 away from the electromagnet 267
and establish the gap between the draw-plate and the
electromagnet.
[0087] The primary housing 251 contains a substantial part of the
ball, and the shaft 255 extends out from an orifice 293 of the
primary housing. The first and second hardened rings 279 & 283
have diameters smaller than the diameter of the spherical portion
253 of the ball. They are concentrically located along the ball
longitudinal axis on longitudinally opposite sides of the center of
the spherical portion, and are in contact with the spherical
portion. The thrust cup 277 is configured to drive the first
hardened ring along the ball longitudinal axis toward the second
hardened ring to hold the spherical portion in place and
frictionally resist its rotational movement.
[0088] Advantageously, the lever arm can be preloaded, thereby
incorporating the functions of the keel and the Belleville washer
of the first embodiment. More particularly, the draw-plate 269 can
be preloaded from above such that the lever arm is configured to
form relaxed-state reaction forces between the thrust cup and the
draw-plate. The relaxed-state reaction force on the thrust cup
drives the first hardened ring towards the second hardened ring and
against the spherical portion of the ball. These components are
configured such that the relaxed state reaction force on the thrust
cup drives the first hardened ring towards the second hardened ring
with the proper amount of force to establish the joint rigidity of
the ball joint, and thus the presence of the relaxed-state reaction
force establishes the unlocked state of the ball joint.
[0089] The relaxed-state reaction force draws the draw-plate 269
away from the electromagnet 267 and maintains the gap. The
configuration of the reaction joint and the lever arm provides a
four to one leverage ratio. Thus, the longitudinal force between
the thrust-cup and the lever arm is four times the longitudinal
force between the lever arm and the draw-plate (i.e., the
electromagnet force is leveraged to a higher value). When the
electromagnet is not energized, there are no system forces drawing
the draw-plate toward the electromagnet against the pull of the
lever arms.
[0090] As in the first embodiment, the electromagnet 267 is not
energized when the switch is actuated to the actuated position.
When the switch is released, a spring bias actuates the switch to a
free position, which causes the electromagnet to be energized. The
energized electromagnet draws the draw-plate 269 toward the
electromagnet to close the gap. The drawn-down draw-plate reacts
the lever arm against the reaction joint to push on the thrust-cup.
Because of the four to one leverage of the lever arm, the
thrust-cup is pushed with four times as much force as the
draw-plate is pulled down by the electromagnet.
[0091] This energized-state reaction force on the thrust cup drives
the first hardened ring 279 towards the second hardened ring 283
and against the spherical portion of the ball to statically hold
the spherical portion of the ball and lock the ball joint from any
rotational movement, thereby firmly holding the members that the
joint connects in a substantially rigid relationship. The presence
of the energized-state reaction force establishes the locked state
of the ball joint.
[0092] Thus, each offset ball joint has an electromagnetic brake
mechanism configured to switch between locked and unlocked states,
wherein the orientation of the ball within the body is statically
held when the brake mechanism is in the locked state, and wherein
the application or removal of electrical energy switches the brake
mechanism between the locked and unlocked states.
[0093] As in the first embodiment, each offset ball joint is
further configured with a retaining cap and a spring 297 spiraling
in three dimensions to form a centering mechanism that laterally
reacts against the shaft 255 so as to drive it laterally back
toward the longitudinal axis when it is not already there. The
spring is received in a circular groove that is cut into the
orifice, and may be held at there by a retainer. Optionally, the
spring may be preloaded such that it axially pulls the shaft away
from the third housing portion, thus preloading the spherical
portion of the ball against the third hardened ring, and thereby
contributing to the joint rigidity of the ball joint. Furthermore,
the spring may optionally be affixed to the shaft so as to react
against rotation of the shaft.
[0094] The offset ball joint of this second embodiment is of an
offset configuration in that its actuation elements (e.g., an
electromagnet, and a draw-plate that establishes a closable gap
with the electromagnet) and its braking elements (e.g., a plurality
of hardened ring brake elements on opposing sides of the ball)
extend and act along two separate, offset and parallel longitudinal
axes. It is also of a levered configuration, in that the lever arm
provides a four to one mechanical advantage, allowing for a smaller
electromagnet to be used.
[0095] If the primary housing is rigidly attached to (or unitary
with) an arm, the offset configuration of this joint provides a
simple way for the masses of the housing, the electromagnetic brake
mechanism (e.g., the electromagnet and draw-plate), and the
spherical portion of the ball to all be placed substantially along
a longitudinal arm axis (i.e., an axis generally defined by the
extent of the arm from its proximal to its distal end), while the
ball shaft extends perpendicular to the longitudinal arm axis. The
configuration of the resulting jointed arm minimizes arm inertia
and balances the arm, while providing the fixture with significant
configuration flexibility.
[0096] The first two embodiments are examples of linear and offset
fixtures, both being levered, and both being characterized by a
failsafe unlocked configuration. More particularly, the
electromagnetic brakes of each joint are locked by the application
of electrical energy. If there should be a system failure, such as
the loss of electrical power, the electromagnetic brakes would
promptly unlock. Further embodiments are envisioned having linear
or offset fixtures, characterized by a failsafe unlocked
configuration, but not being levered.
[0097] Some additional embodiments of fixtures are characterized by
a failsafe locked configuration. For example, a third embodiment of
the invention (which is provided in a more conceptual state) is
configured similar to the first embodiment, except that the ball
joints are characterized by a failsafe locked configuration.
[0098] More particularly, with reference to FIG. 11, each ball
joint is an assembly that includes a housing 301 constructed to
form an annulus 303 characterized by a diameter less than the
overall diameter of a spherical portion 305 of the ball, such that
the spherical portion of the ball is retained within the housing.
The housing annulus 303 allows the movement of a shaft 307 that
extends from the spherical portion 305 of the ball about the center
of rotation of the spherical portion.
[0099] The housing includes a base plate 309 that is composed of a
non-magnetic material. Although not necessary, it may be convenient
for the housing base plate to be fastened to the remainder of the
housing via a threaded means, thereby allowing adjustability in
relative position of these two members. The base plate 309 is
maintained in fixed position relative to an electromagnet 311 such
that an air gap 313 is formed between a face of the electromagnet
311 and a magnetic draw-plate 315 when the electromagnet 311 is not
energized.
[0100] A braking member 317 is positioned between the spherical
portion of the ball 305 and the base plate 309 generally opposite
the region where the ball contacts the annulus 303 of the housing
301. A drive plate 319 is positioned between the braking member 317
and the base plate 309, contacting a face of the braking member 317
opposite that which contacts the spherical portion 305 of the ball.
An elastic member 321 is positioned between the drive plate 319 and
the base plate 309, contacting a face of the drive plate 319
opposite the face that contacts the braking member 317.
[0101] The drive plate 319 is fixed to a connecting rod 323 which
passes through clearance holes in the elastic member 321 and base
plate 309, and fastens to the magnetic draw-plate 315. When the
electromagnet 311 is not energized, the housing 301 and base plate
309 are configured such that an initial compression of the elastic
member 321 creates sufficient normal force between the braking
member 317 and the spherical portion 305 of the ball to maintain
the relative positioning of the assembly (i.e., the position of the
shaft 307 with respect to the housing 301), even in the presence of
additional loads to the shaft 307.
[0102] When current is passed through a wire 325 leading to the
electromagnet 311, it energizes the electromagnet, and an
attractive magnetic force is created which draws the magnetic
draw-plate 315 towards the face of the electromagnet 311 thus
reducing or eliminating the air gap 313. The relative translation
of the electromagnet 311 and the magnetic draw-plate 315 results in
an equidistant translation of the drive plate 319 towards the base
plate 309 and away from the annulus 303 of the housing 301. The
translation of the drive plate 319 towards the base plate 309
results in additional compression of the elastic member 321
relative to the base plate 309, thereby reducing the normal load
between the spherical portion 305 of the ball and the braking
member 317. Inclusion of an additional elastic member between the
drive plate 319 and the braking member 317 can maintain a
predetermined force on the braking member to allow a nominal
resistance to motion (i.e., some joint rigidity) even after the
electromagnet is energized.
[0103] This third embodiment is an example of a fixture
characterized by a failsafe locked configuration, and uses joints
that lack a levered configuration to leverage the applied braking
force to a higher value than that actually generated by their
magnets. Other failsafe, locked joint configurations, such as
offset configurations and/or levered configurations are also
envisioned.
[0104] While the first and third and embodiments were described as
fixtures having a single type of ball joint, the second embodiment
was described as having a first ball joint in a linear, levered,
failsafe unlocked configuration, and a second and third ball joint
in an offset, levered, failsafe unlocked configuration. Embodiments
having other combinations of ball joints are also envisioned. For
example, it is envisioned that a multi-joint fixture could have a
first ball joint characterized by a failsafe locked configuration,
and second and third ball joints characterized by a failsafe
unlocked configuration.
[0105] The switching system of the present invention provides
significant ease-of-use for medical practitioner and is also
envisioned for use with other types of fixtures, such as
pneumatically activated arms. Additionally, the use of the
switching system, drape system and/or electromagnetically driven
locking mechanism of the present invention could be applied to
other technologies that may rely on mechanical means to lock ball
joints, such as a fixture comprising a series of connected ball
joints with a common cable passing through them, the fixture being
configured to become fixed when the cable is tightened via a
threaded mechanism.
[0106] It is to be understood that the invention comprises complete
surgical device holding systems, multi-joint fixtures, multi-joint
fixture control systems, ball joints, switching systems, surgical
drapes, surgical-instrument connection systems, surgical
instruments, and methods for making and using the same.
Additionally, the various embodiments of the invention can
incorporate various combinations of these features. In short, the
above disclosed features can be combined in a wide variety of
configurations within the anticipated scope of the invention.
[0107] Furthermore, embodiments of the invention can incorporate
various combinations of the apparatus described in provisional
Application No. 60/810,265, filed Jun. 1, 2006, which is
incorporated herein by reference for all purposes.
[0108] While particular forms of the invention have been
illustrated and described, it will be apparent that various
modifications can be made without departing from the spirit and
scope of the invention. Thus, although the invention has been
described in detail with reference only to the described
embodiments, those having ordinary skill in the art will appreciate
that various modifications can be made without departing from the
scope of the invention. Accordingly, the invention is not intended
to be limited by the above discussion, and is defined with
reference to the following claims.
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