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BACKGROUND OF THE INVENTION
This invention relates to a head clamp principally for use with
radiological procedures and more particularly to a radiolucent head clamp
having mechanisms for axially and rotationally adjusting the head-engaging
pins of a head clamp, from a single side of the clamp.
An example of a head clamp with a single side control is shown in the Day,
et al. U.S. Pat. No. 5,269,034, assigned to the same assignee as the
present invention, discloses a head clamp having a generally C-shaped
frame with a head-engaging pin on one side of the frame and a pair of
rotationally adjustable head-engaging pins on an opposing side of the
frame. The opposing side of the frame also contains a mechanism for first,
adjusting the rotational angular position of the pair of head-engaging
pins, and a second, translating or linearly moving the pair of pins with
respect to the pin. While the above head clamp works well, it is
constructed of nonradiolucent materials. Therefore, use of the above clamp
may introduce undesirable artifacts in radiological images taken of a
patient with the clamp attached.
Further, radiolucent materials are not well suited for certain components
in the adjusting mechanisms of the above clamp design. For example, the
head clamp disclosed in the Day, et al. '034 patent uses steel balls which
move in and out of detents to move toothed gear rings into and out of
engagement thereby respectively locking and unlocking the rotational
mechanism. That construction requires very precise dimensional tolerances
so that the motion created by the steel balls moving in and out of the
detents consistently separates the toothed rings to disengage the teeth on
the rings. If those components were made from a plastic-type radiolucent
material, the clamping forces would, over time, cause the balls to deform
and lose their circular shape. Further, the surfaces in contact with the
balls would, over time, form tracks in the ball paths. Either or both of
those conditions would eventually result in a loss of dimensional
precision that over time would result in inconsistent and unsatisfactory
clamp operation.
An example of a known radiolucent clamp is shown in the Day, et al. U.S.
Pat. No. 5,276,927, issued to the assignee of the present invention
discloses a radiolucent head support with a radiolucent skull clamp
secured to the head support. The detailed construction of the head clamp
is shown in FIG. 5 herein. Referring to FIG. 5, the radiolucent clamp has
a single pin mounted on an adjusting screw 2 at a first end 1 of the
clamp. A pair of head-engaging pins are mounted on a clevis 3 which is
rotatably mounted in an opposite end 4 the of the head clamp. The clevis 3
is connected to one end of a shaft 5. The opposite end of the shaft
contains threads 6 and a locking nut 7. A first toothed member 8 is
connected to the clevis 3, and a second tooth member 9 is connected to the
opposite end 4 of the head clamp. A compression spring 10 mounted on the
shaft 5 between the toothed members 8,9 is used to apply a biasing force
tending to separate the toothed members 8,9. In operation, the locking nut
7 is rotated on the threads 6 to move the locking nut 7 away from the
opposite end 4 of the clamp. That permits the spring 10 to move the shaft
5 and clevis 3 to the left as illustrated in FIG. 5 thereby separating the
toothed members 8,9 and permitting the clevis 3 to freely rotate. When the
clevis is moved to its desired angular position, the locking nut 7 is
rotated in the opposite direction thereby moving the shaft 5 and clevis 3
to the right as illustrated in FIG. 5 thereby engaging the toothed members
8,9 and locking the clevis 3 in the desired angular position. Thereafter,
the adjusting screw 2 at the first end 1 of the clamp is rotated until the
patient's head is secured in the clamp.
The above construction has several disadvantages. First, after the
patient's head is secured in the clamp, it is difficult to change the
angular position of the clevis 3 because the clamping forces applied by
the adjusting screw 2 override the biasing force of the spring 10 that is
used to separate the toothed members 8,9. Therefore, to change the angular
position of the clevis 3, the adjusting screw 2 must be turned to loosen
the clamp sufficiently that upon loosening the locking nut 7, the toothed
members 8,9 are able to separate. The above mode of operation is less
desirable than a design that permits the angular adjustment of the clevis
3 independent of the clamping screw 2. The prior art clamp of FIG. 5
presents a further inconvenience in the bulkiness of the first end 1 of
the clamp. Further, applying the clamping force through the single pin on
the clamping screw 2, results in less predictable and unequal reactive
forces by the pair of pins on the clevis 3.
SUMMARY OF THE INVENTION
To overcome the non-radiolucency of the head clamps referred to above, the
present invention provides a radiolucent head clamp wherein all of the
adjusting mechanisms are located on a common (single) side of the clamp
and are operably connected to the pair of head-engaging pins.
According to the principles of the present invention, the head clamp has a
frame with opposing radiolucent first and second frame members forming a
generally C-shaped configuration. A first, fixed, head-engaging pin which
may be immovable, is mounted on the first frame member. A radiolucent pin
holding member is fixed to one end of a radiolucent shaft which is
rotatably mounted in the second frame member, and the pin holding member
includes a pair of second and third head-engaging pins. The pin holding
member is located on a side of the second frame member which faces
inwardly, that is, toward the first frame member. A locking mechanism is
mounted at the end of the second frame member and is operably connected to
the pin holding member for releasably locking the pin holding member in
selected angular positions.
The locking mechanism includes a first radiolucent locking member mounted
on an outwardly directed side of the second frame member, i.e., that is,
opposite the inwardly directed side. The locking mechanism further
includes a second radiolucent locking member mounted adjacent the first
locking member and moveable with respect thereto. A fastener preferably
threaded, and made of radiolucent material, is rotatably mounted to the
second frame member adjacent the second locking member such that rotation
of the threaded fastener in one direction moves or pushes the locking
members into engagement, and rotation of the fastener in the opposite
direction permits the locking members to separate.
The invention includes another aspect in which the head clamp has a
radiolucent bushing rotatably mounted within the second frame member. The
shaft supporting the pin holding member is slidably mounted in the bushing
to rotate with the bushing but translate relative thereto. A biasing
spring is located between the first and second locking members to bias the
second locking member, which is slidably mounted on the bushing, away from
the first locking member.
The invention has a further aspect wherein the head clamp has a radiolucent
knob rotatably mounted to the other end of the shaft, but slidable with
respect to the shaft, and a spring located between the knob and the shaft
to limit forces applied to the patient's head by the second and third
head-engaging pins.
A head clamp of the above configuration has the advantage of being made of
radiolucent materials to minimize artifacts or opaque shadows on
radiological images. The radiolucent clamp design provides independent
operation of the angular adjustment of the head-engaging pins thereby
permitting that angular adjustment without having to loosen the clamp. The
radiolucent clamp has the further advantages of providing all of the
head-engaging pin position adjustments on the same, single side of the
clamp. That design has the advantage of convenience of use, as well as
providing a better distribution of clamping forces between the pair of
head-engaging pins as the clamp is tightened. In addition, the clamp is
made of radiolucent materials which has the advantage of reducing
artifacts in images when the clamp is used in radiological applications.
These and other objects and advantages of the present invention will become
more readily apparent from the following detailed description and the
drawings herein.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a preferred embodiment of the radiolucent
surgical head clamp of the present invention showing a patient's head in
phantom.
FIG. 2 is an exploded perspective view of the radiolucent pin rotating,
translating, and locking mechanism of a surgical head clamp in accordance
with a preferred embodiment of the invention.
FIG. 3 is an enlarged axial cross-sectional view of the radiolucent pin
adjusting mechanism, illustrating the radiolucent angular position locking
mechanism in the disengaged or unlocked position.
FIG. 4 is an axial cross-sectional view similar to FIG. 3 but illustrates
the radiolucent angular position locking mechanism in its engaged or
locked position.
FIG. 5 is a side elevation of the prior art radiolucent head clamp shown in
Day, U.S. Pat. No. 5,276,927.
DETAILED DESCRIPTION
The construction and operation of a preferred form of the surgical head
clamp of the present invention will be described with regard to FIGS. 1
through 4. Referring to FIG. 1, the surgical head clamp 12 includes a
C-shaped frame 13 comprised of frame members 14 and 16 which are movable
to "telescope" toward and away from one another. The frame members 14, 16
of the clamp 12 are preferably made of a of a radiolucent polyethersulfone
(PES) and carbon composite material with the carbon component being about
30 percent of the composite by weight. Such a composite material is
available from ICI Advanced Materials of Exton, Pa. under the commercial
name "THERMOCOMP" JC-1006, and is also available from LNP Engineering
Plastics of Thorndale, Pa. under the commercial name "STAT-KON" JC-1006.
Alternatively, other radiolucent materials may be used. Frame members 14
and 16 have parallel first arms 18 and 20, respectively, which are
juxtaposed to each other in an innerfitting, sliding relationship with
first arm 20 of frame member 16 cradling or surrounding the first arm 18
of frame member 14. Extending from one end of the arm 18, frame member 14
has an intermediate arm 22 extending diagonally away from frame member 16
and an upper arm 24 extending angularly back toward frame member 16.
Similarly, extending from first arm 20, frame member 16 has an
intermediate arm 26 extending away from frame member 14 and an upper arm
28 extending back toward frame member 14. The angled geometry of frame
members 14 and 16 maintains frame rigidity and, at the same time, permits
the frame members to be physically smaller than if each of the frame
members were L-shaped.
The first arm 20 of the frame member 16 is formed in a U-shape to receive
the first arm 18 of the frame member 14. The first arm 20 has two sides
30, 31 which extend past the first arm 18. A bottom plate 32 preferably
made from the PES and composite material is mounted between the sides 30,
31 of the first arm 20 such that there is clearance between the bottom
plate 32 and the rack teeth 29 of the first arm 18. The bottom plate 32 is
held in place between the sides 30, 31 of the first arm 20 by fasteners
34, shown in phantom in FIG. 1 and perferably made of nylon. One or more
nylon guide pins 33 having teflon tips (not shown) are threaded into the
surface 31 so that the teflon tips are in contact with the first arm 18 to
help guide the translation of the frame member 14 with respect to frame
member 16. The bottom plate 32 has a cavity 35 which is sized to receive a
retractable rack member 36 which is connected to a release pin 37. The
retractable rack member 36 and release pin 37 are preferably made from the
"DELRIN.RTM." acetal polymer material. The retractable rack member 36 has
teeth 38 are sized to engage the teeth 29 on first arm 18 of frame member
14. A metal compression spring 39 is mounted over the release pin 37 and
extends between the releasable rack member 36 and the bottom plate 32. The
compression spring 39 applies a force against the retractable rack 36
which holds the teeth 38 on retractable rack 36 in engagement with teeth
29 on the first arm 18. The engagement of teeth 38,29 prevents the frame
members 14,16 from moving in a direction away from each other. However,
the configuration of the teeth 38,39 permits frame members 14,16 to be
slid toward each other to size or position the clamp 12 generally with
respect to a patient's head 40, shown in phantom. To release the clamp,
the release pin 37 is pulled downward as illustrated in FIG. 1, thereby
compressing spring 39 and moving the teeth 38 of the releasable rack 36
out of engagement with the teeth 29 of the first arm 18. With the teeth
38,29 disengaged, the frame members 14, 16 may be separated thereby
releasing the clamp from the patient's head 40.
One end 41 of the clamp 12, that is, the outward extending end of the of
frame member 14, preferably has only the minimum size necessary to receive
and support a first head-engaging pin 42 which is generally directed
toward the frame member 16. Therefore, the end 41 of the clamp 12 presents
minimal potential for interference with the surgeon and the operating
procedure. An opposite end 43 of the clamp 12, which is the outward
extending end of frame member 16, has a radiolucent pin holding member 44.
The pin holding member 44 includes a bracket or clevis 45, which may be
made from the PES/carbon composite material previously identified. A pair
of head-engaging pins, that is, a second head-engaging pin 46 and a third
head-engaging pin 48, are mounted proximate the ends of clevis 45 and
generally directed toward the first head-engaging pin 42. The patient's
head 40 is secured in the clamp 12 by and between the first, second and
third head-engaging pins 42,46,48, respectively, which are pressed into
opposite sides of the head. The clevis 45 is pivotally mounted in clevis
support 50 and may be made from the PES and carbon composite material. The
clevis 45 pivots about the centerline of a pivot pin 51 in a plane
transverse to the centerline of the pivot pin 51. The pivot pin is made
from the radiolucent "DELRIN.RTM." acetal polymer material. A rod, or
shaft 52, for example, made from a radiolucent "TORLON" polyamide-imide
material has one end connected to the clevis support 50 by a radiolucent
nylon screw 53 which extends through the clevis support 50 and is threaded
into a threaded center hole of the shaft 52 (see FIGS. 2 and 3).
The clamp 12 includes an angular positioning mechanism 54 for releasably
locking the pin holding clevis 45 in selected angular (rotational)
positions around an axis of rotation 56 which is approximately coincident
with a centerline 58 of pin 42 and preferably passes through the
centerline of pivot pin 51. The clamp also includes a translation or
adjusting mechanism 60 for linearly (axially) moving the pin holding
member longitudinally along the axis of rotation 56.
As best shown in FIG. 2, a generally cylindrical body portion on member 62
is formed on the outwardly extending end of the upper arm 28 at the end 43
of the clamp 12. The body member 62 has a stepped bore 63 which has a
first bore 64 with a layer first diameter that terminates at a shoulder or
flange 65 within the stepped bore 63, and the stepped bore 63 has a
centerline that is coincident with the axis of rotation 56. The stepped
bore 63 extends past the flange 65 and has a second bore 66 concentric
with the first bore 64. As shown in FIG. 3, the stepped bore 63 has a
third bore 67 on the other side of the flange 65 which is concentric with
the first and second bores 63,64 and is sized to receive a closure or cap
68 made from the radiolucent "DELRIN.RTM." acetal polymer material.
Referring back to FIG. 2, the angular positioning mechanism 54 comprises a
first locking ring 70 having interlocking means preferably in the form of
toothed ring 71 on a first end face thereof, which is engagable with a
mating toothed ring 72 of a second locking ring 73. Applicant has found
that when two pieces of PES and carbon material as specified herein are in
sliding contact with each other, there is an abrading action that takes
place between the two parts. That abrading action results in an
undesirable dust or particles of the material collecting on other
components of the clamp. The quantity of undesirable abraded particles can
be reduced by manufacturing the two parts from dissimilar materials.
Therefore, the locking ring 70 is made from the radiolucent PES and carbon
composite material, and locking ring 73 is preferably made from the
radiolucent "DELRIN.RTM." acetal polymer material. The first bore 64 is
sized to receive locking rings 70,73 and maintains the locking rings 70,73
in coaxial alignment as the locking ring 73 is moved longitudinally in the
bore 64 with respect to the locking ring 70. The first locking ring 70 is
immovably secured against the flange 65 such that the first end face and
toothed ring 71 face in a direction away from the first frame member 14,
and the toothed ring 72 of second locking member 73 faces in a direction
toward the first frame member 14. Screws 74 made of nylon or other
radiolucent material extend through holes in the first locking ring 70,
through holes in the flange 65 of the cylindrical body member 62 and are
secured in the cap 68, thereby securing the first locking ring 70 and the
cap 68 to opposite sides of the flange 65 of the cylindrical body member
62. A wave washer, or corrugated spring 75 is located between the locking
rings 70,73 and surrounds toothed rings 71,72. When compressed, the spring
75 produces a force in a direction tending to push the locking rings 70,73
apart, thereby separating the toothed rings 71,72 from interlocking
engagement.
A knob or ring 76 made of the radiolucent "DELRIN.RTM." acetal polymer
material is mounted such that an end surface 77 is in sliding contact with
the second locking member 73. The knob 76, functioning as a manually
operable actuator, is joined to a rotator sleeve 80 by a mechanical
coupling, preferably, internal threads interlocking with external threads
79 of the sleeve 80. The rotator sleeve 80 is a cylindrical bushing which
is made from the earlier described PES and carbon composite material. The
rotator sleeve is rotatably mounted within the body member 62 so that its
centerline is collinear with the axis of rotation 56. An annular flange 81
on the rotator sleeve 80 is sized to mate with and rotatably slides within
the third bore 67, and the second bore 66 is sized to mate with and
rotatably slide about an outer cylindrical surface of the rotator sleeve
80. Referring to FIG. 3, the knob 76 has an annular groove 82 in one face
which is sized to receive the side wall, or face, 83 of the body member
62. The knob 76 has a bore 84 at an opposite end, and a cylindrical keeper
85 which functions to limit motion of the knob 76 is press fit or
otherwise secured within the bore 84. The keeper 85 is made from the
radiolucent "DELRIN.RTM." acetal polymer material and has a bore 86 which
is sized to slide snugly over a "BUNA" nitrile elastomer O-ring 87 which
is mounted on the end of the rotator sleeve 80.
Independent longitudinal (axial) motion of the pin holding member 44 is
generated by a translation mechanism 60. The shaft 52 is slidably mounted
within the rotator sleeve 80 such that the centerline of the shaft is
collinear with the axis of rotation 56. An operating handle, or knob 88
includes a knurled member 90 made from the radiolucent "DELRIN.RTM."
acetal polymer material and a threaded sleeve, or threaded tube 91 made of
"TORLON" polyamide-Imide. "TORLON" polyamide-Imide is a desirable material
because it is commercially available in rod form, thereby reducing
machining costs. The member 90 has a bore which is threaded onto one end
of a external cylindrical surface 92 of the tube 91. The other end of the
threaded external surface 92 of the threaded tube 91 is coupled with an
internal threaded bore 93 of the rotator sleeve 80, thereby rotatably
coupling the knob 88 to the rotator sleeve 80. The opposite end of the
shaft 52 extends through the center of and is slidable with respect to of
the knob 88. A stainless steel screw 89 is threaded into the opposite end
of the shaft 52 and a stainless steel bearing washer 107 limits the linear
motion of the shaft 52 in one direction with respect to the knob 88.
The rotator sleeve 80 has a cross-sectional shape that includes a flat
surface 109 that mates with the cross-sectional shape of shaft 52 that
includes the flat surface 95. Their mating cross-sectional shapes spline,
or key, the rotator sleeve 80 and to the shaft 52 and prevent relative
rotation between the rotator 80 and the shaft 52 but allow them to
translate, or slide, relative to each other. Unitary rotation of the
rotator 80 and the shaft 52 is further provided by a nylon set screw 94
radially threaded into the rotator 80 and slidably engaging the flat
surface 95 on the shaft 52. The rotator sleeve 80 extends through a bore
in the first locking ring 70 and is free to rotate with respect to the
first locking ring 70. However, a flat surface 96 at one end of the sleeve
80 cooperates with a flat surface 97 within an axial bore 98 of the second
locking ring 73 so that the second locking ring 73 slides with respect to
the rotator sleeve 80, but second locking ring 73 and the rotator sleeve
80 rotate in unison.
In use, the angular positioning mechanism 54 is operated to adjust the
angular position of the clevis 45 and the head-engaging pins 46,48 about
the axis 56 independently of the operation of the translating mechanism 60
and independently of whether the clamp is supporting a patient's head 40.
To change the angular position of the clevis 45, the knob 76 is rotated in
a first, or loosening, direction, for example, a counterclockwise
direction, relative to the rotator sleeve 80. The knob 76 backs away (to
the right as viewed in FIG. 3), and the corrugated spring 75 exerts a
force against the second locking ring 73, thereby moving the second
locking ring 73 to the right away from the first locking ring 70 and away
from the first frame member 14 until the respective toothed rings 71,72
disengage. As the knob 76 is rotated in the first direction, the keeper 85
slides over the O-ring 87 until the O-ring 87 contacts the bottom surface
of the bore 86 within the keeper 85. At that point, resistance to further
rotation of the knob in the first direction is encountered by the user,
thereby signaling the user that the toothed rings are disengaged and to
stop rotating the knob 76. The user may then manually rotate the clevis 45
which causes the head 40, clevis 45, support member 50, shaft 52, rotator
sleeve 80 and second locking ring 73 to rotate in unison. As the head
clamp is being tightened, clamping forces parallel to the axis of rotation
56 are applied against the clevis 45 which will tend to move the flange 81
toward and against the flange 65. An low friction O-ring 99 made of
"TEFLON.RTM." polytetrafluoroethylene is located between a bearing surface
100 on a side of the flange 65 of the body member 62 and a bearing surface
101 on a side of the flange 81 of the rotator sleeve 80. The O-ring 99 is
used to reduce the friction between the surfaces 100, 101 when the clevis
45 is rotated to change its angular position; and the clamping force is
transmitted across the bearing surfaces 100,101 by the O-ring 99. The
O-ring 99 and flange 81 are captured between the flange 65 and an end
surface of the cap 68 which is effective to hold the rotator sleeve in its
desired longitudinal position.
When the desired angular position is achieved, the knob 76 is rotated in an
opposite second, or locking, direction, for example, a clockwise
direction, and the knob 76 moves to the left relative to the sleeve 80 as
viewed in FIG. 4. Continued rotation of the knob 76 in the second
direction causes the knob 76 to push the second locking ring 73 toward the
first locking ring 70 and the first frame member 14 until the respective
toothed rings 71, 72 contact each other and reach a fully engaged
position. When the toothed rings 71, 72 contact each other, the user
experiences in increased resistance to rotation which signals the user
that the toothed rings are engaged, and the clevis 45 is locked in the
desired position. With the second locking ring 73 locked from rotational
motion with respect to the first locking ring 70, the rotator sleeve 80 is
prevented from relative rotation with respect to the second locking ring
73 by means of the flat 96 on the sleeve 80 and the mating flat 97 on the
second locking ring 73 (FIG. 2). Further, since the shaft 52 cannot rotate
relative to the sleeve 80, the meshed toothed rings 71,72 are effective to
prevent the clevis 45 from rotating.
The knob 76 threadedly mounted on the end of sleeve 80 functions as a
manually operable actuator that is mechanically coupled to the sleeve 80.
The mechanical coupling, for example, the interlocking threads on the knob
76 and sleeve 80 move the knob 76 away from the first end 41 of the frame
member 14 in response to rotation of the knob 76 in a first direction,
thereby allowing the toothed members 71, 72 to separate. The mechanical
coupling between the knob 76 and sleeve 80 moves the knob, or actuator, 76
toward the first end 41 of the frame member 14 in response to rotation of
the actuator 76 in the opposite direction, thereby moving the toothed
rings 71, 72 into engagement.
The translation mechanism 60 is used to change the position of the clevis
45 and head-engaging pins 46,48 with respect to the head-engaging pin 42
by rotating the knob 88. Rotation of the knob 88 in a first direction, for
example, a clockwise direction, advances the shaft 52 with respect to
sleeve 80 and causes the knob 88, shaft 52 and pin holding member 44 to
translate along the axis of rotation toward the first head-engaging pin
42. Therefore, the pin holding member 44 is linearly adjusted with respect
to the first pin 42 independently of the operation and state of engagement
of the angular position mechanism 54, that is, whether the angular locking
mechanism 54 is in its locked or unlocked position.
A helical compression spring 102 is located within a bore 103 of the
threaded tube 91 and extends over and about the shaft 52. The spring 102
is located between a shoulder of a flange 104 on the shaft 52 and a
bearing washer 105 adjacent the knurled member 90. The flange 104 has a
diameter such that the flange 104 contacts the side wall of the bore 103
at the outer directed end of the threaded tube 91, thereby providing
diametric support for the threaded tube 91 at its outer directed end. The
spring 102 permits the surgeon to measure and control the forces applied
by the second and third head-engaging pins 46, 48 to the patient's head
40. After the pins contact the head, continued rotation of the knob 88
will result in continued translation of the shaft 52 and pin holding
member 44 which is effective to compress the spring 102. With further
rotation of the knob 88, the spring 102 continues to compress; and the
shaft 52 extends beyond the knob 88, i.e., to the right, as shown in FIG.
4. Therefore, the force applied to the patient's head 40 by the
head-engaging pins is determined by the spring constant of the spring 102.
The shaft 52 contains a scale, or markings, 106 so that the clamping force
may be controlled by the surgeon. Typically, each line on the scale 104
represents about 20 pounds of force.
The head clamp of the construction described above may be used in surgical
applications and will result in few if any undesirable artifacts or opaque
shadows when used in radiological applications. The disclosed invention is
especially useful when radiological imagery is used during and to assist
surgical procedures. The design described herein provides a radiolucent
head clamp having an angular head positioning adjustment which can be
operated without having to loosen the clamp, as is required by the prior
art illustrated in FIG. 5. Further, the radiolucent head clamp of the
present invention has one end 42 which is minimal in size, and further has
all of the clamp adjustments conveniently located together at the other
end 43 of the head clamp 12. This again provides a more convenient
operation than the design of the prior art illustrated in FIG. 5. Further,
the individual components of the head clamp of the present invention may
be made of radiolucent materials and withstand the clamping forces and
other forces encountered in use better than the components utilized in the
clamp illustrated in the Day, et al. U.S. Pat. No. 5,269,034 if those
components were made of radiolucent materials. The design provides a
radiolucent clamp having one end 41 which is of minimal size, and wherein
all of the clamp adjustments are conveniently located together at the
other end 43 of the clamp 12.
While the present invention has been set forth by a description of an
embodiment in considerable detail, it is not intended to restrict or in
any way limit the claims to such detail. Additional advantages and
modifications will readily appear to those who are skilled in the art. For
example, the generally cylindrical body member 62 may be a separate piece
which is mechanically attached or bonded to the outward extending end of
the frame member 16. Further, the body member 62 may be made from a
radiolucent "DELRIN.RTM." acetal polymer material or other radiolucent
material. In addition, different radiolucent materials may be used in
place of those identified above. For example, the cap 68 may be made from
the PES and carbon composite material. Further, variations may be made to
the above described constructions. For example, the shaft 52 may be fitted
into the rotator sleeve 80 with sufficient precision that the set screw 94
is not required. Further, the actuator knob 76 may be coupled to the
sleeve 80 by another mechanism such that actuation of the coupling with
respect to the sleeve 80 is operable to move the actuator and either
separate or engage the toothed rings 71,72. Alternatively, the cylindrical
body member 62 and the end of the frame member 14 may be configured with a
mating mechanical coupling, such as a dove tail configuration, and those
members may be mechanically coupled with or without a bonding material.
The invention in its broadest aspects is therefore not limited to the
specific details shown and described. Accordingly, departures may be made
from such details without departing from the spirit and scope of the
invention.
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