U.S. patent number 3,854,208 [Application Number 05/324,957] was granted by the patent office on 1974-12-17 for dental face bow assembly.
Invention is credited to Gene W. Arant.
United States Patent |
3,854,208 |
Arant |
December 17, 1974 |
DENTAL FACE BOW ASSEMBLY
Abstract
A dental face bow adapted to be positioned around and aligned to
the face of a patient; a mouth piece and fixed frame carrying three
adjustable pivot joints for supporting the face bow; and positively
driven positioning mechanisms for adjusting the pivot joints to
provide a desired position and aspect of the face bow.
Inventors: |
Arant; Gene W. (Huntsville,
AL) |
Family
ID: |
23265847 |
Appl.
No.: |
05/324,957 |
Filed: |
January 19, 1973 |
Current U.S.
Class: |
433/73 |
Current CPC
Class: |
A61C
19/045 (20130101) |
Current International
Class: |
A61C
19/04 (20060101); A61C 19/045 (20060101); A61c
009/00 () |
Field of
Search: |
;32/19,20,21 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mancene; Louis G.
Assistant Examiner: Lever; J. Q.
Claims
I claim:
1. A dental face bow assembly comprising:
a rigid fixed frame adapted to be supported from a mouthpiece held
in the mouth of a patient, said fixed frame having left and right
lateral arms and a forward arm;
a unitary, rigid generally U-shaped movable frame adapted to extend
around the face of the patient, having means on its ends for
aligning both of its ends, concurrently, with the hinge axis of the
patient's jaws as represented by a pair of reference points on the
patient's face;
an orbital pointer carried by one of said frames and adapted to be
aligned to a third reference point on the patient's face;
three individually adjustable support means associated with
corresponding ones of said arms for supporting said movable frame
at three corresponding support locations whereby said movable frame
may be supported in a desired alignment position relative to said
three reference points; and
each of said support means including an elevation screw that is
manually operable for controlling the elevation of said movable
frame at the associated support location.
2. The assembly of claim 1 wherein at least one of said elevation
screws has a sphere attached to one end thereof; and which further
includes means coupling said sphere to said movable frame for
3.degree. of twisting movement relative thereto, and also for
longitudinal sliding movement of said movable frame relative to
said sphere.
3. The assembly of claim 2 wherein said movable frame is of tubular
configuration and has an elongated slot formed in its side wall,
said sphere being received within said tubular frame in rotating
and sliding engagement therewith, said elevation screw end
extending through said slot, and the width of said slot being
greater than the width of said screw end.
4. The assembly of claim 1 wherein one of said fixed frame arms has
a slideway extending transversely to said movable frame at the
associated support location, and which further includes a slide
plate movable in said slideway, said slide plate having a threaded
opening which receives the corresponding one of said elevation
screws.
5. A dental face bow assembly comprising:
a rigid fixed frame, including left and right lateral arms and a
forward arm, adapted to be supported from a mouth piece held in the
mouth of a patient;
a unitary, rigid generally U-shaped movable frame adapted to extend
around the face of the patient;
three separate adjustable support means, one associated with each
of said arms, supporting said movable frame from said fixed frame;
and
separate control means manually operable for positively controlling
each of said adjustable support means so as to achieve a desired
alignment of said movable frame relative to the face of the
patient;
each of said lateral support means having six degrees of
adjustability and the forward support means having at least five
degrees of adjustability.
6. A dental face bow assembly comprising:
a rigid fixed frame adapted to be supported from a mouth piece held
in the mouth of a patient;
an integrally formed, rigid generally U-shaped movable frame
adapted to extend around the face of the patient, at least a
portion of the length of said movable frame being of tubular
construction;
an elevation screw having one end threadedly coupled to said fixed
frame, said tubular portion of said movable frame having an
elongated slot formed in the side wall thereof, said elevation
screw extending through said slot and the width of said slot being
greater than the width of said screw;
a sphere attached to the other end of said elevation screw, said
sphere being received within said tubular frame in rotating and
sliding engagement therewith; and
said elevation screw being manually rotatable for adjusting the
elevation of said movable frame relative to said fixed frame
whereby said screw and sphere together provide five degrees of
adjustability of the position of said movable frame relative to
said fixed frame.
7. A dental face bow assembly comprising:
a rigid generally U-shaped movable frame having a tubular
configuration at its center and its lateral side portions, each of
said tubular portions having a longitudinal slot in the exterior
wall thereof;
three spheres received within respective ones of said tubular
portions in rotating and sliding engagement with the interior wall
surfaces thereof;
three posts attached to respective ones of said spheres, each post
extending outward through the associated slot and having a
thickness which is less than the slot width whereby said post and
its associated sphere may rotate in a plane perpendicular to the
longitudinal center line of that portion of said movable frame;
a fixed frame;
and support means adjustably coupling said three posts to said
fixed frame so that said two frames may move in three dimensions
relative to each other.
8. The face bow assembly of claim 7 wherein said movable frame is
integrally formed from a single tubular member.
9. The face bow assembly of claim 7 wherein said posts are
substantially parallel to each other, and said adjustable means
includes means for adjusting the length of each of said posts
relative to said fixed frame.
10. The face bow assembly of claim 9 wherein said adjustable means
also includes means for adjusting the position of each of said
posts in a substantially radial direction relative to the common
center of said posts.
11. The face bow assembly of claim 9 which further includes
separate means for positively driving the length adjustment of each
of said posts.
12. The face bow assembly of claim 10 which further includes
separate means for positively driving the length adjustment of each
of said posts, and separate means for positively driving each of
two of the radial adjustments of said posts.
13. The face bow assembly of claim 12 which further includes
positively driven means for adjusting the rotational position of
said movable frame in its own plane relative to one of said
spheres.
Description
RELATED APPLICATION
The present invention is an improvement over that disclosed in my
prior copending application Ser. No. 259,452, filed June 5, 1972
and now abandoned.
BACKGROUND OF THE INVENTION
In the indirect method of dentistry a dental articulator is used to
simulate the chewing mechanism of a particular patient. It is
necessary to position tooth casts or models in the articulator in
their correct relative position. A transfer face bow is used to
position the casts in the articulator. Such instruments heretofore
in use have been limited in their precision and in their degree of
adjustability.
In the indirect method of dentistry it is also necessary to measure
dynamic movements of the jaws in order to provide an accurate
simulation of the action of the temporomandibular joints. In
recording dynamic jaw movements a recording instrument is used
which includes both an upper face bow and a lower face bow. The
preferred practice is that the upper recording face bow be
precisely aligned to the head of the patient, and more
specifically, with the extended hinge axis of the jaws.
The problem of supporting a transfer face bow in a fully adjustable
position is essentially identical to the problem of supporting a
recording face bow in a fully adjustable position. The present
invention provides apparatus which may be used equally well for
either purpose.
PRIOR ART
Applicable prior art includes:
Face Bow: Hawksworth 1,703,105 Stuart 3,224,096 Lee 3,577,639 Pivot
Joint: Wilt 1,117,123 Groves 1,608,276 Wharam 2,448,851 Pagliuso
2,670,228 Korecky 3,423,115
SUMMARY OF THE INVENTION
According to the present invention the complete dental face bow
assembly includes a fixed frame of rigid construction, a movable
frame of rigid construction, and a set of three support means for
supporting the movable frame from three corresponding points on the
fixed frame. Each of the support means is individually adjustable,
having at least 5.degree. of freedom, so that the movable frame may
be freely adjusted as needed. Each of the support means is also
equipped with positively driven adjustment means.
More specifically, the fixed frame has a mouthpiece, left and right
laterally extending arms, and a forward arm. One of the adjustable
support means is associated with each of the arms of the fixed
frame.
DRAWING SUMMARY
FIG. 1 is an exploded perspective view of an adjustable mechanism
which illustrates some of the mechanical principles of the present
invention;
FIG. 2 is an enlarged fragmentary cross-sectional view of one of
the pivot joints of FIG. 1, taken along the longitudinal axis of
the tubular member;
FIG. 3 is an enlarged fragmentary cross-sectional view of the same
pivot joint but taken transverse to the tubular member;
FIG. 4 is a top plan view of the pivot joint of FIGS. 2 and 3;
FIG. 5 is a perspective view of a transfer face bow assembly in
accordance with the present invention;
FIG. 6 is a side elevation view of the transfer face bow assembly
of FIG. 5;
FIG. 7 is a front elevation view of the assembly of FIG. 5;
FIG. 8 is a fragmentary cross-sectional view taken on the line 8--8
of FIG. 7;
FIG. 9 is a cross-sectional elevational view taken on the line 9--9
of FIG. 6;
FIG. 10 is an exploded perspective view of a portion of one of the
pivot joints together with its associated positive drive mechanisms
and locking mechanisms;
FIG. 11 is an exploded perspective view of a recorder face bow
assembly;
FIG. 12 is a cross-sectional elevational view taken on the line
12--12 of FIG. 11;
FIG. 13 is an exploded perspective view of the frontal adjustment
mechanism for the assembly of FIG. 11;
FIG. 14 is a fragmentary cross-sectional view in its assembled form
of the frontal adjustment mechanism for the assembly of FIG.
11;
FIG. 15 illustrates a construction detail for the instrument of
FIG. 11;
FIG. 16 is a side view of an alternate form of pivot joint;
FIG. 16a is a cross-sectional view of the pivot joint of FIG.
16;
FIG. 17 is an exploded perspective view of an alternate form of the
mechanism of FIG. 10;
FIG. 18 shows an alternate form of elevation screw;
FIG. 19 illustrates a detail of the tubular frame;
FIG. 20 illustrates another form of pivot joint; and
FIG. 21 is a cross-sectional elevational view taken on the line
21--21 of FIG. 20.
THE ADJUSTABLE MECHANISM OF FIGS. 1-4, INCLUSIVE
A rigid fixed frame FF1 is formed from a single flat piece of
material having a forward arm 10 and lateral arms 11 and 12,
respectively. The lateral arms have a common axis 13 while the
forward arm has an axis 14 which is perpendicular thereto. The arm
ends are slotted on their respective axes to form respective
slideways 16, 17, 18.
A rigid generally U-shaped movable frame MF1 is formed from a
single tubular member. In its upper wall it has elongated slots 30,
31, and 32 which are formed in the central portion and the two side
portions, respectively. A round hole 34 is formed at the end of
slot 30, and similar holes 35, 36 are formed at the ends of the
slots 31, 32.
A set of three adjustable support means, or pivot joints 40, 41, 42
support the movable frame from the fixed frame. Each support means
includes an elevation screw 44 and a slide plate 20, 21 or 22.
Each of the slide plates 20, 21, 22 is notched in a suitable manner
so as to slide in the respective slideway of the fixed frame. The
slide plates have respective threaded openings 24, 25, 26 each of
which is aligned perpendicular to the plane of the fixed frame when
the corresponding plate is seated in its associated slideway.
Each elevation screw 44 includes a threaded post 45 having a ball
or sphere 46 attached to its lower end and a screwdriver notch 47
formed on its upper end. The threaded post is adapted to engage the
threaded opening of a corresponding slide or base plate, and the
ball or sphere 46 is of such diameter as to either rotate or slide
longitudinally within the interior wall of the tubular frame MF1.
The ball 46 is inserted through the corresponding opening 34, 35,
or 36.
Reference is now made specifically to FIGS. 2-4, inclusive,
illustrating the operation of pivot joint 40 which includes base
plate 20. The width of slot 30 (FIG. 3) is considerably greater
than the thickness of the lower end of post 45.
The pivot joint of FIG. 2-4, inclusive, has 6.degree. of freedom,
and hence may be adjusted in six different ways, as follows:
1. Elevation adjustment is made by using screwdriver slot 47 to
turn threaded post 45 so as to raise or lower the ball 46 along the
VE axis relative to base plate 20.
2. The base plate 20 may be moved in the slideway 16 of frame arm
10 to accomplish a transverse horizontal movement (relative to MF1)
along the TH axis as indicated in FIG. 4.
3. the tube may slide in longitudinal, horizontal movement along
the LH axis relative to the sphere 46.
4. The vertical angle VA of the tube, shown in FIG. 2, may be
adjusted by lowering one end of the tube and raising the other end
relative to the ball 46.
5. The tube may be twisted in a horizontal plane to vary its
horizontal angle HA as shown in FIG. 4.
6. the tube may rotate about its own longitudinal axis relative to
the elevation screw, as shown by curved arrow R in FIG. 3.
Although there are six adjustments for each of the three pivot
joints, the positioning of movable frame MF1 requires only a total
of six positive adjustments to be made. These are preferably
accomplished by adjusting the three elevation screws along the VE
axis; adjusting the slide plate 20 along its TH axis (the axis 14);
adjusting one of the slide plates 21, 22 along its TH axis (the
axis 13) while permitting the other to slide freely as required;
and rotating the movable frame relative to the fixed frame so that
it moves along the LH axis relative to all three of the balls 46.
It therefore follows that adjustment (1) of each pivot joint will
always be positively controlled, adjustments (2) and (3) are
sometimes positively controlled, and adjustments (4), (5) and (6)
are always dependent or slave adjustments.
TRANSFER FACE BOW ASSEMBLY FIGURES 5-10, INCLUSIVE
Reference is now made to FIGS. 5 to 10, inclusive, illustrating the
transfer face bow assembly of the present invention.
Fixed frame FF2 has a centerpiece 113 and right and left lateral
arms 111, 112 which are integrally formed from a single flat piece
of material. A bite plate or mouthpiece 118 is removably attached
to center piece 113 by screws 119. Fixed frame FF2 also includes a
forward arm 110 having its rearward end turned downwardly and
welded to centerpiece 113 adjacent the left lateral arm 112. An
orbital pointer 116 having three degrees of adjustability is
carried by a universal joint 115 which in turn is attached to the
right lateral arm 111 adjacent centerpiece 113.
Movable frame MF2 is a generally U-shaped frame made of a single
tubular member which passes over the outer ends of the lateral arms
111, 112 of the fixed frame and underneath the outer end of the
forward arm 110. Adjustable support means 140 supports the center
of movable frame MF2 beneath forward arm 110, while support means
141, 142 support the sides of the movable frame above the
respective lateral arms. The ends of movable frame MF2 are fitted
with axis alignment pins 131, 132 which slide on a common axis 133
representing the reference axis of MF2. Each of the axis alignment
pins has an associated depth marker 135, 136 for measuring its
length during an alignment condition.
The instrument is used first with the patient (FIG. 6) and later
with an articulator (FIG. 5).
When used with the patient the bite plate 118 is grasped between
the teeth and orbital pointer 116 is aligned to a tattoo mark on
the nose. The adjustable support mechanisms 140, 141, 142 are
adjusted so as to align the reference axis 133 of movable frame MF2
with the hinge axis of the patient. This is accomplished by placing
the ends of both pointers 131, 132 on respective tattoo marks (not
specifically shown) which represent the hinge axis of the patient.
It is not absolutely essential that the ends of the movable frame
MF2 be equal distances from the hinge axis tattoo marks, because
the pin lengths are recorded by depth markers 135, 136.
When the instrument is aligned to an articulator the orbital
pointer 116 engages an orbital plane indicator in a well known
manner. The ends of pins 131, 132 engage analog blocks 175, 176
shown in dotted lines in FIG. 5, and which are provided with
dimples 177 indicating their reference axis. The analog blocks may
have a fixed lateral separation, hence the lateral separation
between the dimples 177 will be different from the lateral
separation of the hinge axis tattoo marks on the patient's face.
The depth markers are therefore utilized to set both axis pointers
on an either longer or shorter depth than they had when aligned to
the patient, and by equal amounts. In this manner an accurate
static position transfer is achieved even though the frame MF2 may
have been laterally asymmetrical, and even though the separation of
the dimples 177 on the analog blocks is different from the
separation of the tattoo marks on the patient's face.
The adjustable support mechanism 141 shown in FIGS. 5, 6, 7, 9 and
10 will now be described.
Threaded post 145 engages vertical threaded opening 125 in the base
plate 121. Ball or sphere 146 is attached to the upper end of post
145 and is also received within the interior of movable frame MF2.
A jam nut 165 is threaded on the protruding lower end of the post
145. Screwdriver notch 147 is used for adjusting the elevation
screw to its desired position of vertical adjustment, and then the
jam nut 165 is turned in order to lock it in position. Thus the VE
adjustment (1) is positively controlled.
Base plate 121 slides in a slideway 117 formed in the outer end of
the lateral arm 111. A tab 150 formed on an outer, upper corner of
base plate 121 has a horizontal threaded opening 151 formed
therein. A tab 155 with horizontal smooth opening 156 is attached
to the lateral arm 111 adjacent the inner end of slideway 117. A
lead screw 160 is horizontally disposed, parallel to slideway 117,
and has on its inner end a smooth groove 161 which is locked in
opening 156 of tab 155. The outer threaded end of lead screw 160
engages the threaded opening 151 on base plate 121. A screwdriver
notch 162 on the outer end of the lead screw is used to adjust the
base plate either inwardly or outwardly relative to the lateral arm
111. A set screw 153 carried on the underside of base plate 121 is
used to lock it in its selected position of adjustment. Thus the TH
adjustment (2) on the common lateral axis of the slideways of arms
111, 112 is positively controlled.
The adjustable support mechanism 142 is constructed in the same
manner except that lead screw 160, tabs 150 and 155, and set screw
153 may be omitted since the TH adjustment of slide plate 122 moves
in a slave relationship to the slide plate 121.
Adjustable mechanism 140 is constructed the same as the mechanism
141 but is inverted because movable frame MF2 passes underneath the
forward arm 110. Also, provision is made here to lock the LH
adjustment (3) of the movable frame. This is accomplished by a
staple 167 (FIGS. 5 and 8) driven through the tube to lock ball 146
against longitudinal sliding movement. Movable frame MF2 therefore
has only five degrees of adjustability.
Alternatively, it may be preferred to dispense with depth markers
135, 136 as well as the locking means 167. The LH adjustment may
then be positively controlled by a drive mechanism similar to that
shown in FIGS. 13 and 14. The block 210 and associated portion of
plate 200 would be omitted, however.
RECORDER FACE BOW ASSEMBLY FIGURES 11-15
Reference is made to FIGS. 11-15, inclusive, illustrating a
recorder face bow assembly in accordance with the present
invention.
Fixed frame FF3 is identical to fixed frame FF1 shown in FIG. 1,
and movable frame MF3 is identical to movable frame MF1. Relative
positions are reversed, however, with the movable frame being
supported above the fixed frame. The adjustable support means 241
may be identical to the adjustable support means 141 shown in FIG.
10. Adjustable support means 242, not specifically illustrated in
FIG. 11, may be identical to support means 142.
Adjustable support means 240 is somewhat different from those
previously described, and is illustrated in FIGS. 11, 13 and 14. It
includes a slide 220 identical to the slides 120 and 121 as
previously described; an elevation screw 244 identical to elevation
screw 144 as previously described; and other mechanism associated
therewith as previously described in conjunction with FIG. 10. In
addition, it includes means for positively controlling the LH
adjustment (3).
More specifically, a slide member 250 has fingers 251, 252 which
extend into the slot of movable frame MF3 and grasp the ball 246 on
respective sides thereof. Slide member 250 also has a tab portion
projecting perpendicular to MF3 in which a threaded horizontal
opening 253 is formed. A lead screw 260 is received in the opening
253. A support plate 200 is attached to the upper surface of MF3
and extends forwardly thereof. Support plate 200 has a pair of
downwardly depending ears 266, 268 in which openings 267, 269 are
formed. Lead screw 260 has smooth grooves 261, 262 formed adjacent
its respective ends, and which are snapped into the openings 267,
269, respectively. The lead screw may then be driven from either of
the screwdriver slots 263, 264 at its two ends. By rotating the
lead screw 260 the movable frame MF3 is caused to rotate on its
tripod base of support, so that all three of the balls slide
longitudinally within the tubular frame.
The instrument of FIG. 11 also includes a pair of lateral support
plates 201, 202 which are vertically disposed and attached to the
outer surface of the frame MF3 near its respective extremities.
FIG. 15 shows attachment of the plate 201 by welding at the points
201a, 201b.
A pair of alignment blocks 206, 207 are removably attached in
aligned positions to the support plates 201, 202, respectively.
Each alignment block has a horizontal opening therein and the axes
of the two openings are collinear. A pair of axis alignment pins
231, 232 are disposed in respective ones of the alignment blocks,
and their points lie on the common axis 233 representing the
reference axis of the movable frame MF3.
Just to the right of support plate 200 a vertical bolt 215 extends
through a vertical opening in the movable frame MF3 and supports an
orbital pointer 216. A nut 215a on bolt 215 may be loosened to
adjust either the length or angular position of pointer 216.
Pointer 216 and axis 233 lie in a common plane.
The instrument is applied to dentistry in a manner generally
described by R. L. Lee, DDS in the Aug., 1969 issue of The Journal
of Prosthetic Dentistry. Upper clutch 218 is attached to the upper
tooth structure of the patient and fixed frame FF3 is attached
rigidly to the clutch. Then the various support mechanisms are
positively adjusted in order to align the axis pins 231, 232 with
the tattoo marks on the patient's face representing the terminal
hinge axis location. At the same time movable frame MF3 is
laterally positioned so that the pointers 231, 232 project inwardly
from their respective alignment blocks by equal distances. Pointer
216 is also aligned to the nose tattoo mark. The recording position
of frame MF3 has then been established. All of the adjustable
positioning mechanisms are then locked in place utilizing the three
jam nuts 165, the two set screws 153, and any appropriate means for
securing the slide 250 and lead screw 260. Then the pointers 231,
232 are removed. A lower recording face bow, not shown in the
present drawings, is aligned in its proper position by utilizing
the axis alignment blocks 206, 207. Thereafter, the axis alignment
blocks 206, 207 are removed and are replaced with locigraph blocks,
not shown. A third locigraph block 210 is attached to the under
surface of support plate 200. The dynamic jaw movement pattern of
the patient is then recorded by cutting grooves in the three
locigraph blocks.
ALTERNATE CONSTRUCTION DETAILS FIGURES 16-21
FIGS. 16 and 16a show an alternate pivot joint construction. An
elevation screw includes threaded post 245 having ball 246 attached
to one end. The other end of the post engages a threaded opening in
slide plate 321. Movable frame MF4 carries a sliding sleeve 322
which on its upper side has a socket 323 for the ball. The VE, TH,
LH, VA, HA, and R movements are indicated by appropriate
arrows.
While frame MF4 is shown as being of rectangular cross-section, it
may if desired be cylindrical, and sleeve 322 is then made of
circular configuration.
FIG. 17 illustrates an alternate slide construction. The lateral
arm 111a of the fixed frame is relatively thick and has a slideway
117a formed therein with overhanging edges on its two side walls.
The base plate 121a of an elongated octagon configuration is
adapted to be slidingly received in the slideway 117a. The slide
121a has gear teeth 121b formed on one of its longitudinal edges. A
gear wheel 160a is received in a vertical opening in one side of
the arm 111a, its upper end being retained by a cap 155a. The lower
end of the gear wheel has a screwdriver slot 162a which is used to
rotate the gear wheel and hence drive the slide 121a either inward
or outward. A set screw 153a is used to lock the gear wheel 160a
against further rotation, when slide 121a has been positioned.
Slide 121a also has a threaded vertical opening 125a for receiving
an elevation screw, not specifically shown.
Reference is made to FIG. 18 showing an alternate form of elevation
adjustment screw 144a. The threaded post 145b has a relatively
small neck 145a, inserted into an opening in the ball 146 and
fastened therein. The diameter of neck 145a is significantly less
than the diameter of ball 146. The post 145b, however, has a
diameter which is greater than the diameter of the ball 146.
FIG. 19 shows that a hole 170 in movable frame MF5 may be braced by
means of an internal plug 172 which is welded to the hole edge, or
alternatively an outside patch 173 may be used to cover hole
171.
Reference is now made to FIGS. 20 and 21 illustrating still another
pivot joint construction. A frame member MF6 consists of a flat
strip of material having a rectangular cross-sectional
configuration. A short tubular member 185 has its two ends cut off
to form angled surfaces 186, 187, so that when seen from the side
as in FIG. 21 the member 185 has a trapezoidal configuration. A
slot 188 is cut throughout the length of the short side of the side
wall of the tubular member 185. The opposite side wall is flattened
somewhat at 189 and bears against the laterally central portion of
the frame member MF6. The respective ends of tubular member 185 are
riveted to frame member MF6 by means of rivets 190, 191. Threaded
post 145 has one end attached to the ball 146, and it will be noted
as shown in FIG. 20 that the slot 188 is significantly wider than
the width of the post 145. During assembly, the ball 146 is
inserted into the tubular member 185 before the second rivet is in
place. The rivets then serve to captivate the ball 146 so that it
cannot escape. The sloping ends of the tubular member provide
convenient clearance for installation of the rivets. The length of
tubular member 185 is selected as necessary to provide the
longitudinal adjustment capacity for the pivot joint.
While the present invention has been described specifically in at
least one of its forms, such detailed disclosure has been made only
in order to comply with the patent laws and is not intended in any
way to limit the concept or scope of the invention, which is more
particularly defined in the accompanying claims.
* * * * *