BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a hand held
medical device. More particularly, the present invention relates
to a flashlight, and still more particularly to a flashlight that
is constructed of materials having relatively low magnetic
susceptibilities. This provides the flashlight of the present
invention as a useful instrument in the vicinity of a magnetic
resonance scanner.
2. Prior Art
The prior art is replete with various types of hand held
medical devices such as flashlights made of metal materials that
are not useful in the presence of the strong magnetic fields of a
magnetic resonance scanner. Examples include U.S. Patent Nos.
1,067,646 to Downey; 1,877,077 to Stevens; 2,459,702 to Hipwell
et al.; 2,651,763 to Grimsley; 3,890,498 to Toth, Sr.; 4,203,150
to Shamlian; 4,237,527 to Breedlove; 4,286,311 to Maglica;
5,593,222 to Maglica; and 5,601,359 to Sharrah et al.
U.S. Patent No. 4,607,623 to Bauman describes a hand held
laryngoscope constructed of non-ferrous materials such as ABS
with the electrically conductive portions provided by first
applying a thin copper layer to the ABS followed by electroless
plating and then electrolytically plating another copper layer to
form a conductive layer about 0.5 to 2 mils thick. A thin layer
of aluminum is subsequentially applied to the copper coating in
those areas intended to be reflective. The batteries powering
this device are not further described, but may be of a
nickel/cadmium type commonly used for such applications.
Nickel/cadmium batteries are not considered to be relatively
nonmagnetic and would not be useful with the flashlight of the
present invention.
U.S. Patent Nos. 310,004 to Weston; 485,089 to Carhart;
2,282,979 to Murphy; 3,352,715 to Zaromb; 3,673,000 to Ruetschi
and 4,318,967 to Ruetschi disclose anti- or non-magnetic
materials in cells or batteries. Additionally, U.S. Patent
Nos. 2,864,880 to Kaye; 2,982,807 to Dassow et al.; 4,053,687 to
Coiboin et al.; 4,264,688 to Catanzarite; 4,595,641 to Giutino;
5,104,752 to Baughman et al.; 5,149,598 to Sunshine; 5,173,371 to
Huhndorff et al.; 5,194,340 Kasako; 5,418,087 to Klein; and
5,443,924 to Spellman relate to batteries having means for
assuring that proper battery polarity is established. However,
none of these patents describe power sources that are useful with
the hand held medical device of the present invention because
they either include at least some magnetic components, do not
have sufficient energy density for extended use or do not have a
terminal configuration similar to that of the present invention.
U.S. Patent No. 4,613,926 to Heitman et al. discloses an
illuminating assembly for an MRI scanner.
There is needed a flashlight that is predominantly
constructed of metal so that the instrument is capable of
withstanding the abusive treatment conditions which surgical
instruments are sometimes subjected to. For this purpose, the
flashlight of the present invention is constructed largely of
metal components. However, with ever increasing use of magnetic
resonance scanning to aid medical personnel during pre- and post-clinical
and surgical procedures, the metal components must be
constructed of materials that have as low a magnetic
susceptibility as possible.
SUMMARY OF THE INVENTION
The flashlights of the present invention is constructed of
materials including metal components having very low magnetic
susceptibilities. Those parts not made of metal are preferably
formed of a thermoplastic material, for example an acetal
compound such as DELRIN. The battery powering the flashlight
lamp is also constructed of materials having low magnetic
susceptibility. Lithium batteries are preferred, and all
components such as the casing, terminal leads, current collectors
and collector leads, some of which are typically made of nickel,
are constructed of stainless steel nonmagnetic austenitic. The
battery further includes a unique terminal configuration that
prevents the inadvertent use of other batteries, including non-magnetic
batteries, in the laryngoscope.
These and other aspects of the present invention will become
more apparent to those skilled in the art by reference to the
following description and to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a flashlight 10 according to
the present invention.
Fig. 2 is an exploded view of the head 14 and cage 116 parts
of the flashlight 10.
Figs. 3A and 3B are exploded views of the flashlight 10
shown in Fig. 1.
Fig. 4A is a partial, cross-sectional view of a portion of
the handle 12 and the head 14 for the flashlight 10.
Fig. 4B is a partial, cross-sectional view of the handle 12
and end cap 50 for the flashlight 10.
Fig. 5 is a plan view of the battery 32 for the flashlight
10.
Fig. 6 is a side, elevational view of the battery 32.
DETAILED DESCRIPTION OF THE INVENTION
Turning now to the drawings, Figs. 1 to 6 show a flashlight
10 having low magnetic susceptibility characteristics according
to the present invention generally comprised of a handle 12 and a
head 14 supporting a lamp actuation means 16 mounted on the head
14 in a twistable relationship therewith to activate and
deactivate the flashlight as desired. The instrument is utilized
to illuminate an object of interest, for example in a health care
environment and particularly in close proximity of the strong
magnetic fields of a magnetic resonance unit (not shown).
With particular reference to Figs. 3B, 4A and 4B, the handle
12 is a cylindrically-shaped tube comprising an intermediate
section 18 meeting at a step 20 with a proximal section 22 having
internal threads 24, and the intermediate section 18 meeting at a
chamfer 26 with a distal section 28. The outer surface of the
handle 12 is provided with raised, knurled ridges 30 (Fig. 1) to
aid in gripping the flashlight 10. The handle 12 is preferably
constructed of chrome plated brass.
A battery 32 (Figs. 3B, 4A, 4B, 5 and 6) is housed inside
the intermediate handle Section 18 for providing power to a lamp
means as an assembly 34, which will be described in detail
hereinafter. The battery 32 is constructed of materials having
relatively low magnetic susceptibility with a unique terminal
configuration according to the present invention. The battery 32
is preferably an alkali metal battery and more preferably an
alkali metal/liquid catholyte battery. A most preferred
chemistry utilizes the lithium/thionyl chloride-bromine chloride
(Li/BCX) couple. The battery casing adjacent to the distal
handle section 28 is insulated to prevent electrical contact in
the conventional manner.
As shown in Figs. 4A, 5 and 6, the opposite end of the
battery 32 includes a negative contact ring 36 that is
permanently attached to the battery case to provide one terminal
for the battery. The central, positive terminal 38 is recessed
and insulated 40 around its perimeter to prevent accidental
shortening. A non-magnetic fuse 42 prevents inadvertent run-away
electrochemical reaction while a thermoplastic insulator plate 44
supported on a ledge of the insulated material 40 protects the
positive terminal 38 and fuse 42. A central opening 46 in plate
44 provides for access to the positive terminal 38. To provide
the battery 32 having a relatively low magnetic susceptibility,
all external and internal electrical components such as the
casing, the terminals 36, 38, the current collectors and the
contact leads are of stainless steel.
The unique terminal configuration prevents the inadvertent
loading and discharge of batteries into the handle 12 not
intended for use with the flashlight 10. Such inadvertent
battery use could have detrimental affects on the flashlight's
low magnetic susceptibility characteristics.
The battery 32 is secured inside the handle 12 by a cap
spring 48, preferably of silver plated beryllium copper, that
biases between the battery and an end cap 50 snug-fitted into the
distal handle section 28 extending part way into the intermediate
handle section 18. The end cap 50 is of a non-magnetic material,
such as an acetal thermoplastic material with an enlarged head 52
that abuts the distal end of handle 12. A groove 54 formed
between the cap head 52 and an annular protrusion 56 of the cap
receives an O-ring 58 of a flexible elastomeric material for
sealing the cap 50 in the distal section 28 of the handle 12.
As shown in Figs. 3B and 4A, a battery retainer assembly is
threaded into the proximal handle section 22 and includes a
battery retainer 60, preferably of an acetal thermoplastic
material, that threads into the handle 12 to capture a battery
pin 62, a battery spring 64, a tube disk 66 and a pair of spring
contacts 68 therein. The battery pin 62 is preferably of gold
plated brass, the battery spring 64 is preferably of silver
plated beryllium copper, the tube disk 66 is of an acetal
thermoplastic material and the spring contacts 68 are of silver
plated beryllium copper.
The battery retainer 60 comprises a threaded portion 70
sized to threadingly mate with the internal threads 24 of the
proximal handle section 22. The threaded portion 70 of the
battery retainer 60 meets a cylindrically-shaped portion 72 that
extends to a chamfer 74 ending at an end face 76. The battery
retainer 60 has a first, cylindrically-shaped bore 78 that meets
at an internal shoulder 80 with a second, lesser diameter
cylindrically-shaped bore 82 extending to the end face 76. A
pair of diametrically opposed openings 84 are provided through
the thickness of the threaded portion 70. The battery retainer
60 receives the battery pin 62 having a cylindrically-shaped body
86 provided with an annular protrusion 88 adjacent to a proximal
end 90 thereof.
The internal threads 24 at the proximal handle section 22
terminate at an internal shoulder 92. Shoulder 92 supports the
tube disk 66 having a central opening 94. The tube disk 66 also
includes a pair of opposed channels 96 (shown in dashed lines in
Fig. 3B) that communicate between the outer edge thereof and
diametrically opposed portions of the opening 94. The tube disk
66 supports the pair of spring contacts 68, each having a leg
disposed in one of the disk channels 96 with a contact portion 98
of the springs extending from the opposite face of the tube disk
66.
As shown in Fig. 4A, with the tube disk 66 supported on the
internal shoulder 92, the spring contacts 68 are captured between
the shoulder 92 and the disk 66 with the contact portions 98
contacting the annular, negative terminal 36 of battery 32. The
tube disk 66 and spring contacts 68 are secured in this position
by the battery retainer 60 threaded into the proximal handle
section 22. The battery retainer 60 further captures the battery
pin 62 between itself and the tube disk 66 with the proximal end
side of the annular protrusion 88 abutted against the internal
shoulder 80 of the battery retainer by the battery spring 64
surrounding the body 86 of the battery pin 62 and biasing between
the tube disk 66 and the opposite side of the annular protrusion
88. The pair of diametrically opposed openings 84 in the battery
retainer 60 are provided to receive a tool (not shown) such as a
spanner wrench for tightening the battery retainer 60, battery
pin 62, battery spring 64, tube disk 66 and spring contacts 68
into position. The battery retainer assembly together with the
battery 32 loaded into the handle 12 and secured therein by the
cap spring 48 and end cap 50 form the portion of the flashlight
10 of the present invention generally referred to as the battery
pack assembly.
After the battery retainer assembly is threaded into the
proximal handle section 22, the proximal section 22 threadingly
receives the head 14. The head 14 is of copper plated brass. As
shown in Figs. 1, 2, 3A and 4A, the head 14 for the flashlight 10
of the present invention comprises a base portion 100 having
exterior threads 102 that mate with the interior threads 24 of
the proximal handle section 22 for attaching the head 14 to the
handle 12. An external, inwardly curved section 104 is between
the base portion 100 and a mounting portion 106 having an annular
channel 108 which receives an elastomeric O-ring 110.
The mounting portion 110 of head 14 is provided with three
partially overlapping races 112. The races 112 each begin at a
position adjacent to a proximal open end 114 of the mounting
portion 110 and they run towards the base portion 100 of the head
14 as they extend somewhat more than a third of the way around
the circumference thereof. Thus, a beginning portion of a first
race adjacent to the proximal open end 114 overlaps the end of a
second race 112 adjacent to the curved section 104 of head 14
while the end of the first race is overlapped by the beginning a
third race. The races 112 provide for twistingly mounting a cage
116 and sleeve 118 on the mounting portion 110 of head 14 such
that as the cage 116 and sleeve 118 are twisted, they move
axially along the flashlight 10, as will be described in detail
hereinafter.
The interior of the mounting portion 110 of head 14 is
provided with a first, cylindrically-shaped surface 120 that
meets a second cylindrically-shaped surface 122 at an inner step
124. The second cylindrical surface 122 forms into a bevel 126
meeting a shoulder 128 leading to a third, cylindrically-shaped
surface 130 in the curved section 104 of the head. Third
cylindrical surface 130 leads to an outwardly tapering bevel 132
that meets a fourth, cylindrically-shaped surface 134 and a
second bevel 136 in the base portion 100 of head 14.
A spacer 138, preferably of an acetal thermoplastic
material, has a cylindrical outer surface 140 extending into a
distal chamfer 142. The cylindrical outer surface 140 and
chamfer 142 of spacer 138 are received in a closely spaced
relationship by the matching second internal cylindrical surface
122 and bevel 126 of the head member 14 with the chamfer 142
abutting the bevel 126.
The inner step 124 of the head 14 between the first
cylindrical surface 120 and the second lesser diameter
cylindrical surface 122 supports a contact spring 144 thereon.
The contact spring 144 is preferably of beryllium copper plated
with silver.
A lamp holder 146 has a cylindrically-shaped outer surface
148 that is received in a closely spaced relationship with the
third, internal cylindrical surface 130 of head member 14,
directly opposite the inwardly curved section 104. The lamp
holder 146 is preferably of gold plated brass and has a first,
inner cylindrical section 150 that meets at an inner step 152
with a second, inner cylindrical section 154 which in turn meets
at a step 156 with an inner threaded section 158. Threaded
section 158 opens into a fourth, inner cylindrical section 160
that meets an outwardly tapering bevel 162 extending to a
proximal end thereof.
A forward insulator 164, preferably of an acetal
thermoplastic material, is received inside the lamp holder 146
with its end 166 abutting step 156 and its cylindrically-shaped
outer surface 168 contacting the second cylindrical section 154.
Forward insulator 164 has a cylindrically-shaped through bore 170
of a first diameter that opens into an annular inlet portion 172
having a second diameter greater than that of bore 170.
A contact pin 174 comprises a large diameter disk 176
intermediate a forward shaft 178 and a rearward shaft 180
extending to a contact 182. The contact pin 174 is preferably of
gold plated brass and the forward shaft 178 is sized to be
received in the through bore 170 of the forward insulator 164.
With the forward insulator 164 received in the lamp holder 146,
the disk 176 of contact pin 174 is positioned within the second,
inner cylindrical section 154 of the lamp holder 146 adjacent to
step 152. A rear insulator 184, preferably of an acetal
thermoplastic material, has a cylindrically-shaped outer surface
186 meeting opposed end faces 188 and 190. A cylindrical through
bore 192 communicates between the faces 188, 190 and is sized to
fit over the rearward shaft 180 of the contact pin 174 to thereby
lock the pin 174 inside the lamp holder 146 in conjunction with
the forward insulator 164.
A lamp 194 is threaded into the inner threaded section 158
of the lamp holder 146. A lamp 194 useful with the flashlight 10
of the present invention is commercially available from Boehm
under model no. X02.88.044. A reflector 196, preferably of
silver plated beryllium copper, has a step 197 that serves as a
seat for an end of the contact spring 144. When the reflector
196 is fitted into the fourth, inner cylindrical section 160 of
the lamp holder 146 to surround the lamp 194 in a reflective
relationship therewith, the contact spring 144 is captured in a
biasing relationship between the reflector 196 and the inner step
124 of head 14. The reflector 196 is preferably of gold plated
brass. A stainless steel contact spring 198 is received in an
annular channel 200 in the base 202 of the reflector 196, and
spring 198 helps to retain the reflector 196 in position in
addition to serving as an electrical contact between the
reflector 196 and the lamp holder 146.
A sleeve 204, preferably of gold plated brass, comprises an
inner, cylindrical portion 206 having a first diameter meeting a
second, larger diameter inner, cylindrical portion 208 at a step
210. A portion of the outer surface of sleeve 204 adjacent to
the end of the second cylindrical portion 208 is threaded 212.
A cage 214, preferably of an acetal thermoplastic material,
has a cylindrical outer surface with three openings 218 spaced
equidistant around the perimeter of the cage 214. The openings
218 form a plane normal to the longitudinal axis of the
flashlight 10 and receive stainless steel balls 220. With the
cage 214 positioned inside the sleeve 204 resting on step 210 and
with the cage 214 and sleeve 204 mounted over and around the
mounting portion 106 of the head 14, one ball 220 is captured in
each opening 218 and one of the races 112 of the mounting portion
106 and the assembly is held in that position by sleeve 204. The
sleeve 204 is in turn secured in position by a lens 222 and an
associated lens ring 224 which threads onto the mounting portion
106 of head 14. The lens and ring are preferably of an acetal
thermoplastic material.
Fig. 4A shows that with the head 14 threadingly connected to
the proximal handle section 22 and with the sleeve 204 and cage
214 positioned so that each ball 220 is at the beginning of its
race 112 adjacent to the proximal open end 114 of the mounting
portion 106 of head 14, the contact 195 of lamp 194 contacts the
forward shaft 178 of the contact pin 174 having its rearward
shaft 180 contacting the proximal end 90 of the battery pin 62.
However, the opposite, distal end 226 (Figs. 3B and 4A) of the
battery pin 62 is in a raised position, out of contact with the
central, positive terminal 38 of battery 32. The lamp 194 is
energized by twisting or rotating the sleeve 204 with respect to
the head 14 and handle 12. This movement causes the sleeve 204
and the captured cage 214 to move towards the handle 12 as the
balls 220 travel along the races 112 towards their ends thereof.
This movement causes the lamp holder 146, lamp 194, reflector
196, lens 222 and lens ring 224 to move towards the handle 12
against the biasing force of the contact spring 144 which in turn
pushes the contact pin 174 and battery pin 62 towards the battery
32 against the biasing force of the battery spring 64 until the
distal end 226 of the battery pin 62 contacts the central,
positive terminal 38 of battery (as shown in dashed lines in
Fig. 4A). The electrical circuit is completed through the
annular, negative contact ring 36, the spring contacts 68, the
handle 12, the head 14, the lamp holder 146, the reflector spring
198 and reflector 196 contacting the casing of lamp 194. With
the lamp 194 energized, light is directed out through the lens
222, for example to help illuminate a zone of interest during a
medical examination or procedure.
When the sleeve 204 is twisted in the opposite direction,
the sleeve 204 and cage 214 move away from the handle 12 as the
balls 220 travel along the races 112 towards their beginnings
adjacent to the proximal open end 114 of the mounting portion 110
of head 14. As this occurs, the contact spring 144 biases the
lamp holder 146, lamp 194, reflector 196, lens 222 and lens ring
224 away from the handle 12 while the battery spring 64 biases
the battery pin 62 out of contact with the central, positive
battery terminal 38.
In accordance with the stated low magnetic susceptibility
characteristics of the flashlight of the present invention, Table
1 lists the magnetic susceptibilities of the various materials
used to construct the flashlight along with selected other
materials.
Material | Density (g/cc) | Atomic or Molecular Weight | Susceptibility (x 106) |
Carbon (polycrystalline graphite) | 2.26 | 12.011 | -218 |
Gold | 19.32 | 196.97 | -34 |
Beryllium | 1.85 | 9.012 | -24 |
Silver | 10.50 | 107.87 | -24 |
Carbon (diamond) | 3.513 | 12.011 | -21.8 |
Zinc | 7.13 | 65.39 | -15.7 |
Copper | 8.92 | 63.546 | -9.63 |
Water (37°C) | 1.00 | 18.015 | -9.03 |
Human Soft Tissues | ∼1.00-1.05 | - | ∼(-11.0 to - 7.0) |
Air (NTP) | 0.00129 | 28.97 | +0.36 |
Stainless Steel (nonmagnetic, austenitic) | 8.0 | - | 3520-6700 |
Chrome | 7.19 | 51.996 | 320 |
It is known that brass is an alloy of copper and zinc.
In contrast, Table 2 lists the magnetic susceptibilities of
various relatively highly magnetic materials.
Material | Density (g/cc) | Atomic or Molecular Weight | Susceptibility |
Nickel | 8.9 | 58.69 | 600 |
Stainless Steel (magnetic, martensitic) | 7.8 | - | 400-1100 |
Iron | 7.874 | 55.847 | 200,000 |
The data use to construct Tables 1 and 2 was obtained from a
paper authored by John Schneck of General Electric Corporate
Research and Development Center, Schenectady, New York 12309,
entitled "The Role of Magnetic Susceptibility In Magnetic
Resonance Imaging:Magnetic Field Compatibility of the First and
Second Kinds". The disclosure of that paper is incorporated
herein by reference.
Thus, the flashlight of the present invention is an
instrument which is useful for pre and post clinical and surgical
applications, especially in an environment proximate the strong
magnetic field emitted by a magnetic resonance scanner.
It is appreciated that various modifications to the
inventive concepts described herein may be apparent to those of
ordinary skill in the art without departing from the spirit and
scope of the present invention as defined by the appended claims.