U.S. patent number 3,884,228 [Application Number 05/445,845] was granted by the patent office on 1975-05-20 for intravenous feeding system.
This patent grant is currently assigned to The Lynkeus Corporation. Invention is credited to Steven Hahn.
United States Patent |
3,884,228 |
Hahn |
May 20, 1975 |
Intravenous feeding system
Abstract
A closed intravenous infusion system comprises a completely
filled, collapsible bottle of accordion type construction, motor
driven means for mechanically compressing the bottle and forcing
the intravenous fluid out of the bottle into an administration set,
and means for controlling operation of the motor driven means so as
to provide a desired feeding rate and to stop the feed when the
bottle has been emptied to the desired degree, or in the event of a
fluid blockage or other malfunction of the system. The top flange
of the bottle is provided with a diaphragm aperture through which
drugs may be injected into the intravenous solution, while the
lower end or neck of the bottle also contains a diaphragm through
which the administration set may be inserted. The bottom flange is
also provided with another diaphragm subject to the fluid pressure
in the bottle which is operative to stop the feed if the pressure
becomes excessive as a result of fluid blockage downstream. The
neck of the bottle is made of a special material which passes
infrared energy, which is not passed by liquid, and is associated
with an infrared source and detector which detect the failure of
drops of fluid to appear in the drop chamber during operation of
the system and thereupon produce an alarm.
Inventors: |
Hahn; Steven (East Hampton,
NY) |
Assignee: |
The Lynkeus Corporation (East
Hampton, NY)
|
Family
ID: |
23770421 |
Appl.
No.: |
05/445,845 |
Filed: |
February 26, 1974 |
Current U.S.
Class: |
604/131;
128/DIG.12; 222/59; 222/96; 222/103; 340/611; 604/65; 604/245 |
Current CPC
Class: |
A61M
5/1689 (20130101); A61M 5/148 (20130101); A61M
5/16854 (20130101); Y10S 128/12 (20130101) |
Current International
Class: |
A61M
5/145 (20060101); A61M 5/148 (20060101); A61M
5/168 (20060101); A61m 005/14 () |
Field of
Search: |
;222/59,95,96,103,214
;340/239R ;351/51 ;128/214R,214E,214F,214.2,DIG.12,DIG.13 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Truluck; Dalton L.
Attorney, Agent or Firm: Cameron, Kerkam, Sutton, Stowell
& Stowell
Claims
What is claimed is:
1. A closed intravenous feeding system comprising a feed container
of collapsible fluid-tight construction adapted to be completely
filled with fluid to be intravenously administered to a patient, an
administration set detachably connected to said container, means
for mechanically compressing said container and thereby forcing
fluid out of the container into said administration set, means for
controlling the rate of compression of said container and thereby
controlling the rate of feed of fluid to the administration set,
means for disabling said compression means and stopping compression
of said container when the pressure of the fluid therein rises
above a predetermined value, means for disabling said compressing
means when said container has been emptied to a predetermined
extent, means for producing an alarm signal when said compressing
means becomes disabled, a drop chamber between said administration
set and the lower end of said container, means for detecting the
presence of fluid drops in said drop chamber, means for producing
an alarm signal when drops fail to appear within said chamber
during a predetermined period of time, said container being of
accordian construction having upper and lower flanges, and said
compressing means including a pair of vertically extending rods
offset from said container, means for detachably connecting the
upper ends of said rods to the upper flange of said container, and
means including an electric motor and a solenoid operated clutch
for positively moving said rods downwardly at a predetermined
speed.
2. A closed intravenous feeding system as defined in claim 1
wherein said rods and said connecting means are electrically
conductive, and the energizing circuit of said clutch includes said
rods, said connecting means and an electrical circuit in said upper
flange adapted to be closed by said connecting means.
3. A closed intravenous feeding system as defined in claim 1
including a stationary support for the lower flange of said
container, a pressure sensing diaphragm in said lower flange, and a
normally closed pressure actuated switch carried by said support
positioned beneath and in contact with said diaphragm, said switch
being operable to open the energizing circuit of said clutch and
thereby disable said compressing means when the pressure in said
container sensed by said diaphragm exceeds a predetermined
amount.
4. A closed intravenous feeding system as defined in claim 1
wherein said connecting means includes a horizontal bar connecting
the upper ends of said rods, and wherein said means for moving said
rods downwardly includes a vertically extending toothed rack having
its upper end connected to said bar, and gearing driven by said
motor for engaging said rack.
5. A closed intravenous feeding system as defined in claim 4
wherein said rack is rotatable about its longitudinal axis to move
the teeth thereof into and out of engagement with said gearing.
6. A closed intravenous feeding system as defined in claim 1
including means for varying the speed of said motor and thereby
varying the rate at which fluid is fed to said administration
set.
7. A closed intravenous feeding system as defined in claim 1
including an electric circuit for energizing said solenoid operated
clutch, said circuit having a plurality of switches connected in
series all of which must be closed in order to energize said
clutch, and means for selectively opening one of said switches in
the event of a malfunction of the system.
8. a closed intravenous feeding system as defined in claim 1
including an electric circuit for energizing said solenoid operated
clutch, said circuit having a plurality of switches connected in
series all of which must be closed in order to energize said
clutch, and means for opening one of said switches when the fluid
pressure in said container exceeds a predetermined mount.
9. A closed intravenous feeding system as defined in claim 1
including an electric circuit for energizing said solenoid operated
clutch, said circuit having a plurality of switches connected in
series all of which must be closed in order to energize said
clutch, and means for opening one of said switches when said
container has been emptied to a predetermined extent.
10. In a closed intravenous feeding system for use with an airtight
feed container of collapsible construction adapted to be completely
filled with fluid to be intravenously administered to a patient,
said container having upper and lower flanges, a flexible wall
connecting said flanges and an administration set connected to the
lower end thereof, means for mechanically compressing said
container and thereby forcing fluid out of the container into said
administration set comprising a support for the lower flange of
said container, a pair of vertically extending connecting rods
offset laterally from said support, a pair of arms pivotally
mounted on the upper ends of said connecting rods for movement in a
horizontal plane toward and away from the upper flange of said
container when the latter is mounted on said support, means carried
by said arms for releasably engaging the upper flange of said
container, and means for positively moving said rods downwardly
including a vertically extending toothed rack connected to said
connecting rods, an electric motor and gearing driven by said motor
for engaging and driving said rack.
11. In a closed intravenous feeding system, the combination defined
in claim 10 including a solenoid operated clutch for drivingly
connecting said motor to said gearing, and wherein said connecting
rods and said arms are electrically conductive, and the energizing
circuit of said clutch includes said rods, said arms and means
carried by the upper flange of said container for forming a
conductive path between said arms when the latter are in engagement
with said flange.
12. In a closed intravenous feeding system, the combination defined
in claim 10 wherein said toothed rack is rotatable about its
longitudinal axis to move the teeth thereof into and out of
engagement with said gearing.
Description
This invention relates to systems for the intravenous feeding to
patients of fluids such as blood, saline and sugar solutions, and
is particularly directed to an improved apparatus for positively
forcing the fluid into the administration set at a predetermined
rate and automatically stopping the feed when the bottle has been
emptied to a predetermined amount, or if the fluid pressure becomes
excessive as a result of a fluid blockage downstream, or in the
event of some other malfunction of the system. The apparatus also
energizes an alarm when the feeding is stopped, or when the
disappearance of fluid drops in the drop chamber is detected.
The conventional intravenous feeding system consists of a glass
bottle containing the solution, an administration set which usually
comprises a drop chamber and a rudimentary valve to control flow,
and a catheter which is inserted into the patient. In a majority of
cases, these prior systems are gravity fed, although in some
instances some sort of pump, usually peristaltic or hypodermic, may
be employed. A number of problems arise in use of the traditional
intravenous feeding systems, including variations in the desired
feed rate as a result of plastic deformation and bottle head
pressure changes. Furthermore, such systems usually do not include
monitoring features which inform the nursing staff when a bottle is
empty, or when a pronounced deviation has taken place from a preset
feed rate.
A number of devices have been developed for improving the
performance of these prior systems, including that disclosed in the
application of Steven Hahn et al., Ser. No. 350,922, filed Apr. 13,
1973. Other existing systems for feeding intravenous fluid from a
closed container by compressing the container, including devices
for controlling feed rates, and for stopping the feed when the
container is empty or when the fluid pressure therein exceeds a
predetermined amount, are shown in such patents as Cherkin, U.S.
Pat. No. 2,761,445 and Adelberg, U.S. Pat. No. 3,640,277.
The device of the present invention is an improved intravenous
feeding system which operates on the force feed principle and
comprises a completely filled, collapsible bottle of accordion type
construction, motor driven means for mechanically compressing the
bottle and forcing the intravenous fluid out of the bottle into an
administration set, and means for controlling operation of the
motor driven means so as to provide a selected feeding rate, and to
stop the feed, and to sound an alarm, when the bottle has been
emptied to a predetermined extent, or in the event of a fluid
blockage downstream or other malfunction of the system. The top
flange of the bottle is provided with a diaphragm aperture through
which drugs may be injected into the intravenous solution, and the
lower end or neck of the bottle also contains a diaphragm through
which the administration set may be inserted. The bottom flange is
provided with another diaphragm subject to the fluid pressure in
the bottle which is operative to stop the feed if the pressure
becomes excessive. The neck of the bottle includes a window made of
a material which passes infrared wavelengths, and is associated
with an infrared source and detector which detect the absence of
fluid drops in the drop chamber and sound an alarm if this
condition occurs.
The feed control system includes a housing containing a carriage
mounted on two parallel guide rods so as to move freely in a
vertical path; a drive rack attached at its lower end to the
carriage and to a guide bar at its upper end; two parallel
connecting rods similarly attached to both the carriage and the
guide bar; two rotatable contact arms attached to and pivotable
about the upper ends of the connecting rods and adapted to be
detachably connected to the top flange of the bottle; and an
electric motor and associated driving means for pulling the drive
rack downwardly when the system is in operation, the speed of which
motor is accurately controlled dependent upon the setting of a feed
rate member forming part of the contrl system. The top flange of
the bottle is provided with a conductive metal rim which
constitutes part of a series circuit which must be completed
through the contact arms and connecting rods before the motor is
operative to pull the drive rack downwardly and collapse the
bottle.
Referring now to the drawings, wherein like reference characters
indicate like parts throughout the several views:
FIG. 1 is a side view, partially in section, of an intravenous
feeding system constituting one embodiment of the present
invention;
FIG. 2 is a front view, partially in section, of the apparatus of
FIG. 1 with the intravenous fluid bottle (hereinafter referred to
as the IV bottle) and other parts omitted in the interest of
clarity;
FIG. 3 is a partial side view of the housing of the system showing
the reserve solution scale and window, and partially broken away to
show components of the feed limit control;
FIG. 4 is a top view of the system housing with the IV bottle
omitted, showing the guide bar and contact arms, and partially
broken away to illustrate the drop detection means.
FIG. 5 is a partial front view of the housing with the IV bottle
omitted, showing the system controls;
FIG. 6 is a fragmentary top view, partially in section, of the
guide bar and contact arm assembly in closed position;
FIG. 7 is a view similar to FIG. 6 showing the guide bar and
contact arm assembly in open position;
FIG. 8 is a detailed view of one of the lock pins carried by the
guide bar;
FIGS. 9 and 10 are schematic representations of the drive rack and
motor driven worm and driving gear elements in engaged and
disengaged positions, respectively;
FIG. 11 is a perspective view of the feed limit control mechanism
and the reserve solution scale and window relative to the carriage;
and
FIG. 12 is a diagram of the electronic circuitry of the intravenous
feeding system illustrated in FIGS. 1-11.
With reference to FIGS. 1-5, the intravenous feeding system of the
present invention comprises a housing 20 of any suitable material
which contains and supports all of the mechanical and electronic
components of the system and serves as a base on which an IV bottle
is mounted when the system is in operation. As shown in FIG. 3,
housing 20 is provided with a clamping member 22 by which the
housing may be detachably connected to an ordinary IV bottle
standard or any other support adjacent the bedside of a
patient.
Inside the housing 20 a carriage 24, fabricated of electrically
non-conductive plastic, is mounted on a pair of vertically
extending carriage guide rods 26, the upper ends of which are
attached to bosses 28 integrally molded with the top wall of
housing 20 and having their bottom ends attached to sockets 30
which are adjustably connected to the bottom wall of the housing by
means of screws 32 and nuts 34 to permit alignment of the guide
rods. A pair of vertically extending, electrically conductive
connecting rods 36 are pressed at their lower ends into recesses 38
in carriage 24 and are fixed thereto by contact screws 40 which
also form part of the electronic circuit hereinafter described.
Mounted on the upper ends of connecting rods 36 is a horizontal
guide bar 42, also formed of electrically non-conductive plastic,
having openings 44 into which the upper ends of connecting rods 36
are pressed, the guide bar thus extending transversely between and
rigidly interconnecting the upper ends of the connecting rods. The
underside of guide bar 42 is provided at each end with a recess 46
receiving the inner end of a movable contact arm 48 which is
mounted on and free to pivot about connecting rod 36 and is held in
position on the latter by means of a retaining ring 50.
Mounted in a sleeve 52 in carriage 24 and extending upwardly in the
same vertical plane as connecting rods 36, equally spaced from the
latter, is a drive rack 54, the upper end of which passes through a
sleeve 56 in the central portion of guide bar 42 and into a recess
58 formed in the upper surface of the guide bar. Drive rack 54 is
freely rotatable about its longitudinal axis, but it is restrained
from longitudinal axial movement relative to carriage 24 and guide
bar 42 by a retaining ring 60 beneath sleeve 52 at its lower end
and by a knob 62 secured to its upper end by a set screw 64. As
will be seen in FIG. 4, the knob 62 has a knurled edge 66 of a
diameter greater than the width of guide bar 42 so that it may be
manually turned and thereby rotate the drive rack 54 about its
longitudinal axis for a purpose hereinafter described.
As shown in FIG. 2, the connecting rods 36 and the drive rack 54
pass freely through openings 68 for the guide rods and opening 70
for the drive rack, these openings being formed in the top wall of
housing 20, so that in the uppermost position of the carriage 24
the top surface 72 thereof abuts against the bottom ends of bosses
28, while in its lowermost position the bottom surface 74 of the
carriage bears against the tops of sockets 30.
Drive rack 54 is a cylindrical steel rod with gear teeth 76
machined in a plane parallel to the rod axis and tangent to its
circumference, and to a depth proportionate to the standard gear
pitch selected for mating with the worm gear 78 (FIG. 1) of the
motorized rack driving assembly later to be described. The upper
end of drive rack 54 which passes through guide bar 42 beneath the
recess 58 is provided with two transverse blind holes 80 (FIG. 2)
extending parallel to the plane of the gear teeth 76. As shown in
detail in FIGS. 6-8, the lower portion of guide bar 42 between
recesses 46 is provided with a pair of horizontally extending
stepped recesses 82 in which are mounted lock pin assemblies each
consisting of a cam follower portion 84 which is urged outwardly of
recess 82 by a spring 86 interposed between the inner end of the
cam follower portion and the shoulder of recess 82, and a pin 88
having a forced fit in cam follower portion 84 and a rounded end
adapted to extend into one of the blind holes 80 in the drive rack
when the rack is in the position illustrated in FIG. 2. In order to
avoid a short circuit in the safety circuit hereinafter described,
a sleeve 90 (FIG. 8) of insulating material is interposed between
the outer end of each pin 88 and the recess in cam follower 84. The
inner or pivoted end of each contact arm 48 is provided with a cam
surface 92 against which cam follower 84 is maintained by spring
86, so that when the drive rack and the contact arm are in the
positions illustrated in FIGS. 2 and 6, respectively, the
associated pin 88 is forced into one of the blind holes 80 in the
drive rack. The drive rack is then fixed to guide bar 42 against
rotation by knob 62 with its gear teeth 76 in messh with worm gear
78.
Turning now to FIG. 1, the mechanism for pulling the drive rack 54
downwardly, carrying with it the connecting rods 36, guide bar 42
and contact arms 48, comprises a driving motor 94 having a shaft 96
connected to a worm 98 which extends upwardly into engagement with
the worm gear 78, the latter having its horizontal shaft journaled
in a bracket 100 on top of the motor casing. The motor 94 is
connected to shaft 96 through a solenoid operated clutch (not shown
in FIG. 1), and is pivoted at its lower end on a horizontal shaft
102 carried by the housing 20 so that worm gear 78 may be yieldably
urged toward driving engagement with the gear teeth 76 of drive
rack 54 by means of a spring 104 interposed between bracket 100 and
a stop 106 carried by the housing 20. With the parts positioned as
shown in FIGS. 1 and 2 and the motor clutch engaged, motor 94
causes rotation of worm 98 and worm gear 78, and rotation of the
latter is converted into linear downward movement of drive rack
54.
In order to disengage the drive rack 54 from worm gear 78, contact
arms 48 are moved manually outwardly about their pivots on
connecting rods 36 to the position indicated in FIG. 7, at which
time the cam follower portions 84 of the lock pin assemblies will
be urged by springs 86 outwardly against the receding portions of
cam surfaces 92 and the pins 88 will be withdrawn from the blind
holes 80 in the drive rack. Drive rack 54 may then be rotated by
means of knob 62 through an arc of 90.degree. or more, and thus
cause gear teeth 76 to disengage worm gear 78. The subassembly
comprising guide bar 42, connecting rods 36, drive rack 54 and
contact arms 48 may then be moved vertically by manual force
applied to either the guide bar or the contact arms so as to
position the subassembly, including carriage 24, at any point
within the limits of its vertical travel range. When the
subassembly has been moved upwardly or downwardly to the desired
position, drive rack 54 is rotated by knob 62 into the position
illustrated in FIGS. 1 and 2, whereupon the gear teeth 76 are again
in engagement with worm gear 78. Contact arms 48 are then pivoted
to the closed position illustrated in FIGS. 1, 2 and 6 so that the
locking pins 88 again enter the blind holes 80 in the drive rack,
whereupon the subassembly is held in its set position against the
force of gravity.
The apparatus is now ready to receive the IV bottle 108 which, as
shown in FIGS. 1 and 3, is of cylindrical accordion pleated,
collapsible construction, made of any suitable plastic material,
including biodegradable material, and having a relatively thin side
wall 110, a relatively rigid top flange 112, and a relatively rigid
bottom flange 114 providing a base adapted to rest on and to be
supported by a slanting platform 118 forming part of the top wall
of housing 20.
After the subassembly comprising drive rack 54 and the associated
elements previously mentioned has been raised to the proper height,
and the drive rack has been rotated to the engaged position, the IV
bottle 108 is placed on platform 118, contact arms 48 are moved to
their closed position, and the outer ends thereof are fixed to the
top flange 112 of the bottle by means of channel shaped,
flange-embracing clasps 120 and lock screws 122. If the motor
clutch is now engaged, worm gear 78 will exert a downward pull on
drive rack 54 and, through guide bar 42 and contact arms 48, force
the top flange of bottle 108 downwardly so as to compress the
bottle and force the IV fluid through the neck 124 thereof into a
drop chamber 126 which is threaded onto the neck 124. The lower end
of drop chamber 126 is externally threaded to receive the upper end
of an administration set having a hollow needle 128 adapted to
pierce a diaphragm 130 carried by the lower drop chamber 126. The
administration set also includes a length of flexible tubing 132 to
the end of which is attached a conventional catheter 134 adapted to
be inserted in a vein of the patient to be fed intravenously.
The cylindrical wall 136 of the drop chamber is formed of an
optically clear plastic material, such as Plexiglass or Lucite,
which passes infrared light, and is positioned adjacent a window
138 of similar material forming part of housing 20 behind which,
within the housing, is located a source of infrared light 140. At
the side of drop chamber wall 136 opposite the window 138,
diametrically opposite the infrared source 140, is an infrared
detector 142 which forms part of the electronic circuitry of the
system later to be described with reference to FIG. 12. For
convenience of illustration, window 138, infrared source 140 and
detector 142 are shown in FIGs. 1 and 5 at positions 90.degree.
from their actual positions indicated in FIG. 4.
In order to prevent premature engagement of the clutch of rack
drive motor 94 when the rack 54 is in mesh with worm gear 78, a
safety interlock is provided as an integral part of the system. As
previously indicated, the carriage 24 and guide bar 42 are made of
an electrically non-conductive plastic material, while connecting
rods 36 and contact arms 48 are metallic and electrically
conductive. The top flange 112 of IV bottle 108 is provided with a
metallic, electrically conductive collar or rim 144 so that, when
the metallic lock screws 122 of the flange embracing clasps 120 of
contact arms 48 are tightened against the metal collar 144, a
conductive path is established starting at contact screw 40 on the
left (in FIG. 2) connecting rod 36, through left connecting rod 36,
left contact arm 48 and its lock screw 122, through metal collar
144 to right lock screw 122, right contact arm 48, right connecting
rod 36 and ending at the latter's contact screw 40. As will later
appear from FIG. 12, unless the conductive path thus described is
closed, motor 94 cannot drive rack 54. At the same time, the
insulating sleeves 90 (FIG. 8) of the lock pin assemblies prevent
the establishment of a parallel electrical path to the metal ring
144 via the drive rack 54, the blind holes 80 and the lock pin
assemblies. Consequently, no electrical continuity is established
unless the IV bottle 108 is in properly clamped position.
The IV bottle 108 is completely filled with intravenous fluid,
either by the solution manufacturer or at the hospital, and does
not contain any air relief valves. However, the top flange 112 of
the bottle is provided with a small neoprene diaphragm 146 through
which a physician or nurse may hypodermically inject drugs which
are to be administered to the patient in addition to the
intravenous solution. In order to indicate the volumetric condition
of the IV bottle when the system is in operation, a calibrated
scale 148 is adhesively bonded to one side of carriage 24, and a
window 150 having an index line 152 is provided in housing 20
through which the scale 148 is visible, as shown in FIGS. 2, 3 and
11. Motion of the carriage 24 and the scale 148 can be observed
through the window 150, and the calibration numbers on the scale
can be read against the index line 152 to give a quantitative
indication of the volumetric condition of, or the amount of reserve
solution remaining in, the IV bottle.
Means are also provided for presetting the amount of solution to be
dispensed and automatically stopping the downward movement of
carriage 24 when the preset amount of solution has been forced out
of the IV bottle. As shown best in FIG. 11, carriage 24 is provided
with a reed switch 154 which, when closed, produces an electrical
signal which declutches motor 94 from rack driving worm 98 and thus
stops downward movement of carriage 24. Mounted adjacent the path
of movement of carriage 24 is a belt 156, carried by a drive pulley
158 and a spring-loaded idler pulley 160, and fixed to the belt 156
is a magnet 162. Drive pulley 158 is mounted on a shaft 164 which
extends horizontally outward of the housing 20 and is provided at
its outer end with a feed limit control dial 166 calibrated to
indicate the amount of intravenous solution which it is desired to
dispense when the system is activated (see FIG. 5). Rotation of
dial 166, transferred by shaft 164 to drive pulley 158, causes the
belt 156 to move linearly between the pulleys 158 and 160 so as to
move the magnet 162 to a predetermined position parallel to the
path of reed switch 154 as the latter moves with carriage 24. When
the reed switch comes into alignment with magnet 162, the switch is
activated to stop downward movement of carriage 24 at the preset
point representative of the desired volumn of intravenous solution
to be dispensed. In order to signal when the IV bottle is empty, a
normally closed limit switch 168 (FIG. 2) is mounted on the bottom
wall of housing 20 beneath the carriage 24 and is opened by the
latter when it reaches the lower end of its path of movement.
Means are also provided for producing a signal and declutching rack
driving motor 94 in the event that an obstruction or blockage to
the flow of intravenous fluid occurs downstream of the bottle which
increases the fluid pressure within the bottle. To this end, as
indicated in FIGs. 1 and 4, the bottom flange 114 of IV bottle 108
is provided with a relatively thin, pressure sensitive diaphragm
170 which overlies and engages the plunger of a normally closed,
pressure actuated switch 172 carried by the platform 118 of housing
20. When the fluid pressure in bottle 108 increases above a
predetermined amount, switch 172 is opened by downward movement of
diaphragm 170. Like reed switch 154 and limit switch 168, switch
172 is located in the energising circuit of a solenoid which
controls a clutch between the motor 94 and its rack driving worm
98. When any of switches 154, 168 and 172 opens, power is removed
from the clutch operating solenoid, the motor 94 is disconnected
from the worm 98 and the downward movement of drive rack 54 stops.
The electronic circuitry of the motor 94 and its solenoid operated
clutch will be described in detail hereinafter with reference to
FIG. 12.
Referring now to FIG. 12, the electronic circuitry of the
intravenous feeding system of the present invention includes a DC
power supply having a transformer 174, a bridge rectifier 176 and
an integrated circuit 5 volt regulator 176 which furnishes the
regulated DC voltage for operating the system. A push-button switch
180 in the primary circuit of transformer 174 constitutes the
system on/off switch.
The system also includes a 100 KC crystal oscillator 182 and an
associated integrated circuit 184, the frequency of the oscillator
being controlled by a feed rate control variable capacitor 186. The
output of oscillator 182 is fed to an integrated circuit down
divider and buffer amplifier 188, 190, 192 which divides the 100 KC
clock frequency (which is variable over a narrow range by the
setting of the feed rate control capacitor 186) down to 60 cycles
which is again variable in direct proportion to the frequency
variation of the basic oscillator 182. The 60 cycle signal produced
by down divider 190 is fed to the power amplifier 192 from which it
is applied to the 60 cycle synchronous motor 94, the motor which
pulls down the drive rack 54 and thereby empties the IV bottle 108
at a rate depending upon the frequency which is applied across the
motor. This frequency can be made to vary between 50 and 70 cycles
by varying the clock frequency of the 100 KC crystal oscillator
182, thereby causing the motor 94 to speed up or slow down. The
motor 94 runs continuously as long as the on/off switch 180 is
closed, but is connected to the rack driving worm 98 (FIG. 1) by a
solenoid operated clutch 194 (FIG. 12), the functioning of which is
hereinafter described.
At the same time that the clock oscillator 182 is running at
approximately 100 KC, the output signal of the associated
integrated circuit 184 is fed through another series of buffer
amplifiers and down dividers 196, 198, 200 which take the variable
100 KC signal and divide it down to 10 KC through the down divider
198, the output of which is fed to the power amplifier 200 which in
turn drives the infrared light emitting diode 140. As shown in FIG.
1, the infrared diode 140 is located in housing 20 and shines its
narrow 10 KC beam through the window 138 and the drop chamber 126
of the IV bottle 108 onto the phototransistor or infrared detector
142. The detector 142 will thus see a 10 KC signal whenever the
path between it and the diode 140 is open. However, when a drop of
the intravenous solution interrupts the beam, the 10 KC signal will
be removed while the drop is in the path of the beam. Consequently,
the higher the drop rate, the shorter will be the period during
which the 10 KC signal will appear between drops.
The output of infrared detector 142 is fed to a narrow band-pass
amplifier consisting of three stages on an integrated circuit chip
202. The output of band-pass amplifier 202 is fed through a
sensitivity control element 204 to a three stage transistor
amplifier 206, 208, 210, the last stage 210 terminating in a relay
circuit 212 across which a capacitor 214 is placed. As long as a 10
KC signal is received from the infrared transmitter 140 by the
detector 142, a signal will appear through the band-pass filter 202
into the amplifier circuitry 206, 208, 210, the relay 212 will be
energized and its contacts, shown at 216, will remain closed. As
soon as the infrared beam disappears, the amplifier 206, 208, 210
will open the relay 212. However, the relay will not open
immediately because the charged capacitor 214 will tend to hold it
closed for from 5 to 10 seconds. The circuit will thus detect the
absence of a 10 KC signal for periods of time exceeding
approximately ten seconds, but will disregard absence of the
infrared beam caused by drops passing through the beam which is
only a brief phenomenon. Accordingly, when the feed bottle 108 is
empty and drops fail to appear in drop chamber 126, or when some
other malfunction has taken place causing a disappearance of drops,
opening of the contacts 216 will deenergize clutch 194 and thereby
stop the movement of drive rack 54, and also deenergize an alarm
relay 218, the coil of which is connected in parallel with the
winding of clutch 194. When this occurs, an alarm or warning
condition exists which is brought to the attention of the nurce by
means of a signal light 220 and an audible signal member 222, such
as a buzzer.
In addition to feeding the alarm circuit, the band-pass amplifier
202 also feeds to a digital counter system 224 the clock signal
which is interrupted by the drop rate. The digital counter 224
counts the number of cycles between each two drops and displays
this count on a four digit display 226. For example, assume that
the drop chamber of the IV bottle 108 generates a drop every
second, which means that the 10 KC signal is present for 1 second,
then interrupted by a drop is then present another second, then
interrupted by another drop, etc. This means that the input signal
to counter 224 occurs at the rate of 10 KC. If drops should occur
every half second, this rate would be decreased to 5 KC, while if
drops should occur every 2 seconds, the rate would be increased to
20 KC. The integrated circuit of counter 224 receives this
information and converts it into an actual drop rate or feed rate
display with the drop passing through the beam acting as a reset
signal. Consequently, the display 226 will continuously show the
feed rate as it actually appears in the drop chamber. The actual
feed rate is controlled through the synchronous motor 94 which
pulls down the IV bottle 108 at a rate determined by the clock
crystal oscillator 182 and its associated feed rate control
186.
As previously mentioned, the rack driving or feeding motor 94 is
always running when the on/off switch 180 is closed. However, since
the motor 94 is connected to the rack driving worm 98 through the
solenoid operated clutch 194, the clutch must be energized before
the drive rack 54 can be actuated, even though the motor 94 is
running. But before the clutch can be energized, a number of
conditions must exist.
First, as previously described, the IV bottle contains a continuity
circuit indicated at 40, 36, 48, 122, 144, 40 in FIG. 12. As long
as there is no IV bottle in the system, or if the bottle is not
properly clamped in position, the continuity circuit is open and
the clutch 194 will not be energized, Second, the system also
contains the internal pressure sensing switch 172, operated by the
diaphragm 170 in the bottom flange of the IV bottle, which switch
is normally closed and opens when the diaphragm is moved downwardly
as a result of excessive pressure in the bottle due to blockage or
some other malfuntion down in the catheter 134. As soon as pressure
switch 172 opens, power is removed from the solenoid of clutch 194
and the feeding action stops. Third, the system also contains the
normally closed limit switch 168 which, when the carriage 24
reaches the limit of its downward movement and the IV bottle is
fully compressed, opens and again deenergizes the solenoid of
clutch 124. Fourth, the system also includes a partial feed
control, comprising the reed switch 154 and magnet 162, which
permits the nurse to feed only a fraction of the contents of the IV
bottle. The reed switch is normally closed, but when it passes the
magnet 162 in the latter's adjusted position, corresponding to the
portion of the bottle which it is desired to dispense, the switch
will open and once again cause the feeding action to stop. As
previously mentioned, the normally closed contacts 216 of relay 212
also open and deenergize the clutch 194 when drops of the
intravenous fluid fail to appear in the drop chamber 126. A series
of safety devices are thus built into the system, all of which
embody switches in the energizing circuit of clutch 194 which must
be closed before the clutch can be energized so as to couple the
feed motor 94 to the rack driving mechanism.
Alarm relay 218, in addition to producing a warning signal in the
case of a malfunction of the system, also serves another function.
In the energized state, this relay feeds the necessary positive DC
power to the digital counter system 224 and its associated display
226. Since the relay 218 is energized only when the feeding system
is in operation, the display will appear only under normal
operating conditions. If a malfunction occurs, deenergization of
relay 218 will also take DC power off the counter and display
system so that no display is visible when an alarm condition
occurs.
When first putting the IV bottle into the system, it will be
necessary to purge the system. For this purpose, a normally open,
manually actuated purge switch 228 is connected in parallel with
the fault detection circuits and, when closed, permits the nurse to
start feeding the intravenous fluid and watch for the drops
emanating from the needle of catheter 134. Once the drop operation
has been established, involving only a few seconds, the purge
switch 228 can be released, whereupon normal operation of the
system will commence.
There is thus provided by the present invention an improved
intravenous feeding system which operates on the force feed
principle and will automatically feed preset quantities of fluid to
a patient at any desired feed rate. The system is adapted to use
completely filled, collapsible IV bottles of accordion type
construction having transparent drop chambers adapted to be
associated with means which detect the absence of fluid drops in
the drop chamber and produce an alarm if this condition occurs. The
system also includes sophisticated electronic circuitry which
accurately controls and indicates the feed rate, and incorporates
safety devices which stop the feed and provide an alarm in the
event of a malfunction of the system.
Although only one embodiment of the feeding system has been
described and illustrated in the accompanying drawings, it will be
understood that various changes in the mechanical and electronic
elements of the system, which will be obvious to those skilled in
the art, may be made without departing from the inventive concept.
Reference should therefore be had to the appended claims for a
definition of the scope of the invention.
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