Note: Descriptions are shown in the official language in which they were submitted.
1~ 5SQ~8
MODE SEQUENCE CONTROL APPARATUS
BACKGROUND OF THE INVENTION
This invention concerns apparatus for controlling the
operation of apparatus in which proper mode sequence i5
requred. A blood fractionation apparatus is an example
of an apparatus in which proper mode sequence control is
required and the following description will be restricted
to this example, for the sake of convenience.
As used herein, the term "blood fractionation"
includes the separation and/or treatment of any fraction
of whole blood, including but not limited to plasma,
red cells, white cells, platelets and cryoprecipitate.
Typical blood fractionation techniques utilize
the collection of whole blood from donors in bags, and
removal of the bags to a centrifuge where the blood
fraction is separated from the whole blood. The blood
fraction is withdrawn from the bag and the remaining
blood is returned to the donor.
One significant blood fraction which has been
withdrawn by centrifugation for many years is plasma.
In certain plasmapheresis techniques, a bag containing
whole blood is placed in a centrifuge where the plasma
is separated and the remaining blood is returned to
the donor.
; More recently, automated centrifuges have been devised
which continuously withdraw whole blood from the donor,
centrifuge the whole blood to separate the plasma, harvest
the plasma, and return the remaining blood in its plasma-
poor condition to the donor in a continuous fashion.
'
q~
a
~15S~8
It has been proposed that the plasmapheresis be
carried out without using a centrifuge, because of the
inherent complexity and cost of centrifugation equip-
ment. To this end, the filtration of cells from whole
blood using a microporous membrane has been disclosed,
for example, in Blatt, et al. U.S. Patent No. 3,705,100.
It has been found that a membrane-type plasmapheresis
device yields platelet-free plasma while centrifuge
devices yield plasma containing some platelets.
Further, it has also been found that the membrane
plasmapheresis devices can also be designed to yield
much greater quantities of plasma in shorter times
than the centrifuge devices.
A membrane plasmaphersis apparatus, in which a
relatively inexpensive, disposable plasmapheresis
- filter membrane cell is utilized, is disclosed in
- DeVries, et al. Canadian Patent No. 1,127,091. An-
other membrane plasmapheresis filter cell of the
disposable type is disclosed in DeVries, et al. Canadian
20 Patent No. 1,127,092. In these patents, a parallel
membrane type of membrane plasmapheresis apparatus is
disclosed, and the filter cells disclosed therein are
relatively simple in construction and inexpensive to
produce.
On occasions, it is desired to treat the plasma
filtrate with an agent for detoxification, cleansing,
transformation, reaction, elimination of matter,
- addition of matter, or any other treatment character-
istic. A system that permits simultaneous plasma-
pheresis and plasma treatment is disclosed in DeVries,
et al. Canadian Patent No. 1,135,632. In this patent
~155~8
a system is disclosed in which the plasma m~y be
treated without requiring the plasma to be filtered
directly through a treatment reaction chamber.
Experi~.ents with membrane plasmapheresis filter
cells have shown their usefulness. It has been found
desirable to provide relatively automated equipment
that may be used conjointly with the disposable mem-
brane filter cells, to achieve ef~ective blood frac-
tionation.
The object of the present invention is to provide
an improved control apparatus for controlling the opera-
tion of apparatus in which proper mode sequence is
required, such as a blood fractionation apparatus.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the present invention there is
provided control apparatus for controlling the operation
of apparatus in which a proper mode sequence is required.
The control apparatus includes mode switch means, means for
providing a signal representing each mode, means for
encoding said mode signals to output a highest priority
signal only, a comparator, first programmed memory means
for storing proper mode sequence data, means for feeding
the encoded mode signal to an input of said first pro-
grammed memory means, means for feeding the encoded mode
signal to said comparator, means for feeding the memory
means output to the comparator, the comparator being oper-
able to compare the encoded mode signal with the memory
means output, and means coupled to the output of said com-
parator for providing (a) a first signal if there is a
first relationship between the encoded mode signal and the
memory means output, and (b) a second signal lf there is
second relationship between the encoded mode signal and
the memory means output.
llSSQ!q 8
In the illustrative embodiment, the control appara-
tus is disclosed in the enviroment of a blood fractiona-
tion apparatus which comprises a main housing carrying
at least one blood pump, a cell housing for receiving a
disposable blood fractionation filter membrane cell, and
means for coupling the housing to a source of electric
current.
In the illustrative embodiment, the main housing
has a panel defining a plurality of slots for receiving
disposable blood flow tubing within predetermined slots.
The housing carries an occluded vein sensor and a bubble
detector for cooperating with the tubing. Pressure
sensing means is provided for sensing pressure adjacent
the disposable cell. The housing has a manually operable
mode switch for settins control functions of the ap-
paratus.
In the illustrative embodiment, programmed means are
provided for preventing incorrect act~ation of predeter-
mined control functions. A door member covers at least
a portion of the slots to prevent access thereto. Means
inhibit operation of the door member and thus access to
the slots unless the manually operable mode switch is in
a predetermined position.
In the illustrative embodiment, the housing carries
a safety clamp for clamping the tubing to restrict flow
therein. Control means are coupled to the safety clamp
and to the pump for inhibiting operation of the pump
when the tubing is clamped. Audible alarm means are pro-
vided for signaling a selected malfunction. Operator con-
trol means are provided for muting the alarm, with thealarm means being operable to enable predetermine~ func-
tions during selected modes while ot~er functions are in-
hibited.
ll~SC~98
The apparatus of the illustrative embodiment also
includes an anticoagulant pump and means for carrying a
supply of anticoagulant. The presence of anticoagulant
is sensed and operation of the pump is inhibited if no
anticoagulant is sensed.
The apparatus of the illustrative embodiment includes
a fail-safe circuit coupled to the safety clamp, bubble
detector and pump. The fail-safe circuit includes delay
means and means for terminating operation of the apparatus
in response to a predetermined signal from either the
safety clamp, bubble detector or pump, after a predeter-
mined delay from receipt of the predetermined signal.
.
In the illustrative embodiment, the electrical
control apparatus is operable to set control functions
of the apparatus. The control functions include a
load mode enabling the fractionation apparatus to be
loaded with disposable tubing, a prime mode for priming
the system with a selected liquid, a bypass mode
~L15SQ~8
for withdrawing whole blood from a donor and passing the
~ho]e blood through the membrane cell but returning all
blood components to the donor, and a collect mode for
collecting one of the separated components while re-
turning other blood components to the donor. The controlfunctions a]so include an irrigate mode in which the ap-
paratus is not functioning to collect one of the separated
components, but a selected solution is provided to main-
tain venal punctures open and the tubing clean. The
control functions further incl~de a reinfuse mode in
which the other blood components within the tubing are
reinfused to the donor after one of the separated com-
ponents is collected.
In the illustrative embodiment, the blood fractiona-
tion apparatus includes a whole blood pump, a recircula-
tion pump, speed control means coupled to the whole blood
- pump and recirculation pump, blood flow tubing, means for
sensing (a) the whole blood pump rate, (b) the recircula-
tion pump rate, (c) blood pres~ure, (d) amount of blood
component that is collected, (e) air bubbles in the tubing
and (f) hemolysis. Display means are provided for dis-
playing predete~mined control functions and an alarm cir-
cuit is present for providing an audible alarm resultins
from the sensing of predetermined conditions. Safety
clamping means are provided for clamping the tubing under
predetermined condition~. A fail-safe circuit is coupled
to the safety clamping means, air bubble sensing means and
pumps. The fail-safe circuit includes delay means and
means for terminating operation of the apparatus in re-
sponse to a predetermined signal from either the c~ampingmeans, air bubble sensing means or pumps, after a predeter-
mined delay from receipt of the predetermined signal.
A more detailed explanation of a preferred embodi-
ment of the invention in the environment of a blood
fractionation apparatus is provided in the following
description, and is illustrated in the accompanying
drawings.
fi
~. .
~55Q~8
BRIEF DESCRIPTI~N OF THE DRAWINGS
FIGURE l is a perspective vi~ of ablood fractiona- I
tion apparatus;
FIGURE 2 is a front view of the top panel thereof;
~IGURE 3 is a top view of the shelf thereof;
FIGURE 4 is a view of the plasma collection scale
thereof;
FIGURE 5 is a perspective view of the occluded
vein sensor carried by the apparatus of FIGURE l;
FIGURE 6 is an enlarged fragmentary view of the
manually opera~le mode switch carried by the apparatus
of FIGURE 1, with the door in its closed position;
FIGURE 7 is a view similar to the view of FJGURE
6, with the door in its open position;
FIGURE 8 is a fragmentary view of another portion
of the panel of the FIGURE 1 apparatus;
FIGURE 9 is a fragmentary view of another portion
of the front panel of the apparatus of FIGURE l;
FIGURE lOa, lOb and lOc, when connected together,
comprise a block diagram of the elements and circuitry
of the blood fractionation appar~tus;
FIGURE lla and llb, when connected together,
comprise a schematic circuit diagram of the mode
circuit of the blood fractionation apparatus;
FIGURE 12 is a schematic circuit diagram of the
pump start circuit apparatus;
FIGURE 13 is a schematic circuit diagram of the
alarm mute circuit;
llSSQ~98
FIGURE 14 is a schematic circuit diagram of the
pump control circuit;
FIGURE 15 is a schematic circuit diagram of the
alarm circuit of the apparatus;
FIGURE 16 is a schematic circuit diagram of the
clamp circuit of the apparatus;
FIGURE 17 is a schematic circuit diagram of the
fail~safe circuit of the blood fractionation apparatus;
and,
FIGURE 18 is a schematic circuit diagram of the
basic fail-safe power system of the blood fractiona-
tion apparatus.
A
115S098
DETAILED DESCRIPTION OF THE
ILLUSTRATIVE EMBODIMENT
Referring to FIGURES 1-3 in particular, a main
housing 30 is carried by an upright 32 which is generally
L-shaped and includes a base 34 to which casters 36 are
connected. A series of ladd.er rungs 38 are provided to
e~able housing 30 to be moved vertically as desired for
proper height positioning, and a handle 40 is provided
for enabling the housing 30 and base 34 to be moved
along the floor.
Housing 30 includes a front panel 42 and a shelf
44, with front panel 42 carrying display windows and
control switches, racks 46 for receiving disposable
blood flow tubing, a manually operable mode switch 48
for setting control functions of th~ apparatus, and a
cell housing 49 for receiving a disposable blood frac-
tionation filter membrane cell.
Panel 42 also carries a tubing clamp 50, a hemolysis
detector 52 and a bubble detector 54.. Tubing clamp 50,
hemolysis detector 52 and bubble detector 54 are con-
nected to cooperate with the disposable tubing that is
carried by rack 46.
The display windows preferably allow the visi-
bility of light emitting diodes which indicate various
conditions. For example, the status of the apparatus
is displayed at window 56, the various alarms or mal-
functions are displayed at window 58, the whole blood
pump rate is displayed at window 60, the recirculation
pump rate is displayed at window 62, the plasma collec-
3~ tion volume is displayed at window 64 and the membranepressure is displayed at window 66. Panel 42 carries a
main off/on switch 68, an end point switch 69, a pump
start switch in the form of a push button 70, an
~.
l~SSQ98
emergency stop switch 71, mute alarm switch in the form
of a push button 72 for muting the alarm sound, a sensor
override switch 74 in the form of a push button for
overriding a particular sensor that is in an alarm con-
dition and a reset switch 76 in the form of a pushbutton.
The shelf 44 supports blood pump 78 and recircula-
tion pump 80. Pumps 78 and 80 are peristaltic pumps,
with their motors being enclosed within the housing 30.
Shelf 44 also supports an occluded vein sensor 82 and a
writing surface 84. While in the illustrative embodi-
ment the anticoagulant pump is not carried by the
housing, if desired, the anticoagulant pump could be
held on an upright pole 86 and powered by means of an
auxiliary power receptacle.
-~ Upright pole 86 is connected to the housing 30 for
supporting a plasma collection scale 88 and an anti-
coagulant liquid detector 87. Piasma collection scale
88 includes a hook 89 for receiving a plasma collection
container, preferably in the form of a plastic bag de-
fining a hole for being received by hook 89.
Cell housing 49 encloses a membrane cell 90, as
illustrated in FIGURE 2. Cell 90 may comprise a
disposable plasmapheresis membrane cell as described
in De Vries, et al. Canadian Patent No. 1,127,091
or a disposable cell as described in De Vries, et
al. Canadian Patent No. 1,127,092.
Referring to FIGURE 2 in particular, port 100
is the whole blood inlet and port 102 is the red
cells outlet. Port 104 is the plasma outlet. A
Y-site 106 is provided and is coupled to the needle
which is con~ected to the donor's ,vein for the
withdrawal of whole blood. A Y-site inlet 107 is
coupled to the anticoagulant supply and the Y-site
~.
1~55(~8
11
outlet 108 is connected to whole blood tubing 110.
Whole blood tubing 110 is coupled through occluded
vein sensor 82 and it extends through pump 78, and
to a Y-site 112. From the Y-site, the whole blood
travels through tubing 114 to whole blood inlet 100
and also through tubing 116 to a pressure reservoir
118. A pressure transducer is connected to pressure
reservoir 118 for measuring the prPssure with respect
to whole blood flow line 116. A sterile barrier 120
is provided between the pressure reservoir 118 and
the pressure transducer.
A blood outlet line 122 is coupled to red cell
outlet 102 and the red cells flow via line 122
through bubble trap 124 and tubing clamp 50 and to
a Y-site 125 below clamp ~0. Recirculation tubing
_ 126 is coupled to one of the arms of the Y so that
the red blood cells will flow via tubing 126, through
pump 80 and for recirculation via tubing 114 into
blood inlet 100. The other arm of Y-site 125 is coupled
to tubing 128 so that some of the red cells will flow
via tubing 128 to another Y-site 130 and then via
tubing 132 back to the donor. A saline line 134 is con-
nected to the other arm of the Y-site 130 for providing
saline to the donor. A saline line 136 is also coupled
to occluded vein ~ensor 82 for priming the system and
for maintaining patency of the needle.
Tubing 138 is connected to plasma outlet 104
and the pla ma ~ill flow via tubing 138 and through
an optical den~ity chamber 139 and then tubing 141
to the plasma collection bag 143.
As illustrated in FIGURE 7, a Y-site 145 is pro-
vided at the outlet of optical density chamber 139
with one arm of the Y being coupled to tubing 141
and the other arm of the Y being coupled to a bypass
line 147. Bypass line 147 returns the plas~a to the
A
1~l55~8
bubble trap 124. The purpose of the bypass line is
that during start-up, a substantial amount of saline
is found mixed with the plasma. This is detected by
the hemolysis detector 52 and the plasma mixed with
saline will flow in the bypass line 147 until line
138 and optical density chamber 139 shows relatively
clear plasma. At that stage, the hemolysis detector
52 will sense the relatively clear plasma and the
"collect plasma" lamp will be energized to indicate
to the operator that rotary mode switch 48 can be
turned to the "collect" mode.
Hemolysis detector 52 may be constructed in
accordance with the disclosure in U.S. Patent No.
4,305,659 entitled, "Photometric Apparatus and
Method", naming Richard I. Bxown, Arnold C~ silstad
and Michael Wicnienski as inventors. Bubbl-e detec-
tor 54 may be constructed in accordance with the
disclosure of U.S. Patent No. 4,341,116 entitled
"Liquid Absence Detector", naming as inventors
Arnold C. Bilstad and Michael Wicnienski. Occluded
vein sensor ~2 may be constructed in accordance with
the disclosure of U.S. Patent No. 4,309,993 entitled,
"Liquid Flow Sensing Apparatus", naming Richard L.
Brown as inventor. The plasma scale used in
connection with plasma chamber 88 may be constructed
in accordance with the disclosure of U.S. Patent No.
4,294,320 entitled, "Apparatus and Method For
Weighting Material Being Collected", naming Arnold
C. Bilstad and John T. Foley as inventors. The
mode switch 48 may be constructed in accordance with
the disclosure of the Canadian patent application entitled,
~15SQ~98
"Control System for Fluid Flow Apparatus", naming
Arnold C. Bilstad and Richard T. Brown as inventors,
373,735, filed March 24, 1981. Antigoagulant detec-
tor 87 may be constructed in accordance with the
disclosure of United States Patent No. 4,333,~16
entitled, "Liquid Presence Detector", naming
Arnold C. Bilstad and Richard I. Brown as inventors.
In order to understand the functions of the
previously-described structure and the circuitry
to be described below, a brief description of the
_ operation of the system will now be set forth.
First, mode switch 48 is rotated to "load"
position and door 100, on which the mOde switch
48 is carried, is opened from its closed position as
illustrated in FIGURE 6 to its open positions as il-
lustrated in FIGURE 7. It can be seen that door 140
is hinged at 142. The disposable tubing and equip-
ment are then inserted into the slots of the slotted
racks 46 as illustrated in FIGURES 2 and 7-9. Once
; 20 all of the disposable lines are properly connected
and inserted into the slotted racks 46 as described
above, door 100 is closed and "on" switch 68 is turned
to its "on" position. The end point switch 69 is
actuated to set the predetermined amount to be col-
lected. The whole blood pump speed is set by means
of dial 144 and the recirculation pump speed is set by
means of dial 146 tFIGURES 1 and 2).
,~:
. .
1~55~8
From "load" pOSition, the dial switch 48 is turned
to "prime" position and the system is primed. After
priming the system, the lines 110 and 132 are coupled
to the donor and the procedure may then commence. Dial
switch 48 is turned to its "bypass" position. In this
position, the donor's blood is withdrawn via tubing
110, passed through membrane cell ~0, ard bcth the red
blood cells and the plasma are returned to the donor
instead of th~ plasma being collected. In this manner,
the priming solution (e.g., saline solution) is flushed
out of the system and not collected.
Once hemolysis detector 52 senses that plasma is
present instead of saline, status display 56 displays
"collect plasma" and the operator may then turn dial
switch 48 to its "collect" position. In the collect
position, the plasma filtrate from membrane cell 90 is
transferred via line 138, chamber 139 and line 141 to
the plasma collection container 143 that hands from
hook 89 while the red cells are returned to the donor
via lines 122, 128 and 132.
Dial switch 48 is manually operated and carries an
electrical switch which follows the mechanical turning
of the dial switch. The system is programmed so that
the operation will terminate if the dial switch is
turned improperly, such as in the wrong direction or
from one mode to the wrong mode. For example, if the
dial switch is incorrectly turned from "bypass" to
"prime", the status display will show "mode switch" and
shortly thereafter the syste-m will shut off. Any other
incorrect turning of the dial switch will cause the
"mode switch" readout to occur on display 56 and
shortly thereafter the system will turn off. In the
event that the dial switch 48 is not in one of the
discrete positions, but is between.positions, displzy
i~SSQ~8
56 shows "mode switch" but there is a delay preventing
the system from being turned off so that the operator
has time to move from one position on dial switch
48 to another position of the dial switch.
Door 140 cannot be opened unless dial switch
48 is in its "load" position. Referring to FIGURE
7, at the back of dial switch 48 there is a keyway
150 which fits on a key 152. When dial switch 48
is turned, keyway 150 also turns key 152 which is
10 coupled to various camming members that appropriately
clamp the tubing that is within the housing. A
detailed description of switch 48 is set forth in
Bilstad and Brown U.S. application for "Control
System For Fluid Flow Apparatus", Serial No. 139,884,
filed on the same date as the present application.
In order to start the pumps moving, the system
has to be armed by unclamping tubing clamp 50.
Tubing clamp 50 comprises a pair of magnetically
coupled levers which must be squeezed together to
unclamp the tubing. Once the tubing is unclamped,
pump start button 70 may be pressed and the pumps
will start slowly at first and then increase speed
automatically.
The two levers which form the clamp and which are
pushed together to unclamp the tubing are coupled
together by means of an electromagnet. If for some
reason the two levers are forced apart or the electro-
magnet fails so that they come apart, the tubing clamp
will clamp the tubing and the pumps will immediately
stop, as the system is programmed to prevent operation
of the pumps while the tubing is being clamped.
When the tubing is clamped and the levers are apart,
status display 56 shows "return clamped" and when
"return clamped" is displayed, the pumps cannot oper-
ate.
~lSSQ~8
16
It can be seen that the machine is manuallyoperated and under the control of the operator. In
order for the machine to operate, the operator must
perform certain positive actions. In effect, there
are certain allowed modes while other modes are
incorrect and will operate to shut off the system.
Once the system is shut off, it will have to be reset
as if it had not been operating previously. Thus
once the system is shut off, the tubing will be clamped
and the two levers must again be pressed together
in order to arm the system. Further, if mute switch
72 was previously on to prevent the alarm from sounding,
once the system is shut off the mute switch will not
go on automatically when the system is restarted. The
mute switch 72 will again have to be pressedr
If during the "collect" mode there is a problem
and the operator desires to discontinue the collection
of plasma temporarily, the rotary switch 48 can be
turned to "irrigate". In the "irrigate" mode, the
machine is shut down and there is no plasma collection,
but the saline is dripping to keep the venapunctures
open and the lines clear.
When the required amount of plasmâ has been col-
lected, as set by end point switch 69, such as 550
or 650 ml, the alarm activates and there is a readout
on display 56 saying "collection complete". This is
effectively a weight measurement. Once the collection
is completed, no further collection can be performed
nor can the system start again, even if switch 48
is in ~he "collect" or the "bypass" mode.
The "reinfuse" mode may be used after the plasma
is collected. After collection, the rotary switch
48 can be turned to "reinfuse" and'the system is switched
so that saline is pumped from the saline bottle through
A
~S5Q~98
the tubing to push the red cells that are within the
system back into the donor's veins. The rotary
switch 48 is then turned to i~s "load" position and
this effectively becomes an "unload" mode because
5 the combination of "load" with the weight of the full
plasma collection container 143 allows everything to
be removed for another collection. Thus the "unload"
mode is really the "load" position of switch 48 in
combination with the weight of a full plasma container.
10 To get back to the "load" mode, the plasma container
is removed from hook 89 and another collection via
the machine can be performed.
The system is programmed so that inadvertent
turning of the rotary switch can be overridden.
15 For example, assume that the switch is in its "collec-
tion" mode and then turned to "irrigate", which is
an allowed operation. Now assume that the operator
wishes to turn back to "collect" but inadvertently
turns the rotary switch 48 to "reinfuse". The
20 system will then shut off. However, in order to pre-
vent having to start everything up again, the operator
can turn the rotary switch 48 back to "collect"
where he wants to be. He can then push the reset
button 76 and a resume button 156 simultaneously
25 and the program will be overridden so that the system
goes directly into the mode that is shown on switch
48.
A block diagram of the basic system is set forth
in FIGURES lOa-lOb-lOc, when these Figures are connected
30 together. The various sensors or detectors are
shown on the left side of the diagram and include a
whole blood pump tachometer 160, a recirculation pump
tachometer 162, a membrane pressure sensor 164 which
is connected at the hlood inlet side ~ith respect
to membrane cell 90, a plasma strain gauge 166 for
llSSOg8
18
weighing the collected plasma and forms a part of scale
88, an ACD presence sensor 87l bubble detector sensor
54, occluded vein sensor 82, and hemodetector sensor
52. Whole blood pump t.achometer 160 is coupled to
whole blood sensor circuit 170 via line 171 and circuit
170 is coupled to whole blood pump rate and volume
display 60 via line 172. Tachometer 160 is also
coupled to fail-safe circuit 174 via lines 171 and 175
and an emergency stop switch 173 is also coupled to
fail-safe circuit 174.
Recirculation pump tachometer 162 is coupled to
recirculation pump circuit 176 via line 177 and to
fail-safe circuit 174 via lines 177 and 178. Recircu-
lation pump circuit 176 is coupled to recirculation
pump rate display 62 via line 179.
Membrane pressure sensor 164 is coupled to
membrane pressure preamplifier 180 which is coupled
to membrane pressure circuit 182 via line 183. Cir-
cuit 182 is coupled to membrane pressure display
66 via line 184.
Plasma strain gauge 166 is coupled to plasma
scale preamplifier 186 via lille 187. ~reamplifier
186 is coupled to a plasma scale circuit 188 via line
189. Circuit 188 is coupled to plasma volume display
64 via line 190.
ACD sensor 87 is coupled to an ACD detector
preamplifier 192 via line 193. Preamplifier 192 is
coupled to the plasma scale preamplifier via line
194. Line 189 couples the output of the plasma
scale preamplifier 186 to an ~CD detector circuit 196,
the output 198 of which is connected to alarm circuit
200. Fail-safe circuit 174 is also connected to alarm
circuit via line 202. The output of membrane pressure
circuit 182 is also connected to ala~m circuit 200
via line 204. The output of alarm circuit 200 is
t~
1~55Q~8
19
connected yia line 205 to alarm display 58. Alarm
display 58 has the capacity to show the following
readout if a malfunction with respect to one of the
following items occur: "bubble detector", "occluded
vein", "hemolysis detector", "membrane pressure",
"ACD empty" and "fail-safe".
Bubble detector sensor 54 is coupled to bubble
detector circuit 206 via line 207. The output of
bubble detector circuit 206 is coupled via line 208
to fail-safe circuit 174 and another output of bubble
detector circuit 206 is coupled via line 209 to alarm
circuit 200. Occluded vein sensor 82 is coupled to
alarm circuit 200 via line 210. ~emodetector sensor
52 is coupled to hemodetector circuit 2I2 via line
213, with the output of hemodetector circuit 212
being coupled to alarm circuit 200 via line 214.
Sensor override switch 74 is coupled to alarm
circuit 200 via line 216 and to status display 56
via line 218~ Reset switch 76 is coupled to alarm
circuit 200 via line 219 and to mode circuit 220 via
line 221. Resume switch 156 is coupled to mode cir-
cuit 220 via line 222 and mode switch 48 is coupled
to mode circuit 220 via reinfuse signal line 224,
irrigate signal line 225, collect signal line 226,
bypass signal line 227, prime signal line 228, and
load signal line 229.
The output of mode circuit 220 is connected
to pump control circuit 230 via lines 231, 232.
Pump on/off switch 70, whole blood speed pump control
144 and recirculation pump control 146 are also connected
to pump control circuit 230 via lines 233, 234 and
235, respectively. Pump control circuit 230 is
connected to motor control 236 and to motor control
238 via lines 239 and 240, respectively. Fail-safe
circuit 174 is connected to a fail-safe relay 242
via line 243, and fail-safe relay 242 is connected to
~lSSQo~8
motor control 236 and 238 via lines 244 and 245,
respectively.
The plasma scale circuit 188 is connected to mode
circuit 220 via line 246. Line 246 also couples the
plasma scale circuit to mute circuit 248, the output of
which is coupled to an audible alarm 250. When mute
switch 72 is actuated, the audible alarm will be
~eactivated.
Alarm circuit 200 is coupled to the mute cir-
cuit 248 via line 252. The hemodetector circuit
is coupled to the mute circuit via line 253. The
mode circuit 220 is connect~d to the status display
via line 254. Clamp switch 50 is connected to status
display 56 via line 255 and to fail-safe circuit
174 via line 256. The fail-safe relay 242 is con-
nected to clamp magnet 50'via line 258 and mode
circuit 220 is connected to clamp circuit 260 via
line 261, with the clamp circuit 260 outputting to the
status disp1ay 56 via line 262 and to clamp magnet
50'via line 263.
In order to understand the operation of rotary
switch 48 and how certain operations are inhibited
while others are allowed, mode circuit 220, which is
schematically illustrated in FIGURES lla-llb (con-
nected together) will now be described.
Referring to FIGURES lla-llb, mode signal lines
224-229 from rotary mode switch 48 are fed via re-
sistors 270-275, respectively, and inverters 276-
281, respectivelyf to seven of the eight inputs of
a 1 of 8 priority encoder 284. The output 286 of an
AND gate 288 is connected to the highest priority
input of the priority encoder 284. The load signal
line is fed via line 290 to an input of AND fate
288 and the collection complete sig~al line is fed
via line 292 to the other input of AND gate 288.
~55~8
21
Priority encoder 284 provides a binary output via
lines 294, 295 and 296, which are fed thrcugh amplifiers
298, 299 and 300, respectively, to the binary inputs of
a PROM 304.
Referring to priority encoder 284, it is noted
that the load signal on line 229 has the lowest pri-
ority, while the unload signal (which is the combin-
ation of the collection complete signal on line 292 and
the load signal on line 290) has the highest priority.
Encoder 284 takes the highest priority input line and
outputs the highest level. In this manner, the various
modes are given status levels, in the following order
(starting with the lowest status): load, prime, by-
pass, collect, collection complete, irrigate, reinfuse
and unload.
PROM 304 could be a ROM if desired. The output of
PROM 304 is held by latch 306, which is clocked every
second so that the output of PROM 304 is loaded into
latch 306 via lines 307-310 every second. The output
of latch 306 is fed back to the input of PROM 304 via
lines 312-315. Lines 312-215 also feed the output of
latch 306 to inputs of a comparator 320. Comparator
320 compares the binary signal at the input of PROM 304
with a binary signal that is being fed back via lines
312-215. If those binary signals are not equal to each
other, an incorrect mode is indicated and the machine
is shut off. However, during the brief interval of
time that rotary switch 4 8 is being turned, those
binary signals will not be identical and this non-
identity will designate an incorrect mode. Output 322of encoder 284 senses all of the inputs and if there is
no signal from any of the inputs, this would signify
that dial switch 4 8 is between mode positions. When
dial switch 48 is between mode positions, a signal is
1~55Q'~8
22
fed to OR gate 324 via line 325 and this signal is
OR'd with an output signal from comparator 320 fed on
line 326. Thus either a signal on line 325 or a signal
on line 326 will be fed via OR gate output line 328 to
energize a lamp on display 56 which will read "mode
switch", as stated above.
PROM 304 is preferably a 256 x 4 PROM which
allows 256 possible combinations with respect to the
inputs.
The outputs from latch 306 are connected to a
second PROM 330 via lines 331-334. PROM 330 is a 32 x
8 PROM and the eight outputs of PROM 330 feed enable
signals via lines 336-343. For example, the signal on
line 336 is an anticoagulant pump enable signal, the
signal on line 337 is a whole blood pump enable signal,
_ the signal on line 338 is a hemolysis detector enable
signal, the signal on line 339 is a bubble detector
enable signal, the signal on line 340 is a tare/measure
select signal, the signal on line 341 is a clamp magnet
enable signal, the signal on line 34~2 is an occluded
vein sensor enable signal, and the signal on line 343
is a whole blood pump total volume counter enable
signal.
PROM 304 is the PROM (or ROM) which programs
whether the particular mode is correct. The second
PROM (or ROM) 330 is programmed to determine what
should be done when the system is in a valid mode. In
other words, if PROM 304 determines that the system is
in a proper mode, PROM 330 will determine what should
happen as a result of the proper mode (e.g., the
enable signals that should be provided). Thus the
output signals on lines 336-343 do not actually ener-
gize the pumps and other items, but they are enabling
signals. When rotary mode switch 4~ is turned to start
after the system has been loaded and primed, since this
mode is proper, the output of second PROM 330 will enable
~SSQ~8
the pumps. This will allow the operator to turn
the pumps on manually by depressing the pump start
switch 70.
Line 328 is connected to line 350 which represents
an incorrect mode signal. Line 328 is also connected
through inverter 351 and inverter 352 to the mode
switch lamp in display 56.
Referring to FIGURE lla, it is seen that various
reset circuits are provided. To this end, a high
signal on line 380 will effectively override PROM
304. Thus if a resume switch is pressed, a signal
will be fed via line 382 to an input of AND gate 384.
A reset signal from line 386 or a reset signal from
line 388 simultaneously with a resume signal on
line 382 will provide the high signal at the output
of AND gate 384 to override PROM (or ROM) 304.~ Thus,
in the event dial switch 48 has been turned to the
wrong place and it is important to resume operation
of the system instead of having the system completely
turned off, by pressing the resume switch PROM 304
can be overridden. In this manner, the operator
can turn the dial switch 48 to the mode in which
he wants to operate, press the resume switch and the
ROM 304 will be overridden so that the particular mode
selected will be operating. This resume operation
may be useful if the wrong mode has been selected,
but it is important that the operator return to the
right mode as soon as possible.
The pump start circuit is illustrated in FIGURE
12. Referring to FIGURE 12, it is seen that anti-
coagulant pump enable signal line 336 from PROM 330
is fed to an input of ANp gate 360. Whole blood
pump enable signal line 337 is fed~tc an input of
NAND gate 362. A system armed signal from the
clamp (indicating that the clamp is in its unclamped
position) is fed via line 364 to the other input of
~'lSSQ~3
24
NAN~ gate 362. If the tubing clamp is unclamped,
a system armed signal will be provided on line 364
and if at the same time a pump enable signal is provided
via line 337, the output of NAND gate 362, which is
connected to the reset input of flip-flop 366, will
indicate that flip-flop 366 should not reset. When
flip-flop 366 is reset, Q output 367 is O and since
output 367 is connected to an input of AND gate 360,
output line 368 of AND gate 360 will be low so that
the anticoagulant pump is off. When the reset
signal is removed, output 367 remains off until a
pump start signal is fed to flip-flop 366 via line
370. The pump start signal cn line 370 will turn
Q output 367 on and if this occurs simultaneously
with a pump enable signal on line 336, the output of
AND gate 360 will be high to turn the anticoagu]ant
pump on. However, if the armed signal is lost, such
as by clamping the line, a low signal will be fed
- via line 364 to NAND gate 362, thereby resetting
flip-flop 366 and Q output 367 will go to O.
Q output 367 is also connected through an inverter
372 and a resistor 373 to a pump switch signal lamp,
preferably in the form of an ~ED. Q output 367 i~
also fed via amplifier 374 to turn on the whole blood
pump.
It can be seen that one input of AND gate 360
is couple~ to output 367 while the other input of
ANn gate 360 is coupled to the "ACD pump enable"
si~nal, from line 336. There is never a situation
in which the operator would want the anticoagulant
pump on while the whole blood pump was not on. Thus
the anticoagulant pump will be turned on only if both
signals from the "whole blood pump on" line 460 and
from the "anticoagulant pump enab~e" line 336 are
high.
,~, .
1~55Q~8
The mut~ circuit diagram of FIGURE 13 shows the
system for turning off.the alarm sou~d only with
respect to the particular alarm condition that is
occurring. In other words, if there is an abnormal
condition and the alarm sounds, the alarm can be muted
so that it no longer sounds. However, if there is
another abnormal condition, the alarm will sound
notwithstanding the fact that the mute switch has been
energized.
The mute switch is coupled via line 400, resistor
402, inverter 404 and clock 406 to the clock input of
shift register 408. The alarm signal is fed via line
410 to an input 450 of shift register 408 and the
collect plasma signal is fed via line 412 to an AND
15 gate 414. The other input of the AND gate 414 is
connected via line 416 to line 227 which carries the
bypass mode signal. The output of AND gate 414 is
connected to another input 456 of the shift register
408.
An anticipation collection complete signal is fed
via line 420 through resistor 421 and inverter 422 to
another input 452 of shift register 408 and via line
423 to an input of NAND gate 424. A collection com-
plete signal is fed via line 426 through resistor 427
25 and amplifier 428 and via line 429 to another input 454
of shift register 408 and to an input of AND gate 430.
The output of AND gate 414 is connected via line 432 to
an input of AND gate 434 and the signal on line 410 is
connected via line 436 to an input of NAND gate 438.
30 The other inputs of NAND gates 438, 424, 430 and 434
are coupled to outputs of the shift register 408.
The outputs of NAND gates 424, 430 and 434 are
connected to inputs of another NAND gate 440, the
output of which is connected via line 441 to a NAND
35 gate 442. The output of NAND gate 442 is connected
A
~55Q!~8
26
to an input of NAND gate 443, the output of which
provides an audible alarm signal. The output of NAND
gate 438 is connected directly to the other input of
NAND gate 443.
The mute signal on line 400 will actually be a not
mute signal, indicatin~ that the mute switch has not
been energized. When the apparatus is started, the
system is armed by squeezing the clamp levers. This
clears out shift register 408 and effectively puts the
outputs of shift register 408 into a first signal mode.
The outputs of shift register 408 are fed to inputs of
NAND gates 438, 424, 430 and 434 and once reset, shift
register 408 outputs provide a high signal at each of
the respective inputs to the NAND gates. The other
inputs to the NAND gates are the signals from the
various alarm conditions, as previously indicated.
Thus if one of those signals from an alarm condition
also reaches the NAND gate after the shift register has
been xeset, there will be an audible alarm as indicated
in the mute circuit diagram.
The mute switch operates to invert whatever signal
is on the input lines and then transfer that signal to
the output lines. For example, if shift register 408
was reset so that the outputs were all high' 5 and if
the inputs were all low's, if the mute switch was
pressed the outputs would be the inverse of the inputs.
Thus the mute switch also operates to make the re-
spective output the inverse of its input. If input 450
of shift register 408 had a high signal which indicated
an alarm, output 451 of shift register 408 would be
low. Likewise, if input 452 was low, then output 453
would be high if the mute switch were pressed. The
effec~ is th~t if an alarm conditi~n exists and the
mute switch is pressed, the particular alarm for the
particular alarm condition will be shut off.
~155~98
27
The mute switch operates only for the particular
signals that are at the shift register at the moment
that the mute switch is pressed. If after the mute
switch is pressed input 454 has a high signal, output
455 will remain high and both inputs of the respective
N~D gate 430 will have high signals so that there
will be an audible alarm. If the shift register 408
is reset so that all of the outputs 451, 453, 455 and
457 are high, and there is an alarm signal at input
450 and an alarm signal at input 456, normally there
would be an audible alarm. However, if the operator
wishes to obviate the audible alarm, the mute switch
is pressed and output 451 and output 457 have low
signals, thereby muting the audible alarm. On the
other hand, the alarm would not be muted for alarm
signals at input 452 and input 454.
As statcd above, the pump circuit is not started
unless there is both a "pump enable" signal on line
337 and a l'system armed" signal on line 364. In blood
processing, it is desirable that the pump be started
slowly and to this end, an RC circuit is utilized
in a manner so that there is less curr`ent to the
pump motor while a capacitor is being charged.
Thereafter, the pump motor speed is controlled only
by the motor speed control potentiometer which is
manually controlled by knobs 144 and 146 (FIGURES
1 and 2). The purpose of the initial slow speed with
respect to the whole blood pump is to prevent the
occlusion of a vein that might result if the blood
was drawn rapidly from the beginning.
The pump motor ccntrol circuit is illustrated
in FIGURE 14. An identical pump motor control is
utilized for controlling the whole blood pump and the
recirculation pump. The pump on/of~ signal is fed via
line 460 through resistor 461 to the base of a
lJ SS~98
28
transiStOr 462. In the FIGURE 14 embodiment, the
"on" signal is the high while the "off" signal is a
low.
When the "on" signal is provided on line 460,
transistor 462 will become more conductive and an
LED 464, connected in series with the collector of
transistor 462, will be energized to provide a more
positive voltage at the base of an optically isolated
NPN transistor 466. LED 464 and NPN transistor 466
comprise a single unit forming an optical isolator.
Once the optical isolator is energized, the voltage
is placed across the RC circuit comprising resistor
468 and capacitor 470 so capacitor 470 will charge.
At the RC junction 472 there is a diode 474 which is
coupled to an input 475 of an operational amplifier
- 476.
When the power is turned on, there is no voltage
across capacitor 470. There is no voltage at input
475 of amplifier 476 and the current is not flowing.
The capacitor 470 begins charging and the voltage
at the capacitor becomes the voltage at the positive
input 475 of amplifier 476. This same voltage appears
across resistor 477 at emitter 478 of transistor 480
and that voltage is translated into the output current
at collector 481 which is the current to the pump
motor.
A potentiomenter 482 is connected to the col-
lector of transistor 466 and input 475 of amplifier
476 is connected through resistor 484 to the wiper
arm of potentiometer 482. Thus potentiometer 482
forms the whole blood pump speed control which is
operated by manually turning knob 144. The negative
input 485 of amplifier 476 is connected to the e.nitter
478 via line 486.
The alarm circuit is schematically illustrated
in FIGURE 15.
- l~SSQ9~
29
During the operation of the apparatus, certain of
the functions are enabled at certain times while others
are not enabled at these times. For example, during
the "prime" mode, the bubble detector is not enabled
because there are bubbles during "prime" and it would
present an alarm if the bubble detector were enabled.
On FIGURE 15 the lines carrying signals for Yarious
functions are illustrated and it can be seen that some
of the functions, such as the bubble detector, occluded
vein sensor and the hemolysis detector, require enable
and operational signals for a malfunction signal to be
fed to latch 500. Thus operational signals and enable
signals are fed to the inputs of NAND gates 502, 504
and 506, the outputs of which represent, respectively,
the bubble detector signal, the occluded vein detector
signal and the hemolysis detector signal being fed to
latch 500.
Other functions, such as pressure, anticoagulant
empty and the fail-safe provisions, are fed directly to
latch 500 through inverters 508, 510 and 512, respec-
tively, so that any signals on these lines will operate
latch 500. The outpu,s of latch 500 are fed to the
alarm lamps 58 via lines 205, and also to the audible
alarm via lines 252.
Latch 500 is an RS latch (reset-set latch) and the
function signals are fed to the reset inputs. The
reset inputs predominate. If a reset signal is fed to
the set input 513 of the latch, because the reset input
predominates, the functions will predominate notwith-
standing the reset signal at thè set input. As long
as the condition is present, even if a reset signal is
presented at the set input 513 of the latch 500, the
latch will not reset.
Since gates 502, 504 and 506 are NAND gates, and
since inverters 508, 510 and 512 are used, the signals
ilS5Q~?~
that will be fed to latch 500 if there is a malfunc-
tion will be low signals. Any output from the latch
is an alarm signal which shuts down the system and
provides audible and lamp signals.
A sensor override switch 74 allows the operator
to override some of the alarm signals. Switch 74
is connected to a latch 520 which is coupled to an
input of NAND gate 522. Reset switch 76 is also
coupled to latch 520 and to the set input of latch
500. Outputs 524, 525 and 526 of latch 500 are
coupled to the inputs of NAND gate 528 and outputs
529, 530 and 531 of latch 500 are coupled to the
inputs of NAND gate 532. The output of NAND gate
528 is connected to an input of NAND gate 522, the
output of which is connected to an input of NAND
gate 532. The output of NAND gate 532 is connected
~~ to the audible alarm system.
Thus the occluded vein, hemolysis and pressure
lines 524, 525 and 526 are fed to NAND gate 528
which is one of the inputs of NAND gate 522, the other
of which comes from latch 520 which is controlled by
the sensor override switch. Using the sensor over-
ride switch 74, the alarm for the occluded vein
sensor, hemolysis detector and pressure sensor can
be overridden.
The clamp circuit of the present ir.vention is
schematically illustrated in FIGVRE 16.
Referring to FIGURE 16, it can be seen that
clamp switch 50 is connected through an inverter
540 to "return clamped" lamp 542 via line 255. As
illustrated in FIGURE 10c, "return clamped" lamp
542 is one of the lamps within display 56.
Clamp switch 50 is also connected to an input
of AND gate 544 via line 545. Oth~r inputs to the
AND gate 544 include an incorrect mode signal which
is fed through inverter 546 and via line 547 to the
ll~lSQ~8
AND gate 544, magnet enable signal which is fed via line
548 to an input of AND gate 544 and a reset signal which
is fed through inverter 549 and via line 550 to an input
of AND gate 544. The output of AND gate 544 is coupled
through resistor 552 to the base of PNP transistor 554,
the emitter of which is grounded and the collector of
which is connected to the clamp magnet 50'. Clamp magnet
50' comprises a coil 50a and diode 50_, with an appro-
priate voltage source coupled thereto. The output of
AND gate 544 is also connected via line 556, inverter
557 and line 262 to "system armed" lamp 558 which, as
illustrated in FIGURE 10c, forms a portion of the status
display 56.
In order to arm the system, the tubing must be un-
clamped. Once the tubing is unclamped, the system must
be in a proper mode to operate. Therefore, AND gate 544
receives the clamp switch signal in addition to an in-
correct mode signal which is inverted so it actually
becomes a correct mode signal. When all of the signals
are present, there will be an output signal from AND
gate 544 to turn on transistor 554 so that the clamp
magnet 50' will be energized. At the same time, the
system armed lamp 558 will become energized.
A fail-safe circuit is provided in order to shut
off the system if there is a serious maifunction.
The fail-safe circuit is in addition to the alarm cir-
cuit and is responsive to the pump speed tachometers,
the tubing clamp, the bubble detector and an emergency
stop switch (i.e., panic button).
Referring to FIGURE 17, it is seen that the fail-
safe circuit includes whole blood pump tachometer sig-
nal line 175 and recirculation pump tachometer signal
line 178, each of which feeds through a resistor 560,
561 and an inverter 562, 563 to a counter 564, 565
respectively. The reset inputs of counters 564, 565
are clocked by means of a clock 566 which is coupled
.~
1155Q~:t8
32
As a specific example, although no limitation is
intended, counter 564 is programmed to provide an
3utput signal if the tachometer shows that there is a
flow of more than 150 ml per minute. If the tubing
has a predetermined diameter, the flow rate is directly
proportional to the speed of the tachometer and thus
the flow rate can be determined by the tachometer out-
put pulses.
Likewise, counter 565 provides an output signal
if there is a flow rate of greater than 600 ml per
minute. The outputs of counters 564 and 565 represent
2 to the 12th power and the calibration is such that
2 to the 12th power with counter 564 represents 150 ml
per minute while 2 to the 12th power with counter 565
is equivalent to 600 ml per minute. However, the blood
is usually flowing from the donor at up to ioo ml per
~ minute and is recirculated to the donor at approximately
300 ml per minute. Shift register 584 serves to pro-
vide a four second delay. Thus the condition at the
output of OR gate 576 to the reset input of shift
register 584 has to be in the low condition for more
than four seconds for shift register 584 to provide a
high output signal which is inputted to OR gate 571.
This delay is needed to prevent nuisance problems
from latching the fail-safe circuit.
When NOR gates 586 and 588 latch, signals are
provided via line 596 and through resistors 597 and
598, transistors 599 and 600, to a "fail-safe" lamp
via line 601 and to an audible alarm device via line
602. The fail-safe lamp is part of the alarm system
of display 58.
A "power on" reset circuit is provided including
a PNP transistor 6~4 having resistor 605 in its base-
emitter circuit and capacitor 606 i~ its base-col-
lector circuit. When the system is initially turnedon, the latch 586, 588 is set in an armed mode. When
~'
l~lSSQ"8
through a capacitor 567 and a parallel circuit in~
cluding resistor 568 and diode 569. The output of
counter 564 is fed via line 570 to an input of OR gate
571 while the output of counter 565 is fed via line
572 to another input of OR gate 571.
The clamp signal is fed via line 256 through
resistor 574 to an input of OR gate 576. The bubble
detector enable signal is fed via line 208 through
resistor 573 and inverter 579 to another input of OR
gate 576. A second or safety bubble detector signal
is fed via line 580 through resistor 581 and inverter
582 to another input of OR gate 576. The output of OR
gate 576 is fed to a shift register 584. If there are
any inputs at OR gate 576, the output will reset the
shift register 584 to provide a zero or low signal via
line 585 to OR gate 571.
~-Counters 564 and 565 are clocked so that if the
-amount of pulses on either line 175 or line 178 from the
tachometer exceeds the count in one second from counter
564 or counter 565, there will be a high signal from
one of these counters to OR gate 571. A high signal
will then be fed to NOR gate 586 which is coupled with
NOR gate 588 as illustrated to form a latch. When NOR
gates 586 and 588 latch, a low signal provided through
resistor 590 to the base of transistor 592 will provide
a relay off signal along line 593 to shut off the entire
system.
Likewise, if all inputs are low at OR gate 576,
the output will no longer reset shift register 584.
After four clock signals from clock 556, shift register
584 will provide a high signal to OR gate 571 thereby
providing a signal to latch 586, 588 and the system
will shut off in the manner set forth above.
Thus clock 566 provides a one ~econd clock signal
and counters 564 and 565 are read every second. If
there are more counts going into the counter than its
setting, an output signal is provided.
l~S5Q~
34
the latch is armed, any of the events which provide
an output from OR gate 571 acts to set the latch by
feeding a high signal to NOR gate 586 via line 608.
The relay coupled to line 593 is normally ener-
gized if conditions are satisfactory. If there is adisable, the relay is deenergized. The relays are
shown in FIGURE 18 which is a block diagram of the
fail-safe circuit. It can be seen that the primary
power plug 610 is coupled to a suitable source of
alternating current and various power supplies and
circuits are connected across the alternating current
lines 611 and 612. Thus a DC power supply 613 for the
logic circuitry is connected in the AC circuit as is
the DC power supply 614 for the lamps and fail-safe
circuit. In addition, whole blood pump motor control
circuit 616 and recirculation pump motor control 618
- are coupled across the AC lines.
A first circuit breaker power switch 620 ganged
to circuit breaker switch 621 is utilized to open the
AC lines. In addition, relay 622 having ganged con-
tacts 623, 624 and 625 is operable in response to the
fail-safe circuit of FIGURE 17. When contacts 620,
621 are open, current to the entire system ceases and
the apparatus is completely shut off. The opening of
contact 624 will deenergize relay 626 to open contact
627 and 628 which provide the alternating current for
an auxiliary anticoagulant pump. Opening of contacts
624 will also deenergize clamp magnet 50'.
It can be seen that relay 622 effectively oper-
ates off its own DC voltage circuit. Once relay 622
operates to open the line, power to both pumps will
be turned off, power to the clamp will be turned off
and relay 626 will be deenergized to turn off the
auxiliary anticoagulant pump.
Thus if critical problems occur, such as air
bubbles are detected or the motor speed increases past
r~
5 S~^Q 8
a fixed amount, all essential operations of the systemwill be automatically shut off by the fail-safe circuit.
Although an illustrative embodiment of the in-
vention has been shown and described, it is to be
understood that various modifications and substitutions
may be made by those skilled in the art without de-
parting from the novel spirit and scope of the present
invention.
A
