U.S. patent number 3,655,095 [Application Number 04/792,030] was granted by the patent office on 1972-04-11 for apparatus for monitoring the dispensing of liquid.
This patent grant is currently assigned to Smith Kline Instruments, Inc.. Invention is credited to Martin E. Kienitz.
United States Patent |
3,655,095 |
Kienitz |
April 11, 1972 |
APPARATUS FOR MONITORING THE DISPENSING OF LIQUID
Abstract
The system delivers a series of drops of liquid and is
controlled to release each drop in response to a drop rate
generator set at a selected drop rate desired to be delivered. Each
drop actually delivered is detected. By comparing pulses derived
respectively from the drop rate generator and from the actual drops
delivered, any disparity between the rates will be detected. The
disparity detecting means includes means which measures and is
tolerant to a limited degree of measured disparity between the two
rates. When the disparity between the two rates exceeds a
predetermined degree, an alarm condition is established which can
include conditioning the delivery means to positively arrest
further delivery of drops. The delivery means operates in a manner
to automatically compensate for excess drops or reduced drops fed
during transient variations in the actual feeding or delivery of
drops.
Inventors: |
Kienitz; Martin E. (Palo Alto,
CA) |
Assignee: |
Smith Kline Instruments, Inc.
(Palo Alto, CA)
|
Family
ID: |
25155587 |
Appl.
No.: |
04/792,030 |
Filed: |
January 17, 1969 |
Current U.S.
Class: |
222/39; 222/59;
222/52; 604/65 |
Current CPC
Class: |
A61M
5/1689 (20130101) |
Current International
Class: |
A61M
5/168 (20060101); A61m 005/16 () |
Field of
Search: |
;137/487.5
;128/DIG.13,214E ;239/68 ;222/59,39,52,76 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reeves; Robert B.
Assistant Examiner: Handren; Frederick R.
Claims
I claim:
1. In apparatus for delivering a series of drops of liquid, and
having means defining a selected drop delivery rate, delivery means
controlling delivery of the drops in response to the first named
means to normally deliver one drop at a time, means serving to
sense each drop to be delivered and define the actual drop rate,
means serving to detect a sustained disparity in the phase
relationship between actual drop delivery and selected drop
delivery, the last named means including means measuring and
tolerant to a limited degree of measured disparity in said phase
relationship and serving to register varying degrees of said
disparity, said last named means being further responsive to a
predetermined degree of disparity serving to condition the delivery
means to inhibit or release further delivery of drops, said
measuring means including counting means for registering increases
and decreases in said disparity as measured from a normal position
representing no disparity, said counting means being responsive to
alternate receipt from the first named said means and said sensing
means respectively of first and second signals to register a first
and second mutually off-setting count in the counting means, and
means operated by said counting means and responsive to a
predetermined difference in the counted number of said first and
second signals to provide an alarm signal operably coupled to said
delivery means to arrest further delivery of drops.
2. In apparatus for delivering a series of drops of liquid, first
means forming a series of signals at a rate corresponding to a
selected drop rate, delivery means controlling delivery of the
drops in response to said first means, second means serving to
sense each drop to be delivered and provide signals corresponding
to the actual drop rate, and means serving to normally alternately
receive both signals and serving to detect disparity in the phase
between receipt of said different signals, the last named means
including a counting register responsive to delivery of each drop
to change its registered count in a given direction and responsive
to said first means to change its registered count in an opposite
direction, and responsive to increases or decreased in excess of a
predetermined tolerated registered minimum to arrest delivery of
drops.
3. In apparatus for delivering each of a series of drops of liquid
in response to a first signal from a drop rate generator and having
means for developing a second signal in response to actual delivery
of each drop, and means to normally maintain an alternating
relationship between said first and second signals, the improvement
wherein the last named means responds to said signals for detecting
a sustained change in the alternating relationship of said signals,
the last named means serving to detect a condition including the
interposition of an additional one of said signals between
successive ones of the other of said signals and to provide a
control signal, and means operated by said control signal for
indicating existence and degree of said sustained change in the
alternating relationship of said signals.
4. In apparatus for delivering each of a series of drops of liquid
according to claim 3 wherein the means indicating existence of said
sustained change in relationship includes means for arresting
further delivery of drops of liquid in response to detecting
existence of said sustained change in relationship as indicated by
said control signal.
5. In a system for monitoring the dispensing of discrete increments
of liquid in a stream subject to transient variations in the
dispensing rate, the improvement comprising means for dispensing
said increments, means forming a first signal representing the
intended desired rate of dispensing said increments, sensing means
serving to form a second signal representing the actual rate of
dispensing said increments, means normally maintaining a
predetermined phase relationship between said first and second
signals and serving to detect a sustained change in said phase
relationship to provide a control signal, means operating said
dispensing means in response to said control signal to momentarily
vary the rate of the actual dispensing of said increments in a
manner tending to restore said normal predetermined
relationship.
6. In a system for monitoring the dispensing of discrete increments
of liquid according to claim 5 wherein said predetermined
relationship includes an alternating formation of said first and
second signals, and further wherein the last named means restores
said normal alternating relationship by operating said means for
dispensing said increments in a manner to momentarily dispense
additional or fewer increments sufficient to re-establish said
normal alternating relationship, thereby compensating for the
transient variation in flow of the increments being dispensed.
Description
BACKGROUND OF THE INVENTION
This invention relates to apparatus for controlled feeding and
monitoring of drops of liquid or other material delivered in
discrete increments. The apparatus is particularly useful in
maintaining a close watch over intravenous feeding of drops of
liquid material to humans.
Heretofore, systems of the above type have been provided wherein a
drop rate generator provides an output pulse train serving to
establish the selected drop rate desired to be established by the
feeding means. In addition, each drop that is actually delivered is
sensed or detected and a pulse train generated in response thereto
whereby the two pulse rates can be compared. Upon detecting any
disparity between the two, an alarm or other indication of the
existence of change in the drop feeding rate may be indicated.
The foregoing style of system is particularly desirable where a
very close watch over intravenous feeding is demanded. However,
under other circumstances, such a system may prove to be somewhat
too sensitive to slight changes in the rate of drop feeding to the
patient and can provide what might be felt to be premature alarm
signals.
Thus, heretofore, any temporary increase or decrease in the
resistance to flow of fluid in the liquid line which is delivering
the fluid will cause the foregoing type of system to activate an
alarm condition.
It has been observed that a patient may change position, for
example, by bending his arm and affect portions of the drop
delivery tubing, or may, by his movements, cause the opening in the
intravenous feeding needle to press against the wall of the vein so
as to momentarily impede the flow of fluid through the delivery
tube. Heretofore, such conditions could generate a disparity in
what is otherwise a normal feeding situation.
Additional conditions may also exist of the above type or otherwise
which can cause momentary, though unsustained, changes in the
feeding rate of a type which will generate an alarm condition for
the above general type of system.
It has also been observed that the typical momentary change in
fluid rate can generally be expected to be followed by an
equivalent period of fluid delivery at a quickened pace.
Where the disparity in feeding rates between the selected drop rate
generator and the delivery rate for the actual drops being fed to
the patient represents a sustained continuous condition, rather
than merely momentary, then, it is believed, feeding of fluid
should be discontinued until the situation can be adjusted.
OBJECTS
It is an object of the present invention to provide an improved
system of the above type.
It is another object of the invention to provide a system of the
above general type wherein momentary changes in fluid feeding rates
can be tolerated and recognized while a sustained change in the
rate of feeding a liquid serves to generate an alarm condition.
It is another object of the present invention to provide a system
of the above type wherein a momentary change in the rate of either
of the two pulse rate generators accommodates a natural corrective
action in the system.
The foregoing and other objects of the invention will become more
readily apparent from the detailed description of a preferred
embodiment described below when considered in conjunction with the
drawings.
SUMMARY OF THE INVENTION
In general, the system described herein includes means for
delivering a series of drops of liquid and means defining a
selected drop rate for controlling delivery of the drops in
response to the drop rate generated. In addition, means for sensing
each drop of liquid delivered defines the actual drop rate.
Comparison of the two drop rates is made by means serving to detect
a sustained disparity between the two rates by measuring and being
tolerant to a limited degree of measured disparity between the two
rates while serving to register varying degrees of disparity
between the two rates. When the disparity between the two rates
exceeds a predetermined degree, an alarm condition is established,
such as by arresting further delivery of drops, or sounding an
alarm, or both.
BRIEF DESCRIPTION OF THE DRAWING
The single figure of the drawing schematically shows a drop
monitoring system according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Means for delivering a series of drops of liquid includes the
feeding means 10 which feeds discrete drops of liquid 11 from a
container 12 into the arm of a patient receiving intravenous
feeding. Feeding means 10, as schematically shown, includes a
suitable drop forming outlet 14 disposed to deliver drops 19 of
liquid 11 from container 12 to a splash chamber 13.
Means for sensing each drop 19 actually delivered includes an
attachable drop sensor assembly having a light source 15 to direct
a beam of light through an aperture 16, and splash chamber 13, to
be sensed by a suitable photo-responsive device 17. Device 17
serves to generate a signal on line 18 whenever the beam is
interrupted by the presence of a drop, as at 19. Drops 19 travel
along a resilient tube 21 for delivery into the arm of a patient,
usually as by means of a hypodermic needle 23.
It is evident that the foregoing arrangement constitutes flow
control means providing delivery of the drops. Drop delivery is
responsive to a selected drop rate as defined by a drop rate
generator 31. In delivering drops, the flow control means is
arranged to be operable between active and inactive states to
respectively deliver or arrest the liquid.
Means controlling delivery of drops through tube 21 include the
valve member 24, operable in one condition to pass a drop of liquid
and operable in another condition to arrest delivery of liquid
drops through tube 21. A solenoid 25 is arranged whereby when it is
energized, member 24 will be withdrawn against the urging of spring
26. Tube 21 is constructed of a resilient material whereby upon
withdrawal of member 24, the passage within tube 21 will open to
permit a drop to be formed in splash chamber 13.
Notwithstanding the fact that the tube constrictor member 24 is
disposed downstream of splash chamber 13, activatior of the tube
constrictor member 24 exerts a controlling influence on the actual
drop rate, i.e., the actual delivery rate of drops passing into
splash chamber 13.
Thus, the system from the hypodermic needle 23 back to the
reservoir 12 is a closed one and back pressure at the needle 23,
caused by temporary stoppage, reflects back to the reservoir and
prevents further delivery of fluid. This is true, notwithstanding
the fact that the drop chamber or splash chamber 13 will normally
not be full of fluid. As a consequence, it is immaterial where the
pinch clamp is placed along the delivery tube 21. The usual
practice, however, is to place the clamp below splash chamber
13.
De-energizing solenoid 25 permits spring 26 to cause member 24 to
pinch tube 21 between the free end of member 24 and a fixed portion
27 of the solenoid assembly.
From the foregoing, it will be evident that the actual drop rate of
liquid being dispensed is sensed by photo-responsive device 17.
Device 17, therefore, functions as an impulse generator which
provides an impulse corresponding to each drop which is actually
dispensed to the patient.
These impulses appear on the output line 18 from device 17 and are
amplified by a suitable amplifier 49 for transmission along line 22
to a suitable pulse forming and shaping circuit of a type providing
a substantially uniform and constant output pulse on the order of
100 millisecond duration, as shown in the drawing merely as box 23.
Such a circuit may be of the so-called "one-shot" style, as
popularly referred to.
There is also provided another impulse generator which serves to
define the desired or selected drop rate for liquid to be fed to a
particular patient. Thus, a drop rate generator 31 is provided in
the form of a suitable pulse generator which provides a series of
output pulses corresponding to the selected drop rate desired to be
established. Various saw-tooth generators or the like can be
utilized for this purpose and provide a useful pulse train.
The frequency of the output pulses on the output line 33 from drop
rate generator 31 can vary over a wide range, for example, from 5
to 150 drops per minute or the like. On the drawing, there is shown
a variable resistance 31a which can provide a suitable variable
control to establish output pulses within the above range.
Drop rate generator 31 can readily be provided by other
conventional means, such as by certain relaxation oscillators or
the like. See U.S. Pat. No. 3,252,623. The output train of pulses
from generator 31 appears on output line 33 and the pulses are fed
to a suitable pulse forming and shaping circuit 34 of a type for
providing a single output pulse of predetermined duration, such as
the types of the circuit referred to with respect to box 23.
Conventionally, a one-shot multi-vibrator can be employed for this
purpose having an output pulse on the order of 100 millisecond
duration, for example.
To this point, it will be readily evident that means have been
provided for sensing the actual delivery of every drop 19 delivered
to the patient by means of the feeding means 10. In sensing each
drop 19, a pulse is fed via line 22 and ultimately is shaped and
formed to provide the pulse 38 of uniform duration appearing on
lead 39. It is also evident that means have also been provided in
the form of drop rate generator 31 for developing a train of pulses
36 indicative of the selected rate at which drops should be fed to
the patient, pulses 36 appearing via 37.
Means have been provided which serve to detect any sustained
disparity between the two rates of pulse generation. A "sustained
disparity" may be considered to exist whenever, in addition to the
usual pulse 36 or 38 which is normally interposed between
successive ones of the other of the two pulses 38, 36 there is
further included an additional interposed pulse 36, 38. In short,
in normal operation, one of the two pulses 36, 38 will be expected
to be interposed between each successive pair of the other of the
two pulses. However, the disparity between the two rates of pulses
is not herein considered to be "sustained" until a plurality of at
least two or more pulses have become interposed between each
successive pair of the other of the two pulses 36, 38.
The means for detecting a "sustained disparity" between the two
rates includes means which measures and is tolerant to a limited
degree of measured disparity between the rate of occurrence of
pulses 36 and 38 and which also serves to register varying degrees
of disparity between the two rates. In response to a predetermined
degree of disparity which may usually be considered to indicate
that a sustained condition of imbalance between the two rates has
occurred, calling for emergency measures, the apparatus serves to
establish an alarm condition wherein the liquid feeding means 10 is
inactivated in a manner to arrest further delivery of drops.
Having the foregoing general functions in mind, there is further
shown in the drawing a reversible electronic counter 41 of any
suitable type having an input to be coupled to lead 39 and another
input to be coupled to lead 37 whereby the occurrence of a pulse 38
on lead 39 serves to cause the counter to register a single count
in an increasing "direction" (i.e., to increase the registered sum
held by the counter in an amount equal to a single first order
digit). A pulse on lead 37, however, serves to cause counter 41 to
register a count of a single first order digit in an opposite
"direction" (i.e., to subtract from the sum registered in counter
41).
To simplify the foregoing detailed description, it may be better
understood that a pulse 38 on lead 39 serves to cause counter 41 to
be counted "up," i.e., increase the registered sum, while a pulse
36 on lead 37 serves to count the counter 41 "down," i.e., decrease
the registered sum.
Counter 41 includes eight output leads numbered 50-57 respectively.
Each output lead 50-57 is associated with one of the Arabic
numerals 0-7 respectively and indicates when a predetermined
bi-stable voltage state on that particular lead represents a count
of from 0-7 as the case may be.
Counter 41 may be provided by any suitable conventional reversible
electronic counting means and, as shown herein, may be comprised of
three cascaded and cyclically arranged flip-flop circuits
interconnected one to the next, as is known. Each of leads 50-57
registers one or the other of a pair of binary states and, in the
arrangement shown, all of leads 50-57 will be in a common one of
the two states with the exception of a single one of the leads
which will be in the other of its two binary states. The single
existence of this other state will, therefore indicate the sum of
the count registered in counter 41. As is known, the two stable
states may be indicated by the relative voltage level appearing on
the leads 50-57.
The condition of output leads 50-57 is switched from one to the
next either upwardly or downwardly depending upon the sequence of
receipt of pulses 36, 38 from leads 37, 39 in conventional fashion.
Thus, there is provided a counting means for registering, via lead
39, in an increasing amount each drop actually delivered while the
counter 41 registers in a negative direction or counts "down" one
count for each pulse 36 received from drop generator 31.
So long as the rates remain the same, the counts 36, 38 will
provide signals alternately received which mutually offset the
count carried in the counting means 41.
In order to indicate to the human senses the current state of the
count of counter 41, each output lead 50-57 has been provided with
a conventional lamp driver circuit 58 directly connected to a lamp
59 whereby when the state of lead 50 (or any of leads 51-57
associated with a given lamp driver circuit and lamp as shown) is
conditioned to provide that binary state representing the count
registered in counter 41, the lamp 59 (or the others as the case
may be) will be illuminated.
Counter 41 is of conventional construction as indicated above and
is arranged in suitable fashion whereby its initial or "normal"
state represents a count of "four" whereby the lamp 61 will be
illuminated.
Means are provided whereby drop rate generator 31 serves to
dispense a drop of liquid to the patient. Thus, as a pulse appears
at the output line 33 and is shaped and formed into pulse 36 on
lead 37, counter 41 will be counted "down" one count whereby lead
53 will carry the binary state indicating the presence of a "three"
count registered therein and lamp 62 will be illuminated. The
output state or condition on lead 53 constitutes a signal which is
fed through an OR gate 63 of conventional construction to provide
one of the two inputs via line 64 to AND gate 66.
The other input to AND gate 66 via line 67 is supplied from
inverter 68 (via OR gate 69) which operates in response to the
bi-stable condition of lead 57. Inverter 68, as is known, reverses
the binary state indicated on lead 57 whereby the opposite state
will exist on line 67 comparable to that appearing on line 64.
AND gate 66 responds to the coincident occurrence of the two
similar input signals whereby an output signal is supplied on line
71. This signal is then amplified by suitable amplifier means 72
and directed through diode 73 poled to pass the signal and feed it
onto line 74 for operating solenoid 25.
Solenoid 25 will be operated only if the switch armature 76 has
been previously conditioned to a closed state.
Means for closing switch armature 76 at an earlier time have been
provided as now to be described.
A main control switch 77 employs a switch armature 77a which serves
to couple power supply 78 to each of four contact points 75, 79,
85, 90, respectively labeled herein as "off," "reset," "run," and
"flush." In addition, an elongated arcuate conductive contact strip
77b is connected to a line 84 to energize timer 87 via lines 84, 86
and to form the source of power for a holding circuit by energizing
solenoid 89 promptly upon movement of armature 77a from its "off"
position 75.
Thus, upon commencing operation, armature 77a will be rotated
clockwise as shown whereby a connection is made between power
supply 78 and the "reset" contact 79. As soon as power is thus
connected, a circuit is completed via line 81 to ground to operate
coil 82.
Coil 82 closes both switch armatures 76 and 83, the latter forming
a holding circuit.
Thus, contact closure 91, closed by energizing solenoid 89, serves
to energize line 92 whereby the prior movement of armature 77a to
contact the "reset" contact point 79 of switch 77 supplies power in
the holding circuit to be available to hold coil 82 energized (and
armatures 76, 83 closed) as soon as the "reset" contact 79 is
struck.
To briefly summarize the foregoing, upon movement of switch
armature 77a to the "reset" contact point 79, armature 83 forms a
holding circuit whereby armature 76 will be maintained closed to
complete the circuit for solenoid 25. The latter, when energized in
response to a count appearing on counter 41 on any of leads 51, 52
or 53 serves to withdraw member 24 to dispense a drop 19.
In normal operations, drop rate generator 31 will develop a pulse
36 for counting the counter 41 "down" from a "four" count to a
"three" count on lead 53 thereby causing a drop 19 to be dispensed.
Photo-responsive device 17, as above described, serves to generate
a pulse 38 on lead 39 indicating the actual delivery of drop 19
into the splash chamber 13 whereby pulse 38 serves to count the
counter 41 "up," i.e., to increase the sum which is registered in
counter 41 and thereby indicate a registered count of "four."
So long as the feeding of drops of liquid via tube 21 proceeds at
the same rate as the rate established by drop rate generator 31,
the counting means 41 will respond to alternate receipt of signals
from the rate generator 31 and feeding means 10 respectively. These
signals serve to register first and second mutually off-setting
counts in the counting means 41. The mutually off-setting count
will oscillate between state No. 4 and state No. 3 wherein upon
each conditioning of lead 53 for indicating state No. 3, a drop 19
will be delivered by a momentary energizing of solenoid 25.
On the other hand, should a momentary interruption in either of the
two pulse rates occur, for example if a patient should move his arm
in a manner which might cause the delivery of drops to be
momentarily arrested, counting means 41 as shown will receive at
least a plurality of two additional counts in succession from
generator 31 before providing an alarm condition. The alarm
condition preferably may involve fully arresting further delivery
of drops to the patient as well as the sounding of a buzzer of
activating any other suitable alarm recognizable by the human
senses.
Accordingly, it is to be observed that the output state on leads 51
and 52, when representing a registered count in counter 41 in the
amount of "one" or "two" respectively, provides a stable signal on
line 64 whereby solenoid 25 will be energized to deliver liquid
drops to the patient. Thus, in the event that the alternate receipt
of pulses from drop rate generator 31 and feeding means 10 becomes
interrupted in a manner whereby drops are only momentarily
discontinued, drop rate generator 31 will continue to provide
pulses 36 which cause counter 41 to continue to count "down" and
provide an output signal on lead 52 and then on 51.
In the event, however, that the disparity in the rate of actual
delivery of drops 19 and the desired rate of drop generation (as
defined by generator 31) is "sustained" to the point where
generator 31 counts "down" to register a count by the output state
which appears on lead 50 (representing a registered count of zero
in counter 41) the signal on lead 50 serves to establish an alarm
condition which functions to activate an alarm 93 via a circuit
traced from output lead 50, OR gate 69, lead 94 and amplifier 96,
to activate a buzzer or other suitable audible or visual alarm 93
via line 97.
When counter 41 reaches a count of "zero" (as registered by the
output state on lead 50) the signal on lead 50 further serves to
positively preclude further activation of solenoid 25 and hence
serves to block the further delivery of additional drops 19 of
liquid 11.
Accordingly, the signal on lead 50 is fed via OR gate 69 and lead
94 to a junction 98 made with line 99 whereby the output state from
the "zero" count is directed to inverter circuit 68. Circuit 68 is
of conventional design whereby the input signal is inverted to
provide an opposite signal of substantially the same magnitude. For
example, in a typical instance, if the input signal represents a
relatively low voltage state or condition appearing on the input
line 99, the output from inverter 68 may appear as an equal and
opposite relatively high voltage state on output line 67.
Normally, when the count registered in counter 41 lies between "1"
and "6," the inverter 68, as above described, provides an output
state on line 67 comparable to the signal appearing on line 64
whereby the conjoint receipt of two like signals by AND gate 66
serves to pass a signal via line 74 to activate solenoid 25.
However, in the present instance, where a "sustained" disparity in
the rates between drop rate generator 31 and feeding means 10
exists, the signal on line 67 will have been reversed and this
reversal will prevent AND gate 66 from passing signals appearing on
leads 51, 52, 53 to reach solenoid 25.
From the above, it will be readily evident that when counter 41
registers a "zero" count, and the lamp 59 has been lighted by lamp
driver circuit 58, an operator or attendant can readily determine
that the drop feeding has been too slow relative to the rate of
generating signals from drop rate generator 31.
In order to hold the count at "zero" for the attendant to be able
to observe the state of counter 41 and adjust the system before
resetting the system to recommence operation, the output state on
the "zero" output lead 50 acts via OR gate 69, lead 94, junction
98, and line 99 to provide an input 101 to counter 41 which
conditions counter 41 to hold the count at "zero." In this manner,
the attendant will be able to observe the state of counter 41 and
determine that, by the lamp 59 being lighted, the liquid flow rate
in the feeding means 10 has been slower than the selected rate in
drop rate generator 31.
The holding input 101 in known fashion can also serve to permit the
use of conventional reversible cyclic style counters whereby after
the counter has reached a "zero" count, it is prevented from next
moving to a "7" as is conventional in a number of known types of
cyclic counters.
With the above explanation in mind relative to a condition wherein
the drop feeding has progressed too slowly due to a temporary
blockage created by movement of the patient's arm or otherwise, it
is readily evident that as soon as the condition has been
corrected, as for example, when the patient may have readjusted his
arm, any "backed up" liquid (which otherwise would have been fed)
is then, in many instances, readily delivered as drops and the pace
for feeding drops 19 quickens momentarily whereby, in the event
that a "zero" count was not reached, extra pulses 38 will be
generated to cause counter 41 to count "up" until the normal phase
relationship between the alternate generation of pulses 36, 38 is
again resumed.
For example, in the event that counter 41 has counted "down" to a
count of "1" to provide a drop delivery signal on lead 51, no drops
will have been delivered due to a momentary conditioning of tubing
21, or hypodermic needle 23, or otherwise. Such a momentary
blockage of the flow of drops can be expected to usually be
followed by a momentary increase in the rate of formation of drops
19 whereby extra drops are quickly formed and delivered each of
which is sensed by photo device 17 to provide a pulse 38, and
correspondingly cause counter 41 to count "up" one count for each
pulse to the point where the count in counter 41 reaches a count of
"4" indicated by the electrical state on lead 54 whereby the system
resumes the alternate conditioning of leads 54 and 53 to place the
drop rate generator 31 in phase with the feeding means 10.
In the event that drops are formed and fed to the patient too
quickly relative to the selected rate of formation (as represented
by pulses 36 from rate generator 31), it will be readily evident
that the registered count carried in counter 41 as indicated by the
state on output leads 54, 55 and 56 will fail to provide any
signals for energizing solenoid 25 and thus tubing 21 will remain
pinched by member 24 so as to slow the formation and feeding of
drops 19.
Thus, it is clear that the present system contemplates an
arrangement of means operating the dispensing means in response to
a control signal so as to momentarily vary the rate of actual
dispensing of increments of liquid in a manner tending to restore
the normal predetermined relationship desired to be established
between the drop rate generator and the actual dispensing of drops
as sensed by photo-responsive device 17.
Accordingly, it is apparent that the feeding means 10 in
conjunction with the balance of the system operates in a manner
whereby sufficient additional or fewer increments of liquid such as
the drops of liquid being sensed will be dispensed in order to
re-establish the normal alternating relationship so as to
compensate for any transient variation in the flow of the
increments of fluid being dispensed.
In this manner, even though the actual rate of dispensing drops of
liquid may be subject to transient variations in the dispensing
rate intended to be delivered, the system is characterized by means
which serve to cause an automatic restoration of the number of
drops which should have been fed to the patient, provided, of
course, that a "zero" or "7" count is not reached during the period
of such transient variation in the dispensing rate.
Any "sustained" disparity between the rate of formation of drops 19
and the desired rate will cause counter 41 ultimately to count "up"
to "seven" whereby the output state on lead 57 provides a signal
which, not only serves to illuminate the associated lamp coupled to
lead 57, but also, via OR gate 69, serves to activate alarm buzzer
93 and via inverter 68 acts to de-energize solenoid 25 as well as
to provide a signal on line 99 which is fed to the holding input
101.
With lamp 102 lighted and held in its lighted condition by the
holding input 101, it will be readily evident to an attendant that
the alarm condition was caused by the fact that drops were formed
too rapidly relative to the selected rate desired to be established
by rate generator 31.
An attendant will normally be expected to make certain adjustments
in the feeding means 10 so as to adjust the rate of drop feeding
whereby it corresponds closely to the selected rate desired and
then he will reset the system. To reset the system, it is only
necessary to move control switch armature 77a to the "reset"
contact 79 which thereby connects power supply 78 to line 81.
Counter 41 is provided with an input 103 in known manner which
serves to reset the counter 41 to a starting count of "4."
Means are provided whereby in the event of a power failure, alarm
93 will be activated. Thus, a power failure sensor in the form of a
flip-flop circuit 107 of conventional design having a pair of
bi-stable output states represented by the leads 104, 106 is
provided and is reset at the above time by connecting power supply
78 via lines 81, 108. The flip-flop circuit 107 may be of any
suitable conventional type having an input connection or lead 108
which, when subjected to the voltage of the power supply, serves to
establish the bi-stable state represented by a "high" voltage state
on lead 104.
In normal operation, power supply 78 can be expected to be sensed
by input lead 108 from a circuit traced from armature 77a
contacting the arcuate strip 77b and then via line 84, contact
closure point 91 (then in its closed position as held closed by the
energization of solenoid 89) line 92, armature 83, and coil 82 to
ground. The junction point 109 will therefore be at a positive
potential sensed on line 81 so as to condition the power failure
sensor flip-flop circuit 107 to its normal state.
However, when power fails for any reason, then the change in
voltage on line 81 (and at input connection 108) serves to
establish the bi-stable state on lead 106 which provides a signal
via OR gate 69, amplifier 96 and line 97 so that buzzer alarm 93 is
activated.
Means are provided to interrupt the power supply voltage on line 81
and thereby activate the alarm condition in the event that solenoid
25 remains energized for too long a period.
Thus, each signal appearing on leads 51, 52, 53 (as described above
for delivering a drop 19 of liquid 11 to the patient) is also
transmitted from any of these three leads via junction 111 and line
112 to start the timing cycle of timer 87.
Timer 87 is of a conventional type of known construction employing
a pair of input connections whereby a steady state condition
applied to one of the input connections serves to initiate the
timing cycle and the application of a similar pulse to the other
input connection serves to terminate the timing cycle and reset the
timer to an initial starting condition. The function of the timing
circuitry involved in timer 87 is to control the operation of
switch 88 whereby it is normally closed for purposes of permitting
solenoid 89 to be energized from lead 86 but in the event that
feeding of drops continues for too long a period for any given
drop, timer 87 serves to interrupt the operation of the system by
opening the power to de-energize solenoid 25 delivering drops.
Thus, for each steady state condition indicating a count of 1, 2 or
3 on leads 51, 52, 53, the steady state condition will be sensed at
junction 111 and fed via line 112 to the input of timer 87 which
commences the timing cycle. As explained above, whenever a pulse 38
on lead 39 serves to count the counter 41 "up" to the condition
number 4, the steady state condition on lead 53 will be removed
whereby the change in this state is sensed via an inverter circuit
114 which serves to provide a suitable input voltage state to timer
87 via lead 116. This input resets timer 87 whereby the timer is
ready to reinitiate its operation upon receipt of a signal via lead
112.
Finally, as part of the procedure for clearing any blockage from
tubing 21, the attendant may desire to hold solenoid member 24
withdrawn so that the tubing remains open. Then, it may be possible
to flush all materials from tubing 21 using hospital
techniques.
Accordingly, switch armature 77a can be moved to contact point 90
labeled "flush" while continuing to make a parallel wiping contact
with strip 77b. In this manner, power supply 78 will be coupled
directly to line 74 to energize solenoid 25 since armature 76 is
then held closed by the circuit traced from power supply 78, switch
77, lines 84, 92, and via solenoid armature contact 91 (then closed
by action of solenoid 89), armature 83 and coil 82.
A spring 113 is mounted so as to require the attendant to keep his
finger on armature 77a in order to operate the system in the above
"flushing" manner. Whenever the attendant removes his finger from
armature 77a, spring 113 serves to disconnect point 90 from
armature 77a.
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