Syringe pump abstract
A syringe pump comprises a housing and a retainer mounted thereon
for receiving a syringe. The syringe to be received is of the type
including a barrel for holding liquid medication and a plunger movably
positioned in the barrel for expelling the liquid medication therefrom.
A driver is movably mounted on the housing for engagement with the
plunger and for pushing the plunger into the barrel to thereby force
the liquid medication out of the barrel. A control mechanism within
the housing regulates the movement of the driver against the plunger.
This thereby regulates delivery of the liquid medication from the
barrel. Depressible actuation buttons or switches are mounted on
the housing for manual access by a user. These switches are associated
with the control mechanism to permit the user to select one or more
functions under which the control mechanism is to operate. The actuation
switches include an electrically conductive material positioned
to contact the control mechanism when depressed by the user. This
depression causes an electrical energization or de-energization
of the control mechanism for the operation of the selected function.
Syringe pump claims
What is claimed is:
1. A syringe pump comprising:
a housing having an elongate slot therethrough;
a retainer mounted on said housing for receiving therein a syringe
of the type including a barrel for holding liquid medication and
a plunger movably positioned in the barrel for expelling the liquid
medication therefrom;
a driver movably mounted on said housing and being movable with
respect to said slot, said driver positioned for engagement with
said plunger for pushing said plunger into the barrel to thereby
force the liquid medication out of the barrel;
protection means attached to the driver, covering said slot and
movable with respect to the slot to facilitate movement of the driver
with respect to the slot and to move with the driver thereby providing
constant protection of the slot so that foreign materials may be
prevented from entering the housing through the slot;
control means for regulating the movement of the driver against
the plunger to thereby regulate delivery of the liquid medication
from the barrel; and
actuation means on the housing for permitting a user to select
one or more functions under which the control means is to operate.
2. The pump of claim 1 wherein said protection means is a pair
of flexible bands, one band attached to the driver and protectively
extending over the slot in one direction, and the other band attached
to the driver and protectively extending over the slot in the other
direction.
3. A syringe pump comprising:
a housing;
a retainer mounted on said housing and movable relative thereto
for receiving therein different size syringes each of the type including
a barrel for holding liquid medication and a plunger movably positioned
in the barrel for expelling the liquid medication therefrom, said
retainer including first electrical contact means which are position-variable
with respect to the housing depending upon the size of each syringe
received in the retainer;
a driver movably mounted on said housing for engagement with said
plunger and for pushing said plunger into the barrel to thereby
force the liquid medication out of the barrel;
control means within said housing for regulating the movement of
the driver against the plunger to thereby regulate delivery of the
liquid medication from the barrel;
second electrical contact means within said housing positioned
to be contacted by the first electrical contact means of said retainer
for producing an electrical signal representative of the size of
the syringe received in the retainer, said signal being receivable
by the control means so that movement of the driver is related to
the size of the syringe received in the retainer; and
actuation means on the housing for permitting a user to select
one or more functions under which the control means is to operate.
4. The pump of claim 3 wherein said first electrical contact means
includes a plurality of tabs and said second electrical contact
means includes a plurality of strips arranged so that one or more
different strips are contacted by the tabs for different sizes of
syringes received in the retainer.
5. The pump of claim 4 wherein the control means includes memory
storage means for identifying the electrical signal received from
said electrical contact means as representative of a syringe of
one of a series of sizes pre-programmed into said storage means.
6. The pump of claim 4 wherein said control means includes a printed
circuit board positioned within said housing, wherein said electrical
strips are included on said circuit board.
7. The pump of claim 4 wherein the retainer includes a manually
operative clamp of such size and shape to grasp different diameter
barrels of the syringe.
8. The pump of claim 7 wherein said clamp has said tabs mounted
thereon, said clamp being slidably mounted on said housing for linear
movement with respect thereto, said tabs being so arranged to contact
one or more different electrical strips on said printed circuit
board depending upon the linear position of said clamp which is
changeable according to the size syringe barrel held by said clamp.
9. A syringe pump comprising:
a housing having a raised elongate bearing surface on an outside
portion thereof;
a retainer mounted on said housing for receiving therein a syringe
of the type including a barrel for holding liquid medication and
a plunger movably positioned in the barrel for expelling the liquid
medication therefrom, said retainer including first electrical contact
means which are position-variable with respect to the housing depending
upon the size of the syringe received in the retainer;
a driver movably mounted on said housing and in sliding contact
with said raised bearing surface, said driver positioned for engagement
with said plunger and said raised bearing surface for pushing said
plunger into the barrel to thereby force the liquid medication out
of the barrel;
control means within said housing for regulating the movement of
the driver against the plunger to thereby regulate delivery of the
liquid medication from the barrel;
second electrical contact means within said housing positioned
to be contacted by the first electrical contact means of said retainer
for producing an electrical signal representative of the size of
the syringe received in the retainer, said signal being receivable
by the control means so that movement of the driver is related to
the size of the syringe received in the retainer; and
depressible actuation means mounted on said housing for manual
access by a user and associated with said control means to permit
the user to select one or more functions under which said control
means is to operate, said actuation means including an electrically
conductive material positioned to contact an actuation element associated
with said control means when the actuation means is depressed by
the user to electrically energize or de-energize the control means
for operation of the selected function.
Syringe pump description
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to a device to deliver or administer
medication to a patient, and more particularly, concerns a syringe
pump intended for the delivery or administration of such medications.
2. Background Description
Hospitals typically use intravenous (I.V.) administration sets
to deliver liquid medication to patients. When the patient needs
medication, such as an antibiotic, standard practice until recently
has been to deliver such a drug by a "piggy-back" drip
into the primary infusion line. Recently, however, the procedure
for delivering antibiotics and other drugs to patients on I.V. therapy
has been changing Mechanically driven syringes, oftentimes called
or referred to as syringe pumps, are available to hospitals and
other users for the administration of drugs and other liquid medications
which the patient may require.
Indeed, a wide variety of syringe pumps and other liquid medication
delivery devices are becoming available. With particular reference
to a syringe pump, as that term is used herein, such pump employs
a conventional or modified syringe which holds the liquid medication,
the plunger of which is typically driven or pushed by a mechanized
element for the automatic delivery of the liquid contents within
the syringe. These syringe pumps are now available in battery-powered
form, include microprocessor technology for programming rates or
times of medication delivery, have digital displays for ease of
viewing by the user or the patient, include alarm circuits in the
event of duty cycle completion, failure, or line occlusion, and
other features to facilitate the operation or performance of the
syringe pump. As these syringe pumps become more sophisticated,
the technological advances oftentimes have a tendency to increase
the expense of making and using the device, increase the complexity
of use, and increase the opportunities for breakdown and repair
if one or more of the operational elements break down.
For example, many existing syringe pumps include an occlusion circuit
for producing an alarm (visual and/or audible) when the syringe
cycle has been completed, if the I.V. line or syringe is occluded
or if there is a system failure. One common mechanism for activating
the occlusion circuit has been the use of one or more switches which
are tripped after the syringe plunger passes a certain point during
its travel into the syringe barrel. In other instances, the syringe
is mounted on a spring-loaded platform which is subject to a small
linear movement after a certain force level has been reached. Thus,
if the plunger being pushed into the syringe barrel either reaches
the bottom of the syringe or cannot expel the liquid contents due
to an occlusion in the line, the force against the plunger causes
the entire spring-mounted syringe to move in linear fashion This
movement, in turn, either trips a switch or may be sensed by position-sensitive
sensors to send a signal to the occlusion circuit so that the automatic
operation of the syringe pump may be terminated. Improvements in
such an occlusion circuit are not only desirable, but are still
being sought, in order to reduce the expense of the elements heretofore
needed in such an occlusion circuit, as well as to eliminate the
need for switches or sensing elements in order to achieve the desired
results.
Some syringe pumps accept different size syringes for carrying
different kinds or amounts of liquid medication. It is known to
have an automatic measurement or sensing of the syringe size positioned
in the syringe pump so that control of the rate and time of medication
delivery may be automatically determined as a function of the size
of the syringe placed in the syringe pump. Improvements in the sensing
mechanism for accommodating and measuring different size syringes
are desirable to provide a superior product.
Many available syringe pumps employ membrane switches on the front
panel which the user depresses with a finger in order to activate
a function of the syringe pump. These membrane switches, which include
both on and off capabilities, are relatively expensive, and as the
number of these switches increases with the sophistication of the
functions, further it increases the expense of the entire device.
Accordingly, improvements in the panel switches or buttons for access
by the user are also desirable, and are being sought.
It is toward such improvements, as mentioned above, as well as
other improvements to be pointed out below, that the present invention
is directed.
SUMMARY OF THE INVENTION
The syringe pump of the present invention comprises a housing and
a retainer mounted thereon for receiving a syringe. The syringe
to be received is of the type including a barrel for holding liquid
medication and a plunger movably positioned in the barrel for expelling
liquid medication therefrom. A driver is movably mounted on the
housing for engagement with the plunger and for pushing the plunger
into the barrel to thereby force the liquid medication out of the
barrel. Control means within the housing regulate the movement of
the driver against the plunger to thereby regulate delivery of the
liquid medication from the barrel. Depressible actuation means are
mounted on the housing for manual access by a user. The actuation
means are associated with the control means to permit the user to
select one or more functions under which the control means operate.
The actuation means include an electrically conductive material
positioned to contact the control means when depressed by the user
to electrically energize or de-energize the control means for the
operation of the selected function.
In another embodiment of the present invention, the control means
includes an electrically powered motor for moving the driver. An
occlusion circuit is provided to stop the motor from moving the
driver when delivery of liquid medication from the barrel has been
completed or when an occlusion prevents liquid medication from being
expelled from the barrel. This occlusion circuit is operative in
response to a pre-set maximum current for operating the motor which,
when reached, causes the motor to cease operation.
In a further embodiment of the present invention, the retainer
includes first electrical contact means which are position-variable
depending upon the size of the syringe received in the retainer.
Second electrical contact means are within the housing and are positioned
to be contacted by the first electrical contact means of the retainer
for producing an electrical signal representative of the size of
the syringe received in the retainer. The electrical signal is receivable
by the control means so that the movement of the driver may be related
to the size of the syringe received in the retainer.
Another embodiment of the present invention includes a housing
having an elongate bearing surface on an outside portion thereof.
The driver is movably mounted on the housing and is in sliding contact
with the bearing surface. Additionally, the driver is positioned
for engagement with the plunger for pushing the plunger into the
barrel for forcing the liquid medication out of the barrel.
In a further embodiment of the present invention, the housing includes
a slot along which the driver assembly is movable. Protection means
cover the slot and are cooperatively mounted in the housing to facilitate
movement of the driver assembly with respect to the slot. The protection
means provide a shield or curtain to prevent foreign materials from
entering the interior of the syringe housing through the slot.
In accordance with the principles of the present invention, a number
of improvements, such as those mentioned above, and other desirable
advantages are provided by the syringe pump hereof. For example,
the inclusion of an electrically conductive material as part of
the actuation means permits the panel buttons or switches to appear
and function in similar fashion to presently available membrane
switches. However, the expense of the electrically conductive material,
as part of the panel switches for access by the user, should be
substantially lower than presently used flexible membrane switches.
In addition, use of the electrically conductive material, such as
graphite-impregnated silicone rubber, eliminates the need for wire
connections between the front panel of the syringe pump device and
the electrical circuit board included within the housing, as is
presently required.
Another improvement and significant advantage of the present invention
is in the novel occlusion circuit. As mentioned above, existing
occlusion circuits rely on the mechanical tripping of a switching
element or sophisticated sensor arrangements. In the present invention,
these mechanical or mechanically-related switching elements the
present invention operates in conjunction with the current limiting
feature of the electrical motor used to drive the plunger into the
syringe barrel. Accordingly, no switches or electrical elements
need to be tripped in the present invention for the occlusion circuit
to be activated.
A further advantage and improvement is provided by the present
invention in the support arrangement for the sliding movement of
the driver which pushes the plunger into the syringe barrel. In
known and existing syringe pumps, the driver is typically coupled
by a half-nut arrangement to a lead screw which is rotated by the
electrical motor. Guide rails are normally provided as bearing surfaces
to support the linear movement of the driver as it is driven by
the lead screw. Two of these guide rails are normally arranged in
parallel tracks in the same direction as the lead screw. In the
present invention, however, there are no guide rails. Instead of
guide rails, a bearing surface is preferably provided on the outside
surface of the housing, in the form of raised surfaces. The driver
is coupled to a lead screw within the housing, but slides along
the raised bearing surfaces of the housing itself for support while
operation is underway. Elimination of the guide rail arrangement
not only saves expense, but also reduces the weight of the device
since the known guide rails are typically made out of metal such
as stainless steel.
Still further, another advantage of the present invention is found
in the arrangement which permits syringes of different sizes to
be retained on the syringe pump. In addition to accepting syringes
of different sizes, it is a feature of the present invention that
the size of the syringe be automatically measured or sensed so that
size-related information may be directed to the microprocessor which
controls the operations and functions of this syringe pump. In presently
known and available syringe pumps, such a feature for sensing different
size syringes includes the use of electrical contacts within the
syringe clamp mounted on the outside of the housing. Wire connections
had to be made between the electrical contacts on the syringe clamp
outside of the housing and the electrical circuit board within the
housing. In the present invention, however, no such wire connections
are required because electrical contacts are provided directly between
the syringe clamp or retainer and the electrical circuit board inside
the syringe pump housing. This arrangement minimizes manufacturing
steps as well as simplifying the design and operation of the syringe
pump.
Other advantages, improvements, and features of the present invention
will become more apparent upon reading the detailed description
below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of the preferred embodiment of the syringe
pump of the present invention illustrating the front face thereof
as it appears to a user;
FIG. 2 is a side view of the syringe pump of FIG. 1 looking toward
the side having the driver for moving the plunger and the retainer
for mounting the syringe barrel;
FIG. 3 is a cross-sectional view of the front cover of the syringe
pump housing taken along line 3--3 of FIG. 1;
FIG. 4 is a cross-sectional view of the interior face of the front
cover of the syringe pump taken along line 4--4 of FIG. 2;
FIG. 5 is a cross-sectional view of the interior components of
the syringe pump, particularly illustrating one surface of the printed
circuit board, as these components appear just inside the front
face of the syringe pump of the present invention, taken along line
5--5 of FIG. 2;
FIG. 6 is a cross-sectional view of the interior components of
the syringe pump positioned below the printed circuit board as such
components are positioned inside the back cover of the syringe pump
housing, taken along line 6--6 of FIG. 2;
FIG. 7 is an enlarged cross-sectional view of a driver mechanism
of the present invention taken along line 779 of FIG. 2;
FIG. 8 is an enlarged perspective view of the curtain for protectively
covering the elongate slot through which the driver mechanism is
controlled;
FIG. 9 is an enlarged cross-sectional view illustrating the motor
mechanisms and lead screw arrangement inside the syringe housing
taken along line 9--9 of FIG. 1;
FIG. 10 is a graphical representation of the performance of the
DC motor in terms of current versus torque according to the principles
of the present invention;
FIG. 11 is an end view of the syringe pump of FIG. 1 illustrating
the mounting of a syringe by virtue of the retainer clamp, further
illustrating the syringe barrel positioned against the housing and
the clamping position of the retainer clamp shown in phantom; and
FIG. 12 is a plan view of the preferred embodiment of the syringe
pump of the present invention illustrating a syringe mounted thereon
as it appears in preparation for use.
DETAILED DESCRIPTION
While this invention is satisfied by embodiments in many different
forms, there is shown in the drawings and will herein be described
in detail a preferred embodiment of the invention; with the understanding
that the present disclosure is to be considered as exemplary of
the principles of the invention and is not intended to limit the
invention to the embodiment illustrated. The scope of the invention
will be measured by the appended claims and their equivalents.
Adverting now to the drawings, and FIGS. 1 and 2 in particular,
there is shown a syringe pump 20 in a preferred configuration for
purposes of the present invention. In general, syringe pump 20 is
comprised of a housing 22 a driver mechanism 24 and a syringe retainer
26. In the preferred configuration, housing 22 is a compact, light-weight
housing which is assembled in two parts, consisting of an upper
(front) cover 28 and a lower (back) cover 29. Each of covers 28
and 29 is preferably formed in tray-like fashion so as to be able
to include the interior components of the syringe pump, as well
as for ease of assembly with a few screws or the like. When assembled,
it is preferred that covers 28 and 29 form housing 22 which is completely
enclosed except for an elongate slot 30 on one side of the housing.
This slot, as will be described more fully hereinafter, permits
driver 24 to move outside of the housing while being driven by a
drive mechanism within the housing. A ring 31 is connected to the
housing to provide a hook or the like for hanging the syringe pump
on a stand at the location where the patient is to receive the medication
from the syringe pump.
Upper cover 28 includes a front face 32 with a number of controls
and displays. It is understood that many different controls or displays
may be provided in a syringe pump depending upon a variety of factors
and intended functions thereof. For purposes of the present invention,
and while suggesting no limitations, upper face 32 includes five
control mechanisms or buttons, namely, "POWER ON" 34
"INFUSE" 35 "VOLUME DELIVERED" 36 "STOP
INFUSION" 38 and "POWER OFF" 39. Two other buttons
or controls are provided, one such button 40 permitting the user
to increment the rate of delivery of medication by "10's"
and the other control or button 41 permitting the user to increment
the rate of medication delivery by "1's." When buttons
40 and 41 are depressed by the user, a display 42 digitally indicates
the numbers that have been incrementally selected by the user. Each
time buttons 40 and 41 are pushed, the digit in the "1's"
or "10's" columns are incremented by one until the number
selected by the user is displayed. In the embodiment being described,
display 42 usually shows the rate of delivery of medication, in
milliliters per hour, to be selected by the user.
In addition to display 42 INFUSE button 35 has a light display
44 associated therewith so that the light is turned on when the
INFUSE button has been pushed to inform the user that infusion is
taking place. Another panel light 45 is provided to indicate when
the batteries are low. A third panel light 46 is provided as an
ATTENTION indicator serving as a visual alarm to inform the user
that the syringe is empty or that an occlusion has occurred and
infusion has been terminated.
The mechanism of actuation of the various controls on the front
face of the upper cover is more clearly seen by referring to FIGS.
3-5 taken in conjunction with FIG. 1. Looking first at FIG. 4
upper cover 28 is illustrated as it appears looking from the inside.
A number of holes are provided through front face 32 of cover 28
and these holes, designated by numerals 48 49 50 51 52 54 and
55 correspond with buttons 34 35 36 38 39 40 and 41 respectively.
Holes 56 58 and 59 correspond with lights 44 45 and 46 respectively.
The holes associated with the buttons are covered by a thin, flexible
and depressible membrane 60 preferably in one piece extending over
the entire front face of the upper cover, on the left-hand side
thereof as illustrated in FIG. 1. A similar thin, flexible, depressible
membrane 62 covers holes 54 and 55 associated with the buttons for
regulating display 42 and this membrane covers a substantial portion
of the right-hand side of the upper cover as seen in FIG. 1. Of
course, it is understood that the depressible membranes may be separate
for each button or control to be depressed or may be a singular
membrane covering the entire surface of the front cover where depressible
buttons are included. Affixed to the bottom side of membranes 60
and 62 and extending through each hole associated with a button
or control, is an electrically conductive piece of material 64.
Material 64 is preferably in the form of a block so that it has
a substantially flat end surface 65 for electrical contact purposes.
Material 64 may be any electrically conductive material, such as
metal, including copper, aluminum and the like, but is preferably
a compressible material with spring-like qualities so as to be compatible
with being depressed in button-like fashion. For example, this material
may be styrofoam or other lightweight and inexpensive material,
with an electrically conductive end 65 for electrical contact purposes.
On the other hand, an inexpensive and lightweight material such
as graphite-impregnated silicone rubber is quite suitable for the
present invention insofar as this material is electrically conductive
and is compressible as well.
In FIGS. 3 and 5 it can be seen that there is a printed circuit
board 66 mounted within upper cover 28 so that it is spaced inwardly
from front face 32. This printed circuit board includes the electrical
circuitry for operation of the syringe pump and includes a variety
of electrical components including one or more microprocessors 68
and/or associated integrated circuit chips, a digital readout 69
for display 42 panel lights 44 45 and 46 and other circuits and
components well within the purview of the ordinary artisan for completing
the electrical functions as explained herein. Part of the circuitry
on printed circuit board 66 includes switching circuits for controls
34 35 36 38 and 39 and stepper circuits for controls 40 and
41. These circuits are energized by momentarily closing the circuits
associated therewith, and then are de-energized by momentarily closing
the circuits with the same switching mechanism.
For each control button on the front panel of the housing, the
printed circuit board includes an electrically conductive pad 70
in this instance, composed of two electrical elements of the circuit
associated therewith. These electrically conductive pads are positioned
on the printed circuit board so that they are slightly spaced and
directly opposed from face 65 of block of material 64. This close
spacing between face 65 and electrical pad 70 is more clearly illustrated
in FIG. 3. For example, this spacing may be about 0.020 inches (0.51
millimeters). When the user pushes the area of membrane 60 or 62
with one of the control buttons, the membrane deforms under the
force of depression, causing block 64 to move toward electrical
pad 70 so that face 65 of each block 64 makes contact with pad 70.
This electrical contact causes a momentary bridging between the
two electrical elements on the electrical pad in question, in turn
energizing the electrical circuit affected by the control button
being depressed, so that the desired operation of the selected function
may occur. When the depression force is released by the user, contact
is broken between face 65 of block 64 and electrical pad 70 and
the subsequent depression of the same control button against the
related pad causes a momentary electrical contact between face 65
and pad 70 this time de-energizing the affected electrical circuit.
With respect to control buttons 40 and 41 successive deprescriptions
thereof cause the display to increment to the next higher number
in the column associated with the button being pushed. It is observed
that the electrical actuation mechanism, described above, causes
the electrical circuits and functions to be energized and de-energized
without the need for wire connections between the depressible control
button and the printed circuit board on which the circuits are maintained.
Reference is now made to FIGS. 1 2 4 and 5 in which the details
of syringe retainer 26 are more clearly illustrated. Retainer 26
preferably includes a slidable clamp 74 which has a portion extending
outside of the housing in the form of a downwardly depending arm
75 and a portion extending inside the housing in the form of a relatively
flat strip 76. A pair of clamp guides 78 and 79 affixed to upper
cover 28 hold clamp 74 in position and serve to guide the movement
of the clamp for holding the syringe barrel in position with respect
to the housing. Inside upper cover 28 are a pair of tracks 80 and
81 between which flat strip portion 76 of the clamp is positioned.
Thus, guide clamps 78 and 79 and tracks 80 and 81 not only maintain
the clamp in position with respect to the upper cover, but facilitate
the sliding movement of the clamp in and out of the upper cover
in a lateral direction as viewed in FIG. 4. Connected to one of
the walls of upper cover 28 is a pair of springs 82 and 84 which,
in turn, are connected to the interior end of flat strip portion
76 of clamp 74. These springs are selected so that an inward bias
is maintained on clamp 74 so that when the syringe barrel is held
in place against the housing by virtue of depending arm 75 an inward
force is applied to the syringe barrel to keep the syringe barrel
securely in place. It is appreciated that springs 82 and 84 are
stretchable in order to accommodate larger size syringe barrels
by permitting the clamp to slide outwardly a further distance from
the housing surface, as will be described in greater detail hereinafter.
Track 80 includes a shoulder 85 which serves as a stop device to
limit travel of clamp portion 76 inwardly toward the springs, thereby
keeping a constant bias on the clamp.
Mounted on the bottom of clamp portion 76 is an electrical contact
member including two electrical tabs 88 and 89. When housing 22
is assembled, and upper cover 28 is positioned over lower cover
29 electrical tabs 88 and 89 are positioned to be able to contact
printed circuit board 66. Specifically, and with particular reference
to FIG. 5 printed circuit board 66 in the area juxtaposed with
strip portion 76 of the clamp, includes a plurality of electrical
contact strips, in this instance five in number designated by numerals
90 91 92 94 and 95. These electrical strips are arranged laterally
across the face of the printed circuit board in spaced fashion.
Another electrical strip 96 is spaced slightly adjacent to the aforementioned
electrical strips, and this strip 96 extends laterally so that it
traverses the entire width of the separated, individual strips located
slightly therebelow. All of these electrical strips are connected
to the electrical circuitry on the printed circuit board.
Strip portion 76 of clamp 74 is arranged so that it is slidable
inwardly and outwardly along axis 98. Irrespective of the position
of clamp 74 electrical tab 88 is intended to be in constant contact
with electrical strip 96; depending upon the position of clamp 74
electrical tab 89 contacts one of electrical strips 90 91 92
94 or 95. When one of these latter mentioned strips is contacted,
such strip along with electrical strip 96 serves to energize a circuit
sending a signal to the microprocessor representative of the size
of the syringe barrel mounted against the housing.
In particular, strips 90 91 92 94 and 95 are positioned and
spaced on the printed circuit board, and in conjunction with the
design of clamp 74 including the location of electrical tabs 88
and 89 so that certain size syringe barrels may be sensed. For
example, and without suggesting any limitations, if a 5 cc syringe
barrel is mounted against the housing by the retainer clamp, electrical
tab 89 is in electrical contact with electrical strip 90 (electrical
tab 88 also being in contact with electrical strip 96). A closed
circuit is thus established between electrical strips 90 and 96
sending a signal to the microprocessor indicative of the presence
of a 5 cc syringe being used. The microprocessor preferably includes
memory storage capability for identifying this electrical signal
received from the aforementioned electrical contacts so that the
functions of the syringe pump which occur will relate to the performance
of a 5 cc syringe. In similar fashion, contact between tab 89 and
electrical strip 91 may represent a 10 cc syringe; contact between
electrical tab 89 and electrical strip 92 may represent a 20 cc
syringe; electrical contact between tab 89 and electrical strip
94 may represent a 30 cc syringe; and electrical contact between
tab 89 and electrical strip 95 may represent a 60 cc syringe. The
microprocessor and the electrical circuitry is preferably pre-programmed
to identify the different signals caused by the different electrical
contacts so that operation of the syringe pump can be performed
automatically without the necessity of the user having to inform
the syringe pump which size syringe is being utilized. It is appreciated
that the linear traverse of the retainer clamp for making contact
with the electrical strips on the printed circuit board eliminates
the need for any wiring between the clamp and the printed circuit
board for establishing the various circuits for energizing or de-energizing
the functions to be performed by the present syringe pump.
FIGS. 6 and 7 along with FIGS. 1 and 2 more clearly illustrate
the details of driver 24 as it is mounted on housing 22. Driver
24 is an assembly including a body member 100 to which is attached
a slidable latch member 101. Latch member 101 preferably has outwardly
protruding finger flanges 102 for easy grasping by the user. A spring,
such as coil spring 104 is preferably included within body member
100 so that a force is urged against latch member 101 keeping it
biased in an inward direction toward the housing. Latch member 101
may be moved outwardly by grasping the finger flanges and applying
sufficient outward force to overcome the biasing force of spring
104. In conjunction with the slidable movement of latch member 101
there is provided a catch or hook 105 which facilitates the holding
of the plunger of the syringe in position against driver assembly
24. An abutment 106 is provided on body member 100 serving as a
fixed element also for holding the plunger of the syringe in position
against the driver assembly. Positioning of the syringe, with its
extended plunger, will be described more completely hereinafter.
Body member 100 includes a shank 108 extending through slot 30
of housing 22. On the interior side and connected to shank 108 is
a half-nut mechanism 109 positioned to engage the threads of a lead
screw 110. When half-nut 109 is engaged to lead screw 110 rotation
of the lead screw imparts linear movement to driver 24 by virtue
of the half-nut threaded engagement. This type of driving arrangement
is well-known in the art of syringe pumps and no further details
need be provided for a complete appreciation of the working of such
elements.
In order to provide disengagement between half-nut 109 and lead
screw 110 a disengagement rod 112 extends through body member 100
so that its interior end is associated with half-nut 109. Although
not shown in FIG. 7 rod 112 is spring-loaded so that its exterior
end extends a short distance beyond the end of body member 100.
A thumb button 114 is preferably included at the exterior end of
rod 112 so that the thumb or finger of the user may depress rod
112 inwardly. Depression of rod 112 inwardly, with sufficient force
to overcome the spring-loading effect thereof, causes half-nut 109
to become disengaged from lead screw 110. When disengagement of
these parts occurs, driver mechanism 24 is freely slidable along
slot 30 so that it may be moved to any position along the slot,
such as an initial position for latching onto the plunger rod of
the syringe when the syringe is being loaded It is preferred that
the depression of rod 112 for disengagement of the half-nut from
the lead screw be independent of the slidable movement of latch
member 101 for making the connection to the plunger rod of the syringe.
Currently available syringe pumps rely on guide rails or the like
for providing bearing support to the driver mechanism as it moves
in linear fashion as a result of rotation of the lead screw. Instead
of guide rails, the present invention relies upon the unique construction
of housing 22 to provide adequate bearing surfaces for supporting
the driver mechanism during its linear movement along the housing.
Specifically, it can be seen particularly in FIG. 7 that upper housing
28 and lower housing 29 are formed so that slot 30 lies between
the two housing portions when joined together It can be seen that
upper housing portion 28 includes a raised bearing surface 116 and
lower housing portion 29 includes a raised bearing surface 118
with each such bearing surface extending along the elongate dimension
of slot 30 and running substantially parallel thereto. Bearing surfaces
116 and 118 provide sliding support for driver mechanism 24 at portion
119 of body member 100. This support is provided at this interface
when the driver mechanism is engaged to the lead screw and also
when it is disengaged therefrom.
In FIGS. 6 and 7 it can be seen that a small platform 120 is mounted
on the driver mechanism near the half-nut component, on the interior
side of housing 22. Platform 120 is preferably an electrical insulator,
such as rigid plastic or the like. Mounted on platform 120 is an
electrical contact member 121 including one or more electrical contacts
122. These electrical contacts 122 are arranged so that they are
in contact with one side of printed circuit board 66. One or more
electrical pads 124 are provided on the surface of printed circuit
board 66 so that electrical contacts 122 may come in contact therewith.
Electrical pads 124 are preferably positioned on the printed circuit
board at a position near the end of elongate slot 30 where the driver
mechanism will finish its movement when the plunger rod has been
moved all or almost all of the way into the syringe for emptying
the contents thereof. A relative position of electrical pads 124
with respect to slot 30 may be seen by briefly referring to FIG.
3. This contact between electrical contacts 122 and electrical pads
124 is part of an occlusion circuit to be described more fully hereinbelow.
Included in the syringe pump of the present invention is a protective
feature for covering the opening made by the elongate slot along
the side of the housing. In presently known and available syringe
pumps, such a slot is frequently left uncovered, in which case,
fluids may spill therethrough into the interior of the housing;
further, small objects such as portions of clamps, clips or the
like, may slip through the slot and enter the housing, potentially
causing some damage or malfunction. In order to overcome this deficiency
in the known syringe pumps, the present invention provides a protective
covering with respect to the slot. In particular, and as seen in
FIGS. 4-7 upper housing cover 28 includes an elongate groove 126
formed just inside and extending substantially parallel to slot
30. In similar fashion, lower housing cover 29 includes an elongate
groove 128 also formed just inside of and extending substantially
parallel to slot 30. When upper cover 28 and lower cover 29 are
assembled, grooves 126 and 128 face each other and form a channel.
Positioned in this channel, and preferably connected to drive mechanism
24 are two flexible bands 129 and 130. Bands 129 and 130 are preferably
similar in construction, and are substantially flat, elongate and
flexible in nature. As seen in FIG. 8 one end of band 129 includes
a hook 131 which fits into a depression or hole (not shown) on driver
mechanism 24. Band 129 fits in grooves 126 and 128 and extends from
driver mechanism 24 over slot 30 and bends around a drum-like element
132 (primarily used for a screw attachment). Similarly, band 130
sits in grooves 126 and 128 and extends from its attachment to the
driver assembly over the interior portion of slot 30 and bends around
another drum-like element 134 at the other corner of the housing.
The flexible nature of these bands allows them to remain in position
covering the interior side of slot 30 when driver mechanism 24 moves
along the slot. Bands 129 and 130 move with the driver mechanism
thereby providing constant protection of the slot so that foreign
materials may be prevented from entering the housing through the
slot.
Turning now to FIG. 6 it can be seen that lower housing portion
29 includes a compartment 136 which holds one or more batteries
138 to provide electrical power for operating the motor and electrical
circuitry of the present syringe pump. These batteries provide direct
current (DC) to a motor which is preferably a DC motor 139 for
driving and rotating lead screw 110. Motor 139 includes a shaft
140 which is also illustrated in FIG. 9 taken in conjunction with
FIG. 6. Attached to shaft 140 is a small gear 141 which rotates
when shaft 140 rotates when the motor is operating. Another gear
142 in this case a larger gear, is connected to lead screw 110
and is in meshing engagement with smaller gear 140. Accordingly,
operation of motor 139 causes the rotation of lead screw 110 by
virtue of the rotating shaft of the motor and the associated gears.
Lead screw 110 is maintained in position within lower housing portion
29 preferably by means of journal bearings 144 positioned at or
near the respective ends of lead screw 110.
Also connected to drive shaft 140 of DC motor 139 is a wheel 145
which serves as an encoder associated with the timing and the control
circuitry governing the operation of the present syringe pump. Encoder
145 being connected to drive shaft 140 of the motor, therefore
rotates when shaft 140 rotates. It can be seen, particularly when
viewing FIG. 9 that encoder 45 is divided into a plurality of equally
spaced gaps or segments 146 arranged around the periphery thereof.
These gaps or segments pass in front of a light such as a light
emitting diode (LED) 148 connected to printed circuit boards 66
so that the number of segments may be counted for operation of the
control circuit as part of the electrical circuitry hereof.
During operation of DC motor 139 for each passage of a segment
146 of the encoder past LED 148 lead screw 110 rotates to cause
the drive mechanism 24 to move a fixed linear distance. In turn,
this movement causes the movement of the syringe plunger into the
syringe barrel, as will be pointed out below. As the syringe plunger
is moved into the syringe barrel by a known, fixed distance, such
linear movement of the plunger may be translated into a known volume.
Thus, it is possible to calculate the volume of liquid delivery
from the syringe in milliliters per segment or increment, for each
passage of a segment of the encoder. For different size syringes,
this volume per increment will vary. This information o volume per
increment for different size syringes, preferably of the conventional
size syringes used in hospital procedures, is stored in the memory
function of microprocessor 68 included in the electrical circuitry
of the control functions of the present syringe pump. In connection
with the microprocessor and the selectable functions of the present
invention, if the desired delivery rate, in milliliters per hour,
is programmed or selected for operation by a user of the syringe
pump, the time between increments may be determined by dividing
the delivery rate (milliliters per hour) by the volume per increment
(milliliters per increment). This calculation is preferred automatically
by the electrical circuitry and is also storable in the memory function
of the microprocessor hereof to provide the time between increments.
Total volume of liquid medication to be delivered from the syringe
may be established or calculated by multiplying the total number
of increments of the motor by the volume per increment of the particular
syringe in use. As pointed out above, each increment of the motor
is determined by the passage of segment 146 of encoder 145 in conjunction
with LED 148. The electrical circuitry of the present invention
includes a timing circuit which is designed to account for the time
intervals to be calculated as mentioned above, associated with the
desired delivery rates for different size syringes.
An occlusion detection circuit is included in the electrical circuitry
and relies on the physical property of DC motors and the aforementioned
timing circuit to carry out its intended functions. The occlusion
circuit is intended to inform the user when the medication delivery
from the syringes barrel has been completed (sometimes referred
to as end of cycle) and also to inform the suer when delivery of
medication from the syringe is prevented or substantially altered
because of an occlusion or the like in the fluid delivery line.
In connection with the particular properties of DC motors, appropriate
circuitry is provided to the instant DC motor so that it is current
limited. As a result, the amount of torque the motor can apply for
rotating the lead screw, for ultimately pushing the plunger into
the syringe barrel, is also limited, in a relationship such as illustrated
in FIG. 10. For example, under normal operation of the instant DC
motor, the current may typically run about 20 milliamps under normal
torque conditions. In the event that the torque increases to about
40 milliamps, because of the increased pressure in the syringe barrel
due to occlusion or end of cycle, the current increases in linear
fashion to maintain operation of the motor. The current limitation
of the present invention, however, causes the motor to stop operation
when the current reaches the threshold level set by the current
limiting circuitry.
At the beginning of the initial timing increment of operation,
DC motor 139 is turned on and a control circuit is set in accordance
with the electrical circuitry thereof. Should there be a line occlusion
or end of cycle, the force to move the plunger rod into the syringe
barrel increases. This, in turn, causes the torque of the DC motor
to increase. Accordingly, the current increases, and at the current
limiting threshold, the motor stalls and stops operation. As a result,
the DC motor does not complete its movement to the next segment
146 of encoder 145. In normal operation, when motor 139 reaches
next encoder segment 146 it activates the electrical circuitry
to turn the motor off and to reset the control circuitry. However,
in the event of an occlusion which causes DC motor 139 to cease
operation, the control circuitry is not reset. On the other hand,
the control circuit receives the next time increment from the timing
circuit and recognizes that the last increment has not be completed,
and therefore activates the alarm circuitry. This alarm circuitry,
as pointed out above, lights attention signal 46 on the front face
of housing 22 and may also activate an audible alarm
If an occlusion occurs because of fluid delivery line blockage
or the like, the audible alarm is programmed to provide a rapid
beeping sound or rapid flashing of light 46 on the face of the panel.
If, however, the occlusion circuit is activated because of end of
cycle and medication delivery from the syringe barrel has been completed,
a different alarm is preferably activated. In the case of end of
cycle, driver mechanism 24 has moved in linear fashion along slot
30 so that the syringe plunger is almost completely pushed within
the syringe barrel. At this location, electrical contacts 122 on
driver mechanism 24 come in contact with electrical pad 124 on printed
circuit board 66. This contact serves as a switch or the like causing
the occlusion detection circuit to issue an alarm different from
the alarm mentioned above with respect to blockage in the delivery
line. The end of cycle alarm may be a slow beeping signal or slow
flashing of light 46 on the front panel of the housing.
General operation of syringe pump 20 will now be described in connection
with FIGS. 11 and 12. A syringe 150 typically is prepared with liquid
medication to be delivered to a patient at a prescribed delivery
rate, such as in milliliters per hour. Syringe 150 is normally of
the conventional type including a syringe barrel 151 having liquid
medication 152 included therein. Distal tip 154 of the syringe barrel
is provided for connection to a delivery line so that the liquid
contents of the syringe may be passed therethrough and delivered
to the patient. At the proximal end of barrel 151 there is usually
a finger flange 155 on typical or conventional syringes. Extending
out of the proximal end of syringe barrel 151 is a plunger 156 in
the form of an elongate rod, the proximal end of which preferably
terminates in a thumb disk 158 or the like.
Loaded syringe 150 is mounted onto syringe pump 20 in a few straightforward
steps. The user first assures that driver mechanism clears thumb
disk 158 of the syringe plunger by depressing button 114 inwardly
thereby causing disengagement of the half nut from the lead screw
within the interior of the housing. This disengagement allows the
free movement of driver mechanism 24 to clear the plunger of the
syringe Mounting of the syringe is then facilitated by the user
grasping clamp 74 and pulling same outwardly so that the clamp slides
linearly between clamp guides 78 and 79. Syringe barrel 151 is then
positioned so that it rests against the protruding surfaces of cradle
160 and 161 formed on the outside surfaces of upper housing portion
28 and lower housing portion 29. Arm 75 of clamp 74 is then allowed
to contact the outside surface of syringe barrel 151. As mentioned
above, springs 82 and 84 inside the housing urge clamp 74 inwardly
thereby holding the syringe barrel snugly and firmly in the cradle
on the outside surface of the housing. At the same time, finger
flange 155 at the proximal end of the syringe barrel is positioned
so that it rests in contact directly on the outer surface of clamp
guide 78. Accordingly, syringe barrel 151 of the syringe is now
in a fixed and relatively immovable position during operation of
the syringe pump.
Once the syringe barrel has been positioned as explained above,
an automatic assessment and determination of its size takes place.
Depending upon the size or diameter of syringe barrel 151 different
contacts are made between electrical tab 89 on clamp 74 and one
or more of the electrical strips on the printed circuit board, as
set forth above. Thus, and for example only, if syringe 150 has
a barrel of the conventional type of 20 cc capacity, electrical
tab 89 may be in engagement with electrical strip 92. In that event,
a circuit is established by virtue of these electrical contacts,
informing the microprocessor circuitry that a 20 cc syringe is mounted
on the housing. All delivery rates, timing intervals, the timing
circuit, control circuit and calculations, may then be performed
by virtue of the microprocessor and related circuitry in accordance
with the specific size syringe automatically assessed to be in position
for use in the syringe pump. No information need be provided by
the user to the syringe pump with respect to the size of the syringe
being used, since syringe size is automatically detected.
Driver mechanism 24 is brought into engagement with thumb disk
158 by a combination of straight-forward steps. Once again, button
114 may be depressed to release the internal engagement of the half
nut and the lead screw so that the driver 24 may freely be slid
to the position of the extending plunger rod of the syringe. Once
button 114 is released, the internal engagement of the half nut
and lead screw is once again established. Latch member 101 is then
urged slightly outwardly by pulling on finger flanges 102. Thumb
disk 158 of the syringe plunger is then slipped into engagement
with abutment surface 106 on driver mechanism 24. Release of finger
flanges 102 causes latch member 101 to move inwardly so that latch
105 is hooked over the protruding end of thumb disk 158 thereby
capturing same in fixed position. The loaded syringe is now ready
so that its contents may be delivered to the patient.
At this time, syringe pump 20 is typically hanging on a stand or
the like in connection with ring 31. The user starts the procedure
by first depressing POWER ON button 34 thereby activating the electrical
circuitry of the syringe pump in accordance with the elements and
features described above. If the battery power is low, light 45
will glow; if battery power is sufficient, light 45 remains off.
If, for example, the liquid contents of syringe 150 are to be delivered
at the rate of 25 milliliters per hour, the user pushes "tens"
button 40 for two successive increments until the number "2'
appears in the tens column of display 42. In similar fashion, the
"ones" button 41 is depressed until it is incremented
five times whereby the number "5" appears in the ones
column of display 42. Once this rate of delivery has been established
and also shown on display 42 the electrical circuitry of the syringe
pump, having already assessed the size of the syringe mounted on
the housing, functions through its microprocessor capabilities to
deliver the contents of the syringe at the selected rate. The present
invention is contemplated to be operative with conventional syringes
of 5102030 and 60 cc capacity. It is understood that the present
invention, however, is limited to neither these size syringes nor
this number of different syringes.
Having selected the desired rate of delivery, the user depresses
INFUSE button 35 signaling the initiation of DC motor 139 and subsequent
movement of driver mechanism 24. This movement of the driver mechanism,
in turn, causes plunger 156 to be pushed into syringe barrel 152
causing the liquid medication therein to be delivered through distal
tip 154 into a medication line (not shown). Display 42 may be changed
to show volume delivered from the commencement of operation by depression
of VOLUME DELIVERED button 36. Display 42 will then read a number
in milliliters, and may be programmed to display volume for a period
of a few seconds after the VOLUME DELIVERED button has been depressed.
If an occlusion occurs as a result of line blockage or the like,
attention light 46 is lit and an audible alarm sounds, as described
above. If, however, the occlusion detection circuit is activated
as a result of end of cycle when medication delivery from the syringe
barrel has been completed, the DC motor stops operation and attention
light 46 comes on. The visual and audible signal corresponding to
end of cycle, however, is different from the signal for line occlusion.
At any time during operation of the syringe pump, the user may stop
the operation of the syringe pump by depressing STOP INFUSION button
38. The unit is turned off by depressing POWER OFF button 39.
Thus, the present invention provides a syringe pump with a number
of significant and notable improvements over presently known and
available syringe pumps. Automatic sensing and determining of the
size of the syringe mounted to the housing are provided, in which
no wires are needed for connection to the electrical circuitry of
the device. In addition, the front panel membrane buttons are also
operative to energize or de-energize the selected functions without
the need for wire connections between the front panel and the printed
circuit board included within the housing. Elimination of guide
rails for movement of the driver mechanism not only saves expense
but considerable weight of the entire package. Further, the protective
covering over the slot through which the driver mechanism moves
is a significant safety feature for preventing the passage of foreign
materials into the interior of the housing. Most significantly,
the present syringe pump may be fabricated with relatively few components
and inexpensive assembly, while providing the user with sophistication
of operation and versatility of performance. |