Cassette optical identification apparatus for a medication infusion system

A cassette identification system for use with a medication infusion system having disposable cassettes which are mounted onto a main pump unit is disclosed which uses an optical sensor module to read the identifying bits from the cassette. The identification indicia contained on the cassette each either pass light through a portion of the cassette, or diffuse the light to prevent it from passing through the cassette. The optical module is mounted on the main pump unit, and includes light sources and sensors for each of the identification indicia on the cassette; the system may use either redundant or non-redundant coding for identifying the cassettes.

IDENTIFICATION OF RELATED PATENT APPLICATIONS 
This application is related to six other concurrently filed copending 
patent applications. These patent applications are U.S. Ser. No. 127,333, 
entitled "Disposable Cassette for a Medication Infusion System," U.S. Ser. 
No. 127,350, entitled "Piston Cap and Boot Seal for a Medication Infusion 
System," U.S. Ser. No. 128,122, entitled "Pressure Diaphragm for a 
Medication Infusion System," U.S. Ser. No. 128,121, entitled "Air-In-Line 
Detector for a Medication Infusion System," U.S. Ser. No. 127,359, 
entitled "Cassette Loading and Latching Apparatus for a Medication 
Infusion System," and U.S. Ser. No. 127,133, entitled "Mechanical Drive 
System for a Medication Infusion System." 
BACKGROUND OF THE INVENTION 
Field of the Invention 
The present invention relates generally to an optoelectronic identification 
system for use in identifying a disposable component, and more 
particularly to a system for identifying which of a plurality of different 
disposable cassettes is installed onto a main pump unit by using an 
optical sensor unit on the main pump unit which provides a plurality of 
light beams in pathways to light detectors, with the cassette having 
optical identifying indicia which either pass or do not pass the light 
beams to the sensors. 
In the past there have been two primary techniques which have been used to 
deliver drugs which may not be orally ingested to a patient. The first 
such technique is through an injection, or shot, using a syringe and 
needle which delivers a large dosage at relatively infrequent intervals to 
the patient. This technique is not always satisfactory, particularly when 
the drug being administered is potentially lethal, has negative side 
effects when delivered in a large dosage, or must be delivered more or 
less continuously to achieve the desired therapeutic effect. This problem 
results in smaller injections being given at more frequent intervals, a 
compromise approach not yielding satisfactory results. 
Alternatively, the second technique involves administering a continuous 
flow of medication to the patient, typically through an IV bottle. 
Medication may also be delivered through an IV system with an injection 
being made into a complex maze of IV tubes, hoses, and other 
paraphernalia. With drop counters being used to meter the amount of bulk 
fluid delivered, many medications still end up being administered in a 
large dosage through an injection into the IV lines, although the 
medications may be diluted somewhat by the bulk fluid. 
As an alternative to these two techniques of administering medication to a 
patient, the relatively recent addition of medication infusion pumps has 
come as a welcome improvement. Medication infusion pumps are utilized to 
administer drugs to a patient in small, metered doses at frequent 
intervals or, alternatively, in the case of some devices, at a low but 
essentially continuous rate. Infusion pump therapy may be electronically 
controlled to deliver precise, metered doses at exactly determined 
intervals, thereby providing a beneficial gradual infusion of medication 
to the patient. In this manner, the infusion pump is able to mimic the 
natural process whereby chemical balances are maintained more precisely by 
operating on a continuous time basis. 
One of the requirements of a medication infusion system is dictated by the 
important design consideration of disposability. Since the portion of the 
device through which medication is pumped must be sterile, in most 
applications of modern medication infusion equipment some portions of the 
equipment are used only once and then disposed of, typically at regular 
intervals such as once daily. It is therefore desirable that the fluid 
pump portion of the infusion pump device be disposable, with the fluid 
pump being designed as an attachable cassette which is of inexpensive 
design, and which is easily installable onto the main pump unit. 
It will be perceived that it is desirable to have a simple disposable 
cassette design to minimize the cost of construction of the cassette, 
using the minimum number of parts necessary in the design of the cassette. 
The design of the cassette must be mass producible, and yet result in a 
uniform cassette which is capable of delivering liquid medication or other 
therapeutic fluids with a high degree of accuracy. The cassette should 
include therein more than just a fluid pump; other features which have 
formerly been included in peripheral devices may be included in the 
cassette. 
It may be recognized by those skilled in the art that it may be desirable 
to use several different types of disposable cassettes with a medication 
infusion system. Different disposable cassettes may be used which have 
different stroke volumes, and special purpose cassettes such as enteral 
pump cassettes, continuous arterio-venous hemofiltration (CAVH) cassettes, 
continuous blood sampling cassettes, or autotransfusion cassettes may also 
be used with a medication infusion system to give it the broadest possible 
range of uses. The use of the wrong cassette may be dangerous, so it may 
therefore be perceived that it is desirable to provide means to identify 
the particular cassette (or cassettes) installed on the main pump unit. 
It is therefore the primary objective of the present invention to provide a 
disposable cassette containing a plurality of identifying bits for use 
with a main pump unit having apparatus for reading the identifying bits 
contained on the disposable cassette. The disposable cassette of the 
present invention will be of an advanced design retaining all of the 
advantages of such devices known in the past, and will include the 
identifying bits in an integral fashion in the construction of the 
cassette. The main pump unit shall contain integrally a sensor which is 
capable of reading the identifying bits on a disposable cassette installed 
onto the main pump unit. The process whereby the main pump unit identifies 
the particular type of disposable cassette installed must be fully 
automatic, and require no user input whatsoever. In fact, one of the main 
objects is to avoid the possibility of user error in indicating to the 
main pump unit what types of cassettes are installed on the main pump 
unit. 
The identification system must meet several other requirements in order to 
present a system which is practical in addition to being novel. At least 
several different cassettes must be identifiable by the system, and it is 
also desirable to utilize a redundant system to minimize the possibility 
of errors being made in the identification of the cassette when it is 
installed onto the main pump unit. In addition, the inclusion of the 
identifying indicia on the disposable cassette must be done in a fashion 
both minimizing the cost of including the indicia while maximizing the 
reliability of the system. 
Specifically, despite the inclusion of a multiple bit identification 
indicia on the disposable cassette of the present invention, a minimum 
number of parts shall be utilized in the construction of the cassette, all 
of which parts are of inexpensive construction yet affording the assembled 
cassette the high degree of accuracy which must be retained. No 
identification system known in the art even comes close to combining these 
features, or even a majority of the features enumerated above. 
The cassette used with the present invention must be of a design which 
enables it to compete economically with known competing systems. The 
transducer contained in the main pump unit should also be of economical 
construction, yet exhibiting high reliability and accuracy of operation. 
The system must provide an ease of use rivaling the best of such competing 
systems. The system must accomplish all the above objects in a manner 
which will retain all of the advantages of reliability, durability, and 
safety of operation. The cassette identification system of the present 
invention must provide all of these advantages and overcome the 
limitations of the background art without incurring any relative 
disadvantage. All the advantages of the present invention will result in a 
superior medication infusion system having a number of advantages making 
the system a highly desirable alternative to systems presently available. 
SUMMARY OF THE INVENTION 
The disadvantages and limitations of the background art discussed above are 
overcome by the present invention. With this invention, a disposable 
cassette having only seven components therein is described. The cassette 
utilizes a highly accurate and reliable piston-type fluid pump and an 
active valve design of unparalleled accuracy, simplicity, and accuracy of 
operation. A bubble trap is included in the cassette for removing air 
bubble introduced into the system, and a bubble detector is used to ensure 
that fluid supplied to patient is virtually bubble-free. 
This cassette identification system is accomplished by the use of the three 
optical cassette identifying indicia on the cassette, and an optical 
sensor module contained in the main pump unit, which together are the 
subject of the present invention. For the representation of a logical 
"one" the identifying indicia is transmissive of light. In the preferred 
embodiment, a clear plastic cylinder is used, which will transmit light 
from one end to the other. For the representation of a logical "zero" a 
molder plastic prism is used which will disperse the light rather than 
transmitting it therethrough. 
The sensor module, which is mounted on the main pump unit, is essentially 
U-shaped, with one light source for each of the identifying bits mounted 
on one leg of the U, and one light sensor for each of the identifying bits 
mounted on the other leg of the U. When the disposable cassette is 
installed on the main pump unit, the identifying indicia on the cassette 
are located between the light sources and the light sensors on the optical 
module, and the outputs of the light sensors represent the identifying 
bits. By using three binary bits, up to eight different codes may be 
generated. In the preferred embodiment, redundant coding is used to ensure 
fail-safe operation, and at least three different cassettes can be 
identified. In addition, the absence of a cassette can also be detected. 
It is therefore apparent that the present invention provides a disposable 
cassette containing a plurality of optical identifying bits for use with a 
main pump unit which has apparatus for reading the identifying bits 
contained on the disposable cassette. The disposable cassette of the 
present invention is of an advanced design retaining all of the advantages 
of such devices known in the past, and includes the identifying bits in an 
integral fashion in the construction of the cassette. The main pump unit 
contains an optical sensor module which reads the identifying bits on a 
disposable cassette installed onto the main pump unit. The process is 
fully automatic, and requires no user input whatsoever. The possibility of 
user error in indicating to the main pump unit what types of cassettes are 
installed on the main pump unit is thereby avoided. 
With three identification bits, eight different cassettes are identifiable 
by the system, and even with a redundant system being used to minimize the 
possibility of errors being made, three different cassettes may be 
identified. The inclusion of the identifying indicia on the disposable 
cassette is accomplished in a fashion both minimizing the cost of 
including the indicia while maximizing the reliability of the system. A 
minimum number of parts are utilized in the construction of the cassette, 
all of which parts are of inexpensive construction, yet which afford the 
assembled cassette a high degree of accuracy. No identification system 
known in the art has even come close to combining these features. 
The cassette used with the present invention is of a design which enables 
it to compete economically with known competing systems. The transducer 
contained in the main pump unit, while of economical construction, yet 
exhibits high reliability and accuracy of operation. The system provides 
an ease of use rivaling the best of such competing systems. The system 
accomplishes all of the above objects in a manner which retains the 
advantages of reliability, durability, and safety of operation. The 
cassette identification system of the present invention provides all of 
these advantages and overcomes the limitations of the background art 
without incurring an relative disadvantage. All the advantages of the 
present invention result in a superior medication infusion system which 
has a number of advantages making the system a highly desirable 
alternative to systems presently available.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The Cassette 
The preferred embodiment of the cassette incorporating the optical 
identification system of the present invention includes all of the 
features described above in a single compact disposable cassette 
constructed of seven parts. Prior to a discussion of the construction and 
operation of the cassette, the basic construction of which is the subject 
of the above-identified patent application entitled "Disposable Cassette 
for a Medication Infusion System," it is advantageous to discuss the 
construction and configuration of the seven components included in the 
cassette. The first of these components and the one around which the other 
six components are assembled is a cassette body 100, which is shown in 
FIGS. 1 through 8. The cassette body 100 has an upper surface portion 102 
which is essentially flat with a number of protrusions and indentations 
located in the top surface thereof (FIG. 1). The upper surface portion 102 
has a thickness sufficient to accommodate the indentations mentioned 
above, some of which are fluid passageways which will be discussed below. 
Referring generally to FIGS. 1 through 8, a bubble trap 104 is located at 
the front right corner of the cassette body 100 below the upper surface 
portion 102, which bubble trap 104 is essentially square in cross-section 
(FIG. 4). The bubble trap 104 includes therein a bubble chamber 106 which 
is open at the bottom thereof (FIGS. 4, 7, and 8) and closed at the top by 
the bottom of the upper surface portion 102 of the cassette body 100. A 
siphon tube 108 is located in the bubble chamber 106, and the siphon tube 
108 has an aperture 110 therein leading from the bottom of the bubble 
chamber 106 to the top of the upper surface portion 102 of the cassette 
body 100. 
Located behind the bubble trap 104 below the upper surface portion 102 of 
the cassette body 100 on the right side thereof is a pump cylinder 112 
(FIG. 3-5, 8). The pump cylinder 112 does not extend downward as far as 
does the bubble trap 104. The pump cylinder 112 is open on the bottom 
thereof, and is arranged and configured to receive a piston which will be 
discussed below. The inner configuration of the pump cylinder 112 has a 
main diameter bore 114, with a greater diameter bore 116 near the bottom 
of the pump cylinder 112. The interior of the bottom of the pump cylinder 
112 below the greater diameter bore 116 as well as the area immediately 
between the greater diameter bore 116 and the main diameter bore 114 are 
tapered to facilitate entry of the piston. The main diameter bore 114 
terminates at the top thereof in a frustroconical smaller diameter 
aperture 118 leading to the top of the upper surface portion 102 of the 
cassette body 100 (FIG. 1). The smaller diameter aperture 118 is tapered, 
having a smaller diameter at the top thereof than at the bottom. 
Extending from on the back side of the exterior of the bubble trap 104 
facing the pump cylinder 112 are two piston retaining fingers 120 and 122 
(FIGS. 3 and 4) defining slots therein. The slots defined by the two 
piston retaining fingers 120 and 122 face each other, and are open at the 
bottoms thereof to accept in a sliding fashion a flat segment fitting 
between the two piston retaining fingers 120 and 122. The two piston 
retaining fingers 120 and 122 extend from the lower surface of the upper 
surface portion 102 of the cassette body 100 to a location between the 
bottom of the pump cylinder 112 and the bottom of the bubble trap 104. 
Also extending from the bottom side of the upper surface portion 102 of the 
cassette body 100 are two latch supporting fingers 124 and 126 (FIGS. 1-4 
and 7). The latch supporting finger 124 extends downwardly from the left 
side of the bottom of the upper surface portion 102 of the cassette body 
100, and at the bottom extends toward the right slightly to form an 
L-shape in cross section. The latch supporting finger 124 extends toward 
the front of the cassette body 100 further than does the upper surface 
portion 102 of the cassette body 100 (FIG. 1), and terminates 
approximately two-thirds of the toward the back of the upper surface 
portion 102 of the cassette body 100. 
The latch supporting finger 126 extends downwardly from the bottom of the 
upper surface portion 102 of the cassette body 100 at with the left side 
of the bubble trap 104 forming a portion of the latch supporting finger 
126. The latch supporting finger 126 extends toward the left slightly at 
the bottom thereof to form a backwards L-shape in cross section. The latch 
supporting finger 126 parallels the latch supporting finger 124, and is 
equally deep (FIG. 4). The latch supporting fingers 124 and 126 together 
will hold the slide latch, to be described below. 
The passageways located in the top of the upper surface portion 102 of the 
cassette body 100 may now be described with primary reference to FIG. 1. 
The passageways in the top of the upper surface portion 102 are all open 
on the top side of the upper surface portion 102, and are generally 
U-shaped as they are recessed into the top of the upper surface portion 
102. A first passageway 128 communicates with the aperture 110 in the 
siphon tube 108 of the bubble trap 104 at one end thereof, and extends 
toward the back of the upper surface portion 102 of the cassette body 100 
to a location to the right of the smaller diameter aperture 118 of the 
pump cylinder 112. 
A cylindrical pressure plateau 130 which is essentially circular as viewed 
from the top extends above the upper surface portion 102 of the cassette 
body 100 slightly left of the center thereof (best shown in FIGS. 1 
through 3, also shown in FIGS. 5 through 8). The top of the pressure 
plateau 130 is flat, with a channel 132 extending across the flat top of 
the pressure plateau 130. The channel 132 extends from five o'clock to 
eleven o'clock as viewed from the top in FIG. 1, with the back of the 
cassette body 100 being twelve o'clock. The channel 132 is also shown in 
cross-section in FIG. 115, and in a cutaway view in FIG. 116. The depth of 
the channel 132 in the surface of the pressure plateau 130 is not quite 
the height of the pressure plateau 130 above the upper surface portion 102 
of the cassette body 100, with the channel 132 gradually becoming deeper 
with a smooth transition at the edges of the pressure plateau 130 to 
extend into the upper surface portion 102 of the cassette body 100 (FIG. 
116). 
A second passageway 134 in the top of the upper surface portion 102 of the 
cassette body 100 begins at a location to the left of the smaller diameter 
aperture 118 of the pump cylinder 112, and extends toward the front of the 
upper surface portion 102 approximately above the latch supporting finger 
126. The second passageway 134 then travels to the left to connect in 
fluid communication with the end of the channel 132 in the pressure 
plateau 130 located at five o'clock. A third passageway 136 in the top of 
the upper surface portion 102 of the cassette body 100 begins at the end 
of the channel 132 in the pressure plateau 130 located at eleven o'clock, 
and moves toward the back and left of the cassette body 100. 
At the end of the third passageway 136 is a recessed lens portion 138, 
which recessed lens portion is used to focus and reflect light used to 
detect air bubbles passing in front of the recessed lens portion 138. The 
recessed lens portion 138 is also recessed into the top of the upper 
surface portion 102 of the cassette body 100 to allow fluid to pass 
therethrough. The recessed lens portion 138 is part of the apparatus which 
is the subject of the above-identified patent application entitled 
"Air-In-Line Detector for a Medication Infusion System." A fourth 
passageway 140 in the top of the upper surface portion 102 of the cassette 
body 100 begins at the other side of the recessed lens portion 138 from 
the third passageway 136, and extends from the left and back of the 
cassette body 100 toward the front and right of the cassette body 100 
around the pressure plateau 130 to a location at approximately seven 
o'clock on the pressure plateau 130. It should be noted that the fourth 
passageway 140 is spaced away from the pressure plateau 130 to allow for 
sealing means therebetween. 
The end of the fourth passageway 140 terminates at the location at seven 
o'clock to the pressure plateau 130 in an aperture 142 extending through 
the upper surface portion 102 of the cassette body 100 (FIG. 1). Located 
underneath the upper surface portion 102 of the cassette body 100 
concentrically around the aperture 142 is an the outlet tube mounting 
cylinder 144 (FIGS. 3 and 4) which is in fluid communication with the 
aperture 142. The outlet tube mounting cylinder 144 extends downwardly 
from the bottom of the upper surface portion 102 of the cassette body 100 
to a location above the portions of the latch supporting finger 124 and 
the latch supporting finger 126 extending parallel to the upper surface 
102 of the cassette body 100. A support fin 145 extends to the right from 
the front of the outlet tube mounting cylinder 144. 
Located on top of the upper surface 102 of the cassette body 100 is a 
slightly raised border 146 (FIG. 1) which completely surrounds the first 
passageway 128, the smaller diameter aperture 118, the second passageway 
134, the pressure plateau 130, the third passageway 136, the recessed lens 
portion 138, the recessed lens portion 138, and the fourth passageway 140. 
The slightly raised border 146, which is used for sealing purposes, 
closely surrounds the edges of all of the afore-mentioned segments of the 
cassette body 100, except as follows. The slightly raised border 146 is 
spaced away from the portions of the first passageway 128 and the second 
passageway 134 adjacent the smaller diameter aperture 118, and the smaller 
diameter aperture 118. 
The portions of the slightly raised border 146 around the smaller diameter 
aperture 118 resembles a rectangle with its wider sides located to the 
front and back and spaced away from the valve diaphragm 170, and its 
narrower sides to the right of the portion of the first passageway 128 
adjacent the smaller diameter aperture 118 and to the left of the portion 
of the second passageway 134 adjacent the smaller diameter aperture 118. 
The rectangle is broken only at the locations the first passageway 128 and 
the second passageway 134 extend towards the front of the cassette body 
100. 
The slightly raised border 146 has a segment 147 located between the 
portion of the first passageway 128 adjacent the smaller diameter aperture 
118 and the smaller diameter aperture 118 itself, with the segment 147 
extending between the two wider sides of the rectangle. The slightly 
raised border 146 also has another segment 149 located between the portion 
of the second passageway 134 adjacent the smaller diameter aperture 118 
and the smaller diameter aperture 118 itself, with the segment 149 
extending between the two wider sides of the rectangle. The slightly 
raised border 146 is also spaced away from the sides of the pressure 
plateau 130, and the portions of the second passageway 134 and the third 
passageway 136 immediately adjacent the pressure plateau 130. 
Located at the back of the upper surface 102 of the cassette body 100 are 
three cassette identifying indicia 148, 150, and 152. The first and third 
cassette identifying indicia 148 and 152 are small, solid cylinders 
extending upward from the top of the upper surface 102 of the cassette 
body 100 (FIGS. 1 and 3). The second cassette identifying indicia 150 is a 
prism cut into the bottom of the upper surface 102 of the cassette body 
100 (FIG. 4). The first, second, and third cassette identifying indicia 
148, 150, and 152 are the subject of the present invention. It will be 
noted that the cassette identifying indicia 148, 150, and 152 may be in 
any order or configuration, and are used for different ID codes to 
identify up to eight different cassettes. Additional ID bits could also be 
used if more than eight different cassettes are used. If redundant codes 
are desired, the three bits would of course accommodate the use of less 
than eight different cassettes. 
Completing the construction of the cassette body 100 are five hollow 
cylinders 154, 156, 158, 160 and 162 protruding from the top surface of 
the upper surface 102 of the cassette body 100, an aperture 161 and a slot 
164 located in the top surface of the upper surface 102 of the cassette 
body 100, and a slot 166 located in the top surface of the latch 
supporting finger 124. Four of the hollow cylinders 154, 156, 158, and 160 
are located around the pressure plateau 130, with the fifth hollow 
cylinder 162 being located to the left of the aperture 110 over the bubble 
trap 104. The aperture 161 is located in the top surface of the upper 
surface 102 of the cassette body 100 in front and to the right of center 
of the pressure plateau 130. The slot 164 is located in the top surface of 
the upper surface 102 of the cassette body 100 near the back and the right 
side thereof. The slot 166 is located in the top surface of the latch 
supporting finger 124 near the front of the cassette body 100. 
Referring now to FIGS. 9 through 12, a valve diaphragm 170 is shown which 
is arranged and configured to fit over the top of the upper surface 102 of 
the cassette body 100 (FIG. 1). The valve diaphragm 170 is made of 
flexible, resilient material, such as a medical grade silicone rubber. The 
hardness of the material used for the valve diaphragm 170 would be between 
thirty and fifty on the Shore A scale, with the preferred embodiment 
utilizing a hardness of approximately thirty-five. The valve diaphragm 170 
has three primary functions, the first of which is to seal the tops of the 
first, second, third, and fourth passageways 128, 134, 136, and 140, 
respectively. Accordingly, the main surface of the valve diaphragm 170 is 
flat, and is sized to fit over the first, second, third, and fourth 
passageways 128, 134, 136, and 140, respectively, and also over the entire 
slightly raised border 146. The flat portion of the valve diaphragm 170 
has three apertures 172, 174, and 176, and a notch 175 therein to 
accommodate the hollow cylinders 156, 160, and 162 and a pin fitting into 
the aperture 161 (FIG. 1), respectively, and to align the valve diaphragm 
170 in position over the top of the upper surface 102 of the cassette body 
100. It should be noted that the valve diaphragm 170 does not necessarily 
surround the other two hollow cylinders 154 and 158. 
The second primary function of the valve diaphragm 170 is to provide both 
an inlet valve between the first passageway 128 and the smaller diameter 
aperture 118 leading to the pump cylinder 112, and to provide an outlet 
valve between the smaller diameter aperture 118 leading to the pump 
cylinder 112 and the second passageway 134. To fulfill this function the 
valve diaphragm 170 has an essentially rectangular domed portion 178 
(shown in plan view in FIGS. 9 and 10, and in cross-sectional views in 
FIGS. 11 and 12) forming a cavity 180 in the bottom of the valve diaphragm 
170. When the valve diaphragm 170 is installed in position on the top of 
the upper surface 102 of the cassette body 100, the cavity 180 will be 
located just inside the rectangular portion of the slightly raised border 
146 around the smaller diameter aperture 118 leading to the pump cylinder 
112 (FIG. 1). 
The cavity 180 will therefore be in fluid communication with the first 
passageway 128, the smaller diameter aperture 118 leading to the pump 
cylinder 112, and the second passageway 134. Prior to installation of the 
cassette onto the main pump unit, the cavity 180 allows the open fluid 
path to facilitate priming of the cassette, where all air is removed from 
the system. Once primed, the cassette may be inserted onto the main pump 
unit and the cavity 180 will contact valve actuators to prevent free flow 
through the cassette. By using an inlet valve actuator to force the domed 
portion 178 over the segment 147 of the slightly raised border 146 (FIG. 
1), the flow of fluids between the first passageway 128 and the smaller 
diameter aperture 118 will be blocked, but the flow of fluids between the 
smaller diameter aperture 118 and the second passageway 134 will be 
unaffected. Likewise, by using an outlet valve actuator to force the domed 
portion 178 over the segment 149 of the slightly raised border 146 (FIG. 
1), the flow of fluids between the smaller diameter aperture 118 and the 
second passageway 134 will be blocked, but the flow of fluids between the 
first passageway 128 and the smaller diameter aperture 118 will be 
unaffected. Extending around and spaced away from the front and sides of 
the domed portion 178 on the top surface of the valve diaphragm 170 is a 
U-shaped raised rib 181, the legs of which extend to the back of the valve 
diaphragm 170 (FIG. 9). 
The third primary function of the valve diaphragm 170 is to provide a 
pressure diaphragm which may be used to monitor outlet fluid pressure. 
Accordingly, the valve diaphragm 170 has a pressure diaphragm 182 which is 
supported atop an upper cylindrical segment 184, which in turn is located 
atop a lower cylindrical segment 186 extending above the surface of the 
valve diaphragm 170. The upper cylindrical segment 184 and the lower 
cylindrical segment 186 have identical inner diameters, with a lower 
cylindrical segment 186 having a greater outer diameter than the upper 
cylindrical segment 184. A portion of the top of the lower cylindrical 
segment 186 extends outwardly around the bottom of the upper cylindrical 
segment 184, creating a lip 188. In the preferred embodiment, the pressure 
diaphragm 182 may be domed slightly, as seen in FIG. 11. 
Turning now to FIGS. 13 through 23, a retainer cap 190 is shown which fits 
over the valve diaphragm 170 after it is mounted on the top of the upper 
surface 102 of the cassette body 100. The retainer cap 190 thus functions 
to cove the top of the cassette body 100, retaining the valve diaphragm 
170 between the retainer cap 190 and the cassette body 100 in a sealing 
fashion. The retainer cap 190 thus has the same general outline when 
viewed from the top (FIG. 13) as the cassette body 100 (FIG. 1). Located 
in the bottom of the retainer cap 190 (FIG. 14) are six pins 192, 194, 
196, 198, 200, and 199, which are to be received by the hollow cylinders 
154, 156, 158, 160, and 162 and the aperture 161, respectively, in the 
cassette body 100 to align the retainer cap 190 on the cassette body 100. 
Also located in the bottom of the retainer cap 190 is a tab 202 to be 
received by the slot 164, and a tab 204 to be received by the slot 166. 
The retainer cap 190 has three apertures 206, 208, and 210 therethrough 
located to coincide with the locations of the first cassette identifying 
indicia 148, the second cassette identifying indicia 150, and the third 
cassette identifying indicia 152, respectively. The size of the three 
apertures 206, 208, and 210 is sufficient to receive the small, solid 
cylinders which the first cassette identifying indicia 148 and the third 
cassette identifying indicia 152 comprise. 
Located in the retainer cap 190 is a rectangular aperture 212 (FIGS. 13, 
14, 19 and 20) for placement over the domed portion 178 on the valve 
diaphragm 170. The rectangular aperture 212 in the retainer cap 190 is 
slightly larger than the domed portion 178 on the valve diaphragm 170 to 
prevent any closure of the cavity 180 formed by the domed portion 178 when 
the retainer cap 190 is placed over the valve diaphragm 170 and the 
cassette body 100. The domed portion 178 of the valve diaphragm 170 
therefore will protrude through the rectangular aperture 212 in the 
retainer cap 190. In the bottom of the retainer ca 190 around the 
rectangular aperture 212 is a U-shaped groove 214 (FIG. 14) designed to 
accommodate the U-shaped raised rib 181 on the valve diaphragm 170. 
Also located in the retainer cap 190 is a circular aperture 216 (FIGS. 13 
and 14), which has a diameter slightly larger than the outer diameter of 
the upper cylindrical segment 184 on the valve diaphragm 170, to allow the 
upper cylindrical segment 184 and the pressure diaphragm 182 to protrude 
from the circular aperture 216 in the retainer cap 190. The diameter of 
the circular aperture 216 is smaller than the outer diameter of the lower 
cylindrical segment 186 on 170, and on the bottom of the retainer cap 190 
is disposed concentrically around the circular aperture 216 a cylindrical 
recess 218 to receive the lower cylindrical segment 186 on the valve 
diaphragm 170. Disposed in the cylindrical recess 218 on the bottom side 
of the retainer cap 190 is a circular raised bead 220 (FIGS. 14, 19, and 
21) to help in the sealing of the cassette as it is assembled. 
The retainer cap 190 has a front edge 222 (FIG. 16), a back edge 224 (FIG. 
15), and left (FIG. 18) and right (FIG. 17) side edges 226 and 228, 
respectively. The edges 222, 224, 226, and 228 will contact the top of the 
upper surface 102 of the cassette body 100 when the retainer cap 190 is 
assembled onto the cassette body 100 with the valve diaphragm 170 disposed 
therebetween. The retainer cap 190 is attached to the cassette body 100 in 
the preferred embodiment by ultrasonic welding, but adhesives or other 
bonding techniques known in the art may also be used. 
Referring next to FIGS. 22 through 26, a bubble chamber cap 230 is 
illustrated which is for placement onto the open bottom of the bubble trap 
104 (FIG. 4). The bubble chamber cap 230 is on the bottom (FIG. 23) the 
same size as the outer edges of the bottom of the bubble trap 104 (FIG. 
4), and has a tab 232 (FIGS. 22 through 24) on the bottom which will 
project toward the back of the cassette beyond the back edge of the bubble 
trap 104. The bubble chamber cap 230 has a rectangular wall portion 234 
(FIG. 24) extending upward from the bottom of the bubble chamber cap 230 
and defining therein a square space, which rectangular wall portion 234 is 
sized to fit inside the bubble chamber 106 (FIG. 4). 
Located at the front and left sides of the rectangular wall portion 234 and 
extending upwards from the bottom of the bubble chamber cap 230 is an 
inlet cylinder 236 (FIGS. 22, 24, and 26) having an inlet aperture 238 
extending therethrough. The inlet aperture 238 extends through the bottom 
of the bubble chamber cap 230 (FIGS. 23 and 25), and is designed to 
receive from the bottom of the bubble chamber cap 230 a length of tubing 
therein. The bubble chamber cap 230 is attached to the bottom of the 
bubble trap 104 in the cassette body 100 in the preferred embodiment by 
ultrasonic welding, but adhesives or other bonding techniques known in the 
art may also be used. 
When the bubble chamber cap 230 is mounted to the bubble trap 104, the 
inlet cylinder 236 extends up to at least half of the height of the bubble 
chamber 106 (FIG. 7), and the siphon tube 108 (FIG. 7) draws fluid from 
the bottom of the siphon tube 108 in the space within the rectangular wall 
portion 234 of the bubble chamber cap 230 (FIG. 26). It will be 
appreciated by those skilled in the art that fluid will enter the bubble 
chamber 106 through the inlet aperture 238 in the inlet cylinder 236 near 
the top of the siphon tube 108, maintaining all air bubbles above the 
level near the bottom of the bubble chamber 106 at which fluid is drawn 
from the bubble chamber 106 by the siphon tube 108. 
Moving now to FIGS. 27 through 32, a slide latch 240 is disclosed which 
served two main functions in the cassette. The slide latch 240 first 
serves to latch the cassette into place in a main pump unit. It also 
serves to block the flow of fluid through the cassette when it is not 
installed with the closing of the slide latch 240 to lock the cassette 
into place on the main pump unit also simultaneously allowing the flow of 
fluid through the cassette. The slide latch 240 slides from the front of 
the cassette body 100 (FIG. 2) between the latch supporting finger 124 and 
the latch supporting finger 126. 
The slide latch 240 has an essentially rectangular, flat front portion 242 
(FIG. 31) which is of a height equal to the height of the cassette body 
100 with the retainer cap 190 and the bubble chamber cap 230 installed, 
and a width equal to the distance between the left side of the bubble trap 
104 and the left side of the cassette body 100. Two small notches 244 and 
246 are removed from the back side of the front portion 242 at the top 
thereof (FIGS. 27, 28, and 30), the small notch 244 being removed at a 
location near the left corner, and the small notch 246 being removed at 
the right corner. 
Extending from the back side of the front portion 242 about three-quarters 
of the way down towards the back is a horizontal bottom portion 248 (FIG. 
29), which has its edges directly below the closest edges of the small 
notch 244 and the small notch 246. Extending from the inner edge of the 
small notch 244 at the top of the slide latch 240 down to the bottom 
portion 248 is an inverted angled or L-shaped portion 250. Similarly, 
extending from the inner edge of the small notch 246 at the top of the 
slide latch 240 down to the bottom portion 248 is an inverted, backwards 
angled or L-shaped portion 252 (FIGS. 27 and 28). 
Spaced outwardly from the left side of the bottom portion 248 and the left 
side of the leg of the inverted L-shaped portion 250 is a left slide side 
254. Likewise, spaced outwardly from the right side of the bottom portion 
248 and the right side of the leg of the inverted, backwards L-shaped 
portion 252 is a right slide side 256 (FIGS. 28 and 30). The left and 
right slide sides 254 and 256 are located slightly above the bottom of the 
bottom portion 248 (FIG. 30). The left and right slide sides 254 and 256 
are of a height to be engaged in the latch supporting finger 124 and the 
latch supporting finger 126 (FIG. 2), respectively. 
Located in the bottom portion 248 is an elongated, tearshaped aperture 258 
(FIG. 29) with the wider portion thereof toward the front of the slide 
latch 240 and the extended narrower portion thereof toward the back of the 
slide latch 240. When the slide latch 240 is inserted into the latch 
supporting finger 124 and the latch supporting finger 126 on the cassette 
body 100, and the slide latch 240 is pushed fully toward the back of the 
cassette body 100, the wider portion of the elongated, tearshaped aperture 
258 will be aligned with the aperture 142 in the outlet tube mounting 
cylinder 144 (FIG. 4) to allow a segment of tubing (not shown) leading 
from the aperture 142 to be open. When the slide latch 240 is pulled out 
from the front of the cassette body 100 the segment of tubing (not shown) 
will be pinched off by the narrower portion of the elongated, tear-shaped 
aperture 258. 
It is critical that the design and location of the elongated, tear-shaped 
aperture 258 in the slide latch 240 ensure that the slide latch 240 
engages the main pump unit before the tubing is opened up, and fluid is 
allowed to flow through the cassette. Likewise, the tubing must be pinched 
off and the fluid path through the cassette must be blocked before the 
slide latch 240 releases the cassette from the main pump unit. In 
addition, the choice of material for the slide latch 240 is important, 
with a lubricated material allowing the pinching operation to occur 
without damaging the tubing (not shown). Examples of such materials are 
silicone or Teflon impregnated acetals such as Delren. 
Located at the back of the slide latch 240 on the inside of the right slide 
side 256 at the bottom thereof is a tab 257 (FIGS. 27, 30, and 32) which 
is used to engage the main pump unit with the cassette when the slide is 
closed. Located on the top side of the bottom portion 248 to the right of 
the elongated, tear-shaped aperture 258 is a small wedge-shaped retaining 
tab 259 (FIG. 27, 30, and 32). The retaining tab 259 cooperates with the 
bottom of the slightly raised border 146 of the cassette body 100 (FIG. 
2), to resist the slide latch 240 from being freely removed once installed 
into the cassette body 100. When the slide latch 240 is pulled back out 
from the front of the cassette body 100 so that the wider portion of the 
elongated, tear-shaped aperture 258 is aligned with the aperture 142 in 
the outlet tube mounting cylinder 144, the retaining tab 259 will engage 
the slightly raised border 146 (FIGS. 2 and 4), resisting the slide latch 
240 from being drawn further out. 
Referring now to FIGS. 33 through 36, a one-piece piston cap and boot seal 
260 is illustrated, which is the subject of the above-identified patent 
application entitled "Piston Cap and Boot Seal for a Medication Infusion 
System," and which is for use on and in the pump cylinder 112 (FIGS. 3 and 
8). The piston cap and boot seal 260 is of one-piece construction, and is 
made of flexible, resilient material, such as silastic (silicone rubber) 
or medical grade natural rubber. Natural rubber may be used to minimize 
friction, since some sticking of a silicone rubber piston cap and boot 
seal 260 in the pump cylinder 112 (FIG. 8) may occur. Teflon impregnated 
silastic or other proprietary formulas widely available will overcome this 
problem. In addition, the piston cap and boot seal 260 may be lubricated 
with silicone oil prior to installation in the pump cylinder 112. The 
advantage of using silastic is that it ma be radiation sterilized, whereas 
natural rubber must be sterilized using gas such as ethylene oxide. In 
addition, silastic has better wear characteristics than natural rubber, 
making it the preferred choice. 
The piston cap and boot seal 260 includes a piston cap portion indicated 
generally at 262, and a boot seal portion comprising a retaining skirt 264 
and a thin rolling seal 266. The piston cap portion 262 includes a hollow 
cylindrical segment 268 having an enlarged, rounded piston cap head 270 
located at the top thereof. The piston cap head 270 has a roughly 
elliptical cross-section, with an outer diameter on the sides sufficient 
to provide a dynamic seal in the main diameter bore 114 of the pump 
cylinder 112 (FIG. 8). The roughly elliptical configuration of the piston 
cap head 270 closely fits the top of the main diameter bore 114 of the 
pump cylinder 112. Extending from the top of the piston cap head 270 at 
the center thereof is a frustroconical segment 272, with the larger 
diameter of the frustroconical segment 272 being at the bottom thereof 
attached to the piston cap head 270. The frustroconical segment 272 is of 
a size to closely fit in the smaller diameter aperture 118 of the pump 
cylinder 112 (FIG. 8). 
The hollow cylindrical segment 268 and the piston ca head 270 together 
define a closed end of the piston ca and boot seal 260 to receive a 
piston, which will be described below. The hollow cylindrical segment 268 
has located therein a smaller diameter portion 274, which smaller diameter 
portion 274 is spaced away from the bottom of the piston cap head 270 to 
provide retaining means to retain a piston in the hollow cylindrical 
segment 268 between the piston cap head 270 and the smaller diameter 
portion 274. 
The retaining skirt 264 is essentially cylindrical, and is designed to fit 
snugly around the outer diameter of the pump cylinder 112 (FIG. 8). Prior 
to installation and with the piston cap and boot seal 260 in a relaxed 
configuration as shown in FIGS. 33 through 36, the retaining skirt 264 is 
located roughly around the hollow cylindrical segment 268. The retaining 
skirt 264 has an internal diameter sufficiently small to retain the 
retaining skirt 264 in position around the pump cylinder 112 (FIG. 8) 
without moving when the piston cap portion 262 moves. 
Located around the inner diameter of the retaining skirt 264 is a tortuous 
path 276 leading from one end of the retaining skirt 264 to the other. The 
tortuous path 276 is required for sterilization of the assembled cassette, 
to allow the sterilizing gas to sterilize the area between the inside of 
the pump cylinder 112 and the piston cap and boot seal 260, which would be 
closed and may remain unsterilized if the tortuous path 276 did not exist. 
In addition, since the sterilizing gas is hot and cooling occurs rapidly 
after the sterilizing operation, the tortuous path 276 allows pressure 
equalization to occur rapidly where it otherwise would not. In the 
preferred embodiment, the tortuous path 276 is a series of threads in the 
inner diameter of the retaining skirt 264. 
Completing the construction of the piston cap and boot seal 260 is the 
rolling seal 266, which is a segment defined by rotating around the 
centerline of the piston cap and boot seal 260 a U having a first leg at 
the radius of the hollow cylindrical segment 268 and a second leg at the 
radius of the retaining skirt 264, with the top of the first leg of the U 
being attached to the bottom of the hollow cylindrical segment 268 and the 
top of the second leg of the U being attached to the bottom of the 
retaining skirt 264. When the piston cap and boot seal 260 is installed 
and the piston cap portion 262 moves in and out in the main diameter bore 
114 in the pump cylinder 112 (FIG. 8), the legs of the U will vary in 
length, with one leg becoming shorter as the other leg becomes longer. In 
this manner, the rolling seal 266 provides exactly what its name implies- 
a seal between the piston cap portion 262 and the retaining skirt 264 
which rolls as the piston cap portion 262 moves. 
Referring now to FIGS. 37 through 42, a piston assembly 280 is shown which 
drives the piston cap portion 262 of the piston cap and boot seal 260 
(FIG. 36) in the pump cylinder 112 (FIG. 8). The piston assembly 280 has a 
rectangular base 282 which is positioned horizontally and located directly 
behind the bubble chamber cap 230 (FIG. 24) when the piston cap portion 
262 is fully inserted into the pump cylinder 112. The rectangular base 282 
has a notch 284 (FIGS. 41 and 42) in the front edge thereof, which notch 
is slightly larger than the tab 232 in the bubble chamber cap 230 (FIG. 
23). 
Extending upward from the front edge of the rectangular base 282 on the 
left side of the notch 284 is an arm 286, and extending upward from the 
front edge of the rectangular base 282 on the right side of the notch 284 
is an arm 288. At the top of the arms 286 and 288 is a vertically 
extending rectangular portion 290 (FIG. 38). The rectangular portion 290 
as well as the upper portions of the arms 286 and 288 are for insertion 
into and between the piston retaining finger 120 and the piston retaining 
finger 122 in the cassette body 100 (FIG. 4). 
The top of the rectangular portion 290 will contact the bottom of the upper 
surface 102 of the cassette body 100 (FIG. 8) to limit the upward movement 
of the piston assembly 280, the rectangular base 282 being approximately 
even with the bubble chamber cap 230 (FIG. 24) installed in the bottom of 
the bubble trap 104 of the cassette body 100 when the piston assembly 280 
is in its fully upward position. The bottom of the rectangular portion 290 
(FIG. 42) will contact the tab 232 on the bubble chamber cap 230 (FIG. 24) 
when the piston assembly 280, the piston head 296, and the piston cap 
portion 262 (FIG. 36) are fully retracted from the pump cylinder 112 (FIG. 
8). 
Extending upwards from the top of the rectangular base 282 near the back 
edge of the rectangular base 282 and located centrally with respect to the 
side edges of the rectangular base 282 is a cylindrical piston rod 292. At 
the top of the piston rod 292 is a reduced diameter cylindrical portion 
294, and mounted on top of the reduced diameter cylindrical portion 294 is 
a cylindrical piston head 296. The diameter of the piston head 296 is 
larger than the diameter of the reduced diameter cylindrical portion 294, 
and the top of the piston head 296 has rounded edges in the preferred 
embodiment. The piston head 296 is designed to be received in the portion 
of the hollow cylindrical segment 268 between the smaller diameter portion 
274 and the piston cap head 270 in the piston cap portion 262 (FIG. 36). 
The reduced diameter cylindrical portion 294 is likewise designed to be 
received in the smaller diameter portion 274 of the piston cap portion 
262. 
The top of the piston head 296 is slightly above the top of the rectangular 
portion 290, and when the piston assembly 280 is in its fully upward 
position, the piston head 296 will have brought the piston cap head 270 
and the frustroconical segment 272 thereon (FIG. 36) to the top of the 
pump cylinder 112 and into the smaller diameter aperture 118 (FIG. 8), 
respectively, to completely eliminate volume both within the pump cylinder 
112 and within the smaller diameter aperture 118. 
Completing the construction of the piston assembly 280 are two raised beads 
298 and 300, with the raised bead 298 being on the top surface of the 
rectangular base 282 on the left side of the piston rod 292, and the 
raised bead 300 being on the top surface of the rectangular base 282 on 
the right side of the piston rod 292. Both of the raised beads 298 and 300 
extend from the sides of the piston rod 292 laterally to the sides of the 
rectangular base 282. The raised beads 298 and 300 will be used to center 
the piston assembly 280 with the jaws of the main pump unit used to drive 
the piston assembly 280, as well as to facilitate retaining the piston 
assembly 280 in the jaws. 
The assembly and configuration of the cassette may now be discussed, with 
reference to an assembled cassette 302 in FIGS. 43 through 48, as well as 
to other figures specifically mentioned in the discussion The valve 
diaphragm 170 is placed over the top of the upper surface 102 of the 
cassette body 100, with the apertures 172, 174, and 176 placed over the 
hollow cylinders 156, 160, and 162, respectively. The retainer cap 190 is 
then located over the valve diaphragm 170 and the cassette body 100, and 
is secured in place by ultrasonic welding. Note again that while adhesive 
sealing may be used, it is more difficult to ensure the consistent 
hermetic seal required in the construction of the cassette 302. 
The step of firmly mounting the retainer cap 190 onto the cassette body 100 
exerts a bias on the valve diaphragm 170 (FIG. 9) causing it to be 
compressed in certain areas, particularly over the slightly raised border 
146 on the top surface of the upper surface 102 of the cassette body 100 
(FIG. 1). This results in excellent sealing characteristics, and encloses 
the various passageways located in the upper surface 102 of the cassette 
body 100. The first passageway 128 is enclosed by the valve diaphragm 170, 
communicating at one end thereof with the aperture 110 and at the other 
end thereof with the area between the cavity 180 and the upper surface 102 
of the cassette body 100. The second passageway 134 also communicates with 
the area between the cavity 180 and the upper surface 102 of the cassette 
body 100 at one end thereof, with the other end of the second passageway 
134 communicating with one end of the passageway 132 in the pressure 
plateau 130. 
The pressure diaphragm 182 is located above the surface of the pressure 
plateau 130 (FIGS. 115 and 116), and a space exists between the edges at 
the side of the pressure plateau 130 and the inner diameters of the upper 
cylindrical segment 184 and the lower cylindrical segment 186. This allows 
the pressure diaphragm 182 to be quite flexible, a design feature 
essential to proper operation of the pressure monitoring apparatus. It may 
therefore be appreciated that the flow area between the second passageway 
134 and the third passageway 136 is not just the area of the passageway 
132, but also the area between the pressure diaphragm 182 and the pressure 
plateau 130, as well as the area around the sides of the pressure plateau 
130 adjacent the upper cylindrical segment 184 and the lower cylindrical 
segment 186. 
The third passageway 136 (FIG. 1) is also enclosed by the valve diaphragm 
170 (FIG. 9), and communicates at one end with the other end of the 
passageway 132, and at the other end with the recessed lens portion 138. 
The fourth passageway 140 is enclosed by the valve diaphragm 170, and 
communicates at one end with the recessed lens portion 138 and at the 
other end with the aperture 142. 
Next, the bubble chamber cap 230 is placed on the bottom of the bubble 
chamber 106, as shown in FIG. 44, and is secured by ultrasonically sealing 
the bubble chamber cap 230 to the cassette body 100. The piston cap 
portion 262 of the piston cap and boot seal 260 (FIG. 36) is inserted into 
the main diameter bore 11 of the pump cylinder 112 (FIG. 8), and pushed 
toward the top of the main diameter bore 114. Simultaneously, the 
retaining skirt 264 is placed over the outside of the pump cylinder 112 
and is moved up the outer surface of the pump cylinder 112 to the position 
shown in FIGS. 46 and 48, which is nearly to the top of the outer surface 
of the pump cylinder 112. Next, the piston head 296 of the piston assembly 
280 (FIGS. 37 and 40) is inserted into the hollow cylindrical segment 268 
of the piston cap and boot seal 260, and is forced past the smaller 
diameter portion 274 until it snaps home, resting against the bottom of 
the piston cap head 270. 
The slide latch 240 is then inserted into engagement with the cassette body 
100, which is accomplished by sliding the left slide side 254 into the 
latch supporting finger 124 on the right side thereof and by sliding the 
right slide side 256 into the latch supporting finger 126 on the left side 
thereof. The slide latch 240 is then pushed fully forward to align the 
wider portion of the elongated, tear-shaped aperture 258 with the outlet 
tube mounting cylinder 144. An inlet tube 304 is adhesively secured in the 
inner diameter of the inlet aperture 238 in the bubble chamber cap 230, in 
fluid communication with the bubble chamber 106. An outlet tube 306 
extends through the wider portion of the elongated, tear-shaped aperture 
258 and is adhesively secured in the inner diameter of the outlet tube 
mounting cylinder 144 in the cassette body 100, in fluid communication 
with the fourth passageway 140 through the aperture 142. 
The inlet tube 304 and the outlet tube 306 are shown in the figures only in 
part; on their respective ends not connected to the assembled cassette 302 
they may have connector fittings such as standard luer connectors (not 
shown), which are well known in the art. The use of adhesives to attach 
the inlet tube 304 and the outlet tube 306 to the assembled cassette 302 
also utilizes technology well known in the art. For example, adhesives 
such as cyclohexanone, methylene dichloride, or tetrahydrofuron (THF) may 
be utilized. 
The Main Pump Unit 
The preferred embodiment of the main pump unit used with the present 
invention includes a number of components used to hold, latch, and drive 
the cassette described above. Referring first to FIGS. 49 through 53, a 
latch head 310 is illustrated which is used to grasp the raised bead 298 
and the raised bead 300 of the piston assembly 280 (FIG. 37). Extending 
from the front of the latch head 310 at the top thereof on the left side 
is a left jaw 312, and extending from the front of the latch head 310 at 
the top thereof on the right side is a right jaw 314. The left and right 
jaws 312 and 314 have curved indentations on the bottom sides thereof to 
receive the raised bead 298 and the raised bead 300 (FIG. 37), 
respectively. A space between the left jaw 312 and the right jaw 314 
allows them to fit around the piston rod 292 of the piston assembly 280. 
A cylindrical aperture 316 is located in the top of the latch head 310, 
which cylindrical aperture 316 is designed to receive a shaft on which the 
latch head 310 is mounted. A threaded aperture 318 in the back side of the 
latch head 310 communicates with the cylindrical aperture 316, and will 
have locking means installed therein to lock a shaft in the cylindrical 
aperture 316. An aperture 320 extends through the latch head 310 from the 
left side to the right side thereof near the back and bottom of the latch 
head 310. 
A notch 322 is located in the latch head 310 at the bottom and front 
thereof and in the center thereof, leaving a side portion 324 on the left 
side and a side portion 326 on the right side. An aperture 328 is located 
through the side portion 324, and an aperture 330 is located through the 
side portion 326, which apertures 328 and 330 are aligned. In addition, 
the portion of the latch head 310 including the left jaw 312 has a raised 
edge 327 facing upward and backward, and a raised edge 329 facing down and 
forward. The portion of the latch head 310 including the right jaw 314 has 
a raised edge 331 facing downward and forward. The raised edges 327, 329, 
and 331 will be used to limit the movement of the latch jaw, which will be 
discussed below. 
A spring seat 332 is shown in FIGS. 54 and 55, which is designed to fit in 
the notch 322 in the latch head 310 (FIGS. 51 and 53). The spring seat 332 
has an aperture 334 extending therethrough from the left side to the right 
side, which aperture 334 is slightly larger than the apertures 328 and 330 
in the latch head 310. The spring seat 332 also has a cylindrical segment 
336 extending from the front side thereof. 
A latch jaw 340 is illustrated in FIGS. 56 through 58, which latch jaw 340 
is used to grasp the bottom of the rectangular base 282 of the piston 
assembly 280 (FIG. 37) and maintain the left and right jaws 312 and 314 of 
the latch head 310 (FIG. 51) in contact with the raised bead 298 and the 
raised bead 300, respectively. The latch jaw 340 has a front jaw portion 
342 approximately as wide as the left and right jaws 312 and 314 of the 
latch head 310, which jaw portion 342 is the portion of the latch jaw 340 
which contacts the bottom of the rectangular base 282 of the piston 
assembly 280. Extending back from the left side of the jaw portion 342 is 
a left arm 344, and extending back from the right side of the jaw portion 
342 is a right arm 346. 
The left arm 344 has an aperture 348 (not shown) therethrough from the left 
side to the right side at the end of the left arm 344 away from the jaw 
portion 342. Likewise, the right arm 346 has an aperture 350 therethrough 
from the left side to the right side at the end of the right arm 346 away 
from the jaw portion 342. The apertures 348 and 350 are slightly smaller 
in diameter than the aperture 320 in the latch head 310 (FIGS. 49 and 50). 
Extending upward from and at an approximately sixty degree angle with 
respect to the right arm 346 from the end of the right arm 346 away from 
the jaw portion 342 is a driving arm 352. At the end of the driving arm 
352 which is not attached to the right arm 346 is a link pin 354 extending 
to the right. Completing the construction of the latch jaw 340 is a 
cylindrical recess 356 located in the back side of the jaw portion 342, 
which cylindrical recess 356 has an inner diameter larger than the outer 
diameter of the cylindrical segment 336 of the spring seat 332 (FIG. 55). 
Referring now to FIGS. 59 through 61, the construction of a jaws assembly 
360 from the latch head 310, the spring seat 332, and the latch jaw 340 is 
illustrated. The spring seat 332 fits within the notch 322 and between the 
left jaw 312 and the right jaw 314 of the latch head 310. A pin 362 is 
inserted through the aperture 328 in the side portion 324, the aperture 
334 in the spring seat 332, and the aperture 330 in the side portion 326. 
The pin 362 is sized to fit snugly in the apertures 328 and 330, thereby 
retaining the pin 362 in place and allowing the spring seat 332 to rotate 
about the pin 362. 
The latch jaw 340 is mounted onto the latch head 310 with the left jaw 312 
and the right jaw 314 of the latch head 310 facing the jaw portion 342 of 
the latch jaw 340 using a pin 364. The pin 364 is inserted through the 
aperture 348 (not shown) in the left arm 344, the aperture 320 in the 
latch head 310, and the aperture 350 in the right arm 346. The pin 364 is 
sized to fit snugly in the apertures 348 and 350, thereby retaining the 
pin 364 in place and allowing the latch jaw 340 to rotate about the pin 
364. 
A spring 366 has one end thereof mounted over the cylindrical segment 336 
on the spring seat 332, and the other end thereof mounted in the 
cylindrical recess 356 in the latch jaw 340. The spring 366 acts to bias 
the latch jaw 340 in either the open position shown in FIG. 59 with the 
jaw portion 342 of 340 away from the left jaw 312 and the left jaw 312 of 
the latch head 310, or in the closed position shown in FIG. 61, with the 
jaw portion 342 of the latch jaw 340 urged closely adjacent the left jaw 
312 and the right jaw 314 of the latch head 310. The movement of the latch 
jaw 340 in both directions with respect to the latch head 310 is limited, 
to the position shown in FIG. 59 by the driving arm 352 contacting the 
raised edge 327, and to the position shown in FIG. 61 by the right arm 346 
contacting the raised edge 329 and by the left arm 344 contacting the 
raised edge 331. When the assembled cassette 302 is installed, movement of 
the latch jaw 340 to the position of FIG. 61 will also be limited by the 
presence of the piston assembly 280, with the rectangular base 282 being 
grasped by the jaws assembly 360. It will be noted that by moving the pin 
354 either toward the front or toward the back, the latch jaw 340 may 
either be opened or closed, respectively. 
Referring next to FIGS. 62 through 65, a main pump unit chassis 370 is 
illustrated which is designed to mount three independent pump units 
including three drive mechanisms into which three disposable assembled 
cassettes 302 may be installed. The assembled cassettes 302 are mounted on 
the bottom side of the pump chassis 370 shown in FIG. 62, with the motors 
and drive train being mounted on top of the pump chassis 370 (FIG. 64) and 
being installed in a housing (not shown) mounted on top of the pump 
chassis 370. 
Located on the pump chassis 370 are three pairs of angled segments 372 and 
374, 376 and 378, and 380 and 382. Each pair of angled segments 372 and 
374, 376 and 378, and 380 and 382 defines two facing channels 
therebetween. In the preferred embodiment, the angled segments 372 and 
374, 376 and 378, and 380 and 382 are angled slightly further from the 
bottom of the pump chassis 370 near the front, to thereby have a camming 
effect as the assembled cassette 302 is installed and the slide latch 340 
is closed. Specifically, the angled segment 372 defines a channel facing 
the angled segment 374, and the angled segment 374 defines a channel 
facing the angled segment 372. The angled segment 376 defines a channel 
facing the angled segment 378, and the angled segment 378 defines a 
channel facing the angled segment 376. Finally, the angled segment 380 
defines a channel facing the angled segment 382, and the angled segment 
382 defines a channel facing the angled segment 380. 
Each of the pairs of angled segments 372 and 374, 376 and 378, and 380 and 
382 provides means on the bottom of pump chassis 370 for one assembled 
cassette 302 to be securely latched to. The inverted L-shaped portion 250 
and the inverted, backwards L-shaped portion 252 in the slide latch 240 
(FIGS. 29 and 30) of the assembled cassette 302 are designed to facilitate 
attachment to one of the pairs of angled segments 372 and 374, 376 and 
378, and 380 and 382. With the slide latch 240 pulled back away from the 
front of the assembled cassette 302, an area between the front portion 242 
of the slide latch 240 and the top front of the cassette body 100 and the 
retainer cap 190 is open, allowing the top of the assembled cassette 302 
to be placed over one of the pairs of angled segments 372 and 374, 376 and 
378, and 380 and 382. 
By way of example, assume that the assembled cassette 302 is to be mounted 
in the first position (the position on the left end of the pump chassis 
370) on the first pair of angled segments 372 and 374. The top surface of 
the assembled cassette 302, which is the retainer cap 190 (FIG. 43), will 
mount against the bottom of the pump chassis 370 (FIG. 62). In order to 
place the assembled cassette 302 in condition to be installed, the slide 
latch 240 is pulled back fully from the front of the assembled cassette 
302, leaving an area between the front portion 242 of the slide latch 240 
and the front top portion of the assembled cassette 302 (made up of the 
cassette body 100 and the retainer cap 190) facing the front portion 242 
of the slide latch 240 
The top of the assembled cassette 302 is then placed against the bottom of 
the pump chassis 370 with the first pair of angled segments 372 and 374 
fitting in the are between the front portion 242 of the slide latch 240 
and the front top portion of the assembled cassette 302. The slide latch 
240 is then pushed forward into the cassette body 100, sliding the 
inverted L-shaped portion 250 of the slide latch 240 into engagement with 
the angled segment 372, and sliding the inverted, backwards L-shaped 
portion 252 of the slide latch 240 into engagement with the angled segment 
374. The assembled cassette 302 will thus be held in position on the 
bottom of the pump chassis 370 until the slide latch 240 is again pulled 
back, releasing the assembled cassette 302. 
Projecting from the bottom of the pump chassis 370 are a number of segments 
used to position and align the assembled cassettes 302 in the first (the 
position on the left end of the pump chassis 370), second (intermediate), 
and third (the position on the right end of the pump chassis 370) 
positions on the pump chassis 370. Three left lateral support walls 384, 
386, and 388 protrude from the bottom of the pump chassis 370 at locations 
to support the upper left side portion of the assembled cassettes 302 near 
the back thereof in proper positions in the first, second, and third 
positions, respectively. Likewise, three right lateral support walls 390, 
392, and 394 protrude from the bottom of the pump chassis 370 at locations 
to support the rear-most extending upper portion of the assembled 
cassettes 302 on the right side thereof in proper positions in the first, 
second, and third positions, respectively. 
Additional support and positioning for the installation of the assembled 
cassettes 302 into the first, second, and third positions are provided for 
the upper right back corner of the assembled cassettes 302 by three right 
corner support walls 396, 398, and 400, respectively. The three right 
corner support walls 396, 398, and 400 are L-shaped when viewed from the 
bottom (FIG. 62), and support and position the back of the assembled 
cassettes 302 behind the pump cylinders 112 (FIG. 4) and a portion of the 
right side of the assembled cassettes 302 adjacent the pump cylinders 112. 
Note that the three right lateral support walls 390, 392, and 394 and the 
three right corner support walls 396, 398, and 400 together provide 
continuous support and positioning for the assembled cassettes 302 in the 
first, second, and third positions, respectively. 
Located in the raised material forming the left lateral support wall 384 
near the back thereof is a threaded aperture 402. A single segment of 
raised material forms the right lateral support wall 390, the right corner 
support wall 396, and the left lateral support wall 386; located in that 
segment of raised material near the back thereof is a threaded aperture 
404 on the left side near the right lateral support wall 390, and a 
threaded aperture 406 on the right side near the left lateral support wall 
386. Likewise, a single segment of raised material forms the right lateral 
support wall 392, the right corner support wall 398, and the left lateral 
support wall 388; located in that segment of raised material near the back 
thereof is a threaded aperture 408 on the left side near the right lateral 
support wall 392, and a threaded aperture 410 on the right side near the 
left lateral support wall 388. Finally, a single segment of raised 
material forms the right lateral support wall 394 and the right corner 
support wall 400 near the back thereof is a threaded aperture 412 near the 
right lateral support wall 394. 
Located in the segment of raised material forming the right lateral support 
wall 390, the right corner support wall 396, and the left lateral support 
wall 386 near the corner where the right lateral support wall 390 and the 
right corner support wall 396 meet is an aperture 414 which extends 
through the pump chassis 370 from top to bottom. Located in the segment of 
raised material forming the right lateral support wall 392, the right 
corner support wall 398, and the left lateral support wall 388 near the 
corner where the right lateral support wall 392 and the right corner 
support wall 398 meet is an aperture 416 which extends through the pump 
chassis 370 from top to bottom. Located in the segment of raised material 
forming the right lateral support wall 394 and the right corner support 
wall 400 near the corner where the right lateral support wall 394 and the 
right corner support wall 400 meet is an aperture 418 which extends 
through the pump chassis 370 from top to bottom. 
Note that with the assembled cassettes 302 positioned and mounted in the 
first, second, and third positions, the aperture 414, the aperture 416, 
and the aperture 418, respectively, will be directly back of the piston 
rods 292 of the assemble cassettes 302 (FIG. 46). The apertures 414, 416, 
and 418 will be used to mount the drive shafts connected to the jaws 
assembles 360 (FIGS. 59 through 61) used to drive the piston assembly 280. 
Located between the left lateral support wall 384 and the right lateral 
support wall 390 is a longitudinal rectangular recess 420 in the bottom 
surface of the pump chassis 370. Similarly, located between the left 
lateral support wall 386 and the right lateral support wall 392 is a 
longitudinal rectangular recess 422 in the bottom surface of the pump 
chassis 370. Finally, located between the left lateral support wall 384 
and the right lateral support wall 390 is a longitudinal rectangular 
recess 424 in the bottom surface of the pump chassis 370. While the 
rectangular recesses 420, 422, and 424 do not extend through the pump 
chassis 370, oval aperture 426, 428, and 430 smaller than the rectangular 
recesses 420, 422, and 424 are located in the rectangular recesses 420, 
422, and 424, respectively, and extend through to the top side of the pump 
chassis 370. 
The rectangular recesses 420, 422, and 424 will be used to mount sensor 
modules therein, and the oval aperture 426, 428, and 430 are to allow the 
wires from the sensor modules to extend through the pump chassis 370. Note 
that with the assembled cassettes 302 positioned and mounted in the first, 
second, and third positions, the rear-most extending upper portions of the 
assembled cassettes 302 will be located over the rectangular recesses 420, 
422, and 424. 
Located in front of the right corner support wall 396 is a circular recess 
432 in the bottom surface of the pump chassis 370. Similarly, located in 
front of the right corner support wall 398 is a circular recess 434 in the 
bottom surface of the pump chassis 370. Finally, located in front of the 
right corner support wall 400 is a circular recess 436 in the bottom 
surface of the pump chassis 370. While the circular recesses 432, 434, and 
436 do not extend through the pump chassis 370, square apertures 438, 440, 
and 442 smaller than the circular recesses 432, 434, and 436 are located 
in the circular recesses 432, 434, and 436, respectively, and extend 
through to the top side of the pump chassis 370. 
The circular recesses 432, 434, and 436 will be used to mount valve 
actuator guides therein, and the cylindrical aperture 450, 452, and 454 
are to allow valve actuators to extend through the pump chassis 370 and to 
orient the valve actuator guides. Note that with the assembled cassettes 
302 positioned and mounted in the first, second, and third positions, the 
circular recess 432, the circular recess 434, and the circular recess 436, 
respectively, will correspond exactly with the locations of the domed 
portions 178 of the valve diaphragms 170 in the assembled cassettes 302 
(FIG. 43). 
Located to the left of the circular recess 432 and in front of the 
rectangular recess 420 is a circular recess 444 in the bottom surface of 
the pump chassis 370. Similarly, located to the left of the circular 
recess 434 and in front of the rectangular recess 422 is a circular recess 
446 in the bottom surface of the pump chassis 370. Finally, located to the 
left of the circular recess 436 and in front of the rectangular recess 424 
is a circular recess 448 in the bottom surface of the pump chassis 370. 
While the circular recesses 444, 446, and 448 do not extend through the 
pump chassis 370, cylindrical apertures 450, 452, and 454 of a smaller 
diameter than the circular recesses 444, 446, and 448 are located in the 
circular recesses 444, 446, and 448, respectively, and extend through to 
the top side of the pump chassis 370. 
The circular recesses 444, 446, and 448 will be used to mount pressure 
transducers therein, and the cylindrical apertures 438, 440, and 442 are 
to allow wires from the pressure transducers to extend through the pump 
chassis 370. Note that with the assembled cassettes 302 positioned and 
mounted in the first, second, and third positions, the circular recess 
444, the circular recess 446, and the circular recess 448, respectively, 
will correspond with the locations of the pressure diaphragms 182 of the 
valve diaphragms 170 in the assembled cassettes 302 (FIG. 43). 
Projecting from the surface on the top side of the pump chassis 370 are a 
number of raised segments in which threaded apertures are located to 
support the drive assembly. A cylindrical raised segment 456 is located to 
the left of the cylindrical aperture 450 on the top side of the pump 
chassis 370. A laterally extending oval raised segment 458 is located 
between the square aperture 438 and the cylindrical aperture 452 on the 
top side of the pump chassis 370. A second laterally extending oval raised 
segment 460 is located between the square aperture 440 and the cylindrical 
aperture 454 on the top side of the pump chassis 370 A cylindrical raised 
segment 462 is located to the right of the square aperture 442 and is 
laterally aligned with the rear-most portions of the oval raised segments 
458 and 460. Finally, a cylindrical raised segment 464 is located to the 
right of the square aperture 442 and is laterally aligned with the 
front-most portions of the oval raised segments 458 and 460. 
Located in the cylindrical raised segment 456 is a threaded aperture 466. 
Located in the oval raised segment 458 is a threaded aperture 468 near the 
rear-most portion of the oval raised segment 458, a threaded aperture 470 
near the front-most portion of the oval raised segment 458, and a threaded 
aperture 472 centrally located in the oval raised segment 458. Similarly, 
located in the oval raised segment 460 is a threaded aperture 474 near the 
rear-most portion of the oval raised segment 460, a threaded aperture 476 
near the front-most portion of the oval raised segment 460, and a threaded 
aperture 478 centrally located in the oval raised segment 460. Located in 
the cylindrical raised segment 462 is a threaded aperture 480. Finally, 
located in the cylindrical raised segment 464 is a threaded aperture 482. 
The apertures 414, 416, and 418 through the pump chassis 370 terminate in 
raised segments extending from the top surface of the pump chassis 370. A 
raised segment 484 is located around the opening of the aperture 414 on 
top of the pump chassis 370, a raised segment 486 is located around the 
opening of the aperture 416 on top of the pump chassis 370, and a raised 
segment 488 is located around the opening of the aperture 418 on top of 
the pump chassis 370. 
Extending upwardly from the raised segment 484 behind the aperture 414 on 
the left side is a guide finger 490, and on the right side is a guide 
finger 492. The guide fingers 490 and 492 are parallel and have a space 
therebetween. Extending upwardly from the raised segment 486 behind the 
aperture 416 on the left side is a guide finger 494, and on the right side 
is a guide finger 496. The guide fingers 494 and 496 are parallel and have 
a space therebetween. Extending upwardly from the raised segment 488 
behind the aperture 418 on the left side is a guide finger 498, and on the 
right side is a guide finger 500. The guide fingers 498 and 500 are 
parallel and have a space therebetween. 
Referring now to FIGS. 66 through 69, a cassette guide 510 for use in 
guiding the installation of the assembled cassette 302 into the proper 
location for latching on the pump chassis 370 is illustrated. Disposed to 
the rear of the cassette guide 510 at the right side is an aperture 512, 
and at the left side is an aperture 514. The aperture 512 will be aligned 
with the threaded aperture 404 (FIG. 62), the threaded aperture 408, or 
the threaded aperture 412 while the aperture 514 will be aligned with the 
threaded aperture 402, the threaded aperture 406, or the threaded aperture 
410 to install the cassette guide 510 in either the first, second, or 
third position. 
The top side (FIG. 66) of the cassette guide 510 has a rectangular recess 
516 therein, which rectangular recess 516 corresponds in size to the 
rectangular recesses 420, 422, and 424 in the pump chassis 370. The sensor 
modules will be accommodated between the rectangular recesses 516 in the 
cassette guides 510 and the rectangular recesses 420, 422, and 424 in the 
pump chassis 370. The right side of this rectangular recess 516 is exposed 
through a rectangular aperture 518 on the bottom of the cassette guide 510 
(FIG. 67). 
An area 520 on the bottom of the cassette guide 51 immediately to the front 
of the rectangular aperture 518 and an area 522 to the right and to the 
back of the rectangular aperture 518 is recessed upward from the bottom 
surface 524 of the cassette guide 510. At the front right corner of the 
rectangular aperture 518 a square segment 528 extends downward to the 
level of the bottom surface 524 of the cassette guide 510. Located 
immediately forward of the square segment 528 is a thin rectangular track 
530 extending from the right side of the cassette guide 510. The thin 
rectangular track 530 terminates at the front end thereof in a blocking 
segment 532. 
The front end of the cassette guide 510 has a rounded notch 534 therein, 
which rounded notch is positioned when the cassette guide 510 is installed 
on the pump chassis 370 to receive the outlet tube mounting cylinder 144 
on the cassette body 100 (FIG. 4). When the cassette guide 510 in 
installed on the pump chassis 370, the rear-most portion of the assembled 
cassette 302 will fit between the cassette guide 510 and the bottom of the 
pump chassis 370. Accordingly, the cassette guide 510 together with the 
various support walls on the bottom of the pump chassis 370 aids in the 
installation of the assembled cassettes 302 in the proper position for 
latching. 
Referring next to FIG. 70, a pump shaft 540 is illustrated which is 
essentially cylindrical. Near the top end of the pump shaft 540 on the 
front side thereof a cam follower wheel 542 is mounted for rotation about 
a short axle 544 extending orthogonally from the pump shaft 540. On the 
front side of the pump shaft 540 at the same location an alignment wheel 
546 is mounted for rotation about a short axle 548 extending orthogonally 
from the pump shaft 540 on the opposite side of the short axle 544. Near 
the bottom end of the pump shaft 540 on the rear side thereof is a conical 
recess 550, which will be used to attach the jaws assembly 360 (FIG. 59 
through 61) to the pump shaft 540. 
Referring next to FIGS. 71 through 76, a slide lock 560 which is for 
mounting on the thin rectangular track 530 of the cassette guide 510 (FIG. 
67) is illustrated. The slide lock 560 has a U-shaped slide channel 562 at 
the front thereof, with the open portion of the U facing left and 
extending from front to rear. The right side of the slide channel 562, 
which is the bottom of the U, has a rectangular notch 564 located near the 
front thereof, which notch 564 runs from the top to the bottom of the 
slide channel 562. 
Extending back from the rear of the slide channel 562 at the bottom thereof 
is a thin rectangular connecting segment 566, which effectively extends 
from the leg of the U at the bottom of the slide channels 562. Attached at 
the rear edge of the rectangular connecting segment 566 is a U-shaped 
channel 568 with the open portion of the U facing right and extending from 
top to bottom. The forward leg of the U of the U-shaped channel 568 is 
attached to the rectangular connecting segment 566 at the top of the 
U-shaped channel 568. It will be appreciated that the top surface of the 
rectangular connecting segment 566 and the top of the U-shaped channel 568 
(which is U-shaped) are coplanar, and that the interior surface of the 
lowermost leg of the slide channel 562 is also coplanar. 
The upper left edge of the U-shaped channel 568 has a bevel 570 located 
thereon, with the bevel 570 being best illustrated in FIG. 76. The 
function of the bevel 570 is as a light reflector, and will become 
apparent later in conjunction with the discussion of the mechanism for 
latching the assembled cassette 302. 
Referring now to FIGS. 77 through 79, an essentially cylindrical power 
module cam 580 is illustrated. The power module cam 580 has an aperture 
582 therethrough for mounting the power module cam 580 on a shaft (not 
shown), which the aperture 582 is shown from the bottom in FIG. 79. The 
power module cam 580 has apertures 584 and 586 through which means for 
retaining the power module cam 580 in position on a shaft may be 
installed. Located near to the bottom of the power module cam 580 is a 
groove 588 located around the outer circumference of the power module cam 
580. The groove 588 will receive a drive belt which will drive the power 
module cam 580 is a rotary fashion. 
Located above and spaced slightly away from the groove 588 in the power 
module cam 580 is a retaining groove indicated generally at 590 formed in 
the surface of and extending around the circumference of the power module 
cam 580. The retaining groove 590 is of essentially uniform width and 
depth in the surface of the power module cam 580, and varies in distance 
from the top side of the power module cam 580. As best seen in FIG. 77, 
the portion of the retaining groove 590 closest to the top of the power 
module cam 580 is disposed approximately one-hundred-eighty degrees away 
from the portion of the retaining groove 590 furthest from the top of the 
power module cam 580. It will be noted that a non-rotating member having a 
portion thereof engaged in the retaining groove 590 of the power module 
cam 580 will be driven in a reciprocating fashion as the power module cam 
580 is turned. 
Located on the bottom of the power module cam 580 about the outer diameter 
thereof is a cam surface indicated generally at 592. The cam surface 592 
extends lower in one portion 593 than in the other portion 595, as best 
shown again in FIG. 77. It will be apparent to those skilled in the art 
that one or more non-rotating member bearing on the cam surface 592 will 
be driven in reciprocating fashion as the power module cam 580 is turned. 
The configurations of the retaining groove 590 and the cam surface 592 are 
graphically illustrated in FIG. 80, which indicates how three members 
driven by the power module cam 580 are caused to operate as the power 
module cam 580 is rotated through a three-hundred-sixty degree cycle. The 
retaining groove 590 is used to drive a pump member, which draws fluid in 
from a source to fill the pump chamber on an intake stroke, and pumps the 
fluid out on a pumping stroke. The cam surface 592 is used to drive two 
valve members, namely an inlet valve and an outlet valve, which are driven 
by portions of the cam surface 592 which are separated by approximately 
one-hundred-eighty degrees. It will at once be appreciated that the pump 
and valves being driven will be those of the assembled cassette 302. 
The plot of pump displacement in FIG. 80 illustrates that there is a fill 
cycle during which displacement increases from zero (or near zero) to 
full, and a pump cycle during which displacement decreases from full to 
empty (or near empty). The retaining groove 590 has two flat portions 
which correspond to the flat portions of the pump displacement plot. One 
of the flat portions 594 is the portion of the retaining groove 590 which 
is closest to the top thereof, and this flat portion 594 corresponds to 
the zero displacement portion of the pump displacement plot. The other 
flat portion 596 is the portion of the retaining groove 590 which is 
closest to the bottom thereof, and this flat portion 596 corresponds to 
the full displacement portion of the pump displacement plot. 
The portions of the retaining groove 590 which are located intermediate the 
flat portions 594 and 596 are a positive portion 598 which corresponds to 
the increasing displacement portion of the pump displacement plot, and a 
negative portion 600 which corresponds to the decreasing displacement 
portion of the pump displacement plot. It should be noted that the flat 
portions 594 and 596 are substantial enough to allow valve movement 
entirely during the flat portions of the pump displacement plot. In the 
preferred embodiment, the flat portions 594 and 596 each represent 
approximately sixty degrees of rotational movement, while the positive and 
negative portions 598 and 600 each represent approximately 
one-hundred-twenty degrees of rotational movement. 
The cam surface 592 of the power module cam 580 is described with reference 
to the inlet and outlet valve plots of FIG. 80. It will first be noted 
that the plots for the inlet and outlet valves are identical, but are 
located one-hundred-eighty degrees apart. As will become evident later in 
conjunction with the discussion of the valve actuators and the valve 
actuator guide, the inlet and outlet valves are both driven by the cam 
surface 592, but by points on the cam surface which are located 
one-hundred-eighty degrees apart. 
The lower portion 593 of the cam surface 592 corresponds to the closed 
positions of both the inlet and outlet valves, while the higher portion 
595 of the cam surface 592 corresponds to the opened positions of both the 
inlet and outlet valves. All valve movement is accomplished entirely 
during the periods in which pump displacement remains constant. In the 
preferred embodiment where pump displacement is constant during two sixty 
degree periods and either increasing or decreasing during two 
one-hundred-twenty degree periods, all valve movement is accomplished 
during the two sixty degree periods. 
In addition, at least one valve is closed at any given time to prevent free 
flow through the assembled cassette 302. Therefore, it will be appreciated 
by those skilled in the art that the period during which the inlet and 
outlet valves transition between fully open and closed positions will be 
limited to thirty degrees or less in the preferred embodiment. During each 
of the sixty degree periods during which pump displacement is constant, 
the one of the valves which is open will close, and only then will the 
other valve, which was closed, be allowed to open. 
Moving next to FIG. 81, a drive module assembly 602 is illustrated which 
includes the power module cam 580 discussed above. The various parts 
described in conjunction with FIG. 81 are mounted onto a drive module 
chassis 604, which will in turn be mounted onto one of the three pump 
positions on the top side of the pump chassis 370. As shown in FIG. 82, 
the drive module chassis 604 has an aperture 605 therethrough on the left 
side thereof, and two apertures 607 and 609 therethrough on the right side 
thereof. The apertures 605, 607, and 609 are for use in fastening the 
drive module assembly 602 to the pump chassis 370. 
An ironless core DC motor 606 is used to drive the system. The motor 606 
typically has a built-in gear reduction unit to reduce the output speed of 
the motor 606. The end of the motor 606 having the output shaft (not 
shown) is mounted onto the top of the drive module chassis 604 at on side 
thereof with the output shaft extending through the drive module chassis 
604. A drive pulley 608 is mounted on the output shaft and is driven by 
the motor 606. 
A one-way clutch 610 is mounted onto the top of the drive module chassis 
604 at the other side thereof. Such devices are commercially available, 
and are also referred to as DC roller clutches or overrunning clutches. 
The one-way clutch 610 supports a drive shaft 612 for rotation therein; 
both ends of the drive shaft 612 extend from the one-way clutch 610. The 
one-way clutch 610 allows the drive shaft 612 to rotate in one direction 
only; in the preferred embodiment, the rotation is clockwise when viewed 
from the top. The power module cam 580 is mounted on the bottom end of the 
drive shaft 612 extending from the one-way clutch 610. A drive belt 613 is 
mounted over the drive pulley 608 and in the groove 588 in the power 
module cam 580. The motor 606 will thereby drive the power module cam 580 
and the drive shaft 612. 
Fixedly mounted above the one-way clutch 610 is an angular incremental 
position sensor 614. A sensor disk 616 is fixedly mounted on the top end 
of the drive shaft 612, and rotates with the drive shaft 612 and the power 
module cam 580. The position sensor 614 is used to provide angular 
incremental and absolute position feedback for control of the drive 
mechanism and cassette. In the preferred embodiment, the position sensor 
614 should also be capable of direction sensing. 
Referring next to FIGS. 85 through 87, a valve actuator 620 is illustrated 
which is driven by the power module cam 580 (FIGS. 77 through 79). The 
valve actuator 620 includes a thin, essentially rectangular portion 622, 
and has a circular bearing 624 rotatably mounted near the top thereof. The 
circular outer diameter of the bearing 624 extends slightly above the top 
of the rectangular portion 622. The bearing 624 is the portion of the 
valve actuator 620 which will be in contact with the cam surface 592 of 
the power module cam 580. 
The rectangular portion 622 of the valve actuator 620 has chamfered edges 
on the lower end thereof as indicated generally at 625, and has a small 
notch 626, 628 in both lateral sides of the rectangular portion 622 at a 
location above the lower end thereof. The small notches 626 and 628 are 
for receiving means for retaining the valve actuator 620 in position once 
it is installed; this will become evident below in conjunction with the 
discussion of the assembly of the main pump unit. 
Moving next to FIGS. 83 and 84, a valve actuator guide 630 is illustrated 
which is used to guide and retain in position pairs of the valve actuators 
620. The upper portion 632 of the valve actuator guide 630 is square in 
cross-section, and lower portion 634 is circular in cross-section. 
Extending vertically through both the square upper portion 632 and the 
circular lower portion 634 of the valve actuator guide 630 are two 
apertures 636 and 638, which are rectangular in cross-section. The 
apertures 636 and 638 are sized to allow the rectangular portion 622 of 
the valve actuator 620 to slide freely therein in each of the apertures 
636 and 638. 
One of the valve actuator guides 630 will be installed into each of the 
pump positions in the pump chassis 370. In the first pump position, the 
square upper portion 632 of the valve actuator guide 630 will be located 
in the square aperture 438 on the pump chassis 370 and the circular lower 
portion 634 of the valve actuator guide 630 will be located in the 
circular recess 432 on the pump chassis 370. In the second pump position, 
the square upper portion 632 will be located in the square aperture 440 
and the circular lower portion 634 will be located in the circular recess 
434. In the third pump position, the square upper portion 632 will be 
located in the square aperture 442 and the circular lower portion 634 will 
be located in the circular recess 436. 
Referring next to FIGS. 88 through 90, a pressure transducer 660 is 
illustrated. One of the pressure transducers 660 will be installed in the 
pump chassis 370 in each pump position, in the circular recesses 444, 446, 
and 448. The pressure transducer 660 is essentially cylindrical, with a 
groove 662 located around the circumference of the pressure transducer 
660. The groove 662 is to receive an elastomeric O-ring, which will both 
retain the pressure transducers 660 in the circular recesses 444, 446, and 
448, and provide a fluid seal. Located on top of the pressure transducer 
660 is a square segment 664 in which is located the actual transducer, 
which square segment 664 will be received in the cylindrical apertures 
450, 452, and 454. Extending upward from the square segment 664 are 
several leads 666. 
Referring next to FIGS. 91 through 96, an optical sensor module 670 is 
illustrated. The optical sensor module 670 is essentially rectangular in 
cross-section, with a wider rectangular flange 672 on top of the 
rectangular portion, and an oval portion 674 above the rectangular flange 
672. A flex cable 676 extends from the top of the oval portion 674. 
Located around the circumference of the oval portion 674 is a groove 678, 
which will receive an elastomeric O-ring, which will retain the oval 
portion 674 of the optical sensor modules 670 in the oval apertures 426, 
428, or 430. The rectangular flange 672 of the optical sensor modules 670 
will fit into the rectangular recesses 420, 422, or 424, in the first, 
second, or third pump positions, respectively. 
The rectangular portion of the optical sensor module 670 has located in the 
front thereof and immediately under the rectangular flange 672 a notch 
indicated generally by 680, which notch 680 will receive the rearmost 
portion of the assembled cassette 302. The bottom of the rectangular 
portion of the optical sensor module 670 has an optical light source 682 
and an optical light sensor 684 located thereon in locations near and 
equidistant from the right side thereof. The optical light source 682 and 
the optical light sensor 684 are used to detect when the slide lock 560 is 
in the closed position, as will be discussed below. 
Located on the upper surface of the notch 680 in the optical sensor module 
670 are three optical light sources 686, 688, and 690, which extend in a 
line from left to right on the upper surface of the notch 680. The three 
optical light sources 686, 688, and 690, as well as the optical light 
source 682 are typically light emitting diodes. Located immediately below 
the three optical light sources 686, 688, and 690 on the lower surface of 
the notch 680 in the optical sensor module 670 near the right side thereof 
are three optical light sensors 692, 694, and 696, which also extend in a 
line from left to right on the lower surface of the notch 680. The optical 
light sensors 692, 694, and 696, as well as the optical light sensor 684 
are typically phototransistors or like devices. The three optical light 
sources 686, 688, and 690 and the three optical light sensors 692, 694, 
and 696 are used to provide the three cassette identification bits, as 
will be discussed below. 
Also located on the lower surface of the notch 680 in the optical sensor 
module 670 toward the left side thereof is an optical light source 698. 
Located in front of the optical light source 698 is an optical light 
sensor 700. The optical light source 698 and the optical light sensor 700 
are used to detect the presence (or absence) of an air bubble in the fluid 
line in the cassette. The location of the optical light source 698 and the 
optical light sensor 700 as illustrated in FIG. 96 is that of the 
preferred embodiment, and operation of that preferred embodiment as well 
as the configurations and operational descriptions of several alternate 
embodiments are discussed below. 
Referring next to FIGS. 97 and 98, a valve actuator seal 650 is shown which 
is used both to provide a fluid seal and, more importantly, to retain the 
valve actuators 620 (FIGS. 85 through 87) in an upward position with their 
bearings 624 against the lower portion 593 of the power module cam 580. 
The outer circumference of the valve actuator seals 650 is of a size 
allowing them to be retained in a friction fit in the circular recesses 
432, 434, and 436 below the valve actuator guides 630. A metal ring (not 
shown) may be molded into the outer diameter of the valve actuator seals 
650 to better enable them to be better retained in the circular recesses 
432, 434, and 436. 
Two apertures 652 and 654, which are rectangular in configuration, are 
located in the valve actuator seal 650 to receive the bottom portions of 
the rectangular portion 622 of the valve actuator 620. The lengths of the 
apertures 652 and 654 are shorter than the width of the rectangular 
portion 622 of the valve actuator 620, with the small notches 626 and 628 
in the rectangular portion 622 being used to capture to ends of one of the 
apertures 652 and 654. It will be appreciated that the small notches 626 
and 628 of the valve actuators 620 will engage the apertures 652 and 654 
in the valve actuator seal 650, thereby allowing the valve actuator seal 
650 to exert a bias on the valve actuators 620. As will be seen below, the 
bias exerted by the valve actuator seal 650 on the valve actuators 620 is 
an upward one, urging the valve actuators 620 against the lower portion 
593 of the power module cam 580. 
In the previous discussions of the various parts of the main pump unit, the 
function and interrelationship between parts has been briefly discussed. 
Before moving on to the operation of the main pump unit and the assembled 
cassette 302, a brief discussion of the assembly of the main pump unit is 
in order. This discussion specifically refers to FIGS. 62 through 65 (the 
pump chassis 370), FIG. 99, and FIG. 112, and also to other figures which 
are specifically mentioned in the discussion. 
A pump shaft bearing 640 is installed in both the top and the bottom of 
each of the apertures 414, 416, and 418 in the pump chassis 370. The pump 
shaft bearings 640 (FIG. 112) are essentially cylindrical and have a 
cylindrical aperture therethrough. In the preferred embodiment, the outer 
surface of the pump shaft bearings 640 have a raised portion or ridge 641 
near the top thereof and fit in the apertures 414, 416, and 418 from the 
top and the bottom thereof in a interference fit to retain them in the 
apertures 414, 416, and 418 in the pump chassis 370. The pump shaft 
bearing 640 are preferably made of a low friction material such as Teflon 
to allow the pump shafts 540 to move freely therein. It will also be 
appreciated that a single bearing could be used in each of the apertures 
414, 416, and 418 in the pump chassis 370 which bearing would extend all 
the way through the apertures 414, 416, and 418. 
Next, the valve actuator guides 630 are installed from the bottom of the 
pump chassis 370 into the circular recess 432 and the square aperture 438 
in the first pump position, into the circular recess 434 and the square 
aperture 440 in the second pump position, and into the circular recess 436 
and the square aperture 442 in the third pump position. With the valve 
actuator guides 630 installed in the pump chassis 370 the bottom surface 
of the valve actuator guides 630 leaves a portion of the circular recesses 
432, 434, and 436 open from the bottom side of the pump chassis 370. The 
valve actuator seals 650 (FIGS. 97 and 98) will be installed later in the 
circular recesses 432, 434, and 436 below the valve actuator guides 630. 
The next step in the assembly is to install the two sensor modules. The 
pressure transducers 660 (FIGS. 88 through 90) are installed from the 
bottom of the pump chassis 370 into the circular recesses 444, 446, and 
448. The pressure transducers 660 are essentially cylindrical, and with 
O-rings in the grooves 662 fit snugly into the circular recesses 444, 446, 
and 448 with their bottom surfaces flush with the bottom surface of the 
pump chassis 370 around the circular recesses 444, 446, and 448; the tops 
of the cylindrical portion of the pressure transducers 660 fit against the 
cylindrical apertures 450, 452, and 454 in the pump chassis 370. Not shown 
in the drawings is the preferred embodiment's use of a thin membrane 
adhesively placed over the bottom of the pressure transducer 660 and the 
portions of the bottom surface of the pump chassis 370 thereabout. This 
thin membrane protects the pressure transducer 660 from fluids which may 
inadvertently or accidentally end up on the device. 
The optical sensor assembles 570 (FIGS. 91 through 96) are installed in the 
rectangular recesses 420, 422, and 416 of the pump chassis 370, with the 
oval portions 674 of the optical sensor modules 670 fitting into the oval 
apertures 426, 428, and 430. The optical sensor modules 670 are retained 
in position by the pressure of O-rings in the grooves 678 in the optical 
sensor modules 670, and by the cassette guides 510. 
The next step in the assembly of the main pump unit mechanical components 
onto the pump chassis 370 is the installation of the cassette guide 510 
(FIGS. 66 through 69)and the slide lock 560 (FIGS. 71 through 76). The 
slide lock 560 is installed onto the cassette guide 510 by placing the 
portion of the slide lock 560 including the bottom of the slide channel 
562 into the rectangular aperture 518 in the cassette guide 510 from the 
top, with the rectangular connecting segment 566 of the slide lock 560 
extending over the portion of the area 522 in the back of the cassette 
guide 510. This aligns the interior of the U-shaped slide channel 562 on 
the slide lock 560 with the back end of the thin rectangular track 530 on 
the cassette guide 510. The slide lock 560 is then moved forward with 
respect to the cassette guide 510, with the interior of the slide channel 
562 fitting over the thin rectangular track 530 until the blocking segment 
of the cassette guide 510 is contacted by the slide lock 560. 
The cassette guides 510 together with the slide locks 560 may then be 
mounted into the three pump positions on the pump chassis 370, which 
already contain the optical sensor module 670, using two screws (not 
shown). In the first pump position, a screw is placed through the aperture 
514 in the cassette guide 510 into the threaded aperture 402 in the pump 
chassis 370, and a second screw is placed through the aperture 512 in the 
cassette guide 510 into the threaded aperture 404 in the pump chassis 370. 
In the second pump position, a screw is placed through the aperture 514 in 
the cassette guide 510 into the threaded aperture 406 in the pump chassis 
370, and a second screw is placed through the aperture 512 in the cassette 
guide 510 into the threaded aperture 408 in the pump chassis 370. In the 
third pump position, a screw is placed through the aperture 514 in the 
cassette guide 510 into the threaded aperture 410 in the pump chassis 370, 
and a second screw is placed through the aperture 512 in the cassette 
guide 510 into the threaded aperture 412 in the pump chassis 370. By way 
of example, the cassette guide 510 and the slide lock 560 are shown 
mounted in the first pump position in FIG. 99. 
Next, the pump shafts 540 are installed in the pump shaft bearings 640, 
which have previously been installed in the apertures 414, 416, and 418. 
The end of the pump shafts 540 containing the conical recess 550 therein 
are inserted through the pump shaft bearings 640 from the top, with the 
alignment wheel 546 being located between one of the three pairs of guide 
fingers, namely the guide fingers 490 and 492 for the first pump position, 
the guide fingers 494 and 496 for the second pump position, and the guide 
fingers 494 and 496 for the third pump position. For example, the pump 
shaft 540 is shown installed in the first pump position in FIG. 112. 
The valve actuators 620 are installed next, with one pair of the valve 
actuators 620 being installed in each pump position. The bottom ends of 
the valve actuators 620 having the chamfered edges 625 are inserted 
through the top sides of the valve actuator guides 630, with one pair of 
the valve actuators 620 being installed in each of the three valve 
actuator guides 630. The pair of valve actuators 620 are inserted into the 
apertures 636 and 638 in the valve actuator guides 630 with the bearings 
624 on each of the pair of the valve actuator 620 facing away from each 
other. 
It will be appreciated that the rectangular portions 622 of the valve 
actuators 620 will extend downward through the apertures 636 and 638 in 
the valve actuator guides 630. As stated above, valve actuator seals 650 
are used in each of the three pump positions, and are mounted from the 
bottom of the pump chassis 370 into the circular recesses 432, 434, and 
436 below the valve actuator guides 630. The outer circumference of the 
valve actuator seals 650 causes them to be retained in a friction fit in 
the circular recesses 432, 434, and 436. 
The lower ends of the rectangular portions 622 of each pair of the valve 
actuators 620 extend downward through the apertures 652 and 654 in the 
valve actuator seal 650. The small notches 626 and 628 in one of the valve 
actuators 620 in each pair is retained in the aperture 652 in the valve 
actuator seal 650, and the other one of the valve actuators 620 in each 
pair is retained in the aperture 654. As shown in FIGS. 113 and 114, the 
valve actuator seals 650 will tend to urge the valve actuators 620 in an 
upward direction. In the preferred embodiment, the bottoms of the valve 
actuators 620 having the chamfered edges 625 will protrude somewhat from 
the bottom surface of the pump chassis 370 around the circular recesses 
432, 434, and 436 even when the valve actuators 620 are in their open 
position. For example, in their closed position they may protrude 
approximately thirty thousands of an inch, and in their open position they 
may protrude seventy thousands of an inch. 
This upward biasing of the valve actuator 620 is essential both to allow 
the assembled cassettes 302 to be freely inserted, and to maintain the 
valve actuators 620 in an upward position with their bearings 624 against 
the lower portion 593 of the power module cam 580. The valve actuator 
seals 650 accordingly function both to provide a fluid seal and to bias 
the valve actuators 620 in the upward position described. 
The next step in the assembly of the main pump unit is to install a drive 
module assembly 602 (FIG. 81) onto each of the three pump positions on the 
pump chassis 370. In the first pump position, the drive module assembly 
602 will be supported above the top of the pump chassis 370 by the 
cylindrical raised segment 456 and the oval raised segment 458. Three 
screws (not shown) will be used to secure the drive module assembly 602 in 
the first pump position, with a first screw being placed through the 
aperture 605 in the drive module chassis 604 into the threaded aperture 
466 in the pump chassis 370, a second screw being placed through the 
aperture 607 in the drive module chassis 604 into the threaded aperture 
468 in the pump chassis 370, and a third screw being placed through the 
aperture 609 in the drive module chassis 604 into the threaded aperture 
470 in the pump chassis 370. In the first pump position, the power module 
cam 580 is supported directly above the square aperture 438 in the pump 
chassis 370, and the valve actuator guide 630 and the two valve actuators 
620 located in the first pump position. 
In the second pump position, the drive module assembly 602 will be 
supported above the top of the pump chassis 370 by the oval raised segment 
458 and the oval raised segment 460. Three screws (not shown) will be used 
to secure the drive module assembly 602 in the second pump position, with 
a first screw being placed through the aperture 605 in the drive module 
chassis 604 into the threaded aperture 472 in the pump chassis 370, a 
second screw being placed through the aperture 607 in the drive module 
chassis 604 into the threaded aperture 474 in the pump chassis 370, and a 
third screw being placed through the aperture 609 in the drive module 
chassis 604 into the threaded aperture 476 in the pump chassis 370. In the 
second pump position, the power module cam 580 is supported directly above 
the square aperture 440 in the pump chassis 370, and the valve actuator 
guide 630 and the two valve actuators 620 located in the second pump 
position. 
In the third pump position, the drive module assembly 602 will be supported 
above the top of the pump chassis 370 by the oval raised segment 460, the 
cylindrical raised segment 462, and the cylindrical raised segment 464. 
Three screws (not shown) will be used to secure the drive module assembly 
602 in the third pump position, with a first screw being placed through 
the aperture 605 in the drive module chassis 604 into the threaded 
aperture 478 in the pump chassis 370, a second screw being placed through 
the aperture 607 in the drive module chassis 604 into the threaded 
aperture 480 in the pump chassis 370, and a third screw being placed 
through the aperture 609 in the drive module chassis 604 into the threaded 
aperture 482 in the pump chassis 370. In the third pump position, the 
power module cam 580 is supported directly above the square aperture 442 
in the pump chassis 370, and the valve actuator guide 630 and the two 
valve actuators 620 located in the third pump position. 
The final component to be installed is the jaws assembly 360 (FIGS. 59 
through 61), with one jaws assembly 360 being installed in each of the 
three pump positions onto the bottom of the pump shafts 540, which are 
installed in the apertures 414, 416, and 418. The bottom end of the pump 
shaft 540 having the conical recess 550 therein is inserted into the 
cylindrical aperture 316 in the latch head 310 of the jaws assembly 360. A 
retaining screw (not shown) is screwed into the threaded aperture 318 in 
the latch head 310, and into the conical recess 550 of the pump shaft 540 
to retain the jaws assembly 360 in place on the bottom of the pump chassis 
370. 
The location of the installed jaws assembly 360 is shown in FIG. 99, with 
the slide lock 560 and the latch jaw 340 in the open position. The link 
pin 354 on the latch jaw 340 is located in the U-shaped channel 568 of the 
slide lock 560, and movement of the slide lock 560 will accordingly cause 
the latch jaw 340 to move. When the slide lock 560 is fully forward, as 
shown in FIG. 99, the latch jaw 340 will be in the open position, with the 
jaw portion 342 of the latch jaw 340 away from the right jaw 314 of the 
latch head 310. When the slide lock 560 is pushed toward the back of the 
pump chassis 370, as shown in FIG. 100, the latch jaw 340 will be in the 
closed position, with the jaw portion 342 of the latch jaw 340 closely 
adjacent the right jaw 314 of the latch head 310. 
This completes the discussion of the assembly of the main pump unit with 
three pump positions. It will, of course, be appreciated that the main 
pump unit may be constructed with different numbers of pump positions 
without departing from the teachings herein. It is now appropriate to 
discuss the installation of the assembled cassette 302 into the first pump 
position, which is the subject of the above-identified application 
entitled "Cassette Loading and Latching Apparatus for a Medication 
Infusion System," and the operation of the device to pump fluid and to 
perform the other associated functions. The operations of the other two 
pump positions are identical to the operation of the first pump position 
described below. 
With the slide latch 240 pulled back fully away from the front of the 
assembled cassette 302 (FIGS. 43 through 48), the wider portion of the 
elongated, tear-shaped aperture 258 in the slide latch 240 will close the 
outlet tube 306, preventing fluid from flowing through the assembled 
cassette 302. The inlet tube 304 is connected to a fluid source such as an 
IV bag (not shown), and the outlet tube 306 is connected to a fluid 
delivery device such as an injection set (not shown), the use of which is 
well known in the art. The slide latch 240 is opened, together with any 
other closures in the IV bag line, and fluid fills the lines, the 
assembled cassette 302, and the injection set. By tapping or shaking the 
assembled cassette 302 any residual air bubbles will flow out through the 
line. The slide latch 240 is then pulled back and the outlet tube 306 is 
closed, and the system is in a primed condition with the assembled 
cassette 302 ready to be installed onto the main pump unit. 
When the slide latch 240 is pulled back, an opening is left between the 
front portion 242 of the slide latch 240 and the front top portion of the 
assembled cassette 302 (made up of the cassette body 100 and the retainer 
cap 190) facing the front portion 242 of the slide latch 240. By way of 
the example used herein where the assembled cassette 302 is to be mounted 
in the first position (the position on the left end of the pump chassis 
370), the opening between the front portion 242 of the slide latch 240 and 
the front top portion of the assembled cassette 302 will admit the first 
pair of angled segments 372 and 374 as the assembled cassette 302 is 
installed. The top surface of the assembled cassette 302, which is the 
retainer cap 190 (FIG. 43), Will mount against the bottom of the pump 
chassis 370 (FIG. 62). 
Prior to installing the assembled cassette 30 into the main pump unit, the 
slide lock 560 must be fully forward with the latch jaw 340 opened away 
from the latch head 310, as mentioned previously and as shown in FIG. 99. 
In addition, the jaws assembly 360 should be in its fully upward position, 
which may be achieved by using the motor 606 to drive the power module cam 
580 to cause the jaws assembly 360 to be driven to this position using the 
position sensor 614. 
With the rear-most edge of the assembled cassette 302 tilted upward, the 
rear-most edge of the top of the assembled cassette 302 is then placed 
against the bottom of the pump chassis 370 between the pressure transducer 
660 (mounted flush with the bottom of the pump chassis 370) and the top 
side of the cassette guide 510. The rear-most portion of the top of the 
assembled cassette 302 is slid toward the back of the pump chassis 370 
into position between the left lateral support wall 384 on the left side 
thereof and the right lateral support walls 390 on the right side thereof, 
with most of the rear-most portion of the top of the assembled cassette 
302 fitting into the notch 680 in the optical sensor module 670. The upper 
right back corner of the assembled cassette 302 is supported and 
positioned in the back of the assembled cassette 302 behind the pump 
cylinder 112 (FIG. 4) and on the portion of the right side of the 
assembled cassette 02 adjacent the pump cylinder 112 by the right corner 
support wall 396. 
When the assembled cassette 302 is pushed fully back in place, the front of 
the assembled cassette 302 is tilted upward against the bottom of the pump 
chassis 370, with the first pair of angled segments 372 and 374 on the 
bottom of the pump chassis 70 fitting into the area between the front 
portion 242 of the slide latch 240 and the front top portion of the 
assembled cassette 302. The slide latch 240 may then be pushed into the 
cassette body 100, sliding the inverted L-shaped portion 250 of the slide 
latch 240 into engagement with the angled segment 372, and sliding the 
inverted, backwards L-shaped portion 252 of the slide latch 240 into 
engagement with the angled segment 374. The assembled cassette 302 will 
thus be held in position on the bottom of the pump chassis 370 until the 
slide latch 240 is again pulled back, releasing the assembled cassette 
302. 
Simultaneously, the outlet tube 306 will be opened, but fluid will not flow 
through the outlet tube 306 since at least one of the valve actuators 620 
will be in its fully downward position at any given time, thereby 
preventing free flow through the assembled cassette 302 whenever the 
assembled cassette 302 is installed on the main pump unit. It will also be 
noted that in this initially installed position, the piston cap portion 
262 is located at the very top of the pump cylinder 112. 
It will be appreciated as discussed above that the power module cam 580 
will operate both the reciprocations of the piston assembly 280 and the 
movement of the valve actuators 620A and 620B (FIG. 112). This piston and 
valve drive system is the subject of the above-identified application 
entitled "Mechanical Drive System for a Medication Infusion System." The 
movement of the piston assembly 280 and the valve actuators 620A and 620B 
will correspond to the charts of FIG. 80, with the initially installed 
position corresponding roughly to the zero degree position of the charts. 
In this position, both the inlet valve actuator 620A and the outlet valve 
actuator 620B are in their closed positions. 
Note that the open positions of the inlet valve actuator 620A and the 
outlet valve actuator 620B are their fully upward positions, and that 
their closed positions are their fully downward positions. Without the 
inlet valve actuator 620A and the outlet valve actuator 620B in place on 
the domed portion 178 of the valve diaphragm 170 of the assembled cassette 
302, the area including the first passageway 128, the smaller diameter 
aperture 118 to the pump cylinder 112, and the second passageway 134 is 
entirely open and fluid flow therein is unrestricted. When the inlet valve 
actuator 620A is in its closed o fully downward position, the portion of 
the domed portion 178 located intermediate the first passageway 128 and 
the smaller diameter aperture 118 is forced down onto the portion of the 
slightly raised border 146 between the first passageway 128 and the 
smaller diameter aperture 118, thereby preventing fluid flow between the 
first passageway 128 and the smaller diameter aperture 118. This position 
of the inlet valve actuator 620A is referred to as its closed position. 
Similarly, when the outlet valve actuator 620B is in its closed or fully 
downward position, the portion of the domed portion 178 located 
intermediate the smaller diameter aperture 118 and the second passageway 
134 is forced down onto the portion of the slightly raised border 146 
between the smaller diameter aperture 118 and the second passageway 134, 
thereby preventing fluid flow between the smaller diameter aperture 118 
and the second passageway 134. This position of the outlet valve actuator 
620B is referred to as its open position. 
The motor 606 will begin to drive the power module cam 580, causing the 
inlet valve actuator 620A to open, with the outlet valve actuator 620B 
remaining closed, as shown in FIG. 113. As the power module cam 580 
continues to be turned by the motor 606, the piston cap portion 262 will 
be drawn downward in the pump cylinder 112, causing fluid to be drawn into 
the pump cylinder 112 from the fluid source (not shown) through the inlet 
tube 304, the bubble trap 104, and the first passageway 128. When the pump 
cylinder 112 is filled, the inlet valve actuator 620A is closed. Only 
after the inlet valve actuator 620A is fully closed will the outlet valve 
actuator 620B be opened. FIG. 114 shows the system with the outlet valve 
actuator 620B opened, prior to any fluid being pumped out. The main pump 
unit responds to an electronic control system (not shown) which operates 
the system. This electronic control system, which is preferably 
microprocessor-based, may be either conventional as known in the art, or 
it may differ to enhance the unique mechanical design of the system 
discussed herein. 
Fluid will be pumped by the motor 606 turning the power module cam 580 to 
drive the piston cap portion 262 upward in the cylinder, forcing fluid out 
of the pump cylinder 112, and eventually out of the assembled cassette 302 
through the outlet tube 306, from which it is supplied to the patient 
through the injection set (not shown). It will be appreciated by those 
skilled in the art that the system may pump fluid at any rate chosen, by 
operating the motor 606 to pump fluid. In addition, the use of the 
position sensor 614 will provide a feedback signal indicating the exact 
position of the power module cam 580 and the piston assembly 280, thereby 
indicating how much fluid has been pumped by the device. 
As noted previously, the rear-most portion of the assembled cassette 302 is 
located in the notch 680 of the optical sensor module 670 when the 
cassette is installed in the main pump unit. This is illustrated in FIGS. 
101 and 102, which illustrate only the assembled cassette 302 and the 
optical sensor module 670. In some situations it may be desirable to use 
several different types of assembled cassettes 302 with the system 
described herein. For example, different cassettes may require different 
stroke volumes to provide different flow ranges, or require different 
fittings o the inlet tube 304 and/or the outlet tube 306 of the cassettes. 
Special application cassettes such as enteral pump cassettes, continuous 
arterio-venous hemofiltration (CAVH) cassettes, continuous blood sampling 
cassettes, or autotransfusion cassettes may be manufactured. 
The use of the wrong cassette may present a high degree of danger, so it 
will be perceived that it is highly desirable to identify the particular 
cassette installed. This may be accomplished by the use of the three 
cassette identifying indicia 148, 150, and 152, which is the subject of 
the present invention. By making each of these indicia a binary bit, up to 
eight different codes may be generated. By using redundant coding to 
ensure fail-safe operation, three different cassettes can be identified. 
To do this, at least two bits must be identical; for example, a first type 
of cassette would have bits one and two as logical ones with a zero bit 
three, a second type of cassette would have bits two and three as logical 
ones with a zero bit one, and a third type of cassette would have bits one 
and three as logical ones with a zero bit two. In addition, the absence of 
a cassette can also be detected. In the example illustrated in the 
drawings the first cassette identifying indicia 148 and the third cassette 
identifying indicia 152 are of a first type (identified as a logical one 
for convenience), and the second cassette identifying indicia 150 is of a 
second type (identified as a logical zero for convenience). 
With the assembled cassette 302 installed with its rear-most portion 
located in the notch 680 of the optical sensor module 670, the first 
cassette identifying indicia 148 is aligned with the first pair of sensor 
elements, namely the optical light source 686 and the optical light sensor 
692. Similarly, the second cassette identifying indicia 150 is aligned 
with the second pair of sensor elements, namely the optical light source 
688 and the optical light sensor 694. Likewise, the third cassette 
identifying indicia 152 is aligned with the third pair of sensor elements, 
namely the optical light source 690 and the optical light sensor 696. 
The second cassette identifying indicia 150 (the logical zero) and the 
second pair of sensor elements are shown in FIG. 103. Light from the 
optical light source 688 shines through the aperture 208 in the retainer 
cap 190, and onto the cassette body 100, where it is dispersed by the 
second cassette identifying indicia 150, which comprises an inverted V 
molded into the bottom of the upper surface 102 of the cassette body 100. 
Note that various prism types of construction could also be used to 
disperse the light, which does not reach the optical light sensor 694, 
resulting in a logical zero being output by the optical light sensor 694. 
For example, the inverted V could be molded into the top side of the upper 
surface 102 of the cassette body 100. Other alternatives include using 
paint or other physical blocking expedients instead of a dispersing lens, 
or selectively molding or not molding one or more of the apertures 206, 
208, and 210 in the retainer cap 190 (FIGS. 13 and 14). 
The third cassette identifying indicia 152 (the logical one, like the first 
cassette identifying indicia 148, which is not shown here) and the third 
pair of sensor elements are shown in FIG. 104. Light from the optical 
light source 690 shines through the aperture 210 in the retainer cap 190, 
and onto the third cassette identifying indicia 152 on the cassette body 
100. The third cassette identifying indicia 152 is a cylindrical 
projection extending up from the upper surface 102 of the cassette body 
100, which cylindrical projection acts like a light pipe to conduct the 
light to the optical light sensor 696, where it causes the optical light 
sensor 696 to generate a logical one output. Note that in the preferred 
embodiment, the cassette body 100 is constructed of clear plastic to allow 
the first cassette identifying indicia 148 and the third cassette 
identifying indicia 152 to conduct light therethrough. Also in the 
preferred embodiment, when there is no cassette 302 in place, all three 
outputs are logical ones, and this signal is used to indicate that no 
cassette has been installed or that the cassette 302 is improperly 
installed. 
It will therefore be appreciated that the use of the three cassette 
identifying indicia 148, 150, and 152 allows the generation of three 
digital cassette identifying signals which are supplied from the optical 
sensor module 670 to the microprocessor (not shown) to identify the 
particular type of cassette which is installed. By using this cassette 
identifying system, inappropriate use of an installed cassette and/or 
improper cassette installation may be prevented. 
It is desirable to provide an indication that the assembled cassette 302 
has been properly installed on the main pump unit, with the latching 
mechanism properly closed. This occurs when the slide lock 560 is pushed 
fully back against the rear of the cassette guide 510. This is 
accomplished by sliding the slide latch 240 fully into the assembled 
cassette 302, with the tab 257 on the slide latch 240 fitting into the 
notch 564 on the slide lock 560 to drive the slide lock 560 back, thereby 
also latching the jaws assembly 360 onto the piston assembly 280. 
An indication of latching is provided through us of the optical light 
source 682 and the optical light sensor 684 on the bottom of the optical 
sensor module 670. When the slide lock 560 is in its loading or forward 
position shown in FIG. 99, the bevel 570 on the optical sensor module 670 
is adjacent the optical light source 682 and the optical light sensor 684 
on the bottom of the optical sensor module 670, as shown in FIGS. 105 and 
106. The presence of the bevel 570 reflects the light coming from the 
optical light source 682 to the right, away from the optical light sensor 
684, thereby preventing a latch closed signal. When the slide lock 560 is 
pushed fully back to its closed or rear-most position shown in FIG. 100, 
the bevel 570 on the optical sensor module 670 is not adjacent the optical 
light source 682 and the optical light sensor 684 on the bottom of the 
optical sensor module 670, as seen in FIG. 107. Rather, a reflective 
surface 567 installed on the flat bottom of the rectangular connecting 
segment 566 of the slide lock 560 reflects light from the optical light 
source 682 into the optical light sensor 684, thereby generating a latch 
closed signal. The reflective surface 567 acts as a mirror, and may be a 
foil segment which is, for example, hot stamped into the rectangular 
connecting segment 566 or adhesively secured to the bottom of the 
rectangular connecting segment 566. 
Additional confirmation that the slide lock 560 was closed with an 
assembled cassette 302 in place may be obtained by verifying the cassette 
identifying indicia, as described above. In order to result in an 
absolutely positive confirmation that a cassette is properly installed and 
that the slide lock 560 is in the closed position, the preferred 
embodiment will require correct signals from both the optical light sensor 
684, and from the optical light sensors 692, 694, and 696. 
One of the essential functions of the system is to enable the detection of 
air in the fluid line of the system. The air-in-line detection (AILD) 
system of the preferred embodiment is shown in FIG. 108, and includes the 
recessed lens portion 138 in the assembled cassette 302, and a pair of 
sensor elements, namely the optical light source 698 and the optical light 
sensor 700 in the optical sensor module 670. The recessed lens portion 138 
is an optical viewing area in the fluid pathway through the assembled 
cassette 302, and in the preferred embodiment shown in FIG. 108 is an 
inverted prism. The recessed lens portion 138 in any embodiment also 
includes a focusing lens, indicated generally at 697. The optical light 
source 698 and the optical light sensor 700 are both mounted in the 
optical sensor module 670 below the recessed prismatic lens portion 138 in 
the installed cassette 302. 
The optics of the system of FIG. 108 makes use of the properties of light 
as it moves from one media to a less dense media, and is a "reverse 
reflected" configuration. When air is in the fluid channel, the light from 
the optical light source 698 follows the path shown in FIG. 108, 
reflecting off of one bottom side of the recessed prismatic lens portion 
138 onto the other, and thence downward to the optical light sensor 700. 
Even if the upper surfaces of the recessed prismatic lens portion 138 are 
wetted with a fluid film, total internal reflection still occurs. When 
fluid is in the channel, the light refracts through the recessed prismatic 
lens portion 138 into the fluid. If the fluid is clear, the light passes 
through the liquid to 170, where it is either absorbed by the valve 
diaphragm 170 or the retainer cap 190, or passes through both the valve 
diaphragm 170 and the retainer cap 190. Accordingly, the valve diaphragm 
170 may be clear, absorptive of light, or may scatter the light, not 
returning enough light to the optical light sensor 700 to generate a 
signal indicative of air being in the fluid path. If the valve diaphragm 
170 is clear, then the retainer cap 190 may be clear, absorptive of light, 
or may scatter the light, again not returning enough light to the optical 
light sensor 700 to generate a signal indicative of air being in the fluid 
path. If the fluid is opaque, the light is absorbed by the fluid. In any 
event, the light does not return to the photodetector. What little 
reflection of light may occur will be small compared to the air case. 
Material requirements of the preferred embodiment shown in FIG. 108 are 
that the cassette body 100 be made of clear material, that the valve 
diaphragm 170 be made of material which is clear, absorptive to light, or 
effectively scatters light. If the valve diaphragm 170 is clear, the 
retainer cap 190 must then be made of material which is clear, absorptive 
to light, or effectively scatters light. In summary, the fluid channel in 
the assembled cassette 302 is designed so that with the presence of air in 
the fluid channel, light sent by the optical light source 698 will be 
detected by the optical light sensor 700. With fluid contained in the 
fluid channel, little or no light will be detected, irrespective of the 
clarity or opaqueness of the fluid. It will therefore be appreciated by 
those skilled in the art that air bubbles in the line ma be easily 
detected with the apparatus discussed above. 
There are three alternate embodiments to the arrangement illustrated in 
FIG. 108. First, in FIG. 109, a reflective surface 702 is installed on the 
side of the notch 680 in the optical sensor module 670 opposite the 
optical light source 698 and the optical light sensor 700. The recessed 
lens portion 138 in this embodiment is V-shaped, with light being directed 
from the bottom of the V. The materials of the cassette body 100, the 
valve diaphragm 170, and the retainer cap 190 are all clear. When a clear 
fluid is contained in the fluid pathway, light from the optical light 
source 698 will refract through to the reflective surface 702, and return 
to the optical light sensor 700, giving a high signal. When air is present 
in the fluid pathway, the light from the optical light source 698 will 
reflect off of the recessed lens portion 138 without passing therethrough, 
thereby not reaching the optical light sensor 700. However, when lipids 
are contained in the fluid pathway, the light will refract through the 
recessed lens portion 138 and be absorbed by the lipids, giving a signal 
indicative of air in the fluid pathway. It will thereby be appreciated 
that the arrangement shown in FIG. 109 is suitable for use with clear 
fluids only. 
Referring next to FIG. 110, a further variation is illustrated which uses a 
V-shaped channel, with the bottom of the V being flat. Light is directed 
from the optical light source 698, which is mounted on the top of the 
notch 680 in the optical sensor module 670, directly opposite the optical 
light sensor 700 on the bottom of the notch 680 in the optical sensor 
module 670. The materials of the cassette body 100, the valve diaphragm 
170, and the retainer cap 190 are again clear. It will at once be 
appreciated that the signal received by the optical light sensor 700 will 
be low for lipids in the fluid pathway, and high for clear fluids in the 
fluid pathway. When air is present in the fluid pathway, some of the light 
will reflect off of the sides of the V, not reaching the optical light 
sensor 700, while some of the light will pass through the flat bottom of 
the V, reaching the optical light sensor 700. Therefore, for air a medium 
level signal will be received. The system of FIG. 110 is accordingly a 
three level system, and not digital. 
Referring next to FIG. 111, a third variation is illustrated which uses a 
V-shaped recessed lens portion 138, with light being directed from the top 
of the V. In this embodiment, the optical light source 698 and the optical 
light sensor 700 are mounted on the top of the notch 680 in the optical 
sensor module 670, rather than on the bottom. The materials of the 
cassette body 100, the valve diaphragm 170, and the retainer cap 190 are 
again all clear. The signal received by the optical light sensor 700 will 
be high with air in the fluid pathway, low with clear liquids in the fluid 
pathway, and generally medium with lipids contained in the fluid pathway. 
The system of FIG. 111 is a three level system like the system of FIG. 
110, but the optics of the system of FIG. 110 are superior to the optics 
of the system of FIG. 111. 
Referring next to FIGS. 115 and 116, the operation of the pressure 
transducer system, which is the subject of the above-identified 
application entitled "Pressure Diaphragm for a Medication Infusion 
System," may be discussed. As may be seen, the pressure diaphragm 182 
contacts the bottom of the pressure transducer 660, which is flat. 
Additionally, the pressure diaphragm 182 does not contact the pressure 
plateau 130 either on the top or on the sides thereof, making the movement 
of the pressure diaphragm 182 highly accurate and sensitive. 
The pressure transducer 660 has a thin stainless steel diaphragm 710 at the 
bottom thereof. The diaphragm 71 is supported from the edges by a 
stainless steel housing 712, which housing 712 contains therein a 
passageway 714 leading to the square segment 664. The square segment 664 
contains a sensor element (not shown in detail) communicating with the 
passageway 714, which sensor element is a standard silicon piezoresistive 
wheatstone bridge type device 716. The passageway 714 is filled with 
silicone oil to communicate pressure on the diaphragm 710 to the silicon 
piezoresistive wheatstone bridge type device 716. 
It will be appreciated by those skilled in the art that the fluid pressure 
within the assembled cassette 302 will be communicated through the 
pressure diaphragm 182 and the diaphragm 710 to the silicone oil in the 
passageway 714, and thereby to the silicon piezoresistive wheatstone 
bridge type device 716, which provides an electrical indication of 
pressure on the leads 666. Accordingly, pressure may be measured to 
provide an indication of downstream occlusion, pumping, fluid pressure, 
etc. 
Through the above discussion of the entire system, it is apparent that the 
system of the present invention provides a disposable cassette with a 
plurality of optical identifying bits and a main pump unit having 
apparatus for reading the identifying bits contained on the disposable 
cassette. The disposable cassette of the present invention is of an 
advanced design retaining all of the advantages of such devices known in 
the past, and includes the identifying bits in an integral fashion in the 
construction of the cassette. The main pump unit contains an optical 
sensor module which reads the identifying bits on a disposable cassette 
installed onto the main pump unit. The process is fully automatic, and 
requires absolutely no user input. The possibility of user error in 
indicating to the main pump unit what types of cassettes are installed on 
the main pump unit is thereby avoided. 
With three identification bits, eight different cassettes are identifiable 
by the system, and even with a redundant system being used to minimize the 
possibility of errors being made, three different cassettes may be 
identified. The inclusion of the identifying indicia on the disposable 
cassette is accomplished in a fashion minimizing the cost of including the 
indicia while maximizing the reliability of the system. A minimum number 
of parts are utilized in the construction of the cassette, all of which 
parts are of inexpensive construction, yet which afford the assembled 
cassette a high degree of accuracy. 
The cassette used with the present invention is therefor of a design which 
enables it to compete economically with known competing systems. The 
transducer contained in the main pump unit, while of economical 
construction, yet exhibits both high reliability and accuracy of 
operation, and is also quite durable. The system provides an ease of use 
rivaling the best of such competing systems, and accomplishes all of the 
above objects in a manner which retains the advantages of reliability, 
durability, and safety of operation. The cassette identification system of 
the present invention provides all of these advantages and overcomes the 
limitations of the background art without incurring any relative 
disadvantage, resulting in a superior medication infusion system which is 
a highly desirable alternative to systems presently available. 
Although an exemplary embodiment of the present invention has been shown 
and described, it will be apparent to those having ordinary skill in the 
art that a number of changes, modifications, or alterations to the 
invention as described herein may be made, none of which depart from the 
spirit of the present invention. All such changes, modifications, and 
alternations should therefore be seen as within the scope of the present 
invention.