Method and apparatus for power connection in a modular patient care system

A modular patient care system having a central management unit module and one or more detachable functional units is described. Using unique mechanical and electrical features, the modular patient care system is capable of flexibly, bilaterally, and safely providing electrical power from the central management unit to the attached functional units, with exposed power leads of end units being electrically isolated for safety and security. Functional units are capable of detecting the presence of other functional units more distant from the central management unit for passing power to those units, and for otherwise electrically isolating exposed power leads when no further units are attached. Additionally, the modular patient care system provides for a modular connection arrangement wherein modules are detachably connected to each other in a convenient, flexible, interchangeable, and secure manner by providing a hinge connector pair, a specially located latch mechanism, and a guide means between any pair of modules.

FIELD OF THE INVENTION

The present invention relates generally to modular patient care systems. More specifically, the present invention relates to modular connection arrangement wherein modules are detachably connected to each other in a convenient, flexible, interchangeable, and secure manner. Additionally, the present invention relates to a scheme for flexibly, bilaterally, and safely providing electrical power from a central management unit to attached peripheral units.

BACKGROUND OF THE INVENTION

Systems containing multiple infusion pumping units, sensing units such as blood pressure monitors and pulse oximeters, and other patient-care units are known in the medical field. For example, Kerns et al (U.S. Pat. No. 4,756,706; “Kerns”) discloses a centrally managed pump system in which pump and monitoring modules are selectively attached to a central management unit. The central management unit controls the internal setup and programming of the attached modules, and receives and displays information from them. Each module is capable of being detached from the central management unit except for the first module, which is permanently attached. Once attached and programmed, a module which is subsequently detached is still capable of operating independently of the management unit.

Kerns provides for attachment of the modules in a vertical stacking sequence in a manner similar to that shown in FIG.1. Attachment of an additional unit to the modular patient care system involves a multiple step process. These steps include (1) sliding a support plate62of the additional unit into the channel64of a previous unit, and (2) turning a knob120, causing male connectors122and124of the additional unit to pop up and mate with corresponding female portions in the previous unit (Kerns FIG.3and col. 4 lines 7-16). Thus, achieving mechanical and electrical connectivity in Kerns clearly involves a multi-step, two-handed operation.

Further, Kerns provides for distinct, direct electrical connectivity from each stack module to the central management unit. Each module is provided with a separate AC power signal from the central management unit AC+ and AC− leads. Each module also contains its own power supply for autonomous operation when disconnected from the central management unit (Kerns FIG.6).

Kerns has several disadvantages. First, for electrical and mechanical connectivity of an added unit to the central management unit, a multi-step, two-handed operation is needed, which may be cumbersome and time consuming in the medical environment. Second, because each module requires its own set of electrical paths to the central unit, the total number of modules which may be stacked is only one greater than the number of pass-through cables in each module. For example, for the pass-through structure shown in KernsFIG. 4f, only four modules total may be accommodated by a system which uses these modules. Third, there is added weight, cost, and complexity due to the multiple cabling structure. For example, each signal of each cable must have its own contact pin in among the pins122of the contact structure of Kerns FIG.3. Finally, the presence of a power supply in each functional module adds weight and cost.

Rubalcaba (U.S. Pat. No. 4,898,578) also discloses a drug infusion system which includes a plurality of infusion pump modules selectively attached to a central management unit so as to provide for centralized control. In particular, the central management unit obtains infusion parameters from the user and then performs calculations with the parameters to establish the desired infusion rate. Once this rate is determined, the central management unit may control the infusion accordingly. Rubalcaba, however, provides no solution for the problems related to electrical and mechanical connectivity of units described above with respect to Kerns.

Accordingly, it is an object of the present invention to provide a modular patient care system wherein modules are detachably connected to each other in a convenient, flexible, interchangeable, and secure manner.

It is another object of the present invention to provide a modular patient care system wherein each functional unit is powered by the central management unit using a common power bus scheme to avoid a multiplicity of power lines.

It is a further object to provide a flexible, bilateral power scheme wherein any functional unit may be placed anywhere in a linear array of units and be adequately powered. It is a further object of the present invention to make this powering scheme safe by avoiding active power supply voltages at exposed ends of the power bus.

SUMMARY OF THE INVENTION

These and other objects of the present invention are provided in a modular patient care system comprising an interface unit for providing a user interface to the system and for providing electrical power to at least one functional unit, the functional unit being capable of removable connection to the interface unit for providing patient therapies or monitoring the condition of the patient, the functional unit being for removable attachment to the interface unit or other functional units so as to form a linear array of units. The linear array of units comprises an originating end and a terminating end, and each unit has an originating side and a terminating side, the originating side of any unit being capable of removable connection to the terminating side of any other unit. In one embodiment, the originating side is the left side, and the terminating side is the right side of the linear array.

The interface unit according to the present invention has a left power lead for powering left side functional units and a right power lead for powering right side functional units. Power supply aspects of the left and right sides are substantially symmetric. Using the left side as an example, power supplying aspects of the interface unit are arranged so as to connect power to the left power lead when functional units are attached to the left, but to leave the left power lead electrically isolated when no functional units are attached to the left. This prevents the unsafe and insecure situation of a live voltage existing at an exposed left power lead of the linear array of units, which would be subject to shorting out or otherwise undesirably discharging. To accomplish this objective, the interface unit includes a power source for receiving electrical power from a power supply and providing electrical power, a detecting lead for detecting the presence of a right sense signal, such as a ground signal, from a unit attached to the left, means for coupling the power source to the left power lead in the presence of the right sense signal, and means for decoupling the power source from the left power lead in the absence of the right sense signal. In one embodiment, the detecting lead is connected to a gate of a field effect transistor, the power source is connected to a drain of the field effect transistor, and the left power lead is coupled to a source of the field effect transistor.

A flexible, bilateral, and safe powering scheme in the modular patient care system according to the present invention is also provided for by providing an exemplary functional unit having a left lead and a right lead, the left lead for contacting the right lead of a left adjacent functional unit or the right power lead of the left adjacent interface unit in the linear array, the right lead for contacting the left lead of a right adjacent functional unit in the linear array or the right power lead of the right adjacent interface unit in the linear array. The functional unit has a load unidirectionally coupled to the left and right leads and capable of receiving electrical power from either of the leads. The functional unit also has a right sense signal lead for providing a right sense signal to the adjacent right unit, if any, and a left detect lead for detecting the right sense signal from the adjacent left unit, if any. Further, the functional unit also has a left sense signal lead for providing a left sense signal to the adjacent left unit, if any, and a right detect lead for detecting the left sense signal from the adjacent right unit, if any. Finally, the functional unit comprises means for bidirectionally connecting the left power lead to the right power lead only upon detecting both left and right signals.

In this manner, a functional unit which is located between two other units in the linear array is capable of powering its load while also passing power, in either direction as needed, to the adjacent unit which is located farther away from the interface unit. However, if the functional unit is located at the left end of the linear array, the left power lead remains electrically isolated because no right sense signal is detected. Likewise, if the functional unit is located at the right end of the linear array, the right power lead remains electrically isolated because no left sense signal is detected. In this manner, the functional units are capable of flexible, bilateral power connection in the linear array of units, and live power contacts are prevented from existing at the leads located at the ends of the linear array of units for safety and security.

In another embodiment of the invention, a modular patient care system is provided having an interface module for providing a user interface to the system and at least one functional module capable of removable connection to the interface module. The functional module is for providing patient therapies or monitoring the patient's condition and is capable of removable attachment to the interface module or other functional modules so as to form a linear array of modules. The linear array of modules comprises an originating end and a terminating end, and each module has an originating side and a terminating side, the originating side of any module being capable of removable connection to the terminating side of any other module.

Physically, an exemplary functional module according to the present invention comprises a first portion grippable by a user and is configured and dimensioned so as to be capable of being held by a single hand of the user by gripping the first portion. Any pair of modules, including for example the interface module and the exemplary functional module, are easily, flexibly, and interchangeably coupled by including a hinge connector pair for allowing hingeable engagement of the pair, a latch mechanism for securing the pair together, and a guide mechanism located between the hinge connector pair and the latch mechanism for discouraging off-axis engagement of the modules and for providing mechanical stability to the engaged pair. The latch mechanism is designed to automatically secure the pair together, such that engagement of the modules takes place in a single-handed, single step operation, but is designed to require a manual operation by a hand separate from the hand gripping the first portion to unlatch the modules during disengagement. This provides for increased security and prevention of accidental disengagement of modules. Preferably, the latch mechanism springably couples together such that tactile feedback is provided to the user during attachment. An optional fastener for fastening the latching mechanism together may be included, which requires a special tool for unfastening the latching mechanism so as to further increase system security at the option of the user.

DETAILED DESCRIPTION OF THE INVENTION

The following embodiments of the present invention will be described in the context of a modular patient care system, although those skilled in the art would recognize that the disclosed methods and structures are readily adaptable for broader application. Note that whenever the same reference numeral is repeated with respect to different figures, it refers to the corresponding structure in each figure.

FIG. 1discloses a modular patient care system100in accordance with the present invention. Modular patient care system100comprises a plurality of modules or units, including interface unit102and functional units104, detachably coupled to each other to form a linear array. Shown inFIG. 1are exemplary functional units104A,104B,104C, and104D coupled to interface unit102. While four functional units are shown inFIG. 1, a modular patient care system in accordance with the present invention may comprise interface unit102coupled to only a single functional unit104, or may comprise interface unit102coupled to as many as “N” functional units104.

Interface unit102generally performs the functions of (1) providing a physical attachment of the system to structures such as IV poles and bedrails, (2) providing electrical power to the system, (3) providing an interface between the system and external devices, (4) providing a user interface to the system, and (5) providing overall system control, which includes providing information to and receiving information from functional units104. Shown inFIG. 1are certain user interface aspects of interface unit102, which may include an information display106, numerical hardkeys108, and softkeys110.

Functional units104are generally for providing patient therapies or monitoring responsive to information, at least some of which may be received from interface unit102. In many cases, functional units104are also for communicating information to interface unit102. For example, functional unit104A may be an infusion pump unit for delivering fluids to a patient responsive to certain commands received from interface unit102, while functional unit104B may be a blood pressure monitoring unit for providing patient blood pressure information to the interface unit102. The scope of the invention is not so limited, however.

In a preferred embodiment, each functional unit may have a SELECT key on the face of the unit. In order to provide increased safety, it is preferable that the system be designed such that selection of a particular functional unit requires that the SELECT key located on the functional unit be depressed in order to select that functional unit. This requirement will help insure that the proper functional unit is selected, in particular when infusion pump units are used for multiple drug infusions. When the desired functional unit is selected, display106of interface unit102is configured so as to act as the user interface for the selected functional unit. Preferably, display102is configured in accordance with a function specific domain to provide function specific displays and softkeys110as explained in greater detail in incorporated U.S. Pat. No. 5,713,856.

For the purposes of the present invention, the specific function of each individual functional unit104is not critical. Rather, the present invention is directed toward (1) the mechanical and electromechanical coupling of the functional units104to each other and to interface unit102, and (2) the electrical powering scheme of the modular patient care system100. Thus, for purposes of understanding the present invention, it is important only to recognize that functional units104(1) require means for detachably coupling to each other and to interface unit102, and (2) require electrical power.

In a preferred embodiment of the present invention, interface unit102and functional units104are laterally interchangeable. By laterally interchangeable, it is meant that the modules may be placed in any order in forming a linear array of modules. Thus, inFIG. 1, the modular patient care system100may instead have its modules ordered left-to-right in the sequence104C,102,104B,104D,104A without affecting its functionality. In order to be laterally interchangeable, the units102and104ofFIG. 1should have substantially identical interconnection features on their respective left sides, and should have corresponding substantially identical interconnection features on their right sides. If the units were instead for coupling in a vertical linear array, which is within the scope of the present invention, the interconnection features would have substantially identical interconnection features on their respective top sides, and would have corresponding substantially identical interconnection features on their bottom sides. For clarity of explanation, however, only a left-to-right physical arrangement is described.

To achieve the lateral interchangeability described above, each of the units102and104should also have power, unit detection, and communication circuitry which is complementary. By complementary, it is meant that the units102and104generally have power, unit detection, and communications circuit contacts on a first side and on a second side, and that the first side contacts of one unit may be connected to corresponding second side contacts of any other unit, with the overall linear array of units comprising modular patient care system100being fully operational. InFIG. 1, for example, the first side of a unit is the left side, and the second side of a unit is the right side. Further to this example, and as further explained later, functional unit104C must be capable of receiving electrical power from interface unit102to its left and transferring it to unit104D to its right; yet, if physically interchanged with functional unit104B, unit104C must be capable of receiving electrical power from interface unit102to its right and transferring it to unit104A to its left, and so on.

As shown inFIG. 1, each functional unit104may include a unit ID indicator112which identifies a logical address of the functional unit within the linear array. The logical address of a functional unit104indicates its position in the linear array relative to other functional units104. The logical address of a functional unit104, such as unit104B, is used by the interface unit102to identify and uniquely communicate with functional unit104B in a common communications bus environment to be described later. In a preferred embodiment of the invention, the logical address of a functional unit corresponds to its sequential position in the linear array of functional units. Thus, the system shown inFIG. 1may illustratively contain functional units104A-104D with logical addresses A, B, C, and D, ordered left to right. In this embodiment, the left side of the leftmost unit forms an originating end of the linear array, while the right side of the rightmost unit forms a terminating end of the linear array.

Referring now toFIGS. 2 through 4, the mechanical and electromechanical aspects of interface unit102and functional units104as designed in accordance with a first embodiment of the present invention are now described. For purposes of the first embodiment of the present invention, interconnection features of interface unit102are substantially identical to interconnection features of functional units104. Therefore, only an exemplary unit104A will be described. Also, an exemplary unit104B, substantially identical to unit104A and for connecting thereto, will be described when needed for clarity.

FIG. 2shows an oblique representation of exemplary units104A and104B positioned before being matably connected, whileFIGS. 3aand3bshow appropriate cut-away views of units104A and104B during and after the connection process, respectively.

As shown inFIG. 2, unit104A comprises a chassis200having a left side202, a front204, and a right side206. It is to be appreciated that althoughFIG. 2shows numbered components on units104A and104B according to their visibility in the oblique drawing, the units104A and104B contain substantially identical numbered components. Unit104A further comprises a male connector portion208on right side206, a female connector portion210on left side202, a male elevation feature212formed on right side206, a female recess feature214formed in left side202, a catch feature216formed near the bottom of right side206, and a latch218near the bottom of left side202. Unit104A further comprises cover220tethered to male connector portion208for covering the male connector portion208during periods of non-use, and pocket222formed in right side206near male connector portion208for receiving cover220otherwise. Unit104A further comprises cover224tethered to female connector portion210for covering female connector portion210during periods of non-use, and pocket226formed in left side202near female connector portion210for receiving cover220otherwise.

Generally, as shown inFIGS. 3aand3b, units104A and104B are designed to be connected using the steps of (1) tilting the units relative to each other while inserting male connector portion208into female connector portion210, (2) swinging down the units to a nearly parallel position such that male elevation feature212is received into female recess feature214and latch218is received into catch feature216, and (3) pressing the units together such that latch218is locked into catch feature216.

Male connector portion208of unit104A is positioned and formed for hingeable connection with female connector portion210of unit104B for achieving mechanical and electrical coupling of units104and105. In a preferred embodiment of the invention, male connector portion208and female connector portion210also form a 15-pin electrical connector pair for electrically coupling. This electrical connector pair is for electrically coupling electronic components contained in units104A and104B, these electronic components being shown generally as elements300inFIGS. 3aand3b. The geometry of male connector portion208and female connector portion210include lead-in and chamfer to reduce the probability of dropping and off-axis insertion. Advantageously, the geometry of the male-female pair is designed to prevent a unit from falling off if it is hooked but not yet latched. The mechanical characteristics of the male-female pair are detailed in U.S. patent application Ser. No. 08/403,502, cross-referenced above.

Male elevation feature212is formed on right side206of unit104A for mating with female recess feature214formed in left side202of unit104B to provide multiple contact surfaces for improved front to back stability during vibration of the connected units. Further, the geometry of male elevation feature212includes lead-in and chamfer for mechanical guidance into recess feature214such that the probability of off-axis insertion is reduced.

Latch218is for engaging a catch feature216during connection. This keeps the units together mechanically after attachment. In a preferred embodiment, latch218is spring loaded with a pre-load force sufficient to positively engage the catch feature216, close, and remain latched unless disengaged by an operator. Also in a preferred embodiment, techniques known in the art may be used to shape latch218and catch feature216such that a small vibration resonates through units104A and104B upon attachment, to provide tactile feedback to the user.

Cover220is for covering male connector portions208during transport and periods of non-use. In a preferred embodiment of the invention, cover220is made of an elastomeric material which is elastic and waterproof. Cover220is tethered to male connector portion208to reduce the possibility of being lost or misplaced by the user, and is dimensioned and configured to be swung up and over male hook feature208for protection. Pocket222is formed in right side206beneath male connector portion208for receiving cover220, which nests into pocket224when not in use. Cover220may be swung up out of pocket222to cover male connector portion208to protect connector portion208from dust or fluids. Similar purpose, material, and configurations apply to cover224and pocket226. Advantageously, the covers220and224and pockets222and226are configured and dimensioned such that the covers recess flush yet are partially compressed when the units104A and104B are attached, thus providing additional shock cushioning and preventing rattling during vibration or transport.

In a preferred embodiment of the invention, the size and geometry of unit104A is generally such that it may be held by a single hand of a user, although the invention is not necessarily so limited. This is generally the same user hand which receives the tactile feedback described above upon unit attachment.

FIG. 4shows a view of unit104A exploded to more succinctly show male connector portion208and female connector portion210with respect to a preferred embodiment of the invention. Specifically, male connector portion208comprises electrical contacts400contained on a curved lip404formed on a body portion406. Further, female connector portion210comprises electrical contacts408protruding into an aperture410formed in body portion412. In a preferred embodiment of the invention, the contact geometry and orientation of electrical contacts400and408may allow a first set of individual electrical contact pairs formed by joining the connectors to make electrical connection prior to a second set of electrical contacts during connection. A result of this geometry and orientation will be that the first set of contacts will also break after the second set of contacts during disconnection. This ensures, for example, that an electrical ground connection between the units may made first during module attachment, creating a path to dissipate electrostatic discharge.

Also in a preferred embodiment of the invention, body portions406and412are made of a low surface energy/hydrophobic material to shed fluid from exposed surfaces. Also, an a preferred embodiment the electrical contacts400and408are insert-molded into body portions406and412, which prevents extraneous fluids from accumulating adjacent to electrical connections.

FIGS. 5A and 5Bshow units104A and104B with additional features in accordance with a preferred embodiment of the invention.FIG. 5Ashows a bottom view of coupled units104A and104B. Unit104B comprises latch218for engaging catch feature216of unit104A. In this embodiment however, a fastener500may be employed to provide a means for making the attachment of units104A and104B permanent until the fastener500is released by a user using a releasing technique. This releasing technique may employ the use of a special tool (not shown) made available only to specified users.FIG. 5Bshows a side view of latch218engaged to catch feature216, further showing a latch tongue502of latch218which forms a hole504in an area which overlaps catch feature216. Fastener500which is, for example, a screw, is inserted from the bottom of functional unit104A near catch feature216through hole504and into a boss506contained in functional unit104A near catch feature216. The configuration shown advantageously provides for permanent attachment of the units until a user such as a medical technician disengages fastener500. In this manner, for example, miscellaneous persons around and in the area of the modular patient care system100are prevented either from intentionally or accidentally causing disconnection of units.

The unique combination of the module elements described thus far provide for many advantages in stability, safety, security, and ease of use. For example, the attachment of a functional unit may be achieved in a one hand, single step operation, while the presence of latch218and catch feature216dictate that detachment must take place in a two step operation. This is advantageous in a medical environment where quick, easy attachment of units to the linear array may be necessary, but where detachment of units should be permissible only upon an explicit, reasoned desire of a user and not by accident. This feature is enhanced an a preferred embodiment of the invention employing a fastener500, wherein further steps are needed to detach modules.

Further, the ease of the one-handed, single step operation in the attachment of units is enhanced where latch218and catch feature216provide for tactile feedback during the attachment operation. This is advantageous in the medical environment by freeing up the eyes of the user during attachment to pay attention to more sensitive events taking place, such as insuring that needles, lines, fluids, or pumps are not being disturbed during the mechanical movement. Further, the avoidance of the need for visual feedback to the user may save precious moments during medical emergencies when the user's eyes are more advantageously averted to the emergency at hand.

Even further, the presence of male elevation feature212mated to recess feature214provides for additional front to back stability of the units during handling and abuse. These features also provide guidance during connection to prevent off-axis insertion. Vibration of coupled units is further reduced by the compression of covers220and224against each other and pockets222and226.

Even further, several means exist to protect the electrical connections from fluid ingress when units are not connected. First, the contact geometry, contact orientation, and hook geometry as shown inFIG. 4prevent fluid from accumulating on surfaces of the male connector portion208. Similarly, the contact geometry, contact orientation, and contact location of the electrical contacts408prevent fluid from accumulating on surfaces of the female connector portion210. Use of low surface energy/hydrophobic material for body portions406and412, insert-molding of the contacts400and408, and the presence of covers220and224further discourage unwanted fluid accumulation and ingress.

In the modular patient care system100ofFIG. 1, electrical power is supplied to functional modules104by interface unit102. The interface unit102, in turn, may be powered by conventional methods known in the art. At least one electrical power path exists among the electrical contacts408and400at the connecting point of any two units.

The goal of a module powering system designed in accordance with the present invention is, first, for interface unit102to provide power to any attached module or set of modules by powering immediately adjacent modules. Thus, inFIG. 1, interface unit102is to supply electrical power to all functional units104by powering functional units104B and104C, which each use a portion of this power and which, in turn, transfer at least a portion of this power further down the line to units104A and104D, respectively.

Second, the module powering system in accordance with the present invention is to permit lateral interchangeability of the modules, and thus the powering system of any functional unit104is to be bilateral. By bilateral, it is meant that the functional unit104may receive power from either its first or second side, and may transmit this power, if necessary, to attached units on its second or first side, respectively.

Third, it has been found that a module powering system according to the present invention is to comprise an interface unit102and functional units104which, if they are positioned on the originating or terminating end of a linear array, do not allow a live voltage to exist at the open electrical contacts which will exist at these ends. Such a requirement provides, for example, for added security of the unit from power failure due to accidental or intentional shorting of the exposed power leads.

Turning now toFIGS. 6 through 8, a module powering system according to a second embodiment of the present invention is described.FIG. 6shows a functional diagram of the power aspects of interface unit102designed in accordance with the present invention. Interface unit102comprises a microprocessor600, a power source602, a left transistor604, and a right transistor606. Power source602is adapted for providing an 8-volt DC voltage by either generating its own power, as from a DC voltage source such as an internal battery, or for adapting power from an external AC or DC source, as is known in the art. The 8 volts DC provided by power source602is provided by lead607with respect to the ground plane of interface unit102, denoted generally by element608in FIG.6. Interface unit102further comprises left and right power leads610and612, respectively, for coupling to and providing power to left and right adjacent functional units, respectively, when connected. Power leads610and/or612will be left open, however, when adjacent units are not connected. Interface unit102further comprises left and right module detect leads614and616, respectively, for detecting the presence of attached functional units on the left and right sides, respectively. Interface unit102further comprises ground leads618to620for providing left and right sense signals, respectively (which in this embodiment are ground signals) to adjacently attached units. It is noted that additional electrical contacts not shown may provide an overall ground plane signal to attached functional units, as is known in the art.

As shown inFIG. 6, lead607of power source602is coupled to the source of left transistor604and also to the source of right transistor606. In the embodiment shown, transistors604and606are, in this embodiment, P-channel enhancement MOSFETS. The gate of left transistor604is coupled to left module detect lead614, while the gate of right transistor606is coupled to right module detect lead616. Finally, the drain of left transistor604is coupled to left power lead610, while the drain of right transistor606is coupled to right power lead612.

As shown inFIG. 6, transistor604will conduct (i.e., create a “short” between its drain and source) when its gate is low with respect to the source, and will not conduct (i.e., create an “open”) when its gate is high. Transistor606behaves similarly. Thus, if left module detect lead614is grounded by attachment to an external signal, such as a signal provided by an attached functional unit to the left, transistor604will conduct, and thus power lead610will be coupled to power source lead607to provide power. When left module detect lead614is left open, as when a unit is not attached to the left, transistor604does not conduct and leaves power lead610electrically isolated from power source lead607. This, of course, is a desired result. Similar characteristics exist for right module detect lead616, transistor606, and right power lead612.

It is noted that the coupling of the left module detect lead614to microprocessor600at pin MODDETL shown inFIG. 6does not affect the powering aspects described here, as pin MODDETL is only for detection purposes of the microprocessor for purposes to be described later. A similar note applies to right module detect lead616and pin MODDETR of microprocessor600. Finally, it is noted that Schottky diodes626and628are provided across the drain and source of transistors604and606, respectively, for protection against reverse voltages, as is known in the art.

FIG. 7shows a functional diagram of the power aspects of an exemplary functional unit104A designed in accordance with the present invention. Functional unit104A comprises a microprocessor700and a load702such as an infusion pump motor. It is noted that load702may represent any kind of electrical system requiring power, however. Functional unit104A further comprises a left transistor704and a right transistor706. Load702receives electrical power provided between an input node707and a ground plane, generally denoted by element708in FIG.7. Functional unit104A further comprises a left power lead710, a right power lead712, a left module detect lead714, a right module detect lead716, a left ground lead718, and a right ground lead720.

As shown inFIG. 7, the drain of left transistor704is coupled to the drain of right transistor706. Transistors704and706are, in this embodiment, P-channel enhancement MOSFETS. The source of left transistor704is coupled to left power lead710, while the source of right transistor706is coupled to right power lead712. Left power lead710is also coupled through a resistor722to the left module detect lead714, which is in turn coupled directly to the gate of right transistor706. Correspondingly, right power lead712is coupled through a resistor724to the right module detect lead716, which is in turn coupled directly to the gate of left transistor704. Left power lead710is coupled to the cathode of a diode726whose anode is in turn coupled to input node707of load702. Likewise, right power lead712is coupled to the cathode of a diode728whose anode is in turn coupled to the input node707of load702. In this manner, if a positive power voltage is present at lead710, power is supplied to load702without being supplied to lead712unless both transistors704and706are conductive. Likewise, if a positive power voltage is present at lead712, power is supplied to load702without being supplied to lead710unless both transistors704and706are conductive.

As shown inFIG. 7, transistor704will conduct (i.e., create a “short” between its drain and source) when its gate is low with respect to the source, and will not conduct (i.e., create an “open”) when its gate is high. Transistor706behaves similarly. The gate of transistor704will be forced low when right module detect lead716is grounded by an adjacent attached unit to the right. Correspondingly, the gate of transistor706will be forced low when left detect lead714is grounded by an adjacent attached unit to the left. It is noted that Schottky diodes730and732are provided across the drain and source of transistors704and706, respectively, for protection against reverse voltages, as is known in the art. It is noted that, as described above and as shown inFIG. 7, module104A forms a laterally symmetric powering arrangement.

As described herein, a modular patient care system100comprising the interface unit of FIG.6and functional modules according toFIG. 7advantageously provides for bilateral power sourcing and transfer through the functional modules104, while providing electrical isolation of power leads of units at the originating and terminating ends, respectively.

FIG. 8shows the modules of FIG.6andFIG. 7arranged in an exemplary arrangement comprising functional unit104A at the originating (left) end, functional unit104D at the terminating (right) end, and units104B,102, and104C in the middle, respectively. As shown inFIG. 8, the electrical leads between units are arranged according to the following simple scheme. Left power leads (610or710) are coupled to right power leads (712or612) in any pair of adjacent units. Left module detect leads (714or614) are coupled to right ground leads (620or720) in any pair of adjacent units. Finally, left ground leads (618or718) are coupled to right module detect leads (716or616) in any pair of adjacent units.

Serving as an example of a system according to the present embodiment of the present invention, the powering configuration of the modular patient care system100shown inFIG. 8advantageously functions as follows.

Looking to the left of interface unit102, lead720of unit104B grounds the gate of left transistor704of unit102via module detect lead614. Transistor604is turned on, and power is thus supplied through left power lead610of unit102to right power lead712of unit104B, thus powering the load702of unit104B. Left ground lead618of unit102grounds the gate of left transistor704of unit104B through right module detect lead716, making transistor704conductive. Further, right ground lead720of unit104A grounds the gate of right transistor706of unit104B, making transistor706conductive. The result is that both of transistors704and706of unit104B are conductive, and thus power lead712of unit104A will receive power from left power lead710of unit104B. Therefore, load702of unit104A will be powered, and thus left side units104A and104B are fully powered.

However, there is no ground signal provided to left module detect lead714of unit104A because it is the leftmost unit. Thus, right transistor706of unit104A remains turned off. The result is that left power lead710of leftmost unit104A is electrically isolated from right power lead712, which is the desired result. It should be clear to anyone of ordinary skill on the art, given the lateral symmetry of the powering arrangement described above, that right side units104C and104D operate in a similar but reflexive fashion to the left side units104A and104B. Thus, power is provided to both units104C and104D, but right power lead712of rightmost unit104D remains electrically isolated from a power source. This, of course, is the desired result.

Additionally, it should be clear to anyone of ordinary skill in the art that the units102and104A through104D can be arranged in any order inFIG. 8with the desired result of (1) powering of all units, (2) electrical isolation of the left power leads710or610of the leftmost (originating) unit, and (3) electrical isolation of the right power leads712or612of the rightmost (terminating) unit.

Various embodiments of the invention have been described. The descriptions are intended to be illustrative, not limitative. Thus, it will be apparent to those skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.