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ELECTRICAL INTERFACE FOR A PORTABLE ELECTRONIC PHYSIOLOGICAL INSTRUMENT HAVING SEPARABLE COMPONENTS
FIELD OF THE INVENTION
This invention generally relates to portable electronic physiological instruments, and more particularly to an improved electrical interface for linking portable physi- 10 ological instruments having separable first and second components.
BACKGROUND OF THE INVENTION
A well equipped emergency medical technician (EMT) typically carries a portable defibrillator/monitor which allows the EMT to monitor or defibrillate a patient's heart. Several alternative constructions have been adopted by manufacturers of portable physiological units. The assignee of the current invention, Physio-Control Corporation of Redmond, Wash., has adopted a portable construction wherein the physiological unit has two components, an ECG monitor and a defibrillator. Such a construction is described in U.S. Pat. No. 4,096,856 titled "Portable Electronic Physiological Instrument Having Separable First and Second 25 Components, and Improved Mechanical Connector Therefor" (herein incorporated by reference). In U.S. Pat. No. 4,096,856, a physiological instrument was disclosed that had first and second components that could be coupled together by sliding a grooved member located on one of the components onto a tongue member located on the other component. The tongue-and-groove construction allowed the two components to be mechanically attached together. When defibrillation and monitoring was required, both components could therefore be carded to the scene of an accident. When 35 only monitoring was to be performed, however, the units could be separated, and only the monitor used. This con- struction has proved to be reliable and intuitive to use, and has gained wide-spread acceptance among emergency medi cal technicians.
While the tongue-and-groove mechanical connection of a defibrillator and monitor has proven to be a very flexible and successful design, there are still some disadvantages to connecting portable physiological devices in this manner. 45 One of the problems presented by connecting two components with a sliding connector was designing an electrical connection that would allow the units to function cooperatively, such as by exchange of data or timing and control signals. 50
U.S. Pat. No. 4,097,113 to McKelvy titled "Electrical Connectors for Portable Electronic Physiological Instruments Having Separable First and Second Components" disclosed an electrical connector that was developed for interfacing a first and second component that were joined by 55 a sliding tongue-and-groove (herein incorporated by reference). The electrical connector disclosed in McKelvy is constructed with opposing sets of leaf spring contacts, each set being wrapped around a central contact support member on the respective component. When the components were go slid relative to each other to make the mechanical connection, the sets of electrical contacts were brought into engagement with each other. This allowed power and other signals to be transmitted between the defibrillator and the monitor.
While the electrical interface disclosed in McKelvy was 65 sufficient for early defibrillators and monitors, its shortcomings arose as monitors and defibrillators became more
complex. Most problematic was that the McKelvy connector was only able to provide limited communication capacity between the monitor and the defibrillator. As monitors and defibrillators offering more complex functions were considered, it became desirable to pass additional control information and signals between the two components. The McKelvy design, while reliable and sturdy, is limited with respect to the number of communication lines provided, and also is a custom connection not adapted for use with commercially available multipurpose interfaces.
SUMMARY OF THE INVENTION
The present invention provides a novel electrical interface for electrically connecting separable components of a portable physiological instrument that are joined by a tongueand-groove mechanical interface. The electrical interface allows a standard connector on one component to be automatically aligned and connected with a matching connector on a second component as the components are slid together. The interface comprises a floating plug assembly mounted on one of the components and a corresponding socket constructed in the other component. The floating plug assembly includes two guide fingers that extend substantially parallel with the path that a connector on the plug assembly must travel in order to mate with a complementary connector located in the socket. The socket constructed in the second component has a set of guiding surfaces formed by the walls of the socket. The guiding surfaces are designed to capture the guide fingers of the plug assembly, and direct the motion of the plug assembly so that its connector automatically mates precisely with the socket connector.
Three levels of alignment are therefore provided by the electrical interface. A gross alignment is based on the mechanical interface between the first and second components. As the two components are slid together, the tongueand-groove mechanical connection orients the connectors along substantially the same line.
An intermediate alignment is provided as the fingers of the plug assembly carrying one part of the connector are brought into contact with the guiding surfaces formed in the socket. As the first component is slid into the second component, the plug assembly is shifted into more precise alignment with the socket. The guiding surfaces form grooves that are broad at the point where the fingers first come into contact with the grooves, and taper until they are approximately the same width as the fingers. The broad width of the grooves at their start allows the fingers to be captured even if the plug assembly is slightly misaligned. As the two components are slid farther together, the plug assembly is shifted toward the socket connector by the fingers which travel down the set of grooves. When the grooves have narrowed to the size of the fingers, the plug assembly is properly oriented, and the connectors are nearly in contact.
The final precise alignment is provided by guide pegs and holes on the connectors themselves. The guide pegs and holes ensure that the contact pins in one connector accurately fit in the contact sleeves of the other connector without bending. When the two components of the portable physiological unit have been fully mated, the plug assembly connector will have been accurately guided into connection with the socket connector.
It will be appreciated that the above electrical interface offers many advantages over prior designs. Most importantly, the improved electrical interface greatly expands the
communication capability between the two components, while keeping the advantages afforded by the tongue-andgroove mechanical connection in a portable physiological unit. The new connector allows multiple data or power lines to be used to couple a defibrillator to a monitor. 5
It is a further advantage of this interface that the use of grooves and guide fingers to accurately guide one of the connectors into the other connector ensures that the connectors will not be damaged during insertion. An unskilled user may quickly and easily slide the first component into the 10 second component in order to make both the electrical and mechanical connections. The two connectors are brought into contact with each other automatically and with the correct orientation. This prevents damage to the connectors or their mountings. 15
It is also an advantage that both connectors are enclosed when the components are mated. It is therefore nearly impossible to inadvertently come in contact with them.
Finally, it will be appreciated that the above construction allows for manufacturing inaccuracies or less-than-perfect 20 tolerances in the fit between the first component and the second component. The use of a floating plug assembly ensures that even if the components are slightly misaligned as they are being slid together, the connectors will be accurately joined as the plug assembly is guided to the 2S proper orientation by the guides of the second component. This allows the portable physiological units to be constructed inexpensively, since close tolerances do not have to be maintained.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction 35 with the accompanying drawings, wherein:
FIG. 1 is a top front perspective of a portable monitor in the process of being connected to an auxiliary component using a tongue-and-groove mechanical interface, the monitor and auxiliary component having an electrical interface in 40 accordance with the present invention;
FIG. 2 is a top rear perspective of the monitor and the auxiliary component of FIG. 1;
FIG. 3 is an enlarged, fragmentary, rear perspective of a plug assembly and a socket forming the preferred electrical 45 interface between the monitor and the auxiliary component;
FIG. 4 is a side elevation of the monitor and the auxiliary component, with the parts broken away to reveal the plug assembly and socket as they are brought together; and
FIG. 5 is a side elevation corresponding to FIG. 4, but 50 with the monitor and auxiliary component in different positions.
FIG. 1 shows a two-component portable physiological instrument having the novel electrical interface of the present invention. The first component, monitor 20, is a portable electrocardiogram (ECG) monitor/recorder which allows an EMT to record an electrocardiogram of a patient at an accident site. Monitor 20 includes a carrying handle 22 and a LCD display 24 for displaying the electrocardiogram of the patient. The electrocardiogram is taken by connecting a set of electrodes to a connector 26 located on the upper surface of monitor 20. Monitor 20 is an entirely self- 65 contained unit, having a central processing unit, memory, and associated battery packs to operate the device. Portable
ECG monitors/recorders are well known in the art, having been in existence since the late 1960s.
An auxiliary component 28 can be connected to monitor 20. The auxiliary component may perform a number of different functions which complement the operation of monitor 20. For example, the auxiliary component 28 can act as a data storage device to record electrocardiograms that have been taken from patients at accident sites. Alternatively, the auxiliary component 28 could be used to provide a communication link from the monitor 20 to other devices. The communication link may involve the transmission of an ECG over a land line connection, or via a cellular network using a cellular modem. Yet another function auxiliary component 28 could perform is as a unit for monitoring vital signs other than the patient's electrocardiogram. For example, the unit could be used to monitor a patient's SA02, End Tidal C02, or NIBP. Those skilled in the art will recognize that there are a variety of other uses for an auxiliary component that is attached to a portable monitor.
In order to function as a whole, however, auxiliary component 28 must be electrically mated with monitor 20. For convenience, the two components should also be mechanically mated. The mechanical interface ensures that the monitor and the auxiliary component may be transported as a single unit. The mechanical interface must therefore be strong, reliable, and easy to use. The electrical interface allows the two units to exchange data, and to provide other necessary signals such as power or control information. The electrical interface must also be strong, reliable, and easy to use. Unless the mechanical and electrical interfaces meet all of the above criteria, the monitor/auxiliary component instrument will not be truly portable.
As shown in FIG. 1, the mechanical interface between auxiliary component 28 and monitor 20 is a tongue-andgroove system. Those skilled in the art will recognize that the tongue-and-groove system used to connect the monitor with the auxiliary component is essentially that disclosed in U.S. Pat. No. 4,096,856 entitled "Portable Electronic Physiological Instrument Having Separable First and Second Components, an Improved Mechanical Connection Therefor" which is expressly incorporated by reference herein. While the tongue-and-groove system disclosed in that patent has been slightly modified to provide for a slightly broader tongue member, the construction is generally the same. Consequently, the patent should be consulted if more detail is desired than that provided herein.
A tongue member 32 is formed on the left side of the housing of monitor 20. The tongue member 32 has an upper tongue 34 projecting toward the upper surface of the monitor and spaced outward from the adjacent sidewall of the monitor housing. Similarly, tongue member 32 has on its lower extremity a bottom tongue (not shown) projecting toward the bottom surface of the monitor, in vertical alignment with upper tongue 34. Each tongue extends substantially the entire length of monitor 20, and is generally parallel with the adjacent wall of the monitor housing. A notch 36 is provided in upper tongue 34 near the front of the monitor for receiving a nose portion of a swinging latch 40. The top edge of upper tongue 34 terminates in a downwardly sloping surface located adjacent to the rear of monitor 20. Likewise, the bottom edge of the bottom tongue terminates in an upwardly sloping surface located adjacent to the rear of the monitor.
Formed in the fight side of the housing of auxiliary component 28 is an upper angle flange 38, toward the top of the auxiliary component, and a lower angle flange (not shown), toward the bottom surface of the auxiliary component. The angle flanges define grooves opening toward each other for receiving the corresponding tongues of monitor 20. That is, the upper angle flange 38 hooks over the top of
upper tongue 34 on monitor 20, and the lower angle flange fits around the bottom margin of the lower tongue. The flanges and the tongues are complementary in configuration and lie in close proximity to each other when the tongues are inserted into the corresponding grooves. 5
Auxiliary component 28 is brought into mechanical connection with monitor 20 by translating the auxiliary component from the back to the front of the monitor. The angle flanges slide along the tongues as the parts are connected. The motion required to attach the auxiliary component to the monitor must be substantially linear and parallel to the left 10 side of the monitor. For the purposes of this description, the linear path that the auxiliary component must be moved in order to engage the auxiliary component with the monitor will be referred to as the "engagement path." FIG. 1 shows the components in the process of being connected. 15
When the front edge of the upper flange 38 on auxiliary component 28 has slid almost the entire length of the monitor, it comes into contact with a substantially vertically extending stop member 42. The stop member ensures that auxiliary component 28 will not slide beyond the forward- 20 most position it is to reach in relationship with monitor 20. When auxiliary component 28 has reached the front of the unit, latch 40 automatically swings in a direction to latch the two units together. Latch 40 is biased by a torsion spring, not shown, which rotates the latch into a position where a nose portion of the latch is inserted into notch 36. This prevents 25 auxiliary component 28 from sliding further to the front of the monitor and also prevents the auxiliary component from inadvertently sliding off the rear of the monitor.
Those skilled in the art will recognize that the mechanism for connecting auxiliary component 28 with monitor 20 is 30 that disclosed in U.S. Pat. No. 4,096,856. The tongue-andgroove connection used to connect auxiliary component 28 is, however, slightly wider to accommodate the electrical interface in accordance with the present invention which is located at the rear of the unit. 35
FIG.2 shows the rear of monitor 20 and the rear of auxiliary component 28, so that the mechanical linkage between the monitor and the auxiliary component can be seen with additional detail. For example, upper angle flange 38 is shown partially cut away so that the internal structure 40 of the member can be seen. The upper flange has two short arms which protrude downward from the horizontal upper portion of the flange. A first arm 46a is positioned so that the groove formed between first arm 46a and the exterior right side of the housing of auxiliary component 28 is sized to 45 receive the upper tongue 34 of monitor 20. A second arm 46b protrudes downward from the outer edge of the horizontal upper portion of the flange. Second arm 46b is positioned so that the distance between the outer upright face of second arm 46b and the inner upright face of first arm 46a is slightly less than the transverse width of a trough 44 formed by the space between upper tongue 34 and the adjacent wall of the monitor housing. The first and second arms extend the length of the upper angle flange 38, and guide the auxiliary component as it is mated with the monitor.
A similar connection is made between the auxiliary com- 55 ponent and the monitor by a lower angle flange 48. The lower flange has a first arm 50a and a second arm 50b which protrude upward in alignment with arms 46a and 46Z>, respectively. The first and second arms ride in a lower trough formed in tongue member 32. Auxiliary component 28 is 60 attached to monitor 20 by positioning the auxiliary component as shown in FIG. 2 and pulling on the auxiliary component handle toward the front of monitor 20.
As the monitor and the auxiliary component are mechanically mated, an electrical connection between the compo- 65 nents must be made in order for the auxiliary component to interact with the monitor. FIG. 2 provides a perspective view
of the electrical interface. Tongue member 32 on monitor 20 is formed with a socket 60 opening toward the rear of the monitor. Socket 60 is integrally formed with the housing of monitor 20 and has a floor, ceiling, and left, right, and rear walls. Located within socket 60 is a first connector 62. Such first electrical connector is fixedly mounted to the rear wall of socket 60 and oriented so that the connection face of the connector is generally oriented toward the rear of the monitor.
On the auxiliary component, a plug assembly 64 is located between upper flange 38 and lower flange 48. As will be described in further detail below, plug assembly 64 is loosely mounted to the housing of the auxiliary component. A second connector 66 is fixedly attached to plug assembly 64. The second connector is oriented so that its connection face is generally pointing toward the front of auxiliary component 28. As the auxiliary component is mechanically mated with monitor 20, the plug assembly is inserted into socket 60. This causes first connector 62 to mate with second connector 66, linking the auxiliary component with the monitor electrically as well as mechanically.
FIG. 3 is a detailed view of the electrical interface between the monitor and the auxiliary component, including plug assembly 64 and socket 60. Plug assembly 64 includes a back plate 100, two guide fingers 102a and 102£» projecting forward from the back plate, and a body 110 joining the rear end portions of the fingers and mounting the second connector 66. The back plate is transversely oriented with respect to the engagement path and consists of a thin sheet of nonconducting material having an upper tab 106 and a lower tab 108. The black plate is also formed with a hole 101, which allows access to the rear of second connector 66. Nonconducting body 110 is integral with guide fingers 102a and 102b and back plate 100.
Each guide finger is aligned substantially parallel with the engagement path. The guide fingers are formed with vertical tongue portions 103a and 103fo, and horizontal stiffening portions 104a and 1Mb. Tongue portions 103a and 103b are sized to fit within complementary channels formed in socket 60. The leading edge of each tongue portion is slanted generally toward the center of the plug assembly to where the tongue portions meet the stiffening portions. Tapering the forward tips of the tongue portions ensures that the portions will be reliably and smoothly guided into the complementary socket channels. Stiffening portions 104a and 104b are provided to lend strength and rigidity to the corresponding tongue portions, and also to guide the plug assembly laterally. The forward edges of the stiffening portions are beveled inward to aid the insertion into the socket.
Second connector 66 is positioned between guide fingers 102a and 102b. The second connector is fixedly mounted to the body of plug assembly 64, and is oriented so that it faces the front of the auxiliary component.
Plug assembly 64 is held in auxiliary component 28 by a series of upper and lower braces that are constructed in the auxiliary component housing. As shown in FIG. 3, the lower tab 108 is sandwiched between a lower front brace 112a and a lower rear brace U2b. The fit is snug but not tight. This allows back plate 100 to move within the limited range between the lower front and rear braces. Similarly, an upper front brace 114a and an upper rear brace 114b are positioned, respectively, in front of and behind upper tab 106. The upper front and rear braces are spaced apart a distance that is slightly greater than the thickness of the upper tab. This allows upper tab 106 to move between the upper front and rear braces. Similarly, the back plate is sized to move vertically and laterally. By loosely mounting back plate 100 between the upper and lower braces, plug assembly 64 has a limited degree of freedom to move a small amount up or