Battery pack for medical instruments

Abstract: An battery pack (10) for the short term battery power operation of a medical instrument (12) such as an infusion pump. The battery pack (10) comprises a substantially closed and compact housing having one or more rechargeable batteries (40) inaccessibly encased therein, with the battery pack housing being mounted directly onto the casing (14) of the medical instrument. The batteries (40) are mounted on a base plate (32) beneath a foil shield (54) and a housing cap (64), both of which are attached to the base plate (32) in a manner precluding their nondestructive removal, thereby substantially preventing access to the batteries (40). The assembled battery pack housing includes seals (70) for preventing the passage of any gases discharged from the batteries (40) into the medical instrument casing (14), and further defines at least one vent for the passage of such gases to the exterior of the battery pack (10) and medical instrument.

Description: This invention relates generally to a battery pack for use in the short term battery powered operation of a medical instrument, such as an infusion pump of the type used to deliver elected fluids to a patient according to a prescribed time schedule. Modern medical treatment facilities employ a variety of relatively sophisticated electronic instruments in the course of patient diagnosis and treatment. As one common example, electronic fluid infusion instruments are commonly used for administering one or more selected medical fluids to a patient at a prescribed flow rate and time schedule. Such fluid infusion and other electronic equipment require a source of electrical power to maintain the medical instrument in the desired operational state. In this regard, such medical instruments are normally designed to operate on conventional mains AC power and include appropriate power cords for plug-in connection to a standard household power supply. Alternatively, in some cases, the medical instrument is designed to operate on a DC power supply which is obtained by connecting an appropriate transformer to a standard household power supply. In this latter case, medical instruments have been provided with internal transformers integrated directly into the instrument housing, or an external transformer adapted for direct plug-in connection to a power supply outlet. While electrically-powered instruments have significantly enhanced medical diagnosis and treatment, it is often necessary for an electronic instrument to be disconnected from its regular power source to permit patient and/or instrument movement from one location to another within a medical facility. In this regard, some medical instruments have been designed for relatively short term battery operation to accommodate continuous instrument operation as the patient and instrument are moved. In such devices, the battery power source has normally been integrated directly into the housing of the medical instrument, frequently in association with an on-board charger designed to maintain the battery source in a recharged state when the instrument is connected to the normal AC power supply. However, such arrangements have not safeguarded against unauthorised replacement of the battery source with cheaper and potentially inferior batteries. Moreover, such prior arrangements have not effectively isolated the electronic components of the medical instrument from the potentially explosive gases which are sometimes generated in the event of battery malfunction. There exists, therefore, a significant need for improvements in integrating a battery power source with a medical instrument for short term instrument operation, particularly where the battery source is easily accessible for replacement with fresh batteries, when necessary. Moreover, there exists a need for providing a high quality battery power source where the use of potentially inferior batteries is effectively prevented. Still further, there exists a need for providing a short term battery power source in a medical instrument, where the battery source is effectively isolated from the electronic components of the medical instrument. According to the invention, there is provided a battery pack for battery powered operation of an electronic medical instrument, the battery pack comprising: at least one battery; a battery pack housing; and conductor means for connecting the battery to the medical instrument, characterised in that an electrically conducting foil shield surrounds the battery, the conductor means extends from within the housing through an open port formed therein to the exterior of the housing, a sealing means seals the passage of the conductor means through the open port and the housing comprises first and second housing members connected to each other to enclose the battery and to prevent access to the battery without at least partial destruction of one of the housing members. Preferably, the conductor means extends from the housing through an open port formed therein to the exterior of the housing and sealing means for example a grommet are provided for sealing the passage of the conductor means through the open port. Preferably, the first and second housing members are interconnected by a plurality of spaced-apart welds. The battery pack preferably also includes a foil shield mounted onto one of the housing members and co-operating therewith to enclose the battery to prevent access to the battery with at least the partial destruction of the foil shield or the housing member. In a preferred embodiment, the housing members comprise a base plate and a housing cap, the battery is mounted on the base plate, the foil shield is mounted onto the base plate in a position covering the battery and the housing cap co-operating with the base plate to enclose the battery and the foil shield. Preferably, then, the foil shield and base plate co-operate to enclose the battery and to prevent access thereto without at least the partial destruction of the foil shield or the base plate. The battery pack preferably incorporates means for mounting the housing onto the medical instrument, the mounting preferably also providing a means for isolating the medical instrument from gases discharged from the battery. This may comprise at least one screw extending through a screw port formed in the battery pack and fastened into the medical instrument, the isolating means comprising a seal ring lining the screw port. Preferably, the foil shield is mounted onto the base plate by means of a pair of apertured tabs on the foil shield which receive a pair of stake posts on the base plate, the stake posts being deformable subsequent to receiving the tabs to attached the tabs permanently to the base plate. Preferably, the foil shield comprises a paper based shell with a conductive film thereon, the tabs of the foil shield being folded over so that the conductive film contacts the base plate when the foil shield is mounted onto the base plate, the base plate including metalised film for conductively connecting the foil shield to the medical instrument when the battery pack is mounted onto the medical instrument. Preferably, the housing cap and base plate co-operatively define at least one vent for venting gases discharged from the battery. The invention also extends to the combination of a medical instrument having an open-ended casing with electronic components therein, with a battery pack for the battery powered operation of the medical instrument, the battery pack comprising: a base plate having an open port formed therein and adapted for mounting onto the instrument casing to extend over an generally cover the open end of the casing at least one battery mounted on the opposite side of the base plate to the casing; conductor means for connecting the battery to the instrument; the conductor means extending through the open port in the base plate and including a first fitting for connection with a second fitting disposed within the casing; a seal member for sealing the passage of the conductor means through the open port formed in the base plate; a foil shield mounted on the base plate and co-operating therewith to enclose the battery and to prevent access thereto without at least the partial destruction of the shield or the base plate; a housing cap mounted on the base plate and co-operating therewith to enclose the battery and the foil shield and to prevent access thereto without at least the partial destruction of the cap or the base plate; and means for mounting the base plate onto the casing to extend over and generally cover the open end of the casing. Preferably, the means for mounting the base plate onto the casing comprises: at least one screw passing through aligned screw ports formed in the cap and the base plate, the screw being fastened into a threaded receptacle on the casing, and further comprising a seal ring seated within the screw port formed in the base plate. The invention also encompasses a method of making a battery pack for battery powered operation of an electronic medical instrument, the method comprising: mounting at least one battery on a base plate; mounting a foil shield onto the base plate in a position covering the battery; mounting a housing cap onto the base plate, the housing cap co-operating with the base plate to enclose the battery and the foil shield and to prevent access to the battery without at least the partial destruction of the housing cap or base plate; and connecting conductor means to the battery, the conductor means for use to supply power to the medical instrument. Thus, in accordance with the invention, an improved battery pack is provided for short term battery powered operation of a medical instrument such as an infusion pump or the like. The battery pack includes a compact battery pack housing having one or more rechargeable batteries mounted inaccessibly therein. The battery pack housing is adapted for relatively quick and easy mounting directly onto an associated medical instrument, and for simple connection of the rechargeable batteries to electronic components within the medical instrument. The inaccessible mounting of the batteries prevents tampering therewith and/or replacement thereof with potentially inferior batteries. In the preferred form of the invention, one or more rechargeable batteries are mounted securely onto a base plate. Conductors are appropriately connected to the batteries and are passed through a sealing grommet to a suitable connector adapted for mating with a mating connector within the medical instrument. A foil shield is mounted onto the base plate in a position covering the batteries, and in a permanent manner to prevent foil shield removal without its destruction. A housing cap is in turn mounted onto the base plate in a position covering a foil shield, and in a permanent manner to prevent cap and base plate separation without destruction of the battery pack housing. The battery pack housing assembled in this way is sized and shaped for relatively simple yet secure mounting onto the medical instrument, such as by means of a plurality of screws passed through open ports in the battery pack housing and fastened into the casing of the medical instrument. The screw ports formed in the battery pack housing incorporate seal members such as o-rings which cooperate with the sealing grommet to isolate the rechargeable batteries from electronic components within the interior of the medical instrument. Accordingly, any gases discharged by the batteries upon potential malfunction thereof are isolated from the medical instrument and its electronic components. Such gases are vented between the base plate and housing cap through one or more open vents to the exterior of the medical instrument. In addition, in accordance with further preferred features of the invention, the foil shield comprises a paper-based shell having a thin film conductive foil applied thereto. This paper-based shell includes apertured tabs to fit over short upstanding posts on the base plate, after which the posts are deformed as by heat staking to affix the foil shield permanently onto the base plate. The tabs of the foil shield are folded over to provide a continuous conductive path associated with a metalised shielding normally integrated into the medical instrument. The invention may be carried into practice in various ways and one embodiment will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view illustrating a medical instrument in combination with a battery pack embodying the invention; Figure 2 is an enlarged front elevation showing the medical instrument and associated battery pack of Figure 1; Figure 3 is a further enlarged and exploded perspective view illustrating the assembly of battery pack components and their mounting onto the associated medical instrument; Figure 4 is a top plan view taken generally on the line 4-4 of Figure 2; Figure 5 is an enlarged vertical part-section view taken generally on the line 5-5 of Figure 4; and Figure 6 is an enlarged vertical part-sectional view taken generally on the line 6-6 of Figure 4. As shown in Figures 1 and 2, an improved battery pack 10 is provided for alternative short term battery powered operation of a medical instrument 12, such as the illustrated medication infusion pump of a type used to administer one or more medical fluids to a patient in a regulated manner. The battery pack 10 is designed for quick and easy mounting directly onto the associated medical instrument 12, with the battery pack 10 providing a convenient alternative power source for uninterrupted instrument operation while permitting transport of the instrument 12 and associated patient (not shown) from one place to another. The battery pack 10 provides these advantages while substantially precluding access to a battery power source, thereby preventing unauthorised tampering with or replacement of the battery power source with potentially inferior components. Although the battery pack 10 of the present invention may be designed fro use with a wide range of electronic medical instruments, the illustrative drawings show the battery pack 10 in association with a fluid medication infusion pump 12 such as the MiniMed III fluid infusion pump marketed by MiniMed Technologies of Sylmar, California. More particularly, the illustrated infusion pump 12 comprises a relatively compact instrument casing 14 adapted for mounting onto a conventional portable medical equipment pole 16 by means of an appropriate adjustable clamp bracket 18 or the like. The infusion pump 12 includes multiple parallel pumping systems for independent programming control to regulate the administration of multiple medical fluids from appropriate reservoirs 20 to the patient (not shown) via suitable tubing 22. Electronic control components and associated mechanical pumping devices are integrated into the instrument casing 14. The infusion pump 12 is designed for normal operation by connection to an appropriate mains AC power supply, by means of a power cord 24 and an associated plug-in transformer 26. The battery pack 10 can provide several hours of continuous instrument operation when the transformer 26 is unplugged from the normal power supply. As shown best in Figures 1-3, the battery pack 10 of the present invention is adapted for mounting directly onto the top of the casing 14 of the infusion pump 12. A plurality of mounting screws 28 are normally provided with the instrument to attach a cover plate (not shown) directly onto the top of the instrument casing 14. This cover plate normally encloses the top of the instrument casing and thereby prevents access to internal electronic and other components generally indicated by reference numeral 30. The battery pack 10 is mounted onto the top of the infusion pump 12 by removing the normal cover plate, and by using the mounting screws 28 to install the battery pack 10 directly over the top of the instrument casing 14. The battery pack 10 comprises a base plate 32 which is the preferred form constructed from a lightweight moulded plastics material. The base plate 32 has a plurality of screw ports 34 for the respective passage of the mounting screws 28 into threaded receptacles 36 formed in the instrument casing 14. A suitable adhesive 38 or the like is applied to the upper central region of the base plate 32 for securely and permanently attaching one or more rechargeable batteries 40 directly onto the base plate. As shown in Figure 3 the batteries 40 are typically grouped in an appropriate plurality according to the DC operating requirements of the medical instrument, with appropriate plastics casings 42 or 42′ alternatively being used to capture the batteries 40 as a unit for secure mounting onto the base plate 32. Electrical conductors 44 are appropriately connected to the batteries 40 and passed through a sealing grommet 46 adapted for press-fit installation into an open port 48 formed in the base plate 32. The battery conductors 44 terminate in a suitable connector 50 adapted for a mating plug-it connection with a counterpart connector 52 within the instrument casing 14. A foil shield 54 is integrated into the battery pack 10 for shielding the upper region of the infusion pump 12. The illustrative foil shield 54 comprises a downwardly open folded box formed preferably from a lightweight paper base with a thin metalised film of aluminium or the like applied to it. The foil shield 54 is preferably securely fastened over the batteries 40 by means of additional adhesive 56. In addition, the foil shield 54 includes a pair of tabs 58 each folded over upon itself and including suitable apertures 60 to fit over stake posts 62 protruding upwards from the base plate 32. As shown in Figure 5, the stake posts 62 are deformed for example application of heat after the foil shield has been mounted to fix the foil shield 54 permanently in position over the rechargeable batteries 40. With this construction, the batteries 40 are rendered substantially inaccessible without destroying the foil shield 54. A downwardly open housing cap 64 (Figures 4-7) of moulded plastics or the like is then mounted on the base plate 32 in a position overlying the foil shield 54 and batteries 40. A preferred mounting arrangement used a spaced plurality of ultrasonic spot welds 66 (Figure 2) for interconnecting a lower margin of the cap 64 to the outer periphery of the base plate 32. With this arrangement, the assembled cap 64 and base plat 32 are effectively vented to permit the escape of any toxic or hazardous gases which might be generated by the batteries 40 in the event of battery malfunction. Additional adhesive 65 may also be used to attach the batteries 40 via the foil shield 54 permanently to the cap 64. The mounting screws 28 are passed through aligned screw ports 68 in the housing cap 64 and further through the crew ports 34 in the base plate 32 for threaded reception into the instrument casing receptacles 36. As shown in Figure 6, the base plate ports 34 receive seal members such as o-rings 70 held tightly against the base plate by cap cylinders 72 when the mounting screws 28 are installed. With this geometry, the underlying interior of the instrument casing 14 is effectively isolated from the batteries 40 within the battery pack 10, by virtue of the sealing action of the seal rings 70 and the sealing grommet 46. As noted above, any hazardous gases generated by the batteries are vented to the exterior of the instrument, and are not permitted to pass through the base plate 32 into association with the electronic components within the instrument casing 14. The folded end tabs 58 on the foil shield 54 beneficial provide a continuous conductive path between the exterior of the foil shield 54 and the base plate 32. In this regard, selected regions of the base plate 32, including at least the zone between the stake posts 62 and a side edge 32′, incorporate a thin metalised conductive film 33 for continuity of the conductive shield to the instrument casing 14 when the battery pack 10 is assembled therewith. Thus, the foil shield 54 co-operates with the base plate 32 and the underlying casing 14 to provide a continuous shielding of the entire battery pack and instrument, thereby improving instrument performance and reliability. The battery pack 10 of the present invention is thus adapted for rapid mounting directly onto an associated medical instrument, and for rapid connection directly to electronic components 30 within the instrument casing 14. During normal instrument operation by connection to a standard AC power supply, the electronic components 30 of the instrument may be adapted for maintaining the batteries 40 in a fully charged state. In the illustrated embodiment which used the plug-in transformer 26 at an AC wall outlet, such charging of the batteries may be accomplished without requiring an internal battery charger within the instrument casing 14. Instead, battery charging can take place by merely connecting the appropriate DC signal across the batteries 40 for charging purposes. However, when the power cord 24 is disconnected from the instrument casing 14, the electronic components 30 respond automatically to connect the batteries 40 to the instrument so maintaining continuity of instrument operation. In this regard, although various battery types can be used, rechargeable nickel cadmium batteries are preferred for providing several hours of continuous operation for the medical instrument. Importantly, while the battery pack 10 provides for rapid battery pack mounting and/or replacement as may be periodically required, the batteries 40 are substantially inaccessible at all times. That is, the housing cap 64 and the foil shield 54 cannot be removed from the underlying base plate 32 to expose the batteries, without substantially destroying the battery pack in a readily visible manner. With this construction, the integrity of the rechargeable batteries 40 is maintained so that the correct batteries associated with the particular instrument cannot be tampered with or otherwise replaced with potentially inferior batteries which might have an adverse effect.

Claims: A battery pack (10) for battery powered operation of an electronic medical instrument (12), the battery pack (10) comprising: at least one battery (40); a battery pack housing; and conductor means (44) for connecting the battery (40) to the medical instrument (12), characterised in that an electrically conducting foil shield (54) surrounds the battery, the conductor means (44) extends from within the housing through an open port (48) formed therein to the exterior of the housing, a sealing means (46) seals the passage of the conductor means (44) through the open port (48) and the housing comprises first and second housing members (32,64) connected to each other to enclose the battery (40) and to prevent access to the battery (40) without at least partial destruction of one of the housing members. A battery pack as claimed in Claim 1, characterised in that the first and second housing members (32,64) are interconnected by a plurality of spaced-apart welds (66). A battery pack as claimed in any preceding Claim, characterised in that the foil shield (54) is mounted onto one (32) of the housing member and co-operates therewith to enclose the battery (40) to prevent access to the battery (40) without at least the partial destruction of the foil shield (54) or the housing member (32). A battery pack as claimed in Claim 3, characterised in that the housing members comprise a base plate (32) and a housing cap (64), the battery (40) is mounted on the base plate (32), the foil shield (54) is mounted onto the base plate (32) in a position covering the battery (40) and the housing cap (64) co-operates with the base plate (32) to enclose the battery (40) and the foil shield (54) to prevent access to the battery (40) without at least the partial destruction of the foil shield (54) or the base plate (32). A battery pack as claimed in any preceding Claim, characterised in that the battery (40) is rechargeable. A battery as claimed in Claim 4 or Claim 5, characterised by means (28,34,68,70) for mounting the housing onto the medical instrument (12), the mounting means preferably also providing means for isolating the medical instrument (12) from gases discharged from the battery (40). A battery pack as claimed in Claim 6, characterised in that the mounting means comprises at least one screw (28) extending through a screw port (68) formed in the battery pack (10) and fastened into the medical instrument, the isolating means comprising a seal ring (70) lining the screw port (68). A battery pack as claimed in any of Claims 4 to 7, characterised in that the battery (40) is mounted onto the base plate (32) and/or the foil shield(54) is mounted onto the battery (40) by means of an adhesive (38,56). A battery pack as claimed in any of Claim 4 to 8, characterised in that the foil shield (54) is mounted on to the base plate (32) by means of a pair of apertured tabs (58) on the foil shield (54) which receive a respective pair of stake posts (62) on the base plate (32), the stake posts (62) being deformable subsequent to receiving the tabs (58) to attach the tabs permanently to the base plate (32). A battery pack as claimed in any of Claims 4 to 9, characterised in that the foil shield (54) comprises a paper based shell with a conductive film thereon, the tabs (58) of the foil shield (54) being folded over so that the conductive film contacts the base plate (32) when the foil shield (54) is mounted onto the base plate (32), the base plate (32) including metalised film (33) for conductively connecting the foil shield (54) to the medical instrument (12) when the battery pack (10) is mounted onto the medical instrument (12). A battery pack as claimed in any of Claims 54 to 10, characterised in that the housing (64) and cap base plate (32) co-operatively define at least one vent for venting gases discharged from the battery (40). The combination of a medical instrument (12) having a first housing (14) with electronic components therein, with a removable and replaceable battery pack (10) for the battery powered operation of the medical instrument (12), characterised in that the battery pack (10) comprises: a second housing adapted for mounting onto the first housing (14); at least one battery (40) mounted to the second housing conductor means (44) for connecting the battery (40) to the instrument (12), the conductor means (44) extending through an open port (48) in the second housing and including a first fitting (50) for connection with a second fitting (52) disposed within the first housing (14), the fittings adapted to be disconnected from each other for removal of the second housing from the first housing; a seal member (46) for sealing the passage of the conductor means (44) through the open port (48) formed in the second housing; a foil shield (54) mounted on the second housing and co-operating therewith to enclose the battery (40) and to prevent access thereto without at least the partial destruction of the shield (54) or the second housing; and means for mounting (28,34,36) the second housing onto the first housing (14). A combination as claimed in Claim 12, characterised in that the means for mounting the second housing onto the first housing (14) comprises: at least one screw (38) passing through aligned screw ports (68,34) formed in the cap (64) and the second housing, the screw (38) being fastened into a threaded receptacle (36) on the first housing (14), and further comprising a seal ring (70) seated within the screw port (34) formed in the second housing.

Inventors: CHENEY II PAUL S, FLEMING THOMAS W, GORTON LANNY A, CHENEY II, PAUL S., FLEMING, THOMAS W., GORTON, LANNY A.
Applicants: IVAC CORP, IVAC MEDICAL SYSTEMS, INC.
Application year: 1991
Main classification: H01M2
IPC codes: H01M2, A61M5