Abstract:
A housing for a medicinal pump, which is sealed to prevent damage due to exposure of the housing to water or other liquids. The housing includes an extruded case in which the various components comprising the pump are enclosed. The ends of the extruded case are sealed by a top cap and a bottom cap that are overnolded with an elastomeric material. The elastomeric material seals the top and bottom caps against the extruded case and provides shock resistance to protect the pump from damage. An open side of the pump is sealed with a pump chassis that supports a pump cassette used to infuse medicinal fluids into a patient. A bezel assembly on the front surface of the pump is adhesively attached thereto using a double-sided adhesive sheet. The double sided adhesive sheet seals the openings for a display and a keypad formed in the front surface of the extruded case.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a housing for a portable medical device, and more specifically, to a sealed metal housing for an ambulatory infusion pump, having shock absorbing ends. 
     BACKGROUND OF THE INVENTION 
     Housings for portable electronic devices are often fabricated from injection molded plastic to minimize production costs and weight. For example, in a typical plastic clam shell housing for such a device, the two halves of the plastic housing are connected together with fasteners; internal components are typically connected to one half of the housing using fasteners. However, in addition to being relatively lightweight, portable medical devices, such as ambulatory infusion pumps, must also be relatively rugged and resistant to mechanical shock and breakage if accidentally mishandled or dropped. Failure of a portable medical device due to undetected damage sustained in a short drop or as a result of other mechanical shock could be life threatening to a patient. Because infusions pumps of this type are often carried about by a patient for extended periods of time, they are likely to be frequently bumped and occasionally dropped. Lightweight plastic cases or conventional metal housings are generally unable to withstand such rough handling without damage to either the housing or the internal components of an ambulatory infusion pump. A further drawback to using plastic housings for such devices is that it is often necessary to include a metal plate or foil layer within the plastic material to shield against electromagnetic or radio frequency noise. The additional metal shielding adds weight and cost. 
     Also, because an ambulatory infusion pump may have to be coupled to a patient&#39;s vascular system at all times, even when the patient is bathing or showering, the infusion pump must be sufficiently watertight to be briefly immersed in water or exposed to water droplets in a shower. Providing a sealed, watertight housing for an infusion pump that has patient actuated controls and a display panel, and which accepts disposable pumping cassettes is not a trivial task, particularly when the housing must also be lightweight, rugged, and relatively low in cost, as noted above. Previous attempts to provide such a housing fabricated using injection molded plastic or metal have generally not been successful. It is somewhat difficult to provide sealed closure of a battery compartment and of the components that interact with a disposable cassette in a housing that is also lightweight, low cost, and capable of withstanding physical shock. Accordingly, it will be apparent that there is a need for such a housing that is not met by the available prior art. 
     SUMMARY OF THE INVENTION 
     In accord with the present invention, a housing for an ambulatory infusion pump is defined that is impact resistant, sealed and substantially watertight. The housing includes an extruded metal housing in which are disposed a battery compartment, an electronic component compartment, and a pump chassis. The extruded metal housing has opposed first and second ends in which corresponding first and second openings are respectively formed. A first overmolded cap that is sized to fit the first opening includes a substantially rigid internal member covered with an elastomeric material. Similarly, a second overmolded cap, which is sized to fit the second opening, also includes a substantially rigid internal member covered with the elastomeric material. A plurality of fasteners are provided for coupling the first and the second overmolded caps to the extruded metal housing so that the overmolded caps seal the first and the second openings. 
     The extruded metal body includes ports adapted for sealingly mounting a keypad and a display. An adhesive sheet seals around the ports and secures a bezel over the ports In addition, one of the first and the second caps preferably includes an opening into the battery compartment. A battery compartment cover seats within the opening and seals it. 
     Also included is a gripping surface that is applied to an exterior of the extruded metal body, to facilitate gripping the housing. 
     Either the first or the second caps includes an aperture through which a pump cassette ejection button extends for access from outside the housing. The aperture through which the pump cassette ejection button extends is sealed. 
     A preferred form of the invention includes means for mounting an accessory to the housing. Specifically, a pair of generally parallel grooves are formed on the surface of the extruded metal body for mounting a clamp or other accessory thereto. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     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 with the accompanying drawings, wherein: 
     FIG.1A is an isometric view showing the front, side, and top of an ambulatory infusion pump having a housing in accord with the present invention; 
     FIG. 1B is an isometric view of the rear surface and bottom of the housing for the pump; 
     FIG. 2 is a partially exploded isometric view of the pump, showing the end caps spaced apart from an extruded metal case comprising the housing; 
     FIG. 3 is an exploded isometric view showing a bezel assembly, a display, and the extruded metal case; 
     FIG. 4 is an exploded front view of the extruded metal case, a bezel adhesive sheet, a grip, and a grip adhesive sheet; and 
     FIG. 5 is a top end view of the extruded metal case. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1A illustrates an ambulatory infusion pump  10  having a housing in accord with the present invention. The housing includes an extruded case  12  that is preferably produced by extruding aluminum through an appropriately shaped die. The extruded case wraps around one side of the housing, sealing it on that side; however, an open side  30  is provided on the opposite side of the extruded case, for receiving a pump chassis  32  in which a pump cassette (not shown) is latched into a predefined position so that medicinal fluid can be infused into a patient. The housing includes a top cap  14  and a bottom cap  16 . Both the top cap and bottom cap are formed of a rigid internal member having generally the same overall shape as its respective cap, but being slightly smaller in size. This internal rigid member is overmolded with synthetic rubber or another type of elastomeric material suitable for overmolding. 
     Use of the elastomeric material for top cap  14  and bottom cap  16  provides several advantages. First, it facilitates sealing the ends of extruded case  12  so that water or other liquid is excluded from the interior of the case where it might cause damage to the electronic circuitry contained therein. Secondly, the elastomeric material of the top and bottom cap provides mechanical shock absorbency in the event that the housing is dropped by a user or sustains a bump against a surface, since the elastomeric material has substantial resilience for absorbing shock upon impact. The internal rigid members used in the top and bottom cap are preferably fabricated from plastic, however, it is also possible to make the internal member from lightweight metal, such as aluminum. This internal member provides shape and strength to the top cap and bottom cap, without significantly reducing the resilient shock absorbency benefits of the elastomeric material with which the top and bottom cap are overmolded. 
     As shown in FIG. 2, a pump cassette eject button  18  is inserted through top cap  14  and is sealed relative to an inner surface of the opening in the top cap with an O-ring  19 . The pump eject button is depressed by a user to cause the pump cassette to be disengaged from pump chassis  32 . Pump chassis  32  slides into open side  30  of extruded case  12  during assembly of the housing. Although not specifically indicated in the figures, strips of a silicone sealing material are provided along surfaces  21  (shown in FIG. 3) to seal against corresponding surfaces of pump chassis  32  so that the pump chassis effectively seals open side  30  of extruded case  12 . Top cap  14  includes a notch  24  on its end overlying open side  30  of the extruded case, and bottom cap  16  includes a notch  26  that is generally aligned with notch  24 . These two notches are shaped and sized to respectively receive a proximal tubing and a distal tubing (neither shown) that are coupled to the pump cassette when the pump cassette is latched into the predefined position within pump chassis  32 . 
     Referring to FIG. 4, it will be apparent that extruded case  12  includes a generally rectangular display port  34  near the top of its front surface and a generally rectangular keypad cable port  36  near the left corner of its front surface. A battery compartment  38  is disposed just inside the closed side of the extruded case and is sized to accept two storage batteries (not shown), which are inserted therein, coupled in series, with the positive terminal of one battery in contact with the negative terminal of the other. A removable battery compartment cover  39  (shown in FIG. 1B) is disposed in bottom cap  16  for providing access to battery compartment  38  for servicing the batteries, and otherwise seals the opening into the battery compartment. 
     Referring again to FIG. 4, a grip  40  extends around the closed side of extruded case  12  and is held in place by a grip adhesive sheet  42 , which comprises a double-sided adhesive sheet, i.e., a sheet that is sticky on both its front and rear surfaces. The grip adhesive sheet adheres to the outer surface on the closed side of extruded case  12  and provides adhesion to hold grip  40  in place. In addition, grip  40  includes a flange  44  extending longitudinally along one of its edges, and this flange engages a groove  46  formed on the rear surface of the extruded case; groove  46  extends generally longitudinally along the length of the rear surface of extruded case  12 . The end of groove  46  is clearly illustrated in FIG.  1 B. 
     A bezel adhesive sheet  48 , which also has double-sided adhesive surface, includes a display cutout  50  and a keypad cutout  52 . The bezel adhesive sheet is used to adhesively secure a bezel assembly  54  to the front surface of extruded case  12 . Before bezel assembly  54  is attached to the extruded case with bezel adhesive sheet  48 , a display panel  56  (see FIGURES) is inserted into display port  34  and is held in place with display adhesive pads (not shown, which are double-sided adhesive disposed at the upper left and right corners on the rear surface of display panel  56 . In addition, a tab  60  on extruded case  12  has a display adhesive pad (not shown) that uses double-sided adhesive to adhere to display panel  56 , also holding the display panel in place in display port  34 . 
     A clear plastic window  62  (FIG. 3) is provided in bezel assembly  54  overlying display panel  56 . When bezel assembly  54  is adhesively attached to the front surface of extruded case  12 , the bezel adhesive sheet effectively seals the undersurface of bezel assembly  54  around the periphery of the display assembly and keypad, preventing water or other liquid from entering the interior of the extruded case through display port  34  or keypad cable port  36 . A cable (not shown) extends from a keypad  22  that is part of the bezel assembly and into the interior of extruded case  12  through keypad cable port  36 , at the back surface of bezel assembly  54 . This cable is attached to the circuitry within extruded case  12  to receive signals from keypad  22  when the keypad is actuated by the user. 
     A bezel tail  64  is disposed over the upper portion on the closed side of extruded case  12 . A flange  66  on the rear edge of bezel tail  64  snaps into groove  46  on extruded case  12 . A tab  68  formed on the other edge of bezel tail  64  engages bezel assembly  54  to hold bezel tail  64  in place. 
     On the inner surface of bezel assembly  54 , a tab  70  is provided to engage the edge of a groove  72  formed on the adjacent surface of extruded case  12 . Similarly, a tab  73  on the other side of bezel assembly  54  snaps into engagement with the edge of a groove  75  formed adjacent opening  30  on extruded case  12 . The snap engagement of bezel assembly  54  with extruded case  12  further assures that bezel assembly  54  is adhesively attached to the extruded case in an appropriate position and provides additional holding force to secure the bezel assembly and bezel tail assembly in place. 
     A pair of long fasteners  74  extend the length of extruded case  12 , passing through countersunk orifices  76  formed in bottom cap  16 . Long fasteners  74  include threads that threaded into appropriately threaded inserts (not shown) within top cap  14 , securing the top cap to bottom cap  16 . Fasteners  79  pass through countersunk orifices  81  in bottom cap  16  and are threaded into inserts within pump chassis  32 . It should be noted that a printed circuit board assembly  78  is connected into an appropriate edge connector (not shown) attached to the inner side of bottom cap  16 . This printed circuit board assembly is slid into an electronic component compartment  28  within the interior of extruded case  12  as bottom cap  16  is secured to top cap  14 . 
     As shown in FIG. 2, a pair of fasteners  80  extend through countersunk orifices  82  formed in top cap  14 , under pump cassette eject button  18 . The top cap fasteners are threaded into mating inserts disposed within the end of pump chassis  32 . Also, as shown in FIG. 1B, a pair of fasteners  84  are inserted through countersunk holes  86  formed in the rear of extruded case  12  and are also used to hold pump chassis  22  in place within the extruded case. One of fasteners  84  (at the top of rear surface of the housing) extends through pump cassette eject button  18  to secure it in place within the pump chassis. FIG. 1B also shows a data port  92 , which enables data connectors to be electrically coupled to the printed circuit board within the housing for transfer of data and control instructions. 
     A rear label  88  (FIG. 3) is adhesively applied to the rear surface of extruded case  12 , overlying the portion of the extruded case in which pump chassis  32  is disposed. Also provided on the rear surface of extruded case  12 , as shown in FIG. 1B, are a pair of parallel attachment grooves  90 , which extend generally longitudinally along the length of the rear surface of the extruded case. Grooves  90  enable various attachments to be affixed to the rear of extruded case  12 . For example, one attachment, which is not shown, comprises a clamp used to support the housing on a pole (also not shown) adjacent to where a patient is receiving fluid infused by the pump. Various other types of attachments can also be coupled to extruded case  12  by coupling into attachment grooves  90 . 
     From the foregoing description, it will be apparent that the ends of extruded case  12  are generally sealed by top cap  14  and bottom cap  16  and that the display port and keypad cable port in the front surface of the extruded case are sealed with bezel adhesive sheet  48  that secures bezel assembly  54  to the front face of the housing. Further, pump chassis  32  sealingly closes open side  30  of extruded case  12 . In this manner, the housing is made resistant to damage by exposure to water or other liquids. Furthermore, the elastomeric overmolding applied to top cap  14  and bottom cap  16  provides mechanical shock absorbency, minimizing the effect of accidental mishandling, in the event that the housing is bumped or dropped on either of its ends. 
     Although the present invention has been described in connection with the preferred form of practicing it, those of ordinary skill in the art will understand that many modifications can be made thereto within the scope of the claims that follow. Accordingly, it is not intended that the scope of the invention in any way be limited by the above description, but instead be determined entirely by reference to the claims that follow.