Ambulatory Infusion Devices And Piston Pumps For Use With Same

Abstract

An ambulatory infusion device including a fluid transfer device with a piston bore and a piston. The piston bore surface and the piston surface are configured such that they will wear at a very slow rate when cycled in the absence of a lubricant other than the infusible substance.

Description

BACKGROUND OF THE INVENTIONS

[0001] 1. Field of Inventions

[0002] The present inventions relate to ambulatory infusion devices and piston pumps, such as electromagnet piston pumps, for use with ambulatory infusion devices.

[0003] 2. Description of the Related Art

[0004] Ambulatory infusion devices, such as implantable infusion devices and externally carried infusion devices, have been used to provide a patient with a medication or other substance (collectively "infusible substance") and frequently include a reservoir and a pump. The reservoir is used to store the infusible substance and, in some instances, implantable infusion devices are provided with a fill port that allows the reservoir to be transcutaneously filled (and/or re-filled) with a hypodermic needle. The reservoir is coupled to the pump, which is in turn connected to an outlet port. A catheter, which has an outlet at the target body region, may be connected to the outlet port. As such, infusible substance in the reservoir may be transferred from the reservoir to the target body region by way of the pump and catheter.

[0005] Piston pumps, which include a piston that slides within a bore, are frequently used in ambulatory infusion devices. Such pumps are quite small and, with respect to implantable infusion devices, should have a long working life because surgery is required to replace an implantable infusion device with a worn pump. Small pumps must, however, operate at a relatively high pumping frequency in order to compensate for their size, which results in far more pumping cycles over their working lives than would be associated with larger pumps.

[0006] The present inventors have determined that the piston and bore surfaces of conventional pumps employed in ambulatory infusion devices, which are both formed from a relatively soft metal (e.g. ASTM titanium grade 5), produce small wear particles when the piston and bore are rubbed against one another over many pumping cycles. The present inventors have also determined that when a lubricant is employed between the piston and the bore surfaces in an effort to reduce the rate of wear, there is at least the possibility that the lubricant will contaminate the infusible substance.

SUMMARY

[0007] An ambulatory infusion device in accordance with one embodiment of one of the present inventions includes a fluid transfer device with a piston bore and a piston. The piston bore surface may be a relatively hard surface and the piston surface may be a relatively soft surface, or the piston bore surface may be a relatively soft surface and the piston surface may be a relatively hard surface, or the piston bore surface may be a relatively hard surface and the piston surface may be a relatively hard surface. By way of example, but not limitation, a relatively soft surface may be a metal surface, such as a titanium surface, while a relatively hard surface may be non-metal surface, such as a hard ceramic surface, a hard crystalline surface, a glass surface, a titanium impregnated with nitrogen ions surface, a vitreous carbon surface, or a hard graphite surface.

[0008] There are a variety of advantages associated with such an ambulatory infusion device. For example, the surface material combinations described above result in piston and piston bore surfaces that will wear at a slower rate than metal on metal when the piston and piston bore are rubbed against one another over many pumping cycles in the absence of a lubricant other than the infusible substance.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Detailed descriptions of exemplary embodiments will be made with reference to the accompanying drawings.

[0010] FIG. 1 is a side, partial section view of a fluid transfer device in accordance with various embodiments of some of the present inventions.

[0011] FIGS. 2-5 are section views showing a portion of the fluid transfer device illustrated in FIG. 1 in various states.

[0012] FIG. 5A is a side, partial section view of an armature in accordance with various embodiments of some of the present inventions.

[0013] FIG. 6 is a section view showing a portion of a fluid transfer device in accordance with various embodiments of some of the present inventions.

[0014] FIG. 7 is a side, partial section view of a fluid transfer device in accordance with various embodiments of some of the present inventions.

[0015] FIG. 8 is a side, partial section view of a fluid transfer device in accordance with various embodiments of some of the present inventions.

[0016] FIG. 9 is a plan view of an implantable infusion device in accordance with various embodiments of some of the present inventions.

[0017] FIG. 10 is a plan view of the implantable infusion device illustrated in FIG. 1 with the cover removed.

[0018] FIG. 11 is a partial section view taken along line 11-11 in FIG. 9.

[0019] FIG. 12 is a block diagram of the implantable infusion device illustrated in FIGS. 9-11.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0020] The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions. The present inventions have application in a wide variety of apparatus. One example is an implantable infusion device with an electromagnet pump-based fluid transfer device, and the present inventions are discussed in the context of implantable infusion devices with electromagnet pump-based fluid transfer devices. The present inventions are not, however, limited to implantable infusion devices and electromagnet pump-based fluid transfer devices, and are instead also applicable to other ambulatory infusion devices and fluid transfer devices that currently exist, or are yet to be developed. For example, the present inventions are applicable to externally carried infusion devices. The present inventions are also applicable to fluid transfer devices with solenoid pumps, piezoelectric pumps, expandable hot gas pumps, expandable mercury pumps and any other mechanical or electromechanical pulsatile pump that includes components (e.g. a piston and a bore) which slide relative to one another and are likely to produce wear particles when subjected to many pumping cycles.

[0021] One example of a fluid transfer device is illustrated in FIGS. 1-5. The exemplary fluid transfer device, which is generally represented by reference numeral 100, includes a housing 102, an electromagnet pump 104, a bypass valve 106 and a main check valve 107. The housing 102 in the exemplary fluid transfer device 100 is a generally solid, cylindrical structure with various open regions. The open regions accommodate portions of structures, such as the electromagnet pump 104, bypass valve 106, main check valve 107, and also define a fluid flow path. More specifically, the housing 102 includes a piston bore 108 and a hub recess 110 that respectively receive the electromagnet pump armature piston 146 and armature hub 148 (discussed below). A weld ring 112, which is secured to the end of the housing 102 opposite the main check valve 107, defines a pole recess 114 for the armature pole 144 (discussed below). A pair of valve recesses 116 and 118 for the bypass valve 106 and main check valve 107 are also provided. With respect to the fluid flow path, the housing 102 includes an orifice 120 that extends from the piston bore 108 to the bypass valve recess 116, a bypass fluid chamber 122, fluid passages 124 and 126, and an outlet recess 128. Additionally, and as discussed in greater detail below, the exemplary housing 102 is formed from titanium.

[0022] Turning to the pump portion of the exemplary fluid transfer device 100, the electromagnet pump 104 includes an electromagnet 130 and an armature 132. The electromagnet 130, which is carried within in a case 134, includes a core 136 and a coil 138. The case 134 and core 136 are made from a magnetic material. The coil 138 consists of a wire or other conductor that is wound around the core 136. The coil 138 may be insulated from the case 134 electrically non-conductive spacers (not shown), which center the coil within the case, or through the use of potting compound or encapsulant material between the case and the coil.

[0023] The electromagnet case 134 is secured to the housing 102 in the exemplary fluid transfer device 100 through the use of the aforementioned weld ring 112 on the housing and a weld ring 140 on the case. More specifically, the outer diameters of the weld rings 112 and 140 are substantially equal to one another and the outer surfaces thereof are substantially flush. During assembly, the housing 102 and the electromagnet case 134 are positioned on opposite sides of a barrier 142 and are then secured to one another by a weld (not shown) joining the outer surfaces of the weld rings 112 and 140. The barrier separates the pole recess 114, which will ultimately be filled with fluid, from the electromagnet 130.

[0024] The armature 132 in the illustrated embodiment is positioned within a fluid containing region of the housing that is defined by the piston bore 108, the hub recess 110 and the pole recess 114. The exemplary armature 132 consists of a pole 144 formed from a magnetic material (e.g. magnetic steel), which is located within the pole recess 114 such that it will be magnetically attracted to the electromagnet 130 when the electromagnet is actuated, and a cylindrically-shaped piston 146 that extends from the pole and through the piston bore 108 to the main check valve 107. A hub 148 is located within the hub recess 110 and is used to secure the pole 144 to the piston 146. The piston 146 may, for example, be press fit or otherwise fitted into the hub 148 without the use of welding or adhesives.

[0025] A main spring 150 biases the armature 132 to the "rest" position illustrated in FIG. 1. The main spring 150 is compressed between a spring retainer 152 on the hub 148 and a spring retainer plate 154. The spring retainer plate 154, which is held in place by the housing 102 and the weld ring 112, includes an inlet opening 156 that allows fluid to pass from the fluid passage 124 to the pole recess 114 and an outlet opening 158 that allows fluid to pass from the pole recess to the fluid passage 126.

[0026] It should be noted here that there are other ways to secure an armature piston to an armature pole and the present inventions are not limited to any particular method or instrumentalities. By way of example, but not limitation, the exemplary armature 132a illustrated in FIG. 5A includes a pole 144a, with a cylindrical portion 145 and a retainer wall 147, and a piston 146a, with an annular groove 149. The spring retainer 152a is carried on the retainer wall 147 and is secured thereto with a weld or by a press fit. During assembly, the piston 146a is moved into the cylindrical portion 145 of the pole 144a and the retainer wall 147 is swaged or otherwise deformed and moved into the annular groove 149, thereby joining the piston to the pole. The armature 132a may be employed in place of the armature 132 in the fluid transfer device 100 illustrated in FIGS. 1-5 as well as in the fluid transfer devices 100a-100c discussed below in the context of FIGS. 6-8.

[0027] Turning to FIG. 2, the main check valve 107 includes a housing 160, which may be positioned within the valve recess 118 and secured to the housing 102, and a valve element (or "plunger") 162 that is movable relative to the housing 160 within a fluid lumen 164. The valve element 162 includes a head 166 that abuts an elastomeric valve seat 168 when the main check valve 107 is in the closed state illustrated in FIG. 2. The shaft portion of the valve element 162 passes through an opening 169 in the valve seat 168. The valve element 162 is biased to the closed position by a spring 170. One end of the spring 170 abuts the housing 160 and the other end abuts a spring retainer 172 that is secured to the valve element 162.

[0028] The exemplary bypass valve 106 includes a valve element 174 with an integral sealing ring 176. The sealing ring 176, which has a semi-circular cross-sectional shape, engages the wall 178 that defines the end of the valve recess 116 and surrounds the orifice 120 when in the closed position illustrated in FIG. 2. Suitable materials for the valve element 174 include elastomers such as, for example, silicone rubber, latex rubber, urethane, butyl rubber, and isoprene. The valve element 174 is biased to the closed position by a spring 180. One end of the spring 180 abuts the valve element 174, while the other end abuts a plug 182 that may be secured to housing 102 to maintain the bypass valve 106 within the valve recess 116. The plug 182 also forms a fluid tight seal which prevents fluid from escaping from the housing 102 by way of the valve recess 116.

[0029] Otherwise identical valve elements without the sealing ring may also be employed in a bypass valve. Such a valve element may, for example, engage a flat wall (e.g. flat wall 178). Alternatively, and as illustrated for example in FIG. 6, the housing 102a in fluid transfer device 100a (which is otherwise identical to fluid transfer device 100) includes a valve recess 116a with a sealing ring 176a in the wall 178a. The bypass valve 106a includes a valve element 174 with a flat surface that engages the sealing ring 176a. The bypass valve 106a, and corresponding valve recess 116a, may also be employed in fluid transfer devices 100b and 100c discussed below in the context of FIGS. 7 and 8.

[0030] It should also be noted here that the valve element materials listed above can become sticky when dry, which occurs when the pump 104 is not operated for a period of time, or when the pump 104 is new. Thus, it can be difficult to prime a conventional bypass valve (i.e. a valve without a sealing ring 176 or 176a), which can result in pumping cycles, as well as the battery energy associated therewith, being wasted on priming. The priming also causes delays in infusible substance delivery. The sealing rings 176 and 176a in the exemplary bypass valves 106 and 106a create a seal that has a relatively small contact area, as compared to a flat sealing ring and flat wall arrangement, which advantageously reduces the likelihood that valve elements 174 and 174a will stick to the valve recess walls and also increases sealing pressure of the bypass valves. The likelihood of priming problems is further reduced by the natural spring rebound of the bypass valve elements 174 and 174a, which are deformed due to the presence of the sealing rings 176 and 176a when the valves are closed.

[0031] Fluid may be supplied to the exemplary fluid transfer device 100 illustrated in FIG. 1 by way of an inlet tube 184 or other fluid passageway. To that end, and referring to FIG. 2, the main check valve housing 160 includes a recess 186, with a shoulder 188, that receives the inlet tube 184. A filter (not shown) may be positioned within the recess 186 between the inlet tube 184 and the shoulder 188. Fluid exits the fluid transfer device 100 by way of an outlet tube 190, or other fluid passageway, that is received within the outlet recess 128 in the housing 102.

[0032] The exemplary fluid transfer device 100 operates as follows. Referring first to FIGS. 1 and 2, the fluid transfer device 100 is shown here in the "rest" state. The armature 132 is in the rest position, the electromagnet 130 is not energized, and the bypass valve 106 and main check valve 107 are both closed. Under normal operating conditions, there will be no flow through the fluid transfer device 100 when the fluid transfer device is in the rest state and the valves 106 and 107 are closed. Although sufficient pressure at the inlet tube 184 could result in the flow through the fluid transfer device 100 while the fluid transfer device is in the rest state illustrated in FIG. 2, the likelihood that this could occur is greatly reduced by maintaining the fluid source at a relatively low pressure.

[0033] The exemplary fluid transfer device 100 is actuated by connecting the coil 138 in the electromagnet 130 to an energy source (e.g. one or more capacitors that are being fired). The resulting magnetic field is directed through the core 136 and into, as well as through, the armature pole 144. The armature pole 144 is attracted to the core 136 by the magnetic field. The intensity of the magnetic field grows as current continues to flow through the coil 138. When the intensity reaches a level sufficient to overcome the biasing force of the main spring 150, the armature 132 will be pulled rapidly in the direction of arrow A (FIG. 2) until the armature pole 144 reaches the barrier 142. The armature piston 146 and hub 148 will move with armature pole 144 and compress the main spring 140. This is also the time at which fluid exits the fluid transfer device 100 by way of the passage 126 and the outlet tube 190.

[0034] Movement of the armature piston 146 from the position illustrated in FIG. 2 to the position illustrated in FIG. 3 results in a decrease in pressure in the pump chamber 191, i.e. the volume within the piston bore 108 between the armature piston 146 and the valve seat 168. The coil will continue to be energized for a brief time (e.g. a few milliseconds) in order to hold the armature piston 146 in the location illustrated in FIG. 3. The reduction in pressure within the pump chamber 191 will open the main check valve 107 by overcoming the biasing force of the spring 170 and move valve element 162 to the position illustrated in FIG. 4. As a result, the valve head 166 will move away from the valve seat 168 and fluid will flow into the pump chamber 191. The main check valve 107 will close, due to the force exerted by spring 170 on valve element 162, once the pressure within pump chamber 191 is equal to pressure at the inlet tube 184. However, because the coil 138 continues to be energized, the armature 132 will remain in the position illustrated in FIGS. 3 and 4 as fluid flows into the pump chamber 191 and the main check valve 107 closes.

[0035] Immediately after the main check valve 107 closes, the coil 138 will be disconnected from the energy source and the magnetic field established by the electromagnet 130 will decay until it can no longer overcome the force exerted on the armature 132 by the main spring 150. The armature 132 will then move back to the position illustrated in FIGS. 2 and 5. The associated increase in pressure within the pump chamber 191 is sufficient to open the bypass valve 106 by overcoming the biasing force of the spring 180 and moving the valve element 174 to the position illustrated in FIG. 5. The increase in pressure within the pump chamber 191, coupled with movement of the valve element away from the wall 178, results in the fluid flowing through the orifice 120 to the fluid chamber 122. The flow of fluid will cause the pressure in the orifice 120 and the fluid chamber 122 to equalize. At this point, the bypass valve 106 will close, due to the force exerted by spring 180 on the valve element 174, thereby returning the exemplary fluid transfer device 110 to the rest state illustrated in FIG. 2.

[0036] Additional information concerning the structure and operation of electromagnet pump-based fluid transfer devices may be found in U.S. Pat. Nos. 6,227,818 and 6,264,439 and in U.S. application Ser. No. 11/437,571, filed May 19, 2006, which are hereby incorporated by reference.

[0037] With respect to materials, the housing piston bore and the armature piston in the exemplary implantations described above in the context of FIGS. 1-6 and below in the context of FIGS. 7 and 8 are formed from the same or different materials, the properties of which reduce the rate of wear when the surfaces of the piston bore and piston (the "contacting surfaces") are rubbed against one another over many pumping cycles, i.e. at least 1 million pumping cycles of a properly sized and assembled piston and bore. For example, a pump operating at a rate of 2000 strokes per day will not wear the present contacting surfaces to any significant degree over a duration of several years or more.

[0038] Suitable materials that may be used to form the piston bore and the piston, or at least the surfaces thereof, in the exemplary implementations described above in the context of FIGS. 1-6 and below in the context of FIGS. 7 and 8 include relatively soft materials such as titanium (e.g. ASTM titanium grade 5) and relatively hard non-metal materials such as hard ceramics (e.g. zirconia and alumina), hard crystalline materials (e.g. hard gems such as diamond, sapphire and ruby), a titanium base with a hard crystalline material surface coating (e.g. sapphire, diamond-like carbon, and titanium nitride surface coatings), glass, titanium treated by impregnating with nitrogen ions, vitreous carbon, hard graphite (which has lubricious properties). Such materials may be used in any and all combinations, including combinations that result in the same material used to form the piston bore and the piston, or at least the surfaces thereof, with the exception of the titanium bore and titanium piston combination. To that end, it should be emphasized that titanium nitride and titanium treated by impregnating with nitrogen ions are not "titanium" as this term is used in the present application.

[0039] In the exemplary implementations described above in the context of FIGS. 1-6 and below in the context of FIGS. 7 and 8, the combinations of the material enumerated above may result in a bore surface that is relatively hard and a piston surface that is relatively soft; a bore surface that is relatively soft and a piston surface that is relatively hard; or a bore surface that is relatively hard and a piston surface that is relatively hard. By way of example, but not limitation, suitable combinations include a sapphire bore surface and a sapphire piston surface; a ruby bore surface and a sapphire piston surface; a titanium bore surface and a sapphire piston surface; a hard graphite or vitreous carbon bore surface and a glass, ceramic, crystalline material, titanium or vitreous carbon piston surface; and a glass, ceramic, crystalline material, titanium or vitreous carbon bore surface and a hard graphite or vitreous carbon piston surface.

[0040] Referring again to FIG. 1, the exemplary housing 102 is formed from titanium and the surface of the piston bore 108 is a titanium surface. Accordingly, the armature piston 146 may be formed from a hard non-metal material such as a hard ceramic (e.g. zirconia and alumina), a hard crystalline material (e.g. hard gems such as diamond, sapphire and ruby), a titanium base with a hard crystalline material surface coating (e.g. sapphire, diamond-like carbon, and titanium nitride surface coatings), glass, titanium treated by impregnating with nitrogen ions, vitreous carbon, or hard graphite.

[0041] Turning to FIG. 7, the exemplary fluid transfer device generally represented by reference numeral 100b is substantially similar to fluid transfer device 100 illustrated in FIG. 1 and similar elements are represented by similar reference numerals. Here, however, the housing 102b includes a sleeve 192 and a sleeve bore 193 that is configured to receive the sleeve such that the two may be press fit or otherwise secured to one another. The inner surface of the sleeve defines a piston bore 108b in which the armature piston 146 is located. The exemplary sleeve 192 also includes a lumen 194, which is aligned with the housing orifice 120, and a sloping abutment surface 195, which engages a correspondingly sloped housing abutment 196 at the end of the sleeve bore 193. The diameter of the sleeve bore 193 is greater than that of the armature piston 146 in order to provide space for the sleeve 192 and, although the present inventions are not so limited, is the same as that of the valve recess 118 in the exemplary implementation.

[0042] With respect to materials, the armature piston 146 and the sleeve 192 (which defines the piston bore 108b), or at least the contacting surfaces thereof, may be respectively formed from any and all combinations of titanium and hard non-metal materials such as hard ceramics (e.g. zirconia and alumina), hard crystalline materials (e.g. hard gems such as diamond, sapphire and ruby), a titanium base with a hard crystalline material surface coating (e.g. sapphire, diamond-like carbon, and titanium nitride surface coatings), glass, titanium treated by impregnating with nitrogen ions, vitreous carbon, and hard graphite, with the exception of the titanium bore and titanium piston combination. Such combinations include combinations that result in the same material being used to form the armature piston 146 and the sleeve 192, or at least the contacting surfaces thereof, or at least the surfaces thereof, with the exception of the titanium bore and titanium piston combination.

[0043] Another exemplary fluid transfer device is generally represented by reference numeral 100c in FIG. 8. Fluid transfer device 100c is substantially similar to fluid transfer device 100 (FIG. 1) and similar elements are represented by similar reference numerals. Here, however, the housing 102c includes a sleeve 192c and a sleeve bore 193c that is configured to receive the sleeve such that the two may be press fit or otherwise secured to one another. The inner surface of the sleeve 192c defines a piston bore 108c in which the armature piston 146 is located. The exemplary sleeve 192c also includes an abutment surface 195c which engages an abutment 196c at the end of the sleeve bore 193c. The diameter of the sleeve bore 193c is greater than that of the armature piston 146 in order to provide space for the sleeve 192c and, although the present inventions are not so limited, is the same as that of the valve recess 118 in the exemplary implementation.

[0044] With respect to materials, the armature piston 146 and the sleeve 192c (which defines the piston bore 108c), or at least the contacting surfaces thereof, may be respectively formed from any and all combinations of titanium and hard non-metal materials such as hard ceramics (e.g. zirconia and alumina), hard crystalline materials (e.g. hard gems such as diamond, sapphire and ruby), a titanium base with a hard crystalline material surface coating (e.g. sapphire, diamond-like carbon, and titanium nitride surface coatings), glass, titanium treated by impregnating with nitrogen ions, vitreous carbon, and hard graphite, with the exception of the titanium bore and titanium piston combination. Such combinations include combinations that result in the same material being used to form the armature piston 146 and the sleeve 192c, or at least the contacting surfaces thereof, or at least the surfaces thereof, with the exception of the titanium bore and titanium piston combination.

[0045] The fluid transfer devices 100-100c described above may be included in a variety of ambulatory infusion devices. One example of such an ambulatory infusion device is the implantable infusion device generally represented by reference numeral 200 in FIGS. 9-12. As used herein, an "implantable infusion device" is a device that includes a reservoir and an outlet, and is sized, shaped and otherwise constructed (e.g. sealed) such that both the reservoir and outlet can be simultaneously carried within the patient's body. The exemplary infusion device 200 includes a housing 202 (e.g. a titanium housing) with a bottom portion 204, an internal wall 206, and a cover 208. An infusible substance (e.g. medication) may be stored in a reservoir 210 that is located within the housing bottom portion 204. The reservoir 210 may be replenished by way of a refill port 212 that extends from the reservoir, through the internal wall 206, to the cover 208. A hypodermic needle (not shown), which is configured to be pushed through the refill port 212, may be used to replenish the reservoir 210.

[0046] A wide variety of reservoirs may be employed. In the illustrated embodiment, the reservoir 210 is in the form of a titanium bellows that is positioned within a sealed volume defined by the housing bottom portion 204 and internal wall 206. The remainder of the sealed volume is occupied by propellant P, which may be used to exert negative pressure on the reservoir 210. Other reservoirs that may be employed in the present infusion devices include reservoirs in which propellant exerts a positive pressure. Still other exemplary reservoirs include negative pressure reservoirs that employ a movable wall that is exposed to ambient pressure and is configured to exert a force that produces an interior pressure which is always negative with respect to the ambient pressure.

[0047] The implantable ambulatory infusion device 200 illustrated in FIGS. 9-12 also includes a fluid transfer device. Although the fluid transfer device 100 is employed in the illustrated embodiment, any of the other fluid transfer device describe above (e.g. fluid transfer devices 100a-100c) may be employed in its place. The inlet of the fluid transfer device 100 is coupled to the interior of the reservoir 210 by a passageway 216, while the outlet of the fluid transfer device is coupled to an outlet port 218 by a passageway 220. Operation of the fluid transfer device 100 causes infusible substance to move from the reservoir 210 to the outlet port 218. A catheter 222 may be connected to the outlet port 218 so that the infusible substance passing through the outlet port will be delivered to a target body region in spaced relation to the infusion device 200 by way of the outlet 224 at the end of the catheter.

[0048] In the exemplary context of implantable drug delivery devices, and although the volume/stroke magnitude may be increased in certain situations, the fluid transfer devices will typically deliver about 1 microliter/stroke, but may be more or less depending on the particular fluid transfer device employed. Additionally, although the exemplary fluid transfer devices 100-100c are provided with internal valves (e.g. a main check valve and a bypass valve), valves may also be provided as separate structural elements that are positioned upstream of and/or downstream from the associated fluid transfer devices.

[0049] Energy for the fluid transfer device 100, as well for other aspects of the exemplary infusion device 200, is provided by the battery 226 illustrated in FIG. 10 or another suitable energy source. In the specific case of the fluid transfer device 100, the battery 226 is used to charge one or more capacitors 228, and is not directly connected to the fluid transfer device itself. The capacitor(s) 228 are connected to an electromagnet coil in the fluid transfer device 100, and disconnected from the battery 226, when the electromagnet coil is being energized, and are disconnected from the electromagnet coil and connected to the battery when the capacitor(s) are being recharged and/or when the fluid transfer device is at rest. The capacitor(s) 228 are carried on a board 230. A communication device 232, which is connected to an antenna 234, is carried on the same side of the board 230 as the capacitor(s) 228. The exemplary communication device 232 is an RF communication device. Other suitable communication devices include, but are not limited to, oscillating magnetic field communication devices, static magnetic field communication devices, optical communication devices, ultrasound communication devices and direct electrical communication devices.

[0050] A controller 236 (FIG. 12), such as a microprocessor, microcontroller or other control circuitry, is carried on the other side of the board 230. The controller controls the operations of the infusion device 200 in accordance with instructions stored in memory 238 and/or provided by an external device (e.g. the remote control 200 described below) by way of the communication device 232. For example, the controller 236 may be used to control the fluid transfer device 100 to supply fluid to the patient in accordance with, for example, a stored basal delivery schedule or a bolus delivery request. The controller 236 may also be used to monitor sensed pressure in the manner described below.

[0051] Referring to FIGS. 9, 10 and 12, the exemplary infusion device 200 is also provided with a side port 240 that is connected to the passageway 220 between the outlet of the fluid transfer device 100 and the outlet port 218. The side port 240 facilitates access to an implanted catheter 222, typically by way of a hypodermic needle. For example, the side port 240 allows clinicians to push fluid into the catheter 222 and/or draw fluid from the catheter for purposes such as checking catheter patency, sampling CSF, injecting contrast dye into the patient and/or catheter, removing medication from the catheter prior to dye injection, injecting additional medication into the region at the catheter outlet 224, and/or removing pharmaceuticals or other fluids that are causing an allergic or otherwise undesirable biologic reaction.

[0052] The outlet port 218, a portion of the passageway 220, the antenna 234 and the side port 240 are carried by a header assembly 242. The header assembly 242 is a molded, plastic structure that is secured to the housing 202. The housing 202 includes a small aperture through which portions of the passageway 220 are connected to one another, and a small aperture through which the antenna 234 is connected to the board 230.

[0053] The exemplary infusion device 200 illustrated in FIGS. 9-12 also includes a pressure sensor 244 that is connected to the passageway 220 between the outlet of the fluid transfer device 100 and the outlet port 218. As such, the pressure sensor 244 senses the pressure at the outlet port 218 which, in the illustrated embodiment, is also the pressure within the catheter 222. The pressure sensor 244 is connected to the controller 236 and may be used to analyze a variety of aspects of the operation of the exemplary implantable infusion device 200. For example, pressure measurements may be used to determine whether or not the fluid transfer device 100 is functioning properly and whether or not there is a complete or partial blockage in the catheter 222 and, in response to a improper fluid transfer device functioning or a catheter blockage, actuate an audible alarm 248.

[0054] Although the inventions disclosed herein have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. By way of example, but not limitation, the present inventions have application in infusion devices that include multiple reservoirs and/or outlets. It is intended that the scope of the present inventions extend to all such modifications and/or additions and that the scope of the present inventions is limited solely by the claims set forth below.

Claims

1. An ambulatory infusion device, comprising: a reservoir; and a fluid transfer device, operably connected to the reservoir, including a housing having a piston bore defining a relatively soft piston bore surface, and a relatively hard piston at least partially located within the piston bore.

2. An ambulatory infusion device as claimed in claim 1, wherein the relatively soft piston bore surface comprises a titanium piston bore surface.

3. An ambulatory infusion device as claimed in claim 2, wherein the titanium piston bore surface comprises an ASTM titanium grade 5 piston bore surface.

4. An ambulatory infusion device as claimed in claim 1, wherein the relatively soft piston bore surface comprises a titanium piston bore surface; and the relatively hard piston is selected from the group consisting of a hard ceramic piston, a hard crystalline piston, a glass piston, a vitreous carbon piston, and a hard graphite piston.

5. An ambulatory infusion device as claimed in claim 4, wherein the relatively hard piston comprises a sapphire piston.

6-10. (canceled)

11. An ambulatory infusion device as claimed in claim 1, wherein the relatively soft piston bore surface comprises a metal piston bore surface and the relatively hard piston comprises a non-metal relatively hard piston.

12. An ambulatory infusion device as claimed in claim 1, wherein the fluid transfer device includes an armature pole connected to the relatively hard piston and an electromagnet.

13. An ambulatory infusion device as claimed in claim 1, wherein the fluid transfer device includes a bypass valve and a main check valve.

14. An ambulatory infusion device as claimed in claim 1, further comprising: a device housing, including an outlet, that is sized, shaped and sealed in a manner suitable for implantation into a human body; wherein the reservoir and fluid transfer device are located within the housing and the fluid transfer device is operably connected to the outlet.

15. An ambulatory infusion device for supplying an infusible substance, comprising: a reservoir; and a fluid transfer device, operably connected to the reservoir, including a housing having a sleeve bore: a sleeve, within the sleeve bore, formed from a different material than the housing, the sleeve having a piston bore defining a piston bore surface, and a piston, at least partially located within the piston bore, defining a piston surface; wherein the piston bore surface and the piston surface are formed from materials that wear at a slower rate than metal on metal when rubbed together repeatedly over many cycles.

16. An ambulatory infusion device as claimed in claim 15, wherein the piston bore surface and the piston surface are formed from the same material.

17. An ambulatory infusion device as claimed in claim 15, wherein the piston bore surface and the piston surface are formed from different materials.

18. An ambulatory infusion device as claimed in claim 15, wherein the piston surface is a metal surface and the piston bore surface and the piston surface is a non-metal surface.

19-21. (canceled)

22. An ambulatory infusion device as claimed in claim 15, wherein the piston bore surface is formed from material selected from the group consisting of a hard ceramic material, a hard crystalline material, glass, titanium impregnated with nitrogen ions, vitreous carbon, and hard graphite; and the piston surface is formed from material selected from the group consisting of a hard ceramic material, a hard crystalline material, glass, titanium impregnated with nitrogen ions, vitreous carbon, and hard graphite.

23. An ambulatory infusion device as claimed in claim 22, wherein the piston surface is formed from sapphire and the piston bore surface is formed from sapphire.

24. An ambulatory infusion device as claimed in claim 22, wherein the piston surface is formed from sapphire and the piston bore surface is formed from ruby.

25. An ambulatory infusion device as claimed in claim 15, wherein the piston bore surface is formed from material selected from the group consisting of a hard ceramic material, a hard crystalline material, glass, titanium impregnated with nitrogen ions, vitreous carbon, and hard graphite; and the piston surface is formed from titanium.

26. An ambulatory infusion device as claimed in claim 15, wherein the fluid transfer device includes an armature pole connected to the piston and an electromagnet.

27. An ambulatory infusion device as claimed in claim 15, wherein the fluid transfer device includes a bypass valve and a main check valve.

28. An ambulatory infusion device as claimed in claim 15, further comprising: a device housing, including an outlet, that is sized, shaped and sealed in a manner suitable for implantation into a human body; wherein the reservoir and fluid transfer device are located within the housing and the fluid transfer device is operably connected to the outlet.

29. An ambulatory infusion device as claimed in claim 15, wherein the piston bore surface and the piston surface are formed from materials that wear at slower rate than metal on metal when rubbed together repeatedly over at least one million cycles.