Patent Application
20070090321
1) Field of the Invention
This invention generally relates to hermetically-sealed devices that have a sealed barrier (or membrane), and more particularly to such hermetically-sealed devices that include mechanical interaction across the barrier.
2) Discussion of Related Art
A variety of mechanical and electromechanical devices must operate in environments that require the devices to be completely isolated within a protective barrier. In some situations, the “outside environment” (environment located outside the barrier) is hazardous and includes elements or conditions that will adversely affect the operation of the device or shorten its expected useful operative life. In such hazardous environments, the device must be completely sealed and the protective barrier must be made with the particular hazard in mind. For example, in a chemical-production facility, a temperature sensor may have an operative environment that includes a caustic base chemical. In this harsh environment, the relatively delicate temperature sensor would have to be protected from the strong corrosive chemical in such a way that would not hinder or unpredictably affect its temperature-sensing operation.
In other situations, the outside environment is to be protected from potential danger that stems from within the device itself. For example, if an electrical control device of the type that may create a spark of electricity during its operation is to operate within a combustible environment (e.g., explosive gas), the electrical components of the device will have to be completely isolated (hermetically sealed) from the outside environment.
Also, many medical devices that are to be implanted within a human patient, for example, must also be hermetically sealed, primarily, in this delicate living environment, to prevent infection or contamination caused from within the device.
In all these situations, a protective barrier is created to isolate an outside environment from an inside one. Obviously, different devices and environments require different types and levels of seals. For most non-mechanical interactive devices (that is, devices that do not require cross-barrier mechanical interaction), creating the required hermetic seal is fairly straightforward. The device is typically encased within a plastic or metal housing, which is then sealed using any of a variety of techniques and materials. A commonly used method for sealing electrical circuits that do not require access or air-cooling, is to encase the entire device in a “pot” (or small plastic or metal housing) of epoxy or another appropriate air-tight adhesive or polymer. Other devices may be housed within a plastic or metal housing that is later sealed using rubber sheet, rubber grommets, rubber O-rings, gaskets, adhesives, or metal welding or crimping to ensure that no air can cross the barrier.
These sealing methods and materials work well when no mechanical interaction is required during the life of the device. However, should the device require cross-barrier mechanical interaction, such as linear, angular, or rotational displacement, then the barrier must accommodate the mechanical displacement and the corresponding mechanical stress and fatigue that will likely occur. For example, a good flashlight typically includes a water-tight inside environment that houses the electrical components (battery, bulb, switch, and circuit). A user located in the outside environment must activate the switch to operate the. flashlight. To ensure a watertight condition, the inner and outer environments are sealed with a barrier. To allow a user to mechanical displaced the switch across the barrier without creating a leak, a flexible rubber boot is typically positioned over the switch. The flexible boot allows for the switch's mechanical operation, but maintains barrier integrity to the inner environment, as necessary.
Rubber and flexible plastic boots and membranes are often used to accommodate mechanical interaction across a hermetic barrier of many devices. Unfortunately, such rubber and plastic structures, albeit tough and resistant, fail in extreme environmental conditions, including environments having any of a variety of chemicals, radiation, positive and negative pressures, mechanical abrasion, sunlight, and high temperatures (above 300 degrees F.) and those below freezing.
One such harsh environment is that of an autoclave, wherein steam is used to sterilize devices intended to be used within or in connection with a human patient. The super-heated water can easily destroy or severely damage such soft flexible non-metallic materials, even before they reach their intended operative environment.
To this end, implantable devices are typically housed within a sturdy metal case and sealed with metal welds to create a very strong and effective barrier that can easily withstand the otherwise harsh conventional sterilization processes. To provide mechanical “communication” with the device across this impervious barrier, a thin membrane of metal is provided at the point of interaction. A common arrangement includes providing a “communication port” (an opening or portal) in the housing and positioning a thin flat flexible metal disc across the port. The metal disc is typically made from titanium and is brazed or soldered (low-heat welding) or high-heat welded to the surrounding metal housing so that the port is effectively sealed and the integrity of the barrier is maintained. The attached disc may be flexed slightly so that a mechanical displacement between the outside environment and a mating component located within the housing may interface, without direct contact (owing to the interposed metal disc).
The flat metal disc has proved quite useful and effective for many devices and situations, but, in some cases may be limited in operative cycles before succumbing to the persistent mechanically-generated stress and fatigue.
It is a first object of the present invention to provide an effective barrier that allows for cross-barrier mechanical interaction, which overcomes the deficiencies of the prior art.
It is another object of the invention to provide a barrier across a communication port that allows for increased mechanical displacement while minimizing mechanical-related stress and fatigue.
A valve mechanism for use in an implantable infusion pump includes a fluid compartment and a dry-component compartment. The compartments are sealed so that fluid cannot pass between compartments. A flexible membrane is located within a membrane plane, positioned between the compartments and allows limited mechanical displacement between the compartments, yet prevents any fluid communication therebetween. The fluid compartment includes an inlet chamber which is connected to a supply of pressurized liquid medicant by an inlet conduit, an outlet chamber that is connected to an outlet conduit, and a valve that is positioned between the inlet chamber and the outlet chamber. The valve includes a movable trigger member that selectively causes the valve to move between an open position wherein the liquid medicant flows from the inlet chamber to the outlet chamber, and a closed position, wherein medicant flow is prevented. The trigger member is positioned against the membrane. The dry-component compartment includes a displacement actuator, which is positioned against the membrane so that generated movement of the actuator may be selectively transferred to the trigger member through non-invasive deformation of the flexible membrane. In this arrangement, the valve located within the hermitically-sealed fluid compartment is effectively controlled from the dry component compartment. The flexible membrane includes at least one deformed region that extends beyond the membrane plane.
According to other embodiments of the invention, the membrane includes at least one concentric ripple (circular-raised, or circular-lowered ridge), or includes a cylindrically-shaped flexible-bellows structure (either upwardly or downwardly directed within the valve assembly).
According to yet another embodiment, a membrane includes a curved peripheral edge that is sized and shaped to snuggly seat within the peripheral brazing groove located within a membrane support disc. This arrangement helps minimize stress to a braze (or weld) line due to membrane flexure.
Further details, features and advantages of the invention are shown in the following description of an exemplary embodiment by reference to the drawing.
As discussed above, many devices require isolation from a particular operational environment. The environment is either hazardous to the device, could affect the operation of the device, or, alternatively, the device or supporting materials could cause harm to or affect the operational environment.
In many situations, such isolated devices merely require an appropriate, hermetically-sealed chamber or housing into which the devices are mounted and within which they operate. Some situations, however, require that the housed devices establish a mechanical communication across the “hermetic barrier”. The magnitude and frequency of mechanical displacement will, of course, vary depending on the function and type of device, however, some linear or angular displacement across the barrier will be required before, during and/or after the device becomes operational while within the operational environment. In such instance, the chamber or device housing must accommodate mechanical displacement while continuously maintaining its hermetic seal. In fairly harsh environments (such as those of high temperature extremes, or those containing chemical hazards), it is not uncommon to use a barrier that is made from metal, such as steel, brass, copper, or titanium, depending on the device requirements and the operational environment. If a metal housing is used, the portal for mechanical displacement may include a thinned-wall section, which allows sufficient flexibility to accommodate the required mechanical displacement. Alternatively, the portal will be covered (and sealed) with a metal disc or circular membrane that is made from a suitable material, such as titanium. The disc is made from a strong, flexible material and is made thin enough to endure continuous and repeated flexure during the mechanical communication. The discs are typically welded or brazed in place across the communication portal.
The present invention is directed to improved flexible membranes across mechanical access portals of barriers interfacing two isolated environments (hereafter referred to as a “dry side” and a “wet side”). The terms “dry” and “wet” are used to describe two different sides of a barrier and membrane and are not meant to imply environment conditions. Clearly, as is well known, a hermetic barrier can be used to isolate a variety of environments of different conditions and characteristics. Although the present invention can be used in a variety of situations where two environments are isolated and included with a flexible mechanical interface therebetween, the invention is shown and described in connection with a flexible membrane particularly used in the valve-mechanism of implantable infusion pumps of the type that contain a supply of medication and are implanted within a patient.
Referring to
In this exemplary valve structure, piston 16 is positioned within bore 14 and includes an upper sealing end 24 that supports a disk-shaped seal 26. Piston 16 further includes a lower end 28, which includes a downwardly-directed boss 30 that is sized and shaped to receive one end of a compression spring 32. Piston 16 further includes a circumferentially located spiral groove 34 (positioned along the sidewall of the piston and extending the length of the piston), which allows fluid communication between the lower end 20 of bore 14 (and inlet passage 22) and upper sealing end 24 of piston 16. Any fluid entering the lower end 20 of bore 14 (under pressure) may freely advance between the piston 16 and the bore 18 through spiral groove 34.
As shown in
Securely attached (i.e., preferably hermetically sealed) to body 12 and positioned over upper end 36 of bore 14 is a contact disc 38 that is preferably made from a rigid material, such as a metal. Contact disc 38 includes a central opening 40 and an integrally formed, downwardly-directed contact ridge 42. Contact ridge 42 is formed concentrically to central opening 40 and is sized and shaped to fit within bore 14, as shown in
Attached to upper sealing end 24 of piston 16 is an axially-aligned contact pin 25. Contact pin 25 is sized and shaped to loosely fit and slidably move within central opening 40 of contact disc 38 and is long enough so that an upper contact surface 27 extends and remains above contact disc 38. As described in greater detail below, downward displacement of contact pin 25 causes piston 16 to effectively separate disc-shaped seal 26 from sealing contact of contact ridge 42 of contact disc 38, thereby opening the valve.
Securely affixed to body 12 (i.e., preferably hermetically sealed) and positioned over upper end 36 of bore 14 and contact disc 38 is a portal support ring 44, which includes a large central opening 46 and defines a lower surface 48. Attached to the lower surface 48 and covering the large central opening 46 is a thin, flat coin-like, flexible membrane 50, which is, in this instance, considered prior art (and shown in
Membrane 50 is usually made from a strong resilient metal, such as titanium and is brazed or welded to the lower surface 48 of portal support ring 44. Similarly, portal support ring 44 is brazed to body 12 so that piston 16, disk-shaped seal 26, spring 32, inlet passage 18, outlet passage 22, and contact disc 38 all define a “wet side” of membrane 50 (lower side) and are all hermetically sealed within the valve body 12 and isolated from everything located above and outside the valve body 12, a space which defines a “dry side” of membrane 50. Membrane 50 is positioned so that upper surface 27 of contact pin 25 abuts against a lower surface 51 of membrane 50. Spring 32 biases contact pin 25 into firm contact with lower surface 51 of membrane 50.
According to this valve application, the valve is opened and closed repeatedly at a predetermined frequency by applying the mechanical displacement generated by a piezo crystal 53 (in response to an applied electrical signal) to move piston 16 up and down. An actuation pin 55 is used to connect the piezo crystal 53 to contact pin 25, indirectly through membrane 50, as described below. Actuation pin 55 is axially aligned with contact pin 25.
In operation of the above described valve assembly 10, fluid (a liquid drug) is supplied to inlet passage 18 under pressure, but regulated by a fluid pressure regulator 60. Fluid enters lower end 20 of bore 14, and whenever piston 16 is forced downwardly within bore 14, against the action of spring 32, fluid from inlet passage 18 moves past piston 16 by way of groove 34 to the top of piston 16. When piston 16 moves downwardly, disc-shaped seal 26 moves away from contact with contact ridge 42, thereby allowing fluid (still under regulated pressure) to pass by contact disc 38 by way of central opening 40, thereafter entering the collection space 54. Any fluid within collection space 54 will be forced into outlet passage 22 and eventually will be directed to a useful site (such as a desired treatment area of a patient's body).
Downward movement of piston 16 is controlled by applying a specific electric signal to the piezo crystal 53, the crystal will deform and will generate a slight downward displacement. This slight downward movement is transferred to the contact pin 25 through the actuation pin 55 and flexible membrane 50. Therefore, the particular electric signal applied to the piezo crystal 53 will indirectly control the opening of the valve assembly 10 and therefore the amount and effective rate of fluid passing from inlet passage 18 to outlet passage 22.
Referring to
In operation of valve assembly 100, as actuation pin 55 is linearly displaced downward against piston 16, by piezo crystal 53, membrane 102 will allow for greater displacement of piston 16 and concentric ripples 104 will help retain such displacement to within contact circle 110. As actuator pin 55 moves downwardly against contact circle 110 of membrane 102, concentric ripples 104 will effectively absorb such axial movement and will thereby attenuate the movement that reaches the peripheral brazed or welded edge 114 of membrane 102. Ripples 104 will therefore increase the effective life of the membrane by preventing damage to the relatively delicate brazed edge 114 between membrane 102 and the portal support ring 44.
Of course the particular dimensions of the rippled membrane 102, including the number and amplitude of the individual ripples 104 and their respective diameters, as well as the thickness and type of material used will vary depending on the particular application intended.
Referring now to
In operation of valve assembly 200, as actuation pin 55 is linearly displaced downward against piston 16, by piezo crystal 53, bellows membrane 202 will allow for greater displacement of piston 16 and bellows inward and outward bends 204 and 206, will help retain such displacement to within contact circle 208. As actuator pin 55 moves downwardly against contact circle 208 of membrane 202, the bellows structure will effectively absorb such axial movement and will thereby attenuate the magnitude of movement that reaches the mounting flange (and therefore the brazed or welded edge). This bellows structure of membrane 202 will therefore increase the effective life of the membrane by preventing damage to the relatively delicate brazed (or welded) edge between membrane 202 and the portal support ring 44.
Of course the particular dimensions of the bellows structure including the number of inward bends 204 and outward bends 206 and their respective inside diameters, as well as the thickness and type of material used will vary depending on the particular application intended. It should be noted that although the membranes of the present invention have been described in connection with an on-board control valve assembly as part of an implantable drug-infusion pump, the membranes of the present invention may be effectively applied to any hermetically sealed barrier for the purpose of allowing controlled mechanical interaction across the barrier without disrupting the hermetic qualities of the barrier.
According to a fourth embodiment of the invention, referring to
According to a fourth embodiment of the invention, referring to FIGS. 16, 17,18, 19 and 20, a rippled membrane 400 is shown having an upper shallow ripple 402 and a lower shallow ripple 404, with respect to a membrane plane 406, and a center contact circle 408. According to this fourth embodiment of the invention, membrane 400 further includes a curved peripheral edge 410 (may be curved up or down, but is shown curved up to explain the invention).
A portal membrane mounting ring 412 is shown having a central opening 414, a peripheral brazing groove 416 and a rounded support surface 418. According to the invention, membrane 400 is sized and shaped to snuggly fit into portal membrane mounting ring 412 so that upwardly curved peripheral edge 410 is positioned within brazing groove 416 and against rounded support surface 418. The purpose of this curved peripheral edge 410 and the brazing groove 416 is to discourage stress on the brazing weld caused by repeated flexing movement of the membrane 400. The curved peripheral edge 410 of this fourth embodiment can be applied to any shaped membrane described in this application, as well as the flat, coin-like membrane of the prior art.
