US20070128055A1 - Diaphragm pump for medical applications - Google Patents

Abstract

An implantable diaphragm pump for use in medical applications comprising a housing having a pump cap, a valve plate, a diaphragm, and a base plate, wherein the pump cap and the valve plate are separated by the diaphragm, and the valve plate and lower surface of the diaphragm serve to form a pump chamber. A permanent magnet is attached to the pump cap within the diaphragm chamber wherein the lower surface of the permanent magnet is adjacent to the upper surface of the diaphragm. The diaphragm having a coil and a corrugated outer periphery, wherein when electrical current flows in a first direction through the coil, the diaphragm engages the lower surface of the permanent magnet, and when electrical current flows in a direction opposite the first direction, said diaphragm engages the upper surface of the valve plate.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• The present application is a divisional of co-pending U.S. Utility Patent Application Ser. No. 11/025,414, filed Dec. 29, 2004 which claims priority based on provisional application Ser. No. 60/588,668, filed Jul. 19, 2004.
FIELD OF THE INVENTION
• The present invention relates to a pump for medical applications, more particularly, to miniature or micro-pumps used in medical applications for delivering small quantities of therapeutic drugs.
BACKGROUND OF THE INVENTION
• Miniature or micro-pumps are currently used for a variety of medical purposes. Such devices are implantable in the human body and serve to deliver small quantities of therapeutic drugs. Currently, implantable infusion pumps are known to utilize a solenoid to drive a small piston. Because it is essential for these pumps to be both precise and reliable, the stroke length and cylinder bore must be precisely made, thereby allowing the pump to deliver a well controlled volume of fluid with each stroke. Manufacturing and assembly of miniature precision equipment of this type is extremely expensive requiring specialized tooling and inspection techniques.
• Furthermore, because these pumps are to be used as part of an implantable drug system, it is desirable that they be relatively thin so that they may be easily integrated into these systems. Additionally, the cylindrical shape of a piston pump, is cumbersome for such applications, and tends to take up more space than a relatively flat object such as a diaphragm pump would. While many of the prior art pumps contain diaphragms, the systems generally work in conjunction with a piston or solenoid.
• For example, turning now to the prior art patents, U.S. Pat. No. 6,537,268 to Gibson et al. discloses an infusion pump having a compressible source of compliance, such as, a plurality of diaphragms serving as pillows. While the prior art utilizes a pumping mechanism, it specifically requires a piston pump to compress the aforementioned diaphragms.
• Also, U.S. Patent Application Publication 2003/0135160 to Gray et al. discloses a drive mechanism for an infusion device having a coil surrounding a piston channel, the piston is located within the piston channel. In the retracted position the a piston chamber is formed between the piston and valve member, and filled with a fluid. When the piston is moved into the forward position chamber volume is reduced and pressure increases, moving the valve member to the open position to thereby discharge the fluid.
• Finally, U.S. Patent Application Publication 2002/0173773 to Olsen discloses an implantable substance delivery device having a permanent magnet solenoid pump. The pump piston is moveable within the pump cylinder wherein a fluid contained in the inlet chamber is displaced when the pump piston retracts. The fluid contained within the pumping chamber is displaced when the pump piston is actuated.
• Therefore, what is needed in the art is an implantable pump that eliminates the need for components having tight tolerances such as those found in miniature piston pumps.
• Furthermore, what is needed in the art is an implantable pump that is relatively thin and may be integrated easily into medical devices worn just beneath the skin.
SUMMARY OF THE INVENTION
• It is therefore, a primary object of this invention to provide a new and improved micro-pump for use in medical applications such as delivering small quantities of therapeutic drugs.
• An advantage of the present invention is that it eliminates the need for components having tight tolerances such as those found in miniature piston pumps.
• Another advantage of the present invention is that the diaphragm pump is relatively disk-shaped and may be integrated easily into medical devices worn just beneath the skin.
• The present invention provides an implantable diaphragm pump for use in medical applications comprising a housing having a pump cap, a valve plate having a textured surface, a diaphragm, and a base plate, wherein the valve plate and lower surface of the diaphragm serve to form a pump chamber. A permanent magnet is attached to the pump cap wherein the lower surface of the permanent magnet is adjacent to the upper surface to the diaphragm. The diaphragm has a corrugated outer periphery and a coil attached thereto. An electrical current applied to the coil in a first direction causes the diaphragm to engage the lower surface of the permanent magnet. An electrical current applied to the coil in the opposite direction to the first direction, causes the diaphragm to move away from the permanent magnet and engage the upper surface of the valve plate.
• An additional embodiment of the present invention provides an implantable diaphragm pump for use in medical applications comprising a valve plate, a base plate, and a diaphragm. The upper surface of the diaphragm having a piezoelectric material attached thereto, and the lower surface of the diaphragm and the valve plate serve to form a pump chamber. A means for supplying a voltage to the piezoelectric material is included, wherein the application of the voltage to the piezoelectric element shall cause the lower surface of the diaphragm to move toward or away from the upper surface of the valve plate.
BRIEF DESCRIPTION OF THE DRAWINGS
• The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and be better understood by reference to the following description of several embodiments of the invention in conjunction with the accompanying drawings, wherein:
• FIG. 1ais a cross-sectional view of a diaphragm pump according to a first embodiment of the invention;
• FIG. 1bis a plan view of the diaphragm pump ofFIG. 1 with the permanent magnet and inlet and outlet bores shown in phantom;
• FIG. 2 is a plan view of the valve plate ofFIG. 1;
• FIG. 3 is a map of the magnetic flux pattern over the cross-sectional view of the diaphragm pump ofFIG. 1; and
• FIG. 4 is a cross-sectional view of a diaphragm pump according to a second embodiment of the invention.
• Corresponding reference characters indicate corresponding parts throughout the several views. The examples set out herein illustrate several embodiments of the invention but should not be construed as limiting the scope of the invention in any manner.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Referring now to the drawings,FIGS. 1aand1billustrate themicro-diaphragm pump10 of the present invention. The body of the device of the present invention comprises abase plate12, avalve plate14, aspacer ring16, and acap18. Thebase plate12 comprises a pair of cylindrical bores, more particularly aninlet bore20 and an outlet bore22. Generally, a capillary or tube may be inserted within theaforementioned bores20 and22 for delivering and dispensing a fluid as necessary. The addition of the aforementioned tubes serves to assure that the fluids do not come in contact with the material of thebase plate12. Wherever possible, the component parts of the pump that come in contact with the fluid or the human body itself are made from a titanium alloy known to be inert to fluids used in medical applications and inert to body chemistry. Thebase plate12 is constructed of a soft magnetic material such as 29-4 stainless steel which is highly corrosion resistant but also good as a soft magnetic material. Additionally, thebase plate12 further comprises anupper surface24 and alower surface26, wherein the base plateupper surface24 is adjacent to the lower surface of thevalve plate14.
• Thevalve plate14 comprises aninlet valve28 and anoutlet valve30, which are adjacent to theinlet bore20 and the outlet bore22 of thebase plate12, respectively. Theinlet valve28 comprises aninlet valve seat32, an inlet biasing means34, and aninlet valve cover36. Theinlet valve seat32 is formed by the portion of the base plateupper surface24 proximate to the inlet bore20. The inlet biasing means34 abuts against aninlet rim38 formed in thevalve plate14 and biases theinlet valve cover36 against theinlet valve seat32. Theoutlet valve30 comprises anoutlet valve seat40, an outlet biasing means42, and anoutlet valve cover44. Theoutlet valve seat40 is formed by anoutlet rim46 formed in thevalve plate14. The outlet biasing means42 abuts against the base plateupper surface24 proximate to the outlet bore22 and biases theoutlet valve cover44 against theoutlet valve seat40.
• Thespacer ring16 and aprimary diaphragm48 are above the upper surface of thevalve plate14, thereby serving to form a chamber for receiving and dispensing the fluid. Thespacer ring16 may vary in thickness, but it is desirable for the thickness to be adequate to allow the actuator to travel a sufficient distance to maintain a compression ratio at or above 3:1. This minimum ratio is required to assure that trapped air bubbles do not shut down the pump. Theprimary diaphragm48 comprises a corrugated outer periphery49, allowing the diaphragm to travel toward or away from thevalve plate14. The stroke of theprimary diaphragm48 and the resulting volume of fluid delivered by thepump10 is therefore defined by the thickness of thespacer ring16. Varying the thickness of thespacer ring16 allows the pump delivery volume to be controlled in manufacturing. The delivered volume per stroke may also be altered, thus addressing use of thepump10 in a greater variety of applications.
• Adjacent to the upper surface of theprimary diaphragm48, thecap18 houses apermanent magnet50. In operation, thepermanent magnet50 operates in conjunction with acoil52 attached to the upper surface of theprimary diaphragm48, in a similar manner to a speaker, thereby serving as the actuation means for thepump10. Additionally, since thepump10 is designed to operate near atmospheric pressure, abreather hole54 and anequalization diaphragm56 are provided in thecap18, thereby serving to equalize the pressure between the environment and the chamber formed by thecap18 and theprimary diaphragm48. Theequalization diaphragm56 around thebreather hole54 maintains the clean environment around thepermanent magnet50 andcoil52, thus eliminating the need for corrosion protection of the magnet.
• As stated above, the device of the present invention operates on a similar principal as an audio speaker. As illustrated inFIG. 1, acoil52 is fixedly attached to the upper surface of theprimary diaphragm48. Because it is desirable for thepump10 to be as flat as possible, thecoil52 is mounted proximate to thetip58 of thepermanent magnet50, but not in thegap60. Thepermanent magnet50 may be constructed from any suitable material, such as neodymium-iron-boron or samarium-cobalt, having high coercivity and high residual induction. Additionally, a pair of coil leads62 provide a means for energizing thecoil52. WhileFIG. 1 shows a pair of coil leads62 penetrating the sidewall of thecap18, any suitable method of attaching the coil leads62 to thecoil52 is considered to be within the scope of the invention.
• In operation, when the electrical current flowing through thecoil52 changes direction, the polar orientation of thecoil52 reverses. This changes the magnetic forces between thecoil52 and thepermanent magnet50, thereby moving thecoil52 and attachedprimary diaphragm48 toward or away from thevalve plate14. As theprimary diaphragm48 moves away from thevalve plate14, it serves to open theinlet valve28, thereby drawing the fluid through theinlet20, into the area between theprimary diaphragm48 andvalve plate14, hereinafter referred to as thepump chamber64. As theprimary diaphragm48 approaches thevalve plate14, the fluid in thepump chamber64 serves to direct a force on theoutlet valve cover44 sufficient to counter the outlet biasing means42, thereby dispensing the fluid stored in thepump chamber64.
• Theprimary diaphragm48 is made from titanium alloy such at Ti Grade 1-4 or Grade 5 which is desirable for medical applications and does not react with body chemistry or fluids typically used in medical applications. Additionally, thevalve plate14 is made from titanium such as Ti Grade 1-4 or Grade 5. Theinlet valve cover36 and theoutlet valve cover44 are made from silicone rubber. Thebase plate12, which does not come in contact with the fluid, is made from a soft magnetic material such as 29-4 stainless steel which is highly corrosion resistant but also good as a soft magnetic material. As stated above, wherever possible, the component parts of thepump10 that come in contact with the fluid or the human body should be constructed from a titanium alloy known to be inert to fluids used in medical applications and inert to body chemistry.
• Furthermore, the aforementioned soft magnetic material of thebase plate12 has been selected so that it may serve to shield thepermanent magnet50 from large external fields, such as those experienced, during magnetic resonance imaging (MRI). Furthermore, as illustrated inFIG. 1, thepump10 has been designed so that thebase plate12 is an appreciable distance from the face of thepermanent magnet50. Large external fields would otherwise serve to partially de-pole thepermanent magnet50.
• As stated above, the outer periphery of theprimary diaphragm48 has a corrugated section49 so as to permit theprimary diaphragm48 to move up and down. As theprimary diaphragm48 moves toward or away from thevalve plate14, it alternatively comes in contact with thevalve plate14 and thepermanent magnet50. Referring now toFIG. 2, a first raisedpattern66 is machined on thevalve plate14 at the center of thepump10. Additionally, a similar second raisedpattern68 is machined on the surface of themagnet50, proximate to theprimary diaphragm48. The purpose of the raisedpatterns66 and68 is to prevent theprimary diaphragm48 from adhering to thevalve plate14 or thepermanent magnet50. The raisedpatterns66 and68 are generally disposed as groves running in the direction of the fluid flow. This orientation allows any bubbles in the fluid to move through thepump10 in the direction of flow to thereby minimize the trapping of bubbles, a known cause of pump failure. Additionally, as stated earlier, trapped air bubbles can shut down the pump unless a compression ratio of the pump is at least 3:1 is maintained and thespacer ring16 must be thick enough that the actuator travel is sufficient to maintain the compression ratio at or above this level. The compression ratio in this case shall be defined as the ratio between the volume of thepump chamber64 when theprimary diaphragm48 is fully pressed against themagnet50 to the volume of thechamber64 when theprimary diaphragm48 is biased to press against thevalve plate14 when current does not flow through thecoil52.
• Referring now toFIG. 3, the magnetic flux pattern surrounding thepermanent magnet50 is shown. Generally for high energy magnets such as samarium cobalt and neodymium-iron-boron, magnetic flux lines are particularly strong around the tip of the magnet. The magneticallysoft cap18 used for audio speaker motors is typically placed close to themagnet50 in order to concentrate the flux. Additionally, while a thin andlong coil50 is utilized for a particular embodiment of the present invention, any suitable coil is considered to be within the scope of the invention. Additionally, an embodiment is contemplated wherein the entireprimary diaphragm48 is enclosed on the inside of cap to take advantage of the strong field near the tip of themagnet50. The coil leads62 may be constructed from Litz wire, or flat spiral springs made from a material such as phosphor-bronze.
• Referring now toFIG. 4., an alternative embodiment of the present invention is shown. The micro-diaphragm pump110 of this particular embodiment comprises abase plate112, avalve plate114, aspacer ring116, and areturn stop arm170. Thebase plate112 comprises a pair of cylindrical bores, more particularly an inlet bore120 and anoutlet bore122. Generally, a capillary or tube may be inserted in theaforementioned bores120 and122 for delivering and dispensing a fluid as necessary. The addition of the aforementioned tubes serves to assure that the fluids do not come in contact with the material of thebase plate112. Wherever possible, the component parts of the pump110 that come in contact with the fluid or the human body itself are made from a titanium alloy known to be inert to fluids used in medical applications and inert to body chemistry. Thebase plate112 is constructed of a soft magnetic material such as 29-4 stainless steel which is highly corrosion resistant but also good as a soft magnetic material. Thebase plate112 further comprises an base plateupper surface124 and a base platelower surface126, wherein said base plateupper surface124 is adjacent to the lower surface of thevalve plate114.
• Thevalve plate114 comprises aninlet valve128 and anoutlet valve130, which are respectively adjacent to the inlet bore120 and the outlet bore122 of thebase plate112. Theinlet valve128 comprises aninlet valve seat132, an inlet biasing means134, and aninlet valve cover136. Theinlet valve seat132 is formed by the portion of the base plateupper surface124 proximate to the inlet bore120. The inlet biasing means134 abuts against aninlet rim138 formed in thevalve plate114 and biases theinlet valve cover136 against theinlet valve seat132. Theoutlet valve130 comprises anoutlet valve seat140, an outlet biasing means142, and anoutlet valve cover144. Theoutlet valve seat140 is formed by anoutlet rim146 formed in thevalve plate114. The outlet biasing means142 abuts against the base plateupper surface124 proximate to the outlet bore122 and biases theoutlet valve cover144 against theoutlet valve seat140.
• Theconductive spacer ring116 and adiaphragm148 are located above thevalve plate114, thereby serving to form a pump chamber164 for receiving and dispensing a fluid. Varying the thickness of thespacer ring116 allows the pump delivery volume to be controlled in manufacturing. The delivered volume per stroke may also be altered, thus addressing use of the pump110 in a greater variety of applications.
• In the embodiment illustrated inFIG. 4, apiezoelectric actuator172 is used as the motive force to deform the titanium membrane. Thepiezoelectric actuator172 has a high d31 constant and is optimized in thickness to provide the maximum deformation of thediaphragm148. While this particular embodiment uses lead-zirconate-titanate piezoelectric materials such as PZT-5B or PZT-5H, other piezoelectric materials may be used and are considered within the scope of the invention.
• The aforementionedpiezoelectric actuator172 is between anelectrode174 and thediaphragm148. In the illustrated embodiment theelectrode174 is screen printed and fired onto thepiezoelectric actuator172. Furthermore, thediaphragm148 serves as the second electrode. Thediaphragm148 is grounded through theconductive ring spacer116 to thevalve plate114 andbase plate112. A pair ofelectrical leads162 are made of a material such as Litz wire or spiral springs. One of the electric leads162 is bonded to theelectrode174 and the other is bonded to thediaphragm148. Thediaphragm148 bottoms on thevalve plate114 and thereturn stop arm170 limits the travel in the upward or return stroke direction. Both thevalve plate114 and thestop arm170 are textured in such a way as to reduce the surface contact area withrespective patterns166 and168. Thepatterns166 and168 are similar to thepattern66 shown inFIG. 2.
• Alternatively, thepiezoelectric actuator172 is isolated from thebase plate112 simply by replacing theconductive ring spacer116 with a non-conductive spacer ring. In this instance, thepatterns166 and168 are made of a material that is non-conductive, such as a screen printed epoxy compatible with the fluids involved.
• Furthermore, thepiezoelectric actuator172 may be driven bi-directionally against both the upper and the lower stops to reduce the effect of piezoelectric creep.
• The adjustable spacer ring allows simplified manufacture of an accurate pump because tight manufacturing tolerances of the pump components are not needed. Further, the fact that the travel of the diaphragm is controlled by the distance between the valve plate and the magnet in the first embodiment and the return stop arm in the second embodiment means that control of the pump is simplified. This is because the compression ratio is fixed by the spacer ring and is not controlled by the magnitude of the electric current supplied to the pump. The affect the magnitude of the electric current has on the travel of the diaphragm may change over time or be influenced by outside electromagnetic fields.
• While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the present invention using the general principles disclosed herein. Further, this application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims (19)

1. An implantable diaphragm pump for use in medical applications comprising:

a housing comprising a valve plate and a diaphragm;

a pump chamber between said valve plate and said diaphragm;

a permanent magnet being proximate to said diaphragm; and

said diaphragm comprising a coil, wherein varying the direction of electrical current applied to said coil shall cause the diaphragm to engage either the permanent magnet or the valve plate.

2. The diaphragm pump ofclaim 1, wherein said housing further comprises a pump cap that supports said permanent magnet and a base plate that supports said valve plate.

3. The implantable diaphragm pump ofclaim 2, wherein said pump cap and said valve plate are separated by said diaphragm.

4. The implantable diaphragm pump ofclaim 2, wherein:

said pump cap and said diaphragm form a diaphragm chamber; and

said pump cap further comprises a breather hole to equalize pressure between the diaphragm chamber and the environment.

5. The implantable diaphragm pump ofclaim 4 further comprising a membrane between said breather hole and said diaphragm chamber.

6. The diaphragm pump ofclaim 1, wherein said diaphragm further comprises a corrugated outer periphery.

7. The implantable diaphragm pump ofclaim 1, wherein said permanent magnet comprises a textured surface to thereby impede said diaphragm from sticking to said permanent magnet.

8. The implantable diaphragm pump ofclaim 1, wherein said valve plate comprises a textured surface to thereby impede said diaphragm from sticking to said valve plate.

9. The implantable diaphragm pump ofclaim 8 wherein said valve plate textured surface comprises a raised pattern wherein grooves of said raised pattern run in the direction in which fluid flows in said pump chamber.

10. The implantable diaphragm pump ofclaim 1 further comprising a spacer ring between said diaphragm and said valve plate, wherein varying the thickness of said spacer ring shall vary the volume of the pump chamber.

11. The implantable diaphragm pump ofclaim 1 further comprising an inlet and an outlet wherein the pump shall serve to either draw fluid into said pump chamber through said inlet or deliver a metered dose of said fluid through said outlet dependant upon the polarity of the coil.

12. An implantable diaphragm pump for use in medical applications comprising:

a valve plate, a base plate, and a diaphragm:

said diaphragm having an upper surface and a lower surface, wherein said diaphragm upper surface comprises a piezoelectric material, and said valve plate and said diaphragm lower surface form a pump chamber;

wherein the presence of a voltage shall cause said diaphragm to displace relative to said valve plate.

13. The implantable diaphragm pump ofclaim 12 further comprising a spacer ring between said diaphragm lower surface and said valve plate, wherein said spacer ring may serve to vary the volume of the pump chamber.

14. The implantable diaphragm pump ofclaim 12 further comprising a spacer ring between said diaphragm lower surface and said valve plate, wherein said spacer ring may serve to electrically isolate said diaphragm from said valve plate.

15. The implantable diaphragm pump ofclaim 12 further comprising a return stop arm, wherein said return stop arm is mounted to said base plate and suspended above said diaphragm upper surface an appropriate distance to limit travel of said diaphragm in the upward direction.

16. The implantable diaphragm pump ofclaim 15 wherein said return stop arm has a lower surface with a first raised pattern and wherein said valve plate upper surface comprises a second raised pattern.

17. The implantable diaphragm pump ofclaim 12 wherein said valve plate upper surface comprises a raised pattern wherein a plurality of grooves in said raised pattern run in the direction in which fluid flows in said pump chamber.

18. The implantable diaphragm pump ofclaim 12 further comprising an inlet and an outlet wherein the pump shall serve to either draw a fluid into said pump chamber through said inlet or deliver a metered dose of said fluid through said outlet, dependant upon the voltage applied to the piezoelectric material.

19. The implantable diaphragm pump ofclaim 12 wherein said piezoelectric material further comprises a conductive layer for receiving an electrical lead.

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