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Publication Number
US-10258739-B2
Publication Date
2019-04-16
Expiration Date
Abstract
A mechanical driver comprising a wedge shaped member operatively coupled to a shape memory alloy such that the shape memory alloy is able to displace the wedge shaped member in an essentially linear direction. The wedge shaped member is in constant contact with a lever arranged so that it can rotate about a fixed pivot point. A piston is arranged such that it is constant contact with the lever at a point between the pivot point of the lever and the contact point between the lever and the wedge shaped member. Activation of the shape memory alloy displaces the wedge shaped member along its linear direction and this causes the lever to be deflected about its pivot point and the piston to be deflected in an essentially linear direction that is perpendicular to the linear direction of travel of the wedge shaped member.
Core Innovation
The invention relates to a miniature mechanical driver for micro-pumps in which a shape memory alloy, typically as an SMA wire, is operatively coupled to a wedge shaped member. The SMA is held at a predetermined tension in its start position and moves the wedge shaped member relative to a piston so that the wedge deflects the piston.
The wedge shaped member is arranged so that it moves only in a substantially linear direction relative to the piston while remaining in constant contact with the piston. The piston drive point/contact point on the lever and the relationship between the wedge travel and the piston motion are described so that piston motion is essentially perpendicular to wedge travel.
The driver further uses elastomeric return springs, including configurations where the return spring acts on the wedge, lever, and/or piston. In some embodiments, the piston return spring forms a pumping membrane. Wedge geometry, including restrictions on wedge rotation and wedge surfaces such as single or two angled surfaces and planar surfaces, is described to improve accuracy/repeatability and manufacturing scalability under injection molding/casting tolerances.
Claims Coverage
The partial content provides two independent claims, each defining a mechanical driver with a piston and a wedge shaped member driven by a shape memory alloy under predetermined tension, with claim 22 adding a return spring that forms a pumping membrane of a micro pump. The inventive features are primarily centered on constant contact wedge-to-piston coupling with substantially linear wedge motion, SMA held under predetermined tension to deflect the piston, and restoring action via a return spring specifically forming a pumping membrane in claim 22.
Constant-contact wedge deflects a piston via SMA at predetermined tension
A mechanical driver comprising a piston and a wedge shaped member operatively coupled and in constant contact with the piston and moveable relative to the piston; a shape memory alloy operatively coupled to the wedge shaped member to move the wedge shaped member relative to the piston such that the wedge shaped member deflects the piston; wherein the shape memory alloy is held at a predetermined tension in its start position.
Substantially linear wedge motion relative to the piston while in constant contact
The mechanical driver wherein the wedge shaped member is arranged so that it moves only in a substantially linear direction relative to the piston while the wedge shaped member is operatively coupled and in constant contact with the piston.
Return spring returns the piston and forms a pumping membrane
A mechanical driver comprising a piston; a wedge shaped member operatively coupled and in constant contact with the piston and moveable relative to the piston; a shape memory alloy operatively coupled to the wedge shaped member to move the wedge shaped member relative to the piston such that the wedge shaped member deflects the piston, wherein the shape memory alloy is held at a predetermined tension in its start position; and a return spring operatively coupled to the piston, and acting to return the piston to its starting position; wherein the return spring forms a pumping membrane of a micro pump.
Across the independent claims, the core claim coverage is directed to a piston-deflecting wedge driven by an SMA held at predetermined tension, with the wedge constrained to substantially linear motion relative to the piston while maintaining constant contact. One claim additionally requires a return spring that both returns the piston and forms a pumping membrane of a micro pump.
Stated Advantages
Not explicitly described in patent.
Documented Applications
A pump for pumping a liquid therapeutic product, using a pumping chamber with an inlet valve and an outlet valve, wherein the volume of the pumping chamber changes due to actuation of the mechanical driver.
An infusion system for pumping liquid therapeutic products, including a reservoir and therapeutic product pumping using the disclosed pumping chamber volume change driven by piston motion.
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