Drive mechanisms for positive displacement pumps

Abstract

A novel embodiment of a pump system, for example, of the type that would be used in a wearable drug delivery system, comprises, in a preferred embodiment, a reservoir, a plunger, disposed within the reservoir and driven by a scissor mechanism connected to a drive mechanism through a linkage, such that a force imparted by the drive mechanism in causes the scissor mechanism to expand thereby causing the plunger move within the reservoir to force a liquid drug contained within the reservoir through a fluid port to a patient.

1 . A pump mechanism comprising:
 a reservoir comprising a tube-like structure having one open end and one closed end, the closed end configured with a fluid path;   a plunger, disposed in the reservoir, the plunger configured move longitudinally within the reservoir; and   a scissor mechanism coupled to the plunger and extending out through the open end of the reservoir.   
     
     
         2 . The pump mechanism of  claim 1 , further comprising:
 a drive mechanism coupled to the scissor mechanism for driving the scissor mechanism between a contracted position and an expanded position;   wherein movement of the scissor mechanism from the contracted position to the expanded position causes the plunger to move longitudinally in the reservoir toward the closed end of the reservoir.   
     
     
         3 . The pump mechanism of  claim 2  wherein the drive mechanism comprises:
 a leadscrew; and 
 a drive nut in threaded engagement with the leadscrew such that rotational motion of the leadscrew translates to a linear motion of the drive nut; 
 wherein the drive nut is coupled to the scissor mechanism. 
 
     
     
         4 . The pump mechanism of  claim 3  further comprising:
 a linkage coupling the drive nut to the scissor mechanism. 
 
     
     
         5 . The pump mechanism of  claim 1  wherein:
 the scissor mechanism is rotatably coupled to the plunger at one end; and 
 the scissor mechanism is rotatably coupled to a body of a device at an opposite end. 
 
     
     
         6 . The pump mechanism of  claim 5  wherein the reservoir is coupled to the body of the device such that the reservoir and the end of the scissor mechanism coupled to the body of the device are unable to move with respect to each other. 
     
     
         7 . A pump mechanism comprising:
 a reservoir comprising a tube-like structure having one open end and one closed end, the closed end configured with a fluid path;   a plunger, disposed in the reservoir, the plunger configured move longitudinally within the reservoir;   a first scissor mechanism coupled to the plunger and extending out through the open end of the reservoir; and   a second scissor mechanism coupled to the first scissor mechanism via a linkage.   
     
     
         8 . The pump mechanism of  claim 7 , further comprising:
 a drive mechanism coupled to the second scissor mechanism for driving the scissor mechanism between a contracted position and an expanded position;   wherein movement of the second scissor mechanism from the contracted position to the expanded position movement of the first scissor mechanism from the contracted position to the expanded position, thereby causing the plunger to move longitudinally in the reservoir toward the closed end of the reservoir.   
     
     
         9 . The pump mechanism of  claim 8  wherein the drive mechanism comprises:
 a leadscrew; and 
 a drive nut in threaded engagement with the leadscrew such that rotational motion of the leadscrew translates to a linear motion of the drive nut; 
 wherein the drive nut is coupled to the second scissor mechanism. 
 
     
     
         10 . The pump mechanism of  claim 9  wherein the reservoir and the linkage are coupled to a body of a device such that the reservoir and the linkage are unable to move with respect to each other. 
     
     
         11 . A pump mechanism comprising:
 a reservoir comprising a tube-like structure having one open end and one closed end, the closed end configured with a fluid path;   a plunger, disposed in the reservoir, the plunger configured move longitudinally within the reservoir;   a first magnet, coupled to the plunger;   a second magnet, external to the reservoir and able to move longitudinally along an outside surface of the reservoir; and   a drive mechanism coupled to the second magnet for driving the second magnet along the outside surface of the reservoir.   
     
     
         12 . The pump mechanism of  claim 11 , wherein movement of the second magnet longitudinally along the outside surface of the reservoir causes the first magnet, and thus the plunger, to move longitudinally through the interior of the reservoir based on a magnetic engagement between the second magnet and the first magnet. 
     
     
         13 . The pump mechanism of  claim 12  wherein the second magnet is in the shape of a collar surrounding the outside surface of the reservoir; 
     
     
         14 . The pump mechanism of  claim 13  wherein the outside surface of the reservoir is configured with one or more guide ridges to keep the second magnet in alignment as it moves along the outside surface of the reservoir. 
     
     
         15 . The pump mechanism of  claim 11  wherein the drive mechanism comprises:
 a leadscrew; 
 wherein:
 an outside surface of the second magnet is configured with threads; 
 the second magnet and leadscrew are in threaded engagement with each other; 
 rotation of the leadscrew in a first direction will cause movement of the second magnet in a first longitudinal direction along the outside surface of the reservoir; and 
 rotation of the leadscrew in a second direction will cause movement of the second magnet in a second longitudinal direction along the outside surface of the reservoir. 
 
 
     
     
         16 . The pump mechanism of  claim 11  wherein the reservoir and the drive mechanism are rigidly attached to a body of a device such that the reservoir and drive mechanism are unable to move with respect to each other. 
     
     
         17 . A pump mechanism comprising:
 a reservoir comprising a tube-like structure having one open end and one closed end, the closed end configured with a fluid path;   a plunger, disposed in the reservoir, the plunger configured move longitudinally within the reservoir;   a tether, extending through a sealed opening in the closed end of the reservoir and coupled to the plunger; and   a drive mechanism, for pulling the tether through the sealed opening, thereby causing the plunger to move toward the closed end of the reservoir.   
     
     
         18 . The pump mechanism of  claim 17  wherein the drive mechanism comprises a take-up reel, coupled to the tether, such that rotation of the take-up reel will cause the tether to be pulled through the sealed opening of the reservoir. 
     
     
         19 . The pump mechanism of  claim 18  further comprising:
 one or more pulleys to guide the tether from the take-up reel to the sealed opening. 
 
     
     
         20 . The pump mechanism of  claim 17  wherein the reservoir and the drive mechanism are rigidly connected to a body of the device such that the reservoir and the drive mechanism are unable to move with respect to each other. 
     
     
         21 . The pump mechanism of  claim 17  wherein the tether is coupled to a surface of the plunger interior to the reservoir. 
     
     
         22 . The pump mechanism of  claim 17  wherein an end of the tether opposite an end coupled to the drive mechanism is anchored and further wherein the tether is coupled to the plunger via one or more pulleys mounted on a surface of the plunger exterior to the reservoir.