Cover for liquid delivery system with integrated plunger position sensing using focused optical beam and linear potentiometer
A sliding cover for a liquid delivery device, such as a cap ( 100 ) for a pen injector ( 200 ), incorporates a set of sensors including an optical sensor ( 110 ) with an output which changes during uncapping or capping motions on passing of a plunger ( 220 ) of the pen injector. This output is used together with a position sensor ( 120 ) to determine the position of the plunger along a cylinder ( 210 ) of the liquid delivery device. By monitoring changes in the plunger position, the quantity of dosages delivered by the liquid delivery device can be determined, displayed, stored and/or transmitted to an external device for further data processing or storage. Preferred implementations of the invention employ optical sensors with a converging beam ( 115 ), and/or position sensors employing linear potentiometer strips ( 132 ).
1 . An apparatus for use with a liquid delivery system, the liquid delivery system including a transparent cylinder for housing a liquid and an at least partially opaque plunger movable along an axis of the cylinder for expelling the liquid through an outlet, the apparatus comprising:
(a) a sliding cover configured for sliding engagement with the cylinder so as to be slidable along the cylinder parallel to the axis from a first position to a second position;
(b) a set of sensors housed in said sliding cover so as to move together with said sliding cover, said set of sensors comprising:
(i) an optical sensor having an optical emitter for emitting radiation and an optical receiver for generating a first output indicative of an amount of said radiation received by said optical receiver, and
(ii) a position sensor for generating a second output indicative of a current position of said sliding cover between said first position and said second position; and
(c) a processing system associated with said set of sensors so as to receive at least said first output and said second output, said processing system being configured to determine a position of the plunger along the cylinder based on said first output and said second output.
2 . The apparatus of claim 1 , wherein said optical sensor further comprising a focusing element deployed in relation to said optical emitter so as to generate a converging beam of radiation converging towards a focal point, said converging beam being directed inwards.
3 . The apparatus of claim 2 , wherein said focusing element comprises a refractive lens.
4 . The apparatus of claim 2 , wherein said optical emitter and said focusing element are deployed such that said converging beam reaches said focal point after traversing a majority of a width of the transparent cylinder.
5 . The apparatus of claim 2 , wherein said focal point lies at or near a wall of the transparent cylinder.
6 . The apparatus of claim 1 , wherein said sliding cover is implemented as a cap with a central bore for receiving an end portion of a pen injector having a projecting needle.
7 . The apparatus of claim 6 , further comprising a cradle slidingly mounted within said central bore, said cradle configured for receiving the end portion of the pen injector, said cradle being spring biased towards an end position for engaging the end portion of the pen injector when said sliding cover is in said first position, and being retractable to move together with the end portion of the pen injector as said sliding cover slides to said second position.
8 . The apparatus of claim 7 , wherein said position sensor is associated with said cradle so that said second output is indicative of a current position of said cradle within said central bore.
9 . The apparatus of claim 8 , wherein said position sensor comprises a linear potentiometer strip deployed within said cap so as to extend parallel to said axis, and a pressure element mounted to said cradle and biased so as to press against said linear potentiometer strip.
10 . The apparatus of claim 9 , wherein said pressure element comprises a spring-loaded ball.
11 . The apparatus of claim 9 , wherein said pressure element comprises a leaf spring mounted to said cradle, said leaf spring providing a protuberance deployed so as to press against said linear potentiometer strip.
12 . The apparatus of claim 11 , wherein said leaf spring is implemented as a folded cantilever leaf spring, and wherein said folded cantilever leaf spring comprises a first elongated segment anchored to said cradle, and a second elongated segment connected to said first elongated segment via a bend region, wherein said protuberance is provided on said second elongated segment, said first and second elongated segments and said bend region being configured so accommodate radial displacement of said protuberance towards said cradle without generating axial displacement of said protuberance relative to said cradle.
13 . An apparatus for use with a pen injector, the pen injector including a transparent cylinder for housing a liquid and an at least partially opaque plunger movable along an axis of the cylinder for expelling the liquid through an outlet, the apparatus comprising:
(a) a cap with a central bore extending along an axis, said cap configured for sliding engagement with the cylinder so as to be slidable along the cylinder parallel to the axis from a first position to a second position;
(b) a cradle slidingly mounted within said central bore, said cradle configured for receiving an end portion of the pen injector, said cradle being spring biased towards an end position for engaging the end portion of the pen injector when said cap is in said first position, and being retractable to move together with the end portion of the pen injector as said cap slides to said second position;
(c) a set of sensors housed in said cap so as to move together with said cap, said set of sensors comprising:
(i) an optical sensor having an optical emitter for emitting radiation and an optical receiver for generating a first output indicative of an amount of said radiation received by said optical receiver, and
(ii) a position sensor deployed for generating a second output indicative of a current position of said cradle within said central bore; and
(d) a processing system associated with said set of sensors so as to receive at least said first output and said second output, said processing system being configured to determine a position of the plunger along the cylinder based on said first output and said second output.
14 . The apparatus of claim 13 , said position sensor comprises a linear potentiometer strip deployed within said cap so as to extend parallel to said axis, and a pressure element mounted to said cradle and biased so as to press against said linear potentiometer strip.
15 . The apparatus of claim 14 , wherein said pressure element comprises a spring-loaded ball.
16 . The apparatus of claim 14 , wherein said pressure element comprises a leaf spring mounted to said cradle, said leaf spring providing a protuberance deployed so as to press against said linear potentiometer strip.
17 . The apparatus of claim 16 , wherein said leaf spring is implemented as a folded cantilever leaf spring, and wherein said folded cantilever leaf spring comprises a first elongated segment anchored to said cradle, and a second elongated segment connected to said first elongated segment via a bend region, wherein said protuberance is provided on said second elongated segment, said first and second elongated segments and said bend region being configured so accommodate radial displacement of said protuberance towards said cradle without generating axial displacement of said protuberance relative to said cradle.
18 . The apparatus of claim 13 , wherein said optical sensor further comprises a focusing element deployed in relation to said optical emitter so as to generate a converging beam of radiation converging towards a focal point, said converging beam being directed obliquely inwards.
19 . The apparatus of claim 18 , wherein said focusing element comprises a refractive lens.
20 . The apparatus of claim 18 , wherein said optical emitter and said focusing element are deployed such that said converging beam reaches said focal point after traversing a majority of a width of the transparent cylinder, and said focal point lies at or near a wall of the transparent cylinder.