| 摘要 |
PCT No. PCT/AU95/00029 Sec. 371 Date Sep. 16, 1996 Sec. 102(e) Date Sep. 16, 1996 PCT Filed Jan. 20, 1995 PCT Pub. No. WO95/20145 PCT Pub. Date Jul. 27, 1995A syringe pump having a drive head (1) mounted on a lead screw (2) which drives the drive head (1) to cause the plunger (P) of the syringe (S) to be advanced to deliver the contents of the syringe in a controlled manner. The drive head (1) supports a sensing module (3) having a cylindrical outer metallic body supporting a sensor disk (9) to which a sensing button (10) is attached. The disk (9) has a central insulating disk (15) supporting copper plates (16 and 17) and thin layers of dielectric (18, 19) separated from ground plates (20, 21) by an air gap (22) defining separate electrical capacitors each having a significantly different value of capacitance such that a large fall in capacitance occurs in the first capacitor while a large rise in capacitance occurs in the second capacitor. The capacitors are connected to an integrated circuit (23) which detects changes in capacitance caused by small forces applied to the button (10) to provide signals representative of contact with the button (10) and/or the force applied by the button (10) and the plunger (P). The drive head (1) also carries spring loaded pawls (26, 27) which engage behind the flange of the plunger (P) of the syringe (S) to prevent plunger movement caused by siphoning or other undesired movement of the plunger.
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