Syringe pumps

Abstract: A syringe pump has a drive mechanism 7 for moving the plunger 35 of a syringe 3 along a barrel 30. Ears 33 at the rear of the barrel 30 engage against a wall 32 on the pump and an L shape clamp arm 44 is urged against the ears by a spring 49. The clamp arm 44 is mounted about an axis at right-angles to the syringe 3 and is articulated at a point 45 along its length. A lever 52 having a flag 53 at one end is pivoted about a horizontal axis by movement of the arm and moves relative to an optical sensor 54 so that the output of the sensor indicates whether the syringe 3 is correctly loaded in the pump. The clamp arm 44 is rotated away from the barrel 30 by the drive mechanism during loading of the syringe 3.

Description: This invention relates to syringe pumps of the type adapted to receive a syringe of the kind having a plunger movable along a barrel with a nose outlet at its forward end and a rear end having a portion projecting radially outwardly. Syringe pumps are used to supply medication to a patient. A syringe is pre-filled with the medication and this is connected to an infusion line extending to the patient. The syringe is then loaded in the syringe pump, which applies a force to the plunger of the syringe to drive medication into the infusion line at a controlled rate. If the syringe is not correctly loaded in the pump, this could lead to jamming of the pump mechanism and to delays in administering fluid to the patient. EP 0567944 describes a syringe pump having a sensor that is actuated by contact with the barrel of a syringe. It is an object of the present invention to provide an alternative syringe pump. According to the present invention there is provided a syringe pump of the above-specified type, characterised in that the pump includes a movable member movable in a first direction towards engagement with the projecting portion at the rear end of the barrel, and a sensor for sensing the position of the movable member to detect whether or not the portion and hence the syringe is correctly positioned in the pump. The projecting portion at the rear end of the barrel are preferably ears, one side of which may engage a wall on the pump, the movable member engaging the opposite side of the ears. The movable member preferably includes an arm pivoted at one end and having an articulated joint at a location along its length. The sensor may include a lever pivoted by movement of the arm. The movable member preferably has a pad with a forward face and a V-shape edge surface, the forward face engaging the projecting portion at the rear end of the barrel and the V-shape edge surface lying against the plunger. The pump may move the movable member in a direction opposite the first direction prior to loading the syringe. The movable member may be moved in the opposite direction by a member coupled to a syringe drive mechanism. The movable member is preferably moved in the first direction by a spring. The sensor preferably includes an optical sensor. A syringe pump according to the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a simplified view of the front of the pump; and Figure 2 is a perspective view of a part of the pump. With reference first to Figure 1, the pump includes an outer housing 1 with a recess 2 on its front surface shaped to receive a syringe 3 of conventional kind. The syringe 3 has a cylindrical barrel 30 with an outlet or nose 31 at its forward end and an annular projection 32 at its rear end shaped to provide two radially-projecting ears 33 on opposite sides. The syringe 3 contains a medication liquid 34, which is dispensed to a patient via an infusion line 5 connected to the nose 31, by pushing in the plunger 35 of the syringe. The pump has a conventional drive mechanism 7, such as including a lead screw 8 driven by a motor 9, coupled with a mechanism 10 for engaging the head 36 of the plunger 35. The motor 9 is driven by a control unit 11, which receives inputs from a keypad 12, or other user input means, and various sensors. The control unit 11 also provides an output to a display 13. The forward side of the ears 33 on the syringe barrel 30 abut against a fixed vertical wall 37 in the recess 2, whereas the rear side is contacted by a movable clamp mechanism 40, which is shown more clearly in Figure 2. The clamp mechanism 40 includes a vertical crescent-shape pad 41 with a V-shape upper surface 42 located to lie against the underside of the plunger 35, with its forward face 43 contacting the rear face of the ears 33. The pad 41 is mounted at one end of an L-shape clamp arm 44 having an articulated joint 45 at its bend enabling limited angular movement between the forward part 46 of the arm, on which the pad is mounted, and the rear part 47 of the arm. The rear part 47 of the arm extends substantially transversely of the axis of the syringe 3 and has a pivotal joint 48 at its end rotatable about a vertical axis at right angles to the axis of the syringe. A spring 49 bears against the arm 44 urging it in a clockwise sense, as viewed from above, so that the pad 41 is pulled forwardly by the spring to clamp the ears 33 against the wall 37. About midway along its length, the rear part 47 of the arm 44 has a vertically-projecting pawl finger 50, which engages a slot 51 in the lower end of a lever 52. The lever 52 is pivoted about a horizontal axis midway along its length and its upper end is formed with a curved flag 53. The flag 53 is located adjacent an opto-electronic sensor 54 and is moved relative to the sensor in response to movement of the arm 44. The pawl finger 50 also has a vertical, forwardly-facing contact surface 55. The contact surface 55 is located for engagement by a cooperating contact surface on an actuating arm 56 coupled with the plunger engaging mechanism 10. This is arranged so that, when the plunger engaging mechanism 10 is at its rearmost position, such as for loading or unloading of the syringe 3, the actuating arm 56 engages the pawl finger 50 on the arm 44 and displaces the pad 41 rearwardly. In operation, therefore, when the pump is set for loading the syringe 3, the ear clamp mechanism 40 is open to enable the syringe to be loaded freely into the recess 2. As soon as the plunger engaging mechanism 10 is displaced forwardly to engage the plunger head 36, the actuating arm 56 disengages the arm 44, allowing its spring 49 to bring the pad 41 into contact with the rear of the ears 33 on the syringe barrel 30. This clamps the ears 33 and hence the syringe 3 in position. If the syringe 3 is correctly loaded, the arm 44, and the flag 53, will lie at a defined position and the sensor 54 will, therefore, provide an output to the control unit 11 indicative of correct syringe loading. The pump then proceeds with its normal operation. If, however, the syringe 3 were incorrectly loaded in such a way that its ears 33 were not correctly positioned against the wall 37, the arm 44 would either move beyond its correct rest position or would be prevented from moving as far as this. In either case, the control unit 11 would identify an incorrect output from the sensor 54 and prevent further operation of the pump. The control unit 11 would also generate an output to the display 13 to notify the user of incorrect syringe loading. The syringe pump of the present invention provides a rapid warning of incorrect syringe loading, thereby reducing the risk of problems that this might cause.

Claims: A syringe pump adapted to receive a syringe (3) of the kind having a plunger (35) movable along a barrel (30) with a nose outlet (31) at its forward end and a rear end having a portion (33) projecting radially outwardly, characterised in that the pump includes a movable member (40) movable in a first direction towards engagement with the projecting portion (33) at the rear end of the barrel (30), and a sensor (54) for sensing the position of the movable member (40) to detect whether or not the projecting portion (33) and hence the syringe (3) is correctly positioned in the pump. A syringe pump according to Claim 1, characterised in that the projecting portion at the rear end of the barrel are ears (33). A syringe pump according to Claim 2, characterised in that one side of the ears (33) engage a wall (37) on the pump, and that the movable member (40) engages the opposite side of the ears (33). A syringe pump according to any one of the preceding claims, characterised in that the movable member (40) includes an arm (44) pivoted at one end (48) and having an articulated joint (45) at a location along its length. A syringe pump according to Claim 4, characterised in that the sensor (54) includes a lever (52) pivoted by movement of the arm (44). A syringe pump according to any one of the preceding, characterised in that the movable member (40) has a pad (41) with a forward face (43) and a V-shape edge surface (42), and that the forward face (43) engages the projecting portion (33) at the rear end of the barrel (30) and the V-shape edge surface (42) lies against the plunger (35). A syringe pump according to any one of the preceding claims, characterised in that the pump moves the movable member (40) in a direction opposite the first direction prior to loading the syringe (3). A syringe pump according to Claim 7, characterised in that the movable member (40) is moved in the opposite direction by a member (56) coupled to a syringe drive mechanism (7). A syringe pump according to any one of the preceding claims, characterised in that the movable member (4) is moved in the first direction by a spring (49). A syringe pump according to any one of the preceding claims, characterised in that the sensor includes an optical sensor (54).

Inventors: COBB ANTHONY RICHARD, COBB, ANTHONY RICHARD
Applicants: SMITHS GROUP PLC
Application year: 2000
Main classification: A61M5
IPC codes: A61M5