Abstract: Provided is an anesthetic solution-filled cartridge-type electric dental syringe, wherein the plunger has been shortened but the plunger can nevertheless be extended to the distance necessary to evacuate the anesthetic solution from the cartridge. The syringe comprises: an extension tube into which a plunger is movably inserted, the extension tube being movably disposed in the through hole of a support block and having racks formed in the side surface thereof that are coordinated with the racks of the plunger; and a means for the plunger to draw the extension tube to engage the racks of the extension tube with a pinion when the plunger reaches the middle of the distance corresponding to the anesthetic solution accommodation length of the cartridge. By the engagement of the racks of the extension tube with the pinion, the plunger moves together with the extension tube for the remainder of the distance corresponding to the anesthetic solution accommodation length of the cartridge.

Abstract: A motorized syringe for use with two types of dental anesthetic solution-filled cartridges, having a plunger plug in the 1.8 ml cartridge pushed by a push rod by a length required to push a plunger plug in the 1.0 ml cartridge. The syringe includes a cartridge holder for use with 1.0 ml and 1.8 ml cartridges, the push rod having a 1.0 ml position and a 1.8 ml position drawn back from the 1.0 ml position so that push rod movement can end at a common terminal position for both, a sleeve adapted to receive the push rod rear end when pushed back from the common terminal position, and to be not interfered with by the push rod's rear end when it is in the 1.0 ml position, the sleeve being pushed rearward with the push rod's rear end when pushed back to the 1.8 ml position.

Abstract: A motorized syringe for use with two types of dental anesthetic solution-filled cartridges, having a plunger plug in the 1.8 ml cartridge pushed by a push rod by a length required to push a plunger plug in the 1.0 ml cartridge. The syringe includes a cartridge holder for use with 1.0 ml and 1.8 ml cartridges, the push rod having a 1.0 ml position and a 1.8 ml position drawn back from the 1.0 ml position so that push rod movement can end at a common terminal position for both, a sleeve adapted to receive the push rod rear end when pushed back from the common terminal position, and to be not interfered with by the push rod's rear end when it is in the 1.0 ml position, the sleeve being pushed rearward with the push rod's rear end when pushed back to the 1.8 ml position.

Abstract: A linear cartridge-type motorized dental syringe has a plunger rod aligned with a drive shaft of a motor, the externally threaded plunger rod movable longitudinally, but not rotatably, relative to the casing, a cylindrical body rotated by the shaft, a nut having arm-like nut halves with internal threads engaging external threads on the rod, a locking ring for rotation around an axis of the rod and for longitudinal movement between a rearward position where the ring forces the threads on the nut halves to engage the threads on the rod, and forward where the ring releases engagement of the threads, pusher pins for moving the ring rearward when the cartridge holder is inserted, and a spring for pushing the locking ring back to the forward position, with rotation of the cylinder body resulting in rotative motion of the nut around the rod to move it forward.

Abstract: A linear cartridge-type motorized dental syringe has a plunger rod aligned with a drive shaft of a motor, the externally threaded plunger rod movable longitudinally, but not rotatably, relative to the casing, a cylindrical body rotated by the shaft, a nut having arm-like nut halves with internal threads engaging external threads on the rod, a locking ring for rotation around an axis of the rod and for longitudinal movement between a rearward position where the ring forces the threads on the nut halves to engage the threads on the rod, and forward where the ring releases engagement of the threads, pusher pins for moving the ring rearward when the cartridge holder is inserted, and a spring for pushing the locking ring back to the forward position, with rotation of the cylinder body resulting in rotative motion of the nut around the rod to move it forward.

Abstract: Disclosed are a method and apparatus for controlling the injection rate of an anesthetic solution in a cartridge type motor-driven injection syringe for dental use, particularly beginning with the “Low” rate injection at the outset, and switching to the “Medium” or “High” injection rate at an arbitrarily selected time in the course of injection. The speed of revolution of the electric motor is changed among the low, medium and high speed, and a two-step operable type of switch is used as a starter switch 13. The first depression of the starter switch makes the electric motor 9 start at the low speed, thereby making the plunger rubber 5 initially move at the “Low Speed” in the cartridge 6 via the plunger rod 12, and the second depression of the switch makes the electric motor 9 run at the low, medium or high speed, and accordingly the plunger rod moves at the selected “Low Speed”, “Medium Speed” or “High Speed”.

Abstract: There is provided an injection needle removing apparatus for dental cartridge syringe comprising a chuck device (22) mounted within a housing (11) and including chuck jaws (26) for gripping a needle hub (25?), means for opening and closing the chuck jaws, a needle receptacle (14) adapted to rotatably support the housing (11), and means (50, 55, 56) for rotating the housing relative to the receptacle, the rotation of the housing causing the chuck device, together with the housing, to be rotated relative to the injection needle, thereby removing the injection needle from the syringe. In this arrangement, any rotative power transmission mechanism is not required to rotate the chuck device itself relative to the syringe.

Abstract: An electrically-driven dental injector used in orally injecting such an injection liquid as an anesthetic in dental treatment. Electrically-driven dental injectors includes one having a mechanism for disengaging a pinion (82) from a rack (48) in order to retract a plunger rod (44) upon completion of injection; however, it has heretofore been necessary to manually operate the operating part from outside each time. The inventive electrically-driven dental injector is so arranged that the plunger rod can be manually pushed back directly oupon completion of injection without requiring manual operation, and, to this end, the injector comprises a latch mechanism (84) for engaging/disengaging the ring gear (70) of a planetary reduction gear (50) with/from a casing (52), and an operating rod (94) extending through a support member (20) and functionally cooperating with the latch mechanism (84).

Abstract: An electrically-driven dental injector used in orally injecting such an injection liquid as an anesthetic in dental treatment. Electrically-driven dental injectors includes one having a mechanism for disengaging a pinion (82) from a rack (48) in order to retract a plunger rod (44) upon completion of injection; however, it has heretofore been necessary to manually operate the operating part from outside each time. The inventive electrically-driven dental injector is so arranged that the plunger rod can be manually pushed back directly oupon completion of injection without reqiring manual operation, and, to this end, the injector comprises a latch mechanism (84) for engaging/disengaging the ring gear (70) of a planetary reduction gear (50) with/from a casing (52), and an operating rod (94) extending through a support member (20) and functionally cooperating with the latch mechanism (84).