Anesthetic solution-filled cartridge-type electric dental syringe

摘要

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.

主权项

1. A dental anesthetic solution-filled cartridge-type motorized syringe, comprising a pinion rotated by a drive unit with a rack on a pusher rod,
wherein engagement of the pinion rotated by the drive unit with the rack on the pusher rod causes the pusher rod to move, thereby moving a plunger rubber plug in a cartridge for delivery of anesthetic solution from the cartridge through a needle, characterized by comprising an extension tube movably located in a through-hole in a support block into which the pusher rod is movably inserted, and having racks formed on sides of the extension tube in alignment with the rack on the pusher rod, the extension tube comprising a forward portion having an inner diameter equal to an outer diameter of the pusher rod, a rearward portion having an inner diameter larger than the inner diameter of the forward portion, a shoulder defined between the forward portion and the rearward portion, and protrusions provided on the pusher rod adjacent the rear end of the pusher rod and adapted to abut the shoulder by moving in the rearward portion of the extension tube, thereby pulling the extension tube to engage the racks on the extension tube with the rotating pinion when the pusher rod reaches a middle of a distance equal to a length of accommodation of anesthetic solution in the cartridge, wherein the engagement of the racks on the extension tube with the pinion causes the pusher rod to move a remainder of the distance equal to the length of accommodation of anesthetic solution in the cartridge, together with the extension tube.