Abstract: This invention is a single-use syringe (10) having a rd-like plunger (14) and made with a plurality of frusto-conical or bead-like ratchet teeth (28). A radially resilient, spring locking clip (40) dangles on the ratchet portion of the plunger. The location of the clip determines the maximum dosage which can be administered by the syringe. Aspirating gaps (114) can be provided on the plunger rod to allow selective aspiration prior to loading and dispensing medication. In use, a first withdrawal of the plunger with respect to the barrel (12) allows, for aspiration, then medication can be drawn into the cavity of the barrel since the cam tooth (83) of the locking spring clip glides, by radial flexing, over the surface of the ratchet teeth and, yet, the locking spring is maintained in relative position along the barrel by outwardly directed contact points embedding into the interior sidewall of the barrel.

Abstract: An economical hypodermic syringe is provided. A retractable needle head is provided to slide along longitudinal grooves in the barrel of the syringe. Notches in the grooves engage teeth provided on tabs of the needle head, and lock the needle head in a predetermined position. The tabs are resilient, and if squeezed against the resilient bias, will disengage from the notches in the grooves. In this way, the needle may be partially or fully withdrawn into the barrel. In addition or alternatively, a needle cover is included which is adapted to serve as the plunger of the syringe. The outer diameter of the needle cover is narrower than the inner diameter of both the barrel and an ampoule.

Abstract: A single-use syringe is provided with a rod-like plunger having a plurality of frusto-conical ratchet teeth. A radially resilient locking spring clip having a circumferential opening, dangles on the ratchet teeth of the plunger. The original location of the spring clip on the plunger determines the maximum dosage which can be administered by the syringe. In use, a first withdrawal of the plunger allows medication to be drawn into the barrel of the syringe. The spring clip glides, by radial flexing, over the surface of the ratchet teeth during plunger withdrawal. The spring clip is maintained in relative position along the sidewall of the barrel by outwardly directed contact points which embed into the interior sidewall of the barrel. During administration of the medication previously drawn into the barrel, the spring clip moves along with the plunger since an interiorly directed camming tooth of the clip mechanically cooperates with the base of a ratchet tooth of the plunger.

Abstract: A single use syringe is provided having a rod-like plunger comprising a plurality of cylindrical ratchet teeth. A resilient locking spring dangles on the ratchet teeth of the plunger. The original location of the locking spring determines the maximum dosage which may be administered by the syringe. A first withdrawal of the plunger with respect to the barrel allows medication to be drawn into the barrel. The tab of the locking spring resiliently cams over the surface of the ratchet teeth. The locking spring is maintained in position along the barrel by outwardly directed contact points which embed into the interior side wall of the barrel. During administration of the medication, i.e., when the plunger is distally pushed with respect to the barrel, the locking spring tab cooperates with the base of the ratchet teeth and causes the spring to move along with the plunger. A second attempted withdrawal of the plunger is blocked once the locking spring has been moved to its full distal position.

Abstract: A non-reusable syringe is provided with an annular locking groove having a seat proximal to the rear end of the barrel and a second annular locking groove with a second seat located near the proximal end of the barrel. The plunger for the non-reusable syringe is provided with a flexible disc preferably located directly behind the piston head so that when the plunger is inserted with the barrel, the disc can bend upwardly when sliding the plunger downwardly past the first seat of the annular locking groove and, yet, proximal relative movement of the plunger with respect to the barrel is precluded by the cooperation of the disc and the locking groove. When the plunger is fully pushd in the distal direction, the disc, again, can pass in one direction beyond the second locking groove and its seat and, yet, reciprocation or proximal movement of the plunger with respect to the barrel is precluded by the mechanical interaction of the disc with respect to the second locking groove and seat.