Injection System with Hidden Needles

Abstract

An auto-injector confines all functional components inside an enclosed housing, to keep its needle out-of-sight, at all times. Within the housing, a needle holder positions a needle at a location. A drive mechanism then simultaneously engages the needle with a fluid source and accelerates it with a predetermined momentum for insertion into a patient. After fluid delivery, the withdrawn needle is moved to storage within the housing for subsequent disposal.

What is claimed is: 
     
         1 . A housing with a system mounted thereon for injecting a fluid medicament into a patient, said system comprising:
 an elongated hypodermic needle defining an axis and having a sharp proximal end and a sharp distal end;   a fluid reservoir mounted on the housing;   a fluid transfer section formed with a fluid chamber and positioned for movement along a pathway inside the housing, said fluid chamber having an input port and an output port, wherein a septum covers the output port;   a flexible hose interconnecting the input port of the transfer section with the fluid reservoir to establish fluid communication between the fluid reservoir and the needle;   a collar mounted on the hypodermic needle between the proximal end and the distal end thereof with the collar extending radially outward from the needle, wherein the collar limits travel of the needle along the pathway inside the housing between a first position wherein the proximal end of the needle is at a distance from the fluid transfer section and a second position wherein the sharp proximal end of the needle is engaged in fluid communication with the fluid reservoir and the sharp distal end of the needle is inserted into the patient for infusion of the fluid medicament from the reservoir to the patient while said fluid reservoir remains stationary relative to movement of the fluid transfer section wherein the needle and the collar, in combination, establish a needle unit, and wherein the system incorporates a plurality of needle units and the system further comprises a holder mounted on the housing to sequentially present each needle unit for individual travel along the pathway and to subsequently remove the needle unit from the pathway;   an abutment formed on the housing for contact with the collar to limit axial movement of the needle in a distal direction relative to the housing during insertion of the distal end of the needle into the patient;   a recoil mechanism mounted on the abutment for engagement with the collar to bias the needle in a proximal direction relative to the housing for subsequent withdrawal of the needle from the patient when the needle is in its second position; and   a means for driving the fluid transfer section into contact with the needle at the first position to pierce the septum with the needle and to position the sharp proximal end of the needle in the chamber of the fluid transfer section when the collar abuts against the fluid transfer section to establish fluid communication between the needle and the fluid source, and for moving the needle from the first position to the second position.