Preloadable syringe with push rod disengable from piston once syringe is loaded

The hollow cylindrical syringe body (10) has a channel (12) of uniform diameter. A fluid port (14) is situated at one end. The other end defines a funnel-like opening (20) with a diameter greater than that of the channel (12). A piston (24) is moved along the channel (12) by the end of a push rod (26), which is received through the channel opening (20). A ball (30) on the push rod (26) lodges in a socket (36) in the piston (24) as the rod pushes the piston (24) toward the port (14). The socket (36) is formed of resilient fingers (32, 34), which are held by the channel wall in position to retain the ball (30) in the socket (36), such that the piston (24) can be moved along the channel (12) to load the syringe. When the socket (36) aligns with the funnel-like opening (20) of the channel (12), the socket fingers (32, 34) spread apart to release the ball (30) from the socket (36), permitting the push rod (26) to be removed from the loaded syringe.