Single use disposable syringe

Claim 2

A syringe comprising a tubular housing having an entrance for a plunger at one end and an outlet for fluid at the other end, a plunger disposed in said housing and movable relative to the housing between a rear position and a forward position, and means for preventing the plunger from drawing liquid into the syringe once it has been pushed to said forward position; wherein said plunger comprises a piston and piston rod releasably coupled to one another, and means for releasably coupling said piston to said piston rod when initially drawing fluid into said syringe as said plunger is moved to said rear position and for disengaging said piston from said piston rod when ejecting fluid from said syringe as said plunger is pushed toward said forward position so that the piston rod cannot pull the piston back to draw more fluid into the syringe, said means for releasably coupling said piston to said piston rod including a spring washer circumferentially disposed about said piston rod and engaging said piston and piston rod when under radial compression and releasing said piston from said piston rod when the radial compression of the washer is released, and means for radially compressing said washer when initially drawing fluid into said syringe as said plunger is moved to said rear position and releasing the radial compression of said washer as said plunger is moved toward said forward position.

Claim 3

A syringe as in claim 1, wherein said means for radially compressing and releasing the compression of said spring washer includes a first plurality of teeth extending inwardly from an inner surface of said tubular housing and a cylindrical sleeve, disposed about the piston, for radially compressing said spring and including a second plurality of teeth protruding from an outer surface of the sleeve for engagement with the first plurality of teeth of the tubular housing; said first and second plurality of teeth being arranged to permit movement of said sleeve within the tubular housing toward said rear position and to prevent movement of said sleeve within the tubular housing from said rear position toward said forward position.

Claim 4

A syringe as in claim 2, wherein said first plurality of teeth as disposed within a channel provided in the wall of the tubular body.

Claim 5

The syringe of claim 1, further wherein said tubular housing comprises forward and rear compartments, said rear compartment having a smaller inside diameter than said forward compartment.

Claim 6

The syringe of claim 4, further wherein said spring washer is sized and configured so as to be radially compressed in said rear compartment and to released from radial compression in said forward compartment.

Claim 7

The syringe of claim 5, further within said piston comprises an opening adapted to receive the forward end of said piston rod; said piston rod comprises an annular groove adjacent said forward end, said groove being sized to receive said spring washer; and said piston additionally comprises a circumferentially-extending slot sized to receive said spring washer and positioned so as to be radially alignable with said groove when said forward end of said piston rod is received in said opening.

Claim 8

The syringe of claim 6, further wherein said spring washer is sized and configured so that when said spring washer has been compressed radially, said spring washer may be received simultaneously in said slot in said piston rod and in said groove in said piston, and so that when said spring washer is released from radial compression, said spring washer is received in only one of said slot and said groove.

Claim 9

The syringe of claim 1, further comprising a hollow sleeve with an exterior wall having a diameter less than the interior diameter of said tubular housing so as to be slidably contained therein, said tubular housing additionally comprising a first plurality of projections extending radially inwardly and sized and configured so as to restrain movement of said sleeve past said projections in at least one direction.

Claim 10

The syringe of claim 8, further wherein said spring washer is sized and configured so as to be radially compressed when inside said sleeve and to be released from radial compression when slid out of said sleeve.

Claim 11

The syringe of claim 9, further wherein said piston comprises an opening adapted to receive the forward end of said piston rod; said piston rod comprises an annular groove adjacent said forward end, said groove being sized to receive said spring washer; and said piston additionally comprises a circumferentially-extending slot sized to receive said spring washer and positioned so as to be radially alignable with said groove when said forward end of said piston rod is received in said opening.

Claim 12

The syringe of claim 1, additionally comprising a needle releasably coupled to the forward end of said housing, and retraction means for retracting said needle into said housing when said piston rod is moved a predetermined distance away from said forward end of said housing.

Claim 13

A syringe comprising a tubular housing with forward and rear compartments, said forward compartment having a smaller inside diameter than said rear compartment, said housing having an entrance for a plunger at the rear end thereof and an outlet for fluid at the forward end thereof, a plunger disposed in said housing and movable relative to the housing between a rear position and a forward position, and means for preventing the plunger from drawing liquid into the syringe once it has been pushed to said forward position; wherein said plunger comprises a piston and piston rod releasably coupled to one another, and means for releasably coupling said piston to said piston rod when initially drawing fluid into said syringe as said plunger is moved to said rear position and for disengaging said piston from said piston rod when ejecting fluid from said syringe as said plunger is pushed toward said forward position so that the piston rod cannot pull the piston back to draw more fluid into the syringe, said means for releasably coupling said piston to said piston rod comprising: (a) first and second legs attached to said piston in spaced relation to the forward end of said piston rod so that said legs are movable between a first position wherein said legs extend parallel to one another and to the longitudinal axis of said piston rod, and a second position wherein said legs extend toward one another transversely to the longitudinal axis of said piston rod; (b) engagement means attached to said forward end of said piston rod for engaging said first and second legs so as to couple said piston rod to said legs only when said legs are in said first position; and, (c) a spring washer circumferentially disposed about said first and second legs so as to define a central aperture wherein said central aperture has a first inside dimension when said spring washer is in the rear compartment of said housing, said first inside dimension being of a size sufficient to permit said legs to remain in said first position while positioned in said central aperture and a second inside dimension when said spring washer is in the forward compartment of said housing, said second inside dimension being of a size sufficient to accommodate said legs in said central aperture only when said legs are in said second position.

Claim 14

A syringe comprising a tubular housing with forward and rear compartments, said forward compartment having a smaller inside diameter than said rear compartment, said housing having an entrance for a plunger at the rear end thereof and an outlet for fluid at the forward end thereof, a plunger disposed in said housing and movable relative to the housing between a rear position and a forward position, and means for preventing the plunger from drawing liquid into the syringe once it has been pushed to said forward position; wherein said plunger comprises a piston and piston rod releasably coupled to one another, and means for releasably coupling said piston to said piston rod when initially drawing fluid into said syringe as said plunger is moved to said rear position and for disengaging said piston from said piston rod when ejecting fluid from said syringe as said plunger is pushed toward said forward position so that the piston rod cannot pull the piston back to draw more fluid into the syringe, said means for releasably coupling said piston to said piston rod comprising: (a) first and second legs attached to said piston in spaced relation to the forward end of said piston rod so that said legs are movable between a first position wherein said legs extend parallel to one another and to the longitudinal axis of said piston rod, and a second position wherein said legs extend toward one another transversely to the longitudinal axis of said piston rod; (b) engagement means attached to said forward end of said piston rod for engaging said first and second legs so as to couple said piston rod to said legs only when said legs are in said first position; and, (c) a spring washer circumferentially disposed about said first and second legs so as to define a central aperture wherein said central aperture has a first inside dimension when said spring washer is in the rear compartment of said housing, said first inside dimension being of a size sufficient to permit said legs to remain in said first position while positioned in said central aperture and a second inside dimension when said spring washer is in the forward compartment of said housing, said second inside dimension being of a size sufficient to accommodate said legs in said central aperture only when said legs are in said second position.