Battery operated miniature syringe infusion pump and improved halfnut therefor

Claim 1

A syringe infusion pump comprising: a support; a syringe holder on the support; drive means on the support for driving the syringe plunger into the syringe barrel, said drive means includes a rotatably driven leadscrew on the support having a center line; an antisiphon and drive decoupling means on the support movable between a first position at which it is decoupled with the drive means and disengaged with the plunger of the syringe and a second position at which it is coupled with the drive means and engaged with the plunger of the syringe to prevent escape of the plunger and consequent siphoning action by the syringe, and the antisiphoning and drive decoupling means including a pusher block movable longitudinally on the support, a drive means engaging surface means on the block for meshing with the leadscrew, the drive means engaging surface means including a halfnut, the pusher block including floating means for permitting the drive engaging surface means to float freely to find the center line of the line leadscrew, the drive means engaging surface means including contacting points between the halfnut and pusher block spaced apart around the leadscrew substantially at the center line of the leadscrew with the contact points of the halfnut substantially near the center line normal to both the separation direction and the axis of the leadscrew thereby greatly reducing force mechanisms that attempt to separate the leadscrew and halfnut.