Patent ID: 8394061

Claim:
A fluid dispensing device comprising: (a) a first syringe having a reservoir with an outlet port, the reservoir adapted to hold a treatment fluid to be dispensed, and a plunger for ejecting the treatment fluid from the reservoir through the said outlet port; (b) a second syringe having a reservoir with an outlet port, the reservoir of the second syringe adapted to contain a fluid, and a plunger for ejecting the fluid from the second reservoir; (c) a flow rate control device coupled to the outlet port of the reservoir of the second syringe for controlling the rate of displacement of the plunger of the first syringe; (d) a link member coupling the plunger of the second syringe to the plunger of the first syringe; (e) a constant force spring operatively coupled to the plunger of the second syringe to impart a generally constant force to the plunger of the second syringe such that the plunger of the first syringe moves in unison with the plunger of the second syringe over a predetermined range of motion; and (f) a rate selector coupled to the flow rate control device, the rate selector including: (i) tubular linear valve block having a displaceable piston slidable within a longitudinal bore formed in the valve block past first and second pairs of ports to selectively occlude ones of said first and second pairs of ports, the longitudinal bore being connected in a fluid circuit with the outlet port of the second syringe; (ii) a first rate control member joining the first pair of ports to one another; (iii) a second rate control member joining the second pair of ports to one another; and (iv) displacement of the piston serving to selectively block all flow, provide a unit flow, provide one-half the unit flow rate, or provide twice the unit flow.