Abstract
The instrument to be described was developed to fill the need for an infusion pump with which rate of delivery could be continuously varied over a wide range during injection. The present pump has met this need and has been employed for 9 months in experiments on small animals in which rate of injection has been critical.
Details of construction and mode of operation of this pump will be apparent from Fig. 1 and 2. The motor (Bodine Electric Co., Chicago, 1/50 H.P., 1725 rpm, with gear reduction to 11.5 rpm) turns the first drive cone (A). The 4 identical drive cones are knurled cast aluminum. The conical portion is 4′′ long and the large and small diameters are 3′′ and .95′′ respectively. Cone A drives cone B by means of rubber ring (1/4′′ by 18′′ circumference) which provides contact between the 2 cones. The point of contact of the ring with the cones is adjustable by means of yoke K, rod L and setscrew M (Fig. 1). It can be seen that when the largest portion of cone A is driving B, B rotates 3.16 times as rapidly as A; conversely, when the smallest portion of A is driving B, A rotates at 3.16 times the speed of B. Thus, a 10-fold range of speed is achieved by the first pair of cones. Cone C is coupled to B and both turn at the same speed. Cone D, however, is driven by C through a mechanism identical to that linking cones A and B. Range of speed for the 2 pairs of drive cones is therefore 100-fold. To prevent slippage of the cones on the rubber rings it is necessary to have considerable tension on the 2 pairs of drive cones.
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