The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 25, 1994
Filed:
Jul. 31, 1991
Vernon R Natwick, Los Altos, CA (US);
Michael W Lawless, Boulder Creek, CA (US);
Abbott Laboratories, Abbott Park, IL (US);
Abstract
A cam assembly and method for providing a substantially constant load to a motor that drives the cam assembly. A torque compensated cam assembly (142,300) includes a plurality of tracks (140,150,152/310,312,314) that are profiled with a surface that varies radially as the cam rotates, thereby actuating cam followers, each of which rolls along a different track. A tangential force developed by the cam followers as they move over rapid radial changes in the surfaces of the tracks produces a total net torque that at times tends to aid the rotation of the cam and at times tends to impede its rotation. The cam is used in a volumetric pump (30) that accurately delivers a desired volume of fluid at a desire rate. To assist in maintaining the accuracy of these parameters, the torque compensated cam assembly presents a substantially constant load to a motor (146,304) that drives the cam. In one embodiment, the cam assembly includes a torque compensation track (170/316) disposed at one end of the cam, and in another embodiment, the torque compensation track is disposed circumferentially around the cam. A torque compensation roller (172,320) is biased against the torque compensation track by a flexure (174), providing a force that develops the required compensating torque. The profile of the torque compensation track is defined so as to produce a torque that is substantially equal in magnitude, but opposite in the direction, that it tends to rotate the cam assembly, compared to the net torque developed by the cam followers.