Timer mechanism with improved interval accuracy

A timer comprising:

• a control cam having a first and second cam track;
• said second cam track having three arcuate segments of progressively shorter fixed radius lengths defining a three step cam track profile;
• drive means for rotating the control cam about an axis;
• switch means comprising first and second resilient arms carrying opposing contacts and extending generally adjacent said first cam track, said first arm extending between said second arm and said first cam track and said second arm having a lateral projection member in the direction of the second cam track;
• a cam-following member extending between said second arm and said first cam track and biased into cam-following engagement with said first cam track by said second arm;
• a rocker arm having at one end a cam-follower portion and at the other end a lifter portion, said rocker arm having a pivot point between the ends thereof and spring biased to force the cam-follower portion into cam-following engagement with the second cam track;
• said cam-following member and first cam track being operative to prevent closing the contacts when said rocker arm cam-follower portion is riding on the arcuate segment having the longest radius length;
• said cam-following member and first cam track being operative to release the cam-following member from the first cam track and support the first arm on the rocker arm and prevent closing the contacts when said rocker arm cam-follower portion is riding on the arcuate segment having the longest radius length;
• said cam-following member and first cam track being operative to release the cam-following member from the first cam track and close the contacts when said rocker arm cam-follower portion is riding on the arcuate segment having the second longest radius length;
• said rocker arm and second cam track being operative to pivot the rocker arm when the cam follower portion is riding on the arcuate segment having the shortest radius length and the lifter portion engages the lateral projection member of the second arm and opens the contacts;
• and
• means to reset the timer for subsequent cycling.