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Inductively Heated Preload Fixture for Actuator Pivots

IP.com Disclosure Number: IPCOM000013673D
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-18

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Described is a preload fixture that applies heat to a pivot bearing assembly during the thermal cure of its adhesive bond joints. Typically acrylic bond joints in the pivot assembly are batch cured inside a thermal convection oven for 1 to 2 hours held within a temperature range of 60C to 80C. To shorten the cycle time, this new preload fixture incorporates inductive heating elements to heat the pivot internally. These heating coils are contained in a cylindrical jacket that surrounds the pivot, see figure 1. Inductive heating is quick and time efficient because the heat is generated from within the metal part; i.e., pivot components, and can reduce the total cycle time by 50% or more. Inductive heating is uniform within each pivot and uniform from fixture to fixture. Batch oven processes are notorious for having hot and cold zones, so some pivots are not cured completely or lake longer to cure. Batch oven processes require the numerous preload fixtures to be placed inside the oven, at periodic intervals. Opening and closing oven doors lets some of the hot air out; also, the fixtures add thermal mass to the oven. These factors increase the time it takes the oven to heat up and achieve the actual curing temperature in the pivot. This design prevents the entire preload fixture from being heated up to reach thermal equilibrium with the pivot. In an alternate configuration, resistance heat coils could be used instead of inductive heating coils. In either case, the capital cost of batch ovens would be avoided. This idea is applicable to thermally initiated acrylic, urethane or epoxy adhesive systems. Figure 1. Inductive heating coils on pivot preload fixture. 1