Abstract: An infant seat assembly is made up of a resilient frame with a leg rest portion designed to support a displacement mechanism which will either impart a shaking or bouncing motion to the frame; and, when a baby is placed in the seat assembly, the frequency of vibration imparted to the frame can be selectively tuned to be in harmony with the natural frequency of vibration of the frame when an infant is placed in the seat assembly.

Abstract: A novel and improved form of displacement mechanism has been devised for an infant bouncer seat of the type having a resilient frame with a base support located directly beneath the seat proper, the displacement mechanism mounted on the base portion and including a variable speed motor drive which operates through a speed reduction mechanism into a crank arm at one end of a lift arm which is pivotal in response to activation of the motor drive to impart vertical reciprocal motion to the base. The motor speed is adjusted to tune the frequency of reciprocal motion of the base to the natural frequency of the seat for a particular weight baby, and the connection of the lift arm to the base can be adjusted to vary the amplitude of reciprocal motion of the lift arm and the base.