This invention provides a simple and inexpensive vibrator. Upper and lower linked arms are used to hold equal weights attached at the ends of the arms. The arms are attached to collars which spin. A bent axle is used to cause displacement of the upper collar with a resultant shortening of the effective radius of rotation of one of the weights at a determined position in the circle of rotation. This shortening of the effective radius of rotation imparts a vibratory motion to the vibrator.
A vibration generator includes a weight member, a shaft rotatable about an axis of rotation extending longitudinally therethrough and having a mounting area on which the weight member is mounted, and a positioning arm disposed in engagement with the weight member on the shaft and rotatable about the axis of rotation relative to both the shaft and the weight member. The mounting area engages the weight member and prevents movement of the weight member relative to the shaft in a circumferential direction about the axis of rotation but permits movement of the weight member relative to the shaft in a radial direction orthogonal to the axis of rotation and coplanar with the circumferential direction. The weight member also defines an elongate positioning slot and the positioning arm includes an axially extending portion disposed through the positioning slot for slidable movement within the positioning slot during rotation of the positioning member relative to the shaft. The axially extending portion in fact defines a cam surface disposed in engagement with the weight member within the positioning slot. Rotation of the positioning arm relative to both the shaft and the weight member moves the weight member relative to the shaft in a radial direction orthogonal to the axis of rotation thereby altering the moment of inertia of the weight member about the axis of rotation and resulting in a different amplitude of vibration during rotation of the weight member.
