US Patent 8104120 Height adjustable bed with a push chain assembly

A bed includes a base frame 14 having a head end and a foot end, an elevatable frame 16 also having a head end and a foot end, a lift assembly 76 or 78 comprising an actuation system connected to one of the frames, a push chain 106 having an actuator end 124 driven by a lead screw 86 and a distal end 126 connected to the other of the frames. Rotary motion of the lead screw changes elevation of the elevating frame relative to the base frame.